Showing papers by "University of the Aegean published in 2002"

Emotional intelligence in the workplace: exploring its effects on occupational stress and organizational commitment

Abstract: The purpose of the present study is to explore the relationship between emotional intelligence and sources of occupational stress and outcomes on a sample of professionals in mental health institutions. A total of 212 participants were administered the Emotional Intelligence Questionnaire as well as the Organizational Stress Screening Tool (ASSET), a new organizational screening tool, which measures workplace stress. The results were in the expected direction showing a negative correlation between emotional intelligence and stress at work, indicating that high scorers in overall EI suffered less stress related to occupational environment. A positive correlation was also found between emotional intelligence and organizational commitment, which according to the ASSET model is considered as a consequence of stress, suggesting a new role for EI as a determinant of employee loyalty to organizations. Finally, the relationship between EI, job stress, and various demographic variables such as gender, age, and education was investigated and results are discussed in the light of the organizational framework.

The Role of Intermediaries in Electronic Marketplaces: Developing a Contingency Model

Abstract: . Early research in electronic markets seemed to suggest that e- commerce transactions would result in decreased costs for buyers and sellers alike, and would therefore ultimately lead to the elimination of intermediaries from electronic value chains. However, a careful analysis of the structure and functions of electronic marketplaces reveals a different picture. Intermediaries provide many value-adding functions that cannot be easily substituted or ‘internalized’ through direct supplier–buyer dealings, and hence mediating parties may continue to play a significant role in the e-commerce world. In this paper we provide an analysis of the potential roles of intermediaries in electronic markets and we articulate a number of hypotheses for the future of intermediation in such markets. Three main scenarios are discussed: the disintermediation scenario, in which market dynamics will favour direct buyer–seller transactions; the reintermediation scenario, in which traditional intermediaries will be forced to differentiate themselves and re-emerge in the electronic marketplace; and the cybermediation scenario, in which wholly new markets for intermediaries will be created. The analysis suggests that the likelihood of each scenario dominating a given market is primarily dependent on the exact functions that intermediaries play in each case. A detailed discussion of such functions is presented in the paper, together with an analysis of likely outcomes in the form of a contingency model for intermediation in electronic markets.

Variability in interaction strength and implications for biodiversity

Abstract: Summary 1. We examined the species richness of theoretical communities in relation to interaction strength between species. 2. To do so, we used randomly constructed interaction matrices for competitive systems. To determine co-existence, we tested for local stability and equilibrium feasibility of these theoretical assemblages. 3. As expected, we found that a low mean species interaction strength could allow for many species to co-exist. However, variance in the interaction strengths may alter previous results; two systems with the same mean interaction strength show markedly different diversity depending critically on the magnitude of the variance. If species are similar enough then many can co-exist, even if they compete strongly. 4. In addition we found that the species richness of a competitive community can greatly depend on the correlation between interaction strengths, an issue that so far has gone unreported. This correlation, a result of trade-offs between species’ characteristics, may profoundly increase the potential for stable co-existence of a highly species-rich community. 5. Competition may not be an anathema to diversity. Statistical properties of species’ interactions may be critical factors that contribute to the explanation of species diversity in natural communities.

Goal-Oriented Requirements Engineering: A Unifying Framework

Abstract: The study of contemporary requirements engineering (RE) methodologies indicates that modelling of organisational goals constitutes a central activity of the RE process. In particular, goals provide the rationale and drivethe elaboration of the requirements that operationalise them. They also provide the criteria against which the completeness and correctness of the requirements specification is validated. In other words, requirements implement goals in the same way that programs implement design specifications. Despite the significance of goals in RE, research in the field is fragmented. No research has so far taken place in order to define the overall role that goals play in RE. This paper puts forward a unifying view of goal analysis in the context of RE. This allows the identification of similarities and differences between the different conceptions of goal used by different approaches and promotes the understanding of the overall role of goal analysis in RE. Based on this understanding the various approaches can be put together, thus leading to a stronger goal-driven RE framework that takes advantage of the contributions from the many streams of goal-oriented research.

