Suggested research topics in sensitivity and stability analysis for semi-infinite programming problems

We suggest several important research topics for semi-infinite programs whose problem functions and index sets contain parameters that are subject to perturbation. These include optimal value and optimal solution sensitivity and stability properties and penalty function approximation techniques. The approaches proposed are a natural carryover from parametric nonlinear programming, with emphasis on practical applicability and computability.Research supported by National Science Foundation Grant SES 8722504 and Grant ECS-86-19859 and Grant N00014-89-J-1537, Office of Naval Research.     

Dirichlet Problem for Degenerate Quasilinear Elliptic Equations Suggested by the Anisotropic Permeation

By Browder's pseudo-monotone operator theory and the techniques belonging to J. Leray and J. Lions, the existence theorem of the generalized solution of the Dirichlet problem for a strongly degenerate quasilincar elliptic equation has been proved in the anisotropic Sobolev space.     

Finite procedures for sofic systems

A sofic system is a symbolic flow defined by a finite semigroup. We exhibit finite procedures, involving only the defining semigroup, for answering cetain questions about a sofic system and for constructing certain subshifts of finite type associated with a sofic system.     

Discretisation procedures for multi-physics phenomena

Procedures are described for solving the equations governing a multi-physics process. Finite volume techniques are used to discretise, using the same unstructured mesh, the equations of fluid flow, heat transfer with solidification, and solid deformation. These discretised equations ofe then solved in an integrated manner. The computational mechanics environment, PHYSICA, which facilitates the building of multi-physics models, is described. Comparisons between model predictions and experimental data are presented for the casting of metal components.     

Matrix procedures for dimensional analysis

This paper presents an alternative viewpoint to that of Sharp and Moore [1] on the application of matrix methods to dimensional analysis. Using examples from these and other authors the power, succinctity and physical compliance of the echelon matrix method is demonstrated. It is shown that certain aspects of the Sharp and Moore approach are misleading. This leads on to examination of the supposed base position for the Rayleigh procedure and of its essential irrelevance to the actual algebra of that procedure. Here again it is shown how the echelon matrix concept can be adopted in the preliminary setting up of the situation so that singularity, if present, can be encompassed without the need for any unsatisfactory process of arbitrary discardment of the redundant dimensional information.

The fundamental basis for the dimensional analysis procedure is treated in a simple manner by a development of the proposition of Riabouchinski. Some aspects of the historical background are outlined.

Experience gained over a period of nine years of teaching of the echelon matrix method to a great number of undergraduates and postgraduates has shown the value of the method per se,and its usefulness as a means of identifying those with potential in visualization and in engineering synthesis.     

A canonical structure for iterative procedures

In this paper a canonical structure for multistep finite memory algorithms is presented. The concept of characteristic set is introduced and some of the finite and limit properties of the structure are proved. Then it is shown that the use of the theory developed in the paper's first part greatly simplifies the analysis of complicated iterative procedures.     

A programming technique for recursive procedures

A programming technique is described for ALGOL-like recursive procedures in which parameters and local variables are replaced by variables global to the recursive procedure and declared in a surrounding non-recursive procedure. The stack and time required for execution of a variety of recursive procedures has been determined in the languages ALGOL 60, CORAL 66 and ALGOL 68 both when programmed using this technique and when using parameters. Detailed results are presented for the Ackermann function and for tree manipulation.The global technique gives considerable savings in stack for all recursions investigated. For call-dominated recursions the technique speeds up the execution time in ALGOL 60 and CORAL 66 by about 25%. In ALGOL 68 the parameterless recursive procedure must be declared in the closed-clause which forms the particular-program rather than in a surrounding procedure in order to achieve a similar improvement in execution time.     

Numerical differentiation procedures for non-exact data

The numerical differentiation of data divides naturally into two distinct problems:

1. the differentiation of exact data, and
2. the differentiation of non-exact (experimental) data.

In this paper, we examine the latter. Because methods developed for exact data are based on abstract formalisms which are independent of the structure within the data, they prove, except for the regularization procedure of Cullum, to be unsatisfactory for non-exact data. We therefore adopt the point of view that satisfactory methods for non-exact data must take the structure within the data into account in some natural way, and use the concepts of regression and spectrum analysis as a basis for the development of such methods. The regression procedure is used when either the structure within the non-exact data is known on independent grounds, or the assumptions which underlie the spectrum analysis procedure [viz., stationarity of the (detrended) data] do not apply. In this latter case, the data could be modelled using splines. The spectrum analysis procedure is used when the structure within the nonexact data (or a suitable transformation of it, where the transformation can be differentiated exactly) behaves as if it were generated by a stationary stochastic process. By proving that the regularization procedure of Cullum is equivalent to a certain spectrum analysis procedure, we derive a fast Fourier transform implementation for regularization (based on this equivalence) in which an acceptable value of the regularization parameter is estimated directly from a time series formulation based on this equivalence. Compared with the regularization procedure, which involvesO(n ³) operations (wheren is the number of data points), the fast Fourier transform implementation only involvesO(n logn).     

