CUBIT mesh generation environment. Volume 1: Users manual
Energy Technology Data Exchange (ETDEWEB)
Blacker, T.D.; Bohnhoff, W.J.; Edwards, T.L. [and others
1994-05-01
The CUBIT mesh generation environment is a two- and three-dimensional finite element mesh generation tool which is being developed to pursue the goal of robust and unattended mesh generation--effectively automating the generation of quadrilateral and hexahedral elements. It is a solid-modeler based preprocessor that meshes volume and surface solid models for finite element analysis. A combination of techniques including paving, mapping, sweeping, and various other algorithms being developed are available for discretizing the geometry into a finite element mesh. CUBIT also features boundary layer meshing specifically designed for fluid flow problems. Boundary conditions can be applied to the mesh through the geometry and appropriate files for analysis generated. CUBIT is specifically designed to reduce the time required to create all-quadrilateral and all-hexahedral meshes. This manual is designed to serve as a reference and guide to creating finite element models in the CUBIT environment.
Spherical geodesic mesh generation
Energy Technology Data Exchange (ETDEWEB)
Fung, Jimmy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kenamond, Mark Andrew [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Burton, Donald E. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Shashkov, Mikhail Jurievich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2015-02-27
In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.
Finite element mesh generation
Lo, Daniel SH
2014-01-01
Highlights the Progression of Meshing Technologies and Their ApplicationsFinite Element Mesh Generation provides a concise and comprehensive guide to the application of finite element mesh generation over 2D domains, curved surfaces, and 3D space. Organised according to the geometry and dimension of the problem domains, it develops from the basic meshing algorithms to the most advanced schemes to deal with problems with specific requirements such as boundary conformity, adaptive and anisotropic elements, shape qualities, and mesh optimization. It sets out the fundamentals of popular techniques
Cheng, Siu-Wing; Shewchuk, Jonathan
2013-01-01
Written by authors at the forefront of modern algorithms research, Delaunay Mesh Generation demonstrates the power and versatility of Delaunay meshers in tackling complex geometric domains ranging from polyhedra with internal boundaries to piecewise smooth surfaces. Covering both volume and surface meshes, the authors fully explain how and why these meshing algorithms work.The book is one of the first to integrate a vast amount of cutting-edge material on Delaunay triangulations. It begins with introducing the problem of mesh generation and describing algorithms for constructing Delaunay trian
Mesh generation in archipelagos
Terwisscha van Scheltinga, A.; Myers, P.G.; Pietrzak, J.D.
2012-01-01
A new mesh size field is presented that is specifically designed for efficient meshing of highly irregular oceanic domains: archipelagos. The new approach is based on the standard mesh size field that uses the proximity to the nearest coastline. Here, the proximities to the two nearest coastlines
Development of an Immersive Environment to Aid in Automatic Mesh Generation LDRD Final Report
Energy Technology Data Exchange (ETDEWEB)
Pavlakos, Constantine J.
1998-10-01
The purpose of this work was to explore the use of immersive technologies, such as those used in synthetic environments (commordy referred to as virtual realily, or VR), in enhancing the mesh- generation process for 3-dimensional (3D) engineering models. This work was motivated by the fact that automatic mesh generation systems are still imperfect - meshing algorithms, particularly in 3D, are sometimes unable to construct a mesh to completion, or they may produce anomalies or undesirable complexities in the resulting mesh. It is important that analysts and meshing code developers be able to study their meshes effectively in order to understand the topology and qualily of their meshes. We have implemented prototype capabilities that enable such exploration of meshes in a highly visual and intuitive manner. Since many applications are making use of increasingly large meshes, we have also investigated approaches to handle large meshes while maintaining interactive response. Ideally, it would also be possible to interact with the meshing process, allowing interactive feedback which corrects problems and/or somehow enables proper completion of the meshing process. We have implemented some functionality towards this end -- in doing so, we have explored software architectures that support such an interactive meshing process. This work has incorporated existing technologies developed at SandiaNational Laboratories, including the CUBIT mesh generation system, and the EIGEN/VR (previously known as MUSE) and FLIGHT systems, which allow applications to make use of immersive technologies and advanced human computer interfaces. 1
Development of an Immersive Environment to Aid in Automatic Mesh Generation LDRD Final Report
Energy Technology Data Exchange (ETDEWEB)
Pavlakos, Constantine J.
1998-10-01
The purpose of this work was to explore the use of immersive technologies, such as those used in synthetic environments (commordy referred to as virtual realily, or VR), in enhancing the mesh- generation process for 3-dimensional (3D) engineering models. This work was motivated by the fact that automatic mesh generation systems are still imperfect - meshing algorithms, particularly in 3D, are sometimes unable to construct a mesh to completion, or they may produce anomalies or undesirable complexities in the resulting mesh. It is important that analysts and meshing code developers be able to study their meshes effectively in order to understand the topology and qualily of their meshes. We have implemented prototype capabilities that enable such exploration of meshes in a highly visual and intuitive manner. Since many applications are making use of increasingly large meshes, we have also investigated approaches to handle large meshes while maintaining interactive response. Ideally, it would also be possible to interact with the meshing process, allowing interactive feedback which corrects problems and/or somehow enables proper completion of the meshing process. We have implemented some functionality towards this end -- in doing so, we have explored software architectures that support such an interactive meshing process. This work has incorporated existing technologies developed at SandiaNational Laboratories, including the CUBIT mesh generation system, and the EIGEN/VR (previously known as MUSE) and FLIGHT systems, which allow applications to make use of immersive technologies and advanced human computer interfaces. 1
Nanowire mesh solar fuels generator
Energy Technology Data Exchange (ETDEWEB)
Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin
2016-05-24
This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.
GENERATION OF IRREGULAR HEXAGONAL MESHES
Directory of Open Access Journals (Sweden)
Vlasov Aleksandr Nikolaevich
2012-07-01
Decomposition is performed in a constructive way and, as option, it involves meshless representation. Further, this mapping method is used to generate the calculation mesh. In this paper, the authors analyze different cases of mapping onto simply connected and bi-connected canonical domains. They represent forward and backward mapping techniques. Their potential application for generation of nonuniform meshes within the framework of the asymptotic homogenization theory is also performed to assess and project effective characteristics of heterogeneous materials (composites.
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.
Advanced Automatic Hexahedral Mesh Generation from Surface Quad Meshes
Kremer, Michael; Bommes, David; Lim, Isaak; Kobbelt, Leif
2013-01-01
International audience; A purely topological approach for the generation of hexahedral meshes from quadrilateral surface meshes of genus zero has been proposed by M. MÃ¼ller-Hannemann: in a first stage, the input surface mesh is reduced to a single hexahedron by successively eliminating loops from the dual graph of the quad mesh; in the second stage, the hexahedral mesh is constructed by extruding a layer of hexahedra for each dual loop from the first stage in reverse elimination order. In th...
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.
SHARP/PRONGHORN Interoperability: Mesh Generation
Energy Technology Data Exchange (ETDEWEB)
Avery Bingham; Javier Ortensi
2012-09-01
Progress toward collaboration between the SHARP and MOOSE computational frameworks has been demonstrated through sharing of mesh generation and ensuring mesh compatibility of both tools with MeshKit. MeshKit was used to build a three-dimensional, full-core very high temperature reactor (VHTR) reactor geometry with 120-degree symmetry, which was used to solve a neutron diffusion critical eigenvalue problem in PRONGHORN. PRONGHORN is an application of MOOSE that is capable of solving coupled neutron diffusion, heat conduction, and homogenized flow problems. The results were compared to a solution found on a 120-degree, reflected, three-dimensional VHTR mesh geometry generated by PRONGHORN. The ability to exchange compatible mesh geometries between the two codes is instrumental for future collaboration and interoperability. The results were found to be in good agreement between the two meshes, thus demonstrating the compatibility of the SHARP and MOOSE frameworks. This outcome makes future collaboration possible.
Adaptive mesh generation for image registration and segmentation
DEFF Research Database (Denmark)
Fogtmann, Mads; Larsen, Rasmus
2013-01-01
This paper deals with the problem of generating quality tetrahedral meshes for image registration. From an initial coarse mesh the approach matches the mesh to the image volume by combining red-green subdivision and mesh evolution through mesh-to-image matching regularized with a mesh quality...
Parallel octree-based hexahedral mesh generation for eulerian to lagrangian conversion.
Energy Technology Data Exchange (ETDEWEB)
Staten, Matthew L.; Owen, Steven James
2010-09-01
Computational simulation must often be performed on domains where materials are represented as scalar quantities or volume fractions at cell centers of an octree-based grid. Common examples include bio-medical, geotechnical or shock physics calculations where interface boundaries are represented only as discrete statistical approximations. In this work, we introduce new methods for generating Lagrangian computational meshes from Eulerian-based data. We focus specifically on shock physics problems that are relevant to ASC codes such as CTH and Alegra. New procedures for generating all-hexahedral finite element meshes from volume fraction data are introduced. A new primal-contouring approach is introduced for defining a geometric domain. New methods for refinement, node smoothing, resolving non-manifold conditions and defining geometry are also introduced as well as an extension of the algorithm to handle tetrahedral meshes. We also describe new scalable MPI-based implementations of these procedures. We describe a new software module, Sculptor, which has been developed for use as an embedded component of CTH. We also describe its interface and its use within the mesh generation code, CUBIT. Several examples are shown to illustrate the capabilities of Sculptor.
An Adaptive Mesh Algorithm: Mesh Structure and Generation
Energy Technology Data Exchange (ETDEWEB)
Scannapieco, Anthony J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-06-21
The purpose of Adaptive Mesh Refinement is to minimize spatial errors over the computational space not to minimize the number of computational elements. The additional result of the technique is that it may reduce the number of computational elements needed to retain a given level of spatial accuracy. Adaptive mesh refinement is a computational technique used to dynamically select, over a region of space, a set of computational elements designed to minimize spatial error in the computational model of a physical process. The fundamental idea is to increase the mesh resolution in regions where the physical variables are represented by a broad spectrum of modes in k-space, hence increasing the effective global spectral coverage of those physical variables. In addition, the selection of the spatially distributed elements is done dynamically by cyclically adjusting the mesh to follow the spectral evolution of the system. Over the years three types of AMR schemes have evolved; block, patch and locally refined AMR. In block and patch AMR logical blocks of various grid sizes are overlaid to span the physical space of interest, whereas in locally refined AMR no logical blocks are employed but locally nested mesh levels are used to span the physical space. The distinction between block and patch AMR is that in block AMR the original blocks refine and coarsen entirely in time, whereas in patch AMR the patches change location and zone size with time. The type of AMR described herein is a locally refi ned AMR. In the algorithm described, at any point in physical space only one zone exists at whatever level of mesh that is appropriate for that physical location. The dynamic creation of a locally refi ned computational mesh is made practical by a judicious selection of mesh rules. With these rules the mesh is evolved via a mesh potential designed to concentrate the nest mesh in regions where the physics is modally dense, and coarsen zones in regions where the physics is modally
Automatic Mesh Generation of Hybrid Mesh on Valves in Multiple Positions in Feedline Systems
Ross, Douglass H.; Ito, Yasushi; Dorothy, Fredric W.; Shih, Alan M.; Peugeot, John
2010-01-01
Fluid flow simulations through a valve often require evaluation of the valve in multiple opening positions. A mesh has to be generated for the valve for each position and compounding. The problem is the fact that the valve is typically part of a larger feedline system. In this paper, we propose to develop a system to create meshes for feedline systems with parametrically controlled valve openings. Herein we outline two approaches to generate the meshes for a valve in a feedline system at multiple positions. There are two issues that must be addressed. The first is the creation of the mesh on the valve for multiple positions. The second is the generation of the mesh for the total feedline system including the valve. For generation of the mesh on the valve, we will describe the use of topology matching and mesh generation parameter transfer. For generation of the total feedline system, we will describe two solutions that we have implemented. In both cases the valve is treated as a component in the feedline system. In the first method the geometry of the valve in the feedline system is replaced with a valve at a different opening position. Geometry is created to connect the valve to the feedline system. Then topology for the valve is created and the portion of the topology for the valve is topology matched to the standard valve in a different position. The mesh generation parameters are transferred and then the volume mesh for the whole feedline system is generated. The second method enables the user to generate the volume mesh on the valve in multiple open positions external to the feedline system, to insert it into the volume mesh of the feedline system, and to reduce the amount of computer time required for mesh generation because only two small volume meshes connecting the valve to the feedline mesh need to be updated.
Update on Development of Mesh Generation Algorithms in MeshKit
Energy Technology Data Exchange (ETDEWEB)
Jain, Rajeev [Argonne National Lab. (ANL), Argonne, IL (United States); Vanderzee, Evan [Argonne National Lab. (ANL), Argonne, IL (United States); Mahadevan, Vijay [Argonne National Lab. (ANL), Argonne, IL (United States)
2015-09-30
MeshKit uses a graph-based design for coding all its meshing algorithms, which includes the Reactor Geometry (and mesh) Generation (RGG) algorithms. This report highlights the developmental updates of all the algorithms, results and future work. Parallel versions of algorithms, documentation and performance results are reported. RGG GUI design was updated to incorporate new features requested by the users; boundary layer generation and parallel RGG support were added to the GUI. Key contributions to the release, upgrade and maintenance of other SIGMA1 libraries (CGM and MOAB) were made. Several fundamental meshing algorithms for creating a robust parallel meshing pipeline in MeshKit are under development. Results and current status of automated, open-source and high quality nuclear reactor assembly mesh generation algorithms such as trimesher, quadmesher, interval matching and multi-sweeper are reported.
The generation of hexahedral meshes for assembly geometries: A survey
Energy Technology Data Exchange (ETDEWEB)
TAUTGES,TIMOTHY J.
2000-02-14
The finite element method is being used today to model component assemblies in a wide variety of application areas, including structural mechanics, fluid simulations, and others. Generating hexahedral meshes for these assemblies usually requires the use of geometry decomposition, with different meshing algorithms applied to different regions. While the primary motivation for this approach remains the lack of an automatic, reliable all-hexahedral meshing algorithm, requirements in mesh quality and mesh configuration for typical analyses are also factors. For these reasons, this approach is also sometimes required when producing other types of unstructured meshes. This paper will review progress to date in automating many parts of the hex meshing process, which has halved the time to produce all-hex meshes for large assemblies. Particular issues which have been exposed due to this progress will also be discussed, along with their applicability to the general unstructured meshing problem.
Removal of line artifacts on mesh boundary in computer generated hologram by mesh phase matching.
Park, Jae-Hyeung; Yeom, Han-Ju; Kim, Hee-Jae; Zhang, HuiJun; Li, BoNi; Ji, Yeong-Min; Kim, Sang-Hoo
2015-03-23
Mesh-based computer generated hologram enables realistic and efficient representation of three-dimensional scene. However, the dark line artifacts on the boundary between neighboring meshes are frequently observed, degrading the quality of the reconstruction. In this paper, we propose a simple technique to remove the dark line artifacts by matching the phase on the boundary of neighboring meshes. The feasibility of the proposed method is confirmed by the numerical and optical reconstruction of the generated hologram.
Automated quadrilateral mesh generation for digital image structures
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
With the development of advanced imaging technology, digital images are widely used. This paper proposes an automatic quadrilateral mesh generation algorithm for multi-colour imaged structures. It takes an original arbitrary digital image as an input for automatic quadrilateral mesh generation, this includes removing the noise, extracting and smoothing the boundary geometries between different colours, and automatic all-quad mesh generation with the above boundaries as constraints. An application example is...
HypGrid2D. A 2-d mesh generator
Energy Technology Data Exchange (ETDEWEB)
Soerensen, N.N.
1998-03-01
The implementation of a hyperbolic mesh generation procedure, based on an equation for orthogonality and an equation for the cell face area is described. The method is fast, robust and gives meshes with good smoothness and orthogonality. The procedure is implemented in a program called HypGrid2D. The HypGrid2D program is capable of generating C-, O- and `H`-meshes for use in connection with the EllipSys2D Navier-Stokes solver. To illustrate the capabilities of the program, some test examples are shown. First a series of C-meshes are generated around a NACA-0012 airfoil. Secondly a series of O-meshes are generated around a NACA-65-418 airfoil. Finally `H`-meshes are generated over a Gaussian hill and a linear escarpment. (au)
AUTOMATIC MESH GENERATION OF 3-D GEOMETRIC MODELS
Institute of Scientific and Technical Information of China (English)
刘剑飞
2003-01-01
In this paper the presentation of the ball-packing method is reviewed,and a scheme to generate mesh for complex 3-D geometric models is given,which consists of 4 steps:(1)create nodes in 3-D models by ball-packing method,(2)connect nodes to generate mesh by 3-D Delaunay triangulation,(3)retrieve the boundary of the model after Delaunay triangulation,(4)improve the mesh.
Image-Based Geometric Modeling and Mesh Generation
2013-01-01
As a new interdisciplinary research area, “image-based geometric modeling and mesh generation” integrates image processing, geometric modeling and mesh generation with finite element method (FEM) to solve problems in computational biomedicine, materials sciences and engineering. It is well known that FEM is currently well-developed and efficient, but mesh generation for complex geometries (e.g., the human body) still takes about 80% of the total analysis time and is the major obstacle to reduce the total computation time. It is mainly because none of the traditional approaches is sufficient to effectively construct finite element meshes for arbitrarily complicated domains, and generally a great deal of manual interaction is involved in mesh generation. This contributed volume, the first for such an interdisciplinary topic, collects the latest research by experts in this area. These papers cover a broad range of topics, including medical imaging, image alignment and segmentation, image-to-mesh conversion,...
A New Approach to Fully Automatic Mesh Generation
Institute of Scientific and Technical Information of China (English)
闵卫东; 张征明; 等
1995-01-01
Automatic mesh generation is one of the most important parts in CIMS (Computer Integrated Manufacturing System).A method based on mesh grading propagation which automatically produces a triangular mesh in a multiply connected planar region is presented in this paper.The method decomposes the planar region into convex subregions,using algorithms which run in linear time.For every subregion,an algorithm is used to generate shrinking polygons according to boundary gradings and form delaunay triangulation between two adjacent shrinking polygons,both in linear time.It automatically propagates boundary gradings into the interior of the region and produces satisfactory quasi-uniform mesh.
The mesh-matching algorithm: an automatic 3D mesh generator for Finite element structures
Couteau, B; Lavallee, S; Payan, Yohan; Lavallee, St\\'{e}phane
2000-01-01
Several authors have employed Finite Element Analysis (FEA) for stress and strain analysis in orthopaedic biomechanics. Unfortunately, the use of three-dimensional models is time consuming and consequently the number of analysis to be performed is limited. The authors have investigated a new method allowing automatically 3D mesh generation for structures as complex as bone for example. This method called Mesh-Matching (M-M) algorithm generated automatically customized 3D meshes of bones from an already existing model. The M-M algorithm has been used to generate FE models of ten proximal human femora from an initial one which had been experimentally validated. The new meshes seemed to demonstrate satisfying results.
GENERATION AND APPLICATION OF UNSTRUCTURED ADAPTIVE MESHES WITH MOVING BOUNDARIES
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper presents a method to generate unstructured adaptive meshes with moving boundaries and its application to CFD. Delaunay triangulation criterion in conjunction with the automatic point creation is used to generate 2-D and 3-D unstructured grids. A local grid regeneration method is proposed to cope with moving boundaries. Numerical examples include the interactions of shock waves with movable bodies and the movement of a projectile within a ram accelerator, illustrating an efficient and robust mesh generation method developed.``
Finite Element Meshes Auto-Generation for the Welted Bifurcation
Institute of Scientific and Technical Information of China (English)
YUANMei; LIYa-ping
2004-01-01
In this paper, firstly, a mathematical model for a specific kind of welted bifurcation is established, the parametric equation for the intersecting curve is resulted in. Secondly, a method for partitioning finite element meshes of the welted bifurcation is put forward, its main idea is that developing the main pipe surface and the branch pipe surface respectively, dividing meshes on each developing plane and obtaining meshes points, then transforming their plane coordinates into space coordinates. Finally, an applied program for finite element meshes auto-generation is simply introduced, which adopt ObjectARX technique and its running result can be shown in AutoCAD. The meshes generated in AutoCAD can be exported conveniently to most of finite element analysis soft wares, and the finite element computing result can satisfy the engineering precision requirement.
Hexahedral mesh generation via the dual arrangement of surfaces
Energy Technology Data Exchange (ETDEWEB)
Mitchell, S.A.; Tautges, T.J. [Sandia National Labs., Albuquerque, NM (United States)
1997-12-31
Given a general three-dimensional geometry with a prescribed quadrilateral surface mesh, the authors consider the problem of constructing a hexahedral mesh of the geometry whose boundary is exactly the prescribed surface mesh. Due to the specialized topology of hexahedra, this problem is more difficult than the analogous one for tetrahedra. Folklore has maintained that a surface mesh must have a constrained structure in order for there to exist a compatible hexahedral mesh. However, they have proof that a surface mesh need only satisfy mild parity conditions, depending on the topology of the three-dimensional geometry, for there to exist a compatible hexahedral mesh. The proof is based on the realization that a hexahedral mesh is dual to an arrangement of surfaces, and the quadrilateral surface mesh is dual to the arrangement of curves bounding these surfaces. The proof is constructive and they are currently developing an algorithm called Whisker Weaving (WW) that mirrors the proof steps. Given the bounding curves, WW builds the topological structure of an arrangement of surfaces having those curves as its boundary. WW progresses in an advancing front manner. Certain local rules are applied to avoid structures that lead to poor mesh quality. Also, after the arrangement is constructed, additional surfaces are inserted to separate features, so e.g., no two hexahedra share more than one quadrilateral face. The algorithm has generated meshes for certain non-trivial problems, but is currently unreliable. The authors are exploring strategies for consistently selecting which portion of the surface arrangement to advance based on the existence proof. This should lead us to a robust algorithm for arbitrary geometries and surface meshes.
Procedure for the automatic mesh generation of innovative gear teeth
Directory of Open Access Journals (Sweden)
Radicella Andrea Chiaramonte
2016-01-01
Full Text Available After having described gear wheels with teeth having the two sides constituted by different involutes and their importance in engineering applications, we stress the need for an efficient procedure for the automatic mesh generation of innovative gear teeth. First, we describe the procedure for the subdivision of the tooth profile in the various possible cases, then we show the method for creating the subdivision mesh, defined by two series of curves called meridians and parallels. Finally, we describe how the above procedure for automatic mesh generation is able to solve specific cases that may arise when dealing with teeth having the two sides constituted by different involutes.
Adaptive mesh generation for viscous flows using Delaunay triangulation
Mavriplis, Dimitri J.
1990-01-01
A method for generating an unstructured triangular mesh in two dimensions, suitable for computing high Reynolds number flows over arbitrary configurations is presented. The method is based on a Delaunay triangulation, which is performed in a locally stretched space, in order to obtain very high aspect ratio triangles in the boundary layer and the wake regions. It is shown how the method can be coupled with an unstructured Navier-Stokes solver to produce a solution adaptive mesh generation procedure for viscous flows.
Generation of Triangular Meshes for Complex Domains on the Plane
Barbara Glut; Tomasz Jurczyk
2001-01-01
Many physical phenomena can be modeled by partial differential equations. The development of numerical methods based on the spatial subdivision of a domain into finite elements immediately extended interests to the tasks of generating a mesh. With the availability of versatile field solvers and powerful computers, the simulations of ever incrcasing geometrical and physical complexity are attempted. At some point the main bottleneck becomes the mesh generation itself. The paper presents a deta...
Generation of Triangular Meshes for Complex Domains on the Plane
Directory of Open Access Journals (Sweden)
Barbara Glut
2001-01-01
Full Text Available Many physical phenomena can be modeled by partial differential equations. The development of numerical methods based on the spatial subdivision of a domain into finite elements immediately extended interests to the tasks of generating a mesh. With the availability of versatile field solvers and powerful computers, the simulations of ever incrcasing geometrical and physical complexity are attempted. At some point the main bottleneck becomes the mesh generation itself. The paper presents a detailed description of the triangular mesh generation scheme on the plane based upon the Delaunay triangulation. A mesh generator should be fully automatic and simplify input data as much as possible. It should offer rapid gradation from small to large sizes of elements. The generated mesh must be always valid and of good quality. All these requirements were taken into account during the selection and elaboration of utilized algorithms. Successive chapters describe procedures connected with the specification of a modeled domain, generation and triangulation of boundary vertices, introducing inner nodes, improving the quality of the created mesh, and renumbering of vertices.
Automatic Mesh Generation on a Regular Background Grid
Institute of Scientific and Technical Information of China (English)
LO S.H; 刘剑飞
2002-01-01
This paper presents an automatic mesh generation procedure on a 2D domainbased on a regular background grid. The idea is to devise a robust mesh generation schemewith equal emphasis on quality and efficiency. Instead of using a traditional regular rectangulargrid, a mesh of equilateral triangles is employed to ensure triangular element of the best qualitywill be preserved in the interior of the domain.As for the boundary, it is to be generated by a node/segment insertion process. Nodes areinserted into the background mesh one by one following the sequence of the domain boundary.The local structure of the mesh is modified based on the Delaunay criterion with the introduc-tion of each node. Those boundary segments, which are not produced in the phase of nodeinsertion, will be recovered through a systematic element swap process. Two theorems will bepresented and proved to set up the theoretical basic of the boundary recovery part. Exampleswill be presented to demonstrate the robustness and the quality of the mesh generated by theproposed technique.
Development of unstructured mesh generator on parallel computers
Energy Technology Data Exchange (ETDEWEB)
Muramatsu, Kazuhiro [Japan Atomic Energy Research Inst., Tokyo (Japan); Shimada, Akio; Murakami, Hiroyuki; Higashida, Akihiro; Wakatsuki, Shigeto [Fuji Research Institute Corporation, Computational Engineering II, Tokyo (Japan)
2000-09-01
A general-purpose unstructured mesh generator, 'GRID3D/UNST', has been developed on parallel computers. High-speed operations and large-scale memory capacity of parallel computers enable the system to generate a large-scale mesh at high speed. As a matter of fact, the system generates large-scale mesh composed of 2,400,000 nodes and 14,000,000 elements about 1.5 hours on HITACHI SR2201, 64 PEs (Processing Elements) through 2.5 hours pre-process on SUN. Also the system is built on standard FORTRAN, C and Motif, and therefore has high portability. The system enables us to solve a large-scale problem that has been impossible to be solved, and to break new ground in the field of science and engineering. (author)
Robust Generation of Signed Distance Fields from Triangle Meshes
DEFF Research Database (Denmark)
Bærentzen, Jakob Andreas
2005-01-01
is then used to convert the binary volume into a distance field. The method is robust and handles holes, spurious triangles and ambiguities. Moreover, the method lends itself to Boolean operations between solids. Since a point cloud as well as a signed distance is generated, it is possible to extract an iso......-surface of the distance field and fit it to the point set. Using this method, one may recover sharp edge information. Examples are given where the method for generating distance fields coupled with mesh fitting is used to perform Boolean and morphological operations on triangle meshes....
Study on boundary search method for DFM mesh generation
Directory of Open Access Journals (Sweden)
Li Ri
2012-08-01
Full Text Available The boundary mesh of the casting model was determined by direct calculation on the triangular facets extracted from the STL file of the 3D model. Then the inner and outer grids of the model were identified by the algorithm in which we named Inner Seed Grid Method. Finally, a program to automatically generate a 3D FDM mesh was compiled. In the paper, a method named Triangle Contraction Search Method (TCSM was put forward to ensure not losing the boundary grids; while an algorithm to search inner seed grids to identify inner/outer grids of the casting model was also brought forward. Our algorithm was simple, clear and easy to construct program. Three examples for the casting mesh generation testified the validity of the program.
Loft: An Automated Mesh Generator for Stiffened Shell Aerospace Vehicles
Eldred, Lloyd B.
2011-01-01
Loft is an automated mesh generation code that is designed for aerospace vehicle structures. From user input, Loft generates meshes for wings, noses, tanks, fuselage sections, thrust structures, and so on. As a mesh is generated, each element is assigned properties to mark the part of the vehicle with which it is associated. This property assignment is an extremely powerful feature that enables detailed analysis tasks, such as load application and structural sizing. This report is presented in two parts. The first part is an overview of the code and its applications. The modeling approach that was used to create the finite element meshes is described. Several applications of the code are demonstrated, including a Next Generation Launch Technology (NGLT) wing-sizing study, a lunar lander stage study, a launch vehicle shroud shape study, and a two-stage-to-orbit (TSTO) orbiter. Part two of the report is the program user manual. The manual includes in-depth tutorials and a complete command reference.
Generation of high order geometry representations in Octree meshes
Directory of Open Access Journals (Sweden)
Harald G. Klimach
2015-11-01
Full Text Available We propose a robust method to convert triangulated surface data into polynomial volume data. Such polynomial representations are required for high-order partial differential solvers, as low-order surface representations would diminish the accuracy of their solution. Our proposed method deploys a first order spatial bisection algorithm to find robustly an approximation of given geometries. The resulting voxelization is then used to generate Legendre polynomials of arbitrary degree. By embedding the locally defined polynomials in cubical elements of a coarser mesh, this method can reliably approximate even complex structures, like porous media. It thereby is possible to provide appropriate material definitions for high order discontinuous Galerkin schemes. We describe the method to construct the polynomial and how it fits into the overall mesh generation. Our discussion includes numerical properties of the method and we show some results from applying it to various geometries. We have implemented the described method in our mesh generator Seeder, which is publically available under a permissive open-source license.
A Novel Coarsening Method for Scalable and Efficient Mesh Generation
Energy Technology Data Exchange (ETDEWEB)
Yoo, A; Hysom, D; Gunney, B
2010-12-02
matrix-vector multiplication can be performed locally on each processor and hence to minimize communication. Furthermore, a good graph partitioning scheme ensures the equal amount of computation performed on each processor. Graph partitioning is a well known NP-complete problem, and thus the most commonly used graph partitioning algorithms employ some forms of heuristics. These algorithms vary in terms of their complexity, partition generation time, and the quality of partitions, and they tend to trade off these factors. A significant challenge we are currently facing at the Lawrence Livermore National Laboratory is how to partition very large meshes on massive-size distributed memory machines like IBM BlueGene/P, where scalability becomes a big issue. For example, we have found that the ParMetis, a very popular graph partitioning tool, can only scale to 16K processors. An ideal graph partitioning method on such an environment should be fast and scale to very large meshes, while producing high quality partitions. This is an extremely challenging task, as to scale to that level, the partitioning algorithm should be simple and be able to produce partitions that minimize inter-processor communications and balance the load imposed on the processors. Our goals in this work are two-fold: (1) To develop a new scalable graph partitioning method with good load balancing and communication reduction capability. (2) To study the performance of the proposed partitioning method on very large parallel machines using actual data sets and compare the performance to that of existing methods. The proposed method achieves the desired scalability by reducing the mesh size. For this, it coarsens an input mesh into a smaller size mesh by coalescing the vertices and edges of the original mesh into a set of mega-vertices and mega-edges. A new coarsening method called brick algorithm is developed in this research. In the brick algorithm, the zones in a given mesh are first grouped into fixed size
The Cubit: A History and Measurement Commentary
Directory of Open Access Journals (Sweden)
Mark H. Stone
2014-01-01
Full Text Available Historical dimensions for the cubit are provided by scripture and pyramid documentation. Additional dimensions from the Middle East are found in other early documents. Two major dimensions emerge from a history of the cubit. The first is the anthropological or short cubit, and the second is the architectual or long cubit. The wide geographical area and long chronological period suggest that cubit dimensions varied over time and geographic area. Greek and Roman conquests led to standardization. More recent dimensions are provided from a study by Francis Galton based upon his investigations into anthropometry. The subjects for Galton’s study and those of several other investigators lacked adequate sample descriptions for producing a satisfactory cubit/forearm dimension. This finding is not surprising given the demise of the cubit in today’s world. Contemporary dimensions from military and civilian anthropometry for the forearm and hand allow comparison to the ancient unit. Although there appears no pressing need for a forearm-hand/cubit dimension, the half-yard or half-meter unit seems a useful one that could see more application.
MESH2D GRID GENERATOR DESIGN AND USE
Energy Technology Data Exchange (ETDEWEB)
Flach, G.; Smith, F.
2012-01-20
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j{sub 0}) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assigns an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations. The overall mesh is constructed from grid zones that are typically then subdivided into a collection of smaller grid cells. The grid zones usually correspond to distinct materials or larger-scale geometric shapes. The structured grid zones are identified through uppercase indices (I,J). Subdivision of zonal regions into grid cells can be done uniformly, or nonuniformly using either a polynomial or geometric skewing algorithm. Grid cells may be concentrated backward, forward, or toward both ends. Figure 1 illustrates the above concepts in the context of a simple four zone grid.
Techniques on mesh generation for the brain shift simulation
Lobos, Claudio; Payan, Yohan; Hitschfeld, Nancy
2007-01-01
Neurosurgery interventions involve complex tracking systems because a tissue deformation takesplace. The neuronavigation system relies only on preoperative images. In order to overcome the soft tissue deformations and guarantee the accuracy of the navigation a biomechanical model can be used during surgery to simulate the deformation of the brain. Therefore, a mesh generation for an optimal real-time Finite Element Model (FEM) becomes crucial. In this work we present different alternatives from a meshgeneration point of view that were evaluated to optimize the process in terms of elements quantity and quality as well as constraints of a intraoperative application and patient specific data.
A Novel Tetrahedral Mesh Generation Method for Rotating Machines Including End-Coil Region
Yamashita, Hideo; Yamaji, Akihisa; Cingoski, Vlatko; Kaneda, Kazufumi
1996-01-01
In this paper, a novel method for generating tetrahedral finite-element meshes suitable for 3-D finite element analysis of rotating machines is presented. The proposed method enables the easy development of 3-D meshes for various rotating machines, especially in the end-coil region and the surrounding air region. Tessellation of the 3-D region is made possible by simple extension of a previously generated 2-D triangular mesh, used as a model mesh, into the third dimension.
