• Journal of the Korean Ceramic Society
• /
• v.50 no.6
• /
• pp.434-438
• /
• 2013

Monodispersed 3Y-$ZrO_2$ spherical agglomerates were synthesized by thermal hydrolysis process followed by crystallization processes (hydrothermal treatment and calcination). The crystallization process affected the properties of the final particles, such as the primary particle size, the agglomeration state, and the fraction of $ZrO_2$ monoclinic phase. The hydrothermal treated spherical particles were porous microstructures (weak agglomerates) composed of small primary particles with a size of 14 nm, but the calcined spherical particles had a dense microstructure due to the hard aggregation between primary particles. While the calcined particles had a low green density due to the hard aggregation, hydrothermal treated ones were soft agglomerates and had a deflection point at 50 MPa due to the rearrangement of secondary spherical particles and the filling of the interstices with the primary particles. Finally, the green density of hydrothermally treated $ZrO_2$ particles was 58% at 200 MPa.

• Journal of Korean Elementary Science Education
• /
• v.40 no.4
• /
• pp.460-479
• /
• 2021

The crisis of the COVID-19 pandemic has caused significant changes in education systems worldwide, including in Korea. Due to COVID-19's social distancing policies, the education system was suddenly switched to distance learning, resulting in many problems in primary schools without preparation. The purpose of this study was to investigate a teacher's awareness of science education techniques, responses to issues in science classes, including inquiry activities, advantages and disadvantages, and roles after experiencing distance learning. Survey and focus interviews were conducted for primary school teachers who had previously participated in distance learning, such as online content classes and real-time interactive classes. The study findings showed three conclusions: 1) Primary school teachers conducted one-way and interactive lectures in online classes. It is vital to improve a teacher's digital literacy to improve other teaching methods such as investigation and discussion in online classes. 2) Primary school teachers acknowledged the challenges of field feedback, inquiry item preparations, and safety in inquiry activities of science classes, by providing individual experimental packages and videos and using online discussion and feedback among teacher - student and student - student interactions. 3) Primary school teachers recognized that various types of classes using IT devices and individualized learning were possible as advantages of distance learning. As for disadvantages, it was acknowledged that inquiry activities, cooperative learning, immediate feedback, and interaction among students were challenging. Furthermore, learning gaps were wider in distance learning.

• Journal of the Korean Regional Science Association
• /
• v.14 no.1
• /
• pp.163-190
• /
• 1998

This paper examines the policy implications of poverty in terms of its forms: primary and secondary poverty and brings out the synergetic relationship between the reduction of primary and secondary poverty in Urban India. The paper also demonstrates the influence that the alleviation of secondary poverty exerts on the alleviation of the primary poverty and it pinpoints the macro-level policy implications and suggests envisaged strategy for poverty alleviation applicable to the developing world.

• Journal of the Korean earth science society
• /
• v.32 no.4
• /
• pp.422-434
• /
• 2011

The purpose of this research is to investigate the actual conditions of primary school science teaching and ways to improve it. In elementary science teaching, teachers themselves tend to have science misconceptions and insufficient science content knowledge. Experienced teachers argued that it could be hard for elementary teachers with lack of science content knowledge to provide their students with meaningful learning experiences of science. Based on the general characteristics of elementary teaching and the awareness of elementary teachers' insufficient science content knowledge, we explored the real situation of the elementary science classroom. We conducted open-ended interviews with teachers and focus group discussions on a regular basis to analyze and compare classes of five primary school teachers. Data analysis focused on why elementary students avoid science classes in upper grades of elementary school and why elementary science classes always need hands-on activities. We also discussed ways to turn hands-on investigation into minds-on investigation by connecting it to important ideas in science. Based on the results, we suggested ways to improve inservice teacher training such as designing supplementary in-service training focused on content knowledge for primary school teachers, setting up professional exchange or collaboration between primary and secondary teachers, and introducing subject-specialized teachers for the fifth and sixth graders of primary school. In particular, considering elementary teachers' insufficient science content knowledge, employing science subject matter specialists in the elementary school could be a useful strategy.

• Toxicological Research
• /
• v.4 no.1
• /
• pp.37-45
• /
• 1988

Primary cultures of adult rat hepatocytes were used to study in vitro cytotoxic effects of T-2 toxin on liver cells. When T-2 toxin was added to the culture, a significant depression of the hormonal induction of ${\alpha}$-aminoisobutyric acid (AIB) uptake and tyrosine aminotransferase (TAT) activity was observed. However, T-2 toxin did not affect the uptake of ouabain into hepatocytes. Protein synthesis was inhibited by T-2 toxin, but RNA synthesis was not severely affected. The inhibitory effects of T-2 toxin on protein synthesis was diminished rapidly with culture time and the hepatocytes culture maintained control level of protein synthesis within 24 hrs.

• Asian Journal of Business Environment
• /
• v.7 no.1
• /
• pp.31-36
• /
• 2017

Purpose - The purpose of the study was to develop a reliable measurement tool for the evaluation of TQM application in Greek education settings and to examine the factors that determine quality of education. Research design, data, and methodology - A questionnaire commencing from the questions included in the Application Guide of Common Assessment Framework was used for research purposes. Each item was scored on a 5point Likert scale - to a sample of 112 educators (55 men, 57 women), all teachers working in public primary education schools. Factor analysis resulted in a questionnaire of 43 items consisting of five factors, teacher satisfaction, school management and operation, motivation, effectiveness of public school leadership and finance management. Results - Results revealed a positive correlation among all factors. Reliability results using Cronbach's α was high (a=.961) for all factors of the questionnaire ranging from α=.930 (for motivation) to α=.797 (for financial management). Additionally, ICC procedure revealed high values for the above mentioned factors. Conclusions - The study resulted in the construction of a reliable questionnaire focused exclusively on TQM that can be used in future studies using larger samples in different areas so as to draw useful conclusions regarding TQM application in Greek education settings and further identify the factors determining quality in education.

