Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 97-100).

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 199-225).

Meandering rivers across the globe present a striking similarity in their alignment, and this pattern has intrigued scientific curiosity for almost a century. However, still very little is known about ‘unconventional’ river meanders with a “zigzagging” planform appearance, but which occur in rivers from the temperate to the tropic regions. In order to compare the characteristics of flow, morphology and morphodynamics of conventional (‘round’ and ‘fat’) and unconventional (‘sharp’ and ‘angular’) river bends, I studied the Prut (Romania/Moldova), one of the last remaining freely meandering lowland rivers of Europe. The Prut is a clay-bed river that meanders for about 585 km of channel length in its lower section, with an average discharge of c. 90 m3 s-1 and channel width ranging from 39-84 m. For the analysis of long-term channel dynamics (chapter 2), bend morphometry, morphodynamics and temporal trajectories were determined for a section of Prut that included multiple replicates of each bend type. Data were extracted from historical maps and imagery for a c. 250 km long section of the Prut River spread over a 90-year period (1915-2005). For that, I used a geographical information system (GIS) and state-of-the-art software PyRIS to derive measures of bend-scale morphometry and migration features for a total of 118 simple and back-traceable river bends, after exclusion of compound bends and bends that cut-off during those 90 years. Normalized bend curvatures (CmaxB) ranged from 0.01 to 1.44 (as for 2005). Sharp bends were distinguished from round bends and angular bends from fat bend geometries by width normalized bend curvature, CmaxB threshold (round < 0.5 and sharp > 0.5) and the maximum to mean bend curvature ratio, Cr threshold (fat < 3 and angular > 3), respectively. Over the 90 year period, studied bends (N=118) displayed a gradual narrowing and homogenization of channel width (median= 72 m and interquartile range (IQR)= 63-86 m in 1915; median = 52 m and IQR = 50-57 m in 2005), a reduction of migration rates (mean= 0.038 widths/yr, SD=0.028 in 1915-1960 to mean= 0.015 widths/yr, SD = 0.011 in 1980-2005) and a slightly increase of sinuosity (from 1.41 to 1.63). Sharp and angular bends tended to stabilize over longer periods (20-90 years), and concomitantly displayed more unchanged shape transitions (for sharp bends: 1915-1960= 49%; 1960-1980= 61%; 1980-2005= 57%, N=49) compared to their conventional counterparts (for round bends: 1915-1960= 37%; 1960-1980= 22%; 1980-2005= 22%, N=49). These results provide new insights into the formation and maintenance of unconventional bends (sharp and angular), which on the Prut are mainly due to autogenic processes. In unconventional bends, special patterns of erosion and deposition create features like deeper pools or zones of flow separation, with fallen trees possibly acting as additional allogenic factor. These interrelationships among bend form, flow and river bed features in unconventional meanders were then investigated in detail fora set of 14 bends (chapter 3). Boat operated ADCP (Acoustic Doppler Current Profiler) field surveys enabled detailed records of 3-D velocity and depth distribution along these bends.This dataset enabled for the first time to systematically compare flow characteristics of unconventional with that in conventional meanders under field conditions. The studied set of bends comprised at least 2 bends of each simple bend shape types (see chapter 2) i.e. angular, sharp, round and fat bend shapes. A significant linear increase in the lateral extent of the Inner-Bank Flow Separation zone (IBFS) at the bend apex with increasing bend curvature was recorded (IBFS = 6.1+ 45.8 CmaxB + 8.2; R2= 0.55; p < 0.001; N=14). In angular bends, hydraulics was influenced by a locally eroded point bar and a steep sloping upstream riffle to pool transition. This was reflected by the significant increase in depth ratio (ratio of apex pool depth to upstream riffle depth) with stronger bend angularity, as defined by curvature ratio (ratio of maximum to mean of bend curvature) (Hratio = 0.83 + 0.41 Cr; R2 = 0.44; p < 0.005; N=14). These morphological features influenced the extent of the horizontal recirculation occurring within the IBFS zones at the bend apex, and were further associated with the formation of two separate IBFS zones in fat bends compared to a singular zone in angular bends. Pool depth (Hp) displayed an increasing trend with higher curvature but then to stabilize at bend curvatures greater than c. 0.5, suggesting the existence of a negative autogenic feedback at high bend curvature, as pool depth is also weakly related to the IBFS size (IBFS = -14+ 10.3 Hp + 10.2; R2= 0.30; p<0.02; N=14). The observed interdependence between flow patterns and planform shape in angular and fat bends partially explains their different morphodynamics, too. While fat bends are prone to develop multilobing or a delayed cut-offs, angular bends may display increased temporal stability and even inward migration. Hence, this thesis demonstrates for the first time the different characteristics of conventional and unconventional meanders in terms of their morphometry and hydraulic geometry based on the study of bends from a real meandering river, and complemented by documentation of the long-term morphological trajectories of these meander types during a nearly centennial period. Thus, this thesis provides new insights into the so far poorly explored linkages between forms and processes of river bends, and indicates field-based explanations on the formation and relative stability of unconventional bend forms over extended time periods.

