Thèses : « General sources »

1

Cieslak, Rafal. « Power scaling of novel fibre sources ». Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/351186/.

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This thesis explores novel fibre-based coherent light source architectures and strategies for scaling output power. The research focuses on fibre-based amplified spontaneous emission (ASE) sources with broadband output in the ~1 μm spectral region and on internally-frequency-doubled fibre lasers emitting in the visible (green) wavelength range. In Part I: Spectrum-controllable fibre-based amplified spontaneous emission sources modelling, development and characterisation of a versatile ASE source based on Yb-doped fibre gain stages, using power-efficient means for spectrum control is presented. Experiments have culminated in a versatile seed source with polarized output and a reasonable degree of spectral control. In its final configuration, the ASE source was capable of producing either a broad spectrum in the 1-1.1 μm band with a full-width at half-maximum of 15-40 nm and output power > 1 W. Alternatively, single/multiple narrow lines with a full-width at half-maximum ranging from several nanometres to < 0.05 nm and output power spectral densities of up to 100 mW/nm could be generated. The output power was temporally stable with fluctuations at the level < 0.3-0.8% of the total output power. Very high spectral stability was obtained, which was limited mostly by the mechanical stability of the external cavity. The output beam was nearly diffraction limited with M2 ≈ 1.1. Part II: Efficient intracavity frequency doubling schemes for continuous-wave fibre lasers introduces a novel concept for resonant enhancement of the intracavity power in high power continuous-wave fibre lasers that is suitable for a wide range of applications. Using this concept, efficient frequency doubling in continuous-wave Yb-doped fibre lasers has been demonstrated and techniques for using it in devices based on both robustly single-mode and multi-mode fibres have been developed. Finally, this thesis presents wavelength tuning of continuous-wave Yb-doped fibre lasers over ~19 nm in the green spectral region and scaling the generated second harmonic power up to ~19 W with more than 21% pump to second harmonic conversion efficiency.

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Dench, M. « Structural vibration control using multiple synchronous sources ». Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/349006/.

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The advantages of isolating vibrating machinery from its supporting structure are that the chances of vibration induced fatigue failure of structural components are reduced, the structure becomes more inhabitable for people due to less vibration exposure and the sound radiated by the structure into the environment is reduced. This last point is especially important for machinery operating in a marine environment because low frequency sound propagates very well underwater, and the machinery induced sound radiated from a ship or submarine is a primary detection and classification mechanism for passive sonar systems. This thesis investigates the control of vibration from an elastic support structure upon which multiple vibrating systems are passively mounted. The excitations are assumed to occur at discrete frequencies with a finite number of harmonic components and the machines are all assumed to be supplied with power from the same electrical supply. Active vibration control may be achieved by adjusting the phase of the voltage supplied to one or more of the machines, so that a minimum value of a measurable cost function is obtained. Adjusting the phase of a machine with respect to a reference machine is known as synchrophasing and is a well established technique for controlling the sound in aircraft cabins and in ducts containing axial fans. However, the use of the technique for reducing the vibration of machinery mounted on elastic structures seems to have received very little attention in the literature and would appear to be a gap in the current knowledge. This thesis aims to address that gap by investigating theoretically and experimentally how synchrophasing can be implemented as an active structural vibration control technique.

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Hun, Kanal. « Analysis of depth of digital trees built on general sources ». Caen, 2014. http://www.theses.fr/2014CAEN2017.

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Cette thèse effectue des analyses probabilistes de la profondeur des arbres digitaux [ tries et arbres digitaux de recherche(dst) ] quand ils sont construits sur des mots émis par une source générale. Cette étude est liée à des algorithmes de compression de type Lempel-Ziv qui sont basés sur l'utilisation d'arbres digitaux (tries or dst). La complexité des algorithmes qui utilisent ces structures de données sont liés à la forme de ces arbres , et nous sommes ici intéressés par le comportement probabiliste d'un paramètre important , la profondeur typique ou la profondeur. Nous introduisons un nouveau point de vue sur les sources générales et nous nous concentrons alors sur le modèle des sources dynamiques. La source intervient dans l'analyse par sa ``tameness” , et nous définissons les notions précises de ``tameness” qui sont nouveaux. La thèse traite des méthodes de combinatoire analytique et nous introduisons ( Dirichlet ) fonctions génératrices , qui caractérisent le comportement de l'arbre ( trie ou dst ) quand il est construit sur la source. Comme la source est une source dynamique , nous effectuons une analyse dynamique, qui mélange dans une des méthodes de réglage d'origine de la combinatoire et les méthodes de la théorie des systèmes dynamiques d'analyse ( i. E. Transférer les opérateurs , et leurs propriétés spectrales). Nous utilisons également de nombreux objets et méthodes de la combinatoire analytiques classiques , comme Poisson , Laplace , et Mellin transforme , que nous mélangeons à une nouvelle façon. Nous fournissons également un point de vue unifié sur l'analyse des deux types d'arbres digitaux ( tries et dst ) , alors que les analyses classiques sont dédiés à un type précis d'arbres. Enfin , nous montrons que , pour les deux types d'arbres digitaux , pour une large classe de sources , la profondeur typique suit asymptiquement une loi gaussienne , avec une vitesse de convergence optimal
This thesis performs probabilistic analyses of the depth of digital trees [tries and digital search trees (dst)] when they are built on words emitted by a general source. This study is related to compression algorithms of Lempel-Ziv type which are based on the use of digital trees (tries or dst). The complexity of algorithms which use these data structures are related to the shape of these trees, and we are here interested by the probabilistic behaviour of an important parameter, the typical depth, or depth. We introduce a new point of view on general sources, and we then focus on the model of dynamical sources. The source intervenes in the analysis via its tameness, and we define precise notions of tameness which are new. The thesis deals with methods in analytic combinatorics, and we introduce (Dirichlet) generating functions, which characterize the behaviour of the tree (trie or dst) when it is built on the source. As the source is a dynamical source, we perform a dynamical analysis, which mixes in an original setting method from analytic combinatorics and methods from dynamical system theory (namely transfer operators, and their spectral properties). We also use many objects and methods from classical analytic combinatorics, as Poisson, Laplace, and Mellin transforms, that we mix in a new way. We also provide an unified point of view on the analysis of the two types of digital trees (tries and dst), whereas the classical analyses are dedicated to one of the precise types of trees. Finally, we prove that, for the two types of digital trees, for a large class of sources, the typical depth follows an asymptiotic gaussian law, with an optimal speed of convergence

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Soh, Daniel Beom Soo. « Advanced waveguides for high power optical fibre sources ». Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/30236/.

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This thesis reports on theoretical and experimental studies of wavelength-selective waveguide structures for high-power Nd3+- and Yb3+-doped fibre lasers. Cladding-pumped high-power fibre lasers based on these novel waveguide designs and operating at desired unconventional wavelengths were investigated through numerical simulations and fibre laser experiments. Rare earth doped fibres have typically multiple emission bands of different effective strengths. Stimulate emission from strong bands dominates over, and via a reduced population inversion normally even suppresses, emission from weaker bands in conventional step-index waveguides. For efficient emission and laser operation on the weaker emission bands, it is necessary to suppress unwanted stimulated emission on the strong transitions by preventing power from building up at the unwanted wavelengths. Discrete "bulk" (non-waveguide) devices at a single or a few points are ineffective, if the gain at unwanted wavelength is sufficiently high to generate high-power amplified spontaneous emission even between filters. In such cases, waveguide structures which reduce the gain at unwanted wavelengths and prevent build-up of unwanted emission can be considered. The fibre itself acts as a distributed wavelength-selective filter, and a compact all-fibre laser can be made. For short-wavelength operation when the gain at longer wavelengths needs to be suppressed, a helical core fibre is proposed. This induces a large bending loss at unwanted longer wavelengths while the bending loss at desired shorter wavelength remains relatively low. The required bending loss properties, for efficient operation at the desired shorter wavelength, can be achieved by designing the helix pitch and offset along with fibre core diameter and NA (numerical aperture). A Nd3+-doped helical fibre laser operating at 0.92 μm was investigated through computer simulations. Alternatively, there are fibres in which the fundamental mode can be cut off at a certain wavelength. I have studied fibres with a W-type refractive index profile and fibres with a hollow (air-filled) central region surrounded by a core and then a region with depressed refractive index, known as depressed-clad hollow fibre. With these fibre designs, the doped core guides the desired shorter wavelength but not the unwanted longer wavelengths. Nd3+-doped W-type fibre lasers operating at 0.92 μm were simulated and experimentally demonstrated. Also Yb3+-doped depressed-clad hollow fibre lasers operating at 0.98 μm were simulated and experimentally demonstrated. For long wavelength operation, with a suppressed gain at shorter wavelengths, modified W-type designs are proposed. By designing the refractive index profile and using ring-shaped gain regions, the net gain on an intrinsically weak long-wavelength transition may become larger than that on an intrinsically stronger short-wavelength transition. Adopting this technique, Nd3+-doped fibre amplifiers and lasers operating at 1.38 μm were simulated. While fibre lasers that generate a nearly diffraction-limited single-mode beam are normally targeted, a multimode output is often obtained, e.g., in development stages with nonideal fibres. Then it is important to characterise the modal properties of the beam. For this, two different modal power decomposition methods based on intensity measurements are proposed. The first method is based on a tomography technique that uses a Wigner function followed by an inverse Radon transform. The second method adopts a wavelength-sweeping optical source which induces beat patterns after propagation through a certain length of fibre. The feasibilities of the two proposed ideas were verified through numerical simulations.

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Ofiare, Afesomeh. « Components and circuits for tunneling diode based high frequency sources ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7511/.

