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디지털화상처리에 의한 음장의 가시화기법개발에 관한 연구
도덕희,김동혁,강동림 한국해양대학교 해양과학기술연구소 2000 硏究論文集 Vol.9 No.1
A new acoustic field visualization technique is introduced in this study. Small particles of which density is small enough to follow up the air flow are used for the noise field visualization. In order to quantify the noise, PIV(Particle Imaging Velocimetry) has been constructed. When the driving frequency is in the vicinity of the resonance frequency of the simplified 2-dimensional muffler system, an acoustic streaming is shown and of which velocity distribution is obtained through PIV technique. It is experimentally proved that the present technique is able to visualize and quantify the acoustic fields.
도덕희(Doh D. H),황태규(Hwang T.G),조용범(Cho Y.B),백태실(Baek T. S),편용범(Pyun Y.B.) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
3D-PTV measurement was conducted on the wake of a sphere. The Reynolds number is 1130 with the diameter(d=30mm). The measurement system consisted of three CCD cameras, an image grabber, an Ar-Ion laser and a host computer. An eigenvalue analysis was introduced for the analysis on the wake. Statistical turbulent properties were quantitatively clarified using the time-consecutive instantaneous three-dimensional vectors obtained by the 3D-PTV system. The spatial distributions of the sphere wake showed strong elations with spiral motions of the vortcies shedded from the surface of the sphere.
도덕희(D.H. Doh),조효제(H.J. Jo),조경래(K.R. Cho),문경록(K.R. Moon),이재민(J.M. Lee),황태규(T.G. Hwang) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
A new 3D-PTV algorithm (a Volume PTV) based upon a hybrid fitness function has been constructed. A coherency fitness function is introduced using the information of space and time to sort out the correct particle pairs between the two camera images. The measurement system consists of two-high-definition-cameras(1k × 1k), a Nd-Yag laser and a host computer. The developed algorithm has been employed to investigate the flow features of the cylinder wake. The Reynolds numbers with the cylinder diameter (d=10㎜) are 360, 720, 900 and 1260. Two-dimensional displacements of the particles of each camera’s image and neighbouring constraints were introduced to reduce the calculation loads. More than 10,000 instantaneous 3D vectors have been obtained by the constructed algorithm. The constructed algorithm could recover more than 80~90% of the particle numbers in the image.
도덕희(Doh D.H),조효제(Jo H.J),황태규(Hwang T.G),조경래(Cho K.R),편용범(Pyeon Y.B),조용범(Cho Y.B) 한국마린엔지니어링학회 2006 한국마린엔지니어링학회 학술대회 논문집 Vol.2006 No.-
Experimental analyses on the Hrdroelastic Flow-Structure Interactions on pulsed impinged jet is measured with the FSIMS(Flow-Structure Interaction Measurement System. The nozzle diameter is D=15㎜ and two major experiments have been carried out for the cases of the distance between the nozzle tip to the elastic wall is 6.0. The pulsed jets were controlled by a solenoid valve and were impinged onto an elastic plate (material: silicon, diameter: 350㎜, thickness: 0.5㎜, hardness: 15). The Reynolds numbers were 20,000 and 24,000 when the jets were impinged with the volume velocities. The results showed that the elastic plate moved slightly to the opposite direction of the jet direction at the time of valve opening. It has been shown that the vortices travelling over the surface of the wall made the elastic wall distorted locally due to a vector forces between rotating forces of the vortex and a newly-incoming flow.
남영미,정운혁,이대원,도시홍,이종환,김기동 동의대학교 기초과학연구소 1998 基礎科學硏究論文集 Vol.8 No.1
Five different methods were used to determine the trap depth E, the frequency factor s, and the kinetic order associated with the glow peaks in a LiF:Mg, Cu, Na, Si phosphor, which had been newly developed indigenously. The methods used were the initial-rise method, the total glow-peak method, the peak-shaped method, the variable heating-rate method, and the isothermal decay method. The peaks obeyed simple first-order kinetics following the model of Randal and Wilkins. The values of the trap depth E determined for peaks 1 to 4 were 0.69∼0.95, 0.71∼1.17, 1.77∼1.95 and 0.66∼1.22 eV with frequency-factor, s, values of 10^8∼10^11, 10^9∼10^11, 10^19∼10^20 and 10^8∼10^10 s^-1, respectively.
