• PNF and Movement
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• 제5권1호
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• pp.19-28
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• 2007

Proprioception means the ability to perceive the sensation of position and movement of body. As it is transmitted to central nervous system and used in feed-back or feed-forward motor control, proprioception allows us to keep our normal movement and normal balance activity. However, the conditions such as injury, disease, aging and fatigue can damage the proprioceptiive sensation of position, movement and lead to a functional impairment and additional damages in musculoskeletal system, because they alter the amount of proprioceptive ability that transfer into the central nervous system. The purpose of this study was to identify the definition and the function of proprioception, to look into variations in injury, disease, aging and fatigue that can be easily met in clinical application and eventually to provide valuable aid for assessment and treatment.

• Structural Engineering and Mechanics
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• 제17권1호
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• pp.29-50
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• 2004

A total life model was developed to assess the service life of aging aircraft. The primary focus of this paper is the development of crack growth life projection using the response surface method. Crack growth life projection is a necessary component of the total life model. The study showed that the number of load cycles N needed for a crack to propagate to a specified size can be linearly related to the geometric parameter, material, and stress level of the component considered when all the variables are transformed to logarithmic values. By the Central Limit theorem, the ln N was approximated by Gaussian distribution. This Gaussian model compared well with the histograms of the number of load cycles generated from simulated crack growth curves. The outcome of this study will aid engineers in designing their crack growth experiments to develop the stochastic crack growth models for service life assessments.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권1호
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• pp.55-63
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• 2003

In this study was proposed that a new estimating method for investigation of contractile state changes which generated from continuous isometric contraction of skeletal muscle. The physiological changes(EMG, ECG) and the psychological changes by CNS(central nervous system) were measured by experiments, while the muscle of subjects contracted continuously with isometric contraction in constant load. The psychological changes were represented as three-step-change named 'fatigue', 'pain' and 'sick(greatly pain)' from oral test, and the method which compared physiological change with psychological change on basis of these three steps was developed. The result of analyzing the physiological signals, EMG and ECG signal changes were observed at the vicinity of judging point in time of psychological changes. Namely, it is supposed that contractile states have three kind of states pattern (stable, fatigue, pain) instead of two states (stable, fatigue).

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.479-489
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• 2019

Low-cycle fatigue (LCF) tests were performed for Alloy 690 and 316 SS in a simulated pressurized water reactor (PWR) environment. Alloy 690 showed about twice longer LCF life than 316 SS at the test condition of 0.4% amplitude at strain rate of 0.004%/s. Observation of the oxide layers formed on the fatigue crack surface showed that Cr and Ni rich oxide was formed for Alloy 690, while Fe and Cr rich oxide for 316 SS as an inner layer. Electrochemical analysis revealed that the oxide layers formed on the LCF crack surface of Alloy 690 had higher impedance and less defect density than those of 316 SS, which resulted in longer LCF life of Alloy 690 than 316 SS in a simulated PWR environment.

• 대한인간공학회지
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• 제31권6호
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• pp.785-791
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• 2012

Objective: The aim of this study was to investigate the correlation between 3D visual fatigue and physiological measures by canonical correlation analysis enabling to categorical correlation. Background: Few studies have been conducted to investigate the physiological mechanism underlying the visual fatigue caused by processing 3D information which may make the cognitive mechanism overloaded. However, even the previous studies lack validation in terms of the correlation between physiological variables and the visual fatigue. Method: 9 Female and 6 male subjects with a mean age of $22.53{\pm}2.55$ voluntarily participated in this experiment. All participants were asked to report how they felt about their health sate at after viewing 3D. In addition, Low & Hybrid measurement test(Event Related Potential, Steady-state Visual Evoked Potential) and for evaluating cognitive fatigue before and after viewing 3D were performed. The physiological signal were measured with subjective fatigue evaluation before and after in watching the 3D content. For this study suggesting categorical correlation, all measures were categorized into three sets such as included Visual Fatigue set(response time, subjective evaluation), Autonomic Nervous System set(PPG frequency, PPG amplitude, HF/LF ratio), Central Nervous System set(ERP amplitude P4, O1, O2, ERP latency P4, O1, O2, SSVEP S/N ratio P4, O1, O2). Then the correlation of three variables sets, canonical correlation analysis was conducted. Results: The results showed a significant correlation between visual fatigue and physiological measures. However, different variables of visual fatigue were highly correlated to respective HF/LF ratio and to ERP latency(O2). Conclusion: Response time was highly correlated to ERP latency(O2) while the subjective evaluation was to HF/LF ratio. Application: This study may provide the most significant variables for the quantitative evaluation of visual fatigue using HF/LF ratio and ERP latency based human performance and subjective fatigue.

• Structural Engineering and Mechanics
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• 제70권3호
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• pp.311-324
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• 2019

Long-span steel suspension bridges develop significant vibrations under the effect of external time-variable loadings because their slenderness. This causes significant stresses variations that could induce fatigue problems in critical components of the bridge. The research outcome presented in this paper includes a fatigue analysis of a long suspension bridge with 3300 meters central suspended span under wind action and train transit. Special focus is made on the counterintuitive interaction effects between train and wind loads in terms of fatigue damage accumulation in the hanger ropes. In fact the coupling of the two actions is shown to have positive effects for some hangers in terms of damage accumulation. Fatigue damage is evaluated using a linear accumulation model (Palmgren-Miner rule), analyses are carried out in time domain by a three-dimensional non-linear finite element model of the bridge. Rational explanation regarding the above-mentioned counterintuitive behavior is given on the basis of the stress time histories obtained for pertinent hangers under the effects of wind and train as acting separately or simultaneously. The interaction between wind and train traffic loads can be critical for a some hanger ropes therefore interaction phenomena within loads should be considered in the design.

