10 resultados para Electronic apparatus and appliances -- Power supply

em Digital Commons @ DU | University of Denver Research


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This dissertation uses a political ecology approach to examine the relationship between tourism development and groundwater in southwest Nicaragua. Tourism in Nicaragua is a booming industry bolstered by ‘unspoiled’ natural beauty, low crime rates, and government incentives. This growth has led to increased infrastructure, revenue, and employment opportunities for many local communities along the Pacific coast. Not surprisingly, it has also brought concomitant issues of deeper poverty, widening gaps between rich and poor, and competition over natural resources. Adequate provisions of freshwater are necessary to sustain the production and reproduction of tourism; however, it remains uncertain if groundwater supplies can keep pace with demand. The objective of this research is to assess water supply availability amidst tourism development in the Playa Gigante area. It addresses the questions: 1) are local groundwater supplies sufficient to sustain the demand for freshwater imposed by increased tourism development? and 2) is there a power relationship between tourism development and control over local freshwater that would prove inequitable to local populations? Integrating the findings of groundwater monitoring, geological mapping, and ethnographic and survey research from a representative stretch of Pacific coastline, this dissertation shows that diminishing recharge and increased groundwater consumption is creating conflict between stakeholders with various levels of knowledge, power, and access. Although national laws are structured to protect the environment and ensure equitable access to groundwater, the current scramble to secure water has powerful implications on social relations and power structures associated with tourism development. This dissertation concludes that marginalization due to environmental degradation is attributable to the nexus of a political promotion of tourism, poorly enforced state water policies, insufficient water research, and climate change. Greater technical attention to hydrological dynamics and collaboration amongst stakeholders are necessary for equitable access to groundwater, environmental sustainability, and profitability of tourism.

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The goal of this study is to better understand the genetic basis of Reading Disability (RD) and Attention Deficit Hyperactivity Disorder (ADHD) by examining molecular G x E interactions with parental education for each disorder. Research indicates that despite sharing genetic risk factors, RD and ADHD are influenced by different types of G x E interactions with parental education - a diathesis stress interaction in the case of ADHD and a bioecological interaction in RD. In order to resolve this apparent paradox, we conducted a preliminary study using behavioral genetic methods to test for G x E interactions in RD and the inattentive subtype of ADHD (ADHD-I) in the same sample of monozygotic and dizygotic Colorado Learning Disabilities Research Center same-sex twin pairs (DeFries et al., 1997), and our findings were consistent with the literature. We posited a genetic hypothesis for this opposite pattern of interactions, which suggests that only genes specific to each disorder enter into these opposite interactions, not the shared genes underlying their comorbidity. This study sought to further investigate this paradox using molecular genetics methods. We examined multiple candidate genes identified for RD or related language phenotypes and those identified for ADHD for G x E interactions with parental education. The specific aims of this study were as follows: 1) partition known risk alleles for RD and/or related language phenotypes and ADHD-I into those which are pleiotropic and non-pleiotropic by testing each risk allele for association with both RD and ADHD-I, 2) explore the main effects of parental education on both RD and ADHD-I, 3) address G-E correlations, and 4) conduct exploratory G x E interaction analyses in order to test the genetic hypothesis. Analyses suggested a number of pleiotropic genes that influence both RD and ADHD; however, results did not remain after correcting for multiple comparisons. Although exploratory G x E interaction findings were not significant after multiple comparison correction, results suggested a G x E interaction in the bioecological direction with KIAA0319, parental education, and ADHD-I. Given the limited power in the current study, replication of these findings with larger samples is necessary.

