• 오토저널
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• 제14권4호
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• pp.90-96
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• 1992

The effect of base cavities on the drag of a simplified tractor-trailor model for Re=4.1*10$^{5}$ is investigated experimentally. Three different types of base cavities are studied in this work. They are solid-wall, slitted-wall, and slotted-wall cavities. Slotted-wall cavity is found to be most effective for drag reduction. A maximum of 11% reduction in the zero-yaw drag coefficient is achieved with the slotted wall cavity.

• 한국해양공학회지
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• 제13권1호통권31호
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• pp.18-22
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• 1999

One of the problem areas in designing a barge is its resistance and corese stability when it is towed by a tugboat. In this paper, as a part of design of a incinerating vessel, the results of some experimental studies on the effect of various kinds of anti-yawing skegs to the course keeping stability and on the additional resistance caused by them were summarized.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.7-14
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• 2002

In order to achieve high precision machine tools, the research for performance enhancement of feed drive systems is required. Development of the high speed feed drive system has been a major issue for the past few decades in machine tool indestries. Because table levitation system decrease the table weight, an effect of reaction by weight is minimized and lost motion can be removed at maximum. In case fled system is designed with drive motor, ball screw and support bearing load capacity selection, an effect of decrease of the table weight exist. So, the table weight through an effect of decrease call it into the realization of cost down. Stick-slip friction has a great influence on the contouring accuracy of CNC machine tools. In this paper table levitation system has been developed for the stick-slip in a fled drive systems.

• Wind and Structures
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• 제29권6호
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• pp.457-469
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• 2019

In this paper, a numerical solution is presented for supersonic flutter analysis of cantilever non-symmetric functionally graded (FG) sandwich plates. The plate is considered to be composed of two different functionally graded face sheets and an isotropic homogeneous core made of ceramic. Based on the first order shear deformation theory (FSDT) and linear piston theory, the set of governing equations and boundary conditions are derived. Dimensionless form of the governing equations and boundary conditions are derived and solved numerically using generalized differential quadrature method (GDQM) and critical velocity and flutter frequencies are calculated. For various values of the yaw angle, effect of different parameters like aspect ratio, thickness of the plate, power law indices and thickness of the core on the flutter boundaries are investigated. Numerical examples show that wings and tail fins with larger length and shorter width are more stable in supersonic flights. It is concluded for FG sandwich plates made of Al-Al₂O₃ that increase in volume fraction of ceramic (Al₂O₃) increases aeroelastic stability of the plate. Presented study confirms that improvement of aeroelastic behavior and weight of wings and tail fins of aircrafts are not consistent items. It is shown that value of the critical yaw angle depends on aspect ratio of the plate and other parameters including thickness and variation of properties have no considerable effect on it. Results of this paper can be used in design and analysis of wing and tail fin of supersonic airplanes.

• International Journal of Aeronautical and Space Sciences
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• 제1권1호
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• pp.70-80
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• 2000

The attitude knowledge error model is formulated for specifically KOMPSAT attitude determination system using the Lefferts/Markley/Shuster method, and the attitude determination(AD) error analysis is performed so as to investgate the on-board attitude determination capability of KOrea Multi-Purpose SATellite(KOMPSAT) using the covariance analysis method. Analysis results show there is almost no initial value effect on Attitude Determination (AD) error and the sensor noise effects on AD error are drastically decreased as is predicted because of the inherent characteristic of Kalman filter structure. However, it shows that the earth radiance effect of IR-sensor(earth sensor) and the bias effects of both IR-sensor and fine sun sensor are the dominant factors degrading AD error and gyro rate bias estimate error in AD system. Analysis results show that the attitude determination errors of roll, pitch and yaw axes are 0.056, 0.092 and 0.093 degrees, respectively. These numbers are smaller than the required values for the normal mission of KOMPSAT. Also, the selected on-orbit data of KOMPSAT is presented to demonstrate the designed AD system.

• International Journal of Fluid Machinery and Systems
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• 제1권1호
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• pp.47-56
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• 2008

The flow behind the variable area nozzle which corresponds to the flow at the leading edge of the impeller was measured with a 3-hole yaw probe and calculated with CFD. Two nozzle throat-areas were investigated. One is the smallest and the other is the largest opening for the variable nozzle. Test results agreed with the calculated results qualitatively. The leakage flow through the tip clearance of the nozzle vane significantly affected the flow field downstream of the nozzle vane with the smallest opening. However, the effect on leakage flow on the flow field downstream of the nozzle vane with the largest opening was very weak and the effect of wake is dominant.

• 대한기계학회논문집
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• 제8권6호
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• pp.526-535
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• 1984

본 연구에서는 개인용 컴퓨터 정도를 사용하여서도 각 성능을 계산할 수 있고 또 실제 상황이 비교적 잘 반영될 수 있는 모델을 채택하였다. 한편으로 이 모델의 적합성 여부도 검토하여 해석 결과의 적용한계를 추측하고져 하였다.

• 제어로봇시스템학회논문지
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• 제11권3호
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• pp.246-253
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• 2005

An experimenal study on flight control of high-speed AEV(Aero-levitation Electric Vehicle) scale model in wind-tunnel is conducted. The AEV is to fly at very low altitude in predesigned track so that it is always under the wing-in-ground effect. The experiment is intended to fly the scale model to follow the predesigned altitude schedule while holding its attitude (pitch, roll, and yaw). Especially, the altitude changes for climb, cruise, and descent with constant pitch angle are most important maneuvers. The experiment shows that the required mission flights can be performed with appropriate sensors, processors, and actuators.

• 한국정밀공학회지
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• 제24권6호
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• pp.66-71
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• 2007

Development of a locomotive mechanism for the capsule type endoscopes will largely enhance their ability to diagnose disease of digestive organs. As a part of it, there should be provided a detection device of their position in human organs for the purpose of observation and motion control. In this paper, a permanent magnet outside human body was employed to project magnetic field on a capsule type endoscope, while its position dependent flux density was measured by three hall-effect sensors which were orthogonally installed inside the capsule. In order to detect the 2-D position data of the capsule with three hall-effect sensors including the roll, pitch and yaw angle, the permanent magnet was extra translated during the measurement. In this way, the 2-D coordinates and three rotation angles of a capsule endoscope on the same motion plane with the permanent magnet could be detected. The working principle and performance test results of the capsule position detection device were introduced in this paper showing that they could be also applied to 6-DOF position detection.

• 한국해양공학회지
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• 제11권3호
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• pp.100-106
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• 1997

Despite various devices have been developed and applied to stabilize the yaw motion, the superiority of twin skeg over other equi-functioned appendages has been recognized so far. In many cases, these skegs were installed with insufficient study and analysis for design, and this leads to the worse performance of their resistance and course keeping than required. Experimental studies on the effect of various kinds of anti-yawing skegs to the course keeping stability and on the additional resistance caused by them were carried out in the circulating water channel(CWC) at Chosun University(CU). Course keeping stability tests for four different size of skegs, resistance tests for three different shapes of skeg(including deformed skegs) were performed systematically. And the effect of angle of skegs on resistance was studied at the final stage.