【作者】 韩宇南；

【导师】 吕英华；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 生物电磁学(bioelectromagnetics)是研究生物体内和生物体间电磁现象的一门新兴学科。随着技术的发展和电磁环境的复杂度的提高，电磁辐射产生的生物效应问题已经成为人们关注的热点。由于生物体的高度复杂性，科学技术界往往针对一个问题采用多种方法研究，采用计算机模拟是公认的必须的研究方法。该方法可以模拟生命体在自然状态下的过程，这是其他方法所无法取代的。近些年来计算生物学技术已经成为生命科学研究和生物医学工程的关键技术，国内外在该领域的研究正逐步升温。在国家自然科学基金重点项目和北邮创新基金项目的支持下，本文研究了计算电磁学和并行算法在生物电磁学仿真中的应用，特别是研究了人体天线设计和最为重要的阻抗方法和时域有限差分法。这些工作包括仿真了高压输电线、经颅磁刺激对人体内的感应电流密度分布，分析了蓝牙通信系统在人体内产生的比吸收率分布，建立了计算机显示器辐射模型并分析了对人脑的影响，提出了可穿戴式网络的概念，对窄带蓝牙可穿戴式网络进行了估计，设计了用于可穿戴式网络的平面倒F天线和用于无线超宽带通信的对称平面偶极天线(CPD-UWB)。论文的主要贡献包括以下内容：1首次完成了阻抗方法的并行化研究，实现并验证了并行阻抗算法。基于Maxwell方程，通过离散化网格重新推导了三维阻抗方法，得到了可计算的电磁波波长和网格解析度之间的关系以及离散化计算方程的生成方式并给出了迭代解法。进一步给出了实现阻抗方法的并行化的通信方式并在8节点并行计算系统上通过消息传递界面(MPI)实现了并行阻抗方法。验证了并行阻抗算法的正确性并评估了并行计算效率。2根据时域有限差分法(FDTD)在生物电磁学领域中应用的需要，重新推导了分裂场形式的FDTD，给出了求解损耗媒质中散射电磁场的FDTD方法。进一步对标准FDTD的数值色散进行分析，提出了修改介质电参数方式来降低网格数值色散的方法，最后对非均匀网格技术进行了讨论。3基于并行三维阻抗方法，建立了用于仿真暴露在电磁场环境中的人体内感应电流密度的分布情况的通用的数值模型。进一步又仿真了暴露于国际非电离辐射保护委员会(ICNRIP)建议的磁场限值100μT和0.4μT的磁场(流行病学报告显示该磁场强度儿童患白血病的几率会增加一倍)中仿真人体模型中感应电流密度的分布；仿真了暴露在实际高压输电线附近的人体内的感应电流密度分布，仿真了重复经颅磁刺激在高解析度的人体头部产生的感应电流密度分布。4建立了基于可变网格时域有限差分法的仿真微波电磁场与人体近距离互作用的数值模型。仿真了用于蓝牙通信系统的平面倒F天线电磁辐射在人体中产生的比吸收率分布，分析了天线对人体的影响以及人体对天线辐射的影响，为构建人体中心网络和可穿戴网络提供了理论基础。5基于运动电荷的电磁辐射原理针对计算机显示器阴极射线管(CRT)建立了电子束辐射模型，得到了辐射场与电子束电流的对应关系，在此基础上建立了计算机显示器CRT辐射场的数值模型。利用建立的CRT电子束的辐射模型计算了人脑暴露于CRT监视屏的电磁场环境下的比吸收率。基于显示器CRT辐射模型针对一种具体的计算机监视器结构建立了辐射频谱特性并将理论计算结果与实际侦收实验得到的测量结果进行了比较。6随着手机、蓝牙耳机、无线网卡、无线路由器、可穿戴计算机等在人体附近使用的无线设备的逐渐普及，对于人体中心无线网络技术的研究也在不断升温。为此，在人体中心网络的基础上提出了可穿戴式网络的概念。仿真并设计了采用蓝牙技术构成窄带可穿戴式网络的平面倒F天线，对基于蓝牙窄带的可穿戴式网络的传输通道进行了测试和估计，分析了呼吸、佩戴金属饰品和运动对的影响。仿真并设计了采用宽带UWB技术构建可穿戴式的网络天线。更多还原

【Abstract】 Bioelectromagnetics (BEM) is the study of electromagnetic phenomena within and between biological systems. With the development of technologies, the electromagnetic environment becomes more and more complicated, therefore the biological effects caused by electromagnetic radiation and human body-centric wireless network have proved to be the key technologies in BEM. Because life body is very complicated, we should use more research methods to deal with one problem. Computer simulation is the commonly used method, because using this method we can simulate the nature life. Nowadays, the computational biology methods have been becoming the key technology of life science and engineering of biology and medicine. Supported by the national natureal science fundation of China and the innovation fundaiton of Beijing University of Posts and Telecommunications, this paper studies the applications of computational electromagnetics and parallel computing in BEM simulation modeling, especially the parallel impedance method and finite-difference time-domain method for BEM simualtion. These research works include the simulation of the induced current distribution in human body exposed to the electromagnetic fields of power transmition line and transcranial magnetic stimulation, the specific absorbed rate distribution in human body when wearing a Bluetooth RF device, the modeling of the computer video display unit, the biology effect of human brain when working in front of the computer monitor, proposed the concept of wearable network and estimating channel character for narrowband wearable network construced by Bluetooth, and giving the design of the planar inverted-F antenna and coupled planar dipole UWB antenna for narrow and broad band wearable network respectively. The