• Journal of the Korean Society of Physical Medicine
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• v.6 no.4
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• pp.465-473
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• 2011

Purpose : This study was to evaluate gait velocity and muscle activity on 3 different gait conditions in elderly women. Methods : There were one group was 20's generation(n=12), and the other group was over 60's generation (n=12). The velocity of gait was analysed for using the Footscan system, EMG(MP150) for muscle activity. Subjects were measured 3 gait condition(normal, obstacle-10cm, dual obstacle-10cm. Measured values were used by the independent t-test for analysing between groups, and repeated measurement of ANOVA for analysing within group. Results : The results were as follow: velocity and acticities of lower 4 muscles were significantly differences in experimental group. In control group, there were not significantly differences. Contrast-groups were significantly differences of velocity(obstacle, dual obstacle), muscle activities(soleus-dual obstacle, hamstring-all). Conclusion : These results indicate that elderly people are reduced gait ability in dual task, and obstacle gait. So Elderly women need to training obstacle/dual gait for preventing falling.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.127-130
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• 1997

Phase-contrast(PC) methods have been used for quantitative measurements of velocity and volume flow rate. In addition, phase contrast cine magnetic resonance imaging (MRI) combines the flow dependent contrast of PC MRI with the ability of cardiac cine imaging to produce images throughout the cardiac cycle. In this method, the through-plane velocity has been encoded generally. However, the accuracy of the flow data can be reduced by the effect of flow direction, finite slice thickness, resolution, pulsatile flow pattern, and so on. In this study we calculated the error caused by misalignment of tomographic plane and flow directon. To reduce this error and encode the velocity for more complex flow, we suggested 3 directional velocity encoding method.

• Water for future
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• v.16 no.4
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• pp.237-243
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• 1983

This study examines the dilution-dispersion phenomen in the main stream when a polluted branch stream flows into it. A hydraulic model was used for it. As the discharge of the main stream and the branch one were changing, the qualitative dispersion, the stream regimen, the velocity of the flow and the hydraulic properties were observed. It was found that the faster the velocity was and the greater the flow discharge ratio was, the more dilution-dispersion phenomenon occurred. And as the velocity of the flow was increasing, so was the longitudinal dispersion velocity. But the transverse dispersion velocity was relatively reduced. Therefore, it is concluded that the dispersion by the distribution of velocity is increased.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1465-1469
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• 2009

Darrieus wind turbine blade is one of the vertical wind power system in which the lift of blade is used. In the calculation of wind power for the type of that, the multiple streamtubes method is known as an effective method. But it has big difference in the region of higher tip speed ratio because the incoming air velocity is used in the calculation of lift. The incoming air velocity is reduced from inlet to outlet continually by transferring energy to the wind blade. In this study, the air velocity on the blade, which is called blade velocity, is obtained with newly developed algorithm and used to determine the lift. And it is verified that applying blade velocity on the lift calculation cause the power prediction to improve dramatically in the region of higher tip speed ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.1010-1018
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• 2009

An inertial navigation system for pedestrian position tracking is proposed, where the position is computed using inertial sensors mounted on shoes. Inertial navigation system(INS) errors increase with time due to inertial sensor errors, and therefore it needs to reset errors frequently. During normal walking, there is an almost periodic zero velocity instance when a foot touches the floor. Using this fact, estimation errors are reduced and this method is called the zero velocity updating algorithm. When implementing this zero velocity updating algorithm, it is important to know when is the zero velocity interval. The gait states are modeled as a Markov process and each state is estimated using the hidden Markov model smoother. With this gait estimation, the zero or nearly zero velocity interval is more accurately estimated, which helps to reduce the position estimation error.

• Journal of Drive and Control
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• v.15 no.4
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• pp.55-60
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• 2018

Force-controlled electro-hydrostatic actuators have to exhibit high backdrivability, to quickly compensate for force control errors caused by externally disturbed rod movement. To obtain high backdrivability, the servomotor for driving the hydraulic pump, should rotate exactly to such a revolution to compensate for force control errors, compressing or decompressing cylinder chambers. In this study, we proposed a modified velocity control structure, including a robust internal-loop compensator (RIC)-based velocity controller, for the servomotor to improve backdrivability of a force-controlled EHA. Performance improvement was confirmed experimentally, wherein sinusoidal velocity disturbance was applied to the force-controlled EHA, with constant reference input. Its dynamic force control errors reduced effectively, with the proposed control scheme, compared to test results with a conventional motordriver, for motor velocity control.

