Influence of DLC coating thickness on tribological characteristics under sliding rolling contact condition

Diamond-like-carbon (DLC) coating of thickness 3 and 10 μm were developed with and without radical nitriding pretreatment on steel rollers and spur gear pair. The friction coefficient and wear amount were evaluated under sliding rolling contact condition in vacuum and under oil lubrication. Delamination of coatings was observed at the interface of the substrate. The wear resistance of coatings improved with the thickness of the coating. In vacuum both the roller and the gear pair of 10 μm coating thickness with radical nitriding showed identical wear behavior. The radical nitriding seemed to enhance the life of DLC coatings.     

ZrO2／Ni阶梯热障涂层的热冲击行为

研究了ＺｒＯ２／Ｎｉ阶梯热障涂层在火焰喷烧和水淬炳途中热冲击条件下的失效行为,建立了梯度热障涂层在火焰喷烧和水淬热冲击条件下一维温度场应力场的解析模型,实验结果表明,涂层的抗热冲击能力在火焰喷烧条件下随层次折增加而增强,在水淬热冲击条件下却随层次的增加而降低,证实涂层的抗热冲击能力与热冲击条件有关,并取地表面换热系数的大小与方向,故评价涂层的抗热冲击能力时须合理选择热冲击条件,按梯度设计,能大大提     

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.     

Manipulation of micro solid particles and induced flows in water by laser irradiation

Q-switch for pulsing laser beam and Galvano scanner for rapid scanning laser beam were adapted to manipulatemicro solid particles in a water droplet.The trapping of fine particles at micron-sized diameters by a YAG lasersystem,induced flows,and the induced motion of the particles by laser beam irradiations are discussed.Particlerotations are observed by using anisotropic micro objects,and moreover the rotational rate with clockwise direc-tion is 22 r/min.The fragments of a cover glass were mixed in a water droplet,and their size and shape are un-even.The rotation of that non-spheres without scanning by the Galvano scanner is also observed in water.     

A concentrator module of spherical Si solar cell

Spherical Si solar cell, which is made up of Si spheres with a diameter of approximately 1.0 mm, is expected to be a promising candidate for low consumption of Si feedstock and simple process technology. This paper describes the formation process and the structure of a concentrator module in detail. The concentrator lens was formed by casting with ultraviolet light hardening resin. The concentration ratio was 4.4 times and the pitch between the spheres was 2.0 mm. By this module design, it was possible to realize a consumption of the Si feedstock of about 3.0 g/W. Conversion efficiencies of 11.3% from single-sphere cell, 8.5% from a 23-spheres module and 5.2% from a 105-spheres module under AM1.5, 100 mW/cm² illumination were achieved.     

Quantitative risk assessment using a Japanese hydrogen refueling station model

Although hydrogen refueling stations (HRSs) are becoming widespread across Japan and are essential for the operation of fuel cell vehicles, they present potential hazards. A large number of accidents such as explosions or fires have been reported, rendering it necessary to conduct a number of qualitative and quantitative risk assessments for HRSs. Current safety codes and technical standards related to Japanese HRSs have been established based on the results of a qualitative risk assessment and quantitative effectiveness validation of safety measures over ten years ago. In the last decade, there has been much development in the technologies of the components or facilities used in domestic HRSs and much operational experience as well as knowledge to use hydrogen in HRSs safely have been gained through years of commercial operation. The purpose of the present study is to conduct a quantitative risk assessment (QRA) of the latest HRS model representing Japanese HRSs with the most current information and to identify the most significant scenarios that pose the greatest risks to the physical surroundings in the HRS model. The results of the QRA show that the risk contours of 10^?3 and 10^?4 per year were confined within the HRS boundaries, whereas the risk contours of 10^?5 and 10^?6 per year are still present outside the HRS. Comparing the breakdown of the individual risks (IRs) at the risk ranking points, we conclude that the risk of jet fire demonstrates the highest contribution to the risks at all of the risk ranking points and outside the station. To reduce these risks and confine the risk contour of 10^?6 per year within the HRS boundaries, it is necessary to consider risk mitigation measures for jet fires.     

Characterization of Acetylxylan Esterase from White-Rot Fungus Irpex lacteus

The carbohydrate esterase family 1 (CE1) in CAZy contains acetylxylan esterases (AXEs) and feruloyl esterases (FAEs). Here we cloned a gene coding for an AXE belonging to CE1 from Irpex lacteus (IlAXE1). IlAXE1 was heterologously expressed in Pichia pastoris, and the recombinant enzyme was purified and characterized. IlAXE1 hydrolyzed p-nitrophenyl acetate, α-naphthyl acetate and 4-methylumbelliferyl acetate, however, it did not show any activity on ethyl ferulate and methyl p-coumarate. We also examined the activity on partially acetylated and feruloylated xylan extracted from corncob by hydrothermal reaction. Similarly, ferulic and p-coumaric acids were not liberated, and acetic acid was only detected in the reaction mixture. The results indicated that IlAXE1 is an acetylxylan esterase actually reacted to acetyl xylan. However, since IlAXE1 was unable to completely release acetic acid esterifying xylopyranosyl residues, it is assumed that acetyl groups exhibiting resistance to deacetylation by IlAXE1 are present in corn cob xylan.     

Effect of gamma radiolysis on pit initiation of zircaloy-2 in water containing sea salt

In spent fuel pools at the Fukushima Daiichi Nuclear Power Station (1F), seawater was injected for cooling purposes after the tsunami disaster in March 2011. It is well known that the chloride in the seawater has the potential to cause localized corrosion (e.g., pitting corrosion) in metals. In this study, we evaluated the pitting potentials of zircaloy-2, the material used in the fuel cladding tubes in 1F, as a function of chloride concentration. To accomplish this, we used artificial seawater under gamma-ray irradiation and investigated the effect of radiolysis on pit initiation of zircaloy-2 in water containing sea salt. Changes in the composition of water containing sea salt were analyzed as well, both before and after gamma-ray irradiation. The characteristics of the resultant oxide films formed on zircaloy-2 were evaluated by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The experimental results showed that the pitting potential under irradiation was slightly higher than that under conditions in which no radiation was present, and that the pitting potential decreased with increasing chloride concentration in the presence as well as the absence of radiation. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by irradiation. The oxide film was composed of zirconium oxide and was made thicker during the irradiation. The higher pitting potential could thus be explained by the capacity of hydrogen peroxide to oxidize the surface and enhance oxide film formation. Under gamma-ray irradiation, the zircaloy-2 surface with an oxide film formed by radiolysis products was found to be resistant to pitting in the presence of chloride.