A GENERATIVE CAD MODEL OF A WORM GEAR MESHING
Directory of Open Access Journals (Sweden)
Angelika WRONKOWICZ
2014-03-01
Full Text Available This article introduces the term of a generative CAD model, its origins and, thus, a need of creating such a type of models. A process of generative model creation as well as specific forms of knowledge recording applied in the implementation phase in various CAD systems are briefly discussed. The example of a worm gear meshing realized by the CATIA software encapsulates the methodology of generative model construction. Sources and types of knowledge for design and construction required for development of the aforementioned model as well as the UML language as a method of formal knowledge recording are presented. The concept of model creation, i.e. assumptions and the structure as well as logic of the model operation are described. Also, the paper addresses selected elements of the project that present the manner in which the model was constructed.
Unstructured Mesh Movement and Viscous Mesh Generation for CFD-Based Design Optimization Project
National Aeronautics and Space Administration — The innovations proposed are twofold: 1) a robust unstructured mesh movement method able to handle isotropic (Euler), anisotropic (viscous), mixed element (hybrid)...
Moving mesh generation with a sequential approach for solving PDEs
DEFF Research Database (Denmark)
of physical and mesh equations suffers typically from long computation time due to highly nonlinear coupling between the two equations. Moreover, the extended system (physical and mesh equations) may be sensitive to the tuning parameters such as a temporal relaxation factor. It is therefore useful to design...... adaptive grid method (local refinement by adding/deleting the meshes at a discrete time level) as well as of efficiency for the dynamic adaptive grid method (or moving mesh method) where the number of meshes is not changed. For illustration, a phase change problem is solved with the decomposition algorithm.......In moving mesh methods, physical PDEs and a mesh equation derived from equidistribution of an error metrics (so-called the monitor function) are simultaneously solved and meshes are dynamically concentrated on steep regions (Lim et al., 2001). However, the simultaneous solution procedure...
Optimal tetrahedral mesh generation for three-dimensional point set
Institute of Scientific and Technical Information of China (English)
秦开怀; 吴边; 关右江; 葛振州
1997-01-01
Three-dimensional (3D) tnangulation is a basic topic in computer graphics. It is considered very difficult to obtain the global optimal 3D triangulatlon, such as the triangulation which satisfies the max-min solid angle criterion A new method called genetic tetrahedral mesh generation algorithm (GTMGA for short) is presented. GT-MGA is based on the principle of genetic algorithm and aims at the global optimal triangulation. With a multi-objective fitness function, GTMGA is able to perform optimizations for different requirements. New crossover operator and mutation operator, polyhedron crossover and polyhedron mutation, are used in GTMGA. It is shown by the experimental results that GTMGA works better than both the 3D Delaunay triangulation and the algorithm based on local transformations.
Efficient computation of clipped Voronoi diagram for mesh generation
Yan, Dongming
2013-04-01
The Voronoi diagram is a fundamental geometric structure widely used in various fields, especially in computer graphics and geometry computing. For a set of points in a compact domain (i.e. a bounded and closed 2D region or a 3D volume), some Voronoi cells of their Voronoi diagram are infinite or partially outside of the domain, but in practice only the parts of the cells inside the domain are needed, as when computing the centroidal Voronoi tessellation. Such a Voronoi diagram confined to a compact domain is called a clipped Voronoi diagram. We present an efficient algorithm to compute the clipped Voronoi diagram for a set of sites with respect to a compact 2D region or a 3D volume. We also apply the proposed method to optimal mesh generation based on the centroidal Voronoi tessellation. Crown Copyright © 2011 Published by Elsevier Ltd. All rights reserved.
Advances in Parallelization for Large Scale Oct-Tree Mesh Generation
O'Connell, Matthew; Karman, Steve L.
2015-01-01
Despite great advancements in the parallelization of numerical simulation codes over the last 20 years, it is still common to perform grid generation in serial. Generating large scale grids in serial often requires using special "grid generation" compute machines that can have more than ten times the memory of average machines. While some parallel mesh generation techniques have been proposed, generating very large meshes for LES or aeroacoustic simulations is still a challenging problem. An automated method for the parallel generation of very large scale off-body hierarchical meshes is presented here. This work enables large scale parallel generation of off-body meshes by using a novel combination of parallel grid generation techniques and a hybrid "top down" and "bottom up" oct-tree method. Meshes are generated using hardware commonly found in parallel compute clusters. The capability to generate very large meshes is demonstrated by the generation of off-body meshes surrounding complex aerospace geometries. Results are shown including a one billion cell mesh generated around a Predator Unmanned Aerial Vehicle geometry, which was generated on 64 processors in under 45 minutes.
Pamgen, a library for parallel generation of simple finite element meshes.
Energy Technology Data Exchange (ETDEWEB)
Foucar, James G.; Drake, Richard Roy; Hensinger, David M.; Gardiner, Thomas Anthony
2008-04-01
Generating finite-element meshes is a serious bottleneck for large parallel simulations. When mesh generation is limited to serial machines and element counts approach a billion, this bottleneck becomes a roadblock. Pamgen is a parallel mesh generation library that allows on-the-fly scalable generation of hexahedral and quadrilateral finite element meshes for several simple geometries. It has been used to generate more that 1.1 billion elements on 17,576 processors. Pamgen generates an unstructured finite element mesh on each processor at the start of a simulation. The mesh is specified by commands passed to the library as a 'C'-programming language string. The resulting mesh geometry, topology, and communication information can then be queried through an API. pamgen allows specification of boundary condition application regions using sidesets (element faces) and nodesets (collections of nodes). It supports several simple geometry types. It has multiple alternatives for mesh grading. It has several alternatives for the initial domain decomposition. Pamgen makes it easy to change details of the finite element mesh and is very useful for performance studies and scoping calculations.
Challenges in Second-Generation Wireless Mesh Networks
Directory of Open Access Journals (Sweden)
Pescapé Antonio
2008-01-01
Full Text Available Wireless mesh networks have the potential to provide ubiquitous high-speed Internet access at low costs. The good news is that initial deployments of WiFi meshes show the feasibility of providing ubiquitous Internet connectivity. However, their performance is far below the necessary and achievable limit. Moreover, users' subscription in the existing meshes is dismal even though the technical challenges to get connectivity are low. This paper provides an overview of the current status of mesh networks' deployment, and highlights the technical, economical, and social challenges that need to be addressed in the next years. As a proof-of-principle study, we discuss the above-mentioned challenges with reference to three real networks: (i MagNets, an operator-driven planned two-tier mesh network; (ii Berlin Freifunk network as a pure community-driven single-tier network; (iii Weimar Freifunk network, also a community-driven but two-tier network.
Challenges in Second-Generation Wireless Mesh Networks
Directory of Open Access Journals (Sweden)
Thomas Huehn
2008-10-01
Full Text Available Wireless mesh networks have the potential to provide ubiquitous high-speed Internet access at low costs. The good news is that initial deployments of WiFi meshes show the feasibility of providing ubiquitous Internet connectivity. However, their performance is far below the necessary and achievable limit. Moreover, users' subscription in the existing meshes is dismal even though the technical challenges to get connectivity are low. This paper provides an overview of the current status of mesh networks' deployment, and highlights the technical, economical, and social challenges that need to be addressed in the next years. As a proof-of-principle study, we discuss the above-mentioned challenges with reference to three real networks: (i MagNets, an operator-driven planned two-tier mesh network; (ii Berlin Freifunk network as a pure community-driven single-tier network; (iii Weimar Freifunk network, also a community-driven but two-tier network.
2015-01-07
Mesh Generation. Lecture Notes in Computational Vision and Biomechanics , Volume 3. Springer Publisher. Editor: Yongjie (Jessica) Zhang. ISBN-10...Modeling and Mesh Generation. Lecture Notes in Computational Vision and Biomechanics , Volume 3. Springer Publisher. Editor: Yongjie (Jessica) Zhang... Biomechanics , Volume 3. Springer Publisher. Editor: Yongjie (Jessica) Zhang. ISBN-10: 9400742541, ISBN-13: 978-9400742543. 2013. 3. Y. Zhang. Challenges
Hex-dominant mesh generation using 3D constrained triangulation
Energy Technology Data Exchange (ETDEWEB)
OWEN,STEVEN J.
2000-05-30
A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedral are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.
A tuned mesh-generation strategy for image representation based on data-dependent triangulation.
Li, Ping; Adams, Michael D
2013-05-01
A mesh-generation framework for image representation based on data-dependent triangulation is proposed. The proposed framework is a modified version of the frameworks of Rippa and Garland and Heckbert that facilitates the development of more effective mesh-generation methods. As the proposed framework has several free parameters, the effects of different choices of these parameters on mesh quality are studied, leading to the recommendation of a particular set of choices for these parameters. A mesh-generation method is then introduced that employs the proposed framework with these best parameter choices. This method is demonstrated to produce meshes of higher quality (both in terms of squared error and subjectively) than those generated by several competing approaches, at a relatively modest computational and memory cost.
Danilov, A. A.; Salamatova, V. Yu; Vassilevski, Yu V.
2012-12-01
Here, a workflow for high-resolution efficient numerical modeling of bioimpedance measurements is suggested that includes 3D image segmentation, adaptive mesh generation, finite-element discretization, and the analysis of simulation results. Using the adaptive unstructured tetrahedral meshes enables to decrease significantly a number of mesh elements while keeping model accuracy. The numerical results illustrate current, potential, and sensitivity field distributions for a conventional Kubicek-like scheme of bioimpedance measurements using segmented geometric model of human torso based on Visible Human Project data. The whole body VHP man computational mesh is constructed that contains 574 thousand vertices and 3.3 million tetrahedrons.
Generation of Delaunay meshes in implicit domains with edge sharpening
Belokrys-Fedotov, A. I.; Garanzha, V. A.; Kudryavtseva, L. N.
2016-11-01
A variational algorithm for the construction of 3D Delaunay meshes in implicit domains with a nonsmooth boundary is proposed. The algorithm is based on the self-organization of an elastic network in which each Delaunay edge is interpreted as an elastic strut. The elastic potential is constructed as a combination of the repulsion potential and the sharpening potential. The sharpening potential is applied only on the boundary and is used to minimize the deviation of the outward normals to the boundary faces from the direction of the gradient of the implicit function. Numerical experiments showed that in the case when the implicit function specifying the domain is considerably different from the signed distance function, the use of the sharpening potential proposed by Belyaev and Ohtake in 2002 leads to the mesh instability. A stable version of the sharpening potential is proposed. The numerical experiments showed that acceptable Delaunay meshes for complex shaped domains with sharp curved boundary edges can be constructed.
An arbitrary boundary triangle mesh generation method for multi-modality imaging
Zhang, Xuanxuan; Deng, Yong; Gong, Hui; Meng, Yuanzheng; Yang, Xiaoquan; Luo, Qingming
2012-03-01
Low-resolution and ill-posedness are the major challenges in diffuse optical tomography(DOT)/fluorescence molecular tomography(FMT). Recently, the multi-modality imaging technology that combines micro-computed tomography (micro-CT) with DOT/FMT is developed to improve resolution and ill-posedness. To take advantage of the fine priori anatomical maps obtained from micro-CT, we present an arbitrary boundary triangle mesh generation method for FMT/DOT/micro-CT multi-modality imaging. A planar straight line graph (PSLG) based on the image of micro-CT is obtained by an adaptive boundary sampling algorithm. The subregions of mesh are accurately matched with anatomical structures by a two-step solution, firstly, the triangles and nodes during mesh refinement are labeled respectively, and then a revising algorithm is used to modifying meshes of each subregion. The triangle meshes based on a regular model and a micro-CT image are generated respectively. The results show that the subregions of triangle meshes can match with anatomical structures accurately and triangle meshes have good quality. This provides an arbitrary boundaries triangle mesh generation method with the ability to incorporate the fine priori anatomical information into DOT/FMT reconstructions.
ESCHER: An interactive mesh-generating editor for preparing finite-element input
Oakes, W. R., Jr.
1984-01-01
ESCHER is an interactive mesh generation and editing program designed to help the user create a finite-element mesh, create additional input for finite-element analysis, including initial conditions, boundary conditions, and slidelines, and generate a NEUTRAL FILE that can be postprocessed for input into several finite-element codes, including ADINA, ADINAT, DYNA, NIKE, TSAAS, and ABUQUS. Two important ESCHER capabilities, interactive geometry creation and mesh archival storge are described in detail. Also described is the interactive command language and the use of interactive graphics. The archival storage and restart file is a modular, entity-based mesh data file. Modules of this file correspond to separate editing modes in the mesh editor, with data definition syntax preserved between the interactive commands and the archival storage file. Because ESCHER was expected to be highly interactive, extensive user documentation was provided in the form of an interactive HELP package.
ESCHER: An interactive mesh-generating editor for preparing finite-element input
Oakes, W. R., Jr.
1984-01-01
ESCHER is an interactive mesh generation and editing program designed to help the user create a finite-element mesh, create additional input for finite-element analysis, including initial conditions, boundary conditions, and slidelines, and generate a NEUTRAL FILE that can be postprocessed for input into several finite-element codes, including ADINA, ADINAT, DYNA, NIKE, TSAAS, and ABUQUS. Two important ESCHER capabilities, interactive geometry creation and mesh archival storge are described in detail. Also described is the interactive command language and the use of interactive graphics. The archival storage and restart file is a modular, entity-based mesh data file. Modules of this file correspond to separate editing modes in the mesh editor, with data definition syntax preserved between the interactive commands and the archival storage file. Because ESCHER was expected to be highly interactive, extensive user documentation was provided in the form of an interactive HELP package.
Pathogenesis and electrodiagnosis of cubital tunnel syndrome
Institute of Scientific and Technical Information of China (English)
贾志荣; 石昕; 孙相如
2004-01-01
Background Cubital tunnel syndrome is a well-recognized clinical condition and is the second most common peripheral compression neuropathy. This study was designed to investigate the causes of cubital tunnel syndrome by surgical means and to assess the clinical value of the neurophysiological diagnosis of cubital tunnel syndrome. Methods Twenty-one patients (involving a total of 22 limbs from 16 men and 5 women, aged 22 to 63, with a mean age of 49 years) with clinical symptoms and signs indicating a problem with their ulnar nerve underwent motor conduction velocity examinations at different sites along the ulnar nerve and examinations of sensory conduction velocity in the hand, before undergoing anterior transposition of the ulnar nerve.Results Electromyographic abnormalities were seen in 21 of 22 limbs [motor nerve conduction velocity (MCV) range (15.9-47.5) m/s, mean 32.7 m/s] who underwent motor conduction velocity examinations across the elbow segment of the ulnar nerve. Reduced velocity was observed in 13 of 22 limbs [MCV (15.7-59.6) m/s, mean 40.4 m/s] undergoing MCV tests in the forearms. An absent or abnormal sensory nerve action potential following stimulation was detected in the little finger of 14 of 22 limbs. The factors responsible for ulnar compression based on observations made during surgery were as follows: 15 cases involved compression by arcuate ligaments, muscle tendons, or bone hyperplasia; 2 involved fibrous adhesion; 3 involved compression by the venous plexus or a concurrent thick vein; 2 involved compression by cysts. Conclusions Factors inducing cubital tunnel syndrome include both common factors that have been reported and rare factors, involving the venous plexus, thick veins, and cysts. Tests of motor conduction velocity at different sites along the ulnar nerve should be helpful in diagnosis cubital tunnel syndrome, especially MCV tests indicating decreased velocity across the elbow segment of the ulnar nerve.
A tetrahedral mesh generation approach for 3D marine controlled-source electromagnetic modeling
Um, Evan Schankee; Kim, Seung-Sep; Fu, Haohuan
2017-03-01
3D finite-element (FE) mesh generation is a major hurdle for marine controlled-source electromagnetic (CSEM) modeling. In this paper, we present a FE discretization operator (FEDO) that automatically converts a 3D finite-difference (FD) model into reliable and efficient tetrahedral FE meshes for CSEM modeling. FEDO sets up wireframes of a background seabed model that precisely honors the seafloor topography. The wireframes are then partitioned into multiple regions. Outer regions of the wireframes are discretized with coarse tetrahedral elements whose maximum size is as large as a skin depth of the regions. We demonstrate that such coarse meshes can produce accurate FE solutions because numerical dispersion errors of tetrahedral meshes do not accumulate but oscillates. In contrast, central regions of the wireframes are discretized with fine tetrahedral elements to describe complex geology in detail. The conductivity distribution is mapped from FD to FE meshes in a volume-averaged sense. To avoid excessive mesh refinement around receivers, we introduce an effective receiver size. Major advantages of FEDO are summarized as follow. First, FEDO automatically generates reliable and economic tetrahedral FE meshes without adaptive meshing or interactive CAD workflows. Second, FEDO produces FE meshes that precisely honor the boundaries of the seafloor topography. Third, FEDO derives multiple sets of FE meshes from a given FD model. Each FE mesh is optimized for a different set of sources and receivers and is fed to a subgroup of processors on a parallel computer. This divide and conquer approach improves the parallel scalability of the FE solution. Both accuracy and effectiveness of FEDO are demonstrated with various CSEM examples.
Automatic generation of endocardial surface meshes with 1-to-1 correspondence from cine-MR images
Su, Yi; Teo, S.-K.; Lim, C. W.; Zhong, L.; Tan, R. S.
2015-03-01
In this work, we develop an automatic method to generate a set of 4D 1-to-1 corresponding surface meshes of the left ventricle (LV) endocardial surface which are motion registered over the whole cardiac cycle. These 4D meshes have 1- to-1 point correspondence over the entire set, and is suitable for advanced computational processing, such as shape analysis, motion analysis and finite element modelling. The inputs to the method are the set of 3D LV endocardial surface meshes of the different frames/phases of the cardiac cycle. Each of these meshes is reconstructed independently from border-delineated MR images and they have no correspondence in terms of number of vertices/points and mesh connectivity. To generate point correspondence, the first frame of the LV mesh model is used as a template to be matched to the shape of the meshes in the subsequent phases. There are two stages in the mesh correspondence process: (1) a coarse matching phase, and (2) a fine matching phase. In the coarse matching phase, an initial rough matching between the template and the target is achieved using a radial basis function (RBF) morphing process. The feature points on the template and target meshes are automatically identified using a 16-segment nomenclature of the LV. In the fine matching phase, a progressive mesh projection process is used to conform the rough estimate to fit the exact shape of the target. In addition, an optimization-based smoothing process is used to achieve superior mesh quality and continuous point motion.
Mesh Generation and Adaption for High Reynolds Number RANS Computations Project
National Aeronautics and Space Administration — The innovation of our Phase II STTR program is to develop and provide to NASA automatic mesh generation software for the simulation of fluid flows using...
Mesh Generation and Adaption for High Reynolds Number RANS Computations Project
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....
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...
A multilevel adaptive mesh generation scheme using Kd-trees
Directory of Open Access Journals (Sweden)
Alfonso Limon
2009-04-01
Full Text Available We introduce a mesh refinement strategy for PDE based simulations that benefits from a multilevel decomposition. Using Harten's MRA in terms of Schroder-Pander linear multiresolution analysis [20], we are able to bound discontinuities in $mathbb{R}$. This MRA is extended to $mathbb{R}^n$ in terms of n-orthogonal linear transforms and utilized to identify cells that contain a codimension-one discontinuity. These refinement cells become leaf nodes in a balanced Kd-tree such that a local dyadic MRA is produced in $mathbb{R}^n$, while maintaining a minimal computational footprint. The nodes in the tree form an adaptive mesh whose density increases in the vicinity of a discontinuity.
Energy Technology Data Exchange (ETDEWEB)
Balaven-Clermidy, S.
2001-12-01
Oil reservoir simulations study multiphase flows in porous media. These flows are described and evaluated through numerical schemes on a discretization of the reservoir domain. In this thesis, we were interested in this spatial discretization and a new kind of hybrid mesh has been proposed where the radial nature of flows in the vicinity of wells is directly taken into account in the geometry. Our modular approach described wells and their drainage area through radial circular meshes. These well meshes are inserted in a structured reservoir mesh (a Corner Point Geometry mesh) made up with hexahedral cells. Finally, in order to generate a global conforming mesh, proper connections are realized between the different kinds of meshes through unstructured transition ones. To compute these transition meshes that we want acceptable in terms of finite volume methods, an automatic method based on power diagrams has been developed. Our approach can deal with a homogeneous anisotropic medium and allows the user to insert vertical or horizontal wells as well as secondary faults in the reservoir mesh. Our work has been implemented, tested and validated in 2D and 2D1/2. It can also be extended in 3D when the geometrical constraints are simplicial ones: points, segments and triangles. (author)
Automated hexahedral mesh generation from biomedical image data: applications in limb prosthetics.
Zachariah, S G; Sanders, J E; Turkiyyah, G M
1996-06-01
A general method to generate hexahedral meshes for finite element analysis of residual limbs and similar biomedical geometries is presented. The method utilizes skeleton-based subdivision of cross-sectional domains to produce simple subdomains in which structured meshes are easily generated. Application to a below-knee residual limb and external prosthetic socket is described. The residual limb was modeled as consisting of bones, soft tissue, and skin. The prosthetic socket model comprised a socket wall with an inner liner. The geometries of these structures were defined using axial cross-sectional contour data from X-ray computed tomography, optical scanning, and mechanical surface digitization. A tubular surface representation, using B-splines to define the directrix and generator, is shown to be convenient for definition of the structure geometries. Conversion of cross-sectional data to the compact tubular surface representation is direct, and the analytical representation simplifies geometric querying and numerical optimization within the mesh generation algorithms. The element meshes remain geometrically accurate since boundary nodes are constrained to lie on the tubular surfaces. Several element meshes of increasing mesh density were generated for two residual limbs and prosthetic sockets. Convergence testing demonstrated that approximately 19 elements are required along a circumference of the residual limb surface for a simple linear elastic model. A model with the fibula absent compared with the same geometry with the fibula present showed differences suggesting higher distal stresses in the absence of the fibula. Automated hexahedral mesh generation algorithms for sliced data represent an advancement in prosthetic stress analysis since they allow rapid modeling of any given residual limb and optimization of mesh parameters.
Design of computer-generated beam-shaping holograms by iterative finite-element mesh adaption.
Dresel, T; Beyerlein, M; Schwider, J
1996-12-10
Computer-generated phase-only holograms can be used for laser beam shaping, i.e., for focusing a given aperture with intensity and phase distributions into a pregiven intensity pattern in their focal planes. A numerical approach based on iterative finite-element mesh adaption permits the design of appropriate phase functions for the task of focusing into two-dimensional reconstruction patterns. Both the hologram aperture and the reconstruction pattern are covered by mesh mappings. An iterative procedure delivers meshes with intensities equally distributed over the constituting elements. This design algorithm adds new elementary focuser functions to what we call object-oriented hologram design. Some design examples are discussed.
ZONE: a finite element mesh generator. [In FORTRAN IV for CDC 7600
Energy Technology Data Exchange (ETDEWEB)
Burger, M. J.
1976-05-01
The ZONE computer program is a finite-element mesh generator which produces the nodes and element description of any two-dimensional geometry. The geometry is subdivided into a mesh of quadrilateral and triangular zones arranged sequentially in an ordered march through the geometry. The order of march can be chosen so that the minimum bandwidth is obtained. The node points are defined in terms of the x and y coordinates in a global rectangular coordinate system. The zones generated are quadrilaterals or triangles defined by four node points in a counterclockwise sequence. Node points defining the outside boundary are generated to describe pressure boundary conditions. The mesh that is generated can be used as input to any two-dimensional as well as any axisymmetrical structure program. The output from ZONE is essentially the input file to NAOS, HONDO, and other axisymmetric finite element programs. 14 figures. (RWR)
METHOD FOR ADAPTIVE MESH GENERATION BASED ON GEOMETRICAL FEATURES OF 3D SOLID
Institute of Scientific and Technical Information of China (English)
HUANG Xiaodong; DU Qungui; YE Bangyan
2006-01-01
In order to provide a guidance to specify the element size dynamically during adaptive finite element mesh generation, adaptive criteria are firstly defined according to the relationships between the geometrical features and the elements of 3D solid. Various modes based on different datum geometrical elements, such as vertex, curve, surface, and so on, are then designed for generating local refmed mesh. With the guidance of the defined criteria, different modes are automatically selected to apply on the appropriate datum objects to program the element size in the local special areas. As a result, the control information of element size is successfully programmed coveting the entire domain based on the geometrical features of 3D solid. A new algorithm based on Delaunay triangulation is then developed for generating 3D adaptive fmite element mesh, in which the element size is dynamically specified to catch the geometrical features and suitable tetrahedron facets are selected to locate interior nodes continuously. As a result, adaptive mesh with good-quality elements is generated. Examples show that the proposed method can be successfully applied to adaptive finite element mesh automatic generation based on the geometrical features of 3D solid.
Atlas-Based Automatic Generation of Subject-Specific Finite Element Tongue Meshes.
Bijar, Ahmad; Rohan, Pierre-Yves; Perrier, Pascal; Payan, Yohan
2016-01-01
Generation of subject-specific 3D finite element (FE) models requires the processing of numerous medical images in order to precisely extract geometrical information about subject-specific anatomy. This processing remains extremely challenging. To overcome this difficulty, we present an automatic atlas-based method that generates subject-specific FE meshes via a 3D registration guided by Magnetic Resonance images. The method extracts a 3D transformation by registering the atlas' volume image to the subject's one, and establishes a one-to-one correspondence between the two volumes. The 3D transformation field deforms the atlas' mesh to generate the subject-specific FE mesh. To preserve the quality of the subject-specific mesh, a diffeomorphic non-rigid registration based on B-spline free-form deformations is used, which guarantees a non-folding and one-to-one transformation. Two evaluations of the method are provided. First, a publicly available CT-database is used to assess the capability to accurately capture the complexity of each subject-specific Lung's geometry. Second, FE tongue meshes are generated for two healthy volunteers and two patients suffering from tongue cancer using MR images. It is shown that the method generates an appropriate representation of the subject-specific geometry while preserving the quality of the FE meshes for subsequent FE analysis. To demonstrate the importance of our method in a clinical context, a subject-specific mesh is used to simulate tongue's biomechanical response to the activation of an important tongue muscle, before and after cancer surgery.
Mobility Models for Next Generation Wireless Networks Ad Hoc, Vehicular and Mesh Networks
Santi, Paolo
2012-01-01
Mobility Models for Next Generation Wireless Networks: Ad Hoc, Vehicular and Mesh Networks provides the reader with an overview of mobility modelling, encompassing both theoretical and practical aspects related to the challenging mobility modelling task. It also: Provides up-to-date coverage of mobility models for next generation wireless networksOffers an in-depth discussion of the most representative mobility models for major next generation wireless network application scenarios, including WLAN/mesh networks, vehicular networks, wireless sensor networks, and
Detecting Translation Errors in CAD Surfaces and Preparing Geometries for Mesh Generation
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Petersson, N Anders; Chand, K K
2001-08-27
The authors have developed tools for the efficient preparation of CAD geometries for mesh generation. Geometries are read from IGES files and then maintained in a boundary-representation consisting of a patchwork of trimmed and untrimmed surfaces. Gross errors in the geometry can be identified and removed automatically while a user interface is provided for manipulating the geometry (such as correcting invalid trimming curves or removing unwanted details). Modifying the geometry by adding or deleting surfaces and/or sectioning it by arbitrary planes (e.g. symmetry planes) is also supported. These tools are used for robust and accurate geometry models for initial mesh generation and will be applied to in situ mesh generation requirements of moving and adaptive grid simulations.
Jansen, Gunnar; Sohrabi, Reza; Miller, Stephen A.
2017-02-01
Short for Hexahedra from Unique Location in (K)convex Polyhedra - HULK is a simple and efficient algorithm to generate hexahedral meshes from generic STL files describing a geological model to be used in simulation tools based on the finite element, finite volume or finite difference methods. Using binary space partitioning of the input geometry and octree refinement on the grid, a successive increase in accuracy of the mesh is achieved. We present the theoretical basis as well as the implementation procedure with three geological models with varying complexity, providing the basis on which the algorithm is evaluated. HULK generates high accuracy discretizations with cell counts suitable for state-of-the-art subsurface simulators and provides a new method for hexahedral mesh generation in geological settings.
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Spear, A. D. [Department of Mechanical Engineering, University of Utah, Salt Lake City UT USA; Hochhalter, J. D. [NASA Langley Research Center, Hampton VA USA; Cerrone, A. R. [GE Global Research Center, Niskayuna NY USA; Li, S. F. [Lawrence Livermore National Laboratory, Livermore CA USA; Lind, J. F. [Lawrence Livermore National Laboratory, Livermore CA USA; Suter, R. M. [Department of Physics, Carnegie Mellon University, Pittsburgh PA USA; Ingraffea, A. R. [School of Civil & Environmental Engineering, Cornell University, Ithaca NY USA
2016-04-27
In an effort to reproduce computationally the observed evolution of microstructurally small fatigue cracks (MSFCs), a method is presented for generating conformal, finite-element (FE), volume meshes from 3D measurements of MSFC propagation. The resulting volume meshes contain traction-free surfaces that conform to incrementally measured 3D crack shapes. Grain morphologies measured using near-field high-energy X-ray diffraction microscopy are also represented within the FE volume meshes. Proof-of-concept simulations are performed to demonstrate the utility of the mesh-generation method. The proof-of-concept simulations employ a crystal-plasticity constitutive model and are performed using the conformal FE meshes corresponding to successive crack-growth increments. Although the simulations for each crack increment are currently independent of one another, they need not be, and transfer of material-state information among successive crack-increment meshes is discussed. The mesh-generation method was developed using post-mortem measurements, yet it is general enough that it can be applied to in-situ measurements of 3D MSFC propagation.
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
Park, Jae-Hyeung; Kim, Seong-Bok; Yeom, Han-Ju; Kim, Hee-Jae; Zhang, HuiJun; Li, BoNi; Ji, Yeong-Min; Kim, Sang-Hoo; Ko, Seok-Bum
2015-12-28
Fully analytic mesh-based computer generated hologram enables efficient and precise representation of three-dimensional scene. Conventional method assigns uniform amplitude inside individual mesh, resulting in reconstruction of the three-dimensional scene of flat shading. In this paper, we report an extension of the conventional method to achieve the continuous shading where the amplitude in each mesh is continuously varying. The proposed method enables the continuous shading, while maintaining fully analytic framework of the conventional method without any sacrifice in the precision. The proposed method can also be extended to enable fast update of the shading for different illumination directions and the ambient-diffuse reflection ratio based on Phong reflection model. The feasibility of the proposed method is confirmed by the numerical and optical reconstruction of the generated hologram.
Medical Image Processing for Fully Integrated Subject Specific Whole Brain Mesh Generation
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Chih-Yang Hsu
2015-05-01
Full Text Available Currently, anatomically consistent segmentation of vascular trees acquired with magnetic resonance imaging requires the use of multiple image processing steps, which, in turn, depend on manual intervention. In effect, segmentation of vascular trees from medical images is time consuming and error prone due to the tortuous geometry and weak signal in small blood vessels. To overcome errors and accelerate the image processing time, we introduce an automatic image processing pipeline for constructing subject specific computational meshes for entire cerebral vasculature, including segmentation of ancillary structures; the grey and white matter, cerebrospinal fluid space, skull, and scalp. To demonstrate the validity of the new pipeline, we segmented the entire intracranial compartment with special attention of the angioarchitecture from magnetic resonance imaging acquired for two healthy volunteers. The raw images were processed through our pipeline for automatic segmentation and mesh generation. Due to partial volume effect and finite resolution, the computational meshes intersect with each other at respective interfaces. To eliminate anatomically inconsistent overlap, we utilized morphological operations to separate the structures with a physiologically sound gap spaces. The resulting meshes exhibit anatomically correct spatial extent and relative positions without intersections. For validation, we computed critical biometrics of the angioarchitecture, the cortical surfaces, ventricular system, and cerebrospinal fluid (CSF spaces and compared against literature values. Volumina and surface areas of the computational mesh were found to be in physiological ranges. In conclusion, we present an automatic image processing pipeline to automate the segmentation of the main intracranial compartments including a subject-specific vascular trees. These computational meshes can be used in 3D immersive visualization for diagnosis, surgery planning with haptics
A unified approach for a posteriori high-order curved mesh generation using solid mechanics
Poya, Roman; Sevilla, Ruben; Gil, Antonio J.
2016-09-01
The paper presents a unified approach for the a posteriori generation of arbitrary high-order curvilinear meshes via a solid mechanics analogy. The approach encompasses a variety of methodologies, ranging from the popular incremental linear elastic approach to very sophisticated non-linear elasticity. In addition, an intermediate consistent incrementally linearised approach is also presented and applied for the first time in this context. Utilising a consistent derivation from energy principles, a theoretical comparison of the various approaches is presented which enables a detailed discussion regarding the material characterisation (calibration) employed for the different solid mechanics formulations. Five independent quality measures are proposed and their relations with existing quality indicators, used in the context of a posteriori mesh generation, are discussed. Finally, a comprehensive range of numerical examples, both in two and three dimensions, including challenging geometries of interest to the solids, fluids and electromagnetics communities, are shown in order to illustrate and thoroughly compare the performance of the different methodologies. This comparison considers the influence of material parameters and number of load increments on the quality of the generated high-order mesh, overall computational cost and, crucially, the approximation properties of the resulting mesh when considering an isoparametric finite element formulation.
Acute Cubital Tunnel Syndrome Secondary to Anconeus Epitrochlearis Muscle
Directory of Open Access Journals (Sweden)
Ying-Kan Law
2015-12-01
Full Text Available Cubital tunnel syndrome is the most common type of ulnar nerve entrapment that usually associates with chronic sensory and motor symptoms. Having anconeus epitrochlearis muscle is an uncommon cause of cubital tunnel syndrome. In this paper, the author introduces a case of cubital tunnel syndrome due to anconeus epitrochlearis muscle presenting with acute sensory, motor, and sympathetic symptoms. For such cases, there has been much controversy over the choices of surgical treatment, which can be excision of the muscle alone or together with ulnar nerve anterior transposition.
