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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.
181

Geographic scale compatibility study based on process simulation: a case study of meteorological and air quality process.

January 2014 (has links)
由於數據、模型等的尺度依賴性,尺度不匹配可能導致錯誤的結論。尤其在相互作用的地理過程研究,尺度適宜性對認知地理過程起著至關重要的作用。本文結合珠三角地區的氣象場和空氣品質過程模擬,對地理過程研究中的尺度適宜性問題進行了研究。 / 首先,基於尺度概念的定義,本文提出了地理過程研究中的四組尺度適宜性問題:多地理過程層、維度層、類型層和組成成分層。分析了其可操作級別以及評估流程和指標。 / 第二,在WRF模型中引入多解析度地形數據以研究數據與模型在氣象過程模擬的尺度適宜性。結果表明由於DEM數據與模型的尺度不適宜,可能對氣象變數的模擬帶來較大偏差。而3和30秒解析度的DEM數據與1千米解析度的模型可以較好地模擬香港地區的氣象過程。本案例有助於通過考慮尺度適宜性來提高氣象場的模擬能力。 / 第三,針對模擬模型與地理過程的尺度適宜性,應用WRF和CALMET模擬了香港地區的氣象過程。結果表明CALMET可以更好地模擬香港的氣象過程,但是WRF與CALMET模擬結果的差異在空間分佈上是異質的,即複雜地表條件的區域CALMET模擬改進明顯。多尺度模擬的結果也表明了跨尺度地理過程的相互影響,有助於多尺度地理過程模擬與認知。 / 第四,設計並研發了面向空氣品質過程的多尺度虛擬地理環境系統。本系統應用LAMP架構,支援模擬知識的管理、跨平臺及分散式平行計算,亦考慮到模擬的尺度依賴性,將有助於多尺度空氣品質過程的模擬和認知。應用該系統,對多尺度SO₂濃度過程進行模擬並分析了香港當地排放源的分擔率。較低的本地分擔率表明香港政府仍需要加強區域合作來治理空氣污染問題。 / 本論文的研究不僅加強對地理過程研究中的多尺度以及尺度適宜性問題的認知,有助於分解和研究複雜的尺度適宜性問題,研究案例和原型系統亦將會對香港和珠三角地區的空氣品質過程理解和管理作出有益貢獻。 / Although multiscale data and models are taken into account to study geography, due to their scale dependence, the scale mismatching may cause adverse results. Thus, scale compatibility is becoming crucial to decode geographic process, especially, for the interactive geographic processes. This thesis focused on scale compatibility in geographic process with a case study of multiscale meteorological and air quality simulation in Hong Kong Special Administrative Region (HKSAR) and the Pearl River Delta (PRD) region. / Firstly, based on the conceptual definition of scale, this dissertation identifies four groups of scale compatibility in geographic process research: multiple process level, dimension level, type level and component level. By illustrating the different operational levels from the abstract to operational, the author proposes a procedure to implement scale compatibility with potential criteria. / Secondly, scale compatibility in the reproduction of meteorological process is investigated between multiscale digital elevation model (DEM) data and the Weather Research and Forecasting Model (WRF). The experiments show that: DEM data with 3 and 30 arc sec resolutions are relatively more compatible with the WRF model of 1 km resolution to reproduce the meteorological field over Hong Kong; and uncertainty arising from scale mismatching between DEM data and the model may account for 38% of the variance in certain meteorological variables (e.g., temperature). This case study not only helps to improve meteorological simulations by taking the issue of scale compatibility into account, but also explains the significance and implementation of scale compatibility in geographic process research. / Thirdly, this thesis utilizes multiscale meteorological models to study the scale compatibility between dynamic models and interested geographic process. We conduct validation through three steps: daily statistics, spatial comparison and time series. The results support the idea that CALifornia METeorological model (CALMET) is more compatible to reproduce the meteorology process in Hong Kong; however, the discrepancy between the WRF and CALMET is spatially heterogeneous, with larger improvement over the area of complex topography and land use. The results also give evidence about the cross-scale interaction to interpret multi-scale geographic process. / Fourthly, applying the above findings, this dissertation presents a multiscale Virtual Geographic Environments (VGE) system to integrate geographical analysis and multiscale models in a cross-platform and parallel manner. With database system and Linux-Apache-MySQL-Perl (LAMP) architecture, users can manage and retrieve modeling concerning both data and model parameterization to help them reach a consensus on the simulation results and share modeling knowledge. Scale compatibility among data, models and analysis is also considered in the system design. Aided with high-resolved and regulable emission inventory, such multiscale system enables the practical application for various scenarios. As a case study, the VGE is applied to simulate and analyze the SO₂ concentration process and local contribution in HKSAR. / Achievements of this dissertation should greatly contribute to a better cognition of multiscale issues and scale compatibility concerning geographic process, and the VGE is expected to contribute to better understanding and management of air quality for both HKSAR and PRD. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Chunxiao. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 135-157). / Abstracts also in Chinese.
182

