Dr. David C. Smith Profile

Dr. David C. Smith

Applied Research Mathematician

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Publications (12)

Proceedings Article | 23 September 2014 Paper

I-vectors for image classification

David Smith

Proceedings Volume 9217, 92170F (2014) https://doi.org/10.1117/12.2060207

KEYWORDS: Principal component analysis, Data analysis, Expectation maximization algorithms, Data modeling, Factor analysis, Feature extraction, Speaker recognition, Dimension reduction, Digital image processing, Image classification

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Proceedings Article | 26 September 2013 Paper

A comparison of Fisher vectors and Gaussian supervectors for document versus non-document image classification

David Smith, Keri Kornelson

Proceedings Volume 8856, 88560N (2013) https://doi.org/10.1117/12.2023329

KEYWORDS: Principal component analysis, Image classification, Databases, Optical character recognition, Dimension reduction, Expectation maximization algorithms, Visualization, Matrices, Image processing, Distortion

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Proceedings Article | 15 October 2012 Paper

OCR enhancement through neighbor embedding and fast approximate nearest neighbors

D. Smith

Proceedings Volume 8499, 84991I (2012) https://doi.org/10.1117/12.928865

KEYWORDS: Lawrencium, Optical character recognition, Bismuth, Error analysis, Image analysis, Image processing, Image enhancement, Super resolution, Image segmentation, Image resolution

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Proceedings Article | 3 September 2009 Paper

A comparison of two methods for demodulating a target AIS signal through a collision with an interfering AIS signal

D. Smith, D. Nelson

Proceedings Volume 7444, 74440W (2009) https://doi.org/10.1117/12.825383

KEYWORDS: Artificial intelligence, Amplifiers, Modulation, Demodulation, Phase modulation, Phase shift keying, Electronic filtering, Binary data, Interference (communication), Navigation systems

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Proceedings Article | 3 September 2008 Paper

A comparison of two methods for joint time-scale and TDOA estimation for geolocation of electromagnetic transmitters

D. Smith, D. Nelson

Proceedings Volume 7074, 707410 (2008) https://doi.org/10.1117/12.793748

KEYWORDS: Electromagnetism, Signal to noise ratio, Error analysis, Receivers, Transmitters, Super resolution, Statistical analysis, Signal processing, Doppler effect, Motion models

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For wide-band transmission, geolocation modeling using the wide-band cross-ambiguity function (WBCAF) is preferable to conventional CAF modeling, which assumes that the transmitted signal is essentially a sinusoid. We compare the accuracy of two super-resolution techniques for joint estimation of the time-scale (TS) and TDOA parameters in the WBCAF geolocation model. Assuming a complex-valued signal representation, both techniques exploit the fact that the maximum value of the magnitude of the WBCAF is attained when the WBCAF is real-valued. The first technique enhances a known joint estimation method based on sinc interpolation and 2-D Newton root-finding by (1) extending the original algorithm to handle complex-valued signals, and (2) reformulating the original algorithm to estimate the difference in radial velocities of the receivers (DV) rather than time scale, which avoids machine precision problems encountered with the original method. The second technique makes a rough estimate of TDOA on the sampling lattice by peak-picking the real part of the cross-correlation function of the received signals. Then, by interpolating the phase of the WBCAF, it obtains a root of the phase in the vicinity of this correlation peak, which provides a highly accurate TDOA estimate. TDOA estimates found in this way are differentiated in time to obtain DV estimates. We evaluate both super-resolution techniques applied to simulated received electromagnetic signals which are linear combinations of complex sinusoids having randomly generated amplitudes, phases, TS, and TDOA. Over a wide SNR range, TDOA estimates found with the enhanced sinc/Newton technique are at least an order of magnitude more accurate than those found with conventional CAF, and the phase interpolated TDOA estimates are 3-4 times more accurate than those found with the enhanced sinc/Newton technique. In the 0-10 dB SNR range, TS estimates found with the enhanced sinc/Newton technique are a little more accurate than those found with phase interpolation. Moreover, the TS estimate errors observed with both super-resolution techniques are too small for a CAF-type grid search to realize in comparable time.

Proceedings Article | 21 September 2007 Paper

SCAF estimation of time delay and Doppler stretch

D. Smith, D. Nelson

Proceedings Volume 6697, 669708 (2007) https://doi.org/10.1117/12.740178

KEYWORDS: Radar, Receivers, Doppler effect, Super resolution, Signal processing, Modulation, Fourier transforms, Computer simulations, Transmitters, Stars

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Proceedings Article | 25 August 2006 Paper

An efficient high-resolution time-frequency representation

D. Nelson, D. Smith

Proceedings Volume 6313, 63130T (2006) https://doi.org/10.1117/12.681438

KEYWORDS: Signal processing, Signal detection, Picosecond phenomena, Signal to noise ratio, Time-frequency analysis, Interference (communication), Fourier transforms, Signal analyzers, Environmental sensing, Data modeling

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Proceedings Article | 16 September 2005 Paper

A higher order method for concentrating the STFT

D. Nelson, D. Smith

Proceedings Volume 5910, 59100G (2005) https://doi.org/10.1117/12.618153

KEYWORDS: Signal processing, Fourier transforms, Fermium, Frequency modulation, Estimation theory, Nonlinear optics, Iterated function systems, Transform theory, Composites, Defense and security

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Proceedings Article | 26 October 2004 Paper

Linear distribution of signals

Douglas Nelson, David Smith, Robert Masenten

Proceedings Volume 5559, (2004) https://doi.org/10.1117/12.560295

KEYWORDS: Signal processing, Fourier transforms, Fermium, Frequency modulation, Signal detection, Nonlinear optics, Composites, Digital filtering, Linear filtering, Defense and security

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Proceedings Article | 13 November 2003 Paper

Estimating speaker scale factors from vowels

Douglas Nelson, David Smith, Srinivasan Umesh, Leon Cohen

Proceedings Volume 5207, (2003) https://doi.org/10.1117/12.507416

KEYWORDS: Factor analysis, Databases, Ear, Composites, Defense and security, Fourier transforms, Mendelevium, Defense technologies, Wavelets, Signal processing

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Proceedings Article | 13 October 2000 Paper

Biometric speaker classification

Douglas Nelson, David Smith, D. Richman, Goffrey Townsend

Proceedings Volume 4120, (2000) https://doi.org/10.1117/12.403622

KEYWORDS: Databases, Biometrics, Statistical analysis, Detection and tracking algorithms, Algorithm development, Fourier transforms, Ear, Data processing, Signal processing, Standards development

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Proceedings Article | 2 October 1998 Paper

Multivariate speech activity dector based on the syllable rate

David Smith, Jeffrey Townsend, Douglas Nelson

Proceedings Volume 3461, (1998) https://doi.org/10.1117/12.325725

KEYWORDS: Detection and tracking algorithms, Sensors, Algorithm development, Signal detection, Interference (communication), Signal to noise ratio, Signal processing, Signal analyzers, Data analysis, Dimension reduction

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Showing 5 of 12 publications

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