• 비파괴검사학회지
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• 제31권1호
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• pp.68-76
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• 2011

음향방출기법은 구조물에 존재하는 손상 및 손상 메커니즘을 규명하는 가장 유효한 비파괴검사 수단으로 널리 이용되고 있다. 최근 이러한 재료 및 구조의 내부 손상의 실시간 모니터링이 가능한 기법을 활용하여 풍력 블레이드와 같은 대형 구조물의 건전성을 실시간으로 감시 가능하도록 하는 연구가 각광 받고 있다. 이러한 실시간 건전성 모니터링을 위해서는 손상 징후를 조기에 발견 가능하여 손상으로 인한 큰 피해가 발생하지 않도록 하는 능력이 필수적으로 요구된다. 이 논문에서는 신호 맵핑 기법을 이용한 새로운 손상 검출 기법의 제안 및 750 kW 블레이드 부분 시편을 이용한 검증 시험을 다루었다. 검증 시험 결과 신호 맵핑 기법은 시간 도달차 기법과 비교하여 낮은 위치 오차율과 높은 위치 표정 결과를 나타내었다. 신호 맵핑 기법은 기존 기법과 비교하여 센서 부착 위치 선정에서도 유연함을 가지는 것을 확인하였다.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.485-505
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• 2014

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.192-196
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• 2005

Key part of main equipment in a gas turbine may be likely to be damaged due to operation under high temperature, high pressure, high-speed rotation, etc. Accordingly, the cost for maintenance increases and the damaged parts may cause generation to stop. The number of parts for maintenance also increases, but diagnostics technology fur the maintenance actually does not catch up with the demand. Blades are made of precipitation hardening Ni superalloy IN738 and the like for keeping hot strength. The surface of a blade is thermal-sprayed, using powder with main compositions such as Ni, Cr, Al, etc. in order to inhibit hot oxidation. Conventional regular maintenance of the coating layer of a blade is made by FPI (Fluorescent Penetrant Inspection) and MTP (Magnetic Particle Testing). Such methods, however, are complicated and take long time and also require much cost. In this study, defect diagnostics were tested for the coating layer of an industrial gas turbine blade, using an infraredthermography camera. Since the infrared thermography method can check a temperature distribution on a wide range of area by means of non-contact, it can advantageously save expenses and time as compared to conventional test methods. For the infrared thermography method, however, thermo-load must be applied onto a tested specimen and it is difficult to quantify the measured data. To solve the problems, this essay includes description about producing a specimen of a gas turbine blade (bucket), applying thermo-load onto the produced specimen, photographing thermography images by an infrared thermography camera, analyzing the thermography images, and pre-testing for analyzing defects on the coating layer of the gas turbine blade.

• The Journal of Korean Physical Therapy
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• 제25권3호
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• pp.132-135
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• 2013

We presented with a patient who showed injury of the cingulum and fornix by penetration of a foreign body into the brain on diffusion tensor tractography (DTT). A 63-year-old man suffered a brain injury by a part of a power saw blade that was suddenly detached from a power saw during work. A part of the power saw blade penetrated his right frontal skull and advanced to the right posterior horn of the lateral ventricle. This penetration caused traumatic intracerebral hemorrhage in the right frontal lobe and intraventricular hemorrhage in the lateral ventricle. He underwent craniotomy and removal of intracranial foreign bodies (bony pieces and saw blade). The patient's Memory Assessment Scale scores were 74 (4%ile) for global memory, 78 (7%ile) for verbal memory, and 80 (9%ile) for visual memory. DTTs showed disruptions in the anterior portion of the fornical body, right fornical crus, the anterior portion of the right cingulum, and the middle portion of the left cingulum, compared to the control. It seems that the sustained memory impairment of this patient might be related to injury of the cingulum and fornix.

• 한국항공우주학회지
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• 제42권4호
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• pp.336-343
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• 2014

깃끝단 후퇴각을 가지는 현대 터보프롭 항공기의 최신 프로펠러는 고속으로 비행할 수 있는 추력을 얻기 위해 구조적으로 높은 강도가 요구된다. 본 연구에서는 프로펠러 구조 설계 시 고강도 및 고강성의 특성을 지닌 카본/에폭시 복합재료가 적용되었으며, 경량화를 위하여 스킨-스파-폼 샌드위치 구조 형태를 채택하였다. 구조 설계를 위한 구조 하중은 블레이드에 작용하는 공력하중을 분석하여 결정하였으며, 스파 플렌지는 굽힘 하중을 담당하고 스킨은 전단 하중을 담당하도록 복합재료 설계 개념을 반영하였다. 구조 안전성을 평가하기 위하여 상용 유한 요소 해석 코드인 나스트란을 활용하여 구조 해석을 수행하였다. 시제품 블레이드의 구조 시험을 통하여 적용된 구조설계 방법론이 적절함을 확인하였다.

