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Dimosthenis Voivontas Dionysis Xenos Antonios Xanthakis Evangelos Pisias Dionysis Assimacopoulos 《国际水》2013,38(3):330-342
Abstract Types of partnerships between public and private companies in water and sewage services are evaluated on the basis of the economic efficiency of the scheme for each partner. Modeling of public-private partnerships involves the formulation of a contract prototype, which determines the roles, functions, and responsibilities as well as the allocation of costs and revenues for each partner. Alternative water management scenarios are used to identify the investments required for meeting the projected demand for water and sewage services. Investment and operational costs as well as revenues from water and sewage services are estimated according to the allocation defined in the contract prototype. The economic efficiency of the scheme is assessed through a cost benefit analysis for each partner. The evaluation of different water management scenarios indicates that, for the Cyclades Islands, Greece, there is a substantial water market where several forms of partnerships could be attractive for both the public and the private sectors. Such partnerships include, among others, lease purchase, temporary privatization, built operate transfer (BOT), and built own operate transfer (BOOT). These forms of public-private partnerships could also be successful in similar regions where significant improvements and expansion of the infrastructure is required while access to the required funds and expertise is restricted for small public water companies. 相似文献
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Eleni Kampragou Demetris F. Lekkas Dionysis Assimacopoulos 《Water and Environment Journal》2011,25(4):466-476
Current practices for the efficient use and management of water resources are based on the conjunctive application of water supply and demand measures. Even though options for the augmentation of water supply are widely analysed and assessed, water demand management remains an open field for study, as it is highly dependent on the socio‐economic features of a region and has a site‐specific character. This paper summarizes the guiding principles of demand management and presents some successful application examples of demand management measures from regions that cover a wide range of socioeconomic and environmental conditions in an effort to identify the critical factors for the efficient planning and implementation of demand management plans. 相似文献
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In this paper, we investigate the impact of primary user activity, secondary user activity, interface switching, channel fading and finite-length queuing on the performance of decentralized cognitive radio networks. The individual processes of these service-disruptive effects are modeled as Markov chains based on cross-layer information locally available at the network nodes. A queuing analysis is conducted and various performance measures are derived regarding the packet loss, throughput, spectral efficiency, and packet delay distribution. Numerical results demonstrate the impact of various system parameters on the system performance, providing insights for cross-layer design and autonomous decision making in decentralized cognitive radio networks. 相似文献
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Emmanouil Liandris Maria Gazouli Styliani Taka Margarita Andreadou Anna Vaiopoulou Nikolaos Tzimotoudis Ioannis Kasampalidis Dionysis Mpaseas George Fyliousis Palmiro Poltrionieri Nigel Cook John Ikonomopoulos 《Journal of food science》2014,79(3):M362-M368
Foodborne illness is a major cause of morbidity and mortality especially for children, even in the developed world. The aim of this study was to assess the microbial safety of food of animal origin intended for consumption by children in Greece. Sampling involved 8 categories of retail products and was completed with a collection of 850 samples. These were tested by PCR and/or culture for Listeria monocytogenes, Campylobacter spp., Escherichia coli O157, Salmonella spp., Cronobacter sakazakii, Brucella spp., and Mycobacterium avium subsp paratuberculosis (MAP). The number of positive results recorded collectively for the pathogens under investigation over the total number of samples tested was 3.52% and 0.12% by PCR and culture, respectively. The most frequently detected pathogen was enterohemorrhagic E. coli (1.29%) followed by Brucella (0.82%) and Listeria (0.82%). DNA belonging to MAP was detected in 0.35% of samples, which was also the percentage of positivity recorded for Campylobacter. The percentage for Salmonella was 0.12%. It can be concluded from the results that there is no indication of noncompliance for the tested food samples. However, detection of DNA belonging to pathogens that are transmissible to humans through food is indicative that constant vigilance regarding food safety is an absolute necessity. 相似文献
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Dionysis Xenakis Dimitris Tsolkas Nikos Passas Nancy Alonistioti Lazaros Merakos 《Wireless Communications and Mobile Computing》2012,12(11):985-998
