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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.
41

Control of Power Conversion Systems for the Intentional Islanding of Distributed Generation Units

Thacker, Timothy Neil 13 January 2006 (has links)
Within the past decade, talk has arisen of shifting the utility grid from centralized, radial sources to a distributed network of sources, also known as distributed generation (DG); in the wake of deregulation, the California energy crisis, and northeastern blackouts. Existing control techniques for DG systems are designed to operate a system either in the connected or disconnected (islanding) mode to the utility; thus not allowing for both modes to be implemented and transitioned between. Existing detection and re-closure algorithms can also be improved upon. Dependent upon the method implemented, detection algorithms can either cause distortions in the output or completely miss a disturbance. The present re-closure process to reconnect to the utility is to completely shutdown and wait five minutes. The proposed methods of this study improve upon existing methods, via simulation and hardware experimentation, for DG systems that can intentionally islanding themselves. The proposed, "switched-mode", control allows for continuous operation of the system during disturbances by transitioning the mode of control to reflect the change in the system mode (grid-connected or islanding). This allows for zero downtimes without detrimental transients. The proposed detection method can sense disturbances that other methods cannot; and within 25 ms (approximately 1.5 line-cycles at 60 Hz). This method is an improvement over other methods because it eliminates the need to purposely distort the outputs to sense a disturbance. The proposed re-closure method is an improvement over the existing method due to the fact that it does not require the system to de-energize before re-synchronizing and reconnecting to the utility. This allows for DGs to continuously supply power to the system without having to shut down. Results show that the system is generally ready to reconnect after 2 to 5 line cycles. / Master of Science
42

SATELLITE PAYLOAD CONTROL AND MONITORING USING PERSONAL COMPUTERS

Willis, James 10 1900 (has links)
International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Universal acceptance of the Windows NT operating system has made utilization of the personal computer (PC) platform for critical space operations a reality. The software attributes of the operating system allow PC products to attain the reliability necessary for secure control of on-orbit assets. Not only is the software more reliable, it supports better networking interfaces at higher speeds. The software upgrades that the Microsoft Corporation generates on a regular basis allow PCs to offer capabilities previously available only with UNIX-based solutions. As technology matures, PCs will operate faster, offer more graphical user interfaces, and give customers a lower cost versus performance choice. These reasons, and others to be discussed further, clearly demonstrate that PCs will soon take their place at the forefront of mission-critical ground station applications.
43

A Parallel-Series Two Bridge DC/DC Converter for PV Power Conditioning Systems Used in Hybrid Renewable Energy Systems

Servansing, Amish Ansuman 19 April 2012 (has links)
This thesis presents a parallel-series two-bridge DC/DC converter topology with the ability to operate with ZVS over a wide input and load range. The intended application is power conditioning systems (PCS) of photovoltaic (PV) arrays used in hybrid renewable energy system architectures. The proposed topology provides two degrees of freedom which allows the PV-PCS to regulate the DC-link voltage, while tracking the maximum power point (MPP) of the PV array. This topology distributes the main power into two bridges and the phase-shift between the two bridges and provides another degree of freedom for the PCS to track the MPP. The proposed topology is also able to achieve soft-switching over a wide range. The power conditioning system shows a modular structure to efficiently transfer the power to the load as the main power is divided between two bridges. In addition, the proposed control scheme provides complete decoupling between the input side controller from the output side controller in order to perform MPPT and regulate the the DC-link voltage simultaneously. A 2kW Experimental prototype has been provided to validate the feasibility and performance of the converter. Experimental results prove that the converter is able to regulate the DC-link voltage and track the maximum power extracted from the PV array simultaneously. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2012-04-18 19:51:43.405
44

Young South African children’s recognition of emotions as depicted by picture communication symbols

