Showing papers by "University of the Aegean published in 2009"

A survey of modern authorship attribution methods

Abstract: Authorship attribution supported by statistical or computational methods has a long history starting from the 19th century and is marked by the seminal study of Mosteller and Wallace (1964) on the authorship of the disputed “Federalist Papers.” During the last decade, this scientific field has been developed substantially, taking advantage of research advances in areas such as machine learning, information retrieval, and natural language processing. The plethora of available electronic texts (e.g., e-mail messages, online forum messages, blogs, source code, etc.) indicates a wide variety of applications of this technology, provided it is able to handle short and noisy text from multiple candidate authors. In this article, a survey of recent advances of the automated approaches to attributing authorship is presented, examining their characteristics for both text representation and text classification. The focus of this survey is on computational requirements and settings rather than on linguistic or literary issues. We also discuss evaluation methodologies and criteria for authorship attribution studies and list open questions that will attract future work in this area. © 2009 Wiley Periodicals, Inc.

How does climate warming affect plant‐pollinator interactions?

Abstract: Climate warming affects the phenology, local abundance and large-scale distribution of plants and pollinators. Despite this, there is still limited knowledge of how elevated temperatures affect plant-pollinator mutualisms and how changed availability of mutualistic partners influences the persistence of interacting species. Here we review the evidence of climate warming effects on plants and pollinators and discuss how their interactions may be affected by increased temperatures. The onset of flowering in plants and first appearance dates of pollinators in several cases appear to advance linearly in response to recent temperature increases. Phenological responses to climate warming may therefore occur at parallel magnitudes in plants and pollinators, although considerable variation in responses across species should be expected. Despite the overall similarities in responses, a few studies have shown that climate warming may generate temporal mismatches among the mutualistic partners. Mismatches in pollination interactions are still rarely explored and their demographic consequences are largely unknown. Studies on multi-species plant-pollinator assemblages indicate that the overall structure of pollination networks probably are robust against perturbations caused by climate warming. We suggest potential ways of studying warming-caused mismatches and their consequences for plant-pollinator interactions, and highlight the strengths and limitations of such approaches.

A survey on jamming attacks and countermeasures in WSNs

Abstract: Jamming represents the most serious security threat in the field of wireless sensor networks (WSNs), as it can easily put out of order even WSNs that utilize strong highlayer security mechanisms, simply because it is often ignored in the initial WSN design. The objective of this article is to provide a general overview of the critical issue of jamming in WSNs and cover all the relevant work, providing the interested researcher pointers for open research issues in this field. We provide a brief overview of the communication protocols typically used in WSN deployments and highlight the characteristics of contemporary WSNs, that make them susceptible to jamming attacks, along with the various types of jamming which can be exercised against WSNs. Common jamming techniques and an overview of various types of jammers are reviewed and typical countermeasures against jamming are also analyzed. The key ideas of existing security mechanisms against jamming attacks in WSNs are presented and open research issues, with respect to the defense against jamming attacks are highlighted.

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales

Abstract: In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.

Overview of Advanced Computer Vision Systems for Skin Lesions Characterization

Abstract: During the last years, computer-vision-based diagnosis systems have been used in several hospitals and dermatology clinics, aiming mostly at the early detection of skin cancer, and more specifically, the recognition of malignant melanoma tumour. In this paper, we review the state of the art in such systems by first presenting the installation, the visual features used for skin lesion classification, and the methods for defining them. Then, we describe how to extract these features through digital image processing methods, i.e., segmentation, border detection, and color and texture processing, and we present the most prominent techniques for skin lesion classification. The paper reports the statistics and the results of the most important implementations that exist in the literature, while it compares the performance of several classifiers on the specific skin lesion diagnostic problem and discusses the corresponding findings.

Integrated analysis of risks of coastal flooding and cliff erosion under scenarios of long term change

