bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of the Fluctuation Amplitude on the Probe Characteristic
Authors: Klagge S. , Maass M.
Published: July 2007

The time‐averaged probe current is calculated by using a sampling method for sinusoidal and sawtooth‐like oscillations of the space potential. The effect of oscillations on the measured plasma parameters obtained with the aid of the single probe method, double probe method and the method of the second derivative of the probe characteristic is discussed, with the electron saturation current being taken into account. In the ion current the values rp/λD, λ/rp and Mi characterizing the working regime are varied. The calculated results are checked by corresponding measurements in a beam generated plasma.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. V. Excitation of Waves in Strong Dissipative Plasmas by a Monoenergetic Beam
Authors: Kruscha K. J. G. , Kondratenko A. N.
Published: July 2007

A system of nonlinear equations derived in a previous paper which describes the evolution of the beam‐plasma instability in strong dissipative plasmas is solved numerically. It is shown that there are three characteristic solutions of the system of equations: the resonant dissipative instability, the nonresonant instability with strong dissipation and the nonresonant dissipative instability. A physical interpretation of essential features of these instabilities is given. The interaction of resonant and nonresonant waves in the system electron beam‐strong dissipative plasma is examined. Some conclusions for the transport problem of electron beams in strong dissipative plasmas are obtained in this paper.
Distribution Radiale de la Densité des Atomes Métastables dans les Plasmas Produits par un Champ Electrique Continu ou de Haute‐Fréquence
Authors: Pantel R. , Ricard A. , Moisan M.
Published: July 2007

On a déterminé expérimentalement la distribution radiale de la densité des atomes métastables Ar(3P2) et résonnants Ar(1P1) dans deux types de décharges électriques de forme cylindrique: le plasma de la colonne positive d'une décharge en courant continu et le plasma produit par une onde étectromagnétique de surface. En comparant les distributions radiales de densité mesurées pour Ar(3P2) avec les distributions correspondantes calculées à partir du bilan radial création‐destruction de la population de ce niveau, on a pu obtenir les valeurs, en fonction de la position radiale, des coefficients de création et de destruction de ce niveau par collisions électroniques. Ces résultats sont obtenus pour diverses valeurs de la densité électronique sur l'axe. Les valeurs déjà, publiées de ces coefficients dans la colonne positive sont fondées sur l'hypothèse qu'ils ne dépendent pas du courant de la décharge, alors que l'on montre ici que leur valeur décroît en fait lorsque la densité électronique augmente. Ce travail montre de façon plus générale les possibilités considérables qu'offre l'examen de la distribution radiale de densité des atomes excités pour déterminer la cinétique de leur création et destruction.
Average Energy Variations and Trapping of Electrons in the Resonances of Rare Gases
Authors: De'Munari G. M. , Gabba L. , Giusiano F. , Mambriani G.
Published: July 2007

The effect of resonant elastic collisions of electrons in He on their “exact” mean energy variation for free path in the presence of a d.c. electric field is analysed.

Different values of E/N and both isotropic and anisotropic initial velocity distributions, just after collision, are considered.

It is shown that for sufficiently elevated values of E/N a necessary condition for electron (resonance) trapping becomes satisfied.

This result is discussed in the light of an interpretative model advanced to explain some electroluminescence phenomena in rare gases.
Fluctuation‐Dissipation Rellations for Equilibrium and Non‐Equilibrium States. Kinetic Equations for Many‐Particle Distribution Functions
Authors: Klimontovich Yu. L.
Published: July 2007

A kinetic formulation of fluctuation‐dissipation theorems (FDT) has been given.

The transition to the thermodynamic version of the FDT has been discussed.

Among the examples, a non‐equilibrium FDT, a FDT for chemically reacting systems and the interrelation to known kinetic equations has been discussed.
Geschwindigkeitsverteilungsfunktionen von Atomen und Ionen in verschiedenen Anregungs‐ und Ionisationsstufen in Niederdruck‐Entladungen bei hohem Ionisationsgrad
Authors: Valentini H.‐B.
Published: July 2007

Supposing free‐fall conditions the velocity distribution functions of atoms and ions in various levels in gas discharges at low pressures are calculated. In particular, plasmas at high degrees of ionization are considered. Solving the Boltzmann equation for the motions transverse to the wall of the discharge tube it is shown that the velocity distribution functions can considerably deviate from the Maxwellian and become non‐isotropic. Inelastic collisions with electrons and the ionization by electron impacts considerably determine the velocity distribution function of the neutral atoms. The velocity distribution function of the ions is also essentially determined by the electric field within the plasma. For the motions transverse to the wall the half widths of the velocity distribution functions do not only depend on the temperature of the wall, but on the electron density and on the electron temperature as well. At small electron densities the half widths for excited atoms and for ions can be narrower than the one for the ground state atoms. The charge exchange between atoms and ions is shortly taken into consideration.
Power Reflection, Transmission and Absorption Coefficients for a Mobile Collisional Magneto Plasma Slab
Authors: Arora B. B. , Phalswal D. R. , Varma N. L.
Published: July 2007

