• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.397-400
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• 2014

Size- and shape-controlled monodisperse wurtzite structured CdS nanorods have been successfully synthesized using a facile solution-based colloidal method. Depending on the control of injection/growth temperatures and the variation of Cd-to-S molar ratios, the morphology of the CdS nanocrystals (NCs) can be adjusted into bullet-like, rod-like, and dot-like shapes. X-ray diffraction (XRD), transition electron microscopy (TEM), and absorption spectroscopy were used to characterize the structure, morphology, and optical properties of as-synthesized CdS NCs. It was found that uniform CdS nanorods could be successfully synthesized when the injection and growth temperatures were very high (> $360^{\circ}C$). The aspect ratios of different shaped (bullet-like or rod-like) CdS NCs could be controlled by simply adjusting the molar ratios between Cd and S.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.701-705
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• 2002

This paper describes implementation of IPv6-IPv4 transition toolbox named as 6TALK(IPv6 TrAansLator of Krv6) and some scenarios using 6TALK which enables IPv6 island to connect other IPv6 island or IPv4 island seamlessly. 6TALK implements some transition mechanisms suggested in NGTrans Working Group of IETF. Those mechanisms are composed of basic mechanism, tunneling, and applied mechanism such as DSTM. 6TALK provides functions which enable IPv6 network at the edge of existing network to communicate with IPv4 network by using these transition mechanisms. As major transition mechanisms in 6TALK we adopt NAT-PT/SIIT and DSTM/DSTM options and as implementation environment we use Linux Kernel 2.4.18 and Netfilter framework. Software modules implemented in Linux kernel was ported to hardware box using Motorola MPC 8260 processor. The transition mechanisms used in 6TALK are the ones predicted to be used in initial transition step to IPv6.

• Journal of The Korean Association For Science Education
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• v.41 no.5
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• pp.429-440
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• 2021

In this article, we explored the value of interculturalism in developing the discourses of international cooperation in science education. By doing so, we interviewed four teachers who had an experience in teaching science in developing countries, and analyzed their experiences and perceptions in the lens of interculturalism and dialogue. Our analysis of teacher narratives shows the transition in the teachers' perspectives from volunteering and transmission to collaboration and learning. The transition from volunteering to collaboration occurred as the teachers learned how to meet 'the others' as themselves being strangers in the foreign context. Through intervening and colliding, teachers were able to reposition their identities as teachers. Furthermore, their science teaching practices show how the teachers tried to negotiate between the universal or idealistic value of science education and the heterogeneities formed by the country's cultural and specific situation of science education. Through these experiences, the teachers began to understand the importance of the culturally specific 'need' for science education. In conclusion, we proposed a discourse of science education collaboration based on interculturalism in terms of the diversity and complexity of science education practices in developing countries, teacher professionalism, culturally relevant pedagogy and sustainable policy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7093-7100
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• 2014

This study analyzed the factors related to labor market transition of job injured workers. The Workers' Compensation Insurance Panel data ver.1, which that was surveyed by the Korean Workers' Compensation & Welfare Service in 2013, was used. Four key findings were made: first, the economically inactive populations are 7.2% and unemployed is 22.3% of occupational accident workers who finished the treatment period; second, 31.5% of laborers who returned to a new workplace went into another type of occupation; third, the results showed that socio-demographic factors, such as gender, age and education years, injury-related factors, such as the treatment period and work limitation, and workplace factors, such as company size and employment status, were associated with the return to work; and fourth, a relatively higher proportion of people who has received occupational training could not return to work and the disability grade was not associated with the return to work. These results suggest that policy makers need to understand the characteristics of labor market transition of job injured workers and develop efficient intervention programs based on the transitional labor market.

• 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.

• Journal of the Korean Chemical Society
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• v.29 no.1
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• pp.15-22
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• 1985

Kinetic studies of nucleophilic substitution reaction of substituted benzoyl cyanides and benzoyl chlorides with pyridines were conducted at 25$^{\circ}C$ in pure acetone solvent. Results showed that (ⅰ) magnitudes of $_{\rho}_S$, $_{\rho}_N$ and ${\beta}$ associated with a change of substituent in the nucleophile indicate relatively advanced bond-formation in the transition state, (ⅱ) the potential energy surface model is able to predict the reaction mechanism, but it is unable to predict the transition state variation to a more product-like transition state, where bond-formation is much more progressed than bond breaking, upon changing the leaving group to that with better leaving ability (ⅲ) the quantum mechanical model predicted the product-like transition state and slightly better leaving ability of CN- as compared with Cl-.

