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Well-defined silica supported bimetallic catalysts Pt100-x Pdx (where x is the molar ratio of Pd) are prepared by Surface Organometallic Chemistry (SOMC) via controlled decomposition of Pd2(allyl)2Cl2 on Pt/SiO2. For comparison purposes, Pt100-x Pdx bimetallic catalysts is also prepared by ion-exchange (IE). According to the results of STEM, XAS and H2 chemisorption, all bimetallic nanoparticles, prepared using neither SOMC nor IE, produce discrete formation of monometallic species (either Pt or Pd). Most catalysts exhibit a narrow particle size distribution with an average diameter ranging from 1 to 3 nm for samples prepared by IE and from 2 to 5 nm for the ones synthesized by SOMC. For all catalysts investigated in the present work, iso-butane reaction with hydrogen under differential conditions (conversions below 5%) leads to the formation of methane and propane (hydrogenolysis), n-butane (isomerization), and traces of iso-butylene (dehydrogenation). The total rate of reaction decreases with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate (expressed as moles converted per total surface metal per second) of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the results suggest a selective coverage of Pt (100) surface by a Pd layer, followed by a buildup of Pd overcoat onto a Pd layer assuming that each metal keeps its intrinsic catalytic properties. There is no mutual electronic charge transfer between the two metals (DFT). For the PtPd catalysts prepared by IE, the catalytic behavior cannot simply be explained by a surface coverage of highly active Pt metal by less active Pd (not observed), suggesting there is formation of a surface alloy between Pt and Pd collaborated by EXAFS and DFT. The catalytic results are explained by a simple structure activity relationship based on the previously proposed mechanism of C-H bond and C-C Bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

Direction of the master's thesis is design and construct electronic device for testing available accumulators. Than there are in detail subscribe some metods of charging cells and their right usage to select type of cells. Also eventually problems that can become if the choice is false. Next part contains description of principles as several type accumulator works and their loading characteristic witch are important know for choose the best testing way. The most important knowledge is detection of stop point charging when accumulators are charged and following charging can be dangerous. Because there are more methods to detect this point so in thesis are overwrite. The most important part is design of tester. That is mapped to more segments witch communicating together. Controller part of intelligent tester contains ATmega128 microcontroller so there is present a passage of program code. Last section of master's thesis describe a physical consruction and explain division for smaller parts and hole process of tester function.

This work is aimed to design power supply for nodes of wireless sensors networks using solar energy in indoor spaces. The proposal is made for the particular layout, but the process described can be applied generally. The result is the proposed involvement of the operating power circuit for node of wireless sensor network used indoors.

The non-isolated POL converters are widely used in computers, telecommunication systems, portable electronics, and many other applications. These converters are usually constructed using discrete components, and operated at a lower frequency around 200 ~ 600 kHz to achieve a decent efficiency at the middle of 80's%. The passive components, such as inductors and capacitors, are bulky, and they occupy a considerable foot-print. As the power demands increase for POL converters and the limited real estate of the mother board, the POL converters must be made significantly smaller than what they have demonstrated to date. To achieve these goals, two things have to happen simultaneously. The first is a significant increase in the switching frequency to reduce the size and weight of the inductors and capacitors. The second is to integrate passive components, especially magnetics, with active components to realize the needed power density. Today, this concept has been demonstrated at a level less than 5A and a power density around 300-700W/in3 by using silicon-based power semiconductors. This might address the need of small hand-held equipment such as PDAs and smart phones. However, it is far from meeting the needs for applications, such as netbook, notebook, desk-top and server applications where tens and hundreds of amperes are needed. After 30 years of silicon MOSFET development, the silicon has approached its theoretical limits. The recently emerged GaN transistors as a possible candidate to replace silicon devices in various power conversion applications. GaN devices are high electron mobility transistors (HEMT) and have higher band-gap, higher electron mobility, and higher electron velocity than silicon devices, and offer the potential benefits for high frequency power conversions. By implementing the GaN device, it is possible to build the POL converter that can achieve high frequency, high power density, and high efficiency at the same time. GaN technology is in its early stage; however, its significant gains are projected in the future. The first generation GaN devices can outperform the state-of-the-art silicon devices with superior FOM and packaging. The objective of this work is to explore the design of high frequency, high power density 12 V input POL modules with GaN devices and the 3D integration technique. This work discusses the fundamental differences between the enhancement mode and depletion mode GaN transistors, the effect of parasitics on the performance of the high frequency GaN POL, the 3D technique to integrate the active layer with LTCC magnetic substrate, and the thermal design of a high density module using advanced substrates with improved thermal conductivity. The hardware demonstrators are two 12 V to 1.2 V highly integrated 3D POL modules, the single phase 10 A module and two phase 20 A module, all built with depletion mode GaN transistors and low profile LTCC inductors. / Master of Science

