• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3955-3966
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• 2014

With the exponentially increasing Internet traffic and emergence of more versatile and heterogeneous applications, the design of datacenter networks (DCNs) is subject to unprecedented requirements for larger capacity and more flexible switching granularities. Envisioning Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) as a promising candidate for such a scenario, we motivate the use of O-OFDM as the underlying switching technology in order to provide sufficient switching capacity and elastic bandwidth allocation. For this purpose, this article reviews the recent progresses of DCN deployment and assesses the scenario where the O-OFDM transmission and switching technology is employed in the underlying transport plane. We discuss the key issues of the datacenter-oriented O-OFDM optical networks, and in particular, elaborate on a number of open issues and solutions including system interconnection architecture, routing and resource assignment, survivability, and energy-efficiency.

• 한국시스템다이내믹스연구
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• 제8권2호
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• pp.115-140
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• 2007

Changes in material use, energy use and emissions profiles of steel industry are the result of complex interrelationships among a multitude of technological and economic drivers. To better understand and guide such changes requires that attention is paid to the time-varying consequences that technology and economic influences have on an industry's choice of inputs and its associated outputs. We briefly review the range of policy issues in our paper and assess the impact that climate-change policies may have on energy use and carbon emissions in Korea steel industry. We then present the models of Korea steel industry's energy and product flow regarding environmental regulations by using system dynamics simulation methodology(SD). Time series data and engineering information are combined to endogenously specify changes in technologies, fuel mix, and production processes within dynamic simulation model. Through a various scenario, ramifications that the convention of climate change would to steel industry is analyzed, and based on the study results, strategies against environment changes is contemplated in various perspectives to contribute to minimize the risks concerning the uncertain future and to be conducive to Korea steel industry's sustainable development.

• 대한환경공학회지
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• 제34권4호
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• pp.280-287
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• 2012

본 연구에서는 대학 캠퍼스 단위에서의 온실가스 인벤토리 구축을 위해 한양대학교 안산캠퍼스를 대상으로 직접 배출원(도시가스, 실내등유, 이동연소), 간접 배출원(전력), 기타 배출원(항공, 수도) 세 부분으로 온실가스 배출원을 규명하였으며, 2007년부터 2009년까지 온실가스 배출원별 에너지 사용량에 따른 온실가스 배출량을 산정하였다. 그 결과, 전체 온실가스 배출영역 중 가장 많은 부분을 차지하는 것은 간접배출의 전력부문으로 전체 온실가스 배출량의 56.7% 차지하는 것을 확인하였다. 또한, 대학본부에서 수행 가능한 온실가스 감축시나리오 및 학교구성원이 수행 가능한 온실가스 감축 실천시나리오를 대학환경에 적합하게 설계한 후 LEAP 모델을 이용하여 2007년부터 2020년까지의 온실가스 감축잠재량을 평가하였다. 그 결과, 감축시나리오 적용시 2020년 BAU(배출전망치) 대비 2020년에는 직접배출 중 고정연소에서 63.34 ton $CO_{2eq}/yr$, 이동연소에서 221.1 ton $CO_{2eq}/yr$ 감축되었으며, 간접배출 중 조명에서는 4,637.34 ton $CO_{2eq}/yr$ 온실가스가 감축되는 것으로 산출되었다. 또한, 실천시나리오를 통한 온실가스 감축잠재량은 1293.76 ton $CO_{2eq}/yr$으로 산출되었다. 따라서, 한양대학교 안산 캠퍼스에 감축 실천 시나리오를 모두 적용한다면 2020년에는 2020년 BAU 대비 온실가스를 총 24% 감축할 수 있을 것으로 추정된다.

