二乙二醇二甲醚液相导热系数实验研究

本文利用瞬态单热线法对温度区间233～373 K、压力区间0.1～30 MPa的二乙二醇二甲醚(DMDE)的导热系数进行了实验研究,为替代燃料研究提供了基础数据,导热系数测量不确定度为±2%.实验数据拟合成导热系数关于温度和压力的方程,实验数据与拟合方程计算值的最大偏差为-2.56%,平均绝对偏差为0.91%.     

三氟碘甲烷的新气相状态方程和输运物性

提出了三氟碘甲烷（ＣＦ３Ｉ）的新蒸气压方程和新状态方程；给出了ＣＦ３Ｉ的偏心因子、正常沸点等物性参数，并与文献值进行了比较．使用毛细管粘度计测量了ＣＦ３Ｉ的２５３～３３８Ｋ的饱和液粘度，采用以钽丝为热线的双线瞬态热线法测量了ＣＦ３Ｉ的气相导热系数，并分别给出了关联式．     

热线法测量保温材料的导热系数

本文在分析热线法测量导热系数原理的基础上,应用热线法测定了几种保温材料不同温度下的导热系数。并通过Origin7.0对测量结果进行了数据线性拟合,可快捷、精确地获得测量结果。     

径向导热条件下圆柱状样品金属导热系数的测定

由于棒状样品轴向导热法测定导热系数的实验中无法准确测定棒表面的散热,故实验结果误差较大;而稳态平板法又不能用于金属导热系数的测定。另外,这两种方法均无法反映导热系数随温度的变化;故此类方法的意义有限。本文尝试采用圆柱状样品径向导热法来测定金属的导数系数。实验结果显示该方法取得了初步成功。一、轴对称区域上的稳态导热稳态导热条件下,各向异性区域内的温度分布满足▽·(λ▽T)=0 (1) 由于导热系数λ仅为温度的函数,故(1)式可化为     

氦-3熔化压力方程

在广泛收集实验数据和理论关联式的基础上,提出了低温流体3He的宽温区、高精度熔化压力方程。该方程采用国际标准单位制,首次以统一而非分段的形式描述了3He在0．001 K-30 K宽温区熔化压力与温度的关系,方程计算值相对于406个实验数据点的最大和平均偏差分别为3．02％和0．106％。计算表明,该方程在0．31586 K时存在最小压力 2．93113 MPa,这一结论与以往的实验和理论研究非常吻合。     

圆筒形半透明介质内非稳态复合导热与辐射的研究

本文研究细长电加热体在圆筒形半透明介质中的温度响应，通过对控制非稳态导热与辐射复合传热过程的积分-微分方程直接进行数值求解，分析了热辐射对内部径向热流及温度变化的影响．模拟计算结果对热线法测量半透明介质导热系数的研究具有理论指导意义。     

纳米颗粒TiO2/HFC134a工质导热系数实验研究

本文采用瞬态热线法对纳米颗粒TiO2/HFC134a工质的导热系数进行了实验研究.结果表明,相对于HFC134a,纳米颗粒TiO2/HFC134a工质的导热系数增大,提高比例随着颗粒浓度和温度的提高而增大.     

计及温度影响的散体有效导热系数模型

本文导出了基于逾渗理论并考虑温度影响的散体有效导热系数预测模型。针对孔隙中流体的传热机理,诠释了无量纲参数φ的物理意义。对SiC、SiO2和煤灰等散体材料在自行研制的实验系统上采用断电热线法测量了其在50-600℃范围内的有效导热系数。结果表明:实验值与模型预测值吻合良好,这三种散体材料的有效导热系数都随温度的增加而增大。     

气冷涡轮叶片传统热分析中热边界条件的影响

以MarkII气冷涡轮叶片为研究对象,考察了换热系数分布对叶片外表面温度分布的影响。首先分别以温度和换热系数实验值作为热边界条件验证了固体导热计算方法和CFD程序的有效性,然后分析了6种典型热边界条件下的叶片外表面温度分布,并与实验值进行对比。由分析结果可知:叶片外表面温度与换热系数紧密关联,经验关联式(层流、湍流)条件下预测得到的温度偏差较大,当换热系数由能考虑边界层转捩影响的CFD计算得到时,预测得到的温度与实验值较为接近。     

硅晶体热传导性能的分子动力学模拟

基于硅色散关系的实验值,给出硅晶体导热系数的经典分子动力学模拟所必需的温度、导热系数的量子化修正曲线。应用平衡态分子动力学算法模拟了硅晶体在 300～700 K温度区间内的导热系数,模拟结果表明,理想硅晶体的导热系数比自然硅高60％～75％,但随着温度的下降,模拟结果的准确性下降。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.