• 한국해양학회지
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• v.20 no.2
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• pp.28-39
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• 1985

The driving mechanisms for low level jets(LLJ) and coastal surface maximum winds are studied with observed wind data from June, 1976 through August, 1980 at Port Aransas and Victoria, Texas, in connection with a baroclinic model. This model is developed considering the forcing functions such as the synoptic and meso-scale pressure gradient, the frictional force, and the atmospheric stability. The results show that a LLJis observed on over 95% of the occasions when a nighttime coastal wind maximum occurred. Baroclinicity generated by sloping terrain during the summertime causes the diurnal variation in the thermal field. This thermal wind component would then decrease the prevailing synoptic-scale southerly wind by day and allow it to increase at night. Nighttime atmospheric stability leads to frictional decoupling which enhances the nocturnal LLJ. At the coastal site neutral stability prevails, thus all owing downward transfer of momentum from the nocturnal LLJ and results in the nocturnal coastal surface wind maximum. The height of LLJis not uniquely related to the inversion layer, and the results of the computations using this model show a good agreement with the observations.

• KSBB Journal
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• v.13 no.6
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• pp.687-692
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• 1998

Experimental studies were carried out on the use of supercritical fluid in enzymatic hydrolysis of cellulose. In order to effectively perform the hydrolysis the enzyme has to maintain stability and activity in the supercritical carbon dioxide solvent. In the experiment it was found that the stability of cellulase was maintained up to 160 atm for 90 min at $50^{\circ}C$. In the enzymatic hydrolysis of cellulose at supercritical conditions using carbon dioxide at 80 atm and $50^{\circ}C$ for 90 min, the results showed that glucose yield was 100%, which was 1.5 times as compared to that in atmospheric condition when the substrate (Avicel) concentration was 20 g/L. For the substrate concentration of 60 g/L, the glucose yield was increased by 1.2 times as compared to that in atmospheric condition.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.2
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• pp.152-167
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• 2011

MODIS/Terra level 3 and NCEP/NCAR Reanalysis data from 2001 to 2008 have been analyzed to understand long-term aerosol and cloud optical properties, and their relationships around Korea. Interestingly, cloud fraction(CF) has the similar annual variation to aerosol optical depth (${\tau}_a$) without any temporal significant trend. Horizontal distributions of ${\tau}_a$ showed the substantial horizontal gradient from China to Korea, especially with the strong difference over the Yellow Sea, which could represent the evidence of the anthropogenic influence from China in the perspective of long-term average. Specifically the negative correlations between ${\tau}_a$ and liquid-phase cloud effective radius ($r_e$) were shown on the monthly-average basis, only in summer with significant associations over the Yellow Sea, but not in the other seasons and/or specific regions. Relationship between ${\tau}_a$ and CF for the low-level liquid-phase clouds exhibited the overall positive correlation, being consistent with cloud lifetime effect. Meanwhile static stability showed no deterministic relationships with ${\tau}_a$ as well as CF. The dependence of aerosol-cloud relationship on the meteorological conditions should be examined more in detail with the satellite remote sensing and reanalysis data.

• Asian Journal of Atmospheric Environment
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• v.10 no.3
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• pp.125-136
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• 2016

In this study, the effects of the mesh barrier on the free dispersion of ammonia were numerically investigated under different atmospheric conditions. This study presents the detail and flow feature of the dispersion of ammonia through the mesh barrier on various free stream conditions to decline and limit the toxic danger of the ammonia. It is assumed that the dispersion of the ammonia occurred through the leakage in the pipeline. Parametric studies were conducted on the performance of the mesh barrier by using the Reynolds-averaged Navier-Stokes equations with realizable k-${\varepsilon}$ turbulence model. Numerical simulations of ammonia dispersion in the presence of mesh barrier revealed significant results in a fully turbulent free stream condition. The results clearly show that the flow behavior was found to be a direct result of mesh size and ammonia dispersion is highly influenced by these changes in flow patterns in downstream. In fact, the flow regime becomes laminar as flow passes through mesh barrier. According to the results, the mesh barrier decreased the maximum concentration of the ammonia gas and limited the risk zone (more than 500 ppm) lower than 2 m height. Furthermore, a significant reduction occurs in the slope of the upper boundary of $NH_3$ risk zone distribution at downstream when a mesh barrier is presented. Thus, this device highly restricts the leak distribution of ammonia in the industrial plan.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.176-177
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• 2016