Coefficients of power reflection (R), transmission (T) and absorption (A) for a homogeneous, magnetised, collisional and moving plasma slab are derived and discussed by taking p‐polarized wave as the e.m. source wave and without imposing any restriction on the slab velocity. Effects of electron‐neutral collisions (νen), ion‐neutral collisions (νin) and the external magnetic field are included through momentum transfer equations. Plasma slab velocity (β = ν/c), electron ion densities (ωpe,i/ω) and the collision frequencies (νen,in) are found to cause significant change in the values of R, T and A, a numerical study of which is illustrated in the paper.
Experimental Investigations of Discharge Characteristics and Plasma Parameters of a Cylindrical Cathode Discharge in a Magnetic Field I Discharge Characteristics
Authors: Pavelescu G. , Bâlâceanu M. , Popovici C.
Published: July 2007

The experimental research on the correlation between the discharge parameters (electrode geometry, gas pressure, discharge voltage and current, magnetic field) of a cylindrical cathode discharge in magnetic field is presented. V‐I, I‐p und I‐B discharge characteristics are determined under various constructive and operating conditions. Invariant groups of discharge parameters for the discharges in the absence of the magnetic field are obtained. Experimental results are accounted for by a discharge mechanism wherein an important role is played by oscillating primary electrons.
Die Berechnung von Plasmaparametern aus Langmuir‐Sondencharakteristiken auf Digitalrechnern
Authors: Johanning D. , Lehmann H.‐R. , Seifert W.
Published: July 2007

Die vorliegende Arbeit stellt eine Übersicht der physikalischen Probleme dar, die sich bei der Computer‐Auswertung von im Magnetosphärenplasma der Erde gemessenen Langmuir‐Sondencharakteristiken ergaben. Nach einer Abschätzung der Meßbereiche für die Temperatur‐ und Dichtebestimmung wird auf die Ableitung physikalischer Größen aus der Strom‐Spannungs‐Charakteristik unter den besonderen Bedingungen eines kosmischen Experiments eingegangen.

Der zweite Teil der Arbeit ist der rechentechnischen Lösung der Aufgabenstellung gewidmet.
Solitary Surface Waves on a Plasma Confined by External Radiation
Authors: Gradov O. M. , Stenflo L.
Published: July 2007

We consider the nonlinear surface deformation of a plasma which is confined by external fields. It then turns out that a perturbation of the plasma‐vacuum boundary can propagate as a solitary wave with a velocity that depends on the external radiation intensity.
Needle Growth Induced by Corona Discharge
Authors: Okuyama F.
Published: July 2007

It is shown that the growth of a dense array of chromium microneedles is induced on a field cathode tip interacting with a negative corona discharge in ambient Cr(CO)6 of 1 – 5 × 10−2 Torr. The growth begins with the initiation of a corona discharge surrounding the tip, and it proceeds as long as the discharge is sustained. The needles emit field electrons during the growth, thereby sustaining the discharge, while the discharge lengthens the needles by supplying metallic particles to their tips. The morphological structure of the needles is strongly affected by an external magnetic field, leading us to hypothesize that the needle grow axially as the electron avalanches, originating at the cathode tip, propagate outward from tip.
Perturbed Arcs in Turbulent Axial Gas Flow IV. Thermal Reignition Experiments
Authors: Rothhardt L. , Michel G.
Published: July 2007

By means of the short‐circuiting of electric arcs burning in turbulent axial gas coolant flow and their reaction on a (recovering) voltage ramp the reignition in circuit breakers is modelled. Strong stochasticity of thermal reignition is demonstrated even under relatively weak conditions. Channels or nozzles showing flow detachment are further deteriorated by that. Corresponding low‐current test experiments are recommended for in‐scale circuit breaker development tests.
The Influence of Particles Interaction in Low‐Temperature Plasma on its Composition and Optical Properties
Authors: Sevastyanenko V.
Published: July 2007

A model theory of the influence of particles interaction in plasma on its composition and optical properties is developed.

The interaction of charged particles in plasma reduces the ionization energy of atoms and ions. The action of internal microfields in plasma on atoms and ions reduces the statistical weight of electron levels which affects the populations of excited states. The latter effect leads to an effective cutoff of partition functions and determines the behaviour of optical properties of plasma (of absorption coefficient and emissivity) at increased number densities of charged particles.

The formulas are obtained for calculation of the continuous and discrete spectrum in plasma taking into account the particles interaction. A non‐monotonic dependence of optical plasma density upon number density of charged particles is quantitatively explained. A satisfactory agreement is obtained with a large number of experimental data some of which were considered to be contradictory.

