Showing papers by "University of Cyprus published in 1995"
TL;DR: This paper characterize the desirable properties of a solution to models, when the problem data are described by a set of scenarios for their value, instead of using point estimates, and develops a general model formulation, called robust optimization RO, that explicitly incorporates the conflicting objectives of solution and model robustness.
Abstract: Mathematical programming models with noisy, erroneous, or incomplete data are common in operations research applications. Difficulties with such data are typically dealt with reactively-through sensitivity analysis-or proactively-through stochastic programming formulations. In this paper, we characterize the desirable properties of a solution to models, when the problem data are described by a set of scenarios for their value, instead of using point estimates. A solution to an optimization model is defined as: solution robust if it remains "close" to optimal for all scenarios of the input data, and model robust if it remains "almost" feasible for all data scenarios. We then develop a general model formulation, called robust optimization RO, that explicitly incorporates the conflicting objectives of solution and model robustness. Robust optimization is compared with the traditional approaches of sensitivity analysis and stochastic linear programming. The classical diet problem illustrates the issues. Robust optimization models are then developed for several real-world applications: power capacity expansion; matrix balancing and image reconstruction; air-force airline scheduling; scenario immunization for financial planning; and minimum weight structural design. We also comment on the suitability of parallel and distributed computer architectures for the solution of robust optimization models.
1,793 citations
TL;DR: Conceptual as well as methodological issues related to measuring system usage are addressed and it is suggested that system usage should be factored into self-reported system usage and computer-recorded system usage.
Abstract: There is widespread agreement among researchers that system usage, defined as the utilization of information technology IT by individuals, groups, or organizations, is the primary variable through which IT affects white collar performance. Despite the number of studies targeted at explaining system usage, there are crucial differences in the way the variable has been conceptualized and operationalized. This wide variation of system usage measures hinders the efforts of MIS researchers to compare findings across studies, thus impeding the accumulation of knowledge and theory in this area.
The purpose of this paper is to address conceptual as well as methodological issues related to measuring system usage. First, via LISREL measurement modeling techniques, we compare subjective and objective measures of system usage, namely, self-reported versus computer-recorded measures. Next, using a modified form of Davis' Technology Acceptance Model TAM as a nomological net, we test the nomological validity of these system usage constructs and measures.
Results of the LISREL measurement and nomological net analysis suggest that system usage should be factored into self-reported system usage and computer-recorded system usage. Contrary to expectations, these constructs do not appear to be strongly related to each other. Moreover, while self-reported measures of system usage are related to self-reported measures of TAM independent variables, objective, computer-recorded measures show distinctly weaker links.
In the face of such counter-evidence, it is tempting to argue that research that has relied on subjective measures of system usage for example, research confirming TAM may be artifactual. There are several alternative explanations, though, that maintain the integrity of TAM and studies that measure system usage subjectively. These alternative explanations suggest directions for further research as well as new approaches to measurement.
998 citations
TL;DR: The authors investigate why 75 percent of U.S. households do not hold stocks despite the equity premium and predictions of expected-utility models and show that risk aversion per se, heterogeneity of beliefs, habit persistence, time nonseparability, and quantity constraints on borrowing do not account for the phenomenon.
Abstract: The authors investigate why 75 percent of U.S. households do not hold stocks despite the equity premium and predictions of expected-utility models. The question is relevant for privatization, asset pricing, and tax progressivity issues. They show that risk aversion per se, heterogeneity of beliefs, habit persistence, time nonseparability, and quantity constraints on borrowing do not account for the phenomenon. A wedge between borrowing and lending rates, and minimum-investment requirements are plausible but empirically weak factors. More promising explanations are inertia and departures from expected-utility maximization. There is also qualified support for nondiversifiable income risk as a contributing factor. Copyright 1995 by Royal Economic Society.
971 citations
TL;DR: In this paper, the authors reviewed, assessed, and synthesized existing empirical research on factors impeding the initiation, development, or sustainment of export activities, and investigated 35 factors.
Abstract: The article attempts to review, assess, and synthesize existing empirical research on factors impeding the initiation, development, or sustainment of export activities. The investigation covered 35...
343 citations
TL;DR: In this article, an empirical assessment of non-exporters' perceptions on the factors that hinder the initiation of export activities was conducted among a representative random sample of 112 Cypriot manufacturing concerns, which revealed that increasing competitive pressures in the world market constituted the most severe impediment to the export initiation process.
Abstract: Provides an empirical assessment of non‐exporters′ perceptions on the factors that hinder the initiation of export activities. The research investigation, which was conducted among a representative random sample of 112 Cypriot manufacturing concerns, revealed that the increasing competitive pressures in the world market constituted the most severe impediment to the export initiation process. A number of organizational determinants exhibited a discriminating effect on certain export barriers. Specifically, there was a tendency by firms with no prior export experience, of small size and with relatively few years in business, to overstress some of the export barriers addressed. However, the type of goods manufactured did not exhibit any differentiating impact. An attempted classification of the export barriers according to internal/external and domestic/foreign typologies revealed no significant differences in the inhibiting impact of the resulting groups.
