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Study on H atoms diffusion and adsorption properties of MgH_2-V systems

Science china(Technological Sciences) 2008年第7期51卷 979-988页

作者： ZHOU DianWu1,2, LIU JinShui3.& PENG Ping3.1 State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, hunan university, changsha 410082. china 2 college of Mechanical and Automatic {3., hunan university, changsha 410082. china 3.college of materials Science and {3., hunan university, changsha 410082. china 1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan University Changsha 410082 China 2. college of Mechanical and Automatic engineering Hunan University Changsha 410082 China 3. college of materials Science and engineering Hunan University Changsha 410082 China

Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH2 interface is formed due to V alloying MgH2 phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH2 phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH2-V systems is reduced compared with that of MgH2 phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH2 across VH/MgH2 interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH2 phase region.

关键词： plane-wave pseudopotential theory magnesium hydride diffusion adsorption

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Formation and evolution mechanisms of large-clusters during rapid solidification process of liquid metal Al

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Science china(Physics,Mechanics & Astronomy) 2005年第1期48卷 101-112页

作者： LIU Rangsu, DONG Kejun, LIU Fengxiang, ZHENG Caixing, LIU Hairong & LI Jiyong Department of Applied Physics, hunan university, changsha 410082. china college of {3. Science and engineering, hunan university, changsha 410082. china college of Chemistry and Chemical engineering, hunan university, changsha 410082. china 1. Department of Applied Physics Human University 410082 Changsha China 2. college of materials Science and engineering Hunan University 410082 Changsha China 3. college of Chemistry and Chemical engineering Hunan University 410082 Changsha China

A molecular dynamics simulation study has been performed for the formation and evolution characteristics of nano-clusters in a large-scale system consisting of 400000 atoms of liquid metal Al. The center-atom method combined with pair-bond analysis technique and cluster-type index method (CTIM) has been applied here to describe the structural configurations of various basic clusters. It is demonstrated that both the 1551 bond-type and the icosahedral cluster (12 0 12 0) constructed by 1551 bond-types are dominant among all the bond-types and cluster-types, respectively, in the system and play a critical role in the microstructure transitions of liquid metal Al. The nano-clusters (containing up to 150 atoms) are formed by the combination of some middle and small clusters with distinctly different sizes, through mutual competition by unceasing annex and evolution in a seesaw manner (in turn of obtaining and losing),which do not occur as the multi-shell structures accumulated with an atom as the center and the surrounding atoms are arranged according to a certain rule. This is the essential distinction of nano-cluster in liquid metal from those obtained by gaseous deposition, ionic spray methods, and so on. Though the nano-clusters differ from each other in shape and size, all of them possess protruding corners that could become the starting points of various dendrite structures in the solidification processes of liquid metals.

关键词： liquid metal, solidification process, large-cluster configuration, evolution mechanism, computer simulation.

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Research on Uncertainties in Evaluation Indicator System for Ecological Residential Community

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湖南大学学报（自然科学版） 2009年第S1期36卷 177-181页

作者： JIAO Sheng1,GUAN Chen-yin2,ZENG Guang-ming3.LIU Jian-long1,Zhou Jian-fei3.1.college of Architecture,hunan university,{3.,hunan 410082.china 2.Beijin School,hunan university of Commerce,{3.,hunan 410209,china 3.college of Environmental Science and {13.,hunan university,{3.,hunan 410082.china) college of Architecture Hunan University Changsha 410082 China Beijin School Hunan University of Commerce Changsha 410209 China college of Environmental Science and engineering Hunan University Changsha 410082 China

In the process of evaluating,the weights of indicators are firstly determined by AHP and Delphi methods;and the values of indicators are normalized by grey correlative coefficient method.A suit of means were put forward,by which a qualitative and quantitative evaluation indicator system suitable for the situation of china and uncertainties can be *** idiographic and operable methods and process were *** the principle of elasticity,hiberarchy and maneuverability,a three-layer evaluation indicator system was established by AHP in Jiuyi ecological residential community,which includes 5 subsystems and 24 *** weights of indicators are measured by AHP and expert estimate and their best indicators values up to par were determined by fuzzy mathematics and *** whole evaluation indicator system not only has an active and practical effect on estimating ecological residential community,but also guides ecological residential community planning.

关键词： ecological residential community evaluation indicator system ecological risk evaluation uncertainty fuzzy mathematics grey correlative coefficient

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Condensing Heat Recovery of Centrifugal Chiller

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湖南大学学报（自然科学版） 2009年第S1期36卷 123-126页

作者： GONG Guang-cai,JIAO Jun-jun,WANG Li-ping,ZENG Wei(college of Civil engineering,hunan {3.,changsha,hunan 410082.china) college of Civil engineering Hunan University Changsha 410082 China

To a kind of centrifugal water chiller with R22 and about 1 745 kW of cooling capacity,a heat exchanger was added between the outlet of compressor and original condenser to get part of or all the condensing *** heat can be recovered by compound condensing method,which adopts air-cooling model +water-cooling model or water-cooling model +water-cooling model at the condensing side of the *** exergy analysis and experiment research on compound condensing heat recovery of centrifugal chiller,the results are obtained that the capability of the whole system increases,the energy efficiency ratio(EER)becomes 3.2～5.0 from 2.2～3.4,which implies the EER increases about 1.0～1.5,the exergy efficiency increases about 10%,and the chiller runs more stably after reformation.