• Journal of The Korean Association For Science Education
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• v.17 no.2
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• pp.139-148
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• 1997

This study investigated the influences of the cooperative learning strategies upon students' achievement and their perceptions of learning environments in a middle school physical science course. Prior to instruction, the Group Assessment of Logical Thinking was administered, and its score was used as a blocking variable. Mid-term examination score was used as a covariate. For the treatment group with heterogeneous grouping, cooperative learning instruction (the Learning Together model) was used, which emphasized group reward, individual accountability, and role division. For the control group, traditional instruction was used. After instruction, an achievement test consisting of three subtests (knowledge, understanding, and application), and the perception questionnaire of classroom and laboratory environments, were administered. ANCOVA results revealed that there was a significant interaction between instruction and the level of logical reasoning ability although there were no significant differences in all three subtest scores of the achievement test. For the concrete operational reasoners, the treatment group performed better in the subtests of understanding and application than the control group. For students at the formal and transition levels, however, the treatment group scored lower than the control group. Significant interactions were also found in the perceptions of classroom environment and laboratory environment. For the concrete operational reasoners, the treatment group showed more positive perception than the control group. For the students at the formal and transition levels, the control group had positive perception than the treatment group. Educational implications are discussed.

• Computers and Concrete
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• v.21 no.1
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• pp.67-74
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• 2018

A differential scheme based micromechanical framework is proposed to obtain the effective properties of the saturated concrete repaired by the electrochemical deposition method (EDM) considering the interfacial transition zone (ITZ) effects. The constituents of the repaired concrete are treated as different phases, consisting of (micro-)cracks, (micro-)voids and (micro-)pores (occupied by water), deposition products, intrinsic concrete made up by the three traditional solid phases (i.e., mortar, coarse aggregates and their interfaces) and the ITZs. By incorporating the composite sphere assemblage (CSA) model and the differential approach, a new multilevel homogenization scheme is utilized to quantitatively estimate the mechanical performance of the repaired concrete with the ITZs. The CSA model is modified to obtain the effective properties of the equivalent particle, which is a three-phase composite made up of the water, deposition products and the ITZs. The differential scheme is employed to reach the equivalent composite of the concrete repaired by EDM considering the ITZ effects. Moreover, modification procedures considering the ITZ effects are presented to attain the properties of the repaired concrete in the dry state. Results in this study are compared with those of the existing models and the experimental data. It is found that the predictions herein agree better with the experimental data than the previous models.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2002-2010
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• 2006

This study examined the quenching of ofloxacin (OFL) and flumequine (FLU) fluorescence by $Cuj^{2+}$, $Ni^{2+}$, $Co^{2+}$ and $Mn^{2+}$ in an aqueous solution. The change in the fluorescence intensity and lifetime was measured at various temperatures as a function of the quencher concentration. According to the Stern-Volmer plots, the fluorescence emission was quenched by both collisions (dynamic quenching) and complex formation (static quenching) with the same quencher but the effect of static quenching was larger than that of dynamic quenching. Large static and dynamic quenching constants for both OFL and FLU support significant ion-dipole and orbital-orbital interactions between fluorophore and quencher. For both molecules, the static and dynamic quenching constants by $Cu^{2+}$ were the largest among all the metal quenchers examined in this study. In addition, both the static and dynamic quenching mechanisms by $Cu^{2+}$ were somewhat different from the quenching caused by other metals. Between $Ni^{2+}$ and FLU, a different form of chemical interaction was observed compared with the interaction by other metals. The change in the absorption spectra as a result of the addition of a quencher provided information on static quenching. With all these metals, the static quenching constant of FLU was larger than those of OFL. The fluorescence of OFL was quite insensitive to both the dynamic and static quenching compared with FLU. This property of OFL can be explained by the twisted intramolecular charge transfer in the excited state.

• Hwankyungkyoyuk
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• v.20 no.1
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• pp.42-61
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• 2007

This study investigated the effect of the environmental issue analysis instruction on the decision making ability of middle school students. A pretest-posttest control group design was employed. The participants for the research were 288 1st grade male students in middle school in Seoul, the environmental issue analysis lesson group consisted of 142 members and the non-environmental education group consisted of 146 members. The cognitive level of the students were divided into three groups-concrete, transition, formal-as the result of GALT test. Students take issue analysis lessons during 6 weeks, one lesson per a week. Students had studied through worksheets reconstructed and developed by researcher on basis of issue analysis suggested by Ramsey et al. (1997). The results of the research were followings: After lesson for environmental issue analysis, all of the students were improved in decision-making ability regardless of cognitive level (p<.05). Especially, decision-making ability of the transition group students was improved to a high degree. Scores of searching relevant information, generation of alternatives, identification of values for selection criteria, the evaluation of alternatives' merits and demerits, prediction of consequence were increased in experimental group (p<.05). But the ability of selection of alternatives according to value was not reached statistically meaningful improvement. The decision-making ability of the control group students was not improved but ability of selection of alternatives, the evaluation of consequence were increased (p<.05).