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Terahertz (THz) technology has been generating a lot of interest because of the potential applications for systems working in this frequency range. However, to fully achieve this potential, effective and efficient ways of generating controlled signals in the terahertz range are required. Devices that exhibit negative differential resistance (NDR) in a region of their current-voltage (I-V ) characteristics have been used in circuits for the generation of radio frequency signals. Of all of these NDR devices, resonant tunneling diode (RTD) oscillators, with their ability to oscillate in the THz range are considered as one of the most promising solid-state sources for terahertz signal generation at room temperature. There are however limitations and challenges with these devices, from inherent low output power usually in the range of micro-watts (uW) for RTD oscillators when milli-watts (mW) are desired. At device level, parasitic oscillations caused by the biasing line inductance when the device is biased in the NDR region prevent accurate device characterisation, which in turn prevents device modelling for computer simulations. This thesis describes work on I-V characterisation of tunnel diode (TD) and RTD (fabricated by Dr. Jue Wang) devices, and the radio frequency (RF) characterisation and small signal modelling of RTDs. The thesis also describes the design and measurement of hybrid TD oscillators for higher output power and the design and measurement of a planar Yagi antenna (fabricated by Khalid Alharbi) for THz applications. To enable oscillation free current-voltage characterisation of tunnel diodes, a commonly employed method is the use of a suitable resistor connected across the device to make the total differential resistance in the NDR region positive. However, this approach is not without problems as the value of the resistor has to satisfy certain conditions or else bias oscillations would still be present in the NDR region of the measured I-V characteristics. This method is difficult to use for RTDs which are fabricated on wafer due to the discrepancies in designed and actual resistance values of fabricated resistors using thin film technology. In this work, using pulsed DC rather than static DC measurements during device characterisation were shown to give accurate characteristics in the NDR region without the need for a stabilisation resistor. This approach allows for direct oscillation free characterisation for devices. Experimental results show that the I-V characterisation of tunnel diodes and RTD devices free of bias oscillations in the NDR region can be made. In this work, a new power-combining topology to address the limitations of low output power of TD and RTD oscillators is presented. The design employs the use of two oscillators biased separately, but with the combined output power from both collected at a single load. Compared to previous approaches, this method keeps the frequency of oscillation of the combined oscillators the same as for one of the oscillators. Experimental results with a hybrid circuit using two tunnel diode oscillators compared with a single oscillator design with similar values shows that the coupled oscillators produce double the output RF power of the single oscillator. This topology can be scaled for higher (up to terahertz) frequencies in the future by using RTD oscillators. Finally, a broadband Yagi antenna suitable for wireless communication at terahertz frequencies is presented in this thesis. The return loss of the antenna showed that the bandwidth is larger than the measured range (140-220 GHz). A new method was used to characterise the radiation pattern of the antenna in the E-plane. This was carried out on-wafer and the measured radiation pattern showed good agreement with the simulated pattern. In summary, this work makes important contributions to the accurate characterisation and modelling of TDs and RTDs, circuit-based techniques for power combining of high frequency TD or RTD oscillators, and to antennas suitable for on chip integration with high frequency oscillators.

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Albright, Simon. « Security applications of novel neutron sources ». Thesis, University of Huddersfield, 2016. http://eprints.hud.ac.uk/id/eprint/28333/.

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The smuggling of illicit goods poses a significant threat to the safety, security and economy of all nations. Undeclared black market goods, illegal narcotics and weapons are all threats that could ideally be prevented from crossing national borders. At present cargo interrogation is primarily performed using X-rays, which can be defeated by effective shielding and disguising of objects. Neutron interrogation offers an additional line of defence against smuggling, and there are a number of techniques available, which are discussed in this thesis. In this thesis a review of the limitations of current cargo interrogation technology is given. Current technology has limitations, and these are considered. In preparation of this thesis Monte-Carlo transport codes MCNPX and Geant4 were used as well as nuclear inventory code EASY-II, and a description of their key features is given. The possible methods of interrogating cargo with neutrons is discussed. Cargo can be interrogated with a range of neutron spectra, and either the neutrons or the produced gammas can be used. The use of techniques based on detecting neutrons or gammas is discussed, and simulations of gamma production by fast inelastic neutron scattering are presented. This is followed by a review of the principles of compound nucleus based neutron sources. The produced neutron spectra and the decay isotopes are both important considerations, and the results of possible combinations of target and projectile are given. Use of deuterons to produce neutrons through compound nucleus reactions has potential, due to the high Q of some reactions. If deuterons are used there is also a possibility of dissociation, if kinetic energies above the binding energy are used. At present deuteron dissociation cannot be simulated in Geant4 or MCNPX. Two new models of deuteron dissociation, one high and one low precision, have been developed for inclusion in Geant4. The physics and operation of these models is discussed and comparison with experimental data is presented. When interrogating cargo with neutrons it is unavoidable that some level of activation will occur. In particular the activation of food is of significant concern due to the exposure caused by ingestion. To date there has been little investigation of the activation of cargo under neutron interrogation. By using up to date nuclear data libraries and numerical techniques it was possible to extend early work in this field. In addition it is claimed in literature that 24N a is the only isotope of concern, this is shown to only be valid for certain combinations of food composition and irradiating energy.

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Wenz, Alexander. « Sources of error in mobile survey data collection ». Thesis, University of Essex, 2018. http://repository.essex.ac.uk/21943/.

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The proliferation of mobile technologies in the general population offers new opportunities for survey research, but also introduces new sources of error to the data collection process. This thesis studies two potential sources of error in mobile survey data collection: measurement error and nonresponse. Chapter 1 examines how the diagonal screen size of a mobile device affects measurement error. Using data from a non-mobile-optimised web survey, I compare data quality between screen size groups. Results suggest that data quality mainly differs between small smartphones with a screen size of below 4.0 inches and larger mobile devices. Respondents using small smartphones are more likely to break off during the survey, to provide shorter answers to open-ended questions, and to select fewer items in check-all-that-apply questions than respondents using devices with larger screens. Due to the portability of mobile devices, mobile web respondents are more likely to be in distracting environments where other people are present. Chapter 2 explores how distractions during web survey completion influence measurement error. I conducted a laboratory experiment where participants were randomly assigned to devices (PC or tablet) and to one of three distraction conditions (presence of other people who have a loud conversation, presence of music, or no distraction). Although respondents felt more distracted in the two distraction conditions, I did not find significant effects of distraction on data quality. Chapter 3 investigates correlates of nonresponse to data collection using mobile technologies. We asked members of a probability household panel about their willingness to participate in various data collection tasks on their mobile device. We find that willingness varies considerably by the type of activity involved, to some extent by device, and by respondent: those who report higher security concerns and who use their device less intensively are less willing to participate in mobile data collection.

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Yan, Zuanhong. « Control of fluctuating renewable energy sources : energy quality & ; energy filters ». Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8568/.

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This doctoral study discusses how to control fluctuating renewable energy sources at converter, unit, and system layers to deliver smoothed power output to the grid. This is particularly relevant to renewable power generation since the output power of many kinds of renewable energy sources have huge fluctuations (e.g. solar, wind and wave) that needs to be properly treated for grid integration. In this research, the energy quality is developed to describe the friendliness and compatibility of power flows/waveforms to the grid, by contrast with the well-known concept of power quality which is used to assess the voltage and current waveforms. In Chapter 1 & 2, a background introduction and a literature review of studied subjects are presented, respectively. In Chapter 3, the problem of determining the PI parameters in dq decoupling control of voltage source converter (VSC) is studied based on a state-space model. The problems of the conventional method when there is insufficient interface resistance are addressed. New methods are proposed to overcome these drawbacks. In Chapter 4 & 5, energy quality and the energy filters (EFs) are proposed as tools to assess and manage power fluctuations of renewable energy sources. The proposed EFs are energy storage control systems that could be implemented on a variety of energy storage hardware. EFs behave like low-pass filters to the power flows. Finally, in Chapter 6, as an application example of renewable power plant with energy filter control and smoothed power output, a master-slave wave farm system is proposed. The wave farm system uses enlarged rotor inertia of electric machines as self-energy storage devices.

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Alexander, David Alisdair. « The sources of committee influence in the European Parliament ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/8281/.

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The European Parliament (EP) has evolved into a powerful legislative actor over the past 40 years. In order to exercise its hard won legislative competencies in an efficient and effective manner the EP has developed an extensive and influential committee system. The Treaty of Lisbon (ToL) recognised its equal status as co-legislator with the Council of the EU and introduced the Ordinary Legislative Procedure (OLP) as the default EU legislative procedure. Despite the fact that after the introduction of the OLP all EP committees formally operate under the same legal procedure, disparities remain in the levels of influence that each committee commands. This state of affairs demonstrates that if we are to understand what drives committee influence we need to explore the informal sources of influence that committees draw on in addition to the formal rules. This project addresses the lack of understanding of how the committees establish legislative influence by identifying and testing the different resources which committees may be utilising to establish their influence. The thesis puts forward four hypotheses concerning the factors that can account for how committees establish influence. These are developed and tested within three case studies. The case studies comprise the highly influential committees on, firstly, the Environment, Public Health and Food Safety Committee, secondly, the Budget Committee and, thirdly, the International Trade Committee. The research project adopts a qualitative approach to complement and create a different perspective from the quantitative studies which dominate the field. It draws on extensive primary material from thirty semi-structured interviews held with MEPs, advisers, EP staff and party officials active in the 7th legislative term (2009-2014). A number of the current conventions concerning the way in which expertise, partisan dynamics, and policy outputs affect how committees establish legislative influence are challenged and new insights regarding their relative importance are offered. Overall, these original findings, contained within this dissertation, have highly significant implications, not only with regard to the committee system of the EP but, also, for the wider field of legislative politics.

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Balasiny, Basema Kasem. « Regulation and sources of nitric oxide in Escherichia coli ». Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6748/.

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The enteric bacterium \(Escherichia\) \(coli\) is exposed to nitric oxide (NO) in its oxygen-limited environment. Various transcription factors regulate gene expression to provide protection against nitrosative stress, but their respective roles remain controversial. Key questions answered in this thesis were whether S-nitrosylated OxyR directly regulates the expression of NO-regulated genes; whether NsrR is required for the synthesis of an important protective system; and whether FNR is a physiologically relevant sensor of environmental NO. Transcription from the NO-activated \(hcp\) promoter was almost totally dependent upon a functional FNR protein, which is inactivated by oxidative stress, but unaffected by deletion of the \(oxyR\) gene. This indicated that the effects of an \(oxyR\) mutation on resistance to nitrosative stress are indirectly due to inactivation of FNR rather than to direct activation of \(hcp\) transcription by S-nitrosylated OxyR. The NO-sensitive repressor, NsrR, is not essential for protection against nitrosative stress. Nitric oxide produced during nitrite reduction had no effect on the ability of FNR to activate or repress gene expression, which is primarily due to NO sensing by NsrR, not by FNR. Some NO accumulates in the \(E. coli\) cytoplasm even in mutants that lack known sources of NO. The source of most of this residual NO is the NsrR-regulated protein, YtfE. Contrary to the proposal by others that YtfE repairs iron-sulfur centres by replacing iron atoms released during nitrosative stress, it is proposed that YtfE releases NO from nitrosylated iron-sulfur proteins, and that Hcp reduces this NO to the less toxic N2O.

