ppxscal/embedding_network huggingface dataset:
A new efficient primal dual simplex algorithm
Authors: Konstantinos Paparrizos, Nikolaos Samaras, George Stephanides
Venue: Computers and Operations Research (2003)

The purpose of this paper is to present a revised primal dual simplex algorithm (RPDSA) for linear programming problems. RPDSA has interesting theoretical properties. The advantages of the new algorithm are the simplicity of implementation, low computational overhead and surprisingly good computational performance. The algorithm can be combined with interior point methods to move from an interior point to a basic optimal solution. The new algorithm always proved to be more efficient than the classical simplex algorithm on our test problems. Numerical experiments on randomly generated sparse linear problems are presented to verify the practical value of RPDSA. The results are very promising. In particular, they reveal that RPDSA is up to 146 times faster in terms of number of iterations and 94 times faster in terms of CPU time than the original simplex algorithm (SA) on randomly generated problems of size 1200 × 1200 and density 2.5%.
The max-plus algebra of the natural numbers has no finite equational basis
Authors: Luca Aceto, Zoltán Ésik, Anna Ingólfsdóttir
Venue: Theoretical Computer Science (2003)

This paper shows that the collection of identities which hold in the algebra N of the natural numbers with constant zero, and binary operations of sum and maximum is not finitely based. Moreover, it is proven that, for every n, the equations in at most n variables that hold in N do not form an equational basis. As a stepping stone in the proof of these facts, several results of independent interest are obtained. In particular, explicit descriptions of the free algebras in the variety generated by N are offered. Such descriptions are based upon a geometric characterization of the equations that hold in N, which also yields that the equational theory of N is decidable in exponential time.
Coordination and Virtualization: the Role of Electronic Networks and Personal Relationships
Authors: Robert Kraut, Charles Steinfield, Alice P. Chan, Brian Butler, Anne Hoag
Venue: Organization Science (1999)

One view holds that organizations are virtual to the extent that they outsource key components of their production processes, and that electronic networks make it easier to do this. The goal of the present paper is to examine explicitly the effects that use of electronic networks for transactions with suppliers has on firms' degree of virtualization. In so doing, we also highlight factors that influence the use of networks for coordination with suppliers, and the impact such use has on coordination success. Contrary to much recent speculation, the use of electronic networks for transactions was not associated with increased outsourcing, but rather with greater dependence on internal production. Moreover, the use of interpersonal relationships for coordination, which many think of as an alternative to electronic network use, was positively associated with greater network use. Surprisingly, use of electronic networks was negatively associated with such outcomes as order quality and efficiency, and satisfaction with suppliers, while more reliance on personal linkages was associated with better outcomes and mitigated the negative consequences of using electronic networks.
The compass rose and random walk tests
Authors: Yue Fang
Venue: Computational Statistics Data Analysis (2002)

The recent discovery of the compass rose pattern (Crack and Ledoit J. Finance 51(2) (1996) 751) has sparked considerable interest among researchers. This paper explores the significance of the effect of the compass rose pattern on random walk tests and measures to what extent its influence may limit the performance of test statistics. We show that in general, the asymptotic theory of test statistics is invalid for transactions data. However, Monte Carlo simulations indicate that the impact of the pattern, measured by the empirical size, is visible for moderate size samples only when the tick/volatility ratio is above some threshold, a condition that is readily met with intraday but not daily or weekly returns.
Quantitative Analysis of Distance Learning Courseware
Authors: Flora Chia-I Chang
Venue: Multimedia Tools and Applications (2003)

Web-based courseware are widely developed for distance learning programs in continue education, employee training center, and e-learning portals. Usually, a Web-based courseware contains course contents and on-line tests. However, most Web document development tools are not incorporated with a strategic evaluation mechanism, to allow a quantitative analysis of distance learning courseware. We propose an evaluation mechanism and a multimedia tool, based on our Courseware Diagram, to allow a quantitative justification of courseware. Courseware produced by our development system allows an instructor to choose different instruction sequences based on the outcomes of an exam. Alternatively, the courseware may allow self-guided study in a Web-based distance learning program. This paper explains the courseware diagram, the evaluation algorithm, and the design of our courseware development system.
The Effects of Coupling it and Work Process Strategies in Redesign Projects
Authors: Victoria L. Mitchell, Robert W. Zmud
Venue: Organization Science (1999)

