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.

A study of ionospheric response to regional seismic activity by VLF radio sounding

Abstract: Electric field strength nighttime fluctuations in subionospheric signals of very low frequency (VLF) on Omega, Tsushima-Chofu (Tokyo) and NWC, Australia-Chofu propagation paths recorded during March–August, 1997 were studied for searching for correlation with seismic activity. Wave-like anomalies in VLF Omega signal with periods of a few hours were observed 1–3 days before or on the day of moderately strong earthquakes of magnitudes 5–6.1. Analysis of the correlation between regional seismic activity around Tokyo and dispersion of VLF fluctuations revealed that maximal correlation was observed during pre-seismic periods for shallow earthquakes (focal depth less than 40 km) that occurred at distances up to 350–400 km from receiving place. Spectral analysis of the earthquake catalogue has shown rhythmical variations of seismic activity integrated over large areas with periods of 4–14 days. Similar periodic components are observed in fluctuations of VLF signals propagating over the NWC-Chofu path. For both VLF propagation paths, a 27-day periodicity was found in fluctuations of signals that can be referred to as tidal or solar rotation influence.

Multiobjective control of a vehicle with triple trailers

Abstract: We consider the backing-up control of a vehicle with triple trailers using a model-based fuzzy-control methodology. First, the vehicle model is represented by a Takagi-Sugeno fuzzy model. Then, we employ the so-called "parallel distributed compensation" design to arrive at a controller that guarantees the stability of the closed-loop system consisted of the fuzzy model and controller. The control-design problem is cast in terms of linear matrix inequalities (LMIs). In addition to stability, the control performance considerations such as decay rate, constraints on input and output, and disturbance rejection are incorporated in the LMI conditions. In application to the vehicle with triple trailers setup, we utilize these LMI conditions to explicitly avoid the saturation of the steering angle and the jackknife phenomenon in the control design. Both simulation and experimental results are presented. Our results demonstrate that the fuzzy controller effectively achieves the backing-up control of the vehicle with triple trailers while avoiding the saturation of the actuator and "jackknife" phenomenon.

An information-spectrum approach to capacity theorems for the general multiple-access channel

Abstract: The paper deals with the capacity problems for the general multiple-access channel, where the channel transition probabilities are arbitrary for every blocklength n. The approach used here, which is called the information-spectrum approach, is quite different from the standard typical-sequence and/or AEP techniques. The general formula for the capacity region for the general multiple-access channel is thus established. In order to examine the potentiality, we apply it to the mixed channel to obtain the formula for its capacity region. The case where input cost constraints are imposed is also considered.

Effect of Pass Strain on Grain Refinement in 7475 Al Alloy during Hot Multidirectional Forging

Abstract: Effect of pass strain (�" ) on grain refinement was studied in multidirectional forging (MDF) of a coarse-grained 7475 Al alloy at 490 � C under a strain rate of 3 � 10 � 4 s � 1 . Samples of rectangular shape were deformed up to accumulated strains of around 6 with subsequent changes in loading direction 90 � from pass to pass. The pass strains in each compression (�" ) were 0.4 and 0.7. The cumulative flow curves integrated by each compression exhibit significant work softening just after yielding, followed by apparent steady state plastic flow at high strains. Structural changes were characterized by grain fragmentation due to frequent development of deformation and/or microshear bands followed by full evolution of new fine grains in the original grains. Increasing �" accelerates significantly the kinetics of grain refinement, leading to more clear reduction of flow stresses at moderate to high strains. MDF of �" ¼ 0:7 results finally in formation of a finer grained structure with an average size of around 7.5 mm at strains of above 3.5, while, the processing with �" ¼ 0:4 develops a slightly coarser grain structure at higher strain of about 6. The effect of MDF on new grain evolution and the mechanisms of grain refinement are discussed in details.