• Journal of the Korea Organic Resources Recycling Association
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• v.17 no.4
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• pp.112-121
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• 2009

To obtain basic design criteria for underground anaerobic digestion and enhance biogas production from swine slurry, a $20m^3$ underground anaerobic digester (UGAD) was constructed and operated at mesophilic ($31{\sim}37^{\circ}C$) temperature with an organic loading rate (OLR) at $23.6kgVS/m^3/day$. The average biogas and $CH_4$ production rate were observed at 8.62 and $5.78m^3/day$, respectively. The mean percentile of $CH_4$ and $CO_2$ were also observed at 67.5% and 19.6%. The relative biogas yield was explored at $733L/kg\;VS_{added}$ and $CH_4$ yield was at $495L/kg\;VS_{added}$ respectively. The removal rate of biochemical constituents and pathogens were noticed considerably at 68%, 74%, 79%, 86%, 89%, 81%, 55%, 79%, 98% and 100% on TS, VS, TSS, $BOD_5$, $TCOD_{cr}$, $SCOD_{cr}$, $NH_3-N$, available P, fecal coliforms and Salmonella, respectively. This study suggested that, the modified UGAD system is a greatly desirable for anaerobic digestion for swine slurry with regards to high methane yield and biodegradability.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.2
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• pp.98-104
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• 2001

Cultivation area of the plastic film-house has been continuously increased with the increase of consumers' income. Intensive land use without fallowing or crop rotation caused severe problem such as salt accumulation in soils and in turn retarded growth and low productivity. This study was carried out to solve them derived from longterm intensive farming practices. Seven farmers who are practicing plastic film-house cultivation were recommended for case study by municipal government and selected for their excellency of cultivation and soil management. The cultivation periods of these systems were in the range of 5 to 40 years in the regions mainly located in alluvial soil cultivated with cucumber, tomato and red pepper. The soils texture of the excellent farmers' fields were silt loam or sandy loam, ranged from 7 to 15 percents of clay contents. Soil bulk density, depth of plowing layer and soil aggregates contents of the farmers' soils were 0.89, 23.1 cm, 61.6% whereas those in neighboring soils were 1.10, 17.8 cm, 54.2 %, respectively. And pH, OM and $NO_3-N$ of the farmers' soils also were better than those of neighboring soils. There was no difference in population densities of nematode between the good farmers' and neighboring soils, but actinomyces and Fusarium densities of recommended farmers' soils were better than neighboring soils. The major farming practices by the good farmers were characterized by deep plowing with flooding, amendment of crude organic matter, and reduction of chemical fertilizer application before transplanting, and also drip irrigation and liquid manure application after planting. They also conducted solar sterilization with or without flooding, removal of plastic films during rainy days and culturing rice or corn as rotation crops to avoid the problems mentioned above.

• Journal of the Semiconductor & Display Technology
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• v.4 no.4 s.13
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• pp.19-26
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• 2005

The process optimization of ozone concentration and half life time was investigated in ultra pure water and alkaline solutions for the wet cleaning of silicon wafer surface at room temperature. In the ultra pure water,. the maximum concentration (35 ppm) of ozone was measured at oxygen flow rate of 3 liters/min and ozone generator power over 60%. The half life time of ozone increased at lower power of ozone generator. Additive gases such as $N_2$ and $CO_2$ were added to increase the concentration and half life time of ozone. Although the maximum ozone concentration was higher with the addition of $N_2$ gas, a longer half life time was observed with the addition of $CO_2$. When $NH_4OH$ of 0.05 or 0.10 vol% was added in DI water, the pH of the solution was around 10. The addition of ozone resulted in the half life time less than 1 min. In order to maintain high pH and ozone concentration, ozone was continuously supplied in 0.05 vol% ammonia solutions. 3 ppm of ozone was dissolved in ammonia solutions. The static contact angle of silicon wafer surface became hydrophilic. The particle removal was possible alkaline ozone solutions. The organic contamination can be removed by ozonated ultra pure water and then alkaline solution containing ozone can remove the particles on silicon surface at room temperature.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.2
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• pp.92-98
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• 2012

