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.

Electromagnetic precursors to the 2004 Mid Niigata Prefecture earthquake

Abstract: This paper summarizes the electromagnetic precursory phenomena for the 2004 Mid Niigata Prefecture earthquake on October 23, 2004. Three different kinds of seismogenic perturbations have been observed; (1) lithospheric DC/ULF emissions, (2) atmospheric radio noise in the VHF band and (3) ionospheric disturbances. The DC/ULF emissions as observed at Nakatsugawa (in Gifu Prefecture) are detected on October 2–6, and the direction finding result has indicated the possible observed azimuth very close to the epicentral region. Then, we have observed the atmospheric radio noises in the VHF band on October 15–18, which are found to have the azimuth from Chofu very close to the epicentral zone. Finally, nearly at the same time (about one week before the earthquake) we have observed significant ionospheric perturbations on the subionospheric VLF/LF propagation characteristics by means of the shift in terminator time and enhancement in signal fluctuation for one particular path from the JJY (in Fukushima Prefecture) to Kochi. These perturbations not only in the lithosphere, but also in the atmosphere and ionosphere, are likely to be precursors to the 2004 Mid Niigata Prefecture earthquake.

Haptic Sensing Foot System for Humanoid Robot and Ground Recognition With One-Leg Balance

Abstract: This paper presents a haptic sensing foot system for humanoid robot. The two different kinds of implementations are investigated: One is an active tactile sensing technique to recognize a contacting ground slope. The other is to balance the robot body with one leg for human-robot interaction. The proposed sensors are implemented on two robotic feet. Each sensing unit on each foot consists of three thin sheets of force sensitive resistors arranged triangularly with the peripheral circuits. The research objective is to produce an artifact which can be operated in a natural and intuitive manner by utilizing the control of a foot pose to keep the direction of the foot normal to the ground surface. Throughout these works, we aim to realize the tactile sensing foot to detect the ground slope for natural foot posture control in order to assist the biped walking robot to balance its body on various types of ground surfaces. In these applications, the information about the ground floor or orientation is not required in advance.

New grain formation during warm deformation of ferritic stainless steel

Abstract: Microstructural evolution accompanied by localization of plastic flow was studied in compression of a ferritic stainless steel with high stacking fault energy (SFE) at 873 K (≈0.5 Tm). The structure evolution is characterized by the formation of dense dislocation walls at low strains and subsequently of microbands and their clusters at moderate strains, followed by the evolution of fragmented structure inside the clusters of microbands at high strains. The misorientations of the fragmented boundaries and the fraction of high-angle grain boundaries increase substantially with increasing strain. Finally, further straining leads to the formation of new fine grains with high-angle boundaries, which become more equiaxed than the previous fragmented structure. The mechanisms operating during such structure changes are discussed in detail.

Development of ultrafast time-resolved dual-comb spectroscopy

Abstract: Ultrafast time-resolved dual-comb spectroscopy (TR-DCS) has been demonstrated, which enables direct observations of transient responses of complex optical spectra by combining dual-comb spectroscopy with the pump–probe method. TR-DCS achieves two-dimensional spectroscopy with a wide dynamic range for both the temporal and frequency axes. As a demonstration, we investigated the femtosecond relaxation dynamics of a photo-excited InGaAs saturable absorber in the near-infrared frequency region. The transient response of the interferogram was successfully obtained, and both the amplitude and phase spectra of the dynamic complex transmittance were independently deduced without using the Kramers-Kronig relations. A high phase resolution in the order of milliradian was achieved by suppressing the effect from the slow phase drift caused in the experimental system. Our proof-of-principle experiment promotes a pathway to coherent, highly accurate, and multi-dimensional pump–probe spectroscopy using the optical frequ...

ISTP observations of plasmoid ejection: IMP 8 and Geotail

Abstract: IMP 8 and Geotail observations of traveling compression regions (TCRs) and plasmoids, respectively, are used to investigate plasmoid formation and ejection. One year of IMP 8 magnetometer measurements taken during the distant tail phase of the Geotail mission were searched for TCRs, which signal the release of plasmoids down the tail. A total of 10 such intervals were identified. Examination of the Geotail measurements showed that this spacecraft was in the magnetotail for only three of the events. However, in all three cases, clear plasmoid signatures were observed at Geotail. These plasmoids were observed at distances of X = −170 to −197 RE. The in situ plasma velocities in these plasmoids are found to exceed the time-of-flight speeds between IMP 8 and Geotail suggesting that some further acceleration may have taken place following release. The inferred lengths of these plasmoids, ∼27–40 RE, are comparable to the downtail distance of IMP 8. This indicates that TCR at IMP 8 can be caused by plasmoids forming not only earthward but also adjacent to or just tailward of the spacecraft. The closeness of IMP 8 to the point of plasmoid formation is confirmed by the small, ∼0–3 min, time delays between the TCR perturbation and substorm onset. In two of the plasmoid events, high-speed earthward plasma flows and streaming energetic particles were measured in the plasma sheet boundary layer surrounding the plasmoid along with large positive Bz at the leading edge of the plasmoid suggesting that the core of the plasmoid was “snow plowing” into flux tubes recently closed at an active distant neutral line. In summary, these unique two-point measurements clearly show plasmoid ejection near substorm onset, their rapid movement to the distant tail and their further evolution as they encounter preexisting X lines in the distant tail.