Dissociation constants of the ampholyte glycine in 50 mass % methanol-water from 5 to 55°C,with related thermodynamic quantities

The two thermodynamic dissociation constants of glycine at 11 temperatures from 5 to 55°C in 50 mass % methanol-water mixed solvent have been determined from precise emf measurements with hydrogen-silver bromide electrodes in cells without liquid junction. The first acidic dissociation constant (K ₁)for the process HG⁺H⁺+G^± is expressed as a function ofT(^oK) by the equation pK ₁ = 2043.5/T – 9.6504 + 0.019308T. At 25°C, pK ₁is 2.961 in the mixed solvent, as compared with 2.350 in water, with H°=1497 cal-mole^–1, G°=4038 cal-mole^–1, S°=–8.52 cal-°K^–1-mole^–1, and C _p ^o =–53 cal-°K^–1-mole^–1. The second acidic dissociation constant (K ₂)for the process G^±H⁺+G^– over the temperature range studied is given by the equation pK ₂ = 3627.1/T – 7.2371 + 0.015587T. At 25°C, pK ₂is 9.578 in MeOH–H₂O as compared with 9.780 in water, whereas H° is 10,257 cal-mole^–1, G° is 13,063 cal-mole^–1, S° is –9.41 cal-°K^–1-mole^–1, and C _p ^o is –43 cal-°K^–1-mole^–1. The protonated glycine becomes weaker in 50 mass % methanol-water, whereas the second dissociation process becomes stronger despite the lower dielectric constant of the mixed solvent (=56.3 at 25°C).     

Liquid–paper interactions during liquid drop impact and recoil on paper surfaces

The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction.     

用电子散斑干涉法测量材料热膨胀系数

 利用双光束电子散斑干涉法（ESPI）对试件受热变形进行了实时观测，针对一次实验过程中得到的图片较多（300～500幅）的特点，在图像处理时摒弃了以往的手动识别等位移线的办法，用MATLAB语言编写了批处理程序，能够在采集的大量散斑图片中自动快速准确地标定等位移线，得到相应的位移和应变，并结合实时测量的温度值，获得了45钢和LY12铝合金在不同温升率下的热膨胀系数及其随温度的变化。实验结果表明，在涉及的温升率范围内，温升率的改变对材料热膨胀系数的影响不明显，材料的热膨胀系数随温度的升高略有上升。     

高能闪光照相中影响光程确定的几个因素

 利用闪光照相基本原理和成像原理，在直接记录法和转换屏记录法的情况下，研究了闪光照相中影响X射线在材料中光程确定的主要因素。结果表明，影响光程确定的几个因素是：散射效应、光源角分布效应、立体角效应和能谱效应。对于高能闪光照相，散射效应是影响光程确定的最主要因素，散射的存在使光程的测量值比实际值降低20%～40%。因此必须在做CT之前，对散射的影响进行修正。     

Performance of cellular packet CDMA in an integrated voice/data network

This paper presents a simulation-based study of cellular packet CDMA systems operating in an integrated voice/data traffic scenario. Spread-spectrum CDMA provides a suitable framework for resource-shared packet transport capable of combining isochronous (voice, ISDN) and bursty data services. In this work, a general network model for cellular packet CDMA with mixed voice/data traffic is described and used to evaluate the capacity/performance impact of several key system parameters. First, the effect of spreading factor (N) and forward error correction (FEC) rate are studied, confirming earlier work indicating a weak dependence onN and a well-defined optimum code rate in the range of 0.5–0.7 (with BCH coding). Next, the effect of propagation loss coefficient () on network capacity is investigated over a range of possible assumptions for, including both constant and distance-dependent models. The results show that system capacity depends strongly on, varying by as much as a factor of 2 over the range of parameters considered. For a given distance-dependent assumption, performance results are also obtained for different cell sizes in order to understand the overall spatial reuse efficiency achievable in different cellular and microcellular scenarios. This is followed by an investigation of traffic source model effects: first the capacity improvement from voice activity detection VAD) is presented, showing the expected 21 gains. Results for varying proportions of voice and data traffic intensities indicate that the operating efficiency does not change significantly as the proportion of bursty data relative to voice is varied.     

热电制冷红外探测器氧化铍瓷冷板和散热板导热系数的测量

氧化铍恣导热系数是表征热电制冷红外探测器半导体制冷器部件冷板和散热板导热能力的关键参数。本文论述了氧化瓷导热系数的测量原理和方法，推导了计算公式，分析了影响测量的关键因素并提出了相应措施，对样品制作和装配工艺提出了要求。最后，给出了样品实例测并得出结论。     

多次散射激光雷达接收信号的模拟

MonteCarlo方法模拟多次散射激光雷达接收信号是一种经典方法，但这种方法的最大缺点是计算时间很长．为提高计算效率，本文在传统的半解析MonteCarlo方法的基础上，使用Henyey－Greenstein函数的修正公式来表示散射相位函数，计算出每个散射点处光子不发生进一步散射而直接到达接收机的概率．模拟结果显示，一、二、三次散射起主要作用，但随着海水衰减系数和接收机视场角的增大，高次散射对激光雷达的接收信号的作用也越来越强．     

基于自诊断、自适应技术的大型压缩机机组控制系统

随着自诊断、自适应技术在工业生产自动化控制系统中的应用越来越广泛,本文以莱钢大型压缩机机组为例,利用负荷自适应、冲击信号自修正模型、喘振响应仿真等技术手段,设计实现了压缩机节能变负荷运行、预防性喘振响应仿真及检测设备和基础自动化设备的在线故障自诊断和自修复.该系统投运后,大大减少了停机率,提高了设备运行效率和故障处理效率,可以推广到类似的控制系统中.     

掺钛蓝宝石晶体激光放大实验研究

报道了掺钛蓝宝石晶体激光放大实验研究，实验中得到最大的单程放大和双程放大增益分别为１４．７６和２６．３１，对应双程放大的增益系数为１．８１ｃｍ－１，并由此推算出掺钛蓝宝石晶体的增益截面为２．７４×１０－１９ｃｍ２，饱和能量密度为０．９３Ｊ／ｃｍ２．并给出不同的泵浦能量密度所对应的最佳放大介质长度。实验表明小信号近似下，放大增益只与泵浦功率密度有关．与注入种子能量无关。实验还测量了掺钛蓝宝石晶体对不同波长种子光的放大增益。     

频扫天线波瓣指向角的温度修正方法分析

介绍了几种常用的温度影响频扫天线测角误差的消除方法，由于实验设备、条件的限制以及制作频扫天线等效慢波线的材料、形状有别，这些方法在工程应用中都难以采用。本文提出了一种工程上较易实现的慢波线膨胀系数测量修正法，该方法简单实用，且能满足雷达测角精度的要求。