• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.56-64
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• 2024

In this study, a drop impact tester was developed to comprehensively conduct basic testing and academic research on the drop impact characteristics of aerospace structures. A drop tester enables accurate assessment of the dynamic stresses and deformations that occur when an aircraft collides with the ground, thereby enabling the verification of important design factors, such as safety and mechanical strength. The drop tester consists of an electromagnet to attach and drop the test object, a crane to adjust the drop height of the test object, and a drop support structure for vertical drops. Numerical analysis of the drop test object for the test was performed, and basic tests were performed using the drop impact tester. Through the analysis and test results, the structural shape of the landing gear was analyzed, and the behavior of each part was evaluated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.7
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• pp.635-641
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• 2005

This study experimented to understand the effects of transporting ice slurry through elbow and inclined tube. And at this experiment it used propylene glycol-water solution and a diameter of about 2mm ice particle. The experiments were carried out under various conditions, with velocity of water solution at the entry ranging from 1.0 to 3.5 w/s and elbows and inclined tubes of 4 kinds angle with $30^{\circ},\;45^{\circ},\;90^{\circ}\;and\;180^{\circ}$. The pressure drop between the tube entry and exit were measured. According to angle of bending, the highest pressure drop was measured at $30^{\circ}$ elbow and the lowest pressure drop was measured at $90^{\circ}$ elbow, and there are only a little differences of pressure drop between $45^{\circ}$ elbow and $180^{\circ}$ elbow. According to angle of inclined tube, the highest pressure drop was measured at $90^{\circ}$ inclined tube and the pressure drop at $45^{\circ},\;30^{\circ},\;180^{\circ}$ inclined tubes were lower successively. The lowest pressure drop in elbows and inclined tubes was measured at velocity of $2.0\~2.5$ m/s and concentration of $10\;wt\%$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.10
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• pp.51-56
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• 2000

An all fiber coupler-type add/drop filter has been fabricated by writing a Bragg grating in the coupling region of a fused fiber coupler. The fused fiber coupler with 99.8% coupling ratio and 74/m coupling coefficient was used for the add/drop filter. The add/drop filter shows 99% reflectivity and 83% drop efficiency at the operating wavelength of 1536.2nm.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.553-558
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• 2011

This study have goal with conceptual design for offshore structures of high pressure drop control valve for localization valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25. In order to localize the Offshore structures high pressure drop control valve. This study is numerical analysis for zambil offshore project of high pressure drop control valve. The solver which ANSYS workbench used for offshore structures analysis. The working fluids assumed the glycerin(C3H8O3). The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and disk structure. In this study a multi-disk of high pressure drop control valve is designed and manufactured. Then, the flow rate and high pressure dorp of fluids flowing in the high pressure drop control valve is CAE. So, this system can be easily substituted for the existing zambil offshore project system. Finally, safety estimation for trim design of high pressure drop control valve for offshore structures.

• Journal of Power System Engineering
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• v.11 no.1
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• pp.63-69
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• 2007

The evaporation pressure drop of $CO_2$ (R-744) in a horizontal tube was investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and an evaporator (test section). The test section consists of a smooth, horizontal stainless steel tube of 4.57 mm inner diameter. The experiments were conducted at saturation temperature of $-5^{\circ}C\;to\;5^{\circ}C$, and heat flux of 10 to $40kW/m^2$. The test results showed that the evaporation pressure drop of $CO_2$ are highly dependent on the vapor quality, heat flux and saturation temperature. The measured pressure drop during the evaporation process of $CO_2$ increases with increased mass flux, and decreased saturation temperature. The evaporation pressure drop of $CO_2$ is much lower than that of R 22. In comparison with test results and existing correlations, the best fit of the present experimental data is obtained with the previous correlation. But existing correlations failed to predict the evaporation pressure drop of $CO_2$. Therefore, it is necessary to develop reliable and accurate predictions determining the evaporation pressure drop of $CO_2$ in a horizontal tube.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.363-369
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• 2004

We propose, for the first time to our knowledge, a novel gain-clamping method for EDFA in WDM add/drop networks by introducing a disturbance observer technique. The control input signal for gain-clamping is composed of a nominal control signal and an additional control signal of compensating the gain fluctuations caused by channel add/drops. Based on disturbance observer technique, we designed the additional control signal such that it has the compensating information of estimated disturbance resulted from channel add/drops. The circuit for generating additional control signal can easily be implemented by using simple electronic devices. We proved the superiority of the new technique over the previous ones by showing simulation results of minimized dips and spikes that appear in power profile of EDFA in the process of channel add/drops.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.187-194
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• 1999

In the design of catalytic converter, velocity distribution is more important than pressure drop because monolith pressure drop is about 80% of overall pressure drop. For the catalytic converter with single diffuser, pressure drop is decreased as the angle of diffuser decrease, but when the angle is below 18$^{\circ}$, the effect is almost negligible . For the catalytic converter with double diffuser, variation of the angle of the first diffuser shows the same trend as the pressure drop while the shape of diffuser gives little influence on that The outlet shape gives negligible effect on the pressure drop and velocity . distribution . Results show that recirculation region of commercial model is aoubt 30% of the total area in the front of monolith. For the catalytic converter with Model 11 that was presented in the study, recirculation region was not detected more uniform velocity distribution was obtained, and pressure drop was also decreased.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.5
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• pp.497-504
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• 2023

This study analyzes pressure distribution and pressure drop in the receptacle used in charging system of hydrogen fuel cell vehicles. The objective is to minimize receptacle-induced pressure drop by redesigning internal flow channels. Through numerical simulations, three receptacle variants are compared with a baseline case. Results show reduced pressure drop in the filter section. However, the check valve section exhibits higher pressure drop, requiring further improvement. By increasing throat diameter, pressure drop is decreased by 28% between inlet and outlet of the receptacle. This study shows the relationship between dynamic pressure and pressure drop, providing a guideline for receptacle performance optimization. The redesigned receptacle offers potential for enhancing hydrogen charging efficiency.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.3
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• pp.186-193
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• 2003

Floor vibrations in residence and office buildings are typically induced by heel drop and walking movement of occupants. The criteria of most vibration provisions have been developed based on the vibration caused by heel drop impact rather than walking. There may be considerable differences between the vibration characteristics induced by walking and heel drop. The effect of walking vibration was not well reflected on current provisions. In this paper, shaking table test was performed to investigate the human perception level against the vibrations due to walking and heel drop. This study attempts to compare the human Perception level of two different vibration sources. Also, this study investigates the effect of damping on a Perception level under heel drop and walking vibration.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.76-79
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• 2004

Dynamic oscillation motion of a pendant drop has been Investigated experimentally when acoustic wave is applied. This problem is of particular interest in the understanding of transport phenomena, accompanied by liquid drop. In this experiment, pendant drop was made to oscillate by inducing the acoustic wave and the subsequent drop motion was recorded by a high-speed camera. The results obtained indicate that liquid drop hanging on the flat surface has resonant frequencies on each shape oscillation modes. It is also found that exists the swing mode of oscillation on the pendant drop.