• 한국해양학회지
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• v.26 no.4
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• pp.332-339
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• 1991

The sedimentation pattern in Namhaepo Bay, a macrotidal coastal embayment of western Korea, was investigated by means of analysing high-resolution seismic profiles, sediment samples, and tidal currents. Recent sediments up to 20 m which overlie the irregular surface of the acoustic basement. The sediments consist mainly of sandy silt and silt; the mean grain size of these sediments ranges from 4 to 5.5 phi, showing a shoreward-fining distribution pattern. This distribution pattern agrees are largely reversed during ebb, with a maximum velocity of 39 cm/sec. The calculated shear velocity of the tidal currents at sea bed ranges from 0.5 to 3.3 cm/sec during flood and from 0.7 to 2.5 cm/sec during ebb. The mean values of these velocities exceed the critical shear velocity for the silt particles. The data suggest that the tidal currents play an important role in the transportation and deposition of sediments in the bay and the surface topography of the sea floor is largely deter-mined by tidal sedimentation.

• Journal of the Korean Vacuum Society
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• v.10 no.4
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• pp.396-402
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• 2001

MgO thin films with 1000 $\AA$ thickness were deposited on Cu substrates by using an electron gun evaporator at room temperature. A 1000 $\AA$ thick Al layer was deposited on the MgO for removing the charging effect of the MgO thin film during the measurements of the sputtering yields. A Ga ion liquid metal was used as the focused ion beam(FIB) source. The ion beam was focused by using double einzel lenses, and a deflector was employed to scan the ion beams into the MgO layer. Both currents of the secondary particle and the probe ion beam were measured, and they dramatically changed with varying the applied acceleration voltage of the source. The sputtering yield of the MgO layer was determined using the values of the analyzed probe current, the secondary particle current, and the net current. When the acceleration voltage of the FIB system was 15 kV, the sputtering yield of the MgO thin film was 0.30. The sputtering yield of the MgO thin film linearly increases with the acceleration voltage. These results indicate that the FIB system is promising for the measurements of the sputtering yield of the MgO thin film.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.4
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• pp.294-299
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• 2009

To investigate the pollution levels and behavior of PCDD/Fs in ambient air, gaseous and particulate phase concentrations were measured at Cheongju city in 2008. The samples were collected at 3 sites (industrial, residential/commercial and rural region) by season (winter, spring and summer). The concentrations and TEQ concentrations of PCDD/DFs ranged from 0.73 to 2.43 pg/$m^3$ and from 0.007 to 0.122 pg TEQ/$m^3$, respectively. These levels were similar or lower than that of other domestic researches (from n.d. to 2.149 pg TEQ/$m^3$). The concentration of PCDD/Fs in particulate phase (from 54% to 98% against total concentration) were higher than that of gas phase. As a results of comparison of congener patterns and statistical analysis, PCDD/Fs was mainly influenced by a combustion process in ambient air, Cheongju city.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.2
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• pp.259-265
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• 2008

Generally speaking, there are two widely used methods of Nitrogen removal from waste water: 1) nitrification using autotrophic microorganisms, and 2) denitrification using heterotrophic microorganisms. The C/N ratio is an important factor of the denitrification process. In this case, if methanol is added to increase the lacking organic matter, a high economic cost is incurred and methanol is left in the processed water. In an effort to fix these issues, autotrophic denitrification through the use of Hydrogen, Iron and Sulfur is being studied, and among those Sulfur is cheaper and carries out denitrification effectively, and therefore is being studied the most. In this study, after cultivating T. denitrificans, the presence of T. denitrificans was determined and the effectiveness of denitirification via T. denitrificans was studied. In order to find out about the inhibition of T. denitrificans from the loading of organic matter, this shows that the greater the loading of organic matter, the more the denitrification ability of T. denitrificans is hindered. In order to research the hindrance of T. denitrificans resulting from the loading of $NO_3{^-}-N$, these results show that concentrations less than 100mg/L per 100mL of gel volume do not hinder T. denitrificans. In order to research the optimization of denitrification resulting from T. denitrificans, three 500mL samples of Sulfur granules were prepared: 1) one with only T. denitrificans attached (Mode I), 2) one with both T. denitrificans and active sludge attached (Mode II), and 3) one with only active sludge attached (Mode III). The results showed that autotrophic denitrification using S from Mode I was the most active.

