• KSBB Journal
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• v.31 no.1
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• pp.73-78
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• 2016

The aim of this study attempted to verify the possibility of bioethanol production using wasted medium density fiberboard (wMDF). In order to produce bioethanol from wood cellulosic materials must be carried out the process of pretreatment, saccharification, fermentation and distillation. First, the wMDF was pretreated using sodium chlorite and pretreated wMDF was prepared to 8% slurry and then slurry was saccharified with the commercial enzyme (Cellic CTec3). The fermentable sugar and pH of saccharified substrate were about 5.5% glucose and 4.4, respectively. Herein we compared the results of ethanol yield according to the nutrients added or without addition to increase ethanol yield. Ethanol fermentation was finished in about 24 hours, but it was delayed in experimental group without nutrients. Ethanol content and fermentation ratio of the final fermented mash prepared by utilizing jar fermenter was 25.40 g/L and 86.64%, respectively. At this time, the maximum ethanol productivity was confirmed as 1.78 g/Lh (ethanol content 21.38 g/L, 12 h), and the overall ethanol productivity was 1.05 g/Lh (ethanol content 25.27 g/L, 24 h). Using fermented liquid we could produced bioethanol 95.37% by continuous distillator packed with copper element in laboratory scale. These results show that wMDF has a potential valuable for bioethanol production.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.133-142
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• 2006

This study performed earthquake response analyses of underground structures using displacement responses of soil. In this study, spring coefficients of surrounding soil proposed by specifications and researchers were adopted and then their corresponding analysis results were compared. The free field analyses using ProShake were carried out in order to predict ground responses of the field without underground structures. Several earthquakes such as El Centro, Ofunato, and Hachinohe earthquakes were considered to calculate maximum displacements. Numerical examples were analyzed, and then the results were compared and commented depending on spring coefficients of soil for the analyses using displacement responses of soil. The soil coefficients ranged from 0.05 to 14.39 times of those calculated by Korean Bridge Design Specification (2005). In conclusion, the coefficients of soil proposed by standard specifications seemed to be overestimated compared with those by the finite element method(FEM).

• Korean Institute of Interior Design Journal
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• v.18 no.6
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• pp.221-228
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• 2009

Recently severity of ecological adaptation and climatic change due to global warming grows larger. According to the fourth report of IPCC in 2007, emission quantity of the earth greenhouse gas(GHGs) generated by activity of mankind increased with 80% since 1970. And it is forecasted that worldwide greenhouse gas will be increased with 25~90%(corresponding to $CO_2$) between 2000 and 2030. This increment of greenhouse gas($CO_2$) is expected to raise average temperature of the earth with the maximum $6.4^{\circ}C$, and sea surface with 59cm in 2090. Like this, destruction of environment by greenhouse gas is regarded as universal problem threatening the existence, not only the problem of one nation. Consequently, systematic correspondence to the global warming at the aspect of energy consumption is also needed in Korea. From the analysis result of 'Statistics of Energy Consumption' published by Green Korea in 2007, energy consumption increment of domestic universities was higher as many as 3.7 times than 22.5% of the whole energy consumption increment in our country. This says to be the direct example which shows that universities are huge sources of greenhouse gas emission. New constructing and enlarging buildings of each universities within campus are the most major reason for such a large increment of energy consumption in universities. The opinion that the possibility of causing energy waste and efficiency reduction is raised by increased buildings of universities has been propounded. That is, universities should make concrete goal and the plan for reducing emission of green house gas against climatic change, and should practice. Accordingly, there is the meaning that 2 aspects of environment-friendly design characteristics, that is application of energy utilizing technology, material usage of energy efficiency-side and environment-side, and introduction of natural element in the environmental aspect, were analyzed for facilities of university campus designed in environment-friendly point of view from initial stage of plan, and direction of environment-friendly design of university facilities in the future was groped in order to grasp environment-friendly design tendency of internal and external University facilities based on this analysis of this paper.

