• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.851-857
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• 2004

The stabilizing characteristics of heavy metals in the silicate glass (SD), borosilicate glass (BD), and leadsilicate glass (PD) containing Electric Arc furnace (EAF) dust were studied by the Toxic Characterization Leaching Procedure (TCLP) test. Also, the dependence of the amount of EAF dust upon structural changes of SD, BD, and PD glasses and the TCLP results were investigated by the XRD and FT-IR spectroscopy. In the XRD results, all of SD, BD, and PD specimens containing dust up to 30 wt% were amorphous without crystallizing. In the TCLP test, the concentration of heavy metals leached from the glasses increased with the amount of EAF dust added. The SD specimen series showed the lowest heavy metal leaching and the heavy metal leachate of the PD specimens were lower than those of the BD specimens. But, the Pb leaching from the PD specimens was the highest in the PD glass composition due to the high Pb content. The value of oxygen/network former ratio could be used to compare the chemical durability within the same glass series, but not proper to do between the different glass series. Adding the EAF dust to the SD mother glass, decreased the Si-O-Si symmetry and increased the non-bridging oxygen, which weakened the structure and decreased the chemical durability of glasses. In the BD series glasses, the addition of EAF dust caused the structural changes from tetra-borate group to di-borate group and the formation of the 2-dimensional layer structure of pyre- and ortho- borate, which decreased the chemical durability of glasses. It is concluded that SD series glass among the 3 kinds of glasses is the most effective to stabilize the heavy metals of EAF dust.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.553-568
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• 2018

Chromophoric Dissolved Organic Matter (CDOM) plays a dominant role in absorbing UV-VIS light and is also important in the biogeochemical carbon cycle due to the production of carbon dioxide from photo-oxidation at the sea surface in marine environments. Since absorption by CDOM was recently found to be responsible for increasing the energy absorbed in the mixed layer by 40 % over pure seawater, the importance of CDOM absorption in seawater for increasing sea surface temperature has come to be well recognized. We measured aCDOM and the absorption characteristics of CDOM during spring 2012 and 2014 in the southwestern East Sea. Distribution of CDOM in spring 2012 and 2014 was compared and S value was used to find the source of CDOM in the study area. As a result, the average $a_{CDOM}$ was $0.237m^{-1}$ ($0.009{\sim}0.988m^{-1}$) and the average S value was $16{\mu}m^{-1}$,which shows coastal properties. Also a positive correlation between Chl a and CDOM was observed ($r^2=0.34$), with an especially strong correlation near coastal stations. aCDOM in 2014 was about 40 % higher than aCDOM in 2012 during spring in the study area. This difference in aCDOM concentration resulted not only from annual variation but also from stratification and photobleaching in late spring 2012. This observation implies the possibility of flux of carbon dioxide into the atmosphere as a result of photo-oxidation in the East Sea.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.88-95
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• 2017

Chogye basin, which is surrounded by country rock, has a closed-basin form. In such a basin, incident seismic energy can form multiply reflected waves, thus causing energy concentration to occur at this closed-basin area. Microtremor measurement survey was performed at the Chogye basin, which is located in Chogye-myeon and Jeokjungmyeon, Hapcheon-gun, Gyeongsangnam-do, Republic of Korea. Microtremor data were transformed into the frequency domain, and then the horizontal-to-vertical spectral ratios (HVSR) were calculated. Fundamental resonance frequencies were estimated from the HVSR results for every observation point. Using the empirical relationship between site period and thickness for sediment sites in Korea known from the previous study, the distribution of sediment thickness of the Chogye basin was estimated from the fundamental resonance frequencies. Being compared with the mountainous rim with steep slope, the measurement points inside the basin have low values of the fundamental resonance frequency with the minimum of 1.03 Hz, which corresponds to the thickness of sedimentary layer with the maximum depth of about 100 m. A three-dimensional basin model was constructed for bedrock topography of the Chogye basin by an interpolation of basin depths estimated at each measurement site.

