- Email: [email protected]
00428 Finite element spherical harmonics (PN) solutions of the three-dimensional Takeda benchmark problems
16 Fuel science and technology (fundamental science, analysis, instrumentation) performed, where the calculated and measured flame angles of 101 different Bunsen-type flames are compared for operating pressures between 0.1 and 1.0 MPa. Experimental data on 20-mm Bunsen-type flames for lean methane/air, ethylene/air, and propane/air mixtures for different flow and turbulence inlet conditions were provided by the group of Kobayashi (Japan). For each fuel the three parameters of the algebraic relation are varied such that a minimum least-square deviation between computed and measured flame cone angles is achieved. It is found that for all the fuels investigated this relation collapses to a unique equation, in which the Lewis number of the fuel/ air mixture is included. It has been proposed recently that differential molecular transport effects, as described by the Lewis number, may be related not only to laminar flame instability effects at low turbulence but also to visible effects at higher degrees of turbulence. This fits to the finding of the explicit Lewis number dependency in the source term. It is possible to substantiate the applicability of this algebraic closure for methane/air flames for higher pressures up to 3 MPa in reasonable agreement with experimental data, as described in in the paper.
06•00422 Effect of high doses of neutron irradiation on physico-mechanical properties of copper alloys for ITER applications Fabritsiev, S. A. and Pokrovsky, A. S. Fusion Engineering and Design, 2005, 73, (l), 19 34. This work presents results on the influence of neutron irradiation to a dose level of 3 dpa at the irradiation temperature of 150 and 300°C on mechanical properties, structure, fracture character and electrical resistivity of the GlidCopA125IG and CuCrZr IG copper alloys. The investigations made it possible to obtain, for the first time, the dose dependencies of strengthening and embrittlement of alloys, as well as changes in materials electric conductivity in the operation temperature range of ITER materials (150-300°C). As a result, the representative data were obtained for the substantiating the radiation life time of copper alloys in the dose-temperature range expected for ITER.
06•00423 Effects of multi-defects at metal/semiconductor interfaces on electrical properties and their influence on stability and lifetime of thin film solar cells Dharmadasa, I. M. et al. Solar Enei~gy Materials and Solar CelLs', 2005, 86, (3), 373 384. This communication analyses some of the results observed for metal/nCdTe interfaces in the mid-1980s, which could not be interpreted at that time. These observations are analysed on the basis of new understanding using a new model proposed for CdS/CdTe thin film solar cells. The observed behaviour of current-voltage characteristics of electrical contacts to n-CdTe under electrical and illumination stresses are explained and the effects of these changes on CdS/CdTe solar cells are discussed. Future research directions for the development of CdS/CdTe solar cells are proposed and the way forward for improvement of stability and lifetime of solar cells is suggested. A summary of recent electrical contact work on metal/Cu(InGa)(SSe)2 interfaces is also presented and similar behaviour is reported.
06•00424 Electrical conductivity of carbon blacks under compression Simchez-Gonzfilez, J. et al. Carbon, 2005, 43, (4), 741 747. A study was made of the electrical conductivity of six commercial carbon blacks under compression. The influence of the applied pressure, sample volume, mechanical work, and density of the carbons was investigated. The conductivity was measured at room temperature by impedance spectroscopy over the frequency range 20-106 Hz with a voltage of i V. The decrease in volume under compression depended significantly on each particular carbon and on the applied pressure, and for a larger number of carbons it was only important at low pressures. The patterns of variation of the conductivity with pressure and mechanical work were similar. Of the pressure and volume effects comprised in the influence of mechanical work on the conductivity, that of the pressure appeared to predominate. The increase in conductivity with decreasing sample volume was greater for the carbons in which the volume under compression was smaller. The total increase in conductivity was greater for the densest carbons and least for the lightest one. Both the conductivity and its variation under compression were positively related to the density of the carbons.
