• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.502-502
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• 2011

기존 연구에서는 단일 타겟으로부터 증착된 코팅층 내에 다상으로 이루어진 나노 복합구조를 형성하기 위하여, 나노 합금분말을 방전플라즈마 소결법 등으로 급속 소결하여 타겟을 제조하는 방법이 고려되어 왔다. 반면, 비정질 재료가 우수한 비정질 형성능을 가지는 경우 주조 방법에 의해서도 타겟 제조가 가능하며, 특히 최근 들어 금속 비정질 합금에서 합금의 주요 구성 원소들이 양의 혼합열을 가지는 경우, 액상 또는 과냉각 액상에서 상분리 현상이 발생한다는 것이 밝혀졌다. 이러한 사실에 기초하면, 우수한 비정질 형성능을 가지는 합금 시스템에 합금 구성 원소와 양의 혼합열 관계를 갖는 원소를 첨가함으로써, 비정질 기지 내에 화학적 불균일성을 유도하여 다상으로 이루어진 복합 구조를 형성시키는 것이 가능하다. 본 연구에서는 이러한 합금 설계법을 이용하여, 비정질 기지 내에 존재할 수 있는 불균일성 정도를 합금 조성과 주조 조건의 변화를 통하여 나노 크기에서 원자 크기까지 조절하고, 이에 따른 재료 특성과의 상관관계를 밝히고자 하였다. 이를 위하여 우수한 비정질 형성능을 가지는 Cu-(Zr, Hf)-Al 벌크 비정질 합금계에서 (Zr, Hf)과 (Y, Gd)간의 양의 혼합열 관계에 주목하여 Cu-(Zr, Hf)-(Y, Gd)-Al 벌크 비정질 형성 합금계를 설계하였으며, 이 합금계 내에서 조성과 냉각속도의 조절에 따라 나타나는 불균일성의 정도와 특성변화의 영향을 체계적으로 고찰하였다. 결과로서, Cu-(Zr, Hf)-Al 합금계에서 (Zr, Hf)을 (Y, Gd)으로 15 at.% 이상 치환한 경우, Cu-(Zr, Hf)-rich 와 Cu-(Y, Gd)-rich 비정질상으로 이상분리가 일어났으며, 이렇게 생성된 비정질-비정질 복합재는 응력 하에서 소성 변형을 거의 보이지 않았다. 반면, 5 at.% 이하로 (Zr, Hf)을 (Y, Gd)으로 치환한 경우에는 비정질 기지에 SAXS 혹은 WAXS로 확인 가능한 원자 크기의 불균일성이 나타났으며, 이 경우 비정질 합금의 점성 유동의 변화를 통해 합금의 연신 특성이 향상되었다. 특히, 본 연구에서는 비정질 기지내 불균일 제어를 통한 기계적 특성 향상을 위해서 조성 제어뿐 아니라 동역학적인 요소를 고려한 냉각속도 조절을 통한 원자단위 불균일성의 최적화가 필요함을 규명하였다. 이러한 연구 결과는 분말화 및 소결 과정을 배제하고 제조된 단일 타겟을 통해 코팅층에 다수의 합금원소를 혼합하고 나노/원자 스케일의 복합구조 형성 및 고집적화가 가능한, 타겟 모물질 설계의 새로운 방향을 제시함으로써 다기능성 복합소재 코팅층의 연구에 크게 기여할 것으로 사료된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1040-1046
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• 2006

This paper is aimed to investigate the deformation caused by ununiform contraction of injection molding with highly big differences of thickness by the continuity of various curvature radius. By CAE analysis, the uniform cooling structure and optimum molding conditions are found for Jars made of SAN and PMMA materials and applied to the design of chill. In order toevaluate the molding pressure, resin temperature, molding temperature, cooling conditions, Moldflow program is applied. As results of experiments, the deformation and inferiority phenomena in Jars are analyzed for each factor and proposed the injection molding conditions to minimize the cooling structure and reduce the cycle time.

