Investigation and analysis of the electro-hydrodynamic (EHD) effects in asymmetric air gaps. The wire - cylinder case

In this work, the electro-hydrodynamic (EHD) mechanism, in the case of a thin wire parallel to a conducting cylinder of significantly larger diameter, has been studied. The wire-cylinder geometry may be used in a wide range of applications as a corona discharge generating pair, due to its simple structure and the highly inhomogeneous electric field that can be generated under high voltage DC application, which, in turn, is capable of producing significant EHD flow in air. The physical phenomenon of the EHD effect has been studied through simulations, experiments and comparisons. The operational parameters, such as the electric field and potential distribution, in variously dimensioned electrode arrangements have been investigated, while their dependence on geometrical characteristics of the electrodes, such as the electrode length, the electrode gap and the emitter and collector electrode radii, has been examined. On this purpose, both computer modelling and experimental studies have been conducted. The electric field and potential distribution has been studied by implementing Finite Element Analysis (FEA). The simulation results have shown that the maximum electric field intensity (Emax) was mainly associated with the wire-cylinder radii ratio, while the distance between the electrodes strongly affected the distribution along the axis of the gap. Further analysis of the results has shown that Emax may be estimated by an empirical formula which was found to be satisfactory in all cases. An approximate technique for the determination of the unipolar saturation current limit, based on the analysis of the electric field lines has been proposed and the model has been verified through experiments, which have shown that the wire-cylinder unipolar corona discharge current is closely related to the specified theoretical limits. The experimental study of the EHD flow has shown that the corona discharge current is related to the applied voltage through a quadratic relationship following the well-known Townsend’s general model. The ionic wind velocity found to be an approximately linear function of the applied voltage and proportional to the square root of the discharge current, while on the other hand, a linear relationship between the generated thrust and the corona discharge current has been determined. In all cases, the electromechanical efficiency and the thrust efficiency, which is frequently used as an overall performance evaluation factor, have been derived

Large Strain Theory as Applied to Penetration Mechanism in Soils (Plasticity).

A theoretical analysis of a Quasistatic Cone Penetrometer Test (QCPT) is presented in this work. A large strain, elasto-plastic formulation is developed for this purpose and is implemented into a finite element method program. The basic relations of the theory are developed in an Eulerian reference frame, subsequently transformed to a Lagrangian coordinate system, and through simple time differentiation, the necessary rate equations are derived. Both isotropic and kinematic hardening of the Ziegler type are introduced in this theory. The plasticity models implemented are the extended von Mises and the cap model by DiMaggio and Sandler. The pore water pressures are obtained through the introduction of a bulk modulus of the soil-water system. The theory is applied to the solution of a cone penetration problem in a soft cohesive soil (E = 5000 KN/m(\u272), s(,u) = 50 KN/m(\u272)). The displacement strain, stress and pore water pressure fields around the penetrating cone are thus calculated. Interesting conclusions are drawn from this analysis, the most important of which are listed below: (a) The penetration mechanism during the QCPT seems to be a localized phenomenon for soft clays; that is, the recorded response during the test is averaged over small regions, which results in more meaningful and accurate predictions of the soil properties. (b) The kinematic field obtained from the axi-symmetric penetration is different from the one obtained from the plane strain penetration problem. No slip zones appear in the axi-symmetric problem; consequently, an analysis based on this concept is inappropriate for soft cohesive soils. (c) A separation zone occurs between the shaft and the soil above the cone tip. Readings of the soil response in this area could therefore be unreliable. (d) As the penetration acquires steady state characteristics, the pore water pressures generated around the cone probe become more uniform. It can thus be concluded that the position of the pore pressure transducer is not critical

Do Cultural Differences Influence Tourists’ Likelihood to Seek Information Via Social Media in the Event of a Crisis?

This study examined the influence of the cultural backgrounds of international travelers on the likelihood to turn to social media to seek information if a crisis were to occur while traveling. Data for this study were generated by surveys from an online panel of international respondents from South Korea, China, India, Australia, and Brazil. A total of 2,416 completed surveys were used. The results indicated that travelers from different countries varied in their likelihood to seek information via social media during a crisis. Tourists from South Korea were found to be the most likely to access social media to find information about a crisis while traveling. The different cultures also had different preferred sources for seeking information during a crisis. This study demonstrated the significance of examining the influence of characteristics on the potential use of social media during a crisis. Implications and recommendations are presented

Τα όρια της δικαιοδοσίας των δικαιοδοτικών οργάνων του Μέρους XV της Σύμβασης για το Δίκαιο της Θάλασσας : Περιπτώσεις διεύρυνσης και περιορισμού της ratione materiae δικαιοδοσίας

