• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2737
  • 1318
  • 529
  • 466
  • 262
  • 245
  • 123
  • 80
  • 38
  • 35
  • 32
  • 30
  • 27
  • 27
  • 20
  • Tagged with
  • 7385
  • 2107
  • 1239
  • 1064
  • 1018
  • 735
  • 678
  • 650
  • 609
  • 587
  • 477
  • 387
  • 373
  • 325
  • 313
  • 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.
581

The Impact of Monopoly Power on a Commercial Banking Firm

Tribble, John Atwood 01 May 1975 (has links)
The commercial banking industry is oft en criticized on the grounds that there is a high concentration of market power in the hands of a few firms. However, the appropriate measure of market power is Lerner's index of monopoly power, the elasticity of demand, not concentration ratios. The theoretical model developed in the paper is designed to permit the estimation of demand and supply elasticities in the banking industry. Specifically, two assets (loans and state and local funds) and one liability (time deposits) are investigated. The empirical model focuses its attention on the demand and supply conditions. If the bank is a profit maximizer , then the banker adjusts the portfolio of assets and issues of liabilities in accordance with the Euler first order maximization conditions of the expected profits function. In this function administrative costs are expressed as a proportion of total assets. Default risks are ignored. At the optimal solution of the Euler first order conditions transaction costs generated by deposit-liability fluctuations are treated as scalers. These simplifying assumptions permit the estimation of the slope of the loan demand, of the demand for state and local funds, and of time deposit supply, which can be used to estimate the elasticities of the respective functions. The empirical results are based on cross-sectional data for 7.89 standard economic areas in those states where there is an absence of extensive branch banking. The observations are categorized into eight bank classes by per capita income level, by hank density per capita in the standard economic area, and by economic base (agricultural or nonagricultural) in the area. It is assumed that the demand and supply functions are identical for all banks within a bank class. Using, the first order maximization conditions as behavioral equations the slopes of the supply and demand functions are estimated. These estimates are used to calculate elasticities of loan demand, state and local funds demand, and time deposit supply. In general, it is concluded that those banks from low income areas have a lower elasticity of demand for loans than banks in high income areas. These banks have more monopoly power in the loan account. The elasticity of deposit supply is low for all classes of banks. This could be due to monopsony power, but it is more likely due to the legal ceiling on interest rates paid on time deposits. The analysis does not lead to any conclusions for the structural preconditions for the existence of monopoly power, but it does indicate that banks in certain markets may have some degree of monopoly power.
582

The Cryogenic Bonding Evaluation at the Metallic-Composite Interface of a Composite Overwrapped Pressure Vessel with Additional Impact Investigation

Clark, Eric A. 01 December 2009 (has links)
A bonding evaluation that investigated the cryogenic tensile strength of several different adhesives / resins was performed. The test materials consisted of 6061 aluminum test pieces adhered to a wet-wound graphite laminate in order to simulate the bond created at the liner-composite interface of an aluminum lined composite overwrapped pressure vessel. It was found that for cryogenic applications, a flexible, low modulus resin system must be used. Additionally, the samples prepared with a thin layer of cured resin - or prebond - performed significantly better than those without. It was found that it is critical that the prebond surface must have sufficient surface roughness prior to the bonding application. Also, the aluminum test pieces that were prepared using a surface etchant slightly outperformed those that were prepared with a grit blast surface finish and performed significantly better than those which had been scored using sand paper to achieve the desired surface finish. An additional impact investigation studied the post impact tensile strength of composite rings in a cryogenic environment. The composite rings were filament wound with several combinations of graphite and aramid fibers and were prepared with different resin systems. The rings were subjected to varying levels of Charpy impact damage then pulled to failure in tension. It was found that the addition of elastic aramid fibers with the carbon fiber mitigate the overall impact damage and drastically improve the post impact strength of the structure in a cryogenic environment.
583

