Dynamic deformation behavior of ultrafine grained aluminum produced by ARB and subsequent annealing

Commercial purity aluminum (1100-Al) sheets with various grain sizes, ranging from 0.2 to 10 μm, were fabricated through accumulative roll bonding (ARB) and subsequent annealing at various temperatures. Mechanical properties of these materials were examined at various strain rates ranging from 10^?2 to 10³ s^?1 (from quasi-static deformation to dynamic deformation). Yield strength of the UFG specimens did not change so much when the strain rate changed. Yielding behavior of the UFG Al with grain size of 1.4 µm was characterized by yield-drop phenomenon, which appeared at higher strain rate. It was found that strain-hardening of the Al matrix was significantly enhanced at high strain rates, which was independent of the grain size. Uniform elongation increased with increasing strain rate in the specimens with the grain size larger than 1 µm, while post-uniform elongation increased with increasing strain rate in the submicrometer grain-sized specimens. Consequently, total elongation of all specimens was improved as the strain rate increased.     

Development of a cooperative power trading system using satisfaction space technology

Many power trading system models have been proposed, but many of them do not aim at load reduction by making customers cooperate with power suppliers in a power trading market. Some researchers have tried to solve the problem by introducing rewards in the power market. This approach was developed on an evaluation function of satisfaction, but there was a problem in that it could be applied only to customers whose evaluation functions could be estimated beforehand. Therefore, this article proposes a new cooperative power trading system that can cope with various kinds of customer by modeling a power market on a satisfaction space. Satisfaction space technology can deal with customers without the evaluation functions.     

Epigenetic Distribution of Recombinant Plant Chromosome Fragments in a Human–Arabidopsis Hybrid Cell Line

Methylation systems have been conserved during the divergence of plants and animals, although they are regulated by different pathways and enzymes. However, studies on the interactions of the epigenomes among evolutionarily distant organisms are lacking. To address this, we studied the epigenetic modification and gene expression of plant chromosome fragments (~30 Mb) in a human–Arabidopsis hybrid cell line. The whole-genome bisulfite sequencing results demonstrated that recombinant Arabidopsis DNA could retain its plant CG methylation levels even without functional plant methyltransferases, indicating that plant DNA methylation states can be maintained even in a different genomic background. The differential methylation analysis showed that the Arabidopsis DNA was undermethylated in the centromeric region and repetitive elements. Several Arabidopsis genes were still expressed, whereas the expression patterns were not related to the gene function. We concluded that the plant DNA did not maintain the original plant epigenomic landscapes and was under the control of the human genome. This study showed how two diverging genomes can coexist and provided insights into epigenetic modifications and their impact on the regulation of gene expressions between plant and animal genomes.     

New method of evaluation for interatomic interaction potential in LEIS with large-angle scattering using the two-atom scattering model

The interaction potential between an incident ion and a target atom in impact-collision ion scattering spectroscopy (ICISS), which is a specialization of low energy ion scattering (LEIS) and its variants, i.e. ICISS with detection of neutrals (NICISS), coaxial ICISS (CAICISS) and impact-collision atom scattering spectroscopy with detection of neutrals (NICASS), has been evaluated by the new method using the dependence of the total scattering angle on the impact parameter for the first collision in the numerical calculations based on the two-atom scattering model (TWASM). From the comparison of determined values of scaling factor for the Firsov screening length by three-dimensional computer simulations with calculated ones by TWASM, it became obviously that the interatomic potentials for the various combinations of an incident ion and a target atom in LEIS are suitably given by the Moliere potential with the reduced Firsov screening length employing the scaling factor obtained in TWASM calculations.     

Quantitative study of solvent effects on electron injection efficiency for black-dye-sensitized nanocrystalline TiO2 films

The effects of various solvents on the electron injection efficiency for nanocrystalline TiO₂ films sensitized with the black dye trithiocyanato(4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine)ruthenium(II) (Ru(tcterpy)(NCS)₃) have been studied quantitatively. The electron injection efficiency for the film dried in air was estimated as 0.4 using a time-resolved microwave conductivity technique. Using transient absorption measurements, we estimated the efficiency of electron injection for TiO₂ films in various solvents. Acetonitrile, which is widely considered to be the best solvent for solar cell performance, had the highest efficiency (～0.65), and other solvents (3-methoxypropionitrile, γ-butyrolactone, and propylene carbonate) had lower efficiencies. These results suggest that characteristic interactions between the black dye and the –CN groups of solvents are important for achieving higher electron injection efficiency.     

Searching performance of a real-coded genetic algorithm using biased probability distribution functions and mutation

One excellent crossover method for the real-coded genetic algorithm (RGA) is the unimodal normal distribution crossover method (UNDX). The UNDX is superior to the blend crossover method (BLX). The UNDX uses Gaussian distribution functions based on the main and sub searching lines. In this article, we present a method of improving the searching performance of the RGA. We propose the use of biased probability distribution functions (BPDFs) based on the main and sub searching lines in the crossover process. The crossover with BPDFs frequently produces offspring that are close to the best individuals in the current generation, and it is highly likely that these offspring will offer the best solution to the problem. Furthermore, we propose a mutation that has a constant and extended range that is wider than that of the UNDX. Simulations show the efficiency of the proposed method. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Study of Intrusion Bending for Steel Tubes with Thin Wall Thickness

In regard to light-weight structural members for automobiles, attention to hydroforming has been increasing. Intrusion-bending method is well suited to the preliminary bending of hydroformed structural members of automobiles, because straight tubes can be bent into three-dimensional forms by this new method. However, in the case of tubes with a thin wall thickness, wrinkling remains a problem. In this report, application of intrusion bending method to tubes with extremely low ratios of wall thickness to outer diameter (from 1.2 to 1.9%), and whose steel grades are SSPDX, SAFC440R, and SAFC590T was investigated. A summary of this study is as follows. Effects of steel grades and wall thickness ratios on wrinkle formation, eccentricity, and ovality are studied. Relationships between wrinkle generation and gyro movement are investigated. This article was presented at Materials Science & Technology 2007, Automotive and Ground Vehicles symposium held September 16-20, 2007, in Detroit, MI.     

Observation and numerical analysis of quantum subband energies from photoluminescence spectra of organic multiple-quantum wells

The optical properties of organic light-emitting diodes (OLEDs) containing multiple-quantum wells have been studied. Photoluminescence and electroluminescence spectra clearly reveal a blue-shift with narrowing quantum wells (QWs). This indicates that subband energies are created in the organic QWs due to quantum size effect. Numerical analysis was performed to determine subband energies and effective masses of electrons. These results demonstrate that wavelength of OLEDs can be designed on the basis of quantum size effect.     

Computation of heat loads in cryogenic parts of high‐temperature superconductor synchronous machines

High‐temperature superconductor (HTS) synchronous machines are expected to have higher efficiency and smaller size than normal conductor synchronous machines, and are being developed mainly in the USA and Germany. This paper describes a computation method of heat loads in cryogenic parts of HTS synchronous machines, and the evaluation study results of heat loads in HTS synchronous motors for blowers, in which Bi‐2223 is used at 30 K, using the computation method. From the evaluated heat loads, the required capacity of the refrigerator for HTS synchronous machines may be determined. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 62–68, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20338