• 천문학회보
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• 제42권1호
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• pp.42.1-42.1
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• 2017

We investigate the evolutionary properties of red supergiant stars (RSGs), using stellar evolution model of Modules for Experiments in Stellar Astrophysics (MESA). In this study, we calculate models with mass range of 9-39M_sun and several different convection parameters (e.g. mixing length, overshooting, and semiconvection) at SMC, LMC, Milky Way, and M31 metallicities. We compare the calculated evolutionary tracks with observed RSGs in SMC, LMC, Milky Way and M31, and discuss appropriate input physical parameters in model calculation. We find that a larger mixing length parameter is necessary for M31 metallicity to fit the positions of RSGs in H-R diagram, compared to lower metallicity environments. Theoretically predicted numbers of yellow supergiant stars (YSGs) are also compared with the observed population. We find that Ledoux models with semiconvection can better explain the number of YSGs. Finally, we investigate the final radius, final star mass, and final hydrogen envelope mass of RSGs and discussed the their properties as type II-P supernova progenitors.

• 한국과학교육학회지
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• 제32권3호
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• pp.532-540
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• 2012

This research investigated the motivation and interests of a sample of predominately-underrepresented populations to better understand whether informal STEM learning experiences offer support for developing STEM identities. A valid and reliable three-section self-reporting survey was administered to 169 secondary students as the primary data source. Identity was used as a theoretical lens along with descriptive statistics to reveal students' perceived benefits of the informal STEM learning experience, a Mathematics, Engineering, Science Achievement (MESA) program in the western U.S., for improving their understanding of science, mathematics, and engineering concepts, increasing their interest in science, mathematics, and engineering careers, and increasing their belief of the importance of these STEM disciplines. In summary, the findings emerging, considered alongside current identity research, suggest that informal STEM learning experiences offer students from underrepresented STEM populations the space needed for successful STEM identity bids, either for future career pursuits or participation in a STEM literate populace as a non-STEM professional societal member.

• 과학교육연구지
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• 제43권1호
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• pp.1-16
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• 2019

This exploratory study is aimed at exploring the validity of the Science Motivation Questionnaire (SMQ) developed for university students, to measure the science motivation of middle school students and analyze the differences on gender and country factors of SMQ. A total of 371 students participated in this study: 171 middle school students from the USA and 200 secondary students from Korea. All participants were enrolled in the STEM program and activities in Utah, USA (for US students) and at a Korean university institute for gifted and talented students (for Korean students). In this study, exploratory and confirmatory factor analyses and latent mean analysis were used to analyze the gender and country differences. The results indicated that the 25 items of SMQ scale were theoretically meaningful and valid for middle school students. The latent mean difference by gender indicated that male students have higher intrinsic motivation, career motivation, grade motivation, and self-determination than female students. Moreover, a significant difference exists in these factors between the two countries. Further findings reveal that Korean students scored higher than US students in terms of the aforementioned factors. This study will provide significant insights in and contribution to science motivation issues in STEM education and the development of design-based engineering programs.

• Restorative Dentistry and Endodontics
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• 제44권2호
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• pp.16.1-16.12
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• 2019

Objectives: The upper molars generally have three roots; therefore, different combinations of fusion can occur, increasing the possibility of finding more complex root canal systems. The purpose of this study was to evaluate the prevalence and characterization of fused roots in first and second maxillary molars using cone-beam computed tomography (CBCT) in a Colombian population. Materials and Methods: A total of 1274 teeth were evaluated, of which 534 were maxillary first molars and 740 were maxillary second molars. Axial sections were made at the cervical, middle, and apical levels to determine the prevalence of root fusion and the types of fusion. Results: Overall, 43% of the molars (n = 551) presented some type of fused root. Root fusion was present in 23.4% of the maxillary first molars. The most frequent type of fused root was type 3 (distobuccal-palatal; DB-P) (58.9%). Root fusion was observed in 57.6% of the maxillary second molars, and the most prevalent type of fused root was type 6 (cone-shaped) (45.2%). Of the maxillary molars, 12.5% were classified as C-shaped. Conclusion: Within the limitations of this study, there was a high prevalence of fused roots in maxillary molars in the Colombian population, mainly in the maxillary second molars. In first molars, the most common type of fused root was type 3 (DB-P) and in second molars, the most common type was type 6 (cone-shaped). Additionally, molars with root fusion presented variation at different levels of the radicular portion, with implications for treatment quality.

• 센서학회지
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• 제13권2호
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• pp.128-132
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• 2004

Short wave infrared (SWIR) photovoltaic devices have been fabricated from metal organic vapour phase epitaxy (MOVPE) grown n- on p- HgCdTe films on GaAs substrates. The MOVPE grown films were processed into mesa type discrete devices with wet chemical etching employed for meas delineation and ZnS surface passivatlon. ZnS was thermally evaporated from effusion cell in an ultra high vacuum (UHV) chamber. The main features of the ZnS deposited from effusion cell in UHV chamber are low fixed surface charge density, and small hysteresis. It was found that a negative flat band voltage with -0.6 V has been obtained for Metal Insulator Semiconductor (MIS) capacitor which was evaporated at $910^{\circ}C$ for 90 min. Current-Voltage (I-V) and temperature dependence of the I-V characteristics were measured in the temperature range 80 - 300 K. The Zero bias dynamic resistance-area product ($R_{0}A$) was about $7500{\Omega}-cm^{2}$ at room temperature. The physical mechanisms that dominate dark current properties in the HgCdTe photodiodes are examined by the dependence of the $R_{0}A$ product upon reciprocal temperature. From theoretical considerations and known current expressions for thermal and tunnelling process, the device is shown to be diffusion limited up to 180 K and g-r limited at temperature below this.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2008년도 정기학술발표대회 논문집
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• pp.202-206
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• 2008

최근 도시재생에 대한 관심이 높아지면서 재건축사업, 도시환경정비사업 등과 관련된 메가프로젝트 들이 계획되거나 수행되고 있다. 메가프로젝트의 설계단계에서는 다수의 설계업체로 구성된 합동설계조직과 의사결정주체가 참여하여 지속적으로 의견을 조율한다. 현재 메가프로젝트를 진행하는 기관들은 합동설계조직으로부터 작성되는 다수의 다양한 도면들을 효율적으로 관리하기 위해 MA(Master Architect)방식을 도입하고 있다. 그러나 제한된 MA의 능력을 보완해 줄 수 있는 의사결정지원시스템의 부재로 설계일정 지연 등 여러 가지 문제가 발생하고 있다. 따라서 본 연구에서는 선행연구문헌 분석 및 모델프로젝트 선정과 해당 프로젝트 참여 전문가 면담을 통해 MA방식을 도입한 메가프젝트의 설계조직 구성과 의사결정체계의 문제점을 분석한다. 기본설계단계에서의 의사결정 특성을 도출한 후 이를 관리하기 위한 의사결정지원 모델을 구축하고 시스템 개발을 위한 사용자 인터페이스를 제안하였다.