• Advances in concrete construction
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• v.15 no.5
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• pp.313-319
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• 2023

In this paper, the analytic solution has been found by using truncation approach. With the help of suitable substitution, different physical parameters are yielded in their non-dimensional form. The governing boundary layer partial differential equations are reduced to a set of ordinary ones by using appropriate similarity transformations. The velocity profile across the domain have also been taken into account. The effect normal velocity profiles buoyancy parameter, slip parameter, shrinking parameter, Casson fluid parameter on the heat profile. It is found that the normal velocity profiles rise with the buoyancy parameter and for the slip parameter. It is observed that the normal velocity profile decreases with the increase of shrinking parameter. The reverse behiour is found for the Casson fluid parameter. The results are numerically computed, analyzed and discussed. For the efficiency of present model, the results are compared with earlier investigations.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.4
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• pp.3970-3979
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• 1975

On account of the development of the high speed internal combustion engines, several methods for increasing burning velocity has been investigated lately. Installation of a squash area on a cylinder head is one of the simple and practical method to induce the strong tubulant flow of air-fuel mixtureinto a combustion chamber. In this study, a four-stroke engine used for agricultural purpose was tested as an experimental model. A mathematical model of the squash velocity was derived, and also, several characteristics of the squash phenomena during the motoring of the engine used as a modelwere investigated. The results obtained were as follows: (1) Mathematical model of squash velocity was established and cheked (2) Squaash velocity and engine speed were found to be proportional to the squash area while they were inversely proportional to the squash width. (3) Squash velocity and crank angle at which the squash velocity become its peak were influenced by the magnitude of squash clearance: increase of squash clearance made squash velocity reduced acd made the peak of the squash velocity for from the top dead center and (4) When the squash area is divided in small areas baving unit width along the squash section, squash velocity at each unit width was proportional to the magnitude of the squash distance covered by the unit width.

• Geomechanics and Engineering
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• v.17 no.1
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• pp.57-67
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• 2019

Water-induced strength reduction is one of the most critical causes for rock deformation and failure. Understanding the effects of water on the strength, toughness and deformability of rocks are of a great importance in rock fracture mechanics and design of structures in rock. However, only a few studies have been conducted to understand the effects of water on fracture properties such as fracture toughness, crack propagation velocity, consumed energy, and microstructural damage. Thus, in this study, we focused on the understanding of how microscale damages induced by water saturation affect mesoscale mechanical and fracture properties compared with oven dried specimens along three notch orientations-divider, arrester, and short transverse. The mechanical properties of calcite-cemented sandstone were examined using standard uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) tests. In addition, fracture properties such as fracture toughness, consumed energy and crack propagation velocity were examined with cracked chevron notched Brazilian disk (CCNBD) tests. Digital Image Correlation (DIC), a non-contact optical measurement technique, was used for both strain and crack propagation velocity measurements along the bedding plane orientations. Finally, environmental scanning electron microscope (ESEM) was employed to investigate the microstructural damages produced in calcite-cemented sandstone specimens before and after CCNBD tests. As results, both mechanical and fracture properties reduced significantly when specimens were saturated. The effects of water on fracture properties (fracture toughness and consumed energy) were predominant in divider specimens when compared with arrester and short transverse specimens. Whereas crack propagation velocity was faster in short transverse and slower in arrester, and intermediate in divider specimens. Based on ESEM data, water in the calcite-cemented sandstone induced microstructural damages (microcracks and voids) and increased the strength disparity between cement/matrix and rock forming mineral grains, which in turn reduced the crack propagation resistance of the rock, leading to lower both consumed energy and fracture toughness ($K_{IC}$).

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.527-532
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• 2016

The effects of gas velocity and solid circulation rate on the axial solid holdup distribution have been determined in a 10 mm-I.D. ${\times}$ 800 mm-high circulating fluidized bed plasma reactor under reduced pressure (1torr). Polystyrene polymer powder and nitrogen gas are used as solid and gas materials respectively. The change of solid circulation rate by a large gas flow rate of the riser (40~80 sccm) is also possible by a relatively small gas flow rate of the solid recirculation part (6.6~9.9 sccm). The solid circulation rate in the reactor under reduced pressure increases with increasing aeration velocity in the solid recirculation part. The axial solid holdup in the riser decreases from the dense at the bottom to the dilute phase at the top section of the riser. Solid holdups at the axial positions in the riser increase linearly with increasing solid circulating velocity. From these results, we could determine the position of plasma load for good plasma ignition, maintain and plasma reaction.