Cluster mass scaling relations through weak lensing measurements / Relation d’échelle d'amas de galaxies à partir d'observations de lentilles gravitationnelles

Parroni, Carolina 11 September 2017 (has links)
Les amas de galaxies sont des outils cosmologiques et astrophysiques essentiels, car ce sont les objets les plus grands et les plus massifs gravitationnellement liées dans l'Univers. L'étude de leur fonction de masse, de leur fonction de corrélation et des relations d'échelle entre leur masse et différentes observables nous permettent de tester les prévisions des modèles cosmologique et les scenarii de formation des structures. Ils sont aussi d'intéressants laboratoires pour l'étude de la formation et de l'évolution des galaxies, et de leur interactions avec le milieu qui les entourent, dans d’environnements denses. Pour y parvenir, estimer précisément leur masse revêt une importance fondamentale. J’ai étudié la précision de la richesse optique calculée par l’algorithme de détection d’amas RedGOLD (Licitra et al. 2016) en tant que mass proxy, en utilisant des mesures de lentilles gravitationnelles (weak lensing) et des observations en rayon X. J’ai mesuré les masses cumulées d’un échantillon de 1323 amas de galaxies dans le CFHTLS et NGVS à 0.2<z<0.5, dans l’intervalle de richesse 10-70. J'ai testé différents modèles prenant en compte les erreurs sur la position du centre de l'amas, les effets de lentille non faible (non-weak shear), le "two-halo term", la contribution de la galaxie centrale brillante et la dispersion intrinsèque de la relation masse-richesse. J'ai montré que la correction de la position du centre est nécessaire pour éviter un biais dans la mesure de la masse, alors que l'ajout de la galaxie centrale n'affecte pas les résultats. J'ai calculer les coefficients de la relation masse-richesse et ceux de la relation d'échelle entre masses issues du weak lensing et celle estimées à partir d'observations dans les rayons X. Mes résultats sont en accord avec les simulations et les précédents travaux publiés. / Galaxy clusters are essential cosmological and astrophysical tools, since they represent the largest and most massive gravitationally bound structures in the Universe. Through the study of their mass function, of their correlation function, and of the scaling relations between their mass and different observables, we can probe the predictions of cosmological models and structure formation scenarios. They are also interesting laboratories that allow us to study galaxy formation and evolution, and their interactions with the intra-cluster medium, in dense environments. For all of these goals, an accurate estimate of cluster masses is of fundamental importance. I studied the accuracy of the optical richness obtained by the RedGOLD cluster detection algorithm (Licitra et al. 2016) as a mass proxy, using weak lensing and X-ray mass measurements. I measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters in the CFHTLS W1 and in the NGVS at 0.2<z<0.5, in the optical richness range 10-70. I tested different weak lensing mass models that account for miscentering, non-weak shear, the two-halo term, the contribution of the Brightest Cluster Galaxy, and the intrinsic scatter in the mass-richness relation. I found that the miscentering correction is necessary to avoid a bias in the measured halo masses, while the inclusion of the BCG mass does not affect the results. I calculated the coefficients of the mass-richness relation, and of the scaling relations between the lensing mass and X-ray mass proxies. My results are consistent with simulations and previous works in the literature.
183