Ishikawa, Takeo; Matsunami, Michio
This paper proposes a method to generate adaptively 2D and 3D finite element meshes taking into account the continuity requirements of the magnetic field at the interface between two neighboring elements. First, this paper proposes a new error estimator that includes the Zienkiewicz and Zhu error norm estimator and the boundary rules in the electromagnetic field. Using a 2D simple model, this paper decides two parameters of the proposed estimator. Next, this paper presents a 3D mesh generation method based on the Voronoi-Delaunay theory, which ensures that the bounding surface of the domain is contained in the triangulation. The method has the capability to decrease the amount of information on the connectivity of boundary nodes by generating nodes not only in the interior of the domain but also on its surface. Two simple magnetostatic field problems are provided to illustrate the usefulness of the proposed method.
Extending a CAD-Based Cartesian Mesh Generator for the Lattice Boltzmann Method
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Cantrell, J Nathan [ORNL; Inclan, Eric J [ORNL; Joshi, Abhijit S [ORNL; Popov, Emilian L [ORNL; Jain, Prashant K [ORNL
2012-01-01
This paper describes the development of a custom preprocessor for the PaRAllel Thermal Hydraulics simulations using Advanced Mesoscopic methods (PRATHAM) code based on an open-source mesh generator, CartGen [1]. PRATHAM is a three-dimensional (3D) lattice Boltzmann method (LBM) based parallel flow simulation software currently under development at the Oak Ridge National Laboratory. The LBM algorithm in PRATHAM requires a uniform, coordinate system-aligned, non-body-fitted structured mesh for its computational domain. CartGen [1], which is a GNU-licensed open source code, already comes with some of the above needed functionalities. However, it needs to be further extended to fully support the LBM specific preprocessing requirements. Therefore, CartGen is being modified to (i) be compiler independent while converting a neutral-format STL (Stereolithography) CAD geometry to a uniform structured Cartesian mesh, (ii) provide a mechanism for PRATHAM to import the mesh and identify the fluid/solid domains, and (iii) provide a mechanism to visually identify and tag the domain boundaries on which to apply different boundary conditions.
Institute of Scientific and Technical Information of China (English)
ZHOU Guoxiang; CHEN Yinchao; SHEN Guoqiang
2001-01-01
The paper presents an efficient andfast non-uniform, orthogonal mesh generation algo-rithm for the analysis and design of cylindrical mi-crowave devices and integrated circuits using thecylindrical finite-difference time-domain (CFDTD)methods. By using this algorithm, we can easily gen-erate a suitable CFDTD grid fitting for the devel-oped CFDTD Maxwell's solver. In the paper, wewill introduce in detail the algorithm and the graph-ical functions of the corresponding software package,CylinMesh. In addition, we will illustrate the algo-rithm by demonstrating various one, two, and three-dimensional grid patterns for a double-layered cylin-drical microstrip stepped-impedance low pass filter.
Bucki, M; Bucki, Marek; Payan, Yohan
2005-01-01
In this paper, we address the problem of automatic mesh generation for finite elements modeling of anatomical organs for which a volumetric data set is available. In the first step a set of characteristic outlines of the organ is defined manually or automatically within the volume. The outlines define the "key frames" that will guide the procedure of surface reconstruction. Then, based on this information, and along with organ surface curvature information extracted from the volume data, a 3D scalar field is generated. This field allows a 3D reconstruction of the organ: as an iso-surface model, using a marching cubes algorithm; or as a 3D mesh, using a grid "immersion" technique, the field value being used as the outside/inside test. The final reconstruction respects the various topological changes that occur within the organ, such as holes and branching elements.
Shepherd, Jason; Mitchell, Scott A.; Jankovich, Steven R.; Benzley, Steven E.
2007-05-15
The present invention provides a meshing method, called grafting, that lifts the prior art constraint on abutting surfaces, including surfaces that are linking, source/target, or other types of surfaces of the trunk volume. The grafting method locally modifies the structured mesh of the linking surfaces allowing the mesh to conform to additional surface features. Thus, the grafting method can provide a transition between multiple sweep directions extending sweeping algorithms to 23/4-D solids. The method is also suitable for use with non-sweepable volumes; the method provides a transition between meshes generated by methods other than sweeping as well.
Directory of Open Access Journals (Sweden)
Mauro Massayoshi Sakamoto
2008-01-01
Full Text Available In this work, a software package based on the Delaunay´s algorithm is described. The main feature of this package is the capability in applying discretization in geometric domains of teeth taking into account their complex inner structures and the materials with different hardness. Usually, the mesh generators reported in literature treat molars and other teeth by using simplified geometric models, or even considering the teeth as homogeneous structures.
Miyawaki, Shinjiro; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long
2014-11-01
The authors have developed a method to automatically generate non-uniform CFD mesh for image-based human airway models. The sizes of generated tetrahedral elements vary in both radial and longitudinal directions to account for boundary layer and multiscale nature of pulmonary airflow. The proposed method takes advantage of our previously developed centerline-based geometry reconstruction method. In order to generate the mesh branch by branch in parallel, we used the open-source programs Gmsh and TetGen for surface and volume meshes, respectively. Both programs can specify element sizes by means of background mesh. The size of an arbitrary element in the domain is a function of wall distance, element size on the wall, and element size at the center of airway lumen. The element sizes on the wall are computed based on local flow rate and airway diameter. The total number of elements in the non-uniform mesh (10 M) was about half of that in the uniform mesh, although the computational time for the non-uniform mesh was about twice longer (170 min). The proposed method generates CFD meshes with fine elements near the wall and smooth variation of element size in longitudinal direction, which are required, e.g., for simulations with high flow rate. NIH Grants R01-HL094315, U01-HL114494, and S10-RR022421. Computer time provided by XSEDE.
An Application of the Mesh Generation and Refinement Tool to Mobile Bay, Alabama, USA
Aziz, Wali; Alarcon, Vladimir J.; McAnally, William; Martin, James; Cartwright, John
2009-08-01
A grid generation tool, called the Mesh Generation and Refinement Tool (MGRT), has been developed using Qt4. Qt4 is a comprehensive C++ application framework which includes GUI and container class-libraries and tools for cross-platform development. MGRT is capable of using several types of algorithms for grid generation. This paper presents an application of the MGRT grid generation tool for creating an unstructured grid of Mobile Bay (Alabama, USA) that will be used for hydrodynamics modeling. The algorithm used in this particular application is the Advancing-Front/Local-Reconnection (AFLR) [1] [2]. This research shows results of grids created with MGRT and compares them to grids (for the same geographical container) created using other grid generation tools. The superior quality of the grids generated by MGRT is shown.
Large scale generation of micro-droplet array by vapor condensation on mesh screen piece
Xie, Jian; Xu, Jinliang; He, Xiaotian; Liu, Qi
2017-01-01
We developed a novel micro-droplet array system, which is based on the distinct three dimensional mesh screen structure and sintering and oxidation induced thermal-fluid performance. Mesh screen was sintered on a copper substrate by bonding the two components. Non-uniform residue stress is generated along weft wires, with larger stress on weft wire top location than elsewhere. Oxidation of the sintered package forms micro pits with few nanograsses on weft wire top location, due to the stress corrosion mechanism. Nanograsses grow elsewhere to show hydrophobic behavior. Thus, surface-energy-gradient weft wires are formed. Cooling the structure in a wet air environment nucleates water droplets on weft wire top location, which is more “hydrophilic” than elsewhere. Droplet size is well controlled by substrate temperature, air humidity and cooling time. Because warp wires do not contact copper substrate and there is a larger conductive thermal resistance between warp wire and weft wire, warp wires contribute less to condensation but function as supporting structure. The surface energy analysis of drops along weft wires explains why droplet array can be generated on the mesh screen piece. Because the commercial material is used, the droplet system is cost effective and can be used for large scale utilization.
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Wilson, B G; Sonnad, V
2011-02-14
Precise electronic structure calculations of ions in plasmas benefit from optimized numerical radial meshes. A new closed form expression for obtaining non-linear parameters for the efficient generation of analytic log-linear radial meshes is presented. In conjunction with the (very simple) algorithm for the rapid high precision evaluation of Lambert's W-function, the above identity allows the precise construction of generalized log-linear radial meshes adapted to various constraints.
Optimum siting and sizing of a large distributed generator in a mesh connected system
Energy Technology Data Exchange (ETDEWEB)
Elnashar, Mohab M.; El Shatshat, Ramadan; Salama, Magdy M.A. [Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario (Canada)
2010-06-15
This paper proposes a new approach to optimally determine the appropriate size and location of the distributed generator (DG) in a large mesh connected system. This paper presents a visual optimization approach in which the planner plays an important role in determining the optimal siting and sizing of the DG through the choice of the appropriate weight factors of the parameters included in the optimization technique according to the system deficiencies. Losses, voltage profile and short circuit level are used in the algorithm to determine the optimum sizes and locations of the DG. The short circuit level parameter is introduced to represent the protective device requirements in the selection of the size and location of the DG. The proposed technique has been tested on the IEEE 24 - bus mesh connected test system. The obtained results showed clearly that the optimal size and location can be simply determined through the proposed approach. (author)
Computer generated holograms from three dimensional meshes using an analytic light transport model
Ahrenberg, Lukas; Benzie, Philip; Magnor, Marcus; Watson, John
2008-04-01
We present a method to analytically compute the light distribution of triangles directly in frequency space. This allows for fast evaluation, shading, and propagation of light from 3D mesh objects using angular spectrum methods. The algorithm complexity is only dependent on the hologram resolution and the polygon count of the 3D model. In contrast to other polygon based computer generated holography methods we do not need to perform a Fourier transform per surface. The theory behind the approach is derived, and a suitable algorithm to compute a digital hologram from a general triangle mesh is presented. We review some first results rendered on a spatial-light-modulator-based display by our proof-of-concept software.
Comment on "A note on generalized radial mesh generation for plasma electronic structure"
Pain, Jean-Christophe
2011-01-01
In a recent note [High Energy Density Phys. 7, 161 (2011)], B.G. Wilson and V. Sonnad proposed a very useful closed form expression for the efficient generation of analytic log-linear radial meshes. The central point of the note is an implicit equation for the parameter h, involving Lambert's function W[x]. The authors mention that they are unaware of any direct proof of this equation (they obtained it by re-summing the Taylor expansion of h using high-order coefficients obtained by analytic differentiation of the implicit definition using symbolic manipulation). In the present comment, we present a direct proof of that equation.
Definition And Interpolation Of Discrete Metric For Mesh Generation On 3d Surfaces
Barbara Głut; Tomasz Jurczyk
2005-01-01
The article concerns the problem of a deﬁnition of the control space from a set of discretedata (metric description gathered from diﬀerent sources) and its inﬂuence on the eﬃciency ofthe generation process with respect to 2D and 3D surface meshes. Several methods of metricinterpolation between these discrete points are inspected, including an automated selectionof proper method. Some aspects of the procedures of creation and employment of the meshcontrol space based on the discrete set of poi...
Definition And Interpolation Of Discrete Metric For Mesh Generation On 3d Surfaces
Directory of Open Access Journals (Sweden)
Barbara Głut
2005-01-01
Full Text Available The article concerns the problem of a deﬁnition of the control space from a set of discretedata (metric description gathered from diﬀerent sources and its inﬂuence on the eﬃciency ofthe generation process with respect to 2D and 3D surface meshes. Several methods of metricinterpolation between these discrete points are inspected, including an automated selectionof proper method. Some aspects of the procedures of creation and employment of the meshcontrol space based on the discrete set of points are presented. The results of using diﬀerentvariations of these methods are also included.
Cubital tunnel syndrome: A report of two cases
Directory of Open Access Journals (Sweden)
Farhana Ebrahim Suleman
2012-06-01
Full Text Available Cubital tunnel syndrome is the second most common peripheral neuropathy of the upper limb. This is due to the anatomy of the tunnel, the physiological changes that the nerve undergoes during elbow flexion, as well as pathological conditions that occur within the tunnel. We present two cases of ulnar neuropathy occurring at the level of the cubital tunnel, demonstrating that this entity may occur owing to an identifiable cause or may show only signal alteration without a visible cause on MRI.
Energy Technology Data Exchange (ETDEWEB)
Ricard, L.
2005-12-15
The high level geo-statistic description of the subsurface are often far too detailed for use in routine flow simulators. To make flow simulations tractable, the number of grid blocks has to be reduced: an approximation, still relevant with flow description, is necessary. In this work, we place the emphasis on the scaling procedure from the fine scale model to the multi-scale reservoir model. Two main problems appear: Near wells, faults and channels, the volume of flexible cells may be less than fine ones, so we need to solve a down-scaling problem; Far from these regions, the volume of cells are bigger than fine ones so we need to solve an up-scaling problem. In this work, research has been done on each of these three areas: down-scaling, up-scaling and fluid flow simulation. For each of these subjects, a review, some news improvements and comparative study are proposed. The proposed down-scaling method is build to be compatible with existing data integration methods. The comparative study shows that empirical methods are not enough accurate to solve the problem. Concerning the up-scaling step, the proposed approach is based on an existing method: the perturbed boundary conditions. An extension to unstructured mesh is developed for the inter-cell permeability tensor. The comparative study shows that numerical methods are not always as accurate as expected and the empirical model can be sufficient in lot of cases. A new approach to single-phase fluid flow simulation is developed. This approach can handle with full tensorial permeability fields with source or sink terms.(author)
Simulation of tsunamis generated by landslides using adaptive mesh refinement on GPU
de la Asunción, M.; Castro, M. J.
2017-09-01
Adaptive mesh refinement (AMR) is a widely used technique to accelerate computationally intensive simulations, which consists of dynamically increasing the spatial resolution of the areas of interest of the domain as the simulation advances. During the last years there have appeared many publications that tackle the implementation of AMR-based applications in GPUs in order to take advantage of their massively parallel architecture. In this paper we present the first AMR-based application implemented on GPU for the simulation of tsunamis generated by landslides by using a two-layer shallow water system. We also propose a new strategy for the interpolation and projection of the values of the fine cells in the AMR algorithm based on the fluctuations of the state values instead of the usual approach of considering the current state values. Numerical experiments on artificial and realistic problems show the validity and efficiency of the solver.
A GPU implementation of adaptive mesh refinement to simulate tsunamis generated by landslides
de la Asunción, Marc; Castro, Manuel J.
2016-04-01
In this work we propose a CUDA implementation for the simulation of landslide-generated tsunamis using a two-layer Savage-Hutter type model and adaptive mesh refinement (AMR). The AMR method consists of dynamically increasing the spatial resolution of the regions of interest of the domain while keeping the rest of the domain at low resolution, thus obtaining better runtimes and similar results compared to increasing the spatial resolution of the entire domain. Our AMR implementation uses a patch-based approach, it supports up to three levels, power-of-two ratios of refinement, different refinement criteria and also several user parameters to control the refinement and clustering behaviour. A strategy based on the variation of the cell values during the simulation is used to interpolate and propagate the values of the fine cells. Several numerical experiments using artificial and realistic scenarios are presented.
Energy Technology Data Exchange (ETDEWEB)
Flandrin, N.
2005-09-15
During the exploitation of an oil reservoir, it is important to predict the recovery of hydrocarbons and to optimize its production. A better comprehension of the physical phenomena requires to simulate 3D multiphase flows in increasingly complex geological structures. In this thesis, we are interested in this spatial discretization and we propose to extend in 3D the 2D hybrid model proposed by IFP in 1998 that allows to take directly into account in the geometry the radial characteristics of the flows. In these hybrid meshes, the wells and their drainage areas are described by structured radial circular meshes and the reservoirs are represented by structured meshes that can be a non uniform Cartesian grid or a Corner Point Geometry grids. In order to generate a global conforming mesh, unstructured transition meshes based on power diagrams and satisfying finite volume properties are used to connect the structured meshes together. Two methods have been implemented to generate these transition meshes: the first one is based on a Delaunay triangulation, the other one uses a frontal approach. Finally, some criteria are introduced to measure the quality of the transition meshes and optimization procedures are proposed to increase this quality under finite volume properties constraints. (author)
Jou, W.-H.
1982-01-01
An attempt is made to develop a three-dimensional, finite volume computational code for highly swept, twisted, small aspect ratio propeller blades with supersonic tip speeds, in a way that accounts for cascade effects, hub-induced flow, and nonlinear transonic effects. Attention is presently given to the generation of a computational mesh for such a complex propeller configuration, with the aim of sharing developmental process experience. The problem treated is unique, in that blade chord, blade length, hub length and blade-to-blade distance represent several characteristic length scales among which there is considerable disparity. An ad hoc mesh-generation scheme is accordingly developed.
Power generation using carbon mesh cathodes with different diffusion layers in microbial fuel cells
Luo, Yong
2011-11-01
An inexpensive carbon material, carbon mesh, was examined to replace the more expensive carbon cloth usually used to make cathodes in air-cathode microbial fuel cells (MFCs). Three different diffusion layers were tested using carbon mesh: poly(dimethylsiloxane) (PDMS), polytetrafluoroethylene (PTFE), and Goretex cloth. Carbon mesh with a mixture of PDMS and carbon black as a diffusion layer produced a maximum power density of 1355 ± 62 mW m -2 (normalized to the projected cathode area), which was similar to that obtained with a carbon cloth cathode (1390 ± 72 mW m-2). Carbon mesh with a PTFE diffusion layer produced only a slightly lower (6.6%) maximum power density (1303 ± 48 mW m-2). The Coulombic efficiencies were a function of current density, with the highest value for the carbon mesh and PDMS (79%) larger than that for carbon cloth (63%). The cost of the carbon mesh cathode with PDMS/Carbon or PTFE (excluding catalyst and binder costs) is only 2.5% of the cost of the carbon cloth cathode. These results show that low cost carbon materials such as carbon mesh can be used as the cathode in an MFC without reducing the performance compared to more expensive carbon cloth. © 2011 Elsevier B.V.
An Efficient Mesh Generation Method for Fractured Network System Based on Dynamic Grid Deformation
Directory of Open Access Journals (Sweden)
Shuli Sun
2013-01-01
Full Text Available Meshing quality of the discrete model influences the accuracy, convergence, and efficiency of the solution for fractured network system in geological problem. However, modeling and meshing of such a fractured network system are usually tedious and difficult due to geometric complexity of the computational domain induced by existence and extension of fractures. The traditional meshing method to deal with fractures usually involves boundary recovery operation based on topological transformation, which relies on many complicated techniques and skills. This paper presents an alternative and efficient approach for meshing fractured network system. The method firstly presets points on fractures and then performs Delaunay triangulation to obtain preliminary mesh by point-by-point centroid insertion algorithm. Then the fractures are exactly recovered by local correction with revised dynamic grid deformation approach. Smoothing algorithm is finally applied to improve the quality of mesh. The proposed approach is efficient, easy to implement, and applicable to the cases of initial existing fractures and extension of fractures. The method is successfully applied to modeling of two- and three-dimensional discrete fractured network (DFN system in geological problems to demonstrate its effectiveness and high efficiency.
Murr, L E; Gaytan, S M; Medina, F; Lopez, H; Martinez, E; Machado, B I; Hernandez, D H; Martinez, L; Lopez, M I; Wicker, R B; Bracke, J
2010-04-28
In this paper, we examine prospects for the manufacture of patient-specific biomedical implants replacing hard tissues (bone), particularly knee and hip stems and large bone (femoral) intramedullary rods, using additive manufacturing (AM) by electron beam melting (EBM). Of particular interest is the fabrication of complex functional (biocompatible) mesh arrays. Mesh elements or unit cells can be divided into different regions in order to use different cell designs in different areas of the component to produce various or continually varying (functionally graded) mesh densities. Numerous design elements have been used to fabricate prototypes by AM using EBM of Ti-6Al-4V powders, where the densities have been compared with the elastic (Young) moduli determined by resonant frequency and damping analysis. Density optimization at the bone-implant interface can allow for bone ingrowth and cementless implant components. Computerized tomography (CT) scans of metal (aluminium alloy) foam have also allowed for the building of Ti-6Al-4V foams by embedding the digital-layered scans in computer-aided design or software models for EBM. Variations in mesh complexity and especially strut (or truss) dimensions alter the cooling and solidification rate, which alters the alpha-phase (hexagonal close-packed) microstructure by creating mixtures of alpha/alpha' (martensite) observed by optical and electron metallography. Microindentation hardness measurements are characteristic of these microstructures and microstructure mixtures (alpha/alpha') and sizes.
Cubital Tunnel Syndrome Due to Synovial Cyst: A Case Report
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Zahir Kizilay
2016-02-01
Full Text Available We report a rare case of ulnar nerve entrapment caused by a synovial cyst derived from the left elbow joint. A 57-year-old male patient with a seven-month history of pain in his left elbow and a progressive and increasing numbness and weakness complaints in his left hand came to our clinic. Weakness and sensory loss of the 4th and 5th fingers were determined in neurological examination. The results of Tinel’s sign and Phalen’s Test were positive, especially when his left elbow was flexed. In electromyelography, axonal damage and entrapment neuropathy were determined in the left cubital tunnel area. Total excision of the synovial cyst and ulnar nerve anterior subcutaneous transposition were performed in surgical treatment. The patient’s pain decreased immediately after the surgery. In this report, we have discussed the pathopysiology of cubital tunnel syndrome due to synovial cyst and which surgical technique may be suitable as our case report.
Ultrasonographic Findings of the Ulnar Nerves in Cubital Tunnel Syndrome
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Koh, Young Hwan; Chai, Jee Won; Chung, Se Yeong; Choi, Young Ho; Cha, Joo Hee [Seoul Municipal Boramae Hospital, Seoul (Korea, Republic of)
2010-06-15
To determine useful diagnostic criteria of cubital tunnel syndrome (CTS), using ultrasonographic ulnar nerve cross-sectional areas (UNCSA) measurements. The CTS group included 28 patients confirmed with nerve conduction study and the control group included 17 healthy adults. Ulnar nerve cross sectional areas (UNCSA) were measured at the distal 1/3 upper arm level and in the cubital tunnel (CTN). US findings of CTS were ulnar nerve dislocation (n = 2), ulnar nerve subluxation (n = 5), ganglion (n = 1), sever elbow joint osteoarthritis (n = 1) and elbow joint valgus deformity after fracture (n = 1). UNCSA, the ratio of UNCSA in CTN to distal 1/3 upper arm level (CH ratio), and the difference of UNCSA between CTN and distal 1/3 upper arm level (CH difference) were evaluated to obtain the optimal diagnostic cutoff value of CTS, using ROC curve. The mean UNCSA in CTN was 0.168 cm2 in the CTS and 0.067 cm2 in the control. The CTS could be diagnosed when UNCSA, the CH ratio and the CH difference are larger than 0.096 cm2, 1.371 and 0.036 cm2 respectively. The ROC curve area was largest and the sensitivity, specificity was respectively 82.4%, 95.8%, when the CH difference was used as cutoff value. Ultrasound is useful for the detection of CTS pathogenic lesions in CTN. The highest diagnostic accuracy was acquired when the CH difference is larger than 0.036 cm2
Application of morphing technique with mesh-merging in rapid hull form generation
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Ju Young Kang
2012-09-01
Full Text Available Morphing is a geometric interpolation technique that is often used by the animation industry to transform one form into another seemingly seamlessly. It does this by producing a large number of ‘intermediate’ forms between the two ‘extreme’ or ‘parent’ forms. It has already been shown that morphing technique can be a powerful tool for form design and as such can be a useful addition to the armoury of product designers. Morphing procedure itself is simple and consists of straightforward linear interpolation. However, establishing the correspondence between vertices of the parent models is one of the most difficult and important tasks during a morphing process. This paper discusses the mesh-merging method employed for this process as against the already established mesh-regularising method. It has been found that the merging method minimises the need for manual manipulation, allowing automation to a large extent.
Application of morphing technique with mesh-merging in rapid hull form generation
Kang, Ju Young; Lee, Byung Suk
2012-09-01
Morphing is a geometric interpolation technique that is often used by the animation industry to transform one form into another seemingly seamlessly. It does this by producing a large number of `intermediate' forms between the two `extreme' or `parent' forms. It has already been shown that morphing technique can be a powerful tool for form design and as such can be a useful addition to the armoury of product designers. Morphing procedure itself is simple and consists of straightforward linear interpolation. However, establishing the correspondence between vertices of the parent models is one of the most difficult and important tasks during a morphing process. This paper discusses the mesh-merging method employed for this process as against the already established mesh-regularising method. It has been found that the merging method minimises the need for manual manipulation, allowing automation to a large extent.
Generation of the 30 M-Mesh Global Digital Surface Model by Alos Prism
Tadono, T.; Nagai, H.; Ishida, H.; Oda, F.; Naito, S.; Minakawa, K.; Iwamoto, H.
2016-06-01
Topographical information is fundamental to many geo-spatial related information and applications on Earth. Remote sensing satellites have the advantage in such fields because they are capable of global observation and repeatedly. Several satellite-based digital elevation datasets were provided to examine global terrains with medium resolutions e.g. the Shuttle Radar Topography Mission (SRTM), the global digital elevation model by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER GDEM). A new global digital surface model (DSM) dataset using the archived data of the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observing Satellite (ALOS, nicknamed "Daichi") has been completed on March 2016 by Japan Aerospace Exploration Agency (JAXA) collaborating with NTT DATA Corp. and Remote Sensing Technology Center, Japan. This project is called "ALOS World 3D" (AW3D), and its dataset consists of the global DSM dataset with 0.15 arcsec. pixel spacing (approx. 5 m mesh) and ortho-rectified PRISM image with 2.5 m resolution. JAXA is also processing the global DSM with 1 arcsec. spacing (approx. 30 m mesh) based on the AW3D DSM dataset, and partially releasing it free of charge, which calls "ALOS World 3D 30 m mesh" (AW3D30). The global AW3D30 dataset will be released on May 2016. This paper describes the processing status, a preliminary validation result of the AW3D30 DSM dataset, and its public release status. As a summary of the preliminary validation of AW3D30 DSM, 4.40 m (RMSE) of the height accuracy of the dataset was confirmed using 5,121 independent check points distributed in the world.
Cubital tunnel syndrome caused by hypertrophic burn scarring: Sonographic envisage
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Alparslan Bayram Carli
2015-08-01
Full Text Available In nerve entrapment syndromes, an electrodiagnostic study during physical examination would usually suffice to assess localization of injury. However, in daily clinical practice, sometimes it may be necessary to depict the insight; in other words to use an imaging tool. From this point of view, with its manifold advantages, ultrasound (US is superior to other imaging technologies such as magnetic resonance imaging (MRI. According to a study, US increased the sensitivity of electrodiagnostic studies from 78% to 98%. By presenting a patient with cubital tunnel syndrome caused by hypertrophic scarring, we wanted to highlight the complementary role of US in nerve entrapment syndromes in confirming the entrapment, as well as the usefulness of it in the follow-up period of burn patients. [Hand Microsurg 2015; 4(2.000: 44-46
Diffusion-weighted magnetic resonance imaging of the ulnar nerve in cubital tunnel syndrome.
Iba, K; Wada, T; Tamakawa, M; Aoki, M; Yamashita, T
2010-01-01
Diffusion-weighted images based on magnetic resonance reveal the microstructure of tissues by monitoring the random movement of water molecules. In this study, we investigated whether this new technique could visualize pathologic lesions on ulnar nerve in cubital tunnel. Six elbows in six healthy males without any symptoms and eleven elbows in ten patients with cubital tunnel syndrome underwent on diffusion-weighted MRI. No signal from the ulnar nerve was detected in normal subjects. Diffusion-weighted MRI revealed positive signals from the ulnar nerve in all of the eleven elbows with cubital tunnel syndrome. In contrast, conventional T2W-MRI revealed high signal intensity in eight elbows and low signal intensity in three elbows. Three elbows with low signal MRI showed normal nerve conduction velocity of the ulnar nerve. Diffusion-weighted MRI appears to be an attractive technique for diagnosis of cubital tunnel syndrome in its early stages which show normal electrophysiological and conventional MRI studies.
Power generation using an activated carbon and metal mesh cathode in a microbial fuel cell
Zhang, Fang
2009-11-01
An inexpensive activated carbon (AC) air cathode was developed as an alternative to a platinum-catalyzed electrode for oxygen reduction in a microbial fuel cell (MFC). AC was cold-pressed with a polytetrafluoroethylene (PTFE) binder to form the cathode around a Ni mesh current collector. This cathode construction avoided the need for carbon cloth or a metal catalyst, and produced a cathode with high activity for oxygen reduction at typical MFC current densities. Tests with the AC cathode produced a maximum power density of 1220 mW/m2 (normalized to cathode projected surface area; 36 W/m3 based on liquid volume) compared to 1060 mW/m2 obtained by Pt catalyzed carbon cloth cathode. The Coulombic efficiency ranged from 15% to 55%. These findings show that AC is a cost-effective material for achieving useful rates of oxygen reduction in air cathode MFCs. © 2009 Elsevier B.V. All rights reserved.
Shoreline and Bathymetry Approximation in Mesh Generation for Tidal Renewable Simulations
Avdis, Alexandros; Hill, Jon; Piggott, Matthew D; Gorman, Gerard J
2015-01-01
Due to the fractal nature of the domain geometry in geophysical flow simulations, a completely accurate description of the domain in terms of a computational mesh is frequently deemed infeasible. Shoreline and bathymetry simplification methods are used to remove small scale details in the geometry, particularly in areas away from the region of interest. To that end, a novel method for shoreline and bathymetry simplification is presented. Existing shoreline simplification methods typically remove points if the resultant geometry satisfies particular geometric criteria. Bathymetry is usually simplified using traditional filtering techniques, that remove unwanted Fourier modes. Principal Component Analysis (PCA) has been used in other fields to isolate small-scale structures from larger scale coherent features in a robust way, underpinned by a rigorous but simple mathematical framework. Here we present a method based on principal component analysis aimed towards simplification of shorelines and bathymetry. We pr...
Shoulder internal rotation elbow flexion test for diagnosing cubital tunnel syndrome.
Ochi, Kensuke; Horiuchi, Yukio; Tanabe, Aya; Waseda, Makoto; Kaneko, Yasuhito; Koyanagi, Takahiro
2012-06-01
Shoulder internal rotation enhances symptom provocation attributed to cubital tunnel syndrome. We present a modified elbow flexion test--the shoulder internal rotation elbow flexion test--for diagnosing cubital tunnel syndrome. Fifty-five ulnar nerves in cubital tunnel syndrome patients and 123 ulnar nerves in controls were examined with 5 seconds each of elbow flexion, shoulder internal rotation, and shoulder internal rotation elbow flexion tests before and after treatment (surgery in 18; conservative in others). For the shoulder internal rotation elbow flexion test position, 90° abduction, maximum internal rotation, and 10° flexion of the shoulder were combined with the elbow flexion test position. The test was considered positive if any symptom for cubital tunnel syndrome developed rotation elbow flexion test was evaluated by nerve conduction studies in 10 cubital tunnel syndrome nerves and 7 control nerves. The sensitivities/specificities of the 5-second elbow flexion, shoulder internal rotation, and shoulder internal rotation elbow flexion tests were 25%/100%, 58%/100%, and 87%/98%, respectively. Sensitivity differences between the shoulder internal rotation elbow flexion test and the other two tests were significant. Shoulder internal rotation elbow flexion test results and cubital tunnel syndrome symptoms were significantly correlated. Influence of the shoulder internal rotation elbow flexion test on the ulnar nerve was seen in 8 of 10 cubital tunnel syndrome nerves but not in controls. The 5-second shoulder internal rotation elbow flexion test is specific, easy and quick provocative test for diagnosing cubital tunnel syndrome. Copyright © 2012 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Mosby, Inc. All rights reserved.
Dahdouh, S.; Varsier, N.; Serrurier, A.; De la Plata, J.-P.; Anquez, J.; Angelini, E. D.; Wiart, J.; Bloch, I.
2014-08-01
Fetal dosimetry studies require the development of accurate numerical 3D models of the pregnant woman and the fetus. This paper proposes a 3D articulated fetal growth model covering the main phases of pregnancy and a pregnant woman model combining the utero-fetal structures and a deformable non-pregnant woman body envelope. The structures of interest were automatically or semi-automatically (depending on the stage of pregnancy) segmented from a database of images and surface meshes were generated. By interpolating linearly between fetal structures, each one can be generated at any age and in any position. A method is also described to insert the utero-fetal structures in the maternal body. A validation of the fetal models is proposed, comparing a set of biometric measurements to medical reference charts. The usability of the pregnant woman model in dosimetry studies is also investigated, with respect to the influence of the abdominal fat layer.
Berger, Michael; Mokhtar, Marwan; Zahler, Christian; Willert, Daniel; Neuhäuser, Anton; Schleicher, Eckhard
2017-06-01
At Industrial Solar's test facility in Freiburg (Germany), two phase flow patterns have been measured by using a wire mesh sensor from Helmholtz Zentrum Dresden-Rossendorf (HZDR). Main purpose of the measurements was to compare observed two-phase flow patterns with expected flow patterns from models. The two-phase flow pattern is important for the design of direct steam generating solar collectors. Vibrations should be avoided in the peripheral piping, and local dry-outs or large circumferential temperature gradients should be prevented in the absorber tubes. Therefore, the choice of design for operation conditions like mass flow and steam quality are an important step in the engineering process of such a project. Results of a measurement with the wire mesh sensor are the flow pattern and the plug or slug frequency at the given operating conditions. Under the assumption of the collector power, which can be assumed from previous measurements at the same collector and adaption with sun position and incidence angle modifier, also the slip can be evaluated for a wire mesh sensor measurement. Measurements have been performed at different mass flows and pressure levels. Transient behavior has been tested for flashing, change of mass flow, and sudden changes of irradiation (cloud simulation). This paper describes the measurements and the method of evaluation. Results are shown as extruded profiles in top view and in side view. Measurement and model are compared. The tests have been performed at low steam quality, because of the limits of the test facility. Conclusions and implications for possible future measurements at larger collectors are also presented in this paper.
Outcomes of revision surgery for cubital tunnel syndrome.
