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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.
271

Quality of CPTU : Analyses and comparison of data from commercial actors in Stockholm/Mälardalen

Kardan, Caesar January 2015 (has links)
CPTU is one of the most sophisticated geotechnical investigation methods. However, there is a large amount of uncertainties related to this method. The uncertainties depend on different types of factors, for instance lack of accuracy in performance and equipment. The objective of this master thesis is to compare the CPTU-results from a number of commercial actors in Stockholm/Mälardalen in order to analyze these results with respect to the current standards and guidelines. The comparison was made in order to highlight the difference in results which may appear due to different equipment, performance of the operator and evaluation method. Based on this, an invite was sent to the commercial actors in Stockholm/Mälardalen, resulting in the participation of five different commercial actors in this investigation. Execution in the field was conducted over a six week period. During this time 26 CPTU were performed in total in a small area in Hagby, Stockholm, by these different actors. Once the data was collected from all of the actors, the results were evaluated with the aid of the computer softwares Conrad and Excel. The main conclusions from this study are: Not one of the performed CPTU in this master thesis fulfills the requirements for CPT class 1 according to the European standards. The quality of the education of operators should be improved and geotechnical engineers and the clients need to be more familiar with CPTU. The evaluated results from different commercial actors differ, and this can depend on the choice of equipment and performance of the operator during penetration, but it can also depend on systematic errors in the cone penetrometers / CPTU-sonderingar är en av de mest sofistikerade undersökningsmetoderna för geoteknisk analys och bedömning. Det finns emellertid en hög grad av osäkerhet i denna metod. Osäkerheten beror på olika typer av faktorer, bland annat brist på noggrannhet i handhavande och utrustning. Syftet med detta examensarbete är att jämföra CPTU-resultat från de kommersiella aktörerna i Stockholm/Mälardalen för att senare analysera dessa resultat i förhållande till gällande ramverk och riktlinjer. Jämförelsen gjordes med avsikt att lyfta fram skillnaderna i resultat som kan uppstå på grund av olika utrustning, handhavande och utvärderingsmetod. Baserat på detta skickades en inbjudan till de kommersiella aktörerna i Stockholm/Mälardalen, vilket ledde till att fem olika kommersiella aktörer deltog i undersökningen. Utförande i fält genomfördes under en period på sex veckor. Under denna tid utfördes totalt 26 sonderingar i ett avgränsat område i Hagby, Stockholm, av dessa olika aktörer. När all data samlats in från alla aktörer utvärderades resultaten med hjälp av mjukvarorna Conrad och Excel. De viktigaste slutsatserna i denna studie är: Ingen utav de utförda CPTU-sonderingarna uppfyller kraven för CPT klass 1 enligt den europeiska standarden. Kvaliteten på utbildning av fältgeotekniker bör förbättras och geotekniska ingenjörer och även beställare bör bli mer bekanta med CPT. De utvärderade resultaten från de olika aktörerna skiljer sig åt, och detta kan bero på valet av utrustning och fältgeoteknikerns prestation vid sondering men det kan också bero på systematiska fel i de använda sonderna.
272

Scoria cones as climate and erosion markers: morphometric analysis of Erebus Volcanic Province, Antarctica, using high-resolution digital elevation data

