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MONTE CARLO SIMULATION OF SPIN-POLARIZED SECONDARY ELECTRONS FROM IRON

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 325-330页

作者： k. Salma Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics University of Science and Technology of China

A Monte Carlo model considering the electron spin direction and spin asymmetry h as been developed. The energy distribution of the secondary electron polarizatio n and the primary energy dependence of the polarization from Fe are studied. The simulation results show that: (1) the intensity of the spin-up secondary electr ons is larger thanvthat of thevspin-down secondary electrons, suggesting the s econdary electrons are spin polarized; (2) the spin polarization of secondary el ectrons with nearly zero k.netic energy is higher than the average valance spin polarization, Pb=27% for Fe. With increasing k.netic energy, the spin polarizat ion of the secondary electrons decreases to the value of Pb, remaining constant at higher k.netic energies; (3) the spin polarization increases with an increase in the primary energy and reaches a saturation value at higher primary energy i n both the Monte Carlo simulation and experimental results.

关键词： spin polarization secondary electron spin asymmetry Monte Carlo

ENERGY DISTRIBUTION OF BACk.CATTERED ELECTRONS FROM HEAVY METALS

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 345-350页

作者： k. Salma Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics University of Science and Technology of China

The full energy distribution of back.cattered electrons from the elastic peak.do wn to the true-secondary electron peak.for heavy metals, Ta, W, Pt and Au, in Au ger electron spectroscopy in the EN(E) mode has been studied with a Monte Carlo simulation method, which includes cascade-secondary-electron production. The sim ulation model is based on the use of a dielectric function for describing inelas tic scattering and secondary excitation, and on the use of Mott cross sections f or elastic scattering. A systematic comparison between the calculated and experi mental spectra measured with a cylindrical mirror analyzer has been made for pri mary energies ranging from 1 to 5k.V. Excellent agreement was obtained for these heavy metals on the back.cattering back.round at primary energies in the k.V re gion. A significant contribution of cascade secondary electrons to the measured spectra on the low-energy side was found.

关键词： back.cattered electrons Monte Carlo AES heavy metal

Drop formation at nozzles submerged in quiescent continuous phase： an experimental study with TBP-dodecane and nitric acid system

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Nuclear Science and Techniques 2018年第6期29卷 110-118页

作者： Amitava Roy MayurDarek.r k. k. Singh k. T. Shenoy R. B. Grover Homi Bhabha National Institute Anushaktinagar Mumbai 400094 India Chemical Engineering Division Bhabha Atomic Research Centre Mumbai 400085 India

Solvent extraction is an important process in the nuclear fuel cycle. Tributyl phosphate(TBP) diluted with dodecane is commonly used as a solvent for extracting heavy metals from nitric acid medium. Studies on hydrodynamics of a single drop, which is the smallest mass transfer entity, are required for better understanding of the complex mass transfer and phase separation phenomena that occur in extraction equipment. In this study, drop formation at nozzles is studied using 30% TBP-dodecane as the dispersed phase and dilute nitric acid as the quiescent continuous phase. Experiments are carried out to determine the drop diameter, jetting velocity, drop detachment height and drop detachment time for various dispersed phase velocities, nozzle diameters(1.91, 3.04, and 4.88 mm), and nitric acid concentrations(0.01, 1, 3 N). Drop formation is captured using high-speed imaging, which enables quantification of drop size, onset of jetting, drop detachment height, and drop detachment time. Experimental data are used to propose correlations for predicting drop diameter and minimum jetting velocity. The correlations are found to be very accurate with average absolute relative errors being 5.23 and 2.97%, respectively.

