检索结果-南通市图书馆

Ultralight X-type lattice sandwich structure (Ⅱ):Micromechanics modeling and finite element analysis

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2009年第9期52卷 2670-2680页

作者： ZHANG QianCheng1,CHEN AiPing 2,CHEN ChangQing2,3 & LU TianJian2 1 state key laboratory for Mechanical Behavior of Materials,School of Material Science and Engineering,Xi’an jiaotong university,Xi’an 710049,china 2 MOE key laboratory for Strength and Vibration,School of Aerospace,Xi’an jiaotong university,Xi’an 710049,china 3 Department of Engineering Mechanics,AML,Tsinghua university,beijing 100084,china state key laboratory for Mechanical Behavior of Materials School of Material Science and Engineering Xi’an Jiaotong University Xi’an China MOE key laboratory for Strength and Vibration School of Aerospace Xi’an Jiaotong University Xi’an China Department of Engineering Mechanics AML Tsinghua University Beijing China

The methods of homogenization and finite elements are employed to predict the effective elastic constants and stress-strain responses of a new type of lattice structure,the X-structure proposed by the authors in a companion paper. It is shown that in most cases the predictions by the equivalent homogenization theory agree well with the experimental and 3-dimensional finite element calculated results. The theoretical and numerical study supports the argument that the X-structure is superior to the pyramid lattice structure in terms of mechanical strength.

关键词： sandwich panel lattice structure equivalent homogenization finite element model

Mechanism for calcite dissolution and its contribution to development of reservoir porosity and permeability in the Kela 2 gas field,Tarim Basin,china

在线全文

学校读者我要写书评

暂无评论

Science china Earth Sciences 2008年第4期51卷 567-578页

作者： YU BingSong1,3, DONG HailLiang2,3 & RUAN Zhuang1,3 1 state key laboratory of Geological Processes and Mineral Resources, china university of Geosciences, beijing 100083, china 2 Department of Geology, Miami university,Oxford, OH 45056, USA 3 Geomicrobiology laboratory, china university of Geosciences, beijing, 100083, china state key laboratory of Geological Processes and Mineral Resources China University of Geosciences Beijing 100083 China Department of Geology Miami University Oxford OH 45056 USA Geomicrobiology laboratory China University of Geoscien

This study is undertaken to understand how calcite precipitation and dissolution contributes to depth-related changes in porosity and permeability of gas-bearing sandstone reservoirs in the Kela 2 gas field of the Tarim Basin, Northwestern china. Sandstone samples and pore water samples are col-lected from well KL201 in the Tarim Basin. Vertical profiles of porosity, permeability, pore water chem-istry, and the relative volume abundance of calcite/dolomite are constructed from 3600 to 4000 m below the ground surface within major oil and gas reservoir rocks. Porosity and permeability values are in-versely correlated with the calcite abundance, indicating that calcite dissolution and precipitation may be controlling porosity and permeability of the reservoir rocks. Pore water chemistry exhibits a sys-tematic variation from the Na2SO4 type at the shallow depth (3600-3630 m), to the NaHCO3 type at the intermediate depth (3630―3695 m),and to the CaCl2 type at the greater depth (3728―3938 m). The geochemical factors that control the calcite solubility include pH, temperature, pressure, Ca2+ concen-tration, the total inorganic carbon concentration (ΣCO2), and the type of pore water. Thermodynamic phase equilibrium and mass conservation laws are applied to calculate the calcite saturation state as a function of a few key parameters. The model calculation illustrates that the calcite solubility is strongly dependent on the chemical composition of pore water, mainly the concentration difference between the total dissolved inorganic carbon and dissolved calcium concentration (i.e., [ΣCO2] -[Ca2+]). In the Na2SO4 water at the shallow depth, this index is close to 0, pore water is near the calcite solubility. Calcite does not dissolve or precipitate in significant quantities. In the NaHCO3 water at the intermedi-ate depth, this index is greater than 0, and pore water is supersaturated with respect to calcite. Massive calcite precipitation was observed at this depth interval and

关键词： calcite dissolution porosity thermodynamic Tarim Basin

A BATCH ARRIVAL RETRIAL QUEUE WITH STARTING FAILURES,FEEDBACK AND ADMISSION control

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2010年第3期19卷 306-320页

作者： Jinting WANG Peng-Feng ZHOU Department of Mathematics,School of Science,beijing jiaotong university,beijing,china Department of Mathematics School of Science Beijing Jiaotong University Beijing China

