Showing papers by "University of the Aegean published in 2008"

Measuring bee diversity in different european habitats and biogeographical regions

Abstract: Bee pollinators are currently recorded with many different sampling methods. However, the relative performances of these methods have not been systematically evaluated and compared. In response to the strong need to record ongoing shifts in pollinator diversity and abundance, global and regional pollinator initiatives must adopt standardized sampling protocols when developing large-scale and long-term monitoring schemes. We systematically evaluated the performance of six sampling methods (observation plots, pan traps, standardized and variable transect walks, trap nests with reed internodes or paper tubes) that are commonly used across a wide range of geographical regions in Europe and in two habitat types (agricultural and seminatural). We focused on bees since they represent the most important pollinator group worldwide. Several characteristics of the methods were considered in order to evaluate their performance in assessing bee diversity: sample coverage, observed species richness, species richness estimators, collector biases (identified by subunit-based rarefaction curves), species composition of the samples, and the indication of overall bee species richness (estimated from combined total samples). The most efficient method in all geographical regions, in both the agricultural and seminatural habitats, was the pan trap method. It had the highest sample coverage, collected the highest number of species, showed negligible collector bias, detected similar species as the transect methods, and was the best indicator of overall bee species richness. The transect methods were also relatively efficient, but they had a significant collector bias. The observation plots showed poor performance. As trap nests are restricted to cavity-nesting bee species, they had a naturally low sample coverage. However, both trap nest types detected additional species that were not recorded by any of the other methods. For large-scale and long-term monitoring schemes with surveyors with different experience levels, we recommend pan traps as the most efficient, unbiased, and cost-effective method for sampling bee diversity. Trap nests with reed internodes could be used as a complementary sampling method to maximize the numbers of collected species. Transect walks are the principal method for detailed studies focusing on plant-pollinator associations. Moreover, they can be used in monitoring schemes after training the surveyors to standardize their collection skills.

License Plate Recognition From Still Images and Video Sequences: A Survey

Abstract: License plate recognition (LPR) algorithms in images or videos are generally composed of the following three processing steps: 1) extraction of a license plate region; 2) segmentation of the plate characters; and 3) recognition of each character This task is quite challenging due to the diversity of plate formats and the nonuniform outdoor illumination conditions during image acquisition Therefore, most approaches work only under restricted conditions such as fixed illumination, limited vehicle speed, designated routes, and stationary backgrounds Numerous techniques have been developed for LPR in still images or video sequences, and the purpose of this paper is to categorize and assess them Issues such as processing time, computational power, and recognition rate are also addressed, when available Finally, this paper offers to researchers a link to a public image database to define a common reference point for LPR algorithmic assessment

Long-term observation of a pollination network: fluctuation in species and interactions, relative invariance of network structure and implications for estimates of specialization.

Abstract: We analysed the dynamics of a plant-pollinator interaction network of a scrub community surveyed over four consecutive years. Species composition within the annual networks showed high temporal variation. Temporal dynamics were also evident in the topology of the network, as interactions among plants and pollinators did not remain constant through time. This change involved both the number and the identity of interacting partners. Strikingly, few species and interactions were consistently present in all four annual plant-pollinator networks (53% of the plant species, 21% of the pollinator species and 4.9% of the interactions). The high turnover in species-to-species interactions was mainly the effect of species turnover (c. 70% in pairwise comparisons among years), and less the effect of species flexibility to interact with new partners (c. 30%). We conclude that specialization in plant-pollinator interactions might be highly overestimated when measured over short periods of time. This is because many plant or pollinator species appear as specialists in 1 year, but tend to be generalists or to interact with different partner species when observed in other years. The high temporal plasticity in species composition and interaction identity coupled with the low variation in network structure properties (e.g. degree centralization, connectance, nestedness, average distance and network diameter) imply (i) that tight and specialized coevolution might not be as important as previously suggested and (ii) that plant-pollinator interaction networks might be less prone to detrimental effects of disturbance than previously thought. We suggest that this may be due to the opportunistic nature of plant and animal species regarding the available partner resources they depend upon at any particular time.

