• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.27-32
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• 2003

The effect of non-thermal plasma on diffusion flames in co-flow jets has been studied experimentally by adopting a dielectric barrier discharge technique. The generation of streamers was enhanced with a flame due to increased reduced electric fields by high temperature burnt gas and the abundance of ions in the flame region. The effect of streamers on flame behavior reveals that the flame length was significantly decreased as the applied voltage increased and the yellow luminosity by the radiation of soot particles was also significantly reduced. The formation of PAH and soot was influenced appreciably by the non-thermal plasma, while the flame temperature and the concentration of major species were not influence much with the plasma generation. The results demonstrated that the application of non-thermal plasma can be a viable technique in controlling soot generation in flames with low power consumption in the order of 1 W.

• Journal of Power System Engineering
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• v.4 no.1
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• pp.39-44
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• 2000

The purpose of this study is to investigate the flame structure and combustion characteristics in the model gas turbine combustor changing equivalence ratio. For this purpose, temperature and ion current were measured and these data were analyzed by the PDF and power spectra technique. We found that the flame length is longer while increasing the equivalence ratio in experimental condition, and especially ${\psi}=0.19$, combustion reaction was active by the stable swirl flow. and these flames were governed by the random three dimensional eddy.

• Journal of Power Electronics
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• v.11 no.3
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• pp.381-388
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• 2011

This article presents the development of a model for SiC power diodes based on the physics of the semiconductor. The model is able to simulate the behavior of the dynamics of the charges in the N- region based on the stored charge inside the SiC power diode, depending on the working regime of the device (turn-on, on-state, and turn-off). The optimal individual calculation of the ambipolar diffusion length for every phase of commutation allows for solving the ambipolar diffusion equation (ADE) using a very simple approach. By means of this methodology development a set of differential equations that models the main physical phenomena associated with the semiconductor power device are obtained. The model is developed in Pspice with acceptable simulation times and without convergence problems during its implementation.

• Journal of Integrative Natural Science
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• v.2 no.4
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• pp.252-264
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• 2009

Lithographic data obtained from PHS(polyhydroxy styrene) having various functionalities were investigated by using a photoacid generator based on diazo and onium type. Chemically amplified photoresist based on the KrF type photoresist was developed by using a photoacid generator and multi-functional resin. Thermal stability for the photoacid generator showed that the increase of loading amount of photoacid generator resulted in the decrease of glass transintion temperature (Tg). The photoacid generators having methyl, ethyl, or propyl group in their cationic structure produced T-top structure in pattern profile due to the effect of acid diffusion during the generation of acid in the resist. The increase of carbon chain length in the anionic structure of photoacid generators resulted in lower pattern resolution due to the interruption of acid diffusion.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.289-300
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• 2019

We have conducted a preliminary numerical analysis to understand the effects of double-diffusive convection on the molar flux at the crystal region during the growth of mercurous bromide ($Hg_2Br_2$) crystals in 1 g and microgravity (${\mu}g$) conditions. It was found that the total molar fluxes decay first-order exponentially with the aspect ratio (AR, transport length-to-width), $1{\leq}AR{\leq}10$. With increasing the aspect ratio of the horizontal enclosure from AR = 1 up to Ar = 10, the convection flow field shifts to the advective-diffusion mode and the flow structures become stable. Therefore, altering the aspect ratio of the enclosure allows one to control the effect of the double diffusive natural convection. Moreover, microgravity environments less than $10^{-2}g$ make the effect of double-diffusive natural convection much reduced so that the convection mode could be switched over the advective-diffusion mode.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.176-176
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• 2003

The effects of oxide thickness and gate length of MgO/GaN metal oxide semiconductor field effect transistors (MOSFETs) on I-V, threshold voltage and breakdown voltage characteristics were examined using a drift-diffusion model. The saturation drain current scales in an inverse logarithmic fashion with MgO thickness and is < 10$^{-3}$ A.${\mu}{\textrm}{m}$$^{-1}$ for 0.5 ${\mu}{\textrm}{m}$ gate length devices with oxide thickness > 600 $\AA$ or for all 1 ${\mu}{\textrm}{m}$ gate length MOSFETs with oxide thickness in the range of >200 $\AA$. Gate breakdown voltage is > 100 V for gate length >0.5 ${\mu}{\textrm}{m}$ and MgO thickness > 600 $\AA$. The threshold voltage scales linearly with oxide thickness and is < 2 V for oxide thickness < 800 $\AA$ and gate lengths < 0.6 ${\mu}{\textrm}{m}$. The GaN MOSFET shows excellent potential for elevated temperature, high speed applications.

