Fracture analysis of plane piezoelectric/piezomagnetic multiphase composites under transient loading

The transient response of cracked composite materials made of piezoelectric and piezomagnetic phases, when subjected to in-plane magneto-electro-mechanical dynamic loads, is addressed in this paper by means of a mixed boundary element method (BEM) approach. Both the displacement and traction boundary integral equations (BIEs) are used to develop a single-domain formulation. The convolution integrals arising in the time-domain BEM are numerically computed by Lubich’s quadrature, which determines the integration weights from the Laplace transformed fundamental solution and a linear multistep method. The required Laplace-domain fundamental solution is derived by means of the Radon transform in the form of line integrals over a unit circumference. The singular and hypersingular BIEs are numerically evaluated in a precise and efficient manner by a regularization procedure based on a simple change of variable, as previously proposed by the authors for statics. Discontinuous quarter-point elements are used to properly capture the behavior of the extended crack opening displacements (ECOD) around the crack-tip and directly evaluate the field intensity factors (stress, electric displacement and magnetic induction intensity factors) from the computed nodal data. Numerical results are obtained to validate the formulation and illustrate its capabilities. The effect of the combined application of electric, magnetic and mechanical loads on the dynamic field intensity factors is analyzed in detail for several crack configurations under impact loading.     

Fitting optimal piecewise linear functions using genetic algorithms

Constructing a model for data in R² is a common problem in many scientific fields, including pattern recognition, computer vision, and applied mathematics. Often little is known about the process which generated the data or its statistical properties. For example, in fitting a piecewise linear model, the number of pieces, as well as the knot locations, may be unknown. Hence, the method used to build the statistical model should have few assumptions, yet, still provide a model that is optimal in some sense. Such methods can be designed through the use of genetic algorithms. We examine the use of genetic algorithms to fit piecewise linear functions to data in R². The number of pieces, the location of the knots, and the underlying distribution of the data are assumed to be unknown. We discuss existing methods which attempt to solve this problem and introduce a new method which employs genetic algorithms to optimize the number and location of the pieces. Experimental results are presented which demonstrate the performance of our method and compare it to the performance of several existing methods, We conclude that our method represents a valuable tool for fitting both robust and nonrobust piecewise linear functions     

Thermophysical parameters for the combustion products from tetrazole-sodium tetrazolate mixtures

Measurements have been made on the thermal conductivity and specific heat of the powder product from quenching in nitrogen applied to the gas-liquid flame formed by the combustion of a tetrazole-sodium tetrazolate mixture in weight proportion 31. The thermal conductivity on the whole is a nonmonotone function of temperature in the range 100–450 K and has some local turning points associated with the multicomponent structure and the phase transitions associated with chemical and structural transformations.Translated from Inzhenrno-fizicheskii Zhurnal, Vol. 61, No. 3, pp. 422–426, September, 1991.     

Complete structure of glycopeptides isolated from IgG immunoglobulins of cow colostrum

Bovine immunoglobulins (IgG1 type) have been isolated from colostral whey. Hydrolysis by pronase, trypsin and (or) chymotrypsin yield several glycopeptides structural studies of which lead to the following results. 1. IgG1 colostral immunoglobulins possess two glycan moieties which are linked to the peptidic chain by an N-(beta-aspartyl)-N-acetylglucosaminylamine bound. 2. The peptidic sequence around the linkage region has been determined by classical methods and is as follows: Thr-Lys-Pro-Arg-Glu-Glu-Gln-Phe-Asn(Glycan)-Ser-Thr-Tyr-Arg. 3. The following procedures: partial acidic hydrolysis, periodic oxidation, hydrazinolysis-nitrous deamination, methylation and use of specific glycosidases allowed us to determine the structure of the glycan moieties which fit with the general following scheme: (see article) Thus they could be related to the general glycan structure so-called of "N-acetyllactosamine type" because they possess the pentasaccharidic core common to numerous glycoproteins Man alpha 1 leads to [Man alpha 1 leads to 6] Man beta 1 leads to 4 GlcNAc beta 1 leads to 4 GlcNAc beta 1 leads to Asn on which are conjugated 2 N-acetyllactosamine residues. Besides they present a microheterogeneity which is due to the varying number of additional N-acetylneuraminic acid and fucose residues. 4. These structures are compared to various immunoglobulin structures proposed by others: bovine serum IgG and human serum IgG, IgE and IgA.     

