Electromagnetic chirality-induced negative refraction with the same amplitude and anti-phase of the two chirality coefficients

This paper suggests a scheme of electromagnetic chirality-induced negative refraction utilizing magneto-lectric cross coupling in a four-level atomic system. The negative refraction can be achieved with the two chirality coefficients having the same amplitude but the opposite phase, without requiring the simultaneous presence of an electric-dipole and a magnetic-dipole transition near the same transition frequency.

Nonlinear Refractive Index and Absorption Coefficient of Single-Shell Semiconductor Carbon Nanotube

The nonlinear refractive index and absorption coefficient of single\|shell semiconductor carbon nanotubes(CN s ) are calculated based on the two\|band approximation and Genkin\|Mednis approach. The results of nonlinear refractive index and absorption coefficient reach the order of 10 -8 and 10 -4 cm 2\5W -1 separately, which indicates that CN s have wonderful nonlinear optical properties. Taking into account the temperature effect and overlapping of σ and π orbits, the effect of relaxation term and chiral angle is discussed. The results show that the smaller the relaxation term, the larger the nonlinear absorption coefficient and refractive index. At the same time, CN s with different chiral angles have different results due to their different energy gap.

Determination of the Refraction Coefficient and Its Uncertainty by Using Modern Hydrostatic Levelling Systems

In spite of the technological development of the last decades in the field of the geodetic instruments,some parameters,which affect their performance,are difficult to be eliminated.One of these parameters is the geodetic refraction.The refraction describes the alteration in the direction of the light curve as it propagates through the different layers of the lower part of the Earth’s atmosphere.The purpose of this research work is to investigate the uncertainty of the refraction coefficient of a new proposed methodology.This methodology is based on:(a)the exploitation of the full trigonometric height equation,(b)the ability of the Hydrostatic Levelling System(HLS)to provide height differences with±10μm accuracy.The experimental application has been set up in a section of the underground tunnel complex at the European Organization for Nuclear Research.In this indoor application,the determination of the refraction coefficient at a Laser Tracker station using the precise height differences provided by an HLS has been performed.In addition,this methodology has been tested by comparing its results with those that have been obtained from the Temperature Gradient(TG)method for the determination of the refraction coefficient.The results are very encouraging for the efficiency of the methodology.At the same time,some limitations on the implementation of the proposed methodology have been highlighted.

The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry

We present the thermal expansion coefficient （TEC） measurement technology of compensating for the effect of variations in the refractive index based on a Nd： YA G laser feedback system, the beam frequency is shifted by a pair of aeousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-refiectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 29-748K, confirming not only the precision within 5 × 10-7 K-1 and the accuracy within 0.4% from 298K to 448K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.

Refractive Index and Extinction Coefficient of Hg_(1-x)Cd_(x)Te at 77 and 300K

We measured refractive index and extinction coefficient of n type Hg1-xCdxTe with the null ellipsometric spectrum method over the visible light region at 77 and 300K,and the dispersion relation at different temperature is discussed.The value of refractive index at 77K is smaller than that at 300K,and the changes of the extinction coefficient curve at 77K is also smaller than that at 300K.

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids. The propagation of three longitudinal waves is represented through three scalar potential functions. The lone transverse wave is presented by a vector potential function. The displacements of particles in different phases of the aggregate are defined in terms of these potential functions. It is shown that there exist three longitudinal waves and one transverse wave. The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated. For the presence of viscosity in pore-fluids, the waves refracted to the porous medium attenuate in the direction normal to the interface. The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave. The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of the energy across the interface is verified. The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed,

Reflection and refraction of plane waves at the boundary of an elastic solid and double-porosity dual-permeability materials

