bluuebunny/crossref_metadata_2025 huggingface dataset:
Degeneration of vagal efferent axons and terminals in cardiac ganglia of aged rats
Authors: Ai Jing , Gozal David , Li Lihua , Wead William B. , Chapleau Mark W. , Wurster Robert , Yang Baofeng , Li Hulun , Liu Rugao , Cheng Zixi (Jack)
Published: July 2007

Baroreflex control of the heart rate is significantly reduced during aging. However, neural mechanisms that underlie such a functional reduction are not fully understood. We injected the tracer DiI into the left nucleus ambiguus (NA), then used confocal microscopy and a Neurolucida Digitization System to examine qualitatively and quantitatively vagal efferent projections to cardiac ganglia of young adult (5–6 months) and aged (24–25 months) rats (Sprague Dawley). Fluoro‐Gold was injected intraperitoneally to counterstain cardiac ganglionic principal neurons (PNs). In aged, as in young rats, NA axons projected to all cardiac ganglia and formed numerous basket endings around PNs in the hearts. However, significant structural changes were found in aged rats compared with young rats. Vagal efferent axons contained abnormally swollen axonal segments and exhibited reduced or even absent synaptic‐like terminals around PNs, such that the numbers of vagal fibers and basket endings around PNs were substantially reduced (P< 0.01). Furthermore, synaptic‐like varicose contacts of vagal cardiac axons with PNs were significantly reduced by approximately 50% (P< 0.01). These findings suggest that vagal efferents continue to maintain homeostatic control over the heart during aging. However, the marked morphological reorganization of vagal efferent axons and terminals in cardiac ganglia may represent the structural substrate for reduced vagal control of the heart rate and attenuated baroreflex function during aging. J. Comp. Neurol. 504:74–88, 2007. © 2007 Wiley‐Liss, Inc.
Distinct patterns of motor nerve terminal sprouting induced by ciliary neurotrophic factor vs. Botulinum toxin
Authors: Wright Megan C. , Cho Wha‐Ja , Son Young‐Jin
Published: July 2007

Both diffusible and surface‐bound molecules are thought to induce sprouting of motor nerve terminals in response to paralysis. Here we report that the sprouting induced by ciliary neurotrophic factor (CNTF) is qualitatively different from the sprouting induced by botulinum toxin (BoTX). We show first that subcutaneous application of CNTF to levator auris longus muscles of adult mice evokes sprouting from nearly all nerve terminals. Surprisingly, however, most terminal sprouts remain within the boundaries of the endplate region and rarely grow extrasynaptically even if CNTF is administered chronically. In contrast, terminal sprouts induced by BoTX extend vigorously along the extrasynaptic muscle surface. The different patterns of sprout elongation are attributable in part to different patterns of initiation: whereas CNTF‐induced sprouts emerge randomly from the surface of terminal branches, BoTX‐induced sprouts emerge exclusively along the perimeter of terminal branches in direct apposition to muscle fiber membranes. Combined treatment with CNTF and BoTX produces exceptionally robust extraterminal sprouting with little if any intrasynaptic growth of terminal sprouts. We interpret these results as showing that paralysis induces sprouting primarily by muscle‐associated, surface‐bound molecules rather than by diffusible factors. Our findings may be useful in defining the physiological role of the numerous candidate sprouting‐inducers and in promoting compensatory sprouting after nerve injury for therapeutic benefit. J. Comp. Neurol. 504:1–16, 2007. © 2007 Wiley‐Liss, Inc.
Collective communication: theory, practice, and experience
Authors: Chan Ernie , Heimlich Marcel , Purkayastha Avi , van de Geijn Robert
Published: July 2007

We discuss the design and high‐performance implementation of collective communications operations on distributed‐memory computer architectures. Using a combination of known techniques (many of which were first proposed in the 1980s and early 1990s) along with careful exploitation of communication modes supported by MPI, we have developed implementations that have improved performance in most situations compared to those currently supported by public domain implementations of MPI such as MPICH. Performance results from a large Intel Xeon/Pentium 4 (R) processor cluster are included. Copyright © 2007 John Wiley & Sons, Ltd.
Photochemical Z→E Isomerization of a Hemithioindigo/Hemistilbene ω‐Amino Acid
Authors: Cordes Thorben , Heinz Björn , Regner Nadja , Hoppmann Christian , Schrader Tobias E. , Summerer Wolfram , Rück‐Braun Karola , Zinth Wolfgang
Published: July 2007

The molecule HTI, which combines hemithioindigo and hemistilbene molecular parts, allows reversible switching between two isomeric states. Photochromic behaviour of the HTI molecule is observed by irradiation with UV/Vis light. The photochemical reaction, a Z/E isomerization around the central double bond connecting the two molecular parts, is investigated by transient absorption and emission spectroscopy. For a special HTI molecule, namely, an ω‐amino acid, the Z→E isomerization process occurs on a timescale of 30 ps. In the course of the reaction fast processes on the 1–10 ps timescale are observed which point to motions of the molecule on the potential‐energy surface of the excited state. The combination of transient absorption experiments in the visible spectral range with time‐resolved fluorescence and infrared measurements reveal a photochemical pathway with three intermediate states. Together with a theoretical modelling procedure the experiments point to a sequential reaction scheme and give indications of the nature of the involved intermediates.
Association Behavior of a Nitrilotriacetic‐Acid‐Modified Dye in a Poly(Vinyl Alcohol) Film Containing Ni(II)‐Adsorbed Gold Nanoparticles
Authors: Sakamoto Masanori , Tachikawa Takashi , Kim Sung Sik , Fujitsuka Mamoru , Majima Tetsuro
Published: July 2007