Meshless local Petrov-Galerkin method for continuously nonhomogeneous linear viscoelastic solids

A meshless method based on the local Petrov-Galerkin approach is proposed for the solution of quasi-static and transient dynamic problems in two-dimensional (2-D) nonhomogeneous linear viscoelastic media. A unit step function is used as the test functions in the local weak form. It is leading to local boundary integral equations (LBIEs) involving only a domain-integral in the case of transient dynamic problems. The correspondence principle is applied to such nonhomogeneous linear viscoelastic solids where relaxation moduli are separable in space and time variables. Then, the LBIEs are formulated for the Laplace-transformed viscoelastic problem. The analyzed domain is covered by small subdomains with a simple geometry such as circles in 2-D problems. The moving least squares (MLS) method is used for approximation of physical quantities in LBIEs.     

PEO／V2O5纳米复合薄膜的变色特性研究

为改善V2O5薄膜的电致变色性能，采用溶胶-凝胶法将具有高离子电导率并具有水溶性的聚环氧乙烷（PEO）直接嵌入V2O5层间，制备了PEO／V2O5纳米复合薄膜。采用标准三电极法从0．5mol／L LiClO4的PC电解质溶液向PEO／V2O5纳米复合薄膜注入锂离子，测量了纳米复合薄膜在注入不同数量锂离子时的可见光透射光谱以及对应的颜色变化，并运用循环伏安法测试其电化学性能。实验结果表明，PEO／V2O5纳米复合薄膜的循环伏安图出现了2对氧化还原峰，并且具有稳定的循环可逆性。随着应用电压的不同，薄膜呈现黄色、绿色和蓝色的多色可逆变化。PEO／V2O5纳米复合薄膜的电化学稳定性和机械性能都优于V2O5干凝胶薄膜，可以作为电致变色材料得到应用。X射线光电子能谱（XPS）成分分析表明PEO／V2O5纳米复合薄膜的电致变色效应与V、O的化合价和化学环境密切相关。     

A sequential method of calibrating measurement instruments with a Kalman filter

A recurrent algorithm is derived for estimating the parameters of a calibration curve with allowance for the errors in reproducing the inputs. That algorithm is combined with a proposed rule for halting the calibration to reduce considerably the length of the calibration, which promises a real economic advantage. __________ Translated from Izmeritel’naya Tekhnika, No. 4, pp. 32–38, April, 2006.     

Clock Recovery at 160 Gb/s and Beyond, Using a Fiber-Based Optical Power Limiter

We propose a simple all-optical clock recovery technique for short data packets at 160 Gb/s, and beyond, which is based on the concept of using a Fabry-Peacuterot filter (FPF). The novel feature of the technique is the use of a highly nonlinear fiber followed by an optical bandpass filter, centered at the initial carrier wavelength, which acts as an ultrafast power limiter, removing drastically the amplitude modulation of the FPF's output and providing the clock signal     

Development of a Net Shape Manufacturing Method for Ventilated Brake Discs in Single Piece Design

Carbon fibre reinforced ceramic matrix composites (CMC), originally developed for lightweight heat shields of spacecraft, are used for high performance brake discs in sports cars from different manufacturers. In contrast to the CMC materials for space applications, based on woven fabrics and costly manufacturing methods, these low cost friction materials are produced by liquid silicon infiltration of porous Carbon/Carbon (C/C) preforms, based on short fibre reinforced CFRP green bodies manufactured via warm press technique. In this work, different manufacturing methods for ventilated CMC brake discs are compared to each other, and the development of a new technology for the manufacture of single piece C/C‐SiC brake discs in net shape technique is presented.