Abstract: The conditions leading to a point of inflexion, loop cusp for parametric cubic curves and parametric B-spline cubic curves are investigated. Some useful conclusions are obtained.

Abstract: The axial dimensions in an engineering drawing can be used to determine line length so that the drawing will be to scale unless out of scale dimensions are explicitly used. In addition, over and under dimensioning can be detected. Therefore changes can be made to the dimensions and the drawing will be changed automatically. This technique has been used for local scaling of both in-line and out-of-line subpictures.

Abstract: TORNADO is a database management system developed for CAD/CAM application systems. It is a CODASYL-type network system written in FORTRAN, with a very powerful tool for handling complex data structures. There are no restrictions on combinations of object classes and relationships, and it directly handles many-to-many relationships and compound object classes. TORNADO also handles variable object length and dynamic length table records. A second paper will discuss the implementation details.

Abstract: A CAD system based on combining structural optimization methods and graphical interaction is presented. The optimization methods implement the automated decisions and algorithms while the interaction provides the means to implement the designer's decisions. A new interactive optimization procedure for optimal truss design is proposed. The structural topology, geometry and member sizes are treated as design variables. Results show that the system provides a powerful tool to obtain a practical optimum design.

Abstract: A new approach to the interactive solution of optimal floor plan layout problems is presented. The method is based upon the use of probability theory to predict the likely consequences of activity location decisions, combined with use of low-resolution raster graphics displays. It not only generates high quality results, but also provides the designer with a structural understanding of the space of alternatives being explored.

Abstract: The paper discusses integrated FEM (finite-element method) software for structural analysis and CAD applications. The main purpose of this paper is to emphasize the need to use interactive graphics in structural analysis and CAD. An attempt is made to review general-purpose pre- and post-processing programs developed for FEM applications, and integrated FEM programs for structural mechanics applications. Some large integrated systems for sizing and analysing aircraft structures are presented.

Abstract: A new approach to the hidden-line problem is presented. The main tools of the method are calculation of edge intersections, test on appearance or disappearance of edges, and record sort. Special treatment of coherence and singularities is required. The programs are written in FORTRAN and are very short and simple. The computation time of the algorithm is short enough to handle scenes of high complexity.

Abstract: This paper deals with the application of numerical methods to finding approximate solutions for a two-dimensional Reynolds' equation. Pressure height parameters ( P ∗ ) are evaluated at a series of discrete points on a rectangular mesh in the circumferential direction. Using these parameters the Reynold's equation is transformed into its equivalent finite difference form. In this form the equation gives the value of the pressure height parameter P ∗ in terms of the values at neighbouring points and the corresponding influence coefficients. The finite difference equation is solved using an interactive method. Jacobi, Gauss-Seidel and successive over-relaxation methods are discussed. It is observed that by using an optimum over-relaxation factor, much computer time can be saved. Finally a convergence criterion is discussed which decides the iteration process.

Abstract: Bezier's method is one of the most famous in computational geometry. In his book Numerical control Bezier gives excellent expositions of the mathematical foundations of this method. In this paper a new expression of the functions {fn,i(u)} f n,i (u)=1− Σ p=0 i−1 C p n u p (1−u) n−p (i=1,2,…,n) is obtained. Using this formula, we have not only derived some properties of the functions {fn,i(u)} (for instance f n,n (u) n,n−1 (u) n,1 (u) u ϵ [0, 1] and functions {fn,i(u)} increase strictly at [0, 1] etc) but also simplified systematically all the mathematical discussions about Bezier's method. Finally we have proved the plotting theorem completely by matrix calculation.

Abstract: A hidden line algorithm for a restricted class of objects is presented. Internal memory requirements are reduced by sequencing geometrical data on magnetic tapes. The object is represented by a data structure which changes dynamically as the object is scanned. Statistical methods are used to predict an optimal configuration for the structure. A new point-in-polygon test is introduced. The algorithm is compared quantitatively with an earlier method. Examples of pictures are given.

