Showing papers by "University of the Aegean published in 2000"
TL;DR: In this paper, the authors present examples from the areas of ethnographic practice, tourism discourse, and travel narrative to shed light on the process of self-discovery and self-representation which results from the gazing into the elsewhere and the Other.
190 citations
TL;DR: In this paper, a hybrid method was developed that utilizes equilibrium assumptions for the fine aerosol mode (particles with diameters less than 1μm) and the dynamic approach for the coarse aerosolmode.
147 citations
TL;DR: In this article, a simulated annealing approach for solving the buffer allocation problem in reliable production lines is described, which involves the determination of near optimal buffer allocation plans in large production lines with the objective of maximizing their average throughput.
Abstract: We describe a simulated annealing approach for solving the buffer allocation problem in reliable production lines. The problem entails the determination of near optimal buffer allocation plans in large production lines with the objective of maximizing their average throughput. The latter is calculated utilizing a decomposition method. The allocation plan is calculated subject to a given amount of total buffer slots in a computationally efficient way.
109 citations
TL;DR: The ISHTAR training course on information systems security for HCE managers is evaluated against these requirements and improvements to it are proposed.
86 citations
TL;DR: A robust generalized queuing network algorithm is presented as an evaluative procedure for optimizing production line configurations using simulated annealing and its bounded execution time property makes it viable for optimizing very long production line configuration.
Abstract: We present a robust generalized queuing network algorithm as an evaluative procedure for optimizing production line configurations using simulated annealing. We compare the results obtained with our algorithm to those of other studies and find some interesting similarities but also striking differences between them in the allocation of buffers, numbers of servers, and their service rates. While context dependent, these patterns of allocation are one of the most important insights which emerge in solving very long production lines. The patterns, however, are often counter-intuitive, which underscores the difficulty of the problem we address. The most interesting feature of our optimization procedure is its bounded execution time, which makes it viable for optimizing very long production line configurations. Based on the bounded execution time property, we have optimized configurations of up to 60 stations with 120 buffers and servers in less than five hours of CPU time.
85 citations
TL;DR: Sundt and Teugels as mentioned in this paper gave a simple proof of the asymptotic formula for the ruin probability of a risk process with a positive constant interest force, which is based on a formula obtained by Sundt.
Abstract: A simple proof of the asymptotic formula for the ruin probability of a risk process with a positive constant interest force [derived earlier by Asmussen (Asmussen, S., 1998. The Annals of Applied Probability 8, 354–374)] is given. The proof is based on a formula obtained by Sundt and Teugels (Sundt, B., Teugels, J.L., 1995. Insurance: Mathematics and Economics 16, 7–22).
77 citations
TL;DR: In order to delineate the geomorphic features of the island of Lesvos, Greece, fieldwork and digital satellite (LANDSAT-5/TM) data analysis were combined as mentioned in this paper.
74 citations
TL;DR: In this article, an integrated modeling approach is proposed for the assessment of the nutrient loading of a coastal marine ecosystem from terrestrial sources, based on a data set collected on a monthly basis from a Greek gulf surrounded by an intensively cultivated watershed.
68 citations
TL;DR: In this article, an autonomous system of ordinary differential equations can be rewritten as a mixed system of first and second order equations for which point symmetries can be automated without having to make an Ansatz on the detailed structure of the symmetry.
65 citations
TL;DR: Nectary structure in Labiatae is largely shaped by both phylogenetic and climate constraints, implying that, in addition to phylogeny, there are many other ecological parameters interfering in its secretion such as time within the season, life history, and light requirements.
Abstract: We studied the interrelation between nectary structure (13 parameters), nectar characteristics (yield, chemical composition), and flower size of 11 Labiatae species in a Mediterranean shrub community near Athens, Greece. We also explored whether the above attributes are affected by the Mediterranean summer drought constraints. Our findings show that among all nectary parameters studied, nectary size and stomatal opening are the most important in (positively) shaping nectar secretion, nectary size being the most meaningful. Nectary structure is correlated to quantity of the nectar secreted, not its quality. Wide flowers bear wide nectaries with large stomatal openings, whereas deep flowers are not related to any nectary size. Corolla size (both length and width) and nectary stomatal opening decrease with flowering time. This applies also to nectary size, nectar volume and sugar content of the perennials (9 species). All above cases of time dependence show that there is a constraint effect of Mediterranean climate on floral and nectary structure, reflected also as a decrease in nectar secretion. Nectary structure in Labiatae is largely shaped by both phylogenetic and climate constraints. On the other hand, although nectar is largely influenced by nectary structure, it is to a large extent ecologically biased, implying that, in addition to phylogeny, there are many other ecological parameters interfering in its secretion such as time within the season, life history, and light requirements.
