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1
Khokhlov, Nikolai Igorevich, Vladislav O. Stetsyuk und Ivan A. Mitskovets. „Overset grids approach for topography modeling in elastic-wave modeling using the grid-characteristic method“. Computer Research and Modeling 11, Nr. 6 (Dezember 2019): 1049–59. http://dx.doi.org/10.20537/2076-7633-2019-11-6-1049-1059.
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Rosay, Sophie, Simon Weber und Marcello Mulas. „Modeling grid fields instead of modeling grid cells“. Journal of Computational Neuroscience 47, Nr. 1 (08.07.2019): 43–60. http://dx.doi.org/10.1007/s10827-019-00722-8.
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MacDonald, Alexander E., Jacques Middlecoff, Tom Henderson und Jin-Luen Lee. „A general method for modeling on irregular grids“. International Journal of High Performance Computing Applications 25, Nr. 4 (05.12.2010): 392–403. http://dx.doi.org/10.1177/1094342010385019.
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For simulation on a spherical surface, such as global numerical weather prediction, icosahedral grids are superior to their competitors in uniformity of grid mesh distance across the entire globe and lack of neighboring grid cells that share only a single vertex. Use of such a grid presents unique programming challenges related to iteration across grid cells and location of neighboring cells. Here we describe an icosahedral grid with a one-dimensional vector loop structure, table specified memory order, and an indirect addressing scheme that yields very compact code despite the complexities of this grid. This approach allows the same model code to be used for many grid structures. Indirect addressing also allows grid cells to be stored in any order, selectable at run time. This permits easy implementation of different memory layouts for cache blocking, distributed-memory parallelism, and static load balancing. Since indirect addressing can adversely affect execution time we organize arrays to place a directly addressable index innermost. We also describe experiments designed to measure any performance penalties accrued from use of indirect addressing.
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Xu, S., B. Wang und J. Liu. „On the use of Schwarz–Christoffel conformal mappings to the grid generation for global ocean models“. Geoscientific Model Development 8, Nr. 10 (29.10.2015): 3471–85. http://dx.doi.org/10.5194/gmd-8-3471-2015.
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Abstract. In this article we propose two grid generation methods for global ocean general circulation models. Contrary to conventional dipolar or tripolar grids, the proposed methods are based on Schwarz–Christoffel conformal mappings that map areas with user-prescribed, irregular boundaries to those with regular boundaries (i.e., disks, slits, etc.). The first method aims at improving existing dipolar grids. Compared with existing grids, the sample grid achieves a better trade-off between the enlargement of the latitudinal–longitudinal portion and the overall smooth grid cell size transition. The second method addresses more modern and advanced grid design requirements arising from high-resolution and multi-scale ocean modeling. The generated grids could potentially achieve the alignment of grid lines to the large-scale coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the grids are orthogonal curvilinear, they can be easily utilized by the majority of ocean general circulation models that are based on finite difference and require grid orthogonality. The proposed grid generation algorithms can also be applied to the grid generation for regional ocean modeling where complex land–sea distribution is present.
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Xu, S., B. Wang und J. Liu. „On the use of Schwarz–Christoffel conformal mappings to the grid generation for global ocean models“. Geoscientific Model Development Discussions 8, Nr. 2 (13.02.2015): 1337–73. http://dx.doi.org/10.5194/gmdd-8-1337-2015.
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Abstract. In this article we propose two conformal mapping based grid generation algorithms for global ocean general circulation models (OGCMs). Contrary to conventional, analytical forms based dipolar or tripolar grids, the new algorithms are based on Schwarz–Christoffel (SC) conformal mapping with prescribed boundary information. While dealing with the basic grid design problem of pole relocation, these new algorithms also address more advanced issues such as smoothed scaling factor, or the new requirements on OGCM grids arisen from the recent trend of high-resolution and multi-scale modeling. The proposed grid generation algorithm could potentially achieve the alignment of grid lines to coastlines, enhanced spatial resolution in coastal regions, and easier computational load balance. Since the generated grids are still orthogonal curvilinear, they can be readily utilized in existing Bryan–Cox–Semtner type ocean models. The proposed methodology can also be applied to the grid generation task for regional ocean modeling where complex land–ocean distribution is present.
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Baboshin, Andrey. „Ontology modeling of grid-applications“. SPIIRAS Proceedings, Nr. 11 (17.03.2014): 252. http://dx.doi.org/10.15622/sp.11.16.
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Karamchandani, Prakash, Krish Vijayaraghavan und Greg Yarwood. „Sub-Grid Scale Plume Modeling“. Atmosphere 2, Nr. 3 (24.08.2011): 389–406. http://dx.doi.org/10.3390/atmos2030389.
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Ivanenko, Sergey A., und Galina V. Muratova. „Adaptive grid shallow water modeling“. Applied Numerical Mathematics 32, Nr. 4 (April 2000): 447–82. http://dx.doi.org/10.1016/s0168-9274(99)00063-x.
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Chitkusheva-Dimitrovska, Biljana, Marko Cepin, Roman Golubovski und Hristina Spasevska. „Modeling photovoltaic grid inter-shading“. Thermal Science 24, Nr. 6 Part B (2020): 4183–95. http://dx.doi.org/10.2298/tsci200116169c.
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Photovoltaic energy conversion is an efficient renewable source affordable as a technology even on the household level. Several technological aspects are subject to continuous improvement. This paper tackles the possibilities for denser panel population of a photovoltaic plant thus more efficient space utilization. The objective is to develop a mathematical model of inter-shading among the photovoltaic panels. The model calculates the electrical energy obtained from panels and considers the shading among the panels. The geographical location of the plant location, the distances between the solar panels and their angle of inclination, the dimensions of the panels and the time interval under evaluation are the parameters which are important for placing the power plant. The results show how much electric energy can be obtained from a certain set of photovoltaic panels. The results indicate, what are the distances between the panels for better allocation of resources when deciding on the number of solar panels and their arrangement.
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Ludwig, A. „Wire grid modeling of surfaces“. IEEE Transactions on Antennas and Propagation 35, Nr. 9 (September 1987): 1045–48. http://dx.doi.org/10.1109/tap.1987.1144220.
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Sharma, C. „Modeling of an island grid“. IEEE Transactions on Power Systems 13, Nr. 3 (1998): 971–78. http://dx.doi.org/10.1109/59.709085.