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The purpose of this research was to apply the use of direct ablation plasma spectroscopic techniques, including spark-induced breakdown spectroscopy (SIBS) and laser-induced breakdown spectroscopy (LIBS), to a variety of environmental matrices. These were applied to two different analytical problems. SIBS instrumentation was adapted in order to develop a fieldable monitor for the measurement of carbon in soil. SIBS spectra in the 200 nm to 400 nm region of several soils were collected, and the neutral carbon line (247.85 nm) was compared to total carbon concentration determined by standard dry combustion analysis. Additionally, Fe and Si were evaluated in a multivariate model in order to determine their impacts on the model's predictive power for total carbon concentrations. The results indicate that SIBS is a viable method to quantify total carbon levels in soils; obtaining a good correlation between measured and predicated carbon in soils. These results indicate that multivariate analysis can be used to construct a calibration model for SIBS soil spectra, and SIBS is a promising method for the determination of total soil carbon. SIBS was also applied to the study of biological warfare agent simulants. Elemental compositions (determined independently) of bioaerosol samples were compared to the SIBS atomic (Ca, Al, Fe and Si) and molecular (CN, N2 and OH) emission signals. Results indicate a linear relationship between the temporally integrated emission strength and the concentration of the associated element. Finally, LIBS signals of hematite were analyzed under low pressures of pure CO2 and compared with signals acquired with a mixture of CO2, N2 and Ar, which is representative of the Martian atmosphere. This research was in response to the potential use of LIBS instrumentation on the Martian surface and to the challenges associated with these measurements. Changes in Ca, Fe and Al lineshapes observed in the LIBS spectra at different gas compositions and pressures were studied. It was observed that the size of the plasma formed on the hematite changed in a non-linear way as a function of decreasing pressure in a CO2 atmosphere and a simulated Martian atmosphere.