The purpose of this dissertation is to help explain how and why two revolutionary national leaders of Cambodia–Lon Nol and Pol Pot, particularly the latter–had spectacular failures and became pseudotransformational leaders. It aims to build a proposition or theory that revolutionary leaders in the public sector, particularly of undemocratic regimes, tend to become pseudotransformational leaders when a) they lack certain components of emotional intelligence (EI) and/or b) adopt certain leadership styles and use them inappropriately. The author used a mixed methods comparative case study with the quantitative method nested in the qualitative one. He collected empirical data from a quantitative questionnaire survey and qualitative individual interviews and other print and audio-visual data from various primary sources, including the Documentation Center of Cambodia (DC-Cam) and the Extraordinary Chambers in the Courts of Cambodia (E), as well as from secondary sources such as books and articles. The author administered the survey to a sample of over 400 Cambodian participants from different socio-economic and political backgrounds and sectors and conducted individual in-depth interviews with 38 participants selected from the sample. Overall, this study’s findings tend to support the proposed theory, albeit with some limitations. In the main, both Lon Nol and Pol Pot were coercive and authoritative leaders. Only Pol Pot was a pacesetting leader. Both leaders severely lacked emotional intelligence, especially the domain of self-awareness. This dissertation makes some contribution to the existing literature on leadership in general and bad leadership in particular and, more specifically, on the two leaders’ leadership qualities, in that it proposes a linkage between leadership ineffectiveness or failures and lack of emotional intelligence and improper use of leadership styles. The practical implications or lessons drawn from the dissertation include the following. First, a national leader’s distance or isolation from the masses can undermine her or his emotional intelligence and/or leadership effectiveness. Second, national/public interest should take precedence over the leader’s other interests and partisan politics. Third, a leadership team of friends or cronies is, more often than not, harmful to quality decision/policy making and administration because it tends to foster groupthink.

In this thesis, the stabilization and tracking problem of the Van der Pol oscillator is studied by using advanced control techniques. First, the linear state feedback and linear adaptive state feedback controllers for the stabilization problem are designed. Then, non-linear state feedback and output feedback controllers are proposed for the tracking problem with known parameters. Finally, a dynamic output feedback controller based on adaptive backstepping technique is introduced for the tracking problem when all parameters of the Van der Pol system are unknown.

A generalized low order model (LOM) for the fluctuating lift coefficient caused by vortex shedding from a tandem cylinder pair is proposed to expand upon models from previous authors. This model could provide a reduced computational time method for collecting qualitative and quantitive data from a tandem shedding pair. A delay coupled system with sufficient bifurcation characteristics is developed to account for the different flow regimes (extended-body, reattachment, and co-shedding) which occur as cylinder spacing is varied. Coefficient and parameter fitting is performed to fit experimental data. Finally, results and physical interpretations of the interactions in the model are discussed. It was found that many aspects of the flow at varying L/D ratios could be modeled by the LOM, including vortex suppression in the forward cylinder at the critical spacing, and amplitude growth in the rear cylinder in the co-shedding regime.

