• 한국안전학회지
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• 제22권4호
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• pp.20-25
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• 2007

Instrument transformers are a safe measurement device designed to measure high voltage and large current. A current transformer(CT) is a type of instrument transformer designed to provide a current in its secondary winding proportional to the current flowing in its primary. It is commonly used in metering and protective relaying in the electrical power industry where it facilitates the safe measurement of large current. But, care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary, as this will produce a dangerously high voltage across the open secondary, and may permanently affect the accuracy of the transformer. Especially, industrial disaster such as an electric shock and/or a burn accident occurs occasionally by disregard of warning or attention. In this paper, we developed the detector for open of current transformer secondary terminal, and which was tested by the Korea Electrotechnology Research Institute. Test results show that Current Transformer secondary Open Detector(CTOD) interrupted within one second electronically when the 2nd terminal of current transformer opened.

• Journal of Communications and Networks
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• 제11권2호
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• pp.148-156
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• 2009

The fixed spectrum assignment policy in today's wireless networks leads to inefficient spectrum usage. Cognitive radio network is a new communication paradigm that enables the unlicensed users to opportunistically use the spatio-temporally unoccupied portions of the spectrum, and hence realizing a dynamic spectrum access (DSA) methodology. Interference temperature model proposed by Federal Communications Commission (FCC) permits the unlicensed users to utilize the licensed frequencies simultaneously with the primary users provided that they adhere to the interference temperature constraints. In this paper, we formulate two NP-hard optimal scheduling methods that meet the interference temperature constraints for cognitive radio networks. The first one maximizes the network throughput, whereas the second one minimizes the scheduling delay. Furthermore, we also propose suboptimal schedulers with linear complexity, referred to as maximum frequency selection (MFS) and probabilistic frequency selection (PFS). We simulate the throughput and delay performance of the optimal as well as the suboptimal schedulers for varying number of cognitive nodes, number of primary neighbors for each cognitive node, and interference temperature limits for the frequencies. We also evaluate the performance of our proposed schedulers under both additive white gaussian noise (AWGN) channels and Gilbert-Elliot fading channels.

• 대한수학교육학회지:학교수학
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• 제6권1호
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• pp.37-57
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• 2004

본 연구에서는 7차 교육과정에서 요구하는 교실 수업 개선의 한 방법으로 웹 자료의 활용이 초등학교 수학과의 자기 주도적 학습에 어떻게 영향을 주는가를 알아보는데 그 목적이 있다. 본 연구를 통하여 웹 자료가 아동들에게 적극적인 학습태도를 갖게 해 주며, 수학 개념 형성을 용이하게 해 주며 협동학습에 도움을 주며 수준별 학습을 강화시켜 주고 문제해결력을 신장시키고 스스로 객관적 평가를 할 수 있도록 하여 자기 주도적 학습에 긍정적 영향을 주었음을 알 수 있었다.

• 패션비즈니스
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• 제14권1호
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• pp.106-115
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• 2010

This study's purpose is to, first survey the traditional children clothing, clothing which doesn't get studied mostly. Second, to choose the factor that can modernize. Third, to design the present one-piece dress. Fourth, to gather an understanding about traditional children clothing and make a chance for children to wear the clothing that has a traditional factor. Traditional children clothes have a same shape with adults' clothes they use five primary color and use a pattern of a symbolic meaning which means healthy and long life. For ordinary wears there are Chimajogori and Bajijogori and for ceremonial dresses they wore Durumagi, Sagyusam which are Po and Dangui and headdress was added. The shape was considered by the children growth condition so the Gorum got longer. The dragon, cicadas, butterfly, phoenix and lots of flower pattern was used by the difference with the class. 5 one-piece design adapted Jogori, skirt, Dangui, Sagyusam, Magoja and used the traditional fabric by mixing the five primary color and the five secondary color was used to make traditional color. This study expects for a chance of children to wear traditional Hanbok or Hanbok-adapted clothes.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.173.2-173.2
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• 2016

A two-step oxidation method was applied on Al6061 to debate the growth mechanism of plasma electrolytic oxidation (PEO) coating. The specimens were first oxidized in the primary electrolyte solution {$Na_3PO_4$ (8g/l), NaOH (2g/l), consequently, the specimens were transferred into a different electrolyte {$K_2ZrF_6$ (8g/l), NaOH (2g/l), $Na_2SiF_6$ (0.5g/l)} for further oxidation. The processes was conducted for various processing times. It was found the second step electrolyte component were reached to inner layers, in contrast to the primary step components which were thrustle to the outer layer. The presence of the secondary component in the inner layers were significantly varied with processing time which suggest the change in growth properties with processing time. further more the inside growth of the secondary component confirmed the increasing trend in the downward growth of the coating layer. The corrosion and hardness properties of the coatings were found highly improved with change in growth features with increasing the processing time.

