Artykuły w czasopismach: „SUB-GRIDS”

1

Nel, Marko, i Imke de Kock. "AN INVESTIGATION INTO THE APPLICABILITY OF SUPER GRIDS IN A SUB-SAHARAN AFRICAN CONTEXT". South African Journal of Industrial Engineering 32, nr 2 (2021): 162–72. http://dx.doi.org/10.7166/32-3-2612.

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There is a need in energy-poor sub-Saharan Africa for a system to manage energy more efficiently and effectively both within and between countries. An approach that has been proven in other parts of the world to facilitate this is super grids. With their interconnection and information management systems, super grids can contribute to the increasingly effective and efficient management of energy, and they have the potential to increase sustainability. The applicability of such super grids in the sub-Saharan African context is still uncertain and is scientifically under-explored; thus there is a need to establish their applicability in a sub-Saharan African context. In this article, the literature on super grids is analysed and contextualised from a bibliometric and content analysis perspective, in order to draw parallels between such super grids and the sub-Saharan African context, and thus to investigate their applicability in that context.

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Lauritzen, P. H., J. T. Bacmeister, P. F. Callaghan i M. A. Taylor. "NCAR_Topo (v1.0): NCAR global model topography generation software for unstructured grids". Geoscientific Model Development 8, nr 12 (14.12.2015): 3975–86. http://dx.doi.org/10.5194/gmd-8-3975-2015.

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Abstract. It is the purpose of this paper to document the NCAR global model topography generation software for unstructured grids (NCAR_Topo (v1.0)). Given a model grid, the software computes the fraction of the grid box covered by land, the grid-box mean elevation (deviation from a geoid that defines nominal sea level surface), and associated sub-grid-scale variances commonly used for gravity wave and turbulent mountain stress parameterizations. The software supports regular latitude–longitude grids as well as unstructured grids, e.g., icosahedral, Voronoi, cubed-sphere and variable-resolution grids.

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Sarkar, Tanmay, Parveen Kumar, Mridula Dixit Bharadwaj i Umesh Waghmare. "Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study". Physical Chemistry Chemical Physics 18, nr 14 (2016): 9344–48. http://dx.doi.org/10.1039/c5cp07782f.

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A double layer δ-NH₄V₄O₁₀, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids.

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Gao, Qiang, Xiao-Lin Zhao, Ze Chang, Jian Xu i Xian-He Bu. "Structural stabilization of a metal–organic framework for gas sorption investigation". Dalton Transactions 45, nr 16 (2016): 6830–33. http://dx.doi.org/10.1039/c6dt00640j.

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In this contribution, by inserting a ligand intoCo-MOF1, the reformed aggregation of triangle grids (Co-MOF1-tpt) shows enhanced stability. In addition, owing to the maintenance of porosity,Co-MOF1-tptalso reveals a certain CO₂storage ability and CO₂/CH₄adsorption selectivity as expected.

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Fan, Xiaoxia, Dan Zhang, Shiyu Jiang, Heng Wang, Lin-Ting Lin, Bo Zheng, Wen-Hua Xu i in. "Construction and interconversion of anion-coordination-based (‘aniono’) grids and double helicates modulated by counter-cations". Chemical Science 10, nr 25 (2019): 6278–84. http://dx.doi.org/10.1039/c9sc02012h.

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JALSENIUS, MARKUS, i KASPER PEDERSEN. "A SYSTEMATIC SCAN FOR 7-COLOURINGS OF THE GRID". International Journal of Foundations of Computer Science 19, nr 06 (grudzień 2008): 1461–77. http://dx.doi.org/10.1142/s012905410800639x.

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We study the mixing time of a systematic scan Markov chain for sampling from the uniform distribution on proper 7-colourings of a finite rectangular sub-grid of the infinite square lattice, the grid. A systematic scan Markov chain cycles through finite-size subsets of vertices in a deterministic order and updates the colours assigned to the vertices of each subset. The systematic scan Markov chain that we present cycles through subsets consisting of 2×2 sub-grids and updates the colours assigned to the vertices using a procedure known as heat-bath. We give a computer-assisted proof that this systematic scan Markov chain mixes in O( log n) scans, where n is the size of the rectangular sub-grid. We make use of a heuristic to compute required couplings of colourings of 2×2 sub-grids. This is the first time the mixing time of a systematic scan Markov chain on the grid has been shown to mix for less than 8 colours. We also give partial results that underline the challenges of proving rapid mixing of a systematic scan Markov chain for sampling 6-colourings of the grid by considering 2×3 and 3×3 sub-grids.

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7

Elsaidi, Sameh K., Mona H. Mohamed, Herbert T. Schaef, Amrit Kumar, Matteo Lusi, Tony Pham, Katherine A. Forrest i in. "Correction: Hydrophobic pillared square grids for selective removal of CO2 from simulated flue gas". Chemical Communications 51, nr 94 (2015): 16872. http://dx.doi.org/10.1039/c5cc90503f.

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Fiddes, J., i S. Gruber. "TopoSUB: a tool for efficient large area numerical modelling in complex topography at sub-grid scales". Geoscientific Model Development Discussions 5, nr 2 (2.05.2012): 1041–76. http://dx.doi.org/10.5194/gmdd-5-1041-2012.

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Abstract. Mountain regions are highly sensitive to global climate change. However, large scale assessments of mountain environments remain problematic due to the high resolution required of model grids to capture strong lateral variability. To alleviate this, tools are required to bridge the scale gap between gridded climate datasets (climate models and re-analyses) and unresolved (by coarse grids) sub-grid mountain topography. We address this problem with a sub-grid method. It relies on sampling the most important aspects of land surface heterogeneity through a lumped scheme, allowing for the application of numerical land surface models (LSM) over large areas in mountain regions. This is achieved by including the effect of mountain topography on these processes at the sub-grid scale using a multidimensional informed sampling procedure together with a 1-D lumped model that can be driven by gridded climate datasets. This paper provides a description of this sub-grid scheme, TopoSUB, as well as assessing its performance against a distributed model. We demonstrate the ability of TopoSUB to approximate results simulated by a distributed numerical LSM at around 104 less computations. These significant gains in computing resources allow for: (1) numerical modelling of processes at fine grid resolutions over large areas; (2) extremely efficient statistical descriptions of sub-grid behaviour; (3) a "sub-grid aware" aggregation of simulated variables to course grids; and (4) freeing of resources for treatment of uncertainty in the modelling process.