Aleem, Alexander W; Krogue, Justin D; Calfee, Ryan P
2014-11-01
To compare both validated patient-rated and objective outcomes of patients following revision cubital tunnel surgery to a similar group of patients who underwent primary surgery. This case-control investigation enrolled 56 patients treated surgically for cubital tunnel syndrome (28 revision cases, 28 primary controls) at a tertiary center. Patients with a minimum of 2 years of follow-up were eligible. All patients completed an in-office study evaluation. Revision participants represented 55% of potential patients in our practice and controls (treated only with primary surgery) were chosen at random from our practice to reach a 1:1 case to control ratio. Preoperative McGowan grading was confirmed similar between the groups. Outcome measures included validated patient outcome questionnaires (Patient-Rated Elbow Evaluation, Levine-Katz questionnaire), symptoms, and physical examination findings. Statistical analyses were conducted to compare the patient groups. Despite 79% of revision patients reporting symptomatic improvement, revision patients reported worse outcomes on all measured standardized questionnaires compared with primary patients. The Levine-Katz questionnaire indicated mild residual symptoms in the primary group (1.6) versus moderate remaining symptoms following revision surgery (2.3). The Patient-Rated Elbow Evaluation also indicated superior results for the control group (9 ± 10) compared with the revision group (32 ± 22). Revision patients had a higher frequency of constant symptoms, elevated 2-point discrimination, and diminished pinch strength. McGowan grading improved after 25% of revision surgeries versus 64% of primary surgeries, and 21% of revision patients had deterioration of their McGowan grade. Subjective and objective outcomes of revision patients in this cohort were inferior to outcomes of similar patients following primary surgery. Revision surgery can be offered in the setting of persistent or recurrent symptoms that are unexplained
Generating Quality Guaranteed Quadrilateral Mesh on ann-sided Region%平面n边域上高品质四边网格生成方法
Institute of Scientific and Technical Information of China (English)
简群; 蔺宏伟; 曹琦; 卢兴江
2016-01-01
In finite element analysis, the generation of quadrilateral (quad) meshes is harder than that of triangular meshes, especially on planar regions with complicated shape and topology structure. In this paper, we developed an iterative method to produce quad meshes onn-sided connected planar regions with complicated geometric shape and high genus, and the generated quad mesh is guaranteed to be non-self-overlapping. Starting with an ini-tial quad mesh, which is constructed by adaptive pixelization, the boundary of the quad mesh is iteratively fitted to the boundary of the given planar region. After each iteration of the boundary, the positions of inner vertices are changed by the layered Laplace operation. Finally, the quad mesh is generated by further optimizations. In the it-erations, the movements of the mesh vertices are restricted so that the produced quad mesh is guaranteed to be strictly non-self-overlapping. Lots of examples presented in this paper show the efficiency and effectiveness of the developed method.%在有限元分析中，四边网格比三角网格更难以生成，特别是在具有复杂形状和拓扑结构的平面域上。为此，基于几何迭代算法，提出一种在形状复杂和高亏格的 n 边平面域上生成高质量四边网格的方法，并保证生成的四边网格不自交。该方法以自适应像素化离散技术生成的四边网格作为初始网格，网格边界迭代拟合至给定的平面区域边界，其中每次边界迭代后，通过分层的 Laplace 算子改变内部顶点的位置；在迭代过程中，网格顶点的移动都受到限制，保证生成的网格严格不自交。最后通过实验验证了文中算法的效率和有效性。
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I. González-Alaña
2014-09-01
Full Text Available Las quemaduras eléctricas producen lesiones profundas, especialmente las debidas a la entrada y salida de la corriente y al arco voltaico, que pueden dejar expuestas estructuras nobles y afectar áreas de flexo-extensión, como la fosa antecubital. Los defectos resultantes pueden cubrirse mediante colgajos libres o pediculados de brazo y antebrazo. Entre las distintas opciones quirúrgicas, el colgajo medial del brazo evita la interrupción de los ejes vasculares mayores y la secuela en la zona donante es discreta. Sin embargo, su uso está poco extendido por considerarse un colgajo de difícil disección debido a la variabilidad anatómica de las arterias colaterales cubitales superior e inferior que lo irrigan. Presentamos la cobertura para un defecto secundario a quemadura eléctrica en la fosa antecubital mediante un colgajo medial del brazo basado en las ramas perforantes de la arteria colateral cubital inferior. Aunque confirmamos en este caso la variabilidad vascular, la disección resultó sencilla y el resultado estético y funcional fue excelente.
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Kleinstreuer, C.; Patterson, M.R.
1980-05-01
A two- or three-dimensional finite difference mesh generator capable of discretizing subrectangular flow regions (planar coordinates) with arbitrarily shaped bottom contours (vertical dimension) was developed. This economical, interactive computer code, written in FORTRAN IV and employing DISSPLA software together with graphics terminal, generates first a planar rectangular grid of variable element density according to the geometry and local kinematic flow patterns of a given fluid flow problem. Then subrectangular areas are deleted to produce canals, tributaries, bays, and the like. For three-dimensional problems, arbitrary bathymetric profiles (river beds, channel cross section, ocean shoreline profiles, etc.) are approximated with grid lines forming steps of variable spacing. Furthermore, the code works as a preprocessor numbering the discrete elements and the nodal points. Prescribed values for the principal variables can be automatically assigned to solid as well as kinematic boundaries. Cabinet drawings aid in visualizing the complete flow domain. Input data requirements are necessary only to specify the spacing between grid lines, determine land regions that have to be excluded, and to identify boundary nodes. 15 figures, 2 tables.
Mesh Generation from Dense 3D Scattered Data Using Neural Network
Institute of Scientific and Technical Information of China (English)
ZHANGWei; JIANGXian-feng; CHENLi-neng; MAYa-liang
2004-01-01
An improved self-organizing feature map (SOFM) neural network is presented to generate rectangular and hexagonal lattic with normal vector attached to each vertex. After the neural network was trained, the whole scattered data were divided into sub-regions where classified core were represented by the weight vectors of neurons at the output layer of neural network. The weight vectors of the neurons were used to approximate the dense 3-D scattered points, so the dense scattered points could be reduced to a reasonable scale, while the topological feature of the whole scattered points were remained.
Ochi, K; Horiuchi, Y; Nakamura, T; Sato, K; Arino, H; Koyanagi, T
2013-06-01
Simple decompression of the ulnar nerve at the elbow has not been shown to reduce nerve strain in cadavers. In this study, ulnar nerve strain at the elbow was measured intraoperatively in 11 patients with cubital tunnel syndrome, before and after simple decompression. Statistical analysis was performed using a paired Student's t-test. Mean ulnar nerve strain before and after simple decompression was 30.5% (range 9% to 69%) and 5.5% (range -2% to 11%), respectively; this difference was statistically significant (p ulnar nerve strain in all patients by an average of 24.5%. Our results suggest that the pathophysiology of cubital tunnel syndrome may be multifactorial, being neither a simple compression neuropathy nor a simple traction neuropathy, and simple decompression may be a favourable surgical procedure for cubital tunnel syndrome in terms of decompression and reduction of strain in the ulnar nerve.
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M. Farzan
2005-06-01
Full Text Available Anterior transposition of the ulnar nerve is widely implemented for treatment of cubital tunnel syndrome. However, preservation of the extrinsic blood supply of the ulnar nerve may result in better clinical outcomes. Fourteen patients with cubital tunnel syndrome, 11 men and 3 women, were treated by anterior subcutaneous transposition of the ulnar nerve. The extrinsic blood supply of the ulnar nerve was preserved. The average age at the time of operation was 33 years. The average follow-up period was 44 months. Post-operative outcome assessment by an independent examiner was based on the modified Bishop rating system. Nine patients had excellent or good outcomes. Five patients had a fair outcome. There were no complications or recurrence of symptoms. Anterior subcutaneous transposition of the vascularized ulnar nerve is an effective method of surgical treatment for patients with cubital tunnel syndrome.
Efficient Simplification Methods for Generating High Quality LODs of 3D Meshes
Institute of Scientific and Technical Information of China (English)
Muhammad Hussain
2009-01-01
Two simplification algorithms are proposed for automatic decimation of polygonal models, and for generating their LODs. Each algorithm orders vertices according to their priority values and then removes them iteratively. For setting the priority value of each vertex, exploiting normal field of its one-ring neighborhood, we introduce a new measure of geometric fidelity that reflects well the local geometric features of the vertex. After a vertex is selected, using other measures of geometric distortion that are based on normal field deviation and distance measure, it is decided which of the edges incident on the vertex is to be collapsed for removing it. The collapsed edge is substituted with a new vertex whose position is found by minimizing the local quadric error measure. A comparison with the state-of-the-art algorithms reveals that the proposed algorithms are simple to implement, are computationally more efficient, generate LODs with better quality, and preserve salient features even after drastic simplification. The methods are useful for applications such as 3D computer games, virtual reality, where focus is on fast running time, reduced memory overhead, and high quality LODs.
Wu, Shijia; He, Weihua; Yang, Wulin; Ye, Yaoli; Huang, Xia; Logan, Bruce E.
2017-07-01
Microbial fuel cells (MFCs) need to have a compact architecture, but power generation using low strength domestic wastewater is unstable for closely-spaced electrode designs using thin anodes (flat mesh or small diameter graphite fiber brushes) due to oxygen crossover from the cathode. A composite anode configuration was developed to improve performance, by joining the mesh and brushes together, with the mesh used to block oxygen crossover to the brushes, and the brushes used to stabilize mesh potentials. In small, fed-batch MFCs (28 mL), the composite anode produced 20% higher power densities than MFCs using only brushes, and 150% power densities compared to carbon mesh anodes. In continuous flow tests at short hydraulic retention times (HRTs, 2 or 4 h) using larger MFCs (100 mL), composite anodes had stable performance, while brush anode MFCs exhibited power overshoot in polarization tests. Both configurations exhibited power overshoot at a longer HRT of 8 h due to lower effluent CODs. The use of composite anodes reduced biomass growth on the cathode (1.9 ± 0.2 mg) compared to only brushes (3.1 ± 0.3 mg), and increased coulombic efficiencies, demonstrating that they successfully reduced oxygen contamination of the anode and the bio-fouling of cathode.
Generating quality word sense disambiguation test sets based on MeSH indexing.
Fan, Jung-Wei; Friedman, Carol
2009-11-14
Word sense disambiguation (WSD) determines the correct meaning of a word that has more than one meaning, and is a critical step in biomedical natural language processing, as interpretation of information in text can be correct only if the meanings of their component terms are correctly identified first. Quality evaluation sets are important to WSD because they can be used as representative samples for developing automatic programs and as referees for comparing different WSD programs. To help create quality test sets for WSD, we developed a MeSH-based automatic sense-tagging method that preferentially annotates terms being topical of the text. Preliminary results were promising and revealed important issues to be addressed in biomedical WSD research. We also suggest that, by cross-validating with 2 or 3 annotators, the method should be able to efficiently generate quality WSD test sets. Online supplement is available at: http://www.dbmi.columbia.edu/~juf7002/AMIA09.
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Seyitali Gumustas
2014-04-01
Full Text Available Compression of the ulnar nerve in the cubital tunnel is the second most common nerve entrapment syndrome in the upper extremity after carpal tunnel syndrome. Although various etiologies have been described, heterotrophic ossification is rarely seen. Heterotrophic ossification should be kept in mind as a cause of ulnar nerve entrapment after elbow trauma. Early diagnosis and surgical intervention are important in such cases before completion of the maturation phase. We report a case of heterotrophic ossification due to elbow trauma that caused cubital tunnel syndrome. [Hand Microsurg 2014; 3(1.000: 24-28
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Cahn, Frederick [Biomedical Strategies Inc., San Diego, CA (United States); Kyriakides, Themis R [Vascular Biology and Therapeutics, Yale University, New Haven, CT 06536-9812 (United States)], E-mail: themis.kyriakides@yale.edu
2008-09-01
Generation of a stable interface between soft tissues and biomaterials could improve the function of transcutaneous prostheses, primarily by minimizing chronic infections. We hypothesized that inclusion of non-biodegradable biomaterials in an artificial skin substrate would improve integration of the neodermis. In the present study, we compared the biocompatibility of an experimental substrate, consisting of collagen and glycosylaminoglycans, with commercially available artificial skin of similar composition. By utilizing a mouse excisional wound model, we found that the source of collagen (bovine tendon versus hide), extent of injury and wound contraction were critical determinants of inflammation and neodermis formation. Reducing the extent of injury to underlying muscle reduced inflammation and improved remodeling; the improved conditions allowed the detection of a pro-inflammatory effect of hide-derived collagen. To eliminate the complication of wound contraction, subsequent grafts were performed in guinea pigs and showed that inclusion of carbon fibers or non-degradable sutures resulted in increased foreign body response (FBR) and altered remodeling. On the other hand, inclusion of a polyester multi-stranded mesh induced a mild FBR and allowed normal neodermis formation. Taken together, our observations suggest that non-degradable biomaterials can be embedded in an artificial skin construct without compromising its ability to induce neodermis formation.
Institute of Scientific and Technical Information of China (English)
于长华; 熊敏; 方维; 郑澎; 张先红
2016-01-01
Because of the complicated boundary geometric features of multi-solid models, the algorithm for grid-based hexahedral mesh generation had very weak stability and generated some poor boundary elements. Ac-cording to these problems, an algorithm for the automated generation of grid based all-hexahedral element meshes is developed. In the surface matching process, a surface matching algorithm combining the embedding technique is proposed, establishing the corresponding the boundary element relation between solid models and core mesh, and making the hexahedral mesh accurately describe the geometric features of multi-solid models. In the topological optimization process, an optimization technique eliminating the hexahedral elements with bad topological connection is proposed. The effectiveness and robustness of the algorithm in this paper are tested by means of some solid model examples.%基于栅格法的六面体网格生成算法由于多体模型复杂的边界几何特征，导致稳定性较差和产生一些质量较差的边界六面体单元。针对这一问题，提出一套以栅格法为基础的全六面体网格自动生成算法。在边界拟合环节，利用 Embedding 技术提出一种边界拟合算法，建立了实体模型边界元素和核心网格外围边界元素的对应关系，使得六面体网格很好地描述实体模型的几何特征；在拓扑优化环节，利用 Pillowing 技术给出一种消除网格中拓扑连接关系较差的六面体单元的方法。若干实体模型算例结果表明，该算法实用性强，效果良好。
Research on Parallel Unstructured Mesh Generation Technology Based on GPU%基于GPU的并行非结构网格生成技术研究
Institute of Scientific and Technical Information of China (English)
齐龙; 肖素梅; 刘云楚; 廖玲玲; 蔡云龙
2013-01-01
In order to solve the problems of unstructured mesh generation technology in time and memory, the parallel generation method of unstructured grid is researched, and the GPU unstructured mesh generation technology based on the framework of CUDA is put forward. In CUDA programming framework, unstructured mesh generation technology is applied to GPU parallel environment, Combining the high-speed parallel GPU with parallel delaunay generation technology. Its performance is evaluated by the analysis of the speedup rate and efficiency. According to the experimental results, the suggested method is of high efficiency. Compared with traditional methods, it greatly reduces the time consumption in the same mesh quality.%为了解决非结构网格生成在时间和内存上的问题,研究了非结构网格的并行生成方法,提出了一种基于CUDA架构的GPU并行非结构网格生成技术.该技术结合了GPU的高速并行性和并行Delaunay网格生成技术的优点,在CUDA编程框架下,将非结构网格生成的技术应用到GPU并行环境中.通过分析此方法的加速比和效率,对其性能进行了评估.实验结果表明,所提出的方法具备有高效性,与传统方法相比,在保证网格质量的同时,大幅度减少了其时间消耗.
Huang, Wei; Zhang, Pei-Xun; Peng, Zhang; Xue, Feng; Wang, Tian-Bing; Jiang, Bao-Guo
2015-10-01
Although several surgical procedures exist for treating cubital tunnel syndrome, the best surgical option remains controversial. To evaluate the efficacy of anterior subcutaneous transposition of the ulnar nerve in patients with moderate to severe cubital tunnel syndrome and to analyze prognostic factors, we retrospectively reviewed 62 patients (65 elbows) diagnosed with cubital tunnel syndrome who underwent anterior subcutaneous transposition. Preoperatively, the initial severity of the disease was evaluated using the McGowan scale as modified by Goldberg: 18 patients (28%) had grade IIA neuropathy, 20 (31%) had grade IIB, and 27 (42%) had grade III. Postoperatively, according to the Wilson & Krout criteria, treatment outcomes were excellent in 38 patients (58%), good in 16 (25%), fair in 7 (11%), and poor in 4 (6%), with an excellent and good rate of 83%. A negative correlation was found between the preoperative McGowan grade and the postoperative Wilson & Krout score. The patients having fair and poor treatment outcomes had more advanced age, lower nerve conduction velocity, and lower action potential amplitude compared with those having excellent and good treatment outcomes. These results suggest that anterior subcutaneous transposition of the ulnar nerve is effective and safe for the treatment of moderate to severe cubital tunnel syndrome, and initial severity, advancing age, and electrophysiological parameters can affect treatment outcome.
Fascia Wrapping Technique: A Modified Method for the Treatment of Cubital Tunnel Syndrome
Directory of Open Access Journals (Sweden)
Hyun Ho Han
2014-01-01
Full Text Available Variations of the anterior transposition of the ulnar nerve for cubital tunnel syndrome include subcutaneous, submuscular, intramuscular, and subfascial methods. We introduce a modification of subfascial transposition, which is designed to facilitate nerve gliding by wrapping the nerve with fascia. Twenty patients with wrapping surgery following the diagnosis of cubital tunnel syndrome were reviewed retrospectively. Preoperative electrodiagnostic studies were performed in all patients and all of them were rechecked postoperatively. The preoperative mean value of motor conduction velocity (MCV was 37.1±6.7 m/s within the elbow segment and this result showed a decrease compared to the result of MCV with 53.9±6.9 m/s in the below the elbow-wrist segment with statistical significance (P<0.05. Postoperative mean values of MCV were improved in all of 20 patients to 47.6±5.5 m/s (P<0.05. 19 patients of 20 (95% reported good or excellent clinical outcomes according to a modified Bishop scoring system. The surgical treatment methods for cubital tunnel syndrome have their own advantages and disadvantages, and the preferred method differs depending on the surgeon. The wrapping method of anterior transposition is a newly designed alternative method modified from subfascial transposition. This method could be an alternative option to treat cubital tunnel syndrome.
Directory of Open Access Journals (Sweden)
Wei Huang
2015-01-01
Full Text Available Although several surgical procedures exist for treating cubital tunnel syndrome, the best surgical option remains controversial. To evaluate the efficacy of anterior subcutaneous transposition of the ulnar nerve in patients with moderate to severe cubital tunnel syndrome and to analyze prognostic factors, we retrospectively reviewed 62 patients (65 elbows diagnosed with cubital tunnel syndrome who underwent anterior subcutaneous transposition. Preoperatively, the initial severity of the disease was evaluated using the McGowan scale as modified by Goldberg: 18 patients (28% had grade IIA neuropathy, 20 (31% had grade IIB, and 27 (42% had grade III. Postoperatively, according to the Wilson & Krout criteria, treatment outcomes were excellent in 38 patients (58%, good in 16 (25%, fair in 7 (11%, and poor in 4 (6%, with an excellent and good rate of 83%. A negative correlation was found between the preoperative McGowan grade and the postoperative Wilson & Krout score. The patients having fair and poor treatment outcomes had more advanced age, lower nerve conduction velocity, and lower action potential amplitude compared with those having excellent and good treatment outcomes. These results suggest that anterior subcutaneous transposition of the ulnar nerve is effective and safe for the treatment of moderate to severe cubital tunnel syndrome, and initial severity, advancing age, and electrophysiological parameters can affect treatment outcome.
The US, CT and MR findings of cubital bursitis: a report of five cases
Energy Technology Data Exchange (ETDEWEB)
Liessi, G. [Servizio di Radiologia, Ospedale, I-31033 Castelfranco V.to, Ulss 8 (Tuvalu) (Italy); Cesari, S. [Servizio di Radiologia, Ospedale, I-31033 Castelfranco V.to, Ulss 8 (Tuvalu) (Italy); Spaliviero, B. [Servizio di Radiologia, Ospedale, I-31033 Castelfranco V.to, Ulss 8 (Tuvalu) (Italy); Dell`Antonio, C. [Servizio di Radiologia, Ospedale, I-31033 Castelfranco V.to, Ulss 8 (Tuvalu) (Italy); Avventi, P. [Servizio di Radiologia, Ospedale, I-31033 Castelfranco V.to, Ulss 8 (Tuvalu) (Italy)
1996-07-01
Objective. The purpose of the study was to evaluate the appearance of ``cubital bursitis`` on ultrasonography and CT and MR imaging. ``Cubital bursitis`` is a rare pathological condition involving a large swelling of the bicipito-radial or interosseous bursae located at the insertion of the distal biceps tendon on the radial tuberosity. Design and patients. We report on five patients with ``cubital bursitis`` resulting from their work or sporting activities. All patients underwent an ultrasound and MR examination. CT scans were performed on two patients before and after contrast enhancement. Results. Ultrasound studies showed a fusiform anechoic or hypoechoic lesion. CT images showed the lesions but there were some difficulties in determining the exact extent of the bursae. MR imaging showed the enlarged bursae and their fluid content. Four patients each underwent a surgical procedure. Conclusion. Ultrasound and CT were effective in the evaluation of ``cubital bursitis``, but with some diagnostic difficulties. MR imaging is probably the method of choice for determining both the development of the bursae and their fluid content. (orig.)
Delaunay Refinement Mesh Generation
1997-05-18
determinant evaluation that considers floating- point operands, except for one limited example: Ottmann , Thiemt, and Ullrich [74] advocate the use of an...Sandia National Labo- ratories, October 1996. [74] Thomas Ottmann , Gerald Thiemt, and Christian Ullrich. Numerical Stability of Geometric Algorithms
Matrix Norms and the Condition Number: A General Framework to Improve Mesh Quality via Node-Movement
Energy Technology Data Exchange (ETDEWEB)
KNUPP,PATRICK
1999-09-27
Objective functions for unstructured hexahedral and tetrahedral mesh optimization are analyzed using matrices and matrix norms. Mesh untangling objective functions that create valid meshes are used to initialize the optimization process. Several new objective functions to achieve element invertibility and quality are investigated, the most promising being the ''condition number''. The condition number of the Jacobian matrix of an element forms the basis of a barrier-based objective function that measures the distance to the set of singular matrices and has the ideal matrix as a stationary point. The method was implemented in the Cubit code, with promising results.
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.
Miyawaki, Shinjiro; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long
2013-11-01
The authors propose a method to automatically generate three-dimensional subject-specific airway geometries and meshes for computational fluid dynamics (CFD) studies of aerosol delivery in the human lungs. The proposed method automatically expands computed tomography (CT)-based airway skeleton to generate the centerline (CL)-based model, and then fits it to the CT-segmented geometry to generate the hybrid CL-CT-based model. To produce a turbulent laryngeal jet known to affect aerosol transport, we developed a physiologically-consistent laryngeal model that can be attached to the trachea of the above models. We used Gmsh to automatically generate the mesh for the above models. To assess the quality of the models, we compared the regional aerosol distributions in a human lung predicted by the hybrid model and the manually generated CT-based model. The aerosol distribution predicted by the hybrid model was consistent with the prediction by the CT-based model. We applied the hybrid model to 8 healthy and 16 severe asthmatic subjects, and average geometric error was 3.8% of the branch radius. The proposed method can be potentially applied to the branch-by-branch analyses of a large population of healthy and diseased lungs. NIH Grants R01-HL-094315 and S10-RR-022421, CT data provided by SARP, and computer time provided by XSEDE.
Salo, Zoryana; Beek, Maarten; Wright, David; Whyne, Cari Marisa
2015-04-13
Current methods for the development of pelvic finite element (FE) models generally are based upon specimen specific computed tomography (CT) data. This approach has traditionally required segmentation of CT data sets, which is time consuming and necessitates high levels of user intervention due to the complex pelvic anatomy. The purpose of this research was to develop and assess CT landmark-based semi-automated mesh morphing and mapping techniques to aid the generation and mechanical analysis of specimen-specific FE models of the pelvis without the need for segmentation. A specimen-specific pelvic FE model (source) was created using traditional segmentation methods and morphed onto a CT scan of a different (target) pelvis using a landmark-based method. The morphed model was then refined through mesh mapping by moving the nodes to the bone boundary. A second target model was created using traditional segmentation techniques. CT intensity based material properties were assigned to the morphed/mapped model and to the traditionally segmented target models. Models were analyzed to evaluate their geometric concurrency and strain patterns. Strains generated in a double-leg stance configuration were compared to experimental strain gauge data generated from the same target cadaver pelvis. CT landmark-based morphing and mapping techniques were efficiently applied to create a geometrically multifaceted specimen-specific pelvic FE model, which was similar to the traditionally segmented target model and better replicated the experimental strain results (R(2)=0.873). This study has shown that mesh morphing and mapping represents an efficient validated approach for pelvic FE model generation without the need for segmentation.
Murata, K; Omokawa, S; Shimizu, T; Nakanishi, Y; Kawamura, K; Yajima, H; Tanaka, Y
2014-01-01
Anterior dislocation of the ulnar nerve is occasionally encountered after simple decompression of the nerve for treatment of cubital tunnel syndrome. The purpose of this study was to determine whether the incidence of dislocation of the nerve following simple decompression of the nerve is correlated with the patient's preoperative characteristics and/or elbow morphology. We studied 51 patients with cubital tunnel syndrome who underwent surgery at our institution. Intraoperatively, we simulated dislocation of the nerve after simple decompression by flexing the elbow after releasing the nerve in each patient. Univariate and multiple logistic regression analysis showed that young age and a small ulnar nerve groove angle are positively correlated with dislocation of the nerve. Our results suggest that patients who are young and/or have a sharply angled ulnar nerve groove identified radiographically have a high probability of experiencing anterior dislocation of the ulnar nerve after simple decompression.
Cerutti, Guillaume; Ali, Olivier; Godin, Christophe
2017-01-01
Context: The shoot apical meristem (SAM), origin of all aerial organs of the plant, is a restricted niche of stem cells whose growth is regulated by a complex network of genetic, hormonal and mechanical interactions. Studying the development of this area at cell level using 3D microscopy time-lapse imaging is a newly emerging key to understand the processes controlling plant morphogenesis. Computational models have been proposed to simulate those mechanisms, however their validation on real-life data is an essential step that requires an adequate representation of the growing tissue to be carried out. Achievements: The tool we introduce is a two-stage computational pipeline that generates a complete 3D triangular mesh of the tissue volume based on a segmented tissue image stack. DRACO (Dual Reconstruction by Adjacency Complex Optimization) is designed to retrieve the underlying 3D topological structure of the tissue and compute its dual geometry, while STEM (SAM Tissue Enhanced Mesh) returns a faithful triangular mesh optimized along several quality criteria (intrinsic quality, tissue reconstruction, visual adequacy). Quantitative evaluation tools measuring the performance of the method along those different dimensions are also provided. The resulting meshes can be used as input and validation for biomechanical simulations. Availability: DRACO-STEM is supplied as a package of the open-source multi-platform plant modeling library OpenAlea (http://openalea.github.io/) implemented in Python, and is freely distributed on GitHub (https://github.com/VirtualPlants/draco-stem) along with guidelines for installation and use.
Simple in situ decompression for idiopathic cubital tunnel syndrome using minimal skin incision
Directory of Open Access Journals (Sweden)
Jeon In-Ho
2010-01-01
Full Text Available Cubital tunnel syndrome is one of the most frequently occurring compression neuropathy in the upper limb next to carpal tunnel syndrome. Recent minimal invasive technique has prompted us to gain clinical experience with simple in situ decompression with minimal skin incision for idiopathic cubital tunnel syndrome. Sixty six consecutive patients with cubital tunnel syndrome were treated using minimal skin incision technique. The mean age of the patients was 49.7 (range: 15-77 years and average follow up period was 23.9 months (range: 12-60 months. The severity of ulnar neuropathy was classified according to the McGowan classification: there were 17 in grade I , 47 in grade II and 2 in grade III. A preoperative nerve conduction study was done by inching method, which revealed motor conduction delay around the medial epicondyle. All operations were carried out in a day surgery unit under local anesthetics. The postoperative outcome was evaluated by Messina classification. The mean duration of the operation was 12 minutes. The technique was highly satisfactorily esthetic for all. Over 80% of the patients were completely satisfied with the procedure taking into consideration their symptoms. Postoperative outcome measures and patient satisfactions (pain, return to normal activities and work, scar and pillar tenderness were comparable with published series of anterior transposition. The overall satisfactory results were recorded 81% in the patients of McGowan stage I and II. There were 2 cases of hematoma as a postoperative complication. This procedure is comparably effective alternative which involves less surgical trauma, morbidity and rehabilitation time with good surgical outcomes especially in mild and moderate degrees. Minimal skin incision is a simple, safe and effective method to treat patients with idiopathic cubital tunnel syndrome.
Guaranteed-Quality Triangular Meshes
1989-04-01
Defense Ad, : ed Research P: jects Pgency or the U.S- Gower ment° iI Guaranteed-Quality Triangular Meshes DTIC ELECTE L. Paul Chew* JUL 1419891 TR 89-983 S... Wittchen , M. S. Shephard, K. R. Grice, and M. A. Yerry, Robust, geometrically based, automatic two-dimensional mesh generation, International Journal for
Current diagnostics and treatment of the cubital tunnel syndrome in Austria
Directory of Open Access Journals (Sweden)
Harder, Kristina
2016-01-01
Full Text Available According to the vote of the Austrian Society for Surgery of the Hand (ÖGH an investigation to collect data on the current state of the treatment of cubital tunnel syndrome was initiated. Over one year a total of 875 patients with cubital tunnel syndrome were operated in Austria, this means an incidence of this nerve entrapment of 0.011%. Most of the operations were done by trauma surgeons (287; 33%. For diagnosis most of the centers rely on clinical symptoms, electroneurophysiology, and elbow X-ray. 40% of the institutions regard conservative therapy as useless and not indicated. If conservative treatment modalities are applied, physiotherapy (97%, non-steroidal anti-inflammatory medication (77%, and glucocorticoid injections (30% are primarily used. In case of simple nerve entrapment most of the surgeons (72% prefer simple nerve decompression. If there is additional pathology subcutaneous cubital nerve transposition is recommended (62%. Endoscopic techniques are only use by 3% of the surgeons. In the postoperative care, physiotherapy is favored in 51%, whereas 24% do not judge any postoperative care as beneficial.The three most often encountered complications were incomplete remission, scar contracture and hypertrophy, and postoperative bleeding.
Yoshida, A; Okutsu, I; Hamanaka, I
2009-02-01
Experience with the use of the Universal Subcutaneous Endoscope (USE) system in surgical treatment of cubital tunnel syndrome in 35 patients is reported. Patients included in the study had pre- and postoperative clinical and electrophysiological data, and had undergone a minimum follow-up period of 13 months. Mean patient age was 59.5 years and the mean follow-up period was 25.9 months. The operation was performed under local anaesthesia without pneumatic tourniquet and on an out-patient basis. A 1.5 cm portal is made at the cubital tunnel and the USE system is inserted next to the ulnar nerve, first distally and then proximally. The nerve is endoscopically assessed and only the tissue that compresses the nerve is released, in keeping with the principles of minimally invasive treatment. Preoperative tingling sensations disappeared postoperatively in 63% of cases. Pain and sensory disturbance recovered to normal in 92% and 89% of cases, respectively. Abnormal motor nerve conduction velocities improved in 77%. Abductor digiti minimi weakness MMT 0, 1, 2 in 16 hands recovered to MMT 4 or 5 in eight. First-dorsal interosseous weakness in 18 hands recovered to MMT 4 or 5 in seven. There were no complications in this series. The endoscopic approach facilitates inspection of the ulnar nerve so that selective release of the tissue that compresses the nerve can readily be performed. The technique has proven effective in the treatment of cubital tunnel syndrome.
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.
On Linear Spaces of Polyhedral Meshes.
Poranne, Roi; Chen, Renjie; Gotsman, Craig
2015-05-01
Polyhedral meshes (PM)-meshes having planar faces-have enjoyed a rise in popularity in recent years due to their importance in architectural and industrial design. However, they are also notoriously difficult to generate and manipulate. Previous methods start with a smooth surface and then apply elaborate meshing schemes to create polyhedral meshes approximating the surface. In this paper, we describe a reverse approach: given the topology of a mesh, we explore the space of possible planar meshes having that topology. Our approach is based on a complete characterization of the maximal linear spaces of polyhedral meshes contained in the curved manifold of polyhedral meshes with a given topology. We show that these linear spaces can be described as nullspaces of differential operators, much like harmonic functions are nullspaces of the Laplacian operator. An analysis of this operator provides tools for global and local design of a polyhedral mesh, which fully expose the geometric possibilities and limitations of the given topology.
Generating Algorithm of Progressive Mesh Model Based on Edge Collapse%基于边收缩的渐进网格模型生成算法
Institute of Scientific and Technical Information of China (English)
侯宝明; 鄂旭; 毕嘉娜
2013-01-01
为了实现3D模型的渐进式网格模型表示,改进基于边收缩方式模型简化的收缩代价计算方法.本算法首先从SMF数据文件中读取模型数据信息,然后在内存中快速建立起3D模型,重新设计Garland算法中QEM的权值计算方法.以顶点相邻三角平面法向量最大偏差的平方作为顶点的重要程度并将其加入到误差测度公式中,通过简化最终生成渐进式网格模型.实验结果表明,本算法简练,网格模型生成速度快,模型轮廓信息保持完整.%In order to implement progressive mesh representation of 3D model,the calculation method of collapse cost of model simplification based on edge collapse mode is improved.Firstly,model data from SMF data file is obtained,and the 3D model in the memory is established rapidly,and the weight calculation method of Garland's EM algorithm is redesigned.The square of the largest deviation of triangular plane normal adjacent to the vertex is used as the importance degree of vertex,and bring it into error metric formula,by simplifying progressive mesh is generated.The following experiment shows that the algorithm is succinct,and the generating speed of mesh and the contour information of model are completely preserved.
Surface meshing with curvature convergence
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.
