Based on constitutive equations of piezoelectricity and two-port modeling method, the models of piezoelectric materials are investigated. The equivalent circuit models of the piezoelectric element in the energy harvesting system are explored. It is found that there exists an optimal external impedance that gives the maximum output power. Experiments are conducted to verify the optimal impedance theory. / The energy storage devices in the piezoelectric energy harvesting system are analyzed. The charge/discharge efficiencies of the energy storage devices are mainly considered. Based on the analysis of the electric characteristics of the energy storage devices, we find the leakage resistances of the energy storage devices are the dominant factor that influences the charge/discharge efficiency in the piezoelectric energy harvesting system. A quick test method is proposed to experimentally study the charge/discharge efficiencies of the energy storage devices. The experimental results verify our findings. Adaptability, lifetime, and protection circuit of the energy storage devices are also discussed. It can be concluded that the supercapacitors are suitable and more attractive than the rechargeable batteries to store the energy in the piezoelectric energy harvesting system. / Two schemes of piezoelectric energy harvesting circuits are analyzed: one-stage and two-stage energy harvesting schemes. The efficiency of the two-stage harvesting scheme is found to be related to several factors including the energy storage device voltage. Analysis and experiments using one-stage energy harvesting circuit to harvest a varying excitation source are explored. The results show that one-stage energy harvesting scheme can achieve higher efficiency than the two-stage scheme towards a range of energy storage voltages. / Using piezoelectric elements to harvest energy from ambient vibration has been of great interest recently. Because the power harvested from the piezoelectric elements is relatively low, energy storage devices are needed to accumulate the energy for intermittent use and energy harvesting circuits are applied to transfer the electrical energy from the sources to the storage devices. Therefore, a piezoelectric energy harvesting system can be basically divided into three parts: the energy source, the energy harvesting circuit, and the energy storage device. These three parts are explored in this thesis. / Guan Mingjie. / "September 2006." / Adviser: Wei-Hsin Liao. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1822. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 123-128). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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O presente trabalho busca apreender as representaÃÃes sociais de trabalhadores e trabalhadoras do lixo e suas prÃticas cotidianas, a partir da experiÃncia do Centro ComunitÃrio Santa Terezinha, com o Programa Reciclando - Rede SolidÃria de Coleta Seletiva. Parte-se do pressuposto de que as representaÃÃes sociais se constroem no cotidiano e orientam as aÃÃes das pessoas. Nesse processo de interaÃÃo entre a aÃÃo e as reflexÃes, as representaÃÃes sociais modificam as prÃticas sociais e sÃo modificadas pelas mesmas. Na reflexÃo acerca do trabalho realizado pelos agentes analisa-se a forma de ocupaÃÃo espacial que se deu no morro Santa Terezinha bem como os novos sentidos atribuÃdo Ãs vias pÃblicas como locus de trabalho e nÃo como via de acesso que se dà nos bairros nobres ao redor do Morro. A pesquisa foi realizada com agentes recicladores do referido Centro. Os agentes buscam resignificar seu trabalho atribuindo um conjunto de regras que os diferenciam dos outros profissionais que se ocupam da mesma atividade na Ãrea da pesquisa. Dessa forma estes procuram superar os preconceitos existentes em relaÃÃo à atividade da coleta. Observa-se que a coleta seletiva nÃo se dà em virtude da ausÃncia de um investimento em educaÃÃo ambiental que possibilitaria a separaÃÃo do lixo na prÃpria fonte geradora. Os poucos clientes que separam à resultado da iniciativa pontual dos agentes que negociam em alguns condomÃnios essa separaÃÃo. O cotidiano dos agentes consiste em percorrer as ruas e remexendo o lixo deixado nas calÃadas recolher o material reciclÃvel para posterior venda dos mesmos. Transitar nas ruas competindo com os carros representa um risco para os agentes. Outro risco a que estÃo submetidos à o de adquirir doenÃas em decorrÃncia do contato direto com materiais contaminados. A falta de seguranÃas trabalhistas preocupa os agentes. Acredita-se que se impostos sÃo pagos para assegurar a limpeza urbana esse trabalho deveria ser subsidiado pelo poder pÃblico de forma a garantir uma melhor condiÃÃo de vida e trabalho aos agentes. Os problemas ambientais apontam para a urgÃncia de um desenvolvimento sustentÃvel para a sociedade. EducaÃÃo ambiental e coleta seletiva do lixo sÃo instrumentos fundamentais na luta pela sustentabilidade.

The design of a point focus, distributed receiver solar power system is presented. It is shown that a two axis concentrator, with a two axis solar tracker and drive, has significant advantages over other possible optical systems. It is further shown that each concentrator should have its own optical receiver attached. A new dish and mount design is presented. This design provides a much stronger, lower cost dish. It further provides an easy way to attach a cheap drive system. The new mount is a gimbal, or cradle, in which the dish is mounted. The cradle provides a polar axis mount for the dish. The dish and cradle are very strong and will survive high winds in any orientation. Several other significant improvements to other parts of the solar energy collection system are presented. These include an improvement to the receiver cavity design, a thermal shield and secondary reflector to be added to the receiver, an improved steam output system for the receiver, a plumbing system that eliminates the need for flexible couplings in the water lines, and a water distribution system that eliminates nearly half of the thermal insulation needed on the pipes going through the collector array. Two economic optimizations are presented. The first analyses the return on investment for various dish spacings. The second analyses the cost per unit area of the concentrator dish and mount. It is found that the optimum dish diameter is ten meters and the optimum packing density in a conventional array is about 13%. / Graduation date: 1995

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1983. / Vita. Abstract. Includes bibliographical references (leaves 80-82). Also available via the Internet.

Unglazed transpired solar collectors (UTSCs) preheat makeup ventilation air for buildings, thereby reducing energy used for heating. The performance of the UTSC is dependent on the heat loss from the absorber plate, which is strongly affected by the wind speed. To date, correlations to determine UTSC heat loss are limited to flat or sinusoidal plate corrugations. In reality, trapezoidal corrugations have been added to UTSCs to provide them with structural stiffness. These corrugations prevent the attachment of the flow to the absorber plate and cause flow separation which increases the heat loss. In this study, a numerical simulation of a UTSC with trapezoidal shape corrugation has been performed to investigate the heat loss in the developing region due to wind on the UTSCs. It has been found that heat loss from new configuration is up to three times greater than the heat loss from a perforated flat absorber plate. A correlation of heat loss due to the wind speed and suction velocity was developed. This study also includes an evaluation of the effectiveness in the asymptotic region. In this case, wind speed had no effect. A correlation was derived in terms of suction velocity.

Thesis--University of Michigan.

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The shared language, attitudes, practices and patterns of those who participate in “collecting" in the lower mainland area of British Columbia are described. Recurring themes and patterns emerge in the analysis of data obtained through interviews with thirty collector-informants. The generalizability of collecting as a phenomenon which exists outside of what is being collected is established. Collectors' roles as curators and the serious and consuming aspects of collecting, including the cycles of collecting, affection and sentiment held toward collected objects, and the strategies and approaches to the process of collecting are discussed. Propositions set out by previous researchers Belk, Danet and Katriel are examined in light of the data. Implications for museum studies and museum education specifically, are considered.

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