06•00425 Emergy and exergy analyses: Complementary methods or irreducible ideological options? Sciubba, E. and Ulgiati, S. Energy, 2005, 30, (10), 1953 1988. The paper discusses the similarities and the incompatibilities between two forms of energy analysis (exergy and emergy, 'EXA' and 'EMA' in the following), both of which try to represent the behaviour of physical systems by means of cumulative energy input/output methods that result in a double integration over space and time domains. Theoretical background, definitions and balance algebra are discnssed first, in a 'statement-counterstatement' format that helps pinpointing differ-
58
Fuel and Energy Abstracts
January 2006
ences and similarities. A significant, albeit simplified, benchmark case (ethanol production from corn) is used to compare the results and analytically assess the merits of each approach as well as possible synergic aspects. Corn production, transport and industrial conversion to ethanol are included in the analysis. First, mass balance and energy accounting are performed in each step of the process, then, exergy and emergy evaluations are carried out separately to lead to a set of performance indicators, the meaning of which is discussed with reference to their proper scale of application. The authors underline that each method has its own preferred field of application and conclude that the two approaches appear to be characterized not much as different (and therefore competing) tools, but as different paradigms, whose meta-levels (their 'philosophies') substantially differ. In particular, EXA is found to provide the most correct and insightful assessment of thermodynamic features of any process and to offer a clear quantitative indication of both the irreversibilities and the degree of matching between the used resources and the end-use material or energy flows. EXA combined with costing considerations results in thermo-economics (TE), presently the best engineering method for System optimization. One of EXA recent extensions, extended exergy accounting (EEA) includes all externalities in the exergy resource accounting, thus providing a more complete picture of how a process is interacting with its socio-economical environment and with the biosphere. EMA further expands the evaluation to the larger scale of the biosphere and properly accounts for the globality of the energy and resource flows supporting complex living systems. Although some conceptual assumptions and methodological differences appear irreconcilable, important similarities are also found that may lead to further methodological and practical convergences.
06/00426 Evolutionary fuzzy clustering for the Classification of transients in nuclear components Zio, E. and Baraldi, P. Progress in Nuclear Energy, 2005, 46, (3 4), 282 296. The classification of objects or patterns is an important area of research with practical applications in a variety of fields. This study was interested in the classification of signal transients for the reliable monitoring and timely diagnosing of nuclear components and systems. These represent fundamental tasks for the operation, control and accident management of nuclear power plants. The problem is tackled within a fuzzy clustering approach. The choice of the metrics upon which the clustering is based is critical for obtaining geometric clusters in the features space as close as possible to the real physical classes. In this respect, here the a priori known information regarding the true classes to which the objects belong will be exploited to select, by means of an evolutionary algorithm of literature, an optimal metrics for the clustering. In case the classification thereby obtained were still unsatisfactory, an iterative procedure is used to split the less compact physical classes in further subclasses.
06•00427 Experimental and numerical study of threedimensional flow field in mini-environment Cheng, C.-S. and Hung, K.-S. Energy and Buihlings, 2005, 37, (6), 579 586. This study is concerned with three-dimensional air flow field for improving the ventilation performance of a mini-environment in which toxic gas is produced during the coating process. To investigate the air flow field, measurement for the velocity distribution has been made by using a three-dimensional ultrasonic anemometer, and numerical simulation using computational fluid dynamics (CFD) analysis tool has also been performed. Results of the numerical simulation based on the RNG k ~ turbulence model are confirmed by the experiments, and modifications in geometric configuration of the system are investigated. It is found that the numerical and experimental approaches used in this study lead to useful information of flow field and the ventilation performance in the mini-environment may be greatly improved by adjusting the location of the HEPA and modifying the shape of the inlet of the exhaust pipe.
