面向食用油品质鉴别的低场核磁共振检测平台的研制

发布时间：2018-05-29 19:47

  本文选题：射频探头 + 螺线管线圈　； 参考：《东南大学》2017年硕士论文

【摘要】：食用油的品质鉴别一直是社会的热点问题,在众多的检测方法中,核磁共振技术因具有无损、快速和安全的优势,已经被证实为一种非常有价值的检测方法。本文在回顾食用油品质鉴别研究现状和低场核磁共振技术的基础上,通过研究具有稳定调谐匹配特性的射频探头和具有高精密的温度控制系统,在实验室现有研究成果的基础上,研制了一种面向食用油品质鉴别的低场核磁共振检测平台。基于该平台装置,建立食用油品质核磁共振的检测模型,实现对食用油品质的鉴别。论文研究取得的成果如下:(1)基于螺线管线圈的理论模型,以相对信噪比为优化目标,设计和优化了射频螺线管线圈参数。结果表明,当线圈直径D和高度H取5.1mm时,线径为d为0.2mm,匝数n为12匝,线圈的相对信噪比达到最大,即为最优的参数模型。通过改进螺线管线圈的制作工艺,实现了射频线圈参数的精确控制。最后,根据实验测试的信噪比,验证了理论模型的准确性和合理性。(2)改进探头射频电路的匹配网络,有效的增加了探头调谐匹配范围和降低探头的回波损耗,完成了射频电路的实际制作与测试,包括射频电路的仿真、元器件的选择及测试、耐压值测试等。同时,通过研究射频探头品质因素选择,在26.09MHz频率下,集成所设计的射频线圈和调谐匹配电路,完成射频探头的制作。(3)基于低场核磁共振检测平台的温控需求,设计高精度温度控制系统的技术方案,测定温控系统PID(比例-积分-微分)参数。同时,从传感器位置、空气流动性、保温性能、环境温度等方面,优化系统的温控性能和温度梯度场,确定检测系统的共振频率,实现36.0℃±0.1℃的温控目标,完成高精度温控系统的设计制作。(4)搭建食用油品质低场核磁共振检测平台,选取常用的大豆油、花生油和调和油等食用油作为样本,建立食用油横向弛豫时间T2和纵向弛豫时T1与煎炸时间的线性关系,同时与商业核磁共振仪器Bruker Minispec mq60进行对比,完成检测平台装置的性能验证和测试。最后,基于该平台装置检测了福临门、金龙鱼和鲁花三种大豆油食用油样本,引入极性化合物参数和标准检测方法柱层析法,建立核磁共振弛豫曲线与极性化合物含量的交叉模型,能够有效鉴别不同煎炸时间的极性化合物含量。结果表明,大豆油油脂在煎炸43小时后即不可再食用,检测误差在15%以内。因此,本文研究的低场核磁共振检测平台装置可成为食用油检测领域中的重要潜在工具。
[Abstract]:The identification of edible oil quality has always been a hot issue in society. Among the many detection methods, nuclear magnetic resonance (NMR) technology has been proved to be a very valuable detection method because of its advantages of nondestructive, rapid and safe. On the basis of reviewing the present research situation of edible oil quality identification and low field nuclear magnetic resonance (LNMR) technology, the RF probe with stable tuning and matching characteristics and the high precision temperature control system are studied in this paper. A low field nuclear magnetic resonance (NMR) detection platform for edible oil quality identification was developed on the basis of the existing research results in the laboratory. Based on the platform, a nuclear magnetic resonance (NMR) detection model of edible oil quality was established to identify the quality of edible oil. The research results are as follows: 1) based on the theoretical model of solenoid coil, the parameters of RF solenoid coil are designed and optimized with the relative signal-to-noise ratio (SNR) as the optimization target. The results show that when the coil diameter D and height H take 5.1mm, the linear diameter is 0.2mm and the number of turns n is 12 turns. The relative signal-to-noise ratio of the coil reaches the maximum, which is the optimal parameter model. The precise control of RF coil parameters is realized by improving the manufacturing process of solenoid coil. Finally, according to the signal-to-noise ratio of the experimental test, the accuracy and rationality of the theoretical model are verified. (2) the matching network of the probe RF circuit is improved, which effectively increases the tuning range of the probe and reduces the echo loss of the probe. The design and test of RF circuit are completed, including the simulation of RF circuit, the selection and test of components and components, the test of voltage value, etc. At the same time, by studying the selection of RF probe quality factors and integrating the designed RF coil and tuning matching circuit under 26.09MHz frequency, the RF probe is fabricated. The temperature control requirement of low field nuclear magnetic resonance detection platform is realized. The PID (proportional-integral-differential) parameters of the temperature control system were measured by the technical scheme of high precision temperature control system. At the same time, the temperature control performance and temperature gradient field of the system are optimized from the aspects of sensor position, air fluidity, heat preservation performance and ambient temperature. The resonance frequency of the detection system is determined, and the temperature control target of 36.0 鈩，

本文编号：1952162