Breakdown characteristics of oil and paper insulation for a very fast transient voltage

This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043     

An analysis of shielding against DC magnetic fields generated by electric railways. Evaluation of effective permeability of fine structure

This paper describes an effective analysis of magnetic shielding based on homogenization. The analyses become time‐consuming if the problems include the magnetic substances having fine structure. The homogenization of the structure makes it possible to analyze effectively the magnetic fields. The authors introduce a method to estimate the effective permeability of the homogenized substance. This method can be applied to any periodic structure made of magnetic substance. The magnetic shielding effects by the structures against direct‐current (DC) fields generated by electric railways are analyzed by using the present method. As a result, it is found that the overhead way and the protective fence near the railway work as a magnetic shield, whose effects can be improved by appropriate arrangement of those constructions. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 7–15, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20310     

Impulse breakdown voltages of triggered multistage vacuum gap

Several sealed-off triggered vacuum gaps are connected in series to improve hold-off voltage. The characteristics of impulse breakdown voltage of these series-connected gaps are investigated experimentally. The sum hold-off voltage of series-connected gaps decreases to a unit hold-off voltage when the maximum value of voltage division ratio across the gaps increases to unity. Self-breakdown probability of the series-connected gaps is always higher than that of a single gap under the same conditions. Hence, stage efficiency of the multistage gap decreases with increasing number of stages. Its value is 90 percent with 2-stage gap and 75 percent with 5-stage gap, respectively, under the same voltage division ratio and the same gap length (2.0 mm) in each stage. Triggered breakdown voltage of 2- or 3- stage gap is several hundred volts when all gaps are triggered simultaneously at the peak of the main impulse wave and a working voltage range is nearly 100 percent in this case. The working voltage range decreases with number of stages. Its value is 45 percent with 3-stage gap and 15 percent with 5-stage gap, respectively, when one triggered gap is fired for switching.     

Stabilization of bioethanol recovery with silicone rubber‐coated ethanol‐permselective silicalite membranes by controlling the pH of acidic feed solution

In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry     

Solid-Phase Syntheses of Two Deacetyl-Thymosin β4 Analogues with Substitution at Position 12 and Their Effects on Impaired Blastogenic Response of T Lymphocytes of Uremic Patients

Two deacetyl-thymosin β₄ analogues containing Phe(4Br) or D-Phe(4Br) as position 12 were synthesized by the manual solid-phase method, and their immunological effects on the impaired blastogenic response of phytohemagglutinin-stimulated T lymphocytes of uremic patients with infectious diseases were studied. Bromination of the p-position of Phe¹² resulted in a marked restorative effect on the impaired blastogenic response of T lympocytes compared with that of our synthetic deacetyl-thymosin β₄ The synthetic [Phe(4Br)¹²]deacetyl-thymsin β₄ was approximately equal in potency to our synthetic [Phe(4F)¹²]deacetyl-thymosin β₄ in uremic patients, but the other analogue, [D-Phe(4Br)¹²]deacetyl-thymosin β₄, had no effect.     

A high resolution negative working resist,LMR-UV,for g- and i-line lithography

LMR-UV (“low molecular weight resist for uv lithography”), a naphthoquinone-diazide sulfonic acid ester of a novolak resin, is a negative working resist. The mechanism of insolubilization of LMR-UV is based on the facts that the naphthoquinone-diazide moiety is decomposed to indenecarboxylic acid (polar compound) by photolysis upon UV irradiation and that the irradiated resist film insolubilizes in a non-polar developer. LMR-UV reliably forms 0.6 μm lines and spaces over a reflective substrate with steps by using a g-line stepper having a 0.35 NA lens. 0.6 μm-wide aluminum patterns over topography are obtained by use of g-line exposure and reactive ion etching. By use of an i-line aligner (NA = 0.42), LMR-UV resolves 0.25 μm space patterns with overhang profiles. The profiles are due to the large absorption coefficient of 3.8 μm^?1. 0.3 μm wide aluminum patterns are formed by i-line exposure and lift-off metallization.     

An investigation of induced voltages to an underground gas pipeline from an overhead transmission line

This paper investigates induced voltage characteristics from an overhead transmission line by applying a method of modeling of induced voltages proposed by the authors. EMTP simulation results obtained by the modeling method agree with analytical results obtained from a well‐known formula. The induced voltages are significantly dependent on the configuration of the overhead line. A horizontal line induces the largest voltage in a gas pipeline, and the voltage induced by a vertical twin‐circuit line is about 20% smaller than that induced by a vertical single‐circuit line. The method is applied to a real pipeline system and the simulation results show reasonable agreement with field test results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 43–51, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20465     

Changes in the thermomechanical behavior of epoxy glasses under the state of strain aging

Changes in thermomechanical behavior with structural relaxation taking place in epoxy glasses were studied. Differential scanning calorimetry measurements and thermostimulated strain recovery tests were performed for specimens deformed and then aged under fixed strain. In the course of heating, the specimens started to absorb thermal energy, whereas plastic strain was still stable. At higher temperatures, plastic strain started recovery, which was accompanied by exothermic behavior of the specimen. With an increase in the aging duration, the endothermic peak signified and moved to a higher temperature. These results indicated that the longer the aging duration was, the harder the plastic strain and strain energy were frozen in the glassy structure. This freeze‐strain phenomenon was observed for crosslinked epoxy glass, as well as polymeric glasses with linear molecular structures, aged under strain. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Frequency response function of magnetic bearings using high-temperature superconductor

A high-temperature superconductor YBa₂Cu₃O_7-x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction.     

Multiobjective dynamic load-dispatching method for optimal operation of power systems

A new practical method is proposed which gives a quasi-optimal solution of the dynamic load-dispatching problem formulated by a multiconstraint multiobjective optimization problem. Here, the multiple constraints are rate reserve constraints and power flow ones, and the multiple objectives are fuel cost and CO₂ emission. The proposed method is an integration of the following three techniques: (1) “Group Dispatch Scheme,” which is developed by the authors, is used to satisfy a violated constraint easily. This scheme consists of three steps. The first step is to classify all generators into two groups. One is the group which should be more loaded to satisfy the violated constraint, and the other is the should-be less loaded group. The second step is to add some load to the former group, and to subtract the same load from the latter. The third step is to dispatch each group load to each groups generators, respectively; (2) the dynamic load-dispatching algorithm is used which provides, in practical time, quasi-optimal generation trajectories; (3) the conventional weighting parametric method is used to obtain a Pareto optimal solution of multiobjective problems. The effectiveness of the method is clarified by a computer simulation on the actual power system of Kansai Electric Power Company.