06•00428 Finite element spherical harmonics (PN) solutions of the three-dimensional Takeda benchmark problems Ziver, A. K. el at. Annals of Nuclear Energ;y, 2005, 32, (9), 925 948. A set of multi-group eigenvalue (Kerr) benchmark problems in threedimensional homogenized reactor core configurations have been solved using the deterministic finite element transport theory code EVENT and the Monte Carlo code MCNP4C. The principal aim of this work is to qualify numerical methods and algorithms implemented in EVENT. The benchmark problems were compiled and published by the Nuclear Data Agency (OECD/NEACRP) and represent three-dimensional realistic reactor cores which provide a framework in which computer codes employing different numerical methods can be tested. This is an important step that ought to be taken (in the authors' view) before any code system can be confidently applied to sensitive problems in nuclear criticality and reactor core calculations. This paper presents EVENT diffusion theory (P1) approximation to the neutron transport equation
16 Fuel science and technology (fundamental science, analysis, instrumentation) and spherical harmonics transport theory solutions (P3 P3) to three benchmark problems with comparison against the widely used and accepted Monte Carlo code MCNP4C. In most cases, discrete ordinates transport theory (Sv) solutions which are already available and published have also been presented. The effective multiplication factors (Ken-) obtained from transport theory EVENT calculations using an adequate spatial mesh and spherical harmonics approximation to represent the angular flux for all benchmark problems have been estimated within 0.1% (100 pcm) of the MCNP4C predictions. All EVENT predictions were within the three standard deviation uncertainty of the MCNP4C predictions. Regionwise and pointwise multigroup neutron scalar fluxes have also been calculated using the EVENT code and compared against MCNP4C predictions with satisfactory agreements. As a result of this study, it is shown that multi-group reactor core/criticality problems can be accurately solved using the three-dimensional deterministic finite element spherical harmonics code EVENT.
06/00429 Genetic algorithm optimization of a model-free fuzzy control system Marseguerra, M. ef al. Annals qf Nuclear Energy, 2005, 32, (7), 712 728. This paper presents an approach, based on a genetic algorithm optimization search, for determining the values of the parameters of an adaptive stable fuzzy control system suitable to drive a given plant to a desired reference trajectory. The method is demonstrated on a naturally unstable system taken from the literature and then applied to the well-known Chernick's model of a nuclear reactor.
06•00430 Hybrid electro-conductive composites with improved toughness, filled by carbon black Novfik, I. et al. Carbon, 2005, 43, (4), 841 848. The influence of both carbon black (CB), and an ethylene-propylene copolymer grafted by maleic anhydride (EP-g-MA), on the static mechanical properties, impact strength, peel and shear strengths as well as on the electrical conductivity of composites based on highdensity polyethylene (HDPE) matrix, was investigated in this paper. It was found that CB improves the stress at yield, the stress at break, and Young's modulus, as well as the shear strength and peel strength, of the HDPE/CB composites. The percolation threshold was found at 4.5 vol.% of CB. The addition of EP-g-MA to the HDPE/CB composites improves their impact strength, the peel and shear strengths, and the electrical conductivity.
06•00431 Identification of nuclear transients via optimized fuzzy clustering Zio, E. and Baraldi, P. Annals qfNuclear Energy, 2005, 32, (10), 1068 1080. This paper looks into the issue of using cluster analysis for transient classification in nuclear components and systems. In general, the choice of the metrics upon which clustering is based can be critical for obtaining geometric clusters as close as possible to the real physical classes in the feature space. The complexity and variety of cluster shapes and dimensions which can be expected in the transient classification of interest lead us to take an approach based on a different Mahalanobis metric for each cluster. The a priori known information regarding the true classes to which the patterns belong is exploited to select, by means of a supervised evolutionary algorithm, the different optimal Mahalanobis metrics. Further, the diagonal elements of the matrices defining the metrics can be taken as measures of the relevance of the features employed for the classification of the different patterns. The efficiency of the approach is verified with respect to a literature problem and then applied to the case of classification of transients in a nuclear component.
06/00432 Importance of atmospheric turbidity and associated uncertainties in solar radiation and luminous efficacy modelling Gueymard, C. A. Energy, 2005, 30, (9), 1603 1621. For many solar-related applications, it is important to separately predict the direct and diffuse components of irradiance or illuminance. Under clear skies, turbidity plays a determinant role in quantitatively affecting these components. In this paper, various aspects of the effect of turbidity on both spectral and broadband radiation are addressed, as well as the uncertainty in irradiance predictions due to inaccurate turbidity data, and the current improvements in obtaining the necessary turbidity data.