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
Lesões do nervo cubital em costureiras de calçados: abordagem medico-social
Directory of Open Access Journals (Sweden)
Lutero Arno Renck
1981-12-01
Full Text Available Foram estudadas 19 pacientes que apresentavam lesão traumática do nervo cubital. Todas eram costureiras de calçados e apoiavam o cotovelo sobre a mesa de trabalho, causando microtraumatismos ao nervo cubital. Os exames eletromiográficos revelaram lesão do neurônio motor periférico. A velocidade de condução nervosa estava diminuída em todos os casos. O tratamento constou de afastamento do serviço, uso de analgésicos, complexo B, corticóide e fisioterapia. Não havendo melhora era preconizada cirurgia, com transposição do nervo cubital. São esplanadas medidas preventivas para este acidente profissional.
DEFF Research Database (Denmark)
Wienecke, T.; Hansen, J.M.; Petersen, J.;
2008-01-01
Arteriovenous anastomoses (AVAs) may open up during migraine attacks. In studies with anaesthetized and bilaterally vagosympatectomized pigs, triptans reduce AVA blood flow and increase the arteriovenous O-2 difference (AVDO(2)). To investigate whether subcutaneous sumatriptan 6 mg could induce...... changes in the AVDO(2), we measured the AVDO(2) in the external jugular vein in healthy subjects. We also measured the AVDO(2) in the internal jugular and cubital veins. There were no changes in AVDO(2) after subcutaneous sumatriptan, probably because AVA blood flow is limited in humans with an intact...
MR anatomy and pathology of the ulnar nerve involving the cubital tunnel and Guyon's canal.
Shen, Luyao; Masih, Sulabha; Patel, Dakshesh B; Matcuk, George R
2016-01-01
Ulnar neuropathy is a common and frequent reason for referral to hand surgeons. Ulnar neuropathy mostly occurs in the cubital tunnel of the elbow or Guyon's canal of the wrist, and it is important for radiologists to understand the imaging anatomy at these common sites of impingement. We will review the imaging and anatomy of the ulnar nerve at the elbow and wrist, and we will present magnetic resonance imaging examples of different causes of ulnar neuropathy, including trauma, overuse, arthritis, masses and mass-like lesions, and systemic diseases. Treatment options will also be briefly discussed.
Dynamic mesh for TCAD modeling with ECORCE
Michez, A.; Boch, J.; Touboul, A.; Saigné, F.
2016-08-01
Mesh generation for TCAD modeling is challenging. Because densities of carriers can change by several orders of magnitude in thin areas, a significant change of the solution can be observed for two very similar meshes. The mesh must be defined at best to minimize this change. To address this issue, a criterion based on polynomial interpolation on adjacent nodes is proposed that adjusts accurately the mesh to the gradients of Degrees of Freedom. Furthermore, a dynamic mesh that follows changes of DF in DC and transient mode is a powerful tool for TCAD users. But, in transient modeling, adding nodes to a mesh induces oscillations in the solution that appears as spikes at the current collected at the contacts. This paper proposes two schemes that solve this problem. Examples show that using these techniques, the dynamic mesh generator of the TCAD tool ECORCE handle semiconductors devices in DC and transient mode.
Directory of Open Access Journals (Sweden)
Marco Sousa
2014-12-01
Full Text Available Objective:To compare the results from two of the most commonly used surgical techniques: in situ decompression and subcutaneous transposition. The processes of patients treated surgically in a public university hospital between January 2004 and December 2011 were reviewed. Cases of proximal compression of the nerve, angular deformity of the elbow and systemic diseases associated with non-compressive neuropathy were excluded.Methods:Ninety-seven cases were included (96 patients. According to the modified McGowan score, 14.4% of the patients presented grade Ia, 27.8% grade II, 26.8% grade IIb and 30.9% grade III. In situ neurolysis of the cubital was performed in 64 cases and subcutaneous anterior transposition in 33.Results:According to the modified Wilson and Knout score, the results were excellent in 49.5%, good in 18.6%, only satisfactory in 17.5% and poor in 14.4%. In comparing the two techniques, we observed similar numbers of excellent and good results. Grades IIb and III were associated with more results that were less satisfactory or poor, independent of the surgical technique.Conclusion:Both techniques were shown to be efficient and safe for treating cubital tunnel syndrome.
... Prosthetics Hernia Surgical Mesh Implants Hernia Surgical Mesh Implants Share Tweet Linkedin Pin it More sharing options ... majority of tissue used to produce these mesh implants are from a pig (porcine) or cow (bovine) ...
Urogynecologic Surgical Mesh Implants
... Prosthetics Urogynecologic Surgical Mesh Implants Urogynecologic Surgical Mesh Implants Share Tweet Linkedin Pin it More sharing options ... majority of tissue used to produce these mesh implants are from a pig (porcine) or cow (bovine). ...
S, Kyriacou; E, Kontoleontos; S, Weissenberger; L, Mangani; E, Casartelli; I, Skouteropoulou; M, Gattringer; A, Gehrer; M, Buchmayr
2014-03-01
An efficient hydraulic optimization procedure, suitable for industrial use, requires an advanced optimization tool (EASY software), a fast solver (block coupled CFD) and a flexible geometry generation tool. EASY optimization software is a PCA-driven metamodel-assisted Evolutionary Algorithm (MAEA (PCA)) that can be used in both single- (SOO) and multiobjective optimization (MOO) problems. In MAEAs, low cost surrogate evaluation models are used to screen out non-promising individuals during the evolution and exclude them from the expensive, problem specific evaluation, here the solution of Navier-Stokes equations. For additional reduction of the optimization CPU cost, the PCA technique is used to identify dependences among the design variables and to exploit them in order to efficiently drive the application of the evolution operators. To further enhance the hydraulic optimization procedure, a very robust and fast Navier-Stokes solver has been developed. This incompressible CFD solver employs a pressure-based block-coupled approach, solving the governing equations simultaneously. This method, apart from being robust and fast, also provides a big gain in terms of computational cost. In order to optimize the geometry of hydraulic machines, an automatic geometry and mesh generation tool is necessary. The geometry generation tool used in this work is entirely based on b-spline curves and surfaces. In what follows, the components of the tool chain are outlined in some detail and the optimization results of hydraulic machine components are shown in order to demonstrate the performance of the presented optimization procedure.
Litvin, Faydor L.; Nava, Alessandro; Fan, Qi; Fuentes, Alfonso
2002-01-01
New geometry of face worm gear drives with conical and cylindrical worms is proposed. The generation of the face worm-gear is based on application of a tilted head-cutter (grinding tool) instead of application of a hob applied at present. The generation of a conjugated worm is based on application of a tilted head-cutter (grinding tool) as well. The bearing contact of the gear drive is localized and is oriented longitudinally. A predesigned parabolic function of transmission errors for reduction of noise and vibration is provided. The stress analysis of the gear drive is performed using a three-dimensional finite element analysis. The contacting model is automatically generated. The developed theory is illustrated with numerical examples.
Institute of Scientific and Technical Information of China (English)
孟纬; 潘昊鹏; 朱伟
2013-01-01
Objective To investigate the relationship between the elbow flexion angle and the cubital tunnel pressure in patients with cubital tunnel syndrome.Methods Between June 2010 and June 2011,63 patients with cubital tunnel syndrome were treated.There were 47 males and 16 females with an average age of 59 years (range,31-80 years).The lesion was at left side in 18 cases and at right side in 45 cases.During anterior transposition of ulnar nerve,the cubital tunnel pressure values were measured at full elbow extension,elbow flexion of 30,60,and 90°,and full elbow flexion with microsensor.The elbow flexion angle-cubital tunnel pressure curve was drawn.Results The cubital tunnel pressure increased smoothly with increased elbow flexion angle when the elbow flexed less than 60°,and the pressure increased sharply when the elbow flexed more than 90°.The cubital tunnel pressure values were (0.13 ± 0.15),(1.75 ± 0.30),(2.62 ± 0.34),(5.78 ± 0.47),and (11.40 ±0.62) kPa,respectively at full elbow extension,elbow flexion of 30,60,and 90°,and full elbow flexion,showing significant differences among different angles (P ＜ 0.05).Conclusion The cubital tunnel pressure will increase sharply when the elbow flexes more than 90°,which leads to the chronic ischemic damage to ulnar nerve.Long-term ischemic damage will induce cubital tunnel syndrome.%目的 通过测定肘管综合征患者不同屈肘角度时肘管内压力,探讨肘管内压力与屈肘角度间的关系.方法 2010年6月-2011年6月,收治63例单侧肘管综合征患者.男47例,女16例;年龄31～80岁,平均59岁.左侧18例,右侧45例.于尺神经前移术中,采用颅内微型传感器测量最大伸肘位,屈肘30、60、90°和最大屈肘位时肘管内压力,绘制屈肘角度-压力曲线.结果 肘管内压力随屈肘角度增加而增大,屈肘超过90°时显著增大.最大伸肘位,屈肘30、60、90°和最大屈肘位时肘管内压力分别为(0.13±0.15)、(1.75±0.30)、(2.62±0.34)、(5
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
Energy Technology Data Exchange (ETDEWEB)
Palmer, T.S.; Zika, M.R.; Madsen, N.K.
2000-07-27
Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module.
Delaunay triangulation and computational fluid dynamics meshes
Posenau, Mary-Anne K.; Mount, David M.
1992-01-01
In aerospace computational fluid dynamics (CFD) calculations, the Delaunay triangulation of suitable quadrilateral meshes can lead to unsuitable triangulated meshes. Here, we present case studies which illustrate the limitations of using structured grid generation methods which produce points in a curvilinear coordinate system for subsequent triangulations for CFD applications. We discuss conditions under which meshes of quadrilateral elements may not produce a Delaunay triangulation suitable for CFD calculations, particularly with regard to high aspect ratio, skewed quadrilateral elements.
Directory of Open Access Journals (Sweden)
Aya Yoshida
2014-07-01
Full Text Available To minimize damage to healthy tissues, we have been performing endoscopically assisted cubital tunnel syndrome surgery based on endoscopic nerve findings since 1995. This is the first study to focus on endoscopic surgery for cubital tunnel syndrome based on endoscopic ulnar nerve findings and the subsequent postoperative clinical results. We analysed 82 upper extremities of 74 cubital tunnel syndrome patients who had undergone endoscopically assisted release surgery using the Universal Subcutaneous Endoscope system. Endoscopic observations of the ulnar nerve were made from a single 1- to 3-cm endoscopic portal incision at the cubital tunnel to 10 cm proximal and 10 cm distal. The abnormal nerve areas were identified and released based on nerve degeneration findings under endoscopic observation. The abnormal areas spread eccentrically from the entrapment point(s. In 82 diseased upper extremities, ulnar nerve entrapment occurred at the cubital tunnel. However, one extremity suffered from entrapment at the arcade of Struthers' in addition to the cubital tunnel. All patients showed improved clinical symptoms following surgery. There is no statistical relation between pre- and postoperative clinical scores of Dellon's Staging and abnormal nerve length findings. Cubital tunnel syndrome is usually caused by entrapment at the cubital tunnel; however, in some cases, there are other point entrapment(s. Our endoscopically assisted procedure avoids any damage to healthy tissues because the surgeon can observe the entrapment point(s prior to release. Postoperative clinical recovery results clearly indicate that endoscopic nerve findings reveal entrapment points and ulnar nerve degeneration can spread maximally 10 cm distally and proximally from the entrapment point(s, even in clinically mild severity cases. All other possible entrapment points should, therefore, be observed and released using our procedure.
Directory of Open Access Journals (Sweden)
A. León Garrigosa
2017-03-01
Conclusiones: El dolor en el margen cubital de la mano, con tenosinovitis flexora de los tendones del cuarto y quinto dedos y/o manifestaciones de neuropatía cubital distal, cuando se produce en pacientes que practican deporte de empuñadura, obliga a realizar tomografía axial computerizada, y, si hay pseudoartrosis del gancho del hueso ganchoso, intentar su osteosíntesis.
2015-01-01
Cubital tunnel syndrome is often accompanied by paresthesia in ulnar nerve sites and hand muscle atrophy. When muscle weakness occurs, or after failure of more conservative treatments, anterior transposition is used. In the present study, the ulnar nerve and its blood vessels were examined in the elbows of 18 adult cadavers, and the external diameter of the nutrient vessels of the ulnar nerve at the point of origin, the distances between the origin of the vessels and the medial epicondyle of ...
DEFF Research Database (Denmark)
Henriksen, J H; Ring-Larsen, H; Christensen, N J
1986-01-01
The concentration of noradrenaline (NA) and adrenaline (A) was measured in arterial, cubital venous and femoral venous plasma in order to determine possible differences in different vascular beds in the peripheral circulation. In patients with cirrhosis, arterial plasma NA (median 2.54 nmol/l, n ...... the skin of forearm and hand). To assess circulating levels of catecholamines, the importance of arterial sampling is stressed as peripheral venous samples may also reflect local factors....
Li, Mei-Xiu-Li; He, Qiong; Hu, Zhong-Lin; Chen, Sheng-Hua; Lv, Yun-Cheng; Liu, Zheng-Hai; Wen, Yong; Peng, Tian-Hong
2015-01-01
Cubital tunnel syndrome is often accompanied by paresthesia in ulnar nerve sites and hand muscle atrophy. When muscle weakness occurs, or after failure of more conservative treatments, anterior transposition is used. In the present study, the ulnar nerve and its blood vessels were examined in the elbows of 18 adult cadavers, and the external diameter of the nutrient vessels of the ulnar nerve at the point of origin, the distances between the origin of the vessels and the medial epicondyle of the humerus, and the length of the vessels accompanying the ulnar nerve in the superior ulnar collateral artery, the inferior ulnar collateral artery, and the posterior ulnar recurrent artery were measured. Anterior transposition of the vascularized ulnar nerve was performed to treat cubital tunnel syndrome. The most appropriate distance that the vascularized ulnar nerve can be moved to the subcutaneous tissue under tension-free conditions was 1.8 ± 0.6 cm (1.1-2.5 cm), which can be used as a reference value during the treatment of cubital tunnel syndrome with anterior transposition of the vascularized ulnar nerve.
Directory of Open Access Journals (Sweden)
Abolghassem Zarezadeh
2012-01-01
Full Text Available Background: This study was designed to compare two methods of surgery, anterior subcutaneous transposition (ASCT and anterior submuscular transposition (ASMT of the ulnar nerve in treatment of cubital tunnel syndrome. Materials and Methods: This randomized trial study was conducted from October 2008 to March 2009 in the Department of Orthopedic Surgery at University Hospital. Forty-eight patients with confirmed cubital tunnel syndrome were randomized in two groups, and each patient received one of two different surgical treatment methods, either ASCT (n = 24 or ASMT (n = 24. In the ASCT technique, the ulnar nerve was transposed and retained in the subcutaneous bed, whereas in the ASMT, the nerve was retained deep in the transected muscular complex, near the median nerve. Patient outcomes, including pain, sensation, muscle strength, and muscle atrophy were compared between groups. Results: The two groups were similar in baseline characteristics. However, those treated with ASMT had a statistically significant reduction in their pain levels compared with ASCT (21 (87.5% vs 8 (33.3%, P 0.05. Conclusions: Our results indicate that ASMT are more efficient than ASCT for managing cubital tunnel syndrome. In patients who had ASMT, there were significant reductions of pain compared with ASCT.
Directory of Open Access Journals (Sweden)
Mei-xiu-li Li
2015-01-01
Full Text Available Cubital tunnel syndrome is often accompanied by paresthesia in ulnar nerve sites and hand muscle atrophy. When muscle weakness occurs, or after failure of more conservative treatments, anterior transposition is used. In the present study, the ulnar nerve and its blood vessels were examined in the elbows of 18 adult cadavers, and the external diameter of the nutrient vessels of the ulnar nerve at the point of origin, the distances between the origin of the vessels and the medial epicondyle of the humerus, and the length of the vessels accompanying the ulnar nerve in the superior ulnar collateral artery, the inferior ulnar collateral artery, and the posterior ulnar recurrent artery were measured. Anterior transposition of the vascularized ulnar nerve was performed to treat cubital tunnel syndrome. The most appropriate distance that the vascularized ulnar nerve can be moved to the subcutaneous tissue under tension-free conditions was 1.8 ± 0.6 cm (1.1-2.5 cm, which can be used as a reference value during the treatment of cubital tunnel syndrome with anterior transposition of the vascularized ulnar nerve.
Institute of Scientific and Technical Information of China (English)
Mei-xiu-li Li; Qiong He; Zhong-lin Hu; Sheng-hua Chen; Yun-cheng Lv; Zheng-hai Liu; Yong Wen; Tian-hong Peng
2015-01-01
Cubital tunnel syndrome is often accompanied by paresthesia in ulnar nerve sites and hand muscle atrophy. When muscle weakness occurs, or after failure of more conservative treatments, anterior transposition is used. In the present study, the ulnar nerve and its blood vessels were examined in the elbows of 18 adult cadavers, and the external diameter of the nutrient vessels of the ulnar nerve at the point of origin, the distances between the origin of the vessels and the medial epicondyle of the humerus, and the length of the vessels accompanying the ulnar nerve in the superior ulnar collateral artery, the inferior ulnar collateral artery, and the posterior ulnar recurrent artery were measured. Anterior transposition of the vascularized ulnar nerve was per-formed to treat cubital tunnel syndrome. The most appropriate distance that the vascularized ulnar nerve can be moved to the subcutaneous tissue under tension-free conditions was 1.8 ± 0.6 cm (1.1–2.5 cm), which can be used as a reference value during the treatment of cubital tunnel syndrome with anterior transposition of the vascularized ulnar nerve.
Pei Ping; YURY N. PETRENKO
2015-01-01
A Mesh network simulation framework which provides a powerful and concise modeling chain for a network structure will be introduce in this report. Mesh networks has a special topologic structure. The paper investigates a message transfer in wireless mesh network simulation and how does it works in cellular network simulation. Finally the experimental result gave us the information that mesh networks have different principle in transmission way with cellular networks in transmission, and multi...
Results after simple decompression of the ulnar nerve in cubital tunnel syndrome.
Harder, Kristina; Lukschu, Sandra; Dunda, Sebastian E; Krapohl, Björn Dirk
2015-01-01
Cubital tunnel syndrome represents the second most common compression neuropathy of the upper limb. For more than four decades there has been a controversy about the best surgical treatment modality for cubital tunnel syndrome. In this study the results of 28 patients with simple ulnar nerve decompression are presented. Data analyses refers to clinical examination, personal interview, DASH-questionnaire, and electrophysiological measurements, which were assessed pre- and postoperatively. 28 patients (15 females, 13 males) were included in this study. The average age at time of surgery was 47.78 years (31.68-73.10 years). The period from onset of symptoms to surgery ranged from 2 to 24 months (mean 6 months). The mean follow-up was 2.11 years (0.91-4.16 years). Postoperatively there was a significant decrease in DASH score from 52.6 points to 13.3 points (pnerve conduction velocity increased from 36.0 m/s to 44.4 m/s (p=0.008) and the motor nerve action potential reached 5,470 mV compared to 3,665 mV preoperatively (p=0.018). A significant increase of grip strength from 59% (in comparison to the healthy hand) to 80% was observed (p=0.002). Pain was indicated by means of a visual analog scale from 0 to 100. Preoperatively the median level of pain was 29 and postoperatively it was 0 (p=0.001). The decrease of the two-point-discrimination of the three ulnar finger nerves was also highly significant (p<0.001) from 11.3 mm to 5.0 mm. Significant postoperative improvement was also observed in the clinical examination concerning muscle atrophy (p=0.002), clawing (p=0.008), paresthesia (p=0.004), the sign of Froment (p=0.004), the sign of Hoffmann-Tinel (p=0.021), and clumsiness (p=0.002). Overall nearly 90% of all patients were satisfied with the result of the operation. In 96.4% of all cases, surgery improved the symptoms and in one patient (3.6%) the success was noted as "poor" because the symptoms remained unchanged. In 35.7% the success was graded as "moderate", in 10
Results after simple decompression of the ulnar nerve in cubital tunnel syndrome
Directory of Open Access Journals (Sweden)
Harder, Kristina
2015-12-01
Full Text Available Cubital tunnel syndrome represents the second most common compression neuropathy of the upper limb. For more than four decades there has been a controversy about the best surgical treatment modality for cubital tunnel syndrome. In this study the results of 28 patients with simple ulnar nerve decompression are presented. Data analyses refers to clinical examination, personal interview, DASH-questionnaire, and electrophysiological measurements, which were assessed pre- and postoperatively.28 patients (15 females, 13 males were included in this study. The average age at time of surgery was 47.78 years (31.68–73.10 years. The period from onset of symptoms to surgery ranged from 2 to (mean 6 months. The mean follow-up was 2.11 years (0.91–Postoperatively there was a significant decrease in DASH score from 52.6 points to 13.3 points (p<0.001. Also the electrophysiological findings improved significantly: motor nerve conduction velocity increased from 36.0 m/s to 44.4 m/s (p=0.008 and the motor nerve action potential reached 5,470 mV compared to 3,665 mV preoperatively (p=0.018. A significant increase of grip strength from 59% (in comparison to the healthy hand to 80% was observed (p=0.002. Pain was indicated by means of a visual analog scale from 0 to 100. Preoperatively the median level of pain was 29 and postoperatively it was 0 (p=0.001. The decrease of the two-point-discrimination of the three ulnar finger nerves was also highly significant (p<0.001 from 11.3 mm to 5.0 mm. Significant postoperative improvement was also observed in the clinical examination concerning muscle atrophy (p=0.002, clawing (p=0.008, paresthesia (p=0.004, the sign of Froment (p=0.004, the sign of Hoffmann-Tinel (p=0.021, and clumsiness (p=0.002.Overall nearly 90% of all patients were satisfied with the result of the operation. In 96.4% of all cases, surgery improved the symptoms and in one patient (3.6% the success was noted as “poor” because the symptoms remained
Connectivity editing for quadrilateral meshes
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
Peng, Chihan
2011-12-01
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 high-level 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.
Energy Technology Data Exchange (ETDEWEB)
Sohn, Yu Mee; Hong, Suk Joo; Yoon, Joon Shik; Park, Cheol Min [Korea University Guro Hospital, Seoul (Korea, Republic of); Kim, Jung Hyuk [Korea University Auam Hospital, Seoul (Korea, Republic of)
2006-06-15
To prospectively evaluate the accuracy of sonography for diagnosis of cubital tunnel syndrome (CUTS) confirmed by electrodiagnostic study. From February 2004 to March 2005, we prospectively analyzed 24 elbows in 19 patients (8 women, 11 men: mean age, 49.2 years: range 23-65 years) with cubital tunnel syndrome, including 5 bilateral cases. Diagnoses of CUTS were confirmed by both clinical symptom and electrodiagnostic study. Sonographic findings of 20 asymptomatic cases served as controls. In sonographic examination, the cross sectional area of the ulnar nerve was measured at the inlet (at the level of medial epicondyle) and outlet (at the level of convergence of flexor carpi ulnaris tendons) of the cubital tunnel. The shape and echogenicity of the ulnar nerve were also evaluated, as were possible causes of entrapment. The accuracy of using ultrasonographic cross sectional area to diagnose CUTS was evaluated with receiver operating characteristic (ROC) analysis. The cross sectional area of the ulnar nerve at the inlet and outlet levels in CUTS patients was increased much more than in the asymptomatic cases. Decreased echogenicity and distortion of normal parallel echotexture of the ulnar nerve were observed in all CUTS patients. At the inlet level, the area under the ROC curve (AUC) was 0.816, and the ideal cut-off value for CUTS diagnosis was 0.08 cm{sup 2} with a sensitivity of 58.3%, specificity of 100%, positive predictive value (PPV) of 100%, and negative predictive value (NPV) of 66.7%. At the distal outlet level, the AUC was 0.785, and the cut-off value was 0.06 cm{sup 2} with a sensitivity of 79.2%, specificity of 70%, PPV of 76%, and NPV of 73.7%. When the summation value of inlet and outlet cross sectional areas was used, the AUC was 0.853, and cut-off value was 0.14 cm{sup 2} with a sensitivity of 70.8%, specificity of 85%, PPV of 85%, and NPV of 70.8%. Measurement of the cross sectional area of the ulnar nerve at the inlet and outlet of the cubital
Ochi, Kensuke; Horiuchi, Yukio; Nakamura, Toshiyasu; Sato, Kazuki; Morita, Kozo; Horiuchi, Koichi
2014-01-01
Pathophysiology of cubital tunnel syndrome (CubTS) is still controversial. Ulnar nerve strain at the elbow was measured intraoperatively in 13 patients with CubTS before simple decompression. The patients were divided into three groups according to their accompanying conditions: compression/adhesion, idiopathic, and relaxation groups. The mean ulnar nerve strain was 43.5 ± 30.0%, 25.5 ± 14.8%, and 9.0 ± 5.0% in the compression/adhesion, idiopathic, and relaxation groups respectively. The mean ulnar nerve strains in patients with McGowan's classification grades I, II, and III were 18.0 ± 4.2%, 27.1 ± 22.7%, and 33.7 ± 24.7%, respectively. The Jonckheere-Terpstra test showed that there were significant reductions in the ulnar nerve strain among the first three groups, but not in the three groups according to McGowan's classification. Our results suggest that the pathophysiology, not disease severity, of CubTS may be explained at least in part by the presence of ulnar nerve strain.
MR neurography of ulnar nerve entrapment at the cubital tunnel: a diffusion tensor imaging study
Energy Technology Data Exchange (ETDEWEB)
Breitenseher, Julia B.; Berzaczy, Dominik; Nemec, Stefan F.; Weber, Michael; Prayer, Daniela; Kasprian, Gregor [Medical University of Vienna, Department of Biomedical Imaging and Image-guided Therapy, Vienna (Austria); Kranz, Gottfried; Sycha, Thomas [Medical University of Vienna, Department of Neurology, Vienna (Austria); Hold, Alina [Medical University of Vienna, Department of Plastic and Reconstructive Surgery, Vienna (Austria)
2015-07-15
MR neurography, diffusion tensor imaging (DTI) and tractography at 3 Tesla were evaluated for the assessment of patients with ulnar neuropathy at the elbow (UNE). Axial T2-weighted and single-shot DTI sequences (16 gradient encoding directions) were acquired, covering the cubital tunnel of 46 patients with clinically and electrodiagnostically confirmed UNE and 20 healthy controls. Cross-sectional area (CSA) was measured at the retrocondylar sulcus and FA and ADC values on each section along the ulnar nerve. Three-dimensional nerve tractography and T2-weighted neurography results were independently assessed by two raters. Patients showed a significant reduction of ulnar nerve FA values at the retrocondylar sulcus (p = 0.002) and the deep flexor fascia (p = 0.005). At tractography, a complete or partial discontinuity of the ulnar nerve was found in 26/40 (65 %) of patients. Assessment of T2 neurography was most sensitive in detecting UNE (sensitivity, 91 %; specificity, 79 %), followed by tractography (88 %/69 %). CSA and FA measurements were less effective in detecting UNE. T2-weighted neurography remains the most sensitive MR technique in the imaging evaluation of clinically manifest UNE. DTI-based neurography at 3 Tesla supports the MR imaging assessment of UNE patients by adding quantitative and 3D imaging data. (orig.)
Mesh convergence study for hydraulic turbine draft-tube
Devals, C.; Vu, T. C.; Zhang, Y.; Dompierre, J.; Guibault, F.
2016-11-01
Computational flow analysis is an essential tool for hydraulic turbine designers. Grid generation is the first step in the flow analysis process. Grid quality and solution accuracy are strongly linked. Even though many studies have addressed the issue of mesh independence, there is still no definitive consensus on mesh best practices, and research on that topic is still needed. This paper presents a mesh convergence study for turbulence flow in hydraulic turbine draft- tubes which represents the most challenging turbine component for CFD predictions. The findings from this parametric study will be incorporated as mesh control rules in an in-house automatic mesh generator for turbine components.
MOAB : a mesh-oriented database.
Energy Technology Data Exchange (ETDEWEB)
Tautges, Timothy James; Ernst, Corey; Stimpson, Clint; Meyers, Ray J.; Merkley, Karl
2004-04-01
A finite element mesh is used to decompose a continuous domain into a discretized representation. The finite element method solves PDEs on this mesh by modeling complex functions as a set of simple basis functions with coefficients at mesh vertices and prescribed continuity between elements. The mesh is one of the fundamental types of data linking the various tools in the FEA process (mesh generation, analysis, visualization, etc.). Thus, the representation of mesh data and operations on those data play a very important role in FEA-based simulations. MOAB is a component for representing and evaluating mesh data. MOAB can store structured and unstructured mesh, consisting of elements in the finite element 'zoo'. The functional interface to MOAB is simple yet powerful, allowing the representation of many types of metadata commonly found on the mesh. MOAB is optimized for efficiency in space and time, based on access to mesh in chunks rather than through individual entities, while also versatile enough to support individual entity access. The MOAB data model consists of a mesh interface instance, mesh entities (vertices and elements), sets, and tags. Entities are addressed through handles rather than pointers, to allow the underlying representation of an entity to change without changing the handle to that entity. Sets are arbitrary groupings of mesh entities and other sets. Sets also support parent/child relationships as a relation distinct from sets containing other sets. The directed-graph provided by set parent/child relationships is useful for modeling topological relations from a geometric model or other metadata. Tags are named data which can be assigned to the mesh as a whole, individual entities, or sets. Tags are a mechanism for attaching data to individual entities and sets are a mechanism for describing relations between entities; the combination of these two mechanisms is a powerful yet simple interface for representing metadata or application
A comparison of tetrahedral mesh improvement techniques
Energy Technology Data Exchange (ETDEWEB)
Freitag, L.A.; Ollivier-Gooch, C. [Argonne National Lab., IL (United States). Mathematics and Computer Science Div.
1996-12-01
Automatic mesh generation and adaptive refinement methods for complex three-dimensional domains have proven to be very successful tools for the efficient solution of complex applications problems. These methods can, however, produce poorly shaped elements that cause the numerical solution to be less accurate and more difficult to compute. Fortunately, the shape of the elements can be improved through several mechanisms, including face-swapping techniques that change local connectivity and optimization-based mesh smoothing methods that adjust grid point location. The authors consider several criteria for each of these two methods and compare the quality of several meshes obtained by using different combinations of swapping and smoothing. Computational experiments show that swapping is critical to the improvement of general mesh quality and that optimization-based smoothing is highly effective in eliminating very small and very large angles. The highest quality meshes are obtained by using a combination of swapping and smoothing techniques.
On combining Laplacian and optimization-based mesh smoothing techniques
Energy Technology Data Exchange (ETDEWEB)
Freitag, L.A.
1997-07-01
Local mesh smoothing algorithms have been shown to be effective in repairing distorted elements in automatically generated meshes. The simplest such algorithm is Laplacian smoothing, which moves grid points to the geometric center of incident vertices. Unfortunately, this method operates heuristically and can create invalid meshes or elements of worse quality than those contained in the original mesh. In contrast, optimization-based methods are designed to maximize some measure of mesh quality and are very effective at eliminating extremal angles in the mesh. These improvements come at a higher computational cost, however. In this article the author proposes three smoothing techniques that combine a smart variant of Laplacian smoothing with an optimization-based approach. Several numerical experiments are performed that compare the mesh quality and computational cost for each of the methods in two and three dimensions. The author finds that the combined approaches are very cost effective and yield high-quality meshes.
2015-01-01
With the advances in mobile computing technologies and the growth of the Net, mobile mesh networks are going through a set of important evolutionary steps. In this paper, we survey architectural aspects of mobile mesh networks and their use cases and deployment models. Also, we survey challenging areas of mobile mesh networks and describe our vision of promising mobile services. This paper presents a basic introductory material for Masters of Open Information Technologies Lab, interested in m...
MR neurography of ulnar nerve entrapment at the cubital tunnel: a diffusion tensor imaging study.
Breitenseher, Julia B; Kranz, Gottfried; Hold, Alina; Berzaczy, Dominik; Nemec, Stefan F; Sycha, Thomas; Weber, Michael; Prayer, Daniela; Kasprian, Gregor
2015-07-01
MR neurography, diffusion tensor imaging (DTI) and tractography at 3 Tesla were evaluated for the assessment of patients with ulnar neuropathy at the elbow (UNE). Axial T2-weighted and single-shot DTI sequences (16 gradient encoding directions) were acquired, covering the cubital tunnel of 46 patients with clinically and electrodiagnostically confirmed UNE and 20 healthy controls. Cross-sectional area (CSA) was measured at the retrocondylar sulcus and FA and ADC values on each section along the ulnar nerve. Three-dimensional nerve tractography and T2-weighted neurography results were independently assessed by two raters. Patients showed a significant reduction of ulnar nerve FA values at the retrocondylar sulcus (p = 0.002) and the deep flexor fascia (p = 0.005). At tractography, a complete or partial discontinuity of the ulnar nerve was found in 26/40 (65%) of patients. Assessment of T2 neurography was most sensitive in detecting UNE (sensitivity, 91%; specificity, 79%), followed by tractography (88%/69%). CSA and FA measurements were less effective in detecting UNE. T2-weighted neurography remains the most sensitive MR technique in the imaging evaluation of clinically manifest UNE. DTI-based neurography at 3 Tesla supports the MR imaging assessment of UNE patients by adding quantitative and 3D imaging data. • DTI and tractography support conventional MR neurography in the detection of UNE • Regionally reduced FA values and discontinuous tractography patterns indicate UNE • T2-weighted MR neurography remains the imaging gold standard in cases of UNE • DTI-based ulnar nerve tractography offers additional topographic information in 3D.
Chow, James C Y; Papachristos, Athanasios A; Ojeda, Alvaro
2006-10-01
We report on a patient with an unusual anatomic variation along the course of ulnar nerve above the elbow who had cubital tunnel syndrome. The variation consisted of a cutaneous neural branch that was originating at a distance of approximately 40 mm proximal to the medial epicondyle, and from the radial aspect of the main trunk of ulnar nerve. The branch had a superficial course and it was passing distally, anterior to the medial epicondyle without penetrating the fascia of the flexor muscles origin. Anterior intramuscular transposition of the ulnar nerve was performed leaving the newly found branch over the fascia between the muscles and the adipose subcutaneous tissue.
