There is increased interest in building modern roundabouts in Georgia and in the United States because of the safety and operational benefits that can be realized from this type of intersection. With this interest comes the increasing need to be able to estimate the capacity that a roundabout can provide after it is built. In the early 2000s, a National Cooperative Highway Research Program (NCHRP) study was conducted that, among other tasks, developed single-lane and multi-lane roundabout capacity estimation equations. These equations, presented in the Highway Capacity Manual 2010 (HCM 2010), can be calibrated using locally determined values of follow-up headway and critical headway. This study was designed to calibrate the HCM 2010 roundabout capacity equation for single-lane roundabouts to driving conditions in Georgia. In order to develop estimates of the calibration parameters, video imagery was recorded for 13 approaches at six roundabouts in Georgia for approximately two hours during the peak period. A total of 29.5 hours of video was recorded. Data from three of these roundabouts forms the basis of this thesis. The videos were processed by a Java program to collect time stamps that were subsequently used in Microsoft Excel to calculate the follow-up and critical headway values required for calibration. The values of critical headway and follow-up headway that were found from the video data are presented in the results as well as the single-lane capacity equations calibrated from the data. Two types of analysis were done, one that includes exiting vehicles and one that does not include exiting vehicles. When exiting vehicles were excluded, the weighted average of follow-up and critical headway were found to be 3.46 and 4.17 seconds respectively and when exiting vehicles were included in the analysis the weighted averages of the follow-up and critical headway were found to be 2.80 seconds and 3.34 seconds respectively. It was found that exiting vehicles do have an impact on the operations at the roundabout in most cases, and including exiting vehicles in the analysis tends to increase the capacity predicted by the calibrated equations.

<p>TCP (Transmission Control Protocol) is a transport protocol designed for the wired Internet. In wireless networks packet losses occur more frequently due to the unreliability of the physical link. The main problem is that TCP treats all losses as congestion, which leads to a lower throughput. </p><p>Ad hoc networks are multihop wireless networks of mobile nodes, where each node can allow other packets to pass through it. Topology changes often occur and may lead to packet losses and delays, which TCP misinterprets as congestion. We want to modify TCP to recognize the differences between link failure and congestion to improve the capacity. </p><p>In our model we have built a connection in an ad hoc network where packet losses and partitions can be made. Simulation experiments show that we didn't get the problems we expected. This can be explained by low delays and because we buffered the packets during link failure. </p><p>A simple modification of TCP was made and simulated, and showed that an improvement of performance is possible. More research should be done to make a modification of TCP that would further affect the throughput.</p>

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 364-378).

Thesis (doctor of public administration)--University of the Philippines). / Includes bibliographical references (p. 284-286).

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 82-89).

Thesis (Ph.D)--Aerospace Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Mavris, Dimitri N.; Committee Member: Baik, Hojong; Committee Member: DeLaurentis, Daniel; Committee Member: Lewe, Jung-Ho; Committee Member: Schrage, Daniel. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Carbon dioxide capture and storage (CCS) is considered one of the key technologies for reducing atmospheric emissions of CO₂ from human activities (IPCC, 2005). The scale of potential deployment of CCS is enormous spanning manufacturing, power generation and hydrocarbon extraction worldwide. Uncertainty, cost-benefit challenges, market barriers and failures, and promotion and regulation of infrastructure are the main obstacles for deploying CCS technology in a broad scale. In a CCS project, it is the operator’s responsibility to guarantee the CO₂ containment while complying with environmental regulations and CO₂ contractual requirements with the source emitter. Acquiring new information (e.g. seismic, logs, production data, etc.) about a particular field can reduce the uncertainty about the reservoir properties and can (but not necessarily) influence the decisions affecting the deployment of a CCS project. The main objective of this study is to provide a decision-analysis framework to quantify the Value of Information (VOI) in a CCS project that faces uncertainties about permeability values in the reservoir. This uncertainty translates into risks of CO₂ migration out of the containment zone (or lease zone), non-compliance with contractual requirements on CO₂ storage capacity, and leakage of CO₂ to sources of Underground Source of Drinking Water (USDW). The field under analysis has been idealized based on a real project located in Texas. Subsurface modeling of the upper Frio Formation (injection zone) was conducted using well logs, field-specific GIS data, and other relevant published literature. The idealized model was run for different scenarios with different permeability distributions. The VOI was quantified by defining prior scenarios based on the current knowledge of a reservoir, contractual requirements, and regulatory constraints. The project operator has the option to obtain more reliable estimates of permeability, which will help to reduce the uncertainty of the CO₂ behavior and storage capacity of the formation. The accuracy of the information gathering activities is then applied to the prior probabilities (Bayesian inference) to infer the value of such data. / text