• Journal of Radiation Protection and Research
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• 제40권4호
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• pp.231-243
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• 2015

Four different paddy soils collected around the Gyeongju nuclear site were treated with $^{99}TcO_4{^-}$ solution under the assumption of two contrasting contamination scenarios. Scenario I (SN-I) is for a pre-transplanting deposition of $^{99}Tc$ followed by plowing, whereas SN-II is for its deposition onto the water surface shortly after transplanting. Rice plants were grown in lysimeters in a greenhouse. Plant uptake of $^{99}Tc$ was quantified with the $TF_{area}$ ($m^2{\cdot}kg^{-1}-dry$). The SN-II $TF_{area}$ values for straws and brown rice, having been generally higher than the SN-I values, were within the ranges of $6.9{\times}10^{-3}{\sim}4.1{\times}10^{-2}$ and $5.2{\times}10^{-6}{\sim}7.3{\times}10^{-5}$, respectively. Sorption onto clay seems to have decreased $^{99}Tc$ uptake in SN-I, whereas it may have had an insignificant effect in SN-II. A phenomenon characteristic of submerged paddy soil, i.e., the development of a thin oxic surface layer may have greatly affected the rice uptake of SN-II $^{99}Tc$. The surface-water concentrations of $^{99}Tc$ were much higher in SN-II than in SN-I. For the percolating water, however, the opposite was generally true. At most 1.3% of the applied $^{99}Tc$ were leached through such percolation. The use of empirical deposition time-dependent $TF_{area}$ values was considered desirable in assessing the radiological impact of a growing-season deposition of $^{99}Tc$ onto paddy fields.

• Nuclear Engineering and Technology
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• 제41권1호
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• pp.63-70
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• 2009

A steam generator tube rupture (SGTR) accident, which is a partial reactor building bypass scenario, has a low probability and high consequences. SAMG has been used to manage the progression of severe accidents and the release of fission products induced by an SGTR at the Wolsong plants. Four of the six SAGs in the SAMG are used to manage the progression of a severe accident induced by an SGTR at the Wolsong plants. The results of the ISAAC code calculation have shown that the proper use the SAMG can stop a severe accident from progressing and keep the reactor building intact during a severe accident. These results confirm that the SAMG is an effective means of managing the progression of severe accidents initiated by an SGTR at the Wolsong plants.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.665-674
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• 2013

This paper presents the development and validation methods of the FUTURE (FUel cycle analysis Tool for nUcleaR Energy) code, which was developed for a dynamic material flow evaluation and economic analysis of the nuclear fuel cycle. This code enables an evaluation of a nuclear material flow and its economy for diverse nuclear fuel cycles based on a predictable scenario. The most notable virtue of this FUTURE code, which was developed using C# and MICROSOFT SQL DBMS, is that a program user can design a nuclear fuel cycle process easily using a standard process on the canvas screen through a drag-and-drop method. From the user's point of view, this code is very easy to use thanks to its high flexibility. In addition, the new code also enables the maintenance of data integrity by constructing a database environment of the results of the nuclear fuel cycle analyses.

• 농촌계획
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• 제19권3호
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• pp.25-36
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• 2013

This study aims to perform the economic analysis to the use of solar power facilities in rural villages considering the climate change scenario. IPCC climate change scenarios in the recently adopted the RCP scenarios (RCP8.5, RCP6.5, RCP4.5, RCP2.6) was used. By RCP scenarios, solar radiation, depending on the scenario in 2100, respectively, 3.6%, 2.5%, 1.9%, 1.1% was assumed to increase. From the economic analysis(payback period is 25 year) on 8 points of each province, in all cases of normal data and four RCP scenarios, at all points analyzed were NPV indicate a negative, BC ratio less than 1.0, respectively. In the case of Mokpo, Chunnam RCP8.5, BC ratio were found to be up to a 0.92, followed by 0.89 in the case of RCP8.5 in Jinju, Kyungnam shows, while the minimum was in Jeju. BC ratio is 1.0 or bigger, in order for the normal solar radiation data in Mokpo, Chonnam was the minimum that it takes 37 years. Similarly, in the case of RCP scenarios, 30 years in Mokpo, Chonnam RCP8.5 and 31 years in the cases of Jinju, Kyungnam and Jeonju, Cheonbuk RCP8.5 were analyzed. It was analyzed that RCP8.5 has the highest value. BC analysis models for each of the factors, the results of the sensitivity analysis, the initial installation costs, electricity sales price, discount rate in the order of economy showed higher sensitivity, and the rest factors showed lower changes. Although there are some differences of solar radiation by region, but in Korea most facilities in rural areas, the use of solar power was considered to be economical enough, considering change of several factors with high sensitivity, such as increasing of government subsidies for the solar power installation of the facility, rising oil prices due to a rise in electricity sales price, and a change in discount rate. In particular, when considering climate change scenarios, the use of solar energy for rural areas of the judgment that there was more economical.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권4호
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• pp.1392-1413
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• 2022

