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This work presents a mathematical approach for recovering a physical model from a low-rank approximation of measured data obtained via the singular value decomposition (SVD). The general form of a low-rank physical model of the data is often known, so the presented approach learns the proper rotation and scaling matrices from the singular vectors and singular values of the SVD in order to recover...
Full waveform inversion (FWI) delivers high-resolution images of a subsurface medium property by minimizing itera-tively the misfit between observed and simulated seismic data, and is commonly used by the oil and gas industry for geophysical exploration. FWI is a challenging problem because seismic surveys cover ever larger areas of interest and collect massive volumes of data. The dimensionality...
An accurate and fast estimation of microseismic activities from passive microseismic data is a crucial issue to many oil and gas applications. Traditional methods are mainly based on manual picking of the arrival times which require a relative high signal-to-noise ratio (SNR) to produce reliable results. When the sensor array is deployed on the surface, the microseismic events have low magnitude and...
This work focuses on parametric sparse sensing models and looks to improve ℓ1 regularization results when the model dictionary is strongly coherent and/or regularization parameters are unknown. The singular value decomposition (SVD) of the model's dictionary matrix is used to construct signal and noise subspaces. A method that uses the measurements to automatically optimize the subspace division along...
This paper describes a review model for an on-line question and answer (Q&A) system whose objective is to personalize student's study review session in order to improve user conceptual proficiency and limit the number of necessary review questions based on individual and class performance data. The Question Review Model (QRM) structures study review for each user by prioritizing a list of critical...
This paper proposes a novel interference-resistant receiver for wideband long-term evolution (LTE) system which employs orthogonal frequency division multiple access (OFDMA) for the downlink. In case the received spectrum is underutilized, compressed sensing (CS) enables us to operate at a sub-Nyquist sampling rate for lower device cost, higher data transmission rate and faster spectrum sensing speed...
As a measure of chest wall acceleration caused by cardiac motion, the seismocardiogram (SCG) has the potential to supplement the electrocardiogram (ECG) to more accurately trigger cardiac computed tomography angiography (CTA) data acquisition during periods of cardiac quiescence. The SCG was used to identify the systolic and diastolic quiescent periods of the cardiac cycle on a beat-by-beat basis...
Electromagnetic induction (EMI) sensors are commonly used to detect and locate buried metallic objects such as landmines, but they are capable of extracting much more information about objects, e.g., location and magnetic polarizability. Recent research has led to an effective inversion method to extract target orientation by finding the tensor representation of the target [1–3]. The “tensor amplitude”...
Heterogeneous network (HetNet) uses two-tier network architecture in which an unplanned femtocell layer is randomly deployed with no coordination between the coexisting macrocell layer. Both layers share the same spectrum so that spontaneous intercell interference is unavoidable and needs to be identified and canceled afterwards. In order to address the subsequent interference management, this paper...
Cognitive radio (CR) systems offer higher spectrum utilization by opportunistically allocating the unused spectrum from primary users to secondary users. For CR it is vital to perform fast and accurate spectrum sensing in a wideband and noisy channel. Cyclic feature detection performs well in signal detection and is also highly robust to noise uncertainty. However, it requires a high sampling rate...
Sensor array measurements can be inverted to image a region containing targets. The resulting amplitude image is usually interpreted as target strength versus location, but often the imaged amplitude is a function of more parameters than just the location. Sparse target regions can be imaged with dictionary based modeling which relies on enumeration of each parameter with a dense grid. With many parameters,...
This paper presents a novel digital blind calibration method for time interleaved analog to digital converters (TIADCs). A simple cost function based on the cross-correlation of channel statistics is used to derive a steepest descent algorithm for the compensation of timing mismatch errors. Instead of calibrating the timing mismatches independently for each channel, only one adaptation channel needs...
This paper proposes a general structure for FIR filters with adjustable magnitude and phase responses controlled by a few parameters. The Farrow structure which uses one parameter to control the fractional delay of an FIR filter can be viewed as special case. A filter bank structure consisting of different types of linear phase differentiators forms the basis of the structure. The filter bank outputs...
In this paper, we describe an on-line learning platform that enables students to develop conceptual knowledge, organize related concepts around supporting resources, and test their conceptual knowledge and its organization through numerous practice problems. We present these ideas in the context of our ongoing web-based educational platform ITS which we have deployed since 2010 for an introductory...
This paper proposes a new perspective on the relationship between the sampling and aliasing. Unlike the uniform sampling case, where the aliases are simply periodic replicas of the original spectrum, random sampling theory shows that the randomization of sampling intervals shapes the aliases into a noise floor in the sampled spectrum. New insights into both the Fourier random sampling problem and...
A semi-automated method for analyzing cardiac quiescence of anatomical cardiac features from two-dimensional echocardiographic cine data is presented. The method utilizes both active contour and optical flow techniques for feature identification and tracking. A curvature-based potential surface was used in the active contour calculations to attract the contour to regions of inflection on the image...
The EMI response of a target can be accurately modeled by a sum of relaxations. However, it is difficult to obtain the model parameters from measurements when the number of relaxations is unknown. We have previously proposed estimation methods for the model parameters from single measurements. In this paper, we exploit the invariance property of the relaxation frequencies and propose to obtain more...
Compressive sensing (CS) techniques have shown promise for sparse imaging applications such as ground penetrating radar (GPR). However, CS involves the enumeration of a dictionary which implies huge storage requirements when the problem is large and multidimensional. This paper shows that the underlying propagation model can have invariance properties that simplify the dictionary. Specifically, translational...
An iterative reweighted algorithm is proposed for the recovery of jointly sparse vectors from multiple-measurement vectors (MMV). The proposed MMV algorithm is an extension of the iterative reweighted ℓ1 algorithm for single measurement problems. The proposed algorithm (M-IRL1) is demonstrated to outperform non-reweighted MM Valgorithms under noiseless measurements. A regularization of the M-IRL1...
A novel system was developed to acquire synchronous echocardiography, electrocardiography (EKG), and seismocardiography (SCG) data. The system was developed to facilitate the study of the relationship between the mechanical and electrical characteristics of the heart. The system has both a hardware and software component. The hardware component consists of an application-specific device designed and...
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