• Journal of the Society of Disaster Information
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• v.18 no.1
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• pp.19-28
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• 2022

Purpose: One of the methods for preventing disasters such as fire, explosion, and electric shock caused by electricity is to perform grounding. In case of the grounding current includes a frequency component having a high, it is preferable to measure grounding impedance rather than grounding resistance. This study proposes countermeasures to reduce grounding impedance to suppress an ground potential rise due to a grounding current having a frequency component of several kHz or more. Method: General grounding rods and needles-typed grounding rods were buried in the ground, and grounding resistance and grounding impedance were measured, respectively. The characteristics of grounding impedance according to frequency were identified. Result: There was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range lower than 62.5kHz, there was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range higher than 62.5kHz, the grounding impedance of needles-typed grounding rods was reduced by about 15% than the grounding impedance of general grounding rods. Conclusion: In the commercial frequency domain, it is effective to connect several grounding rods (common grounding) to lower the grounding resistance value. In the frequency domain of several kHz or more, it is expected that needles-typed grounding rods can effectively reduce the ground potential rise due to the grounding current.

• Journal of the Korean Society of Earth Science Education
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• v.15 no.2
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• pp.285-298
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• 2022

This study is to investigate the effects and characteristics of science and engineering integrated lessons on elementary students' creative engineering problem solving propensity (CEPSP). The science and engineering integrated lessons used in this study was a 10 lesson-hours STEM program, co-developed by University of Minnesota and Purdue University. The program was implemented in the 6th grade science class of H Elementary School located in P Metropolitan city. The main data of this study are the pre-post CEPSP result and interview with 5 students collected before and after the research. The CEPSP result was analyzed by a paired-sample t-test and hierarchical cluster analysis. As a result of the t-test, it was found that overall, the program has a positive effect on the students' CEPSP score. As a result of cluster analysis, it was confirmed that studnets' CEPSP could be classified into two groups (lower and higher score cluster). Five students whose, CEPSP score has significantly improved after the lessons were interviewed to find out what the characteristics of the program that contribute the significant change are. As a result of conducting centroid analysis of the interview transcription and the hybrid analysis method, it was found that the meaningful experiences that the five students commonly shared were 'problem solving through collaboration' and 'through repeated experiments (redesign)', problem solving' and 'utilization of scientific knowledge'. As minor reactions, 'choice of the best experimental method' and 'difference between science and engineering' appeared.

• Journal of Aquaculture
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• v.21 no.4
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• pp.325-330
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• 2008

Two different Eelwardsiella tarda isolates, KFE and Edk-2, were obtained from Korea and Japan respectively. On the base of the previous results showing higher pathogenicity of E. tarda KFE compared to that of E. tarda Edk-2 isolate, we tried to determine the differences of antigenicities of these two isolates in loach which is one of the important species in freshwater aquaculture in Korea. Concentration of specific antibody in the serum appeared to be much higher in loach immunized with FKC of E. tarda Edk-2 than those found in loach immunized with FKC of E. tarda KFE. Cross-reaction analysis using agglutination test with normal and antigen-absorbed antisera implied the differences epitopes in the antigens of these E. tarda isolates. For the comparison of bactericidal activity of the produced antibody with different antigens, absorption analysis was performed and confirmed the presence of critical epitopes in the FKC of E. tarda KFE strain. The prophylactic agent, polysaccharide-bound protein (PS-K) injected 1 week before the artificial infection with E. tarda KFE isolates decreased the cumulative mortality in loach and would be on effective method to prevent the occurrence of bacterial infection including E. tarda.

