• 제목/요약/키워드: power factor control

검색결과 1,433건 처리시간 0.032초

메조포러스 이산화티타늄 박막 기반 양자점-감응 태양전지 (Quantum Dot-Sensitized Solar Cells Based on Mesoporous TiO2 Thin Films)

  • 이효중
    • 전기화학회지
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    • 제18권1호
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    • pp.38-44
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    • 2015
  • 본 총설은 다공성의 메조포러스 이산화티타늄 박막을 기반으로 하는 양자점-감응 태양 전지의 최근 발전 과정에 대해 정리하였다. 나노스케일의 무기물 양자점이 가지는 본질적 특성에 기반하고 다양한 양자점 구성 물질을 이용하여, 용액-공정 기반의 다양한 3세대 박막 태양전지를 만들 수 있었다. 양자점 감응제는 준비하는 방법에 따라 크게 2가지로 나눌 수 있는데, 첫 번째는 콜로이드 형태로 용액상에서 준비한 다음 $TiO_2$ 표면에 붙이는 것이고 두 번째는 양자점 전구체가 녹아있는 화학조를 이용하여 직접 $TiO_2$ 표면에 성장시키는 것이다. 폴리썰파이드 전해질을 사용하여, 콜로이드 양자점 감응제의 경우는 최근 들어 정밀한 조성 조절을 통하여 전체 광전 변환효율이 ~7%에 이르렀고 화학조 침전법을 이용하여 준비된 대표적 감응제인 CdS/CdSe는 ~5%의 효율을 보이고 있다. 앞으로는 지금까지 보고된 양자점 감응제의 뛰어난 광전류 생성 능력을 유지하면서, 새로운 정공 전달체의 개발 및 계면 조절을 통한 개방 전압과 채움 상수의 개선을 통한 효율 증가 및 안정성에 관한 체계적 연구가 필요한 상황이다.

과학영재학생의 학습동기와 과제집착력과의 관계 (The Relationship between Learning Motivation and Task Commitment of Science-Gifted)

  • 박미진;이용섭
    • 영재교육연구
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    • 제21권4호
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    • pp.961-977
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    • 2011
  • 본 연구의 목적은 학습동기와 과제집착력의 관계를 살펴봄으로써 과제집착력에 영향을 주는 학습동기 요인을 찾는데 두고 있다. 과학영재학생으로 판별된 초등학교 4, 5학년 학생 30명을 대상으로 학습동기 검사와 과제집착력 검사를 실시하여 자료를 수집하였다. 자료분석은 상관 분석과 중다회귀분석을 실시하였다. 연구 결과, 과학영재학생들의 학습동기와 과제집착력은 전체적으로 비슷한 수준을 보여주고 있으나 각 하위 요인별로 강점을 보이는 부분은 다르다고 할 수 있었다. 둘째, 학습동기와 과제집착력은 정적 상관을 보여 학습동기가 높을수록 과제집착력이 높다고 할 수 있었으며 학습동기는 과제집착력에 대해 49.3%의 유의미한 설명력을 가졌다. 특히 학습동기가 높을수록 과제 집착력의 하위요인인 책임감과 자기통제 요인이 높아진다고 할 수 있었다. 또한 학습동기 요인 중 자신감 요인이 과제집착력의 가장 많은 하위 요인과 정적 상관을 가지며 과제집착력에 유의한 영향을 미치는 것으로 나타났다. 이러한 연구 결과는 과제집착력을 향상시키기 위해 학습동기를 개발하는 것이 필요하며 학습동기 프로그램 중에서도 특히 과학영재학생들의 과제집착력 향상을 위해서는 자신감을 길러줄 필요가 있다는 것을 시사해준다.