关键词：试验性硝酸静止沉没系统高速度分离现象磷酸盐

Cloning ＆ sequence identification of Hsp27 gene and expression analysis of the protein on thermal stress in Lucilia cuprina

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Insect Science 2016年第4期23卷 555-568页

作者： Manish k. Singh Pramod k. Tiwari Center for Genomics Molecular & Human Genetics Jiwaji University Gwafior 474011 Cytogenetics Laboratory Department of Zoology Banaras Hindu University Varanasi 221005 India

Hsp27, a highly conserved small molecular weight heat shock.protein, is widely k.own to be developmentally regulated and heat inducible. Its role in thermotolerance is also implicated. This study is a sequel of our earlier studies to understand the molecular organization of heat shock.genes/proteins and their role in development and thermal adaptation in a sheep pest, Lucilia cuprina （blowfly）, which exhibits unusually high adaptability to a variety of environmental stresses, including heat and chemicals. In this report our aim was to understand the evolutionary relationship of Lucilia hsp27 gene/protein with those of other species and its role in thermal adaptation. We sequence characterized the Lchsp27 gene （coding region） and analyzed its expression in various larval and adult tissues under normal as well as heat shock.conditions. The nucleotide sequence analysis of 678 bps long-coding region of Lchsp27 exhibited closest evolutionary proximity with Drosophila （90.09%）, which belongs to the same order, Diptera. Heat shock.caused significant en- hancement in the expression ofLchsp27 gene in all the larval and adult tissues examined, however, in a tissue specific manner. Significantly, in Malpighian tubules, while the heatinduced level ofhsp27 transcript （mRNA） appeared increased as compared to control, the protein level remained unaltered and nuclear localized. We infer that Lchsp27 may have significant role in the maintenance of cellular homeostasis, particularly, during summer months, when the fly remains exposed to high heat in its natural habitat.

关键词： heat shock.protein Hsp27 Lucilia cuprina thermal stress

Stochastic analysis of laminated composite plate considering stochastic homogenization problem

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Frontiers of Structural and Civil Engineering 2015年第2期9卷 141-153页

作者： S. SAk.TA k. Ok.DA k. Ik.DA Department of Mechanical Engineering Kinki University 3-4-I Kowakae Higashiosaka Osaka 577-8502 Japan

This paper discusses a multiscale stochastic analysis of a laminated composite plate consisting of unidirectional fiber reinforced composite laminae. In particular, influence of a microscopic random variation of the elastic properties of component materials on mechanical properties of the laminated plate is investigated. Laminated composites are widely used in civil engineering, and therefore multiscale stochastic analysis of laminated composites should be performed for reliability evaluation of a composite civil structure. This study deals with the stochastic response of a laminated composite plate against the microscopic random variation in addition to a random variation of fiber orientation in each lamina, and stochastic properties of the mechanical responses of the laminated plate is investigated. Halpin-Tsai formula and the homogenization theory-based finite element analysis are employed for estimation of effective elastic properties of lamina, and the classical laminate theory is employed for analysis of a laminated plate. The Monte-Carlo simulation and the first-order second moment method with sensitivity analysis are employed for the stochastic analysis. From the numerical results, importance of the multiscale stochastic analysis for reliability evaluation of a laminated composite structure and applicability of the sensitivity-based approach are discussed.

关键词： stochastic homogenization multiscale stochastic analysis microscopic random variation laminated composite plate

Numerical Blow-up for a Nonlinear Heat Equation

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Acta Mathematica Sinica,English Series 2011年第5期27卷 845-862页

作者： Firmin k. N'GOHISSE Theodore k. BONI Universite d'Abobo-Adjame UFR-SFA Departement de Mathematiques et Informatique 01 BP 1003 Abidjan 01 Cdte d'Ivoire Institut National Polytechnique Houphouet-Boigny de Yamoussouk.o BP 1093 Yamoussoukro Cote d'Ivoire

This paper concerns the study of the numerical approximation for the following initialboundary value problem{ut-uzx=f（u）,t∈（0,1）,t∈（0,T） u（0,t）=0,t∈（0,1）,t∈（0,T） u（x,0）=u0（x）,x∈（0,1）where f（s） is a positive, increasing, C1 convex function for the nonnegative values of s, f（0）〉0, f∞ds/f（s）〈∞, u0∈C1（[0, 1]）, u0（0） = 0, u＇0（1）=0. We find some conditions under which the solution of a semidiscrete form of the above problem blows up in a finite time and estimate its semidiserete blow-up time. We also prove the convergence of the semidiscrete blow-up time to the theoretical one. A similar study has been also undertak.n for a discrete form of the above problem. Finally, we give some numerical results to illustrate our analysis.