The method developed can be used for calculations in the field of atomic spectroscopy and low‐temperature plasma physics including increased densities of charged particles. The use of the formulas obtained in plasma diagnostics will enable one to avoid considerable errors.
[Russian Text Ignored].
Authors: [Russian Text Ignored]. [Russian Text Ignored].
Published: July 2007

Radial distributions of charged particles in an oxygen discharge depending on the relative concentration of negative ions are experimentally investigated. Corresponding change of the selfconsistent field along the radius of the discharge positive column at different pressures and currents are given.
Chaos in einem dissipativen Strahl‐Plasma‐System
Authors: Leven R. W. , Puttke R.
Published: July 2007

A system of four ordinary differential equations is derived to describe the behaviour of an unstable beam‐plasma‐system. Numerical studies show regular as well as chaotic long time behaviour of the wave amplitude. To characterize the chaotic attractors found in the region of maximum growth rates the Poincaré maps and the greatest Lyapunov Characteristic Exponents were calculated.
Zur Diagnostik der Ionenkomponente im Plasma der äußeren positiven Säule einer stromstarken, unmagnetisierten Argon‐Hohlkatodenbogenentladung
Authors: Schielke W. , Schrade F. , Melior J. P.
Published: July 2007

This paper reviews two measuring methods of the ions and their results in low pressure plasmas, if spectroscopical methods are not applicable to this situation. The behaviour of ions in the positive column of a high current argon hollow cathode arc was studied in dependence of various plasma parameters with the help of a gridded probe and a quadrupole mass spectrometer. The obtained results were analysed with simple theoretical models and measured electron distribution functions.
Entwicklung leistungsfähiger Stickstofflaser mit abgeschmolzenem Laserrohr
Authors: Gündel H. , Ross W. , Seliger K. , Volkmann H. , Erbs H. , Harendt A. , Irmer J. , Schöpp H.
Published: July 2007

For an increase of the laser pulse energy from longitudinally excited multiple electrodes tubes, experiments and model calculations have been accomplished. A variation of the electrode spacing in the laser tube has shown, that a maximum pulse energy could be achieved with about 40 mm electrode spacing. If barium titanat capacitors with a dielectric constant of 10000 in the pulse forming unit were applied, a voltage pulse transform occured enabling an increase of the laser power up to 50%. With a sealed off operated laser tube of 100 cm active length, a laser peak power of 600 kW and a pulse duration of 10 ns could be achieved. A tube with 200 cm active length generated a pulse power of 1.2 MW. The decrease of laser pulse energy with increasing pulse repetition rate can be explained by the decrease of impulse breakdown voltage. For an increase of the lifetime of laser tubes, appropriate technologies for the production of the tube have been developed.
Sudden Jumps, Hysteresis, and Negative Resistance in an Argon Plasma Discharge. II. Discharges in Magnetic Fields
Authors: Bosch R. A. , Merlino R. L.
Published: July 2007

Experimental observations on the behavior of low‐pressure, thermionic argon discharges in magnetic cusp and mirror configurations are presented. I–B characteristics showing jump and hysteresis behavior were found. In some cases, the sudden sharp decreases in discharge current that were observed were preceded by the onset of coherent, low‐frequency plasma oscillations, suggesting the possible role of instabilities.
Turbulence Driven Tearing Modes
Authors: Murtaza G. , Yu M. Y. , Shukla P. K. , Salahuddin M.
Published: July 2007

The effect of a turbulent background of density, electrostatic, and magnetic fluctuations on the growth of tearing modes is considered assuming three‐wave interaction. It is found that, depending on the background conditions, the turbulence can cause anomalous electron resistivity or viscosity, leading to enhanced growth rate.
Electrode Temperature in the Arc‐Discharge Zone Attachment
Authors: Zhukov M. F. , Pustogarov A. V. , Zavidei V. I. , Kucherov Ya. R.
Published: July 2007

The paper presents results of electrode‐surface temperature measurements in the arc‐discharge attachment zone. The investigations were carried out on tungsten electrodes in helium atmosphere and on zirconium electrodes in nitrogen atmosphere for currents within the range of 100…200 A.

The contribution of plasma radiation to pyrometer readings has been determined. The real temperature of the tungsten electrode surface was measured using the polarised radiation at the wavelength λ = 0.65μ m.

The energy distribution of arc‐spot radiation has been obtained for the spectral range of 0.4…1.2 μ m. The character of the arc‐spot radiation spectrum has been analysed.
Parametric Excitation of the Electron‐Acoustic Wave in a Multiply Ionized Plasma
Authors: Guha S. , Dwivedi C. B.
Published: July 2007

Parametric excitation of the electron‐acoustic wave (EAW) has been analysed using a hydrodynamical model. The plasma has been assumed to consist of multiply charged ions. The ratio (α) of the hotter ion concentration to that of the electrons is a sensitive parameter. The condition for the occurrence of the EAW is well satisfied for the smaller values of α. The growth rate of the instability gets enhanced by increasing α and the charge state of the hotter ions. The values of α can be varied within short range only.
Dense‐Plasma Research Using Ballistic Compressors
Authors: Hess H.
Published: July 2007

An introduction is given to research on dense (or nonideal) plasmas which can be generated to advantage by ballistic compressors. Some properties of ballistic compressors are discussed especially in comparison with shock tubes. A short review is given on the history of these devices for high‐pressure plasma generation. The present state of the art is reported including research on the two ZIE ballistic compressors.
Multiple‐Scattering Contributions to the Electrical Conductivity of Non‐Ideal Plasmas. I. Two Particle Scattering
Authors: Blümlein J.
Published: July 2007

