检索结果-南通市图书馆

Identification of Nonlinear Dynamic Systems Using Diagonal Recurrent Neural Networks

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 149-151页

作者： Jing Wang Hui chen(Information Engmeering School, University of science and Techaology {2., {2. 100083, china) Information Engineering School University of Science and Technology Beijing Beijing 100083 China

In order to apply a new dynamic neural network- Diagonal Recurrent Neural NetWork (DRNN) to the system identificationof nonlinear dynamic Systems and construct more accurate system models, the structure and learning method (DBP algorithm) of theDRNN are Present6d. Nonlinear system characteriStics can be identified by presenting a set of input / output patterns tO the DRNN andadjusting its weights with the DBP algorithm. Experimental results show that the DRNN has good performances in the identification ofnonlinear dynamic systems in comparison with BP networks.

关键词： neural network system identification intelligent control control system models learning method

The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2009年第8期52卷 2280-2287页

作者： chen MingWen1,2. WANG ZiDong2.& XU JianJun2.3,4 1 School of Applied sciences, University of science and Technology beijing, beijing 100083, china 2.School of Materials science and Engineering, University of science and Technology beijing, beijing 100083, china 3 School of Mathematical sciences, Nankai University, Tianjin 300071, china 4 Department of Mathematics and Statistics, McGill University, Montreal H3A 2.6, Canada School of Applied sciences University of Science and Technology Beijing Beijing China School of Materials science and Engineering University of Science and Technology Beijing Beijing China School of Mathematical sciences Nankai University Tianjin China Department of Mathematics and Statistics McGill University Montreal Canada

The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid.

关键词： binary alloy melt convection dendritic growth interfaces steady-state solution multiple variable expansion method

Simulating the impacts of climate variation and land-cover changes on basin hydrology: A case study of the Suomo basin

在线全文

学校读者我要写书评

暂无评论

science china Earth sciences 2005年第9期48卷 1501-1509页

作者： chen Junfeng1,2. LI Xiubin2.& ZHANG Ming2.1. Institute of Remote Sensing & GIS, Peking University, beijing 100871,{2. 2. Institute of Geographical sciences and Natural Resources Research, Chinese Academy of sciences, beijing 100101,{2. Institute of Remote Sensing & GIS Peking University Beijing China Institute of Geographical sciences and Natural Resources Research Chinese Academy of Sciences Beijing Chin

Impacts of land cover changes on watershed hydrology have been a long-term academic concern with acute dispute. But little attention has been paid to such effects on mesoscale river basins, where the society has a closer link to river hydrology. The present study focuses on a mesoscale river basin, the Suomo Basin that is located on the upper reaches of the Yangtze River. Land covers in the basin in the years 1970, 1986 and 1999 were mapped. A lumped hydrologic model, CHARM, and a distributed hydrologic model, SWAT, were used to model the impacts of both land-cover change and climate variation on river runoff during the past four decades. The results show that the contribution of climate variation to the change of runoff regime makes up 60%―80%, while that of land cover changes only 2.%.

关键词： climate variation, land-cover changes, Suomo Basin, CHARM model, SWAT model.

Anomalous magnetotransport in LaMn_(1-x)Te_xO_3

在线全文

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2009年第7期52卷 987-992页

作者： TAN GuoTai1,2. chen ZhengHao3 & ZHANG XiaoZhong4,5 1 Key Laboratory of Beam Technology & Materials Modification of the Ministry of Education, Institute of Low Energy Nuclear Physics, beijing Normal University, beijing 100875, china 2.beijing Radiation Center, beijing 100875, china 3 Laboratory of Optical Physics, Institute of Physics, Chinese Academy of sciences, beijing 100080, china 4 Key Laboratory of Advanced Materials of the Ministry of Education, Department of Materials science and Engineering, Tsinghua University, beijing 100084, china 5 beijing National Center for Electron Microscopy, Tsinghua University, beijing 100084, china Key Laboratory of Beam Technology & Materials Modification of the Ministry of Education Institute of Low Energy Nuclear Physics Beijing Normal University Beijing China beijing Radiation Center Beijing China Laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences Beijing China Key Laboratory of Advanced Materials of the Ministry of Education Department of Materials Science and Engineering Tsinghua University Beijing China beijing National Center for Electron Microscopy Tsinghua University Beijing China

The LaMn1-xTexO3+δ (x=0.1, 0.2. 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te4+, and Mn3+ ions are partly converted into Mn2. and Mn4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn2., Mn3+ and Mn4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn3+ is much larger or less than the sum of Mn2. and Mn4+; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn3+ is close to the sum of Mn2. and Mn4+. These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.

