• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 307
  • 83
  • 44
  • 44
  • 27
  • 11
  • 10
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • Tagged with
  • 676
  • 190
  • 124
  • 109
  • 63
  • 57
  • 56
  • 51
  • 46
  • 46
  • 45
  • 41
  • 41
  • 40
  • 40
  • 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.
321

INVESTIGATION OF BLAST MITIGATION PROPERTIES OF CARBON AND POLYURETHANE BASED FOAMS

Toon, Bradley E. 01 January 2008 (has links)
Solid foams have been studied for years for their ability to mitigate damage from sudden impact. Small explosive attacks threaten to damage or destroy key structures in some parts of the world. A newly developed material, carbon foam, may offer the ability to mitigate the effects of such blasts. This project investigates the energy absorbing properties of carbon and polyurethane based foams in dynamic compression to illustrate their viability to protect concrete structures from the damaging effects of pressure waves from a small blast. Cellular solid mechanics fundamentals and a survey of the microscopic cellular structure of each type of foam are discussed. Experiments were performed in three strain rate regimes: low strain rate compression testing, middle strain rate impact testing, and high strain rate blast testing to reveal mechanical behavior. Experiments show a 7.62 cm (3”) thick hybrid composite layered foam sample can protect a concrete wall from a small blast.
322

Molecular and Comparative Phylogenetic Analysis of the Polyphenol Oxidase Gene Family in Poplar (Populus spp.)

Tran, Lan T. 29 October 2013 (has links)
Polyphenol oxidases (PPOs) are ubiquitous enzymes that oxidize phenols to quinones in the presence of molecular oxygen, often leading to tissue discolouration. They are sometimes considered as defense proteins but other functions, for example in phenolic compound biosynthesis, have also been found. In this thesis, bioinformatic searches were conducted to identify putative PPO genes from available genomes representing five Viridiplantae lineages: chlorophytes, bryophytes, lycophytes, monocotyledonous anthophytes and eudicotyledonous anthophytes. Duplicated PPO genes were found in most land plant genomes. A detailed investigation of the poplar (Populus trichocarpa) PPO gene family found nine genes that exhibit differential expression profiles during development and following stress, of which PtrPPO1 was the only significant wound-inducible PPO gene. A phylogenetic reconstruction of the poplar PPOs identified PtrPPO13 to be an unusual PPO homolog and it was studied in detail. Experimental evidence indicated that PtrPPO13 is expressed in most organs, and unlike most PPOs, is localized to the vacuole. Together, the phylogeny, gene expression and subcellular localization studies suggest that PPOs are likely to have variable physiological functions in plants and that PtrPPO13 is distinct from most typical PPOs. / Graduate / 0309
323

Utilization Of Industrial Wastes Of Turkey As Abrasive In Surface Preparation Technologies

Ataman, Nihat 01 December 2005 (has links) (PDF)
Surface preparation is the key factor in determining the success of a protective coating system and its ultimate objective is to create proper adhesion of a coating over an underlying substrate. Abrasive blast cleaning involves mechanical cleaning by the continuous impact of abrasive particles at high velocities on to the substrate in a jet stream of compressed air. Industries that use abrasive blasting include the shipbuilding industry, automotive industry, and other industries that involve surface preparation and painting. Materials from different origins can be used as a blasting media including coal slag, smelter slag, mineral abrasives, metallic abrasives, and synthetic abrasives. Purpose of this thesis is to investigate the usability of industrial wastes (coal slag, smelter slags, etc.) of Turkey as abrasives in surface preparation technologies. Four different slag samples of three sources, namely coal furnace slag sample from &Ccedil / ayirhan thermal power plant, ferrochrome slag sample from Eti Krom A.S., granulated blast furnace and converter slag sample from Eregli Iron and Steel Works were studied within the scope of this thesis work. The samples were prepared by crushing and screening. The chemical composition and physical characteristics of the samples were determined. All the samples were tested in industrial scale. Test results showed that the converter slag meet all the specifications for abrasives and it can be used in blast cleaning operations. However, coal furnace slag, granulated blast furnace slag and ferrochrome slag are not suitable to be used as abrasive in surface preparation technologies.
324

The Balloon-borne Large Aperture Submillimeter Telescope and Its Rebirth as a Polarimeter

