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Seidel, Melissa E. "Changes in a pollinator food web in the face of climate change: effects of physiological limitations and species interactions." Bowling Green State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu156352945016303.
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Shai, Pheagane Isaac. "The quest for radical transformation and the limits and limitations of law." Thesis, University of Pretoria, 2017. http://hdl.handle.net/2263/62555.
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At the heart of this thesis lies the urgency of radical transformation. The dawn of constitutionalism in South Africa in 1994 and finally in 1996 is predominantly conceived of as heralding the birth of a new nation and concomitantly the birth of a new South Africa. In this sense constitutionalism in South Africa is regarded as representing a fundamental break with the past characterised by colonialism and apartheid. The idea of a fundamental break with the past correlates with the idea of newness and in South Africa this idea of newness has given rise to a ubiquitous spirit of constitutional optimism. However this constitutional optimism has itself become a terrain of contestation.
The contestation generally relates to how best to interpret and conceive of the Constitution so as to enable the attainment of its objectives. This contestation can roughly be categorised as being between variants of liberal approaches to law and other genres of critique, notably transformative approaches to law. These genres of critique are naturally critical towards liberal formalist/positivist approaches to law.
In this thesis, I impute Christodoulidis's notion of republicanism to all approaches that see in law and constitutionalism the possibility for (radical) transformation. In this sense I argue against legal and constitutional reflexivity. Following a systems theoretical approach, I critique both liberal/formalist/positivist approaches and also genres of critique that optimistically defer the reconstruction and renewal of South Africa through legal and constitutional means. I suggest that because of the inability of systems to steer one another, the suggestion that law can steer the economy and politics is bound to fail. I further suggest that law and constitutionalism, being products of Enlightenment's modernity are more likely to serve the fundamental coordinates of colonialism and apartheid as opposed to the eradication of colonialism and apartheid in all their manifestations.<br>Thesis (LLD)--University of Pretoria, 2017.<br>Jurisprudence<br>LLD<br>Unrestricted
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Childers, Christine Mary. "Motivation and Limits to Physical Activity in Adults Over 80 in an Assisted Living." ScholarWorks, 2018. https://scholarworks.waldenu.edu/dissertations/5994.
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Thirty percent of older adults fall every year with devastating physical and economic consequences. Physical activity is the primary recommendation for fall prevention, but less than 30% of older adults meet the physical activity guidelines of the various professional organizations. Recent work demonstrated that psychological factors were more specific in identifying fall risk but work on psychological issues related to physical activity in the older adult is limited. This study explored motivation and limits to being physically active in 76 adults with a mean age of 88 living in the assisted living setting, using concurrent mixed method research. The theoretical foundation was a 3-pronged method using self-determination, self-efficacy, and resilience theories to explore such issues as autonomy, vicarious experience, and positivism. Quantitative data were used to examine the individual influences of various psychological factors on physical activity participation through multi regression analysis. No significant relationships were found, although it emerged that fear of falling was a greater influence in limiting physical activity than balance confidence or fall efficacy. Qualitative open-ended questions further explored the research question with triangulation through interviews with activity staff. Four primary themes emerged covering function, emotions, influences, and "want" demonstrating a strong desire for healthy living and independence. Results of this study can assist the development of suitable programs for this population. Implications for positive social change include the potential to increase physical activity and possibly decrease the number of devastating falls in the older adult population.
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Stein, Edward D. "Rationality and the limits of cognitive science." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13126.
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Savage, Paul Brian. "Anomalous Phenomena and the Limits of Science." Master's thesis, Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/216528.
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Religion<br>M.A.<br>This paper explores aspects of the scientific method which have proven inadequate to the task of producing verifiable and consistently repeatable experimental evidence for the existence of a particular category of phenomena, anomalous or psychic phenomena. The deficiencies of the method are not necessarily due to the esoteric nature of the phenomena and events being tested. Rather, the protocols of the method contribute to its inadequacy: reliance on observation, isolation of variables, and experimental controls, in short its fundamental functional criteria are perhaps its greatest impediment. The author suggests that applying the scientific method in the examination of anomalous or psychic phenomena was ill-advised from its inception because of these inadequacies, and concludes that it is quite possible that the method will never be the appropriate tool to uncover the mechanism by which anomalous phenomena manifest and operate.<br>Temple University--Theses
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Shen, Yuan Ph D. Massachusetts Institute of Technology. "Fundamental limits of wideband localization." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43069.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.<br>Includes bibliographical references (p. 107-112).<br>Location-awareness is essential for many wireless network applications. However, determining nodes' positions precisely is a challenging task, especially in harsh multipath propagation environments. To address this problem, wide bandwidth signals are envisioned to be used in future localization systems, since such signals can provide accurate range measurements. In this paper, we investigate the localization performance of wideband networks and proposed a performance measure called the squared position error bound (SPEB) to characterize the localization accuracy. We derive the SPEB succinctly by applying the notion of equivalent Fisher information (EFI). The EFI provides insights into the essence of localization problem by unifying the localization information from individual anchors and that from a priori knowledge of the agent's position in a canonical form. We also investigate the use of wideband antenna arrays and the effect of clock asynchronism on the localization accuracy. Our analysis begins with the received waveforms themselves rather than utilizing only signal metrics, such as time-of-arrival and received signal strength, extracted from the waveforms. Our framework exploits all the information inherent in the received waveforms, and therefore the SPEB serves as a fundamental limit of localization accuracy.<br>by Yuan Shen.<br>S.M.
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Homsy, George E. (George Edward) 1965. "Performance limits on chemical computation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30085.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.<br>Includes bibliographical references (p. 167-174).<br>A class of novel computers uses solute concentrations of distinct chemical species as logic signals and diffusion for signal transport. I establish a bound on the speed, density, and error rate of such computers from first principles. I let the chemical computer engineer choose a "design tuple" of independent parameters: number of chemical species, total solute concentration, signal molecule size, and a parameter called the "cell size". I establish a functional relation between the design tuple, and the "performance tuple": (operating frequency, signal density, error rate). I give a lower bound on the probability of a logic error in one computation step, and an upper bound on the frequency of operation, both as functions of the design tuple. I evaluate these bounds for ssDNA oligomers, and conclude that DNA computation has unacceptable error rates if the hybridization regions are less than eight nucleotides in length. I then argue that, given a suitable scalar-valued performance metric as a function over performance tuples, there is a globally optimal design tuple maximizing performance. I present two conjectures seeking to explain (a) why neurons use small molecules to transport information, and (b) why cells have the size they do. In part two I develop such a performance metric based on Toffoli's computation capacity and computation density, extending and generalizing in these ways: * as a local statistic on a uniform system, it can be evaluated for very large systems without exhaustive counting<br>(cont.) * it explicitly takes the error rate of the underlying physical process into account I then show a relation between this metric, and a quantity of dynamic systems called specific ergodicity. This is a novel result of theoretical importance, and is the central result of part two. It allows me to unambiguously compare the utility of computers varying vastly in speed, error rate, and signal density. I compare the maximum possible performance of proposed DNA computers from the literature with current commodity electronic computers, and conclude that diffusion-driven, DNA hybridizaton based computers cannot exceed the performance of current electronic computers by more than a factor of 40000, and probably by much less.<br>by George E. Homsy, II.<br>Ph.D.
