• Carbon letters
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• v.28
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• pp.60-65
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• 2018

Linear carbon chains (LCCs) encapsulated inside the hollow cores of carbon nanotubes (CNTs) have been experimentally synthesized and structurally characterized by Raman spectroscopy and transmission electron microscopy. However, in terms of electronic conductivity, their transportation mechanism has not been investigated theoretically or experimentally. In this study, the density of states and quantum conductance spectra were simulated through density functional theory combined with the non-equilibrium Green function method. The encapsulated LCCs inside (5,5), (6,4), and (9,0) single-walled carbon nanotubes (SWCNTs) exhibited a drastic change from metallic to semiconducting or from semiconducting to metallic due to the strong charge transfer between them. On the other hand, the electronic change in the conductance value of LCCs encapsulated inside the (7,4) SWCNT were in good agreement with the superposition of the individual SWCNTs and the isolated LCCs owing to the weak charge transfer.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.277-284
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• 1993

Interfacial surface crack perpendicular to the surface, which is imbedded into bonded quarter planes under single anti-plane shear load is analyzed. The problem is formulated using Mellin transform, form which single Wiener-Hopf equation is derived. By solving the equation stress intensity factor is obtained in closed form. This solution can be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.162-167
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• 1984

Equilibrium and dynamical behaviors of an n-alkane poymer (decane) in solution have been investigated by a molecuar dynamics simulation method. The polymer is assumed to be a chain of elements $(CH_2)$ interconnected by bonds having a fixed bond length and bond angle, but esch bond of the polymer is allowed to execute hindered internal rotation. The calculation explicitly considers the molecular naturer of solvent by including the intermolecular interactions between slovent-solvent molecules and chain element-solvent molecule. We present the results of calculations on (1) equilibrium properties (the solvent molecule-chain element pair correlation function, chain element-chain element pair correlation function, the mean square end-to-end distance and the mean square radius of gyration of the polymer) and (2) dynamic properties (four different autocorrelation functions, namely, the autocorrelation functions for the end-to-end distance and the radius of gyration, and the velocity autocorrelation functions for the center of mass and the end point of the chain). We found that the physical properties of the polymer chain depends sensitively on temperature. Comparison of the present work with other authors' results is also presented.

• Journal of Digital Convergence
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• v.13 no.8
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• pp.289-294
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• 2015

This paper proposes an autonomous machine learning method applicable to the BCI(Brain-Computer Interface) is based on the self-organizing Kohonen method, one of the exemplary method of unsupervised learning. In addition we propose control method of learning region and self machine learning rule using an interactive function. The learning region control and machine learning was used to control the side effects caused by interaction function that is based on the self-organizing Kohonen method. After determining the winner neuron, we decided to adjust the connection weights based on the learning rules, and learning region is gradually decreased as the number of learning is increased by the learning. So we proposed the autonomous machine learning to reach to the network equilibrium state by reducing the flow toward the input to weights of output layer neurons.

• Journal of Korean Society of Forest Science
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• v.103 no.3
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• pp.462-472
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• 2014

This study is aimed at developing a supply-demand model of wood products, and outlook for mid-term and long-term supply and demand for each products. The main wood products include sawnwood, plywood, particle board, fiberboard (MDF), and pulp. The partial equilibrium model is composed of supply function, import demand function, demand function, price relation function. With given parameters the outlook for year 2050 says that sawnwood, plywood, and fiberboard for domestic productions and imports are decreased. This may result from the increase of log prices from the inside and outside of the country because of the propensity for environment protection and the resource nationalism. On the other hand the supply of particle board and pulp will increase because they are made from wasted wood and chips.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6959-6968
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• 2015

This study aims to update the supply-demand model of wood products(FOSMO-2013) and to forecast mid and long run supply and demand for each products. The subjects of the study include sawnwood, plywood, particle board, fiberboard(MDF), and pulp. The updated partial equilibrium model is composed of supply function, import demand function, demand function, price relation function. The long run outlooks of world prices of wood and wood products are imported from the results of Buongiorno(2012). This study also adopt Buongiorno's scenarios, which includes three scenarios of IPCC(A1B, A2, B2) and the other one with assumption of increasing fuelwood consumption of A1B scenario. The result says that the domestic productions of wood products are expecting to decrease while the imports of them increase even there are some differences among the products as well as scenarios.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.83-92
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• 2018

