• Steel and Composite Structures
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• 제22권1호
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• pp.203-216
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• 2016

To study the stress concentration factors (SCFs) of concrete-filled tubular Y-joints subject to in-plane bending, experiments were used to investigate the hot spot stress distribution along the intersection between chord and brace. Three concrete-filled tubular chords forming Y-joints were tested with different reinforcing components, including doubler-plate, sleeve, and haunch-plate reinforcement. In addition, an unreinforced joint was also tested for comparison. Test results indicate that the three different forms of reinforcement effectively reduce the peak SCFs compared with the unreinforced joint. The current research suggests that the linear extrapolation method can be used for chords, whereas the quadratic extrapolation method must be used for braces. The SCF is effectively reduced and more evenly distributed when the value of the axial compression ratio in the chord is increased. Furthermore, the SCFs obtained from the test results were compared to predictions from some well-established SCF equations. Generally, the predictions from those equations are very consistent for braces, but very conservative for concrete-filled chords.

• 한국정보전자통신기술학회논문지
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• 제6권3호
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• pp.189-194
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• 2013

본 논문에서는 대중음악 코드진행 패턴 분석을 통해 최적의 코드진행을 완성시키고 해당 코드진행의 멜로디 정보 일부를 비트행렬로 구성하여 신경망의 입력 벡터로 사용하였다. 실험결과 신경망 학습을 이용한 컴퓨터의 작곡 가능성을 확인하였다. 제안한 방법을 이용하면 임의의 멜로디를 다양하게 재구성 할 수 있는 방법론을 만들어 낼 수 있다.

• 한국해양공학회지
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• 제12권2호통권28호
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• pp.79-86
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• 1998

A three-dimensional WIG (Wing In Ground effect) moving above free surface is numerically studied by means of finite difference techniques. The air flow field around the WIG is analyzed by MAC (Marker & Cell) method, and interactions between WIG and the free surface are appeared as the variation of pressure distribution acting on the free surface. To analyze the wavemaking phenomena by those pressure distributions, the NS (Navier-Stokes) solver is employed in which nonlinearities of the free surface conditions can be included. Through the numerical simulation, Cp values and lift/drag ratio are carefully reviewed by changing the height/chord ratio. The section shape of model is NACA0012 with the span/chord ratio of 3.0. Through computational results, it is confirmed that the effect of free surface is small enough to treat it as a rigid wavy wall.

• Journal of Mechanical Science and Technology
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• 제15권3호
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• pp.384-391
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• 2001

The aerodynamic effects of a 3-dimensional Wing in Ground Effect (WIG) which moves above the free surface has been numerically investigated via finite difference techniques. The air flow field around a WIG is analyzed by a Marker & Cell (MAC) based method, and the interactions between WIG and the free surface are studied by the pressure distributions on the free surface. Waves are generated by the surface pressure distribution, and a Navier-Stokes solver has been employed, to include the nonlinearities in the free surface conditions. The pressure values Cp and lift/drag ratio are reviewed by changing the height/chord ratio. In the present computations a NACA0012 airfoil with a span/chord ratio of 3.0 are treated. Through computational results, it is confirmed that the free surface can be treated as a rigid wavy wall.

• 대한전자공학회논문지
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• 제22권5호
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• pp.10-16
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• 1985

본 논문에서는 인쇄 양보 서상을 CCTV 카메라로써 마이크로 컴퓨터에 입력시켜, 이 화상을 인식, 스피커로 노래를 내어주는 컴퓨터 비젼 시스템에 관해 논하고 있다. 이때 내보서조의 특징추출 및 인식에는 가산투영법이 적용되구 그 대상 인식 범위는 내보의 여러 요소 중에서 오연 마디, 음표로 하고 있다. 아울러 분제 내보화징을 취급할 때 반드시 고려되어야 할 전처리 및 잡음 제거 과정을 보였고, 인식된 음표로 화음을 내민주는 간단한 하드웨어 시스템을 구성했다. 그 결과 보호한 인식률로 연주 가능함을 보였다.