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MATOS, MARIA CORDEIRO DE FARIAS G. "READING AND WRITING IN SCIENCE CLASSES: POTENTIALITIES AND LIMITATIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2018. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34671@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>O principal objetivo da pesquisa foi investigar relações entre atividades pedagógicas da disciplina escolar Ciências e processos de ensino-aprendizagem de leitura e de escrita. Considerando que a aquisição da linguagem escrita é um compromisso da educação escolar, especialmente em sociedades grafocêntricas atuais, o estudo procurou construir reflexões sobre possíveis contribuições do ensino de Ciências para formação de estudantes leitores e produtores de textos escritos. A investigação incluiu observações de aulas de Ciências de três diferentes professoras em três turmas de sexto ano do ensino fundamental de escolas da rede municipal do Rio de Janeiro. Foram também realizadas entrevistas semiestruturadas com as professoras e grupos de alunos das turmas, e análise dos materiais utilizados nas aulas. Os referenciais teórico-metodológicos baseiam-se em Bakhtin e trazem contribuições da perspectiva sociointeracionista da linguagem. A teoria sócio-histórica de Goodson colabora para a compreensão de características da disciplina escolar Ciências. Os resultados mostram que o espaço-tempo das aulas de Ciências é também um espaço-tempo para ler e escrever. O conhecimento escolar em Ciências é construído através da linguagem escrita, de forma que diferentes atividades envolvendo leitura e escrita acontecem nas aulas de Ciências. As professoras realizam a mediação da interação entre os estudantes e a linguagem escrita, influenciando seus processos de leitura e produção textual. Na mediação, elas atuam mobilizando estratégias e sistemas de conhecimento (linguístico, de mundo e interacional) necessários para que os estudantes leiam e escrevam, possibilitando a construção de sentidos para os textos. No diálogo em torno dos textos, gêneros primários e secundários do discurso aparecem, de maneira que as professoras trazem elementos cotidianos para a interação entre o texto e os alunos e, ao mesmo tempo, contribuem para a complexificação da linguagem, aproximando-a da forma escrita. Na cadeia discursiva da sala de aula, textos de variados gêneros aparecem e se associam às diferentes tradições curriculares da disciplina escolar Ciências. As professoras mesclam em suas falas diferentes concepções, que perpassam desde o entendimento da leitura e da escrita com foco na estrutura do texto até a compreensão destas atividades como uma interação social entre autor-texto-leitor. A centralidade da linguagem escrita nas aulas de Ciências e os conhecimentos e estratégias ativadas para que os estudantes interajam com textos escritos mostram o potencial da disciplina escolar Ciências para o ensino-aprendizagem da leitura e da escrita. Limites são estabelecidos pelas dificuldades relacionadas à formação docente e por questões estruturais, referentes ao controle do trabalho das professoras pelas avaliações externas e à falta de recursos. Espera-se que a investigação possa contribuir com reflexões para o entendimento das aulas de Ciências como um espaço-tempo da linguagem escrita, importante para a formação de leitores e autores críticos e maduros, que possam se inserir em um mundo permeado por práticas sociais de leitura e escrita.<br>The main objective of this research was to investigate the pedagogical activities in Science classes that are related to the development of reading and writing skills. Taking into account that the acquisition of written language is a commitment of school education commitment, especially in current graphocentric societies, the present study sought to reflect on possible contributions of Science classes to the development of readers and writers. Three sixth grade classrooms located in Rio de Janeiro were observed along with their science teachers. Semi-structured interviews were conducted both with the teachers and students, and the didactic materials used by them were analyzed. The theoretical-methodological framework is based on Bakhtin and on the social interactionist perspective of language. Goodson s sociohistorical theory was used for understanding the characteristics of Science as a school discipline. Results show that Science class space-time is also space-time for reading and writing. Science knowledge is constructed in school through written language and, because of that, many different activities involving reading and writing take place in Science classes. The teachers mediate the interaction between the students and the written language, guiding their reading and textual production processes. Through mediation, they act in the mobilization of strategies and systems of knowledge (linguistic, world and interactional ones) that contribute to students’ reading and writing skills, making the meaningful construction of texts possible. When talking about the texts, primary and secondary discourse genres appear, as the teachers bring everyday elements to the interaction between text and students and, at the same time, contribute to the complexity of language, bringing it closer to the written form. In the discursive chain of the classroom, texts of various genres are used and are associated with the different curricular traditions of Science as a school discipline. The teachers mix in their speech different conceptions of reading and writing: from one that focuses on the structure of the text to another that sees it as a social interaction among author-text-reader. The wide presence of written discourse and activities that deal with text interaction in Science classes show the potential of this school discipline for the development of reading and writing skills. Poor teacher education and infrastructure problems, such as influence of external evaluations and lack of resources, present obstacles to this type of work. It is expected that this research may contribute with reflections about the understanding of Science classes as a space-time for written language that is important for the education of critical and mature readers and authors, and who can then be inserted in a world permeated by social practices of reading and writing.
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Moores, John Demeritt. "All-optical soliton communication : devices and limitations." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12212.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.<br>Includes bibliographical references (leaves 140-157).<br>by John Demeritt Moores.<br>Ph.D.
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Eremin, Dmitry V. "Urban Core vs. Suburban Fringe: Asymmetrical Fiscal Effects of Tax and Expenditure Limitations in Metropolitan Areas." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29304.
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This dissertation assesses the effects of tax and expenditure limitations (TELs) on principal items of revenue, largest components of expenditure and the levels of public debt of local governments serving urban cores and suburban fringes of the largest metropolitan areas in the US.
The first part of the dissertation consists of 4 chapters. Chapter 1 examines the formal aspects of TELs; Chapter 2 explores historical evolution of fiscal limits between 1800 and 2009; Chapter 3 examines substantive nature of TELs; and Chapter 4 reviews the extant research on TELs. The past research suggests that TELs are associated with increased centralization, diminished government responsiveness, and suboptimal outcomes of the entire local public sector.
The second part of the dissertation, Chapters 5-6, presents the empirical study of the asymmetrical fiscal effects of TELs on different geographic segments of metropolitan areas. The study employs the quasi-experimental multiple comparison group time series research design and measures fiscal outcomes associated with the imposition of TELs. It relies on a standard fixed effects dummy variable OLS model with constant slope coefficients and variable intercept. The sample (N = 166,530) contains 7 periods of observation at 5 year intervals of 745 metropolitan counties from 270 metropolitan areas. The unit of analysis is the metropolitan county area.
The study found that in the urban cores and suburban fringes of metropolitan areas: 1) overall fiscal effects of TELs follow general asymmetrical trends identified by past research; 2) specific fiscal effects varied by comparison group, type of TEL imposed, and measure of fiscal outcome; 3) local governments in the urban cores are more adversely affected by TELs; 4) general revenues and expenditures declined in all comparison groups but urban core local governments experienced larger declines; 5) in all comparison groups own source revenues declined, intergovernmental revenues increased, spending on public education and public safety declined with larger declines in the urban cores; 6) long-term debt (especially non-guaranteed) has been rising more quickly in the urban core segments of metropolitan areas; and 7) in general, the effects of TELs were more negative and more pronounced for local governments experiencing fiscal stress.<br>Ph. D.
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Gogineni, Usha 1975. "Performance limits of RF power CMOS." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/63070.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 131-136).<br>Wireless and mobile communication systems have become ubiquitous in our daily life. The need for higher bandwidth and thus higher speed and data rates in wireless communications has prompted the exploration of millimeter-wave frequencies. Some of the applications in this regime include high-speed wireless local area networks and high data rate personal area networks at 60 GHz, automotive collision avoidance radar at 77 GHz and millimeter-wave imaging at 94 GHz. Most of these applications are cost sensitive and require high levels of integration to reduce system size. The tremendous improvement in the frequency response of state-of-the-art deeply scaled CMOS technologies has made them an ideal candidate for millimeter-wave applications. A few research groups have already demonstrated single chip CMOS radios at 60 GHz. However, the design of power amplifiers in CMOS still remains a significant challenge because of the low breakdown voltage of deep submicron CMOS technologies. Power levels from 60 GHz power amplifiers have been limited to around 15 dBm with power-added efficiencies in the 10-20% range, despite the use of multiple gain stages and power combining techniques. In this work, we have studied the RF power potential of commercial 65 nm and 45 nm CMOS technologies. We have mapped the frequency, power and efficiency limitations of these technologies and identified the physical mechanisms responsible for these limitations. We also present a simple analytical model that allows circuit designers to estimate the maximum power obtainable from their designs for a given efficiency. The model uses only the DC bias point and on-resistance of the device as inputs and contains no adjustable parameters. We have demonstrated a record output power density of 210 mW/mm and power-added efficiency in excess of 75% at VDs = 1.1 V and f = 2 GHz on 45 nm CMOS devices. This record power performance was made possible through careful device layout for minimized parasitic resistances and capacitances. Total output power approaching 70 mW was measured on 45 nm CMOS devices by increasing the device width to 640 gm. However, we find that the output power scales non-ideally with device width because of an increase in normalized on-resistance in the wide devices. PAE also decreases with increasing device width because of degradation in f. in the wide devices. Additionally PAE decreases as the measurement frequency increases, though the output power remains constant with increasing frequency. Small-signal equivalent circuit extractions on these devices suggest that the main reason for the degradation in the normalized output power and PAE with increasing device width is the non-ideal scaling of parasitic gate and drain resistances in the wide devices.<br>by Usha Gogineni.<br>Ph.D.
