oday, diplomats work hard to restrict the manufacture, sale and use of land mines world- T wide. However, massive

cleanup is still needed to destroy the estimated 100 million land mines buried in 65 countries. Land mines left behind from wars is one of this century’s huge unsolved problems. Humanitarian efforts to detect and remove are focused primarily in Europe, Africa, Asia, Cen- tral and South America.

The big challenge is quickly deter- mining each land mine’s location, in an area, so they all can be removed. An effective solution would have close to 1 0 % of the mines in any area detected rapidly and with few false alarms. (That is, mistaking a buried object, such as a rock, for a mine.) The United Nations, for example, has set the detection goal at 99.6%. The US Army’s allowable false- alarm rate is one false alarm within every 1.25 square meters.

No existing land-mine detection sys- tem meets these criteria. There are limits or flaws in the current technology. How- ever, this failure is also because of the mines, themselves, and the varied envi- ronments they are buried in.

Land mines are of two basic types: antitank and antipersonnel. Antitank mines are larger and more powerful than antipersonnel mines. However, antipersonnel mines are the most com- mon and the most difficult to find. This is because they are small and often made of plastic.

Antitank mines generally contain more metal than do antipersonnel mines; thus, they are more easily found by simple metal detectors. Both types are buried as close to the surface as pos- sible. They both are found in a variety of soils and terrain-rocky or sandy soil, open fields, forested areas, steep terrain and jungle.

For both, detonation is typically

caused by pressure, although some are activated by a trip-wire or other mecha- nisms. Thus, a land-mine detector must do its job without having direct contact with a mine. It also must be able to locate all types of mines individually in a variety of environments.

Various detection technologies are currently used, each with limits or flaws. Dogs, and other “sniffers,” have high ongoing expenses, get tired and can be fooled by masking scents. Metal detectors are sensitive to metal mines and firing pins but cannot reli- ably find plastic mines. Infrared detec- tors effectively detect recently placed mines, but they are expensive and lim- ited to certain temperature conditions. Thermal neutron activation detectors are accurate but are large for field use, slow and expensive.

In early attempts, ground-penetrating radar was sensitive to large mines and had good coverage rate at a distance. With signal processing, it could discrim- inate antitank mines from clutter such as rocks beneath the ground‘s surface. This type of radar, however, remains expen- sive; it cannot detect antipersonnel mines because its resolution is too low; and, it frequently records false alarms from cluttered sources.

The Lawrence Livermore National Laboratory (LANL) has combined its micropower impulse radar and imaging technologies. The system is called the Land-Mine Detection Advanced Radar Concept, or LANDMARC.

This ongoing project stands a good chance of solving the problems to date, especially detecting small plastic antiper- sonnel mines and reducing the false- alarm rate. The LANDMARC system’s enabling technology is Micropower Impulse Radar (MIR). MIR was invent- ed at Livenno= in 1993 as an outgrowth of the Nova laser program. The inven- tion led directly to a battery-operated, pulsed radar that is small, inexpensive, has a wide frequency band and works well at short mges.

MIR’s size, light weight and low power requirements makes it superior to previous attempts to use ground-pene- trating radar. MIR’s ultrawide band- width permits high-resolution imaging capabilities that differentiate LAND- MARC from similar land-mine-detec- tion technologies. Furthermore, the ability to group individual MIR units in arrays increases the speed and coverage area of LANDMARC’S detection work.

MIR units have been combined with an imaging system. It uses computer

OCTOBEFVNOVEMBER 1998 19

algorithms to convert large amounts of raw waveform data from the MIR units to high- resolution, two- and three- dimensional images of the subsurface. The prototype systems enable users to visualize both anti- tank and antipersonnel mines. And the sys- tems can differentiate the mines from rocks, and other clutter of similar size and shape, by the reflected MIR signal. Once the mines are “seen” and ident%ed, they can be recovered and destroyed.

