• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.586-593
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• 2014

The CNUSAIL-1 project aims to develop and operate a 3U-sized cube satellite with solar sail mechanism. The primary mission is to successfully deploy the solar sail in a low earth orbit, and the secondary mission is to collect the scientific data for the effect of the solar sail deployment and operation on orbit maneuver and attitude change of the cube satellite. For this, the bus system will collect and transmit the dynamic data of the satellite and the visual images of the solar sail operation. This paper describes solar sail mission and conceptual design of CNUSAIL-1. The actuation/operation of the solar sail and the bus system are preliminarily designed in terms of attitude control system, communication system, electrical power system, command and data handling system, structure and thermal control system is designed.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.401-418
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• 2000

1. Production of the artificial zeolite from coal ash Coal fly ash is mainly composed of several oxides including $SiO_2$ and $Al_2O_3$ derived from inorganic compounds remained after burning. As minor components, $Fe_2O_3$ and oxides of Mg, Ca, P, Ti (trace) are also contained in the ash. These components are presented as glass form resulting from fusion in the process of the combustion of coal. In other word, coal ash may refer to a kind of aluminosilicate glass that is known to easily change to zeolite-like materials by hydrothermal reaction. Lots of hot seawater is disposing near thermal power plants after cooling turbine generator periodically. Using seawater in the hydrothermal reaction caused to produce low price artificial zeolite by reduction of sodium hydroxide consumption, heating energy and water cost. As coal ash were reacted hydrothermally, peaks of quartz and mullite in the ash were weakened and disappeared, and new Na-Pl peaks were appeared strengthily. Si-O-Si bonding of the bituminous coal ash was changed to Si-O-Al (and $Fe^{3+}$) bonding by the reaction. Therefore the produced Na-Pl type zeolite had high CEC of 276.7 $cmol^+{\cdot}kg^{-1}$ and well developed molecular sieve structure with low concentration of heavy metals. 2. Utilization of the artificial zeolite in agro-environment The artificial zeolite(1g) could remove 123.5 mg of zinc, 164.7 mg copper, 184.4 mg cadmium and 350.6 mg lead in the synthetic wastewater. The removability is higher 2.8 times in zinc, 3.3 times in copper, 4.7 times in cadmium and 4.8 times in lead than natural zeolite and charcoal powder. When the heavy metals were treated at the ratio of 150 $kg{\cdot}ha^{-1}$ to the rice plant, various growth inhibition were observed; brownish discoloration and death of leaf sheath, growth inhibition in culm length, number of panicles and grains, grain ripening and rice yield. But these growth inhibition was greatly alleviated by the application of artificial zeolite, therefore, rice yield increased $1.1{\sim}3.2$ times according to the metal kind. In addition, the concentration of heavy metals in the brown rice also lowered by $27{\sim}75%$. Artificial Granular Zeolites (AGZ) was developed for the purification of wastewater. Canon exchange capacity was 126.8 $cmol^+{\cdot}kg^{-1}$. AGZ had Na-Pl peaks mainly with some minor $C_3S$ peaks in X-ray diffractogram. In addition, AGZs had various pore structure that may be adhere the suspended solid and offer microbiological niche to decompose organic pollutants. AGZ could remove ammonium, orthophosphate and heavy metals simultaneously. Mixing ratio of artificial zeolite in AGZs was related positively with removal efficiency of $NH_4\;^+$ and negatively with that of $PO_4\;^{3-}$. Root growth of rice seedling was inhibited severely in the mine wastewater because of strong acidity and high concentration of heavy metals. As AGZ(1 kg) stayed in the wastewater(100L) for 4days, water quality turned into safely for agricultural usage and rice seedlings grew normally.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.293-304
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• 2017

This study was performed in order to hydrogeological analysis of aquifer, which is a necessary part for evaluating the efficiency of the combined well and open-closed loops geothermal (CWG) systems. CWG systems have been proposed for the effective utilization of geothermal energy by combining open loop geothermal systems and closed loop geothermal systems. Small aperture CWG systems and large aperture CWG systems were installed at a green house land with water curtain facilities in Chungju City. Aquifer tests include pumping tests and step-drawdown tests were conducted to analyse hydrogeological characteristics of aquifer in the study area. The transmissivity was estimated in the range of $13.49{\sim}58.99cm^2/sec$, and the storativity was estimated in the range of $1.13{\times}10^{-5}{\sim}5.20{\times}10^{-3}$. The geochemical analysis showed $Ca^{2+}$ ion and ${HCO_3}^-$ ion were dominant in groundwater. The Langelier Saturation Index and the Ryznar Stability Index showed low scaling potential of groundwater. In the analysis of vertical water temperature change, the geothermal gradient was estimated as $2.1^{\circ}C/100m$, which indicated the aquifer was enough for geothermal systems. In conclusion, groundwater is rich, can stably use geothermal heat, and it is less likely to cause deterioration of thermal energy efficiency by precipitation of carbonate minerals in study area. Therefore, the study area is suitable for installation of the combined geothermal system.