261 citations
TL;DR: In this paper, a review, evaluation and integration of available research on the factors stimulating initiation and subsequent development and sustainment of export operations is presented, focusing on 30 studies conducted mainly in North American and European countries.
154 citations
TL;DR: The parametric pattern recognition (PPR) algorithm that facilitates automatic MUAP feature extraction and Artificial Neural Network (ANN) models are combined for providing an integrated system for the diagnosis of neuromuscular disorders.
Abstract: In previous years, several computer-aided quantitative motor unit action potential (MUAP) techniques were reported. It is now possible to add to these techniques the capability of automated medical diagnosis so that all data can be processed in an integrated environment. In this study, the parametric pattern recognition (PPR) algorithm that facilitates automatic MUAP feature extraction and Artificial Neural Network (ANN) models are combined for providing an integrated system for the diagnosis of neuromuscular disorders. Two paradigms of learning for training ANN models were investigated, supervised, and unsupervised. For supervised learning, the back-propagation algorithm and for unsupervised learning, the Kohonen's self-organizing feature maps algorithm were used. The diagnostic yield for models trained with both procedures was similar and on the order of 80%. However, back propagation models required considerably more computational effort compared to the Kohonen's self-organizing feature map models. Poorer diagnostic performance was obtained when the K-means nearest neighbor clustering algorithm was applied on the same set of data. >
144 citations
TL;DR: The roots of the traditional textbook approach to econometric modeling are traced to two older statistical traditions, Fisher's experimental design paradigm and Gauss's ‘theory of errors’, and it is argued that this approach is ill-suited for nonexperimental (observational) data.
121 citations
TL;DR: A constructive heuristic which provides solutions to the single-row facility layout problem so as to minimize the materials handling cost and results show that the heuristic performs well in terms of computational efficiency and solution quality.
94 citations
TL;DR: In this paper, a rank-3 demand system equivalence scales measuring the cost of demographic characteristics independently of the base utility level can be identified from cross-section data without demographic separability restrictions.
92 citations
TL;DR: In this article, the authors established the meteorological basis for the assessment of wind energy resources in Cyprus and provided suitable data for evaluating the potential wind power for this purpose the mean values, the systematic daily and annual variations, the frequency distributions and the estimation of the extreme values are determined Predictions were also obtained from the WAsP model and the Wind Atlas of the island, in the form of contours of constant wind speed, was produced.
TL;DR: Various optimizations are presented and analyzed in terms of reliability, savings in log writes and network traffic, and reduction in resource lock time and the feasibility and performance of several optimization combinations are analyzed.
Abstract: An atomic commit protocol can ensure that all participants in a distributed transaction reach consistent states, whether or not system or network failures occur. The atomic commit protocol used in industry and academia is the well-known two-phase commit (2PC) protocol, which has been the subject of considerable work and technical literature for some years.
TL;DR: In this article, the role of normality in the context of linear homoskedastic regression models was discussed, and it was shown that assuming joint normality of the regressors and regressands, not just conditional normality, is equivalent to assuming linearity of the reverse regression.
Abstract: The purpose of this note is to discuss the role of normality in the context of linear[zddot]homoskedastic regression models. A new characterization result, relating the joint normal distribution and the linear, homoskedastic regression, sheds some light on the role of normality in this context. It is shown that if the assumptions of (a) linearity and (b) homoskedasticity, are supplemented with the assumption of (c) linearity of the reverse regression, assumptions (a)-(c) are tantamount to assuming joint normality of the regressors and regressands, not just conditional normality.
TL;DR: In this paper, the authors investigate the perceptions of non-exporters regarding factors stimulating export initiation and find that factors of an internal and proactive nature provided the strongest stimulating impact, denoting a positive predisposition towards exporting.
Abstract: Investigates empirically the perceptions of non‐exporters regarding factors stimulating export initiation. Draws on research based on a representative sample of 112 Cyprus‐based manufacturers. Reveals that stimuli relating to the fulfilment of the firm′s traditional objectives exhibited the highest motivating impact, followed by factors aiming at minimizing domestic market‐related risks. These findings generally contrast with the results of previous research on export stimulation. Analysis of perceptions on stimulating factors according to certain organizational determinants showed the firm′s size to have the greatest discriminating effect, followed by the type of goods produced and exposure to export activities; the age of the firm had no differentiating role whatsoever. Finally, classification of the stimuli according to internal/external and proactive/reactive taxonomies demonstrated that factors of an internal and proactive nature provided the strongest stimulating impact, denoting a positive predisposition towards exporting.
