• Journal of Welding and Joining
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• v.23 no.1
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• pp.69-76
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• 2005

Recently, application of arc welding to galvanized carbon steel sheet is on the increasing Ould in the fields of automobile and construction industries. In arc welding process, zinc is evaporated in weld pool, even under the appropriate welding condition and produce blowhole and/or pit. Zinc gas cause instability of arc and increase spatter and fume. This research is purposed to minimize the heat-input and the formation of porosities in the welded joint of the galvanized carbon steel sheet using variable polarity AC wave pulse MIG welding system. An appropriate welding condition which showed low spatter and good bead appearance was acquired by applying the AC pulse MIG welding machine to DC duplicated MIG welding with the solid wire. When oxygen gas was added to shield gas of MIG welding for galvanized steel sheet, arc length was increased and arc stability was improved. In the AC duplicated welding, the loss of galvanized layer was decreased as the amount of heat-input was decreased when the EN ratio was increased under the condition that average welding current was evenly set.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.406-412
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• 1998

Such extraction conditions as the kinds of solvent, extracting temperature, extracting time, ratio of material to solvent and particle size of material, were studied to maximize the extraction of oleoresin from chipi. Larger amount of soluble solids were extracted from seeds with nonpolar solvents (hexane, pentane, ether) for extraction, because the seeds contained large amount of crude fats and monoterpene(limonene) volatile compounds. Larger amount of soluble solids were extracted from peel with polar solvents(methanol, ethanol) of extraction because of large amount of water soluble colors, sugars and oxygenated terpene bolatile compounds in the peel. The application of the solvents in intermediate polarity (dichloromethane, acetone) resulted in more effective extraction of soluble solid and volatile compounds. Expecially, dichloromethane was an excellent solvent in extraction of volatile compounds. In the concern of volatile compound recovery yield, the optimum extraction conditions, such as temperature, time, mixing ratio of material to dichloromethane and mean particle size, were $25^{\circ}C$, 10min, 1:10(w/v), 355~250${\mu}{\textrm}{m}$ for chopi peels and 3$0^{\circ}C$, 10min, 1:8(w/v), 355~250${\mu}{\textrm}{m}$ for chopi seeds, respectively.

• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.352-359
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• 1990

An effecient gas chromatographic method is described to be used routinely for the rapid profiling and identification of biochemically important organic acids. It involves the solid-phase extraction of organic acids from aqueous samples using Chromosorb P as the solid sorbent and diethyl ether as the eluting solvent, with subsequent triethylamine treatment. The resulting triethylammonium salts of acids were directly converted to volatile tert-butyldimethylsiyl derivatives, which were simultaneously analyzed by two capillary columns of different polarity, DB-5 and DB-1701, under the identical temperature programming condition. The retention index (RI) and area ratio (AR) values of each peak measured on DB-5 and DB-1701 enabled rapid identification of acids by computer RI library search and AR comparison. The application of the present method to the organic acid profiling of various complex samples is demonstrated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.251-256
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• 2012

This study deals with the location of partial discharges(PDs) for power cables and GIS using 2 PD sensors and long coaxial signal cables. Throughout the experiments by use of simulated PD pulses and corona discharges in the power cable system, it is found out that the impedance matching between the coaxial signal cable and the measuring equipment should be done for good S/N ratio and the on-site measurement using more than 100m-long coaxial signal cable is possible. In addition, new PD location algorithm with the polarities of PD pulses and the arrival time difference between two pulses was proposed and was proved through the partial discharge experiments for the cable joint defect and artificial void defect.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.187-188
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• 2008

In this paper, we have investigated water content of semiconductive shield materials for power cables, EEA(Ethylene Ethyl Acrylate) is used polymer matrix. And filler is used CNT(Carbon Nanotube) and CB(Carbon Black). EEA, CNT and CB is favor moisture. In case of EEA, it has polyolefin resin that strong polarity combination. To research water content, experimental method used KF(Karl Fischer). KF method is Electrochemical titration based on chemical reaction. As a result, specification by KEPCO(Korea Electric Power Corporation) is lower than 800ppm. CNT and CB ratio of 80 versus 20 is best specimen that had lowest moisture content. It seem likely to increase crosslinking rate, CNT between CB.

• Transactions on Electrical and Electronic Materials
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• v.16 no.5
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• pp.290-292
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• 2015

We have reported about bipolar resistive switching effect on Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]:Graphene oxide composite films, which are sandwiched between aluminum and indium tin oxide electrodes. In this case, I-V sweep curve showed a hysteretic behavior, which varied according to the polarity of the applied voltage bias. The device exhibited excellent switching characteristics, with the ON/OFF ratio being approximately two orders in magnitude. The device had good endurance (10⁵ cycles without degradation) and long retention time (5 × 10³ s) at room temperature. The bistable switching behavior varied according to the trapping and de-trapping of charges on GO sites; the carrier transport was described using the space-charge-limited current (SCLC) model.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.106-111
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• 2001

The freestanding GaN substrates were grown by hydride vapor phase epitaxy (HVPE) on (0001) sapphire substrate and prepared by using laser induced lift-off. After a mechanical polishing on both Ga and N-surfaces of GaN films with 100$\mu\textrm{m}$ thick, their polarities have been investigated by using chemical etching in phosphoric acid solution, 3 dimensional surface profiler and Auger electron spectroscopy (AES). The composition of the GaN film measured by AES indicted that Ga and N terminated surfaces have the different N/Ga peak ratio of 0.74 and 0.97, respectively. Ga-face and N-face of GaN revealed quite different chemical properties: the polar surfaces corresponding to (0001) plane are resistant to a phosphoric acid etching whereas N-polar surfaces corresponding to(0001) are chemically active.

• Transactions on Electrical and Electronic Materials
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• v.11 no.6
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• pp.257-260
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• 2010

Zinc oxide (ZnO) bottom-contact thin-film transistors (TFTs) were prepared by the use of injector type atomic layer deposition. Two hybrid gate oxide systems of different polarity polymers with silicon oxide were examined with the aim of improving the properties of the transistors. The mobility and threshold voltage of a ZnO TFT with a poly(4-dimethylsilyl styrene) (Si-PS)/silicon oxide hybrid gate dielectric had values of 0.41 $cm^2/Vs$ and 24.4 V, and for polyimide/silicon oxide these values were 0.41 $cm^2/Vs$ and 24.4 V, respectively. The good hysteresis property was obtained with the dielectric of hydrophobicity. The solid output saturation behavior of ZnO TFTs was demonstrated with a $10^6$ on-off ratio.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.139.1-139
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• 2001

Nowadays due to the remarkable advance of power electronics and micro controller, a Brushless AC servomotor which has the characteristics of the high inertia to torque ratio, the high power density, the maintenance free, and so on is being used widely in industrial robots, machine tools, and factory automation. In a conventional DC motor, the polarity commutation is performed of itself by mechanical brush and commutator, but the PM synchronous motor requires an electrical commutation according to the rotor position. Then for the maximum torque production PM synchronous motor has to be equipped with a controller which maintains the optimal phase angle between the stator field and the magnetic field ...

• Journal of the Korean Institute of Telematics and Electronics
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• v.16 no.1
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• pp.1-8
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• 1979

This paper describes a simple asynchronous time dime division multiplexing system developed by means of a synchronous delta modulation. In realizing asynchronous multlplexlng system time author deals with a technique of multiplexing communication channels by reversing the polarity of output pulse and superimposing the channels at a certain time Interval. The results of experiments on the number of error pulses, signal-to-noise ratio and frequency characteristics have shown fair agreements with the theoretically predicted ones related to the system.