Showing papers by "University of the Aegean published in 2003"
TL;DR: In this paper, a bivariate Poisson model and its extensions are proposed to model the number of goals of two competing teams in a football game, which is a plausible assumption in sports with two opposing teams competing against each other.
Abstract: Summary. Models based on the bivariate Poisson distribution are used for modelling sports data. Independent Poisson distributions are usually adopted to model the number of goals of two competing teams. We replace the independence assumption by considering a bivariate Poisson model and its extensions. The models proposed allow for correlation between the two scores, which is a plausible assumption in sports with two opposing teams competing against each other. The effect of introducing even slight correlation is discussed. Using just a bivariate Poisson distribution can improve model fit and prediction of the number of draws in football games. The model is extended by considering an inflation factor for diagonal terms in the bivariate joint distribution. This inflation improves in precision the estimation of draws and, at the same time, allows for overdispersed, relative to the simple Poisson distribution, marginal distributions. The properties of the models proposed as well as interpretation and estimation procedures are provided. An illustration of the models is presented by using data sets from football and water-polo.
412 citations
TL;DR: An applicable group decision-making framework for assisting with multi-criteria analysis in renewable energy projects, utilizing the PROMETHEE II outranking method is described, providing a user-friendly approach, promotes the synergy between different actors, and could pave a way towards consensus.
357 citations
TL;DR: Olive tree cultivation in the Mediterranean goes back to ancient times as mentioned in this paper, and even since the Roman Age, olive cultivation spreadto the entire Mediterranean basin and determined its rural landscape.
Abstract: Olive tree cultivation in theMediterranean goes back to ancient times. Evensince the Roman Age, olive cultivation spreadto the entire Mediterranean basin. Thislongevous tree integrates and identifieseconomically, socially, and culturally theinhabitants of this basin and determines itsrural landscape. For the residents of theMediterranean, olive oil constituted the mainsource of nutritional fats, their most valuableexport product, and was identified with theirculture. Even now, olive cultivation has amultiple importance for the Mediterranean. Theolive groves, which grow mostly on inclined,shallow, and low fertility soils, and onhand-made stone terraces, have limited wateringrequirements and sustain the fragile naturalresources of the Mediterranean. Today,olive cultivation in the Mediterranean is anadditional income source and supports thepopulation in rural areas during the winterperiod, which profit from summer and seatourism activity. Although anagro-ecosystem, the olive grove resembles thenatural Mediterranean ecosystem and abandonmenttransforms them into natural Mediterranean typeforests. Their change of use from olivecultivation to pasture degrades the ecosystemand decreases the natural resources, because ofover-grazing. At this time, two major factorsthreaten the traditional olive cultivation (i)the competition of the intensive olive grovesin plain and irrigated areas and (ii) thecheaper seed-oils, which intensify theabandonment of traditional olive groves andchange them into pasture, resulting in thedeterioration of the ecosystem. Olivecultivation has left its mark on life in theMediterranean and has contributed to thesustainability of natural resources.Nevertheless, it succumbs under the pressure ofcurrent socioeconomic situations. Today, theconservation of olives in productionconstitutes a necessity for the fragileMediterranean ecosystems and a challenge foreverybody involved.
324 citations
TL;DR: In this article, the authors define the threats that museum collections may suffer under inappropriate environmental conditions where they are housed and present a set of threats that a museum collection may experience under inappropriate conditions such as pollution, humidity, temperature and lighting.
222 citations
TL;DR: In this article, the relationship between the variability of the North Atlantic oscillation (NAO) indices and the normalized precipitation at 78 stations in Turkey, and the influences of the extreme NAO index and the year-to-year and longer time-scale variations in the NAO on precipitation conditions were investigated.
