• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.234-239
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• 2002

Acoustic sounds generated by a uniform flow around a two-dimensional circular cylinder at Re=200 are simulated using finite difference lattice Boltzmann method. A third-order-accurate up-wind scheme is used for spartial derivatives, and a second-order-accurate Runge-Kutta scheme is used for time marching. The results show that in capturing very small acoustic pressure fluctuation with same frequency of Karman vortex street compared with the pressure fluctuation around a circular cylinder. The propagation velocity of acoustic sound is presented that acoustic which approaches tire upstream due to Doppler effect in the uniform flow slowly propagates, while that for the downstream quickly propagates. It is also apparent that the size of sound pressure is proportional for central distance $r^{-1/2}$ of the cylinder.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.109-115
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• 2003

In this paper we propose an efficient method to broadcast digital television signals using Single Frequency Networks (SFNs) in the Advanced Television Systems Committee (ATSC) transmission systems. Since the proposed schemes to synchronize multiple transmitters minimize the changes from the conventional ATSC system, the hardware complexity for the changes is very low. Our simulation results show that the proposed scheme makes less than 0.1 dB degradation at the threshold of visibility (TOV： BER= 3$\times$$10^{-6}$) in the additive white Gaussian noise (AWGN) channel. It is possible to reduce the performance degradation by increasing an initialization period of the proposed scheme.

• Journal of Astronomy and Space Sciences
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• v.27 no.3
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• pp.221-230
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• 2010

A 4+12+16 amplitude phase shift keying (APSK) modulation outperforms other 32-APSK modulations in a nonlinear additive white Gaussian noise (AWGN) channel because of its intrinsic robustness against AM/AM and AM/PM distortions caused by the nonlinear characteristics of a high-power amplifier. Thus, this modulation scheme has been adopted in the digital video broadcasting-satellite2 European standard. And it has been considered for high rate transmission of telemetry data on deep space communications in consultative committee for space data systems which provides a forum for discussion of common problems in the development and operation of space data systems. In this paper, we present an improved bits-to-symbol mapping scheme with a better bit error rate for a 4+12+16 APSK signal in a nonlinear AWGN channel and propose a simple signal detection algorithm for the 4+12+16 APSK from the presented bit mapping.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.492-495
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• 2003

Fuzzy Min-Max Neural Network(FMMNN) is a powerful classifier, It has, however, some problems. Learning result depends on the presentation order of input data and the training parameter that limits the size of hyperbox. The latter problem affects the result seriously. In this paper, the new approach to alleviate that without loss of on-line learning ability is proposed. The committee machine is used to achieve the multi-resolution FMMNN. Each expert is a FMMNN with fixed training parameter. The advantages of small and large training parameters are used at the same time. The parameters are selected by performance and independence measures. The Decision of each expert is guided by the gating network. Therefore the regional and parametric divide and conquer scheme are used. Simulation shows that the proposed method has better classification performance.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.118-122
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• 2000

In this study, Ringing is investigated by continuous wavelet transform. Ringing is considered to be one of the typical transient phenomena in the field of ocean engineering. The wavelet analysis is adopted to analyze ringing from the point that wavelet analysis is capable of frequency analysis as well as time domain analysis. The use mother wavelet is the Morlet wavelet. The relation between the frequency of the time series and that of wavelet can be clearly defined with Mor1et wavelet. Experimental data obtained by other researchers was used. The wave height time series and acceleration times series of the surface piercing cylinder were analyzed. The results show that the proposed scheme can detect typical frequency region by the time domain analysis which could hardly be detected if one relied on the frequency analysis.

• KCID journal
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• v.18 no.2
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• pp.101-110
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• 2011

There are found rare specific alternatives for sustainable rural development although sustainable development has become popular common concept in international development arena. Korea is trying to reform rural development by introducing a block grants system since 2009 expecting for the efficiency of development investment. However, it seems that such new rural development system is far from realizing the sustainable development. The objectives of the study are to identify the roles and issues of the sustainable development policy and to suggest a policy model for realizing sustainable rural development. Based on the policy model hypothetically established, some policy alternatives were suggested: (i) the establishment of land use system considering sustainability perspectives; (ii) the preparation of environment management measures considering topographical traits; (iii) the improvement of landscape support scheme toward increasing biodiversity; (iv) the systematic implementation of agriculture-environment measures; (v) the implementation of sustainable development projects linking production to housing; (vi) the inclusion of sustainability indicators in rural development evaluation system.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.231-239
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• 2003

A Digital Wave Tank simulation technique based on a finite-difference method and a modified marker-and-cell (MAC) algorithm is applied to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach and Ohkushiri island, and to predict maximum wave run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain and the boundary values updated at each time step by a finite-difference time-marching scheme in the frame of rectangular coordinate system. The fully nonlinear kinematic free-surface condition is satisfied by the modified marker-density function technique. The Nearshore Tsunami is assumed to be a solitary wave and generated from the numerical wavemaker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods based on the shallow-water wave theory.

• Journal of Koreanology Reviews
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• v.1 no.2
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• pp.11-18
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• 2022

International negotiation and cooperation for sustainable development currently emphasize three themes on which environmental policies are developed. South Korea emphasizes two of the three themes; climate change and the 2030 Agenda for Sustainable Development. South Korea has taken a leadership role in the international arena regarding these topics, actively participating in the United Nations Framework Convention on Climate Change (UNFCCC) and the negotiations for the 2030 Agenda (Jung, 2018). South Korea has taken a number of steps to address climate change, both domestically and internationally. Domestically, it has implemented several policies and methods to lessen GHG emissions and transition to a low-carbon economy. It has implemented an Emissions Trading Scheme, the largest in the world, a renewable energy portfolio standard, and aimed at accomplishing carbon neutrality by 2050. South Korea is also actively involved in executing the Sustainable Development Goals (SDGs) and has established a national committee to ensure their successful implementation. The group is made up of representatives from the private sector, government ministries, and civil society organizations. It is focused on monitoring the progress of the SDGs and providing policy and financial support for their implementation.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.226-231
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• 2003

The viscous interaction of stern wave is studied by simulating the free-surface flows, including sub-breaking phenomena around a high speed catamaran hull advancing on calm water. The Navier-Stokes equation is solved by a finite difference method where the body-fitted coordinate system, the wall function and the triple-grid system are invoked. The numerical appearance of the sub-breaking waves is qualitatively supported by the experimental observation They are also applied to study precisely on the stern flow of S-103 as to which extensive experimental data are available. For the catamaran, computations are carried out for the mono ana twin hulls.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.220-226
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• 2001

It is important to estimate exactly wave forces acting on various types of offshore structures under the severe environmental conditions in the ocean site. This paper presents an easy experimental method which deals with transient waves. The proposed scheme made it possible to generate breaking waves at any position in the wave tank by changing the maximum slope of the component waves. The theoretical and experimental methods were investigated by generating concentrated waves which acted on a single and multiple cylinders. The waves forces increased rapidly when the models encountered breaking waves. The theoretical results underestimates the forces due to breaking waves. Therefore, the effects due to breaking waves should be considered carefully in the design process of a structure under the influence of breaking waves.