• Title/Summary/Keyword: 날개설계

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Azimuth Accuracy of Correlative Interferometer Direction Finder on Airborne Scale-down Model (항공기 축소모델의 상관형 위상비교 방향탐지장치의 방위각 정확도)

  • Lim, Joong-Soo
    • Journal of the Korea Convergence Society
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    • v.9 no.10
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    • pp.1-6
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    • 2018
  • This paper describes the azimuth accuracy of correlative interferometer direction finder on a scaled down airplane model. When the antennas are placed on the bottom of an airplane, reflection signals caused by an aircraft structure are arise and caused an azimuth error. In this paper, the F-16 fighter scale-down model was made to 5:1, and five antennas were placed on the bottom of the model. The accuracy was made by numerically analyzing the phases of the radio waves received by the five antennas when the signal of emitter was transmitted on $0-360^{\circ}$ azimuth angles. The azimuth error of the correlative interferometer direction finder on the model was measured to be less than $1.0^{\circ}$ when SNR was larger then 3dB, and it could be very useful for the design of the direction finder on airplane.

CTIO 4m SDSS $u$와 CTIO 1m B filter의 투과함수 특성 및 CTIO 1m Y4KCam의 crosstalk

  • Heo, Hyeon-O;Im, Beom-Du;Seong, Hwan-Gyeong;Bessel, Michael S.
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.155.2-155.2
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    • 2012
  • CTIO 4m 및 CTIO 1m 망원경으로 Westerlund 2의 UBVI 관측을 수행하여, CTIO 4m SDSS $u$ filter의 적색광누출 현상을 발견하였고 그 영향을 분석하였다. 적색광누출 현상은 filter의 투과함수가 설계와는 달리 장파장 영역에서 투과 존재하는 현상으로, CTIO 4m SDSS $u$ filter의 경우 B-V>1.4, V-I>2.0에서 그 영향이 나타나기 시작한다. SDSS $u$ filter의 적색광누출 현상은 별의 고유색지수와 상관없이 관측된 색지수가 클수록 영향이 크며, $B-V{\leq}1.8$, $V-I{\leq}2.8$의 범위에서는 보정이 가능하다. CTIO 1m B filter에서는 성간소광을 받지 않은 별과 성간소광을 많이 받은 별의 표준계변환 결과, $B_{CTIO1m}=B_{Standard}-0.055{\times}E(V-V)$에 해당하는 차이를 보였다. 이러한 차이는 CTIO 1m B filter의 투과함수의 단파장 쪽 날개부분이 표준 Johnson B filter에 비하여 단파장 쪽으로 많이 치우쳐있기 때문으로 보인다. 특히 Ballmer jump에 해당하는 파장인 370 nm에서 filter의 최대투과율에 비하여 32.2%에 달하는 투과율을 보이는데, 이는 Bessell B filter의 3.1%에 비하여 매우 큰 값이다. CTIO 1m 망원경의 Y4KCam CCD에서는 포화된 화소에 의한 crosstalk 뿐 아니라 포화되지 않은 화소에 의한 crosstalk 현상도 보였다. 짧은 노출을 준 영상에서는 5000 ADU 이상에서는 육안에 의한 crosstalk 확인이 가능하며, 포화되지 않은 밝은 별에 의한 crosstalk을 확인하지 않고 측광할 경우 백색왜성으로 오인할 가능성이 있으므로 측광 과정에서 좌표를 통하여 확인할 필요가 있다.

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Structure Design and Experimental Appraisal of the Drag Force Type Vertical Axis Wind Turbine (수직축 항력식 풍력터빈의 구조설계 및 실험평가)

  • Kim Dong-Keon;Keum Jong-Yoon;Yoon Soon-Hyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.3 s.246
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    • pp.278-286
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    • 2006
  • Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades$(\alpha)$ and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, $\alpha=60^{\circ}$ and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of $\Omega=0.33$, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed.

Development of Thermocouple Sensor for Thermal Boundary Layer Measurement (온도 경계층 측정용 열전대 센서 개발)

  • Seo, Jongbeom;Han, S.
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.38 no.12
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    • pp.983-990
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    • 2014
  • This research focused on designing an appropriate thermocouple sensor for a thermal boundary layer with a large temperature gradient. It was designed to minimize the conduction error from a constant temperature wall in a boundary layer. A $79.9-{\mu}m$ thermocouple was chosen, and a five-axis device jig was developed to fabricate a butt-welded thermocouple, which is different from arc-welded junction thermocouples. This was used to minimize the size of the thermocouple junction. In addition to fabricating butt-welded thermocouples, a thorough calibration was conducted to decrease the internal error of a multimeter to ensure that the data from the butt-welded and regular thermocouples were almost the same. Based on this method, a butt-welded thermocouple with a small junction was found to be suitable for measuring the temperature in a thermal boundary layer with very large thermal gradients. Using this thermal boundary layer probe, the thermal boundary layers in a turbine cascade were measured, and the Nusselt numbers were obtained for the turbine endwall.

