Grid Type Research Articles

Algebraic multiscale grid coarsening using unsupervised machine learning for subsurface flow simulation

Subsurface flow simulation is vital for many geoscience applications, including geoenergy extraction and gas (energy) storage. Reservoirs are often highly heterogeneous and naturally fractured. Therefore, scalable simulation strategies are crucial to enable efficient and reliable operational strategies. One of these scalable methods, which has also been recently deployed in commercial reservoir simulators, is algebraic multiscale (AMS) solvers. AMS, like all multilevel schemes, is found to be highly sensitive to the types (geometries and size) of coarse grids and local basis functions. Commercial simulators benefit from a graph-based partitioner; e.g., METIS to generate the multiscale coarse grids. METIS minimizes the amount of interfaces between coarse partitions, while keeping them of similar size which may not be the requirement to create a coarse grid. In this work, we employ a novel approach to generate the multiscale coarse grids, using unsupervised learning methods which is based on optimizing different parameter. We specifically use the Louvain algorithm and Multi-level Markov clustering. The Louvain algorithm optimizes modularity, a measure of the strength of network division while Markov clustering simulates random walks between the cells to find clusters. It is found that the AMS performance is improved when compared with the existing METIS-based partitioner on several field-scale test cases. This development has the potential to enable reservoir engineers to run ensembles of thousands of detailed models at a much faster rate.

Axial Compression Performance Test and Bearing Capacity Calculation of RC Square Column Strengthened by FRP Textile Grid-reinforced ECC

In order to investigate the strengthening effect of FRP textile grid reinforced ECC composite (abbreviated: TRE) restrained RC columns, this study conducted experimental and theoretical studies on the axial compression performance of TRE strengthened RC square columns with RC square columns as the research object. The effects of the chamfer radius of the original column, the type of FRP grid and the number of layers of the grid on the axial compression performance of the TRE-strengthened RC square column were considered. The axial compression tests showed that the strengthened layer exhibited excellent crack control, the reinforced column cracked as a whole without breaking when it was damaged, and the strengthened layer adhered well to the core concrete. Compared with unstrengthened specimens, the compressive strength, ductility and deformation capacity of the RC square column under TRE restraint were significantly higher. The increase of chamfer radius of square column makes the TRE restraint effect better. Increasing the number of grid layers can significantly improve the ultimate bearing capacity and ductility of the strengthened specimens. The effects of TRE strengthening methods with different FRP grids differed, with the same number of grid layers, the ultimate bearing capacity of the specimens strengthened with CFRP grid reinforced ECC was higher, and the cracking load of the specimens strengthened with BFRP grid reinforced ECC was higher. A model for calculating the ultimate bearing capacity of the TRE-constrained RC square column was established, and the validity of the model was verified by comparing the results of this test.

The effects of climate change-induced cooling demand on power grids

The trend towards equipping buildings with active space cooling technology is expected to continue, due to the warming climate. In addition, the electrification of mobility and industry, and the massive rollout of photovoltaics, may put Austria’s power grids under stress if adequate mechanisms are not implemented in time. This study investigates the magnitudes of the loads induced by this increasing demand for cooling, together with the relief that passive cooling measures can provide. Data from current climate models, measured real load profiles from households, building stock models, and dynamic building simulations are utilised, alongside stakeholder and expert opinions, to fine-tune the analysis. This article suggests plausible scenarios for the development of the demand for cooling energy in Austria until 2050, and analyses the aggregated effect of the different options for cooling on the electricity power grid. The integration of cooling loads is expected to cause overloads or voltage violations only for a few types of grid within the periods investigated here. Subsidy programs in the building sector often do not properly consider cooling demand. Building regulations and subsidies should therefore focus on passive measures, and only when these are not sufficient should measures related to active cooling be implemented.

Overview of Membrane Protein Sample Preparation for Single-Particle Cryo-Electron Microscopy Analysis.