Size-Weight Scaling in Healthy Young and Old Adults

Capper, Alyssa Lynn 01 July 2013 (has links)
Visual analysis of an object's size can be used to determine the lifting forces we program to lift the object so that the resulting movements achieve the goals of the lift. These forces are scaled or specified prior to the object moving, that is, before sensory feedback information about the object's weight is available. Sensorimotor memories are relied on to provide relevant information about an object's density and weight if the object was previously manipulated. It is well established that young adults accurately scale their forces based on visual size cues. The purpose of this study was to determine if old adults scale their forces to the size of the object or if they rely on sensorimotor memory of the previous object's weight. There are reports of impaired visuomotor programing for grasp and lift in old adults. In the present study old and young subjects were required to lift four different sized bottles of constant density from a force plate and then place the object on a shelf. Two experiments were performed. Experiment one featured blocks of lifts for three bottles in the following order: large, small and medium. Experiment two took place fifteen minutes after experiment one and featured a bottle slightly larger than the medium bottle used at the end of the experiment one. The second experiment addressed whether imperceptible changes in size cause changes in predictive force scaling. Peak load force rate in the first force pulse (prior to lift-off) was measured for each lift of the objects with the focus being on the initial and last lift of each bottle. Both experiments presented a significant effect for bottle size on lift force rates. This result was found regardless of age. It provides additional support that young adults accurately scale their lift force rate based on the visual size cues of the object. Old adults also demonstrated scaling of their lift force rates based on bottle size which failed to support the hypothesis that old adults would merely reproduce their lift force rates from the previous lift with a different object. While both young and old scale lift forces to object size, the old demonstrated a trend for utilizing high lift force rates throughout the experiment as well as greater differences in lift force rate between the initial lift with an object and the final lift with the same object. Most subjects utilized a target strategy in which they produced a single peak lift force rate pulse. This is indicative of a neural representation of the weight of the object being utilized to program the lift force rate. The remaining subjects exhibited a probing strategy that features several step-wise increases in lift force rate until the object is lifted off. This represents a more cautious approach to lifting novel objects. Our results indicate that old adults, much like young adults, are able to scale their forces based on visual size cues.
184

The Role of Abiotic And Biotic Factors In Suspension Feeding Mechanics Of Xenopus Tadpoles

Ryerson, William G 13 November 2008 (has links)
As a comparison to the suction feeding mechanics in aquatic environments, I investigated buccal pumping in an ontogenetic series of suspension feeding Xenopus laevis tadpoles (4-18 mm snout-vent length) by examining the morphology, kinematics, fluid flow, pressure generated in the buccal cavity, and effects of viscosity manipulation. Investigation of the dimensions of the feeding apparatus of Xenopus revealed that the feeding muscles exhibited strong negative allometry, indicating that larger tadpoles had relatively smaller muscles, while the mechanical advantage of those muscles did not change across the size range examined. Buccal volume and head width also exhibited negative allometry: smaller tadpoles had relatively wider heads and larger volumes. Tadpoles were imaged during buccal pumping to obtain kinematics of jaw and hyoid movements as well as fluid velocity. Scaling patterns were inconsistent with models of geometric growth, which predict that durations of movements are proportional to body length. Only scaling of maximum hyoid distance, duration of mouth closing, and duration of hyoid elevation could not be distinguished from isometry. The only negatively allometric variable was maximum gape distance. No effect of size was found for duration of mouth opening, duration of hyoid depression, and velocity of hyoid elevation. Velocity of mouth opening, velocity of mouth closing, and velocity of hyoid depression decreased with increasing size. Fluid velocity increased with size, and is best predicted by a piston model that includes head width and hyoid depression velocity. Reynolds number increased with size and spanned two flow regimes (laminar and intermediate) ranging from 2 to over 100. Pressure was found to be greatest in the smallest tadpoles and decreased as size increased, ranging from 2 kPa to 80 kPa. The viscosity of the water was altered to explore changes in body size, independent of development (higher viscosity mimicked smaller tadpole size). Viscosity manipulations had a significant effect on the kinematics. Xenopus initially increased velocity and distance of movements as viscosity increased, but these values declined as viscosity increased further. These results suggest that abiotic factors such as fluid viscosity may set a lower size limit on suspension feeding.
185

