• Tribology and Lubricants
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• v.40 no.3
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• pp.71-77
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• 2024

Hydrogen has emerged as an eco-friendly and sustainable alternative to fossil fuels. However, the utilization of hydrogen requires high-pressure compression, storage, and transportation, which poses challenges to the durability of compressor components, particularly the diaphragm. This study aims to improve the durability of 304 stainless steel diaphragms in hydrogen compressors by optimizing their surface roughness and corrosion resistance through wet etching. The specimens were prepared by immersing 304 stainless steel in a mixture of sulfuric acid and hydrogen peroxide, followed by etching in hydrochloric acid for various durations. The surface morphology, roughness, and wettability of the etched specimens were characterized using optical microscopy, surface profilometry, and water contact angle measurements. The friction and wear characteristics were evaluated using reciprocating sliding tests. The results showed that increasing the etching time led to the development of micro/nanostructures on the surface, thereby increasing surface roughness and hydrophilicity. The friction coefficient initially decreased with increasing surface roughness owing to the reduced contact area but increased during long-term wear owing to the destruction and delamination of surface protrusions. HCl-30M exhibited the lowest average friction coefficient and a balance between the surface roughness and oxide film formation, resulting in improved wear resistance. These findings highlight the importance of controlling the surface roughness and oxide film formation through etching optimization to obtain a uniform and wear-resistant surface for the enhanced durability of 304 stainless steel diaphragms in hydrogen compressors.

• Tribology and Lubricants
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• v.40 no.3
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• pp.84-90
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• 2024

This study investigates the effect of the surface microstructure on the tribological characteristics of glass substrates. Chemical etching using hydrofluoric acid and ammonium hydrogen fluoride was employed to create controlled asperity structures on glass surfaces. By varying the etching time from 10 to 50 min, different surface morphologies were obtained and characterized using optical microscopy, surface roughness measurements, and water contact angle analysis. Friction tests were performed using a stainless steel ball as the counter surface to evaluate the tribological behavior of the etched specimens. The results showed that the specimen etched for 20 min exhibited the lowest and most stable friction coefficient, which was attributed to the formation of a uniform and dense asperity structure that effectively reduced the stress concentration and wear at the contact interface. In contrast, specimens etched for shorter (10 min) or longer (30-50 min) durations displayed higher friction coefficients and accelerated wear owing to nonuniform asperity structures that led to local stress concentration. Optical microscopy of the wear tracks further confirmed the superior wear resistance of the 20-minute etched specimen. These findings highlight the importance of optimizing the etching process parameters to achieve the desired surface morphology for enhanced tribological performance, suggesting the potential of chemical etching as a surface modification technique for various materials in tribological applications.

• Preventive Nutrition and Food Science
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• v.1 no.2
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• pp.244-251
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• 1996

Molecular weight and partial amino acid sequence of the cis, 9-cis, 12-octadecadienoate isomerase(linoleate isomerase) of Butyrivibrio fibrisovens A-38 were determined. Linoleate isomerase was isolated from the bac-teria cultured anaerobically and purified by ultracentrifugation in conjunction with Sepharose 6B column chro-matography, Phenyl sepharose 4B column chromatography and fast performance liquid chromatography (EPLC). The isomerase was single polypeptide with 19KD of molecular weight, when determined by SDS-PAGE. Fourteen amino acids sequence of N-terminal of the linoleate isomerase was N-GEIDKYPRIIKQQ determined by Edman method.

• Journal of the Korean Solar Energy Society
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• v.26 no.2
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• pp.69-77
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• 2006

Photovoltaic is an attractive technology to remote power applications, because of its reliability, low maintenance, and zero fuel requirements. In this paper represents residential PV system based on BESS(battery energy storage system) for managing the electric power, a pattern of daily operation considering the load characteristics of the house, the generation characteristics of PV power, and utility power leveling. For apply to control algorithm, we consider the load on monthly power consumption trend and daily usage pattern. As for the control of the proposed system, to increase the conversion efficiency of the PV power, bidirectional converter is used for MPPT and SPWM inverter. An experimental system is implemented, and some experimental results are provided to demonstrate the effectiveness of the proposed system.

• Genomics & Informatics
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• v.4 no.1
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• pp.16-22
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• 2006

The KFDA (Korea Food & Drug Administration) has performed a collaborative toxicogenomics project since 2003. Its aim is to construct a toxicology database of 12 compounds administered to mice at initial phase. We chose 6-MP (6-mercaptopurine) which has been used in the treatment of childhood leukemia. It was administered at low (0.224 mg/kg) and at high (2.24 mg/kg) dose (5 mice per group) intraperitonealy to the postnatal 6 weeks mice, then the serum and liver were collected at the indicated time (6, 24 and 72 h) after scarification. Serum biochemical markers for liver toxicity were measured and histopathologic studies also were carried out. The gene expression profiling was carried out by using Applied Biosystems 1700 Full Genome Expression Mouse. By self-organization maps (SOM), we identified groups with unique gene expression patterns, some of them are supposed to be related to 6-MP induced toxicity, including lipid metabolism abnormality, inflammatory response, oxidative stress, ATP depletion and cell death. The potential toxic effects appearing as gene expression changes are dependent of the time of 6-MP but independent of the dosage of it. This study would contribute to establishment of international database as well as national one about hepatotoxicity.

