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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.
1

New sharing method between the Fixed Satellite Service and the Aeronautical Mobile Satellite Service in the 14.0-14.5 GHz band

Smith, Justin L. 10 February 2003 (has links)
In the US, the 14.0-14.5 GHz band is allocated on a primary basis to the Radio-Navigation and the FSS with a secondary allocation to the LMSS. The Radio-Navigation service is the use of RADAR for navigation. An example of Radio-Navigation is the ground proximity radar used for airplane collision avoidance. FSS stands for the Fixed Satellite Service. In general, an FSS is a satellite network consisting of a geo-stationary satellite and non-movable earth stations on the ground. An example of an FSS is the earth terminals used at gas stations to verify credit cards and centrally track inventory. The 14.0-14.5 GHz band is also allocated on a secondary basis to the LMSS or Land Mobile Satellite Service. This is a satellite network with a satellite and a movable terrestrial non-aeronautical earth station. An example of an LMSS is a system called Omnitracs, which provides a satellite-based data connection for the trucking industry. AMSS stands for the Aeronautical Mobile Satellite Service. An AMSS is an LMSS dedicated only to airplanes. The CPM or Conference Preparatory Meeting after WRC or World Radio Conference-2000 decided there was an urgent need for technical and regulatory studies covering sharing between the FSS and the AMSS. The requirement for a report on the studies was added to the WRC-2003 agenda. The WRC also stipulated that the studies must demonstrate that sharing between the FSS and the AMSS is feasible enough to allocate AMSS a secondary status in the band. The studies need to be completed before WRC-2003. AMSS contends that sharing is feasible if their service can meet the same PFD limits of the LMSS. Presently, the FCC has licensed the AMSS on an experimental non-interference basis. The FSS contends that characteristics are needed of the AMSS system and a detailed sharing study be completed to verify sharing is feasible. The FSS believes that sharing may not be feasible if the same transponder is used for AMSS and FSS. The FSS perceives that the AMSS is asking for a super secondary status. Super secondary status implies that the AMSS would only be required to adhere to PFD limits on individual aircraft and not for multiple aircraft in view of a victim FSS receiver. Future studies will clarify this issue. The issues associated with the sharing analysis are; the modeling of the orbital separation of the satellites, the atmospheric interference into the communication link and the availability of the communication link between the FSS and the AMSS. The issues associated with modeling of the simulation are the static, verses dynamic modeling environments and developing a dynamic software tool to track airplane movement. This thesis plans to propose a new sharing methodology between the FSS and the AMSS that could be contributed to the WRC-2003 agenda. Three systems examples were provided at ITU meetings inresponse to the WRC-2003 agenda item. The three systems will abide by the ITU-R S.728 EIRP limits. The three systems indicate that static analysis shows that sharing is feasible involving only one aircraft as the interfere. This is not a reasonable solution for a real time environment because there is only one aircraft used. It is necessary for the link to support multiple aircraft. The factors that indicate sharing is feasible are: non-harmful interference to the victim and reasonable enough link margin in the interfere system to make it viable. A viable system in the case of aircraft would include high-speed internet and video. The AMSS interfere system cannot propose a power limit that will not allow it to close it's own link. In order to mitigate the interference, systems can agree to certain interference mitigation techniques. The different techniques are: transmitting power control, geostationary arc avoidance angle and orbital arc separation. Power control as described above is the centralized control of the interfering antenna into the victim. This is done by simulating the interference environment and pre-scheduling the decreases of the transmitting power. This is a feasible solution except that it decreases the availability and thru-put of the interfere system. This approach can make the system have unrealistic link margins and spotty availability due to the pre-scheduled power control. Another technique is the geostationary arc avoidance angle. This technique is not applicable since both the AMSS and FSS use geostationary orbits. The third technique is geostationary separation. This technique requires co-channel systems to maintain a certain orbital spacing between them. FSS systems in certain bands have a minimum of 3 degrees of orbital spacing between co-channel systems. Since the AMSS has 01/25/03 a mobile terrestrial system (aircraft) as part of the link, it requires a higher orbital separation between it and the FSS system. The results of dynamic analysis indicate that this technique is feasible at 10 degree orbital spacing. The Monte Carlo analysis completed for this thesis simulated the results of four scenarios: co-located, 3 degree, and 5 and 10-degree orbital separation. It can be determined from the results that the interference decreases as the orbital separation increases. These simulations were done based on a 10 aircraft interfere scenario. / Master of Science
2

