Patched based methods for adaptive mesh refinement solutions of partial differential equations

Energy Technology Data Exchange (ETDEWEB)

Saltzman, J.

1997-09-02

This manuscript contains the lecture notes for a course taught from July 7th through July 11th at the 1997 Numerical Analysis Summer School sponsored by C.E.A., I.N.R.I.A., and E.D.F. The subject area was chosen to support the general theme of that year`s school which is ``Multiscale Methods and Wavelets in Numerical Simulation.`` The first topic covered in these notes is a description of the problem domain. This coverage is limited to classical PDEs with a heavier emphasis on hyperbolic systems and constrained hyperbolic systems. The next topic is difference schemes. These schemes are the foundation for the adaptive methods. After the background material is covered, attention is focused on a simple patched based adaptive algorithm and its associated data structures for square grids and hyperbolic conservation laws. Embellishments include curvilinear meshes, embedded boundary and overset meshes. Next, several strategies for parallel implementations are examined. The remainder of the notes contains descriptions of elliptic solutions on the mesh hierarchy, elliptically constrained flow solution methods and elliptically constrained flow solution methods with diffusion.

Adaptive moving mesh methods for simulating one-dimensional groundwater problems with sharp moving fronts

Science.gov (United States)

Huang, W.; Zheng, Lingyun; Zhan, X.

2002-01-01

Accurate modelling of groundwater flow and transport with sharp moving fronts often involves high computational cost, when a fixed/uniform mesh is used. In this paper, we investigate the modelling of groundwater problems using a particular adaptive mesh method called the moving mesh partial differential equation approach. With this approach, the mesh is dynamically relocated through a partial differential equation to capture the evolving sharp fronts with a relatively small number of grid points. The mesh movement and physical system modelling are realized by solving the mesh movement and physical partial differential equations alternately. The method is applied to the modelling of a range of groundwater problems, including advection dominated chemical transport and reaction, non-linear infiltration in soil, and the coupling of density dependent flow and transport. Numerical results demonstrate that sharp moving fronts can be accurately and efficiently captured by the moving mesh approach. Also addressed are important implementation strategies, e.g. the construction of the monitor function based on the interpolation error, control of mesh concentration, and two-layer mesh movement. Copyright ?? 2002 John Wiley and Sons, Ltd.

Kinetic solvers with adaptive mesh in phase space

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Arslanbekov, Robert R.; Kolobov, Vladimir I.; Frolova, Anna A.

2013-12-01

An adaptive mesh in phase space (AMPS) methodology has been developed for solving multidimensional kinetic equations by the discrete velocity method. A Cartesian mesh for both configuration (r) and velocity (v) spaces is produced using a “tree of trees” (ToT) data structure. The r mesh is automatically generated around embedded boundaries, and is dynamically adapted to local solution properties. The v mesh is created on-the-fly in each r cell. Mappings between neighboring v-space trees is implemented for the advection operator in r space. We have developed algorithms for solving the full Boltzmann and linear Boltzmann equations with AMPS. Several recent innovations were used to calculate the discrete Boltzmann collision integral with dynamically adaptive v mesh: the importance sampling, multipoint projection, and variance reduction methods. We have developed an efficient algorithm for calculating the linear Boltzmann collision integral for elastic and inelastic collisions of hot light particles in a Lorentz gas. Our AMPS technique has been demonstrated for simulations of hypersonic rarefied gas flows, ion and electron kinetics in weakly ionized plasma, radiation and light-particle transport through thin films, and electron streaming in semiconductors. We have shown that AMPS allows minimizing the number of cells in phase space to reduce the computational cost and memory usage for solving challenging kinetic problems.

Incompressible Navier-Stokes inverse design method based on adaptive unstructured meshes

International Nuclear Information System (INIS)

Rahmati, M.T.; Charlesworth, D.; Zangeneh, M.

2005-01-01

An inverse method for blade design based on Navier-Stokes equations on adaptive unstructured meshes has been developed. In the method, unlike the method based on inviscid equations, the effect of viscosity is directly taken into account. In the method, the pressure (or pressure loading) is prescribed. The design method then computes the blade shape that would accomplish the target prescribed pressure distribution. The method is implemented using a cell-centered finite volume method, which solves the incompressible Navier-Stokes equations on unstructured meshes. An adaptive unstructured mesh method based on grid subdivision and local adaptive mesh method is utilized for increasing the accuracy. (author)

Adaptive Mesh Iteration Method for Trajectory Optimization Based on Hermite-Pseudospectral Direct Transcription

Directory of Open Access Journals (Sweden)

Humin Lei

2017-01-01

Full Text Available An adaptive mesh iteration method based on Hermite-Pseudospectral is described for trajectory optimization. The method uses the Legendre-Gauss-Lobatto points as interpolation points; then the state equations are approximated by Hermite interpolating polynomials. The method allows for changes in both number of mesh points and the number of mesh intervals and produces significantly smaller mesh sizes with a higher accuracy tolerance solution. The derived relative error estimate is then used to trade the number of mesh points with the number of mesh intervals. The adaptive mesh iteration method is applied successfully to the examples of trajectory optimization of Maneuverable Reentry Research Vehicle, and the simulation experiment results show that the adaptive mesh iteration method has many advantages.

Conforming to interface structured adaptive mesh refinement: 3D algorithm and implementation

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Nagarajan, Anand; Soghrati, Soheil

2018-03-01

A new non-iterative mesh generation algorithm named conforming to interface structured adaptive mesh refinement (CISAMR) is introduced for creating 3D finite element models of problems with complex geometries. CISAMR transforms a structured mesh composed of tetrahedral elements into a conforming mesh with low element aspect ratios. The construction of the mesh begins with the structured adaptive mesh refinement of elements in the vicinity of material interfaces. An r-adaptivity algorithm is then employed to relocate selected nodes of nonconforming elements, followed by face-swapping a small fraction of them to eliminate tetrahedrons with high aspect ratios. The final conforming mesh is constructed by sub-tetrahedralizing remaining nonconforming elements, as well as tetrahedrons with hanging nodes. In addition to studying the convergence and analyzing element-wise errors in meshes generated using CISAMR, several example problems are presented to show the ability of this method for modeling 3D problems with intricate morphologies.

Adaptive Shape Functions and Internal Mesh Adaptation for Modelling Progressive Failure in Adhesively Bonded Joints

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Stapleton, Scott; Gries, Thomas; Waas, Anthony M.; Pineda, Evan J.

2014-01-01

Enhanced finite elements are elements with an embedded analytical solution that can capture detailed local fields, enabling more efficient, mesh independent finite element analysis. The shape functions are determined based on the analytical model rather than prescribed. This method was applied to adhesively bonded joints to model joint behavior with one element through the thickness. This study demonstrates two methods of maintaining the fidelity of such elements during adhesive non-linearity and cracking without increasing the mesh needed for an accurate solution. The first method uses adaptive shape functions, where the shape functions are recalculated at each load step based on the softening of the adhesive. The second method is internal mesh adaption, where cracking of the adhesive within an element is captured by further discretizing the element internally to represent the partially cracked geometry. By keeping mesh adaptations within an element, a finer mesh can be used during the analysis without affecting the global finite element model mesh. Examples are shown which highlight when each method is most effective in reducing the number of elements needed to capture adhesive nonlinearity and cracking. These methods are validated against analogous finite element models utilizing cohesive zone elements.

Improvement of neutronic calculations on a Masurca core using adaptive mesh refinement capabilities

International Nuclear Information System (INIS)

Fournier, D.; Archier, P.; Le Tellier, R.; Suteau, C.

2011-01-01

The simulation of 3D cores with homogenized assemblies in transport theory remains time and memory consuming for production calculations. With a multigroup discretization for the energy variable and a discrete ordinate method for the angle, a system of about 10"4 coupled hyperbolic transport equations has to be solved. For these equations, we intend to optimize the spatial discretization. In the framework of the SNATCH solver used in this study, the spatial problem is dealt with by using a structured hexahedral mesh and applying a Discontinuous Galerkin Finite Element Method (DGFEM). This paper shows the improvements due to the development of Adaptive Mesh Refinement (AMR) methods. As the SNATCH solver uses a hierarchical polynomial basis, p−refinement is possible but also h−refinement thanks to non conforming capabilities. Besides, as the flux spatial behavior is highly dependent on the energy, we propose to adapt differently the spatial discretization according to the energy group. To avoid dealing with too many meshes, some energy groups are joined and share the same mesh. The different energy-dependent AMR strategies are compared to each other but also with the classical approach of a conforming and highly refined spatial mesh. This comparison is carried out on different quantities such as the multiplication factor, the flux or the current. The gain in time and memory is shown for 2D and 3D benchmarks coming from the ZONA2B experimental core configuration of the MASURCA mock-up at CEA Cadarache. (author)

Refficientlib: an efficient load-rebalanced adaptive mesh refinement algorithm for high-performance computational physics meshes

OpenAIRE

Baiges Aznar, Joan; Bayona Roa, Camilo Andrés

2017-01-01

No separate or additional fees are collected for access to or distribution of the work. In this paper we present a novel algorithm for adaptive mesh refinement in computational physics meshes in a distributed memory parallel setting. The proposed method is developed for nodally based parallel domain partitions where the nodes of the mesh belong to a single processor, whereas the elements can belong to multiple processors. Some of the main features of the algorithm presented in this paper a...

An adaptive mesh refinement approach for average current nodal expansion method in 2-D rectangular geometry

International Nuclear Information System (INIS)

Poursalehi, N.; Zolfaghari, A.; Minuchehr, A.

2013-01-01

Highlights: ► A new adaptive h-refinement approach has been developed for a class of nodal method. ► The resulting system of nodal equations is more amenable to efficient numerical solution. ► The benefit of the approach is reducing computational efforts relative to the uniform fine mesh modeling. ► Spatially adaptive approach greatly enhances the accuracy of the solution. - Abstract: The aim of this work is to develop a spatially adaptive coarse mesh strategy that progressively refines the nodes in appropriate regions of domain to solve the neutron balance equation by zeroth order nodal expansion method. A flux gradient based a posteriori estimation scheme has been utilized for checking the approximate solutions for various nodes. The relative surface net leakage of nodes has been considered as an assessment criterion. In this approach, the core module is called in by adaptive mesh generator to determine gradients of node surfaces flux to explore the possibility of node refinements in appropriate regions and directions of the problem. The benefit of the approach is reducing computational efforts relative to the uniform fine mesh modeling. For this purpose, a computer program ANRNE-2D, Adaptive Node Refinement Nodal Expansion, has been developed to solve neutron diffusion equation using average current nodal expansion method for 2D rectangular geometries. Implementing the adaptive algorithm confirms its superiority in enhancing the accuracy of the solution without using fine nodes throughout the domain and increasing the number of unknown solution. Some well-known benchmarks have been investigated and improvements are reported

Parallel 3D Mortar Element Method for Adaptive Nonconforming Meshes

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Feng, Huiyu; Mavriplis, Catherine; VanderWijngaart, Rob; Biswas, Rupak

2004-01-01

High order methods are frequently used in computational simulation for their high accuracy. An efficient way to avoid unnecessary computation in smooth regions of the solution is to use adaptive meshes which employ fine grids only in areas where they are needed. Nonconforming spectral elements allow the grid to be flexibly adjusted to satisfy the computational accuracy requirements. The method is suitable for computational simulations of unsteady problems with very disparate length scales or unsteady moving features, such as heat transfer, fluid dynamics or flame combustion. In this work, we select the Mark Element Method (MEM) to handle the non-conforming interfaces between elements. A new technique is introduced to efficiently implement MEM in 3-D nonconforming meshes. By introducing an "intermediate mortar", the proposed method decomposes the projection between 3-D elements and mortars into two steps. In each step, projection matrices derived in 2-D are used. The two-step method avoids explicitly forming/deriving large projection matrices for 3-D meshes, and also helps to simplify the implementation. This new technique can be used for both h- and p-type adaptation. This method is applied to an unsteady 3-D moving heat source problem. With our new MEM implementation, mesh adaptation is able to efficiently refine the grid near the heat source and coarsen the grid once the heat source passes. The savings in computational work resulting from the dynamic mesh adaptation is demonstrated by the reduction of the the number of elements used and CPU time spent. MEM and mesh adaptation, respectively, bring irregularity and dynamics to the computer memory access pattern. Hence, they provide a good way to gauge the performance of computer systems when running scientific applications whose memory access patterns are irregular and unpredictable. We select a 3-D moving heat source problem as the Unstructured Adaptive (UA) grid benchmark, a new component of the NAS Parallel

Adaptive mesh refinement for shocks and material interfaces

Energy Technology Data Exchange (ETDEWEB)

Dai, William Wenlong [Los Alamos National Laboratory

2010-01-01

There are three kinds of adaptive mesh refinement (AMR) in structured meshes. Block-based AMR sometimes over refines meshes. Cell-based AMR treats cells cell by cell and thus loses the advantage of the nature of structured meshes. Patch-based AMR is intended to combine advantages of block- and cell-based AMR, i.e., the nature of structured meshes and sharp regions of refinement. But, patch-based AMR has its own difficulties. For example, patch-based AMR typically cannot preserve symmetries of physics problems. In this paper, we will present an approach for a patch-based AMR for hydrodynamics simulations. The approach consists of clustering, symmetry preserving, mesh continuity, flux correction, communications, management of patches, and load balance. The special features of this patch-based AMR include symmetry preserving, efficiency of refinement across shock fronts and material interfaces, special implementation of flux correction, and patch management in parallel computing environments. To demonstrate the capability of the AMR framework, we will show both two- and three-dimensional hydrodynamics simulations with many levels of refinement.

A constrained Delaunay discretization method for adaptively meshing highly discontinuous geological media

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Wang, Yang; Ma, Guowei; Ren, Feng; Li, Tuo

2017-12-01

A constrained Delaunay discretization method is developed to generate high-quality doubly adaptive meshes of highly discontinuous geological media. Complex features such as three-dimensional discrete fracture networks (DFNs), tunnels, shafts, slopes, boreholes, water curtains, and drainage systems are taken into account in the mesh generation. The constrained Delaunay triangulation method is used to create adaptive triangular elements on planar fractures. Persson's algorithm (Persson, 2005), based on an analogy between triangular elements and spring networks, is enriched to automatically discretize a planar fracture into mesh points with varying density and smooth-quality gradient. The triangulated planar fractures are treated as planar straight-line graphs (PSLGs) to construct piecewise-linear complex (PLC) for constrained Delaunay tetrahedralization. This guarantees the doubly adaptive characteristic of the resulted mesh: the mesh is adaptive not only along fractures but also in space. The quality of elements is compared with the results from an existing method. It is verified that the present method can generate smoother elements and a better distribution of element aspect ratios. Two numerical simulations are implemented to demonstrate that the present method can be applied to various simulations of complex geological media that contain a large number of discontinuities.

The strategy of alternate direction adapted to a coarse mesh method for the solution of neutron diffusion problems

International Nuclear Information System (INIS)

Watson, F.V.

1982-01-01

An adaptation of the alternate direction method for coarse mesh calculation, is presented. The algorithm is applicable to two-and three dimensional problems, the last being the more interesting one. (E.G.) [pt

A Numerical Study of Mesh Adaptivity in Multiphase Flows with Non-Newtonian Fluids

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Percival, James; Pavlidis, Dimitrios; Xie, Zhihua; Alberini, Federico; Simmons, Mark; Pain, Christopher; Matar, Omar

2014-11-01

We present an investigation into the computational efficiency benefits of dynamic mesh adaptivity in the numerical simulation of transient multiphase fluid flow problems involving Non-Newtonian fluids. Such fluids appear in a range of industrial applications, from printing inks to toothpastes and introduce new challenges for mesh adaptivity due to the additional ``memory'' of viscoelastic fluids. Nevertheless, the multiscale nature of these flows implies huge potential benefits for a successful implementation. The study is performed using the open source package Fluidity, which couples an unstructured mesh control volume finite element solver for the multiphase Navier-Stokes equations to a dynamic anisotropic mesh adaptivity algorithm, based on estimated solution interpolation error criteria, and conservative mesh-to-mesh interpolation routine. The code is applied to problems involving rheologies ranging from simple Newtonian to shear-thinning to viscoelastic materials and verified against experimental data for various industrial and microfluidic flows. This work was undertaken as part of the EPSRC MEMPHIS programme grant EP/K003976/1.

Adaptive mesh generation for image registration and segmentation

DEFF Research Database (Denmark)

Fogtmann, Mads; Larsen, Rasmus

2013-01-01

measure. The method was tested on a T1 weighted MR volume of an adult brain and showed a 66% reduction in the number of mesh vertices compared to a red-subdivision strategy. The deformation capability of the mesh was tested by registration to five additional T1-weighted MR volumes....

Cartesian anisotropic mesh adaptation for compressible flow

International Nuclear Information System (INIS)

Keats, W.A.; Lien, F.-S.

2004-01-01

Simulating transient compressible flows involving shock waves presents challenges to the CFD practitioner in terms of the mesh quality required to resolve discontinuities and prevent smearing. This paper discusses a novel two-dimensional Cartesian anisotropic mesh adaptation technique implemented for compressible flow. This technique, developed for laminar flow by Ham, Lien and Strong, is efficient because it refines and coarsens cells using criteria that consider the solution in each of the cardinal directions separately. In this paper the method will be applied to compressible flow. The procedure shows promise in its ability to deliver good quality solutions while achieving computational savings. The convection scheme used is the Advective Upstream Splitting Method (Plus), and the refinement/ coarsening criteria are based on work done by Ham et al. Transient shock wave diffraction over a backward step and shock reflection over a forward step are considered as test cases because they demonstrate that the quality of the solution can be maintained as the mesh is refined and coarsened in time. The data structure is explained in relation to the computational mesh, and the object-oriented design and implementation of the code is presented. Refinement and coarsening algorithms are outlined. Computational savings over uniform and isotropic mesh approaches are shown to be significant. (author)

Fully anisotropic goal-oriented mesh adaptation for 3D steady Euler equations

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Loseille, A.; Dervieux, A.; Alauzet, F.

2010-04-01

This paper studies the coupling between anisotropic mesh adaptation and goal-oriented error estimate. The former is very well suited to the control of the interpolation error. It is generally interpreted as a local geometric error estimate. On the contrary, the latter is preferred when studying approximation errors for PDEs. It generally involves non local error contributions. Consequently, a full and strong coupling between both is hard to achieve due to this apparent incompatibility. This paper shows how to achieve this coupling in three steps. First, a new a priori error estimate is proved in a formal framework adapted to goal-oriented mesh adaptation for output functionals. This estimate is based on a careful analysis of the contributions of the implicit error and of the interpolation error. Second, the error estimate is applied to the set of steady compressible Euler equations which are solved by a stabilized Galerkin finite element discretization. A goal-oriented error estimation is derived. It involves the interpolation error of the Euler fluxes weighted by the gradient of the adjoint state associated with the observed functional. Third, rewritten in the continuous mesh framework, the previous estimate is minimized on the set of continuous meshes thanks to a calculus of variations. The optimal continuous mesh is then derived analytically. Thus, it can be used as a metric tensor field to drive the mesh adaptation. From a numerical point of view, this method is completely automatic, intrinsically anisotropic, and does not depend on any a priori choice of variables to perform the adaptation. 3D examples of steady flows around supersonic and transsonic jets are presented to validate the current approach and to demonstrate its efficiency.

Stress adapted embroidered meshes with a graded pattern design for abdominal wall hernia repair

Science.gov (United States)

Hahn, J.; Bittrich, L.; Breier, A.; Spickenheuer, A.

2017-10-01

Abdominal wall hernias are one of the most relevant injuries of the digestive system with 25 million patients in 2013. Surgery is recommended primarily using allogenic non-absorbable wrap-knitted meshes. These meshes have in common that their stress-strain behaviour is not adapted to the anisotropic behaviour of native abdominal wall tissue. The ideal mesh should possess an adequate mechanical behaviour and a suitable porosity at the same time. An alternative fabrication method to wrap-knitting is the embroidery technology with a high flexibility in pattern design and adaption of mechanical properties. In this study, a pattern generator was created for pattern designs consisting of a base and a reinforcement pattern. The embroidered mesh structures demonstrated different structural and mechanical characteristics. Additionally, the investigation of the mechanical properties exhibited an anisotropic mechanical behaviour for the embroidered meshes. As a result, the investigated pattern generator and the embroidery technology allow the production of stress adapted mesh structures that are a promising approach for hernia reconstruction.

Unstructured Adaptive Meshes: Bad for Your Memory?

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Biswas, Rupak; Feng, Hui-Yu; VanderWijngaart, Rob

2003-01-01

This viewgraph presentation explores the need for a NASA Advanced Supercomputing (NAS) parallel benchmark for problems with irregular dynamical memory access. This benchmark is important and necessary because: 1) Problems with localized error source benefit from adaptive nonuniform meshes; 2) Certain machines perform poorly on such problems; 3) Parallel implementation may provide further performance improvement but is difficult. Some examples of problems which use irregular dynamical memory access include: 1) Heat transfer problem; 2) Heat source term; 3) Spectral element method; 4) Base functions; 5) Elemental discrete equations; 6) Global discrete equations. Nonconforming Mesh and Mortar Element Method are covered in greater detail in this presentation.

Adaptive radial basis function mesh deformation using data reduction

Science.gov (United States)

Gillebaart, T.; Blom, D. S.; van Zuijlen, A. H.; Bijl, H.

2016-09-01

Radial Basis Function (RBF) mesh deformation is one of the most robust mesh deformation methods available. Using the greedy (data reduction) method in combination with an explicit boundary correction, results in an efficient method as shown in literature. However, to ensure the method remains robust, two issues are addressed: 1) how to ensure that the set of control points remains an accurate representation of the geometry in time and 2) how to use/automate the explicit boundary correction, while ensuring a high mesh quality. In this paper, we propose an adaptive RBF mesh deformation method, which ensures the set of control points always represents the geometry/displacement up to a certain (user-specified) criteria, by keeping track of the boundary error throughout the simulation and re-selecting when needed. Opposed to the unit displacement and prescribed displacement selection methods, the adaptive method is more robust, user-independent and efficient, for the cases considered. Secondly, the analysis of a single high aspect ratio cell is used to formulate an equation for the correction radius needed, depending on the characteristics of the correction function used, maximum aspect ratio, minimum first cell height and boundary error. Based on the analysis two new radial basis correction functions are derived and proposed. This proposed automated procedure is verified while varying the correction function, Reynolds number (and thus first cell height and aspect ratio) and boundary error. Finally, the parallel efficiency is studied for the two adaptive methods, unit displacement and prescribed displacement for both the CPU as well as the memory formulation with a 2D oscillating and translating airfoil with oscillating flap, a 3D flexible locally deforming tube and deforming wind turbine blade. Generally, the memory formulation requires less work (due to the large amount of work required for evaluating RBF's), but the parallel efficiency reduces due to the limited

Parallel Adaptive Mesh Refinement for High-Order Finite-Volume Schemes in Computational Fluid Dynamics

Science.gov (United States)

Schwing, Alan Michael

For computational fluid dynamics, the governing equations are solved on a discretized domain of nodes, faces, and cells. The quality of the grid or mesh can be a driving source for error in the results. While refinement studies can help guide the creation of a mesh, grid quality is largely determined by user expertise and understanding of the flow physics. Adaptive mesh refinement is a technique for enriching the mesh during a simulation based on metrics for error, impact on important parameters, or location of important flow features. This can offload from the user some of the difficult and ambiguous decisions necessary when discretizing the domain. This work explores the implementation of adaptive mesh refinement in an implicit, unstructured, finite-volume solver. Consideration is made for applying modern computational techniques in the presence of hanging nodes and refined cells. The approach is developed to be independent of the flow solver in order to provide a path for augmenting existing codes. It is designed to be applicable for unsteady simulations and refinement and coarsening of the grid does not impact the conservatism of the underlying numerics. The effect on high-order numerical fluxes of fourth- and sixth-order are explored. Provided the criteria for refinement is appropriately selected, solutions obtained using adapted meshes have no additional error when compared to results obtained on traditional, unadapted meshes. In order to leverage large-scale computational resources common today, the methods are parallelized using MPI. Parallel performance is considered for several test problems in order to assess scalability of both adapted and unadapted grids. Dynamic repartitioning of the mesh during refinement is crucial for load balancing an evolving grid. Development of the methods outlined here depend on a dual-memory approach that is described in detail. Validation of the solver developed here against a number of motivating problems shows favorable

Solution adaptive triangular meshes with application to the simulation of plasma equilibrium

International Nuclear Information System (INIS)

Erlebacher, G.

1984-01-01

A new discrete Laplace operator is constructed on a local mesh molecule, second order accurate on symmetric cell regions, based on local Taylor series expansions. This discrete Laplacian is then compared to the one commonly used in the literature. A truncation error analysis of gradient and Laplace operators calculated at triangle centroids reveals that the maximum bounds of their truncation errors are minimized on equilateral triangles, for a fixed triangle perimeter. A new adaptive strategy on arbitrary triangular grids is developed in which a uniform grid is defined with respect to the solution surface, as opposed to the x,y plane. Departures from mesh uniformity arises from a spacially dependent mean-curvature of the solution surface. The power of this new adaptive technique is applied to the problem of finding free-boundary plasma equilibria within the context of MHD. The geometry is toroidal, and axisymmetry in the toroidal direction is assumed. We are led to conclude that the grid should move, not towards regions of high curvature of magnetic flux, but rather towards regions of greater toroidal current density. This has a direct bearing on the accuracy with which the Grad-Shafranov equation is being approximated

Finite element method for solving Kohn-Sham equations based on self-adaptive tetrahedral mesh

International Nuclear Information System (INIS)

Zhang Dier; Shen Lihua; Zhou Aihui; Gong Xingao

2008-01-01

A finite element (FE) method with self-adaptive mesh-refinement technique is developed for solving the density functional Kohn-Sham equations. The FE method adopts local piecewise polynomials basis functions, which produces sparsely structured matrices of Hamiltonian. The method is well suitable for parallel implementation without using Fourier transform. In addition, the self-adaptive mesh-refinement technique can control the computational accuracy and efficiency with optimal mesh density in different regions

NeuroTessMesh: A Tool for the Generation and Visualization of Neuron Meshes and Adaptive On-the-Fly Refinement

Directory of Open Access Journals (Sweden)

Juan J. Garcia-Cantero

2017-06-01

Full Text Available Gaining a better understanding of the human brain continues to be one of the greatest challenges for science, largely because of the overwhelming complexity of the brain and the difficulty of analyzing the features and behavior of dense neural networks. Regarding analysis, 3D visualization has proven to be a useful tool for the evaluation of complex systems. However, the large number of neurons in non-trivial circuits, together with their intricate geometry, makes the visualization of a neuronal scenario an extremely challenging computational problem. Previous work in this area dealt with the generation of 3D polygonal meshes that approximated the cells’ overall anatomy but did not attempt to deal with the extremely high storage and computational cost required to manage a complex scene. This paper presents NeuroTessMesh, a tool specifically designed to cope with many of the problems associated with the visualization of neural circuits that are comprised of large numbers of cells. In addition, this method facilitates the recovery and visualization of the 3D geometry of cells included in databases, such as NeuroMorpho, and provides the tools needed to approximate missing information such as the soma’s morphology. This method takes as its only input the available compact, yet incomplete, morphological tracings of the cells as acquired by neuroscientists. It uses a multiresolution approach that combines an initial, coarse mesh generation with subsequent on-the-fly adaptive mesh refinement stages using tessellation shaders. For the coarse mesh generation, a novel approach, based on the Finite Element Method, allows approximation of the 3D shape of the soma from its incomplete description. Subsequently, the adaptive refinement process performed in the graphic card generates meshes that provide good visual quality geometries at a reasonable computational cost, both in terms of memory and rendering time. All the described techniques have been

Parallel paving: An algorithm for generating distributed, adaptive, all-quadrilateral meshes on parallel computers

Energy Technology Data Exchange (ETDEWEB)

Lober, R.R.; Tautges, T.J.; Vaughan, C.T.

1997-03-01

Paving is an automated mesh generation algorithm which produces all-quadrilateral elements. It can additionally generate these elements in varying sizes such that the resulting mesh adapts to a function distribution, such as an error function. While powerful, conventional paving is a very serial algorithm in its operation. Parallel paving is the extension of serial paving into parallel environments to perform the same meshing functions as conventional paving only on distributed, discretized models. This extension allows large, adaptive, parallel finite element simulations to take advantage of paving`s meshing capabilities for h-remap remeshing. A significantly modified version of the CUBIT mesh generation code has been developed to host the parallel paving algorithm and demonstrate its capabilities on both two dimensional and three dimensional surface geometries and compare the resulting parallel produced meshes to conventionally paved meshes for mesh quality and algorithm performance. Sandia`s {open_quotes}tiling{close_quotes} dynamic load balancing code has also been extended to work with the paving algorithm to retain parallel efficiency as subdomains undergo iterative mesh refinement.

Visualization of Octree Adaptive Mesh Refinement (AMR) in Astrophysical Simulations

Science.gov (United States)

Labadens, M.; Chapon, D.; Pomaréde, D.; Teyssier, R.

2012-09-01

Computer simulations are important in current cosmological research. Those simulations run in parallel on thousands of processors, and produce huge amount of data. Adaptive mesh refinement is used to reduce the computing cost while keeping good numerical accuracy in regions of interest. RAMSES is a cosmological code developed by the Commissariat à l'énergie atomique et aux énergies alternatives (English: Atomic Energy and Alternative Energies Commission) which uses Octree adaptive mesh refinement. Compared to grid based AMR, the Octree AMR has the advantage to fit very precisely the adaptive resolution of the grid to the local problem complexity. However, this specific octree data type need some specific software to be visualized, as generic visualization tools works on Cartesian grid data type. This is why the PYMSES software has been also developed by our team. It relies on the python scripting language to ensure a modular and easy access to explore those specific data. In order to take advantage of the High Performance Computer which runs the RAMSES simulation, it also uses MPI and multiprocessing to run some parallel code. We would like to present with more details our PYMSES software with some performance benchmarks. PYMSES has currently two visualization techniques which work directly on the AMR. The first one is a splatting technique, and the second one is a custom ray tracing technique. Both have their own advantages and drawbacks. We have also compared two parallel programming techniques with the python multiprocessing library versus the use of MPI run. The load balancing strategy has to be smartly defined in order to achieve a good speed up in our computation. Results obtained with this software are illustrated in the context of a massive, 9000-processor parallel simulation of a Milky Way-like galaxy.

Parallelization of Unsteady Adaptive Mesh Refinement for Unstructured Navier-Stokes Solvers

Science.gov (United States)

Schwing, Alan M.; Nompelis, Ioannis; Candler, Graham V.

2014-01-01

This paper explores the implementation of the MPI parallelization in a Navier-Stokes solver using adaptive mesh re nement. Viscous and inviscid test problems are considered for the purpose of benchmarking, as are implicit and explicit time advancement methods. The main test problem for comparison includes e ects from boundary layers and other viscous features and requires a large number of grid points for accurate computation. Ex- perimental validation against double cone experiments in hypersonic ow are shown. The adaptive mesh re nement shows promise for a staple test problem in the hypersonic com- munity. Extension to more advanced techniques for more complicated ows is described.

Object-Oriented Implementation of Adaptive Mesh Refinement Algorithms

Directory of Open Access Journals (Sweden)

William Y. Crutchfield

1993-01-01

Full Text Available We describe C++ classes that simplify development of adaptive mesh refinement (AMR algorithms. The classes divide into two groups, generic classes that are broadly useful in adaptive algorithms, and application-specific classes that are the basis for our AMR algorithm. We employ two languages, with C++ responsible for the high-level data structures, and Fortran responsible for low-level numerics. The C++ implementation is as fast as the original Fortran implementation. Use of inheritance has allowed us to extend the original AMR algorithm to other problems with greatly reduced development time.

Adaptive mesh refinement and adjoint methods in geophysics simulations

Science.gov (United States)

Burstedde, Carsten

2013-04-01

It is an ongoing challenge to increase the resolution that can be achieved by numerical geophysics simulations. This applies to considering sub-kilometer mesh spacings in global-scale mantle convection simulations as well as to using frequencies up to 1 Hz in seismic wave propagation simulations. One central issue is the numerical cost, since for three-dimensional space discretizations, possibly combined with time stepping schemes, a doubling of resolution can lead to an increase in storage requirements and run time by factors between 8 and 16. A related challenge lies in the fact that an increase in resolution also increases the dimensionality of the model space that is needed to fully parametrize the physical properties of the simulated object (a.k.a. earth). Systems that exhibit a multiscale structure in space are candidates for employing adaptive mesh refinement, which varies the resolution locally. An example that we found well suited is the mantle, where plate boundaries and fault zones require a resolution on the km scale, while deeper area can be treated with 50 or 100 km mesh spacings. This approach effectively reduces the number of computational variables by several orders of magnitude. While in this case it is possible to derive the local adaptation pattern from known physical parameters, it is often unclear what are the most suitable criteria for adaptation. We will present the goal-oriented error estimation procedure, where such criteria are derived from an objective functional that represents the observables to be computed most accurately. Even though this approach is well studied, it is rarely used in the geophysics community. A related strategy to make finer resolution manageable is to design methods that automate the inference of model parameters. Tweaking more than a handful of numbers and judging the quality of the simulation by adhoc comparisons to known facts and observations is a tedious task and fundamentally limited by the turnaround times

Adaptive mesh refinement and multilevel iteration for multiphase, multicomponent flow in porous media

Energy Technology Data Exchange (ETDEWEB)

Hornung, R.D. [Duke Univ., Durham, NC (United States)

1996-12-31

An adaptive local mesh refinement (AMR) algorithm originally developed for unsteady gas dynamics is extended to multi-phase flow in porous media. Within the AMR framework, we combine specialized numerical methods to treat the different aspects of the partial differential equations. Multi-level iteration and domain decomposition techniques are incorporated to accommodate elliptic/parabolic behavior. High-resolution shock capturing schemes are used in the time integration of the hyperbolic mass conservation equations. When combined with AMR, these numerical schemes provide high resolution locally in a more efficient manner than if they were applied on a uniformly fine computational mesh. We will discuss the interplay of physical, mathematical, and numerical concerns in the application of adaptive mesh refinement to flow in porous media problems of practical interest.

Adaptive mesh refinement in titanium

Energy Technology Data Exchange (ETDEWEB)

Colella, Phillip; Wen, Tong

2005-01-21

In this paper, we evaluate Titanium's usability as a high-level parallel programming language through a case study, where we implement a subset of Chombo's functionality in Titanium. Chombo is a software package applying the Adaptive Mesh Refinement methodology to numerical Partial Differential Equations at the production level. In Chombo, the library approach is used to parallel programming (C++ and Fortran, with MPI), whereas Titanium is a Java dialect designed for high-performance scientific computing. The performance of our implementation is studied and compared with that of Chombo in solving Poisson's equation based on two grid configurations from a real application. Also provided are the counts of lines of code from both sides.

Radiation transport code with adaptive Mesh Refinement: acceleration techniques and applications

International Nuclear Information System (INIS)

Velarde, Pedro; Garcia-Fernaandez, Carlos; Portillo, David; Barbas, Alfonso

2011-01-01

We present a study of acceleration techniques for solving Sn radiation transport equations with Adaptive Mesh Refinement (AMR). Both DSA and TSA are considered, taking into account the influence of the interaction between different levels of the mesh structure and the order of approximation in angle. A Hybrid method is proposed in order to obtain better convergence rate and lower computer times. Some examples are presented relevant to ICF and X ray secondary sources. (author)

h-Adaptive Mesh Generation using Electric Field Intensity Value as a Criterion (in Japanese)

OpenAIRE

Toyonaga, Kiyomi; Cingoski, Vlatko; Kaneda, Kazufumi; Yamashita, Hideo

1994-01-01

Finite mesh divisions are essential to obtain accurate solution of two dimensional electric field analysis. It requires the technical knowledge to generate a suitable fine mesh divisions. In electric field problem, analysts are usually interested in the electric field intensity and its distribution. In order to obtain electric field intensity with high-accuracy, we have developed and adaptive mesh generator using electric field intensity value as a criterion.

Solving kinetic equations with adaptive mesh in phase space for rarefied gas dynamics and plasma physics (Invited)

International Nuclear Information System (INIS)

Kolobov, Vladimir; Arslanbekov, Robert; Frolova, Anna

2014-01-01

The paper describes an Adaptive Mesh in Phase Space (AMPS) technique for solving kinetic equations with deterministic mesh-based methods. The AMPS technique allows automatic generation of adaptive Cartesian mesh in both physical and velocity spaces using a Tree-of-Trees data structure. We illustrate advantages of AMPS for simulations of rarefied gas dynamics and electron kinetics on low temperature plasmas. In particular, we consider formation of the velocity distribution functions in hypersonic flows, particle kinetics near oscillating boundaries, and electron kinetics in a radio-frequency sheath. AMPS provide substantial savings in computational cost and increased efficiency of the mesh-based kinetic solvers

Solving kinetic equations with adaptive mesh in phase space for rarefied gas dynamics and plasma physics (Invited)

Energy Technology Data Exchange (ETDEWEB)

Kolobov, Vladimir [CFD Research Corporation, Huntsville, AL 35805, USA and The University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Arslanbekov, Robert [CFD Research Corporation, Huntsville, AL 35805 (United States); Frolova, Anna [Computing Center of the Russian Academy of Sciences, Moscow, 119333 (Russian Federation)

2014-12-09

The paper describes an Adaptive Mesh in Phase Space (AMPS) technique for solving kinetic equations with deterministic mesh-based methods. The AMPS technique allows automatic generation of adaptive Cartesian mesh in both physical and velocity spaces using a Tree-of-Trees data structure. We illustrate advantages of AMPS for simulations of rarefied gas dynamics and electron kinetics on low temperature plasmas. In particular, we consider formation of the velocity distribution functions in hypersonic flows, particle kinetics near oscillating boundaries, and electron kinetics in a radio-frequency sheath. AMPS provide substantial savings in computational cost and increased efficiency of the mesh-based kinetic solvers.

A parallel adaptive mesh refinement algorithm for predicting turbulent non-premixed combusting flows

International Nuclear Information System (INIS)

Gao, X.; Groth, C.P.T.

2005-01-01

A parallel adaptive mesh refinement (AMR) algorithm is proposed for predicting turbulent non-premixed combusting flows characteristic of gas turbine engine combustors. The Favre-averaged Navier-Stokes equations governing mixture and species transport for a reactive mixture of thermally perfect gases in two dimensions, the two transport equations of the κ-ψ turbulence model, and the time-averaged species transport equations, are all solved using a fully coupled finite-volume formulation. A flexible block-based hierarchical data structure is used to maintain the connectivity of the solution blocks in the multi-block mesh and facilitate automatic solution-directed mesh adaptation according to physics-based refinement criteria. This AMR approach allows for anisotropic mesh refinement and the block-based data structure readily permits efficient and scalable implementations of the algorithm on multi-processor architectures. Numerical results for turbulent non-premixed diffusion flames, including cold- and hot-flow predictions for a bluff body burner, are described and compared to available experimental data. The numerical results demonstrate the validity and potential of the parallel AMR approach for predicting complex non-premixed turbulent combusting flows. (author)

Mesh adaptation technique for Fourier-domain fluorescence lifetime imaging

International Nuclear Information System (INIS)

Soloviev, Vadim Y.

2006-01-01

A novel adaptive mesh technique in the Fourier domain is introduced for problems in fluorescence lifetime imaging. A dynamical adaptation of the three-dimensional scheme based on the finite volume formulation reduces computational time and balances the ill-posed nature of the inverse problem. Light propagation in the medium is modeled by the telegraph equation, while the lifetime reconstruction algorithm is derived from the Fredholm integral equation of the first kind. Stability and computational efficiency of the method are demonstrated by image reconstruction of two spherical fluorescent objects embedded in a tissue phantom

Parallel Block Structured Adaptive Mesh Refinement on Graphics Processing Units

Energy Technology Data Exchange (ETDEWEB)

Beckingsale, D. A. [Atomic Weapons Establishment (AWE), Aldermaston (United Kingdom); Gaudin, W. P. [Atomic Weapons Establishment (AWE), Aldermaston (United Kingdom); Hornung, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gunney, B. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gamblin, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Herdman, J. A. [Atomic Weapons Establishment (AWE), Aldermaston (United Kingdom); Jarvis, S. A. [Atomic Weapons Establishment (AWE), Aldermaston (United Kingdom)

2014-11-17

Block-structured adaptive mesh refinement is a technique that can be used when solving partial differential equations to reduce the number of zones necessary to achieve the required accuracy in areas of interest. These areas (shock fronts, material interfaces, etc.) are recursively covered with finer mesh patches that are grouped into a hierarchy of refinement levels. Despite the potential for large savings in computational requirements and memory usage without a corresponding reduction in accuracy, AMR adds overhead in managing the mesh hierarchy, adding complex communication and data movement requirements to a simulation. In this paper, we describe the design and implementation of a native GPU-based AMR library, including: the classes used to manage data on a mesh patch, the routines used for transferring data between GPUs on different nodes, and the data-parallel operators developed to coarsen and refine mesh data. We validate the performance and accuracy of our implementation using three test problems and two architectures: an eight-node cluster, and over four thousand nodes of Oak Ridge National Laboratory’s Titan supercomputer. Our GPU-based AMR hydrodynamics code performs up to 4.87× faster than the CPU-based implementation, and has been scaled to over four thousand GPUs using a combination of MPI and CUDA.

Boltzmann Solver with Adaptive Mesh in Velocity Space

International Nuclear Information System (INIS)

Kolobov, Vladimir I.; Arslanbekov, Robert R.; Frolova, Anna A.

2011-01-01

We describe the implementation of direct Boltzmann solver with Adaptive Mesh in Velocity Space (AMVS) using quad/octree data structure. The benefits of the AMVS technique are demonstrated for the charged particle transport in weakly ionized plasmas where the collision integral is linear. We also describe the implementation of AMVS for the nonlinear Boltzmann collision integral. Test computations demonstrate both advantages and deficiencies of the current method for calculations of narrow-kernel distributions.

A novel partitioning method for block-structured adaptive meshes

Science.gov (United States)

Fu, Lin; Litvinov, Sergej; Hu, Xiangyu Y.; Adams, Nikolaus A.

2017-07-01

We propose a novel partitioning method for block-structured adaptive meshes utilizing the meshless Lagrangian particle concept. With the observation that an optimum partitioning has high analogy to the relaxation of a multi-phase fluid to steady state, physically motivated model equations are developed to characterize the background mesh topology and are solved by multi-phase smoothed-particle hydrodynamics. In contrast to well established partitioning approaches, all optimization objectives are implicitly incorporated and achieved during the particle relaxation to stationary state. Distinct partitioning sub-domains are represented by colored particles and separated by a sharp interface with a surface tension model. In order to obtain the particle relaxation, special viscous and skin friction models, coupled with a tailored time integration algorithm are proposed. Numerical experiments show that the present method has several important properties: generation of approximately equal-sized partitions without dependence on the mesh-element type, optimized interface communication between distinct partitioning sub-domains, continuous domain decomposition which is physically localized and implicitly incremental. Therefore it is particularly suitable for load-balancing of high-performance CFD simulations.

A novel partitioning method for block-structured adaptive meshes

Energy Technology Data Exchange (ETDEWEB)

Fu, Lin, E-mail: lin.fu@tum.de; Litvinov, Sergej, E-mail: sergej.litvinov@aer.mw.tum.de; Hu, Xiangyu Y., E-mail: xiangyu.hu@tum.de; Adams, Nikolaus A., E-mail: nikolaus.adams@tum.de

2017-07-15

We propose a novel partitioning method for block-structured adaptive meshes utilizing the meshless Lagrangian particle concept. With the observation that an optimum partitioning has high analogy to the relaxation of a multi-phase fluid to steady state, physically motivated model equations are developed to characterize the background mesh topology and are solved by multi-phase smoothed-particle hydrodynamics. In contrast to well established partitioning approaches, all optimization objectives are implicitly incorporated and achieved during the particle relaxation to stationary state. Distinct partitioning sub-domains are represented by colored particles and separated by a sharp interface with a surface tension model. In order to obtain the particle relaxation, special viscous and skin friction models, coupled with a tailored time integration algorithm are proposed. Numerical experiments show that the present method has several important properties: generation of approximately equal-sized partitions without dependence on the mesh-element type, optimized interface communication between distinct partitioning sub-domains, continuous domain decomposition which is physically localized and implicitly incremental. Therefore it is particularly suitable for load-balancing of high-performance CFD simulations.

Nyx: Adaptive mesh, massively-parallel, cosmological simulation code

Science.gov (United States)

Almgren, Ann; Beckner, Vince; Friesen, Brian; Lukic, Zarija; Zhang, Weiqun

2017-12-01

Nyx code solves equations of compressible hydrodynamics on an adaptive grid hierarchy coupled with an N-body treatment of dark matter. The gas dynamics in Nyx use a finite volume methodology on an adaptive set of 3-D Eulerian grids; dark matter is represented as discrete particles moving under the influence of gravity. Particles are evolved via a particle-mesh method, using Cloud-in-Cell deposition/interpolation scheme. Both baryonic and dark matter contribute to the gravitational field. In addition, Nyx includes physics for accurately modeling the intergalactic medium; in optically thin limits and assuming ionization equilibrium, the code calculates heating and cooling processes of the primordial-composition gas in an ionizing ultraviolet background radiation field.

Software abstractions and computational issues in parallel structure adaptive mesh methods for electronic structure calculations

Energy Technology Data Exchange (ETDEWEB)

Kohn, S.; Weare, J.; Ong, E.; Baden, S.

1997-05-01

We have applied structured adaptive mesh refinement techniques to the solution of the LDA equations for electronic structure calculations. Local spatial refinement concentrates memory resources and numerical effort where it is most needed, near the atomic centers and in regions of rapidly varying charge density. The structured grid representation enables us to employ efficient iterative solver techniques such as conjugate gradient with FAC multigrid preconditioning. We have parallelized our solver using an object- oriented adaptive mesh refinement framework.

Multiphase flow modelling of volcanic ash particle settling in water using adaptive unstructured meshes

Science.gov (United States)

Jacobs, C. T.; Collins, G. S.; Piggott, M. D.; Kramer, S. C.; Wilson, C. R. G.

2013-02-01

Small-scale experiments of volcanic ash particle settling in water have demonstrated that ash particles can either settle slowly and individually, or rapidly and collectively as a gravitationally unstable ash-laden plume. This has important implications for the emplacement of tephra deposits on the seabed. Numerical modelling has the potential to extend the results of laboratory experiments to larger scales and explore the conditions under which plumes may form and persist, but many existing models are computationally restricted by the fixed mesh approaches that they employ. In contrast, this paper presents a new multiphase flow model that uses an adaptive unstructured mesh approach. As a simulation progresses, the mesh is optimized to focus numerical resolution in areas important to the dynamics and decrease it where it is not needed, thereby potentially reducing computational requirements. Model verification is performed using the method of manufactured solutions, which shows the correct solution convergence rates. Model validation and application considers 2-D simulations of plume formation in a water tank which replicate published laboratory experiments. The numerically predicted settling velocities for both individual particles and plumes, as well as instability behaviour, agree well with experimental data and observations. Plume settling is clearly hindered by the presence of a salinity gradient, and its influence must therefore be taken into account when considering particles in bodies of saline water. Furthermore, individual particles settle in the laminar flow regime while plume settling is shown (by plume Reynolds numbers greater than unity) to be in the turbulent flow regime, which has a significant impact on entrainment and settling rates. Mesh adaptivity maintains solution accuracy while providing a substantial reduction in computational requirements when compared to the same simulation performed using a fixed mesh, highlighting the benefits of an

A DAFT DL_POLY distributed memory adaptation of the Smoothed Particle Mesh Ewald method

Science.gov (United States)

Bush, I. J.; Todorov, I. T.; Smith, W.

2006-09-01

The Smoothed Particle Mesh Ewald method [U. Essmann, L. Perera, M.L. Berkowtz, T. Darden, H. Lee, L.G. Pedersen, J. Chem. Phys. 103 (1995) 8577] for calculating long ranged forces in molecular simulation has been adapted for the parallel molecular dynamics code DL_POLY_3 [I.T. Todorov, W. Smith, Philos. Trans. Roy. Soc. London 362 (2004) 1835], making use of a novel 3D Fast Fourier Transform (DAFT) [I.J. Bush, The Daresbury Advanced Fourier transform, Daresbury Laboratory, 1999] that perfectly matches the Domain Decomposition (DD) parallelisation strategy [W. Smith, Comput. Phys. Comm. 62 (1991) 229; M.R.S. Pinches, D. Tildesley, W. Smith, Mol. Sim. 6 (1991) 51; D. Rapaport, Comput. Phys. Comm. 62 (1991) 217] of the DL_POLY_3 code. In this article we describe software adaptations undertaken to import this functionality and provide a review of its performance.

Block-structured Adaptive Mesh Refinement - Theory, Implementation and Application

Directory of Open Access Journals (Sweden)

Deiterding Ralf

2011-12-01

Full Text Available Structured adaptive mesh refinement (SAMR techniques can enable cutting-edge simulations of problems governed by conservation laws. Focusing on the strictly hyperbolic case, these notes explain all algorithmic and mathematical details of a technically relevant implementation tailored for distributed memory computers. An overview of the background of commonly used finite volume discretizations for gas dynamics is included and typical benchmarks to quantify accuracy and performance of the dynamically adaptive code are discussed. Large-scale simulations of shock-induced realistic combustion in non-Cartesian geometry and shock-driven fluid-structure interaction with fully coupled dynamic boundary motion demonstrate the applicability of the discussed techniques for complex scenarios.

Methods for high-resolution anisotropic finite element modeling of the human head: automatic MR white matter anisotropy-adaptive mesh generation.

Science.gov (United States)

Lee, Won Hee; Kim, Tae-Seong

2012-01-01

This study proposes an advanced finite element (FE) head modeling technique through which high-resolution FE meshes adaptive to the degree of tissue anisotropy can be generated. Our adaptive meshing scheme (called wMesh) uses MRI structural information and fractional anisotropy maps derived from diffusion tensors in the FE mesh generation process, optimally reflecting electrical properties of the human brain. We examined the characteristics of the wMeshes through various qualitative and quantitative comparisons to the conventional FE regular-sized meshes that are non-adaptive to the degree of white matter anisotropy. We investigated numerical differences in the FE forward solutions that include the electrical potential and current density generated by current sources in the brain. The quantitative difference was calculated by two statistical measures of relative difference measure (RDM) and magnification factor (MAG). The results show that the wMeshes are adaptive to the anisotropic density of the WM anisotropy, and they better reflect the density and directionality of tissue conductivity anisotropy. Our comparison results between various anisotropic regular mesh and wMesh models show that there are substantial differences in the EEG forward solutions in the brain (up to RDM=0.48 and MAG=0.63 in the electrical potential, and RDM=0.65 and MAG=0.52 in the current density). Our analysis results indicate that the wMeshes produce different forward solutions that are different from the conventional regular meshes. We present some results that the wMesh head modeling approach enhances the sensitivity and accuracy of the FE solutions at the interfaces or in the regions where the anisotropic conductivities change sharply or their directional changes are complex. The fully automatic wMesh generation technique should be useful for modeling an individual-specific and high-resolution anisotropic FE head model incorporating realistic anisotropic conductivity distributions

Discontinuous finite element solution of the radiation diffusion equation on arbitrary polygonal meshes and locally adapted quadrilateral grids

International Nuclear Information System (INIS)

Ragusa, Jean C.

2015-01-01

In this paper, we propose a piece-wise linear discontinuous (PWLD) finite element discretization of the diffusion equation for arbitrary polygonal meshes. It is based on the standard diffusion form and uses the symmetric interior penalty technique, which yields a symmetric positive definite linear system matrix. A preconditioned conjugate gradient algorithm is employed to solve the linear system. Piece-wise linear approximations also allow a straightforward implementation of local mesh adaptation by allowing unrefined cells to be interpreted as polygons with an increased number of vertices. Several test cases, taken from the literature on the discretization of the radiation diffusion equation, are presented: random, sinusoidal, Shestakov, and Z meshes are used. The last numerical example demonstrates the application of the PWLD discretization to adaptive mesh refinement

Assessment of fusion facility dose rate map using mesh adaptivity enhancements of hybrid Monte Carlo/deterministic techniques

International Nuclear Information System (INIS)

Ibrahim, Ahmad M.; Wilson, Paul P.; Sawan, Mohamed E.; Mosher, Scott W.; Peplow, Douglas E.; Grove, Robert E.

