检索结果-南通市图书馆

upper bound of tunnel face stability using asymmetric yielding

在线全文

学校读者我要写书评

暂无评论

Underground Space 2018年第4期3卷 288-296页

作者： Itai Elkayam Assaf Klar Technion–Israel Institute of Technology HaifaIsrael Technical University of Denmark LyngbyDenmark

Although significant advancement has been made over recent years with respect to three-dimensional upper bound calculations of tun-nel facing,a considerable difference still exists between analytically and empirically based stability *** current work suggests that the difference may well be the outcome of the traditional use of Tresca yield criterion for the upper bound calculations,which,by definition,does not distinguish among the shearing modes(compression,extension,plane strain).Consequently,this paper suggests and discusses a new yield function,which allows for asymmetric *** yielding is only beneficial in the case of three-dimensional and continuous velocity fields,and therefore a numerical procedure that generates relevant kinematically admissible fields for classical upper bound cal-culation is *** procedure involves conversion from a load controlled boundary value problem to a velocity controlled problem at the limit state of *** analysis results in significantly lower upper bound values than those presented earlier(for Tresca mate-rial),and the values are much closer to the stability curves of Kimura and Mair(1981),which are commonly used in design.

关键词： Tunnels Plasticity Stability upper bound

upper bound Limit Analysis of Anisotropic Soils

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

Computers, Materials & Continua 2020年第12期65卷 2607-2621页

作者： Chunguang Li Cuihua Li Cong Sun State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China School of Urban Construction Wuchang University of TechnologyWuhan430223China Wuhan Municipal Construction Group Co. Ltd.Wuhan430023China

In this paper,a novel discretization method inσ-τspace is developed to calculate the upper bound limit loads and failure modes of anisotropic Mohr-Coulomb *** achieve this objective,the Mohr-Coulomb yield criterion is linearized inσ-τspace,which allows for upper bound solution of soils whose cohesion and friction coefficient varying with *** finite element upper limit analysis formulation using the modified anisotropic yield criterion is then *** examples are given to illustrate the capability and effectiveness of the proposed numerical procedure for computing rigorous upper bounds for anisotropic soils.

关键词： Anisotropy limit analysis upper bound finite element

An upper bound for the generalized adiabatic approximation error with a superposition initial state

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

Science China(Physics,Mechanics & Astronomy) 2015年第3期58卷 1-7页

作者： WANG WenHua CAO HuaiXin LU Ling YU BaoMin College of Mathematics and Information Science Shaanxi Normal University Section of Military Operation Research Border Defence Academy College of Mathematics and Information Science Weinan Normal University

The classical adiabatic approximation theory gives an adiabatic approximate solution to the Schr6dinger equation （SE） by choosing a single eigenstate of the Hamiltonian as the initial state. The superposition principle of quantum states enables us to mathematically discuss the exact solution to the SE starting from a superposition of two different eigenstates of the time-dependent Hamiltonian H（0）. Also, we can construct an approximate solution to the SE in terms of the corresponding instantaneous eigenstates of H（t）. On the other hand, any physical experiment may bring errors so that the initial state （input state） may be a superposition of different eigenstates, not just at the desired eigenstate. In this paper, we consider the generalized adiabatic evolution of a quantum system starting from a superposition of two different eigenstates of the Hamiltonian at t = 0. A generalized adiabatic approximate solution （GAAS） is constructed and an upper bound for the generalized adiabatic approximation error is given. As an application, the fidelity of the exact solution and the GAAS is estimated.

关键词： upper bound error quantum adiabatic approximation

Effect of time delay on the upper bound of the time derivative of information entropy in a stochastic dynamical system

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2011年第11期20卷 122-126页

作者：张敏敏王参军梅冬成 Department of Physics Yunnan University Nonlinear Research Institute Baoji University of Arts and Sciences

The effects of the time delay on the upper bound of the time derivative of information entropy are investigated in a time-delayed dynamical system driven by correlated noise. Using the Markov approximation of the stochastic delay differential equations and the Schwartz inequality principle, we obtain an analytical expression for the upper bound UB（t） of the time derivative of the information entropy. The results show that there is a critical value of T （delay time）, and UB（t） presents opposite behaviours on difference sides of the critical value. For the case of the weak additive noise, T can induce a reentrance transition. Delay time T also causes a reversal behaviour in UB（t）-λplot, where λ denotes the degree of the correlation between the two noises.