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9

Zhang, Yu, Qianqian Yang, Jingjing Lu, Mei Guo, Xiao-Lei Li i Jinkui Tang. "Heterometallic {DyIII2FeII2} grids with slow magnetic relaxation and spin crossover". Inorganic Chemistry Frontiers 8, nr 7 (2021): 1779–87. http://dx.doi.org/10.1039/d0qi01471k.

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The self-assembly of a Dy^III ion, an Fe^II ion and a multitopic H₂L ligand produces novel [2 × 2] {DyIII2FeII2} grids exhibiting slow magnetic relaxation and spin crossover.

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Lauritzen, P. H., J. T. Bacmeister, P. F. Callaghan i M. A. Taylor. "NCAR global model topography generation software for unstructured grids". Geoscientific Model Development Discussions 8, nr 6 (22.06.2015): 4623–51. http://dx.doi.org/10.5194/gmdd-8-4623-2015.

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Abstract. It is the purpose of this paper to document the NCAR global model topography generation software for unstructured grids. Given a model grid, the software computes the fraction of the grid box covered by land, the gridbox mean elevation, and associated sub-grid scale variances commonly used for gravity wave and turbulent mountain stress parameterizations. The software supports regular latitude-longitude grids as well as unstructured grids; e.g. icosahedral, Voronoi, cubed-sphere and variable resolution grids. As an example application and in the spirit of documenting model development, exploratory simulations illustrating the impacts of topographic smoothing with the NCAR-DOE CESM (Community Earth System Model) CAM5.2-SE (Community Atmosphere Model version 5.2 – Spectral Elements dynamical core) are shown.

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Mariscotti, Andrea. "Power quality metrics for DC grids with pulsed power loads". ACTA IMEKO 10, nr 2 (29.06.2021): 153. http://dx.doi.org/10.21014/acta_imeko.v10i2.1065.

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<span lang="EN-GB">DC grids can effectively feed pulsed power loads (PPLs), integrating local energy storage to minimize the impact on other connected loads and implementing buffered sub-grids to isolate susceptible loads even more. The identification of regulatory limits for PPL integration and DC grid response and the assessment of PPL impact necessitate suitable Power Quality (PQ) metrics. Existing indexes and limits (e.g. ripple and distortion, voltage fluctuation) are compared to other metrics, derived from control methods and knowledge of the peculiar characteristics of PPL and interaction with DC grids in some examples. The objective is a unified approach for PQ metrics suitable for a wide range of DC grids and in particular to the behavior of PPLs.</span>

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Welsch, Manuel, Morgan Bazilian, Mark Howells, Deepak Divan, David Elzinga, Goran Strbac, Lawrence Jones i in. "Smart and Just Grids for sub-Saharan Africa: Exploring options". Renewable and Sustainable Energy Reviews 20 (kwiecień 2013): 336–52. http://dx.doi.org/10.1016/j.rser.2012.11.004.

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Knight, Helen. "Solar Grids Set to Transform Lives in Sub-Saharan Africa". Engineer 299, nr 7908 (maj 2019): 6. http://dx.doi.org/10.12968/s0013-7758(23)90737-3.

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Razzaq, Syed Abdul, i Vairavasamy Jayasankar. "Energy management system for AC/DC HMGS integrated with interconnected renewable sources and interlinking converter". International Journal of Applied Power Engineering (IJAPE) 12, nr 1 (1.03.2023): 24. http://dx.doi.org/10.11591/ijape.v12.i1.pp24-36.

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AC/DC hybrid micro grid system (HMGS) is designed with renewable energy sources (RES) and battery energy storage system (BESS) with unique control schemes, interfaced with multi terminal interlinking converters (ILCs). This ILC operates on droop control scheme to guarantee bidirectional power sharing to AC/DC sub grids. The power sources in AC/DC sub grids like PV, Fuel cell, BESS are controlled by advance control methods for maximum power extraction with power quality. A three-level control structure is designed for optimal energy management system (EMS). The first level confirms the power balance in AC/DC sub grid with autonomous bidirectional power transfer via ILC in islanded mode. The second level tracks the batteries state of charge (SoC), based on the minimum and maximum SoC the battery operates for charging and discharging. The third level gives the power redundant capability for critical loads connected in AC/DC sub grid for DC system and single-phase system.

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Xu, Lin, Yong-Hong Tang, Wei Pu i Yang Han. "Hybrid electromechanical-electromagnetic simulation to SVC controller based on ADPSS platform". Journal of Energy in Southern Africa 25, nr 4 (19.12.2014): 112–22. http://dx.doi.org/10.17159/2413-3051/2014/v25i4a2244.

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To test the dynamic performance and damping features of a static var compensator (SVC) controller accurately in large-scale interconnected AC/DC hybrid power systems, it is of vital significance to build the detailed electromagnetic transient model. However, it is unrealistic and time-consuming to build the detailed models of all the devices in the actual large-scale power grid. Utilizing the hybrid simulation function in the advanced digital power system simulator (ADPSS) and by dividing the large-scale power grid into the electromagnetic transient sub-grids and electromechanical sub-grids, the computation speed of real-time simulation is remarkably enhanced by the parallel computational capabilities of digital simulator. The SVC controller and the nearby substation are modelled in the electromagnetic transient sub-grid, and the residue sub-networks are modelled in the electromechanical sub-grid. This paper focuses on the mechanism of the hybrid electromechanical and electromagnetic simulation, the detailed modelling and the ADPSS-based digital closed-loop test methodologies of the SVC controller. Eventually, the validity and effectiveness of the modelling and control methods are confirmed by the experimental results.