• Journal of The Korean Association For Science Education
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• v.20 no.1
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• pp.43-51
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• 2000

In this study, the effects of extraversion/introversion grouping and the differences between extroverts and introverts in cooperative learning strategy applied to general science class were investigated. Ninety-three 10th-graders were grouped into homogeneous and heterogeneous cooperative groups with respect to extraversion and introversion, and were taught about matter for 10 class periods. Prior to the instructions, three tests regarding the extraversion/introversion, logical thinking, and learning motivation were administered. After the instructions, their achievements, process skills, self-esteem, communication apprehension, and learning motivation were examined. Two-way ANCOVA results revealed that there were no main and interactive effects in the scores of the achievement and the process skills tests. However, significant interactive effect was found in the self-esteem. While the difference in the self-esteem of the introverts and the extroverts was small in the homogeneous group, the self-esteem of the extroverts was higher than that of the introverts in the heterogeneous group. The communication apprehension of the introverts was significantly lower than that of the extroverts. Students' perceptions to their group activities and group members were also studied.

• The Journal of the Korea Contents Association
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• v.20 no.9
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• pp.129-139
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• 2020

This study was conducted to analyze the subjective perception types of college students majoring in cooking by applying flip-learning teaching and learning methods to the subject of cooking practice to improve the educational efficiency of cooking-related classes. Also, in order to study subjective perception of small students, we tried to grasp the common structure in subjective attitude and perception using Q methodology, and the analysis resulted in four types. Type 1 (N=5): Problem solving ability effect, Type 2 (N=6): Self-directed learning effect, Type 3 (N=3): Mutual cooperation practice effect, Type 4 (N=6) ): Theory learning effect was analyzed for each unique feature type. Flip-learning is applied to cooking practice classes, which is a learner-centered education that leaves the traditional teaching method. Interest was found to have a very positive effect on learners' opinion sharing and learning outcomes. However, it was revealed that all students need to find additional solutions to problems such as the operation plan for flipped learning and the free ride evaluation method in group learning.

• Journal of The Korean Association For Science Education
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• v.41 no.2
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• pp.171-181
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• 2021

The purpose of the study is to explore the personal experiences and efforts of science teachers, who have worked in science core schools over the years, in order to evaluate the educational effects and implications of science core school policies. To achieve this purpose, we conducted semi-structured interviews with twelve individual science teachers who have operated programs and curriculum at science core schools. The results provided three case studies presenting how the teachers operated curriculum and how they perceived the benefits of science core schools and identified some commonalities in their experiences and perceptions through cross-case discussions. Three teachers in case studies presented different teaching orientations for science core schools, but they positively perceived its benefits and were very satisfied with the school environment and financial supports from government even though they had more burdens on work. In cross-case analysis among 12 teachers, the teachers commonly presented their passion and enthusiasm for organizing and implementing various extra-curriculum science activities. They believed that such efforts contributed to encouraging their students to consider their careers in science and engineering fields in college. And the differentiated school program has increased reputation and preference for the school from local parents and students. In addition, they felt that these efforts brought their own growth and professional development as science teachers.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.2
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• pp.95-111
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• 2023

Korea has achieved a high startup rate by promoting government-led startup policies for national economic and industrial development. However, as high as the startup rate is, the closure rate of startup companies can be judged to be insufficient for the qualitative growth of the domestic startup ecosystem. This study aims to investigate how to improve the survival rate of startups by overcoming the valley of death from a location environment perspective. It analyzes the effects of technology orientation and market orientation of start-ups on management performance and the moderating effects of economic, accessibility, and network factors that constitute the location environment. To achieve the research objectives, the empirical analysis was conducted on start-up companies that received corporate support projects from innovation intermediary organizations. The results show that R&D capability of technology orientation has a significant effect on management performance, and market information generation and market information response of market orientation have a significant effect on management performance. As for the moderating effect, accessibility, a sub-factor of the location environment, has a positive moderating effect on the relationship between technological innovation and managerial performance, and the location environment (economy, accessibility, and network) has a positive moderating effect on the relationship between market information generation and managerial performance. This study compared and analyzed previous studies on the success and failure of start-ups and identified common factors. In addition, this study provides policy implications for the sustainable growth of startups through empirical analysis and interview with stakeholders. For future research, it is necessary to compare and analyze start-ups in metropolitan areas and non-metropolitan areas. In addition, it is necessary to study startups that have moved out of the region and into the metropolitan area to find ways to develop the regional startup ecosystem.

