Electromagnetic Pulse To The Human Body And Numerical Methods

There is a close relationship between electromagnetic fields and modern society. As the carrier of energy and information, electromagnetic fields find wide applications in nearly every field of high technologies. How electromagnetic environments affect human health is now of the public's strong concern. Investigation of the effects of electromagnetic fields on human health is of great importance both in understanding the essence of life and in applications to health protection and medical treatments.Generally, bio-effects of electromagnetic fields are classified into thermal and athermal effects according to the degree of change in temperature. The thermal effects have definite physical and biological meaning, which has been basically understood. Now, much attention is paid to its protection and applications. In contrast, the research of athermal effects, with so many problems left unresolved, is still rather immature, which make it the hot spot in the field of bioelectromagnetics.Nowadays, ultra-wide-band and high power microwave techniques develop rapidly and gradually go to practical use. The radiation appears usually in the form of electromagnetic pulses (EMPs). There have been some experiments that indicate pulsed fields are more effective in producing biological effects than continuous waves (CW). Based on this knowledge, we investigate the effects of repeated square waves and nuclear EMPs on L-02 and CHL cells respectively. The experiments demonstrate: (1) Athermal effects exist widely under exposure of EMPs; (2) They are waveform dependent; (3) Athermal effects differ in intensity for different cell species. (4) EMPs can produce both direct and indirect athermal effects. Study of the effects conducted by insulin suggests that the signal system maybe one of the most important objects EMPs act on. We propose SEI (Specific electric impulse, impulse exerted to unit charge by EMP) to quantity interaction of EMPs with biological system and set up a model to unify all our experiment data. One of the greatest advantages of SEI over SA (Specific absorption, electromagnetic energy absorption per unit tissue mass for every EMP) is that it is linearly related to the effects if a proper description quantity is selected. In addition, all the factors associated with biological systems are attributed to a constant, which makes it very simple.The purpose of the research on cellular and macro bio-molecular level is to understand the mechanism and extrapolate the results to human body, but underlying which is a good knowledge of the dosimetry. Restricted by safety and techniques, direct measurement of dose on human body is not available now. Numerical simulation is ordinarily thought to be an applicable way. We meet two difficulties: (1) The geometry structure of human body is rather complex; (2) The dispersive relation of tissue can't be modeled by normal dielectric. Due to the 3D nuclear magnetic resonance imaging and the capability of Finite-Difference Time-Domain (FDTD) technique in modeling unstructured objects, the former is partly alleviated at the cost of large computational resource, but the latter remains to be resolved.The development of more effective numerical methods is essential for thesimulation of EMP's interaction with human body. We make a review on the FDTD method, followed by a derivation of perfectly matched layer (PML) absorbing boundary condition in terms of the wave mode match in different medium and an analysis of its properties in Yee's space. Implementation and validation of PML in 3D space are also given. After the presentation of FDTD equations in the general coordinate system and the associated PML, a novel technique is put forward to overcome the update of field components at singular points for FDTD equations in cylindrical and spherical coordinates. Numerical experiments suggest that it is reliable.Based on proper approximation and periodical continuation, a continuous spectrum problem is converted to a discrete one. Because of the consistence after and before continuation in th...