Phenomena of reflection and refraction of plane harmonic waves at a plane interface between an elastic solid and doubleporosity dual-permeability material are investigated. The elastic solid behaves non-dissipatively, while double-porosity dual-permeability materials behave dissipatively to wave propagation due to the presence of viscosity in pore fluids. All the waves(i.e., incident and reflected) in an elastic medium are considered as homogeneous(i.e., having the same directions of propagation and attenuation), while all the refracted waves in double-porosity dual-permeability materials are inhomogeneous(i.e., having different directions of propagation and attenuation). The coefficients of reflection and refraction for a given incident wave are obtained as a non-singular system of linear equations. The energy shares of reflected and refracted waves are obtained in the form of an energy matrix. A numerical example is considered to calculate the partition of incident energy among various reflected and refracted waves. The effect of incident direction on the partition of the incident energy is analyzed with a change in wave frequency, wave-induced fluid-flow, pore-fluid viscosity and double-porosity structure.It has been confirmed from numerical interpretation that during the reflection/refraction process, conservation of incident energy is obtained at each angle of incidence.

The Mathematical Modelling for Studying the Influence of the Initial Stresses and Relaxation Times on Reflection and Refraction Waves in Piezothermoelastic Half-Space

The present paper concentrates on the study of reflection and refraction phenomena of waves in pyroelectric and piezo-electric media under initial stresses and two relaxation times influence by apply suitable conditions. The generalized theories of linear piezo-thermoelasticity have been employed to investigate the problem. In two-dimensional model of transversely isotropic piezothermoelastic medium, there are four types of plane waves quasi-longitudinal (qP), quasi-transverse (qSV), thermal wave (T-mode), and potential electric waves (φ-mode) The amplitude ratios of reflection and refraction waves have been obtained. Finally, the results in each case are presented graphically.

红外通信特性实验中用解析解计算材料的光学常数

在红外通信特性实验中测量材料的光学常数,可以通过测量反射率和透射率来获得,但现有的近似求解方法存在误差,并因此导致实验只能测量衰减很小或者很大的材料。针对此问题,通过求解关于待测量的方程组得到其解析解,由解析解可直接计算材料的消光系数、衰减系数和折射率,改进的计算方法具有更大的普适性。

大坝一等水平位移监测网数据处理流程及精度保障措施

大坝水平位移监测网是大坝变形监测的平面基准,监测网的精度关系大坝变形监测结果的可靠性和大坝安全鉴定结论的正确性。为了提高监测网数据处理精度,依托大型水电站大坝监测网复测项目,研究分析相对湿度、斜距化平方法、地球曲率半径对边长改化的影响。结果表明:相对湿度修正对边长的影响值最大可达2 ppm,斜距化平时采用高差计算的边长比采用垂直角计算的边长精度高0.05~1.95 ppm,用测区地球平均曲率半径代替测距边法截线地球曲率半径对投影边长的影响值最大可达0.08 ppm;高精度大坝水平位移监测网数据处理时,应用相对湿度修正实测边长,优先选用高差斜距化平,可用测区地球平均曲率半径代替测距边法截线地球曲率半径。研究成果可为类似项目提供有益参考。

基于有限元模拟的超声应力系数标定及分析

应力系数的标定作为超声应力检测最为关键的环节,决定应力检测的精度。应力系数的传统试验标定对于被测物表面粗糙度、耦合剂厚度、声匹配块与被测物接触力等检测因素十分敏感。加之各影响因素之间的耦合作用,使得精确标定出应力系数愈加困难。文章提出把应力系数分为反映材料声弹性效应的基本值和考虑各类检测因素的影响值两部分,可能是当前较为实用的办法。基于有限元软件建立多物理场耦合的超声应力检测模型,施加不同的拉伸载荷,分析临界折射纵波到达时间与不同应力值之间的关系。结果表明:模拟标定45#钢的超声应力系数基本值为13.7 MPa/ns。同时通过4组单轴水平拉伸试验标定出检测因素影响值分别为1.0 MPa/ns、1.7 MPa/ns、2.8 MPa/ns和6.8 MPa/ns。在合理情况下,应力系数基本值直接决定应力系数的大小,检测因素对应力系数值的影响应该较小。检测因素影响值6.8 MPa/ns达到应力系数基本值13.7MPa/ns的49.6%,超出合理范围,观察发现这是声匹配块与被测面耦合后尚存在局部微小间隙的结果,可判定为无效数据。有限元模型在理想检测条件下模拟获得应力系数基本值,通过比较应力系数基本值和检测因素影响值,可以判断检测质量的优劣,减小应力系数标定数据的离散性,提高超声应力检测结果的可信度。

