一个新的声应力系数及其确定

为建立声焦散线与平面应力条件下裂尖应力强度因子的关系,定义了一个新的声应力系数——声程差随应力线性变化的比例系数,该系数的大小既取决于材料常数又取决于耦合介质及声束的传播历程.借助6061-T6铝、EPTI钢两种材料的实验结果,说明了确定新的声应力系数的方法与步骤.所得结论是:只要确定了平面应力条件下超声纵波速度相对变化与主应力和之比,便可确定新的声应力系数.     

火棘黄酮的提取及美白功效研究

采用循环超声提取法提取火棘黄酮,通过正交试验确定其最佳工艺,用D101大孔树脂将其纯化,测定了火棘黄酮的马铃薯酪氨酸酶抑制率。并制备了火棘黄酮美白霜,通过人体实验,评价其美白功效。结果表明:火棘黄酮最佳的提取条件为乙醇体积分数为70%,料液比(g∶m L)为1∶15,提取温度60℃,提取时间为30min。火棘黄酮对马铃薯酪氨酸酶具有明显的抑制作用,抑制率达到50%时火棘黄酮浓度(IC50)为10.36 mg·m L-1,是熊果苷的2倍。火棘黄酮制成的美白霜有一定的美白能力,能显著降低皮肤黑色素含量和增加皮肤亮度而美白皮肤。结果说明火棘黄酮具有一定的美白功效,可以作为天然的美白化妆品添加剂。     

Ultrasonic laser spectroscopy of mechanic-acoustic nonlinearity of cracked rocks

The effect of nonlinearity of rocks caused by the presence of microcracks on the shape of elastic pulses propagating in these rocks is studied by methods of ultrasonic laser spectroscopy. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 3, pp. 174–180, May–June, 2005.     

On Foundations of the Ultrasonic Nondestructive Method for Determination of Stresses in Near-Surface Layers of Solid Bodies

The ultrasonic nondestructive method for determining stresses in near-surface layers of solid bodies is based on the laws governing the propagation of elastic surface waves in bodies with initial (residual) stresses. These laws are established within the framework of the linearized three-dimensional theory of waves in bodies with initial (residual) stresses. The dispersion equations in associated problems are solved by computational methods. The nondestructive method and measuring instruments and devices are described. Some examples of nondestructive determination of welding-induced residual stresses and operating stresses in near-surface layers of materials are presented Presented at the International Conference on Computational and Experimental Engineering and Sciences (ICCES'04) (Madeira, Portugal, July 26–29, 2004) and published in the journal Computer Modeling in Engineering and Sciences (CMES). __________ Published in Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 130–144, August 2005.     

管道超声导波检测专用探头的研制

结合常规超声探头的研制技术，根据检测对象——管道的特殊性，从敏感元件、背衬材料、保护层以及外型等各方面详细介绍了一种管道超声导波检测专用探头的研制过程；利用这种探头分别在板和管中进行了激励接收超声导波的实验，结果表明，这种探头能够激励接收超声导波。     

Laser-induced stress wave thermometry applied to silicon wafer processing: Modeling and experimentation

We present a methodology correlating the group velocity of guided plate waves to temperature in anisotropic silicon substrate. The model is developed through numerical solution and manipulation of the dispersion relations, while elastic constants and plate thickness are treated as functions of temperature. Analytical results demonstrate that adequate thermal resolution is provided by both the lowest-order antisymmetric and symmetric dispersive Lamb wave modes to serve as an effective diagnostic in a noncontact thermometry scheme applicable during rapid thermal processing of silicon waters. Validation is made through a combination of experimentation using laser-generated ultrasound in silicon wafers and analysis employing the Gabor wavelet transform to extract frequency- and temperature-dependent group velocities from the dispersive Lamb waves.     

Optimized Ultrasonic Extraction for the Determination of Polyaromatic Hydrocarbons by Gas Chromatography–Mass Spectrometry

The presence of polycyclic aromatic hydrocarbons (PAHs) in soil is an issue of concern due to their harmful effects on human health. The goal of this study was to optimize ultrasonic extraction to establish an efficient, easy, and low-cost method for the determination of 16 priority PAHs in soil. The time of extraction and solvent systems were optimized with the analysis by gas chromatography–mass spectrometry. The method was validated, and the optimum results were obtained using 1:1 cyclohexane:acetone and 1:1 hexane:acetone solvent systems with 30- and 60-min sonication times.     

Acoustical and thermodynamical parameters of aluminium oxide nanoparticles dispersed in aqueous ethylene glycol

In the present work aluminium oxide (Al₂O₃) nanoparticles were synthesised by the precipitation method using AlCl₃ as a starting material. The synthesised nanoparticles were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). These nanoparticles have been dispersed in base fluid, an aqueous solution of ethylene glycol (EG). Density (ρ), ultrasonic velocity (u), and viscosity (η) for these nanofluids have been measured at different concentrations as a function of temperature (T = 303.15 K, 308.15 K, and 313.15 K). Using their values various acoustical and thermodynamical parameters have been computed.     

基于LabVIEW的时间反转超声检测系统的开发

时间反转技术在超声无损检测中的应用非常广泛,它可以忽略介质的非均匀性及初始信号源的位置,能够在时间和空间上聚焦超声波,实现对介质缺陷的聚焦检测。基于LabVIEW图形化编程软件,结合计算机、信号发生器、示波器、超声换能器、GPIB等的使用,对超声检测系统实验平台进行了构建,实现了超声信号的发射、接收以及时间反转一系列的信号处理过程。系统工作过程中,采用了三种不同的时间反转技术：经典时间反转技术(Time Reversal：TR)、反向滤波技术(Inverse Filter：IF)及1位处理技术(1Bit Processing),来实现信号的聚焦。实验验证该系统可以有效的实现时间反转超声检测过程中对信号的激励、接收、处理和存储等功能,有良好的精确性和适用性。     

Phase Diagram Involving the Thermal Stability of TGB and Induced Smectic Phases in Binary Mixture of Thermotropic Liquid Crystals

We report the results of our studies on the optical and thermal properties of the mixture of terephthalidene-bis-4, n-alkylaniline and cholesteryl nonanoate, which exhibits very interesting liquid crystalline mesophases such as cholesteric, twisted grain boundary, smectic-A, smectic-C^*, smectic-C, smectic-I, and smectic-G, sequentially when the specimen is cooled from its isotropic phase. These phases have been characterized by using microscopic techniques. The temperature variations of optical anisotropy, electrical conductivity, ultrasonic velocity, and molar and adiabatic compressibility have also been discussed.