• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.3
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• pp.1-12
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• 2012

In this study, an analysis method for the earthquake response of an offshore wind turbine model is developed, considering the effects of the fluid-structure-soil interaction. The turbine is modeled as a tower with a lumped mass at the top of it. The tower is idealized as a tubular cantilever founded on flexible seabed. Substructure and Rayleigh-Ritz methods are used to derive the governing equation of a coupled structure-fluid-soil system incorporating interactions between the tower and sea water and between the foundation and the flexible seabed. The sea water is assumed to be a compressible but non-viscous ideal fluid. The impedance functions of a rigid footing in water-saturated soil strata are obtained from the Thin-Layer Method (TLM) and combined with the superstructure model. The developed method is applied to the earthquake response analysis of an offshore wind turbine model. The method is verified by comparing the results with reference solutions. The effects of several factors, such as the flexibility of the tower, the depth of the sea water, and the stiffness of the soil, are examined and discussed. The relative significance of the fluid-structure interaction over the soil-structure interaction is evaluated and vice versa.

• Journal of Korean Society of Transportation
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• v.34 no.1
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• pp.43-54
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• 2016

Although there are continuous demands for activating BSSs(Bicycle Sharing Systems) due to the convenience and positive health effects, it is difficult to make a decision to support the existing systems and build more systems because of the deficit resulting from the operation of BSSs. Consequently, this study estimated the economic effects(WTP; Willingness to Pay) of BSS and analyzed the impact factors of WTP to support the above decision making in Daejeon. For this, we conducted a survey and collected 668 samples from the users and non-users of TASHU that is the BSS operated in Daejeon. Also, we used CVM(Contingent Valuation Method) for the estimation of WTP. The results show that the number of bicycle uses is a determinant factor having a positive relationship with WTP and car ownership and age are also determinant factors having a negative relationship with WTP. On the other hand, income and sex have no significant statistical relationship with WTP. Also, the economic benefit of TASHU was estimated as much as 49.9 billion KRW to 63.6 billion KRW. Considering the operation cost of 2.5 billion KRW, it is quite big benefit. Based on the results, it needs to support TASHU from a user perspective for the efficient operation of the system.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.77-77
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• 2013

최근의 산업활동에서는 신규 원료 개발과 생산 효율성을 높이기 위하여 분체 공정이 증가하고 있는데, 미세 분진의 취급으로 분진운의 형성과 착화가 용이해지므로 분진폭발이나 화재 위험성이 증가하고 있다. 분진을 안전하게 사용하고 저장, 취급하기 위해서는 착화 전의 위험성 지표로서 최저발화온도(MIT ; Minimum Ignition Temperature)를 사전에 파악해 두는 것이 중요하다. 분진농도의 발화온도는 장치 내의 발화위험성이나 분진 취급 공정의 사고예방대책 관리를 위한 실용적 관점에서 중요하게 활용되는 폭발특성값이다. 또한 분진의 발화온도는 분진농도에 의존하며 농도변화에 따른 가장 낮은 온도를 MIT라고 한다. 본 연구에서는 화재폭발사고 빈도가 줄지 않고 있는 Mg 및 Mg-Al합금(60:40 wt%, 50:50 wt%, 40:60 wt%)을 대상으로 조성비율에 따른 최저발화온도를 실험적으로 조사하였다. Mg 및 Mg-Al(60:40 wt%), Mg-Al(50:50 wt%), Mg-Al(40:60 wt%) 시료의 평균입경은 142, 160, 151, $152{\mu}m$이다. MIT실험장치는 IEC 61241-2-1(Methods for Determining the Minimum Ignition Temperatures of Dust, 1994)에 준거하여 제작하여 사용하였다. 실험장치는 가열로, 분진운 시료홀더, 온도조절장치, 압축공기 제어장치 등으로 구성되어 있다. 구체적인 실험방법은 시험분진를 분진홀더에 장착하고 0.5 bar의 압축공기를 0.3 sec 동안 사용하여 일정 온도로 가열된 로의 내부로 분진운을 부유시킬 때에 분진운이 발화하여 가열로 하단부의 개방구에까지 화염이 전파하는지를 디지털비데오카메라로 기록, 평가하여 발화 유무를 판정하였다. Mg합금에 대한 MIT를 측정한 결과 $740^{\circ}C$가 얻어졌으며, Mg-Al(60:40 wt%)의 MIT는 $820^{\circ}C$로 조사되었다. 그러나 Mg-Al(50:50 wt%) 및 Mg-Al(40:60 wt%)에 대해서는 최대 가열로의 설정온도를 $890^{\circ}C$까지로 하여 농도를 변화시키면서 조사하였으나 발화가 일어나지 않았다. 문헌에 따르면 Mg입자 표면의 산화피막은 다공성으로 일정 온도에서 산화반응이 시간에 따라 직선적으로 증가하는데 반하여, Al의 산화피막은 보호 작용을 하여 일정 온도에서 산화반응속도가 표면과 내부의 농도 기울기에 의한 확산속도에 의존한다고 보고하고 있다. 본 연구결과를 토대로 Mg-Al합금의 발화특성을 고찰해 보면, Mg-Al합금에서 자기 전파성이 작은 Al성분의 증가는 착화지연이 증가하여 연소성이 감소하여 최저발화온도의 증가로 이어지는 것으로 추정되었다. 또한 발화온도는 주어진 조건의 온도장에서 분진이 존재하는 시간 길이에 따라 변화하므로, 발화온도를 실험적으로 측정하는 경우에는 측정장치나 방법에 따라 달라지므로 사업장의 현장에 발화온도를 적용하는 경우에는 장치 내의 분진의 존재시간을 고려할 필요가 있다.

