• ETRI Journal
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• v.28 no.5
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• pp.684-687
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• 2006

In this letter, we evaluate the system performance of a space-time block coded (STBC) multicarrier (MC) DS-CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS-CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS-CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.2
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• pp.800-813
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• 2021

With the advent of 5G communications, internet of vehicles technology has been widely used in vehicles. Then the dynamic spread of information between vehicles began to come into focus with more research. It is well known that the identification of nodes with great spread influence has always been a hot topic in the field of information spreading. Most of the existing work measures the propagation influence by degree centrality, betweenness centrality and closeness centrality. In this paper, we will identify influential vehicle nodes based on the mobility characteristics of vehicles to explore the information spreading between vehicles in VANETs. Different from the above methods, we mainly explore the influence of the radius of gyration and vehicle kilometers of travel on information spreading. We use a real vehicle trajectory data to simulate the information transmission process between vehicles based on the susceptible-infected-recovered SIR model. The experimental results show that the influence of information spreading does not enhance with increasing radius of gyration and vehicle kilometers of travel. The fact is that both the radius of gyration and the distance travelled have a significant influence on information spreading when they are close to the median. When the value of both is large or small, it has little influence on information spreading. In view of this results, we can use the radius of gyration and vehicle kilometers of travel to better facilitate the transmission of information between vehicles.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.11c
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• pp.1949-1952
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• 2002

본 연구는 객체지향 컴포넌트 검색을 위해서 개선된 Spreading Activation 방법을 이용하여 다중 패싯 분류된 컴포넌트를 효율적으로 검색할 수 있는 방법을 제안하였다. 객체지향 코드 기반의 관계정의를 위해 특성과 컨텍스트 간에 연관관계를 설정하고, 컨덱스트의 자동 추출을 위한 Spreading Activation 방법의 초기 활성값을 정의하였다. 쿼리에 대해 자동 검색된 컨텍스트에 의해 후보컴포넌트가 선정되고, 쿼리와 컴포넌트 간의 신뢰도가 계산됨으로써 컴포넌트가 검색될 수 있도록 하였다. 본 연구는 다중 패싯 분류된 객체지향 컴포넌트의 검색에 효율적이며, 사용자 수작업의 부담을 최대한 감소시켜 컴포넌트의 재사용성을 높일 수 있도록 하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.3
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• pp.165-172
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• 2006

There are various threats as side effects against the growth of information technology, and malicious codes such as Internet worms may bring about confusions to upset a national backbone network. In this paper, we examine the existed spreading models and propose a new worm spreading model on Internet environment. We also predict and analyze the spreading effects of high-speed Internet worms. The proposed model leads to a better prediction of the worm spreading since various factors are considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.214-220
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• 2006

In this paper, we propose the transmit power controlled adaptive modulated OFDM with frequency symbol spreading and equalization(TPC-AMS/FSS-OFDM) system. In the transmitter of the TPC-AMS/FSS-OFDM, each SP transformed signal is spread by orthogonal spreading codes and combined, so the detected signals obtain the same SINR(signal interference to noise ration) for each frequency symbol spreading block. In this case, we can assign the same modulation level and transmit power for each frequency symbol spreading block. Thus, the proposed system provides the increased throughput performance with reducing the total transmit power, FBI and MLI.

• Journal of the Ergonomics Society of Korea
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• v.28 no.1
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• pp.1-7
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• 2009

As products are getting more diverse and new products are entering the market faster, customers have trouble learning how to use them. User-oriented menu structures may solve this problem. In order to design user-oriented menu structures, spreading activation theory has been studied. The spreading activation test shows that the strong associative relationship between words has shorter response times. Based on the spreading activation test, asymmetric spreading activation was introduced and a hypothesis that in a well-designed menu structure, association between upper-low menu pairs is not affected by an activation direction was tested for this study. In this study the menu of a cellular phone (Model: SPH-w2900) was extracted, and underwent 1st spreading activation tests. Then, on each menu pair, response time differences (asymmetric transition) by accuracy and directions were analyzed to find out problems in labels and improve menu structures and vocabulary. Second spreading activation tests were conducted to check whether asymmetric transitions decreased. The results showed that response time differences (asymmetric transition) for activation directions were found to be dropped significantly. Asymmetric transitions in spreading activation presented in this study will be helpful to define user-oriented menu structures.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2858-2864
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• 2015

Internet worms have been the major Internet threats may disclose important information and can bring about faults of computer systems, which spread with the fastest speed among malicious codes. Simultaneously spreading multiple worms and its variants are revealing the limitation of conventional responses based on single worms. In order to defend them effectively, it is necessary to study how multiple worms propagate and what factors affect worm spreading. In this paper, we improve the existed single worm spreading models and try to describe the correct spreads of multiple worms. Thus we analyze the spreading effects of multiple worms and its variants by various experiments.

• Korean Journal of Computational Design and Engineering
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• v.17 no.1
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• pp.45-53
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• 2012

In this paper, oil spreading simulation model is proposed for analyzing the oil spreading phenomenon rapidly when the ocean is polluted by the oil from a stranded ship. The space occupied by the ocean is converted into the latticed cell, and the each cell contains the information, such as the quantity of the oil, the temperature of the ocean, and the direction of current and wind. Two states, such as "clean" and "polluted" are defined in the each cell, and the oil in the cell spreads to the neighbor cells by the spreading rules. There are three spreading rules. First, the oil in the certain cell only spreads to the neighbor cells that contain larger oil than the certain cell. Second, the oil evaporates in proportion to the temperature of the ocean at the every time step. Third, the oil spreading property is affected by the direction and the speed of the current and the wind. The oil spreading simulation model of the each cell is defined by using the combined discrete event and discrete time simulation model architecture with the information and the spreading rules in the cell. The oil spreading simulation is performed when the oil of 10,000 kL is polluted in the ocean environment of 300 m by 300 m with various current and wind.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.8
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• pp.664-671
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• 2006

We propose the correlation to predict the spreading thermal resistance on a plate with symmetrical four heat sources. The correlation transforms four heat sources to a single equivalent heat source and then the spreading thermal resistance can be obtained with the existing equation for a single heat source. When the four heat sources are mounted on a square base plate, the correlation is expressed as a function of the heat source size, the length of base plate, the plate thermal conductivity and the distance between heat sources. Compared to the results of three-dimensional numerical analysis, the spreading thermal resistance by the proposed correlation is in good agreement within 10 percent accuracy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.551-557
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• 2010

Fast spreading Internet worms will be sure to become one of the new major threats of convergence networks as well as the Internet. In order to defend and respond them, it is necessary to study how Internet worms propagate and what factors affect worm spreading. In this paper, we try to describe the correct spread of worms on convergence network environments. Therefore we propose a spreading model and analyze the spreading effects by various experiments.