Single-particle cryo-electron microscopy (cryo-EM SPA) has recently emerged as an exceptionally well-suited technique for determining the structure of membrane proteins (MPs). Indeed, in recent years, huge increase in the number of MPs solved via cryo-EM SPA at a resolution better than 3.0 Å in the Protein Data Bank (PDB) has been observed. However, sample preparation remains a significant challenge in the field. Here, we evaluated the MPs solved using cryo-EM SPA deposited in the PDB in the last two years at a resolution below 3.0 Å. The most critical parameters for sample preparation are as follows: (i) the surfactant used for protein extraction from the membrane, (ii) the surfactant, amphiphiles, nanodiscs or other molecules present in the vitrification step, (iii) the vitrification method employed, and (iv) the type of grids used. The aim is not to provide a definitive answer on the optimal sample conditions for cryo-EM SPA of MPs but rather assess the current trends in the MP structural biology community towards obtaining high-resolution cryo-EM structures.

Zarzadzanie wymiana transformatorow SN/nn przy wykorzystaniu systemu AMI

The paper presents the extended possibilities of managing the selection and replacement of MV/LV transformers using the measurement data from the Advanced Metering Infrastructure (AMI) system. The analysis was conducted on samples of over 1900 transformers that operate in two different types of MV grids: rural and urban. The analysis has shown that there is a great potential in the field of optimizing the rated power of the transformers.

An Asymmetrical Mixed Higher-Order Discontinuous Galerkin Time Domain Method for Electromagnetic Scattering from the Plasma Sheath around a Hypersonic Vehicle

The plasma sheath during reentry of hypersonic vehicle is an unmagnetized and weakly ionized nonuniform plasma flow, which causes radio frequency blackout and strong plasma attenuation of electromagnetic wave. The physical properties of the nonuniform plasma flow were obtained using computational fluid dynamics software with unstructured grids. In this study, a detailed computational model was reconstructed with the high-order Lagrange grids for the nonuniform plasma flow region and the high-order Serendipity grids for the homogeneous medium region. In order to calculate the numerical flux between the two types of grids in the discontinuous Galerkin time domain (DGTD) algorithm, an asymmetric high-order element is constructed as a transition unit. Finally, the simulation results in the plasma sphere show that the above method improves the computational accuracy and decreases calculation. The amplitude and scattering about electromagnetic wave in nonuniform plasma flow are clarified in detail. It is suggested that the presented method could be an effective tool for investigating interaction between electromagnetic waves and plasma flow.

Analysis of an improved three-phase voltage source converter with high-performance operation under unbalanced conditions

The power system is rapidly transforming into a new large-scale distributed power generation model using renewable energy. Grid-connected converters, particularly voltage control compensators like STATCOM, will be crucial to the functioning of this new situation. Voltage source converter (VSC) is one of the most commonly used topologies in grid connection converters. As a distributed power-generating device, VSCs can be utilized as a means of connecting sustainable energy sources to the power grid. The three-phase voltage source currents or voltage ripples may appear in the DC chain. This study examines the enhanced three-phase VSC, pinpoints the factors that contribute to the great performance of VSCs, and looks at future trends in three-phase VSCs. VSC is a power electronic device capable of converting DC voltages to three-phase AC voltages and is commonly used in areas such as grid connection, reactive power compensation and harmonic suppression. In practical applications, various types of grid or load disturbances pose hidden dangers to the normal operation of the VSC. Due to the presence of unbalanced grids and loads, significant double frequency.

