published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

The efficacy of providing water sources in desert ecosystems to enhance wildlife populations and their distribution continues to be debated among wildlife managers. Some argue wildlife water developments provide a direct benefit to numerous species, while others point to the potential that wildlife water developments alter competition or predation dynamics and disrupt native communities. Additionally, some have argued that the availability of water may become more important to wildlife in the face of vegetative changes associated with expansive fire and conversion of shrub or forest lands to grasslands which alters the thermal landscape available to animals. I evaluated the influence of free water and expansive fire on aspects of the ecology (habitat selection, space use and survival) of Gambel's quail (Callipepla gambelii) in the Mojave Desert of southwestern Washington County, Utah, USA. I attached radio-transmitters to a total of 206 quail (74 adult males, 67 adult females, and 65 juvenile males and females) and monitored them from 2010 – 2013. For chapter one of my thesis, I evaluated the response of marked quail to removal of access to water in a before-after controlled impact (BACI) design. I found little influence of water removal on survival as models with this effect received little to no support and overlap in confidence intervals occurred between treatment and reference groups. Likewise, the distance from the center of the summer home range to the nearest water source did not differ by year (F = 1.63; P = 0.19) or treatment (removal of water) (F = 0.89; P = 0.35) and pairwise comparisons of distances for the treatment by year interaction were not significant (P > 0.05 in all cases). For size of home range area, however, I found strong effects for year (F = 3.07; P = 0.03), treatment (F = 4.67; P = 0.03), and their interaction (F = 7.61; P = 0.01). Mean home range size for quail was 6.10 and 1.63 km2 for animals in the reference area during treatment years (2012 and 2013) compared to 5.07 and 8.99 km2 for quail in the treatment area during 2012 and 2013, respectively. Removal of water influenced size of summer home ranges, but not the location of the summer home range or survival rates. I hypothesize that removal of access to free water required quail in the treatment area to expand their space use patterns in 2013 in order to satisfy water demands via pre-formed water. For chapter two of my thesis, I evaluated habitat selection of Gambel's quail in relation to vegetation type, topographic features, water, and recent (4-7 years) expansive fire. Gambel's quail selected areas of decreased roughness which were closer to water and fire boundaries than random locations. I found that quail preferred moderate (< 10 degrees) hillsides and ravine bottoms. I found no evidence that quail avoided the burned areas within their home ranges and 80% of their telemetry points were <500 meters from a burn edge. The Beaver Dam slope topography strongly influenced habitat selection for Gambel's quail and they showed strong selection for water sources during summer months. These data also suggest that wildfires have had limited impact on habitat selection by this species, four to seven years later.

Jack Capon. / "May 25, 1955." "This report is based on a thesis submitted to the Department of Electrical Engineering, M.I.T., ... for the degree of Master of Science." / Bibliography: p. 53. / Army Signal Corps Contract DA36-039 sc-42607 Project 102B Dept. of the Army Project 3-99-10-022

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

No description available.

The data from Super Dual Auroral Radar Network (SuperDARN) radar and Cluster was used to investigate whether the processes observed by SuperDARN radar in the highlatitude ionosphere leads to the processes that take place in the magnetosphere. SuperDARN is a global network of high-frequency coherent-scatter radars operating in the northern and southern hemispheres and these radars are capable of observing backscatter from ionospheric irregularities. The Tsyganenko T96 field model was used to map the footprint of the Cluster spacecraft into the ionosphere. The SuperDARN radar data analysis software was used to generate time series, fi eld of view and convection plots. The data from Syowa South, Syowa East SuperDARN radars, Advance Composition Explorer (ACE) and Cluster spacecrafts was used in this study. Two events were found and discussed, an event on 09 August 2002 and another event on 30 September 2002. The SuperDARN radar and Cluster data for these events were compared. When a change in electric field was observed by Cluster, SuperDARN radar observed a change in the convection flow. There was a time delay between the change in the electric fi eld and the change in convection flow. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2010.

