• Journal of Communications and Networks
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• v.14 no.5
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• pp.471-480
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• 2012

Reliable detection of primary user activity increases the opportunity to access temporarily unused bands and prevents harmful interference to the primary system. By extracting a global decision from local sensing results, cooperative sensing achieves high reliability against multipath fading. For the effective combining of sensing results, which is generalized by a likelihood ratio test, the fusion center should learn some parameters, such as the probabilities of primary transmission, false alarm, and detection at the local sensors. During the training period in supervised learning, the on/off log of primary transmission serves as the output label of decision statistics from the local sensor. In this paper, we extend unsupervised learning techniques with an expectation maximization algorithm for cooperative spectrum sensing, which does not require an external primary transmission log. Local sensors report binary hard decisions to the fusion center and adjust their operating points to enhance learning performance. Increasing the number of sensors, the joint-expectation step makes a confident classification on the primary transmission as in the supervised learning. Thereby, the proposed scheme provides accurate parameter estimates and a fast convergence rate even in low signal-to-noise ratio regimes, where the primary signal is dominated by the noise at the local sensors.

• Journal of the Korean Society of Earth Science Education
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• v.14 no.1
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• pp.69-79
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• 2021

The purpose of this study was to compare what meanings of earth science pre-service teachers and primary pre-service teachers about science books and reading through science disciplinary reading and how their thoughts on science education are reflected in the science disciplinary reading process. For the study, 24 third-year students majoring in earth science education and 25 second-year students majoring in primary education were selected as subjects for the study at a teacher training college located in the central part of Korea. As a result of the study, first, earth science pre-service teachers used disciplinary reading a lot to acquire knowledge of science content, but primary pre-service teachers used it for the purpose of using it in class, scientific interest, and curiosity solution. Second, earth science pre-service teachers and primary pre-service teachers showed differences in their thinking in using science related books for science education. While earth science pre-service teachers rarely described the use of science books in their classes, primary pre-service teachers actively described science classes. Third, from the perspective of science disciplinary reading, primary pre-service teachers were more actively emphasizing the meaning of disciplinary reading compared to earth science pre-service teachers. In light of the research results that the reading activity in science has a lot of effect, it is thought that a wide range of research on science disciplinary reading should be conducted as a teaching strategy in school field classes.

• Kyungpook Mathematical Journal
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• v.57 no.4
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• pp.559-580
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• 2017

Let G be an arbitrary group with identity e and let R be a G-graded ring. In this paper, we define the concept of graded 2-absorbing and graded weakly 2-absorbing primary ideals of commutative G-graded rings with non-zero identity. A number of results and basic properties of graded 2-absorbing primary and graded weakly 2-absorbing primary ideals are given.

• Journal of Embryo Transfer
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• v.31 no.3
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• pp.169-177
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• 2016

There is a growing interest in the application of primary hepatocytes for treatment of liver diseases in humans and for drug development. Several studies have focused on long-term survival and di-differentiation blocking of primary hepatocytes in an in vitro culture system. Therefore, the present study also aimed to optimize an in vitro culture system using primary rat hepatocytes. Primary rat hepatocytes from 6-week-old male Crl:CD rats were isolated using a modified two-step collagenase perfusion. Healthy $3.5{\times}10^6$ primary rat hepatocytes were seeded into a 2 dimensional (2D) culture in a 25T culture flask coated with collagen type I or into a 3D culture in a 125-ml spinner flask for 7 days. Production of plasma protein (ALB and TF), apoptosis (BAX and BCL2), and CYP (CYP3A1) related genes were compared between the 2D and 3D culture systems. The 3D culture system had an advantage over the 2D system because of the relatively high expression of ALB and low expression of BAX in the 3D system. However, the level of CYP3A1 did not improve in the 3D culture with and without the presence of a dexamethasone inducer. Therefore, 3D culture has an advantage for albumin production and primary rat hepatocyte survivability, but a low expression of CYP3A1 indicated that primary rat hepatocytes require a high-density culture for stress reduction by continuous flow.

• Journal of the Korean Society for Library and Information Science
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• v.33 no.1
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• pp.145-160
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• 1999

The literature may be divided into two broad categories : primary and secondary literature. Primary literature comprises documents which contain the full text of the author's work. On the other hand secondary literature, such as indexes, abstracts, bibliographies reviews and surveys, provides signposts to the primary literature. This paper intended to examine and analyze the relationship between primary and secondary literature through the previous research and the theory, and the actual study which compared it with the lists of journals in three secondary literatures: Library and Information Science Abstracts(LISA). 1998; Library Literature (LL), 1998; Information Science Abstracts (ISA), 1998. Some of the problem involved in the study of journal overlap and coverage patterns of secondary services are discussed. Conclusions are drawn about the impact on library and information science selection policies and organization of library collections.