Crystal structure, DFT study, Hirshfeld analysis and optical third order nonlinear properties of new 1-naphthylaminium hydrogen fumarate salt

This study reports the crystal structure and its supramolecular framework, quantum chemical calculations and nonlinear optical properties of 1-naphthylaminium hydrogen fumarate salt. The supramolecular self-assembly of fumarate anions and 1-naphthylaminium cation of the salt is primarily stabilized by N-H…O, O-H…O and C-H…O interactions. The construction of strong hydrogen bonds such as N-H…O and O-H…O produces two-dimensional corrugated sheet parallel to (010) plane, which resembles a supramolecular grid type architecture in the crystal structure. Two weak C-H…O interactions interlink the parallel (010) supramolecular sheet generating a three-dimensional molecular network. The molecular stability of the experimentally determined structure is theoretically optimized by DFT quantum chemical calculations using 6-31G(++) basis set. The relative molecular interaction-based charge distribution and the chemical reactivity of the titled salt were identified using electrostatic potential contouring and HOMO-LUMO maps. The crystal structure is subjected to Hirshfeld surface analysis to gain better understanding on the intermolecular interactions exhibited by the molecules. The optical nonlinearities of the titled salt are examined using Z-scan experimentation, the optical nonlinear refractive index and optical nonlinear absorption coefficient is estimated by closed and open aperture Z-scan methods. The observed nonlinear values are quite comparable to the conventional optical nonlinear values.

Sub-channel analysis for LBE cooled fuel assembly with grid type spacers of China initiative accelerator driven system

The present study focuses on the thermal hydraulic characteristics of fuel assemblies in the China Initiative Accelerator Driven subcritical System (CiADS), which utilizes grid-type spacers to support lead bismuth eutectic (LBE) cooled fast reactors. While the structural design and mechanical analysis of CiADS triangular fuel assemblies with grid-type spacers have been preliminarily investigated, there is a pressing need to study the thermal hydraulic behavior of liquid LBE within these fuel assemblies. This analysis is crucial for assessing the safety and economy of the CiADS subcritical reactor. The sub-channel analysis code, based on the lumped parameter method, plays a vital role in rapidly evaluating the safety features of LBE-cooled fast reactor fuel assemblies. To comprehensively evaluate the thermal hydraulic performance of fuel assemblies with grid-type spacers in the CiADS LBE cooling system, the flow pressure drop model, turbulent mixing model, and convective heat transfer model for the fuel assembly structure with grid-type spacers were incorporated into the existing CiADS sub-channel analysis code. This enhanced code has been successfully employed in the thermal hydraulic analysis of fuel assemblies utilizing wire-type spacers in the CiADS system. To verify the validity and accuracy of the modified CiADS sub-channel analysis code in calculating triangular fuel assemblies with grid-type spacers, the code was first utilized to replicate a 19-rods flow heat transfer experiment with grid-type spacers cooling liquid LBE. A comparison between the simulation and experimental results confirms that the CiADS sub-channel analysis code can predict the coolant temperature and fuel rod surface temperature in fuel assemblies with grid-type spacers. Subsequently, the structure and thermal hydraulic design of the latest CiADS fuel assembly with grid-type spacers were reviewed. Finally, taking into account the aforementioned enhancements to the CiADS sub-channel analysis code, a comprehensive thermo-hydraulic calculation of the CiADS fuel assembly with grid-type spacers was conducted. The results demonstrate that the coolant outlet temperature, maximum cladding temperature, and maximum fuel pellet temperature all fall within the design parameters of CiADS. Furthermore, the impact of the number of rods in different rod bundles (91, 61, 37, and 7 rods) on thermal hydraulic performance was analyzed. The findings indicate that, while ensuring calculation accuracy and efficiency, the results obtained from the 37-rod bundle can effectively reflect the thermal hydraulic behavior of the reactor core.

Comparison between two types of grids for placement of mini-screw implant in posterior maxillary segment

Use of mini-screw implants is in vogue. It has brought about a drastic change in day to day practise for orthodontists. Despite being the most popular source of anchorage, it is not easy for newer clinicians to perfectly figure out the site of implant placement and the accuracy by which it should be placed to avoid failure. A customised grid or mesh is the simplest way to gain assistance for placement of miniscrew implants. This article focuses on comparison of two types of grids for placement of implant accurately and to guide the clinician in such a way that minimises all the possible errors.