Solution procedures for sizing of warehouses

In the past, researchers presented a linear programming formulation for the economic sizing of warehouses when demand is highly seasonal and public warehouse space is available on a monthly basis. The static model was extended for the dynamic sizing problem in which the warehouse size is allowed to change over time. By applying simplex routine, the optimal size of the warehouse to be constructed could be determined. In this paper, an alternative and simple method of arriving at an optimal solution for the static problem is given. Three extensions of the static model are given. These extensions involve costs varying over time, economies of scale in capital expenditure and/or operating cost and stochastic version. The dynamic warehouse sizing problem is shown to be a network flow problem which could be solved by using network flow algorithms. The structure of an optimal solution is also given. The concave cost version of the dynamic warehouse sizing problem is also discussed and it is shown that this problem can be solved efficiently using dynamic programming.     

Acceleration procedures for matrix iterative methods

In this paper, several procedures for accelerating the convergence of an iterative method for solving a system of linear equations are proposed. They are based on projections and are closely related to the corresponding iterative projection methods for linear systems.     

Hybrid procedures for solving linear systems

Summary. In this paper, we introduce the notion of hybrid procedures for solving a system of linear equations. A hybrid procedure consists in a combination of two arbitrary approximate solutions with coefficients summing up to one. Thus the combination only depends on one parameter whose value is chosen in order to minimize the Euclidean norm of the residual vector obtained by the hybrid procedure. Properties of such procedures are studied in detail. The two approximate solutions which are combined in a hybrid procedure are usually obtained by two iterative methods. Several strategies for combining these two methods together or with the previous iterate of the hybrid procedure itself are discussed and their properties are analyzed. Numerical experiments illustrate the various procedures. Received October 21, 1992/Revised version received May 28, 1993     

A Suggested Mechanism for Nonlinear Wall Roughness Effects on High Reynolds Number Flow Stability

The interactions between an uneven wall and free stream unsteadiness and their resultant nonlinear influence on flow stability are considered by means of a related model problem concerning the nonlinear stability of streaming flow past a moving wavy wall. The particular streaming flows studied are plane Poiseuille flow and attached boundary-layer flow, and the theory is presented for the high Reynolds number regime in each case. That regime can permit inter alia much more analytical and physical understanding to be obtained than the finite Reynolds number regime; this may be at the expense of some loss of real application, but not necessarily so, as the present study shows. The fundamental differences found between the forced nonlinear stability properties of the two cases are influenced to a large extent by the surprising contrasts existing even in the unforced situations. For the high Reynolds number effects of nonlinearity alone are destabilizing for plane Poiseuille flow, in contrast with both the initial suggestion of earlier numerical work (our prediction is shown to be consistent with these results nevertheless) and the corresponding high Reynolds number effects in boundary-layer stability. A small amplitude of unevenness at the wall can still have a significant impact on the bifurcation of disturbances to finite-amplitude periodic solutions, however, producing a destabilizing influence on plane Poiseuille flow but a stabilizing influence on boundary-layer flow.     

Approximative procedures for no-wait job shop scheduling

In this article we consider the no-wait job shop problem with makespan objective. Based on a decomposition of the problem into a sequencing and a timetabling problem, we propose two local search algorithms. Extensive computational tests in which the algorithms compare favorably to the best existing strategies are reported. Although not specifically designed for that purpose, our algorithms also outperform one of the best no-wait flow shop algorithms in literature.     

Generating structure editor interfaces for OR procedures

The quest for OR interface development tools that are both flexible (in terms of interfaces produced) and high-level (in terms of developer specification accepted) is based on work in the DSS and UIMS fields. The DSS literature offers a foundation for understanding possible relationships between OR procedures, the data they can use, and the problem statements that cause their executions. The UIMS literature offers mechanisms for interface production. Of these, structure editing has been singled out here as a candidate for advancing OR research into interface construction. The first implementation of a structure editor interface for OR problem statements is described. The result is a direct manipulation user interface that presents LP problem statement images resembling traditional forms, but which allows variants of a single form to dynamically unfold in response to a user's expansion actions.This research has been supported in part by the Center for Robotics and Manufacturing Systems, University of Kentucky, Lexington, Kentucky.