06•00433 In-situ studies of electron field emission of single carbon nanotubes inside the TEM Jin, C. et al. Carbon, 2005, 43, (5), 1026 1031. Electron field emission characteristics of individual multi-walled carbon nanotubes (MWCNTs) were investigated in situ inside the transmission electron microscope (TEM). For a single MWCNT it was found that while field-emission can hardly occur from the side of the
nanotube, a curved nanotube may result in finite side emission and the best emission geometry is the top emission geometry. Current-voltage ( ~ V ) measurements made at different vacuum conditions and voltage sweeps emphasize the importance of the adsorbates on the electron field emission of MWCNTs. For a contaminated MWCNT, although the field emission current was reduced, the stability of its emission was improved. A current of up to several tens of mA was observed for a single MWCNT, but it was found that long time emission usually results in drastic structure damage that may lead to sudden emission failure.
06100434 coating
Injection and boiling of liquid CO2 with a hydrate
Hirai, S. and Sanda, H. Energy, 2005, 30, ( l l 12), 2275 2283. The effect of a hydrate film on the CO2 droplet size was elucidated when the droplet was injected into high-pressure water. The factors that influence the droplet size and shape are the injection rate, nozzle diameter, temperature, and also the tension and propagation velocity of the hydrate thin film. It was also found that the hydrate film on the droplet will promote the boiling of liquid CO2 when the pressure decreases. These results can be applied to the release of liquid CO2 droplets in the ocean for CO2 sequestration: for example, when the drops rise above 500-m in the ocean, boiling due to decompression should occur.
06100435 Inverse analyses of diffusion processes in type 13X zeolite particles Goubaru, A. et al. Applied Energy, 2005 81 (3), 277 29(/. To determine effective surface self-diffusion coefficients of CO2 within type 13X zeolite particles, at various temperatures (25-70°C), inverse analyses of observed CO2-uptake curves were successfully performed. The obtained effective surface self-diffusion coefficients increase with both the amount adsorbed and the temperature and ranged from 7.8 x 10 m to 1.95 x 10 9 m2/s under the present experimental conditions.
06/00436 Mass attenuation coefficients of saccharides for low-energy X-rays Chitralekha, ef al. Radiation Physics and Chemistcv, 2005, 72, (1), 1 5. Mass attenuation coefficients have been measured for mono- and disaccharides at photon energies 5.947, 6.460 and 14.413 keV. The measured values are compared with theoretical calculations. The agreement between experiment and theory is generally within 5%.
06/00437 Mathematical modelling of NO emissions from high-temperature air combustion with nitrous oxide mechanism Yang, W. and Blasiak, W. Fuel Processing Teclmology, 2005, 86, (9), 943 957. A study of the mathematical modelling of NO formation and emissions in a gas-fired regenerative furnace with high-preheated air was performed. The model of NO formation via N20-intermediate mechanism was proposed because of the lower flame temperature in this case. The reaction rates of this new model were calculated basing on the eddy-dissipation-concept. This model accompanied with thermal-NO, prompt-NO and NO reburning models were used to predict NO emissions and formations. The sensitivity of the furnace temperature and the oxygen availability on NO generation rate has been investigated. The predicted results were compared with experimental values. The results show that NO emission formed by N20intermediate mechanism is of outstanding importance during the hightemperature air combustion (HiTAC) condition. Furthermore, it shows that NO models with N20-route model can give more reasonable profile of NO formation. Additionally, increasing excess air ratio leads to increasing of NO emission in the regenerative furnace.
