• 제목/요약/키워드: Camera Geometry

검색결과 202건 처리시간 0.022초

An Experimental Study of Instability Mode Analysis in a Model Gas Turbine Combustor (모형 가스터빈 연소기에서의 연소 불안정 모드 분석에 관한 실험적 연구)

  • Lee, Jang-Su;Kim, Min-Ki;Park, Sung-Soon;Lee, Jong-Guen;Yoon, Young-Bin
    • Journal of the Korean Society of Combustion
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    • 제15권1호
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    • pp.12-21
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    • 2010
  • The main objective of this study was investigation of combustion instability characteristics in a lean partially premixed gas turbine dump combustor. Dynamic pressure transducers were located on combustor and inlet section to observe combustion pressure oscillation and difference at each measurement places. Also flame shape and $CH^*$ chemiluminescence were measured using a high speed ICCD camera. The combustor length was varied in order to have different acoustic characteristics from 800 to 1090 mm. The first section of this paper shows the stability map in model gas turbine combustor. And the effects of combustor length, mixture velocity in the mixing section and equivalence ratio were studied by the pressure perturbation and heat release oscillation. Also, the instability frequency and mode analysis were studied in last two sections. We observed two dominant instability frequencies in this study. Lower frequencies were obtained at lower equivalence ratio region and it was associated with a fundamental longitudinal mode of combustor length. Higher frequencies were observed in higher equivalence ratio conditions. It was related to secondary longitudinal mode of combustor and mixing section. In this instability characteristics, pressure oscillation of mixing section part was larger than pressure oscillation of combustor. As a result, combustion instability was strongly affected by acoustic characteristics of combustor and mixing section geometry.

PHOTOMETRIC STUDY OF A W UMa TYPE CONTACT BINARY AH CNC (W UMa형 접촉쌍성 AH Cancri에 대한 측광학적 연구)

  • 윤재혁;김호일;이재우;김승리;성언창;경재만;오갑수
    • Journal of Astronomy and Space Sciences
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    • 제20권4호
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    • pp.249-260
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    • 2003
  • CCD photometric observations of a W UMa type contact binary AH Cnc were performed for ten nights from December 1998 to May 1999 using a PM512 CCD camera and BVI filters attached to the 61㎝ reflector at Sobaeksan Optical Astronomy Observatory. New BVI light curves were analyzed with contact Mode 3 of the Wilson-Devinney binary model. We obtained photometric solutions and Roche geometry of this binary system. Through the analysis of the (O-C) diagram with all times of minimum light published so far and including hour's secular variations of orbital period and the mass transfer rate were calculated.

Highly Dense 3D Surface Generation Using Multi-image Matching

  • Noh, Myoung-Jong;Cho, Woo-Sug;Bang, Ki-In
    • ETRI Journal
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    • 제34권1호
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    • pp.87-97
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    • 2012
  • This study presents an automatic matching method for generating a dense, accurate, and discontinuity-preserved digital surface model (DSM) using multiple images acquired by an aerial digital frame camera. The proposed method consists of two main procedures: area-based multi-image matching (AMIM) and stereo-pair epipolar line matching (SELM). AMIM evaluates the sum of the normalized cross correlation of corresponding image points from multiple images to determine the optimal height of an object point. A novel method is introduced for determining the search height range and incremental height, which are necessary for the vertical line locus used in the AMIM. This procedure also includes the means to select the best reference and target images for each strip so that multi-image matching can resolve the common problem over occlusion areas. The SELM extracts densely positioned distinct points along epipolar lines from the multiple images and generates a discontinuity-preserved DSM using geometric and radiometric constraints. The matched points derived by the AMIM are used as anchor points between overlapped images to find conjugate distinct points using epipolar geometry. The performance of the proposed method was evaluated for several different test areas, including urban areas.

