• Journal of the Korean Academy of Clinical Electrophysiology
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• v.10 no.1
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• pp.23-28
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• 2012

Purpose : The objectives of this study were to examine changes in gait parameters related to the COP and gait velocity resulting from the use of ankle foot orthosis, and to provide information for the prescription of ankle foot orthosis and gait rehabilitation training. Methods : We sampled a control group of 14 normal children of the same age as the spastic diplegia (spastic diplegia used ankle foot orthosis) and measured their COP at barefoot gait and their gait parameters at three gait velocities. Change in the COP according to the use of ankle foot orthosis measured one-way ANOVA and Gait parameters according to gait velocity used repeated measures ANOVA. Results : As a result of analyzing change in the COP it became close to that of normal children, and changes in gait parameters such as step width, stride length and stride time also became close to those of normal children. Conclusion : In conclusion, when spastic diplegia used ankle foot orthosis, their balancing ability was improved as a result of decreased change in the COP, and their changes in gait parameters also became close to those of the control group. These results show that the use of ankle foot orthosis improves spastic diplegia gait functions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.3
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• pp.154-161
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• 2017

The purpose of this study was to investigate the change of length, opening width, and number of openings effecting on topography change around artificial reefs under erosive wave condition. Hydraulic model test was conducted to see sediment transport around the structures and the relation among the installation condition of the artificial reefs, generated velocity, wave deformation, and topographic change was reviewed. Experimental results show that the sediment transport rate was reduced; however, the scour around the structures was increased under the condition of having a single opening compared to the structures having a plurality of openings which shows inversely proportional to the size of Lr/W.

• Fire Science and Engineering
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• v.26 no.5
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• pp.99-104
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• 2012

This study investigated the pressure change in the fire room and elevator lobby during the air pressurization to the Elevator lobby with the various egress scenarios and the existence of vent holes in the fire room. The experiments revealed that pressure change was significantly affected by the open/closure scenarios of the front door and stairway door resulting in over pressure, under pressure and performance drop of the door closure. It also revealed that the required smoke defensive air velocity can be obtained only with the existence of vent holes in the fire room by the removal of back pressure in the fire room.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.251-256
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• 2009

In this research, we experimentally studied flow characteristic by applying PIV measuring techniques which could measure the point velocity of all flow field and measuring the unsteady velocity of surrounding disk generated in a short time. Time range of great velocity change following quick closing of the slide valve was within 0.1s and the cycle was presumed to be 0.12s as a result of comparison study between the result of point flow field and of existing pressure change. Also, surrounding disk flow inside the circular pipe was closed from the upper part and flow road was getting narrow and advanced to the lower part incidentally quickly there was a tendency that the size of the flow back velocity to the upper part immeadiately after the closure decreased to 4/120s and increased again. There was flow back velocity component in y/D=0.2 lower part by the influence of flow back to the upper part after complete closure and the vortex flow of 0.2D-size near y/D=0.7, x/D=-0.3 was observed.

• Tunnel and Underground Space
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• v.21 no.2
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• pp.145-150
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• 2011

Variations of physical properties such as weight loss rate, wave velocity and uniaxial compressive strength after performing freeze-thaw cyclic test were measured in order to define weathering characteristics of sandstone and andesite. Weight change in specimens of the two rocks decreased with increasing the repetition number of freeze-thaw cyclic test. In particular, weight loss of andesite specimens was very irregular. P-wave velocity of sandstone specimens decreased more than 5%. On the other hand, P-wave velocity of andesite specimens do not vary up to 500 cycles and decreased more than 5% after 1000 cycles. This implies that the sandstone are easily weakened and loosened by weathering processes, while the andesite are relatively strong. In addition, the wave velocity changes of the andesite specimens coincident with the weight change. Uniaxial compressive strengths of the sandstone specimens slightly decreased at the early stage of the freezing-thawing cyclic test, then tended to be irregular after 64 cycles. In conclusion, the rock specimens showed smaller weight loss, less had lower strength reduction rate.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.340-347
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• 2008

In the case of a melting process, the velocity of waste-gas has been measured to produce the melt of an equal condition and to analyze the combustion situation of the fuel which was inputted in a furnace. Recently, there are many kinds of measuring equipments of gas-velocity on the market. But, the waste-gas produced from a melting process is high temperature, the slow speed and includes much dust. Existent measuring equipments are not suited to these conditions. Therefore, we made the measuring equipment of new method which is enough detailed to react on the slow speed and sustains in high temperature. As shown in the result of field test, the manufactured measuring equipment is so sensitive as to react on a small change of velocity and senses temperature change rapidly, we expect that this equipment helps in temperature control of a melting furnace.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.4
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• pp.40-46
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• 2016

