560868
An Optimal Algorithm for the Orienteering Tour Problem
Orienteering is a sport in which a competitor selects a path from a start to a destination, visiting control points along the path. Each control point has an associated score, and the travel between control points involves a certain cost. The problem is to select a set of control points to visit, so that the total score is maximized subject to a budget constraint on total cost. Several versions of this problem exist. In the version considered in this research, the start and the destination are the same, and the problem is to construct a subtour of the set of control points. The orienteering problem is a variant of the traveling salesman problem, and arises in vehicle routing and production scheduling situations. This problem has been shown to be NP-hard in the literature. We develop an optimal algorithm to solve this problem, using Lagrangean relaxation within a branch-and-bound framework. The Lagrangean relaxation is solved by a degree-constrained spanning tree procedure. Characteristics of the Lagrangea...
32066139
Topographically discounted Internet infrastructure resources: a panel study and econometric analysis
The Internet infrastructure is increasingly utilized for the provision and delivery of a variety of services. The rapid growth and substantial demand fluctuations of the supported services are placing strain on the service providers to effectively manage their infrastructure resources. Capacity Provision Network (CPN) is a market-driven mechanism that enables the service providers to efficiently allocate, share and trade service capabilities. Central to the operation of CPN is the notion of discounted capacities which capture the underlying topology of the Internet. It serves as a practical instrument for service providers to evaluate the utility of capacity services available at remote sites vis-à-vis the capacities available locally and from the content providers. We conducted an Internet based longitudinal field experiment to empirically assess and validate the critical properties of discount factors. Our analysis reveals that discount factors exhibit markedly lower volatility than network delays, and are more stable over seasonal and temporal trend patterns. The results related to size effects suggest that sharing and trade agreements with larger content can be particularly effective. Our finding on the existence of the concavity property points to the ability of intermediation services to enhance the overall gains from resource sharing arrangements.
13648716
EARS: An online bibliographic search and retrieval system based on ordered explosion
Abstract Ergonomics Abstracts Retrieval System (EARS) is an online bibliographic information search and retrieval system using the hierarchical subject classification of the Ergonomics Abstracts . EARS is designed using an inverted file organization and is implemented on CDC-Cyber. The data base of abstracts is organized using a fixed-length record format, where each logical record corresponds to a variable number of fixed-length physical records. Accordingly, an index for the identification of physical records from the logical records is used. The data base is inverted on a three-level hierarchical classification scheme and postings files are used for data base inversion. The data base is accessed after selectively traversing a 4-layer structure of indexes and postings files. EARS provides facilities to perform combinations of searches, limited searches, and certain editing functions. The system is currently used extensively by the Western New York Human Factors research community. The logical and physical designs of EARS, its interactive operational features, and its current expansions are described in this paper.
120648016
Theory of convex cones in multicriteria decision making
We develop the theory of convex polyhedral cones in the objective-function space of a multicriteria decision problem. The convex cones are obtained from the decision-maker's pairwise judgments of decision alternatives and are applicable to any quasiconcave utility function. Therefore, the cones can be used in any progressively articulated solution procedure that employs pairwise comparisons. The cones represent convex sets of solutions that are inferior to known solutions to a multicriteria problem. Therefore, these convex sets can be eliminated from consideration while solving the problem. We develop the underlying theory and a framework for representing knowledge about the decision-maker's preference structure using convex cones. This framework can be adopted in the interactive solution of any multicriteria problem after taking into account the characteristics of the problem and the solution procedure. Our computational experience with different multicriteria problems shows that this approach is both viable and efficient in solving practical problems of moderate size.
62235624
An efficient approach to stochastic jobshop scheduling: algorithms and empirical investigations
Abstract Jobshop scheduling is one of the important classes of problems planning. The jobshop represents a common manufacturing environment, in which a set of machines is used to process a stream of jobs arriving randomly. The stochastic arrival pattern of the jobs, their processing sequences, and processing times render the scheduling of jobs a complex and difficult task. Furthermore, the scheduling task involves multiple conflicting objectives such as the minimization of the flow time, lateness and the number of late jobs among others. In this research,we develop a framework for the efficient scheduling of jobs considering these multiple objectives. The motivation for this research arises from the good performance of the interactive man-machine scheduling systems in achieving significant levels of attainment in the set of objectives, simultaneously. We develop scheduling strategies to the man-machine approach in this research. The algorithms developed in this research have been extensively tested and evaluated against the traditional scheduling methods using simulation studies. The results show that the proposed approach is efficient and viable for solving practical scheduling problems in the presence of multiple objectives.