Volumetric,Viscometric and Refractive Index Behaviors of α-Amino Acids in Aqueous Caffeine Solution at Varying Temperatures

Measurements of density(ρ), viscosity(η), and refractive index(n), were carried out on α-amino acids, DL-alanine (Ala), D-phenylalanine (Phe), and DL-threonine (Thr) (0.01-0.05 mol·L-1), in 0.05 mol·L-1 aqueous caffeine solution at 298.15, 303.15, 308.15, and 313.15 K. These measurements have been carried out to evaluate some important parameters, viz., apparent molar volume (фυ), partial molar volume (фυ0v), transfer volume (фυ0v(tr)), viscosity A and B coefficients of Jones-Dole equation, free energies of activation per mole of solvent (Δμ0#1) and solute (Δμ0#2), enthalpies (ΔH) and entropies (ΔS) of activation of viscous flow, variation of B with temperature (αB/αT)P, and molar refractive index (RD). These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and structure making/breaking ability of solutes in the given solution.

基于衍射原理测量石英玻璃的热光系数

热光系数是描述热光效应的基本物理量之一。目前热光系数的常见测量方法是干涉法和光谱法,但均需复杂的实验设计和较高的仪器成本。为此,提出了一种基于衍射原理测量石英玻璃热光系数的方法,仅采用一台分光计即可实现石英玻璃热光系数的测量。通过测量石英光栅的第三级衍射光栅光谱随温度的漂移曲线,得到石英玻璃热光系数1.092×10^(-5)/K,与石英玻璃热光系数理论值1.0×10^(-5)/K非常接近。

基于多项式求根的双厚度透射率模型确定光学常数

为解决光谱反演法确定物质光学常数的一些问题,基于传统的双厚度透射率模型,建立厚度分别为L和2L的光谱透射率方程,通过代数运算获得与衰减系数有关的八次多项式方程,求解并选择其大于0小于1的实数根来计算衰减系数和消光系数;再求解关于界面反射率的一元二次方程,选择其大于0小于1的根来计算折射率。在确定光学常数的过程中,新方法没有反演误差和迭代计算耗时问题。利用已知文献中庚烷的光学常数验证新方法的可靠性,并分析了双厚度不满足2倍关系时对计算结果的影响,结论是第二厚度2L的相对误差不超过1%时,消光系数的计算误差不超过2.03%,不考虑3个强吸收点时,折射率的计算误差不超过1%。

基于多项式求根的双厚度透射率模型确定透明固体光学常数

为解决光谱反演法确定透明固体光学常数的一些问题,如存在反演误差、计算耗时等。本文基于传统的双厚度透射率模型,建立了厚度满足整数比的两个光谱透射率方程。通过代数运算获得了与消光系数有关的多项式方程,求解并选择大于0小于1的实数根来计算消光系数;然后求解关于界面反射率的一元二次方程,选择大于0小于1的根来计算折射率。在确定光学常数的过程中,新方法没有反演误差、迭代计算耗时及多值问题。作为应用示例,利用已知文献中的双厚度透射率实验数据计算了CaF_(2)和Si的光学常数,并和文献的结果进行了比较。结果表明,新方法优于传统的光谱反演法,新方法为透明固体光学常数的高精度确定提供了新选择。