자궁 절제술을 경험한 여성의 스트레스 대처, 배우자지지, 의도적 반추와 외상 후 성장의 관계 (The Relationship between Stress Coping, Spouse Support, Intentional Rumination and Post-traumatic Growth in Women with Hysterectomy)

  • 채여주;김영란;이옥숙;김보람;고영심;한상미;하영미
    • 한국융합학회논문지
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    • 제11권8호
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    • pp.237-245
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    • 2020
  • 본 연구의 목적은 자궁절제술이라는 외상사건을 경험한 대상자의 스트레스 대처, 배우자지지, 의도적 반추, 외상 후 성장 간의 관계를 파악하기 위해 시도되었다. 본 연구 대상자는 자궁절제술을 경험한 67명의 여성으로 수집된 자료는 t-검정, ANOVA 및 다중회귀분석을 사용하여 분석하였다. 본 연구결과 대상자의 외상 후 성장은 스트레스 대처 중 소극적 대처(r=0.27, p=.026), 적극적 대처(r=0.34, p=.004) 그리고 의도적 반추(r=0.46, p<.001)와 유의한 양의 상관관계가 있는 것으로 나타났으며, 소극적 대처는 적극적 대처(r=0.74, p<.001)와 유의한 양의 상관관계가 있는 것으로 나타났다. 자궁절제술을 경험한 여성의 외상 후 성장에 영향을 미치는 요인으로는 의도적 반추(β=0.42, p<.001)인 것으로 나타났고 이들의 총 설명력은 26%로 확인되었다(F=8.68, p<.001). 그러므로 본 연구의 결과를 토대로 자궁절제술을 가진 대상자의 외상 후 성장을 증진시키기 위해서는 의도적 반추를 증가하여 이들이 겪는 외상에 효과적으로 직면할 수 있도록 하는 중재 프로그램이 필요하다.

큰눈자미 배아의 식물성 스테롤 함량 및 성숙기 흰쥐에서 항산화 효과 (Phytosterols content of Keunnunjami germ and its antioxidative effects in adult rats)

  • 량지에;마징원;정수임;강미영
    • Journal of Nutrition and Health
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    • 제53권2호
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    • pp.99-110
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    • 2020
  • 본 연구에서는 고기능성 쌀인 큰눈자미 배아의 phytosterols 함량 및 in vitro 항산화 활성을 평가하고, 성숙기 흰쥐에게 보충 급여한 당질 대사, 항산화 활성 및 일부 cytokines 개선 효과 여부를 검증하였다. Phytosterols 분석에서 NG보다 KG의 campesterol과 stigmasterol의 함량이 유의하게 높았다. NG에 비해 KG가 DPPH radical 소거 활성, 환원력 및 ABTS radical 소거능 측정에서 유의적으로 높은 값을 나타내었다. 실험동물은 각 10마리씩 3군으로 나누어 일반 식이를 급여하는 NC군, 일반현미배아 3%를 첨가하는 NG3군, 큰눈자미배아 3%를 첨가하는 KG3군으로 나누어 사육하였다. 그 결과 KG3군에서 체중증가량, 신장주위 및 총 지방량이 유의하게 감소하였다. 당질 대사에서 실험군들 간에 glucose, 인슐린, C-peptide 및 HOMA-IR의 수준이 유의적인 차이가 나타나지 않았다. KG3군에서 혈중 TNF-α 수준이 NG3에 비해 유의적으로 감소하고, SOD 활성이 유의하게 증가하였으며, leptin, AOPP 및 IL-6 수준이 감소하는 경향을 나타내었다. 이상의 결과로부터 큰눈자미 배아는 높은 함량의 phytosterols과, 우수한 in vitro 항산화활성, 그리고 in vivo 실험에서 일부의 cytokine 개선 및 항산화에 긍정적인 효과가 있음을 제시하였고 향후 더 많은 생리활성물질 분석, 대사 지표 개선, 작용 기전 규명 등 세부적인 연구가 필요할 것으로 사료된다.

소매업체의 글로벌 확장전략과 공급사슬관리에 관한 연구: 메트로 그룹을 중심으로 (A Study on the Retailer's Global Expansion Strategy and Supply Chain Management : Focus on the Metro Group)

