• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2011년도 정기 학술대회
• /
• pp.415-418
• /
• 2011

Thermal fatigue is one of the life-limiting damage mechanisms in the nuclear power plant conditions. The turbulent mixing of fluids of different temperatures induces rapid temperature changes to the pipe wall. The successive thermal transients cause varying cyclic thermal stresses. These cyclic thermal stresses cause fatigue crack nucleation and growth similar to the cyclic mechanical stresses. The aim of this study was to fulfil the need by developing an real crack manufacturing method, which would produce realistic cracks. The test material was austenitic STS 304, which is used as pipelines in the reactor coolant system of a nuclear power plants. In order to fabricate thermal fatigue crack similar to realistic crack, successive thermal transients were applied to the specimen. Thermal transient cycles were combined with heating (60sec) and cooling cycle (30sec). And, In order to identify ultrasonic characteristic, it was performed the ultrasonic reflection measuring method for the fabricated specimen. From the results of ultrasonic reflection measuring testing, it was conformed that A-scan results(average 83% of real crack depth) for the TFC reference specimen was more enhanced NDT reliability than results(average 38% of real crack depth) for the EDM notch reference specimen.

• 한국콘텐츠학회논문지
• /
• 제7권3호
• /
• pp.160-167
• /
• 2007

국가 경제의 급속한 성장에 따른 국토전반에 걸친 개발로 인해 국토 및 연안해역의 모습은 날로 변화하고 있다. 이러한 국토 및 연안해역의 변화를 효과적으로 탐지하고 적절한 이용계획을 수립하기 위해서는 해안선의 변화관측과 분석을 토대로 연안해역에 대한 모니터링체계의 확립이 시급한 실정이다. 최근 들어, 국토해안선제작 분야에서는 해안선의 경계구분에 대한 불명확한 정립과 관측 자료의 부족으로 정확한 해안선의 길이가 불명확한 상태이며, 기존의 자료에 대한 정확성과 신뢰성이 크게 떨어지고 있는 실정이다. 따라서 본 논문에서는 연구대상의 지역적 범위를 부산근교로 한정하였으며, 일정 간격의 항공사진을 이용하여 이 일대의 송정 해운대 광안리 송도 다대포 해안선에 대한 시계열적 변화를 분석하였다.

• 한국전자통신학회논문지
• /
• 제4권1호
• /
• pp.25-32
• /
• 2009

방송&통신 융합과 무선 인지기술 발전으로 차세대 이동통신 서비스 기술이 다양한 분야에서 중요한 기술로 인정받고 있으며, 이를 이용한 실용 서비스 시스템 구축이 요구되고 있다. 본 논문은 무선인식 기술을 이용 차세대 이동통신의 주요 기술인 제약된 주파수 자원의 활용 효율을 증대시키고, 기존의 주파수 사용자에게 간섭 신호를 발생시키지 않고 비어 있는 주파수를 검색하고, 서비스 간 융 복합 형태의 발전을 고려한 멀티미디어 플랫폼을 설계 한다. 이를 실현하기 위해 서비스 시스템의 성능을 극대화 시킬 수 있고 신뢰도를 향상시키기 위해 연구 모델로 STI를 적용하고 플랫폼 구성 시 요구되는 정보의 지능화 판정 알고리즘(IDMA)을 새롭게 제안함으로 서비스 시스템의 성능을 극대화 시킬 수 있는 방안을 제시한다.

• 한국사회복지학
• /
• 제49권
• /
• pp.296-318
• /
• 2002

The purpose of this study is to empirically analyze whether or not, if a community social service center was affiliated with a governing body running other community social service centers, the center would have better organizational performance in comparing to an independently running center. Data was collected from a nationwide mailed and self-administered survey, which 237 centers out of 343 community social service centers responded. Even if, the response rate was 72%, 218 centers were finally analyzed due to the weakness of reliability and incompleteness. By the way, measurement of organizational performance as the dependent variable has been substituted of the results of nationwide organizational evaluation project as the secondary data. One of findings is that 68% of 218 responding centers appeared to be affiliated with a governing body which running more than three other centers, while 41% being affiliated with a body which running more than five other centers. However, a logistic regression analysis which using organizational performance as the dependent variable, has failed to verify the hypothesis that a center which affiliated with a governing body running other centers has better organizational performance when comparing to an independent center. The researcher assumes that a part of governing bodies has better performance and improves competitiveness while the other larger part of them pursues simple organizational growth. Thus, this situation made that the overall evaluation of being affiliated with a large governing body was not positive.

• 한국간호교육학회지
• /
• 제17권2호
• /
• pp.267-276
• /
• 2011

Purpose: This study was done to develop a performance appraisal tool (PAT) for neonatal intensive care unit (NICU) registered nurses (RNs). Methods: The PAT was developed in three steps: 1) a standard of NICU nursing was established; 2) a draft was made; and 3) the PAT was ratified and its reliability and validity were tested. Results: The standard of practice of NICU nursing was predominantly based on role description and responsibilities for nurses. We identified 4 domains of nursing: professional practice, education, research, and leadership. The validity score for each item ranged from 3.93 to 3.27. The PAT consisted of 76 indicators, 49 reflecting components of professional practice, 5 related to responsibility for education, 3 representing research, and 19 relating to leadership. Cronbach's ${\alpha}$ averaged 0.99 for the 76 items. Conclusions: The PAT for NICU RNs that we created was found to be reliable and valid. This PAT would be very useful in evaluating nursing performance and facilitate the professional growth of nurses.

