• 한국환경과학회지
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• 제16권9호
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• pp.1039-1049
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• 2007

This study analyzed two dimensions hydraulic characteristic for actual flood events in steep meandering channel. It could get analysis results as follows; A water level difference of downstream more great than one of upstream at inner and outer of meandering channel. It judged that a significance of downstream level could appear more greatly in meandering channel bank, hydraulic structure and flood inundation analysis. As velocity and depth analysis was shown that much amount flow passing fast velocity happened in meandering channel, it could help establishment of meandering channel bank. In this study, the results of two dimension hydraulic analysis results could help a counterpaln establishment for the flood inundation and bank collapse.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.836-844
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• 2000

In this research any abnormal motion of a vehicle is detected by utilizing the difference between the reference and actual yaw velocities as sell as the information on vehicle slip angle and slip angular velocity. This information is then used as a criterion for execution of the yaw moment control. A yaw moment control algorithm based on the brake control is proposed for improving the directional stability of the vehicle. The controller executes brake controls to provide each wheel with adequate brake pressures, which generate the needed yaw moment. It is shown that the proposed yaw moment control logic can provide excellent cornering capabilities even on low friction roads. This active control scheme can prevent a vehicle from behaving abnormally, and can assist normal drivers in coping with dangerous situations as well as experienced drivers.

• 해양환경안전학회지
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• 제8권1호
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• pp.101-108
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• 2002

This experimental study was performed to investigate internal flow and unsteady flow characteristics using a model for actual shape of a Plate heat exchanger and visualization of flow through the particle image velocimetry. Seven Reynolds numbers were selected by calculation with the height of grooved channel and sectional mean velocity of inlet flow in the experiment, and instantaneous velocity distributions and flow characteristics were experimently investigated. The triangular grooved channel had a compound flow consisting of the flow in lower channel and the groove flow receiving shear stress by the channel flow in the experiment. The sheared mixing layer, in the boundary between the triangular groove and the channel. affected main flow to raise turbulent in the channel.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1627-1632
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• 2003

The effect of (1) phonon dispersion in thermal conductivity model and (2) the differentiation of group velocity and phase velocity for Ge is examined. The results show drastic change of thermal conductivity regardless of using same relaxation time model. Also the contribution of transverse acoustic (TA) phonon and longitudinal acoustic (LA) phonon is changed by considering more rigorous dispersion model. Holland model underestimates the scattering rate for high frequency TA, so misleading conclusion, i.e. TA is dominant heat transfer mode at high temperature. But the actual reduction of thermal conductivity is much larger than the estimation by Holland model and high frequency TA is no more dominant heat transfer mode. Another heat transfer mechanism may exist for high temperature. Two possible explanations are (1) high frequency LA by Umklapp scattering and (2) optical phonon.

• The Journal of the Acoustical Society of Korea
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• 제15권1E호
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• pp.39-44
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• 1996

Matched field localization schemes often show a high sensitivity to acoustic variabilities due to mismatch between assumed and actual environments. In this paper, we focus on the effect of source motion or Doppler on matched field processing (MEP). to accomplish this, MFP is extended to treat a moving source problem with normal mode description of the sound field. the extension involves both the temporally nonstationary and spatially inhomogeneous nature of the sound field generated by a time-harmonic point source moving uniformly in a stratified oceanic waveguide. It is demonstrated that the impact of source motion can be significant to MEP although the velocity of a moving source is much smaller than the sound velocity of the oceanic waveguide. In addition, a criteria for minimizing the effect of Doppler on MFP is discussed.

• 한국안전학회지
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• 제6권4호
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• pp.34-44
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• 1991

In this study, the general solution of heat balance equation including conductive heat loss were suggested and were determined the constants with the results of experiment in hot tunnel in order to derive the general equation for the response time and to investigate the response time index which represent the characteristics of response of sprinkler head in actual fires. Two types of test were considered, the plunge test, in which the air temperature is represented by a step function, and the ramp test, in which the air temperature increases at a constant rate. As a result, simple equations were derived, which can be predicted the response time for the ramp type fire with the rate of temperature rise and gas velocity, for the plunge type fire with temperature and gas velocity. Also other useful data, such as the effective temperature, time constant, response time index and conduction parameter were obtained.

• Design & Manufacturing
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• 제13권4호
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• pp.28-33
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• 2019

In this study, the flow analysis of fermentation tank, digester and dryer, which are the main equipment in environmental energy facilities, was carried out. Numerical analysis was carried out with the size of the actual plant, and 3D modeling program CATIA V5 R16, grid generation program Gambit, and general purpose flow analysis package ANSYS-FLUENT (v13) were used. Simulation results of the carrier gas flow analysis in the STD dryer using the computational fluid dynamics program showed that the carrier gas smoothly circulated between the shells of the dryer and the flow was uniformly distributed without stagnation or flow. It is also predicted that rotational flow due to shell rotation is active. The average flow velocity of carrier gas in the STD dryer was estimated to be about 0.196m / s, and the average temperature of the carrier gas was calculated to be 424K. Due to the relatively slow carrier gas velocity and high average temperature, the water content of the sludge can be effectively lowered.

• 소성∙가공
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• 제6권6호
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• pp.517-526
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• 1997

The purpose of this study is to investigate changes in the wall thickness of tube sinking and working forces by the upper bound method and ABAQUS code. The independent variables are ; workpiece material, original wall thickness of tube, die angle, friction, and reduction of diameter. The results indicate that these five variables are factors of the increase in wall-thickness and working forces. Three variables, a inner tube wall angle and two angles of the velocity discontinuous surfaces, are optimized in this proposed velocity field by the upper bound method. In this method, we can estimate the working forces and final tube thicknesses similar to actual forming process. Optimum process variables which are obtained by upper bound method are used in ABAQUS pre-model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.219-222
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• 1994

This thesis describes an observer of Switched Reluctance Motor for position. velocity and torque estimation using current sening. Inductance of SRM varies trapezoidally with respect to the rotor position. This means that the inductance of each phase is a periodic function with the same period. Under this condition. the observer with a constant gain can be developed though SRM has nonlinear characteristics. Because SRM has equivalent physical meaning with each period. The stability of error system which is the difference between actual system and observer system. is analyzed using Lyapunov and variable structure theory. The effectiveness of the proposed estimation is shown by various simulation.

• 설비공학논문집
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• 제1권1호
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• pp.32-45
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• 1989

The airflow characteristics of clean tunnel type clean room were experimentally investigated with the change of operating speed and exit type. Distributions of air velocity and pressure were measured in clean room which is located lower than HEPA filters, and the pressure distribution was also measured in upper plenum which is located above the HEPA filters, to identify the performance of clean room. Through the analysis it was turned out that air velocity characteristics in clean room were significantly affected by the upper plenum flow conditions such as pressure distribuion. This results will be useful in the actual clean room design to enhance the performance.