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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.
381

The development of a single nucleotide polymorphism database for forensic identification of specified physical traits

Alecia Geraldine Naidu January 2009 (has links)
<p>Many Single Nucleotide Polymorphisms (SNPs) found in coding or regulatory regions within the human genome lead to phenotypic differences that make prediction of physical appearance, based on genetic analysis, potentially useful in forensic investigations. Complex traits such as pigmentation can be predicted from the genome sequence, provided that genes with strong effects on the trait exist and are known. Phenotypic traits may also be associated with variations in gene expression due to the presence of SNPs in promoter regions. In this project, the identification of genes associated with these physical traits of potential forensic relevance have been collated from the literature using a text mining platform and hand curation. The SNPs associated with these genes have been acquired from public SNP repositories such as the International HapMap project, dbSNP and Ensembl. Characterization of different population groups based on the SNPs has been performed and the results and data stored in a MySQL database. This database contains SNP genotyping data with respect to physical phenotypic differences of forensic interest. The potential forensicrelevance of the SNP information contained in this database has been verified through in silico SNP analysis aimed at establishing possible relationships between SNP occurrence and phenotype. The software used for this analysis is MATCH&trade / .</p>
382

Processing and characterization of silicon carbide (6H-SiC and 4H-SiC) contacts for high power and high temperature device applications

Lee, Sang Kwon January 2002 (has links)
Silicon carbide is a promising wide bandgap semiconductormaterial for high-temperature, high-power, and high-frequencydevice applications. However, there are still a number offactors that are limiting the device performance. Among them,one of the most important and critical factors is the formationof low resistivity Ohmic contacts and high-temperature stableSchottky diodes on silicon carbide. In this thesis, different metals (TiW, Ti, TiC, Al, and Ni)and different deposition techniques (sputtering andevaporation) were suggested and investigated for this purpose.Both electrical and material characterizations were performedusing various techniques, such as I-V, C-V, RBS, XRD, XPS,LEED, SEM, AFM, and SIMS. For the Schottky contacts to n- and p-type 4H-SiC, sputteredTiW Schottky contacts had excellent rectifying behavior afterannealing at 500 ºC in vacuum with a thermally stableideality factor of 1.06 and 1.08 for n- and p-type,respectively. It was also observed that the SBH for p-type SiC(ΦBp) strongly depends on the choice the metal with alinear relationship ΦBp= 4.51 - 0.58Φm, indicating no strong Fermi-level pinning.Finally, the behavior of Schottky diodes was investigated byincorporation of size-selected Au nano-particles in Ti Schottkycontacts on silicon carbide. The reduction of the SBH isexplained by using a simple dipole layer approach, withenhanced electric field at the interface due to the small sizeof the circular patch (Au nano-particles) and large differenceof the barrier height between two metals (Ti and Au) on both n-and p-SiC. For the Ohmic contacts, titanium carbide (TiC) was used ascontacts to both n- and p-type 4H-SiC epilayers as well as onAl implanted layers. The TiC contacts were epitaxiallydeposited using a co-evaporation method with an e-beam Tisource and a Knudsen cell for C60, in a UHV system at low substrate temperature(500 ºC). In addition, we extensively investigatedsputtered TiW (weight ratio 30:70) as well as evaporated NiOhmic contacts on both n- and p-type epilayers of SiC. The bestOhmic contacts to n-type SiC are annealed Ni (&gt;950ºC)with the specific contact resistance of ≈ 8× 10-6Ω cm2with doping concentration of 1.1 × 10-19cm-3while annealed TiW and TiC contacts are thepreferred contacts to p-type SiC. From long-term reliabilitytests at high temperature (500 ºC or 600 ºC) invacuum and oxidizing (20% O2/N2) ambient, TiW contacts with a platinum cappinglayer (Pt/Ti/TiW) had stable specific contact resistances for&gt;300 hours. <b>Keywords</b>: silicon carbide, Ohmic and Schottky contacts,co-evaporation, current-voltage, capacitance-voltagemeasurement, power devices, nano-particles, Schottky barrierheight lowering, and TLM structures.
383

