Showing papers on "Design tool published in 1980"

Propagation of constraints applied to circuit synthesis

Abstract: A major component in the process of design is synthesis, the determination of the parameters of the parts of a network given desiderata for the behaviour of the network as a whole. Traditional automated synthesis techniques are either restricted to small, precisely defined classes of circuit functions for which exact mathematical methods exist or they depend upon numerical optimization methods in which it is difficult to determine the basis for any of the answers generated and their relations to the design desiderata and constraints. We are developing a symbolic computer-aided design tool, SYN, which can be of assistance to an engineer in the synthesis of a large class of circuits. The symbolic methods produce solutions which are clear and insightful. The dependence of each parameter on the individual design desiderata and circuit constraints can be easily traced.

SID: a system for interactive design

Abstract: A System for Interactive Design (SID) is a computer-aided visual facility for hierarchical (or recursive) design of complex systems. SID is built as a provision to make the potential of our graph theoretical design tool RGF (the recursive graph formalism) actually available to system designers. RGF, as we initially proposed in 1978, aimed at providing a logical basis for interactive design evolution from global to detailed, and/or from simple to complex. RGF was actually applied to designs of hospital information systems and petrochemical plants, and was proven useful for logically detecting and preventing human design errors and for computer-aided design evolution. SID includes the capabilities of SARA of UCLA and SADT of SofTech which are known as the system specification methodologies based on hierarchically structured graphs. Related works using similar graphs in other areas are H-graphs in language and automata theory, and DRLH in artificial intelligence.

OPDOT: A computer program for the optimum preliminary design of a transport airplane

Abstract: A description of a computer program, OPDOT, for the optimal preliminary design of transport aircraft is given. OPDOT utilizes constrained parameter optimization to minimize a performance index (e.g., direct operating cost per block hour) while satisfying operating constraints. The approach in OPDOT uses geometric descriptors as independent design variables. The independent design variables are systematically iterated to find the optimum design. The technical development of the program is provided and a program listing with sample input and output are utilized to illustrate its use in preliminary design. It is not meant to be a user's guide, but rather a description of a useful design tool developed for studying the application of new technologies to transport airplanes.

Improved design of tunnel supports. volume i: simplified analysis for ground-structure interaction in tunneling

Abstract: The purpose of this report is to provide the tunneling profession with improved practical tools in the technical or design area, which provide more accurate representations of the ground-structure interaction in tunneling. The design methods range from simple analytical and empirical methods to sophisticated finite element techniques as well as an evaluation of tunneling practices in Austria and Germany. Volume 1 describes a simplified analysis method for ground structure interaction in tunneling, which is necessary because of the indeterminate relationships which describe the realm of tunneling parameters. The method is geared toward hand calculations that incorporate the effects of three of the most significant factors influencing the ground structure behavior. The authors point out that it is doubtful that the complex interrelationships among the nearly countless variables in any real tunneling problem can ever be rigorously analyzed, even using the most sophisticated numerical techniques. As an alternative approach, the simplified method focuses on the essential elements of very complicated phenomena in order to isolate the three major factors that have an overriding influence on support loads. These factors are: (1) the relative stiffness of the support and ground mass; (2) the spatial lag or delay of support construction behind tunnel face; and (3) the yielding of ground mass as its shear strength is exceeded. Using these factors, the intent of Volume 1 is to provide an analysis in which accentuated computational ease, coupled with sufficient accuracy, makes the simplified method a valuable and effective design tool for use in preliminary design, for parametric studies in final design, and for updating the design during construction.

Optimization of the Influence of Problem Modifications on Given Microprogrammed Controllers

Abstract: For the logic design of digital controllers, efficient synthesis algorithms have been published. Most of these assume, that a completely new hardware consisting of the fewest number of components has to be built. The implementation of those algorithms form an important part of a CAD system for logic design. In order to be accepted in practice, a CAD system has to take into account additional requirements. One of these concerns with the minimization of hardware changes caused by subsequent modifications of the control task which often become necessary after the completion of the hardware implementation. This paper describes a method which solves this problem for an universal structure of microprogrammed controllers. This method is implemented as a module of the CAD program system LOGE. LOGE supports the logic design of hardwired, microprogrammed, and microprocessor based controllers. LOGE already proved to be a powerful design tool in several industrial applications.