关键词： information entropy upper bound time delay noise

An upper bound for the adiabatic approximation error

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2014年第2期57卷 218-224页

作者： WANG WenHua GUO ZhiHua CAO HuaiXin College of Mathematics and Information Science Shaanxi Normal University

In this paper, we derive an upper bound for the adiabatic approximation error, which is the distance between the exact solution to a Schrodinger equation and the adiabatic approximation solution. As an application, we obtain an upper bound for 1 minus the fidelity of the exact solution and the adiabatic approximation solution to a SchrOdinger equation.

关键词： upper bound error adiabatic approximation

A Lower and upper bound Method for Complex System Reliability Evaluation

在线全文

学校读者我要写书评

暂无评论

Journal of Donghua University(English Edition) 2011年第5期28卷 445-450页

作者：魏展明周凡陈耀武 College of Biomedical Engineering & Instrument Science Zhejiang University

It is hard for the existing methods to obtain the expression of the system reliability for most of the practical complex systems with a large number of components and possible stales. A new regression algorithm based on the lower and upper bounds is presented in this paper, which can obtain the system reliability analytically without concerning the structure of the complex system. The method has been applied to a real system and the reliability results are compared with those acquired by the classical method and the parametric method. The effectiveness and accuracy of the proposed method have been testified.

关键词： reliability lower bound upper bound regression algorithm

The upper bound of the Moebius Scalar Curvature of Submanifolds in S^n＋p

在线全文

学校读者我要写书评

暂无评论

Chinese Quarterly Journal of Mathematics 2010年第1期25卷 65-73页

作者： ZHONG Ding-xing SUN Hong-an MO Xiao-kai Department of Mathematics Gannan Teachers College Ganzhou 341000 China

The most important Moebius invariants in the Moebius differential geometry of submanifolds in S^n＋p are the Moebius metric g, the Moebius second fundamental form B, the Moebius form φ and the Blaschke tensor A. In this paper, we obtain the upper bound of the Moebius scalar curvature of submanifolds with parallel Moebius form in S^n＋p.

关键词： upper bound Moebius metric Moebius scalar curvature parallel Moebius form

Effect of die inlet geometry on extrusion of clover sections through curved dies:upper bound analysis and experimental verification

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

Transactions of Nonferrous Metals Society of China 2013年第4期23卷 1098-1107页

作者： Tahir ALTINBALIK Onder AYER Department of Mechanical Engineering Faculty of Engineering and ArchitectureTrakya University22180 EdirneTurkey

The effect of die inlet and transition geometry on the extrusion loads and ~aaterial flow for extrusion of clover sections were investigated and presented both theoretically and experimentally. For this purpose, four different die geometries including straight tapered and cosine transition profile and each of them having round and clover inlet geometries were chosen. In the experimental study, commercially pure lead was used because of its hot forming characteristic at room temperature. A newly kinematical admissible velocity field to analyze different profiles of extrusion dies of clover section from round bars was proposed by upper bound analysis. It is clear that the extrusion loads obtained from the theoretical analysis for various die inlet-die transition geometry combinations are in good agreement with the experimental results. Axis deviations of the parts which define the dimensional quality of the products were also investigated.

关键词： extrusion clover section upper bound optimal die profile

Pseudo-static analysis of cantilever retaining walls using upper bound limit analysis approach

在线全文

学校读者我要写书评

暂无评论

Journal of Central South University 2019年第1期26卷 241-255页

作者： Asadollah RANJBAR KARKANAKI Navid GANJIAN Farajollah ASKARI Department of Civil Engineering Science and Research Branch Islamic Azad University Iran International Earthquake Engineering Institute

Given the extensive utilization of cantilever retaining walls in construction and development projects,their optimal design and analysis with proper attention to seismic loads is a typical engineering *** research presents a new algorithm for pseudo-static analysis of retaining walls employing upper bound *** algorithm can be utilized to design and check the external and internal stability of the wall based on the proposed *** of the main features of this algorithm is its ability to determine the critical condition of failure wedges,the minimum safety factor and maximum force acting on the wall,as well as the minimum weight of the wall,simultaneously,by effectively using the multi-objective *** results obtained by the proposed failure mechanisms show that,while using the upper bound limit analysis approach,the active force should be maximized concurrent with optimizing the direction of the plane passing through the back of the *** present study also applies the proposed algorithm to determine the critical direction of the earthquake acceleration *** critical direction of earthquake acceleration coefficient is defined as the direction that maximizes the active force exerted on the wall and minimizes the safety factor for wall *** results obtained in this study are in good agreement with those of similar studies carried out based on the limit equilibrium method and finite element *** critical failure mechanisms were determined via optimization with genetic algorithm.

关键词： retaining wall upper bound pseudo-static analysis safety factor multi-objective optimization