Shadow Detection And Compensation In Aerial Images With An Application To Building Height Estimation

Seref, Ahmet 01 September 2010 (has links) (PDF)
This thesis is devoted to the shadow detection and compensation in aerial images with application of the detection results to building height detection. Shadows could be defined as the parts of the scene that is not directly illuminated by a light source due to obstructing object or objects. Usually the shadows in images or video are undesirable, since they could cause degradation of the expected results during processing of the image or video for object detection, segmentation, scene surveillance or similar purposes. However shadow information could also be used for beneficial purposes like revealing information about the object&rsquo / s shape, orientation and even about the light source. In this thesis firstly shadow detection methods are overviewed. Beside the selected methods from literature, some novel approaches are also proposed and experimented. Then shadow compensation methods are overviewed and experimented. Finally an example of beneficial utilizations of shadow information is studied, where buildings&rsquo / heights are estimated from their shadow length and sun angles.
384

Processing and characterization of silicon carbide (6H-SiC and 4H-SiC) contacts for high power and high temperature device applications

Lee, Sang Kwon January 2002 (has links)
<p>Silicon carbide is a promising wide bandgap semiconductormaterial for high-temperature, high-power, and high-frequencydevice applications. However, there are still a number offactors that are limiting the device performance. Among them,one of the most important and critical factors is the formationof low resistivity Ohmic contacts and high-temperature stableSchottky diodes on silicon carbide.</p><p>In this thesis, different metals (TiW, Ti, TiC, Al, and Ni)and different deposition techniques (sputtering andevaporation) were suggested and investigated for this purpose.Both electrical and material characterizations were performedusing various techniques, such as I-V, C-V, RBS, XRD, XPS,LEED, SEM, AFM, and SIMS.</p><p>For the Schottky contacts to n- and p-type 4H-SiC, sputteredTiW Schottky contacts had excellent rectifying behavior afterannealing at 500 ºC in vacuum with a thermally stableideality factor of 1.06 and 1.08 for n- and p-type,respectively. It was also observed that the SBH for p-type SiC(Φ<sub>Bp</sub>) strongly depends on the choice the metal with alinear relationship Φ<sub>Bp</sub>= 4.51 - 0.58Φ<sub>m</sub>, indicating no strong Fermi-level pinning.Finally, the behavior of Schottky diodes was investigated byincorporation of size-selected Au nano-particles in Ti Schottkycontacts on silicon carbide. The reduction of the SBH isexplained by using a simple dipole layer approach, withenhanced electric field at the interface due to the small sizeof the circular patch (Au nano-particles) and large differenceof the barrier height between two metals (Ti and Au) on both n-and p-SiC.</p><p>For the Ohmic contacts, titanium carbide (TiC) was used ascontacts to both n- and p-type 4H-SiC epilayers as well as onAl implanted layers. The TiC contacts were epitaxiallydeposited using a co-evaporation method with an e-beam Tisource and a Knudsen cell for C<sub>60</sub>, in a UHV system at low substrate temperature(500 ºC). In addition, we extensively investigatedsputtered TiW (weight ratio 30:70) as well as evaporated NiOhmic contacts on both n- and p-type epilayers of SiC. The bestOhmic contacts to n-type SiC are annealed Ni (>950ºC)with the specific contact resistance of ≈ 8× 10<sup>-6</sup>Ω cm<sup>2</sup>with doping concentration of 1.1 × 10<sup>-19</sup>cm<sup>-3</sup>while annealed TiW and TiC contacts are thepreferred contacts to p-type SiC. From long-term reliabilitytests at high temperature (500 ºC or 600 ºC) invacuum and oxidizing (20% O<sub>2</sub>/N<sub>2</sub>) ambient, TiW contacts with a platinum cappinglayer (Pt/Ti/TiW) had stable specific contact resistances for>300 hours.</p><p><b>Keywords</b>: silicon carbide, Ohmic and Schottky contacts,co-evaporation, current-voltage, capacitance-voltagemeasurement, power devices, nano-particles, Schottky barrierheight lowering, and TLM structures.</p>
385

