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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.
151

Image Reconstruction Based On Hilbert And Hybrid Filtered Algorithms With Inverse Distance Weight And No Backprojection Weight

Narasimhadhan, A V 08 1900 (has links) (PDF)
Filtered backprojection (FBP) reconstruction algorithms are very popular in the field of X-ray computed tomography (CT) because they give advantages in terms of the numerical accuracy and computational complexity. Ramp filter based fan-beam FBP reconstruction algorithms have the position dependent weight in the backprojection which is responsible for spatially non-uniform distribution of noise and resolution, and artifacts. Many algorithms based on shift variant filtering or spatially-invariant interpolation in the backprojection step have been developed to deal with this issue. However, these algorithms are computationally demanding. Recently, fan-beam algorithms based on Hilbert filtering with inverse distance weight and no weight in the backprojection have been derived using the Hamaker’s relation. These fan-beam reconstruction algorithms have been shown to improve noise uniformity and uniformity in resolution. In this thesis, fan-beam FBP reconstruction algorithms with inverse distance back-projection weight and no backprojection weight for 2D image reconstruction are presented and discussed for the two fan-beam scan geometries -equi-angular and equispace detector array. Based on the proposed and discussed fan-beam reconstruction algorithms with inverse distance backprojection and no backprojection weight, new 3D cone-beam FDK reconstruction algorithms with circular and helical scan trajectories for curved and planar detector geometries are proposed. To start with three rebinning formulae from literature are presented and it is shown that one can derive all fan-beam FBP reconstruction algorithms from these rebinning formulae. Specifically, two fan-beam algorithms with no backprojection weight based on Hilbert filtering for equi-space linear array detector and one new fan-beam algorithm with inverse distance backprojection weight based on hybrid filtering for both equi-angular and equi-space linear array detector are derived. Simulation results for these algorithms in terms of uniformity of noise and resolution in comparison to standard fan-beam FBP reconstruction algorithm (ramp filter based fan-beam reconstruction algorithm) are presented. It is shown through simulation that the fan-beam reconstruction algorithm with inverse distance in the backprojection gives better noise performance while retaining the resolution properities. A comparison between above mentioned reconstruction algorithms is given in terms of computational complexity. The state of the art 3D X-ray imaging systems in medicine with cone-beam (CB) circular and helical computed tomography scanners use non-exact (approximate) FBP based reconstruction algorithm. They are attractive because of their simplicity and low computational cost. However, they produce sub-optimal reconstructed images with respect to cone-beam artifacts, noise and axial intensity drop in case of circular trajectory scan imaging. Axial intensity drop in the reconstructed image is due to the insufficient data acquired by the circular-scan trajectory CB CT. This thesis deals with investigations to improve the image quality by means of the Hilbert and hybrid filtering based algorithms using redundancy data for Feldkamp, Davis and Kress (FDK) type reconstruction algorithms. In this thesis, new FDK type reconstruction algorithms for cylindrical detector and planar detector for CB circular CT are developed, which are obtained by extending to three dimensions (3D) an exact Hilbert filtering based FBP algorithm for 2D fan-beam beam algorithms with no position dependent backprojection weight and fan-beam algorithm with inverse distance backprojection weight. The proposed FDK reconstruction algorithm with inverse distance weight in the backprojection requires full-scan projection data while the FDK reconstruction algorithm with no backprojection weight can handle partial-scan data including very short-scan. The FDK reconstruction algorithms with no backprojection weight for circular CB CT are compared with Hu’s, FDK and T-FDK reconstruction algorithms in-terms of axial intensity drop and computational complexity. The simulation results of noise, CB artifacts performance and execution timing as well as the partial-scan reconstruction abilities are presented. We show that FDK reconstruction algorithms with no backprojection weight have better noise performance characteristics than the conventional FDK reconstruction algorithm where the backprojection weight is known to result in spatial non-uniformity in the noise characteristics. In this thesis, we present an efficient method to reduce the axial intensity drop in circular CB CT. The efficient method consists of two steps: the first one is reconstruction of the object using FDK reconstruction algorithm with no backprojection weight and the second is estimating the missing term. The efficient method is comparable to Zhu et al.’s method in terms of reduction in axial intensity drop, noise and computational complexity. The helical scanning trajectory satisfies the Tuy-smith condition, hence an exact and stable reconstruction is possible. However, the helical FDK reconstruction algorithm is responsible for the cone-beam artifacts since the helical FDK reconstruction algorithm is approximate in its derivation. In this thesis, helical FDK reconstruction algorithms based on Hilbert filtering with no backprojection weight and FDK reconstruction algorithm based on hybrid filtering with inverse distance backprojection weight are presented to reduce the CB artifacts. These algorithms are compared with standard helical FDK in-terms of noise, CB artifacts and computational complexity.
152

