• Journal of the Korean Magnetics Society
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• v.9 no.2
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• pp.78-84
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• 1999

$(Ni, Zn)Fe_2O_4$ powders were prepared through self-propagating high temperature synthesis reaction and the effects of initial zinc oxide powder size and oxygen pressure on the magnetic properties of the final combustion products were studied. The ferrite powders were combustion synthesized with iron, iron oxide, nickel oxide, and zinc oxide powders under various oxygen pressures of 0.5~10 atmosphere after blended in n-hexane solution for 5 minutes with a spex mill, followed by dried at 120 $^{\circ}C$ in vacuum for 24 hours. The maximum combustion temperature and propagating rate were about 1250 $^{\circ}C$ and 9.8 mm/sec under the tap density, which were decreased with decreasing ZnO size and oxygen pressure. The final product had porous microstructure with spinel peaks in X-ray spectra. As the ZnO particle size in the reactant powders and oxygen pressure during the combustion reaction increase, coercive force, maximum magnetization, residual magnetization, squareness ratio were changed from 1324 Oe, 43.88 emu/g, 1.27 emu/g, 0.00034 emu/gOe, 37.8$^{\circ}C$ to 11.83 Oe, 68.87 emu/g, 1.23 emu/g, 0.00280 emu/gOe, 43.9 $^{\circ}C$ and 7.99 Oe, 75.84 emu/g, 0.791 emu/g, 0.001937 emu/gOe, 53.8 $^{\circ}C$ respectively. Considering the apparent activation energy changes with oxygen pressure, the combustion reaction significantly depended on initial oxygen pressure and ZnO particle size.

• Clean Technology
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• v.24 no.1
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• pp.50-54
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• 2018

In this work, N-methyl-2-pyrrolidone (NMP) was added into diethylenetriamine (DETA) aqueous solution for high $CO_2$ loading via phase splitting of absorbents during $CO_2$ absorption. Immiscible two phases were formed in the range of more than 30 wt% of NMP in 2 M DETA + NMP + water absorbents because of low solubility of DETA-carbamate in NMP solution. As the composition of NMP in the absorbents increased, the difference of $CO_2$ loading between each phase increased and the volume of bottom phase decreased. In $CO_2$ absorption in packed column by 2 M DETA + NMP + water absorbents, the absorption rate decreased in the range of more than 40 wt% of NMP. It is due to the increasing of mass transfer resistance in liquid film of absorbents at the high concentration of NMP. DETA + NMP + water absorbent is expected as the promising one for reducing the regeneration energy of absorbents according to volume reduction of $CO_2-rich$ phase.

• Journal of The Korean Association For Science Education
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• v.34 no.6
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• pp.549-558
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• 2014

Integrated concepts that are broad enough to embrace facts, principles, laws, and concepts of multiple disciplines could become the core of integrated education. Integrated concept-centered education enables effective and practical learning. In this study, the Delphi Method was implemented targeting experts in science (physics, life science, chemistry, and earth science) and humanities (history, geology, economics, ethics, and politics) to find out the integrated concept that can be used to design the concept-centered integrated education in the Republic of Korea. 124 experts participated in this survey. Delphi survey was conducted for three rounds. In the first round, an open questionnaire was given to experts to collect feasible integrated concepts in each major field. Then, in the second round experts were asked to select integrated concepts that could be used practically in the field of their major. In the third round, the integrated concept with selection frequency over medium value were given. They were asked to evaluate the applicability of integrated concepts by using the Likert-scale questionnaire. Through this process, content validity was analyzed. As a result, five integrated concepts (change, interaction, space-time, energy, and equilibrium) were selected for the inter-science integration. And thirteen integrated concepts (conflict, community, relationship, structure, power, diversity, culture, change, society, interaction, freedom, justice, and equality) were chosen for the inter-humanities integration. Finally, for the science-humanities integration, seven integrated concepts (structure, diversity, change, interaction, cycle, system, and environment) were determined.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.37-43
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• 1990

