• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.533-549
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• 2024

Soil conditioning is a critical process when tunneling with an earth pressure balance (EPB) shield tunnel boring machine (TBM) to enhance performance. To determine the optimal additive injection conditions, it is important to understand the rheological properties of conditioned soil, which is typically assessed using a rheometer. However, a rheometer cannot simulate the actual process of muck discharge in a TBM. Therefore, in this study, a scaled-down model of an 8-meter-class EPB shield TBM chamber and screw conveyor, reduced by a factor of 1:20, was fabricated and its applicability was evaluated through laboratory experiments. A lab-scale model experiment was conducted on artificial sandy soil using foam and polymer as additives. The experimental results confirmed that screw torque was consistent with trends observed in previous laboratory pressurized vane shear test data, establishing a positive proportional relationship between screw torque and yield stress. The muck discharge efficiency according to foam injection ratio (FIR) showed similar values overall, but decreased slightly at 60% of FIR and when the polymer was added. In addition, the pressure distribution generated along the chamber and screw conveyor was assessed in a manner similar to the actual EPB TBM. This study demonstrates that the lab-scale screw conveyor model can be used to evaluate the shear properties and muck discharge efficiency.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.3
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• pp.298-307
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• 2010

The purpose of this study was to assess the effect on oxygen inhibition layer(OIL) for the interfacial bonding between resin composite layers, including shear bond strength, fracture modes and degree of conversion. The first layer of specimen was filled with Z-250(shade A3) and was cured for 40s. The second layer of specimen was filled with same composite(shade A1) and was cured for 40s. The first layer of specimens for each group were prepared by methods as followings. Control(curing in atmospheric air), Group1(curing against Mylar strip), Group2(scrubbed with a acetone-soaked cotton), Group3(using Tescera light cup), Group4(using Tescera heat cup), Group5(stored in disti1led water for 30days at $37^{\circ}C$), Group6 (using bonding agent). The results were as follows: 1. There was no statistically significant different shear bond strength between control and group 1(p>0.05). 2. Group 2 showed significantly lower shear bond strength than control and group 1(p<0.05). 3. The observation of the fracture surface leads to the evidence that a major difference occurs in the case of control, group1 and group 3 samples which break mainly cohesively while the other groups break in majority adhesively. 4. The results of FTIR showed that the degree of conversion was the highest in group 2 and the lowest in control group(p<0.05). It can be concluded that an OIL is not necessary for bonding with composite resin. But if a reduced critical amount of the unreacted monomer is present, it was detrimental to bonding additional layers of composite. Further study, such as the quantitative analysis of the unreacted monomer are required.

• Food Science and Preservation
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• v.22 no.3
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• pp.428-436
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• 2015

Five extraction conditions (AE, autoclave extraction; OE, oven extraction; HWSE, hot water and sonication extraction; HWASE, hot water acidified with 0.5% (v/v) acetic acid and sonication extraction; and BE, boiling extraction) were examined to compare the effects of different hot water extraction methods on the antioxidant properties of blueberries. The extraction yields of the AE, OE, HWSE, HWASE, and BE were 7.94%, 8.35%, 8.55% 9.15%, and 8.50%, respectively. The polyphenol and flavonoid contents of AE were 3.47 mg GAE/g and 1.59 mg RE/g, respectively, which were highest centents among others. Those of OE were ranked second to the highest. The total anthocyanin content of HWSE (5.29 mg/g) was significantly higher than that of others whereas that of AE showed the lowest content (0.96 mg/g). The order of ABTS radical and alkyl radical scavenging activities was as follows: AE > BE > OE > HWSE > HWASE. The antioxidant properties were considerably correspondent with the total polyphenol and flavonoid content. DPPH radical scavenging activity was quite high in HWSE, AE, and BE extraction, however, there were no significant differences among the five extraction methods in the aspect of $Fe^{2+}$ ion chelating activities. Moreover, AE showed the highest SOD activity, and protected the dermal fibroblast the best against $H_2O_2$-induced cytotoxicity. In conclusion, it was suggested that the autoclave extraction (AE) would be the most effective method for preparing blueberry hot water extracts with relatively high antioxidant activities.

