Reliability of a Weibull analysis using the maximum-likelihood method

We have performed extensive Monte-Carlo computer simulations of the 2-parameter Weibull statistical distribution using data groups with sizes from 5 up to 100 samples. The maximum-likelihood method was used to evaluate the resulting Weibull modulus and the scale parameter, which may be different to the input values. We confirmed some trends in the evaluation of the statistical parameters for small data groups, such as a significant biasing of the Weibull modulus. We revealed the log-normal statistical distribution of the Weibull parameters obtained from repeated Monte-Carlo simulations for several groups. We also considered the influence of the measurement uncertainty on the determination of the statistical parameters. For the experimental evidence we used bend-strength data for alumina test samples from serial production in this year. The experimental data were randomly divided into several subgroups to compare the corresponding biasing of the Weibull modulus with the Monte-Carlo results.     

Efficient impulse noise removal using hybrid neuro-fuzzy filter with optimized intelligent water drop technique

Impulse noise (IN) affects the digital image, during transmission, digital storage, and image acquisition. IN removal from an image is necessary as it retains the quality of the image. This work concentrates on the IN. A neuro-fuzzy (NF) system based on a fuzzy technique which is trained by a learning algorithm derived from neural network theory was implemented for the removal of noise. A NF network for noise filtering in grayscale images that combines two NF filters with a postprocessor to produce the output was presented. However, Sugeno-type is not intuitive technique and it also less accurate. To overcome these problems, a hybrid NF filter with optimized intelligent water drop (IWD) technique is introduced, where hybridized Sugeno–Mamdani-based fuzzy interference system is implemented in both the NF filters to obtain more efficient noise removal system. To improve the accuracy of the assignment of membership values to each input pixels, the optimized IWD technique is utilized, as the choice of membership function decides the efficiency of the noise removal in the images. Here, Fuzzy rules have been used to obtain the filtered output. The Hybrid method maintains the accuracy of the Sugeno model and also the interpretable capability of the Mamdani model. This method is robust against the IN and it is flexible, efficient, and accurate than existing filtering method in both noise attenuation and detail preservation and it has a great scope for better real-time applications.     

Speckle with a finite number of steps

The statistical properties of classical, fully developed speckle must be modified when the speckle is generated by a random walk with a finite number of steps. It is shown that for such speckle, the standard negative-exponential probability density function for speckle intensity often overestimates the probability that the intensity exceeds a given threshold. In addition, while any linear transformation of the fields in a classical speckle pattern does not change the intensity statistics, the same is not true for finite-step speckle. The implications of these facts in certain applications are discussed.     

Speckle reduction in pulse-echo ultrasonic imaging using a two-dimensional receiving array

An experimental pulse-echo imager was developed for the purpose of reducing speckle in ultrasonic images. The system utilized a 64-element spherically focused segmented annuli array receiver with a common transmitter. Compounded images were formed using subapertures of varying size, shape, and overlap, and the speckle and resolution characteristics of the final images were observed. A pointlike scatterer was imaged to determine the resolution, point spread function, and sensitivity of the system along with a new measure called the resolution cell size. The response of the system was also simulated for comparisons. It was found that lateral resolution, and resolution cell sizes only gradually increased with a decrease in subaperture size and system sensitivity was not greatly diminished. Incoherent summation of signals from small groups of elements decreased the speckle noise by a factor of four while maintaining enough resolution to improve the image quality as measured by the CSR/d by a factor of almost two.     

Speckle suppression in projection displays by using a motionless changing diffuser

Speckle suppression in projection displays with a laser light source can be achieved by imaging a changing diffuser with random phase cells onto the screen. Theoretical expressions for the speckle contrast in this method have been earlier obtained in the case when different realizations of the phase diffuser produced statistically independent patterns of the light field on the screen. In the present paper, these expressions are generalized in the case when different realizations of the phase diffuser produce partly correlated speckle patterns. The possible structure of a motionless changing diffuser is presented. It includes a dynamic diffractive optical element (DDOE) and a light homogenizer. The DDOE can be based on the electrically controlled spatial light modulator (SLM) with a deformable polymer layer. This type of SLM can handle high light power and, therefore, can be used in projection displays with powerful laser beams.     

Spectral multivariate calibration with wavelength selection using variants of Tikhonov regularization

Tikhonov regularization (TR) is a general method that can be used to form a multivariate calibration model and numerous variants of it exist, including ridge regression (RR). This paper reports on the unique flexibility of TR to form a model using full wavelengths (RR), individually selected wavelengths, or multiple bands of selected wavelengths. Of these three TR variants, the one based on selection of wavelength bands is found to produce lower prediction errors. As with most wavelength selection algorithms, the model vector magnitude indicates that this error reduction comes with a potential increase in prediction uncertainty. Results are presented for near-infrared, ultraviolet-visible, and synthetic spectral data sets. While the focus of this paper is wavelength selection, the TR methods are generic and applicable to other variable-selection situations.     