• 가정과삶의질연구
• /
• 제32권2호
• /
• pp.53-75
• /
• 2014

The purpose of this study was to develop and validate the "Authentic Parental Competence Scale" for mothers with school-age children. Based on a literature review, the study found that 'authentic parental competence' could be divided into parenting comperence, self-system competence, and social competence. In addition, the scale comprised three factors consisting of 43. The study collected data through behavior event interview(BEI), focus group interview(FGI), and three times Delphi investigation. The scale for mothers of school-age children consisted of a total of 129 items, which included three different dimensions (knowledge, skill, and attitude), and four factors were extracted from factor analysis following a survey of 362 mothers. The factors were labeled as "ability of developmental positive parenting," "ability of playing a role as a citizen and making social contributions," "ability of self-understanding and interpersonal relations," and "ability of self-growth and self-determination." In addition, the results revealed that the "Authentic Parental Competence Scale" showed an appropriate level of construct validity, reliability of the scales, distribution of item response, and item discrimination.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제51권5호
• /
• pp.204-212
• /
• 2002

In order to improve the reliability of high voltage rotating machines, it is necessary to understand the breakdown mechanism of stator windings. Especially partial discharge(PD) inception and growth are important in stator winding insulation. Recently, many research on the diagnosis of stator winding insulation for large rotating machines have been developed since the 1970s. Capacitive couplers have been the most widely used sensor for on-line partial discharge detection in rotating machines. This paper deals with the electrical on-line monitor characteristics of ceramic coupler(CC) which has been developed to continuously measure the PD activity in operating high voltage motor stator windings on site. We investigated the electrical characteristics(PD quantity, breakdown voltage and frequency response) to develop CC. This paper presents frequency characteristics and laboratory test result to compare conventional 80([F] epoxy-mica coupler(EMC) and 105[pF] CC for PD measurement with 6.6㎸ model stator windings.

• Bulletin of the Korean Chemical Society
• /
• 제25권10호
• /
• pp.1521-1524
• /
• 2004

The effect of $H_2$ gas on the carbon nanotubes (CNTs) synthesis with CO-$H_2$ gas mixture was investigated using mass measurements and scanning electron microscopy (SEM). The maximum weight and yield of the synthesized carbon were obtained when the mixture ratio of $H_2$: CO was 3 : 7 and 9 : 1, respectively. In case of 100% carbon monoxide (CO) without hydrogen ($H_2$) addition, the weight of carbon increased, but CNTs were not observed. The CNTs began to be made when the contents of $H_2$ reaches at least 10%, their structures became more distinct with an increase of $H_2$ addition, and then the shapes of CNTs were more thin and straight. When the contents of $H_2$ was 80% ($H_2$ : CO = 8 : 2), the shapes and growth of CNTs showed an optimal condition. On the other hand, when the contents of $H_2$ was higher than the critical value, the shapes of CNTs became worse due to transition into inactive surface of catalyst. It was considered that the inactive surface of catalyst resulted from decrease of carbon (C) and $H_2$ concentration by facilitation of methane ($CH_4$) gasification reaction (C + 2$H_2$ ${\rightarrow}$ $CH_4$) between C and $H_2$ gases. It was also found that H2 addition had an influence considerably on the shape and structure of CNTs.

• Journal of Advanced Marine Engineering and Technology
• /
• 제31권4호
• /
• pp.385-393
• /
• 2007

The strength evaluation of the most weakest junction part is required for the safety design of all structures. Most of all. in order to enhance the reliability and safety of the welding part. whose use is the highest, it is very important to establish the efficient structure manufacturing technology by studying and investigating the evaluation of fatigue strength in various environments. This study analyzed the relations of da/dN, and th according to the welding methods of SMAW, FCAW, and SAW. In the stage II. the value of stress intensity factor range was the highest in SMAW welding method of stress ration R=0.1, and appeared under the sequence of FCAW and SAW and as the completion section of stress intensity factor was low, threshold stress intensity factor was lowly formed in da/dN - The fatigue life of each welding method is sensitively worked in high stress ratio. judging from the fact that the width of life reduction increases in the high stress ratio zone compared to the width of life reduction in the low stress ratio zone. In the fatigue limit of welding methods before corrosion. the welding of SMAW and FCAW shows the same fatigue limit compared to Base metal, and SAW holds the lowest fatigue limit value.

• 한국기계가공학회지
• /
• 제11권6호
• /
• pp.94-99
• /
• 2012

Due to economic growth, the number of cars has grown rapidly and consequently traffic accidents have grown in direct ratio. This reminds us that braking device of a vehicle is an important factor to prevent traffic accidents. Aim these researches to speed and lighten the braking system of vehicles, to lengthen its durability and to shorten the stopping distance. However, it is still difficult to analyze quantitatively and clearly the reason and solution for abnormal wear of disc and pad or judder in flywheel mode. Therefore this study was carried out to presume for mutual relation of analysis condition to get the optimum temperature by two-way layout. The results shown that coefficient of determination has a fine reliability over 92.57% and temperature is made by two-way layout.