• 소성∙가공
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• 제21권5호
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• pp.305-311
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• 2012

One of the main methods of building LNG tankers uses the Moss spherical tank design since it can be precisely analyzed with respect to reliability and safety of construction by stress analysis. Aluminum alloy 5083 is generally used in the Moss spherical tank design for the wall in constructing the LNG tanker. This aluminum alloy does not have low temperature brittleness, but has good corrosion resistance, good weldability, and excellent material properties for the application. The Moss spherical tank is constructed with several sections of A5083 thick plate with curved surfaces, which are welded together. It is essential to predict the amount of springback for the deformed thick plates in design to insure a reliable construction because the structure needs to be assembled into a perfect sphere. Unless the initial construction meets the design, there are additional processing costs for reworking to meet the specifications as well as a cost penalty paid to a consumer. In this paper, FE analyses were conducted to predict the amount of springback for various forming conditions and forming processes. The various forming processes were evaluated with respect to reducing springback and compared with the conventional forming process used for curved surfaces of thick Al plate.

• 소성∙가공
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• 제24권2호
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• pp.115-120
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• 2015

Deep drawing of cylindrical cups is one of the most fundamental and important processes in sheet metal forming. Circular cups are widely used in industrial fields such as automobile and electronic appliances. Some of these cups are formed by a one-stage process, others such as battery cases and beverage cans are made by a multi-stage process. In the current study the multi-stage deep drawing of aluminum sheet metal is examined. The process consists of two deep drawing operations followed by two ironing operations. The press die, which can be used for the four-stage forming process, was manufactured allowing punch and die components to be easily changed for various experiments. The rolling direction of both the sheet and the drawn cups was always positioned toward the horizontal x-direction on the die face to minimize experimental errors during the progressive forming. The dimensional accuracy of the cylindrical cups formed at each stage and the earing defect due to the anisotropy of sheet were investigated. The influence of anisotropy on the thickness distribution was also examined. Both the thickness and the outer diameter of the cups were measured and compared for each set of experimental conditions. It was found that the dimensional accuracy of cups rapidly improves by employing the ironing process and also by increasing the amount of ironing.

• 한국지반환경공학회 논문집
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• 제4권2호
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• pp.39-46
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• 2003

계면활성제를 이용하여 불포화 지역에 고정화 지역을 설정함으로써, 지하수로 유입되는 유기오염물질의 거동을 지연시킬 수 있다. 본 연구에서는 다양한 수분함량을 보유한 불포화 및 포화 조건에서 연속식 컬럼 실험을 수행함으로써, 수분함량에 따른 계면활성제와 유기오염물질의 거동에 대하여 연구하였다. 산화알루미늄(aluminum oxide)이 충진된 컬럼 실험에서 계면활성제(dialkylated disulfonated diphenyl oxide)의 거동 및 수착 특성은 수분함량이 달라져도 비슷한 결과를 나타내었다. 그러나 계면활성제(DADS)로 개질된 산화알루미늄이 충진된 컬럼 실험에서는 유기오염물질인 나프탈렌(naphthalene)이 수분함량이 감소됨에 따라 거동이 지연되는 현상을 나타내었으며, 또한 더 많은 양의 나프탈렌이 알루미늄 산화물에 흡착된 계면활성제로 흡수되었다. 따라서 본 연구를 통하여 유기오염물질의 고정화 방법이 불포화 지역에도 효과적으로 적용될 수 있음을 알 수 있었다.