An effect of the spin-orbit coupling interaction of ligand orbitals and the intermixing │3d 〉and│4p > transition metal atomic orbitals on the ground state for a 3$d^9$ system in a strong crystal field of tetragonally distorted tetrahedral symmetry that belongs to the $D_{2d}$ point group has been investigated in this work, applying the degenerate perturbation theory. An LCAO-MO analysis in terms of the known energies of the d-d transitions for the tetragonally distorted $CuCl_4^{2-}$ ion in a single crystal of$Cs_2CuCl_4$shows that the covalent mixing of Cu 3d and ligand Cl 3p orbitals decreases dramatically with increasing Cu 4p contribution. The extent of effect on the energy level splitting for the ground state by the spin-orbit coupling interaction of ligand orbitals decreases significantly in orderTEX>$\Gamma_7(E)\;\to\;\Gamma_6(E)\; >\;\Gamma_7(B_2)\;\to\;\Gamma_6(E)\; >\;\Gamma_7(B_2)\;\to\;\Gamma_7(E)$.

• Polymer(Korea)
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• v.37 no.1
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• pp.61-65
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• 2013

In this work, the anodic oxidation of carbon fibers was carried out to enhance the mechanical interfacial properties of carbon fibers-reinforced epoxy matrix composites. The surface characteristics of the carbon fibers were studied by FTIR, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Also, the mechanical interfacial properties of the composites were studied with interlaminar shear strength (ILSS), critical stress intensity factor ($K_{IC}$), and critical strain energy release rate ($G_{IC}$). The anodic oxidation led to a significant change in the surface characteristics of the carbon fibers. The anodic oxidation of carbon fiber improved the mechanical interfacial properties, such as ILSS, $K_{IC}$, and $G_{IC}$ of the composites. The mechanical interfacial properties of the composites anodized at 20% sulfuric/nitric (3/1) were the highest values among the anodized carbon fibers. These results were attributed to the increase of the degree of adhesion at interfaces between the carbon fibers and the matrix resins in the composite systems.

• Journal of Adhesion and Interface
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• v.3 no.4
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• pp.1-9
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• 2002

The main goal of this study was to analyze the effect of process additives, i.e. maleated polypropylene (MAPP), and nucleating agent on the viscoelastic properties of different types of extruded polypropylene-wood plastic composites manufactured from either PP homopolymer, high crystallinity PP or PP impact copolymer using dynamic mechanical thermal analysis. And also, the esterification reaction between wood flour and maleated polypropylene, and its role in determining the mechanical properties of wood flour-polypropylene composites was investigated. The wood plastic composites were manufactured using 60% pine wood flour and 40% polypropylene on a Davis-Standard $Woodtruder^{TM}$. Dynamic mechanical thermal properties, polymer damping peaks(than ${\delta}$), storage modulus (E') and loss modulus (E") were measured using a dynamic mechanical thermal analyzer. XPS (X-ray Photoelectron Spectroscopy), also known as ESCA (Electron Spectroscopy for Chemical Analysis) study of wood flour treated with MAPP was performed to obtain information on the chemical nature of wood fiber before and after treatment. To analyze the effect of frequency on the dynamic mechanical properties of the various composites, DMA tests were performed over a temperature range of -20 to $100^{\circ}C$, at four different frequencies (1, 5, 10 and 25 Hz), and at a heating rate of $5^{\circ}C/min$. From these results, the activation energy of the various composite was measured using an Arrhenius relationship to investigate the effect of maleated PP and nucleating agent on the measurement of the interphase between the wood and plastic of the extruded polypropylene wood plastic composites.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.39 no.1
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• pp.55-63
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• 2013

Applications of nano-emulsion for cosmetics as a means of promoting dermal absorption have been the subject of interest. In this study, the stability of nano-emulsions prepared by low-energy emulsification method and varying the composition of raw materials was investigated. By measuring the particle size of the nano-emulsion against time, the stability of nano-emulsions prepared by adding polyol to water phase was increased significantly compared with the nano-emulsions prepared by adding polyol to ethanol phase. The speed of adding ethanol phase to water phase did not have a significant impact on the particle size and stability. Depending on the type of oil, stability was not affected. However, there would be a correlation between the initial size of the nano-emulsion droplets and the molecular weight and polarity of the oil. Stability and the initial particle size according to the type of polyols showed a similar trend except 1,2 hexanediol. The initial droplet size was affected by the concentration of surfactant and oil. However, the initial droplet size did not change against time. Concentration of ethanol was observed to have a significant impact on the initial particle size and stability.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.227-233
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• 2011