Fast DC Charging Infrastructures for Electric Vehicles: Overview of Technologies, Standards, and Challenges

This paper is an overview of fast charging for electrical vehicles. Specifically, it analyzes the impact of Ultra-Fast Charging Stations (UFCSs) on the distribution grid and their role in the smart grids. Moreover, the paper defines the framework of UFC, its diffusion and the associated new trends. The most frequently used converters in the conversion stages of DC charging stations with integrated generation are analyzed. To achieve this goal four active front end AC-DC converters (unidirectional and bidirectional), three isolated DC-DC converters as well as two control architectures are explored. In comparing the targeted configurations, the main target is set on categorizing them based on supply voltage level, type of smart grid, and power flow of the converters. Further, the paper outlines a broad overview of main standards for UFCSs and evaluation of the reliability, data collection, and operation of UFCSs. The paper aims to to link the needs of the designers of charging stations to preferences of the commercial market.

Impact of grid size on spatiotemporal prediction of fine particulate matter

Incorporating high spatiotemporal resolution in prediction models can significantly improve the accuracy of results. The current study focuses on identifying the most suitable spatial resolution using hexagonal tessellations of different sizes over the study area. Hexagonal grids are selected after comparing different types of grids. Spatial interpolation methods, including inverse distance weighting and ordinary Kriging method, are used for creating augmented datasets for each grid. A hybrid deep-learning-based prediction model is developed combining Convolutional Neural Network (CNN) and Long Short-term Memory (LSTM) for multivariate time series regression to predict PM2.5. Three scenarios are considered based on the size of the hexagonal grids. The results from each model are compared using evaluation indices of Mean Absolute Error (MAE) and Root Mean Square Error (RMSE). The R2 values range from 0.8 to 0.95, which shows that the hybrid model gives accurate predictions. Analysis of models for different-sized grids shows that for 1, 3, and 5 km grid sizes, 17%, 24%, and 6% of the cells have RMSE values less than 20, respectively. Similarly, 39%, 50%, and 46% of the cells have MAE values less than 16 for 1, 3, and 5 km grid sizes, respectively. The comparison showed that the 3 km grid benefits data aggregation per prediction accuracy and computational time. The predictive capability of models is not dependent on the spatial relationship between data from different static monitors. In the future, mobile monitoring data can be included to increase the data points and models’ accuracy.

CFD Analysis of Over-Expanded Flow in Convergent Divergent Nozzles

The classical one-dimensional inviscid theory does not reveal the complex flow features in an over-expanded nozzle accurately. The code Fluent has been used to simulate the viscous fluid (air) flow passing through three different 2-D Convergent-Divergent (C-D) nozzles for nozzle pressure ratios (NPR) corresponding to over-expanded flow. The steady state RANS equation with five different turbulence models has been simulated for turbulence model study. Two different types of boundary layer grids: grid1 (y<sup>+</sup>=1) and grid 2 (y<sup>+</sup=50) have been simulated. Shear Stress Transport k-w (SSTKW) turbulence model with grid 1 has been chosen for turbulence modeling. Both inviscid and viscous flows have been simulated. The converged solutions captured asymmetric lambda shock in all the three nozzles at higher NPRs for viscous flows. It also predicted aftershock and flow separation depending upon NPR. The shock wave angle of the incident and reflected shock generally reduces with increase in NPR for NPR£1.92. The thrust co-efficient of all the theoretical, predicted inviscid and predicted viscous solutions reduce with increase in NPR upto a certain value of NPR and then starts increasing. The predicted viscous results (shock structure, shock location, size of normal shock, aftershock and asymmetric lambda shocks) are close to the experiments in most of the cases. The aftershock phenomenon provides dual mode flow at the exit of the nozzle.

Finite element analysis of low-profile reconstruction plates for atrophic mandibles: a comparison of novel 3D grid and conventional plate designs.