Pocket beach wave processes and current systems investigated via field and numerical modelling studies: A case study of Okains Bay

Eisazadeh Moghaddam, Arash January 2015 (has links)
Confined coasts in general, and pocket beach environments in particular, are under huge development pressures worldwide, not least due to their sheltered nature and perceived shoreline stability. However, understanding of their physical functioning is poor in comparison to that of open coast beaches. This study aims to improve understanding in terms of the existing gaps in knowledge of wave processes and nearshore currents, and also to examine the importance of local wind and tide factors in generating nearshore currents, in micro-tidal pocket beaches. The boundaries of embayments are generally recognized as important controls of their beach processes and responses, yet little detailed knowledge exists of how the exact embayment dimensions and characteristics influences these processes. One key embayment feature the influence of which is poorly understood is the downcoast headland. In this thesis, field observations plus Zanuttigh and Van der Meer’s (2008) approach, and the SWAN wave model were used to evaluate the downcoast headland effects on wave processes within Okains Bay, an example pocket beach environment. The results showed that incident wave heights and directions were significantly influenced by wave reflection processes from the downcoast headland inside the bay. The intensity of reflection effects on wave characteristics inside the pocket beach varied according to approaching wave direction. Reflection effects reduced when waves approached from angles close to parallel to the headlands, increasing towards headland-perpendicular wave approaches. Field observations and the XBeach model were used to examine whether or not tides can significantly influence nearshore currents within example and model pocket beach environments. Results indicated that tides can be the primary driver of nearshore currents close to the bed inside micro-tidal pocket beaches, depending on incident wave conditions. In areas of micro-tidal pocket beaches exposed to direct approaching waves, currents were wave driven, while in areas further into the bay that experienced headland filtering of their wave environment, currents were mainly tide generated. The results of this study demonstrated how the current circulation system within micro-tidal pocket beaches is related to the incoming directions of offshore waves. If high energy waves approach oblique or normal to the shoreline (with the assumption that the shoreline is at 90° to the headlands), the current system was found to consist of longshore currents influenced by headlands, plus a rip current in the center of the shoreline or a toporip in proximity to headlands. The location of the rip current or toporip was determined by the direction of approaching incident waves. This study also examined the behavior of local winds in a pocket beach environment and their consequent effects on nearshore currents. Results for Okains Bay show that local winds tended to blow in offshore and onshore directions, as the bay is located in a valley, so orographic effects channel and shift the wind directions to angles close to offshore and onshore directions inside the bay. Results also indicated that local winds influence the hydrodynamic currents of pocket beaches that are confined by elevated topography, producing semi-cross shore influences since the winds are topographically channelled to blow in predominantly offshore and onshore directions. This research significantly refines our understanding of micro-tidal pocket beach wave and current processes, including quantification of the filtering effects of headlands on their wave environments, revealing the various and variable influences of tides and winds compared to in open coast beaches; and, significantly, highlighting the role of downcoast headland wave reflection effects. With regard to the latter, this research elucidates some key process differences between pocket and embayed beaches and clarifies reasons why the application of embayed beach models that include refraction and diffraction but exclude reflection effects to the study of pocket beaches is inappropriate for studying pocket beaches. This research also provides methodological and topic suggestions for future research on pocket beach environments, including how to use the improved hydrodynamic knowledge of this study in future studies seeking to better understand pocket beach sediment systems, a topic that was beyond the scope of the current research.
386