• Advances in environmental research
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• v.5 no.1
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• pp.1-18
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• 2016

Magnetic nano-based sorbents have been synthesized for the recovery of two rare earth elements (REE: Nd(III) and Yb(III)). The magnetic nano-based particles are synthesized by a one-pot hydrothermal procedure involving co-precipitation under thermal conditions of Fe(III) and Fe(II) salts in the presence of chitosan. The composite magnetic/chitosan material is crosslinked with epichlorohydrin and modified by grafting alanine and serine amine-acids. These materials are tested for the binding of Nd(III) (light REE) and Yb(III) (heavy REE) through the study of pH effect, sorption isotherms, uptake kinetics, metal desorption and sorbent recycling. Sorption isotherms are well fitted by the Langmuir equation: the maximum sorption capacities range between 9 and 18 mg REE $g^{-1}$ (at pH 5). The sorption mechanism is endothermic (positive value of ${\Delta}H^{\circ}$) and contributes to increase the randomness of the system (positive value of ${\Delta}S^{\circ}$). The fast uptake kinetics can be described by the pseudo-second order rate equation: the equilibrium is reached within 4 hours of contact. The sub-micron size of sorbent particles strongly reduces the contribution of resistance to intraparticle diffusion in the control of uptake kinetics. Metal desorption using acidified thiourea solutions allows maintaining sorption efficiency for at least four successive cycles with limited loss in sorption capacity.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.257-265
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• 2012

Since the collapse of MSE walls frequently occurs due to the rainfall, it is necessary to analyze the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill. In order to understand the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill, finite element analyses were performed on the typical MSE wall. With varying ratio of saturated permeability to rainfall intensity, porepressures, displacements and factor of safety were analyzed. As the ratio of the saturated permeability to rainfall intensity increases, the global factor of safety is found to increase. Based on the analyses, the use of permeability of backfill with $2.56{\times}10^{-5}m/sec$ is desirable considering the characteristics of rainfall in Korea.

• Structural Engineering and Mechanics
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• v.87 no.6
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• pp.529-540
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• 2023

A novel laminated-hybrid-composite-beam (LHCB) of glass-epoxy infused with flyash and graphene is constructed for this study. The conventional mixture-rule and constitutive-relationship are modified to incorporate filler and lamina orientation. Eringen's non-local-theory is used to include the filler effect. Hamilton's principle based on fifth-order-layer-wise-shear-deformation-theory is applied to formulate the equation of motion. The analogous shear-spring-models for LHCB with multiple-cracks are employed in finite-element-analysis (FEA). Modal-experimentations are conducted (B&K-analyser) and the findings are compared with theoretical and FEA results. In terms of dimensionless relative-natural-frequencies (RNF), the dynamic-response in cantilevered support is investigated for various relative-crack-severities (RCSs) and relative-crack-positions (RCPs). The increase of RCS increases local-flexibility in LHCB thus reductions in RNFs are observed. RCP is found to play an important role, cracks present near the end-support cause an abrupt drop in RNFs. Further, multiple cracks are observed to enhance the nonlinearity of LHCB strength. Introduction of the first to third crack in an intact LHCB results drop of RNFs by 8%, 10%, and 11.5% correspondingly. Also, it is demonstrated that the RNF varies because of the lamina-orientation, and filler addition. For 0° lamina-orientation the RNF is maximum. Similarly, it is studied that the addition of graphene reduces weight and increases the stiffness of LHCB in contrast to the addition of flyash. Additionally, the response of LHCB to moving mass is accessed by appropriately modifying the numerical programs, and it is noted that the successive introduction of the first to ninth crack results in an approximately 40% to 120% increase in the dynamic-amplitude-ratio.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.199-205
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• 2023

