• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.142-143
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• 2008

In the present work, high-speed video images of the ground take-off flight of a live butterfly were captured and their dynamic motions during the first full-stroke were analyzed. To capture the dynamic images of the take-off motion, the experimental setup consisted of a high-speed camera, a Xenon lamp as a light source and a transparent chamber of $15^W{\times}15^L{\times}17^H$ $cm^3$ in physical size. The ambient temperature and supplementary lighting devices were precisely controlled. The weight and wing span of the butterfly tested in this study was 104 mg and 63.14 mm, respectively. The ground take-off images were captured with 4000 fps with a spatial resolution of (1024${\times}$512) pixels. The period of the first full-stroke was 80.5ms and the flapping speed of downstroke was 2 times faster than that of upstroke. As a result, butterflies used the fling and near-clap motion to generate lifting force and an interesting take-off behavior of early pronation and downstroke was observed.

• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.97-105
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• 2011

The purpose of this study was to investigate the kinetic factors of Stefan holm's take-off motion and provide the technical data. Collected data of the subject(height: 181 cm, weight: 71 kg, record: 230 cm) were used for the last two strides and take-off phase. The results were as follows: The vertical impulse force was 2044.8 N which was 2.49 times and the anterior-posterior impulse force was -1306.4 N which was 1.88 times of the subject's weight. The take-off leg angular velocities($\omega_x,\;\omega_y$) were switched drastically from clockwise to count clockwise direction between two-step touchdown and take-off. The highest jerk of the take-off foot was 368.97 m/s3 during the two step take-off and the take-off foot made an impact to the ground with 1225.07 m/s3 during the one step touchdown.

• Korean Journal of Applied Biomechanics
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• v.16 no.4
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• pp.13-20
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• 2006

A platform diving with categorizing 624C motion was video taped and 3D kinematic variables were analyzed. This motion is consist of 3 parts from the headstand position to the act of turning after take-off. The results indicated that it took a very short time from the moment of take-off to the act of 1/2 turning because the turning motion has already started from preparing motion even before the fingertips have parted from the ground. Also, there was barely any jumping height due to the use of upper limbs segment and there was little difference in the moving distance compared to the standing events judging from horizontal movement of 1.1m. The horizontal velocity of the center of human body was increased before take-off while the vertical velocity was decreased right after take-off and the velocity of lower limbs segment was faster than the upper limbs segment showing contrary results to the standing events. In the aspects of angular velocity, the upper limbs segment starts the turning motion when take-off by rapidly extending its angular velocity while lower limbs segment make large angular velocity even before take-off.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.1
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• pp.94-102
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• 2012

The aim of this paper is to research the change in the turbulent flow and the AOA occurred by $60^{\circ}$ crosswind to the direction of runway through the three-dimensional numerical analysis and to predict the take-off and landing flight stability. As a result, the maximum amplitude of AOA variation on runway reached $4.88^{\circ}$ within 7 second because of the wake formed by the constructions in the vicinity of the airport, and the overall effects appeared as an irregular aperiodic forms. Additionally, it was observed that the layout and shape of the buildings effected on the strength of turbulence directly, and the rapid flow generated between the buildings changed into stronger wake and eventually expected that the flow raises serious take-off and landing flight instability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.54-60
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• 2013

This paper presents a ground altitude determination algorithm using a laser altimeter and GPS for automatic take-off and landing of UAV. The characteristics of the laser altimeter was analyzed in ground tests and a low-pass filter was designed to reduce the effect of signal interruption due to reflectivity problem. The paper shows that a single sensor cannot measure ground altitude appropriately in terms of reliability and accuracy. To complement shortcomings of the laser altimeter, the linear Kalman filter was designed using DGPS vertical speed. Designed filter was validated and tuned through the steps of simulation, ground test and flight test. It was confirmed that the accuracy for automatic landing is achievable.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.393-403
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• 2022

Various studies suggest that the initial operating form of UAM, which is being presented as a solution to the urban traffic problem, will be similar to VTOL aircraft among current aircraft. In a form similar to determining the direction of the runway where fixed-wing aircraft take off and land, the vertiport where take-off and landing of VTOL aircraft takes place determines the flight direction of departure and arrival in consideration of the direction of the wind. Unlike areas where airports are generally built, in the case of downtown areas, it is expected that the characteristics of wind may continuously change depending on the environment of changing terrain or obstacles such as the construction of new buildings. In this study, long-term actual observation data for reviewing the take-off and landing directions at the city center where the location of the vertiport is expected are compared using a wind speed map, and the characteristics of the ground wind and the possibility of change in the direction of the predominant wind depending on the observation period and observation location confirmed.

• Geotechnical Engineering
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• v.12 no.5
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• pp.5-16
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• 1996

When braced excavation with temporary retaining wall installation, is performed in loose sand with high ground water level boiling may be induced and considerable damage on the excavation works and structures in the vicinity can take place. Recently, for the purpose of reinforcement of ground and cut-off of ground water behind the temporary retaining wall, high pressure jet grouting is widely used. The purpose of this paper is to investigate the effects of jet grouting on ground reinforcement and cut -off of the ground water behind temporary retaining walls for braced excavation. A series of both laboratory and field tests has been performed. The test results show that high pressure jet grouting has sufficient effects on reinforcement of stiffness of ground and retaining wall. The permeability of the improved ground was 10-f_ 10-3cm l s smaller than those of the original ground. Therefore, the effect on cut off of ground water behind temporary retaining walls could be improved by high pressure jet grouting method.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.14-19
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• 2005

The paper introduces the state-of-the art of WIG ship and application field of the CFD to WIG ship development. WIG ships are highly efficient and fast transport vehicles which take advantage of benefits of ground effect. Chapter 1 describes the characteristics of WIG ship. Chapter 2 reviews the research works of Russia, German, Chinese, Korea and etc. Chapter 3 explains the kind of WIG ship categorized by the main operational mode and take-off system. Chapter 4 describes about the application field of CFD to WIG ship development procedure.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.109-116
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• 2010

This study aims to comparatively analyze kinetic variables that affect high jump records and thus to provide the basic data for enhancement of physical education teachers' teaching skills and expertise. 10 students who were majoring in physical education in a college of education - five males and five females - were chosen for the experiment in which the 3D image analyzer and ground reaction force measuring unit were adopted. The kinetic variables of the groups, the characteristics and differences were analyzed, and the correlation between each variable and record in each group was examined. The results are as follows: As to the height of center of gravity from one step before stamping to landing, the vertical velocity of the center of gravity at take off, the vertical velocity of the limbs at take off, the angles of the hip joint and ankle joint of the jumping leg, it turned out that male were better than female. As to the angles of the hip joint and ankle joint of the lead leg, female recorded higher values than male. As to the maximum vertical ground reaction force, the maximum horizontal ground reaction force, the vertical impulse, it turned out that male were better than female.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.718-723
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• 2003

The number of jet aircraft is increasing. The aircraft noise making people near airports nervous have become a serious social problem. The aircraft noise can be classified into two groups; noise being generated at take-off or landing and noise form run-up test on the ground. In this paper, we consider the aircraft noise from run-up test on the pound and we suggest the noise suppression system.