istraživanja i projektovanja za privredu - applied engineering science 9(2011)4

Institute for research and design in commerce & industry, Belgrade. All rights reserved. Journal of Applied Engineering Science 9(2011)4

C O N T E N T S

Mr Dragan Komarov, Dr Slobodan Stupar, Zorana PosteljnikREVIEW OF THE CURRENT WIND ENERGY TECHNOLOGIES

AND GLOBAL MARKET437 - 448

Dr Dragan Ćoćkalo, Dr Dejan Đorđević, Dr Zvonko Sajfert, Dr Srđan BogetićSMES IN THE REPUBLIC OF SERBIA: THE DEVELOPING CAPACITIES 449 - 456

Dragan Stamenković, Dr Vladimir Popović, Dr Vesna Spasojević Brkić, Jovan Radivojević

COMBINATION FREE REPLACEMENT AND PRO-RATA WARRANTY POLICY OPTIMIZATION MODEL

457 - 464

Dr Gradimir Danon, Miloš PetrovićPROACTIVE TIRE MAINTENANCE 465 - 472

Dr Časlav Mitrović, Dr Slobodan Radojević, Milan Srećković, Mr Zoran MilanovićFROM IDEA TO IMPLEMENTATION IN PROTECTION

OF ELECTRONIC EDITIONS (BOOK)473 - 479

EVENTS REVIEW 481 - 483

ANNOUNCEMENT OF EVENTS 484 - 486

BOOK RECOMMENDATION 487

INSTRUCTIONS FOR AUTHORS 488 - 489

EDITORIAL AND ABSTRACTS IN SERBIAN LANGUAGE 491 - 495

Journal of Applied Engineering Science 9(2011)4

I M P R E S S U M

Journal of Applied Engineering Science

The journal publishes original and review articles covering the concept of technical science, energy and environment, industrial engineering, quality management and other related sciences. The Journal follows new trends and progress proven practice in listed fi elds, thus creating a unique forum for interdisciplinary or multidisciplinary dialogue.

All published articles are indexed by international abstract base Elsevier Bibliographic Databases through service SCOPUS since 2006 and through service SCImago Journal Rank since 2011.

Serbian Ministry of Education and Science admitted the Journal of Applied Engineering Science in a list of reference journals. Same Ministry fi nancially supports journal’s publication.

Editor in ChiefProf. dr Jovan TodorovićFaculty of Mechanical Engineering, Belgrade;

Assistant EditorDr Predrag Uskoković Institute for Research and Design in Commerce and Industry, Belgrade;

Editorial Board Prof. dr Gradimir Danon, Faculty of Forestry, Belgrade; Doc. dr Dušan Milutinović, Institute for Transport and Traffi c CIP, Belgrade; Mr Đorđe Milosavljević, CPI - Process Engineering Center, Belgrade; Prof. dr Miodrag Zec, Faculty of Philosophy, Belgrade; Prof. dr Nenad Đajić,Mining and Geology Faculty, Belgrade; Prof. dr Vlastimir Dedović, Faculty of Transport and Traffi c Engeneering, Belgrade;Prof. dr Mirko Vujošević,Faculty of organizational sciences, Belgrade;Doc. dr Vladimir Popović,Faculty of Mechanical Engineering, Belgrade;Doc. dr Vesna Spasojević Brkić,Faculty of Mechanical Engineering, Belgrade.

PublisherInstitute for Research and Design in Commerce and Industrywww.iipp.rsFor publisher: Prof. dr Branko Vasić

CopublisherFaculty of Transport and Traffi c Engineering – Belgrade Universitywww.sf.bg.ac.rsFor copublisher: Prof. dr Slobodan Gvozdenović

ISSN 1451-4117 UDC 33Papers are indexed by SCOPUS

Journal of Applied Engineeering Science is also available on www.engineeringscience.rs and http://scindeks-eur.ceon.rs/index.php/jaesDesigned and prepress: IIPP

International Editorial BoardProf. dr Vukan Vučić,University of Pennsylvania, USA;Prof. dr Robert Bjeković, Hochschule Ravensburg-Weingarten, Germany;Prof. dr Jozef Aronov, Research Institute for Certifi cation JSC, Russia;Prof. dr Jezdimir Knežević, MIRCE Akademy, England;Dr Nebojša Kovačević, Geotechnical consulting group, England;Adam Zielinski, Solaris Bus & Coach, Poland;Prof. dr Miloš Knežević, Faculty for Civil Engineering, Montenegro;MSc Siniša Vidović, Energy Testing & Balance Inc, USA;Dr Zdravko Milovanović,Faculty of Mechanical Engineering, Banja Luka.

Publishing CouncilProf. dr Milorad Milovančević,Faculty of Mechanical Engineering, Belgrade; Milutin Ignjatović,Institute for Transport and Traffi c CIP, Belgrade; Dragan Belić,Transport Company “Lasta”, Belgrade;Dr Deda Đelović,Port of Bar, Bar;Dr Drago Šerović,Adriatic Shipyard, Bijela;Cvijo Babić,Belgrade Waterworks and Sewerage, Belgrade;Nenad Jankov,Power Plant Kostolac B, Kostolac;Miroslav Vuković,Mercator Business System, Belgrade;Dušan Đurašević,Euro Sumar, Belgrade.

Editorial Offi ceNada Stanojević, Miloš Vasić, Darko Stanojević,Miloš Dimitrijević, Mirjana Solunac, Ivana Spasojević, Andrija Đurašević, Institute IIPP, Belgrade;Bojan Mančić, Faculty of Mechanical Engineering, Belgrade.Printed by: Beografi ka, Beograd

Institute for research and design in commerce & industry, Belgrade. All rights reserved. Journal of Applied Engineering Science 9(2011)4

E D I T O R I A L

Doc. dr Vladimir Popović

Vehicles which are sold and put into service in a country have to meet the regulations and standards of that country. The registration procedure of that country requires the approval of the vehicle and/or its components. The existence of separate national regulations and approval procedures in the different countries requires expen-sive design modifi cations, additional tests and duplicating approvals. Thus, there is the need to harmonize the different national techni-cal requirements for vehicles and to elaborate a unique international regulation. Once the vehicle or its equipment and parts are manufac-tured and approved according to that regulation, they can be interna-tionally traded without further tests or approvals. Furthermore, these regulations have to be continuously adapted to the technical prog-ress and to the new requirements regarding safety, environmental protection and energy effi ciency.

Currently, in the European vehicle market, there are two key, parallel system for vehicle type ap-proval, which practically defi ne the criteria and conditions for trading vehicles, through:

UNECE Regulations, that is regulations of United Nations Economic Commission for Eu rope (UNECE), passed by The World Forum for Harmonization of Vehicles Regulations - WP.29, within the 1958 Agreement, andEU Directives, that is regulations of The European Union (EU).

The Republic of Serbia is a Contracting Party of the 1958 Agreement and it actively participates in the work of WP.29, while the application of EU regulations depends on the status of our country in the process of joining the EU, which is at this point rather uncertain. The main principle of WP.29 is “Certifi ed once, accepted everywhere”. If we consider the key challenges the UNECE Transport Department is to face in the future, we can see the importance the territory of Southeast Europe is attributed with respect to them. The region in question has signifi cant position because of two, out of six challenges previously mentioned:

Insuffi cient and inadequate infrastructures, particularly in Eastern Europe, the Caucasus and Central Asia;Old, unsafe and highly polluting road vehicle fl eets, particularly in Eastern and South-Eastern Europe, as well as in the Caucasus and Central Asia, which result in higher accident rates and environmental impacts.

The best preventive, regarding the second challenge in particular, is harmonizing regulations to do with vehicles, with the purpose of enhancing their safety and environmental performance. Harmo-nizing certainly leads to market expansion and overcoming certain obstacles. In the last few years, it has become evident that harmonizing regulations connected to vehicle type approval is heading towards substituting EU Directives by UNECE Regulations. This is accounted for by the increas-ing importance of the 1958 Agreement. It is obvious that, in WVTAs themselves, numerous vehicle manufacturers from the EU include an increasing number of individual type approvals according to UNECE Regulations, compared to EU Directives. Among other things, the reason for this is the fact that, apart from all the countries which have signed the Agreement, USA, China, EU (Contracting Party to the Agreement) and India, whose importance in automobile industry is indisputable, actively participate in the WP.29, together with numerous non-governmental international organizations, in-terested in this matter (International Organization for Standardization - ISO; International Organiza-tion of Motor Vehicle Manufacturers - OICA; International Motorcycle Manufacturers Association – IMMA…).Furthermore, it is very important to point out that one of the informal working parties of WP.29 is in charge of the development and implementation of The International Vehicle Type Approval System (IWVTA), to be applied as from 2016, which should, in the long run, replace WVTA, which is the basis of today’s system of type approval in the EU. This trend will most certainly continue in the fu-ture, since it would complete the process of regulation harmonization on the world level, which is an inevitable consequence of globalization, particularly evident in automobile industry.

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Speaking of our region, all countries have signed the 1958 Agreement, except for Albania. Perhaps the key indicator for the development of regulations to do with vehicles on the territory of Southeast Europe is a more or less expressed wish of all the countries and territories of this region to be mem-bers of the EU. However, each country individually, regardless of the fact whether it is a member of the EU or not, has to sign the 1958 Agreement in case it wants to apply it. On the other hand, many countries which have not signed the 1958 Agreement, recognize it unilaterally, and apply UNECE Regulations as equivalent to national regulations, which resulted in the fact that type-approved ve-hicles represent a harmonized level of quality on the international market of vehicles, equipment and components.

Still, this entire process of joining the EU implies two confl icting aspects when it comes to vehicle market. On the one hand, the EU will most certainly require compliance of all regulations of the countries which want to join it with its own, including regulations to do with vehicles. On the other hand, the used vehicles from EU countries must fi nd their own markets where they can be sold, but in practice, a big difference between regulations for importing new and used vehicles in the same country is impossible and economically speaking, unsustainable.

Although regulations on vehicle type approval, formally speaking, have technical nature, it is evident that their change is rather a consequence of global and political trends, since automobile industry is a vital factor of any economy. Therefore, it is important to emphasize that the general political and economic circumstances in the Balkans have always been turbulent and prone to fundamental changes. For that reason, it is very diffi cult to make more accurate predictions regarding the devel-opment of any regulations, those related to vehicle type approval and importing included, for a long-term period, despite the current situation. However, this problem must be addressed with a degree of optimism, and a belief in market stability and economic prosperity of this region.


Paper number: 9(2011)4, 208, 437 - 448

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Beograd, Serbia; [email protected] 437

REVIEW OF THE CURRENT WIND ENERGY TECHNOLOGIES AND GLOBAL MARKET

Mr Dragan Komarov *University of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaDr Slobodan StuparUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaMSc Zorana PosteljnikUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia

The modern wind energy technologies and recent global wind energy market trends are reviewed in the paper. Basic principles of conversion of wind energy to electricity are described with brief overview of the state-of-the-art technologies for subassemblies such as wind turbine blades and drivetrains. Global wind energy market was reviewed in order to attain notion of wind power market developments in the future. The most developed countries in terms of wind energy utilization such as Denmark, Germany, Spain and USA were identifi ed as the key drivers of wind energy technology advances. After the long leadership of European Union in built annual wind power capacities, China and USA have overtook leading positions for the last several years. Wind energy costs per unit of electricity produced after gradual decrease until 2005 have recorded slight increase until the present due to high demand and higher raw materials price. It was predicted that the trend of the wind energy cost will decrease in the future. Steady growth of wind energy capacities was predicted in the next years, with forecast that present global installed capacities of nearly 200 GW should grow to almost one terawatt by the 2020.

Key words: capacity, energy use, globalization, markets, technology, wind turbine, wind energy, winds

INTRODUCTION

Energy demand had rapid growth in the last century. The gross energy needs were sup-plied by conventional energy resources such as coal and oil, as well as newer technolo-gies such as nuclear power plants. High de-mand and limited resources had infl uence on the price growth of the produced electricity.Environmental issues, economy and political factors have infl uenced on renewable energy growth in the last thirty years. Due to large quan-tity of CO2 emissions from power and heavy in-dustries, as well as traffi c, the social awareness have risen of induced climate change. After the oil crisis in 1970s, the interest in renewable en-ergy was growing. Relatively simple design and existing technologies developed mainly for aero-nautical and power-generation purposes made wind energy industry one of the fastest grow-ing in the following decades [09]. As technology has matured, wind energy grew to substantial capacity [19], [23]. Although this capacity is still

incomparable to the total installed power in the world [12], wind energy presents industry that should not be neglected in the recent period and in the future.After the brief introduction, the review of the cur-rent wind turbine technologies was given with emphasis on commercial design. Technology trends and novel concepts of some assemblies were also given in this section. Overview of global wind energy capacities was given with brief sum-mary of the most developed markets as well as emerging ones in the next section. Wind energy costs were described in the following section with breakdown of the costs due to initial investment, operation and maintenance and other costs. Short conclusions were given at the end of the paper.

WIND TURBINE DESIGN CONCEPTS

Wind turbine design has been changing over the years, from being convention-driven to be-ing optimized-driven. As well as becoming larger (the generators in the largest modern wind tur-bines are 100 times the size of those in 1980),

DOI: 10.5937/JAES9 - 1120

Journal of Applied Engineering Science 9(2011)4 438

Mr Dragan Komarov etc. - Review of the current wind energy technologies and global market

, 208

wind turbine designs have been progressing from fi xed-speed, stall-controlled to pitch-con-trolled, variable speed, with or without gear-boxes. Other improvements include the use of different combinations of composite materials to manufacture blades, especially to ensure that their weight is kept to a minimum, as well as modern control system for better compat-ibility with the grid connection. Some of the de-sign drivers for current wind turbine technology are reliability, grid compatibility, maximum effi -ciency, noise reduction, high productivity for low wind speeds, aerodynamic performance, etc.Even though much time and resources are con-tinuously spent on improving the wind technology since its commercial beginnings in the early 1980s, the basic architecture of the mainstream design has maintained its original topology. Wind power technologies can be grouped in three applications:

Large grid connected wind turbines,Small “stand-alone” wind turbines for water pumping, battery charging, heating, etc.Hybrid energy systems – wind turbines in combination with other energy sources.

Generally, wind turbines can be classifi ed, ac-cording to the axis of rotation of main shaft, as

••

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Figure 1. Main components of a horizontal axis wind turbine [13]

horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT), the fi rst being domi-nate in wind power large-scale utilization, fi gure 1. HAWTs are usually classifi ed according to the rotor orientation relative to wind direction (upwind or downwind), hub design (rigid or teetering), rotor control (pitch vs. stall), rotor speed (fi xed or variable), number of blades, their alignment with the wind direction (active or passive yaw). HAWTs can use different number of blades, depend-ing on the purpose of the wind turbine. The determi-nation of the number of blades involves design con-siderations of aerodynamic effi ciency, component costs and system reliability, as well as aesthetics.

The loads on wind turbine rotor are cyclic depend-ing on blade position during the operation. Cyclic loads when combined together at the drivetrain shaft are symmetrically balanced for three blades, [06]. Modern utility-scale wind turbines usually have three-bladed upwind rotor and are actively yawed to preserve alignment with the wind direc-tion. Although the length of the blade can be as long as 60m, blades of the rotor are commonly manufactured as one part using different tech-niques for composite manufacturing. Still, one of the world’s largest wind turbines, the Enercon E-126, adopts a jointed blade design. In the E-126

Journal of Applied Engineering Science 9(2011)4, 439

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208

blade, an outer blade section with a conventional blade root attachment is bolted to a steel inner blade spar. The trailing edge of the inner blade is a separate composite structure. Gamesa has also developed a jointed blade design for the G10X wind turbine. The rotor size will increase in the future, as the trend of manufacturing of the larger multi-megawatt wind turbines will not cease. Beside the reason for the manufacturing of larger blades due to demand for megawatt ma-chines in the range between 3 and 7 megawatts, larger rotors would enable higher energy yield at sites with lower wind speeds. For example, Nordex has revealed the wind turbine with 117 meter rotor diameter with 2.4 MW rated power.

It is claimed that this wind turbine could achieve 3500 full-load hours at typical inland locations, which corresponds to capacity factor around 40 percent, which makes it feasible for construc-tion in lower wind speed sites. In order to attain technology necessary for manufacturing and operation of wind turbines with very long blades (longer than 100 m) it is necessary to develop stronger and lighter materials, to reduce loads using advanced fl exible materials and novel con-cepts of blade operation control, to use innova-tive technologies for wind speed measurements

etc. With these innovations, it is believed that 20 MW wind turbine will be feasible in the future [08].

The rotation of the blades is transferred through the drivetrain on to the generator, creating elec-tricity. At the wind speeds between 10 and 15 m/s, the power output of wind turbine rotor usu-ally reaches its rated capacity. If the rated wind speed is exceeded the power has to be limited, to prevent wind turbine from overloading and to ensure that it has constant output. There are two principal means of limiting rotor power in high op-erating wind speeds – stall regulation and pitch regulation. Stall-regulated machines require a constant rotational speed which can be achieved with a grid-connected induction generator. As wind speed increases and the rotor speed is held constant, fl ow angles over the blade sections in-crease. The blades become increasingly stalled and this limits power to acceptable levels, with-out any additional active control. On the other hand, using pitch regulation the blades have ad-ditional degree of freedom around their longitudi-nal axis so that the aerodynamic characteristics of the blade - and the rotor - can be controlled. In contrast to stall regulation, pitch regulation requires changes of rotor geometry by pitch-ing the blades. This involves an active control

Figure 2. Direct drive of Enercon E-48 [17]

Journal of Applied Engineering Science 9(2011)4 440 , 208

system, which senses blade position, measures output power and instructs appropriate changes of blade pitch [01]. Modern large-scale wind tur-bines are almost exclusively pitch-regulated. As it was mentioned, the drivetrain contains the rotor attached to a main shaft driving the gen-erator through the optional gearbox. However,


there are many signifi cant variations in structural support, in rotor bearing system and in gener-al layout. Vestas adopted the large single front bearing arrangement in the V90 3 MW design, which contributed to a very compact and light-weight nacelle system. Also, there has been a signifi cant trend towards innovative drivetrain

Figure 3. Savonius and Darrieus type of VAWT

systems. There are companies that use directly driven variable speed synchronous generators with large-diameter synchronous ring generator (fi gure 2.), but majority of wind turbine manu-facturers still use six-pole induction (asynchro-nous) generators connected through a gearbox to a rotor. Induction generators have a softer connection to the network frequency than syn-chronous generators, which reduce the loads between rotor and generator during wind gusts.