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Caulfield, Russell Erich 1975. "Power limits influencing retinal prosthesis design." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86600.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2001.<br>Includes bibliographical references (p. 52-55).<br>by Russell Erich Caulfield.<br>S.M.
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Suresh, Kumar Swarun. "Pushing the limits of wireless networks." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103675.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 259-277).<br>Wireless networks are everywhere around us and form a big part of our day-to-day lives. In this dissertation, we address the key challenges and opportunities of modern wireless networks. First, perhaps our biggest expectation from modern wireless networks is faster communication speeds. However, state-of-the-art Wi-Fi networks continue to struggle in crowded environments - airports and hotel lobbies. The core reason is interference - Wi-Fi access points today avoid transmitting at the same time on the same frequency, since they would otherwise interfere with each other. This thesis describes OpenRF, a novel system that enables today's Wi-Fi access points to directly combat this interference and demonstrate significantly faster data-rates for real applications. In addition, it presents MoMIMO, which demonstrates how the natural mobility of mobile users can be used to further mitigate interference. Second, can we use the ubiquitous Wi-Fi infrastructure around us to deliver new services, beyond communication? In particular, this dissertation focuses on indoor positioning, a service that has grabbed the attention of the academia and industry. While GPS has revolutionized outdoor navigation, it does not work indoors. Past work that has explored this problem is either limited in accuracy with errors of several meters, or advocates complete overhaul of the infrastructure with massive antenna-array access points that do not exist on consumer devices. Inspired by radar systems, we present Ubicarse, the first purely-software indoor positioning system for existing Wi-Fi devices that achieves tens of cm in positioning accuracy. Further, we build on this design to develop LTEye, which reveals new insights on how location impacts the performance of commercial AT&T and Verizon LTE cellular networks in the indoor space. Finally, we demonstrate how the tools we develop for indoor positioning open up new connections between wireless networking and robotics, to improve communication and security in multi-robot networks.<br>by Swarun Kumar.<br>Ph. D.
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Kim, Sungtae Jason. "The study of signal integrity limits." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/9845.
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Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.<br>Includes bibliographical references (leaves [88]-[89]).<br>by Sungtae Jason Kim.<br>S.B.and M.Eng.
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Thorne, James E. "Understanding the Limitations of Photoelectrochemical Water Splitting." Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108257.
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Thesis advisor: Dunwei Wang<br>Artificial photosynthesis is achieved by placing a semiconductor in water, where photoexcited charges generate a photovoltage at the surface of the semiconductor. However, solar to fuel efficiencies of earth abundant metal oxides and metal nitrides remain limited by their low photovoltages. Many different treatments have been used to improve the photovoltages of semiconductors, such as photocharging, surface regrowths, or the addition of heterogeneous catalysts. However, in these treatments, it remains unclear whether the enhanced photovoltage arises from improved kinetics or energetics. In many of the following studies, the surface kinetics of different semiconductors are measured in order to quantify how surface kinetics are related to the photovoltage of these materials. Different spectroscopic measurements are made along with detailed analysis of the Fermi level and quasi Fermi level in order to corroborate the kinetic data with energetic data. Together, this dissertation explores a multitude of methods and procedures that demonstrate how the photovoltage of semiconductors can be understood and manipulated for photoelectrochemial artificial photosynthesis<br>Thesis (PhD) — Boston College, 2018<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry
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Colavita, Michael Mark. "Atmospheric limitations of a two-color astrometric interferometer." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15223.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.<br>Bibliography: leaves 381-389.<br>by Michael Mark Colavita.<br>Ph.D.
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Dove, Justin (Justin Michael). "Phase-noise limitations on nonlinear-optical quantum computing." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89857.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>19<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (pages 57-58).<br>Flying in the face of the long-sought-after goal of building optical quantum computers, we show that traditional approaches leveraging nonlinear-optical cross phase modulation (XPM) to construct the critical element, the cphase gate - a gate which seeks to impart a [pi]-radian phase shift on a single photon pulse, conditioned on the presence of a second single photon pulse - are doomed to fail. The traditional story told in common textbooks fails to account for the continuous-time nature of the real world. Previous work addressing this fact - finding that that the proper continuous-time theory introduces fidelity-degrading phase noise that precludes such proposals - was limited in scope to the case of co-propagating pulses with equal group velocities. This left room for criticism that a high-fidelity cphase gate might be constructed using XPM with pulses that pass through each other. In our work, we build such a continuous-time quantum theory of XPM for pulses that pass through each other and evaluate its consequences. We find that fundamental aspects of the real world prevent one from constructing a perfect cphase gate, even in theory, and we show that the best we can do seems to fall far short of what is needed for quantum computation, even if we are extremely optimistic.<br>by Justin Dove.<br>S.M.
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Gkortsas, Vasileios-Marios. "Limits of High Harmonic Generation conversion efficiency." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84887.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 157-164).<br>High Harmonic Generation (HHG) is a fascinating phenomenon from both fundamental and technological point of view. It enables the generation of attosecond pulses and can have applications in EUV lithography and bio-microscopy. HHG can be described by the Three Step Model (TSM), due to the three stages of the process: ionization, propagation and recombination. However, HHG suffers from low efficiencies and a study, which shows the efficiency scaling with laser and material parameters is essential. For a long time experimentalists were using only 800 nm driver pulses from Ti:sapphire lasers. With the advent of new light sources like optical parametric amplifiers, different driving wavelengths became available and thus the scaling of the single atom response versus drive wavelength has attracted a lot of attention. A detailed analysis shows that the efficiency scales with w50 at the cutoff and w60 at the plateau region for a fixed EUV frequency, where w0 is the carrier frequency of the driver pulse. To understand the limitations of such a light source, we have developed a semi-analytic model for the computation of the conversion efficiency into a single harmonic for the plateau and cutoff regions. This model is one-dimensional, uses the TSM for the calculation of the single atom response and takes laser, material parameters and macroscopic effects into account. Closed form expressions for the plateau and cutoff regions are derived and used to calculate efficiencies for 400 and 800 nm driver pulses. The results are compared with experimental ones showing very good agreement. In order to investigate long-wavelength driven HHG efficiency, the 1-D model is extended to three dimensions taking into account spatiotemporal propagation effects, such as plasma defocusing and losses due to electron-neutral inverse bremsstrahlung. These phenomena change the phase matching along propagation, resulting in non-coherent harmonic generation and consequently poor efficiencies. We further study ways to mitigate the effect of plasma defocusing like the use of Supergaussian pulses and the use of Gaussian pulses with larger beam waists. The work presented can help us develop tools for an optimization study of HHG efficiency, in order to make useful EUV sources.<br>by Vasileios-Marios Gkortsas.<br>Ph.D.
