• ETRI Journal
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• 제28권5호
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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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• 제15권2호
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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.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2002년도 추계학술발표논문집 (하)
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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.

• 정보보호학회논문지
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• 제16권3호
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• pp.165-172
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• 2006

누구나 인터넷에 접속할 수 있는 환경이 구축됨에 따라 해킹, 악성코드 등의 다양한 위협도 함께 등장하고 있다. 그 중 인터넷 웜은 1.25 대란과 같이 국가 기간망을 뒤흔들 수 있는 위협으로 인식되고 있다. 본 논문은 인터넷 환경에서 웜 확산의 모델링을 그 목표로 한다. 이를 위해 인터넷 원에 적용 가능한 확산 모델을 제안하고, 인터넷 환경에서 웜에 적용하여 동작을 분석한다. 제안 모델은 고속의 인터넷 웡 확산에 따른 영향을 분석함으로써 인터넷 웜의 확산을 보다 정확하게 예측할 수 있다.

• 한국통신학회논문지
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• 제31권3A호
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• pp.214-220
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• 2006

본 논문에서는 TPC-AMS/FSS-OFDM(transmit power controlled adaptive modulated OFDM with frequency symbol spreading and equalization)시스템을 제안한다. TPC-AMS/FSS-OFDM의 송신기에서 각 S/P(serial-to-parallel)변환된 신호는 직교 확산 코드에 의해 확산 결합되어 송신하고, 수신된 신호는 수신기의 각 주파수 심볼 확산 블록에 의하여 검출되며, 같은 SINR(signal interference to noise ratio)을 얻는다. 이 때 각 주파수 심볼 확산블록에 대해서는 같은 변조 레벨과 송신 전력을 할당할 수 있다. 본 논문에서 제안한 시스템은 전체 송신 전력과 데이터 정보로 전송되는 FBI(feedback information), MLI(modulation level information)를 감소시킴으로서 전체적인 전송속도(throughput)의 성능을 개선할 수 있다.

• 대한인간공학회지
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• 제28권1호
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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.

• 한국정보통신학회논문지
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• 제19권12호
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• pp.2858-2864
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• 2015

최근 인터넷 웜은 악성코드 중 가장 빠른 속도로 확산하면서 정보 유출, 시스템 결함 등을 일으킬 수 있는 주요한 위협이 되고 있다. 특히, 복수의 인터넷 웜과 변종 웜이 동시 다발적으로 확산하면서 기존 인터넷 웜 대응 방식으로는 한계가 된다는 것을 여실히 보여주고 있다. 이러한 다양한 인터넷 웜에 효과적으로 대응하기 위해서는 복수 웜의 확산 방식을 이해하는 것이 필수적이다. 본 논문에서는 기존의 단일 웜 확산 모델을 개선하여 복수 변종 웜 확산에 대한 정확한 모델링을 목표로 하고, 다양한 실험을 통하여 복수 웜 확산의 양상을 분석한다.

• 한국CDE학회논문집
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• 제17권1호
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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.

• 설비공학논문집
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• 제18권8호
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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.

• 한국통신학회논문지
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• 제35권3B호
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• pp.551-557
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• 2010

최근 빠른 속도로 확산되는 인터넷 웜은 인터넷은 물론 융합망에서도 주요한 위협이 될 것으로 예상된다. 이러한 인터넷 웜에 대응하기 위해서는 웜의 확산 방식과 웜 확산에 영향을 끼치는 융합 요소를 연구하는 것이 필수적이다. 본 논문은 융합망 환경에서 웜 확산에 대한 정확한 모델링을 그 목표로 한다. 이를 위하여 다양한 실험을 통하여 융합망 환경에서 웜 확산의 양상을 분석한다.