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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.
61

Organic Fluids and Passive Cooling in a Supercritical Rankine Cycle for Power Generation from Low Grade Heat Sources

Vidhi, Rachana 08 July 2014 (has links)
Low grade heat sources have a large amount of thermal energy content. Due to low temperature, the conventional power generation technologies result in lower efficiency and hence cannot be used. In order to efficiently generate power, alternate methods need to be used. In this study, a supercritical organic Rankine cycle was used for heat source temperatures varying from 125°C to 200°C. Organic refrigerants with zero ozone depletion potential and their mixtures were selected as working fluid for this study while the cooling water temperature was changed from 10-25°C. Operating pressure of the cycle has been optimized for each fluid at every heat source temperature to obtain the highest thermal efficiency. Energy and exergy efficiencies of the thermodynamic cycle have been obtained as a function of heat source temperature. Efficiency of a thermodynamic cycle depends significantly on the sink temperature. At areas where water cooling is not available and ambient air temperature is high, efficient power generation from low grade heat sources may be a challenge. Use of passive cooling systems coupled with the condenser was studied, so that lower sink temperatures could be obtained. Underground tunnels, buried at a depth of few meters, were used as earth-air-heat-exchanger (EAHE) through which hot ambient air was passed. It was observed that the air temperature could be lowered by 5-10°C in the EAHE. Vertical pipes were used to lower the temperature of water by 5°C by passing it underground. Nocturnal cooling of stored water has been studied that can be used to cool the working fluid in the thermodynamic cycle. It was observed that the water temperature can be lowered by 10-20°C during the night when it is allowed to cool. The amount of water lost was calculated and was found to be approximately 0.1% over 10 days. The different passive cooling systems were studied separately and their effects on the efficiency of the thermodynamic cycle were investigated. They were then combined into a novel condenser design that uses passive cooling technology to cool the working fluid that was selected in the first part of the study. It was observed that the efficiency of the cycle improved by 2-2.5% when passive cooling system was used.
62

Analysis on Operation Readiness Strategy -Case Study on Airline Industry & Rail Industry

P. Lin, Samuel 27 July 2007 (has links)
Following the Globalization trend, the policy of Deregulation, Open Sky and BOT had been implemented into the transportation industry in Taiwan. This new policy created the dynamics for transformation both in the Airlines Industry and Railway Industry. The new transportation policy lead to the establishment of E-Airways and T-Rail. This research concentrated on the case study of Operations Readiness Strategy implemented by E-Airways and T-Rail respectively based on the academic theory of SWOT and Five Force Model. E-Airways Case Study covers the strategic items on the establishment of Operations Core Competence, Flight Networks, Innovation of Economy-Deluxe class, Marketing Channel and Airline Strategic Alliance. T-Rail Case Study refers to the Operations Readiness Strategy implemented to import the core competence of High Speed Rail. This research reached the conclusions: 1.To confirm academic theory to be applicable for the successful model of both E-Airways and T-Rail case study; 2.To confirm same strategy model to be applied for different industry; 3.To confirm the strategic competence to be created; 4.That Cross verification of SWOT and Five Force Model will lead to solid strategy. 5.The successful model of E-Airways case study with analysis on the operation readiness strategy is available as reference for any potential airline operator after merge & acquisition of existing airlines. 6.The successful model of T-Rail case study is available as reference model for any ¡§next one¡¨ national HSR (High Speed Rail) Project.
63