Estimates for the ruin probability in the classical risk model with constant interest force in the presence of heavy tails

Abstract: In this paper we investigate the ruin probability in the classical risk model under a positive constant interest force. We restrict ourselves to the case where the claim size is heavy-tailed, i.e. the equilibrium distribution function (e.d.f.) of the claim size belongs to a wide subclass of the subexponential distributions. Two-sided estimates for the ruin probability are developed by reduction from the classical model without interest force.

Gibbs Variable Selection using BUGS

Abstract: In this paper we discuss and present in detail the implementation of Gibbs variable selection as defined by Dellaportas et al. (2000, 2002) using the BUGS software (Spiegelhalter et al. , 1996a,b,c). The specification of the likelihood, prior and pseudo-prior distributions of the parameters as well as the prior term and model probabilities are described in detail. Guidance is also provided for the calculation of the posterior probabilities within BUGS environment when the number of models is limited. We illustrate the application of this methodology in a variety of problems including linear regression, log-linear and binomial response models.

Bayesian Modelling of Outstanding Liabilities Incorporating Claim Count Uncertainty

Abstract: This paper deals with the prediction of the amount of outstanding automobile claims that an insurance company will pay in the near future We consider various competing models using Bayesian theory and Markov chain Monte Carlo methods Claim counts are used to add a further hierarchical stage in the model with log-normally distributed claim amounts and its corresponding state space version This way, we incorporate information from both the outstanding claim amounts and counts data resulting in new model formulations Implementation details and illustrations with real insurance data are provided

OVSF codes assignment and reassignment at the forward link of W-CDMA 3G systems

Abstract: We examine the problem of assigning and reassigning orthogonal variable spreading factor (OVSF) codes at the forward link in 3G mobile communications systems employing W-CDMA Efficient channelization code management results in high code utilization and increased system capacity We introduce a new code selection scheme, which, by means of a very simple measure, attempts to mitigate the problem of scattered codes that fragments the capacity of the OVSF code tree The main advantage of this new scheme is its ability to combine effectively the merits of other previously proposed schemes (see Tseng, Y-C et al, Proc IEEE GLOBECOM, vol1, p562-6,2001) Thus, our proposed scheme is as fast as the random or ordered strategies, while simulation results have shown that it is as efficient, in terms of capacity improvement, as the crowded-first scheme

On the Potential Use of Mobile Positioning Technologies in Indoor Environments

Abstract: A great deal of attention is recently being paid to the potential of mobile communication technologies to redefine and extend the world of traditional eBusiness by rendering its applications available to mobile users. The term Mobile Business (mBusiness) has been coined to denote the ways in which mobile George M. Giaglis, Ada Pateli, Kostas Fouskas, Panos Kourouthanassis, Argiris Tsamakos 414 communication technologies can be applied to address the requirements of mobile users that need to access a varied range of applications and services through wireless access devices. However, the ongoing discussion on mBusiness is restricted almost solely to ‘macro’ applications in outdoor settings. In this paper we extend the definition of mBusiness to include a complementary set of ‘micro’ applications in indoor environments (such as museums, exhibitions, hypermarkets, and others), where location awareness can become a crucial parameter of valueadded service provision. We contend that a wide number of indoor environments can benefit from location-based applications and services, albeit only after overcoming a number of technological and application challenges that exist today. The paper identifies such challenges through the discussion of ongoing research work investigating the potential applicability of indoor location services in the exhibition industry.

A Study of the Development of the Concept of Mechanical Stability in Preschool Children

Abstract: The purpose of this study was to investigate whether preschool children (aged 4.5–6 years) can construct the concept of mechanical stability through structured hands-on activities involving the building of a tower on an inclined plane and through the use of cans of various sizes and weights. The data derived mainly from direct observation and the visual component of video tape recordings of thirty-seven children. These children formed three treatment groups which participated in structured-guided, structured-unguided and unstructured-unguided activities respectively. There is strong evidence that appropriately structured activities involving children's action on objects and the objects immediate reaction, as well as children's opportunity to vary this action, complemented with a scaffolding strategy can help children construct the concept of mechanical stability and apply it in other similar contexts. The paper also presents a theoretical framework for the teaching and learning of physics in the early years.