• The Journal of Korean Academic Society of Nursing Education
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• v.11 no.2
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• pp.287-297
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• 2005

Purpose: This study was to develop teaching-learning lesson plans to provide systematic health education materials to school health educators in middle schools. Method: The concepts of health promotion were redefined in the significance of health promotion in schools were emphasized, and the health problems of middle school students were identified through the literature review of previous studies. The preceding studies on the curriculum development of health education were examined and analyzed. Result: The contents of health education were provided by the learning level of middle school students. The selected contents were composed of total 9 units. The units were again divided into 34 subunits, each of which includes individual learning purposes. How to execute a program utilizing various teaching media and learning materials and how to assess the learning results of health education were presented as well. Conclusion: This study was aimed at developing a teaching-learning lesson plan for health education virtually available on the school scene, required are the follow-up case studies applying the lesson plan: how effectively the activities for promoting the health of middle school students are changed and how appropriate this health education is for promoting the health of middle school students.

• International journal of advanced smart convergence
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• v.3 no.1
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• pp.15-19
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• 2014

This study was compared the variation system of body posture condition for stability by the posture. We used a model of bio parameter on the basis of the move state in the standing posture. We compared the sway movement derived from average of the physical sensing condition. Vision condition of variation average (Vi-${\sigma}_{AVG-AVG}$) was verified slightly greater at $13.746{\pm}4.05$ unit. Vestibular condition of variation average (Ve-${\sigma}_{AVG-AVG}$) was verified slightly larger at $7.829{\pm}1.071$ unit. Somatosensory condition of variation average (So-${\sigma}_{AVG-AVG}$) was verified slightly smaller at $2.592{\pm}0.538$ unit. CNS condition of variation average (C-${\sigma}_{AVG-AVG}$) was verified slightly larger at $0.46{\pm}0.105$ unit. The valuation system will be to deduce the model of body management with falling and stroke and all that sort of things. There will be to infer a data algorithm and the evaluation of processing system.

• Korean Journal of Childcare and Education
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• v.13 no.1
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• pp.65-83
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• 2017

Objective: The purpose of this study was to examine the mediating effect of teaching flow on the relationship between director's servant leadership and early childhood teachers'happiness. Methods: The subjects in this study were 241 early childhood teachers in Busan and South Gyeongsang Province in South Korea. Three different inventories were utilized. The Servant Leadership Scale, Teaching Flow Scale and Happiness Scale were used. As for data analysis, SPSS & AMOS 21.0 and PROCESS macro were utilized. Results: First, the director's servant leadership, teaching flow and happiness of the teachers were all above average, and there was a significant positive correlation between their total scores of servant leadership, teaching flow and happiness. Second, The teaching flow was found to have a partial mediation effect on the on the relationship between director's servant leadership and happiness of the early childhood teachers. Conclusion/Implications: These results indicate that effort to promote director's servant leadership and teaching flow is needed to promote early childhood teachers'happiness.

• Annual Conference on Human and Language Technology
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• 1995.10a
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• pp.73-79
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• 1995

현재 정보 관련 응용 분야 가운데 ISO 2022 를 따르는 분야가 아주 않은데, 현재 쓰고 있는 한글 부호계들은 ISO 2022 를 절대로 지원하지 못하거나, ISO 2022를 지원하더라도 한글을 재대로 지원하지 못하는 문제가 있다. 이러한 문제를 해결하기 위해서 ISO 2022 를 지원하면서 한글을 제대로 지원하는 새로운 한 바이트 한글 부호계를 만들었다. 새로운 한 바이트 한글 부호계는 요즘 한글 11,172 소리마디를 모두 표현 할 수 있으며, 불완전한 소리마디를 나타내는 방법으로 기존의 채움 글자 방식을 버리고 자연스럽고 한글의 특성에 맞는 뗌 글자 방식을 택하였다. 본 연구에서는 새로운 한 바이트 한글 부호계를 지원하는 X-Window용 한글 문서 편집기를 개발해 봄으로써 그 운용 가능성을 검증하였다. 한 바이트 한글 부호계를 지원하는 문서 편집기의 운용 환경으로 유닉스 운영체제 하에서 돌아가는 X-Window 시스템을 택하였고, 한글 입출력 부분을 모티프 (Motif)의 위짓 (widget) 형태로 구현하여 다른 응용 프로그램에서도 쉽게 한 바이트 한글 부호계를 지원할 수 있게 하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.20 no.2
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• pp.166-172
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• 1998

Missing of the upper posterior dentition can cause alveolar bone resorption & pneumatization of Maxillary sinus wall, which makes traditional implant placement impossible, The solution includes various methods to the posterior maxilla to provide adequate bone support for implant installation and long-term survival. -- sinus floor elevation, sinus-lift graft, inlay graft using LeFort I osteotomy, onlay graft, This is a clinical Sr. retrospective study on implant surgery & prosthodontic restoration with upper edentulous posterior jaw from Jan. 1990. to Jun. 1997 at implant clinic of Chonbuk National University Hospital. The results obtained were as follows: 1. Six hundred ninety-nine implants were placed on upper posterior jaw of two hundred seventeen patients, among them one hundred sixty-five implants were placed in forty-four patients with sinus lift. 2. The height of the remained alveolar bone was classified on the base of Misch's concept. This included seventy-nine SA-1s, ninety-seven SA-2s, sixty-five SA-3s and sixty SA-4s. 3. Ninety percent of implants were successfully integrated in non-grafted area and eighty-seven percent of implants were successully integrated in sinus lift area.