This thesis discusses the design, fabrication, and testing of a high efficiency, dual band radio frequency power amplifier. While it is difficult to demonstrate an exact mode of operation for power amplifiers at radio frequencies, based on the characteristics of the transistor itself, the argument can be made that our high efficiency performance is due to an approximation to class E operation. The PA is designed around a CGH40025 transistor manufactured by Cree, Inc, which has developed a very useful nonlinear model of its transistor, which allows use of software load/source pull methods to determine optimum impedances to be presented to the gate and drain (hereafter referred to as source and load) of the transistor at each band of operation. A recent work on dual-band impedance matching is then used to design distributed element networks in order to present conjugate matches of these impedances to the transistor. This is followed by a careful layout, after which the PA is then fabricated on a low-impedance substrate using a LPKF Protomat S63 rapid prototyping machine. Measurements of gain and drain current provide values for power-added-efficiency. Simulated gains were 21 and 18 dB at 800 MHz and 1.85 GHz, respectively, with PAE around 63% for both bands. Measurements taken from the fabricated PA showed gains of 20 and 16 dB at each band, but PAE of 80% at 800 MHz and 43% at 1.85 GHz.

A Dual-Eulerian graph is a plane multigraph G that contains an edge list which is simultaneously an Euler tour in G and an Euler tour in the dual of G. Dual-Eulerian tours play an important role in optimizing CMOS layouts of Boolean functions. When circuits are represented by undirected multigraphs the layout area of the circuit can be optimized through finding the minimum number of disjoint dual trails that cover the graph. This paper presents an implementation of a polynomial time algorithm for determining whether or not a plane multigraph is Dual-Eulerian and for finding the Dual-Eulerian trail if it exists.

In the past, the oil and gas industry has typically used the single gradient system to drill wells offshore. With this system the bottom hole pressure was controlled by a mud column extending from the drilling rig to the bottom of the wellbore. This mud column was used to achieve the required bottom hole pressure. But, as the demand for oil and gas increased, the industry started exploring for oil and gas in deep waters. Because of the narrow margin between the pore and fracture pressures it is somewhat difficult to reach total depth with the single gradient system. This led to the invention of the dual gradient system. In the dual gradient method, heavy density fluid runs from the bottom hole to the mudline and a low density fluid from the mudline to the rig floor so as to maintain the bottom hole pressure. Several methods have been developed to achieve the dual gradient drilling principle. For this research project, we paid more attention to the liquid lift, dual gradient drilling (riser dilution method). This method of achieving dual gradient drilling was somewhat different from the others, because it does not utilize elaborate equipment and no major changes are made on the existing drilling rigs. In this thesis the technical feasibility of using the liquid lift method over the other methods of achieving dual gradient drilling was determined. A computer program was developed to simulate the wellbore hydraulics under static and dynamic conditions, injection rate and base fluid density required to dilute the riser fluid and finally, u-tubing phenomena. In this thesis we also identified some problems associated with the liquid lift method and recommendations were made on how these problems can be eliminated or reduced. Emphases were placed on the effect of u-tubing, injection rate of base fluid at the bottom of the riser and well control issues facing this system.

In the past, the oil and gas industry has typically used the single gradient system to drill wells offshore. With this system the bottom hole pressure was controlled by a mud column extending from the drilling rig to the bottom of the wellbore. This mud column was used to achieve the required bottom hole pressure. But, as the demand for oil and gas increased, the industry started exploring for oil and gas in deep waters. Because of the narrow margin between the pore and fracture pressures it is somewhat difficult to reach total depth with the single gradient system. This led to the invention of the dual gradient system. In the dual gradient method, heavy density fluid runs from the bottom hole to the mudline and a low density fluid from the mudline to the rig floor so as to maintain the bottom hole pressure. Several methods have been developed to achieve the dual gradient drilling principle. For this research project, we paid more attention to the liquid lift, dual gradient drilling (riser dilution method). This method of achieving dual gradient drilling was somewhat different from the others, because it does not utilize elaborate equipment and no major changes are made on the existing drilling rigs. In this thesis the technical feasibility of using the liquid lift method over the other methods of achieving dual gradient drilling was determined. A computer program was developed to simulate the wellbore hydraulics under static and dynamic conditions, injection rate and base fluid density required to dilute the riser fluid and finally, u-tubing phenomena. In this thesis we also identified some problems associated with the liquid lift method and recommendations were made on how these problems can be eliminated or reduced. Emphases were placed on the effect of u-tubing, injection rate of base fluid at the bottom of the riser and well control issues facing this system.

