• 대한치과기공학회지
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• 제40권3호
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• pp.115-123
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• 2018

Purpose: The purpose of this study was establishing process of manufacturing dental prosthesis by using eZIS system(DDS Inc.,Korea). Methods: To evaluate accuracy verification, the test was practiced two ways. First, Comparison of 3D printing models and stone models was practiced by using 3D superimposing software. #36 prepared master model was scanned by eZIS system and three 'Veltz3D' 3D printing models and three 'Bio3D' 3D printing models were manufactured. three stone models were manufactured by conventional impression technique. Second, Fitness test was practiced. the 3D printing models and the stone models was compared by manufacturing same resin crown. #36 prepared master model was scanned 9 times and manufactured (milled) 9 resin crowns by eZIS system. These crowns were cemented three 'Veltz3D' 3D printing models, three 'Bio3D' 3D printing models and three stone models. These crowns were sliced mesiodistal axis and gaps were measured by digital microscope. Results: The average accuracy of Bio3D models were 65.75%. Veltz3D(Hebsiba) models were 60.11% Stone models were 41.00%. Conclusion : This study results showed 3D printing model is similar with stone model. So it was under clinical allow, didn't affect final dental prothesis. There were no significant differences in the appearance of the three types of milling crowns.

• 공업화학
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• 제29권1호
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• pp.43-48
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• 2018

본 연구에서는 PCC (precipitated calcium carbonate) 제조에 있어 칼슘이온 추출 최적화를 위하여 추출 용제, 용제의 농도, 추출원의 투입량, 전처리 공정 등 다양한 추출 조건에 따른 실험을 수행하였다. 칼슘추출원으로 CaO를 사용하였으며, 칼슘이온의 추출량과 CaO의 입자크기를 확인하기 위하여 ICP와 SEM 분석을 수행하였다. 그 결과 2 M의 hydrochloric acid를 용제로 사용한 경우 100%의 칼슘이온이 추출되었으며, 추출원의 최적 투입량은 6 g으로 확인하였다. 반면 반응시간, 반응온도, 입자 분쇄 및 열처리 공정은 칼슘이온 추출량에 큰 영향이 없음을 확인하였다.

• 한국산학기술학회논문지
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• 제21권9호
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• pp.352-357
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• 2020

본 연구는 선박용 디젤엔진 부품인 축류 단조품을 단조작업에 의하여 제작하는 과정에서 발생하는 품질문제를 해결하기 위하여 수행되었다. 1차, 2차 가열 및 열간 단조를 거쳐 완성된 단조품은 최종 후열처리공정을 거치게 되는데 이 과정에서 발생하는 것으로 알려진 내부 결함문제를 해결하기 위하여 냉각공정을 평가하였다. 자유단조작업을 거쳐 제작된 축류 단조품에는 2차 열간 단조작업 후 냉각과정에서 소재 내부에 존재하고 있던 잔류 수소가 기공이나 미세 균열, 입계, 계면 등으로 확산, 집적됨으로써 균열을 유발하여 내부 결함이 발생하는 것으로 알려져 있으며 실제 작업현장에서 균열발생 사례가 보고되고 있다. 이러한 문제를 해결하기 위하여 수치해석 전용 프로그램인 ANSYS를 사용하여 열전달 수치해석을 수행하였으며, 해석모델은 축류 단조품의 특성상 축대칭요소를 사용하여 구성하였고 단조품 초기 온도 1250 ℃에서 단조작업 완료 후 냉각과정에서 시간이 경과함에 따른 온도변화를 평가하였다. 주어진 4종류의 축류 단조품에 대하여 온도이력을 평가한 결과 단조품 내부에 수소유기균열 발생이 예상되는 250 ℃까지 냉각되는데 소요되는 시간을 알 수 있었으며, 이러한 냉각시간은 추후 열처리 작업의 작업표준으로 적용함으로써 축류 단조품 제작 시품질과 생산성을 높일 수 있다는 것을 알 수 있다.

