ppxscal/embedding_network huggingface dataset:
The Multistage Service Facility Start-Up and Capacity Model
Authors: Lode Li, Hongtao Zang
Venue: Operations Research (2000)

In service industries, operations are often split into the "front office" and the "back room." The front office deals directly with customers, whereas the back room engages in manufacturing-like operations. While such an arrangement may enjoy many benefits including reduced customer participation and back room efficiency, it gives rise to the possibility of communication and coordination problems between the front office and the back room. To address such coordination problems, we work from one popular piece of case material in operations management, the National Cranberry Cooperative (NCC) case, and develop and analyze a service facility start-up and capacity model based on a finite-horizon, multistage queueing system. The model allows for general variability that can be either stationary or nonstationary, predictable or unpredictable. We derive the relationships between job start and finish times and primitive parameters and control variables using a sample path construction. We then show that two performance measures, the expected waiting and operating costs, have desirable convexity properties with respect to the control variables; namely, the starting time and the processing capacity of each stage. We also show how to perform marginal analysis on start-up times. Numerical examples based on the NCC case are presented and discussed. The model can be extended and applied to many service and manufacturing situations.
Design and evaluation of a multi-user virtual audio chat
Authors: Maja Matijasevic, Lea Skorin-Kapov
Venue: Future Generation Computer Systems (2003)

As advanced Internet services, networked virtual reality (NVR) applications impose certain quality of service (QoS) requirements, due to rich multimedia content and perceived "real-time" interactivity. Two different representations of QoS are needed at the user/application level and at the communication level, which our approach attempts to relate using as a reference an interconnection model for NVR applications. We present the design and development of a multi-user virtual audio chat application and a performance evaluation based on QoS requirements. Objective and subjective methods for determining QoS have been addressed, and our results analysed for the purpose of possible QoS improvements.
Boundary Feedback Stabilization of a Variant of the SCOLE Model
Authors: Boumediène Chentouf
Venue: Journal of Dynamical and Control Systems (2003)

This paper deals with the boundary feedback stabilization of a variant of the SCOLE model, namely, a flexible beam clamped at one end, and free at the other end where a rigid body is attached. Using the frequency domain method, we first prove that the considered system is uniformly stabilizable if the control force and control moment are simultaneously applied at the free end of the beam. Secondly, if only a control force is applied, we give a sufficient condition on the physical parameters of the system to guarantee the uniform stabilization. Finally, it is shown that the presence of boundary control force is necessary to achieve the uniform stabilization. To verify these theoretical developments, an asymptotic analysis and numerical study of the spectrum are performed.
The Three-Dimensional Bin Packing Problem
Authors: Silvano Martello, David Pisinger, Daniele Vigo
Venue: Operations Research (2000)

The problem addressed in this paper is that of orthogonally packing a given set of rectangular-shaped items into the minimum number of three-dimensional rectangular bins. The problem is strongly NP-hard and extremely difficult to solve in practice. Lower bounds are discussed, and it is proved that the asymptotic worst-case performance ratio of the continuous lower bound is ?. An exact algorithm for filling a single bin is developed, leading to the definition of an exact branch-and-bound algorithm for the three-dimensional bin packing problem, which also incorporates original approximation algorithms. Extensive computational results, involving instances with up to 90 items, are presented: It is shown that many instances can be solved to optimality within a reasonable time limit.
Caching across heterogeneous information sources: an object-based approach
Authors: Athena Vakali, Yannis Manolopoulos
Venue: Information processing and technology (2001)

Information exchange has been increased drastically and rapidly due to the major large scale Internet expansion. The structure of information sources worldwide has been altered and both structured and semi-structured data are stored in various heterogeneous information spaces. Several tools have been developed for facilitating the rapid integration of the different information structures and accessing needs across heterogeneous sources over the Internet. This paper proposes a caching approach to extend the heterogeneous information sources integration process such that distributed objects are better accessed and retrieved. Our caching approach considers objects that are formed in response to certain queries posed over a specified number of distinct information sources. A methodology based on the notion of genetic algorithms is studied aiming at facilitating distributed objects exchange and accessing. In the proposed model, queries refer to documents or objects identified by their information source and their location within that source. Objects remain in the cache area based on their frequency of accesses, their popularity and their server priority, whereas the cache content is regularly updated. The proposed methods are experimented and results are compared with the corresponding results of the conventional Least Recently Used (LRU) cache replacement algorithm. The proposed evolutionary approach based algorithm is proven to be superior than the traditional LRU algorithm with respect to both cache and byte hit ratios.
Interconnecting Lans and a Fddi Backbone Using Transparent Bridges: a Model and Solution Algorithms
Authors: Frederick Kaefer, June S. Park
Venue: INFORMS Journal on Computing (1998)

