• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.218-221
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• 2008

Hot Press Forming (HPF), an advanced sheet forming method in which a high strength part can be produced by forming at high temperature and rapid cooling in dies, is one of the most successful forming process in producing components with complex geometric shape, high strength and a minimum of springback. In order to obtain effectively and accurately numerical finite element simulations of the actual HPF process, the flow stress of a boron steel in the austenitic state at elevated temperatures has been investigated with Gleeble system. To evaluate the formability of the thermo- mechanical material characteristics in the HPF process, the FLDo defined at the lowest point in the forming limit diagrams of a boron steel has been investigated. In addition, the simulation results of thermo-mechanical coupled analysis of an automobile one-piece lower-arm part are compared with the experimental ones to confirm the validity of the proposed simulations.

• 대한기계학회논문집B
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• 제30권2호
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• pp.170-176
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• 2006

A spark discharge aerosol generator using air as a carrier gas has successfully been applied to silver nanoparticle production. The spark discharge between two silver electrodes, which was periodically obtained by discharging the capacitor, produced sufficient high temperatures to evaporate a small fraction of the silver electrodes. The silver vapor was subsequently supersaturated by rapid cooling and condensed to silver nanoparticles by nucleation and condensation. The morphology of the generated particles observed by transmission electron microscope was spherical. The element composition of the nanoparticles was silver, which was determined by energy dispersive X-ray spectroscopy. The crystal phase of the particles spark-generated under air atmosphere was composed of silver and silver oxides phase, which was determined by Xray diffraction analysis. While the nanoparticles generated under nitrogen atmosphere had only silver phase. This XRD data indicates that some fraction of the evaporated silver vapor could be oxidized in air atmosphere by the reaction with oxygen. A stable operation of the spark discharge generator has been achieved. The size and concentration of the particles can be easily controlled by altering the repetition frequency, capacitance, gap distance and flow rate of the spark discharge system.

• Journal of Welding and Joining
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• 제27권5호
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• pp.62-67
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• 2009

Welding deformation during the assembly process is affected by not only local shrinkage due to rapid heating and cooling, but also root gap and misalignment between parts to be welded. Therefore, the prediction and control of welding deformation have become of critical importance. In this study, it was focused on the development of the 3-axis apparatus for real-time measurement of the welded deformation. To achieve the objective, a D-H algorithm has been carried out to check the behavioral and performance evaluation for the developed robot. The sequence experiments were taken the base materials of $400{\times}200{\times}4.5mm$ plate for butt welding. The real-time experimental measurements are in good agreement with the measured results.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.152-157
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• 2002

A cross-flow fan is widely used on many industrial fields: a blower for the general industry, mining industry, automobile and home appliances. The design point of the cross-flow fan is generally chosen by based on the region within low static pressure and high flow rate. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice. However, it has low static pressure efficiency between $30\%$ and $40\%$ because of relative high impact loss. Recently, in the air-conditioning systems, the operating behaviors at the off-design points are highly regarded to broaden the application area for various air-cooling loads. Especially, at the low flow rate, there exists a rapid pressure head reduction, a noise increase and an irregular flow against a rearguider as a scroll of centrifugal fan. Numerical analyses are carried out for cross-flow fan including the impeller, the rearguider and the stabilizer. Numerical domains are discretized by hexahedral cells. Three-dimensional, unsteady governing equations are solved using FVM, SIMPLE algorithm, sliding grid system and standard k-$\epsilon$ turbulence model.

• 대한한의정보학회지
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• 제16권1호
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• pp.9-73
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• 2010

This study is to focus on Ye Tian-Shi's Treatise on Externally Contracted Heat Disease Pattern Identification of warm disease as viewed through the concept of the various warm diseases characterized by rapid onset and shifts, pronounced heat signs, and a tendency to form dryness and damage eum. Finally, when it reaches blood and causes depletion and frenetic movement, treatment involves cooling and dissipating the blood." These lines represent the general outline of the four-aspect pattern identification and treatment system of the doctrine of warm diseases.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.336-341
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• 2008

For the last half a century, Korea has been experienced rapid economic growth and industrialization development, however they cause serious problems that environment pollution and energy shortage are appeared, and the biggest problem that we are now confronted are required solutions through all over the world. Now, Korea's energy consumption is the 10th in the whole world. Among them, energy for buildings, about 25% in the whole Energy which spend in Korea, is very serious. Especially, the energy consumption of school buildings which have heating & cooling system according to improvements of educational environment are rapidly increasing. These features are explicit in the University, Because it has lots of colleges and facilities for lecture, experiment, and research. Especially, electric power consumption account for 75 percent of energy consumption in educational institutions. Accordingly, it is important to understand and analyze the pattern of electricity energy consumption which is used. This study attempts to appoint the place which is one of university and to investigate the characteristics of energy consumption like electricity, gas, oil.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2076-2082
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• 2003

