Author
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NELSON, STUART |
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Submitted to: Journal of Microwave Power and Electromagnetic Energy
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/18/2000 Publication Date: N/A Citation: N/A Interpretive Summary: The electrical characteristics of materials, known as dielectric properties, are important in determining how materials interact with electric fields. In the application of radio-frequency (RF) and microwave heating of materials, such as foods and other relatively poor conductors of electricity, these properties determine how rapidly the materials will absorb energy from the high-frequency electric fields. The possibility of controlling stored-grain insects by selective dielectric heating of the insects was explored earlier as a nonchemical method, and the frequency range from about 10 to 100 MHz was found to offer the best selective heating of the insects infesting cereal grains. Since then, additional data have been published on the dielectric properties of insects, and there is still interest in the possibility of developing RF and microwave methods for insect control. These same dielectric properties are also of interest in using radar for the tracking of insects to study insect migration and behavior. In this paper, the scientific principles necessary for understanding these interactions of electromagnetic fields with insects are briefly presented and the available useful data on dielectric properties of insects are analyzed and collected for reference by those interested in this field of research. In connection with these studies, the densities and moisture contents of some stored-grain insect species were also determined. They are tabulated in this paper for reference along with the dielectric properties data, which will provide assistance to scientists interested in the use of microwave and radio-frequency energy for controlling insects and studying their migratory behavior as well. Technical Abstract: Basic principles and definitions of dielectric properties of materials are presented. Data from the literature on the dielectric properties of insects are briefly reviewed and discussed in relation to insect control by selective dielectric heating. Because early measurements of the dielectric properties of insects were taken on bulk samples of insects (insect and air-space dielectric mixtures), a means for converting the dielectric properties, or permittivities, of bulk samples of particulate materials to those of the solid particles is described. The technique uses the Landau & Lifshitz, Looyenga dielectric mixture equation and information on the bulk densities of air-insect mixtures used for dielectric properties measurements along with the densities of the insects. Such converted data for the dielectric constants and loss factors of the insects are presented and collected for comparison with other measurements of insect tissues and permittivity determinations from more recent microwave measurements of these same parameters. Resulting data are presented for reference, and comparisons are presented and discussed briefly. |