USE OF SELECTED ADVANCED OXIDATION PROCESSES (AOPs) FOR WASTEWATER TREATMENT - A MINI REVIEW

Abstract: Advanced oxidation processes (AOPs) are widely used for the removal of recalcitrant organic constituents from industrial and municipal wastewater. The aim of this study was to review the use of titanium dioxide/UV light process, hydrogen peroxide/UV light process and Fenton’s reactions in wastewater treatment. The main reactions and the operating parameters (initial concentration of the target compounds, amount of oxidation agents and catalysts, nature of the wastewater etc) affecting these processes are reported, while several recent applications to wastewater treatment are presented. The advantages and drawbacks of these methods are highlighted, while some of the future challenges (decrease of operational cost, adoption of strategies for processes integration) are discussed.

A New Global Coastal Database for Impact and Vulnerability Analysis to Sea-Level Rise

Abstract: A new global coastal database has been developed within the context of the DINAS-COAST project. The database covers the world's coasts, excluding Antarctica, and includes information on more than 80 physical, ecological, and socioeconomic parameters of the coastal zone. The database provides the base data for the Dynamic Interactive Vulnerability Assessment modelling tool that the DINAS-COAST project has produced. In order to comply with the requirements of the modelling tool, it is based on a data model in which all information is referenced to more than 12,000 linear coastal segments of variable length. For efficiency of data storage, six other geographic features (administrative units, countries, rivers, tidal basins or estuaries, world heritage sites, and climate grid cells) are used to reference some data, but all are linked to the linear segment structure. This fundamental linear data structure is unique for a global database and represents an efficient solution to the problem of representing and storing coastal data. The database has been specifically designed to support impact and vulnerability analysis to sea-level rise at a range of scales up to global. Due to the structure, consistency, user-friendliness, and wealth of information in the database, it has potential wider application to analysis and modelling of the world's coasts, especially at regional to global scales.

On the Use of Cool Materials as a Heat Island Mitigation Strategy

Abstract: The mitigation of the heat island effect can be achieved by the use of cool materials that are characterized by high solar reflectance and infrared emittance values. Several types of cool materials have been tested and their optical and thermal properties reveal that these materials can be classified as “cool” with the ability to maintain lower surface temperatures. Cool materials can be used on buildings and other surfaces of the urban environment. Based on these results, a modeling study was undertaken to assess the urban heat island effect over Athens, Greece, a densely populated city, by trying to analyze the impacts of large-scale increases in surface albedo on ambient temperature. Numerical simulations were performed by the “urbanized” version of the nonhydrostatic fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5, version 3-6-1). Two scenarios of modified albedo were studied: a moderate and an extreme increase in albedo scenario. It was found that large-scale increas...

Hypotheses, mechanisms and trade-offs of tolerance and adaptation to serpentine soils : from species to ecosystem level

Abstract: Understanding the relative importance of the abiotic environment and species interactions in determining the distribution and abundance of organisms has been a challenge in ecological research. Serpentine substrata are stressful environments for plant growth due to multiple limitations, collectively called the "serpentine syndrome". In the present review, our aim is not only to describe recent work in serpentine ecology, but also to highlight specific mechanisms of species tolerance and adaptation to serpentine soils and their effects on community structure and ecosystem functioning. We present hypotheses of the development of serpentine endemism and a description of functional traits of serpentine plants together with a synthesis of species interactions in serpentine soils and their effects on community structure and ecosystem productivity. In addition, we propose hypotheses about the effects of the 'serpentine syndrome' on ecosystem processes including productivity and decomposition.

Addressing privacy requirements in system design: the PriS method

Abstract: A major challenge in the field of software engineering is to make users trust the software that they use in their every day activities for professional or recreational reasons. Trusting software depends on various elements, one of which is the protection of user privacy. Protecting privacy is about complying with user’s desires when it comes to handling personal information. Users’ privacy can also be defined as the right to determine when, how and to what extend information about them is communicated to others. Current research stresses the need for addressing privacy issues during the system design rather than during the system implementation phase. To this end, this paper describes PriS, a security requirements engineering method, which incorporates privacy requirements early in the system development process. PriS considers privacy requirements as organisational goals that need to be satisfied and adopts the use of privacy-process patterns as a way to: (1) describe the effect of privacy requirements on business processes; and (2) facilitate the identification of the system architecture that best supports the privacy-related business processes. In this way, PriS provides a holistic approach from ‘high-level’ goals to ‘privacy-compliant’ IT systems. The PriS way-of-working is formally defined thus, enabling the development of automated tools for assisting its application.

