scholarly journals Determination of Lateral Modulation Apodization Functions Using a Regularized, Weighted Least Squares Estimation

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
Chikayoshi Sumi
Keyword(s):  
Least Squares ◽  
Spatial Resolution ◽  
Soft Tissues ◽  
Displacement Vector ◽  
Weighted Least Squares ◽  
Strain Tensor ◽  
Estimation Method ◽  
Modulation Method ◽  
Value Decomposition

Recently, work in this group has focused on the lateral cosine modulation method (LCM) which can be used for next-generation ultrasound (US) echo imaging and tissue displacement vector/strain tensor measurements (blood, soft tissues, etc.). For instance, in US echo imaging, a high lateral spatial resolution as well as a high axial spatial resolution can be obtained, and in tissue displacement vector measurements, accurate measurements of lateral tissue displacements as well as of axial tissue displacements can be realized. For an optimal determination of an apodization function for the LCM method, the regularized, weighted minimum-norm least squares (WMNLSs) estimation method is presented in this study. For designed Gaussian-type point spread functions (PSFs) with lateral modulation as an example, the regularized WMNLS estimation in simulations yields better approximations of the designed PSFs having wider lateral bandwidths than a Fraunhofer approximation and a singular-value decomposition (SVD). The usefulness of the regularized WMNLS estimation for the determination of apodization functions is demonstrated.

Submicrometre-resolution polychromatic three-dimensional X-ray microscopy

2012 ◽  
Vol 46 (1) ◽  
pp. 153-164 ◽  
Author(s):  
B. C. Larson ◽  
L. E. Levine
Keyword(s):  
Spatial Resolution ◽  
Elastic Strain ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Direct Determination ◽  
Phase Identification ◽  
Sn Whisker ◽  
X Ray ◽  
Elastic Strain Tensor

The ability to study the structure, microstructure and evolution of materials with increasing spatial resolution is fundamental to achieving a full understanding of the underlying science of materials. Polychromatic three-dimensional X-ray microscopy (3DXM) is a recently developed nondestructive diffraction technique that enables crystallographic phase identification, determination of local crystal orientations, grain morphologies, grain interface types and orientations, and in favorable cases direct determination of the deviatoric elastic strain tensor with submicrometre spatial resolution in all three dimensions. With the added capability of an energy-scanning incident beam monochromator, the determination of absolute lattice parameters is enabled, allowing specification of the complete elastic strain tensor with three-dimensional spatial resolution. The methods associated with 3DXM are described and key applications of 3DXM are discussed, including studies of deformation in single-crystal and polycrystalline metals and semiconductors, indentation deformation, thermal grain growth in polycrystalline aluminium, the metal–insulator transition in nanoplatelet VO2, interface strengths in metal–matrix composites, high-pressure science, Sn whisker growth, and electromigration processes. Finally, the outlook for future developments associated with this technique is described.

A Novel Degree of Observability Used for Measurement Selections in Gas Path Diagnostics

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Xingxing Pu ◽  
Shangming Liu ◽  
Hongde Jiang ◽  
Daren Yu
Keyword(s):  
Gas Turbine ◽  
Weighted Least Squares ◽  
Estimation Method ◽  
Estimation Accuracy ◽  
Heavy Duty ◽  
Weighted Least Squares Estimation ◽  
Heavy Duty Gas Turbine ◽  
Value Decomposition ◽  
High Degree ◽  
Degree Of Observability

A novel method for measurement selections of gas path diagnostics has been developed. This method is based on the singular value decomposition of the observability matrix of linear systems, which are a good approximation of the nonlinear ones for small deviations. It also employs the concept of the degree of observability to formulate the criteria. The states with high degree of observability and the measurement sets with high overall degree of observability result in high estimation accuracy in gas path diagnostics. A heavy-duty gas turbine model is used to validate this method. The influence of the gas turbine nonlinearity, the measurement noise, and the overdetermined measurement on degree of observability is analyzed. The overall degree of observability is calculated for different measurement sets of heavy-duty gas turbine. The gas path diagnostics simulations with different measurement sets using the weighted least-squares estimation method and the extended Kalman filter are conducted. The quality of gas path diagnostics simulation with different measurement sets is assessed and the results demonstrate the capability of the developed method for measurement selections in gas path diagnostics.

Determination of the Regional Function of the Heart

2002 ◽  
Author(s):  
Evren U. Azeloglu ◽  
Glenn R. Gaudette ◽  
Irvin B. Krukenkamp ◽  
Fu-Pen Chiang
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Speckle Pattern ◽  
Strain Tensor ◽  
Ccd Camera ◽  
Speckle Interferometry ◽  
Left Ventricular ◽  
Stroke Work ◽  
Regional Function

Unlike many other engineering designs, the heart, a pressure vessel, shows variations within its chambers and surface in terms of mechanical function. This necessitates a whole field technique with high spatial resolution. Computer aided speckle interferometry (CASI), a nondestructive examination technique, is herein developed for this purpose. A speckle pattern was created on the surface of isolated rabbit hearts. Images of the beating hearts werc acquired with a charge-couple device (CCD) camera for one second at a rate of 50 frames per second. CASI was used to determine the 2-D displacement vectors over regions of approximately 4 × 6 mm. Regional area stroke work (the integral of the left ventricular pressure with respect to area), the first invariant of the 2-D strain tensor, and the principle strains were used to determine the regional function. After occluding the blood supply to a region of the heart, significant changes were detected in all the previously mentioned parameters. Commonly used techniques cannot determine 2-D strain and lack the high spatial resolution of CASI. Determination of the 2-D strain can provide useful data on the functionality of the heart.

Sign in / Sign up

Export Citation Format

Share Document