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Suppression of Log-Normal Distributed Weather Clutter Observed by an S-Band Radar

Wireless Engineering and Technology 2013年第3期4卷 125-133页

作者： shuji sayama Seishiro Ishii Department of Communications Engineering National Defense Academy Yokosuka Japan Department of Information Networks Sendai National College of Technology Sendai Japan.

We have observed weather clutter containing targets (ships) using an S-band radar with a frequency 3.05 GHz, a beam width 1.8°, and a pulsewidth 0.5 μs. To investigate the weather clutter amplitude statistics, we introduce the Akaike Information Criterion (AIC). We have found that the weather clutter amplitudes obey the log-normal, Weibull, and log-Weibull distributions with the shape parameters of 0.308 to 0.470, 4.42 to 4.51, and 15.91 to 16.44, respectively, for small data within the beam width of an antenna. We have proposed the log-normal/CFAR circuit modified a Cell-Averaging (CA) LOG/CFAR circuit. It is found that weather clutter is suppressed with improvement of 51.58 dB by log-normal/CFAR. As a result, we have showed that weather clutter observed by S-band radar does not obey the Rayleigh distribution and our log-normal/CFAR circuit has an effect on suppression of clutter and detection of target, while conventional LOG/CFAR circuit does not. In addition, if our circuit can be realized, we will have an advantage economically.

关键词： CFAR S-Band Radar Weather Clutter Log-Normal Distribution

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Rain Attenuation in the Microwave-to-Terahertz Waveband

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Wireless Engineering and Technology 2016年第2期7卷 59-66页

作者： Seishiro Ishii Masahiro Kinugawa Shunichiro Wakiyama shuji sayama Toshihisa Kamei Department of Information Networks National Institute of Technology Sendai College Sendai Japan Department of Communication Engineering National Defense Academy Yokosuka Japan

In recent years, there has been increased interest in the terahertz waveband for application to ultra-high-speed wireless communications and remote sensing systems. However, atmospheric propagation at these wavelengths has a significant effect on the operational stability of systems using the terahertz waveband, so elucidating the effects of rain on propagation is a topic of high interest. We demonstrate various methods for calculating attenuation due to rain and evaluate these methods through comparison with calculated and experimental values. We find that in the 90 - 225 GHz microwave band, values calculated according to Mie scattering theory using the Best and P-S sleet raindrop size distributions best agree with experimental values. At 313 and 355 GHz terahertz-waveband frequencies, values calculated according to Mie scattering theory using the Weibull distribution and a prediction model following ITU-R recommendations best agree with experimental values. We furthermore find that attenuation due to rain increases in proportion to frequency for microwave-band frequencies below approximately 50 GHz, but that there is a peak at around 100 GHz, above which the degree of attenuation remains steady or decreases. Rain-induced attenuation increases in proportion to the rainfall intensity.

关键词： Terahertz Wave Microwave Rain Attenuation Weibull Distribution ITU-R

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Champagne bottle neck sign in a patient with Moyamoya syndrome

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World Journal of Clinical Cases 2014年第9期2卷 474-477页

作者： Takafumi Shimogawa Takato Morioka Tetsuro sayama Takeshi Hamamura Chiharu Yasuda shuji Arakawa Department of Neurosurgery Kyushu Rosai Hospital Department of Cerebrovascular Disease Kyushu Rosai Hospital

The champagne bottle neck(CBN) sign refers to a reduction in the diameter of the proximal portion of the internal carotid artery that resembles a CBN, and is a characteristic feature of Moyamoya disease. A 43-yearold woman with an infarction of the posterior limb of the left internal capsule was diagnosed with Moyamoya syndrome associated with Graves' disease. The CBN sign was observed bilaterally. Cerebral revascularization surgery was performed, including left-sided superficial temporal artery to middle cerebral artery anastomosis. During four years of follow-up, she maintained a euthyroid state and did not have any further cerebral ischemic events. The CBN signs remained unchanged on both sides during this time. This is the first report of the CBN sign in a patient with Moyamoya syndrome associated with Graves' disease.

关键词： Champagne bottle neck sign Moyamoya disease Moyamoya syndrome Graves’disease Revascularization

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