Point-of-load (POL) converters have been used extensively in IT products. Today, almost every microprocessor is powered by a multi-phase POL converter with high output current, which is also known as voltage regulator (VR). In the state-of-the-art VRs, the circuits are mostly constructed with discrete components and situated on the motherboard, where it can occupy more than 1/3 of the footprint of the motherboard. A compact POL is desirable to save precious space on motherboards to be used for some other critical functionalities. Recently, industry has released many modularized POL converters, in which the bulky inductor is integrated with the active components to increase the power density. This concept has been demonstrated at current levels less than 5A and power density around 600-1000W/in³. This might address the needs of small hand-held equipment such as smart phones, but it is far from meeting the needs for the applications such as laptops, desktops and servers, where tens and hundreds of amperes are needed. A 3D integrated POL module with an output current of tens of ampere has been successfully demonstrated at the Center for Power Electronic Systems (CPES), Virginia Tech. In this structure, the inductor is elaborated with low temperature co-fire ceramic (LTCC) ferrite, as a substrate where the active components are placed. The lateral flux inductor is proposed to achieve both a low profile and high power density. Generally, the size of the inductor can be continuously shrunk by raising the switching frequency. The emerging gallium-nitride (GaN) power devices enable the creation and use of a multi-MHz, high efficiency POL converter. This dissertation firstly explores the LTCC inductor substrate design in the multi-MHz range for a high-current POL module with GaN devices. The impacts of different frequencies and different LTCC ferrite materials on the inductor are also discussed. Thanks to the DC flux cancellation effect, the inverse coupled inductor further improves the power density of a 20A, 5MHz two-phase POL module to more than 1kW/in³. An FEA simulation model is developed to study the core loss of the lateral flux coupled inductor, which shows the inverse coupling is also beneficial for core loss reduction. The ceramic-based 3D integrated POL module, however, is not widely adopted in industrial products because of the relatively high cost of the LTCC ferrite material and complicated manufacturing process. To solve that problem, a printed circuit board (PCB) inductor substrate with embedded alloy flake composite core is proposed. The layerwise magnetic core is laminated into a multi-layer PCB, and the winding of the inductor then is formed by the copper layers and conventional PCB vias. As a demonstration of system integration, a 20A, 1.5MHz integrated POL module is designed and fabricated based on a 4-layer PCB with embedded flake core, which realizes more than 85% efficiency and 600W/in³ power density. The application of standardized PCB processes reduces the cost for manufacturing the integrated modules due to the easy automation and the low temperature manufacturing process. Combining the PCB-embedded coupled inductor substrate and advanced control strategy, the two-phase 40A POL modules are elaborated as a complete integrated laptop VR solution. The coupled inductor structure is slightly modified to improve its transient performance. The nonlinearity of the inductance is controlled by adding either air slots or low permeability magnetic slots into the leakage flux path of the coupled inductor. Then the leakage flux, which determines the transient response of the coupled inductor, can be well controlled. If we directly replace the discrete VR solution with the proposed integrated modules, more than 50% of the footprint on the motherboard can be saved. Although the benefits of the lateral flux inductor have been validated in terms of its high power density and low profile, the planar core is excited under very non-uniform flux. Some parts of the core are even pushed into the saturation region, which totally goes against the conventional sense of magnetic design. The final part of this dissertation focuses on evaluating the performance of the planar core with variable flux. The counterbalance between DC flux and AC flux is revealed, with which the AC flux and the core loss density are automatically limited in the saturated core. The saturation is essentially no longer detrimental in this special structure. Compared with the conventional uniform flux design, the variable flux structure extends the operating point into the saturation region, which gives better utilization of the core. In addition, the planar core with variable flux also provides better thermal management and more core loss reduction under light load. As conclusions, this research first challenges the conventional magnetic design rules, which always assumes uniform flux. The unique characteristics and benefits of the variable flux core are proved. As an example of taking advantages of the lateral flux inductor, the PCB integrated POL modules are proposed and demonstrated as a high-density VR solution. The integrated modules are cost-effective and ready to be commercialized, which could enable the next technological innovation for the whole computing and telecom industry. / Ph. D.

