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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
451

How the Choice of Bed Material Load Equations and Flow Duration Curves Impacts Estimates of Effective Discharge

Cope, Michael James 01 June 2017 (has links)
The purpose of this study is to analyze how estimates of an important geomorphic parameter, effective discharge, are impacted by the choice of bed material load equations and flow duration curves (FDCs). The Yang (1979), Brownlie (1981), and Pagosa equations developed by Rosgen (2006) were compared for predicting bed material load. To calculate the bed material load using the Pagosa equations, the bedload and suspended load are calculated separately and the results are added together. To compare the effectiveness of the equations, measured bed material load data from the USGS Open-File Report 89-67 were used. Following the calculations, the equation results were compared to the measured data. It was determined that the Pagosa equations performed the best overall, followed by Brownlie and then Yang. The superior performance of the Pagosa equations is likely due to the equations being calibrated. USGS regression equations for FDCs were compared to a method developed by Dr. David Rosgen in which a dimensionless FDC (DFDC) is developed. Weminuche Creek in southwestern Colorado was used as the study site. Rosgen's DFDC method requires the selection of a streamgage for a stream that exhibits the same hydro-physiographic characteristics as the site of interest. An FDC is developed for the gaged site and made dimensionless by dividing the discharges by the bankfull discharge of the gaged site. The DFDC is then made dimensional by multiplying by the bankfull discharge of the site of interest and the resulting dimensional FDC is taken as the FDC of the ungaged site. The USGS regression equations underpredicted the discharges while Rosgen's DFDC method overpredicted them. Rosgen's DFDC method produced more accurate results than the USGS regression equations for Weminuche Creek. To calculate the effective discharge, the FDC was used to develop a flow frequency curve which was then multiplied by the sediment rating curve. Effective discharge calculations were performed for Weminuche Creek using several combinations of bed material load prediction equations and FDCs. The USGS regression equations, Rosgen's DFDC method, and streamgage data were all used in conjunction with the Yang and Pagosa equations. The Brownlie equation predicted zero bed material load for Weminuche Creek, and was thus not used to calculate the effective discharge. When the USGS regression equations were used with the Yang and Pagosa equations, the calculated effective discharge was approximately 4.5 cms for both bed material load prediction equations. When Rosgen's DFDC method and streamgage data were used with the Yang and Pagosa equations, the effective discharge was approximately 13.5 cms. From these results, it was determined that the bed material load prediction equations had little impact on the effective discharge for Weminuche Creek while the FDCs did influence the results.
452

Phonological Quantity in Swedish Dialects : Typological Aspects, Phonetic Variation and Diachronic Change

Schaeffler, Felix January 2005 (has links)
<p>This study investigates the realisation of phonological quantity in the dialects of Modern Swedish, based on a corpus containing recordings from 86 locations in Sweden and the Swedishspeaking parts of Finland. The corpus was recorded as part of the national SweDia project.</p><p>The study is explorative in character. Quantity structures in Swedish dialects and their geographical distribution, as described in the dialectological literature, are compared to the results of a data-driven categorisation (cluster analysis). The results reveal an overall good correspondence of the data driven and the traditional categorisation, although with some deviations in the detail.</p><p>The study is divided into two parts. The first part lays the foundation for the data-driven categorisation, which is then described in the second part. First, the phonology and phonetics of quantity in Swedish are described in terms of durational distinctions and vocalic quality differences that typically accompany the durational differences. Preaspiration, which appears to be a normative feature in some dialects, is covered as well. An overview of the historical development of the Swedish quantity system is provided, with special emphasis on a phonological interpretation of quantity changes. Thereafter, dialectological evidence is combined with phonological and typological considerations to develop a categorisation of Swedish dialects.</p><p>The second part explains the methodology of cluster analysis and applies this method to vowel and consonant durations from one contrastive word pair, in order to obtain an alternative dialect categorisation. Analyses of vowel quality and preaspiration are performed in addition to the durational analyses. Hypotheses derived from the cluster analysis are then tested on one additional word pair recorded in 75 locations and on three additional word pairs recorded in four locations.</p><p>The general pattern emerging from the cluster analysis is a categorisation of the dialects into three main types, a Finland-Swedish, a Northern and a Southern type. This categorisation shows a good geographical agreement with the categorisation that is derived from the analysis of the dialectological literature. Therefore, the durational patterns of the three types are interpreted as reflections of three different phonological systems: 4-way systems with vocalic and consonantal quantity, 3-way systems with vocalic quantity and with consonantal quantity only after short vowels, and 2-way systems with complementary quantity. From the historical perspective, the 4-way system constitutes the most conservative and the 2-way system the most recently developed system.</p><p>Finally, it is argued that the historical development is one of the factors behind occasional mismatches between the data-driven and the dialectological categorisation. Data from one of the dialects, which has recently abandoned a 4-way system but has obviously retained the durational properties of the older system, is used as an example to illustrate this historical hypothesis.</p>
453

