• Journal of the Korean earth science society
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• v.31 no.6
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• pp.600-607
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• 2010

In 2008, multiple episodes of large-scale transport of natural airborne particles and anthropogenically affected particles from different sources in the East Asian continent were identified in the National Oceanic and Atmospheric Administration (NOAA) satellite RGB-composite images and the mass concentrations of ground level particulate matters. To analyze the aerosol size distribution during the large-scale transport of atmospheric aerosols, both aerosol optical depth (AOD; proportional to the aerosol total loading in the vertical column) and fine aerosol weighting (FW; fractional contribution of fine aerosol to the total AOD) of Moderate resolution Imaging Spectroradiometer (MODIS) aerosol products were used over the East Asian region. The six episodes of massive natural airborne particles were observed at Cheongwon, originating from sandstorms in northern China, Mongolia and the loess plateau of China. The $PM_{10}$ and $PM_{2.5}$ stood at 70% and 16% of the total mass concentration of TSP, respectively. However, the mass concentration of $PM_{2.5}$ among TSP increased as high as 23% in the episode in which they were flowing in by way f the industrial area in east China. In the other five episodes of anthropogenically affected particles that flowed into the Korean Peninsula from east China, the mass concentrations of $PM_{10}$ and $PM_{2.5}$ among TSP reached 82% and 65%, respectively. The average AOD for the large-scale transport of anthropogenically affected particle episodes in the East Asian region was measured at $0.42{\pm}0.17$ compared with AOD ($0.36{\pm}0.13$) for the natural airborne particle episodes. Particularly, the regions covering east China, the Yellow Sea, the Korean Peninsula, and the east Korean sea were characterized by high levels of AOD. The average FW values observed during the event of anthropogenically affected aerosols ($0.63{\pm}0.16$) were moderately higher than those of natural airborne particles ($0.52{\pm}0.13$). This observation suggests that anthropogenically affected particles contribute greatly to the atmospheric aerosols in East Asia.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.39-42
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• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.696-701
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• 2012

Non-aqueous processes have been developed for stable management and reuse of spent fuels. Nowadays, a plan for the management of spent fuel is being sought focusing on a non-aqueous process in Korea. Named as pyroprocessing, it includes an electrolytic reduction process using molten salt at high temperature for the spent fuels, which provides metallic product for a following electro-refining process. The electrolytic reduction process utilizes electrochemical reaction producing Li to convert oxides into metals in high temperature LiCl medium. Various kinds of elements in the spent fuels would be distributed in the system according to their respective reactivity with the reductant, Li, and the medium, LiCl. This study elucidates the reactions of the elements to understand the behavior of composite elements on the spent fuels by thermodynamic calculations. Uranium and transuranic are reduced into their metallic forms while rare-earth oxides, except for Eu, are stable against the reaction at a process temperature. This study also covers the tendency of reactions with respect to the temperature and, finally, estimates radioactivity and heat load on the distributed phases based on the reference spent fuel characteristics.

• Composites Research
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• v.30 no.5
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• pp.323-330
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• 2017

In this study, multiscale analysis in which the information obtained from molecular dynamics simulation is applied to the continuum mechanics level is conducted to investigate the effects of clustering of silicon carbide nanoparticles reinforced into polypropylene matrix on mechanical behavior of nanocomposites. The elastic behavior of polymer nanocomposites is observed for various states of nanoparticulate agglomeration according to the model reflecting the degradation of interphase properties. In addition, factors which mainly affect the mechanical behavior of the nanocomposites are identified, and new index 'clustering density' is defined. The correlation between the clustering density and the elastic modulus of nanocomposites is understood. As the clustering density increases, the interfacial effect decreased and finally the improvement of mechanical properties is suppressed. By considering the random distribution of the nanoparticles, the range of elastic modulus of nanocomposites for same value of clustering density can be investigated. The correlation can be expressed in the form of exponential function, and the mechanical behavior of the polymer nanocomposites can be effectively predicted by using the nanoparticulate clustering density.

• Journal of Soil and Groundwater Environment
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• v.10 no.5
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• pp.61-69
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• 2005

Changes in pyrene binding by dissolved and kaolinite-associated humic substances (HS) due to HS adsorptive fractionation processes were examined using purified Aldrich humic acid (PAHA) at different pH (4, 7 and 9). Irrespective of solution pH, molecular weight (MW) fractionation occurred upon adsorption of PAHA onto kaolinite, resulting in the deviation of residual PAHA MW from the original MW prior to sorption. Variation in $K_{OC}$ by bulk PAHA was observed at different pH due to relative contributions of partitioning and size exclusion effects (i.e., specific interactions). For all pH conditions investigated, carbon-normalized pyrene binding coefficients for nonadsorbed, residual fractions $(K_{OC}(res))$ were different from the original dissolved PAHA $K_{OC}$ value $(K_{OC}(orig))$ prior to contact with the kaolinite suspensions. Positive correlations between pyrene $(K_{OC}(res))$ and weight-average molecular weight $(MW_W)$ for residual PAHA fractions were observed for pH 7 and 9. However, such a positive correlation was not found at pH 4 due to the absence of the dramatic fractionation observed for high pH conditions (i.e., exclusive fractionation with respect to higher MW), suggesting that actual MW distribution pattern is more important for sorption-fractionated HS than the composite MW value. For adsorbed PAHA, conformational changes of PAHA upon adsorption seem to be important for the extent of pyrene binding. At relatively high pH (7 and 9), lower extent of pyrene binding was observed for adsorbed PAHA versus nonadsorbed PAHA. The conformation effects were more pronounced at higher pH.