Modern wireless orthogonal frequency division multiple access (OFDMA) systems incorporate dynamic resource allocation (DRA), adaptive modulation and coding (AMC), and power control (PC) to exploit multiuser diversity and achieve higher system throughput. In the literature, only a few proposed algorithms deal with the contiguous DRA problem according to which a contiguous collection of resources can be allocated to each user. This paper formulates this high complexity problem, provides a suitable decision metric and a simple yet efficient solution. The proposed algorithm allocates in each step a contiguous collection of resources to the pending user that leads to the highest estimated correctly received number of bits. Simulation results show that, in this way, considerably improved performance can be achieved in terms of overall system throughput, spectral efficiency, and served traffic. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Foued El Ayni Eleni Manoli Semia Cherif Amel Jrad Dionysis Assimacopoulos Malika Trabelsi‐Ayadi 《Water and Environment Journal》2013,27(3):348-361
The purpose of this study is to provide a better understanding of the impact of agricultural activities on groundwater quality in a semi‐arid coastal environment (Korba, Tunisia). Impacts have been assessed through groundwater samples that were analysed for a range of chemical and biological parameters. Results indicate that groundwater overexploitation for irrigation and fertiliser use have affected the quality of the groundwater not only by direct contamination but also seawater intrusion. The implementation of appropriate regulatory and economic instruments to foster sustainable practices in the agricultural sector have been analysed within the framework of the EC (European Community) FP6 (funding program 6) INECO (Institutional and Economic Instruments for Sustainable Water Management in the Mediterranean Region) Project. Through stakeholder involvement processes, the project analysed issues relating to the regulation and control of groundwater abstractions, the promotion of wastewater reuse, efficiency improvements in irrigation water use, as well as instruments to strengthen the socioeconomic and institutional environment towards better managing and conserving available groundwater resources. 相似文献
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Nikolaos Vernadakis Asimenia GioftsidouPanagiotis Antoniou Dionysis IoannidisMaria Giannousi 《Computers & Education》2012
The purpose of this study was to determine whether there is a difference between an exergame-based and a traditional balance training program, in undergraduate Physical Education students. Thirty two third-year undergraduate students at the Democritus University of Thrace were randomly divided into two training program groups of 16 students each, a traditional and a Nintendo Wii group. The two training program groups performed a specific balance program for 8 weeks, two times per week, and 24 min per session. The Nintendo Wii group used the interactive games Wii Fit Plus of the Nintendo Wii console, as a training method to improve their balance, while the traditional group used an exercise program with mini trampoline and inflatable discs. Before and after the completion of the eight-week balance program, participants completed a single leg static balance assessment for both limbs on the Biodex stability system. Two-way analyses of variance (ANOVAs), with repeated measures on the last factor, were conducted to determine effect of training program groups (traditional, Nintendo Wii) and measures (pre-test, post-test) on balance test indices (SI, API, and MLI). Where initial differences between groups were verified, one-way analyses of covariance (ANCOVAs) were applied. Analysis of the data illustrated that both groups demonstrated an improvement in SI, API and MLI mean scores for the right and the left limp as well. Conclusively, findings support the effectiveness of using the Nintendo Wii gaming console as an intervention for undergraduate Physical Education students, and specifically, its effects on physical function related to balance competence. 相似文献
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In this paper we present CoWSAMI, a middleware infrastructure that enables context awareness in open ambient intelligence environments, consisting of mobile users and context sources that become dynamically available as the users move from one location to another. A central requirement in such dynamic scenarios is to be able to integrate new context sources and users at run-time. CoWSAMI exploits a novel approach towards this goal. The proposed approach is based on utilizing Web services as interfaces to context sources and dynamically updatable relational views for storing, aggregating and interpreting context. Context rules are employed to provide mappings that specify how to populate context relations, with respect to the different context sources that become dynamically available. An underlying context sources discovery mechanism is utilized to maintain context information up to date as context sources, and users get dynamically involved. 相似文献
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