Abstract: Relationships between the variability of the North Atlantic oscillation (NAO) indices and the normalized precipitation at 78 stations in Turkey, and the influences of the extreme NAO index (NAOI) episodes and the year-to-year and longer time-scale variations in the NAO on the precipitation conditions were investigated The results of the study have led to the following main conclusions and evaluations for Turkey:
(i) There is a negative relationship between interannual variability of the Turkish precipitation series and the NAO indices Negative relationships that are particularly strong in winter and partly in autumn are detected to be weaker in spring and almost non-existent in summer Correlation coefficients are significant at 61 stations in winter, whereas they are significant at 23 and eight stations in autumn and spring respectively (ii) Composite precipitation means corresponding to the extreme NAOI phases mostly exhibit an apparent opposite anomaly pattern, except in summer, between the negative and positive NAOI phases (iii) Annual, winter, spring, autumn and partly the summer composite precipitation means are mostly characterized by wetter than the long-term average conditions during the negative NAOI phase, whereas the positive NAOI responses mostly exhibit drier than the long-term average conditions annually and in all seasons except summer (iv) Spatially coherent and statistically significant changes in the precipitation amounts during the extreme NAOI phases are more apparent in the west and mid Turkey (v) Low-frequency fluctuations in the circulation over the Atlantic have been closely linked to the coherent large-scale precipitation anomalies that have persisted, particularly in winter, over Turkey since the early 1960s (vi) There is a great resemblance between the spatial distribution and magnitude of the negative correlation coefficients and the spatial distribution patterns and severity of the wet (dry) conditions with negative (positive) NAOI phase, annually and in the winter and autumn seasons (vii) The coherent regions characterized with significant correlation coefficients coincide perfectly with the coherent regions characterized by the extreme NAOI signals These clear associations increase our confidence with the results Copyright © 2003 Royal Meteorological Society
210 citations
TL;DR: A GIS-based methodology is presented here with the goal to identify and rank the candidate landfill sites for the entire island of Lesvos, in which eight sites were finally selected and ranked.
167 citations
TL;DR: A survey undertaken in Northern Greece has shown that organochlorine pesticides are present in the surface waters, including the isomers of hexachlorocyclohexane, aldrin, dieldrin and endosulfan sulfate.
165 citations
TL;DR: This paper demonstrates that the security services offered by Public Key Infrastructure (PKI) can be employed for fulfilling most of the identified security requirements for an integrated e-government platform.
155 citations
TL;DR: It was shown that substrates with high initial lignin contents or high initial HWSM contents were observed to have relatively low and high degradation extents, respectively, and lign in was found to be less inhibitory to the overall substrate decomposition in aerobic environments compared to anaerobic ones.
142 citations
TL;DR: The results show that the science textbooks in comparison to the press material tend to create a sense of higher empowerment for their readers by using the visual mode, as the educational level of the school science textbooks rises, the content specialisation projected by the visual images and the elaboration and abstraction of the corresponding visual code also increases.
Abstract: This paper aims at presenting the application of a grid for the analysis of the pedagogic functions of visual images included in school science textbooks and daily press articles about science and technology. The analysis is made using the dimensions of content specialisation (classification) and social-pedagogic relationships (framing) promoted by the images as well as the elaboration and abstraction of the corresponding visual code (formality), thus combining pedagogical and socio- semiotic perspectives. The grid is applied to the analysis of 2819 visual images collected from school science textbooks and another 1630 visual images additionally collected from the press. The results show that the science textbooks in comparison to the press material: a) use ten times more images, b) use more images so as to familiarise their readers with the specialised techno-scientific content and codes, and c) tend to create a sense of higher empowerment for their readers by using the visual mode. Furthermore, as the educational level of the school science textbooks (i.e., from primary to lower secondary level) rises, the content specialisation projected by the visual images and the elaboration and abstraction of the corresponding visual code also increases. The above results have implications for the terms and conditions for the effective exploitation of visual material as the educational level rises as well as for the effective incorporation of visual images from press material into science classes.
141 citations
TL;DR: It was found that Pb, As and Ni have common sources, which could be vehicles emissions/oil combustion and resuspended road dust, and Cd and a portion of As originate from industrial activities.
01 Jan 2003
TL;DR: This chapter aims at exploring the fascinating world of MLS, identifying the most pertinent issues that will determine its future potential, and laying down the foundation of a new field of research and practice.
Abstract: The emerging world of mobile commerce is characterized by a multiplicity of exciting new technologies, applications, and services. Among the most promising ones will be the ability to identify the exact geographical location of a mobile user at any time. This ability opens the door to a new world of innovative services, which are commonly referred to as Mobile Location Services (MLS). This chapter aims at exploring the fascinating world of MLS, identifying the most pertinent issues that will determine its future potential, and laying down the foundation of a new field of research and practice. The contribution of our analysis is encapsulated into a novel classification of mobile location services that can serve both as an analytical toolkit and an actionable framework that systemizes our understanding of MLS applications, underlying technologies, business models, and pricing schemes.
