• Journal of Advanced Marine Engineering and Technology
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• v.34 no.2
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• pp.250-258
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• 2010

A numerical analysis of reactive flow in a liftoff flame is accomplished to elucidate the characteristics of flame propagation velocity and volume integral of reaction rate with the variation of nozzle diameter and fuel injection flow rate in a liftoff flame consisted with fuel rich region, fuel lean region and diffusion flame region. The increase of fuel injection velocity enhances flame propagation velocity for the selected three nozzle diameter(d=0.25, 0.30, 0.35mm), but its effect on the flame propagation velocity is not much greater than 4.3%. The increase of fuel flow rate is directly and linearly related with the volume reaction rate and so the volume reaction rate, not the flame propagation velocity, might be considered to accommodate the variation of fuel flow rate in a liftoff flame.

• 한국해양학회지
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• v.16 no.1
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• pp.31-37
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• 1981

Saline water movements in relation to tidal condition and river discharge in the estuary of the Nakdong River are discussed on the basis of the observation data. The difference of salinity between the surface and the bottom layer was 1∼3 at spring tide forming a vertically homogeneous estuary, while at neap tide, it ranges up to 7∼15 indicating a sharp salt wedge. The maximum salinity appeared approximately at an hour after the high water, that is, three hours after the landward velocity maximum, while the salinity maximum at around an hour after the low water, that is, three hours after the seaward velocity maximum. The density current speed at a section located 10km landward from the river mouth was observed approximately to be 45cm sec$\^$-1/ at 8m layer.The relations between the salinity at Gupo and the river discharge at Jindong are estimated by means of the least square method. The maximum length of the salt wedge is calculated approximately to be 22km at neap tide and 16km at spring tide, which is in accordance with the observed data. The salinity influence area is deduced to be 45km at spring tide and 35km at neap tide. The diffusion coefficient of salinity was estimated approximately to be 1.5 10$\^$8/$\textrm{cm}^2$ sec$\^$-1/ at Samrak and 8 10$\^$5/$\textrm{cm}^2$ sec$\^$-1/ at Gupo at neap tide, while it was 1.4 10$\^$7/$\textrm{cm}^2$ sec$\^$-1/ at Dongwon at spring tide.

• 한국해양학회지
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• v.28 no.4
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• pp.339-346
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• 1993

Due to the natural increase of human population and the concentration of industrial complexes to coastal area, the uses of nearshore area were increased drastically, and the tendency will not stop for a while. Therefore, the loss of human life and property damages of the present days for a disaster of the same magnitude should be heavy as compared to those of the past. For the better utilization of the sea and the prevention of the frequent marine natural and man-made disaster, and for the preparedness for the ocean pollutions, through ocean researches are required. the circulation, tidal currents, storm surges, sea surface wind, waves and sea fogs of the Yellow Sea should be investigated first from the oceanographic point of view, and then the dispersion and diffusion of spilled oil and pollutants, beach erosion, red tide, and longterm sea level oscillations can be studied. International cooperation is crucial for the investigation of the sea because of the temporal and geographic scales of the oceanic phenomina.

• Computers and Concrete
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• v.2 no.4
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• pp.325-343
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• 2005

Chloride ingress is a common cause of deterioration of reinforced concrete located in coastal zone. Modeling the chloride ingress is an important basis for designing reinforced concrete structures and for assessing the reliability of an existing structure. The modeling is also needed for predicting the deterioration of a reinforced structure. The existing deterministic solution for prediction model of corrosion initiation cannot reflect uncertainties which input variables have. This paper presents an approach to the fuzzy arithmetic based modeling of the chloride-induced corrosion of reinforcement in concrete structures that takes into account the uncertainties in the physical models of chloride penetration into concrete and corrosion of steel reinforcement, as well as the uncertainties in the governing parameters, including concrete diffusivity, concrete cover depth, surface chloride concentration and critical chloride level for corrosion initiation. There are a lot of prediction model for predicting the time of reinforcement corrosion of structures exposed to chloride-induced corrosion environment. In this work, RILEM model formula and Crank's solution of Fick's second law of diffusion is used. The parameters of the models are regarded as fuzzy numbers with proper membership function adapted to statistical data of the governing parameters instead of random variables of probabilistic modeling of Monte Carlo Simulation and the fuzziness of the time to corrosion initiation is determined by the fuzzy arithmetic of interval arithmetic and extension principle. An analysis is implemented by comparing deterministic calculation with fuzzy arithmetic for above two prediction models.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.215-222
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• 1998

The effect of La and Si addition of the thermal stabilization of $\gamma-alumina$ powers have been studied. Reagent grade $La(NO_3)_3{\cdot}6H_2O$ and $Si(OC_2H_5)_4$ were used as starting materials. These additives were introduced by wet impregnation method. Both La and Si additives suppressed the sintering of alumina and were found to be good thermal stabilizers of $\gamma-alumina$. Especially, Si drastically suppressed the phase transition of alumina at high temperatures. The major mechanisms for the thermal stabilization of alumina were seemed to be new phase formation and retardation of surface diffusion by addition of La or Si into alumina matrix.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.306-308
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• 2007