2014-01-01

Highlights: •Calculate the prompt dose rate everywhere throughout the entire fusion energy facility. •Utilize FW-CADIS to accurately perform difficult neutronics calculations for fusion energy systems. •Develop three mesh adaptivity algorithms to enhance FW-CADIS efficiency in fusion-neutronics calculations. -- Abstract: Three mesh adaptivity algorithms were developed to facilitate and expedite the use of the CADIS and FW-CADIS hybrid Monte Carlo/deterministic techniques in accurate full-scale neutronics simulations of fusion energy systems with immense sizes and complicated geometries. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility and resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10-day Monte Carlo calculation. Additionally, because of the significant increase in the efficiency of FW-CADIS simulations, the three algorithms enabled this difficult calculation to be accurately solved on a regular computer cluster, eliminating the need for a world-class super computer

Coupling parallel adaptive mesh refinement with a nonoverlapping domain decomposition solver

Czech Academy of Sciences Publication Activity Database

Kůs, Pavel; Šístek, Jakub

2017-01-01

Roč. 110, August (2017), s. 34-54 ISSN 0965-9978 R&D Projects: GA ČR GA14-02067S Institutional support: RVO:67985840 Keywords : adaptive mesh refinement * parallel algorithms * domain decomposition Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 3.000, year: 2016 http://www.sciencedirect.com/science/article/pii/S0965997816305737

Coupling parallel adaptive mesh refinement with a nonoverlapping domain decomposition solver

Czech Academy of Sciences Publication Activity Database

Kůs, Pavel; Šístek, Jakub

2017-01-01

Roč. 110, August (2017), s. 34-54 ISSN 0965-9978 R&D Projects: GA ČR GA14-02067S Institutional support: RVO:67985840 Keywords : adaptive mesh refinement * parallel algorithms * domain decomposition Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 3.000, year: 2016 http://www.sciencedirect.com/science/ article /pii/S0965997816305737

Thermal-chemical Mantle Convection Models With Adaptive Mesh Refinement

Science.gov (United States)

Leng, W.; Zhong, S.

2008-12-01

In numerical modeling of mantle convection, resolution is often crucial for resolving small-scale features. New techniques, adaptive mesh refinement (AMR), allow local mesh refinement wherever high resolution is needed, while leaving other regions with relatively low resolution. Both computational efficiency for large- scale simulation and accuracy for small-scale features can thus be achieved with AMR. Based on the octree data structure [Tu et al. 2005], we implement the AMR techniques into the 2-D mantle convection models. For pure thermal convection models, benchmark tests show that our code can achieve high accuracy with relatively small number of elements both for isoviscous cases (i.e. 7492 AMR elements v.s. 65536 uniform elements) and for temperature-dependent viscosity cases (i.e. 14620 AMR elements v.s. 65536 uniform elements). We further implement tracer-method into the models for simulating thermal-chemical convection. By appropriately adding and removing tracers according to the refinement of the meshes, our code successfully reproduces the benchmark results in van Keken et al. [1997] with much fewer elements and tracers compared with uniform-mesh models (i.e. 7552 AMR elements v.s. 16384 uniform elements, and ~83000 tracers v.s. ~410000 tracers). The boundaries of the chemical piles in our AMR code can be easily refined to the scales of a few kilometers for the Earth's mantle and the tracers are concentrated near the chemical boundaries to precisely trace the evolvement of the boundaries. It is thus very suitable for our AMR code to study the thermal-chemical convection problems which need high resolution to resolve the evolvement of chemical boundaries, such as the entrainment problems [Sleep, 1988].

A new adaptive mesh refinement data structure with an application to detonation

Science.gov (United States)

Ji, Hua; Lien, Fue-Sang; Yee, Eugene

2010-11-01

A new Cell-based Structured Adaptive Mesh Refinement (CSAMR) data structure is developed. In our CSAMR data structure, Cartesian-like indices are used to identify each cell. With these stored indices, the information on the parent, children and neighbors of a given cell can be accessed simply and efficiently. Owing to the usage of these indices, the computer memory required for storage of the proposed AMR data structure is only {5}/{8} word per cell, in contrast to the conventional oct-tree [P. MacNeice, K.M. Olson, C. Mobary, R. deFainchtein, C. Packer, PARAMESH: a parallel adaptive mesh refinement community toolkit, Comput. Phys. Commun. 330 (2000) 126] and the fully threaded tree (FTT) [A.M. Khokhlov, Fully threaded tree algorithms for adaptive mesh fluid dynamics simulations, J. Comput. Phys. 143 (1998) 519] data structures which require, respectively, 19 and 2{3}/{8} words per cell for storage of the connectivity information. Because the connectivity information (e.g., parent, children and neighbors) of a cell in our proposed AMR data structure can be accessed using only the cell indices, a tree structure which was required in previous approaches for the organization of the AMR data is no longer needed for this new data structure. Instead, a much simpler hash table structure is used to maintain the AMR data, with the entry keys in the hash table obtained directly from the explicitly stored cell indices. The proposed AMR data structure simplifies the implementation and parallelization of an AMR code. Two three-dimensional test cases are used to illustrate and evaluate the computational performance of the new CSAMR data structure.

A moving mesh finite difference method for equilibrium radiation diffusion equations

Energy Technology Data Exchange (ETDEWEB)

Yang, Xiaobo, E-mail: xwindyb@126.com [Department of Mathematics, College of Science, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Huang, Weizhang, E-mail: whuang@ku.edu [Department of Mathematics, University of Kansas, Lawrence, KS 66045 (United States); Qiu, Jianxian, E-mail: jxqiu@xmu.edu.cn [School of Mathematical Sciences and Fujian Provincial Key Laboratory of Mathematical Modeling and High-Performance Scientific Computing, Xiamen University, Xiamen, Fujian 361005 (China)

2015-10-01

An efficient moving mesh finite difference method is developed for the numerical solution of equilibrium radiation diffusion equations in two dimensions. The method is based on the moving mesh partial differential equation approach and moves the mesh continuously in time using a system of meshing partial differential equations. The mesh adaptation is controlled through a Hessian-based monitor function and the so-called equidistribution and alignment principles. Several challenging issues in the numerical solution are addressed. Particularly, the radiation diffusion coefficient depends on the energy density highly nonlinearly. This nonlinearity is treated using a predictor–corrector and lagged diffusion strategy. Moreover, the nonnegativity of the energy density is maintained using a cutoff method which has been known in literature to retain the accuracy and convergence order of finite difference approximation for parabolic equations. Numerical examples with multi-material, multiple spot concentration situations are presented. Numerical results show that the method works well for radiation diffusion equations and can produce numerical solutions of good accuracy. It is also shown that a two-level mesh movement strategy can significantly improve the efficiency of the computation.

A moving mesh finite difference method for equilibrium radiation diffusion equations

International Nuclear Information System (INIS)

Yang, Xiaobo; Huang, Weizhang; Qiu, Jianxian

2015-01-01

An efficient moving mesh finite difference method is developed for the numerical solution of equilibrium radiation diffusion equations in two dimensions. The method is based on the moving mesh partial differential equation approach and moves the mesh continuously in time using a system of meshing partial differential equations. The mesh adaptation is controlled through a Hessian-based monitor function and the so-called equidistribution and alignment principles. Several challenging issues in the numerical solution are addressed. Particularly, the radiation diffusion coefficient depends on the energy density highly nonlinearly. This nonlinearity is treated using a predictor–corrector and lagged diffusion strategy. Moreover, the nonnegativity of the energy density is maintained using a cutoff method which has been known in literature to retain the accuracy and convergence order of finite difference approximation for parabolic equations. Numerical examples with multi-material, multiple spot concentration situations are presented. Numerical results show that the method works well for radiation diffusion equations and can produce numerical solutions of good accuracy. It is also shown that a two-level mesh movement strategy can significantly improve the efficiency of the computation

Error estimation for goal-oriented spatial adaptivity for the SN equations on triangular meshes

International Nuclear Information System (INIS)

Lathouwers, D.

2011-01-01

In this paper we investigate different error estimation procedures for use within a goal oriented adaptive algorithm for the S N equations on unstructured meshes. The method is based on a dual-weighted residual approach where an appropriate adjoint problem is formulated and solved in order to obtain the importance of residual errors in the forward problem on the specific goal of interest. The forward residuals and the adjoint function are combined to obtain both economical finite element meshes tailored to the solution of the target functional as well as providing error estimates. Various approximations made to make the calculation of the adjoint angular flux more economically attractive are evaluated by comparing the performance of the resulting adaptive algorithm and the quality of the error estimators when applied to two shielding-type test problems. (author)

Automatic mesh adaptivity for CADIS and FW-CADIS neutronics modeling of difficult shielding problems

International Nuclear Information System (INIS)

Ibrahim, A. M.; Peplow, D. E.; Mosher, S. W.; Wagner, J. C.; Evans, T. M.; Wilson, P. P.; Sawan, M. E.

2013-01-01

The CADIS and FW-CADIS hybrid Monte Carlo/deterministic techniques dramatically increase the efficiency of neutronics modeling, but their use in the accurate design analysis of very large and geometrically complex nuclear systems has been limited by the large number of processors and memory requirements for their preliminary deterministic calculations and final Monte Carlo calculation. Three mesh adaptivity algorithms were developed to reduce the memory requirements of CADIS and FW-CADIS without sacrificing their efficiency improvement. First, a macro-material approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm de-couples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility. Using these algorithms resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10-day Monte Carlo calculation and, additionally, increased the efficiency of the Monte Carlo simulation by a factor of at least 3.4. The three algorithms enabled this difficult calculation to be accurately solved using an FW-CADIS simulation on a regular computer cluster, obviating the need for a world-class super computer. (authors)

Automatic mesh adaptivity for hybrid Monte Carlo/deterministic neutronics modeling of difficult shielding problems

International Nuclear Information System (INIS)

Ibrahim, Ahmad M.; Wilson, Paul P.H.; Sawan, Mohamed E.; Mosher, Scott W.; Peplow, Douglas E.; Wagner, John C.; Evans, Thomas M.; Grove, Robert E.

2015-01-01

The CADIS and FW-CADIS hybrid Monte Carlo/deterministic techniques dramatically increase the efficiency of neutronics modeling, but their use in the accurate design analysis of very large and geometrically complex nuclear systems has been limited by the large number of processors and memory requirements for their preliminary deterministic calculations and final Monte Carlo calculation. Three mesh adaptivity algorithms were developed to reduce the memory requirements of CADIS and FW-CADIS without sacrificing their efficiency improvement. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility. Using these algorithms resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10-day Monte Carlo calculation and, additionally, increased the efficiency of the Monte Carlo simulation by a factor of at least 3.4. The three algorithms enabled this difficult calculation to be accurately solved using an FW-CADIS simulation on a regular computer cluster, eliminating the need for a world-class super computer

Controlling the error on target motion through real-time mesh adaptation: Applications to deep brain stimulation.

Science.gov (United States)

Bui, Huu Phuoc; Tomar, Satyendra; Courtecuisse, Hadrien; Audette, Michel; Cotin, Stéphane; Bordas, Stéphane P A

2018-05-01

An error-controlled mesh refinement procedure for needle insertion simulations is presented. As an example, the procedure is applied for simulations of electrode implantation for deep brain stimulation. We take into account the brain shift phenomena occurring when a craniotomy is performed. We observe that the error in the computation of the displacement and stress fields is localised around the needle tip and the needle shaft during needle insertion simulation. By suitably and adaptively refining the mesh in this region, our approach enables to control, and thus to reduce, the error whilst maintaining a coarser mesh in other parts of the domain. Through academic and practical examples we demonstrate that our adaptive approach, as compared with a uniform coarse mesh, increases the accuracy of the displacement and stress fields around the needle shaft and, while for a given accuracy, saves computational time with respect to a uniform finer mesh. This facilitates real-time simulations. The proposed methodology has direct implications in increasing the accuracy, and controlling the computational expense of the simulation of percutaneous procedures such as biopsy, brachytherapy, regional anaesthesia, or cryotherapy. Moreover, the proposed approach can be helpful in the development of robotic surgeries because the simulation taking place in the control loop of a robot needs to be accurate, and to occur in real time. Copyright © 2018 John Wiley & Sons, Ltd.

3-D inversion of airborne electromagnetic data parallelized and accelerated by local mesh and adaptive soundings

Science.gov (United States)

Yang, Dikun; Oldenburg, Douglas W.; Haber, Eldad

2014-03-01

Airborne electromagnetic (AEM) methods are highly efficient tools for assessing the Earth's conductivity structures in a large area at low cost. However, the configuration of AEM measurements, which typically have widely distributed transmitter-receiver pairs, makes the rigorous modelling and interpretation extremely time-consuming in 3-D. Excessive overcomputing can occur when working on a large mesh covering the entire survey area and inverting all soundings in the data set. We propose two improvements. The first is to use a locally optimized mesh for each AEM sounding for the forward modelling and calculation of sensitivity. This dedicated local mesh is small with fine cells near the sounding location and coarse cells far away in accordance with EM diffusion and the geometric decay of the signals. Once the forward problem is solved on the local meshes, the sensitivity for the inversion on the global mesh is available through quick interpolation. Using local meshes for AEM forward modelling avoids unnecessary computing on fine cells on a global mesh that are far away from the sounding location. Since local meshes are highly independent, the forward modelling can be efficiently parallelized over an array of processors. The second improvement is random and dynamic down-sampling of the soundings. Each inversion iteration only uses a random subset of the soundings, and the subset is reselected for every iteration. The number of soundings in the random subset, determined by an adaptive algorithm, is tied to the degree of model regularization. This minimizes the overcomputing caused by working with redundant soundings. Our methods are compared against conventional methods and tested with a synthetic example. We also invert a field data set that was previously considered to be too large to be practically inverted in 3-D. These examples show that our methodology can dramatically reduce the processing time of 3-D inversion to a practical level without losing resolution

Parallel Implementation and Scaling of an Adaptive Mesh Discrete Ordinates Algorithm for Transport

International Nuclear Information System (INIS)

Howell, L H

2004-01-01

Block-structured adaptive mesh refinement (AMR) uses a mesh structure built up out of locally-uniform rectangular grids. In the BoxLib parallel framework used by the Raptor code, each processor operates on one or more of these grids at each refinement level. The decomposition of the mesh into grids and the distribution of these grids among processors may change every few timesteps as a calculation proceeds. Finer grids use smaller timesteps than coarser grids, requiring additional work to keep the system synchronized and ensure conservation between different refinement levels. In a paper for NECDC 2002 I presented preliminary results on implementation of parallel transport sweeps on the AMR mesh, conjugate gradient acceleration, accuracy of the AMR solution, and scalar speedup of the AMR algorithm compared to a uniform fully-refined mesh. This paper continues with a more in-depth examination of the parallel scaling properties of the scheme, both in single-level and multi-level calculations. Both sweeping and setup costs are considered. The algorithm scales with acceptable performance to several hundred processors. Trends suggest, however, that this is the limit for efficient calculations with traditional transport sweeps, and that modifications to the sweep algorithm will be increasingly needed as job sizes in the thousands of processors become common

Using high-order methods on adaptively refined block-structured meshes - discretizations, interpolations, and filters.

Energy Technology Data Exchange (ETDEWEB)

Ray, Jaideep; Lefantzi, Sophia; Najm, Habib N.; Kennedy, Christopher A.

2006-01-01

Block-structured adaptively refined meshes (SAMR) strive for efficient resolution of partial differential equations (PDEs) solved on large computational domains by clustering mesh points only where required by large gradients. Previous work has indicated that fourth-order convergence can be achieved on such meshes by using a suitable combination of high-order discretizations, interpolations, and filters and can deliver significant computational savings over conventional second-order methods at engineering error tolerances. In this paper, we explore the interactions between the errors introduced by discretizations, interpolations and filters. We develop general expressions for high-order discretizations, interpolations, and filters, in multiple dimensions, using a Fourier approach, facilitating the high-order SAMR implementation. We derive a formulation for the necessary interpolation order for given discretization and derivative orders. We also illustrate this order relationship empirically using one and two-dimensional model problems on refined meshes. We study the observed increase in accuracy with increasing interpolation order. We also examine the empirically observed order of convergence, as the effective resolution of the mesh is increased by successively adding levels of refinement, with different orders of discretization, interpolation, or filtering.

COSMOLOGICAL ADAPTIVE MESH REFINEMENT MAGNETOHYDRODYNAMICS WITH ENZO

International Nuclear Information System (INIS)

Collins, David C.; Xu Hao; Norman, Michael L.; Li Hui; Li Shengtai

2010-01-01

In this work, we present EnzoMHD, the extension of the cosmological code Enzo to include the effects of magnetic fields through the ideal magnetohydrodynamics approximation. We use a higher order Godunov method for the computation of interface fluxes. We use two constrained transport methods to compute the electric field from those interface fluxes, which simultaneously advances the induction equation and maintains the divergence of the magnetic field. A second-order divergence-free reconstruction technique is used to interpolate the magnetic fields in the block-structured adaptive mesh refinement framework already extant in Enzo. This reconstruction also preserves the divergence of the magnetic field to machine precision. We use operator splitting to include gravity and cosmological expansion. We then present a series of cosmological and non-cosmological test problems to demonstrate the quality of solution resulting from this combination of solvers.

A short note on the use of the red-black tree in Cartesian adaptive mesh refinement algorithms

Science.gov (United States)

Hasbestan, Jaber J.; Senocak, Inanc

2017-12-01

Mesh adaptivity is an indispensable capability to tackle multiphysics problems with large disparity in time and length scales. With the availability of powerful supercomputers, there is a pressing need to extend time-proven computational techniques to extreme-scale problems. Cartesian adaptive mesh refinement (AMR) is one such method that enables simulation of multiscale, multiphysics problems. AMR is based on construction of octrees. Originally, an explicit tree data structure was used to generate and manipulate an adaptive Cartesian mesh. At least eight pointers are required in an explicit approach to construct an octree. Parent-child relationships are then used to traverse the tree. An explicit octree, however, is expensive in terms of memory usage and the time it takes to traverse the tree to access a specific node. For these reasons, implicit pointerless methods have been pioneered within the computer graphics community, motivated by applications requiring interactivity and realistic three dimensional visualization. Lewiner et al. [1] provides a concise review of pointerless approaches to generate an octree. Use of a hash table and Z-order curve are two key concepts in pointerless methods that we briefly discuss next.

Polyhedral shape model for terrain correction of gravity and gravity gradient data based on an adaptive mesh

Science.gov (United States)

Guo, Zhikui; Chen, Chao; Tao, Chunhui

2016-04-01

Since 2007, there are four China Da yang cruises (CDCs), which have been carried out to investigate polymetallic sulfides in the southwest Indian ridge (SWIR) and have acquired both gravity data and bathymetry data on the corresponding survey lines(Tao et al., 2014). Sandwell et al. (2014) published a new global marine gravity model including the free air gravity data and its first order vertical gradient (Vzz). Gravity data and its gradient can be used to extract unknown density structure information(e.g. crust thickness) under surface of the earth, but they contain all the mass effect under the observation point. Therefore, how to get accurate gravity and its gradient effect of the existing density structure (e.g. terrain) has been a key issue. Using the bathymetry data or ETOPO1 (http://www.ngdc.noaa.gov/mgg/global/global.html) model at a full resolution to calculate the terrain effect could spend too much computation time. We expect to develop an effective method that takes less time but can still yield the desired accuracy. In this study, a constant-density polyhedral model is used to calculate the gravity field and its vertical gradient, which is based on the work of Tsoulis (2012). According to gravity field attenuation with distance and variance of bathymetry, we present an adaptive mesh refinement and coarsening strategies to merge both global topography data and multi-beam bathymetry data. The local coarsening or size of mesh depends on user-defined accuracy and terrain variation (Davis et al., 2011). To depict terrain better, triangular surface element and rectangular surface element are used in fine and coarse mesh respectively. This strategy can also be applied to spherical coordinate in large region and global scale. Finally, we applied this method to calculate Bouguer gravity anomaly (BGA), mantle Bouguer anomaly(MBA) and their vertical gradient in SWIR. Further, we compared the result with previous results in the literature. Both synthetic model

An object-oriented and quadrilateral-mesh based solution adaptive algorithm for compressible multi-fluid flows

Science.gov (United States)

Zheng, H. W.; Shu, C.; Chew, Y. T.

2008-07-01

In this paper, an object-oriented and quadrilateral-mesh based solution adaptive algorithm for the simulation of compressible multi-fluid flows is presented. The HLLC scheme (Harten, Lax and van Leer approximate Riemann solver with the Contact wave restored) is extended to adaptively solve the compressible multi-fluid flows under complex geometry on unstructured mesh. It is also extended to the second-order of accuracy by using MUSCL extrapolation. The node, edge and cell are arranged in such an object-oriented manner that each of them inherits from a basic object. A home-made double link list is designed to manage these objects so that the inserting of new objects and removing of the existing objects (nodes, edges and cells) are independent of the number of objects and only of the complexity of O( 1). In addition, the cells with different levels are further stored in different lists. This avoids the recursive calculation of solution of mother (non-leaf) cells. Thus, high efficiency is obtained due to these features. Besides, as compared to other cell-edge adaptive methods, the separation of nodes would reduce the memory requirement of redundant nodes, especially in the cases where the level number is large or the space dimension is three. Five two-dimensional examples are used to examine its performance. These examples include vortex evolution problem, interface only problem under structured mesh and unstructured mesh, bubble explosion under the water, bubble-shock interaction, and shock-interface interaction inside the cylindrical vessel. Numerical results indicate that there is no oscillation of pressure and velocity across the interface and it is feasible to apply it to solve compressible multi-fluid flows with large density ratio (1000) and strong shock wave (the pressure ratio is 10,000) interaction with the interface.

Strategies in edge plasma simulation using adaptive dynamic nodalization techniques

International Nuclear Information System (INIS)

Kainz, A.; Weimann, G.; Kamelander, G.

2003-01-01

A wide span of steady-state and transient edge plasma processes simulation problems require accurate discretization techniques and can then be treated with Finite Element (FE) and Finite Volume (FV) methods. The software used here to meet these meshing requirements is a 2D finite element grid generator. It allows to produce adaptive unstructured grids taking into consideration the flux surface characteristics. To comply with the common mesh handling features of FE/FV packages, some options have been added to the basic generation tool. These enhancements include quadrilateral meshes without non-regular transition elements obtained by substituting them by transition constructions consisting of regular quadrilateral elements. Furthermore triangular grids can be created with one edge parallel to the magnetic field and modified by the basic adaptation/realignment techniques. Enhanced code operation properties and processing capabilities are expected. (author)

A Parallel, Multi-Scale Watershed-Hydrologic-Inundation Model with Adaptively Switching Mesh for Capturing Flooding and Lake Dynamics

Science.gov (United States)

Ji, X.; Shen, C.

2017-12-01

Flood inundation presents substantial societal hazards and also changes biogeochemistry for systems like the Amazon. It is often expensive to simulate high-resolution flood inundation and propagation in a long-term watershed-scale model. Due to the Courant-Friedrichs-Lewy (CFL) restriction, high resolution and large local flow velocity both demand prohibitively small time steps even for parallel codes. Here we develop a parallel surface-subsurface process-based model enhanced by multi-resolution meshes that are adaptively switched on or off. The high-resolution overland flow meshes are enabled only when the flood wave invades to floodplains. This model applies semi-implicit, semi-Lagrangian (SISL) scheme in solving dynamic wave equations, and with the assistant of the multi-mesh method, it also adaptively chooses the dynamic wave equation only in the area of deep inundation. Therefore, the model achieves a balance between accuracy and computational cost.

Tetrahedral meshing via maximal Poisson-disk sampling

KAUST Repository

Guo, Jianwei

2016-02-15

In this paper, we propose a simple yet effective method to generate 3D-conforming tetrahedral meshes from closed 2-manifold surfaces. Our approach is inspired by recent work on maximal Poisson-disk sampling (MPS), which can generate well-distributed point sets in arbitrary domains. We first perform MPS on the boundary of the input domain, we then sample the interior of the domain, and we finally extract the tetrahedral mesh from the samples by using 3D Delaunay or regular triangulation for uniform or adaptive sampling, respectively. We also propose an efficient optimization strategy to protect the domain boundaries and to remove slivers to improve the meshing quality. We present various experimental results to illustrate the efficiency and the robustness of our proposed approach. We demonstrate that the performance and quality (e.g., minimal dihedral angle) of our approach are superior to current state-of-the-art optimization-based approaches.

Energy dependent mesh adaptivity of discontinuous isogeometric discrete ordinate methods with dual weighted residual error estimators

Science.gov (United States)

Owens, A. R.; Kópházi, J.; Welch, J. A.; Eaton, M. D.

2017-04-01

In this paper a hanging-node, discontinuous Galerkin, isogeometric discretisation of the multigroup, discrete ordinates (SN) equations is presented in which each energy group has its own mesh. The equations are discretised using Non-Uniform Rational B-Splines (NURBS), which allows the coarsest mesh to exactly represent the geometry for a wide range of engineering problems of interest; this would not be the case using straight-sided finite elements. Information is transferred between meshes via the construction of a supermesh. This is a non-trivial task for two arbitrary meshes, but is significantly simplified here by deriving every mesh from a common coarsest initial mesh. In order to take full advantage of this flexible discretisation, goal-based error estimators are derived for the multigroup, discrete ordinates equations with both fixed (extraneous) and fission sources, and these estimators are used to drive an adaptive mesh refinement (AMR) procedure. The method is applied to a variety of test cases for both fixed and fission source problems. The error estimators are found to be extremely accurate for linear NURBS discretisations, with degraded performance for quadratic discretisations owing to a reduction in relative accuracy of the "exact" adjoint solution required to calculate the estimators. Nevertheless, the method seems to produce optimal meshes in the AMR process for both linear and quadratic discretisations, and is ≈×100 more accurate than uniform refinement for the same amount of computational effort for a 67 group deep penetration shielding problem.

Adaptive Fault-Tolerant Routing in 2D Mesh with Cracky Rectangular Model

Directory of Open Access Journals (Sweden)

Yi Yang

2014-01-01

Full Text Available This paper mainly focuses on routing in two-dimensional mesh networks. We propose a novel faulty block model, which is cracky rectangular block, for fault-tolerant adaptive routing. All the faulty nodes and faulty links are surrounded in this type of block, which is a convex structure, in order to avoid routing livelock. Additionally, the model constructs the interior spanning forest for each block in order to keep in touch with the nodes inside of each block. The procedure for block construction is dynamically and totally distributed. The construction algorithm is simple and ease of implementation. And this is a fully adaptive block which will dynamically adjust its scale in accordance with the situation of networks, either the fault emergence or the fault recovery, without shutdown of the system. Based on this model, we also develop a distributed fault-tolerant routing algorithm. Then we give the formal proof for this algorithm to guarantee that messages will always reach their destinations if and only if the destination nodes keep connecting with these mesh networks. So the new model and routing algorithm maximize the availability of the nodes in networks. This is a noticeable overall improvement of fault tolerability of the system.

Reference Computational Meshing Strategy for Computational Fluid Dynamics Simulation of Departure from Nucleate BoilingReference Computational Meshing Strategy for Computational Fluid Dynamics Simulation of Departure from Nucleate Boiling

Energy Technology Data Exchange (ETDEWEB)

Pointer, William David [ORNL

2017-08-01

The objective of this effort is to establish a strategy and process for generation of suitable computational mesh for computational fluid dynamics simulations of departure from nucleate boiling in a 5 by 5 fuel rod assembly held in place by PWR mixing vane spacer grids. This mesh generation process will support ongoing efforts to develop, demonstrate and validate advanced multi-phase computational fluid dynamics methods that enable more robust identification of dryout conditions and DNB occurrence.Building upon prior efforts and experience, multiple computational meshes were developed using the native mesh generation capabilities of the commercial CFD code STAR-CCM+. These meshes were used to simulate two test cases from the Westinghouse 5 by 5 rod bundle facility. The sensitivity of predicted quantities of interest to the mesh resolution was then established using two evaluation methods, the Grid Convergence Index method and the Least Squares method. This evaluation suggests that the Least Squares method can reliably establish the uncertainty associated with local parameters such as vector velocity components at a point in the domain or surface averaged quantities such as outlet velocity magnitude. However, neither method is suitable for characterization of uncertainty in global extrema such as peak fuel surface temperature, primarily because such parameters are not necessarily associated with a fixed point in space. This shortcoming is significant because the current generation algorithm for identification of DNB event conditions relies on identification of such global extrema. Ongoing efforts to identify DNB based on local surface conditions will address this challenge

System modelling and online optimal management of MicroGrid using Mesh Adaptive Direct Search

Energy Technology Data Exchange (ETDEWEB)

Mohamed, Faisal A. [Department of Electrical Engineering, Omar Al-Mukhtar University, P.O. Box 919, El-Bieda (Libya); Koivo, Heikki N. [Department of Automation and Systems Technology, Helsinki University of Technology, P.O. Box 5500, FIN-02015 HUT (Finland)

2010-06-15

This paper presents a generalized formulation to determine the optimal operating strategy and cost optimization scheme for a MicroGrid. Prior to the optimization of the MicroGrid itself, models for the system components are determined using real data. The proposed cost function takes into consideration the costs of the emissions, NO{sub x}, SO{sub 2}, and CO{sub 2}, start-up costs, as well as the operation and maintenance costs. A daily income and outgo from sold or purchased power is also added. The MicroGrid considered in this paper consists of a wind turbine, a micro turbine, a diesel generator, a photovoltaic array, a fuel cell, and a battery storage. In this work, the Mesh Adaptive Direct Search (MADS) algorithm is used to minimize the cost function of the system while constraining it to meet the customer demand and safety of the system. In comparison with previously proposed techniques, a significant reduction is obtained. (author)

Behavioural strategy: Adaptability context

Directory of Open Access Journals (Sweden)

Piórkowska Katarzyna

2016-05-01

Full Text Available The paper is embedded in the following fields: strategic management in terms of behavioural strategy concept, adaptability construct, and micro-foundations realm as well as organizational theory and psychology. Moreover, the paper concerns to some extent a multi-level approach in strategic management involving individual, team, and organizational level. The aim of the paper is to contribute to extend, on one hand, the ascertainment set in the field of behavioural strategy as behavioural strategy encompasses a mindboggling diversity of topics and methods and its conceptual unity has been hard to achieve (Powell, Lovallo, Fox 2011, p. 1371, and on the other hand, to order mixed approaches to adaptability especially to gain insights on micro-level adapting processes (individual adaptability and adaptive performance in terms of the multi-level approach. The method that has been used is literature studies and the interference is mostly deductive. The structure of the manuscript is four-fold. The first part involves the considerations in the field of adaptability and adaptive performance at the individual level. The issues of adaptability and adaptive performance at the team level have been presented in the second part. The third part encompasses the organizational adaptability assertions. Finally, the conclusion, limitations of the considerations highlighted as well as the future research directions have been emphasized. The overarching key finding is that the behavioural strategy concept may constitute the boundary spanner in exploring and explaining adaptability phenomenon at different levels of analysis.

Three dimensional adaptive mesh refinement on a spherical shell for atmospheric models with lagrangian coordinates

Science.gov (United States)

Penner, Joyce E.; Andronova, Natalia; Oehmke, Robert C.; Brown, Jonathan; Stout, Quentin F.; Jablonowski, Christiane; van Leer, Bram; Powell, Kenneth G.; Herzog, Michael

2007-07-01

One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL.

Three dimensional adaptive mesh refinement on a spherical shell for atmospheric models with lagrangian coordinates

International Nuclear Information System (INIS)

Penner, Joyce E; Andronova, Natalia; Oehmke, Robert C; Brown, Jonathan; Stout, Quentin F; Jablonowski, Christiane; Leer, Bram van; Powell, Kenneth G; Herzog, Michael

2007-01-01

One of the most important advances needed in global climate models is the development of atmospheric General Circulation Models (GCMs) that can reliably treat convection. Such GCMs require high resolution in local convectively active regions, both in the horizontal and vertical directions. During previous research we have developed an Adaptive Mesh Refinement (AMR) dynamical core that can adapt its grid resolution horizontally. Our approach utilizes a finite volume numerical representation of the partial differential equations with floating Lagrangian vertical coordinates and requires resolving dynamical processes on small spatial scales. For the latter it uses a newly developed general-purpose library, which facilitates 3D block-structured AMR on spherical grids. The library manages neighbor information as the blocks adapt, and handles the parallel communication and load balancing, freeing the user to concentrate on the scientific modeling aspects of their code. In particular, this library defines and manages adaptive blocks on the sphere, provides user interfaces for interpolation routines and supports the communication and load-balancing aspects for parallel applications. We have successfully tested the library in a 2-D (longitude-latitude) implementation. During the past year, we have extended the library to treat adaptive mesh refinement in the vertical direction. Preliminary results are discussed. This research project is characterized by an interdisciplinary approach involving atmospheric science, computer science and mathematical/numerical aspects. The work is done in close collaboration between the Atmospheric Science, Computer Science and Aerospace Engineering Departments at the University of Michigan and NOAA GFDL

An efficient Adaptive Mesh Refinement (AMR) algorithm for the Discontinuous Galerkin method: Applications for the computation of compressible two-phase flows

Science.gov (United States)

Papoutsakis, Andreas; Sazhin, Sergei S.; Begg, Steven; Danaila, Ionut; Luddens, Francky

2018-06-01

We present an Adaptive Mesh Refinement (AMR) method suitable for hybrid unstructured meshes that allows for local refinement and de-refinement of the computational grid during the evolution of the flow. The adaptive implementation of the Discontinuous Galerkin (DG) method introduced in this work (ForestDG) is based on a topological representation of the computational mesh by a hierarchical structure consisting of oct- quad- and binary trees. Adaptive mesh refinement (h-refinement) enables us to increase the spatial resolution of the computational mesh in the vicinity of the points of interest such as interfaces, geometrical features, or flow discontinuities. The local increase in the expansion order (p-refinement) at areas of high strain rates or vorticity magnitude results in an increase of the order of accuracy in the region of shear layers and vortices. A graph of unitarian-trees, representing hexahedral, prismatic and tetrahedral elements is used for the representation of the initial domain. The ancestral elements of the mesh can be split into self-similar elements allowing each tree to grow branches to an arbitrary level of refinement. The connectivity of the elements, their genealogy and their partitioning are described by linked lists of pointers. An explicit calculation of these relations, presented in this paper, facilitates the on-the-fly splitting, merging and repartitioning of the computational mesh by rearranging the links of each node of the tree with a minimal computational overhead. The modal basis used in the DG implementation facilitates the mapping of the fluxes across the non conformal faces. The AMR methodology is presented and assessed using a series of inviscid and viscous test cases. Also, the AMR methodology is used for the modelling of the interaction between droplets and the carrier phase in a two-phase flow. This approach is applied to the analysis of a spray injected into a chamber of quiescent air, using the Eulerian

Energy mesh optimization for multi-level calculation schemes

International Nuclear Information System (INIS)

Mosca, P.; Taofiki, A.; Bellier, P.; Prevost, A.

2011-01-01

The industrial calculations of third generation nuclear reactors are based on sophisticated strategies of homogenization and collapsing at different spatial and energetic levels. An important issue to ensure the quality of these calculation models is the choice of the collapsing energy mesh. In this work, we show a new approach to generate optimized energy meshes starting from the SHEM 281-group library. The optimization model is applied on 1D cylindrical cells and consists of finding an energy mesh which minimizes the errors between two successive collision probability calculations. The former is realized over the fine SHEM mesh with Livolant-Jeanpierre self-shielded cross sections and the latter is performed with collapsed cross sections over the energy mesh being optimized. The optimization is done by the particle swarm algorithm implemented in the code AEMC and multigroup flux solutions are obtained from standard APOLLO2 solvers. By this new approach, a set of new optimized meshes which encompass from 10 to 50 groups has been defined for PWR and BWR calculations. This set will allow users to adapt the energy detail of the solution to the complexity of the calculation (assembly, multi-assembly, two-dimensional whole core). Some preliminary verifications, in which the accuracy of the new meshes is measured compared to a direct 281-group calculation, show that the 30-group optimized mesh offers a good compromise between simulation time and accuracy for a standard 17 x 17 UO 2 assembly with and without control rods. (author)

An h-adaptive mesh method for Boltzmann-BGK/hydrodynamics coupling

International Nuclear Information System (INIS)

Cai Zhenning; Li Ruo

2010-01-01

We introduce a coupled method for hydrodynamic and kinetic equations on 2-dimensional h-adaptive meshes. We adopt the Euler equations with a fast kinetic solver in the region near thermodynamical equilibrium, while use the Boltzmann-BGK equation in kinetic regions where fluids are far from equilibrium. A buffer zone is created around the kinetic regions, on which a gradually varying numerical flux is adopted. Based on the property of a continuously discretized cut-off function which describes how the flux varies, the coupling will be conservative. In order for the conservative 2-dimensional specularly reflective boundary condition to be implemented conveniently, the discrete Maxwellian is approximated by a high order continuous formula with improved accuracy on a disc instead of on a square domain. The h-adaptive method can work smoothly with a time-split numerical scheme. Through h-adaptation, the cell number is greatly reduced. This method is particularly suitable for problems with hydrodynamics breakdown on only a small part of the whole domain, so that the total efficiency of the algorithm can be greatly improved. Three numerical examples are presented to validate the proposed method and demonstrate its efficiency.

TU-AB-202-05: GPU-Based 4D Deformable Image Registration Using Adaptive Tetrahedral Mesh Modeling

International Nuclear Information System (INIS)

Zhong, Z; Zhuang, L; Gu, X; Wang, J; Chen, H; Zhen, X

2016-01-01

Purpose: Deformable image registration (DIR) has been employed today as an automated and effective segmentation method to transfer tumor or organ contours from the planning image to daily images, instead of manual segmentation. However, the computational time and accuracy of current DIR approaches are still insufficient for online adaptive radiation therapy (ART), which requires real-time and high-quality image segmentation, especially in a large datasets of 4D-CT images. The objective of this work is to propose a new DIR algorithm, with fast computational speed and high accuracy, by using adaptive feature-based tetrahedral meshing and GPU-based parallelization. Methods: The first step is to generate the adaptive tetrahedral mesh based on the image features of a reference phase of 4D-CT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. Subsequently, the deformation vector fields (DVF) and other phases of 4D-CT can be obtained by matching each phase of the target 4D-CT images with the corresponding deformed reference phase. The proposed 4D DIR method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its parallel computing ability. Results: A 4D NCAT digital phantom was used to test the efficiency and accuracy of our method. Both the image and DVF results show that the fine structures and shapes of lung are well preserved, and the tumor position is well captured, i.e., 3D distance error is 1.14 mm. Compared to the previous voxel-based CPU implementation of DIR, such as demons, the proposed method is about 160x faster for registering a 10-phase 4D-CT with a phase dimension of 256×256×150. Conclusion: The proposed 4D DIR method uses feature-based mesh and GPU-based parallelism, which demonstrates the capability to compute both high-quality image and motion results, with significant improvement on the computational speed.

TU-AB-202-05: GPU-Based 4D Deformable Image Registration Using Adaptive Tetrahedral Mesh Modeling

Energy Technology Data Exchange (ETDEWEB)

Zhong, Z; Zhuang, L [Wayne State University, Detroit, MI (United States); Gu, X; Wang, J [UT Southwestern Medical Center, Dallas, TX (United States); Chen, H; Zhen, X [Southern Medical University, Guangzhou, Guangdong (China)

2016-06-15

Purpose: Deformable image registration (DIR) has been employed today as an automated and effective segmentation method to transfer tumor or organ contours from the planning image to daily images, instead of manual segmentation. However, the computational time and accuracy of current DIR approaches are still insufficient for online adaptive radiation therapy (ART), which requires real-time and high-quality image segmentation, especially in a large datasets of 4D-CT images. The objective of this work is to propose a new DIR algorithm, with fast computational speed and high accuracy, by using adaptive feature-based tetrahedral meshing and GPU-based parallelization. Methods: The first step is to generate the adaptive tetrahedral mesh based on the image features of a reference phase of 4D-CT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. Subsequently, the deformation vector fields (DVF) and other phases of 4D-CT can be obtained by matching each phase of the target 4D-CT images with the corresponding deformed reference phase. The proposed 4D DIR method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its parallel computing ability. Results: A 4D NCAT digital phantom was used to test the efficiency and accuracy of our method. Both the image and DVF results show that the fine structures and shapes of lung are well preserved, and the tumor position is well captured, i.e., 3D distance error is 1.14 mm. Compared to the previous voxel-based CPU implementation of DIR, such as demons, the proposed method is about 160x faster for registering a 10-phase 4D-CT with a phase dimension of 256×256×150. Conclusion: The proposed 4D DIR method uses feature-based mesh and GPU-based parallelism, which demonstrates the capability to compute both high-quality image and motion results, with significant improvement on the computational speed.

GAMER: A GRAPHIC PROCESSING UNIT ACCELERATED ADAPTIVE-MESH-REFINEMENT CODE FOR ASTROPHYSICS

International Nuclear Information System (INIS)

Schive, H.-Y.; Tsai, Y.-C.; Chiueh Tzihong

2010-01-01

We present the newly developed code, GPU-accelerated Adaptive-MEsh-Refinement code (GAMER), which adopts a novel approach in improving the performance of adaptive-mesh-refinement (AMR) astrophysical simulations by a large factor with the use of the graphic processing unit (GPU). The AMR implementation is based on a hierarchy of grid patches with an oct-tree data structure. We adopt a three-dimensional relaxing total variation diminishing scheme for the hydrodynamic solver and a multi-level relaxation scheme for the Poisson solver. Both solvers have been implemented in GPU, by which hundreds of patches can be advanced in parallel. The computational overhead associated with the data transfer between the CPU and GPU is carefully reduced by utilizing the capability of asynchronous memory copies in GPU, and the computing time of the ghost-zone values for each patch is diminished by overlapping it with the GPU computations. We demonstrate the accuracy of the code by performing several standard test problems in astrophysics. GAMER is a parallel code that can be run in a multi-GPU cluster system. We measure the performance of the code by performing purely baryonic cosmological simulations in different hardware implementations, in which detailed timing analyses provide comparison between the computations with and without GPU(s) acceleration. Maximum speed-up factors of 12.19 and 10.47 are demonstrated using one GPU with 4096 3 effective resolution and 16 GPUs with 8192 3 effective resolution, respectively.

An adaptive mesh refinement-multiphase lattice Boltzmann flux solver for simulation of complex binary fluid flows

Science.gov (United States)

Yuan, H. Z.; Wang, Y.; Shu, C.

2017-12-01

This paper presents an adaptive mesh refinement-multiphase lattice Boltzmann flux solver (AMR-MLBFS) for effective simulation of complex binary fluid flows at large density ratios. In this method, an AMR algorithm is proposed by introducing a simple indicator on the root block for grid refinement and two possible statuses for each block. Unlike available block-structured AMR methods, which refine their mesh by spawning or removing four child blocks simultaneously, the present method is able to refine its mesh locally by spawning or removing one to four child blocks independently when the refinement indicator is triggered. As a result, the AMR mesh used in this work can be more focused on the flow region near the phase interface and its size is further reduced. In each block of mesh, the recently proposed MLBFS is applied for the solution of the flow field and the level-set method is used for capturing the fluid interface. As compared with existing AMR-lattice Boltzmann models, the present method avoids both spatial and temporal interpolations of density distribution functions so that converged solutions on different AMR meshes and uniform grids can be obtained. The proposed method has been successfully validated by simulating a static bubble immersed in another fluid, a falling droplet, instabilities of two-layered fluids, a bubble rising in a box, and a droplet splashing on a thin film with large density ratios and high Reynolds numbers. Good agreement with the theoretical solution, the uniform-grid result, and/or the published data has been achieved. Numerical results also show its effectiveness in saving computational time and virtual memory as compared with computations on uniform meshes.

A moving mesh method with variable relaxation time

OpenAIRE

Soheili, Ali Reza; Stockie, John M.

2006-01-01

We propose a moving mesh adaptive approach for solving time-dependent partial differential equations. The motion of spatial grid points is governed by a moving mesh PDE (MMPDE) in which a mesh relaxation time \\tau is employed as a regularization parameter. Previously reported results on MMPDEs have invariably employed a constant value of the parameter \\tau. We extend this standard approach by incorporating a variable relaxation time that is calculated adaptively alongside the solution in orde...

Dynamic Mesh Adaptation for Front Evolution Using Discontinuous Galerkin Based Weighted Condition Number Mesh Relaxation

Energy Technology Data Exchange (ETDEWEB)

Greene, Patrick T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schofield, Samuel P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nourgaliev, Robert [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-06-21

A new mesh smoothing method designed to cluster mesh cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function being computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered elds, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well for the weight function as the actual level set. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Dynamic cases for moving interfaces are presented to demonstrate the method's potential usefulness to arbitrary Lagrangian Eulerian (ALE) methods.

MHD simulations on an unstructured mesh

International Nuclear Information System (INIS)

Strauss, H.R.; Park, W.; Belova, E.; Fu, G.Y.; Sugiyama, L.E.

1998-01-01

Two reasons for using an unstructured computational mesh are adaptivity, and alignment with arbitrarily shaped boundaries. Two codes which use finite element discretization on an unstructured mesh are described. FEM3D solves 2D and 3D RMHD using an adaptive grid. MH3D++, which incorporates methods of FEM3D into the MH3D generalized MHD code, can be used with shaped boundaries, which might be 3D

Stabilized Conservative Level Set Method with Adaptive Wavelet-based Mesh Refinement

Science.gov (United States)

Shervani-Tabar, Navid; Vasilyev, Oleg V.

2016-11-01

This paper addresses one of the main challenges of the conservative level set method, namely the ill-conditioned behavior of the normal vector away from the interface. An alternative formulation for reconstruction of the interface is proposed. Unlike the commonly used methods which rely on the unit normal vector, Stabilized Conservative Level Set (SCLS) uses a modified renormalization vector with diminishing magnitude away from the interface. With the new formulation, in the vicinity of the interface the reinitialization procedure utilizes compressive flux and diffusive terms only in the normal direction to the interface, thus, preserving the conservative level set properties, while away from the interfaces the directional diffusion mechanism automatically switches to homogeneous diffusion. The proposed formulation is robust and general. It is especially well suited for use with adaptive mesh refinement (AMR) approaches due to need for a finer resolution in the vicinity of the interface in comparison with the rest of the domain. All of the results were obtained using the Adaptive Wavelet Collocation Method, a general AMR-type method, which utilizes wavelet decomposition to adapt on steep gradients in the solution while retaining a predetermined order of accuracy.

Automatic mesh refinement and local multigrid methods for contact problems: application to the Pellet-Cladding mechanical Interaction

International Nuclear Information System (INIS)

Liu, Hao

2016-01-01

This Ph.D. work takes place within the framework of studies on Pellet-Cladding mechanical Interaction (PCI) which occurs in the fuel rods of pressurized water reactor. This manuscript focuses on automatic mesh refinement to simulate more accurately this phenomena while maintaining acceptable computational time and memory space for industrial calculations. An automatic mesh refinement strategy based on the combination of the Local Defect Correction multigrid method (LDC) with the Zienkiewicz and Zhu a posteriori error estimator is proposed. The estimated error is used to detect the zones to be refined, where the local sub-grids of the LDC method are generated. Several stopping criteria are studied to end the refinement process when the solution is accurate enough or when the refinement does not improve the global solution accuracy anymore. Numerical results for elastic 2D test cases with pressure discontinuity show the efficiency of the proposed strategy. The automatic mesh refinement in case of unilateral contact problems is then considered. The strategy previously introduced can be easily adapted to the multi-body refinement by estimating solution error on each body separately. Post-processing is often necessary to ensure the conformity of the refined areas regarding the contact boundaries. A variety of numerical experiments with elastic contact (with or without friction, with or without an initial gap) confirms the efficiency and adaptability of the proposed strategy. (author) [fr

Expressing Adaptation Strategies Using Adaptation Patterns

Science.gov (United States)

Zemirline, N.; Bourda, Y.; Reynaud, C.

2012-01-01

Today, there is a real challenge to enable personalized access to information. Several systems have been proposed to address this challenge including Adaptive Hypermedia Systems (AHSs). However, the specification of adaptation strategies remains a difficult task for creators of such systems. In this paper, we consider the problem of the definition…

Fluid flow and heat transfer investigation of pebble bed reactors using mesh adaptive large-eddy simulation

International Nuclear Information System (INIS)

Pavlidis, D.; Lathouwers, D.

2011-01-01

A computational fluid dynamics model with anisotropic mesh adaptivity is used to investigate coolant flow and heat transfer in pebble bed reactors. A novel method for implicitly incorporating solid boundaries based on multi-fluid flow modelling is adopted. The resulting model is able to resolve and simulate flow and heat transfer in randomly packed beds, regardless of the actual geometry, starting off with arbitrarily coarse meshes. The model is initially evaluated using an orderly stacked square channel of channel-height-to-particle diameter ratio of unity for a range of Reynolds numbers. The model is then applied to the face-centred cubical geometry. Coolant flow and heat transfer patterns are investigated. (author)

Sierra toolkit computational mesh conceptual model

International Nuclear Information System (INIS)

Baur, David G.; Edwards, Harold Carter; Cochran, William K.; Williams, Alan B.; Sjaardema, Gregory D.

2010-01-01

The Sierra Toolkit computational mesh is a software library intended to support massively parallel multi-physics computations on dynamically changing unstructured meshes. This domain of intended use is inherently complex due to distributed memory parallelism, parallel scalability, heterogeneity of physics, heterogeneous discretization of an unstructured mesh, and runtime adaptation of the mesh. Management of this inherent complexity begins with a conceptual analysis and modeling of this domain of intended use; i.e., development of a domain model. The Sierra Toolkit computational mesh software library is designed and implemented based upon this domain model. Software developers using, maintaining, or extending the Sierra Toolkit computational mesh library must be familiar with the concepts/domain model presented in this report.

Efficient computation of the elastography inverse problem by combining variational mesh adaption and a clustering technique

International Nuclear Information System (INIS)

Arnold, Alexander; Bruhns, Otto T; Reichling, Stefan; Mosler, Joern

2010-01-01

This paper is concerned with an efficient implementation suitable for the elastography inverse problem. More precisely, the novel algorithm allows us to compute the unknown stiffness distribution in soft tissue by means of the measured displacement field by considerably reducing the numerical cost compared to previous approaches. This is realized by combining and further elaborating variational mesh adaption with a clustering technique similar to those known from digital image compression. Within the variational mesh adaption, the underlying finite element discretization is only locally refined if this leads to a considerable improvement of the numerical solution. Additionally, the numerical complexity is reduced by the aforementioned clustering technique, in which the parameters describing the stiffness of the respective soft tissue are sorted according to a predefined number of intervals. By doing so, the number of unknowns associated with the elastography inverse problem can be chosen explicitly. A positive side effect of this method is the reduction of artificial noise in the data (smoothing of the solution). The performance and the rate of convergence of the resulting numerical formulation are critically analyzed by numerical examples.

Fluid flow and heat transfer investigation of pebble bed reactors using mesh-adaptive LES

International Nuclear Information System (INIS)

Pavlidis, Dimitrios; Lathouwers, Danny

2013-01-01

The very high temperature reactor is one of the designs currently being considered for nuclear power generation. One its variants is the pebble bed reactor in which the coolant passes through complex geometries (pores) at high Reynolds numbers. A computational fluid dynamics model with anisotropic mesh adaptivity is used to investigate coolant flow and heat transfer in such reactors. A novel method for implicitly incorporating solid boundaries based on multi-fluid flow modelling is adopted. The resulting model is able to resolve and simulate flow and heat transfer in randomly packed beds, regardless of the actual geometry, starting off with arbitrarily coarse meshes. The model is initially evaluated using an orderly stacked square channel of channel-height-to-particle diameter ratio of unity for a range of Reynolds numbers. The model is then applied to the face-centred cubical geometry. coolant flow and heat transfer patterns are investigated

3D Adaptive Mesh Refinement Simulations of Pellet Injection in Tokamaks

International Nuclear Information System (INIS)

Samtaney, S.; Jardin, S.C.; Colella, P.; Martin, D.F.