Abstract: VLSI (very large-scale integration) technology provides and demands new ways of solving large-scale computational problems. A pipelined version of a real-time hidden surface elimination algorithm is proposed. The approach is tuned to the requirements of the VLSI technology: it is simple and regular, employs only local communication, and attains a high degree of parallelism. The feasibility of the technique is demonstrated for a computer graphics system where objects are defined in terms of planar triangular surface elements. A case is made in terms of early 1980s technology. The use of VLSI will make high-power graphics available to the small user as well as the traditional flight simulator customer. This is achieved by enabling system expansion to take place through the addition of more identical chips. Consequently system cost is linear with respect to the number of chips used, a number determined by the maximum number of rendering elements needed by the specific user application.

Abstract: Current CAD/CAM systems employ a variety of spline types, spline representations, and curve design algorithms. The IGES (initial graphic exchange specification) was designed to enable interchange of the more commonly used spline types among CAD/CAM systems, independent of the design algorithms originally used to create them. IGES supports parametric cubic splines through a piecewise polynomial representation. This paper describes the design considerations leading to the interchange common spline curve types. A short introduction to splines and spline representations is included.

Abstract: Professor Bezier examines the progress that has been made in manufacturing and production over the last 25 years. The effects of the introduction of CAD/CAM are discussed. The easy availability of accurate models and the introduction of flexible shops are put forward as major improvements. Possibilities for further improvements are mentioned.

Abstract: In this paper, the authors describe 13 investor motivations for initiating a project. Quantitative criteria to measure success in achieving these motivations are listed. One of the these criteria, net present value, is selected as most capable of reflecting key investor motivations. This measure is manipulated to yield a life-cycle costing relationship which can be used as an objective function in the design decision-making process. It is shown that the life-cycle cost equation in its most general form embodies within it a family of commonly used objective functions which describe financial, technical performance and user criteria. Results from a case study in which different objective functions were used are presented.

Abstract: Designing windows in buildings is a multicriteria, multivariable design problem with many constraints. This paper examines the different natures of the window design information that can be provided through mathematical simulation and optimization models and considers some approaches to choosing a solution.

Abstract: The paper presents a computer system based on a trial-and-error synthesis method for CAD of mechanisms. A database containing a mechanism catalogue and information on previously designed mechanisms furnishes trial mechanisms which can be analysed, modified and stored in a work database. From this database, the characteristics of every mechanism can be retrieved. The results can be stored permanently in the first database. Graphics options are provided.

Abstract: VLSI (very large scale integration) circuits are the most complex chips yet developed, typically having over 50 000 transistors. Some examples are a 16 kbit static RAM chip or a 16 bit microprocessor chip. The complexity of these chips necessitates the invention of new techniques in order to reduce production costs and design time. The design cycle of an IC (integrated circuit) consists of a series of complex tasks often requiring more than a year to complete. As ICs grow in complexity, the cycle time increases and could potentially become too lengthy to be realistic. One of the most time consuming tasks in the design cycle is laying out a circuit. This paper describes a new layout aid that will significantly reduce the layout time. In this new layout aid, a designer is required to digitize an approximate layout, fully routed but loosely placed. From this approximate layout, two graphs are created, one representing the relative vertical position of each circuit element in the loose sketch, and the other representing their relative horizontal position. In the graphs, modes indicate the coordinate locations and branches indicate minimum spacing requirements due to design rules. An optimization technique, namely the longest path algorithm, is invoked to compact the circuit. In the original layout, design rule violations may be overlooked, which will prevent the longest path algorithm from converging. A method is devised to resolve this problem. Results of empirical testing of the new layout aid are reported.

Abstract: This paper gives a definition for the convexity of B-spline surfaces and points out the conditions, on which the convexity depends. A back shift smoothing method is introduced. This method is built on the basis of the convexity conditions. Application of this smoothing method gives a strictly convex curve.