  • 김동윤;문미진;이상윤
    • 유통과학연구
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    • 제11권12호
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    • pp.25-37
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    • 2013
  • Purpose - The structure of retailing has changed as retailers develop markets in response to business environment changes. This study aims to analyze the general situation of retailers in order to predict future global strategy using case studies of overseas expansion strategy and the Metro Group's global strategy. Research design, data, and methodology - The backgrounds to the new retail business model and retailer classification are analyzed as theoretical data. In addition, the key success point of the Metro Group's "cash and carry" strategy is analyzed as is the Metro Group's global CFAR (collaborative planning, forecasting, and replenishment) strategy. Finally, the plan for cooperation and precise forecasting under the Metro Group's supply chain management are analyzed from the promotion environment viewpoint. Related materials analyzed included the 2012 annual report, the Metro Group's web page, and a video interview with the executive in charge of global strategy and the new market development department. Some data were revised to avoid disrupting essential aspects of the case studies. Results - The important finding was that the Metro Group could be a world-class retail company with its successful global expansion strategy. The Metro Group's global strategy's primary goal is to have a leading business position in Eastern and Western Europe. The "cash and carry" strategy is highest priority in its overseas expansion strategy. Moreover, the Metro Group has standardized product planning capacity, which could be applied in various countries with different structural and cultural backgrounds. This is the main reason that the Metro Group could rapidly become successful in the Eastern Europe and Asian markets through its structural overseas expansion strategies. In addition, the Metro Group emphasizes the importance of supply chain management. Conclusions - First, retailers should create additional value through utilizing the domestic market, market power, and economies of scale to launch a global strategy to maximize benefits from diversification. Second, the political, economic, and cultural background of the target country needs to be understood to successfully implement the overseas expansion strategy. Third, the main factor of successful cooperation with a local partner is how quickly the company gains total understanding of the business resources and core competence of its partner. All organizations should focus on the achievement of goals in order to successfully operate the partnership. Fourth, retailers should improve their business, financial and organizational structure. Moreover, the work processes and company culture should also be improved to respond strongly in the competitive global market. Fifth, the essential point of a successful retail business is the control capacity of its branding and format. The retailer could avoid forecasting errors through supply chain management by perfectly distributing the actual amount of its inventory. In addition, the risks along the supply chain are effectively shared between the supply chain partners. Finally, the central tendency of the market is to gain in strength with this taking place across all parts of the business.

클라우드 기지국 시스템에서 효율적 무선 접속을 위한 이른 스펙트럼 감지 기법 (An Early Spectrum Sensing for Efficient Radio Access in Cloud-Conceptual Base Station Systems)

  • 조가희;이재원;나지현;조호신
    • 한국통신학회논문지
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    • 제38A권1호
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    • pp.68-78
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    • 2013
  • 본 논문에서는 다양한 무선 접속 기술(Radio Access Technology : RAT)들이 공존하는 클라우드 기지국 시스템에서의 효율적인 무선 접속 방법으로 무선인지기술(Cognitive radio)을 활용한 이른 스펙트럼 감지(Early Spectrum Sensing : ESS) 기법을 제안한다. 다중 모드 단말은 무선 접속 시도에 앞서 다중 무선 접속 시스템의 전체 주파수 대역을 대상으로 스펙트럼 감지를 수행하여 그 결과 스펙트럼 활용도가 가장 낮은, 즉 가용 스펙트럼이 가장 많을 것으로 예상되는 시스템을 선택하여 무선 접속을 시도함으로써 시스템 접속 성공 확률을 높일 수 있다. 제안 기법의 성능 분석을 위해 컴퓨터 시뮬레이션을 수행 했으며 그 과정에서 최대한 다양한 무선 접속 시스템이 혼재하는 상황을 고려하고자 했다. 우선, 서킷과 패킷 시스템으로 구별한 후, 다시 패킷 시스템을 반송파 결합(Carrier Aggregation : CA) 가능 여부에 따라 다시 구별했으며, 단말기의 경우, 서킷 전용, 패킷 전용, 다중 모드로 구별함과 동시에 CA 능력에 따라서 역시 구별하였다. 또한, 패킷 트래픽의 경우, 실시간 트래픽과 3단계의 패킷 지연 허용 정도를 갖는 비실시간 트래픽으로 구분하였다. 이러한 다양한 무선 접속 환경이 고려된 클라우드 기지국 시스템에서 호 발생에서 호의 서비스 품질(Quality of Service : QoS)이 고려된 자원 할당까지의 일련의 과정을 시뮬레이션에 반영하여 시스템 접속 실패 확률, 평균 시스템 접속 시간, 시스템 균형 인수, 패킷 손실 확률 측면에서 제안 방식의 성능을 분석하였다.

