Study on new GMA welding process with duplex current feeding

Gas metal arc welding (GMAW) under pure argon shielding gas atmosphere (pure argon-GMAW) is suitable to obtain a high-strength and high toughness welded joint. However, it is difficult that pure argon-GMA welding is applied practically welding structure because of arc instability. In order to perform stable pure argon-GMA welding, duplex current feeding GMAW (DCF-GMAW) has been developed. The DCF-GMAW consists of primary GMA welding current and secondary welding current by constant-current power resource. DFC-GMAW can feed larger current near wire tip. This effect makes that weld penetration depth is deeper, weld bead shape is improved using DCF-GMAW.     

Development and characterization of micro-dispersed lacquer

本文利用一种特制的搅拌装置来制备微分散生漆。研究了在不同的搅拌速率和搅拌时间下所获得的生漆微粒子的直径和性能的关系。粒度分布测定表明,经过60分钟且每分钟240转搅拌处理的生漆,其粒子直径分布最窄,平均为0.194微米。凝胶色谱(GPC)分析显示生漆中的寡聚体增加的同时单体的百分含量减少了,意味着在搅拌的过程中发生了聚合反应。另外,微分散生漆的粘度、干燥成膜时间、膜亮度、膜颜色、膜光泽以及耐紫外线等特性也作了深入的探讨。     

Optical and adhesive properties of composite silica-impregnated Ca-α-SiAlON:Eu2+ phosphor films prepared on silica glass substrates

The compaction of a Eu-doped Ca-α-SiAlON phosphor powder was performed by electrophoretic deposition (EPD). The effect on the adhesion and optical properties of the silica precursor as both a binder of the powder and a filler of the air voids were evaluated. The adhesion of the silica impregnated composite film to the silica glass substrate was characterized by the tape test. The improvement of the external quantum efficiency was confirmed from the PL spectra measurement after the silica impregnation. The temperature dependence of the external quantum efficiency was also investigated in order to discuss the advantage of using the silica precursor as a binder for high-brightness LED applications.     

Measurement and correlation of the solid-liquid-gas equilibria for carbon dioxide + normal chain saturated aliphatic hydrocarbon systems

The pressure p-temperature T projections of solid-liquid-gas (S-L-G) three-phase coexistence lines for the carbon dioxide + tetradecanoic acid (C₁₄H₂₈O₂) system, the carbon dioxide + hexadecanoic acid (C₁₆H₃₂O₂) system, and the carbon dioxide + 1-hexadecanol (C₁₆H₃₄O) were measured by the first melting point method in which the initial appearance of the liquid phase was observed. The profiles of the p-T projections of the S-L-G lines for the carbon dioxide + acid systems are similar to each other, the S-L-G equilibria for the carbon dioxide + acid systems are, however, different from that for the carbon dioxide + 1-hexadecanol systems. The experimental p-T projections of the S-L-G lines were also correlated by the Peng-Robinson equation of state and the van der Waals type mixing rules with two binary interaction parameters introduced into attraction term and size terms, respectively. The present model gave good correlation results for all of the experimental S-L-G lines with maximum average absolute relative deviations of 0.075% for the carbon dioxide + tetradecanoic acid system, 0.14% for the carbon dioxide + hexadecanoic acid system and 0.28% for the carbon dioxide + 1-hexadecanol system, respectively.     

Effective synthesis of ethanol from CO2 on polyfunctional composite catalysts

Synthesis of ethanol by hydrogenation of carbon dioxide has been investigated by developing the novel composite catalysts. The three different kinds of elementary reaction functions for ethanol synthesis were undertaken. The catalytic functions are partial reduction of CO₂ to CO, C–C bond formation, and –OH group insertion. For this purpose, supported Rh catalyst, Fe-based modified Fisher–Tropsch catalyst, and Cu-based modified methanol synthesis catalyst were combined by different ways. As a result, high space–time yields of ethanol as high as 0.8–0.9 kg/l h were obtained.     

A communication protocol based on IR-space division transceivers for mobile robots

In this article, we propose MAC protocols based on our infrared-space division transceiver (IR-SDT) for mobile robots. The IR-SDT has eight communication modules, so it can communicate with a maximum of eight other nodes simultaneously. The number of parallel multiple accesses will be improved by using this transceiver and its specialized protocol. In addition, we consider situations in which a packet collision occurs, and propose a protocol that resolves communication conflicts using the signal collision-detection function of IR-SDT. Finally, we consider the performance of these protocols, and discuss the influence of signal collision-detection accuracy.     

