Effect of low segregation coefficient on Ga‐doped multicrystalline silicon solar cell performance

High‐quality Ga‐doped ingots are grown in different casting furnaces at optimized growth parameters; 3·5 kg ingots exhibit normal distribution of diffusion lengths along their height with very high diffusion lengths at the center of the ingot. Effective lifetimes as high as 1·1 ms are realized in 10 Ω cm Ga‐doped wafers after proper P‐diffusion and hydrogen passivation. Average effective lifetimes above 400 µs are also realized after P‐diffusion and hydrogen passivation for Ga‐doped wafers cut from 75 kg ingot where the response to P‐diffusion and hydrogen passivation is pronounced. High effective lifetimes are realized over the whole ingot with minimum values of 20 µs at the top of the ingot, indicating the possible use of about 85% of the ingot for solar cell production. Conversion efficiencies above 15·5% were realized in utilizing more than 80% of the ingot. High efficiencies of about 16% were realized in wafers with resistivities higher than 5 Ω cm p ‐type multicrystalline silicon wafers. Copyright © 2005 John Wiley & Sons, Ltd.     

Stochastic software safety/reliability measurement and its application

Safety and reliability have become important software quality characteristics in the development of safety-critical software systems. However, there are so far no quantitative methods for assessing a safety-critical software system in terms of the safety/reliability characteristics. The metrics of software safety is defined as the probability that conditions that can lead to hazards do not occur. In this paper, we propose two stochastic models for software safety/reliability assessment: the data-domain dependent safety assessment model and the availability-related safety assessment model. These models focus on describing the time- or execution-dependent behavior of the software faults which can lead to unsafe states when they cause software failures. The application of one of these models to optimal software release problems is also discussed. Finally, numerical examples are illustrated for quantitative software safety assessment and optimal software release policies. This revised version was published online in June 2006 with corrections to the Cover Date.     

Preparation of a Barium Titanate-Dispersed-Magnesia Nanocomposite

Ceramic nanocomposites with a perovskite-type ferroelectric dispersoid were studied, to introduce ferroelectricity into structural ceramics. Barium titanate (BaTiO3) was found to be phase compatible with magnesia (MgO) during sintering, and a MgO matrix/BaTiO3 nanocomposite was successfully fabricated by a conventional powder mixing and sintering method. The mechanical strength of the nanocomposite was not degraded, although weak BaTiO3 was incorporated into the composite. The BaTiO3 dispersoid was tetragonal or possibly orthorhombic, although the tetragonality, c/a, was decreased from the starting powder.     

A study on the preparation of supported metal oxide catalysts using JRC-reference catalysts. I. Preparation of a molybdena–alumina catalyst. Part 2. Volume of an impregnation solution

Ten types of 13 wt% MoO₃/Al₂O₃ catalysts were prepared by a conventional impregnation or equilibrium adsorption method using a common extrudate support. These catalysts were subjected to a comprehensive characterization and catalytic reactions to find important preparation parameters in practical preparations. It was demonstrated in the present group study that the formation of crystalline MoO₃ was strongly correlated with the Mo segregation on the outer surface of the extrudate. When the amount of the impregnation solution was large (ca. 10 cm³ g-Al₂O₃⁻¹), a considerably homogeneous distribution and high dispersion of Mo oxide species were attained irrespective of the other preparation parameters. It is suggested that when a pore volume impregnation or incipient wetness technique is employed, drying processes strongly affect the dispersion and distribution of Mo oxide species. Drying at a reduced pressure is suggested to result in a segregation of Mo oxides on the outer surface of the extrudate, and accordingly a formation of crystalline MoO₃.     

Reversible sorption–desorption of NOx by mixed oxides under various atmospheres

Characteristics of MnO_y–ZrO₂ and Pt–ZrO₂–Al₂O₃ as reversible sorbents of NO_x were investigated under dynamic changes in atmosphere. These sorbents can be used reversibly with a change of C₃H₈ concentration in the reaction gases. Catalytic reduction of NO occurred in the presence of propane, which was more pronounced on Pt–ZrO₂–Al₂O₃ than on MnO_y-ZrO₂ due to high activity of Pt surface for this reaction on MnO_y in MnO_y–ZrO₂. The sorption was observed as soon as the atmosphere changed from a reducing to an oxidizing one. This implies that a high equilibrium partial pressure of O₂ is necessary for NO uptake since the sorbed NO⁻₃ species becomes stable. The beginning of NO_x desorption atmospheres was somewhat dependent on the amount of stored NO_x. The presence of propane in the gas phase strongly affected the characteristic sorption and desorption properties of MnO_y–ZrO₂ and Pt–ZrO₂–Al₂O₃. The sorption and desorption properties are different for MnO_y–ZrO₂ and Pt–ZrO₂–Al₂O₃, since the noble metal or metal oxide possesses unique activity for the NO reaction with C₃H₈ and the amount of oxygen available for oxidative sorption of NO.     

