• 대한화장품학회지
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• 제37권4호
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• pp.303-308
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• 2011

레몬 오일과 유칼립투스 오일은 노화방지, 살균작용과 같은 다양한 효능을 가진 것으로 알려져 있다. 그러나 특정 피부 상재균에 대한 항균 효과와 항산화 효과는 아직 연구가 미비한 상황이다. 따라서 본 연구에서는 DPPH 라디칼 소거능 실험과 paper disc 방법을 이용하여 단일 오일들과 혼합오일의 항산화와 항균 활성을 검증하고자 하였다. 레몬 오일은 높은 DPPH 소거능을 보였으나 유칼립투스 오일은 아주 약한 소거능을 보였다. 두 오일을 혼합한 경우에는 효과가 증대되지 않았다. Paper disc 기법을 이용한 항균 효과 시험에서는 두 오일 모두 Candida albicans (C. albicans) 와 Propionibacterium acnes (P. acne)에서 항균력이 우수하며 농도의존적인 효능이 있음을 알 수 있었다. 또한, 두 오일 을 혼합 하였을 때 P. acne에 대하여 항균 활성이 상승됨을 알 수 있었다. 본 연구의 결과를 종합적으로 볼 때, 레몬 오일과 유칼립투스 오일의 혼합 오일은 천연성분으로서 균으로 야기된 문제성 피부나 여드름 피부를 개선시키는데 효과적일 것으로 사료된다.

• Journal of applied mathematics & informatics
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• 제29권1_2호
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• pp.49-53
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• 2011

In this paper, we adopt a numerical method to establish the smallest set to contain all Ger$\v{s}$gorin discs of a given complex matrix and its some similar matrices. With the smallest set, a new estimation for all eigenvalues of the matrix is obtained.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.312-316
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• 2004

The paper presents a technique to identify the boundary of the optic disc in infant retinal digital images using an approach based on active contours (snakes). The technique can be used to be develop a automate system in order to help the ophthalmologist's diagnosis the retinopathy of prematurity (ROP) disease which may occurred on preterm infant,. The optic disc detection is one of the fundamental step which could help to create an automate diagnose system for the doctors we use a new kind of active contour (snake) method has been developed by Chenyang et. al. [1], based on a new type of external force field, called gradient vector flow, or GVF. GVF is computed as a diffusion of the gradient vectors of a gray-level or binary edge map derived from the image. The testing results on a set of infant retinal ROP images verify the effectiveness of the proposed methods. We show that GVF has a large capture range and it's able to move snakes into boundary concavities of optic disc and finally the optic disk boundary was determined.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.236-240
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• 2005

This paper deals with friction-induced vibration of disc brake system under constact friction coefficient. A linear, finite element model to represent the floating caliper disc brake system is proposed. The complex eigenvalues are used to investigate the dynamic stability and in order to verify simulations which are based on the FEM model, The comparison of experimental and analytical results shows a good agreement and the analysis indicates that mode coupling due to friction force and geometric instability is responsible fur disc brake squeal. And the Front brake system reduced the squeal noise using design of experiment method(DOE). This helped to validate the FEM model and establish confidence in the simulation results. Also they may be useful during real disk brake model.

• 동력기계공학회지
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• 제21권6호
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• pp.56-61
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• 2017

The check valves are mechanical valves that permit fluids to flow in only one direction, preventing flow from reversing. It is classified as one way directional valves. There are various types of check valves that used in a marine application. A lift type check valve uses the disc to open and close the passage of fluid. The disc lift up from seat as pressure below the disc increases, while drop in pressure on the inlet side or a build up of pressure on the outlet side causes the valve to close. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. On the other hand, optimization is a process of finding the best set of parameters to reach a goal while not violating certain constraints. The AMESim software provides NLPQL(Nonlinear Programming by Quadratic Lagrangian) and genetic algorithm(GA) for optimization. NLPQL is the implementation of a SQP(sequential quadratic programming) algorithm. SQP is a standard method, based on the use of a gradient of objective functions and constraints to solve a non-linear optimization problem. A characteristic of the NLPQL is that it stops as soon as it finds a local minimum. Thus, the simulation results may be highly dependent on the starting point which user give to the algorithm. In this paper, we carried out optimization design of the check valve with NLPQL algorithm.