06•00438 Modelling of proton exchange membrane fuel cell performance based on semi-empirical equations Sadiq AI-Baghdadi, M. A. R. Renewable Energy, 2005, 30, (10), 1587 1599. Using semi-empirical equations for modelling a proton exchange membrane fuel cell is proposed for providing a tool for the design and analysis of fuel cell total systems. The focus of this study is to derive an empirical model including process variations to estimate the performance of fuel cell without extensive calculations. The model take into account not only the current density but also the process variations, such as the gas pressure, temperature, humidity, and utilization to cover operating processes, which are important factors in determining the real performance of fuel cell. The modelling results are compared well with known experimental results. The comparison shows good agreements between the modelling results and the experimental data. The model can be used to investigate the influence of process variables for design optimization of fuel cells, stacks, and complete fnel cell power system.
Fuel and Energy Abstracts
January 2006
59
06•00422 Effect of high doses of neutron irradiation on physico-mechanical properties of copper alloys for ITER applications Fabritsiev, S. A. and Pokrovsky, A. S. Fusion Engineering and Design, 2005, 73, (l), 19 34. This work presents results on the influence of neutron irradiation to a dose level of 3 dpa at the irradiation temperature of 150 and 300°C on mechanical properties, structure, fracture character and electrical resistivity of the GlidCopA125IG and CuCrZr IG copper alloys. The investigations made it possible to obtain, for the first time, the dose dependencies of strengthening and embrittlement of alloys, as well as changes in materials electric conductivity in the operation temperature range of ITER materials (150-300°C). As a result, the representative data were obtained for the substantiating the radiation life time of copper alloys in the dose-temperature range expected for ITER.
06•00423 Effects of multi-defects at metal/semiconductor interfaces on electrical properties and their influence on stability and lifetime of thin film solar cells Dharmadasa, I. M. et al. Solar Enei~gy Materials and Solar CelLs', 2005, 86, (3), 373 384. This communication analyses some of the results observed for metal/nCdTe interfaces in the mid-1980s, which could not be interpreted at that time. These observations are analysed on the basis of new understanding using a new model proposed for CdS/CdTe thin film solar cells. The observed behaviour of current-voltage characteristics of electrical contacts to n-CdTe under electrical and illumination stresses are explained and the effects of these changes on CdS/CdTe solar cells are discussed. Future research directions for the development of CdS/CdTe solar cells are proposed and the way forward for improvement of stability and lifetime of solar cells is suggested. A summary of recent electrical contact work on metal/Cu(InGa)(SSe)2 interfaces is also presented and similar behaviour is reported.
06•00424 Electrical conductivity of carbon blacks under compression Simchez-Gonzfilez, J. et al. Carbon, 2005, 43, (4), 741 747. A study was made of the electrical conductivity of six commercial carbon blacks under compression. The influence of the applied pressure, sample volume, mechanical work, and density of the carbons was investigated. The conductivity was measured at room temperature by impedance spectroscopy over the frequency range 20-106 Hz with a voltage of i V. The decrease in volume under compression depended significantly on each particular carbon and on the applied pressure, and for a larger number of carbons it was only important at low pressures. The patterns of variation of the conductivity with pressure and mechanical work were similar. Of the pressure and volume effects comprised in the influence of mechanical work on the conductivity, that of the pressure appeared to predominate. The increase in conductivity with decreasing sample volume was greater for the carbons in which the volume under compression was smaller. The total increase in conductivity was greater for the densest carbons and least for the lightest one. Both the conductivity and its variation under compression were positively related to the density of the carbons.
