检索结果-南通市图书馆

一种对噪声干扰鲁棒的模糊末制导律设计与仿真

在线全文

学校读者我要写书评

暂无评论

系统仿真学报 2004年第1期16卷 137-139页

作者：王青毕靖北京航空航天大学自动化科学与电气工程学院北京100083

提出一种对测量噪声干扰鲁棒的模糊末制导律。进行模糊末制导律设计时,在分析导弹和来袭目标运动特性的基础上,根据最优制导律设计专家经验和测量噪声的干扰特性建立模糊规则。数字仿真结果表明所提出的末制导方法与传统比例导引方法比... 详细信息

提出一种对测量噪声干扰鲁棒的模糊末制导律。进行模糊末制导律设计时,在分析导弹和来袭目标运动特性的基础上,根据最优制导律设计专家经验和测量噪声的干扰特性建立模糊规则。数字仿真结果表明所提出的末制导方法与传统比例导引方法比较,在测量噪声干扰和测量数据不精确的情况下,具有弹道更平直、拦截时间更短,对噪声干扰鲁棒的优点。模糊末制导律算法简单可行易于实时实现。

关键词：模糊末制导律最优制导律模糊规则鲁棒性噪声干扰

Mechanical Property and Microstructural Characterization of C-Mn-Al-Si Hot Dip Galvanizing TRIP Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2012年第8期19卷 29-36页

作者： JIANG Hai-tao1, DING Wei1,2, TANG Di1, HUANG Wei1 (1. National engineering Research Center for Advanced Rolling Technology, university of science and Technology {3., beijing 100083, china 2. school of material and Metallurgy, Inner Mongolia university of science and Technology, Baotou 014010, Inner Mongolia, china) [a] National engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China [b] school of material and Metallurgy Inner Mongolia University of Science and Technology Baotou 014010 Inner Mongolia China

Mechanical properties and microstructure in high strength hot dip galvanizing TRIP steel were investigated by optical microscope (OM), transmission electron microscope (TEM), X-ray diffraction (XRD), dilatometry and mechanical testing. On the heat treatment process of different intercritical annealing (IA) temperatures, isothermal bainitic transformation (IBT) temperatures and IBT time, this steel shows excellent mechanical properties with tensile strength over 780 MPa and elongation more than 22%. IBT time is a crucial factor in determining the mechanical properties as it confirms the bainite transformation process, as well as the microstructure of the steel. The microstructure of the hot dip galvanizing TRIP steel consisted of ferrite, bainite, retained austenite and martensite during the short IBT time. The contents of ferrite, bainite, retained austenite and martensite with different IBT time were calculated. The results showed that when IBT time increased from 20 to 60 s, the volume of bainite increased from 14.3.% to 16.95% and the volume of retained austenite increased from 13.64% to 16.28%; meanwhile, the volume of martensite decreased from 7.18% to 1.89%. Both the transformation induced plasticity of retained austenite and the hardening of martensite are effective, especially, the latter plays a dominant role in the steel containing 7.18% martensite which shows similar strength characteristics as dual-phase steel, but a better elongation. When martensite volume decreases to 1.89%, the steel shows typical mechanical properties of TRIP, as so small amount of martensite has no obvious effect on the mechanical properties.

关键词： TRIP steel isothermal bainitic transformation martensite mechanical property

Some basic concepts and problems on the petrogenesis of intra-plate ocean island basalts

在线全文

学校读者我要写书评

暂无评论

Chinese science Bulletin 2009年第22期54卷 4148-4160页

作者： NIU Yaoling1,2,3.1 Department of Earth sciences, Durham university, Durham DH1 3.E, UK 2 school of Earth sciences and Resources, china university of Geosciences, beijing 100083, china 3.school of Earth and Space sciences, Peking university, beijing 100871, china Department of Earth sciences Durham University Durham DH1 3LE UK school of Earth sciences and Resources China University of Geosciences Beijing 100083 China school of Earth and Space sciences Peking University Beijing 100871 China

