检索结果-南通市图书馆

Study of the interaction of multiple cracks in brittle solids

在线全文

学校读者我要写书评

暂无评论

Study of the interaction of multiple cracks in brittle solid...

Boundary element-free method for elastodynamics

The Eighth International Conference on Fundamentals of Fracture（ICFF VIII）

作者： Dong Feng LI~1 Cheng Feng LI~2.Si Qi Shu~1 Jian Lu~(1 *) 1 Department of Mechanical engineering The Hong kong Polytechnic university Hong kong China. 2.{2. and computational engineering centre School of engineering university of wales swansea Singleton Park swansea sa2 {12. u.k.

＜正＞The knowledge about interactions of multiple cracks in solid materials is of fundamental importance in understanding the toughening mechanism of multiple cracks shielding and in predicting the effective elastic moduli of brittle materials including multiple *** often plays a key role in many engineering applications,for instance,the functional gradient materials such as TBC（Thermal Barrier Coating） and the surface crack network generated in nuclear plant structures.

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

Science China(Physics,Mechanics & Astronomy) 2005年第6期48卷 641-657页

作者： CHENG Yumin1 & PENG Miaojuan2.1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai university, Shanghai 2.0072. China 2. Department of civil {2., Shanghai university, Shanghai 2.0072. China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai China Department of civil engineering Shanghai University Shanghai China

The moving least-square approximation is discussed first. Sometimes the method can form an ill-conditioned equation system, and thus the solution cannot be obtained correctly. A Hilbert space is presented on which an orthogonal function system mixed a weight function is defined. Next the improved moving least-square approximation is discussed in detail. The improved method has higher computational efficiency and precision than the old method, and cannot form an ill-conditioned equation system. A boundary element-free method (BEFM) for elastodynamics problems is presented by combining the boundary integral equation method for elastodynamics and the improved moving least-square approximation. The boundary element-free method is a meshless method of boundary integral equation and is a direct numerical method compared with others, in which the basic u.k.owns are the real solutions of the nodal variables and the boundary conditions can be applied easily. The boundary element-free method has a higher computational efficiency and precision. In addition, the numerical procedure of the boundary element-free method for elastodynamics problems is presented in this paper. Finally, some numerical examples are given.

关键词： moving least-square approximation, improved moving least-square approximation, elastodynamics, boundary integral equation, meshless method, boundary element-free method, Fourier eigen transform.

Analysis on ignition and extinction of n-heptane in homogeneous systems

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2005年第5期48卷 556-569页

作者： LIu Yongfeng1 & PEI Pucheng2.1. Mechanical and Electrical engineering Department, Beijing Institute of civil engineering and Architec-ture, Beijing 100044, China 2. State key Laboratory of Automotive safety and Energy, Tsinghua university, Beijing 100084, China Mechanical and Electrical engineering Department Beijing Institute of Civil Engineering and Architecture Beijing China State key Laboratory of Automotive safety and Energy Tsinghua University Beijing China

To calculate ignition delay times, the governing equations about species and temperature, which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor, are deducted. The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. The steady state solution of the reactor equations describes the three ignition temperature regimes and get “S-shaped curve”. The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations, which is solved. The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data. At last, two important parameters are discussed thoroughly and the temperature perturbation is given. It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.

关键词： ignition delay times, thermal runaway, steady state assumptions, continuously stirred flow reactor.

Terrain classification based on adaptive weights with airborne LiDAR data for mining area

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2011年第S3期21卷 648-653页

作者： LI Hui-ying1, WANG Zhi2. SuN Ya-feng1, LI Wen-hui1 1. College of Computer Science and Technology, Jilin university, Changchun 130012. China 2. College of Resources and civil {2., Northeastern university, Shenyang 110004, China College of Computer Science and Technology Jilin University Changchun 130012 China College of Resources and civil engineering Northeastern University Shenyang 110004 China

The fast high-efficiency inspection for mining subsidence of mine area is a reliable way for forecasting accident and evaluating losing expense. In order to monitor mining subsidence of exploitation mine efficiently, LiDAR data were used and a novel strip division method was brought forward based on separating-treatment theory, which divided the mass of discrete three-dimensional point cloud data into a series of parallel strips and reduced the dimension in each strip. Polynomial fitting algorithm based on the adaptive weights, which located in the range of the strip, was used for classification complex terrain data of mine-area. The results show that LiDAR datamation can be greatly reduced. In the mean time, the time spending for calculation is shortened, and computational complexity is simplified. Therefore, high-efficiency terrain classification of LiDAR point cloud method can be great beneficial to monitoring environment of mine area.

