• 제목/요약/키워드: time spreading

검색결과 556건 처리시간 0.024초

Performance Investigation of Space-Time Block Coded Multicarrier DS-CDMA in Time-Varying Channels

  • Narzullaev, Anvar;Ryu, Kwan-Woong;Park, Yong-Wan
    • 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.

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해상에서의 원유 확산 과정 예측을 위한 격자 기반 이산 사건 및 이산 시간 시뮬레이션 (Cell-based Discrete Event and Discrete Time Simulation for the Prediction of Oil Slick Movement and Spreading in Ocean Environment)

  • 하솔;차주환;구남국;이규열
    • 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.

마찰저항이 연속누출과 순간누출을 가지는 액체 풀의 확산에 미치는 영향에 대한 해석적 연구 (Effect of Frictional Resistance Force on a Liquid Pool Spreading Model with Continuous and Instantaneous Release)

  • 김태훈;최병일;김명배;도규형;한용식
    • 한국수소및신에너지학회논문집
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    • 제24권6호
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    • pp.487-494
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    • 2013
  • In this study, solutions for a liquid pool spreading model with continuous and instantaneous release are discussed based on the model used in the FERC's report. The effects of the release time on the liquid pool volume and radius are investigated for the continuous release. For the continuous release with the frictional resistance force in the liquid pool spreading model, the vaporization time decreases as the release time increases. On the other hand, for the continuous release without the frictional resistance force in the liquid pool spreading model, the vaporization time increases as the release time increases. These phenomena are deeply related to the pool radius. In addition, the effects of the initial pool radius for the instantaneous release in the liquid pool spreading model are discussed. For the case with the frictional resistance force in the liquid pool spreading model, as reducing release time in the model with the frictional resistance force for the continuous release, the solution for a continuous release approaches to that for an instantaneous release. On the contrary to this, the pool volume and radius for the instantaneous release without the frictional resistance force are totally different from those for the continuous release without the frictional resistance force.

비대칭 활성화 확산 이론을 이용한 휴대폰 메뉴 구조 디자인 (Menu Structure Design using Asymmetric Spreading Activation in Mobile Phone)

  • 오세응;명노해
    • 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.

확산하는 액체질소의 증발에 관한 실험적 연구 (Experimental Study of the Evaporation of Spreading Liquid Nitrogen)

  • 김명배;최병일;김태훈;도규형;한용식;정경열
    • 한국수소및신에너지학회논문집
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    • 제29권5호
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    • pp.466-472
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    • 2018
  • The investigation of cryogenic liquid pool spreading is an essential procedure to assess the hazard of cryogenic liquid usage. In this experimental study, to measure the evaporation velocity when the pool is spreading, liquid nitrogen was continuously released onto unconfined concrete ground. Almost all of the reported results are based on a non-spreading pool in which cryogenic liquid is instantaneously poured onto bounded ground for a very short period of time. A simultaneous measurement of the pool location using thermocouples and of the pool mass using a digital balance was carried out to measure the evaporation velocity and the pool radius. A greater release flow rate was found to result in a greater average evaporation velocity, and the evaporation velocity decreased with the spreading time and the pool radius.

방염제의 도포량과 침지시간 차이에 따른 목재제품의 방염성능 (Flame Retardancy of Wood Products by Spreading Concentration and Impregnation Time of Flame Retardant)

  • PARK, Sohyun;HAN, Yeonjung;SON, Dong Won
    • Journal of the Korean Wood Science and Technology
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    • 제48권4호
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    • pp.417-430
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    • 2020
  • 4종의 판상형 목재제품의 방염제 도포량과 침지시간에 따른 방염성능을 분석하기 위하여 소방청의 방염성능기준에 따라 목재제품의 탄화길이와 탄화면적을 측정하였다. 잣나무 합판, 낙엽송 합판, 편백 판재, 타공처리된 자작나무 합판에 자체 개발된 방염제를 각각 300, 500 g/㎡씩 도포하고 방염처리되지 않은 시험편과 비교하였다. 일반적으로 방염제의 도포량이 증가함에 따라 탄화길이와 탄화면적이 감소하여 방염성능이 증가하는 경향을 나타냈으나, 낙엽송 합판을 제외하고 탄화길이와 탄화면적의 감소량이 크지 않았다. 타공처리된 자작나무 합판의 침지시간에 따른 방염성능은 60분의 침지시간까지 양의 상관관계를 나타냈으나, 그 이후 점차 완만해지는 경향을 보였다. 방염제의 도포량과 침지시간에 따른 목재제품의 방염성능은 추후 방염성능 기준에 맞는 불연·준불연 목재의 생산을 위한 기초자료로 이용될 것으로 기대된다.