关键词： colossal magnetoresistance La-Te-Mn-O magnetotransport

TEM OBSERVATION OF LOCAL DEFORMATION BAND AT CRACK TIP

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1992年第3期5卷 147-153页

作者： YAO Kefu University of science and Technology beijing,beijing,chinaTANG Naivong chen Nanping Tsinghua University,beijing,china beijing Univ of science and Technology Beijing China

The thin foil specimen of a ferrite-austenite duplex stainless steel was tensiled under transmis- sion electron microscope(TEM).It was found that both in ferrite and austenite the local deformation band at crack tip was formed near to the crack propagating *** forma- tion was related with the crack tip Schmid factor,dislocation shielding,latent hardening and hardening *** the crack tip emitted dislocations to a slip system by the action of pure mode Ⅱ stress resolute,and the decreasing rate of hardening coefficient was suitable,lo- cal deformation band was easy to form.

关键词： crack tip local deformation band dislocation shielding

Indian Ocean-MORB-type isotopic signature of Yushigou ophiolite in North Qilian Mountains and its implications

在线全文

学校读者我要写书评

暂无评论

science china Earth sciences 2006年第6期49卷 561-572页

作者： HOU Qingye1,2. ZHAO Zhidan1,2. ZHANG Hongfei3, ZHANG Benren3 & chen Yuelong2.1. State Key Laboratory of Geological Processes and Mineral Resources, china University of Geo{2.s, beijing 100083, china 2. School of Earth {2. and Mineral Resources, china University of Geo{2.s, beijing 100083, china 3. Faculty of Earth {2.s, china University of Geo{2.s, Wuhan 430074, china State Key Laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing China School of Earth science and Mineral Resources China University of Geosciences Beijing China Faculty of Earth sciences China University of Geosciences Wuhan China

In order to explore the disputed issue concerning the tectonic affinity ofthe ancient ocean mantle of North Qilian Mountains (NQM), geochemical and Sr, Nd, Pb isotopiccompositions of pillow basalts of the Yushigou Ophiolite (YSGO) suite from NQM have been analyzedsystematically. The pillow basalts exhibit tholeiitic characteristics, with flatchondrite-normalized REE patterns ((La/Yb)_N = 0.98—1.2.). They display no Nb, Ta, Zr, Hf negativeanomalies, and show MORB features in 2.b-Zr/4-Y and Ti/100-Zr-YX3 tectonic discrimination *** results indicate that the Yushigou ophiolite is most likely to be formed in a mid-ocean ridgeor mature back-arc basin. Their isotopic data show a relatively broad and enriched ^(87)Sr/^(86)Sr(0.70509 — 0.70700), restricted ^(143)Nd/^(144)Nd (0.512.55-0.512.78). Pb isotopes are in the rangeof ^(2.6)Pb/^(2.4)Pb (18.054-2..562., ^(2.7)Pb/^(2.4)Pb (15.537-15.743) and ^(2.8)Pb/^(2.4)Pb(38.068-38.530). These isotopic data imply that the basalts originated from the depleted mantle(DMM), with the involvement of enriched mantle components (mainly EMII). Geochemical comparisonsbetween the basalts in YSGO and the MORB-type basalts of ophiolite suites occurring in the knownancient Tethyan tectonic domain indicate that the ancient oceanic mantle represented by YSGO suiteforming in early Paleozoic in the North Qilian Moutains is very similar to the Tethyan mantle inboth trace elements and isotopic compositions. The North Qilian Mountains should be a part of theTethyan tectonic domain in early Paleozoic. This further implies that the Tethyan tectonic domaincan be deduced to early Paleozoic in the study area, which will be helpful to discussing thetectonic affinity and evolution of the North Qilian Mountains.