• 한국콘텐츠학회논문지
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• 제14권2호
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• pp.181-191
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• 2014

과거 적외선 사진은 다소 까다로운 제작과정 때문에 쉽게 접근하기 어려운 측면이 있었다. 하지만 최근 디지털 기술의 발전으로 상당히 쉽고 간편해 졌기 때문에 활용 분야와 범위가 넓어질 것으로 예상된다. 따라서 본 연구는 이런 움직임에 맞춰 과학사진을 위한 적외선 대역의 노출과 톤 관리를 위한 표준차트의 필요성이 있다고 판단하여 진행하였다. 적외선 표준 차트의 제작은 두 가지 방법으로 접근하였다. 첫 번째는 알루미늄을 이용한 제작방법이었다. 알루미늄은 양극산화처리를 거쳐 산화피막을 형성하게 되면 높은 내구성과 내식성 내열성을 가지면서도 두께에 따라 적외선 대역에서의 어느 정도의 반사율을 조절할 수 있었다. 두 번째 접근 방법은 안료를 사용하는 방법이었다. 가장 밝은 패치를 위해서 Yellow 10P150라는 특수 안료를 사용하였다. 이 안료는 열에 강하며 높은 적외선 반사율을 가지도록 특수 제작된 안료로 본 실험에 적합하였다. 가장 어두운 패치를 위해 사용한 카본블랙 안료를 사용하였다. 카본블랙은 적외선을 많이 흡수하고 빛에 의해 색이 변하지 않는 안료이기 때문에 적합하였다. 이 두 안료를 섞어 더욱 세밀한 반사율 조절이 가능하였다. 최종적으로 패치들을 모아 실질적인 적외선 반사율을 기준으로 6개의 패치를 선택하였다. 이들을 촬영하여 확인한 결과 피사체의 적외선 반사율을 알아냄과 동시에 적절한 콘트라스트를 가지는 사진을 얻을 수 있다.

• 한국결정성장학회지
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• 제21권5호
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• pp.205-209
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• 2011

ZnO는 반도전성과 초전도성을 나타내며 광학적으로도 독특한 재료로 가스센서, 태양전지, 광학도파관 등 여러 방면에 널리 활용되고 있다. 본 논문에서는 이러한 ZnO에 Al을 첨가함에 따라 광학적 특성에 어떠한 영향을 미치는지 알아보기 위하여 ZnO에 Al 첨가량 변화에 따른 나노구조체를 제작하여 특성을 비교하였다. ZnO 용액은 PVP, ethanol, zinc acetate를 이용하여 Sol의 형태로 제작하였으며, Al첨가용액을 넣어 Al이 첨가된 ZnO Sol을 제작하였다. 제작된 Sol을 전기 방사법을 이용하여 나노구조체를 제조하였다. 제조된 섬유들을 각각 300, 500, $700^{\circ}C$로 열처리 한 후 나노 구조체를 XRD, XPS, SEM을 이용하여 분석하였다. 또한 TGA, DSC를 이용하여 온도변화에 따른 질량 및 열량의 변화를 측정하였다. UVvis를 이용하여 ZnO와 Al이 첨가된 ZnO의 흡광도를 측정 비교하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제44권4호
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• pp.343-350
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• 2021

3D printing technology is an additive manufacturing technology produced through 3D scanning or modeling method. This technology can be produced in a short time without mold, which has recently been applied in earnest in various fields. In the medical field, 3D printing technology is used in various fields of radiology and radiation therapy, but related research is insufficient in the field of nuclear medicine. In this study, we compare the characteristics of traditional nuclear medicine phantom with 3D printing technology and evaluate its applicability in clinical trials. We manufactured the same size phantom of poly methyl meta acrylate(PMMA) and acrylonitrile butadiene styrene(ABS) based on the aluminum step wedge. We used BrightView XCT(Philips Health Care, Cleveland, USA) SPECT/CT. We acquired 60 min list mode for Aluminum, PMMA and ABS phantoms using Rectangular Flood Phantom (Biodex, New York, USA) ^99mTcO₄ 3 mCi(111 MBq), 6 mCi (222MBq) and ⁵⁷Co Flood phantom(adq, New Hampshire, USA). For the analysis of acquired images, the region of interest(ROI) were drawn and evaluated step by step for each phantom. Depending on the type of radioisotope and radiation dose, the counts of the ABS phantom was similar to that of the PMMA phantom. And as the step thickness increased, the counts decreased linearly. When comparing the linear attenuation coefficient of Aluminum, PMMA and ABS phantom, the linear attenuation coefficient of the aluminium phantom was higher than that of the others, and the PMMA and ABS phantom had similar the linear attenuation coefficient. Based on ABS phantom manufactured by 3D printing technology, as the thickness of the PMMA phantom increased, the counts and linear attenuation coefficient decreased linearly. It has been confirmed that ABS phantom is applicable in the clinical field of nuclear medicine. If the calibration factor is applied through further research, it is believed that practical application will be possible.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.857-869
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• 2015