main novel works included in this dissertation are as follows:1 The implemention of the parallelized three-dimensional impedance method is proposed and verified. Based on Maxwell’s equation, the three-dimensional impedance method is deduced and the association numerical model has been found between the minimum incident wave length and the resolution of human body model. Furthermore, a communication scheme to exchange the border data for processors during iteration by message passing interface (MPI) library is designed and a parallel computer system has been set up. The validation and effective of parallel IM is verified by simulation experiment.2 In BEM application, the FDTD method is rededuced into splited formations and scattered fields in lossy medium. Forthermore, the constitutive medium is modified to improve the numerical dispersion. The non-uniform mesh technology is discussed.3 Set up a numerical model for calculating the induced current in humen body when exposed in electromagnetic fields. The simulations of the induced current in human body is made, when exposed to 100μT (1000mG), which is the limit recommended by the ICNIRP for the public and to 0.4μT (4mG), which is the level at which there appears to be a statistical link with a doubled risk of development of childhood leukaemia based on paralled impedance method. The induced current in human body exposure to power line for lineman and dweller and the induced current density distribution in human head model caused by transcranial magnetic stimulation (TMS) are also simulated for clinical application.4 The SAR distribution in a High-Fidelity human body model caused by 2.4GHz band planar inverted-F antenna (PIFA) for Bluetooth application and the PIFA performance affected by human body have been studied by the sub-grid finite-difference time-domain (FDTD) method. The results can provied safety guarantee for body-centric wireless network and wearable network.5 In order to consider the video imformation security, based on the radiation of moving charges, a model is proposed for the electromagnetic field of electron beam in acceleration region of CRT. From this model, the radiation field is directly associated with electron beam’s current, and it can be analyzed and calculated by numerical method. Further, the frequency spectrum of radiation field has been transformed. The character of frequency spectrum is that each lobe has the same video information. The whole spectrum and the video signals can be recovered by processing each lobe. The numerical simulation results are in agreement with experiments.The human head effect is simulated by FDTD.6 With the development of mobilephone, Bluetooth earphone, wireless network card, wireless router and wearable- computers are frequently used near the human body. Quite soon we will see a wide range of unobtrusive wearable and ubiquitous computing equipment integrated into our everyday wear and the body-centric wireless network equipment will be studied bloomingly. Considering the applications, we propose the concept of the wearable network. The planar inverted-F antenna is simulated and designed for Bluetooth wearable network and the on-body channel character is estamated and measured. The effects of deep breath, metal ornament and body movement are studied. The couple planar dipole UWB antenna is also designed for ulta-wide band wearable network.更多还原