Integration of process planning and scheduling functions

Automated process planning (APP) has received a considerable amount of attention in recent years. This has mainly been due to APP allowing for the bridging of the gap between design and manufacturing, and for its automation of the related tedious human task. While there have been several efforts in developing interfaces between computer-aided design (CAD) and APP, little attention has been given to the integration of APP and scheduling, which is likely to be of even higher importance. This paper addresses the basic issues involved in the integration of the two functions, demonstrates a methodology and the potential benefits of the integrated approach by an example, and presents directions for future research.     

Generation of shape functions for straight beam elements

Straight beam finite elements with greater than two nodes are used for edge stiffening in plane stress analyses and elsewhere. It is often necessary to match the number of nodes on the edge stiffener to the number on a whole plane stress element side. Beam elements employ shape functions which are recognised to be level one Hermitian polynomials. An alternative to the commonly adopted method for determining these shape functions is given in this note, using a formula widely reported in mathematical texts which has hitherto not been applied to this task in the finite element literature. The procedure derives shape functions for beams entirely from the set of Lagrangian interpolating polynomials. Examples are given for the derivation of functions for a three and four-noded beam element.     

Lyapunov functions and the control of the Euler-Bernoulli beam

A controller for the Euler-Bernoulli beam is derived using the complete distributed model along with a Lyapunov function approach. Model structure is therefore preserved in the control law whose parameters can be used to balance two different types of behaviour: the gross motion of the beam and the vibration superimposed on it. In the limiting case of a rigid beam, these two types of behaviour become indistinguishable and so the controller reduces to a proportional feedback law. This approach also guarantees that the controller provides asymptotic trajectory tracking for smooth initial conditions. Also, since it is not constrained to linear systems it could, in principle, be used for multi-link flexible robot systems.     

Integration in finite terms with elementary functions and dilogarithms

In this paper, we report on a new theorem that generalizes Liouville’s theorem on integration in finite terms. The new theorem allows dilogarithms to occur in the integral in addition to transcendental elementary functions. The proof is based on two identities for the dilogarithm, that characterize all the possible algebraic relations among dilogarithms of functions that are built up from the rational functions by taking transcendental exponentials, dilogarithms, and logarithms. This means that we assume the integral lies in a transcendental tower.     

Vibrations of moderately thick rectangular plates in terms of a set of static Timoshenko beam functions

In this paper, a set of static Timoshenko beam functions is developed as the admissible functions to study the free vibrations of moderately thick rectangular plates using the Rayleigh–Ritz method. This set of beam functions is made up of the static solutions of a Timoshenko beam under a series of sinusoidal distributed loads. The beam is considered to be a unit width strip taken from the rectangular plate in a direction parallel to the edges of the plate. In addition, the geometric boundary conditions of the plate are exactly satisfied in this set of beam functions, and the effect of the shear correction factor on the admissible functions of the plate is also taken into account. It can be seen that the method is sound in theory and no complicated mathematical knowledge is needed. Each of the beam functions is only a third-order polynomial plus a sine function or a cosine function. Furthermore, a change of the boundary conditions of the plate only results in a change of the coefficients of the polynomial. The method is very simple and a unified computational program can be given for the plates with arbitrary boundary conditions and thickness. Comparison and convergency studies demonstrate the correctness and the accuracy of the method. It can be shown that using a small number of terms of the static Timoshenko beam functions can give rather accurate results for all cases. Finally, the effect of thickness–span ratio on the eigenfrequency parameters of Mindlin rectangular plates is studied in detail.     

信息集成与知识集成

信息集成能够有效提高信息交流、处理和反馈的效率,增强系统之间通过协作解决复杂问题的能力。实现知识集成是信息系统集成的最终目标,因为系统之间交换的数据和信息都是知识的载体,因而知识集成也最具潜力和最难于实现。文章分析了信息系统集成中的知识集成问题、方法和使能技术,并通过一个资源管理模型来进行原理验证。     

CAD系统集成和集成技术剖析

系统集成能从根本上解决工程CAD技术应用中的分散独立和低水平重复问题,是进一步发掘计算机潜力的有效途径。文章以集成化的桥梁CAD系统的开发为背景,提出了由界面、工具和数据等三个层次组成的桥梁集成CAD系统结构,并针对软件工业的最新发展介绍了实现CAD系统集成的软件开发技术,包括面向对象的程序设计、图形界面和基础类库、软件构件化开发及数据库图形库连接等。     

The uniform beam

The development and use of a minicomputer-based interactive graphics program for a uniform beam arbitrarily loaded and arbitrarily supported. The program uses the linear stiffness matrix technique to solve for the reactions, bending moments, shear stress and deflection in the beam and supports. At University College London the program is implemented in FORTRAN on a PDP 11/40 using a VT 11 display. Interactively loading, supporting, changing the characteristics of the beam is accomplished using a light pen. At the U.S. Naval Academy the program is implemented in FORTRAN on a PDP 11/45 with an Evans and Sutherland Picture System. Interactively loading, supporting, changing the characteristics of the beam is accomplished using an analog tablet. The stiffness matrix analysis subroutine is the same in the two implementations; the graphics is, of course, similar in concept but different in implementation. In both cases the programs are educationally oriented. At UCL the program is presently being used with first and second year students. At the U.S. Naval Academy the program is used in Strength of Materials at the sophomore/junior level.     

