• Tunnel and Underground Space
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• v.31 no.4
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• pp.221-242
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• 2021

A numerical study of the performance assesment of coupled thermo-hydro-mechanical (THM) processes in improved Korean reference disposal system (KRS⁺) for high-level radioactive waste is conducted using TOUGH2-MP/FLAC3D simulator. Decay heat from high-level radioactive waste increases the temperature of the repository, and it decreases as decay heat is reduced. The maximum temperature of the repository is below a maximum temperature criterion of 100℃. Saturation of bentonite buffer adjacent to the canister is initially reduced due to pore water evaporation induced by temperature increase. Bentonite buffer is saturated 250 years after the disposal of high-level radioactive waste by inflow of groundwater from the surrounding rock mass. Initial saturation of rock mass decreases as groundwater in rock mass is moved to bentnonite buffer by suction, but rock mass is saturated after inflow of groundwater from the far-field area. Stress changes at rock mass are compared to the Mohr-Coulomb failure criterion and the spalling strength in order to investigate the potential rock failure by thermal stress and swelling pressure. Additional simulations are conducted with the reduced spacing of deposition holes. The maximum temperature of bentonite buffer exceeds 100℃ as deposition hole spacing is smaller than 5.5 m. However, temperature of about 56.1% volume of bentonite buffer is below 90℃. The methodology of numerical modeling used in this study can be applied to the performance assessment of coupled THM processes for high-level radioactive waste repositories with various input parameters and geological conditions such as site-specific stress models and geothermal gradients.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2008.05a
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• pp.290-294
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• 2008

Conversion of the building can be a core strategy to activate the urban regeneration. Especially in the decayed district, the conversion or retrofit of old building can be a core catalyst to stimulate the urban regeneration. Throughout the case study, a conversion from office to dwelling, there were figured out the design strategies to respond to spatial, functional requirements. The results are as follows ; 1) The main design strategy is to articulate the space by embedding the wall, mass in the rectangular space. 2) to respond to the small size of space, the flexible, movable wall system Is adopted. This gives the selectiveness to the use of space. 3) to secure the livability of interior space, the buffer zone, a terrace space, is fully utilized. This space acts as thermal buffer zone as well as a semi-interior space.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.7-14
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• 2019

The compacted bentonite buffer is one of the major components of an engineered barrier system (EBS) for the disposal of high-level radioactive waste (HLW), and it is considered the best candidate for the buffer material. The buffer is located between disposal canisters and near-field rock mass, and it interrupts the release of radionuclide from disposal canisters and protect them from the penetration of groundwater. At initial disposal condition, degree of saturation of the compacted bentonite buffer decreases because of high thermal quantities released from the disposal canisters. However, the degree of saturation of the compacted bentonite buffer gradually increases caused by inflow of groundwater. The saturated and unsaturated behavior of the buffer is a very important input data since it can determine the safety performance of EBS. Therefore, this paper investigated water retention capacity (WRC) for the Korean compacted bentonite buffer. The WRC of the compacted bentonite buffer was derived by measuring volumetric water content and water suction when temperature variation was between 24℃~125℃ considering decrease of degree of saturation with respect to temperature increase. The WRC was also derived with the same volumetric water content under the room temperature condition, and it showed 1~15% larger water suction than high temperature condition.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.34-39
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• 2006

This study provides the electrical model of combustible catalytic gas sensor. Physical characteristics such as thermal behavior, resistance change were included in this model. The finite element method analysis for sensor device structure showed that the thermal behavior of sensor is expressed in a simple electrical equivalent circuit that consists of a resistor, a capacitor and a current source. This thermal equivalent circuit interfaces with real electrical circuit using two parts. One is 'power to heat' converter. The other is temperature dependent variable resistor. These parts realized with the analog behavior devices of the SPICE library. The gas response tendency was represented from the mass transferring limitation theory and the combustion theory. In this model, Gas concentration that is expressed in voltage at the model, is converted to heat and is flowed to the thermal equivalent circuit. This model is tested in several circuit simulations. The resistance change of device, the delay time due to thermal capacity, the gas responses output voltage that are calculated from SPICE simulations correspond well to real results from measuring in electrical circuits. Also good simulation result can be produced in the more complicated circuit that includes amplifier, bios circiut, buffer part.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.50.2-50.2
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• 2009

지구관측위성의 광학탑재체 내부에 장착된 초점면결상장치(FPA, Focal Plane Assembly)는 영상촬영시 많은 열을 발생하며, 최상성능획득을 위해서는 온도가 좁은 온도범위 내에서 유지되어야 한다. 초점면결상장치가 짧은 시간 동안 많은 열을 발생할 때, 이를 효과적으로 냉각시키기 위해 보통 히트파이프와 복사방열판을 이용한다. 이번 연구에서는 초점면결상장치의 최대상승온도를 낮추고, 영상촬영대기시 최적온도유지를 위한 히터작동율을 낮추기 위해 초점면결상장치와 복사방열판 사이에 열완충질량(TBM, Thermal Buffer Mass)을 적용하였는데, 이를 통해 얻을 수 있는 열설계 개선효과에 대해서 기술한다.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.363-373
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• 2018

