• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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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.

• Journal of The Korean Association For Science Education
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• v.32 no.3
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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.

• Journal of Science Education
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• v.43 no.1
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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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• v.44 no.2
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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.

• Journal of Sensor Science and Technology
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• v.13 no.2
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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.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.202-206
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• 2008

Recently, as high level of interest for the city regeneration, large-scale projects are planned or being performed such as reconstruction project. These mesa-projects have different characteristics from a single project in the design phase. It is a number of companies involved in design phase of mega-project and principal decision-making entity manage the project from the initial stage of an ongoing business by coordinating an opinions between design companies. The absence of a decision making support system reflected those characteristic causes a variety of problems such as a loss of cost and schedule. Therefore the final object of this paper is to propose a decision making support tool and system interface.