Revisiting Legal and Regulatory Requirements for Secure E-Voting

Abstract: This paper addresses the democracy-oriented legal and constitutional requirements that an electronic voting system has to comply with. Its scope covers every election or decision-making process, which takes place through voting. Due mainly to the digital divide and to current technological limitation, electronic voting cannot be proposed as a universal means of voting but rather as an alternative option, supplemental to traditional voting means. An electronic voting process must be designed in such a way as to guarantee the general, free, equal and secret character of elections. In a democratic context an electronic voting system should respect and ensure attributes and properties such as transparency, verifiability, accountability, security and accuracy. Only then can it foster and promote the participation of the citizens, the legitimacy and the democratic transaction of the election process.

Explicit approximate inverse preconditioning techniques

Abstract: The numerical treatment and the production of related software for solving large sparse linear systems of algebraic equations, derived mainly from the discretization of partial differential equation, by preconditioning techniques has attracted the attention of many researchers. In this paper we give an overview of explicit approximate inverse matrix techniques for computing explicitly various families of approximate inverses based on Choleski and LU—type approximate factorization procedures for solving sparse linear systems, which are derived from the finite difference, finite element and the domain decomposition discretization of elliptic and parabolic partial differential equations. Composite iterative schemes, using inner-outer schemes in conjunction with Picard and Newton method, based on approximate inverse matrix techniques for solving non-linear boundary value problems, are presented. Additionally, isomorphic iterative methods are introduced for the efficient solution of non-linear systems. Explicit preconditioned conjugate gradient—type schemes in conjunction with approximate inverse matrix techniques are presented for the efficient solution of linear and non-linear system of algebraic equations. Theoretical estimates on the rate of convergence and computational complexity of the explicit preconditioned conjugate gradient method are also presented. Applications of the proposed methods on characteristic linear and non-linear problems are discussed and numerical results are given.

Components of short-term invasibility in experimental Mediterranean grasslands

Abstract: Troumbis, A. Y., Galanidis, A. and Kokkoris, G. D. 2002. Components of short-term invasibility in experimental Mediterranean grasslands. – Oikos 98: 239–250.The paper reports findings of a natural invasibility study in constructed Mediter-ranean grasslands, located in the Greek site of the BIODEPTH project. Threedifferent components of invasibility, i.e. species richness, abundance and rarity ofinvaders, have been monitored in experimental plots where the resident diversityranged from monocultures to 18-species mixtures. Invaders’ richness and abundancewere negatively correlated to the resident diversity, while the occurrence of rareinvaders was strongly positively correlated to the resident diversity. Standing biomassexplained also a significant part of the variation of communities’ invasibility. Soilnutrients and structural traits of the constructed vegetation such as the space-fillingshowed no influence in the definition of the overall pattern of invasibility in thesecommunities. A verbal model of selection of invaders at the neighbourhood scale isproposed to explain these diverging trends of invasibility.

An Appropriate Subdifferential for Quasiconvex Functions

Abstract: In this paper we introduce and study a subdifferential that is related to the quasi- convex functions, much as the Fenchel--Moreau subdifferential is related to the convex ones. It is defined for any lower semicontinuous function, through an appropriate combination of an abstract subdifferential and the normal cone to sublevel sets. We show that this "quasiconvex" subdifferential is always a cyclically quasimonotone operator that coincides with the Fenchel--Moreau subdifferential whenever the function is convex, and that under mild assumptions, the density of its domain in the domain of the function is equivalent to the quasiconvexity of the function. We also show that the "quasiconvex" subdifferential of a lower semicontinuous function contains the derivatives of its differentiable quasiaffine supports. As a consequence, it contains the subdifferential introduced by Martinez-Legaz and Sach in a recent paper [J. Convex Anal., 6 (1999), pp. 1--12]. Several other properties and calculus rules are also established.

The Economy of Complete Symmetry Groups for Linear Higher Dimensional Systems

Abstract: The complete symmetry groups of systems of linear second order ordinary differential equations are considered in the context of the simple harmonic oscillator. One finds that in general the representation of the complete symmetry group is not unique and in the particular case of a four-dimensional system there are two distinct complete symmetry groups. The results for general second order linear systems are indicated in the Conclusion.