Basaltic magmatism that builds intra-plate ocean islands is often considered to be genetically associated with "hotspots" or "mantle plumes". While there have been many discussions on why ocean island basalts (OIB) are geochemically highly enriched as an integral part of the mantle plume hypothesis, our current understanding on the origin of OIB source material remains unsatisfactory, and some prevailing ideas need revision. One of the most popular views states that OIB source material is recycled oceanic crust (ROC). Among many problems with the ROC model, the ocean crust is simply too depleted (e.g., [La/Sm]PM material for highly enriched (e.g., [La/Sm]PM >> 1) OIB. Another popular view states that the enriched component of OIB comes from recycled continental crust (RCC, i.e.; terrigenous sediments). While both CC and OIB are enriched in many incompatible elements (e.g., both have [La/Sm]PM >>1), the CC has characteristic enrichment in Pb and deletion in Nb, Ta, P and Ti. Such signature is too strong to be eliminated such that CC is unsuitable as source material for OIB. Plate tectonics and mantle circulation permit the presence of ROC and RCC materials in mantle source regions of basalts, but they must be volumetrically insignificant in contributing to basalt magmatism. The observation that OIB are not only enriched in incompatible elements, but also enriched in the progressively more incompatible elements indicates that the enriched component of OIB is of magmatic origin and most likely associated with low-degree melt metasomatism. H2O and CO2 rich incipient melt may form in the seismic low velocity zone (LVZ). This melt will rise because of buoyancy and concentrate into a melt rich layer atop the LVZ to metasomatize the growing lithosphere, forming the metasomatic vein lithologies. Erupted OIB melts may have three components: (1) fertile OIB source material from depth that is dominant, (2) the melt layer, and (3. assimilation of the metasomatic

关键词：岩石成因论海洋 OIB 矿物学

Investigation on the Effect of Electron Beam Weld Shape on Fatigue Performance of Thickness Titanium Alloy

在线全文

学校读者我要写书评

暂无评论

稀有金属材料与工程 2011年第S4期40卷 125-129页

作者： Liu Xin1,2,Gong Shuili2,Lei Yongping1 1school of material science and {3.,beijing university of Technology,beijing 100021,china2science and Technology on Power Beam Processes Laboratory,beijing Aeronautical Manufacturing Technology Research Institute,beijing 100024,china beijing Univ Technol Sch Mat Sci & Engn Beijing 100021 Peoples R China beijing Aeronaut Mfg Technol Res Inst Sci & Technol Power Beam Proc Lab Beijing 100024 Peoples R China

Different weld shapes of 45mm thickness TA15 titanium alloy were obtained by choosing appropriate electron beam welding parameters,and the influence of weld shape on fatigue performance of the joints was investigated by analytic hierarchy *** results show that four typical weld shapes were formed,according to their geometry characters,which are respectively named as bell shape,funnel shape,nail shape,and wedge *** shape effect the fatigue life and dispersion of the experiment data of the *** sequencing of fatigue performance of the joints with four different shapes by analytic hierarchy mathematical model is bell shape,funnel shape,wedge shape,and nail *** is validated by trial results that the analytic hierarchy mathematical model is effective and practical.

关键词： weld shape fatigue performance analytic hierarchy process electron beam welding thickness titanium alloy

A note on the derivation of the derivatives of invariants of stretch tensor to the right Cauchy-Green tensor

在线全文

学校读者我要写书评

暂无评论

Progress in Natural science:materials International 2006年第1期16卷 96-99页

作者： TIAN Dongyan, JIN Ming and DUI Guansuo (Institute of engineering Mechanics, school of Civil engineering and Architecture, {3. Jiaotong university, {3. 100044, china) [a]beijing Jiaotong university Institute of Engineering Mechanics School of Civil Engineering and Archtecture Beijing China

A new approach for the derivation of the principal invariants of the stretch tensor with respect to the right Cauchy- Green tensor is presented in this paper. According to the definition of the derivation of tensor function, the three first-order derivatives for the principal invariants of the stretch tensor are obtained through derivation directly to the right Cauchy-Green tensor by incremental method. Then the three second-order derivatives are yielded by the derivation to the right Cauchy-Green strain tensor directly. Furthermore, an explicit expression of the tangent modulus of the general Varga material is given as an example.

关键词： continuum mechanics invariant strain energy tangent modulus.