This study aimed to compare the reconstruction with type 2.4 and three-dimensional (3D) grid plates relating the areas of weakness to anatomical regions of force incidence in atrophic mandibles with and without segmentation using finite element analysis (FEA). Strength and force quality in the mandible were also determined. The atrophic mandible models with and without segmentation were divided into four groups, and the behavior of each plate was analyzed using finite element analysis. In the atrophic mandible without segmentation using the type 2.4 reconstruction plate, the highest stress concentration in the plate was observed in the posterior region of the mandibular body and in the grid type 3D reconstruction plate was observed in the mandibular angle. In the segmented atrophic mandible with the 2.4 reconstruction plate, higher stress concentration was observed in the mandibular segment defect. Analysis of the 3D grid-like reconstruction plate revealed that the geometry of the plate conferred greater stiffness to the assembly, as the most significant stress concentration was observed at the mandibular angle. The width of the plate design may influence the strength, not the thickness.

A Parameter Sensitivity Analysis of Hydropower Units under Full Operating Conditions Considering Turbine Nonlinearity

A parameter sensitivity analysis is an important part of the stability study of hydro turbine regulation systems, which helps operators to deepen their understanding of the characteristics and connections among the various parts of these systems. Considering that large hydropower stations undertake an essential regulation task in the power grid, the safety and stability of their operation cannot be ignored. To this end, taking a unit in a giant hydropower station in China as an example, a hydraulic–mechanical–electrical coupling model of the hydraulic turbine regulation system is established. A comprehensive parameter sensitivity indicator and parameter sensitivity analysis framework are proposed. On this basis, the sensitivity of the main system variables to parameter changes under full operating conditions is investigated by considering two different control modes of the unit (i.e., corresponding to different grid types). The results show that the sensitivity of the system state to the mechanical parameters of the generator is the highest in the power control mode, while the sensitivity to the electrical parameters of the generator and excitation system is higher in the frequency control mode. The sensitivity of the system with these key parameters also shows different patterns of change with a change in the unit operating conditions. The relevant findings can provide some theoretical guidance for the operation of hydropower stations and help to reduce the risk of system instability.

Error Analysis of Sound Source Directivity Interpolation Based on Spherical Harmonics

Precise measurement of the sound source directivity not only requires special equipment, but also is time-consuming. Alternatively, one can reduce the number of measurement points and apply spatial interpolation to retrieve a high-resolution approximation of directivity function. This paper discusses the interpolation error for different algorithms with emphasis on the one based on spherical harmonics. The analysis is performed on raw directivity data for two loudspeaker systems. The directivity was measured using sampling schemes of different densities and point distributions (equiangular and equiareal). Then, the results were interpolated and compared with these obtained on the standard 5° regular grid. The application of the spherical harmonic approximation to sparse measurement data yields a mean error of less than 1 dB with the number of measurement points being reduced by 89%. The impact of the sparse grid type on the retrieval error is also discussed. The presented results facilitate optimal sampling grid choice for low-resolution directivity measurements.

Ultrasonic SH guided wave detection of the defects of switch rails with 3D finite element method

A switch rail is an important part of the high-speed railway system, but it is highly susceptible to defects during service, which threat traffic safety. A switch rail has an asymmetric variable cross-section structure, which makes it challenging to detect its defects with ultrasonic testing. In this study, the finite element model of switch rails and the ultrasonic SH guided wave detection of groove defects were explored. The three-dimensional finite element model of switch rails with the same sizes used under working conditions was established. Furthermore, the influences of grid division method, switch mechanism setting method, and root end variable cross-section grid type on guided wave propagation in the model were analyzed in detail. The switch rail model was experimentally validated. The ultrasonic SH guided wave detection of the defects at the rail head and rail bottom was successfully realized and the echo signals from other special structures of switch rail were also obtained. The finite element model calibrated with experimental results could be used to simulate guided wave detection at any location with any defect. The calibrated model could optimize the switch rail guided wave detection scheme and guide signal identification. The study provides an important basis for the inspection and monitoring of switch rails.

