• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.7 s.262
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• pp.644-652
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• 2007

In this paper, a technique of simultaneously measuring the velocity and the temperature in micro-scale flow is proposed. This method uses particle tracking velocimetry (PTV) for measuring the velocity and laser induced fluorescence (LIE) for measuring the temperature. To measure the accurate velocity and temperature, images for PTV and for LIE are separated by using two light sources and a shutter which is synchronized with a camera. By using only one camera, measurement system can be simplified and the error from complicate optical system can be minimized. Error analyses regarding the concentrations of fluorescent dye and particle and the light source fluctuation are also conducted. It is found that the error of the temperature and the velocity highly depends on the concentration of fluorescent particles which are used for PTV. This technique is applied to the simultaneous measurement of the velocity and the temperature in the electrokinetic flow. It is found that the velocity and temperature vary with the electric field strength and the concentration of electrolyte.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.13-18
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• 1998

The practical use of the particle image velocimetry(PIV), a whole-field velocity measurement method, requires the use of fast, reliable, computer-based methods for tracking velocity vectors. The full search block matching, the most widely studied and applied technique both in area of PIV and Image Coding and Compression, is computationally costly. Many less expensive alternatives have been proposed mostly in the area of Image Coding and Compression. Among others, TSS, NTSS, HPM are introduced for the past PIV analysis, and found to be successful. But, these algorithms are based on small dynamic range, 7 pixels/frame in maximum displacement. To analyze the images with large displacement, Even and Odd field image separation and a simple version of multi-resolution hierarchical procedures are introduced in this paper. Comparison with other algorithms are summarized. A Results of application to the turbulent backward step flow shows the improvement of new algorithm.

• Fire Science and Engineering
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• v.21 no.2 s.66
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• pp.64-73
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• 2007

The absorption characteristics of hazardous materials onto human body and defense mechanism differ from each other region within the respiratory tracts, thus adverse health effects of inhaled smokes are associated with not only the concentration but also the location of the particles deposited. In this work, the deposition fraction per surface area and the deposition sites of the smoke particles in human respiratory tracts for each rest and light exercise conditions together with oral and nasal breathing were calculated by using segmental volume tracking method. The results would be used for deriving the amount of absorption of hazardous materials onto human body, thus contribute to the health risk assessments of inhaled fire smokes.

• Journal of Power Electronics
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• v.19 no.4
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• pp.835-845
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• 2019

This paper presents a robust-optimal control strategy to improve the output-voltage error-tracking and control capability of a DC-DC boost converter. The proposed strategy employs an optimized Fractional-order Proportional-Integral (FoPI) controller that serves to eliminate oscillations, overshoots, undershoots and steady-state fluctuations. In order to significantly improve the error convergence-rate during a transient response, the FoPI controller is augmented with a pre-stage nonlinear error-modulator. The modulator combines the variations in the error and error-derivative via the signed-distance method. Then it feeds the aggregated-signal to a smooth sigmoidal control surface constituting an optimized hyperbolic secant function. The error-derivative is evaluated by measuring the output-capacitor current in order to compensate the hysteresis effect rendered by the parasitic impedances. The resulting modulated-signal is fed to the FoPI controller. The fixed controller parameters are meta-heuristically selected via a Particle-Swarm-Optimization (PSO) algorithm. The proposed control scheme exhibits rapid transits with improved damping in its response which aids in efficiently rejecting external disturbances such as load-transients and input-fluctuations. The superior robustness and time-optimality of the proposed control strategy is validated via experimental results.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.74-85
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• 2016

