Unified boundary integral equation for the scattering of elastic and acoustic waves: solution by the method of moments

A unified boundary integral equation (BIE) is developed for the scattering of elastic and acoustic waves. Traditionally, the elastic and acoustic wave problems are solved separately with different BIEs. The elastic wave case is represented in a vector BIE with the traction and displacement vectors as unknowns whereas the acoustic wave case is governed by a scalar BIE with velocity potential or pressure as unknowns. Although these two waves can be unified in the form of a partial differential equation, the unified form in its BIE counterpart has not been reported. In this work, we derive the unified BIE for these two waves and then show that the acoustic wave case can be derived from this BIE by introducing a shielding loss for small shear modulus approximation; hence only one code needs to be maintained for both elastic and acoustic wave scattering. We also derive the asymptotic Green's tensor for zero shear modulus and solve the corresponding vector equation. We employ the method of moments, which has been widely used in electromagnetics, as a numerical tool to solve the BIEs involved. Our numerical experiments show that it can also be used robustly in elastodynamics and acoustics.     

流动注射化学发光法测定盐酸曲普利啶

在碱性溶液中,N-氯代丁二酰亚胺可以氧化二氯荧光素产生化学发光。盐酸曲普利啶的存在可以显著地增强这一反应的化学发光信号。基于此,结合流动注射技术,优化了实验条件,建立了测定盐酸曲普利啶的流动注射化学发光新方法。该方法测定盐酸曲普利啶的线性范围1.0×10^-9—1.0×10^-7g/mL,检出限为5.0×10^-10g/mL。对浓度为7.0×10^-9g/mL盐酸曲普利啶溶液进行11次平行测定的相对标准偏差为4.1%。该方法已用于药物制剂中盐酸曲普利啶的含量测定,结果令人满意。     

Synthesis and crystal structure of 5-amino-4-cyano-1-[(5-methyl-1-t-butyl-4-pyrazolyl)carbonyl]-3-methylthio-1H-pyrazole

The title compound, 5-amino-4-cyano-1-[(5-methyl-1-t-butyl-4-pyrazolyl)carbonyl]-3-methylthio-1H-pyrazole 5, was synthesized by the treatment of 4 (5-methyl-1-t-butylpyrazole-4-carbohydrazide) with 2-cyano-3, 3-dimethylthio-acrylonitrile, and its crystal structure was determined by X-ray diffraction method. The crystal belongs to monoclinic, space group P2₁/c with unit cell parameters a = 13.566(4) Å, b = 10.833(3) Å, c = 11.202(3) Å, α = 90°, β = 98.073(5)°, γ = 90°, V = 1629.9(8) ų, Z = 4, D _c = 1.298, M _r = 318.40, μ = 0.210 mm⁻¹, F(000) = 672, R ₁ = 0.0488 and wR ₂ = 0.1250.     

Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ bulk metallic glass has a unique quenched-in nuclei/amorphous matrix structure. The crystallization of quenched-in nuclei, when the experimental isothermal annealing time is within its incubation time, may not disturb the enthalpy relaxation, which makes it have the accordingly common enthalpy relaxation behavior with amorphous materials. The alloy's annealing time dependence of recovery enthalpy follows a stretched exponential function with the mean relaxation time obeying an Arrhenius law. The equilibrium recovery enthalpy ΔH_T^eq, mean relaxation time τ and stretching exponent β are all dependent on the annealing temperature, and generally, a higher annealing temperature comes with a lower value of ΔH_T^eq, τ and a higher value of β. Two parameters, β_g and τ_g, representing the stretching exponent and the mean structural relaxation time at the calorimetric glass transition temperature, respectively, are correlated with glass forming ability and thermal stability, respectively. For Ti₄₀Zr₂₅Ni₈Cu₉Be₁₈ BMG, the high value of β_g, which is much higher than 0.84 and approaches unity, reveals its good glass forming ability, while, on the other hand, the low value of τ_g indicates a worse thermal stability compared with typical BMGs.     