On the basis of the Green's function formalism multiple scattering effects due to two‐particle scattering are investigated with respect to their influence on the electrical conductivity of dense, non‐ideal hydrogen plasmas. Both the linear response formalism and the rigorous kinetic treatment via the Kadanoff‐Baym equation yield equivalent results for this case. A local lowering of the conductance isotherms for is found to be a consequence of the disappearence of the last bound state of the shielded electron‐proton complex. Influences due to lowest order dynamical shielding effects are found to cause considerable lowering of the conductivity in this region due to photon polarization. We also discuss effects of multiple two‐particle scattering on the photon‐polarization itself.
Linear Response Theory in Zubarev‐Mc Lennan States and Electrical Transport in Plasmas
Authors: Blümlein J.
Published: July 2007

A generalization of Kubo's linear response theory to Zubarev‐Mc Lennan initial state is presented. In this framework the transport coefficients of nonideal plasmas are derived in the linear‐field limit. The formalism allows for the incorporation of conservation laws and the correct solution of the screening problem. Special characteristics of dilute systems are discussed.
Electron Energy Distribution Functions in RF Molecular Plasmas: The Role of Second Kind Collisions
Authors: Capitelli M. , Dilonardo M. , Winkler R. , Wilhelm J.
Published: July 2007

Electron energy distribution functions in rf molecular plasmas have been calculated by solving the time dependent Boltzmann equation in the presence as well as the absence of vibrationally and electronically excited molecules and thus of first kind and second kind (superelastic) collisions with them. The results, which refer to a model plasma composed by three components (the ground state, a lumped vibrational state and a lumped electronic state), show that these collisions with vibrationally and electronically excited molecules strongly affect the modulation of the electron energy distribution function and related quantities.
A Numerical Study on Current Drive by Electron Cyclotron Waves in a Toroidal Plasma Device
Authors: Some,slan M. L.
Published: July 2007

A survey of the main features of ECR current driving in toroidal plasmas is presented. Numerical calculations are performed in order to obtain the spatial profiles of the ECT energy deposition and of the correlated current density as a function of temperature and of the direction of the wave vector with respect to the toroidal magnetic field. The results indicate a very strong dependence of the ECR absorption profiles and of the driven current densites on the direction of launching of the wave.
Megagauss Magnetic Field Generation in Laser Produced Plasmas due to Self‐Focussing of the Laser Beam
Authors: Prabhakar M. V. H. V. , Srivastava M. P.
Published: July 2007

The magnetic field generated in a plasma due to the irradiation of a Gaussian laser beam is estimated, taking into consideration the self‐focusing effect of the laser. It is found that a self focusing of the beam propagating in a plasma increases the magnitude of the magnetic field and it is comparable with the measured values.
Plasma Production of TiO2 from TiCl4
Authors: Musa G. , Ionescu Gr. , Lungu C. P. , Mustatá I. , Popa S. , Chichirez I. , Seicaru O.
Published: July 2007

The TiO2 production by a 1–10 kW dc power plasmatron from TiCl4 and O2 is described. The reaction chamber material and geometry as well as AlCl3 additive influence on the chemical plasma reactions are presented and discussed.
Study of an Underexpanded Plasma Jet
Authors: Anders A.
Published: July 2007

Supersonic jets (Mach number M = 1.4 – 2.0) of dense plasma were produced by a plasmatron in a pulsed regime. The shock structure was investigated by fast mirror cameras, by the schlieren technique and by probe and spectroscopic methods. It was found that during jet expansion the bow shock ahead the gas‐plasma interface and the shock behind it are superimposed with the quasistationary shock structure which includes the Mach disk. Whereas the plasma in the discharge chamber is in LTE (nE ≈ 5 × 1023 m−3, T ≈ 14000 K), the electron density of the expanding jet plasma falls to a plateau value of nE ≈ 5 × 1019 m−3 below the LTE limit. At this phase, the jet plasma formed a ball‐like turbulent plasmoid which moves at a subsonic velocity through the air up to some milliseconds.
Limits of the Physical Relevance of Numerical Investigations of the Chaotic Beam Relaxation in an Electron Beam‐Plasma System
Authors: Kruscha K. J. G.
Published: July 2007

The chaotic relaxation mechanism of a monoenergetic electron beam in a strongly dissipative plasma is investigated in the framework of the single wave theory. An information theoretical quantity is introduced that describes the information loss of the beam system in course of time. It is shown that the numerical calculation of a discrete macroparticle approximation of the continuous beam system loses its physical relevance if the information loss exceeds a critical value which is determined by the number of macroparticles. Moreover, a method is proposed in order to quantify the degree of chaotic behaviour of the beam‐plasma system with a minimum of additional numerical effort.
Measurements of Electrical Discharge Properties of a Transverse‐Flow CO2 Laser
Authors: Ose E. , Schumann A. , Triebel W.
Published: July 2007

This paper deals with investigations of the spatial structure of the electrical potential, the current density, the gas temperature and the reduced electrical field strength in the discharge volume of a transverse gas flow CO2‐laser in dependence on the geometry of the electrodes. The data were obtained by means of Langmuir double probes. The results are compared with optical measurements applying a probe laser resonator.
Nonequilibrium Ionization by Vibrationally Excited Molecules in Supersonic Flows
Authors: Fomin N. A. , Krauklis A. V. , Rothhardt L. , Samtsov P. P. , Soloukhin R. I.
Published: July 2007

