检索结果-南通市图书馆

Effect of dissolved organic matter on adsorption and desorption of mercury by soils

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2008年第9期20卷 1097-1102页

作者： yang, Yongkui LIANG, Li WANG, Dingyong College of Resources and Environment Southwest University Chongqing 400716 China Chongqing Key Lab of Agricultural Resources and Environment Chongqing 400716 China

Effects of dissolved organic matter (DOM) on adsorption and desorption of Hg were investigated in two kinds of soils, Xanthi-Udic Ferralosols (XUF) and Typic Purpli-Udic Cambosols (TPUC). The DOM was obtained from humus soil (DOMH), rice straw (DOMR), and pig manure (DOMP). The presence of DOM obviously reduced Hg maximum adsorption capacity with up to 40% decreases over the control, being an order of DOMH (250.00 mg/kg)< DOMR (303.03 mg/kg) < DOMP (322.58 mg/kg) < CK (control 416.67 mg/kg) for the...

关键词： mercury (Hg) dissolved organic matter (DOM) adsorption desorption

Towards fully automatic modelling of the fracture process in quasi-brittle and ductile materials:a unified crack growth criterion

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第7期9卷 867-877页

作者： Zhen-jun yang Guo-hua LIU College of Civil Engineering and Architecture Zhejiang University Hangzhou 310027 China

Fully automatic finite element(FE) modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys,is of great significance in assessing structural integrity and presents tre-mendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model(CZM) . The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology,integrating the developed criterion,the CZM to model the crack,a simple remeshing procedure to accommodate crack propagation,the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials,and a local arc-length solver to the nonlinear equation system,is developed and im-plemented in an in-house program. Three examples,i.e.,a plain concrete beam with a single shear crack,a reinforced concrete(RC) beam with multiple cracks and a compact-tension steel specimen,are simulated. Good agreement between numerical predictions and experimental data is found,which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials.

关键词： Finite element method (FEM) Crack propagation criterion Cohesive zone model (CZM) Virtual crack extension(VCE) Arc-length method

Dynamic Analysis and Decoupling Control of Octo-pneumatic Actuator Vibration Isolation Platform

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2009年第1期22卷 116-123页

作者： WANG Xiaolei yang QinNun ZHENG Gangtie Department of Aerospace Engineering Harbin Institute of Technology Harbin 150001 China College of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China Department of Aeronautics andAstronautics Tsinghua University Beijing 100084 China

Control of a six-DOF vibration isolation platform is generally difficult which is due to the strong coupling among its input and output channels. The dynamic behavior and decoupling approach of a six-DOF vibration isolation platform with eight pneumatic actuators are investigated. Owing to the symmetric configuration design of the platform, the coupling among different channels is greatly weakened. When the payload＇s principal axes of inertia parallel to the platform＇s axes of symmetry and the payload＇s center of mass is at the extension line of the platform＇s central axis, the motion can be decomposed into two independent single-input single-output channels and two independent two-input two-output subsystems. The second-order subsystems are decoupled further with the simultaneous matrix diagonalization. Thus a decoupling control strategy is developed. Effectiveness of the decoupling approach is verified through experiments of the platform, and the experimental results show that vibrations of the platform are attenuated obviously owing to the active control.

关键词： decoupling control vibration isolation eight actuators pneumatic actuator

QUADRATIC INVARIANTS AND SYMPLECTIC STRUCTURE OF GENERAL LINEAR METHODS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2001年第3期19卷 269-280页

作者： Xiao, AG Li, SF yang, M Xiangtan Univ Dept Math Xiangtan 411105 Peoples R China

Focuses on a study which presented some invariants and conservation laws of general linear methods applied to differential equation systems. Information on the quadratic invariants; Conservation of symplectic structur... 详细信息

关键词： quadratic invariants symplecticity general linear methods Hamiltonian systems

Development of through-thickness texture gradient and persistence of shear-type textures during annealing of commercial purity aluminium sheet processed by accumulative roll-bonding

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2018年第5期34卷 821-831页

作者： Saiyi Li Liang yang Nan Qin School of Materials Science and Engineering Central South University Changsha 410083 China Key Laboratory of Nonferrous Metal Materials Science and Engineering of the Ministry of Education Central South University Changsha 410012 China

Ultrafine-grained commercial-purity aluminum（AA1070） sheets produced by four cycles of accumulative roll-bonding（ARB） without lubrication are subjected to annealing treatments in the temperature range from 250℃ to 400℃.Microstructures and microtextures in the surface and center regions of the ARBed and annealed sheets are measured by electron backscatter *** results show that annealing treatments at 325℃ or above lead to a reduction in the microstructure gradient but a significant through-thickness texture gradient different from that in the as-deformed *** center region is featured by the development of a strong cube texture at the expense of rolling *** the surface region,shear-type components are either enhanced or largely retained,showing a high persistency upon *** the grain structures are restored predominantly by continuous recrystallization in the surface region,a mixture of continuous and discontinuous recrystallization is envisaged for the center region.

