【作者】 陈莎；

【导师】 祝海江；

【作者基本信息】 北京化工大学 ， 控制科学与工程， 2011， 硕士

【摘要】 材料的基本声学参数包括声速、声衰减系数、非线性声参量B/A等,它们在无损检测中的缺陷定位,仿组织材料的超声特性检测,以及医学成像中都有重要意义。本文对乙醇的声速、声衰减系数及非线性声参量B/A的测量及其在食品安全中的应用进行了研究,主要工作有：1、分别对声速、声衰减系数的测量方法进行比较,利用插入取代法测量了以上两个参数,并对其进行衍射修正以及不确定度分析。2、利用有限振幅插入取代法对非线性声参量B/A进行测量,修正及不确定度分析,并研究了温度、声强以及频率对非线性声参量B/A的影响。结果表明随着温度的升高,B/A值呈现出线性增长,声强对B/A值的影响不大,随着频率的增大B/A值线性减小。3、将声速、声衰减系数应用于掺杂有三聚氰胺的牛奶检测中,结果表明,声速随着牛奶中掺杂三聚氰胺浓度的增大而呈现线性下降的趋势。而声衰减系数对三聚氰胺的浓度变化不敏感,呈现出轻微下降的趋势。将非线性声参量B/A用来监测牛奶的变质过程,结果显示随着牛奶存放时间的增长,B/A值有明显的变化。更多还原

【Abstract】 The basic acoustic parameters of material include the velocity, attenuation coefficient and acoustic nonlinear parameter B/A, etc. They all play important roles in the non-destructive test, ultrasonic tissue-mimicking materials properties testing and medical imaging. In this paper the three parameters and their applications in food safety had been studied, the main work is as follows:1. Compare the measuring methods of velocity and attenuation coefficient. Use the insert substitution method to measure the two parameters, do the diffraction correction and the analysis of the uncertainty.2. Use the finite amplitude insert substitution method to measure the acoustic nonlinear parameter B/A, and do the correction and the uncertainty analysis. Studied the influencing effects of temperature, sound intensity and frequency on the acoustic nonlinear parameter B/A. The results show that the B/A value increases linearly with the temperature increase, the sound intensity has little effect on B/A, and B/A value decreases linearly with the increase of frequency.3. Applying the velocity and the attenuation coefficient to the detection of melamine in milk, the results show:As the melamine concentration in milk increases, the speed of sound shows a linearly downward trend, and the attenuation coefficient shows only a little slight downward trend. Using the acoustic nonlinear parameter B/A to monitor the deterioration process of milk, the result shows:With the growth of storage time, the B/A values are significantly changed.更多还原