• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.463-465
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• 2012

선박근무자의 피로는 해양사고의 잠재적 요인으로 혹은 인적과실에 기여하는 한 요인 정도로만으로 여겨졌으나, 최근 이와 관련한 연구에 의하면 선박근무자의 피로가 임무수행에 밀접하게 영향을 미치며, 인적과실을 유발하는 주요한 원인 중 하나라는 사실이 밝혀지게 되면서 선박 인간공학분야에서의 인간공학적 요소들의 고려 여부가 관심의 대상이 되고 있다. 선박근무자의 피로 발생원인은 명확히 밝혀져 있지 않으며, 선상작업에서 오는 스트레스, 감정 및 작업 등에 의해 영향을 받는 것으로 보이나, 통상 피로는 주로 한 가지 원인보다 복합적인 원인에 의하여 발생되는 것으로 알려져 있다. 본 연구에서는 이러한 선박근무자의 자각피로도와 직무스트레스의 효율적 관리를 위하여 선상에서 간편하게 자각피로도를 측정할 수 있는 방법을 제안하고자 한다.

• 대한근관절건강학회:학술대회논문집
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• 2000.04a
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• pp.174-188
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• 2000

• Rubber Technology
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• v.5 no.2
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• pp.81-93
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• 2004

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.267-269
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• 2004

현재 구조물의 피로설계에는 주로 공칭응력(Nominal Stress) 및 핫스팟 응력(Hot Spot Stress, HSS)이 사용되고 있다. 공칭응력을 바탕으로 구조물에 대한 피로설계를 할 경우에는 각 부재에 사용되는 각각의 용접부 형상에 대한 피로시험을 따로 수행하여 피로수명 곡선을 구해야 하는 번거로움이 있다. (중략)

• Journal of Sensor Science and Technology
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• v.10 no.1
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• pp.42-51
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• 2001

In this study, the effects of embedded optical fibers on the static properties under tensile load and dynamic properties under fatigue load of composite laminates were investigated by experimental tests and finite element analysis. Based on the results, it can be concluded that the embedded optical fiber sensors do not have significant effects on the structural integrity of the smart composite structures except when the sensors are embedded perpendicular to the adjacent reinforcing fibers under fatigue loading. An intensity-based optical fiber sensor was embedded in the crossply composite laminates to monitor the fatigue damage by detecting the stiffness changes of the laminates. The result of this experiment has shown that the intensity-based optical fiber sensor has large potential to monitor the fatigue damage of composite structures by detecting the stiffness changes of the structures with simple and inexpensive instruments and without complex post-processing of measured signals. In addition, the optical fiber sensor showed good resistance to fatigue loading and wide sensing ranges of stiffness.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.14-21
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• 2002

The development of a new experimental method is required to easily observe the growth behavior of fatigue cracks. To satisfy the requirement, an image processing technique was introduced to fatigue testing. The length of surface fatigue crack could be successfully measured by the image processing system. At first, the image data of cracks were stored into the computer while the cyclic loading was interrupted. After testing, crack length was determined using an image processing software which was developed by authors. Various image processing techniques like a block matching method was applied tc the detection of surface fatigue cracks. By comparing the data measured by the image processing system with those by the manual measurement with a microscope, the effectiveness of the image processing system was established. If the proposed method is used to monitor and observe the crack growth behavior automatically, the time and efforts for fatigue test could be dramatically reduced.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.145-152
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• 2010

This study evaluated the fatigue degradation in a SUS316L specimen using the nonlinear ultrasonic method. The nonlinearity of the ultrasonic wave was estimated by a relative nonlinear parameter defined as the ratio of the amplitudes for the fundamental wave to the second harmonic wave. In the experiment, a measurement system with contact transducers was constructed; reliable measurements were assured by keeping measurement conditions consistent and reducing extra harmonics generated in the measurement system. Two types of SUS316L specimen were used in experiments; a rotating bar fatigue specimen and a tensile fatigue specimen. The fatigue condition used was high cycle fatigue. The former specimen had a cylindrical shape and was used to observe the change in the nonlinear parameter after fatigue accumulation in a specimen. The latter was a plate-shaped specimen and was used to confirm the change in the nonlinear parameter at the position where the fatigue stress was concentrated. The measured nonlinear parameter showed a strong correlation to the damage level in both fatigue tests.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.95-103
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• 1996