Full-Field Displacement Measurement of a Speckle Grid by using a Mesh-Free Deformation Function

Abstract:  In the present study, a combined experimental–numerical technique for the determination of the displacement and strain fields in the surface of a deformable body is described. The experimental part of this technique is based on the recording of the pair of images of the surface before and after deformation of the body, by means of a digital camera. This is done after spraying the surface with a random field of speckles (dots). Then the dots (having finite dimensions) of the second image are identified and uniquely paired with the dots of the first image. This permits the experimental determination of the deformation field in the surface. Then, by means of a mesh-free numerical method, a smoothed deformation field can be constructed. For that, the moving least square method is applied. The deformation field being available, the corresponding strain field can easily be obtained. Numerical simulation of this technique in three simple examples indicates that promising applications are expected.     

Speckle photography with different pupils in a multiple-exposure scheme

The use of different multiple-aperture pupils for recording each image in speckle photography is proposed. The introduction of suitable spatial frequency carriers, by internally modulating imaged speckles, allows one to selectively isolate or combine the spectral content of different images into spatially separated regions in the Fourier plane. Theoretical and experimental results extend the speckle photography technique to the depiction of several specklegrams of multiple uniform in-plane displacements. In this case, because different pupils are considered for recording, the cross-correlation functions for the amplitudes and intensities in the image plane are calculated on the basis of the statistical properties of the object. Also, the ensemble-average intensity in the Fourier plane is analytically derived, and fringe visibility is investigated.     

Speckle Patterns Generated by Rough Surfaces with a Periodic Component

Abstract

A real diffraction grating is replaced by a coordinate-dependent surface impedance that is constructed as the sum of two contributions: a perfectly periodic contribution and a randomly varying contributon. Numerical results obtained with this model show the presence of diffuse light bands on the speckle pattern that constitutes the diffuse background of the spectrum. We emphasize the role played by the electromagnetic surface waves supported by this structure on the generation of the bands.     

Numerical analysis of localization using a viscoplastic regularization: influence of stochastic material defects

The finite element reliability method is applied to evaluate the effects of stochastic imperfections on the localization behaviour of elasto‐viscoplastic softening solids. Material properties as the Young's modulus, the softening modulus and the initial yield stress are considered to be random fields. Failure criteria are defined for the peak load and the dissipated energy. Likely configurations of imperfections which lead to failure are obtained and the nature and relative importance of the corresponding localization patterns are analyzed. Copyright © 1999 John Wiley & Sons, Ltd.     

Nitric oxide removal from flue gas with a biotrickling filter using Pseudomonas putida

The development of an effective biotrickling filter (BF) system to inoculate a newly isolated strain of Pseudomonas putida SB1 for the effective treatment of nitric oxide (NO) is described. The experiments were carried out in a bench-scale BF under high concentrations of O(2) and NO in simulated flue gas. A method including alternating aeration in screening and rescreening based on the pH changes for cultivating natural aerobic denitrifying bacteria was employed. The SB1 showed a denitrifying capability of 95% nitrate removal rate over a 24h period in an aerobic environment, with no nitrite accumulation. The BF system was able to consistently remove 82.9-94.2% NO when the inlet NO was 400ppm in an enriched oxygen stream of 2-20%. The oxygen had no negative effect on the aerobic denitrifier SB1, but rather enhanced the total efficiency in part by chemical oxidation and in part by the strain activities. A kinetic relation between the oxygen concentration and biological NO removal was developed to confirm that the microbial metabolism played the main role. 79.3% of the total NO removal can be attributed to bio-denitrifying at 20% oxygen, and most chemical oxidation occurred concurrently. Overall, the study demonstrates that NO removal by the aerobic denitrifying process in BF is feasible in flue gas.     

Desingularized meshless method for solving Laplace equation with over-specified boundary conditions using regularization techniques

The desingularized meshless method (DMM) has been successfully used to solve boundary-value problems with specified boundary conditions (a direct problem) numerically. In this paper, the DMM is applied to deal with the problems with over-specified boundary conditions. The accompanied ill-posed problem in the inverse problem is remedied by using the Tikhonov regularization method and the truncated singular value decomposition method. The numerical evidences are given to verify the accuracy of the solutions after comparing with the results of analytical solutions through several numerical examples. The comparisons of results using Tikhonov method and truncated singular value decomposition method are also discussed in the examples.     

Speckle interferometry: three-dimensional deformation field measurement with a single interferogram

An electronic speckle interferometer, arranged for out-of-plane sensitivity and with an off-axis reference beam to produce spatial phase bias, is used for three-dimensional deformation field measurements. The complex amplitude of the object wave is calculated by application of a Fourier-transform method to a single interferogram. The change in phase after object deformation yields the out-of-plane component of the displacement field. The two in-plane components are obtained by cross correlation of subimages of the reconstructed object wave's intensity, a method that is also referred to as digital speckle photography. The Fourier-transform algorithm is extended and modified, leading to random measurement errors that are below widely accepted theoretical limits and also to an extended measuring range. These properties and the mutually combined information improve the accuracy of both methods compared with their usual single implementation. The performance is evaluated in experiments with pure out-of-plane, pure in-plane, and combined deformations and compared with theoretical values. An example of a practical application is given.     

