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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Simplified CFD modelling of tidal turbines for exploring arrays of devices

Gebreslassie, Mulualem G. January 2012 (has links)
The status of marine current tidal energy technology is currently in the research and development phase, with a few deployments and tests of prototypes under-way in some countries. There is a huge pressure for tidal farms to be of Gigawatt scale in order to have a real, economically viable impact on renewable energy utilization targets outlined for 2020. A route to achieving this is the large scale energy farm philosophy, similar to wind farms, based on very large numbers of unit current tidal stream devices. However, this emerging technology development raises different research questions which lead to further problems in the practical implementation of tidal stream devices. Thus, the aim of this study was: (i) to develop a new, computationally cheap computational fluid dynamics (CFD) based model of the Momentum-Reversal-Lift (MRL) tidal turbine, and (ii) to perform a detailed calculations of the flow field of single and multiple turbines using the developed model to investigate the flow features such as, downstream wake structures, dynamics of the free surface, wake recovery, and the influence of wake interactions on the performance of individual devices. A new CFD based Immersed Body Force (IBF) model has been developed to represent the MRL turbine. The IBF model was developed based on the concept of actuator disc methodology by incorporating additional geometric features that induce energy absorption from the flow which also lead to a downstream wake structure intended to reflect more closely those of the real turbines than simple momentum sink zone models. This turbine model was thoroughly used to investigate the performance of the MRL turbine and the associated flow characteristics and proved its capability in analysing several issues relating to this design of tidal turbines. Several calculations have been carried out and a full range of operating points of the MRL turbine was formulated. A maximum power coefficient of, Cp = 0.665, was obtained with a blockage ratio of, B = 0.016. However, the performance of the turbine was improved at a higher blockage ratio both in a single and tidal stream farm investigations. The power coefficient of a single turbine was improved by about 3% when simulated with a blockage ratio of, B = 0.029, and even a higher value was obtained in a tidal stream farm containing three turbines configured in the spanwise direction which reached up to, CP = 0.761, with a global blockage ratio of, B = 0.027. These power coefficients are higher than the Lanchester-Betz limit of CP = 0.593 obtained at B = 0, which is mainly due to the tidal turbine operating in a constrained environment, high blockage ratio, that increases the thrust force on the device. The power coefficient of the IBF model showed consistently higher values compared to experiments and a detailed CFD model results. This indicates that the power coefficient calculated using the IBF model includes some other losses within the turbine region, such as losses due to viscous, shear etc. Investigations on the influence of closely packed clusters of turbines in a tidal streamfarm showed that a laterally close configuration of turbines improved the performance of individual turbines due to the blockage effect, which is created by the array of turbines in the span-wise direction. In contrast, a small longitudinal spacing between turbines inflicted a massive energy shadowing that affects the performance of downstream turbines. However, a tidal stream farm with a staggered turbine layout can reduce the longitudinal spacing by about 50% with a minimum of 6D lateral spacing compared with a regular turbine layout due to the advantage of using an accelerated bypass flows.
2

The impact of perceived interactivity, control and involvement on bank satisfaction and loyalty : an integrated eService model for eBanking

Chan, Shiu Fai January 2011 (has links)
Control and involvement are well researched concepts in traditional marketing, while interactivity is a relatively new concept associated with Internet marketing and communication. From an Internet interaction perspective, the research examines the impact of interactivity, control and involvement on customer satisfaction and loyalty in an eBanking context. Using Flow Theory as the theoretical foundation, it is proposed that these three Internet communication constructs lead to eService dependency and eService encounter satisfaction, which, in turn, enhance the overall satisfaction and loyalty to the principal bank at corporate level. A mixed methodology using both qualitative and quantitative approaches of data collection is adopted. In-depth interviews with eBankers and focus group studies with eBanking customers support the importance of interactivity, control and involvement in the eService encounter. The in-depth interviews and focus groups facilitate the identification of eService dependency as a new construct in the model. Participants' views also help the operationalisation of constructs and development of questionnaire for quantitative data collection. ii Analysis of the quantitative data using structural equation modelling shows support for all three constructs' hypothesised positive relationships with eService dependency and eService encounter satisfaction i.e. satisfaction at the service encounter level. It is also confirmed that eService dependency and eService encounter satisfaction have a positive impact on overall satisfaction with the principal bank i.e. satisfaction at corporate level. However, the influence of eService dependency and eService encounter satisfaction on loyalty to principal bank is not supported. The research concludes with the theoretical contributions and managerial implications of the research. Strategies to enhance interactivity with, control of and involvement by eBanking customers are recommended to eBankers. Limitations of the research and directions for future research in Internet and eService are also suggested.
3