In the last few decades, attention toward atmospheric pressure plasma (APP) has been greatly increased due to the numerous advantages of those applications, such as non-necessity of high vacuum facility, easy setup and operation, and low temperature operation. The practical applications of APP can be found in a wide spectrum of fields from the functionalization of material surfaces to sterilization of medical devices. In the secondary battery industry, separator film has been typically treated by APP to enhance adhesion strength between adjacent films. In this process, the plasma is required to have high stability and uniformity for better performance of the battery. Dielectric barrier discharge (DBD) was usually adopted to limit overcurrent in the plasma, and we developed the pre-discharge technology to overcome the drawbacks of streamer discharge in the conventional DBD source which makes it possible to produce a super-stable plasma at atmospheric pressure. Simulations for the fluid flow and electric field were parametrically performed to find the optimized design for the linear jet plasma source. The developed plasma source (Plasmapp LJPS-200) exhibits spatial non-uniformity of less than 3%, and the adhesion strength between the separator and electrode films was observed to increase 17% by the plasma treatment.

• Journal of Korean Society for Atmospheric Environment
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• v.28 no.6
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• pp.632-643
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• 2012

Analysis of wind resources in Planetary Boundary Layer (PBL) using long term observation of tall tower located near coast line of the Korean Peninsula were carried out. The data observed at Pohang, Gunsan and Jinhae are wind, temperature and relative humidity with 10 minute interval for one year from 1 October 2010. Vertical turbulence intensity and its deviation at Pohang site is smaller than those of other sites, and momentum flux estimated at 6 vertical layers tend to show small difference in Pohang site in comparison with other sites. The change of friction velocity with atmospheric stability in Pohang is also not so great. These analysis indicate the mechanical forcing due to geographical element of upwind side is more predominant than thermal forcing. On the other hand, wind resources at Gunsan and Jinhae are mainly controlled by thermal forcing.

• Journal of Environmental Science International
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• v.3 no.4
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• pp.367-372
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• 1994

A predictive model is demonstrated for gas removal rates from the aklosphere by dw deposition. Typical deposition velocities are complex functions of surface types, atmospheric stabilities, friction velocities, air pollutants, and so on. In this paper we simulated the calculation of dry deposition velocities near the earth surfaces, simultaneously we estimated real dry deposition velocities using the previous simulation. The measurement taken over a deciduous forest by Padro et d.(1988) were used to verify this model. In the comparison of the value of deposition velocity between numerical computation and observation, there are partially overestimations and underestimations between them, but we can speak that they are in a good accordance.

• Journal of Environmental Science International
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• v.18 no.8
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• pp.833-839
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• 2009

The calculation of the wind field for resource assessment is done by using CFD Reynolds-Averaged Navier-Stokes simulations performed with the commercial software WindSim. A new interface has been created to use mesoscale simulation data from a meteorological model as driving data for the simulations. This method makes it necessary to take into account thermal effects on the wind field to exploit the full potential of this method. The procedure for considering thermal effects in CFD wind field simulations as well as the impact of thermal effects on the wind field simulations is presented. Simulations for non-neutral atmospheric conditions with the developed method are consistent with expected behavior and show an improvement of simulation results compared with observations.

• Journal of Korean Society for Atmospheric Environment
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• v.1 no.1
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• pp.53-70
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• 1985

This study was performed to develop and to evaluate an air quality model for determining long-term average concentration of sulfur-dioxide for the Seoul area. CDMQC, TCM-2, and ISCLT were applied and tested in this comparison studies with same point source, area source emission data, and meteorological data to calculate seasonal concentration. Mean emission height of area sources was assumed 6m. Six different values of initial sigma Z for eah stability class were used for area sources. And decay half life was not considered in the model calculations. The results are highly correlated with measurements, the correlation coefficients of calculated and measured for CDMQC, TCM-2, and ISCLT are 0.85, 0.93, and 0.96, respectively.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.2
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• pp.131-139
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• 1996

The developent of ceramic combustor is being increased beca- use of the excellent physical properties of ceramic material, that is, high-resistant strength, high emissivity power and high corrosin-resistance. Ceramic combustor has been interested in the application of ultra-lean combustion for low NO$_{x}$ emission and gaseuos waste incineration with good combustion. This experimental study was conducted to investigate the combustion and emission characteristics of wall recess type ceramic combustor with equivalence ratio, mixture flow velocity and wall recess depth as parameters. The results in this study are as follows: 1. Wall recess played a important role to extend flame stability region. 2. The peak temperature of gas was peoportional to equivalence ratio, mixture flow velocity and wall recess depth. 3. The static pressure of mixing chamber and inlet temperature depended on the position of flame zone. 4. NO reduction was achieved by lean mixture without lower combustibility.y.