Thomas, Nicholas E 14 December 2011 (has links)
The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) is a 1.8 meter Cassegrain telescope that operates in three bands (250, 350, and 500 μm), each with 30% bandwidth. The detection system is comprised of 280 silicon-nitride micromesh bolometers distributed on three focal plane arrays with 30”, 42”, and 60” FWHM (full width at half max) beam sizes, respectively. BLAST's goal is to study the evolutionary history and processes associated with star formation. Earth's atmosphere is opaque to submillimeter radiation and astronomical observations in this wavelength are best conducted at high altitudes. BLAST is designed to be flown above 99.5% of the atmosphere on a stratospheric balloon. BLAST has made three scientific flights and this thesis covers the last two. The second flight was made in 2006 from McMurdo, Antarctica and studied the evolutionary history and processes associated with star formation. For the third flight, BLAST was reconfigured as a polarimeter (BLAST-Pol) and was also launched from McMurdo in December 2010. BLAST-Pol's objective is to determine what role, if any, magnetic fields play in star formation. This thesis will describe the BLAST-Pol instrument and provide a summery of key observations made by the 2006 flight.
325

Hard Habits to Break: Investigating Coastal Resource Utilisations and Management Systems in Sulawesi, Indonesia.

Idrus, Rijal January 2009 (has links)
This research investigates the paradox that many coastal communities in developing countries are resource rich but income poor. Another aspect of this paradox is the belief that local communities possess traditional knowledge that respects nature. This belief contrasts the fact that major tropical coastal ecosystems, namely coral reefs and mangroves, are being destroyed at rapid and increasing rates, in many cases by the people whose livelihoods depend on them. These paradoxical circumstances lead to a central question: if the sustainability of coastal resources is vital for the livelihood of local communities, why are these resources being degraded, often to the point of complete destruction? This study explores the motives and consequences of destructive methods of coastal resource utilisation and examines the potential for sustainable livelihoods based on coastal resources currently under threat from destructive use patterns. The analysis is based on a field study conducted in 2006 and 2008 in eleven sites around the island of Sulawesi, Indonesia. This area is characterised by great biodiversity, including one of the highest marine biodiversities in the Asia-Pacific region. Coral and mangrove ecosystem resource use was found to be driven by different processes and activities; hence the destructive practices impacting both ecosystems were also different. Blast and poison fishing were the most widespread destructive resource use methods found for coral reefs whereas large-scale habitat conversion was responsible for mangrove ecosystem reduction. In the field both resources were found to be under enormous anthropogenic pressures, with published data suggesting that only 5.8% of Indonesian coral reefs are currently in excellent condition and only 38% of mangrove cover remaining in Sulawesi relative to that of 25 years ago. The dynamics of these coastal resources, and of their destruction, are classic examples of the ’tragedy of the commons’. Research findings further indicate that formal institutions tasked with managing these resources have not been able to promote their effective conservation. An array of competing demands and conflicting interests, coupled with inefficient institutional arrangements and under-investment, have rendered inadequate many resource management efforts, including the externally-imposed concepts, allowing destructive patterns of resource utilization to persist. Local communities are disempowered when confronted with (1) the intricate network of destructive-fishing actors targeting coral reefs, or (2) large company-government bureaucracy collusions allowing mangrove conversion. The existence of this collusive network must be considered in any effort to address problems of effective management. Empirical insights suggest that conservation at local level has to face the challenges of market-driven resource extraction at a global scale. Only when a coastal community manages to overcome the dilemma in managing common-pool resource, conservation measures can be implemented and a degree of sustainability attained. Findings from this research have important implications for the discourses on coastal resource policy and research. This research advances the discussions to the area where the core of conflict of interests among stakeholders took place, and yet has rarely been addressed previously. The synthesis from this study provides a strong basis to understand the nature of asymmetric relations amongst the resource stakeholders, and therefore will help in generating effective policies for a fairer coastal resource management regime.
326

Groundwater remediation using a coal washery discard permeable reactive wall

Gray, Stuart. January 2005 (has links)
Thesis (Ph.D.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 252-266.
327

Identification of Pseudomonas aeruginosa mutants unable to convert ricinoleic acid into 7,10,12-Trihydroxy-8(E)-Octadecenoic acid (TOD) and a survey of the biological activity of TOD

Hatchett, Taylor Boozer, Lawrence, Katheryn Kay Scott, January 2009 (has links)
Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 62-71).
328

Identification of genes involved in the production of a novel antifungal agent (7, 10, 12-trihydroxy-8(E)-octadecenoic acid) in Pseudomonas aeruginosa

Cofield, Jessica, Suh, Sang-Jin, January 2009 (has links)
Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 78-88).
329

Predicting the medical management requirements of large scale mass casualty events using computer simulation

Zuerlein, Scott A. January 2009 (has links)
Dissertation (Ph.D.)--University of South Florida, 2009. / Title from PDF of title page. Document formatted into pages; contains 295 pages. Includes vita. Includes bibliographical references.
330

Turbo-blast : a novel technique for multi-transmit and multi-receive wireless communications /

Sellathurai, Mathini. January 2001 (has links)
Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 174-186). Also available via World Wide Web.

Page generated in 0.0329 seconds