Reflection of plane waves in generalized thermoelasticity of type III with nonlocal effect

The generalized thermoelasticity theory based upon the Green and Naghdi model III of thermoelasticity as well as the Eringen's nonlocal elasticity model is used to study the propagation of harmonic plane waves in a nonlocal thermoelastic medium. We found two sets of coupled longitudinal waves, which are dispersive in nature and experience attenuation. In addition to the coupled waves, there also exists one independent vertically shear-type wave, which is dispersive but experiences no attenuation. All these waves are found to be influenced by the elastic nonlocality parameter. Furthermore, the shear-type wave is found to face a critical frequency, while the coupled longitudinal waves may face critical frequencies conditionally. The problem of reflection of the thermoelastic waves at the stress-free insulated and isothermal boundary of a homogeneous, isotropic nonlocal thermoelastic half-space has also been investigated. The formulae for various reflection coefficients and their respective energy ratios are determined in various cases. For a particular material, the effects of the angular frequency and the elastic nonlocal parameter have been shown on phase speeds and the attenuation coefficients of the propagating waves. The effect of the elastic nonlocality on the reflection coefficients and the energy ratios has been observed and depicted graphically. Finally, analysis of the various results has been interpreted.     

White and some colored marbles as alternative radiation shielding materials for applications

ABSTRACT

In this paper, the radiation shielding parameters such as linear attenuation coefficients (LAC, µ), mass attenuation coefficients (MAC, µ/ρ), effective atomic numbers (Z_eff), effective electron densities (N_eff), half value of layers (HVL), mean free paths (MFP) and buildup factors (exposure (EBF) and energy absorption (EABF)) were investigated for cream (M1), pink (M2), white (M3), maroon (M4) and green (M5) marbles. Attenuation coefficients were measured in the energy region 31.18–661.66 keV photon energies. The values of Z_eff and N_eff were then calculated using these coefficients with logarithmic interpolation method, and HVLs and MFPs were calculated using the values of LAC of marble samples at the same photon energies. The experimental results were compared with the theoretical values obtained from WinXCom program, and good agreements were observed between the experimental and theoretical results. HVLs and MFPs of all marble samples were compared with those of some concretes, glasses and commercial radiation shielding glasses (SCHOTT Co.). The studied marbles were better radiation shielding materials than standard shielding concretes due to lower HVL and MFP values lower than the ordinary concrete. Finally, EBFs and EABFs of the marbles were calculated in the energy region 0.015–1?MeV up to penetration depths of 40 mfps by Geometric Progression method (G-P), and the results were discussed in terms of photon energies and chemical compositions of the marbles.     

Effect of variation in signal amplitude and transit time on reliability analysis of ultrasonic time of flight diffraction characterization of vertical and inclined cracks

The variation of amplitude and transit time of the diffracted signal from the crack-tip in complex geometry components and their resulting effect on the probability of detection (POD) and probability of sizing (POS) was studied. The diffracted signal amplitude has been evaluated from the standard expressions for diffraction coefficient, spatial attenuation and the transit time from the respective mathematical models for both vertical and inclined cracks. The same parameters namely the signal amplitude and the transit time have been measured through experiments conducted on simulated test specimens. It has been observed that the analytical and experimental results compare well with each other. Based on this result the trend and shape (width of the transition zone) of the POD/POS curves can be predicted.     

Selectivity of seismic electric signal (SES) of the 2000 Izu earthquake swarm: a 3D FEM numerical simulation model

Although seismic electric signal (SES) has been used for short-term prediction of earthquakes, selectivity of SES still remains as one of the mysterious features. As a case study, we made a numerical simulation based on a 3D finite element method (FEM) on the selectivity of SES observed in the case of the 2000 Izu earthquake swarm. Our numerical results indicated that the existence of conductive channel under Niijima island could explain the reported SES selectivity.     

Extreme beam attenuation in double-slit experiments: Quantum and subquantum scenarios

Combining high and low probability densities in intensity hybrids  , we study some of their properties in double-slit setups. In particular, we connect to earlier results on beam attenuation techniques in neutron interferometry and study the effects of very small transmission factors, or very low counting rates, respectively, at one of the two slits. We use a “superclassical” modeling procedure which we have previously shown to produce predictions identical with those of standard quantum theory. Although in accordance with the latter, we show that there are previously unexpected new effects in intensity hybrids for transmission factors below a?10⁻⁴$a?10^{-4}$, which can eventually be observed with the aid of weak measurement techniques. We denote these as quantum sweeper effects, which are characterized by the bunching together of low counting rate particles within very narrow spatial domains. We give an explanation of this phenomenology by the circumstance that in reaching down to ever weaker channel intensities, the nonlinear nature of the probability density currents becomes ever more important, a fact which is generally not considered–although implicitly present–in standard quantum mechanics.     

三峡小江回水区水体光学特征及分析

为探讨三峡水库运行初期小江回水区水体的光学特性,研究了2008年1月至12月期间小江回水区5个断面可见光衰减系数Kd(PAR)与透明度的时空分布特征及二者的相关性,进一步分析了可见光衰减系数与透明度、悬浮物浓度、溶解性有机物及叶绿素等水质指标的相关关系。研究区域可见光衰减系数和透明度空间分布差异不明显,但季节变化显著。可见光衰减系数在0.23~4.82 m-1之间变化,均值为(1.03±0.07) m-1,冬季最高,夏季最低。统计分析表明,可见光衰减系数与透明度有显著的相关性(R2=0.7791),表明两者可相互反演。与总颗粒态物质浓度,总无机颗粒态物质浓度的相关性显著(R2 =0.728 5,R2=0.763 7),与溶解性有机碳有一定的相关性(R2=0.128 9),与叶绿素a相关性不明显(R2=0.006),分析表明总无机颗粒态物质是小江回水区水体光学特征的最主要影响因素。     

基于ASD光谱仪的悬浮泥沙光学衰减系数研究

 设计了基于ASD光谱仪的玻璃水槽实验,测量人工光源穿透不同水深、不同质量浓度含沙水体的辐亮度,以纯水为参照,得出了某一粒径组成下不同质量浓度悬浮泥沙在350~920 nm波段范围内的光学衰减系数。实验泥沙样本的光学衰减系数光谱特征单一,随着波长的增大逐渐减小,表现为一条略倾的曲线,且正比于泥沙质量浓度。在0~0.15 m深度范围内的,相同质量浓度的泥沙光学衰减系数随水深的变化可以忽略不计。从350~920 nm,实验泥沙样本的单位质量浓度光学衰减系数从0.084缓慢减小至0.069 m²/g。     

流量折减系数对雨水系统设计标准的影响

我国室外排水设计规范规定采用折减系数计算雨水排水设计流量,造成了设计标准和抗灾能力与国外的类似工程相偏低.在适当假设的基础上,推求出折减系数为1和2时重现期关系的数学表达式,根据实例分析,当折减系数为1时设计重现期为1年不同时刻的设计流量相当于折减系数为2时重现期1.531～4.028年的标准;当折减系数为2时设计重现...     

多单相逆变器线与工作的Multisim仿真

线与的概念来源于数字逻辑电路系统,本文将其应用在逆变驱动系统中,即不借助于任何接口控制电路,将多个单相逆变器的输出端直接并联在一起,共同驱动同一个负载.该技术的关键在于:系统中每一个单相逆变器根据其自身的承载力按比例分担负载的相应分量,本文利用频率、基波电压以及谐波电压的衰减校正算法来完成的,最后用Multisim的仿...