Hamiltonian Sets of Polygonal Paths in 4-Valent Spatial Graphs

Muche, Tilahun Abay 01 January 2012 (has links)
Spatial graphs with 4–valent rigid vertices and two single valent endpoints, called assembly graphs, model DNA recombination processes that appear in certain species of ciliates. Recombined genes are modeled by certain types of paths in an assembly graph that make a ”oper pendicular ” turn at each 4–valent vertex of the graph called polygonal paths. The assembly number of an assembly graph is the minimum number of polygonal paths that visit each vertex exactly once. In particular, an assembly graph is called realizable if the graph has a Hamiltonian polygonal path. An assembly graph ɣ^ obtained from a given assembly graph γ by substituting every edge of γ by a loop is called a loop-saturated graph. We show that a loop- saturated graph ɣ^ has an assembly number a unit larger than the size of ɣ. For a positive integer n, the minimum realization number for n is defined by Rmin(n) = min{|ɣ| : An(ɣ) = n}, where |γ| is the number of 4-valent vertices in γ. A graph γ that gives the minimum for Rmin(n) is called a realization of assembly number n. We denote by Rmin(n) the set of realization graphs for n. We prove that loop-saturated graphs with assembly number nachieve the upper bound of Rmin(n). If a simple assembly graph γ has no loops then γ is not in Rmin(n). With the introduction of left –additive, right–additive and middle additive operations, we study the properties of assembly graphs when composing increases their assembly number. We also introduce the notion of height sequence, a non-increasing sequence of positive integers, that counts the number of 4-valent vertices which the polygonal paths contain. We show properties of a height sequence for loop–saturated graphs. Assembly graphs are represented by double-occurrence words called assembly words. An assembly word is strongly-irreducible if it does not contain a proper subword that is also a double-occurrence word. We prove that, for every positive integer n there is a strongly-irreducible assembly graph with assembly number n, and if a simple assembly graph is strongly-irreducible, then γ ̸∈ Rmin(n).
387

Impacts of the Anomalous Mississippi River Discharge and Diversions on Phytoplankton Blooming in Northeastern Gulf of Mexico

O'connor, Brendan 01 January 2013 (has links)
On April 20, 2010 a tragic explosion aboard the Deepwater Horizon (DWH) drilling rig marked the beginning of one of the worst environmental disasters in history. For 87 days oil and gas were released into the Gulf of Mexico. In August 2010, anomalous phytoplankton activity was identified in the Northeastern Gulf of Mexico, using the Fluorescence Line Height (FLH) ocean color product. The FLH anomaly was bound by approximately 30-28 degrees North and 90 and 86 degrees West and there was a suggestion that this anomaly may have occurred due to the presence of oil. This study was designed to examine alternative explanations and to determine what influence the Mississippi River and the freshwater diversions, employed in the response efforts, may have had on the development of the FLH anomaly. The combination of the anomalously high flow rate in the Mississippi River observed in June-August 2010, the use of freshwater diversions, and three severe storms increased the flow of water through the adjoining marshes. We propose that these conditions reduced the residence time of water and nutrients on the wetlands, and likely mobilized nutrients leading to increased fresh water and nutrients being discharge to the coasts around the Mississippi Delta. Salinity contour maps created from data collected by ships operating in the Northeastern Gulf of Mexico showed that the 31 isohaline was upwards of 250km east of the Mississippi River Birds Foot Delta in August 2010. The American Seas (AmSeas) numerical circulation model was used to examine the dispersal and distribution of water parcels from the Mississippi River and freshwater diversions. Two virtual particle seeding locations were used to trace particles to obtain a measure of the percentage of particles entering a Region of Interest (ROI) located in the center of the FLH anomaly, i.e. 150 km east of the Mississippi Delta. All environmental data examined suggest that the eastward dispersal of the Mississippi River water including that derived from freshwater diversions and storm activity contributed to the development of FLH anomaly in August 2010. Chapter two examines the spectral characteristics of water and oil collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Several peaks in the spectral features of the total radiance of surface oil between 1907nm and 2400nm appear to be absent for water. An algorithm (Spectral Line Height) was created to measure the height of the peak at 2142nm relative to a baseline between 2013nm and 2390nm. A normalized difference technique developed by the USGS was used as a validation tool. Preliminary results of the SLH technique appear to compare favorably with the results derived using the USGS technique. The SLH technique worked in areas that did not show sunglint or shallow bottom features. Sunglint areas would require additional correction to remove the effect of specular reflection. The SLH technique shows promise but will require validation to develop into an operational remote sensing method.
388