In this article, we construct a mathematical model to design the topology of a network interconnecting a number of local area networks (LANs) and a fiber-distributed data interface (FDDI) backbone using IEEE 802.1 transparent bridges. The model allows parallel bridge links between subnets and yields a two-node-connected topology for survivability. The model determines the routing tree on a given topology according to the IEEE Standard protocol, which uses as input only user-supplied parameters such a s bridge IDs, port IDs, and path costs. The model ensures that none of the network components (LANs, FDDI, and bridge links) are congested even in the failure of a LAN or a bridge link. We develop a path cost adjustment algorithm and a tabu search algorithm to find a low-cost feasible topology. Through computational experiments, we identify the characteristics of feasible topologies found under varying traffic conditions. Under light traffic conditions (i.e., when LANs' total slack capacity is large relative to the total intersubnet traffic demand), the topology is close to a ring which costs much less than the conventional star topology. Under heavy traffic, the topology tends to be a ring augmented by parallel bridge links between LANs and the FDDI. Finally, we discuss how effective various heuristic ideas-such as uncapacitated, two-connected topology design heuristics, the short-term tabu list and the long-term tabu list-are with respect to improving the solution quality. We also present a Lagrangian relaxation-based lower bounding procedure and report the gap between the best feasible value and the lower bound. The parsimonious property of uncapacitated, two-connected topology design problems is employed in this dual partitioning procedure.
Symmetry Maps of Free-Form Curve Segments via Wave Propagation
Authors: Hüseyin Tek, Benjamin B. Kimia
Venue: International Journal of Computer Vision (2003)

This paper presents an approach for computing the symmetries (skeletons) of an edge map consisting of a collection of curve segments. This approach is a combination of analytic computations in the style of computational geometry and discrete propagations on a grid in the style of the numerical solutions of PDE's. Specifically, waves from each of the initial curve segments are initialized and propagated as a discrete wavefront along discrete directions. In addition, to avoid error built up due to the discrete nature of propagation, shockwaves are detected and explicitly propagated along a secondary dynamic grid. The propagation of shockwaves, integrated with the propagation of the wavefront along discrete directions, leads to an exact simulation of propagation by the Eikonal equation. The resulting symmetries are simply the collection of shockwaves formed in this process which can be manipulated locally, exactly, and efficiently under local changes in an edge map (gap completion, removal of spurious elements, etc). The ability to express grouping operations in the language of symmetry maps makes it an appropriate intermediate representation between low-level edge maps and high level object hypotheses.
Yes, you can teach ethics!
Authors: Cindy Meyer Hanchey
Venue: Journal of Computing Sciences in Colleges (2002)

The Computing Curricula 2001 (CC2001) project report includes recommendations for both required core and elective components to be included at all levels of the curriculum. One pervasive component is that of ethics. Many computer science faculty members are reluctant to teach even a single module in ethics. This paper and the accompanying presentation will provide a sample lesson that could be used as a module in a variety of courses in the curriculum. The accompanying reference list with URLs provides faculty an outstanding set of resources from which to work as well as opportunities for training in computer ethics.An additional benefit of including such a module is the opportunity for students to consider submitting papers for publication or presentation at conferences. Computer Science faculty can serve as mentors in that process.
A Joint Location-Inventory Model
Authors: Zuo-Jun Max Shen, Collette Coullard, Mark S. Daskin
Venue: Transportation Science (2003)

We consider a joint location-inventory problem involving a single supplier and multiple retailers. Associated with each retailer is some variable demand. Due to this variability, some amount of safety stock must be maintained to achieve suitable service levels. However, risk-pooling benefits may be achieved by allowing some retailers to serve as distribution centers (and therefore inventory storage locations) for other retailers. The problem is to determine which retailers should serve as distribution centers and how to allocate the other retailers to the distribution centers. We formulate this problem as a nonlinear integer-programming model. We then restructure this model into a set-covering integer-programming model. The pricing problem that must be solved as part of the column generation algorithm for the set-covering model involves a nonlinear term in the retailerdistribution-center allocation terms. We show that this pricing problem can (theoretically) be solved efficiently, in general, and we show how to solve it practically in two important cases. We present computational results on several instances of sizes ranging from 33 to 150 retailers. In all cases, the lower bound from the linear-programming relaxation to the set-covering model gives the optimal solution.
Proceedings of the 2003 SIGMIS conference on Computer personnel research: Freedom in Philadelphia--leveraging differences and diversity in the IT workforce
Venue: Special Interest Group on Computer Personnel Research Annual Conference (2003)