64 citations
TL;DR: In this article, the impact of river-transported metal pollution on the metal distribution in coastal sediments was studied in Southern Evoikos Gulf, Greece, a marine area characterized by relatively strong tidal currents.
TL;DR: An investigation into the occurrence of trihalomethanes (THMs) in public water supplies in Greece concludes that brominated THMs dominated and existed at the highest concentration levels, whereas chloroform was the least prevalent compound, while in all the other cases the opposite was observed.
TL;DR: It is demonstrated how the use of reflection, whereby the software is able to examine its own operation, in conjunction with cryptographic hashes as a basis for developing a suitable software verification protocol, can be used to increase the security of mobile phones, devices for the delivery of digital content, and smartcards.
Abstract: The integrity verification of a device's controlling software is an important aspect of many emerging information appliances. We propose the use of reflection, whereby the software is able to examine its own operation, in conjunction with cryptographic hashes as a basis for developing a suitable software verification protocol. For more demanding applications meta-reflective techniques can be used to thwart attacks based on device emulation strategies. We demonstrate how our approach can be used to increase the security of mobile phones, devices for the delivery of digital content, and smartcards.
TL;DR: In this article, the Freyd categories of C were studied in the context of the module theory of triangulated categories, and their applications to the abelian or triangulation categories were discussed.
Abstract: To any additive category C, we associate in a functorial way two additive categories A(C), B(C). The category A(C), resp. B(C), is the re∞ection of C in the category of additive categories with cokernels, resp. kernels, and cokernel, resp. kernel, preserving functors. Then the iteration AB(C) is the re∞ection of C in the category of abelian categories and exact functors. We call A(C) and B(C) the Freyd categories of C since the flrst systematic study of these categories was done by Freyd in the mid-sixties. The purpose of the paper is to study further the Freyd categories and to indicate their applications to the module theory of an abelian or triangulated category.
TL;DR: This paper presents the main architectural and functional characteristics of an “intelligent system” supporting the efficient management of patient's data and highlights how the security features offered by smart cards can be exploited in order to ensure confidentiality and integrity of the medical data stored in the patient cards.
Abstract: The continuously increased mobility of patients and doctors, in conjunction with the existence of medical groups consisting of private doctors, general practitioners, hospitals, medical centers, and insurance companies, pose significant difficulties on the management of patients' medical data. Inevitably this affects the quality of the health care services provided. The evolving smart card technology can be utilized for the implementation of a secure portable electronic medical record, carried by the patient herself/himself. In addition to the medical data, insurance information can be stored in the smart card thus facilitating the creation of an “intelligent system” supporting the efficient management of patient's data. In this paper we present the main architectural and functional characteristics of such a system. We also highlight how the security features offered by smart cards can be exploited in order to ensure confidentiality and integrity of the medical data stored in the patient cards.
TL;DR: The results of the study demonstrate that in communities where tourism plays an important role olive tree cultivation is preserved and the population is stable, and the preservation of the agro-ecosystem is assured while the olive groves remain productive.
Abstract: The objective of this study was to investigate the impact of tourism activities on olive tree cultivation and the human population of the island of Lesbos. The presence or absence of tourism is related with the maintenance or abandonment of olive tree cultivation and population changes for each community. A spatial segregation of the island is evident, related to tourist development, olive tree cultivation, and population change. The results of the study demonstrate that in communities where tourism plays an important role olive tree cultivation is preserved and the population is stable. The preservation of the agro-ecosystem is assured while the olive groves remain productive. Simultaneously, the landscape, which provides specific attractions for tourism, is not altered.
TL;DR: The results show that the reactions are faster in fortified drinking water samples than in ultrapure water solutions, and they are also favored at higher temperature, especially when sodium thiosulfate is present.
TL;DR: Troumbis et al. as discussed by the authors examined the effect of a dominant perennial grass species on the overall diversity and productivity in a mixed Mediterranean grassland, and found that the dominant grass can produce a constant productivity response across the diversity gradient.