Development and Initial Validation of the Multicultural Gender Roles Scale—Black Women (MGRS – BW)

Buque, Mariel January 2019 (has links)
The purpose of this study was to develop and evaluate a scale that measures more accurate and flexible gender role representations of Black women regarding themselves and others. Scholars have called for the development of gender role instruments that measure more culturally relevant interpretations of masculinity and femininity (Dade & Sloan, 2000; Miville, 2013). Instruments that incorporate traditional Euro-centric notions of gender roles do not account well for the unique racial-ethnic contexts that likely influence how Black women construct gender as well as perpetuate the misrepresentation of black femininity, the justification of negative stereotypes of Black women (e.g., the Mammy, Jezebel and Sapphire), and the exclusion of Black women from healthy expressions of womanhood (Dade & Sloan, 2000; Harris, 1994). This study referred to the Multicultural Gender Roles Model (MGRM; Miville, Bratini, Corpus, Lau, and Redway, 2013) in an effort to better describe the gendered experiences Black women. The Multicultural Gender Roles Scale - Black Women (MGRS-BW) reflected a 22 Likert-type item scale reflecting a 3-factor structure. Reliability and construct validity was established in several ways: expert ratings, alpha coefficients, and exploratory and confirmatory factor analyses. Implications for future research and clinical applications also were presented.
186

Fault Scaling And Population Analyses In The Eastern California Shear Zone: Insights Into The Development Of Actively Evolving Plate Boundary Structures

January 2015 (has links)
1 / xu zhou
187

How do young children and adults use relative distance to scale location?

Recker, Kara Marie 01 January 2008 (has links)
The goal of this thesis is to understand how children and adults scale distance. My preliminary work has shown that young children can accurately scale distances along a single dimension (i.e., length) even when the magnitude of the scale difference is very large. In these studies, 4- and 5-year-olds and adults first saw a location marked on a narrow mat placed on the floor of one testing space. They then reproduced that location on another narrow mat that was either the same length (i.e., the memory task) or a different length (i.e., the memory + scaling task) placed on the floor of an adjacent testing space. These experiments illustrated that both children and adults had more difficulty scaling up than scaling down (i.e., had more difficulty going from a small to a large mat than from a large to a small mat). In the present thesis, I used this difference between scaling up and scaling down as a tool to examine the processes underlying the ability to scale distance more generally. I predicted that the difficulty children and adults have scaling up can be attributed to mapping relative distances onto spaces that are too large to be viewed from a single vantage point. Experiment 1 demonstrated that although a visible boundary dividing a large space influenced how children and adults remember locations, scaling up was still more difficult than scaling down. Experiments 2 and 3 examined the influence of absolute size on mapping relative distance. When the absolute size of the test space was reduced, scaling up was no longer more difficult than scaling down. In contrast, when the absolute size was large, both scaling up and scaling down were more difficult, illustrating the importance of absolute size in using relative distance to scale. These findings suggest that when the absolute size of the space is large, children and adults have more difficulty using multiple edges of the space to accurately scale distance. More generally, these experiments underscore how the cognitive system and task structure interact to give rise to the ability to use relative distance to scale.
188