• Journal of The Korean Association For Science Education
• /
• v.29 no.3
• /
• pp.291-303
• /
• 2009

According to social constructivism, group interaction is very important when students construct their knowledge. Many researchers have developed methods of teaching on the basis of group interaction because they recognized the importance of group interaction. There are a large variety of issues related to group interaction including group size, the gender and ability composition of groups, seating arrangements, textbook use, gestures, and role assignments. However, research on group interaction in science learning is still insufficient. In this study, we focused upon the emerging role of the primary leader. We investigated the primary leader's diverse role when students are solving mechanics problems. The participants were one group composed of three students in an upper-level mechanics class. To analyze these students' group interactions, their verbal interactions during meetings were videotaped and audiotaped during one-semester period. We also conducted interviews with the three students and analyzed their reports. As a result, we could find a special student who had the role of primary leader. We could also find the leader's three different leadership roles in different problem situations by inductively; explainer, facilitator and evaluator. Group interaction had different aspect according to the different role of leaders. The group interactions were the most active when the leader played the role of facilitator.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.2
• /
• pp.383-399
• /
• 1998

Tooth development is usually described in four stages such as bud stage, cap stage, bell stage and crown stage. Exact time of appearance of tooth primordia is different among reports, and up to now there is no timetable regarding initial tooth development. To understand the congenital malformations and other disorders of the orofacial region, there is a need to establish a standard timetable on early tooth development. Till now, studies on the tooth development were mainly on later fetuses, and only few reports on early stage. Also, there were no reports on the time when bud stage turns to cap stage, and cap stage to bell stage. In this study, external morphology of face and the early development of the tooth, and transition of bud stage to cap stage, cap stage to bell stage were studied using 27 staged human embryos and 9 serially sectioned human fetuses. The results are as follows: 1. Mandibular region was formed by union of both mandibular arch at stage 15, and maxillary region by union of maxillary arch, medial nasal prominence, and intermaxillary segment at stage 19. 2. Ectodermal thickening which represents the primordia of tooth appeared in mandibular region at stage 13, and maxillary region at stage 15. 3. Bud stage began from mandibular primary central incisor at stage 17, and maxillary primary central incisor at stage 18. And the sequence of appearance was in the mandibular primary lateral incisor at stage 19, maxillary primary lateral incisor at stage 20, mandibular primary canine at stage 22, maxillary primary canine and primary first molar at stage 23, madibular primary first molar and maxillary primary second molar at 9th week, and mandibular primary second molar at 10th week of development. 4. Cap stage began from the primary anterior teeth at 9th week, and primary second molar still had the characteristics of cap stage at 12th week of development. 5. Transition to bell stage started from the primary anterior teeth at 12th week, and primary second molar started at 16th week of development. 6. Trnasition to crown stage started from primary anterior teeth at 16th week, and primary second molar at 26th week of development.

• Proceedings of the KIPE Conference
• /
• 2008.06a
• /
• pp.379-381
• /
• 2008

Generally additional leakage inductance and two clamp diodes are adopted into the conventional phase shift full bridge (PSFB) converter for reducing the voltage stress of secondary rectifier diodes and extending the range of zero voltage switching (ZVS) operation. However, since additional leakage inductance carries the ac current similar to the primary one, the core and copper loss oriented from additional leakage inductance can be high enough to decrease the whole efficiency of DC/DC converter. Therefore, in this paper, a new ZVS phase shift full bridge converter with separated primary winding (SPW) is proposed. Proposed converter makes the transformer and additional leakage inductor with one ferrite core. Using this method, leakage inductance is controlled by the winding ratio of separated primary winding. Moreover, by manufacturing the both magnetic components with one core, size and core loss can be reduced and it turns out the improvement of efficiency and power density of DC/DC converter. The operational principle of proposed converter is analyzed and verified by the 1.2kW prototype.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.24 no.1
• /
• pp.13-16
• /
• 2018

Powdered infant formula is susceptible to oxidation in the presence of oxygen. Even though the product is usually packaged in nitrogen atmosphere, the oxygen ingress through the package layer may occur in case of flexible pouches and affects the oxidation of the product. $O_2$ barrier of the package is thus important variable to protect the product from oxidative deterioration. $O_2$ barrier property was investigated for aluminum-laminated small pillow packs of $3.5{\times}17.5cm$. Storage temperature and combination of primary and secondary packages were evaluated as variables affecting the barrier for conditions of empty pouch flushed with nitrogen. Apparent oxygen transmission rate of the primary package exposed to air was $2.32{\times}10^{-3}mL\;(STP)\;atm^{-1}\;d^{-1}$ at $30^{\circ}C$ and its temperature dependence could be explained by activation energy of $28.5kJ\;mol^{-1}$ in Arrhenius relationship. The additional secondary package of nylon/PE film containing 20 primary packages was ineffective in modulating package $O_2$ transmission and was only marginally helpful when combined with oxygen scavenger. The same was true in suppressing the product oxidation when the primary package was filled with 14 g of the formula.