Level Set interface treatment and its application in Euler method

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 227-236页

作者： WU KaiTeng1,2,HAO Li3.WANG Cheng4 & ZHANG Li1,2 1 Numerical Simulation Sichuan Higher school Key Laboratory,Neijiang Normal university,Neijiang 641112,china 2 College of Mathematics and Information {3.,Neijiang Normal university,Neijiang 641112,china 3.College of {3.,beijing university of Civil engineering and Architecture,beijing 100044,china 4 State Key Laboratory of Explosion {3. and Technology,beijing Institute of Technology,beijing 100081,china 1. Numerical Simulation Sichuan Higher school Key Laboratory Neijiang Normal University Neijiang 641112 China2. College of Mathematics and Information Science Neijiang Normal University Neijiang 641112 China3. College of Science Beijing University of Civil Engineering and Architecture Beijing 100044 China4. State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China

Level Set interface treatment method is introduced into Euler method,which is employed for interface treatment method for multi-materials. Combined with the ghost fluid method,the moving interface is tracked. Fifth-order WENO spatial discretization and third-order TVD Runge-Kutta time discretization methods are used. Shock-wave action on bubble,implosion and velocity field Shock effect bubbles; implosion and velocity field are simulated by means of LS-MMIC3. programmed by C++. Nu-merical results show that the Level Set interface treatment method is effective and feasible for multi-material interface treatment in comparison with the WENO method.

关键词： Euler method Level Set method shock-wave action on bubble implosion numerical simulation

Time Series Prediction on Dynamical Responds Based on Artificial Neural Network

在线全文

学校读者我要写书评

暂无评论

微计算机信息 2007年第16期 305-307页

作者： (Department of Computer science & Technology, Jiaying university Meizhou 514015 china)Yu Linchong Jiao Junting ({3. of Jet Propulsion, beijing university of aeronautics & astronautics beijing 100083 china)Yu Linchong Bai Guangchen

The purpose of the research is to establish complicated nonlinear parameters time series prediction *** in-fluence of friction and flexibleness,the characters of flexible mechanism are highly *** dynamical responses of mechanism become more uncertain because of those *** is more difficult to control the mechanism at the real *** improved El-man dynamical artificial neural network,the prediction model was established to forecast kinetic parameters.A flexible mechanism example was applied to test this *** results proved that the calculate speed of the model was fast and the precision was *** method provided an available way on controlling at the real time for complicated large systems.

关键词： Elman neural network Mechanism Dynamic Response Time Series Prediction

Structure Relaxation of Mg_(65)Cu_(25)Gd_(10) Metallic Glass and Its Effect on Strength

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan university of Technology(materials science) 2009年第2期24卷 210-213页

作者：李国强 school of materials science & {3. Beijing University of Aeronautics and Astronautics china Perfect Machinery Industry Corp. Ltd

To identify the re-arrangement of constituent atoms of an amorphous Mg65Cu25Gd10 alloy happened with annealing, structure relaxation of the alloy was investigated as a function of an- nealing time at 3.3.K through extended X-ray absorption fine structure （EXAFS） analysis procedures. To understand the effect of structure relaxation on strength, compression tests were conducted for both the as-cast and the annealed Mg65Cu25Gd10 samples. It is found that short range order around Cu and Gd atoms exhibits different variation trends with increasing annealing time at 3.3.K, though the structure of the alloy still remains to be amorphous. Based on the fact that the strength of the alloy first exhibits a reduction and then a recovery with annealing time, it is suggested that the enhancement of short range order around Cu should be responsible for the strength reduction, while the enhancement of short range order around Gd should be responsible for the strength recovery.

关键词： Mg-based metallic glass structure relaxation strength annealing

Effect of welding speed on the material flow patterns in friction stir welding of AZ3. magnesium alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2007年第2期26卷 158-162页

作者： ZHANG Hua Wu Huiqiang Huang Jihua LIN Sanbao WU Lin materials science and engineering {3. University of Science and Technology Beijing Beijing 100083 China beijing Institute of Astronautical Systems engineering Beijing 100076 China State Key Lab of Advanced Welding Production Technology Harbin Institute of Technology Harbin 150001 China

The clear zigzag-line pattern on transverse cross sections can be used to explain the formation mechanism of the weld nugget when friction stir welded AZ3. magnesium alloy without any other insert material is used as mark. It provides a simple and useful method to research the joining mechanism of friction stir welding. The rotation speed is kept at 1000 r/min and the welding speed changes from 120 mm/min to 600 mm/min. The macrostructure on the transverse cross section was divided into several parts by faying surface. The results show that the shape and formation procedure of the weld nugget change with the welding speed. There are two main material flows in the weld nugget： one is from the advancing side and the other is from the retreating side. A simple model on the weld nugget formation of FSW is presented in this article.

关键词： AZ3. magnesium alloy friction stir welding faying surface materials flow formation model