基于声弛豫频率的可激发气体压强合成算法

声弛豫频率是声吸收谱峰值点的频率,包含可激发气体成分、环境温度和压强信息.利用声弛豫频率线性正比气体压强的特性,提出一种通过两频点声吸收系数和声速测量值计算声弛豫频率,并通过查表方式合成气体压强的算法.算法的声弛豫频率测量误差具有随声测量值误差线性变换的特性,且当两频点的声吸收测量误差相等时,压强的合成误差为零.对于一定温度下的甲烷及其混合气体,仿真计算证明算法的有效性和声测量误差的稳健性.提供一种简单、稳健性好、可实时连续在线检测可激发气体腔体压强的声学方法.     

海水的低频化学弛豫声吸收

用圆柱共振器法测量了三种混合水溶液的声吸收与pH值的依赖关系,溶液中每种化学成分的浓度均参照Lyman-Fleming人造海水配方中对应成分的浓度来选取。测量的频率为2.9和6.8kHz。温度为12.4℃。结果表明,在海水的pH值范围内,B(OH)_3弛豫的弛豫频率与pH值没有明显依赖关系。另外由实验结果可以看出在B(OH)_3/CO_2/Ca/Mg/NaCl水溶液中还存在一个由MgHCO~+_3引起的低频弛豫,其弛频约为3.5kHz。文末列出了由本文测得的B(OH)_3,MgCO_3和MgHCO~+_3弛豫的弛豫参数。     

基于混合气体分子复合弛豫模型的一氧化碳浓度检测算法

研究了声波通过混合气体时,复合弛豫声吸收和声速与气体各成分浓度和声频率之间的依赖关系.以一氧化碳气体、水蒸气、氮气和氧气的混合气体为例,分别建立了弛豫声吸收和声速与气体浓度的三维模型,以及弛豫声吸收与声频率的二维模型.完成了通过测量弛豫声吸收和声速计算一氧化碳气体浓度的算法推导,提出了一种依据弛豫声吸收和声速检测气体浓度的简化算法.仿真实验结果不仅证明了算法的理论可行性,还给出了算法的最佳适用声频率范围,并估计了将算法应用于实验的误差原因,证明了算法具有实际可行性. 关键词： 气体浓度声学检测 一氧化碳浓度检测 复合弛豫声吸收 声速     

声弛豫过程影响下的气体平衡态热容合成方法及其在气体检测中的应用

声扰动形成的分子振动弛豫过程使得气体热容成为依赖于声频率的有效热容,导致随频率变化的声速频散和声弛豫吸收。本文基于单弛豫过程合成算法,提出一种基于两频点声速和声吸收测量值的气体平衡态热容合成方法。该方法两个测量声频点只需在声弛豫吸收显著的频率范围即可分别合成可激发气体分子内外自由度热容,并有效消除声弛豫过程对气体平衡态热容测量结果的影响。对于室温下由CO₂、CH₄、Cl₂、N₂和O₂组成的多种气体,合成的气体热容值与基于Planck-Einstein公式的热力学理论计算结果相符,相比实验数据最大相对误差为3.51%。合成的转动和振动热容还可应用于气体分子几何结构、振动频率大小和混合气体摩尔分数的检测。      

43O升充水圆柱形声共振器的研究

为了在实验室内用共振法测量海水低频声吸收及研究海水低频弛豫吸收的机理(海水中的硼弛豫其弛豫频率约为1千赫),关键是需要一个容量大而附加损失小的声共振器。     

超声波在悬浮液(水)中的吸收

本文研究了低浓度松花粉悬浮液中由于悬浮粒子引起超声波的附加吸收问题。实验上测量声吸收和声速都是采用脉冲干涉仪(当测量吸收时曾以移板法、多次反射法及比较法配合进行),频率范围为3—20Mc,温度范围为20°—80℃,在不同浓度重复进行。针对这样的具体实验条件,根据Epstein提出的理论进行了较严格的计算,并从实验和计算结果的比较中得出几点结论。同时,作者还总结和评述了其他作者关于石松子悬浮液中超声吸收的研究,通过对他们的实验结果和理论值之间的比较,认为他们简单地应用小球或低频极限情况下所得出的理论来解释实     