06•00425 Emergy and exergy analyses: Complementary methods or irreducible ideological options? Sciubba, E. and Ulgiati, S. Energy, 2005, 30, (10), 1953 1988. The paper discusses the similarities and the incompatibilities between two forms of energy analysis (exergy and emergy, 'EXA' and 'EMA' in the following), both of which try to represent the behaviour of physical systems by means of cumulative energy input/output methods that result in a double integration over space and time domains. Theoretical background, definitions and balance algebra are discnssed first, in a 'statement-counterstatement' format that helps pinpointing differ-
58
Fuel and Energy Abstracts
January 2006
ences and similarities. A significant, albeit simplified, benchmark case (ethanol production from corn) is used to compare the results and analytically assess the merits of each approach as well as possible synergic aspects. Corn production, transport and industrial conversion to ethanol are included in the analysis. First, mass balance and energy accounting are performed in each step of the process, then, exergy and emergy evaluations are carried out separately to lead to a set of performance indicators, the meaning of which is discussed with reference to their proper scale of application. The authors underline that each method has its own preferred field of application and conclude that the two approaches appear to be characterized not much as different (and therefore competing) tools, but as different paradigms, whose meta-levels (their 'philosophies') substantially differ. In particular, EXA is found to provide the most correct and insightful assessment of thermodynamic features of any process and to offer a clear quantitative indication of both the irreversibilities and the degree of matching between the used resources and the end-use material or energy flows. EXA combined with costing considerations results in thermo-economics (TE), presently the best engineering method for System optimization. One of EXA recent extensions, extended exergy accounting (EEA) includes all externalities in the exergy resource accounting, thus providing a more complete picture of how a process is interacting with its socio-economical environment and with the biosphere. EMA further expands the evaluation to the larger scale of the biosphere and properly accounts for the globality of the energy and resource flows supporting complex living systems. Although some conceptual assumptions and methodological differences appear irreconcilable, important similarities are also found that may lead to further methodological and practical convergences.
06/00426 Evolutionary fuzzy clustering for the Classification of transients in nuclear components Zio, E. and Baraldi, P. Progress in Nuclear Energy, 2005, 46, (3 4), 282 296. The classification of objects or patterns is an important area of research with practical applications in a variety of fields. This study was interested in the classification of signal transients for the reliable monitoring and timely diagnosing of nuclear components and systems. These represent fundamental tasks for the operation, control and accident management of nuclear power plants. The problem is tackled within a fuzzy clustering approach. The choice of the metrics upon which the clustering is based is critical for obtaining geometric clusters in the features space as close as possible to the real physical classes. In this respect, here the a priori known information regarding the true classes to which the objects belong will be exploited to select, by means of an evolutionary algorithm of literature, an optimal metrics for the clustering. In case the classification thereby obtained were still unsatisfactory, an iterative procedure is used to split the less compact physical classes in further subclasses.
06•00427 Experimental and numerical study of threedimensional flow field in mini-environment Cheng, C.-S. and Hung, K.-S. Energy and Buihlings, 2005, 37, (6), 579 586. This study is concerned with three-dimensional air flow field for improving the ventilation performance of a mini-environment in which toxic gas is produced during the coating process. To investigate the air flow field, measurement for the velocity distribution has been made by using a three-dimensional ultrasonic anemometer, and numerical simulation using computational fluid dynamics (CFD) analysis tool has also been performed. Results of the numerical simulation based on the RNG k ~ turbulence model are confirmed by the experiments, and modifications in geometric configuration of the system are investigated. It is found that the numerical and experimental approaches used in this study lead to useful information of flow field and the ventilation performance in the mini-environment may be greatly improved by adjusting the location of the HEPA and modifying the shape of the inlet of the exhaust pipe.
06•00428 Finite element spherical harmonics (PN) solutions of the three-dimensional Takeda benchmark problems Ziver, A. K. el at. Annals of Nuclear Energ;y, 2005, 32, (9), 925 948. A set of multi-group eigenvalue (Kerr) benchmark problems in threedimensional homogenized reactor core configurations have been solved using the deterministic finite element transport theory code EVENT and the Monte Carlo code MCNP4C. The principal aim of this work is to qualify numerical methods and algorithms implemented in EVENT. The benchmark problems were compiled and published by the Nuclear Data Agency (OECD/NEACRP) and represent three-dimensional realistic reactor cores which provide a framework in which computer codes employing different numerical methods can be tested. This is an important step that ought to be taken (in the authors' view) before any code system can be confidently applied to sensitive problems in nuclear criticality and reactor core calculations. This paper presents EVENT diffusion theory (P1) approximation to the neutron transport equation
16 Fuel science and technology (fundamental science, analysis, instrumentation) and spherical harmonics transport theory solutions (P3 P3) to three benchmark problems with comparison against the widely used and accepted Monte Carlo code MCNP4C. In most cases, discrete ordinates transport theory (Sv) solutions which are already available and published have also been presented. The effective multiplication factors (Ken-) obtained from transport theory EVENT calculations using an adequate spatial mesh and spherical harmonics approximation to represent the angular flux for all benchmark problems have been estimated within 0.1% (100 pcm) of the MCNP4C predictions. All EVENT predictions were within the three standard deviation uncertainty of the MCNP4C predictions. Regionwise and pointwise multigroup neutron scalar fluxes have also been calculated using the EVENT code and compared against MCNP4C predictions with satisfactory agreements. As a result of this study, it is shown that multi-group reactor core/criticality problems can be accurately solved using the three-dimensional deterministic finite element spherical harmonics code EVENT.
