• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.757-762
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• 2011

We investigate the transient temperature response in biological tissue whose surface is exposed to alternately varying sinusoidal oscillation. Based on the Pennes bio-heat equation, we apply numerical analysis using a finite element method to find the effects of the physical properties of the skin layers. Three layers of tissue-epidermis, dermis, and subcutaneous-are considered as the solution region. We investigate the effects of different properties of the skin layers on the temperature profile. We also investigate the effects of the perfusion rate for the dermis, which is the most sensitive layer. The results show that the temperature profile of tissue depth has a discontinuous point when different physical properties are used.

• Journal of Energy Engineering
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• v.12 no.3
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• pp.184-189
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• 2003

A study of the property of Indolene-Methanol Plus High Alcolhols (MPHA) has been completed. The study invested the measurement of fuel properties. The fuel properties investigated are distillation characteristics, heating value, flash point, specific gravity and water tolerance. The alcohol concentration was varied from 0 to 100 percent by volume in clear Indolene. The measurement of fuel properties indicated that, in general, Indolene-MPHA blends have higher water tolerance, similar specific gravity, similar flash point and different distillation characteristics compared to Indolene-Methanol blends.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.9-9
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• 2017

입자거동해석소프트웨어(EDEM)은 DEM(Discrete Element Method)기법을 이용한 입자 거동 전용 해석툴로 입자 유입량, 위치 등을 조절하여 입자거동과 관련된 제품 개발, 프로세스 최적화를 위한 비용 및 시간 절감에 활용도가 뛰어난 소프트웨어이다. EDEM을 활용하기 위해선 적용대상에 대한 물성치를 적용하여야 한다. 따라서 본 연구에서는 EDEM를 이용하여 현재 연구개발 중인 카드클리너 방식의 고추 선별기의 성능을 분석을 수행하기 위해 고추 물성측정 실험을 수행 하였다. EDEM을 이용한 입자거동해석에 필요한 개인 물성치에는 포아송비, 전단탄성계수, 밀도가 있다. 또한 입자-입자, 입자-Geometry 간의 상호관계를 위한 물성치인 반발계수, 정지마찰계수, 구름마찰계수가 필요하다. 공시 시료인 고추는 광주광역시 남구 승촌동 소재의 개인농가 Plastic 온실로 재배된 '천상'품종을 사용하였다. 푸아송 비와, 전단 탄성계수를 측정하기 위한 인장시험기기로는 만능인장시험기(TA-XT2, Stable Micro, 영국)를 이용하였으며, 인장에 의한 고추의 변형량 축정은 초고속카메라(NX4-SI, IDT, 미국)을 이용하였다. 밀도는 비중병법에 기초하여 질량과 부피를 측정하여 밀도를 계산하였다. 반발계수는 고추의 충돌 실험을 통해 변화한 높이를 이용하여 계산하였고, 충동 실험을 통해 변화한 높이는 초고속카메라를 이용하여 측정하였다. 정지마찰계수와 구름마찰계수는 고추의 미끄러짐이 시작하는 각도와 등속도 운동으로 구르는 각도를 초고속카메라를 이용하여 측정 후 계산하였다. 모든 실험은 3번 반복을 통해 평균값을 시험 결과 값으로 이용하였다. 고추의 대한 물성치 실험결과 고추의 푸아송 비는 0.294(std : 0.2), 전단탄성계수 4.624E+06 Pa, 밀도 $600kg/m^3$로 나타났다. 또한 입자-입자 간의 물성치인 반발계수는 0.383, 정지마찰계수는 0.455, 구름마찰 계수는 0.043로 나타났다. 추후 본 연구에서 측정한 고추의 물성치를 적용한 EDEM 입자거동해석 시뮬레이션을 통해 카드클리너 방식의 고추 선별기의 성능에 대한 분석을 하고자 한다.

• Composites Research
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• v.21 no.3
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• pp.1-8
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• 2008

The main objective of this study is to investigate the effect of salt water on the mechanical properties of a carbon-epoxy composite material. Specimens were made of a carbon-epoxy composite USN125 and tested under inplane tension and shear after 0, 0.5, 1, 2, 3, 6, 9, and 12 months immersion in 3.5% salt water. Waterproof painting and acceleration technique were not applied. The tensile strengths and moduli in fiber and matrix directions did not show any remarkable degradation until 12 months immersion. In contrast to the tensile properties, shear strength and modulus started to degrade from the early stage of the immersion time and gradually decreased to 36% and 46% of dry values, respectively, after 12 months immersion.