6732453
Enterprise computing environments and cost assessment
41350587
Automata-Driven Indexing of Prolog Clauses
Abstract Indexing Prolog clauses is an important optimization step that reduces the number of clauses on which unification will be performed and can avoid the pushing of a choice point. It is quite desirable to increase the number of functors used in indexing as this can considerably reduce the size of the filtered set. However, doing so can cause an enormous increase in code size and running time if indexing is done naively. This paper describes new and efficient indexing techniques that utilize all the functors in the clause heads and the goal. The salient feature of these techniques is that the selected clause head unifies (modulo nonlinearity) with the goal. In unification (modulo nonlinearity) all the variables in the terms being unified are assumed to be unique, so the only operation performed is of matching their constant portions. So use of our indexing techniques can result in sharper discrimination, fewer choice points, and reduced backtracking. These techniques have been incorporated into a Prolog compiler and using this compiler the run-time performance of a broad spectrum of Prolog programs has been improved.
35337405
A dynamic learning model for on-line quality control using the TAGUCHI approach
Abstract An important philosophy of quality control due to Taguchi rests on the belief that, once quality is designed into the product and the process, very little inspection is necessary. Taguchi evaluates quality in terms of costs incurred, including inspection and adjustment costs apart from quality loss. Using these costs, he determines an optimal interval for periodic inspection of products. At each inspection, the first item on the process line is checked for defects. If no defects are found, the process is assumed to be under control. On the other hand, if the first item turns out to be defective, the process is immediately stopped and adjusted. The underlying assumption here is that, once a defect is observed, it is construed that the process has drifted and all subsequent items are defective. This article challenges the underlying assumption by recognizing that the observation of one defective item does not necessarily imply that the process is out of control. Noisy signals may occur as a result ...
14332724
Simultaneous Optimization of Design Tolerance and Total Cost for a Piston and Cylinder Assembly
Rapid changes in the market place have led designers and manufacturers to continuously develop new products to satisfy the demands of more exigent customers. Therefore, to be competitive, designers and manufacturers have to perform those steps accurately to ensure final Product quality and manufacturing cost. So Product quality and manufacturing cost have a significant impact on Tolerance. A more scientific approach is often desirable for better performance to overcome this Tolerance problem. In this paper, Design and machining tolerances have been allocated based on optimum total machining cost. New global nonlinear optimization techniques called Pattern Search algorithm and Genetic algorithm have been implemented to find the optimal tolerance allocation and total cost. Finally with respect to total cost both the methods have been compared.
8380823
Term Matching on Parallel Computers
Term matching is an important problem that arises very often in term rewriting and in functional and equational programming. In this paper, we present a new parallel algorithm for the term-matching problem on the EREW (Exclusive Read Exclusive Write) model of parallel computation. Our algorithm assumes a string representation of the two terms as its input. The string representation is first transformed into two labeled ordered trees and term matching is then performed on these two trees. If n is the length of the input terms then for any constant ∈, (0<#x2208;≤1) our algorithm uses O(n1−∈) processors and takes O(nelog n) time. If e=0 the same algorithm will run in O(log2n) time. The only other known parallel algorithm for this problem is due to Dwork, Kanellakis and Stockmeyer that requires O(n2) processors and takes either O(log n) or O(log2n) time. However, their algorithm uses the stronger CREW (Concurrent Read Exclusive Write) model of parallel computation and assumes a DAG (Directed Acyclic Graph) representation of the two terms as its input. The techniques used in our algorithm are novel and have wide applicability.
206848861
Blind DC Estimation in the Presence of Non-Gaussian Signal
A method of estimating DC offset based solely on the received signal, without using any training information, is presented. This method takes into account the non-Gaussian statistical distribution of the modulated desired signal in order to produce a DC estimate that is more accurate than the conventional sample average of the received signal. Specifically, two iterative algorithms are derived based on the generalized expectation-maximization algorithms for jointly estimating the DC offset, the noise variance, and the parameters that characterize the signal distribution. As an application, we consider the special case where the modulated signal has a constant-envelope characteristic. Using the GSM/EDGE air interface, we demonstrate that the proposed method yields significant reduction in the DC-offset estimation error, which translates into performance gains in receiver sensitivity when used in direct-conversion receivers.