• 대한토목학회논문집
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• 제12권2호
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• pp.109-122
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• 1992

파괴양상, 조도, 하류댐 지점의 수위-유량 관계 및 붕괴여부에 불확실성이 있으나, 소양강댐이 가상 파괴될 경우 댐 파괴파의 전파양상을 DAMBRK로 수치모의하였다. 모의결과, 서울은 6~8시간 내에 범람이 예상되며 표고 30-20m 이하 지역이 침수되고, 춘천의 대부분 지역이 침수된다. 첨두유량은 파괴시간 1~2시간에 대하여 인도교에서 약 7.0만 CMS이고 춘천은 약 22~34만 CMS였다. 민감도 분석결과 하류댐들의 붕괴여부나 파괴양상이 서울지역에 대한 범람양상에 크게 영향을 미치지는 않았다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권11호
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• pp.4483-4501
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• 2015

In this paper, we investigate a security transmission scheme at the physical layer for cooperative wireless relay networks in the presence of a passive eavesdropper. While the security scheme has been previously investigated with perfect channel state information(CSI) in the presence of a passive eavesdropper, this paper focuses on researching the robust cooperative relay beamforming mechanism for wireless relay networks which makes use of artificial noise (AN) to confuse the eavesdropper and increase its uncertainty about the source message. The transmit power used for AN is maximized to degrade the signal-to-interference-plus-noise-ratio (SINR) level at the eavesdropper, while satisfying the individual power constraint of each relay node and worst-case SINR constraint at the desired receiver under a bounded spherical region for the norm of the CSI error vector from the relays to the destination. Cooperative beamforming weight vector in the security scheme can be obtained by using S-Procedure and rank relaxation techniques. The benefit of the proposed scheme is showed in simulation results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3711-3730
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• 2014

Cognitive radio networks (CRNs) have emerged as a promising solution to enhance spectrum utilization by using unused or less used spectrum in radio environments. The basic idea of CRNs is to allow secondary users (SUs) access to licensed spectrum, under the condition that the interference perceived by the primary users (PUs) is minimal. In CRNs, the channel availability is uncertainty due to the existence of PUs, resulting in intermittent communication. Transmission control protocol (TCP) performance may significantly degrade in such conditions. To address the challenges, some transport protocols have been proposed for reliable transmission in CRNs. In this paper we survey the state-of-the-art transport protocols for CRNs. We firstly highlight the unique aspects of CRNs, and describe the challenges of transport protocols in terms of PU behavior, spectrum sensing, spectrum changing and TCP mechanism itself over CRNs. Then, we provide a summary and comparison of existing transport protocols for CRNs. Finally, we discuss several open issues and research challenges. To the best of our knowledge, our work is the first survey on transport protocols for CRNs.

• Nuclear Engineering and Technology
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• 제44권4호
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• pp.355-362
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• 2012

The aim of this study was to develop a bundle position-wise linear model (BPLM) to predict Pressure Tube (PT) diametral creep employing the previously measured PT diameters and operating conditions. There are twelve bundles in a fuel channel, and for each bundle a linear model was developed by using the dependent variables, such as the fast neutron fluences and the bundle coolant temperatures. The training data set was selected using the subtractive clustering method. The data of 39 channels that consist of 80 percent of a total of 49 measured channels from Units 2, 3, and 4 of the Wolsung nuclear plant in Korea were used to develop the BPLM. The data from the remaining 10 channels were used to test the developed BPLM. The BPLM was optimized by the maximum likelihood estimation method. The developed BPLM to predict PT diametral creep was verified using the operating data gathered from Units 2, 3, and 4. Two error components for the BPLM, which are the epistemic error and the aleatory error, were generated. The diametral creep prediction and two error components will be used for the generation of the regional overpower trip setpoint at the corresponding effective full power days. The root mean square (RMS) errors were also generated and compared to those from the current prediction method. The RMS errors were found to be less than the previous errors.

• 한국정보통신학회논문지
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• 제8권6호
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• pp.1068-1075
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• 2004

2.4㎓ 대역 무선통신망을 통해 서비스되는 WLAN과 Bluetooth시스템은 서로 동일한 환경 하에서 상호 보완적인 서비스를 제공하고 있다. 이러한 두 시스템의 상호 패킷이 시간과 가우시안 거리의 불확실성에 존재할 경우 시스템간에 충돌이 발생하게 된다. 따라서 본 논문에서는 두 시스템간의 상호 공존의 방법을 도모하기 위해 상호 간섭의 영향을 분석하고자한다. 반송파 주파수 오프셋에 따른 신호대 잡음간섭신호에 의한 심볼 오차확률의 분석을 통해 두 시스템간의 간섭영향을 분석하였다.

• 한국자기학회지
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• 제10권4호
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• pp.178-182
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• 2000

본연구에서는 서로 직교하는 yoke 장치와 4-채널 과도기록장치를 사용하여 회전하는 자기장을 발생시키고, 회전자화에 의한 자기적 손실을 측정할 수 있는 측정시스템을 구성하였다. 개발된 측정장치를 사용하여 무방향규소강의 회전자화에 의한 자기적특성을 측정하였으며, 회전자화에 의한 손실의 측정에서 자기유도성분의 측정방향과 자화력성분의 측정방향이 일치하지 않아, 시계방향 및 반시계방향으로 측정한 값이 차이를 나타내었다. 그러나 시계방향 및 반시계방향으로 측정한 회전자화에 의한 손실값의 평균은 일정함을 알 수 있었으며, 이를 이용할 경우 회전자화의 폭정오차를 줄일 수 있었다.