Η εργασία περιστρέφεται γύρω από ζητήματα δικαιοδοσίας των δικαιοδοτικών οργάνων της Σύμβασης για το Δίκαιο της Θάλασσας και εξετάζει, κυρίως μέσα από νομολογιακά παραδείγματα, ζητήματα της εφαρμογής ή του αποκλεισμού της εφαρμογής του 2ου τμήματος του Μέρους XV της Σύμβασης για το Δίκαιο της Θάλασσας.Η εργασία περιστρέφεται γύρω από ζητήματα δικαιοδοσίας των δικαιοδοτικών οργάνων της Σύμβασης για το Δίκαιο της Θάλασσας και εξετάζει, κυρίως μέσα από νομολογιακά παραδείγματα, ζητήματα της εφαρμογής ή του αποκλεισμού της εφαρμογής του 2ου τμήματος του Μέρους XV της Σύμβασης για το Δίκαιο της Θάλασσας

Gender, Residence, Past Experience and Communication in Tourist Hurricane Evacuation

The paper discusses the role of gender, residence, and past experience with hurricanes in affecting tourists’ voluntary evacuation in the event of hurricanes. Specifically the study examines how the aforesaid variables influence perceived credibility of the information source and how such perception is translated into actual information search behaviors leading to a voluntary evacuation decision. The paper is guided by utility maximization under environmental risks and bounded rationality. The findings indicate that the aforesaid variables significantly influence the perception of the credibility of information sources and information search behaviors leading to voluntary evacuation decisions. Implications of the findings are also discusse

How the news media set the agenda

El papel de "agenda-setting" desempeñado por los medios informativos condiciona en gran medida no solamente el abanico de cosas que nos llaman la atención, sino también nuestra manera de entender el mundo ingente de asuntos públicos que existe más allá de nuestra experiencia personal. El Chapel Hill Study de 1972 marcó un antes y un después en el desarrollo de la teoría de agenda setting. Hasta este momento clave se había limitado a la influencia que ejercen los medios informativos sobre el público; a partir de este trascendente estudio la teoría abrió sus horizontes y empezó a abordar el proceso más amplio de agenda setting. En este trabajo se presentan los resultados de dos estudios empíricos publicados recientemente en los EEUU. El primero explica cómo la prensa cambia el foco de su atención dentro de un acontecimiento informativo importante, iluminando primero un aspecto y luego otros para así establecer la prominencia de dicho acontecimiento en la agenda mediática. El segundo explica el efecto que ejerce la prominencia en la agenda mediática sobre la actitud del público y las opiniones que se tienen de las personalidades públicas

Congressional Agenda-Building: Examining the Influence of Congressional Communications from the Speaker of the House

This study explored the role of the Speaker of the House in shaping the salience of political issues and attributes in news media coverage and policymaking in 2007. Specifically, it analyzed 533 press releases, 433 news articles, and 47 daily Congressional calendars of business. Significant correlations were found supporting traditional first-level and second-level agenda-building linkages between Congressional communications and media coverage; whereas no relationships were found between issue or attribute salience in news releases and actual Congressional activities. Theoretical and practical implications of the findings are discussed

Rock partridge (Alectoris graeca graeca) population density and trends in central Greece

The rock partridge is an emblematic species of the Greek avifauna and one of the most important game species in the country. The present study, which combined long term in–situ counts with distance sampling methodology in central Greece, indicated that the species’ population in Greece is the highest within its European distribution, in contrast to all prior considerations. Inter–annual trends suggested a stable rock partridge population both within hunting areas and wildlife refuges, whereas during summer, the species presented significantly higher densities in altitudes of more than 1,000 m, most probably due to the effect of predation at lower zones. The similarity of population structure between wildlife refuges and hunting zones along with the stable population trends demonstrate that rock partridge harvest in the country is sustainable

Chikungunya Disease Awareness Among U.S. Travelers to Caribbean Destinations

Introduction: This study investigated chikungunya disease awareness and its predictors, the level of adoption of recommended personal protective behaviors against chikungunya, and the health information-seeking behavior of U.S. travelers to Caribbean destinations.Methods: A cross-sectional retrospective online survey of 653 adult U.S. international travelers who visited any one of 34 Caribbean destinations was conducted in October 2015. Study participants were recruited through Amazon® Mechanical Turk. Travelers who met the inclusion criteria and gave informed consent were subsequently redirected to complete the survey which was domiciled in Qualtrics®.Results: Results regarding health information-seeking behavior indicated that 51% of study participants had never sought information about chikungunya or any vector-borne illnesses. Only thirty percent of study participants reported having heard of chikungunya disease before participating in this study. After adjusting for the presence of other variables in a logistic regression model, gender of female, higher levels of education, more time spent at the destination, and a higher number of hours spent engaging in outdoor activities were factors significantly associated with chikungunya disease awareness. Study results also showed that twenty-two percent of study participants did not engage in any of the three recommended personal protective behaviors under investigation.Conclusion: Study findings highlighted a gap in existing approaches to health information dissemination vis-à-vis adoption of recommended personal protective behaviors, especially for U.S. travelers at risk for chikungunya and other emerging mosquito-borne infectious diseases in Caribbean destinations