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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.
701

Distributed Thermal Response Test on a Grouted U-pipe Borehole Heat Exchanger

Marcucci, Marine January 2014 (has links)
The expansion of the use of geothermal heat pumps makes the study of their performances a keystone in their development. Several parameters are crucial to design properly a geothermal heat pump. Comparing the theoretical characteristics of a system with the actual ones one the field is part of its understanding.  This Master thesis gives a closer look for determining from filed data two central parameters, the borehole thermal  resistance  and  the  ground  thermal  conductivity,  using  a  newly  developed  technique  called Distributed Thermal Response Testing (DTRT). These calculations are applied to a U-pipe heat exchanger installed  in  a  private  household.  From  these  two  parameters,  it  is  possible  to  estimate  the  thermal conductivity of the filling material inside the borehole and thus estimate its influence on the performances of  the  system.  Three  grouting  material  are  studied  here  and  theoretical  values  are  compared  with experimental value in order to try to get a picture of the inside of the borehole.  This  thesis  provides  a  picture  of  the  actual  thermal  parameters  of  the  studied  borehole,  which  clearly reveals the influence of the grouting material in each layer. It is also noticed that the laboratory value of the grout thermal conductivities varies when comparing with theoretical values or manufacturer data. The lack of understanding of the actual drying state of the grouts inside the borehole may by one reason why.
702

The Effects of Vertically Oriented Resistance Training on Golf Drive Performance in Collegiate Golfers

Driggers, Austin R., Sato, Kimitake 01 August 2018 (has links)
The purpose of this study was to examine the effects of vertically oriented resistance training on golf driving performance. Ten Division-I collegiate golfers completed two resistance training sessions per week for 10 weeks during the fall tournament season. Pre- and post-training assessments of strength-power and golf performance were compared. To assess strength-power, jump height, peak force, and peak power were measured from static and countermovement vertical jumps; peak force and rate of force development from 0 to 250 ms were measured from an isometric mid-thigh pull. Golf performance was assessed in terms of ball launch speed, spin rate, carry yardage, and total yardage, averaged from five shots using a driver. Following training, all measures of strength-power improved, with countermovement jump peak power improving significantly (p < 0.00625). The golf performance assessment indicated significant increases (p < 0.0125) in ball speed, carry yardage, and total yardage. These results suggest that vertically oriented resistance training can improve golf driving performance.
703

Ice Wedge Activity in the Eureka Sound Lowlands, Canadian High Arctic

Campbell-Heaton, Kethra 21 September 2020 (has links)
Polygonal terrain underlain by ice wedges (IWs) are a widespread feature in continuous permafrost and make up 20-35%vol of the ground ice in the upper few meters of permafrost. Despite the numerous contemporary studies examining factors that control ice wedge cracking, development and degradation, relatively few have explored ice wedge activity in relation with past climate and vegetation conditions. In the Eureka Sound region, ice wedge polygons dominate the permafrost terrain. Their degradation has started to occur, leading to growth of thaw slumps. The objective of this study is twofold, the principal objective is to investigate the timing of ice wedge activity in the Eureka Sound region using the ¹⁴CDOC dates. The second objective is to evaluate the use of ice wedges as paleotemperature proxies. In July 2018, four ice wedges were sampled at 3-4 depths with each core sample being ~1m in length. In the following summer, eight ice wedges were sampled from the surface, 3-5 core samples were extracted per wedge. Active layer and snow samples were also recovered. Laboratory analyses on the ice wedge samples includes dissolved organic carbon content (DOC) and δ¹³CDOC, radiocarbon dating of DOC, geochemical concentration, and stable water isotopes. The DOC and geochemical results show that snowmelt is the main moisture source for ice wedges in the Eureka Sound region with a minor contribution of leached surface organics. The age (¹⁴CDOC) and size of the studied ice wedges were compared against a cracking occurrence model developed by Mackay (1974), these ice wedges align well with this model and suggest that ice wedge growth is non-linear. Ice wedges in the Eureka Sound region were active during the early to late Holocene (9-2.5 ka). The majority of the activity occurred in the later stage of the early Holocene following regional deglaciation and marine regression. ¹⁴CDOC, high resolution δ¹⁸O and D-excess suggests the occurrence of peripheral cracking in both large and small ice wedges. Rayleigh-type isotopic fractionation was found to occur with depth. As well, post depositional isotopic modification of snow and snowmelt accounts for up to a 4‰ difference of δ18O in surface ice wedge samples. δ¹³CDOC of surface ice wedge samples suggest a habitat transition during the late Holocene from dry meadows to polygonal terrain and the geochemical composition of ice wedges closely reflects that of glacial ice core records.
704

