• Applied Biological Chemistry
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• v.47 no.2
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• pp.170-175
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• 2004

In this paper we studied about Bacillus sp. TBM40-3 producing biosurfactants. The strains were isolated from Taeback Mountain soil and identified as Bacillus sp. by l6S rDNA nucleotides sequence analysis. The TBM40-3 was gram-positive and rod-shaped as observed by field emission scanning microscopy. After the cultivation TBM40-3 in LB broth for 90 h and the surface tension of supernatant was decreased to 29 mN/m. Emulsification activity and stability of crude biosurfactant was measured by using water-immiscible hydrocarbons and oil as substrate. Maximum emulsification activity and stability was obtained from soybean oil. Also, we confirmed that the TBM40-3 producing biosurfactant had an effect on crude oil while showing a superior effect as compared to chemically synthesized surfactants (SDS, Span85, Tween40, Triton X-100). As a result, the Bacillus sp. TBM40-3 producing biosurfactant had potent properties as an emulsifying agent and an emulsion stabilizing agent.

• Journal of Animal Environmental Science
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• v.11 no.1
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• pp.25-34
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• 2005

The study aimed to develop a tractor drawn animal slurry manure sub-soil injector for arable land and thus, can reduce the waste management cost through effective treatment and utilization of animal slurry manure. The application of animal slurry manure to agricultural land will probably be one of the most effective ways to enrich the soil with vital nutrients. However, some existing slurry manure spenders are not suitable in the field because of their adverse effects to the environment. Based on this premise, a prototype was designed and assembled using 5 sub-soiling standards attached to the sin injector device. The traction force of the Prototype measured in the depth of 10 cm and 15 cm from the ground surface of a paddy field was 1,062 kgf and 1,214 kgf, respectively. A unique feature of the machine was that there was an equal volume of slurry manure flowing from each delivery pipe and regulated by a pressurized container that was likewise synchronized with the speed of the tractor The sub-soiling manure injection system can mitigate or reduce the harmful emission of obnoxious gases and malodor during the injection operation.

• Restorative Dentistry and Endodontics
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• v.29 no.6
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• pp.504-514
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• 2004

This study compared the dentin shear bond strengths of currently used dentin bonding agents that were irradiated with an LED (Elipar FreeLight, 3M-ESPE) and a halogen light (VIP, BISCO). The optical characteristics of two light curing units were evaluated. Extracted human third molars were prepared to expose the occlusal dentin and the bonding procedures were performed under the irradiation with each light curing unit. The dentin bonding agents used in this study were Scotchbond Multipurpose (3M ESPE), Single Bond (3M ESPE), One-Step (Bisco), Clearfil SE bond (Kuraray), and Adper Prompt (3M ESPE), The shear test was performed by employing the design of a chisel-on-iris supported with a Teflon wall. The fractured dentin surface was observed with SEM to determine the failure mode. The spectral appearance of the LED light curing unit was different from that of the halogen light curing unit in terms of maximum peak and distribution. The LED LCU (maximum peak in 465 nm) shows a narrower spectral distribution than the halogen LCU (maximum peak in 487 nm). With the exception of the Clearfil SE bond (P < 0.05), each 4 dentin bonding agents showed no significant difference between the halogen light-cured group and the LED light-cured group in the mean shear bond strength (P > 0.05). The results can be explained by the strong correlation between the absorption spectrum of camphoroquinone and the narrow emission spectrum of LED.

• Polymer(Korea)
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• v.36 no.1
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• pp.22-28
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• 2012

Functionalized graphene/epoxy composites were prepared to miprove thermal conductivities of epoxy composites and to maintain electrical insulating property. Graphene oxide (GO) was prepared using Hummers method, and then GO was reacted with aluminum isopropoxide to functionalize $Al(OH)_3$ layer onto GO surface by a simple sol-gel method (Al-GO). GO and Al-GO were characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The analyses confirm that GO was coated with a large and dense coverage of $Al(OH)_3$. GO and Al-GO (1 and 3 wt%) were embedded in bisphenol A (DGEBA) to investigate the effects of electrical insulating property. Electrical resistivity showed that Al-GO had better insulating property than GO. Further, the thermal conductivity of GO and Al-GO/epoxy composites was higher than that of neat epoxy resins. In particular, the thermal conductivity of Al-GO/bisphenol F (DGEBF) improved by 23.3% and Al-GO/DGEBA enhanced by 21.8% compared with pure epoxy resins.

