• Journal of the Korean Chemical Society
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• v.65 no.3
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• pp.185-196
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• 2021

For studying the reaction mechanism of the reactions related to NO in the ozone denitration reactions, the harmonic and anharmonic rate constants were calculated by the transition state (TS) theory and Yao and Lin (YL) method. According to above calculations, the reactions of NO with O₃ and NO₃ play an essential role, and the kinetic parameters considering anharmonic effect were fitted. Furthermore, the rate constants were up as temperature increasing, and the tendencies of high temperature were more gradual than the low temperature. The research will provide theoretical basis for the ozone denitration reactions.

• 한국연소학회:학술대회논문집
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• 2004.06a
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• pp.102-111
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• 2004

Partial quenching structure of turbulent diffusion flames in a turbulent mixing layer is investigated by the method of flame hole dynamics to develope a prediction model for the turbulent lift off. The present study is specifically aimed to remedy the problem of the stiff transition of the conditioned partial burning probability across the crossover condition by adopting level-set method which describes propagating or retreating flame front with specified propagation speed. In light of the level-set simulations with two model problems for the propagation speed, the stabilizing conditions for a turbulent lifted flame are suggested. The flame hole dynamics combined with level-set method yields a temporally evolving turbulent extinction process and its partial quenching characteristics is compared with the results of the previous model employing the flame-hole random walk mapping. The probability to encounter reacting' state, conditioned with scalar dissipation rate, demonstrated that the conditional probability has a rather gradual transition across the crossover scalar dissipation rate in contrast to the stiff transition of resulted from the flame-hole random walk mapping and could be attributed to the finite response of the flame edge propagation.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2628-2632
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• 2011

The nucleophilic substitution reactions of Y-O-aryl phenyl phosphonochloridothioates with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are kinetically investigated in acetonitrile at $55.0^{\circ}C$. The deuterium kinetic isotope effects (DKIEs) invariably increase from an extremely large secondary inverse ($k_H/k_D$ = 0.439; min) to a primary normal ($k_H/k_D$ = 1.34; max) as both substituents of nucleophile (X) and substrate (Y) change from electron-donating to electron-withdrawing. These results are opposite to the DKIEs on Y-O-aryl methyl phosphonochloridothioates, and can be rationalized by the gradual transition state (TS) variation from backside to frontside attack. The trigonal bipyramidal pentacoordinate TS is proposed for a backside attack, while the hydrogen-bonded, four-center-type TS is proposed for a frontside attack. The negative values of the cross-interaction constants (${\rho}_{XY(H)}$ = -0.38 for $XC_6H_4NH_2$ and ${\rho}_{XY(D)}$ = -0.29 for $XC_6H_4ND_2$) indicate that the reactions proceed by a concerted $S_N2$ mechanism.

• Journal of the Korean Society of Combustion
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• v.9 no.2
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• pp.18-29
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• 2004

Partial quenching structure of diffusion flames in a turbulent mixing layer has been investigated by the method of flame hole dynamics in oder to develope a prediction model for the phenomenon of turbulent flame lift off. The present study is specifically aimed to remedy the shortcoming of the stiff transition of the conditioned partial burning probability across the crossover condition by employing the level-set method which enables us to include the effect of finite flame edge propagation speed. In light of the level-set simulation results with two models for the edge propagation speed, the stabilizing conditions for turbulent lifted flame are suggested. The flame hole dynamics combined with the level-set method yields a temporally evolving turbulent extinction process and its partial quenching characteristics is compared with the results of the previous model employing the flame-hole random walk mapping based on three critical scalar dissipation rates. The probability to encounter reacting state, conditioned with scalar dissipation rate, demonstrated that the conditional probability has a rather gradual transition across the crossover scalar dissipation rate. Such a smooth transition is attributed to the finite response of the flame edge propagation.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.545-551
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• 2010

Hydrophobically monoendcapped poly(sodium acrylate)s formed hydrophobic microdomains in water. This was concluded on poly(sodium acrylate)s with a linear $C_{12}$-alkyl chain attached specifically at the end of the polymer. There was no well defined CMC (critical micelle concentration), but rather a gradual transition from a micelle free solution to a micelle solution. Steady state fluorescence spectroscopy indicates that the micro domains are rather hydrophobic. At pH 5 in the abscence of salt and at pH 9 in the prescence of 1 M sodium citrate the CAC (critical aggregation concentration) was in the range of 0.1 to 2.4 mM. However at pH 5 there was a linear increase in the transition concentration with a head-group size due to an increase in steric and electrostatic repulsions between polymer main chains. At pH 9 in the abscence of salt the transition concentration was in the range of 1 to 80 mM. For the larger polymers there was a effect which consisted of a concentration gradient of sodium counterion toward the hydrophobic domain. The effect was larger for the larger polymers because of the higher total sodium concentration and the less steep counterion concentration gradient.

