• Title/Summary/Keyword: Grid convergence test

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Analysis of Added Resistance using a Cartesian-Grid-based Computational Method (직교격자 기반 수치기법을 이용한 부가저항 해석)

  • Yang, Kyung-Kyu;Lee, Jae-Hoon;Nam, Bo-Woo;Kim, Yonghwan
    • Journal of the Society of Naval Architects of Korea
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    • v.50 no.2
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    • pp.79-87
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    • 2013
  • In this paper, an Euler equation solver based on a Cartesian-grid method and non-uniform staggered grid system is applied to predict the ship motion response and added resistance in waves. Water, air, and solid domains are identified by a volume-fraction function for each phase and in each cell. For capturing the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with a weighed line interface calculation (WLIC) method. The volume fraction of solid body embedded in a Cartesian-grid system is calculated by a level-set based algorithm, and the body boundary condition is imposed by volume weighted formula. Added resistance is calculated by direct pressure integration on the ship surface. Numerical simulations for a Wigley III hull and an S175 containership in regular waves have been carried out to validate the newly developed code, and the ship motion responses and added resistances are compared with experimental data. For S175 containership, grid convergence test has been conducted to investigate the sensitivity of grid spacing on the motion responses and added resistances.

Deep Learning-Based Smart Meter Wattage Prediction Analysis Platform

  • Jang, Seonghoon;Shin, Seung-Jung
    • International journal of advanced smart convergence
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    • v.9 no.4
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    • pp.173-178
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    • 2020
  • As the fourth industrial revolution, in which people, objects, and information are connected as one, various fields such as smart energy, smart cities, artificial intelligence, the Internet of Things, unmanned cars, and robot industries are becoming the mainstream, drawing attention to big data. Among them, Smart Grid is a technology that maximizes energy efficiency by converging information and communication technologies into the power grid to establish a smart grid that can know electricity usage, supply volume, and power line conditions. Smart meters are equient that monitors and communicates power usage. We start with the goal of building a virtual smart grid and constructing a virtual environment in which real-time data is generated to accommodate large volumes of data that are small in capacity but regularly generated. A major role is given in creating a software/hardware architecture deployment environment suitable for the system for test operations. It is necessary to identify the advantages and disadvantages of the software according to the characteristics of the collected data and select sub-projects suitable for the purpose. The collected data was collected/loaded/processed/analyzed by the Hadoop ecosystem-based big data platform, and used to predict power demand through deep learning.

Development of Hybrid (Sb/Ca) Flooded Lead-Acid Battery for Minimizing Water Loss (감액 특성 향상을 위한 하이브리드(Sb/Ca) 액식 연축전지 개발)

  • Song, Seung Yun;Lim, Tae Seop;Kim, Sung Jun;Jung, Yeon-Gil;Yang, SeungCheol
    • Korean Journal of Materials Research
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    • v.32 no.3
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    • pp.146-152
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    • 2022
  • One disadvantage of deep cycle flooded lead-acid batteries is increasing water loss caused by use of (+) Pb-Sb / (-) Pb-Sb alloy grid. Water loss is generated by the emission of hydrogen gas from the (-) electrode during battery charging. In this paper, we maintain cycle life aspect through the development of hybrid flooded lead-acid batteries to which a (+) Pb-Sb / (-) Pb-Ca grid is applied and deal with the improvement of water loss. The amount of water loss compared to that of the (-) Pb-Sb grid decreased when Ca was added to the (-) Pb grid. For the (-) Pb-Ca grid, it was confirmed that the time to reach 0.0 V, at which water decomposition occurs, was increased compared to that of the (-) Pb-Sb grid at the NPV (Negative Potential Voltage). In the cycle life test conducted with the BCI (Battery Council International) standard, compared to the (+) Pb-Ca grid, the (+) Pb-Sb grid increased the life cycle of the batteries and the (+) Pb-Ca grid showed an early end of life due to PbO corrosion layer generation, as determined through SEM / EDS and Tear Down analysis. In conclusion, by addition of Sb to (+) Pb grid and Ca to (-) Pb grid, we developed a hybrid flooded lead-acid battery that meets user requirements to improve water loss characteristics and preserve cycle life characteristics.