For the assessment of seawater exchange rates in Danghangpo bay, Dangdong bay, Wonmun bay, Gohyunsung bay, and Masan bay, which are small-scale inner bays of Jinhae bay, an EFDC model was used to reproduce the seawater flow of the entire Jinhae bay, and Lagrange (particle tracking) and Euler (dye diffusion) model techniques were used to calculate the seawater exchange rates for each of the bays. The seawater exchange rate obtained using the particle tracking method was the highest, at 60.84%, in Danghangpo bay, and the lowest, at 30.50%, in Masan bay. The seawater exchange rate calculated based on the dye diffusion method was the highest, at 45.40%, in Danghangpo bay, and the lowest, at 34.65%, in Masan bay. The sweater exchange rate was found to be the highest in Danghangpo bay likely because of a high flow velocity owing to the narrow entrance of the bay; and in the case of particle tracking method, the morphological characteristics of the particles affected the results, since once the particles get out, it is difficult for them to get back in. Meanwhile, in the case of the Lagrange method, when the particles flow back in by the flood current after escaping the ebb current, they flow back in intact. However, when a dye flows back in after escaping the bay, it becomes diluted by the open sea water. Thus, the seawater exchange rate calculated based on the dye diffusion method turned out to be higher in general, and even if a comparison of the sweater exchange rates calculated through two methods was conducted under the same condition, the results were completely different. Thus, when assessing the seawater exchange rate, more reasonable results could be obtained by either combining the two methods or selecting a modeling technique after giving sufficiently consideration to the purpose of the study and the characteristics of the coastal area. Meanwhile, through a comparison of the degree of closure and seawater exchange rates calculated through Lagrange and Euler methods, it was found that the seawater exchange rate was higher for a higher degree of closure, regardless of the numerical model technique. Thus, it was deemed that the degree of closure would be inappropriate to be used as an index for the closeness of the bay, and some modifications as well as supplementary information would be necessary in this regard.

• Journal of the Korean Society for Marine Environment & Energy
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• v.16 no.4
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• pp.255-262
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• 2013

The boltzmann equation is based on the particle distribution function while the Navire-Stokes equation based on the continuum theory. In order to simulate free surface flow, this paper used the Lattice Boltzmann Method of which is the discretized form. The detail study on the characteristics of the Lattice Boltzmann Method for the free surface simulation was investigated. The developed code was validated with the traditional dam breaking problem by tracking the front position of the water. A basic roles of density functions in the Lattice Boltzmann Method is discussed. To have an engineering applications, the simulation is also conducted the free surface behavior with an arbitrary wall geometry.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.635-641
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• 2016

Because of prohibitive data storage requirements in large-scale simulations, the memory problem is an obstacle for Monte Carlo (MC) codes in accomplishing pin-wise three-dimensional (3D) full-core calculations, particularly for whole-core depletion analyses. Various kinds of data are evaluated and quantificational total memory requirements are analyzed based on the Reactor Monte Carlo (RMC) code, showing that tally data, material data, and isotope densities in depletion are three major parts of memory storage. The domain decomposition method is investigated as a means of saving memory, by dividing spatial geometry into domains that are simulated separately by parallel processors. For the validity of particle tracking during transport simulations, particles need to be communicated between domains. In consideration of efficiency, an asynchronous particle communication algorithm is designed and implemented. Furthermore, we couple the domain decomposition method with MC burnup process, under a strategy of utilizing consistent domain partition in both transport and depletion modules. A numerical test of 3D full-core burnup calculations is carried out, indicating that the RMC code, with the domain decomposition method, is capable of pin-wise full-core burnup calculations with millions of depletion regions.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1845_1846
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• 2009

본 논문에서는 특징 벡터를 이용한 강인한 물체 추적 방법을 제안한다. 먼저, 초기 이동 물체의 움직임 영역을 추출하고, KLT알고리즘을 입력 영상에 적용시켜 특징 벡터들을 추출한다. 초기 추출된 이동 물체의 움직임 영역에 추출된 특징 벡터를 적용시켜 1차 정규화 한다. 그 후, RGB 칼라모델과 HSI 칼라모델을 이용하여 이동 물체에 대한 Blob 영역을 설정하고 설정된 Blob 영역에 대해 1차 특징벡터를 Snake 알고리즘으로 동정하여 2차 정규화 과정을 마무리 한다. 최종 정규화 된 특징 벡터를 Particle filter에 입력 데이터로 이용하여 이동 물체를 추적 한다. 마지막으로, 복잡한 환경에서 실험을 통해 그 응용 가능성을 증명한다.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.79-88
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• 2012

Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.140-143
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• 1997

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding, the normal pressure and the contact surface expansion are selected as process parameters governing the bonding condition. The critical pressure required for the bonding at the interface is obtained by solving a "local extrusion" using a slip line meyhod. A viscoplastic finite element method is used to analyze the steady state extrusion process. The boundary profile of bi-metal rod is predicted by tracking a particle path adjacent to interface surface. The variations of contact surface area and the normal pressure along the interface profile are predicted and compared to those by experiments.