Effects of compressive strain on the evolution of interfacial strength of steel/nickel solid-state bonding at low temperature

Solid-state bonding between ultralow-carbon steel and pure nickel was conducted by hot pressing with various compressive strain ranging from 5 to 15% and subsequent isothermal holding at 923?K. It was found that the interfacial strength of contact area is accounted for by the evolution of the intrinsic strength of the interface and the amount of plastic energy dissipation at the crack tip during interface fracture. The compression induces severe deformation around the interface and consequently inhibits the plastic energy dissipation during interface fracture. In the first stage of isothermal holding, the residual strain around the interface on the steel side is reduced by recovery process, which concurrently decreases in the yield stress of the area adjacent to the interface. This promotes plastic energy dissipation of the area, leading to a significant increase in interfacial strength in the first stage.     

Effect of simultaneous surface modification process on wear resistance of martensitic stainless steel

In order to improve the wear resistance of martensitic stainless steel, a surface treatment system was developed that combines high-frequency induction heating (IH) with fine particle peening (FPP). In this system, a compressed air spray from the FPP nozzle rapidly cools the specimen surface, which is heated by the IH system. The specimen surface can be simultaneously modified by work hardening and quenching. Vickers hardness and retained austenite measurements were conducted to characterize the surface-modified layer generated by the developed process. Surface microstructures were also observed by scanning electron microscopy (SEM) and optical microscopy. The process created a surface with a high hardness and an extremely fine-grained microstructure. The fine-grained microstructure was generated by dynamic recrystallization. The process reduced the amount of retained austenite in the surface layer because it increased the precipitated chromium carbide content. Reciprocating sliding wear tests were conducted to evaluate the wear resistance of the surface. The specimen modified by the developed process exhibited higher wear resistance than specimens that had only been quenched. This implies that the developed simultaneous process can significantly improve the wear resistance of steel surfaces.     

Examination of the Mode II fracture behaviour of wood with a short crack in an asymmetric four-point bending test

Asymmetric four-point bending tests of agathis specimens with a short crack along the neutral axis in a tangential–longitudinal system were conducted onto analyse the failure behaviour of wood with a short crack. The nominal shear strength and Mode II critical stress intensity factors of the specimens with various crack lengths were measured, and the influence of crack length on these properties was examined. The nominal shear strength of the cracked specimens was significantly lower than the strength of a crack-free specimen, even when the crack was extremely short. This finding suggests that the fracture mechanics theory is effective for analysing the failure behaviour of wood with a very short crack in this loading condition. However, the Mode II critical stress intensity factor still depends on the crack length. When the crack length was corrected with considering the formation of fracture process zone ahead of the crack tip, the critical intensity factor could be predicted effectively as well as the nominal shear strength.     

Fundamental welding R&D results for manufacturing vacuum vessel of JT-60SA

The real vacuum vessel (VV) manufacturing of JT-60SA has started since November 2009 at Toshiba. Prior to starting manufacturing, fundamental welding R&Ds had been performed by three stages. In the first stage, primary tests for screening welding method were performed. In the second stage, the trial welding for 1 m-long straight and curved double shell samples were conducted. The dependences of welding quality and distortion on the welding conditions, such as arc voltage and current, setting accuracy, welding sequence, and the shape of grooves were studied. In addition, welding condition with low heat input was explored. In the last stage, fabrication sequence was confirmed and established by the trial manufacturing of the 20° upper half mock-up [1]. This paper presents the R&D results obtained in the first and second stages.     

