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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.
11

Modelling, design and energy management of a hybrid electric ship – a case study

Zhu, Haijia 05 May 2020 (has links)
The widely-used passenger and car ferries, sailing regularly and carrying heavy loads, form a unique type of marine vessel, providing vital transportation links to the coastal regions. Modern ferry ships usually are equipped with multiple diesel engines as prime movers. These diesel engines consume a large amount of marine diesel fuel with high fuel costs, and high emissions of greenhouse gas (GHG) and other harmful air pollutants, including CO2, HC, NOx, SO2, CO, and PM. To reduce fuel costs and the harmful emissions, the marine industry and ferry service providers have been seeking clean ship propulsion solutions. In this work, the model-based design (MBD) and optimization methodology for developing advanced electrified vehicles (EV) are applied to the modelling, design and control optimizations of clean marine vessels with a hybrid electric propulsion system. The research focuses on the design and optimization of the hybrid electric ship propulsion system and uses an open deck passenger and car ferry, the MV Tachek, operated by the British Columbia Ferry Services Inc. Canada, as a test case. At present, the ferry runs on the Quadra Island – Cortes Island route in British Columbia, Canada, with dynamically changing ocean conditions in different seasons over a year. The research first introduces the ship operation profile, using statistical ferry operation data collected from the ferry’s voyage data recorder and a data acquisition system that is specially designed and installed in this research. The ship operation profile model with ship power demand, travelling velocity and sailing route then serves as the design and control requirements of the hybrid electric marine propulsion system. The development of optimal power control and energy management strategies and the optimization of the powertrain architecture and key powertrain component sizes of the ship propulsion system are then carried out. Both of the series and parallel hybrid electric propulsion architectures have been studied. The sizes of crucial powertrain components, including the diesel engine and battery energy storage system (ESS), are optimized to achieve the best system energy efficiency. The optimal power control and energy management strategies are optimized using dynamic programming (DP) over a complete ferry sailing trip. The predicted energy efficiency and emission reduction improvements of the proposed new ship with the optimized hybrid propulsion system are compared with those of two benchmark vessels to demonstrate the benefits of the new design methodology and the optimized hybrid electric ship propulsion system design. These two benchmarks include a conventional ferry with the old diesel-mechanical propulsion system, and the Power Take In (PTI) hybrid electric propulsion systems installed on the MV Tachek at present. The simulation results using the integrated ship propulsion system model showed that the newly proposed hybrid electric ship could have 17.41% fuel saving over the conventional diesel-mechanical ship, and 22.98% fuel saving over the present MV Tachek. The proposed optimized hybrid electric propulsion system, combining the advantages of diesel-electric, pure electric, and mechanical propulsions, presented considerably improved energy efficiency and emissions reduction. The research forms the foundation for future hybrid electric ferry design and development. / Graduate
12

Beyond the PTA: mothering work and women's education activism in the deep south

Tingle, Emily L 09 August 2022 (has links) (PDF)
It has long been established that women play unique roles within schools, volunteerism, and school-based community work (Griffith and Smith 2005; Calarco 2020; Lewis and Diamond 2015; Posey-Maddox 2014). Additionally, research suggests that the work done surrounding the institution of education primarily falls on mothers (Griffith and Smith 2005; Haley-Lock and Posey-Maddox 2016; Lareau 2000; Lareau 2011). However, little research has been done that explores how gender dynamics play out in education activism that lies outside of schools. This study seeks to understand how women view gendered expectations of mothering work in regard to education and if/how they perceive that work in relation to their political activism. This study aids in better understanding how activists perceive the roots of their activist work and provide insights about political activism surrounding education. As activism surrounding education can greatly contribute to achieving a more just and equitable society, this work is crucial for scholarship seeking to understand the activists attempting to change our education system.
13

Rättvis värdering av hälsa : En kvantitativ jämförelse mellan Person Trade Off- och Time Trade Off- metoden / Valuing health : A quantitative comparison between Person Trade Off and Time Trade Off

