• Journal of Korean Elementary Science Education
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• v.27 no.2
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• pp.179-188
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• 2008

The purpose of this study is to investigate the effects of the causal thinking activity of Let's Think Through Science(LTTS) program on causal thinking and science process skills of elementary school students. Four classes of 4th graders (N=119) from a elementary school were divided into the control and the experimental groups. Causal thinking activity of LTTS program was used with the experimental group, while the normal curriculum was conducted with the control group. Both groups were given a pre-post test on causal thinking abilities and science process skills. And the experimental group was given 15- item questionnaires analyzing of perception on LTTS program. This study revealed that causal thinking activity of the LTTS program were effective on the development of students' causal thinking abilities and science process skills. ANCOVA results revealed that the scores of causal thinking abilities for the experimental group significantly higher than those of the control group. In the sub-tests of the causal thinking abilities all categories were effective. And ANCOVA results of the science process skills were also effective. Science process elements of observation, recognizing of a problem were significantly higher. And elementary students preferred to the causal thinking activity of LTTS program so that it was interesting, useful, helpful to each other in studying science.

• Journal of Korean Elementary Science Education
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• v.26 no.4
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• pp.395-406
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• 2007

The purpose of this study was to investigate the characteristics of 2nd grade students' interaction in the classification activities of LTTS. For the purposes of this study, three heterogeneous groups, chosen by cognitive level, were selected. The students' interactions were audio/video taped and classified as either cognitive or affective interaction. The results of this study are as follows. In the cognitive interactions, the frequency and quality of the functions of 'questions' and 'making suggestions' were higher than those of 'Responses' and 'Receiving opinions'. In the affective interactions, the frequency of 'induction' and 'dissatisfaction' was higher than that of the other types. The frequency and quality of interactions of students in both the early and mid concrete stage were higher than those of students in the transitional stage. Qualitatively higher-level interactions such as 'making suggestions' and positive interactions such as 'induction' to induce students who were passive in activities were made by the students at higher cognitive levels. However, the low-level of interaction in suggesting their opinion to the constituent's suggestion and 'dissatisfaction' with student in transition period who were passive in activity influenced group working negatively.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.411-418
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• 2019

Light-triggered thyristors (LTTs) are essential components in high-power applications, such as HVDC transmission and several pulsed-power applications. Generally, LTT fabrication includes a deep diffusion of aluminum as a p-type dopant to form a uniform p-base region, which needs careful concern for contamination and additional facilities in silicon semiconductor manufacturing factories. We fabricated 4-inch 5,000 V LTTs with boron implantation and diffusion process as a p-type dopant. The LTT contains a main cathode region, edge termination designed with a variation of lateral doping, breakover diode, integrated resistor, photosensitive area, and dV/dt protection region. The doping concentration of each region was adjusted with different doses of boron ion implantation. The fabricated LTTs showed good light triggering characteristics for a light pulse of 905 nm and a blocking voltage (V_DRM) of 6,500 V. They drove an average on-state current (I_TAVM) of 2,270 A, peak nonrepetitive surge current (I_TSM) of 61 kA, critical rate of rise of on-state current (di/dt) of 1,010 A/㎲, and limiting load integral (I²T) of 17 MA²s without damage to the device.

• Journal of The Korean Association For Science Education
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• v.27 no.7
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• pp.559-569
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• 2007

The purpose of this case study is to analyze the characteristics of social interaction according to gender-grouping in the application of LTTS program. For this study, mixed-gender group A (one boy and three girls or one girl and three boys), mixed-gender group B (two boys and two girls) and same-gender group (4 boys or 4 girls) were formed. Social interactions during group discussions were audio-/video-taped. Social interactions between one boy and one girl in each group were analyzed. The type of social interactions were classified as cognitive and affective interactions. The boy and the girl in the same gender group tended to make suggestion actively, but sometimes they ordered peers to participate or prevented peers from participating. On the other hand, they didn't tend to make suggestion about problem-solving in mixed-gender group A, but made suggestion against peer's opinion using appropriate reasons. The frequency of affective interactions in the mixed gender group B were higher.

• Korean journal of applied entomology
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• v.52 no.4
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• pp.295-304
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• 2013

This study aimed to understand the physiological status of the beet armyworm, Spodoptera exigua at low developmental threshold temperature (LTT) through analysis of gene-expression patterns associated with different functions (metabolism, nervous system, immune, and stress). The estimated LTTs for egg, larval, and pupal developments varied with $5.5{\sim}11.6^{\circ}C$. Larvae were able to develop at the lower temperatures than eggs and pupae. However, the physiological LTT ($15^{\circ}C$) in the fifth instar was much higher than the estimated LTT ($10.3^{\circ}C$). Gene expression patterns estimated by a quantitative RT-PCR (qRT-PCR) indicate that most genes in different functional groups increased their expressions with increase of larval instars. In the same fifth instar, as the treatment temperatures increased, the gene expression levels increased. Moreover, the newly molted fifth instar larvae were different in their gene expression rates according to their previous culturing temperatures. Most gene expressions were suppressed in the fifth instar larvae at the physiological LTT ($15^{\circ}C$). However, the larvae at $15^{\circ}C$ gradually exhibited significant increase in the gene expression rates with rearing time just like those at the higher temperature. These results suggest that S. exigua at LTT exhibits a typical gene expression pattern with maintaining significantly suppressed levels.