• 대한조선학회논문집
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• 제40권4호
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• pp.8-15
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• 2003

This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP(sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using B-spline surface patches. The optimization method is applied to Series 60 hull and KCS(KRISO 3600 TEU Container Ship). The obtained results prove that the method is appropriate for preliminary hull form design.

• 한국표면공학회지
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• 제31권4호
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• pp.181-190
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• 1998

Al ion plating was carried to improve corrosion resistance of Nd-based permanent magnet made by prwder molding method. The effects of applied votage, pressyre and temperature were investigated to find the reation between coating parameters and their properties. Density of coating layer increased with voltage and thus corrosion resistance improved. However when voltage was applied more than 1000V, corrosion resistance whet down because of resputtering effect. Good corrosion resistance was acquired when gas pressure was $5.0\times10^-2$>torr, which is satisfied momentum energy of Ar, Al ions as well as quantity of plasma. The layer coated in low temperature range have better surface density and corrosion resistance than in high temperature. This result is seemed due to the characteristics of substrate itself. All coating layers were showed stong adhesion with substrate.

• 수산해양기술연구
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• 제17권2호
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• pp.109-113
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• 1981

Most existing theories on ship waves and wave resistance are based on the perturbation of the flow field by a small pararr.eter which specifies the slenderness of the ship hull. Since however, ship hulls in practice are neither so slender nor thin enough to secure the validity of the linearized theory, the agreen:ent between the theoretical prediction and the experimental result is not generally satisfactory. The author pointed out that the contribution by the non-linear term in the free surface condition can be represented by sorr.e source distribution over the still water plane. This paper leads to a forrr.ula for the wave resistance of not slender ships at low Froude nurr.bers. and deals with the asynptotic expression. As a nurr.erical example, the wave resistance of Wigley model is calculated, and the result is compared with experimental values. It is concluded that the wave resistance coefficient varies in the rate of Fn6 at low speed limit in general. A comparison with the result derived from the linearized free surface condition shows that the non-linearity of the free surface is irr portant at low speed.

• Corrosion Science and Technology
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• 제21권6호
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• pp.495-502
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• 2022

Anodization is a representative electrochemical surface treatment method that can improve both heat resistance and corrosion resistance by forming an anodization film on the surface of the aluminum. However, these properties can be changed after an additional heat treatment process. In this study, Al 6061 was subjected to an anodization process at 60 V for 1 hour, 5 hours, or 9 hours. An additional heat treatment process was performed at 500 ℃ for 30 minutes. Field emission scanning electron microscopy (FE-SEM) analysis revealed that the thickness of the anodized film was increased in proportion to the anodization time. Both pore size and pore diameter of the anodized film was also increased after anodization. After an additional heat treatment process, there were no significant changes in the thickness, pore size, or pore diameter of the anodized film. Heat resistance was confirmed through thermal analysis and chemical resistance was evaluated with a potentiodynamic polarization test.

• 한국표면공학회지
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• 제36권2호
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• pp.206-213
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• 2003

Effects of plasma nitriding on the surface characteristics of tool steels have been investigated using wear tester, micro-hardness tester and scanning electron microscope (SEM) Commercial SKD 11 and SM45 alloy were used as specimens and were plasma nitrided using a plasma nitriding equipment for 5 hr and 10hr at $500^{\circ}C$. Microstructure and phase analysis were performed using SEM and XRD. It was found that plasma nitriding for lour at $500^{\circ}C$, compared with plasma nitriding for 10hr at $500^{\circ}C$, had a thick nitrided layer and produced a layer with good wear resistance and hardness as nitriding time increased. SKD11 alloy showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with SM45 alloy.

• 한국생산제조학회지
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• 제23권6호
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• pp.576-579
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• 2014

Rails are continuously exposed to severe environments due to increases in train service frequency, passing tonnage, and speed. Wear is one of the most common types of damage observed on rails. The surface of railsis heat treated to secure safety at critical sites, such as curved tracks or turnouts. Ultrasonic nanocrystal surface modification (UNSM), a new approach for rails, was examined to strengthen the rail surface. The effect of UNSM on the wear resistance of rail specimens was compared with that of heat treatment. Wear resistance was improved after UNSM treatment due to increased hardness and surface compressive residual stress.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.505-508
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• 2005

Concrete has a void, which exists as one of defect in concrete. If the porosity of concrete increases, durability of concrete decreases. In this paper, to improve surface void of concrete, surface penetration sealers are applied to specimen. And it were investigated that the resistances of chloride penetration and freezing and thawing for concrete with surface penetration sealer of two types. According to the results, surface penetration sealer has not show a harmful influence on strength and resistance of freezing and thawing. Also, B type surface penetration sealer was more superior in resistance of chloride penetration.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.455-456
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• 2008

In this study, we report that an electrical properties of OLEDs was investigated by the surface etching method of ITO Layer. The electrical properties of OLEDs was measured by IVL and optical properties by EL spectrum. The fundamental structure of OLEDs was ITO anode/TPD(400$\breve{A}$)/$Alq_3(600\breve{A})$/LiF(5$\breve{A}$)/Al(1200$\breve{A}$) cathode. The threshold voltage was low value according to the low resistance of surface. The luminance was increased by decreased surface resistance.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.30-31
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• 2017

The objective of this study is to evaluate the performance of polymer-modified surface preparation mortars with pozzolanic materials for corrosion prevention method in deteriorated sewage treatment structures. The prepackaged-type surface preparation mortars are prepared with a polymer-binder ratio of 10%, ground granulated blast furnace slag contents of 0, 15, 30%, a fly ash content of 15%. And, the specimens are tested for workability, adhesion in tension, water absorption, crack and impact resistance. As a result, the prepackage-type surface preparation mortars for sewage treatment structure are satisfied with quality requirements by KS F 4716, Japan sewage work agency(JS) and JIS A 6916 for surface preparation mortars.

• 한국표면공학회지
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• 제50권6호
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• pp.432-438
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• 2017

AZ91D casting alloy requires an advanced plasma anodizing processing because large amount of defects are liable to generate during anodization. In this study, plasma electrolytic oxidation (PEO) of AZ91D Mg alloy was conducted by the application of either constant voltage or current using a pulse mode and its effects on pore formation, surface roughness and corrosion resistance were investigated. The PEO films showed a three-layer structure. The PEO film thickness was found to increase linearly with voltage. The surface roughness, Ra, ranged between $0.2{\mu}m$ and $0.3{\mu}m$. The corrosion resistance increased from RN 3.5 to 9.5 by the PEO treatment when evaluated according to the 72 hour salt spray test. The PEO-treated surface exhibited higher pitting potential than the raw material.