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Pugliese, Andrea, Domenico Talia und Ramin Yahyapour. „Modeling and Supporting Grid Scheduling“. Journal of Grid Computing 6, Nr. 2 (11.07.2007): 195–213. http://dx.doi.org/10.1007/s10723-007-9083-7.
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Jia, Zhuo, Sixin Liu, Siyuan Cheng, Xueran Zhao und Gongbo Zhang. „Modeling of Complex Geological Body and Computation of Geomagnetic Anomaly“. Mathematical Problems in Engineering 2020 (27.05.2020): 1–10. http://dx.doi.org/10.1155/2020/9839606.
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Modeling plays an important role in engineering exploration. However, the traditional rectangular mesh cannot meet the requirement because the actual shape of the model may be very complex. Therefore, this paper chooses the Delaunay grid for modeling and applies this method to magnetic numerical simulation. At the same time, we make use of the advantages of the Delaunay grid and choose to use grid encryption technology in the boundary and complex area of the model. Then, the formula for calculating the magnetic anomaly of tetrahedron is deduced in detail, and the magnetic anomaly with surface fluctuation is calculated. For a synthetic data model, Delaunay grids with different densities are used to model and calculate surface anomalies. The two results are compared with the analytical solution of the model. The results show that the method has high accuracy. Then, the method is applied to the actual geological body modeling in the Jinchuan mining area. According to local needs, a three-dimensional model with inhomogeneous grid density is established and the surface magnetic field of the model is calculated. Finally, the simulation data are compared with the measured data. The results show that the Delaunay grid modeling method has strong applicability.
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Nilsen, Halvor M., K. A. A. Lie und Jostein R. Natvig. „Accurate Modeling of Faults by Multipoint, Mimetic, and Mixed Methods“. SPE Journal 17, Nr. 02 (07.06.2012): 568–79. http://dx.doi.org/10.2118/149690-pa.
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Summary The predominant way of modeling faults in industry-standard flow simulators is to introduce so-called transmissibility multipliers in the underlying two-point discretization. Although this approach provides adequate accuracy in many practical cases, two-point discretizations are only consistent for K-orthogonal grids and may introduce significant discretization errors for grids that severely depart from being K-orthogonal. Such grid-distortion errors can be avoided by lateral or vertical stair-stepping of deviated faults at the expense of errors in the geometrical fault description. In other words, modelers have the choice of either making (geometrical) errors by adapting faults to a grid that is almost K-orthogonal, or introducing discretization errors because of the lack of K-orthogonality if the grid is adapted to deviated faults. We propose a method for accurate description of faults in solvers based on a hybridized mixed or mimetic discretization, which also includes the MPFA-O method. The key idea is to represent faults as internal boundaries and calculate fault transmissibilities directly instead of using multipliers to modify grid-dependent transmissibilities. The resulting method is geology-driven and consistent for cells with planar surfaces and thereby avoids the grid errors inherent in the two-point method. We also propose a method to translate fault transmissibility multipliers into fault transmissibilities. This makes our method readily applicable to reservoir models that contain fault multipliers.
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Yuan, Rong Chang, Zian Wang, Li Xin Li, Fang Chun Di, Zhi Xiang Ji und Jiao Dai. „Distributed Modeling Technology for Large Power Grid Modeling Based on Cloud Computing“. Applied Mechanics and Materials 448-453 (Oktober 2013): 2721–29. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2721.
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As the original grid model cant meet the needs of smart grid development, a distributed grid modeling and integrated management technologies based on cloud computing are proposed in this paper. In this scheme, a multi-level integrated "model cloud" is developed with horizontal collaboration and vertical cut-through using cloud storage, cloud services, cloud computing and other related technologies. The grid models of levels of dispatching institutions are gathered, stored and managed with unified model service. The scheme can dress the issues of device naming, information sharing, model exchanging and model unifying, reduce the maintenance workload, improve the quality of the model and the degree of coordinated automation and enhance the level of dispatching and analysis of the whole power grid.
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Bohlen, Thomas, und Erik H. Saenger. „Accuracy of heterogeneous staggered-grid finite-difference modeling of Rayleigh waves“. GEOPHYSICS 71, Nr. 4 (Juli 2006): T109—T115. http://dx.doi.org/10.1190/1.2213051.
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Heterogeneous finite-difference (FD) modeling assumes that the boundary conditions of the elastic wavefield between material discontinuities are implicitly fulfilled by the distribution of the elastic parameters on the numerical grid. It is widely applied to weak elastic contrasts between geologic formations inside the earth. We test the accuracy at the free surface of the earth. The accuracy for modeling Rayleigh waves using the conventional standard staggered-grid (SSG) and the rotated staggered grid (RSG) is investigated. The accuracy tests reveal that one cannot rely on conventional numerical dispersion discretization criteria. A higher sampling is necessary to obtain acceptable accuracy. In the case of planar free surfaces aligned with the grid, 15 to 30 grid points per minimum wavelength of the Rayleigh wave are required. The widely used explicit boundary condition, the so-called image method, produces similar accuracy and requires approximately half the sampling of the wavefield compared to heterogeneous free-surface modeling. For a free-surface not aligned with the grid (surface topography), the error increases significantly and varies with the dip angle of the interface. For an irregular interface, the RSG scheme is more accurate than the SSG scheme. The RSG scheme, however, requires 60 grid points per minimum wavelength to achieve good accuracy for all dip angles. The high computation requirements for 3D simulations on such fine grids limit the application of heterogenous modeling in the presence of complex surface topography.
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He, Wei, und Wen Li Wu. „Study on Algorithm for Grid Subdivision and Encryption Based on Technology of Three Dimensional Geological Modeling“. Applied Mechanics and Materials 336-338 (Juli 2013): 1416–21. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.1416.
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To achieve 3D grid models which have a non-uniform size and varying properties, we proposed the algorithm of grid subdivision and encryption by human-computer interaction. This algorithm was the technology based on 3D geological modeling, and achieving process has following three steps. Firstly, we converted many 2D cross sections to 3D space, and reconstructed 3D vector models using the algorithm of optimal path suture, and set the property of abnormal body and surrounding rock. Then, achieving 3D grids subdivided according to the relationship between the center of 3D grid and 3D vector models, the properties of 3D grids were determined. Finally, we encrypted grids in the survey area and expansion area, and modified the properties. The results show that the algorithm can realize the conversion from 3D vector models to 3D grid models, and this process is reliable and efficient.
