检索结果-内蒙古大学图书馆

A weight function methodology for the assessment of embedded and surface irregular plane cracks

ENGINEERING FRACTURE MECHANICS 2006年第17期73卷 2662-2684页

作者： Montenegro, Hugo Lopez Cisilino, Adrian Otegui, Jose Luis Univ Mar del Plata Inst Mat Sci & Technol Welding & Fracture Div INTEMA RA-7600 Buenos Aires DF Argentina

A low cost numerical tool for the calculation of mode I stress intensity factors K in embedded and surface irregular cracks is presented in this paper. The proposed tool is an extension of the O-integral algorithm due to Oore and Burns for the assessment of embedded plane cracks using the weight function methodology. The performance of the O-integral is assessed first by comparing its K results to exact solutions for embedded elliptical and rectangular cracks. From the analysis of this data it is found that the error in the K results systematically depends on the crack aspect ratio and the local crack front curvature. Based on this evidence a corrective function is derived in order to remediate the limitations of the O-integral. Solutions due to Newman and Raju are used to account for the effects of free surfaces and finite thickness. The accuracy of the proposed procedure is assessed by solving a number of examples and by comparing the obtained results to those available in the literature. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： fracture mechanics stress intensity factor three-dimensional cracks numerical algorithms surface cracks

来源：评论

学校读者我要写书评

暂无评论

New one terminal digital algorithm for adaptive reclosing and fault distance calculation on transmission lines

引用

IEEE TRANSACTIONS ON POWER DELIVERY 2006年第3期21卷 1231-1237页

作者： Radojevic, ZM Shin, JR Konkuk Univ Dept Elect Engn Seoul 143701 South Korea

This paper presents a new numerical spectral domain algorithm devoted to blocking unsuccessful automatic reclosing onto permanent faults and fault distance calculation. Are voltage amplitude and fault distance are calculated from the fundamental and third harmonies of the terminal voltages and currents phasors. The electric arc is modeled with its voltage waveshape defined numerically on the basis of a number of arc voltage records obtained in the high-voltage laboratory. From the calculated arc voltage amplitude, it can be concluded whether the fault is a transient arcing fault or a permanent arcless fault. If the fault is permanent, automatic reclosure should be blocked. The algorithm can be applied for adaptive autoreclosure, distance protection, and fault location. The results of algorithm testing through computer simulation and real field record are given.

关键词： arc resistance electric power systems fault location numerical algorithms protection spectral analysis transmission lines

来源：评论

学校读者我要写书评

暂无评论

A continuum analysis of charge induced ferroelectric domain wall motions

引用

JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2006年第1期54卷 86-112页

作者： Kessler, H Balke, H Framatome ANP GmbH FGTM Mech Design D-91050 Erlangen Germany Tech Univ Dresden Inst Solid Mech D-01062 Dresden Germany

A continuum model is presented for the motion of a domain wall in a plane 90 degrees-domain configuration subjected to an isolated extrinsic charge near the surface of a ferroelectric single crystal. Local pinning is postulated for the kinetic law. Before the appearance of the extrinsic charge, all polarization surface charges are taken to be neutralized by environmental charges. The domain wall motion after the appearance of the extrinsic charge is assumed to proceed sufficiently fast without any significant conductive currents on the surface or in the interior of the crystal such that new surface and interface polarization charges remain unscreened and contribute to the ferroelectric anisotropy energy. A non-admissible divergence of the electric field and consequently of the local thermodynamic driving force and of the domain wall velocity appears in the model if the domain wall charged by interface polarization charges intersects the crystal surface charged by surface polarization charges under an arbitrary angle. The physically possible domain wall angle is identified using the condition of a non-divergent driving force. The ferroelectric anisotropy energy and an intrinsic surface energy of the domain wall, however, do not provide stability of the domain wall trajectory against an unlimited increase of its curvature at the surface. The problem has been solved conceptually by proper account of the domain wall bending energy. numerical and dimensional analysis explain also why domain walls driven by extrinsic charges remain almost straight in soft ferroelectrics. (c) 2005 Elsevier Ltd. All rights reserved.

