• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.45-45
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• 2011

알루미늄과 그 합금은 내부식성(corrosion resistance)이 좋고, 밀도가 낮아 높은 연료소비 효율을 필요로 하는 항공기와 자동차 같은 운송수단의 내-외장 소재로 사용되고 있다. 또한 알루미늄의 높은 내부식성을 이용하여 철강소재의 부식을 방지하는 보호막으로도 폭 넓게 사용된다. 물리기상증착(physical vapor deposition)으로 알루미늄을 코팅하면 박막 성장 초기단계에서 핵(nucleus)을 형성하고, 형성된 핵을 중심으로 주상 구조(columnar structure)로 박막이 성장하는 것이 일반적으로 알려진 방식이다. 주상 구조의 알루미늄 박막은 주상정과 주상정 사이에 필연적으로 공극(pore)이 존재하게 되어 부식을 일으키는 물질이 박막으로 침투하게 되고, 부식 물질과 모재가 반응하여 공식(pitting corrosion)이 발생한다. 본 연구에서는 스퍼터링(magnetron sputtering)을 이용하여 치밀한 조직을 갖는 알루미늄 박막을 코팅할 수 있는 공정을 개발하고, 치밀한 알루미늄 조직이 내부식성에 어떠한 영향을 미치는지 평가하였다. 기판은 냉연강판(cold rolled steel sheet)이 사용되었으며, 알루미늄 타겟의 순도는 99.999%, 크기는 직경 4"이었다. 냉연강판은 진공용기(vacuum chamber)에 장착하기 전에 계면활성제를 이용하여 표면에 존재하는 기름성분을 제거하였으며, 진공용기에 장착한 후에는 아르곤 가스를 이용하여 발생시킨 글로우 방전으로 표면에 존재하는 산화물을 제거하였다. 알루미늄 박막의 조직에 영향을 미치는 공정변수를 확인하기 위해서 스퍼터링 파워, 공정 온도, 공정 압력, 외부 자기장 세기 등의 공정 조건을 변화시켜 코팅을 실시하였다. 실험을 통해서 얻어진 최적 조건으로 알루미늄을 코팅할 경우, 알루미늄 bulk의 밀도와 비교하여 약 94.7%의 밀도를 갖는 알루미늄 박막을 코팅할 수 있었다. 알루미늄 박막이 약 3 ${\mu}$m의 두께로 코팅된 냉연강판의 내부식성 평가(salt spray test, 5% NaCl) 결과, 평가를 시작한 후 72시간 후에도 적청이 발생하지 않았다.

• Journal of Powder Materials
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• v.14 no.6
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• pp.354-361
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• 2007

The bi-materials with Al-Mg alloy and its composites reinforced with SiC and $Al_2O_3$ particles were prepared by conventional powder metallurgy method. The A1-5 wt%Mg and composite mixtures were compacted under $150{\sim}450\;MPa$, and then the mixtures compacted under 400 MPa were sintered at $773{\sim}1173K$ for 5h. The obtained bi-materials with Al-Mg/SiCp composite showed the higher relative density than those with $Al-Mg/Al_2O_3$ composite after compaction and sintering. Based on the results, the bi-materials compacted under 400 MPa and sintered at 873K for 5h were used for mechanical tests. In the composite side of bi-materials, the SiC particles were densely distributed compared to the $Al_2O_3$ particles. The bi-materials with Al-Mg/SiC composite showed the higher micro-hardness than those with $Al-Mg/Al_2O_3$ composite. The mechanical properties were evaluated by the compressive test. The bi-materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. Their compressive strength was lower than that of Al-Mg alloy. Moreover, impact absorbed energy of bi-materials was smaller than that of composite. However, the bi-materials with Al-Mg/SiCp composite particularly showed almost similar impact absorbed energy to $Al-Mg/Al_2O_3$ composite. From the observation of microstructure, it was deduced that the bi-materials was preferentially fractured through micro-interface between matrix and composite in the vicinity of macro-interface.

