• Journal of Korean Society for Atmospheric Environment
• /
• v.16 no.5
• /
• pp.511-520
• /
• 2000

The urban atmosphere is characterized by th difference in surface and atmospheric environment between urban and more natural area. To investigate th climatic effect of land use type and anthropogenic heat of urban on wind field, numerical simulations were carried out under typical summer synoptic condition. The wind model PNU_MCM(Pusan National University Mesoscale Circulation Model) is based on the three-dimensional Boussinesq equations, taking into account the hydrostatic assumption . Since lane-use differs over every subdivision on Pusan the surface energy budget model includes sub0grid parameterization scheme which can calculate the total heat flux over a grid surface composed of different surfaces. The simulated surface wind agrees well with the observed value, and average over 6 days which represent typical summer lan-sea breeze days, August 1998, i.e. negligible gradient winds and almost clear skies. Urbanization makes sea-breeze enhance at day and reduce land-breeze at night. The results show that contribution of land-use type is much larger than that of anthropogenic heat in Pusan.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.3
• /
• pp.80-88
• /
• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.8 no.9
• /
• pp.1365-1371
• /
• 2013

We have introduced two dimensional cluster aggregation model to explain theoretically two phase coexistence phenomena such that adsorption is increased sharply discontinuous in particular pressure on the surface. And then, we have derived adsorption isotherms by applying fundamental statistical thermodynamics and Lagrange multipliers to the our model. By analyzing the our derived adsorption isotherms, we can explain well qualitatively that two phase coexistence on the surface adsorption would be a phenomena that occurs with the strong attractive forces between the adsorbed particles.

• Geomechanics and Engineering
• /
• v.21 no.3
• /
• pp.237-245
• /
• 2020

The process of evaporation from free water surface was simulated in a large scale environmental chamber under various controlled atmospheric conditions and also was modelled by a new mass transfer model. Six evaporation tests were conducted with increasing wind speed and air temperature in the environmental chamber, and hence the effect of atmosphere parameters on the evaporation process and the corresponding response of water were investigated. Furthermore, based on the experiment results, seven general types of mass transfer models were evaluated firstly, and then a new model consisted of wind speed function and air relative humidity function was proposed and validated. The results show that the free water evaporation is mainly affected by the atmospheric parameters and the evaporation rate increases with the increasing air temperature and wind speed. Both the air and soil temperatures are affected by the energy transformation during water evaporation. The new model can satisfactorily describe the evaporation process from free water surface under different atmospheric conditions.

• Atmosphere
• /
• v.28 no.2
• /
• pp.153-162
• /
• 2018

The statistical prediction model for wintertime surface air temperature, that is based on snow cover extent and Arctic sea ice concentration, is updated by considering $El-Ni{\tilde{n}}o$ Southern Oscillation (ENSO) and Quasi-Biennial Oscillation (QBO). These additional factors, representing leading modes of interannual variability in the troposphere and stratosphere, enhance the seasonal prediction over the Northern Hemispheric surface air temperature, even though their impacts are dependent on the predicted month and region. In particular, the prediction of Korean surface air temperature in midwinter is substantially improved. In December, ENSO improved about 10% of prediction skill compared without it. In January, ENSO and QBO jointly helped to enhance prediction skill up to 36%. These results suggest that wintertime surface air temperature in Korea can be better predicted by considering not only high-latitude surface conditions (i.e., Eurasian snow cover extent and Arctic sea ice concentration) but also equatorial sea surface temperature and stratospheric circulation.

• The Journal of Asian Finance, Economics and Business
• /
• v.2 no.2
• /
• pp.13-18
• /
• 2015

In this paper the DRC model is presented for solving multi objective problem. The proposed model is a combination of data envelopment analysis, Cuckoo algorithm and the response surface method. Due to reasons like costs, time and irreversible damages, it is not possible to analyze each and every one of the proposed models in practice, so the simulation is used. Since the number of experiments for simulation process is high then the optimization has gone to practice and directs the simulation process. The response surface method is used as one of the approaches of simulation optimization. Furthermore, data envelopment analysis is used to consider several response surfaces as efficiency response surface. Then this efficiency response surface is solved by Cuckoo algorithms. The main advantage of DRC model is to make one efficiency response surface function instate of multi surface function for every output and also using the advantages of Cuckoo algorithms. In order to demonstrate the effectiveness of the proposed approach, the branches of Refah bank in Mashhad is analyzed and the results are presented.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2009.04a
• /
• pp.34-37
• /
• 2009