De Klerk, Hester Magdalena 21 October 2011 (has links)
Experiencing and expressing emotions is an essential part of psychological well-being. It is for this reason that most graphic symbol sets used in the field of AAC include an array of symbols depicting emotions. However, to date, very limited research has been done on children’s ability to recognise and use these symbols to express feelings within different cultural contexts. The purpose of the current study was to describe and compare Afrikaans and Sepedi speaking grade R children’s choice of graphic symbols when depicting four basic emotions, i.e. happy; sad; afraid; and angry. After ninety participants (44 Afrikaans and 46 Sepedi speaking) passed a pre-assessment task, they were exposed 24 emotions vignettes. Participants had to indicate the intensity the protagonist in the story would experience. The next step was for the participants to choose a graphic symbol from a 16 matrix overlay which they thought best represented the symbol and intensity. The results indicated a significant difference at a 1% level between the two groups’ selection of expected symbols to represent emotions. Afrikaans speaking participants more often chose expected symbols than Sepedi speaking participants to represent different basic emotions. Sepedi speaking participants made use of a larger variety of symbols to represent the emotions. Participants from both language groups most frequently selected expected symbols to represent happy followed by those for angry and afraid with expected symbols for sad selected least frequently. Except for a significant difference at the 1% level for happy no significant differences were present between the intensities selected by the different language groups for the other three basic emotions. No significant differences between the two gender groups’ choices of expected symbols to represent emotions or between the intensities selected by the different gender groups were observed. / Thesis (PhD)--University of Pretoria, 2011. / Centre for Augmentative and Alternative Communication (CAAC) / Unrestricted
45

Design of an Ultra-Low Phase Noise and Wide-Band Digital Phase Locked Loop for AWS and PCS Band Applications and CppSim Evaluation

Tiagaraj, Sathya Narasimman 27 September 2016 (has links)
No description available.
46

HEALTH STATUS AND THE DETERMINANTS OF HEALTH IN A CANADIAN OLD ORDER MENNONITE COMMUNITY

Fisher, Kathryn A. 10 1900 (has links)
<p>This thesis presents the results of a study exploring the health status and health determinants in two farming groups in Waterloo, Ontario, Canada: Old Order Mennonites (OOMs) and non-OOM farmers. Physical health and mental health are examined, and Canada’s 12 health determinants (excluding genetics) are included in the analysis. A survey was distributed to both groups in 2010 to obtain information on health status and determinants. Comparing the two groups reduces the likely impact of contextual features impacting both, such as local economic conditions. The mental component summary (MCS) and physical component summary (PCS) of the SF-12 were used to measure mental and physical health. The study compares health in the two populations, and uses ordinary least squares (multiple) regression to determine the relative importance of the determinants in shaping health. The study found that mental health is better in OOMs, mainly due to OOM women’s strong mental health. Physical health was worse in OOMs, and while true for both genders, OOM women appear to be particularly disadvantaged. There is overlap between the groups in the determinants shaping physical and mental health. In both groups, mental health is shaped by social interaction, stress and coping; and physical health by age, childhood disease history, coping and body mass index. This suggests these factors may be important across many populations facing different life circumstances, thus representing priorities for policy action. Interestingly, the key determinants shaping physical health in both groups do not include social factors such as social capital, although social factors do shape mental health (especially in OOMs). This may be due to the rural or farming status of the two groups, or differences between physical and mental health. Determining which is more likely requires reconciling the results of this study with others, an effort hampered by differences in models, methods and health outcomes employed.</p> / Doctor of Philosophy (PhD)
47

Design and Characterization of RFIC Voltage Controlled Oscillators in Silicon Germanium HBT and Submicron MOS Technologies