• Current Optics and Photonics
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• v.1 no.2
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• pp.107-112
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• 2017

An adaptive optics system can be simulated or analyzed to predict its closed-loop performance. However, this type of prediction based on various assumptions can occasionally produce outcomes which are far from actual experience. Thus, every adaptive optics system is desired to be tested in a closed loop on an optical test bench before its application to a telescope. In the close-loop test bench, we need an atmospheric simulator that simulates atmospheric disturbances, mostly in phase, in terms of spatial and temporal behavior. We report the development of an atmospheric turbulence simulator consisting of two point sources, a commercially available deformable mirror with a $12{\times}12$ actuator array, and two random phase plates. The simulator generates an atmospherically distorted single or binary star with varying stellar magnitudes and angular separations. We conduct a simulation of a binary star by optically combining two point sources mounted on independent precision stages. The light intensity of each source (an LED with a pin hole) is adjustable to the corresponding stellar magnitude, while its angular separation is precisely adjusted by moving the corresponding stage. First, the atmospheric phase disturbance at a single instance, i.e., a phase screen, is generated via a computer simulation based on the thin-layer Kolmogorov atmospheric model and its temporal evolution is predicted based on the frozen flow hypothesis. The deformable mirror is then continuously best-fitted to the time-sequenced phase screens based on the least square method. Similarly, we also implement another simulation by rotating two random phase plates which were manufactured to have atmospheric-disturbance-like residual aberrations. This later method is limited in its ability to simulate atmospheric disturbances, but it is easy and inexpensive to implement. With these two methods, individually or in unison, we can simulate typical atmospheric disturbances observed at the Bohyun Observatory in South Korea, which corresponds to an area from 7 to 15 cm with regard to the Fried parameter at a telescope pupil plane of 500 nm.

• Korean Journal of Environment and Ecology
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• v.30 no.2
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• pp.199-213
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• 2016

This study aimed to analyze the vegetation characteristics of the coastal forests and to figure out if there is possibilities to develop the forests into mixed stand multistory forests and to suggest some sound management practices. The vegetat- ion structure and flora of four sites; Kijipo, Chunjangdae, Janghang and Kusipo in the west coastal forests in Korea were investigated and analyzed in the present study. In the every site, Pinus thunbergii was dominating the tree layer in the forests. And P. densiflora, Robinia pseudoacacia, Quercus serrata, Prunus sargentii var. sargentii, Q. acutissima and Castanea crenata were dominating the subtree layers in some sites. P. thunbergii stands in four sites would maintain for a while since the populat- ion density of middle aged group is higher than those of young and old groups. According to the geographical location conditions, there is a possibility that the coastal forests in Kusipo site would progress into oak tree stands in the long run. The biodiversity was quite high to have 205 taxa in the study sites. To induce the coastal forests into multistory forests, P. thunbergii stands need to be thinned. And then creating the environment including making some pathways and site usage rest-riction is needed to let new diverse plants could come in and grow for a success-ful multistory forests.

• Membrane Journal
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• v.8 no.3
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• pp.157-169
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• 1998

The effects of solvents (DMAc, NMP, 1,4-dioxane) and nonsolvents ($H_2O$, Methanol, n-hexane) on the morphology of 6FDA-p-TeMPD polyimide membrane, prepared by the wet phase inversion method, were studied. In the polymer/solvent/nonsolvent ternary system, the binodal curve, the coagulation value and the relative light transmission were measured, and the solubility parameter difference was calculated. The onset state and rate of liquid-liquid alemixing were predicted and the morphology of membrane was analyzed. It is found that the finger-like pores are formed within discontinuous polymer nodules when the binoclal curve is close to the polymer-solvent (P-S) axis, the coagulation value is small, the reduction of light transmission is easy to occur and the order of solubility parameter difference ($\Delta \delta_{i-j}$) is $\Delta \delta_{S-NS} > \Delta \delta_{P-NS} > \Delta \delta_{P-S}$. The dense skin with small nodules and the sponge type sublayer with macrovoid are formed in the case that the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is long and the order of $\Delta \delta_{i-j}$ is $\Delta \delta_{P-NS} >(\Delta \delta_{S-NS} < > \Delta \delta_{P-S})$. The thick layer of fine nodule coagulation and loosely grown sublayer of nodules appear when the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is very long and the order of $\Delta \delta_{i-j}$가 $\Delta \delta_{S-NS} > (\Delta \delta_{P-NS}$\lessgtr$ > (\Delta \delta_{P-NS} < >)\Delta \delta_{P-S}$ ).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.119-125
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• 2017

Ablative material in a rocket nozzle is exposed to high temperature combustion gas, thus undergoes complicated thermal/chemical change in terms of chemical destruction of surface and thermal decomposition of inner material. Therefore, method for conjugate analysis of thermal response inside carbon/phenolic material including rocket nozzle flow, surface chemical reaction and thermal decomposition is developed in this research. CFD is used to simulate flow field inside nozzle and conduction in the ablative material. A change in material density and a heat absorption caused by the thermal decomposition is considered in solid energy equation. And algebraic equation under boundary layer assumption is used to deduce reaction rate on the surface and resulting destruction of the surface. In order to test the developed method, small rocket nozzle is solved numerically. Although the ablation of nozzle throat is deduced to be higher than the experiment, shape change and temperature distribution inside material is well predicted. Error in temperature with experimental results in rapid heating region is found to be within 100 K.