Wiss, Johanna, Kalkan, Almina January 2010 (has links)
<p>One must consider cost effectiveness when deciding how resources within the health sector should be distributed. Quality adjusted life years (QALYs) are used to measure the value of different medical treatments. QALY is based on utility maximization theory, which suggests that a QALY is always a QALY regardless of who receives it. Therefore, a produced QALY is worth the same regardless of the age or the initial health of the patient. Previous research has shown that these assumptions do not seem to fit the real preferences of individuals. Further, there are different methods of acquiring QALYs that give different outcomes. Two of these methods are Time Trade Off (TTO), in which respondents are confronted with a valuation of health change in time, and Person Trade Off (PTO), where respondents are confronted with a valuation in persons. Arguably, PTO is the preferred method that takes greater account of how individuals wish to allocate the resources of the society. From a distribution perspective focusing on age and initial health status, this paper aims to empirically identify the differences between TTO and PTO considering the measurement of preferences for life quality. The aim is also to examine whether the results obtained are consistent with the theoretical assumptions that are required for the preference to be accepted as a cardinal utility. A quantitative survey was carried out with 58 medical and 61 economics students. Half of the students received PTO and the other half TTO questions. The data collected was analyzed comparing the methods, the two student groups and men against women.</p><p>The results from the survey show that, both with TTO and PTO, respondents on average believe that patients who are at a lower initial health level should be given priority over patients who are at a higher initial health level, and younger patients should be given priority over older patients. No significant differences were seen between PTO and TTO when it came to the age of the patient. Conversely, there was a significant difference between the methods for the valuation based on initial health status of patients. Measured with PTO a treatment for patients who are at a lower initial level is valued 28% higher than a treatment for those patients who are at a higher initial level, while the corresponding figure for TTO was 8%. Between medical students and economic students, there were significant differences in the question of age in the PTO. Between men and women differences were found in both methods.</p> / <p>Kostnadseffektivitet är en av faktorerna som ska tas i beaktande vid beslut om hur resurser inom hälso- och sjukvården ska fördelas. Kvalitetsjusterade levnadsår (QALY) används för att mäta effekten av olika insatser. Måttet baseras på nyttomaximeringsteori vilket leder till att en QALY alltid är en QALY oavsett vem den tillfaller - med andra ord är en QALY som produceras hos en patient lika mycket värd oavsett exempelvis patientens ålder eller initiala tillstånd. Dessa antaganden har i tidigare undersökningar visat sig stämma dåligt med individers preferenser men olika metoder för att ta fram QALY verkar ta olika mycket hänsyn till dem. Två av flera metoder är Time Trade Off (TTO), där respondenter ställs inför en värdering av hälsoförändringar i tid och Person Trade Off (PTO) där respondenter ställs inför en värdering i personer. PTO har påståtts vara en mer rättvisande metod som tar större hänsyn till hur individer vill att samhälleliga resurser ska fördelas. Denna uppsats syftar till att, utifrån ett fördelningsperspektiv med fokus på ålder och initialt hälsotillstånd, empiriskt kartlägga förekomsten av skillnader i preferenser för livskvalitet mätt med PTO respektive TTO, samt att undersöka om de erhållna resultaten överensstämmer med de teoretiska grundantagandena som krävs för att preferenser ska accepteras som kardinala nyttor. För att svara mot syftet utfördes en kvantitativ undersökning på 58 läkar- samt 61 ekonomistudenter. Hälften av studenterna fick PTO-frågor och den andra hälften TTO-frågor. En statistisk bearbetning av insamlad data har gjorts där svaren har jämförts mellan metoderna samt mellan läkar- och ekonomistudenter och kvinnor och män.</p><p>Resultaten från undersökningen visar att både med TTO och PTO anser respondenterna att patienter som befinner sig på en lägre initial nivå ska prioriteras framför patienter som befinner sig på en högre initial nivå samt yngre patienter ska prioriteras framför äldre patienter. Vad gäller hänsyn till patienters ålder uppmättes inga signifikanta skillnader mellan PTO och TTO. Däremot uppmättes en signifikant skillnad mellan metoderna vad gäller hänsyn till initialt hälsotillstånd hos patienter. Mätt med PTO värderas en behandling för de patienter som befinner sig på en lägre initial nivå 28 % högre än en behandling för de patienter som befinner sig på en högre initial nivå medan motsvarande siffra för TTO var 8%. Mellan läkare och ekonomer fanns signifikanta skillnader i frågan gällande ålder i PTO och mellan kvinnor och män återfanns skillnader i båda metoder.</p>
14

Rättvis värdering av hälsa : En kvantitativ jämförelse mellan Person Trade Off- och Time Trade Off- metoden / Valuing health : A quantitative comparison between Person Trade Off and Time Trade Off