The results of experimental investigations on thermal nonequilibrium ionization in CO2: N2: He mixtures are presented. Measurements of electron density, ne, in vibrationally excited nitrogen were made in a supersonic flow with different CO2 contents as well as in a CO2: N2: He = 1 : 5 : 4 mixture laser gas. The mixtures were heated in a shock tube and expanded through a supersonic nozzle. Furthermore, supersonic mixing of N2 and CO2 + He was used in some experiments. The measured values of ne in the plenum chamber and in the supersonic nozzle are reported, and the processes responsible for nonequilibrium ionization in a laser‐active medium are discussed.
Influence of surface shape on DC surface breakdown characteristics under metallic‐particle contaminated conditions in SF6 gas
Authors: Hara Masanori , Lee Hyeong‐Ho , Egashira Takashi , Oyama Kazutami
Published: July 2007

The influence of a metallic particle attached to a supporting insulator is remarkable in decreasing the dielectric strength in an SF6 insulated apparatus. To solve this problem, a series of studies has been conducted on a method of improving the particle‐initiated breakdown performance.

In this paper, dc breakdown voltage characteristics and the breakdown mechanism are investigated under metallic‐particle contaminated conditions in SF6 gas by varying the particle condition and the surface shape of the acrylic plate with a rod‐plane electrode.

The main results show that a rib increases the breakdown voltage by a corona stabilization effect and the elongation of discharge path, but a groove decreases its effect drastically at lower gas pressures. The breakdown voltage at pressures higher than 4 atm may be estimated on the basis of the discharge‐maintaining field and the discharge length which depend on the gas pressure and the surface shape.
A monitoring of superconducting magnets by acoustic emission
Authors: Nomura Harehiko , Tateishi Hiroshi , Onishi Toshitada
Published: July 2007

Since superconducting magnetc (SCM) are going to be indispensable for magnetic levitated trains, nuclear fusion, magnetic resonance imaging, rotational machines, etc., great reliance must be placed on their repetitional operations.

However, without appropriate evaluating methods, techniques with such high promise must remain at the scientific level and difficult to tranfer to real human technologies.

SCM, used under dynamical operation and linked with other electromagnetic systems, induce high voltage which makes the monitoring of superconducting to normal transitional voltage difficult to distinguish.

To solve the forementioned problem, monitoring SCM by acoustic emission (AE) has been found to be effective, particularly during their dynamical energizing. To demonstrate this, this paper reports primarily on how to monitor the 3‐MJ SCM, and presents some results of experiment. These results were obtained by the counting and locational mode of AE in pulsed and repeated operations of the magnet.

Finally, some discussions are presented on the AE monitorings regarding the main issues to be addressed in the future.
Research on correlation between flux distribution and flux control characteristics of ferrite orthogonal core
Authors: Oka Hideo , Biringer Paul P.
Published: July 2007

This paper considers the flux distribution in ferrite orthogonal cores. To understand the operation of an FOC, the flux distribution must be known. We classify the flux components into four parts according to the flux pattern by using a flux distribution diagram. The flux control characteristics can be obtained by considering the component fluxes. The result of the analysis is a better understanding of the role of the component fluxes in improving the performance of the flux control characteristics.
Edge effect and independently supplied slot currents in tubular linear induction motors
Authors: Onuki Takashi , Numata Hiroyuki , Yamamura Tsugio
Published: July 2007

The linear induction motor (LIM) is divided structurally into the flat and the tubular‐type. This paper examines one kind of tubular linear induction motor whose primary configuration consists of four pieces of a flat‐type core. We call this type of motor “the square tubular LIM.” The square tubular LIM has various merits of the cylindrical tubular LIM in addition to those of the usual flat‐type LIM. The two remarkable features of the square tubular LIM that the flat‐type LIM does not have are as follows.

The first feature is that it has no edge effect, and the second is that the normal force in secondary conductor is cancelled by that of the opposite side of the secondary conductor. In comparison with the cylindrical tubular LIM, moreover, the square tubular LIM is easy to manufacture and maintain. The tubular LIM also has a feature that its primary winding is a kind of ring winding. Thus we can supply independently the primary current in each slot and hence easily obtain various winding schemes.

Finally, the features of the square tubular LIM are studied. After numerically analyzing an experimental model, the motor is driven by the independently controlled slot currents, resulting in the expected performance.
Arc damage characteristics of inter‐anode insulators in MHD generator
Authors: Kato Ken , Takano Kiyonami
Published: July 2007

The inter‐anode arc caused by a Hall field is driven by a magnetic field into the anode wall in an MHD generator, which limits the lifetime and performance of the generator.

The arc damage to inter‐anode insulators of an MHD generator has been studied experimentally to obtain basic data for the design of the inter‐anode insulation. The experiment was conducted using a pair of electrodes with an insulator between them. Arc currents were supplied from a dc power source and magnetic field was applied perpendicularly to the arc current. Experimental parameters are the insulator thickness, arc current, magnetic field and insulator materials. Quartz glass, boron nitride, magnesia, alumina, silicon carbide, silicon nitride, etc., were tested and evaluated.