The association behavior of the dyes 5(6)‐carboxyfluorescein and nitrilotriacetic acid (NTA)‐modified 5(6)‐carboxyfluorescein (F‐NTA) in a poly(vinyl alcohol) (PVA) film and in a PVA film containing metal nanoparticles is investigated. Well‐dispersed gold nanoparticles (AuNps) and Ni(II)‐adsorbed AuNps are formed in the PVA film using in situ photochemical fabrication method. 5(6)‐carboxyfluorescein and F‐NTA are doped into the films. The F‐NTA forms an H‐aggregate in the PVA film containing Ni(II)‐adsorbed AuNps. It is suggested that the interaction between NTA and Ni(II) adsorbed on the AuNps promotes the formation of the H‐aggregate.
“Why aren't we screening?” A survey examining domestic violence screening procedures and training protocol in community mediation centers
Authors: Clemants Elizabeth , Gross Alan
Published: July 2007

This article analyzes survey data from ninety‐four North American community mediation centers regarding their policies and practices for identifying and managing cases that include a history of domestic violence. We report the rate at which community mediation centers formally screen for cases with a history of domestic violence and the extent to which they mandate domestic violence training for their staff and mediators. We also examine the differences in screening and training related to the differences among the centers' policies for accepting cases with a history of domestic violence.
High‐field dielectric properties of polypropylene films in high‐temperature region
Authors: Tokoro Tetsuroh , Tohyama Kazuyuki , Takusagawa Mamoru , Nagao Masayuki , Kosaki Masamitsu
Published: July 2007

Nonpolar polymers are used widely as electrical insulation materials, and their operating conditions sometimes become high‐electric field and high temperature. Under these conditions, the conduction loss is assumed to affect the dielectric properties and to make the ac dissipation factor (tan δ) increase. Therefore the high‐field dielectric properties of polymeric materials in the high‐temperature region become very important.

This paper describes the high‐field dielectric properties of polypropylene films measured at 50 and 400 Hz above room temperature with the new electrodes developed by authors. At low temperature, the high‐field tan δ is independent of the frequency of the applied field. However, at high‐temperature, the high‐field tan δ becomes almost inversely proportional to the frequency, namely, the conductivity is independent of the frequency. The theoretical analysis shows that the high‐field dielectric loss is governed by two processes: one is the loss which appears only under ac field; and the other is conduction loss which appears also under dc field. The latter loss becomes prominent under high‐electric field at high temperature.
Voltage‐current characteristics of high‐current pulsed discharges in SF
Authors: Akiyama Hidenori , Tanigawa Tetsuro , Maeda Sadao , Takaki Koichi , Kristiansen M.
Published: July 2007

A high‐current pulsed discharge in SF6 has been used as a closing switch for a pulsed power generator. The characteristics of a high‐current pulsed discharge are not clear, since it is difficult to measure the time‐dependent arc voltage accurately.

In the present paper, the voltage‐current characteristics and the time‐dependent arc resistance of the high‐current pulsed discharge in SF6 are obtained accurately from the arc current and the breakdown voltage by solving the circuit equation. The electrode separation and the pressure are changed from 0.1 to 1 cm and from 200 to 760 torr, respectively. The current rise time is about 380 ns. The minimum arc resistance occurs at the maximum arc current, and is from 0.04 to 0.1 Ω under the experimental conditions. The voltage‐current characteristics in SF6, which are characterized by five phases, are similar to the characteristics in air but not in Ar.
Study on grounding in the vicinity of the work site on 1000‐kV power transmission line. Part 2. Electromagnetic induction and its protection
Authors: Yoshioka Masayuki , Kitamura Satoshi
Published: July 2007

In order to clarify the grounding conditions for protecting workers on a de‐energized circuit from induction from a live circuit and to determine the required current capacity of the grounding conductor for a 1,000 kV double‐circuit power transmission line, the phenomena caused by electromagnetic induction resulting from a live circuit are discussed. The electromagnetic induction current Ig flowing through the body of a worker and the electromagnetic induction current IgO flowing through the grounding conductor can be analyzed by dividing the various power line conditions into three main factors, and using electromagnetic induction current calculations for a power line of infinite length. The zone where Ig does not exceed 1 mA is within 1 km of the grounding point on the de‐energized circuit owing to the grounding resistance (0.1 Ω) of the substations at the ends of the line and the difference in the phase configurations on the line when the current I1 of the live circuit is a constant 1 kA through the line. Similarly the value of IgO is determined by the grounding resistance of the substations at the ends of the line and the difference in the phase configurations on the line. IgO is approximately 10 A per 1 kA of I1. The currents Ig and IgO produced by electromagnetic induction are additive, allowing Ig and IgO in the actual power line to be evaluated by summation.
Semiconductor thermoelectric‐energy conversion systems working at low temperature differences
Authors: Ikeda Yoshitaka , Itsumi Jiroh , Haneji Nobuo
Published: July 2007

The present thermoelectric semiconductor integrated into the commercially available thermoelectric units are not designed elaborately for low temperature difference operation. Those elements available in the room‐temperature range are usually applicable for the temperature difference around 60 K with relatively poor coefficient of performance. For air‐conditioning purposes, it is expected that the thermoelectric energy conversion will have a high coefficient of performance as well as economical advantage because of the low temperature difference operation.