Klein, Adam Sherman 18 August 2005 (has links)
Advances in wireless technology have recently led to the potential for higher data rates and greater functionality. Wireless home and business networks and 3G and 4G cellular phone systems are promising technologies striving for market acceptance, requiring low-cost, low-power, and compact solutions. One approach to meet these demands is system-on-a-chip (SoC) integration, where RF/analog and digital circuitry reside on the same chip, creating a mixed-signal environment. Concurrently, there is tremendous incentive to utilize Si-based technologies to leverage existing fabrication and design infrastructure and the corresponding economies of scale. While the SoC approach is attractive, it presents major challenges for circuit designers, particularly in the design of monolithic voltage controlled oscillators (VCOs). VCOs are important components in the up or downconversion of RF signals in wireless transceivers. VCOs must have very low phase noise and spurious emissions, and be extremely power efficient to meet system requirements. To meet these specifications, VCOs require high-quality factor (Q) tank circuits and reduction of noise from active devices; however, the lack of high-quality monolithic inductors, along with low noise transistors in traditional Si technologies, has been a limiting factor. This thesis presents the design, characterization, and comparison of three monolithic 3-4 GHz VCOs and an integrated 5-6 GHz VCO with tunable polyphase outputs. Each VCO is designed around a differential -G_{M} core with an LC tank circuit. The circuits exploit two Si-based device technologies: Silicon Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) for a cross-coupled collectors circuit and Graded-Channel MOS (GC-MOS) transistors for a complementary (CMOS) implementation. The circuits were fabricated using the Motorola 0.4 μm CDR1 SiGe BiCMOS process, which consists of four interconnected metal layers and a thick copper (10 μm) metal bump layer for improved inductive components. The VCO implementations are targeted to meet the stringent phase noise specifications for the GSM/EGSM 3G cellular standard. The specifications state that the VCO output cannot exceed -162 dBc/Hz sideband noise at 20 MHz offset from the carrier. Simultaneously, oscillators must be designed to address other system level effects, such as feed-through of the local oscillator (LO). LO feed-through directly results in self-mixing in direct conversion receivers, which gives rise to unwanted corrupting DC offsets. Therefore, a system-level strategy is employed to avoid such issues. For example, multiplying the oscillator frequency by two or four times can help avoid self-mixing during downconversion by moving the LO out of the bandwidth of the RF front-end. Meanwhile, direct conversion or low-IF (intermediate frequency) receiver architectures utilize in-phase and quadrature (I/Q) downconversion signal recovery and image rejection. Any imbalance between the I and Q channels can result in an increase in bit-error-rate (BER) and/or decrease in the image rejection ratio (IRR). To compensate for such an imbalance, an integrated tunable polyphase filter is implemented with a VCO. Control voltages between the differential I and Q channels can be individually controlled to help compensate for I/Q mismatches. This thesis includes an introduction to design flow and layout strategies for oscillator implementations. A detailed comparison of the advantages and disadvantages of the SiGe HBTs and GC-MOS device in 3-4 GHz VCOs is presented. In addition, an overview of full-wave electromagnetic characterization of differential dual inductors is given. The oscillators are characterized for tuning range, output power, and phase noise. Finally, new measurement techniques for the 5-6 GHz VCO with a tunable polyphase filter are explored. A comparison between the time and frequency approaches is also offered. / Master of Science
48

Hanoi et Haiphong au contact de la colonisation : structuration et restructuration de la société urbaine en Indochine française (1887-1945) : le cas de Hanoi et de Haiphong / Hanoi and Haiphong in contact with the colonization : structuring and restructuring of the urban society in French Indochina (1887-1945) : the case of Hanoi and Haiphong