고교생의 과학적 사고력에 관한 연구-논리적 사고와 추리력을 중심으로- (A Study on Scientific Thinking of Korean High School Students-With Reference to Logical Thinking and Reasoning Power-)

  • 황긍연;박인근;김태성
    • 한국과학교육학회지
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    • 제9권1호
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    • pp.19-37
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    • 1989
  • The purpose of this study was to investigate the development of logical thinking and scientific reasoning pattern of Korean high school students. To carry out this study subjects were selected about 2,000 Junior high school students, and about 4,100 senior high school students throughout the nation. They were identified as concrete, transitional or formal operational stage with the use of TOLT(the Test of Logical Thinking) by Tobin and Capie(1980), and TOSR(the Test of Scientific Reasoning) by W.A Farmer(1986). This study turned out that more than 76% of Junior high school students were classified as the concrete operational stage and about 44% of senior high school students were classified as the formal operational stage, while about 26% of them were still in the concrete operational level. This study showed that the main factor of the intellectual development of students is learning by the gradual advancement of their grades and especially entrance into the senior high school rather than by the physical growth. This study also showed that there are the take-off stage of the development of logical thinking between fourteen and fifteen years of their ages. Less than 25% of junior high school students were in the formal operational stages which are capable of control of variables, probabilistic, correlation and combinational logic in problem-solving situation, while 33-54% of senior high school students were in the formal operational levels. 38% of junior high school students were in the formal operational stage which is capable of proportional logic, while about 55% of senior high school students were in the formal operational stage. Less than 20% of senior high school students were classified as group of highly capable of scientific reasoning, while more than 23% of them were classified as group of poor capability. It also turned out that there are differences or no differences between male and female students of each school in problem-solving situation regarding each logic approach. These differences were proved to be fluctuating depending on the situations and their grades. The other results of this study is similar to those of other researches such as Tomlinson-Keasey 1972, Coleman 1973, Lawson 1973, Lawson and Renner 1974, Neimark 1975, Han 1982, and Kim 1989.

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Study on the procedure to obtain an attainable speed in pack ice

  • Kim, Hyun Soo;Jeong, Seong-Yeob;Woo, Sun-Hong;Han, Donghwa
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제10권4호
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    • pp.491-498
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    • 2018
  • The cost evaluation for voyage route planning in an ice-covered sea is one of the major topics among ship owners. Information of the ice properties, such as ice type, concentration of ice, ice thickness, strength of ice, and speed-power relation under ice conditions are important for determining the optimal route in ice and low operational cost perspective. To determine achievable speed at any designated pack ice condition, a model test of resistance, self-propulsion, and overload test in ice and ice-free water were carried out in a KRISO ice tank and towing tank. The available net thrust for ice and an estimation of the ice resistance under any pack ice condition were also performed by I-RES. The in-house code called 'I-RES', which is an ice resistance estimation tool that applies an empirical formula, was modified for the pack ice module in this study. Careful observations of underwater videos of the ice model test made it possible to understand the physical phenomena of underneath of the hull bottom surface and determine the coverage of buoyancy. The clearing resistance of ice can be calculated by subtracting the buoyance and open water resistance form the pre-sawn ice resistance. The model test results in pack ice were compared with the calculation results to obtain a correlation factor among the pack ice resistance, ice concentration, and ship speed. The resulting correlation factors were applied to the calculation results to determine the pack ice resistance under any pack ice condition. The pack ice resistance under the arbitrary pack ice condition could be estimated because software I-RES could control all the ice properties. The available net thrust in ice, which is the over thrust that overcomes the pack ice resistance, will change the speed of a ship according to the bollard pull test results and thruster characteristics (engine & propulsion combination). The attainable speed at a certain ice concentration of pack ice was determined using the interpolation method. This paper reports a procedure to determine the attainable speed in pack ice and the sample calculation using the Araon vessel was performed to confirm the entire process. A more detailed description of the determination of the attainable speed is described. The attainable speed in 1.0 m, 90% pack ice and 540 kPa strength was 13.3 knots.