• Proceedings of the KAIS Fall Conference
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• 2006.11a
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• pp.261-264
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• 2006

본 논문에서는 다양한 곡률반경의 연속에 의하여 살 두께 차가 큰 사출성형품에 불균일한 수축으로 인한 변형이 생성되어 이를 방지하기 위한 적정 CAE 냉각설계를 수행하였다. SAN 및 PMMA 재질의 Jar용기에 대한 균일냉각구조와 최적성형조건을 금형설계에 적용하고자 사출성형의 중요인자인 사출압력, 수지온도, 금형온도, 냉각조건 등을 moldflow 프로그램을 활용하여 연구를 수행하였다. 연구결과로서, 적정 변수인 사출압력 상승, 수지온도 낮춤, 급속냉각으로 후로우 등의 불량현상을 분석하였고 변형 및 불량을 극소화시킬 수 있는 냉각구조와 사이클 시간을 단축시킬 수 있는 사출성형조건을 제시하였고 적정 냉각모듈로부터 냉각시간을 단축하였다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.273-275
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• 2008

Generally, automobile cooling fan is used to lower the temperature of radiator. The cooling fans are manufactured by plastic injection molding process. The center of gravity of cooling fan is often deviated from the center because of the use of deteriorated materials. As the unbalance of the cooing fan can generate noise, it is required to test the performance of the cooling fans. In this work, automatic fan balancer which can distinguish between the good and the bad, futhermore idenfify the position and magnitude of unbalance is develpoed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.6
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• pp.59-65
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• 2010

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SCM415 steel. The control of heat-treatment deformation must need the progress of production parts for an industry machine. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for the part of the industry machine by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on the thermal deformation and fatigue strength are also investigated.

• Journal of Welding and Joining
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• v.22 no.2
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• pp.1-2
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• 2004

강구조물 제작시 용접프로세스에 의해 용접부 근방에서는 용접열원에 의해 급속가열ㆍ급속냉각의 열 사이클을 받으며, 열원의 이동과 함께 온도장이 변화하므로 용접부에 불균일한 온도분포가 발생된다. 이러한 불균일한 온도분포에 의한 용접부 근방의 열팽창ㆍ수축을 용접부로부터 떨어져 있는 저온상태의 부재가 이를 구속하여 결과적으로 용접변형과 잔류응력이 발생한다.(중략)

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.98-102
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• 2012

These days, Uncooled IR Systems are more popular in the area of defense and aerospace than before. Uncooled IR Systems are widely used as core technology for making unmanned systems and detecting enemy objects during the day and night in the distance. Recently, researches on TEC-less IRFPA have been increased to minimize the power consumption and to make a smaller system than before. For this, it needs to find adequate NUC(Non-Uniformity Correction) coefficients as FPA(Focal Plane Array) temperature changes. In this paper, we propose a new NUC coefficient estimating technique, DCCE-LI(Dynamic Calibration Coefficients Estimation with Linear Interpolation), for TEC-less IRFPA. It is based on a linear interpolation method and it can estimate NUC coefficients in real-time. So, by testing and evaluating it with some IR images, we conclude that the quality of IR images using proposed method is better than applying static coefficients.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.1
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• pp.83-89
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• 2009

Generally, automobile cooling fan is used to lower the temperature of radiator. The cooling fans are manufactured by plastic injection molding process. The center of gravity of cooling fan is often deviated from the center due to the use of deteriorated materials. As the unbalanced of the cooing fan can generate noise, it is required to measure the degree of deviation of center of gravity in the cooling fan. In this work, automatic fan balancer which can effectively detect the magnitude and position of the unbalanced cooling fan is proposed and several experiments are carried out to verify the feasibility of the proposed algorithm.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.219-225
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• 2019

In an infrared optical system, using a cooled detector generates a phenomenon called a narcissus, in which the focal-plane array cooled to very low temperatures is reflected at the lens surface and detected. The narcissus can be removed by non-uniformity correction of the detector pixel, so narcissus is generally ignored in infrared optics. However, non-uniformity correction reduces the sensitivity of the system. Also, as the housing temperature varies due to an environmental temperature change, or a lens is moved for focusing or athermalization purposes, a narcissus may occur even after non-uniformity correction. To minimize such a narcissus, the amount of the effect must be controlled in the lens-design stage. In this paper we designed a midinfrared optical system and analyzed the narcissus by setting the lens surface reflectance to 1%. In addition, the design was divided into stages of an initial design, an improved design, and a minimum design, and the narcissus was improved to about 56% of that in the initial design.

• Journal of the Korean Magnetics Society
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• v.11 no.4
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• pp.173-178
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• 2001

The effects of heat-treatment with magnetic or non-magnetic field on magnetic properties of gas-atomized MPP dust cores subjected to various cooling processes after annealing were investigated. Upon magnetic-field annealing, ac permeability and core loss decreased with the increase of cooling rate, which were attributed to the generation of inhomogeneous internal stress and anomalous eddy current loss, respectively. It was not observed the formation of ordered phase and the related change in magnetic properties at the cooling stage for MPP dust cores. In MPP alloys, magnetic anisotropy was easily induced through the directional order, and permeability and core loss were changed under the conditions of low cooling rate and magnetic annealing.