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Fukuoka, Japan

Nishinippon Institute of Technology is a private university in the city of Kitakyushu in Fukuoka Prefecture, Japan. It was established in 1967. Wikipedia.

Zeng X.,Kyushu Institute of Technology | Yamaguchi T.,Kyushu Institute of Technology | Nishio K.,Nishinippon Institute of Technology
Optics and Laser Technology

A Ti(C, N)/TiB reinforced titanium matrix composite layer was successfully in-situ synthesized by laser melting on Ti-6Al-4V alloy surface with Ti-BN-C mixed powder, aiming at improving the wear resistance. The microstructure, chemical composition, hardness and wear behavior were analyzed. The results showed that, the cross sectional microstructure can be clearly divided into three parts, which were the laser melted layer, heat affected zone and non-affected zone. The reinforcements in laser melted layer consisted of dendritic TiC0.3N0.7 phases and fine-structure TiB phases. The matrix in laser melted layer was in a two-phase structure, being composed of platelet α titanium and intergranular β titanium. The hardness was increased from 320 HV in the substrate to 450-550 HV in the modified layer. The wear resistance was improved that, the wear volume loss of the laser treated sample was approximately half of the as received Ti-6Al-4V alloy after 8 h wear test. © 2016 Elsevier Ltd. All rights reserved. Source

Li S.,University of Science and Technology Beijing | Li S.,Japan National Institute of Materials Science | Akiyama E.,Japan National Institute of Materials Science | Uno N.,Nippon Steel and Sumikin Metal Products Co | And 3 more authors.
Corrosion Science

Delayed fracture properties of AISI 4135 high strength steels with 1490 and 1310. MPa of tensile strength, represented as B15 and B13, respectively, have been studied by means of slow strain rate test (SSRT) of notched bar specimens after outdoor exposure at rural and coastal areas. The exposed specimens were kept at humid medium before SSRT to reproduce active hydrogen entry influenced by the rust layer and to homogenize hydrogen distribution. The influences of exposure site and exposure time on fracture stress have been investigated. The susceptibility of B15 to delayed fracture was obviously higher than that of B13. © 2010 Elsevier Ltd. Source

Hagihara Y.,Sophia University | Shobu T.,NTT Data | Hisamori N.,Sophia University | Suzuki H.,Sophia University | And 2 more authors.
ISIJ International

The delayed fracture characteristics of V-bearing steel were evaluated using conventional strain rate test (CSRT) and the hydrogen absorption and desorption behaviors were studied with the specimens hydrogen- charged and then exposed to air of 30°C for up to 2.5 months. CSRT was carried out at two test sites, and nearly the same delayed fracture resistance was obtained for the V-bearing steel. The fracture appearance changed from quasicleavage to intergranular with increasing hydrogen content. The hydrogen content of the boundary between fracture appearances was approximately 4 mass ppm. The hydrogen introduced into the V-bearing steel was composed of a diffusible one which decreased in concentration in 24 h when exposed to air of 30°C, and two types (weakly and strongly) of trapped ones. The strongly trapped hydrogen remained in the specimen after 2.5 months of exposure in air. By analyzing the thermal desorption profiles with Gaussian function, the peak temperatures of these hydrogen types were 100°C, 167°C and 198°C, corresponding to diffusible, weakly and strongly trapped hydrogen, respectively. The hydrogen-charged specimens of more than 4 mass ppm were fractured in the intergranular mode. After exposure in air and the hydrogen content became less than 4 mass ppm, the fracture mode changed to quasicleavage. After recharging the hydrogen to more than 4 mass ppm, the fracture mode became intergranular again. © 2012 ISIJ. Source

Inoue T.,Nishinippon Institute of Technology | Itahashi T.,Showa University
2014 Joint 7th International Conference on Soft Computing and Intelligent Systems, SCIS 2014 and 15th International Symposium on Advanced Intelligent Systems, ISIS 2014

Blind source separation (BSS) is a method for recovering a set of source signals from the observation of their mixtures without any prior knowledge about the mixing process. On the other hand, a method that recovers only one source signal from the observation is called blind source extraction (BSE). The number of parameters needed to be estimated in BSE is smaller than that in BSS, thereby requiring less computational time. In this paper we show a new BSE algorithm and demonstrate that the algorithm can preserve a signal quality, which is one of the important features for applications, such as speech enhancement. Furthermore, we have showed that a unimodular constraint used in this study can eliminate the indeterminacy in numbering of the sources, which cannot be eliminated in other constraints proposed before. © 2014 IEEE. Source

Zeng X.,Kyushu Institute of Technology | Yamaguchi T.,Kyushu Institute of Technology | Nishio K.,Nishinippon Institute of Technology
Surface and Coatings Technology

The surface nitrocarburizing of a Ti-6Al-4V alloy was performed by YAG laser irradiation in a nitrogen and argon mixed gas flow. The optimal condition was investigated by varying the volume ratio of nitrogen in the mixed gas. The microstructure, chemical composition, hardness and wear behavior of the nitrocarburized Ti-6Al-4V alloy were analyzed. The results indicated that after surface nitrocarburizing, a double-layer composite film, for which the up layer was a Ti(C, N) layer and the down layer was a TiN0.3 layer, formed on the surface of the Ti-6Al-4V alloy. The observed cross sectional microstructure can be clearly divided into three parts: film, heat affected zone (HAZ) and unaffected substrate. When treated in a mixed gas flow of 70vol%N2 and 30vol% Ar, the optimal conditions were obtained with an average nano-indentation hardness of 41.6GPa and a wear volume loss of approximately 22 times less than that of the non-treated substrate. © 2014 Elsevier B.V. Source

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