L’objet de ce travail de thèse est l’étude en soufflerie du sillage lointain des éoliennes à axe horizontal. La complexité phénoménologique du sillage des éoliennes fait que les mécanismes le régissant sont généralement traités d’un point de vue stationnaire : les principaux paramètres (déficit de vitesse, production de turbulence...) sont alors moyennés dans le temps. Néanmoins, considérer les instationnarités du sillage d’une éolienne placée en écoulement atmosphérique permet d’observer un phénomène appelé meandering, traduisant un battement aléatoire du sillage. Ce travail est construit en deux grandes parties : la vision stationnaire et la vision instationnaire du sillage d’un modèle simplifié d’éolienne, basé sur le principe du disque de Froude, placé dans une couche limite atmosphérique (CLA) modélisée en soufflerie à l’échelle 1/400. La première partie est composée de plusieurs études paramétriques sur l’influence du point de fonctionnement d’une éolienne, sur sa hauteur de mât ou encore sur le type de CLA. Une éolienne en situation de dérapage fait également l’objet d’études paramétriques. Celles-ci visent à étudier le comportement du sillage dans différentes situations et il est alors montré les limites des lois empiriques présentes dans la littérature, concernant notamment l’influence de la turbulence ambiante. La seconde partie se focalise sur la vision instationnaire, jusqu’ici rarement considérée. En utilisant l’anémométrie par fil chaud, les résultats montrent le rôle des grandes échelles de la turbulence atmosphérique sur l’apparition du meandering. L’amplitude du battement et les dimensions du sillage instantané sont ensuite appréhendées de façon quantitative par mesures PIV, montrant l’influence du point de fonctionnement de l’éolienne et de l’intensité de turbulence ambiante. / The aim of this work was to study the far wake of horizontal axis wind turbines in wind tunnels. Aerodynamic phenomena within the wakes are very complex and, most of the time, they are studied from a steady point of view : the main parameters (wake deficit, production of turbulence...) are therefore time averaged. Nevertheless, studying the wake unsteadiness of a wind turbine located in the atmospheric boundary layer (ABL) enables the consideration of the meandering phenomenon, which describes random oscillations of the wake. The present work was constructed in two main parts : firstly the steady vision and secondly the unsteady vision of a wind turbine wake, modelled according to the actuator disk theory and placed in an ABL reproduced in a wind tunnel at a geometric scale of 1/400. Several parametric studies are presented in the first part : on the influence of the wind turbine’s operating point, of its mast height and also on the influence of the ABL characteristics. Wind turbines in yaw are also considered. The wake behaviour is then studied in different configurations and the limits of the empirical laws in the literature are highlighted, especially the lack of the ambiant turbulence intensity consideration. The second part focuses on the unsteady point of view, rarely considered until today. Using hot wire anemometry, the role of the atmospheric large turbulent scales on the meandering phenomenon is proven. The oscillation magnitude and the instantaneous wake dimensions are also investigated using PIV, which leads to quantitative results on the meandering characteristics.

Thesis (M.S.)--State University of New York at Binghamton, Geological Sciences & Environmental Studies Department, 2007. / Includes bibliographical references.

Sedimentation is one of the consequences of hydropower plant construction. Such structures not only have an influence on reservoir morphology, but also have great impact on both upstream and downstream river morphology. This study focuses on fluvial morphological changes in between two hydropower plants on the Drava River, Austria. The influence of both reservoir management methods (flushing) and human intervention (groynes) have been investigated. The first stage started with validating an unsteady Delft3D morphodynamic model of the meandering reach. This validation shows the importance of spatial grain size distribution in predicting bed load transport. Analysis of the flushing method includes investigation of the duration of gate-opening before and after peak flood. The results show that the duration of lowering the water level at the hydropower plant (by opening the gate) before starting the peak flood will not have a big influence on the river morphology upstream of the reservoir. However, the duration of maintaining the low water level after the peak flood has a large influence on both the river morphology in the upstream portion of the reservoir and on the sediment transport toward the reservoir In the second part of this study, hydraulic structural groynes were applied in the river reach. The objective was to design a groyne field that will minimize sediment transport to the reservoir. Both emerged and submerged groynes were investigated. In addition, the influences of both groyne head shape and the distribution of sediment grain size in the groyne zone were examined. This study shows that under an unsteady simulation, when the groynes are submerged by 1m at normal flow, the sediment supply to the groyne zone decreases compared to the emerged case. However, if the groynes are submerged by 0.5m, the sediment supply to the groyne zone will be greater than the emerged case for an aspect ratio in between (0.5-2). Finally, applying L-head groynes produces less erosion in the main stream and a higher sediment supply compared to straight groynes.

No description available.

Nowadays, there is a growing demand for reliable assets security and management in various industries. The company SolarWave is eager to implement a comprehensive security system to produce active protection for their expensive product: solar panels. This security system is not only including assets tracking, monitoring but also combined with a control system, which is used to binary control a switch of solar panel to be on in presence of the correct ID and off in absence of the correct ID. One of the technologies that made this concept viable is known as Radio Frequency Identification (RFID). The thesis project is a sub-project in the development project whose content is mentioned as above. It contains two main parts. One is the system solution for the company. The other is RFID tag design which is in parallel with the company solution in order to reach a scientific level of a master thesis. In this thesis, I systematically analyze the operating mechanism and characteristics of RFID, and propose both active and passive RFID solutions for the company. And I also suggest an alternative radio technology ZigBee which can be used instead or as a complement to RFID. Meanwhile, I propose two designs of RFID tag according to the specification of the solar panel. One is modified meandering antenna. This kind of antenna is very effective and popular in RFID tag design in order to minimize the size of antenna. The other is inductively coupled loop antenna. It is a very useful method for conjugate matching in RFID tag antenna. The required input resistance and reactance can be achieved separately by choosing appropriate geometry parameters. It makes the antenna easier to match to the tag chips. Both the RFID antenna designs are simulated on Ansoft HFSS 12.

Thesis (M.Sc.)--York University, 2007. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 80-82). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR29578

Thesis (M.Sc.)--York University, 2005. Graduate Programme in Geography. / Typescript. Includes bibliographical references (leaves 128-133). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11877