Ganglioside GD2 Enhances the Malignant Phenotypes of Melanoma Cells by Cooperating with Integrins

Gangliosides have been considered to modulate cell signals in the microdomain of the cell membrane, lipid/rafts, or glycolipid-enriched microdomain/rafts (GEM/rafts). In particular, cancer-associated gangliosides were reported to enhance the malignant properties of cancer cells. In fact, GD2-positive (GD2+) cells showed increased proliferation, invasion, and adhesion, compared with GD2-negative (GD2−) cells. However, the precise mechanisms by which gangliosides regulate cell signaling in GEM/rafts are not well understood. In order to analyze the roles of ganglioside GD2 in the malignant properties of melanoma cells, we searched for GD2-associating molecules on the cell membrane using the enzyme-mediated activation of radical sources combined with mass spectrometry, and integrin β1 was identified as a representative GD2-associating molecule. Then, we showed the physical association of GD2 and integrin β1 by immunoprecipitation/immunoblotting. Close localization was also shown by immuno-cytostaining and the proximity ligation assay. During cell adhesion, GD2+ cells showed multiple phospho-tyrosine bands, i.e., the epithelial growth factor receptor and focal adhesion kinase. The knockdown of integrin β1 revealed that the increased malignant phenotypes in GD2+ cells were clearly cancelled. Furthermore, the phosphor-tyrosine bands detected during the adhesion of GD2+ cells almost completely disappeared after the knockdown of integrin β1. Finally, immunoblotting to examine the intracellular distribution of integrins during cell adhesion revealed that large amounts of integrin β1 were localized in GEM/raft fractions in GD2+ cells before and just after cell adhesion, with the majority being localized in the non-raft fractions in GD2− cells. All these results suggest that GD2 and integrin β1 cooperate in GEM/rafts, leading to enhanced malignant phenotypes of melanomas.     

In-situ evaluation for activated concrete in accelerator facility with scintillation-type gamma-ray spectrometer

The assessment of activated concrete is particularly difficult during the decommissioning of an accelerator facility.Destructive analysis by core boring is the only method of investigating the activity of concrete material.To address this problem,an in-situ and nondestructive analysis method was developed to determine γ-ray-emitting nuclides and their specific activities in the concrete walls and floor by using a portable germanium semiconductor detector.In this work,we examined a substitute for Ge detector to establish a simpler and more convenient method.As candidates,we focused on some scintillation type spectrometers,and the possibility of a substitute for a Ge detector was examined by both simulation and experiment.The detection limits were roughly estimated through Monte Carlo simulation for various scintillation crystals,and it was found that 1.5-inch LaBr₃,CeBr₃,and SrI₂ could distinguish the clearance level.It was confirmed that the 1.5-inch LaBr₃ could reproduce the calibration curve of the Ge detector in the experiment.The required thickness and length of the radiation shield for suppressing the background radiation during the measurement was also determined for the convenience of an actual decommissioning work.     

确定均质化法中精确周期性边界条件的新解法及其在复合材料刚度预测中的应用

通过引进新的特征函数,提出一种新的求解方法,将均质化法中计算特征函数的非奇次积分方程转化为奇次积分方程,得到具有精确的周期性边界条件的均质化方法。利用该方法预测孔洞材料、短纤维增强复合材料刚度的变化,所得结果与用经典方法得到的结果进行比较,验证该方法的可靠性。对于短纤维增强复合材料,分析纤维排列方式对刚度的影响,这是经典的Halpin—Tsai法和Mori—Tanaka法无法预测的,因而文中的方法具有更高的精确度和更广的适应性。     

Demonstration of loss reduction effect of 66 kV‐classed 30 MVA three phase hybrid‐core transformer by trial manufacture

To realize larger‐capacity “Hybrid‐core transformer: HBT”, this research has assembled a 30‐MVA three‐phase trial HBT and evaluated the loss performances. The hybrid‐core consisting of the wound amorphous‐ and the stacked silicon steel‐cores, is expected having advantages of lower iron loss of the iron‐based amorphous material and the higher mechanical strength and saturation magnetic flux density of the silicon steels simultaneously. Three‐dimensional finite‐element method analysis revealed that the silicon steel core prevented over‐saturation of the amorphous core. The hybrid configuration enabled the design to have an approximately 10% higher magnetic flux density than configurations with only an amorphous core. We then assembled a prototype 30‐MVA three‐phase HBT designed on the basis of our investigation results. Operation tests demonstrated that the HBT has 62%‐reduced iron loss and 0.10%‐higher 50%‐loaded power efficiency from the conventional silicon steel core transformer.