Seaward Landward : Investigations on the archaeological source value of the landing site category in the Baltic Sea region

Ilves, Kristin January 2012 (has links)
There is a tendency in archaeology dealing with watercraft landing sites in a wider context to assume a direct relationship between sites in coastal and shore-bound areas and the practise of landing, without any deeper practical or theoretical exploration of the reality of any such relationship. This problem has its origins in the poor archaeological and conceptual definitions of watercraft landing sites obstructing any real understanding of the role of these sites in the maritime cultural landscape. Landing sites are taken for granted and they are undervalued as an archaeological source of explanation; notwithstanding, the concept of the landing site is readily used in archaeology in order to underpin archaeological interpretations on the maritime activities of past societies. In order to break away from the simplified understandings of past water-bound strategies based on the undefined concept of the landing site, this dissertation suggests a definition of watercraft landing sites in a wider social sense as water-bound contact zones; places of social interaction that can be archaeologically identified and investigated. This perspective integrates the understanding of the intentional character of human activity related to watercraft landing with the remaining archaeological traces. Archaeological definitions of landing sites that can be tested against the archaeological data are provided, and thereby, the dissertation contributes with the possibility to archaeologically evaluate and approach the social function of watercraft landing sites. This dissertation demonstrates that there can be an archaeology of landing sites.
4

Взаимодействие медицинских работников и пациентов в системе сельского здравоохранения : магистерская диссертация / The Interaction of Health Workers and Patients in the System of Rural Healthcare

Kleymenov, M. V., Клейменов, М. В. January 2014 (has links)
Problems of the Russian rural healthcare are considered in the master’s dissertation in light of the conducted reforms and transformations for the relationship health workers and patients. The dissertation presents the modern approach of the system of rural healthcare, which identified the several subsystems: interaction of the social communalities, medical service, medical institutions, management of the healthcare, norms and sanctions. Dissertation’s author described the results of the survey conducted in the villages of Dalmatovo district of Kurgan region. The study is based on the methodology of American philosopher R. Veatch, who classified the relations of health workers and patients on the four models: engineering, paternalistic, collegial and contract. The research identified the problems and contradictions in the system of rural healthcare. The dissertation can be used as a textbook for a university’s students training on the course and specialty “Sociology”. It’s interest for graduate students, university’s teachers, academics of the field of social sciences and humanities. / В магистерской диссертации рассматриваются проблемы сельского здравоохранения России в свете проводившихся реформ и преобразований на предмет взаимоотношений медицинских работников и пациентов. Представлена современная трактовка системы сельского здравоохранения, в которой выделено несколько подсистем: взаимодействия социальных общностей, медицинского обслуживания, медицинских учреждений, управления в сфере здравоохранения, норм и санкций. Автор диссертации описал результаты социологического исследования, проводившегося в селах Далматовского района Курганской области. Исследование методологически основано на концепции американского философа Р. Витча, который классифицирует взаимоотношения медицинских работников и пациентов на четыре модели: инженерная, патерналистская, коллегиальная, контрактная. В ходе исследования были выявлены проблемы и противоречия, возникшие в системе сельского здравоохранения. Магистерская диссертация может быть использована в качестве учебного пособия для студентов высших учебных заведений, обучающихся по направлению и специальности «Социология». Она представляет интерес для аспирантов, преподавателей, ученых в области социально-гуманитарных наук.
5

