Flashover voltage characteristics of contaminated station insulators under temporary ac overvoltages in the ac system connected with a frequency converter station

According to the recent analysis results of temporary ac overvoltage in the ac system connected with a frequency converter station, large-magnitude over-voltages were confirmed to occur under some special system conditions. Most of the station insulators currently used cannot withstand such overvoltages according to an evaluation based on the data obtained earlier. The necessity of tests to be done to evaluate such performance more accurately was recognized. Both power frequency and switching impulse overvoltage flashover tests were made on contaminated insulators by the method well simulating the natural wetting condition. Switching impulse flashover voltage with the waveshape having a long wavefront time of 2 ms can be well correlated with the flashover voltage characteristics of temporary ac overvoltage. Higher flashover voltage characteristics were obtained by a clean fog test method compared with those obtained by equivalent fog test method.     

Structural relationship between thermomechanical history and strength of polymeric solids

Ultimate properties in polymeric solids strongly depend on thermomechanical history. We have shown that the polymer structure which depends on thermomechanical history can be quantitatively described by the relative amounts of enthalpy and entropy. The excess enthalpy decreases upon annealing and increases under the tensile stress. The increase in excess enthalpy reduces the relaxation time; thus a local brittle-to-ductile transition may be induced by stress concentration. It follows that in a well-annealed material, this transition is more difficult to induce. Effects of molecular weight and orientation are also discussed in terms of dissipation of strain energy as the condition required for the strength of polymeric solids.     

Development of next generation PWR in Japan

The demand for energy in Japan is expected to increase steadily into the future, and it seems that the importance of nuclear power generation will be heightened more when the situation of our country which is not rich in energy resources is taken into account.

Furthermore, when we consider the present situation that the light water reactors have become common, recent outlook for the supply and demand for uranium resources, trends in the development of the fast breeder reactor technology, etc., the light water reactors are expected to remain dominant in the nuclear power generation of our country until at least the second half of the 21st century.

Based on such a background five PWR utilities in Japan (Hokkaido, Kansai, Shikoku, Kyushu, and the Japan Atomic Power), and Mitsubishi Heavy Industries, Ltd. have jointly started researching the Next Generation PWR which is expected to be the leading nuclear power plant taking place of APWR.     

Drain structure optimization for highly reliable deep submicrometern-channel MOSFET

A guideline for n^- fully gate overlapped (FOLD) structure design optimization has been studied. From the viewpoint of reliability, the greatest reduction in substrate current directly leads to the most reliable n^- design for the FOLD structure. The current path modulation phenomenon due to the trapped charge at the n ^- extension region dominates the hot-carrier induced characteristics change for conventional lightly doped drain (LDD) structure with side-wall spacer. This phenomenon is minimized in the FOLD structure due to its higher controllability of the gate electrode than the LDD structure at the n^- extension region. Furthermore, it was also confirmed that the 0.3 μm optimized FOLD structure can achieve high circuit performance at 3.3 V operation, maintaining hot-carrier resistance     

Simple and quick turnaround time fabrication process for deepsubmicrometer CMOS generation

Process simplification and turnaround time reduction for deep submicrometer CMOS fabrication are discussed. Process step analysis is carried out for standard 1Poly/1Metal CMOS structure, and consequently, both isolation and gate formation processes are extracted as items for process simplification. A combination of shallow trench isolation with retrograde well structure and single mask step well/gate doping technique is proposed for deep submicrometer CMOS fabrication. This simplified CMOS process can achieve a reduction of five mask steps and eliminates both well drive-in annealing and field oxidation without performance deterioration. As a result, a 10% process step reduction and a 20% manufacturing turnaround time reduction have been realized in comparison to the standard 1Poly/1Metal CMOS process with LOCOS isolation     

Nonmechanical transverse scanning laser Doppler velocimeter using wavelength change

A transverse scanning laser Doppler velocimeter (LDV) that does not require any moving mechanism in its sensor probe is proposed, and the scanning function is demonstrated theoretically and experimentally. In the proposed scanning LDV, the measurement position is transversely scanned on the basis of a wavelength change induced by a tunable laser and a combination of a grating and a Dove prism. To demonstrate the scanning function in the transverse direction, an experiment was carried out using a setup of the sensor probe consisting of bulk optical components. The experimental results indicate that a transverse scanning function was successfully obtained. The scanning range in the vertical direction is estimated to be 11.3 mm over wavelengths of 1520 to 1570 nm.     