2003-01-01

We present results of Adaptive Mesh Refinement (AMR) simulations of the pellet injection process, a proven method of refueling tokamaks. AMR is a computationally efficient way to provide the resolution required to simulate realistic pellet sizes relative to device dimensions. The mathematical model comprises of single-fluid MHD equations with source terms in the continuity equation along with a pellet ablation rate model. The numerical method developed is an explicit unsplit upwinding treatment of the 8-wave formulation, coupled with a MAC projection method to enforce the solenoidal property of the magnetic field. The Chombo framework is used for AMR. The role of the E x B drift in mass redistribution during inside and outside pellet injections is emphasized

Interference Effects Redress over Power-Efficient Wireless-Friendly Mesh Networks for Ubiquitous Sensor Communications across Smart Cities.

Science.gov (United States)

Santana, Jose; Marrero, Domingo; Macías, Elsa; Mena, Vicente; Suárez, Álvaro

2017-07-21

Ubiquitous sensing allows smart cities to take control of many parameters (e.g., road traffic, air or noise pollution levels, etc.). An inexpensive Wireless Mesh Network can be used as an efficient way to transport sensed data. When that mesh is autonomously powered (e.g., solar powered), it constitutes an ideal portable network system which can be deployed when needed. Nevertheless, its power consumption must be restrained to extend its operational cycle and for preserving the environment. To this end, our strategy fosters wireless interface deactivation among nodes which do not participate in any route. As we show, this contributes to a significant power saving for the mesh. Furthermore, our strategy is wireless-friendly, meaning that it gives priority to deactivation of nodes receiving (and also causing) interferences from (to) the rest of the smart city. We also show that a routing protocol can adapt to this strategy in which certain nodes deactivate their own wireless interfaces.

Feature-Sensitive Tetrahedral Mesh Generation with Guaranteed Quality

OpenAIRE

Wang, Jun; Yu, Zeyun

2012-01-01

Tetrahedral meshes are being extensively used in finite element methods (FEM). This paper proposes an algorithm to generate feature-sensitive and high-quality tetrahedral meshes from an arbitrary surface mesh model. A top-down octree subdivision is conducted on the surface mesh and a set of tetrahedra are constructed using adaptive body-centered cubic (BCC) lattices. Special treatments are given to the tetrahedra near the surface such that the quality of the resulting tetrahedral mesh is prov...

A chimera grid scheme. [multiple overset body-conforming mesh system for finite difference adaptation to complex aircraft configurations

Science.gov (United States)

Steger, J. L.; Dougherty, F. C.; Benek, J. A.

1983-01-01

A mesh system composed of multiple overset body-conforming grids is described for adapting finite-difference procedures to complex aircraft configurations. In this so-called 'chimera mesh,' a major grid is generated about a main component of the configuration and overset minor grids are used to resolve all other features. Methods for connecting overset multiple grids and modifications of flow-simulation algorithms are discussed. Computational tests in two dimensions indicate that the use of multiple overset grids can simplify the task of grid generation without an adverse effect on flow-field algorithms and computer code complexity.

Geometrically Consistent Mesh Modification

KAUST Repository

Bonito, A.

2010-01-01

A new paradigm of adaptivity is to execute refinement, coarsening, and smoothing of meshes on manifolds with incomplete information about their geometry and yet preserve position and curvature accuracy. We refer to this collectively as geometrically consistent (GC) mesh modification. We discuss the concept of discrete GC, show the failure of naive approaches, and propose and analyze a simple algorithm that is GC and accuracy preserving. © 2010 Society for Industrial and Applied Mathematics.

A versatile embedded boundary adaptive mesh method for compressible flow in complex geometry

KAUST Repository

Almarouf, Mohamad Abdulilah Alhusain Alali

2017-02-25

We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. A PDE multidimensional extrapolation approach is used to reconstruct the solution in the ghost-fluid regions and imposing boundary conditions on the fluid-solid interface, coupled with a multi-dimensional algebraic interpolation for freshly cleared cells. The CNS equations are numerically solved by the second order multidimensional upwind method. Block-structured adaptive mesh refinement, implemented with the Chombo framework, is utilized to reduce the computational cost while keeping high resolution mesh around the embedded boundary and regions of high gradient solutions. The versatility of the method is demonstrated via several numerical examples, in both static and moving geometry, ranging from low Mach number nearly incompressible flows to supersonic flows. Our simulation results are extensively verified against other numerical results and validated against available experimental results where applicable. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well.

A versatile embedded boundary adaptive mesh method for compressible flow in complex geometry

KAUST Repository

Almarouf, Mohamad Abdulilah Alhusain Alali; Samtaney, Ravi

2017-01-01

We present an embedded ghost-fluid method for numerical solutions of the compressible Navier Stokes (CNS) equations in arbitrary complex domains. A PDE multidimensional extrapolation approach is used to reconstruct the solution in the ghost-fluid regions and imposing boundary conditions on the fluid-solid interface, coupled with a multi-dimensional algebraic interpolation for freshly cleared cells. The CNS equations are numerically solved by the second order multidimensional upwind method. Block-structured adaptive mesh refinement, implemented with the Chombo framework, is utilized to reduce the computational cost while keeping high resolution mesh around the embedded boundary and regions of high gradient solutions. The versatility of the method is demonstrated via several numerical examples, in both static and moving geometry, ranging from low Mach number nearly incompressible flows to supersonic flows. Our simulation results are extensively verified against other numerical results and validated against available experimental results where applicable. The significance and advantages of our implementation, which revolve around balancing between the solution accuracy and implementation difficulties, are briefly discussed as well.

The quasidiffusion method for transport problems on unstructured meshes

Science.gov (United States)

Wieselquist, William A.

2009-06-01

In this work, we develop a quasidiffusion (QD) method for solving radiation transport problems on unstructured quadrilateral meshes in 2D Cartesian geometry, for example hanging-node meshes from adaptive mesh refinement (AMR) applications or skewed quadrilateral meshes from radiation hydrodynamics with Lagrangian meshing. The main result of the work is a new low-order quasidiffusion (LOQD) discretization on arbitrary quadrilaterals and a strategy for the efficient iterative solution which uses Krylov methods and incomplete LU factorization (ILU) preconditioning. The LOQD equations are a non-symmetric set of first-order PDEs that in second-order form resembles convection- diffusion with a diffusion tensor, with the difference that the LOQD equations contain extra cross-derivative terms. Our finite volume (FV) discretization of the LOQD equations is compared with three LOQD discretizations from literature. We then present a conservative, short characteristics discretization based on subcell balances (SCSB) that uses polynomial exponential moments to achieve robust behavior in various limits (e.g. small cells and voids) and is second- order accurate in space. A linear representation of the isotropic component of the scattering source based on face-average and cell-average scalar fluxes is also proposed and shown to be effective in some problems. In numerical tests, our QD method with linear scattering source representation shows some advantages compared to other transport methods. We conclude with avenues for future research and note that this QD method may easily be extended to arbitrary meshes in 3D Cartesian geometry.

SU-D-207-04: GPU-Based 4D Cone-Beam CT Reconstruction Using Adaptive Meshing Method

International Nuclear Information System (INIS)

Zhong, Z; Gu, X; Iyengar, P; Mao, W; Wang, J; Guo, X

2015-01-01

Purpose: Due to the limited number of projections at each phase, the image quality of a four-dimensional cone-beam CT (4D-CBCT) is often degraded, which decreases the accuracy of subsequent motion modeling. One of the promising methods is the simultaneous motion estimation and image reconstruction (SMEIR) approach. The objective of this work is to enhance the computational speed of the SMEIR algorithm using adaptive feature-based tetrahedral meshing and GPU-based parallelization. Methods: The first step is to generate the tetrahedral mesh based on the features of a reference phase 4D-CBCT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. After the mesh generation, the updated motion model and other phases of 4D-CBCT can be obtained by matching the 4D-CBCT projection images at each phase with the corresponding forward projections of the deformed reference phase of 4D-CBCT. The entire process of this 4D-CBCT reconstruction method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its tremendous parallel computing ability. Results: A 4D XCAT digital phantom was used to test the proposed mesh-based image reconstruction algorithm. The image Result shows both bone structures and inside of the lung are well-preserved and the tumor position can be well captured. Compared to the previous voxel-based CPU implementation of SMEIR, the proposed method is about 157 times faster for reconstructing a 10 -phase 4D-CBCT with dimension 256×256×150. Conclusion: The GPU-based parallel 4D CBCT reconstruction method uses the feature-based mesh for estimating motion model and demonstrates equivalent image Result with previous voxel-based SMEIR approach, with significantly improved computational speed

Direct numerical simulation of bubbles with adaptive mesh refinement with distributed algorithms

International Nuclear Information System (INIS)

Talpaert, Arthur

2017-01-01

This PhD work presents the implementation of the simulation of two-phase flows in conditions of water-cooled nuclear reactors, at the scale of individual bubbles. To achieve that, we study several models for Thermal-Hydraulic flows and we focus on a technique for the capture of the thin interface between liquid and vapour phases. We thus review some possible techniques for adaptive Mesh Refinement (AMR) and provide algorithmic and computational tools adapted to patch-based AMR, which aim is to locally improve the precision in regions of interest. More precisely, we introduce a patch-covering algorithm designed with balanced parallel computing in mind. This approach lets us finely capture changes located at the interface, as we show for advection test cases as well as for models with hyperbolic-elliptic coupling. The computations we present also include the simulation of the incompressible Navier-Stokes system, which models the shape changes of the interface between two non-miscible fluids. (author) [fr

A shape and mesh adaptive computational methodology for gamma ray dose from volumetric sources

International Nuclear Information System (INIS)

Mirza, N.M.; Ali, B.; Mirza, S.M.; Tufail, M.; Ahmad, N.

1991-01-01

Indoor external exposure to the population is dominated by gamma rays emitted from the walls and the floor of a room. A shape and mesh size adaptive flux calculational approach has been developed for a typical wall source. Parametric studies of the effect of mesh size on flux calculations have been done. The optimum value of the mesh size is found to depend strongly on distance from the source, permissible limits on uncertainty in flux predictions and on computer Central Processing Unit time. To test the computations, a typical wall source was reduced to a point, a line and an infinite volume source having finite thickness, and the computed flux values were compared with values from corresponding analytical expressions for these sources. Results indicate that the errors under optimum conditions remain less than 6% for the fluxes calculated from this approach when compared with the analytical values for the point and the line source approximations. Also, when the wall is simulated as an infinite volume source having finite thickness, the errors in computed to analytical flux ratios remain large for smaller wall dimensions. However, the errors become less than 10% when the wall dimensions are greater than ten mean free paths for 3 MeV gamma rays. Also, specific dose rates from this methodology remain within the difference of 15% for the values obtained by Monte Carlo method. (author)

Analytic-Numerical Approach to Solving Singularly Perturbed Parabolic Equations with the Use of Dynamic Adapted Meshes

Directory of Open Access Journals (Sweden)

D. V. Lukyanenko

2016-01-01

Full Text Available The main objective of the paper is to present a new analytic-numerical approach to singularly perturbed reaction-diffusion-advection models with solutions containing moving interior layers (fronts. We describe some methods to generate the dynamic adapted meshes for an efficient numerical solution of such problems. It is based on a priori information about the moving front properties provided by the asymptotic analysis. In particular, for the mesh construction we take into account a priori asymptotic evaluation of the location and speed of the moving front, its width and structure. Our algorithms significantly reduce the CPU time and enhance the stability of the numerical process compared with classical approaches.The article is published in the authors’ wording.

Adaptive upscaling with the dual mesh method

Energy Technology Data Exchange (ETDEWEB)

Guerillot, D.; Verdiere, S.

1997-08-01

The objective of this paper is to demonstrate that upscaling should be calculated during the flow simulation instead of trying to enhance the a priori upscaling methods. Hence, counter-examples are given to motivate our approach, the so-called Dual Mesh Method. The main steps of this numerical algorithm are recalled. Applications illustrate the necessity to consider different average relative permeability values depending on the direction in space. Moreover, these values could be different for the same average saturation. This proves that an a priori upscaling cannot be the answer even in homogeneous cases because of the {open_quotes}dynamical heterogeneity{close_quotes} created by the saturation profile. Other examples show the efficiency of the Dual Mesh Method applied to heterogeneous medium and to an actual field case in South America.

Goal based mesh adaptivity for fixed source radiation transport calculations

International Nuclear Information System (INIS)

Baker, C.M.J.; Buchan, A.G.; Pain, C.C.; Tollit, B.S.; Goffin, M.A.; Merton, S.R.; Warner, P.

2013-01-01

Highlights: ► Derives an anisotropic goal based error measure for shielding problems. ► Reduces the error in the detector response by optimizing the finite element mesh. ► Anisotropic adaptivity captures material interfaces using fewer elements than AMR. ► A new residual based on the numerical scheme chosen forms the error measure. ► The error measure also combines the forward and adjoint metrics in a novel way. - Abstract: In this paper, the application of goal based error measures for anisotropic adaptivity applied to shielding problems in which a detector is present is explored. Goal based adaptivity is important when the response of a detector is required to ensure that dose limits are adhered to. To achieve this, a dual (adjoint) problem is solved which solves the neutron transport equation in terms of the response variables, in this case the detector response. The methods presented can be applied to general finite element solvers, however, the derivation of the residuals are dependent on the underlying finite element scheme which is also discussed in this paper. Once error metrics for the forward and adjoint solutions have been formed they are combined using a novel approach. The two metrics are combined by forming the minimum ellipsoid that covers both the error metrics rather than taking the maximum ellipsoid that is contained within the metrics. Another novel approach used within this paper is the construction of the residual. The residual, used to form the goal based error metrics, is calculated from the subgrid scale correction which is inherent in the underlying spatial discretisation employed

Evaluation of optical data gained by ARAMIS-measurement of abdominal wall movements for an anisotropic pattern design of stress-adapted hernia meshes produced by embroidery technology

Science.gov (United States)

Breier, A.; Bittrich, L.; Hahn, J.; Spickenheuer, A.

2017-10-01

For the sustainable repair of abdominal wall hernia the application of hernia meshes is required. One reason for the relapse of hernia after surgery is seen in an inadequate adaption of the mechanical properties of the mesh to the movements of the abdominal wall. Differences in the stiffness of the mesh and the abdominal tissue cause tension, friction and stress resulting in a deficient tissue response and subsequently in a recurrence of a hernia, preferentially in the marginal area of the mesh. Embroidery technology enables a targeted influence on the mechanical properties of the generated textile structure by a directed thread deposition. Textile parameters like stitch density, alignment and angle can be changed easily and locally in the embroidery pattern to generate a space-resolved mesh with mechanical properties adapted to the requirement of the surrounding tissue. To determine those requirements the movements of the abdominal wall and the resulting distortions need to be known. This study was conducted to gain optical data of the abdominal wall movements by non-invasive ARAMIS-measurement on 39 test persons to estimate direction and value of the major strains.

Adaptive mesh refinement with spectral accuracy for magnetohydrodynamics in two space dimensions

International Nuclear Information System (INIS)

Rosenberg, D; Pouquet, A; Mininni, P D

2007-01-01

We examine the effect of accuracy of high-order spectral element methods, with or without adaptive mesh refinement (AMR), in the context of a classical configuration of magnetic reconnection in two space dimensions, the so-called Orszag-Tang (OT) vortex made up of a magnetic X-point centred on a stagnation point of the velocity. A recently developed spectral-element adaptive refinement incompressible magnetohydrodynamic (MHD) code is applied to simulate this problem. The MHD solver is explicit, and uses the Elsaesser formulation on high-order elements. It automatically takes advantage of the adaptive grid mechanics that have been described elsewhere in the fluid context (Rosenberg et al 2006 J. Comput. Phys. 215 59-80); the code allows both statically refined and dynamically refined grids. Tests of the algorithm using analytic solutions are described, and comparisons of the OT solutions with pseudo-spectral computations are performed. We demonstrate for moderate Reynolds numbers that the algorithms using both static and refined grids reproduce the pseudo-spectral solutions quite well. We show that low-order truncation-even with a comparable number of global degrees of freedom-fails to correctly model some strong (sup-norm) quantities in this problem, even though it satisfies adequately the weak (integrated) balance diagnostics

WHITE DWARF MERGERS ON ADAPTIVE MESHES. I. METHODOLOGY AND CODE VERIFICATION

Energy Technology Data Exchange (ETDEWEB)

Katz, Max P.; Zingale, Michael; Calder, Alan C.; Swesty, F. Douglas [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794-3800 (United States); Almgren, Ann S.; Zhang, Weiqun [Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2016-03-10

The Type Ia supernova (SN Ia) progenitor problem is one of the most perplexing and exciting problems in astrophysics, requiring detailed numerical modeling to complement observations of these explosions. One possible progenitor that has merited recent theoretical attention is the white dwarf (WD) merger scenario, which has the potential to naturally explain many of the observed characteristics of SNe Ia. To date there have been relatively few self-consistent simulations of merging WD systems using mesh-based hydrodynamics. This is the first paper in a series describing simulations of these systems using a hydrodynamics code with adaptive mesh refinement. In this paper we describe our numerical methodology and discuss our implementation in the compressible hydrodynamics code CASTRO, which solves the Euler equations, and the Poisson equation for self-gravity, and couples the gravitational and rotation forces to the hydrodynamics. Standard techniques for coupling gravitation and rotation forces to the hydrodynamics do not adequately conserve the total energy of the system for our problem, but recent advances in the literature allow progress and we discuss our implementation here. We present a set of test problems demonstrating the extent to which our software sufficiently models a system where large amounts of mass are advected on the computational domain over long timescales. Future papers in this series will describe our treatment of the initial conditions of these systems and will examine the early phases of the merger to determine its viability for triggering a thermonuclear detonation.

THE PLUTO CODE FOR ADAPTIVE MESH COMPUTATIONS IN ASTROPHYSICAL FLUID DYNAMICS

International Nuclear Information System (INIS)

Mignone, A.; Tzeferacos, P.; Zanni, C.; Bodo, G.; Van Straalen, B.; Colella, P.

2012-01-01

We present a description of the adaptive mesh refinement (AMR) implementation of the PLUTO code for solving the equations of classical and special relativistic magnetohydrodynamics (MHD and RMHD). The current release exploits, in addition to the static grid version of the code, the distributed infrastructure of the CHOMBO library for multidimensional parallel computations over block-structured, adaptively refined grids. We employ a conservative finite-volume approach where primary flow quantities are discretized at the cell center in a dimensionally unsplit fashion using the Corner Transport Upwind method. Time stepping relies on a characteristic tracing step where piecewise parabolic method, weighted essentially non-oscillatory, or slope-limited linear interpolation schemes can be handily adopted. A characteristic decomposition-free version of the scheme is also illustrated. The solenoidal condition of the magnetic field is enforced by augmenting the equations with a generalized Lagrange multiplier providing propagation and damping of divergence errors through a mixed hyperbolic/parabolic explicit cleaning step. Among the novel features, we describe an extension of the scheme to include non-ideal dissipative processes, such as viscosity, resistivity, and anisotropic thermal conduction without operator splitting. Finally, we illustrate an efficient treatment of point-local, potentially stiff source terms over hierarchical nested grids by taking advantage of the adaptivity in time. Several multidimensional benchmarks and applications to problems of astrophysical relevance assess the potentiality of the AMR version of PLUTO in resolving flow features separated by large spatial and temporal disparities.

Wavelet-based Adaptive Mesh Refinement Method for Global Atmospheric Chemical Transport Modeling

Science.gov (United States)

Rastigejev, Y.

2011-12-01

Numerical modeling of global atmospheric chemical transport presents enormous computational difficulties, associated with simulating a wide range of time and spatial scales. The described difficulties are exacerbated by the fact that hundreds of chemical species and thousands of chemical reactions typically are used for chemical kinetic mechanism description. These computational requirements very often forces researches to use relatively crude quasi-uniform numerical grids with inadequate spatial resolution that introduces significant numerical diffusion into the system. It was shown that this spurious diffusion significantly distorts the pollutant mixing and transport dynamics for typically used grid resolution. The described numerical difficulties have to be systematically addressed considering that the demand for fast, high-resolution chemical transport models will be exacerbated over the next decade by the need to interpret satellite observations of tropospheric ozone and related species. In this study we offer dynamically adaptive multilevel Wavelet-based Adaptive Mesh Refinement (WAMR) method for numerical modeling of atmospheric chemical evolution equations. The adaptive mesh refinement is performed by adding and removing finer levels of resolution in the locations of fine scale development and in the locations of smooth solution behavior accordingly. The algorithm is based on the mathematically well established wavelet theory. This allows us to provide error estimates of the solution that are used in conjunction with an appropriate threshold criteria to adapt the non-uniform grid. Other essential features of the numerical algorithm include: an efficient wavelet spatial discretization that allows to minimize the number of degrees of freedom for a prescribed accuracy, a fast algorithm for computing wavelet amplitudes, and efficient and accurate derivative approximations on an irregular grid. The method has been tested for a variety of benchmark problems

Parallel unstructured mesh optimisation for 3D radiation transport and fluids modelling

International Nuclear Information System (INIS)

Gorman, G.J.; Pain, Ch. C.; Oliveira, C.R.E. de; Umpleby, A.P.; Goddard, A.J.H.

2003-01-01

In this paper we describe the theory and application of a parallel mesh optimisation procedure to obtain self-adapting finite element solutions on unstructured tetrahedral grids. The optimisation procedure adapts the tetrahedral mesh to the solution of a radiation transport or fluid flow problem without sacrificing the integrity of the boundary (geometry), or internal boundaries (regions) of the domain. The objective is to obtain a mesh which has both a uniform interpolation error in any direction and the element shapes are of good quality. This is accomplished with use of a non-Euclidean (anisotropic) metric which is related to the Hessian of the solution field. Appropriate scaling of the metric enables the resolution of multi-scale phenomena as encountered in transient incompressible fluids and multigroup transport calculations. The resulting metric is used to calculate element size and shape quality. The mesh optimisation method is based on a series of mesh connectivity and node position searches of the landscape defining mesh quality which is gauged by a functional. The mesh modification thus fits the solution field(s) in an optimal manner. The parallel mesh optimisation/adaptivity procedure presented in this paper is of general applicability. We illustrate this by applying it to a transient CFD (computational fluid dynamics) problem. Incompressible flow past a cylinder at moderate Reynolds numbers is modelled to demonstrate that the mesh can follow transient flow features. (authors)

Adaptive Meshing for Bi-directional Information Flows

DEFF Research Database (Denmark)

Nicholas, Paul; Zwierzycki, Mateusz; Stasiuk, David

2016-01-01

This paper describes a mesh-based modelling approach that supports the multiscale design of a panelised, thin-skinned metal structure. The term multi-scale refers to the decomposition of a design modelling problem into distinct but interdependent models associated with particular scales, and the ...

Direct numerical simulation of bubbles with parallelized adaptive mesh refinement

International Nuclear Information System (INIS)

Talpaert, A.

2015-01-01

The study of two-phase Thermal-Hydraulics is a major topic for Nuclear Engineering for both security and efficiency of nuclear facilities. In addition to experiments, numerical modeling helps to knowing precisely where bubbles appear and how they behave, in the core as well as in the steam generators. This work presents the finest scale of representation of two-phase flows, Direct Numerical Simulation of bubbles. We use the 'Di-phasic Low Mach Number' equation model. It is particularly adapted to low-Mach number flows, that is to say flows which velocity is much slower than the speed of sound; this is very typical of nuclear thermal-hydraulics conditions. Because we study bubbles, we capture the front between vapor and liquid phases thanks to a downward flux limiting numerical scheme. The specific discrete analysis technique this work introduces is well-balanced parallel Adaptive Mesh Refinement (AMR). With AMR, we refined the coarse grid on a batch of patches in order to locally increase precision in areas which matter more, and capture fine changes in the front location and its topology. We show that patch-based AMR is very adapted for parallel computing. We use a variety of physical examples: forced advection, heat transfer, phase changes represented by a Stefan model, as well as the combination of all those models. We will present the results of those numerical simulations, as well as the speed up compared to equivalent non-AMR simulation and to serial computation of the same problems. This document is made up of an abstract and the slides of the presentation. (author)

Strategies to optimize MEDLINE and EMBASE search strategies for anesthesiology systematic reviews. An experimental study.

Science.gov (United States)

Volpato, Enilze de Souza Nogueira; Betini, Marluci; Puga, Maria Eduarda; Agarwal, Arnav; Cataneo, Antônio José Maria; Oliveira, Luciane Dias de; Bazan, Rodrigo; Braz, Leandro Gobbo; Pereira, José Eduardo Guimarães; El Dib, Regina

2018-01-15

A high-quality electronic search is essential for ensuring accuracy and comprehensiveness among the records retrieved when conducting systematic reviews. Therefore, we aimed to identify the most efficient method for searching in both MEDLINE (through PubMed) and EMBASE, covering search terms with variant spellings, direct and indirect orders, and associations with MeSH and EMTREE terms (or lack thereof). Experimental study. UNESP, Brazil. We selected and analyzed 37 search strategies that had specifically been developed for the field of anesthesiology. These search strategies were adapted in order to cover all potentially relevant search terms, with regard to variant spellings and direct and indirect orders, in the most efficient manner. When the strategies included variant spellings and direct and indirect orders, these adapted versions of the search strategies selected retrieved the same number of search results in MEDLINE (mean of 61.3%) and a higher number in EMBASE (mean of 63.9%) in the sample analyzed. The numbers of results retrieved through the searches analyzed here were not identical with and without associated use of MeSH and EMTREE terms. However, association of these terms from both controlled vocabularies retrieved a larger number of records than did the use of either one of them. In view of these results, we recommend that the search terms used should include both preferred and non-preferred terms (i.e. variant spellings and direct/indirect order of the same term) and associated MeSH and EMTREE terms, in order to develop highly-sensitive search strategies for systematic reviews.

Adaptive numerical modeling of dynamic crack propagation

International Nuclear Information System (INIS)

Adouani, H.; Tie, B.; Berdin, C.; Aubry, D.

2006-01-01

We propose an adaptive numerical strategy that aims at developing reliable and efficient numerical tools to model dynamic crack propagation and crack arrest. We use the cohesive zone theory as behavior of interface-type elements to model crack. Since the crack path is generally unknown beforehand, adaptive meshing is proposed to model the dynamic crack propagation. The dynamic study requires the development of specific solvers for time integration. As both geometry and finite element mesh of the studied structure evolve in time during transient analysis, the stability behavior of dynamic solver becomes a major concern. For this purpose, we use the space-time discontinuous Galerkin finite element method, well-known to provide a natural framework to manage meshes that evolve in time. As an important result, we prove that the space-time discontinuous Galerkin solver is unconditionally stable, when the dynamic crack propagation is modeled by the cohesive zone theory, which is highly non-linear. (authors)

Uncertainty quantification in a chemical system using error estimate-based mesh adaption

International Nuclear Information System (INIS)

Mathelin, Lionel; Le Maitre, Olivier P.

2012-01-01

This paper describes a rigorous a posteriori error analysis for the stochastic solution of non-linear uncertain chemical models. The dual-based a posteriori stochastic error analysis extends the methodology developed in the deterministic finite elements context to stochastic discretization frameworks. It requires the resolution of two additional (dual) problems to yield the local error estimate. The stochastic error estimate can then be used to adapt the stochastic discretization. Different anisotropic refinement strategies are proposed, leading to a cost-efficient tool suitable for multi-dimensional problems of moderate stochastic dimension. The adaptive strategies allow both for refinement and coarsening of the stochastic discretization, as needed to satisfy a prescribed error tolerance. The adaptive strategies were successfully tested on a model for the hydrogen oxidation in supercritical conditions having 8 random parameters. The proposed methodologies are however general enough to be also applicable for a wide class of models such as uncertain fluid flows. (authors)

High-resolution multi-code implementation of unsteady Navier-Stokes flow solver based on paralleled overset adaptive mesh refinement and high-order low-dissipation hybrid schemes

Science.gov (United States)

Li, Gaohua; Fu, Xiang; Wang, Fuxin

2017-10-01

The low-dissipation high-order accurate hybrid up-winding/central scheme based on fifth-order weighted essentially non-oscillatory (WENO) and sixth-order central schemes, along with the Spalart-Allmaras (SA)-based delayed detached eddy simulation (DDES) turbulence model, and the flow feature-based adaptive mesh refinement (AMR), are implemented into a dual-mesh overset grid infrastructure with parallel computing capabilities, for the purpose of simulating vortex-dominated unsteady detached wake flows with high spatial resolutions. The overset grid assembly (OGA) process based on collection detection theory and implicit hole-cutting algorithm achieves an automatic coupling for the near-body and off-body solvers, and the error-and-try method is used for obtaining a globally balanced load distribution among the composed multiple codes. The results of flows over high Reynolds cylinder and two-bladed helicopter rotor show that the combination of high-order hybrid scheme, advanced turbulence model, and overset adaptive mesh refinement can effectively enhance the spatial resolution for the simulation of turbulent wake eddies.

Numerical study of Taylor bubbles with adaptive unstructured meshes

Science.gov (United States)

Xie, Zhihua; Pavlidis, Dimitrios; Percival, James; Pain, Chris; Matar, Omar; Hasan, Abbas; Azzopardi, Barry

2014-11-01

The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube. This type of bubble flow regime often occurs in gas-liquid slug flows in many industrial applications, including oil-and-gas production, chemical and nuclear reactors, and heat exchangers. The objective of this study is to investigate the fluid dynamics of Taylor bubbles rising in a vertical pipe filled with oils of extremely high viscosity (mimicking the ``heavy oils'' found in the oil-and-gas industry). A modelling and simulation framework is presented here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rise and reduce the computational effort without sacrificing accuracy. The numerical framework consists of a mixed control-volume and finite-element formulation, a ``volume of fluid''-type method for the interface capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Numerical examples of some benchmark tests and the dynamics of Taylor bubbles are presented to show the capability of this method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

6th International Meshing Roundtable '97

Energy Technology Data Exchange (ETDEWEB)

White, D.

1997-09-01

The goal of the 6th International Meshing Roundtable is to bring together researchers and developers from industry, academia, and government labs in a stimulating, open environment for the exchange of technical information related to the meshing process. In the pas~ the Roundtable has enjoyed significant participation born each of these groups from a wide variety of countries. The Roundtable will consist of technical presentations from contributed papers and abstracts, two invited speakers, and two invited panels of experts discussing topics related to the development and use of automatic mesh generation tools. In addition, this year we will feature a "Bring Your Best Mesh" competition and poster session to encourage discussion and participation from a wide variety of mesh generation tool users. The schedule and evening social events are designed to provide numerous opportunities for informal dialog. A proceedings will be published by Sandia National Laboratories and distributed at the Roundtable. In addition, papers of exceptionally high quaIity will be submitted to a special issue of the International Journal of Computational Geometry and Applications. Papers and one page abstracts were sought that present original results on the meshing process. Potential topics include but are got limited to: Unstructured triangular and tetrahedral mesh generation Unstructured quadrilateral and hexahedral mesh generation Automated blocking and structured mesh generation Mixed element meshing Surface mesh generation Geometry decomposition and clean-up techniques Geometry modification techniques related to meshing Adaptive mesh refinement and mesh quality control Mesh visualization Special purpose meshing algorithms for particular applications Theoretical or novel ideas with practical potential Technical presentations from industrial researchers.

Achieving Extreme Resolution in Numerical Cosmology Using Adaptive Mesh Refinement: Resolving Primordial Star Formation

Directory of Open Access Journals (Sweden)

Greg L. Bryan

2002-01-01

Full Text Available As an entry for the 2001 Gordon Bell Award in the "special" category, we describe our 3-d, hybrid, adaptive mesh refinement (AMR code Enzo designed for high-resolution, multiphysics, cosmological structure formation simulations. Our parallel implementation places no limit on the depth or complexity of the adaptive grid hierarchy, allowing us to achieve unprecedented spatial and temporal dynamic range. We report on a simulation of primordial star formation which develops over 8000 subgrids at 34 levels of refinement to achieve a local refinement of a factor of 1012 in space and time. This allows us to resolve the properties of the first stars which form in the universe assuming standard physics and a standard cosmological model. Achieving extreme resolution requires the use of 128-bit extended precision arithmetic (EPA to accurately specify the subgrid positions. We describe our EPA AMR implementation on the IBM SP2 Blue Horizon system at the San Diego Supercomputer Center.

MeSH Now: automatic MeSH indexing at PubMed scale via learning to rank.

Science.gov (United States)

Mao, Yuqing; Lu, Zhiyong

2017-04-17

MeSH indexing is the task of assigning relevant MeSH terms based on a manual reading of scholarly publications by human indexers. The task is highly important for improving literature retrieval and many other scientific investigations in biomedical research. Unfortunately, given its manual nature, the process of MeSH indexing is both time-consuming (new articles are not immediately indexed until 2 or 3 months later) and costly (approximately ten dollars per article). In response, automatic indexing by computers has been previously proposed and attempted but remains challenging. In order to advance the state of the art in automatic MeSH indexing, a community-wide shared task called BioASQ was recently organized. We propose MeSH Now, an integrated approach that first uses multiple strategies to generate a combined list of candidate MeSH terms for a target article. Through a novel learning-to-rank framework, MeSH Now then ranks the list of candidate terms based on their relevance to the target article. Finally, MeSH Now selects the highest-ranked MeSH terms via a post-processing module. We assessed MeSH Now on two separate benchmarking datasets using traditional precision, recall and F 1 -score metrics. In both evaluations, MeSH Now consistently achieved over 0.60 in F-score, ranging from 0.610 to 0.612. Furthermore, additional experiments show that MeSH Now can be optimized by parallel computing in order to process MEDLINE documents on a large scale. We conclude that MeSH Now is a robust approach with state-of-the-art performance for automatic MeSH indexing and that MeSH Now is capable of processing PubMed scale documents within a reasonable time frame. http://www.ncbi.nlm.nih.gov/CBBresearch/Lu/Demo/MeSHNow/ .

Mesh Optimization for Ground Vehicle Aerodynamics

OpenAIRE

Adrian Gaylard; Essam F Abo-Serie; Nor Elyana Ahmad

2010-01-01

Mesh optimization strategy for estimating accurate drag of a ground vehicle is proposed based on examining the effect of different mesh parameters.  The optimized mesh parameters were selected using design of experiment (DOE) method to be able to work in a...

New 2D adaptive mesh refinement algorithm based on conservative finite-differences with staggered grid

Science.gov (United States)

Gerya, T.; Duretz, T.; May, D. A.

2012-04-01

We present new 2D adaptive mesh refinement (AMR) algorithm based on stress-conservative finite-differences formulated for non-uniform rectangular staggered grid. The refinement approach is based on a repetitive cell splitting organized via a quad-tree construction (every parent cell is split into 4 daughter cells of equal size). Irrespective of the level of resolution every cell has 5 staggered nodes (2 horizontal velocities, 2 vertical velocities and 1 pressure) for which respective governing equations, boundary conditions and interpolation equations are formulated. The connectivity of the grid is achieved via cross-indexing of grid cells and basic nodal points located in their corners: four corner nodes are indexed for every cell and up to 4 surrounding cells are indexed for every node. The accuracy of the approach depends critically on the formulation of the stencil used at the "hanging" velocity nodes located at the boundaries between different levels of resolution. Most accurate results are obtained for the scheme based on the volume flux balance across the resolution boundary combined with stress-based interpolation of velocity orthogonal to the boundary. We tested this new approach with a number of 2D variable viscosity analytical solutions. Our tests demonstrate that the adaptive staggered grid formulation has convergence properties similar to those obtained in case of a standard, non-adaptive staggered grid formulation. This convergence is also achieved when resolution boundary crosses sharp viscosity contrast interfaces. The convergence rates measured are found to be insensitive to scenarios when the transition in grid resolution crosses sharp viscosity contrast interfaces. We compared various grid refinement strategies based on distribution of different field variables such as viscosity, density and velocity. According to these tests the refinement allows for significant (0.5-1 order of magnitude) increase in the computational accuracy at the same

Helsinki Metropolitan Area Climate Change Adaptation Strategy

Energy Technology Data Exchange (ETDEWEB)

NONE

2012-07-01

The Helsinki Metropolitan Area Climate Change Adaptation Strategy has been prepared in close cooperation with the four cities of the metropolitan area (Helsinki, Espoo, Vantaa and Kauniainen), the Helsinki Region Environmental Services Authority HSY and other municipal, regional and state level organisations. In the strategy, strategic starting points and policies with which the metropolitan area prepares for the consequences of climate change, are compiled. The Helsinki Metropolitan Area adaptation strategy concentrates on the adaptation of the built and urban environment to the changing climate. The vision of the strategy is climate proof city - the future is built now. The strategy aims to (1) assess the impacts of climate change in the area, (2) prepare for the impacts of climate change and to extreme weather events and (3) to reduce the vulnerabilities of the area to climate variability and change. The target is to secure the well-being of the citizens and the functioning of the cities also in the changing climate conditions. The preparation of the adaptation strategy started in 2009 by producing the background studies. They include the regional climate and sea level scenarios, modelling of river floods in climate change conditions and a survey of climate change impacts in the region. Also, existing programmes, legislation, research and studies concerning adaptation were collected. The background studies are published in a report titled 'The Helsinki metropolitan area climate is changing - Adaptation strategy background studies' (in Finnish) (HSY 2010). HSY coordinated the strategy preparation. The work was carried out is close cooperation with the experts of the metropolitan area cities, regional emergency services, Ministry of the Environment, Helsinki Region Transport Authority and other regional organisations. The strategy work has had a steering group that consists of representatives of the cities and other central cooperation partners. The

DECISION STRATEGIES AND COGNITIVE ADAPTATIONS TO ECOLOGY

Directory of Open Access Journals (Sweden)

Poleszczuk Jan

2017-06-01

Full Text Available In this paper, I discuss the concept of adaptive rationality. I present a simple model of ecology and the set of decision rules. The basic structure of the process of cognitive adaptation to ecology is described as a structure comprising (1 perceptual space, (2 a function valuating perceived items, (3 a set of available decision rules and (4 the adaptation process - identification and selection of the best strategies in given ecological conditions. The presented model of ecosystem allows a conclusion that completely opposite strategies may be compatible with the assumption of adaptive rationality.

CONSTRAINED-TRANSPORT MAGNETOHYDRODYNAMICS WITH ADAPTIVE MESH REFINEMENT IN CHARM

International Nuclear Information System (INIS)

Miniati, Francesco; Martin, Daniel F.

2011-01-01

We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.

Reactivity perturbation formulation for a discontinuous Galerkin-based transport solver and its use with adaptive mesh refinement

International Nuclear Information System (INIS)

Le Tellier, R.; Fournier, D.; Suteau, C.

2011-01-01

Within the framework of a Discontinuous Galerkin spatial approximation of the multigroup discrete ordinates transport equation, we present a generalization of the exact standard perturbation formula that takes into account spatial discretization-induced reactivity changes. It encompasses in two separate contributions the nuclear data-induced reactivity change and the reactivity modification induced by two different spatial discretizations. The two potential uses of such a formulation when considering adaptive mesh refinement are discussed, and numerical results on a simple two-group Cartesian two-dimensional benchmark are provided. In particular, such a formulation is shown to be useful to filter out a more accurate estimate of nuclear data-related reactivity effects from initial and perturbed calculations based on independent adaptation processes. (authors)

A novel method of the image processing on irregular triangular meshes

Science.gov (United States)

Vishnyakov, Sergey; Pekhterev, Vitaliy; Sokolova, Elizaveta

2018-04-01

The paper describes a novel method of the image processing based on irregular triangular meshes implementation. The triangular mesh is adaptive to the image content, least mean square linear approximation is proposed for the basic interpolation within the triangle. It is proposed to use triangular numbers to simplify using of the local (barycentric) coordinates for the further analysis - triangular element of the initial irregular mesh is to be represented through the set of the four equilateral triangles. This allows to use fast and simple pixels indexing in local coordinates, e.g. "for" or "while" loops for access to the pixels. Moreover, representation proposed allows to use discrete cosine transform of the simple "rectangular" symmetric form without additional pixels reordering (as it is used for shape-adaptive DCT forms). Furthermore, this approach leads to the simple form of the wavelet transform on triangular mesh. The results of the method application are presented. It is shown that advantage of the method proposed is a combination of the flexibility of the image-adaptive irregular meshes with the simple form of the pixel indexing in local triangular coordinates and the using of the common forms of the discrete transforms for triangular meshes. Method described is proposed for the image compression, pattern recognition, image quality improvement, image search and indexing. It also may be used as a part of video coding (intra-frame or inter-frame coding, motion detection).

Challenges of Representing Sub-Grid Physics in an Adaptive Mesh Refinement Atmospheric Model

Science.gov (United States)

O'Brien, T. A.; Johansen, H.; Johnson, J. N.; Rosa, D.; Benedict, J. J.; Keen, N. D.; Collins, W.; Goodfriend, E.

2015-12-01

Some of the greatest potential impacts from future climate change are tied to extreme atmospheric phenomena that are inherently multiscale, including tropical cyclones and atmospheric rivers. Extremes are challenging to simulate in conventional climate models due to existing models' coarse resolutions relative to the native length-scales of these phenomena. Studying the weather systems of interest requires an atmospheric model with sufficient local resolution, and sufficient performance for long-duration climate-change simulations. To this end, we have developed a new global climate code with adaptive spatial and temporal resolution. The dynamics are formulated using a block-structured conservative finite volume approach suitable for moist non-hydrostatic atmospheric dynamics. By using both space- and time-adaptive mesh refinement, the solver focuses computational resources only where greater accuracy is needed to resolve critical phenomena. We explore different methods for parameterizing sub-grid physics, such as microphysics, macrophysics, turbulence, and radiative transfer. In particular, we contrast the simplified physics representation of Reed and Jablonowski (2012) with the more complex physics representation used in the System for Atmospheric Modeling of Khairoutdinov and Randall (2003). We also explore the use of a novel macrophysics parameterization that is designed to be explicitly scale-aware.

Hydrodynamics in full general relativity with conservative adaptive mesh refinement

Science.gov (United States)

East, William E.; Pretorius, Frans; Stephens, Branson C.

2012-06-01

There is great interest in numerical relativity simulations involving matter due to the likelihood that binary compact objects involving neutron stars will be detected by gravitational wave observatories in the coming years, as well as to the possibility that binary compact object mergers could explain short-duration gamma-ray bursts. We present a code designed for simulations of hydrodynamics coupled to the Einstein field equations targeted toward such applications. This code has recently been used to study eccentric mergers of black hole-neutron star binaries. We evolve the fluid conservatively using high-resolution shock-capturing methods, while the field equations are solved in the generalized-harmonic formulation with finite differences. In order to resolve the various scales that may arise, we use adaptive mesh refinement (AMR) with grid hierarchies based on truncation error estimates. A noteworthy feature of this code is the implementation of the flux correction algorithm of Berger and Colella to ensure that the conservative nature of fluid advection is respected across AMR boundaries. We present various tests to compare the performance of different limiters and flux calculation methods, as well as to demonstrate the utility of AMR flux corrections.

An Interpreted Language and System for the Visualization of Unstructured Meshes

Science.gov (United States)

Moran, Patrick J.; Gerald-Yamasaki, Michael (Technical Monitor)

1998-01-01

We present an interpreted language and system supporting the visualization of unstructured meshes and the manipulation of shapes defined in terms of mesh subsets. The language features primitives inspired by geometric modeling, mathematical morphology and algebraic topology. The adaptation of the topology ideas to an interpreted environment, along with support for programming constructs such, as user function definition, provide a flexible system for analyzing a mesh and for calculating with shapes defined in terms of the mesh. We present results demonstrating some of the capabilities of the language, based on an implementation called the Shape Calculator, for tetrahedral meshes in R^3.

Assessing climate change impacts and adaptation strategies for ...

African Journals Online (AJOL)

Assessing climate change impacts and adaptation strategies for smallholder agricultural systems in Uganda. ... from encroaching on swamps, which is one of the reported adaptation strategies to climate related stresses. Improving productivity of important crops (bananas for southwest, and sweet potatoes and bananas

Integrable discretizations and self-adaptive moving mesh method for a coupled short pulse equation

International Nuclear Information System (INIS)

Feng, Bao-Feng; Chen, Junchao; Chen, Yong; Maruno, Ken-ichi; Ohta, Yasuhiro

2015-01-01

In the present paper, integrable semi-discrete and fully discrete analogues of a coupled short pulse (CSP) equation are constructed. The key to the construction are the bilinear forms and determinant structure of the solutions of the CSP equation. We also construct N-soliton solutions for the semi-discrete and fully discrete analogues of the CSP equations in the form of Casorati determinants. In the continuous limit, we show that the fully discrete CSP equation converges to the semi-discrete CSP equation, then further to the continuous CSP equation. Moreover, the integrable semi-discretization of the CSP equation is used as a self-adaptive moving mesh method for numerical simulations. The numerical results agree with the analytical results very well. (paper)

N-body simulations for f(R) gravity using a self-adaptive particle-mesh code

International Nuclear Information System (INIS)

Zhao Gongbo; Koyama, Kazuya; Li Baojiu

2011-01-01

We perform high-resolution N-body simulations for f(R) gravity based on a self-adaptive particle-mesh code MLAPM. The chameleon mechanism that recovers general relativity on small scales is fully taken into account by self-consistently solving the nonlinear equation for the scalar field. We independently confirm the previous simulation results, including the matter power spectrum, halo mass function, and density profiles, obtained by Oyaizu et al.[Phys. Rev. D 78, 123524 (2008)] and Schmidt et al.[Phys. Rev. D 79, 083518 (2009)], and extend the resolution up to k∼20 h/Mpc for the measurement of the matter power spectrum. Based on our simulation results, we discuss how the chameleon mechanism affects the clustering of dark matter and halos on full nonlinear scales.

Dynamic implicit 3D adaptive mesh refinement for non-equilibrium radiation diffusion

Science.gov (United States)

Philip, B.; Wang, Z.; Berrill, M. A.; Birke, M.; Pernice, M.

2014-04-01

The time dependent non-equilibrium radiation diffusion equations are important for solving the transport of energy through radiation in optically thick regimes and find applications in several fields including astrophysics and inertial confinement fusion. The associated initial boundary value problems that are encountered often exhibit a wide range of scales in space and time and are extremely challenging to solve. To efficiently and accurately simulate these systems we describe our research on combining techniques that will also find use more broadly for long term time integration of nonlinear multi-physics systems: implicit time integration for efficient long term time integration of stiff multi-physics systems, local control theory based step size control to minimize the required global number of time steps while controlling accuracy, dynamic 3D adaptive mesh refinement (AMR) to minimize memory and computational costs, Jacobian Free Newton-Krylov methods on AMR grids for efficient nonlinear solution, and optimal multilevel preconditioner components that provide level independent solver convergence.

Dynamic implicit 3D adaptive mesh refinement for non-equilibrium radiation diffusion

International Nuclear Information System (INIS)

Philip, B.; Wang, Z.; Berrill, M.A.; Birke, M.; Pernice, M.

2014-01-01

The time dependent non-equilibrium radiation diffusion equations are important for solving the transport of energy through radiation in optically thick regimes and find applications in several fields including astrophysics and inertial confinement fusion. The associated initial boundary value problems that are encountered often exhibit a wide range of scales in space and time and are extremely challenging to solve. To efficiently and accurately simulate these systems we describe our research on combining techniques that will also find use more broadly for long term time integration of nonlinear multi-physics systems: implicit time integration for efficient long term time integration of stiff multi-physics systems, local control theory based step size control to minimize the required global number of time steps while controlling accuracy, dynamic 3D adaptive mesh refinement (AMR) to minimize memory and computational costs, Jacobian Free Newton–Krylov methods on AMR grids for efficient nonlinear solution, and optimal multilevel preconditioner components that provide level independent solver convergence

Adaptive, Tactical Mesh Networking: Control Base MANET Model

Science.gov (United States)

2010-09-01

pp. 316–320 Available: IEEE Xplore , http://ieeexplore.ieee.org [Accessed: June 9, 2010]. [5] N. Sidiropoulos, “Multiuser Transmit Beamforming...Mobile Mesh Segments of TNT Testbed .......... 11 Figure 5. Infrastructure and Ad Hoc Mode of IEEE 802.11................................ 13 Figure...6. The Power Spectral Density of OFDM................................................ 14 Figure 7. A Typical IEEE 802.16 Network

Interoperable mesh components for large-scale, distributed-memory simulations

International Nuclear Information System (INIS)

Devine, K; Leung, V; Diachin, L; Miller, M

2009-01-01

SciDAC applications have a demonstrated need for advanced software tools to manage the complexities associated with sophisticated geometry, mesh, and field manipulation tasks, particularly as computer architectures move toward the petascale. In this paper, we describe a software component - an abstract data model and programming interface - designed to provide support for parallel unstructured mesh operations. We describe key issues that must be addressed to successfully provide high-performance, distributed-memory unstructured mesh services and highlight some recent research accomplishments in developing new load balancing and MPI-based communication libraries appropriate for leadership class computing. Finally, we give examples of the use of parallel adaptive mesh modification in two SciDAC applications.

Cell adhesion on NiTi thin film sputter-deposited meshes

Energy Technology Data Exchange (ETDEWEB)

Loger, K. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Engel, A.; Haupt, J. [Department of Cardiovascular Surgery, University Hospital of Schleswig-Holstein, Kiel (Germany); Li, Q. [Biocompatible Nanomaterials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Lima de Miranda, R. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); ACQUANDAS GmbH, Kiel (Germany); Quandt, E. [Inorganic Functional Materials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany); Lutter, G. [Department of Cardiovascular Surgery, University Hospital of Schleswig-Holstein, Kiel (Germany); Selhuber-Unkel, C. [Biocompatible Nanomaterials, Institute for Materials Science, Faculty of Engineering, University of Kiel (Germany)

2016-02-01

Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium (NiTi) thin film meshes were produced by means of magnetron sputter deposition. Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm{sup 2} and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133 +) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm{sup 2} and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applications in cardiovascular tissue engineering, particularly for the fabrication of heart valves. - Highlights: • Freestanding NiTi thin film scaffolds were fabricated with magnetron sputtering process. • Effective mechanical properties of NiTi scaffolds can be adapted by the mesh structure parameters. • Cell adhesion on the NiTi thin film scaffold is controlled by the structure parameters of the mesh. • Cells strongly adhere after seven days and form a confluent layer on the mesh.

Cell adhesion on NiTi thin film sputter-deposited meshes

International Nuclear Information System (INIS)

Loger, K.; Engel, A.; Haupt, J.; Li, Q.; Lima de Miranda, R.; Quandt, E.; Lutter, G.; Selhuber-Unkel, C.

2016-01-01

Scaffolds for tissue engineering enable the possibility to fabricate and form biomedical implants in vitro, which fulfill special functionality in vivo. In this study, free-standing Nickel–Titanium (NiTi) thin film meshes were produced by means of magnetron sputter deposition. Meshes contained precisely defined rhombic holes in the size of 440 to 1309 μm 2 and a strut width ranging from 5.3 to 9.2 μm. The effective mechanical properties of the microstructured superelastic NiTi thin film were examined by tensile testing. These results will be adapted for the design of the holes in the film. The influence of hole and strut dimensions on the adhesion of sheep autologous cells (CD133 +) was studied after 24 h and after seven days of incubation. Optical analysis using fluorescence microscopy and scanning electron microscopy showed that cell adhesion depends on the structural parameters of the mesh. After 7 days in cell culture a large part of the mesh was covered with aligned fibrous material. Cell adhesion is particularly facilitated on meshes with small rhombic holes of 440 μm 2 and a strut width of 5.3 μm. Our results demonstrate that free-standing NiTi thin film meshes have a promising potential for applications in cardiovascular tissue engineering, particularly for the fabrication of heart valves. - Highlights: • Freestanding NiTi thin film scaffolds were fabricated with magnetron sputtering process. • Effective mechanical properties of NiTi scaffolds can be adapted by the mesh structure parameters. • Cell adhesion on the NiTi thin film scaffold is controlled by the structure parameters of the mesh. • Cells strongly adhere after seven days and form a confluent layer on the mesh.

A New Adaptive Checkpointing Strategy for Mobile Computing

Institute of Scientific and Technical Information of China (English)

MENChaoguang; ZUODecheng; YANGXiaozong

2005-01-01

Adaptive checkpointing strategy is an efficient recovery scheme, which is suitable for mobile computing system. However， all existing adaptive checkpointing schemes are not correct to recover system when failure occurs in some special period. In this paper， the issues that will lead to system inconsistency are first discussed and then a new adaptive strategy that can recover system to correct consistent state is proposed. Our algorithm improves system recovery performance because only failure process needs rollback through logging.