Sustainability by Design : A Descriptive Model of Interaction and a Prescriptive Framework for Intervention

Devadula, Suman January 2015 (has links) (PDF)
Introduction: Sustainability is humanity’s collective ability to sustain development that meets the needs of the present without compromising the ability of the future generations to meet their own needs. Preceding closely to the World Commission on Environment and Development (WCED) Report of 1987, the General Assembly has adopted the UN Declaration, in 1986 [GA RES. 41/128] and has re-emphasized its importance in the UN Millennium Declaration, 2000. Given this anthropocentric rights basis of sustainability it becomes necessary to understand what this ability and development are with respect to the individual human. Problems of relevance, whose resolution benefits more people in general, are often intractable to the methods of rigorous problem-solving (1). Systemic problems of development score high on relevance, low on being amenable to rigor (1) and are considered wicked in nature (2). Consequently, the concern for sustaining human development is wicked and hence calls for taking a design approach as design is considered good at resolving wicked problems(3). This suggests that the collective ability for sustainability with respect to the individual is design ability i.e. to specify solutions that satisfy requirements arising from having to meet self-determined individual (human) developmental needs. However, literature connecting design, sustainability and human development systemically is found lacking and calls for conducting integrative trans-disciplinary research. Prevention and remedial of consequences of technology to the habitability of earth requires the identification, understanding and control of interactions between humans and between humans and the earth systems. These interactions need to be identified generally and understood systemically in the context of being able to sustain human development. However, despite this need for research in interactions and an integrative framework for informing interventions (4) to prevent or remedy unsustainable situations literature that addresses this need is found inadequate. Research Objective: To develop a descriptive model of interaction to be able to identify and describe interactions and understand interactions at human-scale. To develop a prescriptive framework within which to situate the prevention and remedial of problems related to un sustainability by design and prescribe conditions that ensure coherence of design interventions to principles. Research Method: As is the nature of problems of relevance, the proposed research by nature spans multiple disciplines. Descriptive inquiry into widespread literature spanning conservation, development, systems theory and design is conducted before synthesizing a descriptive model of interaction that situates design cycle as a natural cycle based on interpretation of entropy and Gestalt theory of human perception. A manual discourse analysis of a section of the WCED report is undertaken to inquire into the conceptual system (worldview) behind sustainable development to understand human interactions based on worldview. Addressing the need for choosing alternative goals of development for sustainability, Sen’s capability approach to human development is adopted after critically reviewing literature in this area and synthesizing an appropriate integration of design ability, tools, (cognitive) extension and design capability for human development. Models based on theories spanning design expertise, psychology and systems thinking are reviewed and synthesized into a prescriptive framework and two intervention scenarios based on it. The framework, intervention scenarios and the model are illustrated with evidence from qualitative bibliographic analysis of several cases related to sustaining human development in principle. Results: Sustainability is proposed as a human ability; this human ability is proposed to be design ability to sustain human development. A descriptive model of interaction that situates anthropogenic action as a design cycle is proposed. Based on this model, identifying entities and interactions is demonstrated with examples. It is proposed that humans interact, designing, due to and based on their worldview. Expansion of capabilities as stated in capability approach to lead to human development is ‘extension’ of design ability to design capability mediated by tools. Personal and interpersonal interactions at human scale are described through tool-use categories. A prescriptive framework for sustainability by design that holds human needs as central to interventions for sustainability is proposed. Based on this framework, pro-active and reactive scenarios of design intervention for prevention and remedial of un sustainability are constructed and demonstrated using several cases. Summary: Problems of relevance like sustaining human development are wicked in nature and require knowledge and action mutually informing each other. Addressing the inter-disciplinary nature of the problem requires a design approach as design is known to integrate knowledge from several disciplines to resolve wicked problems. The imperative to be able to sustain human development provides the widest profile of requirements to be met and design is shown to be central to meeting these requirements at the various scales that they surface. Sustainability is defined as humanity’s collective ability to develop meeting needs of the present without compromising the ability of the future generations for meeting their own needs. This collective ability translates to the individual’s design ability to specify solutions that satisfy requirements arising out of having to meet self-determined developmental needs. The process of ‘expansion’ -- of capabilities that free people choose and value – that realizes human development is the process of tools affording the extension of design ability to design capability necessary for progressively satisfying requirements arising out of self-determined needs of increasing complexity. It is proposed that humans interact, designing based on and due to their worldview. Personal and interpersonal interactions at human scale are described through tool-use categories. A prescriptive framework for sustainability by design is developed stating conditions to guide systemic design interventions for preventing and remedying unsustainability within pro-active and reactive scenarios respectively. A descriptive model of interaction is developed to situate and enable understanding of interactions. The framework, scenarios and the model are illustrated using several cases related to sustaining human development.
6

