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Preparation and Characterization of Polylactide/Montmorillonite Nanocomposites

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Journal of Wuhan University of Technology(Materials Science) 2009年第4期24卷 562-565页

作者：吴选军 School of Chemical engineering Wuhan University of Technology

The montmorillonite, a form of layered silicate, was successfully intercalated into polylactide （PLA） matrix through solvent-casting technique. In addition, PLA/MMT nanocomposite films were produced, in which homogenous distribution of the silicate lamellae plays a key role in the mechanical properties of the films. A small amount（5wt%） of OMMT intercalated into the PLA matrix resulted in their flexibility enhancement, from 3.68%（pure PLA film） to 352.65%. The results of wide-angle X-ray diffraction （WAXD） patterns confirmed that the silicate interlayer distance increased from 3.044 nm （for OMMT） to 3.56nm （for 5wt%, maximum） with increasing OMMT contents, but decreased to 3.31. nm when OMMT content was over 8wt%. FT-IR also verified the molecular-level associations between PLA chains and OMMT lamellae by vibration variances of hydrogen bonding. DSC thermograms demonstrated that thermal stabilities of the nanocomposite films enhanced, due to the silicate lamellae dispersed into PLA matrix.

关键词： polylactide montmorillonite nanocomposite characterization thermo-mechanic at property

Application analysis of empirical mode decomposition and phase space reconstruction in dam time-varying characteristic

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Science China(Technological Sciences) 2010年第6期53卷 1711-1716页

作者： ZHANG ZhiJun1.2,3,GU ChongShi1.2,BAO TengFei1.2,ZHANG Lan1.2 & YU Hong1.2 1.State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering,Hohai University,Nanjing 21.098,China 2 {1. engineering Research Center of Water Resources Efficient Utilization and engineering Safety,Hohai University,Nanjing 21.098,China 3 Department of Civil,Environmental and Geomatic engineering,Swiss Federal Institute of Technology,Zurich 8093,Switzerland 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic engineering Hohai University Nanjing 210098 China2. National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety Hohai University Nanjing 210098 China3. Department of Civil Environmental and Geomatic Engineering Swiss Federal Institute of Technology Zurich 8093 Switzerland

In view of some courses of the time-varying characteristics processing in the analysis of dam deformation,the paper proposes a new method to analyze the dam time-varying characteristic based on the empirical mode decomposition and phase space reconstruction *** of all,to reduce the influences on the traditional statistical model from human factors and assure the analysis accuracy,response variables of the time-varying characteristic are obtained by the way of the empirical mode decomposition;and then,a phase plane of those variables is reconstructed to investigate their processing *** methods have already been applied to an actual project and the results showed that data interpretation with the assists of empirical mode decomposition and phase space reconstruction is effective in analyzing the perturbations of response variables,explicit in reflecting the entire development process,and valid for obtaining the evolution rules of the time-varying *** methodology is a powerful technical support for people to further master the rules of dam operation.

关键词： dam safety monitoring dam time-varying characteristic empirical mode decomposition phase space reconstruction

Robust multiuser MIMO scheduling algorithms with imperfect CSI

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Science China(Information Sciences) 2012年第4期55卷 815-826页

作者： MAO JunLing 1.3,GAO JinChun 1.3,LIU YuanAn 1.3,XIE Gang 2,3 & ZHANG Jian 1.3 1.School of Electronic engineering,Beijing University of Posts and Telecommunications,Beijing 1.0876,China 2 School of Information and Communication engineering,Beijing University of Posts and Telecommunications,Beijing 1.0876,China 3 Key Lab of Universal Wireless Communications,Ministry of Education,Beijing University of Posts and Telecommunications,Beijing 1.0876,China 1. School of Electronic engineering Beijing University of Posts and Telecommunications Beijing 100876 China3. Key Lab of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China2. School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Robust multiuser multiple-input-multiple-output (MIMO) scheduling algorithms are proposed in this *** imperfect channel state information (CSI),traditional scheduling algorithms for the multiuser MIMO system based on the zero forcing precoding scheme will lose some performance due to the multi-user interference (MUI).In order to improve the system average throughput,we study the robust multiuser MIMO scheduling problem with imperfect *** the average capacity formula,we derive a robust factor which can transform the robust multiuser MIMO scheduling problem into the traditional one,thus most existing non-robust scheduling algorithms can be robust if this factor is *** results show that compared with the traditional algorithms,the proposed robust algorithms can improve the system average throughput significantly under the CSI error environment.