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AKAZAWA, Masayuki, Kengo SUZUKI, Yutaka TABE i Takemi CHIKAHISA. "Cost and CO₂ reduction effect of distributed CHPs cooperatively networked by grids". Transactions of the JSME (in Japanese) 82, nr 836 (2016): 15–00442. http://dx.doi.org/10.1299/transjsme.15-00442.

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Hong, Jian-Shiung, Wei-Ming Cheng, Meng-Chang Yang, Ruei-Cheng Shiu, Yung-Chiang Lan i Kuan-Ren Chen. "Enhancing Efficiency of Electromagnetic Simulation in Time Domain with Transformation Optics". Applied Sciences 8, nr 7 (12.07.2018): 1133. http://dx.doi.org/10.3390/app8071133.

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With sub-wavelength scaled structures in a large system, the conventional finite-difference time-domain method can consume much computational resources since it includes both the spatial and temporal dimension in the scheme. In order to reduce the computational cost, we combine the novel methodology “transformation optics” in the simulation to map a physical coordinate with designated non-uniform grids to a uniform numerical coordinate. For a demonstration, the transmission spectrum through a sub-wavelength metallic aperture with one-dimensional and two-dimensional coordinate transformation is simulated, and compared with uniform-grid cases. We show that the proposed method is accurate, and the computational cost can be reduced remarkably to at most 5.31%, in comparison with the simulation of the finest uniform grids demonstrated. We are confident that it should be helpful to the simulation study in sub-wavelength optics due to its verified accuracy and efficiency.

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Antonanzas-Torres, Fernando, Javier Antonanzas i Julio Blanco-Fernandez. "Environmental Impact of Solar Home Systems in Sub-Saharan Africa". Sustainability 13, nr 17 (30.08.2021): 9708. http://dx.doi.org/10.3390/su13179708.

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Solar home systems (SHS) represent one of the most promising technologies for a rapid and independent electrification in those areas of Sub-Saharan Africa (SSA) without access to electricity. This study addressed the environmental impact of SHS in SSA through updated life cycle inventories and five impact categories: greenhouse gases (GHG) emissions, fossil fuels, metal and water depletion and human toxicity. Sixteen scenarios were considered, including manufacturing, transportation, recycling and user-related variables, such as the installation site, adequacy of SHS user operation and battery lifespan. The results showed that lead-acid batteries were the largest contributor to environmental impact among the SHS components, accounting for up to 36–76% of the environmental impact indicators. Apart from the components, user training for SHS operation, with the goal of maximizing usable energy and battery lifetime, proved to be critical to achieve improvements in the energy payback time and GHG emissions, which (under scenarios of high solar resources) can reach the range of 5.3–7.1 years and 0.14–0.18 kgCO2 eq/kWh, respectively. In addition, SHS GHG emission factors were benchmarked with those of other electrification approaches, such as national grids, 100% PV and hybrid PV-diesel off-grid mini grids and off-grid diesel generators. SHS achieved GHG emission factor values equivalent to PV-based mini grids in most scenarios and was strikingly lower compared to SSA national grids and diesel generators.

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JADHAV, S. K. "Summer monsoon low pressure systems over the Indian region and their relationship with the sub-divisional rainfall". MAUSAM 53, nr 2 (18.01.2022): 177–86. http://dx.doi.org/10.54302/mausam.v53i2.1633.

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In the present paper performance of the monthly sub-divisional summer monsoon rainfall is studied in association with the position of the Low Pressure System (LPS) over the Indian region. Existence of the LPS over a particular location increases the rainfall activities in certain parts of the country while decreases in some other parts. For this study, the Indian region (5°-35° N and 60° -100° E) is divided into 5° Lat. ´ 5° Long. grids. The duration of LPS is taken in terms of LPS days with respect to the location of LPS in a particular grid. Monthly total number of LPS days in each of the grids are computed during the summer monsoon season, June to September for the period 1891 – 1990. Maximum number of LPS days (more than half of the total) are observed in the latitude belt between 20°-25°N. The percentages of total LPS days in this area are higher in July and August which are peak monsoon months as compared to June and September. When there is a LPS are in the area 20°-25° N and 80°-90° E, there is significant increase in the rainfall activities in the sub-divisions along mean monsoon trough while northeast India and southeast peninsular India experience significant decrease in rainfall in the months of July and August. Owing to the movement of LPS from east to west through central India, most parts of the country, excluding northeast India and south peninsular India get good rainfall activity. Correlation coefficients between monthly LPS days over the different grids and monthly sub-divisional rainfall are computed to study the relationships. The performance of sub-divisional rainfall mostly related with the occurrence of LPS in certain grid- locations. The correlation field maps may give some useful information about rainfall performance due to LPS in a particular grid locations.

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Kim, Namjo, Shinyoung Choi, Seong-Jun Yang, Jewook Park, Jun-Ho Park, Nguyen Ngan Nguyen, Kwanghee Park, Sunmin Ryu, Kilwon Cho i Cheol-Joo Kim. "Graphene Nanoribbon Grids of Sub-10 nm Widths with High Electrical Connectivity". ACS Applied Materials & Interfaces 13, nr 24 (8.06.2021): 28593–99. http://dx.doi.org/10.1021/acsami.1c03437.

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Ren, Quan-yao, Wen-xiong Zhou, Si-jia Du, Zhong-chun Li i Liang-ming Pan. "Sub-channel flow regime maps in vertical rod bundles with spacer grids". International Journal of Heat and Mass Transfer 122 (lipiec 2018): 1138–52. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2018.01.133.

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Ebiloma, Stella. "Identification of the non-tree vegetation of opada forest reserve for conservation". Environment Conservation Journal 21, nr 1&2 (9.06.2020): 31–38. http://dx.doi.org/10.36953/ecj.2020.211204.

