Insulation characteristics of GIS under nonstandard lightning impulse oscillations: Insulation characteristics under double‐frequency oscillations with various frequencies and damping ratios

To improve GIS insulation specifications, it is important to recognize the insulation characteristics under oscillatory overvoltage waveforms occurring in the field. This paper describes investigations of insulation characteristics for double‐frequency oscillatory waveforms with various frequencies and damping ratios. It was found that minimum breakdown voltages (V_min) were irrelevant to frequency changes in the range of experimental conditions under the same damping conditions. On the other hand, V_min rose with the damping ratio rising under the same frequency conditions. The insulation characteristics at a valley of oscillation were investigated using actual breakdown voltages. It was found that the insulation characteristics were treated all‐inclusively based on the characteristics of V_min for damping time. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 11–19, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10245     

Motion and size estimation of a free moving metallic particle in GIS based on propagation properties of acoustic waves

We have investigated the propagation properties of Lamb waves and motion characteristic of free moving metallic particle in a gas‐insulated switchgear (GIS) tank to diagnose the insulation performance of GIS. We have proposed a new identification technique for defect location in GIS based on the time–frequency analysis of the Lamb waves using the Wavelet Transform. In this paper, we measured the acoustic signals excited by a metallic particle colliding with the tank sheath. Furthermore, we measured the moving particles under a high electric field in GIS using a high‐speed video camera. As a result, we examined the relationship between maximum lifting height and the flight time during subsequent impacts of a moving particle. Moreover, we estimated particle size based on the propagation properties of Lamb waves. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(1): 26–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20023     

Studies on the thermal degradation of synthetic polymers: 16. Estimation of the product yield on the basis of intensity function for thermal gasification of polyethylene

The kinetic equation for the pyrolysis gasification reaction of four kinds of polyethylene, differing from one another in average molecular weight, has been established. Differences in the molecular weight of the samples have no effect on the kinetic parameters when the molecular weight is 10⁴ or above. The intensity function, I_F=Tθ^a (K s^a), describing the severity of the decomposition conditions, has experimentally turned out to be a temperature throughout the residence time, θ, for reactions constrained by Arrhenius parameters A and E. The value of the exponent, a, may be found approximately from the kinetic parameters in this experiment. The values of the product yield calculated from the Arrhenius equation, $\text{k = A}\text{exp}\text{(}\text{?E}\text{RI}{}_{\mathrm{F}}\text{)}$, for a particular I_F, agree with the experimental values.     

Graft copolymerization of vinyl monomers in wool fibers

Graft copolymerization of vinyl monomers, mainly methyl methacrylate, in reduced, successively alkylated, or KCN-Treated wool fibers was performed in the redox LiBr–persulfate system without homopolymer. The reduction gives a striking effect in promoting the graft copolymerization. Methylation or ethylene recrosslinking of the reduced wool, especially the former, decreases the graft-on remarkably. By the KCN treatment in which the conversion of disulfide to lanthionine bonds occurs, the grafting is decreased in the bromide–persulfate system but promoted in the system with persulfate alone. Methylation or KCN treatment of wool as well as reduction brings about a great increase in the absorption of persulfate. The grafting of the lanthionine-containing wool in the redox system accompanied by the liberation of bromine might be retarded by the pronounced bromination of monomers over the inhibiting of homopolymerization, because the lanthionine bonds are more stable to bromine than the disulfide bonds. In general, disulfide bonds and the other easily oxidized components of wool may perhaps play an important role in regulating the bromination of monomers and in the graft copolymerization without homopolymer. The molecular weight of graft polymer is decreased distinctly with increasing extent of reduction of wool. From these results, the thiol groups on wool are considered to give predominantly graft centers by the radicalotropy from SO₄, OH·, and/or Br·.     

Estimating Sediment Budget at a River Basin Scale Using a Process-Based Distributed Modelling Approach

The paper presents a process-based distributed modelling approach for estimating sediment budget at a river basin scale with partitions of suspended and bed loads by simulating sediment loads and their interactions. In this approach, a river basin is represented by hillslopes and a network of channels. Hillslopes are divided into an array of homogeneous grid cells for modelling surface runoff and suspended sediments. Channels are defined by incorporating flow hydraulic properties into the respective hillslope grids as sub-grid attributes for modelling both suspended and bed loads. Suspended sediment transport is modelled using one dimensional kinematic wave approximation of Saint-Venant’s principles of conservation of mass and momentum. Transport capacity of runoff or streamflow is used to set the limit of suspended sediment transport rate. Bed load in channels is estimated based on the instantaneous water and hydraulic parameters. Fractional interchange between suspended load and bed load is then back calculated. The performance of the model was evaluated through a case study application in a large river basin in Japan. The model satisfactorily calculated the sediment transport and total sediment budget in the basin. The simulated bed load was found to be reasonable and consistent with the water flow and suspended sediment flux. The results showed the bed load can be expressed as a linear function of the suspended load. The fractions of different sediment loads also exhibit linear relationships with water discharge for the rising and recession limbs of the flood hydrographs. The case study has demonstrated that the process-based distributed modelling approach can efficiently describe the basin-scale sediment budgets with due consideration of the suspended and bed loads and their interactions in the hillslopes and channels.     