This paper describes basic and analytical considerations for low temperature‐difference operation, and also the new design systems desired from viewpoints of the effective and economical use of environmental energy. An appropriate design allows a drastic economy in the material and also a drastic improvement in the coefficient of performance, and it is possible to put the material, with the presently available figure of merit, in practical use.

The availability of a simple cascade connection is discussed for the operation under some increased temperature difference. The concept of the cooling or heating systems using thermoelectric units driven by a solar‐cell array will also be proposed and experimental results will be illustrated.
Ultralow resistivity in the surface direction of LB heterofilms
Authors: Hino Taro , Kushida Masahito
Published: July 2007

LB heterofilms of double layer consisting of arachidic acid and 2‐pentadecyl‐7, 7′, 8, 8′‐tetracyanoquinodimethane (C15 · TCNQ) LB films were sandwiched between Al and Au thin evaporated films. Such layer structures of Al/LB heterofilm/Au were deposited on the SiO2 insulating film of silicon wafters.

Resistance in the surface direction of the above layer structure was measured by the four‐point probe technique. As a result, very low resistance of 10−2 ∼ 10−3 Ω was obtained by the electrode system of gap 3.3 mm with width 10 mm. It was clarified in the experiments that the current flowed through the LB heterofilms of about 200 ∼ 30 Å in thickness; accordingly the resistivity of LB heterofilms was calculated to be 10−8 ∼ 10−9 Ω cm. Such a value of resistivity was much smaller than the metal resistivity of 10−5 Ω cm. Furthermore, the current through the LB film, increased up to 1.3A, was equivalent to the very high current density of 4.1 ∼ 105 A/cm2. However, the resistance was increased suddenly by 106 times at that time and the current was decreased to 3 ∼ 10−4 A. Such a switching phenomenon could be observed repeatedly.

The ultraflow resistance and the very high current density observed in the LB heterofilms will be explained by the model of the potential well filled with electron gas which was generated in the LB hetero‐film by the polarization of C15 · TCNQ LB film.
Study of a future metropolitan electric network adapted to introduction of cryogenic high‐power cables
Authors: Hayakawa Naoki , Kito Yukio , Matsumura Toshiro
Published: July 2007

The authors have investigated the operational feasibility of a future metropolitan electric power system associated with highly densified cryogenic cables. A new concept of power system configuration with cryogenic cables and its operation have been proposed. Three different models of future power transmission systems in large cities of Japan have been constructed as the background systems prior to introduction of cryogenic cables in the 21st century.

This paper considers one of the three models which is characterized by its conventional transmission system constructed mainly by 154‐kV transmission lines stepping down directly from the 500‐kV outer ring without any intermediate voltage class. This paper also discusses whether or not the power system model will be operated effectively together with cryogenic cables to supply demands forecasted in the period subsequent to the first decade of the 21st century. The computer simulations are carried out to obtain power flow and bus voltage distributions for a peak load period as well as for an off‐peak one in the power system model. These simulations reveal that the conventional background power system should be arranged very carefully before introducing the cryogenic cables to facilitate their operations.

(1) On a contingent trip of a cryogenic cable in the peak in the peak load period, not all bus voltages are expected to be kept within a tolerant zone due to the high impedance of 154‐kV conventional transmission lines in the power system model.

(2) Thus it is proposed that the background conventional system prior to introduction of cryogenic cables should be developed not only by extension of 154‐kV conventional transmission lines but also by introduction of 275‐kV lines.

(3) Bus voltage rises induced in the off‐peak load period are reduced by effective utilization of 275‐kV conventional transmission lines.
Classification and analysis of voltage stabilities in power systems
Authors: Yorino Naoto , Masuda Yoshihiko , Sasaki Hiroshi , Nishikame Kazuhiro , Tamura Yasuo , Kitagawa Minoru , Ohshimo Akira
Published: July 2007

The voltage stability problem has long been studied by many researchers mainly by means of two approaches: the static approach in which voltage stability is considered as a load‐flow problem; and the dynamic approach in which it is dealt with as a stability problem in dynamic systems. However, up to now, these separate approaches have not clarified sufficiently the overall aspect of the voltage problem. In fact, there are no proper criteria to determine which approach is suited to analyze voltage stability. Thus, a basic study seems to be needed under such a situation.