TL;DR: An alternative framework, called “Object-oriented Collaboration Analysis Framework (OCAF)” is presented here, according to which the objects of the collaboratively developed solution become the center of attention and are studied as entities that carry their own history.
TL;DR: Activated sludge floc size and structure characterization showed that Cr(VI) concentrations higher than 1 mgl(-1) reduced the filaments abundance, causing the appearance of pin-point flocs and free-dispersed bacteria, indicating that heterotrophic microorganisms are less sensitive to Cr( VI) than nitrifiers.
TL;DR: Full Bayesian inference is described for generalised linear models where uncertainty exists about the structure of the linear predictor, the linear parameters and the link function and an efficient reversible jump Markov chain Monte-Carlo algorithm is proposed for calculating posterior summaries.
TL;DR: In this paper, the authors investigated the stability of random ecosystems and found that it can largely be predicted by simple matrix statistics such as the mean and the variance of the interaction coefficients.
Abstract: Since Robert May’s work on random community matrices it has been known that stability tends to decrease with complexity. Recently, it was shown that this is not necessarily true in competitive ecosystems. We investigated the stability of random ecosystems and found that it can largely be predicted by simple matrix statistics such as the mean and the variance of the interaction coefficients. We use this to explain why stability can increase as well as decrease with complexity in ecological communities. We argue that the variance, and to a lesser extent the mean, of the interaction coefficients go a long way in explaining patterns in the stability of ecosystems.
TL;DR: In this article, a search for single-top production via flavour changing neutral current transitions involving a neutral electroweak vector boson, γ or Z, was performed with the ZEUS detector at HERA using data corresponding to an integrated luminosity of 0.37 fb − 1.
TL;DR: In this article, the authors explored the potential suitability of the press as a teaching resource for raising scientific literacy for citizenship within science education and showed that the media can be used in the science classes in a complementary way to the conventional material already used so as to illuminate crucial aspects of science and technology in the public that seem to be missing from the official pedagogic discourse of science education.
Abstract: This paper aims to explore the potential suitability of the press as a teaching resource for raising scientific literacy for citizenship within science education. Our methodology is based on a content analysis of a sample of 1867 articles about science and technology from four Greek newspapers. The analysis showed that the press is potentially a useful tool for teaching certain aspects of science and technology for citizenship since it (a) provides a constant flow of relevant articles on a regular basis, (b) gives prominence to techno-scientific issues that prevail in the public arena (digital technologies, advances in biotechnology and genetic engineering, environmental degradation), (c) identifies the various social actors and forces (mainly coming from the world of politics and the business world) that impinge on the collective decision-making procedures about these issues, (d) portrays the kind of the social impacts of science and technology in an optimistic way, albeit tempered by considerable levels of concern, and (e) presents all the relevant news in context, thereby adding relevance and meaningfulness to the techno-scientific concepts under discussion. In addition to strong points, the press has also weak points as a teaching resource in science classes. These weaknesses are mostly related to the underpresentation of techno-scientific subject matter and the internal mechanisms that lead to the production of the corresponding knowledge. Consequently, press material can be used in the science classes in a complementary way to the conventional material already used so as to illuminate crucial aspects of science and technology in the public that seem to be missing from the official pedagogic discourse of science education. © 2003 Wiley Periodicals, Inc. Sci Ed87:241–256, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/sce.10054
TL;DR: In this paper, the authors present a method and models for assessing the financial viability of a new Freight village financed by private and public investments, which constitutes an integrated part of a wider planning methodology, with four distinct phases.
TL;DR: Batch experiments showed that Cr(III) cannot be oxidized to Cr( VI) by activated sludge and Cr(VI) reduction is possible and is affected mainly by the initial concentration of organic substrate, which acts as electron donor for Cr(vi) reduction.
01 Jan 2003
TL;DR: This paper examines goal modelling in terms of five methodological orientations and defines a framework for their analysis, which is evaluated in a systematic and consistent manner.