• Journal of Veterinary Clinics
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• v.30 no.3
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• pp.214-217
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• 2013

A 3-year-old intact female hedgehog (Atelerix albiventris) was presented for evaluation of mandibular swelling. Fine needle aspiration of swollen mandibular was performed and smears were stained with Romanowsky type stain for cytological evaluation. Smears were highly cellular with predominance of variably shaped keratinized or non keratinized squamous cells with low numbers of spindloid to abnormally elongated cells. Cytologic impression was squamous cell carcinoma. The mass was surgically removed for histological examination. Microscopically tortuous and anastomosing delicate to broad pegs and nests of neoplastic squamous epithelial cells were supported by a moderate collagenous and spindloid fibroblast stroma. Tumor cells had moderate anisocytosis and mild anisokaryosis and range from moderately to well keratinized, with areas of intratumoral acantholysis accompanied by mixed stromal lymphoplasmacytic, neutrophilic inflammation. The mitotic index is 2-3 per high-power field. Tumor cells were expanding the subcutis subjacent to the layer of skeletal muscle and incorporating the osseous tissue fragments. The final diagnosis was squamous cell carcinoma. The patient survived three months after surgery without any further medical treatments.

• Journal of the Korean Wood Science and Technology
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• v.14 no.1
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• pp.45-54
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• 1986

A study was conducted to determine the physical properties related to drying characteristics, the seasonal air drying curves and the kiln drying schedule for taun lumber imported and utilized. This kiln drying schedule was found by oven drying and developed by pilot testing of green lumber and partially air dried lumber. The results of this study were as follows; 1. Average green specific gravity and standard deviation of heartwood lumber were 0.60${\pm}$0.03 and those of sapwood lumber were 0.64${\pm}$0.02. 2. Radial shrinkage from green to air dry and from green to oven dry were 3.05 percent and 5.96 percent respectively, and tangential shrinkage from green to air dry and to oven dry were 5.49 percent and 8.74 percent respectively. 3. Drying time for 25mm thick green lumber (50 percent moisture content) air dried to 30 percent moisture content were 14 days in springtime. 6 days in summertime, and 12 days in autumntime, whereas for 50mm thick lumber in 36 days in springtime, 18 days in summertime, 38 days in autumntime. 4. Kiln drying schedules developed by oven drying were T8-B3 for 25mm thick lumber and T5-B2 for 50mm thick lumber. 5. Kiln drying curves of green 25mm and 50mm thick lumber were similar to those of partially air dried lumber from the level of 30 percent average moisture content. Green 25mm thick lumber (55.7 percent moisture content) was dried to 9.3 percent moisture content in 101.5 hours and green 50mm thick lumber (65.6 percent moisture content) was dried to 11.5 percent moisture content in 526 hours. 6. End checking for green 25mm thick lumber occured in 49.6 percent moisture content and reached maximum amount in 27.6 percent moisture content and closed in 15.8 percent moisture content. 7. End checking for green 50mm thick lumber and partially air dried lumber developed and reached maximum amount earlier then for 25mm thick lumber. 8. Final moisture content of surface layer for 50mm thick lumber was one half of that of core, and moisture content equalized in the lumber after nine days of room conditioning. 9. Casehardening for 50mm thick lumber was slight and was conditioned after nine days of room stroage. 10. Drying defects, such as end checking and surface checking, were not observed and the quality of dry lumber was first.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1164-1172
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• 2006

Measurements of the local heat transfer coefficients on hemispherical convex and concave surfaces with a turbulent impinging jet were made. The Reynolds number used was 11000, 23000, 50000 and the nozzle- to- surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was a = $0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $40^{\circ}$. In case of concave surface, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit secondary maxima at $0^{\circ}$ $\leq$ a $\leq$ $15^{\circ}$, L/d $\leq$ 4 for X/d<0(upstream) and at $0^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, L/d $\leq$ 4 and at $30^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, 4 < L/d $\leq$ 6 for X/d<0(downstream). The secondary maximum occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. In case of convex, correlations of the stagnation point Nusselt number according to Reynolds number, jet-to-surface distance ratio and dimensionless surface angle are presented. In the stagnation point, in term of Ren, n ranges from 0.43 in case of 2 $\leq$ L/d $\leq$ 6 to 0.45 in case of 6 < L/d $\leq$ 10, there agrees roughly appears to be laminar boundary layer result. The maximum Nusselt number, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. On this condition about surface curvature D/d=10, the maximum displacement is about 0.7 times of the jet nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.