Enhancing impact assessment with extrapolative fiction

Miller, Ruth-Ellen 01 January 1984 (has links)
This dissertation proposes the use of fiction as models to enhance the process of impact assessment (IA) and to improve the quality of IA reports. It demonstrates that works of extrapolative fiction (EF), a subset of science fiction, raise issues and clarify concerns not currently included in the IA process, suggesting the potential for improving the relevance of IA results for decisionmakers. The dissertation also demonstrates that EF stories can enhance the presentation of IA results, making those results more readable. Through literature review and content analysis, the current IA process is shown to lead to results lacking in specific content areas (e.g., effects on emotional well-being and community cohesiveness) necessary for their utility to decisionmakers. The body of literature here called extrapolative fiction is then shown to include many content areas missing in existing assessments. Two alternatives for an IA process that could incorporate extrapolative fiction are presented and discussed by means of examples. The first includes existing EF stories as a part of or an appendage to an IA report. The example is a preliminary combining of published EF stories with an IA report concerning life-extending technologies. The second includes the use of existing EF stories in the assessment process through inclusion of an EF-oriented reader on the IA team. The example is a case description of an IA process regarding the commercialization of guayule as a source of natural rubber, a process in which the author incorporated EF methods. Severa other results emerged from this research: (a) an initial statement of objectives for a unified field of impact assessment (recently emerging as an amalgamation of technology assessment, environmental impact statements and social impact assessment); (b) a working definition for an emerging subgenre of science fiction here called extrapolative fiction; (c) a topical bibliography of some hundred EF stories. These results extend the current understanding of the field of impact assessment and the emerging genre of extrapolative fiction and should be useful to both the impact assessment and science fiction criticism communities.
584

Assessment of Reservoir Quality and Potential Impact of Sequestered Carbon Dioxide in Diverse Lithological Reservoir Units, South Central, Mississippi, USA

Degny, Assonman D 11 May 2013 (has links)
This study was designed to understand the possible impact of carbon dioxide on different reservoir rocks in south-central Mississippi. Eight samples, including six from the Heidelberg field (Mississippi), were exposed to carbon dioxide under simulated subsurface conditions of elevated temperature and pressure and then analyzed using thin section petrography, scanning electron microscopy, X-ray diffraction, and focused ion beam-SEM. Three of the eight samples showed dissolution in calcite and corrosion in smectite. SEM and EDS analysis of treated sample 5 (Se-5/shaly-sandtsone) and sample 8 (S-8/dolomitic-limestone) revealed newly precipitated lath- and fibrous-like crystals composed of sulfur (S), oxygen (O), and calcium (Ca), thus interpreted as gypsum. Three-dimensional analysis using FIB of dolomitic limestone samples (Smackover Formation) revealed that gypsum crystals fill fracture porosity. This study significantly contributes to the understanding of carbon dioxide impact on reservoir rock and promotes better management of natural gas resources.
585

Strain rate effects on energy dissipation during hypervelocity penetration of polymeric materials

Bowering, Michael Hunter 14 December 2018 (has links)
Energy dissipation during penetration is an important consideration in materials selection for lightweight armoring to protect against hypervelocity impacts (HVIs). Impact-induced glass transition in polymeric materials has been observed to increase energy dissipation during penetration. Incorporating unconventional armor materials like polymers could improve performance in these types of applications. A series of HVIs was performed, with impact velocities over the range of 2-7 km/s, on samples of ultra-high molecular weight polyethylene and poly(methyl methacrylate). A relationship between back face debris cloud velocity and impact velocity was developed for each material. Damage zone sizes were compared, offering insights into the effects of molecular architecture on stress delocalization and energy dissipation during hypervelocity perforation. Thermal analysis of the two material systems provides quasi-static glass transition temperatures, as well as melting and crystallization temperatures. The apparent failure mechanisms, in conjunction with thermal analysis, were used to explain the relative performance of each material.
586

Volume of Fluid Simulations for Droplet Impact on Dry and Wetted Hydrophobic and Superhydrophobic Surfaces

Burtnett, Emily Nicole 11 August 2012 (has links)
An aircraft may experience inlight ice accretion and corresponding reductions in performance and control when the vehicle encounters clouds of super-cooled water droplets. The EADS-IW Surface Engineering Group is investigating passive anti-icing possibilities, such as functional and ice phobic coatings. Ice-resistant coatings require investigating droplet impact on dry surfaces and wet films, including microscopic effects such as droplet splashing. To investigate droplet impacts, a volume of fluid (VOF) flow solver was used for droplets impacting dry and wetted hydrophobic and superhydrophobic surfaces, focusing on meso-scale simulations. The effects of structured, micro-scale surface roughness and the effects of a thin wet film on the surface, corresponding to a saturated surface under high humidity conditions, were investigated. Axisymmetric domains produced acceptable results for smooth, dry surfaces. It was determined that in order to properly predict behavior of droplets impacting surfaces with structured micro-scale roughness, three-dimensional simulations are recommended.
587

Exposure to greenness and the natural landscape: understanding the impacts on urban health and heat