• Korean Journal of Food Science and Technology
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• v.23 no.1
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• pp.76-80
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• 1991

To isolate oryzanol from the by-product of rice bran oil refinning, experiment of solvent fractional crystallization was carried out at various conditions with the dark oil obtained by acidifying the soap stock of micella refinning process and the pitch obtained from vacuum distillation of the dark oil. The impurity interfering the crystallization process such as waxes can be removed as precipitates by cooling the 1:1 mixtrue of acetone and dark oil to $0^{\circ}C$, From the dewaxed dark oil, oryzanol concentrate with 51.3% purity was obtained by fractional crystallization at$0^{\circ}C$ with the mixture of 8 part volume of hexane and 1 part of the dewaxed dark oil. The concentrate was recrystallized at room temperature with 20 part volume of methanol to yield oryzanol crystal of 98.3% purity. The optimum condition of vacuum distillation was temperature of $180^{\circ}C\;at\;0.2{\sim}0.4\;torr$ with 2% steam sparging. At this condition, the free fatty acid in the dark oil was removed as distillate without thermal deomposition to yield 82.3% of oryzanol as the pitch of 27.3% purity. After concentration from the pitch with 20 part volume of hexane to yield yellow powder of 75.4% purity, the yellow powder was recrystallized in methanol at room temperature to obtain the crystal containing 99.0% oryzanol. The overall oryzanol yield from the dark oil and the pitch was 9.5 and 28.5%, respectively. The change of the composition of sterols and triterpenoid alcohols in the compounds isolated during fractionation was analyzed by GC-MS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.8-13
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• 2018

Nitrogen oxides (NOx) have recently been very influential in the generation of ultrafine dust, which is of great social interest in terms of improving the atmospheric environment. Nitrogen oxides are generated mainly by the reaction of nitrogen and oxygen in air in a combustion gas atmosphere of high temperature in a combustion apparatus such as thermal power generation. Recently, research has been conducted on the combustion that recirculates the exhaust gas to the cylindrical burner by using a piping using a Coanda nozzle. In this study, three types of burners were carried out through computational fluid analysis. Case 1 burner with the outlet of the combustion gas to the right, Case 2 burner with both sides as gas exit, Case 3 burner with left side gas exit. The pressure, flow, temperature, combustion reaction rate and distribution characteristics of nitrogen oxides were compared and analyzed. The combustion reaction occurred in Case 1 and Case 2 burner in the right direction with combustion gas recirculation inlet and Case 3 burner in the vicinity of mixed gas inlet. The temperature at the outlet was about $100^{\circ}C$ lower than that of the other burners as the Case 2 burner was exhausted to both sides. The NOx concentration of Case 1 burner at the exit was about 20 times larger than that of the other burners. From the present study, it could be seen that it is effective for the NOx reduction to exhaust the exhaust gas to both side gas exits or to exhaust the exhaust gas to the opposite direction of inlet of recirculation gas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.66-73
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• 2020

In the hydrogen compression cycle, which is currently being developed, hydrogen is compressed to a very high pressure using a compressor, and then stored and used in a high-pressure vessel. This shows that an increase in the temperature of hydrogen in the vessel due to a pressure rise during the filling process and the pressure fatigue due to the repeated cycle may cause problems in the reliability of the vessel. In this paper, for the entire processes in a 50 MPa hydrogen compression system, theoretical and numerical methods were conducted to analyze the following: the temperature increase of hydrogen in the vessel and the time required to reach thermal equilibrium with the surroundings, the change in temperature of hydrogen passing through the pressure reducing valve, and the required capacity of the heat exchanger for cooling the vessel. The results will be useful for the design and construction of hydrogen compression systems, such as hydrogen charging stations.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.2
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• pp.49-57
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• 2020

