• Title/Summary/Keyword: Order topology

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The Modified IPv6 NDP Mechanism for Preventing IP Spoofing (IP 스푸핑 방지를 위한 수정된 IPv6 NDP 메커니즘)

  • Kim Ji-Hong;Nah Jae-Hoon
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.16 no.2
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    • pp.95-103
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    • 2006
  • IPv6 is a new version of the Internet protocol, designed as the successor to IPv4. Among the changes from IPv4 to IPv6, we focused on the stateless address auto-configuration mechanism. The address auto-configuration mechanism is used by nodes in an IPv6 network to learn the local topology. The current specifications suggest that IPsec AH may be used to secure the mechanism, but there is no security association during address auto-configuration process because it has no initial IP address. As there are so many suity threats, SEND protocol was designed to counter these threats. In this paper we analyzed the security problems in NDP and SEND protocol. So we proposed the Modified NDP mechanism using PKC and AC in order to solve these problems.

Design and Implementation of Cyber Warfare Training Data Set Generation Method based on Traffic Distribution Plan (트래픽 유통계획 기반 사이버전 훈련데이터셋 생성방법 설계 및 구현)

  • Kim, Yong Hyun;Ahn, Myung Kil
    • Convergence Security Journal
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    • v.20 no.4
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    • pp.71-80
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    • 2020
  • In order to provide realistic traffic to the cyber warfare training system, it is necessary to prepare a traffic distribution plan in advance and to create a training data set using normal/threat data sets. This paper presents the design and implementation results of a method for creating a traffic distribution plan and a training data set to provide background traffic like a real environment to a cyber warfare training system. We propose a method of a traffic distribution plan by using the network topology of the training environment to distribute traffic and the traffic attribute information collected in real and simulated environments. We propose a method of generating a training data set according to a traffic distribution plan using a unit traffic and a mixed traffic method using the ratio of the protocol. Using the implemented tool, a traffic distribution plan was created, and the training data set creation result according to the distribution plan was confirmed.

A High-efficiency Single-phase Photovoltaic Inverter for High-voltage Photovoltaic Panels (고전압 태양광 패널용 고효율 단상 태양광 인버터)

  • Hyung-Min, Ryu
    • Journal of IKEEE
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    • v.26 no.4
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    • pp.584-589
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    • 2022
  • For DC-AC power conversion from a high-voltage photovoltaic panel to a single-phase grid, the two-stage transformerless inverter with a buck-boost converter followed by a full-bridge inverter is widely used. To avoid an excessive leakage current due to the large parasitic capacitance of the photovoltaic panel, the full-bridge inverter can only adopt the bipolar PWM which results in much higher power loss compared to the unipolar PWM. In order to overcome such a poor efficiency, this paper proposes a new topology in which an IGBT and a diode for circuit isolation are added to the buck-boost converter. The proposed circuit isolation method allows the unipolar PWM in the full-bridge inverter without any increase in the leakage current so that the overall efficiency can be improved. The validity of the proposed solution is verified by computer simulation and power loss calculation.

A new method of predicting hotspot stresses for longitudinal attachments with reduced element sensitivities

  • Li, Chun Bao;Choung, Joonmo
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.13 no.1
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    • pp.379-395
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    • 2021
  • For the complicated structural details in ships and offshore structures, the traditional hotspot stress approaches are known to be sensitive to the element variables of element topologies, sizes, and integration schemes. This motivated to develop a new approach for predicting reasonable hotspot stresses, which is less sensitive to the element variables and easy to be implemented the real marine structures. The three-point bending tests were conducted for the longitudinal attachments with the round and rectangular weld toes. The tests were reproduced in the numerical simulations using the solid and shell element models, and the simulation technique was validated by comparing the experimental stresses with the simulated ones. This paper considered three hotspot stress approaches: the ESM method based on surface stress extrapolation, the Dong's method based on nodal forces along a weld toe, and the proposed method based on nodal forces perpendicular to an imaginary vertical plane at a weld toe. In order to study the element sensitivities of each method, 16 solid element models and 8 shell element models were generated under the bending and tension loads, respectively. The element sensitivity was analyzed in terms of Stress Concentration Factors (SCFs) in viewpoints of two statistical quantities of mean and bias with respect to the reference SCFs. The average SCFs predicted by the proposed method were remarkably in good agreement with the reference SCFs based on the experiments and the ship rules. Negligibly small Coefficients of Variation (CVs) of the SCFs, which is measure of statistical bias, were drawn by the proposed method.