[Bi(C10H8N2)(C5H4NCOO)(NO3)2]·0.5H2O的合成与光谱性质

以Bi(NO3)3·5H2O、2-吡啶甲酸和2,2'-联吡啶为原料,合成了配合物[Bi(C10H8N2)(C5H4NCOO)(NO3)2]·0.5H2O,并采用元素分析、红外光谱(FT-IR)、热重分析(TG-DSC)、X射线粉末衍射(XRD)和荧光光谱对其组成和结构进行了表征.结果表明,该配合物具有荧光性质,且Bi3+与2-吡啶甲酸中的两个羧基O原子、2,2'-联吡啶的2个N原子及两个NO3-形成六配位螯合物.在空气中其热分解包括失去结晶水、配体的逐步挥发与氧化分解过程,550℃后完全形成Bi2O3.对其X射线粉末衍射数据进行指标化计算证实该配合物晶体结构属于单斜晶系,晶胞参数为:a=1.810 nm,b=1.285 nm,c =1.214 nm,β=88.83°.     

基于改进型高斯混合模型的嵌入式实时运动检测系统

针对在嵌入式CPU上难以做到复杂背景下运动目标的实时检测,提出了一种基于改进型高斯混合模型的实时运动检测方案,采用改进型高斯混合模型,对高斯混合模型进行简化和结构调整,同时进行了C语言层面和CPU层级的优化,使其更合适于嵌入式平台,并详细分析了DM6446平台的软硬件设计,介绍了该算法在DM6446平台上的实现过程。实验结果表明：该系统能够有效克服外界环境变化带来的干扰,能够实时检测,可以实现多目标跟踪。     

岩质边坡稳定性及预应力锚固分析现状

本文首先对目前常用的各类边坡稳定性分析方法的主要特点进行了评述,包括定性方法类的历史分析法、工程地质类比法、图解法、专家系统法,定量分析方法类的确定性模型法,如极限平衡法,应力应变分析法;非确定性模型法,如可靠性分析法、灰色系统理论法及模糊综合评判法等;及两类方法结合而成的随机有限元法。其次,对预应力锚固边坡的设计及稳定性分析作了阐述。     

硅微陀螺梳齿驱动的面内失准分析

静电梳齿微驱动器因其结构简单、功耗低、灵敏度高、受温度影响小，成为硅微陀螺仪的主要驱动方式。静电梳齿微驱动器通常由活动梳齿和固定梳齿组成。理想情况下，活动梳齿平行地位于两固定梳齿中心位置。但由于加工误差、驱动结构不对称、扰动等因素，使得活动梳齿相对固定梳齿发生偏转。该文应用能量法及虚功原理，建立了梳齿之间的力与力矩平衡方程。得出了非理想情况下，偏离距离和转角的解析表达式，并分析得出了梳齿间的临界电压。经过数值仿真发现，梳齿面内既偏转又转动时的临界电压小于只发生偏转或转动时的临界电压。     

茜素红-铽光谱探针共振瑞利散射法测定加替沙星

提出了共振瑞利散射光谱法测定人体血浆,尿样中加替沙星含量的方法。在p H5.5~6.5的HAc-Na Ac缓冲溶液中,加替沙星(Gatifloxacin,GTFX)与Tb(Ⅲ)反应形成的二元螯合物共振瑞利散射(Resonance Rayleigh Scattering,RRS)强度极弱,但当其进一步与酸性染料茜素红反应形成三元离子缔合物时,RRS显著增强,其最大散射波长分别位于373 nm和605nm处。在373 nm处,方法的线性范围和检出限分别为0~5.26μg·m L-1和7.5 ng·m L-1。本法简便、快速,并具有良好的选择性,用于片剂,人尿液和血浆中加替沙星含量的测定,其回收率在96.1~104.5%。