• Journal of Welding and Joining
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• v.22 no.4
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• pp.43-49
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• 2004

Conventional method for electrode force application in resistance spot welding(RSW) processes is to use pneumatic cylinder. However, due to its inherent problems in pneumatic power system such as compressibility of air and poor transient response characteristics, new electrode force system with servo control are recently introduced in RSW machine. This machine is called “servogun”. The purpose of this study is to evaluate performance of servogun in case of spot welding of aluminum alloy. Aluminum alloy(A5052) sheets are spot welded using pneumatic gun and servogun. Both results are compared by means of macro cross-section etching test and tensile shear strength test. Numerous previous research have reported nugget with many voids and cracks are not uncommon defects in spot welds with aluminum alloy. The experimental results show similar defects in case of pneumatic gun. In contrast, use of servogun considerably reduced generation of voids and cracks. In case of step-wise increased forging force at the end of welding cycle with servogun, crack-free and void-free nuggets have been observed. The performance of servogun has been also verified by series of tensile shear test. Higher strength values have been achieved with servogun in comparison to that of pneumatic gun.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.1
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• pp.35-42
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• 1989

Electrical properties of both a monolayer at the air/water interface and Langmuir-Blodgett films sandwiched between aluminum electrodes are studied using a current-measuring technique. A change in induced charges on an electrode suspended in the air was measured in combination with the surface area isotherm in the electrical measurement of the monolayer. A change in induced charges on an electrode is measured while heating the sample in the electrical measurement of the LB films. From both measurements, we elucidated that a spontaneous polarization plays very important role in the electrical properties of both a monolayer at the air/water interface and LB films sandwiched between aluminum electrodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.115-115
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• 2012

반도체/디스플레이 산업분야의 발전으로 진공 공정 기술력 또한 증진되고 있다. 반도체소자의 초미세화, 진공부품의 대면적화가 진행 되면서 진공 공정 중에 발생하는 오염입자를 제어하는 것이 이슈가 되고 있다. 오염입자는 플라즈마의 물리적인 부식과 활성이 높은 화학반응에 의해 진공부품에서 부식이 진행되어 발생하며, 이는 반도체 및 디스플레이 부품의 신뢰성측면과 수율저하 등 life time의 근본적인 문제점으로 대두되고 있다. 본 연구에서는 반도체/디스플레이 장비용 코팅부품으로 많이 사용되고 있는 Al2O3 코팅막을 이용하였으며, sealing time에 따른 Anodic Aluminum Oxide (AAO) electrode의 물성특성평가 및 진공평가기술을 이용하여 life time을 예측하는 연구를 수행하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.647-648
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• 2009

• Corrosion Science and Technology
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• v.10 no.1
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• pp.37-42
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• 2011

Aluminum was electrochemically etched in acid solution and the surface area was magnified by the formation of etch pits. Etched aluminum was covered with a compact and dense dielectric oxide film by anodization and applied to the aluminum electrolytic capacitor electrode. Capacitance of aluminum electrolytic capacitor is closely related with surface area, which depends on size and number of etch pits. Size of etch pits need to be controlled because inside of the pits can be buried by the formation of dielectric oxide film. In this work, the effect of ultrasound pretreatment on the aluminum etch pit formation and capacitance were investigated. Additionally, the relationship between the second etching effect on pit size and capacitance was studied.

• Journal of Sensor Science and Technology
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• v.19 no.6
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• pp.421-427
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• 2010

Alizarin Red S modified screen printed carbon electrodes were developed for the electrochemical detection of aluminum ion. The electrodes developed use screen-printed carbon electrodes(SPCEs) coupled with chemical modification with an organic chelator, Alizarin Red S(ARS), for aluminum ion detection in aqueous solution. For sensor fabrication ARS was directly immobilized on the surface of SPCEs using PVA-SbQ(The poly(vinyl alcohol) bearing stryrylpyridinium groups). Aluminum concentrations were indirectly estimated by amperometric determination of the non-complexed ARS immobilized on the electrodes, after its complexation with aluminum. The sensitivity of the sensor developed was $3.8\;nA{\mu}M^{-1}cm^{-2}$ and the detection limit for aluminum was $25\;{\mu}M$.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.42-62
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• 1997

