• 한국식품영양과학회지
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• 제45권1호
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• pp.117-125
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• 2016

아질산염과 dimethylamine(DMA)은 발암물질인 N-nitrosodimethylamines(NDMA)의 직접적인 전구물질이다. 본 연구에서는 아질산염과 질산염 함량이 다른 배추가 김치 저장 중에 NDMA, 아질산염, 질산염 그리고 DMA 함량 변화에 미치는 영향을 알아보았다. 배추 1(HNC), 배추 2(MNC) 그리고 배추 3(LNC)의 아질산염 농도는 각각 $47.54{\pm}1.07$, $10.12{\pm}0.31$ 그리고 $6.10{\pm}0.09mg/kg$이었다. 김치는 세 그룹으로 나누었다. 즉 HNC를 사용하여 제조한 HNK, MNC를 사용하여 제조한 MNK 그리고 LNC를 사용하여 제조한 LNK이다. HNK는 저장 10일과 20일째 아질산염과 질산염 수준이 MNK와 LNK의 그것들보다 더 높았다. 모든 김치에서 DMA와 NDMA 함량은 저장기간 동안 감소하였다. HNK는 저장 20일까지 LNK보다 높은 NDMA 함량을 가지고 있었다. 이들 결과들은 배추의 아질산염과 질산염의 함량이 김치 내 NDMA 형성에 현저한 영향력을 가지고 있다는 것을 제안하였다.

• 디자인학연구
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• 제13권1호
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• pp.59-66
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• 2000

차량용 항법장치의 기능들이 더욱 고급화, 다양화되면서 사용자가 사용하는 기능이 증가함에 따라 운전자의 입장에서 순간적으로 가장 단순 명확하게 사용할 수 있는 인터페이스가 중요하다. 그러나 현재 사용중인 자동차 항법장치의 사용환경은 이러한 요구들을 만족시키지 못하고 있다. 본 연구는 이러한 문제점을 개선하기 위하여 자동차 항법장치를 구성하는 일반적인 사용환경을 파악하고 이에 따른 경쟁상 제품의 기능을 비교 분석하여 필요한 기능을 추출한 후, 현대자동차(주) 에쿠스(Equus)차량에 적용되고 있는 현대전자(주) HNK-100 LD 모델을 중심으로 객체 모델과 동적 모델을 분석하였다. 아울러 현대자동차(주) 에쿠스에 장착된 현대전자(주) HNK-100LD 모델에서 사용자가 직접 조작하는 행동을 비디오로 촬영하여 분석하는 관찰기법을 사용하여 사용자의 멘탈 모델 (Mental Model)을 분석하여 자동차 항법 장치의 사용자 인터페이스 디자인 가이드 라인을 제시한다.

• 한국정밀공학회지
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• 제31권7호
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• pp.627-634
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• 2014

Machine tool vibration is well known for reducing machining accuracy. Because vibration response of a linear structure generally depends on its transfer function if the magnitude of excitation were kept constant, this study introduces a RET(Random Excitation Test) based on FRF method to evaluate stiffness of a prototype HDMTL(Heavy-Duty Multi-Tasking Lathe) for large crankshaft of marine engine. Firstly, two force loops of the lathe and corresponding structural loops were identified:1) workpiece - spindle - head stock - main bed, 2) workpiece - tool post - carriage bed. Secondly, compliances of each structural loop were measured respectively using RET with a hydraulic exciter and then converted into stiffness. Finally, the measured stiffness was compared with that obtained previously by FEM analysis. As the result, both measured and computed stiffness were closely in agreement with each other. And the prototype HDMTL has evidently sufficient rigidity above ordinary heavy-duty lathes.

• 한국정밀공학회지
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• 제29권2호
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• pp.129-138
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• 2012

In this study, three types of large scale multi-tasking machine tools together with core technologies involved have been developed and introduced; a multi-tasking machine tool for large scale marine engine crankshafts, a multi-tasking vertical lathe for windmill parts, and a large scale 5-axis machine tool of gantry type. Several special purpose devices has been necessarily developed for the purpose of handling and machining big and heavy workpieces accurately, such as PTD (Pin Turning Device) with revolving ring spindle for machining eccentric crankshaft pins, hydrostatic rotary table and steady rest for supporting and resting heavy workpieces, and 2-axis automatic swiveling head for high-quality free surface machining. Core technologies have been also developed and adopted on their detail design stage; 1) structural design optimization with FEM structural analysis, 2) theoretical hydrostatic analysis for the PTD and rotary table bearings, 3) box-in-box type cross-rail and octagonal ram design to secure machine rigidity and accuracy, 4) constant spindle rpm control against gravitational torque due to unbalanced workpiece.

• Molecules and Cells
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• 제38권3호
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• pp.221-228
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• 2015

Because Schwann cells perform the triple tasks of myelination, axon guidance and neurotrophin synthesis, they are candidates for cell transplantation that might cure some types of nervous-system degenerative diseases or injuries. However, Schwann cells are difficult to obtain. As another option, ectomesenchymal stem cells (EMSCs) can be easily harvested from the nasal respiratory mucosa. Whether fibrin, an important transplantation vehicle, can improve the differentiation of EMSCs into Schwann-like cells (SLCs) deserves further research. EMSCs were isolated from rat nasal respiratory mucosa and were purified using anti-CD133 magnetic cell sorting. The purified cells strongly expressed HNK-1, nestin, $p75^{NTR}$, S-100, and vimentin. Using nuclear staining, the MTT assay and Western blotting analysis of the expression of cell-cycle markers, the proliferation rate of EMSCs on a fibrin matrix was found to be significantly higher than that of cells grown on a plastic surface but insignificantly lower than that of cells grown on fibronectin. Additionally, the EMSCs grown on the fibrin matrix expressed myelination-related molecules, including myelin basic protein (MBP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and galactocerebrosides (GalCer), more strongly than did those grown on fibronectin or a plastic surface. Furthermore, the EMSCs grown on the fibrin matrix synthesized more neurotrophins compared with those grown on fibronectin or a plastic surface. The expression level of integrin in EMSCs grown on fibrin was similar to that of cells grown on fibronectin but was higher than that of cells grown on a plastic surface. These results demonstrated that fibrin not only promoted EMSC proliferation but also the differentiation of EMSCs into the SLCs. Our findings suggested that fibrin has great promise as a cell transplantation vehicle for the treatment of some types of nervous system diseases or injuries.