• Korean Journal of Mathematics
• /
• v.20 no.3
• /
• pp.323-331
• /
• 2012

We present a high-order potential ow model for the motion of the impulsively accelerated unstable interface of infinite density jump. The Layzer model for the evolution of the interface is extended to high-order. The time-evolution solutions of the bubble and the spike in the interface are obtained from the high-order model. We show that the high-order model gives improvement on the prediction of the evolution of the bubble and the spike.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.131-132
• /
• 2011

• Journal of computational fluids engineering
• /
• v.13 no.4
• /
• pp.58-65
• /
• 2008

In the present study, a numerical analysis on electrohydrodynamics (EHD) of the flow and the collection mechanisms inside a electrostatic precipitator with a spiral spike electrode were investigated. The phenomena of the electrostatic precipitator include complex interactions between the electric field, the fluid flow and the particle motion. To validate the numerical method, the numerical computation for the electric field of a simple wire-pipe type electrostatic system having an analytic solution were performed. Using this numerical method, the electric field of the spiked electrostatic precipitator was simulated. And the fluid flow and the particle motion inside the spiked electrostatic precipitator were numerically analyzed.

• Korean Journal of Applied Biomechanics
• /
• v.27 no.3
• /
• pp.219-227
• /
• 2017

Objective: The aim of this study was to analyze the effects of bobsleigh shoes on the lower extremity range of motion and start speed lap time and to develop bobsleigh shoes suitable for winter environments and Korean players based on sports science and optimized biomechanical performance. Background: The bobsleigh shoes used in the start section of the sport are one of the most important equipment for improving athletes' performances. Despite the importance of the start section, there are no shoes that are specifically designed for Korean bobsleigh athletes. Thus, Korean athletes have to wear sprint spike shoes instead of bobsleigh shoes to practice the start. Method: The subjects included four bobsleigh athletes from the Gangwon Province Bobsleigh Skeleton Federation. The study selected the bobsleigh shoe type A (company A) and type B (company B). We analyzed the lower extremity range of motion and sprint time (start line to 10 m) using a Motion Analysis System (USA). Results: In the measurement of the time required for the bobsleigh start section (10 m), the type A shoes demonstrated the fastest section record by $2.765{\pm}0.086sec$ and yielded more efficient movements, hip and knee flexion, hip extension, ankle dorsiflexion, plantar flexion, and inversion than the type B shoes. Conclusion: Type A shoes can yield a better performance via effective lower extremity movements in the bobsleigh start section. Application: In the future, functional analysis should be conducted by comparing the upper material properties, comfort, and muscle fatigue of bobsleigh shoes based on the Type A shoes to develop such shoes suitable for Koreans.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.2
• /
• pp.359-367
• /
• 2009

This study was conducted to provide useful information for the scientific training of spikes and instruction, by analyzing all kinematical variants including time, distance, velocity, angle factors in spike movements of volleyball matches. The subjects were 4 foreigner players, who participated in the V-League of 2008-2009. The conclusion from this study is as follows. Time for a jumping step was .33s, and Angelko had a bit longer takeoff time than other players. In Angelko and Anderson who were leading in attack power, the whole distance of a spike motion was relatively short, less than 4m. The moment when the center of gravity reached the lowest point was when the right foot bearing weight in the jumping step was passing the left foot, and the highest point of gravity was 2.30m, which appeared just before the impact. The horizontal speed of the center of the gravity was highest as 4.19m/s at the beginning of a jumping step, and lowest at the stance phase of the fore foot just before takeoff. The vertical speed of the center of the gravity was lowest after the right foot touched the ground, and highest after the takeoff of the fore foot. Impact was 3.22m, and the highest ball speed was 28.18m/s.

• Aerospace Engineering and Technology
• /
• v.11 no.1
• /
• pp.27-41
• /
• 2012

In this paper, there is analyzed the disturbances to impact on COMS attitude and the attitude error using the received telemetries in KARI ground station during normal mode of COMS. COMS was launched successfully at Kourou, French Guiana on the 26th of June, 2010. Up to now after IOT(in-orbit test), COMS is performing well the main mission to measure meteorology and ocean during about half and one year. The disturbances to impact on COMS attitude are mostly by the Sun, by the motion of payload mirror and by the spike happened during operation of earth sensor mirror and wheel. The analysis result on the other cases happened rarely during the nominal operation, is summarized.

• Korean Journal of Applied Biomechanics
• /
• v.16 no.4
• /
• pp.125-134
• /
• 2006

The purpose of this study was to analyze the Biomechanical elements by looking at the differences on the motions of the right and left spikes of right-handed offense volleyball players, using 3D image analysis and force platform. For that purpose, spike motions of six male university volleyball players were recorded three times each using two 16mm high speed cameras and the speed of recording was set at 60 frames/sec. The coordinated raw data was leveled as 6Hz using low pass filtering method and the calculation of 3D coordinates was done by using a DLT (Direct Linear Transformation) method. Also KWON 3D program was used to analyze the variables. Through the experiments and research, the following results were found: That is, in case of the right spike, the required time from the toss to the impact, which affected the success rate of offense showed as longer and on the take-off, the exact timing to touch the ball was longer because the pace between right and left feet was wider, and also after the jump, the distance between the feet indicated shorter, than the left. In addition, the degree of somersault and horizontal adduction of shoulder joint was smaller and the degree of medial rotation of shoulder joint showed bigger than the left, so it indicated that it was not centered on the body, but by the arm with an axis of shoulder using a swing motion. After the impact, the speed of the ball indicated slower compared to the left spike.