Collins, Andrew L. 19 August 2015 (has links)
No description available.
273

SCHLIEREN IMAGING AND INFRARED HEAT TRANSFER MEASUREMENTS ON A FLARED CONE AND CONE-CYLINDER-FLARE IN MACH-6 QUIET FLOW

Zachary Allen McDaniel (18431658) 26 April 2024 (has links)
<p dir="ltr">Pressure transducer, infrared heat transfer, and schlieren imaging data for a flared cone and cone-cylinder-flare in Mach 6 quiet flow are presented. Flared cone pressure transducer results show second-mode RMS values comparable to that found in prior experimental work. Second-mode frequency is found to linearly increase with increasing freestream unit Reynolds number, and frequency varies little between sensors for a given freestream unit Reynolds number. Turbulent intermittency begins to increase at a freestream unit Reynolds number 2x10<sup>6</sup>/m greater than the unit Reynolds number corresponding to peak second-mode RMS. peak RMS. High-speed schlieren imaging on the downstream section of the flared cone shows the second-mode disturbance following trends in power which correlate with PCB RMS. Infrared heat transfer results contain the azimuthal heating streak pattern observed for the flared cone in prior research, but the hot-cold-hot streak pattern is not seen due to limited model length. Streak heating occurs downstream of second-mode peak RMS over the freestream unit Reynolds number range of 6.4x10<sup>6</sup>/m to 10.4x10<sup>6</sup>/m. The heat transfer of streaks is found to vary significantly from streak to streak, while mean streak heating variation with freestream unit Reynolds number is small.</p><p dir="ltr">PCB results of the cone-cylinder-flare show intermittent turbulence at a freestream unit Reynolds number of 16.0x10<sup>6</sup>/m. Examination of shear-layer and second-mode instabilities show significant increases in RMS moving downstream along the flare and with increasing freestream unit Reynolds number. High-speed schlieren imaging of the shear-layer reattachment region on the flare show the presence of the shear-layer and second-mode instabilities when the model is configured with a sharp nose tip. The instabilities are not present with a blunt 5 mm radius nose tip. Heat transfer is observed to increase along the downstream portion of the flare. The sharp nose tip configuration has higher heat transfer rates than the 5 mm radius nose tip configuration.</p>
274

Comparison of the shock arrival times for Earth-directed ICMEs provided by the WSA-Enlil+Cone model and in-situ observations at L1: A Case Study

Werner, Anita Linnéa Elisabeth January 2016 (has links)
A case study which examines the agreement between prediction and data is performed for three, complex interplanetary shocks which were detected at the Sun-Earth Lagrange point L1 and induced moderate to intense geomagnetic storms. We use model output from previous runs of the coupled coronal-heliosphere WSA-Enlil+Cone model, available through the Community Coordinated Modeling Center (CCMC), and in-situ data from the OMNI data set. Code written in MATLAB is used to compare the model output with the in-situ measurements of the interplanetary magnetic field as well as the density, speed and temperature of the solar wind. In addition, the difference between the predicted and actual shock arrival time is computed and regions of potential temperature depression are identified. A considerable discrepancy is found between data and model for the studied events. The main reason is deemed to be an inadequate representation of the ambient solar wind as well as the complex interactions between interplanetary coronal mass ejections and corotating interaction regions. We suggest future steps to be taken for the further development of the model as well as for the general understanding of space weather and the Sun-Earth connection. / Denna fallstudie undersöker överensstämmelsen mellan modell och data för tre interplanetära chockvågor, som kunde detekteras vid jordens Lagrangepunkt 1, och som orsakade geomagnetiska stormar av måttlig till kraftig styrka. Vi använder oss av tidigare genomförda körningar av den sammansatta WSA-Enlil+Cone modellen, som avbildar fortplantningen av temporära störningar med ursprung i solens korona, såsom koronamassutkastningar, ut i heliosfären. Modellen gjordes tillgänglig av Community Coordinated Modeling Center (CCMC) och datan inhämtades från OMNI. Kod skriven i MATLAB nyttjades för att göra en jämförelse mellan modell och faktiska mätningar av det interplanetära magnetfältet samt solvindens hastighet, densitet och temperatur. Utöver detta, beräknas också skillnaden mellan förväntad och faktisk ankomsttid av respektive interplanetär chock, och tidsperioder med en temperatursänkning utöver det normala identifieras. Vi finner en omfattande avvikelse mellan modell och data, i synnerhet för de fall där på varandra följande koronamassutkastningar förväntas interagera eller rent av slås ihop samt för uppskattningen av den omgivande solvindens egenskaper och det interplanetära fältet under pågående geomagnetisk störning. Interaktionen mellan koronamassutkastningar och närliggande ko-roterande interaktionsregioner har ej heller återskapats väl av modellen ifråga. Slutligen ger vi förslag på möjliga, framtida åtgärder som kan bör tas i åtanke vid konstruerandet av framtida versioner av nämnda modell, liksom för den allmänna förståelsen för rymdvädrets inverkan på Jorden.
275