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Alhamrouni, Ibrahim, Wira Wahab, M. Salem, Nadia H. A. Rahman und Lili Awalin. „Modeling of micro-grid with the consideration of total harmonic distortion analysis“. Indonesian Journal of Electrical Engineering and Computer Science 15, Nr. 2 (01.08.2019): 581. http://dx.doi.org/10.11591/ijeecs.v15.i2.pp581-592.
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<p>With the rapid expansion of electricity grid, there yet still places to be covered considering their remote location. Micro-grid (MG) is a solution in this scenario, in fact, there is actually many cases where MG is used in case of emergency and act as a backup to the main electrical grid. By disconnecting itself from the larger grid, a grid that can have many problems, the micro-grid becomes much more flexible in its operations and by continuing to power households and communities alike. Besides grid-connected mode, it is necessary for the MG to operate in autonomous mode. By operating in islanded mode, micro-grids must be able to supply critical load without interruption, run at specific values for voltage and power and extract the maximum power from the distributed generations (DG). Therefore, the modeling of microgrid network considering solar photovoltaic(PV) and wind turbine generation (WTG) system as the distributed generation have been modeled using Matlab/Simulink in this research. Apart from that, the observation of total harmonic distortion(THD) between two operation modes of grid-connected and the islanded-mode is presented in order to analyze the power quality stability towards two operations MG network with same loads size and network parameters.</p>
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Melosh, Robert J. „Modeling Accuracy in FEA of Vibrations of a Drumhead“. Shock and Vibration 1, Nr. 1 (1993): 15–20. http://dx.doi.org/10.1155/1993/485825.
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The study of the problem of predicting values of Rayleigh’s quotient for a square drumhead provides a basis for assessing the relation between grid size, accuracy of analysis results, and efficiency of data processing in finite element analysis. The analysis data indicate that unacceptable grid sampling can occur even for the fine grids, that strictly monotonic convergence is attainable for vibration analysis, and that more efficient computer analysis associates with use of curve fitting analysis of conventional finite element analysis results.
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Mallison, Brad, Charles Sword, Thomas Viard, William Milliken und Amy Cheng. „Unstructured Cut-Cell Grids for Modeling Complex Reservoirs“. SPE Journal 19, Nr. 02 (30.01.2014): 340–52. http://dx.doi.org/10.2118/163642-pa.
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Summary Effective workflows for translating Earth models into simulation models require grids that preserve geologic accuracy, offer flexible resolution control, integrate tightly with upscaling, and can be generated easily. Corner-point grids and pillar-based unstructured grids fail to satisfy these objectives; hence, a truly 3D unstructured approach is required. This paper describes unstructured cut-cell gridding tools that address these needs and improve the integration of our overall reservoir-modeling workflows. The construction of simulation grids begins with the geologic model: a numerical representation of the reservoir structure, stratigraphy, and properties. Our gridding uses a geochronological (GeoChron) map from physical coordinates to an unfaulted and unfolded depositional coordinate system. The mapping is represented implicitly on a tetrahedral mesh that conforms to faults, and it facilitates accurate geostatistical modeling of static depositional properties. In the simplest use case, we create an explicit representation of the geologic model as an unstructured polyhedral grid. Away from faults and other discontinuities, the cells are hexahedral, highly orthogonal, and arranged in a structured manner. Geometric cutting operations create general polyhedra adjacent to faults and explicit contact polygons across faults. The conversion of implicit models to explicit grids is conceptually straightforward, but the implementation is nontrivial because of the limitations of finite precision arithmetic and the need to remove small cells formed in the cutting process. In practice, simulation grids are often constructed at coarser resolutions than Earth models. Our implementation of local grid coarsening and refinement exploits the flexibility of unstructured grids to minimize upscaling errors and to preserve critical geologic features. Because the simulation grid and the geologic model are constructed by use of the same mapping, fine cells can be nested exactly inside coarse cells. Therefore, flow-based upscaling can be applied efficiently without resampling onto temporary local grids. This paper describes algorithms and data structures for constructing, storing, and simulating cut-cell grids. Examples illustrate the accurate modeling of normal faults, y-faults, overturned layers, and complex stratigraphy. Flow results, including a field-sector model, show the suitability of cut-cell grids for simulation.
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Gibson, Richard L., Kai Gao, Eric Chung und Yalchin Efendiev. „Multiscale modeling of acoustic wave propagation in 2D media“. GEOPHYSICS 79, Nr. 2 (01.03.2014): T61—T75. http://dx.doi.org/10.1190/geo2012-0208.1.
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Conventional finite-difference methods produce accurate solutions to the acoustic and elastic wave equation for many applications, but they face significant challenges when material properties vary significantly over distances less than the grid size. This challenge is likely to occur in reservoir characterization studies, because important reservoir heterogeneity can be present on scales of several meters to ten meters. Here, we describe a new multiscale finite-element method for simulating acoustic wave propagation in heterogeneous media that addresses this problem by coupling fine- and coarse-scale grids. The wave equation is solved on a coarse grid, but it uses basis functions that are generated from the fine grid and allow the representation of the fine-scale variation of the wavefield on the coarser grid. Time stepping also takes place on the coarse grid, providing further speed gains. Another important property of the method is that the basis functions are only computed once, and time savings are even greater when simulations are repeated for many source locations. We first present validation results for simple test models to demonstrate and quantify potential sources of error. These tests show that the fine-scale solution can be accurately approximated when the coarse grid applies a discretization up to four times larger than the original fine model. We then apply the multiscale algorithm to simulate a complete 2D seismic survey for a model with strong, fine-scale scatterers and apply standard migration algorithms to the resulting synthetic seismograms. The results again show small errors. Comparisons to a model that is upscaled by averaging densities on the fine grid show that the multiscale results are more accurate.
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He, Hong Peng, Yan Hao Huang, Jun Liu und Jian Lei Fan. „Research on Ontology Modeling Method of Smart Grid“. Applied Mechanics and Materials 291-294 (Februar 2013): 2079–83. http://dx.doi.org/10.4028/www.scientific.net/amm.291-294.2079.
