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Wavelets for computationally efficient hyperspectral derivative analysis

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 2001年第7期39卷 1540-1546页

作者： Bruce, LM Li, J Mississippi State Univ Dept Elect & Comp Engn Mississippi State MS 39762 USA

Smoothing followed by a derivative operation is often used in the analysis of hyperspectral signatures. The width of the smoothing and/or derivative operator can greatly affect the utility of the method. If one is unsure of the appropriate width or would like to conduct analysis for several widths, scale-space images can be used. This paper shows how the wavelet transform modulus-maxima method can be used to formalize and generalize the smoothing followed by derivative analysis and how the wavelet transform can be used to greatly decrease computational costs of the analysis. The Mallat/Zhong wavelet algorithm is compared to the traditional method, convolution with Gaussian derivative filters, for computing scale-space images. Both methods are compared on two points: 1) computational expense and 2) resulting scalar decompositions. The results show that the wavelet algorithm can greatly reduce the computational expense while practically no differences exist in the subsequent scalar decompositions. The analysis is conducted on a database of hyperspectral signatures, namely, hyperspectral digital image collection experiment (HYDICE) signatures. The reduction in computational expense is by a factor of about 30, and the average Euclidean distance between resulting scale-space images is on the order of 0.02.

关键词： computation time computer-aided analysis remote sensing signal processing wavelet transforms

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Efficient ABR service engine for ATM networks

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IEE PROCEEDINGS-CIRCUITS DEVICES AND SYSTEMS 2001年第6期148卷 323-327页

作者： Choi, Y Kang, S Chong, S LG Elect Inc Display Div Seoul South Korea Yonsei Univ Dept Elect & Elect Engn Seoul 120749 South Korea Korea Adv Inst Sci & Technol Dept Elect Engn & Comp Sci Taejon 305701 South Korea

In the recent ATM Forum activities, considerable efforts have been focused on the available bit rate (ABR) service, which enables maximal link utilisation in the ATM network. An ABR service engine is presented, which provides optimal hardware solution for all functions of the ABR service algorithm. To compute congestion control information, the ABR service engine consists of an ER engine, a queueing connection (QC) estimation unit, and a cell decoder/encoder (CIDE). To implement the algorithm efficiently, the new engine uses the following schemes. The ER is periodically computed in order to provide sufficient computation time. Through a periodical computation, a low cell delay is achieved when cells pass through the ABR service engine. Using a QC corrector, the implementation of the QC estimation unit is simplified. A register control block efficiently controls internal variables, and arithmetic units are designed for precise computation with simple architecture. Therefore, the ABR service engine is very small in size and provides high speed. In addition, it realises the computation of the congestion control information without a cell delay.

关键词： maximal link utilisation cell decoder/encoder register control block queueing connection estimation unit optimal hardware solution asynchronous transfer mode ABR service engine periodical computation ATM networks available bit rate service field programmable gate arrays switching networks arithmetic units telecommunication congestion control computation time cell delay internal variables delays congestion control information

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A multidomain approach of the Fourier pseudospectral method using discontinuous grid for elastic wave modeling

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EARTH PLANETS AND SPACE 2001年第3期53卷 149-158页

作者： Wang, YB Takenaka, H Kyushu Univ Dept Earth & Planetary Sci Fukuoka 8128581 Japan

Pseudospectral method is an efficient and high-accuracy numerical modeling technique that has been applied to the simulation of seismic wavefields in realistic models with complex structures such as sedimentary basin. However, if the sedimentary layers are included in the model, high velocity contrasts arise because of the very low S-wave velocities of the sediments as compared with the bedrock. The grid spacing then has to be very small, which leads to spatial oversampling in regions with higher velocities. As a result, we also have to use very small time interval for time marching, so that the computation requires much CPU time. A treatment of this problem is use of a multidomain approach that can employ different grid spacings in different regions, i.e. "discontinuous grid". In this study, we propose a scheme for the Fourier pseudospectral method using discontinuous grid, which uses an interpolation by the FFT. This scheme can reduce the computation time and the required computer memory as compared with the conventional one. The accuracy and efficiency of this approach are demonstrated in the present paper through examples of 2-D elastic wave modeling.