Neuroprotection of cone photoreceptors in retinitis pigmentosa

Lipinski, Daniel Mark January 2013 (has links)
Retinitis pigmentosa (RP) is a genetically and phenotypically heterogeneous condition that affects approximately 1 in 4000 individuals worldwide. The most common presentation of RP is a rod-cone dystrophy, where the degeneration of cone photoreceptors occurs secondary to advanced rod loss, leading to a significant decline in central vision and a corresponding reduction in patient quality of life. The mechanisms underlying secondary cone loss are poorly understood, particularly in disorders where the gene defect is unknown or manifest only in rod photoreceptors. Consequently, the thesis presented herein proceeds on several fronts. First, in the long term a greater understanding of the causes underlying cone loss in RP is likely to be beneficial, and so in chapter one a dominant cone degeneration is characterized using intrinsically fluorescent cone photoreceptors to track the degenerative process. Second, as we develop a greater understanding of the genetic etiology underlying RP it is likely that the number of large genes identified as being causative will increase. As currently there is no efficient way to deliver large genes to photoreceptors, chapter two explores the use of alternate viral vectors that might be used to deliver a large therapeutic transgene. Lastly, whilst our understanding of cone loss in RP remains incomplete, it is necessary to develop a broadly applicable therapy to slow or attenuate further cone loss in RP patients regardless of the underlying cause. In chapters three and four we examine the use of low molecular weight "growth factors‟, such as ciliary neurotrophic factor (CNTF), to preserve cone photoreceptors long-term using a rhodopsin knockout model of RP.
276

Iterative Filtered Backprojection Methods for Helical Cone-Beam CT

Sunnegårdh, Johan January 2009 (has links)
State-of-the-art reconstruction algorithms for medical helical cone-beam Computed Tomography (CT) are of type non-exact Filtered Backprojection (FBP). They are attractive because of their simplicity and low computational cost, but they produce sub-optimal images with respect to artifacts, resolution, and noise. This thesis deals with possibilities to improve the image quality by means of iterative techniques. The first algorithm, Regularized Iterative Weighted Filtered Backprojection (RIWFBP), is an iterative algorithm employing the non-exact Weighted FilteredBackprojection (WFBP) algorithm [Stierstorfer et al., Phys. Med. Biol. 49, 2209-2218, 2004] in the update step. We have measured and compared artifact reduction as well as resolution and noise properties for RIWFBP and WFBP. The results show that artifacts originating in the non-exactness of the WFBP algorithm are suppressed within five iterations without notable degradation in terms of resolution versus noise. Our experiments also indicate that the number of required iterations can be reduced by employing a technique known as ordered subsets. A small modification of RIWFBP leads to a new algorithm, the Weighted Least Squares Iterative Filtered Backprojection (WLS-IFBP). This algorithm has a slightly lower rate of convergence than RIWFBP, but in return it has the attractive property of converging to a solution of a certain least squares minimization problem. Hereby, theory and algorithms from optimization theory become applicable. Besides linear regularization, we have examined edge-preserving non-linear regularization.In this case, resolution becomes contrast dependent, a fact that can be utilized for improving high contrast resolution without degrading the signal-to-noise ratio in low contrast regions. Resolution measurements at different contrast levels and anthropomorphic phantom studies confirm this property. Furthermore, an even morepronounced suppression of artifacts is observed. Iterative reconstruction opens for more realistic modeling of the input data acquisition process than what is possible with FBP. We have examined the possibility to improve the forward projection model by (i) multiple ray models, and (ii) calculating strip integrals instead of line integrals. In both cases, for linearregularization, the experiments indicate a trade off: the resolution is improved atthe price of increased noise levels. With non-linear regularization on the other hand, the degraded signal-to-noise ratio in low contrast regions can be avoided. Huge input data sizes make experiments on real medical CT data very demanding. To alleviate this problem, we have implemented the most time consuming parts of the algorithms on a Graphics Processing Unit (GPU). These implementations are described in some detail, and some specific problems regarding parallelism and memory access are discussed.
277