High frequency gas temperature and surface heat flux measurements

Iliopoulou, Vasiliki 14 September 2005 (has links)
Further improvements of the thermal efficiency of gas turbine cycle are closely coupled to the increase of turbine inlet temperature. This requires intensive and efficient cooling of the blades. In this perspective, experimental investigations of the gas temperature and heat transfer distribution around the airfoil are of primary importance. The present work aims at the development of two measurement techniques based on applications of the thin film sensors: the two-layer gauge for the wall heat transfer determination and the dual thin film probe for flow temperature measurements. Both techniques are used in short duration tunnels of the von Karman Institute (VKI) under engine representative conditions and are able to resolve both time-averaged component and time-resolved component i.e. periodic blade passing events at ~5-7 kHz with harmonics up to 50 kHz. In order to derive the wall heat flux with the two-layer gauge, the unsteady conduction equation is solved in the two-layer substrate using the measured value of the wall temperature as a boundary condition. The gauges are extensively calibrated and the data reduction method is validated on a blade of the second stator of the VKI turbine. A very good repeatability is achieved. Measurements are also performed on the complex geometry of a blade tip in a cascade configuration revealing the high three dimensionality of the flow. The dual thin film probe combines the operation of two thin films and determines the flow temperature from two independent heat flux measurements. The probe is calibrated and then validated with measurements downstream a cascade. The robustness and the reliability of the probe are also demonstrated by measurements downstream of the rotor and the second stator of the VKI turbine.
454

Phonological Quantity in Swedish Dialects : Typological Aspects, Phonetic Variation and Diachronic Change

Schaeffler, Felix January 2005 (has links)
This study investigates the realisation of phonological quantity in the dialects of Modern Swedish, based on a corpus containing recordings from 86 locations in Sweden and the Swedishspeaking parts of Finland. The corpus was recorded as part of the national SweDia project. The study is explorative in character. Quantity structures in Swedish dialects and their geographical distribution, as described in the dialectological literature, are compared to the results of a data-driven categorisation (cluster analysis). The results reveal an overall good correspondence of the data driven and the traditional categorisation, although with some deviations in the detail. The study is divided into two parts. The first part lays the foundation for the data-driven categorisation, which is then described in the second part. First, the phonology and phonetics of quantity in Swedish are described in terms of durational distinctions and vocalic quality differences that typically accompany the durational differences. Preaspiration, which appears to be a normative feature in some dialects, is covered as well. An overview of the historical development of the Swedish quantity system is provided, with special emphasis on a phonological interpretation of quantity changes. Thereafter, dialectological evidence is combined with phonological and typological considerations to develop a categorisation of Swedish dialects. The second part explains the methodology of cluster analysis and applies this method to vowel and consonant durations from one contrastive word pair, in order to obtain an alternative dialect categorisation. Analyses of vowel quality and preaspiration are performed in addition to the durational analyses. Hypotheses derived from the cluster analysis are then tested on one additional word pair recorded in 75 locations and on three additional word pairs recorded in four locations. The general pattern emerging from the cluster analysis is a categorisation of the dialects into three main types, a Finland-Swedish, a Northern and a Southern type. This categorisation shows a good geographical agreement with the categorisation that is derived from the analysis of the dialectological literature. Therefore, the durational patterns of the three types are interpreted as reflections of three different phonological systems: 4-way systems with vocalic and consonantal quantity, 3-way systems with vocalic quantity and with consonantal quantity only after short vowels, and 2-way systems with complementary quantity. From the historical perspective, the 4-way system constitutes the most conservative and the 2-way system the most recently developed system. Finally, it is argued that the historical development is one of the factors behind occasional mismatches between the data-driven and the dialectological categorisation. Data from one of the dialects, which has recently abandoned a 4-way system but has obviously retained the durational properties of the older system, is used as an example to illustrate this historical hypothesis.
455

Study into the Potential and Feasibility of a Standalone Solar-Wind Hybrid Electric Energy Supply System