The MIR units are configured in a hand-held wand or mounted on a small robotic cart (Fig. 1). In either confgura- tion, the MIR array is passed over the ground with the antennas of the units about 10 centimeters above the surface.

The units rapidly emit microwave impulses with very short risetimes (100 trillionths of a second). The impulses radi- ate from transmitting antennas and pene- trate the ground. These impulses strike and penetrate buried objects then bounce back to a receiving antenna. They are sampled and processed by an onboard computer to measure changes in the dielectric and conductivity properties of the subsurface.

In a few seconds, the data reconstmc- tion algorithms convert the raw radar data into high-resolution, two- and three- dimensional tomographic images of the subsurface (Fig. 2) On the system current- ly under development, the images will appear on either a laptop computer or the operator’s headset screen.

One chief contribution to land-mine detection technology has been combining MIR units with a high performance imag- ing system. The imaging software was originally developed for radar inspection of steel-reinforced concrete bridge decks. But, it also works well in sorting out clutter-

the most difticult imaging task-and low- ering false alarms.

Central to perfecting LANDMARC’S imaging capabilities is the comprehensive signal and noise models being developed. These models are based on the contribu- tions from temperature differences, inho- mogeneity in the soil, increased noise resulting from multiple reflections in M I R arrays, surface reflections and sub- surface clutter such as rocks, roots and voids. They identify conditions where radar likely will work well and where dif- ferent types of sensors would be better.

More important, the models are used to design algorithms to help reduce the false-alarm rate and increase the positive identification rate in laboratory and field tests. These, in turn, improve LAND- MARC’S ability to discriminate between mines and clutter.

Prelimmary experiments identified the operational requirements of the prototype systems. The LANDMARC team devel- oped the reconstruction algorithms that generate a 3-D image. They are using them to investigate design tradeoffs such as array size, sampling rate and overall speed. In laboratory tests, the prototype clearly distinguished plastic antipersonnel mines from surrounding soils. In field tests at Fort Carson in Colorado and Fort AP Hill in Virginia, funded by the US Defense Advanced Research Projects Agency @AFWA), the system performed well, though at a slow pace. The images indicated that progress has been made in removing the strong, ground-surface reflection and other noise sources. That is, it has improved the signal-to-clutter ratio.

Field tests also indicated areas for additional refinement. They include using higher frequencies (that is, wider band-

width) to improve resolution and better distinguish mines from clutter. Also, the system needs a way to communicate more accurate field positions of the imaged mines.

sts with the prototypes are complete, the LANDMARC team plans to conduct blind tests at US Army mine fields to measure detection proba- bilities under realistic conditions. In addi- tion, plans to speed up the scan rate with advanced arrays are under way. Already experienced in industrial licensing of the MIR technology, the team will then direct LANDMARC toward external sponsor- ship for deployment in actual mine fields. The Department of Defense, US indus- tries, nongovernmental organizations such as Operation USA and the World Bank, and foreign governments have all shown interest in using Livermore’s land- mine detection technology.

Stephen Azevedo is the Micropower Impulse Radar Project Leader in the Laser Programs Directorate. In electrical engi- neering, he received a BS (1977) from the University of California at Berkeley, an MS (1978) from Carnegie-Mellon Uni- versity, and a PhD (1991) from the Uni- versity of California at Davis. Azevedo joined Lawrence Livermore National Laboratory in 1979 and since has been a principal investigator in computed tomog- raphy research and radar remote sensing. He is the author or co-author of over 40 publications.

For further information contact Stephen Azevedo (510) 422-8538 <azevedo3 @ 1 lnl.gov>. Also see the MIR home page <http://www-lasers.llnl.gov/ lasers/idp/mir/mir. htmb.