Poly(ethylene glycol) dimethyl ether (PEGDME)/fumed silica/ 1-methyl -3-propylimidazolium iodide (MPII)/$I_2$ mixtures were used as polymer electrolytes in solid state dye-sensitized solar cells (DSSCs). The contents of MPII were changed and the concentration of $I_2$ was fixed at 0.1 mole% with respect to the MPII. The maximum ionic conductivity was obtained at [EG]:[MPII]:[$I_2$]=10:1.5:0.15. It was supposed that the maximum of ionic conductivities would match with that of cell efficiencies, if the ionic conductivity is a rate determining step in the sol id state DSSCs. However, the maximum composition did not show the maximum solar cell performance, indicating the mismatch between ionic conductivity and cell performance. This suggests that the ionic conductivity may not be the rate controlling step in determining the cell efficiency in these experimental conditions, whereas other parameters such as the electron recombination might play an important role. Thus, we tried to modify the surface of the $TiO_2$ particles by coating a thin metal oxide such as $Al_2O_3$ or $Nb_2O_5$ layer to prevent electron recombination. As a result, the maximum of the cell efficiency was shifted to that of the ionic conductivity. The peak shifts were also attempted to be explained by the diffusion coefficient and the lifetime of electrons in the $TiO_2$ layer.

• Journal of the Korean Institute of Gas
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• v.19 no.1
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• pp.57-63
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• 2015

The hydrogen was charged TRIP steel by electrochemical method under 0.5M $H_2SO_4$ electrolyte and 0.5M NaOH electrolyte with hydrogen charging conditions respectively. The degree of hydrogen embrittlement of TRIP steel was evaluated by using micro Vickers hardness tests. These results showed that the degree of hydrogen embrittlement in acidic electrolyte with hydrogen penetration and hydrogen diffusion through the depth of specimen was more sensitive than its alkaine electrolyte between two type electrolytes. However, it was investigated that micro Vickers hardnesses of surface in acidic electrolyte under two electrolyte were higher than those of alkaine electrolyte. It was thought that in case of hydrogen embrittlement in acid-ice electrolyte, hydrogen charging time was more effective than current density, in case of alkaine electrolyte, hydrogen current density was more effective than charaging time.

• Transactions of the KSME C: Technology and Education
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• v.1 no.2
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• pp.179-186
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• 2013

Far-infrared radiation therapies are becoming more popular for blood circulation disorders, cardiovascular disease, skin diseases, inhibit cancer cell, etc replacing conventional operations. In this research, thermal characteristics of heating part in panel radiators, which is effective on the blood circulation disorders were experimentally analyzed. The heating line supplies heat energy to insulation coatings with heat flux of $150mW/m^2$ in normal status and as a result the coatings reached 20% of the heating line temperature. In other words, the insulation itself could increase surface temperature of heating plates by 20% and raise thermal time constant promote blood circulation effect. We also found that space arrangement of the heating lines was an important factor in designing heating parts and both coefficient of heat conduction and density of the heating plate should be also considered for superimpose of thermal diffusion.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.5
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• pp.582-588
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• 2016

Seventy-nine Vibrio parahaemolyticus isolates from surface seawater from Gomso Bay, west coast of Korea, were analyzed for the presence of virulence genes and their susceptibility to 30 different antimicrobials. All 79 isolates were examined for the presence of two virulence genes (tdh or trh) using polymerase chain reaction (PCR); however, no isolates possessed either the tdh or trh gene. According to a disk diffusion susceptibility test, all of the strains studied were resistant to oxacillin, penicillin, and vancomycin, followed by ticarcillin (97.5%), ampicillin (96.2%), clindamycin (86.1%), erythromycin (10.1%), streptomycin (7.6%), cefoxitin (6.3%), amikacin (2.5%), and cephalothin (2.5%). However, all of the strains were susceptible to 19 other antimicrobials including cefepime, cefotaxime, chloramphenicol, gentamycin, nalidixic acid, sulfamethoxazole/trimethoprim, and trimethoprim. All 79 isolates (100%) were resistant to four or more classes of antimicrobials, and two strains exhibited resistance to eight antimicrobial agents. The average minimum inhibitory concentrations (MICs) for V. parahaemolyticus for ampicillin, penicillin, ticarcillin, and vacomycin were 946.5, 1,305.9, 1,032.3, and 45.0 µg/mL, respectively.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.146-151
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• 2013

This paper reveals the performance decrease and recovery of PEMFC when the contaminated fuel gas and air source with sulfur impurities such as hydrogen sulfide and sulfur dioxide were simultaneously introduced to anode and cathode, respectively. Three different GDLs were fabricated with different carbon black and activated carbon to prevent an introduction of sulfur compound impurities into MEA. components. The severity of $SO_2$ and $H_2S$ poisoning was depended on concentrations(3 ppm - 10 ppm) of sulfur impurities. Especially, cell performance degradation rate was rapid when MEA fabricated with CN-2 GDL because it had little porosity on GDL surface. Moreover, the cell performance can be recovered up to 90%-95% only with neat hydrogen and fresh air feeding.. Conclusively, MEA fabricated with porous CN-1 GDL showed the best cell performance and recovery efficiency during exposure to poisoning condition by simultaneous sulfur impurities.