• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.2
• /
• pp.47-54
• /
• 2008

In this paper, we studied how and why did abnormal IMC growth at component affect on board level mechanical reliability. First, interfacial reactions between Sn2.5Ag0.5Cu solder and electrolytic Ni/Au UBM of component side were investigated with reflow times and thermal aging time. Also, to compare mechanical reliability of component level, shear energy was evaluated using the ball shear test conducted with variation of shear tip speed. Finally, to evaluate mechanical reliability of board level, we surface-mounted component fabricated with each condition on PCB side. After conducting of 3 point bending test and impact test, we confirmed solder joint crack mode using cross-sectioning and dye & pry penetration method.

• Korean Journal of Ichthyology
• /
• v.18 no.2
• /
• pp.87-96
• /
• 2006

Reproduction and organ system of the oily bitterling, Acheilognathus koreensis in Isa stream were investigated by means of histological methods. Sex ratio was observed 1 : 1 in female to male. The gonadosomatic index (GSI) of the female showed two peak in December and April. The ovipositor length index (OLI) represented irregular change. From the histological analysis of the organ system, epidermal atrophy and hyperplasia of pigment cell were observed in the skin. Epithelial layer lifting of the lamella and bifurcation of the filament were observed in the gill. Also histological changes as congestion, cytoplasmic degeneration of hepatic cell, glomerular dilatation, hyaline droplet degeneration of renal tubule epithelium and pycnosis of interstitial cell were identified in the liver and kidney, respectively.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.2
• /
• pp.8-15
• /
• 2014

The objective of this paper is to suggest a design topology of permanent magnet synchronous generator with 2,000kW capacities for wind turbine. The suggested topology is to provide 3 split magnet PMSG instead of single magnet, and performed an analysis of eddy current loss and iron loss for suggested type using ansoft maxwell commercial program. The simulation results of suggested magnet type show there duction of eddy current loss as 13.87kW with loadless conditions and23.48kW with rated conditions, but iron loss for rotor yoke show the in creasing trend as2.2kW with loadless conditions and 0.2kW with rated conditions. The suggested 3 split maget type is to identified as more useful for 2,000kW PMSG.

• Journal of Korean society of Dental Hygiene
• /
• v.15 no.5
• /
• pp.841-847
• /
• 2015

Objectives: The purpose of the study was to investigate the satisfaction with instruction medium according to learner attitude and lecture mode in the dental hygiene students. Methods: A web-based self-reported questionnaire was complected by 155 dental hygiene students in Cheonan from May 26 to June 5, 2015. The questionnaire consisted of general characteristics of the subjects, school adaptation, interest to learn, effort to learn, faculty centered lecture, learner centered lecture, self-directed learning, motivation to learn, characteristics of each subject, and satisfaction with lecture mode. The study was approved by institutional review board (IRB) by Baekseok University. Chi-square test and multivariate logistic regression were used to evaluate the satisfaction to medium of instruction according to explanation factors. Results: The lecture mode, opportunity and motivation to learn, interest to learn and effort to learn were the significant factors to satisfaction with instruction medium. In multivariate logistic regression model, the adjusted odds ratio was 6.28 for the opportunity to learn and 4.87 for the interesting to learn. Conclusions: The satisfaction with instruction medium is the most important factor that decides the lecture mode and learner attitude including opportunity to learn and concern to learn.

• Applied Chemistry for Engineering
• /
• v.5 no.1
• /
• pp.81-89
• /
• 1994

A study on Mm type electrode which is relatively high in electrode capacity and low in material cost was performed to develope high performance nickel-metal hydride battery. The electrode characteristics were investigated by P-C-T, charge-discharge and microencapsulation treatment experiments. The plateau pressure and hydrogen absorption capacity obtained from the P-C-T experiment were 0.4 atm and 310 mAh/g, respectively. The electrode capacity and stability of microencapsulated electrode were improved than those of conductor mixed electrode and the microencapsulation was possible without pretreatment. The electrode capacity of microencapsulated Mm type alloy was 240~250 mAh/g(0.2 C).

