On Failure-Time Distributions for Systems of Dissimilar Units

Certain reliability problems of systems of dissimilar units with repair are described. The mean time to system failure is based on the relation of mean first passage times between states of the system. The failure-time distribution is obtained from an integral equation of the renewal type. The two approaches can be also applied to a system of dissimilar units under an overload. Finally, it is shown that these results include many earlier results as special cases.     

Immobilized-OPG-Fc on a titanium surface inhibits RANKL-dependent osteoclast differentiation in vitro

The purpose of the present study was to examine the effect of osteoprotegerin (OPG)-Fc fusion protein immobilized on a titanium surface on the initial differentiation of osteoclast precursor RAW264.7 cells. These cells were cultured on titanium specimens over which OPG-Fc was immobilized. The enhancement of tartrate-resistant acid phosphatase (TRAP) and cathepsin K mRNA expression in RAW264.7 cells exposed to receptor activator of NF-κB ligand (RANKL) stimulation on OPG-Fc-coated titanium was significantly lower than that in RAW264.7 cells exposed to RANKL on titanium specimens without immobilized OPG-Fc (ANOVA, P < 0.01). Preincubation of OPG-Fc-coated titanium, in a medium supplemented with 10% fetal bovine serum at 37°C for two days before the cells were seeded, had no significant effect on the decrease in mRNA expression (ANOVA, P < 0.01). Taken together, these results indicate that OPG-Fc immobilized on a titanium surface blocks the differentiation of RAW264.7 cells induced by RANKL stimulation.     

X-ray photoelectron spectroscopy for analysis of plasma-polymer interactions in Ar plasmas sustained via RF inductive coupling with low-inductance antenna units

Plasma-polymer interactions have been investigated on the basis of hard X-ray photoelectron spectroscopy (HXPES) together with conventional X-ray photoelectron spectroscopy (XPS) for analysis of chemical bonding states in the surface nano-layers of polymethylmethacrylate (PMMA) films, which were exposed to argon plasmas sustained via RF inductive coupling with multiple low-inductance antenna units. The PMMA films were exposed to argon plasmas on a water-cooled substrate holder. Average ion energies bombarding onto PMMA films were varied in the range of 6-16 eV, which were evaluated as ion kinetic energies at the sheath edge to the ground potential using a mass-separated ion-energy analyzer. The etching of PMMA surface after Ar plasma exposure with an ion dose of 3.4 × 10¹⁸ ions/cm² was measured to be insignificant (less than 20 nm). Surface roughness of PMMA slightly increased from 0.3 nm to 0.4 nm with increasing ion bombardment energy from 6 eV to 16 eV. HXPES was carried out together with conventional XPS to examine chemical bonding states of the PMMA surface in deeper regions (about 54 nm) with HXPES as compared to those observed in shallower regions (8 nm) with the conventional XPS.     

A procedure for constructing social network using Web search engines: the case for Japanese automotive industry

Recently, search engines have enabled us to access immense quantities of useful information in an instant. In this paper, we propose a procedure for analyzing the social relationship and structure using Web search engines, which includes novel ways to create a search query and to use the number of hits. This allows us to construct various networks that reflect directed and undirected relationships among actors under arbitrary contexts. As a case study for evaluations of the proposed procedure, we focus on 50 companies belonging to the automotive industry in Japan. We constructed several directed and undirected networks under different temporal and geographical contexts. It is shown that we can acquire a general understanding of the industrial community through the analyses of these created networks and their centrality measures.     