• Food Science and Preservation
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• v.24 no.8
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• pp.1129-1137
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• 2017

The fringe tree, Chionanthus retusus (Oleaceae) has been used as a natural remedy that helps a paralytic stroke, dementia, phlegm and malaria. This study was conducted to investigate the antioxidant and anti-aging activities of water extracts obtained from the flesh of C. retusus by reflux extraction at room temperature and $80^{\circ}C$, and pressure heating extraction at $110^{\circ}C$, for an increment of their practical use. The highest extraction yield from the flesh of C. retusus was 67.94% extract by pressure heating extraction at $110^{\circ}C$. The content of total polyphenol compounds was the highest by 72.71 mg/g in $80^{\circ}C$ extract by reflux extraction. The highest content of total flavonoid compounds was 7.60 mg/g at $110^{\circ}C$ extract. The results of soluble protein and reducing sugar contents showed the highest content of 4.93 mg/g and 46.77 mg/g in $110^{\circ}C$ extract, respectively. In the analysis of DPPH radical scavenging activity, all extracts showed an excellent effect of 92% in 1.0 mg/mL concentration. The highest effect of ABTS radical scavenging activity was 88.67% at $110^{\circ}C$ extraction in 1.0 mg/mL concentration. Nitrite scavenging ability was the highest as 66.16% at $110^{\circ}C$ extract at pH 1.2 and 1.0 mg/mL concentration. The results of SOD-like activity and xanthine oxidase inhibition activities showed the highest effect of 14.95% and 59.45% at $110^{\circ}C$ extract in 1.0 mg/mL, respectively. Tyrosinase inhibition activity for whitening effect was the highest of 35.31% at $85^{\circ}C$ in 1.0 mg/mL. In the analysis of anti-aging effect, collagenase and elastase inhibition activity showed the highest effects of 37.78% at $110^{\circ}C$ and 20.39% at $80^{\circ}C$, respectively. All results of antioxidant activities and anti-aging effects increased along with the concentration increases. These results indicated that the extracts extracted from the flesh of C. retusus at $80^{\circ}C$ and $110^{\circ}C$ have a large amount of useful ingredients, an excellent antioxidant activity, like as DPPH and ABTS radical scavenging activity, and anti-aging effects to develop functional products than those of $25^{\circ}C$.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.871-877
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• 2018

Storing the surplus energy from renewable energy resource is one of the challenges related to intermittent and fluctuating nature of renewable energy electricity production. $CO_2$ methanation is well known reaction that as a renewable energy storage system. $CO_2$ methanation requires a catalyst to be active at relatively low temperatures ($250-500^{\circ}C$) and selectivity towards methane. In this study, the catalytic performance test was conducted using a pressurized bubbling fluidized bed reactor (Diameter: 0.025 m and Height: 0.35 m) with $Ni/{\gamma}-Al_2O_3$ (Ni70%, and ${\gamma}-Al_2O_3$30%) catalyst. The range of the reaction conditions were $H_2/CO_2$ mole ratio range of 4.0-6.0, temperature of $300-420^{\circ}C$, pressure of 1-9 bar, and gas velocity ($U_0/U_{mf}$) of 1-5. As the $H_2/CO_2$ mole ratio, temperature and pressure increased, $CO_2$ conversion increases at the experimental temperature range. However, $CO_2$ conversion decreases with increasing gas velocity due to poor mixing characteristics in the fluidized bed. The maximum $CO_2$ conversion of 99.6% was obtained with the operating condition as follows; $H_2/CO_2$ ratio of 5, temperature of $400^{\circ}C$, pressure of 9 bar, and $U_0/U_{mf}$ of 1.4-3.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.3
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• pp.191-201
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• 1987