• Korean Business Review
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• v.17
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• pp.83-110
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• 2004

In modern society, there exists a growing tendency that the product image, rather than the substance of the product, is given more and more emphasis. In other words, consumers tend to purchase a product whose brand image coincides with their self image. Today, it is one of the essential factors for marketing strategy of a modern enterprise to have brand image perceived by consumer self-image. The image, by affecting the perception of consumers, explains the reason why some consumers choose one brand out of many brands that are available to them. Furthermore, brand-image perceived by consumers becomes more important factor in improving the company's market share. For this research, we investigated the theoretical background based on previous studies and collected statistical data through a market survey. The results of the actual research indicate that the attributes of the images differ notably depending upon demographic attributes; that the brand image judged by a customer is positively correlated to the customer's self image; and that the regression analysis of the purchase intention in accordance with coincidence of independent variables proved to be insignificant. But the correlation analysis of the variables shows that the sensuous image of a perceived brand image product notable differences in the purchase intention. Most of Consumers tend to prefer certain brand of causal wears in accordance with their cognized brand-image and self-image: social self-image and actual self-image. Corporate must not spare any effort to establish differential advantage. through better image or changing image. Also marketers have to identify the strengths and weakness of their brand in relation to the competition in setting up their brand management strategy. In conclusion, the outcomes of the study suggest that the consumers purchase the images of the brands, rather than the products themselves. Accordingly, in the clothes markets with similar quality levels, the emphasis should be put on differentiation of the brand images in order to further increase sales and maximize profits.

• Journal of Korea Game Society
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• v.15 no.1
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• pp.63-76
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• 2015

The purposes of this study are, firstly, to investigate the relationship between the online and mobile game players' psychological aspects (reference group, government regulation, game contents) and their game experience and overindulgence in games and, secondly, to suggest possible ways to reduce overindulgence in games. The implications of this research are as follows; Firstly, families and school authorities should strive to make sports and other pastime activities popular among peer groups rather than allowing online and video games to become only source of popularity among peer groups. Secondly, it is better for families members to establish a set of rules for controlling their children's time spent on online and mobile games rather than entirely forbidding the games. Family members should also strive to have more family conversations and to find a common source of interests. Thirdly, government should strive to develop policy responses to the overindulgence in games based on practical research and analysis. Fourthly, game makers should pay more attention to the components and expressions used in their games so as to draw game players' interests to the story and design of the games. Game makers also need to consider elements in their games that may potentially cause overindulgence in the development stage. Lastly, game players should strive to find new leisure activities besides online and mobile games that they can enjoy and have good experience with.

• Journal of The Korean Association For Science Education
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• v.38 no.3
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• pp.355-367
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• 2018

The purposes of this study are 1) to identify systems thinking level and definition, 2) to develop a framework for the assessment of systems thinking level, and 3) to develop a rubric for scoring open-ended written responded test. In order to achieve these purposes, a total of 60 articles were analyzed by using the literature analysis framework. The systems thinking level and definition are identified through the results of systems thinking literature analysis. Based on the systems thinking level and definitions, the research derived a framework that includes the core ideas and evaluation content of each level. In addition, rubric for the scoring of open-ended response test items was revised and supplemented. It is concluded that a content validity test on the tools (systems thinking level and definition, framework for item development, rubric) has been developed in the study. The content validity was verified by 7-science education experts. According to the result of CVI, it was found to be more than .95 in all three tools. Based on the results of this study, the research will develop items that can measure students' level of systems thinking. The construct validity and criterion validity of the developed items should be verified systematically. The research could carry out a validation study for the systems thinking measurement related to the core competence emphasized in the 2015 revised curriculum.