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Smart grid makes new request for the representation and application of power grid knowledge. To solve the problem of “information isolated island” caused by the continuous development of power grid and the ineffectively use of massive domain knowledge, ontology technology is introduced into the smart grid field. Each link of smart grid is analyzed and new request for knowledge it makes is introduced. Then a simple introduction of ontology and ontology modeling is made. Referring to the defects of existing ontology modeling methods and considering the specific reality of smart grid, an ontology modeling method suitable for the smart grid field is presented, which is aiming at providing guidance on ontology modeling of smart grid. Finally a modeling example is given which proves the feasibility and efficiency of the method.
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Cuda, G., P. Veltri und M. Cannataro. „Modeling and Designing a Proteomics Application on PROTEUS“. Methods of Information in Medicine 44, Nr. 02 (2005): 221–26. http://dx.doi.org/10.1055/s-0038-1633951.
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Summary Objectives: Biomedical applications, such as analysis and management of mass spectrometry proteomics experiments, involve heterogeneous platforms and knowledge, massive data sets, and complex algorithms. Main requirements of such applications are semantic modeling of the experiments and data analysis, as well as high performance computational platforms. In this paper we propose a software platform allowing to model and execute biomedical applications on the Grid. Methods: Computational Grids offer the required computational power, whereas ontologies and workflow help to face the heterogeneity of biomedical applications. In this paper we propose the use of domain ontologies and workflow techniques for modeling biomedical applications, whereas Grid middleware is responsible for high performance execution. As a case study, the modeling of a proteomics experiment is discussed. Results: The main result is the design and first use of PROTEUS, a Grid-based problem-solving environment for biomedical and bioinformatics applications. Conclusion: To manage the complexity of biomedical experiments, ontologies help to model applications and to identify appropriate data and algorithms, workflow techniques allow to combine the elements of such applications in a systematic way. Finally, translation of workflow into execution plans allows the exploitation of the computational power of Grids. Along this direction, in this paper we present PROTEUS discussing a real case study in the proteomics domain.
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Martynenko, S. I. „Remarks on Generation of the Orthogonal Structured Grids“. Herald of the Bauman Moscow State Technical University. Series Natural Sciences, Nr. 82 (2019): 16–26. http://dx.doi.org/10.18698/1812-3368-2019-1-16-26.
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Grid generation techniques have contributed significantly toward the application of mathematical modeling in large-scale engineering problems. The structured grids have the advantage that very robust and parallel computational algorithms have been proposed for solving (initial-)boundary value problems. Orthogonal grids make it possible to simplify an approximation of the differential equations and to increase computation accuracy. Opportunity of the orthogonal structured grid generation for solving two- and three-dimensional (initial-)boundary value problems is analyzed in the article in assumption that isolines or isosurfaces of d (=2,3) functions form this grid. Condition of the isolines/isosurfaces orthogonality is used for formulation of the boundary value problems, the solutions of which will be form the orthogonal grid. A differential substitution is proposed to formulate the boundary value problems directly from the orthogonality condition of the grid. The substitution leads to the general partial differrential equations with undetermined coefficients. In the two-dimensional case, it is shown that the orthogonal grid generation is equivalent to the solution of partial differential equations of either elliptic or hyperbolic type. In three-dimensional domains, an orthogonal grid can be generated only in special cases. The obtained results are useful for mathematical modeling of the complex physicochemical processes in the technical devices
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Choi, Jin-Woo, Min-Yong Choi und Wan-Kyun Chung. „Topological Modeling using Sonar Grid Map“. Journal of Korea Robotics Society 6, Nr. 2 (31.05.2011): 189–96. http://dx.doi.org/10.7746/jkros.2011.6.2.189.
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Mayhan, J. T. „Characteristic modes and wire grid modeling“. IEEE Transactions on Antennas and Propagation 38, Nr. 4 (April 1990): 457–69. http://dx.doi.org/10.1109/8.52263.
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Yu, Ming, und Nirwan Ansari. „Smart grid communications: Modeling and validation“. Journal of Network and Computer Applications 59 (Januar 2016): 247–49. http://dx.doi.org/10.1016/j.jnca.2015.11.006.
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Haines, Seth S., und Steven R. Pride. „Seismoelectric numerical modeling on a grid“. GEOPHYSICS 71, Nr. 6 (November 2006): N57—N65. http://dx.doi.org/10.1190/1.2357789.
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Our finite-difference algorithm provides a new method for simulating how seismic waves in arbitrarily heterogeneous porous media generate electric fields through an electrokinetic mechanism called seismoelectric coupling. As the first step in our simulations, we calculate relative pore-fluid/grain-matrix displacement by using existing poroelastic theory. We then calculate the electric current resulting from the grain/fluid displacement by using seismoelectric coupling theory. This electrofiltration current acts as a source term in Poisson’s equation, which then allows us to calculate the electric potential distribution. We can safely neglect induction effects in our simulations because the model area is within the electrostatic near field for the depth of investigation (tens to hundreds of meters) and the frequency ranges ([Formula: see text] to [Formula: see text]) of interest for shallow seismoelectric surveys.We can independently calculate the electric-potential distribution for each time step in the poroelastic simulation without loss of accuracy because electro-osmotic feedback (fluid flow that is perturbed by generated electric fields) is at least [Formula: see text] times smaller than flow that is driven by fluid-pressure gradients and matrix acceleration, and is therefore negligible. Our simulations demonstrate that, distinct from seismic reflections, the seismoelectric interface response from a thin layer (at least as thin as one-twentieth of the seismic wavelength) is considerably stronger than the response from a single interface. We find that the interface response amplitude decreases as the lateral extent of a layer decreases below the width of the first Fresnel zone. We conclude, on the basis of our modeling results and of field results published elsewhere, that downhole and/or crosswell survey geometries and time-lapse applications are particularly well suited to the seismoelectric method.
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Jin, Kang-Ren, und Yegang Wu. „Boundary-fitted grid in landscape modeling“. Landscape Ecology 12, Nr. 1 (Februar 1997): 19–26. http://dx.doi.org/10.1007/bf02698204.
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Mohd Sakri, Fadhilah, Mohamed Sukri Mat Ali und Sheikh Ahmad Zaki. „Benchmark on the Dynamics of Liquid Draining Inside a Tank“. E3S Web of Conferences 95 (2019): 02009. http://dx.doi.org/10.1051/e3sconf/20199502009.