Ion beam analyses of particulate matter in exhaust gas of a ship diesel engine

There is an urgent need to reduce emission of the particulate matter (PM) in the exhaust gas from ship diesel engines causing various health hazards and serious environmental pollution. Usually the heavy fuel oil (HFO) for ships is of low quality, and contains various kinds of impurities. Therefore, the emission of PM along with exhaust gas from ship diesel engines is one of the most serious environmental issues. However, the PM fundamental properties are not well known. Therefore, it is important to perform elemental analysis of the PM. The HFO contains sulfur with a relatively high concentration of a few percent. It is important to make quantitative measurements of sulfur in the PM, because this element is poisonous for the human body. In the present work, PM samples were collected from exhaust gas of a test engine, and RBS and PIXE analyses were applied successfully to quantitative analysis of the PM samples. The RBS analysis enabled quantitative analysis of sulfur and carbon in the collected PM, while heavier elements such as vanadium and iron were analyzed quantitatively with the PIXE analysis. It has been found that the concentration ratio of sulfur to carbon was between 0.007 and 0.012, and did not strongly depend on the output power of the engine. The S/C ratio is approximately equal to the original composition of the HFO used in the present work, 0.01. From the known conversion ratio 0.015 of sulfur in the HFO to sulfates, the conversion ratio of carbon in the HFO to the PM is found to be 0.01-0.02 by the RBS measurements. On the other hand, the PIXE analysis revealed a vanadium enrichment of one order of magnitude in the PM.     

水附着对球墨铸铁拉抻性能的影响

研究了水附着对不同基体组织球铁的拉伸性能的影响，结果表明，水附着拉伸试验中，奥贝球铁、球光体球铁、淬火回火球铁的拉伸强度和伸长率同时下降，发生显著的水脆化；而铁素体球铁几乎无水脆化现象，这种水脆化现象是在超过屈服点的塑性变形中球铁表面附着水分解的氢的氢脆而导致的。     

Dependence of Generator Parameters on Pulsed Power Ice Breaking

In this research, an investigation on breaking of ice using a pulsed power generator for navigation of an icebreaker in an ice‐covered ocean is described. In these experiments, a pulsed arc discharge was formed using a Marx generator. In order to investigate the dependence of the input energy required for ice‐breaking on the circuit parameters of the generator, the capacitance of the generator was varied. The input energy for ice‐breaking was calculated from the waveforms of the electric power. It was found that the input energy for ice‐breaking decreased as the peak power increased with a decrease in the capacitance of the generator. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 1–9, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22317     

A verification of the thermal stress analysis,including the furan sand mold,used to predict the thermal stress in castings

The restraint exerted on a casting by a furan sand mold on the casting and the contraction of the casting during cooling was dynamically and simultaneously measured using a device that we developed. The measurements were compared during cooling with thermal stress analyses. The thermal stress analyses were based on the representative mechanical models for the furan sand mold, i.e., the elastic and elasto-plastic models used in previous studies. The comparison demonstrated that the elasto-plastic model simulates the restraint force more accurately than the elastic model. In the thermal stress analysis, it was important to describe the development of inelastic deformation and the fracture of the sand mold. However, the simulated restraint force was still twice as large as the measured force even in the elasto-plastic model. This error is most likely attributable to using the temperature-independent mechanical properties of the furan sand mold and the mechanical model of the casting alloy, which neglected the viscoplasticity at high temperature in the thermal stress analysis.     

Effects of monomer and ether structure on metal-free living cationic polymerization of various vinyl ethers using hydrogen chloride with ether

A highly effective initiating system has been achieved for living cationic polymerization of vinyl ethers consisting of HCl alone without Lewis acid. This system is a facile metal-free living cationic polymerization using no HCl/Lewis acid but the already adopted complex HCl·Et₂O. In this study, we investigated the effects of a monomer and ether structure on the polymerization behavior. The monomers are classified into three kinds of monomers: alkyl vinyl ether, vinyl ether with electron-donating groups in the pendant, and vinyl ether with bulky group next to the electron-donating substituent in the pendant. The HCl·Et₂O systems were applicable for the polymerizations of all vinyl ethers used. However the structure around electron-donating groups in the pendant of monomer affected the polymerizations rate and induction period. The initiation reactions can be successfully achieved using ether effectively dissociating HCl, especially symmetrical ether.