Due to the sewage sludge's characteristics of high water content and low calorific value, it is hard to use sewage sludge as an energy source. In this study, we investigated production of bio-solid fuel which is mixed both sewage sludge and woody biomass in order to improve the sewage sludge's characteristics and replace fossil fuels. A thermogravimetric analysis was used to investigate the co-combustion characteristics of the mixed coal and bio-solid fuel of 5%, 10%, 15%, respectively. The analysis was carried out under non-isothermal conditions by raising the internal temperature of 25℃ to 900℃ with an increment of 10℃/min. In the case of comparing single coal sample and mixture sample of coal and bio-solid fuel, the initiation combustion temperature has slightly changed. However, both the maximum combustion temperature and the termination start combustion temperature were hardly noticeable. The initiation combustion was occurred between 200~315℃ and the thermal decomposition causing a significant weight change occurred between 350~700℃. As a result of the kinetic analysis of the co-combustion, the activation energy was decreased as the mixing rate was higher. Therefore, it is able to co-combust the mixed coal and bio-solid fuel in power plants.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.713-719
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• 2016

The NOx conversion properties of Mn-Cu-$TiO_2$ and $V_2O_5$/$TiO_2$ catalysts were studied for the selective catalytic reduction (SCR) of NOx with ammonia. The performance of the catalysts was investigated in terms of their $NOx$ conversion activity as a function of the reaction temperature and space velocity. The activity of the Mn-Cu-$TiO_2$ catalyst decreased with increasing reaction temperature and space velocity. However, the activity of the $V_2O_5$/$TiO_2$ catalyst increased with increasing reaction temperature. High activity of the Mn-Cu-$TiO_2$ catalyst was observed at temperatures below $200^{\circ}C$. H2-TPR and XPS analyses were conducted to explain these results. It was found that the activity of the Mn-Cu-$TiO_2$ catalyst was influenced by the thermal shock caused by the change of the initial reaction temperature, whereas the $V_2O_5$/$TiO_2$ catalyst was not affected by the initial reaction temperature. In the case of catalyst C, the $NO_x$ conversion efficiency decreased with increasing space velocity. The decrease in the $NO_x$ conversion efficiency with increasing space velocity was much less for catalyst D than for catalyst C.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.1
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• pp.71-76
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• 2002

To understand the effect of heated effluent from a nuclear power plant on marine organism, experimental culture of Halocynthia roretzi was carried out at heated effluent of Wolsung nuclear power plant from January to December 1996. Temperature was $11.2\~27.9^{\circ}C$ and salinity was $32.54\~34.59\%_{\circ}$ during the culture period, The Growth of H. roretzi on lower area of Bonggil-ri (St. 1) was not normal in height, breadth and weight due to heated effluent. Daily growth rate (DGR) of H. roretzi about Kampo area (St, 4) was significant other station, and St. 1 was significant from other station except St. 4, Mytilus edulis was major fouling organism (over $90\%$) that were M. edulis, Dideninum moseleyi, Styela clava in experiment culture farm. St. 1 was higher (mean 143 individual) and St. 4 was lower (mean 56 individual) appearance attached of M. edulis. Growth of H. roretzi reduced when attached number of M. eduiis was increased, because correlation between DGR and number of M. edulis was negative.

• Journal of Microbiology and Biotechnology
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• v.23 no.11
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• pp.1519-1528
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• 2013

Bacillus pumilus SG2, a halotolerant strain, expresses two major chitinases designated ChiS and ChiL that were induced by chitin and secreted into the supernatant. The present work aimed to obtain a mutant with higher chitinolytic activity through mutagenesis of Bacillus pumilus SG2 using a combination of UV irradiation and nitrous acid treatment. Following mutagenesis and screening on chitin agar and subsequent formation of halos, the mutated strains were examined for degradation of chitin under different conditions. A mutant designated AV2-9 was selected owing to its higher chitinase activity. To search for possible mutations in the whole operon including ChiS and ChiL, the entire chitinase operon, including the intergenic region, promoter, and two areas corresponding to the ChiS and ChiL ORF, was suquenced. Nucleotide sequence analysis of the complete chitinase operon from the SG2 and AV2-9 strains showed the presence of a mutation in the catalytic domain (GH18) of chitinase (ChiL). The results demonstrated that a single base change had occurred in the ChiL sequence in AV2-9. The wild-type chitinase, ChiL, and the mutant (designated ChiLm) were cloned, expressed, and purified in E. coli. Both enzymes showed similar profiles of activity at different ranges of pH, NaCl concentration, and temperature, but the mutant enzyme showed approximately 30% higher catalytic activity under all the conditions tested. The results obtained in this study showed that the thermal stability of chitinase increased in the mutant strain. Bioinformatics analysis was performed to predict changes in the stability of proteins caused by mutation.