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Niroui, Farnaz. "Engineering at the limits of the nanoscale." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114004.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 135-144).<br>At the nanoscale, unique properties and phenomena emerge that can lead to scientific and technological paradigms beyond those classically envisioned. Exploring these opportunities at the few-nanometer regime requires unprecedented precision, resolution, control and uniformity, not readily feasible through conventional fabrication and metrology techniques. In particular, the dynamic, reliable and reversible structural tuning of such small dimensions remains a great challenge, yet a promising platform to enable devices of new and improved functionalities. To overcome these challenges, alternative techniques are necessary to push the frontiers of nanoscale processing. In this thesis, the challenges and prospects of engineering active devices at the limits of the nanoscale are evaluated using a case study that focuses on developing a new platform for nanoelectromechanical (NEM) switches. The proposed NEM switches that rely on electromechanical modulation of the tunneling current in <5 nm switching gaps possess the potential to overcome the limitations of the conventional counterparts - minimizing stiction and lowering the actuation voltage. Combined top-down and bottom-up fabrication methodologies are introduced for achieving active structures of the desired complexity with nanometer precision, resolution and control. Integration of device engineering and physics with chemistry and materials science leverages an understanding of material synthesis, surfaces and interfaces to achieve manipulation of matter in the nanometer regime with a precision and control otherwise not feasible. Accordingly, two example hybrid fabrication techniques are introduced allowing precise fabrication of electrically-active nanogaps. Molecules are proposed as nanoscale structural components which can also control surface interactions and forces utilizing their chemical and mechanical properties. When used as interconnects between neighboring surfaces, they can precisely define nanoscale spacings. Uniquely, the mechanics of the molecular layer can be used to allow controlled and reversible tuning of the spacing where the elastic restoring force of the molecules balances the dominating surface adhesive forces to allow for stable yet mechanically active structures. Feasibility of molecules as nanoscale scaffolds and springs are demonstrated in this work in an electromechanically tunable molecular tunneling junction. In such a junction, changes in the tunneling gap leads to an exponential modulation of the tunneling current. If sufficiently large, this modulation can serve as a NEM switching mechanism. The molecules provide precision in defining small switching gaps necessary to reduce the actuation voltage while the force control provided through the molecular layer's mechanics helps control the surface adhesion. These proposed tunneling-based switches, referred to as "squitches", form a promising platform towards a more energy-efficient operation. Two- and multi-terminal designs of squitches are proposed and experimentally demonstrated with example devices showing actuation voltages <2 V and current modulations >10⁴. The design of squitches pushes the limits of nanoscale processing and broadly helps reveal the challenges and prospects of engineering at dimensions few nanometers in size. By implementing a multidisciplinary approach, one can gain access to the limits of the nanoscale to investigate the emerging physical phenomena and develop next generation nanodevices beyond squitches. The key is continuous development of versatile processing techniques allowing nanoscale manipulation and characterization with high precision and control.<br>by Farnaz Niroui.<br>Ph. D.
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Bhardwaj, Siddharth. "Limits of long wavelength High Harmonic Generation." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58455.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. [75]-76).<br>Many researchers are pushing for long wavelength driver pulses for High Harmonic Generation (HHG). The advantage of longer wavelengths is that the cut-off of the harmonic spectrum can be increased without the need for large electric fields. Large electric field is undesirable because it leads to large plasma generation which reduces harmonic generation due to phase mismatch and ground state depletion. Most of the current literature on HHG uses the Dipole Approximation for calculation of harmonic spectrum. The physical ramification of the Dipole Approximation is that it neglects the magnetic field component to the driver field. It is well known that a charge moving in a magnetic field experiences a Lorentz force. In HHG, harmonics are generated by recombination of an electron wave packet, moving under the influence of the driver pulse, with its parent atom. The Lorentz force can displace the electron wave packet perpendicular to the direction of polarization and as a result reducing the recombination amplitude. This Lorentz displacement increases as we move towards longer wavelengths and higher intensities. In this thesis, intensity and wavelength limits at which the Lorentz displacement becomes significant have been investigated. By numerically solving the time-dependent Schrödinger equation, we investigate the optimum driver pulse duration for 400 nm, 800 nm and 2 micron driver pulses for a given harmonic for hydrogen.<br>(cont.) It was found that longer wavelength have smaller efficiencies (neglecting phase matching condition). Finally, the harmonic spectrum of Hydrogen driven by 800 nm pulse predicted by analytic Three Step Model (TSM) has been compared with the harmonic spectrum generated by numerical solution of time-dependent Schrödinger equation. It was found, as the current theories predict, that TSM becomes less reliable as the Keldysh Parameter increases. It was also observed that for low harmonic energies, the TSM spectrum deviates from the numerical spectrum by many orders of magnitude.<br>by Siddharth Bhardwaj.<br>S.M.
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Sun, John Zheng. "Compressive sensor networks : fundamental limits and algorithms." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54653.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 85-92).<br>Compressed sensing is a non-adaptive compression method that takes advantage of natural sparsity at the input and is fast gaining relevance to both researchers and engineers for its universality and applicability. First developed by Candis et al., the subject has seen a surge of high-quality results both in its theory and applications. This thesis extends compressed sensing ideas to sensor networks and other bandwidth-constrained communication systems. In particular, we explore the limits of performance of compressive sensor networks in relation to fundamental operations such as quantization and parameter estimation. Since compressed sensing is originally formulated as a real-valued problem, quantization of the measurements is a very natural extension. Although several researchers have proposed modified reconstruction methods that mitigate quantization noise for a fixed quantizer, the optimal design of such quantizers is still unknown. We propose to find the optimal quantizer in terms of minimizing quantization error by using recent results in functional scalar quantization. The best quantizer in this case is not the optimal design for the measurements themselves but rather is reweighted by a factor we call the sensitivity. Numerical results demonstrate a constant-factor improvement in the fixed-rate case. Parameter estimation is an important goal of many sensing systems since users often care about some function of the data rather than the data itself.<br>(cont.) Thus, it is of interest to see how efficiently nodes using compressed sensing can estimate a parameter, and if the measurements scalings can be less restrictive than the bounds in the literature. We explore this problem for time difference and angle of arrival, two common methods for source geolocation. We first derive Cramer-Rao lower bounds for both parameters and show that a practical block-OMP estimator can be relatively efficient for signal reconstruction. However, there is a large gap between theory and practice for time difference or angle of arrival estimation, which demonstrates the CRB to be an optimistic lower bound for nonlinear estimation. We also find scaling laws 'for time difference estimation in the discrete case. This is strongly related to partial support recovery, and we derive some new sufficient conditions that show a very simple reconstruction algorithm can achieve substantially better scaling than full support recovery suggests is possible.<br>by John Zheng Sun.<br>S.M.
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Fuentes, Graciela. "Constitutional guarantees and normative limits to free communication." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26444.
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The purpose of this work is to analyze the principles of human rights theory underlying the protection of freedom of expression and the normative limits imposed on communication. The analysis involves those principles argued in American and Canadian judicial review.<br>The curtailment of sexual expression is at the core of the discussion of the nature of human beings and their relationship with the state power. By analyzing the way in which governments ban sexual messages, one can infer with a great degree of accuracy how they will react toward other forms of expression. This connection can be established because arguments justifying restrictions on pornography may be extended to justify prohibitions on other form of communication.<br>Inasmuch as freedom of expression meets the basic need for communication inherent to autonomous and morally responsible individuals, any restriction on it must stem from the principle that rights-protection is the highest value as supreme law rather than from a majority assertion of what is good for the individual and society as a whole.
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Rider, Todd H. (Todd Harrison). "Fundamental limitations on plasma fusion systems not in thermodynamic equilibrium." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11412.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.<br>Includes bibliographical references (leaves 292-305).<br>by Todd Harrison Rider.<br>Ph.D.
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Wise, Raydiance (Raydiance Raychele). "Optoelectronic implementations of Pulse-Coupled Neural Networks : challenges and limitations." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40539.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.<br>Includes bibliographical references (leaves 76-79).<br>This thesis examines Pulse Coupled Neural Networks (PCNNs) and their applications, and the feasibility of a compact, rugged, cost-efficient optoelectronic implementation. Simulation results are presented. Proposed optical architectures are discussed and analyzed. A new optoelectronic PCNN architecture is also presented. Tradeoffs of optical versus electronic implementations of PCNNs are discussed. This work combines concepts from optical information processing and pulse-coupled neural networks to examine the challenges, limitations, and opportunities of developing an optoelectronic pulse coupled neural network. The analysis finds that, despite advances in optoelectronic technology, fully electronic implementations will still outperform today's proposed optoelectronic implementations in cost, size, flexibility, and ease of implementation.<br>by Raydiance Wise.<br>S.M.