Low overall effi ciency during low speed winds can be overcome using two induction genera-tors, smaller and larger one. The motivation for direct drive application is to simplify the nacelle systems, increase reliability, increase effi ciency and avoid gearbox issues. Enercon and Sie-mens established the direct drive system, as well as some other manufacturers like Vensys, whose wind turbines are based on the genera-tor concept of a synchronous machine with per-manent magnet excitation [15]. There are also a number of hybrid systems. Clipper Windpower (after research into systems with multiple induc-tion generators) developed a system with an in-

novative gearbox with ouputs to four permanent magnet generators (PMGs). Northern Power Systems (after initially adopting a wound ro-tor direct drive design) and GE Energy in their 2.5 XL series, have all adopted PMG systems.

Generator and gearbox of the vertical axis wind turbines can be placed near the ground, hence avoiding the need of a tower and im-proving accessibility for maintenance, fi gure 3. Wind turbines of this type have low rotational speed with a consequential higher torque and higher cost of the drivetrain, lower power coef-fi cient, but they don’t need to be pointed into wind to be effective. There are several sub-types of vertical axis wind turbine such as Darrieus, Savonius wind turbine and giromill. Regarding offshore wind energy, currently, Eu-rope is the world leader. As of 2010, there are no offshore wind farms in the United States. Howev-er, there are some projects under development. Siemens and Vestas are the leading turbine suppliers for offshore wind energy. Commercial-scale offshore wind farms currently are similar to the onshore wind farms, but with modifi cations



Figure 4. World wind energy capacities (1990-2010)

to withstand higher wind loads, prevent corro-sion and protect against wave and wind interac-tions. Offshore wind turbines are bottom found-ed (driven monopiles or conventional concrete gravity bases as foundations) or of the fl oating type. For large water depths and soft seabeds, fl oating wind turbines may be attractive due to a cheaper anchor installation than the cost of a fi xed foundation. These fl oating foundations are mainly in research phase. Some of the proposed solutions are: spar-buoy, tension-leg platform, semi-submersible (column stabilized) and pon-toon (barge) type [21]. The fi rst grid-connected deep water fl oating wind turbine in the world is an Siemens Wind Power 2.3 called Hywind [14].

GLOBAL WIND ENERGY MARKET

In the last two decades the growth of the in-stalled wind power capacities in the world was rapid. At the beginning of the 1990s there were 1742 MW of installed wind turbines glob-ally. In the early period of commercial utiliza-tion of wind power, wind turbines were mainly installed in Denmark and USA as the result of research efforts in these countries. USA expe-

rienced a wind power expansion from 1982 to 1986 when thousands of Danish and American wind turbines were installed in massive arrays. As the wind power technology matured and awareness of renewable energy sources (RES) utilization grew, Europe overtook the leading role as the wind power market with the highest growth from the mid-nineties, fi gure 4. Denmark, Germany and Spain may be attributed as main drivers of high annual growth of wind power ca-pacities during the period from 1990 until 2007.

Denmark was one of the key countries for wind power technology development. The knowledge acquired during the eighties based on commer-cially developed wind turbines up to 100 kW of rated power presented excellent basis for further research and development of megawatt wind turbines, which was implemented by strong col-laboration between research institutions and interested companies with lasting support from the society. The main driver of the swift tech-nology development was learning-by-doing, i.e. construction of demonstration and commercial wind farms. As early as 1999, Denmark had 1749 MW of total wind energy capacities with more than 6000 wind turbines erected, which


have presented 50% of capacities in 2010. On-shore wind power capacities in Denmark from 1739 MW in 1999 grew to 2600 MW in 2003 and are in stagnation until present. In the same time, number of wind turbines has been reduced to 5000 in 2009. Future development of wind energy market in Denmark is oriented towards off-shore wind power utilization. Installed wind energy capacities in Denmark (3479 MW) can attribute roughly 20 % of national electric energy

Figure 5. Countries with the largest cumulative wind power capacities (MW) [24]

Figure 6. Countries with the highest growth of installed wind power capacities (%) [24]

consumption. Market maturity and high share of wind energy in overall energy capacities present good basis for transfer of the best practices from Denmark in terms of operation and maintenance of wind turbines, as well as wind power integra-tion in national power system. Despite relatively small overall installed capacities comparing to other wind energy markets, Denmark remained one of the key countries in terms of exporting of wind power technologies and had great sig-




nifi cance and impact on development of other national markets. Germany and Spain also had high wind power growth during the period be-tween 1997 and 2008. In the early nineties sev-eral wind power companies emerged in Germany that had driven research and development efforts in order to commercialize wind power which later had impact on the global market. Wind energy in Germany in 1997 accounted for roughly 3000 MW, and at the end of 2008 there were 23903 MW of installed wind power with 21164 wind tur-

bines. In the same period in Spain was installed 15906 MW for total capacity of 16740 MW. Early development of the wind power market in Spain during mid-nineties is due to wind turbine im-port and technology transfer from Denmark. In the following years domestic companies over-took larger part of the market until the present. At the end of 2010 Spain had a total capacity of 20676 MW and Germany 27215 MW which accounted for 55 % of European installed wind power capacities. It should be mentioned that

Table 1. Market share of top ten wind turbine manufacturers for period 2005-2010 [5]

Wind turbine manufacturer

2005(11471MW)

2006(12042MW)

2007(23590MW)

2008(26180MW)

2009(38863MW)

2010(36864MW)

Vestas 27.9 27.4 23 17.8 12.5 14.8Sinovel N/A N/A 3.4 4.5 9.2 11.1GE Wind 17.7 15.3 16 16.7 12.4 9.6Goldwind 1.2 2.9 4.2 3.6 7.2 9.5Enercon 14.2 14.5 14 9.0 8.5 7.2Suzlon 6.1 7.5 10.5 8.1 6.4 6.9Dongfang N/A N/A N/A 3.4 6.5 6.7Gamesa 12.9 15.5 15.4 10.8 6.7 6.6Siemens 5.5 7.1 7.1 6.2 5.9 5.9Nordex 2.6 3.3 3.4 3.4 N/A N/AOther 11.9 6.5 3 16.5 24.7 21.7

annual electricity generation in Germany in 2009 and 2010 was 38000 GWh and 36500 GWh re-spectfully, while in Spain 42976 GWh has been produced by wind power capacities in 2010.

After US government adopted tax incentives for wind energy in 2004, substantial capacities were to be built in USA in the following years. From initial 9147 MW of installed wind power in 2005, the capacities were enlarged to 34863 MW at the end of 2009 making USA country with the largest total wind power capacity in the world. In 2010 annual growth rate in USA was 15.25 % which is the lowest growth rate since 2004, resulted in total wind power capacities of 40180 MW at the end of 2010. Intensive wind power market growth was seen in China between 2005 and 2010, with annual growth around 100%. Total installed wind power was increased from 1260 MW in 2005 to 41800 MW at the end of 2010, which made China the world larg-est wind energy market in 2010, fi gure 5. [24].

The markets in surrounding countries showed the signs of huge investments made in wind power for the last two years. Romania had to-tal installed capacity of 591 MW in 2010, with added 577 MW in the previous year, fi gure 6.

During the 2010 in Bulgaria was installed 198 MW of wind power for total capacity of 347.5 MW. Hungary has added 94 MW during 2010, with total capacity of 295 MW at the end of 2010. It has been erected 43 MW of new capacities in Croatia, for the total capacity of 69.8 MW [24].

World market annual share of the leading wind turbine manufacturers has been shown for pe-riod between 2005 and 2010 in table 1. It can be noticed that eight largest wind turbine manufac-turers were involved in production of at least 80% of the world’s wind power capacities until 2009.

The individual manufacturers have chosen dif-ferent ways to market success [02]. Vestas has been one of the world’s leading manu-


facturers of wind turbines. Vestas technology is generally particularly lightweight. Their in-novation in nacelle systems design has con-tributed to this characteristic. Currently, Ves-tas is working on the development of a 7MW wind turbine. Siemens (along with Vestas) is among a few companies increasingly success-ful in the offshore wind energy market. Its 3.6 MW SWT turbines of 107 m diameter are now fi guring prominently in offshore projects. The advanced technology used in Gamesa G128-4.5 MW wind turbine makes for a more reliable system. Technological developments applied to improve reliability include load-reducing mul-tivariable control, powertrain without the high-

speed rotating components and modular electric power system which isolates the mechanical train from loads caused by voltage drops. Game-sa ranks among the world leaders in the mar-ket, having installed 20,834 MW until 2010 [11].

The Enercon E 40/500kW horizontal-axis turbine was the fi rst system with a direct-drive generator to establish itself in the market with great suc-cess in a very short time. Today, Enercon has dominated supply of direct drive turbines [10]. Nordex is developing new control techniques and has a condition monitoring system, which moni-tors component wear, also incorporating ice sen-sors and an automatic fi re extinguishing system.

Figure 7. Breakdown of the capital costs

Manufacturers from EU have been dominating the world market for years, although with the expansion of markets in China during the last several years their shares were in decline as several local Chinese companies has developed own well established positions at national level, table 1. This was a consequence of the strong support for wind power from government with high incentives for wind power manufacturing related activities. Despite lower relative shares of well established wind turbine manufacturers such as Vestas, GE Wind, Enercon and Game-sa during 2009 and 2010, all of these compa-nies had rapid growth in the production due to the growth of the world’s wind power capacities (11471 MW were installed in 2005, while 36864

MW were installed during 2010). The forecasts are made that until 2020 the global capacity will be close to one terawatt, and present capacities of the leading manufacturers will be in expan-sion, as well as newly established manufacturing companies. One of the indicators of intensifi ed activities in the wind power manufacturing sec-tor is the growth of the market share that was held by smaller and emerging wind power com-panies. Almost one quarter of the world mar-ket was held by such manufacturers in 2009 which is more than double comparing to 2005.

WIND ENERGY COSTS




The cost of electricity produced by wind turbines consist of investment (capital) costs and cost due to operating and maintenance. The invest-ment costs include initial costs of the project such as feasibility study cost, the cost of project management including acquiring all necessary permits, wind turbines procurement, civil works, electrical infrastructure, grid connection, installa-tion and other costs (insurance cost, bank fees etc.). Breakdown of the capital costs according to [7] is shown in fi g. 7.Although there are varia-tions in the capital cost structure introduced in the existing literature, there are certain trends that are widely confi rmed. Capital costs account for more than 80% of all costs for a wind farm during lifetime. The larger part of the capital cost is due to wind turbine procurement. According to several sources [03], [18] at least 70% of capital cost is due to wind turbine procurement exclud-ing works (transportation is included in the price).

Other capital costs such as grid connection, civil works and installation costs are highly depen-dent on location of the wind farm. Factors such as the local legislative framework for obtaining operating permits, grid connection availability and type (distributive or transmission grid), soil structure, availability and the cost of local labor and machinery infl uence on other capital costs.

The capital costs vary from 1200 euros per kW of rated power to 1850 euros per kW for on-shore wind farms. The unit price for off-shore wind power plants can be substantially higher.

After the steady decay of wind turbine costs from 1980s until 2000s, from 2005 the growth of in-vestment costs has been observed. It should be pointed out that the capital costs in Europe (more specifi cally in European Union), USA and China and other markets in Asia are notably differ-ent, as well as wind turbine procurement costs.

Operation and maintenance (O&M) costs are variable costs that are usually ex-pressed in term of the fraction of the produced electricity price. They comprise of costs for regular maintenance, repair, spare parts, in-surance, taxes, management, administra-tion, land rental and grid integration costs.

According to [07] O&M costs could have share of 20-25% of total levelised costs per produced kWh over the lifetime of the turbine. Based on the ex-perience in the leading European markets, O&M costs are generally estimated to be between 1.2 and 1.5 c€/kWh of power produced over the total lifetime of wind farm (wind turbine). Usually, wind turbines have warranty period for two to three years. In this period the maintenance cost can be as low as 0.3-0.4 c€/kWh. For older turbines it is reported that this cost can be between 0.6 and 0.7 c€/kWh. It has been reported that average O&M costs could vary from 1.5 c€/kWh to 2.6 c€/kWh [16]. It must be pointed out that this men-tioned values are based on the data mainly con-sisted of wind turbines that are no more than ten years in operation. This variable cost is augment-ed during the operating lifetime. Some means of

Figure 8. Wind energy costs per kWh of produced electricity


reducing O&M costs through wind turbine condi-tion monitoring system were described in [20].

On contrary to conventional fossil fuel-fi red pow-er plants, where 40-60% of total costs are related to the fuel and O&M costs, wind energy is capital intensive with more than 70% of production costs, as mentioned, accounted to initial investment, i.e. capital costs. Therefore, the cost of capital (interest rate) is an important factor that infl u-ences the overall cost of wind-generated power. The total cost per kWh produced is usually cal-culated by discounting and levelising investment and O&M costs over the lifetime of the turbine. In order to obtain the price per kWh of produced electricity it is necessary to predict annual elec-tricity production. One of the methods is to esti-mate capacity factor of a wind turbine according to available wind resource which is considered to be representative over the wind turbine life-time. Capacity factor is defi ned as the ratio of the calculated annual energy production and energy that would be produced if the wind turbine would operate at rated power over the whole year. System operators are faced with the challenges in order to maintain system stability, as wind en-ergy share increase in overall energy portfolio of energy systems and emerging balancing costs. Although there are options for balancing of wind power plants output, which are highly variable but predictable to certain extent, practical so-lutions are the fi eld of wide research in which must be included wind project owners, sys-tem operators and other utility companies [22].European wind energy association (EWEA) published [7] that calculated costs per kWh of wind-generated electricity range from 8 to 11 c€/kWh at sites with low average wind speeds (with capacity factor lower than 18%) to ap-proximately 5-7 c€/kWh at windy coastal sites with capacity factor between 30 and 33%. The average cost of electricity produced from wind energy is 7 c€/kWh according to EWEA, which should be related to capacity factor around 25%.Wind energy costs per unit of electricity pro-duced gradually decreased from mid-eighties until 2000s, fi g. 8. The average total cost has decreased from 9.5 c€/kWh to around 5 c€/kWh. Cost decrease can be attributed to gradually in-crease in wind turbine capacity (from average 50 kW machines at the beginning of 1980s to average 1500 kW wind turbines in 2000s), ac-quired know-how and innovations in wind turbine

design, gained experience by the wind turbine manufacturers, owners and grid operators and economy of scale. The trend of cost decrease lasted until early 2000s. Gradual cost increase that was observed after the 2005 in the world (or 2002. in USA according to [04]) led to approxi-mately 20% costs rise. Some of the identifi ed reasons for higher costs are due to a continual high demand for new wind turbines, constraints in the supply chain in the delivery of turbine components, the price growth of raw materials and even higher profi t share of manufacturers. The gradual cost decrease trend is expected to continue in 2012, but with lower rate than the previous trend at the end of 20th century.

CONCLUSION

Wind power industry had high growth in the last decade. Steady growth during the next ten years is anticipated. Current installed capacities of nearly 200 GW should grow to almost one terawatt until 2020. Rapid technology development was initi-ated by researches led by several institutions in Europe and USA, such as Risoe – Danish Tech-nical University (Risoe DTU), Energy research Centre of Netherlands (ECN), Fraunhofer, Deut-ches Windenergie Institut (DEWI) and National Renewable Energy Laboratory (NREL) during the eighties and nineties of the twentieth cen-tury. With commercialization of the wind power technologies during early nineties, manufactur-ers signifi cantly contributed to industry develop-ment as the reduction of the price of produced energy was the main driver of research activi-ties. Modern on-shore wind turbines became large structures with good reliability tailored to specifi c wind sites and operating conditions. Current research trends are oriented towards manufacturing of even larger wind turbines with more than 7 MW of rated power. This trend cor-responds to exploitation of off-shore wind re-sources, for which there are still many barriers that remain to be overcome in the future. Nev-ertheless, there is a space for further improve-ment of current mainstream on-shore technolo-gies, such as rotor load alleviation using novel materials and load control methods, further im-provements of reliability and availability, mass reduction, integration in power systems etc. Dynamic global wind power market is mainly driven by utilization of the best available wind sites and government incentives both for man-



ufacturing and installation of wind turbines and wind farms. EU remained the biggest wind power market during early 2000s (particularly markets in Germany and Spain). With adop-tion of wind power incentives in China and steady development of national manufacturers and wind farms between 2005 and 2010, the new market expanded taking leading role in annual installed capacities in 2010. During the same period the wind power industry regained momentum in USA. With all mentioned above, installed capacities were more than doubled in four years: from 2007 until 2010 wind power ca-pacities grew from 94104 MW to 196630 MW.After the steady price reduction of electricity produced by wind power from 1980s until early 2000s, the price has began to increase due to high demand for wind turbines and price growth of base materials. It is expected that the wind turbine price will gradually be reduced to the level from 2002 until 2013. Wind power tech-nology improvements and better grid integra-tion should attribute to the costs reduction. High wind turbine demand predictions, rap-id technology and market growths are some of the indicators that should alert the public and private sector for broader involvement of available capacities in order to acquire nec-essary skills for wind power utilization and manufacturing, including participation in sup-ply chains of large wind turbine manufacturers.

ACKNOWLEDGEMENT

This paper is a contribution to the research TR 35035 “Research and Development of Advanced Design Approaches for High Performance Com-posite Rotor Blades”, that has been funded by Min-istry of Education and Science of Republic Serbia.

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Wang C.M., Utsunomiya T., Wee S.C., Choo Y.S. (2010) Research on fl oating wind tur-bines: a literature survey, The IES Journal Part A: Civil &Structural Engineering; 3(4), 267-277.

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Paper sent to revision: 19.10.2011.

Paper ready for publication: 23.11.2011.

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Paper number: 9(2011)4, 209, 449 - 456

* University of Novi Sad, Technical faculty “Mihajlo Pupin”, Djure Djakovića bb, 23000 Zrenjanjin, Serbia; [email protected]

SMES IN THE REPUBLIC OF SERBIA: THE DEVELOPING CAPACITIES

Dr Dragan Ćoćkalo *University of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, SerbiaDr Dejan ĐorđevićUniversity of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, SerbiaDr Zvonko SajfertUniversity of Novi Sad, Technical faculty “Mihajlo Pupin”, Zrenjanin, SerbiaDr Srđan BogetićBelgrade Business School, Belgrade, Serbia

Small and mid-sized enterprises (SMEs) represent one of the main generators of econom-ic development in every market economy. In the last thirty years the SME sector has been suc-cessful all over the world, especially in newly industrialized and transitional countries. The management process in SMEs is specifi c because their business activities are performed in conditions of insuffi cient resources. The development of SMEs is one of the crucial develop-mental priorities in the Republic of Serbia. This paper represents a review and recommenda-tions for further developmenti of the developing capacities of SMEs in the Republic of Serbia.

