• Nuclear Engineering and Technology
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• v.26 no.4
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• pp.516-525
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• 1994

Since the TMI and Chernobyl accidents, many passive safety features are suggested in advanced reactors in order to enhance the safety in future nuclear power plants. In order to verify the effectiveness and provide the data for detailed design of passive cooling system, in the present work, the effects of air inlet position and external condition on the natural circulated air flow rate and the natural and forced convective heat transfer coefficient have been investigated for the one-side heated closed path such as the passive containment cooling system of the Westinghouse's AP-600. A series of experiments have been peformed with the 1/26th scaled segment type test facility of the AP-600 passive containment. Under natural and forced convection, the air velocities and temperatures are measured at several points of the air flow path. The experimental result are compared with a simple one-dimensional model and it shows a good agreement.

• The Journal of the Convergence on Culture Technology
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• v.9 no.5
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• pp.529-534
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• 2023

Although line printing technology is capable of high-speed and large area printing, residual stresses generated during the manufacturing process can deform the feedhole, causing nozzle plate crack or ink leaks. Therefore, in this paper, we propose a new thermal inkjet print head that is robust, reliable and more suitable for line-printing. The amount of deformation of the conventional line printing head measured through the experiment was converted into an equivalent load, and the validity of the load estimation method was verified through FEA analysis. In addition, in order to minimize deformation without increasing the head size, the head structure was designed to increase internal rigidity by reinforcing the unit nozzle with a pillar or support wall or by adding a support beam or dry/wet etched bridge. The FEA analysis results show that the feedhole deformation was reduced by up to 90%, and it is confirmed that the suggested print head with dry etched feedhole bridge operates normally without nozzle plate cracks and ink leakage through fabrication.

• (The)Study of the Eastern Classic
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• no.69
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• pp.147-178
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• 2017

This study examined at the literature of Choi Young(崔瑩). Choi Young(崔瑩) does not have a collection. Thus I looked at the records currently remaining about the words and actions of Choi Young(崔瑩). Among them, many discovered a piece of work in the midst of History of Goryeo History(高麗史) yeoljeon(列傳). This led to a review of the whole of literature. As a result, I could find many Prose works. This enabled us to examine one aspect of his literature. Here are some of the most popular works. First, a writing that was demoted to Gyerimyun(鷄林尹) because of the slander of Shin Don(辛旽), second a pact written to suppress Cheju Island, third a letter sent to persuade the minister of Cheju Park Yoon-Cheong(朴允淸), forth a statement against the king's will to relocate the capital, fifth a message to the king expressing his willingness to fight Hongshan(鴻山), sixth a message expressing deep despondency at defeat in Ganghwado Island and a message to the king about measures to defend, seventh a loyalty remonstrance for the king Wu(禑王). The method tried in this manuscript is significant. I have reindistributed the works of Mumingong(武愍公) in the records. Based on such achievements, new emphasis can be placed on the historical assessment of the achievements of the contemporary or later writers of the literary world.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.519-526
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• 2015

To measure the physical parameters of the simple microlayer model for the prediction of the heat flux and heat transfer rate due to the evaporation of the microlayer during nucleate boiling, the microlayer geometry was experimentally examined. The parameters, including initial thickness, moving velocity and microlayer radius, were measured by total reflection and interferometry techniques using a laser. Single-bubble nucleate boiling experiments were conducted using saturated water on a horizontal surface under atmospheric pressure. The geometric characteristics of the microlayer underneath the bubbles periodically nucleating at a nucleation site at an average heat flux of $200kW/m^2$ were analyzed. The experimental results in the present study show that the maximum initial thickness of the microlayer and the horizontal moving velocity are $5.4{\mu}m$ and 0.12 m/s, respectively.

• Fashion & Textile Research Journal
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• v.17 no.3
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• pp.462-475
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• 2015

This paper investigated the characteristics of the physical properties of woven fabrics according to the yarn structure and fibre property. It was found that wicking property of woven fabrics made of sheath/core hybrid yarn were better than those of siro spun and siro-fil hybrid yarns, which was caused by platform for transport of moisture vapor by filaments on the core part of sheath core hybrid yarns. In drying property, the fabric specimen woven by PP/Tencel sheath core hybrid yarns as a warp and Coolmax/Tencel spun yarn as a weft showed quick drying property, which was caused by the sheath core hybrid yarn structure as drainage of water moisture and coolmax fibre characteristics as quick dry material. Concerning to breathability and thermal conductivity as heat transport phenomena, it was observed that breathability of fabrics woven with hybrid yarns such as sheath core and siro-fil in the warp and hi-multi filaments in the weft showed the lowest water vapor resistance, which was explained as due to for air gap in the fibres of the spun yarns to restrict the wet heat transport from perspiration vapor. Thermal conductivities of the fabrics woven with PET/Tencel siro-fil yarns in the weft and hybrid yarns such as sheath core and siro-fil in the warp revealed the highest values, which was observed as due to higher thermal conductivity of PET than PP and more contact point between fibres in the siro-fil and sheath core hybrid yarns.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.274-275
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• 2000

