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Molecular Dynamics Investigation of Benzene in Supercritical Water

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Chinese Journal of Chemical Engineering 2001年第2期9卷 196-199页

作者：周健汪文川仲崇立 beijing univ Chem Technol Coll Chem Engn Beijing 100029 Peoples R China

Microscopic structure and diffusion properties of benzene in ambient water (298 K, 0.1 MPa) and super critical water (673－773 K, 25－35 MPa) are investigated by molecular dynamics simulation with site-site models. It is found that at the ambient condition, the water molecules surrounding a benzene molecule form a hydrogen bond network. The hydrogen bond interaction between supercritical water molecules decreases dramatically under supercritical conditions. The diffusion coefficients of both the solute molecule and solvent molecule at supercritical conditions increase by 30－180 times than those at the ambient condition. With the temperature approaching the critical temperature, the change of diffusion coefficient with pressure becomes pronounced.

关键词： supercritical water benzene diffusion coefficients molecular dynamics molecular simulation

Microstructures of Sintered Mo-Cu Alloys with Mechanically Activated Powder

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Rare Metals 2001年第2期20卷 112-116页

作者： Chengchang Jia, Zhong He, Xuekuan Su, Ziqin Yang, Jun Zhao, Zizhang Xie (School of Materials Science and Engineering, university of Science and Technology beijing, beijing 100083, China Beliing Polytechnic university, beijing 100022, beijing) univ Sci & Technol beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China beijing Polytech univ Beijing 100022 Peoples R China

Mechanical activation and liquid phase sintering were used to manufacture high performance Mo-Cu alloy and develop new processes. The microstructures and properties of the alloy were investigated. The experimental results showed that: (1) the ball milled Mo/Cu powder has lamellar structure, (2) the microstructures of the sintered Mo-Cu alloy were homogenous compound structures of adhesive phase Cu linking Mo grains, (3) Mo grains frequently strung or gathered in Cu phase, and (4) the full densities of Mo-Cu alloy was achieved through sintering and special densification process. As a result, the properties of the alloy are good enough to satisfy various requirements.

关键词： Mo-Cu alloy powder metallurgy mechanical activation microstructure

High Performance Speech Compression System

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Journal of university of Science and Technology beijing 2001年第3期8卷 229-233页

作者： Ke Liu, Zhichun Mu, Zhong Wang Information Engineering School, university of Science & Technology beijing, beijing 100083, China univ Sci & Technol beijing Informat Engn Sch Beijing 100083 Peoples R China

Since Pulse Code Modulation emerged in 1937, digitized speech has experienced rapid development due to its outstanding voice quality, reliability, robustness and security in communication. But how to reduce channel width without loss of speech quality remains a crucial problem in speech coding theory. A new full-duplex digital speech communication system based on the Vocoder of AMBE-1000(TM) and microcontroller ATMEL 89C51 is introduced. It shows higher voice quality than current mobile phone system with only a quarter of channel width needed for the latter. The prospective areas in which the system can be applied include satellite communication, IP Phone, virtual meeting and the most important, defence industry.

关键词： digital signal processing digital speech compression digital communication full-duplex coding rate

Effect of La_2O_3 nanoparticles on properties of molybdenum powder

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中国有色金属学会会刊：英文版 2001年第6期11卷 860-862页

作者：王金淑周美玲聂祚仁张久兴左铁镛刘娟 beijing Polytech univ Sch Mat Sci & Engn Beijing 100022 Peoples R China

The properties of La 2O 3 doped molybdenum powder were studied. The La 2O 3 nanoparticles on the surface of molybdenum powder which is produced by the reduction of La(NO 3) 3 doped MoO 2 in hydrogen decrease the intensity of feature energy loss peak of molybdenum substrate; but increase that of peak of Mo?3d. The surface of molybdenum powder exposed to the atmosphere can be reduced because the surface is mainly covered with La 2O 3 nanoparticles. As a result, the capability of anti oxidation of molybdenum is improved.

关键词： La 2O 3 doped molybdenum powder XPS nanoparticle

Molecular Simulation of Carbon Dioxide Adsorbed in a Slit Carbon Pore

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Chinese Journal of Chemical Engineering 2001年第1期9卷 34-38页

作者：周健汪文川 beijing univ Chem Technol Coll Chem Engn Beijing 100029 Peoples R China

Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.