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Polyakova, Evgenia I. « A general theory for evaluating joint data interaction when combining diverse data sources / ». May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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Gabor, Nadine. « Energy sources in Germany and Brazil general aspects and foundation solutions for eolic structures ». reponame:Repositório Institucional da UFPR, 2010. http://hdl.handle.net/1884/24305.

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Jones, Owen Anthony. « The sources of goal incongruence in a public service network ». Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/57423/.

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Goal incongruence, both within organisations and between organisations operating in a network context, has long been acknowledged as an important influence on organisational behaviour. This work presents the findings from an ethnographic study of goal incongruence in a public service network located in the UK. The study develops a conceptual framework for defining and researching the extent and sources of goal incongruence within public service networks. The author defines incongruence as contradiction between goals, draws evidence from organizationally enacted behaviours and recognises distinctions between formal goals and the operative goals of network groups. Empirical evidence is used to evaluate two explanations of goal incongruence: that goal incongruence is produced by the nature of bureaucratic delegation (the hierarchical model) and that it is produced by professional difference (the horizontal model). The findings of the study indicate that bureaucratic delegation is the source of goal incongruence. However, several elements of the hierarchical model are questioned. The evidence does not support the orthodox view that incongruence between formal and operative goals increases as conceptions of desired ends are transmitted downward within hierarchies. The study finds that the operative goals of actors at the apex of the network were most highly incongruent with the formal goals of the network. Professional difference was not a source of goal incongruence. Indeed the study provided evidence that operational staff who exhibited different professional identities co-operated to integrate practice and reduce goal-incongruence. The study concludes that the application of the novel conceptual framework provides a more selective, detailed and convincing account of goal incongruence than those found in the recent literature. The sources of goal incongruence were hierarchical elites putting the resources of the network to their own purposes as social agents and hierarchically imposed systems of organisational obligation and performance control. Finally, the study suggests that evidence for interprofessional integration indicates that the role of peer groups in moderating goal incongruence is under-represented in theoretical and empirical accounts of goal incongruence.

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Regan, Heather Christine. « Modelling the sources, variability and fate of freshwater in the Bellingshausen Sea, Antarctica ». Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/103393/.

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During the second half of the twentieth century, the Antarctic Peninsula exhibited a rapid increase in air temperatures. This was accompanied by a reduction in sea ice extent, increased precipitation and a dramatic retreat of glaciers associated with an increase in heat flux from deep ocean water masses. Isotopic tracers have been used previously to investigate the relative importance of the different freshwater sources to the adjacent Bellingshausen Sea, but the data coverage is strongly biased toward summer and unambiguous determination of the different meteoric water contributions remains challenging. Here a high-resolution model is used to investigate the ocean's response to the observed changes in its different freshwater inputs (sea ice melt/freeze, precipitation/evaporation, iceberg melt, ice shelf melt and glacier melt). By developing the code to enable tracing of the sources and pathways of the individual components of the freshwater budget, it is shown that sea ice dominates the seasonal changes in freshwater content, but all sources contribute approximately equally to annual-mean freshwater fluxes and interannual freshwater flux anomalies. Ice shelf melting is shown to be the largest contributor to freshwater content on the annual mean. Decadal trends in the salinity and stratification of the ocean are investigated, and a 20-year surface freshening trend is found to be predominantly driven by decreasing autumn sea ice growth. By partitioning the freshwater in this way, insight is gained into the long-term freshwater balance and variability, and therefore the potential effects of a changing climate.

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Alharbi, Khalid Hamed. « High performance terahertz resonant tunnelling diode sources and broadband antenna for air-side radiation ». Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7524/.

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Resonant tunnelling diode (RTD) is known to be the fastest electronics device that can be fabricated in compact form and operate at room temperature with potential oscillation frequency up to 2.5 THz. The RTD device consists of a narrow band gap quantum well layer sandwiched between two thin wide band gap barriers layers. It exhibits negative differential resistance (NDR) region in its current-voltage (I-V) characteristics which is utilised in making oscillators. Up to date, the main challenge is producing high output power at high frequencies in particular. Although oscillation frequencies of ~ 2 THz have been already reported, the output power is in the range of micro-Watts. This thesis describes the systematic work on the design, fabrication, and characterisation of RTD-based oscillators in microwave/millimetre-wave monolithic integrated circuits (MMIC) form that can produce high output power and high oscillation frequency at the same time. Different MMIC RTD oscillator topologies were designed, fabricated, and characterised in this project which include: single RTD oscillator which employs one RTD device, double RTDs oscillator which employs two RTD devices connected in parallel, and coupled RTD oscillators which combine the powers of two oscillators over a single load, based on mutual coupling and which can employ up to four RTD devices. All oscillators employed relatively large size RTD devices for high power operation. The main challenge was to realise high oscillation frequency (~ 300 GHz) in MMIC form with the employed large sized RTD devices. To achieve this aim, proper designs of passive structures that can provide small values of resonating inductances were essential. These resonating inductance structures included shorted coplanar wave guide (CPW) and shorted microstrip transmission lines of low characteristics impedances Zo. Shorted transmission line of lower Zo has lower inductance per unit length. Thus, the geometrical dimensions would be relatively large and facilitate fabrication by low cost photolithography. A series of oscillators with oscillation frequencies in the J-band (220 – 325 GHz) range and output powers from 0.2 – 1.1 mW have been achieved in this project, and all were fabricated using photolithography. Theoretical estimation showed that higher oscillation frequencies ( > 1 THz) can be achieved with the proposed MMIC RTD oscillators design in this project using photolithography with expected high power operation. Besides MMIC RTD oscillators, reported planar antennas for RTD-based oscillators were critically reviewed and the main challenges in designing high performance integrated antennas on large dielectric constant substrates are discussed in this thesis. A novel antenna was designed, simulated, fabricated, and characterised in this project. It was a bow-tie antenna with a tuning stub that has very wide bandwidth across the J-band. The antenna was diced and mounted on a reflector ground plane to alleviate the effect of the large dielectric constant substrate (InP) and radiates upwards to the air-side direction. The antenna was also investigated for integration with the all types of oscillators realised in this project. One port and two port antennas were designed, simulated, fabricated, and characterised and showed the suitability of integration with the single/double oscillator layout and the coupled oscillator layout, respectively.

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Colton, W. Paul. « Sources of law of the Church of Ireland : identification, investigation and reform ». Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/47412/.

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Since the disestablishment of the Church of Ireland in 1871 there has been negligible academic exploration and scrutiny of its laws. This enterprise seeks to advance scholarship of that law generally. As an initial contribution, the sources of law of the Church of Ireland, until now never the subject of singular study, are identified and investigated. Part One identifies the sources: in the law of the State; in the Church’s primary and secondary sources; and in tertiary sources (quasi-legislation and soft law), including putative sources – custom, the wider Anglican legal economy, and ecumenical input. In Part Two, case studies in each of the arenas – civil, primary and secondary, and tertiary – investigate three concerns. First, the increasing impact of civil law on church law is evaluated as a recent phenomenon. Second, the internal church sources are examined to assesstheir accessibility, a test fundamental to the Rule of Law. Third, the extensive materials of recent decades are scrutinised and demonstrate an ever-growing reliance on informal instruments – quasi-legislation and soft law – governing the life of the Church. A detailed survey of the opinions and knowledge of church members undertaken in 2011 tests and informs the analysis of the sources. Throughout the study, however, the principal reliance is on a formidable array of primary materials: a broad spectrum of State laws; contemporary ecclesiastical legal materials (national and local); a wide range of historical documents, including the original papers of the General Convention 1870, the Minutes of the Legal Committee, one-hundred and forty-four Journals of the General Synod, eight centuries of pre-disestablishment statutes, and one thousand and fifty-four statutes of the General Synod. This identification and investigation of the sources of law of the Church of Ireland highlights weaknesses and makes the case for reform. The conclusion sets out the proposals for reform.

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Zang, Lei. « Study and optimisation of undulator-based polarised positron sources for linear colliders ». Thesis, University of Liverpool, 2010. http://livrepository.liverpool.ac.uk/1445/.

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High-energy accelerators play an important role in physics research. The International Linear Collider (ILC) and Compact Linear Collider (CLIC) are proposed future accelerators which will require of order 1014 positrons per second to fulfil their luminosity requirements. In addition, polarisation of the positron beam will increase the scope of the physics studies that can be performed using a linear collider. Production of large quantities of polarised positrons is one of the major challenges for the research, development and design of any future linear collider. A polarised positron source based on gamma rays produced by a high energy electron beam in a helical undulator has been selected as the baseline option for ILC. The design is relatively mature, and previous studies have shown that it should be capable of producing the required positron beam intensity and polarisation. We review the design using a range of analytical and simulation tools. We also consider, in more detail than in previous studies, two options for the design of a photon collimator that could be used to improve the positron polarisation. Although a Compton source is presently the baseline choice for the positron source for CLIC, an undulator-based scheme remains an option. We discuss the possibility of an undulator-based polarised positron source for CLIC Stage 1 (500 GeV centre of mass collision energy), and consider options for an undulator-based positron source in the upgrade to Stage 2 (3 TeV centre of mass collision energy). For both ILC and CLIC, energy deposition from the gamma rays striking the positron production target is a concern. For ILC, the energy density can be reduced by rotating the target at high speed; however, this raises concerns about the eddy currents induced by the strong field of the matching device. We report the results of experiments at Daresbury Laboratory to understand the eddy current effects, and to validate models for predicting the effects in the final system.

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Frisoni, Pietropaolo. « Canonical formalism for compact sources ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19296/.