Purpose: To assess the performance of a Dual-Energy chest radiography system. Methods: A cohort of 129 patients was recruited from population referred for CT guided biopsy of a lung lesion. Digital radiography (DR) and Dual Energy (DE) images were acquired. Receiver operating characteristic (ROC) tests were performed to evaluate performance of DE images compared to DR. Five chest radiologists scored images. Performance was analyzed for all cases pooled and sub groups based on gender, nodule size, density, location, and chest diameter. Results: There was no significant difference between DE and DR for all cases (p = 0.61). There was a significant advantage for DE imaging of small nodules, and nodules located in right-upper lobe. (p = 0.02 and 0.01) Conclusions: DE imaging demonstrated significant improvement in diagnosis of sub-centimeter lung nodules and lesions in the upper lung zones which are common characteristic of early stage lung malignancy.

Purpose: To assess the performance of a Dual-Energy chest radiography system. Methods: A cohort of 129 patients was recruited from population referred for CT guided biopsy of a lung lesion. Digital radiography (DR) and Dual Energy (DE) images were acquired. Receiver operating characteristic (ROC) tests were performed to evaluate performance of DE images compared to DR. Five chest radiologists scored images. Performance was analyzed for all cases pooled and sub groups based on gender, nodule size, density, location, and chest diameter. Results: There was no significant difference between DE and DR for all cases (p = 0.61). There was a significant advantage for DE imaging of small nodules, and nodules located in right-upper lobe. (p = 0.02 and 0.01) Conclusions: DE imaging demonstrated significant improvement in diagnosis of sub-centimeter lung nodules and lesions in the upper lung zones which are common characteristic of early stage lung malignancy.

Moving through varied and complex environments every day is something that most people do with ease. However, if the input from the visual system is unavailable (e.g., damage to the optic nerves or smoke in a burning building), navigating and avoiding obstacles becomes much more demanding. It is therefore desirable to develop a navigation aide for use where visual input has become unavailable. There is a small body of research concerning such navigation aides and their efficacy. However, many issues that may have serious human factors repercussions for such a system are unexplored. This study was conducted in order to examine the effect of an attentionally demanding distractor task on wayfinding performance with an audio only navigation aide, in this case the System for Wearable Audio Navigation (SWAN). The distractor task was found to have a significant impact on wayfinding performance, which decreased when both tasks were performed simultaneously. However, performance on the distractor task improved during this time, in some cases reaching performance levels similar to when the distractor task was performed by itself. This result may be due to participants shifting attention to the task they perceive to be more difficult when asked to do both simultaneously, in this case the distractor task.

In the past, the oil and gas industry has typically used the single gradient system to drill wells offshore. With this system the bottom hole pressure was controlled by a mud column extending from the drilling rig to the bottom of the wellbore. This mud column was used to achieve the required bottom hole pressure. But, as the demand for oil and gas increased, the industry started exploring for oil and gas in deep waters. Because of the narrow margin between the pore and fracture pressures it is somewhat difficult to reach total depth with the single gradient system. This led to the invention of the dual gradient system. In the dual gradient method, heavy density fluid runs from the bottom hole to the mudline and a low density fluid from the mudline to the rig floor so as to maintain the bottom hole pressure. Several methods have been developed to achieve the dual gradient drilling principle. For this research project, we paid more attention to the liquid lift, dual gradient drilling (riser dilution method). This method of achieving dual gradient drilling was somewhat different from the others, because it does not utilize elaborate equipment and no major changes are made on the existing drilling rigs. In this thesis the technical feasibility of using the liquid lift method over the other methods of achieving dual gradient drilling was determined. A computer program was developed to simulate the wellbore hydraulics under static and dynamic conditions, injection rate and base fluid density required to dilute the riser fluid and finally, u-tubing phenomena. In this thesis we also identified some problems associated with the liquid lift method and recommendations were made on how these problems can be eliminated or reduced. Emphases were placed on the effect of u-tubing, injection rate of base fluid at the bottom of the riser and well control issues facing this system.

The traditional displayer ¡V CRT has already been substituted by liquid crystal displayer (LCD).The a-Si TFT is used to be a switch, while the size of the displayer increases, the require of the performance and quality of TFTs is more and more better. Therefore, it is very important subject to study the stability and to improve the performance of a-Si TFTs. In this study, it simulated the process of the degradation on the TFTs by changing the sizes of TFTs and bias modes to find to stability mechanism of the TFTs. It can be known that under AC stress the degradation depends on the channel length, longer channel length with less degradation. In order to improve the traditional dual-gate structure TFTs, it had made dual-gate TFTs with ITO back-gate, the process of the new structure TFTs are fully compatible with the conventional BCE TFT fabrication process. With dual-channel conduction, the dual-gate TFTs exhibit higher on current and lower photo leakage current performance than the conventional inverted staggered TFTs In this study it also use the dual-gate structure to investigate how the back-channel influence the front-channel conduction. Apply DC bias on the back-gate to from defects at the interface of the active layer and passvation layer, it is found that after stress the on-current show almost the same quantities, and the photo leakage current is obvious decreased.

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