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Objectives of study: to identify the non-tree vegetation of Opada Forest Reserve (OFR) and provide comprehensive vegetation data for monitoring, conservation and management of present biodiversity. OFR is about 215.76km2 in size. Its map was gridded at an interval of one degree and each grid was 3.61 km2. Using a table of random numbers, ten of the grids were randomly selected. Within each grid, straight line transects of 2km long were randomly laid using Global Positioning System, to locate transects in the right grids and prismatic compass to maintain straight transects, 25m × 25m quadrates were taken at regular intervals of 500m. Each transect accommodated four quadrats which were 40 altogether. 1m2 sub-plots were located at the four corners of the quadrates for identification and counting of species. There were 160 sub-plots for this assessment. About 48- grass species, 12- climbers, 37- herbs, 4- shrubs and 5- sedges were identified.

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BIEN, R., B. FUCHS i R. WIELEN. "High Spatial Resolution Using the Conventional Particle-Mesh Technique". International Journal of Modern Physics C 02, nr 01 (marzec 1991): 3–13. http://dx.doi.org/10.1142/s0129183191000020.

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The use of the particle-mesh technique has a long and successful history in the field of computer simulations of collisionless gravitational systems, such as galaxies. Since the method allows the treatment of large numbers of particles statistical noise has only a small effect. On the other hand, severe problems arise when high density peaks must be resolved. In order to master these difficulties we have worked out a procedure which is an extension of the standard particle-mesh code in three-dimensional Cartesian coordinates. The basic idea is simply to introduce additional grids and sub-grids in regions with steep density gradients such that the system of grids is re-arranged at each integration step. In this way we are able to simulate single and interacting galaxies. In the present paper a short review of some frequently used methods of galaxy simulations is given and our own method is outlined.

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Fiddes, J., i S. Gruber. "TopoSUB: a tool for efficient large area numerical modelling in complex topography at sub-grid scales". Geoscientific Model Development 5, nr 5 (10.10.2012): 1245–57. http://dx.doi.org/10.5194/gmd-5-1245-2012.

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Abstract. Mountain regions are highly sensitive to global climate change. However, large scale assessments of mountain environments remain problematic due to the high resolution required of model grids to capture strong lateral variability. To alleviate this, tools are required to bridge the scale gap between gridded climate datasets (climate models and re-analyses) and mountain topography. We address this problem with a sub-grid method. It relies on sampling the most important aspects of land surface heterogeneity through a lumped scheme, allowing for the application of numerical land surface models (LSMs) over large areas in mountain regions or other heterogeneous environments. This is achieved by including the effect of mountain topography on these processes at the sub-grid scale using a multidimensional informed sampling procedure together with a 1-D lumped model that can be driven by gridded climate datasets. This paper provides a description of this sub-grid scheme, TopoSUB, and assesses its performance against a distributed model. We demonstrate the ability of TopoSUB to approximate results simulated by a distributed numerical LSM at around 104 less computations. These significant gains in computing resources allow for: (1) numerical modelling of processes at fine grid resolutions over large areas; (2) efficient statistical descriptions of sub-grid behaviour; (3) a "sub-grid aware" aggregation of simulated variables to coarse grids; and (4) freeing of resources for computationally intensive tasks, e.g., the treatment of uncertainty in the modelling process.

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Boubaker, K., A. Colantoni i E. Allegrini. "Renewable Energy in Eastern North Africa in Terms of Patterns of Coupling to Czisch European HVDC Super Grid". International Journal of Renewable Energy Development 2, nr 2 (17.06.2013): 125–29. http://dx.doi.org/10.14710/ijred.2.2.125-129.

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In this study, wind energy potential and perspectives in the eastern North Africa region (Tunisia) have been investigated in terms of connectivity to the projected Czisch European HVDC super grid. A simplified extracted scheme of this grid has been used as a guide to optimize transportation efficiency through the whole net. Wind, as an available and easily exploitable renewable energy was showing to have a promising future for 2025 horizon in the context of a connected net with the European Union, despite local sub-grids disparities. This is also to emphasis HVDC technology adequacy for economical power transmission over very long distances andconnection between differently established grids.

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Serebryannikov, Andriy E., Akhlesh Lakhtakia i Ekmel Ozbay. "Thermally switchable, bifunctional, scalable, mid-infrared metasurfaces with VO₂ grids capable of versatile polarization manipulation and asymmetric transmission". Optical Materials Express 12, nr 12 (16.11.2022): 4594. http://dx.doi.org/10.1364/ome.465468.

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We conceptualized three-array scalable bifunctional metasurfaces comprising only three thin strip grids and numerically determined their characteristics in the mid-infrared spectral regime for switchable operation scenarios involving polarization manipulation and related diodelike asymmetric transmission (AT) as one of two functionalities. A few or all of the grids were taken to be made of VO2, a bifunctionality-enabling phase-change material; there are no layers and/or meta-atoms comprising simultaneously both metal and VO2. For each proposed metasurface, two effective structures and, therefore, two different functionalities exist, corresponding to the metallic and insulating phases of VO2. The achieved scenarios of functionality switching significantly depend on the way in which VO2 is incorporated into the metasurface. Switchable bands of polarization manipulation are up to 40 THz wide. The AT band can be modulated when Fabry–Perot (anti-) resonances come into play. Besides, transmission regimes with the cross-polarized component insensitive to VO2 phase change are possible, as well as the ones with all co- and cross-polarized components having the same magnitude for both linear polarizations of the incident wave.

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Quan, Dang Minh, i Odej Kao. "ON ARCHITECTURE FOR SLA-AWARE WORKFLOWS IN GRID ENVIRONMENTS". Journal of Interconnection Networks 06, nr 03 (wrzesień 2005): 245–63. http://dx.doi.org/10.1142/s0219265905001411.