Purpose: The aim of this study was to evaluate the effects of different abutment materials on abutment screw loosening and settling-down effect in conical connection type implant system. Materials and methods: Three types of abutment, cementation, gold UCLA, and metal UCLA abutment were used. Two UCLA groups were fabricated in a similar pattern to cementation abutment. Type III gold alloy and Nickel-Chromium alloy was used for casting gold UCLA abutment and metal UCLA abutment, respectively. Fixture and abutment were tightened to 30 Ncm by using digital torque controller and re-tightening was conducted with same force after 10 minutes. Digital torque gauge was used to measure loosening torque and fixture/abutment length was measured by digital micrometer. Dynamic loads between 25 N and 250 N were applied with $0^{\circ}$ angle to the abutment axis. After loading, fixture/abutment length was re-measured and amount of settlement was calculated. Loosening torque value was also measured for comparison Results: All three groups showed significant differences of length when comparing before and after loading, but there was no significant difference of settling amount in all groups. Loosening torque values were significantly decreased when comparing before and after loading in all groups($P$<.05). However, there was no significant difference in loss of loosening torque values when compared to groups. Conclusion: In internal conical connection type implants, dynamic load affected on settlement and loosening torque of implant, but there was no differences between abutments materials. Likewise gold UCLA abutment, metal UCLA abutment might be able to withstand functional load.

• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.664-671
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• 2005

In this study, the effect of sosurfactant on microemulsion phase behavior was investigated in ternary systems containing alkyl ethoxylates nonionic surfactant, water and d-limonene. The addition of a cosurfactant produced a microemulsion phase over a wide range of temperature and promoted formation of a microemulsion phase at lower temperatures. In particular, small amounts of n-propanol, as a cosurfactant, were found to be the most effective in extending a microemulsion phase region over a wide range of temperature. Temperature sensitivity of a nonionic surfactant system was effectively relieved by addition of the anionic surfactant sodium dodecyl sulfate. And the formation of one phase microemulsion was not affected by pH, hardness concentration and addition of an antioxidation agent. The cleaner candidates were determined from microemulsion phase behavior study, and their cleaning efficiency was tested using a dipping method. All the cleaner candidates selected during this study showed excellent removal efficiency for abietic acid over a temperature range from 30 to $40^{\circ}C$ presumably due to a decrease in interfacial tension.

• Membrane Journal
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• v.15 no.2
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• pp.114-120
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• 2005

The purpose of this study is to obtain practical information about membrane coupled $ A_2O$ system for muncipal wastewater treatment. A flat-plate microfiltration (MF) module with a pore size $0.25\;{\mu}m$ was submerged into the aeration basin and treated water was filtrated through the membrane by continuous suction with low pressure. The system was operated with synthetic wastewater to find operational parameters of internal recycle ratio and maximum MLSS showing best water quality and long-term stability. The internal recycle was defined as type 1 for aerobic to anoxic tank and type 2 for anoxic to anaerobic tank, respectively When the flux was maintained at $0.015\;m^3/m^2/hr$ (15 LMH) with 2Q type 1 internal recycle ratio, the optimal operational setting were 10 internal recycle ratio for type 2 and maximum MLSS of 11,000 mg/L among tested conditions. At this condition, removal efficiencies of BOD, CODcr, T-N and T-P showed $97.3\%,\;94.2\%,\;64.0\%,\;63.0\%$, respectively.

• Korean Journal of Microbiology
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• v.37 no.3
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• pp.197-203
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• 2001

An ubiquitous bacterium, Pseudomonar cepacia KH410 was isolated from fresh water plant root and identified. Adsorption of heavy metals of lead, cadmium and copper by this strain was investigated. Optimal conditions foradsorption was 1.0 dry g-biomass, at pH 4.0 and temperature of $40^{\circ}C$. Adsorption equilibrium reached max-imum after 120 min in 1000 mg/l metal solutions. The adsorption capacity (K) of lead was 5.6 times higher thancadmium and 4.0 times higher than that of copper. Adsorption of lead was applicable for Langmuir modelwhereas Freundlich model for cadmium and copper, respectively. Adsorption strength (1/n) of heavy metal ionswere in the order of lead>copper>cadmium. Uptake capacity of lead, cadmium and copper by dried cell was83.2,42.0,65.2 mg/g-biomass, respectively. Effective desorption was induced 0.1 M HCI for lead and 0.1 $HNO_3$ for cadmium and copper. Pretreatment to increase ion strength was the most effective with 0.1 M KOH.Uptake by immobilized cell was 77.8,58.5,71.2 mg/g-biomass for lead, cadmium and copper, respectively. Theimmobilized cell was more effective than ion exchange resin on removal of heavy metals in solution containinglight metals.