Seasoned sardine meat was prepared to extend the use of sardine for human consumption, and processing conditions and storage stability of frozen seasoned sardine meat were studied during storage at $-20^{\circ}C$. The fish was beheaded, gutted and cleaned in a washing tank. The washed fish was then put through a belt-drum type meat separator which separates the flesh iron the bone and skin. Mechanically deboned fish meat was mixed with $20.6\%$ emulsion curd, $0.5\%$ table salt, $2.0\%$ sugar, $0.4\%$ sodium bicarbonate, $0.2\%$ polyphosphate, $0.1\%$ monosodium glutamate, $0.3\%$ onion powder, $0.1\%$ garlic powder, $0.1\%$ ginger powder, $3.0\%$ soybean protein and $0.1\%$. In sodium erythorbate. This seasoned sardine meat was frozen with contact freezer, packed in a carton box and then stored at $-20^{\circ}C$. The pH, volatile basic nitrogen, viable cell counts, peroxide value, carbonyl value, thiobarbituric acid value, taste compounds, fatty acid composition, salt extractable nitrogen, drip, texture, and color values of the products were determined during frozen storage. The results showed that lipid content in products could be controlled by using emulsion curd, and flavor and texture could be improved by adding spices and soybean protein, and lipid oxidation could be retarded by $0.1\%$ sodium erythorbate. Judging from the results of chemical experiments and sensory evaluation, the products can be preserved in a good quality for 120 days during frozen storage.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.219-222
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• 1996

