• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.6
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• pp.433-439
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• 2022

Muscle fatigue models to predict maximum endurance time (MET) are broadly classified as either 'empirical' or 'theoretical'. Empirical models are based on fitting experimental data and theoretical models on mathematical representations of physiological process. This paper examines the effectiveness of dynamic muscle fatigue model as theoretical model to predict maximum endurance time during forearm isometric contraction. Forty volunteers (20 females, 20 males) are participated in this study. Empirical models (exponential model and power model) and theoretical model (dynamic muscle fatigue model) are used to compare. Mean absolute deviation (MAD), correlation coefficient (r) and intraclass correlation (ICC) are calculated between theoretical model and empirical models. MAD are below 3.5%p, r and ICC are above 0.93 and 0.87, respectively. This results demonstrate that dynamic muscle fatigue model as theoretical model is valid to predict MET.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.584-587
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• 2010

본 연구는 40~60세의 중년여성을 대상으로 뉴로피드백 실험군 17명, 두개천골요법 실험군 17명, 혼합요법 실험군 19명, 대조군에 18명 등 총 71명을, 2007년 10월 1일부터 12월 14일까지 11주 동안 뉴로피드백(이하 NF), 두개천골요법(이하 CST) 및 이 두 요법의 혼합요법(이하 MT)을 적용하여 중년기 여성의 피로와 스트레스 감소 및 뇌기능 향상과 MT군의 시너지효과를 검증하고자 시도한 비동등성 대조군 전후 설계인 유사 실험 연구이다. 그 결과 1)NF, CST 및 MT는 중년여성의 피로와 스트레스를 감소시키고 두뇌 활성화를 통한 뇌기능을 향상시키는데 효과가 있었다. 2)전두엽의 활성화는 NF는 좌뇌를 CST는 우뇌를 활성화시켰다. 3)MT군은 두 군에 비하여 약간 더 효과가 있었다. 4)차시별 효과는 실험군 모두에서 10차시에서 유의한 증가를 보였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.240-244
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• 2017

Experimental verification in the rig test stage for component development is a vital link between the aeromechanical design and structural integrity validation process. Based on this premise, Non-Intrusive Stress Measuring System was adopted on the axial compressor test rig to measure the static and dynamic tip deflection of all blades by using tip-timing sensors. Through analyzing vibration characteristics, we evaluated the vibratory stresses seen on the blades fatigue critical location; detected synchronous resonances which are the source of High Cycle Fatigue (HCF) in blades; presented non-synchronous vibration response by aerodynamic excitation and individual blade mis-tuning patterns.

• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.458-465
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• 2018

Ice-going ships such as icebreakers, icebreaking tankers, and icebreaking LNG carriers are subjected to wave loads in open water and ice loads in ice-covered water. In terms of the ship's structural design, the local ice load is important. The fatigue failure due to repeated ice loads is also important. ISO 19906 specifies the assessment of the fatigue limit for a polar offshore structures. In addition, Lloyd's Register refers to fatigue damage based on ShipRight FDA ICE. In ShipRight FDA ICE, the fatigue damage indices due to wave and ice loads are simply presented as 0.5 for each load. It also states that the sum of the two fatigue damage indices should not exceed one. This study calculated and analyzed the fatigue damage index and fatigue life considering ARAON's voyage schedules and the assumed Antarctic voyage based on data measured during the Arctic voyage of ARAON in 2010.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.723-730
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• 2008

Due to the higher ratio of live load to total loads of railway bridges, the accumulated damage by cyclic fatigue is significant. Moreover, it is highly possible that the initiated crack grows faster than that of highway bridges. Therefore, it is strongly needed to assess the safety for the accumulated damage analytically. The initiation and growth of fatigue-crack are related with the stress range, number of cycles, and the stiffness of the structural system. The stiffness of the structural system includes uncertainties of the planning, design, construction and maintenance, which varies as time goes. In this study, the authors developed the design and risk assessment techniques based on the reliability theories considering the uncertainties in load and resistance. For the probabilistic risk assessment of crack growth and the remaining life of the structures by the cyclic load of railway and subway bridges, response surface method (RSM) combined with first order second moment method were used. For composing limit state function, the stress range, stress intensity factor and the remaining life were selected as input important random variables to the RSM program. The probabilities of failure and the reliability indices of fatigue life for the considered specimen under cyclic loads were evaluated and discussed.