Key words: SMEs, economy, development, Serbia.

INTRODUCTION

One of the important trends in the last 15 years has been a decrease in the average size of en-terprises. Even at the beginning of the 1990s the strategic signifi cance of the SME sector for the development of the economy and the process of economic fl ux internationalization was noted. Ac-cording to Drucker [08], a step ahead from a big company to a mid-sized one which represents the centre of an economy is, in fact, a radical turn in the ruling trend of developed countries. This trend has been dominant in developed countries for more than a century. It is Drucker’s belief that in the future it will no longer be de-sirable to be “big”. Achieving successful results will be in direct relation to the size of a company – a mid-sized company will be an imperative. SMEs are of special importance for the success-ful development of transitional countries. In this regard “market orientation and entrepreneurial orientation are correlated, but distinct constructs. market orientation refl ects the degree to which fi rms’ strategic market planning is driven by cus-tomer and competitor intelligence. Entrepreneur-ial orientation refl ects the degree to which fi rms’

growth objectives are driven by the identifi cation and exploitation of untapped market opportuni-ties.” [01]. The development of the SME sector is of vital signifi cance for privatisation because it facilitates its acceleration – SMEs represent an autochthonous private sector and they enable the development of domestic private capital [06].Mahajan [16] says: “The state does not create business opportunities. Entrepreneurs are those who create them. Whatever the state does, it must stimulate entrepreneurship. On this exceptional-ly competitive market the entrepreneur who has better ideas and who knows how to realize them better than the others is important. Entrepreneur-ship is not the monopoly of the French, Germans, Americans, Chinese or Indians. The Region of the West Balkans is full of entrepreneurs. The prob-lem is in the small size of West Balkan countries. They are faced with a challenge – how to grow further? For further development they should have a global vision, they should turn around and search for opportunities on a global level”.The development of the SME sector is a vital pri-ority for our economy. The Serbian Government has adopted the strategy for developing compet-itiveness and innovations of SMEs for the period

DOI: 10.5937/JAES9 - 1131


Dr Dragan Ćoćkalo and etc. - SMEs in the Republic of Serbia: The developing capacities

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from 2008-2013. This strategy should contribute to increasing competitiveness and exports, the further strengthening of the innovative capacity of companies, a dynamic increase in employ-ment and more equal regional development [14].

SMEs: THE BASIC CHARACTERISTICS

For many years SMEs have represented the generators of economic development, both in developed and newly developed countries – especially in transitional ones. The development of enterprising initiative en-ables the formation of autochthonous pri-vate capital and the development of the SME sector creates the conditions for faster lo-cal development, the strengthening of private property and solutions to certain macroeco-nomic problems, such as unemployment [11].SMEs play a signifi cant role in all OECD coun-tries: they represent over 95% of the total number of all active companies and partici-pate with 60-70% in total employment [04]. Be-tween 30% and 60% of SMEs can be called innovative and 10% of them are high- techno-logical companies. It is obvious that SMEs rep-resent a segment which considerably deter-mines the development of national economies. The development of SMEs is certainly the fastest and cheapest way to achieve the overall devel-opment of national economies. There are sev-eral reasons for this: the risk of SMEs business is mostly on the side of entrepreneurs, SMEs are more fl exible in comparison with big companies, they are better adjusted to market requirements, they have low business expenses and lower pric-es for services/products, they offer greater reli-ability and effi ciency, they have greater possibili-ties for specialization, they introduce innovations faster, they introduce IT more easily and cheaply. The most signifi cant values of SMEs are market and technological fl exibility, an innovative ap-proach and their ability to take risks more easily.

THE ROLE AND POSITION OF SMEs IN THE REPUBLIC OF SERBIA

As in other countries which have begun the tran-sitional process, SMEs in the Republic of Ser-bia have shown a constant growth in the last ten years. According to data from 2000, there were 60,552 active companies in the Republic of Serbia and the majority of them were small

companies - 56,993, while mid-sized companies numbered 2,573, and big companies 986. At the same time, out of the total number of registered companies (50.041) 82.6% were private and they mostly belonged to the group of SMEs [03]. In 2000, the most favourable fi nancial results were on the side of small companies in which in-come exceeded expenses by 0.5%, while in mid-sized and big companies the total income covered 98.4% or 97.8% of expenses. Small companies made 33.9% of the profi t and they recorded 16.8% of the total defi cit, in other words, 8.8% of the whole defi cit from the previous and current years. These results were achieved by small companies with 9.3% participation in the total capital of all domestic companies from the Republic of Ser-bia and with 22% participation in the total num-ber of employed persons in Serbian companies. There were 367,367 employed people in 2001, which represents a slight fall in comparison with the previous year. Big companies employed 777,059 people, or 1.4% more than the previous year. It is also obvious that the number of em-ployed persons in small companies increased to a total of 314,894 (23%), (compared with 309,710 the year before). However, the num-ber of employees in mid-sized companies de-creased. Therefore, in mid-sized companies in 2000 there were 313.303 (22.4%) employees compared with 275,414 or 20.1% in 2001 [13].In the last few years the state administration has facilitated the establishment of certain institution-al mechanisms for the development of the SME sector and the promotion of entrepreneurship.

The Central Agency for the Development of SMEs and Entrepreneurship was established (by the Serbian Government), whose aim is the stimulation of entrepreneurship, the de-velopment of an enterprising climate and IT support in the SME sector. This agency works as a consistuent part of the Agency for Regional Development. An independent network of agencies for the development of the SME sector was also or-ganized. The main fi nancier of this activity was EAR together with the local administra-tion. The National Employment Offi ce and Agen-cy for the Development of SMEs worked to-gether on the implementation of the concept of entrepreneurship centres at local level.

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Dr Dragan Ćoćkalo and etc. - SMEs in the Republic of Sebia: The developing capacities

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SMEs participate in the total number of compa-nies in the Republic of Serbia with 99.8%, in em-ployment with 65.5%, with 67.6% in turnover and approximately 36% in the GNP (Table 1). As re-gards exports, the SME sector participates with

50.2%, in imports the percentage is 64% and in investments in the nonfi nancial sector 51.2%. Micro companies are dominant in the SME sec-tor, making up 95.6% of the total number and employing almost 50% of all employees [14].

Size Number of companies Number of employeesUp to 50 employees 88.264 300.000

Up to 250 employees 2.218 280.000Over 250 employees 503 420.000

Table 1. The number of companies according to size and employment [05]

In 2009 the number of SMEs and entrepreneur-ship companies increased by 9,337, which is 45% less than in the previous year. According to data from the Agency for Economic Records, in the fi rst nine months of 2010 the number of new-ly established companies and shops was only 3,196 bigger than those which closed business in the same period. This drastic fall in the num-ber of potential entrepreneurs who see a chance for new employment in starting a new business points to the considerably more diffi cult condi-tions for starting and maintaining a new business and the consequences of the global economic crisis are also a contributing factor. During 2009 the SME sector could use EUR 369 million. About EUR 318.1 million was from public sources. Out of EUR 252.8 million which was available only EUR 50.8 million was used from foreign sources. The main problems in the development of SMEs on the national market are the following [04]:

There is no systemic base which could create favourable conditions for the development of the SME sector. The institutions are not con-nected and the required level of coordination does not exist. Lack of fi nancial means (although they exist). Namely, fi nancial resources for the develop-ment of SMEs are distributed selectively and are not available to all companies and entre-preneurs. This is especially related to state bodies which fi nance the development of SMEs. Realization of fi nancial means – When com-mercial banks are in question, both domestic and foreign, the procedure of obtaining loans is very long (minimum three months). The is-sue is even more complex with those state institutions which give fi nancial support to

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SMEs – approximately 3-6 months is need-ed for funds to be approved. Most analysis dealing with the attitudes of entrepreneurs and SME owners show that it is very diffi cult to obtain loans despite several credit lines which state institutions and a considerable number of commercial banks offer. The current chamber system is bureaucrat-ic and is not coordinated with the needs of SMEs. Moreover, it is mostly oriented towards big state systems in the process of privatiza-tion. The chamber system mainly deals with issues of international regional cooperation. It is focused on big companies and fails to support the requirements of the SME sec-tor, especially the private sector. Regional chambers of commerce are somewhat more fl exible but this depends exclusively on the given local economic structure. The owners of SMEs and entrepreneurs are not well enough informed. Despite the existence of numerous economic journals and programmes there is no one who deals with the problems of SMEs especially in the sphere of permanent and current informa-tion. The majority of SME directors and owners lack the relevant knowledge and skills from the fi eld of management necessary for the successful management of their companies (such as making business plans or invest-ment studies). Although courses and semi-nars from this fi eld are organized in regional development centres and regional cham-bers, they are usually too expensive for the owners of small shops and companies.

There are a number of studies dealing with mo-tivation, and intentions – the elements which in-

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fl uence enterprising behaviour and starting-up businesses in different ways, in other words, en-terprising behaviour of the young and students and self-employment. This trend is expanding, depending on time (historical) and space (geo-graphical) dimensions [06], [05].

POSSIBILITIES FOR IMPROVING THE COMPETITIVENESS OF SMEs IN SERBIA

Competitive capacity of Serbian companiesAccording to the Strategy for the Development of Competitiveness and Innovations of SMEs from 2008-2013, the basic pillars of development policy related to SMEs are: encouraging the opening of new companies, improving the man-agement skills of employees, improving fi nanc-ing and taxation, promoting exports and innova-

Country PlaceSlovenia 45Montenegro 48Croatia 77Macedonia 79Serbia 96BandH 102

Table 2. Ranking West Balkan countries according to competitiveness in 2010 [11]

tions, and improving legislation and the business environment. On the other hand, the competitive position of Serbian companies is unfavourable because they have failed to focus on business ef-forts in their development. According to the glob-al index of competitiveness issued by the World Economic Forum in 2009 Serbia fi nished in 93rd place out of 133 countries. In one year alone Serbia fell eight places according to the same in-dex. Slovenia, Montenegro, Croatia, Macedonia, Hungary, Romania and Bulgaria are all ahead of Serbia as are countries such as Panama and Kazakhstan. In our region only Bosnia and Her-zegovina is behind Serbia, in 109th place. Table 2 presents the review of West Balkan countries according to the global index of competitiveness issued by the World Economic Forum in 2010.

Out of date technology, poor quality, unattract-ive packaging and high prices are the main rea-sons for Serbia’s poor competitive position. The manufacturing industry is the least competitive, followed by the metal industry and electronics in which there have been no investments in tech-nology for many years. Businessmen are of the opinion that tax and customs relief are necessary in order to increase competitiveness, accompa-nied by a reduction in state taxes, as well as lower prices of electrical energy, gas and fuel. Increas-ing the level of technological equipment is of ma-jor signifi cance because the average age of ma-chinery in Serbia is 30 years. Compared to other countries in the region it is lagging behind by 12 years. In terms of technology the Serbian econ-omy is 29.5 years behind the EU as determined by a representative sample of 154 small, mid-sized and big companies in six economic branch-es with similar production programmes [17].The research results dealing with the competi-tive index of Serbian companies show that as

regards the competitive capacity of our com-panies, 47.93% of those interviewed think that it partially satisfi es international requirements, 43.28% of them think that domestic companies do not satisfy these requirements while only 5.69% of interviewees consider these conditions competitive enough for the international market. The most important factors which Serbian com-panies lack concerning the development of com-petitiveness are presented in the fi gure 1. When asked about the level of innovations in domes-tic companies the majority of those interviewed, 60.17%, think that our companies partially sat-isfy this factor, 30.52% are of the opinion that our companies are not innovative, while only 6.55% consider domestic companies innovative. It is their view that the necessary elements for the development of the competitive capacity of our companies are presented in the fi gure 2.[07]




Figure 1. The most important factors which Serbian companies lack concerning the development of competitiveness /13/

Figure 2. The necessary elements for the development of the competitive capacity of Serbian companies [13]

Forms of improvements in performing business activities in the SME sectorThe principles which should be applied in per-forming business activities in the SME sector are as follows [11], [12]:

A small business does not mean small invest-ments. It only means smaller investments in relation to capacity and the number of em-ployees. A small business means a small number of employees who achieve a high degree of work productivity, the use of mod-

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ern technology achievements and the real-ization of development aims (a company’s profi t and growth).A small business requires the implementation of high technologies but, fi rst of all, it requires knowledge application and the permanent improvement of knowledge productivity.Money does not come easily and quickly. Running a small business requires hard work, competence and diligence from all employees so that productivity of knowledge and work can be achieved.

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The market is everything. Getting to know the market, buyers and customers, but com-petitors as well, establishes the conditions for successful business. The modern market does not tolerate bad-quality business. Products and services of poor quality cannot be sold on global mar-kets because high technologies are available to all nowadays. The global aim of SMEs is a permanent in-crease in business productivity. This increase in productivity infl uences the quality of prod-ucts which in turn serves to increase produc-tivity. Finally, this results in market expansion and higher employment. Marketing is not advertising. Marketing is not sales. Marketing is a management process which should create the conditions for per-manent business performance along with ful-fi lling a company’s development aims. Profi t is not the only aim in a modern econ-omy. Profi t is a result of well created and realized business. Customer interests and society’s welfare are always priorities. Profi t comes as a result of satisfi ed customers who ensure the development of the organization by their loyalty. Small programmes can be stimulated only if they are profi table. Small companies are founded in great num-bers but they are also often closed in great numbers because they are not competitive on the market. Not everybody can be suc-cessful. Only those fi rms which can accept the fact that knowledge represents the base of business and increased productivity of work the imperative of modern business will be successful. In addition, such companies should constantly strive to improve quality and satisfy market requirements.

SMEs are leaders in development in relation to innovations and mid-sized organizations are be-coming the best options for achieving business success. Reducing the average size of compa-nies creates the necessity for different forms of associations and cooperation between compa-nies which enter the international market – they should achieve a synergic effect. Finally, this assumes the need to form associations and al-liances not only for SMEs but for big companies as well. Small and mid-sized enterprises real-

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ize this through different forms of associations based on common interests, such as agree-ment on common investment, associations for the realization of innovations, joint appear-ance on the market, and overcross licensing. Clusters represent one of the signifi cant forms of associating SMEs. The notion of clusters was introduced by the American economist Mi-chael Porter. Clusters represent the geographi-cally limited concentration of similar or comple-mentary businesses with active channels for business transactions, communications and cooperation. Regional clusters represent the concentration of mutually dependent companies in one geographical region. They are limited to one geographical region and consist of a great number of companies and employees within a small number of related industrial sectors. The organization of SMEs is certainly a question of entrepreneurship initiative – entrepreneurs have to fi nd their own interest in associating but they should not be destimulated in the realization of their interests. Although it is up to administra-tive bodies to establish an institutional frame-work that will facilitate free entrepreneur asso-ciations, the problem of their organization should be the problem of the entrepreneurs themselves. Entrepreneurs should be organized on the ba-sis of private initiative in order to ensure a suc-cessful appearance on the market, especially on the international market. These issues are not adequately represented on the Serbian market. According to the Strategy for the Development of Competitiveness and Innovations of SMEs for the period from 2008-2013 clusters are consid-ered as instruments for increasing competitive-ness on international markets [14]. Nowadays, there are 22 clusters in the Republic of Serbia, and in 2008, 14 clusters were fi nancially support-ed by the state – the Ministry for the Economy and Regional Development provided a grant in the amount of RSD 52 million for the start-up and development of clusters (31 million were budget funds and 21 million a donation from Norway) [15]. Four out of 14 clusters were in the process of establishment – the medical tourism cluster, the tourist cluster in Srem, the association for the development of business and manifesta-tion tourism and computers cluster. Only two out of 22 clusters are national – the car industry cluster and the wood industry cluster, while the remaining 19 clusters are regional ones. Clus-ters are organized as associations of citizens.



Education for entrepreneurshipKnowledge is becoming a decisive factor for the development of entrepreneurship in transitional economies. One of the possible options for the improvement of entrepreneurship is the educa-tional process in the fi eld of entrepreneurship. This is related to the training of professionals and company executives, regardless of the ownership type, because of the identical principles of entre-preneurial business. The basic task of this type of education is achieving the knowledge necessary for the successful management of businesses and/or companies so as to increase productivity of work and knowledge. The fi nal aim is business literacy for appropriate business management. Education for entrepreneurship must create the conditions and climate that ensure that newly acquired knowledge can be applied to both work and knowledge (the emphasis is not only on what but also on how something should be done). This means that the total result of educa-tion for entrepreneurship should be a manager and an entrepreneur – the generally accepted defi nition “the one who is responsible for the ap-plication and practical use of knowledge” must be applied to him/her. Education for entrepre-neurship also includes the following issues: [10]:

Acquiring knowledge and the development of creative, problem solving abilities, the development of entrepreneurial style in the population of youth and adults within formal education.Building-up the business management knowl-edge and abilities of current entrepreneurs and executives (fi nancial and low business, informatics, management, marketing, busi-ness communication).Training the unemployed and redundant for the start-up of their own businesses.Special attention must be paid to the implementation of new management approaches, both in a conceptual and organizational sense. Enter-prises, including a great number of those or-ganizations which do not belong to enterpris-es (universities, institutes, etc.), should begin with experiments related to new corporative forms and they should carry out pilot stud-ies especially in cooperation with partners or associations – they should defi ne common tasks, structures and activities.