Attention has been focused on geothermal energy as an alternative energy because it is continuously operable without external supply. Most of geothermal anomalies in Korea are related to deep circulation of groundwater through a fracture system in granite area. Therefore it is very important to understand the distribution of the fracture system which is the main channel of ground water. In this research, we constructed the velocity models with a fracture system and the layered sediments, respectively, and generated synthetic data sets with them to verify the presented vertical seismic profiling (VSP) preprocessing scheme. We compared the results from conventional VSP preprocessing flow to those from VSP preprocessing flow considering fracture system. We noticed that the preprocessing flow considering fracture system retains more sufficient signal including down-going wave than conventional preprocessing. In addition, we applied 3D VSP prestack phase screen migration to the preprocessed reversed VSP (RVSP) data from Seokmo Island so that we were able to image fracture structure of the geothermal site in Seokmo Island.

• Journal of Sasang Constitutional Medicine
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• v.10 no.2
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• pp.163-180
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• 1998

In 1492 year, the corn originated in America continent had spread all over the world after spreading into Europe by Columbus. Since the Corn had a similar shape with adlai's one (Yulmoo(율무)), it had been written by the different name of adlai (Yulmoo) at the "訓蒙字會(Hun-mong-ja-hoe)(1527)". Therefore we should consider "Hun-mong-ja-hoe" is the first record of the corn and it is a significant historic record in the civilization exchange between the Orient and the Occident that this record has the only difference of around 30 years later after the spreading corn to Europe. However, this is on the assumption that it is correct for a scholar of Korean literature to persist in that '叡山本' of "Hun-mong-ja-hoe" could be considered as the first edition. The corn had been once classified as a same kind of the Chinese millet because the people had been recognized the corn as a similar group of the Chinese millet and the Indian millet. The Chinese millet contains a summer vigor and becomes as an ingredient of alcoholic drink. And we can find out that $C_4$ type plant (such as corn, Chinese millet, Indian millet, foxtail millet) mostly have a tendency to belong to the food for "Taeumin(太陰人)", because of its high energy efficiency, a flourishing absorption of fertilizing and a strong emission power. The fried corn with a strong summer vigor and a raised feature has a good effect to the treatment of the teethridge disease. And the tea of corn with an warm feature, thanks to its functions of making the stomach and intestines comfortably as well as urination, is a proper food for the 'Taeumin" who is apt to overeat themselves.

• Journal of Life Science
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• v.21 no.9
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• pp.1336-1345
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• 2011

The purpose of this study was to analyze and compare the effects of exercise science of shoes for Aged' health promotion. Kinematic and kinetic data were collected using cinematography and the Zebris system (Zebris Emed Sensor Platform, GR-DVL9800) to analyze pressure of foot and ground reaction force. Subjects recruited were 20 healthy elderly men. They walked at 1.36m/sec velocity wearing type A (domestic), type B (foreign) and walking shoes (A company). One-way ANOVA was used to analyze statistics. The results were as following: no significant differences were observed in gait variables among the three groups (p<0.05). There was a significant difference in max pronation angle of heels examined among the three groups (p<0.05). There were no significant differences in kinetic variables (ground reaction force and max pressure) among the three groups (p<0.05). A physiology study was performed to analyze the effects of walking with shoes with silver added to them on percent body fat, resting metabolic rate and energy expenditure. Sixty adults males were recruited from the public health center. They were divided into four groups. C: control group (n=20), EY: elderly Y group (n=20), and EO: elderly O group (n=20). The results of this study were as follows: percent body fat was decreased following each exercise period, however, not all the groups showed a significant difference. The change of resting metabolic rate was significantly increased in HI (high intensity) and LI (low intensity) periods in the C and EY groups. However, there was no significant difference in the EO group. The mean energy expenditure during and after exercise were significantly lowered in all periods compared to the control group.