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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.
401

Freehand three dimensional ultrasound for imaging components of the musculoskeletal system

Ross, Erin January 2010 (has links)
There have been reports on the use of Ultrasound (US) for monitoring fracture repair and for measuring muscle volume. Change in muscle mass is a useful bio-marker for monitoring the use and disuse of muscle, and the affects of age, disease and injury. The main modality for imaging bone is X-ray and for muscle volume Magnetic Resonance (MR). Previous studies have shown US to have advantages over X-ray and MR. US can image all stages of the fracture repair process and can detect signs of healing 4-6 weeks before X-ray allowing earlier detection of possible complications. Compared to MR, US is less resource intensive, easier to access and also has fewer exclusion criteria for patients. Despite these advantages, the limited field of view that US can provide results in high operator dependency for scan interpretation and also for length and volume measurements. Three-dimensional Ultrasound (3D US) has been developed to overcome these limitations and has been used to provide extended field of view images of the foetus and the heart and to obtain accurate volume measurements for organs. In this thesis it is hypothesized that 3D US can provide a more comprehensive method of imaging fracture repair than X-ray and is also a viable alternative to MR for determining muscle volumes in vivo. Initially, an electromagnetically (EM) tracked 3D US system was evaluated for clinical use using phantom-based experiments. It was found that the presence of metal objects in or near the EM field caused distortion and resulted in errors in the volume measurements of phantoms of up to ±20%. An optically tracked system was also evaluated and it was found that length measurements of a phantom could be made to within ±1.3%. Fracture repair was monitored in five patients with lower limb fractures. Signs of healing were visible earlier on 3D US with a notable, although variable, lag between callus development on X-ray compared to 3D US. 3D US provided a clearer view of callus formation and the changes in density of the callus as it matured. Additional information gained by applying image processing methods to the 3D US data was used to develop a measure of callus density and to identify the frequency dependent appearance of the callus. Volume measurements of the rectus femoris quadricep muscle were obtained using 3DUS from eleven healthy volunteers and were validated against volume measurements derived using MR. The mean difference between muscle volume measurements obtained using 3D US and MR was 0.53 cm3 with a standard deviation of 1.09 cm3 and 95% confidence intervals of 0.20 - 1.27 cm3 In conclusion, 3D US demonstrates great potential as a tool for imaging components of the musculoskeletal system and as means of measuring callus density.
402

Independence Screening in High-Dimensional Data

Wauters, John, Wauters, John January 2016 (has links)
High-dimensional data, data in which the number of dimensions exceeds the number of observations, is increasingly common in statistics. The term "ultra-high dimensional" is defined by Fan and Lv (2008) as describing the situation where log(p) is of order O(na) for some a in the interval (0, ½). It arises in many contexts such as gene expression data, proteomic data, imaging data, tomography, and finance, as well as others. High-dimensional data present a challenge to traditional statistical techniques. In traditional statistical settings, models have a small number of features, chosen based on an assumption of what features may be relevant to the response of interest. In the high-dimensional setting, many of the techniques of traditional feature selection become computationally intractable, or does not yield unique solutions. Current research in modeling high-dimensional data is heavily focused on methods that screen the features before modeling; that is, methods that eliminate noise-features as a pre-modeling dimension reduction. Typically noise feature are identified by exploiting properties of independent random variables, thus the term "independence screening." There are methods for modeling high-dimensional data without feature screening first (e.g. LASSO or SCAD), but simulation studies show screen-first methods perform better as dimensionality increases. Many proposals for independence screening exist, but in my literature review certain themes recurred: A) The assumption of sparsity: that all the useful information in the data is actually contained in a small fraction of the features (the "active features"), the rest being essentially random noise (the "inactive" features). B) In many newer methods, initial dimension reduction by feature screening reduces the problem from the high-dimensional case to a classical case; feature selection then proceeds by a classical method. C) In the initial screening, removal of features independent of the response is highly desirable, as such features literally give no information about the response. D) For the initial screening, some statistic is applied pairwise to each feature in combination with the response; the specific statistic chosen so that in the case that the two random variables are independent, a specific known value is expected for the statistic. E) Features are ranked by the absolute difference between the calculated statistic and the expected value of that statistic in the independent case, i.e. features that are most different from the independent case are most preferred. F) Proof is typically offered that, asymptotically, the method retains the true active features with probability approaching one. G) Where possible, an iterative version of the process is explored, as iterative versions do much better at identifying features that are active in their interactions, but not active individually.
403