Conservation Genetics of Black Bears in Arizona and Northern Mexico

Varas-Nelson, Angela Cora January 2010 (has links)
Because American black bears (Ursus americanus) are an important game species in Arizona and are endangered in México, an understanding of the population structure, gene flow, and connectivity are important for effective management. Black bears inhabit coniferous and broadleaf deciduous woodlands in southern Arizona and northern México, usually in sky islands (sky islands are mountains that rise from the desert and are isolated from each other). Because a single sky island is too small to support a viable bear population, black bears move through desert lowlands to reach other sky islands. My objective was to assess genetic structure, connectivity, and conservation implications for sky island black bears in southern Arizona and northern México. I addresses 4 components of bear ecology and genetics: a literature review of genetic information available for black bears in North America; the use of 2 mitochondrial DNA genes (Control Region and ATP synthase protein 8) to study the phylogenetic relationship of black bears from the sky islands of southern Arizona and northern México relative to all North America; the use of 10 microsatellite loci to detect the current genetic structure of black bears in the sky islands in Arizona and northern México; and the use of noninvasive samples collected from the field to determine bear density and population size for black bear in Sierra San Luis, Sonora, México. These studies provide information that can be used by biologists, land managers, and others to assist in the conservation of black bears and their habitat.
64

Developing a method for regional food system planning in the Sea to Sky Region, British Columbia

Raimondi, Laura Joanne 08 May 2012 (has links)
This study set out to test the potential of an environmental management planning method to be adapted into a food system planning framework, referred to as a Regional Food System Management Plan (RFSMP). The RFSMP approach is a valuable and useful tool for regional food systems planning as it promotes community and environmental sustainability through enhanced food self-reliance. The RFSMP framework was developed and tested in the context of the Sea to Sky Region of British Columbia. The main components of the RFSMP framework included delineation of regional boundaries, stakeholder values identification and calculation of food self-reliance. Implementation of the RFSMP framework focused on the planning stage and the crop production components of the food system. This study recommends future work to address agricultural data gaps, complete the RFSMP framework beyond the planning phase and production component of the food system, and test the planning framework in other regions.
65

Definitions of Clear-sky Fluxes and Implications

Verma, Abhishek 2011 December 1900 (has links)
Clear-sky top-of-atmosphere (TOA) fluxes are important in estimating the impact of clouds on our climate. In this study, we quantitatively compare the clear-sky fluxes measurements of the Clouds and the Earths Radiant Energy System (CERES) instrument to clear-sky fluxes from two reanalysis, NASA's Modern Era Retrospective-analysis for Research and Application (MERRA), and the European Center for Medium Range Weather Forecast Interim reanalysis (ERA-Interim). In the first comparison, we compare observed fluxes from individual cloud-free field-of- views to the reanalyses. In the second comparison, we compare monthly averaged observed clear-sky fluxes to those from the reanalyses. Monthly clear-sky fluxes are calculated by averaging fluxes from cloud-free regions. In both comparisons, the fluxes generally agree within +/- 10 W/m^2. Finally, we show that, while the differences between the fluxes of observations and the reanalyses are several W/m2, the inter-annual anomalies agree much better, with zonal and global average inter-annual anomalies typically agreeing within 1 W/m^2. The longwave clear-sky anomalies show excellent agreement even when comparing individual grid points, whereas the shortwave clear-sky anomalies are generally smaller at individual grid points.
66

A New Set of Spectroscopic Metallicity Calibrations for RR Lyrae Variable Stars

Spalding, Eckhart 01 January 2014 (has links)
RR Lyrae stars are old, iron-poor, Helium-burning variable stars. RR Lyraes are extremely useful for tracing phase-space structures and metallicities within the galaxy because they are easy to identify, have consistent luminosities, and are found in large numbers in the galactic disk, bulge, and halo. Here we present a new set of spectroscopic metallicity calibrations that use the equivalent widths of the Ca II K, Hγ, and Hδ lines to calculate metallicity values. Applied to spectroscopic survey data, these calibrations will help shed light on the evolution of the Milky Way and other galaxies.
67