• 대한기계학회논문집A
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• 제41권3호
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• pp.199-204
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• 2017

현재 진동이 심한 산업현장에서 많은 종류의 풀림방지 너트가 사용되고 있다. 왜냐하면 진동의 풀림은 큰 사고를 유발할 수 있기 때문이다. 하지만 대부분의 풀림방지너트는 복잡한 가공과정을 거치기 때문에 가격 경쟁력에서 불리하다. 때문에 본 연구에서는 가공이 쉬운 새로운 유형의 커브드 너트를 개발 하고자 한다. 탄성에너지와 너트의 풀림메커니즘 사이의 탄성에너지를 연구하고 분석한 뒤, 나사의 풀림테스트를 한다. 커브드 너트는 기존너트에 밀링 공구를 이용하여 수직으로 한번 또는 두 번 너트의 밑면을 가공한다. 결과적으로 너트의 탄성에너지가 클수록 너트의 풀림을 막게 된다. 본 연구에서는 NAS3350의 진동테스트 장비를 이용하여 시험을 하고 결과를 분석한다.

• Restorative Dentistry and Endodontics
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• 제41권1호
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• pp.37-43
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• 2016

Objectives: The purpose of this study was to compare the marginal and internal fit of nano-composite CAD-CAM restorations. Materials and Methods: A full veneer crown and an mesio-occluso-distal (MOD) inlay cavity, which were prepared on extracted human molars, were used as templates of epoxy resin replicas. The prepared teeth were scanned and CAD-CAM restorations were milled using Lava Ultimate (LU) and experimental nano-composite CAD/CAM blocks (EB) under the same milling parameters. To assess the marginal and internal fit, the restorations were cemented to replicas and were embedded in an acrylic mold for sectioning at 0.5 mm intervals. The measured gap data were pooled according to the block types and measuring points for statistical analysis. Results: Both the block type and measuring point significantly affected gap values, and their interaction was significant (p = 0.000). In crowns and inlays made from the two blocks, gap values were significantly larger in the occlusal area than in the axial area, while gap values in the marginal area were smallest (p < 0.001). Among the blocks, the restorations milled from EB had a significantly larger gap at all measuring points than those milled from LU (p = 0.000). Conclusions: The marginal and internal gaps of the two nano-composite CAD/CAM blocks differed according to the measuring points. Among the internal area of the two nano-composite CAD/CAM restorations, occlusal gap data were significantly larger than axial gap data. The EB crowns and inlays had significantly larger gaps than LU restorations.

• Physical Therapy Rehabilitation Science
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• 제6권2호
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• pp.71-76
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• 2017

Objective: The purpose of this study was to investigate the musculoskeletal diseases (MSDs) that occur in heavy industrial workers according to the occupational category, prevalence, environment, and number of physical therapy visits. Design: Retrospective cohort study. Methods: For this study, data was collected of workers who were engaged in heavy industry in Korea and who visited the company physicians and received physical therapy in 2016. Data was collected from 855 subjects and was analyzed. With the data collected, analysis of the type and prevalence of MSDs and the number of physical therapy visits that have occurred according to the occupational category and environment was performed. Results: The most common MSDs were lumbar sprains and spasms (31.1%), and shoulder sprain and spasm (19.4%). In addition, the most common type of MSDs according to the occupational category and environment (occupational type) were lumbar sprain and spasms in 11 occupations, including white collar workers, and in milling, inspection, crane operation, and finishing jobs, shoulder muscle sprain and strain were the most common disorders. Also, the prevalence of MSDs according to occupational category and environment (occupational type) was the highest in workers involved with welding, which was 29.7%. Conclusions: Through this study, the type and prevalence of MSDs according to the occupational category and environment of heavy industrial workers have been confirmed. Further studies are necessary to study the future types of the work patterns of industrial workers and to develop a system for preventing and managing MSDs that may occur.

