摘要:

A multiple‐cell calorimetric system was constructed, and the experimental procedure for its use was developed. An associated data‐readout system is small, relatively inexpensive, and provides automated thermistor calibration, precise temperature measurements, and a printout of whole‐body SARs. One system was used to determine the SAR of each of 18 mice that were simultaneously exposed to 2.6‐GHz ra

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00001

年代:1979

数据来源: WILEY

摘要:

The second edition of theRadiofrequency Radiation Dosimetry Handbookextends the data contained in the first edition, which was published by the United States Air Force School of Aerospace Medicine in September 1976 [Johnson et al., 1976]. Several additional techniques have been used to extend the frequency range over which the specific absorption rate or mass‐normalized rate of energy absorption (SAR) is calculated for models of human beings and animals, which results in useful theoretical data over the frequency range 10 kHz to 100 GHz. Some information is also given about ground‐plane effects, experimental data found in the literature, and thermal effects of irradiat

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00005

年代:1979

数据来源: WILEY

摘要:

The NFM‐1 near‐field‐strength meter developed in the German Democratic Republic utilizes two dipole probes designed for 60 kHz to 350 MHz. The measuring ranges of the probes overlap each other from 10 MHz to 30 MHz. The meter operates over the temperature range −10°C to +40°C. Field strength meters of 2 V m−1to 2500 V m−1sensitivity with a measuring error of ⩽ 20% must be calibrated by special equipment designed for the purpose. A calibrating stand based on the principle of a parallelplate capacitor is used in the frequency range from 60 kHz to 18 MHz, and a triplate‐stripline (TEM‐cell) is used in the frequency range from 10 MHz to 350 MHz, for calibrating the probes. Large‐scale measurements were made in 1976 by which the NFM‐1 meter was compared with the corresponding near‐field‐strength meters used in the USSR,

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00009

年代:1979

数据来源: WILEY

摘要:

Fine structure in the whole‐body resonant curve for radio‐frequency energy deposition in man can be attributed to part‐body resonances. As for head resonance, which occurs near 350 MHz in man, the absorptive cross section is nearly three times the physical cross section of the head. The arm has a prominent resonance at 150 MHz. Numerical solutions, antenna, theory, and experimental results on animals have shown that whole‐body energy deposition may be increased by 50 percent or more because of multiple bodies that are strategically located in the field. Empirical equations for SARs are also presented along with test data for several species of laboratory animals. Barbiturate anesthesia is sufficiently disruptive of thermoregulation that ΔTsof colonie temperature yield energy dose values in several mammals that compare quite favorably with those based on whole‐body c

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00015

年代:1979

数据来源: WILEY

摘要:

Image theory has been used to obtain moment‐method solutions of the deposition of electromagnetic energy in standard man as a function of grounding and reflector effects. The calculated values are in good agreement with experimental data. For the EIĽ orientation, the resonant frequency of standard man shifts from 77 MHz in free space to 47 MHz when standing on a ground plane. The dependence of reflector effects on spacing and frequency are in agreement with the gain enhancement calculated for dipoles by antenna theo

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00023

年代:1979

数据来源: WILEY

摘要:

There are several hundred radio‐frequency (RF) heaters in industrial use in Finland. No exposure or performance standards have been established for this kind of device in our country. This paper describes measurements of strength of electric and magnetic fields near 35 plastic‐welding machines, all operating at 27 MHz at nominal power outputs that range from 0.5 to 35 kW. Approximately 70% of the heaters radiated RF energy at strengths that exceeded common standards (200 V m−1, 0.5 A m−1). The Finnish proposed safety standard (60 V m−1, 0.2 A m−1) was exceeded in 80% of the cases. The results indicate that both electric and magnetic fields should be measured in

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00031

年代:1979

数据来源: WILEY

摘要:

A geometrical‐optics approximation was used to calculate the mass‐normalized rate of RF energy absorption (the specific absorption rate or SAR) in cylindrical models of man and in experimental animals irradiated by an electromagnetic (EM) plane wave at high radio frequencies. Comparison of these results with corresponding geometrical‐optics calculations for prolate spheroidal models showed that the relative absorptive cross section of the prolate spheroidal and cylindrical models of man are essentially the same at frequencies above 20 GHz. The exact solution for the SAR in a lossy, infinitely long homogeneous circular cylinder exposed to an electromagnetic plane wave, for perpendicular incidence and with the incidentEfield both perpendicular and parallel to the axis, is also given. Although the formal solution is in the literature, data showing SARs for very lossy cylinders have apparently not been calculated. Curves showing SAR versus frequency for cylindrical models of man and animals in comparison with composite curves obtained from prolate spheroidal calculation are presented. It is shown that the exact solution for SARs in cylindrical models of animals and human beings appears to be a good approximation in the frequency range just below the geometrical‐optics limit, thus providing an important method for extending the calculation of SARs into a range of frequencies where calculations were not available pre

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00035

年代:1979

数据来源: WILEY

摘要:

Theoretical calculations of absorption of radio‐frequency (RF) energy by appropriate models of man have heretofore failed to yield numerical results much beyond the first absorptive peak of whole‐body resonance. Current efforts are directed toward a better definition of whole‐body absorption at supraresonant frequencies. A method based on geometrical optics has been developed recently, and it was used by us to compute absorptive characteristics of a prolate spheroidal model of man to a high‐frequency limit. The technique approximates the surface of the prolate spheroid by small planar subareas. The energy being transmitted into each subarea is determined and is assumed to be completely absorbed due to the small depth of penetration of electromagnetic waves into lossy biological bodies in the supraresonant region. The total energy absorbed is found by summing over all subareas. Validity testing with Mie theory, in conjunction with consideration of the localization principle of geometrical optics, indicates that this technique is applicable to the model of man at frequencies beyond 6 GHz. Computer‐generated results for a 70‐kg prolate spheroidal model of man indicate that (1) the dependence of energy absorption on the incident wave's polarization and angle of incidence is markedly different from dependencies observed at lower frequencies; (2) the rate of energy absorption increases with frequency within the asymptotic limit; and (3) the use of simple planar models is inadequate to determine energy‐absorption characteristics of biological bodies at high R

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00043

年代:1979

数据来源: WILEY

摘要:

A numerical method based on a tensor integral equation has been employed to quantify the induced EM heating in realistic models of the human and infrahuman head. The head consists of a brain of realistic shape and eyes that are surrounded by a bony structure. The numerical method has also been used to determine the induced EM heating in spherical models of human and infrahuman heads and brains. The EM heating induced in the brain of the realistic model is lower than that induced in the brain of the spherical model. The bony stucture of the skull tends to attenuate heating of the brain, including the eyes.

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00051

年代:1979

数据来源: WILEY

摘要:

A system developed to expose chronically a large number of small animals to 918‐MHz microwave has been modified to permit exposure at 2450 MHz. Special transmitting and termination transducers were used to retrofit the exposure chambers of the 918‐MHz system. The use of separate cells that consist of cylindrical waveguides, which are excited by circularly polarized, guided waves, provides a relatively constant and easily quantifiable coupling of microwave energy to each animal, regardless of their position, posture, or movement. The VSWR in each cell is sufficiently low that any number of cells can be coupled to a single source through a power splitter without the need for an isola

ISSN:0048-6604    

DOI:10.1029/RS014i06Sp00063

年代:1979

数据来源: WILEY