• Atmosphere
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• v.21 no.3
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• pp.229-241
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• 2011

The continuous urbanizations by a rapid economic growth and a steady increase in population are expected to have a possible impact on meteorology in the downwind region. Long-term (1972~2007) trends of precipitation have been examined in the mid-Korean peninsula for the westerly condition only, along with the sensitivity simulations for a golden day (11 February 2009). During the long-term period, both precipitation amount (PA) and frequency (PF) in the downwind region (Chuncheon, Wonju, Hongcheon) of urban area significantly increased for the westerly and light precipitation ($PA{\leq}1mm\;d^{-1}$) cases, whereas PA and PF in the mountainous region (Daegwallyeong) decreased. The enhancement ratio of PA and PF for the downwind region vs. urban region remarkably increased, which implies a possible urbanization effect on downwind precipitation. In addition, the WRF simulation applied for one golden day demonstrates enhanced updraft and its associated convergence in the downwind area (about 60 km), leading to an increase in the cloud mixing ratio. The sensitivity experiments with the change in surface roughness demonstrates a slight increase in cloud water mixing ratio but a negligible effect on precipitation in the upwind region, whereas those with the change in heat source represents the distinctive convergence and its associated updraft in the downwind region but a decrease in liquid water, which may be attributable to the evaporation of cloud droplet by atmospheric heating induced by an increase in an anthropogenic heat. In spite of limitations in the observation-based analysis and one-day simulation, the current result could provide an evidence of the effect of urbanization on the light precipitation in the downwind region.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.555-562
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• 2019

This study was undertaken to develop a stable self-microemulsifying drug delivery system (SMEDDS) for trans-cinnamaldehyde, a known antibacterial and antifungal agent. A simultaneous analytical method was established for quantification of trans-cinnamaldehyde and its degradant, cinnamic acid. Various surfactants were applied to assess their effect on the aqueous solubility of trans-cinnamaldehyde, and pseudo-ternary phase diagrams were plotted. Of the various formulations tested, the liquid SMEDDS composed of trans-cinnamaldehyde (oil), Cremophor EL (surfactant) and Transcutol P (cosurfactant) at a volume ratio of 10/70/20, produced the smallest emulsion droplet size (around 23 nm). The stability test determined the superior stability of the trans-cinnamaldehyde SMEDDS with constant trans-cinnamaldehyde content and z-average diameter of emulsion, under accelerated and heat stressed condition. Thus, we believe that this novel trans-cinnamaldehyde SMEDDS formulation has the potential to be applied for the development of trans-cinnamaldehyde medicines in the pharmaceutical industry.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.747-757
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• 2010

The ice accreted on the airfoil is one of the critical drivers that causes the degradation of aerodynamic performance as well as aircraft accidents. Hence, an efficient numerical code to predict the accreted ice shape is crucial for the successful design of de-icing and anti-icing devices. To this end, a numerical code has been developed for the prediction of glaze ice accretion shape on 2D airfoil. Constant Source-Doublet method is used for the purpose of computational efficiency and heat transfer in the icing process is accounted for by Messinger model. The computational results are thoroughly compared against available experiments and other computation codes such as LEWICE and TRAJICE. The direction and thickness of ice horn are shown to yield similar results compared to the experiments and other codes. In addition, the effects of various parameters - temperature, free-stream velocity, liquid water contents, and droplet diameter - on the ice shape are systematically analyzed through parametric studies.

