04/03147 the photon attenuation coefficients of barite,marble and limra: akkurt, i. et al. annals of...
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area plate model is not suitable to be used to analyse insulated polyhedra. There exists quite a large error even in situations with large container size with medium insulation thickness.
04/03147 The photon attenuation coefficients of barite, marble and limra Akkurt, I. et al. Annals of Nuclear Energy. 2004. 31, (5), 577-582. The linear attenuation coefficients rt (cm -~) and ],otal mass attenuation coefficients (g/p (cm 2 g-l) of 7-rays for barite, marble and limra have been calculated using the XCOM program (Version 3.1) at energies from 1 keV to 300 MeV. The calculated results were compared with the estimation coefficients (g/p) based on the measured total linear attenuation coefficients (rt).
04/03148 The second order Raman spectroscopy in carbon crystallinity Lee, Y.-J. Journal of Nuclear Materials, 2004, 325, (2-3), 174 179. Cellulose was heated in the absence/presence of B to determine crystallinity changes due to heat treatment and B doping with the objectives of evaluating the characteristics of the second order Raman spectroscopy in comparison with X-ray diffraction (XRD) and the first order Raman spectroscopy. The crystallinity determined by XRD was similar to those of tile first order Raman spectroscopy; crystallinity increases as heat treatment temperature (HTT) increases until 2300C. This increase in crystallinity was overturned at 2600C in B-doped carbon due to loss of B. But both techniques were not comparative on the determination of crystallite height (La) and did not evidently present the crystallinity changes. The second order Raman spec- troscopy was used as an alternative technique to clearly quantify the difference in crystallinity. It was confirmed that this new evaluation methodology from the second order Raman spectroscopy is effective for the determination of carbon crystallinity.
04/03149 The sun's total and spectral irradiance for solar energy applications and solar radiation models Gueymard, C. A. Solar Energy, 2004, 76, (4), 423 453. Using the most recent composite time series of total solar irradiance spaceborne measurements, a solar constant value of 1366.1 W m -2 is confirmed, and simple quadratic expressions are proposed to predict its daily value from the Zurich sunspot number, the MgII index, or the 10.7 cm radio flux index. Whenever these three indices are available on a daily basis (since 1978), it is possible to predict the sun's irradiance within 0.1% on average, as accurately as current measurements. Based on this value of the solar constant, an improved approximation of the extraterrestrial solar spectrum from 0 to 1000 ~tm is proposed. It is obtained by dividing the spectrum into nine bands and selecting representative (and recent) spectra, as well as appropriate scaling coefficients for each band. Comparisons with fiequently used spectra are discussed, confirming previous findings of the literature. This synthetic and composite spectrum is proposed at 0.5-nm intervals in the UV (280-400 nm), 1-nm intervals between 0-280 and 400-1705 nm, 5- nm intervals between 1705 and 4000 nm, and progressively larger intervals beyond 4 ~tm, for a total of 2460 wavelengths.
04/03150 Theoretical and experimental modelling of an open oscillatory heat pipe including gravity Dobson, R. T. International Journal of Thermal Sciences, 2004, 43, (2), 113-119. An open oscillatory heat pipe is a two-phase flow device capable of transferring heat from a source to a sink below the source, against the force of gravity, without the aid of a wick or any moving mechanical parts. A theoretical model of such a device taking gravity, surface tension, friction and pressure into account is presented. The model uses vapour bubble, liquid plug and liquid film control volumes. An experimental model was constructed and tested using water as the working fluid. It was found that the device could operate indefinitely provided the heat source is less than 30 mm above the heat sink and that the temperature of the heat source is less than 160C. The theoretical model was able to predict these experimentally determined values. By calculating Lyapunov exponents it is shown that the theoretical model is able to reflect the characteristic chaotic behaviour of these devices. It was concluded that the model represents the experimental situation well and that it is important to consider the evaporation of liquid deposited on the surface by the trailing edge of the liquid plug. It is recommended that convective heat transfer is further investigated and the water pumping ability of the device is exploited.
