• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1585-1589
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• 2007

The HANARO, a 30 MW multi-purpose research reactor in Korea, will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. The functions of the in-pile plug assembly are to shield the reactor environment from a nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical device to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the mechanical design of the in-pile plug assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

• 한국해안해양공학회지
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• 제7권4호
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• pp.289-304
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• 1995

북태평양에서 선택한 조석 정점에서 상대 해수면의 시계열 자료와 하와이 제도에서 해안선 변화의 항공 사진을 분석하였다. 대부분의 정점에서 해면의 장기적 상승 추이는 +1 내지 +5 mm/yr의 범위를 보이는데, 주로 지구 온난화 및 지질학적 판(plate)의 이동에 의해 나타나고 있다. 해면의 연변화 및 수년 주기의 변화는 각각 태양 복사의 연변화에 의한 표층수의 팽창 및 수축과, ENSO 주기와 관계된 대기-해양의 상호작용으로부터 기인한다. 이러한 세 가지의 다른 시간 규모로 발생하는 해면변화(장기적 해면상승 추이, 연변화, 수년주기 변화)가 장기적으로 이안 퇴적물 수송의 결과로서 나타나는 해안선 변화에 어떻게 정량적으로 기여하는지 추정하는 가설이 제시된다.

• 한국대기환경학회지
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• 제25권6호
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• pp.539-549
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• 2009

The purpose of this study is to estimate hourly Asian dust emission flux in springtime by using the optimized Weather Research Forecasting model (WRF) in order to accurately predict the horizontal flux of Asian dusts. Asian dust emission flux using 5 empirical formulas such as US EPA, Park and Inn, Wang, The Goddard Chemistry Aerosol Radiation and Transport (GOCART) and Dust Entrainment and Deposition (DEAD) were calculated and compared by using classified land-use types and size distribution at various locations in China and Mongolia together with the hourly meteorological elements of the WRF model. As a result, the empirical formula in US EPA among them, which was considered the various conditions such as vegetation, soil type and terrain, was better than the other 4 empirical formulas. However, these formulas were adjusted hourly and vertically in time and space because there was different order and time resolution of dust emissions from original empirical formulas.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.459-473
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• 2018

Temperature fields and temperature deformations induced by time-varying solar radiation, shadow, and heat exchange are of great importance for the ride safety and quality of the maglev system. Accurate evaluations of their effects on the dynamic performances are necessary to avoid unexpected loss of service performance. This paper presents a numerical approach to determine temperature effects on the maglev train/guideway interaction system. Heat flux density and heat transfer coefficient of different components of a 25 m simply supported concrete guideway on Shanghai High-speed Maglev Commercial Operation Line is calculated, and an appropriate section mesh is used to consider the time-varying shadow on guideway surfaces. Based on the heat-stress coupled technology, temperature distributions and deformation fields of the guideway are then computed via Finite Element method. Combining guideway irregularities and thermal deformations as the external excitations, a numerical maglev train/guideway interaction model is proposed to analyze the temperature effect. The responses comparison including and excluding temperature effect indicates that the temperature deformation plays an important role in amplifying the response of a running maglev, and the parameter analysis results suggest that climatic and environmental factors significantly affect the temperature effects on the coupled maglev system.

• 한국응용과학기술학회지
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• 제15권4호
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• pp.11-20
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• 1998

The propagation of light radiation in a turbid medium is an important problem that confronts dosimetry of therapeutic laser delivery and the development of diagnostic spectroscopy. Scattered light is measured as a function of the position(distance r, depth z) between the axis of the incident beam and the detection spot. Turbid sample yields a very forward-directed scattering pattern at short range of position from source to detector, whereas the thicker samples greatly attenuated the on-axis intensity at long range of position. The portions of scattered light reflected from or transmitted throughphantom depend upon internal reflectance and absorption properties of the phantom. Monte Carlo simulation method for modelling light transport in tissue is applied. It uses the photon is moved a distance where it may be scattered, absorbed, propagated, internally reflected, or transmitted out of tissue. The photon is repeatedly moved until it either escape from or is absorbed by the phantom. In order to obtain an optimum therapeutic ratio in phantom material, optimum control the light energy fluence rate is essential. This study is to discuss the physical mechanisms determining the actual light dose in phantom. Permitting a qualitative understanding of the measurements. It may also aid in designing the best model for laser medicine and application of medical engineering.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권4호
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• pp.235-245
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• 2004