ROLES OF EMX2 IN ODORANT RECEPTOR GENE EXPRESSION AND OLFACTORY SENSORY NEURON AXON GROWTH

McIntyre, Jeremy Colin 01 January 2009 (has links)
The sense of smell relies upon the detection of odorants by neurons located in the nasal cavity. These neurons, referred to as olfactory sensory neurons (OSNs), line the olfactory epithelium and extend axons that make synaptic connections with mitral/tufted cells in the olfactory bulb. The mechanisms by which these synaptic connections form remain largely unknown. The development of these synaptic connections relies on the axons of immature OSNs innervating the olfactory bulb. The primary goal of this dissertation was to identify components of the mechanisms used by immature OSN axons to innervate the olfactory bulb. To accomplish this goal, a knockout mouse model was used. OSN axons, of Emx2 knockout mice fail to innervate the olfactory bulb. As EMX2 is a transcription factor, this model was used investigate the possible causes of the defective OSN axon growth. To gain a better understanding of OSN axon growth, differences in expression of axon growth and guidance genes in immature and mature OSNs was investigated. This analysis revealed that many axon growth and guidance genes are differential expressed, and helped to identify immature OSN specific genes. The data also revealed a previously unrecognized developmental stage, termed nascent OSNs, identified by the expression of Cxcr4. Analysis of Emx2-/- mice revealed that EMX2 is necessary for OSN survival, odorant receptor expression and expression of the axonogenesis related gene Ablim1. EMX2 is necessary for the expression of many odorant receptor genes; however the loss of odorant receptor expression does not explain the axon growth defects. Apoptosis is increased in Emx2-/- mice, an outcome that may be due to the failed axon growth. Analysis of axon guidance gene expression identified a large reduction in Ablim1 expression in Emx2-/- mice. Ablim1 is expressed by immature OSNs, placing it in the proper cell type to regulate OSN axon growth. The loss of Ablim1 expression in Emx2-/- mice indicates defective signaling in the axon growth cone and a possible mechanism regulating OSN axon growth into the olfactory bulb. The data presented in this dissertation provide new insight into the regulation of odorant receptor gene expression and OSN axon growth.
278

Charge Transfer Mechanisms in Electrospinning

Stanger, Jonathan Jeffrey January 2008 (has links)
Electrospinning is a method of producing nano structured material from a polymer solution or melt using high strength electric fields. It is a process that has yet to find extensive industrial application yet shows promise if obstacles such as low rate of production overcome perhaps by more complete theoretical modelling. This work examines the effects of adding an ionic salt to a solution of poly(vinyl alcohol) in water. The direct effect was an increase the charge density and electric current. It was found that an increase in charge density decreases the mass deposition rate and forms a thinner initial jet. When the sign of the charge on the polymer solution was changed from positive to negative the charge density increased and the initial jet diameter and mass deposition rate also decreased. It was proposed that a smaller radius of curvature is formed by the Taylor cone at higher charge densities resulting in a smaller “virtual orifice”. The extent of the bending instability was explored and it was found that adding ionic salt results in a decrease in the bending instability resulting in thicker fibres. Changing the sign of the charge on the polymer solution from positive to negative resulted in an increase in the bending instability and resulted in thinner fibres. The charge transfer mechanisms used in different electrospinning models are explored and some assumptions not explicitly stated are discussed. From this discussion a generalized equation describing the charge transport mechanisms is proposed.
279

Leukocyte Response to Elastin-Like Polypeptide Coatings

Rooney, Meghan 15 October 2013 (has links)
Small diameter synthetic vascular grafts have yet to be clinically successful due to luminal narrowing from thrombosis and intimal hyperplasia. Current attempts to address this issue include the development of materials that support endothelialisation and protein modification to the material surfaces that reduce thrombosis. The extracellular matrix protein elastin has been found to be one of the least thrombogenic components of blood vessels, and its purified and recombinant forms have shown reduced thrombogenicity in both in vitro and in vivo models. Biomaterial coatings of elastin-like polypeptides (ELPs) recombinantly produced in the Woodhouse laboratory showed reduced fibrinogen adsorption, platelet adhesion, and platelet activity. However, the reason for their relative non-thrombogenicity is still not fully understood. In this work, the leukocyte response to ELP-coated materials was investigated. In particular, ELP1 and ELP4, which differ in molecular weight and sequence length, were physically adsorbed to a polyethylene terephthalate surface (MylarTM), yielding 0.22 ± 0.13 μg/cm2 and 0.37 ± 0.19 μg/cm2 surface coverage, respectively, as determined by the colorimetric assay, FastinTM Elastin. These surfaces were exposed to flowing citrated whole blood for surface and bulk evaluation of leukocyte activity using scanning electron microscopy and flow cytometry, respectively. Little leukocyte activation was observed on the surface of the controls, low-density polyethylene and uncoated MylarTM. In the bulk, tissue factor (TF) expression (monocytes: ELP1 = 38.6 ± 16.3 %, ELP4 = 33.9 ± 18.1 %) and platelet-leukocyte aggregates determined by CD61 (monocytes: ELP1 = 63.1 ± 17.1 %, ELP4 = 61.8 ± 16.8 %; granulocytes: ELP1 = 62.7 ± 17.0 %, ELP4 = 60.5 ± 20.1 %) were both decreased compared to uncoated MylarTM, while CD11b upregulation (monocytes: ELP1 = 18.7 ± 2.2 %, ELP4 = 19.7 ± 2.7 %; granulocytes: ELP = 21.4 ± 3.7 %, ELP4 = 22.0 ± 3.2 %) was increased. The statistical dependence of TF expression and platelet-monocyte aggregates was tested; however, no correlation was found. Overall, platelet-leukocyte aggregate formation was reduced and there were conflicting results with regards to the reduction of leukocyte activation for the ELP coatings on MylarTM. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-10-10 15:34:51.802
280