Abstract: Troumbis, A. Y., Dimitrakopoulos, P. G., Siamantziouras, A.-S. D. and Memtsas,D. 2000. Hidden diversity and productivity patterns in mixed Mediterranean grass-lands. – Oikos 91: 549–559.A detailed study of the variation in productivity across a diversity gradient in anexperimental Mediterranean grassland examines the effects of a dominant perennialgrass species upon the overall diversity–productivity relationship. The experimenttook place at the Greek site of the European-wide BIODEPTH programme. Theexperimental design is characterized by the use of a number of communities contain-ing annuals and perennials within the total set of manipulated plots. The main resultsare: 1) a log-linear relationship between diversity and productivity exists in Mediter-ranean grasslands synthesized by annuals only, 2) in mixed communities wheremultiple growth forms coexist, the performance of a dominant or keystone speciesmay reverse or hide the diversity–productivity pattern of a functional or growth formgroup of species taken separately, and 3) the introduction of the dominant grass inthe low-diversity mixtures creates an ‘inverted’ sampling effect which can produce asan artefact a constant productivity response across the diversity gradient.
TL;DR: The existence of conserved currents in completely integrable classical models, including chiral and Toda models as well as the KP and self-dual Yang-Mills equations, is traced back to a simple construction of an infinite chain of closed (respectively, covariantly constant) 1-forms in a (gauged) bi-differential calculus as discussed by the authors.
Abstract: The existence of an infinite set of conserved currents in completely integrable classical models, including chiral and Toda models as well as the KP and self-dual Yang-Mills equations, is traced back to a simple construction of an infinite chain of closed (respectively, covariantly constant) 1-forms in a (gauged) bi-differential calculus. The latter consists of a differential algebra on which two differential maps act. In a gauged bi-differential calculus these maps are extended to flat covariant derivatives.
TL;DR: The field observational evidence on the diversity-biomass production relationship from eastern Mediterranean shrublands dominated by Cistus salviifolius suggests that there is strong differentiation along the structural niche axis, and thus functional redundancy is weak.
Abstract: This paper reports field observational evidence on the diversity-biomass production relationship from eastern Mediterranean shrublands dominated by Cistus salviifolius. The main results are: (1) plant diversity and ecosystem primary production are positively correlated in the Cistus shrublands, which are multigrowth form systems; (2) the taxonomic and growth form diversity in Cistus shrublands suggests that there is strong differentiation along the structural niche axis, and thus functional redundancy is weak; (3) the performance of the dominant Cistus in terms of biomass production did not affect the overall diversity-biomass production of the studied communities.
TL;DR: In this article, a deformation quantized version (ncKdV) of the KdV equation has been constructed, which possesses an infinite set of conserved densities via a kind of Seiberg-Witten map.
TL;DR: An investigation into the occurrence of volatile organic compounds (VOCs) in the surface waters of Northern Greece was conducted for a period of two years and the most commonly encountered VOCs were chloroform, carbon tetrachloride, trichloroethylene, dichlorobromomethane, and chlorodibromometHane.
TL;DR: Two stochastic approaches for solving the buffer allocation problem in large reliable production lines using simulated annealing and genetic algorithms are presented.
Abstract: The allocation of buffers between workstations is a major optimization problem faced by manufacturing systems designers. It entails the determination of optimal buffer allocation plans in production lines with the objective of maximizing their throughput. We present and compare two stochastic approaches for solving the buffer allocation problem in large reliable production lines. The allocation plan is calculated subject to a given amount of total buffer slots using simulated annealing and genetic algorithms. The throughput is calculated utilizing a decomposition method.
TL;DR: The purpose was the development of a final map illustrating the spatial distribution of eutrophication in the study area, based on the integration of unsupervised and supervised classification methods widely used in the field of remote sensing.
01 Jan 2000
TL;DR: The concept of carrying capacity as a planning tool is investigated in a systematic and comprehensive manner, by analysing its major dimensions as mentioned in this paper, to increase our understanding of this important and intrinsically too extensive and complex multifaceted concept, to discuss its applicability in the studies of the growing tourist industry and demonstrate how composite perspectives of the concept can provide valuable insights into some phenomena of interest.
Abstract: The relationship of tourism and the main components of the man-nature system are subject to much discussion but relatively little investigation. This chapter is based on the hypothesis that tourism generates environmental externalities and is often affected by them. When the negative effects of such externalities exceed certain levels of disturbance of the environment, significant and irreversible changes occur which alter the basic processes and characteristics of the environment. The carrying capacity (C.C.) concept has often been used to identify the limits of a system to absorb changes. The concept of carrying capacity as a planning tool is investigated in a systematic and comprehensive manner, by analysing its major dimensions. The aim of this analysis is to increase our understanding of this important and intrinsically too extensive and complex multifaceted concept, to discuss its applicability in the studies of the growing tourist industry and demonstrate how composite perspectives of the concept can provide valuable insights into some phenomena of interest to academic observers and researchers in allied disciplines such as resource management, planning, economics, sociology, anthropology, geography, business administration, as well as to those involved in the development and management of the tourist industry at various levels. There is in addition a new opportunity for detailed consideration of the resource base tourism in a period where the industry shows many signs of approaching a point of crisis caused by considerable weaknesses in understanding the relationship of increasing pressure — demand to natural, cultural and heritage resources (Parpairis, 1992).