Ein einheitliches vertikales Referenzsystem für Südamerika im Rahmen eines globalen Höhensystems

Sánchez-Drewes, Laura Marlene 19 March 2015 (has links) (PDF)
Ziel dieser Arbeit ist die Vereinheitlichung der in Südamerika existierenden Höhensysteme, die sich auf verschiedene Meerespegel beziehen, in einem globalen vertikalen Referenzsystem, das die Erfordernisse moderner geodätischer Verfahren erfüllt. Dabei werden folgende Themen bearbeitet: a) Alternativen für die Definition und Realisierung eines konventionellen Welthöhensystems; b) Diagnostik und Standardisierung der südamerikanischen Höhensysteme; c) Strategien für die genaue Transformation der lokalen Höhensysteme in das Welthöhensystem. Unter der Voraussetzung, dass ein modernes Höhensystem die genaue Kombination von physikalischen und geometrischen Höhen unterstützen muss, werden zwei Komponenten betrachtet: a) eine geometrische Komponente bestehend aus ellipsoidischen Höhen als Koordinaten und ein Niveauellipsoid als Referenzfläche und b) eine physikalische Komponente bestehend aus geopotentiellen Koten als Koordinaten und eine durch einen bestimmten W0-Wert definierte Äquipotentialfläche als Referenzniveau. Die physikalische Komponente wird durch Potentialparameter definiert, damit sie als Bezug für jeden Typ von physikalischen Höhen (d.h. orthometrische Höhen, Normalhöhen, usw.) dienen kann. Die Umwandlung von geopotentiellen Koten in metrische Höhen und die Modellierung der Bezugsfläche (Geoid- bzw. Quasigeoid-Bestimmung) werden als ein Teil der Realisierung betrachtet. Da das ganze Konzept sich auf die Kombination von geometrischen und physikalischen Parametern bezieht, war es nötig, eine Inventur der zurzeit angewendeten Konventionen zu machen und diese zu analysieren, um systematische Fehler zu reduzieren und die zeitlichen Veränderungen der verschiedenen Daten zu berücksichtigen. Hauptprodukte dieser Arbeit sind: a) Detaillierte Beschreibung der Charakteristiken des Festpunktfeldes, das das globale vertikale Bezugsystem realisieren soll. Diese Beschreibung enthält genaue Formulierungen für die Berücksichtigung der notwendigen Konventionen und die Bereitstellung von Normalgleichungssystemen der nationalen Höhennetze, um ihre Kombination durch überregionale Ausgleichungen zu ermöglichen. b) Bestimmung eines W0-Referenzwertes unter Anwendung verschiedener Ansätze und der Kombination neuester Modelle der Erdoberfläche und des Erdschwerefeldes. Dabei wurde besonders auf die rigorose Fehlerfortpflanzung der Rechnungen geachtet, um die Zuverlässigkeit dieses Wertes zu schätzen. c) Formulierung der Bobachtungsgleichungen für die Bestimmung der Niveaudifferenzen zwischen den lokalen Höhensystemen und dem Welthöhenbezugssystem. Dies wurde in drei Ansätzen betrachtet: ein Ozean-Ansatz (im Meeresgebiet um die Referenzpegel), ein Küsten-Ansatz (auf dem Festland an den Referenzpegeln) und ein Kontinent-Ansatz (mit kontinentalen Festpunktfeldern des geometrischen Referenzsystems). d) Vereinheitlichung der existierenden Höhensysteme Südamerikas in dem globalen vertikalen Referenzsystem. Die Genauigkeit der Ergebnisse liegt derzeit um ±5 cm für die Gebiete mit der größten Anzahl von Beobachtungen (Argentinien, Brasilien-Imbituba, Kolumbien, Ecuador, Uruguay und Venezuela) und um ±2 … 3 dm für Gebiete mit geringer Verfügbarkeit und großer Unsicherheit der Daten (Brasilien-Santana, Bolivien, Peru und Chile). Die geschätzten Höhenniveaus sind größtenteils positiv, d.h. die lokalen vertikalen Datums liegen über dem globalen Referenzwert W0. Dieses sowie auch der Nord-Süd-Anstieg am Atlantik und der Süd-Nord-Anstieg am Pazifik spiegelt die Meeresoberflächentopographie in der Region wieder. e) Vorschläge zur Fortführung der Arbeiten mit zusätzlichen Daten in den einzelnen Ländern. / The objective of this study is the unification of the South American height systems into a global vertical reference system satisfying the requirements of modern Geodesy. The following topics are discussed: a) Definition and realisation of a conventional global vertical reference system; b) Review and standardisation of the geodetic data referring to the South American height systems; c) Strategies for the precise transformation