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Immense information and details observation of flow physics inside a draining tank can be achieved by adopting reliable numerical simulations. Yet the accuracy of numerical results has been always debatable and it is mainly affected by the grid convergence error and computational modeling approaches. Hence, this study is divided into two stages. In the first stage, this paper determines a systematic method of refining a computational grid for a liquid draining inside a tank using OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is also examined. In order to study the effect of grid dependency, three different grid refinements are investigated: fine, medium and coarse grids. By using a form of Richardson extrapolation and Grid Convergence Index (GCI), the level of grid independence is attained. In this paper, a monotonic convergence criteria is reached when the fine grid has the GCI value below 10% for each parameter. In the second stage, different computational modeling approaches (DNS, RANS k-ε, RANS k-ω and LES turbulence models) are investigated using the finer grid from the first stage. The results for the draining time and flow visualization of the generation of an air-core are in a good agreement with the available published data. The Direct Numerical Simulation (DNS) seems most reasonably satisfactory for VOF studies relating air-core compared to other different turbulence modeling approaches.
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Zeng, Kaiwen, Fusheng Li, Jianing Liu, Haizhu Wang, Dan Lin, Weicong Wu und Tao Yu. „An Exploratory Investigation on Modelling Technologies to Flexible Loads Dispatching in A Smart Grid Environment“. E3S Web of Conferences 194 (2020): 03013. http://dx.doi.org/10.1051/e3sconf/202019403013.
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As the proportion of flexible load resources in smart grids continues to rise, resulting in increasingly complex grid structures, significant changes in grid characteristics, and increased risks to grid operation and control, it will be difficult to intelligently regulate the grid solely by relying on traditional resource regulation methods, and the dispatchable space for traditional resources will become smaller and smaller. To this end, this paper conducts an exploratory investigation on the modeling techniques for flexible loads participation in smart grid dispatching. First, a classification of the flexible loads involved in grid regulation is made. Secondly, according to the flexible load classification, the modeling techniques of different classes of flexible loads are reviewed and studied; then, the flexible load dispatching modes for different operating states and different control tasks, and under different control methods are discussed deeply. Moreover, the technological economics and feasibility of these different flexible load dispatching modes are compared. Finally, an outlook and conclusion are made.
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Feoktistov, Aleksandr, Olga Basharina, Yuri Dyadkin und Evgeny Fereferov. „AUTOMATION OF QUEUING SYSTEM SIMULATION MODELING IN GRID“. Proceedings of Irkutsk State Technical University 21, Nr. 12 (Dezember 2017): 105–13. http://dx.doi.org/10.21285/1814-3520-2017-12-105-113.
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Wang, Ning, Jian-Wen Bao, Jin-Luen Lee, Fanthune Moeng und Cliff Matsumoto. „Wavelet Compression Technique for High-Resolution Global Model Data on an Icosahedral Grid“. Journal of Atmospheric and Oceanic Technology 32, Nr. 9 (September 2015): 1650–67. http://dx.doi.org/10.1175/jtech-d-14-00217.1.
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AbstractModern Earth modeling systems often use high-resolution unstructured grids to discretize their horizontal domains. One of the major challenges in working with these high-resolution models is to efficiently transmit and store large volumes of model data for operational forecasts and for modeling research.A newly developed compression technique is presented that significantly reduces the size of datasets produced by high-resolution global models that are discretized on an icosahedral grid. The compression technique is based on the wavelet transform together with a grid rearrangement algorithm and precision-controlled quantization technology. The grid rearrangement algorithm converts an icosahedral grid to a set of 10 rhombus grids that retain the spatial correlation of model data so that a three-dimensional wavelet transform can be effectively applied. The precision-controlled quantization scheme guarantees specified precision of compressed datasets.The technique is applied to the output of a global weather prediction model, the Flow-Following, Finite-Volume Icosahedral Model (FIM) developed by NOAA’s Earth System Research Laboratory. Experiments show that model data at 30-km resolution can be compressed up to 50:1 without noticeable visual differences; at specified precision requirements, the proposed compression technique achieves better compression compared to a state-of-the-art compression format [Gridded Binary (GRIB) with JPEG 2000 packing option]. In addition, model forecasts initialized with original and compressed initial conditions are compared and assessed. The assessment indicates that it is promising to use the technique to compress model data for those applications demanding high fidelity of compressed datasets.
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Ha, Wansoo, und Changsoo Shin. „Efficient Laplace-domain modeling and inversion using an axis transformation technique“. GEOPHYSICS 77, Nr. 4 (01.07.2012): R141—R148. http://dx.doi.org/10.1190/geo2011-0424.1.
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We tested an axis-transformation technique for modeling wave propagation in the Laplace domain using a finite-difference method. This technique enables us to use small grids near the surface and large grids at depth. Accordingly, we can reduce the number of grids and attain computational efficiency in modeling and inversion in the Laplace domain. We used a dispersion analysis and comparisons between modeled wavefields obtained on the regular and transformed axes. We demonstrated in a synthetic Laplace-domain inversion technique shows that this method is efficient and yields a result comparable to that of a Laplace-domain inversion using a regular grid. In a synthetic inversion example, the memory usage reduced to less than 33%, and the computation time reduced to 39% of those required for the regular grid case using a logarithmic transformation function.
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Pitarka, Arben. „3D Elastic finite-difference modeling of seismic motion using staggered grids with nonuniform spacing“. Bulletin of the Seismological Society of America 89, Nr. 1 (01.02.1999): 54–68. http://dx.doi.org/10.1785/bssa0890010054.
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Abstract This article provides a technique to model seismic motions in 3D elastic media using fourth-order staggered-grid finite-difference (FD) operators implemented on a mesh with nonuniform grid spacing. The accuracy of the proposed technique has been tested through comparisons with analytical solutions, conventional 3D staggered-grid FD with uniform grid spacing, and reflectivity methods for a variety of velocity models. Numerical tests with nonuniform grids suggest that the method allows sufficiently accurate modeling when the grid sampling rate is at least 6 grid points per shortest shear wavelength. The applicability for a finite fault with non-uniform distribution of point sources is also confirmed. The use of nonuniform spacing improves the efficiency of the FD methods when applied to large-scale structures by partially avoiding the spatial oversampling introduced by the uniform spacing in zones with high velocity. The significant reduction in computer memory that can be obtained by the new technique improves the efficiency of the 3D-FD method at handling shorter wavelengths, larger areas, or more realistic 3D velocity structures.