04/03151 Theoretical estimates of air bubble behavior in dense pipeline slurry flows Eskin, D. et al. Chemical Engineering and Processing, 2004, 43, (6), 727- 737. In the paper an approach to simulation of air bubbles behaviour in dense slurry flowing in a pipeline is explored. It is based on establishing a relationship between the flow dissipation energy rate and the
collisional dynamics of solid particles. This problem is important in hydrotransport technology of bitumen extraction from the oil sands. The dynamics of air bubbles distributed in slurry is investigated based on two models: a model of turbulence and a model describing particles collisional motion. The rate of air bubbles break-up as well as that of coalescence are estimated. The main parameters governing the bubbles break-up and coalescence are discussed.
04/03152 Theoretical study of stability of graphite intercalation compounds with Bronsted acids Savoskin, M. V. et al. Carbon, 2003, 41, (14), 2757-2760. The instability of acceptor graphite intercalation compounds (GICs) with BrOnsted acids is a main obstacle to their extensive industrial use. Electron transfer from the solvated anion to the positively charged graphene layer is considered to be the first and rate-limiting step in the decomposition process, with the ionization potential of the intercalated anion being a measure of the stability of GICs. The effects of the hydrogen bonding and Coulomb interaction on the GIC stability are discussed.
04/03153 Thermal modeling of a greenhouse with an integrated earth to air heat exchanger: an experimental validation Ghosal, M. K. et al. Energy and Buildings, 2004, 36, (3), 219 227. A simplified analytical model is developed to study the year round effectiveness of a re-circulation type earth air heat exchanger coupled with a greenhouse located in IIT Delhi, India. The performance of the system was evaluated in terms of thermal load levelling and coefficient of performance. Calculations were done for typical winter and summer day in year 2002. Temperatures of greenhouse air were found to be on an average 6-7C more in winter and 3-4C less in summer than the same greenhouse when operating without earth air heat exchanger. Predicted and measured values of greenhouse air temperatures exhibited fair agreement.
04/03154 Using random set theory to propagate epistemic uncertainty through a mechanical system Tonon, F. Reliability Engineering & System Safety, 2004, 85, (1-3), 169-181. The Epistemic Uncertainty Project of Sandia National Laboratories (NM, USA) proposed two challenge problems intended to assess the applicability and the relevant merits of modern mathematical theories of uncertainty in reliability engineering and risk analysis. This paper proposes a solution to Problem B: the response of a mechanical system with uncertain parameters. Random set theory is used to cope with both imprecision and dissonance affecting the available information. Imprecision results in an envelope of cumulative distribution functions (CDFs) of the system response bounded by an upper CDF and a lower CDF. Different types of parameter discretizations are introduced. It is shown that: (i) when the system response presents extrema in the range of parameters considered, it is better to increase the fineness of the discretization than to invoke a global optimization tool; (ii) the response expectation differed by less than 0.5% when the number of function calls was increased 15.7 times; (iii) larger differences (4-5%) were obtained for the lower tails of the CDFs of the response. Further research is necessary to investigate (i) parameter discretizations aimed at increasing the accuracy of the CDFs (lower) tails; (ii) the role of correlation in combining information.
04/03155 Using scanning tunneling microscopy to characterize adsorbates and reactive intermediates on transition metal oxide surfaces Altman, E. I. and Tanner, R. E. Catalysis Today, 2004, 85, (2-4), 101- 111. Scanning tunnelling microscopy (STM) is demonstrated to be a powerful tool to characterize adsorption and reaction on oxide surfaces by imaging molecular adsorbates and reactive intermediates. The molecules were used to probe surface structure and to study surface reactivity spatially at the atomic level. Results for three systems are presented: alcohol adsorption on WO3(0 0 1), earboxylates on the anatase polymorph of TiO3, and propene adsorption on a PdO monolayer on Pd(i 0 0). When the alcohols were exposed to the WO3(0 0 1)-c(2 2) surface at room temperature the molecules could not be imaged. Heating the surface to temperatures above a water desorption peak associated with alcohol deprotonation, however, allowed 1-propoxide to be imaged. The images reveal that the alkoxide has no preference for defects, rather it binds to W 6+ ions exposed on the fully oxidized c(2 x 2) surface. Temperature-programmed deso- rption revealed that alkoxides at these sites undergo only dehydration reactions. To probe the structure of the unusual (1 x 4) reconstruction on anatase (0 0 1), formic and acetic acid adsorption were used. Following dissociative adsorption, both formate and acetate adsorb solely centred atop the bright rows that define the surface reconst