Assessing port governance models: process and performance components

Abstract: This paper develops a conceptual framework that integrates various relevant port performance components in a way that can be used for a comprehensive port evaluation and adjustment of existing port governance models. The paper presents a synthesis of the literature on port governance models and port performance, arguing that the process of change is a dynamic one, and that the performance outcome of a reform process influences the next round of reforms. It also explores the potential for decomposing performance into two different, although related, port performances components, namely efficiency and effectiveness. Bringing into the analysis concepts like the need to integrate users’ satisfaction in port performance assessment, the paper explores the content of each of these components and their relationship. This discussion, along with empirical evidence provided by port authorities, leads to the conclusion that governance decisions, both at firm and government levels, are largely based on a very limited ...

Author identification: Using text sampling to handle the class imbalance problem

Abstract: Authorship analysis of electronic texts assists digital forensics and anti-terror investigation. Author identification can be seen as a single-label multi-class text categorization problem. Very often, there are extremely few training texts at least for some of the candidate authors or there is a significant variation in the text-length among the available training texts of the candidate authors. Moreover, in this task usually there is no similarity between the distribution of training and test texts over the classes, that is, a basic assumption of inductive learning does not apply. In this paper, we present methods to handle imbalanced multi-class textual datasets. The main idea is to segment the training texts into text samples according to the size of the class, thus producing a fairer classification model. Hence, minority classes can be segmented into many short samples and majority classes into less and longer samples. We explore text sampling methods in order to construct a training set according to a desirable distribution over the classes. Essentially, by text sampling we provide new synthetic data that artificially increase the training size of a class. Based on two text corpora of two languages, namely, newswire stories in English and newspaper reportage in Arabic, we present a series of authorship identification experiments on various multi-class imbalanced cases that reveal the properties of the presented methods.

Summarization system evaluation revisited: N-gram graphs

Abstract: This article presents a novel automatic method (AutoSummENG) for the evaluation of summarization systems, based on comparing the character n-gram graphs representation of the extracted summaries and a number of model summaries. The presented approach is language neutral, due to its statistical nature, and appears to hold a level of evaluation performance that matches and even exceeds other contemporary evaluation methods. Within this study, we measure the effectiveness of different representation methods, namely, word and character n-gram graph and histogram, different n-gram neighborhood indication methods as well as different comparison methods between the supplied representations. A theory for the a priori determination of the methods' parameters along with supporting experiments concludes the study to provide a complete alternative to existing methods concerning the automatic summary system evaluation process.

Global estimates of the impact of a collapse of the West Antarctic ice sheet: an application of FUND

Abstract: The threat of an abrupt and extreme rise in sea level is widely discussed in the media, but little understood in practise, especially the likely impacts of such a rise including a potential adaptation response. This paper explores for the first time the global impacts of extreme sea-level rise, triggered by a hypothetical collapse of the West Antarctic Ice Sheet (WAIS). As the potential contributions remain uncertain, a wide range of scenarios are explored: WAIS contributions to sea-level rise of between 0.5 and 5 m/century. Together with other business-as-usual sea-level contributions, in the worst case this gives an approximately 6-m rise of global-mean sea level from 2030 to 2130. Global exposure to extreme sea-level rise is significant: it is estimated that roughly 400 million people (or about 8% of global population) are threatened by a 5-m rise in sea level, just based on 1995 data. The coastal module within the Climate Framework for Uncertainty, Negotiation and Distribution (FUND) model is tuned with global data on coastal zone characteristics concerning population, land areas and land use, and then used for impact analysis under the extreme sea-level rise scenarios. The model considers the interaction of (dry)land loss, wetland loss, protection costs and human displacement, assuming perfect adaptation based on cost-benefit analysis. Unlike earlier analyses, response costs are represented in a non-linear manner, including a sensitivity analysis based on response costs. It is found that much of the world’s coast would be abandoned given these extreme scenarios, although according to the global model, significant lengths of the world’s coast are worth defending even in the most extreme case. This suggests that actual population displacement would be a small fraction of the potential population displacement, and is consistent with the present distribution of coastal population, which is heavily concentrated in specific areas. Hence, a partial defence can protect most of the world’s coastal population. However, protection costs rise substantially diverting large amounts of investment from other sectors, and large areas of (dry)land and coastal wetlands are still predicted to be lost. Detailed case studies of the WAIS collapse in the Netherlands, Thames Estuary and the Rhone delta suggest greater abandonment than shown by the global model, probably because the model assumes perfect implementation of coastal protection and does not account for negative feedbacks when implementation is imperfect. The significant impacts found in the global model together with the potential for greater impacts as found in the detailed case studies shows that the response to abrupt sea-level rise is worthy of further research.

