Numerical research is reported on the propagation of short microwave pulses into living, biological materials. These materials are dispersive, and data on the dielectric constant and conductivity for these materials follow a Debye model. A Fourier-series calculation is presented that predicts the occurrence of Brillouin precursors when the incident pulses have sufficiently short rise times. These transients are attenuated with increasing propagation distance but are attenuated more slowly than the carrier frequency of the pulse, which is attenuated exponentially with distance. An analysis of the numerical error resulting from truncation of the Fourier series is giv-in. Upperbound estimates of truncation error show good series convergence., -
The quantitative interrogation of the human body or environmental s m c t m s such as plants or soils using electromagnetic or acoustic waves and solutions to inverse problems appears promising in clinical and environmental medicine. This paper reviews applications and methods of inverse electromagnetic and acoustic scattering.
SUMMARYThe relative risk is an important parameter in certain epidemiological studies. It is given by the ratio of the rates of developing a certain disease between the exposed and the control group. This paper deals with the Bayesian estimation of the relative risk using: (a) uniform [0,1] priors; (b) restricted uniform priors; (c) beta priors. The appropriateness of such priors is discussed in the medical setting and analytical expressions are obtained for the distributions of the relative risk in the above three cases. Data taken from the Air Force Health study are analysed and 95 per cent con®dence limits are presented for the three types of priors. Finally, for the Bayesian intervals, the estimated probabilities that the relative risk is greater than 1 are exhibited.
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