• Communications of Mathematical Education
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• v.25 no.3
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• pp.497-524
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• 2011

This study was to understand students' learning about the function of math combined with molecular motions of science using the block scheduling. It was based on the revised Class Structure Model of Lee et al.(2010) where MBL as a tool was used to increase students' participation and understanding in the integrated concepts. The researcher provided the 6th grade students who lived in Sung Nam-Si, Kyung Gi-Do with 8 unit lessons, consisting of 5 stages of CSM. As a result of the study, the integrated education of Mathematics and Science showed synergic effect in studying both subjects and brought a positive result in gradual mathematization. It may be hard to combine all the contents of mathematics and science together. However, learning the relation between volume and pressure, and between volume and temperature of gas used as an example of function shown in our daily life was appropriate through Fogarty's integrated education model because it supported the objective of both subjects. Also, it was a good idea to develop CSM because it was composed of the contents from both subjects held in the same period of a year. Through the five stages, students were able to establish and generalize the definitions and the concepts of function.

• Korean Journal of Social Welfare
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• v.57 no.3
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• pp.195-222
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• 2005

This study was a comparative analysis by youth's internet addiction types. Distribution of internet addiction types, relative influence of risk and protective factors in each addiction type, and common and different risk and protective factors among the internet addiction types were investigated. And, the level of youth's mental health and the effect of internet to youth's mental health were identified. A total of 1,830 youth were surveyed, and the findings were as below: Firstly, 62.3% of the surveyed youth were addicted to internet. In detail, 15.9% had internet game addiction and 10.9% had internet sex addiction. Secondly, in all types of internet addiction, the risk factors gave severer influence than the protective factors did, and the protective factors gave compensation effect to each type of addiction. Thirdly, among the internet addiction types, the common risk factors were depression, aggression, parents' control, and friends' influence, while the protective factor was self control. Among the internet addiction types, a different risk factor was PC access, and the different protective factors included self-efficacy, teacher's support, friend's support, and parents' relationship. Fourthly, in all the three addiction pattern, the addicted adolescents had experienced more psychological symptoms than general internet users had. Finally, in the aspects of psychiatric symptoms, sex addiction gave the worst negative effect, and then game addiction, and internet addiction came in order. And the adolescents who had the higher degree of addiction were more likely to experience psychiatric symptoms.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.6
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• pp.187-202
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• 2015

The continued development of smart devices representing smart phones and tablet PC has made significant changes to the ICT ecosystem. Along the development of smart devices, consumers' needs are also becoming increasingly diversified in addition to their rising expectations. Thus, in order to fulfill the changing customer needs, corporations in the ICT ecosystem have recently focused on appcessory products that are interlinked and utilized in existing smart devices. This study particularly analyzes the two corporations, Samsung Electronics and SK Telecom, which recently plunged into appcessory business. By the case study of these two companies based on the theories of ecosystem and platforms, this study analyzes the current status of the appcessory market, the potentials and significances of the business, business background of the two corporations, and the status of leadership competition in the appcessory market. In the case of Samsung Electronics and SK Telecom, the study shows that both corporations acquired new growth powers in the appcessory market with their entry into existing or other relating markets. Also, since the appcessory business is highly related to their existing businesses, each company was able to take advantages based on the capability that they already possessed and this relationship had positive effects on their overall businesses. In addition, the two corporations had common strategies in increasing their competitiveness by identifying internal weaknesses and building external cooperations. On the other hand, since the two companies have different business areas, their business background, business strategies, and the effects of expectations varied to each other. Thus, this study identifies commonalities and differences between recent smart platforms and corporations' engagement in the fierce leadership competition in the appcessory market.