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Wear Evaluation of Technical Polyethylene Terephthalate Yarn for Seat Belt Fabric
조대환,Cho, Dae-Hwan The Korean Fiber Society 2011 한국섬유공학회지 Vol.48 No.6
Friction is an important characteristic of the technical yarn. An understanding of this phenomenon is essential for controlling the properties of yarn in a manufacturing process. In order, to evaluate its wear behavior, the mechanical property and the friction coefficient of the yarn used in the seat belt fabric were measured. Different types of technical polyethylene terephthalate(PET) yarns were prepared by varying the yarn denier and the diameter of constituent filaments in the yarn (commonly used as denier per filament or DPF). This was done using a conventional spin-draw melt spinning machine. The yarn of a low DPF showed a higher friction coefficient than that of a high DPF. In a wear test of yarn-to-metal, the low denier yarns lost less strength than high denier yarns. To enhance the wear performance of the seat belt fabric on the basis of the yarn property, the mechanical strength and the wear property of the yarn were coincidently evaluated. As the strength of the seat belt fabric was estimated by using the results of the strength retention ratio after the wear test, a yarn type may be optimally suggested for better wear performance of the seat belt fabric.
입자영상유속계에 의한 기포붐의 Plume 거동특성에 관한 연구
조대환,오병주,이영호 해양환경안전학회 2000 海洋環境安全學會誌 Vol.6 No.1
Bubble boom may be a good alternative for the prevention of oil spill pollution due to its easy deployment and clean post-process tasks. The present work is focused on the experimental investigation of air bubble movement for the bubble boom by visualization and quantitative PIV measurements. Bubble plume was generated by adjusting the pressure of pressure vessel ranging 6.7 kpa to 14.7 kpa. The results showed at lower inlet velocity and higher supply air flow rate that bubble boom maintained its containing capability reasonably well up to the maximum containing limit.
조대환,강태진 한국섬유공학회 1996 한국섬유공학회지 Vol.33 No.10
Objective method to evaluate the fabric wrinkle properties has been studied by using Image Analysis System and the results has been companied with the AATCC Wrinkle Recovery Replicas. The image of each replica was obtained through image capturing system, then the noise in the image was reduced using Gaussian and Median filters. The parameters which well describe the quantity of fabric wrinkle were defined, and the objective evaluation of degree of wrinkle was obtained using those parameters. The grey intensity in the grey scale image was assumed to be the relative height of fabric wrinkle. Those defined parameters are the deviation of grey intensity at each profile of horizontal scanning of grey scale image, total numbers of peak points which the wave of profile are tumid at each profile, and the numbers of peak point in fixed uniform domains. Another parameter defined was the sharpness of wrinkle crimp. In the method of projecting grid phase analysis, the uniform grid on the replica surface was made first, then the gridded image of each replica was captured, and the projecting grid phase was analyzed. The 3-D shape of the wrinkle of each replica was reconstructed with the data obtained from the deformation ratios of grid lines. Based on the reconstructed 3-D information of each replica, the degree of wrinkle in the fabric was qualltified using the parameters defined to describe the degree of wrinkle. By examining the parameters obtained for each of the five replicas at the method of grey scale image and projecting grid phase analysis, the quantified wrinkle degrees among these five standard replicas show good relationship of logarithmic function.
일정간격을 갖는 사각 요철 주위의 유동가시화에 관한 연구
조대환,정하균,심의보 한국기계기술학회 2015 한국기계기술학회 학술대회논문집 Vol.2015 No.11
In physical engineering, the turbulent flow on the surface roughness is very important. The roughness of the surface changed the distance of the interval. The roughness coefficient occurred with increasing turbulence intensities was stronger. The turbulence intensity away from the roughness in the shape was zero. The variation of turbulence intensity at the experimental flow conditions change was not affected.
조대환,최주열,이철재 한국기계기술학회 2013 한국기계기술학회 학술대회논문집 Vol.2013 No.02
This experimental study was investigated the flow characteristics around staggered cooling tube arrays. A particle image velocimetry technique was employed to obtain detailed measurements at inlet-velocity-based three Reynolds numbers and the frequency characteristics of the wake were analyzed by using spectral analysis of the measured wake velocity signals. As a results, the flow exhibits strong Reynolds number dependence in the developing region but no significant Reynolds number effects are observed in the spatially periodic region.
조대환,최주열,이철희 해양환경안전학회 2010 해양환경안전학회 학술발표대회 논문집 Vol.2010 No.04
해안 지역은 해수의 운동에너지의 대부분은 해안에서 소산되며 이 과정에서 해안의 토사 등이 유실된다. 수면에 돌출된 방 파제에 비해 수중구조물은 해수의 유통을 가능하게 하고 해안선을 따라 해수순환을 가능케 한다. 이 연구에서는 해안 침식을 방지 기 능을 갖는 수중구조물을 수중장애물로 형상화 하고 후방의 흐름특성을 입자영상유속계를 이용하여 규명하였다. 그 결과 유선의 곡률 효과가 현저히 나타났으며 전단층 주위 유체의 유입 등의 영향으로 박리 전단층 내에서 커다란 와구조가 연속적으로 발생하였다. The coastal zone is a delicate and dynamic area in which the majority of a water kinetic energy is dissipated. These processes is subsequent transport of the beach materials. In comparison to emerged breakwaters, submerged structures permit the passage of some wave energy and in turn allow for circulation along the shoreline zone. This research is to examine the beach erosion prevention capability of submerged structure by laboratory model. The flow characteristics behind a submerged obstacle were experimentally investigated using the two-frame PIV(CACTUS 2000) system. Streamline curvature field behind the obstacle has been obtained by using the data of time-averaged mean velocity information. And the large eddy structure in the separated shear layer seems to have signification influence on the development of the separated shear layer.