• 한국추진공학회지
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• 제9권1호
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• pp.46-52
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• 2005

무인표적기의 성능 향상을 위해 추진시스템인 프로펠러를 재설계하였다. Vortex 이론을 이용한 설계 및 해석 프로그램을 사용하였으며, 설계 변수는 반경 방향에 따른 코드 길이, 블레이드의 반경 변화, 그리고 비틀림각 등이다. 저속과 고속일 때 모두 향상된 추력을 내도록 엔진 회전수 변경을 포함하여 프로펠러를 재설계 하였다.

• 산업기술연구
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• 제18권
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• pp.335-341
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• 1998

A numerical investigation was performed to determine the effect of a Gurney flap on a NACA 23012 airfoil. A Navier-Stokes code, RAMPANT, was used to calculate the flow field about airfoil. The fully turbulent results were obtained using the standard $k-{\varepsilon}$ two-equation turbulence model. To provide a check case for our computational method, computations were performed for NACA 4412 airfoil which compared with Wedcock's experimental data. Gurney flap sizes of 0.5, 1.0, 1.5, and 2% of the airfoil chord were studied. The numerical solutions showed the Gurney flap increased both lift and drag. These results suggested that the Gurney flap served to increased the effective camber of the airfoil. But Gurney flap provided a significant increase in lift-to-drag ratio relatively at low angle of attack and for high lift coefficient. Also, it turned out that 0.5% chord size of flap was best one among them.

• Fibers and Polymers
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• 제7권2호
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• pp.191-194
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• 2006

This paper adopts nonlinear vibration method to analyze the fluctuation process of fiber movement. Based on Hamilton Principle, this paper establishes differential equation of fiber axial direction movement. Using variable-separating method, this paper separates time variable from space variable. By using the disperse movement equation of Galerkin method, this paper also discusses stable region of transition curve and points out those influencing factor and variation trend of fiber vibration.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.759-764
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• 2003

Numerical simulations are conducted to investigate the mechanism of hovering flight by single flapping wing, and to examine the effect of the phase difference between the fore- and hindwings in hovering flight by two flapping wings. The numerical method used is based on an immersed boundary method in Cartesian coordinates. The Reynolds number considered is Re=150 based on the maximum translational velocity and chord length of the wing. For single flapping wing, the stroke plane angles are $0^{\circ}$, $30^{\circ}$, $60^{\circ}$, $75^{\circ}$ and $90^{\circ}$ and the downstroke angles of attack are varied for each stroke angle. Results show that for each stroke plane angle, there is an optimal angle of attack to maximize the vertical force. Below the stroke angle of $60^{\circ}$, wake capturing reduces the negative vertical force during the upstroke. For two flapping wings, The phase lags of the hindwing are $0^{\circ}$, $90^{\circ}$, $180^{\circ}$ and $270^{\circ}$. The amplitudes of the stroke are 2.5 and 4.0 times the chord length at each phase lag. The results show that maximum vertical force is generated when the phase lag is zero, and the amplitude of the vertical force is minimum at the phase lag of $180^{\circ}$.

• Journal of Ecology and Environment
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• 제30권2호
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• pp.195-199
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• 2007

Statistical tools for determining sex in the sexually monomorphic black-billed magpie based on morphological characters have been developed based on studies of European and North American populations. However, since no morphological method has been developed for black-billed magpies in Korea, it has been difficult to conduct field studies that require information about the sex of individuals. We present two discriminant equations for determining sex of second-year (SY) and after-second-year (ASY) magpies in north- and midwestern part of South Korea. Based on morphological measurements on 105 SY (56 females, 49 males) and 72 ASY (36 females, 36 males) individuals, we found body mass, wing chord, and head length to be the most useful features for morphological sex determination. The accuracy of our method was 86.5% for SYs and 93.1% for ASYs, which is similar to values reported previously from American and European magpies. Since the equations contain morphological traits which are only minimally susceptible to seasonal variation and measurement errors, our discriminant equations should be both useful and robust for sex determination on black-billed magpies in the northern and mid-western regions of South Korea.