• Geomechanics and Engineering
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• v.29 no.1
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• pp.1-11
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• 2022

A semi-analytical solution to responses of overconsolidated (OC) unsaturated soils surrounding an expanding spherical cavity under constant suction condition is presented. To capture the elastoplastic hydro-mechanical property of OC unsaturated soils, the unified hardening (UH) model for OC unsaturated soil is adopted in corporation with a soil-water characteristic curve (SWCC) and two suction yield surfaces. Taking the specific volume, radial stress, tangential stress and degree of saturation as the four basic unknowns, the problem investigated is formulated by solving a set of first-order ordinary differential equations with the help of an auxiliary variable and an iterative algorithm. The present solution is validated by comparing with available solution based on the modified Cam Clay (MCC) model. Parametric studies reveal that the hydraulic and mechanical responses of spherical cavity expanding in unsaturated soils are not only coupled, but also affected by suction and overconsolidation ratio (OCR) significantly. More importantly, whether hydraulic yield will occur or not depends only on the initial relationship between suction yield stress and suction. The presented solution can be used for calibration of some insitu tests in OC unsaturated soil.

• Journal of the Korean Mathematical Society
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• v.45 no.1
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• pp.137-150
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• 2008

In this paper we will prove that the simple groups $B_p(3)\;and\;G_p(3)$, p an odd prime number, are 2-recognizable by the set of their order components. More precisely we will prove that if G is a finite group and OC(G) denotes the set of order components of G, then OC(G) = $OC(B_p(3))$ if and only if $G{\cong}B_p(3)\;or\;C_p(3)$.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.629-637
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• 1998

The HF-SCF, MP2 and B3LYP calculations have been performed on the two conceivable clusters $(HF)_2(CO)$ trimers as well as their dimer complexes FH…FH, FH…CO and FH…OC applying $6-31+G^{\ast}^{\ast}$, and $6-311+G^{\ast}^{\ast}$ basis sets. A variety of ground state properties of these trimer complexes have been listed, and compared with corresponding properties of isolated monomers and combined dimers. It was calculated that FH…CO is more stable than FH…OC by average 0.85 kcal/mol and F-H…F-H…C≡O is more stable than F-H…F-H…O≡C by 1-2 kcal/mol. The C≡O stretching bands of the F-H…F-H…C≡O and F-H…F-H…O≡C were red shifted by 24, $37\;cm^{-1}$ compared with the FH…CO and FH…OC respectively. Also, H-F stretching bands were red shifted by 54 and $353\;cm^{-1}$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1201-1208
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• 2022

In general, to maximize the supply and efficiency of floating offshore wind power generation energy, the motion caused by wave attenuation of the substructure must be reduced. According to previous studies, the motion response was reduced due to the vortex viscosity generated by the damping plate installed in the lower structure among the waves. In this study, a 5 MW semi-submersible OC5 platform and two platforms with attenuation plates were designed, and free decay experiments and numerical calculations were performed to confirm the effect of reducing motion due to vortex viscosity. As a result of the model test, when the heave free decay tests were conducted at drop heights of 30 mm, 40 mm, and 50 mm, compared with the OC5 platform, the platform with two types of damping plates attached had relatively improved motion damping performance. In the model test and numerical calculation results, the damping plate models, KSNU Plate 1 and KSNU Plate 2, were 1.1 times and 1.3 times lower than OC5, respectively, and the KSNU Plate 2 platform showed about two times better damping performance than OC5. This study shows that the area of the damping plate and the vortex viscosity are closely related to the damping rate of the heave motion.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.E1
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• pp.11-20
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• 2003

To characterize airborne particulate carbon and its temporal variation in the heavily industrialized metropolitan city, Seoul in South Korea, aerosol sampling was performed from 1986 to 1996. Correlation coefficients of elemental carbon (EC) and organic carbon (OC) with mass concentration of fine particles ($\underline{\leq}$2.1 ${\mu}m$) are 0.73 and 0.51, respectively. EC concentrations of the fine particle mode are 10.1, 5.9, 4.5, and 7.4 ${\mu}g\;m^{-3}$ in winter, spring, summer, and autumn, respectively. On the other hand, OC concentration shows maximum value in winter and followed by autumn, summer, and spring. A seasonal peak in the ratio of OC to EC in fine particles was observed during the summer photochemical season from June to August. Concentrations of EC and OC in Asian dust storm events are generally higher than in non- Asian dust storm events except in 1990. The difference of EC concentrations between Asian dust storm periods and non-Asian dust storm periods are much larger than those of OC concentrations. There are slight increases of EC concentration between 1987 and 1990 and a gradual decrease between 1990 and 1996.