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Chu, Chunlei, und Paul L. Stoffa. „Application of normalized pseudo-Laplacian to elastic wave modeling on staggered grids“. GEOPHYSICS 76, Nr. 5 (September 2011): T113—T121. http://dx.doi.org/10.1190/geo2011-0069.1.
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We extended the pseudo-Laplacian to staggered grids based on the concept of normalized pseudo-Laplacian and applied it to constructing the pseudoanalytical formulations for the variable-density acoustic wave equation and the elastic wave equation. Acoustic wavefields only contain P-waves and therefore only P-wave pseudo-Laplacians are required for acoustic wave propagation. In comparison, two sets of staggered grid pseudo-Laplacians are needed in the elastic case in order to properly compensate for time stepping errors for both P-waves and S-waves. We gave a thorough derivation of the pseudoanalytical method for the elastic wave equation, based on normalized pseudo-Laplacians implemented on staggered grids, and presented the resulting complete discretized formulas. We proved that the staggered grid pseudo-Laplacian reduces to the pseudo-Laplacian for the scalar wave equation on standard grids. When using zero compensation velocities for normalized pseudo-Laplacians, the pseudoanalytical formulas simply reduce to the pseudospectral equations. We demonstrated with numerical examples that staggered grid pseudo-Laplacians effectively compensate for second-order time stepping errors and help generate highly accurate acoustic and elastic wave solutions in variable-density media.
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Liu, Chao, und Zhong Cheng Yu. „Research of Modeling Moving Objects Database over Space-Time Grid“. Advanced Materials Research 268-270 (Juli 2011): 1301–6. http://dx.doi.org/10.4028/www.scientific.net/amr.268-270.1301.
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It is important to manage the dynamic information of moving objects in database technique, it is crucial that how to manage and query the dynamic information of moving objects effectively. In this paper, a system to manage moving object is discussed, which changes time-space into ST-GRlD (space-time grid) model and changes the moving tract of the moving object into poly line in the ST-GRlD .The Ripple Insert algorithm to produce poly line tract and the solution of moving object abruptly changing destination are given.
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Muir, Francis, Joe Dellinger, John Etgen und Dave Nichols. „Modeling elastic fields across irregular boundaries“. GEOPHYSICS 57, Nr. 9 (September 1992): 1189–93. http://dx.doi.org/10.1190/1.1443332.
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Geologists often see the earth as homogeneous blocks separated by smoothly curving boundaries. In contrast, computer modeling algorithms based on finite‐difference schemes require elastic constants to be specified on the vertices of a regular rectangular grid. How can we convert a continuous geological model into a form suitable for a finite‐difference grid? One common way is to lay the finite‐difference grid down on the continuous geological model and use whatever elastic constants happen to lie beneath each of the grid points.
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Tao, Hao, Yao H¨ua Tang, Xu Zhan Zhou und Hong Wei Wang. „Frequency Response Model of Regional Power Grid Based on Parameter Identification on Trip Process of Transmission Line“. Applied Mechanics and Materials 448-453 (Oktober 2013): 2406–10. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.2406.
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Many large power grid accidents show that the tripped transmission line has great impact on system stability. The primary frequency regulation effects of generation units play key roles during a trip procedure. In this paper, a frequency stability dynamic mathematic model of regional power grid was built based on records of a practical trip accident of transmission line between regional grids. Key parameters of the model were identified. The identified parameters are within their reasonable regions. The simulation results show that the modeling method based on parameter identification can be used for modeling of transmission line trip accident procedure and relative frequency stability analyses on power grids.
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Xiao, Xiao Ping, Zi Sheng Li und Wei Gong. „Fuzzy Fractal Interpolation Surface and its Applications“. Advanced Materials Research 542-543 (Juni 2012): 1141–44. http://dx.doi.org/10.4028/www.scientific.net/amr.542-543.1141.
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Tackling of uncertain data is a major problem in analysis, modeling and simulation. Fractal interpolation surface and fuzzy set method are employed to solve the issue of uncertainty in modeling irregular surface. Initial interpolation data grid point is used as the kernel of Gaussian fuzzy membership function and its fuzzy numbers can be calculated by specifying λ of λ-cut set. These fuzzy numbers are used as uncertain data, which are the boundaries of the fluctuation of initial grid, and defined as a new kind of fuzzy interpolation grids. With these interpolation grids fractal interpolation surface algorithm is applied to act on. By these definitions, experimental data for modeling rock surface is illustrated to show that how the interpolation scheme proposed in this paper enhances the controllability for manipulating uncertain data.
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Kovalov, Serhii, und Svitlana Botvinovska. „VARYING THE SHAPE OF A SURFACE WHICH IS DISCRETE PRESENTED BY AN IRREGULAR BALANCED GRID“. Management of Development of Complex Systems, Nr. 45 (01.03.2021): 89–96. http://dx.doi.org/10.32347/2412-9933.2021.45.89-96.
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The article discusses a problem, the solution of which is related to the research previously described in previous publications. This paper demonstrates the solution of the problem of forming a discrete frame, in the form of a balanced irregular grid, discretely represented surface. The described problem is solved by one of the methods of discrete modeling, using the static-geometric method of Professor Kovalev S.N. (SGM). The initial conditions for the formation of such irregular balanced discrete networks are the coordinates of the nodes of the reference loop, the topological organization of the grid and the z-coordinate of one of the internal nodes. Note that irregular grids are characterized by different node and cell topologies. This fact can greatly complicate the modeling process, namely, performing the necessary calculations when calculating the coordinates of discrete grid nodes. To facilitate calculations and simplify numbering of discrete grid nodes, it is proposed to use a topological grid scheme based on a regular grid. For regular grids, each node has a specific number, which greatly facilitates the calculation of node coordinates. The operative change in the shape of the grid can be carried out by connecting the classical coordinate calculations of the discrete SGM grid, that is, by solving the system of equilibrium equations of nodes, with an affine transformation, namely the introduction of the scaling factors of coordinates. The disadvantage of this synthesis of the two methods will be the change in the preassigned reference of contour of the mesh, due to the fact that all coordinates of absolutely all grid nodes are multiplied by the corresponding transformation coefficients. To avoid changing the shape of a given reference contour, it is proposed to use a synthesis of three methods in the work, namely SGM, affine coordinate transformation and a method of functional addition of coordinates. This synthesis of methods will maintain the balance of the discrete grid during the modeling process, and will allow you to simply vary (change) the shape of the simulated surface.
