• 한국기계가공학회지
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• 제11권3호
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• pp.160-165
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• 2012

The packing, among the components comprising the gate valve, is used to sustain the air-tightness and the study on change of shape or pattern has been carried out to maximize the functions, but the study on changing the location or the size of the packing in a bid to prevent the freezing has rarely been implemented. Thus, This study is intended to evaluate the thermal strain of packing by heat transfer from territory of extremely low temperature as well as the temperature distribution to the upper part of the packing using numerical analysis method.

• International Journal of Internet, Broadcasting and Communication
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• 제6권2호
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• pp.20-24
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• 2014

These days the large-scale car accidents have often been occurred by overspeeding in disregard of sharp curve, foggy and freezing regions. This paper has proposed the algorithm to calculate the safety speed in real time that can protect the car accidents under these weather and road conditions using Fuzzy reasoning theory. Under raining and snowing, drivers have to slow down the traffic safety speed by 1/3 of the traffic safety speed indicated on the existing speed sign plate based on their decision. So it is difficult to calculate and then observe the safety speed. This paper has performed the simulation that provides the deivers with the optimal safety speed considering the road and weather conditions in real time to improve these problems. We have proved this method can improve more 25% than the existing one.

• 대한화장품학회지
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• 제30권1호
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• pp.53-58
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• 2004

본 연구에서는 에멀젼의 미세구조 분석을 위한 동결처리 전자현미경 분석의 응용에 대해 소개하였다. 동결처리 전자현미경 분극법은 에멀젼의 미세구조 분석 및 해석에 유용하며, 이러한 미세구조 해석을 통해 에멀젼의 유동 특성 발현에 대한 메카니즘의 설명이 가능할 것으로 사료된다.

• 대한기계학회논문집
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• 제16권2호
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• pp.348-355
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• 1992

Casting structures and properties are determined by the solidification speed in the metal mold. The heat transfer characteristics of the interface between the mold and the casting is one of the major factors that control the solidification speed. According to Sully's research, the thermal resistance exists due to the air-gap formation at the mold-casting interface during the freezing process and the interface heat transfer coefficient is used to describe the degree of it. In this study, one-dimensional Stefan problem with air-gap resistance in the cylindrical geometry is considered and heat transfer characteristics is numerically examined. The temperature distribution and solidification speed are obtained by using the modified variable time step method. And the effects of the major parameters such as mold geometry, thermal conductivity, heat transfer coefficient and initial temperature of casting on the thermal characteristics are investigated.

• Journal of Mechanical Science and Technology
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• 제15권1호
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• pp.125-138
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• 2001

An efficient correction storage scheme on a structured grid is applied to a sequence of approximate Jacobian systems arising at each time step from a linearization of the discrete nonlenear system of equations, obtained by the implicit time discretization of the conservation laws for unsteady fluid flows. The contribution of freezing the Jacobian matrix to computing costs is investigated within the correction storage scheme. The performance of the procedure is exhibited by measuring CPU time required to obtain a fully developed laminar vortex shedding flow past a circular cylinder, and is compared with that of a collective iterative method on a single grid. In addition, some computed results of the flow are presented in terms of some functionals along with measured data. The computational test shows that the computing costs may be saved in favor of the correction storage scheme with the frozen Jacobian matrix, to a great extent.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.775-780
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• 2003

The propose of this study is to discover concrete secondary products for proper mixing by lightweight concrete. The standard of water ratio 50% and weight substition 0%, 10%, 20% by Fly-ash. When produce manufactures, there use for maintain its form weight substition and addition among the viscosity agent each Silica-fume and Hydroxy propyl methyl cellulos. Testing method was to operate slump, air content, compressive strength test, rapid freezing and thawing test. The result of this study is appeared when substition Fly-ash generally it had better use Silica-fume.

• Applied Microscopy
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• 제27권4호
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• pp.453-460
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• 1997

주사 전자현미경상에서 Hypoxylon속 4종(H. archeri, H. bovei, H. fragiforme와 H. stygium)의 자낭자좌 조직 형태를 중점적으로 관찰하였다. 본 연구는 Hypoxylon속의 자낭자좌의 각 층의 조직상 형태를 가장 심도있게 연구하였으며, 이 자낭자좌들은 동결파쇄법에 의하여 종단 및 횡단 절단되었다. 여러 개의 균일 된 자낭자좌 조직의 형태가 속내의 종간에 각기 다르게 형성되었다. 자낭자좌 조직의 형태는 Hypoxylon속의 종 수준에서의 분리동정을 위한 주검색 표로서는 미흡하나 보조 검색 표로는 매우 유용하다.

• 대한전기학회논문지
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• 제39권11호
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• pp.1207-1218
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• 1990

The lack of persistent excitation (PE) can be the reason of freezing in the recursive least square estimators and the covariance windup in the exponential weighted least square estimators. We present a theoretical analysis of these phenomena and a simple method to check the exciting condition in real time. Using these results and under some conditions such as slowly time varying Plant and a tracking problem for set point, a robust self-tuning regulators without PE is proposed. In this algorithm, when PE is not satisfied, only plant gain is estimated, and then the system parameters are corrected by it. It is shown that the gain adaptive scheme makes the robustness to be improved against modeling error, off-set, and correlated noise etc, by the results of analysis and simulations.

• 설비공학논문집
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• 제7권3호
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• pp.382-395
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• 1995

A numerical study has been performed on flow characteristics in a domestic refrigerator whose size is $540mm{\times}1,530mm{\times}680mm$, considering existence of a fan and evaporator. The flow field has been simulated with the low Reynolds number $k-\bar{\varepsilon}$ turbulent model and SIMPLE algorithm based on the finite volume method. The region of fan which makes driving force for cold air distribution was modeled as a region in which momentum sources are generated uniformly. The concept of the distributed pressure resistance was applied to describe the momentum loss from evaporator. The result showed that the rate of cold air distribution into freezing room and cold storage room was almost 7 : 3.

• 한국태양에너지학회 논문집
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• 제31권5호
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• pp.41-46
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• 2011

In the present work, a new freeze protection method has been proposed for a natural circulation system of solar water heater. Though electrothermal wire is popularly used for the purpose, there are freezing troubles by wire cut-off and excessive electric power consumption. In the experimental device, hot water in a storage tank was circulated by a small pump and used to heat the outdoor pipes if the cold water pipe surface temperature falls lower than a set point. As a result, It was observed that there was no hot water waste while the solar water heating system operated without freeze and burst.