Arsenic is a highly toxic element, and its contamination is widespread around the world. The natural materials with high selectivity and efficiency toward pollutants are important in wastewater treatment technology. In this study, the mesoporous synthetic hectorite was synthesized by facile hydrothermal crystallization of gels comprising silica, magnesium hydroxide, and lithium fluoride. Additionally, the naturally available clay was modified using zirconium at room temperature. Both synthetic and modified natural clays were employed in the removal of arsenate from aquatic environments. The materials were fully characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) analyses. The synthesized materials were used to remove arsenic (V) under varied physicochemical conditions. Both materials, i.e., Zr-bentonite and Zr-hectorite, showed high percentage removal of arsenic (V) at lower pH, and the efficiency decreased in an alkaline medium. The equilibrium-state sorption data agrees well with the Langmuir and Freundlich adsorption isotherms, and the maximum sorption capacity is found to be 4.608 and 2.207 mg/g for Zr-bentonite and Zr-hectorite, respectively. The kinetic data fits well with the pseudo-second order kinetic model. Furthermore, the effect of the background electrolytes study indicated that arsenic (V) is specifically sorbed at the surface of these two nanocomposites. This study demonstrated that zirconium intercalated synthetic hectorite as well as zirconium modified natural clays are effective and efficient materials for the selective removal of arsenic (V) from aqueous medium.

• Korean Journal of Agricultural Science
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• v.48 no.4
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• pp.787-796
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• 2021

Nitrogen (N) is the most important element during the process of plant growth, and the quality of crops varies depending on the amount of nitrogen present. Most of the nitrogen is used for plant growth, but approximately 10 - 20% of Nitrogen is carried away by the wind in the form of NH₃. This volatilized NH₃ reacts with various oxides in the atmosphere to generate secondary particulate matter. To address this, the present study attempts to reduce NH₃ occurring in the soil using biochar at a specific pH. Biochar was used as a treatment with 1% (w·w^-1) of the soil, and urea was applied at different levels of 160, 320, and 640 kg·N·ha^-1. NH₃ generated in the soil was collected using a dynamic column and analyzed using the indophenol blue method. NH₃ showed the maximum emission within 4 - 7 days after the fertilizer treatment, decreasing sharply afterward. NH₃ emission levels were reduced with the biochar treatment in all cases. Among them, the best reduction efficiency was found to be approximately 25% for the 320 kg·ha^-1 + pH 6.7 biochar treatment. Consequently, in order to reduce the amount of NH₃ generated in the soil, it is most effective to use pH 6.7 biochar and a standard amount (320 kg·N·ha^-1) of urea.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.95-103
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• 2023

In this paper, in order to evaluate the deformation characteristics of the hydrogen gas storage vessel(Type 1) when considering gas pressure, the VMS generated in the hydrogen gas storage vessel according to the notch shape of ISO 18119 was interpreted as a FEM(Finite Element Method). According to the analysis results, the maximum VMS generated in the longitudinal notch was higher than the transverse notch. In addition, the stress of the storage vessel was analyzed by the stress ratio, which is the yield strength ratio of the material to the VMS generated. According to the analysis results, in the case of a storage vessel with a notch formed in the longitudinal direction, the inside and outside of the storage vessel increased to 0.85 and 0.50 at a gas pressure of 50 MPa, respectively, but were analyzed to be lower than 1.

• Steel and Composite Structures
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• v.46 no.2
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• pp.221-236
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• 2023

In order to study the seismic response of the main plant of steel reinforced concrete (SRC) structure of the CAP1400 nuclear power plant under the influence of different high-mode vibration, the 1/7 model structure was manufactured and its dynamic characteristics was tested. Secondly, the finite element model of SRC frame-bent structure was established, the seismic response was analyzed by mode-superposition response spectrum method. Taking the combination result of the 500 vibration modes as the standard, the error of the base reactions, inter-story drift, bending moment and shear of different modes were calculated. Then, based on the results, the influence of high-mode vibration on the seismic response of the SRC frame-bent structure of the main plant was analyzed. The results show that when the 34 vibration modes were intercepted, the mass participation coefficient of the vertical and horizontal vibration mode was above 90%, which can meet the requirements of design code. There is a large error between the seismic response calculated by the 34 and 500 vibration modes, and the error decreases as the number of modes increases. When 60 modes were selected, the error can be reduced to about 1%. The error of the maximum bottom moment of the bottom column appeared in the position of the bent column. Finally, according to the characteristics of the seismic influence coefficient αj of each mode, the mode contribution coefficient γj•Xji was defined to reflect the contribution of each mode to the seismic action.