Ultrasonic densitometer using a multiple reflection technique

This work presents recent improvements in a density measurement cell with a double-element transducer that can eliminate diffraction effects. A new mechanical design combined with the use of more appropriate materials has resulted in better parallelism between interfaces, more robust assembly, and chemical resistance. A novel method of signal processing, named the energy method, is introduced to obtain the reflection coefficient, reducing sensitivity to noise and improving accuracy. The measurement cell operation is verified both theoretically, using an acoustic wave propagation model, and experimentally, using homogeneous liquids with different densities. The accuracy in the density measurement is 0.2% when compared with the measurements made with a pycnometer.     

Nonlinear analysis using a modal-based reduction technique

This paper presents a solution to nonlinear formulated problems using eigenfunctions computed by a linear free vibration solution. The system of equations is extremely reduced. The solution is unique in its formulation as the governing equations represent the problem continuously and do not require an iterational or incremental solution. Energy consideration is used and the Ritz method is applied to render the governing equations. The eigenfunctions are computed by a linear solution option of the F.E. code MSC/NASTRAN. Several numerical examples are presented and compared to solutions from the literature.     

Miniaturized SAW filters using a flip-chip technique

This paper describes a miniature surface acoustic wave (SAW) filter, 3.2×2.5×0.9 mm³, which is applicable for radio frequency (RF) stage filters in mobile phones. The SAW filter is reduced in size by using a flip-chip assembly technique. The technique uses gold bumps on the SAW chip and gold-gold thermosonic face-down bonding. The gold bumps are formed onto the wafer by a conventional wire bonding machine using gold wire. The thermosonic face-down bonding enables the connection of gold bumps on the SAW chip, with gold metallized pads, on a ceramic package at a temperature below 200°C. This bonding ensures that the SAW chip is fixed mechanically, and connected electrically, with the package. Frequency responses of a 950-MHz flip-chip SAW filter are compared with responses of a SAW filter with a conventional package. The results of reliability tests for flip-chip SAW filters are shown     

Singular element construction using a mapping technique

Conformal mapping regularizes (in the new plane) the singular stress field around the crack tip. So, conventional finite elements can be used in the transformed plane. The inverse mapping of the above elements gives another class of ‘mapped elements’. The crack-tip mapped element is a singular element. Thus, using various elements (the ‘parent elements’) in the mapped plane we obtain an infinity of singular elements, the ‘product elements’. These singular elements are introduced naturally and have no defect, as many other singular elements have.     

Transonic wing flow computations using the field-panel method with a shock-fitting technique

An integral equation field-panel scheme for solving the full-potential equation for compressible flows with and without shocks is presented. The full-potential equation is written in the form of the Poisson's equation. Compressibility is treated as non-homogeneity. The integral equation solution in terms of velocity field is obtained by Green's theorem. The solution consists of wing (or a general body) surface integral term(s) of vorticity/source distribution(s), wake surface integral term(s) of free-vortex sheet(s), a volume integral term of compressibility over a small limited domain around the source of disturbance, and a shock surface integral term of source distributions for the shock-fitting purpose. Solutions are obtained through an iterative procedure. Instead of using a grid (field-panel) refinement procedure, a shock-fitting technique is used to fit the shock. The present scheme is applied to non-lifting flows around both sharp and round leading edge rectangular wings at high-subsonic and transonic flow conditions.     

Experimental reconstruction of a highly reflecting fiber Bragg grating by using spectral regularization and inverse scattering

We demonstrate experimentally, for the first time to our knowledge, a reconstruction of a highly reflecting fiber Bragg grating from its complex reflection spectrum by using a regularization algorithm. The regularization method is based on correcting the measured reflection spectrum at the Bragg zone frequencies and enables the reconstruction of the grating profile using the integral-layer-peeling algorithm. A grating with an approximately uniform profile and with a maximum reflectivity of 99.98% was accurately reconstructed by measuring only its complex reflection spectrum.     

Absolute interferometric distance measurement using a FM-demodulation technique

We propose an interferometric method for measuring absolute distances larger than the wavelength. A laser diode is used as a light source. The principle of operation is based on multiple-wavelength interferometry that uses a modulated light source. This method uses the fact that the wavelength of light emitted by the laser diode can be varied by means of the injection current. The modulation of the injection current in combination with the optical heterodyne technique causes a high-frequency phase-modulated detector signal. The phase deviation of the signal is a measure of the optical path difference in the interferometer. By FM demodulation of the detector output with a phase-locked loop demodulator, the optical path difference can be determined directly without the classical ambiguity problem of interferometry. The measuring range in the experiments was limited to 50 mm by the maximum travel range of the used specimen translation stage. Because of the inherent light sensitivity of the method described, the rangefinder can be used for three-dimensional profile measurements on a wide variety of objects, even on diffuse scattering surfaces.