RF Energy Deposition in a Heterogeneous Model of Man: Near-Field Exposures

The electric field strength was measured in a full-scale heterogeneous model of man exposed in the near field of resonant dipoles. The model was comprised of skull, spinal cord, rib cage, all other major bones, brain, lung, and muscle tissue. Electrical properties of these simulated tissues were the same as respective live tissue properties at test frequencies of 160, 350, and 915 MHz. The rates of energy absorption were calculated on the basis of the measured field strengths and tissue conductivities. Patterns of the energy deposition are compared for two orientations of the antennas with respect to the body. Also the results for the heterogeneous model are compared to data for homogeneous model having average tissue electrical properties.     

RF Energy Deposition in a Heterogeneous Model of Man: Far-Field Exposures

Distributions of the specific absorption rate (SAR) were measured in a full-scale heterogeneous model of man. The model contained a skeleton, brain, lungs, and muscle. All these tissues had dielectric properties close to those of the respective in vivo properties of actual tissues at the test frequencies. SAR's were measured for exposures in the far field at 160, 350, and 915 MHz for the E and H polarizations. A computer-controlled scanning system and an implantable, minimally perturbing electric field probe were used. The results are also compared with the SAR distributions previously measured in a homogeneous model.     

Numerical Calculation of Electromagnetic Energy Deposition for a Realistic Model of Man

Numerical calculations of absorbed energy deposition have been made for a block model of man that is defined with careful attention given to the biometric and anatomical features of a human being. CalcuIated post-resonant absorption and distribution of energy deposition through the body have better agreement with experimental results than previous calculations made using less realistic models.     

Comment on "Numerical Calculation of Electromagnetic Energy Deposition for a Realistic Model of Man"

In the above paper , Hagmann et al. compared their numencal results on the energy deposition in a model of man with ours, and indicated that our results are low compared with their numerical and experimental results. Our low SAR values were obtained because they were based on a simplified model of man which has a reasonable shape but an excessive weight of about 200 kg. We have since published a considerable amount of results based on a more realistic model of man, which has a more realistic shape and a weight of about 100 kg. Our numerical results based on the realistic model of man are quite close to the numerical and experimental results of Hagmann et al. as shown in Table I.     

Power Deposition in a Spherical Model of Man Exposed to I-20-MHz Electromagnetic Fields

The induced fields and the associated power deposition in mail exposed to HF electromagnetic (EM) fields have been investigated theoretically using spherical models. The induced electric fields inside the model exposed to either plane wave or near fields can be described adequately by a combination of quasi-static electric and magnetic induction solutions. It is shown that for field impedances less than 1200/spl pi//spl Omega/ the magnetically induced energy absorption predominates. Therefore, H fields must be measured to obtain any estimate of the hazards due to HF exposure. For a 70-kg model of man exposed to a plane wave field, the theory indicates that the time-average power absorption per unit volume is less than 2.5x10/sup -3/ mW/g for each milliwatt per square centimeter incident at 20 MHz and below. This suggests that the thermal safe-exposure levels for the HF band are many orders of magnitude in excess of the 10-mW/cm/sup 2/ level recommended for the microwave region.     

Dependence of Deposition Upon Electromagnetic Energy Angle of Incidence for an Inhomogeneous Block Model of Man Under Plane-Wave Irradiation

Whole-body and part-body energy deposition in a realistic inhomogeneous block model of man is presented as a function of angle of incidence for plane-wave irradiation for two cases: E arm-to-arm, with man in free space, H arm-to-arm, with man in free space, and also with man standing on a conducting plane. At the frequencies considered (27.12 and 77 MHz), the variation with angle is smooth and extrema occur at or near angles corresponding to the standard polarizations considered earlier by others. Part-body energy deposition and some of the fine structure in the angular dependence would not be seen with less realistic modes of man.     

Electromagnetic-Energy Deposition in an Inhomogeneous Block Model of Man for Near-Field Irradiation Conditions

The plane-wave spectrum approach is used to calculate the electromagnetic-energy deposition and its distribution in a 180-cell, inhomogeneous block model of man for a prescribed two-dimensional Ieakage electric field generated by RF sealers and other electronic equipment. The whole-body-averaged energy dose increases approximately as (Delta/sup 2//sub 1/Delta/sup 2//sub 2//Lamda/sup 4/) to the asymptotic plane-wave value, where Delta /sub1//Lamda and Delta/sub2//Lamda are the vertical and horizontal widths (in wavelengths) of the best fit half-cycle cosine functions to the prescribed leakage fields. The effect of phase variations shows that the worst case (maximum deposition) is always obtained for constant phase in the prescribed fields. The need for exact phase measurements is, therefore, obviated since the upper bound on the deposited energy is often the desired quantity.     

Electromagnetic Absorption in a Multilayered Model of Man

A multilayered planar model is used to examine the dependence of whole-body power absorption on the configuration of surface layers, e.g., skin, fat, and muscle which normally occur in biological bodies. It is found that the layering resonance for three-dimensional bodies (as opposed to the geometrical resonance) can be predicted quite accurately by a planar model. Calculations for a multilayered prolate spheroidal model of man predict a whole-body layering resonance at 1.8 GHz with a power absorption 34 percent greater than that predicted by a homogeneous model.     