• Particle and aerosol research
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• v.10 no.3
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• pp.119-130
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• 2014

Home is a major living environment of children. In urban area, indoor air at home could be severely influenced by combustion sources such as vehicle exhaust and cooking. In this work, the air quality of a high-rise apartment was investigated by monitoring combustion-related air pollutants at both indoor and outdoor in winter of 2014. From 48-h continuous monitoring data, large amount of $NO_x$ was observed at the balcony of the high-rise apartment during the morning traffic hours. It deteriorated indoor air quality of the apartment. During the cooking activity, high peak episodes of ultrafine particles were seen. It was concluded that effects of vehicle exhaust and cooking activity on the indoor air of the high-rise apartment could be easily checked by $NO_x$ and ultrafine particle indicators, respectively.

• Particle and aerosol research
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• v.14 no.3
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• pp.65-72
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• 2018

Core-shell structured $Fe_3O_4/graphene$ composites were synthesized by aerosol spray drying process from a colloidal mixture of graphene oxides and $Fe_3O_4$ nanoparticles. The structural and electrochemical performance of $Fe_3O_4/graphene$ were characterized by the field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, cyclic voltammetry, and galvanometric discharge-charge method. Core-shell structured $Fe_3O_4/GR$ composites were synthesized in different mass ratios of $Fe_3O_4$ and graphene oxide. The composite particles were around $3{\mu}m$ in size. $Fe_3O_4$ nanoparticles were encapsulated with a graphene. Morphology of the $Fe_3O_4/graphene$ composite particles changed from a spherical ball having a relatively smooth surface to a porous crumpled paper ball as the content of GO increased in the composites. The $Fe_3O_4/GR$ composite fabricated at the weight ratio of 1:4 ($Fe_3O_4:GO$) exhibited higher specific capacitance($203F\;g^{-1}$) and electrical conductivity than as-fabricated $Fe_3O_4/GR$ composite.

• Journal of Ocean Engineering and Technology
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• v.28 no.2
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• pp.93-101
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• 2014

In general, particle simulation methods such as the MPS(Moving Particle Simulation) or SPH(Smoothed Particle Hydrodynamics) methods have some serious drawbacks for pressure solutions. The pressure field shows spurious high fluctuations both temporally and spatially. It is well known that pressure fluctuation primarily occurs because of the numerical approximation of the partial differential operators. The MPS and SPH methods employ a pre-defined kernel function in the approximation of the gradient and Laplacian operators. Because this kernel function is constructed artificially, an accurate solution cannot be guaranteed, especially when the distribution of particles is irregular. In this paper, we propose a particle simulation method based on the moving least-square technique for solving the partial differential operators using a Taylor-series expansion. The developed method was applied to the hydro-static pressure and dam-broken problems to validate it.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.1-8
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• 1977

A base of photographic posi-film which is commecially available has been found to be a possible alpha-particle track detector. Its neutron dosimetric characteristics, i. e., alpha-particle track registrating efficiency and optimum condition of track formation by chemical etching, have been determined experimentally. The range of neutron fluence and dose capable of being measured by a neutron dosimeter consisting of alpha-particle radiator foils $(^{10}B\;and\;^{27}Al)$ and posi-flim solid state track detector, has been estimated on the basis of experimental results and theoryetical background. This detector seems to be useful for neutron dosimetry because of many favorable properties, i. e., simplicity, cheapness and a wide range of sensitivitiy.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.517-523
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• 1997

We have been studied that combustion efficiency and the production of air pollution of anthracite-bituminous coal blend in a fluidized bed coal combustor. Also, the reaching time of steady state condition have been studied. This experimental results are presented as follows. As the height of fluidized bed combustor becomes higher, the concentrations of $SO_2$ and NOx mainly increased. Also, as anthracite fraction increased, the emission of $SO_2$ concentration was increased but, the variation of $NO_X$ concentration was negligible according to anthracite fraction. When anthracite fraction ratio was increased, elutriation rate was increased and exit combustible content over feeding combustible content was increased. Regardless of anthracite fraction ratio the uncombustible weight percentage according to average diameter of elutriation particles were approximately high in the case of fine particles. Over bed temperature $850^{\circ}C$ and excess air 20%, the difference of combution at the velocity 0.3m/s, bed temperature $850^{\circ}C$, the excess air 20%.

• Clean Technology
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• v.13 no.4
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• pp.237-243
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• 2007

Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dimethyl ether (DME) and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing DME as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of DME and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the DME composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature.