检索结果-南通市图书馆

Rose solutions with three petals for planar 4-body problems

在线全文

学校读者我要写书评

暂无评论

Science china Mathematics 2010年第12期53卷 3085-3094页

作者： DENG ChunHua 1,2 , ZHANG ShiQing 1, & ZHOU Qing 3 1 Yangtze center of Mathematics and College of Mathematics, Sichuan University, Chengdu 610064, china 2 Faculty of Mathematics and Physics, Huaiyin Institute of technology, Huai’an 223001, china 3 Department of Mathematics, East china Normal University, shanghai 200062, china 1. Yangtze center of Mathematics and College of Mathematics Sichuan University Chengdu 610064 China2. Faculty of Mathematics and Physics Huaiyin Institute of Technology Huai’an 223001 China3. Department of Mathematics East China Normal University Shanghai 200062 China

For planar Newtonian 4-body problems with equal masses, we use variational methods to prove the existence of a non-collision periodic choreography solution such that all bodies move on a rose-type curve with three pet... 详细信息

关键词： 4-body problems with Newtonian potentials rose solutions with three petals winding numbers variational minimization methods

Studies of low-lying states of even-even Xe isotopes within the nucleon pair approximation

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2011年第S1期54卷 103-108页

作者： ZHANG LiHua1, JIANG Hui1,2 & ZHAO YuMin1,3,4 1Institute of Nuclear, Particle, Astrophysics and Cosmology, Department of Physics, shanghai Jiao Tong University, shanghai 200240, china 2School of Arts and Sciences, shanghai Maritime University, shanghai 200135, china 3center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000, china 4CCAST, World Laboratory, P.O. Box 8730, Beijing 100080, china 1. Institute of Nuclear Particle Astrophysics and Cosmology Department of Physics Shanghai Jiao Tong University Shanghai 200240 China2. School of Arts and Sciences Shanghai Maritime University Shanghai 200135 China3. Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator Lanzhou 730000 China4. CCAST World Laboratory P.O. Box 8730 Beijing 100080 China

We study the relevance of nucleon pairs with higher spins, in addition to spin-zero and spin-two pairs (i.e., S D pairs), in low-lying states of even-even Xe nuclei. By including those higher-spin pairs in our configuration, we recalculate energy level schemes, elec trical quadrupole moments, magnetic moments and electric quadrupole transition rates, for low-lying states of even-even 128-142Xe nuclei. The agreement between our calculated results and the experimental data is substantially improved in comparison with previous studies.

关键词： nucleon pair approximation shell model configuration space low-lying states

Large-eddy simulations and vortex structures of turbulent jets in crossflow

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 118-132页

作者： GUAN Hui1,2 & WU ChuiJie2 1 School of Mechanical and Power Engineering,East china University of Science and technology,shanghai 200237,china 2 Research center for Fluid Dynamics,PLA University of Science and technology,Nanjing 211101,china 1. School of Mechanical and Power Engineering East China University of Science and Technology Shanghai 200237 China 2. Research center for Fluid Dynamics PLA University of Science and Technology Nanjing 211101 China

Using the method of large-eddy simulation, the 3-dimensional turbulent jets in crossflow with stream-wise and transverse arrangements of nozzle are simulated, emphasizing on the dynamical process of generation and evolution of vortex structures in these flows. The results show that the basic vortex structures in literatures, such as the counter-rotating vortex pair, leading-edge vortices, lee-side vortices, hanging vortices, kidney vortices and anti-kidney vortices, are not independent physical substances, but local structures of the basic vortex structure of turbulent jets in crossflow-the 3-D stretching vortex rings originating from the orifice of the nozzle, which is discovered in this study. Therefore, the most important large-scale structures of turbulent jets in crossflow are unified to the 3-D vortex rings which stretch and twist in stream-wise and swing in transverse directions. We also found that the shedding frequencies of vortex rings are much lower than the one corresponding to the appearance of leading-edge and lee-side vortices in the turbulent jets.