弹簧近似法在二维非结构动网格生成技术中的应用%Spring analogy method for generating of 2D unstructured dynamic meshes
Institute of Scientific and Technical Information of China (English)
霍世慧; 王富生; 岳珠峰
2011-01-01
Spring analogy method (SAM) was improved through controlling mesh quality here. Then, its results were compared with those obtained through the traditional SAM. It was shown from numerical simulations that mesh quality declines with increase in rotation angle in the unstructured dynamic meshes based on SAM; the quality of the mesh generated with the improved SAM is better than that generated with the traditional SAM for the same rotation angles; mesh deformation capability of the improved SAM is larger than that of the traditional SAM; the max rotation angle of the model boundary is about 13° with the traditional SAM and 27° with the improved SAM. Finally, numerical simulations of a two-dimensional airfoil using the improved SAM were conducted. It was found that the results of the improved SAM show a better agreement with the experiment ones; the improved SAM can be used in real numerical simulations effectively.%通过控制网格质量改进弹簧近似法,并将其结果与传统方法进行比较.数值模拟结果显示:基于弹簧近似法的非结构动网格随着模型边界旋转角度的增加网格质量逐渐下降;在发生相同旋转角度时,改进弹簧近似法生成网格的质量较传统方法有了较大的改善;传统弹簧近似法模型边界最大旋转角度为13°左右,改进方法可达到27°,较大地提高了网格的变形能力.最后,运用改进的弹簧近似法对二维翼型进行数值模拟,并与传统方法及实验数据进行比较,得到了较满意的结果,该方法能够较好地运用于实际数值模拟中.
Directory of Open Access Journals (Sweden)
Nilton Alves
2012-12-01
Full Text Available O objetivo deste estudo é contribuir para o conhecimento que auxilie o profissional de enfermagem na identificação dos tipos mais comuns de formações venosas da região da fossa cubital e, ainda, enfocar a importância de estar sempre atento aos casos pouco comuns como o aqui relatado. Através de uma revisão bibliográfica, constatamos que as formações venosas dessa região podem ser classificadas em 5 tipos mais comuns, sendo o tipo II o mais frequente. Constatamos ainda, que a VICo é o local de punção mais indicado, seguido pela VIB. Descrevemos também uma variação anatômica, onde observamos ausência de comunicação entre VC e VB no nível da fossa cubital e VIA drenando na VB, estando presente a VCA.El objetivo de esta investigación es contribuir al conocimiento que auxilie al profesional de enfermería en la identificación de los tipos más comunes de formaciones venosas de la fosa cubital, además de advertir sobre la importancia de fijar la atención a los casos poco comunes, como lo aquí reportado. A través de la revisión bibliográfica, clasificamos las formaciones venosas de esta región en cinco tipos más comunes, siendo lo más frecuente el Tipo II. La utilización de la VICo se recomienda como el mejor sitio de punción, seguido por la VIB. Además, describimos una variación anatómica, donde se observó la ausencia de comunicación entre VC y VB a nivel de fosa cubital y VIA drenando en VB, con presencia de la VCA.The aim of this study is to contribute to the knowledge to assists the nursing staff to identify the most common types of venous formations of the cubital fossa region, and also focus on the importance of always being alert to unusual cases as that reported here. Through a literature review, we found that the venous formations of this region can be classified into five common types, bring the Type II the was most frequent. We also found that MCV is considered the best puncture site, followed by MBV
Robust moving mesh algorithms for hybrid stretched meshes: Application to moving boundaries problems
Landry, Jonathan; Soulaïmani, Azzeddine; Luke, Edward; Ben Haj Ali, Amine
2016-12-01
A robust Mesh-Mover Algorithm (MMA) approach is designed to adapt meshes of moving boundaries problems. A new methodology is developed from the best combination of well-known algorithms in order to preserve the quality of initial meshes. In most situations, MMAs distribute mesh deformation while preserving a good mesh quality. However, invalid meshes are generated when the motion is complex and/or involves multiple bodies. After studying a few MMA limitations, we propose the following approach: use the Inverse Distance Weighting (IDW) function to produce the displacement field, then apply the Geometric Element Transformation Method (GETMe) smoothing algorithms to improve the resulting mesh quality, and use an untangler to revert negative elements. The proposed approach has been proven efficient to adapt meshes for various realistic aerodynamic motions: a symmetric wing that has suffered large tip bending and twisting and the high-lift components of a swept wing that has moved to different flight stages. Finally, the fluid flow problem has been solved on meshes that have moved and they have produced results close to experimental ones. However, for situations where moving boundaries are too close to each other, more improvements need to be made or other approaches should be taken, such as an overset grid method.
2011-11-01
triangles in two dimensions and tetrahedra ( tets ) in three dimensions. There are many other ways to discretize a region using unstructured meshes, but this...The boundary points associated with the airfoil surface were moved, but all of the interior points remained stationary , which resulted in a mesh
An Adaptive Mesh Algorithm: Mapping the Mesh Variables
Energy Technology Data Exchange (ETDEWEB)
Scannapieco, Anthony J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-07-25
Both thermodynamic and kinematic variables must be mapped. The kinematic variables are defined on a separate kinematic mesh; it is the duel mesh to the thermodynamic mesh. The map of the kinematic variables is done by calculating the contributions of kinematic variables on the old thermodynamic mesh, mapping the kinematic variable contributions onto the new thermodynamic mesh and then synthesizing the mapped kinematic variables on the new kinematic mesh. In this document the map of the thermodynamic variables will be described.
Automatic Scheme Selection for Toolkit Hex Meshing
Energy Technology Data Exchange (ETDEWEB)
TAUTGES,TIMOTHY J.; WHITE,DAVID R.
1999-09-27
Current hexahedral mesh generation techniques rely on a set of meshing tools, which when combined with geometry decomposition leads to an adequate mesh generation process. Of these tools, sweeping tends to be the workhorse algorithm, accounting for at least 50% of most meshing applications. Constraints which must be met for a volume to be sweepable are derived, and it is proven that these constraints are necessary but not sufficient conditions for sweepability. This paper also describes a new algorithm for detecting extruded or sweepable geometries. This algorithm, based on these constraints, uses topological and local geometric information, and is more robust than feature recognition-based algorithms. A method for computing sweep dependencies in volume assemblies is also given. The auto sweep detect and sweep grouping algorithms have been used to reduce interactive user time required to generate all-hexahedral meshes by filtering out non-sweepable volumes needing further decomposition and by allowing concurrent meshing of independent sweep groups. Parts of the auto sweep detect algorithm have also been used to identify independent sweep paths, for use in volume-based interval assignment.
Formações venosas superficiais da fossa cubital: aspectos de interesse para a prática da Enfermagem
Directory of Open Access Journals (Sweden)
Nilton Alves
Full Text Available O objetivo deste estudo é contribuir para o conhecimento que auxilie o profissional de enfermagem na identificação dos tipos mais comuns de formações venosas da região da fossa cubital e, ainda, enfocar a importância de estar sempre atento aos casos pouco comuns como o aqui relatado. Através de uma revisão bibliográfica, constatamos que as formações venosas dessa região podem ser classificadas em 5 tipos mais comuns, sendo o tipo II o mais frequente. Constatamos ainda, que a VICo é o local de punção mais indicado, seguido pela VIB. Descrevemos também uma variação anatômica, onde observamos ausência de comunicação entre VC e VB no nível da fossa cubital e VIA drenando na VB, estando presente a VCA.
Formações venosas superficiais da fossa cubital: aspectos de interesse para a prática da Enfermagem
Directory of Open Access Journals (Sweden)
Nilton Alves
2012-12-01
Full Text Available O objetivo deste estudo é contribuir para o conhecimento que auxilie o profissional de enfermagem na identificação dos tipos mais comuns de formações venosas da região da fossa cubital e, ainda, enfocar a importância de estar sempre atento aos casos pouco comuns como o aqui relatado. Através de uma revisão bibliográfica, constatamos que as formações venosas dessa região podem ser classificadas em 5 tipos mais comuns, sendo o tipo II o mais frequente. Constatamos ainda, que a VICo é o local de punção mais indicado, seguido pela VIB. Descrevemos também uma variação anatômica, onde observamos ausência de comunicação entre VC e VB no nível da fossa cubital e VIA drenando na VB, estando presente a VCA.
21st International Meshing Roundtable
Weill, Jean-Christophe
2013-01-01
This volume contains the articles presented at the 21st International Meshing Roundtable (IMR) organized, in part, by Sandia National Laboratories and was held on October 7–10, 2012 in San Jose, CA, USA. The first IMR was held in 1992, and the conference series has been held annually since. Each year the IMR brings together researchers, developers, and application experts in a variety of disciplines, from all over the world, to present and discuss ideas on mesh generation and related topics. The technical papers in this volume present theoretical and novel ideas and algorithms with practical potential, as well as technical applications in science and engineering, geometric modeling, computer graphics, and visualization.
Effect of Elbow Position on Short-segment Nerve Conduction Study in Cubital Tunnel Syndrome
Institute of Scientific and Technical Information of China (English)
Zhu Liu; Zhi-Rong Jia; Ting-Ting Wang; Xin Shi; Wei Liang
2016-01-01
Background:The appropriate elbow position of short-segment nerve conduction study (SSNCS) to diagnose cubital tunnel syndrome (CubTS) is still controversial.The goal of this study was to determine the effect of different elbow positions at full extension and 70° flexion on SSNCS in CubTS.Methods:In this cross-sectional study,the clinical data of seventy elbows from 59 CubTS patients between September,2011 and December,2014 in the Peking University First Hospital were included as CubTS group.Moreover,thirty healthy volunteers were included as the healthy group.SSNCS were conducted in all subjects at elbow lull extension and 70° elbow flexion.Paired nonparametric test,bivariate correlation,Bland-Altman,and Chi-squared test analysis were used to compare the effectiveness of elbow full extension and 70° flexion elbow positions on SSNCS in CubTS patients.Results:Data of upper limit was calculated from healthy group,and abnormal latency was judged accordingly.CubTS group's latency and compound muscle action potential (CMAP) of each segment at 70° elbow flexion by SSNCS was compared with full extension position,no statistically significant difference were found (all P ＞ 0.05).Latency and CMAP of each segment at elbow full extension and 70° flexion were correlated (all P ＜ 0.01),except the latency of segment of 4 cm to 6 cm above elbow (P =0.43),and the latency (P =0.15) and the CMAP (P =0.06) of segment of 2 cm to 4 cm below elbow.Bivariate correlation and Bland-Altman analysis proved the correlation between elbow full extension and 70° flexion.Especially in segments across the elbow (2 cm above the elbow and 2 cm below it),latency at elbow full extension and 70° flexion were strong direct associated (r =0.83,P ＜ 0.01; r =0.55,P ＜ 0.01),and so did the CMAP (r =0.49,P ＜ 0.01; r =0.72,P ＜ 0.01).There was no statistically significant difference in abnormality of each segment at full extension as measured by SSNCS compared with that at 70° flexion (P ＞ 0
Effects of mesh style and grid convergence on numerical simulation accuracy of centrifugal pump
Institute of Scientific and Technical Information of China (English)
刘厚林; 刘明明; 白羽; 董亮
2015-01-01
In order to evaluate the effects of mesh generation techniques and grid convergence on pump performance in centrifugal pump model, three widely used mesh styles including structured hexahedral, unstructured tetrahedral and hybrid prismatic/tetrahedral meshes were generated for a centrifugal pump model. And quantitative grid convergence was assessed based on a grid convergence index (GCI), which accounts for the degree of grid refinement. The structured, unstructured or hybrid meshes are found to have certain difference for velocity distributions in impeller with the change of grid cell number. And the simulation results have errors to different degrees compared with experimental data. The GCI-value for structured meshes calculated is lower than that for the unstructured and hybrid meshes. Meanwhile, the structured meshes are observed to get more vortexes in impeller passage. Nevertheless, the hybrid meshes are found to have larger low-velocity area at outlet and more secondary vortexes at a specified location than structured meshes and unstructured meshes.
Held, Gilbert
2005-01-01
Wireless mesh networking is a new technology that has the potential to revolutionize how we access the Internet and communicate with co-workers and friends. Wireless Mesh Networks examines the concept and explores its advantages over existing technologies. This book explores existing and future applications, and examines how some of the networking protocols operate.The text offers a detailed analysis of the significant problems affecting wireless mesh networking, including network scale issues, security, and radio frequency interference, and suggests actual and potential solutions for each pro
Mesh implants: An overview of crucial mesh parameters
Institute of Scientific and Technical Information of China (English)
Lei-Ming; Zhu; Philipp; Schuster; Uwe; Klinge
2015-01-01
Hernia repair is one of the most frequently performed surgical interventions that use mesh implants. This article evaluates crucial mesh parameters to facilitate selection of the most appropriate mesh implant, considering raw materials, mesh composition, structure parameters and mechanical parameters. A literature review was performed using the Pub Med database. The most important mesh parameters in the selection of a mesh implant are the raw material, structural parameters and mechanical parameters, which should match the physiological conditions. The structural parameters, especially the porosity, are the most important predictors of the biocompatibility performance of synthetic meshes. Meshes with large pores exhibit less inflammatory infiltrate, connective tissue and scar bridging, which allows increased soft tissue ingrowth. The raw material and combination of raw materials of the used mesh, including potential coatings and textile design, strongly impact the inflammatory reaction to the mesh. Synthetic meshes made from innovative polymers combined with surface coating have been demonstrated to exhibit advantageous behavior in specialized fields. Monofilament, largepore synthetic meshes exhibit advantages. The value of mesh classification based on mesh weight seems to be overestimated. Mechanical properties of meshes, such as anisotropy/isotropy, elasticity and tensile strength, are crucial parameters for predicting mesh performance after implantation.
Botsch, Mario; Pauly, Mark; Alliez, Pierre; Levy, Bruno
2010-01-01
Geometry processing, or mesh processing, is a fast-growing area of research that uses concepts from applied mathematics, computer science, and engineering to design efficient algorithms for the acquisition, reconstruction, analysis, manipulation, simulation, and transmission of complex 3D models. Applications of geometry processing algorithms already cover a wide range of areas from multimedia, entertainment, and classical computer-aided design, to biomedical computing, reverse engineering, and scientific computing. Over the last several years, triangle meshes have become increasingly popular,
Geometrically Consistent Mesh Modification
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.
MeSH Now: automatic MeSH indexing at PubMed scale via learning to rank.
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 F1-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/ .
Bucki, Marek; Payan, Yohan; 10.1016/j.media.2010.02.003
2010-01-01
Finite Element mesh generation remains an important issue for patient specific biomechanical modeling. While some techniques make automatic mesh generation possible, in most cases, manual mesh generation is preferred for better control over the sub-domain representation, element type, layout and refinement that it provides. Yet, this option is time consuming and not suited for intraoperative situations where model generation and computation time is critical. To overcome this problem we propose a fast and automatic mesh generation technique based on the elastic registration of a generic mesh to the specific target organ in conjunction with element regularity and quality correction. This Mesh-Match-and-Repair (MMRep) approach combines control over the mesh structure along with fast and robust meshing capabilities, even in situations where only partial organ geometry is available. The technique was successfully tested on a database of 5 pre-operatively acquired complete femora CT scans, 5 femoral heads partially...
基于图像频谱分析三维网格模型数字浮雕生成算法%Frequency Domain Approach to Generating Bas-relief from 3D Mesh
Institute of Scientific and Technical Information of China (English)
江嘉晋; 刘胜兰; 李博
2011-01-01
由3维模型生成2.5维数字浮雕曲面是最近国内外数字浮雕研究的热点,通过对三维网格模型频率域的能量进行压缩来得到几何高度被压缩的浮雕模型.算法通过对三维模型进行重新采样,获得视线方向上的规则化深度图,然后利用图像傅里叶变换对深度图进行频谱分析,最后将模型高度的压缩转换为频谱域能量系数的压缩来得到浮雕曲面模型.在压缩过程中,应用高通滤波器工具对低频能量进行压缩、应用对数压缩函数对高频边缘压缩,从而使得生成的浮雕达到较好的效果.实例表明在频率域对三维模型的能量进行压缩来生成浮雕是可行的,算法对细节不太丰富的模型同样具有较好的效果.%Automatic generation of 2.5D digital bas-relief from 3D model recently becomes a hot spot in relief design. This paper proposes the algorithm for semi-automatic generation of bas-relief from 3D triangle mesh,and compresses the 3D model through non-linear decreasing geometric energy in the frequency domain. In order to meet the image spectral analysis,the triangle mesh of original models is changed into range image by resampling. In the compression process, the low frequency energy is compressed through high pass filter tools and application of methods such as logarithmic compression function on edge of mesh models to achieve better results. Examples show that generating the bas-relief in frequency domain is feasible,and the model without rich details is used to produce the same better digital bas-relief.
Puckett, B N; Gaston, R G; Lourie, G M
2011-02-01
The purpose of this study was to assess subjective and objective outcomes in treating recurrent cubital tunnel at secondary neurolysis by nerve wrapping with a tissue engineered three-dimensional biomatrix. Five patients with a mean age of 44.1 years and an average follow-up of 13.3 months were included in the study. All patients had improvement in visual analogue scales. Four patients that had preoperative intrinsic atrophy with clawing had no clawing or intrinsic atrophy at final follow-up. Postoperatively, four of the five patients had two-point discrimination of 5 mm. Grip strength on average increased 90%. Three patients had an excellent outcome, one patient had a good outcome, and one patient had a fair outcome. All five patients said they would have surgery again.
Triangulated manifold meshing method preserving molecular surface topology.
Chen, Minxin; Tu, Bin; Lu, Benzhuo
2012-09-01
Generation of manifold mesh is an urgent issue in mathematical simulations of biomolecule using boundary element methods (BEM) or finite element method (FEM). Defects, such as not closed mesh, intersection of elements and missing of small structures, exist in surface meshes generated by most of the current meshing method. Usually the molecular surface meshes produced by existing methods need to be revised carefully by third party software to ensure the surface represents a continuous manifold before being used in a BEM and FEM calculations. Based on the trace technique proposed in our previous work, in this paper, we present an improved meshing method to avoid intersections and preserve the topology of the molecular Gaussian surface. The new method divides the whole Gaussian surface into single valued pieces along each of x, y, z directions by tracing the extreme points along the fold curves on the surface. Numerical test results show that the surface meshes produced by the new method are manifolds and preserve surface topologies. The result surface mesh can also be directly used in surface conforming volume mesh generation for FEM type simulation. Copyright © 2012 Elsevier Inc. All rights reserved.
Locking paralleled GPU-based method research for unstructured mesh generation%基于GPU的加锁并行化非结构网格生成方法研究
Institute of Scientific and Technical Information of China (English)
蔡云龙; 肖素梅; 齐龙
2014-01-01
Defects of consuming time and memory consist in unstructured mesh generation. This paper proposes a novel approach, terming GPU-PDMG, which is GPU parallel unstructured mesh generation based on the framework of CUDA. The technology combines the high-speed parallel GPU and advantages of Delaunay triangulation. It develops a method of locking parallel area dividing, using the CUDA programming model on nVidia GPUs. By analyzing the tested examples’ speedup rate and efficiency, it has evaluated their computing performance. This result is identified in NACA0012 and multi-element airfoil experiment with both the analysis of speedup rate and efficiency and GPU-PDMG is better than any existing GPU algorithms.%非结构网格的生成在时间和内存上有一定的缺陷，这里提出了一种新的方法，命名为GPU-PDMG，是基于CUDA架构的GPU并行非结构网格生成技术。该技术结合了GPU的高速并行计算能力与Delaunay三角化的优点，在英伟达GPU模块下采用CUDA程序模型，开发出了加锁并行区划分技术，通过对NACA0012翼型、多段翼型等算例进行测试，分析此方法的加速比和效率，对其计算性能展开评估。实验结果表明，GPU-PDMG优于现存在的CPU算法的速度，在保证网格质量的同时，提高了效率。
CSIR Research Space (South Africa)
Bogaers, Alfred EJ
2010-01-01
Full Text Available = 30 units, with the initial mesh shown in Figure 1(a). The contour plots use an element shape-size quality indicator defined in [9], where 0 ? fss ? 1, for degenerate and perfect elements respectively. 4.1 Snapshot Generation The first requirement... mesh, generated using NETGEN [17]. (b) Full order mesh optimization. (c) ROM: Coefficient Interpolation. (d) ROM: Coefficient Optimization. Figure 1: Rotation and translation test case. Mesh quality contour plots using quality metric 0 ? fss ? 1 [3...
Gill, S P D; Gibson, B K; Flynn, C; Ibata, R A; Lewis, G F; Gill, Stuart P.D.; Knebe, Alexander; Gibson, Brad K.; Flynn, Chris; Ibata, Rodrigo A.; Lewis, Geraint F.
2002-01-01
An adaptive multi grid approach to simulating the formation of structure from collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle Mesh) is one of the most efficient serial codes available on the cosmological 'market' today. As part of Swinburne University's role in the development of the Square Kilometer Array, we are implementing hydrodynamics, feedback, and radiative transfer within the MLAPM adaptive mesh, in order to simulate baryonic processes relevant to the interstellar and intergalactic media at high redshift. We will outline our progress to date in applying the existing MLAPM to a study of the decay of satellite galaxies within massive host potentials.
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.
Isotopic Implicit Surface Meshing
Boissonnat, Jean-Daniel; Cohen-Steiner, David; Vegter, Gert
2004-01-01
This paper addresses the problem of piecewise linear approximation of implicit surfaces. We first give a criterion ensuring that the zero-set of a smooth function and the one of a piecewise linear approximation of it are isotopic. Then, we deduce from this criterion an implicit surface meshing algor
Institute of Scientific and Technical Information of China (English)
薛倩
2015-01-01
According to the basic idea and the applications of grid ,a kind of quick and accurate algebraic method which is developed by Fortran development system is formulated and used for interpolating coordinates of turbo‐machinery blade section points .The numerical examples show that the new algorithm has rapid convergence ,that the grids generated by pres‐ent method have adjustable density and good orthogonality near the boundary ,the grid generated is practical and mesh quality is good .The method is very useful for generating complicated grids automatically for CFD researchers ,and can be general‐ized for point interpolating of all kinds of 3‐dimensional curves .%论文根据网格法的基本思想和应用，用 Fortran 语言建立了一种快速而精确的代数算法，用于插值计算叶片截面空间点坐标，并给出了相应算例。算例表明生成的网格边界间距可以调节，正交性好，非常实用，质量令人满意。适用于计算流体力学工作者构造各种复杂的计算网格，并可以推广到各种复杂的空间曲线点的插值计算。
GRChombo: Numerical relativity with adaptive mesh refinement
Clough, Katy; Figueras, Pau; Finkel, Hal; Kunesch, Markus; Lim, Eugene A.; Tunyasuvunakool, Saran
2015-12-01
In this work, we introduce {\\mathtt{GRChombo}}: a new numerical relativity code which incorporates full adaptive mesh refinement (AMR) using block structured Berger-Rigoutsos grid generation. The code supports non-trivial ‘many-boxes-in-many-boxes’ mesh hierarchies and massive parallelism through the message passing interface. {\\mathtt{GRChombo}} evolves the Einstein equation using the standard BSSN formalism, with an option to turn on CCZ4 constraint damping if required. The AMR capability permits the study of a range of new physics which has previously been computationally infeasible in a full 3 + 1 setting, while also significantly simplifying the process of setting up the mesh for these problems. We show that {\\mathtt{GRChombo}} can stably and accurately evolve standard spacetimes such as binary black hole mergers and scalar collapses into black holes, demonstrate the performance characteristics of our code, and discuss various physics problems which stand to benefit from the AMR technique.
NASA Lewis Meshed VSAT Workshop meeting summary
Ivancic, William
1993-11-01
NASA Lewis Research Center's Space Electronics Division (SED) hosted a workshop to address specific topics related to future meshed very small-aperture terminal (VSAT) satellite communications networks. The ideas generated by this workshop will help to identify potential markets and focus technology development within the commercial satellite communications industry and NASA. The workshop resulted in recommendations concerning these principal points of interest: the window of opportunity for a meshed VSAT system; system availability; ground terminal antenna sizes; recommended multifrequency for time division multiple access (TDMA) uplink; a packet switch design concept for narrowband; and fault tolerance design concepts. This report presents a summary of group presentations and discussion associated with the technological, economic, and operational issues of meshed VSAT architectures that utilize processing satellites.
Directory of Open Access Journals (Sweden)
Chun-Hua Liu
Full Text Available To pool reliable evidences for the optimum anterior transposition technique in the treatment of cubital tunnel syndrome by comparing the clinical efficacy of subcutaneous and submuscular anterior ulnar nerve transposition.A comprehensive search was conducted in PubMed MEDLINE, Cochrane Library, EMBASE, Web of Science, OVID AMED, EBSCO and potentially relevant surgical archives. Risk of bias of each included studies was evaluated according to Cochrane Handbook for Systematic Reviews of Interventions. The risk ratio (RR and 95% confidence intervals (CI were calculated for the clinical improvement in function compared to baseline. Heterogeneity was assessed across studies, and subgroup analysis was also performed based on the study type and follow-up duration.Three studies with a total of 352 participants were identified, and the clinically relevant improvement was used as the primary outcomes. Our meta-analysis revealed that no significant difference was observed between two comparison groups in terms of postoperative clinical improvement in those studies (RR 1.04, 95% CI 0.86 to 1.25, P = 0.72. Meanwhile, subgroup analyses by study type and follow-up duration revealed the consistent results with the overall estimate. Additionally, the pre- and postoperative motor nerve conduction velocities were reported in two studies with a total of 326 patients, but we could not perform a meta-analysis because of the lack of concrete numerical value in one study. The quality of evidence for clinical improvement was 'low' or 'moderate' on the basis of GRADE approach.Based on small numbers of studies with relatively poor methodological quality, the limited evidence is insufficient to identify the optimum anterior transposition technique in the treatment of cubital tunnel syndrome. The results of the present study suggest that anterior subcutaneous and submuscular transposition might be equally effective in patients with ulnar neuropathy at the elbow. Therefore
Coupling of non-conforming meshes in a component mode synthesis method
Akcay-Perdahcioglu, D.; Doreille, M.; Boer, de A.; Ludwig, T.
2013-01-01
A common mesh refinement-based coupling technique is embedded into a component mode synthesis method, Craig–Bampton. More specifically, a common mesh is generated between the non-conforming interfaces of the coupled structures, and the compatibility constraints are enforced on that mesh via L2-minim
Efficient Packet Forwarding in Mesh Network
Soumen Kanrar
2012-01-01
Wireless Mesh Network (WMN) is a multi hop low cost, with easy maintenance robust network providing reliable service coverage. WMNs consist of mesh routers and mesh clients. In this architecture, while static mesh routers form the wireless backbone, mesh clients access the network through mesh routers as well as directly meshing with each other. Different from traditional wireless networks, WMN is dynamically self-organized and self-configured. In other words, the nodes in the mesh network au...
Tang, Zhao; Wei, Qingshan; Wei, Alexander
2011-12-01
Metal-mesh lithography (MML) is a practical hybrid of microcontact printing and capillary force lithography that can be applied over millimeter-sized areas with a high level of uniformity. MML can be achieved by blotting various inks onto substrates through thin copper grids, relying on preferential wetting and capillary interactions between template and substrate for pattern replication. The resulting mesh patterns, which are inverted relative to those produced by stenciling or serigraphy, can be reproduced with low micrometer resolution. MML can be combined with other surface chemistry and lift-off methods to create functional microarrays for diverse applications, such as periodic islands of gold nanorods and patterned corrals for fibroblast cell cultures.
Parallel Adaptive Mesh Refinement
Energy Technology Data Exchange (ETDEWEB)
Diachin, L; Hornung, R; Plassmann, P; WIssink, A
2005-03-04
As large-scale, parallel computers have become more widely available and numerical models and algorithms have advanced, the range of physical phenomena that can be simulated has expanded dramatically. Many important science and engineering problems exhibit solutions with localized behavior where highly-detailed salient features or large gradients appear in certain regions which are separated by much larger regions where the solution is smooth. Examples include chemically-reacting flows with radiative heat transfer, high Reynolds number flows interacting with solid objects, and combustion problems where the flame front is essentially a two-dimensional sheet occupying a small part of a three-dimensional domain. Modeling such problems numerically requires approximating the governing partial differential equations on a discrete domain, or grid. Grid spacing is an important factor in determining the accuracy and cost of a computation. A fine grid may be needed to resolve key local features while a much coarser grid may suffice elsewhere. Employing a fine grid everywhere may be inefficient at best and, at worst, may make an adequately resolved simulation impractical. Moreover, the location and resolution of fine grid required for an accurate solution is a dynamic property of a problem's transient features and may not be known a priori. Adaptive mesh refinement (AMR) is a technique that can be used with both structured and unstructured meshes to adjust local grid spacing dynamically to capture solution features with an appropriate degree of resolution. Thus, computational resources can be focused where and when they are needed most to efficiently achieve an accurate solution without incurring the cost of a globally-fine grid. Figure 1.1 shows two example computations using AMR; on the left is a structured mesh calculation of a impulsively-sheared contact surface and on the right is the fuselage and volume discretization of an RAH-66 Comanche helicopter [35]. Note the
Institute of Scientific and Technical Information of China (English)
高伟; 耿建华
2013-01-01
介绍一种基于离散粒子理论地震波传播数值模拟的网格剖分计算方法.根据离散粒子理论,将研究区域划分为由一系列相互作用的粒子组成的正六边形网格,这些粒子在它们的接触点处发生相互作用,并用Hooke定律和Newton定律描述.为解决六边形网格带来的网格交错而难以计算以及波场输出问题,将横向网格进行加密,加密处赋予假想的粒子,输出波场时选取偶数行偶数列点或奇数行奇数列点的波场值.均匀介质和层状介质模型的数值模拟结果表明,该网格剖分计算方法能够将离散粒子理论用于模拟弹性波在非均匀各向同性介质中地震波的传播.%A mesh generation calculation method based on discrete particle scheme for numerical modeling seismic waves is presented.According to the discrete particle theory,the study area can be divided into regular hexagon grid composed of a series of interacting particles.These particles interact at their contact points and the motion of particles in space is described by Hook's Law and Newton's Law.To solve the problem of the grid crisscross brought by hexagon grids which may lead to difficulty in calculation and output wave field's value,we encrypt the imaginary particles at the horizontal grids and output the wave field value of the even lines＇ points in the even column or odd lines＇ points in odd column.The numerical simulation results of homogeneous model and layer model proved that this mesh generation calculation method based on discrete particle theory is capable of modeling the propagation of elastic waves through heterogeneous isotropic media.
Lattice Cleaving: Conforming Tetrahedral Meshes of Multimaterial Domains with Bounded Quality.
Bronson, Jonathan R; Levine, Joshua A; Whitaker, Ross T
2013-01-01
We introduce a new algorithm for generating tetrahedral meshes that conform to physical boundaries in volumetric domains consisting of multiple materials. The proposed method allows for an arbitrary number of materials, produces high-quality tetrahedral meshes with upper and lower bounds on dihedral angles, and guarantees geometric fidelity. Moreover, the method is combinatoric so its implementation enables rapid mesh construction. These meshes are structured in a way that also allows grading, in order to reduce element counts in regions of homogeneity.
Mesh Algorithms for PDE with Sieve I: Mesh Distribution
Directory of Open Access Journals (Sweden)
Matthew G. Knepley
2009-01-01
Full Text Available We have developed a new programming framework, called Sieve, to support parallel numerical partial differential equation(s (PDE algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or arrows, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode not only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete description of an algorithm to encode a mesh partition and then distribute a mesh, which is independent of the mesh dimension, element shape, or embedding. Moreover, data associated with the mesh can be similarly distributed with exactly the same algorithm. The use of a high level of abstraction within the Sieve leads to several benefits in terms of code reuse, simplicity, and extensibility. We discuss these benefits and compare our approach to other existing mesh libraries.
Directory of Open Access Journals (Sweden)
Nishida,Keiichiro
2013-02-01
Full Text Available The purpose of this study was to quantitatively evaluate Akahori's preoperative classification of cubital tunnel syndrome. We analyzed the results for 57 elbows that were treated by a simple decompression procedure from 1997 to 2004. The relationship between each item of Akahori's preoperative classification and clinical stage was investigated based on the parameter distribution. We evaluated Akahori's classification system using multiple regression analysis, and investigated the association between the stage and treatment results. The usefulness of the regression equation was evaluated by analysis of variance of the expected and observed scores. In the parameter distribution, each item of Akahori's classification was mostly associated with the stage, but it was difficult to judge the severity of palsy. In the mathematical evaluation, the most effective item in determining the stage was sensory conduction velocity. It was demonstrated that the established regression equation was highly reliable (R＝0.922. Akahori's preoperative classification can also be used in postoperative classification, and this classification was correlated with postoperative prognosis. Our results indicate that Akahori's preoperative classification is a suitable system. It is reliable, reproducible and well-correlated with the postoperative prognosis. In addition, the established prediction formula is useful to reduce the diagnostic complexity of Akahori's classification.
Resolución microquirúrgica de aneurisma de arteria cubital en paciente pediátrico
Directory of Open Access Journals (Sweden)
A. Aguilera-Salgado
2015-09-01
Full Text Available Presentamos el caso clínico de un paciente varón de 6 años de edad con antecedente de caída desde su propia altura un mes antes de su valoración en consulta, en donde se identifica una tumoración pulsátil en región hipotenar de mano derecha, no dolorosa y no fija a planos profundos. El ultrasonido doppler informa de una tumoración con pared definida, heterogénea, con flujo sanguíneo a través de la misma. En base a los antecedentes y a los resultados del ultrasonido se decide intervenir quirúrgicamente para evitar posibles complicaciones, encontrando un aneurisma de la arteria cubital de 3 x 3 cm de diámetro, no trombosado, que resecamos, practicando reconstrucción mediante injerto venoso término-terminal. El paciente evolucionó sin complicaciones.