Organizational adaptation to competition often means inventing or adopting a process innovation and the daunting challenge of implementing it. Increasingly, process innovations rely on the capabilities embedded in an organization's IT infrastructure. Successfully implementing an IT-enabled process innovation depends largely on how a project's IT and work process designs fit and evolve with this IT infrastructure. However, little empirical research guides the formulation of IT and work process strategies. This study addresses the question: How does the degree of coupling between a redesign project's IT strategy and work process strategy affect project performance? Data collection utilized a multistage research design employing comprehensive phone interviews and matched surveys among three sets of respondents (project managers, IT managers, and process users) across 43 process redesign projects in the health care industry. Our findings indicate project performance improves with tightly coupled IT and work process strategies when implementing process inventions, and with loosely coupled strategies when implementing imitations.
Price and Time Competition for Service Delivery
Authors: Kut C. So
Venue: Manufacturing Service Operations Management (2000)

Many service firms use delivery time guarantees to compete for customers in the marketplace. In this research we develop a stylized model to analyze the impact of using time guarantees on competition. Demands are assumed to be sensitive to both the price and delivery time guarantees, and the objective of each firm is to select the best price and time guarantee to maximize its operating profit. We first analyze the optimization problem for the individual firms and then study the equilibrium solution in a multiple-firm competition. Using a numerical study, we further illustrate how the different firm and market characteristics would affect the price and delivery time competition in the market. Our results suggest that the equilibrium price and time guarantee decisions in an oligopolistic market with identical firms behave in a similar fashion as the optimal solution in a monopolistic situation from a previous study. However, when there are heterogeneous firms in the market, these firms will exploit their distinctive firm characteristics to differentiate their services. Assuming all other factors being equal, the high capacity firms provide better time guarantees, while firms with lower operating costs offer lower prices, and the differentiation becomes more acute as demands become more time-sensitive. Furthermore, as time-attractiveness of the market increases, firms compete less on price, and the equilibrium prices of the firms increase as a result. Our findings provide important implications about firm behaviour under price and time competition.
E Media's Global Zero: Design for Environment in a Small Firm
Authors: Susan Carlson-Skalak, John Leschke, Mark Sondeen, Paul Gelardi
Venue: Interfaces (2000)

Shape, Inc. is the last remaining videocassette manufacturer in the United States. It successfully competes against foreign suppliers with a nearly 50-fold labor-cost advantage using a combination of automation and innovative design. One of its products, the Global Zero (G0) videocassette, exemplifies many of the precepts outlined by sustainable design. Developed over a period of three years by the design firm E Media and coming into production in January 1993, the Global Zero offers an alternative that is cost-effective to manufacture, offers consumer advantages, is 100-percent recyclable, and has the potential for a closed-loop material usage cycle.
Fixed Point Approaches to the Estimation of O/D Matrices Using Traffic Counts on Congested Networks
Authors: Ennio Cascetta, Maria Nadia Postorino
Venue: Transportation Science (2001)

Over recent years, increasing attention has been devoted to the problem of estimating Origin/Destination (O/D) matrices by using traffic counts, named in the following O/D Count Based Estimation (ODCBE) problem. These methods combine traffic flow measures with other available information to "correct" and improve an initial estimate of the O/D trip matrix. Virtually all models and procedures proposed in the literature are formulated as mathematical programming problems. Most ODCBE models use a relationship relating traffic counts to the unknown O/D matrix; this relationship is often in the form of an explicit estimate of the assignment matrix, i.e., of the fractions of O/D flows using each link of the network for which traffic counts are available. The computation of the assignment matrix is not trivial for congested networks, where travel costs and path choice fractions depend on flows. This problem has been dealt with in relatively few papers in the literature, usually formulated as a bilevel optimisation model under the assumption of a Deterministic User Equilibrium (DUE) assignment model. In this paper, the general within-day static ODCBE problem for congested networks is formulated as a fixed-point problem of an implicit function which results from the solution of a mathematical programming problem. In other words, the solution of the ODCBE problem is an O/D matrix that, once assigned to the network, reproduces flows and costs consistent with the values used to compute the assignment matrix. Fixed-point theorems and algorithms have been extended to the problem at hand. Different fixed-point algorithms, namely, Functional Iteration, Method of Successive Averages, and Method of Successive Averages with Decreasing Reinitialisation are proposed, and their performances are compared on a small test network. It has been verified that all algorithms converge to the same solution, though with different speeds. Furthermore, the fixed-point solution outperforms the initial solution, both in terms of bias and capability to reproduce both counted and noncounted flows.
A survey of computer science curricula at liberal arts colleges: a pilot study
Authors: James T. Streib, Curt M. White
Venue: Journal of Computing Sciences in Colleges (2002)

The purpose of this paper is to gain information about computer science curricula at liberal arts colleges. This survey examines the web sites of liberal arts colleges from a small geographic area to answer various questions in such areas as a depth first versus a breadth first curriculum, the first programming language used, and the use of closed laboratories. It also examines whether courses such as networks, computer systems, capstone courses, and internships are offered. This survey is also a pilot to determine the usefulness for a larger survey.
Iterating Bregman Retractions
Authors: Heinz H. Bauschke, Patrick L. Combettes
Venue: SIAM Journal on Optimization (2002)

