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 99 for “"rough surface"”.
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Kirchhoff approximation for rough surface scattering
Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 1993
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Applications of numerical models for rough surface scattering
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.
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Rough Surface Interactions of Micro/nano-Scale Contact Systems
… and elastic modulus values. Second, an improved rough surface contact model suitable for miniature systems has been developed accounting for both asperity and substrate deformation during contact. Compared to a representative asperity-based contact model, it was found that the proposed model is …
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The Monte Carlo techniques with pulse compression for rough surface scattering
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering, 1996.
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Rough surface scattering under Gaussian beam illumination and the Kirchhoff approximation
… this thesis, an analysis of the scattering of a rough perfect electric conductor (PEC) surface under illumination by a Gaussian beam using the Kirchhoff approximation is presented. The analysis assumes a source distribution which yields a Gaussian beam solution as a radiated field. This field is …
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Rough Surface Scattering and Propagation over Rough Terrain in Ducting Environments
The problem of rough surface scattering and propagation over rough terrain in ducting environments has been receiving considerable attention in the literature. One popular method of modeling this problem is the parabolic wave equation (PWE) method. In this method, the Helmholtz wave equation is …
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Effect of correlation between shadowing and shadowed points in rough surface scattering
Shadowing of random surfaces is accounted for by multiplying the Kirchhoff electric current density by a shadowing function. The shadow-corrected incoherent intensity is computed in the backscatter direction and is found to be proportional to the probability of a specular point being illuminated …
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Heat Transfer Analysis of an Oblique Jet Impingement Cooling on CMC Rough Surface
… cooling will still likely be required. The surface of the CMC varies significantly from traditional super-alloy used in a modern engine, with large level of roughness and significant three-dimensional waviness. These complex features will impact the behavior of the near wall flows, and …
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A Curvature-Corrected Rough Surface Scattering Theory Through The Single-Scatter Subtraction Method
… is presented to study radio propagation and rough surface scattering problems based on a reformulation of the Magnetic Field Integration Equation (MFIE) called the Single-Scatter Subtraction (S^3) method. This technique amounts to a physical preconditioning by separating the single- and …
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A Study of Rough Surface Scattering Phenomena in the LMDS Band (28 GHz)
… from each power delay profile to analyze the rough surface scattering phenomena. We found that limestone and brick walls exhibited some diffuse scattering. The reflected pulse of a limestone wall had more maximum excess delay spread than did a brick wall at -15dB power threshold. The mean …
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Statistical approach for determining the extent of an oil spill over a rough surface.
Massachusetts Institute of Technology. Dept. of Mechanical Engineering. Thesis. 1972. M.S.
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Efficient integral equation based algorithms for parasitic extraction of interconnects with smooth or rough surface
… The program is based on a recently developed surface integral formulation and a Pre-corrected FFT accelerated iterative method, but includes a new piecewise quadrature panel integration scheme, a new scaling and preconditioning technique as well as a generalized grid interpolation and …
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Numerical study on the validity of the quasi-specular and two-scale models for rough surface parameter estimation: one dimensional surfaces
… and two-scale models in estimating rough surface parameters from the average radar cross section of randomly rough surfaces, with the goal of understanding what scattering mechanisms limit their applicability. The ranges of validity of these models are ascertained by comparing the …
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ΣΚΕΔΑΣΗ ΗΛΕΚΤΡΟΜΑΓΝΗΤΙΚΟΥ ΚΥΜΑΤΟΣ ΑΠΟ ΑΓΩΓΙΜΗ ΕΠΙΦΑΝΕΙΑ ΣΤΟΧΑΣΤΙΚΑ ΑΝΩΜΑΛΗ ΚΑΙ ΧΡΟΝΙΚΑ ΜΕΤΑΒΑΛΛΟΜΕΝΗ
… PLANE ELECTROMAGNETIC WAVES FROM RANDOMLY UNEVEN SURFACES ISTHEORETICALLY INVESTIGATED BY USING MORE COMPLICATED MODELS FOR THE SCATTERING SURFACE. IN THE FIRST PART OF THE WORK A TIME-VARYING RANDOM ROUGH SURFACE IS EXAMINED. THE STOCHASTIC PROCESS, THAT DESCRIBES THE ELEVATION FROM ITS …
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Modeling of conductor surface roughness effect
Conductor surface roughness effect refers to the influence of surface roughness on the current flow inside a conductor and the subsequent effect on electromagnetic properties of the conductor. The existence of surface roughness on a conductor disturbs current flow and results in a higher than usual …
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An Investigation on the Effect of Ground Plane Roughness on Antenna Radiation Characteristics
… both a flat ground plane and a randomly-varying rough surface. The Method of Moments with the Electric Field Integral Equation (EFIE) is used to account for all coupling interactions. Monte Carlo averaging is used to compute results over multiple rough surface realizations, which follow the …
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MULTI-SCALE DYNAMICS OF MECHANICAL SYSTEMS WITH FRICTION
Contact between rough surfaces occurs in numerous engineering systems and in many instances influences the macro behavior of the system. In many instances, the interaction between rough surfaces, affect the macro behavior of the system. Effective treatment of systems containing rough surface …
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Propagation and Scattering of Waves by Terrain Features
… and scattering of waves. It begins with the rough knife obstruction case, moves into rough surfaces and finally concludes with several approaches to a foliage covered rough surface. Each of these problems is encountered in radar, remote sensing and communication systems. The first topic in …
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Efficient Spectral-Element Methods For Acoustic Scattering And Related Problems
… 2) the scattering from doubly layered, unbounded rough surface. For both cases, we first apply the transformed field expansion (TFE) method to reduce the two-dimensional Helmholtz equation with complex scattering surface into a successive sequence of the transmission problems with a plane …
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Interfaces in disordered media. Scaling growth, avalanche dynamics, and microfluidic fronts
… to classify the <i>scaling growth</i> of a rough surface in terms of <i>universality classes</i> has become a considerably ambitious task, not to say impossible in some cases. <br></br><br></br> This is particularly true, for instance, in the problem of a fluid filling a disordered medium …
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