• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.55-60
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• 2010

The honeycomb composite joint structure designed for application to a tilting KTX railroad car body is subjected to bending loads of a cantilever type. Honeycomb sandwich composite panel-joint attached in the real tilting car body was fabricated and sectioned as several beam-joint specimens for the bending test. The fracture behaviors of these specimens under static loads were different from those under cyclic loads. Static bending loads caused shear deformation and fracture in the honeycomb core region, while fatigue cyclic bend loading caused delamination along the interface between the composite skin and the honeycomb core, and/or caused a fracture in the welded part jointed with the steel under-frame. These fracture behaviors could occur in other industrial honeycomb composite joints with similar sub-structures, and be used for improving design parameters of a honeycomb composite joint structure.

• The Journal of the Korea Contents Association
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• v.12 no.4
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• pp.292-303
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• 2012

This study was performed to examine the effects of Dan Jeon Breathing on depression, anxiety and fatigue of hemodialysis patients. This study used the nonequivalent control group pretest-posttest design. Before applying the Dan Jeon Breathing program, the patients were divided into the experimental group and the control group, respectively, and were requested to report their self-ratings to measure their depression, anxiety and fatigue. The Dan Jeon Breathing program was given to both groups for 60 minutes a day and 2 times a week for 12 weeks. The data collected from the program were analysed by means of ${\chi}^2$ test, Fisher's exact probability test, Shapiro-Wilk, t-test and Mann-Whitney U test. The analyses revealed that the depression (t=-2.459, ${\rho}$=.019) and anxiety (t=-2.541, ${\rho}$=.016) levels of the experimental group decreased after Dan Jeon Breathing compared to those of the control group. The difference in fatigue level was statistically insignificant (Z=-1.871, ${\rho}$=.061), though. From the above results, it was verified that Dan Jeon Breathing could be used as nursing intervention for hemodialysis patients to mitigate their depression and anxiety.

• Journal of Digital Convergence
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• v.14 no.3
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• pp.329-335
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• 2016

This paper's objective is to investigate the display fatigue quantitatively according to watching 2D and 3D videos on the display. Though it has been known commonly that display fatigue by 3D is greater than one by 2D, there have been few researches with an aim to measure display fatigue scientifically. Flicker fusion frequency and cybersickness degree were measured before/after sixteen subjects(Male 8, Female 8) watch the 2D, 3D images. Two dependent variables affected by 2D and 3D videos were analyzed and compared statistically based on scientific evidences and researches. 3D showed a value 4 times as much as 2D in cybersickness increase rate, and the reduction rate of 3D was 2 times as much as that of 2D.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1145-1148
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• 2005

In this paper, we introduce a probabilistic model based on Bayesian networks (BNs) for inferring human fatigue by integrating information from various visual cues and certain relevant contextual information. Visual parameters, typically characterizing the cognitive states of a person including parameters related to eyelid movement, gaze, head movement, and facial expression, serve as the sensory observations. But, an individual visual cue or contextual Information does not provide enough information to determine human fatigue. Therefore in this paper, a Bayesian network model was developed to fuse as many as possible contextual and visual cue information for monitoring human fatigue. At the experiment results, display the utility of the proposed BNs for predicting and modeling fatigue.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.220-226
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• 2003

This paper presents the result of an investigation on the application of the acoustic emission method to the monitoring of fatigue crack initiation, growth and track location in welded joints. Fatigue test was carried out for a typical fillet welded joint of ship structure. AE parameter such as ring down count was analyzed in time domain and crack locations were examined by source location and cluster option which is one of the functions of AE signal processor The usability of AE mettled was confirmed for the detection of the initiation and location of through crack.

• Journal of the Korea Convergence Society
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• v.12 no.6
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• pp.259-266
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• 2021

This is a descriptive research was to find out fatigue, musculoskeletal pain and job satisfaction in rehabilitation centers employees. The research subject was 199 rehabilitation center employees, and the collected data were analyzed through descriptive statistics, t-test, ANOVA, Scheffé's test, Pearson's correlation coefficients and multiple regression. The results revealed that the significant predictors of job satisfaction for rehabilitation center employees were working duration(β=-.033, p=.010), fatigue(β=-.051, p=.015), and musculoskeletal pain(β=-.020, p=.047), explaining 8.4% of the variation in job satisfaction(F=5.549, p<.001). These results can be recommended as preliminary data for preventing and managing fatigue and musculoskeletal pain of rehabilitation centers employees who play an important role in the community.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.1
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• pp.167-174
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• 2003

Fatigue damage of 2.2Ni-1Cr-0.5Mo steel used fir high strength pressure tubes and vessels was evaluated using uniaxial specimens subjected to strain-controlled fatigue loading. Based on the fatigue test results from different strain ratios of -2. -i 0, 0.5, 0.75, the fatigue damage of the steel was represented by using a cyclic strain energy density. Mean stress relaxation depended on the magnitude of the applied strain amplitude. The high pressure vessel steel exhibited the cyclic softening behavior. Total strain energy density consisting of the plastic strain energy density and the elastic tensile strain energy density described fairly well the fatigue life of the steel, taking the mean stress effects into account. Compared to other fatigue damage parameters, fatigue life prediction by the cyclic strain energy density showed a good correlation with the experimental fatigue lift within a factor of 3.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.567-580
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• 2000

This paper proposes an integrated approach, which is independent of specimen geometry and loading type, for predicting the fatigue life of spot welded specimens. We first establish finite element models reflecting the actual specimen behaviors observed on the experimental load-deflection curves of 4 types of single spot welded specimens. Using finite element models elaborately established, we then evaluate fracture parameter J-integral to describe the effects of specimen geometry and loading type on the fatigue life in a comprehensive manner. It is confirmed, however, that J-integral concept alone is insufficient to clearly explain the generalized relationship between load and fatigue life of spot welded specimens. On this ground, we introduce another effective parameter $J_e$ composed of $J_I$, $J_{II}$, $J_{III}$, which has been demonstrated here to more sharply define the relationship between load and fatigue life of 4 types of spot welded specimens. The crack surface displacement method is adopted for decomposition of J, and the mechanism of the mixed mode fracture is also discussed in detail as a motivation of using $J_e$.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1503-1512
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• 1992

The strength evaluation and life prediction on the corrosion part of structure is one of the most important subjects, as a viewpoint of reducing economic loss by regular inspection, maintenance, repair and replace. For this purpose, it has been difficult to obtain the available data on growth of pit depth or growth rate of each pit which depends on time. In this paper, the life prediction and strength evaluation method was suggested for the structure with irregular stress concentration part by surface corrosion. The statistical distribution pattern of corrosion depth and the degree of fatigue strength decline were confirmed according to corrosion period by artificial corrosion of SS41 steel. The life prediction and the fatigue strength evaluation of materials with consideration of the corrosion period on the extreme value statistic analysis by the data of maximum depth of corrosion and on random variable was studied.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1186-1192
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• 1990

It is well known that the fatigue crack growth retardation following overloads can be estimated reasonably well by the models of Wheeler and Willenborg. These models, however, can not explain the delayed-retardation revealed by every experimental result. This means that they necessarily have some qualitative defects in themselves despite of a fair approximation of quantity. In fact, they did not take into account the effects of the compressive portion of the overload cycle such as the change of reversed plastic zone size. The present study is focused on the acceleration effect in the reversed plastic zone in order to analyze qualitatively delayed-retardation phenomenon following single peak overload on the fatigue crack growth behavior using 2024-T3 aluminum alloy.