• Journal of Information Technology Applications and Management
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• v.18 no.1
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• pp.41-53
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• 2011

The rapid development and widespread application of Internet has provided a platform for people to participate and discuss social hotspot events. In the meantime, social events may be spread throughout the Internet more quickly and widely than they did ever before, and possibly lead to serious social problems due to opinion violence or seditious rumour. This paper analyzed the Internet spread of social events, and presented a five-stage model to describe the evolution process of that spread. Furthermore, the improved IBF algorithm was applied to extract a pruned connected graph aiming to find the key nodes and the shortest spread path for the control of that spread. After analyzing the different factors that may cause the netizens' attention, this paper concluded BBS type, the visit quantity and the opinion leader are key factors which affect the Internet spread. Based on those researches, a life-cycle emergency management methodology and the related strategies were proposed for the achievement of healthy spreading environment on Internet.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1248-1255
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• 2006

The velocity and pressure fields of a ship's propulsion mechanism of the Weis-Fogh type, in which a airfoil moves reciprocally in a channel, are studied in this paper using the advanced vortex method. The airfoil and the channel are approximated by a finite number of source and vortex panels, and the free vortices are introduced from the body surfaces. The viscous diffusion of fluid is represented using the core-spreading model to the discrete vortices. The velocity is calculated on the basis of the generalized Biot-Savart law and the pressure field is calculated from integrating the equation given by the instantaneous velocity and vorticity fields. Two-dimensional unsteady viscose flows of this propulsion mechanism are numerically clarified, and the calculated results agree well with the experimental ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.263-270
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• 2020

In this study, the physical mechanism and diffusion effects in aluminium implanted silicon was investigated. For fabricating power semiconductor devices, an aluminum implantation can be used as an emitter and a long drift region in a power diode, transistor, and thyristor. Thermal treatment with O₂ gas exhibited to a remarkably deeper profile than inert gas with N₂ in the depth of junction structure. The redistribution of aluminum implanted through via thermal annealing exhibited oxidation-enhanced diffusion in comparison with inert gas atmosphere. To investigate doping distribution for implantation and diffusion experiments, spreading resistance and secondary ion mass spectrometer tools were used for the measurements. For the deep-junction structure of these experiments, aluminum implantation and diffusion exhibited a junction depth around 20 ㎛ for the fabrication of power silicon devices.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.456-463
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• 1997

Atrium buildings are commonly found in Hong Kong since 1980. Those spaces are usually crowded with people and so fire protection systems have to be installed for providing a safe environment. Smoke control system was identified to be important but no clear design guidelines are available because the smoke filling process was not well-understood. In this paper., Computational Fluid Dynamics(CFD) or fire field model is applied to study the smoke filling pattern in atrium. Two common cases on smoke spreading out from a shop adjacent to the atrium; and with a fire located at the atrium floor itself were considered. Simulations with a modified form of the CFD package TEAM were performed. Application of the predicted results Is illustrated.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.20-27
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• 2003

The nonparametric method was employed to obtain detailed broadband attenuation characteristics of horizontal Fourier spectra without generally assigned constraint that derived path terms be zeros at a reference distance. Instead, path terms fer a reference distance were obtained based on the physical phenomenon that the seismic phase is stable over the hypocentral distance range from 200km to 400km so that the Q-values evaluated at several distances inside that region should be the same. The inverted path terms show three distinct linear regions roughly divided by hypocentral distances at 65km and 115km. Also complex behavior at the near distance range below 100km was revealed which can not be properly fitted by combination of single $Q_{0}$ $f^{η}$ model and any geometrical spreading models.s.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06c
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• pp.16-21
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• 2010