关键词： .PSM interpolation FFT velocities time interval grid spacings CPU time elastic wave seismic wave computation time computer memory

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Fast motion-estimation algorithm based on progressive partial norm matching

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ELECTRONICS LETTERS 2001年第14期37卷 890-892页

作者： Hong, WG Oh, TM Ko, SJ Myongi Coll Dept Elect Engn Seoul 120728 South Korea Korea Univ Dept Elect Engn Seoul 136701 South Korea

A fast block-motion-estimation algorithm, based on progressive partial norm matching, is proposed. This fast algorithm obtains the best estimate of motion vectors with a significantly reduced computational load by successively exploiting the partial norms Of the variable partitioned subblocks and thus effectively eliminating invalid search points. Simulation results demonstrate that computation time has been reduced dramatically, while the performance of the proposed algorithm is the same as that using an exhaustive search.

关键词： motion vectors motion estimation Image and video coding motion-estimation algorithm computational load computation time progressive partial norm matching computational complexity variable partitioned subblocks exhaustive search Video signal processing video coding invalid search points computational complexity block codes

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Integer wavelet transform for embedded lossy to lossless image compression

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IEEE TRANSACTIONS ON IMAGE PROCESSING 2001年第3期10卷 383-392页

作者： Reichel, J Menegaz, G Nadenau, MJ Kunt, M Swiss Fed Inst Technol Signal Proc Lab CH-1015 Lausanne Switzerland

The use of the discrete wavelet transform (DWT) for embedded lossy image compression is now well established. One of the possible implementations of the DWT is the lifting scheme (LS). Because perfect reconstruction is granted by the structure of the LS, nonlinear transforms can be used, allowing efficient lossless compression as well. The integer wavelet transform (IWT) is one of them. This is an interesting alternative to the DWT because its rate-distortion performances is similar and the differences can be predicted. This topic is investigated in a theoretical framework. A model of the degradations caused by the use of the IWT instead of the DWT for lossy compression is presented. The rounding operations are modeled as additive noises. The noises are then propagated through the LS structure to measure their impact on the reconstructed pixels. This methodology is verified using simulations with random noise as input. It predicts accurately the results obtained using images compressed by the well-known EZW [1] algorithm. Experiments are also performed to measure the difference in terms of bitrate and visual quality. This allows to a better understanding of the impact of the IWT when applied to lossy image compression.

关键词： computation time computational complexity image coding image processing integer-to-integer wavelet transforms lossy compression performance low bit rates noise performance evaluation transform coding wavelet transforms

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Mosaic and warping for forward moving images 01

Mosaic and warping for forward moving images

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IEL Citation

作者： Su Zhang Hanfeng Chen Pengfei Shi

ISBN: (纸本)0769510078

Discusses mosaicking and warping for forward-motion (or forward-moving) images (FMI). In FMI, the field of view of one frame is wider than that of a later one; however, the resolution of the later frame is higher than that of previous one. Warp-function algorithms based respectively on a mesh warp and a triangle grid are presented, and a multi-resolution mosaic based on the wavelet transform is given. In-between images could be warped from the single mosaic image. An experiment with a real scene shows that the mesh warp algorithm is more time-consuming than that of triangle grid, but the image quality of the latter is better than that of the former. It also shows that the multi-resolution mosaic image is smooth and natural, eliminating the impact of the seams.

关键词： image motion analysis image morphing image segmentation image resolution mesh generation wavelet transforms forward-moving images forward-motion images image mosaicking image warping field of view image resolution warp-function algorithms mesh warp algorithm triangle grid algorithm multi-resolution mosaic image wavelet transform in-between images computation time image quality smooth natural image mosaic seams

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A computationally efficient Lyapunov-based scheduling procedure for control of nonlinear systems with stability guarantees

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IEEE TRANSACTIONS ON AUTOMATIC CONTROL 2000年第1期45卷 33-49页

作者： McConley, MW Appleby, BD Dahleh, MA Feron, E Charles Stark Draper Lab Inc Cambridge MA 02139 USA MIT Dept Elect Engn Cambridge MA 02139 USA MIT Dept Aeronaut & Astronaut Cambridge MA 02139 USA

