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Large-eddy simulation of formation of three-dimensional aeolian sand ripples in a turbulent field

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science china(Physics,Mechanics & Astronomy) 2008年第8期51卷 945-960页

作者： WU ChuiJie1,WANG Ming2 & WANG Liang3 1 State Key Laboratory of Structural Analysis for Industrial Equipment,Dalian university of Technology,Dalian 116024,china 2 Yellow River Institute of Hydraulic Research,Zhengzhou 450003,china 3 Research center for Fluid Dynamics,science School,PLA university of science and Technology,nanjing 211101,china State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology Dalian 116024 China Yellow River Institute of Hydraulic Research Zhengzhou 450003 China Research center for Fluid Dynamics Science School PLA University of Science and Technology Nanjing 211101 China

With the method of large-eddy simulation,the equation of spherule motion and the method of immersed boundary condition,numerical simulations of three-dimen-sional turbulent aeolian motion and the formation of sand ripples under three-di-mensional turbulent wind and the mutual actions of saltation and creeping motion were carried out. The resulting sand ripples have the form that is flat on the upwind side and steep on the leeward,which is identical to the sand ripples in nature. We also realized the self-restoration process of three-dimensional sand ripples,which shows the correctness of the method of numerical simulation and the models of saltation and creeping. Finally,We analyzed the influence of sand ripples on the three-dimensional turbulent wind field,and found that due to the appearance and development of sand ripples,in the normal direction of ground there exists stronger energy exchange,and moreover,there is close correspondence between the forms of sand ripples and the vorticity close to the ground surface.

关键词： large-eddy simulation equation of spherule motion sand ripples saltation creep

A new measure to characterize multifractality of sleep electroencephalogram

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science Bulletin 2006年第24期51卷 3059-3064页

作者： MA Qianli1,2,NING Xinbao1,WANG Jun2 & BIAN Chunhua1 1. State Key Laboratory of Modern Acoustics,Department of Electronics science and Engineering,Institute for Biomedical Electronic Engi-neering,nanjing university,nanjing 2.0093,china 2. Province Key Laboratory of Image Processing & Image Communica-tion,College of Telecommunications and Information Engineering,nanjing university of Posts & Telecommunications,nanjing 210003,china State Key Laboratory of Modern Acoustics Department of Electronics Science and Engineering Institute for Biomedical Electronic Engineering Nanjing University Nanjing 210093 China Province Key Laboratory of Image Processing & Image Communication College of Telecommunications and Information Engineering Nanjing University of Posts & Telecommunications Nanjing 210003 China

Traditional methods for nonlinear dy-namic analysis,such as correlation dimension,Lyapunov exponent,approximate entropy,detrended fluctuation analysis,using a single parameter,cannot fully describe the extremely sophisticated behavior of electroencephalogram (EEG). The multifractal for-malism reveals more “hidden” information of EEG by using singularity spectrum to characterize its nonlin-ear dynamics. In this paper,the zero-crossing time intervals of sleep EEG were studied using multifractal analysis. A new multifractal measure Δasα was pro-posed to describe the asymmetry of singularity spec-trum,and compared with the singularity strength range Δα that was normally used as a degree indi-cator of multifractality. One-way analysis of variance and multiple comparison tests showed that the new measure we proposed gave better discrimination of sleep stages,especially in the discrimination be-tween sleep and awake,and between sleep stages 3 and 4.

关键词： sleep electroencephalogram multifractality.

Investigation of fine and complex vortex circulation structures

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science china Earth sciences 2010年第10期53卷 1552-1558页

作者： LUO ZheXian1,MA GeLan1 & PING Fan2 1 Remote Sensing College,nanjing university of Information science and Technology,nanjing 210044,china 2 Laboratory of Cloud-Precipitation Physics and Severe Storms(LACS),Institute of Atmospheric Physics,Chinese Academy of sciences,Beijing 100029,china 1. Remote Sensing College Nanjing University of Information Science and Technology Nanjing 210044 China2. Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

The formation and evolution of fine and complicated vortex circulation structures were investigated using a two-dimensional quasi-geostrophic barotropic model *** find that the highly localized asymmetric and complex configuration of energy transfer flux between large-and small-scale components is caused by the nonlinear interaction between a large-scale vortex with an initial axi-symmetric flow and four beta meso-scale *** complex structure is characterized by a fine pattern,which contains seven closed systems with spatial scales of less than 100 km,embedded in a positive flux wave train and a negative wave train,*** average wind speed decreased with time in the positive flux region,but was nearly unchanged in the negative flux *** pattern reveals the evolutionary asymmetry and localization of wind speed of the major *** track of the major vortex center has a trend toward the center of the negative flux center,indicating that there is a certain relation between the complex structure of the energy transfer flux and the motion of the major vortex *** results imply that the formation and evolution of the fine and complex structure should be attributed to the nonlinear interaction between the vortices at different spatial scales.

