• Journal of Advanced Marine Engineering and Technology
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• v.26 no.4
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• pp.485-492
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• 2002

The present study is aimed to reveal macroscopic aerodynamic characteristics of two-dimensional rectangular prisms with three aspect ratios(D/H=1, 2 and 3) and six angles of attack($0^{circ}, 10^{circ}, 13.5^{circ}, 20^{circ}, 30^{circ} and 45^{\circ}$). The Reynolds number is fixed as $1\times10^4$. The SOLA-based revised finite difference method for the conservation form on irregular grid was adopted as a new numerical method. Instantaneous flow patterns at $45^{\circ}$ in case of D/H=2 and D/H=3 show larger asymmetric wake development which is closely related to the sharp decrease of drag coefficients at higher angles of attack range. Vorticity propagation into enlarged wake region is conjectured to be responsible for this phenomenon. The Strouhal number is found to be sensitive to the angle of attack at higher aspect ratios(D/H=2 and 3).

• Journal of The Korean Society of Grassland and Forage Science
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• v.12 no.4
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• pp.253-259
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• 1992

The esterase isozyme in tissue of wild legume plants were separated by horizontal starch gel electrophoresis. Extracts used in this study were prepared from fully expanded young leaf, cotyledon and radicle of seedling and root-nodule of Glycine sola, Vigna vexillata var. tsuscmensis and Trifoliwn repens. The results are as follows; 1. Each tissue examined had a characteristic banding pattcrn. Number of bands in each species, G. soja, V. vexillata, and T . repens, were 14, 8 and 1 1 bands, respectively. And difference in esterase isozyme bands were greater from tissue to tissue than difference between habitat. 2. Est-I, Est-2. Est-3 and Est-4 in G. soja, Est-I in V. vexillata and Est-l and Est-2 in T. repens showed strong cnzyme activity than other enzyme. 3. Esterase isozyme variation in G. soja and T . repens showed more variety than V. vexillata. This is resulted from many genotypic differences within species. 4. The main enLyme among thc esterase isozyme were Est-I. Est-2, Est-3 and Est-4.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.38-40
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• 2012

해상 교통량 증가로 급증하는 선박 사고 위험을 줄이기 위해 안전 운항 관리를 위한 연구가 필수적이다. 최근 SOLAS에서 300톤 이상 급에 대해서는 AIS의 의무 장착이 제정되면서 선박 운항의 안전에 크게 기여하고 있다. 본 연구에서는 AIS의 정적, 동적 데이터를 수집하여 항계내 통항 선박의 궤적의 곡률을 분석하여 불규칙 이동 조종선박의 움직임을 파악하였다. 기존의 과거 누적 데이터의 퍼지이론을 활용한 이상 거동의 선박식별 시스템은 전문가 시스템에 의존하여 항적의 비정상성을 판단하므로 항로의 특성에 따른 실 항해상황을 간과할 수 있는 문제점이 있다. 본 연구는 선박 움직임에 대한 궤적의 시간 AIS 정보를 활용하여 항로이탈의 변화율에 해당하는 곡률분석, 항로선으로부터 좌우의 변동을 보다 정확하게 모니터링 할 수 있는 이상 거동 선박을 식별하는 방법을 제안한다. 본 연구는 VTS 및 VMS의 응용서비스로서 해양사고의 사전예방을 위한 연안 및 항만수로의 효율적인 관리에 기여할 것이다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.64-66
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• 2016

국제항해에 종사하는 500GT 이상의 상선에서는 SOLAS에 의해 2012년부터 ECDIS 사용이 강제화 됨에 따라 선박에서는 기존의 종이해도 대신 전자해도를 가지고 항해해야하는 극적인 변화를 맞이하였다. ECDIS는 H/W, S/W, data가 어우러진 복합전자장비로서 안전항해를 위해서는 ECDIS에서 제공받는 데이터의 신뢰성, 시스템 안전성을 확보하고 ECDIS에 대한 사용자의 올바른 이해와 숙련이 매우 중요하다. 하지만 선박에 새로운 항해 장비가 등장함으로서 예측하지 못한 다양한 문제가 식별되었고 또다른 문제가 추가적으로 발견될 수 있는 위험성을 내포하고 있다. 이러한 문제점을 보완하고 ECDIS 장비의 안정적인 선박 도입이 진행되도록 IMO에서는 식별된 ECDIS의 이상현상과 주의사항에 대한 회람문서가 하나의 통합된 문서로 발행되었다. 이 연구에서는ECDIS의 올바른 사용을 위해서 2015년 발행된 통합 ECDIS 회람문서 'ECDIS-Good Practice'를 바탕으로 선박에서 ECDIS를 안정적으로 사용하고 받아들일 수 있는 방법에 대해서 분석하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.35-44
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• 1999