• Korean Journal of Social Welfare
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• v.58 no.3
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• pp.135-168
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• 2006

This study reviewed pension reform's overall characteristic and(anticipated) positive negative effect in OECD countries's and then analysed middle-old age's retirement transition and determinants of full/gradual retirement through the $3{\sim}7th$ Korea Labor and Income Panel considering that Korea has been aging society quickly and it is necessary to suggest not only solution of early retirement and working age reduction but also pension reform. As a result of this study, about 1/4 of 50 years and older have been continuing to work through various pathways after retirement and 98% among fully retired older who passed by re-employment step of occupational status including retirement are still searching for jobs. This showed that it is also inappropriate to typical retirement concept itself on the lines of labour market participation in Korea and part-time/temporary work or self-employment have been used by means of alternatives of maintaining works for middle-old ages. However, the duration of changed occupational status of gradual retirees is mostly only $1{\sim}2$ years. Therefore it is necessary to support the gradual retirement to minimize a term of income insecurity and promote the work of the old ages who have will and capacity of work. Most of all, partial pension system which is main program of gradual retirement, should make the rules that beneficiaries are those who age less than pensionable age and benefit levels should be actuarial fairness together with pension system and provide substantial help. But, the introduction of partial pension system is not the only way to solve and needs overall social economic approach. Especially guarantee the increase of quantitative qualitative employment for middle-old ages linking labor market policy and supporting gradual retirement not ought to be abused to force the part time works and early retirement route against their own will.

• Journal of the Korean housing association
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• v.26 no.3
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• pp.11-24
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• 2015

There have not been many debates on the subject of Korean architecture during the transformative period of Gae Wha Gi (開化期: Enlightenment Period of Korea), when Western-style buildings first appeared in Seoul. This study begins by finding and recording those buildings in Seoul that show the gradual adoption and appropriation of Western architectural elements at the turn of the 20th century. By exploring the confluence of two different architectural styles, this paper attempts to look carefully at the hybrid conditions that resulted from encounters between the Koreans and the Westerners in the late 19th and early 20th century. Beginning with discovering the first products of the Western architectural influence in Seoul, this study explores the uneasy co-existence between the traditional Korean architectural style, and the Western architectural style. This co-existence ultimately bred new building techniques, and interior layouts; the appearance of these hybrid buildings illustrate the gradual transition from the traditional way, in which users modified, combined and appropriated various elements from both styles. Analyzing historical documents and photos, this study tries to capture a detailed image of the period when the influence of the Western architecture had an unavoidable impact and brought change to the traditional architecture of Korea.

• Journal of Korea Water Resources Association
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• v.44 no.6
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• pp.461-470
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• 2011

Abrupt and gradual levee breach analyses on the flat domain were implemented by laboratory experiments and numerical simulations. To avoid the reflective wave from the side wall the experiment was performed in a large domain surrounded by waterway. A numerical model was developed for solving the two-dimensional gradual levee breach flow. The results of the numerical simulation developed in this study showed good agreement with those of the experimental data. However, even if the numerical schemes effectively replicated the trends of the observed water depth for the first shock, there were little differences for the second shock. In addition, even though the model considered the Smagorinsky horizontal eddy viscosity, the location and height of the hydraulic jump in the numerical simulation were not fairly well agree with experimental measurements. This shows the shallow water equation solver has a limitation which does not exactly reproduce the energy dissipation from the hydraulic jump. Further study might be required, considering the energy dissipation due to the hydraulic jump or transition flow from reflective wave.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.12
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• pp.955-963
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• 2017

Nowadays, fintech becomes the key technology of the mobile banking and payments. Financial market is moved to fintech-based non-face-to-face trade/payment from traditional face-to-face process in Korea. Core of this transition is the smartphones, which have several sensitive sensors for personal identifications such as fingerprint and iris recognition sensors. But it has some originated security risks by data path attacks, for instance, hacking and pharming. Multi-level certification and security systems are applied to avoid these threats effectively, while these protections can be cause of some inconvenience for non-face-to-face certifications and financing processes. In this paper, I confirmed that it have sensible differences correspond with the data connection paths such as WiFi networks and mobile communication networks of the smartphones, and I propose a gradual certification method which alleviates the inconvenience by risk-level definitions of the data-paths.

• Journal of the Korean Magnetic Resonance Society
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• v.11 no.2
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• pp.64-72
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• 2007

[ $^1H$ ] nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal $(NH_4)_3H(SO_4)_2$. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the $^1H$ NMR MAS spectrum at 340 K. As temperature decreases, the $^1H$ NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of $T_1$ for ammonium and hydrogen-bond protons are similar in the whole range of temperature. $T_1$ of $^1H$ NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then $T_1$ shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and $T_1$ clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.