• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.416-421
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• 2000

We have developed a simple model for describing the non-spherical particle growth phenomena using modified 1-dimensional sectional method. In this model, we solve simultaneously particle volume and surface area conservation sectional equations which consider particles' irregularities. From the correlation between two conserved properties of sections, we can predict the evolution of the aggregates' morphology. We compared this model with a simple monodisperse-assumed model and more rigorous two dimensional sectional model. For the comparison, we simulated silica and titania particle formation and growth in a constant temperature reactor environment. This new model shows a good agreement with the detailed two dimensional sectional model in total number concentration, primary particle size. The present model can also successfully predict particle size distribution and morphology without costing very heavy computation load and memory needed for the analysis of two dimensional aerosol dynamics.

• 한국입자에어로졸학회지
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• 제9권3호
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• pp.163-171
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• 2013

Soot particles emitted from combustion processes are often coated by non-absorbing organic materials, which enhance the global warming effect of soot particles. It is of importance to study the condensation characteristics of soot particles experimentally and theoretically to reduce the uncertainty of the climate impact of soot particles. In this study, the condensational growth of soot particles in a tubular coater was modeled by a one-dimensional (1D) plug flow model and a two-dimensional (2D) laminar flow model. The effects of 2D heat and mass transports on the predicted particle growth were investigated. The temperature and coating material vapor concentration distributions in radial direction, which the 1D model could not accounted for, affected substantially the particle growth in the coater. Under the simulated conditions, the differences between the temperatures and vapor concentrations near the wall and at the tube center were large. The neglect of these variations by the 1D model resulted in a large error in modeling the mass transfer and aerosol dynamics occurring in the coater. The 1D model predicted the average temperature and vapor concentration quite accurately but overestimated the average diameter of the growing particles considerably. At the outermost grid, at which condensation begins earliest due to the lowest temperature and saturation vapor concentration, condensing vapor was exhausted rapidly because of the competition between condensations on the wall and on the particle surface, decreasing the growth rate. At the center of the tube, on the other hand, the growth rate was low due to high temperature and saturation vapor concentration. The effects of Brownian diffusion and thermophoresis were not high enough to transport the coating material vapor quickly from the tube center to the wall. The 1D model based on perfect radial mixing could not take into account this phenomenon, resulting in a much higher growth rate than what the 2D model predicted. The result of this study indicates that contrary to a previous report for a thermodenuder, 2D heat and mass transports must be taken into account to model accurately the condensational particle growth in a coater.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.2-3
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• 2001

Characteristics of two-dimensional slab photonic crystal lasers will be summarized. Room temperature c.w operation is demonstrated at 1.6 $\mu\textrm{m}$ by using InGaAsP slab-waveguide triangular photonic crystal on top of wet-oxidized aluminum oxide. Recently, 2-D PBG structures have attracted a great deal of attention due to their simplicity in fabrication and theoretical study as compared to the three-dimensional counterparts [1]. Air-guided 2-D slab PBG lasers were reported by Caltech group (2). However, this air-slab structure is mechanically fragile and thermally unforgiving. Therefore, a new structure that can remove this thermal limitation is dearly sought after for 2-D PBG laser to have practical meaning. In this talk, we report room-temperature continuous operation of 2-D photonic bandgap lasers that are thermally and mechanically stable.(omitted)

• Journal of Forest and Environmental Science
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• 제30권2호
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• pp.226-232
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• 2014

To understand transition characteristics from wood to charcoal the dimensional changes of carbonized woods at low temperature from $300^{\circ}C$ to $350^{\circ}C$ at the intervals of $10^{\circ}C$ were investigated. Three species of hardwoods and two species of softwoods were used in this study. Measurements of dimensional changes of cells were observed by stereoscopic microscope and an image analyzer. The apparent volume of each specimen decreased greatly with increasing temperature. Severe cracks and collapse were observed frequently in hardwoods and hardly in softwoods. Vessel diameter and tracheid cell wall thickness of the wood samples were decreased with increasing carbonization temperature. Contraction of vessel diameter in tangential direction was greater than that in radial direction. Cell wall thickness of tracheids decreased with increasing carbonization temperature. Consequently, even though it was small range of carbonization temperature, dimensions of wood components were changed considerably.