The notion of a Bregman retraction of a closed convex set in Euclidean space is introduced. Bregman retractions include backward Bregman projections and forward Bregman projections, as well as their convex combinations, and are thus quite flexible. The main result on iterating Bregman retractions unifies several convergence results on projection methods for solving convex feasibility problems. It is also used to construct new sequential and parallel algorithms.
A quasi-local Gross-Pitaevskii equation for attractive Bose-Einstein condensates
Authors: Juan J. García-Ripoll, Vladimir V. Konotop, Boris Malomed, Víctor M. Pérez-García
Venue: Mathematics and Computers in Simulation (2003)

We study a quasi-local approximation for a nonlocal nonlinear Schrödinger equation. The problem is closely related to several applications, in particular to Bose-Einstein condensates with attractive two-body interactions. The nonlocality is approximated by a nonlinear dispersion term, which is controlled by physically meaningful parameters. We show that the phenomenology found in the nonlocal model is very similar to that present in the reduced one with the nonlinear dispersion. We prove rigorously the absence of collapse in the model, and obtain numerically its stable soliton-like ground state.
A Flexible Java Representation for Uncertainty in Online Operations-Research Models
Authors: Joel A. Shapiro, Warren B. Powell, David Bernstein
Venue: INFORMS Journal on Computing (2000)

Online OR models have been the subject of increased attention in recent years with the rapid expansion of the Internet. Although much has been written about the implementation, as well as the formal analysis of online models, little has been said about how to handle uncertainty in an online setting. In particular, the dynamic nature of uncertainty that is so characteristic of online models, where estimates and distributions evolve in parallel with the state of the model, has been largely ignored. In this paper, we present a new representation for uncertainty in online models. This representation is object-oriented and, as such, provides several important software-engineering advantages over traditional representations for uncertainty. Moreover, by using the event listener paradigm it provides an explicit mechanism for handling dynamic uncertainty in an elegant and extensible manner. A series of computational experiments demonstrates that there is no significant overhead to our representation when compared to traditional representations on a realistic application and, in some cases, our representation can be noticeably faster.
An Object-Oriented Random-Number Package with Many Long Streams and Substreams
Authors: Pierre L'Ecuyer, Richard Simard, E. Jack Chen, W. David Kelton
Venue: Operations Research (2002)

Multiple independent streams of random numbers are often required in simulation studies, for instance, to facilitate synchronization for variance-reduction purposes, and for making independent replications. A portable set of software utilities is described for uniform random-number generation. It provides for multiple generators (streams) running simultaneously, and each generator (stream) has its sequence of numbers partitioned into many long disjoint contiguous substreams. The basic underlying generator for this implementation is a combined multiple-recursive generator with period length of approximately 2 191, proposed by L'Ecuyer (1999a). A C++ interface is described here. Portable implementations are available in C, C++, and Java via the online companion to this paper on theOperations Research Web site. .
Ripple down rules: a technique for acquiring knowledge
Authors: Debbie Richards
Venue: Decision making support systems: achievements, trends and challenges for (2002)

Knowledge is becoming increasingly recognized as a valuable resource. Given its importance it is surprising that expert systems technology has not become a more common means of utilizing knowledge. In this chapter we review some of the history of expert systems, the shortcomings of first generation expert systems, current approaches and future decisions. In particular we consider a knowledge acquisition and representation technique known as Ripple Down Rules (RDR) that avoids many of the limitations of earlier systems by providing a simple, user-driven knowledge acquisition approach based on the combined use of rules and cases and which support online validation and easy maintenance. RDR has found particular commercial success as a clinical decision support system and we review what features of RDR make it so suited to this domain.
Developing reproducible and comprehensible computational models
Authors: Peter C. R. Lane, Fernand Gobet
Venue: Artificial Intelligence (2003)

Quantitative predictions for complex scientific theories are often obtained by running simulations on computational models. In order for a theory to meet with wide-spread acceptance, it is important that the model be reproducible and comprehensible by independent researchers. However, the complexity of computational models can make the task of replication all but impossible. Previous authors have suggested that computer models should be developed using high-level specification languages or large amounts of documentation. We argue that neither suggestion is sufficient, as each deals with the prescriptive definition of the model, and does not aid in generalising the use of the model to new contexts. Instead, we argue that a computational model should be released as three components: (a) a well-documented implementation; (b) a set of tests illustrating each of the key processes within the model; and (c) a set of canonical results, for reproducing the model's predictions in important experiments. The included tests and experiments would provide the concrete exemplars required for easier comprehension of the model, as well as a confirmation that independent implementations and later versions reproduce the theory's canonical results.
MCMR: a fluid view on time dependent volume data
Authors: Wim de Leeuw, Robert van Liere
Venue: Proceedings of the symposium on Data visualisation 2003 (2003)

