An improved method to approximate closest saddle node bifurcation based on multiple load flow solutions: A new method of voltage stability monitoring and control

Although a closest bifurcation point (CBP) is known to be a superior security measure against voltage collapse, no fast computation methods exist presently. In such a circumstance, the authors proposed an approximation method for CBP in Ref. 11 where two major problems were left unsolved: (1) the method cannot take into Q limits of generators and (2) it utilizes a low‐voltage power flow solution, which is not easily obtained unless a suitable initial estimate is available. This paper presents a series of techniques to solve these problems. It is shown that the proposed method can provide fairly accurate CBP without suffering any major problems. The total computation time is not more than that of ten power flows even when no information of low‐voltage solution is available in advance. The proposed method will make possible a reliable on‐line monitoring and control of voltage stability. © 2000 Scripta Technica, Electr Eng Jpn, 133(1): 19–30, 2000     

Effect of Zr/Ti Ratio on Microstructure and Electrical Properties of Lead Zirconate Titanate Thin Films Derived by Pulsed Laser Deposition

PZT films were fabricated using various targets of Pb(Zr_xTi_{1 – x})O₃ with Zr/Ti ratios of 70/30, 58/42, 52/48, 45/55 and 30/70, and with excess PbO of 20 wt% on Pt/Ti/SiO₂/Si(100) substrates. The rosette structure was observed in the films derived from the target with a Zr/Ti ratio of 70/30 and disappeared with increasing titanium composition. The observations on surface and cross-sectional microstructure were consistent with a higher perovskite nucleation for the higher Ti content films. The PZT films derived from the target with a Zr/Ti ratio of 45/55 had a polycrystalline columnar microstructure extending throughout the thickness of the film and no pyrochlore phase on the surface was observed. The PZT films derived from the target with a Zr/Ti ratio of 45/55 exhibited better electric properties than those derived from the target with a Zr/Ti ratio of 52/48.     

Discussion of electrode conditioning mechanism based on pre‐breakdown current under nonuniform electric field in vacuum

Electrode conditioning is a very important technique for improvement of the insulation performance of vacuum circuit breakers (VCBs). This paper discusses the spark conditioning mechanism under a nonuniform electric field, focusing on the pre‐breakdown current. We quantitatively evaluated the spark conditioning effect by analyzing the pre‐breakdown current based on the Fowler‐Nordheim equation. The field enhancement factor β was found to decrease with increasing breakdown voltage at the beginning of the conditioning process, and finally became saturated with the saturation of the breakdown voltage. In addition, in the case of a nonuniform field, we found that β on a high‐voltage rod electrode after conditioning varied according to the electric field strength on the rod electrode. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(2): 21‐28, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21059     

Recent progress in sputtering PZT thin films for ferroelectric memories

Abstract

This paper describes amorphous Pb(Zr, Ti)O₃ (PZT) thin films deposited by cosputtering Pb(Zr_0.5 Ti_0.5)O₃ and PbO targets. By optimizing the amount of the excess Pb and the deposition temperature, PZT thin films with a single perovskite phase were obtained successfully on Ir substrates and Pt substrates at 520°C. 250-nm-thick PZT films crystallized by rapid thermal annealing (RTA) at 600°C for 20 s exhibited excellent ferroelectric properties: a coercive voltage of 1.0 V, a remanent polarization density of about 40 μC/cm², and a polarization switching endurance over 1x109 cycles. Although a heat treatment in a reductive ambient causes degradation of ferroelectric properties of PZT thin films, their degraded ferroelectric properties can be easily recovered from by a 1-min RTA in an oxygen at 400°C.     

1000MW单轴多缸汽轮发电机组的开发

为优化化石燃料电厂的建设投资,在保证高可靠性和高效率的同时,设备的布置应更加合理。因此１０００ＭＷ化石燃料汽轮发电机组的布置趋向于从双轴布置改为单轴置。本文介绍了日立公司开发的１０００ＭＷ单轴多缸汽轮发电机组部件技术的情况,目前,末级叶片分别为１０１６ｍｍ及１０９２．２ｍｍ的单轴多缸４排汽汽轮机已分别应用到６０Ｈｚ和５０Ｈｚ发电机上。     

Thermal and chemical recycle of waste polymers

Catalytic degradations of polyethylene into fuel oils and of polystyrene into styrene monomer have been studied using solid acids and bases as catalysts. Solid acids such as silica-aluminas and ZSM-5 zeolite were found to be effective to degrade waste polyethylene into fuel oils, and solid bases such as BaO and K₂O were concluded to be effective to convert waste polystyrene into styrene monomer. A design of recyclable polystyrene films will be briefly mentioned.     

Serum Autotaxin is not a Useful Biomarker for Ovarian Cancer

Autotaxin (ATX) is a glycoprotein that was first identified in the conditioned medium of human melanoma cells as an autocrine motility factor. It possesses lysophospholipase D activity, producing the bioactive lipid mediator lysophosphatidic acid (LPA) from lysophosphatidylcholine. Enhanced expression of ATX mRNA has been reported in various cancer cells and tissues, and it has been speculated that ATX overexpression in cancer cells may be associated with aberrant LPA production. LPA and ATX have been implicated in cancer progression and metastasis, and ovarian cancer is a representative example. In the present study, we measured the serum ATX antigen levels in patients with ovarian cancer and evaluated the usefulness of this parameter for clinical laboratory testing. The serum ATX antigen levels were not increased in ovarian cancer patients as compared with the levels in healthy subjects, and the serum ATX may not be useful as a biomarker for ovarian cancer.     

Effect of scratch velocity on scratch behavior of injection-molded polypropylene

Scratch tests of polypropylene injection moldings were conducted with a progressive load scratch test according to ISO 19252. Effect of scratch velocity on scratch visibility and damage initiation was investigated. The results showed that the critical normal load for onset of scratch visibility was independent of scratch velocity in the range from 1 to 10 mm/s. However, the critical normal load decreased with increase of scratch velocity higher than 10 mm/s. The other scratch damage transitions such as onset of fish-scale and cutting pattern, the critical normal load also decreased with increase of scratch velocity. A correlation between scratch behavior and subsurface deformation was observed by polarized optical microscope. The formation of yielded zone under scratch groove was clearly observed at onset of scratch visibility. It was found that the yielded zone size becomes shallower at higher scratch velocity. The results suggested that localized stress was generated near the surface at higher scratch velocity. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Reflectance spectra of extreme ultraviolet mirrors for synchrotron radiation

Reflectance spectra have been measured for many materials in the wavelength range from 90 Å to 400 Å. The angle of incidence ranged from 20° to 85°. The samples were chemical-vapor-deposited silicon carbide (CVD-SiC), a single crystal of silicon with (100) surface, fused quartz, zerodur, pyrex, gold, platinum, copper and two kinds of steel. To obtain reflectances for surfaces for practical use, measurements were made on surfaces sufficiently exposed to air. Reflectances for s-polarized light (R_s) were measured for all samples. On CVD-SiC, gold and platinum, reflectances for p-polarized light (R_P) were also observed. At short wavelengths and large angles of incidence, the difference between R_s and R_P is small, and R_P happened to exceed R_s in contrast to the result from the Fresnel equation. This may be due to the deviation of the present surfaces of mirrors from an ideal plane. Reflectance spectra of surfaces prepared by some feasible techniques are also presented.