잠재 의미를 색인하는 것은 문서 색인에 있어서 그 색인 품질에 주요한 요인을 차지한다. 본 논문에서 살펴보는 의미 확산 방법은 문서 집합에 나타나는 단어들의 의미적 연관성을 바탕으로 활성화 작용 모델(spreading activation model)을 구축하고 색인 대상 문서의 단어 분포를 출발점으로 삼아, 그 모델 안에서 의미적으로 수렴할 수 있도록 랜덤 워크 방법(random walk method)1)을 수정한 변형 방법을 이용해 확률을 확산시킨다. 이 방법은 단어 사이의 연관성을 따라 탐색하며 동의어와 다의어 등 단순 단어 일치로는 알 수 없는 의미적 유사 단어들이 의미 있는 확률 분포를 갖게 한다. 이는 단어들의 의미 분포를 가중치 그래프를 통해 보다 합리적으로 다루게 된다. 실험에서는 문서 분류를 시행하여 평균 정확도 및 정확도-재현율 곡선을 산출하였고, 비교 실험을 통해서 전반적인 우수성을 관찰할 수 있었다.

• Journal of Korea Multimedia Society
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• v.22 no.6
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• pp.684-694
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• 2019

Information spread in networks is universal in many real-world phenomena such as propagation of infectious diseases, diffusion of a new technology, computer virus/spam infection in the internet, and tweeting and retweeting of popular topics. The problem of finding the information source is to pick out the true source if information spread. It is of practical importance because harmful diffusion can be mitigated or even blocked e.g., by vaccinating human or installing security updates. This problem has been much studied, where it has been shown that the detection probability cannot be beyond 31% even for regular trees if the number of infected nodes is sufficiently large. In this paper, we study the impact of an anti-information spreading on the original information source detection. We consider an active defender in the network who spreads the anti-information against to the original information simultaneously and propose an inverse Voronoi partition based inference approach, called Voronoi Inference to find the source. We perform various simulations for the proposed method and obtain the detection probability that outperforms to the existing prior work.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.876-880
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• 2011

유무선 네트워크의 발달로 온라인 환경에서 다양한 정보 교환 및 데이터 공유를 보다 쉽게 사용할 수 있다. 이러한 네트워크의 신뢰성을 보장하고 악의적인 사용자의 공격에 저항하기 위해 가장 중요한 필요조건은 구성원 상호 신뢰 관계를 확립하는 것이다. 다른 사람의 신뢰도를 정확하게 평가하고 신뢰도가 전체적인 신뢰도에 반영된다면 많은 위험을 회피할 수 있다. 본 논문에서는 악의적인 피어가 제공하는 신뢰할 수 없는 자원의 확산을 감소시키기 위해 네트워크에 참여하는 노드에 대한 신뢰도를 측정한다. 신뢰도는 노드들이 선택하는 다른 노드의 선호도를 이용하여 노드들의 신뢰도에 가중한다. 실험결과는 계산된 신뢰도를 이용하여 신뢰할 수 있는 노드에게 유효한 파일을 수신할 수 있어 네트워크의 신뢰성을 보장하고 데이터에 대한 정확성을 높일 수 있다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1050-1059
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• 2005

Heat and $SF_6$ gas dispersions over a complex terrain were investigated using wind tunnel. The wind speed, temperature and concentration profiles were measured for the 1/1000 scale complicated terrain model in an Eiffel type boundary layer wind tunnel with test section of 2.5m in height and 4.5m in width. The scale model was mounted on the top of a plate which can rotate with respect to the approaching wind. Dispersion processes from a continuous emission source driven by various wind direction were investigated, including plume climbing over the steep up-slope of the mountain and down-spreading toward the lower level of the valley. Extensive dispersion experiment data (wind speeds and concentration profiles) were provided for verification and validation of dispersion models. Under the identical flow and emission conditions, the independently measured profiles of the temperature and $SF_6$ concentration showed an excellent agreement which ensured the credibility of the results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.1
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• pp.54-64
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• 1991

To accurately estimate the rate of sediment transport in shallow water bodies, it is necessary to investigate the irregular waves transformation characteristics and nearshore currents produced by random sea waves. Most of studies on numerical models for nearshore currents are based on the theory of monocromatic waves and thus, very few nearshore models take into account the effect of irregularities in the hight, period and directional spreading of incident waves. The numerical simulation model for nearshore currents used in this paper considers the effect of irregularities of incident waves, based on Individual Wave Analysis. The computational results are compared and shown in a reasionable agreement with the experimental data.