TL;DR: In this article, the authors construct a two-country general equilibrium trade model, where an income transfer that takes place between the two countries is used by the recipient to finance a public consumption good.
25 Apr 1995
TL;DR: It is proved that the non-monotonic learning algorithm that realizes these ideas converges asymptotically to the concept to be learned.
Abstract: In this paper we present a framework for learning non-monotonic logic programs. The method is parametric on a classical learning algorithm whose generated rules are to be understood as default rules. This means that these rules must be tolerant to the negative information by allowing for the possibility of exceptions. The same classical algorithm is then used to learn recursively these exceptions.
We prove that the non-monotonic learning algorithm that realizes these ideas converges asymptotically to the concept to be learned. We also discuss various general issues concerning the problem of learning nonmonotonic theories in the proposed framework.
TL;DR: The design and implementation of an algorithm for the solution of large scale optimization problems with embedded network structures using a linear-quadratic penalty function and a simplicial decomposition is discussed.
TL;DR: The Greek Cypriot population will be studied further for elucidating the effect(s) and the role of APOE in cardiovascular disease and the APOE4 allele as a possible metabolic factor affecting the rate of expression of both Alzheimer's disease and vascular dementia.
Abstract: Apolipoprotein E (APOE) plays an important role in the multifactorial etiology of both cardiovascular disease and Alzheimer's disease. Polymerase chain reaction (PCR) was used to investigate the APOE gene polymorphism in 335 unrelated Greek Cypriots living on the island of Cyprus. For the most common APOE genotypes, the Greek Cypriots followed the general Caucasian European pattern of having higher genotypic frequencies of E3/3, followed by E3/4, and then E2/3. Among the European populations compared, Greek Cypriots exhibited the lowest relative frequency of the E3/4 genotype (12.83%). Also, the relative frequencies of the E2 and E4 alleles in Greek Cypriots were among the lowest around the world (5.4% and 7.0%, respectively). This was also demonstrated by using the complete and the average clustering methods of analysis where the APOE allele relative frequencies in Greek Cypriots were compared to 46 other populations. The Greek Cypriot population in these analyses clustered with populations mainly from south Europe and Japan which have low E2 and E4 allele frequencies. The Greek Cypriot population will be studied further for elucidating the effect(s) and the role of APOE in cardiovascular disease and the APOE4 allele as a possible metabolic factor affecting the rate of expression of both Alzheimer's disease and vascular dementia.
TL;DR: The degree of family cohesion was found to be as able to discriminate students in terms of school achievement as their family's SES, in contrast to gender and place of residence (urban vs rural).
Abstract: The purpose of this study was to examine the extent to which family cohesion, a functional characteristic of family life, is related to school achievement. It is already established in the international literature that such a relationship does exist between school achievement and a number of structural characteristics of the family, particularly socioeconomic status (SES). Demographic data were collected from all the ninth grade students of two Greek Cypriot high schools, one serving a suburban and the other serving a rural population. The students (N= 391) completed a self report questionnaire that was designed to measure the degree of their family cohesion or the emotional togetherness that they felt existing among the members of their family. It was found that the degree of family cohesion was as able to discriminate them in terms of school achievement as their family's SES. Both variables produced statistically significant differences, in contrast to gender and place of residence (urban vs rural). The results are discussed in relation to the Greek Cypriot family context.
TL;DR: In this paper, an upper bound of a few times 10 −5 on the branching ratio Z → χχ′ and Z→ χ′χ> was given for the lightest neutralino with m χ less than 18 GeV.
TL;DR: In this paper, the total and differential cross sections for the process e+e- → γγ(γ) were measured at energies around 91 GeV using the data collected with the L3 detector from 1991 to 1993.
TL;DR: In this article, an exact solution of the Navier-Stokes equations is used as the background state to develop an asymptotic theory valid for thin annular layers, which leads to a novel nonlinear evolution describing the spatio-temporal evolution of the interface.
Abstract: In this paper the nonlinear stability of two-phase core-annular flow in a pipe is examined when the acting pressure gradient is modulated by time harmonic oscillations and viscosity stratification and interfacial tension is present. An exact solution of the Navier-Stokes equations is used as the background state to develop an asymptotic theory valid for thin annular layers, which leads to a novel nonlinear evolution describing the spatio-temporal evolution of the interface. The evolution equation is an extension of the equation found for constant pressure gradients and generalizes the Kuramoto-Sivashinsky equation with dispersive effects found by Papageorgiou, Maldarelli & Rumschitzki, Phys. Fluids A 2(3), 1990, pp. 340-352, to a similar system with time periodic coefficients. The distinct regimes of slow and moderate flow are considered and the corresponding evolution is derived. Certain solutions are described analytically in the neighborhood of the first bifurcation point by use of multiple scales asymptotics. Extensive numerical experiments, using dynamical systems ideas, are carried out in order to evaluate the effect of the oscillatory pressure gradient on the solutions in the presence of a constant pressure gradient.