• Korean Journal of Food Science and Technology
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• v.4 no.4
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• pp.265-270
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• 1972

An attempt was made in this study to investigate the possibility of processing squid along with pork into an intermediate moisture food, as an acceptable new item in Korea. To obtain a palatable and low cost product, portions of mixture consisting of equal amounts of ground squid and pork were cooked in soy sauce for 20 min, soaked in glycerol for 20 min at $80^{\circ}C$, and then air dried for 90 min at $60^{\circ}C$. During storage for 42 days in saturated humidity incubator at $37^{\circ}C$, the total microbial counts of the products packaged in polyethylene (0.05 mm), polypropylene (0.05 mm) and plastic laminated aluminum foil were decreased from 230 per gram to 40, 20 and 10 per gram respectively. In another long range storage test of 6 months, the results paralleled the above trends. Even though the TBA value of the samples increased during the storage, it was not so serious as to damage on the organoleptic quality of this product. The results indicate that stored product was as acceptable as the freshly prepared one.

• Journal of Korea Foundry Society
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• v.36 no.2
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• pp.67-74
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• 2016

The effects of scrap content on the hot tearing property and tensile property were investigated in AC2BS alloy. The hot tearing strengths were $16.4kgf/cm^2$, $15.2kgf/cm^2$, $14.9kgf/cm^2$ and $13.3kgf/cm^2$, respectively, under the constant solid fraction of 29.3% when the scrap contents of the specimens were 0%, 20%, 35% and 50%. In the same way, tensile strengths of the as-cast condition were $24.5kgf/mm^2$, $23.7kgf/mm^2$, $17.3kgf/mm^2$ and $16.0kgf/mm^2$, respectively, and the corresponding tensile strengths of the T6 heat treatment condition were $27.2kgf/mm^2$, $26.7kgf/mm^2$, $24.2kgf/mm^2$ and $23.9kgf/mm^2$. Hot tearing strength and tensile strength decreased as scrap content of the specimen increased. According to the evaluation of the quantitative hot tearing and tensile test results, the decrease of these strengths is due to the presence of oxide films which act as crack initiation site of the specimens. Therefore, elimination of oxide films of aluminum melt to maintain melt cleanliness is required.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.137-141
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• 2015

The purpose of this study is examining thermal dissipation materials for the lighting and radiate efficiency improvement of 8W LED and confirming the properness of the thermal dissipation materials for LED heat sink. Solid Works flow simulation on 8W class COB was done based on the material characteristics of thermal conductive polymer materials. According to the result of simulation, Al had better thermal dissipation performance than PET. Highest temperature was $7.6^{\circ}C$ higher while lowest temperature was $7.8^{\circ}C$ lower. The test on the heat sinks made by the materials, highest temperature was $4.1^{\circ}C$ higher and lowest temperature was $3.9^{\circ}C$ lower. It is possible to confirm that Al heat sink has better thermal dissipation efficiency because it has better dispersion of heat generated at junction temperature and less heat cohesion. The weight of PET heat sink was reduced than Al heat sink by 46.9% by the density difference between Al and PET. In conclusion, thermal dissipation performance of thermal conductive polymer is lower than Al material however, it is possible to lighting heat sink because thermal conductive polymer has better formability, has lower specific weight and enables various design options.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.350-352
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• 2009

The effect of porosity on the high-cycle fatigue properties of Al-Si-Mg casting aluminum alloys was investigated in this study. Microstructure examination, tensile and high-cycle fatigue test were conducted on both Al-Si-Mg casted (F) and heat-treated (T6) conditions. Porosity characteristics on the fracture surfaces of fatigue-tested samples were examined using SEM and image analysis. The microstructure observation results showed that eutectic Si particles were homogeneously dispersed in the matrix of the Al-Si-Mg casting alloys, but there were porosities formed as cast defects. The high-cycle fatigue results indicated that the fatigue strength of the 356-T6 alloy was higher than that of the 356-F alloys because of the significant reduction in volume fraction of pores by heat treatment. The SEM fractography results showed that porosity affected detrimental effect on the fatigue life: 80% of all tested samples fractured as a result of porosity which acted as the main crack initiation site. It was found that fatigue life decreased as the size of the surface pore increased. A comparison was made between surface pore and inner pore fur its effect on the fatigue behavior. The results showed that the fatigue strength with the inner pores was higher than that of the surface pore.