Risk factors and knowledge of dental fluorosis in three communities in the far north region of Cameroon

Ebot Etta, Barnabas January 2020 (has links)
Magister Scientiae Dentium - MSc(Dent) / BACKGROUND: Fluorine is an abundant trace element in the Earth’s crust. The presence of fluorine in bedrocks is the primary source fluoride in ground water, though fluoride occurrence varies with the different rock types. High concentrations of fluoride ions are found in regions of volcanic activities. Volcanoes are the main persistent natural source of fluoride in ground water and in the atmosphere. The occurrence of high concentrations of fluoride in ground water has been reported worldwide. Dental fluorosis is a developmental disturbance of enamel that results from ingestion of high amounts of fluoride during tooth mineralization. Consumption of untreated fluoridated ground water remains the main cause of dental fluorosis in rural settlements. AIM: To establish the risk factors and knowledge of dental fluorosis in three communities of the Far North Region of Cameroon. METHODOLOGY: This study was descriptive and cross-sectional study with an analytic component and was conducted in three communities in Far North Region of Cameroon. The study population was a convenience sample irrespective of age, but who must have been living in the selected study sites for a minimum of 6 to 8 years. Structured questionnaires were administered to elicit socio-demographic characteristics, perceptions dental fluorosis and oral health practices. Oral examination was conducted to determine the extent of dental fluorosis that was scored according to the Thylstrup and Fejerskov index. Participants declared their water sources and water samples were obtained from these sources. Samples of commercial bottled mineral water was purchased from various local outlets. These samples were sent to a certified laboratory for fluoride analysis and are reported in milligrams of fluoride per litre.
705

A Prototype Polarimetric Camera for Unmanned Ground Vehicles

Umansky, Mark 26 August 2013 (has links)
Unmanned ground vehicles are increasingly employing a combination of active sensors such as LIDAR with passive sensors like cameras to perform at all levels of perception, which includes detection, recognition and classification. Typical cameras measure the intensity of light at a variety of different wavelengths to classify objects in different areas of an image. A polarimetric camera not only measures intensity of light, but can also determine its state of polarization. The polarization of light is the angle the electric field of the wave of light takes as it travels. A polarimetric camera can identify the state of polarization of the light, which can be used to segment highly polarizing areas in a natural environment, such the surface of water. The polarimetric camera designed and built for this thesis was created with low cost in mind, as commercial polarimetric cameras are very expensive. It uses multiple beam splitters to split incoming light into four machine vision cameras. In front of each machine vision camera is a linear polarizing filter that is set to a specific orientation. Using the data from each camera, the Stokes vector can be calculated on a pixel by pixel basis to determine what areas of the image are more polarized. Test images of various scenes that included running water, standing water, mud, and vehicles showed promise in using polarization data to highlight and identify areas of interest. This data could be used by a UGV to make more informed decisions in an autonomous navigation mode. / Master of Science
706

