• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.1
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• pp.25-31
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• 2019

An underwater glider is a type of autonomous unmanned vehicle and it advances using a vertical zig-zag glide. For this purpose, the position of an internal battery is regulated to control its attitude, and the amount of water in a buoyancy bag is regulated to control the depth. Underwater glider is suitable for a long-distance mission for a long time, because the required energy is much smaller than the conventional autonomous unmanned vehicle using propeller propulsion system. In this paper, control of horizontal tail wing is newly added to the conventional battery position and buoyancy control. The performance of the proposed controller is shown through Matlab simulation.

• Korean Journal of Poultry Science
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• v.45 no.3
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• pp.155-165
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• 2018

Chicken feathers could be classified into early-feathering (EF) and late-feathering (LF) depending on the development and patterns of the wing and tail feathers. Currently, feather-sexing is a widely used chick sexing method in the industry. This study was carried out to suggest the method of classifying of EF and LF chicks to establish auto-sexing Korean native chicken (KNC) strains. The development and morphology of wing feathers and tail feathers in 856 KNCs from hatching to 55-days old were analyzed to classify EF and LF chicks. We also performed PCR analysis using K-specific gene primers to confirm the agreement between the phenotypes and genotypes of EF and LF chickens. In the results, the EF chicks had long primaries and coverts, and there was a significant difference in length between primaries and coverts. The LF chicks had shorter primaries and coverts than the EF chicks, and showed little difference in the length between primaries and coverts. LF chicks could be classified into four groups: LF-Less, LF-Scant, LF-Equal and LF-Reverse according to their wing feather patterns. EF chicks had 1.5 times longer primaries than LF chicks until they were 15-days old, but the lengths were almost the same at 50-days old. The tail feathers of the EF chicks were apparent at 5-days old, but those of the LF chicks were short and indefinite at that time. When EF and LF chicks were classified by the length of primaries being more or less than 9 mm, the classification accuracies for EF and LF chicks were 96.2% and 85.4%, respectively, compared to the PCR results. In conclusion, juvenile EF and LF KNC showed distinct differences in feather development and morphology, and could be easily distinguished at one day-old.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.1
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• pp.1-12
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• 2022

Wind tunnel test for a small scale electric ducted fan with a 104mm diameter was conducted to analyze the aerodynamic characteristics when it was used as a propulsion system of tilt-propeller UAV. Experimental conditions were derived from flight conditions of a sub-scaled OPPAV. Forces and moments of the ducted fan model were measured by a 6-axis balance and 3-dimensional wake vectors which could induce an aerodynamic influence in the vehicle were measured by 5-hole probes. Thrust and torque on hover and cruise conditions were measured and analyzed to drive out the operating conditions when it was applied in the sub-scaled OPPAV. On transition conditions, thrust keep its value with tilt angle variation below 40° and increase after that. But, sideforce increase constantly until 75°. The maximum axial velocity in the wake on hover and cruise conditions was around 60m/s and tangential velocity was around 12m/s. The position of the maximum axial velocity and vortex center move off the fan rotation center line as the tilt angle increases.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.335-342
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• 2020

Tailless aircraft designed for stealth efficiency uses spoilers instead of rudders for the directional control. When the spoiler is rapidly deployed, highly nonlinear and unsteady aerodynamic characteristics can be generated, resulting in adverse effects on aircraft flight performance. This paper investigates the aerodynamic characteristics of an airfoil with moving spoiler using dynamic mesh CFD technique. The effects of spoiler operation speed, mounting location, and deployment scheduling are analyzed to reduce the adverse effects of the spoiler's dynamic operation. The results shows that the adverse effects of dynamic spoiler can be reduced by appropriate selection of the spoiler mounting location and deployment scheduling.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.109-112
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• 2004

Of late, the thrust vectoring control, using fluidic co-flow and counter-flow concepts, has been received much attention since it not only improves the maneuverability of propulsive engine but also reduces an additional material load due to the trailing control wings, which in turn reduce the aerodynamic drag. However, the control effects are not understood well since the flow field involves very complicated non: physics such as shock wave/boundary layer interaction, separation and significant unsteadiness. Existing data are not enough to achieve the effectiveness and usefulness of the thrust vectoring control, and systematic work is required for the purpose of practical applications In the present study, computational study has been performed to investigate the effects of the thrust vector control using the fluidic co-and counter-flow concepts. The results obtained show that, for a given pressure ratio, the thrust deflection angle has a maximum value at a certain suction flow rate, which is at less than $5\%$ of the mass flow rate of the primary jet. With a longer collar, the same vector angle is achievable with smaller mass flow rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.997-1004
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• 2020