광결정(photonic crystal)으로 광원의 자발 방출을 조절하면 문턱전류 없는 레이저, 고효율 다이오드, 파장 크기에서 손실 없이 급격히 꺾을 수 있는 광도파로 등 기존의 광소자에서 얻을 수 없는 좋은 성능을 얻을 수 있을 것으로 예상된다. 이러한 광결정은 유전체를 파장정도 크기에서 주기적으로 배치시킨 인공적인 결정인데 고체에서 원자의 주기적인 배치로 전자가 전파할 수 없는 진동수 영역, 즉 밴드갭이 생기는 것과 유사하게 빛에 대해서 빛이 전파할 수 없는 진동수 영역인 광밴드갭(photonic bandgap)을 가진다. 그런데 관심있는 광영역에서 3차원 모든 방향으로 광밴드갭이 있는 구조물은 마이크로미터보다 작은 내부 구조를 가지는 복잡한 3차원 구조물로 제작이 어렵다. 이러한 어려움을 극복하기 위해 제작이 비교적 용이한 3차원 광밴드갭 구조물이 찾아지고 있다. 다른 접근 방법으로 평면(x-y)에서는 2차원 광밴드갭을 이용하고 제 3의 방향(z축)으로는 전반사를 이용하는 구조는 제작이 용이할 뿐만 아니라 처음부터 광원의 편광을 TE 또는 TM 모드로만 방출 되도록 준비해 줄 수 있으면 거의 3차원 광결정에서 얻을 수 있는 효과를 낼 수 있는 것으로 발표되었다.$^{(1)}$ 이 방법을 이용하여 최근에 미국의 캘리포니아 공과대학(Caltech)을 중심으로 레이저 동작을 보여 주었다.$^{(2.3)}$ 공기로 둘러싸인 얇은 유전체 평판에서 생기는 전반사와 평판 위에 2차원 삼각형살창(triangular lattice)에 구멍을 뚫어 얻는 2차원 광밴드갭을 이용해 3차원 공진모드를 형성하였다. 이러한 구조에서 1개만 구멍을 매워서 만든 공진기는 저온(143 K)에서 레이저 발진을 보였고 여러 개의 구멍을 매운 경우는 상온에서 펌프 펄스의 유지시간이 0.5% 인 경우 레이저가 동작하는 것을 보여주었다. 이는 구조내에서 열전도가 문제가 된다는 것을 의미하는데 위아래가 공기로 둘러 싸여 있어 발생한 열이 가는 유전체 네트웍을 통해서만 전달 될 수 있기 때문이다. (중략)

• 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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.5
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• pp.279-288
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• 2013

Heat transfer and pressure drop characteristics of fin-and-tube heat exchangers having sine wave fins and oval tubes were investigated. Oval tubes having an aspect ratio of 0.6 were made, by deforming 12.7 mm round tubes. Twelve samples, having different fin pitch and tube row, were tested. The effect of fin pitch on the j and f factors was negligible. The effect of the tube row on the j factor, however, was different from that of common fin-and-tube heat exchangers having plain fins and round tubes. The highest j factor was obtained for a two-row configuration, while the lowest one was obtained for a one-row configuration. A possible reason was attributed to the flow mixing characteristics of the sine wave channel of the present geometry. Comparison with a plain fin-and-tube heat exchanger having 15.88 mm O. D. round tube reveals that the present oval fin-and-tube heat exchanger shows generally superior thermal performance, except for the one-row configuration.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1763-1773
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• 1991

본 연구에서는 포화수증기와 공기의 혼합기내에서 분무수적으로의 열 및 질량 전달률을 계산하기 위하여 수적의 부분혼합모형과 비혼합모형에 대하여 수적내 과도온 도분포의 해석해를 적용성이 보장되면서도 계산상의 어려움이 수반되지 않는 형태로 구하기 위하여 수적내부의 열전도해석에 있어서 적분법을 적용하였다. 적분법으로 얻어지는 과도온도분포의 해는 유한차의 다항식으로 표시되어 비혼합모형인 경우 각시 간 구간의 경계에서의 온도분포가 연속성을 유지하면서 물성치들의 온도에 대한 종속 성이 쉽게 고려되고 계산도 용이한 형태이다. 본 보에서 제시하는 해석결과의 적용 성을 조사하기 위하여 완전혼합모형을 포함하는 세가지 수적모형들에 대한 계산결과들 로부터 얻어진 시간변화에 따른 수적의 무차원 체적평균온도변동을 유효한 실험결과들 과 비교, 검토하였으며, 부분혼합모형에 대하여 혼합기의 압력, 수적의 초기온도, 혼 합기 속에 포함되어 있는 수증기의 체적분율, 수적의 초기크기, 수적의 초기속도 및 분사각도가 주위혼합기로부터 수적으로 전달되는 열 및 질량전달에 미치는 영향을 조] 사하고 도출된 대표적인 검토 결과를 제시하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.983-991
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• 1992

This investigation is carried out numerically for the two dimensional natural convection and surface radiation heat transfer in a square enclosure. The bottom and top walls are isothermal at hot and cold temperatures respectively whereas the left and right side walls are adiabatic except a transparent window on the right side partially. The exchange of radiant energy is obtained by the net radiation method and the shape factor by the crossed string method. The changes in temperature and Nusselt number distributions of the walls due to the surface radiation and insolation are also investigated.