关键词： centrifugal chiller condensing heat recovery compound condensing method EER

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A linear ridgelet network approach for fault diagnosis of analog circuit

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Science china(Information Sciences) 2010年第11期53卷 2251-2264页

作者： XIAO YingQun& HE YiGang college of Electrical and Information engineering, hunan university,{3. 1. college of Electrical and Information engineering Hunan University Changsha 410082 China

A linear ridgelet network combining ridgelet, linear term and the standard feed-forward neural network used for diagnosing the faults of analog circuit is constructed, and a training algorithm based on the steepest gradient descent method and momentum method for this network and the procedure for diagnosing these faults are proposed. The resulting linear ridgelet network can learn more rapidly from training samples and handle more effectively the complicated fault information of circuit under test than wavelet network and ridgelet network, classifying these faults effeciently and correctly and achieving a high classification accuracy. The simulation results demonstrate the effectiveness of this approach.

关键词： fault diagnosis of analog circuit ridgelet linear ridgelet network wavelet packet decomposition

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Experimental Study of Thermoelectric Heat Pump Water Heater with Exhaust Heat Recovery from Kitchens

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湖南大学学报（自然科学版） 2009年第S1期36卷 131-135页

作者： LIU Zhong-bing,ZHANG Ling,YANG Zhang,XU Ming,HAN Tian-he(college of Civil engineering,hunan {3.,changsha,hunan 410082.china) college of Civil engineering Hunan University Changsha 410082 China

A new kind of thermoelectric heat pump water heater for kitchens exhaust heat recovery was presented,and its performances were investigated under different operating *** experiment results show that the coefficient of performance decreases and the temperature difference between the hot and cold sides becomes larger with the increase of the operating voltage,but the heating time becomes *** higher the temperature of water,the greater the temperature difference between the hot and cold sides,leading to a smaller coefficient of *** an exhaust temperature of 3. ℃,the coefficient of performance decreases from 1.66 to 1.22 when the temperature of water increases from 28 ℃ to 46 ℃ with operating voltage 16 *** tests illustrate that,compared with the conventional electrical water heaters,the new kind of thermoelectric heat pump water heater is more coefficient.

关键词： thermoelectric heat pump kitchens exhaust water heater coefficient of performance

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Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

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Science china(Technological Sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2 & LUO ChengPing2 1 Center for High Resolution Electron Microscopy, college of materials Science and engineering,{3., changsha 410082. china 2 college of Mechanical engineering, South china university of Technology, Guangzhou 510641, china 1. Center for High Resolution Electron Microscopy College of Materials Science and Engineering Hunan University Changsha 410082 China 2. college of Mechanical engineering South China University of Technology Guangzhou 510641 China

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-S relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the γN and the α-matrix deviate from the accurate K-S OR, and the OR between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 20, nitriding, composite chromizing

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Influence of Horizontal Flow on Atrium in High-Rise Residential Building

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湖南大学学报（自然科学版） 2009年第S1期36卷 15-18页

作者： LI Nian-ping,LI Jing,HE Dong-yue,ZHANG Min-hui,HOU Su-juan(college of Civil engineering,hunan {3.,changsha,hunan 410082.china) college of Civil engineering Hunan University Changsha 410082 China

In this study a 10-storied residential building model was employed to clarify the ventilation characteristics of the atrium and the rooms,which were effected by the different forms of lateral *** experiment was conducted under the combined effect of wind force and thermal buoyancy,and the similarity requirements were *** results have shown that the different forms of lateral openings cause the different ventilation effect of the building,and also have some certain *** conclusions provide a theoretical foundation for how to use the ventilation of atrium better in high-rise residential building.

关键词： high-rise residential building atrium model experiment horizontal flow natural ventilation

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Optimal design study of high order FIR digital filters based on neural network algorithm

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Journal of Systems engineering and Electronics 2004年第2期15卷 115-119,130页

作者： Wang Xiaohua & He Yigangcollege of Electrical and Information engineering, hunan university, {3. 410082. P. R. china college of Electrical and Information engineering, {3. university of Science and Technology,{3. 410077, P. R. china college of Electrical and Information engineering Hunan University Changsha 410082 P. R. China college of Electrical and Information engineering Changsha University of Science and Technology Changsha 410077 P. R. China

An optimal design approach of high order FIR digital filter is developed based on the algorithm of neural networks with cosine basis function . The main idea is to minimize the sum of the square errors between the amplitude response of the desired FIR filter and that of the designed by training the weights of neural networks, then obtains the impulse response of FIR digital filter . The convergence theorem of the neural networks algorithm is presented and proved, and the optimal design method is introduced by designing four kinds of FIR digital filters , i.e., low-pass, high-pass, bandpass , and band-stop FIR digital filter. The results of the amplitude responses show that attenuation in stop-bands is more than 60 dB with no ripple and pulse existing in pass-bands, and cutoff frequency of passband and stop-band is easily controlled precisely .The presented optimal design approach of high order FIR digital filter is significantly effective.

关键词： high order FIR digital filters amplitude-frequency response neural network convergence theorem optimal design.

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Experimental Study of Performance of Thermoelectric Refrigerator under Different Intensity of Heat Emission

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湖南大学学报（自然科学版） 2009年第S1期36卷 127-130页

作者： HAN Tian-he,TANG Guang-fa,GONG Guang-cai,LI Tao,LIU Zhong-bing(college of Civil engineering,hunan {3.,changsha,hunan 410082.china) college of Civil engineering Hunan University Changsha 410082 China

Heat emission and the voltage are the main factors affecting the refrigerating capacity of semiconductor *** experiments were designed to obtain their influence on refrigerating capacity of semiconductor and the interaction between heat emission and the *** results show that fixing the heat dissipation,there is an optimal working voltage for the semiconductor module;and if improving the heat emission,the refrigerating capacity increases and the optimal voltage becomes *** can provide the basis for the optimal design of semiconductor refrigeration.

关键词： semiconductor refrigeration heat emission optimal working voltage

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