06/00429 Genetic algorithm optimization of a model-free fuzzy control system Marseguerra, M. ef al. Annals qf Nuclear Energy, 2005, 32, (7), 712 728. This paper presents an approach, based on a genetic algorithm optimization search, for determining the values of the parameters of an adaptive stable fuzzy control system suitable to drive a given plant to a desired reference trajectory. The method is demonstrated on a naturally unstable system taken from the literature and then applied to the well-known Chernick's model of a nuclear reactor.
06•00430 Hybrid electro-conductive composites with improved toughness, filled by carbon black Novfik, I. et al. Carbon, 2005, 43, (4), 841 848. The influence of both carbon black (CB), and an ethylene-propylene copolymer grafted by maleic anhydride (EP-g-MA), on the static mechanical properties, impact strength, peel and shear strengths as well as on the electrical conductivity of composites based on highdensity polyethylene (HDPE) matrix, was investigated in this paper. It was found that CB improves the stress at yield, the stress at break, and Young's modulus, as well as the shear strength and peel strength, of the HDPE/CB composites. The percolation threshold was found at 4.5 vol.% of CB. The addition of EP-g-MA to the HDPE/CB composites improves their impact strength, the peel and shear strengths, and the electrical conductivity.
06•00431 Identification of nuclear transients via optimized fuzzy clustering Zio, E. and Baraldi, P. Annals qfNuclear Energy, 2005, 32, (10), 1068 1080. This paper looks into the issue of using cluster analysis for transient classification in nuclear components and systems. In general, the choice of the metrics upon which clustering is based can be critical for obtaining geometric clusters as close as possible to the real physical classes in the feature space. The complexity and variety of cluster shapes and dimensions which can be expected in the transient classification of interest lead us to take an approach based on a different Mahalanobis metric for each cluster. The a priori known information regarding the true classes to which the patterns belong is exploited to select, by means of a supervised evolutionary algorithm, the different optimal Mahalanobis metrics. Further, the diagonal elements of the matrices defining the metrics can be taken as measures of the relevance of the features employed for the classification of the different patterns. The efficiency of the approach is verified with respect to a literature problem and then applied to the case of classification of transients in a nuclear component.
06/00432 Importance of atmospheric turbidity and associated uncertainties in solar radiation and luminous efficacy modelling Gueymard, C. A. Energy, 2005, 30, (9), 1603 1621. For many solar-related applications, it is important to separately predict the direct and diffuse components of irradiance or illuminance. Under clear skies, turbidity plays a determinant role in quantitatively affecting these components. In this paper, various aspects of the effect of turbidity on both spectral and broadband radiation are addressed, as well as the uncertainty in irradiance predictions due to inaccurate turbidity data, and the current improvements in obtaining the necessary turbidity data.