Micro-/nanostructural investigation of laser-cut surfaces of single- and polycrystalline diamonds

Micrometer- to nanometer-scale structures of the cut surfaces of single- and polycrystalline diamonds by a pulsed ultraviolet laser have been thoroughly investigated by scanning and transmission electron microscopy. Within the laser-cut grooves, the processed diamond surfaces are extensively covered with laser-modified debris which consists of complex layered units of graphite with various crystallinities. The units consist of 1) highly oriented graphite, 2) corrugated graphite, and 3) nanocrystalline graphite, which are sequentially located from the surface of the underlying diamond substrate to the center of the grooves. Detailed textural examinations revealed that the highly oriented graphite unit is a product of the initial graphitization of diamond by a solid-state diffusion process, whereas the latter two units are deposition products from the liquid and/or vapor phases of carbon in the later stage. The present study demonstrates that the laser-cutting of diamonds proceeds in a two-step process: 1) extensive graphitization of laser-scanning path and 2) subsequent sublimation of the pre-formed graphite. These processes are basically identical among the three different types of diamonds (single crystal type Ib, single crystal type IIa and nano-polycrystalline aggregate) tested in this study.     

Self-organization of conceptual generalities and pattern-directed learning

Human expert decision makers can be characterized by their ability to perceive a hypothetical conceptual generality or pattern that is underlying a given collection of objects. The conventional cluster analysis is unable to generate such patterns since its clustering process is far from what the human experts actually do. That is, human experts form some concepts inductively from individual observations based on the conceptual “meaning” which the objects have. In this paper, by introducing an idea of prototype theory from a psychological domain with respect to human concept formation, an algorithm for human classification process is proposed. Based on this, the role of human generalization capability in his classification process is discussed with respect to the background semantic knowledge. The algorithm can be roughly divided into two phases; inductive prototype formation from training examples in a bottom-up fashion, and pattern-directed clustering of the instances being affected by the acquired concepts in a top-down fashion. Using a schematically-modelled example, the algorithm is illustrated with its implemented results. Our modelling method for the human classification process can be utilized for conceptual clustering that classifies a number of unknown objects into a distinguished group being affected by pre-acquired concepts.     

Safety Analysis of ITER EDA Design by GEMSAFE

General Methodology of Safety Analysis and Evaluation for Fusion Systems (GEMSAFE) was applied to the International Thermonuclear Experimental Reactor (ITER) design in the stage of Engineering Design Activities (EDA) to identify Design Basis Events (DBEs) and the related safety features, which were compared with those of the ITER design in the stage of Conceptual Design Activities (CDA). As a result, 18 DBEs for the EDA design were selected in comparison with 25 DBEs for the CDA design. DBEs related to the fuel area were categorized in higher event category than those of the CDA design due to the increase of the mobile tritium contained in some components. It was necessary to reduce the inventory of the tritium absorbed in the tokamak dust in the EDA design as well as in the CDA design. Some measures were recommended to reduce mobile tritium dissolved in the coolant in the single cooling loop due to the increase of this estimated inventory.     

Effects of loading mode and water chemistry on stress corrosion crack growth behavior of 316L HAZ and weld metal materials in high temperature pure water

The stress corrosion cracking (SCC) growth rates of 316L weld heat-affected zone (HAZ) and weld metal materials in high temperature pure water at 288 °C were measured using contoured double cantilever beam (CDCB) specimens and an alternating current potential drop (ACPD) in situ crack-length monitoring system. The effects of loading mode and dissolved oxygen and hydrogen on crack growth rate (CGR) were experimentally quantified. Typical intergranular SCC was found in the HAZ specimen and interdendritic SCC was identified in the weld metal specimen. The HAZ specimen and the weld metal specimen showed quite a similar response to the applied loading modes and the water chemistry, even though their absolute CGR values were different. The crack growth rates under trapezoidal loading were moderately higher than those under constant loading by several tenths percent. Switching the water chemistry from the oxygen-bearing water to the hydrogen-bearing water drastically decreased the electrochemical potential and the crack growth rate, and vice versa. A time-lag period for crack growth was observed after switching the water chemistry back to the oxygen-bearing water, where the crack growth rate was low even the dissolved oxygen concentration and the electrochemical potential had become high. Strain hardening and the resultant uneven distribution of deformation contribute to the enhanced intergranular SCC growth behavior in the HAZ area. The crack growth kinetics is analyzed based on the deformation/oxidation interaction at the crack tip, considering the importance of the electric-charge transfer, mass transport kinetics and the crack tip strain rate.