• Nutrition Research and Practice
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• v.7 no.6
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• pp.453-459
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• 2013

The abnormal content of blood lipids often results in metabolic diseases, such as hyperlipidemia and obesity. Many agents, including natural sources from traditional food, have been developed to regulate the blood lipid contents. In this study, we examined the anti-hyperlipidemic activity of Rhynchosia nulubilis seeds pickled with brown rice vinegar (RNSpBRV), a Korean traditional pickled soybean food. Since RNSpBRV is made of R. nulubilis seeds (RNS) soaked in brown rice vinegar (BRV), we compared the anti-adipogenic activity between RNS, BRV and solid fraction of RNSpBRV (SF-RNSpBRV), liquid fraction of RNSpBRV (LF-RNSpBRV). For this, the inhibitory effect of lipid accumulation in 3T3-L1 adipocyte was checked by adding methanol extracts of mixed RNS and BRV, LF-RNSpBRV, and SF-RNSpBRV. The addition of each methanol extract up to 1 mg/ml showed no cytotoxicity on 3T3-L1 adipocyte, and approximately 20% of the lipid droplet formation was suppressed with the methanol extract of BRL or SF-RNSpBRV. The highest suppression (42.1%) was achieved with LF-RNSpBRV. In addition, mice fed a high fat diet (HFD) supplemented with 5% RNSpBRV powder led to increased high density lipoprotein (HDL) cholesterol and lower blood glucose, triglyceride, and total cholesterol compared to mice fed with a HFD diet only. Interestingly, the size of the epididymis cells gradually decreased in HFD + 1% RNSpBRV and HFD + 5% RNSpBRV-fed mice if compared those of HFD-fed mice. Taken together, these results provide evidence that RNSpBRV has a regulatory role in lipid metabolism that is related to hyperlipidemia.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.62-68
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• 2005

An injector for fuel rich gas generator was designed and experimentally investigated. Five variations of F-O-F triplet impinging type injector were tested to evaluate spray characteristics with kerosene/water simulant propellant. Test was focused to find the effect of design variables of impinging angle, and impinging distance, on the atomization performance. A mixing efficiency is used to compare droplet distribution and local O/F ratio of each injector in the range of momentum ratio of 0.2~1.3. Test results shows the max value of mixing efficiency locates about the 0.8 in momentum ratio. And the injector with an impinging angle of 45 degree and impinging distance of 6mm shows the very good performance result suitable for fuel rich gas generator. A combustion test will be also conducted with selected injector to verify the spray pattern and mixing efficiency.

• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.133-138
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• 2002

A 3-D axisymmetric computer program is developed to predict the NO behavior in SNCR system for the stoker incinerator with the waste treatment capacity, 200ton/day. To this end a turbulent reacting flow field calculation is made using proper assumption and empiricism. The stoker bed is assumed to be a homogeneous waste-volatilized gaseous state. The initial composition or reactants are assumed based on the data of the ultimate analysis. Turbulent is resolved by k-e model and turbulent reaction is handled by eddy-breakup model harmonized with empirical chemistry data for gaseous combustion, NO and urea reaction. The liquid droplet is traced by Lagrangian method incorporated by aerodynamic drag, Coriolis and crntrifugal forces. Radiation is treated by sensible heat loss model. Calculation results are in good agreement with experimental data at the outlet of post combustion chamber in Daejon 4th industrial complex. The flue gas shows the temperature range of $900\sim1000^{\circ}C$, velocity of 5m/s and NO concentration of 140ppm at the exit while the measured temperature, flue gas velocity and NO concentration are $967^{\circ}C$, $3\sim4m/s$ and $100\sim200ppm$respectively. Using the developed computer program a parametric study has been made with the variation of heat content of waste, castable length and SNCR variables for the determination of proper injector location. In general, the calculated results are consistent and physically acceptable.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.330-342
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• 2003

