Public-Private Partnerships in the Water Sector

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.     

Stress in interactive applications: analysis of the valence-arousal space based on physiological signals and self-reported data

Measuring users’ emotional reaction to interactive multimedia and hypermedia is important. One particularly popular self-reported method for emotion assessment is the Valence-Arousal (VA) Scale: a 9?×?9 affective grid. This paper aims to identify specific stress region(s) in the VA space by combining self-reported ratings (pairs of VA) and physiological signals (skin conductance). To this end, 31 healthy volunteers participated in an experiment by performing five stressful interaction tasks while their skin conductance was monitored. The selected interaction tasks were most frequently listed as stressful by a separate group of 15 interviewees. After each task, participants expressed their perceived emotional experience using the VA rating space. Our findings show which regions in the VA rating space may reliably indicate self-reported stress that is in alignment with one’s measured skin conductance while using interactive applications. One additional important contribution of this work is the proposed approach for the empirical identification of affect regions in the VA space based on physiological signals.     

Ionospheric radio wave propagation finite element method modeling

In this work, a transionospheric propagation model is presented. The application analyzed here uses data from the Rome ionospheric station together with data from the theoretical IRI-95 and MSIS-E-90 models, in order to simulate the ionosphere. Using formulas from ionospheric propagation theory, these data form the wave equation, which is solved by means of the finite element method. Post-processing of the solution leads to the determination of the main wave propagation parameters.     

Direct and Differential Effects of the Internet on Political and Civic Engagement

Given the significant rise in the number of Americans who turn to the Internet for political information, we examine the effects of these behaviors on political and civic engagement in an evolving media landscape. Specifically, we test hypotheses derived from competing models—the instrumental approach, which posits direct effects of Internet use and a psychological approach, which predicts contingent effects. Analyses of the 2004 American National Election Studies ( N = 1,212) reveal a pattern of direct effects of Internet use on basic information acquisition and use but contingent effects for concrete acts of civic or political engagement. These results provide an important window on the political impacts of contemporary Internet use and suggest that future reassessments of the Internet's role in public life should continue to probe for direct as well as differential effects.     

Biological chromium(VI) reduction using a trickling filter

A pilot-scale trickling filter was constructed and tested for biological chromium(VI) removal from industrial wastewater. Indigenous bacteria from industrial sludge were enriched and used as inoculum for the filter. Sodium acetate was used as carbon source and it was found to inhibit chromate reduction at high concentrations. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter one was found to achieve removal rates up to 530 g Cr(VI)/m2 d, while aeration was taking place naturally without the use of any external mechanical means. The low operating cost combined with the high hexavalent chromium reduction rates indicates that this technology may offer a feasible solution to a very serious environmental problem.     

An Efficient Hybrid Parabolic Equation – Integral Equation Method for the Analysis of Wave Propagation in Highly Complex Indoor Communication Environments

An efficient, full-wave computational technique to investigate the electromagnetic wave propagation within a complex building environment, resulting from contemporary indoor communication systems, is proposed. Unlike a standard ray-tracing technique, this new methodology is based on the parabolic wave equation (PE), appropriately modified to deal with the extremely wide-angle propagation cases, encountered in a typical wireless system of this kind. It is also successfully applied to model the field in the presence of walls, doors or other penetrable structures, taking into account the exact geometric configuration of the environment under consideration. Next, the PE technique is significantly enhanced by an integral equation formulation, in which the computed field in the interior of the walls and other obstacles is used as a secondary equivalent current source and a corrected version of the electromagnetic field is recalculated in the whole indoor environment. This combined approach has all the advantages of a full wave method, does not call for a highly dense mesh, and it also has moderate requirements of computational resources.     

Pulsatile cerebrospinal fluid dynamics in the human brain

Disturbances of the cerebrospinal fluid (CSF) flow in the brain can lead to hydrocephalus, a condition affecting thousands of people annually in the US. Considerable controversy exists about fluid and pressure dynamics, and about how the brain responds to changes in flow patterns and compression in hydrocephalus. This paper presents a new model based on the first principles of fluid mechanics. This model of fluid-structure interactions predicts flows and pressures throughout the brain's ventricular pathways consistent with both animal intracranial pressure (ICP) measurements and human CINE phase-contrast magnetic resonance imaging data. The computations provide approximations of the tissue deformations of the brain parenchyma. The model also quantifies the pulsatile CSF motion including flow reversal in the aqueduct as well as the changes in ICPs due to brain tissue compression. It does not require the existence of large transmural pressure differences as the force for ventricular expansion. Finally, the new model gives an explanation of communicating hydrocephalus and the phenomenon of asymmetric hydrocephalus.     

阿卡迪亚Ⅲ山羊与人

本项目结合当代语境,对“阿卡迪亚”(希腊南部地区,在诗歌和小说中常用来指代世外桃源)进行重新解读.阿卡迪亚曾经代表了人与自然的理想关系,没有文化因素的介入,常被人们用来表达浪漫主义的乌托邦想象.而本项目将畜牧业工作流程视为人与自然关系中的主要行为,剥去了原有的浪漫主义与田园想象的色彩. 人类文化的发展以及与之相伴的技术进步影响着畜牧业.不同时代的畜牧业状况都反映了当时的社会经济架构.如今的社会状况也蕴含着畜牧业的现代化及其为适应兴起中的增强生态而进行的流程改造.费利克斯·加塔利将思想、社会和环境的生态三角定义为生态智慧,而这正是让人类、动物与技术和谐共生的新型畜牧模式的动力所在.     

Tropospheric ducting phenomena over the Hellenic region

The variation of the refractivity profiles of the troposphere and especially of the ducting effect, affects the radio wave propagation causing various phenomena such as refraction, fading and interference between radio‐stations. In this work, the tropospheric ducting phenomena over the Hellenic region are studied using data from Helleniko and Thessaloniki Airports for the time period from 1991 to 1999. The data are analysed, corrected and enhanced using interpolation techniques and after a final statistical process the ducting conditions over the Hellenic region are summarized. Copyright © 2004 John Wiley & Sons, Ltd.     

A survey on student dropout rates and dropout causes concerning the students in the Course of Informatics of the Hellenic Open University

This paper focuses on university-level education offered by methods of distance learning in the field of computers and aims at the investigation of the main causes for student dropouts. The presented study is based on the students of the Course of “Informatics”, Faculty of Science and Technology of the Hellenic Open University and investigates the particularities of education provided through the use of computers and technology in general. This paper presents information about the students' profile, the use of computer technology, the percentage of dropouts, as well as a classification of the reasons for dropouts based on interviews with the students. The study shows that dropouts are correlated with the use of technological means and, based on this fact, the Hellenic Open University implemented interventions in the use of such means. It also proves that a correlation exists between dropouts and students' age, but not gender, although female students are more reluctant to start following a course. However, it is also shown that female students' commitment to a course is stronger and thus, they do not drop out as easily as male students do. Furthermore, the results of this study strongly correlate dropouts to the existence of previous education in the field of Informatics or to working with computers, but not to the degree of specialisation in computers. Finally, the paper presents the reasons provided by the students for drooping out, with the main reasons being the inability to estimate the time required for university-level studies and the perceived difficulty of the computers course.