Abstract: In the field of Requirements Engineering, goal modelling approaches have received much attention in recent years by researchers and practitioners alike. In this paper we identify the uses of these approaches in different contexts of requirements analysis phases. We examine goal modelling in terms of five methodological orientations and define a framework for their analysis. Using this framework we evaluate goal modelling in a systematic and consistent manner and reflect on current investigations and open issues that provide a foundation for further research in this important area of Requirements Engineering methodology.
01 Jan 2003
TL;DR: The notion of pseudomonotone operators was introduced in this paper, where the Clarke subdifierential of a locally Lipschitz pseudoconvex function is shown to be D-maximal.
Abstract: £is called pseudomonotone (in Karamardian’s sense) if for all (x;x £ ) and (y;y £ ) in its graph, hx £ ;y † xi µ 0 implies hy £ ;y † xi µ 0. We deflne an equivalence relation on the set of pseudomonotone operators. Based on this relation, we deflne a notion of ’D-maximality‘ and show that the Clarke subdifierential of a locally Lipschitz pseudoconvex function is D-maximal pseudomonotone. We generalize some well-known results on upper semicontinuity and generic single-valuedness of monotone operators by showing that, under suitable assumptions, a pseudomonotone operator has an equivalent operator that is upper semicontinuous, generically single-valued etc.
TL;DR: In this article, the authors examined the willingness to pay of individuals to ensure the full operation of a wastewater treatment plant in Greece, leading to significant improvements in the water quality of Thermaikos Bay, which is adjacent to Thessaloniki.
Abstract: Greece has a large number of wastewater treatment plants (WWTP) under construction or recently completed. However, whilst the European Union provides funds for the capital development of WWTPs, there is often a lack of funding to maintain full operation of these plants. This study examines the case of a WWTP in Thessaloniki, Greece, which is currently only partially operational. We use the contingent valuation method to examine the willingness to pay of individuals to ensure the full operation of the WWTP, leading to significantimprovements in the water quality of Thermaikos Bay, which is adjacent to Thessaloniki. The average amount pledged of Euro 15.23 due every four months as an incremental increase in water rates matches the funding required to fully operate the plant. By examining the motivations of those willing to pay, we find that a complex combination of consumer and citizen modes of cognition, linked to self identity and pride in the city as well as moral and ethical concerns, determine individuals' commitment to the water quality improvement scheme. These findings have serious policy implications for gauging public support for environmental improvements.
TL;DR: An integrated database is proposed as a means for a more robust and universally accepted design procedure for secondary settling tank design and simulation by the use of an integrated and unified settling characteristics database.
TL;DR: It is argued that because M. citrina faces pollen limitation in the small islets of Columbretes, it presents an interesting case study of pollination related to island endemism and diversity.
Abstract: The reproductive ecology of Medicago
citrina was studied in the Columbretes archipelago (Mediterranean Sea), where bees are absent. The flowers were self-compatible, homogamous, nectar producers, depended on large floral visitors for tripping and pollination. Several characteristics of the reproductive biology of M.
citrina indicate an adaptation to an isolated environment characterised by scarcity of appropriate pollinators. As a result of this scarcity, fruit and seed set under natural conditions were significantly lower compared to hand-pollination treatments. The main flower visitors were mostly flies and blowflies, with Eristalis tenax (Syrphidae) and Calliphora
vicina (Calliphoridae) being the most efficient pollinators. We argue that because M. citrina faces pollen limitation in the small islets of Columbretes, it presents an interesting case study of pollination related to island endemism and diversity.
24 Apr 2003
TL;DR: A general decision support system architecture for the heart sound diagnosis problem, which can be combined using arbitration rules to give the final diagnosis of difficult to distinguish heart diseases.
Abstract: Decision trees algorithms were used with promising results in various critical problems, concerning heart sound diagnosis. In general this diagnostic problem can be divided in many sub problems, each one dealing either with one morphological characteristic of the heart sound or with difficult to distinguish heart diseases. The sub problems of the discrimination of aortic stenosis from mitral regurgitation and the discrimination between the second heart sound split, opening snap and third heart sound, are used as case studies. Using signal-processing methods, we extracted the heart sound feature vector. Relevance analysis was performed using the uncertainty coefficient. Then for each heart sound diagnosis sub problem, a specific decision tree (DT) was constructed. decision tree pruning was also investigated. Finally, a general decision support system architecture for the heart sound diagnosis problem, is proposed. The partial diagnosis, given by these DT, can be combined using arbitration rules to give the final diagnosis. These rules can be implemented by another DT, or can be based on different methods, algorithms, or even on expert knowledge. All these can lead to an integrated decision support system architecture for heart sound diagnosis.