The aluminum 7075-T6 is known as an alloy widely used in aircraft structural applications, which does not exhibit strain rate sensitivity during dynamic compressive tests. Despite mechanical importance of the material, there is not enough attention to determine appropriate sample dimensions such as a sample diameter relative to the device bar diameter and sample length to diameter (L/D) ratio for dynamic tests and how these two parameters can change mechanical behaviors of the sample under dynamic loading condition. In this study, various samples which have different diameters of 31.8, 25.4, 15.9, and 9.5 mm and sample L/D ratios of 2.0, 1.5, 1.0, 0.5, and 0.25 were tested using Split Hopkinson Pressure Bar (SHPB), as this testing device is proper to characterize mechanical behaviors of solid materials at high strain rates. The mechanical behavior of this alloy was examined under ${\sim}200-5,500s^{-1}$ dynamic strain rate. Aluminum samples of 2.0, 1.5 and 1.0 of L/D ratios were well fitted into the stress-strain curve, Madison and Green's diagram, regardless of the sample diameters. Also, the 0.5 and 0.25 L/D ratio samples having the diameter of 31.8 and 25.4 mm followed the stress-strain curve. As results, larger samples (31.8 and 25.4 mm) in diameters followed the stress-strain curve regardless of the L/D ratios, whereas the 0.5 and 0.25 L/D ratios of small diameter sample (15.9 and 9.5 mm) did not follow the stress-strain diagram but significantly deviate from the diagram. Our results indicate that the L/D ratio is important determinant in stress-strain responses under the SHPB test when the sample diameter is small relative to the test bar diameter (31.8 mm), but when sample diameter is close to the bar diameter, L/D ratio does not significantly affect the stress-strain responses. This suggests that the areal mismatch (non-contact area of the testing bar) between the sample and the bar can misrepresent mechanical behaviors of the aluminum 7075-T6 at the dynamic loading condition.

• 대한치과보철학회지
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• 제40권3호
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• pp.296-305
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• 2002

The main disadvantage of cement-retained implant restorations is their difficulty in retrievability. Advocates of cemented implant restorations frequently state that retrievability of the restoration can be maintained if a provisional cement is used. The purpose of this study was to find the optimal properties of provisional luting cements and the surface treatment of abutments in single implant abutment system. 30 prefabricated implant abutments, height 8mm, diameter 6mm, 3-degree taper per side, with light chamfer margins were obtained. Three commercially available provisional luting agents which were all zinc oxide eugenol type ; Cavitec, TempBond and TempBond NE were evaluated. No cement served as the control. TempBond along with vaseline, a kind of petrolatum (2:1 ratio) was also evaluated. Ten out of thirty abutments were randomly selected and abutment surfaces were sandblasted with $50{\mu}m$ aluminum oxide. Another ten abutments were sandblasted with $250{\mu}m$ aluminum oxide. A vertical groove, 1 mm deep and 5mm long was cut in each twenty abutments. Ten of them were sandblasted with $50{\mu}m$ aluminum oxide. The full coverage casting crowns were cemented to the abutments with the designated provisional luting agent. Specimens were stored in distilled water at $37^{\circ}C$ for 24 hours. Each specimen was attached to a universal testing machine. A crosshead speed of 0.5mm/min was used to apply a tensile force to each specimen. Within the limitations of this in vitro study, the following conclusions were drawn: 1. Tensile bond strength of provisional luting cements in no surface treatment decreased with the sequence of TempBond NE, TempBond, Cavitec, TempBond with vaseline, no cement. 2. Tensile bond strength more increased by surface treatment. Sandblasting with $250{\mu}m$ aluminum oxide exhibited the highest tensile bond strength in the abutment cemented with TempBond NE and sandblasting with $50{\mu}m$ aluminum oxide exhibited the highest tensile bond strength in cemented with TempBond. 3. In the aspect of a groove formation, tensile bond strength significantly increased in TempBond with vaseline only and the others had no significant effect on tensile bond strength.

