• Membrane Journal
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• v.26 no.4
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• pp.310-317
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• 2016

Lithium ion secondary battery (LISB) is an energy conversion system operated via charging-discharging cycle based on Lithium ion migration. LISB has a lot of advantages such as high energy density, low self-discharge rate, and a relatively high lifetime. Recently, increasing demands of electric vehicles have been encouraging the development of LISB with high capacity. Unfortunately, it causes some critical safety issues. It includes dendrite formation on negative electrode, resulting in electric shortage problems and battery explosion. Also, the elevated temperatures occurred during the LISB operation induces thermal shrinkage of polyolefin (e.g., polyethylene and polypropylene) separators. Consequently, the low thermal stability leads to decay of LISB performances and the reduction of lifetime. In this study, sulfonated poly (arylene ether sulfone) (SPAES) random copolymers were used as key materials to prepare polyolefin pore-filling separator. The resulting separators were evaluated in the term of metal ion chelation capability associated with dendrite formation, $Li^+$ ion conductivity and thermal durability.

• Journal of Korean Elementary Science Education
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• v.39 no.2
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• pp.183-203
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• 2020

The purpose of this study is to investigate the factor for improving elementary and secondary students' positive experiences about science (PES). In-depth interviews with 32 students and 8 teachers from 8 elementary and secondary Science Core schools were conducted to explore the factors for improving the student's PES. The analysis of the results reveal that the eight key factors which had a decisive impact on a student's PES were 'practice-centered exploratory activities', 'student-led class', 'positive and professional feedback', 'construction of knowledge through exploration', 'class considering student's interest and aptitude', 'use of materials related to real life', 'smooth communication and collaboration in group activities', and 'appropriate difficulty in learning content'. There were also five environmental factors that affected these key factors: 'teacher's professionalism for science classes', 'science class environment', 'teacher community in unit schools', 'change in curriculum', and 'scientific activities other than regular classes'. Based on these results, the practical implications for improving the student's PES are suggested.

• Composites Research
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• v.23 no.2
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• pp.31-39
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• 2010

In this paper, composite panels with hat-shaped stiffeners were made using the co-curing, co-bonding and secondary bonding methods. Co-curing is a manufacturing method in which the hat part and the plate are cured simultaneously in a manner that is more cost effective than other methods. Co-bonding is a method in which the stacked prepregs are cured with other cured parts, and secondary bonding is a method in which cured parts are bonded together using an adhesive. A rubber mold was manufactured for co-curing of composite panel with hat-shaped stiffeners, and finite element analyses were done to evaluate the expanding pressure of the rubber mold consistent with the curing temperature. The manufactured panels were also evaluated using a 3-D measurement tester and an ultrasonic tester. Pull-off tests were performed to evaluate their mechanical properties.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.15
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• pp.6615-6619
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• 2015

Background: The expression of HER-2 in prostate cancer has been linked to disease progression. We analysed the presence of HER-2 expression in primary tumors in men undergoing radical prostatectomy, its association with clinical and pathological findings, and its expression in secondary circulating prostate cells (CPCs) during follow up, as well as links with biochemical failure and the effects of androgen blockade. Materials and Methods: Consecutive men undergoing radical prostatectomy for histologically confirmed prostate cancer were analyzed. HER-2 expression in the primary tumor was assessed using the HercepTest(R), CPCs were identified from blood samples using standard immunocytochemistry with anti-PSA and positive samples with the HercepTest(R) to determine HER-2 expression. The influence of HER-2 expression on the frequency of biochemical failure and effects of androgen blockade was determined. Results: 144 men with a mean age of $64.8{\pm}10.3$ years participated, with a median follow up of 8.2 years. HER-2 was expressed in 20.8% of primary tumors; it was associated with vascular infiltration and older age, but not with other clinical pathological findings. Some 40.3% of men had secondary CPCs detected, of which 38% expressed HER-2. Men CPC (+) had a higher frequency of biochemical failure, but there was no difference in HER-2 expression of CPCs with the frequency of biochemical failure. After androgen blockade, men with HER-2 (+) positive secondary CPCs had a higher frequency of disease progression to castrate resistant disease. Conclusions: HER-2 plays a dual role in the progression of prostate cancer; firstly it may increase the potential of tumor cells to disseminate from the primary tumor via the blood by increasing vascular infiltration. In the presence of androgens, there is no survival advantage of expressing HER-2, but once biochemical failure has occurred and androgen blockade started, HER-2 positive cells are resistant to treatment, survive and grow leading to castration resistant disease.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.1
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• pp.64-74
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• 2017

In this study, we have analyzed relationship between the measured Water Soluble Organic Carbon (WSOC) concentrations and the estimated aerosol water content of $PM_{10}$ (particulate matter with an aerodynamic diameter of less than or equal to $10{\mu}m$) for the period between September 2006 and August 2007 at Seoul, Korea. Water content of $PM_{10}$ was estimated by using a gas/particle equilibrium model, Simulating composition of Atmospheric Particles at Equilibrium 2 (SCAPE2). The WSOC concentrations showed low correlation with Elemental Carbon (EC), but Water Insoluble Organic Carbon (WISOC) were highly correlated with EC. It seemed that hydrophilic groups were produced by secondary formation rather than primary formation. As with the previous studies, WSOC showed good correlation with secondary ions ($NO_3{^-}$, $SO_4{^{2-}}$, $NH_4{^+}$), especially WSOC was highly correlated with $NO_3{^-}$ that is a secondary ion formed by photochemical oxidation from more local sources than $SO_4{^{2-}}$. No apparent correlation between the measured WSOC and estimated water content was observed. However, WSOC showed good correlation with estimated water content when it was assumed that relative humidity was higher than the deliquescence relative humidity of the system. In conclusion, WSOC is correlated with water content by hygroscopic ions and it is expected that nitrate play an important role among the water content and WSOC.