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Service Level Agreements (SLAs) are currently one of the major research topics in Grid Computing, as they serve as a foundation for reliable and predictable Grids. SLAs define an explicit statement of expectations and obligations in a business relationship between provider and customer. Thus, SLAs should guarantee the desired and a-priori negotiated Quality of Service (QoS), which is a mandatory prerequisite for the Next Generation Grids. This development is proved by a manifold research work about SLAs and architectures for implementing SLAs in Grid environments. However, this work is mostly related to SLAs for standard, monolithic Grid jobs and neglects the dependencies between different steps of operation. The complexity of an SLA-specification for workflows grows significantly, as characteristics of correlated sub-jobs, the data transfer phases, the deadline constraints and possible failures have to be considered. Thus, an architecture for an SLA-aware workflow implementation needs sophisticated mechanisms for specification and management, sub-job mapping, data transfer optimization and fault reaction. Therefore, this paper presents an architecture for SLA-aware Grid workflows. The main contributions are an improved specification language for SLA-aware workflows, a mapping and optimization algorithm for sub-job assignment to Grid resources and a prototype implementation using standard middleware. Experimental measurements prove the quality of the development.

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Dalal, Nisha, Martin Mølna, Mette Herrem, Magne Røen i Odd Erik Gundersen. "Day-Ahead Forecasting of Losses in the Distribution Network". AI Magazine 42, nr 2 (20.10.2021): 38–49. http://dx.doi.org/10.1609/aimag.v42i2.15097.

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Utility companies in the Nordics have to nominate how much electricity is expected to be lost in their power grid the next day. We present a commercially deployed machine learning system that automates this day-ahead nomination of the expected grid loss. It meets several practical constraints and issues related to, among other things, delayed, missing and incorrect data and a small data set. The system incorporates a total of 24 different models that performs forecasts for three sub-grids. Each day one model is selected for making the hourly day-ahead forecasts for each sub-grid. The deployed system reduced the mean average percentage error (MAPE) with 40% from 12.17 to 7.26 per hour from mid-July to mid-October, 2019. It is robust, flexible and reduces manual work. Recently, the system was deployed to forecast and nominate grid losses for two new grids belonging to a new customer. As the presented system is modular and adaptive, the integration was quick and needed minimal work. We have shared the grid loss data-set on Kaggle.

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Das, Soumya Ranjan, Alok Kumar Mishra, Prakash Kumar Ray, Surender Reddy Salkuti i Seong-Cheol Kim. "Application of Artificial Intelligent Techniques for Power Quality Improvement in Hybrid Microgrid System". Electronics 11, nr 22 (21.11.2022): 3826. http://dx.doi.org/10.3390/electronics11223826.

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The hybrid AC-DC microgrid (MG) has gained popularity recently as it offers the benefits of AC and DC systems. Interconnecting AC-DC converters are necessary since the MG has both DC and AC sub-grids. Adding an extra harmonic adjustment mechanism to the interlinking converters is promising because non-linear AC loads can worsen the quality of the voltage on the AC bus. The interlinking converters’ primary function is to interchange real and reactive power between DC and AC sub-grids, so the typical harmonic controlling approach implemented for active power filters (APFs) might not be appropriate for them. When the MG’s capacity is high, it is desirable that the switching frequency be lesser than the APFs. The performance of harmonic correction or even system stability may suffer at low switching frequencies. In this study, a harmonic compensating technique appropriate for hybrid AC-DC interlinking converters with lower switching frequencies is planned. The suggested strategy, modeling techniques, stability analysis, and a thorough virtual impedance design are discussed in this work.

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Ren, Quan-yao, Liang-ming Pan, Wen-xiong Zhou, Hang Liu i Ting-pu Ye. "Drift-flux model of sub-channel in vertical rod bundles with spacer grids". International Journal of Heat and Mass Transfer 126 (listopad 2018): 946–56. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2018.05.135.

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Kurniati, Titi, Adrial Sy i Purnawan Purnawan. "The accessibility of tsunami prone areas society towards potential shelters: a case study in Padang Barat sub-district". E3S Web of Conferences 156 (2020): 04001. http://dx.doi.org/10.1051/e3sconf/202015604001.

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Padang city, which is located on the western coast of Sumatra, has the potential to experience a powerful earthquake and thus generate tsunami. After the earthquake, with or without a tsunami warning, the society is required to evacuate. Because of the short time, vertical evacuation is the best alternative for the safety of society. Evacuation on foot to the temporary rescue building (Temporary Evacuation Shelter, TES) is more advisable than evacuation using motorized vehicles that tends to cause congestion. Temporary evacuation maps and potential shelters in Padang have been established by BPBD (Disaster Management Agency). In the Padang Barat sub-district, there are 13 potential shelters. This study aims to determine the level of accessibility to potential shelters based on travel time and road width parameters. In determining accessibility, the study area is divided into 50x50m size grids. The travel time is determined based on the distance from the center of the grid to the nearest TES through the road network. The limitation of evacuation time is 10 minutes. The results of data analyzing showed that among the 4358 grids which were occupied by society, there were 2272 grids (52.1%) which have low accessibility (based on travel time) and 30% has a low level of accessibility based on travel time and width road parameter.

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SUN, MING BO, XUE SONG BAI, WEI DONG LIU, JIAN HAN LIANG i ZHEN GUO WANG. "A MODIFIED SUB-CELL-FIX METHOD FOR RE-INITIALIZATION OF LEVEL-SET DISTANCE FUNCTION AND ITS DEPENDENCE TESTS ON GRID STRETCHING". Modern Physics Letters B 24, nr 15 (20.06.2010): 1615–29. http://dx.doi.org/10.1142/s0217984910024018.

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The sub-cell-fix (SCF) method proposed by Russo and Smereka3 computes the distance function of the cells adjacent to the zero level-set without disturbing the original zero level-set. A modified sub-cell-fix scheme independent of local curvature is developed in this paper, which makes use of a combination of the points adjacent to zero level-set surfaces and preserves the interface in a second-order accuracy. The new sub-cell-fix scheme is capable of handling large local curvature, and as a result it demonstrates satisfactory performance on several challenging test cases. The limitations of the modified scheme on stretched grids are tested and it is found that the highly stretched grid causes large numerical errors, and needs further assessment and modification.

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Dkhili, Nouha, Sorin Olaru, Alessio Iovine, Manuel Ruiz, Jean Maeght i Patrick Panciatici. "Predictive control based on stochastic disturbance trajectories for congestion management in sub-transmission grids". IFAC-PapersOnLine 55, nr 16 (2022): 302–7. http://dx.doi.org/10.1016/j.ifacol.2022.09.041.