This paper investigates the voltage stability problem from the viewpoint of mechanism causing voltage instability. Various dynamic factors which affect voltages are studied as much as possible. First, possible voltage instability patterns are classified based on singular perturbation theory. That is, four categories of instabilities are defined mathematically. Second, a method of stability assessment for each instability is presented. It is clarified that the determinant of the load‐flow Jacobian is an effective index to approximately assess two types of instabilities. On the other hand, the remaining instabilities require eigenvalue analyses or direct nonlinear analyses. The validity of these results is verified through numerical simulations and eigenvalue analyses in which dynamic characteristics of generating units, loads and tap‐changing transformers are taken into account.
Experimental analysis of lightning overvoltages induced on low‐voltage distribution lines
Authors: Imai Yasutomo , Tsuchihashi Hachiro , Asakawa Akira , Yokoyama Shigeru
Published: July 2007

Problems have often been caused in low‐voltage distribution lines such as single‐phase 100/200 V and three‐phase 200‐V systems. For instance, the burning of low‐voltage devices and the unnecessary operation of ground fault interrupters have occurred, which are caused possibly by lightning overvoltages.

Experimental analysis was performed on the generation modes of lightning overvoltages on low‐voltage distribution lines.

A scale model line, one‐fourth the size of an actual power distribution line of Tokyo Electric Power Company (TEPCO), was installed for experimental analysis on the lightning protection of an overhead ground wire, an overhead common grounding wire (system neutral conductor), surge arresters and pole transformers against the overvoltages induced on low‐voltage distribution lines due to a nearby lightning stroke.

A balloon was flown at a location 30 km away from the scale model line in a normal direction to it. A 200‐m long wire is suspended from the balloon to simulate a lightning path. Pulse current is applied to the simulated path using a pulse generator and the voltages induced on the line conductors are measured.

This paper analyzes those overvoltages by means of the experimental and the theoretical methods.
Analysis and evaluation of integrated energy system
Authors: Matsuhashi Ryuji , Hayashi Takehito , Kaya Yoichi
Published: July 2007

Future energy supplies are uncertain, especially in view of environmental problems, fuel prices, and energy demand.

In this paper two types of novel energy plants and a novel energy system have been proposed to cope with these conditions. The first type can utilize multiple kinds of fossil fuels and economically remove CO2 and the second can produce multiple kinds of final energy to cope with fluctuations in the energy demand.

Characteristics of a novel energy system (a Flexibly Integrated Energy System; FIES), which includes novel energy plants as described in the foregoing, have been investigated with a linear programming model. A reference system has also been represented which behaves similarly to the present energy system for comparison. Computed results have demonstrated that CO2 emissions can be reduced more economically and efficiently than in the reference system if it is combined with CO2 removal systems.
Preparation of Y‐Ba‐Cu‐O tapes by pyrolysis of organic acid salts
Authors: Shiono Takeo , Nakamoto Takao , Nasu Hiroyuki
Published: July 2007

High‐TC superconducting Y‐Ba‐Cu‐O films were prepared on certain ceramic and metal substrates by pyrolysis of 2‐ethylhexanoates. Only the films on MgO, yttria‐stabilized zirconia (YSZ), and Ag substrates exhibited the superconducting transition above liquid nitrogen temperature. Transition temperatures (TC) of 82, 85, and 82 K were observed in films of MgO, YSZ, and Ag substrates. The important factors in preparing superconducting films on substrates are the reactivity of the films and the substrates and the difference in their thermal expansions. The Y‐Ba‐Cu‐O films were well suited for use with MgO, YSZ, and Ag substrates. Long superconducting tapes were produced on Ag substrate; flexible tape with a critical current density JC of 3 · 103 A/cm2 at 77 K has now been prepared.
An application of the residual voltage for diagnoses for detecting irradiated degradation of insulating materials
Authors: Yamanaka Sanshiro , Kabeya Takashi , Fukuda Tadashi , Sawa Goro , Ieda Masayuki , Ito Masayuki , Kawakami Waichiro
Published: July 2007

Electrical cables in nuclear power generating stations must be highly reliable. For further improvement of reliability, the development of nondestructive diagnoses seems desirable for cable maintenance. The authors have been studying residual voltage for developing a diagnosis of electrical cables. The purpose of this paper is to give a foundation for development of diagnostic technology for detecting the irradiated degradation; the relations between γ‐irradiation dose and the leakage current, the discharge current, and the residual voltage were studied and attempts made to calculate the amount of polarized charge and characteristic dielectric relaxation times by using data on the residual voltage. The calculated results agreed with the results obtained from the leakage current and the discharge current. These results suggest that the residual voltage in diagnostic technology for detecting the irradiated degradation can be employed.
Effect of the small arc current generated by a poor contact on the breakdown voltage in SF6 gas
Authors: Sekiya Yoshihisa , Hosokawa Tatsuzo , Morita Tadashi , Sugiyama Shuichi , Mukaiyama Yoku , Takagi Isao
Published: July 2007

One of the failures related to gas‐insulated switchgear is caused by the poor contact between conductors. This causes breakdown between the contact and the wall of chamber, initiated by the small discharge due to the poor contact.