Bekele, Getachew January 2009 (has links)
The tendency to use renewable energy resources has grown continuouslyover the past few decades, be it due to fear over warnings of globalwarming or because of the depletion and short life of fossil fuels or evenas a result of the interest which has developed among researchers doingscientific research into it. This work can be considered as joining any ofthese groups with an objective of giving electric light to the poorpopulation living in one of the poorest nations in the world.The aim of the work is to investigate supplying electric energy fromsolar-wind hybrid resources to remotely located communities detachedfrom the main grid line in Ethiopia. The communities in mind are one oftwo types; the first is the majority of the poor population residing in thecountryside; and the other is people relocated by the Government fromthe over used and dry regions to relatively productive and fertile ones inline with the long-term poverty reduction plan.The work was begun by investigating wind energy and solar energypotentials at four geographically different locations in Ethiopia bycompiling data from different sources and analyzing it using a softwaretool. The locations are Addis Ababa (09:02N, 038:42E), Mekele (13:33N,39:30E), Nazret (08:32N, 039:22E), and Debrezeit (8:44N, 39:02E).The results related to wind energy potential are given in terms of themonthly Average wind speed, the wind speed probability densityfunction (PDF), the wind speed cumulative density function (CDF), thewind speed duration curve (DC), and power density plots for all fourselected sites. According to the results obtained through the analysis, thewind energy potential, even if it is not exceptional, is irrefutably highenough to be exploited for generating electric energy.The solar energy potential, based on sunshine duration data collectedover a period of 7 - 11 years and radiation data obtained from differentsources, has been calculated using regression coefficients specific to thesites in question. Based on the sunshine duration data, the monthlyaverage daily sunshine amount for each of the places has also beencomputed and given in a form of plot. Through additional work on theresults of the calculations, the solar energy potential has been given inthe form of solar radiation plots for each of the selected sites. Asexpected, the results indicated an abundance of solar energy potential.It is based on the promising findings of these two energy resourcepotentials, wind and solar, that the feasibility study for a standalonesolar-wind hybrid energy supply system has proceeded, targeting thecommunity mentioned earlier. The hybrid system consisted of Windturbine, Photovoltaic panel, diesel generator and a bank of batteries, witha power conditioning converter included in the system.The hybrid standalone supply system is intended to provide electricity toa model community of 200 families with five to six family members ineach. The community is equipped with a primary load, a deferrable load,a community school and a health post. An electric load which includeslighting, water pumping, a radio receiver, and some clinical equipmenthas been suggested. Hybrid Optimization Model for ElectricRenewables, HOMER, software has been used for the analysis. Theaverage wind speed and average solar radiation calculated from the datafor all of the selected sites has been used to input into the software.The hybrid system design is approached in three different ways. The firstapproach is to include within the hybrid system those components whichare locally available, without giving special attention to their efficienciesand proceed with the design work. The second approach is tothoroughly search the market for the best and most efficienttechnological products and to select the best components for theanalysis. A third approach considered in an attempt of cost minimizationis to see if a self-contained type of design can be a better solution. Whatthis means is every household will have its own supply system that mayconsist of any combination of PV and wind turbine including converter,battery and charge controller.After running the simulations, lists of power supply systems have beengenerated, sorted according to their net present cost. Sensitivity variables,such as range of wind speeds, range of radiation levels and diesel pricehave been defined as inputs into the software and the optimizationprocess has been carried out repeatedly for the sensitivity variables andthe results have been refined accordingly. / QC 20100623
456

The Power of Timelessness and the Contemporary Influence of Modern Thought

Moss, Katie Reece 27 June 2008 (has links)
In this dissertation I examine a variety of modern and postmodern texts by applying the theories of French philosopher Henri Bergson. Specifically, I apply Bergson's theories of time, memory, and evolution to the texts in order to analyze the meaning of the poem and novels. I assert that all of the works disrupt conventional structure in order to question the linear nature of time. They do this because each must deal with the pressures of external chaos, and, as a result, they find timeless moments can create an internal resolution to the external chaos. I set out to create connections between British, Irish, and American literature, and I examine the influence each author has on others. The modern authors I examine include T. S. Eliot, James Joyce, Virginia Woolf, and William Faulkner. I then show the ways this application can elucidate the works of postmodern authors Toni Morrison and Michael Cunningham.
457

Experimental study and numerical simulations of the spectral properties of XUV lasers pumped by collisional excitation.