Conditions of Strongest Electromagnetic Power Deposition in Man and Animals

Strongest power deposition for biological bodies is found for fields polarized along the longest dimension for frequencies such that the major length is about 0.4 times the free-space wavelength of radiation. Peak absorption in the presence of ground effects is observed at frequencies about one-half as much as for bodies isolated in free space. At resonance, an effective absorption area 34 times the shadow cross section is measured. Using biological-phantom figurines of the human body, distribution of power absorption is determined. Maximum power deposition is observed for the neck region. Initial experiments with anesthetized and dead rats have confirmed this observation.     

人体坐姿模型吸收电磁能量计算的研究＊

本文揭示,不同姿态的人体在同样的电磁环境中所吸收的电磁能量有明显的不同。作者在立式人体电磁模型的基础上,建立了坐式非均匀电磁块状模型,并用时域有限差分法进行了计算。结果表明,在人体电磁剂量学中考虑姿态是重要的。     

Electromagnetic Fields and Power Deposition in Body-of-Revolution Models of Man

Internal electromagnetic (EM) fields and power absorption in a homogeneous Iossy dielectric body of revolution are evaluated using the surface integral equation method. The method yields moment method solutions for the induced current densities on the body surface. The interior fields to the body are then evafuated via the reciprocity theorem and the measurement matrix concept. The bulk body power deposition is obtained by the integration of the surface Poynting vector. The method applies for a wide range of dielectric parameters (with epsilon/sub r/ from 1.1 to 10/sup 2/ and sigma from 0 to 10/sup 3/ mhos/m) in the resonance region. Numerical results for EM fields and power deposition in a body-of-revolution model of a human torso with height of 1.78 m are evaluated for frequencies of 30, 80, and 300 MHz. It is found that the strongest power deposition in the torso model occurs for fields polarized along the longest dimension and for frequencies near the first resonance (i.e., 80 MHz) of the torso body. Hot spots are also observed in the neck region of the torso body.     

A Model for Impedance Determinations and Power Deposition Characterization in Three-Electrode Configurations for Capacitive Radio Frequency Hyperthermia?Part B: Current Flow and Power Deposition

The 2-D rectangular model for three-electrode radio frequency hyperthermia applicators established in Part A is applied to the determination of the current lines and the potential lines inside the system. Any electrode voltage distributions can be considered. Two figures illustrate the impact of the electric and the geometric parameters on these lines. They show that important changes in local current density, in electric field strength, and in electric field orientation are tied to the adjustments of the relevant parameters. Two successive sampling processes lead to the determination of the local power deposition. The figures which are displayed demonstrate the ability to move this deposition inside any useful area by means of proper trimming of the electrode voltage phases and magnitudes.     

Correction to "Power Deposition in a Spherical Model of Man Exposed to 1-20 MHz Electromagnetic Fields" (Letters)

In the above paper, Fig. 5 on page 794 should be as shown here in Fig. 1. An error occurred in translating the tabulated data into graphic form. The corrected figure is consistent with the results shown in Fig. 3 of the above paper.     

RF－PECVD制备类金刚石碳膜的沉积机理

本文综合评述了用射频等离子体化学气相沉积（ＲＦ－ＰＥＣＶＤ）法制备类金刚石碳膜过程中的等离子体化学反应和等离子体与材料表面反应机理的研究概况。着重介绍射频ＣＨ＿４等离子体中，各种离子和中性基因的产生和传输机理，以及等离子体与材料表面反应的动力学基本理论。     

对称局部能量模型:改进的局部能量模型

本文对局部能量模型进行改进,提出了一种新的基于相位信息的图像特征检测算法——对称局部能量模型(SLE)。该算法以log Gabor小波为基本工具,只用四个对称相位进行图像特征检测,检测结果符合人类视觉系统特性。SLE不但可以检测阶跃特征、线特征等亮度特征,还可以同时检测到马赫带现象和正弦网格中的特征,而基于亮度梯度的算法和局部能量模型都不能做到这一点。与局部能量模型相比,SLE还提高了抗噪能力和特征定位性能。     

The Effects of Driving Frequency and Antenna Length on Power Deposition Within a Microwave Antenna Array Used for Hyperthermia

The theory of the linear, insulated antenna embedded in an electrically dense medium is applied to microwave antennas used for hyperthermia cancer therapy. The pattern of power deposition is computed for a square array of four antennas with a side length of 3 cm under the assumption of no coupling among antennas. The driving frequency is set to seven values between 300 and 915 MHz, and the antenna halflength is set to three values: 3 cm, 6 cm, and the resonant value.     

On Effects of Frequency Offset on Simulink Model of OFDM

Wireless Personal Communications - OFDM is a multicarrier transmission technique, widely preferred due to advantages like high data rate, less bandwidth consumption and channel robustness. IEEE...     

Electromagnetic Power Deposition in Prolate Spheroid Models of Man and Animals at Resonance

The Extended Boundary Condition Method is used to calculate resonance region power deposition in prolate spheroid models of animals and man. The mathematical models consist of homogeneous distributions of muscle tissue, although in the case of the man model calculations, a model consisting of homogenized muscle, fat, and bone is also considered. Calculations are made for bodies isolated in free space and irradiated by a plane wave. Resonant frequencies and power absorption characteristics are predicted for man and a number of commonly used experimental animals. The results given here will be useful in providing a theoretical basis for the interpretation of experimental results and in extrapolating experimentally derived animal results to man's body configuration.     

RF化学气相淀积金刚石薄膜

本文论述了金刚石薄膜的优点，比较了化学淀积金刚石薄膜的常用方法的优缺点，主要介绍了电容耦合射频化学气相淀积金刚石薄膜的原理和近期国际对典型电容耦合气相淀积设备的改进研究。