Brochu, Paige A. 26 July 2023 (has links)
BACKGROUND: In the past decade urbanization has increased, with over half the world’s population and 83% of the total United States population, residing in urban areas as of 2021. Urbanization has the potential to decrease connectivity between nature and humans, impacting health and exacerbating urban heat islands. Previous research has found that the natural environment (i.e., trees and bluespace) provide vital ecosystem services through both direct and indirect pathways that positively impact health. Objective: The objective of my dissertation was to assess the current state of the natural environment in urban areas and gain a better understanding of the relationship between exposure to nature, health, and heat. METHODS: Research aims were addressed by focusing on publicly available data and a range of metrics used in previous literature to characterize exposure to greenness and natural landscapes and their associations with health and land surface temperature. In Chapter 2, I report on a nationwide quantitative health impact assessment to estimate the reduction in all-cause mortality in populations aged 65 and older in the largest metropolitan areas (n=35) in the United States associated with an increase in greenness in selected years across twenty years (2000, 2010, and 2019). Census tract mean seasonal greenness exposure was estimated by using the Normalized Difference Vegetation Index (NDVI) from Landsat 30 m 16-day satellite imagery from April to September. All-cause mortality estimates were downscaled from county to tract-level from the CDC WONDER Portal. Mortality reduction was estimated using a recently published exposure-response function. Chapter 3 focuses on urban census tracts in Massachusetts (n=525), in order to assess the cumulative exposure of the urban natural environment. Thirty candidate, validated measures of the natural landscape space were derived from data published between 2016 and 2019. Principal component analysis was used to reduce the number of candidate items and confirmatory factor analysis was used to test the underlying hypothesized latent structure of three sub-domains: green space, parks and recreation and blue space. Items hypothesized to measure each latent structure were summed using equal weights and each sub-domain was rescaled from 0–100. The tract-level cumulative exposure index was the sum of the three sub-domains. Lastly, in Chapter 4 using generalized linear models, I investigated the relationship between urban heat and nature using the natural landscape index created in Chapter 3 and mean five-year Land Surface Temperature (LST). The City of Boston was then used as a case-study to identify vulnerable tracts with low nature and high heat to inform planning for climate adaptation strategies and public health planning. RESULTS: In Chapter 2, overall greenness in the largest metropolitan areas in the US increased from 3% between 2000 and 2010 to 11% between 2010 and 2019. Approximately 34,000 to 38,000 all-cause mortality deaths could have been prevented with an increase in 0.1 NDVI units from 2000 to 2019. In developing the cumulative natural landscape index, in Chapter 3, we found that greenness measures (NDVI, tree canopy, percent impervious, etc.) explained the most variance among all of the items hypothesized to measure the cumulative natural landscape index. The three sub-domains explained 69% of the total variance, with greenness accounting more than half the total variance explained. Lastly, in Chapter 4, we report that with an interquartile shift in overall nature, LST decreased by 0.8°C. More specifically, higher overall greenness, higher percent tree canopy, and higher percent impervious surfaces resulted in the largest change in LST. With an increase in greenness and tree canopy we found a decrease in LST by over 1°C. In contrast, an increase in impervious surfaces resulted in an increase in LST by 1.31°C. Within the City of Boston, we found that 9% of the total population resides in tracts that were within the highest quartile of LST and lowest quartile of overall nature. CONCLUSION: Overall, this work finds that large urban areas in the United States saw a small increase in overall greenness across the past two decades. With a trend of increasing greenness there is also the potential to reduce all-cause mortality in those 65 years and older. Going beyond overall greenness, we created a cumulative natural landscape index to capture simultaneous exposures to the urban natural environment. Greenness measures such as tree canopy, NDVI, open space, and impervious surfaces explained the most variance in the cumulative nature index and was the most associated with LST as compared to parks and recreation and bluespace. We assessed the impacts of the natural landscape on temperature, and found that an increase in nature resulted in a significant decrease in LST with greenness measures having the largest impact. Results from these studies can be used to support climate action plans and greening initiatives to show the co-benefits of increased exposure to the natural environment and help identify areas that are lacking in these exposures to better implement initiatives.
588

Differential Model and Impact Response of a Flexible Beam Attached to a Rigid Supporting Structure

Chandra, Harish 20 May 2008 (has links)
No description available.
589

Damage and Fatigue in Cross-Linked Rubbers

Melnikov, Alexei 09 August 2010 (has links)
No description available.
590

Effects Of Petroleum Hydrocarbons On Salt Marsh Communities

Hershner, Carleton H., Jr. 01 January 1977 (has links) (PDF)
This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia. The effects of petroleum hydrocarbons on salt marsh grasses and gastropods were examined under three different circumstances. In the first study reported, a small pocket marsh was repeatedly dosed with small amounts of a No. 2 fuel oil. The second study investigated the effects of a large accidental spill of No. 6 fuel oil. The third study involved single doses of a fresh and a weathered crude oil on artificially enclosed segments of marsh.

Page generated in 0.0527 seconds