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Corrosion Behavior of Zn and Zn-Al Alloy Coated Steels under Cyclic Wet-dry Environments
Nishikata, Atsushi,Yadav, Amar Prasad,Tsutsumi, Yusuke,Tsuru, Tooru 한국부식방식학회 2003 Corrosion Science and Technology Vol.2 No.4
Atmospheric corrosion behaviors of Zn, Zn-5%Al and Zn-55%Al coated steels have been investigated under cyclic wet-dry environments containing chloride ions. The wet-dry cycle was camed out by alternate exposure to immersion in 0.5 M (or 0.05 M) NaCl solutions and dring at 25℃ and 60 %RH. The polarization resistance R_p and solution resistance R_s, were monitored by AC impedance technique. From the obtained I/(R_p), and I/(R_s), values, the corrosion rate of the coatings and the Time of Wetness (TOW) were estimated, respectively. Effects of chloride ions and TOW on the corrosion rates of Zn, Zn-5%Al, Zn-55%Al coatings and amearance of red rust (onset of underlying steel corrosion) under wet-dry cycles are discussed on the basis of the corrosion monitoring data.
Shoji Nishikata,Tatsunori Sato,Akira Ishizaki 전력전자학회 1995 ICPE(ISPE)논문집 Vol.1995 No.10
A new and simple analytical approach for a self-controlled synchronous motor in which the magnetic saturation is taken into account is proposed. The operation limit for constant-power driving with field weakening is discussed, and it is shown that the speed control region becomes narrow if the magnetic saturation is considerable. The effects of short-circuit ratio are also examined, and it is shown that a wide speed range is obtained if short-circuit ratio is large. The effects of saturation on the allowable transient change in the field voltage are finally discussed.
Kim, Je Kyoung,Nishikata, Atsushi,Tsuru, Tooru 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.5
When the steel, containing scrap elements like copper, is used as reinforcing steel bars for concrete, the steel is exposed to alkaline environments. In this study, AC impedance technique has been applied to the monitoring of corrosion rates of iron and several Fe-Cu (0.4,3,10wt%) alloys in a wet-dry cycle condition. The wet-dry cycle was conducted by exposure to alternate conditions of Ihour-immersion in a simulated pH10 concrete solution (Ca(0H)₂) containing 0.01M NaCl and 3hour-drying at 298K and 50%RH. The corrosion rate of the iron is greatly accelerated by the wet-dry cycles. Because the active FeOOH species, which are produced by the oxidation of Fe(Ⅱ, Ⅲ)oxide in air during drying, act as very strong oxidants to the corrosion in the wet condition. As the drying progresses, iron shows a large increase in the corrosion rate and a small shift of the corrosion potential to the positive values. This can be explained by acceleration of oxygen transport through the thin electrolyte layer. In contrast to iron, the Fe-Cu alloys show low corrosion rates and the high corrosion potentials in whole cycles.
Yamashita, Ken-Ichiro,Nishikata, Shoji Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.1
An electric power compensation system for a DC transmission system with an integrated wind turbine generator is proposed. The proposed compensation system consists of a synchronous generator and a duplex reactor. This apparatus is connected to the sending-end circuit of the DC transmission system. A set of steady-state equations of the system is first derived. Then, the effect of the duplex reactor, which can eliminate the sending-end grid current distortion due to commutation of the converter, is explored. The relationships among power at the sending-end circuit are also revealed. It is shown that fluctuations in the sending-end grid power due to changes in wind velocities are compensated with the proposed system. Finally, the effects of the sending-end grid conditions on the steady-state characteristics of the system are studied.
Studies on a Wind Turbine Generator System using a Shaft Generator System
F. Tatsuta,T. Tsuji,N. Emi,S. Nishikata 대한전기학회 2006 Journal of Electrical Engineering & Technology Vol.1 No.2
- In this paper a new dc-link type wind turbine generator system using a shaft generatorproposed wind turbine generating system is first explained. And the equations expressing the system are derived. Then the steady-state characteristics of the generating system are discussed. We use an experimental system that can simulate the characteristics of a wind turbine in this study, because it is hard to operate an actual wind turbine in a laboratory. In addition, the transient responses of this system are investigated when the velocity of the wind is changed. It is shown that experimental results were very close to the simulated ones, suporting the usefulness of theory.
Galvanic Corrosion of Zn/Steel Couple in Aqueous MgCl₂
( E. Tada ),( S. Katakami ),( A. Nishikata ) 한국부식방식학회(구 한국부식학회) 2017 Corrosion Science and Technology Vol.16 No.4
Galvanic corrosion tests of Zn/steel couples were conducted in 1 M NaCl and 1 M MgCl₂ solutions to investigate the impact of magnesium ion on corrosion behavior of the couples. Two types of Zn/steel couples were used for measurements of open circuit potential (OCP) and galvanic current. From the results of OCP transient of Zn/steel couples, the corrosion potential in 1 M MgCl₂ was a more positive value than that in 1 M NaCl during the sacrificial dissolution of Zn. However, earlier increase of OCP of the couples in 1 M MgCl₂ solution indicates that the sacrificial dissolution rate of Zn in 1 M MgCl₂ was enhanced more than that in 1 M NaCl, agreeing with the results on transients of galvanic current. This result is due to that cathodic reaction on the steel surface of the Zn/steel couple was enhanced in 1 M MgCl₂ by the occurrence of hydrogen evolution reaction.
Tatsuo Fujikawa,Ryuji Sugiura,Rie Nishikata,Tetsuya Nishimoto 제어로봇시스템학회 2017 제어로봇시스템학회 국제학술대회 논문집 Vol.2017 No.10
The peak mean contact pressure and the total transferred energy are discussed as the dominant parameters of bruise tolerance by blunt impact in order to obtain safety criteria for robot design in human-robot interaction. Impact tests are conducted using live pigs with the permission of the ethical committee. A 25 mm-diameter cylindrical impactor is used to represent moving parts of robots. Samples of soft tissue are stained, and capillary damages are investigated by microscopy. The results show that there is no capillary damage if the peak mean contact pressure is less than 1.3 MPa and the total transferred energy is less than 87 kJ/m2. The probability of injury as a function of these parameters is obtained using logistic regression of the the experiment results.