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Chinese Annals of Mathematics,Series B 2004年第3期25卷 287-318页

作者： K.h.KARLSEN J.d.TOWERS departmentofMathematics UniversityofBergenJohs.Brunsgt.12N-5008BergenNorway MiraCostaCollege 3333ManchesterAvenueCardiff-by-the-SeaCA92007-1516USA

The authors give the first convergence proof for the Lax-Friedrichs finite differencescheme for non-convex genuinely nonlinear scalar conservation laws of the formu_t + f(k(x, t), u)_x = 0,where the coefficient k(x, t) is allowed to be discontinuous along curves in the (x, t)plane. In contrast to most of the existing literature on problems with discontinuouscoefficients, here the convergence proof is not based on the singular mapping approach,but rather on the div-curl lemma (but not the Young measure) and a Lax type en-tropy estimate that is robust with respect to the regularity of k(x, t). Following [14],the authors propose a definition of entropy solution that extends the classical Kruzkovdefinition to the situation where k(x, t) is piecewise Lipschitz continuous in the (x, t)plane, and prove the stability (uniqueness) of such entropy solutions, provided that theflux function satisfies a so-called crossng condition, and that strong traces of the solu-tion exist along the curves where k(x, t) is discontinuous. It is shown that a convergentsubsequence of approximations produced by the Lax-Friedrichs scheme converges tosuch an entropy solution, implying that the entire computed sequence converges.

关键词： Conservation law discontinuous coefficient Nonconvex flux LaxFriedrichs difference scheme Convergence Compensated compactness Entropy condition Uniqueness

Structural,optical and mechanical properties of ternary CaO-CaF_(2)-P_(2)O_(5) glasses

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Journal of Advanced Ceramics 2014年第2期3卷 109-116页

作者： G.VENKATESWARA RAO h.d.ShAShIKALA department of Physics National Institute of Technology KarnatakaSurathkalPost SrinivasanagarMangalore-575025KarnatakaIndia

The ternary phosphate glass series(50-x)CaO-xCaF_(2)-50P_(2)O_(5)(x=0-20 mol%)were synthesized using melt quench ***,optical and mechanical properties were investigated with increase in CaF_(2) *** X-ray diffraction(XRd),synthesized glasses were confirmed to be amorphous in *** of oxygen ions by fluorine ions increased the values of *** in refractive index due to the low polarizability of fluorine ions in the glass matrix was *** Fourier transform infrared(FTIR)spectra,the slight variation in v_(as)(PO_(2))band position and intensity could be attributed to replacement of fluorine ions for oxygen ions in phosphate glass *** data were well supported by Raman *** band gap energy increased from 3.44 eV to 3.64 eV with increase in CaF_(2) content,and Urbach energy decreased suggesting that the fluorine ions reduced the tail energy states in the band gap compared to the oxygen *** parameters such as Vickers hardness,fracture toughness and brittleness were evaluated from the Vickers micro indentation *** in Vickers hardness,decrease in fracture toughness and increase in brittleness were observed with increase in CaF_(2) content.

关键词： phosphate glass Fourier transform infrared(FTIR)spectra Raman spectra mechanical properties

A study on Cr(Ⅵ)reduction from aqueous solutions by bauxite

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Journal of Central South University 2014年第5期21卷 1961-1967页

作者： M.d.TURAN h.S.ALTUNdOGAN department of Metallurgical and Materials Engineering Firat University department of Bioengineering Firat University

The reduction of Cr（Ⅵ） in aqueous solution by using bauxite ore was *** results for Cr（Ⅵ）reduction in aqueous solution depending on some factors such as time,sulfuric acid amount,bauxite dosage,initial Cr（Ⅵ）concentration,formic acid concentration,daylight and temperature were *** obtained results show that sulfuric acid amount,bauxite dosage and initial Cr（Ⅵ） concentration of solution are most effective parameters on the reduction ***,it has been found that the 60 g/L of bauxite dosage is sufficient to reduce up to 100% of Cr（Ⅵ） from acidic solution under the condition of low initial Cr（Ⅵ） mass concentrations such as 10 mg/*** reduction reaction is completed within 30 min at 25 ℃ under the experimental conditions：bauxite dosage of 60 g/L,amount of sulfuric acid 40-60 stoichiometric and initial mass concentration of Cr（Ⅵ）,10 mg/*** was determined that reduction percentage is decreasing with increasing initial Cr（Ⅵ） *** chemical oxygen demand of bauxite ore was found to be 26 mg COd/g.

