LF seismogenic emissions and its application on the earthquake prediction

The authors are building a multi-point network system for the prediction of earthquake epicenter location by means of the seismogenic emission phenomena around Tokyo area. The network system consists of eight observation points with 50 km from each other and at each point a new digital type direction finding detector is set up with two loop sensors tuned to 82kHz. The output signals of the receivers are added into the digital vector composition circuit to obtain the direction angle of the source point,and this signal is transmitted to the center computer through a telemeter line. In order to protect from local man-made noise interferences,the warning is only anounced when the computation results of the center computer pointed one small area with high cross-corelation values for area from between all points.The source mechanism of emission related to precursors of earthquakes can be explained as electtromagnetic emissions for the rocks around the focus when they are crushed completely by the distortion pressure.And these emission energies are propagated in the ground along the boun-dary surface of the fault as a surface wave mode and radiated from the slit antenna which consists of the boundary at the ground surface of the fault.The authors will present the computer flow and try to explain the source mechanism of these emission in this paper.利用は著作権の範囲内に限られ

Power Line Radiation over Eastern Asia Observed by the Satellite OHZORA

Statistically improved results of power line radiation (PLR) over Eastern Asia observed at 50 and 60 Hz are described in this paper. A total number of 150 orbits, which had been observed from June 1984 to January 1986, by the Japanese scientific satellite OHZORA, are used to detect PLR over Eastern Asia around the Japanese Islands. Depending on the increase in the number of data points, the statistical characteristics of the background noise can be precisely determined by using the improved technique compared with the initial analysis. Statistically reasonable data points are detected as PLR based on the +3σ criterion, where σ is the standard deviation of the background noise. Therefore, the statistical reliability for rejecting the background noise is 99.85%. Then, these detected data are applied to the cause-and-effect test. When the statistically detected data points are placed on the map of Eastern Asia, the points cover Eastern Japan and the east coast of China for 50 Hz, and they cover Western Japan for 60 Hz. The maps of the detection ratios and those of the average field strengths indicate the positive correlation with the ground maps of the electric power generation at 50 and 60 Hz. The positive correlation is more clearly seen at 50 Hz since the background noise is somewhat weaker than that at 60 Hz. This close relationship between the satellite observation and the electric power generation suggests that the detection of PLR is not caused by chance, and that PLR penetrates into the ionosphere and propagates approximately just upward. The decrease of field strength with altitude can be interpreted as the gradual decrease of the refractive index from to 700 km. Therefore, the detection ratio and the average field strength with respect to the satellite altitude suggest PLR propagating from the bottom of the ionosphere. According to these observational results, it is concluded that PLR in Eastern Asia is high above the high electric power generating regions over Japan and China, and that the satellite observation is capable of estimating PLR field below the ionosphere. These results are the first direct indication that the PLR field is enhanced over the high electric power generation region, and is penetrating into the ionosphere

Coexistence of Continuous Variable Quantum Key Distribution and 7 ×\times 12.5 Gbit/s Classical Channels

We study coexistence of CV-QKD and 7 classical 12.5 Gbit/s on-off keying channels in WDM transmission over the C-band. We demonstrate key generation with a distilled secret key rate between 20 to 50 kbit/s in experiments running continuously over 24 hours.Comment: 2018 IEEE Summer Topicals, paper MD4.

Relaxation kinetics of photoinduced surface relief grating on azopolymer films

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Tatsunosuke Matsui, Shin-ichiro Yamamoto, Masanori Ozaki, Katsumi Yoshino, and Francois Kajzar, Journal of Applied Physics 92, 6959 (2002) and may be found at https://doi.org/10.1063/1.1516264

Quantum key distribution with an efficient countermeasure against correlated intensity fluctuations in optical pulses

Quantum key distribution (QKD) allows two distant parties to share secret keys with the proven security even in the presence of an eavesdropper with unbounded computational power. Recently, GHz-clock decoy QKD systems have been realized by employing ultrafast optical communication devices. However, security loopholes of high-speed systems have not been fully explored yet. Here we point out a security loophole at the transmitter of the GHz-clock QKD, which is a common problem in high-speed QKD systems using practical band-width limited devices. We experimentally observe the inter-pulse intensity correlation and modulation-pattern dependent intensity deviation in a practical high-speed QKD system. Such correlation violates the assumption of most security theories. We also provide its countermeasure which does not require significant changes of hardware and can generate keys secure over 100 km fiber transmission. Our countermeasure is simple, effective and applicable to wide range of high-speed QKD systems, and thus paves the way to realize ultrafast and security-certified commercial QKD systems

日本列島周辺における電力線誘導・放射電磁界 : 気球観測

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