• Journal of ILASS-Korea
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• v.7 no.3
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• pp.18-23
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• 2002

An evaporating diesel spray of a common rail lnjector was visualized by LIEF technique. This technique makes it possible to separate the vapor and liquid phase images. The experiment was conducted in a constant volume vessel to make a high temperature and high pressure condition. Three images(vapor and liquid phase images from LIEF and a liquid phase image from Mie scattering) were taken simultaneously in one spray event. The major experimental parameters are the injection pressure and the ambient gas pressure. Also, a relative SMD distribution in a liquid phase was obtained by the ratio of the intensities of the fluorescence and the Mie scattering. The results show that the injection pressure and the ambient gas pressure have a close relation with the spray development and air-fuel muting process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.10
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• pp.679-688
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• 2008

Air-heating vaporizer usually is used to regasify LNG at satellite areas because of the small demand of natural gas there. The common type of air heating vaporizer which exists in the market is the longitudinally finned type with 8 fins, 55 mm fin length and 2mm fin thickness. To contribute in developing an efficient air-heating vaporizer, experiment on finned type air-heating vaporizer using 8 fins, 50mm(fin length) with 2 mm(fin thickness) which exist in the market and 4 fins, 75 mm(fin length) with 2 mm(fin thickness), which is proposed, were conducted. Then, both types of vaporizers are compared. The experiments were conducted in one hour by varying the ambient condition and the length of the vaporizer. The ambient air was controlled so that it has the same temperature, humidity and air velocity with air condition in every season available and the length was varied 4000 mm, 6000 mm and 8000 mm for each type of vaporizer. Additional experiment with longer duration, i.e. In this experiment, the main aspects in analyzing the characteristics of the air heating vaporizer the inlet-outlet enthalpy difference and the outlet temperature of the working fluid. $LN_2$ is used to substitute LNG because of safety reason. The results show that the characteristics of the finned type 4fin75le vaporizer are comparable to finned type 8fin50le vaporizer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.682-691
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• 2006

This study was conducted to assess the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the various ambient conditions. Spray structure and spatial distribution of liquid phase concentration are investigated using a thin laser sheet illumination technique on the multi-component mixed fuels. A pulsed Ar+ laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contain $i-octane(C_8H_{18}),\;n-dodecane(C_{12}H_{26})$ and $n-hexadecane(C_{16}H_{34})$ that are selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 25Mpa, 42MPa, 72MPa and 112MPa in injection pressure, $5kg/m^3,\;15kg/m^3\;and\;20kg/m^3$ in ambient gas density, 400K, 500K, 600K and 700K in ambient gas temperature, 300K and 368K in fuel temperature, and different fuel mass fraction. Experimental results indicate that the more high-boiling point component, the longer the liquid phase it were closely related to fuel physical properties, but injection pressure had no effect on. And there was a high correlation between the liquid phase length and boiling temperature at 75% distillation point.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.63-72
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• 2011

This study describes the impact of positive sampling artifact caused by a filter-based sampling in the determination of ambient organic carbon (OC). Three different sampling media combinations were employed for this investigation: (1) Quartz filter-alone (Q-alone), (2) quartz filter behind quartz-fiber filter (QBQ), and (3) quartz filter and quartz filter behind Teflon filter (Q-QBT). The measurement of ambient OC was carried out at a semi-urban site near oceanside at the end of November of 2008. It was found that Q-alone sampling configuration resulted in a higher OC than QBQ and Q-QBT by 14% and 28%, respectively due to no correction for positive artifact caused by adsorption of gas-phase OC onto the filter. A lower quantity of OC was collected from the backup quartz filter on QBQ than that from Q-QBT. A possible explanation is that the front quartz filter of QBQ was not fully saturated with gas-phase OC during the sampling period, allowing smaller amount of gas-phase OC to reach the backup quartz filter. The contribution of positive artifact to $PM_{2.5}$ mass was approximately 2.15 ${\mu}g/m^3$ which is equivalent to 6% in terms of Q-QBT sampling configuration. The positive artifact was found to be more dominated during summer than during winter, showing temperature dependence. It was concluded that Q-QBT sampling configuration offers less impact of positive artifact on ambient OC sampling than QBQ in quantification of OC.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.17-24
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• 2005

The characteristics of diesel spray have effect on the engine Performance such as power. fuel consumption and emissions. Therefore, This study was Performed to investigate the effect of various injection parameters. In this study. the experiment is performed by using the high temperature and high pressure chamber. Spray behaviors are visualized by using the high speed camera and spray angle. Penetration etc. are measured. Experimental results are summarized as follows ; 1) Correlations of spray Penetration is expressed as follows $$0 $$t_b 2) Correlations of spray Angle is expressed as follows $$T_a=293K \;;\; tan({\theta}/2)=0.59({\rho}_a/{\rho}_f)^{0.437}$$ $$T_a=473K\;;\; tan({\theta}/2)=0.588({\rho}_a/{\rho}_f)^{0.404}$$ 3) The measured macro characteristics - spray tip penetration and spray angle agreed well with established correlations.