Connectivity editing for quad-dominant meshes

KAUST Repository

Peng, Chihan

2013-08-01

We propose a connectivity editing framework for quad-dominant meshes. In our framework, the user can edit the mesh connectivity to control the location, type, and number of irregular vertices (with more or fewer than four neighbors) and irregular faces (non-quads). We provide a theoretical analysis of the problem, discuss what edits are possible and impossible, and describe how to implement an editing framework that realizes all possible editing operations. In the results, we show example edits and illustrate the advantages and disadvantages of different strategies for quad-dominant mesh design. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and John Wiley & Sons Ltd.

Opfront: mesh

DEFF Research Database (Denmark)

2015-01-01

Mesh generation and visualization software based on the CGAL library. Folder content: drawmesh Visualize slices of the mesh (surface/volumetric) as wireframe on top of an image (3D). drawsurf Visualize surfaces of the mesh (surface/volumetric). img2mesh Convert isosurface in image to volumetric m...... mesh (medit format). img2off Convert isosurface in image to surface mesh (off format). off2mesh Convert surface mesh (off format) to volumetric mesh (medit format). reduce Crop and resize 3D and stacks of images. data Example data to test the library on...

Affect-Aware Adaptive Tutoring Based on Human-Automation Etiquette Strategies.

Science.gov (United States)

Yang, Euijung; Dorneich, Michael C

2018-06-01

We investigated adapting the interaction style of intelligent tutoring system (ITS) feedback based on human-automation etiquette strategies. Most ITSs adapt the content difficulty level, adapt the feedback timing, or provide extra content when they detect cognitive or affective decrements. Our previous work demonstrated that changing the interaction style via different feedback etiquette strategies has differential effects on students' motivation, confidence, satisfaction, and performance. The best etiquette strategy was also determined by user frustration. Based on these findings, a rule set was developed that systemically selected the proper etiquette strategy to address one of four learning factors (motivation, confidence, satisfaction, and performance) under two different levels of user frustration. We explored whether etiquette strategy selection based on this rule set (systematic) or random changes in etiquette strategy for a given level of frustration affected the four learning factors. Participants solved mathematics problems under different frustration conditions with feedback that adapted dynamic changes in etiquette strategies either systematically or randomly. The results demonstrated that feedback with etiquette strategies chosen systematically via the rule set could selectively target and improve motivation, confidence, satisfaction, and performance more than changing etiquette strategies randomly. The systematic adaptation was effective no matter the level of frustration for the participant. If computer tutors can vary the interaction style to effectively mitigate negative emotions, then ITS designers would have one more mechanism in which to design affect-aware adaptations that provide the proper responses in situations where human emotions affect the ability to learn.

Adaptive mesh refinement for a finite volume method for flow and transport of radionuclides in heterogeneous porous media

International Nuclear Information System (INIS)

Amaziane, Brahim; Bourgeois, Marc; El Fatini, Mohamed

2014-01-01

In this paper, we consider adaptive numerical simulation of miscible displacement problems in porous media, which are modeled by single phase flow equations. A vertex-centred finite volume method is employed to discretize the coupled system: the Darcy flow equation and the diffusion-convection concentration equation. The convection term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion-dispersion term is discretized by piecewise linear conforming finite elements. We introduce two kinds of indicators, both of them of residual type. The first one is related to time discretization and is local with respect to the time discretization: thus, at each time, it provides an appropriate information for the choice of the next time step. The second is related to space discretization and is local with respect to both the time and space variable and the idea is that at each time it is an efficient tool for mesh adaptivity. An error estimation procedure evaluates where additional refinement is needed and grid generation procedures dynamically create or remove fine-grid patches as resolution requirements change. The method was implemented in the software MELODIE, developed by the French Institute for Radiological Protection and Nuclear Safety (IRSN, Institut de Radioprotection et de Surete Nucleaire). The algorithm is then used to simulate the evolution of radionuclide migration from the waste packages through a heterogeneous disposal, demonstrating its capability to capture complex behavior of the resulting flow. (authors)

Documentation for MeshKit - Reactor Geometry (&mesh) Generator

Energy Technology Data Exchange (ETDEWEB)

Jain, Rajeev [Argonne National Lab. (ANL), Argonne, IL (United States); Mahadevan, Vijay [Argonne National Lab. (ANL), Argonne, IL (United States)

2015-09-30

This report gives documentation for using MeshKit’s Reactor Geometry (and mesh) Generator (RGG) GUI and also briefly documents other algorithms and tools available in MeshKit. RGG is a program designed to aid in modeling and meshing of complex/large hexagonal and rectilinear reactor cores. RGG uses Argonne’s SIGMA interfaces, Qt and VTK to produce an intuitive user interface. By integrating a 3D view of the reactor with the meshing tools and combining them into one user interface, RGG streamlines the task of preparing a simulation mesh and enables real-time feedback that reduces accidental scripting mistakes that could waste hours of meshing. RGG interfaces with MeshKit tools to consolidate the meshing process, meaning that going from model to mesh is as easy as a button click. This report is designed to explain RGG v 2.0 interface and provide users with the knowledge and skills to pilot RGG successfully. Brief documentation of MeshKit source code, tools and other algorithms available are also presented for developers to extend and add new algorithms to MeshKit. RGG tools work in serial and parallel and have been used to model complex reactor core models consisting of conical pins, load pads, several thousands of axially varying material properties of instrumentation pins and other interstices meshes.

(YIP 2011) Unsteady Output-based Adaptive Simulation of Separated and Transitional Flows

Science.gov (United States)

2015-03-19

Investigator Aerospace Eng. U. Michigan Marco Ceze Ph.D. student/postdoctoral associate Aerospace Eng. U. Michigan Steven Kast Ph.D. student Aerospace...13] S. M. Kast , M. A. Ceze, and K. J. Fidkowski. Output-adaptive solution strategies for unsteady aerodynamics on deformable domains. Seventh...International Conference on Computational Fluid Dynamics ICCFD7-3802, 2012. [14] S. M. Kast and K. J. Fidkowski. Output-based mesh adaptation for high order

A general boundary capability embedded in an orthogonal mesh

International Nuclear Information System (INIS)

Hewett, D.W.; Yu-Jiuan Chen

1995-01-01

The authors describe how they hold onto orthogonal mesh discretization when dealing with curved boundaries. Special difference operators were constructed to approximate numerical zones split by the domain boundary; the operators are particularly simple for this rectangular mesh. The authors demonstrated that this simple numerical approach, termed Dynamic Alternating Direction Implicit, turned out to be considerably more efficient than more complex grid-adaptive algorithms that were tried previously

Modeling NIF experimental designs with adaptive mesh refinement and Lagrangian hydrodynamics

Science.gov (United States)

Koniges, A. E.; Anderson, R. W.; Wang, P.; Gunney, B. T. N.; Becker, R.; Eder, D. C.; MacGowan, B. J.; Schneider, M. B.

2006-06-01

Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs.

Modeling NIF Experimental Designs with Adaptive Mesh Refinement and Lagrangian Hydrodynamics

International Nuclear Information System (INIS)

Koniges, A E; Anderson, R W; Wang, P; Gunney, B N; Becker, R; Eder, D C; MacGowan, B J

2005-01-01

Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs

Modeling Nif experimental designs with adaptive mesh refinement and Lagrangian hydrodynamics

International Nuclear Information System (INIS)

Koniges, A.E.; Anderson, R.W.; Wang, P.; Gunney, B.T.N.; Becker, R.; Eder, D.C.; MacGowan, B.J.; Schneider, M.B.

2006-01-01

Incorporation of adaptive mesh refinement (AMR) into Lagrangian hydrodynamics algorithms allows for the creation of a highly powerful simulation tool effective for complex target designs with three-dimensional structure. We are developing an advanced modeling tool that includes AMR and traditional arbitrary Lagrangian-Eulerian (ALE) techniques. Our goal is the accurate prediction of vaporization, disintegration and fragmentation in National Ignition Facility (NIF) experimental target elements. Although our focus is on minimizing the generation of shrapnel in target designs and protecting the optics, the general techniques are applicable to modern advanced targets that include three-dimensional effects such as those associated with capsule fill tubes. Several essential computations in ordinary radiation hydrodynamics need to be redesigned in order to allow for AMR to work well with ALE, including algorithms associated with radiation transport. Additionally, for our goal of predicting fragmentation, we include elastic/plastic flow into our computations. We discuss the integration of these effects into a new ALE-AMR simulation code. Applications of this newly developed modeling tool as well as traditional ALE simulations in two and three dimensions are applied to NIF early-light target designs. (authors)

OPTIMASI OLSR ROUTING PROTOCOL PADA JARINGAN WIRELESS MESH DENGAN ADAPTIVE REFRESHING TIME INTERVAL DAN ENHANCE MULTI POINT RELAY SELECTING ALGORITHM

Directory of Open Access Journals (Sweden)

Faosan Mapa

2014-01-01

Full Text Available Normal 0 false false false IN X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Wireless Mesh Network (WMN adalah suatu konektivitas jaringan yang self-organized, self-configured dan multi-hop. Tujuan dari WMN adalah menawarkan pengguna suatu bentuk jaringan nirkabel yang dapat dengan mudah berkomunikasi dengan jaringan konvensional dengan kecepatan tinggi dan dengan cakupan yang lebih luas serta biaya awal yang minimal. Diperlukan suatu desain protokol routing yang efisien untuk WMN yang secara adaptif dapat mendukung mesh routers dan mesh clients. Dalam tulisan ini, diusulkan untuk mengoptimalkan protokol OLSR, yang merupakan protokol routing proaktif. Digunakan heuristik yang meningkatkan protokol OLSR melalui adaptive refreshing time interval dan memperbaiki metode MPR selecting algorithm. Suatu analisa dalam meningkatkan protokol OLSR melalui adaptive refreshing time interval dan memperbaiki algoritma pemilihan MPR menunjukkan kinerja yang signifikan dalam hal throughput jika dibandingkan dengan protokol OLSR yang asli. Akan tetapi, terdapat kenaikan dalam hal delay. Pada simulasi yang dilakukan dapat disimpulkan bahwa OLSR dapat dioptimalkan dengan memodifikasi pemilihan node MPR berdasarkan cost effective dan penyesuaian waktu interval refreshing hello message sesuai dengan keadaan

Fitting polynomial surfaces to triangular meshes with Voronoi squared distance minimization

KAUST Repository

Nivoliers, Vincent

2012-11-06

This paper introduces Voronoi squared distance minimization (VSDM), an algorithm that fits a surface to an input mesh. VSDM minimizes an objective function that corresponds to a Voronoi-based approximation of the overall squared distance function between the surface and the input mesh (SDM). This objective function is a generalization of the one minimized by centroidal Voronoi tessellation, and can be minimized by a quasi-Newton solver. VSDM naturally adapts the orientation of the mesh elements to best approximate the input, without estimating any differential quantities. Therefore, it can be applied to triangle soups or surfaces with degenerate triangles, topological noise and sharp features. Applications of fitting quad meshes and polynomial surfaces to input triangular meshes are demonstrated. © 2012 Springer-Verlag London.

N-body simulations for f(R) gravity using a self-adaptive particle-mesh code

Science.gov (United States)

Zhao, Gong-Bo; Li, Baojiu; Koyama, Kazuya

2011-02-01

We perform high-resolution N-body simulations for f(R) gravity based on a self-adaptive particle-mesh code MLAPM. The chameleon mechanism that recovers general relativity on small scales is fully taken into account by self-consistently solving the nonlinear equation for the scalar field. We independently confirm the previous simulation results, including the matter power spectrum, halo mass function, and density profiles, obtained by Oyaizu [Phys. Rev. DPRVDAQ1550-7998 78, 123524 (2008)10.1103/PhysRevD.78.123524] and Schmidt [Phys. Rev. DPRVDAQ1550-7998 79, 083518 (2009)10.1103/PhysRevD.79.083518], and extend the resolution up to k˜20h/Mpc for the measurement of the matter power spectrum. Based on our simulation results, we discuss how the chameleon mechanism affects the clustering of dark matter and halos on full nonlinear scales.

A cellular automaton - finite volume method for the simulation of dendritic and eutectic growth in binary alloys using an adaptive mesh refinement

Science.gov (United States)

Dobravec, Tadej; Mavrič, Boštjan; Šarler, Božidar

2017-11-01

A two-dimensional model to simulate the dendritic and eutectic growth in binary alloys is developed. A cellular automaton method is adopted to track the movement of the solid-liquid interface. The diffusion equation is solved in the solid and liquid phases by using an explicit finite volume method. The computational domain is divided into square cells that can be hierarchically refined or coarsened using an adaptive mesh based on the quadtree algorithm. Such a mesh refines the regions of the domain near the solid-liquid interface, where the highest concentration gradients are observed. In the regions where the lowest concentration gradients are observed the cells are coarsened. The originality of the work is in the novel, adaptive approach to the efficient and accurate solution of the posed multiscale problem. The model is verified and assessed by comparison with the analytical results of the Lipton-Glicksman-Kurz model for the steady growth of a dendrite tip and the Jackson-Hunt model for regular eutectic growth. Several examples of typical microstructures are simulated and the features of the method as well as further developments are discussed.

Use of adaptive diffusion theory based monitors in optimizing boiling water reactor core designs

International Nuclear Information System (INIS)

Congdon, S.P.; Martin, C.L.; Crowther, R.L.

1988-01-01

Three-dimensional coarse mesh models are routinely used to predict the performance of boiling water reactors. In the adaptive monitory model, the three-dimensional solutions are permanently adapted to incore probe data. The corrections resulting from the adaptive process lead to reliable predictions of future reactor states. The corrections can also be carried forward to future operating cycles. This can shorten the time required to introduce an validate new design and operating strategy improvements. (orig.) [de

A mesh density study for application to large deformation rolling process evaluation

International Nuclear Information System (INIS)

Martin, J.A.

1997-12-01

When addressing large deformation through an elastic-plastic analysis the mesh density is paramount in determining the accuracy of the solution. However, given the nonlinear nature of the problem, a highly-refined mesh will generally require a prohibitive amount of computer resources. This paper addresses finite element mesh optimization studies considering accuracy of results and computer resource needs as applied to large deformation rolling processes. In particular, the simulation of the thread rolling manufacturing process is considered using the MARC software package and a Cray C90 supercomputer. Both mesh density and adaptive meshing on final results for both indentation of a rigid body to a specified depth and contact rolling along a predetermined length are evaluated

Connectivity editing for quad-dominant meshes

KAUST Repository

Peng, Chihan; Wonka, Peter

2013-01-01

and illustrate the advantages and disadvantages of different strategies for quad-dominant mesh design. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and John Wiley & Sons Ltd.

Stepping strategies for regulating gait adaptability and stability.

Science.gov (United States)

Hak, Laura; Houdijk, Han; Steenbrink, Frans; Mert, Agali; van der Wurff, Peter; Beek, Peter J; van Dieën, Jaap H

2013-03-15

Besides a stable gait pattern, gait in daily life requires the capability to adapt this pattern in response to environmental conditions. The purpose of this study was to elucidate the anticipatory strategies used by able-bodied people to attain an adaptive gait pattern, and how these strategies interact with strategies used to maintain gait stability. Ten healthy subjects walked in a Computer Assisted Rehabilitation ENvironment (CAREN). To provoke an adaptive gait pattern, subjects had to hit virtual targets, with markers guided by their knees, while walking on a self-paced treadmill. The effects of walking with and without this task on walking speed, step length, step frequency, step width and the margins of stability (MoS) were assessed. Furthermore, these trials were performed with and without additional continuous ML platform translations. When an adaptive gait pattern was required, subjects decreased step length (padaptations resulted in the preservation of equal MoS between trials, despite the disturbing influence of the gait adaptability task. When the gait adaptability task was combined with the balance perturbation subjects further decreased step length, as evidenced by a significant interaction between both manipulations (p=0.012). In conclusion, able-bodied people reduce step length and increase step width during walking conditions requiring a high level of both stability and adaptability. Although an increase in step frequency has previously been found to enhance stability, a faster movement, which would coincide with a higher step frequency, hampers accuracy and may consequently limit gait adaptability. Copyright © 2012 Elsevier Ltd. All rights reserved.

Strategy correlations and timing of adaptation in Minority Games

OpenAIRE

Galla, Tobias; Sherrington, David

2005-01-01

We study the role of strategy correlations and timing of adaptation for the dynamics of Minority Games, both simulationally and analytically. Using the exact generating functional approach a la De Dominicis we compute the phase diagram and the behaviour of batch and on-line games with correlated strategies, complementing exisiting replica studies of their statics. It is shown that the timing of adaptation can be relevant; while conventional games with uncorrelated strategies are nearly insens...

Dynamic mesh adaptation for front evolution using discontinuous Galerkin based weighted condition number relaxation

International Nuclear Information System (INIS)

Greene, Patrick T.; Schofield, Samuel P.; Nourgaliev, Robert

2017-01-01

A new mesh smoothing method designed to cluster cells near a dynamically evolving interface is presented. The method is based on weighted condition number mesh relaxation with the weight function computed from a level set representation of the interface. The weight function is expressed as a Taylor series based discontinuous Galerkin projection, which makes the computation of the derivatives of the weight function needed during the condition number optimization process a trivial matter. For cases when a level set is not available, a fast method for generating a low-order level set from discrete cell-centered fields, such as a volume fraction or index function, is provided. Results show that the low-order level set works equally well as the actual level set for mesh smoothing. Meshes generated for a number of interface geometries are presented, including cases with multiple level sets. Lastly, dynamic cases with moving interfaces show the new method is capable of maintaining a desired resolution near the interface with an acceptable number of relaxation iterations per time step, which demonstrates the method's potential to be used as a mesh relaxer for arbitrary Lagrangian Eulerian (ALE) methods.

Interoperable mesh and geometry tools for advanced petascale simulations

International Nuclear Information System (INIS)

Diachin, L; Bauer, A; Fix, B; Kraftcheck, J; Jansen, K; Luo, X; Miller, M; Ollivier-Gooch, C; Shephard, M S; Tautges, T; Trease, H

2007-01-01

SciDAC applications have a demonstrated need for advanced software tools to manage the complexities associated with sophisticated geometry, mesh, and field manipulation tasks, particularly as computer architectures move toward the petascale. The Center for Interoperable Technologies for Advanced Petascale Simulations (ITAPS) will deliver interoperable and interchangeable mesh, geometry, and field manipulation services that are of direct use to SciDAC applications. The premise of our technology development goal is to provide such services as libraries that can be used with minimal intrusion into application codes. To develop these technologies, we focus on defining a common data model and data-structure neutral interfaces that unify a number of different services such as mesh generation and improvement, front tracking, adaptive mesh refinement, shape optimization, and solution transfer operations. We highlight the use of several ITAPS services in SciDAC applications

Mesh Excision: Is Total Mesh Excision Necessary?

Science.gov (United States)

Wolff, Gillian F; Winters, J Christian; Krlin, Ryan M

2016-04-01

Nearly 29% of women will undergo a secondary, repeat operation for pelvic organ prolapse (POP) symptom recurrence following a primary repair, as reported by Abbott et al. (Am J Obstet Gynecol 210:163.e1-163.e1, 2014). In efforts to decrease the rates of failure, graft materials have been utilized to augment transvaginal repairs. Following the success of using polypropylene mesh (PPM) for stress urinary incontinence (SUI), the use of PPM in the transvaginal repair of POP increased. However, in recent years, significant concerns have been raised about the safety of PPM mesh. Complications, some specific to mesh, such as exposures, erosion, dyspareunia, and pelvic pain, have been reported with increased frequency. In the current literature, there is not substantive evidence to suggest that PPM has intrinsic properties that warrant total mesh removal in the absence of complications. There are a number of complications that can occur after transvaginal mesh placement that do warrant surgical intervention after failure of conservative therapy. In aggregate, there are no high-quality controlled studies that clearly demonstrate that total mesh removal is consistently more likely to achieve pain reduction. In the cases of obstruction and erosion, it seems clear that definitive removal of the offending mesh is associated with resolution of symptoms in the majority of cases and reasonable practice. There are a number of complications that can occur with removal of mesh, and patients should be informed of this as they formulate a choice of treatment. We will review these considerations as we examine the clinical question of whether total versus partial removal of mesh is necessary for the resolution of complications following transvaginal mesh placement.

Adaptation of an unstructured-mesh, finite-element ocean model to the simulation of ocean circulation beneath ice shelves

Science.gov (United States)

Kimura, Satoshi; Candy, Adam S.; Holland, Paul R.; Piggott, Matthew D.; Jenkins, Adrian

2013-07-01

Several different classes of ocean model are capable of representing floating glacial ice shelves. We describe the incorporation of ice shelves into Fluidity-ICOM, a nonhydrostatic finite-element ocean model with the capacity to utilize meshes that are unstructured and adaptive in three dimensions. This geometric flexibility offers several advantages over previous approaches. The model represents melting and freezing on all ice-shelf surfaces including vertical faces, treats the ice shelf topography as continuous rather than stepped, and does not require any smoothing of the ice topography or any of the additional parameterisations of the ocean mixed layer used in isopycnal or z-coordinate models. The model can also represent a water column that decreases to zero thickness at the 'grounding line', where the floating ice shelf is joined to its tributary ice streams. The model is applied to idealised ice-shelf geometries in order to demonstrate these capabilities. In these simple experiments, arbitrarily coarsening the mesh outside the ice-shelf cavity has little effect on the ice-shelf melt rate, while the mesh resolution within the cavity is found to be highly influential. Smoothing the vertical ice front results in faster flow along the smoothed ice front, allowing greater exchange with the ocean than in simulations with a realistic ice front. A vanishing water-column thickness at the grounding line has little effect in the simulations studied. We also investigate the response of ice shelf basal melting to variations in deep water temperature in the presence of salt stratification.

An Immersed Boundary - Adaptive Mesh Refinement solver (IB-AMR) for high fidelity fully resolved wind turbine simulations

Science.gov (United States)

Angelidis, Dionysios; Sotiropoulos, Fotis

2015-11-01

The geometrical details of wind turbines determine the structure of the turbulence in the near and far wake and should be taken in account when performing high fidelity calculations. Multi-resolution simulations coupled with an immersed boundary method constitutes a powerful framework for high-fidelity calculations past wind farms located over complex terrains. We develop a 3D Immersed-Boundary Adaptive Mesh Refinement flow solver (IB-AMR) which enables turbine-resolving LES of wind turbines. The idea of using a hybrid staggered/non-staggered grid layout adopted in the Curvilinear Immersed Boundary Method (CURVIB) has been successfully incorporated on unstructured meshes and the fractional step method has been employed. The overall performance and robustness of the second order accurate, parallel, unstructured solver is evaluated by comparing the numerical simulations against conforming grid calculations and experimental measurements of laminar and turbulent flows over complex geometries. We also present turbine-resolving multi-scale LES considering all the details affecting the induced flow field; including the geometry of the tower, the nacelle and especially the rotor blades of a wind tunnel scale turbine. This material is based upon work supported by the Department of Energy under Award Number DE-EE0005482 and the Sandia National Laboratories.

Numerical methods and analysis of the nonlinear Vlasov equation on unstructured meshes of phase space

International Nuclear Information System (INIS)

Besse, Nicolas

2003-01-01

This work is dedicated to the mathematical and numerical studies of the Vlasov equation on phase-space unstructured meshes. In the first part, new semi-Lagrangian methods are developed to solve the Vlasov equation on unstructured meshes of phase space. As the Vlasov equation describes multi-scale phenomena, we also propose original methods based on a wavelet multi-resolution analysis. The resulting algorithm leads to an adaptive mesh-refinement strategy. The new massively-parallel computers allow to use these methods with several phase-space dimensions. Particularly, these numerical schemes are applied to plasma physics and charged particle beams in the case of two-, three-, and four-dimensional Vlasov-Poisson systems. In the second part we prove the convergence and give error estimates for several numerical schemes applied to the Vlasov-Poisson system when strong and classical solutions are considered. First we show the convergence of a semi-Lagrangian scheme on an unstructured mesh of phase space, when the regularity hypotheses for the initial data are minimal. Then we demonstrate the convergence of classes of high-order semi-Lagrangian schemes in the framework of the regular classical solution. In order to reconstruct the distribution function, we consider symmetrical Lagrange polynomials, B-Splines and wavelets bases. Finally we prove the convergence of a semi-Lagrangian scheme with propagation of gradients yielding a high-order and stable reconstruction of the solution. (author) [fr

Nutritional strategies to influence adaptations to training.

Science.gov (United States)

Spriet, Lawrence L; Gibala, Martin J

2004-01-01

This article highlights new nutritional concerns or practices that may influence the adaptation to training. The discussion is based on the assumption that the adaptation to repeated bouts of training occurs during recovery periods and that if one can train harder, the adaptation will be greater. The goal is to maximize with nutrition the recovery/adaptation that occurs in all rest periods, such that recovery before the next training session is complete. Four issues have been identified where recent scientific information will force sports nutritionists to embrace new issues and reassess old issues and, ultimately, alter the nutritional recommendations they give to athletes. These are: (1) caffeine ingestion; (2) creatine ingestion; (3) the use of intramuscular triacylglycerol (IMTG) as a fuel during exercise and the nutritional effects on IMTG repletion following exercise; and (4) the role nutrition may play in regulating the expression of genes during and after exercise training sessions. Recent findings suggest that low doses of caffeine exert significant ergogenic effects by directly affecting the central nervous system during exercise. Caffeine can cross the blood-brain barrier and antagonize the effects of adenosine, resulting in higher concentrations of stimulatory neurotransmitters. These new data strengthen the case for using low doses of caffeine during training. On the other hand, the data on the role that supplemental creatine ingestion plays in augmenting the increase in skeletal muscle mass and strength during resistance training remain equivocal. Some studies are able to demonstrate increases in muscle fibre size with creatine ingestion and some are not. The final two nutritional topics are new and have not progressed to the point that we can specifically identify strategies to enhance the adaptation to training. However, it is likely that nutritional strategies will be needed to replenish the IMTG that is used during endurance exercise. It is not

Self-gravitational Hydrodynamics with Three-dimensional Adaptive Mesh Refinement: Methodology and Applications to Molecular Cloud Collapse and Fragmentation

International Nuclear Information System (INIS)

Truelove, J.K.; Klein, R.I.; McKee, C.F.; Holliman, J.H. II; Truelove, J.K.; McKee, C.F.; Truelove, J.K.; Holliman, J.H. II; Klein, R.I.; Woods, D.T.; McKee, C.F.; Woods, D.T.; Howell, L.H.; Greenough, J.A.

1998-01-01

We describe a new code for numerical solution of three-dimensional self-gravitational hydrodynamics problems. This code utilizes the technique of local adaptive mesh refinement (AMR), employing multiple grids at multiple levels of resolution and automatically and dynamically adding and removing these grids as necessary to maintain adequate resolution. This technology allows solution of problems that would be prohibitively expensive with a code using fixed resolution, and it is more versatile and efficient than competing methods of achieving variable resolution. In particular, we apply this technique to simulate the collapse and fragmentation of a molecular cloud, a key step in star formation. The simulation involves many orders of magnitude of variation in length scale as fragments form at positions that are not a priori discernible from general initial conditions. In this paper, we describe the methodology behind this new code and present several illustrative applications. The criterion that guides the degree of adaptive mesh refinement is critical to the success of the scheme, and, for the isothermal problems considered here, we employ the Jeans condition for this purpose. By maintaining resolution finer than the local Jeans length, we set new benchmarks of accuracy by which to measure other codes on each problem we consider, including the uniform collapse of a finite pressured cloud. We find that the uniformly rotating, spherical clouds treated here first collapse to disks in the equatorial plane and then, in the presence of applied perturbations, form filamentary singularities that do not fragment while isothermal. Our results provide numerical confirmation of recent work by Inutsuka ampersand Miyama on this scenario of isothermal filament formation. copyright copyright 1998. The American Astronomical Society

Computational methods and modeling. 3. Adaptive Mesh Refinement for the Nodal Integral Method and Application to the Convection-Diffusion Equation

International Nuclear Information System (INIS)

Torej, Allen J.; Rizwan-Uddin

2001-01-01

The nodal integral method (NIM) has been developed for several problems, including the Navier-Stokes equations, the convection-diffusion equation, and the multigroup neutron diffusion equations. The coarse-mesh efficiency of the NIM is not fully realized in problems characterized by a wide range of spatial scales. However, the combination of adaptive mesh refinement (AMR) capability with the NIM can recover the coarse mesh efficiency by allowing high degrees of resolution in specific localized areas where it is needed and by using a lower resolution everywhere else. Furthermore, certain features of the NIM can be fruitfully exploited in the application of the AMR process. In this paper, we outline a general approach to couple nodal schemes with AMR and then apply it to the convection-diffusion (energy) equation. The development of the NIM with AMR capability (NIMAMR) is based on the well-known Berger-Oliger method for structured AMR. In general, the main components of all AMR schemes are 1. the solver; 2. the level-grid hierarchy; 3. the selection algorithm; 4. the communication procedures; 5. the governing algorithm. The first component, the solver, consists of the numerical scheme for the governing partial differential equations and the algorithm used to solve the resulting system of discrete algebraic equations. In the case of the NIM-AMR, the solver is the iterative approach to the solution of the set of discrete equations obtained by applying the NIM. Furthermore, in the NIM-AMR, the level-grid hierarchy (the second component) is based on the Hierarchical Adaptive Mesh Refinement (HAMR) system,6 and hence, the details of the hierarchy are omitted here. In the selection algorithm, regions of the domain that require mesh refinement are identified. The criterion to select regions for mesh refinement can be based on the magnitude of the gradient or on the Richardson truncation error estimate. Although an excellent choice for the selection criterion, the Richardson

ADAPTIVE STRATEGIES OF THE HALOPHYTE POPULATIONS

Directory of Open Access Journals (Sweden)

O. Z. Glukhov

2013-11-01

Full Text Available Studies of the adaptive strategies of halophytes at different levels of their organization are important not only for assessment of their health condition and prognosticating their future behaviors, but also for testing potential suitability of technogenic edaphotopes for plant growth without making additional analyses. We investigated the population structure and morphological variation of three halophilic Gypsophyla L. species which actively spread in different technogenic ecotopes of Ukraine by methods generally accepted in ecology and phytocenology. By the type of strategy populations of species of the genus Gypsophila in technogenic edaphotopes can change the primary type of strategy for the secondary, or gain the stress-tolerant type, mainly due to the changes of parameters of seed productivity. The studied populations are stable with predominance of individuals which reached the prereproductive and reproductive stages of their development. At the organism level the species differ by phenotypic plasticity revealing in compensatory development of vegetative and generative organs. This reflects not only in absolute values of parameters of features, but also when calculating the coefficients of divergence, variation, as well as the vitality classes in populations.By the adaptive strategy halophytes are candidates for use in local phytoremediation of disturbed lands.

Adaptation Strategies to Climate Change by Food Crop Farmers in ...

African Journals Online (AJOL)

... constraints to farmers adaptation strategies. Inputs supply to the local farmers should also come with government subsidy. This will go a long way in alleviating the sufferings of the farmers, as regards inadequate supply and delivery of agricultural inputs. Key words: Adaptation, Strategies, Climate, Change, Food, Crop,

Robust, multidimensional mesh motion based on Monge-Kantorovich equidistribution

Energy Technology Data Exchange (ETDEWEB)

Delzanno, G L [Los Alamos National Laboratory; Finn, J M [Los Alamos National Laboratory

2009-01-01

Mesh-motion (r-refinement) grid adaptivity schemes are attractive due to their potential to minimize the numerical error for a prescribed number of degrees of freedom. However, a key roadblock to a widespread deployment of the technique has been the formulation of robust, reliable mesh motion governing principles, which (1) guarantee a solution in multiple dimensions (2D and 3D), (2) avoid grid tangling (or folding of the mesh, whereby edges of a grid cell cross somewhere in the domain), and (3) can be solved effectively and efficiently. In this study, we formulate such a mesh-motion governing principle, based on volume equidistribution via Monge-Kantorovich optimization (MK). In earlier publications [1, 2], the advantages of this approach in regards to these points have been demonstrated for the time-independent case. In this study, demonstrate that Monge-Kantorovich equidistribution can in fact be used effectively in a time stepping context, and delivers an elegant solution to the otherwise pervasive problem of grid tangling in mesh motion approaches, without resorting to ad-hoc time-dependent terms (as in moving-mesh PDEs, or MMPDEs [3, 4]). We explore two distinct r-refinement implementations of MK: direct, where the current mesh relates to an initial, unchanging mesh, and sequential, where the current mesh is related to the previous one in time. We demonstrate that the direct approach is superior in regards to mesh distortion and robustness. The properties of the approach are illustrated with a paradigmatic hyperbolic PDE, the advection of a passive scalar. Imposed velocity flow fields or varying vorticity levels and flow shears are considered.

TU-H-CAMPUS-JeP3-01: Towards Robust Adaptive Radiation Therapy Strategies

International Nuclear Information System (INIS)

Boeck, M; Eriksson, K; Hardemark, B; Forsgren, A

2016-01-01

Purpose: To set up a framework combining robust treatment planning with adaptive reoptimization in order to maintain high treatment quality, to respond to interfractional variations and to identify those patients who will benefit the most from an adaptive fractionation schedule. Methods: We propose adaptive strategies based on stochastic minimax optimization for a series of simulated treatments on a one-dimensional patient phantom. The plan should be able to handle anticipated systematic and random errors and is applied during the first fractions. Information on the individual geometric variations is gathered at each fraction. At scheduled fractions, the impact of the measured errors on the delivered dose distribution is evaluated. For a patient that receives a dose that does not satisfy specified plan quality criteria, the plan is reoptimized based on these individual measurements using one of three different adaptive strategies. The reoptimized plan is then applied during future fractions until a new scheduled adaptation becomes necessary. In the first adaptive strategy the measured systematic and random error scenarios and their assigned probabilities are updated to guide the robust reoptimization. The focus of the second strategy lies on variation of the fraction of the worst scenarios taken into account during robust reoptimization. In the third strategy the uncertainty margins around the target are recalculated with the measured errors. Results: By studying the effect of the three adaptive strategies combined with various adaptation schedules on the same patient population, the group which benefits from adaptation is identified together with the most suitable strategy and schedule. Preliminary computational results indicate when and how best to adapt for the three different strategies. Conclusion: A workflow is presented that provides robust adaptation of the treatment plan throughout the course of treatment and useful measures to identify patients in need

Unstructured Grid Adaptation: Status, Potential Impacts, and Recommended Investments Toward CFD Vision 2030

Science.gov (United States)

Park, Michael A.; Krakos, Joshua A.; Michal, Todd; Loseille, Adrien; Alonso, Juan J.

2016-01-01

Unstructured grid adaptation is a powerful tool to control discretization error for Computational Fluid Dynamics (CFD). It has enabled key increases in the accuracy, automation, and capacity of some fluid simulation applications. Slotnick et al. provides a number of case studies in the CFD Vision 2030 Study: A Path to Revolutionary Computational Aerosciences to illustrate the current state of CFD capability and capacity. The authors forecast the potential impact of emerging High Performance Computing (HPC) environments forecast in the year 2030 and identify that mesh generation and adaptivity continue to be significant bottlenecks in the CFD work flow. These bottlenecks may persist because very little government investment has been targeted in these areas. To motivate investment, the impacts of improved grid adaptation technologies are identified. The CFD Vision 2030 Study roadmap and anticipated capabilities in complementary disciplines are quoted to provide context for the progress made in grid adaptation in the past fifteen years, current status, and a forecast for the next fifteen years with recommended investments. These investments are specific to mesh adaptation and impact other aspects of the CFD process. Finally, a strategy is identified to diffuse grid adaptation technology into production CFD work flows.

Notes on the Mesh Handler and Mesh Data Conversion

International Nuclear Information System (INIS)

Lee, Sang Yong; Park, Chan Eok

2009-01-01

At the outset of the development of the thermal-hydraulic code (THC), efforts have been made to utilize the recent technology of the computational fluid dynamics. Among many of them, the unstructured mesh approach was adopted to alleviate the restriction of the grid handling system. As a natural consequence, a mesh handler (MH) has been developed to manipulate the complex mesh data from the mesh generator. The mesh generator, Gambit, was chosen at the beginning of the development of the code. But a new mesh generator, Pointwise, was introduced to get more flexible mesh generation capability. An open source code, Paraview, was chosen as a post processor, which can handle unstructured as well as structured mesh data. Overall data processing system for THC is shown in Figure-1. There are various file formats to save the mesh data in the permanent storage media. A couple of dozen of file formats are found even in the above mentioned programs. A competent mesh handler should have the capability to import or export mesh data as many as possible formats. But, in reality, there are two aspects that make it difficult to achieve the competence. The first aspect to consider is the time and efforts to program the interface code. And the second aspect, which is even more difficult one, is the fact that many mesh data file formats are proprietary information. In this paper, some experience of the development of the format conversion programs will be presented. File formats involved are Gambit neutral format, Ansys-CFX grid file format, VTK legacy file format, Nastran format and CGNS

An adaptive simplex cut-cell method for high-order discontinuous Galerkin discretizations of elliptic interface problems and conjugate heat transfer problems

Science.gov (United States)

Sun, Huafei; Darmofal, David L.

2014-12-01

In this paper we propose a new high-order solution framework for interface problems on non-interface-conforming meshes. The framework consists of a discontinuous Galerkin (DG) discretization, a simplex cut-cell technique, and an output-based adaptive scheme. We first present a DG discretization with a dual-consistent output evaluation for elliptic interface problems on interface-conforming meshes, and then extend the method to handle multi-physics interface problems, in particular conjugate heat transfer (CHT) problems. The method is then applied to non-interface-conforming meshes using a cut-cell technique, where the interface definition is completely separate from the mesh generation process. No assumption is made on the interface shape (other than Lipschitz continuity). We then equip our strategy with an output-based adaptive scheme for an accurate output prediction. Through numerical examples, we demonstrate high-order convergence for elliptic interface problems and CHT problems with both smooth and non-smooth interface shapes.

Advanced Variance Reduction Strategies for Optimizing Mesh Tallies in MAVRIC

International Nuclear Information System (INIS)

Peplow, Douglas E.; Blakeman, Edward D; Wagner, John C

2007-01-01

More often than in the past, Monte Carlo methods are being used to compute fluxes or doses over large areas using mesh tallies (a set of region tallies defined on a mesh that overlays the geometry). For problems that demand that the uncertainty in each mesh cell be less than some set maximum, computation time is controlled by the cell with the largest uncertainty. This issue becomes quite troublesome in deep-penetration problems, and advanced variance reduction techniques are required to obtain reasonable uncertainties over large areas. The CADIS (Consistent Adjoint Driven Importance Sampling) methodology has been shown to very efficiently optimize the calculation of a response (flux or dose) for a single point or a small region using weight windows and a biased source based on the adjoint of that response. This has been incorporated into codes such as ADVANTG (based on MCNP) and the new sequence MAVRIC, which will be available in the next release of SCALE. In an effort to compute lower uncertainties everywhere in the problem, Larsen's group has also developed several methods to help distribute particles more evenly, based on forward estimates of flux. This paper focuses on the use of a forward estimate to weight the placement of the source in the adjoint calculation used by CADIS, which we refer to as a forward-weighted CADIS (FW-CADIS)

Block Fusion on Dynamically Adaptive Spacetree Grids for Shallow Water Waves

KAUST Repository

Weinzierl, Tobias

2014-09-01

© 2014 World Scientific Publishing Company. Spacetrees are a popular formalism to describe dynamically adaptive Cartesian grids. Even though they directly yield a mesh, it is often computationally reasonable to embed regular Cartesian blocks into their leaves. This promotes stencils working on homogeneous data chunks. The choice of a proper block size is sensitive. While large block sizes foster loop parallelism and vectorisation, they restrict the adaptivity\\'s granularity and hence increase the memory footprint and lower the numerical accuracy per byte. In the present paper, we therefore use a multiscale spacetree-block coupling admitting blocks on all spacetree nodes. We propose to find sets of blocks on the finest scale throughout the simulation and to replace them by fused big blocks. Such a replacement strategy can pick up hardware characteristics, i.e. which block size yields the highest throughput, while the dynamic adaptivity of the fine grid mesh is not constrained - applications can work with fine granular blocks. We study the fusion with a state-of-the-art shallow water solver at hands of an Intel Sandy Bridge and a Xeon Phi processor where we anticipate their reaction to selected block optimisation and vectorisation.

An unsupervised adaptive strategy for constructing probabilistic roadmaps

KAUST Repository

Tapia, L.

2009-05-01

Since planning environments are complex and no single planner exists that is best for all problems, much work has been done to explore methods for selecting where and when to apply particular planners. However, these two questions have been difficult to answer, even when adaptive methods meant to facilitate a solution are applied. For example, adaptive solutions such as setting learning rates, hand-classifying spaces, and defining parameters for a library of planners have all been proposed. We demonstrate a strategy based on unsupervised learning methods that makes adaptive planning more practical. The unsupervised strategies require less user intervention, model the topology of the problem in a reasonable and efficient manner, can adapt the sampler depending on characteristics of the problem, and can easily accept new samplers as they become available. Through a series of experiments, we demonstrate that in a wide variety of environments, the regions automatically identified by our technique represent the planning space well both in number and placement.We also show that our technique has little overhead and that it out-performs two existing adaptive methods in all complex cases studied.© 2009 IEEE.

Resolution convergence in cosmological hydrodynamical simulations using adaptive mesh refinement

Science.gov (United States)

Snaith, Owain N.; Park, Changbom; Kim, Juhan; Rosdahl, Joakim

2018-06-01

We have explored the evolution of gas distributions from cosmological simulations carried out using the RAMSES adaptive mesh refinement (AMR) code, to explore the effects of resolution on cosmological hydrodynamical simulations. It is vital to understand the effect of both the resolution of initial conditions (ICs) and the final resolution of the simulation. Lower initial resolution simulations tend to produce smaller numbers of low-mass structures. This will strongly affect the assembly history of objects, and has the same effect of simulating different cosmologies. The resolution of ICs is an important factor in simulations, even with a fixed maximum spatial resolution. The power spectrum of gas in simulations using AMR diverges strongly from the fixed grid approach - with more power on small scales in the AMR simulations - even at fixed physical resolution and also produces offsets in the star formation at specific epochs. This is because before certain times the upper grid levels are held back to maintain approximately fixed physical resolution, and to mimic the natural evolution of dark matter only simulations. Although the impact of hold-back falls with increasing spatial and IC resolutions, the offsets in the star formation remain down to a spatial resolution of 1 kpc. These offsets are of the order of 10-20 per cent, which is below the uncertainty in the implemented physics but are expected to affect the detailed properties of galaxies. We have implemented a new grid-hold-back approach to minimize the impact of hold-back on the star formation rate.

Growing assisted migration: Synthesis of a climate change adaptation strategy

Science.gov (United States)

Mary I. Williams; R. Kasten Dumroese

2013-01-01

Assisted migration may be necessary as a climate change adaptation strategy for native plant species that are less adaptive or mobile. Moving plants has been practiced a long time in human history, but movement of species in response to climate change is a new context. First proposed in 1985, assisted migration has gained attention since 2007 as a strategy to prevent...

Structures in Detonation Waves in Low-Pressure H2–O2–Ar Mixtures: A Summary of Results Obtained with the Adaptive Mesh Refinement Framework AMROC

Directory of Open Access Journals (Sweden)

Ralf Deiterding

2011-01-01

Full Text Available Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniques in practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.

Parallel Performance Optimizations on Unstructured Mesh-based Simulations

Energy Technology Data Exchange (ETDEWEB)

Sarje, Abhinav; Song, Sukhyun; Jacobsen, Douglas; Huck, Kevin; Hollingsworth, Jeffrey; Malony, Allen; Williams, Samuel; Oliker, Leonid

2015-01-01

© The Authors. Published by Elsevier B.V. This paper addresses two key parallelization challenges the unstructured mesh-based ocean modeling code, MPAS-Ocean, which uses a mesh based on Voronoi tessellations: (1) load imbalance across processes, and (2) unstructured data access patterns, that inhibit intra- and inter-node performance. Our work analyzes the load imbalance due to naive partitioning of the mesh, and develops methods to generate mesh partitioning with better load balance and reduced communication. Furthermore, we present methods that minimize both inter- and intranode data movement and maximize data reuse. Our techniques include predictive ordering of data elements for higher cache efficiency, as well as communication reduction approaches. We present detailed performance data when running on thousands of cores using the Cray XC30 supercomputer and show that our optimization strategies can exceed the original performance by over 2×. Additionally, many of these solutions can be broadly applied to a wide variety of unstructured grid-based computations.

Adaptive moving grid methods for two-phase flow in porous media

KAUST Repository

Dong, Hao

2014-08-01

In this paper, we present an application of the moving mesh method for approximating numerical solutions of the two-phase flow model in porous media. The numerical schemes combine a mixed finite element method and a finite volume method, which can handle the nonlinearities of the governing equations in an efficient way. The adaptive moving grid method is then used to distribute more grid points near the sharp interfaces, which enables us to obtain accurate numerical solutions with fewer computational resources. The numerical experiments indicate that the proposed moving mesh strategy could be an effective way to approximate two-phase flows in porous media. © 2013 Elsevier B.V. All rights reserved.

An object-oriented decomposition of the adaptive-hp finite element method

Energy Technology Data Exchange (ETDEWEB)

Wiley, J.C.

1994-12-13

Adaptive-hp methods are those which use a refinement control strategy driven by a local error estimate to locally modify the element size, h, and polynomial order, p. The result is an unstructured mesh in which each node may be associated with a different polynomial order and which generally require complex data structures to implement. Object-oriented design strategies and languages which support them, e.g., C++, help control the complexity of these methods. Here an overview of the major classes and class structure of an adaptive-hp finite element code is described. The essential finite element structure is described in terms of four areas of computation each with its own dynamic characteristics. Implications of converting the code for a distributed-memory parallel environment are also discussed.

Mesh Generation and Adaption for High Reynolds Number RANS Computations, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — This proposal offers to provide NASA with an automatic mesh generator for the simulation of aerodynamic flows using Reynolds-Averages Navier-Stokes (RANS) models....

Mesh Generation and Adaption for High Reynolds Number RANS Computations, Phase II

Data.gov (United States)

National Aeronautics and Space Administration — This proposal offers to provide NASA with an automatic mesh generator for the simulation of aerodynamic flows using Reynolds-Averages Navier-Stokes (RANS) models....

Adaptive Landing Gear: Optimum Control Strategy and Potential for Improvement

Directory of Open Access Journals (Sweden)

Grzegorz Mikułowski

2009-01-01

Full Text Available An adaptive landing gear is a landing gear (LG capable of active adaptation to particular landing conditions by means of controlled hydraulic force. The objective of the adaptive control is to mitigate the peak force transferred to the aircraft structure during touch-down, and thus to limit the structural fatigue factor. This paper investigates the ultimate limits for improvement due to various strategies of active control. Five strategies are proposed and investigated numerically using a~validated model of a real, passive landing gear as a reference. Potential for improvement is estimated statistically in terms of the mean and median (significant peak strut forces as well as in terms of the extended safe sinking velocity range. Three control strategies are verified experimentally using a laboratory test stand.

Resilience, human agency and climate change adaptation strategies in the Arctic

DEFF Research Database (Denmark)

Sejersen, Frank

2009-01-01

and work with a number of barriers for resilience. The objective of the article is first to address the position of institutional barriers in the studies and strategies. Second the article analyses the role human agency is ascribed in proposed strategies and projects in Nunavut and Greenland. With a focus......  In the Arctic, indigenous peoples, researchers and governments are working to develop climate change adaptation strategies due to the rapid changes in sea ice extent, weather conditions and in the ecosystem as such. These strategies are often based on specific perceptions of vulnerability...... on institutions and human agency the question is not only ‘how do people manage to adapt?' but moreover ‘what constrains people in pursuing a given adaptation strategy?' The article introduces the concept of double agency which stresses two different aspects of human agency that can be used to understand...

Assessment of the effectiveness of flood adaptation strategies for HCMC

Science.gov (United States)

Lasage, R.; Veldkamp, T. I. E.; de Moel, H.; Van, T. C.; Phi, H. L.; Vellinga, P.; Aerts, J. C. J. H.

2014-06-01

Coastal cities are vulnerable to flooding, and flood risk to coastal cities will increase due to sea-level rise. Moreover, Asian cities in particular are subject to considerable population growth and associated urban developments, increasing this risk even more. Empirical data on vulnerability and the cost and benefits of flood risk reduction measures are therefore paramount for sustainable development of these cities. This paper presents an approach to explore the impacts of sea-level rise and socio-economic developments on flood risk for the flood-prone District 4 in Ho Chi Minh City, Vietnam, and to develop and evaluate the effects of different adaptation strategies (new levees, dry- and wet proofing of buildings and elevating roads and buildings). A flood damage model was developed to simulate current and future flood risk using the results from a household survey to establish stage-damage curves for residential buildings. The model has been used to assess the effects of several participatory developed adaptation strategies to reduce flood risk, expressed in expected annual damage (EAD). Adaptation strategies were evaluated assuming combinations of both sea-level scenarios and land-use scenarios. Together with information on costs of these strategies, we calculated the benefit-cost ratio and net present value for the adaptation strategies until 2100, taking into account depreciation rates of 2.5% and 5%. The results of this modelling study indicate that the current flood risk in District 4 is USD 0.31 million per year, increasing up to USD 0.78 million per year in 2100. The net present value and benefit-cost ratios using a discount rate of 5 % range from USD -107 to -1.5 million, and from 0.086 to 0.796 for the different strategies. Using a discount rate of 2.5% leads to an increase in both net present value and benefit-cost ratio. The adaptation strategies wet-proofing and dry-proofing generate the best results using these economic indicators. The information

Trans-Vaginal Mesh Revision: A Comprehensive Review on Etiologies and Management Strategies with Emphasis on Postoperative Pain Outcomes.

Science.gov (United States)

Mock, Stephen; Reynolds, William S; Dmochowski, Roger R

2014-05-01

The use of polypropylene mesh to augment surgery aimed to correct pelvic organ prolapse and stress urinary incontinence stems largely from the high recurrence rates of native tissue repairs. While objective outcomes were improved, mesh related complications began to emerge that included mesh exposures, extrusions, dyspareunia and other pain issues. However, the indication for and benefit of surgical intervention(s) to address these complications are lacking. We aim to review to current literature regarding postoperative pain outcomes following vaginal mesh revision. Evidence based literature indicates that mesh complications are not rare and surgery that aims to address them generally have an overall benefit. However, studies available are generally small case series of a retrospective nature with short follow up. Some themes are evident: there is a long lag period from mesh insertion to removal; there is a lack of a true denominator of total mesh insertions making it hard to gauge the real scope of the problem; mesh material found not along the expected trocar path or coursing close to neurovascular structures thus raises the possibility of technical errors during insertion. Transvaginal mesh revision(s) for mesh complications generally have a positive effect on pain outcomes, but better controlled studies are needed. Additionally, since technical issues may be a factor in the development of mesh complications, rigorous training and sufficient surgical case volume should be emphasized. © 2014 Wiley Publishing Asia Pty Ltd.

Adaptative mixed methods to axisymmetric shells

International Nuclear Information System (INIS)

Malta, S.M.C.; Loula, A.F.D.; Garcia, E.L.M.

1989-09-01

The mixed Petrov-Galerkin method is applied to axisymmetric shells with uniform and non uniform meshes. Numerical experiments with a cylindrical shell showed a significant improvement in convergence and accuracy with adaptive meshes. (A.C.A.S.) [pt

Strategies to intervene on causal systems are adaptively selected.

Science.gov (United States)

Coenen, Anna; Rehder, Bob; Gureckis, Todd M

2015-06-01

How do people choose interventions to learn about causal systems? Here, we considered two possibilities. First, we test an information sampling model, information gain, which values interventions that can discriminate between a learner's hypotheses (i.e. possible causal structures). We compare this discriminatory model to a positive testing strategy that instead aims to confirm individual hypotheses. Experiment 1 shows that individual behavior is described best by a mixture of these two alternatives. In Experiment 2 we find that people are able to adaptively alter their behavior and adopt the discriminatory model more often after experiencing that the confirmatory strategy leads to a subjective performance decrement. In Experiment 3, time pressure leads to the opposite effect of inducing a change towards the simpler positive testing strategy. These findings suggest that there is no single strategy that describes how intervention decisions are made. Instead, people select strategies in an adaptive fashion that trades off their expected performance and cognitive effort. Copyright © 2015 Elsevier Inc. All rights reserved.