This paper is concerned with the analysis of a feedback M^[X]/G/1 retrial queue with starting failures and general retrial times. In a batch, each individual customer is subject to a control admission policy upon arrival. If the server is idle, one of the customers admitted to the system may start its service and the rest joins the retrial group, whereas all the admitted customers go to the retrial group when the server is unavailable upon arrival. An arriving customer （primary or retrial） must turn-on the server, which takes negligible time. If the server is started successfully （with a certain probability）, the customer gets service immediately. Otherwise, the repair for the server commences immediately and the customer must leave for the orbit and make a retrial at a later time. It is assumed that the customers who find the server unavailable are queued in the orbit in accordance with an FCFS discipline and only the customer at the head of the queue is allowed for access to the server. The Markov chain underlying the considered queueing system is studied and the necessary and sufficient condition for the system to be stable is presented. Explicit formulae for the stationary distribution and some performance measures of the system in steady-state are obtained. Finally, some numerical examples are presented to illustrate the influence of the parameters on several performance characteristics.

关键词： Batch arrival feedback repair retrial queue starting failure

Weight hierarchies of linear codes satisfying the Near-Chain condition

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第9期15卷 784-792页

作者： LIU Zihui1** and CHEN Wende2(1. School of Mathematical Sciences, Peking university, beijing 100871, china 2. laboratory of Systems and control and key state laboratory of Information Security, Institute of Systems Science, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, beijing 100080, china) School of Mathematical Sciences Peking University Beijing 100871 China. laboratory of Systems and control and key state laboratory of Information Security Institute of Systems Science Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100080 China

The weight hierarchies of a linear [n,k;q] code C satisfying the Near-Chain condition are studied, almost all the weight hierarchies of such code are determined.

关键词： weight hierarchy Near-Chain condition difference sequence linear code.

Optimized simulation on the intersection traffic control and organization based on combined application of simulation softwares

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Optimized simulation on the intersection traffic control and...

Identification and functional analysis of a CDE/CHR element in the POLD1 promoter

第24届中国控制与决策会议

作者： Yuehui Yang 1, Yao Lu 1 , Limin Jia 2, Yong Qin 2 , Honghui Dong 2 * 1.School of traffic and Transportation, beijing jiaotong university, beijing 100044, china2.beijing jiaotong university, rail traffic control and safety state key laboratory, beijing 100044, china

This paper first describe the role of microscopic traffic simulation in optimize organization, and the advantages in combining VISSIM and Synchro to optimize simulation. Then this paper proposes the method system of simulation optimization for intersection with the combination of microscopic traffic software and the analysis of data. On the basis of practical data and VISSIM simulation, this paper makes strategy optimization for typical cross intersection on the aspects of geometric optimization and signal timing. The optimum strategy can be found through the improvements on comparing the average delay, average queue length, the remaining capacity and saturation with VISSIM and Synchro. The specific intersection given in this paper has an obviously improvement through geometry and signal timing optimization. The average queue length is improved significantly;the saturation of the intersection reduces from 0.65 to 0.51, and the average delay per vehicle decreased from 54.2s to *** shows that this method system has good operability and practicality.

关键词： traffic engineering traffic control VISSIM simulation Synchro system Intersection Organizational optimization

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science china(Life Sciences) 2009年第6期52卷 551-559页

作者： SONG NanMeng1,ZHU XiaoYu1,2,SHI Lei1,AN Jing1,WU YanWei1 & SANG JianLi1 1 key laboratory of Cell Proliferation and Regulation of Ministry of Education,beijing Normal university,beijing 100875,china 2 state key laboratory for Infectious Disease Prevention and control,Institute for Communicable Disease control and Prevention,Chinese Center for Disease control and Prevention,beijing 102206,china 1. key laboratory of Cell Proliferation and Regulation of Ministry of Education Beijing Normal University Beijing 100875 China 2. state key laboratory for Infectious Disease Prevention and control Institute for Communicable Disease Control and Prevention Chinese Center for Disease Control and Prevention Beijing 102206 China