In order to improve air quality of indoor environment, studies of the underfloor air distribution (UFAD) system for application in buildings are actively in progress based on temperature and air flow distribution. However, although the age of air is the major evaluation parameter, there has been very little study on this parameter for the UFAD system. In this study, we investigated the age of air to reach the air diffuser, which is installed at the bottom of the interior by the UFAD system. Computational fluid dynamics simulations showed no regular pattern to the maximum value of the age of air in accordance with air flow rate and the velocity at air diffuser. These factors can be deduced from air movement by considering that air emitted from air conditioners was rotated according to the bottom shape of the floor, and then, the age of air in the rotation center was increased. The average age of air of internal interior was reduced considerably as the flow velocity at the underfloor air diffuser was increased from 0.5 m/s to 1.0 m/s However, the age of air was not substantially affected with change in the air volume. Moreover, when the flow velocity at the underfloor air diffuser was higher than 1.0 m/s, the age of air showed no significant difference with change in air volume or height of measurement. These results imply that indoor air quality is more substantially influenced by flow velocity than air volume, and the appropriate flow velocity is 1 m/s or more.

• The Journal of Internal Korean Medicine
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• v.36 no.4
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• pp.478-485
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• 2015

Objectives: The purpose of this study was to analyze the change of area and average velocity of the center of pressure (COP) according to gait improvement in post-stroke hemiplegic patients.Methods: We measured the area and the average velocity of COP displacement of ten post-stroke hemiplegic patients while they stood quietly on a force plate at the time of dependent and independent gait . We also measured the area and the average velocity of COP displacement of normal persons to verify differences between them and post-stroke hemiplegic patients.Results: The area of COP displacement decreased significantly, and the average velocity of COP displacement tended to decrease, but not significantly. There were significant differences in the area and the average velocity of COP displacement between post-stroke hemiplegic patients and normal persons.Conclusions: The results of this study show that postural control ability improves as gait improves.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1043-1054
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• 1988

The optimum cutting condition of rake angle in turning was investigated in SM45C and SM20C. Results of experiments in SM45C and SM20C are as follow. Specific cutting resistance became higher as the depth of cutting, feed or cutting velocity decreases at same rake angle and resistance became low value at 20.deg.(SM45C), 10.deg.(SM20C). The optimum cutting condition for SM45C is depth of cutting 0.7mm, rake angle 30.deg., cutting velocity 200mm/min, feed 0.1mm/rev, and for SM20C is depth of cut 0.5mm, rake angle 10.deg., cutting velocity 150mm/min, feed 0.1mm/rev.The rake angle for good roughness is 15.deg for SM45C, and that for SM20C is 25.deg. The roughness is influenced by feed and it has the lowest value at 0.1mm/rev and the cutting condition is closely related with the change of cutting velocity and feed.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.3
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• pp.170-184
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• 2024

With the advancement of autonomous navigation technology in maritime domain, there is an active research on swarming Unmanned Surface Vehicles (USVs) that can fulfill missions with low cost and high efficiency. In this study, we propose a formation control algorithm that maintains a certain shape when multiple unmanned surface vehicles operate in a swarm. In the case of swarming, individual USVs need to be able to accurately follow the target state and avoid collisions with obstacles or other vessels in the swarm. In order to generate guidance commands for swarm formation control, the potential field method has been a major focus of swarm control research, but the method using the potential field only uses the position information of obstacles or other ships, so it cannot effectively respond to moving targets and obstacles. In situations such as the formation change of a swarm of ships, the formation control is performed in a dense environment, so the position and velocity information of the target and nearby obstacles must be considered to effectively change the formation. In order to overcome these limitations, this paper applies a method that considers relative velocity to the potential field-based guidance law to improve target following and collision avoidance performance. Considering the relative velocity of the moving target, the potential field for nearby obstacles is newly defined by utilizing the concept of Velocity Obstacle (VO), and the effectiveness and efficiency of the proposed method is verified through swarm control simulation, and swarm control experiments using a small scaled unmanned surface vehicle platform.