• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.229-234
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• 2003

As electrorheological fluid(ER fluid) has a characteristic that apparent viscosity varies when electric field applied, so rheological characteristic(yield stress & viscosity) changes in proportion to the electric field applied and the response time is very short within a few miliseconds . In case of using ER fluid for journal bearing as lubricant, it is estimated that it's possible to realize very effective journal bearing system that is not complicate and has a very quick response time. It is necessary to examine the influence of rheological characteristic that varies with electric field applied on bearing characteristic to apply ER fluid to journal bearing, however there are few studies for about that. As for the journal bearing, it comes under high shear flow mode that has shear rate range of $10^3\~10^4s^{-1}$ because rotational speed is very high and clearance is small. But most of the studies for about ER fluid issued until now is about the range of $10\~10^2s^{-1}$. So, there are a lot of difficulties to understand the characteristic offish shear flow mode and furthermore it is restricted to make an experiment for about the characteristic of ER fluid because of the limitation of experimental equipment. The equipment was prepared to make an experiment lot high shear flow mode that has the range of $10^3\~10^4s^{-1}$ using ER fluid that is composed of silicon oil with dispersed particle of starch. Using the above system, the fluid characteristic of ER fluid was studied.

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.214-221
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• 2001

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a $Ti:LiMbO_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1 V/cm to 60 V/cm at 60Hz through 100 kHz. Using a probe antenna of $10\;mm{\times}10\;mm$, the output voltage of $10^{-2}\;mV$ was measured with respect to the electric field strength of 0.1 V/cm at 60 Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.433-436
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• 2016

In the area of environmental chemistry of power plant, flow analysis of the reactor with built-in impeller is a very important part from the perspective of the improvement of the efficiency of the entire process. As a wide range of methods are being proposed for the analysis of the flow pattern within the reactor, this study analyzed the flow within the reactor according to the baffle structure (height) installed on the internal wall of the reactor in order to improve the reaction efficiency through the inducing of the up and down stirring with the reactor. As the results of the execution of the flow analysis for each of a diverse range of cases by utilizing the Computational Fluid Dynamics (CFD) method, it was possible to confirm that the flow is markdely improved by inducing the up and down stirring among the reactants within the reactor if the baffle is elevated to the level below the water surface. In particular, as the results of the analysis of the general cases in which the baffle is elevated all 4 steps and the cases in which the baffle is elevated only 2 steps, elevating the baffle only 2 steps achieve the same effect as the elevating of the baffle by 4 steps. Therefore, it was possible to expect to improve the efficiency with out the need to increase the use of electric power substantially if the outcomes of this study is applied to the actual sites of power plants in the future.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.6
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• pp.1-7
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• 2002

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a Ti:LiNbO$_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1V/cm to 60V/cm at 60Hz through 100KHz. Using a probe antenna of 10mm$\times$10mm, the output voltage of 10㎷ was measured with respect to the electric field strength of 0.1V/cm at 60Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.

• Journal of Sensor Science and Technology
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• v.31 no.1
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• pp.45-50
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• 2022

Multi-rod type Ag-AgCl electrodes have been developed for use in underwater electric field sensors. The developed cylindrical electrode had a diameter of 50 mm and a height of 130 mm. The electrode had five Ag-AgCl rods with a diameter of 2 mm and a height of 80 mm to enlarge the reaction surface area. Each Ag-AgCl rod was fabricated under the same conditions as the usual anodizing method in an electrolyte. The two developed electrodes were placed in the center of a 500-mm long, 400-mm wide, and 300-mm high acrylic tank filled with artificial seawater, at an interval of 100 mm, to evaluate their characteristics as uniaxial underwater electric field sensors. The underwater external electric field was generated using titanium plate electrodes installed at both ends of the tank. The noise level at 1 Hz of the developed electrode was approximately 3.7 nV/√Hz. The reception of the underwater electric field signal using the developed electrode was linear, within an error of approximately 0.6 %, in the range of 1-10000 ㎶/m at 1 Hz. In addition, its frequency response was flat within an error of 1.1 % in the range of 1-1000 Hz at 10000 ㎶/m.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.138-144
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• 2012

Recent environmental issues such as exhaust gas and greenhouse effect make the agricultural machinery market takes into account the hybrid and electric propulsion technology used in automotive engineering. Generally the agricultural machinery, particularly an agricultural tractor, needs large load capacity and long continuous operating time comparing with conventional vehicles. In case of a pure electric tractor, it is necessary for considering large capacity batteries and long charging time. Therefore we take an AER extended PHEV (All Electric Range extended Plug-in Hybrid Electric Vehicle) power transmission system in developing an electric tractor in this study. First we propose a PHEV powertrain structure in order to substitute the conventional diesel engine equipped tractor. And we performed the road tests using a conventional mechanical tractor with various load conditions, which were classified and statistically treated real agricultural works. The test results were analysed with respect to the power characteristics of the power source. Finally using the test result, we designed two-stepped reduction gear ratios in the proposed an electric tractor powertrain for carrying out typical agricultural works.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.220-226
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• 2002

Amorphous $Sb_{2-x}Bi_xTe_3$ (x = 0.0, 0.5 and 1.0) thin films were prepared by vacuum evaporation. The resistivity of 7he films decreases from 1.4{\times}10^{-2}$ to $8.84{\times}10^{-5}\Omega cm$ and the type of conductivity changes from p to n with the increase of the x value of the films. D.C. conduction studies on these films ate performed at various electric fields in the temperature range of 303-403 K. At low electric fields, two types of conduction mechanisms, i.e. the variable range hopping and the phonon assisted hopping are found to be responsible for the conduction, depending upon the temperature. The activation energy decreases from 0.082 to 0.076 eV in the temperature range of 303-363 K and from 0.47-0.456 eV in the second range of 363-403 K, indicating the shift of the Fermi level towards the conduction band edge and hence the change of the conduction from P to n type with the increase of the Bi concentration. Poole-Frankel emission dominates at high fields. The shape of the potential well of the localized centre is deduced and the mean free path of the charge carriers is also calculated.

• JOURNAL OF ELECTRICAL WORLD
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• no.10 s.154
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• pp.8-15
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• 1989

• Journal of the Korean Society for Railway
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• v.11 no.6
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• pp.569-574
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• 2008

Catenary and Pantograph are used to transmit electrical energy to electric railways. Catenary (Overhead Contact Lines) should be installed precisely and managed for stable train operations. But external factors such as weather, temperature, etc., or aging affect catenary geometry. Changed catenary stagger and height cause high voltage spark or instant electric contact loss. Big spark derived from contact loss can damage the pantograph carbon strip and overhead contact lines that might interrupt the train operations. Therefore, to prevent a big scale spark or electric contact loss, catenary maintenance are required catenary geometry measurement systems with catenary maintenance capability. In this paper, we describe the development of catenary height and stagger measurement system. The catenary height and stagger measurement system uses Acuity company's AR4000 Laser Range Finder for distance measurement and AccuRange Line Scanner for degree measurement. This system detects suspicious overhead line sections with excessive stagger and height stagger variance.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1096-1106
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• 2013

This paper presents the control of a Permanent Magnet Electric Variable Transmission (PM-EVT) for Hybrid Electric Vehicles (HEVs). Consisting of two electric machines, the EVT realizes the power split function in an electromagnetic way rather than in a mechanical way. A specific PM-EVT has been designed for Toyota Prius II. The control scheme of the entire vehicle is deduced using the Energetic Macroscopic Representation methodology. The energy management strategy yields local control references. A specific attention is paid for the field weakening for wide speed range. Simulation results are provided to illustrate the EVT modeling and control.