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CONCLUSIONSSME-s facilitate the development of an entrepre-neurial climate, especially in transitional coun-tries. The main role of entrepreneurship in mod-ern economies is refl ected in innovative actions which create the conditions for technological de-velopment, fl exible organizations and new em-ployment. The development of SMEs and private entrepreneurship in transitional countries serve to boost employment in the whole economy. Ac-cording to the Strategy for the Development of Competitiveness and Innovations of SMEs for the period from 2008-2013 [14], the economic progress and development of the Republic of Serbia require the development of a competitive economy based on knowledge, new technologies and innovations. Entrepreneurship is expected to make an important contribution to economic and social development. In addition, the readiness of SMEs to enter EU markets, adopt necessary standards and reduce differences concerning the level of development is of special signifi cance. The hope of the global economy is in enabling regions to bring wealth from the rest of the world. In order to accomplish this task regions have to be equipped with highly educated and disciplined people led by visionary leaders able to communicate with the rest of the world [09]. Some of these regions are Hainan island (South China, Guandong Province), Vancouver and British Columbia (Canada), Estonia, Cho Shi Minn (Vietnam), Coastal and Sahalin is-land (Russia), Sao Paolo (Brazil), and Kiu-shiu (Japan). Serbia has all the preconditions to be-come one such region in the near future under one condition – our businessmen must change their business philosophy as quickly as possible. Serbia has all the preconditions to become one of these regions in the near future, under one condition – our businessmen must change their business philosophy as quickly as pos-sible. Capital owners and executive manage-ment should establish new elements of com-petitiveness in our companies [02]. Old policies and management techniques must be aban-doned in favour of new ones, and we need to learn from the experiences of global leaders and companies from newly industrialized coun-tries which are successful on the global market. Small and mid-sized enterprises can only sur-vive on the global market if they are associ-ated in clusters. However, the state also has a crucial role to play in cluster formation. Cluster


Dr Dragan Ćoćkalo and etc. - SMES in the Republic of Serbia: The developing capacities

policy assumes an initiative on the part of the state in the process of their formation, as well as in improving business contacts and relations among associates which is based on commer-cial and innovation links, knowledge fl ow and the provision of specialized infrastructural sup-port. Clusters provide SMEs with the following advantages: greater access to new knowledge and skills, common services, partnership sup-port, branding products, the development of marketing strategies, joint work on innovations, more effi cient implementation of QMS, and the co-fi nancing of private and state organizations.Economic growth and development of the Re-public of Serbia requires the development of such an economy which is competitive and based on knowledge, new technologies and innovations. In order to achieve this objective it is expected from entrepreneurship to give a signifi cant contri-bution to social and economic development. Be-sides, it is of special importance the readiness of SME sector to enter and win EU market together with applying necessary standards and reducing differences concerning the level of development.

REFERENCES

Baker, W.A., & Sinkula, J.M. (2009). “The Complementary Effects of Market Orientation and Entrepreneurial Orientation on Profi tabil-ity in Small Businesses,” in Journal of Small Business Management 47(4), 443–464.Ćockalo, D., Đorđević, D., & Đurin, S. (2011). Business Strategy of Providing Customer Satisfaction: An Exploratory Study in QM Certifi ed Serbian Companies. Journal of Ap-plied Engineering Science, 9(2), 339-348.Đorđević, D. (2001). Mala i srednja preduzeća [in Serbian]. Belgrade: KAS.Đorđević, D. (2005). “The Situation of SMEs Regarding Financing in Serbia and Monte-negro,” in International Workshop “Financ-ing of SMEs”. Belgrade: Organization of the Black Sea Economic Cooperation, Konrad Adenaure Stiftung Belgrade and Chamber of Commerce of Serbia.Đorđević, D., Bogetić, S., Ćoćkalo, D., & Bešić, C. (2009) Analiza preduzetničkog ponašanja kod mladih u Republici Srbiji, Megatrend revija, 6(1), 221-234.Đorđević, D., D. Ćoćkalo, & Bogetić S. (2010). “Preduzetničko ponašanje kod mladih – re-zultati istrživanja u Srbiji (The Youth’s Enter-

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prising Behaviour –The Research Results From Serbia),“ in Ekonomske teme (Eco-nomic Themes) 3/2010, 467-479.Đorđević, D., D. Ćoćkalo, & Bogetić, S. (2011). “The Role of Knowledge in Improving the Quality of Business within Serbian Com-panies,” in VI International working confer-ence Total Quality Management – Advanced and intelligent approaches. Belgrade: UASQ, 265-270.Drucker, P. (1996). Menadžment za budućnost [in Serbian]. Belgrade: PS Grmeč-Privredni pregled.Ohmae, K. (2007). Nova Globalna Pozornica [in Croatian]. Zagreb: Mate.Sajfert, Z., C. Besic, & Petrovic, N. (2008). “The Role of Corporate Entrepreneurship in the Process of Improving the Quality of the Business of Domestic Companies,” [in Ser-bian] in International convention on quality “Quality for European and World Integra-tions”. Belgrade: UASQ, 259-260.Sajfert, Z., D. Đorđević, & Bešić, C. (2006). Menadžment Trendovi [in Serbian]. Zren-janin: Tehnički fakultet “Mihajlo Pupin”.Spasojević-Brkić, V., Klarin, M., & Curović, D. (2009). Dimenzije menadžmenta kvalite-tom isporučioca u industrijskim preduzećima Srbije. Istraživanja i projektovanja za privre-du, 7(23-24), pp. 67-71.*** (September 2002). “Twenty Percent of the Capital With a Fifty Percent Obtain,” [in Serbian] in SME’s News. Belgrade.*** (2008). “Strategy for the Development of SMEs Competitiveness and Innovation for 2008-2013,” [in Serbian] in Službeni glasnik RS, br.55/05, 71/05-ispravka, 101/07 i 65/08. Belgrade: Offi cial Gazette RS.*** (04.10.2008). “With Clusters in the Hunt For Markets,” [in Serbian] in Novac. Bel-grade: Ringier.*** (11.07.2009). “Developing Countries A New Marketing Eldorado,” in Novac. Bel-grade: Ringier.*** (16.07.2009). “Serbia Technologically Lags Three Decades Behind EU,” [in Ser-bian] in Blic. Belgrade: Ringier.*** (2010). “The Global Competitiveness Re-port 2010-2011,” World Economic Forum.

Paper sent to revision: 27.10.2011.Paper ready for publication: 21.11.2011.

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Paper number: 9(2011)4, 210, 456 - 464

DOI: 10.5937/JAES9 - 1202

Figure 1. Risk perception [2]

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade, Serbia, [email protected] 457

COMBINATION FREE REPLACEMENT AND PRO-RATA WARRANTY POLICY OPTIMIZATION

MODELMSc Dragan StamenkovićUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaDr Vladimir PopovićUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaDr Vesna Spasojević-BrkićUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaMSc Jovan RadivojevićUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, Serbia

Product development risk increases more and more every day. One of the factors that affect this risk is product warranty. Warranty is a powerful marketing instrument for the manufacturer and a good protection for both the manufacturer and the customer, but it always involves additional costs to the manufacturer. These costs depend on the product reliability and the warranty parameters. This pa-per deals with the optimization of these parameters for known product failure distribution to reduce the warranty costs to the manufacturer while retaining the promotional function of the warranty. Combination free replacement and pro-rata warranty policy is chosen as a model and the length of free replacement and pro-rata policy periods are varied, as well as the coeffi cients that defi ne the pro-rata cost function. Warranty costs are obtained by using analytical equations and by simulation. The obtained results are shown and discussed and some concluding remarks are given.

Key words: free replacement warranty, pro-rata warranty, combination, costs, optimization

INTRODUCTION

More and more increasing product development risk is affected by the competition, schedule pressure, short deadlines, failure costs, rapid development of new materials, methods and complex systems, need for product cost reduc-tion and safety issues [11]. Figure 1 shows the effects on an overall risk perception [09]. These effects are: customer requirements, safety, de-velopment risks, market pressure, legal and statutory regulations, management emphasis, warranty and service costs, competition, public liability and many more. Successful control of these risk factors is the main goal of reliability engineering development [10]. The focus of this paper is on the reduction of the effects warran-ty has on the product risk by choosing the best warranty policy.

Product unavailability depends on its reliability,

maintainability and logistic support [06,12]. Prod-uct may become unavailable due to a hardware or software failure, human error or preventive maintenance (which requires the product to be excluded from service). When product or service becomes unavailable, a number of consequen-tial costs can arise. These costs are called un-availability costs and may include [11]:

warranty costs;• liability costs;•


MSc Dragan Stamenković and etc. - Combination free replacement and pro-rata warranty policy optimization model

costs caused by the decrease of the production function output;costs of providing the alternative services.

Unavailability costs should be identifi ed by us-ing the risk analysis techniques to determine the costs caused by the negative publicity which could eventually lead to customer loss. Costs of recovery from the negative effects that such publicity has on the company image, reputation and respectability and costs of reducing these risks are also unavailability costs. In many cases these costs are hard to asses, but it is some-times possible to quantify them. For example, they can be assessed as a public campaign and marketing costs, or costs of compensation in or-der to keep the customers. These costs should be calculated whenever possible.One of the key factors in the customer’s deci-sion-making process is product warranty. When choosing between several products with similar characteristics, customer will usually buy the product that provides a better warranty. A war-ranty is a contract or an agreement between the manufacturer and the customer. Under this agreement the manufacturer is obligated to re-pair, replace or provide service when the prod-uct fails to perform its function before the end of the warranty period. From the customer’s point of view warranty has two functions – protective and informative. Warranty performs its protec-tive function by assuring the customer that faulty products will either be repaired or replaced at no cost or at a reduced cost. Informative function of warranty means that it indirectly gives the cus-tomer the information about the product quality. From the manufacturer’s point of view warranty also has two functions – protective and promo-tional. Protective function is refl ected in warranty terms that specify the use of the product and lim-ited coverage or no coverage at all in the case of misuse of the product. Promotional function from the manufacturer’s point of view is associated with the informative function from the customer’s point of view. As said before, when choosing be-tween similar products, customer tends to buy the product with better warranty. This led to the competition between the manufacturers in offer-ing the better warranty to attract more customers.Warranty costs are usually borne by the manu-facturer, depending on the reliability characteris-tics, maintainability and the performance of the product logistic support. The manufacturer could

•

•

take important measures to control these char-acteristics during the design, development and manufacturing process and lower the warranty costs.Warranties are defi ned by their terms and are usually time limited. Rarely they include con-sumer protection against unavailability costs due to the product unavailability. Warranties could be supplemented or replaced by a service agree-ment according to which the manufacturer per-forms complete preventive and corrective main-tenance during the specifi c period of time, which could be extended to a limited period, or even to the end of the product life-cycle. There are three commonly used types of warranty policies [03,04]:Free replacement warranty (FRW) – under this warranty, if a product fails before the end of the warranty period, the manufacturer is required to either repair the product or provide a new prod-uct at no cost to the customer. This type of policy is usually offered for repairable products. There are two types of free replacement warranty policy:

ordinary free replacement warranty – un-der this warranty, the repaired product is cov-ered by the same type of warranty policy as it was before the failure. Warranty length for the repaired product is equal to the remaining length of the original warranty. This type of warranty is usually used for products such as home appliances, computers and vehicles;unlimited free replacement warranty – un-der this warranty, the repaired product is cov-ered by a new unlimited free replacement warranty. The length of the new warranty is equal to the original warranty length. This type of warranty policy is used for small elec-tronic appliances with high early failure rates. The length of the unlimited free replacement warranty is usually short;

Pro-rata warranty (PRW) – under this warranty, if a product fails before the end of the warranty period, the manufacturer is required to replace the product at a cost, which is called pro-rata cost, that depends on the age of the product at the time of failure, and can be either a linear or non linear function of the remaining time in the warranty length. The replacement product is then covered by an identical new warranty. This type of warranty is usually offered with non-repairable products such as tyres, bulbs and batteries;

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Journal of Applied Engineering Science 9(2011)4,

(1)

Figure 2. FRW/PRW policies with different values of proportionality coeffi cients

(2)

(3)

(4)

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Combination free replacement and pro rata warranty (FRW/PRW) – this type of policy is of-ten used as a compromise, since the FRW policy is the most favourable to the customer and the PRW policy is the most favourable to the manu-facturer. This type of warranty is comprised of two periods – a period of free replacement followed by a period of pro rata policy. Such combination has a signifi cant promotional value to the manu-facturer and at the same time provides adequate cost control for both manufacturer and customer in most cases [02,07]. Like the pro-rata warranty policy, combination warranty policy is usually of-fered with non repairable products. A more comprehensive study on the types of warranty policies can be found in [03,04]. War-ranty cost calculation is covered in [01,08,13]. In this paper a fully renewing combination free re-placement and pro-rata policy will be considered with the objective to fi nd the optimal warranty pa-rameters. The optimal warranty parameters are those which lower the warranty costs, but still attract the customers. Parameters considered for optimization are: total warranty length, free replacement period length and two coeffi cients that defi ne the pro-rata cost function, which will be defi ned later in the text.

WARRANTY MODELFully renewing combination free replacement and pro-rata policy specifi es two warranty peri-ods, denoted w’ and w. The manufacturer agrees to replace the product with a new product at no cost to the customer if it fails before w’ (w’ < w) expires. If a failure occurs in the time interval from w’ to w the product is replaced by the man-ufacturer at a fraction of the replacement cost (pro-rata cost) to the customer. Warranty analysis in this paper is done for one type of passenger car batteries. This type of bat-teries has been on the market for 16 years and the manufacturer wanted to launch the new war-ranty policy along with the start of a new mar-keting campaign. According to the collected data from a 16 year long exploitation it is determined that life of this type of battery follows Weibull dis-tribution with a shape parameter = 1.63 and a scale parameter η = 4380 days. The price per battery unit excluding the warranty cost is = 82 €. It is assumed that every failure results in a warranty claim, all warranty claims are valid and all failures are statistically independent.

In this warranty model the pro-rata cost is a linear function of time. Replacement cost to the manu-facturer is calculated by the following equation [02,07]:

For w’ = 0 FRW/PRW policy becomes PRW pol-icy, and for w’ = w FRW/PRW policy becomes FRW policy. Figure 2 illustrates how different val-ues of proportionality coeffi cients k and affect the FRW/PRW policy.Probability density function for a Weibull distribu-tion is given by:

and the cumulative distribution function is:

The number of failures for one battery unit by time t has a geometric distribution, so the ex-pected number of failures for one battery unit by time t is:

The expected number of failures for the whole lot by time t can be calculated by multiplying the


(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

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expected number of failures for one battery by the product lot size:

The total number of failures for the whole lot in the interval from t to t+dt is:

and the expected total cost to the manufacturer for the failures from t to t+dt is:

where C(t) is the replacement cost to the manu-facturer at time t. Total expected cost to the man-ufacturer for the whole warranty period is then calculated by the following equation:

Warranty cost to the manufacturer per unit is ob-tained by dividing the total cost with the lot size L:

For the purpose of this paper, analytical equa-tions (8) and (9) are solved numerically using MATLAB. Warranty cost can also be obtained by performing the simulation in order to compare the simulated results with those obtained using the analytical equations. The life-cycle of every battery unit in a lot is simulated using MATLAB. Lot size for the simulation is set to 10 000 units. If one battery unit fails, simulation of life-cycle of the replacement battery starts from the begin-ning. This process is repeated until one of the re-placement batteries reaches full warranty period without a failure for every battery in the lot. Total expected cost to the manufacturer then can be calculated using the equation:

where N1 and N2 are the numbers of failures in the free replacement period and pro-rata war-ranty period, respectively. After dividing the both sides by the lot size L equation (10) becomes:

The warranty cost to the manufacturer per unit then can be calculated as:

Warranty costs are calculated and simulated for the warranty period length w ranging from 1 to 6 years and the free replacement period length w’ ranging from 0 to w for three different polices: the fi rst policy with proportionality coeffi cients k = 1 and = 1, the second with k = 0.5 and , = 1 and fi nally, the third with k = 1 and = 0.5.

DISCUSSION OF RESULTS

Tables 1 to 3 show unit prices after adding the warranty cost for different warranty and free replacement period length for all three policies considered. In these tables cs and ca denote the price values obtained by simulation and by using analytical equations, respectively. For equal val-ues of w an w’ FRW/PRW becomes FRW policy, so the analytical price values for these cases are identical for all three policies. Because of this, unit price curves start at the same points on all three diagrams. Displayed results also show that simulated price values follow analytical ones closely.Figures 3 to 5 show the analytical unit price val-ues after adding the warranty cost as a function of warranty period length w and free replacement period length w’ for all three policies. These dia-grams show the effects that change of the pro-portionality coeffi cients k and and free replace-

Journal of Applied Engineering Science 9(2011)4,

w

w’

0 1 2 3 4 5 6

Cs Ca Cs Ca Cs Ca Cs Ca Cs Ca Cs Ca Cs Ca

1 82.57 82.55 83.26 83.47

2 83.66 83.74 85.13 84.98 86.98 86.81

3 85.53 85.51 87.14 87.06 89.41 89.26 91.94 92.14

4 88.52 87.87 90.44 89.80 93.58 92.43 95.82 95.83 100.69 100.19

5 92.05 90.95 94.55 93.33 98.65 96.49 102.38 100.56 106.55 105.78 112.54 112.53

6 96.99 94.92 99.37 97.85 104.33 101.71 110.11 106.66 116.79 113.05 123.92 121.39 131.73 132.55

Table 1. Simulated and analytical unit price values after adding the warranty cost for k = 1 and = 1

w

w’

0 1 2 3 4 5 6


1 82.32 82.27 83.45 83.47

2 82.95 83.47 84.20 84.21 87.19 86.81

3 83.59 83.72 85.65 85.23 88.38 88.02 92.22 92.14

4 85.01 84.83 86.87 86.52 90.45 89.53 94.38 93.95 100.43 100.19

5 86.68 86.24 89.17 88.12 92.46 91.39 97.84 96.17 105.54 102.91 111.75 112.53

6 88.87 87.99 91.41 90.09 95.89 93.67 102.74 98.87 111.37 106.23 120.42 116.79 133.12 132.55

Table 2. Simulated and analytical unit price values after adding the warranty cost for k = 0.5 and = 1

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ment period length w’ has on the unit price–warranty length relation. By reducing the proportionality coeffi cient k price curve slope decreases, while reduction of proportionality coeffi cient has the opposite effect.


Table 3. Simulated and analytical unit price values after addingthe warranty cost for k = 1 and = 0.5

Figure 3. Analytical unit price values after adding the warranty cost for k = 1 and = 1

w

w’

0 1 2 3 4 5 6


1 83.07 83.00 83.46 83.47

2 85.04 85.25 85.48 85.88 86.97 86.89

3 89.03 88.70 88.94 89.53 91.02 90.68 92.45 92.14

4 94.37 93.63 95.37 94.71 95.67 96.15 98.09 97.96 99.25 100.19

5 100.78 100.60 103.25 102.03 103.65 103.89 107.13 106.21 109.03 109.05 112.64 112.53

6 111.73 110.62 114.30 112.59 116.58 115.10 117.83 118.21 124.51 122.03 127.88 126.73 131.56 132.55

462 , 210


Beside the costs to the manufacturer, the pro-motional effect needs to be considered for ev-ery warranty policy variant. For example, for the warranty policy defi ned by k = 0.5 and = 1 (Figure 4), analytical unit price value after add-ing the warranty cost for w = 5 and w’ = 0 (ca = 86.245) is less than the price value for w = 2 and

w’ = 2 (ca = 86.808). Although longer, and thus potentially having greater promotional value, the fi rst of two variants is characterised by less cost to the manufacturer. The analysis of promotional value of warranty policies is not the subject of this paper and should by acquired through mar-ket research.


