• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.507-510
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• 2009

The small size of hybrid rocket using PE-$LN_2O$ was designed, constructed and launched for a development basic technology of Hybrid rocket vehicle. The hybrid engine ignition system was designed with valve system using external actuator and confirmed working without any fault. To design fuel grain an internal ballistics design was carried out, and to estimate rockets flight path an external ballistics analysis was carried out. So the rocket was designed and constructed, and the launch test proves that hybrid rocket's design was suitable. The hybrid rocket(weight : 9kg, diameter : 110 mm, height : 1.7 m) was launched successfully. But parachute was deployed on mid-flight and the mission could not finish its purposed flight. Some of problems were found in this activity but next launch vehicle will be improved.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.31-39
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• 2008

The purposes of this study were to compare and analyze the world elite hurdler and the domestic hurdler 3-D kinematic and kinetic techniques about hurdling motion in the 110m hurdles. After analyzing variables in the 110m hurdle run the following conclusions were obtained; In a preparation phase, the domestic hurdler came out running more 0.13m then world elite hurdler from grounding to taking off in the height of center of gravity and the distance by 1.04m. In a flight phase, the domestic hurdler came out taking off 0.33m less then world elite hurdler from taking off to flight peak in the height of center of gravity and the distance by 1.63m. In a flight peak phase, domestic hurdler came out landing more 0.37m then world elite hurdler by 159m. More over, during the hurdling, the horizontal velocity of center of gravity came out decreasing from taking off to landing with domestic hurdler by 0.75m/s. the take off percentage and the landing percentage is 53:47. In a acceleration phase, domestic hurdler came out going slower 0.54m/s than world elite hurdler from landing in the horizontal velocity of center of gravity by 8.78m/s.

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.551-556
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• 2018

In recent years, drones have been used to measure aircraft flights data and weather information. Related applications include the measure for low-altitude atmospheric data, the measure for atmospheric fine dust, and the measure for air pollution. However, the mounting position of the atmospheric measurement sensor should be mounted by considering the effects of propeller flow, the EMI effects, and the changes in the weight of the drone. Among these, the upper flow of the propeller affects the wind speed and direction, so the optimal position should be selected. This study deals with the proper height of the atmospheric data measurement sensor. Through the flow analysis, we study the flow characteristics of around a drone and suggest the proper sensor mounting height.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.3
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• pp.157-163
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• 2019

As the drone industry has grown greatly in recent years, drones are being used or developed in many industrial fields such as image shooting, pesticide application, delivery service, food delivery etc. In this paper, therefore, we developed a program that takes a user's desired area at a certain height using a camera-equipped drone and obtains the area of the zone the user wants through image processing. The first user selects an area or a path. Afterwards, the drone flies and takes pictures, and then measures the user's needs. A digital image taken at a constant height and with the same resolution is composed of pixels, the area can be calculated easily if we know the number of pixels in the zone the user wants. Particularly, it is easy to calculate the area of various shaped zones, not terrain shapes such as triangles and squares. In addition, the total area of specific places of the entire zone can be calculated. With the program of this paper, anyone can easily calculate the area of the place the user wants using a drone rather than calculating the area through difficult formulas or specialized equipment.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.18 no.6
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• pp.151-165
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• 2015

This study surveys and analyzes the ecology of Gangseo area to be developed near Nakdonggang River and West Nakdonggang River in Busan - before its development. With the result of the surveys as its basis, the study also finds ways to conserve the area's bird habitats in response to the planned development. According to the site surveys over four seasons, West Nakdonggang River which is near the targeted development area is a wintering ground for migratory birds. Some representative bird types in this area are ducks, geese, and other water birds. There are even six legally protected species. The average altitude of their flight is calculated to be $92.4{\pm}18.8m$ and the main purpose for the migration is determined to be for food. According to evalution of the conservation value of the area, Nakdonggang River and West Nakdonggang River turns out to have the highest conservation value. Other areas are developable as long as it was environmentally friendly. Therefore, this study suggests incorporation of ecological parks and biotopes within the targeted development area along with the proposal for spaces in the surroundings where the wintering birds can rest and feed. Especially for the wintering birds that rest at Nakdonggang River and West Nakdonggang River, their flight direction and pattern was examined to determine that their resting ground should be located 50~100m off of the river bank. Furthermore, this study proposes ways to maximize bird habitat by building ecological corridors between the agricultural channel and other small streams in the targeted development area and the habitats in the surroundings. Lastly, the study suggests the construction of low buildings, at most 20m in height, near Nakdonggang River and West Nakdonggang River considering the birds' flight altitude and direction.

• Korean journal of applied entomology
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• v.57 no.2
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• pp.105-115
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• 2018

The comstock mealybug is one of the serious insect pest in pear. It is necessary effective control methods such as attractive sex pheromone. Using sex pheromones is necessary for studying the physiology and ecology of insect pests. In the present study, the sex pheromone of comstock mealybug was used for investigating the flying acts of the adult male. As temperature increased, the development period of eggs shortened, but it was longer at $30^{\circ}C$. The mean number of eggs laid was 482 at $25^{\circ}C$ and males constituted 37% of the experimental population at $30^{\circ}C$. The flight of the male comstock mealybug was mostly restricted to a 2-4 hour period after sunrise, even if condition of light period is changed. Male mealybugs were incapable of upwind flight towards an attractant when air velocity was 1.5 mph. Preference of height was tested in a pear orchard. The ineffective heights of the traps were 2 and 2.5 m, whereas the effective heights were 1 and 1.5 m. Many captured males at 0.5, 1, and 5 m, and the number of captured males were similar in 10, 15, and 20 m. Male mealybugs were captured up to a distance of 50 m, suggesting that it is possible to control the male mealybugs that are more than 50 m away when sex pheromone traps are used.