Fiber optic surface topography measurement sensor and its design study

This paper presents some aspects of design approach, modeling, and experimental measurement results of a fiber optic-based surface topography measurement sensor that can measure surface roughness as well as the distance between the sensor tip and a surface and surface inclination angles. The working principle of the sensor is based on the detection of light intensity reflecting from the surface being measured. The sensor is very small and easy to operate. It can be attached to a coordinate measuring machine (CMM) to measure surface position coordinates, inclination angles, and surface roughness in a noncontact manner at one measurement setup. A theoretical model of intensity distribution and intensity detection has been established for the sensor. A three-factor and three-level experiment was designed to investigate the relationship between sensor performance and sensor design parameters. Two second-order regression models have been generated, which show that the central distance between the emitting and receiving fibers of a sensor has the strongest influence on the effective range of the sensor; whereas, the critical angle of a receiving fiber influences the sensitivity of the sensor most.     

AT oligonucleotides inducing B lymphocyte activation exist in probiotic Lactobacillus gasseri

This study determined oligonucleotide sequences of mitogenic DNA derived from lactic acid bacteria (LAB). The chromosomal DNA, which was purified from 12 out of 16 strains of Lactobacillus acidophilus group LAB, induced proliferation of splenic lymphocytes. When DNA from L. gasseri JCM1131T was cloned and amplified using PCR, the mitogenic activities of B lymphocytes were significantly increased by 108 of 321 DNA clones. Ten high homologous nucleotide sequences were found as possible DNA sequences of mitogens, and were then chemically synthesized (sOL-LG1 to sOL-LG10). Two nucleotide sequences (sOL-LG7 and sOL-LG10) that consist of only A and T nucleotides (AT oligonucleotides) were characterized as B lymphocyte specific mitogens because they resulted in proliferation of B lymphocytes but not of T lymphocytes. sOL-LG7 preferentially bound to large B lymphocytes and enhanced the expression of the CD86 antigen more than the CD69 antigen on B lymphocytes. The findings show that mitogenic AT oligonucleotides are likely to restrict pre-activated subsets of B lymphocytes. This study demonstrated that novel AT oligonucleotides triggering B lymphocyte mitogenic responses exist in the nucleoids of L. gasseri and proposed that they have potential as applicants for the production of new functional foods, "Bio-Defense Foods".     

800 MHz v.c.o. for land mobile radio synthesisers

A compact voltage-controlled oscillator, covering 1000 channels with a single range, has been designed and fabricated using GaAs varactor diodes. A c.n.r. of more than 76 dB with 25 kHz offset from carrier and an s.n.r.of more than 52 dB are obtained. Their performance characteristics are described.     

Improvement of the longitudinal vibration system for the hybrid transducer ultrasonic motor

This paper presents a symmetric hybrid transducer ultrasonic motor designed to produce large longitudinal vibration stress in the rotor/stator contact interface for high-torque operation. The nodal plane of the longitudinal vibration mode was adjusted to match the rotor/stator contact interface, and the piezoelectric ceramic disks for the longitudinal vibration were installed at the nodal plane of the longitudinal vibration mode for effective excitation. An experimental motor, 20 mm in diameter, using the first torsional vibration mode and the second longitudinal vibration mode was manufactured. A maximum torque of 0.8 N.m was achieved in the prototype, an improvement over previous versions.     

An ultrasonically levitated noncontact stage using traveling vibrations on precision ceramic guide rails

This paper presents a noncontact sliding table design and measurements of its performance via ultrasonic levitation. A slider placed atop two vibrating guide rails is levitated by an acoustic radiation force emitted from the rails. A flexural traveling wave propagating along the guide rails allows noncontact transportation of the slider. Permitting a transport mechanism that reduces abrasion and dust generation with an inexpensive and simple structure. The profile of the sliding table was designed using the finite-element analysis (FEA) for high levitation and transportation efficiency. The prototype sliding table was made of alumina ceramic (Al2O3) to increase machining accuracy and rigidity using a structure composed of a pair of guide rails with a triangular cross section and piezoelectric transducers. Two types of transducers were used: bolt-clamped Langevin transducers and bimorph transducers. A 40-mm long slider was designed to fit atop the two rail guides. Flexural standing waves and torsional standing waves were observed along the guide rails at resonance, and the levitation of the slider was obtained using the flexural mode even while the levitation distance was less than 10 microm. The levitation distance of the slider was measured while increasing the slider's weight. The levitation pressure, rigidity, and vertical displacement amplitude of the levitating slider thus were measured to be 6.7 kN/m2, 3.0 kN/microm/m2, and less than 1 microm, respectively. Noncontact transport of the slider was achieved using phased drive of the two transducers at either end of the vibrating guide rail. By controlling the phase difference, the slider transportation direction could be switched, and a maximum thrust of 13 mN was obtained.