Equivalent instances of the simple plant location problem

In this paper we deal with a pseudo-Boolean representation of the simple plant location problem. We define instances of this problem that are equivalent, in the sense that each feasible solution has the same goal function value in all such instances. We further define a collection of polytopes whose union describes the set of instances equivalent to a given instance. We use the concept of equivalence to develop a method by which we can extend the set of instances that we can solve using our knowledge of polynomially solvable special cases. We also present a new preprocessing rule that allows us to determine sites in which facilities will not be located in an optimal solution and thereby reduce the size of a problem instance.

Data aggregation for p-median problems

In this paper, we use a pseudo-Boolean formulation of the p-median problem and using data aggregation, provide a compact representation of p-median problem instances. We provide computational results to demonstrate this compactification in benchmark instances. We then use our representation to explain why some p-median problem instances are more difficult to solve to optimality than other instances of the same size. We also derive a preprocessing rule based on our formulation, and describe equivalent p-median problem instances, which are identical sized instances which are guaranteed to have identical optimal solutions

Obfuscator Synthesis for Privacy and Utility

We consider the problem of synthesizing an obfuscation policy that enforces privacy while preserving utility with formal guarantees. Specifically, we consider plants modeled as finite automata with predefined secret behaviors. A given plant generates event strings for some useful computation, but meanwhile wants to hide its secret behaviors from any outside observer. We formally capture the privacy and utility specifications using the automaton model of the plant. To enforce both specifications, we propose an obfuscation mechanism where an edit function “edits” the plant’s output in a reactive manner. We develop algorithmic procedures that synthesize a correct-by-construction edit function satisfying both privacy and utility specifications. To address the state explosion problem, we encode the synthesis algorithm symbolically using Binary Decision Diagrams. We present EdiSyn, an implementation of our algorithms, along with experimental results demonstrating its performance on illustrative examples. This is the first work, to our knowledge, to successfully synthesize controllers satisfying both privacy and utility requirements

A polyhedral approach to quadratic assignment problem

Ankara : Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 1994.Thesis (Master's) -- Bilkent University, 1994.Includes bibliographical references.In this thesis, Quadratic Assignment Problem is considered. Since Quadratic Assignment Problem is JVP-bard, no polynomial time exact solution method exists. Proving optimality of solutions to Quadratic Assignment Problems has been limited to instances of small dimension. In this study, Quadratic Assignment Problem is handled from a polyhedral point of view. A graph theoretic formulation of the problem is presented. Later, Quadratic Assignment Polytope is defined and subsets of valid equalities and inequalities for Quadratic Assignment Polytope is given. Finally, results of the experiments with a polyhedral cutting plane algorithm using the new formulation is also presented.Köksaldı, Ahmet Sertaç MuratM.S

Strong component-based methodology for facility layout design

Among many issues involved within the field of manufacturing systems, the design of facilities layout is an ongoing and interesting research field, where new solutions and approaches are sought to determine the appropriate location and physical organisation of the resources in manufacturing systems. Issues such as space, material handling, machine placement and orientation, utilities location, and environmental factors are important features that may be considered when establishing the requirements of a facility layout design. The facility layout design can be thought of in terms of interconnecting work centres that can be represented by a set of interrelated vertices in a graph. Directed graphs can be used to characterise each product operation sequence, which combined into a single directed graph, be used to represent appropriately a layout design. Doing this together with the material handling system requirements, will allow better facilities planning and may improve process sequences that should be reflected in better designs. The Strong Component Based Methodology proposed here, obtains a graphical structure from the integration of various products and using their operation sequences to produce a relationship diagram. The attributes of the resultant structure are used to create this diagram. The objective is to obtain layouts that minimise material handling, that is, as close as possible to that which can be obtained with dedicated facilities for each product family but without the capital costs involved in the case of the latter. Encouraging results have been obtained by considering strong components, a feature of directed graphs, because less computational resources than in the case of many previous methods, which use Quadratic Assignment Problem approaches, are required to formulate and produce a relationship diagram. Moreover, this approach produces faster designs than other graph theoretic approaches because it avoids using planar and dual graphs. These characteristics allow the Strong Components approach to address more complex situations and obtain comparable or better solutions than previous approaches. The proposed Strong Component approach is a robust and versatile tool to support layout designs. It is a robust methodology because it provides efficient relationship diagrams even in cases when the resultant structure has relatively few strong component relationships. It is a versatile approach, because it can address various situations and can use different criteria to create layouts. Thus, the proposed approach offers effective-economical relationship diagrams to produce the same set of products as when producing them in dedicated facilities

Structure evolving systems and control in integrated design

Existing methods in Systems and Control deal predominantly with Fixed Systems, that have been designed in the past, and for which the control design has to be performed. The new paradigm of Structure Evolving Systems (SES), expresses a new form of system complexity where the components, interconnection topology, measurement-actuation schemes may not be fixed, the control scheme also may vary within the system-lifecycle and different views of the system of varying complexity may be required by the designer. Such systems emerge in many application domains and in the engineering context in problems such as integrated system design, integrated operations, re-engineering, lifecycle design issues, networks, etc. The paper focuses on the Integrated Engineering Design (IED), which is revealed as a typical structure evolution process that is strongly linked to Control Theory and Design type problems. It is shown, that the formation of the system, which is finally used for control design evolves during the earlier design stages and that process synthesis and overall instrumentation are critical stages of this evolutionary process that shapes the final system structure and thus the potential for control design. The paper aims at revealing the control theory context of the evolutionary mechanism in overall system design by defining a number of generic clusters of system structure evolution problems and by establishing links with existing areas of control theory. Different aspects of model evolution during the overall design are identified which include cases such as: (i) Time-dependent evolution of system models from “early” to “late” stages of design. (ii) Design stage-dependent evolution from conceptualisation to process synthesis and to overall instrumentation. (iii) Redesign of given systems and constrained system evolution. Within each cluster a number of well defined new Control Theory problems are introduced, which may be studied within the structural methodologies framework of Linear Systems. The problems posed have a general systems character, but the emphasis here is on Linear Systems; an overview of relevant results is given and links with existing research topics are established. The paper defines the Structural Control Theoretic context of an important family of complex systems emerging in engineering design and defines a new research agenda for structural methods of Control Theory