Wiss, Johanna, Kalkan, Almina January 2010 (has links)
One must consider cost effectiveness when deciding how resources within the health sector should be distributed. Quality adjusted life years (QALYs) are used to measure the value of different medical treatments. QALY is based on utility maximization theory, which suggests that a QALY is always a QALY regardless of who receives it. Therefore, a produced QALY is worth the same regardless of the age or the initial health of the patient. Previous research has shown that these assumptions do not seem to fit the real preferences of individuals. Further, there are different methods of acquiring QALYs that give different outcomes. Two of these methods are Time Trade Off (TTO), in which respondents are confronted with a valuation of health change in time, and Person Trade Off (PTO), where respondents are confronted with a valuation in persons. Arguably, PTO is the preferred method that takes greater account of how individuals wish to allocate the resources of the society. From a distribution perspective focusing on age and initial health status, this paper aims to empirically identify the differences between TTO and PTO considering the measurement of preferences for life quality. The aim is also to examine whether the results obtained are consistent with the theoretical assumptions that are required for the preference to be accepted as a cardinal utility. A quantitative survey was carried out with 58 medical and 61 economics students. Half of the students received PTO and the other half TTO questions. The data collected was analyzed comparing the methods, the two student groups and men against women. The results from the survey show that, both with TTO and PTO, respondents on average believe that patients who are at a lower initial health level should be given priority over patients who are at a higher initial health level, and younger patients should be given priority over older patients. No significant differences were seen between PTO and TTO when it came to the age of the patient. Conversely, there was a significant difference between the methods for the valuation based on initial health status of patients. Measured with PTO a treatment for patients who are at a lower initial level is valued 28% higher than a treatment for those patients who are at a higher initial level, while the corresponding figure for TTO was 8%. Between medical students and economic students, there were significant differences in the question of age in the PTO. Between men and women differences were found in both methods. / Kostnadseffektivitet är en av faktorerna som ska tas i beaktande vid beslut om hur resurser inom hälso- och sjukvården ska fördelas. Kvalitetsjusterade levnadsår (QALY) används för att mäta effekten av olika insatser. Måttet baseras på nyttomaximeringsteori vilket leder till att en QALY alltid är en QALY oavsett vem den tillfaller - med andra ord är en QALY som produceras hos en patient lika mycket värd oavsett exempelvis patientens ålder eller initiala tillstånd. Dessa antaganden har i tidigare undersökningar visat sig stämma dåligt med individers preferenser men olika metoder för att ta fram QALY verkar ta olika mycket hänsyn till dem. Två av flera metoder är Time Trade Off (TTO), där respondenter ställs inför en värdering av hälsoförändringar i tid och Person Trade Off (PTO) där respondenter ställs inför en värdering i personer. PTO har påståtts vara en mer rättvisande metod som tar större hänsyn till hur individer vill att samhälleliga resurser ska fördelas. Denna uppsats syftar till att, utifrån ett fördelningsperspektiv med fokus på ålder och initialt hälsotillstånd, empiriskt kartlägga förekomsten av skillnader i preferenser för livskvalitet mätt med PTO respektive TTO, samt att undersöka om de erhållna resultaten överensstämmer med de teoretiska grundantagandena som krävs för att preferenser ska accepteras som kardinala nyttor. För att svara mot syftet utfördes en kvantitativ undersökning på 58 läkar- samt 61 ekonomistudenter. Hälften av studenterna fick PTO-frågor och den andra hälften TTO-frågor. En statistisk bearbetning av insamlad data har gjorts där svaren har jämförts mellan metoderna samt mellan läkar- och ekonomistudenter och kvinnor och män. Resultaten från undersökningen visar att både med TTO och PTO anser respondenterna att patienter som befinner sig på en lägre initial nivå ska prioriteras framför patienter som befinner sig på en högre initial nivå samt yngre patienter ska prioriteras framför äldre patienter. Vad gäller hänsyn till patienters ålder uppmättes inga signifikanta skillnader mellan PTO och TTO. Däremot uppmättes en signifikant skillnad mellan metoderna vad gäller hänsyn till initialt hälsotillstånd hos patienter. Mätt med PTO värderas en behandling för de patienter som befinner sig på en lägre initial nivå 28 % högre än en behandling för de patienter som befinner sig på en högre initial nivå medan motsvarande siffra för TTO var 8%. Mellan läkare och ekonomer fanns signifikanta skillnader i frågan gällande ålder i PTO och mellan kvinnor och män återfanns skillnader i båda metoder.
15

Étude de la substance blanche par diffusion tensiorelle : tractographie des fibres d'association de la région temporo-pariéto-occipitale

Bérubé, Josée January 2007 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.
16

Hybrid powertrain performance analysis for naval and commercial ocean-going vessels

