• The Bulletin of The Korean Astronomical Society
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• v.34 no.2
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• pp.52.1-52.1
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• 2009

• Proceedings of the Ginseng society Conference
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• 2008.05a
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• pp.82-82
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• 2008

• Journal of Environmental Science International
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• v.20 no.4
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• pp.483-491
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• 2011

Harvesting of marshfire glasswort (Salicornia europaea) by local people has been increased recently since this plant was known for a well-being food. Even though some harvesting sites are facing high risk of environmental pollution, Salicornia europaea is still harvested on a large scale. Therefore, to investigate safety of Salicornia europaea as a food resource, salt marsh environment, potential harvestable biomass, element and heavy metal accumulations in Salicornia europaea has been studied in three salt marshes, west-coast of Korea. Salicornia europaea showed 150 - 230$g/m^2/yr$ harvestable biomass. Biomass and nitrogen contents of Salicornia europaea were closely related to soil nitrogen and carbon concentrations. Average Na, Zn, Fe, Cr accumulations in Salicornia europaea were 41479, 18, 297, 1.5 (mg/kg), indicating valuable trace element contents. However, average heavy metal accumulations such as As, Cd, Cu, Pb, Hg accumulations were 1.5, 7.1, 4.2, 1.5, 0.1 (mg/kg), which were even or higher than national standards (0.5, 0.5, 2, 2, 0.1) of salts. These results imply that harvesting and eating of Salicornia europaea in west-coast research sites would be harmful because the contents would be much higher if it is calculated as only considering salts and minerals. Therefore, harvesting of Salicornia europaea from some salt marsh in west-coast of Korea should be done cautiously.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2013.05a
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• pp.154-154
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• 2013

In this work, we investigated the characteristics and the effects of light on the negative gate bias stress stability (NBS) in high mobility polycrystalline IGO TFTs. IGO TFT showed a high drain current on/off ratio of ${\sim}10^9$, a field-effect mobility of $114cm^2/Vs$, a threshold voltage of -4V, and a subthresholdslpe(SS) of 0.28V/decade from log($I_{DS}$) vs $V_{GS}$. IGO TFTs showed large negative $V_{TH}$ shift(17V) at light power of $5mW/cm^2$ with negative gate bias stress of -10V for 10000seconds, at a fixed drain voltage ($V_{DS}$) of 0.5V.

• Journal of The Korean Association For Science Education
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• v.14 no.3
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• pp.304-311
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• 1994

Four science concepts were selected from high school science textbook to investigate the differences in priorities of students knowledge activated during solving earth science problems in laboratory and earth science environmental contexts. Two items, one for laboratory context and the other for earth environmental context, were developed for earth selected concept The subjects were constituted of 192 students in 11th grade and 196 in 12th grade in one senior high school. Students' responses were categorized using graph models and analyzed in terms of 'Common Activated Knowledge'(CAK). and 'Specific Activated Knowledge'(SAK) across students' cognitive frames, grades, and sex. As contextual differences of the problems increased, context effects in priorities of CAK were reported in favor of laboratory context, on the contrary those of SAK in favor of earth environmental context. Context effects were reported across cognitive frames, especially students with laboratory cognitive frames showed more significant context effects than others. Lower graders and girls showed relatively large context effects. The results of this study showed that science concepts learned in a laboratory context are not easily transferred to earth environmental context. Therefore, special instructional strategies should be developed to overcome the context effect s according to activated knowledges with high priorities in laboratory and earth environmental context.

• Proceedings of KHEA Conference
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• 1997.07a
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• pp.192-192
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• 1997

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.383-392
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• 2016

This paper proposes the design considerations of resonant network and transformer magnetics for 500 kHz high switching frequency LLC resonant converter. The high power density can be effectively achieved by adopting high switching frequency which allows small size passive components in the converter. The design methodology of magnetizing inductance is derived for zero voltage switching (ZVS) condition, and the design methodology of the transformer and output capacitance is derived to achieve high power density at high operating frequency. Moreover, the structure of transformer is analyzed to obtain the proper inductance value for high switching operation. To verify the proposed design methodology, simulation and experimental results will be presented including temperature of passive and active components, and power conversion efficiency to evaluate dominant power loss. In addition, the validity of magnetics design will be evaluated with operating waveforms of the prototype converter.