Performance Evaluation Of Fan-beam And Cone-beam Reconstruction Algorithms With No Backprojection Weight On Truncated Data Problems

Sumith, K 07 1900 (has links) (PDF)
This work focuses on using the linear prediction based projection completion for the fan-beam and cone-beam reconstruction algorithm with no backprojection weight. The truncated data problems are addressed in the computed tomography research. However, the image reconstruction from truncated data perfectly has not been achieved yet and only approximately accurate solutions have been obtained. Thus research in this area continues to strive to obtain close result to the perfect. Linear prediction techniques are adopted for truncation completion in this work, because previous research on the truncated data problems also have shown that this technique works well compared to some other techniques like polynomial fitting and iterative based methods. The Linear prediction technique is a model based technique. The autoregressive (AR) and moving average (MA) are the two important models along with autoregressive moving average (ARMA) model. The AR model is used in this work because of the simplicity it provides in calculating the prediction coefficients. The order of the model is chosen based on the partial autocorrelation function of the projection data proved in the previous researches that have been carried out in this area of interest. The truncated projection completion using linear prediction and windowed linear prediction show that reasonably accurate reconstruction is achieved. The windowed linear prediction provide better estimate of the missing data, the reason for this is mentioned in the literature and is restated for the reader’s convenience in this work. The advantages associated with the fan-beam reconstruction algorithms with no backprojection weights compared to the fan-beam reconstruction algorithm with backprojection weights motivated us to use the fan-beam reconstruction algorithm with no backprojection weight for reconstructing the truncation completed projection data. The results obtained are compared with the previous work which used conventional fan-beam reconstruction algorithms with backprojection weight. The intensity plots and the noise performance results show improvements resulting from using the fan-beam reconstruction algorithm with no backprojection weight. The work is also extended to the Feldkamp, Davis, and Kress (FDK) reconstruction algorithm with no backprojection weight for the helical scanning geometry and the results obtained are compared with the FDK reconstruction algorithm with backprojection weight for the helical scanning geometry.
153

The Controversial Identity of Flamenco Jazz: A New Historical and Analytical Approach

Pamies, Sergio, 1983- 05 1900 (has links)
There are certain recordings by important artists such as Lionel Hampton, Miles Davis, John Coltrane, Pedro Iturralde, Chick Corea, and Paco de Lucía, among others, that have been associated with the label flamenco jazz. This label is entering jazz discourse, and it needs to be better understood in order to clarify its history, its identity, and its impact on recent developments in flamenco that are labeled nuevo flamenco. There is a lack of agreement in the existent literature on flamenco jazz on the evaluation of these recordings and these artists' achievements and contributions to this field. These writings encompass authors from different backgrounds: journalists, critics, and musicologists, who have approached their analysis of the recordings from different perspectives. The differences in professional backgrounds, approaches, and purpose of the writings of these authors has resulted in controversy about this label. Therefore, the flamenco jazz scholarly conversation needs more objective writings from an analytical point of view. This historiographical study presents a more comprehensive evaluation of flamenco jazz by discussing selected recordings using analytical tools from jazz studies. These analytical arguments clarify the aesthetics of flamenco jazz and the artistic processes that these artists went through when combining musical elements from flamenco and jazz, which in some cases are described as creative misreading. In this century of cultural globalization, where jazz has become a diverse expression of world music because of its capacity to absorb traits from other musical practices, this study can be a resource for international jazz musicians who are seeking to combine jazz with their musical cultural heritage.
154

Sonic Overlook: Blackness between Sound and Image

Linscott, Charles P. 17 September 2015 (has links)
No description available.
155

What Is at Stake in Jazz Education? Creative Black Music and the Twenty-First-Century Learning Environment