• Computers and Concrete
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• v.26 no.6
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• pp.515-531
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• 2020

Due to the construction difficulties of steel reinforced concrete (SRC), a new composite structure of steel and steel fiber reinforced concrete (SSFRC) is proposed for solving construction problems of SRC. This paper aims to investigate the bond properties and composition of interfacial bond stress between steel and steel fiber reinforced concrete. Considering the design parameters of section type, steel fiber ratio, interface embedded length and concrete cover thickness, a total of 36 specimens were fabricated. The bond properties of specimens were studied, and three different methods of calculating interfacial bond stress were analyzed. The results show: relative slip first occurs at the free end; Bearing capacity of specimens increases with the increase of interface embedded length. While the larger interface embedded length is, the smaller the average bond strength is. The average bond strength increases with the increase of concrete cover thickness and steel fiber ratio. And calculation method 3 proposed in this paper can not only reasonably explain the hardening stage after the loading end curve yielding, but also can be applied to steel reinforced high-strength concrete (SRHC) and steel reinforced recycled coarse aggregate concrete (SRRAC).

• Korean Journal of Materials Research
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• v.25 no.4
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• pp.202-208
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• 2015

Alumina dispersion strengthening copper(ADSC) alloy has great potential for use in many industrial applications such as contact supports, frictional break parts, electrode materials for lead wires, and spot welding with relatively high strength and good conductivity. In this study, we investigated the oxidation behavior of ADSC alloys. These alloys were fabricated in forms of plate and round type samples by surface oxidation reaction using Cu-0.8Al, Cu-0.4Al-0.4Ti, and Cu-0.6Al-0.4Ti(wt%) alloys. The alloys were oxidized at $980^{\circ}C$ for 1 h, 2 h, and 4 h in ambient atmosphere. The microstructure was observed with an optical microscope(OM) and a scanning electron microscope(SEM) equipped with energy-dispersive X-ray spectroscopy(EDS). Characterization of alumina was carried out using a 200 kV field-emission transmission electron microscope(TEM). As a result, various oxides including Ti were formed in the oxidation layer, in addition to ${\gamma}$-alumina. The thickness of the oxidation layer increased with Ti addition to the Cu-Al alloy and with the oxidation time. The corrected diffusion equation for the plate and round type samples showed different oxidation layer thickness under the same conditions. Diffusion length of the round type specimen had a value higher than that of its plate counterpart because the oxygen concentration per unit area of the round type specimen was higher than that of the plate type specimen at the same diffusion depth.

• Economic and Environmental Geology
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• v.53 no.1
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• pp.11-21
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• 2020

One-dimensional analytical solutions were used for forward and back diffusion of trichloroethylene (TCE) and tetrachloroethylene (PCE) in a single system with high- and low-permeability layers. Concentration profiles in a low-permeability layer, diffusive fluxes at the interface between the high- and low-permeability layers, and contaminant persistence in the high-permeability layer due to back diffusion were simulated with a comparison of semi-infinite and finite analytical solutions. In order to validate the analytical solutions used in this study, the results of one-dimensional analytical solutions developed by Yang et al. (2015) were compared with Nash-Sutcliffe model efficiency coefficient (NSE). When compared with Yang et al. (2015), the analytical solutions used in this study showed good agreements (NSE = 0.99). When compared with semi-infinite analytical solutions, TCE and PCE concentration profiles in the low-permeability layer, the diffusive fluxes, and the contaminant tailings of the high-permeability layer were underestimated. In order to determine the appropriate analytical solutions based on the effective diffusion coefficient, the thickness of the low-permeability layer, and the diffusion time in the TCE and PCE contaminated site, a term of dimensionless diffusion length (Z_d) was used. If the Z_d is less than 0.7, the semi-infinite solutions can be used to simulate accurate concentration profiles in low-permeability layers. If the Z_d is greater than 0.7, the reliability of simulations may be improved by using the finite solutions.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.25-34
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• 2011

Dredged and reclaimed ground in progress at the West Coast has a high content of coarse particles. There will be different behaviors depending on the location of outlet and engineering properties of soil when its ground is dredged by a pump. Therefore, the experiments were conducted that were manufactured about the chamber equipment of length 2,650mm, width 770mm, height 735mm, experimented step filling method and water content about 300%, 500% and 700% respectively with SM and ML samples in order to realize segregating sediment characteristics of dredged ground with changing much fine. With results of analysis, ML sample by higher initial water content was reached to the period of complete sedimentation and coefficient of sedimentation consolidation increased with increases of diffusion distance. SM samples showed behavior of coarse soil with diffusion distance 120cm, diffusion distance of more than 120cm showed a similar tendency with ML sample under the influence of fines. In ML sample, it could be also found that lower depth and the more increasing diffusion distance increase in percentage of sieve #200 but water content decreases. In SM sample, it could be also found that coarse soil was piled at near the diffusion distance zone but fine soil was piled at the far diffusion distance zone and prominent difference showed between percentage of sieve #200 and water content(%) by boundary point 120cm~160cm of both samples. Also, shear strength was expressed ML-maximum 2.97kPa, SM-maximum 10.2kPa with diffusion distance.