EMTP simulation of SLF interrupting performance for two serially connected arcs with different arc parameters

This paper shows the calculation of SLF interrupting performance for two serially connected Mayr‐type arc models with different arc parameters by using EMTP‐ATP Models. Arc model 1, assuming an air circuit breaker, has large arc time constant and large arc power loss. Arc model 2, assuming a vacuum circuit breaker, has small arc time constant and small arc power loss. It was not possible for arc model 1 to interrupt 300 kV‐63 kA‐90% SLF by itself. However, by connecting these arc models in series, interruption became successful, even if arc model 2 was reignited at low voltage a few microseconds after current zero. These computations suggested that serial connection of the two circuit breakers with different breaking characteristics would give a totally excellent circuit breaker by making the best use of advantages of each circuit breaker. EMTP‐ATP Models were very useful in solving the arc models, which are expressed by differential equations and coupled with the electric circuit. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 25–33, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10020     

Numerical simulation of dispersed flows and evaluation of interfacial area and volume fraction

Dispersed flows are numerically simulated using the lattice BGK method. The boundary condition for the lattice BGK method is proposed to simulate steady-state flow fields. The time variation and the spatial distribution of the interfacial area and the volume fraction are evaluated. It is shown that the dispersed phase is distributed similarly in time and space in the flow field. The interfacial area obtained by the numerical simulation is compared with that given by empirical correlations, and it is found that the dependency of the interfacial area on the volume fraction is reasonably simulated.     

Network centric approach to protection,control, and monitoring for power system

Due to the explosion in use of the Internet, it is expected that a variety of services will be provided through the communication network in the near future. Protection and control systems using the latest communication and information technology also allow for innovative solution to a wide range of power system problems. This paper describes a network‐centric approach to protection, control, and monitoring systems. When the proposed “Network” devices, server, and browser can communicate with each other, they can share information which can enhance the overall protection and control of the power systems. The paper includes: overview of network devices, key technologies, protection and control applications, issues, and conclusion. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 31–41, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20006     

A study on read‐back signal degradation of a pseudo‐contact head during seek motion of a hard disk drive

The read‐back signal degradation in seek motion with a pseudo‐contact head in a hard disk drive was studied. It was found by AES analysis that the pole tip surface of NiFe was covered with a decomposed layer of NiFe and carbon following seek motion. The read‐back signal degradation became larger with increasing thickness of the decomposed layer. An MFM study of the seek‐tested pole tip surface showed that the magnetic properties of the pole tip surface deteriorated by seek motion, and that the read‐back signal degradation increased with increase of deterioration of the magnetic properties of the pole tip surface. These results suggest that either the poor permeability of the decomposed layer on the pole tip surface and increase of spacing between the fresh pole tip surface under the decomposed layer and the disk surface decrease the flux flow from the disk magnetic layer into the pole tip, or that the decomposed layer on the gap short‐circuits the flux flow. It was found that the additive, cyclotriphosphazene, in a lubricant film, and a protective layer of carbon on a slider surface drastically reduced degradation. This revised version was published online in June 2006 with corrections to the Cover Date.     

Preface

Journal of Materials Synthesis and Processing -     

Magnetic suspension force in an induction bearingless motor with a squirrel cage rotor

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearing‐less motor, both 4‐pole and 2‐pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three‐phase windings, thus a 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and a simulation model of suspension force is then constructed. It is shown that the response and the phase of suspension force are delayed in the case of cage rotors. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 77–87, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20340     

Observations of cellular responses to diamagnetic forces acting on cell components

The magnetooptical measurements of the properties of living cells have a potentially large impact on cellular engineering and biotechnology because the noninvasive approach to applying magnetic fields on cells enables the detection of the dynamics of intracellular components under natural conditions. In this study, we examine a magnetooptical response in smooth muscle cells exposed to a vertical magnetic field of 5 T. The time course of the linearly polarized light transmittance of cells showed both a gradual decrease and fluctuations during exposure at 5 T. Real-time observations of smooth muscle cells and giant rodlike vesicles revealed that magnetic fields cause morphological changes in the cells and vesicles. In addition, results of the optical transmittance measurement of a fish scale indicate that cellular or tissue components are diamagnetically reoriented by magnetic fields.     

Reduction method for residual stress of welded joint using random vibration

Welded joints are used for construction of many structures. Residual stress is induced near the bead caused by locally given heat. Tensile residual stress on the surface may reduce fatigue strength. In this paper, a new method for reduction of residual stress using vibration during welding is proposed. As vibrational load, random vibration, white noise and filtered white noise are used. Two thin plates are butt-welded. Residual stress is measured with a paralleled beam X-ray diffractometer with scintillation counter after removing quenched scale chemically. It is concluded that tensile residual stress near the bead is reduced by using random vibration during welding.