Gully, Benjamin Houston 11 October 2012 (has links)
The need for a reduced dependence on fossil fuels is motivated by a wide range of factors: from increasing fuel costs, to national security implications of supply, to rising concern for environmental impact. Although much focus is given to terrestrial systems, over 90% of the world's freight is transported by ship. Likewise, naval warfighting systems are critical in supporting U.S. national interests abroad. Yet the vast majority of these vessels rely on fossil fuels for operation. The results of this thesis illustrate a common theme that hybrid mechanical-electrical marine propulsion systems produce substantially better fuel efficiency than other technologies that are typically emphasized to reduce fuel consumption. Naval and commercial powertrains in the 60-70 MW range are shown to benefit substantially from the utilization of mechanical drive for high speed propulsion; complemented by an efficient electric drive system for low speed operations. This hybrid architecture proves to be able to best meet the wide range of performance requirements for each of these systems, while also being the most easily integrated technology option. Naval analyses evaluate powertrain options for the DDG-51 Flight III. Simulation results using actual operational profile data show a CODLAG system produces a net fuel savings of up to 12% more than a comparable all-electric system, corresponding to a savings of 37% relative the existing DDG-51 powertrain. These results prove that a mechanical linkage for the main propulsion engine greatly reduces fuel consumption and that for power generation systems requiring redundancy, diesel generators represent a vastly superior option to gas turbines. For the commercial application it is shown that an augmented PTO/PTI hybrid system can better reduce cruise fuel consumption than modern sail systems, while also producing significant benefit with regard to CO2 emissions. In addition, using such a shaft mounted hybrid system for low speed electric drive in ports reduces NOx emissions by 29-43%, while CO is reduced 57-66% and PM may be reduced up to 25%, depending on the specific operating mode. As an added benefit, fuel consumption rates under these conditions are reduced 20-29%. / text
17

Étude de la substance blanche par diffusion tensiorelle : tractographie des fibres d'association de la région temporo-pariéto-occipitale

Bérubé, Josée January 2007 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
18

Small-scale wave energy converter for wave tank facility

Asseh, Samir January 2023 (has links)
A small-scale wave energy converter was designed and built for teaching and academic purposes to be used at The Division for Electricity, in the Ångström Laboratory at Uppsala University. The design of the power take-off (PTO) makes use of magnets passing through a copper coil for electricity generation. The magnets are attached by a string to the floating buoy in the small-scale wave tank which leads to a joint oscillation. Design parameters are executed using COMSOL Multiphysics which illustrates the total voltage output generated as well as the total magnetic field. Simulations and calculations in MATLAB were performed to extract the expected damping coefficient and plots of the buoy position compared to the wave amplitude. Lastly, a PTO prototype were built and compared with the simulations. The PTO shows electricity generation with the aid of a voltmeter showcasing the voltage. Additional information on future improvements to further aid teaching and academic understanding of wave energy converter are mentioned in the final section of this study.
19

Prediction horizon requirement  in control and extreme load analyses for survivability : Advancements to improve the performance of wave energy technologies

Shahroozi, Zahra January 2021 (has links)
The main objective of wave energy converters (WECs) is to ensure reliable electricity production at a competitive cost. Two challenges to achieving this are ensuring an efficient energy conversion and offshore survivability.         This thesis work is structured in three different sections: Control and maximum power optimization, forces and dynamics analysis in extreme wave conditions, and statistical modeling of extreme loads in reliability analysis.        The need for prediction and future knowledge of waves and wave forces is essential due to the non-causality of the optimal velocity relation for wave energy converters. Using generic concepts and modes of motion, the sensitivity of the prediction horizon to various parameters encountered in a real system is elaborated. The results show that through a realistic assumption of the dissipative losses, only a few seconds to about half a wave cycle is sufficient to predict the required future knowledge for the aim of maximizing the power absorption.          The results of a 1:30 scaled wave tank experiment are used to assess the line force and dynamic behaviour of a WEC during extreme wave events. Within the comparison of different wave type representations, i.e. irregular, regular and focused waves, of the same sea state, the results show that not all the wave types deliver the same maximum line forces. As a strategy of mitigating the line forces during extreme wave events, changing the power take-off (PTO) damping may be employed. With consideration of the whole PTO range, the results indicate an optimum damping value for each sea state in which the smallest maximum line force is obtained. Although wave breaking slamming and end-stop spring compression lead to high peak line forces, it is possible that they level out due to the overtopping effect. Waves with a long wavelength result in large surge motion and consequently higher and more damaging forces.         On the investigation of reliability assessment of the wave energy converter systems, computing the return period of the extreme forces is crucial. Using force measurement force data gathered at the west coast of Sweden, the extreme forces are statistically modelled with the peak-over-threshold method. Then, the return level of the extreme forces over 20 years for the calm season of the year is computed.
20

Li<sup>+</sup>/H<sup>+</sup> Ion-exchanged Li<sub>2</sub><i>M</i>O<sub>3</sub> (<i>M</i> = Ir, Pt) and Carbonate Melt Oxidized IrO<sub>x</sub> <i>p</i><sub>H</sub> Sensors

O'Malley, Matthew J. 29 September 2008 (has links)
No description available.

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