An Improved Face Recognition Method Using SIFT-Grid (SIFT-Grid를 사용한 향상된 얼굴 인식 방법)

  • Kim, Sung Hoon;Kim, Hyung Ho;Lee, Hyon Soo
    • Journal of Digital Convergence
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    • v.11 no.2
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    • pp.299-307
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    • 2013
  • The aim of this paper is the improvement of identification performance and the reduction of computational quantities in the face recognition system based on SIFT-Grid. Firstly, we propose a composition method of integrated template by removing similar SIFT keypoints and blending different keypoints in variety training images of one face class. The integrated template is made up of computation of similarity matrix and threshold-based histogram from keypoints in a same sub-region which divided by applying SIFT-Grid of training images. Secondly, we propose a computation method of similarity for identify of test image from composed integrated templates efficiently. The computation of similarity is performed that a test image to compare one-on-one with the integrated template of each face class. Then, a similarity score and a threshold-voting score calculates according to each sub-region. In the experimental results of face recognition tasks, the proposed methods is founded to be more accurate than both two other methods based on SIFT-Grid, also the computational quantities are reduce.

A Direction of Convergence and Security of Smart Grid and Information Communication Network (스마트그리드(Smart Grid) 전력망과 정보통신망 융합 보안 방향)

  • Seo, Woo-Seok;Jun, Moon-Seog
    • The Journal of the Korea institute of electronic communication sciences
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    • v.5 no.5
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    • pp.477-486
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    • 2010
  • This Study suggests security directions to reconstruct separate network of Smart Grid and information communication network as one communications system and implement Smart Grid integrated information communication network. In addition, it suggests prevention directions to prevent future cyber attacks by reorganizing network as the key three-stage network and separating TCP/IP four layers that consist of existing information communication network from Smart Grid. Moreover, it suggests the foundation for the study and the test by providing current problems of Smart Grid, weak points, and three security models. This study is meaningful to suggest development directions and situations as a technology of future-oriented electric industries, integrate attacks and preventions of TCP/IP Layers with Smart Grid, and seek for a new technology of Smart Grid and future tasks for Smart Grid information security.

Calculation of the incompressible Navier-stokes equations in generalized nonorthogonal body fitted coordinate system (일반 비직교 표면좌표계에서의 비압축성 Navier-Stokes방정식의 수치해석)

  • Gang, Dong-Jin;Bae, Sang-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.3
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    • pp.1015-1027
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    • 1996
  • In this paper, a numerical procedure for the calculation of the incompressible Navier-Stokes equations in a generalized nonorthogonal body fitted coordinate system is proposed and is validated through three test problems. Present numerical procedure derives the pressure equation by using the pressure substitution method on the regular grid system, and discretized momentum equations are based on the covariant velocity components. Cavity flow, backward facing step flow, and two dimensional channel flow with a sinusoidal wavy wall are chosen as three test problems. Numerical solutions obtained by present procedure shows a good agreement with previous numerical and/or experimental results. Convergence rate is also satisfactory.

A Study on the Optimization of Power Consumption Pattern using Building Smart Microgrid Test-Bed (Building Smart Microgrid Test-Bed를 이용한 전력사용량 패턴 최적화방안 연구)

