• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.494-499
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• 1996

와이어 스프링은 재료 조사시험용 캡슐을 노내에 장·탈착할 때 안내역할을 하고, 조사 시험중 캡슐에 수평방향의 외력이 작용하였을 때 이를 완화해 주는 역할을 하도록 설계되었다. 와이어 스프링의 강성은 특히 내진으로 인한 캡슐의 구조건전성 확보에 중요하므로, 본 연구에서는 스프링 강성에 스프링 와이어의 직경, 길이 그리고 형상이 미치는 영향을 해석하였다. 또한 실험을 통하여 해석 결과와 비교·검토하여 설계 요구사항을 만족하도록 하였다.

• Polymer(Korea)
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• v.37 no.3
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• pp.356-361
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• 2013

Microcapsules of two different self-healing agents, 5-ethylidene-2-norbornene (ENB) and ENB with a crosslinker, surrounded by a melamine-urea-formaldehyde shell were manufactured. In this work, a red dye was incorporated into the self-healing agents as a tracer for better visual observations. It revealed that the incorporation of a red dye into self-healing agents did not disturb the formation of microcapsules from the examination of thermal resistance, particle size/size distribution and morphology of the resulting microcapsules. Releasing of self-healing liquid into the induced crack from ruptured microcapsules and filling between crack planes were observed using an optical microscope. Also observed was the reaction of filled healing agent with embedded Grubbs' catalyst in an epoxy coating layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.9
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• pp.605-612
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• 2016

In this study, numerical simulations were conducted for conjugate heat transfer around ice balls in an encapsulated ice thermal storage system. Four shapes of ice balls were modeled; the default one was a sphere, and the other three shapes were designed to enhance convective heat transfer through the ball surface. The flow around the ball was laminar, for which the Reynolds number was 300, and both forced and natural convections inside and outside the balls were considered. The simulations revealed that the magnitude of convective heat transfer for the different shapes decreased in the following order: bone, dimple, hole, and sphere. For the entire simulation, the maximum difference in the average temperatures of water inside the capsules was found to be $0.9^{\circ}C$. Therefore, it can be said that the effect of ice-ball shape on the performance of the ice thermal storage system is significant, considering that more than 0.3 million balls are used in this system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.11
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• pp.964-971
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• 2002

A numerical investigation of the constrained melting of phase change materials within spherical-like capsule is presented. A single-domain enthalpy formulation is used for simulation of the phase change phenomenon. The solution methodology is verified with the melting process inside an isothermal spherical capsule. Especially, the effect of capsule shape on the heat storage is emphasized. Two shape parameters are considered from the real capsule shape showing good characteristics of heat storage and the effect of these parameters is examined. Early during the melting process, the conduction mode of heat transfer is dominant. Thus the capsule shape with large surface area is desirable. However, the capsule shape with large surface area plays negative role on the strength of buoyancy-driven convection that becomes more important as melting continues.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.295-295
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• 2002

• Polymer(Korea)
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• v.39 no.1
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• pp.56-63
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• 2015

The object of this study is to prepare microcapsules containing a diisocyanate compound, apply them to self-healing protective coating, and evaluate the self-healing capability of the coating by atmospheric moisture. Isophorone diisocyanate (IPDI) polymerized under humid atmosphere, indicating that IPDI can be used as a healing agent. Microencapsulations of IPDI were conducted via interfacial polymerization of a polyurethane prepolymer with diol compounds. The formation of microcapsules was confirmed by Fourier-transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The mean diameter, size distribution, morphology and shell wall thickness of microcapsules were investigated by optical microscopy and scanning electron microscopy (SEM). The properties of microcapsules were studied by varying agitation rates and diol structure. The self-healing coatings were prepared on test pieces of CRC board. When scratch was generated in the coatings, the core material flew out of the microcapsules and filled the scratch. The self-healing coatings were damaged and healed under atmosphere with 68~89% relative humidity for 48 h, and SEM and impermeability test for the specimens showed that the scratch could be healed by atmospheric moisture.

• Journal of the Korean Applied Science and Technology
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• v.29 no.2
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• pp.286-294
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• 2012

This study is a review paper on powders for makeup cosmetics. They play the roles of the camouflage of skin defect, UV screening, skin adhesion, makeup sustainability, and skin protection. This function is endowed on the powders by shape control, surface treatment, and encapsulation. The future powders are expected to be evolved into the smart model responding to the environmental change.

• Polymer(Korea)
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• v.39 no.1
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• pp.64-70
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• 2015

Thermally expandable microcapsules (TEMs) can be expanded upon heating since the activation energy of liquid hydrocarbon at the core of the TEMs increased at high temperature. Due to this property, TEMs are widely used in the industry as blowing agents or light-weight fillers. In this article, chemical blowing agent and TEM were used for making polypropylene (PP) foams, and their mechanical properties were compared. Physical properties (tensile strength, impact strength etc.) of PP foams decreased with increasing the amount of blowing agents while weight of specimen decreased. However, PP foam produced with TEMs showed higher impact strength than the one with a chemical blowing agent. In order to figure out the difference of impact strength, the morphology of PP foamed was investigated. Expanding properties of TEM can be controlled by changing core back distance.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.224-232
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• 1999

Latent heat storage system using micro-encapsuled phase change material is effective method for floor heating of house and building. The temperature profile in capsule block and flow rate of hot water are important parameters for the development of heat storage system. In the present study, a mathematical model based on 3-D, non-steady state, Navier-Stokes equations, scalar conservation equations and turbulence model ($\kappa$-$\varepsilon$), is used to predict the temperature profiles in capsule and the velocity vectors in hot water pipe. The multi-block grids and fine grids embedding are used to join the circle in hot water pipe and square in capsule block. The phase change process of the capsule is quite complex not only because the size of phase change material is very small, but also because phase change material is mixed with the cement to form thermal storage block. In calculation, it's assumed that the phenomena of phase change is limited only the thermal properties of phase change material and the change of boundary is not happened in capsule. The purpose of this study is to calculate the temperature profiles in capsule block and velocity vectors in hot water pipe using the numerical calculation. Two kinds of thermal boundary condition were considered, the first (case 1) is the adiabatic condition for the both outside surfaces of the wall, the second (case 2) is the case in which one surface is natural convection with atmosphere and another surface is adaibatic. Calculation results are shown that the temperature profile in capsule block for case 1 is higher than that for case 2 due to less heat loss in adaibatic surface. Specially, in the domain of near Y=0, the difference of temperature is greater in case 1 than in case 2. The detailed experimental data of capsule block on the temperature profile and the thermal properties such as specific heat and coefficient of heat transfer with the various temperature are required to predict more exact phenomena of heat transfer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1849-1855
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• 2003

Newly commercialized wireless capsule endoscope has many advantages compared to conventional push-type endoscopes. However, it is moved by the peristaltic waves. Therefore, it can not diagnose desired zones actively. In this paper, a locomotive mechanism for wireless capsule endoscope is proposed to increase the efficiency of endoscopy. We designed and fabricated a prototype using SMA springs and bio-mimetic clamping device. The hollow space in the prototype is allocated for further system integration of a camera module, a RF module and a battery. And the sequential control scheme is employed to improve the efficiency of its locomotion. To validate the performance of the locomotive mechanism, experiments on a silicone rubber pad and in vitro tests are carried out. The results of the experiments indicate that proposed mechanism is effective in harsh environments such as digestive organs of a human.