• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.99-111
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• 1999

The purpose of this study was to evaluate crystalline silica contents in airborne respirable dusts from various manufacturing industries and to compare analytical ability of two different methods of quantifying crystalline silica, X-ray diffraction(XRD) and Fourie transform infrared spectroscopy(FTIR). Various manufacturing industries with a history of having pneumoconiosis cases and also known to generate dusts containing crystalline silica were investigated. These industries include: ceramics, brick, concrete, and abrasive material etc. The personal respirable dust samples were collected using l0mm, Dorr-Oliver nylon cyclone equipped with 37mm, $5{\mu}m$ pore size. polyvinylchloride (PVC) filters as collection media. All samples were weighed before and after sampling and were pretreated according to the NIOSH sampling and analytical methods 7500, and 7602 for dust collection and quartz analysis. A total of 48 samples were collected from these industries. Initial analyses of these samples showed log-normal distributions for dust and quartz concentrations. Some results from ceramics and stone exceeded current Korean Occupational Exposure Limits. The average concentrations of personal respirable dust by cyclone were 0.43, 0.24, 0.26, 0.42, 0.53 and $0.29mg/m^3$ in ceramics, stone, concrete, glass, briquets, and others, respectively. A comparison of performance of two analytical methods for quantifying crystalline silica was performed using data from ceramics. The results showed that no significant difference was found between two methods for ceramics. The mean crystalline silica contents determined by XRD were 3.41 % of samples from briquets and 7.18 % from ceramics and were 2.58 % from concrete and 10.33 % from ceramics by FTIR. For crystalline silica analysis, two analytical techniques were highly correlated with $r^2=0.81$ from ceramics. Both cristobalite and tridymite were not detected by XRD and FTIR.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.261-269
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• 2015

In this study, we applied a membrane distillation process to investigate a feasibility of treating a wastewater with high concentration of organic matters including nitrogen and phosphorus. The laboratory scale experiment was performed by using a hydrophobic PVDF membrane with the pore size of $0.22{\mu}m$ and porosity of 75%. The installation was direct contact type where the temperature difference between a feed and permeate side was controlled to have a range from 20 to $60^{\circ}C$. We observed a flux variation and a concentration changes of COD, $PO{_4}^{3-}$-P, $NH_4{^+}$-N and conductivity of feed side as well as permeate side with various temperature differences (20 to $60^{\circ}C$), cross flow velocities (0.09 to 0.27 m/s) through the module, and pH (6.6 to 12.0) of the feed that has the initial concentration of COD about 1,000 mg/L, total nitrogen 390 mg/L, total phosphorus 10 mg/L, conductivity of $7,000{\mu}s/cm$. The results showed that the average flux was ranged from 4 to $40L/m^2/hr$ which was almost similar with the flux of NaCl and deionized water used as a feed solution. The lowest flux was obtained at the operating condition with the temperature difference of $20^{\circ}C$ and cross flow velocity of 0.09 m/s while the highest one was measured with $60^{\circ}C$ and 0.27 m/s. Above 99% of COD and $PO{_4}^{3-}$-P in the feed could be rejected regardless of an operating condition. However, the removal rate of ammonium nitrogen was varied from 64 to 99% depending on the pH of feed solution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.371-377
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• 2014

In tissue engineering, a scaffold is a three-dimensional(3D) structure that serves as a template for regeneration the functions of damaged tissues or organs. Among materials for scaffolds, polycaprolactone(PCL) and ${\beta}$-tricalcium phosphate(${\beta}$-TCP) are biodegradable and biocompatible. In this study, we fabricated 3D PCL, blended PCL (60 wt %)/${\beta}$-TCP (40 wt %), and pure ${\beta}$-TCP scaffolds by a multi-head scaffold fabrication system. Scaffolds with a pore size of $600{\pm}20{\mu}m$ was observed by scanning electron microscopy. The effects of 3D PCL, blended PCL (60 wt %)/${\beta}$-TCP (40 wt %) and pure ${\beta}$-TCP scaffolds were analyzed by evaluating their mechanical characteristics. In addition, in an in-vitro study using osteoblast-like saos-2 cells, we confirmed the effects of 3D scaffolds on cellular behaviors such as cell adhesion and proliferation. In summary, the 3D blended PCL (60 wt %)/${\beta}$-TCP (40 wt %) scaffold was found to be suitable for human cancellous bone in terms of its the compressive strength, biocompatibility, and osteoconductivity. Thus, blending PCL and ${\beta}$-TCP could be a promising approach for fabricating 3D scaffolds for effective bone regeneration.