In this paper, the modeled experimental apparatus for the contact portion of the gas‐insulated switchgear assumed a rod‐to‐plane gap with small arc current. The influence of the arc current on the breakdown into the chamber was investigated experimentally, and the breakdown mechanism between the contacts and the wall was studied.

It was clarified that the breakdown voltage between the contact and the wall decreased by increasing the current, and the small arc current in the contact portion played an important role in the breakdown between the contact and the wall.

The reduction ratio of the breakdown voltage increased with increasing gap length of the small gap. The breakdown voltage was different depending on the duration of the small arc current.
Development of a 275‐kV liquid cooling‐type gas‐insulated transformer
Authors: Hasegawa Taizo , Betsui Takashi , Onishi Shuichi , Itoh Katsuaki , Kohan Toyakazu , Makino Yoshihiro , Nakazawa Hiroshi
Published: July 2007

Construction of 275‐kV and 500‐kV substations in densely populated areas is thought to be necessary in the future to maintain a stable supply of electricity. The use of gas‐insulated transformers is now considered for substations because such transformers are non‐flammable and nonexplosive. Since the completion of the 77‐kV gas‐insulated transformer in 1979, we have continued research to develop gas‐insulated transformers applicable to a higher voltage level up to 500 kV. As the results of the research, 275‐kV, 300‐MVA a liquid cooling‐type gas‐insulated transformer has been developed.
A method of transient stability estimation for power systems by lyapunov function
Authors: Taira Eikichi , Miyagi Hayao , Yamashita Katsumi
Published: July 2007

The power system stability problem has been one of the major subjects concerning power system engineering, and is becoming much more significant today due to the increasing size and complexity of interconnected power systems. In this problem, it is well known that the direct method of Lyapunov is the most suitable method of on‐line transient estimation for power systems, and several different techniques have been proposed for the construction of functions up to this time. However, the effectiveness of these Lyapunov functions for power systems have been demonstrated using only digital computer simulations.

The purpose of this paper is to construct a microprocessor‐based, on‐line, transient‐stability estimation system using the Lyapunov function constructed by the Lagrange‐Charpit method, and to estimate the transient stability of an alternator connected to a large system. The experimental results show that this system can act satisfactorily for estimating the transient stability of the power systems.
Insulation performance and flashover mechanism of bridged vacuum gaps
Authors: Yamamoto Osamu , Hara Takehisa , Ohmae Kimihito , Hayashi Muneaki
Published: July 2007

The insulation performance and the flashover mechanism of a vacuum gap bridged by an insulator in the shape of a conical frustum have been studied. The cone angle of the insulator is varied from 0 to 45 deg and the thickness of the insulator is varied from 5 to 15 mm. The gap is subjected to a lightning impulse voltage of 2/50 μs. The insulation performance is investigated by observing the ratio of the flashover voltage of the bridged gap to that of the gap without insulators.

The flashover mechanism is investigated by observing the distribution of traces on the cathode surface due to flashovers and by analyzing the electric field near the insulator‐cathode junction. Charging of the insulator due to electron collisions on its surface is considered in this analysis. As a result, it is found that the ratio is greater than 90 percent for a cone angle greater than a critical one when the top of the frustum is subjected to the positive impulses. It is found also that the trace distribution is related closely to the insulation performance.
Measurement of AC dissipation current in oil‐film composite insulating system
Authors: Tokoro Tetsuroh , Nagao Masayuki , Kosaki Masamitsu
Published: July 2007

The electric field dependence of tanδ in oil‐film composite insulating system sometimes has a peak and then decreases. This is known as the Garton effect. It is caused by the fact that at high voltages, the contribution of carriers in oil to the conduction loss does not last through an entire alternating field cycle. Since the separation of the loss current from the extremely large capacitive current is usually very difficult, the nonlinear ac dissipation current waveform caused by the Garton effect has not been measured.

The authors developed a new method for the measurement of high‐field ac dissipation current in polymeric insulating materials. This technique was applied to the detection of nonlinear dissipation current and its waveform in oil‐film composite insulating system associated with the Garton effect. We measured the variation of dissipation current with applied field and its frequency.
Electromagnetic field analysis by boundary element method using spatial eigenmodes
Authors: Tsuboi Hajime , Naito Tadashi , Sakurai Akihiro
Published: July 2007

This paper proposes a boundary‐element method using spatial eigenmodes for electromgnetic field analysis. Mapping the computation model with rotational symmetries, reflective symmetries or rotational symmetries including reflective symmetries to a group of spatial eigenmodes, the equivalent reduced models are obtained. In the method, the applicability becomes wide because arbitrary external source terms can be chosen. Furthermore, in a model including asymmetry regions, a new method which can save the merit of the symmetries is proposed. Finally, the validity of the proposed method is proved by numerical simulations.
Experimental study of squirrel‐caged damper structure for superconducting generator
Authors: Maeda Susumu , Izumi Akifumi , Ueda Akinori , Sakabe Sigekazu , Kometani Haruyuki , Nomura Tatsuei , Tanaka Massaki
Published: July 2007

In this paper a double‐layer damper is developed which will consist of a squirrelcaged warm damper and a cylindrical cold damper as a part of a 70‐MW superconducting generator development project. To evaluate the characteristics of unbalance current capability, magnetic shielding and damping for rotor swing, a one‐half scale rotor model is constructed and an experimental study is made. From analysis of the experimental results, design guidelines have been developed and the FEM magnetic field analysis technique is refined.