基于声吸收谱峰值点的天然气燃烧特性检测理论

天然气的成分构成会随产地来源变化而不同, 使其具有不同的燃烧特性和经济价值.本文利用声吸收谱峰值点随气体成分变化而改变的声分子弛豫现象, 提出一种天然气燃烧特性检测理论.它基于两频点上声测量值可合成声吸收谱峰值点, 且依赖于频率的声吸收谱可由峰值点重建的物理原理; 可利用峰值点对应的特征量——弛豫频率和弛豫吸收最大值与气体成分的关系, 从两个维度同时定量检测天然气成分.该理论避免了传统上测量声吸收谱峰值点方法需要不断改变气体腔体压强的问题, 还具有无需测量气体密度的优点.     

2种液体间界面张力的动态测量

利用自制仪器对2种液体间界面张力进行动了动态测量,通过嵌套软件在计算机上实时记录测量过程中的电压值,避免了人工读数带来的实验测量误差,并绘制出相应的电压变化曲线.根据电压变化曲线对金属吊环在2种液体中的拉脱过程分4个阶段进行详细讨论,并通过受力分析建立了力平衡方程.以纯净水和硅油、纯净水和乙酸乙酯为样品,对其界面张力分别进行了实验测量.     

可激发气体振动弛豫时间的两频点声测量重建算法

振动弛豫时间是可激发气体分子内外自由度能量转移速率的宏观体现,它决定了声吸收谱峰值点对应的弛豫频率.本文给出了等温、绝热定压和绝热定容三种不同热力学过程下振动弛豫时间的相互关系;基于Petculescu和Lueptow[2005 Phys.Rev.Lett.94 238301]的弛豫过程合成算法,推导了单一压强下两频点声测量值的弛豫时间重建算法.该算法可应用于等温、绝热定压、绝热定容弛豫时间和弛豫频率的重建测量,并避免了弛豫时间传统声测量方法需要不断改变气体腔体压强的问题.仿真结果表明,对于室温下CO_2,CH_4,Cl_2,N_2和O_2组成的多种气体,重建的弛豫时间和弛豫频率与实验数据相符.     

氢分子在几种高铬镍合金钢中微扩散所引起的内耗峰

用扭摆作内耗测量,发现八种高铬镍合金钢中含氢可以引起内耗峰。当振动频率约为每秒1.5周时,内耗峰的巅值温度在610—640℃附近。用其中一种高铬镍合金钢试样(18Cr 12Ni)进行了系统的实验,指出这个内耗峰的基元过程是一种弛豫过程,所包含的激活能约为46,000—50,000卡/克分子。根据激活能的数值以及内耗峰在升温、降温和保温时的变化情况,可以认为这个新内耗峰是由於氢分子在钢中微扩散所引起来的。内耗测量的结果也指出了在18Cr 12Ni钢中在特定的升温、降温速度下氢分子舆氢原子的转变温度范围,所得的结果舆资料上的相合。     

Molekulare Schallabsorption in Benzol und Zyklohexan

The sound absorption in liquid benzene and cyclohexane measured in the frequency range from 3 to 150 Mc/s is proportional to the square of the frequency. In polycrystalline benzene and cyclohexane an additional grain boundary absorption was found, which can be neglected above 100 Mc/s. In all cases the absorption which is proportional to the square of the frequency is ascribed to a vibrational relaxation process. In each substance the extrapolated relaxation times of the solid and liquid states differ from each other very little.     

Intramolecular relaxation processes of some aromatic esters

Dielectric absorption measurements have been made in the frequency range 10²?10⁵ Hz over a variety of temperatures on dimethyl terephthalate, dimethyl 2,6-naphthalene dicarboxylate, methyl and ethyl benzoates, ethyl-p-chlorobenzoate, methyl and ethyl cinnamates, and methyl salicylate. The solutes have been dispersed in a polystyrene matrix and in four cases also in a polyphenyl ether medium. One compound, methyl salicylate, was also examined as a pure compressed solid. The Eyring parameters have been determined and employed to characterize the relaxation processes. The results are discussed in terms of molecular and intramolecular processes involving the whole ester grouping or the methoxy group or an overlap of both processes. In the case of methyl salicylate the barrier for the methoxy group relaxation has been determined in the compressed solid state.     