A synchropter is a type of rotorcraft in which a pair of blades inclined with each other rotates in synchronization. Removing the tail rotor enables an efficient and compact configuration similar to a coaxial-rotor helicopter. This paper describes the design and flight test results of a small synchropter to examine the suitability of a drone system for the army. The synchropter in this paper is a small vehicle with a rotor diameter of 1.4m and a weight of 7kg and was assembled based on commercial parts to examine flight characteristics effectively. The flight control system adopted Pixhawk, which is designed based on an open-architecture. The model-based design technique is applied to develop the control law of the synchropter and a new firmware embedded on the Pixhawk. Through qualitative flight tests, we analyzed the flight characteristics. As a result of the analysis, we confirmed the possibility of application as a drone system of the synchropter.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.42-42
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• 2022

본 연구는 한반도의 중심 생태 축인 백두대간의 최북단이자 산림유전자원보호구역인 향로봉(1296m) 및 칠절봉(1172m), 둥굴봉(1305m)의 관속식물상을 조사하여 생태적 가치를 연구하고 생물 종 다양성 보전을 위해 진행하였다. 향로봉을 중심으로 2021년 6월부터 2022년 8월까지 총 5회 현장 조사를 실시한 결과, 총 70과 181속 237종 12아종 21변종 1품종 등 총 271분류군으로 확인되었다. 산림청 지정 희귀식물은 총 7분류군으로, 멸종위기(CR) 등급은 날개하늘나리, 끈끈이장구채, 봉래꼬리풀로 3분류군, 취약(VU) 등급은 만삼, 금강초롱꽃 등 2분류군, 위기(EN) 등급은 두메닥나무, 국화방망이로 2분류군이 확인되었다. 북방계식물은 껍질용수염, 개시호, 만삼 등 80분류군으로, 전체 분류군 중 28.8%를 차지하는 것으로 확인되었다. 한국특산식물은 한라사초, 할미밀망, 토현삼 등 17분류군이 확인되었다. 외래식물은 서양민들레, 애기수영, 토끼풀 등 11분류군이 확인되어 전체 분류군 중 3.9%를 차지하는 것으로 나타났다. 확인된 식물구계학적 특정식물 중 V급은 날개하늘나리, 솜다리 등 2분류군으로 나타났으며, 그 외 IV급 15분류군, III급 25분류군, II급 38분류군, I급 14분류군이 확인되었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.899-904
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• 2007

During the conceptual design phase of fighter class aircraft, the high speed wind tunnel test with 1/20 scale wing-body-tail model has been conducted to investigate the effects of leading edge flap deflection on the supersonic cruise performance of the aircraft. To select the proper leading edge flap deflection for the wind tunnel test, the aerodynamic characteristics due to various leading edge flap deflections have been analyzed by using corrected supersonic panel method. Based on the results obtained from the experimental and numerical approaches, the effects of leading edge flap deflection have shown to be useful to enhance the supersonic cruise performance of fighter class aircraft.

• Journal of Korean Society for Quality Management
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• v.42 no.3
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• pp.325-338
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• 2014

Purpose: The purpose of this study was to explain de-painting phenomenon of KUH-1 tail blade and to propose useful solution of it by test. The proposed solution was evaluated by real flight, and then it applied to mass product to improve the paint qual ity of KUH-1 tail blade. Methods: This study investigated an adhesive ability of primer following surface sanding condition. The cross cut and scratch test were conducted to evaluate the adhesive strength. And the water flow test was designed to simulate a real flight condition under rain. Through water flow test, an optimal condition of tail blade to prevent a de-painting phenomenon was deduced. Finally, the improvement method was evaluated by real flight under rain. Results: The results of this study are as follows; The sequential polishing was most excellent method in primer painting quality. The results of test including cross cut, scratch and water flow showed that MIL-DTL-53039 paint with epoxy primer has excellent adhesive ability. To proof the effect of improvement, a real flight during a rain condition was conducted. Finally, the comparison between original and improved configuration was conducted. Conclusion: The painting quality of KUH-1 tail blade was improved through deriving an optimal painting condition. In detail, a condition of optimal sanding and a sort of primer and paint was showed. Finally, the reliability of tail blade was guaranteed through improving the quality of painting.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.114-121
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• 2019

Tailless aircraft have advantages of low visibility compared to conventional aircraft, but drawback of poor stability as well which makes designing controller difficult. The controller design is more difficult, especially when the center of gravity moves due to store release or fuel consumption during flight. In this paper, an L1 adaptive controller is proposed as a way to overcome these problems. The reliability and performance of the controllers were verified by non-linear simulations. RPV Flying Quality Design criteria were used for design criteria. Using the simulation, it is shown that the adaptive controller maintains stability of the unmanned aircraft for sudden large change in the inertial properties. It is also shown that the calculation burden can be reduced when it is used with the gain scheduling method.