Synthesis, spark plasma sintering and electrical conduction mechanism in BaTiO3-Cu composites

BaTiO₃-Cu composite powders were prepared via an alkoxide-mediated synthesis approach. As-synthesized BaTiO₃ nanoparticles were as small as 40 nm and coated partially larger Cu particles of approximately 1 μm in size. Thermogravimetric analysis (TGA) and dilatometry revealed a gradual increase in weight loss and retarded shrinkage with the increase of Cu addition. BaTiO₃-Cu composites were successfully densified by spark plasma sintering (SPS). The microstructures show an average grain-size for BaTiO₃ of around 100 nm and a crystallite size of about 1 μm for the Cu inclusions. The AC conductivity of the BaTiO₃-Cu composites increased with increasing Cu content or with temperature. The dominant electrical conduction mechanism in SPSed BaTiO₃-Cu composites changed from migration of oxygen vacancies to band conduction of trapped electrons in oxygen vacancies with the increase of Cu content.     

Fluorometric detection of interaction between lipase and glyceride

Previously, we devised the efficient modification of lipase, which can be dissolved and still maintain its activity in organic solvents. In this work, the fluorescence of the modified lipase could be detected in chloroform. When glycerides were added to the modified lipase solution, the intrinsic tryptophan fluorescence of the modified lipase decreased, which suggests that the environment of the tryptophan residue was affected by the substrate. The interaction between the modified lipase and glyceride was studied kinetically in terms of fluorescence intensity of the tryptophan residue. Because glyceride is not subject to hydrolysis in nonaqueous solution, the dissociation constant of the enzyme-substrate complex could be determined. Thus, insight into the direct interaction between enzyme and substrate provided some structural information regarding the active site of lipase.     

Novel Conjugated Organic Dyes for Efficient Dye‐Sensitized Solar Cells

Novel conjugated organic dyes that have N,N‐dimethylaniline (DMA) moieties as the electron donor and a cyanoacetic acid (CAA) moiety as the electron acceptor were developed for use in dye‐sensitized nanocrystalline‐TiO₂ solar cells (DSSCs). We attained a maximum solar‐energy‐to‐electricity conversion efficiency (η) of 6.8 % under AM 1.5 irradiation (100 mW cm^–2) with a DSSC based on 2‐cyano‐7,7‐bis(4‐dimethylamino‐phenyl)hepta‐2,4,6‐trienoic acid (NKX‐2569): short‐circuit photocurrent density (J_sc) = 12.9 mA cm^–2, open‐circuit voltage (V_oc) = 0.71 V, and fill factor (ff) = 0.74. The high performance of the solar cells indicated that highly efficient electron injection from the excited dyes to the conduction band of TiO₂ occurred. The experimental and calculated Fourier‐transform infrared (FT‐IR) absorption spectra clearly showed that these dyes were adsorbed on the TiO₂ surface with the carboxylate coordination form. A molecular‐orbital calculation indicated that the electron distribution moved from the DMA moiety to the CAA moiety by photoexcitation of the dye.     

Properties of extracellular products produced by group A streptococci isolated from patients with streptococcal toxic shock syndrome

Extracellular products of group A streptococci isolated from patients with streptococcal toxic shock syndrome (STSS) were examined. The outline of the discussion of the 3 products are as follows; streptolysin O (SLO), proteinase and erythrogenic toxin. SLO and proteinase showed a relatively large amount of products more than erythrogenic toxin. SLO produced by group A streptococci isolated from the patient with STSS had an isoelectric point (pI) of 6.0 and a molecular weight of 64,000 and showed hemolytic activity in the presence of 2-mercaptoethanol (2-ME). Furthermore, the hemolytic activities of all components were inhibited by gamma-globulin and cholesterol. Proteinase had pIs of 8.7 and 8.9, and a molecular weight of 21,000. These data suggest that STSS clinical criteria probably reflects a characteristic of a large amount of products of individual S. pyogenes isolates.     

A new erasing and row decoding scheme for low supply voltageoperation 16-Mb/64-Mb flash memories

To improve the performance of high-density flash memories, several circuit technologies have been developed. A word-line boost and clamp scheme realizes low supply voltage read operations. A flash programming scheme utilizing Fowler-Nordheim (F-N) tunneling for programming before erasure and a negative gate biased erasing scheme accomplish low-power, high-speed, and 5-V-only erase operations. The chip size penalty is estimated to be only 3% for the 16-Mb flash memories