• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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• pp.133-139
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• 2012

Dynamic characteristic of lift gate supported by plane truss is studied by a model test scaled with the ratio of 1 : 31.25 in the four major rivers project. The vibrations of gate supported by the plane truss is assessed in comparison with those of gate supported by the space truss which was tested formerly. The gate model is made of acryl panel and calibrated by lead. A model test is conducted under the different gate opening and upstream water levels conditions in the concrete test flume dimensioned 1.6 m in width, 0.8 m in height and 24 m in length. In order to verify the model, natural frequencies of the model gate are measured, and compared with the numerical results. The vibrations of gate model supported by the plane truss in opening height of 1.0 cm~2.0 cm shows greater than one supported by the space truss. It is found that the gate model supported by the plane truss is less desirable than one supported by the space truss. thus, the latter type of gate model is requested to design.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.422-429
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• 1997

Thermal stress induced by hydration heat may produce cracks in mass concrete structure, which can result in structural problems as well as bad appearance. To minimize crack occurrence in massive structural, thus, the study put an emphasis on the determination of optimized lift height and block size. In the parametric study different sizes and lift heights were used to measure the magnitudes of hydration heat and thermal stresses for 3 different types of concrete fabricated with 1 pure cement and 2 blended Portland cements. As a result of analysis. it was found that magnitude of hydration heat and the occurrence of thermal cracks depend on the restriction conditions and material characteristics, especially adiabatic material parameters. It was also found that optimized lift height and block size can be determined from an appropriate combination of the degree of inner and outer structural restrictions.

• Journal of Environmental Science International
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• v.13 no.10
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• pp.929-938
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• 2004

Sludge discharger applied the principle of the air lift pump was investigated experimentally for the different design( diameter of discharge pipe, diameter and height of the inside and outside wall) and operating parameters(air flow rate, water level). And it was conducted that performance comparison about sludge discharger and conventional air lift pump. The result indicated that discharged liquid were increased with the increase of air flow rate and water level and decrease distance between inside and outside wall. The discharge pressure was increased with an increase of air flow rate and a decrease of the diameter of the discharge pipe, for both the sludge discharger and the airlift pump. The discharge pressures of the sludge discharger were 3-6 times higher than those of the air lift pump.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.7-14
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• 2004

The lift-off characteristics of the triple flame have been studied experimentally with various mean velocities and concentration gradients using a multi-slot burner, which can control the concentration gradient and the mean velocity independently, Lift-off height, axial maximum velocity, flame temperature, and some other characteristics were examined for methane and propane flame, It was found that minimum values of the lift-off heights exist at a certain concentration gradient for constant mean velocity, and this result implies that the propagation velocity has a maximum value at this condition, OH radical distribution was measured with LIF method and velocity variation along streamline was measured with PlV system. In addition maximum temperature along streamline was measured with CARS system. The intensity of the diffusion flame affects on the propagation velocity of triple flame in the region of very weak concentration gradient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.160-166
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• 2004

Combustion using oxygen enriched air is known as a technology which can increase flame stability as well as thermal efficiency due to improving the burning rate. Lift-off, blowout limit and flame length were examined as a function of jet velocity, coflow velocity and OEC(Oxygen Enriched Concentration). Blowout limit of the flame below OEC 25% decreased with increase of coflow velocity, but the limit above OEC 25% increased inversely. Lift-off height decreased with increase of OEC. In particular, lift-off hardly occurred in the condition above OEC 40%. Flame length of the flames above OEC 40% was increased until the blowout occurred. Great flame stability was obtained since lift-off and blowout limit significantly increased with increase of OEC.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.326-331
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• 2003

Combustion using oxygen enriched air is known as a technology which can increase flame stability as well as thermal efficiency due to improvement of the burning rate. Lift-off, blowout limit and flame length were examined as a function of jet velocity, coflow velocity and OEC(Oxygen Enriched Concentration). Blowout limit of the flame below OEC 25% decreased with coflow velocity, but the limit above OEC 25% increased inversely. Lift-off height decreased with increase of OEC. Especially lift-off hardly occurred in the condition above OEC 40%. Flame length of the flames above OEC 40% was increased until the blowout occurred. Flame stability became improved since lift-off and blowout limit increased much with increase of OEC.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.4
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• pp.152-159
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• 1999

This paper describes the rmtion characteristics of a particle in GIS under AC voltage. To measure the motion characteristics of the particle, a model gas chamber and parallel plain electrodes were designed and manufactured lift-off voltages of wire and spherical particles on the electrode were calculated and rreasured, and electric charge was calculated. By using a high speed carrera, the rmtion characteristics of various particles with aw}ied voltages, such as motion pattern, lift-off time, lift-off height, were analyzed 1be lift-off voltages were greatly affected by diarreters of wire and spherical particles. At voltage around lift-off voltage, the stand-up particle in vertical state rmved up and down between electrodes and the height of the lift-off particle was low. At voltage around breakdown voltage, the particle repeated vertical rotation a few times while they were being lifted off, and then, they were floating between the electrodes.trodes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.337-345
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• 2012

A model test is performed to investigate the dynamic behavior of truss type lift gate which is being constructed by the four major rivers project. The gate dimensioned 40 m in width, 9m in height is scaled with the ratio of 1:25 and is made of acryl panel and supplemented weight by lead in the concrete test flume dimensioned 1.2 m in width, 0.5 m in height and 30m in length. Firstly natural frequencies of the model gate are measured and compared with the numerical results for the calibration. The amplitudes of the vibration are measured under the different gate opening, upstream water level conditions. Also models with bottom angle $20^{\circ}$, $35^{\circ}$ and $50^{\circ}$ are tested and compared to find out a proper shape of bottom structure which minimizes the gate vibration. These test results presents a basic data for the guide manuals of gate management and a design method to reduce the gate vibration of truss type lift gate.

• 한국연소학회:학술대회논문집
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• 2007.05a
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• pp.13-18
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• 2007

When triple flames propagated in a diverging channel, the effects of fuel dilution on the lift-off characteristics of triple flames were investigated. A multi-slot burner was used to stabilize the lift-off flame especially at weak fuel concentration gradients. It was reported that there is a maximum propagation velocity at a critical concentration gradient in an open jet regardless of fuel dilution. The enhancement of a diffusion flame affected to increase the propagation velocity around critical concentration gradients. However, the influence of a confined channel on the structure of triple flames according to fuel dilution needs to be investigated compared with an open jet case. This study aimed to examine the effect of a confined channel on the structure and the propagation velocity of the triple flames according to fuel dilution. Lift-off height and propagation velocity of triple flames were investigated by employing three kinds of fuel compositions diluted by nitrogen (0%, 25%, 50% $N_2$), Fuel dilution reduced the propagation velocity of triple flame in a confined channel mainly due to the decrease of flame temperature in premixed branch. Despite the difference in fuel dilution, the propagation velocity has a maximum value at a specific fuel concentration gradient even though the critical concentration gradient increases with fuel dilution. And the critical concentration gradient in a confined channel is larger than that in an open jet due to enhancement of convective diffusion.

• Journal of Mechanical Science and Technology
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• v.14 no.9
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• pp.1013-1019
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• 2000

A numerical investigation was performed to determine the effect of the Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about the airfoil. Fully-turbulent results were obtained using the standard ${\kappa}-{\varepsilon}$ two-equation turbulence model. The numerical solutions showed that the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increase the effective camber of the airfoil. The Gurney flap provided a significant increase in the lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. It turned out that 0.6% chord size of flap was the best. The numerical results exhibited detailed flow structures at the trailing edge and provided a possible explanation for the increased aerodynamic performance.