Trust, Privacy and Security in Digital Business

Abstract: Trust, Privacy and Security in Digital Business : Proceedings of the 6th International Conference, TrustBus 2009, Linz, Austria, September 3-4, 2009

Public–private partnership projects in Greece: risk ranking and preferred risk allocation

Abstract: Project participants, through experience, have an initial perception and predisposition towards risk and the types of risks they are willing and able to undertake. This is equally true for parties interested in public–private partnership (PPP) projects. These initial positions have been registered for the major Greek PPP market stakeholders potentially involved in a PPP arrangement through a survey covering all candidate construction companies, interested financing institutes and a number of public sector entities to be involved in PPPs. Findings revealed that stakeholders were, for the majority of risks identified, in agreement as to preferred risk allocation. Risk allocation preferences for construction companies were compared with similar findings for the UK, a mature PPP market, indicating a possible learning/maturing process based on the particular country background. Conclusions add to other surveys carried out on the subject and should enable public sector clients to establish a more efficient fram...

Socioeconomic Dimensions of Changes in the Agricultural Landscape of the Mediterranean Basin: A Case Study of the Abandonment of Cultivation Terraces on Nisyros Island, Greece

Abstract: Agricultural landscapes illustrate the impact of human actions on physical settings, and differential human pressures cause these landscapes to change with time. Our study explored changes in the terraced landscapes of Nisyros Island, Greece, focusing on the socioeconomic aspects during two time periods using field data, cadastral research, local documents, and published literature, as well as surveys of the islanders. Population increases during the late 19th to early 20th centuries marked a significant escalation of terrace and dry stone wall construction, which facilitated cultivation on 58.4% of the island. By the mid-20th century, the economic collapse of agricultural activities and consequent emigration caused the abandonment of cultivated land and traditional management practices, dramatically reducing farm and field numbers. Terrace abandonment continued in recent decades, with increased livestock grazing becoming the main land management tool; as a result, both farm and pasture sizes increased. Neglect and changing land use has led to deterioration and destruction of many terraces on the island. We discuss the socioeconomic and political backgrounds responsible for the land-use change before World War II (annexation of Nisyros Island by the Ottoman Empire, Italy, and Greece; overseas migration opportunities; and world transportation changes) and after the war (social changes in peasant societies; worldwide changes in agricultural production practices). The adverse landscape changes documented for Nisyros Island appear to be inevitable for modern Mediterranean rural societies, including those on other islands in this region. The island’s unique terraced landscapes may qualify Nisyros to become an archive or repository of old agricultural management techniques to be used by future generations and a living resource for sustainable management.

SQL-IDS: a specification-based approach for SQL-injection detection

Abstract: Vulnerabilities in web applications allow malicious users to obtain unrestricted access to private and confidential information. SQL injection attacks rank at the top of the list of threats directed at any database-driven application written for the Web. An attacker can take advantages of web application programming security flaws and pass unexpected malicious SQL statements through a web application for execution by the back-end database. This paper proposes a novel specification-based methodology for the detection of exploitations of SQL injection vulnerabilities. The new approach on the one hand utilizes specifications that define the intended syntactic structure of SQL queries that are produced and executed by the web application and on the other hand monitors the application for executing queries that are in violation of the specification.The three most important advantages of the new approach against existing analogous mechanisms are that, first, it prevents all forms of SQL injection attacks; second, its effectiveness is independent of any particular target system, application environment, or DBMS; and, third, there is no need to modify the source code of existing web applications to apply the new protection scheme to them.We developed a prototype SQL injection detection system (SQL-IDS) that implements the proposed algorithm. The system monitors Java-based applications and detects SQL injection attacks in real time. We report some preliminary experimental results over several SQL injection attacks that show that the proposed query-specific detection allows the system to perform focused analysis at negligible computational overhead without producing false positives or false negatives. Therefore, the new approach is very efficient in practice.