• Applied Biological Chemistry
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• v.43 no.1
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• pp.24-28
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• 2000

This study was conducted to evaluate the effect of ultrafiltration (UF) process variables on permeate flux and membrane resistance and to clarify apple vinegar for quality improvement. Apple vinegar was clarified in a laboratory ultrafiltration system with hollow fiber membrane made of polysulfone and MWCO 30,000 and 10,000. The permeate flux increased with the increase of flow rate and the optimum pressure was $1.5\;kgf/cm^2$ in this system. The turbidity of clarified apple vinegar treated UF largely decreased. pH and acidity of treated samples showed the same level as those of untreated apple vinegar. The permeate flux continuously declined while the fouling material accumulated on the membrane as the operation time increased. Resistance decreased with lower pressure, which could be explained by expansion of pore size at lower pressure and minor compaction of the polarized layer at lower pressure.

• Korean Journal of Food Science and Technology
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• v.30 no.5
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• pp.1146-1151
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• 1998

To prevent deterioration of the jujube wine quality by using heat sterilization while commercial production, ultrafiltration and microfiltration were applied. The permeate flux and physicochemical properties of jujube wine determined by MF and UF membrane ($0.2\;{\mu}m$ pore size and 50 K dalton cut off) were investigated. The permeate flux increasing caused the increased operating pressure. The Hunter L value of jujube wine treated MF and UF was increased and that of b value was decreased. The turbidity of jujube wine treated MF and UF was largely decreased. And the values of pH, ethanol, total acid and soluble solid were decreased or were at the same level comparing with untreated jujube wine. Retention percentage of sugar and organic acid was more than 80% and was not influenced by operating pressure. Results of sensory evaluation indicated that the color of UF was superior to un-treatment and commercial ones. And the flavor and taste were not significantly different with untreated jujube wine. The quality deterioration of commercial jujube wine could be improved by MF and UF. According to the sensory evaluation, there was also not difference between MF and UF for preference test. Therefore, the quality of jujube wine could be improved by MF having better separation yield efficiency than UF.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.3
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• pp.226-233
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• 1997

To investigate the salt accumulation in the plastic film house soils, bulk density, electrical conductivity(EC), exchangeable canons and water soluble anions were determined at different depths(0~60cm) in the salt-accumulated plastic film house soils in Yesan, Chungnam, Korea. Bulk density were increased from $1.2Mg/m^3$ to $1.5Mg/m^3$ as the depth changed from 0cm(top soil) to 30cm(subsoil) below the soil surface, whereas the bulk densities between 30cm to 60cm slightly decreased to $1.42Mg/m^3$. These changes of soil bulk densities might influence the porosity and pore size distribution, resulting in affecting the water flow throughout, soil layers. Electrical conductivity and Exchangeable sodium percentage(ESP) for 0 to 10cm soil layer were 5.08 dS/m and 6.4, respectively, while the EC was decreased to less than 1.63 dS/m in 20~30cm depth and about 0.7 dS/m. Salt accumulation patterns in the plastic film house soils might be influenced by the changes of the bulk densities in soil.