Figure 4. Analytical unit price values after adding the warranty cost for k = 0.5 and = 1

Figure 5. Analytical unit price values after adding the warranty cost for k = 1 and = 0.5

463, 210


CONCLUSION

Product warranty is one of the key factors that af-fect the risk involved with product development. By choosing the best warranty policy manufac-turer can reduce this risk. The best policy is one having the best ratio of warranty cost to the man-ufacturer to promotional value to the buyer. In

the present paper the effects that change of pa-rameters k and that defi ne warranty has on its cost to the manufacturer was considered. It was done by both calculating and simulating the war-ranty costs for three different FRW/PRW policy variants and different length of warranty period and free replacement period. It is also impor-tant to notice that conducted simulation proved


Paper sent revision: 21.11.2011.Paper ready for publication: 13.12.2011.

, 210


useful in the determination of warranty costs.Shown results defi ne the relation between the proportionality coeffi cients k and and warranty cost to the manufacturer that is depicted through the change of unit price after adding the war-ranty cost. These results, after conducting the market research and obtaining the promotional value for all of three warranty variants, enable the manufacturer to conduct cost-benefi t analy-sis and choose the best warranty policy.

ACKNOWLEDGEMENTS

This paper is a part of two important projects of The Ministry of Science and Technological De-velopment of Serbia (project number TR 35045 – “Scientifi c-Technological Support to Enhancing the Safety of Special Road and Rail Vehicles” and TR 35040 – “Developed New Methods for Diagnosis and Examination Mechanical Struc-tures”). The authors wish to express their grati-tude to the investors in these projects, and to all persons who helped making this paper better.

NOTATIONS

- Weibull distribution shape parameterη - Weibull distribution scale parameterc’ - battery unit price before adding the warranty costr - expected warranty cost per battery unitc - unit price after adding the warranty cost,c = c’ + rk - proportionality coeffi cient of c - proportionality coeffi cient of time of failure in the warranty intervalN(t) - number of failures at time tL - battery lot size for warranty cost determina-tionw - warranty period lengthw’ - free replacement period lengthC(t) - replacement cost to the manufacturer at time tTC - total warranty cost of a lot of size L.Most of the notations are taken from [5].

REFERENCES

Balcer, Y., Sahin, I., (1986) Replacement Costs Under Warranty: Cost Moments and Time Variability, Operations Research, 34(4), 554–559.

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Blischke, W.R., Murthy, D.N.P., (1996) Prod-uct Warranty Handbook, New York: Marcel Dekker.Blischke, W.R., Rezaul, M.K., Murthy, D.N.P., (2011) Warranty Data Collection and Analy-sis, London: Springer Verlag.Guangbin, Y., (2007) Life Cycle Reliability Engineering, Hoboken: John Wiley & Sons.http://www.weibull.com/hotwire/issue100/relbasics100.htm, consulted 7 September 2011.Mitic, S., Rakicevic, B., Stamenkovic, D., Popovic, V., (2011) Advanced Theoreti-cal–Experimental Method for Optimization of Dynamic Behaviour of Firefi ghting Vehicle Modular Superstructure, Journal of Applied Engineering Science, 9(1), 267–275.Mitra, A., Patankar, J.G., (1997) Market Share and Warranty Costs for Renewable Warranty Programs, International Journal of Production Economics, 50(2–3), 155–168.Nguyen, D.G., Murthy, D.N.P., (1984) Cost Analysis of Warranty Policies, Naval Re-search Logistics Quarterly, 31(4), 525–541.O’Connor, P., (2002) Practical Reliability En-gineering (4th edn), Hoboken: John Wiley & Sons.Popovic, V., Vasic, B., (2008) Review of Hazard Analysis Methods and Their Basic Characteristics, FME Transactions, 36(4), 181–187.Popovic, V., Vasic, B., Petrovic, V., (2010) The Possibility for FMEA Method Improve-ment and Its Implementation into Bus Life Cycle, Strojniski vestnik – Journal of Me-chanical Engineering, 56(3), 179–185.Popovic, V., Vasic, B., Rakicevic, B., Voro-tovic, G., (in press) Optimization of Mainte-nance Concept Choice Using Risk Decision Factor – a Case Study, International Journal of Systems Science (Accepted for publica-tion April 2011, doi: 10.1080/00207721.2011.563868).Ritchken, P.H., (1985) Warranty Policies for Non-Repairable Items under Risk Aversion, IEEE Transactions on Reliability, 34(2), 147–150.

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DOI: 10.5937/JAES9 - 1267

Paper number: 9(2011)4, 211, 465 - 472

PROACTIVE TIRE MAINTENANCEDr Gradimir Danon * University of Belgrade, Faculty of Forestry, Belgrade, SerbiaMiloš PetrovićInstitute for research and design in commerce and industry, Belgrade, Serbia

* Faculty of Forestry, Kneza Višeslava 1, 11000 Belgrade, Serbia, [email protected]

Objective of the paper is to promote the proactive approach in tire maintenance for commer-cial vehicles and application of the Tire Pressure Monitoring System (TPMS). Researches have confi rmed that the installation of TPMS on commercial vehicles is technically and economically justifi ed, namely traffi c safety and comfort of passengers would thus be signifi cantly improved and operating costs would be decreased. Example of articulated city bus shows that the invest-ment in the Tire Pressure Monitoring System would be recovered in the second year of operation.

Key words: tire, pressure control, traffi c accident, costs

INTRODUCTION

From the end of the 1980’s a lot of attention has been paid in professional and scientifi c journals to the problems connected with tire use and main-tenance and potential dangers if the tires are not controlled and/or maintained regularly. It was determined that tires are very frequent cause of vehicle stopping. For example, in 2002 AAA (The American Automobile Association, Inc.) received 2.4 million calls from drivers who stayed on the roads because of defl ated tires [15]. It was more than 50% of the total number of calls, namely almost 0.5 of tire failures per million vehicle/ki-lometres in the USA in the same year (2002). Number of failures is probably higher as it can be assumed that a signifi cant number of drivers solved the “problem” and replaced the defl ated tire with a spare one. The stated researches did not confi rm usual statements that tire failures during driving were mostly the consequence of tire punctures. On the contrary, it was deter-mined that more frequently these are failures as a consequence of thermal-mechanic loads of in-suffi ciently infl ated or overloaded tires, i.e. accel-erated fatigue of material the tires were made of. Researches conducted in the USA showed that tires, beside the large number of failures, are not frequent cause of traffi c accidents (only 0.5% of 6.3 million accidents that occurred in the USA in 2003) [01], however they have a high partici-pation in “technical” accidents i.e. the accidents the cause of which was a vehicle system. For

example, tire failures compose 21% of all tech-nical accidents of trucks [15] or even 50% ac-cording to the data from Germany [07]. Figure 1 shows the structure of tire failures (causes of ac-cidents with casualties or fatalities) in Germany.

Figure 1: Causes of tire failures causing accidents with casualties or fatalities in Germany [11]

On the Figure it can be seen that negligence and poor maintenance of tires are the most frequent cause of accidents for which tires are marked as the main cause (43%). Insuffi cient maintenance, or negligence, primarily implies insuffi ciently frequent control of tire pressure. According to the researches of the National Highway Traffi c Safety Administration (NHTSA) on over 10,000 passenger and light trucks conducted in 2001 [15], 36% of the tested passenger vehicles and 40% of light trucks were found to have one or more tires under-infl ated (by more than 20%). The situation was not better among commer-


cial vehicles. According to the study [02], almost 44% of tires on trucks and buses had the pres-sure ranging about 0.4 bar of the recommended pressure, and about 7% of tires had the pres-sure lower by more than 1.5 bar than the rec-ommended pressure. Researchers in Serbia reached similar results as well [14, 05]. The situ-ation is especially worrying regarding the pres-sure maintenance of dual tires for which (Figure 2) air pressure control could not be performed due to the lack of valve stem extender [05].

Figure 2: Results of air pressure control on city busses /16/

Common conclusion that can be made based on these researches is that the present main-tenance of tires on passenger and commercial vehicles is not on adequate level, users do not pay suffi cient attention to tires and they do not realize the importance of tires for safe driving. Also, it can be concluded that a large num-ber of failures with happy ending was found which could act as a reminder that luck can be changeable and that lack of tire mainte-nance can signifi cantly jeopardize traffi c safety.One of the available opportunities for solving the problem of monitoring air pressure in tires is wider application of the Tire Pressure Monitoring System (TPMS) on cars and commercial vehi-cles. This idea is not new. More than fi fteen years ago (in 1996) an article on TPMS for passenger and freight vehicles was published in “Commer-cial Carrier” journal [06]. The article analyzed devices used for monitoring air pressure in tires available at that time, as well as devices that en-able pressure equalization in dual tires or pres-sure regulation, i.e. air infl ation in tires. Based on this article and the information obtained from the companies that developed or sold these devices, an impression could be reached that these were already developed systems already commercial-ly applied [09]. Unfortunately, the situation was not such. Lack of legislation (which appeared much later, fi rst in the USA) and their price at

that time limited the application of these devices to luxury passenger cars equipped with run-fl at tires. Only after Ford – Firestone scandal [10] did the extensive researches start in the USA re-garding the justifi cation of using these devices [13]. These researches resulted with the TREAD regulation [11] that forbids the sale of new pas-senger cars without a TPMS device in the USA after 2006. The European Community adopted a similar regulation in 2009 with obligatory ap-plication for new vehicles from November 2014. Based on positive experience with passenger cars, the introduction of obligatory installation of TPMS also on trucks and busses is expect-ed as the next step. To that effect, adequate researches have been conducted for several years already focused on the quantifi cation of the impact of maintaining proper air pres-sure in tires of commercial vehicles in busses on safety and operating costs. Conclusion of these studies [02, 04] is that the realized sav-ings in tire and fuel costs for commercial ve-hicles would pay off the investment in installing TPMS already in the second year of operation.

TIRE PRESSURE MONITORING SYSTEM (TPMS) DEVICES

Drivers traditionally avoid their obligations re-garding tire maintenance. Despite various edu-cational activities, no special advancement has been done and producers of tires and vehicles have searched for solutions which would “make the drivers’ life easier” eliminating at the same time the main cause of tire failures, namely (in-stantaneous or gradual) loss of air pressure in tire. The simplest way is the sealants injected in the tire through the valve stem. The advance-ment in this area was made by Goodyear which offered tires with built-in sealants between two tire layers several years ago [12]. The best solu-tion, however for passenger vehicles only, is the so called “run fl at” tires. Run-fl at tires are always accompanied with TPMS devices. These devic-es are, as previously mentioned, obligatory for all new vehicles sold in the USA from 2008 and from 2014 similar law will be in force in the Euro-pean Community countries. Today, there are two types of these devices on the market, namely the ones that indirectly measure air pressure in tires by calculating the change of wheel radius from extensive tire speed and the others that directly measure the pressure (usually the temperature as well) and send the data to the driver’s cab.

Dr Gradimir Danon and etc. - Proactive tire maintenance

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Indirect systems – use the speed sensors of anti-lock braking systems. These sensors mea-sure angular velocity of each wheel and based on this the computer calculates rolling radius which is in correlation with tire pressure among other things. Smaller rolling radius on a wheel means lower tire pressure. Too large differences in the calculated rolling radii activate alert sig-nals in the driver’s cab. Advantage of this system is that additional costs of installation are small if the vehicle is already equipped with ABS system.

Disadvantages of these devices are numerous: Proper functioning of the system requires re-set after each infl ation and set-up of the new condition. If the device is not set on the rec-ommended pressure, calculation of rolling diameter will not be correct and the system will not react timely; Current indirect systems have different re-actions for different speeds usually reacting only when the pressure drops to 30% lower value than the recommended pressure;Tires of different producers can have different elasticity characteristics and different rolling diameters (for the same load and air pres-sure), which can also impact the moment of system reaction; Insuffi cient pressure on all four wheels at the same time (which is a frequent case) is dif-fi cult to detect because of the manner of de-vice operation.If the vehicle is not already equipped with ABS system, installation costs for indirect TPMS are signifi cantly higher.

Direct systems – TPMS measures actual (over)infl ation and temperature of air in tires. Sen-sors can be placed in the deepest groove on the wheel rim interior (in tubeless tires) or integrated with tire valve stem. Device in the cab receives signals from the transmitter and compares them with the previously given limit values for pres-sure and temperature. If the measured pressure or temperature exceeds the set limits, sound and/or light alert is activated in the driver’s cab.

Advantages of these systems are:Sensors are factory calibrated and do not have to be recalibrated;They operate with all usual tire types;They can also be used as measuring devices of air pressure in tires if the driver does not have it;

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It alerts the driver when the pressure drops below the set limit (which the driver can also change) and identifi es the wheel where it oc-curred.

Disadvantage of direct TPMS systems is costs of procurement and installation in new and exist-ing vehicles.Regulations in the USA and Europe so far give preference to direct systems, therefore only these systems will be discussed hereafter. The set consists of a certain number of sensors (de-pending on the number of wheels on a vehicle) and receiver installed in the driver’s cab. Exam-ple of the system for monitoring air pressure in truck tires is given on Figure 3.

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Figure 3: Example of tire pressure monitoring system for freight vehicles

Appropriate sensors (5) are installed on each wheel. Sensors measure air (over)infl ation and temperature in tires. Signal from the sensors is transmitted via antennas (6) to the receiver (3 and 4) and fi nally to the display in the driver’s cab (1). The measured (over)pressure is recal-culated in the receiver for standard conditions (20oC) and compared with the set limit values.Many devices with sensors can be found on the market which are mounted on wheel rim by means of steel belt (see Figure 4).

Sensors for passenger cars, light trucks and heavy trucks are developed. The second group consists of the sensors in-stalled on the interior of the valve stem of tube-less tires (see Figure 5). These sensors and valve stems are specially developed for the installation on the wheels of commercial vehicles. The sensor is installed on a standard valve stem and does not hinder


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infl ation and manual pressure control. There

Sensor for passenger vehicles Transmitter installed on wheel rim Sensor for passenger vehicles

are two types of valve stems: the one made for steel and the other made for aluminium wheels. The advantage of these systems is that they are tougher, they have low profi le, they are not easily damaged when mounting/dismounting tires and there is no need for a special anten-na because the valve stem itself acts as one.

The third group consists of TPMS installed as valve caps. They are a simple and cheap do-it-yourself solution, which can be used for passen-ger and freight vehicles (Figure 6).

Disadvantage of these sensors is that they have to be removed during infl ation and they could become the target of inquisitive persons. Technical solu-tions allowing manual control or infl ation of tires to their proper pressure without taking off the sensors can also be found on the market (Figure 7). These are the so called “Flow–Through” sensors which can be dismantled by means of special tools only.

The simplest solutions do not have this option. Sensors act as valve caps at the same time. Air pressure control in tires is done in various ways depending on the applied technical solution:

a) for passenger vehicles b) for freight vehicles

Figure 6: Valve caps – sensors for monitoring tire pressure

In the driver’s cab – most existing technical solutions also have adequate display in the driver’s cab where it is possible to read tem-peratures and pressures in each tire sepa-rately. Driver can react on time and infl ate

• the tire on the fi rst petrol station or in the garage. Also, the system should react with sound or light signal if the pressure in one of the tires is lower than the set threshold (usu-ally 80% of the recommended pressure);


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Figure 5: Sensor installed on valve stem

Figure 4: Devices installed on wheel rim


Figure 7: „Flow–Through“ sensors for external installation

Figure 8: Control point for remote control of air pressure in tires

In the garage – a stationary device is mount-ed which controls tire pressure on vehicles that enter or leaving the facility provided that they have adequate transmitters installed on wheels (see Figure 8). These way vehicles with defl ated tires can be prevented from leaving.

The system is primarily intended for garages with a lot of vehicles whose daily movement radius and daily kilometres are relatively low.

By means of a handheld device – mainte-nance worker has a personal digital assistant (PDA) and adequate software by means of which it can read air pressures in tires and re-cord air pressure in tires in contact-less man-ner. If RFID (Radio frequency identifi cation) is also installed in the tire, this device can also be used to read other data about tires.

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All text paragraphs should be single spaced, with fi rst line intended by 10 mm. Double spacing should only be used before and after headings and subheadings as shown in this example. Position and style of headings and subheadings should follow this example. No spaces should be placed between paragraphs.

JUSTIFICATION OF USING TPMS ON COMMERCIAL VEHICLES

In the last several years, a lot of researches have been done with the objective to reject or confi rm economic justifi cation for applying TPMS devic-es [02, 08, 12]. Frequency of tire failures on passenger and freight vehicles, causes and consequences of these failures were researched. Objective of these researches was to determine if the real-ized savings would be higher than the costs of procurement, installation and maintenance of this equipment. Results of these and many oth-er researches unambiguously indicate that im-proper air pressure in tires reduces the safety of passengers and vehicles and increases to-tal operating costs. To quantify the effects of improper tire infl ation, it was necessary to use “impact profi le curves,” which describe the cor-relation between the amounts a tire is under-in-fl ated or over-infl ated and the percentage impact on tire life, tread wear, and/or fuel economy [02].

Reduced tire life (total useable kilometres includ-ing all retreads - Inadequate tire infl ation, spe-cifi cally underinfl ation, causes a reduction in the useable life of a tire because the tire is running in an overloaded condition. Overloading causes the sidewall of the tire to extend and contract, causing heat generation inside the tire. Exces-sive heat leads to fatigue of the rubber and cords thus further exacerbating the sidewall fl exing. The weakened structure increases the likelihood of punctures and cuts, and the increased temper-ature leads to premature separation between the tire cords and the rubber. In effect, the increased heat and motion reduces the number of times that a tire could be safely retreaded (see Figure 10). A common rule is that a constant 20% under-in-fl ated condition will reduce the life of a tire by 30% and 40% under-infl ation will reduce tire life by 50%.


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Figure 10: Underinfl ation impact of tire life [8]

Increased tire wear (miles between retreading) - In addition to impacting the usable life of a tire, improper tire infl ation also affects tread wear. Both over and under-infl ation change a tire’s footprint thus affecting tire traction and leading to irregular wear (see Figure 11). Under-infl a-tion causes many types of irregular and accel-erated wear patterns including shoulder wear, block-pumping wear, spot wear, diagonal wear, rib wear, and block-edge wear. Over-infl ation also can cause shoulder and block-edge wear, and accelerates heel and toe wear.