The Innovative Research on Sustainable Microgrid Artwork Design Based on Regression Analysis and Multi-Objective Optimization

One of the most vital issues in electrical systems involves optimally operating microgrids (MGs) using demand-side management (DSM). A DSM program lowers utility operational costs in one sense but also needs policies that encourage financial incentives in the other. The present study formulates the optimum functioning of MGs using DSM in the form of a problem of optimization. DSM considers load shifting to be a viable option. There are operational limitations and executive limitations that affect the problem, and its objective function aims at minimizing the overall operational prices of the grid and the load-shifting prices. The major problem has been solved using an improved butterfly optimization scheme. Furthermore, the suggested technique was tested in various case studies that consider types of generation unit, load types, unit uncertainties, grid sharing, and energy costs. A comparison was made between the suggested scheme and various algorithms on the IEEE 33-bus network to demonstrate the proficiency of the suggested scheme, showing that it lowered prices by 57%.

The role of the perceived environment for recreational walking among adults in socioeconomically disadvantaged situations: A study using walk-along interviews

BackgroundPersons in socioeconomically disadvantaged situations (PSEDS) are generally less likely to engage in recreational walking (RW) compared to higher socioeconomic groups and are often more dependent on their local environment. Studies on RW have primarily focused on the role of the built environment for the general adult population and the older population in urban areas. The aim of this study is to qualitatively identify the perceived environmental factors affecting RW among PSEDS in peri-urban areas. MethodsIn two peri-urban municipalities in Belgium, walk-along interviews were conducted until data saturation with a purposeful convenience sampling of 38 PSEDS (25-65y/o) to identify local environmental factors affecting RW. A subsample of 22 participants joined a focus group (n = 4) to categorize the identified factors into environmental types (physical, sociocultural, political, and economic) of the Analysis Grid for Environments Linked to Obesity (ANGELO) framework. The interviews were transcribed and analyzed thematically using Maxqda 2022.0. ResultsThe information environment (dissemination, retrieving and understanding of information) was added to the ANGELO framework, highlighting the importance of digital literacy. Availability and accessibility of well-maintained walking surfaces, toilets, street lighting and seating options (physical environment), social support, dog-ownership, stigmatization, social isolation, and a sense of belonging (sociocultural environment) and indirect costs (economic environment) were identified as important environmental factors in RW among PSEDS. The identified political and economic factors are intertwined with the other environments. ConclusionsPerceived environmental factors affect RW among PSEDS and peri-urban settings offer specific challenges. Local governments should incorporate citizen perception into decision-making processes to create supportive environments that have the potential to promote RW among PSEDS in a peri-urban setting.

Influence of the spatial grid type on the result of calculating the neutron fields in the nuclear power plant shielding

The paper considers the influence of the spatial grid type on the result of solving the equation of neutron transport in the nuclear power plant (NPP) shielding. Neutron fields were calculated in a realistic model of a liquid metal cooled fast neutron tank reactor with an integral equipment layout. Structured cubic and unstructured hexahedral grids (pmsnsys and FRIGATE codes) and unstructured tetrahedral and prismatic grids (RADUGA T code) are used. Limiting values of the group fluxes averaged over the material zones for refined grids have been obtained. It has been shown that the calculation results depend on the type of approximation for the curvilinear inner boundaries between the material zones rather than on the grid cell type (cube, hexahedron, tetrahedron, prism). Using “toothed” approximations for curvilinear boundaries leads to an increase in the area of the boundaries, as well as to the neutron flux refraction condition arising on them. These effects lead to an upward bias in the transport equation solution, and for all energy groups. Conclusion. When solving an equation of neutron transport in the NPP shielding by a grid technique, it is necessary to use grids other than leading to “toothed” approximations of the inner boundaries. Tetrahedral or prismatic grids, or grids of arbitrary hexahedrons can be recommended, as well as composite grids in which cubic cells are located inside the material zone, and hexahedron cells are located near the zone boundary.