关键词： multiuser MIMO (MU-MIMO) scheduling robust imperfect CSI

Optimal guaranteed cost control for fuzzy descriptor systems with time-varying delay

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Journal of Systems engineering and Electronics 2008年第3期19卷 584-591页

作者： Tian Weihua1.2 & Zhang Huaguang3 1. School of Information Science and engineering, Northeastern Univ., Shenyang 1.0004, P. R. China 2. Dept. of Automatic Control, Shenyang Inst. of engineering, Shenyang 1.01.6, P. R. China 3. School of Information Science and engineering, Northeastern Univ., Shenyang 1.0004, P. R. China. (Received December 27, 2006) [a]School of Information Science and engineering Northeastern Univ. Shenyang 1.0004 P. R. China [b]Dept. of Automatic Control Shenyang Inst. of engineering Shenyang 1.01.6 P. R. China [c]School of Information Science and engineering Northeastern Univ. Shenyang 1.0004 P. R. China

Based on the delay-independent rule, the problem of optimal guaranteed cost control for a class of Takagi-Sugeno （T-S） fuzzy descriptor systems with time-varying delay is studied. A linear quadratic cost function is considered as the performance index of the closed-loop system. Sufficient conditions for the existence of guaranteed cost controllers via state feedback are given in terms of linear matrix inequalities （LMIs）, and the design of an optimal guaranteed cost controller can be reduced to a convex optimization problem. It is shown that the designed controller not only guarantees the asymptotic stability of the closed-loop fuzzy descriptor delay system, but also provides an optimized upper bound of the guaranteed cost. At last, a numerical example is given to illustrate the effectiveness of the proposed method and the perfect performance of the optimal guaranteed cost controller.

关键词： fuzzy descriptor systems optimal guaranteed cost control time-varying delay linear matrix inequalities (LMIs).

3D mathematical model for suspended load transport by turbulent flows and its applications

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Science China(Technological Sciences) 2004年第2期47卷 237-256页

作者： LU Yongjun1.DOU Guoren1.HAN Longxi2,SHAO Xuejun3 & YANG Xianghua1.3 1.Nanjing Hydraulic Research Institute,Nanjing 21.029,China 2.College of Environmental engineering of Hohai University,Nanjing 21.098,China 3.Department of Hydraulic engineering,Tsinghua University,Beijing 1.0084,China 1. Nanjing Hydraulic Research Institute 210029 Nanjing China 2. College of Environmental engineering of Hohai University 210098 Nanjing China 3. Department of Hydraulic engineering Tsinghua University 100084 Beijing China

This paper presents a 3D mathematical model for suspended load transport in turbulent flows. Based on Dous stochastic theory of turbulent flow, numerical schemes of Reynolds stresses for anisotropic turbulent flows were obtained. A refined wall function was employed to treat solid wall boundaries. The equations for 2D suspended load motion and sorting of bed material have been expanded into 3D cases. Numerical results are validated by the measured data of the Gezhouba Project, and proved to be in good agreement with the experimental. The present method has been employed to simulate sediment erosion and deposition in the dam area of Three Gorges Project, and for the operation of the project, siltation process and deposition pattern in the near-dam area of the reservoir, size distribution of the deposits and bed material, and flow fields and sediment concentration fields at different time and elevations are predicted. The predicted results are close to the experimental observations in physical model studies. Thus, a new method is established for 3D simulation of sediment motion in dam areas of multi-purpose water projects.

关键词： turbulent flows, Dou's stochastic theory, nonuniform suspended load, riverbed erosion and deposition, 3D mathematical model, Three Gorges Project.

Pressure effects on the absorption spectra of Na doped in solid Ar

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Science China(Physics,Mechanics & Astronomy) 2004年第5期47卷 550-560页

作者： CUI Tian1. HE Wenjiong1. YIN Hongwei1. MA Yanming1. CHEN Changbo1. ZOU Guangtian1. WEI Mengfu2 & CHEN Changan2 1. national Laboratory of Superhard Materials, Jilin University, Changchun 1.001., China 2. China Academy of {1. Physics, Box 91.-71. Mianyang 621.00, China 1. national Laboratory of Superhard Materials Jilin University 130012 Changchun China 2. China Academy of engineering Physics Box 919-71 621900 Mianyang China

In this work, the pressure influence on the absorption spectra of Na in solid Ar for various trapping sites is extensively investigated at T = 1. K and in the pressure range from 0 to 2.4 GPa by using Monte Carlo method with a constant pressure ensemble (NPT). For the trapping sites of nv = 1. 2, the absorption spectral widths increase progressively, the absorption peaks and the centroid spectral shift (CSS) tend to have a red shift with pressure increasing, even though there is no local structural symmetry change around Na atom caused by pressure. Highly symmetrical trapping site structure (nv = 1. determines a highly symmetrical triplet absorption feature at a low pressure. With the increase in pressure, the action from the Ar crystal field on the three energy levels of the 3p excited state of Na atom increases, resulting in the overlap of the three peaks. Low symmetrical trapping site structure (nv = 2) yields a low symmetrical triplet absorption pattern in which a large separation between the single?and the double?peaks exists at a low pressure. With the increase in pressure, the splitting between the singlet and the doublet increases, and the doublet merges as the pressure is larger than 2.4 GPa.

关键词： Monte Carlo, simulation, absorption spectra, doped system, pressure effect.

