A Two-Level Algorithm for Large-Scale Terrain Using Nested Regular Grids

2009 ◽  
Author(s):  
Bing He ◽  
Lei Sui
Keyword(s):  
Large Scale ◽  
Regular Grids

scholarly journals Parallelisation of sparse grids for large scale data analysis

2006 ◽  
Vol 48 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Jochen Garcke ◽  
Markus Hegland ◽  
Ole Nielsen
Keyword(s):  
Large Scale ◽  
Predictive Modelling ◽  
Sparse Grids ◽  
Sparse Grid ◽  
High Dimensional ◽  
Combination Technique ◽  
Parallel Solvers ◽  
Regular Grids ◽  
Timing Model ◽  
Dimensional Approximation

AbstractSparse grids are the basis for efficient high dimensional approximation and have recently been applied successfully to predictive modelling. They are spanned by a collection of simpler function spaces represented by regular grids. The sparse grid combination technique prescribes how approximations on a collection of anisotropic grids can be combined to approximate high dimensional functions.In this paper we study the parallelisation of fitting data onto a sparse grid. The computation can be done entirely by fitting partial models on a collection of regular grids. This allows parallelism over the collection of grids. In addition, each of the partial grid fits can be parallelised as well, both in the assembly phase, where parallelism is done over the data, and in the solution stage using traditional parallel solvers for the resulting PDEs. Using a simple timing model we confirm that the most effective methods are obtained when both types of parallelism are used.

scholarly journals GLOFRIM v1.0 – A globally applicable computational framework for integrated hydrological-hydrodynamic modelling

2017 ◽  
Author(s):  
Jannis M. Hoch ◽  
Jeffrey C. Neal ◽  
Fedor Baart ◽  
Rens van Beek ◽  
Hessel C. Winsemius ◽  
...  
Keyword(s):  
Large Scale ◽  
Distributed Model ◽  
Free Access ◽  
Test Case ◽  
Hydrodynamic Modelling ◽  
Hydrodynamic Models ◽  
Computational Framework ◽  
Entire Study ◽  
Regular Grids ◽  
Inundation Extent

Abstract. To increase the representation of physical processes in inundation modelling, current research approaches aim to integrate both hydrological and hydrodynamic models. A previous study by Hoch et al. (2017) showed that spatially explicit coupling approaches can outperform stand-alone runs by single-purpose models as they combine spatially distributed model forcing by hydrological models with more sophisticated routing schemes in hydrodynamic models. We here present GLOFRIM, a globally applicable computational framework for integrated hydrological-hydrodynamic modelling, to facilitate such coupling approaches and to cater for an ensemble of models to be coupled. It currently allows for coupling the global hydrological model PCR-GLOBWB with either Delft3D Flexible Mesh (DFM), solving the full shallow-water equations and allowing for spatially flexible meshing, or LISFLOOD-FP (LFP), solving the local inertia equations and running on regular grids. The main advantages of the framework are its open and free access, its global applicability, its versatility, and its extensibility with other hydrological or hydrodynamic models. Before applying GLOFRIM to an actual test case, we benchmarked both DFM and LFP for a synthetic test case. Results show that for sub-critical flow conditions, discharge response to the same input signal is near identical for both models, which agrees with previous studies. We subsequently applied the framework to the Amazon River basin to test the framework thoroughly and, in addition, to perform a first-ever benchmark of flexible and regular grids at the large-scale. Both DFM and LFP produce comparable results in terms of simulated discharge with LFP exhibiting slightly higher accuracy as expressed by a Kling-Gupta-Efficiency of 0.82 compared to 0.76 for DFM. However, benchmarking inundation extent between DFM and LFP over the entire study area, a critical success index of 0.46 was obtained, indicating that the models disagree as often as they agree. Differences between models in both simulated discharge and inundation extent is to a large extent attributable to the gridding techniques employed. In fact, the result show that the numerical scheme of the inundation model and the gridding technique can contribute as strongly to deviations in simulated inundation extent as, unlike the global flood model inter-comparison by Trigg et al. (2016), we control for model forcing and boundary conditions. This study shows that the presented computational framework is robust and widely applicable. GLOFRIM is designed as open access and to be easily extendable, and thus we hope that other large-scale hydrological and hydrodynamic models will be added, eventually capturing more locally relevant processes as well as allowing for more robust model inter-comparison, benchmarking, and ensemble simulations of flood hazard at the large scale.

scholarly journals GLOFRIM v1.0 – A globally applicable computational framework for integrated hydrological–hydrodynamic modelling

2017 ◽  
Vol 10 (10) ◽  
pp. 3913-3929 ◽  
Author(s):  
Jannis M. Hoch ◽  
Jeffrey C. Neal ◽  
Fedor Baart ◽  
Rens van Beek ◽  
Hessel C. Winsemius ◽  
...  
Keyword(s):  
Large Scale ◽  
Flood Hazard ◽  
Free Access ◽  
Test Case ◽  
Hydrodynamic Modelling ◽  
Hydrodynamic Models ◽  
Computational Framework ◽  
Entire Study ◽  
Regular Grids ◽  
Inundation Extent