Geographic Factors and the Modeling of Rice Culture under Normal Season in Korea (지리적환경조건에 따른 수도 보통기 재배시기 추정에 관한 연구)

  • Lim, M.S.;Chung, G.S.;Cho, C.Y.;Park, L.K.;Bae, S.H.;Ham, Y.S.;Lee, E.U.;Choi, H.O.
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.29 no.2
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    • pp.118-127
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    • 1984
  • In order to find an appropriate model for rice crop-season, the possibility to utilize the geographical conditions instead of meteorological factors was examined on the data from the Local Adaptability Test(LAT) conducted over the country from 1962 to 1980. The mutiple regression model, $Y={\Upsilon}={\ss}{\sum}_{i=1}^n{\beta}^1X^iwas applied on seeding, transplanting, heading and marginal heading date, and multiple regression coefficients(\beta) and multiple correlation coefficients (R) were tested. Two varietal groups, japonica(1962-l971) and indica/japonica(l972-1980) were separately tested. The application of these established models, growth duration in nursery and paddy field, cultural season, and the relation between heading date and yield are reviewed.

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Review of Typical Fault Current Limiter Types and Application Effect to Improve Power System Reliability (전력 계통 신뢰도 개선을 위한 대표적인 한류기 유형 및 적용 효과 분석)

  • Yun-Seok Ko;Woo-Cheol Lee
    • The Journal of the Korea institute of electronic communication sciences
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    • v.18 no.6
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    • pp.1133-1142
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    • 2023
  • A rapid increase in power capacity in a power system can seriously reduce system reliability by causing the fault capacity to exceed the breaking capacity of circuit breaker. Fault current limiter is a practical and effective way to improve reliability by limiting fault capacity to the breaking capacity level. In this study, in order to help develop an application methodology when applying fault current limiters to power systems, first the topology and operating principles of each type of fault current limiters was reviewed, and the main advantages and disadvantages was compared. Next, to verify the effect of applying fault current limiter to the power system, the power system in which the fault current limiter was introduced was modeled. Finally, after simulating a three-phase short-circuit fault using EMTP-RV, the effect of application was verified by comparing the fault current before and after application of the fault current limiter and confirming that the fault current was reduced by the fault current limiter.

Holocarpic oomycete parasites of red algae are not Olpidiopsis, but neither are they all Pontisma or Sirolpidium (Oomycota)

  • Giuseppe C. Zuccarello;Claire M. M. Gachon;Yacine Badis;Pedro Murua;Andrea Garvetto;Gwang Hoon Kim
    • ALGAE
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    • v.39 no.1
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    • pp.43-50
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    • 2024
  • Oomycetes are ubiquitous heterotrophs of considerable economic and ecological importance. Lately their diversity in marine environments has been shown to be greatly underappreciated and many lineages of intracellular holocarpic parasites, infecting micro- and macro-algae, remain to be fully described taxonomically. Among them, pathogens of marine red algae have been studied extensively as they infect important seaweed crops. Throughout the 20th century, most intracellular, holocarpic biotrophic oomycetes that infect red algae have been assigned to the genus Olpidiopsis Cornu. However, 18S rRNA sequencing of Olpidiopsis saprolegniae, the species considered the generitype for Olpidiopsis, suggests that this genus is not closely related to the marine pathogens and that the latter requires a nomenclatural update. Here, we compile and reanalyze all recently published 18S rRNA sequence data for marine holocarpic oomycetes, with a particular focus on holocarpic pathogens of red algae. Their taxonomy has been revised twice over the past four years, with suggestions to transfer them first into the genus Pontisma and then Sirolpidium, and into a monogeneric order, Pontismatales. We show however, that previously published topologies and the proposed taxa Pontisma, Sirolpidium, and Pontismatales are unsupported. We highlight that name changes that are unfounded and premature create confusion in interested parties, especially concerning pathogens of marine red algae that infect important seaweed crops. We thus propose that the names of these holocarpic biotrophic parasites of red algae are retained temporarily, until a supported topology is produced with more genetic markers to enable the circumscription of species and higher-level taxa.