Reading the Sky : From Starspots to Spotting Stars

Eriksson, Urban January 2014 (has links)
This thesis encompasses two research fields in astronomy: astrometry and astronomy education and they are discussed in two parts. These parts represent two sides of a coin; astrometry, which is about constructing 3D representations of the Universe, and AER, where for this thesis, the goal is to investigate university students’ and lecturers’ disciplinary discernment vis-à-vis the structure of the Universe and extrapolating three-dimensionality. Part I presents an investigation of stellar surface structures influence on ultra-high-precision astrometry. The expected effects in different regions of the HR-diagram were quantified. I also investigated the astrometric effect of exoplanets, since astrometric detection will become possible with projects such as Gaia. Stellar surface structures produce small brightness variations, influencing integrated properties such as the total flux, radial velocity and photocenter position. These properties were modelled and statistical relations between the variations of the different properties were derived. From the models it is clear that for most stellar types the astrometric jitter due to stellar surface structures is expected to be of order 10 μAU or greater. This is more than the astrometric displacement typically caused by an Earth-sized exoplanet in the habitable zone, which is about 1–4 μAU, making astrometric detection difficult. Part II presents an investigation of disciplinary discernment at the university level. Astronomy education is a particularly challenging experience for students because discernment of the ‘real’ Universe is problematic, making interpretation of the many disciplinary-specific representations used an important educational issue. The ability to ‘fluently’ discern the disciplinary affordances of these representations becomes crucial for the effective learning of astronomy. To understand the Universe I conclude that specific experiences are called. Simulations could offer these experiences, where parallax motion is a crucial component. In a qualitative study, I have analysed students’ and lecturers’ discernment while watching a simulation video, and found hierarchies that characterize the discernment in terms of three-dimensionality extrapolation and an Anatomy of Disciplinary Discernment. I combined these to define a new construct: Reading the Sky. I conclude that this is a vital competency needed for learning astronomy and suggest strategies for how to implement this in astronomy education.
68

Reading the sky : from starspots to spotting stars

Eriksson, Urban January 2014 (has links)
This thesis encompasses two research fields in astronomy: astrometry and astronomy education and they are discussed in two parts. These parts represent two sides of a coin; astrometry, which is about constructing 3D representations of the Universe, and AER, where for this thesis, the goal is to investigate university students’ and lecturers’ disciplinary discernment vis-à-vis the structure of the Universe and extrapolating three-dimensionality. Part I presents an investigation of stellar surface structures influence on ultra-high-precision astrometry. The expected effects in different regions of the HR-diagram were quantified. I also investigated the astrometric effect of exoplanets, since astrometric detection will become possible with projects such as Gaia. Stellar surface structures produce small brightness variations, influencing integrated properties such as the total flux, radial velocity and photocenter position. These properties were modelled and statistical relations between the variations of the different properties were derived. From the models it is clear that for most stellar types the astrometric jitter due to stellar surface structures is expected to be of order 10 μAU or greater. This is more than the astrometric displacement typically caused by an Earth-sized exoplanet in the habitable zone, which is about 1–4 μAU, making astrometric detection difficult. Part II presents an investigation of disciplinary discernment at the university level. Astronomy education is a particularly challenging experience for students because discernment of the ‘real’ Universe is problematic, making interpretation of the many disciplinary-specific representations used an important educational issue. The ability to ‘fluently’ discern the disciplinary affordances of these representations becomes crucial for the effective learning of astronomy. To understand the Universe I conclude that specific experiences are called. Simulations could offer these experiences, where parallax motion is a crucial component. In a qualitative study, I have analysed students’ and lecturers’ discernment while watching a simulation video, and found hierarchies that characterize the discernment in terms of three-dimensionality extrapolation and an Anatomy of Disciplinary Discernment. I combined these to define a new construct: Reading the Sky. I conclude that this is a vital competency needed for learning astronomy and suggest strategies for how to implement this in astronomy education.
69

Transgressing boundaries and cultural haunting in Chinese American and Chinese Canadian 'talk stories' /

Morfetas, Elpida, January 1900 (has links)
Thesis (M.A.)--Carleton University, 2002. / Includes bibliographical references (p. 158-165). Also available in electronic format on the Internet.
70

Exploring the Milky Way halo with SDSS-II SN survey RR Lyrae stars

De Lee, Nathan. January 2008 (has links)
Thesis (Ph. D.)--Michigan State University. Dept. of Physics and Astronomy, 2008. / Title from PDF t.p. (viewed on July 22, 2009) Includes bibliographical references (leaves 170-174). Also issued in print.

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