Developing Interfacial Carbon-Boron-Silicon Coatings for Silicon Nitride-Fiber-Reinforced Composites for Improved Oxidation Resistance

C-B-Si coatings were formed on a Si₃N₄ fiber using chemical vapor deposition and embedded in a Si-N-C matrix using polymer impregnation and pyrolysis. The boron-containing layer was anticipated to form borosilicate glass and seal oxygen-diffusion passes. Two types of C-B-Si coatings were tested on the fiber–matrix interface, and they improved the oxidation resistance of the composite. The first coating was multilayered: a crystalline sublayer composed of B-Si-C was sandwiched between two graphitelike carbon sublayers. The second coating was a graphitelike carbon layer containing a small amount of boron and silicon. The carbon (sub)layer of both coatings weakened the fiber–matrix bonding, giving the composites a high flexural strength (1.1 GPa). The composites retained 60%–70% of their initial strength, even after oxidation at 1523 K for 100 h. The mechanism for improved oxidation resistance was discussed through the microstructure of the interface, morphology of the fracture surface, and oxygen distribution on a cross section of the oxidized composite.     

A multi‐agent approach to unit commitment

This paper proposes a multiagent system to power system unit commitment problems. Multiagent is a new paradigm for developing software applications. Coordinating the behavior of autonomous agents is a key issue in agent‐oriented programming techniques today. Recently, agents are being used in an increasingly wide variety of applications, ranging from comparatively small systems such as E‐mail filters to large, open, complex systems such as air traffic control. Though some agent frameworks have been proposed in the power system field, the number of studies is limited. In this paper, we developed a power system unit commitment application by multiagent architecture. Our multiagent system has the following characteristics: (1) The system consists of a single facilitator agent, two mobile agents, and one or more generator agents which are elements of power system network. (2) The facilitator agent is developed to act as a manager for the process by using the singleton design pattern. The mobile agents migrate to generator‐agents to increase or decrease their power generations. The generator agents have their operational data. (3) Message object is developed to communicate between the agents using KQML‐like object. The proposed approach is applied to a simple model system, and the results show that the multiagent system is an efficient decentralized approach for solving power system unit commitment problems. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 41–47, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10057     

Moving mask deep X-ray lithography system with multi stage for 3-D microfabrication

 Based on a moving mask deep X-ray lithography concept, a new deep X-ray exposure system with multi stage has been built up, which can fabricate 3 dimensional microstructures with controllable free shaped wall such as inclined, curved and vertical wall. The system has 6 stages, an X-stage and a Y-stage for substrate scanning, a substrate tilt stage and a substrate rotation stage for controlling an incident X-ray angle to a substrate, an X–Y stage for mask movement and X–Y stage for substrate and mask alignment. The system performance has been confirmed by fabricating microstructures such as gratings, micro grid and micro prism. Received: 10 August 2001/Accepted: 24 September 2001     

Promotion effect of bifunctional five‐membered cyclic dithiocarbonate on curing of one‐component epoxy resin by imines as latent initiator

This article deals with curing of a one‐component epoxy resin containing a bifunctional five‐membered cyclic dithiocarbonate 1 with an imine 2 as a latent initiator. When 1 was added to a mixture of epoxy resin and 2 , the curing rate and initial adhesive strength increased higher than that without 1 . It was supposed that the reaction of 1 and an amine released from 2 was much faster than the amine–epoxide reaction, and a thiol group formed by the reaction of 1 with the amine accelerated the amine–epoxide reaction. The adhesive strength of the one‐component epoxy resin containing 10 mol % of 1 exhibited the highest value. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 961–964, 2004     

Effect of additives on gelation and tissue adhesion of gelatin-poly(L-glutamic acid) mixture

Gelation and tissue adhesion of mixtures of gelatin and poly (L-glutamic acid) (PLGA) aqueous solution were investigated in the presence of additives following the addition of a water-soluble carbodiimide (WSC) that induced chemical cross linking between gelatin and PLGA. To prevent spontaneous gelation of the mixed solution through physical cross linking between gelatin molecules at room temperature, additives were added to the mixed solution. Among the additives studied, starch and urea were effective in preventing the spontaneous physical gelation. The mixed gelatin and PLGA solution set to a cross-linked hydrogel within scores of second by WSC addition, irrespective of the presence of urea, whereas the viscosity of the solution with added starch was too high to measure the gelation time. The cross-linked gelatin-PLGA hydrogels with and without urea showed higher bonding strength to soft tissues than fibrin glue. This was in marked contrast to gelatin-PLGA hydrogels with soluble starch. Irrespective of the presence of urea, the gelatin-PLGA hydrogels gradually biodegraded in the back subcutis of mice over 3 months and no severe inflammatory response to the hydrogels was observed. These findings indicate that urea is promising as an additive to prevent spontaneous physical gelation of the mixed gelatin and PLGA aqueous solution without changing the characteristics of WSC-induced cross linking and tissue adhesion of the formed hydrogel.     