Experimental and Numerical Modeling of Heat Transfer in Wall Assemblies

2014 April 1900 (has links)
It is critical for the construction industry to ensure that new building designs and materials, including wall and floor assemblies, provide an acceptable level of fire safety. A key fire safety requirement that is specified in building codes is the minimum fire resistance rating. A manufacturer of building materials (e.g., insulation or drywall) is currently required to perform full-scale fire furnace tests in order to determine the fire resistance ratings of assemblies that use their products. Due to the cost of these tests, and the limited number of test facilities, it can be difficult to properly assess the impact of changes to individual components on the overall fire performance of an assembly during the design process. It would be advantageous to be able to use small-scale fire tests for this purpose, as these tests are relatively inexpensive to perform. One challenge in using results of small-scale fire tests to predict full-scale fire performance is the difficulty in truly representing a larger product or assembly using a small-scale test specimen. Another challenge is the lack of established methods of scaling fire test results. Cone calorimeter tests were used to measure heat transfer through small-scale specimens that are representative of generic wall assemblies for which fire resistance ratings are given in the National Building Code of Canada. Test specimens had a surface area of 111.1 mm (4.375 in.) by 111.1 mm (4.375 in.), and consisted of single or double layers of gypsum board, stone wool insulation and spruce-pine-fir (SPR) studs. As the specimens were designed to represent a one-quarter scale model of a common wall design, with studs spaced at a centre-to-centre distance of 406.4 mm (16 in.), the wood studs were made by cutting nominal 2x4 studs (38 mm by 89 mm) into 9.25 mm by 89 mm (0.375 in. by 3.5 in.) pieces. The scaled studs were then spaced at a centre-to-centre distance of 101.6 mm (4 in.). Three types of gypsum board were tested: 12.7 mm (0.5 in.) regular and lightweight gypsum board, and 15.9 mm (0.625 in.) type X gypsum board. Temperature measurements were made at various points within the specimens during 70 min exposures to an incident heat flux of 35, 50 and 75 kW/m2 using 24 AWG Type K thermocouples and an infrared thermometer. Temperature measurements made during cone calorimeter tests were compared with temperature measurements made during fire resistance tests of the same generic assemblies and the result show a very good agreement for the first 25 min of testing at the unexposed side. A one-dimensional conduction heat transfer model was developed using the finite difference method in order to predict temperatures within the small-scale wall assemblies during the cone calorimeter tests. Constant and temperature-dependent thermal properties were used in the model, in order to study the effects of changes to materials and thermal properties on fire performance. A comparison of predicted and measured temperatures during the cone calorimeter tests of the generic wall assemblies is presented in this thesis. The model had varying degrees of success in predicting temperature profiles obtained in the cone calorimeter tests. Predicted and measured times for temperatures to reach 100C and 250C on the unexposed side of the gypsum board layer closest to the cone heater were generally within 10%. There was less agreement between predicted and measured times to reach 600C at this location, and the temperature increase on the unexposed side of the test specimen. The model did not do a good job in predicting temperatures in the insulated double layer walls. Sensitivity studies show that the thermal conductivity of the gypsum board has the most significant impact on the predicted temperature.

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