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IEEE International Conference on Image processing

作者： G.I. Chiou Jenq-Neng Hwang Boeing Computer Services Inc. Seattle WA USA Information Processing Laboratory Department of Electrical Engineering University of Washington Seattle WA USA

Contour finding of distinct features in 2D/3D images is essential for image analysis and computer vision. To overcome the potential problems associated with existing contour finding algorithms, the authors propose a neural network based active contour model (NN-SNAKE), which integrates a neural network classifier for systematic knowledge building, and an active contour model (also known as "Snake") for automated contour finding using energy functions. The paper describes work on image sequence classification using the proposed NN-SNAKE and hidden Markov models. The "snake" model was applied to extract visual features from a sequence of mouth images and a hidden Markov model was applied to perform word recognition on the visual features. With the visual information alone, the authors were able to achieve 93% recognition rate for 11 isolated words. The models performed lip-reading in a hand-free car audio system.< >

关键词： Image sequences Neural networks Hidden Markov models Active contours Image sequence analysis computer vision Data mining Feature extraction Mouth Image recognition

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Maximum likelihood parameter estimation for non-Gaussian prior signal models

Maximum likelihood parameter estimation for non-Gaussian pri...

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IEEE International Conference on Image processing

作者： R.R. Schultz R.L. Stevenson A. Lumsdaine Laboratory for Image and Signal Analysis Electrical Engineering University of Notre Dame Notre Dame IN USA Department of Computer Science and Engineering University of Notre Dame Notre Dame IN USA

For signals containing discontinuities, the usual assumptions of Gauss-Markov distributed signal sources do not hold. To preserve edges, non-Gaussian prior models have been developed for use in Bayesian restoration. These models are generally dependent upon two parameters, one controlling the size of reconstructed discontinuities, and the other controlling data smoothing. The authors propose a maximum likelihood technique for automatically estimating these parameters, resulting in the optimization of an expression dependent upon the prior model partition function. An exact expression is derived for the 1D signal model partition function, while an approximation is proposed for the 2D image model partition function. Parameters estimated from degraded signals result in high quality restorations.< >

关键词： Maximum likelihood estimation Parameter estimation Image restoration signal restoration Automatic control Size control Gaussian distribution Bayesian methods Image reconstruction Smoothing methods

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Importance sampling for the efficient simulation of adaptive systems in frequency nonselective slow Rayleigh fading

Importance sampling for the efficient simulation of adaptive...

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1994 IEEE GLOBECOM. Communications: The Global Bridge

作者： W.A. Al-Qaq J.K. Townsend Compact Software Inc. Paterson NJ USA Center for Communications and Signal Processing Department of Electrical & Computer Engineering North Carolina Agriculture and Technical State University Raleigh NC USA

Importance sampling (IS) is recognized as an efficient technique in reducing the simulation run time needed to estimate low bit error rates (BERs) in digital communication systems. In this paper. We present an IS stochastic gradient descent technique for the efficient simulation of adaptive systems which employ diversity in the presence of frequency nonselective slow Rayleigh fading and AWGN. After accounting for the overhead of the optimization algorithm, average speed-up factors of up to 6 orders of magnitude (over conventional Monte Carlo (MC)) were attained for error probabilities as low as 10/sup -11/.

关键词： Monte Carlo methods Adaptive systems Frequency Rayleigh channels AWGN Fading Bit error rate signal processing algorithms Computational modeling Error probability

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Generalized optimum dynamic bit allocation scheme for source compression

Generalized optimum dynamic bit allocation scheme for source...

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IEEE International Conference on Image processing

作者： Kai-Kuang Ma S.A. Rajala Institute of Microelectronics (IME) National University of Singapore Singapore Singapore Department of Electrical & Computer Engineering Ctr. for Communication & Signal Processing North Carolina State University Raleigh NC USA

Dynamic bit allocation directly impacts the overall coding performance in block transform (e.g., DCT, Hadamard, etc.) coding, subband coding, and wavelet coding. In very low bit rate coding (such as the evolving MPEG-4 standard), additional factors impacting the bit allocation process need to be identified and properly exploited to achieve optimal coding performance. In the paper, a generalized optimum dynamic bit allocation algorithm is presented. The algorithm is based on the Shannon rate-distortion bound and a weighted distortion criterion using a Lagrange multiplier optimization technique. The results look promising for applications in real-time multimedia communications.< >

关键词： Bit rate Wavelet transforms Discrete cosine transforms Error correction Error correction codes MPEG 4 Standard Heuristic algorithms Rate-distortion Lagrangian functions Multimedia communication

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Real-time frame-to-frame automatic contour detection on echocardiograms

Real-time frame-to-frame automatic contour detection on echo...

