• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.601-608
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• 2003

Thermal analyses have been carried out for a spent fuel dry storage cask under normal and off-normal conditions. Environmental temperature is assumed to be $15^{\circ}C$ under the normal condition. The off-normal condition has an environmental temperature of $38^{\circ}C$. An additional off-normal condition is considered as a partial blockage of the air inlet ducts. Two of the four air inlet ducts are assumed to be completely blocked. The maximum temperatures of the fuel rod and concrete overpack were lower than the allowable values under the normal condition. Temperature distributions for the off-normal conditions were slightly higher than the normal conditions.

• Tribology and Lubricants
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• v.22 no.6
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• pp.329-334
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• 2006

In CNG (Compressed natural gas) fuel supply line, whose main components are receptacle and check valve are used to charge high pressure gas to the tank of NGV (Natural gas vehicle). It is reported that the seal is separated occasionally form valve seat and results in blockage of gas flow. In this paper, MARC is used to investigate the reasons of seal separation and suggest design improvements. The static gas pressure distributions acting on the seal which calculated using FLUENT are considered to investigate accurate seal deformation behaviors. Deformed seal shapes are obtained for various amounts of seal interference and its location, gas pressure distributions and Young's modulus of the rubber used. The results showed that the reasons of seal separation problems are verified theoretically, and suggested examples of new design method. Therefore the present numerical methods can be applied in designing and performance analysis of rubber seals adopted in high pressure fluid machineries.

• The KSFM Journal of Fluid Machinery
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• v.19 no.6
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• pp.5-13
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• 2016

Three-dimensional unsteady numerical analysis has been performed to observe aerodynamic characteristics of a H-rotor. Generally, the structure of the H-rotor is simple but the aerodynamic characteristics are exceptionably complicated since the angle of attacks and incident velocities to a blade are considerably varied according to the azimuth angles and solidities. The blade in the upwind revolution between 0 to 180 degree obtains aerodynamic energy from the free stream but the blade in the downwind revolution between 180 to 360 degree does not. When the rotating speed increases, the blade in the downwind revolution accelerates the air around the blade like a fan and it consumes the energy and shows negative torque in the area. On the other hand, the direction of the free stream is bent because of the interaction between blade the free stream. Therefore, the operation point (highest power coefficient) appears at a lower tip-speed-ratio what it is expected.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.1
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• pp.13-22
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• 2004

This study presents the thermal analyses of a spent fuel dry storage cask under normal and off-normal conditions. The environmental temperature is assumed to be 15 $^{\circ}C$ under the normal condition. The off-normal condition has an environmental temperature of 38 $^{\circ}C$. An additional off-normal condition is considered as a partial blockage of the air inlet ducts. Two of the four air inlet ducts are assumed to be completely blocked. The significant thermal design feature of the storage cask is the air flow path used to remove the decay heat from the spent fuel. Natural circulation of the air inside the cask allows the concrete and fuel cladding temperatures to be maintained below the allowable values. The finite volume computational fluid dynamics code FLUENT was used for the thermal analysis. The maximum temperatures of the fuel rod and concrete overpack were lower than the allowable values under the normal and off-normal conditions.

• Journal of the Korean earth science society
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• v.38 no.7
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• pp.496-510
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• 2017

This study presents a new nationwide quantitative precipitation estimation (QPE) based on the hybrid surface rainfall (HSR) technique using the weather radar network of Korea Meteorological Administration (KMA). This new nationwide HSR is characterized by the synthesis of reflectivity at the hybrid surface that is not affected by ground clutter, beam blockage, non-meteorological echoes, and bright band. The nationwide HSR is classified into static (STATIC) and dynamic HSR (DYNAMIC) mosaic depending on employing a quality control process, which is based on the fuzzy logic approach for single-polarization radar and the spatial texture technique for dual-polarization radar. The STATIC and DYNAMIC were evaluated by comparing with official and operational radar rainfall mosaic (MOSAIC) of KMA for 10 rainfall events from May to October 2014. The correlation coefficients within the block region of STATIC, DYNAMIC and MOSAIC are 0.52, 0.78, and 0.69, respectively, and their mean relative errors are 34.08, 30.08, and 40.71%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.650-658
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• 1997

Analysis and control of intake charge motion such as swirl and tumble are very important factors in improving the gasoline engine performance. In this paper, single-frame PTV (particle tracking velocimetry) is used to investigate intake tumble patterns in a steady flow test rig of gasoline engine with dual-intake-valve and pent-roof combustion chamber. Intake tumble pattern is quantified in accordance with blockage ratio of TIV (tumble intensifying valve) with single- frame PTv.The view of the instantaneous 2-D velocity field gives a realistic understanding of in-cylinder flow field. Thus it is confirmed that PTV is a effective tool in engine design. In conventional port, two tumble structures appear clearly, and the larger one is observed under the exhaust valve side and the smaller is right below the intake valve side. The larger vorticity is observed in TIV port, thus it is concluded that TIV have an effect on intensified tumble motion in cylinder flow.