基于太赫兹光谱的乙二醇含水率检测方法研究

乙二醇水分含量检测标准方法为卡尔·费休法,该方法操作繁琐、耗时长,且存在人为误差等缺点,提出基于太赫兹时域光谱技术检测乙二醇中含水率的新方法,采用透射式太赫兹时域光谱系统对不同含水率(0~50)的乙二醇溶液进行测定,获得其时域光谱,计算得到不同含水率乙二醇样本的吸收系数和折射率;采用标准正态变换、Savitzky Golay平滑等方法组合对光谱数据进行预处理,基于处理后折射率和吸收系数建立PCR、PLSR、SVR三种预测模型,通过对比模型的相关系数和均方根误差,选出最优的定量分析模型。结果表明:在基于吸收系数建立的预测模型中,经SNV处理后乙二醇吸收系数的SVR模型预测性能最佳,其预测集R^(2)与RMSEP分别为09941和000451;在基于折射率建立的预测模型中,经S G平滑预处理后乙二醇折射率的SVR模型预测性能最佳,预测集R^(2)与RMSEP分别为09988和000507;均具有较高的预测精度。研究表明,文章实现了乙二醇含水率快速、无损和高精度检测,所提方法能为乙二醇质量快速评价提供技术指导,也为有机溶剂水分含量检测提供一种新思路。

基于故障暂态低频分量积聚值的新能源送出线路保护方案研究

高比例新能源接入使得传统工频量保护难以适用,而行波保护是目前解决新型电力系统可靠性问题的有效途径之一。现有电流行波极性比较式保护方案依赖于首波头的准确捕捉。对此,首先分析了区内外故障时行波的折反射过程,明确了初始行波与后续折反射波间的极性和幅值关系,并定性分析了区内外故障时电流波形的变化趋势。在此基础上,利用故障暂态电流低频分量积聚值表征初始行波极性特征,进而提出了一种新型行波极性比较式纵联保护方案,可以有效解决高阻或小故障初相角情况下传统保护方案可靠性不足问题。最后,大量的PSCAD/EMTDC仿真实验表明,新方案能够可靠识别区内外故障,且具有较好的耐过渡电阻以及抗噪声干扰的能力。

平面波在异向介质界面反射与折射条件研究

采用数值计算方法研究了平面波在异向介质界面的反射与折射条件.研究发现,当系数α>1时,TE与TM波反射与透射系数相等,且对同一入射角随着α的增大,TE和TM波反射系数随之增大,而透射系数随之减小;当系数α=1时,波在界面处发生全折射;当系数α<1时,以大于临界角入射时,TE和TM波均发生全反射,复反射系数幅值为1;当μ2=-αμ1时,只有在α=1时,按arctan(√-ε2/ε1)角入射时电场平行分量会全透射;当ε2=-αε1时,只有在α=1时,按arctan(√-μ2/μ1)角入射时电场垂直分量可全透射.研究结论对分析异向介质电磁传输特性及人工合成新型异向介质都具有重要指导意义.

一种新型的大气污染物消光测量系统

基于光在长光程吸收池中的传输特性,设计了一套新型的大气污染颗粒物消光模拟测量系统。该系统由消光测量装置和大气污染颗粒物模拟装置构成。消光测量装置主要由激光器、开放式Herriot长光程吸收池和光功率计构成。在消光测量装置中,开放式Herriot长光程吸收池将某一波长的光经固定角度的镜片多次反射达到增大光程的目的;同时有利于对其内部反射镜表面的清洁,提高消光测量的灵敏度;还能够实时检测用于消光的颗粒物浓度。消光系数通过吸收池入口和出口处监测到的光功率计算获得,光功率的测量中利用差分法降低了激光器本身能量波动带来的误差,提高消光系数测量的准确性。通过与真实大气雾霾情况下激光雷达测量到的消光系数进行对比,验证了所搭建消光模拟测量系统的合理性。

考虑区域影响的焊接残余应力超声法试验研究

为提高超声法检测焊接残余应力的准确性,对母材区、热影响区和熔融区的声弹性系数进行标定。基于声弹性系数标定值和零应力基准,修正Q345qD焊接钢板残余应力检测结果,并采用盲孔法对超声法检测结果进行验证。试验结果表明:母材区、热影响区和熔融区的声弹性系数存在较大差异;通过对热影响区域进行声弹性系数及零应力基准修正,可减少该区域的高估应力值;盲孔法和超声法测量结果趋势相同,数值接近,验证了超声法检测焊接残余应力结果的准确性。