关键词： Accumulative roll-bonding Texture Annealing Recrystallization Shear deformation

Semantic separator learning and its applications in unsupervised Chinese text parsing

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2013年第1期7卷 55-68页

作者： Yuming WU Xiaodong LUO Zhen yang Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China Graduate University of the Chinese Academy of Sciences Beijing 100049 China China Telecom Corporation Limited Shanghai Branch Shanghai 200120 China Shanghai Research Institute of China Telecom Corporation Limited Shanghai 200120 China

Grammar learning has been a bottleneck problem for a long time. In this paper, we propose a method of seman- tic separator learning, a special case of grammar learning. The method is based on the hypothesis that some classes of words, called semantic separators, split a sentence into sev- eral constituents. The semantic separators are represented by words together with their part-of-speech tags and other infor- mation so that rich semantic information can be involved. In the method, we first identify the semantic separators with the help of noun phrase boundaries, called subseparators. Next, the argument classes of the separators are learned from cor- pus by generalizing argument instances in a hypernym space. Finally, in order to evaluate the learned semantic separators, we use them in unsupervised Chinese text parsing. The exper- iments on a manually labeled test set show that the proposed method outperforms previous methods of unsupervised text parsing.

关键词： semantic separator separator learning unsuper vised text parsing

MCHOKeM algorithm with assured bandwidth allocation in DiffServ networks

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2010年第4期21卷 531-536页

作者： Haifeng Du yang Xiao Kiseon Kim Institute of Information Science Beijing Jiaotong University Beijing 100044 P. R. China Department of Information and Communications Gwangju Institute of Science and Technology Gwangju 500-712 Korea

An active queue management（AQM） algorithm called MCHOKeM is presented,which is borrowed from CHOKeW that draws multi-packets at random from the buffer,the multi-packets are compared with an arriving packet and abandoned if they are from the same *** MCHOKeM uses multiple virtual queues for different priority packets and enhances the drawing function by adjusting the maximum number of draws based on the current status of virtual queue *** number of parameters that MCHOKeM needs to maintain is determined by the number of priority levels being supported by the router,which usually has a small limited *** order to explain the features of MCHOKeM,an analytical model is used.A series of simulation tests to evaluate the performance are given.

关键词： congestion control theory differentiated services(DiffServ) transaction control protocol(TCP) protection fairness analysis.

SENSOR SELECTION FOR RANDOM FIELD ESTIMATION IN WIRELESS SENSOR NETWORKS

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2012年第1期25卷 46-59页

作者： yang WENG Lihua XIE Wendong XIAO College of Mathematics Sichuan University School of Electrical and Electronic Engineering Nanyang Technological University School of Automation and Electrical Engineering University of Science and Technology Beijing

This paper studies the sensor selection problem for random field estimation in wireless sensor networks. The authors first prove that selecting a set of I sensors that minimize the estimation error under the D-optimal criterion is NP-complete. The authors propose an iterative algorithm to pursue a suboptimal solution. Furthermore, in order to improve the bandwidth and energy efficiency of the wireless sensor networks, the authors propose a best linear unbiased estimator for a Gaussian random field with quantized measurements and study the corresponding sensor selection problem. In the case of unknown covariance matrix, the authors propose an estimator for the covariance matrix using measurements and also analyze the sensitivity of this estimator. Simulation results show the good performance of the proposed algorithms.

关键词： BLUE covarianee matrix exchange algorithm NP-completeness quantization random field sensor selection.

Design and Optimization of Wheel-legged Robot:Rolling-Wolf

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2014年第6期27卷 1133-1142页

作者： LUO yang LI Qimin LIU Zhangxing State Key Laboratory of Mechanical Transmission Chongqing University

Though the studies of wheel-legged robots have achieved great success, the existing ones still have defects in load distribution, structure stability and carrying capacity. For overcoming these shortcomings, a new kind of wheel-legged robot（Rolling-Wolf） is designed. It is actuated by means of ball screws and sliders, and each leg forms two stable triangle structures at any moment, which is simple but has high structure stability. The positional posture model and statics model are built and used to analyze the kinematic and mechanical properties of Rolling-Wolf. Based on these two models, important indexes for evaluating its motion performance are analyzed. According to the models and indexes, all of the structure parameters which influence the motion performance of Rolling-Wolf are optimized by the method of Archive-based Micro Genetic Algorithm（AMGA） by using Isight and Matlab software. Compared to the initial values, the maximum rotation angle of the thigh is improved by 4.17%, the maximum lifting height of the wheel is improved by 65.53%, and the maximum driving forces of the thigh and calf are decreased by 25.5% and 12.58%, respectively. The conspicuous optimization results indicate that Rolling-Wolf is much more excellent. The novel wheel-leg structure of Rolling-Wolf is efficient in promoting the load distribution, structure stability and carrying capacity of wheel-legged robot and the proposed optimization method provides a new approach for structure optimization.

关键词： wheel-leg multi-objective optimization Rolling-Wolf hybrid locomotion robot