Mass Conservative Motion Reconstruction is a new method for estimating motion in time dependent volume data. A time dependent vector field representing the movement of the data is computed from a sequence of scalar volume data sets. The principle of mass conservation in a continuum is used during the reconstruction. Standard fiow visualization techniques are used for the visualization of the derived vector field.This paper presents the underlying concepts of MCMR, its implementation, its accuracy and applicability.
Model of diffusion in partially fissured media
Authors: Horia I. Ene, Dan Polisěvski
Venue: Zeitschrift f&uuml;r Angewandte Mathematik und Physik (ZAMP) (2002)

We consider an ε-periodic structure formed by two interwoven and connected components which stand for the fissure system and the porous matrix. We assume that on the matrix-fissure interface the pressure has a jump of order ε-1 with respect to the fluid flux which is continuous. We prove that the corresponding homogenized system is exactly that proposed by Barenblatt and al. [1].
Dynamic Workforce Scheduling for British Telecommunications plc
Authors: David Lesaint, Christos Voudouris, Nader Azarmi
Venue: Interfaces (2000)

British Telecommunications plc (BT) employs thousands of field engineers across the UK to maintain networks, repair faults, and provide service to customers. To allocate work efficiently, BT developed Work Manager, an information system that automates work management and field communications. In 1996, the Intelligent Systems Research group of BT enhanced Work Manager with a dynamic scheduler (DS) based on a combination of heuristic search and constraint-based reasoning. Rolled out in 1997 and reaching 20,000 engineers in 1998, DS with Work Manager is saving BT $150 million a year on operational costs. When deployed over the targeted workforce of 40,000 people, the system will save an estimated $250 million a year.
Interactive Traditional Japanese Crafting System using Virtual Reality Technique over Highspeed Network
Authors: Akihiro Miyakawa, Masamitsu Sugimoto, Mikako Hosokawa, Yoshitaka Shibata
Venue: Proceedings of the 22nd International Conference on Distributed Computing Systems (2002)

In this paper, we propose a user-friendly three-dimensional CG presentation system for a typical traditional Japanese crafting industry based on agent and virtual reality functions over Japan Gigabit Network (JGN) which is a testbed highspeed backbone networkwith 2.4Gbps. A large number of traditional Japanese fittings in a local city are redesigned by three-dimensional computer graphics into CAD data and stored in the database servers distributed over JGN. Although each fitting data consists of more than several Mbytes size, user can interactively retrieve the desired fittings and put those into the traditional Japanese interior to design more creative and original houses, hotels and other buildings in realtime. We prototyped a presentation system using VRML and JAVA on networked CG workstations. User can walk through the desired virtual space as a Japanese interior organized by various Japanese traditional fittings and iteractively change those fittings by selecting from the database and replacing by simple operations. As a result, we could verify the usefulness of our suggested system not only for Japanese crafting but also for worldwide design industries.
A parallel version of KIVA-3 based on general purpose numerical software and its use in two-stroke engine applications
Authors: Luigi Arnone, Pasqua D'Ambra, Salvatore Filippone
Venue: Practical parallel computing (2001)

Numerical simulations of reactive flows are among the most computational demanding applications in the scientific computing world; the relevant codes are often difficult to maintain and improve, and the solution methods employed may not always be the most up-to-date.In this work we focus on an activity carried out in the context of the PINEAPL project, funded by the European Commission. We have developed a parallel version of the KIVA-3 application software by integrating routines from the parallel sparse solvers of the PINEAPL library in the code, an obtained some interesting results in terms of speed, efficiency and robustness.KIVA-3 is a widely used CFD software for numerical simulation of chemically reactive flows, specifically tailored for engine applications. The parallel version of KIVA-3 is currently in use at Piaggio for the simulation of the scavenging process in two-stroke engines. The reduction of the simulation times obtained with the new code produced important effects on the overall simulation procedure of new engines.
Learning default mappings and exception handling
Authors: Fredrik Linåker, Nicklas Bergfeldt
Venue: Proceedings of the seventh international conference on simulation of adaptive behavior on From animals to animats (2002)

We show how a layered neural adaptation process comes to learn a simple default mapping from inputs to outputs. Then, as a succeeding step, it learns to use context for detection and handling of exceptions from this default mapping. Thereby tasks can be learnt in a step-wise manner, and the system exhibits graceful degradation if higher structures in the system are damaged.