Effects of Froude Scaling on Velocity-Induced Vorticles in Physical Models

Budge, Michael S. 01 May 2014 (has links)
Velocity-induced vortices are common occurrences at hydraulic intakes and are detrimental to the operation and efficiency of hydraulic structures. Velocity-induced vortices also form in physical hydraulic models and although Froude scaling principles account for initial and gravity forces, the scale effects associated with vortices in Froude are less certain. This work examines scale effects on vortex formation in physical models through the use of four identical experiments built at differing Froude scales with the largest of the four being defined as a prototype. Each experiment created velocityinduced vortices at the intake to a sluice gate. The unique approach conditions caused surface swirl, downward velocity towards the sluice gate opening, and vortex flow. This study contributes to the existing literature by providing a set of both qualitative and quantitative observations made from images in multiple perspectives and measured data. It was found that vortex behavior scaled as expected using Froude scaling principles with relatively small length ratios (~1:2 to ~1:3). As model size decreased, scaling accuracy decreased due to low approach and vortex tangential velocities. For example, identical conditions in an experimental model at a scale 8 times smaller than the prototype experienced vortex formation of vastly decreased strength and size. Instead of an air core vortex, only a weak vortex having a shallow surface depression and swirl was formed at the same flow condition. Other model sizes showed a clear trend of decreasing vortex size and strength as the model size decreased. Decrease in strength is due largely to a decrease of approach and tangential velocity in the smaller models. Results from this study are also presented visually as a series of photographs and overlaid outline profiles for comparison. Additionally, other quantifiable results including dimensionless parameters are reported.
189

Charge and Exciton Transport in DNA

January 2013 (has links)
acase@tulane.edu
190

The influence of small scale variability on scaling relationships describing atmospheric turbulence

Howell, James Frederick 19 May 1993 (has links)
The statistics describing variations of turbulent motions within the so called inertial range of length scales depend on the scale over which the motions are varying and the "average" rate at which the turbulent kinetic energy is being dissipated on the molecular scale. This hypothesis stemmed from the similarity arguments published by A. N. Kolmogorov in 1941 and implies specific scaling relations between the average amplitude and length scale of turbulent motions. Turbulent motions agree to a good approximation with Kolmogorov scaling provided the fluid flow admits to the underlying assumptions. More recently it has been recognized that the large spatial variations in the rate of turbulent kinetic energy dissipation may be a partial explanation for deviations from Kolmogorov scaling. This recognition is due in part to the observation that the total volume occupied by turbulent motions of a given scale decreases as the scale decreases. These observations imply that active small scale turbulence is intermittent. This study aims to better understand how scaling relations describing more active regions are different from the relations describing turbulence where the small scales are less active. The thesis is that the relations are different. An 18 hour segment of wind data measured in near-neutral stratification 45 meters above a relatively flat ground is analyzed. There is virtually no trend in the mean wind speed, so the describing statistics are essentially stationary. Small scale activity is measured in terms of the difference in wind speed (structure function) at a separation distance of 1/16 of a second, which translates to about a meter. The differences in wind speed are raised to the sixth power and then averaged over 4 second (50 meter) windows. Non-overlapping windows containing a local maximum in the averaged sixth order structure function form one (MASC) ensemble of more active small scale samples and the local minima form another (LASC) ensemble of less active small scale samples. The variations in wind speed as a function of length scale within each ensemble are decomposed five different ways. Each of the five decompositions obey scaling relationships that are approximately linear in log-log coordinates. The MASC and LASC ensembles include 32% and 46% of the record, respectively. The turbulent kinetic energy as a function of scale falls off at a slower rate in the MASC ensemble versus the LASC ensemble and in magnitude the energy is greater at all scales in the MASC ensemble. This implies the transfer rate of turbulent kinetic energy toward small scales is more rapid on average in the MASC samples. Samples in the MASC ensemble occupied 30% less of the record, implying the flattening effect on the spectral slope exhibited by the samples contained in the MASC ensemble is less influential than the steepening influence of samples of the type in the LASC ensemble. The results are robust with respect to the choice of a basis set in representing the variance as a function of scale. / Graduation date: 1994

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