Erweiterung der Verkehrsnachfragemodellierung um Aspekte der Raum- und Infrastrukturplanung

Schiller, Christian 11 July 2007 (has links)
Diese Arbeit stellt grundlegend zwei Modellentwicklungen der Verkehrsangebots- und Verkehrsnachfragemodellierung vor. Die erste Entwicklung bezieht sich auf die simultane Ziel- und Verkehrsmittelwahl in Abhängigkeit von Strukturgrößen und/oder Lagegunst. Es werden neue Randsummenbedingungen beschrieben und vorhandene neu definiert. Der neue Modellansatz erlaubt eine Bestimmung minimaler und maximaler Verkehrsaufkommen und stellt eine Erweiterung der theoretischen Grundlagen als auch der praktischen Anwendbarkeit dar. So können alle derzeit bekannten Randsummenbedingungen durch einen Algorithmus (auch innerhalb einer Quelle-Ziel-Gruppe) berechnet werden. Der zweite Ansatz ist ein Werkzeug, welches in Abhängigkeit des vorhandenen Verkehrsangebotes verkehrsplanerisch wünschenswerte quantitative Flächen- bzw. Gebietsnutzungen abschätzt. Aufbauend auf der Verkehrsangebots- und Verkehrsnachfragemodellierung werden Infrastrukturgrößen durch eine aufzustellende Zielfunktion (z. B. minimale Verkehrsarbeit), unter Beachtung vorhandener Freiheitsgrade der Flächennutzung je Verkehrsbezirk, optimiert. Diese Freiheitsgrade werden als minimale und maximale Strukturgrößengrenzen durch die Raum- und Stadtplanung definiert, womit sie den vielfältigen Einflussgrößen dieser Planungen unterliegen und dadurch städtebaulich verträglich sind. Der Modellansatz bildet die für die Infrastrukturplanung wichtigen Wechselwirkungen des durch den Stadt- und Verkehrsplaner angestrebten Systemoptimums (Infrastrukturgrößenverteilung eines Gebietes) mit dem durch den einzelnen Verkehrsteilnehmer angestrebten Nutzenoptimum (Verkehrsnachfrage) ab. / This work basically introduces two model developments of traffic supply and traffic demand modeling. The first development refers to the simultaneous destination and mode choice into dependence of structure sizes and/or accessibility. New constraints are described and available constraints were defined newly. The new model enables the determination of minimal and maximum volumes of traffic (constraints). The new explanatory model is an expansion of the theoretical bases and the practical applicability. So all currently known constraints can be calculated by one algorithm (also within an origin destination group). The second approach is a tool which describes desirable quantitative traffic planningly land uses against the available traffic supply. It uses an algorithm that keeps minimal and maximum structure size limits while it determining e.g. minimal traffic work. Within the algorithm the complete traffic demand will be calculated. The complete model shows the important interactions of the infrastructure planning by the town and transport planer (a striven system optimum) with the traffic demand by the single road user (a striven user equilibrium).

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