• 동력기계공학회지
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• 제11권1호
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• pp.5-15
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• 2007

In the recently released accident-investigation report on blade failure, almost 70% of blade failures was found at low pressure turbine blades, and it is well known that main cause is due to the vibration modes. This paper describes the systematic approach on the root cause of the blade failure at L 0 stage, 30MW single flow industrial steam turbine which had tripped by high vibration after ten-month commercial operation. A fracture was found at the only one damping wire hole of 59 blades, and crack was detected at three damping wire holes by NDT. According to the analysis result for the crack fracture surface and the chain of the sequential operational events, we come to the conclusion that a typical high cycle fatigue is the most dominant factor caused to the blade failure, the resonance frequency margin was narrowed by the cut damping wire and the high cycle vibration was amplified, and then the blade was broken at once by the centrifugal force when the crack reached the critical size.

• 한국철도학회논문집
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• 제12권5호
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• pp.738-743
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• 2009

철도의 선로변에서 선로나 신호설비의 유지보수 작업을 장기간 수행할 경우 감각차단 현상에 의해 작업 전후방에 열차가 접근하고 있어도 작업자가 열차를 인지하지 못하는 경우가 발생할 수 있다. 이러한 경우 작업자는 접근하는 열차와 접촉사고가 발생하여 사상사고가 자주 발생하게 된다. 이러한 철도선로변 유지보수 작업자의 사상사고의 저감을 위해 열차에서 특정 신호를 무선으로 주기적으로 전송하고 선로변의 작업자가 휴대하고 있는 단말장치에서 차상으로 부터의 무선신호를 수신하여 작업자에서 진동, 소리, LED 등 다양한 경보신호를 제공하여 사고를 예방하는 안전설비를 제안하였으며, 이를 바탕으로 안전경보장치를 개발하였고, 현장시험을 통해 그 적용성을 확인하였다.

• Nuclear Engineering and Technology
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• 제47권1호
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• pp.59-65
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• 2015

Background: After the Fukushima accident, the importance of hazard analysis for extreme external events was raised. Methods: To analyze typhoon-induced hazards, which are one of the significant disasters of East Asian countries, a statistical analysis using the extreme value theory, which is a method for estimating the annual exceedance frequency of a rare event, was conducted for an estimation of the occurrence intervals or hazard levels. For the four meteorological variables, maximum wind speed, instantaneous wind speed, hourly precipitation, and daily precipitation, the parameters of the predictive extreme value theory models were estimated. Results: The 100-year return levels for each variable were predicted using the developed models and compared with previously reported values. It was also found that there exist significant long-term climate changes of wind speed and precipitation. Conclusion: A fragility analysis should be conducted to ensure the safety levels of a nuclear power plant for high levels of wind speed and precipitation, which exceed the results of a previous analysis.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.982-996
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• 2016

In this paper, new tethered aerial robots including roaming tethered aerial robots (RTARs) for radioactive material sampling and stationary tethered aerial robots (STARs) for environment monitoring are proposed to meet extremely-long-endurance missions of nuclear power plants. The flight of the proposed tethered aerial robots may last for a few days or even a few months as long as the tethered cable provides continuous power. A high voltage AC or DC power system was newly adopted to reduce the mass of the tethered cable. The RTAR uses a tethered cable spooled from the aerial robot and an aerial tension control system. The aerial tension control system provides the appropriate tension to the tethered cable, which is accordingly laid down on the ground as the RTAR roams. The STAR includes a tethered cable spooled from the ground and a ground tension control system, which enables the STAR to reach high altitudes. Prototypes of the RTAR and STAR were designed and successfully demonstrated in outdoor environments, where the load power, power type, operating frequency, and flight attitude of the RTAR and STAR were: 180 W, AC 100 kHz, and 20 m; and 300 W, AC or DC 100 kHz, and 80 m, respectively.

• 한국안전학회지
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• 제27권3호
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• pp.111-116
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• 2012

This study is about the quantitative safety assessment of hydrogen station in Korea operating with on-site type. This was written by background information that before qualitative safety assessment to write. For the qualitative safety assessment method, the study used FMEA(failure mode & effect analysis) and HAZOP(hazard & operability), and adopted the FTA(fault tree analysis) as the quantitative safety assessment method. To write the FTA, we wrote FT by Top event that hydrogen leakage can be called most serious accident of hydrogen station. Each base event collect reliability data by reliability data handbook, THERP-HRA and estimation of the engineering. Assessment looked at the high frequency and the possible risk through Gate, Importance, m.cutsets analysis.

