• Title/Summary/Keyword: 백청

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Corrosion Resistance of Sol-Gel Films Coated on Meal with Inhibitors (부식 억제제와 결합된 졸-겔 코팅막의 내부식성 특성)

  • 황영영;김재홍;석상일
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.03a
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    • pp.206-206
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    • 2003
  • 현재, 메탈의 내부식성 코팅막 제조에 사용되고 있는 크로메이트 기반 코팅제는 유독성 물질에 대한 환경 규제에 따라 조만간 사용이 금지 될 예정이다. 본 연구에서는 이러한 유독성 금속 내부식성 코팅제를 대체할 새로운 코팅 재료로 부식 억제제가 결합된 수용성 졸을 제조하고 그 특성을 보고하고자 한다 부식 억제제가 결합된 수용성 졸은 부분 가수 분해된 GPS((3-glycidoxypropyltriethoxysilane)에 Zirconiumoxychlorideoctahydrate 혹은 cerium nitrate를 일정 양 첨가하고 이온 교환수에 희석하여 제조하였다. 이 코팅 졸을 아연 도금 강판에 딥 코팅법으로 코팅한 후 상온에서 건조하고, 80~15$0^{\circ}C$에서 열처리하여 염수 분무 시험으로 백청 발생 정도를 관찰하여 내 부식성을 조사하였다. 코팅막의 두께는 수직으로 절단한 면을 전자 현미경으로 관찰하여 측정하였으며, 표면의 경도는 연필 경도계로 조사하였다. 또한 코팅막의 부식 전위는 전기화학적인 방법으로 분석되어 부식억제제의 종류에 따른 효과도 정량적으로 비교되었다.

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AN UNSTRUCTURED STEADY COMPRESSIBLE NAVIER-STOKES SOLVER WITH IMPLICIT BOUNDARY CONDITION METHOD (내재적 경계조건 방법을 적용한 비정렬 격자 기반의 정상 압축성 Navier-Stokes 해석자)

  • Baek, C.;Kim, M.;Choi, S.;Lee, S.;Kim, C.W.
    • Journal of computational fluids engineering
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    • v.21 no.1
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    • pp.10-18
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    • 2016
  • Numerical boundary conditions are as important as the governing equations when analyzing the fluid flows numerically. An explicit boundary condition method updates the solutions at the boundaries with extrapolation from the interior of the computational domain, while the implicit boundary condition method in conjunction with an implicit time integration method solves the solutions of the entire computational domain including the boundaries simultaneously. The implicit boundary condition method, therefore, is more robust than the explicit boundary condition method. In this paper, steady compressible 2-Dimensional Navier-Stokes solver is developed. We present the implicit boundary condition method coupled with LU-SGS(Lower Upper Symmetric Gauss Seidel) method. Also, the explicit boundary condition method is implemented for comparison. The preconditioning Navier-Stokes equations are solved on unstructured meshes. The numerical computations for a number of flows show that the implicit boundary condition method can give accurate solutions.

Evaluation of Effective Jamming/Deception Area of Active Decoy against Ground Tracking Radars on Dynamic Combat Scenarios (동적 교전 시나리오에서 지상 추적 레이다에 대한 이탈방사체의 효과적 재밍/기만 영역 분석)

  • Rim, Jae-Won;Lee, Sangyeob;Koh, Il-Suek;Baek, Chung;Lee, Seungsoo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.4
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    • pp.269-278
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    • 2017
  • We analyze the jamming/deception performance of an active decoy against ground tracking radars on dynamic combat scenarios. Based on the movement and the interference flow of an airborne platform, the trajectories of the active decoy is accurately calculated by solving 6-degree of freedom equations of motion. On realistic combat scenarios, numerical simulations are examined to analyze the jamming performance of the decoy for various movements of the platform and RF specifications of the active decoy. Effective jamming/deception area against the ground tracking radars is estimated from the simulation.

Development of Steady/Unsteady Aerodynamic Analysis Program Using 3-Dimensional Subsonic Unstructured Panel Method (3차원 아음속 비정렬 패널법을 이용한 정상/비정상 공력 해석 프로그램 개발)

  • Park, Jinyi;Baek, Chung;Lee, Seungsoo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.6
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    • pp.367-376
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    • 2022
  • In this study, a steady and unsteady aerodynamic analysis program using a 3-dimensional subsonic unstructured panel method is developed and verified. Surfaces of bodies are modeled with the source and doublet distributions on triangular or quadrilateral panels. Geometry modeling of complex geometries and multi-body, therefore, can be easily accomplished. The Kelvin theory and the unsteady Kutta condition allow the doublet strength of the wake panels determined for unsteady flows. Various steady and unsteady flows in two and three dimensions are computed and compared with the analytical and the published computational results.