• The Korean Journal of Elementary Counseling
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• v.11 no.1
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• pp.21-33
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• 2012

This study examined the differences of academic achievement by social status types through sociometry. This study analyzed 201 students in grade 6 in S elementary school. The social status is classified by 7 (popular, average, rejected, aggressive-rejected, submissive-rejected, neglected, controversial) with academic achievement of each type as dependent variables to figure out the relation between social status types and academic achievement. To classify 5 social status types, a sociometry program developed by Ahn, Ie-Hwan (2007) was used, 2 social status types was classified with experimental condition, and its dependent variable was the score by subjects in the mid-term exam of the 1st semester in 2011. The average values of humanities courses (Korean and social studies) and natural science courses (math and science) were compared by both sexes and 7 social status types. The reference group was average group. As a result, as to male students, N type had the highest score both in humanities courses and natural science courses while C type had the lowest score in both groups. As to female students, P, N, C types had the highest score in both groups with similar range while R type had the lowest score in both groups. This result demonstrates that the academic achievement of students had relatively high relevance with social status. and also, suggestion that how teachers can do to enhance the academic achievement of elementary school students.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.8
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• pp.3748-3759
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• 2013

The purpose of this study was to examine the classification accuracies of ML, MAP, and EAP methods under DINA model. For this purpose, this study examined the classification accuracies of the classification methods under the various conditions: the number of attributes, the ability distribution of examinees, and test length. To accomplish this purpose, this study used a simulation method. For the simulation study, data was simulated under the various simulation conditions including the number of attributes (K= 5, 7), the ability distribution of examinees (high, middle, low), and test length (J= 15, 30, 45). Additionally, the percent of agreements between true skill patterns(true ${\alpha}$) and skill patterns estimated by the ML, MAP, and EAP methods were calculated. The summary of the main results of this study is as follows: First, When the number of attributes was 5 and 7, the EAP method showed relatively higher average in the percent of exact agreement than the ML and MAP methods. Second, under the same conditions, as the number of attributes increased, the average percent of exact agreement decreased in ML, MAP, and EAP methods. Third, when the prior distribution of examinees ability was different from low to high under the conditions of the same test length, the EAP method showed relatively higher average in the percent of exact agreement than those of the ML and MAP methods. Fourth, the average percent of exact agreement increased in all methods, ML, MAP, and EAP when the test length increased from 15 to 30 and 45 under the conditions of the same the ability distribution of examinees.

• Journal of Korean Society of Forest Science
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• v.103 no.4
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• pp.639-645
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• 2014

This study was conducted to evaluate the management efficiency of oak mushroom farms in Korea using the Data Envelopment Analysis (DEA), which is one of the non-parametric estimation methods. The data that was analyzed in this study was from the result of 2013 survey entitled "Standard Diagnostic Table for Oak Mushroom Management", which was conducted from March 2012 to October 2012. This survey was based on the inputs and outputs of 20 oak mushroom farms. Specifically, this study analyzed the technical efficiency, pure-technical efficiency and scale efficiency using CCR and BCC model of the DEA methods. Furthermore, this study compares the management efficiency between the full time oak mushroom production farms and part time oak mushroom production farms. Results showed that mean value for the technical efficiency was 0.655 which is considered as inefficient in general. For the pure-technical efficiency and scale efficiency, the mean values were 0.830 and 0.747, respectively which showed that inefficiency in the management was observed in the mushroom farms. Results also showed that there were seven farms with a total efficiency of 1, namely Decision Making Unit(DMU)2, DMU5, DMU6, DMU8, DMU10, DMU15 and DMU20. The management efficiency of DMU7 specifically the inputs for production was analyzed and compared to DMU5 and DMU6 and results showed that the DMU7 had an excessive inoculation and site development cost. Lastly, it was also observed that the full time mushroom production farms were more efficient as compared to the part time mushroom farms because of the lower scale efficiency value or smaller area for mushroom production allotted in the part time farms.

• Journal of The Korean Association For Science Education
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• v.34 no.8
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• pp.745-754
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• 2014

Students experience a variety of achievement-related emotions during the process of learning the science curriculum. The purpose of this study is to develop an achievement emotions questionnaire for Korean middle school science curriculum to measure the achievement emotions that middle school students experience during study of this curriculum, and verified its validity. The Achievement Emotions Questionnaire-Korean Middle School Science is based on the English version of the Achievement Emotions Questionnaire, developed with reference to Korean middle school science curriculum and the characteristics of science study, from the perspective of the control-value theory of achievement. It has 232 questions, configured to measure nine achievement emotions across three types of academic settings. The questionnaire results can be treated with a high degree of confidence according to the result of our validation, which also verified that the achievement emotions of these students are configured with four internal criteria (learning strategy, achievement motivation and course grade), as suggested by the control-value theory; this in turn verifies that the nine achievement emotions are sufficiently distinctive across study situations. Last, it was verified that the questionnaire has sufficient external validity based on a comprehensive examination of the relation between science achievement emotions and the four criterion variables for each student. This suggests that through the development and implementation of this quantitative questionnaire, basic ground was provided to understand the achievement emotions experienced by middle school students learning the science curriculum.