http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Nishimoto, Kazutoshi,Woo, In Su,Kang, Chang Yun 대한금속재료학회(대한금속학회) 2001 METALS AND MATERIALS International Vol.7 No.4
The factors affecting intergranular liquation cracking susceptibility in electron beam welds were investigated for cast alloy 718. The materials used were as-received plates and heat-treated plates with three different levels of grain size. Liquation cracking susceptibility in HAZ was evaluated by a bead-on-plate test and a restraint/relaxation U-type hot cracking test. The penetrated shapes in the welds were classified into wine cup-like Type W and nail head-like Type N. For a given beam current, Type W and Type N were observed at the lower and higher welding speeds, respectively. Welding defects, i.e., underfills and microcracks were seen in the electron beam welds. Compared with Type W, the liquation cracking was more sensitive for the Type N bead cross sectional shape. Furthermore, it easily occurred at grain boundaries in Region II, i.e., very near the nail head necked part. According to the restraint/relaxation U-type hot cracking test, the liquation cracking susceptibility decreased with decreasing grain size or with homogenization heat treatment. These results suggested that the liquation cracking susceptibility in cast alloy 718 electron beam welds could be improved by using the Type W bead cross sectional shape, a decreasing the grain size and using appropriate heat treatment before welding.
Nishimoto, Kazutoshi,Woo, In Su 대한금속재료학회(대한금속학회) 2001 METALS AND MATERIALS International Vol.7 No.3
A study was carried out to determine the effect of cerium addition on HAZ cracking susceptibility in cast alloy 718 welds. The cause of HAZ cracking was also investigated using commercial cast alloy 718 varying in grain size at three levels. The hot cracking test results for commercial cast alloy 718 indicated that the fine-grained alloy was less sensitive to HAZ cracking. Furthermore, cerium addition of up to 0.3 wt.% was found to have a beneficial effect in reducing HAZ cracking susceptibility. When cerium addition exceeds 0.3 wt.%, HAZ cracking susceptibility increased further. The mechanism of HAZ cracking was found to be related to intergranular liquation caused by the eutectic melting of sulfur containing a laves cluster at the grain boundaries. The degree of grain boundary liquation in the fine-grained specimen was less than that of the coarse-grained specimen due to a decrease in the amount of laves cluster and sulfur segregation in it at the grain boundaries, which seems to be responsible for a reduction in hot cracking susceptibility in the fine-grained specimen. Microscopic observation suggested that the improved HAZ cracking susceptibility in cerium containing alloy could be attributed to a reduction in the amount of laves cluster and sulfur segregation in it at grain boundaries due to the grain size reduction and sulfur-scavenging effects of cerium.
Ni기 초내열합금 용접부의 고온균열에 관한 연구(I) - 용접금속의 응고균열 감수성에 미치는 Fe의 영향 -
우인수,강정윤,Kazutoshi Nishimoto 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.6
A study was carried out to determine the solidification cracking susceptibility of Ni-base superalloy as a function of Fe content in base metal. Three kinds of Ni-base superalloys with three different levels of Fe content were used. The solidification cracking susceptibility was evaluated by the Trans-Varestraint test at four different strain levels. Quantitative analysis of crack revealed that the solidification crack length and the temperature range in which hot cracking occurred in fusion zone (Brittle Temperature Range, BTR) decreased with a decrease in Fe content. Further, the thermo-calc data indicated that the solidification temperature range also decreased with decreasing Fe content. From these results, it was deduced that the improvement of the solidification cracking susceptibility with decreasing Fe content was attributed to the decrease of the solidification temperature range.
Bonding Phenomena of Transient Liquid Phase Bonded Joints of a Ni Base Single Crystal Superalloy
Kim, Dae-Up,Kazutoshi, Nishimoto 대한금속학회 2002 METALS AND MATERIALS International Vol.8 No.4
The bonding phenomena of Ni base single crystal superalloy CMSX-2 during transient liquid phase (TLP) bonding have been investigated using MBF-80 and F-24 insert metals. TLP bonding of the superalloy was carried out at 1373-1548K for 0-19.6ks in vacuum and the (100) plane of each test specimen was always aligned perpendicular to the joint interface. The dissolution width increased when the bonding temperature and holding time increased. The eutectic width decreased linearly with the square root of holding time during isothermal solidification. After homogenization treatment, the microstructure, distributions of hardness and alloying elements in the bonded interlayer become similar to those of the base metal.
전은준,Hayato Baba,Kazutoshi Nishimoto,Kazuyoshi Saida 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.3
In order to quantitatively evaluate the solidification cracking susceptibility in laser welds of type 310S stainless steel, a transverse-Varestraint testing system using a laser beam welding apparatus was newly constructed. The timing-synchronization between the laser oscillator, welding robot and hydraulic pressure devices was established by employing high-speed camera observations together with electrical signal control among the three components. Moreover, the yoke-drop time measured by the camera was used to prevent underestimation of the crack length. The laser beam melt-run welding used a variable welding speed from 10.0 to 40.0 mm/s, while the gas tungsten arc welding varied the welding speed from 1.67 to 5.00 mm/s. As the welding speed increased from 1.67 to 40.0mm/s, the solidification brittle temperature range of type 310S stainless steel welds was reduced from 146 to 120 K. It follows that employing the laser beam welding process mitigates the solidification cracking susceptibility for type 310S stainless steel welds.
Firmicutes in Gut Microbiota Correlate with Blood Testosterone Levels in Elderly Men
Matsushita Makoto,Fujita Kazutoshi,Motooka Daisuke,Hatano Koji,Hata Junya,Nishimoto Mitsuhisa,Banno Eri,Takezawa Kentaro,Fukuhara Shinichiro,Kiuchi Hiroshi,Pan Yue,Takao Toshifumi,Tsujimura Akira,Yach 대한남성과학회 2022 The World Journal of Men's Health Vol.40 No.3
Purpose: In males, testosterone levels have been implicated in various diseases. Recently, the influence of gut microbialderived compounds on host metabolism has become evident, and it has been suggested that some gut bacteria may be involved in testosterone metabolism. In the present study, we examined the relationship between testosterone levels and gut microbiota in elderly Japanese men. Materials and Methods: We collected samples from Japanese male subjects suspected of having prostate cancer and underwent prostate biopsies and excluded patients with positive biopsies to avoid the effect of prostate cancer on the gut microbiota. In total, 54 Japanese males with negative biopsy results were included in our study. The gut microbiota was analyzed by 16S rRNA gene sequencing of bacterial DNA extracted from rectal swabs. Gut microbiota compositions were compared between the two groups according to the level of serum testosterone (above or below 3.5 ng /mL). Results: The median age of the cohort was 71 years, and the quartile range was 67 to 73 years. We observed no significant difference in alpha or beta diversity, but some bacteria belonging to the phylum Firmicutes (Clostridiales, Turicibacter, and Gemella) were increased in the high testosterone group. Serum testosterone levels positively correlated with the relative amount of Firmicutes (rS=0.3323, p=0.0141), and the amount of Firmicutes affected serum testosterone levels independent of host factors (age, body mass index, triglyceride, and total cholesterol; β=0.770, p=0.0396). Conclusions: Some intestinal bacteria belonging to the phylum Firmicutes were associated with testosterone levels in elderly males. Therefore, the gut microbiota could affect testosterone metabolism in elderly males.