• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.451-456
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• 2002

This paper describes the properties of Temperature-Viscosity characteristics of hydrous and anhydrous ER fluids containing starch and titanium particle in silicone oil. ER effects arise from electrostatic forces between the starch particles and titanium particles dispersed in the electrically insulating silicone oil induced when electric field is applied. ER fluids under electric field have been found to provide resonable estimates of ER fluid viscosity variation characteristics. Yield shear stress of the ER fluids were measured on the couette cell type rheometer as a function of electric fields. The outer cup is connected to positive electrode(+) and bob becomes ground(-). The electric field is applied by high voltage DC power supply. In this experiment shear rates were increased from 0 to 200/equation omitted/ in 2 minutes.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.739-745
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• 2014

We have demonstrated a $Ti:LiNbO_3$ electro-optic electric-field sensor utilizing a $1{\times}2$ Y-fed balanced-bridge Mach-Zehnder interferometric (YBB-MZI) modulator, which uses a 3-dB directional coupler at the output and has two complementary output waveguides. A dc switching voltage of ~25 V and an extinction ratio of ~12.5 dB are observed at a wavelength of $1.3{\mu}m$. For a 20 dBm rf input power, the minimum detectable electric fields are ~8.21, 7.24, and ~13.3 V/m, corresponding to dynamic ranges of ~10, ~12, and ~7 dB at frequencies of 10, 30, and 50 MHz respectively. The sensors exhibit almost linear response for an applied electric-field intensity from 0.29 V/m to 29.8 V/m.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.354-356
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• 1997

In this paper, we study the distribution of surface charge density on polymer insulators. The electric field of polymer insulators is calculated by axisymetric 3-D FEM with dc source. And the surface charge density is calculated by electric scalar potential and boundary condition for electrostatic fields. Simulation model is the inclined type polymer insulator with a shed.

• 전력전자학회논문지
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• 제25권4호
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• pp.243-250
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• 2020

Energy harvesting is a recent technology involving the harvest and utilization of extremely small surrounding energy. Energy harvesting research is conducted in various fields. Triboelectric nanogenerators (TENGs) are energy harvesting technologies that use static electricity generated by physical movement or friction. Although TENGs generate output power in microwatt levels, they experience high internal impedance compared with other energy harvesting generators, thereby making the continuous transfer of electric power to loads difficult. This study proposes a power management system for TENGs that consists of three stages, that is, an AC/DC rectifier, an impedance coupler switch with a capacitor bank, and a DC/DC converter. In addition, the selection method of the AC/DC rectifier and DC/DC converter is proposed to maximize the amount of power transferred from energy harvesting areas. Furthermore, the impedance coupler switch and capacitor bank are discussed in detail. The validity and performance of the proposed three-stage power management system for TENGs are verified using a prototype system.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.73-77
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• 2015

Offshore wind farms extend a distance from an onshore grid to increase their generating power, but long distance and high power transmissions raise a lot of cost challenges. LFAC (Low Frequency AC) transmission is a new promising technology in high power and low cost power transmission fields against HVDC (High Voltage DC) and HVAC (High Voltage AC) transmissions. This paper presents an economic comparison of LFAC and HVDC transmissions for large offshore wind farms. The economic assessments of two different transmission technologies are analyzed and compared in terms of wind farm capacities (600 MW and 900 MW) and distances (from 25 km to 100 km) from the onshore grid. Based on this comparison, the economic feasibility of LFAC is verified as a most economical solution for remote offshore wind farms.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.27-33
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• 2004

Electro-theological fluid is recently used for the micro polishing of 3-dimensional micro-aspherical lens. It's also used for polishing small area defects on the wide flat wafer. Since ER fluid shows a behavior of viscosity changing under certain electric fields. micro polishing efficiency may be enhanced for certain cases. In this paper, a perfluorinated carbonyl fluoride oil based ER fluids was used to improve surface polishing rate and submicron-scale accuracy. As the polishing electrodes, micro size cylindrical tools had been used for maximizing the electric field. An experimental device, which was applied for micro polishing a number of wafers of 4inches in size and other workpiece. was made on a precision polishing system. It consisted of a steel electrode. a wafer fixture. l0㎃ current and DC 5㎸ power supply unit, and a controller unit. From the Experiments. the ER fluid is applicable for micro polishing of small parts.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전기설비전문위원
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• pp.233-234
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• 2008

We observed internal space charge behavior for two types of epoxy composites under dc electric fields to investigate the influence of water at high temperature. In the case of glass/epoxy specimen, homocharge is observed at water-treated specimen, and spatial oscillations become clearer in the water-treated specimens. Electric field in the vicinity of the electrodes shows the injection of homocharge. In aramid/epoxy specimens, heterocharge is observed at water-treated specimens, i.e. negative charge accumulates near the anode, while positive charge accumulates near the cathode. Electric field is enhanced just before each electrode. In order to further examine the mechanism of space charge formation, we have developed a new system that allows in situ space charge observation during ion migration tests at high temperature and high humidity. Using this in situ system.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.178-183
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• 2000

Electrorheological(ER) effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of zeolite and starch based ER fluid were reported. The ER fluids were constructed by mixing zeolite and starch power with two different dielectric oils. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply. The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to $200s^{-1}$ in 2 minutes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.2307-2308
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• 2008

We observed internal space charge behavior for two types of epoxy composites under dc electric fields to investigate the influence of water at high temperature. In the case of glass/epoxy specimen, homocharge is observed at water-treated specimen, and spatial oscillations become clearer in the water-treated specimens. Electric field in the vicinity of the electrodes shows the injection of homocharge. In aramid/epoxy specimens, heterocharge is observed at water-treated specimens, i.e. negative charge accumulates near the anode, while positive charge accumulates near the cathode. Electric field is enhanced just before each electrode. In order to further examine the mechanism of space charge formation, we have developed a new system that allows in situ space charge observation during ion migration tests at high temperature and high humidity. Using this in situ system.

• 한국연소학회지
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• 제17권1호
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• pp.37-47
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• 2012

Experimental study on comparison of diffusive-thermal self-excitation with buoyancy-driven one due to accumulation of partially premixed, preheated mixture in front of edge flame was conducted in horizontally and vertically injected laminar free-jet flames with an applied DC electric field of -10 kV. The application of horizontal injection method with the DC electric field to jet flames was experimentally designed to suppress heat-loss-induced self-excitation and thereby to highlight the definite difference between both diffusive-thermal and buoyancy-driven self-excitations with the same order of O(1.0 Hz), in that diffusive-thermal self-excitation has not been so far found experimentally in laminar jet flames. Flame stability maps in vertically and horizontally injected jet flames are presented. The distinct modes of individual self-excitation are shown to be well described by their own phase diagrams. The results show that buoyancy-driven self-excitation due to the accumulation of partially premixed, preheated mixtures in front of edge flame is branched from the buoyancy-induced self-excitation with O(10 Hz) due to a flame flicker. Once the buoyancy-driven self-excitation appears, it suppresses buoyancy-induced as well as diffusive-thermal self-excitation. The key characteristics for individual self-excitation are discussed and their functional dependencies of Strouhal number upon related physical parameters are also presented.