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Babb, Jonathan William. "Virtual wires--overcoming pin limitations in FPGA-based logic emulation." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12274.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.<br>Includes bibliographical references (p. 99-102).<br>by Jonathan William Babb.<br>M.S.
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Wareham, Christopher. "Liberal aristocracy & the limits of democracy." Thesis, Rhodes University, 2004. http://eprints.ru.ac.za/124/.
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Raz, Edny. "Self-determination for the Palestinians : scope and limits." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69766.
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Since 1991, the Israeli-Palestinian drama has shifted from the tragic course of war and violence, to a framework for peace. Israel's sovereignty is a fait accompli. The geo-political form of Palestinian self-determination is to be shaped by both parties, taking into account regional reality and international law.<br>This study serves as a modest examination of the application of certain international law concepts in settling two conflicting national aspirations within a unique factual context.<br>The main theoretical definitions of self-determination and its legal status in international law are first reviewed, along with the socio-juridical aspect of nationhood. The analysis of those topics constitutes a starting point for discussing basic Palestinian legal arguments related to Israel's right to exist, as well as to the scope of Palestinian national entity.<br>The abandonment of "armed struggle" as a legitimate course of action, and of Palestinian legal claims justifying a hostile policy against Israel, are necessary pre-conditions for co-existence, in which each nation determines its political fate.<br>Another vital element for the realization of such a modus vivendi is the development of a relationship built on trust. A restrained application of Palestinian self-determination might be necessary in the interim. The complete expression of Palestinian free will is, for many, still a utopian idea. Its achievement is largely dependant upon the negation of Palestinian legal claims which are aimed at the invalidation of Israel as a legitimate, sovereign state.
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Hashimoto, Tatsunori B. (Tatsunori Benjamin). "Continuous representations and models from random walk diffusion limits." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105670.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 193-202).<br>Structured data such as sequences and networks pose substantial difficulty for traditional statistical theory which has focused on data drawn independently from a vector space. A popular and empirically effective technique for dealing with such data is to map elements of the data to a vector space and to operate over the embedding as a summary statistic. Such a vector representation of discrete objects is known as a 'continuous representation'. Continuous space models of words, objects, and signals have become ubiquitous tools for learning rich representations of data, from natural language processing to computer vision. Even in cases that the embedding is not explicit, many algorithms operate over similarity measures which implicitly embed the original dataset. In this thesis, we attempt to understand the intuition behind continuous representations. Can we construct a general theory of continuous representations? Are there general principles for semantically meaninguful representations? In order to answer these questions, we develop a framework for analyzing continuous representations through diffusion limits of random walks. We show that measureable quantities of discrete random walks with a latent metric structure have closed form diffusion limits. These diffusion limits allow us to approximate attributes of the discrete random walk such as the stationary distribution, hitting time, or co-occurrence using closed-form expressions from diffusions. We establish limits which guarantee asymptotic consistency of such estimators, and show they work well in practice. Using this new approach, we solve three classes of problems: first, we derive principled network algorithms which connect statistical estimation tasks such as density estimation to network algorithms such as PageRank. Next, we demonstrate that continuous representations of words are a type of random walk metric estimator with close connections to manifold learning. Finally, we apply our theory to single-cell RNA seq data, and derive a way to learn time-series models without trajectories by using stochastic recurrent neural networks.<br>by Tatsunori B. Hashimoto.<br>Ph. D.
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Teherani, James Towfik. "Fundamental limits of the switching abruptness of tunneling transistors." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99853.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 114-123).<br>The tunneling field-effect transistor (TFET) is one of the most promising candidates for future low-power electronics because of its potential to achieve a subthreshold swing less than the 60 mV/decade thermal limit at room temperature. It can surpass this limit because the turn-on of tunneling does not sample the Maxwell-Boltzmann distribution of carriers that gives rise to the 60 mV/decade limit in conventional devices. However, theoretical predictions and experimental measurements of TFET device characteristics have differed by a wide margin-experimental subthreshold characteristics have not achieved the switching steepness (i.e., the change in drain current with applied gate voltage) of theoretical simulations. Non-ideal effects, such as non-abrupt band edges, phonon-assisted tunneling, and trap states, are discussed as mechanisms that may degrade theoretical predications. A strained-Si/strained-Ge bilayer TFET is used as a test-bed device to better understand the discrepancy between simulation and experiment. The bilayer TFET studied in this work eliminates channel doping and uses the strained-Si/strained-Ge heterostructure. Band-to-band tunneling occurs perpendicular to the gate, in-line with the gate electric field. Multiple gates are used so that the impact of the directionality of tunneling on switching abruptness can be studied. The band alignment of the strained-Si/strained-Ge heterostructure is extracted from a MOS-capacitor structure though an experimental quasistatic CV technique. The extracted effective band gap (related to the tunneling barrier) is shown to be only -200 meV for the heterostructure, and the valence band offset is shown to be -100 meV larger than predicted by density-functional theory. New deformation potentials are suggested for the Si-Ge material system based on the experimentally extracted band alignments. The impact of quantization on the turn-on voltage and gate-leakage current in a thin-body bilayer TFET structure is studied, and large confinement energy is shown to be especially problematic at body thicknesses less than 10 nm. An InAs structure with a body thickness less than 7 nm is shown to require a larger turn-on voltage than either Si or Ge homostructures due to the very light electron mass in InAs that leads to a large confinement energy. The strained- Si/strained-Ge heterostructure is shown to dramatically reduce the turn-on voltage due to its small effective band gap. Quantization is shown to limit the gate efficiency since increasing the body voltage, in order to align the electron and hole eigenstates in energy, increases the electric field across the structure, which in turn increases quantization. Gate leakage current increases exponentially as the body thickness decreases because the body voltage (and hence, the electric field) at turn-on increases with decreasing body thickness and gate leakage is exponentially dependent on the electric field. Non-ideal two-dimensional effects are investigated as mechanisms that degrade the switching characteristics of perpendicular TFETs (i.e. devices with tunneling perpendicular to the gate). Abrupt termination of a heavily doped semiconductor layer, often present in perpendicular TFET structures, can lead to large in-plane electric fields that give rise to parasitic diagonal tunneling paths, as opposed to the desired perpendicular tunneling paths. While the turn-on of each leakage path may be individually sharp, the sum of all tunneling paths is smeared by the multiple turn-ons and results in a degraded transfer characteristic for the device. The characteristic length, used for determining the length scale of potential fluctuations in short-channel MOSFETs, is suggested as a parameter that can be used to evaluate the likelihood of parasitic tunneling paths in a perpendicular TFET structure. The fabrication of the 3Gate strained-Si/strained-Ge bilayer TFET is detailed. The process includes epitaxial growth of a highly strained heterostructure, planarization of a bottom gate, wafer bonding of an epitaxial wafer to a handle wafer, etch-back of the epitaxial wafer leaving the thin strained-Si/strained-Ge heterostructure, and standard processing to create devices. Future work on electrical characterization of the experimental 3Gate bilayer TFET is discussed. Several test configurations are suggested as a way to probe the effects of diagonal tunneling on the abruptness of the switching characteristics.<br>by James Towfik Teherani.<br>Ph. D.
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Castillo, Alexandra Paige. "Challenging Democracy: Latin American Attitudes on Presidential Term Limits." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu155561348366265.