Measurement of pH in the vicinity of a cathode during the chloride electrowinning of nickel

An antimony microelectrode was prepared by quenching a molten Sb-Sb₂O₃ mixture (2 pct Sb₂O₃). The local pH in the vicinity of a nickel-plated copper cathode was directly measured using the microelectrode during the chloride electrowinning of nickel for a MCLE (matte chlorine leach electrowinning) process, where nickel metal is electrodeposited with a high current efficiency, 94 to 97 pct, from low-pH baths. The local pH at 328 K was increased by proton consumption during the electrolysis of aqueous electrolytes containing NiCl₂ (1.20 mol dm⁻³) and NaCl (0.43 mol dm⁻³) with the same concentrations as employed for the MCLE process. The difference in pH between the cathode surface and bulk solution increased with increasing cathodic current density. Nickel deposits with a metallic luster were obtained when the difference was not more than 1.2 pH units. The current efficiency was a maximum for electrolysis with a current density of 265 A m⁻² and bulk pH of 1.0 to 1.5; these optimal conditions coincided with those reported for the MCLE process: temperature 328 to 333 K, bulk pH 1.1 to 1.5, and current density 230 to 260 A m⁻². Electrolytes with lower NiCl₂ and NaCl concentrations resulted in a drop in current efficiency.     

Three-dimensional analysis of the interface between an Sn-8wt.%Zn-3wt.%Bi solder and a substrate by using an angle-lapping method

The validity of application of the angle-lapping method to investigate the microstructure between an Sn-8wt.%Zn-3wt.%Bi Pb-free solder and an Auimmersed Ni-7.0%P plate or a Cu substrate was studied using transmission electron microscopy. The method enabled a three-dimensional analysis of the interface layers. The morphology of the Au layer was clarified as an intermetallic compound with Zn with numerous voids that looked like cracks spreading in all directions. Sn and Bi could diffuse into the interface layer only when the Ni-P plate was used, but Ni did not diffuse actively and formed a narrow interface layer. When a Cu substrate was used, Cu diffused, rather than Sn or Bi, and formed a relatively wide interface layer. These results were obtained with the angle-lapping method.     

Production and structural characterization of carbon soot with narrow UV absorption feature

In the present study, by a simple method, carbon soot with a narrow absorption features at around 220 nm was produced by pyrolysis of methane gas at a hot (1400-2800 °C) filament. A detailed correlation between the structure and the optical spectra of carbon soot was carried out using a high-resolution transmission electron microscope. It appears that the origin of the narrow absorption peak is an onion-like graphitic structure. Interestingly, we found that the absorption peak position and the size of the soot can be controlled by the production temperature. The absorption peak is located at 217.5 nm, i.e., at the position of an intense interstellar absorption, when the onion structure has about 5 nm diameter. Infrared spectroscopy was applied to further elucidate the chemical composition of the obtained soot.     

Diacetylene-Containing Polymers XIV: Poly(octa-3,5-diynylene-1,8-dicarboxyalates) containing some polar azo dyes

Abstract A series of novel polymers having polar azo dyes were synthesized and characterized. Although their chromophore contents are very high, their second order nonlinear (2-NLO) response was very poor. The poor 2-NLO responses are thought to be due to poor orientation because of their improper main chain conformations, as well as their low glass transition temperatures. They undergo slow cross-linking on standing at room temperature, and rapidly on heating at temperalures above 150°C, through the diacetylene units of the main chains. Nevertheless, these polymers are interesting materials as azo-polymers because of their very high concentration of azo dyes, which are distributed homogeneously in the polymers. Synthesis and characterization are described, and the most important factor for the 2-NLO polymers is discussed.     

Economic Evaluation of a Residential Photovoltaic System based on a Probability Model using Actual Meteorological Data

To design a photovoltaic (PV) generation system economically, it is necessary to use data of the total insolation on a horizontal surface. However, such data is only the total daily value and does not represent the power variation caused by the cloud cover. This paper presents the probability method which represents not only the average but also the variance of the PV generation power, and shows simulated results using this methodology. This study's results indicate that the distribution of the PV power divided by the estimated value of the total insolation on a tilted surface is similar to a normal distribution and that a residential (privately-owned) system without storage, whose PV capacity is more than 2 kWp, has little effect upon the reduction of the energy of an average Japanese household.