• Journal of the Korean Society for Heat Treatment
• /
• v.13 no.6
• /
• pp.412-419
• /
• 2000

There has been a considerable attention on Invar alloys due to its low thermal expansion property. A low thermal expansion property of Invar alloys, lower than $10^{-6}$ near the room temperature, is attractive for electric transmission lines and precision machine tools. However, the expansion property of Invar alloys is limited below about 520K, and mechanical properties are relatively low to apply to electric transmission line. In order to improve mechanical properties in this alloy, Ti alloying element was added to the $Ni_{38}-Mo_2-Cr_1-Fe$ invar alloy. The microstructure Ti added alloy showed finer than that of the unalloyed one. It was found that the (Mo, Ti), Mo carbide formed by Ti addition obstacled grain growth by pinning effect and supplyed recrystallization sites during heat-treatment. Optimum heat-treatment conditions with Ti addition were also discussed in the modified Invar alloy.

• The Journal of the Korea Contents Association
• /
• v.21 no.8
• /
• pp.137-149
• /
• 2021

This study examined whether and how personal traits such as SNS self-efficacy, comparison orientation, fear of missing out are associated with SNS addiction proneness. An online survey of 232 Chinese students in Korea showed that the personal traits are positively associated with sub-dimensions of SNS addiction proneness. Fear of missing out is found to be positively associated with all three sub-dimensions of SNS addiction proneness. On the other hand, SNS self-efficacy and comparison orientation is positively related to some of the sub-dimensions.

• Economic and Environmental Geology
• /
• v.33 no.1
• /
• pp.19-30
• /
• 2000

The Sannae-Eonyang granitic rocks are a large fossil hydrothermal system containing the Sannae Mo-W fissure-vein type and the Eonyang amethyst deposits in the southeastern Kyongsang Basin. They evolved through similar stages showing the similarities in chemical and mineralogical compositions, fractionation trends and early magmatic fluids. Major, trace and rare earth element(REE) variations can be accounted for fractional crystallization combined with variable degrees of metasomatism. Based on the aqueous fluids exsolved directly from the crystallizing melt, the Sannae-Eonyang granitic rocks were emplaced at similar depth or pressure conditions. High temperature fluid interaction with the granitic rocks affects the elements such as K, Na, Rb, Ba, Sr, Eu, and heavy REE (HREE) mostly through feldspar re-equilibration. Although hydrothermal fluids produced partly positive Eu anomalies and HREE depletion in the granitic rocks at the Sannae Mo-W mine, the chemical concentrations defining fractionnation trends have survived the effects of alteration. Aqueous fluids exsolved from the crystallizing melt appears to be widespread, whereas fluids of moderate to low salinity and low-density with relatively high homogenization temperatures and $Co_2$-rich fluids appear to be mainly restricted and responsible for Mo-W and amethyst mineralization, respectively. Hydrothermal system of the Sannae-Eonyang granitic rocks represents repeated fluid events; from exsolution of aqueous fluids from the crystallizing melt, through fluid immiscibility and meteoric convection to later mineralization.

• Journal of the Korean Magnetics Society
• /
• v.3 no.4
• /
• pp.314-319
• /
• 1993

The Effects of additional element X (X = Si, Mo, Cu, Gd) on magnetic properties and microstructure of Co-1Zat%Cr-Zat%Ta/Cr-X magnetic thin film were investigated. The thickness changes of Cr-X underlayer and CoCrTa magnetic layer were in the range of $1000~2000\AA$ and $200~800\AA$. respectively. Substrate temperatures were controlled from $100^{\circ}C$ to $200^{\circ}C$. Increase of coercivity by about 100~200 Oe was observed in CoCrTa/Cr-X thin films compared to those without additional X element. Cu was the most effective additional element for increasing coercivity. CoCrTa/Cr-Cu thin film shows relatively high coercivity in $1500\AA$ underlayer thickness and $600\AA$ magnetic layer thickness.

• Journal of the Korean Chemical Society
• /
• v.24 no.1
• /
• pp.15-19
• /
• 1980

CNDO/2, EHT molecular orbital methods are used to investigate the electronic structure and reactivity of glycinato, glycine ester ligands. The results show that bidentate glycinato has a more stable structure, Gly-I with a $105.9^{\circ}$dihedral angle between ${\Delta}O_4C_3C_2$ and ${\Delta}C_3C_2N_1$ than Gly-Ⅱ. The electron inductive effects in the alkyl group substituted glycine ester ligands can also be derived from the calculation. According to the electron density, qN of ligands on the basis of CNDO/2 MO calculations, it is concluded that the stabilities are in the order of glycinato > Gly-Et-ester > Gly-i-Pr-ester > Gly-Me-ester.

• Journal of the Korean Chemical Society
• /
• v.30 no.2
• /
• pp.195-200
• /
• 1986

MO studies have been carried out on 1,5-hydrogen shifts between tautomeric forms (6${\pi}$ system) of ${\beta}$-diketones, ${\beta}$-thioxoketones and ${\beta}$-dithioketones by determining transition state and analyzing structural stability effects on the activation barriers using MNDO method. The barrier was found to increase with the stability of the ground state having greater charge separation and with the increase (less stabilization) in the one electron energy ${\Delta}(2\sum\limits^{occ}{\varepsilon}i)^{\neq}$ in the activation process.

