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.

Generation of radially polarized mode in Yb fiber laser by using a dual conical prism

Abstract: For the first time to our knowledge, a radially polarized beam is generated in an Yb-doped multimode double-clad fiber laser by using an intracavity dual conical prism. Up to 6.2 mW of output power is obtained from a 2 m long gain fiber with 7.4% slope efficiency. This research opens a new window to obtaining a radially polarized beam directly from an active fiber.

Anomalies in VLF radio signals prior the Abruzzo earthquake (M=6.3) on 6 April 2009

Abstract: . The VLF/LF radio signals method for studying preseimic activity is applied to the Abruzzo earthquake (M=6.3, 6 April 2009). The data collected by three receivers located in Moscow (Russia), Graz (Austria) and Bari (Italy) at about 3000 km, 1000 km and 500 km from the epicenter were used. The signals received from the Sardinia (20.27 kHz) and the Sicily (45.9 kHz) transmitters, both located in Italy, were compared with those received from the Iceland (37.5 kHz), the Great Britain (19.58 kHz) and the Germany (23.4 kHz) transmitters. The propagation paths of the two Italian transmitters cross the epicentral area (seismic paths) unlike the paths of the other three signals (control paths). Using two different analyses, that are the study of the night-time signal and the research of shifts in the evening terminator times, clear anomalies were revealed 2–8 days before the occurrence of the Abruzzo earthquake in the seismic paths, while no anomalies have been found in the control paths.

Representation for knot-tying tasks

Abstract: The learning from observation (LFO) paradigm has been widely applied in various types of robot systems. It helps reduce the work of the programmer. However, the applications of available systems are limited to manipulation of rigid objects. Manipulation of deformable objects is rarely considered, because it is difficult to design a method for representing states of deformable objects and operations against them. Furthermore, too many operations are possible on them. In this paper, we choose knot tying as a case study for manipulating deformable objects, because the knot theory is available and the types of operations possible in knot tying are limited. We propose a knot planning from observation (KPO) paradigm, a KPO theory, and a KPO system.

Tool path generation using C-space for 5-axis control machining

Abstract: The paper deals with the method of tool path generation for 5-axis control machining using a ball end mill. 5-axis control machining has been used for aircraft parts as well as for complicated shapes such as mold and dies. However, most of the present CAM systems for 5-axis control machining have limited functions in terms of tool collision, workpiece shapes and machining methods. For that reason, in many cases the optimal cutter location (CL) data cannot be obtained or considerable time is consumed. To solve this problem, we applied a 3-dimensional configuration space (C-Space) and showed the relationship between all tool positions and postures and the existence of tool collision. The method of tool path generation devised in the study enables users to generate CL data reflecting their own machining strategy such as smooth change in tool posture and the state of machining without considering the gouging. The validity of this method was experimentally confirmed by successfully milling an impeller without tool collision occurring.

Grain Refinement under Multiple Warm Deformation in 304 Type Austenitic Stainless Steel

Abstract: The dynamic process of fine grain evolution as well as deformation behaviour under warm working conditions was studied in compression of a 304 type austenitic stainless steel. Multiple compression tests were carried out at a strain rate of 10-3 s-1 to produce high cumulative strains, with changing of the loading direction in 90o and decreasing temperature from 1223 to 873 K (0.7-0.5Tm) in each pass. The steel exhibits two types of deformation behaviours with different mechanical and structural characteristics. In the deformation region where flow stresses are below about 400 MPa, conventional dynamic recrystallization takes place accompanied mainly by bulging of serrated grain boundaries. The dynamic grain size evolved can be related to the high temperature flow stress through a power law function with a grain size exponent of -0.72. On the other hand, in the region of higher stresses above 400 MPa the flow stresses show small strain rate and temperature dependence, and so it is suggested to be in an athermal deformation region. The stress-strain curves show a steady state like flow without any strain softening, while the multiple deformation to high cumulative strains brings about the evolution of fine grained structures with grain sizes less than one micron. The relationship between the warm temperature flow stresses and the grain sizes evolved also can be expressed by a unique power law function of grain size with an exponent of -0.42. The interrelations between the mechanisms of plastic deformation and microstructure evolution at warm and high temperatures are analysed in detail and also the multiple compression method for obtaining ultra fine grained structure is discussed as a simple thermomechanical processing.