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Hitko, Donald A. (Donald Anthony). "Circuit design and technological limitations of silicon RFICs for wireless applications." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8117.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.<br>Includes bibliographical references (p. 201-206).<br>Semiconductor technologies have been a key to the growth in wireless communication over the past decade, bringing added convenience and accessibility through advantages in cost, size, and power dissipation. A better understanding of how an IC technology affects critical RF signal chain components will greatly aid the design of wireless systems and the development of process technologies for the increasingly complex applications that lie on the horizon. Many of the evolving applications will embody the concept of adaptive performance to extract the maximum capability from the RF link in terms of bandwidth, dynamic range, and power consumption-further engaging the interplay of circuits and devices is this design space and making it even more difficult to discern a clear guide upon which to base technology decisions. Rooted in these observations, this research focuses on two key themes: 1) devising methods of implementing RF circuits which allow the performance to be dynamically tuned to match real-time conditions in a power-efficient manner, and 2) refining approaches for thinking about the optimization of RF circuits at the device level. Working toward a 5.8 GHz receiver consistent with 1 GBit/s operation, signal path topologies and adjustable biasing circuits are developed for low-noise amplifiers (LNAs) and voltage-controlled oscillators (VCOs) to provide a facility by which power can be conserved when the demand for sensitivity is low. As an integral component in this effort, tools for exploring device level issues are illustrated with both circuit types, helping to identify physical limitations and design techniques through which they can be mitigated.<br>(cont.) The design of two LNAs and four VCOs is described, each realized to provide a fully-integrated solution in a 0.5 tm SiGe BiCMOS process, and each incorporating all biasing and impedance matching on chip. Measured results for these 5-6GHz circuits allow a number of poignant technology issues to be enlightened, including an exhibition of the importance of terminal resistances and capacitances, a demonstration of where the transistor fT is relevant and where it is not, and the most direct comparison of bipolar and CMOS solutions offered to date in this frequency range. In addition to covering a number of new circuit techniques, this work concludes with some new views regarding IC technologies for RF applications.<br>by Donald A. Hitko.<br>Ph.D.
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Herath, Narmada Kumari. "Fundamental limitations between noise and back-action in bio-molecular networks." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82396.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 63-64).<br>In an interconnection of two components in a bio-molecular network, noise in the downstream component can be reduced by increasing the magnitude of the down-stream signal. However, this method of reducing noise increases the back-effect to the upstream system, called 'retroactivity', thereby increasing the perturbation to the upstream system. In this thesis, we seek to quantify the total error in the system caused by the perturbations due to retroactivity and noise, and to analyze the trade-off between the two errors. We model the system as a set of non-linear chemical Langevin equations and quantify the trade-off for two different approximations of this non-linear model. First we consider a system linearized about a fixed point and quantify the trade-off using transfer functions. Next we use a linear approximation of the propensity functions in the Langevin equation and quantify the error by calculating upper bounds using contraction theory for deterministic and stochastic systems. Future research directions in improving the upper bounds are discussed.<br>by Narmada Kumari Herath.<br>S.M.
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LaWhite, Leif E. (Leif Eric). "Active filters for 1 MHz power circuits under strict ripple limitations." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/35336.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1987.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.<br>Title as it appeared in Massachusetts Institute of Technology Graduate List, February 1987: Active filters for high frequency power circuits under strict ripple limitations.<br>Bibliography: leaf 85.<br>by Leif E. LaWhite.<br>M.S.
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Pereira, Figueira José Márcio. "The use of offline simulation tools to estimate ship-helicopter operating limitations." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0511/document.
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Les limitations d’atterrissage des hélicoptères ne sont pas valables dans l'environnement à bord d’un navire. Il n'existe aucune méthodologie approuvée de l'analyse ou de la simulation pour évaluer la compatibilité des hélicoptères-navires et préparer les essais de qualification hélicoptères-navires. Dans ce contexte, le présent travail présente le développement et l'analyse d'une méthodologie hors ligne pour déterminer les limites opérationnelles hélicoptères-navires, SHOLs, en fonction des prédictions d’un modèle de pilote humain. Pour cela, des essais pilotés par des humains sont effectués au simulateur de l’ONERA, Salon de Provence. Sur la base des résultats de ces tests, une méthodologie innovante est validée pour déterminer la limitation de la charge de travail de pilotage, à partir des mesures des déplacements des contrôles d'hélicoptère. En outre, sont validés des modifications innovantes sur un modèle de pilote humain pour pouvoir suivre les trajectoires souhaitées et fournir le même niveau d'activité aux contrôles qu'un véritable pilote. Un ensemble de critères objectifs, correspondant aux marges de sécurité, s'ajoute aux critères subjectifs, correspondant aux limitations de la charge de travail du pilote. Une routine de simulation hors ligne, appelée SholSim, est programmée pour réaliser des simulations avec le modèle pilote et vérifier l'acceptabilité des conditions de vol, selon les critères subjectifs et objectifs. Par conséquent, le présent travail présente la première estimation, dans la littérature, des SHOLs entièrement obtenus à partir d'outils hors ligne, basés uniquement sur les prédictions de modèle pilote<br>Helicopter land-based limitations are not valid in the shipboard environment. There is no analytical or simulated approved methodology for evaluating shipboard helicopter compatibility issues and preparing for at-sea flight tests. In this context, the present work presents the development and analysis of an offline methodology to determine the Ship-Helicopter Operating Limitations, SHOLs, based on pilot model predictions. For this, pilot-in-the-loop simulation trials are performed at the engineering fixed-base simulation facility of ONERA, Salon de Provence. Based on these test results, an innovative methodology is proposed and validated to determine the safe pilot workload limitation, from the measurements of the helicopter control displacements. In addition, it is proposed and validated innovative modifications on a classical pilot model enabling to follow complex predefined desired trajectories and provide the same level of control activity of a real pilot. A set of objective criteria, corresponding to the safety margins, is established in addition to the subjective criteria, corresponding to the safe pilot workload limitations. An offline simulation routine, so-called SholSim, is coded to run all models and verify the acceptability of the flight conditions, according to the subjective and objective criteria. Therefore, the present work presents the first estimation, in the literature, of the SHOLs fully obtained from offline tools, based only on pilot model predictions. The proposed methodology is promising, confirmed by predicting coherent limits when compared to the ones defined by the pilot-in-the-loop simulation trials
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Fucetola, Corey Patrick. "Resolution limits and process latitude of comformable contact nano-lithography." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41640.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.<br>Includes bibliographical references (p. 78-80).<br>Conformable Contact Lithography enables researchers to attain high-resolution lithographic patterning at manageable cost. This thesis characterizes the minimum resolvable feature size and process latitude of Conformable Contact Lithography. Beginning with a review of current lithographic patterning techniques, choice of Conformable Contract Lithography as an exposure technique is discussed. A design for a trilayer stack that optimizes optical properties is established using experimental and simulated reflectance data to choose appropriate stack film thicknesses. The simulated process latitude is constructed using electromagnetic simulations of grating patterns. Image analysis of experimentally-exposed diffraction grating patterns is described and used to characterize the effect of exposure dose on printed linewidth. The resulting simulated and experimental process latitudes for printed gratings are presented for masks utilizing protruding chrome lines and embedded chrome lines. Experimental and simulated reflectance for single-layer and bilayer film stacks are compared to yield an optimized trilayer stack design of 225nm of anti-reflection-coating chemically separated from the resist by 70nm of evaporated silicon oxide. This design results in less than 1.5% back-reflection from the oxide into the resist for 10% film thickness variation. Finite-difference time-domain simulations are optimized by comparing higher variable-resolution, more realistic simulations to more efficient, lower variable-resolution simulations. Building on the trilayer stack and optimal simulation specification, simulated exposures of diffraction gratings are analyzed assuming a clipping model of development. Exposures of dense grating patterns with two geometries are performed on trilayer-stack-coated silicon wafers for a range of doses.<br>(cont.) Transferred grating patterns are analyzed to establish the effect of exposure dose on printed linewidth. A 5% experimental process latitude is achieved at a printed linewidth tolerance of ±15% for the embedded chrome mask exposures and of 25% for the protruding chrome mask exposures. Within the resist, contrast is higher at smaller gratings using the embedded mask.<br>by Corey Patrick Fucetola.<br>M.Eng.