Abstract: The risks to human populations in coastal areas are changing due to climate and socio-economic changes, and these trends are predicted to accelerate during the twenty-first century. To understand these changing risks, and the resulting choices and pathways to successful management and adaptation, broad-scale integrated assessment is essential. Due to their complexity the two risks of flooding and erosion are usually managed independently, yet frequently they are interconnected by longshore exchange of sediments and the resulting broad scale morphological system behaviour. In order to generate new insights into the effects of climate change and coastal management practises on coastal erosion and flood risk, we present an integrated assessment of 72 km of shoreline over the twenty-first century on the East Anglian coast of England which is a site of significant controversy about how to manage coastal flood and erosion risks over the twenty-first century. A coupled system of hydrodynamic, morphological, reliability and socio-economic models has been developed for the analysis, implemented under scenarios of coastal management, climate and socio-economic change. The study is unique in coastal management terms because of the large spatial scale and extended temporal scale over which the analysis is quantified. This study for the first time quantifies what has for some years been argued qualitatively: the role of sediments released from cliff erosion in protecting neighbouring low-lying land from flooding. The losses and benefits are expressed using the common currency of economic risk. The analysis demonstrates that over the twenty-first century, flood risk in the study area is expected to be an order of magnitude greater than erosion risk. Climate and socio-economic change and coastal management policy have a significant influence on flood risk. This study demonstrates that the choices concerning coastal management are profound, and there are clear tradeoffs between erosion and flood impacts.

Measurement of D ± and D 0 production in deep inelastic scattering using a lifetime tag at HERA

Abstract: The production of D-+/-- and D-0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb(-1). The measurements cover the kinematic range 5 < Q(2) < 1000 GeV2, 0.02 < y < 0.7, 1.5 < p(T)(D) < 15 GeV and |eta(D)| < 1.6. Combinatorial background to the D-meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD, which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, F-2(c (c) over bar), to the proton structure function, F-2.

Invasive plant integration into native plant–pollinator networks across Europe

Abstract: The structure of plant–pollinator networks has been claimed to be resilient to changes in species composition due to the weak degree of dependence among mutualistic partners. However, detailed empirical investigations of the consequences of introducing an alien plant species into mutualistic networks are lacking. We present the first cross-European analysis by using a standardized protocol to assess the degree to which a particular alien plant species (i.e. Carpobrotus affine acinaciformis , Impatiens glandulifera , Opuntia stricta , Rhododendron ponticum and Solanum elaeagnifolium ) becomes integrated into existing native plant–pollinator networks, and how this translates to changes in network structure. Alien species were visited by almost half of the pollinator species present, accounting on average for 42 per cent of the visits and 24 per cent of the network interactions. Furthermore, in general, pollinators depended upon alien plants more than on native plants. However, despite the fact that invaded communities received more visits than uninvaded communities, the dominant role of alien species over natives did not translate into overall changes in network connectance, plant linkage level and nestedness. Our results imply that although supergeneralist alien plants can play a central role in the networks, the structure of the networks appears to be very permeable and robust to the introduction of invasive alien species into the network.

Human factors and qualitative pedagogical evaluation of a mobile augmented reality system for science education used by learners with physical disabilities

Abstract: Technology-enhanced learning, employing novel forms of content representation and education service delivery by enhancing the visual perception of the real environment of the user, is favoured by proponents of educational inclusion for learners with physical disabilities. Such an augmented reality computer-mediated learning system has been developed as part of an EU funded research project, namely the CONNECT project. The CONNECT project brings together schools and science centres, and produces novel information and communication technologies based on augmented reality (AR) and web-based streaming and communication, in order to support learning in a variety of settings. The CONNECT AR interactive learning environment can assist users to better contextualize and reinforce their learning in school and in other settings where people learn (i.e. science centres and home). The CONNECT concept and associated technologies encourage users to visit science centres and perform experiments that are not possible in school. They can also build on these experiences back at school and at home with visual augmentations that they are communicated through web-based streaming technology. This paper particularly focuses on a user-centred evaluation approach of human factors and pedagogical aspects of the CONNECT system, as applied to a special needs user group. The main focus of the paper is on highlighting the human factors issues and challenges, in terms of wearability and technology acceptance, while elaborating on some qualitative aspects of the pedagogical effectiveness of the instructional medium that AR technology offers for this group of learners.