• 한국초지조사료학회지
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• 제7권2호
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• pp.79-86
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• 1987

This study was carried out to investigate the relationships and the variations of agronomic characteristics in the shoot and root part of grasses for the basic data of the development, the management and the utilization of pasture in the forest. This study was conducted with 0% (full sunlight), 25%, 50% and 75% of shading degrees after orchardgrass, timothy, perennial ryegrass, ladino clover and orchardgrass dominated mixture were planted on Aug. 25 in 1984. The results are summarized as follows: 1. Dry matter yield in 25% of shading was increased 3-1 7% compared with 0% (full sunlight), while 50 and 75% of shading were decreased 28-35% and 44-60%, respectively. Dry matter yield of timothy, perennial ryegrass and ladino clover were decreased 10, 8 and 33%, respectively, compared with orchardgrass, but there was little difference between orchard grass and mixture. 2. Root distribution by different shading degrees was the maximum at 25%, followed by 0, 50 and 75% of shading degrees. Root distribution among different species was the maximum at orchardgrass, followed by perennial ryegrass and timothy. Especially, root distribution of timothy was very little compared with different species. And significantly positive correlation was observed in the relationship between root weight and dry matter yield (r=0.8 102**). 3. The physiological activity of root by different shading degrees was declined by more shading. 4. The length and the percentage of blade by different shading degrees was an increase tendency by more shading. The length and the percentage of blade among different species was followed by timothy, perennial ryegrass and orchardgrass, in that order. And the correlation between the percentage of blade and dry matter yield was significantly negative.

• 한국작물학회지
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• 제35권3호
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• pp.211-217
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• 1990

팔당호밀과 신기호밀에 대한 전엽시기와 전엽정도가 종실의 발육에 미치는 영향을 구명코자 시험을 실시한 결과를 요약하면 다음과 같다. 1. 엽신중은 2엽, 3엽, 지엽 경으로 무거웠다. 2. 엽록소함량은 지엽, 2엽, 3엽 순으로 높았으며, 엽소도 같은 경향이었고 신기호밀보다 팔당호밀에서 높았다. 3. 립중은 전엽시기가 늦고 전엽정도가 적을수록 무거웠다. 4. 엽신들의 생산효과는 지엽, 2엽, 3엽 순으로 높았다. 5. 이삭부위별 립중은 중부, 하부, 상부 순으로 무거웠다.

• 한국레이저가공학회지
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• 제1권1호
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• pp.24-29
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• 1998

A new wide laser beam optical system for the laser materials processing has been developed with a polygonal mirror. It consists of polygonal mirror and cooling part that prevents the surface of rotating polygonal mirror from damage by heat. The polygonal minors have been designed and made as 24 and 30 facets in pyramid type. This system provides a uniform linear laser heat source with the surface scanning width from 15 to 50mm according to the scanning height To examine the wide laser beam, He-Ne laser is used. Also, Acryl is used to confirm the laser beam pattern by bum-pattern print To analyze the energy distribution of the wide laser ben empirical values and theoretical values are compared and discussed. To improve the efficiency of the wide laser beam optical system, methods are suggested by the optical theories. For larger area processing like turbine blade, drawing blade, cold roller and guide plate, optimal overlapping locations have been calculated and analyzed by geometric and optical theories.

• Journal of Plant Biology
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• 제37권1호
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• pp.53-67
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• 1994

대표적인 규소축적 식물 중에 하나인 벼(Orzy sativa)의 규소체를 기관별로 광학현미경과 주사전자현미경 하에서 조사하였다. 또한 규소체의 명칭에 대하여 가능한 기원조직에 근거하여 정리하였다. 벼의 조사된 주요 기관 7개 부위, 즉 엽신, 엽초, 줄기, 뿌리, 포영, 호영, 그리고 내영에서 특징적인 규소체가 확인되었다. 각 기관에 형성된 규소체 중 특히 장세포 기원의 규소체, 단세포 기원의 규소체 그리고 표피부속체 기원의 규소체 등은 기관별로 그 형태가 다양하게 나타났다. 또한 엽신에서는 벼의 다른 기관에서 형성되는 대부분의 규소체가 형성되는 것으로 밝혀졌다.

• 항공우주시스템공학회지
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• 제12권3호
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• pp.58-63
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• 2018

본 연구는 수직축 풍력 발전 시스템의 복합재 블레이드에 대한 설계 및 제작 연구이다. 본 연구에서 수직축 풍력 발전용 복합재 블레이드의 공력 및 구조 설계를 수행하였다. 1차적으로 복합재 블레이드의 공력 및 구조 설계 요구 조건이 분석되었다. 구조 설계 이후 유한 요소 해석 기법을 활용하여 풍력 블레이드 구조의 구조 해석이 수행되었다. 적용 하중 조건에서 응력 및 변위 해석이 수행되었다. 단계적 구조 해석을 통해 취약 부위의 개선 설계 방안을 제시하였다. 구조 해석을 통해 최종 설계된 블레이드 구조는 안전한 것으로 확인되었다.