The following conclusions are evident from the experiments. Boron nitride and quartz glass are the most promising inter‐anode insulators. Boron nitride has a higher arc voltage and longer cutting time than quartz glass, and it is the best material. The cutting time is approximately proportional to the −0.4th power of the magnetic field. The loss of insulator is approximately proportional to the 0.7th power of the arc current. The arc voltage increases linearly with the inter‐anode gap length. Also, it increases with magnetic field, but decreases with increase of arc current. An equation which approximates to such relations of arc voltage versus inter‐anode gap length, arc current and magnetic field has been obtained. The standard deviation of the error of this equation is 12 percent for boron nitride and 15 percent for quartz glass.
Methods to build neural networks for evaluation of state variable patterns
Authors: Nishimura Kazuo , Kawasaki Miho , Shimada Tsuyoshi
Published: July 2007

Evaluation of the system state is becoming imperative in supervising and controlling huge systems such as power generation and transmission systems and industrial plants.

This paper discusses two methods of building the neural networks: one is based upon backpropagation, and the other is a new method proposed herein. Unlike backpropagation which forms the completely distributed activation structure of neurons, the proposed method enables self‐organization of the modules which are activated selectively to an input pattern. The new method not only makes a biologically natural structure of neural network but also shortens considerably the learning time by localizing the links to be updated in the learning process.
Output voltage control method of PWM‐controlled cycloconverters with space vectors
Authors: Ishiguro Akio , Furuhashi Takeshi , Okuma Shigeru , Uchikawa Yoshiki , Ishida Muneaki
Published: July 2007

A new output voltage control method for PWM‐controlled cycloconverters with space vectors is proposed in this paper. Results are as follows:.

(1) The classification and the systematic behavior of the space vectors of PWM‐controlled cycloconverters are clarified through the analysis.

(2) A new output voltage control method that makes excellent output voltage waveforms is proposed using the results of this analysis.

(3) Feasibility of the proposed output voltage control method is confirmed by simulation.

(4) Output voltage waveforms of the PWM‐controlled cycloconverters are compared with those of the PWM‐controlled inverters, using the performance index of variance of time‐integral of higher harmonic components. Therefore, the proposed control method may reduce both acoustic noise and torque ripple of induction motors.
A method for locating fault section by using sequential information at substations
Authors: Goda Tadahiro , Kyomoto Sumie , Takegaki Morikazu
Published: July 2007

This paper presents a new real‐time method for locating fault section at substations. When a fault occurs, considerable information resulting from protective relay operation and circuit‐breaker operation is recorded. Using this information an attempt is made to locate the fault section, especially by considering the sequential relationship of the information and by dividing fault areas.

Primarily, in this method, the fault area is divided into several sections based on protection area and operation time of protective relays. Next, expecting subsequent operation of backup relays, the “waiting time” for reasoning is given to each divided section. After a lapse of “waiting time,” all the suspected fault sections are extracted and given priority based on the empirical knowledge of experts.

A prototype of the expert system was developed for fault section location, which was applied to various complicated fault cases. The effectiveness of the method was proved even in case of multiple faults and no‐operation of protective relays the circuit breakers.
Barrier effect under nonuniform field in atmospheric pressure SF6 gas
Authors: Miyagawa Masaru , Yoshida Tetsuo , Masaki Nobuo , Ohtake Shiro , Ohshima Iwao
Published: July 2007

Generally, it is known that insertion of a barrier under a nonuniform field in air increases the flashover voltage. This is called the barrier effect. However, there are many uncertainties that remain to be clarified about the barrier effect in SF6 gas. Therefore, the influence of the barrier shapes and positions on the flashover voltage for the lightning impulse voltages and voltages (50 Hz) is examined by inserting a barrier between a hemispheric‐end rod and a plate in SF6 gas under near‐atmospheric pressure. As a result, the following findings were obtained:.

(1) Insertion of a disk‐shaped barrier reduces the flashover voltage; a cup‐shaped barrier whose surface curves almost along the equipotential line increased the flashover voltage by 30 to 40 percent;.

(2) trapped charge on the barrier surface is of the same polarity as the applied voltage and the magnitude of positive charge was greater than that of negative charge. It was found also that there is a correlation between the amount of trapped charge and the flashover voltage; and.

(3) application of a barrier under a nonuniform field in the atmospheric pressure SF6 gas helps reduce the size of, for example, a cubic‐type gas‐insulated switchgear.
Zero magnetic field type magnetic field sensor
Authors: Sonoda T. , Ueda R.
Published: July 2007

This paper presents a new magnetic field sensor named the zero magnetic field type, on the basis of its principle of operation, which is as follows: when the magnetic field level in the core used as a sensor is shifted by an unknown field to be detected, a controlled field is so superimposed in the opposite direction to the unknown field that the original zero magnetic field state is resotred. Then the unknown field can easily be detected from the controlled field. Consequently, detection performance is expected to be unaffected by geometrical configurations, magnetization properties, and demagnetization effects of the core used as a sensor. Moreover, temperature variations of the core and the existence of resistance and leakage inductance in the windings arranged on the core also do not directly degrade performance.