This thesis evaluates the benefits of Multiple Input Multiple Output (MIMO) techniques on the capacity of Multimode Fiber (MMF) links. Optical MMF MIMO systems take advantage of the spatial diversity present in the multiple propagating paths in multimode fibers. By using multiple lasers at the input facet of the fiber and multiple photodetectors at the output, we show that the capacity of the link is improved from the single device link, hence demonstrating the usefulness of MIMO in such optical systems. An initial simulation of butt-coupling a Vertical Cavity Surface Emitting Laser (VCSEL) to multimode fiber reveals that the placement position of the laser axis with respect to the fiber axis is critical in exciting a large number of modes. More specifically, we show that there exists a tradeoff between total power coupled into the fiber and the number of modes launched. We then consider a mathematical description of the fiber channel and use it to simulate the capacity of a 1x1, 2x2, and 3x3 MIMO links over a statistical ensemble of channel realizations. This simulation reveals that a 2x2 system is capable of approximately a 50% increase in capacity over the 1x1 case while the 3x3 system is capable of approximately an 80% increase. Moreover, we show that the choice of the placement positions on the facets of the fiber affects the channel capacity, thereby implying that an optimal device position exists. We find the optimal device geometry by an exhaustive search and compare the capacities for the optimal geometry and that of a suboptimal one. A capacity tolerance study is then developed that considers perturbations about the optimal device locations and shows that the capacity of a rotated laser plane is over 90% of the capacity of the original device locations. A second perturbation study considers lateral offsets and shows that systems with a higher number of devices show good tolerance with poorer lateral tolerances for systems with less devices. When small lasers and a large grid of possible device locations are used, an exhaustive search for the optimal device location becomes computationally infeasible. We show that the problem of searching for the optimal detector locations while holding the laser positions fixed is submodular. This property allows a greedy algorithm to select the device positions at a small fraction of the computational complexity, however, only guaranteeing that the capacity of the resulting configuration is greater than a (1 - e^-1) fraction of the optimal configuration. We use this technique to compare the exhaustive search and the greedy search for coarse grids, and then exclusively use the greedy algorithm to select a device configuration for a fine grid whereby an exhaustive search is computationally infeasible. / text

As more renewable resources are added into the grid and environmental regulations are imposed to reduce emissions, there will be dramatic changes in the generation portfolio. Assessing the impact of these changes is important for policy makers, market participants, and general public to understand trends in the electricity market. This paper addresses this issue by analyzing how the ERCOT market is affected by CO2 penalty and wind penetration. In order to assess the future power system, the study model should represent the long term dynamics of various factors to find out how investment decisions are made economically in a competitive market with appropriate assumptions. Another important aspect is the short term market dynamics from real operation of power system. For this study, AURORAxmp, a commercially available market simulator, is utilized to capture both long term and short term dynamics. This study runs 5 different scenarios: two base cases with and without CO2 price, 20%, 27%, and 33% wind penetration level. The result shows that, increasing wind penetration reduces production and capacity of both coal and gas units, electricity market prices, and amount of emissions. However, increasing wind penetration has greater impacts on a decrease in generation from thermal units than reduction in thermal capacity, resulting in 11.4% capacity value of wind power. The study also confirms that CO2 price impacts capacity and generation of coal (negatively) and gas (positively) units in opposite ways, and reduces emission, but increases power prices and generation cost. Especially, the impact on retirement of coal units is noticeable. Almost half of the current coal capacity (19 GW), 9,390 MW, is retired by 2040 in this study. / text

Personality research has long been an area of interest in the study of consumer behavior. Currently, common practice is to segment prospective audiences by demographic variables (age, gender, and race) instead of psychographics (values, attitudes, personality). In this research, the author investigates the relationship between personality type (introversion/extraversion) and message recall. Using 122 undergraduate and graduate students, recall was examined across two forms of stimulus (incongruent and congruent messages). Results indicated that while there is no relationship between personality type and message recall, there is a relationship between the frequency of advertising messaging and recall. Results are discussed individually by messaging frequency and personality type with further suggestions for future research. / text