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Oates, Thomas W. H., Babak Dastmalchi, Christian Helgert, Lars Reissmann, Uwe Huebner, Ernst-Bernhard Kley, Marc A. Verschuuren i in. "Optical activity in sub-wavelength metallic grids and fishnet metamaterials in the conical mount". Optical Materials Express 3, nr 4 (1.03.2013): 439. http://dx.doi.org/10.1364/ome.3.000439.

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Nesliturk, A. I. "On the choice of stabilizing sub-grid for convection–diffusion problem on rectangular grids". Computers & Mathematics with Applications 59, nr 12 (czerwiec 2010): 3687–99. http://dx.doi.org/10.1016/j.camwa.2010.04.002.

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Zhao, Shuqiang, Nan Wang, Ren Li, Benfeng Gao, Bingbing Shao i Siheng Song. "Sub-synchronous control interaction between direct-drive PMSG-based wind farms and compensated grids". International Journal of Electrical Power & Energy Systems 109 (lipiec 2019): 609–17. http://dx.doi.org/10.1016/j.ijepes.2019.02.021.

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Jacq, Pascal, Pierre-Henri Maire i Rémi Abgrall. "A Nominally Second-Order Cell-Centered Finite Volume Scheme for Simulating Three-Dimensional Anisotropic Diffusion Equations on Unstructured Grids". Communications in Computational Physics 16, nr 4 (październik 2014): 841–91. http://dx.doi.org/10.4208/cicp.310513.170314a.

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AbstractWe present a finite volume based cell-centered method for solving diffusion equations on three-dimensional unstructured grids with general tensor conduction. Our main motivation concerns the numerical simulation of the coupling between fluid flows and heat transfers. The corresponding numerical scheme is characterized by cell-centered unknowns and a local stencil. Namely, the scheme results in a global sparse diffusion matrix, which couples only the cell-centered unknowns. The space discretization relies on the partition of polyhedral cells into sub-cells and on the partition of cell faces into sub-faces. It is characterized by the introduction of sub-face normal fluxes and sub-face temperatures, which are auxiliary unknowns. A sub-cellbased variational formulation of the constitutive Fourier law allows to construct an explicit approximation of the sub-face normal heat fluxes in terms of the cell-centered temperature and the adjacent sub-face temperatures. The elimination of the sub-face temperatures with respect to the cell-centered temperatures is achieved locally at each node by solving a small and sparse linear system. This systemis obtained by enforcing the continuity condition of the normal heat flux across each sub-cell interface impinging at the node under consideration. The parallel implementation of the numerical algorithm and its efficiency are described and analyzed. The accuracy and the robustness of the proposed finite volumemethod are assessed bymeans of various numerical test cases.

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Chaurase, Payal, i Pankaj Ramtekkar. "A new design of control & power management strategies of hybrid ac-dc microgrids toward high power quality". Journal of Physics: Conference Series 2089, nr 1 (1.11.2021): 012036. http://dx.doi.org/10.1088/1742-6596/2089/1/012036.

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Abstract The micro grid idea provides for the lack of several reversing switches to unitary AC-DC grid that enables connection and charges (loads) to the electrical systems with changeable regenerative AC and CC sources. Safe operation and gadget safety involve digital integration with utilities/grid through power converters. Enhanced client reliability, decreased input losses, local voltages are supported, and waste heat efficiency increased, voltage drop or interruptible supply of electricity can be customized to satisfy their unique customer demands. Work at present Analyses the performance in grid tie mode of hybrid AC/DC systems. Here are PV systems, PV systems, For the construction of microgrids wind turbine generators and batteries are employed. Convert procedures for the correct coordination of AC sub-grids to DC subs-grids have also been established for converters. MATLAB/SIMULINK environment results are generated.

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Chang, Che-Hao, Riki Rahmad, Shiang-Jen Wu i Chih-Tsung Hsu. "Spatial Frequency Analysis by Adopting Regional Analysis with Radar Rainfall in Taiwan". Water 14, nr 17 (31.08.2022): 2710. http://dx.doi.org/10.3390/w14172710.

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This study proposed a spatially and temporally improving methodology adopting the Regional Frequency Analysis with an L-moments approach to estimate rainfall quantiles from 22,787 grids of radar rainfall in Taiwan for a 24-hour duration. Due to limited radar coverage in the eastern region, significant discordant grids were found in the coastal area of the eastern region. A total of 171 grids with Di > 6 were set as discordant grids and removed for further analysis. A K-means cluster analysis using scaled at-site characteristics was used to group the QPESUMS grids in Taiwan into 22 clusters/sub-regions based on their characteristics. Spatially, homogeneous subregions with QPESUMS data produce more detailed homogeneous subregions with clear and continuous boundaries, especially in the mountain range area where the number of rain stations is still very limited. According to the results of z-values and L-moment ratio diagrams, the Wakeby (WAK), Generalized Extreme Value (GEV), and Generalized Pareto (GPA) distributions of rainfall extremes fitted well for the majority of subregions. The Wakeby distribution was the dominant best-fitted distribution, especially in the central and eastern regions. The east of the northern part and southern part of Taiwan had the highest extreme rainfall especially for a 100-year return period with an extreme value of more than 1200 mm/day. Both areas were frequently struck by typhoons. By using grid-based (at-site) as the basis for assessing regional frequency analysis, the results show that the regional approach in determining extreme rainfall is very suitable for large-scale applications and even better for smaller scales such as watershed areas. The spatial investigation was performed by establishing regions of interest in small subregions across the northern part. It showed that regionalization was correct and consistent.

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Dalal, Nisha, Martin Mølnå, Mette Herrem, Magne Røen i Odd Erik Gundersen. "Day-Ahead Forecasting of Losses in the Distribution Network". Proceedings of the AAAI Conference on Artificial Intelligence 34, nr 08 (3.04.2020): 13148–55. http://dx.doi.org/10.1609/aaai.v34i08.7018.

