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.
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Showing 1 to 20 of 21 for “"Angular spectrum"”.
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Angular spectrum measurements of an underwater optical communication channel.
Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
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ΣΚΕΔΑΣΗ ΗΛΕΚΤΡΟΜΑΓΝΗΤΙΚΟΥ ΚΥΜΑΤΟΣ ΑΠΟ ΑΓΩΓΙΜΗ ΕΠΙΦΑΝΕΙΑ ΣΤΟΧΑΣΤΙΚΑ ΑΝΩΜΑΛΗ ΚΑΙ ΧΡΟΝΙΚΑ ΜΕΤΑΒΑΛΛΟΜΕΝΗ
… SURFACE STATISTICS. ON THE OTHER HAND THE ANGULAR SPECTRUM OF THE FIRST-ORDER SCATTERING CROSS SECTION PER UNIT AREA OF A STATIONARY AND NONHOMOGENEOUS ROUGH SURFACE IS PROVEN TO BE PROPORTIONAL TO THE AVERAGE OF ITS POSITION-VARYINGSPATIAL-TEMPORAL WAVENUMBER SPECTRUM. (SHORTENED)
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Fast estimation model of pressure-temperature response for planning focused ultrasound surgery
… method. When compared with the Angular Spectrum method, these errors are 0.50%, 1.00% and 0.77%, respectively. For heterogeneous viscera, kidney and pancreas tissues, average percentages of error in pressure estimation compared to Rayleigh-Sommerfeld method are 0.10%, 0.05% and …
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A three-dimensional coupled modes solution for range-dependent waveguides
… (2) that energy is propagating within a limited angular spectrum around the main propagation direction. The last category of models based on finite-difference and finite-element solutions of the full wave equation([22]) is well suited for providing solutions for propagation in general …
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Synthesis of Optimal Arrays For MIMO and Diversity Systems
… maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the power radiated by each antenna as well as the level of supergain allowed …
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A study of stone fragmentation in shock wave lithotripsy by customizing the acoustic field and waveform shape
… customization was achieved by employing the angular spectrum approach for modeling the forward wave propagation and regression of least square errors to determine the optimal set of delays. Results from the acoustic field customization routine and its implications on stone fragmentation will …
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Paraxial approximations for ultrasonic beam propagation in liquid and solid media with applications to nondestructive evaluation
… eigenfunctions. Both models are derived from the angular spectrum of plane waves approach and have made use of the paraxial, or Fresnel, approximation. The latter, more general, Gauss-Hermite model is validated by comparison with experimentally mapped ultrasonic beam fields in a range of …
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Optical Characterisation of Astronomical Submillimetre Receivers including ALMA Bands 5 and 9
… diffraction patterns is developed using the Angular Spectrum of Plane Waves (ASPW). The general GBMA technique is supplemented by the commercially available Physical Optics (PO) package GRASP9 developed by TICRA. A comprehensive analysis of the ALMA Band 5 front end optics was conducted in …
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Development of a discrete numerical approach to the Fredholm Integral Method for evaluating microwave scattering by irregular hydrometeors
… the spatial frequency domain. As a result, the angular scattering pattern is strongly connected to the Spatial Fourier Transform of the scatterer; hence, for electrically small particles the angular spectrum is relatively smooth and the number of pivots required for integration is relatively …
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Assessment and Diagnosis of Human Colorectal and Ovarian Cancer using Optical Imaging and Computer-aided Diagnosis
… (OCT) system. A novel feature called the angular spectrum index quantifies the scattering coefficient distribution. In addition to scattering, subsurface morphological changes are also associated with the development of colorectal cancer. We have observed a specific mucosa structure …
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Reconstruction Resolution Of Coherent Point Sources With Helmholtz Equation Least Squares
… and its affect on the definition of SNR and the angular spectrum. However, HELS, and in particular Modified HELS, show a significant increase in accuracy in comparison to Fourier Acoustics for the parameters tested.</p> <p>The main conclusion of this dissertation is that Standard and Modified …
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Intensyvių femtosekundinių šviesos bangų paketų sklidimo Kero terpėse laikinis ir erdvinis charakterizavimas /
… normal group velocity dispersion the far-field angular spectrum of the wave packet takes a characteristic X shape, whereas in anomalous group velocity dispersion regime – a characteristic O shape. In both cases the localization of the wave packet is observed, however the quantitative differences …
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Investigation of plenoptic imaging systems: a wave optics approach
… developing an original method derived from the angular spectrum of plane waves theory of propagation. The second was implemented using a phase mask. The code was developed to optimize the signal to noise ratio and the computational time. Two different configurations of plenoptic imaging systems …
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Ultrasound Wave Patterning for Spatiotemporal Control of Acoustic Power Transfer: Pathways from Transmission to Reception
… inverse design method called the Iterative Angular Spectrum Approach (IASA) is applied for the first time for elastic wave manipulation, overcoming the limitations of the conventional forward design methods. This technique helps create advanced materials known as elastic metasurfaces, which …
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Characterization of liquid crystal on silicon SLMs for in-situ Raman imaging for quality control of processed lunar regolith
… integrated into a wavefront simulation using the Angular Spectrum Method (ASM). The model was verified using an analog optical laboratory setup. By combining results from the model and Raman measurements on vitrified regolith simulant material (LRS), a mission envelope of a sample area with a …
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Evaluation of Millimetre-wave Coherent Scattering from a Sea surface covered by Foam modelled as Sequences of Thin Phase-Scattering Screens using Split-Step Fourier Method
… from the split-step Fourier method represent the angular spectrum as a distorted wavefront and field intensity at the sea surface after forward and backward propagation for thin and deep phase screens. The attenuation in dB and specific attenuation (dB/mm) for incident angles θi = 30◦,45◦ and 60◦ …
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On The Use Of Variable Coherence In Inverse Scattering Problems
… wavelength, polarization, wavefront curvature or angular spectrum, have been commonly manipulated in a variety of remote 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 …
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Trans-skull Ultrasound for Imaging and Therapy
Ultrasound has emerged as a novel modality for the treatment and imaging of brain diseases. When enhanced by circulating microbubble agents, which scatter sound and vibrate in response to the incident ultrasound, it can enable a range of new therapeutic interventions and open new possibilities for …
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Diffraction-based Optical Architectures for Processing One-dimensional Data
… Fresnel and Fraunhofer approximations, and angular spectrum formulations, with the Fourier relationships between various formulations elucidated. Results are expanded further to extend the range of applicability of the planar Rayleigh-Sommerfeld diffraction formulae to arbitrary boundary …
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Talbotův jev
Táto bakalárska práca sa zaoberá teoretickým modelovaním a experimentálnym overením frakčného Talbotovho javu na dvojosových mriežkach. Hlavným cieľom bolo vytvoriť dva výpočtové programy v prostredí Python: analytický model využívajúci Gaussove sumy a numerický model založený na metóde uhlového …
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