自由体积理论下液体声速、声速系数及非线性声参量B/A的研究

用液体自由体积理论研究了有机液体的声速、声速系数及非线性声参量与分子结构和分子势能的关系。结果表明分子间的作用力是影响声速、声速系数及非线性声参量的主要原因。同时非线性声参量Ｂ／Ａ也体现了液体分子结构方面的信息。本文有助于对自由体积理论下液体状态方程的进一步研究。为揭示声速及其相关特性与微观机制的关系并为其定量计算作了有益的探索。     

非线性声参量B/A和声速与物质结构的关系研究

本文用我们改进的热力学方法，在温度２０℃和５ＭＨＺ的频率下，测量了三类有机液的同分异构体──正丙醇、异丙醇；正丁醇、异丁醇、叔丁醇；正戊醇、异戊醇、仲戊醇、叔戊醇的非线性声参量Ｂ／Ａ。旨在直接探讨物质结构的变化与非线性声参量的关系。实验结果表明：物质结构对Ｂ／Ａ的影响确实存在的。这对于医学超声的临床应具有重要实际意义。     

有机液非线性声参量B/A的改进算法

1　引　言非线性声参量 B/ A定义为媒质状态方程在绝热条件下作泰勒展开后 ,其二阶项系数与一阶项系数之比。由于和目前广泛应用于超声诊断中的线性声参量相比较 ,它反映了组织的动力学特征 ,可以提供更多的组织结构信息 ,能成为生物组织定征及超声医学诊断的一个重要的新参量 [1-3 ] ,因而对该参量的研究成为近十多年来超声医学研究的持续热点及前沿课题之一。目前对生物媒质的非线性参量 B/ A的研究取得了重要的进展 ,尤其是 B/ A成像技术已越来越接近临床应用的水平 [3 -4 ] ,但是已进行的研究多偏向于实验和技术 ,到目前为止 ,还未见…     

非线性声参量B/A与媒质关系理论进展

本文系统地回顾了自非线性声参量Ｂ／Ａ提出以来有关Ｂ／Ａ与媒质关系的各种理论，对其优缺点作了简单评述。     

物质的结构特性对非线性声参量B/A的影响

物质的结构特性对非线性声参量Ｂ／Ａ的影响刘杰惠鲁志劬龚秀芬（南京大学声学研究所近代声学国家重点实验室南京·２１００９３）１引言非线性声参量Ｂ／Ａ是非线性声学中的一个基本参量，它定义为声速对压力的依赖关系，是表示声波与媒质的非线性相互作用强弱的物理量，...     

非线性参量B/A超声成像的仿真与仿体实验研究

非线性参量B/A是描述生物组织非线性效应的重要参量,其对组织特性的敏感度较线性参量高出1~2个数量级。将非线性参量B/A用于生物组织成像,更有利于组织定征与医学超声诊断。目前已有的B/A成像效果大多依赖于B/A测量技术的准确性。为了获取较好的B/A成像,通过仿真与仿体实验比较了有限振幅声波法测量非线性参量B/A的几种经典方法,仿真和仿体实验结果均表明:扩展比较法(Extended Comparative Method,ECM)测量准确性高,其测量误差低于3%。运用该方法结合滤波反投影仿真实现B/A参量层析成像,成像结果能较好描述简单组织中的B/A参量分布。     

多元有机混合液体声速温度系数的预测方法

根据Jacobson理论及液体声速与分子自由程的关系 ,导出了多元有机混合液体声速与各组分声速之间的关系 ;推导出多元有机混合液体声速温度特性的预测公式 ,并根据组成多元有机混合液各组分特性参量 (摩尔分数、密度、自由程、等压膨胀系数等 ) ,利用文中给出的多元有机混合液声速的温度特性预测公式 ,对由丙酮、四氯化碳、苯、甲醇组成的三元系、四元系有机混合液体的声速温度特性进行了理论值的预测 ,理论预测结果与实验测量结果符合较好     

焊缝组织及应力对声速、幅值及谐波系数的影响

运用超声波(f=15MHz)水浸聚焦透射检测法,对消除应力退火前后的45钢摩擦焊接头进行了检测研究,发现了焊逢、热影响区组织及残余应力对超声声速、幅值及谐波系数的影响规律.     