The evaluation of Thermo-Hydro-Mechanical (THM) coupling behavior is important for the development of underground space for various purposes. For a high-level radioactive waste repository excavated in a deep underground rock mass, the accurate prediction of the complex THM behavior is essential for the long-term safety and stability assessment. In order to develop reliable THM analysis techniques effectively, an international cooperation project, Development of Coupled models and their Validation against Experiments (DECOVALEX), was carried out. In DECOVALEX-2015 Task B2, the in situ THM experiment that was conducted at Horonobe Underground Research Laboratory(URL) by Japan Atomic Energy Agency (JAEA), was modeled by the research teams from the participating countries. In this study, a THM coupling technique that combined TOUGH2 and FLAC3D was developed and applied to the THM analysis for the in situ experiment, in which rock, buffer, backfill, sand, and heater were installed. With the assistance of an artificial neural network, the boundary conditions for the experiment could be adequately implemented in the modeling. The thermal, hydraulic, and mechanical results from the modeling were compared with the measurements from the in situ THM experiment. The predicted buffer temperature from the THM modelling was about $10^{\circ}C$ higher than measurement near by the overpack. At the other locations far from the overpack, modelling predicted slightly lower temperature than measurement. Even though the magnitude of pressure from the modeling was different from the measurements, the general trends of the variation with time were found to be similar.

• Fisheries and Aquatic Sciences
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• v.13 no.1
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• pp.36-48
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• 2010

An agar-degrading Agarivorans sp. AG17 strain was isolated from the red seaweed Grateloupia filicina collected from Jeju Island. A beta-agarase gene from Agarivorans sp. AG17 was cloned and designated as agrA. agrA has a 2,985 bp coding region encoding 995 amino acids and was classified into the glycoside hydrolase family (GHF)-50. Predicted molecular mass of the mature protein was 105 kDa. His-tagged agrA was overexpressed in Escherichia coli and purified as a fusion protein. The enzyme showed 158.8 unit/mg specific activity (optimum temperature at $65^{\circ}C$ and pH 5.5 in acetate buffer) with unique biochemical properties (high thermal and pH stabilities). Enzyme produced neoagarohexaose, neoagarotetraose and neoagarobiose by degrading agar, and hydrolyzed neoagaro-oligosaccharides were biologically active. Hence the purified enzyme has potential for use in industrial applications such as the development of cosmetics and pharmaceuticals.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.485-490
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• 2003

We have developed a new way of the constant growth technique to maintain a grating height of originally-etched V-groove of submicron gratings up to 1.5 $\mu\textrm{m}$ thickness by a low pressure metalorganic chemical vapor deposition. The constant growth technique is well performed on two kinds of submicron gratings that made by holography and electron (e)-beam lithography GaAs buffer layer grown on thermally deformed submicron gratings has an important role in recovering the deformed grating profile from sinusoidal to V-shaped by reducing mass transport effects. The thermal deformation effect on submicron gratings made by e-beam lithography is less than that on submicron gratings made by holography. The constant growth technique is an important step to realize complex optoelectronic devices such as one-step grown distributed feedback lasers and two-dimensional photonic crystals.

• Journal of Microbiology and Biotechnology
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• v.17 no.4
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• pp.624-631
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• 2007

Thermostable protease is very effective to improve the industrial processes in many fields. Two thermostable extracellular proteases from the culture supernatant of the thermophilic fungus Chaetomium thermophilum were purified to homogeneity by tractional ammonium sulfate precipitation, ion-exchange chromatography on DEAE-Sepharose, and Phenyl-Sepharose hydrophobic interaction chromatography. By SDS-PAGE, the molecular mass of the two purified enzymes was estimated to be 33 kDa and 63 kDa, respectively. The two proteases were found to be inhibited by PMSF, but not by iodoacetamide and EDTA. The 33 kDa protease (PRO33) exhibited maximal activity at pH 10.0 and the 63kDa protease (PRO63) at pH5.0. The optimum temperature for the two proteases was $65^{\circ}C$. The PRO33 had a $K_m$ value of 6.6mM and a $V_{max}$ value of $10.31{\mu}mol/l/min$, and PRO63 l7.6mM and $9.08{\mu}mol/l/min$, with casein as substrate. They were thermostable at $60^{\circ}C$. The protease activity of PRO33 and PRO63 remained at 67.2% and 17.31%, respectively, after incubation at $70^{\circ}C$ for 1h. The thermal stability of the two enzymes was significantly enhanced by $Ca^{2+}$. The residual activity of PRO33 and PRO63 at $70^{\circ}C$ after 60min was approximately 88.59% and 39.2%, respectively, when kept in the buffer containing $Ca^{2+}$. These properties make them applicable for many biotechnological purposes.

• Archives of Pharmacal Research
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• v.25 no.1
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• pp.39-44
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• 2002

Recently, we have reported that 2-bromopropane might have an immunotoxic potential in rats when exposed for 28 days. In the present studies, the possibility of 2i-deoxyguanosine abduct formation by 2- bromopropane was investigated in vitro to elucidate molecular mechanism of 2-bromopropane-induced immunosuppression. $N^7-Guanine adduct$ of 2'-bromopropane (i.e., $N^7-isopropyl$ guanine) was chemically synthesized and structurally characterized by analysis of UV,$^1H-NMR,{\;}^{13}C-NMR$, COSY and fast atom bombardment mass spectrometry to use as a reference material. Incubation of 2'-deoxyguanosine with an excess amount of 2-bromopropane in PBS buffer solution, pH 7.4, at $37^{\circ}C$ for 16 h, followed by a thermal hydrolysis, produced a detectable amount of $N^7-isopropyl$ guanine by an HPLC and UV analysis. The present results suggest that 2-bromopropane might form a DNA adduct in $N^7-position$ of 2'-deoxyguanosine at 3 Physiological condition.