Okada, Tomokazu 31 May 2013 (has links)
Cette thèse tente d'étudier la structure sociale des villes coloniales en Indochine française. Il s'agit d'une étude sur l'histoire de l'influence de la colonisation sur la société et les habitants urbains au Viêtnam, en prenant principalement le cas de Hanoi et Haiphong dans la première moitié du XXe siècle.Aprés avoir bien examiné la méthode, la politique et l'organisation de la colonisation de l'Indochine, nous mettons d'abord les questions comme suit : comment les villes de Hanoi et Haiphong ont-elles été construites ? ; À quels problèmes ont-elles fait face dans les processus de sa formation et son développement ? Ensuite, nous avons jeté un regard sur les habitants à la ville coloniale de Hanoi en remarquant la répartition géographique et démographique des professions et catégories socioprofessionnelles (PCS), notamment des petits commerçants-artisans. Les cadres indochinois auraient peut-être mieux exploités surtout en ce qui concerne le salaire et niveau de vie à la veille de l'indépendance.De cela, on pourra relever certaines caractéristiques de la structure sociale et de la stratification sociale de la ville coloniale de Hanoi. À ce propos, nous analysons le mouvement social dans le contexte mondial de la crise économique après 1930 et l'application du réglementation général du travail en Indochine de 1936, en mettant en scène une grève des ouvriers déclenchée à Hanoi en 1937, qui a permis d'exécuter la politique sociale au même niveau que la métropole. En conclusion, cette grève "légale" a eu pour résultat une création de « nouveaux réseaux sociaux indigènes » en regroupant les patrons et les ouvriers par même profession au Nord-Viêtnam. / This Thesis examines the social structure of colonial cities in French Indochina, which means that it aimes to reveal link between the colonial system and the colonial society. But we're talking about a study of history of the influence of colonization on society and urban inhabitants in Vietnam. Therefor it will take the case of Hanoi and Haiphong during the first half of the twentieth century.After examining method, policy and organization of the Indochinese colonization, we ask some questions as follows : how Hanoi was built ; what problem this city was faced with in the process of its formation and development. This subject will be treated from a comparative perspective with one of the most principal city in Vietnam : Haiphong.Then, we are intersted in the inhabitants of colonial city Hanoi pointing out the geographic distribution of "professions et catégories socioprofessionnelles" (PCS : professions and social-occupational categories). The best part of this research is characterized by demography of new PCS, especially of small marchants and craftmen.From such approach, we extract some caracteristics of social structure and social stratification of colonial city Hanoi. In this connection, we analyze, moreover, social movement in the worldwide contexte of economic crisis after 1930 and application of labour law of Indochina in 1936, directing labour strike broke out at Hanoi in 1937, only which allowed exercise the social policy at the same level as metropolitain France. In conclusion, this "legal" strike had the effect of creating « a new indigenous social network » grouping management and workers into same professions in North-Vietnam.
49

筆記型電腦之使用對壽險業者營運之影響 / The Impacts From the Use of Notebook PCs On A Life Insurance Com- pany

蔡金德, Tsai,Chin Te Unknown Date (has links)
本研究的目的是要探討筆記型電腦對壽險業者所產生的影響,以及,筆記 型電腦在使用上所可能發生的效益與問題,俾對業者宜否引進筆記型電腦 和引進時應注意之事項提出建議。整個研究所欲探討的四個核心問題為 :1.目前筆記型電腦在壽險業內的應用範疇為何? 2.壽險業者採用筆記型 電腦與否,是否受到其本身之特徵、所採策略以及外在環境的影響? 3.筆 記型電腦如何影響公司的營運? 4.筆記型電腦對壽險業者營運績效的影響 如何?本論文屬於探索性研究,旨在發展一些假設供後續研究者從事驗證 性研究,及對後續研究提供一些建議。本研究在研究方法上是採用單一個 案研究的方式進行。而分析層級包括公司整體、公司內之部門以及個人等 三層。採行的資料蒐集方法則有:1.次級資料蒐集。2.人員深入訪談。3. 記錄表施測。4.問卷施測。其中關於筆記型電腦影響壽險銷售績效之探討 ,係用準實驗設計─不相等實驗組設計組前測後測設計─並輔以共變數分 析 (ANCOVA)、卡方檢定、平均數和標準差等統計方法來處理。由於整個 研究涵括了非數量分析與數量分析,因此,實際上已對部分假設進行了初 步的驗證。研究結論如下:1.壽險業者因筆記型電腦成本降低與產業競爭 加劇,故考慮引進使用筆記型電腦。2.採用筆記型電腦的壽險業者的共同 點為:中小規模,銷售多類壽險產品、尋求業績快速成長,且面臨較強烈 之市場競爭及較低之顧客需求可預測性。3.筆記型電腦在壽險業內的應用 範疇,仍侷限於壽險銷售活動上。只能算是輔助壽險銷售的工具,適合於 較機械化的銷售步驟。4.筆記型電腦的使用方式會受到教育訓練的影響, 且長期使用筆記型電腦可能讓業務人員產生依賴,因而降低業務人員計算 保費的能力。5.筆記型電腦在提昇個人業績上之心理效果較實質效果更明 顯。此外,「專業導向」的業務人員比「關係導向」者,更傾向於攜帶筆 記型電腦去從事壽險銷售活動。6.筆記型電腦對個人的工作滿意度的作用 並不明顯,而且業務人員資訊(使用)滿意度的高低,主要是取決於管理 實務上之配合程度。綜合而言,筆記型電腦的影響層級主要是在「個人」 ,它對業務人員個人的心理建設和績效確有幫助。至於公司整體的表現方 面,則因仍會受到其它因素的影響,故其作用較不明顯。
50