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Yuan, Wen Hua, Yi Ma, Jun Fu, Yuan Tang, Wei Chen und Zhi Guo Zhu. „Impact of Grid Type on the Stress-Strain of 175F Diesel Engine Piston Structure Calculated by the Finite Element“. Applied Mechanics and Materials 635-637 (September 2014): 584–88. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.584.
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The finite element modeling is based on the aluminum-silicon alloy piston compression performance test by using both 10-node tetrahedron element and 10-node hexahedron element. After analyzing four grid types, we found that employing both tetrahedron element and hexahedron element can obtain stress-strain nephogram, but with a difference between the four modeling results. In the context of having the same grid size, 10-node hexahedron element reflects a fairly accurate piston stress-strain status than the 10-node tetrahedron element, and among the four schemes, the result calculated by analyzing the locally refined grid that containing both 2mm and 1mm sized 10-node hexahedron grids is the one that matches the experimental value best.
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Ma, Yue, Guoqing Li, Xiaochuang Yao, Qianqian Cao, Long Zhao, Shuang Wang und Lianchong Zhang. „A Precision Evaluation Index System for Remote Sensing Data Sampling Based on Hexagonal Discrete Grids“. ISPRS International Journal of Geo-Information 10, Nr. 3 (23.03.2021): 194. http://dx.doi.org/10.3390/ijgi10030194.
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With the rapid development of earth observation, satellite navigation, mobile communication, and other technologies, the order of magnitude of the spatial data we acquire and accumulate is increasing, and higher requirements are put forward for the application and storage of spatial data. As a new form of data management, the global discrete grid can be used for the efficient storage and application of large-scale global spatial data, which is a digital multiresolution georeference model that helps to establish a new model of data association and fusion. It is expected to make up for the shortcomings in the organization, processing, and application of current spatial data. There are different types of grid systems according to the grid division form, including global discrete grids with equal latitude and longitude, global discrete grids with variable latitude and longitude, and global discrete grids based on regular polyhedrons. However, there is no accuracy evaluation index system for remote sensing images expressed on the global discrete grid to solve this problem. This paper is dedicated to finding a suitable way to express remote sensing data on discrete grids, as well as establishing a suitable accuracy evaluation system for modeling remote sensing data based on hexagonal grids to evaluate modeling accuracy. The results show that this accuracy evaluation method can evaluate and analyze remote sensing data based on hexagonal grids from multiple levels, and the comprehensive similarity coefficient of the images before and after conversion is greater than 98%, which further proves the availability of the hexagonal-grid-based remote sensing data of remote sensing images. This evaluation method is generally applicable to all raster remote sensing images based on hexagonal grids, and it can be used to evaluate the availability of hexagonal grid images.
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Hu, Dian Gang, Jie Zheng, Yu Hong Zhang, Hao Liang Xu, Hai Ming Zhou, Jian Kang Yang und Tian Jiao Pu. „Study on Technological Evaluation Modeling of Smart Grid“. Applied Mechanics and Materials 494-495 (Februar 2014): 1747–52. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.1747.
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The Smart Grid is the development trend of grid technology. For guiding the construction of smart grid scientifically, quantitative evaluation for the level of technology maturity of the Smart Grid construction is necessary. The evaluation results can be used for determining the stage of the current construction of Smart Grid and summarizing the problems which came up during the process of construction, also finding the gap between current satiation and individual goals to determine the direction and key job in next step. This paper take the characteristics and goals of domestic Smart Grid into account, build a maturity evaluation model which assess the smart grid maturity in three dimensionstime, production processes and technical features separately. By setting the primary and secondary parameter the model can be used for smart grid assessment in any time, scenes and region. The model make a comprehensive coverage of various aspects in the smart grid construction process and the results of evaluation can be analyzed from different dimension to find the short slab to guide the work in next step.
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Vu, Tu Phan, Nam Nhat Nguyen, Van Van Huynh und Viet Quoc Huynh. „SIMULATION OF LIGHTNING TRANSIENT RESPONSES OF GROUNDING GRID USING FINITE ELEMENT METHOD“. Science and Technology Development Journal 13, Nr. 1 (30.03.2010): 49–55. http://dx.doi.org/10.32508/stdj.v13i1.2069.
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This paper presents the application of the Finite Element methods to calculating and modeling the lightning transient responses on grounding grid. The uniform and optimized grids are used in this work. The tested results obtained on many different models of the conductor and grids have seen the effectiveness of the proposed method and the influence of conductor compression to the transient values when the lightning current into the grid at the different positions.
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Khokhlov, Nikolay, und Polina Stognii. „Novel Approach to Modeling the Seismic Waves in the Areas with Complex Fractured Geological Structures“. Minerals 10, Nr. 2 (30.01.2020): 122. http://dx.doi.org/10.3390/min10020122.
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This paper presents a novel approach to modeling the propagation of seismic waves in a medium containing subvertical fractured inhomogeneities, typical for mineralization zones. The developed method allows us to perform calculations on a structural computational grid, which avoids the construction of unstructured grids. For the calculations, the grid-characteristic method is used. We also present a comparison of the proposed method with the one described at earlier works and discuss the areas of its practical application. As an example, the numerical results for a cluster of subvertical fractures are given. A new approach for modeling fractures makes it quite easy to incorporate fractured objects into the seismic models and perform calculations without using algorithms on unstructured and curved grids.
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Gao, Jingyu, Maxim Smirnov, Maria Smirnova und Gary Egbert. „3-D DC Resistivity Forward Modeling Using the Multi-resolution Grid“. Pure and Applied Geophysics 177, Nr. 6 (18.11.2019): 2803–19. http://dx.doi.org/10.1007/s00024-019-02365-3.
