充粘液管材中超声纵向轴对称导波的频散特性分析

模拟分析充粘液管内径-壁厚比和超声纵向轴对称导波波包宽度的关系。考虑了衰减的情况下,在各传播距离、频厚积和激发脉冲周数上,采用脉冲回波法,分析了导波的频散特性。结果表明:对于特定的材料,当频厚积一定时,充粘液管材中传播的导波特性只与内径-壁厚比有关;各高阶模式的截止频厚积随内径-壁厚比的增大而减小。用L(0,1)模式检测内径-壁厚比在4附近的充粘液管时灵敏度较低;而用L(0,2)模式检测内径-壁厚比在9.2附近的管时灵敏度较低。对于不同内径-壁厚比的充粘液管,检测中应当用不同的纵向轴对称导波模式,所用的激发脉冲周数和频厚积也应当不同。     

Inverse determinations of the parameters of three-layered plate using angle probe generated Lamb waves

The study on the inverse problems in the ultrasonic nondestructive testing (NDT) has a wide application field in various industries. An error function based inversion algorithm is introduced to determine the parameters of three-layered plates from the measured velocity of multi-mode Lamb waves. A mixed-spectral estimation is proposed to combine FFT with AR model for exact determination of the ultrasonic phase velocity. Experiments are performed using two conventional angle probes as transmitter and receiver on the same surface of three-layered laminates. Inverse analyses of one parameter (thickness) and two parameters (longitudinal and transverse wave velocities in a layer, or thickness of two layers) of three-layered laminates are made. The experimental results show that the inverse approach is in good agreement with the actual value.     

邻羟基萘甲醛缩对二甲氨基苯甲酰腙的合成及其对锌离子的识别

设计并合成了用于识别锌离子的荧光传感分子——2-羟基-1-萘甲醛缩-4-二甲氨基苯甲酰腙(1),其结构经1H NMR,IR和MS表征。利用荧光光谱研究了在乙腈中1对过渡金属离子(Zn2+,Cd2+,Cu2+,Hg2+,Pb2+和N i2+)的识别能力。结果表明:1表现出对Zn2+的良好选择性,Zn2+的加入导致1的长波长荧光增强449倍。Job曲线确定1与Zn2+形成1∶1型配合物。     

定量超声骨检测技术研究进展

骨骼健康是人口老龄化社会面临的重要医疗问题之一,骨结构及物理性质是临床骨病诊断的重要依据。定量超声技术通过构建超声信号参数与骨结构物理性质、骨病理状况的映射关系实现骨骼健康的非侵入安全诊断。近年来超声骨检测理论和方法得到了快速发展和应用;其中光声骨检测技术为骨组织成分及结构性质的综合评价提供了可能,促进了骨病精确诊断技术的发展。该文从超声骨检测理论、检测方法、成像技术等方面介绍了传统超声和光声骨检测研究的热点问题,分析了超声/光声体波和导波对骨结构物理性质的特异性和敏感性、高分辨率超声骨成像技术的研究现状,最后展望了定量超声骨检测技术的发展趋势和前景。     

Joint spectrogram segmentation and ridge-extraction method for separating multimodal guided waves in long bones

Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.     

超声诊断骨质疏松症中松质骨的模型

骨质疏松症(OP)是老龄化社会中影响健康的一个重要问题,超声技术已成为诊断骨质疏松症的一种常用方法。文中综述了近年来用超声诊断骨质疏松症中松质骨模型研究的进展,对棒状模型、流体多孔介质模型(Biot理论)和层状模型(schoenberg理论)进行了分析和讨论,指出了各理论模型存在的缺陷,对下一步的研究工作提出了建议。     

超声轴向传播技术评价长骨的研究

用超声轴向传播技术评价长骨状况已成为近年来的一个研究热点。本文首先介绍了第一到达波(FAS)法、超声Lamb波及柱面导波法在评价长骨皮质骨状况方面的研究进展,最后分析和讨论了当前研究中存在的问题及应该研究的方向。     

骨小梁中超声背散射信号的频率分析及其微结构的估计

骨质疏松症是一种骨强度下降的全身性骨骼疾病,骨强度的下降是骨量减少和骨微结构退化的共同结果。相比于传统的超声透射方法,超声背散射法可提供更多的骨微结构信息,而对于松质骨结构的建模能有助于结构信息的获取。本文将骨小梁简化为单圆柱模型(圆柱状的单根骨小梁浸于骨髓中),并基于此模型对超声背散射与频率的关系进行分析。用铝线代替骨小梁做仿体实验,通过实验与理论结果的比较来验证单圆柱模型的可行性。