• Environmental Engineering Research
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• v.25 no.3
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• pp.393-399
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• 2020

The use of different types of wastewater (WW) for the cultivation of microalgae and cyanobacteria during recent decades has provided important economic and environmental benefits. However, direct use of WW can lead to growth inhibition and biomass contamination. In the present study, we separated the key WW nutrients, namely nitrate and phosphate, by adsorption and regeneration and used the resulting regenerated water to cultivate the cyanobacterium Spirulina platensis. The adsorbent was granular γ-alumina derived from waste aluminum cans. This procedure recovered 19.9% of nitrate and 23.7% of phosphate from WW. The cyanobacterial cultures efficiently assimilated the nutrients from the medium prepared using regenerated WW, and the growth and nutrient uptake were similar to those in a synthetic medium. In addition, imposing nutrient limitations to increase carbohydrate productivity was easily achieved using regenerated wastewater nutrients, without requiring additional dilution or complex processing. In acute toxicity tests, the harvested biomass in a regenerated medium had similar toxicity levels compared to the biomass obtained from a synthetic medium. The proposed method of using regenerated WW to produce contamination-free biomass has broad potential applications.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.34-40
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• 2011

From the present paper researched about the Design of Image Rejection SSB Modulator for X-Band Monopulse RADAR using Waveguide Hybrid Coupler. Generally, SSB modulator mixes IF(RF) and LO signals, and then it converts to RF(IF) frequency band. In this case, in order to transmit one sideband from RF band, SSB modulator is demanded the removal of image and LO signal. The balanced mixer was designed using waveguide hybrid coupler and crystal mixer diode to mix LO and IF signal. And also the IF Amplifier was designed for IF(+) and IF(-) signal generation which have $90^{\circ}$ phase differences which are suitable in two crystal mixer diode inputs. In order to maintain a high electric reliability from high frequency band the waveguide and IF amplifier's case were manufactured with aluminum using deep brazing techniques. The test result of SSB modulator, LO and sideband signal rejection ratio were 14.2dB and 18.5dB respectively.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.82-87
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• 2017

Recent trends in shipbuilding and offshore industries are a huge increase in the ship size and the exploration and production of oil and natural gas in the arctic offshore region. High performance steel plates are required by these industrial trends. Also in IMO(International Maritime Organization) has begun to regulate of fuel of ship to environmental protection, therefore it is little bit difficult to use bunker-C oil to working ship. As the problem of environmental change such as global warming is emerged, the operation of the ship is considered to be involved in the environmental change problem, and the regulation of environmental pollution is gradually strengthened. As these environmental regulations are strengthened demand for LNG fuel ships is rapidly increasing. Currently, cryogenic steels used in LNG tanks include aluminum alloy, SUS 304, and 9%-Ni steel. Those steels are has high cost to construction of large LNG carrier. The new materials were suggested several steel mills to decrease construction cost and easy construction. The new cryogenic steel should be evaluate safety to applied real structure include LNG ship. Therefore, in this study, fracture toughness of weld joints were investigated with cryogenic steel for application of LNG tank.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.177-184
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• 2015

In order to use the high-volume slag cement as a construction materials, a proper activator which can improve the latent hydraulic reactivity is required. The dissolved aluminum silicon ions from ground granulated blast furnace slag (GGBFS) react with sulfate ions to form ettringite. The proper formation of ettringite can increase the early-age strength of high-volume GGBFS (80%) cement. The aim of this study is to investigate the hydration properties with sulfate activators (sodium sulfate, anhydrite). In this paper, the effects of $Na_2SO_4$ and $CaSO_4$ on setting, compressive strength, hydration, micro-structure were investigated in high-volume GGBFS cement and compared with those of without activator. Test results indicate that equivalent $SO_3$ content of 3~5% improve the early-age hydration properties such as compressive strength, heat evolution rate, micro-pore structure in high-volume GGBFS cement.