• Journal of Multimedia Information System
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• 제7권2호
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• pp.189-196
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• 2020

We have developed a device for recording biological data by inserting three electrodes and a needle with an angular velocity sensor into the moth for the purpose of measuring the electromyogram of the flapping and the corresponding lift force. With this measurement, it is possible to evaluate the moth-physiological function of moths, and the amount of pesticides that insects are exposed to (currently LD50-based standards), especially the amount of chronic low-concentration exposure, can be reduced the dose. We measured and recorded 2-channel electromyography (EMG) and angular velocity corresponding to pitch angle (pitch-like angle) associated with wing flapping for 100 sweet potato hawkmoths (50 females and 50 males) with the animals suspended and constrained in air. Overall, the angular velocity and amplitude of EMG signals demonstrated high correlation, with a correlation coefficient of R = 0.792. In contrast, the results of analysis performed on the peak-to-peak (PP) EMG intervals, which correspond to the RR intervals of ECG signals, indicated a correlation between ΔF fluctuation and angular velocity of R = 0.379. Thus, the accuracy of the regression curve was relatively poor. Using a DC amplification circuit without capacitive coupling as the EMG amplification circuit, we confirmed that the baseline changes at the gear change point of wing flapping. The following formula gives the lift provided by the wing: angular velocity × thoracic weight - air resistance - (eddy resistance due to turbulence). In future studies, we plan to attach a micro radio transmitter to the moths to gather data on potential energy, kinetic energy, and displacement during free flight for analysis. Such physiological functional evaluations of moths may alleviate damage to insect health due to repeated exposure to multiple agrochemicals and may lead to significant changes in the toxicity standards, which are currently based on LD50 values.

• 한국음향학회지
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• 제32권3호
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• pp.191-198
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• 2013

본 논문에서는 광대역 Tonpilz 트랜스듀서를 설계하고, 설계 결과의 타당성을 실험적으로 검증하였다. 광대역 주파수 특성을 이루기 위해서 전면추의 flapping 모드를 트랜스듀서의 종방향 공진 모드와 결합시켰으며, 유한요소 해석과 유전자 알고리즘을 이용하여 주어진 설계조건, 구동조건 하에서 가장 넓은 송신 비대역폭(fractional bandwidth)을 확보할 수 있는 트랜스듀서의 최적 구조를 설정하였다. 최적화된 구조는 단일모드 트랜스듀서에 비해 월등히 넓은 -6 dB 송신 비대역폭을 나타내었다. 설계 결과의 타당성을 검증하기 위하여 도출된 최적 구조대로 트랜스듀서 시험편을 제작하여 주파수 특성을 측정하였으며, 측정결과는 설계 결과와 잘 일치하였다.

• Journal of Mechanical Science and Technology
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• 제15권5호
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• pp.646-655
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• 2001

This paper reports the effects of nozzle exit boundary layer swirl on the instability modes of underexpanded supersonic jets emerging from plane rectangular nozzles. The effects of boundary layer swirl at the nozzle exit on thrust and mixing of supersonic rectangular jets are also considered. The previous study was performed with a 30°boundary layer swirl (S=0.41) in a plane rectangular nozzle exit. At this study, a 45°boundary layer swirl (S=1.0) is applied in a plane rectangular nozzle exit. A three-dimensional unsteady compressible Reynolds-Averaged Navier-Stokes code with Baldwin-Lomax and Chiens $\kappa$-$\xi$ two-equation turbulence models was used for numerical simulation. A shock adaptive grid system was applied to enhance shock resolution. The nozzle aspect ratio used in this study was 5.0, and the fully-expanded jet Mach number was 1.526. The \"flapping\" and \"pumping\" oscillations were observed in the jets small dimension at frequencies of about 3,900Hz and 7,800Hz, respectively. In the jets large dimension, \"spanwise\" oscillations at the same frequency as the small dimensions \"flapping\" oscillations were captured. As reported before with a 30°nozzle exit boundary layer swirl, the induction of 45°swirl to the nozzle exit boundary layer also strongly enhances jet mixing with the reduction of thrust by 10%.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.152-161
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• 2013

This paper presents a control effectiveness analysis of the hawkmoth Manduca sexta. A multibody dynamic model of the insect that considers the time-varying inertia of two flapping wings is established, based on measurement data from the real hawkmoth. A six-degree-of-freedom (6-DOF) multibody flight dynamics simulation environment is used to analyze the effectiveness of the control variables defined in a wing kinematics function. The aerodynamics from complex wing flapping motions is estimated by a blade element approach, including translational and rotational force coefficients derived from relevant experimental studies. Control characteristics of flight dynamics with respect to the changes of three angular degrees of freedom (stroke positional, feathering, and deviation angle) of the wing kinematics are investigated. Results show that the symmetric (asymmetric) wing kinematics change of each wing only affects the longitudinal (lateral) flight forces and moments, which implies that the longitudinal and lateral flight controls are decoupled. However, there are coupling effects within each plane of motion. In the longitudinal plane, pitch and forward/backward motion controls are coupled; in the lateral plane, roll and side-translation motion controls are coupled.

• 한국가시화정보학회지
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• 제3권2호
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• pp.63-70
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• 2005

Birds and insects flap their wings to fly in the air and they can change their wing motions to do steering and maneuvering. Therefore, we created various wing motions with the parameters which affected flapping motion and evaluated the aerodynamic characteristics about those cases in this study. As the wing rotational velocity was fast and the rotational timing was advanced, the measured aerodynamic forces showed drastic increase near the end of stroke. The mean lift coefficient was increased until angle of attack of $50^{\circ}$ and showed the maximum value of 1.0. The maximum mean lift to drag ratio took place at angle of attack of $20^{\circ}$. Flow fields were also visualized around the wing using particle image velocimetry (PIV). From the flow visualization, leading-edge vortex was not shed at mid-stroke until angle of attack of $50^{\circ}$. But it was begun to shed at angle of attack of $60^{\circ}$.