An innovative mobile electronic tourist guide application

Abstract: "Mobile tourism" represents a relatively new trend in the field of tourism and involves the use of mobile devices as electronic tourist guides. While much of the underlying technology is already available, there are still open challenges with respect to design, usability, portability, functionality and implementation aspects. Most existing "mobile tourism" solutions either represent of-the-shelf applications with rigidly defined content or involve portable devices with networking capabilities that access tourist content with the requirement of constant airtime, i.e., continuous wireless network coverage. This paper presents the design and implementation issues of a "mobile tourism" research prototype, which brings together the main assets of the two aforementioned approaches. Namely, it enables the creation of portable tourist applications with rich content that matches user preferences. The users may download these personalized applications (optimized for their specific device's model) either directly to their mobile device or first to a PC and then to a mobile terminal (through infrared or bluetooth). Thereafter, network coverage is not further required as the applications execute in standalone mode and may be updated when the user returns online. The dynamically created tourist applications also incorporate a "push model", wherein new tourist content is forwarded to the mobile terminal with minimal user intervention as soon as it is added or updated by the administrator. Our prototype has been developed on the top of Java 2 Micro Edition (J2ME) which offers an ideal platform for the development of full-fledged, interactive and portable applications tailored for resource-constrained mobile devices. The paper presents our development experiences with J2ME and highlights its main advantages and shortcomings in relation to the implementation of such kind of applications. Finally, an empirical evaluation of user experience with the mobile application prototype is presented.

Service quality effect on satisfaction and word of mouth in the health care industry

Abstract: Purpose – This paper aims to study the effect of service quality (SQ) dimensions on satisfaction and word of mouth (WOM) for maternities in Greece.Design/methodology/approach – Based on Parasuraman et al.'s SERVQUAL variables, the authors tried to identify the effects of each variable to satisfaction and WOM. Data were collected through field research among 1,000 mothers who have given birth to a child during the last five years, and the data were analysed using SEM.Findings – The results suggest that, in addition to “satisfaction”, the only service quality dimension that directly affects WOM, is “empathy”. In addition, “empathy” affects “responsiveness”, “assurance” and “tangibles” which in turn have only an indirect effect to WOM through “satisfaction”.Research limitations/implications – Limitations relate to the use of a non‐probability sample and the restricted geographical area of the field research. This study contributes to the body of academic knowledge by shedding more light into the role of SQ d...

Firm‐specific and economy wide determinants of firm profitability: Greek evidence using panel data

Abstract: Purpose – The purpose of this paper is to examine the determinants of profitability for a sample of Greek non‐financial firms listed in the Athens Stock Exchange for the period 1995‐2003. This is a very important period for the Greek economy on the way to European monetary union (EMU).Design/methodology/approach – The methodologies employed include panel data estimation techniques. This research attempts to exploit the determinants of firm profitability of non‐financial Greek firms listed in Athens Exchange utilizing firm‐specific publicly available accounting variables using panel data estimation techniques rather than cross‐sectional analysis.Findings – According to the findings, firm profitability was positively affected by size, sales growth and investment and negatively by leverage and current assets. Additionally, we found that the EMU participation and the adoption of the euro were negatively related to firm profitability.Practical implications – Taking into account the fact that the Greek economy ...

An intelligent system for automated breast cancer diagnosis and prognosis using SVM based classifiers

Abstract: In recent years, computational diagnostic tools and artificial intelligence techniques provide automated procedures for objective judgments by making use of quantitative measures and machine learning techniques. In this paper we propose a Support Vector Machines (SVMs) based classifier in comparison with Bayesian classifiers and Artificial Neural Networks for the prognosis and diagnosis of breast cancer disease. The paper provides the implementation details along with the corresponding results for all the assessed classifiers. Several comparative studies have been carried out concerning both the prognosis and diagnosis problem demonstrating the superiority of the proposed SVM algorithm in terms of sensitivity, specificity and accuracy.

Intrinsic Plagiarism Detection Using Character n-gram Profiles

Abstract: The task of intrinsic plagiarism detection deals with cases where no reference corpus is available and it is exclusively based on stylistic changes or inconsistencies within a given document. In this paper a new method is presented that attempts to quantify the style variation within a document using character n-gram profiles and a style change function based on an appropriate dissimilarity measure originally proposed for author identification. In addition, we propose a set of heuristic rules that attempt to detect plagiarism-free documents and plagiarized passages, as well as to reduce the effect of irrelevant style changes within a document. The proposed approach is evaluated on the recently-available corpus of the 1 st Int.

Energy efficiency in wireless sensor networks using sleep mode TDMA scheduling

Abstract: Power saving is a very critical issue in energy-constrained wireless sensor networks. Many schemes can be found in the literature, which have significant contributions in energy conservation. However, these schemes do not concentrate on reducing the end-to-end packet delay while at the same time retaining the energy-saving capability. Since a long delay can be harmful for either large or small wireless sensor networks, this paper proposes a TDMA-based scheduling scheme that balances energy-saving and end-to-end delay. This balance is achieved by an appropriate scheduling of the wakeup intervals, to allow data packets to be delayed by only one sleep interval for the end-to-end transmission from the sensors to the gateway. The proposed scheme achieves the reduction of the end-to-end delay caused by the sleep mode operation while at the same time it maximizes the energy savings.

