Retrieval of Parameters for Layered non-Smooth Interface Media: Theory and Experiment.

Many naturally occurring or manmade objects can be modeled as three layer media with non-smooth interfaces. Most of the existing forward and inverse scattering models that can be applied to such media are either too inefficient or have limited regions of validity. In this dissertation an efficient forward scattering model based on the Extended Boundary Condition Method is developed for a three layer medium. The boundary between the first and the second layers is periodic while the boundary between the second and third layers is rough. The model is then extended by including an arbitrarily shaped cylinder placed into the third layer. Both TM and TE polarizations and PEC and Dielectric cylinder cases are considered. The Method of Moments (MOM) is used to obtain an impedance matrix, which is then transformed into a T-matrix. The T-matrix is transformed into a scattering matrix and cascaded with scattering matrices for the periodic and rough interfaces to obtain a generalized scattering matrix for the total system. A solution to the inverse problem for a three-layer medium is developed using simulated radar data. The retrieval of the layered- medium parameters is accomplished by sequential nonlinear optimizaxiii tion starting from the top layer and progressively characterizing the layers below. The optimization process is achieved by an efficient iterative technique built around the solution of the forward scattering problem. To be efficiently utilized in the inverse problem, the forward scattering model is simulated over a wide range of unknowns to obtain a complete set of subspace-based equivalent closed-form models that relate radar backscattering coefficients to the sought-for parameters, including the dielectric constants of each layer and the thickness of the middle layer. The inversion algorithm is implemented as a modified conjugate-gradient-based nonlinear optimization. It is shown that this technique results in accurate retrieval of surface and subsurface parameters, even in the presence of noise. To validate forward and inverse scattering models, a compact tower-based radar system is built. The data collected with the instrument is used to demonstrate sensitivity of radar measurements to changes in soil moisture and the potential for estimating surface and subsurface parameters.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89647/1/yuriy_1.pd

CHANNEL MODELING FOR FIFTH GENERATION CELLULAR NETWORKS AND WIRELESS SENSOR NETWORKS

In view of exponential growth in data traffic demand, the wireless communications industry has aimed to increase the capacity of existing networks by 1000 times over the next 20 years. A combination of extreme cell densification, more bandwidth, and higher spectral efficiency is needed to support the data traffic requirements for fifth generation (5G) cellular communications. In this research, the potential improvements achieved by using three major 5G enabling technologies (i.e., small cells, millimeter-wave spectrum, and massive MIMO) in rural and urban environments are investigated. This work develops SPM and KA-based ray models to investigate the impact of geometrical parameters on terrain-based multiuser MIMO channel characteristic. Moreover, a new directional 3D channel model is developed for urban millimeter-wave (mmW) small cells. Path-loss, spatial correlation, coverage distance, and coherence length are studied in urban areas. Exploiting physical optics (PO) and geometric optics (GO) solutions, closed form expressions are derived for spatial correlation. Achievable spatial diversity is evaluated using horizontal and vertical linear arrays as well as planar 2D arrays. In another study, a versatile near-ground field prediction model is proposed to facilitate accurate wireless sensor network (WSN) simulations. Monte Carlo simulations are used to investigate the effects of antenna height, frequency of operation, polarization, and terrain dielectric and roughness properties on WSNs performance

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal

College of Engineering

Cornell University Courses of Study Vol. 102 2010/201

College of Engineering

Cornell University Courses of Study Vol. 102 2010/201