The formation of emulsions and micelles in water/ceramide PC104/CholE $O_{20}$/C$_{16}$E $O_{20}$ and water/ceramide PC104/CholE $O_{20}$ mixtures was investigated through the phase behavior studies. The phase diagrams showed the existence of micelle and emulsion regions in both systems. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) showed the wider micellar and emulsion regions than the single surfactant system (CholE $O_{20}$). From FT-IR measurements, it was found that the polyoxyethylene (POE) groups of surfactants formed the hydrogen bonds with amido carbonyl group in ceramide PC104. This result indicated that the hydrophilic part (EO) of surfactants could stabilize the lamellar structure and emulsion of ceramide PC104. The mixed surfactant system (CholE $O_{20}$/C$_{16}$E $O_{20}$) resulted in the smaller emulsion droplet size due to the effect of curvature at the interface, thus further increasing emulsion stability. With the penetration of $C_{16}$E $O_{20}$into the interfacial layer of surfactants in emulsion, the curvature of the interface might be altered for the formation of smaller emulsion droplets. The mixed surfactant system could incorporate up to 4 wt. % of ceramide PC104 into emulsion more than single surfactant system.ystem.m.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.131-137
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• 2020

A number of piping components in the secondary system of nuclear power plants (NPPs) are exposed to aging mechanisms, such as flow-accelerated corrosion (FAC), cavitation, flashing, solid particle erosion, and liquid droplet impingement erosion. Those mechanisms may lead to thinning, leaking, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 in the USA in 1986 and Mihama unit 3 in Japan in 1994, pipe wall thinning management has emerged as one of the most important issues in the nuclear industry. To manage pipe wall thinning, a foreign program has been utilized for NPPs in Korea since 1996. As our experience and knowledge of pipe wall thinning management have accumulated, our program needs to reflect our experience, requests from users, and the result of recent experiments using Flow Accelerated Corrosion Testing System (FACTS). FACTS is the empirical experimental facility developed by Korea Atomic Energy Research Institute (KAERI) for tests. Accordingly, KEPCO-E&C developed a 3D-based pipe wall thinning management program called ToSPACE in 2016. This paper describes a comparison between the FAC analysis results using ToSPACE and the experimental results using FACTS to verify their applicability to pipe wall thinning management in NPPs.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.203-210
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• 2013

The objective of this conducted research is to study the iodine removal efficiency in a self-priming venturi scrubber for submerged and non-submerged operating conditions experimentally and theoretically. The alkaline solution is used as an absorbent, which is prepared by dissolving sodium hydroxide (NaOH) and sodium thiosulphate ($Na2S_2O_3$) in water to remove the gaseous iodine ($I_2$) from the gas. Iodine removal efficiency is examined at various gas flow rates and inlet concentrations of iodine for submerged and non-submerged operating conditions. In the non-submerged venturi scrubber, only the droplets take part in iodine removal efficiency. However, in a submerged venturi scrubber condition, the iodine gas is absorbed from gas to droplets inside the venturi scrubber and from bubbles to surrounding liquid at the outlet of a venturi scrubber. Experimentally, it is observed that the iodine removal efficiency is greater in the submerged venturi scrubber as compare to a non-submerged venturi scrubber condition. The highest iodine removal efficiency of $0.99{\pm}0.001$ has been achieved in a submerged self-priming venturi scrubber condition. A mathematical correlation is used to predict the theoretical iodine removal efficiency in submerged and non-submerged conditions, and it is compared against the experimental results. The Wilkinson et al. correlation is used to predict the bubble diameter theoretically whereas the Nukiyama and Tanasawa correlation is used for droplet diameter. The mass transfer coefficient for the gas phase is calculated from the Steinberger and Treybal correlation. The calculated results for a submerged venturi scrubber agree well with experimental results but underpredicts in the case of the non-submerged venturi scrubber.

• Journal of Adhesion and Interface
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• v.15 no.2
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• pp.57-62
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• 2014

Pythagolas rule was used for investigation of static contact angle in particular figures. Static contact angle measurement was important to evaluate the wettability between solid and liquid. Optimum measurement method and standardization of calculation for static contact angle were investigated for practical application. Optimum diameter of droplet for static contact angle measurement was confirmed as 1 mm. Contact angle measurement using Pythagolas rule was also used to calculate advancing, receding angle and wettability of different surface condition. At last, it was concluded that the Pythagolas rule method was more accurate than general lineation method for static contact angle measurement.