• 열병합발전
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• s.50
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• pp.18-22
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• 2006

The tilting pad journal bearing has widely used to support high pressure/high rotating turbine rotors owing to their inherent dynamic stability characteristics. However, fatigue damages in the upper unlcaded pads and the break of locking pins etc. by pad spragging were continuously taken place in the actual steam turbines. The purpose of this paper is to develope a new bearing model that can prevent bearing damage problem effectively by pad spragging in a tilting pad journal bearing. A new bearing model which has a wedged groove is suggested from the studies of spragging mechanism performed by previously research works. The spragging characteristics of the upper unloaded pad are studied experimentally in order to verify the reliability of a new bearing model. It can be known that the phenomenon of pad spragging nearly does not occur in the new bearing model under the various experimental conditions. And it is observed that any kinds of bearing failures by pad spragging does not detect in the application of actual steam turbines.

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.50-57
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• 1998

The leak before break(LBB) concept is generalized on the design of LNG tanks, pressure vessels and nuclear reactor in that any leakage of containment, in whatever amount, will not result in catastropic failure. For this purpose it is necessary to determine the surface crack shape, the opening displacement and the risk of catastropic brittle fracture when it becomes a through crack. In this study the crack propagation behavior of surface flaws and the crack opening displacement of through cracks under combined membrane and bending stresses were investigated with fatigue tests and fracture toughness test of aluminium alloy A5083-O. And fracture mechanics analysis of the crack opening displacement of through cracks were made in order to develop a new model expressing the behaviors of COD under combined membrane and bending stresses.

• Journal of Welding and Joining
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• v.12 no.3
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• pp.90-100
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• 1994

In this study the fatigue crack growth behavior was investigated for the surface cracks in aluminum alloy A5083-O plate and its weldment. Several kinds of specimens were tested at room temperature. The Eccentric specimens(E1.0, E2.5) subjected to combined stresses(tension+bending) were tested and the welded specimens with weld toes(TOE1, TOE2) were tested in order to verify the method to consider the stress concentration such as weld toe. It was ascertained that the surface crack growth property in the weld toe could be predicted by the corrected Pang's equation proposed in this study.

• The Journal of Korean Medicine
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• v.24 no.2
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• pp.109-120
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• 2003

Objectives: This study was conducted to evaluate the clinical efficacy of EC102, a composition containing oriental medicine, for relieving VDT syndrome, including eye symptoms and musculo-skeletal symptoms. Methods: The study was conducted by using a double blind randomized controlled trial design. 40 subjects were randomly assigned to the placebo group or the EC102 group. The visual analogous scale (VAS) was used to evaluate various VDT symptoms, including eye pain, eye fatigue, back pain, shoulder pain and so on. Refractory indexes were measured using refractometer, and tear film break-up time (BUT) were measured using fluorescein strip. Blood circulation was measured using photo-plethysmography. Blood pressure and blood biochemistry were also measured. Statistical analysis was conducted by a Mann-Whitney test using SPSS 9.0 software. Results: The EC102 group showed a statistically significant reduction of eye symptoms including eye fatigue, eyelid fatigue, itching, pain, and photophobia when compared with the placebo group (P<0.05). The EC102 group also showed a statistically significant reduction of back pain compared with the placebo group (P<0.05). No side effects on liver function and blood biochemistry were observed. Conclusions: EC102 has significant clinical efficacy for relieving symptoms of VDT syndrome.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1445-1453
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• 2009

The dropper supports the contact wire and is attached using thimbles and various types of dropper clips on the catenary. Consequently droppers are subject to mechanical loads from friction and buckling during the passage of pantographs. If such mechanical loads occur repeatedly with every passing pantograph, it is possible that the dropper wire will break due to fatigue. In order to investigate failure causes for the high speed line dropper, theoretical analyses and experiments have been carried out. In this paper, mathematical formulas are derived for the prediction of the dropper static load. The measured values in the experiment agree well with the theoretical predictions. And, we performed measurement for the variation of forces on the dropper. To analyze the cause analysis on fracture of dropper wire, we have conducted experiment such as fatigue test of new products, SEM(Scanning Electron Microscope) and EDX(Energy Dispersive X-ray) of fractured specimens in the field. Finally, we also measured the vertical displacements when a pantograph moved at 300km/h under the Korean high speed overhead line.

• Journal of the Korean Institute of Gas
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• v.3 no.1
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• pp.1-7
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• 1999

Fatigue behavior of before-and-after penetration was examined experimentally using surface pre-cracked specimens of aluminium alloy 5083-0. The fatigue crack shape before penetration is almost semicircular, and the measured aspect ratio is larger than the value obtained by calculation using K values proposed by Newman-Raju. It is found that the crack growth behavior on the back side after penetration is unique and can be divided into three stages. By using a crack propagation rule in case of long surface crack, the change in crack shape after penetration can be evaluated quantitatively.

• Physical Therapy Rehabilitation Science
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• v.10 no.2
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.1
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• pp.47-54
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• 2014

Endurance of ship hull can be estimated by existing regulations and fatigue estimation methods. These can be applied to the hull materials that are recommended by ship regulations but can't be applied to new materials. In this study, structural force in the worst sailing condition is obtained by the acceleration measurement test of small polyethylene boat and the endurance of small polyethylene hull is estimated by rainflow cycle counting method and linear cumulative damage rule. Maximum Von-Mises stress on the polyethylene boat is 1.8MPa and much lower than the fatigue strength of at least 5.9MPa for the fatigue life of $1{\times}10^9$ cycles. Fatigue life of the polyethylene boat hull is estimated to be 6,229 years.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.725-726
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• 2008

This paper proposes elastic stress intensity factors and crack opening displacements (CODs) for a slanted axial through-wall cracked cylinder under an internal pressure based on detailed 3-dimensional (3-D) elastic finite element (FE) analyses. Based on the elastic FE results, the stress intensity factors along the crack front and CODs through the thickness at the center of the crack were provided. These values were also tabulated for three selected points, i.e., the inner and outer surfaces and at the mid-thickness. The present results can be used to evaluate the crack growth rate and leak rate of a slanted axial through-wall crack due to stress corrosion cracking and fatigue. Moreover, the present results can be used to perform a detailed Leak-Before-Break analysis considering more realistic crack shape development.

• Journal of Music and Human Behavior
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• v.14 no.1
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• pp.41-62
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• 2017

The purpose of this study was to examine the effect that preferred music listening had on police officers' occupational stress and fatigue. The musical intervention took place over a total of six sessions from October 11 to October 19, 2016. At each session, the experimental group (n = 19) received 20 minutes of music listening with individually customized playlists that were compiled based on their preferred music list. The control group (n = 21) simply took a break from work for 20 minutes. Every participant checked his or her occupational stress and fatigue level before and after the experiment using the Occupational Stress Inventory and Subjective Symptoms of Fatigue Test. The data were then analyzed by the SPSS 22.0 statistics program. To examine the homogeneity and pretest-posttest results between groups, an independent t test was conducted, and a paired t test was used to examine the pretest-posttest results within groups. The results confirmed all hypotheses. Findings support that the use of preferred music listening is an effective way to help police officers to control their occupational stress and fatigue. This study used a convenience sample and has limited generalizability. Future research should explore interactive approaches in music therapy as well as receptive music listening for alleviating police officers' occupational stress and fatigue.