High negative pressure coefficient is formed in the corner of the bluff body structures. For many curtain wall designers this phenomena is of interest because this high negative pressure coefficient is adopted in structural calculation. The present study is aimed to investigate shedding vortex characteristics of two-dimensional rectangular prism flow. Unsteady calculation by finite difference method based upon SOLA is carried out for three aspect ratios(1:1, 1:2, 1:3) of Re=10$^4$ in viscous incompressible flow within infinite domain. Fluctuation of velocity components at various pick-up points and time variation of drag and lift coefficients are analysed by FFT method to reveal shedding vortex frequency patterns. At aspect ratio 1:1, one primary Strouhal number appears for about all pick-up points. At aspect ratio 1:2, two representative Strouhal numbers are classified by pick-up positions and their flows show two different reattachment patterns. For aspect ratio 1:3, frequency spectrum maintains multiple peaks.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2004.04a
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• pp.466-469
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• 2004

In this paper, real-time voice change method using pitch change technique is proposed to change one's voice to the other voice. For this purpose, sampling rate change method using DFT (Discrete Fourier Transform) method and time scale modification method using SOLA (Synchronized Overlap and Add) method is combined to change pitch. In order to evaluate the performance of the proposed method, voice transformation experiments were conducted. Experimental results showed that original speech signal is changed to the other speech signal in which original speaker's identity is difficult to find. The system is implemented using TI TMS320C6711DSK board to verify the system runs in real time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1168-1176
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• 2003

Internet telephony service is very cheap and very easy to introduce the value-added service than the POTS, but is difficult to the QoS of telephone service. The existing internet typically offers "best effort" services only, which do not make any commitment about delay, packet loss and jitter. This paper compensates the low quality of the speech for packet loss or delay using FEAPT algorithm in Internet phone. In the FEAPT algorithm, the receiver expands the received packet under resonable threshold, and hence compensates the QoS of speech.of speech.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.127-132
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• 1998

The present study is aimed to investigate flow characteristics of Two dimensional backward-facing step by numerical approach. A convection conservative difference scheme based upon SOLA algorithm is used for the solution of the two-dimensional incompressible Navier-Stokes equations to simulate the laminar, transitional and turbulent flow conditions at which the experimental data can be available for the backward-facing step. The twenty kinds of Reynolds number are used for the calculations. In an effort to demonstrate that the reported solutions are dependent on the mesh refinement, computations are performed on seven different meshes of uniformly increasing refinement. Also to investigate the result of inflow dependence, two kinds of the inflow profile are chosen for the laminar flow. As criterion of benchmarking the result of numerical simulation, reattachment length is used for the selected Reynolds numbers.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.122-129
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• 1997

Flow characteristics of two-dimensional closed square cavities near unsteady critical Reynolds numbers were studied numerically at five Reynolds numbers : 8${\times}10^3$, 8.5${\times}10^3$, 9${\times}10^3$, 9.5${\times}10^3$ and $10^4$ were investigated. A convection conservative difference scheme based upon SOLA to maintain the nearly 2nd-order spatial accuracy was adopted on irregular grid formation. Irregular grid number is 80${\times}$80 and its minimum size is about 1/400 of the cavity height(H) and its maximum is about 1/53 H. The result shows that the critical Reynolds number indicating the emergence of flow unsteadiness exists near Re=8.5${\times}10^3$ and their flow patterns reveal periodic fluctuation during transient and fully-developed stages.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.5
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• pp.22-29
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• 1996

Flow characteristics of two-dimensional closed square cavities near unsteady critical Reynolds numbers were studied numerically at four Reynolds numbers : $8{\times}10^3,\;8.5{\times}10^3,\;9{\times}10^3\;and\;9.5{\times}10^3.$ A convection conservative difference scheme based upon SOLA to maintain the nearly 2nd-order spatial accuracy is adopted on irregular grid formation. Irregular grid number is $80{\times}80$ and its minimum size is about 1/400 of the cavity height(H) and its maximum is about 1/53 H. The result shows that the critical Reynolds number indicating the emergence of flow wnsteadiness is ranging from Re=$8{\times}10^3\;to\;8.5{\times}10^3$ and their flow patterns reveal periodic fluctuation during transient and fully developed stages. But macroscopic flow behavior in terms of instantaneous and time-mean characteristics represent remarkable difference.