Radical high polymerization of di-tert-butyl fumarate and novel synthesis of high molecular weight poly(fumaric acid) from its polymer

Summary Di-tert-butyl fumarate (DtBF) was found to homopolymerize easily with 1,1-azobisisobutyronitrile and benzoyl peroxide as radical initiators at 50~80°C to give a nonflexible rod-like polymer, poly(tert-butoxycarbonylmethylene) with number-average molecular weight of more than 100,000. The colorless powderlike polymer thus obtained was soluble in benzene, toluene, carbon tetrachloride and tetrahydrofuran, and gave a transparent film or fiber from its toluene solution. This polymer did not melt, but it underwent degradation with a quantitative elimination of isobutene at 180~190°C. The remaining polymer was confirmed to be a pure poly(fumaric acid), poly(hydroxycarbonylmethylene). Therefore, the degradation of poly(DtBF) in solution at 180~190°C was found to be a new route for synthesizing of a high molecular weight poly(fumaric acid).Polymers from 1,2-Disubstituted Ethylenic Monomers. XI. Parts I~X of this series are Refs. 1~10.     

Relationship between electron sensitivity and chemical structures of polymers as electron beam resist. VII: Electron sensitivity of vinyl polymers containing pendant 1,3-dioxolan groups

Vinyl polymers containing pendant acetal groups were synthesized using (2,2-dimethyl-l,3-dioxolan-4-yl)methyl acrylate (DMA) and (2,2-dimethyl-l,3-dioxo-lan-4-yl)methyl methacrylate (DMM), and were evaluated as negative electron beam (EB) resists. It was found that the EB sensitivity of polymers containing acetal groups in the side chain was higher than that of polymers containing acetal groups in the main chain. A high sensitivity of 3.6 × 10^?8 C/cm² was observed. Copolymers of DMA or DMM with styrene were also synthesized in order to improve the durability for dry etching process. It was found that the copolymers had an excellent dry etching durability and were adaptable to EB lithography.     

Aerial firefighting against urban fire: Mock-up house experiments of fire suppression by helicopters

The Great Hanshin Earthquake in 1995 claimed approximately 6400 lives. The majority was killed in large fires after the earthquake. Roads were cut off and collapsed buildings blocked the access of fire engines to fire fields. Water mains were broken and lack of water prevented firefighting efforts. If aerial firefighting had been effectively applied, many lives could have been saved.     

CW Lasing at 1.35 $mu$m From Ten InAs–Sb : GaAs Quantum-Dot Layers Grown by Metal–Organic Chemical Vapor Deposition

We report the fabrication of GaAs-based quantum-dot (QD) lasers grown by metal-organic chemical vapor deposition (MOCVD) above 1.3 m. We fabricated a laser diode with ten stacked InAs-Sb:GaAs(100) QD layers, grown by antimony-surfactant-mediated growth. Ground-state lasing was obtained under continuous-wave operation at room temperature at 1.35 mum, with a maximum ground state modal gain of 19.3 cm^-1. These values are the highest values reported for MOCVD-grown GaAs-based QD laser.     

Integrated data structure and scheduling approach for manufacturing and transportation using hybrid genetic algorithm

The scheduling systems in industries are required to construct schedule considering many kind of elements. The Advanced Planning and Scheduling (APS) is an approach for combined problems. To realize APS system, it is important to integrate data structure and scheduling algorithm using these data. In this paper, we propose integrated data structure based on Bill of Manufacturing with information technology of XML family and new Multistage Operation-based Genetic Algorithm for scheduling subsystem. The results of numerical experiment validate effectiveness of the proposal methods. Received: June 2005/Accepted: December 2005     

Cavitation damage prediction for spallation target vessels by assessment of acoustic vibration

Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalent pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown.     

Theoretical and experimental study on a partially driven array antenna with simplified dipole elements

A novel design is proposed to reduce the number of driven elements by replacing them with passive elements or wires in an array antenna. The study is based on the analysis of electromagnetic wave fields by considering of the coupling between the half-wavelength dipoles. An array antenna of two driven elements and two passive elements is considered as a model. After optimising the element arrangement, the antenna gain can match that of the equivalent four-driven element case. The simulation result is confirmed by an experiment that uses dipoles with simplified matching technique. Feeding networks in a high-power radiating system are analysed in terms of the length and matching of feed lines, and the number of amplifiers.     

Long‐term reliability evaluation of power semiconductor devices used in power station rectifiers and substation rectifiers

In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipment is designed on the assumption that power semiconductor devices are semipermanent, since their service life is much longer than that of capacitors and resistors. Therefore, it is hard to find studies that have systematically examined the long‐term reliability of semiconductor devices. Such studies are very important from the viewpoint of ensuring reliability and improving the renewal period by proper equipment maintenance. This paper discusses the long‐term reliability of power semiconductor devices used in power station rectifiers and substation rectifiers. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 67–75, 2001     

A DLC/W-DLC multilayered structure for strain sensing applications

The strain dependence in tungsten-containing diamond-like carbon (W-DLC) film was investigated. The W-DLC film was deposited onto Si substrate by plasma enhanced chemical vapor deposition and DC magnetron co-sputtering of tungsten metal target. The strain dependence of resistance was measured by four-point bending test under well controlled temperature condition. The observed dependence was linear one and calculated gauge factor is 6.1. The high value of the gauge factor is originated from the piezoresistive effect. In addition, double layered structure of DLC/W-DLC film was fabricated. The double layerness and interface structure were investigated by transmission electron microscope. No clear boundary between DLC and W-DLC was observed. This was because of the continuous carbon matrix from the bottom layer of W-DLC to top DLC layer.     

Electrochemical oxidation of highly oriented pyrolytic graphite during potential cycling in sulfuric acid solution

Oxidation of highly oriented pyrolytic graphite (HOPG) under potential cycling conditions is investigated to understand the stability of graphite used in polymer electrolyte fuel cells (PEFCs) under their dynamic operation conditions. Electrochemical methods, AFM and XPS are applied to examine the surface oxidation of HOPG. The current peaks corresponding to quinone–hydroquinone redox reaction begin to appear on cyclic voltammograms after potential cycling between 0.6 V and 0.8 V vs. SHE (standard hydrogen electrode), indicating that the surface of HOPG is partially oxidized to form surface functional groups containing oxygen, whereas HOPG is relatively stable during potential cycling between 0.4 V and 0.6 V. An increase in potential range to 0.8–1.0 V extends the oxidation and forms pits on the surface of HOPG that is caused by the loss of surface carbon through the oxidation to gaseous products. The high rate of potential cycling accelerates the surface oxidation of HOPG.