A study of ultra-precision interrupt machining for an polygon mirror (초정밀 단속 절삭을 이용한 다각형 미러의 절삭특성에 관한 연구)

  • Park, Soon-Sub;Lee, Ki-Young;Kim, Hyoung-Mo;Lee, Jae-Seol
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • 제6권3호
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    • pp.65-70
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    • 2007
  • Generally, the core component of small precise optical device demands high accuracy of manufacturing processes. Although, the geometry of it is simple, the manufacturing technique to materialize is categorized as the ultra-precision machining and it must be done with the specialized machines and by the trained operator. Typical examples of small precise optical device are laser printer and phone camera. As a core part of laser printer, polygon mirror is used in laser scanning unit(LSU). It couldn't be fabricated with conventional machine but specified machine for polygon mirror machining. In this study, Polygon mirror with 16 surfaces was manufactured in the process of ultra-precision fly-cutting with Al material and investigated optimum machining conditions in terms of feedrate, pitch per cycle and depth of cut. Owing to process of polishing has bad influence on reflection angle, surface roughness, $R_{max}$=10nm, and form error, $Ra={\lambda}/10({\lambda}=632nm)$, are prerequisites for polygon mirror.

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A Study on the Flow Field Characteristics of Air Induction System for Reducing the Signal-to-Noise in the MAFS Output

  • Yoo, Seoung-Chool
    • Journal of ILASS-Korea
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    • 제5권1호
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    • pp.49-57
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    • 2000
  • This study presents the flow visualization results, velocity and turbulence intensity measurements made within an air filter cover and entry region of a mass air flow sensor (MAFS) which is used in an induction system of 3.8L engine. Flow structure in two air filter cover assemblies were examined. The first was a clear plastic replica of the production cover while the second was a modified clear plastic cover with a geometry configured to reduce fluctuations. High speed flow visualization and laser doppler velocimetry (LDV) systems were used to reveal and analyze the flow field characteristics encountered in the sensor design process under steady flow conditions. A 40-watt copper vapor laser was used as a light source. Its beam is focused down to a sheet of light approximately 1.5mm thick. The light scattered off the particles was recorded by a 16mm high speed rotating prism camera at 5000 frames per second. A comparison of the flow patterns and LDV measurements in the original and modified air filter covers is presented to illustrate the controlling effect of the cover design on the turbulence structure formation near the bypass and on the sensor output signal. In both axial and radial planes of the main passage it was found that the turbulence flow pattern is remarkably influenced by the air filter cover and main passage configuration.

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Effect of channel hight on Bubble growth under Saturated Nucleate Pool Boiling for Various Channel Height using Heater with Artificial Cavity (인공 캐비티를 가진 히터를 이용한 가열면의 채널 높이가 풀비등시 기포성장에 미치는 영향에 대한 기초연구)

  • Kim, Jeong-Bae;Park, Moon-Hee;Jeon, Woo-Cheol
    • Journal of the Korean Solar Energy Society
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    • 제30권5호
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    • pp.93-99
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    • 2010
  • Nucleate pool boiling experiments with constant heat flux condition were performed using pure R113 for various channel heights under saturated pool condition. A circular heater of 1mm diameter, with artificial cavity in the center, fabricated using MEMS technique and the high-speed controller were used to maintain the constant heat flux. Images of bubble growth were taken at 5,000 frames per second using a high-speed CCD camera. The bubble geometry was obtained from the captured bubble images. The effects of channel height on the bubble growth behaviors were analyzed as dimensional scales for the initial and thermal growth regions. The parameters for the bubble growth behaviors were bubble radius, bubble growth rate, and bubble shapes. These phenomena require further analysis for various surface angles, but this study will provide good experimental data with constant heat flux boundary condition for such works.