A cross-flow fan is widely used on many industrial fields: mining industry, automobile and home appliances, etc. The design point of the cross-flow fan is generally based on the region within low static pressure and high flow rate. It relatively makes high dynamic pressure at low speed because a working fluid passes through an impeller blade twice. However, it has low static pressure efficiency between 30% and 40% because of relative high impact loss. Recently, in the air-conditioning systems, the operating behaviors at the off-design points are highly regarded to broaden the application area for various air-cooling loads. Especially, at the lower flow rate, there exists a rapid pressure head reduction, a noise increase and an irregular flow field against a rearguider as a scroll of centrifugal fan. Numerical analyses are carried out for investigating the flow characteristics in a cross-flow fan including the impeller, the rearguider and the stabilizer. Especially, various types of rearguiders are estimated by numerical and experimental methods to insure the stable operation in the region of lower flow rate. Numerical domains are discretized by hexahedral cells. Three-dimensional, unsteady governing equations are solved using FVM, PISO algorithm, sliding grid system and standard ${\kappa}-{\varepsilon}$ turbulence model. ASHRAE standard fan tester is also used to estimate the performance of the modeled crossflow fan.

• 한국광학회지
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• 제13권6호
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• pp.530-536
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• 2002

열팽창계수의 정확한 측정은 재료과학이나 공업기술 분야에서 가장 중요한 요구량 중의 하나이다. 음향광변조기(AOM)를 이용한 고분해능 간섭식 열팽창계를 제작하여 성능검사를 하였다. 이 계는 이중광로 헤테로다인 간섭계와 복사열 전기로로 구성되어, 정밀한 변위의 측정과 시료의 신속한 가열 및 냉각이 가능토록 하였다. 또한 레이저의 주파수 안정화를 위하여 2차 맥놀이 주파수를 이용한 3종모드 안정화 He-Ne 레이저를 제작하였으며, 이때의 주파수 안정도는 5$\times$$10^{-9}$이었다. 제작된 계의 길이 측정은 실온에서 1100k온도영역에서 나노미터 정도의 정밀도를 주었다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2011년도 정기 학술대회
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• pp.415-418
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• 2011

Thermal fatigue is one of the life-limiting damage mechanisms in the nuclear power plant conditions. The turbulent mixing of fluids of different temperatures induces rapid temperature changes to the pipe wall. The successive thermal transients cause varying cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack nucleation and growth similar to the cyclic mechanical stresses. The aim of this study was to fulfil the need by developing an real crack manufacturing method, which would produce realistic cracks. The test material was austenitic STS 304, which is used as pipelines in the reactor coolant system of a nuclear power plants. In order to fabricate thermal fatigue crack similar to realistic crack, successive thermal transients were applied to the specimen. Thermal transient cycles were combined with heating (60sec) and cooling cycle (30sec). And, In order to identify ultrasonic characteristic, it was performed the ultrasonic reflection measuring method for the fabricated specimen. From the results of ultrasonic reflection measuring testing, it was conformed that A-scan results(average 83% of real crack depth) for the TFC reference specimen was more enhanced NDT reliability than results(average 38% of real crack depth) for the EDM notch reference specimen.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1173-1178
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• 2006

In a primary reactor cooling system(RCS), a dissimilar weld zone exists between cast stainless steel(CF8M) in a pipe and low-alloy steel(SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and $330^{\circ}C$, while no effect is observed in SA508 cl.3. The specimens are prepared by an artificially accelerated aging technique maintained for 300, 1800 and 3600 hrs at $430^{\circ}C$, respectively. The specimens for elastic-plastic fracture toughness tests are according to the process in the thermal notch is created in the heat affected zone(HAZ) of CF8M and deposited zone. From the experiments, the $J_{IC}$ value notched in HAZ of CF8M presented a rapid decrease up to 300 hours at $430^{\circ}C$ and slowly decreased according to the process in the thermal aging time. Also, the $J_{IC}$ value presented a lower value than that of the CF8M base metal. And, the $J_{IC}$ of the deposited zone presented the lowest value of all other cases.