• Journal of the Korean Wood Science and Technology
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• v.47 no.6
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• pp.732-750
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• 2019

Air drying was carried out on 15 Korean red pine logs to provide a prediction model of the moisture content (MC) change in the wood during drying. The final MC was 17.4% after 880 days since the beginning of air drying in the summer for 6 Korean red pine logs with 68.7% initial MC. The final MC was 16.0% after 760 days since the beginning of air drying in the winter for 9 Korean red pine logs with 35.8% initial MC. A regression model with R-squared of 0.925 was obtained as a result of multiple regression analyses with initial MC, top diameter, temperature, relative humidity, and wind speed as independent variable and and MC change during air drying as dependent variable. The initial MC and top diameter, which is the characteristic of Korean red pine, have greater effect on the MC decrease during air drying compared to meteorological factors such as the temperature, relative humidity, and wind speed. Two-dimensional mass transfer analysis was performed to predict the MC distribution of Korean red pine logs during air drying. Two prediction models with different air drying days and different meteorological factors for the determination of the diffusion coefficient and surface emission coefficient were presented. The error between the different two methods ranged from 0.1 to 0.8% and the difference from the measured value ranged from 2.2 to 3.6%. By measuring the internal MC during air drying of Korean pine logs with various initial MC and diameter, and calculating the moisture transfer coefficient in wood for each meteorological condition, the error of the prediction model can be reduced.

• Journal of Integrative Natural Science
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• v.4 no.1
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• pp.38-43
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• 2011

The recent global warming may be estimated to give lots of impacts to the human society and biosphere of influencing climate change included by the natural climate variations through the human activity which can directly and/or indirectly play a major role of total atmospheric composition overall. Therefore it currently appears evidences such as hot wave, typhoon, and biosphere disturbance, etc. over the several regions to be influenced by global warming due to increasing the concentration of greenhouse gases in the atmosphere through inducing forest destruction, fossil fuel combustion, greenhouse gases emission, etc. since industrial revolution era. Through the working group report of IPCC (Intergovernmental Panel on Climate Change) for climate change was analyzed by the individual country's current status and figure out the important issues and problems related to the future trend of climate change science with advanced countries preparedness and research, In this study, the first working group report of IPCC focuses on those aspects of the current understanding of the physical science of climate change that are judged to be most relevant to policymakers. As this report was assessed and analyzed by including the progress of climate change science, the role of climate models and evolution in the treatment of uncertainties. This consists of the changes in atmospheric constituents(both aerosols and gases) that affect the radiative energy balance in the atmosphere and determine the Earth's climate, considering the interaction between biogeochemical cycles that affect atmospheric constituents and climate change, including aerosol/cloud interactions, the extensive range of observations snow available for the atmosphere and surface, for snow, ice, and frozen ground and for the oceans, respectively and changes in sea level, the paleoclimate perspective and assessment of evidence for past climate change and the extension, the ways in which physical processes are simulated in climate models and the evaluation of models against observed climate, the development plans and methods of improving expert and building manpower urgently and R&D fund expansion in detail for climate change science in Korea will be proposed.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.332-339
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• 2015

