• 제목/요약/키워드: Entrance hole

검색결과 46건 처리시간 0.033초

수직분사각도를 갖는 직사각 막냉각홀 내부에서의 유동 및 열/물질전달 특성 (Flow and Heat Transfer Within a Rectangular Film Cooling Hole of Normal Injection Angle)

  • 홍성국;이동호;강승구;조형희
    • 대한기계학회논문집B
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    • 제28권4호
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    • pp.456-466
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    • 2004
  • An experimental study has been conducted to investigate the flow and heat/mass transfer characteristics within a rectangular film cooling hole of normal injection angle for various blowing ratios and Reynolds numbers. The results are compared with those for the square hole. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code (FLUENT). The heat/mass transfer around the hole entrance region is enhanced considerably due to the reattachment of separated flow and the vortices generated within the hole. At the hole exit region, the heat/mass transfer increases because the main flow induces a secondary vortex. It is observed that the overall heat/mass transfer characteristics are similar to those for the square hole. However, the different heat/mass transfer patterns come out due to increased aspect ratio. Unlike the square hole, the heat/mass transfer on the trailing edge side of hole entrance region has two peak regions due to split flow reattachment, and heat/mass transfer on the hole exit region is less sensitive to the blowing ratios than the square hole.

솔수염하늘소의 유충침입공과 성충탈출공의 측정과 소나무 내 분포 (Measurement and Within-tree Distribution of Larval Entrance and Adult Emergence Holes of Japanese Pine Sawyer, Monochamus alternatus(Coleoptera: Cerambycidae))

  • 정영진;이상명;김동수;최광식;이상길;박정규
    • 한국응용곤충학회지
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    • 제42권4호
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    • pp.315-321
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    • 2003
  • 1999년부터 2002년까지 경남 진주의 소나무재선충에 의한 피해임지 내에서 고사목을 대상으로 솔수염하늘소 유충침입공과 성충탈출공 및 번데기방의 크기와 갱도길이 등을 측정하고, 소나무 내 분포를 분석하였다. 소나무 내 솔수염하늘소의 유충 침입공수는 1$m^2$당 수관부가 56.2 개인데 비해 수간부는 27.7개로서 수관부가 훨씬 많았다. 직경이 8-l0 cm인 공시목에 침입공의 27.5%와 우화공의 22.4%가 분포하였고 이보다 굵거나 가는 공시목에는 적었다. 침입공의 형태는 타원형으로 입구의 표면적은 평균 65.8$\textrm{mm}^2$ 이었다. 성충탈출공은 원형으로서 직경은 평균 7.0mm 이었다. 공시목의 표면에서 번데기방까지의 깊이는 평균 24.8 mm이었고 번데기 방의 부피는 200-2,000 ㎣이었다 성충의 탈출공은 수관부가 수간부보다 많았으며, 공시목의 직경이 8-10cm에서 22.4%로 가장 많이 분포하였다. 유충 침입공과 성충 탈출공까지의 목질부 표면에서 직선거리는 평균 3.3 cm이었으며, 침입공에서 탈출공까지의 갱도 길이는 평균 46.2 nm이었다.

터널 입구에서의 블랙홀 현상 완화를 위한 카메라 기반의 전면유리 투과율 제어 방법 (A Windshield Transparency Control Method Using an Automobile Camera for Alleviating Black-Hole Phenomenon at the Tunnel Entrance)

  • 이중현;이동욱
    • 전기학회논문지
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    • 제65권8호
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    • pp.1392-1399
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    • 2016
  • Blackout effect occurs when a driver misadapts to the changed lighting conditions upon entering a tunnel. This could lead to a decrease in visibility especially in the daylight, depending on the difference in the degree of brightness between inside and outside the tunnel. To alleviate such a problem, we decrease windshield transparency before the driver arrives at the tunnel entrance. Controlled amount of light inside the car can allow the drivers to adjust to the dark prior to entering. The windshield transparency coefficient is to be determined by the arrival time at the tunnel and difference in the level of brightness between inside and outside the tunnel. Navigation, road sign detection, and tunnel entrance detection provide the arrival time. We also designed an opto-electronic conversion function to estimate the level of brightness. The black-hole phenomenon alleviation method is verified by field experiments using an automobile camera and a navigation. The result shows that the adjusted windshield transparency is able to provide an environment with a comfortable level of brightness with which the drivers can enter tunnels without the visibility problem.