关键词： electromechanical processes ferro-electric material analytic functions numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

Computation of the generalized Mittag-Leffler function and its inverse in the complex plane

引用

INTEGRAL TRANSFORMS AND SPECIAL FUNCTIONS 2006年第9期17卷 637-652页

作者： Hilfer, R. Seybold, H. J. Univ Stuttgart ICP D-70569 Stuttgart Germany Univ Mainz Inst Phys D-55099 Mainz Germany

The generalized Mittag-Leffler function E-alpha,E-beta (z) has been studied for arbitrary complex argument z is an element of C and parameters alpha is an element of R+ and beta is an element of R. This function plays a fundamental role in the theory of fractional differential equations and numerous applications in physics. The Mittag-Leffler function interpolates smoothly between exponential and algebraic functional behaviour. A numerical algorithm for its evaluation has been developed. The algorithm is based on integral representations and exponential asymptotics. Results of extensive numerical calculations for E-alpha,E-beta (z) in the complex z -plane are reported here. We find that all complex zeros emerge from the point z =1 for small alpha. They diverge towards -infinity+(2 k -1)pi i for alpha -> 1(-) and towards -infinity+2 k pi i for alpha -> 1(+) ( k is an element of Z). All the complex zeros collapse pairwise onto the negative real axis for alpha -> 2. We introduce and study also the inverse generalized Mittag-Leffler function L-alpha,L-beta (z) defined as the solution of the equation L-alpha,L-beta (E-alpha,E-beta (z )) = z . We determine its principal branch numerically.

关键词： special functions of mathematical physics fractional calculus generalized Mittag-Leffler functions numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

A time-integration scheme for thermomechanical evolutions of shape-memory alloys

引用

COMPTES RENDUS MECANIQUE 2006年第4期334卷 266-271页

作者： Peigney, M Lab Cent Ponts & Chaussees Cellule Mecan & Struct F-75732 Paris 15 France

This Note presents a time-integration strategy for computing the evolution of structures embedding shape-memory alloys in a thermomechanical setting. A variational formulation is associated with the scheme proposed, which allows one to study the existence and unicity of solutions depending on the material model considered. A numerical example is presented to illustrate the method and discuss the influence of the thermomechanical coupling.

关键词： solids and structures shape-memory alloys phase transformation thermomechanical coupling numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

Proposal of a new computational method for the analysis of the systematic differences in star catalogues

引用

JOURNAL OF COMPUTATIONAL METHODS IN SCIENCES AND ENGINEERING 2006年第5-6期6卷 429-437页

作者： Lopez Orti, J. A. Marco Castillo, F. J. Martinez Uso, M. J. Univ Jaume 1 Dept Matemat Castellon de La Plana Spain Univ Politecn Valencia Dept Matemat Aplicada E-46022 Valencia Spain

The aim of this paper is the analysis of the bias contained in star catalogues, these errors can be obtained by means of kinematics or dynamical methods. In this paper a general method, suitable when the sample is not... 详细信息

关键词： Approximation of functions star catalogues reference frames numerical algorithms

来源：评论

学校读者我要写书评

暂无评论

Computing curve intersection by means of simultaneous iterations

引用

numerical algorithms 2006年第2期43卷 151-175页

作者： Bini, Dario A. Marco, Ana Univ Pisa Dipartimento Matemat I-56100 Pisa Italy Univ Alcala de Henares Dept Matemat Madrid Spain

A new algorithm is proposed for computing the intersection of two plane curves given in rational parametric form. It relies on the Ehrlich-Aberth iteration complemented with some computational tools like the properties of Sylvester and Bezout matrices, a stopping criterion based on the concept of pseudo-zero, an inclusion result and the choice of initial approximations based on the Newton polygon. The algorithm is implemented as a Fortran 95 module. From the numerical experiments performed with a wide set of test problems it shows a better robustness and stability with respect to the Manocha-Demmel approach based on eigenvalue computation. In fact, the algorithm provides better approximations in terms of the relative error and performs successfully in many critical cases where the eigenvalue computation fails.