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This thesis aims to describe the ADM formalism of General Relativity and to use the latter to describe a spherical compact source consisting of a perfect fluid. With two different choices for three-dimensional metric on hypersurfaces, we analyze the constraints of the system in the non-static case and the resulting equations of motion, both for canonical gravitational variables and those of matter. After examining some special cases, we also show that it is possible, in the case of static nature, to obtain the value of the Misner-Sharp mass from the Hamiltonian constraint, while near the trapping surfaces we obtain a relationship between the density of matter and the dynamic variables of the metric. Finally we propose a possible method for quantizing the constraints using the procedure that in the vacuum leads to the Wheeler-DeWitt equations.

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Molnár, Peter. « Elemental composition of fine particles : exposure in the general population and influence from different sources / ». Göteborg : Sahlgrenska Academy at Göteborg University, Institute of Medicine, Dept. of Public Health and Community Medicine, Occupational and Environmental Medicine, 2007. http://hdl.handle.net/2077/3124.

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Musgrave, Ian. « Study of the physics of the power-scaling of end-pumped solid-state laser sources based on Nd:YVO ». Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/46103/.

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Using a modified Mach-Zehnder interferometer the thermal lensing in Nd:YV04 was measured for several different operating conditions. The thermal lens focal length can be determined from the measured transverse phase profile. It was found that the thermal lensing was weakest for p-polarised light and that the bulk expansion plays a part in modifying the power of the thermal lenses. By comparing the thermal lensing with cooling direction it was found that the providing cooling along the a-axis generated the weakest thermal lensing. Comparing the thermal lensing under lasing and non-lasing conditions demonstrated that the heating in the laser crystal under non-lasing conditions is significantly greater than under lasing conditions. The thermal lenses are almost 5 times stronger under non-lasing conditions than lasing condition for the 1% doped crystal. By comparing the effect of dopant concentration on thermal lensing the effect of ETU could be seen, with the thermal lensing for the 0.3% doped crystal being much lower than that of the 1% doped crystal under non-lasing conditions.An amplitude modulated mode-locked laser was built based on Nd:YVO4 generating 600mW of diffraction limited output and l00ps pulses. Multipass amplification was then investigated as a means to increase the average power of the source. This was achieved with 5W of output achieved, with the beam remaining diffraction limited. The prospects for further power scaling are investigated and it was shown that the limit to power scaling via amplifiers is the eventual beam quality degradation that will be suffered as the signal beam passes through the thermal lenses in the laser crystal. An equation was finally presented that analysed the limitations of scaling via amplifiers, finding that when stress-fracture and beam quality degradation are considered, Nd:YVO4 represents an excellent choice for further power scaling.

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Nshii, Chidi Christopher. « Tunable mid-infrared light sources based on intersubband transitions ». Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2603/.

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This thesis describes how for the first time, unidirectional operation and coupled ring tuning were realised on a quantum cascade laser material; specifically on a new strain compensated In0.7Ga0.3As/AlAs0.6Sb0.4 grown on InP substrate and operates in pulsed mode in the 3-4 micron hydrocarbon absorption region. Unidirectional ring lasers have the advantages that, in the favoured emission direction, they can have up to double the quantum efficiency of bidirectional lasers and do not suffer from spatial hole burning. In this work, this operation was realised by incorporating an "S"-crossover waveguide into the ring cavity in a manner that it introduces non reciprocal loss and gain in the counter-clockwise (CCW) and clockwise (CW) directions respectively. The measured result showed higher quantum efficiency in the CW. In fact at 1.5 times the threshold current, 90 % of the light was emitted in the favoured CW. On the other hand, the coupled ring quantum cascade laser showed nearly single mode operation, with side mode suppression ratio ~22 dB. Continuous wavelength tuning of about 13 nm was observed from one of these devices, at a tuning rate of approximately 0.4 nm/mA.

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Port, Lukas. « Hegemonic discourse and sources of legitimacy in Cuba : comparing Mariel (1980) and the Maleconazo (1994) ». Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/14147/.

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This research project investigates the sources of legitimacy in hegemonic Cuban discourse, understood to have supported the stability of the Cuban system during crises and challenging times, such as the end of the Cold War and the 1990s Special Period. Evidence was drawn from the Cuban press, namely Granma, Bohemia and Verde Olivo, in two critical periods: the 1980 Mariel episode and the 1994 Maleconazo disturbances as two examples before and after 1989 in order to compare the sources of legitimacy and identify continuities and shifts. The two periods represent recent examples of instability, which dominated the attention of the whole nation. The evidence is based on textual examination using discourse analysis as the method of investigation. The research is written in the discipline of political history, with elements taken from cultural studies and political communication. The project is based on the assumption that the sources of legitimacy represented a significant, but not exclusive factor which may have encouraged the population's loyalty by reflecting their attitudes and concerns and channelling them in a particular direction. The discourse also interpreted reality to support the legitimacy of the system. This might have contributed significantly to the stability of the whole system, and its ability to survive the post-1989 transitions experienced in other communist countries. The research examines the content and internal mechanics of the discourse, its assumptions and endogenous references, taking into account the specific context of the single-party communist state in control of the country's media and mass organisations. By suppressing alternative discourses, the system increased the impact of the hegemonic discourse, especially if compared to pluralist political systems. The discourse might have contributed to the continuing loyalty of the population by explicitly and implicitly stressing endogenous sources of legitimacy intelligible to the Cuban audience, reflecting its particular historical experience and political culture. The research investigates the sources of legitimacy traceable in the discourse, to demonstrate what made it tick internally and why some Cubans might have decided to remain loyal to a system that they perceived as legitimate and defending their interests, attitudes, concerns and identities. Collaterally, the research addresses the topic of migration, which was a main issue during both crises, and the way the perceptions of migration shifted over time in order to protect the legitimacy of the system confronting large outflows of discontented people. The research demonstrates how the system interpreted events in its favour, and how it prioritised different sources of legitimacy, such as independence, patriotism, socialism, material prosperity, social provision, culturalism and the US embargo in order to encourage loyalty. The research takes into account the regional Hispano-Caribbean context, reflecting the identities of the Cuban population in their perceived difference from Anglo-Saxon America and its socio-political model. The research looks in more detail at the key sources of legitimacy during the challenging 1990s when the system was near a possible collapse. The research enhances our understanding of how the sources of legitimacy shifted over time to reflect new realities and to support the system. The research sheds further light on the system and the structure of the system's endogenous ideology in a post-structuralist sense, stressing the role of language and the complex and extended definition of ideology. For this reason it takes into account Cuban semantics, linguistics and endogenous meaning of words and concepts. The existing academic literature focuses on explaining the stability of the system before and after 1989 by analysing Cuban history, institutions, culture, international relations and other aspects, but there is insufficient focus on legitimacy, politics and media addressed to the population as a possible factor in the system's stability. It does not investigate sources of legitimacy in relation to the content and internal mechanics of the discourse constructed to appeal to Cubans. This research answers these questions and thus enhances our understanding of the system. The research provides one possible answer to the question of how the system might have maintained stability, what sources of legitimacy it argued for, how it argued for them and how it interpreted current issues to encourage loyalty. It demonstrates how the system interpreted migration to cancel its potentially destabilising impact, and how it shifted the interpretations of the sources of legitimacy over time, especially in relation to the different global context before and after 1989.

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Larkin, Peter J. « Psychosocial sources of aggression in young adults with intellectual disabilities ». Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/3008/.

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BACKGROUND: Aggression can have a wide range of damaging consequences for both perpetrators and victims. Theoretical and empirical studies into problems of aggression increasingly show the importance of social and cognitive factors in aggressive behaviour. Such research has commonly been approached through the framework of the Social-Information Processing (SIP) model. SIP explains social behaviours by the sequence of cognitive processes that occur between encountering a social stimulus and enacting a response to it. Crucially, it is apparent that particular processing styles, such as the way in which people interpret others’ behaviour, play important roles in aggression. However, while SIP has long been used to explain aggression in the non-disabled population, it is only in more recent years that this approach has been applied to people with intellectual disabilities (IDs). This is important because a significant minority of people with IDs demonstrate frequent aggressive behaviour. Although several studies have already indicated that particular cognitive processing tendencies and aptitudes contribute to aggression in adults with ID, no research has considered younger people in the transition to adulthood. To this end, the present thesis sought to investigate the possible influences of certain psychosocial factors on this group of young people with mild to moderate IDs. OBJECTIVES: To identify which specific factors to investigate, a systematic review was conducted of existing research into SIP and aggression with people who have IDs. On the basis of these findings, the thesis examined 1) the social interactions that typically elicit anger, 2) experiences of parental aggression 3) ability to discern affect from dynamic social cues and 4) beliefs about the consequences of aggressive and submissive behaviour. With the review also stressing the importance of examining aggression at specific developmental stages, the studies focused on individuals in the transition from adolescence to adulthood (between 16 and 20 years). Although this stage is thought to be important in the development of cognitive factors associated with aggression, there is little or no research in this area with young adults with IDs. METHODS: The thesis comprised four distinct research studies. Each adopted a group-comparison design, comparing aggressive and non-aggressive young people with IDs. To evaluate the extent to which findings were specific to people with IDs, additional comparisons were conducted between aggressive and non-aggressive individuals without IDs. For Study 1, 26 young adults with IDs and 20 non-disabled young adults completed a semi-structured interview about a recent experience of interpersonal conflict. Participants were asked to describe their beliefs and feelings about the event and their subsequent response. Studies 2, 3 and 4 used data from a second phase of data collection involving 46 young people with and 48 people without IDs. Study 2 used a task in which participants were asked to rank different types of social conflict in order of provocativeness. The author developed these scenarios to reflect the experiences of conflict reported by participants in Study 1. Participants also indicated how recently they had encountered each type of scenario. Study 3 used motion-capture stimuli of people walking in different emotional states to examine whether groups differed in how they encode dynamic social cues. Study 4 used provocative vignettes to examine whether aggressive young people with IDs expect different outcomes from aggressive and submissive responses to such scenarios. RESULTS: Study 1 found that participants with IDs were more likely to encounter conflict with strangers or peers outside their friendship group. They were also more likely to describe incidents of aggression and to characterise people with whom they were in conflict globally as “bad” and to perceive their actions as being personally directed at them. Study 2 did not suggest that experiences of being victimised by peers were more common for people with IDs, but did show that aggressive individuals were more likely to encounter incidents of physical aggression from peers. Parental conflict was the most recently encountered, but was perceived to be the least provocative form of conflict for all groups. In Study 3, no group differences were found in accuracy or response tendencies for the emotion recognition task. Aggressive and non-aggressive participants with IDs in Study 4 did not predict different outcomes form aggression and submission. However, the aggressive participants without IDs predicted more positive outcomes from aggression and more negative outcomes for submission. While aggressive participants with IDs were more likely to give aggressive responses, they were just as likely as the non-aggressive group to respond actively (assertively or aggressively) rather than passively. CONCLUSION: The findings of this thesis, viewed from the perspective of the SIP model, suggest that there are key cognitive and contextual differences between individuals who show frequent aggression, both with and without IDs. Although, somewhat surprisingly, emotion recognition skills did not appear to be associated with a tendency toward aggressive behaviour, the non-ID aggressive and non-aggressive groups differed in their anticipated outcomes for aggressive and submissive behaviour. The context in which conflict occurred also appeared to differ between those young people with and without IDs. However, the absence of some predicted findings from these studies may be related to methodological shortcomings; these possible limitations are considered, and directions for future work are suggested. Applications for clinical practice and policy are also discussed and recommendations for future research are given.

