• Fire Science and Engineering
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• v.22 no.2
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• pp.38-43
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• 2008

Recently, the application of transverse ventilation system in accordance with oversized exhaust ports has been increased in bidirectional road tunnel in order to improving smoke exhaust ability. In this study, numerical simulations were carried out by using FDS (ver. 4.0) which includes variations of exhaust flow rates and heat release rate of fire to obtain the optimal smoke exhaust rate in case of fire in the transversely ventilation system. As a result, smoke exhaust amount tends to increase when the inner velocity is existing in the tunnel. In case of internal longitudinal air velocity 2.5m/s face to the fire, smoke moving distance should be restricted within 250m when the smoke exhaust rate which exceeds $244.8m^3/s$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1561-1569
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• 2000

Flying attitudes of the slider, which are flying height, pitch and roll, are affected by the air flow velocity, the skew angle, and the manufacturing tolerances. Traditional designs of the air bearing surface have considered only the flying performances for the variations in the air flow velocity and the skew angle, which are determined by the radial position. In this study, we present the new shape design of the air bearing surface by considering the track seek performance and the air bearing stiffness as well as the traditional design requirements. The optimization technique is used to improve the dynamic characteristics and operating performance of the newly proposed air bearing surface shape design further. The optimized configuration is obtained automatically and the optimally designed sliders show the enhanced flying and dynamic characteristics.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.3
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• pp.199-207
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• 2002

In this paper, a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype is discussed. Experimental results using a 1/4-ear simulator are discussed. Also, a suspension ECU prototype targeting real implementation is provided.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.468-473
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• 2014

This paper describes the in-flight alignment of SDINS (Strapdown Inertial Navigation Systems) using an EKF (Extended Kalman Filter) and a UKF (Unscented Kalam Filter), which allow large initial attitude error uncertainty. Regardless of the inertial sensors, there are nonlinear error dynamics of SDINS in cases of large initial attitude errors. A UKF that is one of the nonlinear filtering approaches for IFA (In-Flight Alignment) are used to estimate the attitude errors. Even though the EKF linearized model makes velocity errors when predicting incorrectly in case of large attitude errors, a UKF can represent correctly the velocity errors variations of attitude errors with nonlinear attitude error components. Simulation results and analyses show that a UKF works well to handle large initial attitude errors of SDINS and the alignment error attitude estimation performance are quite improved.

• Atmosphere
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• v.22 no.3
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• pp.331-344
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• 2012

The changes in the Hadley circulation during the second half of the 20th century were examined using observations and the 20C3M (Twentieth Century Climate in Coupled Models) simulations by the 21 IPCC AR4 models. Multi-model ensemble (MME) mean shows that the mean features of the Hadley circulation, such as the intensity, magnitude, and the seasonal variations, are very realistically reproduced, compared to the ERA40 reanalysis. But the long-term trends of the Hadley circulation in 20C3M MME are quite different to those of observations. The observed intensity of the Hadley cell is persistently enhanced, particularly during boreal winter. In comparison, the meridional overturning circulations reproduced in the MME mean remains invariant in time, and even weakened in boreal summer. This discrepancy between the ERA40 and 20C3M MME is consistently shown in the overall structure of the Hadley circulations, such as mass streamfunction, the velocity potential, the vertical shear of meridional wind, and the vertical velocity in the tropical region. This results indicate that the current climate models are skill-less to capture the long-term trend of Hadley circulation yet, and should be improved in simulation of the large-scale features to enhance the confidence level of future climate change projection.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.487-497
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• 2011

