【作者】 刘东红；

【导师】 吴昭同；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2006， 博士

【摘要】 低能量超声检测技术（Low-intensity Ultrasonic Measurements）是一种利用能量低于1W／cm²而频率高于100kHz的超声波获取被测媒质内部结构、物化特性等信息的测量技术。该技术已广泛应用于工业探伤和医学影像学等研究领域，由于其具有非破坏性、精确、设备廉价，能够对高浓度液体和非透明性材料进行检测的独特优势，不仅在工业检测上有其应用价值，而且在食品加工过程监控和食品质量控制上有着广阔的应用前景。本文以食品中常见的液态食品和配料为研究载体，探讨了超声特性与液态食品微观结构特性之间的关系，分析了液态食品品质超声定性分析技术和定量分析技术，同时将超声检测技术应用于复杂液态食品体系—牛乳的检测分析，为超声检测技术在食品工业中的应用奠定基础。主要研究结果如下： 1．研究了超声传播特性—声速与液态食品—醇溶液、糖溶液微观分子结构特性的关系，结果表明超声传播速度受醇、糖溶液的微观结构、立体化学特性和浓度的影响，这表明可应用超声研究手段对液态食品的微观特性进行研究： （1） 分子自由程、分子自由体积以及分子内部压力是液体的重要微观特性。用声速可以直接确定这些微观参数的数值，本研究发现单纯从热力学特性和分子体积特性推导的模型计算结果与醇溶液分子结构（分子量、羟基数目、烃链长度）有一定差别，而结合超声传播特性推导的模型与醇溶液分子结构更加一致。建立了声速和分子自由体积、内部压力间关系的模型（c=K₀ρ^aVf^bπi^c），同时利用回归分析确定了模型的参数，并将该模型应用于醇溶液的分析，与实际检测结果差别很小。 （2） 混合溶液偏摩尔体积（partial molar volume）、偏摩尔绝热压缩系数（partial Adiabatic compressibility）和水合数（solvation number）是反映混合溶液中各组分相互作用的参数。本研究推导了利用声速确定混合溶液偏摩尔体积和偏摩尔绝热压缩系数的方法，并利用超声检测确定了糖溶液的偏摩尔体积、偏摩尔绝热压缩系数及水合数。通过分析糖的立体化学结构与上述参数的关系，发现声速与糖溶液的立体化学结构以及和水相互作用的方式有关，表明声速可以用来研究混合溶液中溶质与溶剂的相互作用及立体化学结构。 2．研究了一种快速识别单一醇种类的方法。通过分析超声波在不同醇溶液（甲醇、乙醇、乙二醇、异丙醇、丙三醇、正丁醇）中传播的时域和频域信号，分别提取了对溶液进行定性研究的时域特征（声速、声衰减）和频域（谐频频率、谐频峰值及频域能量）；利用时域特征和频域特征建立了BP人工神经网络的识别模型，通过对不同模型的训练和识别比较，发现采用多更多还原

【Abstract】 Low-intensity ultrasound frequently ranges at intensities lower than 1W/cm² and at frequencies higher than 100 kHz. When traveling through a medium, the ultrasonic waves change their characteristics and the analysis of this change allows assessment of inner structure and physico-chemical properties of the medium. Ultrasonic measurement has been widely used in the fields of non-destructive detection and medical image. For their particular advantages of rapid, nondestructive, noninvasive and inexpensive, low-intensity ultrasound has great potential in food industries both for process control and for product quality evaluation, especially for testing of high concentration solution and some opaque material. In this dissertation, two popular liquid food ingredients, alcohol and sugar solution, were used as a material, the relation of their microstructure and ultrasonic properties was investigated. The potentiality of quantitative determination and qualitative analysis by means of ultrasonic for these liquids was discussed. An instrument for determination of milk composition was designed and developed. The main results were as follows.1. Ultrasonic propagation properties in different kinds of alcohol and sugar solutions were studied as affected by their microstructure. It was found that ultrasonic velocity of alcohol and sugar solution was affected by their microstructures, stereo-chemical structures and concentrations. These findings indicate that it is possible to measure microstructure properties of liquids by ultrasonic properties, especially ultrasonic velocity.（ 1 ） Intermolecular free length （IMFL）, molecular free volume（MFV） and molecular internal pressure （MIP） are important microstructure properties of solution. A laboratory model study for relation of ultrasonic velocity and IMFL, MFV, MIP was carried out. It was found that there existed some significant correlation between ultrasonic velocity and IMFL, MFV, MIP. IMFL, MFV, MIP could be determined by ultrasonic velocity. It was found that there were some differences of molecular structure （molecular weight, hydroxyl number, length of hydrocarbon chain） between theoretic data and data calculated both from thermodynamic principle and volume properties. This problem could be improved by assisting of ultrasonic properties analysis. Furthermore a model for relation of ultrasonic velocity and MIP, IMFL was obtained in c=K₀ ρ^aVf^b π i^c with very high regressive coefficient Experimental data determined by this model showed that three are no difference between true and that from model. These results suggest that ultrasonic velocity could be used as a main parameter to measure更多还原