Development of an evaluation methodology for triple bottom line reports using international standards on reporting.

Abstract: The purpose of this article is twofold. First, evaluation scoring systems for triple bottom line (TBL) reports to date are examined and potential methodological weaknesses and problems are highlighted. In this context, a new assessment methodology is presented based explicitly on the most widely acknowledged standard on non-financial reporting worldwide, the Global Reporting Initiative (GRI) guidelines. The set of GRI topics and performance indicators was converted into scoring criteria while the generic scoring devise was set from 0 to 4 points. Secondly, the proposed benchmark tool was applied to the TBL reports published by Greek companies. Results reveal major gaps in reporting practices, stressing the need for the further development of internal systems and processes in order to collect essential non-financial performance data. A critical overview of the structure and rationale of the evaluation tool in conjunction with the Greek case study is discussed while recommendations for future research on the field of this relatively new form of reporting are suggested.

Handoff prioritization and decision schemes in wireless cellular networks: a survey

Abstract: Handoff is a key element in wireless cellular networks in order to provide quality of service (QoS) to the users and to support users' mobility. Handoff failure will result in the forced termination of an ongoing call. From the user's point of view, the service of a handoff request is more important, as the forced termination of an ongoing call is more annoying than the blocking of new calls. Therefore, in order to support QoS to the users and to provide ubiquitous coverage, the handoff procedure ought to be further investigated. This paper provides a comprehensive survey of the basic elements, the different types and phases of the handoff procedure. Moreover, particular interest has been given in the horizontal handoff execution phase by discussing and classifying the most recent handoff prioritization schemes into categories based on the concepts that these schemes adopt, e.g. channel reservation, handoff queueing, channel transferred, subrating, genetic and hybrid schemes and in the vertical handoff decision phase by presenting different decision algorithms.

Teachers' Burnout, Depression, Role Ambiguity and Conflict.

Abstract: The present study investigates issues associated with teachers’ burnout in primary education as related to depression and role conflict–ambiguity. At the time of the study the participants (562 teachers) were working in seventy nine (79) Primary Education State Schools in Greece (Athens and two prefectures in the southern part of the country). The results showed that of the three factors comprising the Burnout inventory (MBI, Maslach and Jackson, MBI: Maslach Burnout Inventory; manual research edition, 1986), (i.e., Emotional exhaustion, Personal accomplishment, Depersonalization) Emotional Exhaustion showed a statistically significant (positive) correlation with the factors that comprise: (a) the Scale of Depression (CES-D: Ensel, in: Lin et al. (eds.) Social support, life events and depression, 1986; Radloff, Applied Psychological Measurement 1: 385–401, 1977) such as Depressed affect, Somatic retarded activity and (b) Degree of Role Conflict (Role Conflict and Role Ambiguity Scale, Rizzo et al., Administrative Science Quarterly, 15:150–163, 1970, adapted in Greek by Koustelios and Kousteliou, Psychological Reports, 82:131–136, 1998); similarly, Positive affect (CES-D) and Degree of Role Clarity (Role Conflict and Role Ambiguity Scale) showed a statistically significant (negative) correlation with the same factor (Emotional exhaustion). Furthermore, a regression analysis performed with Personal accomplishment as the dependent variable showed that the (combined) factors of Role Ambiguity, Positive Affect and Somatic Retarded Activity contributed significantly to the prediction of the dependent variable; A third regression analysis performed with Depersonalization as dependent variable showed that Somatic Retarded Activity, Role Conflict, Positive Affect, Interpersonal Affect and Role Ambiguity contributed significantly to the prediction of this variable. Overall, the results showed that Greek teachers experience low-moderate levels of Burnout, Depression, Role conflict and Role ambiguity.

Sudden expansion of a single brown bear maternal lineage across northern continental Eurasia after the last ice age: a general demographic model for mammals?

