Spectrum of a frequency modulated pulse width modulation signal

In power electronics, the switching elements are controlled by pulse width modulated (PWM) signals making their currents on and off repeatedly. This might cause electromagnetic interference (EMI) problems especially in switched mode power supplies. One method for mitigating the EMI is to use the frequency modulation technique in the control signal of the switching metal–oxide–semiconductor field‐effect transistor. According to this approach, frequency of the PWM signal is modulated in order to spread its spectrum and hence reduce the EMI levels. This paper presents the theoretical analysis for the spectrum of a frequency modulated PWM signal. Copyright © 2013 John Wiley & Sons, Ltd.     

Revised stratigraphy of the Tertiary deposits of Istanbul and their engineering properties

For over 50 years, the Upper Oligocene–Upper Miocene sedimentary sequence in Istanbul has been considered to be formed of two distinct sequences separated by an unconformity. However, recent field observations and an analysis of numerous borehole data indicate the Gürp?nar, Çukurçe?me and Güngören Formations are in fact a single sequence of alternating clay–sand/sandstone beds/lenses, here named the Avc?lar Formation. The Bak?rköy Formation, which is typically composed of carbonate rocks, conformably overlies the Avc?lar Formation. The paper provides the geotechnical parameters of the units within the Avc?lar Formation which it is hoped will facilitate selecting suitable geotechnical and engineering geological parameters to represent the deposits and minimize errors in the interpretation/evaluation of in-situ conditions.     

Use of Thiourea Leaching During Gold-Containing Dump Treatment

Metallurgist - In Tadzhikistan the volume of gold-containing waste converted to gold is 18 tons. This waste is products of amalgamation and cyaniding processes., and with respect to end component...     

Active Packaging Applications for Food

The traditional role of food packaging is continuing to evolve in response to changing market needs. Current drivers such as consumer's demand for safer, “healthier,” and higher‐quality foods, ideally with a long shelf‐life; the demand for convenient and transparent packaging, and the preference for more sustainable packaging materials, have led to the development of new packaging technologies, such as active packaging (AP). As defined in the European regulation (EC) No 450/2009, AP systems are designed to “deliberately incorporate components that would release or absorb substances into or from the packaged food or the environment surrounding the food.” Active packaging materials are thereby “intended to extend the shelf‐life or to maintain or improve the condition of packaged food.” Although extensive research on AP technologies is being undertaken, many of these technologies have not yet been implemented successfully in commercial food packaging systems. Broad communication of their benefits in food product applications will facilitate the successful development and market introduction. In this review, an overview of AP technologies, such as antimicrobial, antioxidant or carbon dioxide‐releasing systems, and systems absorbing oxygen, moisture or ethylene, is provided, and, in particular, scientific publications illustrating the benefits of such technologies for specific food products are reviewed. Furthermore, the challenges in applying such AP technologies to food systems and the anticipated direction of future developments are discussed. This review will provide food and packaging scientists with a thorough understanding of the benefits of AP technologies when applied to specific foods and hence can assist in accelerating commercial adoption.     

Variability of Stress in Alumina Corrosion Layers Formed in Thermal-Barrier Coatings

Residual stress distributions have been measured and mapped usingphotoluminescence, piezo spectroscopy in thermally grown alumina oxides(TGO) formed on platinum-aluminide bond coats with thermal-barrier coatings(TBC) of thickness 0, 3, and 200 m. When there is a 3-m TBC or noTBC, the residual stress varies substantially with position and the meanstress is much lower than expected from simple thermoelastic, plane-stressanalysis. This is partly explained by the stress being relaxed by surfaceroughness, but stress mapping indicates that local fracture hasoccurred. The stress in the TGO formed under 200 m TBCs appear muchmore uniform and the mean value is approximately equal to the estimatedthermoelastic plane stress. This could be due to the extra constraintimposed by the TBC. The luminescence line width is much greater forspecimens with 200-m TBC and is too large to be explained by varyingmacroscopic stresses due to interface roughness. The effects of oxidationtime and reactive-element additions to the substrate at the level of30 ppm, on the residual stress, are relatively minor over the rangesexplored in these experiments.     

Reverse avalanche breakdown in gated diodes

A two dimensional study of reverse avalanche breakdown in high voltage gated diodes is presented. The numerical method uses the finite difference solution of Poisson's equation with appropriate boundary conditions. A modified two dimensional depletion region approximation is used to take into account the effects of accumulation and inversion near the insulator-semiconductor interface. It has been found that although the effects of surface states and accumulation on the breakdown is small, inversion changes the breakdown characteristics substantially. Breakdown voltage versus gate voltage curves are given for various geometries and doping properties. Good agreement has been achieved between the computed and experimental values of breakdown voltages for a large range of gate potentials.     

Using prior knowledge in SVD-based parameter estimation for magnetic resonance spectroscopy--the ATP example

We introduce the knowledge-based singular value decomposition (KNOB-SVD) method for exploiting prior knowledge in magnetic resonance (MR) spectroscopy based on the SVD of the data matrix. More specifically, we assume that the MR data are well modeled by the superposition of a given number of exponentially damped sinusoidal components and that the dampings alphakappa, frequencies omegakappa, and complex amplitudes rhokappa of some components satisfy the following relations: alphakappa = alpha (alpha = unknown), omegakappa = omega + (kappa- 1)delta (omega = unknown, delta = known), and rhokappa = Ckapparho (rho = unknown, ckappa = known real constants). The adenosine triphosphate (ATP) complex, which has one triple peak and two double peaks whose dampings, frequencies, and amplitudes may in some cases be known to satisfy the above type of relations, is used as a vehicle for describing our SVD-based method throughout the paper. By means of numerical examples, we show that our method provides more accurate parameter estimates than a commonly used general-purpose SVD-based method and a previously suggested prior knowledge-based SVD method.     

The mode III axisymmetric crack problem in a non-homogeneous interfacial region between homogeneous half-spaces

In this study, the mode III axisymmetric crack problem in a non-homogeneous interfacial region between two homogeneous half-spaces is considered. The shear modulus of the interfacial layer is assumed to be μ₂(z)=μ₀ e_mz. It is also assumed that this shear modulus varies continuously between that of the two half-spaces. By using the Hankel transform technique the problem is reduced to a singular integral equation. The problem is solved for various material combinations, crack geometries and for three different sets of crack surface tractions, and the corresponding stress intensity factors are tabulated. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of Covariance Controllers on the Basis of the System Embedding Technology

A new approach to the synthesis of stochastic control systems, which is called the theory of covariance control, is set out in this paper. Its essence involves securing a prescribed steady-state value of the state covariance matrix of a linear system with the aid of feedback. The necessary and sufficient conditions of the attainability of the state covariance matrix are defined and formulas for the entire set of stabilizing covariance controllers are derived.__________Translated from Avtomatika i Telemekhanika, No. 6, 2005, pp. 126–137.Original Russian Text Copyright © 2005 by Sel’vesyuk.