• Journal of Korean Home Economics Education Association
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• v.1 no.1
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• pp.63-85
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• 1989

The Change of environment related to human life, science, technology, economics and education level have much effect on home life. Therefore Home Economics Education have to get out of past trite concept that it is only a method to become good housewife and take the role to widen the human life and to grow creative power as a academic part of science. For these, Home Economics should become life education, life education of secondary school has to have relation to lifelong education. To achieve effective result from Home Economics Education, the object, system and methods of Home Economics Education, the object, system and methods of Home Economics Education have to be improved and teaching material has to be studied systematically. As an object of aboves and education planning in clothing is made for deep understanding the study of Home Economics Teaching Material. And to understand the real state, made some questions, had interview with 63-teaching in Kangweon province and show the results. 1) Tab 1~20 are the level of recognition about object, teaching content, time structure of secondary school. The object is recognized as cultural education and basic job education. 2) Tab 21~30 show the real state of textbook and study of it. To take effect from school lecture other teaching material except textbook is required. 3) Tab 31~40 are the result of sewing and handicraft practice. Sewing and handicraft needs much time and almost all time is used in practicing. 4) Tab 42~54 are the planning of textbook study for effective teaching, self-estimation and teaching material making is also considered. All above is collarless blouse’s planning. Base on above result, all objects of clothing life should be teached. For the development of Home Economics Education 1) Understanding and affection of teachers is required. 2) To solve indicated problem, national policy, education plan in school and education finance are fully supported. 3) More studies is required in Home Economics Education.

• Journal of The Korean Association For Science Education
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• v.25 no.2
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• pp.146-161
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• 2005

This case study searched two secondary school science teachers' faiths on experiments in science classes. For this study, scaled questionnaires, open-ended questionnaires, structured and semi-structured interviews were conducted. Classroom activities were observed, and instructional plans and materials were collected. In addition, students of the two teachers' classes were interviewed with respect to their thoughts on the lessons. Data sources were analyzed inductively. The triangulation and the member checking guaranteed the validity of this study. As the results, the teachers' faiths on experiments were related to the constructivism, but the faiths were not in accord with their classroom practices. From these results, it was concluded that the teachers' misjudgments about the students' inquiry levels and unfit reorganizations of the experimental activities were the causes of the gap between the teachers' faiths on experiments and classroom practices.

• Journal of the Korean earth science society
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• v.27 no.3
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• pp.289-301
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• 2006

The purpose of this study is to investigate beginning secondary science teachers' teaching practices in terms of motivating and understanding students. Six first-year teachers participated in this study. Data were collected by classroom observations and structured interviews. Instructional materials used during the class were also collected to understand teaching practice. Lessons observed were video-tape recorded and the teachers were interviewed. Video- and audio-tape recording were transcribed. The framework, developed by Knowles Project Team of Michigan State University, was adopted and revised according to Korean classroom context and employed as an analytical tool for teaching practices. The beginning secondary science teachers intention ranged from 'Managing Work' to 'School Science.' No teachers revealed 'Reform Science Teaching' orientation. For the execution of science lessons, one teacher with 'Managing Work' orientation showed 'expert' level of execution, but the others executed at a 'novice' level. Beginning science teachers need to be guided and informed about 'Reform Science Teaching' for motivating and understanding students to develop professionally.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.368-372
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• 2011

Aluminum nitride (AlN) has excellent thermal conductivity, whereas it has some disadvantage such as low sinterability. In this study, the effects of sintering additive content and sintering condition on thermal conductivity of pressureless sintered AlN ceramics were examined on the variables of 1~3 wt% sintering additive ($Y_2O_3$) content at $1900^{\circ}C$ in $N_2$ atmosphere with holding time of 2~10 h. All AlN specimens showed higher thermal conductivity as the $Y_2O_3$ content and holding time increase. The formation of secondary phases (yttrium aluminates) by reaction of $Y_2O_3$ and $Al_2O_3$ from AlN surface promoted the thermal conductivity of AlN specimens, because the secondary phases could reduce the oxygen contents in AlN lattice. Also, thermal conductivity was increased by long sintering time because of the uniform distribution and the elimination of the secondary phases at the grain boundary by the evaporation effect during long holding time. A carbothermal reduction reaction was also affected on the thermal conductivity. The thermal conductivity of AlN specimens sintered at $1900^{\circ}C$ for 10 h showed 130~200W/mK according to the content of sintering additive.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.45 no.1
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• pp.29-33
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• 2019

Objectives: Bone density seems to be an important factor affecting implant stability. The relationship between bone density and primary and secondary stability remains under debate. The aim of this study was to compare primary and secondary stability measured by resonance frequency analysis (RFA) between different bone types and to compare implant stability at different time points during 3 months of follow-up. Materials and Methods: Our study included 65 implants (BioHorizons Implant Systems) with 3.8 or 4.6 mm diameter and 9 or 10.5 mm length in 59 patients. Bone quality was assessed by Lekholm-Zarb classification. After implant insertion, stability was measured by an Osstell device using RFA at three follow-up visits (immediately, 1 month, and 3 months after implant insertion). ANOVA test was used to compare primary and secondary stability between different bone types and between the three time points for each density type. Results: There were 9 patients in type I, 18 patients in type II, 20 patients in type III, and 12 patients in type IV. Three implants failed, 1 in type I and 2 in type IV. Stability values decreased in the first month but increased during the following two months in all bone types. Statistical analysis showed no significant difference between RFA values of different bone types at each follow-up or between stability values of each bone type at different time points. Conclusion: According to our results, implant stability was not affected by bone density. It is difficult to reach a certain conclusion about the effect of bone density on implant stability as stability is affected by numerous factors.