Enlargement of Anti-corrosion of Zinc Plating by the Trivalent Chromium Sulfate Conversion Coating (3가 크롬황산염의 크로메이트에 의한 아연도금내식성 증대)

  • Lee, Chul-Tae
    • Applied Chemistry for Engineering
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    • v.18 no.3
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    • pp.296-302
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    • 2007
  • A trivalent chromate conversion coating solution which is composed with $KCr_2(SO_4)$ as main component was investigated to test a feasibility of use as an alternative six-valent chromate conversion coating for improvement of anti-corrosion of zinc plating. The proposed trivalent convesion coating was consisted of $KCr(SO_4)$ 35~45 g/L as trivalent chromium source, $NaH_2PO_4$ 20~30 g/L as phosphate, $CoSO_4$, 10~20 g/L, $ZnSO_4$ 10~20 g/L as metallic sulfates. This trivalent chromate films which are coated by this chromate conversion coating solution under pH 2.0~2.2, immersion time of 20~25 s at room temperature are able to achieve over 120 h in neutral salt spray test to 5% white rust.

Corrosion Resistance of Galvanized Steel by Treating Modified Si Organic/Inorganic Hybrid Coating Solution (Si 변성 유/무기 하이브리드 코팅액에 의한 아연도금강판의 내식특성)

  • Seo, Hyun-Soo;Moon, Hee-Joon;Kim, Jung-Ryang;Kim, Jong-Soon;Ahn, Seok-Hwan;Moon, Chang-Kwon;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.25 no.1
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    • pp.32-38
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    • 2011
  • Galvanized steel has gone through a chemical process to keep it from corroding. The steel gets coated in layers of zinc because rust will not attack this protective metal. For countless outdoor, marine, or industrial applications, galvanized steel is an essential fabrication component. The reduction of the corrosion rate of zinc is an important topic. In the past, a very popular way to reduce the corrosion rate of zinc was to use chemical conversion layers based on $Cr^{+6}$. However, a significant problem that has arisen is that the use of chromium salts is now restricted because of environmental protection legislation. Therefore, it is very important to develop new zinc surface treatments that are environmentally friendly to improve the corrosion resistance of zinc and adhesion with a final organic protective layer. In this study, a Urethane solution (only Urethane 20 wt.%; S-700) and an organic/inorganic solution with Si (Si polysilicate 10 wt.% + Urethane 10 wt.%; LRO-317) are used. Based on the salt spray test of 72 h, S-700 and LRO-317 had a superior effect for the corrosion resistance on EGI and HDGI, respectively.

Evaluation of the Corrosion Resistance of Steel Coated with Zinc Using a Cr-free Coating Solution as a Function of Heat Treatment Time (Cr-free 코팅액에 의한 아연도금강판의 건조시간에 따른 내식특성)

  • Seo, Hyun-Soo;Moon, Hee-Joon;Kim, Jong-Soon;Ahn, Seok-Hwan;Moon, Chang-Kwon;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.24 no.5
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    • pp.67-74
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    • 2010
  • Chromate conversion coating is a coating technique used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, tin, and their alloys to slow corrosion. The process uses various toxic chromium compounds, which may include hexavalent chromium. The industry is developing less toxic alternatives in order to comply with substance restriction legislation, such as RoHS. One alternative is to develop a Cr-free coating solution. In this study, eco-friendly, Cr-free solutions (urethane solution S-700, organic/inorganic solution with Si LRO-317) were used. Test specimens were dried in a drying oven at $190^{\circ}C$ for 3, 5, 7, and 9 minutes. Corrosion resistance was evaluated using a salt spray test for 72 hours. The results show that the optimum corrosion resistance was achieved at $190^{\circ}C$ for five minutes for EGI and three or five minutes for HDGI, respectively. The adhesive properties of the two types of coating solutions were superior regardless of drying time.