关键词： geochemistry, Indian Ocean-MORB-type isotopic signatures, Tethyan tectonic domain, Yushigou ophiolite, North Qilian Mountains.

MEAM Potential with Angular Dependence for TiAl

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2001年第1期20卷 13-17页

作者： Xiaodong Ni, Xitao Wang, Guoliang chen (Physics Department, University of science and Technology {2., {2. 100083, china State Key Laboratory for Advanced Metals and Materials, University of science and Technology {2., {2. 100083, china) 北京科技大学新金属材料国家重点实验室北京 100083 北京科技大学北京 100083

The modified embedded atom method (MEAM) is an empirical extension of the embedded atom method (EAM) that includes angular forces. By fitted to the lattice constants, the cohesive energy, the APE (anti-phase boundary) energy, and the vacancy formation energy of TiAl, an accurate MEAM potential is obtained for the TiAl system with L10 structure. The calculation results of the properties of TiAl are in good agreement with experiments and the results of first principle (F.P.) calculations.

关键词： embedded atom method TiAl alloy angular dependence potential intermetallics

Fuzzy interface treatment in Eulerian method

在线全文

学校读者我要写书评

暂无评论

science china(Technological sciences) 2004年第5期47卷 550-568页

作者： NING Jianguo1 & chen Longwei1,2.1. National Key Laboratory of Protection and Control of Explosive Disaster, beijing Institute of Technology, beijing 100081, china 2. The Faculty of Land Resource Engineering, Kunming University of science and Technology, Kunming 650093, china Correspondence should be addressed to Ning Jianguo National Key Laboratory of Protection and Control of Explosive Disaster Beijing Institute of Technology Beijing China The Faculty of Land Resource Engineering Kunming University of Science and Technology Kunming China

In this paper, we incorporate fuzzy mathematics approach into the Eulerian method to simulate three dimensional multi-material interfaces. In particular, we propose a fuzzy interface treatment for describing interfaces, designing transport plans, and computing transport quantities. Using a set of three-dimensional inviscid isothermal elastic-plastic hydrodynamic equations, we simulate shaped charge jet in different filled dynamite structures. Strain and stress have been under consideration in simulations. Numerical results demonstrate that the fuzzy interface treatment is correct and efficient for three-dimensional multi-material problems.

关键词： Eulerian method, multi-material, fuzzy interface, shaped charge jet, three-dimensional numerical simulation.

Approach to synthesis of novel chiral 3-chloro-2.5H)- furanone and its application in asymmetric reactions

在线全文

学校读者我要写书评

暂无评论

Chinese science Bulletin 2000年第8期45卷 711-716页

作者： HUANG Hui & chen Qinghua1. Department of Chemistry, Tonghua Teacher’s College, Tonghua 134002. china 2. Department of Chemistry, {2. Normal University, {2. 100875, china Department of Chemistry Tonghua Teacher’s College Tonghua China Department of Chemistry Beijing Normal University Beijing China

The synthetic method of the novel chiral synthon, 5-/-menthyloxy-3-chloro-2.(5H)-furanone 5a and its application in asymmetric reactions were investigated. 5a is easily obtained in highly optical purity, and acts as a stable acceptor of Michael addition with oxygen nucleophiles in tandem double Michael addition / internal nucieophilic substitution to offer the spiro-cyclopropane derivative containing four stereogenic centers 8, which it is difficult to obtain by routine methods. The synthetic methods for 5a and 8 are reported in detail and the new compounds are identified on the basis of their analytical data and spectroscopic data, such as UV, IR, H NMR,13 C NMR, MS and elementary analysis. The absolute configuration of the interesting spiro-cyclopropanes, spiro [1-chloro-4-(/-menthyloxy)-5-oxo-6-oxa-biscyclo[3.1.0]hexane-2.3i(4’-/-menthyloxy-5’-/-menthyloxy- butyrolactone)] 8 was established by X-ray crystallography. This result can provide important synthetic strategy in synthesis of some complex

关键词： new chiral synthon. 5-l-menthyloxy-3-chloro-2.(5H)-furanone absolute configuration spiro-cyclopropane derivative containing multiple chiral centers.