关键词： bauxite ore chromium reduction sulfitric acid

Leaching of copper from chalcopyrite concentrate by using ammonium persulphate in an autoclave:determination of most suitable impeller type by using response surface methodology

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Journal of Central South University 2013年第3期20卷 622-628页

作者： M.d.Turan h.S.Altundogan department of Metallurgical and Materials Engineering Fιrat UniversityElaz 23279Turkey department of Bioengineering F rat UniversityElaz 23279Turkey

Some effective parameters on the copper extraction from Kiire chalcopyrite concentrate were optimized by using response surface methodology （RSM）. Experiments designed by RSM were carried out in the presence of ammonium persulfate （APS） and different types of impeller in an autoclave system. Ammonium persulfate concentration and leaching temperature were defined numerically and three types of impellers were defined categorically as independent variables using experimental design software. The optimum condition for copper extraction from the chalcopyrite concentrate is found to be ammonium persulfate concentration of 277.77 kg/m3, leaching temperature of 389.98 K and wheel type of impeller. The proposed model equation using RSM has shown good agreement with the experimental data, with correlation coefficients R2 and RaZaj for the model as 0.89 and 0.84, respectively.

关键词： copper chalcopyrite leaching response surface methodology ammonium persulfate optimization

Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

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Acta Mechanica Sinica 2017年第5期33卷 846-854页

作者： h.W.Zhu P.d.Cheng W.Li J.h.Chen Y.Pang d.Z.Wang Shanghai Investigation Design & Research Institute Co. Ltd Institute of Environmental Science and Engineering Hohai University Key Laboratory for Mechanics in Fluid Solid Coupling System Institute of Mechanics Chinese Academy of Science Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

Vertical distribution processes of sediment contaminants in water were studied by flume experiments. Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants, especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.

关键词： Sediment resuspension Pollutants Concentration distribution desorption Partition coefficient

dRYING OF GRANULAR MATERIALS IN AGITATEd FLUIdIZEd BEd

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Journal of hydrodynamics 2001年第2期13卷 29-31页

作者： Ma, J.h. Liu, h. Feng, d.Z. dept. of Air-Condition Eng. Shandong Inst. of Civil Eng. Jinan 250014 China

An experimental study of the drying characteristics of an agitated fluidized bed dryer is presented and discussed. In the study, the citric acid particles were used as bed material with the diameters ranging from 0.2 mm to 1.3 mm. The variables affecting apparently the drying rate were found to be the mass flow rate, the inlet air temperature, the rotary speed of agitating mechanism and the particles feed rate. Comparing with other variables considered, mass flow rate was found to have the least important influence on the drying rate. The agitated fluidized bed dryer is suitable to drying agglomerating or sticky materials.

关键词： dryers (equipment) drying Experiments Mass transfer

Phase Formation and Magnetic Properties of Nanocomposite Nd-Fe-B Adjusted by Small Amount of dy and Co

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Journal of Rare Earths 2004年第z2期22卷 89-94页

作者： T S Jang T W Lim h S Aum d h Lee M B Kim division of Materials and Chemical Engineering Sun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Mechanical EngineeringSun Moon University 100 Kalsan LiTangjung MyonAsan CityChoongnam 336-708Korea Division of Materials and Chemical EngineeringSun Moon UniversityKorea Division of Materials and Chemical EngineeringSun Moon UniversityKorea

In order to improve and stabilize the magnetic properties of nanocomposite Nd2Fe14B/α-Fe magnetic alloys by a compositional adjustment, small amount of dy and/or Co was added to Nd9Fe84B7 alloys. dTA analysis on the amorphous of the alloys took place as the soft magnetic phases were crystallized, and then the hard magnetic Nd2Fe14B was precipitated from them. While α-Fe and a metastable 1:7 (TbCu7-type) phase were formed simultaneously in dy and Co-free alloys, they were crystallized separately at different temperatures after dy or Co was added. This phase separation occurred more clearly in the dy-treated alloys and the other soft magnetic phase Fe3B was also stabilized by dy and/or Co. The 1: 7 phase that was stabilized by dy and/or Co was not eliminated at 700 ℃, decreasing magnetic properties of the alloys. It was eventually disappeared above 725 ℃, but Fe3B was not eliminated even at 750 ℃ when dy was added more than 0.5 at% or Co was added more than 2.0 at%. Amount of Nd2Fe14B in the alloys tended to increase as dy addition increased,whereas Co addition did not lead to any appreciable change in the ratio of α-Fe and Nd2Fe14B. Moreover, dy addition apparently increased coercivity of an alloy while Co addition had a beneficial effect on remanence. The grains in the dytreated alloys were usually finer than those in the Co-treated alloys. The grain size of both α-Fe and Nd2Fe14B in the alloys exhibiting mr ≥ 0.72 was in the range of 20 ～ 40 nm or even larger 50 nm, which is larger than the theoretical optimum size ( ～ 10 nm). Typical magnetic properties obtained from a Nd7.5dy1.5Fe82.5Co1.5B7 alloy annealed for 12 min at 725 ℃were ihc=4.85 kOe, Br= 11.32 kG, (Bh)max = 15.73 MGOe, and mr=0.73.

