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.

Temperature effect on fine-grained structure formation in high-strength Al alloy 7475 during hot severe deformation

Abstract: The effect of deformation temperature on grain refinement was studied in a high-strength 7475 Al alloy during multi-directional forging at temperatures from 573 to 763 K. Fine-grained structure is developed mainly by formation of microshear bands (MSBs) followed by increase in their number and boundary misorientation. With increase in processing temperature, the mechanism of plastic flow is gradually changed from that controlled by dislocation motion to that controlled mainly by grain boundary sliding (GBS). In the intermediate temperature range 573– 673 K, ultra-fine-grained (UFG) structure is developed in colony only near original grain boundaries in early deformation. At larger strains, GBS operating locally in these UFGed regions evolved may enhance non-homogeneous deformation, followed by MSBs crossing in original grain interiors, leading to acceleration of the kinetics of grain refinement. The main factors promoting grain refinement at elevated temperatures and the role of the operating deformation mechanisms in new grain formation are analyzed and discussed in detail.

A new 3D-CAD system for set-based parametric design

Abstract: So far, there has been an extraordinary development of computer-aided tools intended to generate, present or communicate 3D models. But there has not been a comparable progress in the development of 3D-CAD systems intended to assist designers in representing and manipulating both geometric and non-geometric design information based on solid models, thus facilitating concurrent engineering (CE). Design objects continue to be produced by traditional means using the computer as little more than a drafting tool. In addition, the state-of-the-art 3D-CAD systems are incapable of encoding engineering uncertainties since only precise single-valued assignments are allowed for their modeling operations. Recently, set-based CE (SBCE) has been attracting public attention as an emerging CE paradigm. Such a set-based design (SBD) approach presents many possibilities in handling the uncertainties that are intrinsic at the early phases of design. This paper addresses a novel concept – set-based parametric design (SBPD) – which combines the SBD practice with the parametric modeling technique widely used in most 3D-CAD systems. A preference set-based design (PSD) model and a design information solid (DIS) model are proposed to incorporate the SBPD concept into the current 3D-CAD systems. Finally, a prototype system is implemented to illustrate the potential to achieve a SBPD practice.

Broken-axisymmetry phase of a spin-1 ferromagnetic Bose-Einstein condensate

Abstract: A spin-1 ferromagnetic Bose-Einstein condensate subject to a certain magnetic field exhibits a broken-axisymmetry phase in which the magnetization tilts against the applied magnetic field due to the competition between ferromagnetism and linear and quadratic Zeeman effects. The Bogoliubov analysis shows that in this phase two Goldstone modes associated with U(1) and SO(2) symmetry breakings exist, in which phonons and magnons are coupled to restore the two broken symmetries.

Active learning strategies for rating elicitation in collaborative filtering: A system-wide perspective

Abstract: The accuracy of collaborative-filtering recommender systems largely depends on three factors: the quality of the rating prediction algorithm, and the quantity and quality of available ratings. While research in the field of recommender systems often concentrates on improving prediction algorithms, even the best algorithms will fail if they are fed poor-quality data during training, that is, garbage in, garbage out. Active learning aims to remedy this problem by focusing on obtaining better-quality data that more aptly reflects a user's preferences. However, traditional evaluation of active learning strategies has two major flaws, which have significant negative ramifications on accurately evaluating the system's performance (prediction error, precision, and quantity of elicited ratings). (1) Performance has been evaluated for each user independently (ignoring system-wide improvements). (2) Active learning strategies have been evaluated in isolation from unsolicited user ratings (natural acquisition). In this article we show that an elicited rating has effects across the system, so a typical user-centric evaluation which ignores any changes of rating prediction of other users also ignores these cumulative effects, which may be more influential on the performance of the system as a whole (system centric). We propose a new evaluation methodology and use it to evaluate some novel and state-of-the-art rating elicitation strategies. We found that the system-wide effectiveness of a rating elicitation strategy depends on the stage of the rating elicitation process, and on the evaluation measures (MAE, NDCG, and Precision). In particular, we show that using some common user-centric strategies may actually degrade the overall performance of a system. Finally, we show that the performance of many common active learning strategies changes significantly when evaluated concurrently with the natural acquisition of ratings in recommender systems.

Exchange coupling in TbCu and DyCu single-molecule magnets and related lanthanide and vanadium analogs

Abstract: Heterometallic coordination compounds [CuII(L)(C3H6O)LnIII(NO3)3] and [VIVO(L)(C3H6O)LnIII(NO3)3] (abbreviated as LnCu and LnV, respectively; H2L = N,N′-bis(3-methoxysalicylidene)-1,3-diamino-2,2-dimethylpropane; Ln = Gd, Tb, Dy, Ho, and Er) were synthesized, and the X-ray crystallographic analysis shows that their structures are isomorphous for each series. The single-molecule magnet behavior was observed for TbCu and DyCu, and the activation energies of magnetization reversal were 42.3(4) and 11.5(10) K, respectively. The magnetic exchange couplings in LnCu and LnV were precisely evaluated by means of combined high-frequency EPR and pulsed-field magnetization studies, to give JTb–Cu/kB ≥ 3.3 K, JDy–Cu/kB = 1.63(1) K, JHo–Cu/kB = 1.09(2) K, and JEr–Cu/kB = 0.24(1) K. A monotonic decrease of ferromagnetic JLn–Cu was found in the order of the atomic number, 64Gd to 68Er. The corresponding exchange parameters in LnV are smaller than those of the Cu derivatives, and JGd–V was antiferromagnetic (−3.0 K determined from the magnetization jump). A possible mechanism for the exchange coupling and chemical trend is discussed.