• Proceedings of the KWS Conference
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• 2003.11a
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• pp.162-164
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• 2003

Spot welding, a kind of electric resistance welding, has been used in many fields such as automobile, aircraft, and appliance industry. This paper is to investigate the relationship between tensile shear strength and indentation depth under various welding conditions. The tensile shear strength increases with increasing the welding current in the range of 6-l3kA. The optimum welding conditions were 200∼250kg welding force and 10∼15 cycles welding time at 9kA welding current for EZNCEN. The indentation depth for optimum welding condition was 0.6mm at 9kA welding curent and 200kg welding force, 0.17mm at 9kA welding current and 300kg welding force, 0.19mm at 9kA welding current and 10cycle, 0.17mm at 9kA welding current and 15cycle welding time, respectively.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1442-1443
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• 2008

본 논문에서는 인쇄회로기판과 도전체 샤시(Chassis)가 연결되었을 때의 복사성 방사(Radiated Emission)의 감소에 대해서 연구하였다. Current Driven 메커니즘 등가회로를 사용하여 전자파 방사의 주요한 원인중 하나인 Common-mode Current를 인쇄회로기판과 Chassis가 연결된 구조에 적용하였다. Chassis의 유무에 따라 복사성 방사의 감소를 확인하고자 2-layer 인쇄회로기판과 SECC(Steel Electro galvanized Cold-rolled Coil) 재질의 Chassis를 나사(Screw)를 통하여 전기적으로 연결하였을 때를 시뮬레이션 하였고, 제작된 구조물을 3m 무반향실에서 복사성 방사를 측정한 후 시뮬레이션과 결과를 비교하였다. 결과로 30MHz$\sim$45MHz에서 최대 10dB 감소의 효과가 있음을 확인하였다.

• KIEAE Journal
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• v.7 no.1
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• pp.73-80
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• 2007

This paper aims to develop the diffused reflection material in order to reduce the solar absorption coefficient, and to compare the thermal properties with the different roof structure system; one is using the diffused reflection material applied the upper side of the rigid sheet waterproof system and the other is using the conventional up-side down waterproof system on the roof. For this purpose two experimental test boxes were made of same iso-panel wall and floor with different roof system. The experiment was carried out under these process; measure the surface temperature exposed solar radiation of the variation of the reflection materials(cement paste, silica, galvanized steel and titanium dioxide(TiO2)), measure and analyze the variation of the temperature distribution of the each roof system and indoor air in order to evaluate the thermal properties according to the different roof system. The result shows clearly that using the titanium dioxide(TiO2) might be more effective to reduce the solar insolation.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1558-1562
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• 2007

To elucidate the influence of pipe materials on the VBNC (viable but nonculturable) state and bacterial numbers in drinking water, biofilm and effluent from stainless steel, galvanized iron, and polyvinyl chloride pipe wafers were analyzed. Although no HPC (heterotrophic plate count) was detected in the chlorinated influent of the model system, a DVC (direct viable count) still existed in the range between 3- and 4-log cells/ml. Significantly high numbers of HPC and DVC were found both in biofilm and in the effluent of the model system. The pipe material, exposure time, and the season were all relevant to the concentrations of VBNC and HPC bacteria detected. These findings indicate the importance of determining the number of VBNC cells and the type of pipe materials to estimate the HPC concentration in water distribution systems and thus the need of determining a DVC in evaluating disinfection efficiency.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.175-180
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• 2005

Experiments on the improvement in durability of pipe framework for plastic greenhouse were carried out. Effect of protection treatment such as primer and paint coating for new pipes and old rusted ones were evaluated by change of rusty degree and yield strength. The experiments have been conducted during five years until now but it was too short to find the clear differences. However, there was a little improvement in durability of greenhouse pipes by painting after removal of rust. And also component and corrosion characteristics of pipes being used in greenhouses were analyzed, and several countermeasures for protection from corrosion were reviewed.

• Journal of Magnetics
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• v.16 no.4
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• pp.453-456
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• 2011

Demagnetization for a tube sample which was made of a galvanized steel sheet was performed by applying a magnetic field with a decrement to remove the remanent magnetization of the material. An orthogonal fluxgate magnetic field sensor was used to measure a magnetic field created from a ferromagnetic material. To evaluate the remanent magnetization, the measured magnetic fields were separated into two magnetic field components by the remnant magnetization and the induced one. The horizontal and the vertical bias fields should be controlled separately during demagnetization to remove the horizontal and the vertical components of the remanent magnetization of the tube sample.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.189-191
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• 2001

This study introduces the new way for the evaluation criteria of the Mash-Seam Tailored Blank weldability, The materials used are low carbon automotive galvanized and high strength steels and the evaluation of weldability are examined with various thickness. Welding tests were conducted for both similar thickness and dissimilar thickness cases. The criteria developed for optimum welding conditions were based on the relationship among results of die press forming test, weld transverse tensile test, Erichsen test and microhardness measurements. The application of the developed criteria(fracture ratio, strength ratio, etc) in obtaining optimum welding condition revealed that a weld which satisfied ant of the criteria did not fracture during actual die press test.

• Journal of Surface Science and Engineering
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• v.37 no.4
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• pp.200-207
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• 2004

Molybdate chemical conversion coating layer formed on EGI has been studied in view of corrosion resistance, surface morphologies, and phases formed. It was found that coating layer consists of$ MoO_3$, $MoO_2$, Mo oxides having lower valences than 4 and ZnO. It is interesting to note that the coating layer formed at high Mo concentration (30 g/l) in the temperature range of $40-60^{\circ}C$ exhibited relatively high corrosion resistance, although thickness of coating layer is nearly identical with those formed under the other conditions. It was believed that an increase of driving force due to high Mo concentration plays an important role in the formation of corrosion-resistant coating layer, probably due to tile formation of dense coating layer.

• Corrosion Science and Technology
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• v.9 no.2
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• pp.87-91
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• 2010

It is pointed out that non-wetting behavior of liquid Zn alloy occurs on high-tensile strength steels, which usually contain Si and Mn. There have been a lot of investigations to improve the above wettability of liquid Zn alloy with steels containing Si and Mn. Although those studies evaluated the wettability qualitatively by observation of the surface of steels galvanized by Zn or exfoliation test of Zn with substrate steels and so on, it is required to evaluate the wettability of liquid Zn with steels by measuring contact angle, work of adhesion, spreading velocity etc. which are usually used to assessment of general wetting behavior. In the present work, we evaluated the wettability of liquid Zn with steels containing Si and Mn by applying a sessile drop method to measure the change in contact angle and diameter of liquid Zn droplet wetted on steels.

• Journal of Surface Science and Engineering
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• v.36 no.1
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• pp.42-47
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• 2003

Hot-dip galvanizing process is used widely in industry to achieve corrosion resistant coatings. Poor drainage during this process often leads to problems such as icicle formation and bridging In this work, mild steel specimens were hot-dip galvanized. Influence of the addition of bismuth, aluminum and both (bismuth and aluminum) to the zinc bath on the zinc drainage were determined. Bismuth additions improved the drainage significantly. Zinc bath containing 0.1 wt.% Bi and 0.025∼0.05 wt.% Al showed uniformity of coatings. Industrial trials with this bath composition showed reduction in zinc consumption, reduction of ash and dross, and good luster of workpiece.