Gest?o de res?duos s?lidos: um estudo da conscientiza??o ambiental em uma cidade do Brasil / Gest?o de res?duos s?lidos: um estudo da conscientiza??o ambiental em uma cidade do Brasil / Waste solid management: a study on environmetal awareness in a city of Brazil / Waste solid management: a study on environmetal awareness in a city of Brazil

Santos, Esmeraldo Mac?do dos 09 September 2002 (has links)
Made available in DSpace on 2014-12-17T14:53:22Z (GMT). No. of bitstreams: 1 EsmeraldoMS.pdf: 701694 bytes, checksum: 2eb58a7ede296ca49c8a7bf7218b2208 (MD5) Previous issue date: 2002-09-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present study inserts on the international environmental thematic, approaching the integrated management of solid waste and the participation of the social actors in the search of the sustainable development. The awareness in combining it still describes a Selective Collection Program SCP of solid waste, in partnership with the municipal public power, in the development of joint actions that result in better alternatives of waste management in the urban centers, providing better life quality for the population and conservation of the environment. The aim of this research is to study problematic of the management of solid waste under the point of view of the environmental awareness and the participation of the population in a city of Brazil. In this matter, the target of the work is focusing on the strategy of solid waste management, through the attitudes and the respondents behaviors to aid in the making decision of the public manager related to the implantation of a selective collection program in Natal/RN. The methodology used in this work constitutes in the application of a questionnaire with scales of the type Likert being constituted of variables that compose the aspects of attitudes and of behaviors, besides a social-demographic scale. For analysis statistics is used the Pearson s Chi-Square Method in order to verify the dependence of the associations between the social-demographic variables and the attitude and the behavior ones. The results appear for a larger participation in a SCP, since this provides a better quality of life of the population (28,3 %), followed for offering a financial advantage (27,3%). Other results indicate the existence of the variables that exercise influence on the environmental awareness of the population to its demographic aspects / O presente estudo insere-se na tem?tica ambiental internacional, abordando a gest?o integrada de res?duos s?lidos e a participa??o dos atores sociais na busca do desenvolvimento sustent?vel atrav?s de sua conscientiza??o ambiental. Descreve ainda a conscientiza??o em integrar-se a um Programa de Coleta Seletiva PCS de res?duos s?lidos em parceria com o poder p?blico municipal, no desenvolvimento de a??es conjuntas que resultem em melhores alternativas de gest?o para os res?duos nos centros urbanos, proporcionando melhor qualidade de vida para a popula??o e preserva??o do meio ambiente. O objetivo desta pesquisa ? estudar a problem?tica da gest?o de res?duos s?lidos sob o ponto de vista da conscientiza??o e participa??o ambiental da popula??o em uma cidade do Brasil. Desta forma, o escopo do trabalho versa sobre a estrat?gia de gest?o de res?duos s?lidos, atrav?s das atitudes e comportamentos dos entrevistados para auxiliar na tomada de decis?o do gestor p?blico quanto ? implanta??o de um programa de coleta seletiva em Natal/RN. A metodologia empregada neste trabalho constitui na aplica??o de um question?rio com escalas do tipo Likert constituindo-se de vari?veis que comp?em os aspectos atitudinais e comportamentais, al?m de uma escala s?cio-demogr?fica. Foi utilizado na an?lise estat?stica o m?todo Chi-Square de Pearson de modo a verificar a depend?ncia das associa??es entre as vari?veis s?cio-demogr?ficas e as vari?veis atitudinais e comportamentais. Os resultados apontam para uma maior participa??o em um PCS, desde que este proporcione uma melhor qualidade de vida da popula??o (28,3 %), seguido por oferecer uma vantagem financeira (27,3%). Outros resultados indicam a exist?ncia de vari?veis que exercem influ?ncia sobre a conscientiza??o ambiental da popula??o quanto ao seus aspectos demogr?ficos

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