Resistance spot welding has been widely used in the sheet metal joining processes because of its high productivity and convenience. Recently, automobile industries are trying to replace partly steel sheets with aluminum alloy sheets. Among currently produced aluminum alloys, Al alloy sheets of Al-Mg-Si(6000 series) are being tested. Especially, 6000 series are the most probable substitute in view of strength and weldability. In this paper, an attempt was made to apply resistance spot welding to joining of dissimilar sheet metals (KS6383+SCPZn or KS6383+SHCP). An effort was made to balance heating rate in the Al alloy with that in the steel sheets by increasing electrode tip diameter. Although resistance spot welding of Al alloy sheet and sheet metals does not produce desirable nugget, it proved to have reasonable strength if optimal weld condition is found by tensile-shear strength and fatigue life test. Since spot weld joints in automobile are always experiencing repeated load, spot welding methodology proposed in this paper is found to be not suitable to automobile body manufacturing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.89-93
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• 2014

Variable polarity (VP) arc welding is known as an effective solution for aluminum thanks to the cleaning effect, which means oxide removal, during the DCEP (direct current electrode positive) period. In this research, VP GTAW (gas tungsten arc welding) is adopted for lap joint fillet welding of 3mm thickness 5052 aluminum alloy. Various welding currents and DCEP duty cycles are applied as welding conditions with a fixed welding speed to investigate the influence of DCEP characteristics on weld bead formation. Results show a tendency of higher heat input for higher DCEP duty cycle, which result does not follow conventional arc theory because it is known that DCEN (DC electrode negative) polarity is more efficient for heat input than is DCEP. This phenomenonhas recently been reported by several VP-GTA researchers and is still controversial because the mechanism of oxide removal is not yet clear except for the previous, well-known idea of "ion bombardment", which cannot explain the situation. Finally, proper usage conditions for VP-GTAW are suggested; then, further, related theoretical topics in the field of cathode physics are brieflyintroduced.

• Journal of Sensor Science and Technology
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• v.27 no.5
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• pp.340-344
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• 2018

Electrodes are an important part of electrocardiography (ECG); disposable electrodes have been extensively used. However, personal ECG monitoring devices for Internet of Things applications require reusable electrodes. As there have been no systematic studies on the characteristics of reusable electrodes to date, we conducted this study to assess the performance and feasibility of electrodes with different materials. We built reusable electrodes using twelve different metallic materials, including commonly used copper, silver, zinc, plating materials, chemically inert titanium, stainless steel, and aluminum. Each electrode was fabricated to a size of $5{\times}10mm$. Their characteristics such as offset, baseline drift, stabilization time, and chemical inertness were compared. A personal ECG monitoring system was used to test the manufactured electrodes. The performances of the Ag, Cu, and Zn electrodes were better than the performances of other electrodes. However, these materials may not be used owing to the chemical changes that occur when the electrodes are in contact with the skin, such as discoloration and corrosion, which deteriorate their electrical characteristics. Titanium, stainless steel, and aluminum are chemically stable. The titanium electrode showed the best performance among the three, and it is our recommendation as a material for manufacturing reusable electrodes.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.767-775
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• 2011

In this study we verified if the electro-coagulation process can treat properly the nitrate and fluoride that are not removed well in the conventional small water treatment plants which usually employ chlorination and filtration only. As we gave a change of electrode material and gap-distance between electrodes, removal efficiency of the nitrate and fluoride was determined by electro-coagulation process which were equipped with aluminum and stainless steel (SUS304) electrodes. In addition, electrode durability was investigated by determination of electrodes mass change during the repetitive experiments. Removal efficiency was great when aluminum was used as an anode material. Nitrate removals increased as electric density and number of electrodes increased, but fluoride removal was less sensitive to both parameters than nitrate. After 10 minutes of contact time with the current density from $1{\times}10^{-3}$ to $3{\times}10^{-3}A/cm^{2}$, nitrate and fluoride concentration ranged from 9.2 to 1.2mg/L and from 0.02 to 0.01mg/L, which satisfied the regulation limits. Regardless of the repeating number of experiments, removal efficiency of both ions were almost similar and the change of electrode mass ranged within ${\pm}$0.5%, indicating that the loss of the electrode mass is not so much great under the limited circumstances.