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Development of transparent oxide semiconductors (TOS) from Earth-abundant materials is of great interest for cost-effective thin film device applications, such as solar cells, light emitting diodes (LEDs), touch-sensitive displays, electronic paper, and transparent thin film transistors. The need of inexpensive or high performance electrode might be even greater for organic photovoltaic (OPV), with the goal to harvest renewable energy with inexpensive, lightweight, and cost competitive materials. The natural abundance of zinc and the wide bandgap ($sim$3.3 eV) of its oxide make it an ideal candidate. In this dissertation, I have introduced various concepts on the modulations of various surface, interface and bulk opto-electronic properties of ZnO based semiconductor for charge transport, charge selectivity and optimal device performance. I have categorized transparent semiconductors into two sub groups depending upon their role in a device. Electrodes, usually 200 to 500 nm thick, optimized for good transparency and transporting the charges to the external circuit. Here, the electrical conductivity in parallel direction to thin film, i.e bulk conductivity is important. And contacts, usually 5 to 50 nm thick, are optimized in case of solar cells for providing charge selectivity and asymmetry to manipulate the built in field inside the device for charge separation and collection. Whereas in Organic LEDs (OLEDs), contacts provide optimum energy level alignment at organic oxide interface for improved charge injections. For an optimal solar cell performance, transparent electrodes are designed with maximum transparency in the region of interest to maximize the light to pass through to the absorber layer for photo-generation, plus they are designed for minimum sheet resistance for efficient charge collection and transport. As such there is need for material with high conductivity and transparency. Doping ZnO with some common elements such as B, Al, Ga, In, Ge, Si, and F result in n-type doping with increase in carriers resulting in high conductivity electrode, with better or comparable opto-electronic properties compared to current industry-standard indium tin oxide (ITO). Furthermore, improvement in mobility due to improvement on crystallographic structure also provide alternative path for high conductivity ZnO TCOs. Implementing these two aspects, various studies were done on gallium doped zinc oxide (GZO) transparent electrode, a very promising indium free electrode. The dynamics of the superimposed RF and DC power sputtering was utilized to improve the microstructure during the thin films growth, resulting in GZO electrode with conductivity greater than 4000 S/cm and transparency greater than 90 %. Similarly, various studies on research and development of Indium Zinc Tin Oxide and Indium Zinc Oxide thin films which can be applied to flexible substrates for next generation solar cells application is presented. In these new TCO systems, understanding the role of crystallographic structure ranging from poly-crystalline to amorphous phase and the influence on the charge transport and optical transparency as well as important surface passivation and surface charge transport properties. Implementation of these electrode based on ZnO on opto-electronics devices such as OLED and OPV is complicated due to chemical interaction over time with the organic layer or with ambient. The problem of inefficient charge collection/injection due to poor understanding of interface and/or bulk property of oxide electrode exists at several oxide-organic interfaces. The surface conductivity, the work function, the formation of dipoles and the band-bending at the interfacial sites can positively or negatively impact the device performance. Detailed characterization of the surface composition both before and after various chemicals treatment of various oxide electrode can therefore provide insight into optimization of device performance. Some of the work related to controlling the interfacial chemistry associated with charge transport of transparent electrodes are discussed. Thus, the role of various pre-treatment on poly-crystalline GZO electrode and amorphous indium zinc oxide (IZO) electrode is compared and contrasted. From the study, we have found that removal of defects and self passivating defects caused by accumulation of hydroxides in the surface of both poly-crystalline GZO and amorphous IZO, are critical for improving the surface conductivity and charge transport. Further insight on how these insulating and self-passivating defects cause charge accumulation and recombination in an device is discussed. With recent rapid development of bulk-heterojunction organic photovoltaics active materials, devices employing ZnO and ZnO based electrode provide air stable and cost-competitive alternatives to traditional inorganic photovoltaics. The organic light emitting diodes (OLEDs) have already been commercialized, thus to follow in the footsteps of this technology, OPV devices need further improvement in power conversion efficiency and stable materials resulting in long device lifetimes. Use of low work function metals such as Ca/Al in standard geometry do provide good electrode for electron collection, but serious problems using low work-function metal electrodes originates from the formation of non-conductive metal oxide due to oxidation resulting in rapid device failure. Hence, using low work-function, air stable, conductive metal oxides such as ZnO as electrons collecting electrode and high work-function, air stable metals such as silver for harvesting holes, has been on the rise. Devices with degenerately doped ZnO functioning as transparent conductive electrode, or as charge selective layer in a polymer/fullerene based heterojunction, present useful device structures for investigating the functional mechanisms within OPV devices and a possible pathway towards improved air-stable high efficiency devices. Furthermore, analysis of the physical properties of the ZnO layers with varying thickness, crystallographic structure, surface chemistry and grain size deposited via various techniques such as atomic layer deposition, sputtering and solution-processed ZnO with their respective OPV device performance is discussed. We find similarity and differences in electrode property for good charge injection in OLEDs and good charge collection in OPV devices very insightful in understanding physics behind device failures and successes. In general, self-passivating surface of amorphous TCOs IZO, ZTO and IZTO forms insulating layer that hinders the charge collection. Similarly, we find modulation of the carrier concentration and the mobility in electron transport layer, namely zinc oxide thin films, very important for optimizing device performance.

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This dissertation engages the question of why German political elites accepted the use of force during the 1990s and started to commit the country's armed forces to multilateral peacekeeping missions. Previous governments of the Federal Republic had opposed foreign deployment of the military and Germany was characterized by a unique strategic culture in which the efficacy of military force was widely regarded as negative. The rediscovery of the use of force constituted a significant reorientation of German security policy with potentially profound implications for international relations. I use social role theory to explain Germany's security policy reorientation. I argue that political elites shared a national role conception of their country as a dependable and reliable ally. Role expectations of the international security environment changed as a result of a general shift to multilateral intervention as means to address emerging security problems after the Cold War. Germany's resistance to the use of force was viewed as inappropriate conduct for a power possessing the economic and military wherewithal of the Federal Republic. Elites from allied countries exerted social pressure to have Germany contribute commensurate with capabilities. German political elites adapted role behavior in response to external expectations in an effort to preserve the national role conception of a dependable and reliable ally. Security policy reorientation to maintain Germany's national role conception was pursued by conservative elites who acted as 'role entrepreneurs'. CDU/CSU politicians initiated a process of role adaptation to include the use of force for non-defensive missions. They persuaded Social Democrats and Alliance 90/Green party politicians that the maintenance of the country's role conception necessitated a reorientation in security policy to accommodate the changes in the security environment.