• A common principle is that a constant 20% un-derinfl ation will increase tread wear by 25%.

Reduced fuel economy - Fuel economy is also impacted by inadequate tire infl ation. Increased fl exing and the irregular footprint caused by underinfl ation, yields increased rolling resistance which leads to increased fuel consumption as more power is required to move the vehicle. In fact, for every 1 bar underinfl ation there is a 0.75% reduction in fuel economy. Figure 12 shows the impact profi le of underinfl ation on fuel economy.

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Tire failures from sudden loss of tire tread and blow-outs, leading to an out-of-service condition (road calls) - Under-infl ation causes excessive deformation of the sidewalls and heat built up, which weakens adhesion be-tween the rubber and steel cords. Improper tire infl ation also increases the potential for

• tire failures from sudden loss of tire. Over-in-fl ated tires also can lead to major tire failures since they are more vulnerable to tread sur-face cutting, impact breaks, punctures, and shock damage.

Based on the data from the same source [02], impact of under-infl ated tires on operating costs

Figure 11: Infl ation pressure versus tread wear [8]


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Figure 12: Underinfl ation impact on fuel economy

Reduction of tire life Increase of protector wear Increased fuel consumption-7.67% +6.89% +0.19%

Table 1: Impact of improperly infl ated tires of an articulated bus on operating costs [02]

is calculated using a city bus in Belgrade as an example (see table 1). Due to the reduction of tire life, the average of 7.67% of the price of a new tire is lost. Tire wear is 6.89% higher, which impacts the reduction of life of a new or renewed protector. Regarding fuel

consumption, it is about 0.2% higher due to neg-ligence in tire maintenance. Table 2 gives the re-quired data for the calculation of possible savings. For this example, based on the assumed input data (given in table 3) and on the assumption that effects amounting to 80% of the expect-

ed effects are realized with the introduction of TPMS, savings for one articulated bus in the amount of 471 EUR annually would be obtained.Vehicle with installed TPMS does not require frequent controls of air pressure in tires; how-

ever, they are needed for occasional controls of proper functioning of the installed devices. Taking into consideration all these points and assuming that it will be possible to realize only 80% of the expected benefi ts, a bit reduced amount of savings is obtained (see table 4).

Number of wheels on articulated bus Number 10Average annual kilometres km 70,000Average tire life km 54,000Average consumption for articulated buses l/100km 70Coeffi cient of tire retreading – average number of retreading in tire life - 0.11Price of a new tire EUR 300Price of diesel EUR 1Average price of retreading EUR 150Price of intervention in the fi eld for 1 tire EUR 65

Number of interventions per vehicle annually Number of interventions 1

Table 2: Input data required for the calculation [03]


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New tires EUR 298Retreaded tires EUR 15Fuel EUR 93Interventions on the road 65Total 471

Reduced amount of savings for tires and fuel (80% of 471 EUR) 377

Retreaded tires EUR 80TPMS maintenance for one year EUR -50

Possible savings EUR 407

Receiver EUR 300Sensors (10*40) EUR 400Total* EUR 700

Item AmountCosts of installing TPMS on articulated city bus EUR 700

Possible annual savings EUR 407

CBR (Cost-Benefi t Ratio) 1.72

Table 3: Possible savings that would be realized by installing TPMS on articulated bus [14]

Calculated savings should be compared with the costs of the user. These are the costs of procur-ing receivers and sensors (table 5).

* Costs of installation are included in the price of a new bus. Now possible costs and possible benefi ts of installing TPMS on city buses can be determined (table 6).It arises from the analysis that the funds invest-ed in the installation of the system for controlling and monitoring air pressure and temperature in tires would be returned in less than two years or 21 month, i.e. by installing these systems the traffi c would become safer, more comfortable and cost-effective.

REFERENCESAnon. 2003. National Highway Traffi c Safety Administration. Traffi c Safety Facts 2003, DOT HS 809 775.

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Table 4: Possible savings that can be achieved by installing TPMS on articulated bus [02, 08]

Table 5: Costs of installing TPMS on articulated city bus

Table 6: Comparison of costs and benefi ts

Commercial Vehicle Tire Condition Sen-sors, Final Report, Booz Allen Hamilton Inc., Commercial Vehicle Safety Technology Di-agnostics and Performance Enhancement Program Contract Number: DTFH61-99-C-00025, 2003, p 97.Cross R. Tire Pressure Monitors, Commer-cial Carrier Journal, No 64, 1996, pp 7 – 16.Danon G, Mitrović Č. Opravdanost primene TMPS na gradskim autobusima GSP Beo-grad. Istraživanja i projektovanja za privredu, 6 (21), 2008, pp. 35-44.Danon G, Petković M. Propisi i nove ten-dencije u proizvodnji i korišćenju pneuma-tika, u knjizi „Ka održivom razvoju“, Papić, V, Manojlović A, Univerzitet u Beogradu, Saobraćajni Fakultet 2011, pp 97-107.Danon G. Važnost održavanja pritiska u pneumaticima komercijalnih vozila i mogućnosti njegove kontrole, XX Majski skup održavalaca, 1998. godina, pp 132 – 145.Federal Statistical Offi ce Germany, (Statis-tisches Bundesamt Deutschland), Accident reports by police at the accident location.Gavrić P, Danon G, Momčilović V, Bunčić S. “Eksploatacija i održavanje pneumatika ko-mercijalnih vozila”, Istraživanja i projektovan-ja za privredu, 2009, vol. 7, no. 25, pp. 1-10.Govindjee S. Firestone Tire Failure Analysis, Confi dential Bridgestone/Firestone Docu-ment, 2001, p 73.Grygier P, Garrott R, Mazzae E. An Evalua-tion of Existing Tire Pressure Monitoring Sys-tems, DOT HS 809 297, National Highway Traffi c Safety Administration, p 161.http://www.bartecautoid.com/tyre_pressure_monitoring_system.htmlhttp://www.goodyear.com/cfmx/web/truck/line.cfm?prodline=160926http://www.tireindustry.org/pdf/TREAD_ACT_Summary.pdf.Lipovac K, Vukašinović M. Analiza stanja pneumatika na putničkim vozilima u Beogra-du, Naučno- stručni skup “Pneumatici 2000”, Vrnjačka Banja 1. - 3. juna 2000, Zbornik ra-dova, OMO Beograd, pp 120 - 128.Winsor J. 2003. Breakdown: 10 Top Reasons. Heavy Duty Trucking• January 2003, 38.

Paper sent to revision: 14.11.2011.Paper ready for publication: 16.12.2011.

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Paper number: 9(2011)4, 212, 471 - 479

* Faculty of Mechanical Engineering, Kraljice Marije 16, 11000 Belgrade, Serbia; [email protected]

FROM IDEA TO IMPLEMENTATION IN PROTECTION OF ELECTRONIC EDITIONS (BOOK)

DOI: 10.5937/JAES9 - 1194

This paper presents a study of electronic editions protection on optical discs (CD/DVD) based on basic principles of logic and côde protection. The design of this solution is rather simple, but it is mainly similar to complex methods used nowadays in protection of great number of commercial electronic editions. The implementation and usage are adapted to users (students/professors) who are interested in electronic editions that are published on Criminal-Police Academy in Belgrade.

Dr Časlav Mitrović *University of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaDr Slobodan RadojevićUniversity of Belgrade, Faculty of Mechanical Engineering, Belgrade, SerbiaMilan SrećkovićAcademy of criminalistic and police studies, Belgrade, SerbiaMr Zoran MilanovićAcademy of criminalistic and police studies, Belgrade, Serbia

Key words: CD, DVD, data, protective, editing, electrons, implementation, logics.

INTRODUCTION

Ensuring protection of data, information and knowledge is one of the most important and most delicate issue encountered by all social and information systems. The need for data, information and knowledge is vast, as well as the possibility of their abuse. In order to pre-vent their abuse and to provide system pro-tection, different social, legal, technical, or-ganizational and other measures are taken.

Figure 1. – Preliminary design

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Nowadays the greatly accepted opinion is that the protection of information systems in infor-mation environment is something that shouldn’t be foreign but domestic product. Although there is a great number of software manufactures that offer commecial solutions (Multimedia Pro-tector [01], CD FrontEnd [02], DeployLX [03] , SerialShield [04] , CopyMinder [05] ), as well as a number of websites that offer free ideas, solutions and parts of the open côde (The Côde Project [06]), we chose an example of the study in which a preliminary design of the process of logic and côde protection is given.Namely, the process can be described in few steps. The fi rst step is provision of an electronic edition (hereinafter book) on a media, usually CD-ROM. Then there is an attempt of opening the book on user’s computer. What follows is the in-troducing screen on which the user has choice of starting the book or the installation of the required the appropriate software for starting the book. If the user chooses to open the book, the next step is the dialogue for activation where the unique number of this computer is displayed to user, contact phone or e-mail address of the publisher or responsible person for contacting in order to


Figure 2. – Appearance of the fi rst window when starting media with book

Figure 3. – Dialogue for entering the activation côde

Figure 4. – View of the book

Dr Časlav Mitrović and etc. - From idea to implementation in protection of electronic editions (book)

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get the activation côde as well as the fi eld where the user enters the given côde. If the côde is cor-rect, further access to the book is allowed to user.Technically, the solution is performed in the fol-lowing procedure (Figure 1). The project is set in VisualStudio 2008 [7] (the language used is Visu-alBasic.NET) which manages of the book review. The book itself is in PDF format and put in Re-source fi le of the project. By compiling, the book is integrated in EXE fi le together with the execut-able côde from where it is later called. During program execution the book is temporarily un-packed into temp directory from where it is taken over by the PDF fi le reading control which is inte-grated into the program. After closing the program the book is erased from the temporary location.

PROGRAM FUNCTIONS DESCRIPTION

When starting the program from the disc, the fi rst thing seen on the screen is a menu with three options (Figure 2). It offers the book

opening, installation of the accompany-ing package and the exit from the program.The accompanying package is actually .NET Framework 2.0 [08] a set of libraries for running the programs written on VisualStudio.NET plat-form. This component is necessary for starting the book and the information about it can be obtained by placing the pointer over the .NET 2 button. By clicking the exit button is the path to leaving the application.In order to start the book, it is neces-sary to choose the fi rst option - “Otvori knjigu”.Once the book is started, the next what ap-pears on the screen is the dialogue for entering the activation côde (Figure 3). The explanation is here provided to the user about which phone to contact so that the activation côde could be assigned to him based on his unique number, thus enabling the starting of the book. After entering the correct activation côde, clicking the button «Aktiviraj kopiju» will make the program

record that number in Registry base and open the window for reading the book itself (Figure 4).

BOOK PROTECTION

Electronic book is protected on several levels.As mentioned above, PDF fi le is integrat-ed into the executable EXE fi le. In this way, the book is not only protected from simple copying of the fi le, but its isolation in an in-dependent fi le is made more complex.Dotsfucator [09] supplement is used during the compiling whose task is to further encrypt the EXE fi le and thus protects it from reverse en-gineering. This is another step in protecting the PDF within the program, but, what is more important, it is a very strong protection from at-



Figure 5. – Project tree structure

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tempts of hacking into the program in order to avoid the activation procedure and try to fi nd out the algorithm for computing the activation côde.After a successful activation, the côde is record-ed in Registry database, in the section of the ac-tive user. It is thus enabled that only that user canopen the book. In multiuser systems, if the user is not in the administrator group, his right of access to write into the database is limited to only his section and that is where it is only possible to record the data. If it is necessary to write some-thing in the section that applies to all users, the user would then be required to call the system administrator in order to start the book [10]. Fur-thermore, from that moment on, all the users of that computer would have the access to the book, which may not be the intention of the person who purchased it. Once the côde is recorded, it is no more necessary to enter it through the mask, yet each time when starting the program it is being checked in order to avoid the attempt of using someone else’s côde by simple reconstructing the tree of Registry database from another computer.The côde itself is calculated according to the se-rial number of the processor on which the pro-gram is installed. Each produced processor has it own unique serial number that is added to it. That basically means that the book will be run on a certain computer until its processor is changed.A corresponding activation côde generator is on the publisher or distributor of the edition side which helps in making the côde necessary for the program activation on user’s computer.

PROGRAM OPERATION PRINCIPLE-SOURCE CÔDE

The project itself consists of two sub-projects:

Book.Worm – program that protects the book, activates it, checks the activation côde and its recording in Registry databasePDFView – a set of routines, functions and li-braries that perform the conversion from PDF fi le to TIFF image and display it in the graphics

PDFView is the part that is mostly taken from the Internet database of open côde and embed-ded in the unit which is used for conversion of pages from PDF fi les to images in TIFF format which a re drawn in a given frame (Figure 5). In this way the control is made which is later used in the main program to display the PDF fi le.

PDFView contains the following modules:

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GhostScriptLib – a set of functions that man-age the library gsdll32.dll which contains the functions necessary for the access to PDF database and interpretation of PDF descrip-tive languageImageUtil – a set of functions for the conver-sion of image; manages the libraries FreeIm-age.dll and FreeImageNET.dll

iTextSharpUtil – a set of functions used for accurate text rendering in the picture; it man-ages the library itextsharp.dllPrinterUtil – a set of functions for page print-ingPDFViewer – the central form that contains the control loos and which combines all the functions of this sub-project.[11]

When compiling, the sub-project PDFView is compiled in the independent library PDFView.dll which contains ready-made control that can be used in other projects and not only in this one.

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Book.Worm is the main project and it man-ages the protection logic. It contains two forms:

fProvera – the form that verifi es the activa-•


Imports System.ManagementPublic ISBN As String = “123456789”

Public Function fRacunajAktivacioni() As IntegerDim A, B, C, D As IntegerA = fSaberiClanove() * 1.2B = A * 34 + 56C = B / 0.78D = C - 9Return DEnd Function

Public Function fGetProcessorID() As StringDim objMOS As ManagementObjectSearcherDim objMOC As Management.ManagementObjectCollectionDim objMO As New Management.ManagementObjectDim ProcID As String = “”objMOS = New ManagementObjectSearcher(“Select * From Win32_Processor”)objMOC = objMOS.GetFor Each objMO In objMOCProcID = objMO(“ProcessorID”)NextobjMOS.Dispose ()objMOS = NothingobjMO.Dispose()objMO = NothingReturn ProcIDEnd Function


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tion côde if it exists, and if it does not or if it is incorrect, it requests its entering, andfWorm.Book – the form that contains the control which displays the book.

Beside these two forms, Worm.Book also con-

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tains the module mFunctions held by func-tions used in the program and Skladiste.resx resurs fi le where the book itself is located.Module mFunctions starts with the following two lines:

A set of functions is introduced in the program in the fi rst line which will enable to read the se-rial number of the processor. They are the integral part of .NET 2 environment. The sec-ond line initializes the variable ISBN string type in a value. This value is important be-cause it is the identifi er of the book. Each book has its unique ISBN number. It is useful for the data recording in Registry, because it is the way to know that the activation côde is en-tered for a certain book and it is impossible that two books have the same activation côde.

The module function follow.

The function fRacunajAktivacioni takes the value that fSaberiClanove function returned and trans-forms it through a series of arithmetic operations with the values for that book which are randomly selected in advance.


Public Function fSaberiClanove() As IntegerDim Brojac As IntegerDim Rez1 As IntegerDim Rez2 As Integer = 0Dim ProcID As String

ProcID = fGetProcessorID()For Brojac = 1 To Len(ProcID)Rez1 = AscW(Mid(ProcID, Brojac, 1))Rez2 = Rez2 + Rez1Next

Return Rez2 * 28End Function

Public Function fSnimiAktivacioni(ByVal Broj As String)SaveSetting(“Knjiga”, ISBN, “Aktivacioni”, Broj)Return 0End Function

Public Function fProcitajAktivacioni() As IntegerDim SSer As StringDim ISer As IntegerSSer = GetSetting(“Knjiga”, ISBN, “Aktivacioni”)ISer = Int(Val(SSer))Return ISerEnd Function

Me.Visible = FalseIf fRacunajAktivacioni() = fProcitajAktivacioni() ThenfWormBook.Show()ElseMe.Visible = TruelJedinstveniBroj.Text = fSaberiClanove()End If


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The function fGetProcessorID reads the serial number of the processor from the sister by means of Windows Management Instrumentation set of instructions that are embedded in Windows operat-ing systems and forwards that number.

The function fSaberiClanove converts each individual symbol from the processor serial number in the ASCII value, then adds them and in the end multiplies the sum with the value for that book which is randomly selected in advance.

The function fSnimiAktivacioni puts the correct activation côde in Registry.

The function fProcitajAktivacioni reads the activation côde from Registry database and forwards it.These are the main functions that are performed either by calling each other or by being called from other places during the execution of the program.The fi rst place encountered when the program starts is the event fProveraLoad(). It contains the following instructions.


If tAktivacioniKod.Text = fRacunajAktivacioni() ThenfSnimiAktivacioni(tAktivacioniKod.Text)fWormBook.Show()Else

MsgBox(“Uneti broj nije ispravan!” + Chr(13) + “Pokušajte ponovo.”, MsgBoxStyle.Exclamation)

End If

Private Sub PrilagodiVelicinu()PdfViewer1.Location = New Point(0, 0)PdfViewer1.Width = Me.Width - 15PdfViewer1.Height = Me.Height - 40End Sub

fProvera.Close()PutanjaFajla = IO.Path.GetTempPath & “B.pdf”IO.File.WriteAllBytes(PutanjaFajla, My.Resources.Skladiste.Lorem)PdfViewer1.FileName = PutanjaFajlaPrilagodiVelicinu()


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The form is hidden from the user in the fi rst line. Then the comparison of the calculated activa-tion côde and the one read from the database is performed. If the database does not contain any data, the function fProcitajAktivacioni will return the value 0. If it is determined by compar-ing that those two numbers are the same, the program will open the next form for viewing the book. Otherwise, a dialogue with the information necessary for activation will be displayed.After contacting the technical support and obtaining the activation côde, the user is ex-pected to press the button “Aktiviraj kopiju”. It is covered by the event bAktiviraj_Click().

This event starts with confi rming the activation côde that the user entered. If the côde is correct, the program will call the function that records it in Registry, and then the book will open. Otherwise, the user will receive the message about error.