关键词： turbulent jet in crossflow coherent structure large-eddy simulation

Orbit determination and prediction accuracy analysis for a regional tracking network

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第6期53卷 1130-1138页

作者： ZHOU ShanShi 1,2,3 ,HU XiaoGong 1 & WU Bin 1 1 shanghai Astronomical Observatory,Chinese Academy of Sciences,shanghai 200030,china 2 Graduate University of Chinese Academy of Sciences,Beijing 100049,china 3 Research center of GNSS,Wuhan 430079,china 1. shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. Research Center of GNSS Wuhan 430079 China

china's COMPASS satellite navigation system relies on a regional tracking network to provide navigation services. Limited by its geographic border,the regional network is able to cover only 30% of the medium-earth-orbits(MEO). Accuracy of determined and predicted orbits is not able to satisfy system requirements if the tracking data processing strategy for global tracking network processing is used for the regional network. Two major error sources for orbital prediction are accuracy of initial orbital elements and dynamical modeling. To achieve better prediction accuracy,we propose a two-step orbit determination and prediction strategy. For step 1,only solar radiation pressure(SRP) parameters are estimated along with the orbital elements and other parameters; for step 2,all parameters are estimated but the SRP parameters are tightly constrained to their step 1 estimates. Experimenting with data from a regional GPS network,we conclude for orbital prediction using the proposed two-step strategy,the average user range error(URE) for 24-h prediction arcs is better than 0.6 m.

关键词： orbit determination and prediction regional tracking network URE

Rietveld Quantitative Analysis of Carbides Precipitation in Normalized-tempered 2.25Cr-1Mo-0.25V Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of technology(Materials Science) 2009年第6期24卷 922-926页

作者：张永涛张汉谦 School of Materials Science and Engineering Shanghai Jiaotong University Research Institute Baoshan Iron & Steel Co.Ltd.

The quantitative determination of the mass fractions of precipitates in steels is very difficult using traditional materials characterization techniques. The Rietveld full-pattern fitting algorithm was introduced to solve this problem. The precipitated multicomponents’ mass fraction of M3C, MC, M7C3 and M23C6 were evaluated precisely and relatively quickly. It is found evolution of carbides apparently occurs during tempering at high temperatures, and a two-step transformation mechanism is proposed for M7C3 during early tempering treatment. The method is an effective way on the investigation of precipitation kinetics, which may play a promising role in propertities’ enhancement and design of the heat-resistant steels.

关键词： 2.25Cr-1Mo-0.25V steel rietveld quantitative analysis precipitates

Behavior of Medium-frequency Core Loss in Fe-based Nanocrystalline Soft Magnetic Alloys

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & technology 2000年第3期16卷 332-336页

作者： Yanzhong ZHANG, Huijuan JIN and Ying SHI (Research Centre, shanghai Iron and Steel Research Institute, shanghai 200940, china) Research Centre Shanghai Iron and Steel Research Institute Shanghai 200940 China

The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz<= f<=25000 Hz and 0.1 T< =Bm <=1.0 T for three main original magnetic states in five sorts of Fe-based nanocrysta... 详细信息

The dependences of the power loss per cycle on frequency have been investigated in the ranges of 100 Hz3 kHz～5 kHz depending on both the magnetic state and the value of Dm, whereas it showed a quasi-linear behavior above this range. The total loss was decomposed into hysteresis loss, classical eddy current loss and excess loss, the obvious nonlinear behavior has been confirmed to be completely determined by the dependence of the excess loss on frequency. It has been indicated that the change rate of the excess loss per cycle with respect to frequency sharp decreases with increasing frequency in the range below about 3 kHz～5 kHz, wherease the rate of change slowly varies above this range, thus leading to the quasilinear behavior of the total loss per cycle. In this paper, some linear expressions of the total loss per cycle has been given in a wider medium-frequency segment, which can be used for roughly estimating the total loss.