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We present a commercially deployed machine learning system that automates the day-ahead nomination of the expected grid loss for a Norwegian utility company. It meets several practical constraints and issues related to, among other things, delayed, missing and incorrect data and a small data set. The system incorporates a total of 24 different models that performs forecasts for three sub-grids. Each day one model is selected for making the hourly day-ahead forecasts for each sub-grid. The deployed system reduces the MAE with 41% from 3.68 MW to 2.17 MW per hour from mid July to mid October. It is robust and reduces manual work.

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Zhang, Yu, Zhe Yan, Cui Cui Zhou, Tie Zhou Wu i Yue Yang Wang. "Capacity allocation of HESS in micro-grid based on ABC algorithm". International Journal of Low-Carbon Technologies 15, nr 4 (6.05.2020): 496–505. http://dx.doi.org/10.1093/ijlct/ctaa014.

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Abstract The hybrid energy storage system (HESS) is a key component for smoothing fluctuation of power in micro-grids. An appropriate configuration of energy storage capacity for micro-grids can effectively improve the system economy. A new method for HESS capacity allocation in micro-grids based on the artificial bee colony (ABC) algorithm is proposed. The method proposed a power allocation strategy based on low pass filter (LPF) and fuzzy control. The strategy coordinates battery and supercapacitor operation and improves the battery operation environment. The fuzzy control takes the state of charge (SOC) of the battery and supercapacitors as the input and the correction coefficient of the time constant of the LPF filter as the output. The filter time constant of the LPF is timely adjusted, and the SOC of the battery and supercapacitor is stable within the limited range so that the overcharge and over-discharge of the battery can be avoided, and the lifetime of the battery is increased. This method also exploits sub-algorithms for supercapacitors and battery capacity optimization. Besides, the Monte Carlo simulation of the statistic model is implemented to eliminate the influence of uncertain factors such as wind speed, light intensity and temperature. The ABC algorithm is used to optimize the capacity allocation of hybrid energy storage, which avoids the problem of low accuracy and being easy to fall into the local optimal solution of the supercapacitors and battery capacity allocation sub-algorithms, and the optimal allocation of the capacity of the HESS is determined. By using this method, the number of supercapacitors required for the HESS is unchanged, and the number of battery is reduced from 75 to 65, which proves the rationality and economy of the proposed method.

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Liu, Wenyan, Xiangyang Luo, Qing Mu, Yimin Liu i Fenlin Liu. "An indoor Wi-Fi access points localization algorithm based on improved path loss model parameter calculation method and recursive partition". International Journal of Distributed Sensor Networks 15, nr 5 (maj 2019): 155014771985203. http://dx.doi.org/10.1177/1550147719852034.

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The localization accuracy of the existing methods for indoor Wi-Fi access points ranging-based localization depends on the accuracy of the received signal strength measured. Because the existing ranging-based methods are interfered by various indoor environmental factors, it is difficult to accurately measure the received signal strength, which leads to the problem of low localization accuracy of the indoor Wi-Fi access points. An indoor Wi-Fi access points localization algorithm based on improved path loss model parameter calculation method and recursive partition is proposed in this article. The algorithm recursively partitions the region where the target Wi-Fi access points are located according to the idea of quadtree partition, and partitions it into same sub-grids, which is sequentially performed until the sub-grids are smaller than the set threshold. The detection device is used at the detection location of the grids to measure the received signal strength, which is from the detection points to the target access point, the grid center point is used as the location of the candidate target access point, the parameters in the path loss model are calculated by using the signal strength differences between the detection points, and then the distances between the detection points and the target access point are calculated by using the signal strength values from the detection points to the target access point. Finally, the location of the target access point is estimated by executing a localization algorithm, and the location of the grid center point closest to the target access point is taken as the location of the target access point. The experimental results show that under the premise that the target access point can be found, the proposed algorithm reduces the use of the device and improves the localization accuracy compared with the typical localization method.

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Uher, Vojtěch, Petr Gajdoš, Václav Snášel, Yu-Chi Lai i Michal Radecký. "Hierarchical Hexagonal Clustering and Indexing". Symmetry 11, nr 6 (28.05.2019): 731. http://dx.doi.org/10.3390/sym11060731.

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Space-filling curves (SFCs) represent an efficient and straightforward method for sparse-space indexing to transform an n-dimensional space into a one-dimensional representation. This is often applied for multidimensional point indexing which brings a better perspective for data analysis, visualization and queries. SFCs are involved in many areas such as big data analysis and visualization, image decomposition, computer graphics and geographic information systems (GISs). The indexing methods subdivide the space into logic clusters of close points and they differ in various parameters including the cluster order, the distance metrics, and the pattern shape. Beside the simple and highly preferred triangular and square uniform grids, the hexagonal uniform grids have gained high interest especially in areas such as GISs, image processing and data visualization for the uniform distance between cells and high effectiveness of circle coverage. While the linearization of hexagons is an obvious approach for memory representation, it seems there is no hexagonal SFC indexing method generally used in practice. The main limitation of hexagons lies in lacking infinite decomposition into sub-hexagons and similarity of tiles on different levels of hierarchy. Our research aims at defining a fast and robust hexagonal SFC method. The Gosper fractal is utilized to preserve the benefits of hexagonal grids and to efficiently and hierarchically linearize points in a hexagonal grid while solving the non-convex shape and recursive transformation issues of the fractal. A comparison to other SFCs and grids is conducted to verify the robustness and effectiveness of our hexagonal method.

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Cartland, Richard, Al-Mas Sendegeya i Jean de Dieu Khan Hakizimana. "Socio-economic analysis of solar photovoltaic-based mini-grids in rural communities: A Ugandan case study". Journal of Energy in Southern Africa 33, nr 3 (26.09.2022): 36–50. http://dx.doi.org/10.17159/2413-3051/2022/v33i3a10441.