• Polymer(Korea)
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• v.32 no.2
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• pp.131-137
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• 2008

We have fabricated polystyrene (PS) nanofibrous scaffold for hepatocyte culture by electrospinning method and subsequently coated with specific ligand of Poly[N-p-vinylbenzyl-O-$\beta$-D-galactopyranocyl-($1{\rightarrow}4$)-D-gluconamide](PVLA) to enhance hepatocytes attachment. Rat hepatocytes behavior on the PVLA-coated and non-coated PS nanofibrous matrices have been investigated. Electrospun PS nanofiber structures revealed randomly aligned fibers with average diameter of 500 nm. It is observed that PS nanofibrous matrix could incorporate many cells into the interior of the matrix probably due to the suitable pore size. Cell viabilities cultured on PVLA-coated PS nanofibrous mats were maintained for 3 weeks, while it was decreased rapidly on PVLA-coated PS dishes. High hepatic functions especially for albumin secretion and ammonia removal were maintained at least for 2 weeks on nanofibrous mats but rapidly decreased on flat PS dishes. These results indicate that nanofibrous structure enabled 3-D culture with high level of cell-cell contact results in providing cell-cell communications and subsequent long-term maintenance of specific cell functions.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.2
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• pp.145-153
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• 2022

Background: Postoperative analgesia (POA) is an important determinant of successful treatment. Dexmedetomidine (DEX) has recently gained attention as a promising adjuvant to local anesthetics (LA). The present study aimed to evaluate the efficacy and safety of levobupivacaine (LB) as an adjuvant during inferior alveolar nerve block (IANB) in the extraction of lower impacted third molars (LITM). Methods: A prospective, randomized, placebo-controlled, triple-blind, parallel-arm, and clinical study was performed on 50 systemically healthy participants who required removal of an asymptomatic LITM. Using a 1:1 distribution, the participants were randomized into two groups (n = 25). Group L (control group) received 1.8 mL of 0.5% LB and 0.2 mL normal saline (placebo) and Group D (study group) received a blend of 1.8 mL of 0.5% LB and 0.2 mL (20 ㎍) DEX. The primary outcome variable was the duration of POA and hemodynamic stability, and the secondary variable was the total number of analgesics required postoperatively for up to 72 h. The participants were requested to record the time of rescue analgesic use and the total number of rescue analgesics taken. The area under the curve was plotted for the total number of analgesics administered. The pain was evaluated using the visual analog scale. Data analysis was performed using paired students and unpaired t-test, Mann-Whitney U test, Chi-square test, and receiver operating characteristic analysis. Statistical significance was set at P < 0.05. Results: The latency, profoundness of anesthesia, and duration of POA were statistically significant (P < 0.05). The differences between mean pain scores at 6, 12, 24, 48, and 72 h were found to be significant (each P = 0.0001). Fewer analgesics were required by participants in group D (2.12 ± 0.33) than in L (4.04 ± 0.67), with a significant difference (P = 0.0001). Conclusion: Perineurally administered LA with DEX is a safe, effective, and therapeutic approach for improving latency, providing profound POA, and reducing the need for postoperative analgesia.

• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.395-400
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• 2004

The effects of compositions of binders on the rheological properties of mixtures and the preparation conditions on the formation of defects and the debinding characteristics of compacts for the injection molding of ceramic powders (65 wt% aluminaㆍ35 wt% feldspar) were studied. Ceramic powders were coated with 2 wt% of stearic acid and then mixed with 15, 20, and 25 wt% of Paraffin Wax (PW) and High Density Polyethylene (HDPE) as binders at $160^{\circ}C$ for 2 h. Rheological properties were investigated by using capillary rheometer. Apparent viscosities of mixtures were 80∼300 Paㆍs at 1,000$s^{-1}$ of a shear rate, it was good for the injection molding and depending on the compositions of binders. Short shot was formed at 15H5P5 (the ratio of HDPE : PW=5 : 5 in 15 wt% of binders) compacts without injection pressures and any noticeable defects were not formed at 45 kgf/$cm^{2}$ in 20H5P5 compacts. PW and HDPE were removed by the solvent extraction and thermal debinding method. Thermal debinding of HDPE at $450^{\circ}C$ for 5 h, which followed the extraction of PW was using n-heptane solvent at $70^{\circ}C$ for 5 h. Continuous pores in compacts, which facilitate the removal of HDPE by the thermal debinding, were found to form in the compacts when PW was removed by the solvent extraction. The optimum composition of binder at which binder was removed by thermal debinding without defects while maintaining the compact strength was 20H5P5. Bulk density, porosity and 3-point bending strength of 20H5P5 compact sintered at 1,30$0^{\circ}C$ for 5 h were 2.8, < 3%, and 2,400 kgf/$cm^{2}$, respectively, and can be used as a structural materials.