• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.3
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• pp.179-184
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• 2015

In this study, the flap fatigue test of a 48 m long wind turbine blade was performed for 1 million cycles to evaluate the characteristics of acoustic emission signals generated from fatigue damage of the wind blades. As the number of hits and total energy continued to increase during the first 0.6 million cycles, blade damage was constant. The rise-time result showed that the major aspects of damage were initiation and propagation of matrix cracks. In addition, the signal analysis of each channel showed that the most seriously damaged sections were the joint between the skin and spar, 20 m from the connection, and the spot of actual damage was observable by visual inspection. It turned out that the event source location was related to the change in each channel's total energy. It is expected that these findings will be useful for the optimal design of wind turbine blades.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1340-1345
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• 2003

In this paper, an integrated optimal design software system for structural components has been developed which interfaces existing commercial codes for CAD, CAE and Optimization. They include specialized optimal design software codes such as iSIGHT and VisualDOC, optimization module imbedded in CAD software developed by CAD developers, and optimal design software systems based on API of commercial CAD software. The advantages of the CAD imbedded optimal design approach and those of specialized optimal design software are taken to develop the system. The user defines optimal design formulation in the user interface for problem definition in the CAD control stage, where design variables are directly selectable from the CAD model and various properties and performance functions defined. The commercial CAD codes, Open I-DEAS are used for the development. The resulting software is minimally connected to CAD and CAE systems while keeping maximum independence from each other. This assures flexibility and freedom for problem definition. Fatigue life optimization is taken as a nontrivial application area. As a specific example, the shape design of a knuckle part of an automobile is performed, where the minimum fatigue life over the material domain in terms of the number of cycles of a curb strike are maximized under the constraint of not exceeding the current mass. The fatigue life has been improved by four times of the initial life. The developed software is illustrated to maintain the advantages of existing optimal design software systems while improving independency and flexibility.

• The Journal of Internal Korean Medicine
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• v.41 no.3
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• pp.293-305
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• 2020

Purpose: This study aimed to develop a questionnaire for the diagnosis of chronic fatigue syndrome (CFS) designed based on the systematic exertion intolerance disorder (SEID) criteria, and to validate the reliability of the questionnaire. Methods: A literature search on questionnaires for CFS diagnosis was conducted to develop a SEID questionnaire (SEID-Q27), followed by a pilot survey to identify the reliability of the questionnaire. Adults (Daejeon university personnel) with a Chalder fatigue scale (CFQ) score ≥15 were invited for the survey. We commenced the survey in November 2019 with a two weeks of interval for the test and retest method. The reliability of the questionnaire was investigated in three angles: 1. Cronbach's α, 2. correlations (r) of the questions, numerical rating scale (NRS), and visual analog scale (VAS), and 3. kappa (k) analysis. Results: Among the total 275 adults registered, 55 (20%) participants with a CFQ score ≥15 were invited, and 31 (11%) [15 male, 16 female] completed the questionnaire. The total Cronbach's α was 0.944 for the test and 0.949 for the retest. The reliability (r) of questions by CFQ score (≥15, ≥18, ≥20) ranged from 0.533-0.928 (p <0.05), and the r score of the NRS and VAS were the highest in CFQ scores ≥20, at 0.933 (p<0.001). The agreement rate of the SEID-Q27 between the test and retest was 87% (kappa k=0.743). Conclusions: The SEID-Q27 seems to be reliable. Further studies are needed to measure the validity of the tool and the cutoff point.

• 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.

• Journal of the Korea Safety Management & Science
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• v.14 no.4
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• pp.93-105
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• 2012

The purpose of this study was to investigate drivers' postures in different car pedal systems and skilled levels under fatigue. Twenty four subjects participated in this experiment. For three-dimensional analyses, six cameras (Proreflex MCU-240, Qualisys) were used to acquire raw data. The parameters were calculated and analyzed with Visual-3D. In conclusion, ROAs of two leg-pedal system were less than one leg pedal system by pattern analysis. Through statistical tests, skilled levels have effects on ROAs(X, Y, Z) of ankle joint at breaking a pedal and ROAs(Y, Z) of ankle joint at accelerating a pedal. Also, car pedal systems have effects on ROAs(Y, Z) of ankle joint, and ROA(Z) of knee joint at accelerating a pedal. In addition, skilled levels and car pedal systems (cross effects) have an effect on ROA(Z) of ankle joint. These findings suggested that we should improve a present single pedal system.

