• Journal of Korea Foundry Society
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• v.7 no.4
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• pp.322-326
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• 1987

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.302-308
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• 2015

Isothermal vapor liquid equilibria for the binary system of 3-methylpentane with ethylene glycol monopropyl ether ($C_3E_1$) and ethylene glycol isopropyl ether ($iC_3E_1$) were measured at 303.15, 318.15, and 333.15K. In our previous work, phase equilibria for the binary system of $C_3E_1$ mixtures were investigated according to the chain length of alkane, alcohol or those isomer. But in this study, we discussed the different effect of $C_3E_1$ and its isomer, $iC_3E_1$, on the phase equilibria. The measured systems were correlated with a Peng-Robinson equation of state (PR EOS) combined with Wong-Sandler mixing rule for the vapor phase, and NRTL, UNIQUAC, and Wilson activity coefficient models for the liquid phase. All the measured systems showed good agreement with the correlation results. And it was found that the phase equilibria showed very little difference between the $iC_3E_1$ mixture system and the $C_3E_1$ mixture system.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.3
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• pp.17-27
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• 2009

Purpose: This review article was written to determine the effects of parameters characterizing a hard contact lens (RGP included), such as BCs, diameters, edge angles, on the time interval for tight fitted lens to return to the equilibrium when it was decentered from blinking. Methods: A mathematical formulation was established to relate or calculate the restoring forces and thickness of lacrimal layer beneath the cornea with the various lens parameters when the tight fitted lens was decentered from blinking. Based on this formulation the differential equations and their numerical solution program were set up to describe the time dependence of the lens on the position and to estimate the time for the lens's return to the equilibrium after blink. Results: It is found that the time interval for the tight fitted lens to return to the equilibrium decreases as either the BC decreases or the diameter increases because both the reduction in BC and increase in diameter result in the increase in the lacrimal layer thickness between the lens and cornea increase which yielded the lowering of the viscous friction in the lens motion. As the edge angle of tight fitted lens increases the time for recentering decreases due to the increase in restoring force without change in lacrimal thickness beneath the lens. In the case of flat fitted hard lens (RGP included), the lacrimal layer thickness under the lens increases as either BC or diameter increases which results in reduction in viscous friction so that the time for the lens's return to the equilibrium were to decrease. The edge angle of flat fitted lens does not affect the lens motion. Conclusions: The effect of BCs on the lens motion (time to approach the equilibrium) was concluded to be significant with both tight and flat fitted lens where its results are contrary with each other. The edge angle of lens only affects the motion in tight fitted lenses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.409-418
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• 1988

Steam turbines, gas turbines, multistage centrifugal compressors are operated over the range of the first critical speed. In these rotors flexible rotor balancing technique is necessary. In such balancing, influence coefficients are measured by rotating a rotor with trial weight. But for the large rotor, the measurement of influence coefficient takes much time and it reduces the cost efficiency. In this paper the new influence coefficient with rotation of rotor is proposed. First the theoretical background of the method is presented and it is applied to the simple flexible rotor model. Then the experiments are performed and the results of presented method are compared with those of analytical method. By using the obtained influence coefficient, balancing of the flexible rotor is performed.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.33-41
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• 2003

The large planar failure has occurred in a rock cut slope of highway construction site in Boeun. This area is considered to be unstable since the discontinuity, whose orientation is similar to the orientation of the failure plane, is observed in many areas. Therefore, several analysis techniques such as SMR, stereographic analysis, limit equilibrium, numerical analysis, which are commonly used in rock slope stability analysis, are adopted in this area. In order to analyze the stress redistribution and nonlinear displacement caused by cut, which are not able to be obtained in limit equilibrium method, DEM and shear strength reduction technique were used in this study. Then the factors of safety evaluated by shear strength reduction technique and limit equilibrium were compared. In addition, the factor of safety under fully saturated slope condition was calculated and subsequently, the effect of the reinforcement was evaluated.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.47-57
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• 2000

It is difficult to calculate factor of safety of a tunnel by applying any analytical method based upon limit equilibrium method since the shape of failure plane in tunnel analysis can not be easily assumed in advance. To cope with this shortcoming, a method is suggested to calculate safety factor of a tunnel by numerical analysis using strength reduction technique. A circular tunnel excavated in a homogeneous rock was selected as an example problem and factors of safety were calculated for no-supported, partly-supported, and completely-supported cases respectively. Meshes with 3 different sizes were examined for a sensitivity analysis. For the verification of the proposed method, a limit equilibrium analysis was conducted and compared with the numerical analysis. The proposed method herein can be used to calculate factor of safety of a tunnel regardless of tunnel shape or geological conditions, and thus can contribute for the improved design and stability assessment of tunnels.

• Journal of the Korean Society for Marine Environment & Energy
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• v.3 no.2
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• pp.33-40
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• 2000

Dispersion of high temperature and high salinity water discharged from a desalination plant is numerically estimated to investigate its impact on marine environment. The plant is installed on a floating barge located in Jinhae Bay and takes 200 tons of seawater per day. Fifty tons of intake are changed into fresh water, while 150 tons of those are discharged as the water of 15℃ warmer and 1.33 times saltier than surrounding seawater. In this dispersion model, advection is described by two-dimensional tidal currents and turbulent diffusion is simulated by Monte Carlo technique. Decay of water temperature is modelled by heat exchange between the atmosphere and the ocean, while decay of water salinity is ignored. The distributions of temperature and salinity come to equilibrium when the dispersion model is run for 100 days for temperature and for 365 days for salinity, respectively. At equilibrium state the water temperature and salinity rise 0.01℃ and 0.001‰ higher than ambient seawater, respectively.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.447-450
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• 2010

This study was conducted to explore the flow contamination in the $CH_4-O_2$ vitiated air heater. Non-equilibrium and equilibrium calculation were made of the flow processes in the heater and nozzle assuming the inviscid and one dimensional flow. The results were compared with the measurement data. The overall results of this study showed additional non-equilibrium calculation should be considered to assess the presence of NO, which species could yield the combustion delay or no reaction, as a contaminant.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.864-869
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• 1998

In this work, the solid-liquid equilibria (SLE) of some aromatic organic mixtures including benzene, widely used as an industrial solvent, were measured by static method using our own made experimental apparatus. The accuracy and reproducibility of apparatus were tested by comparing experimental results with literature values for 1-dodecanol+cyclohxane and benzene + p-xylene systems. The SLE for new binary systems of benzene+aniline, benzene+nitrobenzene, p-xylene+cyclohexane were measured afterwards and compared with the calculated values by modified UNIFAC(Dortmund) equation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1026-1034
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• 1988

An efficient method for designing balancing springs to be used for dynamic balancing of planar mechanisms was studied. In spite of its wide application in the field of balancing problems such as balancing of input torques, clearance effects etc., there have been few efficient ways of determining the specifications of the balancing springs. To improve this problem, a method of approximating the characteristic of linear springs was suggested and its validity was checked through an analysis of errors. Further, through an example of a balancing problem to reduce the fluctuation of input torques of a 4bar mechanism, it was shown that the proposed method of approximation simplifies the design equations and a satisfactory result can be found efficiently.