This thesis has investigated radioclimatological study in a clear-air environment as applicable to terrestrial line of sight link design problems. Radioclimatological phenomena are adequately reviewed both for the precipitation effect and clear-air effect. The research focuses more on the clear-air effect of radioclimatological studies. Two Southern African countries chosen for case study in the report are Botswana and South Africa. To this end, radiosonde data gathered in Maun, Botswana and Durban, South Africa are used for model formulation and verification. The data used in the thesis ranges from three years to ten years in these two stations. Three to ten years of refractivity data gathered in Botswana and South Africa is used for the model formulation. On the other hand, eight months signal level measurement data recorded from the terrestrial line of sight link set up between Howard College and Westville Campuses of the University of KwaZulu-Natal, Durban South Africa is used for model verification. Though various radioclimatic parameters could affect radio signal propagation in the clear-air environment, this report focuses on two of these parameters. These two parameters are the geoclimatic factor and effective earth radius factor (k-factor). The first parameter is useful for multipath fading determination while the second parameter is very important for diffraction fading, modeling and characterization. The two countries chosen have different terrain and topographical structures; thus further underlying the choice for these two parameters. While Maun in Botswana is a gentle flat terrain, Durban in South Africa is characterized by hilly and mountainous terrain structure, which thus affects radioclimatological modeling in the two countries. Two analytical models have been proposed to solve clear-air radioclimatic problems in Southern Africa in the thesis. The first model is the fourth order polynomial analytical expression while the second model is the parabolic equation. The fourth order polynomial model was proposed after an extensive analysis of the eight month signal level measurement data gathered in Durban, South Africa. This model is able to predict the fade exceedance probabilities as a function of fade depth level. The result from the fourth order polynomial model is found to be comparable with other established multipath propagation model reviewed in the thesis. Availability of more measurement data in more location will be necessary in future to further refine this model. The second model proposed to solve clear-air propagation problem in the thesis is the modified parabolic equation. We chose this technique because of its strength and its simplistic adaptation to terrestrial line of sight link design problem. This adaptation is possible because, the parabolic equation can be modified to incorporate clear-air parameters. Hence this modification of the parabolic equation allows the possibility of a hybrid technique that incorporates both the statistical and mathematical procedures perfectly into one single process. As a result of this, most of the very important phenomena in clear-air propagation such as duct occurrence probabilities, diffraction fading and multipath fading is captured by this technique. The standard parabolic equation (SPE) is the unmodified parabolic equation which only accounts for free space propagation, while the modified parabolic equation (MPE) is the modified version of the parabolic equation. The MPE is classified into two in the thesis: the first modified parabolic equation (MPE1) and second modified parabolic equation (MPE2). The MPE1 is designed to incorporate the geoclimatic factor which is intended to study the multipath fading effect in the location of study. On the other hand, MPE2 is the modified parabolic equation designed to incorporate the effective earth radius factor (k-factor) intended to study the diffraction fading in the location of study. The results and analysis of the results after these modifications confirm our expectation. This result shows that signal loss is due primarily to diffraction fading in Durban while in Botswana, signal loss is due primarily to multipath. This confirms our expectation since a flatter terrain attracts signal loss due to multipath while hilly terrain attracts signal loss due to diffraction fading. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2010.

Providing guarantees in the Quality of Service (QoS) has become essential to the transmission of multimedia traffic over wireless links with fading channels. However this poses significant challenges due to the variable nature of such channels and the diverse QoS requirements of different applications including voice, video and data. The benefits of dynamic adaptation to system and channel conditions have been accepted, but the true potential of optimized adaptation is lost if the layers operate independently, ignoring possible interdependencies between them. Cross-layer design mechanisms exploit such interdependencies to provide QoS guarantees for the transmission of multimedia traffic over fading channels. Channel adaptive M-QAM schemes are examples of some of the earliest works in the area of cross-layer design. However, many of the original schemes use the assumption that thresholds designed for AWGN channels can be directly applied to slow-fading channels. The thresholds are calculated with a commonly used approximation bit error rate (BER) expression and the first objective of the thesis was to study the accuracy of this commonly used expression in fading channels. It is shown that that the inaccuracy of the expression makes it unsuitable for use in the calculation of the threshold points for an adaptive M-QAM system over fading channels. An alternative BER expression is then derived which is shown to be far more accurate than the previous one. The improved accuracy is verified through simulations of the system over Nakagami-m fading channels. Many of the cross-layer adaptation mechanisms that address the QoS provisioning problem only use the lower layers (physical and data link) and few explore the possibility of using higher layers. As a result, restrictions are placed on the system which introduces functional limitations such as the inability to insert more than one class of traffic in a physical layer frame. The second objective in this thesis was to design a physical and application layer cross-layer adaptation mechanism which overcomes this limitation. The performance results of the scheme in both AWGN and fading channels show that the cross-layer mechanism can be efficiently utilized for the purposes of providing error rate QoS guarantees for multimedia traffic transmissions over wireless links. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2009.