• 한국항공우주학회지
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• 제36권11호
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• pp.1063-1071
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• 2008

단일층 압전작동기에 적절한 압축하중을 가하면, 압전세라믹 층에 가해지는 압축 응력에 의한 재료비선형적 특성과 기계적 좌굴현상에 의하여 작동 변위와 작동력이 동시에 향상된다. 본 논문에서는 날갯짓 기구를 압축하중을 받는 단일층 압전 작동기로 구동하는 경우, 날갯짓 각도와 공기력에 어떠한 영향이 발생하는가를 조사하였다. 또한 날개 형상과 수동 날갯 회전 각도가 공기력 발생에 미치는 영향도 실험적으로 조사하였다. 인공 날개를 2차원으로 가정한 전산유체해석을 통하여 얻은 평균 수직력이, 실험으로 얻은 값과 잘 일치함을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.181-186
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• 1999

The effects of the frequency of upstream gust on the unsteady boundary characteristics on a downstream blade was simulated by using a Navier-Stokes code. The Navier-Stokes code is based on an unstructured finite volume method and uses a low Reynolds k-e turbulence model to close the momentum equations. The MIT flapping foil experiment set-up is used to simulate the interaction between the upstream wake and a blade. The frequency of the upstream wake is simulated by varying rate of pitching motion of the flapping airfoils. Three reduced frequencies. 3.62. 7.24. and 10.86. are simulated. As the frequency increases, the unsteady fluctuation on the surfaces of the downstream hydrofoil is shown to decrease while the upstream flapper wake has larger first harmonics of y-velocity component. The unsteady vortices are shown to interact with each other and. as a result. the upstream wake becomes undiscernible inside the inner layer. The turbulence kinetic energy shows a similar behavior. Limiting streamlines around the trailing edge of the flapper are shown to conform with the unsteady Kutta condition for a round trailing edge. while limiting streamlines around the trailing edge of the hydrofoil conforms with the unsteady Kutta condition for a sharp edge.

• Smart Structures and Systems
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• 제19권5호
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• pp.553-565
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• 2017

Structural modeling of unencapsulated ionic polymer metal composite (u-IPMC) actuators that are used for flapping the insect scale-flapping wing of micro air vehicles (FMAV) in dry environmental conditions is carried out. Structural modeling for optimization of design parameters for retention of water, maximize actuation performance and to study the influence of water activity on the actuation characteristics of u-IPMC is explored for use in FMAV. The influence of equivalent weight of Nafion polymer, cations, concentration of cations, pre-treatment procedures on retention of water of u-IPMCs and on actuation parameters, flapping angle, flexural stiffness and actuation displacement are investigated. IPMC designed with Nafion having equivalent weight 900-1100, pre-heated at $30^{\circ}C$ and with sodium as the cations is promising for optimum retention of water and actuation performance. The actuation parameters while in operation in dry and humid environment with varying water activity can be tuned to desirable frequency, deflection, flap angle and flexural stiffness by changing the water activity and operational temperature of the environment.

• 한국해양공학회지
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• 제33권2호
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• pp.189-195
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• 2019

In this study, experiments with a floater using flapping foils were performed to develop a new station keeping system that can maintain its position in waves without mooring lines. The foils applied to this system generate thrust using wave energy. In this experiment, the motion of the floater was analyzed in three different wave periods. Sixteen foils were attached to the cylindrical floater. The thrust of each foil was controlled by changing its azimuth angle, and three cases were compared. Based on the previous data, we made more precise measurements and found an optimal model for stationkeeping under each wave condition. We verified the potential of this new stationkeeping system using flapping foils, and conclusions were drawn from the results.

• 항공우주시스템공학회지
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• 제17권6호
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• pp.54-62
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• 2023

자유로운 이착륙과 뛰어난 비행능력을 가진 플랩핑 날갯짓 비행체에 관한 집중적 연구개발이 진행되고 있다. 대부분의 플랩핑 날갯짓에 관한 연구는 동기화된 운동의 다양한 운동변수에 대한 연구들로 비동기 운동을 수행하는 에어포일의 비정상 공력 특성에 미치는 영향에 대한 관심은 크지 않았다. 본 연구에서는 히브와 피치 진동운동 주파수가 서로 다른 에어포일의 비정상 공력특성을 수치적으로 연구했다. 먼저 비동기 운동에 따른 운동특성과 받음각 변화를 파악하였다. 해석 결과 진동수 비가 1.0인 경우 양력은 발생하지 않았고 추력이 크게 발생했다. r=0.5인 경우 양력이 크게 발생하였다. 에어포일 주변의와 분포와 표면에서의 압력계수를 분석하여 비동기 진동운동을 하는 에아포일의 공력특성을 분석했다. r=0.5인 경우 r=1.0인 경우 보다 더 큰 앞전 및 뒷전 와들이 관찰되었으며, 이 와들이 비동기 진동운동을 하는 에어포일의 공력특성에 큰 영향을 미친 것을 발견하였다. 향후 피치진동의 진폭이 비동기 진동운동을 하는 에어포일의 비정상 공력특성에 미치는 영향을 연구할 계획이다.