Efficiency Evaluation of Genetic Algorithm Considering Building Block Hypothesis for Water Pipe Optimal Design Problems (상수관로 최적설계 문제에 있어 빌딩블록가설을 고려한 유전 알고리즘의 효율성 평가)

  • Lim, Seung Hyun;Lee, Chan Wook;Hong, Sung Jin;Yoo, Do Guen
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.5
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    • pp.294-302
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    • 2020
  • In a genetic algorithm, computer simulations are performed based on the natural evolution process of life, such as selection, crossover, and mutation. The genetic algorithm searches the approximate optimal solution by the parallel arrangement of Schema, which has a short definition length, low order, and high adaptability. This study examined the possibility of improving the efficiency of the optimal solution by considering the characteristics of the building block hypothesis, which are one of the key operating principles of a genetic algorithm. This study evaluated the efficiency of the optimization results according to the gene sequence for the implementation in solving problems. The optimal design problem of the water pipe was selected, and the genetic arrangement order reflected the engineering specificity by dividing into the existing, the network topology-based, and the flowrate-based arrangement. The optimization results with a flowrate-based arrangement were, on average, approximately 2-3% better than the other batches. This means that to increase the efficiency of the actual engineering optimization problem, a methodology that utilizes clear prior knowledge (such as hydraulic properties) to prevent such excellent solution characteristics from disappearing is essential. The proposed method will be considered as a tool to improve the efficiency of large-scale water supply network optimization in the future.

3D Node Deployment and Network Configuration Methods for Improvement of Node Coverage and Network Connectivity (커버리지와 네트워크 연결성 향상을 위한 3차원 공간 노드 배치 및 망 구성 방법)

  • Kim, Yong-Hyun;Kim, Lee-Hyeong;Ahn, Mirim;Chung, Kwangsue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37B no.9
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    • pp.778-786
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    • 2012
  • Sensors that are used on wireless sensor networks can be divided into two types: directional sensors, such as PIR, image, and electromagnetic sensors; and non-directional sensors, such as seismic, acoustic and magnetic sensors. In order to guarantee the line-of-sight of a directional sensor, the installation location of the sensor must be higher than ground level. Among non-directional sensors, seismic sensors should be installed on the ground in order to ensure the maximal performance. As a result, seismic sensors may have network connectivity problems due to communication failure. In this paper, we propose a 3D node deployment method to maximize the coverage and the network connectivity considering the sensor-specific properties. The proposed method is for non-directional sensors to be placed on the ground, while the directional sensor is installed above the ground, using trees or poles, to maximize the coverage. As a result, through the topology that the detection data from non-directional sensors are transmitted to the directional sensor, we can maximize the network connectivity. Simulation results show that our strategy improves sensor coverage and network connectivity.

In Situ Spectroscopy in Condensed Matter Physics

  • Noh, Tae Won
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.92-92
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    • 2014
  • Recently, many state-of-art spectroscopy techniques are used to unravel the mysteries of condensed matters. And numerous heterostructures have provided a new avenue to search for new emergent phenomena. Especially, near the interface, various forms of symmetry-breaking can appear, which induces many novel phenomena. Although these intriguing phenomena can be emerged at the interface, by using conventional measurement techniques, the experimental investigations have been limited due to the buried nature of interface. One of the ways to overcome this limitation is in situ investigation of the layer-by-layer evolution of the electronic structure with increasing of the thickness. Namely, with very thin layer, we can measure the electronic structure strongly affected by the interface effect, but with thick layer, the bulk property becomes strong. Angle-resolved photoemission spectroscopy (ARPES) is powerful tool to directly obtain electronic structure, and it is very surface sensitive. Thus, the layer-by-layer evolution of the electronic structure in oxide heterostructure can be investigated by using in situ ARPES. LaNiO3 (LNO) heterostructures have recently attracted much attention due to theoretical predictions for many intriguing quantum phenomena. The theories suggest that, by tuning external parameters such as misfit strain and dimensionality in LNO heterostructure, the latent orders, which is absent in bulk, including charge disproportionation, spin-density-wave order and Mott insulator, could be emerged in LNO heterostructure. Here, we performed in situ ARPES studies on LNO films with varying the misfit strain and thickness. (1) By using LaAlO3 (-1.3%), NdGaO3 (+0.3%), and SrTiO3 (+1.7%) substrates, we could obtain LNO films under compressive strain, nearly strain-free, and tensile strain, respectively. As strain state changes from compressive to tensile, the Ni eg bands are rearranged and cross the Fermi level, which induces a change of Fermi surface (FS) topology. Additionally, two different FS superstructures are observed depending on strain states, which are attributed to signatures of latent charge and spin orderings in LNO films. (2) We also deposited LNO ultrathin films under tensile strain with thickness between 1 and 10 unit-cells. We found that the Fermi surface nesting effect becomes strong in two-dimensions and significantly enhances spin-density-wave order. The further details are discussed more in presentation. This work was collaborated with Hyang Keun Yoo, Seung Ill Hyun, Eli Rotenberg, Ji Hoon Shim, Young Jun Chang and Hyeong-Do Kim.

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