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Through-the-wall radar imaging (TWRI) and sensing is emerging as an important area of research and development. A TWRI system provides enhanced situational awareness in operational environments for a variety of civilian and military applications. In particular, a TWRI system facilitates realtime information gathering and intelligent decision-making about(More)
A data-adaptive stepped-frequency synthetic aperture radar system based on quadratically constrained Capon beamforming is presented for through-the-wall wideband microwave imaging applications. Various effects of the presence of the wall, such as refraction, change in speed, and attenuation, are incorporated into the beamformer design. Proof of concept is(More)
Stationary target detection in through-the-wall radar imaging (TWRI) using image segmentation techniques has recently been considered in the literature. Specifically, histogram thresholding methods have been used to aid in removing the clutter, resulting in ‘clean’ radar images with target regions only. In this paper, we show that histogram thresholding(More)
This study presents a new scheme for performing integration point constitutive updates for anisotropic, small strain, non-linear viscoelasticity, within the context of implicit, non-linear "nite element structural analysis. While the basic scheme has been presented earlier by the authors for linear viscoelasticity, the present work illustrates the(More)
In this paper, we demonstrate the micro-Doppler signatures of rotational/vibrational targets enduring simple harmonic motions (SHM). The SHM, whether it represents vibrations or rotations, induces frequency modulations on radar returns. The returns capture certain extrinsic motion characteristics of the target which have a sinusoidal instantaneous(More)
In this paper, we examine the use of image segmentation approaches for target detection in TWRI. The betweenclass variance thresholding, entropy-based segmentation, and Kmeans clustering are applied to segment target and clutter regions. Real 2D polarimetric images are used to demonstrate that simple histogram-based segmentation methods produce either(More)
This paper presents a finite element formulation for analyzing interlaminar stress fields in nonlinear viscoelastic laminated composites. The hygrothermal analysis is also included in the formulation and numerical results are compared against experimental data. Excellent agreement is obtained between these results. Using the present formulation, inplane and(More)
Finite element analyses are utilized on a CRAY T94 to calculate hygrothermally induced anisotropic viscoelastic deformations and stresses in plastic IC packages during surface mounting processes, which is an interdisciplinary coupled hygro-thermo-structure interaction problem. The subroutine for element stiffness calculation is dominated by vector(More)
In this paper, we propose a Gaussian mixture model (GMM) based approach to discriminate stationary humans from their ghosts and clutter in indoor radar images. More specifically, we use a mixture of Gaussian distributions to model the image intensity histograms corresponding to target and ghost/clutter regions. The mixture parameters, namely, the means,(More)
This paper demonstrates the effectiveness of narrowband source localization techniques in indoor environments. Experiments are conducted using multiple antennas and a network analyzer. An active RF source is placed at different locations in a medium-sized office. Three sensors, placed at known positions, are used to estimate the location of the source using(More)