An efficient approach to unstructured mesh hydrodynamics on the cell broadband engine

Energy Technology Data Exchange (ETDEWEB)

Ferenbaugh, Charles R [Los Alamos National Laboratory

2010-01-01

Unstructured mesh physics for the Cell Broadband Engine (CBE) has received little or no attention to date, largely because the CBE architecture poses particular challenges for unstructured mesh algorithms. The most common SPU memory management strategies cannot be applied to the irregular memory access patterns of unstructured meshes, and the SPU vector instruction set does not support the indirect addressing needed by connectivity arrays. This paper presents an approach to unstructured mesh physics that addresses these challenges, by creating a new mesh data structure and reorganizing code to give efficient CBE performance. The approach is demonstrated on the FLAG production hydrodynamics code using standard test problems, and results show an average speedup of more than 5x over the original code.

Small Firm Adaptive Capability, Competitive Strategy and Performance Outcomes: Competing Mediation vs Moderation Perspectives

OpenAIRE

Chryssochoidis, George; Dousios, Dimitrios; Tzokas, Nikolaos

2016-01-01

In small firms, adaptive capability exercises a handling grip on competitive strategy for superior performance primarily acting as a mediator and may offset, through attenuation, the adverse impact of limited resources. Besides exercising a handling grip on competitive strategy adaptive capability is more important than competitive strategy per se for superior performance. Adaptive capability simultaneously undertakes additional secondary roles reinforcing innovation competitive strategy for ...

Introducing Enabling Computational Tools to the Climate Sciences: Multi-Resolution Climate Modeling with Adaptive Cubed-Sphere Grids

Energy Technology Data Exchange (ETDEWEB)

Jablonowski, Christiane [Univ. of Michigan, Ann Arbor, MI (United States)

2015-07-14

The research investigates and advances strategies how to bridge the scale discrepancies between local, regional and global phenomena in climate models without the prohibitive computational costs of global cloud-resolving simulations. In particular, the research explores new frontiers in computational geoscience by introducing high-order Adaptive Mesh Refinement (AMR) techniques into climate research. AMR and statically-adapted variable-resolution approaches represent an emerging trend for atmospheric models and are likely to become the new norm in future-generation weather and climate models. The research advances the understanding of multi-scale interactions in the climate system and showcases a pathway how to model these interactions effectively with advanced computational tools, like the Chombo AMR library developed at the Lawrence Berkeley National Laboratory. The research is interdisciplinary and combines applied mathematics, scientific computing and the atmospheric sciences. In this research project, a hierarchy of high-order atmospheric models on cubed-sphere computational grids have been developed that serve as an algorithmic prototype for the finite-volume solution-adaptive Chombo-AMR approach. The foci of the investigations have lied on the characteristics of both static mesh adaptations and dynamically-adaptive grids that can capture flow fields of interest like tropical cyclones. Six research themes have been chosen. These are (1) the introduction of adaptive mesh refinement techniques into the climate sciences, (2) advanced algorithms for nonhydrostatic atmospheric dynamical cores, (3) an assessment of the interplay between resolved-scale dynamical motions and subgrid-scale physical parameterizations, (4) evaluation techniques for atmospheric model hierarchies, (5) the comparison of AMR refinement strategies and (6) tropical cyclone studies with a focus on multi-scale interactions and variable-resolution modeling. The results of this research project

Towards a national adaptation strategy in view of climate changes

Directory of Open Access Journals (Sweden)

E. DOUKAKIS

2004-06-01

• The general national adaptation principles. The presentation analyses all the above concepts and proposes specific guidelines to formulate a Greek National Adaptation Strategy to mitigate the impacts of anthropogenic climate changes.

An adaptable navigation strategy for Virtual Microscopy from mobile platforms.

Science.gov (United States)

Corredor, Germán; Romero, Eduardo; Iregui, Marcela

2015-04-01

Real integration of Virtual Microscopy with the pathologist service workflow requires the design of adaptable strategies for any hospital service to interact with a set of Whole Slide Images. Nowadays, mobile devices have the actual potential of supporting an online pervasive network of specialists working together. However, such devices are still very limited. This article introduces a novel highly adaptable strategy for streaming and visualizing WSI from mobile devices. The presented approach effectively exploits and extends the granularity of the JPEG2000 standard and integrates it with different strategies to achieve a lossless, loosely-coupled, decoder and platform independent implementation, adaptable to any interaction model. The performance was evaluated by two expert pathologists interacting with a set of 20 virtual slides. The method efficiently uses the available device resources: the memory usage did not exceed a 7% of the device capacity while the decoding times were smaller than the 200 ms per Region of Interest, i.e., a window of 256×256 pixels. This model is easily adaptable to other medical imaging scenarios. Copyright © 2015 Elsevier Inc. All rights reserved.

Employee stress management: An examination of adaptive and maladaptive coping strategies on employee health.

Science.gov (United States)

Holton, M Kim; Barry, Adam E; Chaney, J Don

2015-01-01

Employees commonly report feeling stressed at work. Examine how employees cope with work and personal stress, whether their coping strategies are adaptive (protective to health) or maladaptive (detrimental to health), and if the manner in which employees cope with stress influences perceived stress management. In this cross-sectional study, a random sample of 2,500 full-time university non-student employees (i.e. faculty, salaried professionals, and hourly non-professionals) were surveyed on health related behaviors including stress and coping. Approximately 1,277 completed the survey (51% ). Hierarchical logistic regression was used to assess the ability of adaptive and maladaptive coping strategies to predict self-reported stress management, while controlling for multiple demographic variables. Over half of employees surveyed reported effective stress management. Most frequently used adaptive coping strategies were communication with friend/family member and exercise, while most frequently used maladaptive coping strategies were drinking alcohol and eating more than usual. Both adaptive and maladaptive coping strategies made significant (p stress management. Only adaptive coping strategies (B = 0.265) predicted whether someone would self-identify as effectively managing stress. Use of maladaptive coping strategies decreased likelihood of self-reporting effective stress management. Actual coping strategies employed may influence employees' perceived stress management. Adaptive coping strategies may be more influential than maladaptive coping strategies on perceived stress management. Results illustrate themes for effective workplace stress management programs. Stress management programs focused on increasing use of adaptive coping may have a greater impact on employee stress management than those focused on decreasing use of maladaptive coping. Coping is not only a reaction to stressful experiences but also a consequence of coping resources. Thereby increasing the

Tensile Behaviour of Welded Wire Mesh and Hexagonal Metal Mesh for Ferrocement Application

Science.gov (United States)

Tanawade, A. G.; Modhera, C. D.

2017-08-01

Tension tests were conducted on welded mesh and hexagonal Metal mesh. Welded Mesh is available in the market in different sizes. The two types are analysed viz. Ø 2.3 mm and Ø 2.7 mm welded mesh, having opening size 31.75 mm × 31.75 mm and 25.4 mm × 25.4 mm respectively. Tensile strength test was performed on samples of welded mesh in three different orientations namely 0°, 30° and 45° degrees with the loading axis and hexagonal Metal mesh of Ø 0.7 mm, having opening 19.05 × 19.05 mm. Experimental tests were conducted on samples of these meshes. The objective of this study was to investigate the behaviour of the welded mesh and hexagonal Metal mesh. The result shows that the tension load carrying capacity of welded mesh of Ø 2.7 mm of 0° orientation is good as compared to Ø2.3 mm mesh and ductility of hexagonal Metal mesh is good in behaviour.

Tree-based solvers for adaptive mesh refinement code FLASH - I: gravity and optical depths

Science.gov (United States)

Wünsch, R.; Walch, S.; Dinnbier, F.; Whitworth, A.

2018-04-01

We describe an OctTree algorithm for the MPI parallel, adaptive mesh refinement code FLASH, which can be used to calculate the gas self-gravity, and also the angle-averaged local optical depth, for treating ambient diffuse radiation. The algorithm communicates to the different processors only those parts of the tree that are needed to perform the tree-walk locally. The advantage of this approach is a relatively low memory requirement, important in particular for the optical depth calculation, which needs to process information from many different directions. This feature also enables a general tree-based radiation transport algorithm that will be described in a subsequent paper, and delivers excellent scaling up to at least 1500 cores. Boundary conditions for gravity can be either isolated or periodic, and they can be specified in each direction independently, using a newly developed generalization of the Ewald method. The gravity calculation can be accelerated with the adaptive block update technique by partially re-using the solution from the previous time-step. Comparison with the FLASH internal multigrid gravity solver shows that tree-based methods provide a competitive alternative, particularly for problems with isolated or mixed boundary conditions. We evaluate several multipole acceptance criteria (MACs) and identify a relatively simple approximate partial error MAC which provides high accuracy at low computational cost. The optical depth estimates are found to agree very well with those of the RADMC-3D radiation transport code, with the tree-solver being much faster. Our algorithm is available in the standard release of the FLASH code in version 4.0 and later.

[Adaptation strategies faced with chronic pain].

Science.gov (United States)

Bioy, Antoine

2017-05-01

Chronic pain constitutes a challenge for patients. It makes them uneasy with regard to their personality, their corporality and their life balance, and leaves long-lasting effects on their experience as a patient. The development of adaptation strategies and resources to deal with chronic pain is therefore essential. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

ADAPTIVE MESH REFINEMENT SIMULATIONS OF GALAXY FORMATION: EXPLORING NUMERICAL AND PHYSICAL PARAMETERS

International Nuclear Information System (INIS)

Hummels, Cameron B.; Bryan, Greg L.

2012-01-01

We carry out adaptive mesh refinement cosmological simulations of Milky Way mass halos in order to investigate the formation of disk-like galaxies in a Λ-dominated cold dark matter model. We evolve a suite of five halos to z = 0 and find a gas disk formation in each; however, in agreement with previous smoothed particle hydrodynamics simulations (that did not include a subgrid feedback model), the rotation curves of all halos are centrally peaked due to a massive spheroidal component. Our standard model includes radiative cooling and star formation, but no feedback. We further investigate this angular momentum problem by systematically modifying various simulation parameters including: (1) spatial resolution, ranging from 1700 to 212 pc; (2) an additional pressure component to ensure that the Jeans length is always resolved; (3) low star formation efficiency, going down to 0.1%; (4) fixed physical resolution as opposed to comoving resolution; (5) a supernova feedback model that injects thermal energy to the local cell; and (6) a subgrid feedback model which suppresses cooling in the immediate vicinity of a star formation event. Of all of these, we find that only the last (cooling suppression) has any impact on the massive spheroidal component. In particular, a simulation with cooling suppression and feedback results in a rotation curve that, while still peaked, is considerably reduced from our standard runs.

Event driven adaptation, land use and human coping strategies

DEFF Research Database (Denmark)

Reenberg, Anette; Birch-Thomsen, Torben; Fog, Bjarne

perceive cause-effect relationships between societal and environmental events and their individual and collective management of resources. The coupled human-environment timelines are used to discuss ways in which the local communities' adaptive resource management strategies have been employed in the face......The paper focuses on assessing the wider perspectives of adaptive resource management strategies in former subsistence agriculture societies in the SW Pacific. Firstly, we will briefly introduce the theoretical context related to the livelihood framework, adaptation to socio-environmental change...... and the concept of coupled human-environmental timelines. Secondly, with point of departure in a baseline characterization of Bellona Island derived from a comprehensive survey in the late 1960s and resent fieldwork in late 2006, we present the case of Bellona Island. Key issues addressed concern climatic events...

Seeking new surgical predictors of mesh exposure after transvaginal mesh repair.

Science.gov (United States)

Wu, Pei-Ying; Chang, Chih-Hung; Shen, Meng-Ru; Chou, Cheng-Yang; Yang, Yi-Ching; Huang, Yu-Fang

2016-10-01

The purpose of this study was to explore new preventable risk factors for mesh exposure. A retrospective review of 92 consecutive patients treated with transvaginal mesh (TVM) in the urogynecological unit of our university hospital. An analysis of perioperative predictors was conducted in patients after vaginal repairs using a type 1 mesh. Mesh complications were recorded according to International Urogynecological Association (IUGA) definitions. Mesh-exposure-free durations were calculated by using the Kaplan-Meier method and compared between different closure techniques using log-rank test. Hazard ratios (HR) of predictors for mesh exposure were estimated by univariate and multivariate analyses using Cox proportional hazards regression models. The median surveillance interval was 24.1 months. Two late occurrences were found beyond 1 year post operation. No statistically significant correlation was observed between mesh exposure and concomitant hysterectomy. Exposure risks were significantly higher in patients with interrupted whole-layer closure in univariate analysis. In the multivariate analysis, hematoma [HR 5.42, 95 % confidence interval (CI) 1.26-23.35, P = 0.024), Prolift mesh (HR 5.52, 95 % CI 1.15-26.53, P = 0.033), and interrupted whole-layer closure (HR 7.02, 95 % CI 1.62-30.53, P = 0.009) were the strongest predictors of mesh exposure. Findings indicate the risks of mesh exposure and reoperation may be prevented by avoiding hematoma, large amount of mesh, or interrupted whole-layer closure in TVM surgeries. If these risk factors are prevented, hysterectomy may not be a relative contraindication for TVM use. We also provide evidence regarding mesh exposure and the necessity for more than 1 year of follow-up and preoperative counselling.

Large fog collectors: New strategies for collection efficiency and structural response to wind pressure

Science.gov (United States)

Holmes, Robert; Rivera, Juan de Dios; de la Jara, Emilio

2015-01-01

Most studies of large fog collectors (LFC) have focused on the collection efficiency, the amount of water collected, or economic and social aspects, but have not addressed the effects of strong winds on the system. Wind pressure is directly related to fog water collection efficiency but on the other hand may cause serious damage on the structure of LFCs. This study focuses in the effects of wind pressure on the components of the LFC as an integral system, and the ways to face strong winds with no significant damage. For this purpose we analysed cases of mechanical failure of LFCs both in our experimental station at Peña Blanca in Chile and elsewhere. The effects of wind pressure can be described as a sequence of physical processes, starting with the mesh deformation as a way of adapting to the induced stresses. For a big enough pressure, local stress concentrations generate a progressive rupture of the mesh. In cases where the mesh is sufficiently strong the wind force causes the partial or total collapse of the structure. Usually the weakest part is the mesh, especially close to where it is attached to the structure. The way the mesh is attached to the frame or cable of the structure is particularly important since it can induce significant stress concentrations. Mesh failure before the structure failure may be considered as a mechanical fuse, since it is cheaper to repair. However, more practical mechanical fuses can be conceived. In relation to structural performance and water collection efficiency, we propose a new design strategy that considers a three-dimensional spatial display of the collection screen, oblique incidence angle of wind on mesh and small mesh area between the supporting frame. The proposed design strategies consider both the wind pressure on mesh and structure and the collection efficiency as an integral solution for the LFC. These new design strategies are the final output of this research. Applying these strategies a multi-funnel LFC is

Climate adaptation in NVE's areas of responsibility - Strategy 2010 - 2014; Klimatilpasning innen NVEs ansvarsomraader - Strategi 2010 - 2014

Energy Technology Data Exchange (ETDEWEB)

Hamarsland, Arne T. (ed.)

2010-09-15

NVE has developed a comprehensive climate change strategies within their areas of responsibility. There is a systematic review of how a future climate change will affect NVE management areas; how to meet challenges, vulnerabilities, opportunities and proposals for adaptation measures. Climate adaptation is a dynamic process. It is therefore necessary to follow up the work continuously and correct direction at regular intervals. Climate change adaptation strategy of adaptation measures is a foundation and a direction sensor in NVE's business planning. (AG)

Biometeorology - a science supporting adaptation strategies

Science.gov (United States)

Matzarakis, A.; Cegnar, T.

2010-09-01

Biometeorology as an interdisciplinary science deals with the interactions between atmospheric processes and living organisms (plants, animals and humans). If and in what way weather and climate affect the well-being of all the living creatures? This is the most important question biometeorology is answering. The International Society of Biometeorology (ISB) has built an international forum for the promotion of interdisciplinary collaboration between meteorologists, health professionals, biologists, climatologists, ecologists and other scientists. The Society acts as a community of scientists with similar interests, and fulfills an important role in providing information, expertise and advice for international organizations requiring this assistance. The ISB represents the most comprehensive organization, which brings together people with expertise in these areas. Another specific aim of the ISB is the stimulation of research. Therefore, groups of members are working on several topics organized in commissions for specific targets. The recent five commissions are working in the several fields including climate change issues. Some of examples will be presented, which have been initiated by the members of the ISB and how they can be included as a solid scientific basis to develop efficient adaptation strategies. One such example is a project combining natural and social sciences (in the fields of cooperation processes, tourism analysis and strategy, weather and climate change analysis, information and communication and knowledge transfer) in a transdisciplinary approach that includes players from tourism policy and business and which focuses on the North Sea Coast and the Black Forest. The project "Climate trends and sustainable development of tourism in coastal and mountain range regions was divided into four phases - diagnosis, assessment, strategy/design of solutions, and evaluation - where scientific subprojects and practical partners meet regularly to discuss the

The Role of Chronic Mesh Infection in Delayed-Onset Vaginal Mesh Complications or Recurrent Urinary Tract Infections: Results From Explanted Mesh Cultures.

Science.gov (United States)

Mellano, Erin M; Nakamura, Leah Y; Choi, Judy M; Kang, Diana C; Grisales, Tamara; Raz, Shlomo; Rodriguez, Larissa V

2016-01-01

Vaginal mesh complications necessitating excision are increasingly prevalent. We aim to study whether subclinical chronically infected mesh contributes to the development of delayed-onset mesh complications or recurrent urinary tract infections (UTIs). Women undergoing mesh removal from August 2013 through May 2014 were identified by surgical code for vaginal mesh removal. Only women undergoing removal of anti-incontinence mesh were included. Exclusion criteria included any women undergoing simultaneous prolapse mesh removal. We abstracted preoperative and postoperative information from the medical record and compared mesh culture results from patients with and without mesh extrusion, de novo recurrent UTIs, and delayed-onset pain. One hundred seven women with only anti-incontinence mesh removed were included in the analysis. Onset of complications after mesh placement was within the first 6 months in 70 (65%) of 107 and delayed (≥6 months) in 37 (35%) of 107. A positive culture from the explanted mesh was obtained from 82 (77%) of 107 patients, and 40 (37%) of 107 were positive with potential pathogens. There were no significant differences in culture results when comparing patients with delayed-onset versus immediate pain, extrusion with no extrusion, and de novo recurrent UTIs with no infections. In this large cohort of patients with mesh removed for a diverse array of complications, cultures of the explanted vaginal mesh demonstrate frequent low-density bacterial colonization. We found no differences in culture results from women with delayed-onset pain versus acute pain, vaginal mesh extrusions versus no extrusions, or recurrent UTIs using standard culture methods. Chronic prosthetic infections in other areas of medicine are associated with bacterial biofilms, which are resistant to typical culture techniques. Further studies using culture-independent methods are needed to investigate the potential role of chronic bacterial infections in delayed vaginal mesh

How climate compatible are livelihood adaptation strategies and development programs in rural Indonesia?

Directory of Open Access Journals (Sweden)

R.M. Wise

2016-01-01

Full Text Available Achieving climate compatible development (CCD is a necessity in developing countries, but there are few examples of requisite planning processes, or manifestations of CCD. This paper presents a multi-stakeholder, participatory planning process designed to screen and prioritise rural livelihood adaptation strategies against nine CCD criteria. The process also integrated three principles of adaptation pathways: interventions should be (1 ‘no regrets’ and maintain reversibility to avoid mal-adaptation; (2 address both proximate and underlying systemic drivers of community vulnerability; and (3 linked across spatial scales and jurisdictional levels to promote coordination. Using examples of two rural sub-districts in Indonesia, we demonstrate the process and resulting CCD strategies. Priority strategies varied between the sub-districts but all reflected standard development interventions: water management, intensification or diversification of agriculture and aquaculture, education, health, food security and skills-building for communities. Strategies delivered co-benefits for human development and ecosystem services and hence adaptive capacity, but greenhouse mitigation co-benefits were less significant. Actions to deliver the strategies’ objectives were screened for reversibility, and a minority were potentially mal-adaptive (i.e. path dependent, disproportionately burdening the most vulnerable, reducing incentives to adapt, or increasing greenhouse gas emissions yet highly feasible. These related to infrastructure, which paradoxically is necessary to deliver ‘soft’ adaptation benefits (i.e. road access to health services. Only a small minority of transformative strategies addressed the systemic (i.e. institutional and political drivers of vulnerability. Strategies were well-matched by development programs, suggesting that current interventions mirror CCD. However, development programs tackled fewer systemic drivers, were poorly

Convergence study of global meshing on enamel-cement-bracket finite element model

Science.gov (United States)

Samshuri, S. F.; Daud, R.; Rojan, M. A.; Basaruddin, K. S.; Abdullah, A. B.; Ariffin, A. K.

2017-09-01

This paper presents on meshing convergence analysis of finite element (FE) model to simulate enamel-cement-bracket fracture. Three different materials used in this study involving interface fracture are concerned. Complex behavior ofinterface fracture due to stress concentration is the reason to have a well-constructed meshing strategy. In FE analysis, meshing size is a critical factor that influenced the accuracy and computational time of analysis. The convergence study meshing scheme involving critical area (CA) and non-critical area (NCA) to ensure an optimum meshing sizes are acquired for this FE model. For NCA meshing, the area of interest are at the back of enamel, bracket ligature groove and bracket wing. For CA meshing, area of interest are enamel area close to cement layer, the cement layer and bracket base. The value of constant NCA meshing tested are meshing size 1 and 0.4. The value constant CA meshing tested are 0.4 and 0.1. Manipulative variables are randomly selected and must abide the rule of NCA must be higher than CA. This study employed first principle stresses due to brittle failure nature of the materials used. Best meshing size are selected according to convergence error analysis. Results show that, constant CA are more stable compare to constant NCA meshing. Then, 0.05 constant CA meshing are tested to test the accuracy of smaller meshing. However, unpromising result obtained as the errors are increasing. Thus, constant CA 0.1 with NCA mesh of 0.15 until 0.3 are the most stable meshing as the error in this region are lowest. Convergence test was conducted on three selected coarse, medium and fine meshes at the range of NCA mesh of 0.15 until 3 and CA mesh area stay constant at 0.1. The result shows that, at coarse mesh 0.3, the error are 0.0003% compare to 3% acceptable error. Hence, the global meshing are converge as the meshing size at CA 0.1 and NCA 0.15 for this model.

Coping and adaptive strategies of traumatic brain injury survivors and primary caregivers.

Science.gov (United States)

Adams, Deana; Dahdah, Marie

2016-06-27

Qualitative research methods allowed the investigator to contribute to the development of new theories and to examine change in processes over time, which added rich detail to existing knowledge of the use of coping and adaptive strategies by traumatic brain injury survivors and their primary caregivers (Ponsford, Sloan, & Snow, 2013). The advantages of phenomenological study were that it allows flexibility to explore and understand meanings attached by people to well-studied concepts such as coping, resiliency, and adaptation or compensation. Phenomenological study was sensitive to contextual factors. It also permitted the study of in-depth dynamics of coping and adaptive strategies of TBI survivors and primary caregivers, while understanding the social and psychological implications of the phenomenon. To explore the needs and deficits of adult traumatic brain injury (TBI) survivors and primary caregivers; and to identify their self-initiated coping and adaptive strategies. Significant to this study was the development of coping and adaptive strategies by the participants after their discharge from inpatient and rehabilitation treatment. The compensatory skills taught in treatment settings did not transfer to the home environment. Therefore, these strategies developed independently from previous treatment recommendations contributed to the development of theory related to rehabilitation and counseling. Distinctive to this study was the similarity of coping and adaptive strategies developed from both mild and severe traumatic brain injury survivors. This study consisted of eleven with TBI and six primary caregivers (N = 17), who participated in a series of semi-structured interviews aimed at discovering the coping and adaptive strategies utilized in dealing with the effects of brain injury. A Qualitative Phenomenological design was employed. Patience and understanding, support, and professional help were identified by TBI survivors and caregivers as being their

Sleep Strategies of Night-Shift Nurses on Days Off: Which Ones are Most Adaptive?

Science.gov (United States)

Petrov, Megan E; Clark, C Brendan; Molzof, Hylton E; Johnson, Russell L; Cropsey, Karen L; Gamble, Karen L

2014-01-01

To determine the off-shift sleep strategies of bi-ethnic night-shift nurses, the relationship between these sleep strategies and adaptation to shift work, and identify the participant-level characteristics associated with a given sleep strategy. African-American and non-Hispanic White female, night-shift nurses from an academic hospital were recruited to complete a survey on sleep-wake patterns (n = 213). Participants completed the standard shiftwork index and the biological clocks questionnaire to determine sleep strategies and adaptation to night-shift work. In addition, chronotype was determined quantitatively with a modified version of the Munich ChronoType Questionnaire. Most participants worked ~3 consecutive 12-h night-shifts followed by several days off. Five sleep strategies used on days off were identified: (a) night stay, (b) nap proxy, (c) switch sleeper, (d) no sleep, and (e) incomplete switcher. Nap proxy and no sleep types were associated with poorer adaptation to night-shift work. The switch sleeper and incomplete switcher types were identified as more adaptive strategies that were associated with less sleep disturbance, a later chronotype, and less cardiovascular problems. Behavioral sleep strategies are related to adaptation to a typical night-shift schedule among hospital nurses. Nurses are crucial to the safety and well-being of their patients. Therefore, adoption of more adaptive sleep strategies may reduce sleep/wake dysregulation in this population, and improve cardiovascular outcomes.

Design strategies for irregularly adapting parallel applications

International Nuclear Information System (INIS)

Oliker, Leonid; Biswas, Rupak; Shan, Hongzhang; Sing, Jaswinder Pal

2000-01-01

Achieving scalable performance for dynamic irregular applications is eminently challenging. Traditional message-passing approaches have been making steady progress towards this goal; however, they suffer from complex implementation requirements. The use of a global address space greatly simplifies the programming task, but can degrade the performance of dynamically adapting computations. In this work, we examine two major classes of adaptive applications, under five competing programming methodologies and four leading parallel architectures. Results indicate that it is possible to achieve message-passing performance using shared-memory programming techniques by carefully following the same high level strategies. Adaptive applications have computational work loads and communication patterns which change unpredictably at runtime, requiring dynamic load balancing to achieve scalable performance on parallel machines. Efficient parallel implementations of such adaptive applications are therefore a challenging task. This work examines the implementation of two typical adaptive applications, Dynamic Remeshing and N-Body, across various programming paradigms and architectural platforms. We compare several critical factors of the parallel code development, including performance, programmability, scalability, algorithmic development, and portability

An efficient approach to unstructured mesh hydrodynamics on the cell broadband engine (u)

Energy Technology Data Exchange (ETDEWEB)

Ferenbaugh, Charles R [Los Alamos National Laboratory

2010-12-14

Unstructured mesh physics for the Cell Broadband Engine (CBE) has received little or no attention to date, largely because the CBE architecture poses particular challenges for unstructured mesh algorithms. SPU memory management strategies such as data preloading cannot be applied to the irregular memory storage patterns of unstructured meshes; and the SPU vector instruction set does not support the indirect addressing needed by connectivity arrays. This paper presents an approach to unstructured mesh physics that addresses these challenges, by creating a new mesh data structure and reorganizing code to give efficient CBE performance. The approach is demonstrated on the FLAG production hydrodynamics code using standard test problems, and results show an average speedup of more than 5x over the original code.

Nordic national climate adaptation and tourism strategies – (how) are they interlinked?

DEFF Research Database (Denmark)

Landauer, Mia; Goodsite, Michael Evan; Juhola, Sirkku

2018-01-01

, there is a need to review adaptation actions for tourism within the national adaptation framework supported by research based evidence. Next, by means of Nordic cooperation, guidance for both public and private tourism actors within and across Nordic countries can be provided. This can enhance the competitiveness......The tourism sector is affected by climate change. Nordic tourism destinations have also experienced changes, such as changing precipitation patterns, lack of snow in winter and shifts in seasons. The sector has to implement adaptation strategies but it is unclear whether the current public climate...... policy is sufficient to support considering adaptation actions. We reviewed national climate strategies of the Nordic countries from the perspectives of tourism, but excluding the transport sector. We also reviewed Nordic national tourism strategies from the perspective of climate change, particularly...

Climate changes and farmers' endogenous adaptation strategies ...

African Journals Online (AJOL)

It has been claimed that climate changes impact studies often assume certain adaptations and little explicit examination of how, when, why, and under what conditions they occur. This research aims at analysing the endogenous strategies developed by farmers in agricultural land and crop management. With random ...

GALAXY CLUSTER RADIO RELICS IN ADAPTIVE MESH REFINEMENT COSMOLOGICAL SIMULATIONS: RELIC PROPERTIES AND SCALING RELATIONSHIPS

International Nuclear Information System (INIS)

Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Smith, Britton D.; O'Shea, Brian W.; Turk, Matthew J.

2011-01-01

Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at shock fronts, which is thought to be responsible for radio relics-extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron shock acceleration.

Climate change perceptions and local adaptation strategies of hazard-prone rural households in Bangladesh

Directory of Open Access Journals (Sweden)

G.M. Monirul Alam

2017-01-01

Full Text Available Adaptation is a key strategy that can alleviate the severity of climate change impacts on agriculture and food production. Adaptation strategies are unlikely to be effective without an understanding of the farmers’ perceptions of climate change. This paper explores the local knowledge of adaptation in response to the perceived impacts of climate change and climatic hazards using a survey of 380 resource-poor riverbank erosion-prone households in Bangladesh. The results indicate that the respondents’ perceptions of changes in the climate and of extreme climatic events are similar to the observed climate data. Households have recognized the impacts on their livelihood and resources, resulting in an increased sense of vulnerability. To build resilience, households have undertaken a range of farming and non-farming adaptation strategies, which vary significantly among the farming groups. The important adaptation strategies include adopting new crop varieties, changing planting time, homestead gardening, planting trees and migration. Improved access to finance and to information about appropriate strategies appears to be crucial to support adaptation processes locally and thus to enhance the resilience of vulnerable households.

Adaptive Strategies, Gender Ideology, and Work-Family Balance among Dutch Dual Earners

Science.gov (United States)

Wierda-Boer, Hilde H.; Gerris, Jan R. M.; Vermulst, Ad A.

2008-01-01

Using questionnaire data on 149 Dutch dual-earner couples with young children participating in the European Famwork study, we examine how adaptive strategies and gender ideology relate to parents' perceived success in balancing work and family. Path analysis indicates that some adaptive strategies may harm individuals' work-family balance,…

Urogynecologic Surgical Mesh Implants

Science.gov (United States)

... procedures performed to treat pelvic floor disorders with surgical mesh: Transvaginal mesh to treat POP Transabdominal mesh to treat ... address safety risks Final Order for Reclassification of Surgical Mesh for Transvaginal Pelvic Organ Prolapse Repair Final Order for Effective ...

Assessment of the effectiveness of participatory developed adaptation strategies for HCMC

Science.gov (United States)

Lasage, R.; Veldkamp, T. I. E.; de Moel, H.; Van, T. C.; Phi, H. L.; Vellinga, P.; Aerts, J. C. J. H.

2014-01-01

Coastal cities are vulnerable to flooding, and flood risk to coastal cities will increase due to sea-level rise. Moreover, especially Asian cities are subject to considerable population growth and associated urban developments, increasing this risk even more. Empirical data on vulnerability and the cost and benefits of flood risk reducing measures are therefore paramount for sustainable development of these cities. This paper presents an approach to explore the impacts of sea level rise and socio-economic developments on flood risk for the flood prone District 4 in Ho Chi Minh City, Vietnam, and to develop and evaluate the effects of different adaptation strategies (new levees, dry- and wet flood proofing of buildings). A flood damage model was developed to simulate current and future flood risk using the results from a household survey to establish stage-damage curves for residential buildings. the model has been used to assess the effects of several participatory developed adaptation strategies to reduce flood risk, expressed in Expected Annual Damage (EAD). Adaptation strategies were evaluated assuming combinations of both sea level scenarios and land use scenarios. Together with information on costs of these strategies, we calculated the benefit-cost ratio and net present value for the adaptation strategies until 2100, taking into account depreciation rates of 2.5% and 5%. The results of this modeling study indicate that the current flood risk in District 4 is 0.31 million USD yr-1, increasing up to 0.78 million USD yr-1 in 2100. The net present value and benefit-cost ratios using a discount rate of 5% range from USD -107 to -1.5 million, and from 0.086 to 0.796 for the different strategies. Using a discount rate of 2.5% leads to an increase in both net present value and benefit cost ratio. The adaptation strategies wet proofing and dry proofing generate the best results using these economic indicators. The information on different strategies will be used by

Intravesical midurethral sling mesh erosion secondary to transvaginal mesh reconstructive surgery

Directory of Open Access Journals (Sweden)

Sukanda Bin Jaili

2015-05-01

Conclusion: Repeated vaginal reconstructive surgery may jeopardize a primary mesh or sling, and pose a high risk of mesh erosion, which may be delayed for several years. Removal of the mesh erosion and bladder repair are feasible pervaginally with good outcome.

Mesh versus non-mesh repair of ventral abdominal hernias

International Nuclear Information System (INIS)

Jawaid, M.A.; Talpur, A.H.

2008-01-01

To investigate the relative effectiveness of mesh and suture repair of ventral abdominal hernias in terms of clinical outcome, quality of life and rate of recurrence in both the techniques. This is a retrospective descriptive analysis of 236 patients with mesh and non-mesh repair of primary ventral hernias performed between January 2000 to December 2004 at Surgery Department, Liaquat University of Medical and Health Sciences, Jamshoro. The record sheets of the patients were analyzed and data retrieved to compare the results of both techniques for short-term and long-term results. The data retrieved is statistically analyzed on SPSS version 11. There were 43 (18.22%) males and 193 (81.77%) females with a mean age of 51.79 years and a range of 59 (81-22). Para-umbilical hernia was the commonest of ventral hernia and accounted for 49.8% (n=118) of the total study population followed by incisional hernia comprising 24% (n=57) of the total number. There was a significant difference in the recurrent rate at 3 years interval with 23/101 (22.77%) recurrences in suture-repaired subjects compared to 10/135 (7.40%) in mesh repair group. Chronic pain lasting up to 1-2 years was noted in 14 patients with suture repair. Wound infection is comparatively more common (8.14%) in mesh group. The other variables such as operative and postoperative complications, total hospital stay and quality of life is also discussed. Mesh repair of ventral hernia is much superior to non-mesh suture repair in terms of recurrence and overall outcome. (author)

A posteriori estimator and adaptive mesh refinement for finite volume finite element method for monophasic flow and solute transport in porous media

International Nuclear Information System (INIS)

Amor, H.; Bourgeois, M.

2012-01-01

using an adaptive mesh refinement strategy was introduced in MELODIE for the simulation of groundwater flow and solute transport in saturated porous media in 2 dimensions. The selected estimator, based on the explicit residual error, is expected to allow local refinements and thus minimization of the discretization error at an optimal computational cost. Test case: a realistic heterogeneous case with fracturing. In addition to theoretical test cases a more complex case was tested. The purpose of this test case was twofold: - to move from pure theoretical work to an illustrative case within a realistic generic context; however parameter values for hydrodynamic characteristics were chosen so as to highlight the investigated phenomena; - to account for large time and space scales, representative for those required for the simulation of radioactive waste repositories. The general shape of the geological media was designed to cover main features representative of sedimentary formations. Three distinct radionuclide source locations were chosen in order to obtain a set of flow and transport configurations. The entire layer sequence was structured into three hydrogeological units intersected by three sub-vertical faults. The vertical 2D cross-section dimensions are 5 km long by 500 m thick. Two source terms are located in a 100 m-thick layer in the right part of the domain and another one is located in a larger layer in the left part. These two 'host rock' layers consist of the same sedimentary unit with a low permeability, though an offset due to the middle fault. Faults are considered as conductive features. Radionuclides are assumed to be instantaneously released from the three source term locations at t = 0. The a posteriori error estimator and the adaptive mesh algorithm were applied to this heterogeneous problem. Preliminary calculations showed that the implemented a posteriori error estimator method is efficient to solve the equations of flow and advective

Anisotropic mesh adaptation for solution of finite element problems using hierarchical edge-based error estimates

Energy Technology Data Exchange (ETDEWEB)

Lipnikov, Konstantin [Los Alamos National Laboratory; Agouzal, Abdellatif [UNIV DE LYON; Vassilevski, Yuri [Los Alamos National Laboratory

2009-01-01

We present a new technology for generating meshes minimizing the interpolation and discretization errors or their gradients. The key element of this methodology is construction of a space metric from edge-based error estimates. For a mesh with N{sub h} triangles, the error is proportional to N{sub h}{sup -1} and the gradient of error is proportional to N{sub h}{sup -1/2} which are optimal asymptotics. The methodology is verified with numerical experiments.

Characterizing mesh size distributions (MSDs) in thermosetting materials using a high-pressure system.

Science.gov (United States)

Larché, J-F; Seynaeve, J-M; Voyard, G; Bussière, P-O; Gardette, J-L

2011-04-21

The thermoporosimetry method was adapted to determine the mesh size distribution of an acrylate thermoset clearcoat. This goal was achieved by increasing the solvent rate transfer by increasing the pressure and temperature. A comparison of the results obtained using this approach with those obtained by DMA (dynamic mechanical analysis) underlined the accuracy of thermoporosimetry in characterizing the macromolecular architecture of thermosets. The thermoporosimetry method was also used to analyze the effects of photoaging on cross-linking, which result from the photodegradation of the acrylate thermoset. It was found that the formation of a three-dimensional network followed by densification generates a modification of the average mesh size that leads to a dramatic decrease of the meshes of the polymer.

Key Parameters Estimation and Adaptive Warning Strategy for Rear-End Collision of Vehicle

Directory of Open Access Journals (Sweden)

Xiang Song

2015-01-01

Full Text Available The rear-end collision warning system requires reliable warning decision mechanism to adapt the actual driving situation. To overcome the shortcomings of existing warning methods, an adaptive strategy is proposed to address the practical aspects of the collision warning problem. The proposed strategy is based on the parameter-adaptive and variable-threshold approaches. First, several key parameter estimation algorithms are developed to provide more accurate and reliable information for subsequent warning method. They include a two-stage algorithm which contains a Kalman filter and a Luenberger observer for relative acceleration estimation, a Bayesian theory-based algorithm of estimating the road friction coefficient, and an artificial neural network for estimating the driver’s reaction time. Further, the variable-threshold warning method is designed to achieve the global warning decision. In the method, the safety distance is employed to judge the dangerous state. The calculation method of the safety distance in this paper can be adaptively adjusted according to the different driving conditions of the leading vehicle. Due to the real-time estimation of the key parameters and the adaptive calculation of the warning threshold, the strategy can adapt to various road and driving conditions. Finally, the proposed strategy is evaluated through simulation and field tests. The experimental results validate the feasibility and effectiveness of the proposed strategy.

Farmers Ideas of Climate Change and Strategies for Adaptation in ...

African Journals Online (AJOL)

Farmers Ideas of Climate Change and Strategies for Adaptation in Northern Part of Katsina State. ... The study reveals that changes in temperature and precipitation cause changes in crop varieties, changes in planting dates, a shorter growing season, and increased use of water conservation techniques. Various adaptation ...

Mesh removal following transvaginal mesh placement: a case series of 104 operations.

Science.gov (United States)

Marcus-Braun, Naama; von Theobald, Peter

2010-04-01

The objective of the study was to reveal the way we treat vaginal mesh complications in a trained referral center. This is a retrospective review of all patients who underwent surgical removal of transvaginal mesh for mesh-related complications during a 5-year period. Eighty-three patients underwent 104 operations including 61 complete mesh removal, 14 partial excision, 15 section of sub-urethral sling, and five laparoscopies. Main indications were erosion, infection, granuloma, incomplete voiding, and pain. Fifty-eight removals occurred more than 2 years after the primary mesh placement. Mean operation time was 21 min, and there were two intraoperative and ten minor postoperative complications. Stress urinary incontinence (SUI) recurred in 38% and cystocele in 19% of patients. In a trained center, mesh removal was found to be a quick and safe procedure. Mesh-related complications may frequently occur more than 2 years after the primary operation. Recurrence was mostly associated with SUI and less with genital prolapse.

Multilevel Optimization Framework for Hierarchical Stiffened Shells Accelerated by Adaptive Equivalent Strategy

Science.gov (United States)

Wang, Bo; Tian, Kuo; Zhao, Haixin; Hao, Peng; Zhu, Tianyu; Zhang, Ke; Ma, Yunlong

2017-06-01

In order to improve the post-buckling optimization efficiency of hierarchical stiffened shells, a multilevel optimization framework accelerated by adaptive equivalent strategy is presented in this paper. Firstly, the Numerical-based Smeared Stiffener Method (NSSM) for hierarchical stiffened shells is derived by means of the numerical implementation of asymptotic homogenization (NIAH) method. Based on the NSSM, a reasonable adaptive equivalent strategy for hierarchical stiffened shells is developed from the concept of hierarchy reduction. Its core idea is to self-adaptively decide which hierarchy of the structure should be equivalent according to the critical buckling mode rapidly predicted by NSSM. Compared with the detailed model, the high prediction accuracy and efficiency of the proposed model is highlighted. On the basis of this adaptive equivalent model, a multilevel optimization framework is then established by decomposing the complex entire optimization process into major-stiffener-level and minor-stiffener-level sub-optimizations, during which Fixed Point Iteration (FPI) is employed to accelerate convergence. Finally, the illustrative examples of the multilevel framework is carried out to demonstrate its efficiency and effectiveness to search for the global optimum result by contrast with the single-level optimization method. Remarkably, the high efficiency and flexibility of the adaptive equivalent strategy is indicated by compared with the single equivalent strategy.

Adaptive local routing strategy on a scale-free network

International Nuclear Information System (INIS)

Feng, Liu; Han, Zhao; Ming, Li; Yan-Bo, Zhu; Feng-Yuan, Ren

2010-01-01

Due to the heterogeneity of the structure on a scale-free network, making the betweennesses of all nodes become homogeneous by reassigning the weights of nodes or edges is very difficult. In order to take advantage of the important effect of high degree nodes on the shortest path communication and preferentially deliver packets by them to increase the probability to destination, an adaptive local routing strategy on a scale-free network is proposed, in which the node adjusts the forwarding probability with the dynamical traffic load (packet queue length) and the degree distribution of neighbouring nodes. The critical queue length of a node is set to be proportional to its degree, and the node with high degree has a larger critical queue length to store and forward more packets. When the queue length of a high degree node is shorter than its critical queue length, it has a higher probability to forward packets. After higher degree nodes are saturated (whose queue lengths are longer than their critical queue lengths), more packets will be delivered by the lower degree nodes around them. The adaptive local routing strategy increases the probability of a packet finding its destination quickly, and improves the transmission capacity on the scale-free network by reducing routing hops. The simulation results show that the transmission capacity of the adaptive local routing strategy is larger than that of three previous local routing strategies. (general)

Simulation of geothermal water extraction in heterogeneous reservoirs using dynamic unstructured mesh optimisation

Science.gov (United States)

Salinas, P.; Pavlidis, D.; Jacquemyn, C.; Lei, Q.; Xie, Z.; Pain, C.; Jackson, M.

2017-12-01

It is well known that the pressure gradient into a production well increases with decreasing distance to the well. To properly capture the local pressure drawdown into the well a high grid or mesh resolution is required; moreover, the location of the well must be captured accurately. In conventional simulation models, the user must interact with the model to modify grid resolution around wells of interest, and the well location is approximated on a grid defined early in the modelling process.We report a new approach for improved simulation of near wellbore flow in reservoir scale models through the use of dynamic mesh optimisation and the recently presented double control volume finite element method. Time is discretized using an adaptive, implicit approach. Heterogeneous geologic features are represented as volumes bounded by surfaces. Within these volumes, termed geologic domains, the material properties are constant. Up-, cross- or down-scaling of material properties during dynamic mesh optimization is not required, as the properties are uniform within each geologic domain. A given model typically contains numerous such geologic domains. Wells are implicitly coupled with the domain, and the fluid flows is modelled inside the wells. The method is novel for two reasons. First, a fully unstructured tetrahedral mesh is used to discretize space, and the spatial location of the well is specified via a line vector, ensuring its location even if the mesh is modified during the simulation. The well location is therefore accurately captured, the approach allows complex well trajectories and wells with many laterals to be modelled. Second, computational efficiency is increased by use of dynamic mesh optimization, in which an unstructured mesh adapts in space and time to key solution fields (preserving the geometry of the geologic domains), such as pressure, velocity or temperature, this also increases the quality of the solutions by placing higher resolution where required

Funding climate adaptation strategies with climate derivatives

Directory of Open Access Journals (Sweden)

L. Richard Little

2015-01-01

Full Text Available Climate adaptation requires large capital investments that could be provided not only by traditional sources like governments and banks, but also by derivatives markets. Such markets would allow two parties with different tolerances and expectations about climate risks to transact for their mutual benefit and, in so doing, finance climate adaptation. Here we calculate the price of a derivative called a European put option, based on future sea surface temperature (SST in Tasmania, Australia, with an 18 °C strike threshold. This price represents a quantifiable indicator of climate risk, and forms the basis for aquaculture industries exposed to the risk of higher SST to finance adaptation strategies through the sale of derivative contracts. Such contracts provide a real incentive to parties with different climate outlooks, or risk exposure to take a market assessment of climate change.

Make way for the climate. National adaptation strategy. The interdepartmental memorandum

International Nuclear Information System (INIS)

2007-11-01

This memorandum describes the outline of a national strategy for adaptation to the consequences of climate change. The memorandum is the first report of the Adapting Spatial Planning to Climate Change programme (ARK). [mk] [nl

Online adaptive approach for a game-theoretic strategy for complete vehicle energy management

NARCIS (Netherlands)

Chen, H.; Kessels, J.T.B.A.; Weiland, S.

2015-01-01

This paper introduces an adaptive approach for a game-theoretic strategy on Complete Vehicle Energy Management. The proposed method enhances the game-theoretic approach such that the strategy is able to adapt to real driving behavior. The classical game-theoretic approach relies on one probability

Polygonal Prism Mesh in the Viscous Layers for the Polyhedral Mesh Generator, PolyGen

International Nuclear Information System (INIS)

Lee, Sang Yong; Park, Chan Eok; Kim, Shin Whan

2015-01-01

Polyhedral mesh has been known to have some benefits over the tetrahedral mesh. Efforts have been made to set up a polyhedral mesh generation system with open source programs SALOME and TetGen. The evaluation has shown that the polyhedral mesh generation system is promising. But it is necessary to extend the capability of the system to handle the viscous layers to be a generalized mesh generator. A brief review to the previous works on the mesh generation for the viscous layers will be made in section 2. Several challenging issues for the polygonal prism mesh generation will be discussed as well. The procedure to generate a polygonal prism mesh will be discussed in detail in section 3. Conclusion will be followed in section 4. A procedure to generate meshes in the viscous layers with PolyGen has been successfully designed. But more efforts have to be exercised to find the best way for the generating meshes for viscous layers. Using the extrusion direction of the STL data will the first of the trials in the near future

Command Resiliency: An Adaptive Response Strategy for Complex Incidents

National Research Council Canada - National Science Library

Pfeifer, Joseph W

2005-01-01

.... Unless organizations develop a resilient response strategy that can adapt organizational and operational elements to respond to new terrorist incidents, they will find themselves with the same...

Multiagents-based wide area protection with best-effort adaptive strategy

Energy Technology Data Exchange (ETDEWEB)

Zhu, Yongli; Wang, Dewen [North China Electric Power University, Baoding (China); Song, Shaoqun [Fuzhou Electric Power Industry Bureau, Fujian Province (China)

2009-02-15

Abstract - Multi-trips of circuit breakers often occur within a short period in a severe blackout, and the tripping usually relates to relays' mal-operations. In fact, when two ore more electric primary devices are isolated by circuit breakers, the settings of most relays to protect their power system are getting infeasible and uncoordinated. Adaptive settings are needed to prevent them from wrong operation. This paper presents an adaptive protection scheme based on wide area information with best-effort protection strategy, and the outline of multiagents and WAN Based Adaptive Protection System (MAWAPS). In the scheme, the best-effort adaptive strategy is used to guarantee the adaptive settings to operate safely and effectively in most situations. The IP/SDH-based wide area network (WAN) is used to realize real-time wide area information exchange in the proposed protection scheme. Adaptive setting algorithms for the second stage zero-sequence current and phase overcurrent relays are proposed, which can provide larger line coverage than traditional relays. Moreover, multiagent techniques and IEC 61850 are employed to realize the fast communication between different agents, and MMS plays a prominent role in real-time remote communication. A simulating system has been developed according to the above ideas and approaches, and the experimental results show that the proposed adaptive protection scheme is feasible from the view of protective performance including the executing time. (author)

M-Adapting Low Order Mimetic Finite Differences for Dielectric Interface Problems

Energy Technology Data Exchange (ETDEWEB)

McGregor, Duncan A. [Oregon State Univ., Corvallis, OR (United States); Gyrya, Vitaliy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Manzini, Gianmarco [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-03-07

We consider a problem of reducing numerical dispersion for electromagnetic wave in the domain with two materials separated by a at interface in 2D with a factor of two di erence in wave speed. The computational mesh in the homogeneous parts of the domain away from the interface consists of square elements. Here the method construction is based on m-adaptation construction in homogeneous domain that leads to fourth-order numerical dispersion (vs. second order in non-optimized method). The size of the elements in two domains also di ers by a factor of two, so as to preserve the same value of Courant number in each. Near the interface where two meshes merge the mesh with larger elements consists of degenerate pentagons. We demonstrate that prior to m-adaptation the accuracy of the method falls from second to rst due to breaking of symmetry in the mesh. Next we develop m-adaptation framework for the interface region and devise an optimization criteria. We prove that for the interface problem m-adaptation cannot produce increase in method accuracy. This is in contrast to homogeneous medium where m-adaptation can increase accuracy by two orders.

Multi-morbidity, disability and adaptation strategies among community-dwelling adults aged 75 years and older.

Science.gov (United States)

Yuen, Hon K; Vogtle, Laura K

2016-10-01

The impact of multi-morbidity and disability on the use of adaptation strategies in older adults has not been well researched. This study investigated categories of adaptation strategies that community-dwelling older adults use to complete their daily activities, identified factors that are associated with the use of behavioral adaptations, and examined the relationship among multi-morbidity, disability and adaptation strategies in this population. A mixed methods research design was used. 105 community-dwelling older adults with ages ranging from 75 to 94 years completed a questionnaire and semi-structured interview on types of chronic illnesses (multi-morbidity), amount of difficulty in completing daily activities (degree of disability), and types of behavioral efforts made to complete daily activities that are challenging (adaptation strategies). The model of selective optimization with compensation (SOC) was used to categorize these strategies. The findings revealed that older adults use a wide range of adaptations with compensation and selection the most (40.4%) and least (16.5%) frequently reported respectively. Degree of disability was uniquely associated with the frequency of using SOC strategies while controlling for other factors. Furthermore, degree of disability was a mediator for multi-morbidity in predicting frequency of using SOC strategies. The findings support that older adults using behavioral adaptations to cope with functional decline is prevalent. Knowing the types of adaptation that older adults employed and the indirect relationship between multi-morbidity and frequency of using SOC strategies, with degree of disability as the mediator will be helpful in planning interventions and prevention programs for educating older adults. Copyright © 2016 Elsevier Inc. All rights reserved.

Adaptation strategies of airline travel agencies to the dynamics of ...

African Journals Online (AJOL)

The role of airline travel agencies in a changing operational environment depends on their ability to adapt and survive in the airline travel industry. This paper examines the adaptation strategies airline travel agencies adopt to remain in business. Data for this paper was obtained through multi-stage sampling system that ...

Solution adaptive grids applied to low Reynolds number flow

Science.gov (United States)

de With, G.; Holdø, A. E.; Huld, T. A.

2003-08-01

A numerical study has been undertaken to investigate the use of a solution adaptive grid for flow around a cylinder in the laminar flow regime. The main purpose of this work is twofold. The first aim is to investigate the suitability of a grid adaptation algorithm and the reduction in mesh size that can be obtained. Secondly, the uniform asymmetric flow structures are ideal to validate the mesh structures due to mesh refinement and consequently the selected refinement criteria. The refinement variable used in this work is a product of the rate of strain and the mesh cell size, and contains two variables Cm and Cstr which determine the order of each term. By altering the order of either one of these terms the refinement behaviour can be modified.