Tactical web services using XML and Java web services to conduct real-time net-centric sonar visulization

Rosetti, Scott 09 1900 (has links)
Approved for public release, distribution unlimited / With the unveiling of ForceNet, the Navy's architectural framework for how naval warfare is to be conducted in the information age, much of the technological focus has been placed on Web technology. One of the most promising technologies is Web services. Web services provide for a standard way to move and share data more reliably, securely, and quickly. The capabilities imbedded in Extensible Markup Language (XML) and Simple Object Access Protocol (SOAP) can merge previously disparate systems into one integrated environment. Already proven successful in the administrative realm, wide-area networks such as the Secure Internet Protocol Network (SIPRNET) have become secure and reliable enough to pass data between systems and units to support tactical operations. The Modeling, Virtual Environments and Simulation (MOVES) Institute at the Naval Postgraduate School is currently working to extend these precepts into the modeling and simulation world under the Extensible Modeling and Simulation Framework (XMSF) project. By leveraging existing Web service technology, warfighters at the "tip of the spear" can have access to previously unrealized amounts of tactically-relevant data, analysis, and planning tools. The goal of this thesis is to apply the XMSF and Extensible 3D (X3D) graphics to the field of sonar visualization. Undersea warfare is a complex operation that requires a continuous and detailed analysis of the acoustic environment. Tactical sensor employment without a firm understanding of the complete undersea picture can lead to fatal consequences. The Navy has spent significant resources to develop training systems and tactical decision aids in an effort to integrate training, rehearsal and execution. Unfortunately, many of the high-resolution analysis tools that can provide high-resolution sonar prediction results are not easily accessible to the fleet. By taking advantage of Web services and XMSF technology, warfighters will need only access to the network to be able to pull real-time environmental analysis data from large databases, remotely run sonar prediction models on supercomputers, and view detailed three-dimensional (3D) virtual worlds that visualize the undersea picture.
404

Measurement strategy for geometrical verification : A state-of-the-art study, analysis and development of working methodology framework

Johansson, Marcus January 2016 (has links)
Geometrical and dimensional metrology is used to verify that manufactured and assembled products satisfy the defined geometrical requirements and thereby the functional requirements. The dimensional measurement planning operation is carried out to define how the measurements are going to be collected and it has to consider the reliability, uncertainty and economics of the measurement procedure. The thesis work has been performed to map the current knowledge regarding measurement strategies and principles and to develop recommendations regarding a framework which defines how the measurement planning work should be carried out. The purpose of the work was thereby to perform a state-of-the-art study to map the available theoretical and empirical measurement strategies and principles. The purpose was also to test the impact of the strategies in a measurement experiment in order to validate the methodology. To fulfil the purpose of the work, a literature review and a case study was initially performed. The literature review investigated the available academically knowledge and the requirements defined in international standards regarding the measurement planning work. The case study mapped the methodologies and principles which were used in industry through contextual research and qualitative interviewing. The majority of the case study was carried out at Saab Aeronautics but to obtain a wider understanding of the topic a survey were also conducted where additional manufacturing companies were participating. The outcome of the case study and the literature review were thereafter merged and further analysed though the measurement analysis. The case study and the literature review shown that there existed several different methodologies and guidelines regarding how the work should be and was performed. Some of the factors which were further investigated were the impact of the number of measurement points, distance between the measurement points, uncertainty of the strategy and the considerations connected to the selection of the geometrical features. The measurement analysis provided insights regarding the impact on average, minimum-, maximum deviation and the variance due to the amount and distribution of the inspection points. The findings were presented as a resulting outcome of the recommended measurement strategy framework methodology. The methodology of analysing the impact of the measurement strategy was therefore implemented into the recommendations regarding the measurement planning framework. The purpose of the framework is to offer a reliable, standardized and traceable measurement planning process where knowledge sharing and continuous improvements are possible to implement. In addition to the analysis of the measurement planning strategy the most important findings to consider in the adjacent process steps were investigated and presented. These findings are presented to enable a broad understanding of the requirements throughout the measurement process at Saab Aeronautics. The knowledge obtained in the literature review, case study and the measurement experiment was included in the measurement strategy framework which was the delivery of the thesis work.
405

