Abstract: This paper discusses the development of APL, emphasizing and illustrating the principles underlying its design. The principle of simplicity appears most strongly in the minimization of rules governing the behavior of APL objects, while the principle of practicality is served by the design process itself, which relies heavily on experimentation. The paper gives the rationale for many specific design choices, including the necessary adjuncts for system management.

Abstract: Applications of the move limit method are described in the least weight design of elastic stressed-skin structures, using finite elements, when the design variables consist of member cross sections and skin thicknesses. Numerical examples presented involve up to two load conditions with active constraints on stresses and displacements and on the design variables themselves which are subjected to upper and lower bounds. Convergence is compared where appropriate with that of a fully-stressed design iteration. Computational efficiency achieved confirms the usefulness of the sequence of linear programs approach. HE power of the digital computer in the analysis of complex structures is now universally recognized and the associated computational techniques have reached an advanced stage of development. The computer can also be used in the automation of more general portions of the design process when these consist of repetitive sequences of computations interspersed with decisions that are taken on a factual rather than a subjective basis. The useful range of such applications is increasing as more efficient hardware, software and numerical techniques become available; benefits achievable may include an acceleration of the design process, a more efficient deployment of design effort and an improved final design resulting from a more thorough examination of possible alternatives. One class of such applications, which is the subject of this paper, is the choice of reinforcing member cross sections and skin thicknesses in stressed-skin elastic structures of specified basic geometry which are represented by finite element idealizations. Optimum designs are sought to carry several distinct loadings in turn when constraints are imposed on behavioral variables such as stresses and displacements and on the permissible range of the design variables themselves. In aeronautical applications optimality is usually synonymous with least weight once the over-all configuration and the structural material have been selected (fail safe features can be looked upon as behavioral constraints), so attention is restricted here to least weight design, although the approach employed can be used with any merit function with continuous first derivatives with respect to the design variables. For simplicity, weights of joints and connections are omitted but these may readily be incorporated. Techniques of two distinct types have received vigorous development in recent years for use in this context. Firstly there are techniques based on the general methods of mathematical programing, which are reviewed in Pope and Schmit,1 and secondly there are those based on optimality criteria which have been evolved for use in specific classes of application; an approach of the latter type may be firmly established when constraints on displacement only are involved2 but applications of this3 and similar approaches4'5 to airframe structures usually include an element of semi-intuitive reasoning when constraints on stresses are active. The mathematical programing techniques converge in general

Abstract: The Naval Ship Research and Development Center began formal work in computer aided design in 1965. The initial tasks undertaken were the development of individual batch application programs which were little more than the computerization of manual design methods. The programs developed included those shown in Figure 1.

Abstract: The design process for large aerospace vehicles is discussed, with particular emphasis on structural design. Problems with current procedures are identified. Then, the contributions possible from automating the design process (defined as the best combination of men and computers) are considered. Progress toward automated design in the aerospace and other communities is reviewed, including NASA studies of the potential development of Integrated Programs for Aerospace-Vehicle Design (IPAD). The need for and suggested directions of future research on the design process, both technical and social, are discussed. Although much progress has been made to exploit the computer in design, it is concluded that technology is available to begin using the computer to speed communications and management as well as calculations in the design process and thus build man-computer teams that can design better, faster and cheaper.

Abstract: : Contents: Elements of computer aided design; Finite dimensional unconstrained optimization; Linear programming; Nonlinear programming and finite dimensional optimal design; Finite dimensional optimal structural design; The calculus of variations and optimal process theory; Optimal structural design by the indirect method; Methods of steepest descent for optimal design problems; Application of steepest descent methods to optimal structural design.

Abstract: The advantages and possibilities offered by EDP facilities in the field of engineering design are illustrated by the example of a sodium/sodium intermediate heat exchanger. The program system discussed is capable of designing the heat exchanger for steady state operating conditions. The usual thermal design is followed by mechanical strength design calculations. Besides the usual print output a plot output is also possible, consisting of diagrams and simple cross-sectional drawings to scale. (GE)

Abstract: Systems design consists of a tremendously complex series of choices in which no decision point is completely independent of other decisions which have already been made or have yet to be made. A systems approach to the design of document-handling information systems would require a detailed examination of the choices to be made in the design process and the ramifications of possible choices in terms of the capabilities, performance, cost, and other characteristics of the system. The authors advocate a systematic procedure involving six steps: 1) identification of fixed parameters, 2) identification of variable parameters, 3) identification of available options for each variable parameter, 4) identification of factors affecting a choice among available options, 5) identification of factors affected by a choice among available options, and 6) logical analysis of the picture thus presented to determine the optimum sequence in which decisions should be made during the design process and the nature of the deci...

Abstract: : A review of the naval ship concept design development process is presented and methods for modeling the design process and improve convergence in the iterative design sequence are discussed. The use of GERT type network techniques for modeling the design process and determining improvements in design convergence, as well as in design process time and cost is advocated. Design optimization is always subject to uncertainty in the performance weighing of component systems as well as risk in their actual performance to design criteria. Methods for design optimization under risk are reviewed. (Modified author abstract)

Abstract: This paper describes a medium being developed for abstraction and expression of program structure. The medium is to be used to represent programs during the design process; It forms the basis for their implementation.The following point of view is adopted. Program design is an iterative, trial-and-error process, in which a basic solution to part of the problem is refined, added to, and modified into a complete solution. The final result should be well-structured in the sense described by Dijkstra (1) in order for the designer to understand the program sufficiently to be confident in its correctness.

Abstract: These are only a few examples from among the great number of events we needed to take into account and to process in order to achieve an accurate knowledge of the river behaviour during floods; and, in conclusion, we want to emphasize again how the use of an interactive system and a video unit have made it possible to set up our model very quickly, through the fitting of a great number of past events, and to use it very easily for any purpose, such as studying the concurrence of different parameters on the phenomenon, supplying the engineering design with the necessary data (water levels and discharges), simulating the behaviour of engineering hydraulic works to be built, and giving objective and timely data for flood control.