TL;DR: The proposed methodology could be used as a design tool for those who are interested in landfill siting by utilizing dispersion models under extreme atmospheric conditions to determine the acceptable distance between new landfills and residential areas.
Abstract: The estimation of odor production and dispersion from landfill sites is a very complicated task because of the different chemical species that exist in biogas. To site a new landfill, it is necessary to know the distance that odors can travel around the landfill under atmospheric conditions that increase the concentration of pollutants. Although CH4 is an odorless gas, it can be used as an index to determine the dispersion of low-reactivity odorous species around a landfill site. Methane production rates, estimated by biogas production models, were used by an air dispersion model to determine the spatial distribution of CH4 around landfill sites. By utilizing dispersion models under extreme atmospheric conditions, a maximum CH4 concentration around the landfills was determined. Based on the ratio between CH4 and odorous chemical species, the spatial distribution of the concentration of an odorous species was determined for those species with low reactivity in the atmosphere. For odorous species w...
01 Jan 2003
TL;DR: The extent to which current voting protocols comply with the identified requirements is investigated and discussed to examine the feasibility of organising and conducting an Internet based election in a secure, efficient and reliable way.
Abstract: This paper presents the security requirements and the system wide properties that the voting protocol of an electronic voting system is expected to fulfil. Then, an overview of the existing voting protocols, together with a brief analysis of their characteristics, is provided. The aim is to investigate and discuss the extent to which current voting protocols comply with the identified requirements and thus examine the feasibility of organising and conducting an Internet based election in a secure, efficient and reliable way.
TL;DR: In this paper, the automorphisms of all four-dimensional, real Lie algebras are presented in a comprehensive way, and their action on the space of 4 × 4, real, symmetric and positive definite matrices defines equivalence classes which are used for the invariant characterization of the fourdimensional homogeneous spaces which possess an invariant basis.
Abstract: The automorphisms of all four-dimensional, real Lie algebras are presented in a comprehensive way. Their action on the space of 4 × 4, real, symmetric and positive definite matrices defines equivalence classes which are used for the invariant characterization of the four-dimensional homogeneous spaces which possess an invariant basis.
TL;DR: The results of the analyses have shown the presence of disinfection byproducts belonging to all categories studied in all water samples collected after prechlorination, the major categories of DBPs detected were THMs and HAAs, while the other volatile DBPs occurred at lower concentrations.
Abstract: Application of chlorination for the disinfection of drinking water results in the formation of a wide range of organic compounds, called disinfection by-products (DBPs), which occur due to the reaction of chlorine with natural organic materials. The occurrence of DBPs was studied in samples from four drinking-water treatment plants (WTPs) and from the distribution network of Athens, Greece. Twenty-four compounds, which belong to different categories of DBPs, were monitored, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HAKs), chloral hydrate (CH) and chloropicrin (CP). Sampling was performed monthly for a period of two years, from three different points at each WTP and from eight points at the distribution network. Samples were analyzed by GC-ECD methods, which included pretreatment with liquid-liquid extraction for volatile DBPs and acidic methanol esterification for HAAs. The results of the analyses have shown the presence of disinfection byproducts belonging to all categories studied in all water samples collected after prechlorination. The major categories of DBPs detected were THMs and HAAs, while the other volatile DBPs occurred at lower concentrations. The concentrations of DBPs did not in any case exceed the maximum contaminant levels (MCL) set by USEPA and WHO. However, monitoring these compounds needs to be continued, because their levels could increase due to changes in the quality of water entering the water treatment plants. Reduction of the concentrations of DBPs could be achieved by optimization of the chlorination conditions, taking into account the effect of time. Moreover, research on alternative disinfection methods (e.g. ozone, chlorine dioxide, chloramines) and their by-products should be conducted to evaluate their applicability in the case of the drinking water of Greece.