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Tang, Jennifer (Jennifer Susan). "Physical redundancy for defect tolerance : example designs and fundamental limits." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101588.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (page 75).<br>This project analyzes designs for physical redundancy which are modeled abstractly as a bipartite graph. The goal is to determine the characteristics of graph structures which optimize the trade-off between the number of edges and the number of redundant components or nodes needed while correcting a deterministic number of worst-case errors. This thesis looks at finite-sized designs, asymptotically large designs with finite error correcting values, and designs with asymptotically large error correcting values. Results include some small optimal graph structures and fundamental limits on what the optimal design structure can achieve for the cases where a small number of errors are corrected and for where the number of errors to be correctly grows asymptotically.<br>by Jennifer Tang.<br>S.M.
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Yao, Wenjie S. M. Massachusetts Institute of Technology. "Fundamental limits to local density of states in absorptive system." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128348.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, February, 2020<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 57-62).<br>Fundamental limits to optical responses such as absorption, scattering and local density of states (LDOS) are proposed given intrinsic material losses by Owen, etc. The absorption and scattering limits are validated in Owen's work while the LDOS of common structures fall short of the limits. To validate those theoretical limits in LDOS, comprehensive studies are conducted in the metallic cavity structures, as typical resonant cavities will produce high LDOS. A novel shape optimization method based on the adjoint method is presented in this work, several numerical methods (BEM, CGAL, etc.) and optimization methods are implemented to enable more efficient evaluation and reduce the computation costs.<br>by Wenjie Yao.<br>S.M.<br>S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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King, Mark D. "Moral violence Levinas and the limits of role morality /." [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3232569.
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Thesis (Ph.D.)--Indiana University, Dept. of Religious Studies, 2006.<br>"Title from dissertation home page (viewed July 9, 2007)." Source: Dissertation Abstracts International, Volume: 67-08, Section: A, page: 3021. Adviser: Richard B. Miller.
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Fawzi, Hamza. "Power and limitations of convex formulations via linear and semidefinite programming lifts." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107331.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 155-162).<br>Convex relaxation methods play an important role in mathematical optimization to tackle hard nonconvex problems, and have been applied successfully in many areas of science and engineering. At the heart of such methods lies the question of obtaining a tractable description of the convex hull of a set. In this thesis we focus on the question of finding tractable representations of convex sets via the method of lifting, whereby the "hard" convex set is expressed as the projection of a simpler one living in higher-dimensional space. We derive new results and insights on the power and limitations of such liftings. In the first part of the thesis we study limitations of the lifting method and develop lower bounds on the sizes of linear programming (LP) and semidefinite programming (SDP) lifts of polytopes. For LP lifts the bound we develop applies generally for the nonnegative rank of matrices and we compare our method with existing combinatorial and non-combinatorial techniques. For SDP lifts we focus on so-called equivariant lifts that respect symmetry, and obtain lower bounds on the size of such lifts for certain combinatorial polytopes by exploiting the connection with the sum-of-squares method. In the second part of the thesis, we study the power of the lifting procedure and show how to obtain small semidefinite lifts for certain classes of polytopes via the idea of sparse sums of squares. We develop a graph-theoretic method to construct such lifts and use it to resolve a conjecture of Laurent from 2003 on the cut polytope, and to give an explicit sequence of polytopes with a gap between LP and SDP lifts. Finally we depart from the specific question of constructing lifts and consider the general problem of certifying nonnegativity of functions. We study a class of certificates rooted in convex duality and show that they encompass many existing methods for proving nonnegativity based on convex optimization. In particular we propose a new proof system to certify nonnegativity of entropy-like functions, which we illustrate on the problem of computing the logarithmic Sobolev constant of finite Markov chains.<br>by Hamza Fawzi.<br>Ph. D.
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Irving, James 1971. "Freedom's limits : self-determination and international law." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85216.
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This work seeks to settle the doctrine of self-determination in international law. Drawing upon a selection of historical thinkers who have concentrated upon the value of freedom, a theory of political liberty, is developed. This is situated in relation to political history from the Age of Revolutions on. The development of the formal principle of self-determination is discussed. This reveals a doctrine lacking coherence. The philosophy of political liberty is proposed as a foundation for self-determination in law. The way this new approach manifests itself in practice, and its merits, are considered in relation to the politics of Crimea, with a focus on the immediate post-Soviet period of 1991-2002. In conclusion, a programme for implementation and refinement is offered. It is also noted that one could fashion a new approach to international law as a whole on the basis of the logic that is employed here to settle the doctrine of self-determination.
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Damato, Antonio Leonardo. "Capabilities and limitations of Phase Contrast Imaging techniques with X-rays and neutrons." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/53263.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, February 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>Phase Contrast Imaging (PCI) was studied with the goal of understanding its relevance and its requirements. Current literature does not provide insight on the effect of a relaxation in coherence requirements on the PCI capabilities of an imaging system. This problem is all the more important since coherent X-ray and Neutron sources are mostly unavailable. We develop a model for PCI contribution to imaging for partially incoherent systems, and develop a methodology to identify a minimum and an optimum coherence length 4min and opt. We propose a figure-of-merit KPcI that quantifies the PCI capabilities of an imaging system. Our calculations show that X-ray PCI systems based on free space propagation using microfocus X-ray tubes have little PCI capabilities. We develop a model to explain the edge enhancement observed with those systems; our results suggest that scatter reduction is the process responsible for the observed edge enhancement. We performed experiments that show good agreement with the model. Coded Source Imaging (CSI) is proposed as a tool to produce highly coherent sources. The general theory of CSI is developed. We propose two possible systems: Fluorescent Coded Sources (FCS) and the AEB Encoded X-ray tube.<br>by Antonio Leonardo Damato.<br>Ph.D.
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Limaye, Satu Prakash. "United States-Indian relations, 1981-1989 : the pursuit and limits of accommodation." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315903.
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Wang, Da S. M. Massachusetts Institute of Technology. "Distinguishing codes from noise : fundamental limits and applications to sparse communication." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/60710.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 99-100).<br>This thesis investigates the problem of distinguishing codes from noise. We develop a slotted channel model where in each time slot, the channel input is either a codeword or a noise sequence. In this model, successful communication requires both correctly detecting the presence of a codeword and decoding it to the correct message. While the decoding problem has been extensively studied, the problem of distinguishing codes from noise is relatively new, and we ask the following question regarding the "distinguishability" of a channel code: given a noisy channel and a code with a certain rate, what are the fundamental limits of distinguishing this code from noise at the output of the channel? The problem of distinguishing codes from noise involves both detection and decoding. In our analysis, we first extend the classical channel coding problem to incorporate the requirement of detection, which admits both miss and false alarm errors. Then we investigate the fundamental limits of code distinguishing in terms of the error exponents of miss and false alarm error probabilities. In a scenario that miss probability is required to vanish asymptotically but not necessarily exponentially, we characterize the maximum false alarm error exponent at each rate, and show that an i.i.d. codebook with typicality decoding is sufficient to achieve the maximum exponent. In another scenario that requires certain miss error exponent, we show that for DMC channels, the i.i.d. codebook is suboptimal and the constant composition codebook achieves the best known performance. For AWGN channels, we develop a clustered spherical codebook that achieves the best known performance in all operating regimes. This code distinguishability problem is strongly motivated by the synchronization problem in sparse communication, a new communication paradigm where transmissions take place intermittently and each transmission consists of a small amount of data. Our results show that, in sparse communication, the traditional approach of conducting synchronization and coding separately is suboptimal, and our approach of designing codes for joint synchronization and information transmission achieves better performance, especially at high rates. Therefore, for systems with sparse transmissions such as sensor networks, it is beneficial to adopt the joint sync-coding architecture instead of the traditional separate sync-coding architecture.<br>by Da Wang.<br>S.M.
