• Advances in materials Research
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• v.6 no.3
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• pp.279-301
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• 2017

Thermo-mechanical vibration characteristics of in homogeneousporous functionally graded (FG) micro/nanobeam subjected to various types of thermal loadings are investigated in the present paper based on modified couple stress theory with consideration of the exact position of neutral axis. The FG micro/nanobeam is modeled via a refined hyperbolic beam theory in which shear deformation effect is verified needless of shear correction factor. A modified power-law distribution which contains porosity volume fraction is used to describe the graded material properties of FG micro/nanobeam. Temperature field has uniform, linear and nonlinear distributions across the thickness. The governing equations and the related boundary conditions are derived by Extended Hamilton's principle and they are solved applying an analytical solution which satisfies various boundary conditions. A comparison study is performed to verify the present formulation with the known data in the literature and a good agreement is observed. The parametric study covered in this paper includes several parameters such as thermal loadings, porosity volume fraction, power-law exponents, slenderness ratio, scale parameter and various boundary conditions on natural frequencies of porous FG micro/nanobeams in detail.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1061-1066
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• 1999

The adsorption of CO on W(111) surface in the range of adsorption temperature between 300 K and 1000 K has been studied using AES, LEED, and TDS in an UHV system. After CO saturation at 300 K, four desorption peaks are observed at temperatures (K) of about 400, 850, 1000, and 1100 in thermal desorption spectra, called as α, β1, β2, and β3 state, respectively. The state was attributed to molecular species of CO, which is well known. Because the CO in βstates (especially the β3 state) is still debated as to whether it is dissociative or non-dissociative, the β3 state is mainly discussed. By using the variation method of heating rate in the thermal desorption spectrometry, the desorption energy and pre-exponential factor for the β3 state are evaluated to be 280 kJ/mol and 1.5×10 12 s-1 , respectively. A lateral interaction energy of 5.7 kJ/mol can also be estimated by Bragg-Williams approximation. To interpret the thermal desorption spectra for the β3 state, moreover, those for the model of a first order and a second order desorption are simulated using quasi-chemical approximation. In this study, a model of lying-down CO species is proposed for the β3 state of CO adsorption.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.287-296
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• 2006

In this paper, optimal control strategy of the air-conditioning system with slab thermal storage was investigated based on the optimal control theory. An optimal heat output to the plenum chamber and the air-conditioned room was determined based on two kinds of criterion functions. The first one requires small deviation in room air temperature from a set-point value and low energy consumption. It is shown that the optimized control is to store heat through the whole storage time and to increase storage rate gradually with time. As the second case, a criterion that both a deviation of operative temperature from a set-point temperature and the energy consumption should be minimized was adopted. The room air temperature was a little high and the cooling load during storage time was reduced, compared with the results when a criterion function considering only the room air temperature is used.

• Macromolecular Research
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• v.17 no.11
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• pp.870-873
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• 2009

In this study, 2-diglycidylether of benzotrifluoride (2-DGEBTF) and 4-diglycidylether of benzotrifluoride (4-DGEBTF) epoxy resins, which contained fluorine groups in the main chain, were synthesized. The resins were characterized by FTIR, $^1H$ NMR, $^{13}C$ NMR and $^{19}F$ NMR spectroscopy. The 2-DGEBTF and 4-DGEBTF epoxy resins were cured with triethylene tetramine (TETA), and the effect of the fluorine group on the synthesized epoxy resin on the cure behavior, thermal, and mechanical properties was investigated. The 2-DGEBTF/TETA system was more reactive than the 4-DGEBTF/TETA system, whereas the thermal stability factor i.e., the decomposition activation energy ($E_d$), of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. These results can be explained by the decrease in cross-linking density and decomposition of the short side chains, resulting in the $CF_3$ group at the para position. However, the $K_{IC}$ value of 4-DGEBTF/TETA was higher than that of 2-DGEBTF/TETA. This was attributed to the increase in flexibility in the epoxy backbone, resulting in a difference in steric hindrance and polarlizability.