• Journal of Satellite, Information and Communications
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• v.3 no.1
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• pp.41-47
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• 2008

Line-of-sight communications cannot easily support korean armed forces because of mountainous terrain. ADD(Agency for Defense Development) introduced ANASIS(Army Navy Air-force Satellite Information System) to meet the Korean warfighter's operational needs. Currently, army's military satcom terminal is designed for either fixed site or on-the-pause operation. The US army is under development of multi-band integrated on-the-move satellite terminals to let the army's communication capability to keep pace with globally deployable Joint Task Force for network-centric application. In this paper we analyzed X-band and Ka-band link and subsystem requirement. Our focus here is to describe key technical issues. Especially, On the basis of 3dB beam width of 0.9m antenna, Tracking accuracy and disturbances compensation signal processing on-the-move of Antenna Tracking system is analyzed. Also, protocol is analyzed that minimize blockage on the move due to an obstacle. when the received signal blocked, it stop to transmit burst signal and retransmit when blockage removed through received synchronization signal monitoring. Analyzed specification will be used to make prototype terminal to analyze risk for mass production

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.6
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• pp.553-560
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• 2014

The road tunnel install a vent for the purpose of ventilation and smoke control. Ventilation equipment capacity(number of jet fans) depends on from the condition that of the pressure and ventilation resistance. Pressure and the resistance under operating vehicle have affected on the drag coefficient. The drag coefficient of the tunnel have affected by the blockage effect and slipstream effects. However, when calculating the ventilation fan, are not properly consider taking into account such effects. Therefore, ventilation force may have been slightly overestimated. This paper describes the drag coefficient through a numerical analysis to calculate the equivalent resistance area that reflects the vehicle distance, and examined the equivalent resistance area. The ventilation coefficient corresponding to the result heavy vehicle mixing ratio of the present study was not clear. Equivalent resistance area had reduced by about 86% compared to the road design handbook current standards. Also it had analyzed and reduced to 62.2% compared to Korea Highway Corporation ventilation design criteria ratio, which is the old standard.

• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.31-38
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• 2011

This study aimed to determine the effects of the blockage of visual feedback on joint dynamics of the lower extremity. Fifteen healthy male subjects(age: $24.1{\pm}2.3\;yr$, height: $178.7{\pm}5.2\;cm$, weight: $73.6{\pm}6.6\;kg$) participated in this study. Each subject performed single-legged landing from a 45 cm-platform with the eyes open or closed. During the landing performance, three-dimensional kinematics of the lower extremity and ground reaction force(GRF) were recorded using a 8 infrared camera motion analysis system (Vicon MX-F20, Oxford Metric Ltd, Oxford, UK) with a force platform(ORG-6, AMTI, Watertown, MA). The results showed that at 50 ms prior to foot contact and at the time of foot contact, ankle plantar-flexion angle was smaller(p<.05) but the knee joint valgus and the hip flexion angles were greater with the eyes closed as compared to with the eyes open(p<.05). An increase in anterior GRF was observed during single-legged landing with the eyes closed as compared to with the eyes open(p<.05). Time to peak GRF in the medial, vertical and posterior directions occurred significantly earlier when the eyes were closed as compared to when the eyes were open(p<.05). Landing with the eyes closed resulted in a higher peak vertical loading rate(p<.05). In addition, the shock-absorbing power decreased at the ankle joint(p<.05) but increased at the hip joints when landing with the eyes closed(p<.05). When the eyes were closed, landing could be characterized by a less plantarflexed ankle joint and more flexed hip joint, with a faster time to peak GRF. These results imply that subjects are able to adapt the control of landing to different feedback conditions. Therefore, we suggest that training programs be introduced to reduce these injury risk factors.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1750-1757
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• 2003

This paper describes the flow measurements inside the blade passage of an axial flow fan by using a rotating hot-wire probe sensor from a relative flame of reference fixed to the rotor blades. The validity of fan rotor designed by a streamline curvature equation was performed by the measurement of the three-dimensional flow upstream and downstream of the fan rotor using a 5-hole pitot tube. The vortical flow structure near the rotor tip can be clearly observed by the measurements of a relative velocity and its fluctuation on quasi-orthogonal planes to a tip leakage vortex. Larger vortical flow, which results in higher blockage in the main flow, is formed according to decrease a flow rate. The vortical flow spreads out to the 30 percent span from the rotor tip at near stall condition. In the design operating condition, the tip leakage vortex is moved downstream while the center of the vortex keeps constant in the spanwise direction. Detailed characteristics of a velocity fluctuation with relation to the vortex were also analyzed.