bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parametric Excitation of the Electron‐Acoustic Wave in a Multiply Ionized Plasma
Authors: Guha S. , Dwivedi C. B. 
Published: July 2007

AbstractParametric 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

AbstractAn 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

AbstractOn 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

AbstractA 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

AbstractElectron 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractSupersonic 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

AbstractThe 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractSince 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

AbstractThis 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

AbstractThe 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

AbstractThe 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

AbstractEvaluation 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

AbstractA 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

AbstractThis 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

AbstractGenerally, 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

AbstractThis 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

AbstractThis 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

AbstractThe 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

AbstractThe 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.