Advanced polyimide materials: Syntheses, physical properties and applications

Polymer electronic memories: Materials, devices and mechanisms

An asymptotically optimum receiver designed for detecting coherent pulse trains in compound-Gaussian clutter is introduced and assessed. The proposed receiver assumes knowledge of the structure of the clutter covariance matrix, but does not require that of its amplitude probability density function (apdf). Performance is analytically evaluated, showing that the loss, as measured with respect to the corresponding optimum structure, is kept within a few dBs even for a relatively small number of integrated pulses and that it largely outperforms the matched-filter detector under all instances of practical interest. Interestingly, the proposed detector achieves constant false alarm rate (CFAR), regardless of the clutter envelope distribution and, consequently, its power. >

http://lops.perso.enseeiht.fr/papers/Conte_IEEE_TAES_1995.pdf

Asymptotically optimum radar detection in compound-Gaussian clutter

Complex elliptically symmetric (CES) distributions have been widely used in various engineering applications for which non-Gaussian models are needed. In this overview, circular CES distributions are surveyed, some new results are derived and their applications e.g., in radar and array signal processing are discussed and illustrated with theoretical examples, simulations and analysis of real radar data. The maximum likelihood (ML) estimator of the scatter matrix parameter is derived and general conditions for its existence and uniqueness, and for convergence of the iterative fixed point algorithm are established. Specific ML-estimators for several CES distributions that are widely used in the signal processing literature are discussed in depth, including the complex t -distribution, K-distribution, the generalized Gaussian distribution and the closely related angular central Gaussian distribution. A generalization of ML-estimators, the M-estimators of the scatter matrix, are also discussed and asymptotic analysis is provided. Applications of CES distributions and the adaptive signal processors based on ML- and M-estimators of the scatter matrix are illustrated in radar detection problems and in array signal processing applications for Direction-of-Arrival (DOA) estimation and beamforming. Furthermore, experimental validation of the usefulness of CES distributions for modelling real radar data is given.

Complex Elliptically Symmetric Distributions: Survey, New Results and Applications

Speckle noise is an inherent property of medical ultrasound imaging, and it generally tends to reduce the image resolution and contrast, thereby reducing the diagnostic value of this imaging modality. As a result, speckle noise reduction is an important prerequisite, whenever ultrasound imaging is used for tissue characterization. Among the many methods that have been proposed to perform this task, there exists a class of approaches that use a multiplicative model of speckled image formation and take advantage of the logarithmical transformation in order to convert multiplicative speckle noise into additive noise. The common assumption made in a dominant number of such studies is that the samples of the additive noise are mutually uncorrelated and obey a Gaussian distribution. The present study shows conceptually and experimentally that this assumption is oversimplified and unnatural. Moreover, it may lead to inadequate performance of the speckle reduction methods. The study introduces a simple preprocessing procedure, which modifies the acquired radio-frequency images (without affecting the anatomical information they contain), so that the noise in the log-transformation domain becomes very close in its behavior to a white Gaussian noise. As a result, the preprocessing allows filtering methods based on assuming the noise to be white and Gaussian, to perform in nearly optimal conditions. The study evaluates performances of three different, nonlinear filters - wavelet denoising, total variation filtering, and anisotropic diffusion - and demonstrates that, in all these cases, the proposed preprocessing significantly improves the quality of resultant images. Our numerical tests include a series of computer-simulated and in vivo experiments.

/pdf/despeckling-of-medical-ultrasound-images-4pyoujatk0.pdf

Despeckling of medical ultrasound images

PURPOSE:To automatically suppress an arbitrary noise into a receiver noise, by converting a signal whose amplitude distribution is a Weibull distribution, into a signal whose amplitude distribution is a Rayleigh distribution, and thereafter processing the latter signal. CONSTITUTION:An input signal X(n) is changed into a signal W(n) by a logarithmic converter 310. The signal W(n) is applied to shift registers 321-32(H+1). A mean value calculator 320 computes the mean value E1(m) of signals W(m-H)- W(m+H). At the same time, the signal W(n) is changed into a signal W (n) by a multiplier 350 and the latter signal is applied to shift registers 331-33(2H+1). When the output of a shift register (H+1) becomes a signal W(m), the output of the register 33(H+1) becomes a signal W (m) and the output E2(m) of the calculator 320 is obtained. After that, parameters for the Weibull distribution of (2H+1) input signals are automatically determined by parameter calculators 360, 365 and computed by a subtracter 370. The computed parameters are processed through a multiplier 351 and a calculator 112 and summed up by an adder 375 so that the parameters are converted into a Rayleigh distribution. After that, suppression can be easily effected by LOG/CFAR processing.

Noise suppression circuit

Amplitude Statistics of Sea Clutter Using an X-Band Radar

We have measured the optical responses up to 18 GHz in patterned YBa2Cu3O7−δ thin films at various wavelengths by optical heterodyne mixing. The responsivity of the detectors is higher than 50 V/W below 1 Hz at various wavelengths and the responsivity is 20 mV/W at 780 nm and 150 mV/W at 1.55 μm wavelengths in the regime of the modulation frequency from 3 GHz to 18 GHz.

Highly sensitive and wideband optical detection in patterned YBa2Cu3O7-δ thin films

Based on a preon model satisfying both theSU(2) and Lorentz invariances, it is shown thatCP is violated, and anomalies are also eliminated.

Anomaly freedom inCP violation preon model

We have fabricated all-Nb thin film microbridges by using newly developed nanometer process. These microbridges show the high sensitivity of the radiation detection. We have investigated the properties of microbridges by changing the bridge-region parameters.

Matsuo Sekine

Papers

Noise suppression circuit

Amplitude Statistics of Sea Clutter Using an X-Band Radar

Highly sensitive and wideband optical detection in patterned YBa2Cu3O7-δ thin films

Anomaly freedom inCP violation preon model

Properties of all-Nb thin film microbridges fabricated by nanometer process