TL;DR: In this paper, a methodological framework with models is provided, which correlates behavioral and perceptual issues related to the use of intermodal transportation with the commonly used physical and economic criteria in modal choice approaches.
Abstract: A methodological framework with models is provided, which correlates behavioral and perceptual issues related to the use of intermodal transportation with the commonly used physical and economic criteria in modal choice approaches. With factor analysis, key variables and common decision patterns related to the choice of intermodal transportation are identified. Factor analysis is applied to capture the actors' perception of the importance of variables affecting the decision-making process. With multiple regression analysis, models simulating the decision-making process are developed for actor groups, utilizing actual quantitative data of cost and performance of intermodal transportation services. Three decision patterns and the respective actor groups' profiles are identified. The first group consists of actors who decide almost exclusively according to the cost criterion; these actors are intensive users of intermodal transportation. The second group has actors who decide according to both quality and co...
TL;DR: In this paper, a numerical mesoscale model is used to study the wind field and the boundary layer structure of the island of Sardinia during typical summer conditions using a higher-order turbulence closure scheme.
Abstract: A numerical mesoscale model is used to study the wind field and the boundary layer structure of the island of Sardinia during typical summer conditions The numerical model is three-dimensional and employs a higherorder turbulence closure scheme The model simulations were performed for summer conditions characterized by weak synoptic forcing from the northwest and clear skies These conditions favor the development of thermal circulations, the most significant of which are the sea-breeze systems The nighttime wind patterns generally are dominated by topography, which leads to the development of strong drainage flow On the other hand, as revealed in the simulated wind field, at midday the wind has an onshore component at virtually every coastline The well-organized sea-breeze systems interact to produce convergence zones Another interesting feature is the development of a cyclonic eddy pattern during late-afternoon hours The model results are compared with observations taken at a network of near-surface wind stations and rawinsonde profiles from the Cagliari airport Available observations agreed relatively well with model predictions
01 Jan 2000
TL;DR: In this article, an integrated framework for the analysis and evaluation of the environmental impacts of tourism is proposed, which is based on the integrated modelling framework proposed in the first edition of this volume.
Abstract: Tourism grew rapidly during the 1960s and 1970s, but it was soon realised that this growth was not without costs. The social, cultural, economic, and environmental impacts of tourist growth became subjects of serious study and research, and entered in the policy agendas of national and international organisations. Tourism is no longer considered a ‘clean industry’ as opposed, say, to heavy manufacturing. Tourism planning is advocated as a tool for controlling the negative impacts of tourism development and for protecting the very same resources upon which the profitability of the industry depends. However, many tourism development studies and plans as well proposed policies have not been (and still are not) based on rigorous quantitative and integrated analyses of the several dimensions of tourism, neither have they placed the impacts of tourism development within the broader spatio-temporal context of their occurrence. There are many reasons for this omission, the analytical complexity of the task and the lack of proper data being among the most important of them. This chapter focuses on the environmental impacts of tourism and proposes an integrated framework for their analysis and evaluation. It is a revised version of the original chapter which appeared seven years ago in the first edition of this volume. It keeps the essential methodological orientation and gist but attempts to refine the integrated modelling framework, which was proposed originally. Moreover, it addresses explicitly the question of sustainability, which, in the meantime, became a central concern in all discussions about tourism development. The first section of the chapter reviews briefly the literature on tourism and its environmental impacts and identifies the main methodological issues in their analysis. The second section details the proposed methodological framework while the last section discusses its advantages and drawbacks.
TL;DR: In this article, the authors associate bicomplexes with several integrable models in such a way that conserved currents are obtained by a simple iterative construction, and several examples are presented, including the nonlinear Schrodinger and sine-Gordon equations.
Abstract: We associate bicomplexes with several integrable models in such a way that conserved currents are obtained by a simple iterative construction. Gauge transformations and dressings are discussed in this framework and several examples are presented, including the nonlinear Schrodinger and sine-Gordon equations, and some discrete models.
TL;DR: In this paper, a relation between bicomplexes and integrable models is discussed, and corresponding non-commutative (Moyal) deformations are considered, as well as a non-computative version of a Toda field theory.
Abstract: We discuss a relation between bicomplexes and integrable models, and consider corresponding noncommutative (Moyal) deformations. As an example, a noncommutative version of a Toda field theory is presented.