This paper certifies that the proposed sensor certainly has the forementioned properties. In addition, the following are clarified: (1) the upper limit of the detectable range does not exist in principle; (ii) the accuracy is 0.02 percent for the full scale 20 kA/m and realizes the order of 4 × 10−4 percent/oC for temperature variations of −76o C to 300oC; (iii) the magnetization property required of the core used as a sensor is that it has as sharply a rectangular B‐H loop as possible; (iv) as a result, sensor design is greatly simplified.
Robust stabilization of a magnetic suspension system using H∞ Control Theory
Authors: Matsumura Fumio , Fujita Masayuki , Shimizu Masanao
Published: July 2007

This paper presents the robust control design of a magnetic suspension system for a flexible beam which is a simplified model of an elastic rotor in a magnetic bearing system. To stabilize this magnetic suspension system which is unstable in nature, the Hinfin; control theory is applied for a design of the control system.

To apply the Hinfin; control theory, a statespace model of an augmented plant with frequency‐weighting functions is constructed. This augmented plant has two inputs which are the exogenous inputs and the control inputs, and two outputs which are the sensor outputs and the regulated outputs. Here we consider the mixed sensitivity problem. The Hinfin; controller is implemented by a digital controller which is able to execute the computations very quickly.

For the evaluation of the control performance, several experiments are made. The robustness of the closed‐loop system is confirmed by the experimental results. The result of this study is useful for the control design of a magnetic bearing system.
An expert system for XPLE cable deterioration diagnosis and life forecasting
Authors: Asari Masahiro , Iwamoto Shinichi , Okamoto Tatsuki , Fukagawa Hiromasu
Published: July 2007

The recent increase in the demand for power in urban areas has caused changes in the way power is supplied. Underground distribution systems have been introduced for convenience in urban areas and to prevent injuries in case of a crisis. As a result, many new types of power cables are being used. One type, XPLE cables (also called CV cables) have been rapidly taking the place of conventional cables such as OF or SL cables since the 1960s because of their relatively easy installation and maintainability. However, distribution cables used under severe environmental conditions deteriorate rapidly (due mainly to water treeing), and some cables experience insulation breakdown. Therefore, many diagnostic methods have been developed, though they have not been very effective. By combining methods, a high reliability can be achieved in comparison to the use of a single method. However, processing the data is difficult for on‐site personnel, so many experts are required. But there is a lack of qualified experts, hence we have turned to the development of expert systems.
Development of advanced power system analog simulator
Authors: Doi Hirosuke , Goto Masuo , Kawai Tadao , Suzuki Tomohiro , Yokokawa Sumio
Published: July 2007

The digital simulation method has been utilized to analyze phenomena in power systems. Since different algorithms can be applied, depending on the phenomena to be analyzed, digital simulation allows for high‐precision analysis.

However, it also has a disadvantage: it produces continuous phenomena which occur in actual systems only fragmentarily. Thus, when discussing important projects at research centers such as IREQ in Canada, an analog simulator issued to continuously analyze the phenomena from the moment the fault occurs until steady state.

These analog simulators, however, consist of only a few generator models. They are only effective for analyzing phenomena in small‐scale systems and do not allow for analysis of phenomena in large‐scale systems over a long period of time.

For this reason, the Kansai Electric Power Company (KEPCO) in cooperation with Hitachi, Ltd., and Fuji Electric Co., Ltd., has developed the world's largest power system simulator (APSA: Advanced Power System Analyzer). The simulator will be used to analyze the evolution of accidents in actual systems and to analyze continuous system phenomena over a long period.

This paper describes an outline of the simulator.
Adaptive control‐based high‐performance drive system implementation of traveling‐wave‐type ultrasonic motor
Authors: Izuno Yuji , Nakaoka Mutsuo
Published: July 2007

In recent years, ultrasonic motors (USM) as new actuators have attracted special interest. Several kinds of constructions and characteristics of USMs have been reported so far. Of these USMs, a traveling wave‐type USM has many characteristics such as: high torque in the low‐speed range, large holding torque based upon frictional force, flexible free forms, compactness in size and low magnetic noise. In practice, an inherent mechanical resonant frequency and a velocity amplitude of USM are changed largely according to operating temperature due to frictional drive, load disturbance torque, and applied voltage levels. Therefore, it is necessary to develop a new control system which solves these items and always supplies the required power with high efficiency and high performance in the practical applications.