The main results are summarized as follows:

The squirrel‐caged warm damper has sufficient capability against negative sequence current;

Damping characteristics can be designed to be effective near the rotor swing frequency;

Flux shielding at low frequencies corresponding to quick response excitation is sufficiently small so as not to prevent field flux change; and

Magnetic field can be analyzed by the refined FEM field analysis technique which now takes into account the effects of the rotor end region by estimating the end resistance based on the eddy current flow path.
H∞ optical control applied to a generator control system
Authors: Ohtsuka Kei , Taniguchi Toshiyuki , Sato Takayuki , Yokokawa Sumio , Uyeki Yoshiteru
Published: July 2007

The advantages and disadvantages of H∞ optimal control as compared with LQ optimal control in generator control systems are investigated, focusing on such disturbances as 1LG faults, clearing and reclosing in the power system, and changes in terminal voltage settings and generator outputs.
Estimation method of frequency bias using normal operating data
Authors: Hamaba Kunihiro , Yokoyama Naoto , Kato Masakazu , Takabayashi Yoshiki
Published: July 2007

A technique of calculating the frequency bias of an electric power system from frequency fluctuation data and total output power is described. An evaluation method for testing the calculations by the new method is developed. The results are in good agreement with estimates based on generator speed regulation but the method gives an excessively high figure for the load frequency bias.
A compensation method of ripple voltage on DC tachogenerator
Authors: Sekine Hideomi , Ishikawa Takeo , Sato Shinichi , Suto Tugumasa
Published: July 2007

A dc tachogenerator has been used widely in such applications as computer peripherals and machine tools. However, this generator has some problems, e.g., the ripple voltage involved in the output voltage and the abrasion of the brush and the commutator. The ripple voltage of a general dc tachogenerator is from 1.5 to 5 percent of the output voltage. This voltage must be reduced to very small value in consideration of the influences on control systems.

A compensation network of the ripple voltage on this generator was proposed in a previous paper. Here, the network is improved so as to operate effectively without losing the high response even when the rotating speed is changed slightly. The performance of the proposed network is discussed in detail, and the method for the design of the network to satisfy the requirements both of the ripple voltage and of the response time is proposed. The experimental results show that the ripple voltage is eliminated perfectly at the steady state, and that the high response is not lost.
Nonlinear magnetic levitation control by four‐point attraction
Authors: Tsuji Teruo , Takahashi Kazuo , Oguro Ryuichi
Published: July 2007

Rubber components of production equipment are a significant source of contamination in the fabrication of VLSI devices and other semiconductor products. One approach to solving this problem is to use a magnetic levitation system for noncontact transfer. The force nonlinearity of magnetic circuits presents a problem, particularly when the gap between the magnets and the levitated vehicle is small. Linearization methods that allow effective control do exist, but in this paper an alternative method not based on linearization is proposed. The design involves magnetic levitation control by 4‐point attraction. The experimental results indicate that the idea is an effective one.
Electrical breakdown and space‐charge effect in polyphenylene sulfide films
Authors: Umemura Akihiro , Hikita Masayuki , Kaneko Kazue , Mizutani Teruyoshi , Ieda Masayuki
Published: July 2007

Electrical breakdown of polyphenylene sulfide (PPS) films, one of the high‐temperature engineering plastics, has been investigated. The results show that the dc breakdown strength is lower than the impulse one, and that the difference in electric strength between dc and impulse becomes wider as the sample thickness decreases. The result suggests space‐charge accumulation when dc voltage is applied.

Further, the impulse breakdown strength in the presence of a dc prestressing voltage is measured in order to elucidate the space‐charge effect. The data on the contribution of the prestress voltage to electrical breakdown are used to estimate the amount of space charge accumulated in the specimen during the dc prestressing.
Effect of heat treatment on electrical properties of zinc oxides
Authors: Kawamura Hideaki , Yamada Katsuhisa , Nawata Masahito , Ieda Masayuki
Published: July 2007

The electrical properties of ZnO ceramics were studied from their voltage‐current characteristics, thermally stimulated current (TSC), and heat‐treatment effects.

ZnO ceramic samples with a few mol% of insulating oxide components were prepared. After sintering at 1200°C in air, some of the sample were heat treated at various temperatures between 450 and 900°C in air.

On the voltage‐current curves, the current varies as a function of applied dc voltage according to the relation I = CVα, where α is the nonlinear exponent. The nonlinear exponent α decreased with the heat‐treatment temperature in the low‐temperature region, became the lowest around 600–750°C, and almost recovered at 900°C.

Three TSC peaks (designated by P1, P2 and P3 from the low‐temperature side) were observed in the nonheat‐treated samples. The samples heat treated at 600 and 750°C showed only the P1 and P2 peaks; the P3 peak increased in magnitude with the increase of biasing temperature tb, and it shifted toward the high‐temperature side.