Flow instability of buoyant-Marangoni convection in the LEC GaAs melt

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Science China(Technological Sciences) 2008年第4期51卷 397-406页

作者： CHEN ShuXian1.& LI MingWei2,3 1.Aviation engineering Institute, Civil Aviation Flight University of China, Guanghan 61.307, China 2 Institute of Power engineering of Chongqing University, Chongqing 400030, China 3 Research Center of Biological Function Information and Instruments of Chongqing University by Sec-ond-Term national 985 Project, Chongqing University, Chongqing 400030, China Aviation engineering Institute Civil Aviation Flight University of China Guanghan 618307 China Institute of Power engineering of Chongqing University Chongqing 400030 China Research Center of Biological Function Information Instruments of Chongqing University by Second-Term national 985 Project Chongqing University Chongqing 400030 China

Flow transitions and instabilities have significant effects on the quality of the crystals. The flow and heat transfer in the LEC GaAs melt are numerically studied by a time-dependent and three-dimensional turbulent flow model. The effects of the change of the buoyancy and Marangoni force on the flow state are analyzed by changing the temperature difference between the crystal and the crucible walls. The results show that the flow will transform from axisymmetric steady flow to non-axisymmetric oscillatory flow when the temperature difference exceeds the critical value, and that the mechanism of the transition is attributed to the Marangoni instability. The critical temperature differences for the flow transitions corresponding to different melt depth H are numerically predicted. Several important characteristics of the non-axisymmetric buoyant-Marangoni convection are numerically observed and compared with that of the non-axisymmetric mixed convection coupled with crystal rotation.

关键词： flow transition flow instability buoyant-Marangoni convection mixed convection LEC GaAs melt

Research on stability of the accumulated rock-soil body of reservoir bank under rainfall condition

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Science China(Technological Sciences) 2009年第9期52卷 2528-2535页

作者： GU ChongShi1.2,WU HaiZhen1.2 & SU HuaiZhi1.2 1.College of Water Resources and Hydropower engineering,Hohai University,Nanjing 21.098,China 2 {1. engineering Research Center of Water Resources Efficient Utilization and engineering Safety,Hohai University,Nanjing 21.098,China 3 Jiangxi Water Conservancy Research Institute,Nanchang 330029,China 1. College of Water Resources and Hydropower engineering Hohai University Nanjing 210098 China 2. national {1. Research Center of Water Resources Efficient Utilization and {1. Safety Hohai University Nanjing 210098 China 3. Jiangxi Water Conservancy Research Institute Nanchang 330029 China

The shear strength parameters property of rock-soil aggregates in embankment slope of reservoir,that is,the relationship between cohesion and gravel content,between friction angle and gravel content,and the relationship between cohesion and water content,between friction angle and water content,is studied based on the direct shear test results,the shear strength change law of the rock-soil aggregates is given,and the unsaturated shear strength formulation of rock-soil aggregates that could consider suction and saturation degree influence is put forward in this paper,through which the sliding or failure physical mechanism of this type of slope under the condition of rainfall infiltration is studied. Also the 3D unsteady saturated-unsaturated seepage field and its FEM resolving mode are established based on the analysis of the slope rainfall infiltration process. Case study with this method indicates that the minimum safety factor of the accumulated rock-soil aggregates dose not arrive at the moment of rainfall cessation,but appears several hours after the rainfall cessation,this phenomenon is in accordance with the practical slope engineering's failure process and could explain appropriately the slope failure caused by rainfall infiltration. Research results in this paper have an important reference value for the research on stability of the accumulated rock-soil aggregates in embankment slope of reservoir,and can enrich the stability analysis method and relevant theory of reservoir embankment slope.

关键词： reservoir bank slope rock-soil aggregates rainfall infiltration saturated/unsaturated seepage

Effects of binders on the performance of electric double-layer capacitors of carbon nanotube electrodes

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Progress in Natural Science:Materials International 2005年第5期15卷 453-457页

作者： LI Chensha1.*, WANG Dazhi1. ZHANG Baoyou2, WANG Xiaofeng1. CAO Maosheng3 and LIANG Ji1.1. Department of Mechanical engineering, Tsinghua University, Beijing 1.0084, China 2. Center for Analysis and Measurement, Harbin Institute of Technology, Harbin 1.0001. China 3. School of Material Science and engineering, Tsinghua University, Beijing 1.0084, China) Department of Mechanical engineering Tsinghua University Beijing 100084 China Center for Analysis and Measurement Harbin Institute of Technology Harbin 150001 China School of Material Science and engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitor (EDLCs) were made from carbon nanotubes. Effects of different binders, which are phenolic resin (PF) and polytetrafluoroethylene (PTFE), on the properties of polarizable electrodes are studied. Results indicate that the microstructure, pore size distribution and specific capacitance of the electrodes with PTFE binder are superior to those electrodes with PF binder after carbonization. The suitable binder (PTFE) for carbon nanotubes electrodes is proposed.

关键词： carbon nanotubes electric double-layer capacitors phenolic resin polytetrafluoroethylene.