• Membrane Journal
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• v.19 no.3
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• pp.189-193
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• 2009

The present work was attempted to improve the performance for the removal of water from ethanol/water mixtures through the ion-exchanged zeolite membrane in which $Na^{+}$ ion was substituted to either $K^{+}$ or $Ca^{2+}$ ion. The membranes were ion-exchanged with 0.5 mole/L aqueous solution of either KCl or $CaCl_2$ at $80^{\circ}C$ for 4 hrs. In case of the ion-exchanged membrane in which $Na^{+}$ ion was substituted to $K^{+}$ ion, the total flux was decreased from $900\;g/m^2{\cdot}hr{\sim}2,500\;g/m^2{\cdot}hr$ to $600\;g/m^2{\cdot}hr{\sim}2,000\;g/m^2{\cdot}hr$ and the separation factor was increased from $600{\sim}2,200$ to $850{\sim}2,500$ compared to the NaA type zeolite membrane. And in case of the ion-exchanged membrane in which $Na^{+}$ ion is substituted to $Ca^{2+}$ ion, both the total flux and selectivity of water showed the similar tendency compared to the NaA type zeolite membrane. It is thought that the improved separation would be possible if the pore size of the zeolite membrane is controlled by the ion exchange.

• Analytical Science and Technology
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• v.16 no.6
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• pp.450-457
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• 2003

The determination of uranium and its isotopes in spent nuclear fuels by isotope dilution mass spectrometry (IDMS) has been studied. The spent fuel samples were dissolved in 8 M $HNO_3$ or its mixture with 14 M $HNO_3-0.05M$ HF. The dissolved solutions were filterred on membrane filter with $1.2{\mu}m$ pore size. The uraniums in the spiked and unspiked sample solutions were quantitatively adsorbed by anion exchange resin, AG 1X8 and eluted with 0.1 M HCl. The contents of uranium and its isotopes ($^{234}U$, $^{235}U$, $^{236}U$ 및 $^{238}U$) in the spent fuel samples were determined by isotope dilution mass spectrometric method using $^{233}U$ as spike. The spike reference solution was standarized by reverse isotope dilution mass spectrometry (R-IDMS) using natural and depleted uranium. The results from IDMS were in average relative difference of 0.34% when compared with those by the potentiometric titration method.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.381-391
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• 2011

Weathering can reduce rock strength and eventually affect the structural stability of a rock mass, which is important in the field of engineering geology. Several methods have been developed to evaluate the degree of weathering, including the chemical weathering index. In this study, we analyzed the weathering degree and characteristics of microtextures and pores in crystalline rocks (gneiss and granites) based on petrographic observations, the chemical weathering index, mineralogy by XRD, microtextural analysis by SEM/EDS, measurements of pore size and surface area by the BET method, and microporosity by X-ray CT. The formation of secondary minerals and microtexture in gneiss and granitic rocks are assumed to be affected by complex processes such as dissolution, precipitation, and fracturing. Hence, it is clear that some chemical weathering indices that are based solely on whole-rock chemistry (e.g., CIA and CWI) are unable to provide reliable assessments of the degree of weathering. Great care is needed to evaluate the degree of chemical weathering, including an understanding of the mineralogy and microtexture of the rock mass, as well as the characteristics of micropores.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.304-309
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• 1999

Aluminum-pillared clay was prepared by the intercalation of Al-hydroxy oligomer into domestic bentonite. The solid products are characterized by XRD, nitrogen adsorption/desorption, EDX, and SEM. The solid products show relatively high specific surface areas in the range of $104{\sim}228m^2/g$, and their specific surface area, micropore surface area, and micropore volume increase with increasing the mole ratio of OH/Al. From the results of pore size distribution calculated by BJH equation, it was found that aluminum-pillared clay also contains much mesopore near $40{\AA}$. These results indicate that Al-hydroxy oligomer was intercalated into bentonite, and aluminum oxide was pillared among the layers of bentonite, and micropore and mesopore was finally developed into layers. As OH/Al mole ratio increases, the thermal stability of aluminum-pillared clay increases. This result can be explained by the fact that the density of layers is increased due to the formation of aluminum pillars.