• Environmental Engineering Research
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• v.22 no.4
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• pp.347-355
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• 2017

This study investigated how the combined changes in environmental conditions and nitrogen (N) deposition influence the mineralization processes and carbon (C) dynamics of wetland soil. For this objective, we conducted a growth chamber experiment to examine the effects of combined changes in environmental conditions and N deposition on the anaerobic decomposition of organic carbon and the emission of greenhouse gases from wetland soil. A chamber with elevated $CO_2$ and temperature showed almost twice the reduction of total decomposition rate compared to the chamber with ambient atmospheric conditions. In addition, $CO_2$ fluxes decreased during the incubation under the conditions of ambient $CO_2$ and temperature. The decrease in anaerobic microbial metabolism resulted from the presence of vegetation, which influences the litter quality of soils. This can be supported by the increase in C/N ratio over the experimental duration. Principle component analysis results demonstrated the opposite locations of loadings for the cases at the initial time and after three months of incubation, which indicates a reduction in the decomposition rate and an increasing C/N ratio during the incubation. From the distribution between the decomposition rate and gas fluxes, we concluded that anaerobic decomposition rates do not have a significantly positive relationship with the fluxes of greenhouse gas emissions from the soil.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.12
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• pp.1091-1098
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• 1998

Thermal stability of the electroless deposited Cu thin film was investigated. Cu/TaN/Si multilayer was fabricated by electroless-depositing Cu thin layer on TaN diffusion barrier layer which was deposited by MOCVD on the Si substrate, and was annealed in $H_2$ ambient to investigate the microstructure of Cu film with a post heat-treatment. Cu thin film with good adhesion was successfully deposited on the surface of the TaN film by electroless deposition with a proper activation treatment and solution control. Microstructural property of the electroless-deposited Cu layer was improved by a post-annealing in the reduced atmosphere of $H_2$ gas up to $600^{\circ}C$. Thermal stability of Cu/TaN/Si system was maintained up to $600^{\circ}C$ annealing temperature, but the intermediate compounds of Cu-Si were formed above $650^{\circ}C$ because Cu element passed through the TaN layer. On the other hand, thermal stability of the Cu/TaN/Si system in Ar ambient was maintained below $550^{\circ}C$ annealing temperature due to the minimal impurity of $O_2$ in Ar gas.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1321-1328
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• 2005

The characteristics of the diesel spray have affected certain aspects of engine performance, such as the power, fuel consumption, and emissions. Therefore, this study was performed to investigate the effects of various injection parameters. In order to obtain the effect of injection parameters on diesel spray characteristics, the experiment is performed by using a high temperature and pressure chamber. The behaviors of the spray are visualized by using a high speed video camera, spray angle, penetration, and various other things. The results of the experiment are summarized as follows. (1) The correlation of the spray penetration can be expressed as follows. $$0< t $$t_{b} (2) The correlation of the spray angle can be expressed as follows $$T_a=293K\;tan({\theta}/2)=0.59({\rho}a/{\rho}f)^{0.437}$$ $$T_a=473K\;tan({\theta}/2)=0.588({\rho}a/{\rho}f)^{0.404}$$ (3) The measured macro characteristics that include the spray tip penetration and spray angle corresponded with the established correlations.

• Journal of the Korean Society of Combustion
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• v.13 no.3
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• pp.17-23
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• 2008

The spray combustion and spray cooling depends on droplet evaporation. So, evaporation model for spray has been requested and lots of investigation has been done and various reliable models have been developed also for last few decades. In the present study, One dimensional quasi-steady spherically symmetric droplet evaporation model for micro-gravity is developed. The gas phase was assumed as steady state and the thermophysical properties are calculated as a function of temperature, pressure and composition and the properties used in the model was validated by NIST web data and overall evaporation history results was compared with experimental results by Nomura and Qasim and gave satisfactory agreements. Through this model, diverse phenomenon was investigated, especially regarding the effects of ambient pressure and temperature. The effects of pressure for the droplet evaporation time were studied. The high pressure increased the droplet surface temperature and made effect on the evaporation time depend on atmospheric temperature. The role of the ambient temperature was investigated and explained. The basic investigation for the evaporation process according to variation of droplet diameter and surface temperature were also investigated and the well-known phenomena, like D-square-law, were reported, too.

• Journal of the Korean Institute of Gas
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• v.15 no.4
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• pp.51-55
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• 2011

This paper describes the temperature compensation algorithm using thermopile detector for nondispersive infrared methane gas sensor. From the output voltage of thermistor that is attached onto the infrared detector, the ambient temperature was extracted. The effects of temperatures on the properties of sensor module (the characteristics of narrow bandpass filter, optical cavity and infrared lamp, and gas absorption coefficient times optical path length) have been introduced in order to implement the temperature compensation algorithm. Even though the measurement error of developed sensor module was in the range of $\pm$ 1,500 ppm, after programming the temperature compensation algorithm, the developed sensor module shows a high accuracy less than +180 ppm error within $20^{\circ}C$ temperature variation.