Earthquake ground-motion in presence of source and medium heterogeneities

Vyas, Jagdish Chandra January 2017 (has links)
This dissertation work investigates the effects of earthquake rupture complexity and heterogeneities in Earth structure on near-field ground-motions. More specifically, we address two key issues in seismology: (1) near-field ground-shaking variability as function of distance and azimuth for unilateral directive ruptures, and (2) impact of rupture complexity and seismic scattering on Mach wave coherence associated with supershear rupture propagation. We examine earthquake ground-motion variability associated with unilateral ruptures based on ground-motion simulations of the MW 7.3 1992 Landers earthquake, eight simplified source models, and a MW 7.8 rupture simulation (ShakeOut) for the San Andreas fault. Our numerical modeling reveals that the ground-shaking variability in near-fault distances (< 20 km) is larger than that given by empirical ground motion prediction equations. In addition, the variability decreases with increasing distance from the source, exhibiting a power-law decay. The high near-field variability can be explained by strong directivity effects whose influence weaken as we move away from the fault. At the same time, the slope of the power-law decay is found to be dominantly controlled by slip heterogeneity. Furthermore, the ground-shaking variability is high in the rupture propagation direction whereas low in the directions perpendicular to it. However, the variability expressed as a function of azimuth is not only sensitive to slip heterogeneity, but also to rupture velocity. To study Mach wave coherence for supershear ruptures, we consider heterogeneities in rupture parameters (variations in slip, rise time and rupture speed) and 3D scattering media having small-scale random heterogeneities. The Mach wave coherence is reduced at near-fault distances (< 10 km) by the source heterogeneities. At the larger distances from the source, medium scattering plays the dominant role in reducing the Mach wave coherence. Combined effect of the source and medium heterogeneities on the supershear ruptures produce peak ground accelerations consistent with the estimates from empirical ground motion prediction equations. Therefore, we suggest that supershear ruptures may be more common in nature than detected.
707

EFFECT OF BUILDING ORIENTATION ON STRUCTURAL RESPONSE OF REINFORCED CONCRETE MOMENT RESISTING FRAME STRUCTURES

Parsa, Amanullah 01 May 2020 (has links)
In time history analysis of structures, the geometric mean of two orthogonal horizontal components of ground motion in the as-recorded direction of sensors, have been used as measure of ground motion intensity prior to the 2009 NEHRP provision. The 2009 NEHRP Provisions and accordingly the seismic design provisions of the ASCE/SEI 7-10, modified the definition of ground motion intensity measure from geometric mean to the maximum direction ground motion, corresponding to the direction that results in peak response of the oscillator. Maximum direction response spectra are assumed to envelope the range of maximum possible responses over all nonredundant rotation angles. Two assumptions are made in the use maximum ground motion as the intensity measure: (1) the structure’s strength and stiffness properties are identical in all directions and (2) azimuth of the maximum spectral acceleration coincides with the one of the principal axes of the structure. The implications of these assumptions are examined in this study, using 3D computer models of multi-story structures having symmetric and asymmetric layouts and elastic vibration period of 0.2 second and 1.0 second subjected to a set of 25 ground-motion pairs recorded at a distance of more than 20 km from the fault. The influence of the ground-motion rotation angle on structural response (here lateral displacement and story drift) is examined to form benchmarks for evaluating the use of the maximum direction (MD) ground motions. The results of this study suggest that while MD ground motions do not always result in largest structural response, they tend to produce larger response than the as-recorded ground motions. On the other hand, more research on non-linear seismic time history analysis is recommended, especially for asymmetric layout plan buildings.
708

Gravarna från Nygårds : en rumslig analys av ett järnåldersgravfält i Västerhejde socken / The graves from Nygårds : a spatial analysis of an Iron Age burial ground at the parish of Västerhejde.

Kynman, Saga January 2019 (has links)
Throughout Scandinavia the funeral practices of the Iron Age were, in general, inhumation or cremation. The Iron Age society held many overarching beliefs but with a great ritual flexibility where practices could vary between communities. This study examines the Iron Age burial ground at Nygårds in the parish of Västerhejde, Gotland. The graves consist of both cremated and skeletal remains dating to the period of 400–600 AD. Thus, two different funeral customs were practiced at the burial ground during the same time period. Although excavated in the 1970s, no detailed analyses have been carried out on the Iron Age remains from Nygårds or their grave goods. This study aim is consequently to contribute with new information about the burial ground at Nygårds and the individuals who were interred there. By examining the spatial composition of the two burial customs, their demographic and grave goods, differences and similarities emerge. With the burial grounds spatial structure as a framework, this study discusses the different aspects of the Iron Age life and what the actions of the living can tell us about their dead.
709

Comparison of Beef Flavor Compounds from Steaks and Ground Patties of Three USDA Quality Grades and Varied Degrees of Doneness