An immersed interface vortex particle-mesh solver

Science.gov (United States)

Marichal, Yves; Chatelain, Philippe; Winckelmans, Gregoire

2014-11-01

An immersed interface-enabled vortex particle-mesh (VPM) solver is presented for the simulation of 2-D incompressible viscous flows, in the framework of external aerodynamics. Considering the simulation of free vortical flows, such as wakes and jets, vortex particle-mesh methods already provide a valuable alternative to standard CFD methods, thanks to the interesting numerical properties arising from its Lagrangian nature. Yet, accounting for solid bodies remains challenging, despite the extensive research efforts that have been made for several decades. The present immersed interface approach aims at improving the consistency and the accuracy of one very common technique (based on Lighthill's model) for the enforcement of the no-slip condition at the wall in vortex methods. Targeting a sharp treatment of the wall calls for substantial modifications at all computational levels of the VPM solver. More specifically, the solution of the underlying Poisson equation, the computation of the diffusion term and the particle-mesh interpolation are adapted accordingly and the spatial accuracy is assessed. The immersed interface VPM solver is subsequently validated on the simulation of some challenging impulsively started flows, such as the flow past a cylinder and that past an airfoil. Research Fellow (PhD student) of the F.R.S.-FNRS of Belgium.

Toward An Unstructured Mesh Database

Science.gov (United States)

Rezaei Mahdiraji, Alireza; Baumann, Peter Peter

2014-05-01

Unstructured meshes are used in several application domains such as earth sciences (e.g., seismology), medicine, oceanography, cli- mate modeling, GIS as approximate representations of physical objects. Meshes subdivide a domain into smaller geometric elements (called cells) which are glued together by incidence relationships. The subdivision of a domain allows computational manipulation of complicated physical structures. For instance, seismologists model earthquakes using elastic wave propagation solvers on hexahedral meshes. The hexahedral con- tains several hundred millions of grid points and millions of hexahedral cells. Each vertex node in the hexahedrals stores a multitude of data fields. To run simulation on such meshes, one needs to iterate over all the cells, iterate over incident cells to a given cell, retrieve coordinates of cells, assign data values to cells, etc. Although meshes are used in many application domains, to the best of our knowledge there is no database vendor that support unstructured mesh features. Currently, the main tool for querying and manipulating unstructured meshes are mesh libraries, e.g., CGAL and GRAL. Mesh li- braries are dedicated libraries which includes mesh algorithms and can be run on mesh representations. The libraries do not scale with dataset size, do not have declarative query language, and need deep C++ knowledge for query implementations. Furthermore, due to high coupling between the implementations and input file structure, the implementations are less reusable and costly to maintain. A dedicated mesh database offers the following advantages: 1) declarative querying, 2) ease of maintenance, 3) hiding mesh storage structure from applications, and 4) transparent query optimization. To design a mesh database, the first challenge is to define a suitable generic data model for unstructured meshes. We proposed ImG-Complexes data model as a generic topological mesh data model which extends incidence graph model to multi

THREE-DIMENSIONAL ADAPTIVE MESH REFINEMENT SIMULATIONS OF LONG-DURATION GAMMA-RAY BURST JETS INSIDE MASSIVE PROGENITOR STARS

Energy Technology Data Exchange (ETDEWEB)

Lopez-Camara, D.; Lazzati, Davide [Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States); Morsony, Brian J. [Department of Astronomy, University of Wisconsin-Madison, 2535 Sterling Hall, 475 N. Charter Street, Madison, WI 53706-1582 (United States); Begelman, Mitchell C., E-mail: dlopezc@ncsu.edu [JILA, University of Colorado, 440 UCB, Boulder, CO 80309-0440 (United States)

2013-04-10

We present the results of special relativistic, adaptive mesh refinement, 3D simulations of gamma-ray burst jets expanding inside a realistic stellar progenitor. Our simulations confirm that relativistic jets can propagate and break out of the progenitor star while remaining relativistic. This result is independent of the resolution, even though the amount of turbulence and variability observed in the simulations is greater at higher resolutions. We find that the propagation of the jet head inside the progenitor star is slightly faster in 3D simulations compared to 2D ones at the same resolution. This behavior seems to be due to the fact that the jet head in 3D simulations can wobble around the jet axis, finding the spot of least resistance to proceed. Most of the average jet properties, such as density, pressure, and Lorentz factor, are only marginally affected by the dimensionality of the simulations and therefore results from 2D simulations can be considered reliable.

Parallel implementation of a Lagrangian-based model on an adaptive mesh in C++: Application to sea-ice

Science.gov (United States)

Samaké, Abdoulaye; Rampal, Pierre; Bouillon, Sylvain; Ólason, Einar

2017-12-01

We present a parallel implementation framework for a new dynamic/thermodynamic sea-ice model, called neXtSIM, based on the Elasto-Brittle rheology and using an adaptive mesh. The spatial discretisation of the model is done using the finite-element method. The temporal discretisation is semi-implicit and the advection is achieved using either a pure Lagrangian scheme or an Arbitrary Lagrangian Eulerian scheme (ALE). The parallel implementation presented here focuses on the distributed-memory approach using the message-passing library MPI. The efficiency and the scalability of the parallel algorithms are illustrated by the numerical experiments performed using up to 500 processor cores of a cluster computing system. The performance obtained by the proposed parallel implementation of the neXtSIM code is shown being sufficient to perform simulations for state-of-the-art sea ice forecasting and geophysical process studies over geographical domain of several millions squared kilometers like the Arctic region.

Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors

KAUST Repository

Zhang, Fang

2011-02-01

Mesh current collectors made of stainless steel (SS) can be integrated into microbial fuel cell (MFC) cathodes constructed of a reactive carbon black and Pt catalyst mixture and a poly(dimethylsiloxane) (PDMS) diffusion layer. It is shown here that the mesh properties of these cathodes can significantly affect performance. Cathodes made from the coarsest mesh (30-mesh) achieved the highest maximum power of 1616 ± 25 mW m-2 (normalized to cathode projected surface area; 47.1 ± 0.7 W m-3 based on liquid volume), while the finest mesh (120-mesh) had the lowest power density (599 ± 57 mW m-2). Electrochemical impedance spectroscopy showed that charge transfer and diffusion resistances decreased with increasing mesh opening size. In MFC tests, the cathode performance was primarily limited by reaction kinetics, and not mass transfer. Oxygen permeability increased with mesh opening size, accounting for the decreased diffusion resistance. At higher current densities, diffusion became a limiting factor, especially for fine mesh with low oxygen transfer coefficients. These results demonstrate the critical nature of the mesh size used for constructing MFC cathodes. © 2010 Elsevier B.V. All rights reserved.

How will the EU climate adaptation strategy affect EU agricultural policies?

DEFF Research Database (Denmark)

Nielsen, Helle Ørsted; Karali, Eleni; Castellari, Sergio

A key objective in the EU Strategy on adaptation to climate change (COM (2013) 216 final) is to ensure mainstreaming, i.e. integration, of adaptation measures into European sectoral policies. The Common Agricultural Policy (CAP) is one such sectoral policy which is prioritised in the strategy...... as an area to be climate proofed. The CAP is under revision and will be reformed for the 2014-2020 period with the explicit objectives of strengthening the competitiveness and the sustainability of agriculture (EC). Climate change adaptation objectives are included in the proposal for a greening...... of the single payment scheme (2011/0280 (COD), and the proposal for the Rural Development Fund also specifically sets out climate change adaptation as a cross-cutting objective to which rural development funding must contribute 2011/0282 (COD). This paper therefore examines the most important challenges...

[Expandable metal mesh stents for treatment of tracheal stenoses and tracheomalacia].

Science.gov (United States)

Müller, C; Dienemann, H; Hoffmann, H; Berger, H; Storck, M; Jolk, A; Schildberg, F W

1993-01-01

The treatment of tracheo-bronchial stenosis or tracheomalacia is mainly carried out by means of resection or tracheoplastic operative strategies. Since the introduction of metal-mesh stents, a definitive endoluminal therapy has to be considered under new aspects. Six patients with malignant stenosis or tracheomalacia due to compression were treated by implantation of Palmaz- or Wallstents. Immediately after the implantation, patients were relieved from dyspnoea, the forced inspiratory volume-1 (FIV1) was normalized. All implanted stents were well tolerated, even in the long-time follow-up (19 months). Bronchoscopic control showed overgrowth of the metal meshes by respiratory epithelium. The implantation of metal-mesh stents is an adequate alternative in the treatment of malignant stenosis and tracheomalacia.

Transitions in optimal adaptive strategies for populations in fluctuating environments

Science.gov (United States)

Mayer, Andreas; Mora, Thierry; Rivoire, Olivier; Walczak, Aleksandra M.

2017-09-01

Biological populations are subject to fluctuating environmental conditions. Different adaptive strategies can allow them to cope with these fluctuations: specialization to one particular environmental condition, adoption of a generalist phenotype that compromises between conditions, or population-wise diversification (bet hedging). Which strategy provides the largest selective advantage in the long run depends on the range of accessible phenotypes and the statistics of the environmental fluctuations. Here, we analyze this problem in a simple mathematical model of population growth. First, we review and extend a graphical method to identify the nature of the optimal strategy when the environmental fluctuations are uncorrelated. Temporal correlations in environmental fluctuations open up new strategies that rely on memory but are mathematically challenging to study: We present analytical results to address this challenge. We illustrate our general approach by analyzing optimal adaptive strategies in the presence of trade-offs that constrain the range of accessible phenotypes. Our results extend several previous studies and have applications to a variety of biological phenomena, from antibiotic resistance in bacteria to immune responses in vertebrates.

Reduced order modelling techniques for mesh movement strategies as applied to fluid structure interactions

CSIR Research Space (South Africa)

Bogaers, Alfred EJ

2010-01-01

Full Text Available of Laplacian or Bi-harmonic equations [7], radial basis function (RBF) interpolation [3, 15] or through mesh optimization [1, 6]. Despite the successes of these algorithms in reducing the frequency and necessity for re- meshing, they still account for a... simulations of a real system. What makes POD remarkable is that the selected modes are not only appropriate but make up the optimal linear basis for describing any given system. POD has been applied in a wide range of disciplines including image processing...

Adaptive Finite Volume Method for the Shallow Water Equations on Triangular Grids

Directory of Open Access Journals (Sweden)

Sudi Mungkasi

2016-01-01

Full Text Available This paper presents a numerical entropy production (NEP scheme for two-dimensional shallow water equations on unstructured triangular grids. We implement NEP as the error indicator for adaptive mesh refinement or coarsening in solving the shallow water equations using a finite volume method. Numerical simulations show that NEP is successful to be a refinement/coarsening indicator in the adaptive mesh finite volume method, as the method refines the mesh or grids around nonsmooth regions and coarsens them around smooth regions.

Distinct motor strategies underlying split-belt adaptation in human walking and running.

Science.gov (United States)

Ogawa, Tetsuya; Kawashima, Noritaka; Obata, Hiroki; Kanosue, Kazuyuki; Nakazawa, Kimitaka

2015-01-01

The aim of the present study was to elucidate the adaptive and de-adaptive nature of human running on a split-belt treadmill. The degree of adaptation and de-adaptation was compared with those in walking by calculating the antero-posterior component of the ground reaction force (GRF). Adaptation to walking and running on a split-belt resulted in a prominent asymmetry in the movement pattern upon return to the normal belt condition, while the two components of the GRF showed different behaviors depending on the gaits. The anterior braking component showed prominent adaptive and de-adaptive behaviors in both gaits. The posterior propulsive component, on the other hand, exhibited such behavior only in running, while that in walking showed only short-term aftereffect (lasting less than 10 seconds) accompanied by largely reactive responses. These results demonstrate a possible difference in motor strategies (that is, the use of reactive feedback and adaptive feedforward control) by the central nervous system (CNS) for split-belt locomotor adaptation between walking and running. The present results provide basic knowledge on neural control of human walking and running as well as possible strategies for gait training in athletic and rehabilitation scenes.

Distinct motor strategies underlying split-belt adaptation in human walking and running.

Directory of Open Access Journals (Sweden)

Tetsuya Ogawa

Full Text Available The aim of the present study was to elucidate the adaptive and de-adaptive nature of human running on a split-belt treadmill. The degree of adaptation and de-adaptation was compared with those in walking by calculating the antero-posterior component of the ground reaction force (GRF. Adaptation to walking and running on a split-belt resulted in a prominent asymmetry in the movement pattern upon return to the normal belt condition, while the two components of the GRF showed different behaviors depending on the gaits. The anterior braking component showed prominent adaptive and de-adaptive behaviors in both gaits. The posterior propulsive component, on the other hand, exhibited such behavior only in running, while that in walking showed only short-term aftereffect (lasting less than 10 seconds accompanied by largely reactive responses. These results demonstrate a possible difference in motor strategies (that is, the use of reactive feedback and adaptive feedforward control by the central nervous system (CNS for split-belt locomotor adaptation between walking and running. The present results provide basic knowledge on neural control of human walking and running as well as possible strategies for gait training in athletic and rehabilitation scenes.

Reactor physics verification of the MCNP6 unstructured mesh capability

International Nuclear Information System (INIS)

Burke, T. P.; Kiedrowski, B. C.; Martz, R. L.; Martin, W. R.

2013-01-01

The Monte Carlo software package MCNP6 has the ability to transport particles on unstructured meshes generated from the Computed-Aided Engineering software Abaqus. Verification is performed using benchmarks with features relevant to reactor physics - Big Ten and the C5G7 computational benchmark. Various meshing strategies are tested and results are compared to reference solutions. Computational performance results are also given. The conclusions show MCNP6 is capable of producing accurate calculations for reactor physics geometries and the computational requirements for small lattice benchmarks are reasonable on modern computing platforms. (authors)

Reactor physics verification of the MCNP6 unstructured mesh capability

Energy Technology Data Exchange (ETDEWEB)

Burke, T. P. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Kiedrowski, B. C.; Martz, R. L. [X-Computational Physics Division, Monte Carlo Codes Group, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States); Martin, W. R. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States)

2013-07-01

The Monte Carlo software package MCNP6 has the ability to transport particles on unstructured meshes generated from the Computed-Aided Engineering software Abaqus. Verification is performed using benchmarks with features relevant to reactor physics - Big Ten and the C5G7 computational benchmark. Various meshing strategies are tested and results are compared to reference solutions. Computational performance results are also given. The conclusions show MCNP6 is capable of producing accurate calculations for reactor physics geometries and the computational requirements for small lattice benchmarks are reasonable on modern computing platforms. (authors)

Adaptive Control Based Harvesting Strategy for a Predator-Prey Dynamical System.

Science.gov (United States)

Sen, Moitri; Simha, Ashutosh; Raha, Soumyendu

2018-04-23

This paper deals with designing a harvesting control strategy for a predator-prey dynamical system, with parametric uncertainties and exogenous disturbances. A feedback control law for the harvesting rate of the predator is formulated such that the population dynamics is asymptotically stabilized at a positive operating point, while maintaining a positive, steady state harvesting rate. The hierarchical block strict feedback structure of the dynamics is exploited in designing a backstepping control law, based on Lyapunov theory. In order to account for unknown parameters, an adaptive control strategy has been proposed in which the control law depends on an adaptive variable which tracks the unknown parameter. Further, a switching component has been incorporated to robustify the control performance against bounded disturbances. Proofs have been provided to show that the proposed adaptive control strategy ensures asymptotic stability of the dynamics at a desired operating point, as well as exact parameter learning in the disturbance-free case and learning with bounded error in the disturbance prone case. The dynamics, with uncertainty in the death rate of the predator, subjected to a bounded disturbance has been simulated with the proposed control strategy.

Intelligent fault recognition strategy based on adaptive optimized multiple centers

Science.gov (United States)

Zheng, Bo; Li, Yan-Feng; Huang, Hong-Zhong

2018-06-01

For the recognition principle based optimized single center, one important issue is that the data with nonlinear separatrix cannot be recognized accurately. In order to solve this problem, a novel recognition strategy based on adaptive optimized multiple centers is proposed in this paper. This strategy recognizes the data sets with nonlinear separatrix by the multiple centers. Meanwhile, the priority levels are introduced into the multi-objective optimization, including recognition accuracy, the quantity of optimized centers, and distance relationship. According to the characteristics of various data, the priority levels are adjusted to ensure the quantity of optimized centers adaptively and to keep the original accuracy. The proposed method is compared with other methods, including support vector machine (SVM), neural network, and Bayesian classifier. The results demonstrate that the proposed strategy has the same or even better recognition ability on different distribution characteristics of data.

Practical implementation of tetrahedral mesh reconstruction in emission tomography

Science.gov (United States)

Boutchko, R.; Sitek, A.; Gullberg, G. T.

2013-05-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

Practical implementation of tetrahedral mesh reconstruction in emission tomography

International Nuclear Information System (INIS)

Boutchko, R; Gullberg, G T; Sitek, A

2013-01-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

A software platform for continuum modeling of ion channels based on unstructured mesh

International Nuclear Information System (INIS)

Tu, B; Bai, S Y; Xie, Y; Zhang, L B; Lu, B Z; Chen, M X

2014-01-01

Most traditional continuum molecular modeling adopted finite difference or finite volume methods which were based on a structured mesh (grid). Unstructured meshes were only occasionally used, but an increased number of applications emerge in molecular simulations. To facilitate the continuum modeling of biomolecular systems based on unstructured meshes, we are developing a software platform with tools which are particularly beneficial to those approaches. This work describes the software system specifically for the simulation of a typical, complex molecular procedure: ion transport through a three-dimensional channel system that consists of a protein and a membrane. The platform contains three parts: a meshing tool chain for ion channel systems, a parallel finite element solver for the Poisson–Nernst–Planck equations describing the electrodiffusion process of ion transport, and a visualization program for continuum molecular modeling. The meshing tool chain in the platform, which consists of a set of mesh generation tools, is able to generate high-quality surface and volume meshes for ion channel systems. The parallel finite element solver in our platform is based on the parallel adaptive finite element package PHG which wass developed by one of the authors [1]. As a featured component of the platform, a new visualization program, VCMM, has specifically been developed for continuum molecular modeling with an emphasis on providing useful facilities for unstructured mesh-based methods and for their output analysis and visualization. VCMM provides a graphic user interface and consists of three modules: a molecular module, a meshing module and a numerical module. A demonstration of the platform is provided with a study of two real proteins, the connexin 26 and hemolysin ion channels. (paper)

Suppressing traffic-driven epidemic spreading by adaptive routing strategy

International Nuclear Information System (INIS)

Yang, Han-Xin; Wang, Zhen

2016-01-01

The design of routing strategies for traffic-driven epidemic spreading has received increasing attention in recent years. In this paper, we propose an adaptive routing strategy that incorporates topological distance with local epidemic information through a tunable parameter h. In the case where the traffic is free of congestion, there exists an optimal value of routing parameter h, leading to the maximal epidemic threshold. This means that epidemic spreading can be more effectively controlled by adaptive routing, compared to that of the static shortest path routing scheme. Besides, we find that the optimal value of h can greatly relieve the traffic congestion in the case of finite node-delivering capacity. We expect our work to provide new insights into the effects of dynamic routings on traffic-driven epidemic spreading.

TESS: A RELATIVISTIC HYDRODYNAMICS CODE ON A MOVING VORONOI MESH

International Nuclear Information System (INIS)

Duffell, Paul C.; MacFadyen, Andrew I.

2011-01-01

We have generalized a method for the numerical solution of hyperbolic systems of equations using a dynamic Voronoi tessellation of the computational domain. The Voronoi tessellation is used to generate moving computational meshes for the solution of multidimensional systems of conservation laws in finite-volume form. The mesh-generating points are free to move with arbitrary velocity, with the choice of zero velocity resulting in an Eulerian formulation. Moving the points at the local fluid velocity makes the formulation effectively Lagrangian. We have written the TESS code to solve the equations of compressible hydrodynamics and magnetohydrodynamics for both relativistic and non-relativistic fluids on a dynamic Voronoi mesh. When run in Lagrangian mode, TESS is significantly less diffusive than fixed mesh codes and thus preserves contact discontinuities to high precision while also accurately capturing strong shock waves. TESS is written for Cartesian, spherical, and cylindrical coordinates and is modular so that auxiliary physics solvers are readily integrated into the TESS framework and so that this can be readily adapted to solve general systems of equations. We present results from a series of test problems to demonstrate the performance of TESS and to highlight some of the advantages of the dynamic tessellation method for solving challenging problems in astrophysical fluid dynamics.

An adaptation strategy of sandland peasants in Yogyakarta toward climate change

Science.gov (United States)

Rusdiyana, E.; Suminah

2018-03-01

This study aims to explore and describe the adaptation strategies of sandland peasants toward climate change. Qualitative research method was employed and the data were collected through observation. In addition, the recording of the data, interview and the validity of data were determined by triangulation of sources. The results of the research showed that the adaptation strategies of sandland peasants toward climate change were; (1) the adjustment of crop varieties, (2) the utilization of productive crops as wind breaking, and (3) the irrigation system using “sumur panthek”.

Laparoscopic appendicectomy for suspected mesh-induced appendicitis after laparoscopic transabdominal preperitoneal polypropylene mesh inguinal herniorraphy

Directory of Open Access Journals (Sweden)

Jennings Jason

2010-01-01

Full Text Available Laparoscopic inguinal herniorraphy via a transabdominal preperitoneal (TAPP approach using Polypropylene Mesh (Mesh and staples is an accepted technique. Mesh induces a localised inflammatory response that may extend to, and involve, adjacent abdominal and pelvic viscera such as the appendix. We present an interesting case of suspected Mesh-induced appendicitis treated successfully with laparoscopic appendicectomy, without Mesh removal, in an elderly gentleman who presented with symptoms and signs of acute appendicitis 18 months after laparoscopic inguinal hernia repair. Possible mechanisms for Mesh-induced appendicitis are briefly discussed.

Use of a dynamic grid adaptation in the asymmetric weighted residual method

International Nuclear Information System (INIS)

Graf, V.; Romstedt, P.; Werner, W.

1986-01-01

A dynamic grid adaptive method has been developed for use with the asymmetric weighted residual method. The method automatically adapts the number and position of the spatial mesh points as the solution of hyperbolic or parabolic vector partial differential equations progresses in time. The mesh selection algorithm is based on the minimization of the L 2 norm of the spatial discretization error. The method permits the accurate calculation of the evolution of inhomogeneities, like wave fronts, shock layers, and other sharp transitions, while generally using a coarse computational grid. The number of required mesh points is significantly reduced, relative to a fixed Eulerian grid. Since the mesh selection algorithm is computationally inexpensive, a corresponding reduction of computing time results

Climate change adaptation strategies by small-scale farmers in ...

African Journals Online (AJOL)

Mburu

SPSS) ... were financial constraints (93.4%), lack of relevant skills (74.5%) and lack of ... Key words: Climate change, small-scale farmers, adaptation strategies. ... investment in irrigation infrastructure, high post-harvest ..... 72.0 School drop out.

Paradoxical cardiovascular effects of implementing adaptive emotion regulation strategies in generalized anxiety disorder.

Science.gov (United States)

Aldao, Amelia; Mennin, Douglas S

2012-02-01

Recent models of generalized anxiety disorder (GAD) have expanded on Borkovec's avoidance theory by delineating emotion regulation deficits associated with the excessive worry characteristic of this disorder (see Behar, DiMarco, Hekler, Mohlman, & Staples, 2009). However, it has been difficult to determine whether emotion regulation is simply a useful heuristic for the avoidant properties of worry or an important extension to conceptualizations of GAD. Some of this difficulty may arise from a focus on purported maladaptive regulation strategies, which may be confounded with symptomatic distress components of the disorder (such as worry). We examined the implementation of adaptive regulation strategies by participants with and without a diagnosis of GAD while watching emotion-eliciting film clips. In a between-subjects design, participants were randomly assigned to accept, reappraise, or were not given specific regulation instructions. Implementation of adaptive regulation strategies produced differential effects in the physiological (but not subjective) domain across diagnostic groups. Whereas participants with GAD demonstrated lower cardiac flexibility when implementing adaptive regulation strategies than when not given specific instructions on how to regulate, healthy controls showed the opposite pattern, suggesting they benefited from the use of adaptive regulation strategies. We discuss the implications of these findings for the delineation of emotion regulation deficits in psychopathology. Copyright © 2011 Elsevier Ltd. All rights reserved.

Use of dynamic grid adaption in the ASWR-method

International Nuclear Information System (INIS)

Graf, U.; Romstedt, P.; Werner, W.

1985-01-01

A dynamic grid adaption method has been developed for use with the ASWR-method. The method automatically adapts the number and position of the spatial meshpoints as the solution of hyperbolic or parabolic vector partial differential equations progresses in time. The mesh selection algorithm is based on the minimization of the L 2 -norm of the spatial discretization error. The method permits accurate calculation of the evolution of inhomogenities like wave fronts, shock layers and other sharp transitions, while generally using a coarse computational grid. The number of required mesh points is significantly reduced, relative to a fixed Eulerian grid. Since the mesh selection algorithm is computationally inexpensive, a corresponding reduction of computing time results

Persistent pelvic pain following transvaginal mesh surgery: a cause for mesh removal.

Science.gov (United States)

Marcus-Braun, Naama; Bourret, Antoine; von Theobald, Peter

2012-06-01

Persistent pelvic pain after vaginal mesh surgery is an uncommon but serious complication that greatly affects women's quality of life. Our aim was to evaluate various procedures for mesh removal performed at a tertiary referral center in cases of persistent pelvic pain, and to evaluate the ensuing complications and outcomes. A retrospective study was conducted at the University Hospital of Caen, France, including all patients treated for removal or section of vaginal mesh due to pelvic pain as a primary cause, between January 2004 and September 2009. Ten patients met the inclusion criteria. Patients were diagnosed between 10 months and 3 years after their primary operation. Eight cases followed suburethral sling procedures and two followed mesh surgery for pelvic organ prolapse. Patients presented with obturator neuralgia (6), pudendal neuralgia (2), dyspareunia (1), and non-specific pain (1). The surgical treatment to release the mesh included: three cases of extra-peritoneal laparoscopy, four cases of complete vaginal mesh removal, one case of partial mesh removal and two cases of section of the suburethral sling. In all patients with obturator neuralgia, symptoms were resolved or improved, whereas in both cases of pudendal neuralgia the symptoms continued. There were no intra-operative complications. Post-operative Retzius hematoma was observed in one patient after laparoscopy. Mesh removal in a tertiary center is a safe procedure, necessary in some cases of persistent pelvic pain. Obturator neuralgia seems to be easier to treat than pudendal neuralgia. Early diagnosis is the key to success in prevention of chronic disease. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Determinants of climate change adaptive strategies among small ...

African Journals Online (AJOL)

Identified adaptation strategies used by farmers to mitigate the effect of climate change included planting beside the river(86%), planting disease and pest resistant crop (73%) and changes on planting and harvesting dates(63%). Results of Tobit regression analysis showed that level of education, farm size and access to ...

An adaptive deep Q-learning strategy for handwritten digit recognition.

Science.gov (United States)

Qiao, Junfei; Wang, Gongming; Li, Wenjing; Chen, Min

2018-02-22

Handwritten digits recognition is a challenging problem in recent years. Although many deep learning-based classification algorithms are studied for handwritten digits recognition, the recognition accuracy and running time still need to be further improved. In this paper, an adaptive deep Q-learning strategy is proposed to improve accuracy and shorten running time for handwritten digit recognition. The adaptive deep Q-learning strategy combines the feature-extracting capability of deep learning and the decision-making of reinforcement learning to form an adaptive Q-learning deep belief network (Q-ADBN). First, Q-ADBN extracts the features of original images using an adaptive deep auto-encoder (ADAE), and the extracted features are considered as the current states of Q-learning algorithm. Second, Q-ADBN receives Q-function (reward signal) during recognition of the current states, and the final handwritten digits recognition is implemented by maximizing the Q-function using Q-learning algorithm. Finally, experimental results from the well-known MNIST dataset show that the proposed Q-ADBN has a superiority to other similar methods in terms of accuracy and running time. Copyright © 2018 Elsevier Ltd. All rights reserved.

Climate change perceptions and local adaptation strategies of hazard-prone rural households in Bangladesh

OpenAIRE

G.M. Monirul Alam; Khorshed Alam; Shahbaz Mushtaq

2017-01-01

Adaptation is a key strategy that can alleviate the severity of climate change impacts on agriculture and food production. Adaptation strategies are unlikely to be effective without an understanding of the farmers’ perceptions of climate change. This paper explores the local knowledge of adaptation in response to the perceived impacts of climate change and climatic hazards using a survey of 380 resource-poor riverbank erosion-prone households in Bangladesh. The results indicate that the respo...

Early experience with mesh excision for adverse outcomes after transvaginal mesh placement using prolapse kits.

Science.gov (United States)

Ridgeway, Beri; Walters, Mark D; Paraiso, Marie Fidela R; Barber, Matthew D; McAchran, Sarah E; Goldman, Howard B; Jelovsek, J Eric

2008-12-01

The purpose of this study was to determine the complications, treatments, and outcomes in patients choosing to undergo removal of mesh previously placed with a mesh procedural kit. This was a retrospective review of all patients who underwent surgical removal of transvaginal mesh for mesh-related complications during a 3-year period at Cleveland Clinic. At last follow-up, patients reported degree of pain, level of improvement, sexual activity, and continued symptoms. Nineteen patients underwent removal of mesh during the study period. Indications for removal included chronic pain (6/19), dyspareunia (6/19), recurrent pelvic organ prolapse (8/19), mesh erosion (12/19), and vesicovaginal fistula (3/19), with most patients (16/19) citing more than 1 reason. There were few complications related to the mesh removal. Most patients reported significant relief of symptoms. Mesh removal can be technically difficult but appears to be safe with few complications and high relief of symptoms, although some symptoms can persist.

Mesh erosion after abdominal sacrocolpopexy.

Science.gov (United States)

Kohli, N; Walsh, P M; Roat, T W; Karram, M M

1998-12-01

To report our experience with erosion of permanent suture or mesh material after abdominal sacrocolpopexy. A retrospective chart review was performed to identify patients who underwent sacrocolpopexy by the same surgeon over 8 years. Demographic data, operative notes, hospital records, and office charts were reviewed after sacrocolpopexy. Patients with erosion of either suture or mesh were treated initially with conservative therapy followed by surgical intervention as required. Fifty-seven patients underwent sacrocolpopexy using synthetic mesh during the study period. The mean (range) postoperative follow-up was 19.9 (1.3-50) months. Seven patients (12%) had erosions after abdominal sacrocolpopexy with two suture erosions and five mesh erosions. Patients with suture erosion were asymptomatic compared with patients with mesh erosion, who presented with vaginal bleeding or discharge. The mean (+/-standard deviation) time to erosion was 14.0+/-7.7 (range 4-24) months. Both patients with suture erosion were treated conservatively with estrogen cream. All five patients with mesh erosion required transvaginal removal of the mesh. Mesh erosion can follow abdominal sacrocolpopexy over a long time, and usually presents as vaginal bleeding or discharge. Although patients with suture erosion can be managed successfully with conservative treatment, patients with mesh erosion require surgical intervention. Transvaginal removal of the mesh with vaginal advancement appears to be an effective treatment in patients failing conservative management.

Surgical management of lower urinary mesh perforation after mid-urethral polypropylene mesh sling: mesh excision, urinary tract reconstruction and concomitant pubovaginal sling with autologous rectus fascia.

Science.gov (United States)

Shah, Ketul; Nikolavsky, Dmitriy; Gilsdorf, Daniel; Flynn, Brian J

2013-12-01

We present our management of lower urinary tract (LUT) mesh perforation after mid-urethral polypropylene mesh sling using a novel combination of surgical techniques including total or near total mesh excision, urinary tract reconstruction, and concomitant pubovaginal sling with autologous rectus fascia in a single operation. We retrospectively reviewed the medical records of 189 patients undergoing transvaginal removal of polypropylene mesh from the lower urinary tract or vagina. The focus of this study is 21 patients with LUT mesh perforation after mid-urethral polypropylene mesh sling. We excluded patients with LUT mesh perforation from prolapse kits (n = 4) or sutures (n = 11), or mesh that was removed because of isolated vaginal wall exposure without concomitant LUT perforation (n = 164). Twenty-one patients underwent surgical removal of mesh through a transvaginal approach or combined transvaginal/abdominal approaches. The location of the perforation was the urethra in 14 and the bladder in 7. The mean follow-up was 22 months. There were no major intraoperative complications. All patients had complete resolution of the mesh complication and the primary symptom. Of the patients with urethral perforation, continence was achieved in 10 out of 14 (71.5 %). Of the patients with bladder perforation, continence was achieved in all 7. Total or near total removal of lower urinary tract (LUT) mesh perforation after mid-urethral polypropylene mesh sling can completely resolve LUT mesh perforation in a single operation. A concomitant pubovaginal sling can be safely performed in efforts to treat existing SUI or avoid future surgery for SUI.

Evaluation of delivered dose for a clinical daily adaptive plan selection strategy for bladder cancer radiotherapy

International Nuclear Information System (INIS)

Lutkenhaus, Lotte J.; Visser, Jorrit; Jong, Rianne de; Hulshof, Maarten C.C.M.; Bel, Arjan

2015-01-01

Purpose: To account for variable bladder size during bladder cancer radiotherapy, a daily plan selection strategy was implemented. The aim of this study was to calculate the actually delivered dose using an adaptive strategy, compared to a non-adaptive approach. Material and methods: Ten patients were treated to the bladder and lymph nodes with an adaptive full bladder strategy. Interpolated delineations of bladder and tumor on a full and empty bladder CT scan resulted in five PTVs for which VMAT plans were created. Daily cone beam CT (CBCT) scans were used for plan selection. Bowel, rectum and target volumes were delineated on these CBCTs, and delivered dose for these was calculated using both the adaptive plan, and a non-adaptive plan. Results: Target coverage for lymph nodes improved using an adaptive strategy. The full bladder strategy spared the healthy part of the bladder from a high dose. Average bowel cavity V30Gy and V40Gy significantly reduced with 60 and 69 ml, respectively (p < 0.01). Other parameters for bowel and rectum remained unchanged. Conclusions: Daily plan selection compared to a non-adaptive strategy yielded similar bladder coverage and improved coverage for lymph nodes, with a significant reduction in bowel cavity V30Gy and V40Gy only, while other sparing was limited

Aranha: a 2D mesh generator for triangular finite elements

International Nuclear Information System (INIS)

Fancello, E.A.; Salgado, A.C.; Feijoo, R.A.

1990-01-01

A method for generating unstructured meshes for linear and quadratic triangular finite elements is described in this paper. Some topics on the C language data structure used in the development of the program Aranha are also presented. The applicability for adaptive remeshing is shown and finally several examples are included to illustrate the performance of the method in irregular connected planar domains. (author)

Acculturation Strategies, Social Support, and Cross-Cultural Adaptation: A Mediation Analysis

Science.gov (United States)

Ng, Ting Kin; Tsang, Kwok Kuen; Lian, Yi

2013-01-01

Previous acculturation research has established the influences of acculturation strategies and social support on cross-cultural adaptation. The present study attempted to elaborate these direct associations by proposing that social support and the use of the integration and marginalization strategies might affect psychological adaptation…

Adaptive discrete-ordinates algorithms and strategies

International Nuclear Information System (INIS)

Stone, J.C.; Adams, M.L.

2005-01-01

We present our latest algorithms and strategies for adaptively refined discrete-ordinates quadrature sets. In our basic strategy, which we apply here in two-dimensional Cartesian geometry, the spatial domain is divided into regions. Each region has its own quadrature set, which is adapted to the region's angular flux. Our algorithms add a 'test' direction to the quadrature set if the angular flux calculated at that direction differs by more than a user-specified tolerance from the angular flux interpolated from other directions. Different algorithms have different prescriptions for the method of interpolation and/or choice of test directions and/or prescriptions for quadrature weights. We discuss three different algorithms of different interpolation orders. We demonstrate through numerical results that each algorithm is capable of generating solutions with negligible angular discretization error. This includes elimination of ray effects. We demonstrate that all of our algorithms achieve a given level of error with far fewer unknowns than does a standard quadrature set applied to an entire problem. To address a potential issue with other algorithms, we present one algorithm that retains exact integration of high-order spherical-harmonics functions, no matter how much local refinement takes place. To address another potential issue, we demonstrate that all of our methods conserve partial currents across interfaces where quadrature sets change. We conclude that our approach is extremely promising for solving the long-standing problem of angular discretization error in multidimensional transport problems. (authors)

A MATLAB Script for Solving 2D/3D Minimum Compliance Problems using Anisotropic Mesh Adaptation

DEFF Research Database (Denmark)

Jensen, Kristian Ejlebjerg

2017-01-01

We present a pure MATLAB implementation for solving 2D/3D compliance minimization problems using the density method. A filtered design variable with a minimum length is computed using a Helmholtz-type differential equation. The optimality criteria is used as optimizer and to avoid local minima we...... apply continuation of an exponent that controls the stiffness associated with intermediate design variables. We constrain the volume from above and use the implementation to show that optimizations with dynamic meshes can save significant amounts of computational time compared to fixed meshes without...

Impact assessment of adaptation options and strategies for coping ...

International Development Research Centre (IDRC) Digital Library (Canada)

Impact assessment of adaptation options and strategies for coping with climate change on the livelihoods of pastoral and agro-pastoral communities in Sudan' Butana area. Ibrahim, Abdelhamed M.M.. URI: http://hdl.handle.net/10625/53410. Date: 2013-11 ...

Surface meshing with curvature convergence

KAUST Repository

Li, Huibin; Zeng, Wei; Morvan, Jean-Marie; Chen, Liming; Gu, Xianfengdavid

2014-01-01

Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

Surface meshing with curvature convergence

KAUST Repository

Li, Huibin

2014-06-01

Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

HIGH-RESOLUTION SIMULATIONS OF CONVECTION PRECEDING IGNITION IN TYPE Ia SUPERNOVAE USING ADAPTIVE MESH REFINEMENT

International Nuclear Information System (INIS)

Nonaka, A.; Aspden, A. J.; Almgren, A. S.; Bell, J. B.; Zingale, M.; Woosley, S. E.

2012-01-01

We extend our previous three-dimensional, full-star simulations of the final hours of convection preceding ignition in Type Ia supernovae to higher resolution using the adaptive mesh refinement capability of our low Mach number code, MAESTRO. We report the statistics of the ignition of the first flame at an effective 4.34 km resolution and general flow field properties at an effective 2.17 km resolution. We find that off-center ignition is likely, with radius of 50 km most favored and a likely range of 40-75 km. This is consistent with our previous coarser (8.68 km resolution) simulations, implying that we have achieved sufficient resolution in our determination of likely ignition radii. The dynamics of the last few hot spots preceding ignition suggest that a multiple ignition scenario is not likely. With improved resolution, we can more clearly see the general flow pattern in the convective region, characterized by a strong outward plume with a lower speed recirculation. We show that the convective core is turbulent with a Kolmogorov spectrum and has a lower turbulent intensity and larger integral length scale than previously thought (on the order of 16 km s –1 and 200 km, respectively), and we discuss the potential consequences for the first flames.

Adapting qualitative research strategies to technology savvy adolescents.

Science.gov (United States)

Mason, Deanna Marie; Ide, Bette

2014-05-01

To adapt research strategies involving adolescents in a grounded theory qualitative research study by conducting email rather than face-to-face interviews. Adolescent culture relies heavily on text-based communication and teens prefer interactions mediated through technology. Traditional qualitative research strategies need to be rethought when working with adolescents. Adapting interviewing strategies to electronic environments is timely and relevant for researching adolescents. Twenty three adolescents (aged 16-21) were interviewed by email. A letter of invitation was distributed. Potential participants emailed the researcher to convey interest in participating. If the inclusion criteria were met, email interviews were initiated. Participants controlled the interviews through their rate of response to interview questions. A grounded theory methodology was employed. Initial contact with participants reiterated confidentiality and the ability to withdraw from the study at any time. Interviews began with the collection of demographic information and a broad opening based on a semi-structured interview guide. All data were permissible, including text, photos, music, videos or outside media, for example YouTube. The participant was allowed to give direction to the interview after initial questions were posed. Email interviews continued until saturation was reached in the data. Participants were enthusiastic about email interviewing. Attrition did not occur. Email interviewing gave participants more control over the research, decreased power differentials between the adolescent and researcher, allowed the study to be adapted to cultural, linguistic and developmental needs, and maintained confidentiality. As participants said that email communication was slow and they preferred instant messaging, replication in faster-paced media is recommended. Repetition in face-to-face settings is warranted to evaluate how technology may have influenced the findings. Implications for

Adaptation Strategies and Resilience to Climate Change of Historic Dwellings

Directory of Open Access Journals (Sweden)

Carlos Rubio-Bellido

2015-03-01

Full Text Available Historic city centres have a large amount of dwellings in Europe, which were built to provide a comfortable shelter with the absence of mechanical means. The knowledge of climate responsive design strategies can play a significant role in reducing the energy demand of extant buildings, paving the way for its sustainable development in the face of the rising threat to its occupants of climate change. The residential architecture, developed, in most cases, in dense urban centres, was built using both available materials and traditional and academic construction technologies. This paper thoroughly investigates the extant urban conglomerate in Cádiz and analyses, in a qualitative and quantitative manner, which bioclimatic design strategies were applied and the city’s adaptation for future climate scenarios. The results indicate that historic housing in Cádiz is creatively adapted to the local natural conditions by means of a combination of climate responsive strategies, and there is significant scope for improvement in the ongoing response to global warming.

Climate Change Mitigation and Adaptation Strategies Used by ...

African Journals Online (AJOL)

The majority (73.6%) of the farmers opined that in recent times, flooding had increased which is an indication of climate change. Reduction in the use of generator to get power in the farmers' houses (69.1%) and crop rotation practices (67.3%) were mitigation and adaptation strategies employed by the farmers against the ...

Robust a Posteriori Error Control and Adaptivity for Multiscale, Multinumerics, and Mortar Coupling

KAUST Repository

Pencheva, Gergina V.

2013-01-01

We consider discretizations of a model elliptic problem by means of different numerical methods applied separately in different subdomains, termed multinumerics, coupled using the mortar technique. The grids need not match along the interfaces. We are also interested in the multiscale setting, where the subdomains are partitioned by a mesh of size h, whereas the interfaces are partitioned by a mesh of much coarser size H, and where lower-order polynomials are used in the subdomains and higher-order polynomials are used on the mortar interface mesh. We derive several fully computable a posteriori error estimates which deliver a guaranteed upper bound on the error measured in the energy norm. Our estimates are also locally efficient and one of them is robust with respect to the ratio H/h under an assumption of sufficient regularity of the weak solution. The present approach allows bounding separately and comparing mutually the subdomain and interface errors. A subdomain/interface adaptive refinement strategy is proposed and numerically tested. © 2013 Society for Industrial and Applied Mathematics.

Mesh size in Lichtenstein repair: a systematic review and meta-analysis to determine the importance of mesh size.

Science.gov (United States)

Seker, D; Oztuna, D; Kulacoglu, H; Genc, Y; Akcil, M

2013-04-01

Small mesh size has been recognized as one of the factors responsible for recurrence after Lichtenstein hernia repair due to insufficient coverage or mesh shrinkage. The Lichtenstein Hernia Institute recommends a 7 × 15 cm mesh that can be trimmed up to 2 cm from the lateral side. We performed a systematic review to determine surgeons' mesh size preference for the Lichtenstein hernia repair and made a meta-analysis to determine the effect of mesh size, mesh type, and length of follow-up time on recurrence. Two medical databases, PubMed and ISI Web of Science, were systematically searched using the key word "Lichtenstein repair." All full text papers were selected. Publications mentioning mesh size were brought for further analysis. A mesh surface area of 90 cm(2) was accepted as the threshold for defining the mesh as small or large. Also, a subgroup analysis for recurrence pooled proportion according to the mesh size, mesh type, and follow-up period was done. In total, 514 papers were obtained. There were no prospective or retrospective clinical studies comparing mesh size and clinical outcome. A total of 141 papers were duplicated in both databases. As a result, 373 papers were obtained. The full text was available in over 95 % of papers. Only 41 (11.2 %) papers discussed mesh size. In 29 studies, a mesh larger than 90 cm(2) was used. The most frequently preferred commercial mesh size was 7.5 × 15 cm. No papers mentioned the size of the mesh after trimming. There was no information about the relationship between mesh size and patient BMI. The pooled proportion in recurrence for small meshes was 0.0019 (95 % confidence interval: 0.007-0.0036), favoring large meshes to decrease the chance of recurrence. Recurrence becomes more marked when follow-up period is longer than 1 year (p < 0.001). Heavy meshes also decreased recurrence (p = 0.015). This systematic review demonstrates that the size of the mesh used in Lichtenstein hernia repair is rarely

Upscaling the Impacts of Climate Change in Different Sectors and Adaptation Strategies

DEFF Research Database (Denmark)

Bouwer, Laurens; Capriolo, Alessio; Chiabai, Aline

2018-01-01

This chapter aims to provide up-to-date quantitative estimates of the costs and benefits related to adaptation strategies for different sectors in Europe. This is done by critically evaluating modeling frameworks and contexts applied to adaptation and by describing new developments achieved...

Perception, Mitigation and Adaptation Strategies of Irrigated Paddy Farmer Community to Face Climate Change

Directory of Open Access Journals (Sweden)

Siska Rasiska Suantapura

2016-06-01

Full Text Available Climate change has a real impact on the condition of agriculture in developing countries, including Indonesia. Irrigated paddy farmers are the ones really feeling the impact of climate change. Therefore, we need to understand the perceptions, mitigation and adaptation strategies of irrigated paddy farmer community to face climate change. The study is conducted in Indramayu and Tasikmalaya Regency in West Java by using descriptive survey method, regression analysis and path analysis through Structural Equation Modelling approach with Lisrel TM 8.5. The results showes that: (1 changes to climate variability affects the productivity of rice; (2 perception of irrigated paddy farmer community on climate change and its affects are influenced by internal and external factors; and (3 adaptation strategy are influenced by internal and external factors, whereas no mitigation strategy. Therefore, mitigation and adaptation strategies with site specific location are very necessary improving climate information services, increasing empowerment of farmers through field schools, and providing the provision of facilities that are practical and adaptive to climate.

Farmers’ Adaptation Strategies to Climate Change and Their Implications in the Zou Department of South Benin

Directory of Open Access Journals (Sweden)

Adégnandjou Mahouna Roland Fadina

2018-01-01

Full Text Available Climate change is a global phenomenon. Its impact on agricultural activities in developing countries has increased dramatically. Understanding how farmers perceive climate change and how they adapt to it is very important to the implementation of adequate policies for agricultural and food security. This paper aims to contribute to an understanding of farmers’ adaptation choices, determinants of the adaptation choices and the long-term implications of the adaptation choices. Data were collected from 120 respondents in the Zou Department of Benin. A binary logit model was used to analyze the factors influencing household decisions to adapt to climate change. Multinomial logistic regression analysis was estimated to analyze the factors influencing households’ choice of adaptation strategies to climate change. The results show that farmers have a developed perception of climate change. These changes are translated by rainfall disturbances (rainfall delays, early cessation, bad rainfall distribution etc., shortening of the small dry season, increasing of temperature and sometimes, violent winds. The survey reveals that Benin farmers adopt many strategies in response to climate change. These strategies include “Crop–livestock diversification and other good practices (mulching, organic fertilizer,” “Use of improved varieties, chemical fertilizers and pesticides,” “Agroforestry and perennial plantation” and “Diversification of income-generating activities.” The findings also reveal that most of the respondents use these strategies in combination. From the binary logit model, we know that “farming experience” and “educational level of household head” positively influence adaptation decisions. The result of the multinomial logit analysis shows that farming experience, educational level, farm size and gender have a significant impact on climate change adaptation strategies. Based on in-depth analysis of each strategy, we

Using a social justice and health framework to assess European climate change adaptation strategies.

Science.gov (United States)

Boeckmann, Melanie; Zeeb, Hajo

2014-11-28

Climate change puts pressure on existing health vulnerabilities through higher frequency of extreme weather events, changes in disease vector distribution or exacerbated air pollution. Climate change adaptation policies may hold potential to reduce societal inequities. We assessed the role of public health and social justice in European climate change adaptation using a three-fold approach: a document analysis, a critical discourse analysis of a subgroup of strategies, and a ranking of strategies against our social justice framework. The ranking approach favored planning that includes various adaptation types, social issues and infrastructure changes. Themes on values identified in the five subgroup documents showed that risks are perceived as contradictory, technology is viewed as savior, responsibilities need to be negotiated, and social justice is advocated by only a few countries. Of 21 strategy documents assessed overall, those from Austria, England and Sweden received the highest scores in the ranking. Our qualitative assessment showed that in European adaptation planning, progress could still be made through community involvement into adaptation decisions, consistent consideration of social and demographic determinants, and a stronger link between infrastructural adaptation and the health sector. Overall, a social justice framework can serve as an evaluation guideline for adaptation policy documents.

Voltammetry at micro-mesh electrodes

Directory of Open Access Journals (Sweden)

Wadhawan Jay D.

2003-01-01

Full Text Available The voltammetry at three micro-mesh electrodes is explored. It is found that at sufficiently short experimental durations, the micro-mesh working electrode first behaves as an ensemble of microband electrodes, then follows the behaviour anticipated for an array of diffusion-independent micro-ring electrodes of the same perimeter as individual grid-squares within the mesh. During prolonged electrolysis, the micro-mesh electrode follows that behaviour anticipated theoretically for a cubically-packed partially-blocked electrode. Application of the micro-mesh electrode for the electrochemical determination of carbon dioxide in DMSO electrolyte solutions is further illustrated.

Real-Time Adaptation of Influence Strategies in Online Selling

NARCIS (Netherlands)

Kaptein, M.C.; Parvinen, P.

2014-01-01

Real-time adjustments in online selling are becoming increasingly common. In this paper we describe a novel method of real-time adaptation, and introduce influence strategies as a useful level of analysis for personalization of online selling. The proposed method incorporates three perspectives on

Streaming simplification of tetrahedral meshes.

Science.gov (United States)

Vo, Huy T; Callahan, Steven P; Lindstrom, Peter; Pascucci, Valerio; Silva, Cláudio T

2007-01-01

Unstructured tetrahedral meshes are commonly used in scientific computing to represent scalar, vector, and tensor fields in three dimensions. Visualization of these meshes can be difficult to perform interactively due to their size and complexity. By reducing the size of the data, we can accomplish real-time visualization necessary for scientific analysis. We propose a two-step approach for streaming simplification of large tetrahedral meshes. Our algorithm arranges the data on disk in a streaming, I/O-efficient format that allows coherent access to the tetrahedral cells. A quadric-based simplification is sequentially performed on small portions of the mesh in-core. Our output is a coherent streaming mesh which facilitates future processing. Our technique is fast, produces high quality approximations, and operates out-of-core to process meshes too large for main memory.

A Climate Change Adaptation Strategy for Management of ...

Science.gov (United States)

Sea level rise is causing shoreline erosion, increased coastal flooding, and marsh vulnerability to the impact of storms. Coastal marshes provide flood abatement, carbon and nutrient sequestration, water quality maintenance, and habitat for fish, shellfish, and wildlife, including species of concern, such as the saltmarsh sparrow (Ammodramus caudacutus). We present a climate change adaptation strategy (CCAS) adopted by scientific, management, and policy stakeholders for managing coastal marshes and enhancing system resiliency. A common adaptive management approach previously used for restoration projects was modified to identify climate-related vulnerabilities and plan climate change adaptive actions. As an example of implementation of the CCAS, we describe the stakeholder plans and management actions the US Fish and Wildlife Service and partners developed to build coastal resiliency in the Narrow River Estuary, RI, in the aftermath of Superstorm Sandy. When possible, an experimental BACI (before-after, control-impact) design, described as pre- and post-sampling at the impact site and one or more control sites, was incorporated into the climate change adaptation and implementation plans. Specific climate change adaptive actions and monitoring plans are described and include shoreline stabilization, restoring marsh drainage, increasing marsh elevation, and enabling upland marsh migration. The CCAS provides a framework and methodology for successfully managing coa

Mesh Plug Repair of Inguinal Hernia; Single Surgeon Experience

Directory of Open Access Journals (Sweden)

Ahmet Serdar Karaca

2013-10-01

Full Text Available Aim: Mesh repair of inguinal hernia repairs are shown to be an effective and reliable method. In this study, a single surgeon%u2019s experience with plug-mesh method performs inguinal hernia repair have been reported. Material and Method: 587 patients with plug-mesh repair of inguinal hernia, preoperative age, body / mass index, comorbid disease were recorded in terms of form. All of the patients during the preoperative and postoperative hernia classification of information, duration of operation, antibiotics, perioperative complications, and later, the early and late postoperative complications, infection, recurrence rates and return to normal daily activity, verbal pain scales in terms of time and postoperative pain were evaluated. Added to this form of long-term pain ones. The presence of wound infection was assessed by the presence of purulent discharge from the incision. Visual analog scale pain status of the patients was measured. Results: 587 patients underwent repair of primary inguinal hernia mesh plug. One of the patients, 439 (74% of them have adapted follow-ups. Patients%u2019 ages ranged from 18-86. Was calculated as the mean of 47±18:07. Follow-up period of the patients was found to be a minimum of 3 months, maximum 55 months. Found an average of 28.2±13.4 months. Mean duration of surgery was 35.07±4.00 min (min:22mn-max:52mn, respectively. When complication rates of patients with recurrence in 2 patients (0.5%, hematoma development (1.4% in 6 patients, the development of infection in 11 patients (2.5% and long-term groin pain in 4 patients (0.9% appeared. Discussion: In our experience, the plug-mesh repair of primary inguinal hernia repair safe, effective low recurrence and complication rates can be used.