Adaptive-mesh algorithms for computational fluid dynamics
Powell, Kenneth G.; Roe, Philip L.; Quirk, James
1993-01-01
The basic goal of adaptive-mesh algorithms is to distribute computational resources wisely by increasing the resolution of 'important' regions of the flow and decreasing the resolution of regions that are less important. While this goal is one that is worthwhile, implementing schemes that have this degree of sophistication remains more of an art than a science. In this paper, the basic pieces of adaptive-mesh algorithms are described and some of the possible ways to implement them are discussed and compared. These basic pieces are the data structure to be used, the generation of an initial mesh, the criterion to be used to adapt the mesh to the solution, and the flow-solver algorithm on the resulting mesh. Each of these is discussed, with particular emphasis on methods suitable for the computation of compressible flows.
Kinetic Solvers with Adaptive Mesh in Phase Space
Arslanbekov, Robert R; Frolova, Anna A
2013-01-01
An Adaptive Mesh in Phase Space (AMPS) methodology has been developed for solving multi-dimensional 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 data structure. The mesh in r-space is automatically generated around embedded boundaries and dynamically adapted to local solution properties. The mesh in v-space is created on-the-fly for each cell in r-space. Mappings between neighboring v-space trees implemented for the advection operator in configuration space. We have developed new algorithms for solving the full Boltzmann and linear Boltzmann equations with AMPS. Several recent innovations were used to calculate the full Boltzmann collision integral with dynamically adaptive mesh in velocity space: importance sampling, multi-point projection method, and the variance reduction method. We have developed an efficient algorithm for calculating the linear Boltzmann collision integral for elastic and inelastic...
A Survey of Solver-Related Geometry and Meshing Issues
Masters, James; Daniel, Derick; Gudenkauf, Jared; Hine, David; Sideroff, Chris
2016-01-01
There is a concern in the computational fluid dynamics community that mesh generation is a significant bottleneck in the CFD workflow. This is one of several papers that will help set the stage for a moderated panel discussion addressing this issue. Although certain general "rules of thumb" and a priori mesh metrics can be used to ensure that some base level of mesh quality is achieved, inadequate consideration is often given to the type of solver or particular flow regime on which the mesh will be utilized. This paper explores how an analyst may want to think differently about a mesh based on considerations such as if a flow is compressible vs. incompressible or hypersonic vs. subsonic or if the solver is node-centered vs. cell-centered. This paper is a high-level investigation intended to provide general insight into how considering the nature of the solver or flow when performing mesh generation has the potential to increase the accuracy and/or robustness of the solution and drive the mesh generation process to a state where it is no longer a hindrance to the analysis process.
toolkit computational mesh conceptual model.
Energy Technology Data Exchange (ETDEWEB)
Baur, David G.; Edwards, Harold Carter; Cochran, William K.; Williams, Alan B.; Sjaardema, Gregory D.
2010-03-01
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.
Sibeyn, J.; Rao, P; Juurlink, B.
1996-01-01
Algorithms for performing gossiping on one- and higher dimensional meshes are presented. As a routing model, we assume the practically important worm-hole routing. For one-dimensional arrays and rings, we give a novel lower bound and an asymptotically optimal gossiping algorithm for all choices of the parameters involved. For two-dimensional meshes and tori, several simple algorithms composed of one-dimensional phases are presented. For an important range of packet and mesh sizes it gives cle...
Synthesized Optimization of Triangular Mesh
Institute of Scientific and Technical Information of China (English)
HU Wenqiang; YANG Wenyu
2006-01-01
Triangular mesh is often used to describe geometric object as computed model in digital manufacture, thus the mesh model with both uniform triangular shape and excellent geometric shape is expected. But in fact, the optimization of triangular shape often is contrary with that of geometric shape. In this paper, one synthesized optimizing algorithm is presented through subdividing triangles to achieve the trade-off solution between the geometric and triangular shape optimization of mesh model. The result mesh with uniform triangular shape and excellent topology are obtained.
Directory of Open Access Journals (Sweden)
Sara Lima
2012-01-01
Full Text Available OBJETIVO: Avaliar os resultados da transposição anterior subcutânea do nervo cubital no tratamento da síndrome do túnel cubital (STC e a influência de fatores de prognóstico, tais como o estádio de McGowan pré-operatório, a idade e a duração dos sintomas. MÉTODOS: Foram avaliados 36 doentes com STC submetidos à transposição anterior subcutânea do nervo cubital entre 2006 e 2009, com um tempo médio de follow-up de 28 meses. A idade média foi de 41,6 anos. Nove doentes foram incluídos no estádio I de McGowan, 18 no estádio II e nove no estádio III. RESULTADOS: Obteve-se melhoria estatisticamente significativa dos défices motores e sensitivos. 78% dos doentes com neuropatia severa melhoraram após a cirurgia. Segundo a escala de Bishop modificada, obtiveram-se 21 (58,3% resultados excelentes, sete (19,4% bons, seis (16,7% satisfatórios e dois maus (5.55%. A taxa de satisfação foi de 86% e 72% dos doentes recuperaram as atividades diárias sem limitações. CONCLUSÕES: A gravidade da neuropatia e a duração pré-operatória dos sintomas, mas não a idade, tiveram uma influência negativa no outcome. A transposição anterior subcutânea do nervo cubital é segura e eficaz no tratamento da STC com diversos graus de gravidade. Tendo em conta os principais fatores de prognóstico identificados, o tratamento cirúrgico deve ser aconselhado logo que a perda axonal se torne clinicamente evidente.OBJECTIVE: To evaluate the results from subcutaneous anterior transposition of the cubital nerve for treating cubital tunnel syndrome (CTS and the influence of prognostic factors such as preoperative McGowan stage, age and duration of symptoms. METHODS: 36 patients with CTS who underwent subcutaneous anterior transposition of the cubital nerve between 2006 and 2009 were evaluated after an average follow-up of 28 months. Their mean age was 41.6 years. Nine patients were in McGowan stage I, 18 in stage II and nine in stage III. RESULTS
Isotropic 2D quadrangle meshing with size and orientation control
Pellenard, Bertrand
2011-12-01
We propose an approach for automatically generating isotropic 2D quadrangle meshes from arbitrary domains with a fine control over sizing and orientation of the elements. At the heart of our algorithm is an optimization procedure that, from a coarse initial tiling of the 2D domain, enforces each of the desirable mesh quality criteria (size, shape, orientation, degree, regularity) one at a time, in an order designed not to undo previous enhancements. Our experiments demonstrate how well our resulting quadrangle meshes conform to a wide range of input sizing and orientation fields.
An unstructured-mesh atmospheric model for nonhydrostatic dynamics
Smolarkiewicz, Piotr K.; Szmelter, Joanna; Wyszogrodzki, Andrzej A.
2013-12-01
A three-dimensional semi-implicit edge-based unstructured-mesh model is developed that integrates nonhydrostatic anelastic equations, suitable for simulation of small-to-mesoscale atmospheric flows. The model builds on nonoscillatory forward-in-time MPDATA approach using finite-volume discretization and admitting unstructured meshes with arbitrarily shaped cells. The numerical advancements are evaluated with canonical simulations of convective planetary boundary layer and strongly (stably) stratified orographic flows, epitomizing diverse aspects of highly nonlinear nonhydrostatic dynamics. The unstructured-mesh solutions are compared to equivalent results generated with an established structured-grid model and observation.
Directory of Open Access Journals (Sweden)
Zhu Liu
2015-01-01
Full Text Available Background: To study lesions′ location and prognosis of cubital tunnel syndrome (CubTS by routine motor nerve conduction studies (MNCSs and short-segment nerve conduction studies (SSNCSs, inching test. Methods: Thirty healthy subjects were included and 60 ulnar nerves were studied by inching studies for normal values. Sixty-six patients who diagnosed CubTS clinically were performed bilaterally by routine MNCSs and SSNCSs. Follow-up for 1-year, the information of brief complaints, clinical symptoms, and physical examination were collected. Results: Sixty-six patients were included, 88 of nerves was abnormal by MNCS, while 105 was abnormal by the inching studies. Medial epicondyle to 2 cm above medial epicondyle is the most common segment to be detected abnormally (59.09%, P < 0.01. Twenty-two patients were followed-up, 17 patients′ symptoms were improved. Most of the patients were treated with drugs and modification of bad habits. Conclusions: (1 SSNCSs can detect lesions of compressive neuropathy in CubTS more precisely than the routine motor conduction studies. (2 SSNCSs can diagnose CubTS more sensitively than routine motor conduction studies. (3 In this study, we found that medial epicondyle to 2 cm above the medial epicondyle is the most vulnerable place that the ulnar nerve compressed. (4 The patients had a better prognosis who were abnormal in motor nerve conduction time only, but not amplitude in compressed lesions than those who were abnormal both in velocity and amplitude. Our study suggests that SSNCSs is a practical method in detecting ulnar nerve compressed neuropathy, and sensitive in diagnosing CubTS. The compound muscle action potentials by SSNCSs may predict prognosis of CubTS.
Institute of Scientific and Technical Information of China (English)
Zhu Liu; Zhi-Rong Jia; Ting-Ting Wang; Xin Shi; Wei Liang
2015-01-01
Background:To study lesions' location and prognosis of cubital tunnel syndrome (CubTS) by routine motor nerve conduction studies (MNCSs) and short-segment nerve conduction studies (SSNCSs,inching test).Methods:Thirty healthy subjects were included and 60 ulnar nerves were studied by inching studies for normal values.Sixty-six patients who diagnosed CubTS clinically were performed bilaterally by routine MNCSs and SSNCSs.Follow-up for 1-year,the information of brief complaints,clinical symptoms,and physical examination were collected.Results:Sixty-six patients were included,88 of nerves was abnormal by MNCS,while 105 was abnormal by the inching studies.Medial epicondyle to 2 cm above medial epicondyle is the most common segment to be detected abnormally (59.09％),P ＜ 0.01.Twenty-two patients were followed-up,17 patients' symptoms were improved.Most of the patients were treated with drugs and modification of bad habits.Conclusions:(1) SSNCSs can detect lesions of compressive neuropathy in CubTS more precisely than the routine motor conduction studies.(2) SSNCSs can diagnose CubTS more sensitively than routine motor conduction studies.(3) In this study,we found that medial epicondyle to 2 cm above the medial epicondyle is the most vulnerable place that the ulnar nerve compressed.(4) The patients had a better prognosis who were abnormal in motor nerve conduction time only,but not amplitude in compressed lesions than those who were abnormal both in velocity and amplitude.Our study suggests that SSNCSs is a practical method in detecting ulnar nerve compressed neuropathy,and sensitive in diagnosing CubTS.The compound muscle action potentials by SSNCSs may predict prognosis of CubTS.
Rinkel, Willem D; Schreuders, Ton A R; Koes, Bart W; Huisstede, Bionka M A
2013-12-01
To provide an evidence-based overview of the effectiveness of interventions for 4 nontraumatic painful disorders sharing the anatomic region of the elbow: cubital tunnel syndrome, radial tunnel syndrome, elbow instability, and olecranon bursitis. The Cochrane Library, PubMed, Embase, PEDro, and CINAHL were searched to identify relevant reviews and randomized clinical trials (RCTs). Two reviewers independently extracted data and assessed the quality of the methodology. A best-evidence synthesis was used to summarize the results. One systematic review and 6 RCTs were included. For the surgical treatment of cubital tunnel syndrome (1 review, 3 RCTs), comparing simple decompression with anterior ulnar nerve transposition, no evidence was found in favor of either one of these. Limited evidence was found in favor of medial epicondylectomy versus anterior transposition and for early postoperative therapy versus immobilization. No evidence was found for the effect of local steroid injection in addition to splinting. No RCTs were found for radial tunnel syndrome. For olecranon bursitis (1 RCT), limited evidence for effectiveness was found for methylprednisolone acetate injection plus naproxen. Concerning elbow instability, including 2 RCTs, one showed that nonsurgical treatment resulted in similar results compared with surgery, whereas the other found limited evidence for the effectiveness in favor of early mobilization versus 3 weeks of immobilization after surgery. In this review no, or at best, limited evidence was found for the effectiveness of nonsurgical and surgical interventions to treat painful cubital tunnel syndrome, radial tunnel syndrome, elbow instability, or olecranon bursitis. Well-designed and well-conducted RCTs are clearly needed in this field.
Mesh Algorithms for PDE with Sieve I: Mesh Distribution
Knepley, Matthew G
2009-01-01
We have developed a new programming framework, called Sieve, to support parallel numerical PDE algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or \\emph{arrows}, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode not only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete des...
On the Support of Multimedia Applications over Wireless Mesh Networks
Directory of Open Access Journals (Sweden)
Chemseddine BEMMOUSSAT
2013-05-01
Full Text Available For next generation wireless networks, supporting quality of service (QoS in multimedia application likevideo, streaming and voice over IP is a necessary and critical requirement. Wireless Mesh Networking isenvisioned as a solution for next networks generation and a promising technology for supportingmultimedia application.With decreasing the numbers of mesh clients, QoS will increase automatically. Several research arefocused to improve QoS in Wireless Mesh networks (WMNs, they try to improve a basics algorithm, likerouting protocols or one of example of canal access, but in moments it no sufficient to ensure a robustsolution to transport multimedia application over WMNs.In this paper we propose an efficient routing algorithm for multimedia transmission in the mesh networkand an approach of QoS in the MAC layer for facilitated transport video over the network studied.
Prevention of Adhesion to Prosthetic Mesh
van ’t Riet, Martijne; de Vos van Steenwijk, Peggy J.; Bonthuis, Fred; Marquet, Richard L.; Steyerberg, Ewout W.; Jeekel, Johannes; Bonjer, H. Jaap
2003-01-01
Objective To assess whether use of antiadhesive liquids or coatings could prevent adhesion formation to prosthetic mesh. Summary Background Data Incisional hernia repair frequently involves the use of prosthetic mesh. However, concern exists about development of adhesions between viscera and the mesh, predisposing to intestinal obstruction or enterocutaneous fistulas. Methods In 91 rats, a defect in the muscular abdominal wall was created, and mesh was fixed intraperitoneally to cover the defect. Rats were divided in five groups: polypropylene mesh only (control group), addition of Sepracoat or Icodextrin solution to polypropylene mesh, Sepramesh (polypropylene mesh with Seprafilm coating), and Parietex composite mesh (polyester mesh with collagen coating). Seven and 30 days postoperatively, adhesions were assessed and wound healing was studied by microscopy. Results Intraperitoneal placement of polypropylene mesh was followed by bowel adhesions to the mesh in 50% of the cases. A mean of 74% of the mesh surface was covered by adhesions after 7 days, and 48% after 30 days. Administration of Sepracoat or Icodextrin solution had no influence on adhesion formation. Coated meshes (Sepramesh and Parietex composite mesh) had no bowel adhesions. Sepramesh was associated with a significant reduction of the mesh surface covered by adhesions after 7 and 30 days. Infection was more prevalent with Parietex composite mesh, with concurrent increased mesh surface covered by adhesions after 30 days (78%). Conclusions Sepramesh significantly reduced mesh surface covered by adhesions and prevented bowel adhesion to the mesh. Parietex composite mesh prevented bowel adhesions as well but increased infection rates in the current model. PMID:12496539
Risk Factors for Mesh Exposure after Transvaginal Mesh Surgery
Institute of Scientific and Technical Information of China (English)
Ke Niu; Yong-Xian Lu; Wen-Jie Shen; Ying-Hui Zhang; Wen-Ying Wang
2016-01-01
Background:Mesh exposure after surgery continues to be a clinical challenge for urogynecological surgeons.The purpose of this study was to explore the risk factors for polypropylene (PP) mesh exposure after transvaginal mesh (TVM) surgery.Methods:This study included 195 patients with advanced pelvic organ prolapse (POP),who underwent TVM from January 2004to December 2012 at the First Affiliated Hospital of Chinese PLA General Hospital.Clinical data were evaluated including patient's demography,TVM type,concomitant procedures,operation time,blood loss,postoperative morbidity,and mesh exposure.Mesh exposure was identified through postoperative vaginal examination.Statistical analysis was performed to identify risk factors for mesh exposure.Results:Two-hundred and nine transvaginal PP meshes were placed,including 194 in the anterior wall and 15 in the posterior wall.Concomitant tension-free vaginal tape was performed in 61 cases.The mean follow-up time was 35.1 ± 23.6 months.PP mesh exposure was identified in 32 cases (16.4％),with 31 in the anterior wall and 1 in the posterior wall.Significant difference was found in operating time and concomitant procedures between exposed and nonexposed groups (F =7.443,P =0.007;F =4.307,P =0.039,respectively).Binary logistic regression revealed that the number of concomitant procedures and operation time were risk factors for mesh exposure (P =0.001,P =0.043).Conclusion:Concomitant procedures and increased operating time increase the risk for postoperative mesh exposure in patients undergoing TVM surgery for POP.
Institute of Scientific and Technical Information of China (English)
郭瑞军; 于亚东; 邵新中; 王明花; 田德虎; 张文云; 张经歧; 张晓丽
2000-01-01
目的 探讨高频超声对肘管、腕管综合征的诊断价值.方法 /应用高频超声观察30例正常人的肘管及腕管的超声解剖并对20例肘管综合征、10例腕管综合征患者术前行超声检查.结果 高频超声不仅能清晰显示构成肘管及腕管的骨质、软组织及其内容物,而且能够明确肘管和腕管综合征的病因以及尺神经和正中神经的形态学变化.结论 高频超声在肘管、腕管综合征的诊断及鉴别诊断中具有重要价值.%Objective To evaluate the diagnostic value of high frequency ultrasound in cubital and carpal tunnel syndrome. Methods High frequency ultrasonography of normal cubital and carpal tunnel were performed in 30 healthy volunteers. Then sonorgraphic examination was carried out in 20 patients with cubital tunnel syndrome and 10 patients with carpal tunnel syndrome before operation. Results Not only the structure of cubital and carpal tunnel cauld be showed clearly, but also the cause of the cubital and carpal tunnel syndrome could be distinct. Conclusion High frequency ultrasound is of high diagnostic value in cubital and carpal tunnel syndrome.
Viscous flow modelling using unstructured meshes for aeronautical applications
Szmelter, J.; Pagano, A.
The novel application of viscous coupling to unstructured meshes has been proposed and developed. The method allows fro viscous flows modelling and avoids the difficulty of generating highly stretched tetrahedral in 3D or triangular in 2D elements required for Navier-Stokes solvers. The time step allowed by the explicit euler solver is limited by the size of the "Euler" mesh, resulting in faster algorithms than standard explicit Navier-Stokes solvers.
Parameterization for fitting triangular mesh
Institute of Scientific and Technical Information of China (English)
LIN Hongwei; WANG Guojin; LIU Ligang; BAO Hujun
2006-01-01
In recent years, with the development of 3D data acquisition equipments, the study on reverse engineering has become more and more important. However, the existing methods for parameterization can hardly ensure that the parametric domain is rectangular, and the parametric curve grid is regular. In order to overcome these limitations, we present a novel method for parameterization of triangular meshes in this paper. The basic idea is twofold: first, because the isotherms in the steady temperature do not intersect with each other, and are distributed uniformly, no singularity (fold-over) exists in the parameterization; second, a 3D harmonic equation is solved by the finite element method to obtain the steady temperature field on a 2D triangular mesh surface with four boundaries. Therefore, our proposed method avoids the embarrassment that it is impossible to solve the 2D quasi-harmonic equation on the 2D triangular mesh without the parametric values at mesh vertices. Furthermore, the isotherms on the temperature field are taken as a set of iso-parametric curves on the triangular mesh surface. The other set of iso-parametric curves can be obtained by connecting the points with the same chord-length on the isotherms sequentially. The obtained parametric curve grid is regular, and distributed uniformly, and can map the triangular mesh surface to the unit square domain with boundaries of mesh surface to boundaries of parametric domain, which ensures that the triangular mesh surface or point cloud can be fitted with the NURBS surface.
An Improved Moving Mesh Algorithm
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
we consider an iterative algorithm of mesh optimization for finite element solution, and give an improved moving mesh strategy that reduces rapidly the complexity and cost of solving variational problems.A numerical result is presented for a 2-dimensional problem by the improved algorithm.
Adaptive and Unstructured Mesh Cleaving
Bronson, Jonathan R.; Sastry, Shankar P.; Levine, Joshua A.; Whitaker, Ross T.
2015-01-01
We propose a new strategy for boundary conforming meshing that decouples the problem of building tetrahedra of proper size and shape from the problem of conforming to complex, non-manifold boundaries. This approach is motivated by the observation that while several methods exist for adaptive tetrahedral meshing, they typically have difficulty at geometric boundaries. The proposed strategy avoids this conflict by extracting the boundary conforming constraint into a secondary step. We first build a background mesh having a desired set of tetrahedral properties, and then use a generalized stenciling method to divide, or “cleave”, these elements to get a set of conforming tetrahedra, while limiting the impacts cleaving has on element quality. In developing this new framework, we make several technical contributions including a new method for building graded tetrahedral meshes as well as a generalization of the isosurface stuffing and lattice cleaving algorithms to unstructured background meshes. PMID:26137171
Semi-structured meshes for axial turbomachinery blades
Sbardella, L.; Sayma, A. I.; Imregun, M.
2000-03-01
This paper describes the development and application of a novel mesh generator for the flow analysis of turbomachinery blades. The proposed method uses a combination of structured and unstructured meshes, the former in the radial direction and the latter in the axial and tangential directions, in order to exploit the fact that blade-like structures are not strongly three-dimensional since the radial variation is usually small. The proposed semi-structured mesh formulation was found to have a number of advantages over its structured counterparts. There is a significant improvement in the smoothness of the grid spacing and also in capturing particular aspects of the blade passage geometry. It was also found that the leading- and trailing-edge regions could be discretized without generating superfluous points in the far field, and that further refinements of the mesh to capture wake and shock effects were relatively easy to implement. The capability of the method is demonstrated in the case of a transonic fan blade for which the steady state flow is predicted using both structured and semi-structured meshes. A totally unstructured mesh is also generated for the same geometry to illustrate the disadvantages of using such an approach for turbomachinery blades. Copyright
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.
Gamra: Simple Meshes for Complex Earthquakes
Landry, Walter
2016-01-01
The static offsets caused by earthquakes are well described by elastostatic models with a discontinuity in the displacement along the fault. A traditional approach to model this discontinuity is to align the numerical mesh with the fault and solve the equations using finite elements. However, this distorted mesh can be difficult to generate and update. We present a new numerical method, inspired by the Immersed Interface Method, for solving the elastostatic equations with embedded discontinuities. This method has been carefully designed so that it can be used on parallel machines on an adapted finite difference grid. We have implemented this method in Gamra, a new code for earth modelling. We demonstrate the correctness of the method with analytic tests, and we demonstrate its practical performance by solving a realistic earthquake model to extremely high precision.
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.
Mesh Adaptation and Shape Optimization on Unstructured Meshes Project
National Aeronautics and Space Administration — In this SBIR CRM proposes to implement the entropy adjoint method for solution adaptive mesh refinement into the Loci/CHEM unstructured flow solver. The scheme will...
Calculating the vertex unknowns of nine point scheme on quadrilateral meshes for diffusion equation
Institute of Scientific and Technical Information of China (English)
YUAN GuangWei; SHENG ZhiQiang
2008-01-01
In the construction of nine point scheme, both vertex unknowns and cell-centered unknowns are introduced, and the vertex unknowns are usually eliminated by using the interpolation of neighboring cell-centered unknowns, which often leads to lose accuracy. Instead of using interpolation,here we propose a different method of calculating the vertex unknowns of nine point scheme, which are solved independently on a new generated mesh. This new mesh is a Voronoi mesh based on the vertexes of primary mesh and some additional points on the interface. The advantage of this method is that it is particularly suitable for solving diffusion problems with discontinuous coefficients on highly distorted meshes, and it leads to a symmetric positive definite matrix. We prove that the method has first-order convergence on distorted meshes. Numerical experiments show that the method obtains nearly second-order accuracy on distorted meshes.
Calculating the vertex unknowns of nine point scheme on quadrilateral meshes for diffusion equation
Institute of Scientific and Technical Information of China (English)
2008-01-01
In the construction of nine point scheme,both vertex unknowns and cell-centered unknowns are introduced,and the vertex unknowns are usually eliminated by using the interpolation of neighboring cell-centered unknowns,which often leads to lose accuracy.Instead of using interpolation,here we propose a different method of calculating the vertex unknowns of nine point scheme,which are solved independently on a new generated mesh.This new mesh is a Vorono¨i mesh based on the vertexes of primary mesh and some additional points on the interface.The advantage of this method is that it is particularly suitable for solving diffusion problems with discontinuous coeffcients on highly distorted meshes,and it leads to a symmetric positive definite matrix.We prove that the method has first-order convergence on distorted meshes.Numerical experiments show that the method obtains nearly second-order accuracy on distorted meshes.
Planet-disc interaction on a freely moving mesh
Munoz, Diego J; Springel, Volker; Hernquist, Lars
2014-01-01
General-purpose, moving-mesh schemes for hydrodynamics have opened the possibility of combining the accuracy of grid-based numerical methods with the flexibility and automatic resolution adaptivity of particle-based methods. Due to their supersonic nature, Keplerian accretion discs are in principle a very attractive system for applying such freely moving mesh techniques. However, the high degree of symmetry of simple accretion disc models can be difficult to capture accurately by these methods, due to the generation of geometric grid noise and associated numerical diffusion, which is absent in polar grids. To explore these and other issues, in this work we study the idealized problem of two-dimensional planet-disc interaction with the moving-mesh code AREPO. We explore the hydrodynamic evolution of discs with planets through a series of numerical experiments that vary the planet mass, the disc viscosity and the mesh resolution, and compare the resulting surface density, vortensity field and tidal torque with ...
System Supporting Automatic Generation of Finite Element Using Image Information
Institute of Scientific and Technical Information of China (English)
J; Fukuda
2002-01-01
A mesh generating system has been developed in orde r to prepare large amounts of input data which are needed for easy implementation of a finite element analysis. This system consists of a Pre-Mesh Generator, an Automatic Mesh Generator and a Mesh Modifier. Pre-Mesh Generator produces the shape and sub-block information as input data of Automatic Mesh Generator by c arrying out various image processing with respect to the image information of th e drawing input using scanner. Automatic Mesh Generato...
Institute of Scientific and Technical Information of China (English)
寇淑清; 杨慎华; 黄良驹; 傅沛福
2001-01-01
The 3-D tool surface description together with the automatic 3-D meshing methods and the contact search is carried out for the FEM numerical simulation of complicated massive forming based on the cubic B-spline. The complex geometry for die-cavity and forging surface is described; the spline technique for 3-D mesh generation as well as piecewise mesh generation is proposed and the region-section search algo rithm is done for the advantages of B-spline such as visualization, localization, generalization, flexibility and adaptation for graphic model.%以三次B样条曲面描述为基础，对体成形数值模拟中的复杂模具型腔、锻件三维网格自动划分、锻件与模具接触的状态进行了一体化研究。利用B样条曲面的直观性、局部性、通用性和造型灵活性，构造了复杂模具型腔及锻件边界，提出了三维网格样条生成法、改进的分块样条生成法及接触判断区域层次搜索技术。
Gaussian curvature analysis allows for automatic block placement in multi-block hexahedral meshing.
Ramme, Austin J; Shivanna, Kiran H; Magnotta, Vincent A; Grosland, Nicole M
2011-10-01
Musculoskeletal finite element analysis (FEA) has been essential to research in orthopaedic biomechanics. The generation of a volumetric mesh is often the most challenging step in a FEA. Hexahedral meshing tools that are based on a multi-block approach rely on the manual placement of building blocks for their mesh generation scheme. We hypothesise that Gaussian curvature analysis could be used to automatically develop a building block structure for multi-block hexahedral mesh generation. The Automated Building Block Algorithm incorporates principles from differential geometry, combinatorics, statistical analysis and computer science to automatically generate a building block structure to represent a given surface without prior information. We have applied this algorithm to 29 bones of varying geometries and successfully generated a usable mesh in all cases. This work represents a significant advancement in automating the definition of building blocks.
Mersiline mesh in premaxillary augmentation.
Foda, Hossam M T
2005-01-01
Premaxillary retrusion may distort the aesthetic appearance of the columella, lip, and nasal tip. This defect is characteristically seen in, but not limited to, patients with cleft lip nasal deformity. This study investigated 60 patients presenting with premaxillary deficiencies in which Mersiline mesh was used to augment the premaxilla. All the cases had surgery using the external rhinoplasty technique. Two methods of augmentation with Mersiline mesh were used: the Mersiline roll technique, for the cases with central symmetric deficiencies, and the Mersiline packing technique, for the cases with asymmetric deficiencies. Premaxillary augmentation with Mersiline mesh proved to be simple technically, easy to perform, and not associated with any complications. Periodic follow-up evaluation for a mean period of 32 months (range, 12-98 months) showed that an adequate degree of premaxillary augmentation was maintained with no clinically detectable resorption of the mesh implant.
Image-driven mesh optimization
Energy Technology Data Exchange (ETDEWEB)
Lindstrom, P; Turk, G
2001-01-05
We describe a method of improving the appearance of a low vertex count mesh in a manner that is guided by rendered images of the original, detailed mesh. This approach is motivated by the fact that greedy simplification methods often yield meshes that are poorer than what can be represented with a given number of vertices. Our approach relies on edge swaps and vertex teleports to alter the mesh connectivity, and uses the downhill simplex method to simultaneously improve vertex positions and surface attributes. Note that this is not a simplification method--the vertex count remains the same throughout the optimization. At all stages of the optimization the changes are guided by a metric that measures the differences between rendered versions of the original model and the low vertex count mesh. This method creates meshes that are geometrically faithful to the original model. Moreover, the method takes into account more subtle aspects of a model such as surface shading or whether cracks are visible between two interpenetrating parts of the model.
Gradient Domain Mesh Deformation - A Survey
Institute of Scientific and Technical Information of China (English)
Wei-Wei Xu; Kun Zhou
2009-01-01
This survey reviews the recent development of gradient domain mesh deformation method. Different to other deformation methods, the gradient domain deformation method is a surface-based, variational optimization method. It directly encodes the geometric details in differential coordinates, which are also called Laplacian coordinates in literature. By preserving the Laplacian coordinates, the mesh details can be well preserved during deformation. Due to the locality of the Laplacian coordinates, the variational optimization problem can be casted into a sparse linear system. Fast sparse linear solver can be adopted to generate deformation result interactively, or even in real-time. The nonlinear nature of gradient domain mesh deformation leads to the development of two categories of deformation methods: linearization methods and nonlinear optimization methods. Basically, the linearization methods only need to solve the linear least-squares system once. They are fast, easy to understand and control, while the deformation result might be suboptimal. Nonlinear optimization methods can reach optimal solution of deformation energy function by iterative updating. Since the computation of nonlinear methods is expensive, reduced deformable models should be adopted to achieve interactive performance. The nonlinear optimization methods avoid the user burden to input transformation at deformation handles, and they can be extended to incorporate various nonlinear constraints, like volume constraint, skeleton constraint, and so on. We review representative methods and related approaches of each category comparatively and hope to help the user understand the motivation behind the algorithms. Finally, we discuss the relation between physical simulation and gradient domain mesh deformation to reveal why it can achieve physically plausible deformation result.
Finite element meshing approached as a global minimization process
Energy Technology Data Exchange (ETDEWEB)
WITKOWSKI,WALTER R.; JUNG,JOSEPH; DOHRMANN,CLARK R.; LEUNG,VITUS J.
2000-03-01
The ability to generate a suitable finite element mesh in an automatic fashion is becoming the key to being able to automate the entire engineering analysis process. However, placing an all-hexahedron mesh in a general three-dimensional body continues to be an elusive goal. The approach investigated in this research is fundamentally different from any other that is known of by the authors. A physical analogy viewpoint is used to formulate the actual meshing problem which constructs a global mathematical description of the problem. The analogy used was that of minimizing the electrical potential of a system charged particles within a charged domain. The particles in the presented analogy represent duals to mesh elements (i.e., quads or hexes). Particle movement is governed by a mathematical functional which accounts for inter-particles repulsive, attractive and alignment forces. This functional is minimized to find the optimal location and orientation of each particle. After the particles are connected a mesh can be easily resolved. The mathematical description for this problem is as easy to formulate in three-dimensions as it is in two- or one-dimensions. The meshing algorithm was developed within CoMeT. It can solve the two-dimensional meshing problem for convex and concave geometries in a purely automated fashion. Investigation of the robustness of the technique has shown a success rate of approximately 99% for the two-dimensional geometries tested. Run times to mesh a 100 element complex geometry were typically in the 10 minute range. Efficiency of the technique is still an issue that needs to be addressed. Performance is an issue that is critical for most engineers generating meshes. It was not for this project. The primary focus of this work was to investigate and evaluate a meshing algorithm/philosophy with efficiency issues being secondary. The algorithm was also extended to mesh three-dimensional geometries. Unfortunately, only simple geometries were tested
Method and system for mesh network embedded devices
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.