• 한국보건간호학회지
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• 제18권1호
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• pp.103-118
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• 2004

The purpose of this study was to understand the process and investigate basic theory of fatigue experience of shift work nurses. The present study adopted grounded theory methodology on fatigue of shift work nurses. The participants for this study were 15 shift work nurses who were in the age of 25 to 35, the clinical experience of 2 to 14 years and the work department of ICU. ER. ward and delivery room. The data were collected from 2000 to 2003 by using interviews and observations. The contents of the interviews were tape-recorded and were drawn through repeated method. And then were analyzed into the concept, subcategories, and categories with the open coding process and axial coding was done to identify the relationships of the concepts and categories according to the paradigm models. The core category generated, which was a central phenomena of the exhaustion process. The causal condition is change events. The central condition of exhaustion were sorted as physical discomfort, decreasing vigor, psychological instability, feeling of sleeping desire, changing face impression and being heavy body. The intervening condition were discovered as social$\cdot$ psychology$\cdot$physical resist and positive$\cdot$negative interaction strategies. The consequences of the fatigue process is the short term exhaustion relief and long term residual exhaustion. The fatigue process of this study was 'break through exhaustion' of change event-exhaustion-resist-resolve intervention-adaptation. This study offers better understanding on fatigue process of shift work nurses and may facilitate more appropriate interventive strategies to support, information and knowledges according to fatigue process.

• 한국항공우주학회지
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• 제31권2호
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• pp.35-40
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• 2003

홀 확장법은 홀 주위에 압축 잔류응력을 생성시켜 홀에서의 균열발생을 지연시키고 피로수명을 향상시키기 위한 효과적인 방법이다. 여러 연구들이 이러한 이로운 효과에 초점을 맞추어 온 반면, 홀 확장 잔류응력이 존재하는 홀 쪽으로 성장해 가는 균열의 피로균열 성장에 관해서는 연구가 거의 이루어져 있지 않다. 본 논문의 목적은 홀 확장 잔류응력하의 피로특성을 평가하는 것이다. 중앙 홀을 갖는 평판에 대해 홀 확장법을 적용한 후 피로시험을 수행하여 홀 확장 잔류응력이 피로수명에 미치는 영향을 평가하였다. 또한 CT 시험편에 홀 확장법을 적용하여 잔류응력을 생성시킨 후 피로균열성장 시험을 수행하여, 홀 확장 잔류응력에 의한 피로균열성장 특성의 변화를 고찰하였고, 홀 확장률의 영향을 평가하였다.

• 대한한의학회지
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• 제41권1호
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• pp.93-106
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• 2020

Objectives: The aim of this review is to ascertain whether Bojungikgi-tang and its modifications is more effective than non-specific management in chronic fatigue syndrome (CFS). Methods: We collected clinical trials to investigate the effects of Bojungikgi-tang and non-specific management on general symptoms, fatigue, and sleep quality in CFS patients. The databases used for data retrieval were Pubmed, Central Cochrane, CNKI, VIP, CiNii, OASIS, RISS, and Koreamed. We performed selection/exclusion process from the found records according to prespecified criteria, and assessed the final included trials according to the Cochrane risk of bias tool. The included studies were classified on the basis of interventions in experimental group. Results: Seven randomized controlled trials (476 participants) were eligible and their results were synthesized in the meta-analysis. The synthesis showed a substantial effect of Bojungikgi-tang (relative risk 0.20 [95% CI 0.13 to 0.31], Z=7.44, P<0.00001; I²=0%) and combination of Bojungikgi-tang and Sosiho-tang (relative risk 0.15 [95% CI 0.08 to 0.28], Z=5.85, P<0.00001; I²=0%) compared with non-specific management on improvement of general symptoms. However, we could not find sufficient clinical research records to determine their effects of improvement on fatigue and sleep quality. Conclusions: Bojungikgi-tang and its modifications are more effective than non-specific management for improvement of general symptoms in CFS post-treatment.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1301-1308
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• 1996

In order to save the energy and protect the environment, it were studied about ecomaterials with the developed countries as central figure. In the Metal Matrix Composites(MMCs), this trends appeared the development of the MMCs which had excellent mechanical properties in spite of the low volume fraction of reinforcement. Therefore, in this study, fatigue crack growth test, tensile and hardness test were conducted in order to investigate the mechanical and fatigue properties of 5 %, and 10 % $SiC_{p}$/Al composites. As the results, in the tensile and hardness test, tensile strength and hardness increased but fatigue crack growth rate decreased with $SiC_{p}$/Al volume fraction. And in the view of fatigue failured surface through the SEM, fatigue crack initiated around the SiC particle and in low $\Delta{K}$ regions, fatigue creck detoured the SiC particle but crack propagated through the SiC particle in the high $\DeltaK$ regions.