• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.80-86
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• 1997

This experiment was undertaken to investigate spray characteristics of the conventional injection system and the ultrasonic energy added injection system. Sauter mean diameter was measured under the variation of injection pressure and the spray distance. To measure the droplet size, we used the Malvern system 2600C. The spray angle and mass distribution were analyzed to the CCD camera and the patternater. After experiment, it was found that the ultrasonic energy added injection system had smaller Sauter mean diameter of droplet, wider mass distribution and wider spray angle than the conventional injection system had.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.79-86
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• 1998

This study was performed to suggest to suggest suitable design conditions of water curtain system through analysis on pressure down in boreholes by hydraulic tests carried out I construction fields for underground oil storages. The influence by hydraulic conductivities of rock mass around boreholes on pressure down in boreholes was analysed. The relationship between array of boreholes and their pressure down was also analysed. Groundwater flow analysis on crude oil and LPG storages was carried out to evaluate results of field tests and to investigate distribution of hydraulic gradient in rock mass around cavern using finite difference method. As the results, hydraulic tests showed that pressure down in boreholes was inverse proportional to the hydraulic conductivity of surrounding rock mass. The rate of pressure down of boreholes was not influenced by water curtain system more than 20m over cavern and was proportional to installation interval of boreholes. The hydraulic gradient in rock mass around cavern was proportional to distance and interval of boreholes and its value was not satisfactory to oil tightness condition in case of no water curtain system.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.29.5-30
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• 2020

We present an improved weak-lensing (WL) study of the high-z (z=0.87) merging galaxy cluster ACT-CL J0102-4915 ("El Gordo"), the most massive system known to date at z > 0.6. El Gordo has been known to be an exceptionally massive and rare cluster for its redshift in the current ΛCDM cosmology. Previous multi-wavelength studies have also found that the cluster might be undergoing a merging event showing two distinctive mass clumps and radio relics. The previous WL study revealed a clear bimodal mass structure and found that the entire system is indeed massive (M200a = (3.13 ± 0.56) × 1015 Msun). This mass estimate, however, was obtained by extrapolation because the previous HST observation did not extend out to the virial radius of the cluster. In this work, we determine a more accurate mass estimate of the cluster using WL analysis utilizing a new set of WFC3/IR and wide-field ACS observations. While confirming the previous bimodal mass structure, we find that the new data yield a ~20% lower mass for the entire system (M200a = (2.37 ± 0.28) × 1015 Msun). We also discuss the rarity of the cluster in the ΛCDM paradigm and suggest an updated merging scenario based on our new measurement.

• Proceedings of the Membrane Society of Korea Conference
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• 1994.04a
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• pp.51-52
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• 1994

High permeability, selectivity and stability are the basic properties also required for membrane gas separations. The $CO_2$ separation by liquid membranes has been developed as a new technique to improve the permeability and selectivity of polymeric membranes. Sirkar et al.(1) have atlempted the hollow-fiber contained liquid membrane technique under four different operational modes, and permeation models have been proposed for all modes. Compared to a conventional liquid membrane, the diffusional resistance decreased by the work of Teramoto et al.(2), who referred to a moving liquid membrane. Recently, Shelekhin and Beckman (3) considered the possibility of combining absorption and membrane separation processes in one integrated system called a membrane absorber. Their analysis could be predicted effectively the performance of flat sheet membrane, however, there are restrictions for considering a flow effect. The gas absorption rate is determined by both an interfacial area and a mass transfer coefficient. It can be easily understood that although the mass transfer coefficients in hollow fiber modules are smaller than in conventional contactors, the substantial increase of the interfacial area can result in a more efficient absorber (4). In order to predict a performance in the general system of hollow-fiber membrane absorber, a gas-liquid mass transfor should be investigated inevitably. The influence of liquid velocity on both a mass transfer and a performance will be described, and then compared with experimental results. A present study is attempted to provide the fundamentals for understanding aspects of promising a hollow-fiber membrane absorber.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.79.1-79.1
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• 2016

We investigated the dynamical properties of the K2-3 multi-planet system. Recently three transiting planets are discovered using the extended Kepler2 (K2) mission (Crossfield et al. 2015). We extended their preliminary stability study by considering a substantial longer integration time. Since planet mass is not known from photometry we calculated exoplanets masses using empirical mass-radius relations (Weiss & Marcy 2014). Forward numerical integration was done using the MERCURY integration package (Chambers 1999). Our results demonstrate that this system is stable over a time scale of $10^8years$. Furthermore, we investigated the dynamical effects of a hypothetical planet in the semi-major axis vs eccentricity space. For stable orbits of the hypothetical planet we calculated transit-timing variation (TTV) and radial velocity signals. We find that for a hypothetical perturber with mass 1-13 Mjup, semi-major axis 0.2 - 0.8 AU and eccentricity 0.00-0.47 the following timing signals for the planet K2-3 b is ~ 5 sec, K2-3 c is ~ 130 sec and for K2-3 d is ~ 190 sec. The radial velocity signal of the hypothetical planet is ~ 4 m/s. Using typical transit-timing errors from the K2 mission, we find that the above hypothetical planet would not be detectable. Its radial velocity signal, however, would be detectable using the APF 2.4m telescope or HARPS at the ESO/La Silla Observatory in Chile.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.144-147
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• 2003

In this study, the mass transfer behaviors of phenanthrene, anthracene, and pyrene in soil slurry reactor (SSR) using two-liquid phase (TLP) system were investigated. The mass transfer ratio and rate of PAH in the TLP system using light paraffine oil, which has the highest solubility of PAH, were influenced by the amount of light paraffine oil and mixing speed. When the amount of light paraffine oil decreased from 15 % to 2.5 % (v/v), the mass transfer ratio of anthracene decreased significantly compared with that of phenanthrene and pyrene. As mixing speed increased, the initial mass transfer rate of PAH within 1 day was enhanced. However, each final mass transfer ratio of three PAHs after 5 day was similar irrespective of mixing speed.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.125-131
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• 2000

The local heat/mass transfer coefficients for arrays of impinging circular air jets on a plane surface are determined by means of the naphthalene sublimation method. Spent fluid makes a crossflow in the confined space. The crossflow reduces heat/mass transfer at the small gap distance between the jet plate and impingement surface because of reentrainment of the spent fluid. The present study suggests a new exhaust system having effusion holes in the impinging jet plate. The spent air flow out after impingement just through effusion holes located in the upper plate. This system increases heat/mass transfer coefficients and uniformity for small gap distances$(H/d{\leq}2)$

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.111-115
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• 2006

To clarify the hydraulic and thermal characteristics of ice slurry which made from 6.5% ethylene glycol-water solution flow in the double tube and plate type heat exchanger, experimental studies were performed. The mass flux and Ice fraction of ice slurry were varied from 800 to $3,500 kg/m^2s$(or 7 to 17 kg/min) and from 0 to 25%, respectively. During the experiment, it was found that the measured pressure drop and heat transfer rate increase with the mass flux and ice fraction; however the effect of ice fraction appears not to be significant at high mass flux region. At the region of low mass flux, a sharp increase in the pressure drop and heat transfer rate were observed depends on mass flux.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.332-335
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• 1997

In the industrial motor drive system, a shift torsional vibration si often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. In this paper, the state feedback controller of the two-mass resonant system using the H$\infty$ filter is proposed. The H$\infty$ filter is robust in noise and disturbance. Simulation results show the validity proposed controller.