Nest Box Preference by Secondary Cavity-Nesting Birds in Forested Environments

  • Choi, Chang-Yong;Nam, Hyun-Young;Lee, Eun-Jae;Chung, Ok-Sik;Park, Yong-Su;Lee, Jong-Koo;Hyun, Jee-Yun;Lee, Woo-Shin
    • Journal of Ecology and Environment
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    • 제30권1호
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    • pp.49-56
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    • 2007
  • We placed and monitored 2,137 nest boxes to determine how the size of the entrance hole and the box placement influenced nest box selection by secondary cavity-nesting birds and to derive recommendations for the use of nest boxes for management of cavity-nesting birds in forested environments. A total of 566 pairs of seven bird species used the nest boxes from 1997 to 2006, 562 of which were secondary cavity-nesters. Sympatric tits such as varied tits (Parus varius), great tits (P. major), and marsh tits (P. palustris) were common breeding birds in nest boxes, and showed clear preferences for 4.0 cm, 3.5 cm and 3.0 cm nest holes, respectively. Tree sparrows (Passer montanus) and Eurasian nuthatches (Sitta europaea) preferred 4 cm and 3.5 cm holes, respectively. We did not detect selection for the directional orientation for the entrance hole, but the birds appeared to avoid nest boxes that faced steep or gentle upward slopes and those less than 1.8 m from the ground. These results are probably related to avoidance of disturbance and predation. We suggest that diverse species can be supported by the placement of nest boxes with entrance holes of various sizes and that specific species can be targeted by selecting the hole sizes preferred by those species. To attract secondary cavity-nesters, managers should avoid placing nest boxes close to the ground and facing hills. This study also suggests that careful selection and placement of nest boxes is needed to avoid biases in research using nest boxes.

극세선용 압출다이의 미세구멍 가공기술 연구 (A study on the micro-hole machining for micro-extruding die)

  • 민승기;제태진;이응숙;이동주
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 추계학술대회 논문집
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    • pp.202-205
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    • 2002
  • The micro-extruding die is a die for manufacturing of fine-wire by extruding process. The fine-wire made from the micro-extruding can be effectively applied to fields of semiconductor parts and medical parts etc. It is predicted that the demand of fine-wire in industry is more and more increasing. In this study $\Phi$ 50${\mu}{\textrm}{m}$ micro-drill which is coated with diamond is used for drilling of super micro-hole sues. For the machining of taper parts of entrance and exit, drill having $\Phi$ 9mm inclination angle 20$^{\circ}$ is used. This is useful for anti tool-breakage in drilling process. After micro-drilling, the polishing process by abrasive is carried out for increasing surface roughness.

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무수축 기판 상에 UV 레이저 가공에 의한 Taper 현상 (Taper phenomenon of UV-laser punching process on zero-shrinkage substrate)

  • 안익준;여동훈;신효순;심광보
    • 한국결정성장학회지
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    • 제25권6호
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    • pp.285-289
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    • 2015
  • 프로브카드의 소형화, 고기능화. 고집화에 따라 고강도 무수축 기판에 레이저 가공 공정을 이용한 미세 홀 천공에 대한 관심이 높아지고 있다. 그린 상태에서 레이저 펀처로 미세 홀을 천공 시 테이퍼 현상이 중요한 공정 문제가 되고 있다. Entrance hole과 exit hole의 크기 차이는 홀 크기가 작을수록 커지고, 홀 크기가 커질수록 작아지는 경향을 나타내었다. 테이퍼 현상을 개선하기 위해 second hole 가공 공정을 적용하였다. 기판의 두께가 $380{\mu}m$인 기판 상에 $80{\mu}m$ 홀 천공시 최적의 second hole 크기를 찾기 위해 $70{\sim}79{\mu}m$ 홀을 천공하였을 경우 $76{\mu}m$$77{\mu}m$에서 테이퍼는 11.9 %로 가장 낮게 나타났다. 천공된 무수축 기판을 소결한 후에는 테이퍼가 7 %로 개선되었다. First hole 크기와 비교하였을 때 second hole 크기는 first hole 크기의 약 95~97 % 일 때 테이퍼가 가장 적었다.