• Korean Journal of Pharmacognosy
• /
• v.44 no.1
• /
• pp.60-69
• /
• 2013

The worldwide prevalence and severity of allergic diseases including atopic and contact dermatitis has increased dramatically over the past decade, especially in developed countries. Mast cells are important effector cells in allergic reactions. The purpose of this study was undertaken to investigate the anti-allergic and anti-pruritic effects of Diospyros lotus leaf extract (DLE). DLE was prepared by extracting with distilled water. In the present study, we investigated the effect of DLE on the production of tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$), interleukin-$1{\beta}$ (IL-$1{\alpha}$) and histamine in rat peritoneal mast cells (RPMCs), and on the skin lesion, leukocyte infiltration and scratching behavior in mice. Phorbol 12-myristate 13-acetate (PMA) plus calcium ionophore A23187 significantly increased TNF-${\alpha}$ and IL-$1{\beta}$ production compared with media control. However, TNF-${\alpha}$ and IL-6 production increased by PMA plus A23187 treatment were significantly inhibited by DLE in a dose-dependent manner. DLE also inhibited the histamine release from RPMCs stimulated by compound 48/80, which promotes histamine release. Moreover, DLE administration had an inhibitory effects on the scratching behavior induced by pruritogen (compound 48/80, histamine) in ICR mice. Furthermore, DLE inhibited the skin lesions, inflammatory and mast cells in hairless mice sensitized by 2,4-dinitrofluorobenzene (DNFB). DLE administration reduced the IL-4 and IgE production induced by DNFB sensitization in hairless mice. These results suggest that DLE has a potential use as a herb medicine for treatment against allergy and pruritus-related disease.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.1
• /
• pp.84.1-84.1
• /
• 2010

2009 세계 천문의 해(International Year of Astronomy 2009, IYA2009) 한국조직위원회는 지난 1년간 148개 참가국의 일원으로 다양한 활동을 펼쳤다. IYA2009 활동은 강연, 별 축제와 같은 고전적인 이벤트로부터 시, 수필, 에세이, 음악, 미술, 만화, 영화, 대회, 인터넷 생중계, 플래시 동영상과 같이 새롭게 시도된 프로그램에 이르기까지 다양하게 기획, 운영되었다. 또한 우리는 시민천문대와 과학관, 미술관은 물론, 지하철, 기차역, 시청, 놀이공원, 쇼핑몰, 백화점, 병원, 그리고 경찰서에 이르기까지, 기존의 전통적인 전시공간을 벗어나 다양한 장소에서 전시회와 동영상 상영을 시도했다. 우리는 지난 1년간 90여 종의 행사를 410여 회에 걸쳐 진행했으며, 총 11,700,000여 명의 일반 시민과 학생들이 2009 세계 천문의 해에 참여한 것으로 추산하고 있다. IYA2009는 강연 200여 회, 전시 80여 회, 공연 15회, 학회 7회 등으로 요약할 수 있으며, 공식책자 4종, 도록 3종이 발간되었다. 관련 보도자료는 40 차례 배포했으며, 그 결과 2,500여 건이 언론을 통해 보도되었고, 총 248편의 연재기사가 실렸다. 2009 세계 천문의 해 한국조직위원회 공식 웹진 '이야진' 접속자는 999,890명, 총 페이지 뷰 건수는 131,963,473을 기록했다.

• Journal of the Korea Convergence Society
• /
• v.9 no.10
• /
• pp.149-157
• /
• 2018

This study was conducted using the National Health and Nutrition Survey data for 2010-2014 to investigate the relationship between pregnancy-related health factors and periodontitis in adult women. Dependent variable was periodontitis, and independent variables, pregnancy-related health factors(duration of lactation and number of pregnancies) were analyzed. Socioeconomic variables and health-related behaviors were corrected by confounding variables. The number of pregnancies and periodontitis were highly correlated after adjusting for various confounding factors [odds ratio for women with 2-3 pregnancies: 2.66 (95% confidence interval(CI): 1.56-4.54); The odds ratio for women with four or more pregnancies 3.02 (95% CI: 1.70-5.36). In conclusion, periodontitis is closely related to the number of pregnancies and this will be used as basic data for development of oral health education programs for women and pregnant women.

• Journal of the Korean Data and Information Science Society
• /
• v.24 no.6
• /
• pp.1429-1437
• /
• 2013

Research articles in food related to climate change were analyzed by implementing a text-mining algorithm, which is one of nonstructural data analysis tools in big data analysis with a focus on frequencies of terms appearing in the abstracts. As a first step, a term-document matrix was established, followed by implementing a hierarchical clustering algorithm based on dissimilarities among the selected terms and expertise in the field to classify the documents under consideration into a few labeled groups. Through this research, we were able to find out important topics appearing in the field of food related to climate change and their trends over past years. It is expected that the results of the article can be utilized for future research to make systematic responses and adaptation to climate change.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.433-434
• /
• 2015

Dictionary meaning of circuit-breaker is a mechanical switching device, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit. and it had been recognized as being operated simultaneously. Controlled Switching System(CSS), which is technology for individual pole operation, are widely used to reduce transient phenomenon, for example switching surges, inrush current, for a all switching cases and nowadays it have become and economical solution for a switching place. The conventional solution to these problem is the use of pre-insertion resistors of $520{\Omega}$. However, it is recognised that the cost for products and maintenance are expensive and this apparatus makes more complex the circuit-breaker mechanism. Korea Electric Power Cooperation (KEPCO) has been study for relevant CCS technology since pilot application in substation in 2003 and plan to apply the actual power grid in 2017. This paper deals with the investigation of international CCS operation status and preview for application in KEPCO power grid.