Seismic stability of reinforced earth retaining walls

Abstract: This paper describes a simplified seismic design approach proposed by the author (1979), based on limiting deformations. Limitations of the method are outlined and results of a simple computer programme presented. With further analysis, charts may be developed to provide a useful design tool.

Computer-aided design of stub-girder system

Abstract: This paper presents discussion and comparison of three analysis models. The Non-Prismatic Beam Model, the simplist of the three, uses the method of numerical integration for analysis of the stub-girder system as a variable cross section beam. In the numerical procedure, distributed and concentrated external loads are replaced by equivalent concentrated loads spaced equally along the beam at specified pivot points. The Vierendeel Truss Model, which lends itself especially well to the stub-girder system due to its structural nature, analyzes the system by the stiffness method for plane frames. The Finite Element Model is comprised of two-dimensional quadrilateral elements. In comparing the three models, the non-prismatic beam program provides consistently unconservative results when compared to the more accurate Viernendeel Truss Program and Finite Element Program; however, the simplicity of the program and its capabilities for use as a design tool make the non- prismatic beam program a desirable resource. Also included in this paper is a discussion of three parametic studies- stub-girder stiffness ratio, stub-girder length ratio, and stub length ratio, and of design procedure.

Static and Dynamic Analysis Of Reed Valves Using a Minicomputer Based Finite Element Systems

Abstract: The purpose of this paper is to present a minicomputer based finite element design procedure and describe its use as a valve design tool. The report consists of a discussion of automatic mesh generation, the finite element method, solution of the static and eigenvalue problems, and two examples where the techniques have been applied to real valve geometries. A comparison of predicted and experimental values of stress, natural frequencies and mode shapes for the two test cases is also included.

Nomographs for the design of steel reinforcement in continuously reinforced concrete pavement

Abstract: This study sought to develop graphic procedures (nomographs) for the design of continuously reinforced concrete pavement (CRCP) by the Texas State Department of Highways and Public Transportation for a range of specified local conditions. This set of nomographs, when used as a supplementary design tool with the CRCP-2 computer program model, will facilitate CRCP design. This will substantially reduce both the time and the cost involved in the design process, while at the same time taking into account the effect of regional and local environments. First, regression equations were developed for the prediction of three design parameters (crack spacing, crack width,and steel stress), and then principles of nomography were applied to these mathematical relations to prepare three corresponding nomographs. The choice of equations was made following multiple linear and nonlinear least-squares fits to a fractional factorial of simulated observations that were output from the CRCP-2 computer program. Theoretical models, developed at the Center for Highway Research in Austin, Texas, and variations of the three design parameters with each of the relevant input variables over the range of the simulated data were considered in deciding on the form of the regression equations. Standard-error-of-residuals and R squared (proportion of variance explained by the regression equation) statistics were considered in the final choice of coefficients for the regression equations. Confidence prediction limits were determined by using multiple linear- regression techniques for application to nomograph predictions. A recommended procedure for the use of the nomographs with appropriate limiting criteria is out-lined and an example given.

A cad program for suboptimal linear regulators

Abstract: A number of suboptimal linear regulator design strategies is discussed and it is shown that they may be incorporated within a general problem formulation. It is therefore possible to adopt a common numerical approach to the solution of these problems and a gradient minimization technique is selected as the solution method following a study of four alternative schemes. This method requires the solution of a pair of Liapunov matrix equations during each iterative step and it is found that these equations are best solved by application of the Bartels-Stewart algorithm. An interactive CAD program has been developed and it functions both as a design tool and as a research aid. As a design tool it offers access to a number of existing design strategies, provides added flexibility in the choice of controller configuration and enables different strategies to be merged to form an effective overall design procedure. As a research aid the program is easily modified to include new controller configurations or test new performance index specifications; it may also be extended to handle linear discrete-time systems and linear stochastic systems.

Gaelic logic simulator: an interactive CAD tool

Abstract: The use of digital logic simulation in the design of integrated circuits has long been established. In this role, however, simulation in general has remained a non-interactive CAD tool. In an attempt to alter this situation a simulator has been developed which will permit the designer to interact with the circuit, thus making simulation an even more effective design tool particularly in its use for debugging incorrect designs.