Adaptive finite element analysis of incompressible viscous flow using posteriori error estimation and control of node density distribution

International Nuclear Information System (INIS)

Yashiki, Taturou; Yagawa, Genki; Okuda, Hiroshi

1995-01-01

The adaptive finite element method based on an 'a posteriori error estimation' is known to be a powerful technique for analyzing the engineering practical problems, since it excludes the instinctive aspect of the mesh subdivision and gives high accuracy with relatively low computational cost. In the adaptive procedure, both the error estimation and the mesh generation according to the error estimator are essential. In this paper, the adaptive procedure is realized by the automatic mesh generation based on the control of node density distribution, which is decided according to the error estimator. The global percentage error, CPU time, the degrees of freedom and the accuracy of the solution of the adaptive procedure are compared with those of the conventional method using regular meshes. Such numerical examples as the driven cavity flows of various Reynolds numbers and the flows around a cylinder have shown the very high performance of the proposed adaptive procedure. (author)

MeshVoro: A Three-Dimensional Voronoi Mesh Building Tool for the TOUGH Family of Codes

Energy Technology Data Exchange (ETDEWEB)

Freeman, C. M.; Boyle, K. L.; Reagan, M.; Johnson, J.; Rycroft, C.; Moridis, G. J.

2013-09-30

Few tools exist for creating and visualizing complex three-dimensional simulation meshes, and these have limitations that restrict their application to particular geometries and circumstances. Mesh generation needs to trend toward ever more general applications. To that end, we have developed MeshVoro, a tool that is based on the Voro (Rycroft 2009) library and is capable of generating complex threedimensional Voronoi tessellation-based (unstructured) meshes for the solution of problems of flow and transport in subsurface geologic media that are addressed by the TOUGH (Pruess et al. 1999) family of codes. MeshVoro, which includes built-in data visualization routines, is a particularly useful tool because it extends the applicability of the TOUGH family of codes by enabling the scientifically robust and relatively easy discretization of systems with challenging 3D geometries. We describe several applications of MeshVoro. We illustrate the ability of the tool to straightforwardly transform a complex geological grid into a simulation mesh that conforms to the specifications of the TOUGH family of codes. We demonstrate how MeshVoro can describe complex system geometries with a relatively small number of grid blocks, and we construct meshes for geometries that would have been practically intractable with a standard Cartesian grid approach. We also discuss the limitations and appropriate applications of this new technology.

An Adaptive Classification Strategy for Reliable Locomotion Mode Recognition

Directory of Open Access Journals (Sweden)

Ming Liu

2017-09-01

Full Text Available Algorithms for locomotion mode recognition (LMR based on surface electromyography and mechanical sensors have recently been developed and could be used for the neural control of powered prosthetic legs. However, the variations in input signals, caused by physical changes at the sensor interface and human physiological changes, may threaten the reliability of these algorithms. This study aimed to investigate the effectiveness of applying adaptive pattern classifiers for LMR. Three adaptive classifiers, i.e., entropy-based adaptation (EBA, LearnIng From Testing data (LIFT, and Transductive Support Vector Machine (TSVM, were compared and offline evaluated using data collected from two able-bodied subjects and one transfemoral amputee. The offline analysis indicated that the adaptive classifier could effectively maintain or restore the performance of the LMR algorithm when gradual signal variations occurred. EBA and LIFT were recommended because of their better performance and higher computational efficiency. Finally, the EBA was implemented for real-time human-in-the-loop prosthesis control. The online evaluation showed that the applied EBA effectively adapted to changes in input signals across sessions and yielded more reliable prosthesis control over time, compared with the LMR without adaptation. The developed novel adaptive strategy may further enhance the reliability of neurally-controlled prosthetic legs.

Laparoscopic mesh explantation and drainage of sacral abscess remote from transvaginal excision of exposed sacral colpopexy mesh.

Science.gov (United States)

Roth, Ted M; Reight, Ian

2012-07-01

Sacral colpopexy may be complicated by mesh exposure, and the surgical treatment of mesh exposure typically results in minor postoperative morbidity and few delayed complications. A 75-year-old woman presented 7 years after a laparoscopic sacral colpopexy, with Mersilene mesh, with an apical mesh exposure. She underwent an uncomplicated transvaginal excision and was asymptomatic until 8 months later when she presented with vaginal drainage and a sacral abscess. This was successfully treated with laparoscopic enterolysis, drainage of the abscess, and explantation of the remaining mesh. Incomplete excision of exposed colpopexy mesh can lead to ascending infection and sacral abscess. Laparoscopic drainage and mesh removal may be considered in these patients.

Climate change adaptation strategies by local farmers in Kilombero ...

African Journals Online (AJOL)

This article examines current adaptation strategies developed by local farmers against climate change effects in Kilombero District. Research questions guided the study include; what are the past and current climatic stresses? What are local farmers' perception on climate change and response to the adverse climatic ...

Mesh optimization for microbial fuel cell cathodes constructed around stainless steel mesh current collectors

KAUST Repository

Zhang, Fang; Merrill, Matthew D.; Tokash, Justin C.; Saito, Tomonori; Cheng, Shaoan; Hickner, Michael A.; Logan, Bruce E.

2011-01-01

that the mesh properties of these cathodes can significantly affect performance. Cathodes made from the coarsest mesh (30-mesh) achieved the highest maximum power of 1616 ± 25 mW m-2 (normalized to cathode projected surface area; 47.1 ± 0.7 W m-3 based on liquid

SUPERIMPOSED MESH PLOTTING IN MCNP

Energy Technology Data Exchange (ETDEWEB)

J. HENDRICKS

2001-02-01

The capability to plot superimposed meshes has been added to MCNP{trademark}. MCNP4C featured a superimposed mesh weight window generator which enabled users to set up geometries without having to subdivide geometric cells for variance reduction. The variance reduction was performed with weight windows on a rectangular or cylindrical mesh superimposed over the physical geometry. Experience with the new capability was favorable but also indicated that a number of enhancements would be very beneficial, particularly a means of visualizing the mesh and its values. The mathematics for plotting the mesh and its values is described here along with a description of other upgrades.

Adapt and cope : strategies for safeguarding the quality of life in a shrinking ageing region

OpenAIRE

Steinführer, Annett; Küpper, Patrick; Tautz, Alexandra

2014-01-01

"This article examines the adaptation and coping strategies that are in place to safeguard the quality of life in a shrinking ageing region. In particular, it is investigated which resources are available to local policy-makers and the older population in order to pursue this goal. Following an introduction to the debate of regional science about demographic change and its consequences, we introduce a theoretical differentiation between adaptation and coping. Adaptation strategies refer to th...

Bessel smoothing filter for spectral-element mesh

Science.gov (United States)

Trinh, P. T.; Brossier, R.; Métivier, L.; Virieux, J.; Wellington, P.

2017-06-01

Smoothing filters are extremely important tools in seismic imaging and inversion, such as for traveltime tomography, migration and waveform inversion. For efficiency, and as they can be used a number of times during inversion, it is important that these filters can easily incorporate prior information on the geological structure of the investigated medium, through variable coherent lengths and orientation. In this study, we promote the use of the Bessel filter to achieve these purposes. Instead of considering the direct application of the filter, we demonstrate that we can rely on the equation associated with its inverse filter, which amounts to the solution of an elliptic partial differential equation. This enhances the efficiency of the filter application, and also its flexibility. We apply this strategy within a spectral-element-based elastic full waveform inversion framework. Taking advantage of this formulation, we apply the Bessel filter by solving the associated partial differential equation directly on the spectral-element mesh through the standard weak formulation. This avoids cumbersome projection operators between the spectral-element mesh and a regular Cartesian grid, or expensive explicit windowed convolution on the finite-element mesh, which is often used for applying smoothing operators. The associated linear system is solved efficiently through a parallel conjugate gradient algorithm, in which the matrix vector product is factorized and highly optimized with vectorized computation. Significant scaling behaviour is obtained when comparing this strategy with the explicit convolution method. The theoretical numerical complexity of this approach increases linearly with the coherent length, whereas a sublinear relationship is observed practically. Numerical illustrations are provided here for schematic examples, and for a more realistic elastic full waveform inversion gradient smoothing on the SEAM II benchmark model. These examples illustrate well the

Climate change effects and adaptation strategies in the wine sector: a quantitative literature review

Directory of Open Access Journals (Sweden)

Sandro Sacchelli

2016-12-01

Full Text Available This paper presents a quantitative literature review focusing on how scientific research analysed climate change impact on wine chain as well as potential adaptation strategies. The work is based on content analysis and text mining and takes into account researches from 1990 to 2015. A particular emphasis was given to the evaluation of suggested or implemented adaptation strategies at both global and national levels. Data were analysed using cluster analysis, multidimensional scaling and specificity evaluation. Results show that the study of climate change impacts on the wine sector is a recently emerging research topic. Adaptation strategies have not yet been explored thoroughly in the literature, and in-depth uncertainty quantification is also needed. Finally, additional research gaps and potential future issues are suggested.

Cache-Oblivious Mesh Layouts

International Nuclear Information System (INIS)

Yoon, S; Lindstrom, P; Pascucci, V; Manocha, D

2005-01-01

We present a novel method for computing cache-oblivious layouts of large meshes that improve the performance of interactive visualization and geometric processing algorithms. Given that the mesh is accessed in a reasonably coherent manner, we assume no particular data access patterns or cache parameters of the memory hierarchy involved in the computation. Furthermore, our formulation extends directly to computing layouts of multi-resolution and bounding volume hierarchies of large meshes. We develop a simple and practical cache-oblivious metric for estimating cache misses. Computing a coherent mesh layout is reduced to a combinatorial optimization problem. We designed and implemented an out-of-core multilevel minimization algorithm and tested its performance on unstructured meshes composed of tens to hundreds of millions of triangles. Our layouts can significantly reduce the number of cache misses. We have observed 2-20 times speedups in view-dependent rendering, collision detection, and isocontour extraction without any modification of the algorithms or runtime applications

User Manual for the PROTEUS Mesh Tools

Energy Technology Data Exchange (ETDEWEB)

Smith, Micheal A. [Argonne National Lab. (ANL), Argonne, IL (United States); Shemon, Emily R. [Argonne National Lab. (ANL), Argonne, IL (United States)

2015-06-01

This report describes the various mesh tools that are provided with the PROTEUS code giving both descriptions of the input and output. In many cases the examples are provided with a regression test of the mesh tools. The most important mesh tools for any user to consider using are the MT_MeshToMesh.x and the MT_RadialLattice.x codes. The former allows the conversion between most mesh types handled by PROTEUS while the second allows the merging of multiple (assembly) meshes into a radial structured grid. Note that the mesh generation process is recursive in nature and that each input specific for a given mesh tool (such as .axial or .merge) can be used as “mesh” input for any of the mesh tools discussed in this manual.

Anisotropic evaluation of synthetic surgical meshes.

Science.gov (United States)

Saberski, E R; Orenstein, S B; Novitsky, Y W

2011-02-01

The material properties of meshes used in hernia repair contribute to the overall mechanical behavior of the repair. The anisotropic potential of synthetic meshes, representing a difference in material properties (e.g., elasticity) in different material axes, is not well defined to date. Haphazard orientation of anisotropic mesh material can contribute to inconsistent surgical outcomes. We aimed to characterize and compare anisotropic properties of commonly used synthetic meshes. Six different polypropylene (Trelex(®), ProLite™, Ultrapro™), polyester (Parietex™), and PTFE-based (Dualmesh(®), Infinit) synthetic meshes were selected. Longitudinal and transverse axes were defined for each mesh, and samples were cut in each axis orientation. Samples underwent uniaxial tensile testing, from which the elastic modulus (E) in each axis was determined. The degree of anisotropy (λ) was calculated as a logarithmic expression of the ratio between the elastic modulus in each axis. Five of six meshes displayed significant anisotropic behavior. Ultrapro™ and Infinit exhibited approximately 12- and 20-fold differences between perpendicular axes, respectively. Trelex(®), ProLite™, and Parietex™ were 2.3-2.4 times. Dualmesh(®) was the least anisotropic mesh, without marked difference between the axes. Anisotropy of synthetic meshes has been underappreciated. In this study, we found striking differences between elastic properties of perpendicular axes for most commonly used synthetic meshes. Indiscriminate orientation of anisotropic mesh may adversely affect hernia repairs. Proper labeling of all implants by manufacturers should be mandatory. Understanding the specific anisotropic behavior of synthetic meshes should allow surgeons to employ rational implant orientation to maximize outcomes of hernia repair.

Impacts of climate change, variability and adaptation strategies on ...

African Journals Online (AJOL)

Impacts of climate change, variability and adaptation strategies on agriculture in semi arid areas of Tanzania: The case of Manyoni District in Singida Region, Tanzania. ... The changes have affected crops and livestock in a number of ways resulting in reduced productivity. Empirical analysis of rainfall suggest decreasing ...

To mesh or not to mesh: a review of pelvic organ reconstructive surgery

Directory of Open Access Journals (Sweden)

Dällenbach P

2015-04-01

Full Text Available Patrick Dällenbach Department of Gynecology and Obstetrics, Division of Gynecology, Urogynecology Unit, Geneva University Hospitals, Geneva, Switzerland Abstract: Pelvic organ prolapse (POP is a major health issue with a lifetime risk of undergoing at least one surgical intervention estimated at close to 10%. In the 1990s, the risk of reoperation after primary standard vaginal procedure was estimated to be as high as 30% to 50%. In order to reduce the risk of relapse, gynecological surgeons started to use mesh implants in pelvic organ reconstructive surgery with the emergence of new complications. Recent studies have nevertheless shown that the risk of POP recurrence requiring reoperation is lower than previously estimated, being closer to 10% rather than 30%. The development of mesh surgery – actively promoted by the marketing industry – was tremendous during the past decade, and preceded any studies supporting its benefit for our patients. Randomized trials comparing the use of mesh to native tissue repair in POP surgery have now shown better anatomical but similar functional outcomes, and meshes are associated with more complications, in particular for transvaginal mesh implants. POP is not a life-threatening condition, but a functional problem that impairs quality of life for women. The old adage “primum non nocere” is particularly appropriate when dealing with this condition which requires no treatment when asymptomatic. It is currently admitted that a certain degree of POP is physiological with aging when situated above the landmark of the hymen. Treatment should be individualized and the use of mesh needs to be selective and appropriate. Mesh implants are probably an important tool in pelvic reconstructive surgery, but the ideal implant has yet to be found. The indications for its use still require caution and discernment. This review explores the reasons behind the introduction of mesh augmentation in POP surgery, and aims to

User Manual for the PROTEUS Mesh Tools

Energy Technology Data Exchange (ETDEWEB)

Smith, Micheal A. [Argonne National Lab. (ANL), Argonne, IL (United States); Shemon, Emily R [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-09-19

PROTEUS is built around a finite element representation of the geometry for visualization. In addition, the PROTEUS-SN solver was built to solve the even-parity transport equation on a finite element mesh provided as input. Similarly, PROTEUS-MOC and PROTEUS-NEMO were built to apply the method of characteristics on unstructured finite element meshes. Given the complexity of real world problems, experience has shown that using commercial mesh generator to create rather simple input geometries is overly complex and slow. As a consequence, significant effort has been put into place to create multiple codes that help assist in the mesh generation and manipulation. There are three input means to create a mesh in PROTEUS: UFMESH, GRID, and NEMESH. At present, the UFMESH is a simple way to generate two-dimensional Cartesian and hexagonal fuel assembly geometries. The UFmesh input allows for simple assembly mesh generation while the GRID input allows the generation of Cartesian, hexagonal, and regular triangular structured grid geometry options. The NEMESH is a way for the user to create their own mesh or convert another mesh file format into a PROTEUS input format. Given that one has an input mesh format acceptable for PROTEUS, we have constructed several tools which allow further mesh and geometry construction (i.e. mesh extrusion and merging). This report describes the various mesh tools that are provided with the PROTEUS code giving both descriptions of the input and output. In many cases the examples are provided with a regression test of the mesh tools. The most important mesh tools for any user to consider using are the MT_MeshToMesh.x and the MT_RadialLattice.x codes. The former allows the conversion between most mesh types handled by PROTEUS while the second allows the merging of multiple (assembly) meshes into a radial structured grid. Note that the mesh generation process is recursive in nature and that each input specific for a given mesh tool (such as .axial

Adapting to climate change in forest based land use systems: A guide to strategy

Energy Technology Data Exchange (ETDEWEB)

Secrett, C M

1997-12-31

The prospect of climate change and sea level rise as a result of greenhouse gas emissions presents a serious challenge to decision-makers concerned with ensuring sustainable development. This report provides a guide to means of reducing the potential impact of the global warming problem on the forest sector whilst ensuring that more immediate development priorities are met. The most effective response strategy will be one that simultaneously brings both immediate development and longer-term adaptive benefits. This report outlines ways of constructing an adaptive response strategy that can help achieve these ends. The approach is referred to as sustainable adaptation. A prototype methodological framework of the sustainable adaptation approach has been provided with the summary. The first priority of sustainable adaption is to base climate change responses on actions that meet basic ecological and social needs now and in the future. Solutions should necessarily include relieving current development pressures in the tropical forest sector. The key is to couple adaptive responses to climate change with sustainable development solutions to present-day forest use problems. Implementing adaptive land-use policies and management practices which are likely to minimise the adverse impacts of anticipated climate change should meet current sustainable management goals. Implementing sustainable land-use and forestry management practices should meet adaptation goals. This report presents a discussion of the fundamental issues underlying the development of a sustainable adaptation strategy and a prototype methodological framework. The findings are based on case studies conducted in Central America (Costa Rica and Nicaragua); SADCC countries in Africa (Zimbabwe, Botswana, Tanzania); and Asia (Vietnam). 450 refs

Adapting to climate change in forest based land use systems: A guide to strategy

Energy Technology Data Exchange (ETDEWEB)

Secrett, C.M.

1996-12-31

The prospect of climate change and sea level rise as a result of greenhouse gas emissions presents a serious challenge to decision-makers concerned with ensuring sustainable development. This report provides a guide to means of reducing the potential impact of the global warming problem on the forest sector whilst ensuring that more immediate development priorities are met. The most effective response strategy will be one that simultaneously brings both immediate development and longer-term adaptive benefits. This report outlines ways of constructing an adaptive response strategy that can help achieve these ends. The approach is referred to as sustainable adaptation. A prototype methodological framework of the sustainable adaptation approach has been provided with the summary. The first priority of sustainable adaption is to base climate change responses on actions that meet basic ecological and social needs now and in the future. Solutions should necessarily include relieving current development pressures in the tropical forest sector. The key is to couple adaptive responses to climate change with sustainable development solutions to present-day forest use problems. Implementing adaptive land-use policies and management practices which are likely to minimise the adverse impacts of anticipated climate change should meet current sustainable management goals. Implementing sustainable land-use and forestry management practices should meet adaptation goals. This report presents a discussion of the fundamental issues underlying the development of a sustainable adaptation strategy and a prototype methodological framework. The findings are based on case studies conducted in Central America (Costa Rica and Nicaragua); SADCC countries in Africa (Zimbabwe, Botswana, Tanzania); and Asia (Vietnam). 450 refs

Assessing Strategies for Urban Climate Change Adaptation: The Case of Six Metropolitan Cities in South Korea

Directory of Open Access Journals (Sweden)

Jae-Seung Lee

2018-06-01

Full Text Available As interest in climate change adaptation grows, an increasing number of national and local governments are developing adaptation strategies. This study assesses the strategies for urban climate change adaptation of municipal governments in South Korea. The adaptation plans and budget expenditures of six metropolitan cities in South Korea were compared, based on the Implementation Plan for Climate Change Adaptation Strategy (IPCCAS 2012–2016 and annual expenditure reports of each city. The results show that the actual implementation of these adaptation programs varied vis-à-vis the original plans, in terms of the level of overall expenditure and sector-specific expenditure. The following findings were drawn from the analysis: First, in most cases, the highest adaptation priorities were disaster/infrastructure, water management, and the health sector. Second, actual expenditure on climate change adaptation programs was smaller than the planned budget in the IPCCAS. Third, the prioritized sectors matched for planning and implementation in Seoul, Daegu, Daejeon, and Incheon, but not in Busan and Ulsan. Fourth, the adaptation programs of South Korean metropolitan cities do not seem to have been well-tailored to each case.

A Tissue Relevance and Meshing Method for Computing Patient-Specific Anatomical Models in Endoscopic Sinus Surgery Simulation

Science.gov (United States)

Audette, M. A.; Hertel, I.; Burgert, O.; Strauss, G.

This paper presents on-going work on a method for determining which subvolumes of a patient-specific tissue map, extracted from CT data of the head, are relevant to simulating endoscopic sinus surgery of that individual, and for decomposing these relevant tissues into triangles and tetrahedra whose mesh size is well controlled. The overall goal is to limit the complexity of the real-time biomechanical interaction while ensuring the clinical relevance of the simulation. Relevant tissues are determined as the union of the pathology present in the patient, of critical tissues deemed to be near the intended surgical path or pathology, and of bone and soft tissue near the intended path, pathology or critical tissues. The processing of tissues, prior to meshing, is based on the Fast Marching method applied under various guises, in a conditional manner that is related to tissue classes. The meshing is based on an adaptation of a meshing method of ours, which combines the Marching Tetrahedra method and the discrete Simplex mesh surface model to produce a topologically faithful surface mesh with well controlled edge and face size as a first stage, and Almost-regular Tetrahedralization of the same prescribed mesh size as a last stage.

Management of complications of mesh surgery.

Science.gov (United States)

Lee, Dominic; Zimmern, Philippe E

2015-07-01

Transvaginal placements of synthetic mid-urethral slings and vaginal meshes have largely superseded traditional tissue repairs in the current era because of presumed efficacy and ease of implant with device 'kits'. The use of synthetic material has generated novel complications including mesh extrusion, pelvic and vaginal pain and mesh contraction. In this review, our aim is to discuss the management, surgical techniques and outcomes associated with mesh removal. Recent publications have seen an increase in presentation of these mesh-related complications, and reports from multiple tertiary centers have suggested that not all patients benefit from surgical intervention. Although the true incidence of mesh complications is unknown, recent publications can serve to guide physicians and inform patients of the surgical outcomes from mesh-related complications. In addition, the literature highlights the growing need for a registry to account for a more accurate reporting of these events and to counsel patients on the risk and benefits before proceeding with mesh surgeries.

User Manual for the PROTEUS Mesh Tools

International Nuclear Information System (INIS)

Smith, Micheal A.; Shemon, Emily R.

2015-01-01

This report describes the various mesh tools that are provided with the PROTEUS code giving both descriptions of the input and output. In many cases the examples are provided with a regression test of the mesh tools. The most important mesh tools for any user to consider using are the MT M eshToMesh.x and the MT R adialLattice.x codes. The former allows the conversion between most mesh types handled by PROTEUS while the second allows the merging of multiple (assembly) meshes into a radial structured grid. Note that the mesh generation process is recursive in nature and that each input specific for a given mesh tool (such as .axial or .merge) can be used as ''mesh'' input for any of the mesh tools discussed in this manual.

To mesh or not to mesh: a review of pelvic organ reconstructive surgery

Science.gov (United States)

Dällenbach, Patrick

2015-01-01

Pelvic organ prolapse (POP) is a major health issue with a lifetime risk of undergoing at least one surgical intervention estimated at close to 10%. In the 1990s, the risk of reoperation after primary standard vaginal procedure was estimated to be as high as 30% to 50%. In order to reduce the risk of relapse, gynecological surgeons started to use mesh implants in pelvic organ reconstructive surgery with the emergence of new complications. Recent studies have nevertheless shown that the risk of POP recurrence requiring reoperation is lower than previously estimated, being closer to 10% rather than 30%. The development of mesh surgery – actively promoted by the marketing industry – was tremendous during the past decade, and preceded any studies supporting its benefit for our patients. Randomized trials comparing the use of mesh to native tissue repair in POP surgery have now shown better anatomical but similar functional outcomes, and meshes are associated with more complications, in particular for transvaginal mesh implants. POP is not a life-threatening condition, but a functional problem that impairs quality of life for women. The old adage “primum non nocere” is particularly appropriate when dealing with this condition which requires no treatment when asymptomatic. It is currently admitted that a certain degree of POP is physiological with aging when situated above the landmark of the hymen. Treatment should be individualized and the use of mesh needs to be selective and appropriate. Mesh implants are probably an important tool in pelvic reconstructive surgery, but the ideal implant has yet to be found. The indications for its use still require caution and discernment. This review explores the reasons behind the introduction of mesh augmentation in POP surgery, and aims to clarify the risks, benefits, and the recognized indications for its use. PMID:25848324

Adaptive finite element methods for differential equations

CERN Document Server

Bangerth, Wolfgang

2003-01-01

These Lecture Notes discuss concepts of `self-adaptivity' in the numerical solution of differential equations, with emphasis on Galerkin finite element methods. The key issues are a posteriori error estimation and it automatic mesh adaptation. Besides the traditional approach of energy-norm error control, a new duality-based technique, the Dual Weighted Residual method for goal-oriented error estimation, is discussed in detail. This method aims at economical computation of arbitrary quantities of physical interest by properly adapting the computational mesh. This is typically required in the design cycles of technical applications. For example, the drag coefficient of a body immersed in a viscous flow is computed, then it is minimized by varying certain control parameters, and finally the stability of the resulting flow is investigated by solving an eigenvalue problem. `Goal-oriented' adaptivity is designed to achieve these tasks with minimal cost. At the end of each chapter some exercises are posed in order ...

Streaming Compression of Hexahedral Meshes

Energy Technology Data Exchange (ETDEWEB)

Isenburg, M; Courbet, C

2010-02-03

We describe a method for streaming compression of hexahedral meshes. Given an interleaved stream of vertices and hexahedral our coder incrementally compresses the mesh in the presented order. Our coder is extremely memory efficient when the input stream documents when vertices are referenced for the last time (i.e. when it contains topological finalization tags). Our coder then continuously releases and reuses data structures that no longer contribute to compressing the remainder of the stream. This means in practice that our coder has only a small fraction of the whole mesh in memory at any time. We can therefore compress very large meshes - even meshes that do not file in memory. Compared to traditional, non-streaming approaches that load the entire mesh and globally reorder it during compression, our algorithm trades a less compact compressed representation for significant gains in speed, memory, and I/O efficiency. For example, on the 456k hexahedra 'blade' mesh, our coder is twice as fast and uses 88 times less memory (only 3.1 MB) with the compressed file increasing about 3% in size. We also present the first scheme for predictive compression of properties associated with hexahedral cells.

A third-order moving mesh cell-centered scheme for one-dimensional elastic-plastic flows

Science.gov (United States)

Cheng, Jun-Bo; Huang, Weizhang; Jiang, Song; Tian, Baolin

2017-11-01

A third-order moving mesh cell-centered scheme without the remapping of physical variables is developed for the numerical solution of one-dimensional elastic-plastic flows with the Mie-Grüneisen equation of state, the Wilkins constitutive model, and the von Mises yielding criterion. The scheme combines the Lagrangian method with the MMPDE moving mesh method and adaptively moves the mesh to better resolve shock and other types of waves while preventing the mesh from crossing and tangling. It can be viewed as a direct arbitrarily Lagrangian-Eulerian method but can also be degenerated to a purely Lagrangian scheme. It treats the relative velocity of the fluid with respect to the mesh as constant in time between time steps, which allows high-order approximation of free boundaries. A time dependent scaling is used in the monitor function to avoid possible sudden movement of the mesh points due to the creation or diminishing of shock and rarefaction waves or the steepening of those waves. A two-rarefaction Riemann solver with elastic waves is employed to compute the Godunov values of the density, pressure, velocity, and deviatoric stress at cell interfaces. Numerical results are presented for three examples. The third-order convergence of the scheme and its ability to concentrate mesh points around shock and elastic rarefaction waves are demonstrated. The obtained numerical results are in good agreement with those in literature. The new scheme is also shown to be more accurate in resolving shock and rarefaction waves than an existing third-order cell-centered Lagrangian scheme.

RGG: Reactor geometry (and mesh) generator

International Nuclear Information System (INIS)

Jain, R.; Tautges, T.

2012-01-01

The reactor geometry (and mesh) generator RGG takes advantage of information about repeated structures in both assembly and core lattices to simplify the creation of geometry and mesh. It is released as open source software as a part of the MeshKit mesh generation library. The methodology operates in three stages. First, assembly geometry models of various types are generated by a tool called AssyGen. Next, the assembly model or models are meshed by using MeshKit tools or the CUBIT mesh generation tool-kit, optionally based on a journal file output by AssyGen. After one or more assembly model meshes have been constructed, a tool called CoreGen uses a copy/move/merge process to arrange the model meshes into a core model. In this paper, we present the current state of tools and new features in RGG. We also discuss the parallel-enabled CoreGen, which in several cases achieves super-linear speedups since the problems fit in available RAM at higher processor counts. Several RGG applications - 1/6 VHTR model, 1/4 PWR reactor core, and a full-core model for Monju - are reported. (authors)

Evolving local climate adaptation strategies: incorporating influences of socio–economic stress

OpenAIRE

Hjerpe, Mattias; Glaas, Erik

2012-01-01

Socio-economic and climatic stresses affect local communities’ vulnerability toflooding. Better incorporation of socio-economic stress in local vulnerability assessments isimportant when planning for climate adaptation. This is rarely done due to insufficientunderstanding of their interaction, in both theory and practice. The omission leads to criticalweaknesses in local adaptation strategies. This study analyses how socio-economic stressinteract with climatic stress and shape local vulnerabi...

Climate change adaptation strategies by small-scale farmers in ...

African Journals Online (AJOL)

Mburu

Climate change is a great environmental challenge facing humanity today. In Yatta District, residents report frequent crop failures, water shortages and relief food has become a frequent feature of their life. This study examines the adaptation strategies to climate change adopted by the dry-land farming communities in Yatta ...

Properties of meshes used in hernia repair: a comprehensive review of synthetic and biologic meshes.

Science.gov (United States)

Ibrahim, Ahmed M S; Vargas, Christina R; Colakoglu, Salih; Nguyen, John T; Lin, Samuel J; Lee, Bernard T

2015-02-01

Data on the mechanical properties of the adult human abdominal wall have been difficult to obtain rendering manufacture of the ideal mesh for ventral hernia repair a challenge. An ideal mesh would need to exhibit greater biomechanical strength and elasticity than that of the abdominal wall. The aim of this study is to quantitatively compare the biomechanical properties of the most commonly used synthetic and biologic meshes in ventral hernia repair and presents a comprehensive literature review. A narrative review of the literature was performed using the PubMed database spanning articles from 1982 to 2012 including a review of company Web sites to identify all available information relating to the biomechanical properties of various synthetic and biologic meshes used in ventral hernia repair. There exist differences in the mechanical properties and the chemical nature of different meshes. In general, most synthetic materials have greater stiffness and elasticity than what is required for abdominal wall reconstruction; however, each exhibits unique properties that may be beneficial for clinical use. On the contrary, biologic meshes are more elastic but less stiff and with a lower tensile strength than their synthetic counterparts. The current standard of practice for the treatment of ventral hernias is the use of permanent synthetic mesh material. Recently, biologic meshes have become more frequently used. Most meshes exhibit biomechanical properties over the known abdominal wall thresholds. Augmenting strength requires increasing amounts of material contributing to more stiffness and foreign body reaction, which is not necessarily an advantage. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

An Alternative Treatment Strategy for Complicated Chronic Wounds: Negative Pressure Therapy over Mesh Skin Graft

Directory of Open Access Journals (Sweden)

Michele Maruccia

2017-01-01

Full Text Available Extensive skin defect represents a real problem and major challenge in plastic and reconstructive surgery. On one hand, skin grafts offer a practical method to deal with skin defects despite their unsuitability for several complicated wounds. On the other hand, negative pressure wound therapy (NPWT, applied before skin grafting, promotes granulation tissue growth. The aim of the study is to evaluate the improvement in wound healing given by the merger of these two different approaches. We treated 23 patients for large wounds of multiple factors. Of these, 15 were treated with the application of V.A.C.® Therapy (KCI Medical S.r.l., Milan, Italy, in combination with skin grafts after a prior unsuccessful treatment of 4 weeks with mesh skin grafts and dressings. Another 8 were treated with only mesh skin graft. Pain reduction and wound area reduction were found statistically significant (p<0.0009, p<0.0001. Infection was resolved in almost all patients. According to our study, the use of the negative pressure wound therapy over mesh skin grafts is significantly effective especially in wounds resistant to conventional therapies, thereby improving the rate of skin graft take.

An innovative cross-sectoral method for implementation of trade-off adaptation strategy assessment under climate change

Science.gov (United States)

Tsao, Jung-Hsuan; Tung, Ching-Pin; Liu, Tzu-Ming

2014-05-01

Climate change will increase sharp risks to the water and food supply in coming decades. Although impact assessment and adaptation evaluation has been discussed a lot in recent years, the importance of adaptation implement should not be ignored. In Taiwan, and elsewhere, fallow is an option of adaptation strategy under climate change. Fallow would improve the water scarcity of domestic use, but the food security might be threatened. The trade-off effects of adaptation actions are just like the side effects of medicine which cannot be avoided. Thus, managing water resources with an integrated approach will be urgent. This study aims to establish a cross-sectoral framework for implementation the trade-off adaptation strategy. Not only fallow, but also other trade-off strategy like increasing the percentage of national grain self-sufficiency would be analyzed by a rational decision process. The recent percentage of grain self-sufficiency in Taiwan is around 32, which was decreasing from 53 thirty years ago. Yet, the goal of increasing grain self-sufficiency means much more water must be used in agriculture. In that way, domestic users may face the water shortage situation. Considering the conflicts between water supply and food security, the concepts from integrative negotiation are appropriate to apply. The implementation of trade-off adaptation strategies needs to start by quantifying the utility of water supply and food security were be quantified. Next, each side's bottom line can be found by BATNA (Best Alternative to a Negotiated Agreement) and ZOPA (Zone of Possible Agreement). ZOPA provides the entire possible outcomes, and BATNA ensures the efficiency of adaptation actions by moving along with Pareto frontier. Therefore, the optimal percentage of fallow and grain self-sufficiency can be determined. Furthermore, BATNA also provides the pathway step by step which can be a guideline of adaptation strategies. This framework allows analysts and stakeholder to

Evidence for replacement of an infected synthetic by a biological mesh in abdominal wall hernia repair

Directory of Open Access Journals (Sweden)

Agneta eMontgomery

2016-01-01

Full Text Available The incidence of deep infection using a synthetic mesh in inguinal hernia repair is low and reported to be well below 1%. This is in contrast to incisional hernia surgery where the reported incidence is 3% respective 13% comparing laparoscopic to open mesh repair reported in a Cochrane review. Main risk factors were long operation time, surgical site contamination and early wound complications. An infected mesh can be preserved using conservative treatment were negative pressure wound therapy (VAC® could play an important role. If strategy fails, the mesh needs to be removed. This review aims to look at evidence for situations were a biological mesh would work as a replacement of a removed infected synthetic mesh. Material and MethodsA literature search of the Medline database was performed using the PubMed search engine. Twenty publications were found relevant for this review.ResultsFor studies reviewed three options are presented: removal of the infected synthetic mesh alone, replacement with either a new synthetic or a new biological mesh. Operations were all performed at specialist centers. Removal of the mesh alone was an option limited to inguinal hernias. In ventral/incisional hernias the use of a biological mesh for replacement resulted in a very high recurrence rate, if bridging was required. Either a synthetic or a biological mesh seems to work as a replacement when fascial closure can be achieved. Evidence is though very low. ConclusionWhen required, either a synthetic or a biological meshes seems to work as a replacement for an infected synthetic mesh if the defect can be closed. It is however not recommended to use a biological mesh for bridging. Mesh replacement surgery is demanding and is recommended to be performed in a specialist center.

Code meshing: Online bilingual tutoring in Higher Education

Directory of Open Access Journals (Sweden)

Batyi, Thelma Thokozile

2016-12-01

Full Text Available Students’ academic writing literacies are required to express their knowledge, as academic writing is the common mode of assessment in higher education. 28 isiXhosa-speaking first-year diploma students, who failed an academic literacies admission test evaluating the level of their academic writing literacies in the Business faculty, participated once a week over a period of eight months in a course including the practice of code meshing. In the June and November Tourism Communication tests, which also evaluated their academic writing literacies, there was a significant difference in the mean scores when compared to the admission test in the Business faculty. Their academic writing had also improved, according to their assignment marks. The researcher in this project provides evidence that code meshing as a bi/multilingual strategy could be used to improve academic writing literacies in students.

Dynamically Adapted Mesh Construction for the Efficient Numerical Solution of a Singular Perturbed Reaction-diffusion-advection Equation

Directory of Open Access Journals (Sweden)

Dmitry V. Lukyanenko

2017-01-01

Full Text Available This  work develops  a theory  of the  asymptotic-numerical investigation of the  moving fronts  in reaction-diffusion-advection models.  By considering  the  numerical  solution  of the  singularly perturbed Burgers’s  equation  we discuss a method  of dynamically  adapted mesh  construction that is able to significantly  improve  the  numerical  solution  of this  type of equations.  For  the  construction we use a priori information that is based  on the  asymptotic analysis  of the  problem.  In  particular, we take  into account the information about  the speed of the transition layer, its width  and structure. Our algorithms  are able to reduce significantly complexity and enhance stability of the numerical  calculations in comparison  with classical approaches for solving this class of problems.  The numerical  experiment is presented to demonstrate the effectiveness of the proposed  method.The article  is published  in the authors’  wording. 

Three-dimensional h-adaptivity for the multigroup neutron diffusion equations

KAUST Repository

Wang, Yaqi

2009-04-01

Adaptive mesh refinement (AMR) has been shown to allow solving partial differential equations to significantly higher accuracy at reduced numerical cost. This paper presents a state-of-the-art AMR algorithm applied to the multigroup neutron diffusion equation for reactor applications. In order to follow the physics closely, energy group-dependent meshes are employed. We present a novel algorithm for assembling the terms coupling shape functions from different meshes and show how it can be made efficient by deriving all meshes from a common coarse mesh by hierarchic refinement. Our methods are formulated using conforming finite elements of any order, for any number of energy groups. The spatial error distribution is assessed with a generalization of an error estimator originally derived for the Poisson equation. Our implementation of this algorithm is based on the widely used Open Source adaptive finite element library deal.II and is made available as part of this library\\'s extensively documented tutorial. We illustrate our methods with results for 2-D and 3-D reactor simulations using 2 and 7 energy groups, and using conforming finite elements of polynomial degree up to 6. © 2008 Elsevier Ltd. All rights reserved.

Mesh refinement and numerical sensitivity analysis for parameter calibration of partial differential equations

Science.gov (United States)

Becker, Roland; Vexler, Boris

2005-06-01

We consider the calibration of parameters in physical models described by partial differential equations. This task is formulated as a constrained optimization problem with a cost functional of least squares type using information obtained from measurements. An important issue in the numerical solution of this type of problem is the control of the errors introduced, first, by discretization of the equations describing the physical model, and second, by measurement errors or other perturbations. Our strategy is as follows: we suppose that the user defines an interest functional I, which might depend on both the state variable and the parameters and which represents the goal of the computation. First, we propose an a posteriori error estimator which measures the error with respect to this functional. This error estimator is used in an adaptive algorithm to construct economic meshes by local mesh refinement. The proposed estimator requires the solution of an auxiliary linear equation. Second, we address the question of sensitivity. Applying similar techniques as before, we derive quantities which describe the influence of small changes in the measurements on the value of the interest functional. These numbers, which we call relative condition numbers, give additional information on the problem under consideration. They can be computed by means of the solution of the auxiliary problem determined before. Finally, we demonstrate our approach at hand of a parameter calibration problem for a model flow problem.

Adaptation and Validation of the Teacher Emotional Labour Strategy Scale in China

Science.gov (United States)

Yin, Hongbiao

2012-01-01

The present study reports the adaptation and validation of the Teacher Emotional Labour Strategy Scale (TELSS) as tested on samples of 633 Beijing teachers and 648 Chongqing teachers in Chinese mainland. Results show that the 13-item TELSS adapted for this study had good internal consistency on three subscales which measure three types of teacher…

On Reducing Delay in Mesh-Based P2P Streaming: A Mesh-Push Approach

Science.gov (United States)

Liu, Zheng; Xue, Kaiping; Hong, Peilin

The peer-assisted streaming paradigm has been widely employed to distribute live video data on the internet recently. In general, the mesh-based pull approach is more robust and efficient than the tree-based push approach. However, pull protocol brings about longer streaming delay, which is caused by the handshaking process of advertising buffer map message, sending request message and scheduling of the data block. In this paper, we propose a new approach, mesh-push, to address this issue. Different from the traditional pull approach, mesh-push implements block scheduling algorithm at sender side, where the block transmission is initiated by the sender rather than by the receiver. We first formulate the optimal upload bandwidth utilization problem, then present the mesh-push approach, in which a token protocol is designed to avoid block redundancy; a min-cost flow model is employed to derive the optimal scheduling for the push peer; and a push peer selection algorithm is introduced to reduce control overhead. Finally, we evaluate mesh-push through simulation, the results of which show mesh-push outperforms the pull scheduling in streaming delay, and achieves comparable delivery ratio at the same time.

Analysis of the Numerical Diffusion in Anisotropic Mediums: Benchmarks for Magnetic Field Aligned Meshes in Space Propulsion Simulations

Directory of Open Access Journals (Sweden)

Daniel Pérez-Grande

2016-11-01

Full Text Available This manuscript explores numerical errors in highly anisotropic diffusion problems. First, the paper addresses the use of regular structured meshes in numerical solutions versus meshes aligned with the preferential directions of the problem. Numerical diffusion in structured meshes is quantified by solving the classical anisotropic diffusion problem; the analysis is exemplified with the application to a numerical model of conducting fluids under magnetic confinement, where rates of transport in directions parallel and perpendicular to a magnetic field are quite different. Numerical diffusion errors in this problem promote the use of magnetic field aligned meshes (MFAM. The generation of this type of meshes presents some challenges; several meshing strategies are implemented and analyzed in order to provide insight into achieving acceptable mesh regularity. Second, Gradient Reconstruction methods for magnetically aligned meshes are addressed and numerical errors are compared for the structured and magnetically aligned meshes. It is concluded that using the latter provides a more correct and straightforward approach to solving problems where anisotropicity is present, especially, if the anisotropicity level is high or difficult to quantify. The conclusions of the study may be extrapolated to the study of anisotropic flows different from conducting fluids.

Transrectal Mesh Erosion Requiring Bowel Resection.

Science.gov (United States)

Kemp, Marta Maria; Slim, Karem; Rabischong, Benoît; Bourdel, Nicolas; Canis, Michel; Botchorishvili, Revaz

To report a case of a transrectal mesh erosion as complication of laparoscopic promontofixation with mesh repair, necessitating bowel resection and subsequent surgical interventions. Sacrocolpopexy has become a standard procedure for vaginal vault prolapse [1], and the laparoscopic approach has gained popularity owing to more rapid recovery and less morbidity [2,3]. Mesh erosion is a well-known complication of surgical treatment for prolapse as reported in several negative evaluations, including a report from the US Food and Drug Administration in 2011 [4]. Mesh complications are more common after surgeries via the vaginal approach [5]; nonetheless, the incidence of vaginal mesh erosion after laparoscopic procedures is as high as 9% [6]. The incidence of transrectal mesh exposure after laparoscopic ventral rectopexy is roughly 1% [7]. The diagnosis may be delayed because of its rarity and variable presentation. In addition, polyester meshes, such as the mesh used in this case, carry a higher risk of exposure [8]. A 57-year-old woman experiencing genital prolapse, with the cervix classified as +3 according to the Pelvic Organ Prolapse Quantification system, underwent laparoscopic standard sacrocolpopexy using polyester mesh. Subtotal hysterectomy and bilateral adnexectomy were performed concomitantly. A 3-year follow-up consultation demonstrated no signs or symptoms of erosion of any type. At 7 years after the surgery, however, the patient presented with rectal discharge, diagnosed as infectious rectocolitis with the isolation of Clostridium difficile. She underwent a total of 5 repair surgeries in a period of 4 months, including transrectal resection of exposed mesh, laparoscopic ablation of mesh with digestive resection, exploratory laparoscopy with abscess drainage, and exploratory laparoscopy with ablation of residual mesh and transverse colostomy. She recovered well after the last intervention, exhibiting no signs of vaginal or rectal fistula and no recurrence

Efficient community-based control strategies in adaptive networks

International Nuclear Information System (INIS)

Yang Hui; Tang Ming; Zhang Haifeng

2012-01-01

Most studies on adaptive networks concentrate on the properties of steady state, but neglect transient dynamics. In this study, we pay attention to the emergence of community structure in the transient process and the effects of community-based control strategies on epidemic spreading. First, by normalizing the modularity, we investigate the evolution of community structure during the transient process, and find that a strong community structure is induced by the rewiring mechanism in the early stage of epidemic dynamics, which, remarkably, delays the outbreak of disease. We then study the effects of control strategies started at different stages on the prevalence. Both immunization and quarantine strategies indicate that it is not ‘the earlier, the better’ for the implementation of control measures. And the optimal control effect is obtained if control measures can be efficiently implemented in the period of a strong community structure. For the immunization strategy, immunizing the susceptible nodes on susceptible–infected links and immunizing susceptible nodes randomly have similar control effects. However, for the quarantine strategy, quarantining the infected nodes on susceptible–infected links can yield a far better result than quarantining infected nodes randomly. More significantly, the community-based quarantine strategy performs better than the community-based immunization strategy. This study may shed new light on the forecast and the prevention of epidemics among humans. (paper)

An analysis of climatic impacts and adaptation strategies in Tanzania

CSIR Research Space (South Africa)

Ojoyi, MM

2015-03-01

Full Text Available International Journal of Climate Change Strategies and Management An analysis of climatic impacts and adaptation strategies in Tanzania Mercy M. Ojoyi School of Environmental Sciences, University of KwaZulu-Natal, Pietermaritzburg, South Africa... of feedback results from analysis of variance tests conducted. Major indicators of climate variability and change include: increased dry spells (39.7 per cent), drying of rivers (34.7 per cent), a reduction in water flows (14.6 per cent) and poor economy...

Mesh-morphing algorithms for specimen-specific finite element modeling.

Science.gov (United States)

Sigal, Ian A; Hardisty, Michael R; Whyne, Cari M

2008-01-01

Despite recent advances in software for meshing specimen-specific geometries, considerable effort is still often required to produce and analyze specimen-specific models suitable for biomechanical analysis through finite element modeling. We hypothesize that it is possible to obtain accurate models by adapting a pre-existing geometry to represent a target specimen using morphing techniques. Here we present two algorithms for morphing, automated wrapping (AW) and manual landmarks (ML), and demonstrate their use to prepare specimen-specific models of caudal rat vertebrae. We evaluate the algorithms by measuring the distance between target and morphed geometries and by comparing response to axial loading simulated with finite element (FE) methods. First a traditional reconstruction process based on microCT was used to obtain two natural specimen-specific FE models. Next, the two morphing algorithms were used to compute mappings from the surface of one model, the source, to the other, the target, and to use this mapping to morph the source mesh to produce a target mesh. The microCT images were then used to assign element-specific material properties. In AW the mappings were obtained by wrapping the source and target surfaces with an auxiliary triangulated surface. In ML, landmarks were manually placed on corresponding locations on the surfaces of both source and target. Both morphing algorithms were successful in reproducing the shape of the target vertebra with a median distance between natural and morphed models of 18.8 and 32.2 microm, respectively, for AW and ML. Whereas AW-morphing produced a surface more closely resembling that of the target, ML guaranteed correspondence of the landmark locations between source and target. Morphing preserved the quality of the mesh producing models suitable for FE simulation. Moreover, there were only minor differences between natural and morphed models in predictions of deformation, strain and stress. We therefore conclude that

Goal-Oriented Self-Adaptive hp Finite Element Simulation of 3D DC Borehole Resistivity Simulations

KAUST Repository

Calo, Victor M.

2011-05-14

In this paper we present a goal-oriented self-adaptive hp Finite Element Method (hp-FEM) with shared data structures and a parallel multi-frontal direct solver. The algorithm automatically generates (without any user interaction) a sequence of meshes delivering exponential convergence of a prescribed quantity of interest with respect to the number of degrees of freedom. The sequence of meshes is generated from a given initial mesh, by performing h (breaking elements into smaller elements), p (adjusting polynomial orders of approximation) or hp (both) refinements on the finite elements. The new parallel implementation utilizes a computational mesh shared between multiple processors. All computational algorithms, including automatic hp goal-oriented adaptivity and the solver work fully in parallel. We describe the parallel self-adaptive hp-FEM algorithm with shared computational domain, as well as its efficiency measurements. We apply the methodology described to the three-dimensional simulation of the borehole resistivity measurement of direct current through casing in the presence of invasion.

Soft Ultrathin Electronics Innervated Adaptive Fully Soft Robots.

Science.gov (United States)

Wang, Chengjun; Sim, Kyoseung; Chen, Jin; Kim, Hojin; Rao, Zhoulyu; Li, Yuhang; Chen, Weiqiu; Song, Jizhou; Verduzco, Rafael; Yu, Cunjiang

2018-03-01

Soft robots outperform the conventional hard robots on significantly enhanced safety, adaptability, and complex motions. The development of fully soft robots, especially fully from smart soft materials to mimic soft animals, is still nascent. In addition, to date, existing soft robots cannot adapt themselves to the surrounding environment, i.e., sensing and adaptive motion or response, like animals. Here, compliant ultrathin sensing and actuating electronics innervated fully soft robots that can sense the environment and perform soft bodied crawling adaptively, mimicking an inchworm, are reported. The soft robots are constructed with actuators of open-mesh shaped ultrathin deformable heaters, sensors of single-crystal Si optoelectronic photodetectors, and thermally responsive artificial muscle of carbon-black-doped liquid-crystal elastomer (LCE-CB) nanocomposite. The results demonstrate that adaptive crawling locomotion can be realized through the conjugation of sensing and actuation, where the sensors sense the environment and actuators respond correspondingly to control the locomotion autonomously through regulating the deformation of LCE-CB bimorphs and the locomotion of the robots. The strategy of innervating soft sensing and actuating electronics with artificial muscles paves the way for the development of smart autonomous soft robots. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An adaptive radiotherapy planning strategy for bladder cancer using deformation vector fields

International Nuclear Information System (INIS)

Vestergaard, Anne; Kallehauge, Jesper Folsted; Petersen, Jørgen Breede Baltzer; Høyer, Morten; Søndergaard, Jimmi; Muren, Ludvig Paul

2014-01-01

Purpose: Adaptive radiotherapy (ART) has considerable potential in treatment of bladder cancer due to large inter-fractional changes in shape and size of the target. The aim of this study was to compare our clinically applied method for plan library creation that involves manual bladder delineations (Clin-ART) with a method using the deformation vector fields (DVFs) resulting from intensity-based deformable image registrations (DVF-based ART). Materials and methods: The study included thirteen patients with urinary bladder cancer who had daily cone beam CTs (CBCTs) acquired for set-up. In both ART strategies investigated, three plan selection volumes were generated using the CBCTs from the first four fractions; in Clin-ART boolean combinations of delineated bladders were used, while the DVF-based strategy applied combinations of the mean and standard deviation of patient-specific DVFs. The volume ratios (VRs) of the course-averaged PTV for the two ART strategies relative the non-adaptive PTV were calculated. Results: Both Clin-ART and DVF-based ART considerably reduced the course-averaged PTV, compared to non-adaptive RT. The VR for DVF-based ART was lower than for Clin-ART (0.65 vs. 0.73; p < 0.01). Conclusions: DVF-based ART for bladder irradiation has a considerable normal tissue sparing potential surpassing our already highly conformal clinically applied ART strategy

An adaptive radiotherapy planning strategy for bladder cancer using deformation vector fields.