• 공업화학
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• 제23권1호
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• pp.1-7
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• 2012

본 총론에서는 원자층 증착을 이용한 친환경 소재의 개발에 대한 최근 연구 결과들을 간단하게 소개하려 한다. 원자층 증착의 장점은 박막의 두께를 미세하게 조절할 수 있다는 것과, 3차원적으로 복잡한 구조를 가지는 담체의 형상을 유지하면서 균일한 박막을 제조할 수 있다는 것이다. 이러한 원자층 증착의 장점은 친환경소재를 제조하는 데 중요한 역할을 할 수 있다. Anodic aluminum oxide (AAO)와 같은 다공성 membrane을 담체로 이용하여, 다공성 구조는 그대로 유지하면서 10나노미터 정도의 $TiO_2$박막을 균일하게 증착할 경우 톨루엔 등의 휘발성 유기물 필터로 사용할 수 있는데, 이는 AAO의 특이한 기하학적 구조와 비정질 $TiO_2$의 강한 휘발성 유기물 흡착력의 조합에 의한 결과이다. 톨루엔 분해용 광촉매 및 이산화탄소 개질 반응에 의한 수소 생산 촉매 반응에 있어서도 나노다이아몬드나 니켈 담체 위에 $TiO_2$의 증착량을 미세하게 조절하여 $TiO_2$가 표면을 완전히 덮지 않고 부분적으로만 덮고 있는 구조를 만들 경우 촉매의 효율 및 수명을 극대화할 수 있게 된다. 이러한 예들은 원자층 증착이 기존의 반도체산업뿐만 아니라 환경소재의 개발에도 중요한 도구가 될 수 있음을 의미한다.

• Archives of Reconstructive Microsurgery
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• 제17권2호
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• pp.120-125
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• 2008

Purpose: Heat therapy by heat lamp after microvascular surgery is being used for preventing blood vessels's contraction and blood-flow's disturbance. As usually, incandescent lamp has been used. But there have been several problems and need for improvement in the existing heat lamp treatment. So we would like to introduce improved heat lamp to keep an appropriate temperature and intensity of illumination. Methods: The existing heat lamps are the ones of general light stands covered with newspaper, having 60 watt light bulb of incandescence and lampshade made of aluminum. We have tried to improve shortcomings of the existing heat lamps by enlarging the size of aluminum lampshade and attaching a curtain that can block heat and light. We conducted a comparative study between the existing and improved heat lamps. Under the assumption that there are several affected parts, we have also measured the distance from heat lamp to patients' eye region and then intensity of illumination. Result: The target temperature of surface was realized in 11 minutes with the maximum temperature reaching at 36.6 degrees C in 28 minutes at the existing heat lamp while the target temperature reached in 7 minutes with the maximum temperature reaching at 39.0 degrees C in 17 minutes at the improved heat lamp. The existing and improved heat lamp showed 38 lx and 0.1 lx of intensity of lumination, respectively. Conclusion: Using improved heat lamps, we can keep an appropriate temperature and we think we can make contribution to patients' treatment by making them and their neighbors able to sleep with minimized disturbance thanks to low intensity of illumination secured by blocking light.