• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.853-858
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• 2004

In order to develop a high speed train, various conditions have been considered. Fatigue strength assessment by the fluctuation of pressure is an important one. When high speed train passing though tunnels, the pressure wave is generated in tunnels and pressure variation by the wave is acting on carbody structure with dynamic load repeatedly. In this study, formulation for reliability based fatigue assessment method has been performed when the high speed train passes through tunnels. The formulation was based on structural reliability index method and followed the proposed ISO method. The result by this study would be a good guidance to calculate the fatigue life and reliability index of body structure.

• 대한예방한의학회지
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• 제21권2호
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• pp.35-44
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• 2017

Objectives : The purpose of this study was to investigate the association between quality of life and Mibyeong index of abnormal symptoms by the Mibyeong state. Methods : A total of 1,100 people were recruited into this study and were collected by specialized research company. The data were collected by personal information using MBI(Mibyeong Index) and SF-12 (Short form-12) and were analyzed with SPSS (version 21.0) computer program, and included Pearson's chi-square test, ANOVA, Pearson's correlation coefficient, and multiple regression analysis. Results : The Mibyeong Index which represents abnormal symptom type showed significant difference for Mibyeong state (p<.001). In Total subject, fatigue, pain, low sleep quality and indigestion were found to be significant predictors of PCS(Physical Component Summary). In Healthy group, pain was found to be significant predictor of PCS. In MI 1 group, fatigue, pain, indigestion and anxiety were found to be significant predictors of PCS. In MI 2 group, fatigue, pain and low sleep quality were found to be significant predictors of PCS. In Total subject, fatigue, depression, anger and anxiety were found to be significant predictors of MCS (Mental Component Summary). In Healthy group, indigestion and anxiety were found to be significant predictors of MCS. In MI 1 group, depression and anger were found to be significant predictors of MCS. In MI 2 group, fatigue and depression were found to be significant predictors of MCS. Conclusions : The relationship between Quality of life and MBI changes according to Mibyeong state. We expect that this result could be contribute to health management of people in Mibyeong state.

• Composites Research
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• 제12권2호
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• pp.62-69
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• 1999

복합재료가 피로하중을 받으면 재료 내부에 손상이 누적되며, 이는 재료의 물성 변화로 나타난다. 본 연구에서는 손상을 나타내는 인자로 피로계수를 사용하였다. 피로계수와 참고계수로 정의되는 손상함수로부터 복합재료의 피로수명 예측을 이론적으로 연구하였다. 제안된 모델들은 인가 응력 수준, 피로주기 및 피로수명의 함수로 유도하였다. 예측 결과는 유리섬유/에폭시 복합재료와 유리섬유/폴리에스터 복합재료를 사용한 다중응력 피로 실험 데이터를 이용하여 검증하였다.

• 항공우주시스템공학회지
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• 제15권2호
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• pp.16-25
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• 2021

Reliability of fatigue strength on Aircraft Composites(GFRP) Structures was assessed in this paper. Fatigue strength of GFRP was used through the existing fatigue test data with Monte Carlo method. The S_a-N_f curve of composites fatigue strength was assumed as normal distribution and reliability was analyzed using SSIT model. Fatigue stress was designed IAW ASTM F3114-15 with special safety factor of S_sf=1.2~2.0. Reliability was calculated by analytic method and FORM. Sensitivity for the effect of mean and standard deviation of fatigue strength as well as fatigue stability was evaluated. This result can be usefully applied to reliability and fatigue design for composite structures of light weight aircraft.