关键词： mining subsidence airborne LiDAR strip division adaptive weights

An effective and practical method for solving an unnegligible problem inherent in the current calculation model for multi-support seismic analysis of structures

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2010年第7期53卷 1774-1784页

作者： LIu GuoHuan2. GuO Wei1 & LI HongNan2.1 National engineering Laboratory for High Speed Railway Construction, School of civil engineering and Architecture, Central South university, Changsha 410075, China 2.Faculty of Infrastructure engineering, Dalian university of Technology, Dalian 11602., China Faculty of Infrastructure engineering Dalian University of Technology Dalian China National engineering Laboratory for High Speed Railway Construction School of Civil Engineering and Architecture Central South University Changsha China

In the seismic analysis of extended structures subject to spatially varying motions, the displacement input model instead of acceleration model is usually adopted for accurate results. In this paper, a more detailed and comprehensive analysis of the displacement input model is carried out and the research shows that there exists an unnegligible problem in the current displacement model, which leads to the irrationality and unconvergence of some calculated results such as base shear etc. Based on the situation, an effective method named massless rigid element (MRE) method is presented to solve the problem. Moreover, the rationality and accuracy of the method are further assessed and the method is applied to a transmission tower-line system project using the commercially available structural analysis software saP2.00. The theoretical and numerical analyses indicate that the MRE approach is not only feasible with sufficient computational accuracy but also practical and can be easily implemented using the commercially available finite element software such as saP2.00.

关键词： extended structures seismic responses spatially varying motions displacement input model massless rigid element (MRE) transmission tower-line system

computational theory of cavitating flows for hydraulic turbomachinery with consideration of influence of water quality

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2010年第12期53卷 3341-3348页

作者： WANG Lei1,2.& CHANG JinShi2.1 Huadian Electric Power Research Institute, Hangzhou 310030, China 2.College of Water Conservancy and civil engineering, China Agricultural {2., Beijing 100083, China Huadian Electric Power Research Institute Hangzhou China College of Water Conservancy and civil engineering China Agricultural University Beijing China

Previously it was assumed that the pressure within the cavity or on the cavity surface remained constant and the vapor pressure of clean water at 2.°C and 0 m altitude was utilized as the computational boundary for cavitating flows in hydraulic turbomachinery. Cavitation was confused with vaporization, and the effect of water quality on cavitation pressure characteristics was not taken into account. In recent years, lots of experiments of cavitation pressure characteristics of different water qualities including different sand concentrations of sand water and different altitudes of clean water have been performed by the authors, and the important influences of water quality on cavitation pressure characteristic have been validated. Thus the water quality should be involved in the cavitating flows computation. In the present paper, the effect of water quality on the cavitation pressure characteristic is analyzed and the computational method and theory of cavitating flows for hydraulic turbomachinery that considers the influence of water quality are proposed. The theory is suitable for both the potential flow method and the two-phase flow method for cavitating flows simulation. Finally, the validation results for cavitating flows in a hydraulic tur- bine indicate the significant influences of water quality on the cavitating flow performance.

关键词： cavitating flows cavitation pressure water quality hydraulic turbomachinery

Interactions of Marsh Orchid(Dactylorhiza spp.)and Soil Microorganisms in Relation to Extracellular Enzyme Activities in a Peat Soil

在线全文

学校读者我要写书评

暂无评论

Pedosphere 2007年第6期17卷 681-687页

作者： H. kANG C. FREEMAN Department of civil and Environmental engineering Yonsei University Seoul 120- 749 （Korea） School of Biological Sciences University of Wales Bangor LL57 2UW （UK）

The nature of the interactions between microbes and roots of plants in a peaty soil were studied in a laboratory- based experiment by measuring activities ofβ-glucosidase,phosphatase,N-acetylglucosaminidase,and *** experiment was based on control(autoclaved),bacteria-inoculated,and plant(transplanted with Dactylorhiza)treatments, and samples were collected over 4 sampling *** enzyme activities were associated with the bacteria-inoculated treatment,suggesting that soil enzyme activities are mainly of microbial *** example,β-glucosidase activity varied between 2.-30μmol g^(-1)min^(-1)in the bacteria-inoculated samples whilst the activity of the control ranged between 4-12.mol g^(-1)min^(-1)A similar pattern was found for all other enzymes. At the end of the incubation,the microcosms were destructively sampled and the enzyme activities determined in bu.k.soil,rhizospheric soil,and on the root *** measurement in different fractions of the peat indicated that higher activities were found in ***,the higher activities ofβ-glucosidase,N-acetylglucosaminidase,and arylsulphatase appeared to be associated with bacterial proliferation on the root surface,whilst a larger proportion of phosphatase appeared to be released from root surface.