• Journal of Korean Gerontological Nursing
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• v.20 no.3
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• pp.204-216
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• 2018

Purpose: The purpose of this study was to examine effects of a muscle strength reinforcement exercise program (MSREP) for older adult patients with hemodialysis (OAPHD) which was designed to improve health status and quality of life of these older adult patients. Methods: Participants were 40 patients with OAPHD: 20 in the experimental group and 20 in the control group. MSREP was conducted with the experimental group for 12 weeks at H geriatric hospital. An assessment was done to determine effects on physical performance, inflammation index, fatigue, muscle strength and quality of life. Short physical performance battery, C-Reactive Protein (CRP), visual analog scale for fatigue, object lifting' proposed by the Life Options Rehabilitation Advisory Council, sit-to-stand test, and quality of life index were used to gather data. Results: Between the 2 groups there was no significant difference in scores for physical performance, fatigue or quality of life. However, the 2 groups showed significant difference in CRP values and muscle power scores on post-test. Conclusion: Findings provide evidence for the potential utility of education for older adult patients with hemodialysis. Also, this program could allow these patients to increase muscle strength, and contribute to achieving better health conditions in OAPHD care.

• Proceedings of the ESK Conference
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• 1998.04a
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• pp.194-199
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• 1998

The purpose of this study is conducted to evaluate the psycho-physiological effects of the dynamic lighting on VDT workers and to establish the dynamic lighting design guides. The main experimental factors are changes of illuminance. There were five conditions including 1) ripid change, 2) slow change at 300lx .approx. 500lx, 3) a static illuminance level at 300lx, and 4) rapid chante, 5) slow change at 200lx .approx. 300lx. The ranges of change were set typical illuminance level for the simple visual task requirement and reasonable to a VDT task ; 200-300-500lx. The psycho-physiological measurements used were EEG, R-R interval, CFF, near point accommodation, feeling perceived fatigue, and work performance. Analysis of psycho-physiological factors shows that higher illumination level conditions are more affirmative effects than lower on VDT workers under 500lx except for the results of feeling perceived fatigue. And about the speed of changes of illuminance level. The conditions of slow change were better than the others in terms of the work performance as well as psycho-physiological results.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.569-579
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• 1994

현행 TV 브라운관용 panel의 투과검사 작업장에서의 조명설계에 대한 문제점을 규명한 결과, 투과검사 작업시 사용되지 않는 광원부분으로 인한 glare가 있음이 파악되었다. 본 연구에서는 glare가 직접적으로 visibility를 감소시키는지의 여부와 장시간 glare에 노출되어 누적된 눈의 피로가 결과적으로 작업에 영향을 미치는지를 알아보았다. 이를 위해 glare광원의 각도와 투과검사작업의 work period가 변화함에 따라 작업수행도가 어떻게 변화하는가를 정량적으로 관찰하였다. 연구결과, visibility에 직접적으로 영향을 미치지 않는 소량의 glare도 장시간 누적되면, 눈의 피로를 유발하여, 작업수행도에 영향을 미치며, 육안검사작업의 작업수행도 저하에 대한 indicator로서 DGR(discomfort glare rating)이 활용될 수 있음이 파악되었다. 또한, 작업특성에 관계없이 일률적으로 적용되는 VCP(visual comfort probabilities)를 기준으로 실제작업장의 조명을 설계하기는 어려울 것으로 판단된다.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.359-362
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• 1999

Partially prestressed concrete members are concrete members reinforced with a combination of prestressed and non-prestressed reinforcement, and also can offer advantages of reinforced concrete. The objective of this study is to develop a design program using Visual Basic language according to the limit state design method which controls crack and check fatigue effectively for partially concrete members.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1500-1503
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• 2007

Auto-stereoscopic 3D of 60-view number is made using slanted lenticular lens array and LCD of 15.1 inch diagonal size and 3200 by 2400 pixel numbers. Due to its large view number, smooth motion parallax is observed and the visual fatigue is reduced.