These results suggest that the electrical properties of ZnO ceramics will be associated with the phase transition of the Bi2O3‐ rich intergranular layers by heat treatment.
A method of power system simulation considering armature transients of synchronous machines
Authors: Tamura Junji , Takeda Ikuo , Hasegawa Jun
Published: July 2007

This paper presents a new method of simulating transient responses of multimachine power systems following a large disturbance. The conventional model used in the simulation is composed mainly of synchronous machine models in which the armature transients are neglected, and steady‐state transmission system equations. This is because it is very difficult to treat the transmission system and the armature circuits of synchronous machines as differential equations. Naturally, the model cannot evaluate the effects of these neglected transients. The new method proposed herein uses the new synchronous machine model and the steady‐state transmission system model. The former is obtained by modifying slightly the conventional armature‐transient neglected model. Thus the resultant simulation model has almost the same structure as the conventional one. However, it can evaluate approximately the effects of armature transients on the dynamical behavior of the synchronous machines. For example, it can evaluate easily the angular backswing following a three‐phase short‐circuit fault. In addition, the new method can also estimate the maximum values of developed torque, induced voltage and armature current of synchronous machines at the moment when the disturbance occurred and when it was cleared.
Generalization of transient stability solution using neural network theory
Authors: Ikenono Katsumi , Iwamoto Shinichi
Published: July 2007

This paper presents a generalized online transient stability solution technique using the backpropagation method of the neural network theory. The proposed solution technique can be used for general generator models, including controllers such as AVRs and governors, that have been difficult for the energy function method to handle. The proposed method also considers alterations of network configurations and changes of the number of operating generators. Further, the relationship between input data and effects on the results of the neural network is considered.
A dual thyristor converter reducing harmonics of power supply without input transformer
Authors: Matsui Keiju
Published: July 2007

In general, the thyristor‐controlled rectifier circuit (thyristor converter) generates a large amount of harmonics in the input power supply. Consequently, in the power system, the harmonics become more increased for larger capacity of such a converter, thus it is important to improve their harmonic characteristics. Among such converters, the double three‐phase bridge converter with transformer of star and delta windings is well known. By application of such techniques, Miyairi and his group proposed a thyristor converter which has excellent harmonic characteristics. On the other hand, the multiple‐connected inverter circuit without output transformer had been already proposed. However, it contains the lower‐order harmonics.

This paper proposes a converter which can reduce the harmonics similarly to the forementioned double‐bridge converter. This circuit has the center‐tapped reactor that can control the dc current like the current control of Miyairi's interphase reactor. This novel converter need not use the input three‐phase transformers that usually make the cost higher. The proposed circuit has a commutation one with capacitor that is analogous to the series diode‐type thyristor inverter. This circuit maintains the commutation to operate successfully with constant reverse bias time. The entire circuit operation and the commutation circuit operation are discussed and confirmed experimentally and theoretically.
Single‐phase PWM converter using balanced two‐phase rectification
Authors: Hashimoto Tatusaki , Sone Satoru
Published: July 2007

Energy storage devices, such as inductors or capacitors, are needed in single‐phase ac to dc converters because instantaneous power flow of input single‐phase ac is inherently pulsating and output dc power must have as little ripple as possible. Energy storage devices (such as smoothing inductors or capacitors) are usually inserted on the dc side. In those converters, energy storage ability of the devices cannot be used effectively, especially when dc power ripple is required to be very small.

To solve such a problem, this paper presents novel single‐phase ac/dc conversion circuits, in which energy storage devices are used at the ac rather than at the dc side. That is, after converting single‐phase ac into balanced (rectangular) two‐phase ac using variable reactance element, reconversion of it into dc is carried out.

This paper presents a control method for the converters and the variable reactance devices, and performance of the proposed circuits is confirmed using computer simulation.
Air gap flux analysis for cage rotor diagnosis
Authors: Morita Ikuro
Published: July 2007

The relationship between the magnetomotive force distribution of a three‐phase induction motor and various cage rotor faults, such as broken bars and end rings, is discussed in detail. Search coil output and its harmonic components are analyzed to allow the determination of faults from the air‐gap flux density. The results obtained in tests on a motor into which faults were intentionally introduced confirm the effectiveness of this method of analysis.
AC losses in superconducting coils
Authors: Akita Shirabe , Ishikawa Tadao , Tanaka Toshikatsu
Published: July 2007

AC superconducting wire is being developed for such electrical equipment as superconducting transformers and superconducting generators. AC loss reduction is of primary concern in the development of such high‐efficiency equipment. In reducing ac losses, it is necessary to develop assessment methods for ac loss in test samples which have shapes similar to the end‐product equipment.

This paper describes a least‐square calculation of ac losses of superconducting wire as a function of frequency and magnetic field strength measured in test coils.

Two sample solenoid coils were made to test the influence of different capacities and winding methods on ac losses in ac superconducting coils with rated capacities of 500 kVA and 20 kVA, and impregnated (epoxy resin) and nonimpregnated windings.

