振动声成像系统分辨率研究

本文从振动声成像的基本原理出发，通过引入点扩展函数PSF和定义轴向响应函数ARF，研究了由凹球面聚焦换能器分割而成的一种典型共焦换能器参数对振动声成像系统侧向分辨率和轴向分辨率的影响。计算研究表明：增大凹球面换能器的口径、减小几何焦距和提高中心频率均可以提高系统的侧向分辨率和轴向分辨率；但改变凹球面换能器的分割比例对两种分辨率影响不尽相同。综合考虑超声换能器激励、聚焦性能以及产生的辐射力效果等因素，则换能器应按等辐射面积原则分割为宜。文中还分析了介质的声衰减系数对实际轴向分辨率的影响。     

液体核磁共振 HSQC 实验的量子化学计算与模拟

核磁共振（NMR）异核单量子相干（HSQC）实验因具有较高的灵敏度和分辨率而被广泛用于液体大分子化合物的结构鉴定和研究．然而由于HSQC脉冲的复杂性,需要严格控制实验参数和实验条件才能得到高质量的谱图．本文基于量子力学原理对HSQC实验进行数学建模,通过理论推导、数值计算求解自旋1/2的IS双核体系在每个脉冲节点作用后的密度矩阵,然后结合二维NMR信号采样方法,使用计算机程序完成了该体系HSQC谱图的模拟,同时,还实现了乙醇分子的HSQC谱图模拟． HSQC实验的成功模拟基于对复杂演化过程的精确计算,可用于预测谱图以及实验参数改变对NMR谱图的影响,指导高质量HSQC实验谱图的采集．     

A Novel Method to Measure Acoustic Power of Focusing Transducer with Spherical Surface Based on Self-Reciprocity Theorem

A novel method to measure acoustic power of focusing transducer based on the self-reciprocity theorem of convergent spherical acoustic wave is proposed. The performance of this reciprocity method is compared with that of the radiation force balance (RFB) method and the admittance circle method. The average deviations of the reciprocity method from RFB in measurements of the acoustic power and the radiation conductance for a focusing transducer of 1.525 MHz are 7.5% and 3.6% respectively, and for another focusing transducer of 5.27 MHz,they are 1.7% and 1.1%. The measured radiation conductance deviation by the reciprocity method from the admittance circle method for the focusing transducer of 1.525 MHz is 7.9%. It presents encouraging results even in measuring low acoustic power level. The overall uncertainty of acoustic power measurement using the method is evaluated below 10%, and it has many advantages such as high signal-to-noise ratio, good stability and less interference of bubbles and environment.     

超声激发生物组织声发射的原理及应用

介绍一种利用双频共焦超声波获取组织内部特性信息的新方法一超声激发声发射(USAE)。本文着重说明了USAE的基本工作原理，然后介绍了USAE在医学成像和组织无损测温两方面的重要应用。最后指出了一些有待研究的问题。