Meng, Limin 20 December 2012 (has links) (PDF)
Improving the knowledge of the spectral and temporal properties of plasma-based XUV lasers is an important issue for the ongoing development of these sources towards significantly higher peak power. The spectral properties of the XUV laser line actually control several physical quantities that are important for applications, such as the minimum duration that can be achieved (Fourier-transform limit). The shortest duration experimentally achieved to-date is ~1 picosecond. The demonstrated technique of seeding XUV laser plasmas with a coherent femtosecond pulse of high-order harmonic radiation opens new and promising prospects to reduce the duration to a few 100 fs, provided that the gain bandwidth can be kept large enough.XUV lasers pumped by collisional excitation of Ni-like and Ne-like ions have been developed worldwide in hot plasmas created either by fast electrical discharge, or by various types of high-power lasers. This leads to a variety of XUV laser sources with distinct output properties, but also markedly different plasma parameters (density, temperature) in the amplification zone. Hence different spectral properties are expected. The purpose of our work was then to investigate the spectral behaviour of the different types of existing collisional excitation XUV lasers, and to evaluate their potential to support amplification of pulses with duration below 1 ps in a seeded mode.The spectral characterization of plasma-based XUV lasers is challenging because the extremely narrow bandwidth (typically ∆λ/λ ~10-5) lies beyond the resolution limit of existing spectrometers in this spectral range. In our work the narrow linewidth was resolved using a wavefront-division interferometer specifically designed to measure temporal coherence, from which the spectral linewidth is inferred. We have characterized three types of collisional XUV lasers, developed in three different laboratories: transient pumping in Ni-like Mo, capillary discharge pumping in Ne-like Ar and quasi-steady state pumping in Ne-like Zn. Besides the accurate measurement of the temporal coherence of the laser in each case, we have studied the spectral behaviour when the laser is operated in the saturation regime and (in Ni-like Mo) when it is seeded with high-order harmonic radiation. We have also investigated the temporal behaviour of the Ni-like Mo transient XUV laser, using an ultrafast X-ray streak camera. Our linewidth measurements are compared with detailed numerical calculations including relevant broadening mechanisms as well as radiative transfer effects. The evolution of the spectral profile with amplification and saturation was studied for different plasma parameters, and corresponding Fourier-transform limit duration were evaluated.The shortest temporal coherence (ie the largest bandwidth) is measured for the quasi-steady state pumping XUV laser, which operates at the highest density and ionic temperature.
458

Development Of An Activity Based Risk Assessment Tool Using Integrated Duration

Ozer, Ahmet Hamdi 01 September 2006 (has links) (PDF)
As the construction sector is becoming more competitive in recent years, it has become more important to estimate the duration and cost of the construction projects and to calculate the risks&rsquo / effects correctly. The aim of this thesis is to estimate the duration and cost of construction projects accurately using an activity based risk assessment method which is based on the integrated duration &ndash / cost influence network diagram model proposed by Tah and Poh (2006). Within the context of this thesis, a web based risk assessment tool using the integrated duration &ndash / cost influence network at an activity level is developed to estimate the possible cost overrun and delay in construction projects. Risk breakdown structure for construction projects is created which enables the evaluation of risk effects at an activity level. The developed tool uses Monte Carlo Simulation Technique and Risk Rating Method. The results of the developed tool are compared with those of traditional methods and the reliability of the developed tool is validated.
459

Prospective Duration Judgments: The Role Of Attention And Secondary Tasks

Duzcu, Halil 01 February 2011 (has links) (PDF)
It is known that concurrent secondary tasks or attentionally salient stimuli shorten reproduced temporal durations. The main aim of this thesis is to use three types of secondary tasks to see their effects on duration judgments. The Attentional Gate Model (Block &amp / Zakay, 2006) served as theoretical background for a series of 4 experiments. There were 2 baseline/control experiments for studying the effect of 2 different and novel secondary tasks which are temporal comparison and non-temporal executive tasks. Three duration lengths (short-moderate-long) were used (15, 30 and 45 sec) that subjects had to reproduce. In Exp-1 (control experiment for Exp-2) subjects had to reproduce almost empty time intervals. Exp-2, which investigated the role of a secondary temporal task, revealed significantly decreased reproduced durations as compared to Exp-1 which is in line with our hypothesis. In Exp-3 (control experiment for Exp-4) subjects carried out a non-temporal/non-executive secondary task. Exp-4, in which a Simon task was used as a non-temporal executive secondary task, resulted in significantly decreased reproduced durations as compared to Exp-3 as well. Moreover, duration length effects were found for all experiments that included an attention consuming secondary tasks (Exp-2-3-4), i.e., longer durations were more underestimated than shorter ones in the presence of attention demanding tasks. We conclude that secondary temporal tasks and even more so executive non-temporal tasks can lead to decreased temporal duration judgements, thus affecting subjects&rsquo / time perception, in line with the Attentional Gate Model.
460

Ereignisbezogene Veränderungen der visuellen Fixationsdauer / Event related prolongations of visual fixation duration