关键词： nanocomposite Nd-Fe-B magnetic properties remanence coercivity

Optimization of Mass Bleed Control for Base drag Reduction of Supersonic Flight Bodies

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Journal of Thermal Science 2006年第3期15卷 206-212页

作者： Y.-K.Lee h.-d.Kim School of Mechanical Engineering Andong National University388 Songcheon-dongAndong760-749Korea

The minimization of base drag using mass bleed control is examined in consideration of various base to orifice exit area ratios for a body of revolution in the Mach 2.47 freestream Axisymmetric, compressible, rmss-averaged Navier-Stokes equations are solved using the standard k-ω model, a fully implicit finite volume scheme, and a second order upwind scheme. Base flow charcteristics are explained mgaarding the base configuration as well as the injection parameter which is defined as the mass flow rate of bleed jet non-dimensionalized by the product of the base area and fieestream mass flux. The results obtained through the present study show that for a smaller base area, the optimum mass bleed condition leading to minimum base drag occurs at relatively larger mass bleed, and a lalger orifice exit can offer better drag control.

关键词： base drag mass bleed drag reduction separation supersonic flow

The multi-impurity system in CdSe nanoplatelets:electronic structure and thermodynamic properties

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Communications in Theoretical Physics 2024年第3期76卷 165-173页

作者： d A Baghdasaryan V A harutynyan E M Kazaryan h A Sarkisyan Russian-Armenian University H Emin 1230051YerevanArmenia Institute of Applied Problems of Physics 25 Nersisyan St0014YerevanArmenia

This paper theoretically studies the impurity states and the effects of impurity concentration and configuration on the optical,electrical,and statistical properties of CdSe nanoplatelets(NPLs).An image charge-based model of electron-impurity interaction is *** charge-carrier energy spectra and corresponding wave functions depending on the impurity number and configuration are *** electron binding energies are calculated for different NPL *** is shown that the image charge-based interaction potential that arises due to the dielectric constants mismatch is much stronger than the interaction potential that does not take such a mismatch into ***,it is demonstrated that the binding energies are increasing with the number of *** calculate the canonical partition function using the energy levels of the electron,which in turn is used to obtain the mean energy,heat capacity,and entropy of the non-interacting electron *** thermodynamic properties of the non-interacting electron gas that depend on the geometric parameters of the NPL,impurity number,configuration,and temperature are studied.

关键词： nanoplateletes thermodynamic properties impurity states

Atomic-scale simulations of material behaviors and tribology properties for BCC metal film

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Chinese Physics B 2016年第1期25卷 412-418页

作者： h d Aristizabal P A Parra P Lopez E Restrepo-Parra PCM Computational Applications Universidad Nacional de Colombia-Sede ManizalesA.A.127ManizalesColombi Universidad Cató1ica de Manizales A.A.357ManizalesColombia

This work has two main purposes：（i） introducing the basic concepts of molecular dynamics analysis to material scientists and engineers, and （ii） providing a better understanding of instrumented indentation measurements, presenting an example of nanoindentation and scratch test simulations. To reach these purposes, three-dimensional molecular dynamics （Md） simulations of nanoindentation and scratch test technique were carried out for generic thin films that present BCC crystalline structures. Structures were oriented in the plane （100） and placed on FCC diamond substrates. A pair wise potential was employed to simulate the interaction between atoms of each layer and a repulsive radial potential was used to represent a spherical tip indenting the sample. Mechanical properties of this generic material were obtained by varying the indentation depth and dissociation energy. The load-unload curves and coefficient of friction were found for each test; on the other hand, dissociation energy was varied showing a better mechanical response for films that present grater dissociation energy. Structural change evolution was observed presenting vacancies and slips as the depth was varied.

关键词： molecular dynamics pair wise potential repulsive radial potential dissociation energy