University of Electro-Communications

About: University of Electro-Communications is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Laser & Robot. The organization has 8041 authors who have published 16950 publications receiving 235832 citations. The organization is also known as: UEC & Denki-Tsūshin Daigaku.

Anomalous effect in Schumann resonance phenomena observed in Japan, possibly associated with the Chi-chi earthquake in Taiwan

Abstract: . The Schumann resonance phenomenon has been monitored at Nakatsugawa (near Nagoya) in Japan since the beginning of 1999, and due to the occurance of a severe earthquake (so-called Chi-chi earthquake) on 21 September 1999 in Taiwan we have examined our Schumann resonance data at Nakatsugawa during the entire year of 1999. We have found a very anomalous effect in the Schumann resonance, possibly associated with two large land earthquakes (one is the Chi-chi earthquake and another one on 2 November 1999 (Chia-yi earthquake) with a magnitude again greater than 6.0). Conspicuous effects are observed for the larger Chi-chi earthquake, so that we summarize the characteristics for this event. The anomaly is characterized mainly by the unusual increase in amplitude of the fourth Schumann resonance mode and a significant frequency shift of its peak frequency (~1.0Hz) from the conventional value on the By magnetic field component which is sensitive to the waves propagating in the NS meridian plane. Anomalous Schumann resonance signals appeared from about one week to a few days before the main shock. Secondly, the goniometric estimation of the arrival angle of the anomalous signal is found to coincide with the Taiwan azimuth (the unresolved dual direction indicates toward South America). Also, the pulsed signals, such as the Q-bursts, were simultaneously observed with the "carrier" frequency around the peak frequency of the fourth Schumann resonance mode. The anomaly for the second event for the Chia-yi earthquake on 2 November had much in common. But, most likely due to a small magnitude, the anomaly appears one day before and lasts until one day after the main shock, with the enhancement at the fourth Schumann resonance mode being smaller in amplitude than the case of the Chi-chi earthquake. Yet, the other characteristics, including the goniometric direction finding result, frequency shift, etc., are nearly the same. Although the emphasis of the present study is made on experimental aspects, a possible generation mechanism for this anomaly is discussed in terms of the ELF radio wave scattered by a conducting disturbance, which is likely to take place in the middle atmosphere over Taiwan. Model computations show that the South American thunderstorms (Amazon basin) play the leading role in maintaining radio signals, leading to the anomaly in the Schumann resonance.

Rectified momentum transport for a kicked Bose-Einstein condensate.

Abstract: We report the experimental observation of rectified momentum transport for a Bose-Einstein condensate kicked at the Talbot time (quantum resonance) by an optical standing wave. Atoms are initially prepared in a superposition of the 0 and $\ensuremath{-}2\ensuremath{\hbar}{k}_{l}$ momentum states using an optical $\ensuremath{\pi}/2$ pulse. By changing the relative phase of the superposed states, a momentum current in either direction along the standing wave may be produced. We offer an interpretation based on matter-wave interference, showing that the observed effect is uniquely quantum.

Experimental and theoretical investigation of the impact of ultra-fast carrier dynamics on high-speed SOA-based all-optical switches.

Abstract: The impact of ultra-fast carrier dynamics in semiconductor optical amplifiers (SOAs) on switches based on cross-gain and cross-phase modulation is analyzed theoretically and experimentally. We find that ultra-fast effects lead to additional spectral broadening, which improves the optical signal-to-noise ratio for switches based on an SOA and an optical filter. For such switches, the influence of ultra-fast effects on the so-called nonlinear patterning effect is analyzed for three filter configurations: the asymmetric Mach-Zehnder interferometer (AMZI), a band-pass filter (BPF), and a cascade of an AMZI and a BPF. We conclude that fast carrier dynamics dramatically reduces nonlinear patterning and that the successful high-speed (>100 Gb/s) demonstrations in the literature rely on these effects.

Summary report of NASDA's earthquake remote sensing frontier project

Abstract: After the disastrous Kobe earthquake, the former Science and Technology Agency (STA) of Japanese Government proposed the Integrated Earthquake Frontier Project. Within the framework of this project, two institutions (RIKEN and NASDA (National Space Development Agency of Japan)) were asked to carry out over five years a feasibility study of the use of electromagnetic phenomena in short-term earthquake prediction. Since 1996 the RIKEN group has been engaged in the study of earth current and related phenomena. Meanwhile, under the NASDA project named “Earthquake Remote Sensing Frontier Project”, we performed an overall study of seismo-electromagnetic phenomena occurring not only in the lithosphere, but also in the atmosphere and ionosphere. Our five-year study has yielded that the seismic effect expresses itself not only in the lithosphere (such as by ULF electromagnetic emissions, acoustic emissions etc.), but also in the atmosphere and ionosphere (by means of pre-existing transmitter signals). Most importantly, we find convincing evidence for seismo-ionospheric perturbations on the basis of subionospheric VLF/LF signals. We have established a new challenging science field, “Lithosphere–atmosphere–ionosphere coupling” or “Electromagnetics in the coupled lithosphere–atmosphere–ionosphere system”. The study of this coupling would contribute to the scientific short-term earthquake prediction.

Atomic Magnetic Moment and Exchange Interaction between Mn Atoms in Intermetallic Compounds in Mn–Ge System

Abstract: Magnetic properties of four intermetallic compounds, e, e 1 , κ and η, in manganese-germanium system are studied by means of magnetization measurement and neutron diffraction. Exchange coefficients of the interaction between Mn atoms in the compounds are estimated quantitatively using the molecular field approximation, based on the localized moment model. The exchange coefficient between Mn atoms on different sublattices is found to depend largely on the interatomic distance: The exchange coefficient is found to be negative for smaller interatomic distances than r c =2.9 A and positive for larger distances. The magnitude of atomic magnetic moment in the compounds is consistently discussed using the Pauling valence, after Mori and Mitsui (J. Phys. Soc. Jpn. 25 (1968) 82).