Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 49 for “"Spatial Coherence"”.
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Spatial coherence and rough bottom scattering in shallow water
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.
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Spatial Coherence-Based Adaptive Acoustic Output Selection for Diagnostic Ultrasound
… as the measure of acoustic output, and lag-one coherence (LOC) was the image quality feedback parameter. LOC is the average spatial correlation between backscattered echoes received on neighboring ultrasound transducer array elements. Previous work has shown that LOC is predictive of local …
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Backscatter Spatial Coherence for Ultrasonic Image Quality Characterization: Theory and Applications
… explores the application of backscatter spatial coherence as an alternative image quality metric for adaptive imaging. Adaptive ultrasound methods applying spatial coherence feedback are evaluated in the context of three different applications: 1) the automated selection of acoustic …
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Temporal and Spatial Coherence: chronological and affective narrative within holographic and lenticular space.
The thesis for this practice-based study maintains that the Z and X axes of lenticular and holographic space can be used to store images chronologically, providing an audience with a new experience with affective and authentic impact. My contribution to knowledge has been to create a new element to …
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On The Use Of Variable Coherence In Inverse Scattering Problems
… sensing procedures, controlling the degree of coherence of light did not find wide applications until recently. Since the emergence of optical coherence tomography, a growing number of scattering techniques have relied on temporal coherence gating which provides efficient target selectivity in …
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Accelerated Ray Traced Animations Exploiting Temporal Coherence
… calculations. Both of these techniques exploit spatial coherence. These acceleration techniques are expanded not only to exploit spatial coherence but also to exploit temporal coherence in order to reduce calculations by treating animation information as a whole as opposed to isolating …
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Performance analysis of subaperture processing using a large aperture planar towed array
… main performance degradation mechanisms: limited spatial coherence of signals and nonstationarity of high bearing rate interference sources common in littoral regions of strategic importance. This thesis presents subarray processing as a method of improving passive detection performance using such …
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Four-Dimensional Coherence Sensing
… possible. Using the framework of optical spatial coherence theory, this thesis proposes and investigates new combinations of optics and algorithms with capabilities not possessed by standard lens-based cameras. This thesis proposes and demonstrates how cone-beam tomographic algorithms can …
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Efficient Array Processing for Partial Signal Coherence
… location comes the need to better understand the spatial properties of the received signals. To allow for simple and efficient implementation required in real-time processing applications, conventional array processing algorithms assume perfect coherence of the signal wavefronts. Unfortunately …
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Coherent flow power Doppler imaging
… imaging technique detects blood flow from the spatial coherence of the blood signal. The short-lag spatial coherence (SLSC) beamformer is used for the measurement of spatial coherence. Because blood signals and common noise sources, including thermal noise reverberation clutter, have different …
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1/f noise in semiconductors and metals
… Results bearing on the Gaussian nature and the spatial coherence of 1/f noise are also given. The discovery of thermally activated spectral features in the noise from silicon-on-sapphire (SOS) samples is documented. A model for the origin of 1/f noise in SOS and one for that in bismuth are …
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1/f noise in semiconductors and metals
… Results bearing on the Gaussian nature and the spatial coherence of l/f noise are also given. The discovery of thermally activated spectral features in the noise from silicon-on-sapphire (SOS) samples is documented. A model for the origin of l/f noise in SOS and one for that in bismuth are …
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Development of a Fourier Domain Low Coherence Interferometry Optical System for Applications in Early Cancer Detection
… of one such technique called Fourier domain low coherence interferometry (fLCI). </p><p>The presented work first describes a detailed analysis of temporal and spatial coherence. The study shows that temporal coherence information in time frequency distributions contains valuable structural …
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Probing Power-Absorbing Structures at Near-Infrared Wavelengths using Energy Absorption Interferometry
… A detector’s output can be written as the full spatial contraction of the external field correlation tensor and detector response correlation tensor representing their respective spatial coherence states; EAI recovers the latter, solely using power measurements. EAI is essentially a …
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Coherent X -Ray Diffraction
… for x-ray diffraction and from the temporal and spatial coherence of radiation. The antiphase domain structure of Cu 3Au is described, along with the associated reciprocal-space structure which is measured by CXD. CXD measurements place relatively stringent requirements on the coherence …
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157nm F₂laser characterization and application to polymer ablation
… limitations on surface roughness set by mode coherence effects. White light interferomety, and optical and scanning electron microscopy (SEM) measurements are carried out to identify the processing conditions for micron scale size structures (cones) produced on the surface, and the realization …
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Registration and variability of side scan sonar imagery
… This experiment also characterizes temporal and spatial coherence of intensity fluctuations. A third experiment is presented in which a side scan sonar towfish images the bottom adjacent to the pier while running along an underwater track which reduces towfish instability. Imagery from this …
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Three-dimensional nanofabrication of photonic crystals and polarization splitters and rotators
… Some requirements, such as nanometer-level spatial coherence, are beyond the capability of current semiconductor manufacturing.
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Cerebral Hemodynamics and Its Oxygenation: Study of Their Baseline and Spontaneous Oscillation
… vasomotion is temporally coherent as well as spatially coherent. The correlation lengths for temporal and spatial coherence are about 3min and 1--2 cm in our measurements. Cerebral vasomotion couples to brain activity by changing the phase of the oxy and deoxy-hemoglobin concentration waves to …
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Real-Time Stylized Rendering for Large-Scale 3D Scenes
… This task poses challenges in the form of spatial coherence, feature extraction, and stroke line rendering. Previous research on this topic has also struggled to overcome specific performance bottlenecks, which have limited use of this technology in real-time applications. Specifically, …
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