• 대한인간공학회지
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• 제28권4호
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• pp.125-137
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• 2009

Recently, the frequency in use of electric adjustable bed is going up by an increase in the elderly population. In bad ergonomic design for an electric adjustable bed causes some problems in the aspects of usability and safety. In particular, lots of accidents came from going up or going down an electric adjustable bed. In that case, the height of bed is very important factor for preventing an accident. This problem is related to its anthropometric factors. Therefore we carried out its anthropometric analysis and old people's standing action according the height of electric adjustable bed as an experimental study. As a result, we proposed some anthropometric design criteria and identified the effect of bed height when old people use it.

• 대한안전경영과학회지
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• 제13권2호
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• pp.77-82
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• 2011

In the industrial site of 21st century, there are many and various powders of material, product and fuel of coal, chemical, detergent, paint, feed and more. Therefore, there always is a possible danger of dust explosion in each and every procedure and actually, there are increasing frequency of dust explosion as the use of dust and its amount increases in processes. Therefore, if we leave the current status like now, the unexpected massive dust explosion and its risk cannot be effectively prevented so there has to be effective application of understanding and development of explosion-prevention technology about dust explosion. Therefore, this research set the limit of research to systematically arrange the research results about dust explosion phenomenon and its prevention up to date and has its purpose to theoretically establish the prevention technology about dust explosion based on these theories.

• 대한안전경영과학회지
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• 제13권2호
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• pp.51-59
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• 2011

The objective of this study is to develop an evaluation model for the National highway risky areas. Thus, for the purposes of doing this, National highway risky area evaluated targeting to provide determination ranking and suggesting rival-superiority factors as well as under-inferiority factors in ten National highway risky areas. This study developed for modules of risky areas evaluation, using fuzzy set theory and analytic hierarchy process for evaluation model of National highway risky area in transport environment. The preceding studies assess risk analysis through analysis of causal relationships by National highway safety sector not only handles rating scale development suitable for assessment area by referring to accident frequency model but also geometric structures model. As result of this study, this model of Fuzzy Ahp Risk Analysis (FARA) apply for programmable design in real time processing through easily derive strategy for improvement activities to provide a decision-making effectively. Furthermore, this study contributes frame for improvements of National highway construction for renovation's priority strategy as well as future's policy schemes.

• 재활간호학회지
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• 제16권1호
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• pp.55-62
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• 2013

Purpose: The purpose of this study was to identify the factors affected with nurses' prevention activity against hospital fall. Methods: The data were collected from 325 nurses at C University Hospital in G City by using the structured questionnaires from February 21, 2011 to March 12, 2011. The data were analyzed by stepwise multiple regression. Results: The main factor associated with prevention activity against hospital fall was the attitude towards hospital fall (${\beta}$=.26, p<.001), the next one was the educational level (${\beta}$=.16, p=.002), and the last one was the frequency of fall prevention education (${\beta}$=.14, p=.009). The all factors could explain 11.1% of the variance in the nurses' prevention activities against hospital fall. Conclusion: Hospital managers need to make hospital culture to enhance the nurse's positive attitude about hospital fall prevention. In addition, educators need to develop educational programs including hospital fall prevention through academic curriculum and continuing education.

• 지역사회간호학회지
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• 제18권3호
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• pp.410-419
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• 2007

Purpose: This study is a descriptive survey to find out musculoskeletal symptoms in care workers working at medical welfare facilities for elders and factors affecting such symptoms. Methods: Data were collected from 115 care workers selected through convenient sampling from 6 medical welfare facilities in Seoul and Gyeonggi-do during the period from May 15th to May 19th. 2006. The Korean version of Job Content Questionnaire (JCQ) were used. Result: Of the subjects, 81.7% complained of musculoskeletal symptoms in two or more parts of their body. The frequency of body parts with musculoskeletal symptoms was high in order of shoulder, leg/foot, waist, neck/hand/wrist/finger and arm/elbow. The average job insecurity instability in the age group of 50-59 was 9.19, the average degree of regular exercise was 59.68. and the average job demand in those diagnosed with musculoskeletal diseases was 47.06, and the average job demand in those wounded during exercise or by an accident was 47.78, and all these were statistically significant. The heavier physical load in their work was, the higher their complaint of musculoskeletal symptoms was. In the lower social support group, the degree of complaint on musculoskeletal symptoms was remarkably high. Conclusion: The physical load of their duty and social support worked as the factors affecting musculoskeletal symptoms in care workers.