06•00433 In-situ studies of electron field emission of single carbon nanotubes inside the TEM Jin, C. et al. Carbon, 2005, 43, (5), 1026 1031. Electron field emission characteristics of individual multi-walled carbon nanotubes (MWCNTs) were investigated in situ inside the transmission electron microscope (TEM). For a single MWCNT it was found that while field-emission can hardly occur from the side of the
nanotube, a curved nanotube may result in finite side emission and the best emission geometry is the top emission geometry. Current-voltage ( ~ V ) measurements made at different vacuum conditions and voltage sweeps emphasize the importance of the adsorbates on the electron field emission of MWCNTs. For a contaminated MWCNT, although the field emission current was reduced, the stability of its emission was improved. A current of up to several tens of mA was observed for a single MWCNT, but it was found that long time emission usually results in drastic structure damage that may lead to sudden emission failure.
06100434 coating
Injection and boiling of liquid CO2 with a hydrate
Hirai, S. and Sanda, H. Energy, 2005, 30, ( l l 12), 2275 2283. The effect of a hydrate film on the CO2 droplet size was elucidated when the droplet was injected into high-pressure water. The factors that influence the droplet size and shape are the injection rate, nozzle diameter, temperature, and also the tension and propagation velocity of the hydrate thin film. It was also found that the hydrate film on the droplet will promote the boiling of liquid CO2 when the pressure decreases. These results can be applied to the release of liquid CO2 droplets in the ocean for CO2 sequestration: for example, when the drops rise above 500-m in the ocean, boiling due to decompression should occur.
06100435 Inverse analyses of diffusion processes in type 13X zeolite particles Goubaru, A. et al. Applied Energy, 2005 81 (3), 277 29(/. To determine effective surface self-diffusion coefficients of CO2 within type 13X zeolite particles, at various temperatures (25-70°C), inverse analyses of observed CO2-uptake curves were successfully performed. The obtained effective surface self-diffusion coefficients increase with both the amount adsorbed and the temperature and ranged from 7.8 x 10 m to 1.95 x 10 9 m2/s under the present experimental conditions.
06/00436 Mass attenuation coefficients of saccharides for low-energy X-rays Chitralekha, ef al. Radiation Physics and Chemistcv, 2005, 72, (1), 1 5. Mass attenuation coefficients have been measured for mono- and disaccharides at photon energies 5.947, 6.460 and 14.413 keV. The measured values are compared with theoretical calculations. The agreement between experiment and theory is generally within 5%.
06/00437 Mathematical modelling of NO emissions from high-temperature air combustion with nitrous oxide mechanism Yang, W. and Blasiak, W. Fuel Processing Teclmology, 2005, 86, (9), 943 957. A study of the mathematical modelling of NO formation and emissions in a gas-fired regenerative furnace with high-preheated air was performed. The model of NO formation via N20-intermediate mechanism was proposed because of the lower flame temperature in this case. The reaction rates of this new model were calculated basing on the eddy-dissipation-concept. This model accompanied with thermal-NO, prompt-NO and NO reburning models were used to predict NO emissions and formations. The sensitivity of the furnace temperature and the oxygen availability on NO generation rate has been investigated. The predicted results were compared with experimental values. The results show that NO emission formed by N20intermediate mechanism is of outstanding importance during the hightemperature air combustion (HiTAC) condition. Furthermore, it shows that NO models with N20-route model can give more reasonable profile of NO formation. Additionally, increasing excess air ratio leads to increasing of NO emission in the regenerative furnace.
06•00438 Modelling of proton exchange membrane fuel cell performance based on semi-empirical equations Sadiq AI-Baghdadi, M. A. R. Renewable Energy, 2005, 30, (10), 1587 1599. Using semi-empirical equations for modelling a proton exchange membrane fuel cell is proposed for providing a tool for the design and analysis of fuel cell total systems. The focus of this study is to derive an empirical model including process variations to estimate the performance of fuel cell without extensive calculations. The model take into account not only the current density but also the process variations, such as the gas pressure, temperature, humidity, and utilization to cover operating processes, which are important factors in determining the real performance of fuel cell. The modelling results are compared well with known experimental results. The comparison shows good agreements between the modelling results and the experimental data. The model can be used to investigate the influence of process variables for design optimization of fuel cells, stacks, and complete fnel cell power system.
Fuel and Energy Abstracts
January 2006
59