• Plant Journal
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• v.4 no.4
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• pp.71-77
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• 2008

The sulfur oxides is one of important materials to come about air pollution at thermal plant consuming fossil fuel. The several flue gas desulfurization equipments are installed and operated to decrease sulfur oxides. The flue gas desulfurization of our thermal plant is designed for optimizing flue gas desulfurization technical development and research by Korea Electric Power Research Institute. We operate this desulfurization equipment. Now, our country imports nearly 97 percentage of the energy source and competes with the world for the energy because of the sudden rise of raw materials cost. The fuel cost decrease of power plants is the most important factor of the operation. The fuel used in the experiment is the domestic anthracite from Kangwon Taeback and the bituminous coal from Taldinsky Mine in Russia. This Study is experimental investigations of desulfurization characteristics for domestic anthracite power plant by increasing bituminous coal. We surveyed possible parameters and conducted the performance about desulfurization equipment in Yong Dong thermal power plant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.372-376
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• 2022

Since the ZnO varistor is a semiconductor device, the internal thermal distribution during the varistor operation is recognized as an important factor in the performance and deterioration of the varistor. For an optimal varistor structure design, the thermal runaway phenomenon during the varistor operation was interpreted using the Comsol 5.2 analysis program by a finite element analysis. The maximum temperature of the center measured in the cross section of the ZnO varistor was confirmed to increase as the temperature moved from the lower electrode to the center towards the upper electrode up to 572.6 K. The electrodes are thinned so that the influence of the Schottky barrier is not great. The heat gradient balance is determined to be improved when the electrode of the hybrid form is introduced. The thickness, density, pore distribution, impurity uniformity, and particle size of the ZnO varistor are required, and it is determined that the pyrolysis gradient will be improved regardless of the electrode thickness. When these results are applied to design the ZnO varistor, the optimal structure of the ZnO varistor can be obtained.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.206-207
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• 2020

Accurate estimation of concrete strength development at early ages is a critical factor to secure structural stability as well as to speed up the construction process. The temperature generated from the heat of hydration is considered as a key parameter in predicting the early age strength. Conventionally, concrete temperature has been measured by temperature sensors installed inside concrete. However, considering the measurement on building structures with multiple floors, this method requires reinstallation and repositioning of hardware such as sensors, data loggers and routers for data transfer. This makes the temperature monitoring work cumbersome and inefficient. Concrete temperature monitoring by using thermal remote sensing can be an effective alternative to supplement those shortcomings. In this study, image processing was carried out through K-means clustering technique, which is a unsupervised learning method, and the classification results were analyzed accordingly. In the future, research will be conducted on how to automatically recognize concrete among various objects by using deep learning techniques.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.64-68
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• 2020

In this study, metal copper clad laminate can be prepared using epoxy composite filled with thermally conductive fillers. In order to improve the thermal conductivity of epoxy composites, it is important factor to form conductive networks through appropriate packing of conductive fillers in epoxy composite matrix and to decrease the amount of thermally resistant junctions involving a epoxy composite matrix layer between adjacent filler units. This is because epoxy has a thermal conductivity of only 0.2-0.3W, so in order to maintain high thermal conductivity, thermally conductive fillers are connected to each other, so that the gap between particles can be reduced to reduce thermal resistance. The purpose of this study is to find way to achieve highly thermally conductive in the epoxy composite matrix filled with Al₂O₃ and Boron Nitride(BN) filler by filler loading and uniform dispersion. As a results, the use of Al₂O₃/BN hybrid filler in epoxy matrix was found to be effective in increasing thermal conductivity of epoxy composite matrix due to the enhanced connectivity offered by more continuous thermally conductive pathways and uniform dispersion without interfacial voids in epoxy composite matrix. In addition, surface treatmented s-BN improves the filler dispersion and adhesion between the filler and the epoxy matrix, which can significantly decrease the interfacial thermal resistance and increase the thermal conductivity of epoxy composite matrix.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.121-141
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• 2017

The thermal analysis of an underground power conduit for electrical cables is essential to determine their current capacity with an increasing number of demands for high-voltage underground cables. The temperature rises around a buried cable, caused by excessive heat dissipation, may increase considerably the thermal resistance of the cables, leading to the danger of "thermal runaway" or damaging to insulators. It is a key design factor to develop the mechanism on thermal behavior of backfilling materials for underground power conduits. With a full-scale field test, a numerical model was developed to estimate the temperature change as well as the thermal resistance existing between an underground power conduit and backfill materials. In comparison with the field test, the numerical model for analyzing thermal behavior depending on density, moisture content and soil constituents is verified by the one-year-long field measurement.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.7
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• pp.571-577
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• 2006

The characteristics of ice packing factor (IPF) at the ice slurry system using one line type are compared with the system using two lines type. The installation space for one transporting line is saved at the one line system. For the one line type, the ice packing factor is reduced along the downstream, but for the two lines type, the ice packing factor is fixed. For the one line system, mass flow rate in the main line is fixed along the down-stream, but for two lines system, the mass flow rate in the main line is reduced along the downstream. For one line system, along the down stream after IPF=0, the temperature at the main steam is increased, and the extracted mass flow is increased. The initial IPF, at which the IPF is not arrived at zero upto the final node, is proposed for the B area.