Made available in DSpace on 2015-04-14T13:46:52Z (GMT). No. of bitstreams: 1 412614.pdf: 2660281 bytes, checksum: d205a79fb7c75040c54fcd18ed6fc044 (MD5) Previous issue date: 2009-03-30 / Esta disserta??o trata dos quarenta e um casos de expurgos de professores da Universidade Federal do Rio Grande do Sul (UFRGS) ocorridos em 1964 e 1969, durante a Ditadura Civil- Militar (1964-1985). Buscou-se analisar o recurso ? medida repressiva quanto ?s suas causas, quanto ?s institui??es respons?veis por sua aplica??o e quanto aos modos de execu??o das mesmas, percebendo-a como parte de um conjunto de medidas repressivas utilizadas no per?odo para a domina??o via coer??o. Como fontes, foram utilizados: documentos da UFRGS e de outras institui??es (MEC, DSI/MEC, CISMEC, DOPS/RS e 3? Ex?rcito); entrevistas e depoimentos; legisla??o; Di?rio Oficial da Uni?o e peri?dicos de Porto Alegre e Pelotas; publica??es e discursos da ?poca. A base metodol?gica consistiu da an?lise cr?tica das fontes, adotando-se a perspectiva da curiosidade epistemol?gica (P. Freire). Procurou-se observar suas especificidades, sujeitos produtores e contextos de produ??o. Quanto ?s fontes orais, optou-se pelo uso de informantes (P. Thompson) e de entrevistas tem?ticas semiestruturadas. O embasamento te?rico alicer?ou-se na tradi??o marxista, com ?nfase para A. Gramsci. Em todos os casos analisados, os expurgos foram promovidos com a inten??o de reprimir indiv?duos e grupos percebidos, por setores da sociedade pol?tica e por setores da universidade, como amea?as reais ou potenciais ao bloco dominante, em fun??o de motivos diversos, derivados de pelo menos um dos seguintes fatores: perfis pol?tico-ideol?gicos; v?nculos pol?tico-partid?rios com partidos e movimentos pol?ticos de oposi??o; e a??es diversas (como a defesa de estudantes e protestos contra expurgos) suposta ou efetivamente praticadas dentro ou fora da institui??o. A par disso, observou-se que, em absolutamente nenhum caso, os expurgos foram promovidos por corrup??o ou improbidade administrativa qualquer, mas apenas por motivos pol?tico-ideol?gicos. Em rela??o ?s institui??es respons?veis pela aplica??o do expurgo, verificou-se que majoritariamente eram externas ? universidade e, somente em casos excepcionais, internas ? mesma. Sobre os modos de execu??o dos afastamentos sum?rios, em todos os casos percebeu-se a atua??o de indiv?duos e institui??es externos e internos ? universidade. Entretanto, quanto ao processo decis?rio sobre quais indiv?duos deveriam ser expurgados, foram identificados tr?s tipos distintos: interno, quando foi realizado exclusivamente no interior da universidade; externo, quando se deu em institui??o externa (independentemente de ter contado com a participa??o de setores da UFRGS nos est?gios preliminares de investiga??o ); e indireto, quando o pr?prio expurgado tomou a iniciativa de se afastar da institui??o, demitindo-se, exonerando-se ou simplesmente abandonando o cargo, em fun??o de constrangimentos relacionados com o contexto ditatorial. Tamb?m foi poss?vel constatar e analisar a atua??o de setores da estrutura universit?ria no controle pol?tico-ideol?gico de docentes, discentes e servidores t?cnico-administrativos, inclusive atrav?s da cria??o de ?rg?os para esse fim (CEIS/UFRGS e ASI/UFRGS) e do estabelecimento de v?nculos com o Aparato Repressivo.Percebeu-se a atua??o do MEC no controle pol?tico-ideol?gico direto e na repress?o a indiv?duos e grupos no interior da universidade, bem como a rela??o entre tal minist?rio e o Aparato Repressivo. Observou-se ainda a cria??o (CISMEC) e a reativa??o/adapta??o (DSI/MEC) de ?rg?os de seguran?a e informa??es no interior da estrutura do MEC, para a execu??o de tarefas repressivas e de investiga??o pol?tico-ideol?gica, aprimorando o v?nculo entre o referido minist?rio e o Aparato Repressivo.