离子液体/磷酸锆抗菌材料的制备及耐热性研究

以α-磷酸锆(分子式: Zr(HPO₄)₂·H₂O, 以下简称α-ZrP)为载体, 三种季铵型离子液体: 溴化十六烷基三甲基咪唑(C₁₆MIMBr)、氯化十六烷基二甲基苄基铵(C₁₆HDBACCl)和氯化十六烷基三甲基铵(C₁₆CTACCl)被引入α-ZrP层间, 制备得到三种离子液体/α-磷酸锆(IL-ZrP)复合抗菌材料. 通过X射线衍射法(XRD)、红外光谱分析(FTIR)、热重-红外联用分析(TG-FTIR)对材料的结构、组成和热稳定性进行表征. XRD结果表明: 相对于α-ZrP, 三种复合抗菌材料的层间距明显增大, 这证明离子液体已经成功地嵌入到α-ZrP的层间. TG-FTIR实验显示三种离子液体在复合抗菌材料中分别占53.11wt%、50.65wt%和51.25wt%. 三种纯离子液体的热分解起始温度分别为174℃、198℃和219℃, 而离子液体/α-ZrP(IL-ZrP)复合抗菌材料中所含的离子液体的热分解起始温度为219℃、225℃和263℃, 这表明α-ZrP能有效提高离子液体的耐热性. 抗菌性能检测结果表明: 在三种复合材料中, C₁₆MIMBr-ZrP具有较好的抗菌效果(在24 h内, 其对大肠杆菌、金色葡萄球菌的最小抑菌浓度均小于19 mg/L).     

Measurement of the compressibility and sound velocity of neon up to 1 GPa

The density of neon has been determined at 298.15 K as a function of pressure from 80 MPa to 1 GPa. The precision of the measurements is 0.03%, while the estimated absolute accuracy is between 0.05 and 0.09%. The sound velocity has been measured between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.06%. The adiabatic compressibility and the ratio of the specific heats are calculated by combining pVT with velocity-of-sound data at 298 K. Several equations of state are fitted to the density data at 298.15 K.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Experimental study of the ultrasonic velocity in liquid cesium at high temperatures and pressures

The sound velocity in liquid cesium under pressures up to 60 MPa and temperatures to 1500 K is measured using a modified-pulses phase-sensitive technique. The sound velocity (at frequency 10 MHz) is determined by means of the pulse propagation time measurement through the cesium sample. The experimental error is 0.2%. The results obtained are discussed.Paper submitted to the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Measurement of the compressibility and sound velocity of helium up to 1 GPa

By using a gas expansion technique, the density of helium has been determined at 298.15 K as a function of pressure from 100 MPa to 1 GPa. The precision of the measurements is 0.02%, while the estimated absolute accuracy is about 0.08%. The sound velocity has been measured by a phase-comparison pulseecho technique between 98 and 298 K with intervals of 25 K and at pressures up to 1 GPa, with an accuracy generally better than 0.04%. By combining pVT with velocity-of-sound data at 298 K, the adiabatic compressibility and the ratio of the specific heats are calculated. The experimental sound velocities are compared with the values, predicted from an equation of state as proposed by Hansen.     

基于航迹-航深信息的声学测速基阵校准技术研究

针对声学多普勒测速仪安装过程中存在的基阵坐标系与载体坐标系之间的不重合问题,以实际工程应用为背景,提出了综合采用测速仪的速度推算航迹及其波束域斜距信息的三维安装偏角精确校准方法。利用航偏角校准精度受纵、横摇偏角影响小的特点,采用载体上的高精度全球定位系统(Global Positioning System,GPS)、姿态装置推算航迹建立航偏角观测方程,实现航偏角校准。在此基础上,利用波束域斜距与纵、横摇偏角之间的几何方程,精确解算纵、横摇偏角。仿真分析了校准算法性能,并通过外场试验数据验证了校准算法的有效性。结果均表明该方法能够实现基阵三维安装偏角的精确校准,有效提高了导航精度,具有较好的工程应用价值。     

Effect of surface stress and irregularity of the interface on the propagation of SH-waves in the magneto-elastic crustal layer based on a solid semi space

The object of the present paper is to investigate plane SH waves through a magneto-elastic crustal layer based over an elastic, solid semi space under the influence of surface stress on the free surface of the crustal layer and irregularity of the interface. Two types of irregularities of the interface namely, rectangular and parabolic have been considered. Modulations of wave velocity due to the presence of surface stress, irregularity and the magnetic field have been studied separately. Their combined effect has also been investigated. Graphs are drawn to highlight some important peculiarities. It is observed that surface stress, irregularity and magnetic field have their respective role to play in the propagation of SH waves in the crustal layer. Further modulation of wave velocity occurs due to their combined effect.