• Journal of the Korean Society of Food Culture
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• v.25 no.4
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• pp.400-409
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• 2010

This study investigated the food and dietary educational content in primary, middle and high school textbooks in order to provide fundamental data for the development of educational programs on Korean traditional food culture. The research objects consisted of 51 kinds of textbooks (15 kinds of primary school textbooks, 29 kinds of middle school home economics textbooks and 7 kinds of high school home economics textbooks), and the contents related to food and dietary education were counted and analyzed. The content analysis was performed using two categories: application method and subject matter. Application method included texts, cases, visual aids (pictures, photos, illustrations, chart, etc.) and activities, whereas subject matter consisted of seven types (well balanced nutrition and health, understanding of food and nutrition, cooking principles, cooking lessons, traditional foods and culture, others). The results of the application method in primary school textbooks show that visual aids were the most common in all six grades. For the subject matter, 'understanding of food and nutrition' was most abundant in primary school textbooks while 'well balanced nutrition and health' accounted for a large part of the contents in middle school textbooks. However, the contents regarding traditional foods and culture were insufficient in primary and middle school textbooks. These results suggest that educational contents on traditional foods and culture should be added to primary and middle school textbooks and covered in various subjects. Furthermore, high school 'home economics' contents need to emphasize comprehensive food and dietary education and adjust to 'science & technology for life'.

• Journal of Korea Foundry Society
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• v.23 no.1
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• pp.40-46
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• 2003

Semisolid forming requires alloys with non-dendritic microstructure of the thixotropy. Recently, low pouring temperture method without stirring, i.e. liquidus casting has been found out new fabrication method of the semisolid metals. Effects of melt superheat and mold conditions on the globulization of primary Al of $AlSi_7Mg$ alloy were investigated in gravity casting process without stirring. The microstructures of primary Al as function of melt superheat and mold temperature show globular, rosette and dendritic shapes. The conditions for globular microstructure of primary Al were low melt superheat < 35 K and low mold temperature < 500 K. The thermal conditions for globular microstructure of primary Al were undercooled melt at early solidification stages and slow cooling < 0.6 K/s. It was found that the initial microstructure was maintained throughout the solidification and the globules of primary Al can be obtained by high nucleation of fine and spherical nuclei due to enhanced undercooling of melt.

• Analytical Science and Technology
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• v.34 no.5
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• pp.202-211
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• 2021

Volatile organic compounds (VOCs) in hazardous air pollutants (HAPs) have been regulated by the Air Pollution Control Act (1978) and their atmospheric concentrations have been monitored in 39 monitor sites in Korea. However, measurement standards of volatile organic compounds (VOCs) in HAPs at ambient levels have not been established in Korea. Primary reference gas mixtures (measurement standards) at ambient levels are required for accurately monitoring atmospheric VOCs in HAPs and managing their emissions. In this study, primary reference gas mixtures (PRMs) at 5 nmol/mol were developed in order to establish primary national standards of VOCs in HAPs at ambient levels. Primary reference gas mixtures (PRMs) were prepared in pressurized aluminum cylinders with special internal surface treatment using gravimetric method. Analytical methods using gas chromatography-flame ionization detector (GC-FID) coupled with a cryogenic preconcentrator were also developed to verify the consistency of gravimetrically prepared HAP VOCs PRMs. Three different columns installed in the GC-FID were evaluated and compared for the retention times and separation of eighteen target components in a chromatogram. Results show that the HAP VOCs PRMs at 5 nmol/mol were consistent within a relative expanded uncertainty (k=2) of less than 3 % except acrylonitrile (less than 6 %) and the 18 VOCs were stable for 1 year within their associated uncertainties.

• Journal of Korean Elementary Science Education
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• v.24 no.5
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• pp.571-582
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• 2005

This study aims to examine primary school teachers' interest and understanding of bioethical issues, and to analyze their perception of bioethics teaching in the primary school education. For this purpose, the questionnaires were constructed. The data were collected from 553 primary teachers in the whole country. Major findings of the studys are as follows. First, most primary school teachers showed high level of interest about bioethical issues, but they had the limited understanding about bioethical issues. Primary teachers showed the highest interest about' respect for human life' and the lowest understanding of 'awareness of current biotechnology' Second, the prior reasons why primary teachers wanted to teach specific bioethical issues in the classes were that 'they were closely related to social phenomena' and 'they were appropriate for enhancing students' awareness of the value of life'. Third, the lack of the teachers' knowledge about bioethics and limited supply of teaching materials were found to be barriers, which prevent them from teaching bioethical issues. The implications of these results are discussed for the improvement of bioethics teaching in primary school education.

• Journal of the Korean Society of Earth Science Education
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• v.7 no.1
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• pp.99-109
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• 2014

The purpose of this study was to obtain consensus from the expert community on the aims of Elementary Science Classes for the Gifted(ESCG) and teaching professionalism of Elementary Science Teachers for the Gifted(ESTG). For the delphi study, nineteen experts were consulted with open-ended and closed questions. Delphi research was conducted a total of 3 times. The Delphi survey was done by e-mail. The experts can express their opinions freely during the research. The results of this study were as follows : First, there were six aims for ESCG. The six aims of ESCG are scientific inquiry ability growth, creative problem solving ability growth, primary science gifted's giftedness development, the future science-talented-children training, the growth of attitudes toward science, scientific attitudes growth. Second, there were four teaching professionalism about teaching professionalism of ESTG. Four teaching professionalism are understanding the characteristics of primary science gifted, the ability to understand and apply the learning methods suitable for primary science gifted education, professional knowledge and ability to understand the science curriculum, the ability to develop and apply primary science education programs.