The ac losses in the superconducting coils were measured by a calorimetric method using the evaporating rates of liquid helium. Estimated ac losses in the superconducting wire of the two coils were compared with Joule losses of copper conductors at ambient temperature. As a result of this comparison, a low‐loss ac superconducting wire winding can be made for electrical equipment rather than employing conventional copper winding when used under low magnetic fields under 0.5 T.
Performance and conceptual design of superconducting magnet for disk MHD generator
Authors: Okamura Tetsuji , Kabashima Shigeharu , Shioda Susumu , Okuno Yoshihiro
Published: July 2007

This paper describes superconducting magnets coupled with two kinds of disk‐type MHD generators. One is coupled with a disk generator in the closed‐cycle MHD experimental facility FUJI‐1. The other is for a full‐scale disk MHD generator. These are split‐pair magnets.

In the magnet for the FUJI‐1 facility, a unique structure which supports the coils against the electromagnetic force has been fabricated and the magnet has been operating stably. During MHD power generation experiments, an induced voltage across the terminals of the coil was measured. A magnitude of the Faraday current in the generator was calculated from this induced voltage.

A possible construction of magnetics for a full‐scale disk MHD generator is indicated. It is suggested that a high performance of the generator (output power density of 0.3‐1 GW/m3) can be obtained with high magnetic field up to 10 T.
High‐frequency power transmission and selective distribution among loads by using distributed constant lines
Authors: Shimizu Toshihisa , Kimura Gunji , Shioya Mitsuo
Published: July 2007

A widely used high‐frequency induction heating system usually consists of a high‐frequency power source and a load circuit to be heated. Since such a system can heat only one load circuit, heating two or more loads requires that other sytems be devised. Several problems result, including the need for many power sources, switches, and high‐frequency power transmission lines.

To solve these problems, the authors propose a new system that can selectively supply two induction heating circuits with high‐frequency power. This system is composed of a high‐frequency voltage‐type inverter, a parallel resonant load circuit, and a series resonant load circuit, which are connected in series by distributed constant lines of specific length. Analysis of the operating characteristics of the system confirms that the system can supply the loads with high‐frequency power selectively and efficiently, with minimum interference between loads.

The authors have compared theoretical simulation waveforms with actual waveforms observed on experimental equipment with output ratings of 1 to 2 MHz and 1 kW. As a result, experimental data agree well with theoretical data.

This paper describes an operating principle and operating conditions of the system, and verifies that the theory we discuss is reasonable.
Evaluation methods on polymer materials for surface of outdoor insulators
Authors: Komatsubara Minoru , Ishii Masaru
Published: July 2007

Performance of nonceramic insulators is strongly related to hydrophobicity of the surface. Therefore, it is useful to evaluate the characteristics of the surface of organic insulating materials. To characterize the methods for the evaluation, some measurements were conducted on silicon rubber (SR), EPDM, PMMA and polyethylene (PE). The influence of irradiation with a mercury lamp was detected through measurements of contact angle, formation time of water film, and mass analysis of released gases under irradiation of electron beam.

Measurement of the contact angle by using polar and nonpolar liquids revealed that silicon rubber (SR) was the most resistant against UV radiation. SR also showed recovery of hydrophobicity after UV irradiation. Measurement of the current flowing across the surface of materials exposed to artificial fog showed good agreement to the measurement of contact angle. Infrared absorption spectroscopic analysis enabled the intensity of oxidation of highly UV‐deteriorated organic insulating materials to be detected. Radicals on the surface of specimens were specified from the result of mass analysis of released gases. From these results, the nature of deterioration of organic insulating materials irradiated by UV is discussed.
A new test method for internal partial discharge resistance of insulating materials
Authors: Kako Yasuhiko , Watanabe Shigetaka , Higashimura Yutaka
Published: July 2007

A new test method for internal PD resistance of insulating materials has been studied intensively by a task force at CIGRE for over ten years. Recently, Method II, which was developed by the authors, is now being studied as the international round robin test proposed by a domestic task force.

This paper describes the new test method concretely and shows some typical test results. The test electrode system is characterized by adhesion of test specimen to the embedded sphere electrode, and it may be applicable to all sorts of insulating material for the internal PD resistance test under uniform partial discharges. The most important point of this method is to realize the complete adhesion by skillful techniques. It was ascertained that the spread of test data may depend only on the uniformity of materials by this method, and excellent life data can be obtained for some specific materials.
Improved combined cycle power plant operation design using optimization method
Authors: Fukushima Izu , Hino Shiro , Nakamoto Masahi , Takamiya Shigeru
Published: July 2007

Combined cycle power plant takes advantage of the efficiency, fast startup, and small environmental impact. The operation design of this plant is required to make best use of this plant advantage. A large‐scale nonlinear mathematical model of this plant was developed to check the plant condition. This simulation model was combined with the optimization using Rosenbrock method. The operation design is optimized in two steps; [Step 1]: Some points of plant condition can be checked roughly; [Step 2]: This plant operation is optimized to design using Rosenbrock method. This optimization is applied to design the combined cycle power plant operation. It is confirmed that this method is effective for the design of plant operation. From this study, plant operation can be designed with this optimization to make best use of this plant advantage. Then operation design point is decided using the optimization method on some evaluation instead of heuristic method.