• 한국산학기술학회논문지
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• 제15권11호
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• pp.6406-6411
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• 2014

본 논문은 자동차 디스크 브레이크에서 발생하는 스퀼 현상을 보다 효과적으로 해석할 수 있는 스퀼 융합모델을 소개한다. 시스템의 형상 및 진동모드 추출은 유한요소법을 따르고 각 부품별 접촉부의 기술은 수학적 모델을 이용한다. 특히 회전하는 디스크와 정지상태의 패드 간 마찰력을 수학적으로 정교하게 기술하여 이를 유한요소 운동방정식에 접목한다. 이를 통해 선형안정성의 해의 정확도를 개선한다. 또한 다양한 시스템 파라메터 연구를 통하여 접촉강성에 대한 스퀼 민감도 및 모드연성 메카니즘을 구현한다.

• 한국정밀공학회지
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• 제25권12호
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• pp.132-138
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• 2008

Recently, mastering processes for high density optical disc such as Blu-ray disc rely on electron beams, which are operable in only vacuum. In the mastering process, one of the most important tasks is to design precision stages for providing precise positioning of the works with respect to the source in a high vacuum environment. In this paper, we have developed a precision rotation table usable in the electron beam mastering. The rotation table adopted air bearings for a high positioning repeatability and velocity stability. The air leakage from the air bearings has been minimized by employing the differential exhaust scheme using three steps of air drain. The design parameters such as diameters of exhaust lines, seal lengths, and pumping speeds were decided according to the optimization method using genetic algorithm. The performance on the vacuum level of the rotation table was evaluated experimentally and theoretically. The results indicate that a vacuum level of $10^{-4}$ Pa is achieved with operation of air bearings in a vacuum chamber, which is sufficient for the electron beam mastering.

• 정보저장시스템학회논문집
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• 제3권1호
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• pp.1-4
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• 2007

A high density optical data storage device has been required for many years. In the field of the optical data storage, a near-field recording (NFR) technology is considered as a next generation one for achieving the high data density. Due to an evanescent wave effect occurred under 100nm distance which is the excessively small distance between the SIL and the disc, the most significant and difficult problem in this technology is to maintain a gap between a solid immersion lens (SIL) and a disc. Also, maintaining the gap under at least 50nm is required in the NFR gap servo system to use the evanescent wave effect efficiently. There are some institutes that have shown the novel gap servo control. In general, they use a mode switching servo method which consists of approach, hand-over and gap control mode. However there is a critical problem such as an overshoot at the tuning point from the approach mode to the hand-over mode, which may cause a collision between the SIL and the disc. In this paper, we show our NFR system and an improved gap servo system using an exponential function as the approach mode which can reduce the overshoot.

• 자동차안전학회지
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• 제11권1호
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• pp.23-29
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• 2019

Recently, use of composite materials has been increasing for body structures and chassis parts in the car industry because of weight reduction effect and excellent mechanical thermal characteristics. However, application of composite materials in brake system is very difficult because it is hard to obtain enough brake performance due to low heat storage capacity of the composite materials. In this paper, we will present new carbon ceramic composite disc with high flow characteristic. To obtain this characteristic, new vent structures were designed by using ARIZ method and substance-field model analysis. The flow effect of these vent structures on the brake performance was verified by pugh matrix and cooling test. The test results show improvement of cooling performance up to $30^{\circ}C$. Finally, These results will improve brake the reliability of the brake performance for the high performance vehicles and electric vehicles.

• 한국응용과학기술학회지
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• 제37권1호
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• pp.145-152
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• 2020

본 연구에서는 붉나무 열매 Ethanol extract(ET)과 Ethyl acetate fraction(EA) 및 Butanol fraction(BT)을 천연보존제로서의 활용 가능성을 평가하기 위하여 항균활성을 측정 하였다. 항균활성은 Staphylococcus aureus(S. aureus), Staphylococcus epidermidis(S. epidermidis), Escherichia coli(E. coli), Pseudomonas aeruginosa(P. aeruginosa), Candida Albicans(Candida. A)에 대하여 Paper disc법으로 생육저해환과 최소저해농도(MIC)를 평가하였다. Paper disc법으로 생육저해환을 측정한 결과 ET, EA, BT 모든 시료에서 S. aureus, S. epidermidis, E. coli, P. aeruginosa 균주에서 생육저해환이 관찰되었고 BT에서는 Candida. A 균주에 대한 생육저해환이 추가로 관찰 되었다. MIC 측정결과 EA 시료가 S. aureus, S. epidermidis, E. coli, P. aeruginosa 대하여 가장 낮은 농도를 보였다. 따라서 본 연구의 결과는 붉나무 열매 추출물이 다양한 항균스펙트럼을 가지고 있어 화장품에서 천연보존제로 활용 가능성이 높다고 사료 된다.