• Transactions on Electrical and Electronic Materials
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• v.14 no.6
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• pp.329-333
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• 2013

SiOC films were prepared by capacitively coupled plasma chemical vapor deposition, and the correlation between the binding energy by X-ray photoelectron spectroscopy and Arrhenius equation for ionization energy was studied. The ionization energy decreased with increase of the potential barrier, and then the dielectric constant also decreased. The binding energy decreased with increase of the potential barrier. The dielectric constant and electrical characteristic of SiOC film was obtained by Arrhenius equation. The dielectric constant of SiOC film was decreased by lowering the polarization, which was made from the recombination between opposite polar sites, and the dissociation energy during the deposition. The SiOC film with the lowest dielectric constant had a flat surface, which depended on how carbocations recombined with other broken bonds of precursor molecules, and it became a fine cross-linked structure with low ionization energy, which contributed to decreasing the binding energy by Si 2p, C 1s electron orbital spectra and O 1s electron orbital spectra. The dielectric constant after annealing decreased, owing to the extraction of the $H_2O$ group, and lowering of the polarity.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.948-950
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• 2009

A few organosilicon compounds (OC) - both cyclic and linear siloxanes with different structure of the substituents - have been synthesized. Properties of the LC anchoring on OC films have been measured. The OC investigated provide the homogeneous planar alignment with LC tilt angle in the range from $0.7^{\circ}$ to $1.9^{\circ}$. An increase of the microrelief depth results in a small increase of the tilt angle. The azimuthal anchoring is better for the films of the OC without molecular microrelief or the OC comprising polar groups.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.205-205
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• 2007

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane and oxygen mixed precursor by the chemical vapor deposition. The chemical properties of the SiOC film were analyzed by the I-V measurement and FTIR spectra. The main bond of 950~1200 cm-1 was composed of the Si-C, Si-O-C and Si-O bonds. The leakage current of the SiOC film increased with the increasing of the carbon content, and the drift of the current was similar to the Si-O-C bond content.

• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.341-345
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• 2008

The SiOC film of carbon centered system was prepared using bistrimethylsilylmethane and oxygen mixed precursor by the chemical vapor deposition. The chemical properties of the SiOC film were analyzed by the contact anlge and FTIR spectra. The dielectric constant of the deposited films decreased after annealing process, and the correlation between the increasing the BTMSM/$O_2$ flow rate ratio and the dielectric constant did not exist. However, the trend of increasing or decreasing of the dielectric constant repeated and there is the correlation ship between the dielectric constant and the Si-O-C bond in the range of $950{\sim}1200\;cm^{-1}$. The dielectric constant decreased between samples with the chemical shift. The lowest dielectric constant was 1.65 at the sample, which was observed the chemical shift.

• Atmosphere
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• v.27 no.1
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• pp.41-54
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• 2017

Organic carbon (OC) and elemental carbon (EC) in $PM_{2.5}$ were measured using Sunset OC/EC Field Analyzer at Seoul Hwangsa Monitoring Center from March to April, 2016. The mean concentrations of OC and EC during the entire period were $4.4{\pm}2.0{\mu}gC\;m^{-3}$ and $1.4{\pm}0.6{\mu}gC\;m^{-3}$, respectively. OC/EC ratio was $3.4{\pm}1.0$. The average concentrations of $PM_{10}$ and $PM_{2.5}$ were $57.4{\pm}25.9$ and $39.7{\pm}19.8{\mu}g\;m^{-3}$, respectively, which were detected by an optical particle counter. The OC and EC peaks were observed in the morning, which were impacted by vehicle emission, however, their diurnal variations were not noticeable. This is determined to be contributed by the long-range transported OC or secondary formation via photochemical reaction by volatile organic compounds at afternoon. A conditional probability function (CPF) model was used to identify the local source of pollution. High concentrations of $PM_{10}$ and $PM_{2.5}$ were observed from the westerly wind, regardless of wind speed. When wind velocity was high, a mixing plume of dust and pollution during long-range transport from China in spring was observed. In contrast, pollution in low wind velocity was from local source, regardless of direction. To know the effect of long-range transport on pollution, a concentration weighted trajectory (CWT) model was analyzed based on a potential source contribution function (PSCF) model in which 75 percentiles high concentration was picked out for CWT analysis. $PM_{10}$, $PM_{2.5}$, OC, and EC were dominantly contributed from China in spring, and EC results were similar in both PSCF and CWT. In conclusion, Seoul air quality in spring was mainly affected by a mixture of local pollution and anthropogenic pollutants originated in China than the Asian dust.