In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength ...In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength impedance transformer. All the calculation is simpler than that given by Y. S. Wu, et al[1-7]. Typical performances of the 2-4GHz Y-junction stripline circulator are insertion loss 0.35dB (max), isolation 21dB (min), VSWR 1.25 (max). An octave low-loss and high isolation performance is demonstrated without the need of repeated design cycles.展开更多
Twenty-four guinea pigs with normal Preyer's reflex were exposed to the octave bands of noise centered at 63 Hz and 4 kHz, 110 dB SPL. The duration of exposure was 4 and 8 hours respectively. The permanent shift o...Twenty-four guinea pigs with normal Preyer's reflex were exposed to the octave bands of noise centered at 63 Hz and 4 kHz, 110 dB SPL. The duration of exposure was 4 and 8 hours respectively. The permanent shift of the guinea pigs at the above two frequencies was at 4-8 kHz. As the duration of exposure were 4 hours, the threshold shift at 63 Hz was smaller than that at 4 kHz. But as the duration of exposure was 8 hours, the threshold shift at 63 Hz and 4 kHz was almost the same. No morphological change of the inner ear was observed in the guinea pigs exposed for 4 hours at the octave bands of noise centered at 63 Hz and 4 kHz, but ultrastruetural abnormalities were noted. After the animals were exposed for 8 hours, morphological, nltrastructural changes in the inner ear were observed. The main pathologic changes were seen at the second torn of the cochlea. These changes in hearing physiology and pathology suggest that a high intensive low frequency noise can result in high frequency hearing loss and that the use of A-weighted levels of specific damage risk criteria for noise sources may be inappropriate.展开更多
文摘In this paper, a new design method for high performance octave-band stripline circulator is given. The optimum design program is given by a construction with double-Y junction aided by a section of quarter-wavelength impedance transformer. All the calculation is simpler than that given by Y. S. Wu, et al[1-7]. Typical performances of the 2-4GHz Y-junction stripline circulator are insertion loss 0.35dB (max), isolation 21dB (min), VSWR 1.25 (max). An octave low-loss and high isolation performance is demonstrated without the need of repeated design cycles.
文摘Twenty-four guinea pigs with normal Preyer's reflex were exposed to the octave bands of noise centered at 63 Hz and 4 kHz, 110 dB SPL. The duration of exposure was 4 and 8 hours respectively. The permanent shift of the guinea pigs at the above two frequencies was at 4-8 kHz. As the duration of exposure were 4 hours, the threshold shift at 63 Hz was smaller than that at 4 kHz. But as the duration of exposure was 8 hours, the threshold shift at 63 Hz and 4 kHz was almost the same. No morphological change of the inner ear was observed in the guinea pigs exposed for 4 hours at the octave bands of noise centered at 63 Hz and 4 kHz, but ultrastruetural abnormalities were noted. After the animals were exposed for 8 hours, morphological, nltrastructural changes in the inner ear were observed. The main pathologic changes were seen at the second torn of the cochlea. These changes in hearing physiology and pathology suggest that a high intensive low frequency noise can result in high frequency hearing loss and that the use of A-weighted levels of specific damage risk criteria for noise sources may be inappropriate.