In order to meet the rapid development of the unmanned aerial vehicle (UAV) communication needs, cooperative spectrum sensing (CSS) helps to identify unused spectrum for the primary users (PU). However, multi-UAV mode (MUM) requires the large communication resource in a cognitive UAV network, resulting in a severe decline of spectrum efficiency (SE) and energy efficiency (EE) and increase of energy consumption (EC). On this account, we extend the traditional 2D spectrum space to 3D spectrum space for the UAV network scenario and enable UAVs to proceed with spectrum sensing behaviors in this paper, and propose a novel multi-slot mode (MSM), in which the sensing slot is divided into multiple mini-slots within a UAV. Then, the CSS process is developed into a composite hypothesis testing problem. Furthermore, to improve SE and EE and reduce EC, we use the sequential detection to make a global decision about the PU channel status. Based on this, we also consider a truncation scenario of the sequential detection under the sensing delay constraint, and further derive a closed-form performance expression, in terms of the CSS performance and cooperative efficiency. At last, the simulation results verify that the performance and cooperative efficiency of MSM outperforms that of the traditional MUM in a low EC.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.896-908
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• 2022

As a part of probabilistic risk (or safety) assessment (PRA or PSA) of nuclear power plants (NPPs), the primary role of human reliability analysis (HRA) is to provide credible estimations of the human error probabilities (HEPs) of safety-critical tasks. In this regard, it is vital to provide credible HEPs based on firm technical underpinnings including (but not limited to): (1) how to collect HRA data from available sources of information, and (2) how to inform HRA practitioners with the collected HRA data. Because of these necessities, the U.S. Nuclear Regulatory Commission and the Korea Atomic Energy Research Institute independently developed two dedicated HRA data collection systems, SACADA (Scenario Authoring, Characterization, And Debriefing Application) and HuREX (Human Reliability data EXtraction), respectively. These systems provide unique frameworks that can be used to secure HRA data from full-scope training simulators of NPPs (i.e., simulator data). In order to investigate the applicability of these two systems, two papers have been prepared with distinct purposes. The first paper, entitled "SACADA and HuREX: Part 1. The Use of SACADA and HuREX Systems to Collect Human Reliability Data", deals with technical issues pertaining to the collection of HRA data. This second paper explains how the two systems are able to inform HRA practitioners. To this end, the process of estimating HEPs is demonstrated based on feed-and-bleed operations using HRA data from the two systems.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.484-497
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• 2021

This paper proposes an extended time uncertainty analysis approach in Level 2 human reliability analysis (HRA) considering severe accident management (SAM) strategies. The method is a time-based model that classifies two time distribution functions-time required and time available-to calculate human failure probabilities from delayed action when implementing SAM strategies. The time required function can be obtained by the combination of four time factors: 1) time for diagnosis and decision by the technical support center (TSC) for a given strategy, 2) time for strategy implementation mainly by the local emergency response organization (ERO), 3) time to verify the effectiveness of the strategy and 4) time for portable equipment transport and installation. This function can vary depending on the given scenario and includes a summation of lognormal distributions and a choice regarding shifting the distribution. The time available function can be obtained via thermal-hydraulic code simulation (MAAP 5.03). The proposed approach was applied to assess SAM strategies that use portable equipment and safety depressurization system valves in a total loss of component cooling water event that could cause reactor vessel failure. The results from the proposed method are more realistic (i.e., not conservative) than other existing methods in evaluating SAM strategies involving the use of portable equipment.