단순 전단연결 구조를 가진 강철도교의 세로보 단부의 절취부위에서 많은 피로균열이 발견되었으며, 이러한 부위의 피로균열은 피로손상의 전형적인 예이다. 피로균열을 가진 세로보 절취부위의 보강방법을 연구하기 위하여 가로보 및 세로보의 상부 플랜지에 인장판을 부착한 경우와 부착하지 않은 경우로 구분하여 피로실험을 수행하였다. 피로실험에 사용된 하중은 현장에서 측정된 실동응력을 기초하여 빈도해석을 통해 산정하였다. 피로실험 결과, 인장판으로 보강한 모멘트 저항 연결구조상세가 철도교에서 균열성장을 효과적으로 정지시킬 수 있는 것으로 판명되었으며, 피로손상을 가진 절취부위의 보강방법으로 제시될 수 있을 것으로 사료된다.

• Proceedings of the ESK Conference
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• 1993.04a
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• pp.79-87
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• 1993

등척성 수축에서 국소근육피로의 연구에는 표면전극을 사용한 근전도신호의 스펙트럼분석 이 효과적이다. 많은 연구결과에서 자발적 수축동안 근전도신호의 주파수 성분이 근육의 피로에 의해 낮은 쪽으로 천이 된다는 사실이 밝혀졌으며, 이를 근육피로의 지수로 사용하려는 노력이 계속되어 왔다. 본 연구에서는 실제와 유사한 형태의 주기적 작업수행시에 얻어진 근전도신호의 중간주파수 천이양상을 지속적 수축에서 얻어진 중간주파수의 천이양상과 비교하여, 주기적 작업의 피로축적은 지속적 수축에서의 피로축적과 같은 경향성을 지님을 찾아냈으며, 이 결과를 근거로 주기적 수축의 수축지속시간으로 정규화된 개념의 피로지수를 개발하였다. 이러한 피로지수는 정량적으로 제시될 수 있음은 물론, 작업설계와 허용한계의 설정등에 응용될 수 있을 것이다.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.533-538
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• 2014

Purpose: This study is to investigate correlation between eye fatigue and letter contrast according to letter contrast changes on monitor display. Methods: Reading speed test were carried out for 53 subjects (mean age: $22.68{\pm}1.85$ years) who have over Best-corrected visual acuity (BCVA) 1.0, and 45 subjects, who could read over 123 out of 163 letters among 53 subjects were selected. They were asked to read the letters which were composed of Black (contrast 100%), Dark gray (contrast 80%), Gray (contrast 80%), Light gray (contrast 30%) randomly. The change of their eye fatigue by letter contrast on monitor display was measured by monitoring their eyes with an eye-tracker while they were reading letters. Results: Event Duration (sec) was 33.635 for Black, 32.266 Dark gray, 33.936 for Gray, and 34.848 for Light gray. Average of Fixation Duration (sec) was 0.224 for Black, 0.218 for Dark gray, 0.239 for Gray and 0.243 for Light gray. Average of Pupil diameter (mm) was 41.133 mm for Black, 41.160 mm for Dark gray, 40.880 mm for Gray and 40.459 mm for Light gray. Frequency (blinks/sec) was 0.211 for Black, 0.206 for Dark gray, 0.221 for Gray, and 0.238 for Light gray. Conclusions: Event Duration and average of Fixation Duration were the shortest for Dark gray and the longest for Light gray. In average Pupil diameter was the biggest Dark gray and the smallest for Light gray. Blink Frequency (blinks/sec) was the lowest for Dark gray and the highest for Light gray. Visual fatigue by brightness of letters on monitor display was the least for Dark gray followed by Black, Gray and Light gray.