Introduction to Social TV: Enhancing the Shared Experience with Interactive TV

Abstract: Previous research on the social impact of communication technologies has followed two distinct directions and has considered independently either the interpersonal communication or the mass communication. In this context, the human–computer interaction aspects of integrated media and social communication are examined. The design of “Social TV” systems that support interpersonal communication, which is motivated by mass media consumption and which takes place within colocated groups or over distance, is explored. In terms of the temporal dimension, Social TV might be synchronous, which happens in real time, or asynchronous, which happens with a time difference. This article provides an overview of research findings and outlines evaluation methods and user requirements for usability and sociability in interactive TV.

Generation and Sizing of Particles for Aerosol-Based Nanotechnology

Abstract: Traditionally, the generation of nanoparticles for technological applications has been mostly performed by classical wet chemistry or lithographic methods, and their size has been commonly determined in situ by electron microscopy techniques. Advances in aerosol technology over the past 30 years have provided methods that enable the generation and measurement of nanosize building blocks, and have opened up new oppor tunities in the assembly of nanostructured materials and nanodevices. This article provides a brief review on state-of-the-art techniques for generating nanoparticles of well-defined size and chemical composition in view of applications in nanotechnology. Covering atomization techniques from the liquid phase and nanoparticle synthesis from the gas phase, we discuss the advantages and limitations of each method. Considering the advantages of on-line methods that aerosols instruments of fer, we describe the most ef ficient techniques for measuring the size distributions of airborne nanosize particles. Finally, we provide a brief discussion on existing and emerging applications of aerosol-based nanotechnology.

Supplier selection in pharmaceutical industry

Abstract: Purpose – Evaluating and selecting the best among the offers provided by various suppliers is a complex problem that takes into account both tangible and intangible criteria, which incorporate interdependencies and feedback The decision making is aggravated by the complexity of supply chain relationships and enterprise strategies especially within enterprise clusters The aim of this paper is to present a comprehensive method for the evaluation and selection of suppliers' offers in parapharmaceutical industry clustersDesign/methodology/approach – The proposed approach consists of two parts The former is the comprehension of the supply chain processes within the parapharmaceutical industry in Greece, and the latter is the use of an analytic network process (ANP)‐based method for the selection of the best offerFindings – The proposed approach enables the decision maker to visualize the impact of various criteria on the final outcome and documents the evaluation results in such a way that they can be com

Concession Agreements and Market Entry in the Container Terminal Industry

Abstract: In this paper, we describe the capabilities and strategies required for obtaining a concession to operate a terminal in a seaport. The extent to which concession procedures create entry barriers and lower the contestability of the market is assessed. Recent studies and policy initiatives have stressed the importance of lowering economic, institutional, and locational entry barriers in seaports. Concession procedures have an effect on market entry. Tenders may lower entry barriers by ensuring transparency, restricting discrimination and exclusivity, and limiting concessions to certain periods. However, tender procedures may also introduce entry barriers in a number of ways, including the requirement of capabilities and track records to win a tender. This paper examines relevant empirical material of recently completed or intended concessions in major European ports to evaluate these issues.

Advanced patient or elder fall detection based on movement and sound data

Abstract: The paper presents am initial implementation of a patient monitoring system that may be used for patient activity recognition and emergency treatment in case a patient or an elder falls. Sensors equipped with accelerometers and microphones are attached on the body of the patients and transmit patient movement and sound data wirelessly to the monitoring unit. Applying Short Time Fourier Transform (STFT) and spectrogram analysis on sounds detection of fall incidents is possible. The classification of the sound and movement data is performed using Support Vector Machines. Evaluation results indicate the high accuracy and the effectiveness of the proposed implementation.

After‐sales service quality as an antecedent of customer satisfaction: The case of electronic appliances

Abstract: Purpose – The purpose of this paper is to investigate the effect of after‐sales services on customers' satisfaction as well as on their behavioural intentions, namely “repurchase intention” and “word‐of‐mouth” (WOM).Design/methodology/approach – The research conducted followed a quantitative methodology. The selected research tool was a questionnaire, which was administered via phone interviews using the CATI process. The study conducted was targeted to customers of a large retail chain marketing electrical appliances in Greece and 420 usable responses were utilised. A path analysis was performed using the “Amos 4.0” software.Findings – After‐sales service quality affect satisfaction, which in turn affects behavioural intentions. Hence, after‐sales services affect the overall offering and thus, the quality of the relationship with customers.Research limitations/implications – Limitations are related to the use of only two after‐sales services and the restricted geographical area of the field research.Prac...