This paper proposes mainly a new sensorless high‐performance control scheme of an inverter‐fed ultrasonic motor, which is based on a control system technology with two feedbacks incorporating automatic resonant frequency tracking and constant velocity amplitude control strategies. This control system is realized in terms of a high‐frequency chopper and a two‐phase series/parallel resonant inverter. The experimental results are demonstrated and discussed compared with the theoretical ones.
66/77‐kV C‐GIS using composite insulation in SF6 gas
Authors: Masaki Nobuo , Yoshida Tetsuo , Miyagawa Masaru , Ohshima Iawo , Matsuzawa Kikuo
Published: July 2007

A second‐generation model of cubicletype gas‐insulated switchgear (C‐GIS) with composite insulation incorporating SF6 gas has been developed. The design does not require a gas process in field assembly; it has high reliability and its installation is more rapid; and a further reduction in size is achieved. The design principles are described in detail.
A new calculation method of voltage rise of transmission towers and transmission lines by lightning stroke and calculated results
Authors: Motoyama Hideki , Matsubara Hiroji
Published: July 2007

New formulas for the surge impedances of transmission towers and transmission lines in lightning surge are derived. A comparison of results calculated by the proposed formulas with the experimental results show nearly the same wave crest values and wave‐forms. It is demonstrated that a large portion of the input current flows into the tower and only a small current flows into the ground wires. This fact is very important in investigating lightning performance in transmission towers and transmission lines. The results will be helpful in developing improved modes of transmission system performance.
Recognition of partial discharge pattern of electrode voids by neural network
Authors: Yanagisawa Takashi , Iwamoto Shinichi , Okamoto Tatsuki , Fukagawa Hiromasa
Published: July 2007

A back‐propagation neural network model is used to identify electrode types involved in partial discharge (tree, IEC (b), CIGRE method I) and to estimate the shapes of the cylindrical electrode voids, based on the specific charge‐phase characteristics of the different electrode types.
Approximate method for calculating the impedances of multiconductors with cross sections of arbitrary shapes
Authors: Ametani Akirhiro , Fuse Ikuko
Published: July 2007

This paper proposes an approximate impedance formula of a conductor with an arbitrary cross section, and also a method of approximating the conductor by an equivalent circular conductor. Thus, a multiconductor system consisting of arbitrary cross section conductors is represented by circular cross section conductors, the impedance of admittance of which are evaluated by the existing impedance and admittance formulas.

The calculated results by the proposed method agree satisfactorily with measured results and numerical results by a finite‐element method which is, at present, the only way of calculating such impedance, but requires a large computation time and large memory. The proposed method might be very useful in evaluating the impedance and admittance of a multiconductor system consisting of arbitrary cross section conductors.
A VAR planning method with multiple power‐flow states
Authors: Aoki Kenichi , Nishikori Akimine , Fan Mingtian , Satoh Taiji , Nara Koichi
Published: July 2007

The goal of reactive power (VAR) planning is to find the minimum cost installation plan of new reactive power sources so that the system voltage is maintained within an acceptable level. The consideration of multiple contingency states, together with the discrete nature of VAR facilities, creates a large‐scale nonlinear mixed‐integer programming (MIP) problem.

To overcome the discrete nature of VAR facilities, an approximate method for the MIP problem is employed since the method is linear‐programming based and thus efficient for large‐scale problems. To treat the multiple contingencies, a resource directive decomposition approach is used in the proposed algorithm. If the number of installed VAR sources is fixed, the overall problem can be reduced to independent subproblems. Then subproblems are coordinated to give a VAR installation pattern in which installation cost becomes less than before. The algorithm proposed is tested for a 135‐node real‐size system and the results show the validity and effectiveness of the algorithm.
Control of magnetic bearing using the observer for unbalance
Authors: Mizuno Takeshi , Higuchi Toshiro
Published: July 2007

An unbalance on a rotor causes whirling motions of the rotor and alternating forces of the bearings in rotating machines. The authors have shown a magnetic bearing control system in which an unbalanced rotor can be suspended without whirling. The concept of designing the control system involved an observer estimating the effects of unbalance and then cancelling using the electromagnetic forces of the bearing.

With the control method applied, the position of the rotor can be maintained at the desired position with high precision. However, it is suitable for some machines to minimize the variation of exciting currents or vibratory force transmitted to the base through the bearing.

This paper presents control methods that can eliminate stationary alternating components from exciting currents or electromagnetic forces by using the output of the observer.

Another control method is presented in which feedback of the estimated signals of the displacements of the principal axis occurs; such signals are obtained by compensating synchronous observatory disturbances by use of the output of the observer. It is shown that the proposed three control methods are equivalent when unbalance stiffness due to the bias magnetic flux is null.
A case‐based construction method for a fault‐restoration support system in secondary power systems
Authors: Okuda Kenzo , Nakagawa Kazumitsu , Yamazaki Katsuhiro
Published: July 2007

The authors have already clarified that case‐based reasoning (CBR) is very useful for the fault‐restoration support system in electrical power networks. This paper describes the case‐based construction method, adaptation and modification method of a case which is a fundamental process of CBR, and the results of evaluation.

The following points were clarified through the simulations of fault restoration under various conditions with electrical power networks of practical scale: (1) a case‐based construction method and the guide to the selection of cases which should be included in the case were made clear. Restoration plans which include many cases are registered in the base. Cases which would require long computation time are also registered in the case base. In the application which requires high‐speed processing, such as fault restoration, there exists an optimum value in the total numbers of cases in the case base; (2) the function of load switching which is essential to perform adaptation and modification of a case flexibly was studied and embedded in the system herein. Inference power was augmented by the implemented of this function, and optimum for suboptimum solutions were obtained. Processing time with CBR is considerably shorter than other methods, and this feature is remarkable with complicated cases.