• Journal of the Korean Chemical Society
• /
• v.17 no.3
• /
• pp.145-153
• /
• 1973

The temperature effects on the equilibria between polymolybdatd anions in 1M sodium perchlorate solution has been investigated in the temperature range of 20~50$^{\circ}$C. The polymolybdate anions formed are heptamolybdate ($Mo_7O_{24}^{6-}$) ions and the protonized forms of heptamolybdate ions ($H_LMo_7O_{24}^{(6-L)-}$). The equilibrium constants for the formation of heptamolybdate ions calculated by Sillen's method are as follow;$8H^{+}+7MoO_4^{2-}=Mo_7O_{24}^{6-}+4H_2O$, $k_{7.8}=2.77{\times}10^{53}:20^{\circ}C= 9.29{\times}10^{51}:40^{\circ}C$,$k_{7.8}= 4.22{\times}10^{52}:30^{\circ}C = 9.29{\times}10^{51}:50^{\circ}C$ The enthalpy change for calculated for the above reaction is 31.51 kcal/mole. A method of calculation of the equilibrium constants for the formation of protonized heptamolybdate ions from heptamolybdate ions and hydrogen ions has been derived. The equilibrium constants calculated for the formation of protonized heptamolybdate ions are as follow; $ LH^++ Mo_7O_{24}^{-6} = H_LMo_7O_{24}^{(6-L)-} : L = 1\;or\;2$, $k_1 = 2.31{\times}10^4=2.53{\times}10^4=2.76{\times}10^4= 3.10{\times}10^4$, $k_2 = 6.19{\times}10^7\;20^{\circ}C = 7.80{\times}10^7\;30^{\circ}C = 1.22{\times}10^8\;40^{\circ}C = 2.03{\times}10^8\;50^{\circ}C$The enthalpy change for the following step reactions are as follow;$H^{+}+Mo_7O_{24}^{6-}= HMo_7O_{24}^{5-}\;{\Delta}H^{\circ}=1.90 kcal/mole$, $2H^{+}+Mo_7O_{24}^{6-}=H_2Mo_7O_{24}^{4-}\;{\Delta}H^{\circ}=7.50kcal/mole$

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2483-2488
• /
• 2008

To mitigate the effects of cavitation and flashing, several types of orifices have been installed in the pipeline of new nuclear power plants. To review the effects of wall thinning caused by flow-accelerated corrosion by the types of orifices, which are cone and plate, and the relation between flow behavior and local wall thinning, experiments and numerical analyses for the downstream pipe of two types of orifices were performed. The experimental results in terms of static pressure obtained for the experimental facilities were compared with those of three-dimensional (3D) numerical analyses using the FLUENT code. As the results of review of flow-accelerated corrosion effects based on the experiment and numerical analysis, it was identified that the orifice of cone-type can be comparatively mitigated the effects of cavitation and flashing, but can not be mitigated the effect of flow-accelerated corrosion.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.34 no.1
• /
• pp.30-35
• /
• 2024

In order to improve the efficiency of the water splitting system for hydrogen production, the high overvoltage in the electrochemical reaction caused by the catalyst in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) must be reduced. Among them, transition metal-based compounds are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metal porous material, was used as a support, and Fe-doped β-Ni(OH)₂ microcrystals were synthesized through a hydrothermal synthesis process. In addition, in order to improve OER properties, changes in the shape, crystal structure, and water splitting characteristics of Fe-Mo co-doped β-Ni(OH)₂ microcrystals synthesized by co-doping with Mo were observed. The changes in the shape, crystal structure, and applicability as a catalyst for water splitting were examined.

• Research in Plant Disease
• /
• v.26 no.2
• /
• pp.103-108
• /
• 2020

Evaluations were made for the effects of cheese whey treatment on infection of pepper plants by cucumber mosaic virus-Vch (CMV-Vch) and pepper mottle virus-Kr (PepMoV-Kr). In a greenhouse, pepper plants sprayed with whey, prior to inoculation by CMV-Vch using aphids, showed a viral infection rate significantly lower (6.6%) than for the control (23.3%). In an open field experiment, in which CMV infection relied on natural transmission by aphids, pepper plants were sprayed with undiluted whey once a week, starting on the transplanting date (May 2) to the end of June. On June 5, these whey-sprayed plants showed a CMV infection rate reduced by 18.9% and 16.7%, compared to untreated and pesticide-treated plants, respectively. In the greenhouse, pepper plants inoculated with PepMoV-Kr mixed with whey showed a viral infection rate decreased by 60% compared to the control. The accumulated amount of PepMoV-Kr coat protein was less than that for the virus-only control at 6 days post inoculation (dpi), but increased up to a similar level as the control at 9 dpi. This study showed that cheese whey is effective in reducing infection of both CMV and PepMoV in pepper plants.