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Dewez, Véronique. « Sources, limites d'extension et fusion des glaciers au Wisconsinien supérieur dans la chaine Ruby et le bassin d'Aishihik, Territoire du Yukon ». Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5110.

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Welch, Denise Claire. « A methodology for the measurement of distributed agricultural sources of ammonia outdoors ». Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/13268/.

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Ammonia is the most prevalent alkaline gas in the atmosphere and plays an important role in environmental pollution through acidification and eutrophication. Livestock are the largest source of ammonia in the UK, mainly originating during storage and spreading of animal manure. The aim of this study was to validate the collection efficiency of recurved passive ammonia flux (PAF) samplers and the flux frame method to provide a robust methodology for measurement of distributed agricultural sources of ammonia outdoors. The collection efficiency of recurved PAF samplers was determined in a wind tunnel under controlled conditions of ammonia flux (0.771 - 13.49 mg NH3 m-2 s-1), and at angles of orientation to the flow direction (0, 30, 60, 70, 80, 90°). The samplers were effective up to a wind speed of 7 m s-1 and an angle of 80°, with a mean collection efficiency of 71%. The flux frame method had a mean collection efficiency of 87.4% when used with ground level point sources under controlled conditions in the Atmospheric Flow Laboratory. However, in controlled field releases, the efficiency fell to 56.4%. The flux frame method was also suitable for line sources, although assumptions must be made about the source homogeneity and plume dispersion. ADMS modelling was used to predict the collection efficiencies for the flux frame method and these agreed with measured collection efficiencies to within 37.3%. A comparison of source strengths determined using a full size flux frame and portions of the flux frame showed that a full size flux frame was unnecessary as one column of samplers produced a very similar estimate to that of the whole frame. The validated method was then used to measure ammonia emissions from free-range pigs. The amount of ammonia emitted from this source was very low and less than 0.16 g (kg of sow)-1 day-1.

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Menary, Jonathan. « Innovation in the UK fresh produce industry : sources, barriers and innovative capacity ». Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/104208/.

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The UK fresh produce industry faces a number of challenges, including new pests and diseases, foreign competition and the cost of and access to seasonal labour. ‘Innovation’ has been promoted to meet these challenges, but the sources of innovation, and what holds it back, have not been explored. This thesis aims to: 1) identify the sources of innovation in the fresh produce industry, 2) determine the barriers to innovation in the industry and 3) seek ways to improve the overall innovative capacity of the sector. It does so by using the Agricultural Innovation Systems (AIS) approach as an underpinning framework within a case study design. 32 industry practitioners, including growers, technologists, researchers and retailers took part in semi-structured interviews, which were analysed using Framework Analysis. The study finds an increasingly consolidated and competitive industry, influenced heavily by retail groups and the need for constant innovation. It describes ‘types’ of innovation and their interlinked nature, as well as the inherent uncertainty around innovation and the difficulties in ‘measuring’ change. It finds that innovation often originates overseas and through experimentation or interaction with a given product or process. It describes both positive and negative communication in the industry and explores other blocking mechanisms to innovation including horizontal and vertical fragmentation, diverging innovation agendas and a “defensive” innovation culture. It also identifies a number of enabling factors for change. Interactivity and network formation are recognised as vital components of the innovation system. However, considerable emphasis is placed on non-systemic factors, such as entrepreneurialism. These findings are combined with existing literature in a functional-structural analysis to offer recommendations to bolster innovative capacity in the industry. The study makes several original contributions to knowledge, particularly with respect to the AIS approach: that innovation systems routinely extend beyond national borders, facilitated in part by another understudied issue – producer organisations – is an area for further research.

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Abdallah, Mohamed Abdel Galil Abou-Elwafa. « Investigating the sources and magnitude of human exposure to halogenated organic pollutants using advanced methods for environmental analysis ». Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/546/.

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Analytical methods based on LC-ESI-MS/MS or LC-APPI-MS/MS were developed and/or validated for the separation and determination of BDE-209 and TBBP-A, in addition to HBCD diastereomers, enantiomers and degradation products in a wide range of samples including air, dust, diet, simulated GIT fluid, human serum and breast milk. The obtained concentrations were used to estimate the exposure of adults, toddlers and nursing infants to the target BFRs via inhalation, dust ingestion and diet using different exposure scenarios and the relative importance of each exposure pathway was assessed for the studied age groups. Causes of variability in concentrations of HBCDs in indoor dust were elucidated and forensic microscopy techniques were used to study the mechanisms of transfer of BDE-209 and HBCDs to indoor dust. A colon-enhanced physiologically based extraction model was developed and applied for the first time to study the bioaccessibility of target BFRs from human GIT. Exposure via dust ingestion, but not diet, correlated significantly (p<0.01) with ΣHBCDs in serum of 16 adults. The levels of target BFRs were reported for the first time in 28 human milk samples from the UK. The relationship between adult intake of BFRs and the observed body burdens was studied using a pharmacokinetic model. Although no enantioselective enrichment was detected in either dust or diet, enrichment of (-)-α-HBCD was observed in both human serum and milk which may be attributable to enantioselective absorption, metabolism and/or excretion.

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Sanchez, Aida Cuni. « Predicting suitable areas for cultivation and conservation of the baobab tree and investigating superior sources of planting material ». Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/196555/.

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The baobab tree (Adansonia digitata L.), with more than 300 uses and commercial value in EU and US, has been identified as one of the most important edible savannah trees to be conserved, domesticated and valorised in Africa. A decline in baobab populations due to overexploitation and/or changes in climate could have a significant negative effect on African livelihoods. Therefore, it is important to determine potential strategies for conservation and cultivation. The present and potential future distributions of the baobab tree were studied using Maxent niche modelling framework. And, in order to contribute to the selection of superior materials for cultivation, fruit morphology was studied in situ (in Malawi and Mali) while leaf and seedling morphology were studied in situ (in Benin and Malawi) and in a greenhouse experiment. Maxent modelling suggests that predicted changes in climate will have a negative effect on baobab tree distribution in Africa: only a percentage of the present distribution was predicted to be suitable in the future. Some countries were found not to have any suitable habitats for the baobab tree in the future. Several conservation strategies are recommended, such as in situ conservation in Protected Areas; ex situ conservation in Seed Banks and conservation through ‘sustainable utilisation’. Modelling results also showed that the baobab tree could be widely cultivated in most countries in south-eastern Africa and in the Sudano-Sahelian zone of West Africa. India, north-west Australia, Madagascar, north-east Brazil and Mexico could be other suitable places for cultivating the baobab tree outside Africa. Although results from modelling should be validated with in situ seedling experiments, there seems to be potential for the wide cultivation of this species. Significant differences in leaf, fruit and seedling morphology were observed between Benin, Mali and Malawi and also within each country. While some characteristics were correlated with environmental differences between study sites, others might be genetically determined. It seems that genetic and physiological effects play a role in baobab fruit, leaf and seedling morphology. Thus, there is room for selecting high quality baobab planting materials

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Chandran, Predeesh. « Different sources of resistance in soybean against soybean aphid biotypes ». Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/7061.

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Master of Science
Department of Entomology
John C. Reese
The soybean aphid, Aphis glycines Matsumura, arrived first to North America during the midst of 2000. It is a very fast spreading insect and causes a high yield loss of above 50% in most of the soybean growing tracts of United States. Another important economic threat is it’s ability to transmit some viruses to soybean. Studies to control this exotic pest started early during the year of its arrival. But a complete integrated pest management (IPM) approach that includes a combination of different control measures has yet to be completely developed. Host plant resistance is one component of integrated pest management and is more sustainable than any other control methods against this insect. In the first study, more than 80 genotypes were screened with two given aphid biotypes, biotype 1 and biotype 2. It was found that the genotypes that were earlier resistant to biotype 1 (K1639, K1642, K1613 K1621, Dowling and Jackson) were susceptible to the new biotype 2 with large populations developing on these genotypes. But we found three new Kansas genotypes that showed resistance only against biotype 1, but not against biotype 2. However, the two of the Michigan genotypes (E06902 and E07906-2) showed resistance to both biotype 1and biotype 2. In second study, the feeding behavior analyses of aphid biotypes were done using the EPG, Electrical penetration graph, technique for a recorded 9 hrs probing time. The resistant and susceptible genotypes show significant differences in their EPG parameters, especially for the sieve element duration in both biotypes. Most of the aphids reached sieve element phase (> 90%) in susceptible genotypes, but only few (<30%) were reached in resistant genotypes. But, no differences were found in any other probing phases between resistant and susceptible genotypes, except the number of potential drops (PDs) in biotype 2. Thus, it is concluded that resistance is largely associated with phloem tissues and there could be some biochemical, physical or morphological factors that affect the stylet penetration in aphids.

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Seifert, Anthony J. Ermoshkin Ilia K. « Analysis of Government Accountability Office and Department of Defense Inspector General reports and commercial sources on contracts ». Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/MBAPR/2010/Jun/10Jun%5FSeifert%5FMBA.pdf.

