• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.1020-1024
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• 1987

Image segmentation based on the curvature of bi-directiona distribution functions of histogram with no mode informations is proposed. The curvature is an oscillating function and can be approximated to a polynomial form with a least square method using the Chebyshev basis. Nonhomogeneous linea equations are solved by Gauss-elimination method. In the proposed algorithm, critical points of the curvature are obtained on each direction to compensate the segmentation parameters, which can be ignored in only one-directional histogram.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3598-3606
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• 1996

The finite volume method for radiation is applied to investigate a radiative heating of rocket base plane due to searchlight and plume emissions. Exhaust plume is assumed to absorb, emit and scatter the radiant energy isotropically as well as anisotropically, while the medium between plume boundary and base plane is cold and nonparticipating. Scattering phase function is modelled by a finite series of Legendre polynomials. After validating benchmark solution by comparison with that of previous works obtained by the Monte-Carlo method, further investigations have been done by changing such various parameters as plume cone angle, scattering albedo, scattering phase function, optical radius and nozzle exit temperature. The results show that the base plane is predominantly heated by the plume emission rather than the searchlight emission when the nozzle exit temperature is the same as that of plume.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.1
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• pp.39-45
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• 2004

The vibration characteristics of rotating machinery are directly related withits condition such as rotor types, thereby it should be acquired the information fromthe vibration signal so that operating conditions may be rationally decided.Accordingly, the study is to focus on developing the analysis for identifying theoperational feature of rotor systems. For this purpose the complex frequencyanalysis for identification, which utilizes the directionaI spectrum for effectiveidentification of rotor systems, is introduced. From this proposed method, theanalysis of dynamic model of the rotors is performed including the stabilitybehavior of the general rotor by Ftoquet theory. Through this process theexcitation methodology to identify the types of rotors is investigated and theeffective way to identification is also suggested.

• The Korean Journal of Zoology
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• v.33 no.3
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• pp.247-254
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• 1990

Chicken monocular head and eye optokinetic nystagmus (OKN) were observed by coil recordings after intravitreal administration of GABA antagonists (picrotoxin and bicuculline) into the opened and closed eye. Before injection of drugs the chicken displayed an OKN for T-N stimulation being more efficient in evoking this visuomotor reflex than for N-T stimulation. The injection of GABA antagonist into the opened eye provoked a decrease or disappearance of the head and eye OKN. On the other hand, the injection of GABA antagonist into the closed eye, the head and eye OKN augmented. Thus, GABA antagonist abolished the directional asymmetry of the head and eye OKN, indicating the involvement of GABAergic mechanisms in the inhibition of the N-T component of the monocular OKN.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.917-920
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• 2007

무선 Ad-hoc 네트워크에서는 주로 IEEE 802.11 MAC 프로토콜을 이용한다. IEEE 802.11 MAC 프로토콜은 제어 메시지인 RTS-CTS를 통해서 채널 예약을 하고 데이터를 전송하는 방식으로 모든 통신에 Omni-directional 안테나를 이용하여 전송한다. 본 논문에서는 기존 IEEE 802.11 MAC 프로토콜보다 성능을 향상시키기 위해서 directional 안테나를 이용한 MAC 프로토콜을 사용한다. Directional 안테나를 사용한 MAC 프로토콜은 IEEE 802.11 MAC 프로토콜에 비해서 Spatial Reuse를 증가함으로서 채널 자원을 더욱 효율적으로 사용하는 것이 가능하다. 또한 Directional 안테나의 사용은 안테나의 지향성에 따른 안테나 이득 및 전송 범위의 증가 그리고 전송 범위를 Omni-directional 안테나와 동일하게 적용할 경우에는 저 전력 통신이 가능하다는 장점을 가지고 있다. 그러나 Directional 안테나의 사용은 IEEE 802.11 MAC보다 좋은 성능을 갖기는 하지만 새로운 문제들이 발생한다. 이러한 문제들로는 New Hidden Terminal, Deafness, Capture, 그리고 위치 인식에 관련된 문제들이 발생한다. 본 논문에서서 위에서 언급한 Directional 안테나의 이점과 그리고 문제점에 대해서 설명하고, 이러한 문제들 중에 Deafness 문제를 완화시킬 수 있는 방법을 제안한다. 그리고 QualNet 4.0을 이용한 시뮬레이션을 통해서 제안된 프로토콜의 성능을 평가한다.