• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.27-40
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• 1997

The heat in Czochralski method is transfered by all transport mechanisms such as convection, conduction and radiation and convection is caused by the temperature difference in the molden pool, the rotations of crystal or crucible and the difference of surface tension. This study delvelops the simulation model of Czochralski growth by using the finite difference method with fixed grids combined with new latent heat treatment model. The radiative heat transfer occured in the surfce of the system is treated by calculating the view factors among surface elements. The model shows that the flow is turbulent, therefore, turbulent modeling must be used to simulate the transport phenomena in the real system applied to 8" Si single crystal growth process. The effects of a cusp magnetic field imposed on the Czochralski silicon melt are studied by numerical analysis. The cusp magnetic field reduces the natural and forced convection due to the rotation of crystal and crucible very effectively. It is shown that the oxygen concentration distribution on the melt/crystal interface is sensitively controlled by the change of the magnetic field intensity. This provides an interesting way to tune the desired O concentration in the crystal during the crystal growing.

• Journal of the Korean Home Economics Association
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• v.32 no.3
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• pp.1-10
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• 1994

Major studies of Home Economics have had an intention to keep the standard scientific perspective based on value-free and positivism. But in the early 20C there was a change within scientific philosophy and the holistic perspective has risen in the part of scocial and natural science. The phenomenon dealt in the field of Home Economics is the interaction between human and environment and it regards human and family behavior in the context of the environment as a major object. This interaction can be micro/macro and objectiv $e_jective, So it has a very complex trait. The goal of this study is to verify the applicability of Human Ecology as an alternative framework to explain each level of the family phenomena. Further it is concluded that it is very efficient to present Human Ecology as a general theory for Home Economics because there are increasing demands for understanding interdependence and persuing for balanced co-existence between human and encironment. Finally this study concludes that Human Ecology is not a past theory but a very comprehensive one to construct and abstract theory-building.ng.

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.3
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• pp.11-38
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• 1986

Past and present developments in the alignment procedures of the line shafting are discussed. It is shown that the effects of the propeller hydrodynamics and of the oil-films, built up in the journal bearings, can essentially change the static alignment. However, the inclusion of these phenomena in the alignment is not yet standard. Also the dynamic effects of natural frequencies and vibratory excitations are not yet accounted for in the general case, although also these aspects can influence the safe operation of the line shafting. Therefore a plea is made to develop a more complete and thus a more rational alignment procedure.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.4
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• pp.392-397
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• 1983

In the present study, improvement of the solar collector performance by utilizing honeycomb structures is being investigated. Installation of honeycomb structures inside of the collector induces the suppression of would-be natural convection phenomena within the collector enclosure spacing. It also minimizes infrared radiation heat loss from the collector absorber plate to the surrounding. Experiments have been carried out a collector with 40*20mm rectangular honeycombs, 20*20mm square honeycombs and without honeycombs. The results are presented for the three cases for comparisons. The collector model has been installed at various tilt angle from 15.deg. to 60.deg. measured from the ground. The influence of the tilt angle to the heat performance of the collector is also presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.97-103
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• 1997

Effects of fuel injection timing on the lean misfire limit of a sequential MPI SI engine has been investigated. To investigate the interaction of injection timing and intake flow characteristics, so called axial stratification phenomena, 4 kinds of different intake swirl port of the same combustion chamber geometry have been teated in a single cylinder engine test bench. And 2 kinds of fuel, gasoline and compressed natural gas(CNG), were used to see the effect of liquid fuel vaporization. Result shows that combination of port swirl and injection timing governs the lean misfire limit and lean misfire limit envelopes remain almost the same for a given ratio regardless of engine speed. It is also found that two phase flow has some effects on lean misfire limit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.348-353
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• 2008

A vibration analysis for a rotating cantilever beam with the tapered cross section is presented in this study. The stiffness changes due to the stretching caused by centrifugal inertia forces when a tapered cantilever beam rotates about the axis perpendicular to its longitudinal axis. When the cross section of cantilever beam are assumed to decrease constantly, the mass and stiffness also change according to the variation of the thickness and width ratio of a tapered cantilever beam. Such phenomena result in variations of natural frequencies and mode shapes. Therefore it is important to the equations of motion in order to be obtained accurate predictions of these variations. The equations of motion of a rotating tapered cantilever beam are derived by using hybrid deformation variable modeling method and numerical results are obtained along with the angular velocity and the thickness and width ratio.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1450-1454
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• 2006

Empirical mode decomposition (EMD) is applied to analyze time series characterized with nonlinearity and nonstationarity. This decomposition could be utilized to construct finite and small number intrinsic mode functions (IMF) that describe complicated time series, while admitting the Hilbert transformation properties. EMD has the capability of being adaptive, capture local characteristics, and applicable to nonlinear and nonstationary processes. Unlike discrete wavelet transform (DWT), IMF eliminates spurious harmonics and retains meaningful instantaneous frequencies. Examples based on data representing natural phenomena are given to demonstrate highlight the power of this method in contrast and comparison of other ones. A presentation of the energy-frequency-time distribution of these signals found to be more informative and intuitive when based on Hilbert transformation.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.322-326
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• 1997

The condensate in a single vertical reflux condenser with a tube of the large L/D ratio could carried over in both ways of fill-and-dump and the annular occurrent to steam flow. From the experimental observation made, a theoretical model based on the lumped parameter method is made to understand the dynamics of the reflux condenser. The present model predicts well the time period of fill-and-dump model and the natural vibrational frequency of the water column. This could be a first step to understand the complex phenomena in the reflux condenser such as itd improved thermal performance due to the well controlled pulsation in steam flow and the tube-to tube effect in the multi tube reflux condenser.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.24-29
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• 1998

This study was carried out in order to elucidate the deterioration mechanism of paper according to various sizing chemicals. No additive paper and four kinds of papers containing rosin-alum, alum only, alkylketene dimer(AKD)-cation polymer and cation polymer only were treated by UV light to study changes of water-resistant, optical and mechanical properties from the view points of natural deterioration of paper. Since rosin chemicals have UV absorption at the relatively long wavelength region, rosins are degraded to form hydrophilic groups such as carboxylic acid from their double bonds by UV treatments. These phenomena caused the decreasing of sizing degree and wetting time in case of rosin-sized paper, while the UV treatments brought about the slight increase of wetting time in rosin-free papers such as no additive, alum and kymene only paper owing to the auto-sizing effect. Optical properties were primarily influenced by sizing chemicals. Rosin-sized paper showed lower brightness after UV and near UV treatment because of its UV instability.

• Korean Management Science Review
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• v.15 no.2
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• pp.153-159
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• 1998

Clustering or classification is a very fundamental task that may occur almost everywhere for the purpose of grouping. Optimal clustering is an example of very complicated combinatorial optimization problem and it is hard to develop a generally applicable optimal algorithm. In this paper we propose a general-purpose algorithm for the optimal clustering based on SA(simulated annealing). Among various iterative global optimization techniques imitating natural phenomena that have been proposed and utilized successfully for various combinatorial optimization problem, simulated annealing has its superiority because of its convergence property and simplicity. We first present a version of accelerated simulated annealing(ASA) and then we apply ASA to develop an efficient clustering algorithm. Application examples are also given.