Fracture of a rectangular piezoelectromagnetic body

The singular stress, electric fields and magnetic fields in a rectangular piezoelectromagnetic body containing a center Griffith crack under longitudinal shear are obtained. Fourier transforms and Fourier sine series are used to reduce the mixed boundary value problems of the crack, which is assumed to be impermeable, to dual integral equations. The solution of the dual integral equations is then expressed in terms of Fredholm integral equations of the second kind. Expressions for stresses, electric displacements and magnetic inductions in the vicinity of the crack tip are derived. Also obtained are the field intensity factors and the energy release rates. Numerical results obtained show that the geometry of the rectangular body have significant influence on the field intensity factors and the energy release rates.     

Statistical Analysis of the Effect of Intensity Pattern Noise on the Displacement Measurement Precision of Digital Image Correlation Using Self-correlated Images

This paper discusses the effect of intensity pattern noise on the displacement measurement precision of digital image correlation (DIC). Through mathematical deduction, a formula is presented to estimate the displacement measurement error caused by intensity pattern noise. The resulting formula synthetically reflects the effects of the variance of noise, the intensity variance and the subset size on the displacement measurement precision. To verify the correctness of the resulting formula, two experiments are done. The first one is a real self-correlation experiment, and aims to analyze the effect of the subset size, while the second is a numerical self-correlation experiment, and is to analyze to the effect of the different noise levels. The experimental results are in good agreement with the theoretical predictions. The project is supported by the National Science Foundation of China (10572103).     

Interaction of a screw dislocation with a notch in a piezoelectric bi-material

Summary The electro-elastic interaction of a screw dislocation and a notch in a piezoelectric bi-material is analyzed. The electro-elastic fields induced by the dislocation are derived using the conformal mapping and the image-dislocation approach, where the solution for a piezoelectric bi-material without a notch is used as a base. The stress and the electric displacement intensity factors of the notch and the image force on the dislocation are given explicitly. We find that intensity factors are expressed in terms of the effective material constants, while the radial component of the image force is independent of the notch angle and the angular position of the dislocation in the polar coordinate system. Numerical results for the image force are provided for the use when one of the two media is purely elastic. They illustrate the behavior of the dislocation in the neighborhood of the notch.     

On the definition of cavitation intensity

Cavitation intensity has already been used to character the activity or strength of cavitation, and several methods are developed to measure the cavitation intensity. However, the previous definitions of cavitation intensity are often either vague or biased. In this paper, from the point of view of energy, the authors proposed a generalized definition of cavitation intensity, derived an approximate formula to calculate the cavitation intensity and discussed its measure method.     

Study on compressed sensing imaging based on intensity modulation in Fourier domain

In 4F system, compressed sensing is usually implemented by using phase modulation in Fourier domain. In this paper, we present a type of 4F system based on intensity modulation in Fourier domain as the measurement system for compressed sensing. The feasibility of this system is demonstrated. At the point of coherence, the two modulation methods are compared and superiority of intensity modulation in Fourier domain was verified. Simulations are presented and the conclusion we presented is validated. Finally, we analyze the results.     

Effect of external pressure on the Kβ/Kα X-ray intensity ratios of 3d metals

The occupation numbers of the 3d transition metals are calculated as a function of pressure by means of the linear muffin-tin-orbital method. This data is used with the multiconfiguration Dirac-Fock (MCDF) X-ray intensity ratios (R) to estimate the variation of the intensity ratios of 3d metals with pressure. It is found that R decreases with pressure for the early 3d metals whereas it increases for the heavier 3d transition metals.     

The fluctuating phase error analysis in the digital grating phase-shifting profilometry

The nonlinear response of the experimental system and the saturation of fringe patterns can induce the fluctuating phase error in the projection grating phase-shifting profilometry. Two major factors of the fluctuating phase error are discussed by simulation. The fluctuating phase error caused by the nonlinear response of the system is four times the frequency of the fringe pattern when the conventional four-frame phase extracting algorithm is used. However, such error can be decreased by five-frame algorithm. On the other hand, the fluctuating phase error caused by the fringe saturation is five times the frequency of the fringe pattern by using conventional five-frame phase extracting algorithm. A novel phase recovering algorithm is used to decrease the phase error caused by the saturation. Furthermore, the applicability range of the proposed phase recovering algorithm is analyzed by simulation and experiments with different saturation degree of the fringe pattern and nonlinearity of the measurement system.     

Single fringe projection profilometry based on sinusoidal intensity normalization and subpixel fitting

A novel fringe projection profilometry using a single sinusoidal fringe pattern projected is proposed. Computer-generated sinusoidal fringe and uniform intensity patterns are firstly projected on a testing object by a liquid crystal display projector. The variable reflection intensity of a fringe pattern is then roughly normalized by division operation applied to the grabbed fringe and uniform intensity patterns projected. Fringe intensity is further normalized by employing an interpolation algorithm. The deformed sinusoidal pattern encoding object shape is converted to a wrapped phase map without using phase-shifting or Fourier transform. Computer simulation and experimental performance are evaluated to demonstrate the validity of the proposed method. The experimental results compared with those of the four-step phase-shifting and fast Fourier transform methods are also presented.     

静电场对静止液体压强的影响

论述了由于静电场的存在,在大气压力场中,静止液体内任意两点间的压强差与重力和静电场力的关系.     

Ultrasonic degradation of butadiene, styrene and their copolymers

Ultrasonic degradation of commercially important polymers, styrene-butadiene (SBR) rubber, acrylonitrile-butadiene (NBR) rubber, styrene-acrylonitrile (SAN), polybutadiene rubber and polystyrene were investigated. The molecular weight distributions were measured using gel permeation chromatography (GPC). A model based on continuous distribution kinetics approach was used to study the time evolution of molecular weight distribution for these polymers during degradation. The effect of solvent properties and ultrasound intensity on the degradation of SBR rubber was investigated using different pure solvents and mixed solvents of varying volatility and different ultrasonic intensities.