• 한국환경과학회지
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• 제12권9호
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• pp.949-955
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• 2003

The subject basin of the research was the basin of Yeongcheon Dam located in the upper reaches of the Kumho River. The parameters of the model were derived from the results of abstracting topological properties out of rainfall-runoff observation data about heavy rains and Digital Elevation Modeling(DEM) materials. This research aimed at suggesting the applicability of the CELLMOD Model, a distribution-type model, in interpreting runoff based on the topological properties of a river basin, by carrying out runoff interpretation far heavy rains using the model. To examine the applicability of the model, the calculated peaking characteristics in the hydrograph was analyzed in comparison with observed values and interpretation results by the Clark Model. According to the result of analysis using the CELLMOD Model proposed in the present research for interpreting the rainfall-runoff process, the model reduced the physical uncertainty in the rainfall-runoff process, and consequently, generated improved results in forecasting river runoff. Therefore it was concluded that the algorithm is appropriate for interpreting rainfall-runoff in river basins. However, to enhance accuracy in interpreting rainfall-runoff it is necessary to supplement heavy rain patterns in subject basins and to subdivide a basin into minor basins for analysis. In addition, it is necessary to apply the model to basins that have sufficient observation data, and to identify the correlation between model parameters and the basin characteristics(channel characteristics).

• Journal of Communications and Networks
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• 제14권5호
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• pp.566-577
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• 2012

In randomly deployed networks, such as sensor networks, an important problem for each node is to discover its neighbor nodes so that the connectivity amongst nodes can be established. In this paper, we consider this problem by incorporating the physical layer parameters in contrast to the most of the previous work which assumed a collision channel. Specifically, the pilot signals that nodes transmit are successfully decoded if the strength of the received signal relative to the interference is sufficiently high. Thus, each node must extract signal parameter information from the superposition of an unknown number of received signals. This problem falls naturally in the purview of random set theory (RST) which generalizes standard probability theory by assigning sets, rather than values, to random outcomes. The contributions in the paper are twofold: First, we introduce the realistic effect of physical layer considerations in the evaluation of the performance of logical discovery algorithms; such an introduction is necessary for the accurate assessment of how an algorithm performs. Secondly, given the double uncertainty of the environment (that is, the lack of knowledge of the number of neighbors along with the lack of knowledge of the individual signal parameters), we adopt the viewpoint of RST and demonstrate its advantage relative to classical matched filter detection method.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.100-100
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• 2015

자연유역은 주어진 강우에 대해 다양한 형태의 유출반응을 나타내는데, 이는 순간반응함수(Instantaneous Response Function; IRF)로 표현될 수 있다. IRF는 유역의 DEM(Digital Elevation Model)으로부터 지표수 흐름방향을 추출한 뒤 지형분석을 통하여 구한 인자를 이용해 구하는 것이 일반적인 이론이다. 여기서 DEM의 모든 셀에 대해 흐름방향을 부여할 수 있지만, 모든 셀이 하천에 해당하지는 않는다. 따라서 최상류의 셀들은 사면으로, 하류의 셀은 하천으로 구분하여 IRF모의에 적용하게 된다. 사면과 하천은 지표수이송에 전혀 다른 경향을 보이므로 전체적인 유역의 유출반응에 큰 영향을 미친다. 예를 들어 사면과 하천에서의 유속 차이는 IRF의 왜도(skewness)에 주된 영향을 미치는 것으로 알려져 있다 (Botter and Rinaldo, 2003). 하지만, DEM에서 사면과 하천을 정확하게 구분하는 것은 매우 어렵기 때문에 하천시점을 정의하는 데에는 불확실성이 내재되어 있으며, 이러한 점은 추정된 IRF의 불확실성으로 연결된다. 본 연구에서는 하천시점의 불확실성으로 인한 IRF의 불확실성을 정량화하고, 그것의 유의수준을 평가하고자 한다. 이를 위해 다양한 유원면적 기준에 대해 IRF를 계산하고, 그 결과를 심도 있게 고찰한다.

• 농업과학연구
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• 제48권2호
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• pp.311-331
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• 2021

Climate change with extreme hydrological events has become a significant concern for agricultural water systems. Climate change affects not only irrigation availability but also agricultural water requirement. In response, adaptation strategies with soft and hard options have been considered to mitigate the impacts from climate change. However, their implementation has become progressively challenging and complex due to the interconnected impacts of climate change with socio-economic change in agricultural circumstances, and this can generate more uncertainty and complexity in the adaptive management of the agricultural water systems. This study was carried out for the agricultural water supply system in Seongju dam watershed in Seonju-gun, Gyeongbuk in South Korea. The first step is to identify system disturbances. Climate variation and socio-economic components with historical and forecast data were investigated Then, as the second step, problematic trends of the critical performance were identified for the historical and future climate scenarios. As the third step, a system structure was built with a dynamic hypothesis (causal loop diagram) to understand Seongju water system features and interactions with multiple feedbacks across system components in water, agriculture, and socio-economic sectors related to the case study water system. Then, as the fourth step, a mathematical SD (system dynamics) model was developed based on the dynamic hypothesis, including sub-models related to dam reservoir, irrigation channel, irrigation demand, farming income, and labor force, and the fidelity of the SD model to the Seongju water system was checked.