Fabrication of colorless organic materials exhibiting white luminescence using normal and excited-state intramolecular proton transfer processes

Organic, white luminescent materials were fabricated using a mixture of proton-transfer and nonproton-transfer fluorophores. 2'-Methoxy and 2'-hydroxy derivatives of 2-phenylimidazo[1,2-a]pyridine (PIP) have similar UV-absorption properties; however, they exhibit mechanistically different luminescence respectively ascribable to the normal (～420 nm) and excited-state intramolecular proton transfer processes (～530 nm) in the solid state. UV-irradiation of mixed solids excites both components concurrently and results in efficient white luminescence composed of two independent emissions without involving energy transfer process. White luminescent solids are easily transformed into vapor-deposited films under mild conditions, and a colorless and transparent thin film by dissolving in PMMA.     

Selective modification of the N-terminal structure of polytheonamide b significantly changes its cytotoxicity and activity as an ion channel

Chemical point mutation: Polytheonamide?B is a naturally occurring polypeptide containing 48 amino acids. It both displays potent cytotoxicity and acts as a monovalent cation channel in?vitro. Chemoselective methods to modify the 44th, N-, and C-terminal residues of the natural product have been developed, and evaluation of the resultant derivatives suggests that the intrinsic activities of the peptide can only be altered by switching its N-terminal substitution.     

Morphologic Control of Pt Supported Titanate Nanotubes and Their Photocatalytic Property

Morphologic control of Pt supported titanate nanotubes was attempted by the hydrothermal hot-pressing (HHP) technique in order to improve the handleability as a photocatalyst. The bulk of Pt-nanocrystal supported titanate nanotubes was successfully fabricated without the H₂ reduction process by applying the HHP technique. The bulky Pt-nanocrystal supported titanate nanotubes possessed dense microstructures, significantly sharp distributions of mesopores, and high Brunauer–Emmett–Teller (BET) surface area. Furthermore, the bulky Pt-nanocrystal supported titanate nanotubes showed the photocatalytic degradation activities of 2-propanol aqueous solution under UV-light irradiation.     

Application of Highly Functional Ti-Oxide-Based Photocatalysts in Clean Technologies

Various Ti-oxide based photocatalysts such as the highly dispersed Ti-oxide species within zeolite frameworks, TiO₂ nano-particles hybridized with hydrophobic zeolite adsorbents as well as visible light responsive TiO₂ thin films have been successfully prepared. Characterization studies at the molecular level, such as X-ray absorption fine structure (XAFS) and photoluminescence (PL), revealed that the highly dispersed Ti-oxide species within the nano-spaces of zeolites possess a tetrahedral coordination and that they demonstrate unique and high performance for the photocatalytic decomposition of NOx and the photocatalytic reduction of CO₂ with H₂O. A high photocatalytic reactivity for the TiO₂ semiconducting photocatalysts could be achieved by blending them with hydrophobic siliceous zeolites which was equal to the performance of TiO₂ deposited with expensive Pt particles. The role of the siliceous zeolites can be described as a so-called “catch and release effect of organic compounds”, i.e., (i) the condensation of the reactants within the hydrophobic cavities of zeolites and; (ii) the efficient diffusion of the reactant onto the TiO₂ photocatalytic sites. Furthermore, a novel photocatalytic system which can convert abundant solar energy into renewable H₂ energy by the decomposition of H₂O into H₂ and O₂ can also be achieved by using visible light responsive TiO₂ thin film photocatalysts prepared by a RF-magnetron sputtering deposition method. The conversion efficiency of solar energy into H₂ energy may be estimated at ca. 0.1% from the initial rate of H₂ evolution.