Gardner, Kourtney 01 May 2017 (has links)
This study determined how quality grade and degree of doneness influence the development of beef flavor compounds among whole muscle and ground patties. Proximate composition, pH, cooking duration, neutral and polar lipid fatty acids, free and total amino acids, total reducing sugars, and volatile compounds were evaluated in beef strip steaks and ground patties of Longissimus lumborum from three USDA quality grades (Prime, Low Choice, and Standard; n=8 per quality grade) and six degrees of doneness (4, 25, 55, 60, 71, and 77°C). In the split-plot experiment, quality grade was the whole-plot, product-type was a sub-plot, and degree of doneness was the sub-sub-plot. The 3-way interaction of quality grade, degree of doneness, and product type impacted moisture (P = 0.004) and protein content (P = 0.006); pH (P < 0.001); neutral and polar lipid fatty acids (P ≤ 0.048); free and total amino acids (P ≤ 0.044); total reducing sugars (P < 0.001); and volatile compounds (P ≤ 0.029). The 2-way interaction of quality grade and degree of doneness impacted free amino acids (P ≤ 0.036); PUFA within the neutral lipid fraction (P ≤ 0.033); fatty acids within the polar lipid fraction (P ≤ 0.043); volatile compounds (P ≤ 0.038); and the total fat percentage (P = 0.046). The 2-way interaction of quality grade and product type impacted fatty acids within the neutral lipid fraction (P ≤ 0.042); fatty acids within the polar lipid fraction (P ≤ 0.015); and volatile compounds (P ≤ 0.047). The 2-way interaction of product type and degree of doneness affected fatty acids within the neutral lipid fraction (P ≤ 0.046); fatty acids within the polar lipid fraction (P ≤ 0.035); free amino acids (P ≤ 0.005) and total amino acids (P ≤ 0.004); volatile compounds (P ≤ 0.029); and cooking duration (P < 0.001). Overall the results of this study indicated that quality grade, grinding, and cooking have interacting effects on flavor related compounds. Thus, each factor must be considered during any model development which aims to predict beef flavor.
710

Albedo of the Earth's Surface -- A Comparison of Measurements Taken on the Ground and from Flying Platforms

Eaton, Frank D. 01 May 1976 (has links)
The main objectives of this study were to develop the indicatri es of reflected solar radiation from different natural surfaces and to show comparisons between values sensed in space of emergent radiation to ground values obtained from accounting for anisotropic reflection and estimating the effect of the intervening atmosphere. Thus, this study demonstrated that a prior knowledge of the angular distribution of reflected radiation allows determining the true hemispherical reflected radiation from a narrow field of view instrument such as found on a flying platform. Measurements for determining the indicatrices were made from a tower-mounted Nimbus MRIR and, in one case, with a hand-held TIROS five-channel radiometer. Anisotropy of reflected radiation was found for all surfaces examined and increased with decreasing solar angle. Different surfaces showed different degrees and patterns of fonvard and backscatter. A clearly defined anti-solar point was found for plowed field, various agricultural crops and vegetated desert surfaces, while snow, the Alkali Flats, and Bonneville Salt Flats showed a broad pattern of backscatter. As a consequence of surfaces exhibiting well-defined antisolar points the anisotropic correction factors relating normal reflectances to 2π reflected values were less than 100 percent for solar angles greater than approximately 60°. All surfaces examined showed anisotropic correction factors increasing with decreasing solar angles. The albedo over the White Sands dune field decreased with decreasing solar angles due to large shadow patterns which are produced at low solar angles. The sand dunes values were derived from aircraft measurements. Comparisons were made between estimated emergent radiation from the top of the earth 's atmosphere accounting for anisotropy of the ground reflection pattern and estimates of atmospheric attenuation to values of reflected radiation obtained from the MSS subsystem of the ERTS program for the lava beds region and White Sands area in New Mexico. Also comparisons were shown between the estimated emergent radiation from the earth's surface for the same features and spectral bands to the values sensed in space. Under high albedo conditions as found in the White Sands area there was a decrease in emergent radiation to space while with low surface albedo, such as the lava beds region, the extra-terrestrial radiation increased from the ground values.

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