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Robert Kennedy's announcement of the assassination of Martin Luther King, Jr., in an Indianapolis urban community that did not revolt in riots on April 4, 1968, provides one significant example in which feelings, energy, and bodily risk resonate alongside the articulated message. The relentless focus on Kennedy's spoken words, in historical biographies and other critical research, presents a problem of isolated effect because the power really comes from elements outside the speech act. Thus, this project embraces the complexities of rhetorical effectivity, which involves such things as the unique situational context, all participants (both Kennedy and his audience) of the speech act, aesthetic argument, and the ethical implications. This version of the story embraces the many voices of the participants through first hand interviews and new oral history reports. Using evidence provided from actual participants in the 1968 Indianapolis event, this project reflects critically upon the world disclosure of the event as it emerges from those remembrances. Phenomenology provides one answer to the constitutive dilemma of rhetorical effectivity that stems from a lack of a framework that gets at questions of ethics, aesthetics, feelings, energy, etc. Thus, this work takes a pedagogical shift away from discourse (verbal/written) as the primary place to render judgments about the effects of communication interaction. With a turn to explore extra-sensory reasoning, by way of the physical, emotional, and numinous, a multi-dimensional look at public address is delivered. The rhetorician will be interested in new ways of assessing effects. The communication ethicist will appreciate the work as concepts like answerability, emotional-volitional tone, and care for the other, come to life via application and consideration of Kennedy's appearance. For argumentation scholars, the interest comes forth in a re-thinking of how we do argumentation. And the critical cultural scholar will find this story ripe with opportunities to uncover the politics of representation, racialized discourse, privilege, power, ideological hegemony, and reconciliation. Through an approach of multiple layers this real-life tale will expose the power of the presence among audience and speaker, emotive argument, as well as the magical turn of fate which all contributes the possibility of a dialogic rhetoric.

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The Vernacular Discourse of the "Arab Spring" is a project that bridges the divide between the East and the West by offering new readings to Arab subjectivities. Through an analysis of the "Arab Spring" through the lens of vernacular discourse, it challenges the Euro-Americo-centric legacies of Orientalism in Western academia and the new wave of extremism in the Arab world by offering alternative representations of Arab bodies and subjectivities. To offer this new reading of the "Arab Spring," it explores the foundations of critical rhetoric as a theory and a practice and argues for a turn towards a critical vernacular discourse. The turn towards critical vernacular discourse is important as it urges the analyses of different artifacts produced by marginalized groups in order to understand their perspectives that have largely been foreclosed in traditional cultural studies research. Building on embodied/performative critical rhetoric, the vernacular discourses of the Arab revolutionary body examines other forms of knowledge productions that are not merely textual; more specifically, through data gathered in the Lhbib Bourguiba, Tunisia. This analysis of the political revolutionary body unveils the complexity underlining the discussion around issues of identity, agency and representation in the Middle East and North Africa, and calls for a critical study towards these issues in the region beyond the binary approach that has been practiced and applied by academics and media analysts. Hence, by analyzing vernacular discourse, this research locates a method of examining and theorizing the dialectic between agency, citizenry, and subjectivity through the study of how power structure is recreated and challenged through the use of the vernacular in revolutionary movements, as well as how marginalized groups construct their own subjectivities through the use of vernacular discourse. Therefore, highlighting the political prominence of evaluating the Arab Spring as a vernacular discourse is important in creating new ways of understanding communication in postcolonial/neocolonial settings.