Interval Integration

Editorial Commentary

Interval Integration     

Calculation of associated functions for rational modified weight functions

Let be a sequence of polynomials orthogonal with respect to a measure dω on the real line and the sequence of their associated functions (they are essentially the Hilbert transforms of these polynomials). We show how to get associated functions Q _n ^[m,l] if the measure dω changes to , where Φ_m and ϕ _l are polynomials of degree m resp.l. The results can be used for example to construct Gaussian quadrature rules for rational modified weight functions.     

浅谈现场总线开放系统的系统集成与应用集成

本文讨论现场总线国际标准多元化趋势下基于现场总线开放系统的集成技术。通信协议、标准功能块、OPC、OFC在系统集成、应用集成中的作用。     

面向集成情景的信息系统集成研究

随着计算机技术的不断发展与应用,信息系统集成建设成为发展的必然趋势,也是相关部门以及工作人员研究的重点内容之一。笔者以面向集成情景的信息系统集成为研究对象,运用一定的研究工具,从多种角度对信息系统集成进行了分析,对信息系统集成情景下的面向供应链管理的信息系统集成以及面向企业组织管理的信息系统集成,进行了理论与实践的研究,以供参考。     

医疗应用集成中基于语义的信息交换与集成

异构系统的应用集成和信息集成瓶颈已经成为企业信息化进程的严重障碍.为实现有效的企业应用与信息集成,我们以医疗行业为应用背景,建立了应用集成的语义模型,该模型包括资源语义模型、计算语义模型以及二者之间的绑定三部分基于此模型,提出了一个平台结构的应用集成方案,将应用系统发布为面向平台的服务,并在平台中建立对服务和领域资源的语义描述,实现服务请求和服务提供的基于语义的映射.这种方式使得应用系统可以以一种统一的方式通过平台与其他系统进行信息的交互,增强了系统的独立性、灵活性和可维护性.     

包装的整体化设计

包装设计已经不再停留在仅需要考虑造型、色彩、图案等外形装饰设计的阶段,现代的包装设计需要更多的注重材质、工艺、环保甚至生产、运输、消费、个性化选择等方面,同时也不再仅仅聚焦在单一产品上,而需要从整体的角度考虑提升包装企业的品牌和内涵,所以现代的商品包装需要进行一种整体化的设计。     

教练机的航电综合

军用飞机的航电系统日趋综合化,费用也很可观。由于教练机的主要任务是培训飞行员,而不是实战,所以,针对某型教练机,在综合数据、任务、显示控制的基础上,通过建立GPS、火控雷达、CCRP等仿真模型,在平显火控/多功能显示系统中用软件模拟实现了这些功能,从而简化了航电系统,大大降低了成本。利用这种成功的仿真模式,还可以根据需求建立先进武器如导弹、战场态势、防御等仿真模型,在航电系统中进行模拟,使航电系统能进一步得到超值使用。     

Consistent curved beam element

Curved beam finite elements with shear deformation have required the use of reduced integration to provide improved results for thin beams and arches due to the presence of a spurious shear strain mode. It has been found that the spurious shear strain mode results from an inconsistency in the displacement fields used in the formulation of these elements. A new curved beam element has been formulated. By providing a cubic polynomial for approximation of displacements, and a quadratic polynomial for approximation of rotations a consistent formulation is ensured thereby eliminating the spurious mode. A rotational degree of freedom which varies quadratically through the thickness of the element is included. This allows for a parabolic variation of the shear strain and hence eliminates the need for use of the shear correction factor k as required by the Timoshenko beam theory. This rotational degree of freedom also provides a cubic variation of displacements through the depth of the element. Thus, the normal to the centroidal axis is neither straight nor normal after shearing and bending allowing for warping of the cross section. Material nonlinearities are also incorporated, along with the modified Newton-Raphson method for nonlinear analysis. Comparisons are made with the available elasticity solutions and those predicted by the quadratic isoparametric beam element. The results indicate that the consistent beam element provides excellent predictions of the displacements, stresses and plastic zones for both thin and thick beams and arches.