The lapse of time may cause in the slope structure various deterioration phenomenon progresses in the ground of slope, and collapse due to deterioration of strength, resulting in a decrease in the service life. The approach to slope stability due to the ground deterioration is a different concept from the existing limit equilibrium analysis, which is limited to the physical characteristics and geometrical structure of ground. In this study, we conducted a comparative analysis of various literature studies related to the slope failure characteristics and behaviors to presented the optimal formulas for shear strength reduction, such as the exponential function, the logarithmic function and the inverse hyperbolic function. And then a case study was performed on cut slope of Gyeongbu High Speed Rail construction site along the Yangsan fault zone, where the slope failure of shale layer vulnerable to deterioration occurred. As a result, it was confirmed that landslide occurred due to reduction of shear strength by deterioration, as safety factor is approx. 1.0 at the time when the slope failure occurred. Based on the comprehensive case study, as a quantitative approach to the evaluation of slope stability due to deterioration of ground, finally we propose a method for evaluating slope stability with optimal strength reduction curves.

• Advances in nano research
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• v.7 no.3
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• pp.209-221
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• 2019

Graphene, with impressive electronic properties, have high potential in the microelectronic field. However, graphene itself is a zero bandgap material which is not suitable for digital logic gates and its application. Thus, much focus is on graphene nanoribbons (GNRs) that are narrow strips of graphene. During GNRs fabrication process, the occurrence of defects that ultimately change electronic properties of graphene is difficult to avoid. The modelling of GNRs with defects is crucial to study the non-idealities effects. In this work, nearest-neighbor tight-binding (TB) model for GNRs is presented with three main simplifying assumptions. They are utilization of basis function, Hamiltonian operator discretization and plane wave approximation. Two major edges of GNRs, armchair-edged GNRs (AGNRs) and zigzag-edged GNRs (ZGNRs) are explored. With single vacancy (SV) defects, the components within the Hamiltonian operator are transformed due to the disappearance of tight-binding energies around the missing carbon atoms in GNRs. The size of the lattices namely width and length are varied and studied. Non-equilibrium Green's function (NEGF) formalism is employed to obtain the electronics structure namely band structure and density of states (DOS) and all simulation is implemented in MATLAB. The band structure and DOS plot are then compared between pristine and defected GNRs under varying length and width of GNRs. It is revealed that there are clear distinctions between band structure, numerical DOS and Green's function DOS of pristine and defective GNRs.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.4
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• pp.413-420
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• 2008

In order to utilize cinder melting slag as a filter media to control the quality of early rainwater, its environmental stability was verified by heavy metal elution experiment and improved by pre-treatment. Possibilities of improving its function as an absorbent was considered. Absorption characteristics of melting slag before and after the pre-treatment were analyzed by heavy metal equilibrium and stationary-phase column experiments, which in turn were analyzed by comparison experiment with activated carbon. As a result of heavy metal elution experiment, every metal item existed in a much lower amount than the criteria or was not detected, implying that there is no problem recycling it. Absorption equilibrium experiment showed that the time for pre-treatment melting slag to reach the equilibrium was reduced, while the absorbed amount was greatly increased. Stationary-phase column experiment assures us that the elimination rate was not changed much by influx rate, pH and the change in packing volume rate, indicating that this melting slag can be used not only as a filter media to control the quality of early rainwater but also in many areas of water-processing.

• Environmental Engineering Research
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• v.11 no.1
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• pp.33-44
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• 2006

The objective of this study was to develop and assess a method for estimating the rain scavenging ratios (RSRs) of particle-bound PAHs and PCBs using measured scavenging ratio of particulate matters (PM) and routinely available data of physico-chemical properties of PM. Paired atmospheric and rainwater sampling was conducted for a total of 4 rain events. Assuming equilibrium partitioning in rainwater-gas-PM system, an equation was derived for estimating the RSR of particle-bound chemicals as a function of RSR of PM and three equilibrium partition constants (i.e. dimensionless Henry's law constant, gas-particle partition coefficient, and water-particle partition coefficient). For all PAHs, the model significantly under-predicted the RSR while the model prediction for PCBs agreed with observation mostly within a factor of 5. The RSR model for the chemicals is of limited use as its accuracy critically depends on how close the observed partitioning of the chemicals in the gas-PM-rainwater system is to that estimated under the equilibrium assumption.