이중 내부구조를 갖는 도자기보틀 (Ceramic Bottle Having Dual Structure)

  • 김석호
    • 한국콘텐츠학회논문지
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    • 제8권4호
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    • pp.92-99
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    • 2008
  • 대부분의 기존 도자기보틀(bottle)은 입구가 상부를 향하고 있어 입구가 외부에 노출되기 때문에 발생하는 문제점을 갖고 있다. 이러한 문제점을 보안하여 이중 내부구조를 갖는 보틀을 제작하였다. 이 보틀은 컵 등에 따라질 내용물을 수용하며 하부에 입구를 갖는 수용부와 수용부와 연결되는 다수개의 구멍을 상부에 가지며 수용부의 둘레에 형성되어 내용물을 저장하는 저장부를 포함하며 수용부의 입구의 끝단이 바닥 표면에 맞닿는 저장부의 하부면 보다 상부에 위치하도록 구성된다. 이 보틀은 입구가 하부 쪽을 향하도록 이중 내부구조로 구성함으로써 이물질 등의 유입을 방지할 뿐만 아니라 알코올 성분의 발산을 억제할 수 있어 알코올 성분을 갖는 제품을 비롯한 내용물의 장기 보관이 가능하다. 또한 연결구멍을 통한 수용부에 의해 한 잔에 해당하는 일정량의 내용물을 컵 등에 항상 따를 수 있다. 따라서 이 연구는 앞서 설명한 바와 같은 종래기술의 문제점을 해결하여 보다 편리하고 실용적인 보틀을 만드는데 그 목적이 있다.

퍼지추론을 적용한 터널 조명제어시스템 (Tunnel Lighting Control System using Fuzzy Reasoning)

  • 이정은;최홍규
    • 전기학회논문지
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    • 제63권8호
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    • pp.1140-1145
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    • 2014
  • Tunnel lighting is composed of entrance zone, interior zone and exit zone by KS C 3703. We have to consider adaptation at entrance zone and exit zone lighting to prevent deteriorate visibility like black hole and white hole phenomenon. So External luminance, vehicle velocity and traffic volume should be considered in threshold zone lighting and vehicle speed and traffic volume should be considered in interior zone lighting. But existing tunnel lighting system is not good at visibility and economic because that is only controled by external luminance. So in this paper, We improve visibility and economic of tunnel lighting system using fuzzy reasoning according to external luminance, vehicle velocity, traffic volume.

마이크로 드릴링을 이용한 미세압출다이 가공에 관한 연구 (A study on the machining of micro-extruding die using micro-drilling)

  • 민승기;제태진;이응숙;이동주
    • 한국공작기계학회:학술대회논문집
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    • 한국공작기계학회 2003년도 춘계학술대회 논문집
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    • pp.161-166
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    • 2003
  • The micro-extruding die is a die for manufacturing of fine-wire by extruding process. The fine-wire made from the micro-extruding can be effectively applied to fields of semiconductor parts and medical parts etc. It is predicted that the demand of fine-wire in industry is more and more increasing. In this study $\phi50\mu m$ micro-drill which is coated with diamond is used for drilling of super micro-hole sizes. For the machining of taper parts of entrance and exit, drill having $\phi50\mu\textrm{mm}$ inclination angle $20^{\circ}$and angle $30^{\circ}$ is used. This is useful for anti tool-breakage and excessive too-wear in drilling process. After micro-drilling, the polishing process by diamond abrasive and polishing wood s carried out for increasing surface roughness.

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정사각 막냉각홀 내부에서의 열/물질전달 및 유동 특성 (I) - 분사비 및 레이놀즈 수 효과 - (Heat/Mass Transfer and Flow Characteristics Within a Film Cooling Hole of Square Cross Sections (I) - Effects of Blowing Ratio and Reynolds Number -)

  • 강승구;이동호;조형희
    • 대한기계학회논문집B
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    • 제26권7호
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    • pp.927-936
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    • 2002
  • An experimental study has been conducted to investigate the heat/mass transfer characteristics within a film cooling hole of square cross-section for various blowing ratios and Reynolds numbers. The experiments have been performed using a naphthalene sublimation method and the flow field has been analyzed by numerical calculation using a commercial code. A duct flow enters into a film cooling hole in a cross-direction. For the film cooling hole with square cross-section, it is observed that the reattachment of separated flow and the vortices within the hole enhance considerably the heat/mass transfer around the hole entrance region. The heat/mass transfer on the leading edge side of hole exit region increases as the blowing ratios decrease because the main flow induces a secondary vortex. Heat/mass transfer patterns within the square film cooling hole are changed little with the various Reynolds numbers.