EEG changes and stress reactions in rat induced by millimeter wave / 生物医学工程学杂志

The present paper is aimed to study the processes of stress reaction and their judgment bases in rat induced by 35 GHz millimeter wave quantitatively. The relative change in the average energy of each EEG frequency band decomposed by wavelet analysis was calculated for extracting the stress indicator for the purpose. The rat would experience quiet period, guarding period, deadlock period and prostrating period in sequence. The judgment bases of different stress periods in rat induced by millimeter wave were obtained by analyzing the skin temperature, skin injury and changes of blood biochemical indexes during each stress period. The stress period changed from quiet period to guarding period when the skin temperature of irradiated area reached the thermal pain threshold. It was from guarding period to deadlock period when the skin had gotten serious injury. Then the rat reaction sensitivity decreased, and injury of its visceral organs occurred. The rat got to prostrating period when the sustained irradiation caused the rat's visceral organs to get more serious injury. The further sustained irradiation finally induced death of the rat.

Comparison of digital filter and wavelet transform for extracting electroencephalogram rhythm / 生物医学工程学杂志

It is very important to extract electroencephalogram (EEG) rhythm in clinical diagnoses. Digital filter and wavelet transform are used to extract the rhythm from a piece of EEG at the sampling rate of 2 kHz. The Daubechies order 4 wavelet (db4) was used to decompose the EEG at 8 levels. According to the filter characteristic of wavelet decomposition, the reconstructions of aS, d8, d7, d6 and d5 component are nearly corresponding to the rhythms of delta, theta, alpha, gamma separately. The 6 order ellipse infinite impulse response (IIR) filter is also used to decompose the EEG. As the quality factor of wavelet decomposition filter is constant, the wavelet transform obtains better extracted rhythm than the digital filter. Furthermore, the wavelet transform method can be used to extract the low frequency rhythm from wide frequency band.