TL;DR: In this article, a sample of Z → b b events was obtained by tagging muons in 1.6 million hadronic Z decays collected in 1991, 1992 and 1993.
TL;DR: The authors examined the behavior of some key macroeconomic variables under alternative exchange rate regimes by looking at persistence, volatility, and the relative importance of symmetric (worldwide) versus asymmetric (nation-specific) shocks as a driving force of business cycles.
25 Jun 1995
TL;DR: The notion of a time-object is proposed as an appropriate ontological primitive for modelling medical concepts, and generic models for patient data, disorders, and actions based on time-objects are discussed.
Abstract: Time is intrinsically related to medical problem-solving in general Modelling time from the perspective of computer-based, competent, solution derivation of real-life medical problems is a challenging undertaking Starting from the premise that temporal reasoning is an integral aspect of medical problem-solving, necessary requirements for medical temporal reasoning are listed, the notion of a time-object is proposed as an appropriate ontological primitive for modelling medical concepts, and generic models for patient data, disorders, and actions based on time-objects are discussed
TL;DR: In this article, the authors investigated Luscher's method of including dynamical Wilson fermions in a lattice simulation of QCD with two quark flavors and measured the accuracy of the approximation by comparing it with Hybrid Monte Carlo results for gauge plaquette and Wilson loops.
TL;DR: In this article, Gibbs et al. reported that the catalytic activity of metallic residues in steam and carbon dioxide results in homogeneous and localised surface pits, respectively, for polyarylamide-derived Nomex and Kevlar chars.
26 Jun 1995
TL;DR: A proof theory and a proof procedure for nonmonotonic reasoning based on the acceptability semantics for logic programming, formulated in an argumentation framework are presented.
Abstract: We present a proof theory and a proof procedure for nonmonotonic reasoning based on the acceptability semantics for logic programming, formulated in an argumentation framework. These proof theory and procedure are defined as generalisations of corresponding proof theories and procedures for the stable theory and preferred extension semantics. In turn, these can be seen as generalisations of the Eshghi-Kowalski abductive procedure for logic programming.
TL;DR: In this article, a search for rare charmless decays of B d 0 and B s 0 mesons has been performed in the exclusive channels B d(s) 0 → ηη, B d (s) 1 → π π 0 π, and B d 1 → 0π 0, and no candidate event has been observed.
TL;DR: In this paper, the authors considered the axisymmetic Newtonian extrudate swell problem and examined the effect of compressibility on the shape of the free surface and the final extensor swell ratio.
Abstract: SUMMARY We solve the compressible Newtonian extrudate swell problem in order to investigate the effect of compressibility on the shape of the extrudate. We employ a first-order equation of state relating the density to the pressure and use finite elements for the numerical solution of the problem. Our results show that the shape of the extrudate and the final extrudate swell ratio are not significantly affected even at high compressibility values. The extrudate swell problem has been one of the most extensively studied problems in the area of polymer-processing simulations. Since the first solution of the two-dimensional Newtonian problem by Nickell et ul.,’ who used a Picard iteration, finite element scheme, considerable progress has been made in extrusion modelling. Ruschak’ proposed the full Newton iteration method in which the position of the free surface is computed simultaneously with the velocity and pressure fields. Om~dei~.~ presented complete series of results at various Reynolds and capillary numbers for both the planar and axisymmetic Newtonian extrudate swell problems. Crochet and Keunings’ solved the viscoelastic extrudate swell problem using differential constitutive models and Papanastasiou et ~1.~ developed the streamlined finite element method for integral constitutive models. Georgiou et ~l.’~* developed singular finite elements for the solution of the Newtonian problem. More recent progress includes the development of new techniques for integral three-dimensional extrusion simulations’ ‘-I3 and die design.13-” In this paper we consider the axisymmetic Newtonian extrudate swell problem and examine the effect of compressibility on the shape of the free surface and the final extrudate swell ratio. A simple first-order equation of state is used to express the density of the fluid as a function of pressure. The density is eliminated and a standard finite element method is employed for the numerical solution of this free surface problem. The numerical results show that the free surface profile and the final extrudate swell ratio are not significantly affected even when the fluid is highly compressible. It should be added, however, that compressibility combined with slip at the wall can alter dramatically the dynamics of the flow. This has been demonstrated in Reference 16 for time-dependent compressible Poiseuille flow. In Section 2 we present the governing equations and boundary conditions. In Section 3 we give a brief description of the finite element formulation. The numerical results are presented and discussed in Section 4.