A Cognitive Approach to Predicting Academic Success in Computing

Goettel, Colby 01 April 2018 (has links)
This research examines the possible correlations between a computing student's learning preference and their academic success, as well as their overall satisfaction with their major. CS and IT seniors at BYU were surveyed about their learning preferences and satisfaction with their major. The research found that IT students who are more reflective in their learning preference tend to have higher grades in their major. Additionally, it found that student age and their parents' education level were significant players in their academic success. However, there were no correlations found between major satisfaction and academic performance.
3

Computer Aided Long-Bone Segmentation and Fracture Detection

Donnelley, Martin, martin.donnelley@gmail.com January 2008 (has links)
Medical imaging has advanced at a tremendous rate since x-rays were discovered in 1895. Today, x-ray machines produce extremely high-quality images for radiologists to interpret. However, the methods of interpretation have only recently begun to be augmented by advances in computer technology. Computer aided diagnosis (CAD) systems that guide healthcare professionals to making the correct diagnosis are slowly becoming more prevalent throughout the medical field. Bone fractures are a relatively common occurrence. In most developed countries the number of fractures associated with age-related bone loss is increasing rapidly. Regardless of the treating physician's level of experience, accurate detection and evaluation of musculoskeletal trauma is often problematic. Each year, the presence of many fractures is missed during x-ray diagnosis. For a trauma patient, a mis-diagnosis can lead to ineffective patient management, increased dissatisfaction, and expensive litigation. As a result, detection of long-bone fractures is an important orthopaedic and radiologic problem, and it is proposed that a novel CAD system could help lower the miss rate. This thesis examines the development of such a system, for the detection of long-bone fractures. A number of image processing software algorithms useful for automating the fracture detection process have been created. The first algorithm is a non-linear scale-space smoothing technique that allows edge information to be extracted from the x-ray image. The degree of smoothing is controlled by the scale parameter, and allows the amount of image detail that should be retained to be adjusted for each stage of the analysis. The result is demonstrated to be superior to the Canny edge detection algorithm. The second utilises the edge information to determine a set of parameters that approximate the shaft of the long-bone. This is achieved using a modified Hough Transform, and specially designed peak and line endpoint detectors. The third stage uses the shaft approximation data to locate the bone centre-lines and then perform diaphysis segmentation to separate the diaphysis from the epiphyses. Two segmentation algorithms are presented and one is shown to not only produce better results, but also be suitable for application to all long-bone images. The final stage applies a gradient based fracture detection algorithm to the segmented regions. This algorithm utilises a tool called the gradient composite measure to identify abnormal regions, including fractures, within the image. These regions are then identified and highlighted if they are deemed to be part of a fracture. A database of fracture images from trauma patients was collected from the emergency department at the Flinders Medical Centre. From this complete set of images, a development set and test set were created. Experiments on the test set show that diaphysis segmentation and fracture detection are both performed with an accuracy of 83%. Therefore these tools can consistently identify the boundaries between the bone segments, and then accurately highlight midshaft long-bone fractures within the marked diaphysis. Two of the algorithms---the non-linear smoothing and Hough Transform---are relatively slow to compute. Methods of decreasing the diagnosis time were investigated, and a set of parallelised algorithms were designed. These algorithms significantly reduced the total calculation time, making use of the algorithm much more feasible. The thesis concludes with an outline of future research and proposed techniques that---along with the methods and results presented---will improve CAD systems for fracture detection, resulting in more accurate diagnosis of fractures, and a reduction of the fracture miss rate.

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