An equation to calculate the equilibrium constant of 1:1 complexes from dielectric relaxation measurements

The dielectric measurements of 1:1 mixture of acetates, namely ethyl acetate, butyl acetate and benzyl acetate and phenol and n-butyl alcohol in carbon tetrachloride at 9.8 GHz microwave frequency were carried out. A method has been proposed to calculate the equilibrium constant of 1:1 hydrogen bonded complexes. These values are in close agreement to the values obtained using the Few and Smith method.     

非晶态快离子导体(AgI)x(Ag4P2O7)1-x的声学性质

用液氮骤冷方法制备了(AgI)_x(Ag₄P₂O₇)_1-x系列非晶态快离子导体。对AgI摩尔浓度x=0.50,0.60,0.67,0.75,0.80的样品,在77—300K温度范围及2,5,10,15MHz的频率上测量了纵波和横波的超声衰减和声速。发现在200—240K附近存在一个异常强的弛豫型超声吸收峰,随AgI含量的增加,该峰的位置向低温方向移动,且峰的高度增大。在实验的温度范围内,观察到纵波和 关键词：     

利用自发布里渊散射测量液体声速

为了克服共振干涉法在液体的热力学声速和高频声速测量方面精度不高的问题, 本文建立了一种基于自发布里渊散射原理的测定液体声速的实验装置. 利用法布里-珀罗干涉仪对散射光进行扫描滤波, 数据采集卡结合光子计数器对散射光进行探测, 设计了一种散射光信息采集分析方法. 该实验方法有效的解决了传统布里渊散射方法中信号失真的问题, 显著地提升了液体声速测量精度. 对308.6–906.2 MHz内298.15 K饱和液相CCl₄声速进行了测量, 测量结果与文献值具有较好一致性. 利用法布里-珀罗干涉仪周期性扫描的滤波原理, 通过在测量得到的布里渊频移上加减整数倍个自由波谱区, 得到了更大频率的波谱信息, 进而设计一种测定介质高频声速的方法. 对CCl₄在5406.1–5521.0 MHz频段内的声速进行了测量. 实验结果显示, CCl₄的热力学声速随频率无明显变化, 而高频声速随频率的增大呈增大趋势且远大于热力学声速, 证实CCl₄具有色散现象.     

On the ultrasonic attenuation in glasses at low temperatures

The ultrasonic attenuation in glasses at low temperatures is calculated using the model proposed by Anderson, Halperin, and Varma. It is found that the resonant absorption of sound by the localized two-level systems saturates and can be observed only if the sound amplitude is extremely small. A second contribution to the sound absorption is derived which arises from the relaxation of the localized excitations and does not saturate. Qualitative agreement with recent measurements of the ultrasonic attenuation in fused silica is obtained.     

Ultrasound absorption in liquid metals

The excess longitudinal ultrasonic absorption over and above the classical value has been attributed to the solid-like mechanisms of the interaction of sound waves with the conduction electrons and the thermal phonons in liquid metals, both exhibiting a quadratic dependence on the sound frequency.     

Ultrasonic absorption constant in liquids by an improved optical method

The optical diffraction set up as originally employed byDebye andSears andLucas andBiqdard has been used with various modifications to estimate the intensity of sound fields at two or more points along the axis of an ultrasonic beam travelling in a liquid and thereby to determine the absorption coefficient of the liquid medium. Almost all these methods involve a two step operation with the attendant possibility of errors due to variation in the conditions under which the two observations are made. In the method here reported two axially parallel beams of parallel monochromatic light are made to traverse the liquid normally to the direction of propagation of the sound beam and the resulting diffraction spectra are brought to focus on a common photographic plate. Sound intensities at two points separated by a known distance are thus measured simultaneously under identical conditions. Absorption coefficients calculated for half a dozen liquids by this method are reported. The values compare very favourably with those obtained by other precision methods.