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.50-57
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• 2011

For effective and accurate prediction of overpressure in the Efomeh field, located in the Niger delta basin of Nigeria, integrated seismic and borehole analyses were undertaken. Normal and abnormal pore pressure zones were delineated based on the principle of normal and deviation from normal velocity trends. The transition between the two trends signifies the top of overpressure. The overpressure tops were picked at regular intervals from seismic data using interval velocities obtained by applying Dix's approximation. The accuracy of the predicted overpressure zone was confirmed from the sonic velocity data of the Efomeh 01 well. The variation to the depth of overpressure between the predicted and observed values was less than 10mat the Efomeh 01 well location, with confidence of over 99 per cent. The depth map generated shows that the depth distribution to the top of the overpressure zone of the Efomeh field falls within the sub-sea depth range of 2655${\pm}$2m (2550 ms) to 3720${\pm}$2m (2900 ms). This depth conforms to thick marine shales using the Efomeh 01 composite log. The lower part of the Agbada Formation within the Efomeh field is overpressured and the depth of the top of the overpressure does not follow any time-stratigraphic boundary across the field. Prediction of the top of the overpressure zone within the Efomeh field for potential wells that will total depth beyond 2440m sub-sea is very important for safer drilling practice as well as the prevention of lost circulation.

• Journal of Korea Port Economic Association
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• v.26 no.1
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• pp.195-221
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• 2010

Kunsan port based on the selection of Kunsan Free Trade Area is expected to develop into a regional beach-head port and foreign investment area, and as the result it will play a great role in accelerating the coming age of the west sea. To promote the foreign competitiveness of Kunsan port as a central container port it can be pointed out that 1) to raise up the utilization ratio of Kunsan port as the front base of export and import by multinational corporations, 2) to hustle up the development of Kunsan container port toplay the central role as the composite container linkage central port, 3) to strengthen the attraction activities of foreign investment into the Kunsan Free Trade Area for the balanced development between regions in nation, 4) the support of both central and local governments to accelerate the comingage of the west sea are necessary.

• Applied Biological Chemistry
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• v.43 no.4
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• pp.271-276
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• 2000

Dry noodles were prepared with wheat flour and immature Rubes coreanus (Bogbunja) powder, and the effects of added immature bogbunja powders on dough rheology and noodle quality were examined. Particle size distribution of immature bogbunja powder ranged from 0.04 to $500\;{\um}m$, which was different from that of wheat flour. The initial pasting temperature, peak and final viscosities as well as setback increased in amylograph with the increase of immature bogbunja powder. The water absorption and dough development time increased, but the dough stability decreased in farinograph with the increase of immature bogbunja powder. Decrease of L and b values and increase of a value were shown with the increase of immature bogbunja powder in wheat flour-immature bogbunja powder composite as well as dry noodles. The cooked weight and volume of noodles decreased, but the cooking loss increased with the addition of immature bogbunja powder. Most of texture parameters (hardness, cohesiveness, chewiness, gumminess and tension) of cooked noodles decreased with the addition of immature bogbunja powder. From the result of sensory evaluation, dry noodles containing 1 and 2% immature bogbunja powder were rated as higher quality dry noodles than the others.

• Composites Research
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• v.23 no.2
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• pp.1-9
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• 2010

This study analyzes the apparent fracture toughness of a thick-walled cylinder with a functionally graded material (FGM) coating at the inner surface of the cylinder. The cylinder is assumed to have a single radial edge crack emanating from its inner surface. The crack surfaces and the inner surface of the cylinder are subjected to an internal pressure. The incompatible eigenstrain developed in the cylinder due to nonuniform coefficient of thermal expansion as a result of cooling from sintering temperature is taken into account. Based on a method of evaluating stress intensity factor introduced in our previous study, an approach is developed to calculate apparent fracture toughness. The approach is demonstrated for a cylinder with a TiC/$Al_{2}O_{3}$ FGM coating and some numerical results of apparent fracture toughness are presented graphically. The effects of material distribution profile, cylinder wall thickness, application temperature, and coating thickness on the apparent fracture toughness are investigated in details. It is found that all of these factors play an important role in controlling the apparent fracture toughness of the cylinder.

• Anxiety and mood
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• v.5 no.1
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• pp.29-35
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• 2009

Background : In spite of the worldwide relevance of obsessive-compulsive disorder Ed-highlight : Unclear. Perhaps consider changing word choice. (OCD), there are considerable differences in prevalence, sex ratio, comorbidity patterns, and sociodemographic correlates. Data on subclinical OCD have been sparse to date. Methods : Data stemmed from the Korea Epidemiologic Catchment Area (KECA) study which had been carried out from April to December 2001. Korean versions of DSM-IV adapted Composite International Diagnostic Interview were administered to a representative sample of 6275 persons aged 18-64 living in the community. DSM-IV based criteria for subclinical OCD were applied. Results : The lifetime prevalence rates for OCD and subclinical OCD were 0.8% and 6.6%, respectively. In both OCD and subclinical OCD, the rates for males and females were not statistically different. OCD was demonstrated to be associated with depressive disorder, bipolar disorder, social phobia, generalized anxiety disorder, and alcohol and nicotine dependence. Additionally, subclinical OCD was associated with posttraumatic stress and somatoform disorders. Comorbidity rates in subclinical OCD were lower than those in OCD. Conclusions : The lifetime prevalence rate for OCD was less than 1% in the Korean general population. Age distribution and comorbidity patterns suggest that subclinical OCD represents a broad and heterogeneous syndrome and not simply a milder form of OCD.