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"Submitted in partial fulfillment of the requirements for the degree of Master of Business Administration from the Naval Postgraduate School, June 2010."
Advisor(s): Apte, Uday M. ; Rendon, Rene G. "June 2010." "MBA Professional report"--Cover. Description based on title screen as viewed on July 15, 2010. Author(s) subject terms: Accountability, Benchmarking, Best Practices, Building Information Modeling, Contract Administration, Contract Closeout, Contract Termination, Contracting Officer Representative, GAO Reports, Government Contracts, IG Reports, Price Growth, Program Growth, Procurement, Service Contracts, Solicitation, Source Selection, Total Ownership Cost. Includes bibliographical references (p. 69-70). Also available in print.

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Seifert, Anthony J., et Ilia K. Ermoshkin. « Analysis of Government Accountability Office and Department of Defense Inspector General reports and commercial sources on contracts ». Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/10535.

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MBA Professional Report
The purpose of this MBA Project was to investigate and provide a comprehensive analysis of data based on government service contracts during the six phases of the government contract process (procurement/planning, solicitation planning, solicitation, source selection, contract administration and contract closeout/termination). Primary deficiencies and best practices in contracting will be identified for each government report, and an analysis will be conducted to identify trends within and across the above categories. Specifically, this research will identify common deficiencies and best practices in contracting based on GAO reports, DoD IG reports, and articles based on services acquisition in the commercial sector. This will provide the basis for further study of the subject, as well as material for improvement of DoD contracting practices as compared to commercial best practices in contracting.

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Erdogan, Celil. « Ethnic Interest Groups And American Foreign Policy : Sources Of Influence ». Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12611525/index.pdf.

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Ethnic interest groups have historically played a role in the making of American foreign policy but their influence has increased especially following the end of the Cold War. This influence has important repercussions on American foreign policy towards the home countries of the powerful ethnic groups and the regions that these countries are located in. Within this context, this thesis examines the sources or the reasons of the influence of ethnic interest groups on American foreign policy, which has also affected Turkish-American relations significantly. It first focuses on the structural factors that make ethnic influence possible such as the characteristics of the American political system and the important role that Congress plays in the formulation of foreign policy. It then discusses the organizational factors such as organizational strength and using of successful persuasion and dissuasion methods that make it possible to influence American foreign policy. It ends with a normative discussion on the desirability of ethnic influence on American foreign policy.

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Vlcek, Brian J. « Beyond the standard model| Ihc phenomenology, cosmology from post-inflationary sources, and dark matter physics ». Thesis, The University of Wisconsin - Milwaukee, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3613650.

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It is the goal of this dissertation to demonstrate that beyond the standard model, certain theories exist which solve conflicts between observation and theory -- conflicts such as massive neutrinos, dark matter, unstable Higgs vacuum, and recent Planck observations of excess relativistic degrees of freedom in the early universe. Theories explored include a D-brane inspired construct of U(3) × Sp(1) × U(1) × U(1) extension of the standard model, in which we demonstrate several possible observables that may be detected at the LHC, and an ability to stabilize the Higgs mechanism. The extended model can also explain recent Planck data which, when added to HST data gives an excess of relativistic degrees of freedom of Δ N = 0.574 ± 0.25 above the standard result. Also explored is a possible non-thermal dark matter model for explanation of this result. Recent observations of Fermi bubble results indicate a signal of a 50 GeV dark matter particle annihilating into b b-bar, with a thermally averaged annihilation cross section corresponding to <σ v> = 8 × 10

(-27) cm

3/s, spurs interestin a Higgs portal model suggested by Steven Weinberg. Other implications of this model are also explored such as its ability to explain dark matter direct detection results along with LHC Higgs data, and Planck data. Particle physics is complimented by possible stochastic gravitational wave searches for which a model of second order global phase transitions is explored. These transitions generate gravitational wave spectra with amplitudes of order Ω(gw) h

2 = 10

(-24) - 10

(-15). Furthermore, techniques into such calculationsare investigated in hopes to improve the stability required in such lattice simulations.

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Hong, Qian. « Monte Carlo calculation and analysis of neutron and gamma fields at spallation neutron sources for simulating cosmic radiation ». Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/16647/.

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The research of the neutron induced Single Event Effect (SEE) at aircraft altitudes or at ground level are very important since the neutron radiation is able to cause serious errors or damages on electronic components and system. TheWeapons Neutron Research (WNR) facility at Los Alamos Neutron Science Center (LANSCE), and ANITA (Atmospheric-like Neutrons from thIck TArget) facility at The Svedberg Laboratory (TSL) both provide spallation neutron source for radiation testing of electronic components. A local beam monitoring system was successfully developed by S. Platt and L. Zhang in the University of Central Lancashire for measuring neutron dosimetry during accelerated SEE testing of electronic devices with using silicon photodiode. However, such silicon photodiode is sensitive to gamma-ray as well. For above reasons, characterization of neutron and gamma fields at spallation neutron sources used for accelerated SEE testing has become the purpose of this work. Monte Carlo calculation of radiation fields at spallation neutron source was used to characterize neutron and gamma energy spectra for accelerated single event effect testing. Geant4 (GEometry ANd Tracking version 4) toolkit, using Monte Carlo method, was used to simulate a preliminary model of spallation neutron source at LANSCE (ICE House, WNR) and TSL (ANITA) for understanding physical mechanisms of neutron and gamma interactions with matter. At first, two preliminary spallation neutron sources on basis of WNR (ICE House) and ANITA facilities were modeled with using two intra-nuclear cascade models (bertini, binary) provided by Geant4 reference physics lists. The result of neutron spectrum with binary INC model agrees well with LANSCE measurement data and independent calculation results in each case. In this computation, gamma dose rates at WNR and ANITA were calculated, and gamma dose rate from the simulation is consistent with the ANITA measurement results. The results of photon energy spectra with using Geant4 toolkit presents a continuum between 0.1MeV and 10MeV, and the annihilation peak at 0.5MeV. However, calculation results of neutron spectrum at ANITA facility with using binary INC model match ANITA measurements less well in absolute neutron yield above 20MeV, which is likely due to the missing geometry components in preliminary spallation neutron source simulation. A more complex model of ANITA facility was constructed with adding bending magnet, shielding components, detector system, and collimator, which makes modelling as realistically as possible. The discrepancy in absolute neutron yield between simulation results and measurements data has improved at Standard User Position (SUP) of ANITA facility, in contrast with the preliminary modelling of ANITA neutron source. At the same time, a new position referred as Close User Position (CUP) was investigated in order to compare with ANITA measurement informed by Monte Carlo N-Particle eXtended (MCNPX) simulation results. The neutron spatial distribution, radius effect for neutrons, neutron beam profiles, and time of flight spectra were calculated at the SUP and CUP positions for different collimator apertures of 3 cm, 10.2 cm, and 30 cm, respectively. A comparison of simulated neutron beam profiles folded with 238U (n, f) cross-section with ANITA measurements at the SUP and CUP-TOF positions was used for validating improved ANITA neutron source modelling. The neutron beam profiles in the horizontal direction were predicted with using Geant4, which filled the gap of geometrical limitation at ANITA facility for accelerated single event effect testing. It is the first time to predict gamma dose rate at the SUP and CUP positions for 3 cm, 10.2 cm, and 30 cm collimators with using Geant4 modelling of ANITA neutron source. In addition, the gamma dose rate at the SUP position is consistent with ANITA measurement data. Finally, the gamma yield, photon spatial distribution, dose rate against energy are considered for gamma field at the SUP and CUP positions, which have contributed to understand and analyse gamma interactions with matter.

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Meegahawatte, Danushka Hansitha. « A design method for specifying power sources for hybrid power systems ». Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1215/.

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Many efforts have been made in recent years to address issues surrounding the use of fossil fuels for energy. However, it must be conceded that world’s dependence on fossil fuels cannot cease overnight. In reality, the switch is expected to be a relatively slow migration of technologies over many decades. During this transition period the world will need bridging technologies to aid in the transition to alternate energy sources. One such technology, which shows much promise in boosting energy efficiency while reducing emissions and costs, is the adoption of hybrid power systems. This thesis investigates the motives behind seeking alternate energy sources and discusses the future need to move away from fossil fuels and the likely role hybrid power systems will play in the future. A general outline of a hybrid power system is presented, and its key subsystems identified and discussed, paying attention to power generation, energy storage technologies and the performance of these systems. A novel method of specifying the power sources in bespoke hybrid power systems are presented. A custom software tool aimed at evaluating how different hardware configurations and output duty cycles affect the performance of a hybrid power system is then presented and used in several case studies to investigate the effectiveness of the presented method in specifying power sources for a given application. It was found that the hardware, output application and control strategy of a hybrid power system affects the overall performance of the system. Furthermore, if the output duty cycle of a hybrid power system is repetitive and predictable in nature, it was found that the hardware and control strategy of the system can be fine-tuned using simple techniques to optimise the overall system configuration and performance.

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Panov, Stoyan Minkov. « The obligation aut dedere aut judicare ('extradite or prosecute') in international law : scope, content, sources and applicability of the obligation 'extradite or prosecute' ». Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6521/.

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The thesis focuses on the scope, content, sources and applicability of the obligation aut dedere aut judicare pertaining to certain international crimes such as genocide, war crimes, crimes against humanity, the prohibition of torture, drug trafficking, hijacking of civil aviation and terrorist bombing and financing of terrorism in international law. The general framework of the thesis focuses on the legal base of the obligation aut dedere aut judicare, the scope and content of the obligation, the triggering mechanisms of the duty, and state responsibility for preaches of the obligation. The relevant core crimes and transnational crimes are examined in relation to the obligation, based on and formulated in various multilateral, widely-ratified conventions and state practice. State practice and opinio juris indicate that a customary aut dedere aut judicare duty has formed or crystallized for certain international crimes such as the prohibition of torture, genocide, grave breaches of international humanitarian law, including war crimes, and crimes against humanity. As regards the offences against the safety of civil aviation and hijacking, terrorism-related crimes, international drug trafficking, and crimes against UN personnel, the evidence is mixed and it is more appropriate to conclude that an emerging custom of the obligation 'extradite-or-prosecute' for these crimes is forming.

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Agustí, Batlle Jordi. « Nonlinear micro/nano-optomechanical oscillators for energy transduction from IR sources ». Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285101.

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En aquesta tesi es proposa un nou dispositiu que combina antenes òptiques i micro/nanoestructures mecàniques amb l'objectiu de transformar energia electromagnètica en energia mecànica. El principal objectiu de la feina realitzada és l'estudi dels mecanismes de transducció implicats. El principi de funcionament d'aquest nou dispositiu es pot resumir de la manera següent: les antenes absorbeixen la radiació electromagnètica en l'espectre infraroig i la transformen en una distribució de temperatura en l'estructura mecànica, a causa de les propietats tèrmiques del material estructural la resposta tèrmica es converteix en una deflexió mecànica que eventualment pot conduir a l'autooscil·lació del dispositiu. Donades les transformacions d'energia involucrades, el modelatge de les físiques acoblades esdevé un pas fonamental per tal de dissenyar, fabricar i caracteritzar un dispositiu de prova de concepte. La conversió d'energies es demostra que és més eficient quan el dispositiu autooscil·la. No obstant això, a causa de la naturalesa altament no lineal d'aquest fenomen, saber exactament si aquesta oscil·lació es pot aconseguir utilitzant el dispositiu de prova de concepte implica caracteritzar-lo físicament per tal d'aplicar el model desenvolupat.
In this thesis, a new device merging optical antennas and micro/nano-mechanical structures is proposed with the aim to transform electromagnetic energy into mechanical energy. The study of the involved transduction mechanisms is the main objective of the presented work. The working principle of this new device can be summarized as follows: the antennas acting as absorbers in the infrared spectrum capture the electromagnetic radiation and transform it into a temperature field in the mechanical structure. Due to the thermal properties of the structural material the thermal response is converted to a mechanical deflection which eventually can lead to the self-oscillation of the device. Given the involved energy transformations, the modeling of the coupled physics becomes a fundamental step in the path of designing, fabricating and characterizing a proof-of-concept device. The energy conversion is shown to be more efficient when the device auto-oscillates. However, due the the highly nonlinear nature of such phenomenon precisely knowing if such oscillation can be achieved using the proof-of-concept device imply its physical characterization in order to apply the developed model.

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Hassan, Luna. « Assessing the information needs of historians working with digitised primary sources in the UK : a sequential mixed methods study ». Thesis, University of Huddersfield, 2013. http://eprints.hud.ac.uk/id/eprint/19321/.

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The way that historians do research has changed as more and more digitised primary sources have become available online. Whilst desktop access to historical resources is becoming the norm in the digital age, many historians prefer working with original sources. This observation triggered an investigation into the information needs and behaviour of historians with a view to identifying ways in which information retrieval system (IRS) might be enhanced to meet their specific needs. During the investigation it became apparent that the information-seeking behaviour (ISB) of historians involves a great deal of creative thinking and that IRS aimed at historians would benefit from features specifically designed to stimulate their creativity. The research described here follows a “mixed methods” approach in which quantitative and qualitative research techniques have been applied sequentially. The first, quantitative, phase of the study concerned the question of which format of primary sources (original or digitised) historians prefer to work with and why. Results from an online questionnaire, distributed to historians in the UK, revealed the historians’ preference for originals but with a very positive attitude towards digitised sources, which were considered to be more “useful”. This led the study to explore ways in which the “usefulness” of IRS could be further improved to support historical research. The exploration of these issues involved a qualitative analysis based on “grounded theory” techniques and led to certain specific recommendations to the designers of future IRS intended to support historical research.

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McArthur, Rachel. « Unraveling the Sources of Adolescent Substance Use : A Test of Rival Theories ». University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1321367411.

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Barbaresi, Adrien. « Construction de corpus généraux et spécialisés à partir du Web (Ad hoc and general-purpose corpus construction from web sources) ». Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL0993.

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Le premier chapitre s'ouvre par un description du contexte interdisciplinaire. Ensuite, le concept de corpus est présenté en tenant compte de l'état de l'art. Le besoin de disposer de preuves certes de nature linguistique mais embrassant différentes disciplines est illustré par plusieurs scénarios de recherche. Plusieurs étapes clés de la construction de corpus sont retracées, des corpus précédant l'ère digitale à la fin des années 1950 aux corpus web des années 2000 et 2010. Les continuités et changements entre la tradition en linguistique et les corpus tirés du web sont exposés. Le second chapitre rassemble des considérations méthodologiques. L'état de l'art concernant l'estimation de la qualité de textes est décrit. Ensuite, les méthodes utilisées par les études de lisibilité ainsi que par la classification automatique de textes sont résumées. Des dénominateurs communs sont isolés. Enfin, la visualisation de textes démontre l'intérêt de l'analyse de corpus pour les humanités numériques. Les raisons de trouver un équilibre entre analyse quantitative et linguistique de corpus sont abordées.Le troisième chapitre résume l'apport de la thèse en ce qui concerne la recherche sur les corpus tirés d'internet. La question de la collection des données est examinée avec une attention particulière, tout spécialement le cas des URLs sources. La notion de prétraitement des corpus web est introduite, ses étapes majeures sont brossées. L'impact des prétraitements sur le résultat est évalué. La question de la simplicité et de la reproducibilité de la construction de corpus est mise en avant.La quatrième partie décrit l'apport de la thèse du point de vue de la construction de corpus proprement dite, à travers la question des sources et le problèmes des documents invalides ou indésirables. Une approche utilisant un éclaireur léger pour préparer le parcours du web est présentée. Ensuite, les travaux concernant la sélection de documents juste avant l'inclusion dans un corpus sont résumés : il est possible d'utiliser les apports des études de lisibilité ainsi que des techniques d'apprentissage artificiel au cours de la construction du corpus. Un ensemble de caractéristiques textuelles testées sur des échantillons annotés évalue l'efficacité du procédé. Enfin, les travaux sur la visualisation de corpus sont abordés : extraction de caractéristiques à l'échelle d'un corpus afin de donner des indications sur sa composition et sa qualité
At the beginning of the first chapter the interdisciplinary setting between linguistics, corpus linguistics, and computational linguistics is introduced. Then, the notion of corpus is put into focus. Existing corpus and text definitions are discussed. Several milestones of corpus design are presented, from pre-digital corpora at the end of the 1950s to web corpora in the 2000s and 2010s. The continuities and changes between the linguistic tradition and web native corpora are exposed.In the second chapter, methodological insights on automated text scrutiny in computer science, computational linguistics and natural language processing are presented. The state of the art on text quality assessment and web text filtering exemplifies current interdisciplinary research trends on web texts. Readability studies and automated text classification are used as a paragon of methods to find salient features in order to grasp text characteristics. Text visualization exemplifies corpus processing in the digital humanities framework. As a conclusion, guiding principles for research practice are listed, and reasons are given to find a balance between quantitative analysis and corpus linguistics, in an environment which is spanned by technological innovation and artificial intelligence techniques.Third, current research on web corpora is summarized. I distinguish two main approaches to web document retrieval: restricted retrieval and web crawling. The notion of web corpus preprocessing is introduced and salient steps are discussed. The impact of the preprocessing phase on research results is assessed. I explain why the importance of preprocessing should not be underestimated and why it is an important task for linguists to learn new skills in order to confront the whole data gathering and preprocessing phase.I present my work on web corpus construction in the fourth chapter. My analyses concern two main aspects, first the question of corpus sources (or prequalification), and secondly the problem of including valid, desirable documents in a corpus (or document qualification). Last, I present work on corpus visualization consisting of extracting certain corpus characteristics in order to give indications on corpus contents and quality

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O'Connor, Daryl Brian. « An investigation of job strain and sources of occupational stress on mental well-being, and physiological activity in general practitioners ». Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367009.

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Лахтіонова, Людмила Анатоліївна, Людмила Анатольевна Лахтионова, Lyudmila Lakhtionova, Наталія Петрівна Муранова, Наталья Петровна Муранова, Natalia Muranova, Олександр Євгенович Бугайов, Александр Евгеньевич Бугаев et Oleksandr Bugaiov. « A general assessment of the Russian venture company financing sources according to the balance sheet : the Ukrainian methods of analysis ». Thesis, Monaco : Plateforme scientifique européenne, 2020. http://er.nau.edu.ua/handle/NAU/42207.

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The article evaluates the sources of financing of the Russian Venture Company based on the balance sheet data based on the latest achievements of the Ukrainian method of financial analysis.
В статі оцінюються джерела фінансування Російської венчурної компанії за даними балансу на основі останніх досягнень української методики фінансового аналізу.
В статье оцениваются источники финансирования Российской венчурной компании по данным баланса на основе последних достижений украинской методики финансового анализа.

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Murphy, Eric J., Emmanuel Momjian, James J. Condon, Ranga-Ram Chary, Mark Dickinson, Hanae Inami, Andrew R. Taylor et Benjamin J. Weiner. « The GOODS-N Jansky VLA 10 GHz Pilot Survey : Sizes of Star-forming μ JY Radio Sources ». IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/624727.

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Our sensitive (sigma(n) approximate to 572 nJy beam(-1)), high-resolution (FWHM theta(1/2) = 0"22 approximate to 2 kpc at z greater than or similar to 1), 10 GHz image covering a single Karl G.. Jansky Very Large Array (VLA) primary beam (FWHM circle minus(1/2) approximate to 4.'25) in the GOODS-N field contains 32 sources with S-p greater than or similar to 2 mu Jy beam(-1) and optical and/or near-infrared (OIR) counterparts. Most are about as large as the star-forming regions that power them. Their median FWHM major axis is = 167 +/- 32 mas approximate to 1.2 +/- 0.28 kpc, with rms scatter approximate to 91 mas approximate to 0.79 kpc. In units of the effective radius re that encloses half their flux, these radio sizes are re approximate to 69 +/- 13 mas approximate to 509 +/- 114 pc, with rms scatter approximate to 38 mas approximate to 324 pc. These sizes are smaller than those measured at lower radio frequencies, but agree with dust emission sizes measured at mm/sub-mm wavelengths and extinction-corrected H alpha sizes. We made a lowresolution (theta(1/2) = 1."0) image with approximate to 10x better brightness sensitivity, in order to detect extended sources and measure matched-resolution spectral indices alpha(10 GHz)(1.4 GHz) 10 GHz. It contains six new sources with Sp. 3.9 mJy beam-1 and OIR counterparts. The median redshift of all 38 sources is similar to z similar to = 1.24 +/- 0.15. The 19 sources with 1.4 GHz counterparts have a median spectral index of = -0.74 +/- 0.10 10 GHz, with rms scatter approximate to 0.35. Including upper limits on a for sources not detected at 1.4 GHz flattens the median to greater than or similar to -0.61 10 GHz, suggesting that the mu Jy radio sources at higher redshifts-and hence those selected at higher rest-frame frequencies-may have flatter spectra. If the non-thermal spectral index is alpha(NT) approximate to -0.85, the median thermal fraction of sources selected at median rest-frame frequency approximate to 20 GHz is greater than or similar to 48%.

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RAFI, Selwa. « Chaînes de Markov cachées et séparation non supervisée de sources ». Phd thesis, Institut National des Télécommunications, 2012. http://tel.archives-ouvertes.fr/tel-00995414.

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Le problème de la restauration est rencontré dans domaines très variés notamment en traitement de signal et de l'image. Il correspond à la récupération des données originales à partir de données observées. Dans le cas de données multidimensionnelles, la résolution de ce problème peut se faire par différentes approches selon la nature des données, l'opérateur de transformation et la présence ou non de bruit. Dans ce travail, nous avons traité ce problème, d'une part, dans le cas des données discrètes en présence de bruit. Dans ce cas, le problème de restauration est analogue à celui de la segmentation. Nous avons alors exploité les modélisations dites chaînes de Markov couples et triplets qui généralisent les chaînes de Markov cachées. L'intérêt de ces modèles réside en la possibilité de généraliser la méthode de calcul de la probabilité à posteriori, ce qui permet une segmentation bayésienne. Nous avons considéré ces méthodes pour des observations bi-dimensionnelles et nous avons appliqué les algorithmes pour une séparation sur des documents issus de manuscrits scannés dans lesquels les textes des deux faces d'une feuille se mélangeaient. D'autre part, nous avons attaqué le problème de la restauration dans un contexte de séparation aveugle de sources. Une méthode classique en séparation aveugle de sources, connue sous l'appellation "Analyse en Composantes Indépendantes" (ACI), nécessite l'hypothèse d'indépendance statistique des sources. Dans des situations réelles, cette hypothèse n'est pas toujours vérifiée. Par conséquent, nous avons étudié une extension du modèle ACI dans le cas où les sources peuvent être statistiquement dépendantes. Pour ce faire, nous avons introduit un processus latent qui gouverne la dépendance et/ou l'indépendance des sources. Le modèle que nous proposons combine un modèle de mélange linéaire instantané tel que celui donné par ACI et un modèle probabiliste sur les sources avec variables cachées. Dans ce cadre, nous montrons comment la technique d'Estimation Conditionnelle Itérative permet d'affaiblir l'hypothèse usuelle d'indépendance en une hypothèse d'indépendance conditionnelle

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Geary, Ryan D. « A review of offshore wind technology and the development of the Virginia coastline and outer continental shelf / ». Full-text of dissertation on the Internet (1.84 MB), 2009. http://www.lib.jmu.edu/general/etd/2009/Masters/Geary_RyanD/gearyrd_masters_12-10-2009_01.pdf.

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Padavich, Andrew J. « Perceptions of an Air Campaign : the 1991 Persian Gulf War as portrayed by major American print media sources ». Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/468.

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Ramírez, Jávega Francisco. « Graph-based techniques for compression and reconstruction of sparse sources ». Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/385349.

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The main goal of this thesis is to develop lossless compression schemes for analog and binary sources. All the considered compression schemes have as common feature that the encoder can be represented by a graph, so they can be studied employing tools from modern coding theory. In particular, this thesis is focused on two compression problems: the group testing and the noiseless compressed sensing problems. Although both problems may seem unrelated, in the thesis they are shown to be very close. Furthermore, group testing has the same mathematical formulation as non-linear binary source compression schemes that use the OR operator. In this thesis, the similarities between these problems are exploited. The group testing problem is aimed at identifying the defective subjects of a population with as few tests as possible. Group testing schemes can be divided into two groups: adaptive and non-adaptive group testing schemes. The former schemes generate tests sequentially and exploit the partial decoding results to attempt to reduce the overall number of tests required to label all members of the population, whereas non-adaptive schemes perform all the test in parallel and attempt to label as many subjects as possible. Our contributions to the group testing problem are both theoretical and practical. We propose a novel adaptive scheme aimed to efficiently perform the testing process. Furthermore, we develop tools to predict the performance of both adaptive and non-adaptive schemes when the number of subjects to be tested is large. These tools allow to characterize the performance of adaptive and non-adaptive group testing schemes without simulating them. The goal of the noiseless compressed sensing problem is to retrieve a signal from its lineal projection version in a lower-dimensional space. This can be done only whenever the amount of null components of the original signal is large enough. Compressed sensing deals with the design of sampling schemes and reconstruction algorithms that manage to reconstruct the original signal vector with as few samples as possible. In this thesis we pose the compressed sensing problem within a probabilistic framework, as opposed to the classical compression sensing formulation. Recent results in the state of the art show that this approach is more efficient than the classical one. Our contributions to noiseless compressed sensing are both theoretical and practical. We deduce a necessary and sufficient matrix design condition to guarantee that the reconstruction is lossless. Regarding the design of practical schemes, we propose two novel reconstruction algorithms based on message passing over the sparse representation of the matrix, one of them with very low computational complexity.
El objetivo principal de la tesis es el desarrollo de esquemas de compresión sin pérdidas para fuentes analógicas y binarias. Los esquemas analizados tienen en común la representación del compresor mediante un grafo; esto ha permitido emplear en su estudio las herramientas de codificación modernas. Más concretamente la tesis estudia dos problemas de compresión en particular: el diseño de experimentos de testeo comprimido de poblaciones (de sangre, de presencia de elementos contaminantes, secuenciado de ADN, etcétera) y el muestreo comprimido de señales reales en ausencia de ruido. A pesar de que a primera vista parezcan problemas totalmente diferentes, en la tesis mostramos que están muy relacionados. Adicionalmente, el problema de testeo comprimido de poblaciones tiene una formulación matemática idéntica a los códigos de compresión binarios no lineales basados en puertas OR. En la tesis se explotan las similitudes entre todos estos problemas. Existen dos aproximaciones al testeo de poblaciones: el testeo adaptativo y el no adaptativo. El primero realiza los test de forma secuencial y explota los resultados parciales de estos para intentar reducir el número total de test necesarios, mientras que el segundo hace todos los test en bloque e intenta extraer el máximo de datos posibles de los test. Nuestras contribuciones al problema de testeo comprimido han sido tanto teóricas como prácticas. Hemos propuesto un nuevo esquema adaptativo para realizar eficientemente el proceso de testeo. Además hemos desarrollado herramientas que permiten predecir el comportamiento tanto de los esquemas adaptativos como de los esquemas no adaptativos cuando el número de sujetos a testear es elevado. Estas herramientas permiten anticipar las prestaciones de los esquemas de testeo sin necesidad de simularlos. El objetivo del muestreo comprimido es recuperar una señal a partir de su proyección lineal en un espacio de menor dimensión. Esto sólo es posible si se asume que la señal original tiene muchas componentes que son cero. El problema versa sobre el diseño de matrices y algoritmos de reconstrucción que permitan implementar esquemas de muestreo y reconstrucción con un número mínimo de muestras. A diferencia de la formulación clásica de muestreo comprimido, en esta tesis se ha empleado un modelado probabilístico de la señal. Referencias recientes en la literatura demuestran que este enfoque permite conseguir esquemas de compresión y descompresión más eficientes. Nuestras contribuciones en el campo de muestreo comprimido de fuentes analógicas dispersas han sido también teóricas y prácticas. Por un lado, la deducción de la condición necesaria y suficiente que debe garantizar la matriz de muestreo para garantizar que se puede reconstruir unívocamente la secuencia de fuente. Por otro lado, hemos propuesto dos algoritmos, uno de ellos de baja complejidad computacional, que permiten reconstruir la señal original basados en paso de mensajes entre los nodos de la representación gráfica de la matriz de proyección.

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Nassif, Alaa Abdullah. « Organisational and social aspects, specific safety measures, cultural conditions impact on risk sources control, and general safety on manned offshore oil platform facilities in Saudi Arabia ». Thesis, University of Salford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402046.

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Akcaoglu, Mustafa Ozturk. « An Assessment Of Academic Writing Needs Of Graduate Students ». Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613608/index.pdf.

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This study mainly aimed at investigating the academic writing needs and writing self-efficacy beliefs of graduate students studying at an English-medium university, Ankara. Furthermore, such areas that have a crucial role in determining writing needs as the frequency of writing tasks, usefulness of written sources, perceived importance of academic writing, and role of Turkish while writing were explored. In this study, quantitative data via &ldquo
Academic Writing Needs Assessment Survey for Graduate Students&rdquo
were collected from 213 graduate students enrolled at Graduate School of Social Sciences. Descriptive statistics, exploratory factor analysis, and multiple regression analyses were employed to analyze the data. The results of descriptive statistics indicated that the graduate students need a wider vocabulary repertoire in order to cope with the challenges of academic writing and they are mostly assigned longer research papers. In addition, using journal articles published in the area of specialization during writing was the most common method and more than half of the graduate students stated that when stuck with finding the right word, they first look for a Turkish word first. The exploratory factor analysis produced two factors and the regression analyses were carried out. The results yielded that the predictors accounted for 24% of the variance in productivity-related academic writing needs, and 22% of the variance in accuracy-related academic writing needs. For the productivity-related academic writing needs, writing self-efficacy and academic status made a significant contribution and for the accuracy-related academic writing needs, writing self-efficacy and English proficiency exam score were significant.

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Venter, Christo. « Millisecond pulsars and pulsar wind nebulae as sources of gamma rays and cosmic rays / C. Venter ». Thesis, North-West University, 2008. http://hdl.handle.net/10394/2067.

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Thèses sur le sujet « General sources »

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