본 논문에서는 원자적 계산(atomistic calculation)을 이용한 나노박막의 평형상태(self-equilibrium state)에 대한 해석기법을 제시한다. 두께가 얇은 나노박막은 표면 응력(surface stress)에 의한 영향으로 원자간 거리가 벌크상태의 거리보다 작아진다. 두께가 얇은 나노박막에서의 원자 사이의 거리는 표면 응력과 탄성계수들의 표현식으로 계산이 가능하며, 본 논문에서는 {100}, {111}, {110} 표면을 가지는 나노박막의 평형상태의 해석을 위한 해석적 방법을 제시한다. 원자 사이의 거리를 계산하기 위해서는 보다 정확한 표면 응력의 계산방법이 필요하다. 본 연구에서는 나노박막의 평형상태에 대한 해석을 위해 surface relaxation model을 제시하고, 이 모델을 이용하여 표면응력(surface stress)과 표면강성계수(surface stiffness tensor)와 같은 surface parameter의 계산을 수행한다. 본 논문에서 제시된 surface relaxation model을 검증하기 위하여 분자동역학 전산모사(molecular dynamics simulation)의 수치 결과를 제시하고, 본 연구에서 계산한 equilibrium strain과 비교 검증한다.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.5
• /
• pp.48-54
• /
• 2007

Surface of rapid prototype has inevitably stair-stepping error, which is attributed to the continuous building process of 2 dimensional area. In this study, rounded edge model was established to estimate the roughness of inclined surface which has stair-stepping error. To investigate the roughness of rapid prototypes, specimens that have various surface inclinations were manufactured by various types of RP machines. As the surface inclination increased, the roughness of the specimens manufactured by SL, FDM, or LOM process decreased, which coincides with the simulation results. However, surface roughness of 3DP specimen was almost independent of the inclination. Furthermore, as the angle of surface increased, roughness of poly-jet specimen also increased, which is attributed to the frictional behavior between writing head and scanned area.

• Ocean and Polar Research
• /
• v.25 no.1
• /
• pp.9-20
• /
• 2003

A solar radiation model was used to investigate the UV radiation at the surface offing Sejong Station in West Antarctica. The results calculated by this model were compared with the values measured by UV-Biometer and UV-A meter during 1999-2000. In this study, the parameterization of solar radiative transfer process was based on Chou and Lee(1996). The total ozone amounts measured by Breve. Ozone Spectrophotometer and the aerosol amounts by Nakajima et al.(1996) was used as the input data of the solar radiative transfer model. And the surface albedo is assumed to be 0.20 in summer and 0.85 in winter. The sensitivity test of solar radiative transfer model was done with the variation of total ozone, aerosol amount, and surface albedo. When the cosine of solar zenith angle is 0.3, Erythemal UV-B radiation decreased 73% with the 200% increase of total ozone from 100 DU to 300 DU, but the decrease of UV-A radiation is about 1%. Also, for the same solar zenith angle, UV-A radiation was decreased 31.0% with the variation of aerosol optical thickness from 0.0 to 0.3 and Erythemal UV-B radiation was decreased only 6.1%. The increase of Erythemal W-B radiation with the variation of surface albedo was twice that of UV-A increase. The surface Erythemal UV-B and UV-A radiation calculated by solar raditive transfer model were compared with the measured values fer the relatively clear day at King Sejong Station in West Antarctica. The model calculated Erythemal UV-B radiation at the surface coincide well with the measured values except for cloudy days. But the difference between the model calculated UV-A radiation and the measured value at the surface was large because of cloud scattering effect. So, the cloud property data is needed to calculate the UV radiation more exactly at King Sejong Station in West Antarctica.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.12 no.1
• /
• pp.37-49
• /
• 2004

Four different data reduction methods for the heat transfer coefficients from experimental data under dehumidifying conditions are compared. The four methods consist of two heat and mass transfer models and two fin efficiency models. Data are obtained from two heat exchanger samples having plain fins or wave fins. Comparison of the reduced heat transfer coefficients revealed that the single potential heat and mass transfer model yielded the humidity-independent heat transfer coefficients. Two fin efficiency models-enthalpy model and humidity model-yielded approximately the same fin efficiencies, and accordingly approximately the same heat transfer coefficients. The heat transfer coefficients under wet conditions were approximately the same as those of the dry conditions for the plain fin configuration. For the wave fin configuration, however, wet surface heat transfer coefficients were approximately 12% higher. The pressure drops of the wet surface were 10% to 45% larger than those of the dry surface.