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AbstractWe implemented a novel multi-resolution grid approach to direct current resistivity (DCR) modeling in 3-D. The multi-resolution grid was initially developed to solve the electromagnetic forward problem and helped to improve the modeling efficiency. In the DCR forward problem, the distribution of the electric potentials in the subsurface is estimated. We consider finite-difference staggered grid discretization, which requires fine grid resolution to accurately model electric potentials around the current electrodes and complex model geometries near the surface. Since the potential variations attenuate with depth, the grid resolution can be decreased correspondingly. The conventional staggered grid fixes the horizontal grid resolution that extends to all layers. This leads to over-discretization and therefore unnecessary high computational costs (time and memory). The non-conformal multi-resolution grid allows the refinement or roughening for the grid’s horizontal resolution with depth, resulting in a substantial reduction of the degrees of freedom, and subsequently, computational requirements. In our implementation, the coefficient matrix maintains its symmetry, which is beneficial for using the iterative solvers and solving the adjoint problem in inversion. Through comparison with the staggered grid, we have found that the multi-resolution grid can significantly improve the modeling efficiency without compromising the accuracy. Therefore, the multi-resolution grid allows modeling with finer horizontal resolutions at lower computational costs, which is essential for accurate representation of the complex structures. Consequently, the inversion based on our modeling approach will be more efficient and accurate.
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Cho, Yongchae, und Richard L. Gibson, Jr. „Reverse time migration via frequency-adaptive multiscale spatial grids“. GEOPHYSICS 84, Nr. 2 (01.03.2019): S41—S55. http://dx.doi.org/10.1190/geo2018-0292.1.
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Reverse time migration (RTM) is widely used because of its ability to recover complex geologic structures. However, RTM also has a drawback in that it requires significant computational cost. In RTM, wave modeling accounts for the largest part of the computing cost for calculating forward- and backward-propagated wavefields before applying an imaging condition. For this reason, we have applied a frequency-adaptive multiscale spatial grid to enhance the efficiency of the wave simulations. To implement wave modeling for different values of the spatial grid interval, we apply a model reduction technique, the generalized multiscale finite-element method (GMsFEM), which solves local spectral problems on a fine grid to simulate wave propagation on a coarser grid. We can enhance the speed of computation without sacrificing accuracy by using coarser grids for lower frequency waves, while applying a finer grid for higher frequency waves. In the proposed method, we can control the size of the coarse grid and level of heterogeneity of the wave solutions to tune the trade-off between speedup and accuracy. As we increase the expected level of complexity of the wave solutions, the GMsFEM wave modeling can capture more detailed features of waves. After computing the forward and backward wavefield on the coarse grid, we reproject the coarse wave solutions to the fine grid to construct the RTM gradient image. Although wave solutions are computed on a coarse grid, we still obtain the RTM images without reducing the image resolution by projecting coarse wave solutions to the fine grid. We determine the efficiency of the proposed imaging method using the Marmousi-2 model. We compare the RTM images using GMsFEM with a fixed coarse mesh and a multiple frequency-adaptive coarse meshes to indicate the image quality and computational speed of the new approach.
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Hojati, Majid, und Colin Robertson. „Integrating cellular automata and discrete global grid systems: a case study into wildfire modelling“. AGILE: GIScience Series 1 (15.07.2020): 1–23. http://dx.doi.org/10.5194/agile-giss-1-6-2020.
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Abstract. With new forms of digital spatial data driving new applications for monitoring and understanding environmental change, there are growing demands on traditional GIS tools for spatial data storage, management and processing. Discrete Global Grid System (DGGS) are methods to tessellate globe into multiresolution grids, which represent a global spatial fabric capable of storing heterogeneous spatial data, and improved performance in data access, retrieval, and analysis. While DGGS-based GIS may hold potential for next-generation big data GIS platforms, few of studies have tried to implement them as a framework for operational spatial analysis. Cellular Automata (CA) is a classic dynamic modeling framework which has been used with traditional raster data model for various environmental modeling such as wildfire modeling, urban expansion modeling and so on. The main objectives of this paper are to (i) investigate the possibility of using DGGS for running dynamic spatial analysis, (ii) evaluate CA as a generic data model for dynamic phenomena modeling within a DGGS data model and (iii) evaluate an in-database approach for CA modelling. To do so, a case study into wildfire spread modelling is developed. Results demonstrate that using a DGGS data model not only provides the ability to integrate different data sources, but also provides a framework to do spatial analysis without using geometry-based analysis. This results in a simplified architecture and common spatial fabric to support development of a wide array of spatial algorithms. While considerable work remains to be done, CA modelling within a DGGS-based GIS is a robust and flexible modelling framework for big-data GIS analysis in an environmental monitoring context.
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Vershkov, V. A. „ALGORITHM OF MESH DEFORMATION FOR ACCOUNTING CYCLIC BLADE CONTROL AND BLADES FLAPPING IN THE PROBLEM OF HELICOPTER MAIN ROTOR MODELING“. Civil Aviation High TECHNOLOGIES 22, Nr. 2 (24.04.2019): 62–74. http://dx.doi.org/10.26467/2079-0619-2019-22-2-62-74.
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This paper presents the developed algorithm for numerical grid deformation for solving the problems of modeling the flow around the helicopter main rotor in the horizontal flight mode with allowance for flapping movements and cyclic changes in the angle of the blade installation. In general, this algorithm can be applied to simulate the aerodynamics of solid bodies deviating from its initial position at angles up to 90 degrees in the vertical and horizontal planes relative to the origin point, and also performing a rotational motion at an angle up to 90 degrees around the axis through the center of coordinates and the body mass center. The first part provides a brief overview of the existing methods of the computational grid deformation for solving various problems of numerical simulation. These include methods for rebuilding the grid, moving grids and "Chimera" grids. The second part describes the algorithms for allocating of grid deformation and for finding the final coordinate of the computational grid nodes in the presence of a predetermined blade control law. The equations of the deformation zones shape in numerical grid are given. The influence of variables on zones sizes is shown. The third part presents the results of methodological calculations confirming the performance and limitations when choosing mesh deformation zones. The influence of the size and shape of the deformation zones of the numerical grid on the quality of the mesh elements is also shown. This work is methodical in nature and is a preliminary stage in the numerical modeling of the flow around the helicopter main rotor taking into account the automatic main rotor balancing and blades flapping.