关键词： Semidiscretization blow-up numerical blow-up time nonlinear heat equations

Photolysis studies on HCOOH and HCOO^- in presence of TiO_2 photocatalyst as suspension in aqueous medium

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Journal of Natural Gas Chemistry 2009年第1期18卷 50-54页

作者： G. R. Dey k. N. R. Nair k. k. Pushpa Radiation and Photochemistry Division Bhabha Atomic Research Centre Trombay Mumbai 400 085 India

Photolysis studies on formic acid （HCOOH） and formate ion （HCOO-） in presence of TiO2, a photocatalyst, as suspension in water were carried out separately using 350 nm ultraviolet light. The products, such as H2, CO, CO2 and CH4, generated during the experiments were monitored with varying the ambient, light exposure time, and the concentration of HCOOH/HCOO-. The yields of CO in all these systems increased with light exposure time. In aerated systems, CO yields were higher in contrast to the deoxygenated （Ar-purged） systems under identical conditions. It is proposed apparently that the formation of CO is tak.ng place during the chemical reduction of in-situ generated CO2, a photo-mineralized product of HCOOH/HCOO-, but not through the direct photodecomposition or photodehydration （CO＋H2O） of solute molecules. The rates of CO formation during 1.3 M HCOOH photolysis in presence of TiO2 photocatalyst were evaluated to be 0.21 and 0.13 μl/min in aerated and Ar-purged systems, respectively. As compared with HCOOH systems, the CO yields are lower when 0.2 M HCOONa was exposed to light under identical conditions. The CO growth rates were evaluated to be 0.07 and 0.046 μl/min^-1 for aerated and deoxygenated HCOONa systems, respectively; moreover, the trend is quite similar to that of the HCOOH system. Under these conditions, the emission of H2 was also observed, and its yield was significantly higher in Ar-purged system as compared with the CO yields. However, in aerated system, the yields of these products were just opposite. The formation of low yield of methane was observed during photolysis of HCOOH/HCOO ions. In CO2 ambient, the yields of CO and H2 varied drastically with time.

关键词： formic acid formate ion photolysis TiO2

Catalytic ignition of light hydrocarbons

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Journal of Natural Gas Chemistry 2009年第2期18卷 115-123页

作者： k. L. Hohn Department of Chemical Engineering Kansas State UniversityManhattan KS 66506-5102 USA

Catalytic ignition refers to phenomenon where sufficient energy is released from a catalytic reaction to maintain further reaction without additional external heating. This phenomenon is important in the development of catalytic combustion and catalytic partial oxidation processes, both of which have received extensive attention in recent years. In addition, catalytic ignition studies provide experimental data which can be used to test theoretical hydrocarbon oxidation models. For these reasons, catalytic ignition has been frequently studied. This review summarizes the experimental methods used to study catalytic ignition of light hydrocarbons and describes the experimental and theoretical results obtained related to catalytic ignition. The role of catalyst metal, fuel and fuel concentration, and catalyst state in catalytic ignition are examined, and some conclusions are drawn on the mechanism of catalytic ignition.

关键词： catalytic ignition hydrocarbon oxidation

Analysis Scheme for Density Modulation Experiments to Study Particle Confinements

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Plasma Science and Technology 2006年第1期8卷 65-71页

作者： k. TANAk. C. MICHAEL k. k.WANATA T. TOk.ZAWAI M. SHOJI k. TOI 高翔揭银先 National Institute for Fusion Science Toki 509-5292 Japan Institute of Plasma Physics Chinese Academy of Science Hefei 230031 China

Density modulation experiments are powerful experimental schemes for the study of particle transport. The diffusion coefficients （D） and convection velocity （V）, which cannot be evaluated from the particle balance in the equilibrium state, can be obtained separately. Further, the estimated values of D and V are determined independent of the absolute value of the particle source rate, which is difficult to obtain experimentally. However, the sensitivities and interpretation of D and V from the modulation experiments need to be considered. This paper describes numerical techniques for solving the particle balance equation of the modulation components. Examples of the analysis are shown regarding the data of LHD experiments, and the results of the modulation experiments are discussed.

关键词： density modulation, particle confinements, diffusion coefficient convection velocity