Abstract. We here present GLOFRIM, a globally applicable computational framework for integrated hydrological–hydrodynamic modelling. GLOFRIM facilitates spatially explicit coupling of hydrodynamic and hydrologic models and caters for an ensemble of models to be coupled. It currently encompasses the global hydrological model PCR-GLOBWB as well as the hydrodynamic models Delft3D Flexible Mesh (DFM; solving the full shallow-water equations and allowing for spatially flexible meshing) and LISFLOOD-FP (LFP; solving the local inertia equations and running on regular grids). The main advantages of the framework are its open and free access, its global applicability, its versatility, and its extensibility with other hydrological or hydrodynamic models. Before applying GLOFRIM to an actual test case, we benchmarked both DFM and LFP for a synthetic test case. Results show that for sub-critical flow conditions, discharge response to the same input signal is near-identical for both models, which agrees with previous studies. We subsequently applied the framework to the Amazon River basin to not only test the framework thoroughly, but also to perform a first-ever benchmark of flexible and regular grids on a large-scale. Both DFM and LFP produce comparable results in terms of simulated discharge with LFP exhibiting slightly higher accuracy as expressed by a Kling–Gupta efficiency of 0.82 compared to 0.76 for DFM. However, benchmarking inundation extent between DFM and LFP over the entire study area, a critical success index of 0.46 was obtained, indicating that the models disagree as often as they agree. Differences between models in both simulated discharge and inundation extent are to a large extent attributable to the gridding techniques employed. In fact, the results show that both the numerical scheme of the inundation model and the gridding technique can contribute to deviations in simulated inundation extent as we control for model forcing and boundary conditions. This study shows that the presented computational framework is robust and widely applicable. GLOFRIM is designed as open access and easily extendable, and thus we hope that other large-scale hydrological and hydrodynamic models will be added. Eventually, more locally relevant processes would be captured and more robust model inter-comparison, benchmarking, and ensemble simulations of flood hazard on a large scale would be allowed for.

scholarly journals Benchmarking flexible meshes and regular grids for large-scale fluvial inundation modelling

2018 ◽  
Vol 121 ◽  
pp. 350-360 ◽  
Author(s):  
Jannis M. Hoch ◽  
Rens van Beek ◽  
Hessel C. Winsemius ◽  
Marc F.P. Bierkens
Keyword(s):  
Large Scale ◽  
Regular Grids ◽  
Inundation Modelling

scholarly journals Benchmarking flexible meshes and regular grids for large-scale fluvial inundation modelling

2018 ◽  
Author(s):  
Jannis Hoch ◽  
Rens van Beek ◽  
Hessel Winsemius ◽  
Marc Bierkens
Keyword(s):  
Large Scale ◽  
Regular Grids ◽  
Inundation Modelling

Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

1999 ◽  
Vol 173 ◽  
pp. 243-248
Author(s):  
D. Kubáček ◽  
A. Galád ◽  
A. Pravda
Keyword(s):  
Image Processing ◽  
Large Scale ◽  
Harvard College ◽  
Oak Ridge ◽  
Large Scale Structures ◽  
Short Period Comet ◽  
Short Period ◽  
Scale Structures ◽  
Harvard College Observatory ◽  
Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Large-scale Motion of Solar Filaments

2000 ◽  
Vol 179 ◽  
pp. 205-208
Author(s):  
Pavel Ambrož ◽  
Alfred Schroll
Keyword(s):  
Magnetic Flux ◽  
Proper Motion ◽  
Time Scale ◽  
Large Scale ◽  
Accuracy Of Measurements ◽  
Solar Filaments ◽  
General Movement ◽  
Scale Motion ◽  
Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

Some applications of electron beam microanalysis techniques in VLSI process evaluation

1983 ◽  
Vol 41 ◽  
pp. 160-161
Author(s):  
Simon Thomas
Keyword(s):  
Integrated Circuits ◽  
Process Evaluation ◽  
Large Scale ◽  
Technology Development ◽  
Analytical Techniques ◽  
Successful Implementation ◽  
Analysis Of Failures ◽  
Characterization Of Materials ◽  
Circuits Vlsi

Trends in the technology development of very large scale integrated circuits (VLSI) have been in the direction of higher density of components with smaller dimensions. The scaling down of device dimensions has been not only laterally but also in depth. Such efforts in miniaturization bring with them new developments in materials and processing. Successful implementation of these efforts is, to a large extent, dependent on the proper understanding of the material properties, process technologies and reliability issues, through adequate analytical studies. The analytical instrumentation technology has, fortunately, kept pace with the basic requirements of devices with lateral dimensions in the micron/ submicron range and depths of the order of nonometers. Often, newer analytical techniques have emerged or the more conventional techniques have been adapted to meet the more stringent requirements. As such, a variety of analytical techniques are available today to aid an analyst in the efforts of VLSI process evaluation. Generally such analytical efforts are divided into the characterization of materials, evaluation of processing steps and the analysis of failures.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

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