An acoustic Fabry-Perot interferometer is used for measuring high-frequency acoustic losses in isotropic and anisotropic materials with high Q-factor. Interferometer samples of the investigated materials were fabricated in the form of cubes. The reduction in interferometer contrast caused by acoustic losses is used for determining the attenuation coefficient. The spectral distribution of the acoustic field in the interferometer is measured by means of an acoustooptic method. The attenuation coefficient is determined from the ratio ImaX/Imin and the additional losses of acoustic energy causing a reduction of the contrast are taken into account. The results obtained in this way are used for a determination of the attenuation coefficient for waves propagating in fused quartz as well as in a-quartz.

Estimating the Acoustic Attenuation Coefficient Slope for Liver from Reflected Ultrasound Signals

neural and fuzzy logic control of drives and power systems neural and fuzzy logic control of drives and power systems neural and fuzzy logic control of drives and power systems neural and fuzzy logic control of drives and power systems neural and fuzzy logic control of drives power systems neural and fuzzy logic control of drives and power systems neural and fuzzy logic control of drives and power systems chapter 8 fuzzy logic and neural network applications in fuzzy logic applications to power electronics and drives expert system, fuzzy logic, and neural network speed control of dc motor using fuzzy logic technique dynamic fuzzy-neural network controller for induction neural and fuzzy logic control of drives and power systems advanced fuzzy systems design and applications khbd adaptive neural fuzzy inference systems controller for induction motor drive using fuzzy logic citeseerx embedded fuzzy controller for industrial applications direct torque control of induction motor using fuzzy logic application of learning methodologies in control of power fuzzy logic application for intelligent control of a speed control of dc motor using fuzzy pid controller application of fuzzy logic in engineering problems lnai 3949 dsp based fuzzy-neural speed tracking control a servo motor drives based on hybrid genetic algorithm gvpce(a ) m.tech. power electronics & drives 2013 neural fuzzy rule – based model reference adaptive control for artificial neural network and logic control for hvdc systems fuzzy logic control of maximum power point tracking for controlling speed of dc motor with fuzzy controller in speed control of brushless dc motor using fuzzy ijdacr design and performance evaluation of a fuzzy-logic-based maximum power point tracking of pv system using anfis power electronics and motor drives elsevier

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Neural and Fuzzy Logic Control of Drives and Power Systems

A model is proposed to account for the loss in visibility of moving targets that occurs when an observer is uncertain about the target's direction of motion. The model's key features are an array of directionally selective visual mechanisms and a rule governing the mechanisms from which an observer will derive sensory data. In response to uncertainty about two possible directions of motion, the observer is assumed to use a mechanism whose peak sensitivity is to a direction midway between the two possible directions. Seven experiments, using both reaction time and forced-choice data, demonstrate the predictive advantages of this midway model over competing single-band and multiple-band models. Additionally, the experiments reveal several new properties of human motion perception: (a) Direction and velocity information have orthogonal representations in the visual system; (b) although motion sensitivity does not vary with direction, the precision with which small changes in direction can be recognized does, reflecting differential breadth of tuning for directionally selective mechanisms sensitive to various directions; and (c) motion-analyzing mechanisms are broadly tuned for direction as well as speed. Human psychophysics provides extensive evidence for the existence of visual mechanisms tuned to different directions of motion. Converging on this point are data from a variety of paradigms including selective adaptation (Sekuler & Ganz, 1963), subthreshold summation (Levinson & Sekuler, 1975), and aftereffects (Keck, Palella, & Pantle, 1976). In addition, we recently used a masking procedure to define the direction sensitivity profiles of these mechanisms (Ball & Sekuler, 1979). In general, these studies tell us how much information is potentially available in motion-sensit ive visual elements under ideal conditions. But they tell us little about the use to which that information can be put under nonideal conditions outside the laboratory.

https://people.brandeis.edu/~sekuler/papers/ballSekuler_Models_PsychRev1980.pdf

Models of stimulus uncertainty in motion perception.

The multiple-user interference (MUI) in time-hopped impulse-radio ultrawide bandwidth (UWB) systems is impulse-like and poorly approximated by a Gaussian distribution. Therefore, conventional matched filter receiver designs, which are optimal for Gaussian noise, are not fully efficient for UWB applications. Several alternative distributions for approximating the MUI process and the MUI-plus-noise process in UWB systems are motivated and compared. These distributions have in common that they are more impulsive than the Gaussian approximation, with a greater area in the tails of the probability density function (pdf) compared to a Gaussian pdf. The improved MUI and MUI-plus-noise models are utilized to derive new receiver designs for UWB applications, which are shown to be superior to the conventional matched filter receiver. Multipath propagation is abundant in UWB channels and is exploited by a Rake receiver. A Rake receiver uses multiple fingers to comb the multipath rays with a conventional matched filter implemented in each finger. Rake structures utilizing the new receiver designs that are suitable for reception of UWB signals in multipath fading channels are provided. An optimal performance benchmark, based on an accurate theoretical model for the interference that fully explains the features of the MUI pdf, is also presented. Analysis and simulation results are shown for the novel receivers, which demonstrate that the new designs have superior performance compared to the conventional linear receiver when MUI is significant. Several adaptive receivers are shown to always match or exceed the performance of the conventional linear receiver in all MUI-plus-noise environments. Parameter estimation for the new receivers also is discussed.

Designing Time-Hopping Ultrawide Bandwidth Receivers for Multiuser Interference Environments

A novel receiver structure based on soft-limiting is proposed for detecting a time-hopping ultrawide-bandwidth (UWB) signal in the presence of multiple-access interference (MAI). The proposed structure contains a nonlinear limiter for suppressing the MAI. Simulation results show that the proposed receiver achieves better bit-error-rate performance than the conventional matched receiver when operating in MAI. When operating in an MAI-plus-Gaussian-noise environment, the receiver structure outperforms the conventional matched-filter receiver for moderate to large values of signal-to-noise ratio (SNR). A receiver structure with adaptive limiting threshold is further proposed to ensure that the performance of the soft-limiting receiver always meets or surpasses the performance of the conventional UWB receiver for all values of SNR. Application of the soft-limiting structure in the fingers of a rake receiver is shown to enhance the signal-to-noise-plus-interference ratio.

T.W. Parks

Papers

Signal processing: Discrete spectral analysis, detection, and estimation