In this paper, fault tolerant mechanisms are presented for a servo manipulator system designed to operate in a hot cell. A hot cell is a sealed and shielded room to handle radioactive materials, and it is dangerous for people to work in the hot cell. So, remote operations are necessary to handle the radioactive materials in the hot cell. KAERI has developed a servo manipulator system to perform such remote operations. However, since electric components such as servo motors may fail by radiation, fault tolerant mechanisms have to be considered. For fault tolerance of the servo manipulator system, duplication mechanism increasing the reliability of the transport's driving motors and reconfiguration algorithm accommodating the slave's motor failure have been presented. The reconfiguration algorithm recovering the end effector's motion in spite of one motor's failure is based on control allocation redistributing redundant axes. The constrained optimization method and pseudo inverse method have been adopted for control allocation. Simulation examples and real test results have been presented to verify the Proposed methods.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.365-368
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• 2002

The design of industrial arc plasma systems is still largely based on trial and error although the situation is rapidly improving because of the available computational power at a cost which is still fast coming down. The desire to predict the behavior of arc plasma system, thus reducing the development cost, has been the motivation of arc research. To interrupt fault current, the most enormous duty of a circuit breaker, is achieved by separating two contacts in a interruption medium, $SF_{6}$ gas or air etc., and arc plasma is inevitably established between the contacts. The arc must be controlled and interrupted at an appropriate current zero. In order to analyze arc behavior in $SF_{6}$ gas circuit breakers, a numerical calculation method combined with flow field and electromagnetic field has been developed. The method has been applied to model arc generated in the Aachen nozzle and compared the results with the experimental results. Next, we have simulated the unsteady flow characteristics to be induced by arcing of AC cycle, and conformed that the method can predict arc behavior in account of thermal transport to $SF_{6}$ gas around the arc, such as increase of arc voltage near current zero and dependency of arc radius on arc current to maintain constant arc current density.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.149-154
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• 2001

The emission characteristics, flame stability, the composition of the flame zone and temperature profile were studied experimentally. The compositions of oxydant were varied by substituting $N_2$ with $CO_2$ at the constant $O_2$ concentration. Results showed that flame became unstable due to the high heat capacity, low transport rate and strong radiation effect of $CO_2$ in comparison with those of $N_2$. The reaction zone was cooled, broadened, as the conversion ratio of $CO_2$ to $N_2$ was increased. Temperature has a large effect on the NOx emission. The concentration of NOx in flue gas decreased due to the decreased temperature of reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the conversion ratio of $CO_2$ to $N_2$ was increased, the emission of CO and the higher temperature zone increased due to the decrease of reaction rate by the cooling effect.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권3호
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• pp.158-166
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• 2001

Based on uniform hot carrier injection (optically assisted electron injection) across the $Si-SiO_2$ interface into the gate insulator of n-channel IGFETs, the threshold voltage shifts associated with electron injection of $1.25{\times}l0^{16}{\;}e/\textrm{cm}^2 between 0.5 and 7 MV/cm were found to decrease from positive to negative values, indicating both a decrease in trap cross section ($E_{ox}{\geq}1.5 MV/cm$) and the generation of FPC $E_{ox}{\geq}5{\;}MV/cm$). It was also found that FNC and large cross section NETs were generated for $E_{ox}{\geq}5{\;}MV/cm$. Continuous, uniform low-field (1MV/cm) electron injection up to $l0^{19}{\;}e/\textrm{cm}^2 is accompanied by a monatomic increase in threshold voltage. It was found that the data could be modeled more effectively by assuming that most of the threshold voltage shift could be ascribed to generated bulk defects which are generated and filled, or more likely, generated in a charged state. The injection method and conditions used in terms of injection fluence, injection density, and temperature, can have a dramatic impact on what is measured, and may have important implications on accelerated lifetime measurements.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.967-972
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• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.