关键词： carbon dioxide molecular simulation grand canonical Monte Carlo molecular dynamics adsorption diffusion slit pore

Fluid Inclusions and Daughter Minerals of Taibai Gold Deposit, ShaanXi Province, China

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Journal of university of Science and Technology beijing 2001年第1期8卷 6-9页

作者： YulingXie, Jiuhua Xu, Dayi Qian, Jianping Li Resources Engeneering School, university of Science and Technology beijing, beijing 100083, China univ Sci & Technol beijing Resources Engn Sch Beijing 100083 Peoples R China

A discovery of daughter minerals in fluid inclusions of Taibai gold deposit, Shaanxi province has been focused on, which is a unique breccia-cemented gold-bearing system. The breccia zone strikes NWW-SEE, occurring in Devonian strata of Southern Qinling Mountains. The cement is mainly composed of ankerite, pyrite, calcite and quartz, which may be divided into four main tectonic-mineralizing stages. Gold mainly occurs in pyrite and ankerite of stage II and IV. It is found that three types of fluid inclusions can be distinguished: (1) aqueous inclusions (type B); (2) CO2-rich inclusions (type C); (3) daughter minerals-containing inclusions (type A). LRM. (Laser Raman Micro-probe) analyses shows that the content of CO2 occupies 54.4%-70.7% (mole fraction, so as the follows) in vapor phases of different type fluid inclusions. CH4 (5.2%-7.3%) and H2S (6.0%-12.7%) exist in both vapor and liquid phases. Many daughter minerals in fluid inclusions of ankerite and quartz have been found. Several kinds of daughter minerals, including ankerite, pyrite, arsenopyrite and halite, were determined by using SEM (scanning electron microscope)/EDS (energy dispersive spectrometer) technique. EPMA (electron probe micro-analysis) technique was also applied to study the daughter minerals exposed to the surface of polished thin sections.

关键词： daughter minerals fluid inclusions gold deposit breccia

Function mechanism of carbide layer on surface of La2O3 Mo cathode

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Transactions of Nonferrous Metals Society of China 2001年第1期11卷 26-29页

作者：王金淑周美玲张久兴姚草根聂祚仁左铁镛 beijing Polytech univ Sch Mat Sci & Engn Beijing 100022 Peoples R China

The ion implanting method has been taken for implanting lanthanum ions into the surface layer of molybdenum wires in order to study the function of carbide layer on the surface of La 2O 3 Mo cathode in the emission. The function mechanism has been discussed by using XPS and AES methods. The results show that the carbide layer mainly acts as a reduction reagent to produce metallic lanthanum. Moreover, it can store the activator substance and carry them to the surface. Based on the research results, the carbonization technique has been changed. By applying the new technique, the lifetime of the La 2O 3 Mo cathode has been improved from 14 h to more than 1 000 h—the minimum lifetime for practical uses. [

关键词： carbide layer La 2O 3 Mo cathode reduction lifetime

Emission mechanism of Mo-Y_2O_3 cathode

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中国有色金属学会会刊：英文版 2000年第5期10卷 576-579页

作者：王金淑周美玲聂祚仁张久兴罗丰华左铁镛 beijing Polytech univ Sch Mat Sci & Engn Beijing 100022 Peoples R China

The valence of element yttrium of Y 2O 3 Mo cathode material was studied by thermal analysis, X ray diffraction analysis, scanning electron microscopy and X ray photoelectron spectra, and the emission mechanism of Mo Y 2O 3 cathode was discussed. It was proved that reaction between powder Y 2O 3 and Mo 2C can happen at 1 173 K, and Y 2O 3 be reduced to metallic yttrium. After the powder mixture of Y 2O 3 and Mo 2C is heat treated at 1 873 K, yttrium exists in two kinds of state—yttrium of zero valence and yttrium of three valences. The formation of monoatomic layer of metallic yttrium at the surface of filament is the cause of emissivity of the cathode. Yttrium at the surface doesn’t provide emission current, but the momoatomic active surface layer has a lower work function than clean molybdenum. [

关键词： emission mechanism Mo Y 2O 3 cathode valence yttrium

Surface Carbonization of Mo La_2O_3 Cathode

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中国有色金属学会会刊：英文版 1999年第3期9卷 442-445页

作者： Nie Zuoren(聂祚仁), Zuo Tieyong(左铁镛), Zhou Meiling(周美玲), Liu Danmin(刘丹敏), Wang Jinshu(王金淑) School of Materials Science and Engineering, beijing Polytechnic university, beijing 100022, P.R. China beijing Polytech univ Sch Mat Sci & Engn Beijing 100022 Peoples R China

The carbonized structures of Mo La 2O 3 cathode specimens have been investigated by means of FESEM and XRD, respectively. The substructure of carbonized layer in the Mo La 2O 3 cathode has been found for the first time. The results showed that the carbonized layer with uniform Mo 2C was helpful to emission, while the demixing carbonized layer with a compact MoC outside layer was harmful to emission. The uniform Mo 2C layer consists of coarse particles with lots of grain boundary crevices as well as holes arranging perpendicular to the wire axle and up to surface, which was beneficial to the migration of activated rare earth in activation and operating.

关键词： microstructure cathodes Mo La 2O 3 carbonization emissionDocument code:A