The form that opens the book contains three events: fWormBook_Load(), fWormBook_Resize() and fWormBook_FormClosing; and one function – PrilagodiVelicinu.

The function PrilagodiVelicinu serves for adopting the size of the container PDFView control to the size of the form so as to touch its edges from the inside.

This is the body of the event fWorkBook_Load(). In the fi rst line the program closes the previ-ous form. Then the value of the variable Pu-tanjaFajla is formed which contains the path to the fi le where the book will be temporarily un-packed. This location in within the implied Win-dows Temp directory, and the name of the fi le is b.pdf. In Windows operating systems that are based on NT technology, the implied temporary directory is formed for each user separately and is usually located on the path: c:\documents and settings\user\local settings\temp. What follows is the drawing the book in user’s control and adopting its size to the dimensions of the form.

CONCLUSION

When estimating the degree of protection ac-complished, one should bear in mind that the absolute protection cannot be achieved, but it is necessary to strive for maximum safety at any time. In that sense any real protection system requires continuous upgrading and improve-ment, regardless of the quality achieved so far. Corrective actions should be focused to modi-fi cations of the solutions with noticed weak-nesses to the acceptable satisfactory solutions, or their elimination from the system in case of impossible modifi cation; as well as fi nding, de-


Paper sent to revision: 15.11.2011.

Paper ready for publication: 01.12.2011.


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veloping and applying of individual original solu-tions for protecting, as it is shown in this work.The practical contribution of the paper is refl ected in the design and implementation of new techni-cal solutions to protect electronic books, which is now increasingly used in scientifi c research and educational institutions. This solution is not pre-vented from copying a physical media on which the issue is, but it is practically diffi cult to use it without the appropriate activation procedures.

This type of protection is more interesting and „rigid“ than the physical protection of media. Naimely, nowadays it is easy to fi nd tools that very profi ciently emulate different mechanisms for media protection, and the procedure with the activation of software is still diffi cult to avoid, partly because it is unique for each edition and partly because of its complex procedure.The solution shown in this paper is only the ex-ample of protection technology used. For pro-ducing it, it is necessary to introduce some more improvements. Another possible way of improv-ing it to introduce the serial numbers. In this way the monitoring of each individual edition would be enabled as well as the number of activation performed. The second way is to introduce more complex algorithm for côde calculation. The third way is to provide the activation over the Inter-net, but the implementation of serial numbers is necessary for this step. In more advanced stage of development, a cross-platform solution could be an option, that is a software that could run on multiple systems (Windows, Linux, OSX,…).

REFERENCES

Mirage systems: All-In-One Protector (http://www.mirage-systems.info/download/mp/ marketing/ fl yer-multimedia-protector-en.pdf)http://www.cdfrontend.com/cd_dvd_presen-tation_brochure_00002e.htmhttp://xheo.com/products/copy-protection?gclid=CJvszfqdq6YCFY0r3wodg2w8pAhttp://www.ionworx.com/serialshield.html?gclid=CNnw06KNoaYCFYUw3wod9G-goQhttp://www.microcosm.co.uk/copyminder.php?gclid=CLj8j8KSoaYCFUco3wodBVQ9oAhttp://www.côdeproject.com/KB/applica-tions/opensrcprot_part2.aspx

Visual Studio 2008, http://msdn.microsoft.com/en-us/vstudio/default.aspx .NET Framework 2.0, http://msdn.microsoft.com/en-us/netframework/aa731542.aspx

Dot Fuscator, http://www.preemptive.com/products/dotfuscator/overviewMitrović, Č., Vorotović, G. Modeliranje in-formacionog sistema za praćenje sastava i načina eksploatacije pneumatika u vazduho-plovstvu. Journal of Applied Engineering Sci-ence, 1 (2003) 2, 35-52.), PDF Viewer Control Without Acrobat Reader Installed, (http://www.côdeproject.com/KB/ applications/PDFViewerControl.aspx?msg=3127440)

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E V E N T S R E V I E W

The Conference on Sustainable Development of Energy, Water and Environment Systems (SDEWES), was held for its 6th consecutive time, on September 25 - 29, 2011 in Du-brovnik in Croatia. VI SDEWES was successfully organized by the University of Zagreb with the help of research and academic institutions partners from Europe and America. Institute of Nuclear Sciences “Vinča” from Belgrade is one of them. The Conference was dedicated to the improvement and dissemination of knowledge on methods, policies and technologies for increasing the sustainability of development by de-coupling growth from natural resources and replacing them with knowledge based economy, taking into account its economic, environmental and social pillars, as well as meth-ods for assessing and measuring sustainability of develop-ment, regarding energy, transport, water, environment andfood production systems and their many combinations. Conference was attended by about 450 participants from all continents. Large number of papers was presented.Sustainability being also a perfect fi eld for interdisciplinary and multi-cultural evaluation of complex system, the Dubrovnik Conference has during the fi rst decade of the 21st century become a signifi cant venue for researchers in those areas to meet, and originate, discuss, share, and disseminate new ideas. In parallel with the main program a special section dedicated to various topical issues took place:

Future Sustainable Electricity Supply Grids mesh with Supplies for Heat, Cold and TransportEnergy and Buildings Effi ciency for Sustainable Future: from smart buildings to sustainable be-haviorsEnergy and Water Effi ciency for Sustainable FutureUtilization of industrial byproducts towards sustainabilityBiofuels sustainabilityUnderstanding environment- society interactions for sustainable developmentResearch and Governance for Sustainability and etc.

The conference was also attended by researchers from Serbia. They were from “Vinča”, the Univer-sity of Belgrade and the University of Niš.

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6TH DUBROVNIK CONFERENCE ON SUSTAINABLE DEVELOPMENT OF ENERGY WATER AND ENVIRONMENT SYSTEMS



482

Conference “TOWARDS SUSTAINABLE TRANSPORT 2011”

For the second time, Faculty of Transport and Traffi c Engineering from Belgrade and Transportlog, have organized a Conference “Toward Sustainable Transport 2011”. This conference was held on October 20th and 21st 2011 at Hotel Park in Ivanjica, supported by the Ministry of Education and Science, the Public Enterprise Electric Power Industry of Serbia and the Ministry of Environment, Mining and Spatial Planning.The conference program was conceived in four thematic sections with eighteen papers that were presented by the most relevant experts in their corresponding areas of expertise. These papers were related to:

vehicles and environment,vehicle fl eet insurance,vehicle inspection,vehicle fl eets organization, operation and maintenance.

The presentations were dealing with contemporary issues and everyday challenges of the road trans-port industry practices. Besides their initial meaning, they were very useful in improving the knowl-edge-base of road transport experts and engineers, as well as giving them necessary guidelines and best practices for further development in all of the presented areas. At the end of each daily presenta-tion sections, round tables were organized meant to open discussion regarding the presentations and problems in transport industry and profession in general. From fruitful discussions some guidelines were drawn for the selection of themes and issues that will be considered at the next conference “To-wards Sustainable Transport 2013”. Further dialogue and informal discussion of participants continued in a more pleasant atmosphere at the Conference dinner held at the end of the fi rst conference day.More than 150 participants attended the conference from the fi eld of transport, vehicle insur-ance, public authorities (Ministries, Cities, and Municipalities), secondary and higher educa-tion, vehicle dealers, spare parts and materials suppliers (including tires, fuels, lubricants, etc.), managers of vehicle inspection, maintenance and repair centres, recycling centres and others.The organization of the conference and presentations were held at a high professional level. From an extremely positive feedback from the majority of participants, the organizers remain convinced that the objectives of this conference were fully accomplished by assembling relevant road transport and associated experts.

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SCHOOL OF MAINTENANCEIH-HOUSE TRAINING FOR BELGRADE AIRPORT COMPANY

During fi rst half of December 2011, In-house training on most relevant aspects of mainte-nance of technical systems was realized for the Belgrade Airport Company.

In-house training was organized in line with specifi c request of the Client and from De-cember 1st till December 14th was held in the premises of the Belgrade Airport.

Training was organized for the senior man-agers of the Technical Maintenance Depart-ment, including Electrical, Termotechnical, ICT, Technical, Safety and Quality division. In its program, training included the best local knowledge and experience, modernized and harmo-nized with the recommendations EFNMS (European Federation of National Maintenance Societies). Through this in-house School of Maintenance participants had the opportunity to hear and learn about: Concepts, Organization and Technology of maintenance, Systems theory, Information theory, Outsourcing concepts in maintenance, Risk, Life Cycle Cost, Resources, Methods of failure analysis, Maintenance facilities design, Project management, Key Performance Indicators in maintenance, Structural analysis of the system, Re-engineering concepts, Benchmarking, Quality Management Systems, Inventory management, etc.

Training was conducted as combination of theoretical lectures and practical examples, performed by prof. dr Jovan Todorović, prof. dr Branko Vasić and Nada Stanojević. At the last day of the training the participants did the test. Achieved test results were at very high level, and therefore all partici-pants were promoted at National Experts in Maintenance Management.

Since training connected and unifi ed the local tradition and experience in the maintenance process with the European norms and requirements, its result is thus multiple. It is quite certain that this kind of training and certifi cation brings recognition to the people and profession, but apart of the fact that Belgrade Airport now has certifi ed Maintenance experts in national level with high competences, this training and certifi cates opens a way toward the International recognized European Maintenance Manager certifi cates and contributes to further regional development of Belgrade Airport .


A N N O U N C E M E N T O F E V E N T S

484

IIPP QUALITY MANAGEMENT SCHOOL

Considering business conditions of European market, quality has a signifi cant role, not only in pro-viding new markets, but also in maintaining the existing ones. Nowadays, customers do not only expect a quality product, but they require a proof that the company is capable to produce high quality products and provide quality services. Obtaining of this evidence should be the fi rst goal for each company that has high aspirations when it comes to new markets but also standard’s procedure in order to maintain its reputation. Implementation is not complete if employees are not familiar with standards.

With the aim to closer inform the employees of the meaning and signifi cance of ISO standards, Insti-tute for research and design in commerce & industry – IIPP organize training “School of Quality”.

During the training participants will:expend their knowledge about implementation of ISO standards,learn how to maintain and improve quality level of companies learne how to verify and improve business performance of companies

Training will be held during four days in two locations. First lectures will be held at the Faculty of Mechanical Engineering in Belgrade, while the fi nal lecture and the test will take place in attractive location in Serbia - Zlatibor.

ProgrammeFundamentals of quality concepts, defi nitions, approachesStandards, review and interpretationManagement ResponsibilitySystem and process approachData management, information systemStatistical methods (engineering methods, quality

management methods)RISK, FMEA, FTASupply and storage, evaluation of supplier MaintenanceEvaluation, audit, certifi cation Examples, practice, Deming management experimentPAS 99 - Integrated Management Systems

ResultAfter implemented training, Qiipp consultant is able to assume responsibility for independent work in the following fi elds of activity:

Implementation of quality standardsMaintaining a high level of qualityConstant improvement of the quality systemAssessment and audits of own companies and their suppliers

Candidates who passe the test will get a diploma “Qiipp consultant for implementation, maintenance, analysis, evaluation and testing, design and improvement of the quality system”.

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Institute for research and design in commerce & industryPhone: 011/6300750; Fax: 011/6300751; E-mail: offi [email protected]; web: www.iipp.rs

Time and location:17.03.2012. - Belgrade, Faculty of Mechanical Engineering19 - 21.03.2012. - Zlatibor, Hotel Dunav



Belgrade, Serbia on June 14-15, 2012 organized by

INDUSTRIAL ENGINEERING DEPARTMENT, FACULTY OF MECHANICAL ENGINEERING UNIVERSITY OF BELGRADE, SERBIA

andSTEINBEIS ADVANCED RISK TECHNOLOGIES, STUTTGART, GERMANY

Venue Faculty of Mechanical Engineering, University of Belgrade

Kraljice Marije 16, 11120 Belgrade,Serbia http://ie.mas.bg.ac.rs

http://www.sie2012.risk-technologies.com/e-mail: [email protected]

The aim of the 5th International Symposium of Industrial Engineering – SIE 2012 is to contribute to a better comprehension of the role and importance of Industrial Engineering and to mark the twenti-eth anniversary of the Industrial Engineering program in Serbia, established at FME, Belgrade. The Symposium is expected to foster networking, collaboration and joint effort among the conference participants to advance the theory and practice as well as to identify major trends in Industrial Engi-neering today.

CALL FOR PAPERSTopics covering industrial issues/applications and academic research include, but are not limited to:

Decision Analysis and Methods E-Business and E-Commerce Engineering Economy and Cost Analysis Engineering Education and Training Enterprise Information SystemsEntrepreneurshipEngineering EconomyEngineering Management SystemsFacilities Planning and Management Global Manufacturing and Management Human Factors Intelligent Manufacturing Systems Inventory ManagementLogistics and Supply Chain Managemen

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Manufacturing Systems Operations Research Production Planning and Control Project Management Quality Control and Management Reliability and Maintenance EngineeringService Innovation and Management Systems Modelling and Simulation Operations ManagementService Engineering Safety, Security and Risk Management in-cluding special topic “ Risks and Opportuni-ties of New Industrial Technologies “

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SUBMISSIONS AND DATESApril 15, 2012 - Deadline for paper and registration form submission online on addresss http://www.sie2012.risk-technologies.com or http://ie.mas.bg.ac.rsApril 25, 2012 - Notifi cation of acceptationApril 25-May 20, 2012 - Early Registration fee payment May 20, 2012 - June 14, 2012 – Registration fee payment June 14-15, 2012- Symposium

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IIPP MAINTENANCE MANAGEMENT SCHOOL Maintenance Management School presents practical experience in combination with adopted theo-retical knowledge, thus creating maintenance management experts capable to perform and coordi-nate the maintenance of complex technical systems. Use unique opportunity to expand knowledge in the fi eld of technical systems maintenance.

During fourdays training focus will give to the following topics:

Result: More than 240 national certifi cates and 16 internationally recognized certifi cates:European Maintenance Manager.

Time and location:17.03.2012. - Belgrade, Faculty of Mechanical Engineering19 - 21.03.2012. - Zlatibor, Hotel Dunav

Maintenance Objectives and PoliciesMaintenance ConceptsMaintenance TerminologyLaws and RegulationsCondition MonitoringFault Finding TechniquesSpare Part Management

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Corporate/Company EnvironmentWork PlanningTeam Working and CommunicationsInformation TechnologyQuality Assurance (Systems)Environment and Occupational Health and Safety

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The school program merges best local knowledge and experience modernized and harmonized with the recommendations of European Federation of National Maintenance Societies.Since Maintenance Management School connected and unifi ed local tradition and experience in the maintenance process with the European norms and requirements, it’s result is thus twofold - to all who signed up gives a chance to gain national certifi cate ’’Expert for maintenance management” and to those who can and want more, Maintenance management school opens the possibility of obtaining the International certifi cate “European maintenance manager”.



B O O K R E C O M M E N D A T I O N

QUALITY MANAGEMENT SYSTEM AND BUSINESS PERFORMANCES

By: Vesna Spasojević Brkić, Dragan Milanović, Snežana Knežević, Danijela Lazić and Tanja Milanović

In the Serbian business context, there is not enough knowl-edge about quality management organizational aspects, support systems and its impact on effectiveness and ef-fi ciency of enterprises. In order to overcome these uncer-tainties and aimed by the acquisition of new knowledge, in this monograph, after theoretical examination, three independent studies were experimentally conducted con-sidering the following aspects of quality management:

Quality management and its correlation with business performances in Serbian companies.The issue of structuring quality management system and resistances caused by this change.The information system as a support system of inte-grated management systems and their interactions with business performances.

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The fi rst study identifi ed critical factors of quality management that can lead to improvements in key per-formance areas. Measurement instrument is developed, followed by choice of QM critical factors and performance measures and association measurement within these factors on a representative sample of Serbian companies. Theme of the second study examined the mutual interaction of the process, cul-ture, structure and distribution of power changes in structuring QMS. The third research dealing with the determination of the interdependence of information systems, integrated systems and business per-formance management provides solution for building competitive advantage in today’s business world.

The monograph is written on around 250 pages and is divided into 8 chapters. The conceptual contribution of the monograph is that quality management is not as universally applicable, but is considered in the light of theories of organization. The methodological contribution of the mono-graph lies in the application of the method of “fi eld studies”, with the statistical modeling methods applied. The empirical contribution of the monograph is pointed by large number of companies in survey. The practical contribution of the monograph is refl ected in usefulness for: a) researchers in the fi eld and b) experts in business and c) consultants engaged in the implementation of quality management systems. The importance of the monograph “Quality management system and busi-ness performance” is refl ected in the attractive research topics on a global scale, in the multi-causal understanding of interaction between quality management and business performances, with special emphasis on organizational change and integrated management systems, and with modern math-ematical methods and models applied in describing the phenomena discussed on representative samples of local companies, so monograph is a signifi cant contribution to the spread of knowl-edge limits and possibilities of solving the problems of competitiveness of domestic enterprises.

Prof.dr Miroslav Radojičić

Publisher: Faculty of Mechanical Engineering, University of Belgrade, SerbiaForthcoming: 2012; Format B5; Pages 254; ISBN: 978-86-7083-741-6

Recommended by: Prof. dr Branko Vasić


I N S T R U C T I O N S F O R A U T H O R S

488

The benefi ts of publishing in Journal for Applied Engineering Science are:No page charges World wide exposure of your workAccelerate publication timesOnline author service Automatic transfer of metacontent in SCOPUS, SJR, SCIndeks and other bases supporting international protocols for data transferAssignment of numerical identifi ers DOIFair, constructive and able to follow reviewing processDedicated team to manage the publication process and to deal with your needs

Submission of the papers has to be done online, trough journal e-service at http://scindeks-eur.ceon.rs/index.php/jaes. For assistance during the process of submission and publication, please contact graphical editor Mr. Darko Stanojevic at [email protected] or +381 116300750Every manuscript submitted to JAES will be considered only if the results contained in the paper were not already published, that are not currently in the process of publishing and not to be published in another journal. Each paper is sent to a review by two independent experts and the authors are obligated to adopt the observations and comments of the reviewers. Articles presented at conferences may also be submitted, provided these articles do not appear in substantially the same form in published conference proceedings.All articles are treated as confi dential until they are published.Manuscripts must be in English free of typing errors. The maximum length of contributions is 10 pages.