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This research provides an institutional explanation of the practices of external intervention in the Arab state system from the fall of the Ottoman Empire in 1922 to the Arab Spring. My explanation consists of two institutional variables: sovereignty and inter-state borders. I examine the changes in regional and international norms of sovereignty and their impact on the practices of external intervention in the Arab state system. I also examine the impact of the level of institutionalization of inter-state borders in the Arab World on the practices of external intervention. I argue that changes in regional and international norms of sovereignty and changes in the level of institutionalization of inter-state borders have constituted the significant variation over time in both the frequency and type of external intervention in the Arab state system from 1922 to the present. My institutional explanation and findings seriously challenge the traditional accounts of sovereignty and intervention in the Arab World, including the cultural perspectives that emphasize the conflict between sovereignty, Arabism, and Islam, the constructivist accounts that emphasize the regional norm of pan-Arabism, the comparative politics explanations that focus on the domestic material power of the Arab state, the post-colonial perspectives that emphasize the artificiality of the Arab state, and the realist accounts that focus on great powers and the regional distribution of power in the Middle East. This research also contributes to International Relations Theory. I construct a new analytical framework to study the relations between sovereignty, borders, and intervention, combining theoretical elements from the fields of Role Theory, Social Constructivism, and Institutionalization. Methodologically, this research includes both quantitative and qualitative analysis. I conduct content analysis of official documents of Arab states and the Arab League, Arabic press documents, and Arab political thought. I also utilize quantitative data sets on international intervention.

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Reactive power is critical to the operation of the power networks on both safety aspects and economic aspects. Unreasonable distribution of the reactive power would severely affect the power quality of the power networks and increases the transmission loss. Currently, the most economical and practical approach to minimizing the real power loss remains using reactive power dispatch method. Reactive power dispatch problem is nonlinear and has both equality constraints and inequality constraints. In this thesis, PSO algorithm and MATPOWER 5.1 toolbox are applied to solve the reactive power dispatch problem. PSO is a global optimization technique that is equipped with excellent searching capability. The biggest advantage of PSO is that the efficiency of PSO is less sensitive to the complexity of the objective function. MATPOWER 5.1 is an open source MATLAB toolbox focusing on solving the power flow problems. The benefit of MATPOWER is that its code can be easily used and modified. The proposed method in this thesis minimizes the real power loss in a practical power system and determines the optimal placement of a new installed DG. IEEE 14 bus system is used to evaluate the performance. Test results show the effectiveness of the proposed method.

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This dissertation looks at the creative identity of an American yoga, both rooted in its Indic origins and radically transformed in its U.S. manifestations. It traces the broad historical transactions of yoga in terms of East and West, Secular and Religious, authenticity and idealized conception, as well as provides a critical historical genealogy of Anusara and Sridaiva yoga. Furthermore, the project relates yoga to the identity, power, and knowledge dynamics of pre-modern, modern, and postmodern histories and interpretations of yoga and Tantra, multiple theoretical discourses, and the embodied practices of individuals within Indian and American contexts. I argue that there is a unique and polysemous yogic identity in America, and that this identity has developed from a messy process of transaction between Indian and Western modes of being and knowing. Furthermore, the current Americanized culture of yoga brings along with it narratives of specific value. American yoga displays a particularly consumptive quality of yogic lifestyle that reflects a cultural atmosphere of reinvention and a merging of profit and personal purpose. American yoga’s identity today is entrepreneurial, branded, business oriented, and marketed for consumption. This dissertation shows how the American yogic identity is in flux, continuously fracturing and multiplying into various and novel understandings that relate to yoga’s past and to the market value for today’s American consumer. It examines the moving nature of yoga in the American landscape as what Jared Farmer calls a “center of creativity” and as a display of excess and choice. The discussion of yoga is further located in John Friend’s styles of yoga and/or lifestyle practices, Anusara and Sridaiva, as they both redefine and further remove yoga from established Indian markers of identity. My locations as American yogi, as comparativist, as ethnographer, and as a Bachelor of Science in Advertising and Marketing also situate this analysis.