Experimental and Numerical Study of Thermal Properties about various forms of Micro-heater (다양한 형상을 갖는 마이크로 히터의 열특성에 관한 실험 및 전산해석적 연구)

  • Kim, Jin-Woo;Kim, Jae-Choon;Lee, Jun-Yub;Chung, Jin-Taek
    • Proceedings of the KSME Conference
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    • 대한기계학회 2008년도 추계학술대회A
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    • pp.1957-1962
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    • 2008
  • As a field of MEMS, micro-heater fabricated by Au is being introduced and developed in recent years. Previous studies about thermal properties of various forms of micro-heater were not sufficient. In this work, numerical and experimental analysis of the heat generation and the temperature distribution of micro-heater packages for 8 different geometric cases were studied. We fabricated a micro-heater package with silicon wafer, on which Cr/Au layer was laminated before 8 geometric forms of micro-heater were patterned. In each cases, temperature distribution was measured with IR thermal camera. According to the experimental results, which show a good agreement with the results analyzed by CFD, it was found that at 0.5W, the temperature of micro-heater chip which contained $20000{\mu}m$-long, serpentine shaped micro-heater was elevated to a relatively high temperature of $78^{\circ}C$ Consequently, we proposed a geometry of micro-heater which has effective thermal characteristics.

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Characterization of the internal flow and fuel spray from an impinging flow nozzle (노즐분공내 유체충돌이 있는 디젤노즐의 유동 및 분무특성 연구)

  • Ha, Seong-Eop;Kim, Heung-Yeol;Gu, Ja-Ye;Ryu, Gu-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • 제21권12호
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    • pp.1635-1646
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    • 1997
  • The nozzle length to diameter ratio of real diesel nozzles is about 2-8 which is not long enough for a fully developed and stabilized flow. The characteristics of the flow such as turbulence at the nozzle exit which affect the development of the spray can be enhanced by impinging the flow inside nozzle. The flow details inside the impinging nozzles have been investigated both experimentally and numerically. The mean velocities, the fluctuating velocities, and discharge coefficients in the impinging inlet nozzles, round inlet nozzle, and sharp inlet nozzle were obtained at various Reynolds number. The developing feature of the external spray were photographed by still camera and the droplet sizes and velocities were also measured by laser Doppler technique. The spray angle was greater and the droplet sizes near the spray axis were smaller with the impinging flow inside nozzle.

3D Reconstruction Algorithm using Stereo Matching and the Marching Cubes with Intermediate Iso-surface (스테레오 정합과 중간 등위면 마칭큐브를 이용한 3차원 재구성)

  • Cho In Je;Chai Young Ho
    • Journal of KIISE:Software and Applications
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    • 제32권3호
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    • pp.173-180
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    • 2005
  • This paper proposes an effective algorithm that combines both the stereo matching and the marching cube algorithm. By applying the stereo matching technique to an image obtained from various angles, 3D geometry data are acquired, and using the camera extrinsic parameter, the images are combined. After reconstructing the combined data into mesh using the image index, the normal vector equivalent to each point is obtained and the mesh smoothing is processed. This paper describes the successive processes and techniques on the 3D mesh reconstruction, and by proposing the intermediate iso- surface algorithm. Therefore it improves the 3D data instability problem caused when using the conventional marching cube algorithm.

Experimental Study of Heating Surface Angle Effects on Single Bubble Growth

  • Kim, Jeong-Bae;Kim, Hyung-Dae;Lee, Jang-Ho;Kwon, Young-Chul;Kim, Jeong-Hoon;Kim, Moo-Hwan
    • Journal of Mechanical Science and Technology
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    • 제20권11호
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    • pp.1980-1992
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    • 2006
  • Nucleate pool boiling experiments were performed using pure R11 for various surface angles under constant heat flux conditions during saturated pool boiling. A 1-mm-diameter circular heater with an artificial cavity in the center that was fabricated using a MEMS technique and a high-speed controller were used to maintain the constant heat flux. Bubble growth images were taken at 5000 frames per second using a high-speed CCD camera. The bubble geometry was obtained from the captured bubble images. The effects of the surface angle on the bubble growth behavior were analyzed for the initial and thermal growth regions using dimensional scales. The parameters that affected the bubble growth behavior were the bubble radius, bubble growth rate, sliding velocity, bubble shape, and advancing and receding contact angles. These phenomena require further analysis for various surface angles and the obtained constant heat flux data provide a good foundation for such future work.