THE FORMAT OF THE MANUSCRIPTThe manuscript should be written in the following format:

A Title, which adequately describes the content of the manuscript.An Abstract should not exceed 250 words. The Abstract should state the principal objectives and the scope of the investigation, as well as the methodology employed. It should summa-rize the results and state the principal conclusions.Not more than 10 signifi cant key words should follow the abstract to aid indexing.An Introduction, which should provide a review of recent literature and suffi cient background information to allow the results of the article to be understood and evaluated.A Theory or experimental methods used.An Experimental section, which should provide details of the experimental set-up and the methods used for obtaining the results.A Results section, which should clearly and concisely present the data using fi gures and tables where appropriate.A Discussion section, which should describe the relationships and generalizations shown by the results and discuss the signifi cance of the results making comparisons with previously published work. (It may be appropriate to combine the Results and Discussion sections into a single section to improve the clarity).Conclusions, which should present one or more conclusions that have been drawn from the results and subsequent discussion and do not duplicate the Abstract.References, which must be cited consecutively in the text using brackets [1] and collected together in a reference list at the end of the manuscript and in alphabetic order.

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I N S T R U C T I O N S F O R A U T H O R S

Units - standard SI symbols and abbreviations should be used.

Abbreviations should be spelt out in full on fi rst appearance, e.g., variable time geometry (VTG). Meaning of symbols and units belonging to symbols should be explained in each case or quoted in a special table at the end of the manuscript before References.

Figures must be cited in a consecutive numerical order in the text and referred to in both the text and the caption as Fig. 1, Fig. 2, etc. Figures should be prepared without borders and on white grounding and should be sent separately in their original formats.

Pictures may be saved in resolution good enough for printing in any common format, e.g. BMP, GIF or JPG.

Tables should carry separate titles and must be numbered in consecutive numerical order in the text and referred to in both the text and the caption as Table 1, Table 2, etc. The tables should each have a heading. Tables should not duplicate data found elsewhere in the manuscript.

Acknowledgement of collaboration or preparation assistance may be included before References. Please note the source of funding for the research.

REFERENCES must be written in alphabetical order and in the following form:Journal:/Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publica-tion). Article title: secondary title. Title of the Journal (italic), volume number (number of the journal), page number.// Petrović, G., Petrović, N., Marinković, Z. (2008). Primena teorije Markova u mrežnim sistemima masovnog opsluživanja. FACTA UNIVERSITATIS Series Mechanical Engineering, 6 (1), 45 – 56.

Book:/Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publica-tion) Book title: secondary title, Place of publishing: Publisher./2/ Vasić, B., Popović, V. (2007) Inženjerske metode menadžmenta, Beograd: Institut za istraživanja i projektovanja u privredi.

Book chapter:/Number/ (must match number in the text), Last name, Initial of the authors name, (Year of publica-tion) Chapter title: secondary title, Book title: secondary title, Place of publishing: Publisher, page numbers./3/ Vasić, B. (2004) Model Hardverskog resursa, Menadžment i inženjering u održavanju, Beograd: Institut za istraživanja i projektovanja u privredi, 95 – 97.

Internet source:/Number/ (must match number in the text), link to the page from which the text is taken, retrieved on (state the date)/4/ http://www.autogume.net/veleprodaje/kelena/, retrieved on November 7th, 2010


S A D R Ž A J

OD UREĐIVAČKOG ODBORA

491 - 492Doc. dr Vladimir PopovićUVODNIK

REZIMEI RADOVA

493Mr Dragan Komarov, Dr Slobodan Stupar, Zorana PosteljnikPREGLED STANJA VETROENERGETSKIH TEHNOLOGIJA I TRŽIŠTAVETROTURBINA U SVETU

493 Dr Dragan Ćoćkalo, Dr Dejan Đorđević, Dr Zvonko Sajfert, Dr Srđan BogetićSMEs U REPUBLICI SRBIJI: RAZVOJ KAPACITETA

494

Dragan Stamenković, Dr Vladimir Popović, Dr Vesna Spasojević Brkić, Jovan RadivojevićMODEL OPTIMIZACIJE KOMBINACIJE GARANCIJE BESPLATNE ZAMENE I PARCIJALNE GARANCIJE

494Dr Gradimir Danon, Miloš PetrovićPROAKTIVNO ODRŽAVANJE PNEUMATIKA

495Dr Časlav Mitrović, Dr Slobodan Radojević, Milan Srećković, Mr Zoran MilanovićOD IDEJE DO IMPLEMENTACIJE U ZAŠTITI ELEKTRONSKIH IZDANJA

490


O D U R E Đ I V A Č K O G O D B O R A


Vozila koja se prodaju i učestvuju u saobraćaju u bilo kojoj državi moraju da ispunjavaju propise i standarde te države. Postupak registracije vozila u većini država uglavnom zahteva homologac-iju vozila i/ili njegovih komponenti. Postojanje posebnih naciona-lnih propisa i homologacionih procedura u različitim zemljama zahteva skupe promene konstrukcije, dodatne testove i dupliranje homologacija. Stoga, postoji potreba da se harmonizuju različiti nacionalni tehnički zahtevi za vozila i da se razrade jedinstveni međunarodni propisi. Jednom kada su vozila ili njihova oprema i delovi proizvedeni i odobreni u skladu sa tim propisima, njima se može trgovati u međunarodnoj razmeni, bez ikakvog daljeg ispi-tivanja ili odobrenja. Osim toga, ovi propisi treba da budu stalno prilagođavani tehničkom progresu i novim zahtevima u pogledu

bezbednosti, zaštite životne sredine i energetske efi kasnosti.

Trenutno na tržištu vozila u Evropi funkcionišu dva ključna, paralelna sistema za homologaciju vozi-la, koji praktično defi nišu i uslove i kriterijume za promet vozilima, i to kroz:

UNECE Pravilnike, odnosno propise Ekonomske komisije za Evropu Ujedinjenih nacija (UN-ECE), koje donosi Svetski forum za harmonizaciju Pravilnika za vozila - WP.29, u okviru Sporazuma iz 1958., iEU Direktive, odnosno propise Evropske unije (EU).

Republika Srbija je potpisnik Sporazuma iz 1958. i veoma aktivno učestvuje u radu WP.29, dok primena propisa EU zavisi i od statusa naše države u procesu pristupanja EU, koji je za sada prilično neizvestan. Osnovni moto WP.29 je “Certifi kovano jednom, prihvaćeno bilo gde”. Ako pogledamo ključne izazove sa kojima će se suočiti sektor transporta UNECE-a u budućnosti, možemo videti koliki se značaj u istim pridaje regionu jugoistočne Evrope. Naš region se u dva od tih šest izazova eksplicitno pominje:

Nedovoljna i neadekvatna infrastruktura, posebno u istočnoj Evropi, regionu Kavkaza i cen-tralnoj Aziji;Stari, nebezbedni i ekološki neprihvatljivi vozni parkovi, posebno u istočnoj i jugoistočnoj Evropi, kao i u regionu Kavkaza i centralnoj Aziji, što rezultuje velikim brojem saobraćajnih incidenata i aerozagađenjem.

Najbolja preventiva, posebno u pogledu ovog drugog izazova, je harmonizacija propisa u oblasti vozila, u cilju podizanja nivoa njihovih bezbedonosnih i ekoloških performansi. Ona svakako vodi ka proširenju tržišta i oslobađanju od određenih barijera. Poslednjih godina je očigledno da se harmo-nizacija propisa odvija u pravcu zamene EU Direktiva sa UNECE Pravilnicima. Ovo se objašnjava sve većim značajem koji ima Sporazum iz 1958. Evidentno je da veliki broj proizvođača vozila iz EU, u okviru homologacije tipa vozila (WVTA), ima sve više pojedinačnih saopštenja prema UNECE Pravilnicima, a sve manje prema EU Direktivama. Razlog za to je i činjenica da u radu WP.29, pored svih država potpisnica Sporazuma, aktivno učestvuju i SAD, Kina, EU (koja je potpisnik Sporazuma) i Indija, o čijem značaju u autoindustriji ne treba posebno govoriti, kao i brojne zainteresovane nev-ladine međunarodne organizacije (International Organization for Standardization - ISO; International Organization of Motor Vehicle Manufacturers - OICA; International Motorcycle Manufacturers As-sociation - IMMA…).

Nadalje, jako je bitno naglasiti da je jedna od neformalnih radnih grupa pri WP.29 zadužena za raz-voj i implementaciju Međunarodnog sistema homologacije tipa vozila (IWVTA), koji bi trebao da se primenjuje od 2016. godine, i koji bi trebalo da u dogledno vreme zameni WVTA, na kome se danas bazira sistem homologacije vozila u EU. U tom pravcu će se sigurno ići i nadalje, jer se na taj način kompletira proces harmonizacije propisa na svetskom nivou, što je neminovna posledica i sveopšte globalizacije, koja je naročito izražena u automobilskoj industriji.

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O D U R E Đ I V A Č K O G O D B O R A

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Kada je reč o našem regionu, sve države su potpisnice Sporazuma iz 1958., osim Albanije. Možda i ključni pokazatelj za razvoj propisa u oblasti vozila u regionu jugoistočne Evrope je, više ili manje izražena, želja svih država i teritorija ovog regiona da budu članice EU. Međutim, svaka država za sebe, bez obzira da li je član EU ili ne, mora da potpiše Sporazum iz 1958., ako želi da primen-juje isti. Sa druge strane, mnoge države koje nisu potpisnice Sporazuma iz 1958., isti unilateralno priznaju, i primenjuju UNECE Pravilnike kao ekvivalente nacionalnim propisima, što je dovelo do toga da homologovana vozila predstavljaju harmonizovani nivo kvaliteta na međunarodnom tržištu vozila, opreme i delova.

Ipak, ceo ovaj proces pridruživanja EU sadrži u sebi dve suprotnosti, kada je reč o tržištu vozila. Sa jedne strane, EU će sigurno zahtevati usklađivanje svih propisa država koje žele da joj pristupe, sa svojim propisima, uključujući i propise u oblasti vozila. Sa druge strane, korišćena vozila iz zemalja EU moraju da nađu tržišta na kojima će se prodavati, a u praksi je nemoguća i ekonomski gledano neodrživa velika razlika u propisima za uvoz novih i korišćenih vozila u jednoj državi.

Iako su propisi o homologaciji vozila, formalno gledano, tehničke prirode, evidentno je da na promenu istih itekako utiču globalna i regionalna politička kretanja, jer je autoindustrija veoma bitan činilac svake ekonomije. Zbog toga je važno naglasiti i to da su opšte političke i ekonomske prilike na Balkanskom poluostrvu uvek bile turbulentne i sa velikim zaokretima, pa je na duži rok gledano, bez obzira na sadašnju situaciju, jako teško dati preciznija predviđanja u pogledu razvoja bilo kojih propisa, pa i onih vezanih za uvoz i homologaciju vozila. Ipak, ovom problemu se mora pristupiti i sa određenom dozom optimizma, i verovati u stabilizaciju tržišta i ekonomski prosperitet ovih prostora.



R E Z I M E I R A D O V A

DOI: 10.5937/JAES9 - 1120

Broj rada: 9(2011)4, 208

PREGLED STANJA VETROENERGETSKIH TEHNOLOGIJA I TRŽIŠTAVETROTURBINA U SVETU

Mr Dragan Komarov Univerzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaDr Slobodan StuparUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaMSc Zorana PosteljnikUniverzitet u Beogradu, Mašinski fakultet, Beograd, Srbija

U radu je dat pregled modernih vetroenergetskih tehnologija i trendova razvoja tržišta. Ukratko su opisani osnovni principi koverzije energije vetra u električnu energiju sa kratkim osvrtom na moderne konstrukcije podsklopova kao što su lopatice vetroturbina i agregati. Izvršen je pregled stanja vetroen-ergetike u svetu u cilju dobijanja predstave o budućem razvoju tržišta. Najrazvijenije države u pogledu iskorišćenja energije vetra, kao što su Danska, Nemačka, Španija i SAD identifi kovane su kao glavni pokretači daljeg napredovanja vetroenergetike. Nakon dugog vođstva Evropske Unije u pogledu izgrad-nje vetroenergetskih kapaciteta na godišnjem nivou, Kina i SAD su preuzele vodeće pozicije u posledn-jih nekoliko godina. Troškovi proizvodnje električne energije korišćenjem energije vetra su posle poste-penog opadanja do 2005. godine zabeležile blagi rast usled visoke tražnje i viših cena repromaterijala. Procenjeno je da će troškovi proizvodnje električne energije iz energije vetra u budućnosti imati trend opadanja. U narednim godinama predviđa se stabilan rast vetroenergetskih kapaciteta, uz očekivanja da će sadašnji instalisani kapaciteti u svetu od oko 200 GW porasti do skoro 1 TW do 2020. godine.

Ključne reči: kapacitet, energija, globalizacija, tržište, tehnologija, vetroturbine, vetroenergija, vetar

DOI: 10.5937/JAES9 - 1131

Broj rada: 9(2011)4, 209

Dr Dragan Ćoćkalo Univerzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, SrbijaDr Dejan ĐorđevićUniverzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, SrbijaDr Zvonko SajfertUniverzitet u Novom Sadu, Tehnički fakultet “Mihajlo Pupin”,Zrenjanin, SrbijaDr Srđan BogetićBeogradska poslovna škola, Beograd, Srbija

SMEs U REPUBLICI SRBIJI: RAZVOJ KAPACITETA

Mala i srednja preduzeća (SMEs) predstavljaju jedan od glavnih generatora ekonomskog razvoja u svakoj tržišnoj ekonomiji. U poslednjih trideset godina sektor (SMEs) je bio uspešan u celom svetu, posebno u novo industrijalizovanim zemljama u tranziciji. Proces upravljanja SMEs je specifi čan jer se poslovne aktivnosti obavljaju u uslovima nedovoljnih resursa. Razvoj srdnjih i malih preduzeća je jedan od ključnih razvojnih prioriteta u Republici Srbiji. Ovaj rad predstavlja pregled i preporuke za dalji razvoj kapaciteta malih i srednjih preduzećau Republici Srbiji.

Ključne reči: SMEs, ekonomija, razvoj, Srbija



Broj rada: 9(2011)4, 210

DOI: 10.5937/JAES9 - 1202

MODEL OPTIMIZACIJE KOMBINACIJE GARANCIJE BESPLATNE ZAMENE I PARCIJALNE GARANCIJE

MSc Dragan StamenkovicUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaDr Vladimir PopovicUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaDr Vesna Spasojevic-BrkicUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaMSc Jovan RadivojevicUniverzitet u Beogradu, Mašinski fakultet, Beograd, Srbija

Rizik koji prati razvoj proizvoda raste iz dana u dan. Jedan od faktora koji utiču na ovaj rizik je garan-cija proizvoda. Garancija je moćno marketinško oružje za proizvođača i istovremeno dobra zaštita za proizvođača i kupca, ali uvek podrazumeva dodatne troškove za proizvođača. Ovi troškovi za-vise od karakteristika pouzdanosti proizvoda i parametara garancije. Ovaj rad se bavi optimizacijom ovih parametara za poznatu raspodelu otkaza proizvoda u cilju smanjivanja troškova garancije i istovremenog zadržavanja njene promotivne funkcije. Kombinacija garancije besplatne zamene i parcijalne garancije je izabrana kao model, pri čemu su varirane dužine perioda besplatne zamene i perioda parcijalne garancije, kao i koefi cijenti koji defi nišu funkciju parcijalnih troškova. Vrednosti troškova garancije dobijene su pomoću analitičkih jednačina i simulacije. Dobijeni rezultati su prika-zani i razmotreni i izneta su zaključna opažanja.

Ključne reči:garancija besplatne zamene, parcijalna garancija, kombinacija, troškovi, optimizacija

Dr Gradimir DanonUniverzitet u Beogradu, Šumarski fakultet, Beograd, SrbijaMiloš PetrovićInstitut za istraživanja i projektovanja u privredi, Beograd, Srbija

DOI: 10.5937/JAES9 - 1267

Broj rada: 9(2011)4, 211

PROAKTIVNO ODRŽAVANJE PNEUMATIKA

Cilj rada je da promoviše proaktivan pristup u održavanju pneumatika za komercijalna vozila i primenu sistema za kontrolu pritiska guma (TPMS). Istraživanja su potvrdila da instalacija TPMS sistema na komercijalnim vozilima je tehnički i ekonomski opravdano, odnosno bezbednost saobraćaja i udob-nost putnika bi na taj način bila značajno poboljšana i cena operativnih troškova znatno samnjena. Primer artikulisanog gradskog autobusa pokazuje da ulaganje u sistem za kontrolu pritiska u pneu-maticima je pokriveno u drugoj godini eksploatacije.Ključne reči: pneumatic, kontrola pritiska, saobraćajna nezgoda, troškovi;



Broj rada: 9(2011)4, 212

DOI: 10.5937/JAES9 - 1194

Dr Časlav MitrovićUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaDr Slobodan RadojevićUniverzitet u Beogradu, Mašinski fakultet, Beograd, SrbijaMilan SrećkovićKriminalističko policijska akademija, Beograd, SrbijaMr Zoran MilanovićKriminalističko policijska akademija, Beograd, Srbija

OD IDEJE DO IMPLEMENTACIJE U ZAŠTITI ELEKTRONSKIH IZDANJA

Ovaj rad predstavlja studiju zaštite elektronskih izdanja na optičkim diskovima (CD/DVD), na osnovu osnovnih principa logike i kodne zaštite. Dizajn ovog rešenja je prilično jednostavan, ali je uglavnom sličan kompleksu metoda koje se danas koriste u zaštiti velikog broja komercijalnih elektronskih iz-danja. Implementacija i upotreba je prilagođena korsnicima (studentima/profesorima) koji se intere-suju za elektronska izdanja objavljenja na kriminalističko - policijskoj akademiji u Beogradu.

Ključne reči: CD, DVD, podaci, zaštita, prikazivanje, elektroni, implementacija, logika

Slika 1. – Idejni projekat Slika 2. – Dijalog za ulazak u aktivacioni kod


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Istraživanja i projektovanja za privredu = Journal of Applied Engineering Science: naučno-stručni časopis / glavni urednik Jovan Todorović; odgovorni urednik Predrag Uskoković. - God. 1, br. 1 (2003) - Beograd (Vatroslava Lisinskog 12a): Institut za istraživanja i projektovanja u privredi, 2003 - (Beograd: Beografi ka). - 29 cm

Tromesečno

Drugo izdanje na drugom medijumu:Istraživanja i projektovanja za privredu (Online) = ISSN 1821-3197

ISSN 1451-4117 = Istraživanja i projektovanja za privredu

COBISS.SR-ID 108368396

istraživanja i projektovanja za privredu - applied engineering science 9(2011)4

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