采用常规状态方程计算氦-3热力性质的可行性研究

3He作为一种特殊的工质在低温工程、基础物理学和空间技术等领域获得重要应用,这些应用需要可靠的3He热力学性质数据。但是目前没有适用于3He的宽范围状态方程。不仅如此,而且有关的热物性实验数据也十分稀缺,这给应用3He的研究人员带来了困难。本文基于全面收集和整理有关3He的各类数据,通过编写计算机程序,考察了五种常用的状态方程(理想气体状态方程,范德瓦尔方程,RK方程,RKS方程和PR方程)用于计算3He在4K~100K温区定压下比容-温度关系的可行性,并将计算结果与实验数据进行了比较。这些比较结果将为3He状态方程的研究提供有价值的参考。     

PR状态方程的二元混合制冷剂热力性质计算

基于PR状态方程法和剩余函数法建立了混合制冷剂在过冷区、两相区以及过热区的热力学参数计算模型,将混合制冷剂R410A的计算结果与NIST数据库进行比对以验证模型精度.在此基础上,对二元混合制冷剂CO2/R600a(33.546/66.454,mass％)在不同相区的热力性质进行了推算,其计算结果可以用于以CO2/R600a为制冷剂的制冷系统的热力计算分析和性能优化.     

二氧化碳热力学性质的理论计算

用HF、MP2、QCISD和B3LYP四种方法,在6-311G* *基集合水平上对气态CO2(X1Σg)分子全优化,可直接得到热力学性质熵S和定压热容CP,在这四种方法中,B3LYP方法算得的结果与实验值最吻合,其相对误差分别只有0.00%和-0.15%;CO2分子的生成焓包含电子焓(为-393.31 kJ.mol-1)和核部分焓(为1.653 kJ.mol-1)两部分,其生成焓相对误差为0.37%.结果表明,所用理论方法计算气态CO2分子在1atm下的热力学性质是可行的.     

一个改进的三次型状态方程

本文提出了一个改进的 Van Der Waals (VDW) 型状态方程p=RT/(v-b)-aa(T)/(v+mb)(v-nb)其中m,n是偏心因子ω的函数,a(T)是温度和临界压缩因子的函数。检验结果表明:本方程一般都比 RKS 方程和 PR 方程精度要高,对某些物质则和这两个方程相当,对液相体积的计算精度提高尤为明显。最后,本文还提出了相应的混合规则。     

超临界CO2热力学性质的理论计算

应用BWR方程在温度为310～600 K、压强为75～300 bar范围内拟合的超临界CO2流体状态方程,计算了超临界状态下CO2体系的熵、热容和焓.研究表明,这些热力学函数具有明显的超临界特性;与文献值相比,超临界状态下CO2熵的相对误差小于0 .4%,而定压热容的相对误差稍大,为2.45%(T:330～360 K),其数据为进一步从理论上研究超临界CO2与金属铀表面反应的热力学行为奠定了基础.     

无损贮存及涨罐饱和相热力学模型研究

在低温液体无损贮存及涨罐研究方面,经常采用一种假设容器内气、液相均为饱和相的热力学模型.这种模型比较符合实际,并能够大大简化容器内的热力学状态,是一种比较常用的热力学模型.文中利用一个5m3低温贮罐进行的液氮无损贮存及涨罐试验,对该热力学模型进行了对比研究,讨论了饱和相热力学模型误差产生的原因,对于无损贮存和涨罐研究具...     

花生壳吸附水中苯酚的热力学与动力学研究

利用废弃的花生壳对水中苯酚进行吸附试验,考察了吸附的最佳条件、吸附热力学和动力学特征.采用Langmuir和Freundlich等温线对平衡数据进行了线性拟合,结果表明,花生壳对苯酚的吸附平衡符合Freundlich等温方程.在298K下,吸附焓变△H=-5.12kJ ·moL^-1,自由能变△G=-4.41 kJ·moL^-1,熵变△S=-2.38J·mo1-1·K-1.表明：该吸附过程为自发进行的放热过程,其动力学行为更好的符合Lagergren准二级动力学模型.     

CO2气、液、固三相饱和态下pVT的计算

本文基于分子聚集理论和硬球引力场模型应用分子热力学方法导出CS-vdW状态方程,应用上述方程计算了CO2气-液和气-固平衡相的饱和态下pVT性质.取得了很满意的结果.本方法的优点是使用简便,可供工程计算使用.     

流体的格鲁尼森数及其对状态方程的检验

格鲁尼森数是一个无量纲的热力学参数,通常被用来描述固体的热力学性质.由于其对流体的临界点不敏感,它对于检验非理想流体的热力学性质也有指导意义.本文通过计算多种流体在不同温度和压力下的格鲁尼森数,发现其数值在宽广区域里变化稳定,进而论述了格鲁尼森数与其他热力学参数的关系.以PR方程和BWR方程为例,阐述了格鲁尼森数对于检验状态方程完善性的标尺性作用.     

超临界CO2钝化金属铀的理论研究

考察超临界CO2 对金属铀表面的钝化作用.首先计算UC、C、UO2 和超临界CO2 的结构和热力学性质,基于这些性质,应用化学平衡原理计算,计算结果指出,反应U(α) +CO2 (g) UO2 (s) +C(Graphite)的△G°为-149. 8~-632. 0kJ,反应2U(α) +CO2 (g) UO2 (s) +UC(s)的△G°为-725. 1~-730. 2kJ,两者均远小于零,即△G<0,且平衡很接近产物一端UC、C、UO2.同时,已经熟知超临界流体的动力学性质极活泼,所以,产物UC、C和UO2 是很稳定的主要成分.根据所计算的产物分子比可以得到元素计量比为UC0. 65±0. 01O1. 30±0. 01,这显然不代表某种分子,但是,这对XPS分析很有用.     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

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.