Excerpted and repnnted with p e n m w n by the Uruversity of Calzjomq Lawrence L*vemre Nahonal Laboratory and the US Dept. of Energy j?om the Science &Technology Renew (Nov 1997)

20 IEEE POTENTIALS

etting things done and/or getting people to behave certain ways is what power is all about. This is also what surviving on this planet is all about. Very few of us exist as hermits. There are two main theories on eties/groups work. Functionalist theory basically says

each society is relatively stable and integrated, held together by its members’ shared values. Everyone contributes and enables the society to function.

Conflict theory states each society is in constant flux with everyone contributing to the society’s change. This is because the demand for things such as power, wealth and prestige always seems to exceed the supply. Those who gain control of these resources protect them at other people’s expense. Tactics employed typically include traditions, laws, tax regulations, executive positions, family structures and moral attitudes.

Social change is influenced by power plays. Circumstances, such as new technology, trade or a crisis, permit cracks in the old system. A new system develops and spreads as well as cre- ates a new group: its developerdparticipants. They, in tum, demand and fight for change (a share in the resources). The resulting conflict creates tension, hostility, competition, dis- agreement over goals and values and, sometimes, outright vio- lence. The fight may take on the form of demands for free trade or protection, for changes in taxation, labor or immigration pol- icy. It can be political or have religious or ethnic overtones. These social conflicts can have positive results for more than just the initiating group. Often, conflict binds different groups together and focuses attention on social problems producing constructive changes.

In actuality, societies operate along both theory lines. “As Ralf Dahrendorf (1958) points out, societies are sta- ble enduring systems and they do experience conflict and continuous change. The functionalist and conflict approaches are just focusing on different aspects of social reality,” writes Ian Robertson in Sociology (0 1981, Worth Publishers, Inc.).

es of ~ h ~ n ~ ~ “No significant socioeconomic change takes place

without conflict, especially large-scale, high-speed eco- nomic change,” state Alvin and Heidi Toffler. According to the Tofflers, “Wave conflict is a struggle over an entire way of life-a civilization.” One example they give is China. Many peasants still operate under First Wave (agrarian) conditions, tilling the fields, even as Second Wave (industrial) manufacturing (low-tech, low wage fac- tories) laborers proliferate. Concurrently, a small group of Third Wave (knowledge-based) high-tech entrepreneurs is growing. This group is forming interests different from the other two “wave” groups. The Third Wave group’s inter- ests are closer to people located in Singapore, Vancouver and Silicon Valley and such than their compatriots. This creates internal conflict which creates change.

These waves of change form a three-tiered po structure with the Third Wave, knowledge-based se on top. As a result, those in the agrarian state seek skip a stage.” Even Second Wave factories provide less value than the Third Wave knowledge needed to run them. For while a factory will stay put in a geographic area, knowledge tends to wander off. “Knowledge, despite intellectual property treaties, has a way of seeping out, or worse yet, becoming obsolete,” point out the Tofflers.

U S e ower comes m various sizes, shapes and forms. Sometimes

it is awarded based on conferred status. Sometimes power is earned. Power arises from the various relations and processes between the members in a group or groups involved. For instance, US elected officials must act in ways their contingen- cies’ approve of or risk being voted out. This creates conflict. Often, many interest groups need pampering to gain consensus (i.e., garner enough votes to stay in power). However, Michael Foucault (1926-1984) rejected the view that power is some- thing which can be possessed. Foucault argued that power sim- ply exists; it is exercised by a person or group, rather than owned. Foucault stressed that keeping tabs (i.e., playing Big Brother) is vital to power as well as its intricate links with knowledge (Key ideas in human thought, edited by Kenneth McLeish, 0 1993, Facts On File).

Thus technology, itself, is at a point where the balance can be tipped. Technology is a major catalyst for change. Thanks to the Internet, individuals worldwide can link up to create poten- tially influential groups, based on similar interests.

However, technology also enables current groups to stay in power. Keeping tabs on individuals just gets easier and easier with technology’s ability to monitor up close and personal-like. In the end, will the fishbowl water spill? The answer rests on the dog’s ability to stay on the ball.

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