Numerical analysis has been performed to investigate the rotor speed and pitch range variations when the airspeed is increased in autorotation. Transient Simulation Method(TSM) was used to obtain the steady states of autorotation. The rotor blade was analyzed by the two-dimensional compressible Navier-Stokes solver in order to adapt to the airspeed increase and the results were used in the transient simulation method. Meanwhile, the Pitt/Peters inflow theory was used to supply the induced velocity fields. For the prescribed torque equilibrium state, the combinations of velocity, shaft angle, and pitch angle were produced to investigate the rotor speeds and variable ranges. The rotor tip Mach number and rotor speed were correlated and the trim range of pitch angle was observed with respect to the shaft angle decrease.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.21-29
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• 1995

Among the index properties of granite and andesite, the relation between porosity and water content is highly correlated, but specific gravity, porosity and water content have loW relation with P wave velocity and their relationship showed dispersed zone type. With raising the temperature, Brazilian tensile strength was not changed remarkably, but decreased near $100^{\circ}C$. After the strength increased at $150^{\circ}C$, it decreased near $200^{\circ}C$ in granite. In andesite, however, the strength was increased up to $200^{\circ}C$, and then decreased. The variations of P wave velocity at each temperature zone are similar to those of tensile strength.

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.148-151
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• 2005

Field-scale DNAPL dissolution is controlled by the topology of DNAPL distributions with respect to the velocity field. A high resolution percolation model was developed and employed to simulate the distribution of DNAPL within source zones. Statistically anisotropic permeability values and capillary parameters were generated for 10${\times}$10${\times}$10 m domains at a resolution of 0.05 to 0.1 m for various statistical properties. TCE leakage was simulated at various rates and the distribution of residual DNAPL in 'fingers' and 'lenses' was computed. Variations in finger and lens geometries, frequencies, average DNAPL saturations, and overall source topology were predicted to be strongly influenced by statistical properties of the medium as well as by injection rate and fluid properties. Model results were found to be consistent with observations from controlled DNAPL release experiments reported in the literature. The computed distributions of aquifer properties and DNAPL were utilized to perform high-resolution numerical simulations of groundwater flow and dissolved transport. Simulations were performed to assess the effect of grout or foam injection in bore holes within the source zone and of shallow point-releases of fluids with various properties on dissolution in DNAPL dissolution rate, even for widely spaced injection points. The results indicate that measures that induced partial flow reductions through DNAPL source zones can significantly decrease dissolution rates from residual DNAPL. The benefit from induced partial flow reductions is two-fold: 1) local flow reduction in DNAPL contaminated zones reduces mass transfer rates, and 2) contaminant flux reductions occur due to the decrease in groundwater velocity

• Fisheries and Aquatic Sciences
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• v.9 no.4
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• pp.167-174
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• 2006

Two typical responses have been documented for flatfish when they encounter the ground gear of bottom trawls: herding response and falling back response. These two responses were analyzed from video recordings of fish and were characterized by time sequences for four parameters: swimming speed, angular velocity, acceleration, and distance between the fish and the ground gear. When flatfish displayed the falling-back response, absolute values of the three swimming parameters and their deviations were significantly higher than those during the herding response. However, the swimming parameters were not dependent on the distance between the flatfish and the ground gear, regardless of which response occurred. The dominant periods for most of the movement parameters ranged from 2.0 to 3.7 s, except that no periodicity was observed for swimming speed or angular velocity during the falling-back response. However, variations in the four parameters during the falling -back response revealed greater irregularity in periodicity and higher amplitudes. This complex behavior is best described as a chaos phenomenon' and is discussed as the building block for a model predicting the responses of flatfish to ground gear as part of the general understanding of the fish capture process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.152-156
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• 2007

It is very important to understand about mass flow rate variations of propellants generated by pressure fluctuation in the combustion chamber. Therefore, we have studied quantifying the variation of mass flow rate generated by pressure fluctuation. The flow velocity in orifice is acquired through theoretical approach after measuring the pressure in orifice and the flow area in orifice is measured by film thickness measuring device. Our results agreed with it in the very small error range comparing our results with velocity and mass flow rate in steady state. Thus, our result based on theoretical approach will help about measuring mass flow rate in non-steady state.