of the local height datums into the global vertical reference system. It is expected that a modern vertical reference system supports the combination of physical and geometric heights with high accuracy globally. Therefore, two components are considered: a) A geometric component consisting of ellipsoidal heights as coordinates and a level ellipsoid as the reference surface, and b) A physical component comprising geopotential numbers as coordinates and an equipotential surface defined by a conventional W0 value as the reference surface. The definition of the physical component is based on potential parameters in order to provide reference to any type of physical heights (normal, orthometric, etc.). The conversion of geopotential numbers into metric heights and the modelling of the reference surface (geoid or quasigeoid determination) are considered as steps of the realisation. Since the approach developed in this study is based on the combination of geometric and physical parameters, it was necessary to include an inventory of the standards used in the determination of the vertical coordinates. This inventory is the basis for the identification and consequent removal of systematic errors caused by the application of different models and methods in the generation of the data available for this study. The main results of this study are: a) A detailed description of the characteristics to be satisfied by the reference stations realising the global vertical reference system. This description includes the needed conventions for the standardisation of the vertical coordinates and the computation of normal equations for the national levelling networks. These equations are required to integrate the local height systems into the global one. b) Estimation of the reference value W0 following different approaches and applying the latest geodetic models of the Earth\'s surface and gravity field. This procedure also includes a rigorous error propagation analysis to assess the reliability of the W0 estimate. c) Observation equations for the determination of the level discrepancies between the local height datums and the global W0. This is performed in three approaches: in the ocean areas around the reference tide gauges (ocean approach), at the reference tide gauges (coastal approach), and at the reference stations of the geocentric reference system (continental approach). d) Vertical datum parameters for the unification of the South American height systems into a global vertical reference system. The accuracy is assessed to be about ±5 cm for those countries with a good coverage of measurements (Argentina, Brazil-Imbituba, Colombia, Ecuador, Uruguay, and Venezuela). For those regions with poor data coverage or high uncertainties in the data quality (Brazil-Santana, Bolivia, Peru, and Chile), the accuracy is estimated to be about ±2 … 3 dm. The obtained level differences are in general positive, i.e., local vertical datums are above the global reference level W0. This and the north-south increase along the Atlantic coast and the south-north increase along the Pacific coast reflect well the behaviour of the sea surface topography in these regions. e) A description of the further activities to be developed by each country to improve the results of this study.
389

Eglės medienos vertės dinamikos analizė / Analysis of spruce wood value dynamics

Mačiulaitis, Mindaugas 06 June 2006 (has links)
2923 in I storey and 1995 in II storey live spruce trees from Lithuanian national forest inventory were selected using criteria formed in advance. It was assessed that the height class varies marginally in a 5 year period. The value of the spruce wood is more determined by assortment yield than by the volume. The wood volume stock increased by 17,8% and the value increased by 26,6% in a 5 year period.The biggest mean value variation was estimated in site type Lc and reaches 0,76 Lt/m3 in one year period.
390

Site index curve and table for trembling aspen in the boreal white and black spruce zone of British Columbia

Klinka, Karel, Chen, Han Y. H., Chourmouzis, Christine January 1997 (has links)
No description available.

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