关键词： Dactylorhiza extracellular enzyme peat rhizosphere wetland

Modeling and Assessment of Buoyancy-Driven Stratified Airflow in High-Space Industrial Hall

在线全文

学校读者我要写书评

暂无评论

湖南大学学报（自然科学版） 2009年第S1期36卷 19-22页

作者： WANG Han-qing1,2.CHEN ke1,Hu Jian-jun1,3,kOu Guang-xiao2.WANG Zhi-yong2.1.School of Energy Science and engineering,Central South university,Changsha,Hunan 410083,China 2.Department of {2. engineering,Hunan university of Technology,Zhuzhou,Hunan 412.08,China 3.School of Mechanical engineering,Purdue university,West Lafayette,usa) School of Energy Science and engineering Central South University Changsha 410083 China Department of civil engineering Hunan University of Technology Zhuzhou 412008 China School of Mechanical engineering Purdue University West Lafayette United States

In industrial environment,heat sources often are contaminant sources and health threatening contaminants are mainly passive,so a detailed understanding of airflow mode can assist in work environment hygiene measurement and *** paper presented a numerical investigation of stratified airflow scenario in a high-space industrial hall with validated commercial code and experimentally acquired boundary *** upon an actually undergoing engineering project,this study investigated the performance of the buoyancy-driven displacement ventilation in a large welding hall with big components *** results have demonstrated that stratified airflow sustained by thermal buoyancy provides zoning effect in terms of clean and polluted regions except minor stagnant eddy *** competition between negative buoyant jets from displacement radial diffusers and positive buoyant plume from bu.k.object constitutes the complex transport characteristics under and above stratification ***,downdraft and turbulent eddy motion complicate the upper mixing zone,but the exhaust outlet plays a less important role in the whole field *** the corresponding suggestions concerning {2. stability and convergence,further improvements in modelling and measurements were given.

关键词： modelling buoyancy-driven large enclosure industrial ventilation

Guided wave propagation in multilayered piezoelectric structures

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 1094-1104页

作者： GuO YongQiang1, CHEN WeiQiu2.3 & ZHANG YongLiang4 1 key Laboratory of Mechanics on Disaster and Environment in Western China, Ministry of Education, and School of civil engineering and Mechanics, Lanzhou {2., Lanzhou 730000, China 2.key Laboratory of Soft Soils and Geoenvironmental engineering, Ministry of Education, and Department of civil engineering, Zhejiang {2., Hangzhou 310058, China 3 Department of engineering Mechanics, Zhejiang {2., Hangzhou 31002., China 4 School of civil engineering, Lanzhou Jiaotong {2., Lanzhou 730070, China key Laboratory of Mechanics on Disaster and Environment in Western China Ministry of Education and School of Civil Engineering and Mechanics Lanzhou University Lanzhou China key Laboratory of Soft Soils and Geoenvironmental engineering Ministry of Education and Department of Civil Engineering Zhejiang University Hangzhou China Department of engineering Mechanics Zhejiang University Hangzhou China School of civil engineering Lanzhou Jiaotong University Lanzhou China

A general formulation of the method of the reverberation-ray matrix (MRRM) based on the state space formalism and plane wave expansion technique is presented for the analysis of guided waves in multilayered piezoelectric structures. Each layer of the structure is made of an arbitrarily anisotropic piezoelectric material. Since the state equation of each layer is derived from the three-dimensional theory of linear piezoelectricity, all wave modes are included in the formulation. Within the framework of the MRRM, the phase relation is properly established by excluding exponentially growing functions, while the scattering relation is also appropriately set up by avoiding matrix inversion operation. Consequently, the present MRRM is unconditionally numerically stable and free from computational limitations to the total number of layers, the thickness of individual layers, and the frequency range. Numerical examples are given to illustrate the good performance of the proposed formulation for the analysis of the dispersion characteristic of waves in layered piezoelectric structures.

关键词： multilayered piezoelectric structures the method of reverberation-ray matrix guided waves dispersion characteristic