• Magazine of the Korean Society of Hazard Mitigation
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• v.2 no.4 s.7
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• pp.40-47
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• 2002

Since it is important to understand the bio-climatic change in Seoul for ecological city planning in the future, this paper gives an overview on bio-climate analysis of urban environments at Seoul. We analyzed its characteristics in recent years using the observations of 24 of Automatic Weather Station (AWS) by Korea Meteorological Administration (KMA). In urbanization, Seoul metropolitan area is densely populated and is concentrated with high buildings. This urban activity changes land covering, which modifies the local circulation of radiation, heat and moisture, precipitation and creating a specific climate. Urban climate is evidently manifested in the phenomena of the increase of the air temperature, called urban heat Island and in addition urban sqall line of heavy rain. Since a city has its different land cover and street structure, these form their own climate character such as climate comfort zone. The thermal fold in urban area such as the heat island is produced by the change of land use and the air pollution that provide the bio-climate change of urban eco-system. The urban wind flow is the most important climate element on dispersion of air pollution, thermal effects and heavy shower. Numerical modeling indicates that the bio-climatic transition of wind wake in urban area and the dispersion of the air pollution by the simulations of the wind variation depend on the urban land cover change. The winds are separately simulated on small and micro-scale at Seoul with two kinds of kinetic model, Witrak and MUKLIMO.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.337-340
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• 2008

When high surge voltage invaded into the ground rod contacted with ground water, the ionization phenomena are happened in the water. Although some researchers have surveyed the ionization phenomena in soil, they have just analyzed the variation of the ground resistance. The most important role of the ground rod is to elect human beings from potential rise and to dissipate energy to the earth safely. In this wort we presented the method evaluating the potential reduction and energy dispersion. Also we analyzed theses factors as a function of charging voltages at the water resistivity of $50\;{\Omega}{\cdot}m$ using the Matlab Program. As a result the ground rod potential was reduced to 38 kV by ionization just below breakdown voltage. The energy more than half of the total injected energy was dispersed through the grounding electrode caused due to ionization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.10 no.6
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• pp.335-342
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• 1985

A planar waveguide model is presented for calculating dispersion characteristics with the frequency dependent effective dielectric constant in microstrip lines and results are compared by the variation of each parameter. It is compared to use a wide range of relative dielectric constants and the strip $h_{width}$strate height, W/h ratios, 0.9$\leq$W/h$\leq$2. As the result of a computer simulation, the normalized phase velocity using a planar waveguide model for each case is more closely approached to 1/$\sqrt{\epsilon_r}$ as the increasing of the frequency than the other method that has already been presented.

• Analytical Science and Technology
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• v.18 no.5
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• pp.436-443
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• 2005

A study of physical properties and their application using K-powdered activated carbon system followed powdered carbon dispersion was carried out at laboratory. scale. Two types of K-powdered activated carbon for the dispersion have been used in this study to investigate the catalytic removal efficiency of pollutants from the wastewater. From the surface properties obtained for carbon samples treated with aqueous solutions containing potassium salts, main investigations were subjected to isotherm shape, SEM, EDX and surface functional groups. K-powdered activated carbons were dispersed to wastewater with pH variation to investigate the removal efficiency for the color, COD, T-N and T-P. From these removal results of the piggery waste using K-powdered activated carbon, satisfactory removal performance in the region of pH 6~8 was achieved. The excellent effects for the dispersion of the K-powdered activated carbon were proved by the above mentioned properties of the material for adsorption and trapping of organics, and catalytic effects.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.277-282
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• 1997

The complex refractive index of Diamond-like Carbon (DLC) thin films, which can be applied to optical devices or electrical devices, have been determined using optical methods. DLC thin films are grown on Si(100) substrates and vitreous silica substrates respectively, using the technique of plasma enhanced chemical vapor deposition (PECVD). The spectroscopic ellipsometry data($\psi$, $\Delta$) and the transmission spectra of these DLC films are obtained. These optical spectra are analyzed with the help of the Sellmeier dipersion relation and a quantum mechanically derived dispersion relation. Using spectroscopic ellipsometry data at their transparent region, the refractive index and the effective thickness of DLC films on vitreous silica are model calculated, Then the transmission spectra are inverted to yield the extinction coefficient spectra k(λ) at absorbing region. These spectra are fit to the quantum mechanical dispersion relation and the best fit dispersion constants are determined. The complex refractive indices are easily calculated with these constants. The spectroscopic ellipsometry data at the absorbing region in model calculated to give the packing densities and the degrees of surface microroughness of DLC films. Discussions are made in correlation with the growth condition of DLC films.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.E2
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• pp.63-73
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• 2008