关键词： vortex complex structure non-linear interaction energy cascade

Eutectic Solidification in Al-13.0%Si Alloys with Combined Addition of Strontium and Boron

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Journal of Materials science & Technology 2009年第4期25卷 437-440页

作者： Hengcheng Liao,Ke Ding,Juanjuan Bi,Min Zhang,Huipin Wang and Lei Zhao School of Materials science and Engineering,Southeast university,nanjing 211198,china Jiangsu Key Laboratory for Advanced Metallic Materials,nanjing 211189,china SE Univ Sch Mat Sci & Engn Nanjing 211198 Peoples R China

The influence of addition of boron （B） on eutectic solidification in a near-eutectic Al-13.0%Si alloy modified with strontium （Sr） was investigated using thermal analysis and macro/microstructure observation. Addition of B in the Sr-modified alloy leads to a considerable increase in nucleation temperature （TN, the minimum temperature prior to recalescence （TM） and growth temperature （To）. In the Sr-modified alloy, nucleation of eutectic might originate at the heterogeneous sites on the mold wall or in the melt near the wall, and eutectic solidification proceeds gradually towards the center, controlled by undercooling of melt. However, with addition of B in the Sr-modified alloy, undercooling required for eutectic nucleation became small, and hence eutectic solidification might occur almost simultaneously within whole casting, controlled by amount of heterogeneous sites. With excessive addition of B in the Sr-modified alloy, nucleation of eutectic grains was explosive within the whole casting and the power of Sr on eutectic solidification was completely poisoned.

关键词： Al-Si alloys Solidification Microstructure Thermal analysis

Design,analysis and control of hybrid excited doubly salient stator-permanent-magnet motor

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science china(Technological sciences) 2010年第1期53卷 188-199页

作者： ZHU XiaoYong1,2 & CHENG Ming1 1 Engineering Research center for Motion Control of MOE,School of Electrical Engineering,Southeast university,nanjing 210096,china 2 School of Electrical and Information Engineering,Jiangsu university,Zhenjiang 212013,china 1. Engineering Research center for Motion Control of MOE School of Electrical Engineering Southeast University Nanjing 210096 China2. School of Electrical and Information Engineering Jiangsu University Zhenjiang 212013 China

In this paper,a new hybrid excited doubly salient stator-permanent-magnet motor is proposed,where both permanent magnets and DC field windings are located in the *** theory,the mathematical model and design method of the motor are *** corresponding output power equation and the relationship between the flux control capability and the extended speed range are deduced in *** using an efficient "one-step" three-dimensional(3D) finite element method,the electromagnetic performances are analyzed,in which the leakage flux outside the stator circumference and end-effect are taken into *** on the operation principle of the motor,the control strategy and scheme are developed and implemented *** experimental results and finite element analysis show that the proposed motor not only maintains the advantages of doubly salient permanent magnet motors,but also offers high energy efficiency over a wide speed range,which makes the motor an interesting candidate for electric vehicles.

关键词： stator permanent magnet motor hybrid excitation doubly salient finite element method flux weakening control

Interhemispheric atmospheric mass oscillation and its relation to interannual variations of the Asian monsoon in boreal summer

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science china Earth sciences 2010年第9期53卷 1343-1350页

作者： LU ChuHan, GUAN ZhaoYong & CAI JiaXi Key Laboratory of Meteorological Disaster of Ministry of Education and College of Atmospheric sciences, nanjing university of Information science & Technology, nanjing 210044, china 1. Key Laboratory of Meteorological Disaster of Ministry of Education and College of Atmospheric sciences Nanjing University of Information Science & Technology Nanjing 210044 China

Using NCEP/NCAR reanalysis and precipitation records of Chinese stations, we have investigated the relationship of interhemispheric oscillation of air mass (IHO) with global lower-level circulation and monsoon anomalies in boreal summer. Our results show that the summer IHO explains a greater portion of variance in the abnormal distribution of atmospheric mass over 30°S-60°N as well as the Antarctic. The IHO strongly correlates to the variations of sea level pressure (SLP) in these regions. It is shown that IHO has some influences on both atmospheric mass transports and water vapor fluxes over 30°S-60°N in association with three anomalous cyclonic circulations over land areas of the eastern hemisphere, which is in close relation to the changes in summer monsoon intensity in eastern Asia and western Africa. Composites of summer rainfall anomalies in china for high and low IHO-index years indicate that the eastern Asian summer monsoon is more intense, with positive precipitation anomaly centers in northern and northeastern parts of china, as opposed to the negative center over the mid-lower reaches of the Yangtze River (MLRYR) in stronger IHO years. In weak IHO years, a feeble summer monsoon appears in eastern Asia, leading to positive center of precipitation anomalies displaced into the MLRYR. Furthermore, a teleconnection in wind fields between the western African and eastern Asian monsoon regions was observed in the middle and higher troposphere in the scenario of IHO. The anomalous cyclonic (anticyclonic) circulations along the path of this Africa-East Asia teleconnection were found to be just over the diabatic heating (cooling) centers, suggesting that diabatic forcings are responsible for the formation of this Africa-East Asia teleconnection.