• Smart Structures and Systems
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• v.29 no.4
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• pp.641-652
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• 2022

High-rise structures prone to large vibrations under the action of strong winds, resulting in fatigue damage of the structural components and the foundation. A novel compound damping cable system (CDCS) is proposed to suppress the excessive vibrations. CDCS uses tailored double cable system with increased tensile stiffness as the connecting device, and makes use of the relative motion between the high-rise structure and the ground to drive the damper to move back-and-forth, dissipating the vibration mechanical energy of the high-rise structure so as to decaying the excessive vibration. Firstly, a third-order differential equation for the free vibration of high-rise structure with CDCS is established, and its closed form solution is obtained by the root formulas of cubic equation (Shengjin's formulas). Secondly, the analytical solution is validated by a laboratory model experiment. Thirdly, parametric analysis is conducted to investigate how the parameters affect the vibration control performance. Finally, the dynamic responses of the high-rise structure with CDCS under harmonic and stochastic excitations are calculated and its vibration mitigation performance is further evaluated. The results show that the CDCS can provide a large equivalent additional damping ratio for the vibrating structures, thus suppressing the excessive vibration effectively. It is anticipated that the CDCS can be used as a good alternative energy dissipation system for vibration control of high-rise structures.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.273-279
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• 2015

Effects of passive film quality by chemical passivation and solution flow on the corrosion behavior of 304 stainless steel in HCl solution were investigated using a coloration indicator, and by corrosion weight loss, electrochemical polarization and element dissolution measurements. A high redness degree suggests a low passive-film integrity for 304 stainless steel following air exposure, while the minimum redness degree for the samples after chemical passivation suggests a high passive-film integrity. In the static condition, samples subjected to air exposure exhibited a high corrosion rate and preferential dissolution of Fe. Chemical passivation inhibited the corrosion rate due to the intrinsically high structural integrity of the passive film and high concentrations of Cr-rich oxides and hydroxide. Solution flow accelerated corrosion by promoting both the anodic dissolution reaction and the cathodic reaction. Solution flow also altered the preferential dissolution to fast uniform dissolution of metal elements.

• Journal of The Korean Association For Science Education
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• v.39 no.6
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• pp.695-706
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• 2019

This study conducted a case study on the process-centered evaluation competency of a middle-school/high-school science teacher using Teacher's Process-centered Evaluation Competency (T-PEC) measurement tool. The case analysis shows that teacher A in a middle school represents high competency of process-centered evaluation planning and cooperative communication while the competency of utilizing process-centered evaluation results is low owing to the characteristics of non-standardized areas. Teacher B in a high school shows high level of cooperative communication competency whereas low level of process-centered evaluation execution competency because the freedom given to students is not enough during the process of evaluation. The teacher also shows very low level of utilizing process-centered evaluation results due to the lack of time and the school culture not giving feedback to the students. According to cross-case analysis, teacher A and B both represent the highest level of collaborative communication competency and the lowest level of utilization process-centered evaluation results competency. And the lack of clear criteria for process-centered evaluation leads to different understanding of process-centered evaluation between the two teachers, and teacher B shows low the level of utilizing process-centered evaluation affects results due to the students not being concerned on feedback, security problem, and the reality focusing on the university entrance examination in high schools. Based on the results, this study suggests providing clear guidelines of process-centered evaluation to teachers, introducing an application in order to solve the time-lack problem pointed out as the biggest problem of process-centered evaluation, ensuring objectivity and security about process-centered evaluation results, and building the school culture such as the expanded application of standardized areas in order to implementing process-centered evaluation.