Three-dimensional electromagnetic induction in thin sheets

Dawson, Trevor William 09 September 2016 (has links)
A fairly general method for studying electromagnetic induction in cases where any lateral variations in conductivity are confined to the near-surface region is developed using the thin-sheet technique. The significant feature is that extended anomalies, subject only to the restriction that well-defined two-dimensional problems are approached at infinity, can be handled. The approximate boundary condition is that gradients parallel to the coordinate axes vanish at infinity. / Graduate
406

Industrial Application of Three-dimensional Engineering Models to Development of Product Design and Its Relation to Industrial Arts Programs

Hocking, John S. 01 1900 (has links)
The problem encountered in this study was threefold: 1. To analyze the field of engineering models used in design studies and identify and define the way in which they are applied to product development. 2. To determine the degree and extent of skills and knowledge necessary for constructing engineering models. 3. To compare the skills and knowledge associated with model building to course content offered in industrial arts.
407

Existential Influences on the Use of Space by a Contemporary Painter

Carlman, Sandra Marcom 05 1900 (has links)
The aim of this study is to seek to determine the philosophic grounds which prompt this painter in particular to incorporate both two- and three-dimensional space within each painting.
408

A Comparison of Velocities Computed by Two-Dimensional Potential Theory and Velocities Measured in the Vicinity of an Airfoil

Copp, George 06 1900 (has links)
In treating the motion of a fluid mathematically, it is convenient to make some simplifying assumptions. The assumptions which are made will be justifiable if they save long and laborious computations in practical problems, and if the predicted results agree closely enough with experimental results for practical use. In dealing with the flow of air about an airfoil, at subsonic speeds, the fluid will be considered as a homogeneous, incompressible, inviscid fluid.
409

3D RECONSTRUCTION OF RyR1 AND STRUCTURAL VALIDATION UNDER DIFFERENT LEVELS OF NOISE

Lobo, Joshua J 01 January 2014 (has links)
Ryanodine receptors (RyR) are intracellular channels that are intricately involved in Ca2+ release. These channels large membrane proteins~2.26MDa in size. In this multi-goal project firstly we successfully studied the gating mechanics of the RyR1 in the presence of Mg2+. We used single particle reconstruction and image processing techniques to obtain the 3D structure of the RyR1 with Mg2+. The 3D structure in the presence of Mg2+ and an ATP analog is the closest representation of human physiological conditions. The open and closed state structures of RyR1 are known. However, the physiologically closed state has not been studied before. Understanding this structure will help in the understanding of protein interactions. Our second goal was the validation of this 3D structure under different levels of noise. Validation under different noise levels analyzed the problem of noise bias is present in the field of cryo-EM and single particle reconstruction in select cases.
410

Three dimensional image synthesis: theory and application

Adams, Charles N. 06 1900 (has links)
Approved for public release; distribution is unlimited. / Inverse Synthetic Aperture Radar (ISAR) provides full range detection and classification of sea and air based targets through two-dimensional range-Doppler imaging. The Naval Postgraduate School has developed a custom integrated circuit that can simulate false ISAR images in order to fool enemy ISAR platforms. To validate specific hardware choices within this design, this thesis explores the effect on image quality of an overflow occurring within the final 16-bit summation adder of this circuit. Three solutions to the problem of overflows are presented and analyzed. The logical extension of ISAR development, that of three-dimensional target imaging, is next presented through the discussion of 3D monopulse radar, 3D interferometric ISAR, and a 3D, three receiver ISAR. The relative strengths of each approach are compared, along with both MATLAB and X3D software models created for one specific 3D ISAR implementation. Through the superposition of 2D ISAR images it is shown how 3D ISAR images may be created. Moreover, emphasis is placed on using this knowledge to both enhance current 2D ISAR techniques and to modify the false-target chip to handle 3D ISAR return signals. The thesis concludes with a study of Non-Uniform Rational B-Splines, through which the X3D software model was created. / Ensign, United States Naval Reserve

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