关键词： interhemispheric oscillation Asian monsoon precipitation china boreal summer

Rb-Sr isochron ages and significance of bimodal volcanic association in Baimianshi uranium ore-field, South china

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Chinese science Bulletin 1999年第S2期44卷 3-4页

作者： CHEN Peirong~1, WANG Yinxi~2, NI Qisheng~1, KONG Xinggong~2 and ZHANG Bangtong~2 1. State Key Laboratory of Mineral Deposits, Department of Earth sciences, nanjing university, nanjing 2.0093, china 2. center of Modern Analysis, nanjing university, nanjing 2.0093, china State Key Laboratory of Mineral Deposits Department of Earth Sciences Nanjing University Nanjing 210093 China center of Modern Analysis Nanjing University Nanjing 210093 China

1 Geologic background THE volcanic U-deposits are generally associated with felsic to intermediate volcanic rock and their sedimentary derivatives. However, uranium mineralization has been found to be spatially associated with thebasalt of bimodal volcanic associations in Baimianshi uranium ore field. Baimianshi uranium ore-field islocated in Baimianshi volcanic-sedimentary basin of south Jiangxi Province. The cover rocks of the basinconsist of a suite of bimodal volcanic-sedimentary sequences. Its basement rocks are two-mica granites ofBaimianshi rock body. The basalt of cover rocks is interbedded with arkoses in lower sequence, and rhyolite or rhyolitic tuff in upper sequence. Uranium minerals mainly occur as disseminations in the

关键词： Rb-Sr isochron ages bimodal volcanic rocks uranium ore-field south china.

Mechanical behavior of a shelter system based on cable-strut structures

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Journal of Zhejiang university-science A(Applied Physics & Engineering) 2012年第12期13卷 895-903页

作者： Jian-guo CAI1,2,Ya ZHOU1,Jian FENG1,2,Yi-xiang XU3 (1Key Laboratory of C&PC Structures of Ministry of Education,Southeast university,nanjing 210096,china) (2National Prestress Engineering Research center,Southeast university,nanjing 210096,china) (3Department of Civil Engineering,Strathclyde university,Glasgow,UK) 1. Key Laboratory of C&PC Structures of Ministry of Education Southeast University Nanjing 210096 China 2. National Prestress Engineering Research center Southeast University Nanjing 210096 China 3. Department of Civil Engineering Strathclyde University Glasgow UK

A shelter system based on cable-strut structures,consisting of compressive struts and high-tensile elements,is described in this *** deployment of the shelter is achieved by tightening inclined *** cables are used to terminate the *** state of self-stress of the cable-strut structures in the fully deployed configuration is given,and the minimum strut length and the maximum load design of the shelter are *** mechanical behavior of the system was studied under symmetrical and asymmetrical load *** results show that the shelter in the deployed configuration satisfies the ultimate limit and the serviceability limit state ***,the stability of the cable-strut system is investigated,considering the effect of imperfections on the buckling of the *** conclude that the influence of imperfections based on the consistent imperfection mode method is not significant.

关键词： Foldable structures Cable-strut structures Mechanical behavior Self-stress Stability

nonlinear ergodic theorem for semitopological semigroups of non-Lipschitzian mappings in Banach spaces

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Chinese science Bulletin 1997年第1期42卷 8-11页

作者： LI Gang and MA Jipu1. Department of Mathematics, Yangzhou Normal College, Yangzhou 225002, china 2. Department of Mathematics, nanjing university, nanjing 2.0093, china Department of Mathematics Yangzhou Normal College Yangzhou China Department of Mathematics Nanjing University Nanjing China

LET G be a semitopological semigroup, i. e. G is a semigroup with a Hausdorff topology such that for each s∈G the mapping s|→s·t and s|→t·s from G to G are continuous. G is called right reversible if any two closed left ideals of G have non-void intersection. In this case, (G,≤) is a directed system when the binary relation '≤' on G is defined by a≤b if and only if Let E be the uniformly convex Banach space

关键词： nonlinear semigroup ergodic theorem non-Lipschitzian mapping.