• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.120-131
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• 2004

In this paper, we propose the method of a motion planning generation in which the movement of the 3-link leg subsystem is constrained to a slider-link and a singular posture can be easily avoided. The proposed method is the jumping control moving in vertical direction which mimics a cat's behavior. That is, it is jumping toward wall and kicking it to get a higher-place. Considering the movement from the point of constraint mechanical system, the robotic system which realizes the motion changes its configuration according to the position and it has several phases such as; ⅰ) an one-leg phase, ⅱ) in an air-phase. In other words, the system is under nonholonomic constraint due to the reservation of its momentum. Especially, in an air-phase, we will use a control method using state transformation and linearization in order to control the landing posture. Also, an iterative learning control algorithm is applied in order to improve the robustness of the control. The simulation results for jumping control will illustrate the effectiveness of the proposed control method.

• Journal of Ocean Engineering and Technology
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• v.31 no.1
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• pp.14-21
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• 2017

The erosion of solid particles in a pipe elbow was numerically investigated. A numerical procedure to estimate the sand erosion rate, as well as the particle motion, in the pipe elbow flow was introduced. This procedure was performed based on the combined empirical erosion model and computational fluid dynamics (CFD) analysis to consider the interaction between the particle motion and the eroded surface. The underlying turbulent flow on an Eulerian frame is described by the Reynolds averaged Navier-Stokes (RANS) equations with a $k-{\epsilon}$ turbulent model. The one-way coupled Eulerian-Lagrangian motion of the air flow and sand particles is employed to simulate the particle trajectories and particle-wall interactions on the pipe surfaces. The predicted CFD erosion magnitudes are compared with experimental data from pipe elbows. The erosion rate results do not reveal a good accordance between the simulation and experimental results. It seems that the CFD shows a slightly over-predicted erosion ratio.

• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.7-10
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• 2006

An experimental study has been conducted to quantitatively characterize the motion of neutrally buoyant particles in 2-dimensional Poiseuille flow through the micron-sized circular capillaries in the range of Re (Reynolds number) $\approx0.1\sim100$. $A{\mu}-PTV$ (Particle Tracking Velocimetry) system is adopted, which consists of a double-headed Nd:YAG laser, an epi-fluorescence microscope and a cooled CCD camera. Since high shear rate can be induced due to the scale effect even at low Re, it is shown that in micro scale neutrally buoyant particles in Poiseuille flow drift away from the wall and away from the center of the capillary. Consequently, particles accumulate at the equilibrium position of $0.52\sim0.64R$ with R being the radius of the capillary, which is analogous to that of tube flow in macro scale. There is a plateau in equilibrium position at small Re, while equilibrium position starts increasing at $Re\approx30$. The outermost edge of particle cluster is closer to the center of the capillary than that in previous studies due to low Re effect. The present study quantitatively presents characteristics of particle motion in circular capillaries. Furthermore, it is expected to give optimum factors for designing microfluidic systems that are to be used fur plasma separation from the blood.

• Progress in Medical Physics
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• v.30 no.3
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• pp.65-73
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• 2019

Purpose: We evaluated the motion-induced dosimetric effects on the field-in-field (FIF) technique for whole-breast irradiation (WBI) using actual patient organ motion data obtained from cine electronic portal imaging device (cine EPID) images during treatment. Materials and Methods: Ten breast cancer patients who received WBI after breast-conserving surgery were selected. The static FIF (SFIF) plan involved the application of two parallel opposing tangential and boost FIFs. To obtain the amplitude of the internal organ motion during treatment, cine EPID images were acquired five times for each patient. The outside contour of the breast (OCB) and chest wall (CW) contour were tracked using in-house motion analysis software. Intrafractional organ motion was analyzed. The dynamic FIF (DFIF) reflecting intrafractional organ motion incorporated into the SFIF plan was calculated and compared with the SFIF in terms of the dose homogeneity index (DHI_90/10) for the target and V₂₀ for the ipsilateral lung. Results: The average motion amplitudes along the X and Y directions were 1.84±1.09 mm and 0.69±0.50 mm for OCB and 1.88±1.07 mm and 1.66±1.49 mm for CW, respectively. The maximum motion amplitudes along the X and Y directions were 5.53 and 2.08 mm for OCB and 5.22 and 6.79 mm for CW, respectively. Significant differences in DHI_90/10 values were observed between SFIF and DFIF (0.94 vs 0.95, P<0.05) in statistical analysis. The average V₂₀ for the lung in the DFIF was slightly higher than that of the SFIF in statistical analysis (19.21 vs 19.00, P<0.05). Conclusion: Our findings indicate that the FIF technique can form a safe and effective treatment method for WBI. Regular monitoring using cine EPID images can be effective in reducing motion-induced dosimetric errors.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.203.2-203.2
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• 2007

• Proceedings of the KOSOMBE Conference
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• v.1994 no.05
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• pp.111-114
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• 1994

Three component velocity measurements with a refractive index-matching technique was used to investigate the flow characteristics in the atrio-pulmomnary (AP) Fontan connection under the steady flow condition. A strong swirl was observed in the extra-cardiac conduit and the main pulmonary artery (MPA). Maximum velocity magnitude in the MPA was about 0.8 m/s near the posterior wall at 6 liter/min. Swirling motion of the flow as well as geometric abnormalities of the connection are important factors in energy loss across Fontan connections.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10b
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• pp.508-510
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• 2001

건강과 장수에 관심이 많은 현대인에게 심장 질환은 꾸준히 증가하고 있다. 심장 질환을 측정하기 위하여 정확한 진단은 꼭 필요한 부분인데, 정확한 측정을 위해서 원하는 부분의 정확한 이미지 획득은 중요한 부분이다. 기존의 M-mode 이미지와 2자원 이미지는 각자의 장점과 단점을 가지고 있는데, 이 이미지들을 이용하여 정확한 결과를 얻기는 어려운 일이다. 본 논문에서는 기존의 두 이미지의 장점을 혼합하여 새로운 이미지를 생성하였다. 즉, Synthetic M-mode 이미지라고 불리는 새로운 좌심실 이미지는 사용자가 측정하고 싶은 부분의 이미지를 정확히 재 생성하여 보다 좋은 결과를 얻게 하고 있다.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.157-157
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• 2009

• Proceedings of the Korean Magnestics Society Conference
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• 2009.05a
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• pp.97-98
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• 2009

• Proceedings of the Korean Magnestics Society Conference
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• 2014.05a
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• pp.47-47
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• 2014