These proceedings provide a compilation of the presentations at the 2003 annual conference of the Association for Computing Machinery's Special Interest Groups on Computer Personnel Research (SIGCPR) and Management Information Systems (SIGMIS), in Philadelphia, Pennsylvania. In addition to the topics of traditional and ongoing interest to the SIGs, this conference sought research related to the conference theme of diversity in the IT workforce.With growing frequency, it seems, external pressures are presenting significant challenges to the IT profession. At the dawn of the twenty-first century, the challenge of ensuring a supply of appropriately qualified IT personnel is increasingly bound up with issues of diversity. The goal of valuing differences applies to both intellectual and demographic diversity. Part of the aftermath of September 11, 2001 is that IT skills once seen as on the periphery of the field have moved to center stage. Those who possess expertise in security, authentication, encryption and risk management, for example, are suddenly in great demand much as those with telecommunications expertise were highly sought a decade ago after the introduction of the World Wide Web. Consequently, a research challenge is to explore ways to ensure that there is sufficient intellectual diversity in the educational preparation of IT professionals to enable us to quickly respond to these unexpected problems and opportunities.As the appetite for IT continues to grow, the IT profession is challenged with meeting the demand to enlarge the IT workforce by recruiting and retaining personnel from historically underrepresented groups. Further, as the global economy expands, CIO's are faced with managing a geographically dispersed and culturally disparate IT labor force. As a result of these pressures on the IT profession, new questions arise about the educational and professional development the IT workforce. A host of research questions emerge: Should there be special recruitment and retention strategies for historically underrepresented groups in the IT profession? What can be done to recruit and retain women and racial/ethnic minorities in the IT field? What are the management challenges for a multicultural IT workforce? Should diversity only be seen as a social goal or can it also be seen as a resource to be leveraged for competitive advantage? The conference theme of leveraging differences and diversity sought to explore these issues relating to diverse skill sets, diverse personnel, and diverse cultures.This is a year of transition for this conference. As the conference was being prepared the merger of SIGCPR and SIGMIS was underway. It is perhaps fitting, therefore, that the conference theme be about diversity and the benefits that derive from change.
Some discrete multiple orthogonal polynomials
Authors: J. Arvesú, J. Coussement, W. Van Assche
Venue: Journal of Computational and Applied Mathematics (2003)

In this paper, we extend the theory of discrete orthogonal polynomials (on a linear lattice) to polynomials satisfying orthogonality conditions with respect to r positive discrete measures. First we recall the known results of the classical orthogonal polynomials of Charlier, Meixner, Kravchuk and Hahn (T.S. Chihara, An Introduction to Orthogonal Polynomials, Gordon and Breach, New York, 1978; R. Koekoek and R.F. Swarttouw, Reports of the Faculty of Technical Mathematics and Informatics No. 98-17, Delft, 1998; A.F. Nikiforov et al., Classical Orthogonal Polynomials of a Discrete Variable, Springer, Berlin, 1991). These polynomials have a lowering and raising operator, which give rise to a Rodrigues formula, a second order difference equation, and an explicit expression from which the coefficients of the three-term recurrence relation can be obtained. Then we consider r positive discrete measures and define two types of multiple orthogonal polynomials. The continuous case (Jacobi, Laguerre, Hermite, etc.) was studied by Van Assche and Coussement (J. Comput. Appl. Math. 127 (2001) 317-347) and Aptekarev et al. (Multiple orthogonal polynomials for classical weights, manuscript). The families of multiple orthogonal polynomials (of type II) that we will study have a raising operator and hence a Rodrigues formula. This will give us an explicit formula for the polynomials. Finally, there also exists a recurrence relation of order r + 1 for these multiple orthogonal polynomials of type II. We compute the coefficients of the recurrence relation explicitly when r = 2.
Software engineering: a new approach for small departments
Authors: Jennifer A. Polack-Wahl
Venue: Journal of Computing Sciences in Colleges (2003)

To provide an appropriate curriculum of electives from a small department is difficult but not impossible. Rarely can faculty teach a wide spread of courses when they are limited to two electives per academic year and overwhelmed with core courses and general education courses. Over the past several years by combining topics into such classes as software engineering, computer graphics, and computer ethics, a small department has expanded the basic electives. This paper describes the evolution of a software engineering course and how the course incorporates multiple topics.
Heavy Traffic Analysis of the Dynamic Stochastic Inventory-Routing Problem
Authors: Martin I. Reiman, Rodrigo Rubio, Lawrence M. Wein
Venue: Transportation Science (1999)