  • Lee, Sang-Woo;Kang, Jin-Kyu;Lee, Dong-Ha
    • Journal of the Korean Solar Energy Society
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    • v.34 no.4
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    • pp.1-7
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    • 2014
  • The microgrid system is the combination of photovoltaic(PV) array, load, and battery energy storage system. The control strategies were defined as multi-modes of operation, including rest operation without use of battery, power charging, and power discharging, which enables grid connected mode or islanded mode. Photovoltaic power is a problem of the uniformity of power quality because the power generated from solar light is very sensitive to variation of insolation and duration of sunshine. As a solution to the above problem, energy storage system(ESS) is considered generally. There fore, in this study, we did basic research activities about optimization method of the amount of energy used, using a smart microgrid test-bed constructed in building. First, we analyzed the daily, monthly and period energy pattern amount of power energy used, and analyzed PV power generation level which is built on the roof. Utilizing building energy pattern analysis data, we was studied an efficient method of employing the ESS about building power consumption pattern and PV generation.

AN EXTENSION OF THE SMAC ALGORITHM FOR THERMAL NON-EQUILIBRIUM TWO-PHASE FLOWS OVER UNSTRUCTURED NON-STAGGERED GRIDS (과도상태 2상유동 해석을 위한 비정렬.비엇갈림 격자 SMAC 알고리즘)

  • Park, I.K.;Yoon, H.Y.;Cho, H.K.;Kim, J.T.;Jeong, J.J.
    • Journal of computational fluids engineering
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    • v.13 no.3
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    • pp.51-61
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    • 2008
  • The SMAC (Simplified Marker And Cell) algorithm is extended for an application to thermal non-equilibrium two-phase flows in light water nuclear reactors (LWRs). A two-fluid three-field model is adopted and a multi-dimensional unstructured grid is used for complicated geometries. The phase change and the time derivative terms appearing in the continuity equations are implemented implicitly in a pressure correction equation. The energy equations are decoupled from the momentum equations for faster convergence. The verification of the present numerical method was carried out against a set of test problems which includes the single and the two-phase flows. The results are also compared to those of the semi-implicit ICE method, where the energy equations are coupled with the momentum equation for pressure correction.

Application Development and Type Test for Smart Inverter Based on IEEE 1547-2018 Utilizing Power HILS (Power HILS를 활용한 IEEE 1547-2018 기반 스마트 인버터의 기술개발 및 형식시험 연구)

  • Shin, Danbi;Kang, Moses;Lee, Hyuna;Hong, Seonri;Yoon, Gihwan;Baek, Jongbok
    • Journal of IKEEE
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    • v.26 no.1
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    • pp.1-9
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    • 2022
  • In order to secure the reliability of the power system and to increase the penetration level of distributed energy resources (DERs), requirements such as IEEE 1547 have been revised to strengthen the grid connection standards for DER. This paper proposes a control scheme for smart inverter functions based on IEEE 1547-2018 that satisfy these standards, and introduces a power HILS-based test platform built for verification of smart inverter. Among the smart inverter functions, Volt-var and Frequency-watt allow the curve to be set from the upper level to comply with the interoperability and operation time of enable signals for each function are controlled by references from the upper level. According to the requirement, Volt-var and Frequency-watt are performed via power HILS platform and verified through the measurement results that all of the specified type tests were satisfied.

A study on advanced PV operation algorithm to improve the PV Power-Hardware-In-Loop Simulator (PV PHIL-시뮬레이터의 성능 개선을 위한 최적의 운영제어 알고리즘 연구)

  • Kim, Dae-Jin;Kim, Byungki;Ko, Hee-Sang;Jang, Moon-Seok;Ryu, Kyung-Sang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.9
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    • pp.444-453
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    • 2017
  • This paper proposes an operational algorithm for a Photovoltaic Power-Hardware-In-Loop Simulator that is designed to improve the control algorithm and reliability of the PV Inverter. There was an instability problem in the PV PHILS with the conventional algorithm when it was connected tothe PV inverter. Initially, a real-time based computing unit with mathematical modeling of the PV array is implemented and a DC amplifier and an isolated device for DC power measurement are integrated. Several experiments were performed based on theabove concept undercertain conditions, which showed that the proposed algorithm is more effective for the PV characteristic test and grid evaluation test than the conventional method.