• Composites Research
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• v.29 no.1
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• pp.33-39
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• 2016

In this study, geometric modeling and finite element analysis of 3-dimensional plain weave composite unit cell consisting of 3 interlaced fiber tows and resin pocket were performed to predict effective properties. First, tow properties were obtained from micro-mechanics finite element unit cell analysis, which were then used in the meso-mechanics analysis. The effective properties were obtained from a series of unit cell analyses simulating uniaxial tensile and shear tests. Analysis results were compared to the analysis and experimental results in the literature. Various crimp angles were considered and the effect on the effective properties was investigated. Initial failure strengths and failure sequence were also examined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.9
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• pp.923-930
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• 2012

The wall heat transfer of backward-facing step laminar flows with different Prandtl numbers and a pulsating inlet is investigated by unsteady simulations. The inlet is perturbed by the variation of frequency and amplitude. Temperature-dependent transport properties are adopted. Various characteristics of the wall heat transfer are explained by the variation of the thermal boundary layer. For Pr < 1, the wall heat transfer of temperature-dependent properties is decreased compared to that of constant properties, whereas it increases for Pr < 1. In addition, the wall heat transfer increases depending on the pulsating amplitude. However, the results of frequency variation for St < 0.2 show that the heat transfer is strongly enhanced at a specific frequency. In particular, the increase in the wall heat transfer is strongly related to the root mean square of the fluctuations of the reattachment length.

• Proceedings of the Korea Contents Association Conference
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• 2010.05a
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• pp.469-471
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• 2010

본 연구는 한국전통건축 중 한옥을 중심으로 건축설계물 내부의 기류현상을 분석하여 전통건축의 설계에 있어서 에너지 효율을 높이기 위한 방안을 과학적으로 검증하고자 하는 것이다. 이를 위해서 전통 건축물의 주요부재에 관한 열역학적 물성치를 대표 값으로 설정하고 물성치의 변화를 실험 결과를 활용하여 보정하여 한옥 내부의 유동장과 온도분포 예측하여 그 결과를 제시한다. 이를 통해 건축 부재의 열역학적 특성이 현대의 다양한 기능재료에 비해 열악할지라도 이를 부재간의 배치와 조합을 통해 소정의 에너지 효율을 달성한 사례를 규명할 것이다.

• Journal of the Korean Applied Science and Technology
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• v.29 no.4
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• pp.618-625
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• 2012

In this study, prepared synthesis waterborne acrylic resin and water soluble milk casein resin. And than extent of casein contents in acrylic resin. We measured property of these samples by Lamb leather which is coated by acrylic-casein resins. According to measure data for solvent resistance, WAR resin and Hybrid resins had good property. Among this result knew that increase of casein constant did not influence to big change of hybrid resin property. As test of tensile strength, WAR had lowest strength($1.399kg_f/mm^2$) and WAC-3 had highest strength($1.426kg_f/mm^2$). Also we knew that best property of abrasion was WAC-3(69.774 mg.loss). In elongation case, WAR had best property(820%) in this experiment.

• Composites Research
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• v.18 no.5
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• pp.21-26
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• 2005

The validity of Eshelby-type model with Mori-Tanaka's mean field theory to predict the effective material properties of composites have been investigated in terms of filler size and its arrangement. The 2-dimensional plate composites including constant volume fraction of fillers are used as the model composite for the analytical studies, where the filler size and its arrangement are considered as parameters. The exact effective material properties of the composites are computed by finite element analysis(FEA), which are compared with effective material properties from the Eshelby-type model. Although the fillers are periodically or randomly arranged, the average Young's moduli by Eshelby-type model and FEA are in good agreement, specially for the ratio of specimen size to filler size being smaller than 0.03. However, Poisson's ratio of the composite by the Eshelby-type model is overestimated by $20\%$.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.113-121
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• 1998

In natural convection flows, the fluid velocities are highly dependent on the thermal field and property variations can have a strong effect on both the flow and thermal fields. To examine the effect of property variations, at first, numerical analyses covering wide range of the Prandtl number under the same Rayleigh numbers have been carried out. Next, we have modeled the viscosity and thermal conductivity as parabolic functions of temperature and a comprehensive set of numerical solutions have been obtained to understand the effect. The Prandtl number dependence of Nusselt number is fairly strong even though the effect is still weak compared to the Rayleigh number dependence. When thermophysical properties are dependent on temperature, the flow field showed a fairly weak variation except near boundaries, whereas the temperature field is strongly affected, especially by the temperature dependent thermal conductivity.