• Journal of Astronomy and Space Sciences
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• v.20 no.1
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• pp.29-42
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• 2003

The KSR-3 magnetometers consist of the fluxgate magnetometer (MAG/AIM) for acquiring the rocket flight attitude information, and the search-coil magnetometer (MAG/SIM) for the observation of the Earth's magnetic fluctuations. The position (latitude, longitude, and height) and flight condition (the transformation angle) of the rocket is measured after the data based on these two magnetometers are compared with IGRF The gap in the vector of magnetic field between the position of the launching point and an impact point is taken into account in data reduction. Angular variation of pitch, yaw, and roll can be researched when the data is applied to the coordinate system of the rocket.

• Korean Journal of Applied Biomechanics
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• v.15 no.4
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• pp.1-11
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• 2005

The study were to assess technical factors between the high score group and the low score group, from the subjects of 8 male national gymnasts, and to analyze the kinematical characteristic and main technical cause on technique of Kasamatsu movement on Vault. The result of this study is this. In case of horse contact time the high score group was swifter than low score group, and there was significant difference between the high score group and the low score group(<.01). On high score group the time of taking on from horse showed shorter than that of taking off from horse, while of the low score group the time of taking on the horse was similar to that of taking off from horse on the average. And in time of pre-flight the high score group on average the was 0.16sec shorter times than the low score group, and so there was significantly difference between groups(<.05). Also It is a characteristic that the high score group was short in horse contact time and longer in post-flight. In the horizontal distance of post-flight, the high score group was 0.11m longer than the low score group and there was significantly statistic difference between groups(<.05). In the vertical height of the cog in Post-flight's phrase, the high score group was 0.15m higher than the low score group and there was significantly statistic difference between groups(.<01). The horizontal velocity and vertical velocity in the event of taking on and off Beat board and Vault weren't significantly statistic differences between two groups. In the slow-down of average horizontal velocity during keeping contact with the beat board, the high score group was larger than the low score group. And in an increased average vertical velocity during keeping contact with the beat board, the high score group was even larger than the low score group. In the projectile angle of cog in taking off the beat board, 40.2deg., the angle of low score group and 39.5deg., the angle of high score group are nearly alike. In the projectile angle of cog in taking off the beat, the high score group showed 1.6Wt larger on average than the low score group. However the average reaction force on the board and Vault wasn't almost different between two groups, showed 0.3~0.6Wt larger in the high score group.

• Korean Journal of Applied Biomechanics
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• v.17 no.1
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• pp.165-174
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• 2007

The subject of this study was male apparatus gymnastics athlete who had scored high points doing basket with 1/2 turn on parallel bars. Then 3D motion analysis were used to calculate & analyse kinematic variables of Basket with 1/2 turn to Handstand. 1. The total average time spent for Basket with 1/2 turn took $2.16{\pm}.08sec$, at the downward upward phase took $.58{\pm}0.00sec$, $.23{\pm}.00sec$, at flight phase took $.28{\pm}.01sec$, at connected area phase took $.72{\pm}0.21sec$, at rotation area phase took $.35{\pm}.14sec$. To have a successful performance, there should be faster speed and velocity to rotate at the downward upward phase, then the upward velocity and height must be used adequately. Moreover, the speed must be faster at the flight connect phase to stabilize Center of Mass(CM) for the body, and must secure more time at the rotation area to have more stable performance. 2. After handstand on parallel bars while moving CM to right hand side, and It must be performed with big and magnificent performance with putting both hand's center to far away from the parallel bars. 3. Furthermore, CM must be moved fast from downwards to right hand side, and CM must be moved fast in vertical movement at upward and flight phase to avoid CM from moving back and forth, and left and right. 4. At downwards, the subject must rotate as bis as possible using hip-joint as wide as possible and at upwards, must put his body to vertical to have stable performance. While rotating or turning, it is better to do with bigger shoulder angle and have to make sure that trunk angle must be not scattered. To perform better and more positive in basket with 1/2 turn on parallel bars, the centrifugal force must be used big and fast at downward, and at upward and flight phase, downward movement must change to vertical movement as soon as possible while turning movement must happen at handstand position. Time spent must be shorten at connected area to stabilize CM and turning must be natural as possible while securing the necessary time of movement to well-balanced. Also, the body must be vertically closed from the ground.

• Smart Media Journal
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• v.9 no.4
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• pp.176-186
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• 2020

The size and shape of crops are diverse, and the growing environment is also different. Therefore, when one uses a drone to spray pesticides, the characteristics of each crop must be considered, and flight conditions such as the flight height and forwarding velocity of the drone should be changed. The droplet flow of pesticides is affected by various flight conditions, and a large change occurs in the sprayed area. As a result, an uneven distribution of liquid may be formed at the wake, and the transport efficiency will be decreased as well as there would be a risk of toxic scatter. Therefore, this paper analyzes the degree of distribution of pesticides to the crops through numerical analysis when pesticide is sprayed onto the selected three crops with different characteristics by using agricultural drones with different flight conditions. On the purpose of establishing a guideline for spraying pesticides using a drone in accordance with the characteristics of crops, this paper compares the amount of pesticides distributed in the crops at the wake of nozzle flow using the figure of merit, and the sum of transported liquid rate divided by the root mean square of the probability density function.