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The provision of electricity in rural areas has been an outstanding need in trying to achieve the United Nations sustainable development goals (SDGs) by 2030. However, most sub-Saharan countries have found this difficult due to financial constraints. Uganda tried to increase rural electrification to more than 20% of its population by 2020 through Rural Electrification Agency programmes. In an attempt to realise SDGs and the National Vision by 2040, Uganda is investing more in renewable energy sources, especially solar photovoltaic mini-grids to ensure that rural areas access affordable, reliable, and sustainable modern energy. This paper assesses the operation, causes of failure, causes of discomfort for mini-grid connected customers, and customer behavior of two solar photovoltaic mini-grids located in Kyenjojo District in western Uganda. It was found that the current energy demand exceeds the generation supply and that the systems need phase upgrades and clustering to remain economically viable and sustainable. The methodology involved re-sizing the existing load demand of the connected users, well-designed and administered questionnaires, analysis of published literature, review of the existing records, and interviews. Analysis was done in an Excel software program. The paper concludes by identifying the benefits and challenges of solar photovoltaic mini-grids in Kyenjojo District.

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Zhang, Yonghui, Zhaoxiong Wang i Fei Xing. "Enhancement of polarization response in UVA and UVC wavelength with integrated sub-wavelength metal-grids". Microelectronic Engineering 242-243 (kwiecień 2021): 111555. http://dx.doi.org/10.1016/j.mee.2021.111555.

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Wang, Zhibo, Caixia Ou i Seakweng Vong. "A second-order scheme with nonuniform time grids for Caputo–Hadamard fractional sub-diffusion equations". Journal of Computational and Applied Mathematics 414 (listopad 2022): 114448. http://dx.doi.org/10.1016/j.cam.2022.114448.

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Maire, Pierre-Henri. "A unified sub-cell force-based discretization for cell-centered Lagrangian hydrodynamics on polygonal grids". International Journal for Numerical Methods in Fluids 65, nr 11-12 (30.03.2010): 1281–94. http://dx.doi.org/10.1002/fld.2328.

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Sofwan, Muhammad, i Mira Hafizhah Tanjung. "Evaluation Study Of Walkability Index In Central Business District (CBD) Area, Pekanbaru City". Journal of Geoscience, Engineering, Environment, and Technology 5, nr 3 (1.09.2020): 175–85. http://dx.doi.org/10.25299/jgeet.2020.5.3.4181.

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Walkable cities emphasize cities with high walkability values, where walkability can be defined as the degree to which the environment can be pedestrian friendly. Walkable city is considered to be able to increase people's desire to walk so that it can make the environment more humanistic and can also help realize one of the objectives of sustainable transportation. The value of walkability can be viewed from the perspective of the urban form (macro level) of an area. The Central Business District (CBD) Pekanbaru City walkability index assessment uses the WAI IPEN Project model that measures the form of the Urban Form. The walkability assessment process in the Pekanbaru Kota Sub-District Area (CBD) divides the study area into 6 grids. The analysis shows that there are 4 grids that have a negative walkability value. In the analysis of the walkability value pattern it can be seen that the area dominated by office activities has a lower walkability value compared to the area that has mixed land use.

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Abdullah, Monir, MOHAMED Othman, Hamidah Ibrahim i Shamala Subramaniam. "SIMULATED ANNEALING ALGORITHM FOR SCHEDULING DIVISIBLE LOAD IN LARGE SCALE DATA GRIDS". IIUM Engineering Journal 10, nr 1 (29.09.2010): 59–68. http://dx.doi.org/10.31436/iiumej.v10i1.105.

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In many data grid applications, data can be decomposed into multiple independent sub datasets and distributed for parallel execution and analysis. This property has been successfully exploited using Divisible Load Theory (DLT). Many Scheduling approaches have been studied but there is no optimal solution. This paper proposes a novel Simulated Annealing (SA) algorithm for scheduling divisible load in large scale data grids. SA algorithm is integrated with DLT model and compared with the previous approaches. Experimental results show that the proposed model obtains better solution in term of makespan.

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Meegahapola, Lasantha, Alfeu Sguarezi, Jack Stanley Bryant, Mingchen Gu, Eliomar R. Conde D. i Rafael B. A. Cunha. "Power System Stability with Power-Electronic Converter Interfaced Renewable Power Generation: Present Issues and Future Trends". Energies 13, nr 13 (3.07.2020): 3441. http://dx.doi.org/10.3390/en13133441.

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The energy sector is currently undergoing a rapid transformation with the integration of power electronic converter (PEC)-interfaced renewable energy sources (RES), such as wind and solar photovoltaic (PV) systems, at both the transmission and distribution networks. Power system stability has been significantly influenced by this power grid transformation. This paper comprehensively reviews major power system stability issues affected due to large-scale integration of PEC-interfaced RES in power grids, with some example case studies relevant for each stability category. According to the review, stability issues are mainly originating from reduction in synchronous inertia, reduction in reactive power reserve, low short-circuit strength of the power network, and fault ride-through (FRT) strategy/capability of the PEC-interfaced RES. Decrease in synchronous inertia could affect both the rotor angle stability and the frequency stability, while decrease in short-circuit strength and reactive power reserve could cause voltage stability and rotor angle stability issues in power networks. Sub-synchronous control interactions are also receiving a lot of attention by the power industry due to increasing oscillatory stability incidents reported in power networks with PEC-interfaced RES. FRT capabilities/strategies of PEC-interfaced RES are also playing a pivotal role in power grid stability due to its influence on active and reactive power, hence more emphasis should be placed on FRT schemes of PEC-interfaced RES, since future power grids are expected to operate with 100% PEC-interfaced generation sources. Stability improvement strategies could be implemented to address multiple stability issues in PEC-interfaced power networks; however, rigorous stability studies are required to identify the optimal conditions to implement these improvement strategies. Furthermore, ongoing structural changes in power grids to accommodate remotely sited PEC-interfaced RES are also influencing the stability of power grids. Therefore, all these factors must be carefully considered by system operators when planning and operating power grids in a secure and stable manner with high penetration levels of PEC-interfaced RES.

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