关键词： curve intersection structured matrices numerical algorithms Sylvester resultant simultaneous iterations

来源：评论

学校读者我要写书评

暂无评论

Computational experience with robust pole assignment algorithms

Computational experience with robust pole assignment algorit...

引用

IEEE Conference on Computer-Aided Control System Design

作者： Sima, Vasile Tits, Andre L. Yang, Yaguang Natl Inst Res & Dev Informat Bucharest 011455 Romania Univ Maryland Syst Res Inst College Pk MD 20742 USA Orbital Sci Corp Guidance Navigat & Control Dept Dulles VA USA

ISBN: (纸本)9780780397972

Two algorithms for robust pole assignment by state feedback, proposed by Kautsky, Nichols and Van Dooren (1985) and by Tits and Yang (1996) are briefly reviewed. MATLAB code implementations of these algorithms, place (from the MATLAB Control System Toolbox) and robpole (from SLICOT), are then numerically compared on randomly generated test data sets, as well as on examples from two benchmark collections, in terms of the robustness (insensitivity of poles to variations in plant parameters) of the closed-loop systems they produce. The functions place and robpole are also compared with each other, as well as with the (non robust) pole assignment code pass (from SLICOT) in terms of CPU time and accuracy of the pole assignment.

关键词： computer-aided control system design numerical algorithms numerical linear algebra pole assignment software library

来源：评论

学校读者我要写书评

暂无评论

Start vector generation for implicit Newmark time integration of the wave equation

Start vector generation for implicit Newmark time integratio...

引用

15th Biennial Conference on Computation of Electromagnetic Fields

作者： Skarlatos, A Clemens, M Weiland, T Tech Univ Darmstadt Inst Theorie Elektromagnet Felder D-64289 Darmstadt Germany Helmut Schmidt Univ Univ Fed Armed Forces Hamburg Dept Elect Engn Chair Theory Elect Engn D-22043 Hamburg Germany

Different extrapolation strategies are presented for the construction of starting values in implicit Newmark time-stepping schemes used for the solution of the electromagnetic wave equation. The implicit character of this schemes implies the solution of a system of linear equations in each time step. The choice of a good start value derived from the extrapolation of the equation system is shown to improve the convergence of the iterative conjugate gradient solver which reduces the total simulation time.

关键词： electromagnetic wave propagation numerical algorithms time-domain methods

来源：评论

学校读者我要写书评

暂无评论

Health monitoring of a satellite system

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2006年第3期29卷 593-605页

作者： Chen, Robert H. Ng, Hok K. Speyer, Jason L. Guntur, Lokeshkumar S. Carpenter, Russell Univ Calif Los Angeles Dept Mech & Aerosp Engn Los Angeles CA 90095 USA NASA Goddard Space Flight Ctr Flight Dynam Anal Branch Greenbelt MD 20771 USA

A health monitoring system based on analytical redundancy is developed for satellites on elliptical orbits. Analytical redundancy, which reduces the need for hardware redundancy, uses the modeled dynamic relationship between system inputs and measured system outputs to form a residual process that is used for detecting and identifying faults. First, the dynamics of the satellite including orbital mechanics and attitude dynamics is modeled as a periodic system. Then, periodic fault detection filters are designed to detect and identify the satellite's actuator and sensor faults. In addition, parity equations are constructed using the algebraic redundant relationship among actuators and sensors. Furthermore, a residual processor is designed to generate the probability of each fault by using a sequential probability test. Finally, the health monitoring system, consisting of periodic fault detection filters, parity equations, and residual processor, is evaluated in the simulation in the presence of disturbances and uncertainty.

关键词： Satellites Horizon Sensors Periodic Fault Detection Attitude Dynamics Actuators Orbital Mechanics Elliptical Orbit Accelerometer numerical algorithms GPS

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：