• Journal of the Korean Magnetics Society
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• v.10 no.3
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• pp.143-148
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• 2000

We made MnZn ferrites by conventional ceramic processing method and observed magnetic domain structures by Bitter method. The Bitter method revealed that the domain structure of the surface is stripe-like. When a magnetic field was applied, the domain wall motion was observed during the initial magnetization process and the irregular motion of domain wall or domain rotation was observed near the saturation magnetic field (90∼120 Oe).

• Journal of Chest Surgery
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• v.33 no.10
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• pp.806-811
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• 2000

Background : The authors have modified the method of Ravitch technique. Material and Method ; This technique was applied to 6 patients out of 18 patients who underwent corrective surgery from May 1987 to July 1999. The technique is quite different from that of Ravitch. We did not divide the intercostal muscle bundles from the laterals of sternum and the Akin's struts were placed retrosternally crossing the chest horizontally to prevent flail motion during immediate post-operative period and retraction of the sternum afterwards. Anterior sternal osteotomy instead of the posterior one was performed for the latest 3 cases which made operative procedure more simple and easy. The struts were removed one year later. Result : Compared to the hospital stay of the patients who received standard Ravitch method that of the six cases who received our modification was definitely shortened from 13.1 days to 8.3 days(p<0.0000). Flail motion was not noted in any patient and chest wall stability was obtained more easily with this technique. Conclusion : Our modification is recommendable for correction of funnel chest in regards to shorter operation time better chest wall stability shorter hospital stay and less complication.

• International Journal of Control, Automation, and Systems
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• v.2 no.2
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• pp.238-246
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• 2004

In displaying a virtual wall using a passive haptic device equipped with passive actuators such as electric brakes, unsmooth motion frequently occurs. This undesirable behavior is attributed to time delay due to slowness in the virtual environment update and force approximation due to the inability of a brake to generate torque in arbitrary directions. In this paper a new control scheme called direct control is proposed to achieve smooth display on the wall-following task with a passive haptic device. In direct control, brakes are controlled so that the normal component of a resultant force at the end-effector vanishes, based on the force analysis at the end-effector of the passive haptic device using the passive FME (Force Manipulability Ellipsoid). Various experiments have been conducted to verify the validity of the direct control scheme with a 2-link passive haptic system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.188-189
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• 2013

The purpose of this research is to comprehend experimentally the characteristic of human dynamic load and provide the result as basic data to suggest a valid impact-resistance evaluation method. Human motions exerting dynamic load are classified to 3 types. Selecting 3 ranks of motion strength, 3 ranks of load plane stiffness (A:20kN/cm, B:4.7kN/cm, C:2.2kN/cm), and 30 male grownup inspectors in their twenties, load was measured when they applied force on load plane. Result of this research is as follows: (1) Human dynamic load has different nature from object collision in the highest load ratio depending on the load plane stiffness and action time (2) The highest load ratio for each motion was 10.06 for kicking, 4.44 for hitting with shoulder, and 5.58 for fist blow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1327-1336
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• 2001

The structural modes driven by the low wave-number components of smooth elastic wall pressure provide a relatively weak coupling between the flow and the wall motion. If the elastic thin plate has any resonant mode whose wave-number of resonance coincides with $\omega$/U$\sub$c/, the power will be transmitted to those modes of vibration by the flows. We examine the problem in which the elastic thin plate is subject to pressure fluctuations under turbulent boundary layer. Measurements are presented of the frequency spectra of the near- and far-field pressures and radiated sound contributed by the various wave modes of the thin elastic plate. Dispersion equation for wave motions of elastic plate is used to investigate the effect of bending waves of relatively low wave number on radiated sound. The low wave-number motion of elastic plate is observed to have much less influence on the low-frequency energy of wall pressure fluctuations than that of the rediated sound. High amplitude events of the wall pressure are observed to weakly couple with high-frequency energy of radiated sound for case of low tension applied to the plate. The sound source localization is applied to the measurement of radiated sound by using acoustic mirror system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.3
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• pp.392-404
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• 1997

The flow induced by the oscillatory motion of a solid body is important in a number of practical problems. As the solid boundary oscillates harmonically, there is steady streaming motion invoked by the Reynolds stresses, which could cause extensive migration of the fluid during a period of fluid motion. We here analyzed the flow in a square cavity with an oscillating top wall for the parameters which make the time derivatives and the convective terms equally important in the entire cavity flow. The full Navier-Stokes equations are solved by the second-order time accurate Momentum Coupling Method which is devised by the authors. The particular numerical scheme does not need subiteration at each time step which is usually a required process to calculate the incompressible Navier-Stokes equations. The effect of two parameters, the Reynolds number and the frequency parameter, on the oscillatory flow has been investigated.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.99-102
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• 2002

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank The SOLA-VOF (Volume of fluid) method uses a fixed mesh for calculating the motion of flow and the free-surface. This Eulerian approach enables the VOF method to use only a small amount of computer memory for simulating sloshing problems with complicated free-surface contours. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the locating of the free-surface filling any some fraction of cells with fluid. Using SOLA-VOF method, the study describes visualization about simulation of the sloshing of flows and damping effect by baffle. Translation and pitching motion of the forms have been investigated The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Baffle was Installed to reduce the force on the wall by sloshing of flows. Damping effects was extensively expressed under the conditions such as baffle shape and position.

• Journal of the Korean Society of Visualization
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• v.9 no.1
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• pp.17-19
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• 2011

The bubble oscillations play an important role in ultrasonic cleaning processes. In the ultrasonic cleaning of semiconductor wafers, the cleaning process often damages micro/nano scale patterns while removing contaminant particles. However, the understanding of how patterns in semiconductor wafers are damaged during ultrasonic cleaning is far from complete yet. Here, we report the observations of the motion of bubbles that induce solid wall damage under 26 kHz continuous ultrasonic waves. We classified the motions into the four types, i.e. volume motion, shape motion, splitting or jetting motion and chaotic motion. Our experimental results show that bubble oscillations get unstable and nonlinear as the ultrasonic amplitude increases, which may exert a large stress on a solid surface raising the possibility of damaging microstructures.

• Journal of the Korean Society of Safety
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• v.19 no.3 s.67
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• pp.108-117
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• 2004

Dynamic analysis method is Presented for analyzing rectangular liquid storage structures excited by horizontal and vertical ground motions. The irrotational motion of invicid and incompressible ideal fluid in rigid rectangular liquid storage structures subjected to horizontal and vertical ground motions and the motion of fluid induced by structural deformation are expressed by analytic solutions. Analysis methods are obtained by applying analytic solutions of the fluid motion to finite element equation of the structural motion. The fluid-structure interaction effect is reflected into the coupled equation as added fluid mass matrix. The free surface sloshing motion, hydrodynamic pressure acting on the wall and structural behavior due to horizontal and vertical ground motions are obtained by the presented method.

• Journal of Biomedical Engineering Research
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• v.39 no.4
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• pp.153-160
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• 2018

3D ultrasound bladder scanners are getting popular in hospitals for the patients with bladder dysfunction. A current bladder scanner adopts a mechanical scan to acquire 3D images and requires two motors and complicated mechanical devices. In this paper, we propose a new ultrasound bladder scanner using hand-motion scan. Instead of two motors and mechanical devices, it has a motion sensor to record transducer positions during hand-motion scan. The experiments with a bladder phantom and volunteers showed similar measurement accuracy to a conventional 3D ultrasound bladder scanner. We expect that the proposed method will reduce the cost and size of the bladder scanner.