Abstract: The brown bear has proved a useful model for studying Late Quaternary mammalian phylogeography. However, information is lacking from northern continental Eurasia, which constitutes a large part of the species' current distribution. We analysed mitochondrial DNA sequences (totalling 1943 bp) from 205 bears from northeast Europe and Russia in order to characterize the maternal phylogeography of bears in this region. We also estimated the formation times of the sampled brown bear lineages and those of its extinct relative, the cave bear. Four closely related haplogroups belonging to a single mitochondrial subclade were identified in northern continental Eurasia. Several haplotypes were found throughout the whole study area, while one haplogroup was restricted to Kamchatka. The haplotype network, estimated divergence times and various statistical tests indicated that bears in northern continental Eurasia recently underwent a sudden expansion, preceded by a severe bottleneck. This brown bear population was therefore most likely founded by a small number of bears that were restricted to a single refuge area during the last glacial maximum. This pattern has been described previously for other mammal species and as such may represent one general model for the phylogeography of Eurasian mammals. Bayesian divergence time estimates are presented for different brown and cave bear clades. Moreover, our results demonstrate the extent of substitution rate variation occurring throughout the phylogenetic tree, highlighting the need for appropriate calibration when estimating divergence times.

E-service quality and Web 2.0: expanding quality models to include customer participation and inter-customer support

Abstract: Web 2.0 empowers online customers and social networks to engage in e-service processes such as service design, production and marketing. Although the impact of customer participation and inter-customer support on service quality is recognised, e-service quality conceptualisations and measurement models have failed to incorporate the impact of Web 2.0 on e-service delivery. After examining the role of Web 2.0 on customer participation and the gaps of previously developed e-service quality models, an extended e-service quality model is proposed that considers customer participation and inter-customer support in e-service settings. The theoretical and practical implications of the proposed model for website design and management are discussed.

An Experimental Study of the Effects of Improvisation on the Development of Children's Creative Thinking in Music.

Abstract: This article reports a quasi-experimental study of the effects of improvisation on the development of children's creative thinking in music. The study was conducted in a primary school classroom with two matched groups of 6-year-old children over a period of six months. The music lessons for the experimental group were enriched with a variety of improvisatory activities, while those in the control group did not include any improvisation, but instead were didactic and teacher-centred. Children in the experimental group were offered several opportunities to experience improvisation through their voices, their bodies, and musical instruments. Webster's Measure of Creative Thinking in Music - MCTM II (Webster, 1987, 1994) was administered before and after the six-month teaching programmes (i.e., pre-test and post-test) to assess children's creative thinking in terms of four musical parameters: extensiveness, flexibility, originality, and syntax. Analysis revealed that improvisation affects significantly the development of creative thinking; in particular, it promotes musical flexibility, originality, and syntax in children's music-making.

Eutrophication assessment of coastal waters based on indicators: a literature review.

Abstract: Numerous methods have been developed for the quantitative assessment of eutrophication: statistical techniques, simulation models and water quality indicators are the most widely used techniques to assess trophic levels. All these methods share a common goal: to evaluate the environmental impact due to high nutrient concentrations / phytoplankton biomass and classify the waters into oligotrophic, mesotrophic and eutrophic water types. This classification provides a useful tool for assessing environmental quality and help coastal managers and planners in the decision making. In the present work the indicators used for eutrophication assessment are reviewed. They provide useful information because voluminous amounts of data can be expressed through a single number. Variable indices such as chlorophyll and nutrient concentrations, phytoplankton biomass and water transparency are examined and ranges defining levels of eutrophication are proposed. Among the flux measurements, primary productivity has also been considered as an indicator useful in assessing trophic levels and a productivity scaling is also given. Community indices and their application in eutrophication studies are overviewed and their effectiveness in describing eutrophic trends is evaluated; their assumptions, advantages and shortcomings are also discussed. Among the twelve community indices evaluated for assessing eutrophication, only four were found to respond to eutrophic conditions; in nutrient and phytoplankton variables used as indicators, their frequency distribution showed overlapping between water types; this seems to be a problem in defining boundary values discriminating trophic levels. As the indices express ecosystem status and conditions, if they are going to be used under the Water Framework Directive, special consideration is needed since different scales seem to apply at regional level rather than forming a universal tool applicable to all European coastal waters.

Consumers' Environmental Concerns and Behaviors in the Lodging Industry: A Comparison between Greece and the United States

Abstract: This study utilizes data collected from Greece and the United States to examine consumer attitudes and behavior intentions toward the environmentally responsible practices (ERP) of hotels. Specifically examined is the impact of ERP on consumers' willingness to pay (WTP) for such hotel practices. The results indicate that consumers in both countries were more likely to patronize and demonstrate a strong WTP for hotels that provide ERP. Furthermore, the results reveal that consumers in Greece have higher environmental concerns and WTP than those in the United States, confirming that differences in culture and social structure determine a consumer's Green orientation and WTP.