표준화상을 이용한 2차원 PIV 와 3차원 PIV 계측 및 성능비교검정
도덕희(Doh D. h),황태규(Hwang T.G),송주석(Song J. S),백태실(Baek.T.S),편용범(Pyun Y.B.) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Quantitative performance test on the conventional 2D-PLV and the hybrid hygular 3D-PIV(Stereosecpic PIV) was carried out. LES Data sets on an impinging jet which are provided on the webpage(http://www.vsj.or.jp/piv) for the PIV Standard project were used for the generation of vitual images. The generated virtual images were used for the 2D-PIV and 3D-PIV measurements. The measurement results showed that the results obtained by 2D-PIV on average values are clouser to the LES date than those those obtained by 3D-PIV, but turbulent properties obtained by 2D-PIV are largely anderestimated than those obtained by 3D-PIV.
Unified 2D and 3D cell-based high-throughput screening platform using a micropillar/microwell chip
Lee, D.W.,Doh, I.,Nam, D.H. Elsevier Sequoia 2016 Sensors and actuators. B Chemical Vol.228 No.-
A unified high-throughput screening (HTS) platform is proposed for both 2D and 3D cell culture models in a single chip platform. Comparison studies between well-established 2D models and in vivo-like 3D models are important to understand the underlying mechanisms of chemotherapeutic drugs. In the present unified platform, cells were seeded on top of micropillars and cultured with 2D or 3D cell culture protocols. Through a simple assembly of a micropillar/microwell chip, the cells on the micropillars were dipped into a microwell array, thus providing a one-step quick media exchange without additional washing steps. To demonstrate the utility of the proposed platform, drug-response assays for human lung cancer cells (A375) in both 2D and 3D models were done with 12 different compounds. Most of the IC<SUB>50</SUB> values of the drugs in the 3D model were higher than those in the 2D case; however, cancer cells exposed to a hypoxia-activated drug (TPZ) showed higher resistance in the 2D model. The proposed unified platform represents an opportunity to achieve effective and reliable cell assessment standards by linking various model-based studies with biochemical and pharmaceutical applications.
도덕희(Doh D. H),김동혁(Kim D.H),조용범(Cho Y. B),편용범(Pyun Y. B) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Turbulent properties of the wake of a circular cylinder was measured. The diameter of the cylinder is 10mm and the Reynolds number is 420. A new 3D-PTV system was constructed and a genetic algorithm (GA) was introduced in order to increase the number of instantaneous three-dimensional velocity vectors. In the GA, two fitness functions were introduced in order to enhance the correspondences of the particles. The measurement system consists of three CCD cameras, Ar-ion laser, an image grabber and a host computer. More than 3000 instantaneous three-dimensional velocity vectors were obtained by the system. The results measured by the constructed 30-PTV system showed Quite good agreements with others.
Doh, D. H.,Jo, H. J.,Hwang, T. G.,Koo, B. Y.,Takei, M.,Tanaka, T.,Uemura, T. Taylor Francis 2009 Chemical engineering communications Vol.196 No.12
<P> An adaptive stereoscopic-PIV system has been constructed for flow analyses around a cylinder body (length = 60 mm, diameter = 10 mm, polystyrene). The body is floated by the swirling flows in a vertical pipe with a length of 1100 mm and an inner diameter of 100 mm. Four optical sensors (LEDs) were installed onto the pipe wall to detect the posture of the cylinder body. The constructed stereoscopic-PIV system is activated by the signals of the optical sensors when the cylinder is in the upright posture. The measurement system consists of two cameras, a Nd-Yag laser, and a host computer. Flow characteristics around the floating cylinder body and the motional characteristics of the body itself are investigated when the body is in the upright posture. It has been verified that the motion of the floating cylinder becomes stable when the azimuthal velocity component (W component) of the swirl flow is maintained at stable states.</P>