Evaluation of the Corrosion Resistance of Zn-Coated Steel as a Function of the Temperature of the Cr-free Solution Used to Coat the Steel (Cr-free 코팅액에 의한 아연도금강판의 열처리 온도에 따른 내식특성)

  • Seo, Hyun-Soo;Moon, Hee-Joon;Kim, Jong-Soon;Ahn, Seok-Hwan;Moon, Chang-Kwon;Nam, Ki-Woo
    • Journal of Ocean Engineering and Technology
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    • v.24 no.5
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    • pp.60-66
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    • 2010
  • Zinc has a number of characteristics that make it well suited for use as a coating to protecting iron and steel products from corrosion. Its excellent corrosion resistance in most environments accounts for its successful use as a protective coating on a variety of products and in many exposure conditions. The excellent field performance of zinc coatings results from their ability to form dense, adherent films that corrode at a rate that ranges from 1% to 10% of the corrosion rate of ferrous materials, depending on the environment. Recently, EU RoHS and EU ELV prohibited the use of materials that adversely affect the environment, such as Pb, Hg, Cd, and $Cr^{+6}$. In this study, environmentally-friendly, Cr-free solutions (epoxy solution, acrylic solution, and urethane solution S-700) and organic/inorganic solution with Si; LRO-317) were used to evaluate the corrosion resistance of zinc-coated steel subjected to a saltwater spray for 72 hours. The coating of urethane solution (S-700) was best among the three kinds of solution with heat treatment during five minutes at $190^{\circ}F$. Test specimens with S-700 and LRO-317 coating were heat treated in a drying oven at 170, 180, 190, 200, and $210^{\circ}C$ for five minutes. The results show that the optimum corrosion resistance was $190^{\circ}C$ in EGI and $170^{\circ}C$ in HDGI, respectively.

Supersonic Multi-species Jet Interactions of Hit-to-Kill Interceptor with High Temperature Effect (고온효과를 고려한 직격 요격체 다화학종 초음속 제트 간섭)

  • Baek, Chung;Lee, Seungsoo;Huh, Jinbum
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.3
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    • pp.187-194
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    • 2020
  • In this study, computational analyses are carried out to investigate the interference flows and the aerodynamic characteristics of a hit-to-kill intercepter due to lateral jets at medium altitude. In addition, the analyses are performed for air and multi-species gas used in the side jet. The results indicate that the position of the barrel shock are shifted upstream and the structure of the shock wave are changed for the multi-species jet when compared to the air jet. As a result, the high pressure region with multi-species jet moves forward and the pitching moment is higher under the same flow condition. Moreover, the inclusion of high temperature effects makes drastic changes in pressure distribution. The jet width is much bigger, and the jet diffuses over wider range in medium altitude than in low altitude, because of the low density of the freestream.

Effect of Different Nutrient Solution and Light Quality on Growth and Glucosinolate Contents of Watercress in Hydroponics (배양액의 종류 및 광질이 물냉이의 생육 및 Glucosinolate 함량에 미치는 영향)

  • Choi, Jae Yun;Kim, Sung Jin;Bok, Kwon Jeong;Lee, Kwang Ya;Park, Jong Seok
    • Journal of Bio-Environment Control
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    • v.27 no.4
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    • pp.371-380
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    • 2018
  • Aim of this study was to investigate the effects of different nutrient solutions and various light qualities generated by LED on the growth and glucosinolates contents of watercress (Nasturtium officinale) grown under hydroponics for 3 weeks. The seeds of watercress were sown on crushed rockwool media and raised them for two weeks. They were transplanted in a semi-DFT (deep flow technique) hydroponics system. A controlled-environment room was maintained at $20{\pm}1^{\circ}C$ and $16{\pm}1^{\circ}C$ temperatures and $65{\pm}10%$ and $75{\pm}10%$ relative humidity (day and night, respectively), with a provided photosynthetic photon flux density (PPFD) of $180{\pm}10{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ and a photoperiod of 16/8h. To find out the best kinds of nutrient solutions for growing watercress, Otsuka House 1A (OTS), Horticultural Experiment Station in Korea (HES), and Netherland's Proefstaion voor Bloemisterij en Gasgroente (PBG) were adapted with initial EC of $1.0-1.3dS{\cdot}m^{-1}$ and pH of 6.2, irradiating PPFD with fluorescent lamps (Ex-1). Either monochromatic (W10 and R10) or mixed LEDs (R5B1, R3B1, R2B1G1, and W2B1G1) were irradiated with a differing ratio of each LED's PPFD to understanding light quality on the growth and glucosinolates contents of watercress (Ex-2). Although significant difference in the shoot growth of watercress was not found among three nutrient solutions treatments, but the root fresh weight increased by 13.7% and 55.1% in PBG and OTS compared to HES, respectively. OTS increased the gluconasturtiin content by 96% and 65% compared to PBG and HES. Compared with the white light (W10), the red light (R10) showed a 101.3% increase in the shoot length of watercress. Increasing blue light portion positively affected plant growth. The content of total glucosinolates in watercress was increased by 144.5% and 70% per unit dry weight in R3B1 treatment compared with R2B1G1 and W10 treatments, respectively. The growth and total glucosinolates contents of the watercress were highest under R3B1 among six light qualities.