• Korean Journal of Adult Nursing
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• v.18 no.2
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• pp.284-292
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• 2006

Purpose; This study was aimed to identify the effect of foot reflexology massage on climacteric symptom, fatigue and physiologic parameters of middle-aged women. Method; A non-equivalent pretest-posttest experimental design was used. Participants were recruited from the Community Health Center in Busan, Korea. Forty participants were assigned to either an experimental group(20) or a control group(20). Foot reflexology massage was administered twice a week for 6 weeks in the participant in experimental group. Results: There were statistically significant differences in climacteric symptom, fatigue, total cholesterol and cortisol level. However, there were no statistically significant differences in triglyceride, high density lipoprotein and low density lipoprotein. Conclusion; These results suggest that foot reflexology massage could be utilized as an effective nursing intervention to reduce climacteric symptom and fatigue in middle-aged women.

• 한국기계연구소 소보
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• s.18
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• pp.169-175
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• 1988

The influence of mean strain on the behavior of early stage stress amplitude was investigated quantitatively in low cycle fatigue. It was obtained that the exponent of cyclic strain(n') and the coefficient of cyclic strain(C') decreased with increasing cycle numbers in compressive mean strain level. But it was the opposite in 0% mean strain and tensile mean strain level. And the cyclic yield strength ($\delta_(yc)$) was constant irrespective of mean strain or cyclic strain

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.4
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• pp.87-96
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• 1993

Spectrum analysis of surface electromyogram (FMG) signals is an effective approach to the study of localized muscular fatigue during isometric contraction. Many investigators have con firmed the frequency of the EMG signals being lowered during sustained contaction. In this study, the cyclic loading tasks were performed, and a comparison was made for the median power frequency shift pattern of the EMG signals with the sustained contraction of the same load. The median power frequency shift of the EMG signals for the cyclic loading task was found to be a part of that for the sustained contraction. Based on this result, a new muscle fatigue index was computed by normalizing the duration of the sustained contraction. A fatigue index was obtained as a function of exertion level and the work/rest schedule. With the proposed fatigue index, it is possible to evaluate or predict the degree of muscular fatigue for a physically demanding task.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1142-1147
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• 2006

A practical method for reducing the number of spot welds in automotive structures considering fatigue crack initiation life is suggested. At first, an influence index for the durability and the fatigue life of a spot weld itself is defined and then taken as the main effect of the DOE analysis. Spot welds that can be removed without serious reduction of durability through numerical experiments are selected by the results of DOE. The proposed method was applied to the shock tower and LCA(lower control arm) structure of a vehicle, which are important components in durability-related point of view.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.185-187
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• 2013

일반적으로 사람은 육체적, 정신적 그리고 심리적 자극에 반응할 경우 스트레스(Stress)가 유발된다. 이 스트레스는 정상적인 업무수행 뿐만 아니라 건강에 악영향을 미칠 수 있고, 피로누적의 한 원인이 되기 한다. 특히 열악한 환경에서 직무를 수행하는 선원에게 있어서 스트레스는 해양사고의 직간접적인 요인이 될 수 있기 때문에 선박 인적자원관리의 한 측면으로 중요하게 다루어질 필요가 있다. 이 연구는 해운기업이 선원의 인사 및 안전관리 시스템에 활용할 수 있는 선원용 스트레스 평가도구를 개발하기 위한 것으로, 기본영역, 가족생활영역, 재정영역, 직업 및 선박생활영역에 대하여 90개의 항목으로 구성된 설문도구를 개발하여 설문조사를 수행하였고, Holmes & Rahe의 사회적응평가도구의 항목 및 평가지수와 비교분석하여 한국 선원의 문화적 차이를 고려한 설문도구를 개발하기 위한 기초적 연구를 수행하였다.