关键词： Behavior of Medium-frequency Core Loss in Fe-based Nanocrystalline Soft Magnetic Alloys Core Fe high

Effects of cooling rate on the microstructure and electrical properties of Dy_2O_3-doped ZnO-based varistor ceramics

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2007年第1期26卷 39-44页

作者： LIU Hongyu KONG Hui JIANG Dongmei SHI Wangzhou MA Xueming ZHANG Huining Department of Physics East China Normal University Shanghai 200062 China College of Science Wuhan University of Science and Technology Wuhan 430081 China shanghai Research Institute of Petrochemical technology Shanghai 201208 China

The microstructure, electrical properties, and density of Dy2O3-doped ZnO-based varistor ceramics, prepared using high-energy ball milling （HEBM） and sintered at 800℃, were investigated by increasing the cooling rate in the order of H （slow cooling in furnace） → L （cooling in furnace） → K （cooling in air）. With the increase in cooling rate, the grain size and density decreased, the breakdown voltage （VImA/mm） increased, and the nonlinear coefficient （α） and leakage current （IL） exhibited extremum. The sample with the cooling type L showed the best properties with the breakdown voltage of 2650 V/ram, o：of 20.3, IL of 5.2 laA, and density of 5.42 g/cm^3. The barrier height （ФB）, donor concentration （Nd）, density of the interface states （Nd）, and barrier width （ω） all exhibited extremum during the alteration in cooling rate. The different relative amount of Bi-rich phase and its distribution as well as the characteristic parameters of grain boundary, resulting from the alteration of cooling rate, led to the changes in the properties of varistor ceramics.

关键词： varistor ZnO Dy2O3 microstructure electrical properties high-energy ball milling low-temperature sintering

Accurate tracking control in LOM application

在线全文

学校读者我要写书评

暂无评论

Journal of University of Science and technology Beijing 2003年第1期10卷 74-78页

作者： Yadong Liu, Congxin Li, Xingui Guo, and Decai WangNational Die & Mould CAD Engineering Research center, shanghai Jiaotong University, shanghai 200030, china National Die & Mould CAD Engineering Research center Shanghai Jiaotong University Shanghai 200030 China

The fabrication of accurate prototype from CAD model directly in short time depends on the accurate tracking control and reference trajectory planning in (Laminated Object Manufacture) LOM application. An improvement on contour accuracy is acquired by the introduction of a tracking controller and a trajectory generation policy. A model of the X-Y positioning system of LOM machine is developed as the design basis of tracking controller. The ZPETC (Zero Phase Error Tracking Controller) is used to eliminate single axis following error, thus reduce the contour error. The simulation is developed on a Maltab model based on a retrofitted LOM machine and the satisfied result is acquired.

关键词： tracking control LOM ZPETC trajectory planning

A MULTI-SCALE APPROACH FOR THE ANALYSIS OF PROPER SAMPLED DATA SCALE IN HOT-WIRE EXPERIMENT OF SQUARE DUCT FLOW

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2010年第3期22卷 438-444页

作者： ZHANG Bin WANG Tong GU Chuan-gang IDAI Zheng-yuan Key Laboratory for Power Machinery and Engineering Ministry of Education Shanghai Jiao Tong University Shanghai 200240 China Key Laboratory for Power Machinery and Engineering Ministry of Education Shanghai Jiao Tong UniversityShanghai 200240 China Trane＇s Asia-Pacific Research center Shanghai 200001 China

Without rational criteria to determine the Proper Sampled Data Scale （PSDS）, it would result in the expense of the too much unnecessary processing time and storage space in turbulent experiments. A novel approach for PSDS was established herein on the basis of turbulence theory and statistics. The specific procedure was given by using wavelet tools. A case study to prove the reliability and rationality of this approach was reported, where the sampled hot-wire data were from the experiment of square duct flow and turbulence kinetic energy was selected as the concerned turbulence parameter. It is shown that 2^20 quantities of the sampled data are enough to analyze turbulence kinetic energy in the present experiment. The PSDSs of three turbulence parameters at different Reynolds numbers （Re = 4.60×10^4, 7.68×10^4 and 1.23×10^5） were studied. The results illustrate that the PSDSs increase with the increment of the Reynolds number and the order of concerned turbulence parameter.

关键词： PSDS turbulence statistics wavelet hot-wire square duct flow