We analyze three queueing control problems that model a dynamic stochastic distribution system, where a single capacitated vehicle serves a finite number of retailers in a make-to-stock fashion. The objective in each of these vehicle routing and inventory problems is to minimize the long run average inventory (holding and backordering) and transportation cost. In all three problems, the controller dynamically specifies whether a vehicle at the warehouse should idle orembark with a full load. In the first problem, the vehicle must travel along a prespecified (TSP) tour of all retailers, and the controller dynamically decides how many units to deliver to each retailer. In the second problem, the vehicle delivers an entire load to one retailer (direct shipping) and the controller decides which retailer to visit next. The third problem allows the additional dynamic choice between the TSP and direct shipping options. Motivated by existing heavy traffic limit theorems, we make a time scale decomposition assumption that allows us to approximate these queueing control problems by diffusion control problems, which are explicitly solved in the fixed route problems, and numerically solved in the dynamic routing case. Simulation experiments confirm that the heavy traffic approximations are quite accurate over a broad range of problem parameters. Our results lead to some new observations about the behavior of this complex system.
Running a virtual enterprise
Authors: K. V. K. K. Prasad
Venue: Ubiquity (2003)

The story of a software division that managed to survive in spite of the downturn in the industry.
Sumt (Revisited)
Authors: R. Garbe, K. D. Glazebrook, Stephen G. Nash
Venue: Operations Research (1998)

Fiacco and McCormick's 1968 book is a classic. It arose out of the authors' activities at the Research Analysis Corporation, and as such it is the record of an ambitious and productive collaboration. But it is more than that. The topics they studied and the situations they encountered are representative of the experiences of other researchers in the 1960s. At a deeper level, Fiacco and McCormick's book illustrates the influence of two great traditions of research: one based on linear programming, and the other based on the calculus of variations. The work of Fiacco and McCormick remains influential, as do the influences of these two traditions. An understanding of these influences illuminates not only the history of nonlinear programming, but also its present and future.
Security enhancement for Optimal Strong-Password Authentication protocol
Authors: Chih-Wei Lin, Jau-Ji Shen, Min-Shiang Hwang
Venue: ACM SIGOPS Operating Systems Review (2003)

In 2001, Lin et al. proposed an optimal strong-password authentication protocol called the OSAP protocol. However, Chen and Ku pointed out that it is vulnerable to the stolen-verifier attack. In this paper, we shall propose an improved version of the OSAP protocol to enhance the security.
Periodic solutions to functional evolution equations
Authors: Gabriela Litcanu
Venue: Nonlinear Analysis: Theory, Methods Applications (2003)

The object of the present paper is the study of a class of functional evolution equations of the type: u'(t)+ A(t,ut)u(t)= 0, t ∈ R, where A(t, φ) are nonlinear operators acting on a Banach space, X. We establish, under certain additional assumptions on X and the operator A, the existence of a ω-periodic generalized solution.
Codes, graphs, and schemes from nonlinear functions
Authors: E. R. van Dam, D. Fon-Der-Flaass
Venue: European Journal of Combinatorics (2003)

We consider functions on binary vector spaces which are far from linear functions in different senses. We compare three existing notions: almost perfect nonlinear functions, almost bent (AB) functions, and crooked (CR) functions. Such functions are of importance in cryptography because of their resistance to linear and differential attacks on certain cryptosystems. We give a new combinatorial characterization of AB functions in terms of the number of solutions to a certain system of equations, and a characterization of CF in terms of the Fourier transform. We also show how these functions can be used to construct several combinatorial structures; such as semi-biplanes, difference sets, distance regular graphs, symmetric association schemes, and uniformly packed (BCH and Preparata) codes.
Determining the optimal production-maintenance policy with inspection errors: using a Markov chain
Authors: Chih-Hsiung Wang, S. H. Sheu
Venue: Computers and Operations Research (2003)

Lee and Park examine the effects of an imperfect production process on the optimal production-inventory policy; They consider an imperfect production process which can go out of control after an exponentially distributed production time and then produce some proportion of defective items. The defective item cost is equivalent to the reworking cost and the warranty cost. Some maintenance-inspection mechanisms are introduced to monitor and restore the process to enhance process reliability and thereby lower the number of defective items produced. However, in many situations, a deteriorating production system possesses an increasing failure rate. In general, such a process will not be as good as new after maintenance but will be younger than its real age. Besides, Lee and Park did not investigate the possibility of imperfect inspection based on consideration of type I and type II errors. In this paper, we consider the effects of general time to shift distributions, two types of process inspection errors and general repair policy on the optimal production/inspection/maintenance policy. A mathematical model representing the expected average cost is developed using a Markov chain to jointly determine the production cycle, process inspection intervals, and maintenance level. An optimal production/inspection/maintenance policy is determined by minimizing the expected average cost. A numerical example is given to illustrate the use of the method. Based on this proposed Markov structure model, some process-related assumptions such as maintenance that can cause the system to go out of control and that the random results of general repairs can also be easily relaxed, and they are described in the section of model extensions. An extended production-maintenance model for a deteriorating production system is established.