건강개염(健康槪念)의 사상의학적(四象醫學的) 고찰(考察) (A Study on 'Health' concept of Sasang Constitutional Medicine)

  • 황민우;임진희;정용재;김상복;이수경;고병희;송일병;이태규
    • 사상체질의학회지
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    • 제15권3호
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    • pp.88-99
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    • 2003
  • Background and Objective : The status of development of instruments to assess the 'health status' reflecting the concept of Sasang Constitutional Medicine is still far from satisfaction, despite their importance in building basic data for health promotion, evaluation of effectiveness of treatment, health policy and so on. for these reasons the health scale of Sasang Constitutional Medicine shod be developed. Therefore as from of preliminary research, this study is to review the concept of health and symptoms in health status in Sasang Constitutional Medicine. Methods : It was researched as bibliologically with Dong-mu's chief medical writings such as ${\ulcorner}Dongyi$ Soose $Bowon{\lrcorner}$(東醫壽世保元)${\ulcorner}Dongyi$ Soose Bowon Sasang Chobongyun(東醫壽世保元四象草本卷)${\lrcorner}$ - Results and conclusion : 1. In Sasang Constitutional Medicine, it is suggested that Inherent vitality(命脈實數) has relations to health and Knowledge-Acting(知行) is a primary factor which affects health. And it is thought that Healthy condition(完實無病) is that human being has enough Healthy energy(保命之主) of Small viscera. 2. In Sasang Constitutional Medicine, it is thought that stool, urine, sweating and digestion become important indexes to measure the physical health state. 3. In Sasang Constitutional Medicine, it is thought that the mental health is in control of inclination of mind by golden mean(中庸) and in tranquillity of constant mind according to constitution. 4. In Sasang Constitutional Medicine, it is thought that the social health is state thar can do social acting harmoniously by keeping away from alcohol, sexual appetite, property and power.

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방사선학과(放射線學科)의 4년제(年制) 대학(大學) 교육과정(敎育課程)에 대한 연구(硏究) (A Study on Four-year College Curriculum for the Education of Radiological Technology in Korea)

  • 최종학;이상석;김영일;권달관;김흥태;임한영
    • 대한방사선기술학회지:방사선기술과학
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    • 제18권2호
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    • pp.87-102
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    • 1995
  • The education of radiologic technology began in the regular institute of higher education in Korea in 1963. Up to now from then, our education to bring up the radiologic technologists has developed greatly in quality and quantity, and now departments of radio-technology are founded in the 16 junior colleges in March, 1995. This study was done to verify the necessity and propriety to reform the education system of radiologic technology which was run as two or three year system of college curriculum for 32 years since 1963, and to search for the method to reform in the future. We got the following results from this research. 1. In the survey, on the desirable education year for radiologic technologists, 63.9 % of professors of department of radio-technology and 63.0 % of radiologic technologists chose the 4 year system, 27.9 % of professors and 34.6 % of radiologic technologists chose the 4 year system added to graduate school. 2. In the survey, on the future development of radiologic equipments and technique, 67.2 % of professors of department of radiologic technology and 86.4 % of radiologic technologists have a view of "revolutional development". Also, on the future tasks or roles of radiologic technologists 95.1% of professors and 94.9% of radiologic technologists have a view that "They will increase". 3. On the necessity of extension of education year to 4 years from 3 years, the factor is that development of medical technique and machinery and tools, advance of qualification of radiologic technologists, enlargement and specialization of the business of the radiologic technologists, ballance of education year with other medical sciences, international competitive power and cooperation of radiologic technology, and education continuation of the graduates of department of radiologic technology. 4. They suggested that in the 4 year curriculum of department of radiologic technology, clinical medicine, quality control of radiation and radiologic equipment, related subjects to the radiologic application and computer application should be enforced and clinical practice should be extended more. 5. On the device to found the 4 year college curriculum of radiologic technology, they suggested that first, 4 year curriculum should be founded through the variety of educational year, secondly, department of radiologic technology should be founded in the 4 year health sciences college, thirdly, educational continuation of the radiologic technologists should be systematized on the basis of life-long education.

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