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Osqui, Mitra M. 1980. "Frequency selective analog to digital converter design : optimality, fundamental limitations, and performance bounds." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79152.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 131-137).<br>In this thesis, the problem of analysis and design of Analog to Digital Converters (ADCs) is studied within an optimal feedback control framework. A general ADC is modeled as a causal, discrete-time dynamical system with outputs taking values in a finite set. The performance measure is defined as the worst-case average intensity of the filtered input-matching error, i.e., the frequency weighted difference between the input and output of the ADC. An exact analytic solution with conditions for optimality of a class of ADCs is presented in terms of the quantizer step size and range, resulting in a class of optimal ADCs that can be viewed as generalized Delta-Sigma Modulators (DSMs). An analytic expression for the performance of generalized DSMs is given. Furthermore, separation of quantization and control for this class of ADCs is proven under some technical conditions. When the technical conditions needed for establishing separation of quantization and control and subsequently optimality of the analytical solution to ADC design problem are not satisfied, suboptimal ADC designs are characterized in terms of solutions of a Bellman-type inequality. A computational framework is presented for designing suboptimal ADCs, providing certified upper and lower bounds on the performance.<br>by Mitra M. Osqui.<br>Ph.D.
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Golooba-Mutebi, F. "Decentralisation, democracy and development administration in Uganda, 1986-1996 : limits to popular participation." Thesis, London School of Economics and Political Science (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299458.
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Harrison, Judith. "Marx, Yugoslavia and the limits of revolutionary philosophy : roots of the unperfect society." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239451.
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Thorburn, Emelie. "Security and Limits to Democracy : A Critical Study of the Danish Ghetto Package." Thesis, Försvarshögskolan, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-9393.
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This thesis departs from two arguments articulated by Jef Huysmans. First, security, as it is increasingly dispersed and part of every-day decision-making, undermines democracy in previously unprecedented ways. In order to under- stand security, scholars must look beyond insecurities framed as existential threats. They must equally adopt a fractional approach to democracy. Limits to democracy are increasingly found beyond democratic institutional frames of reference. In an empirical endeavour, this thesis builds on theoretical concepts by Huysmans and others in examining the Danish ghetto package as a cluster of securitising techniques. I make the argument that as the ghetto package entails more dispersed securitising techniques, it enacts limits to democracy.
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Marouga, Aspasia. "Limitations of democratic theories in modern state : a critical approach to liberal and Marxist perspectives." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240955.
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Radin, Andrew M. (Andrew Marc). "The limits of state building : the politics of war and the ideology of peace." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74462.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Political Science, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>When can the international community build strong state institutions - such as security forces or electoral institutions - in post-conflict societies? An influential technical perspective argues that authority, resources, and expertise enable the international community to build its preferred institutions. In Bosnia, East Timor, and Kosovo, the international community established international administrations with executive powers and a state building mandate. Each international administrations had extensive authority, resources, and expertise, which make them crucial test cases for the technical perspective. I examined seventeen reform efforts in these societies related to security, representation, and revenue. While some institution-building efforts succeeded, many failed and provoked violence or undercut political development. To explain this variation, I propose a theory that specifies the mechanisms of the reform process. The theory is based on the interaction between the international administration, local elites, and the mass public of the post-conflict society. The mass public will protest when demands threaten nationalist goals, such as independence. Local elites, on the other hand, will privately obstruct reform to protect their informal patronage and corruption networks. International officials are ideologically committed to human rights and bureaucracy, which lead them to make overambitious demands. Moreover, competing goals and political friction among international organizations causes disagreement about which demands to make to local elites. The theory predicts that reform efforts only fully succeed when the international administration is unified and its demands threaten neither nationalist goals nor informal networks. I test the theory by conducting causal process tracing in the seventeen reform efforts. The case studies draw from fieldwork in each of these societies, as well as primary and secondary sources. Within these seventeen efforts, I identify fifty-seven stages of reform. Of these, forty confirm the theory's predictions and thirteen partially confirm the predictions. The case studies also demonstrate that the technical perspective, and other alternative hypotheses, cannot consistently explain state building. The dissertation has implications for broader state building efforts by the international community, and urges the adoption of an incremental approach to institution building that takes account of the realities of local politics and the corresponding limits of international authority.<br>by Andrew M. Radin.<br>Ph.D.
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Feizi, Soheil (Feizi-Khankandi). "On the analysis of complex networks : fundamental limits, scalable algorithms, and applications." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107334.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 457-496).<br>Network models provide a unifying framework for understanding dependencies among variables in data-driven and engineering sciences. Networks can be used to reveal underlying data structures, infer functional modules, and facilitate experiment design. In practice, however, size, uncertainty and complexity of the underlying associations render these applications challenging. In this thesis, we illustrate the use of spectral, combinatorial, and statistical inference techniques in several network science problems. In Chapters 2-4, we consider network inference challenges. In Chapter 2, we introduce Network Maximal Correlation (NMC) as a multivariate measure of nonlinear association suitable for evaluation on large datasets. We characterize a solution of the NMC optimization using geometric properties of Hilbert spaces for finite discrete and jointly Gaussian random variables. We illustrate an application of NMC and multiple MC in inference of graphical models for bijective, possibly non-monotone, functions of jointly Gaussian variables. As a demonstration of NMC's utility, we infer nonlinear gene association networks and modules in cancer datasets and validate them using survival times of patients. In Chapter 3, we develop a network integration framework to infer gene regulatory networks in human and model organisms fly and worm using diverse and high-throughput datasets. Inferred regulatory interactions have significant overlap with known edges, indicating the robustness and accuracy of the proposed network inference framework. In Chapter 4, we formulate the transitive noise problem in networks as the inverse of matrix transitive closure and introduce an algorithm to solve it efficiently. We demonstrate the effectiveness of our approach in several applications such as regulatory network inference, protein contact map inference and strong collaboration tie inference. In Chapters 5-8, we consider network analysis challenges. In Chapter 5, we consider the problem of network alignment where the goal is to find a bijective mapping between nodes of two networks to maximize their overlapping edges while minimizing mismatches. This problem is essential in comparative analysis across large datasets and networks. To solve this combinatorial problem, we present a new scalable spectral algorithm which creates an eigenvector relaxation for the underlying optimization. We prove the optimality of the method under certain technical conditions, and show its effectiveness over various synthetic networks as well as in comparative analysis of gene regulatory networks across human, fly and worm species. In Chapter 6, we consider the source inference problem where the goal is to identify the source(s) of propagated signals across biological, social and engineered networks. To solve this problem, we propose a computationally tractable general method based on a path-based network diffusion kernel. We prove mean-field optimality of this method for different scenarios and show its effectiveness over several synthetic networks as well as in identifying sources in a Digg social news network. In Chapter 7, we consider the problem of learning low dimensional structures (such as clusters) in large networks. Here we introduce logistic Random Dot Product Graphs (RDPGs) as a new class of networks which includes most stochastic block models as well as other low dimensional structures. Using this model, we propose a scalable spectral method that solves the maximum likelihood inference problem asymptotically exactly. This leads to a new scalable spectral network clustering algorithm that is robust under different clustering setups. In Chapter 8, we consider the biclustering problem, the analog of clustering on bipartite graphs. This problem has several applications such as inference of co-regulated genes, document classification, and so on. Here we propose an algorithm based on message-passing that closely approximates a general likelihood function and excels at resolving the overlaps between biclusters. In Chapters 9-12, we consider design challenges of systems and algorithms for engineering networks such as communication networks. In Chapters 9-10, we create a connection between compressive sensing and traditional information theoretic techniques in source, channel and network coding and propose a joint coding scheme over wireless networks based on random projection and restricted eigenvalue principles. Moreover, we characterize fundamental results on the trade-off between the communication rate and the decoding complexity. In Chapters 11-12, we propose an adaptive nonuniform sampling framework, in which time increments between samples are determined as a function of the most recent increments and sample values, obviating the need to track time stamps. We analyze the performance of the proposed method for different stochastic and deterministic signal models and show its effectiveness to enhance measurements of heart ECG signals.<br>by Soheil Feizi.<br>Ph. D.