Science.gov (United States)

Vestergaard, Anne; Kallehauge, Jesper Folsted; Petersen, Jørgen Breede Baltzer; Høyer, Morten; Søndergaard, Jimmi; Muren, Ludvig Paul

2014-09-01

Adaptive radiotherapy (ART) has considerable potential in treatment of bladder cancer due to large inter-fractional changes in shape and size of the target. The aim of this study was to compare our clinically applied method for plan library creation that involves manual bladder delineations (Clin-ART) with a method using the deformation vector fields (DVFs) resulting from intensity-based deformable image registrations (DVF-based ART). The study included thirteen patients with urinary bladder cancer who had daily cone beam CTs (CBCTs) acquired for set-up. In both ART strategies investigated, three plan selection volumes were generated using the CBCTs from the first four fractions; in Clin-ART boolean combinations of delineated bladders were used, while the DVF-based strategy applied combinations of the mean and standard deviation of patient-specific DVFs. The volume ratios (VRs) of the course-averaged PTV for the two ART strategies relative the non-adaptive PTV were calculated. Both Clin-ART and DVF-based ART considerably reduced the course-averaged PTV, compared to non-adaptive RT. The VR for DVF-based ART was lower than for Clin-ART (0.65 vs. 0.73; p<0.01). DVF-based ART for bladder irradiation has a considerable normal tissue sparing potential surpassing our already highly conformal clinically applied ART strategy. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Laboratory Evolution to Alternating Substrate Environments Yields Distinct Phenotypic and Genetic Adaptive Strategies

DEFF Research Database (Denmark)

Sandberg, Troy E.; Lloyd, Colton J.; Palsson, Bernhard O.

2017-01-01

conditions and different adaptation strategies depending on the substrates being switched between; in some environments, a persistent "generalist" strain developed, while in another, two "specialist" subpopulations arose that alternated dominance. Diauxic lag phenotype varied across the generalists...... maintain simple, static culturing environments so as to reduce selection pressure complexity. In this study, we investigated the adaptive strategies underlying evolution to fluctuating environments by evolving Escherichia coli to conditions of frequently switching growth substrate. Characterization...... of evolved strains via a number of different data types revealed the various genetic and phenotypic changes implemented in pursuit of growth optimality and how these differed across the different growth substrates and switching protocols. This work not only helps to establish general principles of adaptation...

Cell-centered particle weighting algorithm for PIC simulations in a non-uniform 2D axisymmetric mesh

Science.gov (United States)

Araki, Samuel J.; Wirz, Richard E.

2014-09-01

Standard area weighting methods for particle-in-cell simulations result in systematic errors on particle densities for a non-uniform mesh in cylindrical coordinates. These errors can be significantly reduced by using weighted cell volumes for density calculations. A detailed description on the corrected volume calculations and cell-centered weighting algorithm in a non-uniform mesh is provided. The simple formulas for the corrected volume can be used for any type of quadrilateral and/or triangular mesh in cylindrical coordinates. Density errors arising from the cell-centered weighting algorithm are computed for radial density profiles of uniform, linearly decreasing, and Bessel function in an adaptive Cartesian mesh and an unstructured mesh. For all the density profiles, it is shown that the weighting algorithm provides a significant improvement for density calculations. However, relatively large density errors may persist at outermost cells for monotonically decreasing density profiles. A further analysis has been performed to investigate the effect of the density errors in potential calculations, and it is shown that the error at the outermost cell does not propagate into the potential solution for the density profiles investigated.

An adaptive EFG-FE coupling method for elasto-plastic contact of rough surfaces

International Nuclear Information System (INIS)

Liu Lan; Liu Geng; Tong Ruiting; Jin Saiying

2010-01-01

Differing from Finite Element Method, the meshless method does not need any mesh information and can arrange nodes freely which is perfectly suitable for adaptive analysis. In order to simulate the contact condition factually and improve computational efficiency, an adaptive procedure for Element-free Galerkin-Finite Element (EFG-FE) coupling contact model is established and developed to investigate the elastoplastic contact performance for engineering rough surfaces. The local adaptive refinement strategy combined with the strain energy gradient-based error estimation model is employed. The schemes, including principle explanation, arithmetic analysis and programming realization, are introduced and discussed. Furthermore, some related parameters on adaptive convergence criterion are researched emphatically, including adaptation-stop criterion, refinement or coarsening criterion which are guided by the relative error in total strain energy with two adjacent stages. Based on pioneering works of the EFG-FE coupling method for contact problems, an adaptive EFG-FE model for asperity contact is studied. Compared with the solutions obtained from the uniform refinement model, the adaptation results indicate that the adaptive method presented in this paper is capable of solving asperity contact problems with excellent calculation accuracy and computational efficiency.

Coarse mesh code development

Energy Technology Data Exchange (ETDEWEB)

Lieberoth, J.

1975-06-15

The numerical solution of the neutron diffusion equation plays a very important role in the analysis of nuclear reactors. A wide variety of numerical procedures has been proposed, at which most of the frequently used numerical methods are fundamentally based on the finite- difference approximation where the partial derivatives are approximated by the finite difference. For complex geometries, typical of the practical reactor problems, the computational accuracy of the finite-difference method is seriously affected by the size of the mesh width relative to the neutron diffusion length and by the heterogeneity of the medium. Thus, a very large number of mesh points are generally required to obtain a reasonably accurate approximate solution of the multi-dimensional diffusion equation. Since the computation time is approximately proportional to the number of mesh points, a detailed multidimensional analysis, based on the conventional finite-difference method, is still expensive even with modern large-scale computers. Accordingly, there is a strong incentive to develop alternatives that can reduce the number of mesh-points and still retain accuracy. One of the promising alternatives is the finite element method, which consists of the expansion of the neutron flux by piecewise polynomials. One of the advantages of this procedure is its flexibility in selecting the locations of the mesh points and the degree of the expansion polynomial. The small number of mesh points of the coarse grid enables to store the results of several of the least outer iterations and to calculate well extrapolated values of them by comfortable formalisms. This holds especially if only one energy distribution of fission neutrons is assumed for all fission processes in the reactor, because the whole information of an outer iteration is contained in a field of fission rates which has the size of all mesh points of the coarse grid.

Farmers´ perceptions of climate change and agricultural adaptation strategies in rural Sahel

DEFF Research Database (Denmark)

Mertz, Ole; Mbow, Cheikh; Reenberg, Anette

2009-01-01

Farmers in the Sahel have always been facing climatic variability at intra- and inter-annual and decadal time scales. While coping and adaptation strategies have traditionally included crop diversification, mobility, livelihood diversification, and migration, singling out climate as a direct driver...... of changes is not so simple. Using focus group interviews and a household survey, this study analyzes the perceptions of climate change and the strategies for coping and adaptation by sedentary farmers in the savanna zone of central Senegal. Households are aware of climate variability and identify wind...

MeSH: a window into full text for document summarization.

Science.gov (United States)

Bhattacharya, Sanmitra; Ha-Thuc, Viet; Srinivasan, Padmini

2011-07-01

Previous research in the biomedical text-mining domain has historically been limited to titles, abstracts and metadata available in MEDLINE records. Recent research initiatives such as TREC Genomics and BioCreAtIvE strongly point to the merits of moving beyond abstracts and into the realm of full texts. Full texts are, however, more expensive to process not only in terms of resources needed but also in terms of accuracy. Since full texts contain embellishments that elaborate, contextualize, contrast, supplement, etc., there is greater risk for false positives. Motivated by this, we explore an approach that offers a compromise between the extremes of abstracts and full texts. Specifically, we create reduced versions of full text documents that contain only important portions. In the long-term, our goal is to explore the use of such summaries for functions such as document retrieval and information extraction. Here, we focus on designing summarization strategies. In particular, we explore the use of MeSH terms, manually assigned to documents by trained annotators, as clues to select important text segments from the full text documents. Our experiments confirm the ability of our approach to pick the important text portions. Using the ROUGE measures for evaluation, we were able to achieve maximum ROUGE-1, ROUGE-2 and ROUGE-SU4 F-scores of 0.4150, 0.1435 and 0.1782, respectively, for our MeSH term-based method versus the maximum baseline scores of 0.3815, 0.1353 and 0.1428, respectively. Using a MeSH profile-based strategy, we were able to achieve maximum ROUGE F-scores of 0.4320, 0.1497 and 0.1887, respectively. Human evaluation of the baselines and our proposed strategies further corroborates the ability of our method to select important sentences from the full texts. sanmitra-bhattacharya@uiowa.edu; padmini-srinivasan@uiowa.edu.

Development of parallel implementation of adaptive numerical methods with industrial applications in fluid mechanics

International Nuclear Information System (INIS)

Laucoin, E.

2008-10-01

Numerical resolution of partial differential equations can be made reliable and efficient through the use of adaptive numerical methods.We present here the work we have done for the design, the implementation and the validation of such a method within an industrial software platform with applications in thermohydraulics. From the geometric point of view, this method can deal both with mesh refinement and mesh coarsening, while ensuring the quality of the mesh cells. Numerically, we use the mortar elements formalism in order to extend the Finite Volumes-Elements method implemented in the Trio-U platform and to deal with the non-conforming meshes arising from the adaptation procedure. Finally, we present an implementation of this method using concepts from domain decomposition methods for ensuring its efficiency while running in a parallel execution context. (author)

Synergies, Conflicts, and Trade-offs of C40 Cities Adaptation Strategies

DEFF Research Database (Denmark)

Driscoll, Patrick Arthur; De Rosa, Michele; Lehmann, Martin

2013-01-01

There is a growing body of literature in the field of urban climate change adaptation planning that indicate a need to address climate change planning measures from a more holistic sustainable development perspective. This paper presents the findings from a recently completed study that indicates...... there remain significant unresolved tensions between the development pathways and the climate change adaptation strategies of the 58 cities within the C40 Cities Climate Leadership Group....

F:ACTS! : Forms for adapting to climate change through territorial strategies : the handbook

NARCIS (Netherlands)

Garcia, A.M.; Ónega, J.; Crecente, R.; Holst, van F.; Abts, E.; Timmermans, W.; Stolk, M.

2014-01-01

The F:ACTS! project contributed to generating knowledge on how to develop territorial strategies to adapt to climate change, facilitating the interchange of experience and information among its 14 partners across 8 countries. Integrated territorial strategies incorporate local diversity since they

A multi-attribute approach to choosing adaptation strategies: Application to sea-level rise

International Nuclear Information System (INIS)

Smith, A.E.; Chu, H.Q.

1994-01-01

Selecting good adaptation strategies in anticipation of climate change is gaining increasing attention as it becomes increasingly clear that much of the likely change is already committed, and could not be avoided even with aggressive and immediate emissions reductions. Adaptation decision making will place special requirements on regional and local planners in the US and other countries, especially developing countries. Approaches, tools, and guidance will be useful to assist in an effective response to the challenge. This paper describes the value of using a multi-attribute approach for evaluating adaptation strategies and its implementation as a decision-support software tool to help planners understand and execute this approach. The multi-attribute approach described here explicitly addresses the fact that many aspects of the decision cannot be easily quantified, that future conditions are highly uncertain, and that there are issues of equity, flexibility, and coordination that may be as important to the decision as costs and benefits. The approach suggested also avoids trying to collapse information on all of the attributes to a single metric. Such metrics can obliterate insights about the nature of the trade-offs that must be made in choosing among very dissimilar types of responses to the anticipated threat of climate change. Implementation of such an approach requires management of much information, and an ability to easily manipulate its presentation while seeking acceptable trade-offs. The Adaptation Strategy Evaluator (ASE) was developed under funding from the US Environmental Protection Agency to provide user-friendly, PC-based guidance through the major steps of a multi-attribute evaluation. The initial application of ASE, and the focus of this paper, is adaptation to sea level rise. However, the approach can be easily adapted to any multi-attribute choice problem, including the range of other adaptation planning needs

Method and system for mesh network embedded devices

Science.gov (United States)

Wang, Ray (Inventor)

2009-01-01

A method and system for managing mesh network devices. A mesh network device with integrated features creates an N-way mesh network with a full mesh network topology or a partial mesh network topology.

Fog water collection effectiveness: Mesh intercomparisons

Science.gov (United States)

Fernandez, Daniel; Torregrosa, Alicia; Weiss-Penzias, Peter; Zhang, Bong June; Sorensen, Deckard; Cohen, Robert; McKinley, Gareth; Kleingartner, Justin; Oliphant, Andrew; Bowman, Matthew

2018-01-01

To explore fog water harvesting potential in California, we conducted long-term measurements involving three types of mesh using standard fog collectors (SFC). Volumetric fog water measurements from SFCs and wind data were collected and recorded in 15-minute intervals over three summertime fog seasons (2014–2016) at four California sites. SFCs were deployed with: standard 1.00 m2 double-layer 35% shade coefficient Raschel; stainless steel mesh coated with the MIT-14 hydrophobic formulation; and FogHa-Tin, a German manufactured, 3-dimensional spacer fabric deployed in two orientations. Analysis of 3419 volumetric samples from all sites showed strong relationships between mesh efficiency and wind speed. Raschel mesh collected 160% more fog water than FogHa-Tin at wind speeds less than 1 m s–1 and 45% less for wind speeds greater than 5 m s–1. MIT-14 coated stainless-steel mesh collected more fog water than Raschel mesh at all wind speeds. At low wind speeds of steel mesh collected 3% more and at wind speeds of 4–5 m s–1, it collected 41% more. FogHa-Tin collected 5% more fog water when the warp of the weave was oriented vertically, per manufacturer specification, than when the warp of the weave was oriented horizontally. Time series measurements of three distinct mesh across similar wind regimes revealed inconsistent lags in fog water collection and inconsistent performance. Since such differences occurred under similar wind-speed regimes, we conclude that other factors play important roles in mesh performance, including in-situ fog event and aerosol dynamics that affect droplet-size spectra and droplet-to-mesh surface interactions.

Make way for the climate. National adaptation strategy. The policy paper

International Nuclear Information System (INIS)

2007-11-01

The policy paper is a background document of the interdepartmental memorandum 'Make way for climate', in which the outline is described for a national strategy for adaptation to the consequences of climate change. [mk] [nl

Meshes optimized for discrete exterior calculus (DEC).

Energy Technology Data Exchange (ETDEWEB)

Mousley, Sarah C. [Univ. of Illinois, Urbana-Champaign, IL (United States); Deakin, Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Knupp, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mitchell, Scott A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-12-01

We study the optimization of an energy function used by the meshing community to measure and improve mesh quality. This energy is non-traditional because it is dependent on both the primal triangulation and its dual Voronoi (power) diagram. The energy is a measure of the mesh's quality for usage in Discrete Exterior Calculus (DEC), a method for numerically solving PDEs. In DEC, the PDE domain is triangulated and this mesh is used to obtain discrete approximations of the continuous operators in the PDE. The energy of a mesh gives an upper bound on the error of the discrete diagonal approximation of the Hodge star operator. In practice, one begins with an initial mesh and then makes adjustments to produce a mesh of lower energy. However, we have discovered several shortcomings in directly optimizing this energy, e.g. its non-convexity, and we show that the search for an optimized mesh may lead to mesh inversion (malformed triangles). We propose a new energy function to address some of these issues.

General relativistic hydrodynamics with Adaptive-Mesh Refinement (AMR) and modeling of accretion disks

Science.gov (United States)

Donmez, Orhan

We present a general procedure to solve the General Relativistic Hydrodynamical (GRH) equations with Adaptive-Mesh Refinement (AMR) and model of an accretion disk around a black hole. To do this, the GRH equations are written in a conservative form to exploit their hyperbolic character. The numerical solutions of the general relativistic hydrodynamic equations is done by High Resolution Shock Capturing schemes (HRSC), specifically designed to solve non-linear hyperbolic systems of conservation laws. These schemes depend on the characteristic information of the system. We use Marquina fluxes with MUSCL left and right states to solve GRH equations. First, we carry out different test problems with uniform and AMR grids on the special relativistic hydrodynamics equations to verify the second order convergence of the code in 1D, 2 D and 3D. Second, we solve the GRH equations and use the general relativistic test problems to compare the numerical solutions with analytic ones. In order to this, we couple the flux part of general relativistic hydrodynamic equation with a source part using Strang splitting. The coupling of the GRH equations is carried out in a treatment which gives second order accurate solutions in space and time. The test problems examined include shock tubes, geodesic flows, and circular motion of particle around the black hole. Finally, we apply this code to the accretion disk problems around the black hole using the Schwarzschild metric at the background of the computational domain. We find spiral shocks on the accretion disk. They are observationally expected results. We also examine the star-disk interaction near a massive black hole. We find that when stars are grounded down or a hole is punched on the accretion disk, they create shock waves which destroy the accretion disk.

A TN adaptive ray effect mitigation for Styx 3D

International Nuclear Information System (INIS)

Aussourd, Ch.

2003-01-01

Ray effect (RE) is a non-physical flaw of discrete ordinate methods characterized by spurious rays becoming sharper when small bright neutron sources radiate through low scattering media. While this effect has low impact on integral parameters (α and K eff ), it can ruin simulations of diagnostic problem in terms of neutron dose received by a detector. 3 cumulative factors may affect the RE intensity: the source size, the scattering cross-sections, and the mesh size. We introduce an adaptive Ray Effect Mitigation (REM) aimed at locally improving the angular accuracy of the 3 dimension AMR (adaptive mesh refinement) deterministic neutron transport code Styx. Promising preliminary results have been obtained using a recursively refined octahedron based sphere tessellation in place of the standard S N quadrature. This angular mesh, referred to as T N , has valuable features for local refinement

Strategies for adding adaptive learning mechanisms to rule-based diagnostic expert systems

Science.gov (United States)

Stclair, D. C.; Sabharwal, C. L.; Bond, W. E.; Hacke, Keith

1988-01-01

Rule-based diagnostic expert systems can be used to perform many of the diagnostic chores necessary in today's complex space systems. These expert systems typically take a set of symptoms as input and produce diagnostic advice as output. The primary objective of such expert systems is to provide accurate and comprehensive advice which can be used to help return the space system in question to nominal operation. The development and maintenance of diagnostic expert systems is time and labor intensive since the services of both knowledge engineer(s) and domain expert(s) are required. The use of adaptive learning mechanisms to increment evaluate and refine rules promises to reduce both time and labor costs associated with such systems. This paper describes the basic adaptive learning mechanisms of strengthening, weakening, generalization, discrimination, and discovery. Next basic strategies are discussed for adding these learning mechanisms to rule-based diagnostic expert systems. These strategies support the incremental evaluation and refinement of rules in the knowledge base by comparing the set of advice given by the expert system (A) with the correct diagnosis (C). Techniques are described for selecting those rules in the in the knowledge base which should participate in adaptive learning. The strategies presented may be used with a wide variety of learning algorithms. Further, these strategies are applicable to a large number of rule-based diagnostic expert systems. They may be used to provide either immediate or deferred updating of the knowledge base.

Impacts of adaptive flood management strategies on the Socio-Hydrological system in Ganges - Brahmaputra river basin, Bangladesh

Science.gov (United States)

Sung, K.; Jeong, H.; Sangwan, N.; Yu, D. J.

2017-12-01

Human societies have tried to prevent floods by building robust infrastructure such as levees or dams. However, some scholars raise a doubt to this approach because of a lack of adaptiveness to environmental and societal changes in a long-term. Thus, a growing number of studies now suggest adopting new strategies in flood management to reinforce an adapt capacity to the long-term flood risk. This study addresses this issue by developing a conceptual mathematical model exploring how flood management strategies effect to the dynamics human-flood interaction, ultimately the flood resilience in a long-term. Especially, our model is motivated by the community-based flood protection system in southwest coastal area in Bangladesh. We developed several conceptual flood management strategies and investigated the interplay between those strategies and community's capacity to cope with floods. We additionally analyzed how external disturbances (sea level rise, water tide level change, and outside economic development) alter the adaptive capacity to flood risks. The results of this study reveal that the conventional flood management has potential vulnerabilities as external disturbances increase. Our results also highlight the needs of the adaptive strategy as a new paradigm in flood management which is able to feedback to the social and hydrological conditions. These findings provide insights on the resilience-based, adaptive strategies which can build flood resilience under global change.

A parallel direct solver for the self-adaptive hp Finite Element Method

KAUST Repository

Paszyński, Maciej R.; Pardo, David; Torres-Verdí n, Carlos; Demkowicz, Leszek F.; Calo, Victor M.

2010-01-01

measurement simulations problems. We measure the execution time and memory usage of the solver over a large regular mesh with 1.5 million degrees of freedom as well as on the highly non-regular mesh, generated by the self-adaptive h p-FEM, with finite elements

Socio-economic vulnerability of coastal communities in southern Thailand: the development of adaptation strategies

Science.gov (United States)

Willroth, P.; Massmann, F.; Wehrhahn, R.; Revilla Diez, J.

2012-08-01

The tsunami of December 2004 impacted large areas of Thailand's coastline and caused severe human and economic losses. The recovery period revealed differences in the vulnerabilities of communities affected. An understanding of the causal factors of vulnerability is crucial for minimising the negative effects of future threats and developing adaptive capacities. This paper analyses the vulnerabilities and the development of adaptation strategies in the booming tourist area of Khao Lak and in the predominantly fishing and agricultural area of Ban Nam Khem through a comprehensive vulnerability framework. The results show that social networks played a crucial role in coping with the disaster. Social cohesion is important for strengthening the community and developing successful adaptation strategies. The development of tourism and the turning away from traditional activities have a significant positive influence on the income situation, but create a dependency on a single business sector. It could be shown that households generating their income in the tourism sector were vulnerable unless they had diversified their income previously. Income diversification decreased the vulnerability in the study areas. Adaptation strategies and processes developed in the aftermath clearly address these issues.

Connectivity editing for quadrilateral meshes

KAUST Repository

Peng, Chihan

2011-12-12

We propose new connectivity editing operations for quadrilateral meshes with the unique ability to explicitly control the location, orientation, type, and number of the irregular vertices (valence not equal to four) in the mesh while preserving sharp edges. We provide theoretical analysis on what editing operations are possible and impossible and introduce three fundamental operations to move and re-orient a pair of irregular vertices. We argue that our editing operations are fundamental, because they only change the quad mesh in the smallest possible region and involve the fewest irregular vertices (i.e., two). The irregular vertex movement operations are supplemented by operations for the splitting, merging, canceling, and aligning of irregular vertices. We explain how the proposed highlevel operations are realized through graph-level editing operations such as quad collapses, edge flips, and edge splits. The utility of these mesh editing operations are demonstrated by improving the connectivity of quad meshes generated from state-of-art quadrangulation techniques. © 2011 ACM.

Connectivity editing for quadrilateral meshes

KAUST Repository

Peng, Chihan; Zhang, Eugene; Kobayashi, Yoshihiro; Wonka, Peter

2011-01-01

We propose new connectivity editing operations for quadrilateral meshes with the unique ability to explicitly control the location, orientation, type, and number of the irregular vertices (valence not equal to four) in the mesh while preserving sharp edges. We provide theoretical analysis on what editing operations are possible and impossible and introduce three fundamental operations to move and re-orient a pair of irregular vertices. We argue that our editing operations are fundamental, because they only change the quad mesh in the smallest possible region and involve the fewest irregular vertices (i.e., two). The irregular vertex movement operations are supplemented by operations for the splitting, merging, canceling, and aligning of irregular vertices. We explain how the proposed highlevel operations are realized through graph-level editing operations such as quad collapses, edge flips, and edge splits. The utility of these mesh editing operations are demonstrated by improving the connectivity of quad meshes generated from state-of-art quadrangulation techniques. © 2011 ACM.

Leveraging the power of mesh

Energy Technology Data Exchange (ETDEWEB)

Glass, H. [Cellnet, Alpharetta, GA (United States)

2006-07-01

Mesh network applications are used by utilities for metering, demand response, and mobile workforce management. This presentation provided an overview of a multi-dimensional mesh application designed to offer improved scalability and higher throughput in advanced metering infrastructure (AMI) systems. Mesh applications can be used in AMI for load balancing and forecasting, as well as for distribution and transmission planning. New revenue opportunities can be realized through the application's ability to improve notification and monitoring services, and customer service communications. Mesh network security features include data encryption, data fragmentation and the automatic re-routing of data. In order to use mesh network applications, networks must have sufficient bandwidth and provide flexibility at the endpoint layer to support multiple devices from multiple vendors, as well as support multiple protocols. It was concluded that smart meters will not enable energy response solutions without an underlying AMI that is reliable, scalable and self-healing. .refs., tabs., figs.

New adaptive differencing strategy in the PENTRAN 3-d parallel Sn code

International Nuclear Information System (INIS)

Sjoden, G.E.; Haghighat, A.

1996-01-01

It is known that three-dimensional (3-D) discrete ordinates (S n ) transport problems require an immense amount of storage and computational effort to solve. For this reason, parallel codes that offer a capability to completely decompose the angular, energy, and spatial domains among a distributed network of processors are required. One such code recently developed is PENTRAN, which iteratively solves 3-D multi-group, anisotropic S n problems on distributed-memory platforms, such as the IBM-SP2. Because large problems typically contain several different material zones with various properties, available differencing schemes should automatically adapt to the transport physics in each material zone. To minimize the memory and message-passing overhead required for massively parallel S n applications, available differencing schemes in an adaptive strategy should also offer reasonable accuracy and positivity, yet require only the zeroth spatial moment of the transport equation; differencing schemes based on higher spatial moments, in spite of their greater accuracy, require at least twice the amount of storage and communication cost for implementation in a massively parallel transport code. This paper discusses a new adaptive differencing strategy that uses increasingly accurate schemes with low parallel memory and communication overhead. This strategy, implemented in PENTRAN, includes a new scheme, exponential directional averaged (EDA) differencing

Local multigrid mesh refinement in view of nuclear fuel 3D modelling in pressurised water reactors

International Nuclear Information System (INIS)

Barbie, L.

2013-01-01

The aim of this study is to improve the performances, in terms of memory space and computational time, of the current modelling of the Pellet-Cladding mechanical Interaction (PCI), complex phenomenon which may occurs during high power rises in pressurised water reactors. Among the mesh refinement methods - methods dedicated to efficiently treat local singularities - a local multi-grid approach was selected because it enables the use of a black-box solver while dealing few degrees of freedom at each level. The Local Defect Correction (LDC) method, well suited to a finite element discretization, was first analysed and checked in linear elasticity, on configurations resulting from the PCI, since its use in solid mechanics is little widespread. Various strategies concerning the implementation of the multilevel algorithm were also compared. Coupling the LDC method with the Zienkiewicz-Zhu a posteriori error estimator in order to automatically detect the zones to be refined, was then tested. Performances obtained on two-dimensional and three-dimensional cases are very satisfactory, since the algorithm proposed is more efficient than h-adaptive refinement methods. Lastly, the LDC algorithm was extended to nonlinear mechanics. Space/time refinement as well as transmission of the initial conditions during the re-meshing step were looked at. The first results obtained are encouraging and show the interest of using the LDC method for PCI modelling. (author) [fr

Hernia Surgical Mesh Implants

Science.gov (United States)

... knitted mesh or non-knitted sheet forms. The synthetic materials used can be absorbable, non-absorbable or a combination of absorbable and non-absorbable materials. Animal-derived mesh are made of animal tissue, such as intestine or skin, that has been processed and disinfected to be ...

Recruitment of hard-to-reach population subgroups via adaptations of the snowball sampling strategy.

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Sadler, Georgia Robins; Lee, Hau-Chen; Lim, Rod Seung-Hwan; Fullerton, Judith

2010-09-01

Nurse researchers and educators often engage in outreach to narrowly defined populations. This article offers examples of how variations on the snowball sampling recruitment strategy can be applied in the creation of culturally appropriate, community-based information dissemination efforts related to recruitment to health education programs and research studies. Examples from the primary author's program of research are provided to demonstrate how adaptations of snowball sampling can be used effectively in the recruitment of members of traditionally underserved or vulnerable populations. The adaptation of snowball sampling techniques, as described in this article, helped the authors to gain access to each of the more-vulnerable population groups of interest. The use of culturally sensitive recruitment strategies is both appropriate and effective in enlisting the involvement of members of vulnerable populations. Adaptations of snowball sampling strategies should be considered when recruiting participants for education programs or for research studies when the recruitment of a population-based sample is not essential.

Coping strategies and resources as predictors of psychosocial adaptation among people with spinal cord injury.

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Livneh, Hanoch; Martz, Erin

2014-08-01

The onset of a spinal cord injury (SCI) is accompanied by a massive amount of stress, on which professionals in the medical field focus attention and care. The subsequent cascade of psychological stressors related to SCI often receives lesser attention. When individuals experience new forms of stress, they typically respond with attempts to cope, which may or may not be adaptive in reducing their stress levels. The twofold purpose of this study was to investigate whether SCI survivors' use of coping resources (i.e., hope, sense of coherence) and coping strategies (e.g., engagement coping, seeking social support) influences their psychosocial adaptation, and whether their use of coping strategies moderates the effect of coping resources, after controlling for the influence of depression and anxiety, on psychosocial adaptation. This cross-sectional study involved a self-report survey of survivors of SCI. Inclusion criteria included: (a) being 18 years of age or older, (b) having received inpatient rehabilitation services following the SCI, and (c) not having traumatic head injury at the time of the SCI onset. The sample consisted of 95 individuals with SCI who received outpatient rehabilitation services at a center in the midsouthern United States. Results indicated that coping resources and coping strategies were significantly associated with psychosocial adaptation. Furthermore, engagement coping explained a significant portion of the variance in psychosocial adaptation both individually and as an interactive variable with the 2 coping resources of sense of coherence and hope. Findings indicate that both coping resources and strategies (especially engagement coping) are reliably linked to adaptation to SCI. The findings further suggest that engagement coping positively influences psychosocial adaptation even when coping resources are mostly absent. Other implications for the field of rehabilitation are briefly outlined.

Climate Variability and Household Adaptation Strategies in Southern Ethiopia

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Wassie Berhanu

2015-05-01

Full Text Available This paper examines the determinants and implied economic impacts of climate change adaptation strategies in the context of traditional pastoralism. It is based on econometric analysis of survey data generated from household level interviews in southern Ethiopian rangelands. Pastoralists’ perception of climate change in the region is found to be very consistent with the actually recorded trends of increased temperature and the evident secular declines in precipitation. Not only long-term declines, trends in the region’s rainfall also appear to have taken a shift towards the direction of more unpredictability. Pastoralist adaptation response strategies broadly involve adjustments in pastoral practices and shifts to non-pastoral livelihoods. Results of the estimated models confirm that pastoral mobility is still quite essential in the present context of climate-induced household vulnerabilities. Increased mobility and diversification of pastoral herd portfolios in favor of a drought-tolerant species (camel are found to be positively associated with pastoral household net income. A policy stance that ignores the detrimental impacts of the currently pervasive private rangeland enclosures or intends to hasten pastoralist sedentarization in the area is simply untenable in the present context of climate-induced risks and pastoral livelihood vulnerability.

A highly efficient sharp-interface immersed boundary method with adaptive mesh refinement for bio-inspired flow simulations

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Deng, Xiaolong; Dong, Haibo

2017-11-01

Developing a high-fidelity, high-efficiency numerical method for bio-inspired flow problems with flow-structure interaction is important for understanding related physics and developing many bio-inspired technologies. To simulate a fast-swimming big fish with multiple finlets or fish schooling, we need fine grids and/or a big computational domain, which are big challenges for 3-D simulations. In current work, based on the 3-D finite-difference sharp-interface immersed boundary method for incompressible flows (Mittal et al., JCP 2008), we developed an octree-like Adaptive Mesh Refinement (AMR) technique to enhance the computational ability and increase the computational efficiency. The AMR is coupled with a multigrid acceleration technique and a MPI +OpenMP hybrid parallelization. In this work, different AMR layers are treated separately and the synchronization is performed in the buffer regions and iterations are performed for the convergence of solution. Each big region is calculated by a MPI process which then uses multiple OpenMP threads for further acceleration, so that the communication cost is reduced. With these acceleration techniques, various canonical and bio-inspired flow problems with complex boundaries can be simulated accurately and efficiently. This work is supported by the MURI Grant Number N00014-14-1-0533 and NSF Grant CBET-1605434.

''A Parallel Adaptive Simulation Tool for Two Phase Steady State Reacting Flows in Industrial Boilers and Furnaces''; FINAL

International Nuclear Information System (INIS)

Michael J. Bockelie

2002-01-01

; -mesh adaption, data management, and parallelization software and technology being developed by users of the BoxLib library at LBNL; and -solution methods for problems formulated on block structured grids that were being developed in collaboration with technical staff members at the University of Utah Center for High Performance Computing (CHPC) and at LBNL. The combustion modeling software used by Reaction Engineering International represents an investment of over fifty man-years of development, conducted over a period of twenty years. Thus, it was impractical to achieve our objective by starting from scratch. The research program resulted in an adaptive grid, reacting CFD flow solver that can be used only on limited problems. In current form the code is appropriate for use on academic problems with simplified geometries. The new solver is not sufficiently robust or sufficiently general to be used in a ''production mode'' for industrial applications. The principle difficulty lies with the multi-level solver technology. The use of multi-level solvers on adaptive grids with embedded boundaries is not yet a mature field and there are many issues that remain to be resolved. From the lessons learned in this SBIR program, we have started work on a new flow solver with an AMR capability. The new code is based on a conventional cell-by-cell mesh refinement strategy used in unstructured grid solvers that employ hexahedral cells. The new solver employs several of the concepts and solution strategies developed within this research program. The formulation of the composite grid problem for the new solver has been designed to avoid the embedded boundary complications encountered in this SBIR project. This follow-on effort will result in a reacting flow CFD solver with localized mesh capability that can be used to perform engineering calculations on industrial problems in a production mode

A THREE-YEAR EXPERIENCE WITH ANTERIOR TRANSOBTURATOR MESH (ATOM AND POSTERIOR ISCHIORECTAL MESH (PIRM

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Marijan Lužnik

2018-02-01

Full Text Available Background. Use of alloplastic mesh implantates allow a new urogynecologycal surgical techniques achieve a marked improvement in pelvic organ static and pelvic floor function with minimally invasive needle transvaginal intervention like an anterior transobturator mesh (ATOM and a posterior ischiorectal mesh (PIRM procedures. Methods. In three years, between April 2006 and May 2009, we performed one hundred and eightyfour operative corrections of female pelvic organ prolapse (POP and pelvic floor dysfunction (PFD with mesh implantates. The eighty-three patients with surgical procedure TVT-O or Monarc as solo intervention indicated by stress urinary incontinence without POP, are not included in this number. In 97 % of mesh operations, Gynemesh 10 × 15 cm was used. For correction of anterior vaginal prolapse with ATOM procedure, Gynemesh was individually trimmed in mesh with 6 free arms for tension-free transobturator application and tension-free apical collar. IVS (Intravaginal sling 04 Tunneller (Tyco needle system was used for transobturator application of 6 arms through 4 dermal incisions (2 on right and 2 on left. Minimal anterior median colpotomy was made in two separate parts. For correction of posterior vaginal prolapse with PIRM procedure Gynemesh was trimmed in mesh with 4 free arms and tension-free collar. Two ischiorectal long arms for tension-free application through fossa ischiorectale – right and left, and two short arms for perineal body also on both sides. IVS 02 Tunneller (Tyco needle system was used for tension-free application of 4 arms through 4 dermal incisions (2 on right and 2 on left in PIRM. Results. All 184 procedures were performed relatively safely. In 9 cases of ATOM we had perforation of bladder, in 5 by application of anterior needle, in 3 by application of posterior needle and in one case with pincette when collar was inserted in lateral vesico – vaginal space. In 2 cases of PIRM we had perforation of rectum

Gear selectivity of large-mesh nets and drumlines used to catch ...

African Journals Online (AJOL)

Catches of sharks and bycatch in large-mesh nets and baited drumlines used by the Queensland Shark Control Program were examined to determine the efficacy of both gear types and assess fishing strategies that minimise their impacts. There were few significant differences in the size of both sharks and bycatch in the ...

Goal orientation and work role performance: predicting adaptive and proactive work role performance through self-leadership strategies.

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Marques-Quinteiro, Pedro; Curral, Luís Alberto

2012-01-01

This article explores the relationship between goal orientation, self-leadership dimensions, and adaptive and proactive work role performances. The authors hypothesize that learning orientation, in contrast to performance orientation, positively predicts proactive and adaptive work role performances and that this relationship is mediated by self-leadership behavior-focused strategies. It is posited that self-leadership natural reward strategies and thought pattern strategies are expected to moderate this relationship. Workers (N = 108) from a software company participated in this study. As expected, learning orientation did predict adaptive and proactive work role performance. Moreover, in the relationship between learning orientation and proactive work role performance through self-leadership behavior-focused strategies, a moderated mediation effect was found for self-leadership natural reward and thought pattern strategies. In the end, the authors discuss the results and implications are discussed and future research directions are proposed.

Intermediate Collaborative Adaptive Management Strategies Build Stakeholder Capacity

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Martha C. Monroe

2013-06-01

Full Text Available Efforts to implement collaborative adaptive management (CAM often suffer from challenges, such as an unwillingness of managers to share power, unresolved conflicts between stakeholders, and lack of capacity among stakeholders. Some aspects considered essential to CAM, e.g., trust and stakeholder capacity, may be more usefully viewed as goals for intermediate strategies rather than a set of initial conditions. From this perspective, intermediate steps that focus on social learning and building experience could overcome commonly cited barriers to CAM. An exploration of Springs Basin Working Groups, organized around major clusters of freshwater springs in north Florida, provides a case study of how these intermediate steps enable participants to become more reasonable and engaged. This strategy may be easily implemented by agencies beginning a CAM process.

Epidemic propagation on adaptive coevolutionary networks with preferential local-world reconnecting strategy

International Nuclear Information System (INIS)

Song Yu-Rong; Jiang Guo-Ping; Gong Yong-Wang

2013-01-01

In the propagation of an epidemic in a population, individuals adaptively adjust their behavior to avoid the risk of an epidemic. Differently from existing studies where new links are established randomly, a local link is established preferentially in this paper. We propose a new preferentially reconnecting edge strategy depending on spatial distance (PR-SD). For the PR-SD strategy, the new link is established at random with probability p and in a shortest distance with the probability 1 − p. We establish the epidemic model on an adaptive network using Cellular Automata, and demonstrate the effectiveness of the proposed model by numerical simulations. The results show that the smaller the value of parameter p, the more difficult the epidemic spread is. The PR-SD strategy breaks long-range links and establishes as many short-range links as possible, which causes the network efficiency to decrease quickly and the propagation of the epidemic is restrained effectively. (general)

Fog water collection effectiveness: Mesh intercomparisons

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Fernandez, Daniel; Torregrosa, Alicia; Weiss-Penzias, Peter; Zhang, Bong June; Sorensen, Deckard; Cohen, Robert; McKinley, Gareth; Kleingartner, Justin; Oliphant, Andrew; Bowman, Matthew

2018-01-01

To explore fog water harvesting potential in California, we conducted long-term measurements involving three types of mesh using standard fog collectors (SFC). Volumetric fog water measurements from SFCs and wind data were collected and recorded in 15-minute intervals over three summertime fog seasons (2014–2016) at four California sites. SFCs were deployed with: standard 1.00 m2 double-layer 35% shade coefficient Raschel; stainless steel mesh coated with the MIT-14 hydrophobic formulation; and FogHa-Tin, a German manufactured, 3-dimensional spacer fabric deployed in two orientations. Analysis of 3419 volumetric samples from all sites showed strong relationships between mesh efficiency and wind speed. Raschel mesh collected 160% more fog water than FogHa-Tin at wind speeds less than 1 m s–1 and 45% less for wind speeds greater than 5 m s–1. MIT-14 coated stainless-steel mesh collected more fog water than Raschel mesh at all wind speeds. At low wind speeds of wind speeds of 4–5 m s–1, it collected 41% more. FogHa-Tin collected 5% more fog water when the warp of the weave was oriented vertically, per manufacturer specification, than when the warp of the weave was oriented horizontally. Time series measurements of three distinct mesh across similar wind regimes revealed inconsistent lags in fog water collection and inconsistent performance. Since such differences occurred under similar wind-speed regimes, we conclude that other factors play important roles in mesh performance, including in-situ fog event and aerosol dynamics that affect droplet-size spectra and droplet-to-mesh surface interactions.

Comparison of a lightweight polypropylene mesh (Optilene® LP) and a large-pore knitted PTFE mesh (GORE® INFINIT® mesh)--Biocompatibility in a standardized endoscopic extraperitoneal hernia model.

Science.gov (United States)

Jacob, Dietmar A; Schug-Pass, Christine; Sommerer, Florian; Tannapfel, Andrea; Lippert, Hans; Köckerling, Ferdinand

2012-02-01

The use of a mesh with good biocompatibility properties is of decisive importance for the avoidance of recurrences and chronic pain in endoscopic hernia repair surgery. As we know from numerous experiments and clinical experience, large-pore, lightweight polypropylene meshes possess the best biocompatibility. However, large-pore meshes of different polymers may be used as well and might be an alternative solution. Utilizing a totally extraperitoneal technique in an established animal model, 20 domestic pigs were implanted with either a lightweight large-pore polypropylene (PP) mesh (Optilene® LP) or a medium-weight large-pore knitted polytetrafluorethylene (PTFE) mesh (GORE® INFINIT® mesh). After 94 days, the pigs were sacrificed and postmortem diagnostic laparoscopy was performed, followed by explantation of the specimens for macroscopic, histological and immunohistochemical evaluation. The mean mesh shrinkage rate was 14.2% for Optilene® LP vs. 24.7% for INFINIT® mesh (p = 0.017). The partial volume of the inflammatory cells was 11.2% for Optilene® LP vs. 13.9% for INFINIT (n.s.). CD68 was significantly higher for INFINIT (11.8% vs. 5.6%, p = 0.007). The markers of cell turnover, namely Ki67 and the apoptotic index, were comparable at 6.4% vs. 12.4% (n.s.) and 1.6% vs. 2.0% (n.s.). In the extracellular matrix, TGF-β was 35.4% for Optilene® LP and 31.0% for INFINIT® (n.s.). Collagen I (pos/300 μm) deposits were 117.8 and 114.9, respectively. In our experimental examinations, Optilene® LP and INFINIT® showed a comparable biocompatibility in terms of chronic inflammatory reaction; however, the shrinkage rate was significantly higher for INFINIT® after 3 months. The higher shrinkage rate of INFINIT® should be taken into account when choosing the mesh size for an adequate hernia overlap.

Mesh fixation in laparoscopic incisional hernia repair: glue fixation provides attachment strength similar to absorbable tacks but differs substantially in different meshes.

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Rieder, Erwin; Stoiber, Martin; Scheikl, Verena; Poglitsch, Marcus; Dal Borgo, Andrea; Prager, Gerhard; Schima, Heinrich

2011-01-01

Laparoscopic ventral hernia repair has gained popularity among minimally invasive surgeons. However, mesh fixation remains a matter of discussion. This study was designed to compare noninvasive fibrin-glue attachment with tack fixation of meshes developed primarily for intra-abdominal use. It was hypothesized that particular mesh structures would substantially influence detachment force. For initial evaluation, specimens of laminated polypropylene/polydioxanone meshes were anchored to porcine abdominal walls by either helical titanium tacks or absorbable tacks in vitro. A universal tensile-testing machine was used to measure tangential detachment forces (TF). For subsequent experiments of glue fixation, polypropylene/polydioxanone mesh and 4 additional meshes with diverse particular mesh structure, ie, polyvinylidene fluoride/polypropylene mesh, a titanium-coated polypropylene mesh, a polyester mesh bonded with a resorbable collagen, and a macroporous condensed PTFE mesh were evaluated. TF tests revealed that fibrin-glue attachment was not substantially different from that achieved with absorbable tacks (median TF 7.8 Newton [N], range 1.3 to 15.8 N), but only when certain open porous meshes (polyvinylidene fluoride/polypropylene mesh: median 6.2 N, range 3.4 to 10.3 N; titanium-coated polypropylene mesh: median 5.2 N, range 2.1 to 11.7 N) were used. Meshes coated by an anti-adhesive barrier (polypropylene/polydioxanone mesh: median 3.1 N, range 1.7 to 5.8 N; polyester mesh bonded with a resorbable collagen: median 1.3 N, range 0.5 to 1.9 N), or the condensed PTFE mesh (median 3.1 N, range 2.1 to 7.0 N) provided a significantly lower TF (p < 0.01). Fibrin glue appears to be an appealing noninvasive option for mesh fixation in laparoscopic ventral hernia repair, but only if appropriate meshes are used. Glue can also serve as an adjunct to mechanical fixation to reduce the number of invasive tacks. Copyright © 2010 American College of Surgeons. Published by Elsevier

Adaptive Crack Modeling with Interface Solid Elements for Plain and Fiber Reinforced Concrete Structures.

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Zhan, Yijian; Meschke, Günther

2017-07-08

The effective analysis of the nonlinear behavior of cement-based engineering structures not only demands physically-reliable models, but also computationally-efficient algorithms. Based on a continuum interface element formulation that is suitable to capture complex cracking phenomena in concrete materials and structures, an adaptive mesh processing technique is proposed for computational simulations of plain and fiber-reinforced concrete structures to progressively disintegrate the initial finite element mesh and to add degenerated solid elements into the interfacial gaps. In comparison with the implementation where the entire mesh is processed prior to the computation, the proposed adaptive cracking model allows simulating the failure behavior of plain and fiber-reinforced concrete structures with remarkably reduced computational expense.

Stakeholders' participatory diagnosis of climate change impacts on subsistence agriculture in Sikkim, India, for identifying adaptation strategies

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Azhoni, A.; Goyal, M. K.

2017-12-01

Narrowing the gap between research, policy making and implementing adaptation remains a challenge in many parts of the world where climate change is likely to severely impact subsistence agriculture. This research aims to narrow this gap by matching the adaptation strategies being framed by policy makers and perspectives of consultants and researchers which are expected to be implemented by development agencies farmers in the state of Sikkim in India. Our case study examined the framing and implementation of State Action Plan on Climate Change through semi-structured interviews carried out with decision makers in the State Government, Scientific Organisations, consultants, local academia, implementing and development agencies, and farmers for whom the adaptation strategies are targeted. Using Social Network and Stakeholder Analysis approach, this research unravels the complexities of perceiving climate change impacts, identifying adaptation strategies, and implementing climate change adaptation strategies. While farmers are less aware about the global phenomenon of climate change impacts for their subsistence livelihood, their knowledge of the local conditions and their close interaction with the State Government Agriculture Department provides them an access to new and high value crops. Although important steps are initiated through the Sikkim State Action Plan on Climate Change it is yet to deliver effective means of adaptation implementation and identifying the networks of close coordination between the various implementing agencies will likely to pay rich dividends. While Sikkim being a small and hilly state with specific contextual challenges of climate change impacts, the results from this study highlights how the internal and external networks between various types of stakeholders informs decision makers in identifying local impacts of climate change and plan adaptation strategies.

Research of Ant Colony Optimized Adaptive Control Strategy for Hybrid Electric Vehicle

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Linhui Li

2014-01-01

Full Text Available Energy management control strategy of hybrid electric vehicle has a great influence on the vehicle fuel consumption with electric motors adding to the traditional vehicle power system. As vehicle real driving cycles seem to be uncertain, the dynamic driving cycles will have an impact on control strategy’s energy-saving effect. In order to better adapt the dynamic driving cycles, control strategy should have the ability to recognize the real-time driving cycle and adaptively adjust to the corresponding off-line optimal control parameters. In this paper, four types of representative driving cycles are constructed based on the actual vehicle operating data, and a fuzzy driving cycle recognition algorithm is proposed for online recognizing the type of actual driving cycle. Then, based on the equivalent fuel consumption minimization strategy, an ant colony optimization algorithm is utilized to search the optimal control parameters “charge and discharge equivalent factors” for each type of representative driving cycle. At last, the simulation experiments are conducted to verify the accuracy of the proposed fuzzy recognition algorithm and the validity of the designed control strategy optimization method.

Prolapse Recurrence after Transvaginal Mesh Removal.

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Rawlings, Tanner; Lavelle, Rebecca S; Coskun, Burhan; Alhalabi, Feras; Zimmern, Philippe E

2015-11-01

We determined the rate of pelvic organ prolapse recurrence after transvaginal mesh removal. Following institutional review board approval a longitudinally collected database of women undergoing transvaginal mesh removal for complications after transvaginal mesh placement with at least 1 year minimum followup was queried for pelvic organ prolapse recurrence. Recurrent prolapse was defined as greater than stage 1 on examination or the need for reoperation at the site of transvaginal mesh removal. Outcome measures were based on POP-Q (Pelvic Organ Prolapse Quantification System) at the last visit. Patients were grouped into 3 groups, including group 1--recurrent prolapse in the same compartment as transvaginal mesh removal, 2--persistent prolapse and 3--prolapse in a compartment different than transvaginal mesh removal. Of 73 women 52 met study inclusion criteria from 2007 to 2013, including 73% who presented with multiple indications for transvaginal mesh removal. The mean interval between insertion and removal was 45 months (range 10 to 165). Overall mean followup after transvaginal mesh removal was 30 months (range 12 to 84). In group 1 (recurrent prolapse) the rate was 15% (6 of 40 patients). Four women underwent surgery for recurrent prolapse at a mean 7 of months (range 5 to 10). Two patients elected observation. The rate of persistent prolapse (group 2) was 23% (12 of 52 patients). Three women underwent prolapse reoperation at a mean of 10 months (range 8 to 12). In group 3 (de novo/different compartment prolapse) the rate was 6% (3 of 52 patients). One woman underwent surgical repair at 52 months. At a mean 2.5-year followup 62% of patients (32 of 52) did not have recurrent or persistent prolapse after transvaginal mesh removal and 85% (44 of 52) did not undergo any further procedure for prolapse. Specifically for pelvic organ prolapse in the same compartment as transvaginal mesh removal 12% of patients had recurrence, of whom 8% underwent prolapse repair

Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation.

Science.gov (United States)

Cantin, Audrey; Gingras, Luc; Lachance, Bernard; Foster, William; Goudreault, Julie; Archambault, Louis

2015-12-01

The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. A retrospective study was conducted on five prostate cancer patients with 7-13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well as the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. The minimum daily prostate D95% is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D95% remains constant across the strategies, except for the gradient approach

Dosimetric evaluation of three adaptive strategies for prostate cancer treatment including pelvic lymph nodes irradiation

International Nuclear Information System (INIS)

Cantin, Audrey; Gingras, Luc; Archambault, Louis; Lachance, Bernard; Foster, William; Goudreault, Julie

2015-01-01

Purpose: The movements of the prostate relative to the pelvic lymph nodes during intensity-modulated radiation therapy treatment can limit margin reduction and affect the protection of the organs at risk (OAR). In this study, the authors performed an analysis of three adaptive treatment strategies that combine information from both bony and gold marker registrations. The robustness of those treatments against the interfraction prostate movements was evaluated. Methods: A retrospective study was conducted on five prostate cancer patients with 7–13 daily cone-beam CTs (CBCTs). The clinical target volumes (CTVs) consisting of pelvic lymph nodes, prostate, and seminal vesicles as well as the OARs were delineated on each CBCT and the initial CT. Three adaptive strategies were analyzed. Two of these methods relied on a two-step patient positioning at each fraction. First step: a bony registration was used to deliver the nodal CTV prescription. Second step: a gold marker registration was then used either to (1) complete the dose delivered to the prostate (complement); (2) or give almost the entire prescription to the prostate with a weak dose gradient between the targets to compensate for possible motions (gradient). The third method (COR) used a pool of precalculated plans based on images acquired at previous treatment fractions. At each new fraction, a plan is selected from that pool based on the daily position of prostate center-of-mass. The dosimetric comparison was conducted and results are presented with and without the systematic shift in the prostate position on the CT planning. The adaptive strategies were compared to the current clinical standard where all fractions are treated with the initial nonadaptive plan. Results: The minimum daily prostate D 95% is improved by 2%, 9%, and 6% for the complement, the gradient, and the COR approaches, respectively, compared to the nonadaptive method. The average nodal CTV D 95% remains constant across the strategies