• 대한기계학회논문집
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• 제14권5호
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• pp.1166-1180
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• 1990

본 연구에서는 열간 반경단조를 해석하는데 있어서 재료의 변형 해석은 강-점 소성해석법으로 해석하고 온도분포도 유한 요소법으로 해석한다.

• 대한설비공학회지:설비저널
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• 제16권2호
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• pp.204-215
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• 1987

Laminar natural convective heat transfer within a two-dimensional rectangular enclosure with horizontal conducting walls and partitions was investigated by numerical analysis and experiment. The enclosure consists of two isothermal vertical walls and two adiabatic horizontal walls. This combined heat transfer problem of conduction and natural convection was solved using finite difference method with SIMPLE algorithm, and temperature distribu-tions in the air filled enclosure was obtained using Mach-Zehnder interferometer. Good agree-ment was obtained between the predicted and measured results. The effect of geometric parameters and thermal properties on heat transfer was studied far Grashof numbers in range, $1\times10^4\;{\leqslant}\;G^r\;{\leqslant}\;6.4\times10^5.$ It was found that both velocity and temperature fields were in-fluenced significantly by thermal conductivity of the conducting walls and the partitions, and by geometry of partitions.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.711-727
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• 2017

This article is concerned with a two-dimensional problem of micropolar generalized thermoelasticity for a half-space whose surface is traction-free and the conductive temperature at the surface of the half-space is known. Theory of two-temperature generalized thermoelasticity with phase lags using the normal mode analysis is used to solve the present problem. The formulas of conductive and mechanical temperatures, displacement, micro-rotation, stresses and couple stresses are obtained. The considered quantities are illustrated graphically and their behaviors are discussed with suitable comparisons. The present results are compared with those obtained according to one temperature theory. It is concluded that both conductive heat wave and thermodynamical heat wave should be separated. The two-temperature theory describes the behavior of particles of elastic body more real than one-temperature theory.

• Progress in Superconductivity
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• 제11권1호
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• pp.72-77
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• 2009

Low temperature scanning laser microscopy (LTSLM) can be used for a two-dimensional display of bolometric response arising from the localized excitation of a sample by the focused laser beam. In this study, the distribution of critical temperature ($T_c$) and critical current density ($J_c$) in YBCO coated conductor were analyzed using LTSLM. For improving the temperature stability, we have modified the system into a double-shielding type. Through the modification, the temperature stability was successfully improved from ${\pm}10mK\;to\;{\pm}2mK$. The superconducting properties of YBCO coated conductors were measured for the sample of a narrow bridge type using wet etching process. The spatial non-uniformity of the ac voltage response, ${\delta}V(x)$, which is proportional to ${\partial}\rho(x,J_B)/{\partial}T$ in the transition temperature region could be observed and displayed in a two-dimensional image.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.114-120
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• 2000

EHL analysis of connecting rod bearing is proposed which includes effects of temperature variation in lubrication film. Lubrication film temperature is treated as a time-dependent, two-dimensional variable which is averaged over the film thickness, while connecting rod big end temperature is assumed to be time-independent and three-dimensional. It is assumed that a portion of the heat generated by viscous dissipation in the lubrication Him is absorbed by the film itself, and the remainder flows into the bearing surface. Mass-conserving cavitation algorithm is applied and the effect of variable viscosity is included to solve the Reynolds equation. Simulation results of the connecting rod bearing of internal combustion engine are presented. It is shown that the temperature variation has remarkable effects on the bearing performance. It is concluded that the EHL analysis considering effects of the temperature variation is strongly recommended to predict the bearing performance of connecting rod big end On internal combustion engine.

• Tribology and Lubricants
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• 제17권3호
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• pp.228-235
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• 2001

EHL analysis of connecting rod bearing is proposed which includes effects of temperature variation in lubrication film. Lubrication film temperature is treated as a time-dependent, two-dimensional variable which is averaged over the film thickness, while connecting rod big end temperature is assumed to be time-independent and three-dimensional. It is assumed that a portion of the heat generated by viscous dissipation in the lubrication film is absorbed by the film itself, and the remainder flows into the bearing surface. Mass-conserving cavitation algorithm is applied and the effect of variable viscosity is included to solve the Reynolds equation. Simulation results of the connecting rod bearing in internal combustion engine are presented. It is shown that the temperature variation has remarkable effects on the bearing performance. It is concluded that the EHL analysis considering effects of the temperature variation is strongly recommended to predict the connecting rod bearing performance in internal combustion engine.