Goecke, Norman Michael 27 September 2016 (has links)
No description available.
156

“The Best Possible Time for War?” The USS Panay and American Far Eastern Policy During the Roosevelt Presidency

Schnurr, Jeremy 13 December 2011 (has links)
This thesis examines American Far Eastern policy from the beginning of the Franklin Roosevelt presidency through the early months of 1938. This study is chiefly concerned with the attack by Japanese aircraft on the USS Panay and its effect on the course of U.S. foreign policy. Particular attention is paid to the Anglo-American dialogue which occurred throughout the Far Eastern Crisis. Prior to the end of 1938, the U.S. administration’s position in Asia was dictated both by policies inherited from preceding administrations and by the extreme isolationism of the American people. This foundation effectively inhibited any cooperation with foreign powers. Relying on a reactive policy in the Far East, Washington remained aloof from entanglement as the President sought a plan which would permit U.S. involvement without inviting isolationist wrath. This paper traces an evolution in American Far Eastern policy, highlighting the Panay incident as a distinctly identifiable turning point whereby isolationism gave way to internationalism.
157

“The Best Possible Time for War?” The USS Panay and American Far Eastern Policy During the Roosevelt Presidency

Schnurr, Jeremy 13 December 2011 (has links)
This thesis examines American Far Eastern policy from the beginning of the Franklin Roosevelt presidency through the early months of 1938. This study is chiefly concerned with the attack by Japanese aircraft on the USS Panay and its effect on the course of U.S. foreign policy. Particular attention is paid to the Anglo-American dialogue which occurred throughout the Far Eastern Crisis. Prior to the end of 1938, the U.S. administration’s position in Asia was dictated both by policies inherited from preceding administrations and by the extreme isolationism of the American people. This foundation effectively inhibited any cooperation with foreign powers. Relying on a reactive policy in the Far East, Washington remained aloof from entanglement as the President sought a plan which would permit U.S. involvement without inviting isolationist wrath. This paper traces an evolution in American Far Eastern policy, highlighting the Panay incident as a distinctly identifiable turning point whereby isolationism gave way to internationalism.
158

“The Best Possible Time for War?” The USS Panay and American Far Eastern Policy During the Roosevelt Presidency

Schnurr, Jeremy 13 December 2011 (has links)
This thesis examines American Far Eastern policy from the beginning of the Franklin Roosevelt presidency through the early months of 1938. This study is chiefly concerned with the attack by Japanese aircraft on the USS Panay and its effect on the course of U.S. foreign policy. Particular attention is paid to the Anglo-American dialogue which occurred throughout the Far Eastern Crisis. Prior to the end of 1938, the U.S. administration’s position in Asia was dictated both by policies inherited from preceding administrations and by the extreme isolationism of the American people. This foundation effectively inhibited any cooperation with foreign powers. Relying on a reactive policy in the Far East, Washington remained aloof from entanglement as the President sought a plan which would permit U.S. involvement without inviting isolationist wrath. This paper traces an evolution in American Far Eastern policy, highlighting the Panay incident as a distinctly identifiable turning point whereby isolationism gave way to internationalism.
159

“The Best Possible Time for War?” The USS Panay and American Far Eastern Policy During the Roosevelt Presidency

Schnurr, Jeremy January 2012 (has links)
This thesis examines American Far Eastern policy from the beginning of the Franklin Roosevelt presidency through the early months of 1938. This study is chiefly concerned with the attack by Japanese aircraft on the USS Panay and its effect on the course of U.S. foreign policy. Particular attention is paid to the Anglo-American dialogue which occurred throughout the Far Eastern Crisis. Prior to the end of 1938, the U.S. administration’s position in Asia was dictated both by policies inherited from preceding administrations and by the extreme isolationism of the American people. This foundation effectively inhibited any cooperation with foreign powers. Relying on a reactive policy in the Far East, Washington remained aloof from entanglement as the President sought a plan which would permit U.S. involvement without inviting isolationist wrath. This paper traces an evolution in American Far Eastern policy, highlighting the Panay incident as a distinctly identifiable turning point whereby isolationism gave way to internationalism.
160

The Surprising Role of Legal Traditions in the Rise of Abolitionism in Great Britain’s Development

Buchsbaum, Robert Michael, III January 2014 (has links)
No description available.

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