• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2121-2123
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• 2003

Distributed Control Systems(DCS) arc used in a wide range of process applications such as power plants. This paper presents calculated network capacity of a DCS that developed for nuclear power plant. The network hierarchies are 3 layed of information network, control network and field network. The assumed total node number of maximum DCS network is 64. Worst case network utilization of the DCS is simulated and analyzed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.9 s.351
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• pp.88-98
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• 2006

VANET has several different characteristics from MANET such as high mobility of nodes and frequent change of node density and network topology. Due to these characteristics, the network topology based protocol, often used in MANET, can not be applied to VANET. In this paper, we propose an emergency warning message broadcast protocol using range based relay node selecting algorithm which determines the minimal waiting time spent by a given node before rebroadcasting the received warning message. Because the time is randomly calculated based on the distance between sender node and receiver node, a node chosen as a relay node is assured to have a minimal waiting time, even though it is not located at the border of radio transmission range. The proposed emergency warning message broadcast protocol has low network traffic because it does not need to exchange control messages for message broadcasting. In addition, it can reduce End-to-End delay under circumstances of low node density and short transmission range in VANET.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.1
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• pp.88-95
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• 2015

For the frequency-domain spectral fatigue analysis, the probability density function of stress range needs to be estimated based on the stress spectrum only, which is a frequency domain representation of the response. The probability distribution of the stress range of the narrow-band spectrum is known to follow the Rayleigh distribution, however the PDF of wide-band spectrum is difficult to define with clarity due to the complicated fluctuation pattern of spectrum. In this paper, efforts have been made to figure out the links between the probability density function of stress range to the structural response of wide-band Gaussian random process. An artificial neural network scheme, known as one of the most powerful system identification methods, was used to identify the multivariate functional relationship between the idealized wide-band spectrums and resulting probability density functions. To achieve this, the spectrums were idealized as a superposition of two triangles with arbitrary location, height and width, targeting to comprise wide-band spectrum, and the probability density functions were represented by the linear combination of equally spaced Gaussian basis functions. To train the network under supervision, varieties of different wide-band spectrums were assumed and the converged probability density function of the stress range was derived using the rainflow counting method and all these data sets were fed into the three layer perceptron model. This nonlinear least square problem was solved using Levenberg-Marquardt algorithm with regularization term included. It was proven that the network trained using the given data set could reproduce the probability density function of arbitrary wide-band spectrum of two triangles with great success.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1307-1312
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• 2015

As smart-phones become popular, mobile data traffic has been dramatically increasing and intensive researches on the next-generation mobile communication network is in progress to meet the increasing demand for mobile data traffic. In particular, heterogeneous network (HetNet) is attracting much interest because it can significantly enhance the network capacity by increasing the spatial reuse with macro and small cells. In the HetNet, we have several problems such as load imbalance and interference because of the difference in transmit power between macro and small cells and cell range expansion (CRE) can mitigate the problems. In this paper, we propose a new cell selection scheme with adaptive cell range expansion bias (CREB) for ultra dense HetNet and we analyze the performance of the proposed scheme in terms of average cell transmission rate through system-level simulations and compare it with those of other schemes.

• KIEAE Journal
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• v.16 no.6
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• pp.69-75
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• 2016

Climate change has resulted in the urban heat island (UHI) effect throughout the globe, contributing to heat-related illness and fatalities. In order to reduce such damage, it is necessary to improve the climate observation network for precise observation of the urban thermal environment and quick UHI forecasting system. Purpose: This study analyzed the effective range of the climate observation network and the distribution of the existing Automatic Weather Stations (AWS) in Seoul to propose optimal locations for additional installment of AWS. Method: First, we performed quality analysis to pinpoint missing values and outliers within the high-density temperature data measured. With the result from the analysis, a spatial autocorrelation structure in the temperature data was tested to draw the effective range and correlation distance for each major time period. Result: As a result, it turned out that the optimal effective range for the climate observation network in Seoul in July was a radius of 2.8 kilometers. Based on this result, population density, and temperature data, we selected the locations for additional installment of AWS. This study is expected to be used to generate urban temperature maps, select and move measurement locations since it is able to suggest valid, specific spatial ranges when the data measured in point is converted into surface data.

• Journal of Digital Contents Society
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• v.7 no.2
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• pp.103-108
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• 2006

Short-range wireless communication and networking technologies are becoming increasingly important in enabling useful mobile applications. for example, ZigBee technology is expected to provide low cost and low power connectivity for equipment that needs battery life as long as several months to several years. In addition, ZigBee can be implemented in mesh networks larger than is possible with Bluetooth. The main features of this ZigBee standard are network flexibility, low cost, very low power consumption, and low data rate in an adhoc self-organizing network among fixed, portable and moving devices. Home network/Home automation is one of the key market areas for Zigbee, with an example of a simple network This paper investigates the effect of short range wireless channel on the performance of Zigbee system and DSSS-BPSK signal transmission in AWGN, interference and Rician fading environments. And we investigate performance degradation due to interference and fading effects in short range wireless channel. In particular, the impacts of the fading and interference level on the bit error probability is shown in BER performance figures.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1601-1604
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• 1997

The most important topic in research of mobile robot is path planning in order to avoid with obstacle. In this study the path planning algorithm using a neural network model is proposed. The inputs of neural network are range data which are acquired form laser range finderm and weights are based on difference with goal direction. The thresholds are made by consdiering the marginal distance between mobile robot and obstacle. Consequently the outputs are obtained by multiplying input and weight. The obtained heading directiion enables the mobile robot to approach the goal, without any collision with obstacles around. The effectiveness of the this method of real-time navigation of a mobile robot is estimated by computer simulation in complex environment.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1059-1062
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• 2005

A hybrid ad-hoc network consists of a wired network and a mobile ad-hoc network connected by the internet gateway. To provide seamless service for internet user in hybrid ad-hoc network, an efficient internet gateway selection technique and a fast handover technique are needed. In this paper, we propose a seamless handoff technique for providing mobility of mobile hosts in hybrid ad-hoc networks. The proposed technique improves general handoff performance by an internet gateway re-registration algorithm for ad-hoc networks. Moreover, it reduces handoff processing time in the range of certain region by using mobility management agent (MMA) and also the packet loss when handoff occurs out of the range of MMA by tunneling technique.

• KIEAE Journal
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• v.10 no.6
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• pp.3-10
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• 2010

The subject is to find green roofs' location as stepping stones in green-network in fine scale. The study site is Junggu, Seoul, which has core areas(Bukaksan and Namsan) and green areas(parks, etc.). Through literature review, the closer to core areas and green areas, target species reach green roof easier, and target species must be avifauna(flying species) and high class in food chain, because of possibility of reaching. So, Great Tits, inhabited in Namsan and urban bird, is target species. The location standard of green roofs, realized birds' reaching distance, consists of home range(horizontal range and vertical range) and roof-greening capable area. The green roofs' distribution of location was resulted through GIS analysis of feasible site finding, and classified with weight of score. In discussion, Namsan gives more effect to locate green roofs than Bukaksan does and selected buildings which are grouped in some parts need to be managed with group, green roof district.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.308-308
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• 2010

실리콘 나이트라이드 박막의 굴절률과 lifetime을 유전자 알고리즘과 일반화된 회귀 신경망을 이용하여 모델링하였다. 종래의 모델링에서 평가한 Spread Range 범위보다 더 작은 0.04~1.0 범위에서 평가를 수행하였다. 통계적 실험계획법을 적용해서 수집한 데이터가 이용되었다. 평가결과 보다 낮은 spread range에서 보다 우수한 예측모델이 개발될 수 있음을 확인하였다.