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computers in Cardiology (CinC)

作者： J.G. Bosch G. van Burken S.S. Schukking R. Wolff A.J. van de Goor J.H.C. Reiber Laboratory for Clinical and Experimental Image Processing Department of Diagnostic Radiology University Hospital Leiden Netherlands Department of Computer Architecture Faculty of Electrical Engineering Delft University of Technnology Netherlands

A PC-based system for real-time left ventricular endocardial contour detection on echocardiographic images has been developed in our laboratories. The system consists of an IBM-compatible PC equipped with a commercially available frame grabber and the special-purpose Minimum Cost Contour Detector (MCCD) board developed for this project. The MCCD board uses 1 or 2 Intel i960 processors and receives digital images (512*512*8 bit) from the frame grabber over a digital video bar in real time. The contour detection algorithm is based on dynamic programming. Detected contours and other results are transferred to the host via the AT-bus. processing time is short enough for real-time performance in a practical situation. Area of contours and regional areas in 8 segments are calculated in real time and displayed in graphs on the host system. The MCCD board is fully programmable and may be used for similar real-time contour detection applications, e.g. for X-ray angiography and intravascular ultrasound.< >

关键词： Real time systems Laboratories Costs Digital images Detection algorithms Dynamic programming X-ray detection X-ray detectors Angiography Ultrasonic imaging

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System identification and modeling of non-stationary signals using the Wold-Cramer representation

System identification and modeling of non-stationary signals...

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IEEE-SP International Symposium on Time-Frequency and Time-Scale Analysis

作者： A.I. Al-Shoshan L.F. Chaparro Dept. of Electr. Eng. Pittsburgh Univ. PA USA Department of Electrical Engineering Real Time Signal Processing Laboratory University of Pittsburgh Pittsburgh PA USA

In this paper we present an application of the Wold-Cramer representation of non-stationary signals to system identification and modeling. According to the Wold-Cramer representation, a non-stationary signal can be expressed as an infinite sum of sinusoids with time-varying random magnitudes and phases. For the identification of linear time-invariant (LTI) systems, we relate the Wold-Cramer representations of the system's input and output to obtain estimates of the magnitude and phase frequency responses of the system. Our procedure permits the identification of non-minimum phase systems. Furthermore, we show that when the system output is noisy, and the noise is stationary it is possible to avoid the effects of the noise in the identification. If the noise is non-stationary and Gaussian, one needs to consider the evolutionary bispectrum, recently introduced by Priestley, to get rid of the noise. The analysis also provides a model for a non-stationary signal, as the output of a cascade of a linear time-varying and a linear time-invariant systems with stationary white noise as input. To illustrate our procedure, we present a simulation of the identification of a non-minimum phase system.< >

关键词： System identification signal processing Frequency estimation Gaussian noise Phase estimation Time varying systems White noise Density functional theory Real time systems Laboratories

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Error performance of the blind decision feedback equalizer using decorrelation

Error performance of the blind decision feedback equalizer u...

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MILCOM, Military Communications Conference

作者： R.E. Kamel Y. Bar-Ness Center for Communications and Signal Processing Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ USA Telecommunications & Traffic-Control Systems Group Delft University of Technnology Delft Netherlands

The decision feedback equalizer has the advantage of compensating for channel amplitude distortion without enhancing noise. Conventional decision feedback equalizers require a training sequence to help them adapt to unknown channel characteristics. Training sequences are not always appropriate. In such situations blind equalizers are more suitable. The blind decision feedback equalizer inherits from the conventional the advantage of not enhancing noise, while compensating for severe ISI. It is thus superior over the blind linear equalizer. On the other hand the blind decision feedback equalizer also suffers from error propagation. In this paper we study the transient behavior of the blind DFE. This is done by deriving an upper bound on the probability of error due to residual ISI and show that it vanishes for the noiseless case. We also determine lower and upper bounds on the probability of error for the additive white Gaussian noise case. The upper bound obtained is the same as that of Duttweiler, et al. (1974). Using a different approach from that of Duttweiler, et al., we derive a lower bound. This bound is tighter than tile "no ISI" lower bound.< >

关键词： Decision feedback equalizers Decorrelation Upper bound Blind equalizers Intersymbol interference Additive white noise Steady-state Convergence Gaussian noise AWGN

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A blind adaptive MAP algorithm for the recovery of cochannel signals

A blind adaptive MAP algorithm for the recovery of cochannel...