We propose an alternative to gain scheduling for stabilization of nonlinear systems. For a useful class of nonlinear systems, the characterization of a region of stability based on a control Lyapunov function is computationally tractable, in the sense that computation times vary polynomially with the state dimension for a fixed number of scheduling variables. Using this fact, we develop a procedure to expand the region of stability by constructing control Lyapunov functions to various trim points of the system, A Lyapunov-based control synthesis algorithm is used to construct a control law that guarantees closed-loop stability for initial conditions in the expanded region of state space. This control asymptotically recovers the optimal stability margin in the sense of a Lyapunov derivative, which in turn can be seen as a performance measure. Robustness to bounded disturbances and stabilization under bounded control are easily incorporated into this framework. In the worst case, the computational complexity of the analysis problem that develops in the new method is increased by an exponential in the disturbance dimension. Similarly, we can handle control constraints with an increase in computational complexity of no more than an exponential in the control dimension. We demonstrate the new control design procedure on an example.

关键词： computation time control systems Lyapunov methods nonlinear systems robustness

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computational complexity of general fuzzy logic control and its simplification for a loop controller

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FUZZY SETS AND SYSTEMS 2000年第2期111卷 215-224页

作者： Kim, YH Ahn, SC Kwon, WH Seoul Natl Univ Sch Elect Engn Control Informat Syst Lab Kwanak Gu Seoul 151742 South Korea

This paper analyzes the number of operations and parameters of general fuzzy logic control algorithms. And limitations of loop controllers to implement the fuzzy logic control are investigated in terms of computation time and required memory. Using analysis of general fuzzy logic control algorithms, it is shown that general fuzzy logic control algorithms are not suitable for loop controllers. A simplified fuzzy logic control for loop controllers is presented using a fixed control table with mapping parameters. This simplified fuzzy logic control is shown to be suitable for a loop controller with regard to the computation time and the required memory. For easy programming of the simplified fuzzy logic control, a fuzzy logic control block is suggested as a specific block for general graphical block diagram editors. Experiments show that the simplified fuzzy logic control overcomes the limitations of loop controllers and provides good performance. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： fuzzy logic control loop controllers computation time memory

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Faster than Fourier: Ultra-efficient time-to-frequency-domain conversions for FDTD simulations

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IEEE ANTENNAS AND PROPAGATION MAGAZINE 2000年第6期42卷 24-34页

作者： Furse, CM Utah State Univ Dept Elect & Comp Engn Logan UT 84322 USA

This tutorial compares several methods of converting from the time to the frequency domain for FDTD simulations. Applications include calculations of field or power distributions, antenna impedance, and radiation patterns. The traditional Fourier-transform methods are compared to two methods based on the solution of linear equations. This tutorial describes how to program and use these techniques, and evaluates their effectiveness for several applications, including analysis of a millimeter-resolution human model underneath a 60-Hz power line, antenna-radiation pattern and impedance calculations, the calculation of the coupling of a cellular telephone to the human head, and geophysical-prospecting simulations.

关键词： FDTD methods computation time frequency domain analysis time domain analysis discrete Fourier transform antenna radiation patterns

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Signal bias removal with orthogonal transform for adverse Mandarin speech recognition

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ELECTRONICS LETTERS 2000年第9期36卷 851-852页

作者： Wang, WJ Chen, SH Natl Chiao Tung Univ Dept Commun Engn Taipei Taiwan Chunghwa Telecommun Labs Appl Res Lab Yangmei Taiwan

A new method for applying orthogonal transforms in signal bias removal (SBR) for adverse Mandarin speech recognition (MSR) is proposed. The orthogonal transform process is performed in a moving window manner to extract features from the input speech. Codewords are then obtained by matching high-order, bias-free features with pre-trained codebooks for bias estimation. The effectiveness of the method has been confirmed by an experiment involving multi-speaker adverse continuous MSR. Significant improvements in the recognition accuracy and computation time were achieved as compared with the conventional SBR method.

关键词： transforms orthogonal transform multi-speaker adverse continuous recognition speech coding bias estimation signal bias removal feature extraction computation time pre-trained codebooks adverse Mandarin speech recognition recognition accuracy high-order bias-free features speech recognition

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