수열법은 밀폐용기중에서 10$0^{\circ}C$이상의 가열, 가압된 수용액이 반응에 관여하는 것으로써, 수정, CaCO3, AlPO4, GaPO4 등과 같은 단결정의 육성 뿐만 아니라 균일분산계로부터 균일한 결정성의 미립자 합성에도 폭넓게 이용되고 있다. 세라믹분말의 합성에 있어서, 이 방법은 특히 형상, 입자크기의 제어가 용이할 뿐만 아니라 고상법, 졸-겔법, 공침법에서와 같은 열처리, 분쇄과정이 필요없기 때문에 고순도의 초미립자를 얻을 수 있는 장점이 있다. 근년 미국, 일본에서는 수열법을 이용한 유전, 압전체 등 세라믹분말의 일부가 공업적인 규모로 대량 생산되고 있다. 그러나 이에 대한 국내 기술은 아직 초기단계에 이르고 있는 실정이다. 따라서 본 연구실에서는 수열법에 의한 단결정 육성 (예; 자수정, CaCO3, AlPO4, GaPO4, KTP, Emerald 등), 박막제조 (예; GaP, PbTiO3, BaTiO3 등), 정제 (고령토, 장석, 도석 등), 원석처리 (진주, 인공 emerald, 비취 등) 그리고 각종 세라믹분말의 합성 등과 같은 다양한 기반기술의 축적과 동시에 공업화에 대응한 수열장치를 위하여 반응용기의 대형화, 엄밀한 밀폐방식, 실용적인 수열조건 등을 개발해 오고 있다. 본 발표에서는 현재까지의 연구개발 내용 중에서 결정성 미립자에 관련한 세라믹분말의 합성에 대한 일부의 결과들을 보고한다. 일반적으로 수열장치는 전기로, 반응용기, 온도 및 압력제어계 등을 기본으로 하고 있으며 시판용의 대부분이 교반기가 부착된 수직형 (vertical type)이다. 이와 같은 방식에 있어서는 엄밀한 밀폐가 곤란, 반응온도의 한계성 (25$0^{\circ}C$ 이하), 증진율의 한계성 (소량생산) 등과 같은 점이 있기 때문에 본 연구실에서는 개폐식 전기로내에 엄밀한 밀폐가 가능한 수평식(horizontal type)의 반응용기를 채택한 뒤 이를 회전 또는 시이소(seesaw)식으로 움직일 수 있도록 하여 연속공정화, 온도구배의 자율조절 그리고 보다 저온에서도 인위적인 이온의 확산을 효율적으로 유도할 수 있도록 하였다. 이와 같은 방식은 기존의 방식과 비교하여 반응용기 내에 응집현상과 미반응물이 존재하지 않으며 또한 단분산으로 결정성 미립자를 대량적으로 얻을 수 있는 장점이 있었다. 다음은 이상과 같이 본 연구실에서 자체 개발한 수열장치를 이용하여 PbTiO3, (Pb,La)TiO3Mn, BaTiO3, ZnSiO4:Mn, CaWO4 등과 같은 세라믹분말에 대한 합성 실험의 결과이다. 압전성, 초전성이 우수한 PbTiO3 및 (Pb,La)TiO3:Mn 분말의 수열합성은 PbO, TiO2, La2O3 등의 분말을 출발원료로 하여 합성도도 25$0^{\circ}C$부근의 알카리성 용액중에서 결정성 PbTiO3 및 (Pb,La)TiO3:Mn 미립자를 단상으로 얻었으며 입자의 형상 및 크기는 합성온도와 수열용매의 종류에 의존하였다. 유전체로서 폭넓게 응용되고 있는 BaTiO3 분말은 Ba(OH)2.8H2O, TiO2와 같은 최적의 출발원료를 선택함으로써 15$0^{\circ}C$ 부근의 저온영역에서도 용이하게 합성할 수 있었다. 특히 본 연구에서는 수용성인 Ba(OH)2.8H2O를 사용함으로써 host-guest적인 반응을 유도시키는데 있어 물의 가장 실용적이고 효과적인 수열용매임도 알았다. ZnSiO4:Mn, CaWO4, MgWO4와 같은 형광체 분말은 공업적으로 고상반응 또는 습식법에 의해 얻어지고 있으나 이들 방법에 있어서는 분쇄공정으로 인한 형광특성의 저하와 같은 문제점이 있다. 따라서 본 연구에서는 수열법을 이용하여 이들 화합물의 합성을 시도하였으며 그 결과 합성온도 30$0^{\circ}C$ 부근의 알칼리성 용액중에서 수열적으로 얻어짐을 알았다. 여기서의 합성분말을 이용하여 실제 조명램프로 제조한 결과 녹색, 청색 발광용 형광체로서 우수한 형광특성을 나타내었다. 천연에서 소량 산출되고 있는 고가의 (Li,Al)MnO2(OH)2:Co 분말은 도자기의 전사지용 청색안료로써 이용되고 있다. 본 연구실에서는 LiOH.H2O, Al(OH)3, MnO2 등의 분말을 출발원료로 하고 24$0^{\circ}C$ 온도 부근 그리고 물을 수열용매로 하여 천연산에 필적하는 (Li,Al)MnO2(OH)2:Co 분말을 인공적으로 합성하였다.

• Tunnel and Underground Space
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• v.32 no.5
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• pp.285-297
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• 2022

We report results of Extended Leak-Off Test (XLOT) conducted in a large diameter borehole, which is drilled for installation of deep borehole geophysical monitoring system to monitor micro-earthquakes and fault behavior of major fault zones in the southeastern Korean Peninsula. The borehole was planned to secure a final diameter of 200 mm (or more) at a depth of ~1 km, with 12" diameter wellbore to intermediate depths, and 7-7/8" (~200 mm) to the bottom hole depth. We drilled first the 12" borehole to approximately 504 m deep and installed American Petroleum Institute standard 8-5/8" casing, then annulus between the casing and bedrock was fully cemented. XLOT was carried out for several purposes such as confirming casing and cementing integrity, measuring rock stress states. To that end, we drilled additional 4 m long open hole interval to directly inject water and pressurize into the rock mass using the upper API casings. During the XLOT, flow rates and interval pressures were recorded in real time. Based on the logs we tried to analyze hydraulic conductivity of the test interval.