Kinematic Analysis of Levering Systems in Compound Bows (컴파운더 보우 지레 시스템의 기구학적 해석)

  • Lee, Yong-Sung;Kim, Hong Seok;Cheong, Seong-Kyun;Choi, Ung-Jae;Kim, Young-Keun;Park, Kyung-Rea;Shin, Ki-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.1
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    • pp.55-60
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    • 2013
  • Compound bows use levering systems consisting of cables and cam pulleys to bend limbs that are much stiffer than those of recurve bows, thus storing more energy while requiring less force for the archer to hold the bow at a fully drawn position. Many patents have thus far been proposed to improve the efficiency and performance of compound bows through empirical methods, whereas only a few analytical methods have been proposed. In this light, this paper presents a method for the kinematic analysis of levering systems in compound bows so that a designer can easily predict the effects of changes in the cam profiles and limb materials.

A Study of the Thrust Vectoring Control Using Secondary Co- and Counter-Streams (2차 순유동과 역유동을 이용한 추력벡터 제어법에 관한 연구)

  • Lim Chae-Min;Kim Heuy-Dong
    • 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.

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A Vibration Problem and Countermeasures for the Deck House and Stern of a Ro/Ro Ship (차량운반선의 거주구와 선미의 연성진동문제 및 방진대책)

  • Man-Cheol Han;Sang-Heon Oh;Il-Cook Baik
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.3
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    • pp.135-144
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    • 1994
  • The coupled vibration of the deck house and stern structure, which was experienced on a 12,900 TDW Ro/Ro ship, has been studied. It was a large-scale vibration problem where the structure resonates with the propeller excitation at the first blade passing frequency. After discussing the structural characteristics of the ship, the vibration characteristics measured ducting the sea-trial are presented and compared with the analysis results which are based on a 3 dimensional finite element(FE) model. The FE model is also used to verify various reinforcement options and to predict their effectiveness. A substantial reduction or the vibration was confirmed during the sea-trial after installing a few selected reinforcement. The forced vibration response, which is computed using the FE model, is compared with the measured data. The change of the vibration characteristics according to loading conditions is also studied.

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Evaluation of Reinforcement Effects According to Reinforcement Type and Grouting Method (지반보강재의 형상과 그라우팅 방법에 따른 보강효과 평가)

  • Park, Jongseo;Kim, Taeyeon;Lee, Bongjik
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.8
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    • pp.13-20
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    • 2019
  • In order to ground reinforcement, the chemical grouting, the anchor, the soil nailing system, the micropile, etc. can be mentioned by the methods widely used in domestic. The above ground reinforcement methods are developed by various methods depending on the type of reinforcement, installation method, presence of prestress, grouting method, etc. However, in common, the strength of reinforcement, the friction force of grout and reinforcement and the friction force of grout and ground are the main design variables. Therefore, the optimized ground reinforcement is a material with a high tensile strength of the reinforcement itself, the friction force between the reinforcement and the grout is high, and the application of an optimal grouting method is necessary to improve the friction force between the grout and the ground. In this study, a total of 20 model tests were conducted to analyze the reinforcement effects according to the shape of the reinforcement and the grouting method. As a result of the test, As a result of the experiment, it is judged that the reinforcing effect is superior to the perforated + wing type reinforcement and post grouting method.

Geometric Modeling of the Skin-Stringer Integrated Panel with Three-Dimensional Woven Composite (3차원 직조 복합재료 스킨-스트링거 일체형 패널의 기하학적 모델링)

  • Yeonhi, Kim;Hiyeop, Kim;Jungsun, Park;Joonhyung, Byun
    • Journal of Aerospace System Engineering
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    • v.16 no.6
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    • pp.8-17
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    • 2022
  • This paper presents a novel geometric modeling technique to predict the mechanical properties of an aircraft wing's skin-stringer integrated panel. Due to mechanical and adhesive fastening, this panel is vulnerable to stress concentration and debonding, so we designed it to integrate the skin and stringer using three-dimensional woven composites. Geometric modeling was conducted by measuring the geometric parameters of the specimen and defining the pattern of the yarns as functions. We used a weighted average model with iso-strain and iso-stress assumptions to predict the mechanical properties of the panel parts. We then compared the results of a finite element analysis with a compression test to verify the accuracy of our model. Our proposed technique proved to be more efficient than the traditional experimental method for predicting the mechanical properties of skin-stringer integrated panels.

Cumulative control output compensation technique for voice coil actuator used in small guided missiles (소형 유도무기용 보이스 코일 구동장치의 누적 제어 출력 보상 기법)

  • Wonsung Lee;Gwang Tae Kim;Choonghee Lee;Yongseon Lee;Seungho Jeong;Sungho Choi
    • Journal of Aerospace System Engineering
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    • v.18 no.4
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    • pp.1-9
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    • 2024
  • In this study, we researched control compensation techniques to enhance control robustness against external forces and responsiveness to output dead zones in direct-actuated voice coil actuators for small guided missiles. An aircraft's wings must optimally control the command angle while managing various nonlinear external forces such as drag, lift, and thrust during flight. The small direct -drive voice coil actuator, when applied, benefits from small current requirements in no-load situations but suffers from diminished control robustness due to rapid increases in control current during external force applications. To address this issue, we designed and implemented a system that compensates for errors by accumulating additional output, thus improving the actuator's responsiveness in control scenarios with external forces. This was verified through experimental results.