東海의 起源과 板構造論 (Origin of the East Sea (Japan Sea) and Plate Tectonics)

  • 김소구
    • 한국해양학회지
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    • 제19권1호
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    • pp.94-102
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    • 1984
  • 東海(Japan Sea)의 起源에 관해서 板構造論(Plate tectonecs)과 海底擴張설 (Se-floor spreading)과 같은 現代地球物理學 理論이 최근에 많이 논의되고 있다. 동해의 기원은 後期白堊期 혹은 Paleocene 시대만큼 일찍이 거슬러 올라가서 일어난 Back-aec spreading의 장력에 기인되었다고 본다. 이 해저확장의 시잔은 동쪽 혹은 남동쪽으로 빠른 운동을 하였지만 서쪽으로는 느린 운동을 하게 되어서 非對稱성 확장을 이루게 되었다. 그러나 Eocene 동안 北北西에서 南北西로 이동 하게 된 태평양판의 새로운 운동방향의 변화와 Philippine 판의 생성 때문에 동해의 확장은 오늘날의 일본 열도에 제한되어 멈추게 되었다고 본다. 第四紀 以後 동해의 확장은 소멸되고, 太平洋板, Pilippine板 및 Eurasia板의 서로 만남 으로 하나의 Triple junction을 형성하여 힘의 평형을 이루고 있는지에 대해서는 충분한 地球物理學, 地質學的 자료는 물론 地震資料의 더욱 정밀한 분석에 기초를 둔 연구가 수행됨으로 풀릴 것이다.

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중력-점성력에 의한 유출유 퍼짐에 관한 연구 (A study on the spreading of an oil slick under the influence of gravitational and viscous forces)

  • 김창제;채양범
    • 해양환경안전학회지
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    • 제3권2호
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    • pp.63-67
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    • 1997
  • In this study, some approximate theoretical solutions about oil spreading under the influence of gravitational and viscous forces have been derived from the viewpoint of energy conservation. The theoretical model which derived newly is in agreement with Toi's one derived from a different hypothesis, and shown to predict well the spreading distance of oil front at an initial step of outflow, but further study is necessary to evaluate the spreading distance after longer time.

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Generalization of the Spreading Function and Weyl Symbol for Time-Frequency Analysis of Linear Time-Varying Systems

  • Iem, Byeong-gwan
    • 한국지능시스템학회논문지
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    • 제11권7호
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    • pp.628-632
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    • 2001
  • We propose time-frequency (TF) tools for analyzing linear time-varying (LTV) systems and nonstationary random processes. Obtained warping the narrowband Weyl symbol (WS) and spreading function (SF), the new TF tools are useful for analyzing LTV systems and random processes characterized by generalized frequency shifts, This new Weyl symbol (WS) is useful in wideband signal analysis. We also propose WS an tools for analyzing systems which produce dispersive frequency shifts on the signal. We obtain these generalized, frequency-shift covariant WS by warping conventional, narrowband WS. Using the new, generalized WS, we provide a formulation for the Weyl correspondence for linear systems with instantaneous of linear signal transformation as weighted superpositions of non-linear frequency shifts on the signal. Application examples in signal and detection demonstrate the advantages of our new results.

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Personalized Agent Modeling by Modified Spreading Neural Network

  • Cho, Young-Im
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • 제3권2호
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    • pp.215-221
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    • 2003
  • Generally, we want to be searched the newest as well as some appropriate personalized information from the internet resources. However, it is a complex and repeated procedure to search some appropriate information. Moreover, because the user's interests are changed as time goes, the real time modeling of a user's interests should be necessary. In this paper, I propose PREA system that can search and filter documents that users are interested from the World Wide Web. And then it constructs the user's interest model by a modified spreading neural network. Based on this network, PREA can easily produce some queries to search web documents, and it ranks them. The conventional spreading neural network does not have a visualization function, so that the users could not know how to be configured his or her interest model by the network. To solve this problem, PREA gives a visualization function being shown how to be made his interest user model to many users.