Pannasch, Sebastian 21 September 2003 (has links) (PDF)
Der Ansatz der Arbeit lässt sich auf zwei Gebiete aus der Blickbewegungsforschung zurückführen. Einerseits basieren die Studien auf Experimenten zum remote distractor effect, andererseits auf Untersuchungen beim Lesen bzw. der Wahrnehmung komplexer Szenen. Innerhalb beider Ansätze findet eine Analyse der Auswirkungen unterschiedlichen Reizmaterials (z.B. Texte oder Bilder) auf die Fixationsdauer statt. Aktuelle Erklärungsansätze werden im Bezug zu den gefundenen Ergebnissen dargestellt und kritisch bewertet. Anhand der Ergebnisse einer Voruntersuchung wird vorgeschlagen, die gefundenen Effekte im Rahmen der Orientierungsreaktion (OR) zu betrachten. In einer Serie von vier Untersuchungen wird dargelegt, dass die Dauer von Fixationen auch durch externe Ereignisse moduliert wird. In der ersten Untersuchung wurden die zeitlichen Aspekte des Distraktoreffekts untersucht. Dafür erschienen Distraktoren mit verschiedenen Latenzen nach Fixationsbeginn. Zusätzlich wurde untersucht, welche Auswirkungen unterschiedliche Distraktormodalitäten (visuell und akustisch) zeigen. Die Ergebnisse demonstrierten eine deutliche Verlängerung der jeweils vom Distraktor betroffenen Fixation für alle Latenzen. Für Distraktoren beider Modalitäten zeigte sich eine vergleichbare Verlängerung betroffener Fixationen. Bei der zweiten Untersuchung wurde für visuelle Distraktoren geprüft, inwieweit sich die vorgeschlagene Interpretation im Rahmen der OR bestätigen lässt. Dafür wurde der Effekt hinsichtlich einer Habituation untersucht. Für die Studie wurden Distraktoren mit zwei verschiedenen Latenzen auf umweltbezogenen vs. retinal fixierten Koordinaten präsentiert. Die Ergebnisse zeigten, dass eher Störungen auf gleichen retinalen Positionen eine Abnahme des Effektes zur Folge haben (also habituieren). Für Distraktoren auf konstanten Bildpositionen konnte keine systematische Abnahme des Distraktoreffektes gemessen werden. Für die dritte Untersuchung wurden Augenbewegungen und blickkontingente ereigniskorrelierte Potentiale (EKP?s) parallel aufgezeichnet. Bisher liegen keine Erkenntnisse vor, wie anhand von Parametern der Augenbewegungen Habituation nachweisbar ist, die Abnahme der N1-Komponente der EKP?s hingegen gilt als etablierter Nachweis einer Habituation. Die Ergebnisse zeigten, neben der Verlängerung der Fixationsdauer für visuelle und akustische Distraktoren, eine deutliche Auswirkung auf die N1-Komponente. Bei der Prüfung der Habituation über die betrachteten Bilder zeigte sich eine Verringerung des Effektes in der Fixationsdauer und der N1-Komponente. Auf Schwierigkeiten in Bezug auf den Nachweis einer ausgeprägten Habituation wurde an entsprechender Stelle hingewiesen. Die letzte Studie (N=1) testete, ob sich die Neuinterpretation des Effektes mit neurophysiologischen Erkenntnissen vereinbaren lässt. Bei dem Probanden wurde aufgrund eines Unfalls eine Schädigung des frontalen Augenfeldes (FEF) angenommen. Es wurden Distraktoren links, rechts, ober- und unterhalb des Fixationsorts dargeboten. Beim ersten Versuch, 12 Monate nach dem Unfall, zeigte sich für Distraktoren links des Fixationsortes keinerlei Verlängerung der betroffenen Fixationen. Beim zweiten Versuch, acht Monate später, zeigte sich der Distraktoreffekt auf allen Positionen. Dies lässt sich als Unterstützung der Annahme einer Schädigung der FEF interpretieren, da sich in verschiedenen Studien selbst bei operativer Entfernung der FEF eine deutliche Verringerung der entstandenen Defizite nach einigen Wochen zeigte. Mögliche Alternativen der dargestellten Interpretation wurden an entsprechender Stelle diskutiert. Diese Untersuchungen bestätigen, dass sich ereignisbezogene Verlängerungen der visuellen Fixationsdauer mit dem Rahmenkonzept der OR in Verbindung bringen lassen. Es gilt jedoch zu berücksichtigen, dass eine Reihe weiterer Einflussfaktoren an der Modulation des Effektes beteiligt sind, obwohl es sich offenbar um eine Reaktion subkortikalen Ursprungs handelt.

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