• 한국직업건강간호학회지
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• 제23권3호
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• pp.171-179
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• 2014

Purpose: The purpose of this research was to provide baseline data by utilizing solutions to health problems caused by work-related stress and to examine a way of treatment by comparing and analyzing how the stresses link to fatigue and quality of researchers' life. Methods: A survey was conducted with 50 researchers working for in H research institute in Daejeon Metropolitan City from April 10th to May 10th, 2012 to examine the correlation of work stress, fatigue and quality of life. The data were analyzed using the Kruskal-Wallis test to look into examine the difference in work stress, fatigue, and quality of life. Also, the correlation of work stress, fatigue and quality of life was measured through by the Pearson correlation coefficient. The data collected through the questionnaires was were analyzed by SPSS 21.0 based on the significant level with a p-value, 0.05. Results: The results showed that fatigue was caused by work stresses in researchers and quality of life was ranked in a relatively low level. Correlation of work stresses, quality of life and fatigue and work stresses against mental health index was negative and fatigue against physical index was also negative. Conclusion: It is necessary to maintain more detailed provisions in order to improve mental health and stress level of researchers. Moreover, systematic, in-depth evaluation should be done to reduce researcher's work-related stress and fatigue. In addition, stress management and prevention program should be implemented for these researchers.

• Physical Therapy Rehabilitation Science
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• 제10권2호
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• pp.134-140
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• 2021

Objective: The purpose of this study was to investigate the alteration of upper cervical manipulation to autonomic nervous system (ANS) through the heart rate variability(HRV) analysis in young healthy individuals. Design: Two-group pretest-posttest design. Methods: Thirty four young healthy participants (17 males and 17 females) were randomized into the 2 groups, such as the upper cervical manipulation group (UCM group, n=17), neck stretching group (NS group, n=17). UCM group received a upper cervical manipulation, especially on the atlas, and NS group did stretch for both side of upper trapezius and levator scapular. For the UCM, Atlas mobility was checked by therapist and thrust was given once at the posterior arch of Atlas. HRV was measured before and after intervention to investigate ANS alteration. After the intervention, both groups were given 3 minutes break-time before measuring HRV. Results: The UCM group showed significant differences in ANS Activity, Stress Resistance, Stress index and Fatigue Index (p<0.05) while no differences in NS group with before and after intervention. There were significant differences in ANS Activity, Stress Resistance, and Fatigue Index between groups (p<0.05). Conclusions: This study suggected that upper cervical manipulationhas positive effects on the ANS activity, stress resistance, and fatigue index.

• 한국도로학회논문집
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• 제16권6호
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• pp.105-113
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• 2014

PURPOSES: The objective of this paper is to select the confidential intervals by utilizing the second moment reliability index(Hasofer and Lind; 1974) related to the number of load applications to failure which explains the fatigue failure and rut depth that it indicates the permanent deformation. By using Finite Element Method (FEM) Program, we can easily confirm the rut depth and number of load repetitions without Pavement Design Procedures for generally designing pavement depths. METHODS : In this study, the predictive models for the rut depth and the number of load repetitions to fatigue failure were used for determining the second moment reliability index (${\beta}$). From the case study results using KICTPAVE, the results of the rut depth and the number of load repetitions to fatigue failure were deducted by calculating the empirical predictive equations. Also, the confidential intervals for rut depth and number of load repetitions were selected from the results of the predictive models. To determine the second moment reliability index, the spreadsheet method using Excel's Solver was used. RESULTS : From the case studies about pavement conditions, the results of stress, displacement and strain were different with depth conditions of layers and layer properties. In the clay soil conditions, the values of strain and stresses in the directly loaded sections are relatively greater than other conditions. It indicates that the second moment reliability index is small and confidential intervals for rut depth and the number of load applications are narrow when we apply the clay soil conditions comparing to the applications of other soil conditions. CONCLUSIONS : According to the results of the second moment reliability index and the confidential intervals, the minimum and maximum values of reliability index indicate approximately 1.79 at Case 9 and 2.19 at Case 22. The broadest widths of confidential intervals for rut depth and the number of load repetitions are respectively occurred in Case 9 and Case 7.