Abstract: The citations in this bibliography are presented by subject: airport planning and design, automobile design, citizen participation, downtown people-mover (dpm) systems planning and design, highway facilities, highway route planning, highway safety, human figure simulation, planning and design of ride sharing systems, rearload analysis and planning simulation of outer space and aircraft operations, simulation of traffic movements, traffic signal optimization, transit facilities and operations analysis and planning, transit system planning and design, transportation data display and editing, transportation education, transportation systems planning. (TRRL)

Abstract: The paper outlines SPA, a computer system which allows for the automatic design of bathrooms. Frames are used to represent design knowledge and bargaining is employed as the principle design procedure. It is suggested that SPA can be extended to design houses and that an interactive version with a natural language interface can be developed.

Abstract: Probabilistic structural design is a degree of difficulty greater than deterministic design and effectively is only tractable using a computer. This paper outlines one approach to the design of framed structures subject to random loading. In particular stochastic approximation is used iteratively to improve the value of the optimality criterion, leading to a guaranteed optimal solution in the limit. Two framed structures are used to illustrate the computations which are performed in conjunction with a random number generator to simulate the probabilistic aspects of the loading. The approach is independent of the probability model assumed for the loading. It is straightforward to implement and has good solution convergence characteristics.

Abstract: This paper looks at the problem of verification of the weight coefficients in multiattribute decision making. A procedure is developed based on a priori qualitative evaluations used to form a partial linear ordering of the alternatives. A suitable algorithm is presented.

Abstract: Nonlinear programming is one method of solving process design problems. The formulation of a problem is: given a revenue or cost function subject to both equality and inequality constraints, find the optimal vector of design variables or operating conditions. Difficulties in meshing codes that solve nonlinear programming problems with process models and simulation packages are discussed here. Major difficulties arise because the representation of operations in a chemical plant involves highly modular equations. subroutines from which the equations cannot be readily extracted, implicit relations between subroutines and associated databases, and large numbers of constraints and variables. In addition, certain problems arise because of the iterative numerical techniques of solution employed in the optimization problems such as: how can suitable initial guesses for the independent variables be obtained, how can numerical computational errors be reduced, how can ill-conditioning of the matrices used be diminished, and how can undefined arguments of the constraints and objective function be avoided. All of these factors and ways to resolve them are considered. We also discuss briefly the relative performance of nonlinear programming codes that can be employed in design.

Abstract: This paper describes a pilot interactive computer program used by midshipmen in the early phases of design of a low-temperature solar energy collector. The model has been made as simple as possible without losing the fundamental relationships of thermodynamics, fluid dynamics and heat transfer theory. The subjects covered include solar radiation, flat plate collectors, application loads and economics. Design parameters are location, time duration, absorptivity, reflectivity, tilt angle, number of cover glasses, collector temperature, air temperature, insulation condition, etc. The program provides enough information to allow users to evaluate and design their own solar thermal processes.

Abstract: A dynamic programming algorithm which chooses types, heights and sites of towers along a given transmission line route is described. On the basis of estimated data for the ground strength along the line path, and the criterion of minimum construction costs, a set of consecutive cheapest solutions of the problem is determined (ie the optimal and the required number of suboptimal solutions). It is proposed to submit the obtained set of solutions for further analysis based on some additional criteria and a more accurate survey of ground strength in tower locations already known. The analysis may prove that one of the suboptimal solutions is most advantageous. Some specific features of the computer program and the results of experimental calculations are presented.

Abstract: A five-node circuit model containing a single energy-storage element emulating the static characteristics of a triac is presented. The model consists of 12 resistors, one inductor, one current-controlled current source, three constant-voltage sources and two constant-current sources, all having fixed values, and three switches. Using the model would result in a significant reduction in computing time — a factor which is of paramount importance for optimization runs.

Abstract: Architectural drawing systems are discussed, with emphasis on quality of user-interfaces and improvement offered by new computing technology. EdCAAD's STAG drawing system is described, demonstrating the benefits of newer technology.