• 한국식품조리과학회지
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• 제31권6호
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• pp.781-790
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• 2015

Germinated brown rice (GBR) flour (0%, 25%, 50%, 75% and 100%) was added to brown rice (BR) and white rice (WR) flours and the densities of pound cake batters, morphology, color value, textural properties, sensory preference test, and hardness during storage were investigated, in order to develop health functional gluten-free rice pound cakes with high nutritional value. The rice was milled with the newly developed rice milling method. The entire shape and cross section of all cakes were symmetrical and desirable. The density of pound cake batter and weight of cake increased with addition of increasing GBR. Specific volume was not significantly different (2.1-2.4 mL/g). Textural properties of cakes between WR-GBR and BR-GBR showed different trends with adding GBR. On the sensory test, overall quality of rice pound cake did not significantly differ between rice flour types. Hardness of rice pound cakes and brittleness decreased with increasing addition of GBR flour. The hardness and the peak intensity at $2{\theta}=17^{\circ}$ decreased with increasing addition of GBR. The results, that addition of GBR flour improved the nutrition value and functionality of gluten free rice pound cakes and prevented staling of rice pound cakes during storage.

• 한국분말재료학회지
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• 제23권6호
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• pp.426-431
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• 2016

The Fe-Cr-Al alloy system shows an excellent heat resistance because of the formation of an $Al_2O_3$ film on the metal surface in an oxidizing atmosphere at high temperatures up to $1400^{\circ}C$. The Fecralloy needs an additive that can act as a binder because of its bad compactability. In this study, the green compacts of STS434L and Al powder added to Fecralloy are oxidized at $950^{\circ}C$ for up to 210 h. Fecralloy and Al is mixed by two types of ball milling. One is vented to air and the other was performed in a sealed jar. In the case of Al addition, there are no significant changes in the electrical resistance. Before the oxidation test, Al oxides are present in the Fecralloy surface, as determined from the energy dispersive spectroscopy results. The addition of Al improves the compactability because of an increased density, and the addition of STS434L increases the electrical resistivity by forming a composite oxide.

• Journal of Microbiology and Biotechnology
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• 제22권5호
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• pp.637-641
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• 2012

TPDex, a putative dextranase from Thermoanaerobacter pseudethanolicus, was purified as a single 70 kDa band of 7.37 U/mg. Its optimum pH was 5.2 and the enzyme was stable between pH 3.1 and 8.5 at $70^{\circ}C$. A half-life comparison showed that TPDex was stable for 7.4 h at $70^{\circ}C$, whereas Chaetominum dextranase (CEDex), currently used as a dextranase for sugar milling, was stable at $55^{\circ}C$. TPDex showed broad dextranase activity regardless of dextran types, including dextran T2000, 742CB dextran, and alternan. TPDex showed the highest thermostability among the characterized dextranases, and may be a suitable enzyme for use in sugar manufacture without decreased temperature.

• 한국식품과학회지
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• 제8권3호
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• pp.179-184
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• 1976

국내에서 새로이 보급된 Indica형 장려품종인 통일쌀녹말과 진흥쌀녹말의 특성을 조사한 결과는 다음과 같다. 1) 통일, 유신과 진흥쌀 호화온도는 각각 $72^{\circ}C,\;70^{\circ}C$ 및 $68{\sim}89^{\circ}C$이였다. 호화온도는 Indica 형이 Japonica형 보다 높았다. 2) 통일, 유신과 진흥쌀녹말의 blue value는 0.40, 0.39, 및 0.35이였고 품종간에 약간의 차이가 있었다. 3) 세가지 쌀품종의 녹말의 요오드정색도는 $610{\sim}625nm$에서 흡수극대를 보였다. 4) 통일, 유신과 진흥쌀녹말의 amylose 함량은 각각 23.2%, 21.3% 및 20.6%였고 이들 amylose 함량은 다른 곡물의 함량보다 낮았다. Amylose 함량은 Indica형이 Japonica형 보다 많았다. 5) 통일, 유신과 진흥쌀녹말의 alkali number는 각각 7.0 및 6.8로 품종간의 차이는 거의 없었다. 이들 값은 찹쌀녹말의 alkali number 보다 컸다.