In this study, neural network models (NNMs) were examined as alternatives to dispersion models in predicting the short-term $SO_2$ concentrations in a coastal area because the performances of dispersion models in coastal areas have been found to be unsatisfactory. The NNMs were constructed for various combinations of averaging time and prediction time in advance by using the historical data of meteorological parameters and $SO_2$ concentrations in 2002 in the coastal area of Boryeung, Korea. The NNMs were able to make much more accurate predictions of 1 hr $SO_2$ concentrations at ground level in the morning in coastal area than the atmospheric dispersion models such as fumigation models, ADMS3 and ISCST3 for identical conditions of atmospheric stability, area, and weather. Even when predictions of 24-h $SO_2$ concentrations were made 24 hours in advance, the predictions and measurements were in good accordance(correlation coefficient=0.65 for n=216). This accordance level could be improved by appropriate expansion of training parameters. Thus it may be concluded that the NNMs can be successfully used to predict short-term ground level concentrations averaged over time less than 24 hours even in complex terrain. The prediction performance of ANN models tends to improve as the prediction lagging time approaches the concentration averaging time, but to become worse as the lagging time departs from the averaging time.

• KSBB Journal
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• v.11 no.4
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• pp.405-410
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• 1996

This paper discussed the dispersion effect according to the geometrical variation of an internal-loop spparatus by the method of pulse injection of a tracer. The Bodenstein number, which is the dimensionless group characterizing the effect of dispersion, was decreased with increasing the superficial gas velocity in the 50L and the 500L apparatus. But, in the 5L apparatus, the Bodenstein number was increased with increasing the superficial gas velocity in the range of 0 to 2cm/sec but above that range the rate of increase was dropped down to give a constant value because of the phenomenon of gas disengagement. The principle of similarity based on dimensional analysis was applied to design a pilot scale internal-loop apparatus. The effect of dispersion was examined in three different internal-loop apparatus to give the following correlation with major geometric and fluid dynamic properties as variables. B0=4.4014ReG0.117 ReL-0.0065(Hr/Dr)0.76(Dd/Dr)-0.76

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.61-70
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• 2006

3-D S-wave velocity model in the southern Korean Peninsula is investigated by using the joint inversion of receiver functions and surface-wave dispersion. A peninsula average Rayleigh-wave phase velocity in the 10-150 seconds range and tomographic estimates of the Rayleigh and Love wave group velocities in the 0.5-20 seconds period range determined using a $12.5{\times}12.5\;km$ grid for the southern part of the peninsula are used for the inversion. Receiver functions were determined from broadband (STS-2), short-period (SS-1) and acceleration (Episensor) channels of 95 stations. The dense distribution of the stations in the Peninsula permits us to examine the 3-D crustal structure in detail. The inversion result shows the variation and characteristics of S-wave velocity in the crust and upper mantle of the southern Korean Peninsula very well.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.100-106
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• 2017

Nanosized and aggregated $Y_2O_3:Eu$ Red phosphors were prepared by template method from metal salt impregnated into crystalline cellulose. The particle size and photoluminescent property of $Y_2O_3:Eu$ red phosphors were controlled by variation of the calcination temperature and time. Dispersed nanosol was also obtained from the aggregated $Y_2O_3:Eu$ Red phosphor under bead mill wet process. The dispersion property of the $Y_2O_3:Eu$ nanosol was optimized by controlling the bead size, bead content ratio and milling time. The median particle size ($D_{50}$) of $Y_2O_3:Eu$ nanosol was found to be around 100 nm, and to be below 90 nm after centrifuging. In spite of the low photoluminescent properties of $Y_2O_3:Eu$ nanosol, it was observed that the photoluminescent property recovered after re-calcination. The dispersion and photoluminescent properties of $Y_2O_3:Eu$ nanosol were investigated using a particle size analyzer, FE-SEM, and a fluorescence spectrometer.

• Journal of the Korean Geophysical Society
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• v.8 no.2
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• pp.67-74
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• 2005

Two-dimensional S-wave velocity sections from SH-wave refraction tomography and surface wave dispersions were obtained by inverting traveltimes of first arrivals and surface wave dispersions, respectively. For the purpose of comparison, a P-wave velocity tomogram was also obtained from a P-wave refraction profiling. P and Rayleigh waves generated by vertical blows on a plate with a sledgehammer were received by 100- and 4.5-Hz geophones, respectively. SH-waves generated by horizontal blows on both sides of a 50 kg timber were received by 8 Hz horizontal geophones. The shear-wave signals were enhanced subtracting data of left-side blows from ones of the right-side blows. Shear-wave velocities from tomography inversion of first-arrival times were compared with ones from inverting dispersion curves of Rayleigh waves. Although the two velocity sections look similar to each other in general, the one from the surface waves tends to have lower velocities. First arrival picking of SH waves is troublesome since P and PS-converted waves arrive earlier than SH waves. Application of the surface wave method, on the other hand, is limited where lateral variation of subsurface tructures is not mild.