DNA polymerase delta is encoded by the POLD1 gene,the transcription of which is strictly cell ***,the means by which POLD1 transcription is regulated by the cell cycle mechanism is currently *** discovered a novel element in the POLD1 promoter known as a CDE(cell cycle-dependent element)/CHR(cell cycle gene homology region) element.A series of luciferase reporter constructs containing various POLD1 promoter mutations were used to investigate the role of the CDE/CHR element in POLD1 *** the CDE/CHR element was mutated,the promoter activity was up-regulated,and the cell-cycle related factors E2F1 and p21 stopped regulating the ***,cell cycle-dependent changes in the promoter activity required the integrative CDE/CHR *** mobility shift assay(EMSA) revealed the presence of at least three types of DNA/protein complexes binding to the CDE/CHR *** findings provide strong evidence that the CDE/CHR-like sequence is an active functional element in the POLD1 promoter,which is important for the cell cycle regulation of the POLD1 gene.

关键词： POLD1 gene promoter CDE/CHR element site mutant

Cooperation Enforcement Mechanism Considering Battery Cost in Ad hoc Networks

在线全文

学校读者我要写书评

暂无评论

Cooperation Enforcement Mechanism Considering Battery Cost i...

Spatial Structural Characteristics of Chinese railway Passenger Network Based on Complex Network Theory

IEEE 2007 International Symposium on Microwave,Antenna,Propagation and EMC Technologies for Wireless Communications(ISMAPE-2007)

作者： Wu Hao Ding Yi-ming Li Cheng-shu state key laboratory of rail traffic control and safety beijing jiaotong university,beijing,P.R.china 100044

Mobile ad hoc networks have been an active research area for several *** nodes' selfish behavior to save the battery for their own communication cannot be neglect. However,general cooperation enforcement mechanisms do not consider node battery,so hotspot node issue may exist;even badly lead to network *** paper proposes a kind of cooperation enforcement reputation mechanisms considering node battery in ad hoc *** analysis and numerical simulation results show that the reputation mechanism considering battery cost,comparing with the traditional reputation mechanisms,can prolong networks existence time and improve network throughput,but at the cost of a little more packets delay.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Spatial Structural Characteristics of Chinese Railway Passen...

Analysis of junction temperatures in high-power GaN-based LEDs

2011年全国电子信息技术与应用学术会议

作者： Xuejing GU 1,Dewei LI 2,Lu QIN 3 1 School of traffic and Transportation,beijing jiaotong university,beijing,china 2 state key laboratory of rail traffic control and safety of china,beijing jiaotong university,beijing,china 3 School of traffic and Transportation,beijing jiaotong university,beijing,china

The railway network provides transport services for clients,it is very important for railway managers to analyzing the spatial structure of the *** article analyzes the spatial structure of Chinese railway network with indicators of degree distribution,the clustering coefficient,the average path length and *** to the definition of the small world network,the results illustrate that Chinese railway passenger network shows the characteristic of a small world network and is evolving to a scale-free ***’s more,the top level of the network has been formed.

关键词： raiway passenger transportation spatial structure complex network china

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2010年第2期53卷 297-300页

作者： JIANG YuXuan1, LI Zheng1, SUN YongJian1, YU TongJun1, CHEN ZhiZhong1, ZHANG GuoYi1, ZHANG GuangChen2 & FENG ShiWei2 1 state key laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking university, beijing 100871, china 2 School of Electronic Information & control Engineering, beijing university of Technology, beijing 100124, china 1. state key laboratory of Artificial Microstructure and Mesoscopic Physics School of Physics Peking University Beijing 100871 China2. School of Electronic Information & Control Engineering Beijing University of Technology Beijing 100124 China

We presented the analysis of the incomplete conduction in bonding medium in high power GaN-based light-emitting diode (LED) packages. A numerical study was carried out with parametric model to understand the junction temperature variation due to bonding medium defects. Transient thermal measurement was performed to evaluate LED’s junction temperature. Thermal resistance from chip to lead frame was 20 K/W in our sample LED. It was suggested that only 60% of the surface area of the bonding medium was involved in the thermal conduction. This result was also supported by the SEM image. Blocking of thermal path induced by ineffective area of the bonding medium was regarded as a factor of its thermal resistance. Thus, the effective area of the bonding medium should be included in the FEM model and considered as another important factor in high power LED’s thermal management.

关键词： junction temperature bonding medium FEM simulation effective area