• 대한가정학회지
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• 제47권2호
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• pp.81-95
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• 2009

The purpose of this study is to examine gender equity in the quantity and flow experience of leisure time of urban dual-earner couples having preschool children. The quantity of leisure time is measured by primary activity and the flow experience of leisure time is measured by primary and secondary activities. The data collected by Korean National Statistical Office in 2004 is used. The sample for this study consists of 255 couples, and the statistical methods are frequency, percentage, paired t-test, and one-way ANOVA. The following is a summary of the major findings. The first, the pattern of the leisure time was different between husbands and wives. The quantity of leisure time of husbands was longer than that of wives. The husbands spent more time to perform social activities, media contact, sports and outdoor activities, while women did more in religious activities. The second, husband's leisure flow experience was higher than that of wives. The pure leisure time of wives was shorter than that of husbands and wives experienced more contaminated leisure time by a secondary activity. In other words, wives's leisure is more likely to be interrupted, to involve episodes of shorter duration, and to be associated with personal care and unpaid work.

• 대한골관절종양학회지
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• 제17권2호
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• pp.95-99
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• 2011

악성 연부조직 종양 수술 후 이시성(metachronous)으로 발생하는 악성 골졸양은 매우 드물다. 이시성 종양은 두 경부 또는 복부에 주로 발생하며, 사지에 발생하는 경우는 더욱더 드물다. 저자들은 48세 남자환자에서 근위 대퇴부 악성 지방 육종의 광범위 변연 절제술 후 발생한 근위 경골 유잉육종/원시 신경 외배엽 세포종 1예를 경험하여 문헌 고찰과 함께 보고하는 바이다. 육종 환자들에게서는 이와 같이 이차적으로 악성 종양이 발생할 확률이 높아지기 때문에 추시 기간 동안 잠복 종양(occult tumor)에 대한 검사가 필요하겠다.

• 대한족부족관절학회지
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• 제24권2호
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• pp.69-74
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• 2020

Osteochondral lesions of the talus (OLT) can heal and remain asymptomatic, or they can progress to deep ankle pain on weight bearing and the formation of subchondral cysts. Treatment varies from nonoperative treatment to open and arthroscopic procedures. Operative procedures include marrow stimulation techniques (abrasion chondroplasty, multiple drilling, microfracture), osteochondral autografts or allografts, and autologous chondrocyte implantation. Among these treatments, arthroscopic marrow stimulation techniques have been the preferred initial surgical treatment for most OLT. Despite these treatments, many patients complain of persistent pain even after surgery, and many surgeons face the challenge of determining a second line of treatments. This requires a thorough re-evaluation of the patient's symptoms as well as radiological measures. If the primary surgical treatment has failed, multiple operative treatments are available, and relatively more invasive methods can be administered. On the other hand, it is inappropriate to draw a firm conclusion in which methods are superior.

• 조명전기설비학회논문지
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• 제18권1호
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• pp.98-104
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• 2004

본 논문에서는 사고나 계획정전 등으로 인한 건전 정전구간에 신속하게 전원을 공급하는 방안을 제시하였다. 제시한 부하복구방안은 연계개폐기로부터 공급피더 방향으로 계통을 역방향으로 탐색하고 탐색시 저장된 경로와의 조합을 이용하여 구해짐으로써 계통의 탐색공간이 대폭 줄어들게 되어 신속한 복구방안의 제시가 가능하다. 또한 공급 여유량을 미리 확보하는 2단계의 부하복구, 모든 구간에 대한 복구가 불가능한 경우 부하를 차단하는 방안 등이 포함되어 있으므로 광역정전이나 다중사고 및 중요수용가를 고려한 부하복구, 배전자동화시스템과 연계된 부하 복구에도 이용할 수 있다.

• 전력전자학회논문지
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• 제23권4호
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• pp.256-264
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• 2018

This paper proposes a three-bridge LLC resonant converter with auxiliary switches for a wide output voltage control range. This converter can be controlled in two ways to achieve a wide controllable output voltage control range of $V_o$ to $3V_o$. The first control mechanism is achieved through the pulse width modulation (PM) of the auxiliary switches and primary switching devices, while the second control mechanism is achieved through the frequency modulation (FM) of the primary switching devices that are configured to operate in the full-bridge switching mode when the auxiliary switches are turned off. The feasibility of using the proposed converter is verified by the results of an experiment with a 2kW prototype.