• 정신신체의학
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• 제9권2호
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• pp.164-173
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• 2001

연구목적: 피로는 일차 진료에서 흔한 증상이지만 비특이적 주관적 특성상 명확한 정의와 객관적 평가가 어렵고, 특히 기질적 질환이 없는 피로의 평가는 더욱 힘들다. 이에 저자들은 기질적 질환이 없는 피로 환자에게 Fatigue severity scale (FSS) 을 적용하여 그 유용성을 알아보고자 하였다. 방법: 피로환자 44명, 우울 또는 불안증의 정신과 환자 43명과 대조군 45명에게 피로도, 스트레스, 우울 불안 척도를 이용하여 FSS의 신뢰도와 타당도를 조사하였다. 결과: FSS의 신뢰도 계수는 0.935이었고 재검사의 상관관계 계수는 0.916이었다 (p<0.01). FSS 점수는 피로 군에서 유의하게 가장 높았고 대조군에서 가장 낮았다 (p<0.01). FSS와 Chalder fatigue scale의 상관관계 계수는 0.782로 높았다 (p<0.01). 피로군과 대조군에 대한 FSS index의 최적의 절단점은 민감도 84.1%. 특이도 85.7%인 3.22로 조사되었다. 결론: FSS는 일차진료에서 기질적 질환이 없는 피로환자와 우울 또는 불안증 환자에서 피로도를 평가할 수 있는 유용한 도구이며, 향후 보다 많은 환자를 대상으로 한 연구가 필요하리라 생각된다.

• 한국운동역학회지
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• 제24권2호
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• pp.111-119
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• 2014

The purpose of this study was to investigate the effects of localized muscle fatigue and whole body fatigue on postural control during single-leg stance after impairment induced by heel raise and the Harvard step test. Thirty-eight university students (19 men: age, $20.1{\pm}0.2$ yrs; height, $175.0{\pm}5.23cm$; weight, $66.8{\pm}5.6kg$; body mass index, $21.8{\pm}1.7kg/m^2$, 19 women: age, $20.6{\pm}1.1yrs$ ; height, $163.6{\pm}6.7cm$; weight, $58.8{\pm}4.6kg$; body mass index, $22.0{\pm}2.2kg/m^2$) were participated in this study. Subjects performed a series of single-leg postural tasks prior to, following, and 24 hours after completing: heel raise or the Harvard step test. This study showed that the root mean squared distance and velocity in the anteroposterior and mediolateral planes of the center of pressure decreased significantly due to heel raise exercise-induced fatigue. Furthermore, the root mean squared distance in the anteroposterior and mediolateral planes, and the 95% confidence ellipse area of the center of pressure also decreased significantly 24 hours after completing the Harvard step test. In conclusion, this study showed that both heel raise exercise- and Harvard step exercise-induced fatigue affects postural control during single-leg stance in AP and ML planes. Furthermore, this study suggests that changes in the postural control strategy may have occurred after the fatigue protocols during single-leg stance. Also vision can attenuate the postural deficits associated with the fatigues. In order to clarify these results, further studies using other equipment and variables are necessary.

• Steel and Composite Structures
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• 제15권4호
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• pp.357-377
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• 2013

In order to study the degradation and damage behaviors of steel frame welded connections, two series of tests in references with different connection constructions were carried out subjected to various cyclic loading patterns. Hysteretic curves, degradation and damage behaviours and fatigue properties of specimens were firstly studied. Typical failure modes and probable damage reasons were discussed. Then, various damage index models with variables of dissipative energy, cumulative displacement and combined energy and displacement were summarized and applied for all experimental specimens. The damage developing curves of ten damage index models for each connection were obtained. Finally, the predicted and evaluated capacities of damage index models were compared in order to describe the degraded performance and failure modes. The characteristics of each damage index model were discussed in depth, and then their distributive laws were summarized. The tests and analysis results showed that the loading histories significantly affected the distributive shapes of damage index models. Different models had their own ranges of application. The selected parameters of damage index models had great effect on the developing trends of damage curves. The model with only displacement variable was recommended because of a more simple form and no integral calculation, which was easier to be formulated and embedded in application programs.