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MILCOM, Military Communications Conference

作者： K. Giridhar A. Mathur J.J. Shynk Information Systems Laboratory Department of Elec. Engineering University of Stanford Stanford CA USA Center for Information Processing Research Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

This paper describes a blind adaptive algorithm for the recovery of cochannel data signals in the presence of intersymbol interference. Assuming unknown finite impulse response channel characteristics, the principle of maximum a posteriori symbol detection (MAPSD) is employed to jointly estimate the channels and the transmitted data. In order to reduce the complexity of this joint blind MAPSD algorithm, a cascaded multistage structure is proposed whereby each stage recovers one of the cochannel sources. This suboptimal approach is expected to perform well when the cochannel signals have sufficiently different power levels. computer simulations for a primary signal and a single interferer illustrate the rapid convergence properties of the algorithm.< >

关键词： Maximum likelihood estimation Interchannel interference Intersymbol interference Information systems Laboratories Information processing Data engineering Adaptive algorithm computer simulation Convergence

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Subnanometer alignment system for x‐ray lithography

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1994年第6期12卷 3261-3264页

作者： H. Zhou M. Feldman R. Bass Department of Electrical and Computer Engineering and Center for Advanced Microstructures and Devices (CAMD) Louisiana State University Baton Rouge Louisiana 70803‐5901 Nanoelectronics Processing Facility Naval Research Laboratory Washington DC 20375

Proximity printing with soft x rays is a leading contender for very large scale integrated circuit lithography below 0.25 μm. It will require overlay accuracy far below the 100 nm (3σ) typical of today’s systems. In addition, it should use wafer marks which permit planar resist flow, so their apparent position is not distorted. We report an alignment system which uses a linear zone plate on the mask to focus laser light into a line on the wafer. The wafer mark is the boundary between two adjacent fine pitch gratings. These gratings diffract the light into photodiodes. The gratings either differ slightly in pitch or by 180° in phase. This configuration minimizes the disturbance to the resist as it flows over the alignment mark. In the case of gratings with slightly different pitch the light from each grating is detected by one‐half of a split photodiode. This arrangement has good sensitivity and a very wide capture range. The phase shift gratings have reduced capture range but enhanced sensitivity because of the improved resolution from the phase shift. We observe that the full width at half‐maximum (FWHM) of the alignment signal is 0.6 μm when the FWHM of the zone plate focus is 1.0 μm. By collecting all of the light focused by the zone plate and diffracted by the gratings we obtain strong alignment signals with signal to noise ratios of more than 1000:1. We routinely obtain a reproducibility in a bench setup equivalent to less than 1 nm (3σ). This alignment technique is currently undergoing installation in a commercially available x‐ray exposure tool.

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Fabrication using x‐ray nanolithography and measurement of Coulomb blockade in a variable‐sized quantum dot

Journal of Vacuum Science & Technology B: Microelectronics a...

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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures processing, Measurement, and Phenomena 1994年第6期12卷 3611-3613页

作者： M. Burkhardt Henry I. Smith D. A. Antoniadis T. P. Orlando M. R. Melloch K. W. Rhee M. C. Peckerar Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge Massachusetts 02139 School of Electrical Engineering Purdue University West Lafayette Indiana 47907 Nanoelectronics Processing Facility U.S. Naval Research Laboratory Washington D.C. 20375

We report on the fabrication and measurement of a novel type of quantum dot device in which the shape and size of the dot can be controlled. The device consists of four uniformly spaced quantum point contacts which can be biased to produce quantum dots ranging in size from 600 nm to below 200 nm. The capacitances of the gates controlling the dot are small. Measurements were made at a temperature of 0.3 K for three different dot sizes. Devices were fabricated in three lithography steps, with x‐ray nanolithography used to define the final gate layer. The device exhibits conductance maxima whose spacing depends on which quantum point contacts are used to define the quantum dot.

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