The objective of this study was to evaluate the effectiveness of different biochars on the removal of heavy metals from aqueous media. The experiment was carried out in aqueous solutions containing $200mg\;CdL^{-1}$ or $200mg\;PbL^{-1}$ using two different biochars derived from soybean stover and orange peel (20 mg Cd or $Pbg^{-1}$ biochar). After shaking for 24 hours, biochars were filtered out, and Cd and Pb in the filtrate were analyzed by flame atomic absorption spectrophotometer (FAAS). In order to provide information regarding metal binding strength on biochars, sequential extraction was performed by modified SM&T (formerly BCR). The results showed that 70~100% of initially added Cd and Pb was adsorbed on biochars and removed from aqueous solution. The removal rate of Pb (95%, 100%) was higher than that of Cd (70%, 91%). In the case of Cd, orange peel derived biochar (91%) showed higher adsorption rate than soybean stover derived biochar (70%). Cd was adsorbed on the biochar mainly in exchangeable and carbonates fraction (1st phase). In contrast, Pb was adsorbed on it mainly in the form of Fe-Mn oxides and residual fraction (2nd and 4th phase). The existence of Cd and Pb as a form of surface-precipitated complex was also observed on the surfaces of biochars detected by field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDAX).

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.768-773
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• 2019

The Fenton reaction, which evaluates the electrochemical durability of polymer membranes of polymer electrolyte fuel cells (PEMFC), and the degradation of polymer membranes by OCV holding method are compared. The Fenton reaction is a method that can evaluate the chemical durability of the polymer membrane at outside the cell in a shorter time than the OCV Holding method. The Fenton reaction was carried out at 30% hydrogen peroxide, 10 ppm iron, and $80^{\circ}C$ for 24 hours. OCV Holding was driven at $90^{\circ}C$, 30% relative humidity and OCV for 168 hours. The Fenton reaction caused a lot of degradation inside the polymer membrane. On the other hand, in OCV Holding, the membrane thickness was thinned by the entire surface and internal degradation. The fluorine emission rate was more than 10 times higher than that of OCV Holding due to the Fenton reaction. The hydrogen permeation rate increased about 30% at 24 hours of Fenton reaction. At OCV Holding, hydrogen permeability decreased after 24 hours and then increased. As a whole, there was a difference in a membranes deteriorated by Fenton reaction and OCV Holding.

• Resources Recycling
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• v.30 no.5
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• pp.38-48
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• 2021

In this study, we determine the optimal process conditions for selectively recovering Si from a solar cell surface by removal of impurities (Al, Zn, Ag, etc.). To selectively recover Si from solar cells, leaching is performed using HCl solution and an ultrasonic cleaner. After leaching, the solar cells are washed using distilled water and dried in an oven. Decompression filtration is performed on the HCl solution, and ICP-OES (Inductively Coupled Plasma Optical Emission spectroscopy) full scan analysis is performed on the filtered solution. Furthermore, XRD (X-ray powder diffraction), XRF (X-ray fluorescence), and ICP-OES are performed on the dried solar cells after crushing, and the purity and recovery rate of Si are obtained. In this experiment, the concentration of acid solution, reaction temperature, reaction time, and ultrasonic intensity are considered as variables. The results show that the optimal process conditions for the selective recovery of Si from the solar cells are as follows: the concentration of acid solution = 3 M HCl, reaction temperature = 60℃, reaction time = 120 min, and ultrasonic intensity = 150 W. Further, the Si purity and recovery rate are 99.85 and 99.24%, respectively.

• Journal of Climate Change Research
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• v.4 no.2
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• pp.141-158
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• 2013

In this study, the projection of future heating and cooling degree days (HDDs and CDDs) has been conducted over South Korea for the period 1996~2005 with 2046~2055 and 2091~2100, using CCSM3 and MM5 simulations driven by the six IPCC SRES emission scenarios (A2, A1B, A1FI, A1T, B1, and B2). Annual mean surface air temperature increases by $1.2{\sim}3.4^{\circ}C$ at the end of the 21st century comparing to the present-day (1996~2005) in South Korea. HDDs decrease by 8~25% and CDDs increase up to 242~1,448% with corresponding changes in temperature. These increases and decreases also change the duration of HDDs and CDDs. HDDs duration decreases by 1 month, while the expansion of CDDs duration is much longer than 2 months. Thus, projected future HDDs and CDDs changes appear that cooling energy demand in summer season would increase and heating energy demand in winter would decrease in the future. Especially, these remarkable changes would be obvious at high mountain area, Gangwon-do and at south area, Jeju island. In the sense of future energy supply and policy, electrical energy for cooling in summer could be getting much more its importance rather than fossil energy used for heating in winter.