Takada Junior College

Dissimilar welding of thin plates of conventional pure titanium and steel was investigated using an insert metal of the chromium plate to avoid the formation of brittle intermetallic compounds consisting of Ti and Fe. The Cr atom also can form intermetallic compounds with Ti atom though the formability is less than that of Ti/Fe. Therefore, the effect of dilution of Cr on the forming of intermetallic compounds in the weld metal by laser welding process, which has larger cooling rate comparing to the conventional arc welding, was evaluated. The weld metals with various level of dilution by Cr were obtained by adjusting the offset of laser beam irradiation from the interface of titanium and chromium plates. As the result it was found that the formation of intermetallic compound was prevented in the condition of the dilution lower than about 40%. However, the excess offset to reduce the dilution of chromium plate can cause weld defects such as the lack of fusion. That problem was solved by achieving low dilution with the addition of titanium wire in the laser welding process without offset. In conclusion, it was confirmed the sound dissimilar welded joints resulting in sufficient mechanical properties were obtained by applying the proper welding condition based on the findings in this work.

Immunohistochemical studies have revealed that the tumor of a patient with basal cell carcinoma exhibited activation of the Hedgehog and Wnt/β-catenin signaling pathways. The glioma-associated oncogene1 overexpression leads to transcriptional activation making it an attractive molecular target in anticancer therapies due to the main downstream effectors of the cascade.

In the present paper the attention is focused on the vortex shedding from the tube banks with closely mounted serrated fin. The tube banks were installed rigidly in the test section of the wind tunnel. We measured the spectrum and the gap velocity in the simulated tube banks which has same pitch ratio as that of a boiler heat exchanger. We found two types of vortex shedding with different Strouhal number of 0.36 and 0.19 in the case of Reynolds number R_e, based on equivalent diameter and gap velocity, between 1.9×(10)^4 and 5.1×(10)^5. Strouhal numbers S_t were calculated by using the measured values of vortex frequency, gap velocity and the equivalent diameter. the vortex shedding of S_t=0.36 mainly formed within the fin-tube banks and the other vortex of S_t=0.19 was in the wake of the fin-tube banks and the other vortex of S_t=0.19 was in the wake of the fin-tube banks. Strouhal number of vortex within the fin-tube banks changes from 0.36 to 0.3 between R_e=7.0×(10)^4 and 0.9×(10)^5. The applicability of the equivalent diameter obtained by a single circular cylinder with serrated fin to the fin-tube banks was examined. Strouhal number 0.3 agreed well with Strouhal number 0.3 obtained from Fitz-hugh's map for tube banks without fin and other Strouhal number of 0.19 is similar to vortex shedding from a circular cylinder.

Microbiologically influenced corrosion was suspected in a corrosion failure of stainless steel (SUS316L) piping, carrying saline groundwater. Laboratory simulation studies were planned to find out the mechanism of the corrosion. The groundwater from the same plant was transferred to the laboratory aseptically and used for the experiment. Both SUS316L and SUS304L welds (base metal, heat affected zone, weld metal) were exposed to the test solution. After 40 d, corrosion sites were observed on the surface of coupons exposed to non-sterile groundwater supplemented with nutrients. In case of both sterile and non-sterile groundwater devoid of nutrient, the corrosion sits were not observed. Therefore, it is assumed that the corrosion occurrence requires bacteria, their activity and metabolism. The form of corrosion was pitting for base metal and heat affected zone, whereas, weld metal showed skeletal corrosion caused by preferential attack on γ-austenite.Generally, the pH showed no change during exposure test. The potential increased during exposure to nutrient contained non-sterile groundwater for all coupons. In the case of both sterile and non-sterile groundwater devoid of nutrient, the potential did not show an increase for all the coupons. The potential increase that is influenced by bacteria is assumed to be the reason for the easy occurrence of corrosion.

Substantial superplasticity, where total tensile elongation to failure reaches 550 % at 1773 K, can be attained in a l()-vol%.-ZrO 2 -disperse alumina when the alumina grain size is reduced to 0.45 μm by colloidal processing. Although the same grain size is attainable by conventional dry processing, the resultant tensile elongation stays about 260%. The cxamination of undeformed and deformed microstructures revealed that both homogeneous particle dispersion and reduction in the size and density of residual defects in the sintered bodies are the prerequisites for obtaining large superplastic tensile ductility in zirconia dispersed alumina.