Liu, Chun-Hua; Wu, Shi-Qiang; Ke, Xiao-Bin; Wang, Han-Long; Chen, Chang-Xian; Lai, Zhan-Long; Zhuang, Zhi-Yong; Wu, Zhi-Qiang; Lin, Qin
2015-07-01
Subcutaneous and submuscular anterior ulnar nerve transposition have been widely used in patients with cubital tunnel syndrome. However, the reliable evidence in favor of 1 of 2 surgical options on clinical improvement remains controversial. To maximize the value of the available literature, we performed a systematic review and meta-analysis to compare subcutaneous versus submuscular anterior ulnar nerve transposition in patients with ulnar neuropathy at the elbow. PubMed, Cochrane Library, and EMBASE databases were searched for randomized and observational studies that compared subcutaneous transposition with submuscular transposition of ulnar nerve for cubital tunnel syndrome. The primary outcome was clinically relevant improvement in function compared to the baseline. Randomized and observational studies were separately analyzed with relative risks (RRs) and 95% confidence intervals (CIs). Two randomized controlled trials (RCTs) and 7 observational studies, involving 605 patients, were included. Our meta-analysis suggested that no significant differences in the primary outcomes were observed between comparison groups, both in RCT (RR, 1.16; 95% CI 0.68-1.98; P = 0.60; I2= 81%) and observational studies (RR, 1.01; 95% CI 0.95-1.08; P = 0.69; I2 = 0%). These findings were also consistent with all subgroup analyses for observational studies. In the secondary outcomes, the incidence of adverse events was significantly lower in subcutaneous group than in submuscular group (RR, 0.54; 95% CI 0.33-0.87; P = 0.01; I2 = 0%), whereas subcutaneous transposition failed to reveal more superiority than submuscular transposition in static two-point discrimination (MD, 0.04; 95% CI -0.18-0.25; P = 0.74; I = 0%). The available evidence is not adequately powered to identify the best anterior ulnar nerve transposition technique for cubital tunnel syndrome on the basis of clinical outcomes, that is, suggests that subcutaneous and submuscular anterior transposition might be equally
3D Mesh Compression and Transmission for Mobile Robotic Applications
Directory of Open Access Journals (Sweden)
Bailin Yang
2016-01-01
Full Text Available Mobile robots are useful for environment exploration and rescue operations. In such applications, it is crucial to accurately analyse and represent an environment, providing appropriate inputs for motion planning in order to support robot navigation and operations. 2D mapping methods are simple but cannot handle multilevel or multistory environments. To address this problem, 3D mapping methods generate structural 3D representations of the robot operating environment and its objects by 3D mesh reconstruction. However, they face the challenge of efficiently transmitting those 3D representations to system modules for 3D mapping, motion planning, and robot operation visualization. This paper proposes a quality-driven mesh compression and transmission method to address this. Our method is efficient, as it compresses a mesh by quantizing its transformed vertices without the need to spend time constructing an a-priori structure over the mesh. A visual distortion function is developed to govern the level of quantization, allowing mesh transmission to be controlled under different network conditions or time constraints. Our experiments demonstrate how the visual quality of a mesh can be manipulated by the visual distortion function.
Mesh refinement strategy for optimal control problems
Paiva, Luis Tiago; Fontes, Fernando,
2013-01-01
International audience; Direct methods are becoming the most used technique to solve nonlinear optimal control problems. Regular time meshes having equidistant spacing are frequently used. However, in some cases these meshes cannot cope accurately with nonlinear behavior. One way to improve the solution is to select a new mesh with a greater number of nodes. Another way, involves adaptive mesh refinement. In this case, the mesh nodes have non equidistant spacing which allow a non uniform node...
Unbiased sampling and meshing of isosurfaces
Yan, Dongming
2014-11-01
In this paper, we present a new technique to generate unbiased samples on isosurfaces. An isosurface, F(x,y,z) = c , of a function, F , is implicitly defined by trilinear interpolation of background grid points. The key idea of our approach is that of treating the isosurface within a grid cell as a graph (height) function in one of the three coordinate axis directions, restricted to where the slope is not too high, and integrating / sampling from each of these three. We use this unbiased sampling algorithm for applications in Monte Carlo integration, Poisson-disk sampling, and isosurface meshing.
... Gardening Safety Turkey Carving Removing a Ring Español Artritis de la base del pulgar Dedo en gatillo ... Gardening Safety Turkey Carving Removing a Ring Español Artritis de la base del pulgar Dedo en gatillo ...
Tangle-Free Mesh Motion for Ablation Simulations
Droba, Justin
2016-01-01
Problems involving mesh motion-which should not be mistakenly associated with moving mesh methods, a class of adaptive mesh redistribution techniques-are of critical importance in numerical simulations of the thermal response of melting and ablative materials. Ablation is the process by which material vaporizes or otherwise erodes due to strong heating. Accurate modeling of such materials is of the utmost importance in design of passive thermal protection systems ("heatshields") for spacecraft, the layer of the vehicle that ensures survival of crew and craft during re-entry. In an explicit mesh motion approach, a complete thermal solve is first performed. Afterwards, the thermal response is used to determine surface recession rates. These values are then used to generate boundary conditions for an a posteriori correction designed to update the location of the mesh nodes. Most often, linear elastic or biharmonic equations are used to model this material response, traditionally in a finite element framework so that complex geometries can be simulated. A simple scheme for moving the boundary nodes involves receding along the surface normals. However, for all but the simplest problem geometries, evolution in time following such a scheme will eventually bring the mesh to intersect and "tangle" with itself, inducing failure. This presentation demonstrates a comprehensive and sophisticated scheme that analyzes the local geometry of each node with help from user-provided clues to eliminate the tangle and enable simulations on a wide-class of difficult problem geometries. The method developed is demonstrated for linear elastic equations but is general enough that it may be adapted to other modeling equations. The presentation will explicate the inner workings of the tangle-free mesh motion algorithm for both two and three-dimensional meshes. It will show abstract examples of the method's success, including a verification problem that demonstrates its accuracy and
Final Report for LDRD Project on Rapid Problem Setup for Mesh-Based Simulation (Rapsodi)
Energy Technology Data Exchange (ETDEWEB)
Brown, D L; Henshaw, W; Petersson, N A; Fast, P; Chand, K
2003-02-07
Under LLNL Exploratory Research LDRD funding, the Rapsodi project developed rapid setup technology for computational physics and engineering problems that require computational representations of complex geometry. Many simulation projects at LLNL involve the solution of partial differential equations in complex 3-D geometries. A significant bottleneck in carrying out these simulations arises in converting some specification of a geometry, such as a computer-aided design (CAD) drawing to a computationally appropriate 3-D mesh that can be used for simulation and analysis. Even using state-of-the-art mesh generation software, this problem setup step typically has required weeks or months, which is often much longer than required to carry out the computational simulation itself. The Rapsodi project built computational tools and designed algorithms that help to significantly reduce this setup time to less than a day for many realistic problems. The project targeted rapid setup technology for computational physics and engineering problems that use mixed-element unstructured meshes, overset meshes or Cartesian-embedded boundary (EB) meshes to represent complex geometry. It also built tools that aid in constructing computational representations of geometry for problems that do not require a mesh. While completely automatic mesh generation is extremely difficult, the amount of manual labor required can be significantly reduced. By developing novel, automated, component-based mesh construction procedures and automated CAD geometry repair and cleanup tools, Rapsodi has significantly reduced the amount of hand crafting required to generate geometry and meshes for scientific simulation codes.
Mesh Router Nodes placement in Rural Wireless Mesh Networks
Ebongue, Jean Louis Fendji Kedieng; Thron, Christopher; Nlong, Jean Michel
2015-01-01
The problem of placement of mesh router nodes in Wireless Mesh Networks is known to be a NP hard problem. In this paper, the problem is addressed under a constraint of network model tied to rural regions where we usually observe low density and sparse population. We consider the area to cover as decomposed into a set of elementary areas which can be required or optional in terms of coverage and where a node can be placed or not. We propose an effective algorithm to ensure the coverage. This a...
Tetrahedral meshing via maximal Poisson-disk sampling
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.
Signos clínicos del nervio cubital en el canal epitroclear del codo en una población normal
2014-01-01
Introducción: El síndrome del túnel cubital (STCU) del codo es subdiagnosticado por su similitud con la epicondilitis medial. Presenta con frecuencia variabilidad en las pruebas de provocación. Se quiere determinar en una población sana asintomática la aparición de estos signos. Materiales y métodos: En 380 codos de 190 estudiantes de 18 a 35 años, se les realizó la prueba de Tinel, la prueba de Flexión del Codo, de Rotación interna y flexión del codo, el Scratch- Collapse y una nueva prueba ...
Efficient Packet Forwarding in Mesh Network
Kanrar, Soumen
2012-01-01
Wireless Mesh Network (WMN) is a multi hop low cost, with easy maintenance robust network providing reliable service coverage. WMNs consist of mesh routers and mesh clients. In this architecture, while static mesh routers form the wireless backbone, mesh clients access the network through mesh routers as well as directly meshing with each other. Different from traditional wireless networks, WMN is dynamically self-organized and self-configured. In other words, the nodes in the mesh network automatically establish and maintain network connectivity. Over the years researchers have worked, to reduce the redundancy in broadcasting packet in the mesh network in the wireless domain for providing reliable service coverage, the source node deserves to broadcast or flood the control packets. The redundant control packet consumes the bandwidth of the wireless medium and significantly reduces the average throughput and consequently reduces the overall system performance. In this paper I study the optimization problem in...
A REGIONAL REFINEMENT FOR FINITE ELEMENT MESH DESIGN USING COLLAPSIBLE ELEMENT
Directory of Open Access Journals (Sweden)
Priyo Suprobo
2000-01-01
Full Text Available A practical algorithm for automated mesh design in finite element analysis is developed. A regional mixed mesh improvement procedure is introduced. The error control%2C algorithm implementation%2C code development%2C and the solution accuracy are discussed. Numerical example includes automated mesh designs for plane elastic media with singularities. The efficiency of the procedure is demonstrated. Abstract in Bahasa Indonesia : regional+refinement%2C+mesh+generation%2C+isoparametric+element%2C+collapsible+element
THM-GTRF: New Spider meshes, New Hydra-TH runs
Energy Technology Data Exchange (ETDEWEB)
Bakosi, Jozsef [Los Alamos National Laboratory; Christon, Mark A. [Los Alamos National Laboratory; Francois, Marianne M. [Los Alamos National Laboratory; Lowrie, Robert B. [Los Alamos National Laboratory; Nourgaliev, Robert [Los Alamos National Laboratory
2012-06-20
Progress is reported on computational capabilities for the grid-to-rod-fretting (GTRF) problem of pressurized water reactors. Numeca's Hexpress/Hybrid mesh generator is demonstrated as an excellent alternative to generating computational meshes for complex flow geometries, such as in GTRF. Mesh assessment is carried out using standard industrial computational fluid dynamics practices. Hydra-TH, a simulation code developed at LANL for reactor thermal-hydraulics, is demonstrated on hybrid meshes, containing different element types. A series of new Hydra-TH calculations has been carried out collecting turbulence statistics. Preliminary results on the newly generated meshes are discussed; full analysis will be documented in the L3 milestone, THM.CFD.P5.05, Sept. 2012.
Dahlgaard, Katja; Raposo, Alexandre A S F; Niccoli, Teresa; St Johnston, Daniel
2007-10-01
Mutants in the actin nucleators Cappuccino and Spire disrupt the polarized microtubule network in the Drosophila oocyte that defines the anterior-posterior axis, suggesting that microtubule organization depends on actin. Here, we show that Cappuccino and Spire organize an isotropic mesh of actin filaments in the oocyte cytoplasm. capu and spire mutants lack this mesh, whereas overexpressed truncated Cappuccino stabilizes the mesh in the presence of Latrunculin A and partially rescues spire mutants. Spire overexpression cannot rescue capu mutants, but prevents actin mesh disassembly at stage 10B and blocks late cytoplasmic streaming. We also show that the actin mesh regulates microtubules indirectly, by inhibiting kinesin-dependent cytoplasmic flows. Thus, the Capu pathway controls alternative states of the oocyte cytoplasm: when active, it assembles an actin mesh that suppresses kinesin motility to maintain a polarized microtubule cytoskeleton. When inactive, unrestrained kinesin movement generates flows that wash microtubules to the cortex.
E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
Springel, Volker
2009-01-01
Hydrodynamic cosmological simulations at present usually employ either the Lagrangian SPH technique, or Eulerian hydrodynamics on a Cartesian mesh with adaptive mesh refinement. Both of these methods have disadvantages that negatively impact their accuracy in certain situations. We here propose a novel scheme which largely eliminates these weaknesses. It is based on a moving unstructured mesh defined by the Voronoi tessellation of a set of discrete points. The mesh is used to solve the hyperbolic conservation laws of ideal hydrodynamics with a finite volume approach, based on a second-order unsplit Godunov scheme with an exact Riemann solver. The mesh-generating points can in principle be moved arbitrarily. If they are chosen to be stationary, the scheme is equivalent to an ordinary Eulerian method with second order accuracy. If they instead move with the velocity of the local flow, one obtains a Lagrangian formulation of hydrodynamics that does not suffer from the mesh distortion limitations inherent in othe...
Load Balancing in Wireless Mesh Network: a Survey
Directory of Open Access Journals (Sweden)
Maryam Asgari
Full Text Available Wireless Mesh network (WMN is a state of the art networking standard for next generation of wireless network. The construction of these networks is basis of a network of wireless routers witch forwarding each other`s packets in a multi-hop manner. All us ...
All inorganic semiconductor nanowire mesh for direct solar water splitting.
Liu, Bin; Wu, Cheng-Hao; Miao, Jianwei; Yang, Peidong
2014-11-25
The generation of chemical fuels via direct solar-to-fuel conversion from a fully integrated artificial photosynthetic system is an attractive approach for clean and sustainable energy, but so far there has yet to be a system that would have the acceptable efficiency, durability and can be manufactured at a reasonable cost. Here, we show that a semiconductor mesh made from all inorganic nanowires can achieve unassisted solar-driven, overall water-splitting without using any electron mediators. Free-standing nanowire mesh networks could be made in large scales using solution synthesis and vacuum filtration, making this approach attractive for low cost implementation.
Inching toward 'push-button' meshing
National Research Council Canada - National Science Library
James Masters
2015-01-01
While "push-button" meshing remains an elusive goal, advances in 2015 have brought the technology to the point where meshes can be constructed with relative ease when appropriate surfaces are available...
Particle Collection Efficiency for Nylon Mesh Screens
Cena, Lorenzo G.; Ku, Bon-Ki; Peters, Thomas M.
2011-01-01
Mesh screens composed of nylon fibers leave minimal residual ash and produce no significant spectral interference when ashed for spectrometric examination. These characteristics make nylon mesh screens attractive as a collection substrate for nanoparticles. A theoretical single-fiber efficiency expression developed for wire-mesh screens was evaluated for estimating the collection efficiency of submicrometer particles for nylon mesh screens. Pressure drop across the screens, the effect of part...
Geometric and Meshing Properties of Conjugate Curves for Gear Transmission
Directory of Open Access Journals (Sweden)
Dong Liang
2014-01-01
Full Text Available Conjugate curves have been put forward previously by authors for gear transmission. Compared with traditional conjugate surfaces, the conjugate curves have more flexibility and diversity in aspects of gear design and generation. To further extend its application in power transmission, the geometric and meshing properties of conjugate curves are discussed in this paper. Firstly, general principle descriptions of conjugate curves for arbitrary axial position are introduced. Secondly, geometric analysis of conjugate curves is carried out based on differential geometry including tangent and normal in arbitrary contact direction, characteristic point, and curvature relationships. Then, meshing properties of conjugate curves are further revealed. According to a given plane or spatial curve, the uniqueness of conjugated curve under different contact angle conditions is discussed. Meshing commonality of conjugate curves is also demonstrated in terms of a class of spiral curves contacting in the given direction for various gear axes. Finally, a conclusive summary of this study is given.
Connectivity-Based Segmentation for GPU-Accelerated Mesh Decompression
Institute of Scientific and Technical Information of China (English)
Jie-Yi Zhao; Min Tang; Ruo-Feng Tong
2012-01-01
We present a novel algorithm to partition large 3D meshes for GPU-accelerated decompression.Our formulation focuses on minimizing the replicated vertices between patches,and balancing the numbers of faces of patches for efficient parallel computing.First we generate a topology model of the original mesh and remove vertex positions.Then we assign the centers of patches using geodesic farthest point sampling and cluster the faces according to the geodesic distance to the centers.After the segmentation we swap boundary faces to fix jagged boundaries and store the boundary vertices for whole-mesh preservation.The decompression of each patch runs on a thread of GPU,and we evaluate its performance on various large benchmarks.In practice,the GPU-based decompression algorithm runs more than 48x faster on NVIDIA GeForce GTX 580 GPU compared with that on the CPU using single core.
Mesh Resolution Effect on 3D RANS Turbomachinery Flow Simulations
Yershov, Sergiy
2016-01-01
The paper presents the study of the effect of a mesh refinement on numerical results of 3D RANS computations of turbomachinery flows. The CFD solver F, which based on the second-order accurate ENO scheme, is used in this study. The simplified multigrid algorithm and local time stepping permit decreasing computational time. The flow computations are performed for a number of turbine and compressor cascades and stages. In all flow cases, the successively refined meshes of H-type with an approximate orthogonalization near the solid walls were generated. The results obtained are compared in order to estimate their both mesh convergence and ability to resolve the transonic flow pattern. It is concluded that for thorough studying the fine phenomena of the 3D turbomachinery flows, it makes sense to use the computational meshes with the number of cells from several millions up to several hundred millions per a single turbomachinery blade channel, while for industrial computations, a mesh of about or less than one mil...
Box truss analysis and technology development. Task 1: Mesh analysis and control
Bachtell, E. E.; Bettadapur, S. S.; Coyner, J. V.
1985-01-01
An analytical tool was developed to model, analyze and predict RF performance of box truss antennas with reflective mesh surfaces. The analysis system is unique in that it integrates custom written programs for cord tied mesh surfaces, thereby drastically reducing the cost of analysis. The analysis system is capable of determining the RF performance of antennas under any type of manufacturing or operating environment by integrating together the various disciplines of design, finite element analysis, surface best fit analysis and RF analysis. The Integrated Mesh Analysis System consists of six separate programs: The Mesh Tie System Model Generator, The Loadcase Generator, The Model Optimizer, The Model Solver, The Surface Topography Solver and The RF Performance Solver. Additionally, a study using the mesh analysis system was performed to determine the effect of on orbit calibration, i.e., surface adjustment, on a typical box truss antenna.
2010-10-01
... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Mesh size. 300.110 Section 300.110... Antarctic Marine Living Resources § 300.110 Mesh size. (a) The use of pelagic and bottom trawls having the mesh size in any part of a trawl less than indicated is prohibited for any directed fishing for the...
Markov Random Fields on Triangle Meshes
DEFF Research Database (Denmark)
Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jakob Andreas
2010-01-01
mesh edges according to a feature detecting prior. Since we should not smooth across a sharp feature, we use edge labels to control the vertex process. In a Bayesian framework, MRF priors are combined with the likelihood function related to the mesh formation method. The output of our algorithm...... is a piecewise smooth mesh with explicit labelling of edges belonging to the sharp features....
Mesh network achieve its fuction on Linux
Pei Ping; PETRENKO Y.N.
2015-01-01
In this paper, we introduce a Mesh network protocol evaluation and development. It has a special protocol. We could easily understand the Linux operation principles which are in use in mesh network. In addition to our comprehension, we describe the graph which shows package routing way. At last according to testing we prove that Mesh protocol AODV satisfy Linux platform performance requirements.
The mesh network protocol evaluation and development
Pei Ping; PETRENKO Y.N.
2015-01-01
In this paper, we introduce a Mesh network protocol evaluation and development. It has a special protocol. We could easily to understand that how different protocols are used in mesh network. In addition to our comprehension, Multi – hop routing protocol could provide robustness and load balancing to communication in wireless mesh networks.
Practical implementation of tetrahedral mesh reconstruction in emission tomography
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
GRChombo : Numerical Relativity with Adaptive Mesh Refinement
Clough, Katy; Finkel, Hal; Kunesch, Markus; Lim, Eugene A; Tunyasuvunakool, Saran
2015-01-01
Numerical relativity has undergone a revolution in the past decade. With a well-understood mathematical formalism, and full control over the gauge modes, it is now entering an era in which the science can be properly explored. In this work, we introduce GRChombo, a new numerical relativity code written to take full advantage of modern parallel computing techniques. GRChombo's features include full adaptive mesh refinement with block structured Berger-Rigoutsos grid generation which supports non-trivial "many-boxes-in-many-boxes" meshing hierarchies, and massive parallelism through the Message Passing Interface (MPI). GRChombo evolves the Einstein equation with the standard BSSN formalism, with an option to turn on CCZ4 constraint damping if required. We show that GRChombo passes all the standard "Apples-to-Apples" code comparison tests. We also show that it can stably and accurately evolve vacuum black hole spacetimes such as binary black hole mergers, and non-vacuum spacetimes such as scalar collapses into b...
Boxlib with tiling: an adaptive mesh refinement software framework
Unat, Didem; Zhang, W.; Almgren, A.; Day, M.; Nguyen, T.; Shalf, J.
2016-01-01
In this paper we introduce a block-structured adaptive mesh refinement software framework that incorporates tiling, a well-known loop transformation. Because the multiscale, multiphysics codes built in boxlib are designed to solve complex systems at high resolution, performance on current and next generation architectures is essential. With the expectation of many more cores per node on next generation architectures, the ability to effectively utilize threads within a node is essential, and t...
Mamy, Laurent; Letouzey, Vincent; Lavigne, Jean-Philippe; Garric, Xavier; Gondry, Jean; Mares, Pierre; De Tayrac, Renaud
2010-01-01
International audience; INTRODUCTION AND HYPOTHESIS: The aim of this study was to evaluate a link between mesh infection and shrinkage. METHODS: Twenty-eight Wistar rats were implanted with synthetic meshes that were either non-absorbable (polypropylene (PP), n = 14) or absorbable (poly (D: ,L: -lactic acid) (PLA94), n = 14). A validated animal incisionnal abdominal hernia model of mesh infection was used. Fourteen meshes (n = 7 PLA94 and n = 7 PP meshes) were infected intraoperatively with 1...
Confined helium on Lagrange meshes
Baye, Daniel
2015-01-01
The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.
The moving mesh code Shadowfax
Vandenbroucke, Bert
2016-01-01
We introduce the moving mesh code Shadowfax, which can be used to evolve a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. The code is written in C++ and its source code is made available to the scientific community under the GNU Affero General Public License. We outline the algorithm and the design of our implementation, and demonstrate its validity through the results of a set of basic test problems, which are also part of the public version. We also compare Shadowfax with a number of other publicly available codes using different hydrodynamical integration schemes, illustrating the advantages and disadvantages of the moving mesh technique.
The moving mesh code SHADOWFAX
Vandenbroucke, B.; De Rijcke, S.
2016-07-01
We introduce the moving mesh code SHADOWFAX, which can be used to evolve a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. The code is written in C++ and its source code is made available to the scientific community under the GNU Affero General Public Licence. We outline the algorithm and the design of our implementation, and demonstrate its validity through the results of a set of basic test problems, which are also part of the public version. We also compare SHADOWFAX with a number of other publicly available codes using different hydrodynamical integration schemes, illustrating the advantages and disadvantages of the moving mesh technique.
On the flexibility of Kokotsakis meshes
Karpenkov, Oleg
2008-01-01
In this paper we study geometric, algebraic, and computational aspects of flexibility and infinitesimal flexibility of Kokotsakis meshes. A Kokotsakis mesh is a mesh that consists of a face in the middle and a certain band of faces attached to the middle face by its perimeter. In particular any 3x3-mesh made of quadrangles is a Kokotsakis mesh. We express the infinitesimal flexibility condition in terms of Ceva and Menelaus theorems. Further we study semi-algebraic properties of the set of fl...
Image meshing via hierarchical optimization
Institute of Scientific and Technical Information of China (English)
Hao XIE; Ruo-feng TONG‡
2016-01-01
Vector graphic, as a kind of geometric representation of raster images, has many advantages, e.g., defi nition independence and editing facility. A popular way to convert raster images into vector graphics is image meshing, the aim of which is to fi nd a mesh to represent an image as faithfully as possible. For traditional meshing algorithms, the crux of the problem resides mainly in the high non-linearity and non-smoothness of the objective, which makes it diﬃcult to fi nd a desirable optimal solution. To ameliorate this situation, we present a hierarchical optimization algorithm solving the problem from coarser levels to fi ner ones, providing initialization for each level with its coarser ascent. To further simplify the problem, the original non-convex problem is converted to a linear least squares one, and thus becomes convex, which makes the problem much easier to solve. A dictionary learning framework is used to combine geometry and topology elegantly. Then an alternating scheme is employed to solve both parts. Experiments show that our algorithm runs fast and achieves better results than existing ones for most images.
Image meshing via hierarchical optimization＊
Institute of Scientific and Technical Information of China (English)
Hao XIE; Ruo-feng TONGS
2016-01-01
Vector graphic, as a kind of geometric representation of raster images, has many advantages, e.g., definition independence and editing facility. A popular way to convert raster images into vector graphics is image meshing, the aim of which is to find a mesh to represent an image as faithfully as possible. For traditional meshing algorithms, the crux of the problem resides mainly in the high non-linearity and non-smoothness of the objective, which makes it difficult to find a desirable optimal solution. To ameliorate this situation, we present a hierarchical optimization algorithm solving the problem from coarser levels to finer ones, providing initialization for each level with its coarser ascent. To further simplify the problem, the original non-convex problem is converted to a linear least squares one, and thus becomes convex, which makes the problem much easier to solve. A dictionary learning framework is used to combine geometry and topology elegantly. Then an alternating scheme is employed to solve both parts. Experiments show that our algorithm runs fast and achieves better results than existing ones for most images.
Soto, Dan; Le Helloco, Antoine; Clanet, Cristophe; Quere, David; Varanasi, Kripa
2016-11-01
A drop thrown against a mesh can pass through its holes if impacting with enough inertia. As a result, although part of the droplet may remain on one side of the sieve, the rest will end up grated through the other side. This inexpensive method to break up millimetric droplets into micrometric ones may be of particular interest in a wide variety of applications: enhancing evaporation of droplets launched from the top of an evaporative cooling tower or preventing drift of pesticides sprayed above crops by increasing their initial size and atomizing them at the very last moment with a mesh. In order to understand how much liquid will be grated we propose in this presentation to start first by studying a simpler situation: a drop impacting a plate pierced with a single off centered hole. The study of the role of natural parameters such as the radius drop and speed or the hole position, size and thickness allows us to discuss then the more general situation of a plate pierced with multiple holes: the mesh.
Cluster parallel rendering based on encoded mesh
Institute of Scientific and Technical Information of China (English)
QIN Ai-hong; XIONG Hua; PENG Hao-yu; LIU Zhen; SHI Jiao-ying
2006-01-01
Use of compressed mesh in parallel rendering architecture is still an unexplored area, the main challenge of which is to partition and sort the encoded mesh in compression-domain. This paper presents a mesh compression scheme PRMC (Parallel Rendering based Mesh Compression) supplying encoded meshes that can be partitioned and sorted in parallel rendering system even in encoded-domain. First, we segment the mesh into submeshes and clip the submeshes' boundary into Runs, and then piecewise compress the submeshes and Runs respectively. With the help of several auxiliary index tables, compressed submeshes and Runs can serve as rendering primitives in parallel rendering system. Based on PRMC, we design and implement a parallel rendering architecture. Compared with uncompressed representation, experimental results showed that PRMC meshes applied in cluster parallel rendering system can dramatically reduce the communication requirement.
Triangle geometry processing for surface modeling and cartesian grid generation
Aftosmis, Michael J [San Mateo, CA; Melton, John E [Hollister, CA; Berger, Marsha J [New York, NY
2002-09-03
Cartesian mesh generation is accomplished for component based geometries, by intersecting components subject to mesh generation to extract wetted surfaces with a geometry engine using adaptive precision arithmetic in a system which automatically breaks ties with respect to geometric degeneracies. During volume mesh generation, intersected surface triangulations are received to enable mesh generation with cell division of an initially coarse grid. The hexagonal cells are resolved, preserving the ability to directionally divide cells which are locally well aligned.
Balla, Andrea; Quaresima, Silvia; Smolarek, Sebastian; Shalaby, Mostafa; Missori, Giulia; Sileri, Pierpaolo
2017-04-01
This review reports the incidence of mesh-related erosion after ventral mesh rectopexy to determine whether any difference exists in the erosion rate between synthetic and biological mesh. A systematic search of the MEDLINE and the Ovid databases was conducted to identify suitable articles published between 2004 and 2015. The search strategy capture terms were laparoscopic ventral mesh rectopexy, laparoscopic anterior rectopexy, robotic ventral rectopexy, and robotic anterior rectopexy. Eight studies (3,956 patients) were included in this review. Of those patients, 3,517 patients underwent laparoscopic ventral rectopexy (LVR) using synthetic mesh and 439 using biological mesh. Sixty-six erosions were observed with synthetic mesh (26 rectal, 32 vaginal, 8 recto-vaginal fistulae) and one (perineal erosion) with biological mesh. The synthetic and the biological mesh-related erosion rates were 1.87% and 0.22%, respectively. The time between rectopexy and diagnosis of mesh erosion ranged from 1.7 to 124 months. No mesh-related mortalities were reported. The incidence of mesh-related erosion after LVR is low and is more common after the placement of synthetic mesh. The use of biological mesh for LVR seems to be a safer option; however, large, multicenter, randomized, control trials with long follow-ups are required if a definitive answer is to be obtained.
Toward a Consistent Framework for High Order Mesh Refinement Schemes in Numerical Relativity
Mongwane, Bishop
2015-01-01
It has now become customary in the field of numerical relativity to couple high order finite difference schemes to mesh refinement algorithms. To this end, different modifications to the standard Berger-Oliger adaptive mesh refinement algorithm have been proposed. In this work we present a fourth order stable mesh refinement scheme with sub-cycling in time for numerical relativity. We do not use buffer zones to deal with refinement boundaries but explicitly specify boundary data for refined grids. We argue that the incompatibility of the standard mesh refinement algorithm with higher order Runge Kutta methods is a manifestation of order reduction phenomena, caused by inconsistent application of boundary data in the refined grids. Our scheme also addresses the problem of spurious reflections that are generated when propagating waves cross mesh refinement boundaries. We introduce a transition zone on refined levels within which the phase velocity of propagating modes is allowed to decelerate in order to smoothl...
Exact mesh shape design of large cable-network antenna reflectors with flexible ring truss supports
Liu, Wang; Li, Dong-Xu; Yu, Xin-Zhan; Jiang, Jian-Ping
2014-04-01
An exact-designed mesh shape with favorable surface accuracy is of practical significance to the performance of large cable-network antenna reflectors. In this study, a novel design approach that could guide the generation of exact spatial parabolic mesh configurations of such reflector was proposed. By incorporating the traditional force density method with the standard finite element method, this proposed approach had taken the deformation effects of flexible ring truss supports into consideration, and searched for the desired mesh shapes that can satisfy the requirement that all the free nodes are exactly located on the objective paraboloid. Compared with the conventional design method, a remarkable improvement of surface accuracy in the obtained mesh shapes had been demonstrated by numerical examples. The present work would provide a helpful technical reference for the mesh shape design of such cable-network antenna reflector in engineering practice. [Figure not available: see fulltext.
h-Refinement for simple corner balance scheme of SN transport equation on distorted meshes
Yang, Rong; Yuan, Guangwei
2016-11-01
The transport sweep algorithm is a common method for solving discrete ordinate transport equation, but it breaks down once a concave cell appears in spatial meshes. To deal with this issue a local h-refinement for simple corner balance (SCB) scheme of SN transport equation on arbitrary quadrilateral meshes is presented in this paper by using a new subcell partition. It follows that a hybrid mesh with both triangle and quadrilateral cells is generated, and the geometric quality of these cells improves, especially it is ensured that all cells become convex. Combining with the original SCB scheme, an adaptive transfer algorithm based on the hybrid mesh is constructed. Numerical experiments are presented to verify the utility and accuracy of the new algorithm, especially for some application problems such as radiation transport coupled with Lagrangian hydrodynamic flow. The results show that it performs well on extremely distorted meshes with concave cells, on which the original SCB scheme does not work.
Determination of an Initial Mesh Density for Finite Element Computations via Data Mining
Energy Technology Data Exchange (ETDEWEB)
Kanapady, R; Bathina, S K; Tamma, K K; Kamath, C; Kumar, V
2001-07-23
Numerical analysis software packages which employ a coarse first mesh or an inadequate initial mesh need to undergo a cumbersome and time consuming mesh refinement studies to obtain solutions with acceptable accuracy. Hence, it is critical for numerical methods such as finite element analysis to be able to determine a good initial mesh density for the subsequent finite element computations or as an input to a subsequent adaptive mesh generator. This paper explores the use of data mining techniques for obtaining an initial approximate finite element density that avoids significant trial and error to start finite element computations. As an illustration of proof of concept, a square plate which is simply supported at its edges and is subjected to a concentrated load is employed for the test case. Although simplistic, the present study provides insight into addressing the above considerations.
Secure Mechanism for Handling Targeted Attacks in Infrastructure Based Wireless Mesh Networks
Shafi, Rehan; Rahim, Aneel; Bin Muhaya, Fahad; Ashraf, Shehzad; Sher, Muhammad
Infrastructure based Wireless mesh networks allow heterogeneous types of networks to be connected at a time through wireless mesh routers. Since the nodes of every network have different processing power, bandwidth, amount of energy etc. so this situation can lead to targeted attacks. An Internet connected node can easily generate flood over a node of sensor network. So to handle these types of attacks we in this paper introduced a new secure authentication mechanism that works when a potential of attack is detected. Moreover we also authorized the nodes of the wireless mesh network to demand data according to their capacity by using pull data traffic control mechanism. We applied this solution first on mesh routers to discourage targeted attacks and secondly we applied the solution on an individual node that lies in between a node and mesh router.
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.
Baxes, Gregory A. (Inventor); Linger, Timothy C. (Inventor)
2011-01-01
Systems and methods are provided for progressive mesh storage and reconstruction using wavelet-encoded height fields. A method for progressive mesh storage includes reading raster height field data, and processing the raster height field data with a discrete wavelet transform to generate wavelet-encoded height fields. In another embodiment, a method for progressive mesh storage includes reading texture map data, and processing the texture map data with a discrete wavelet transform to generate wavelet-encoded texture map fields. A method for reconstructing a progressive mesh from wavelet-encoded height field data includes determining terrain blocks, and a level of detail required for each terrain block, based upon a viewpoint. Triangle strip constructs are generated from vertices of the terrain blocks, and an image is rendered utilizing the triangle strip constructs. Software products that implement these methods are provided.
An effective quadrilateral mesh adaptation
Institute of Scientific and Technical Information of China (English)
KHATTRI Sanjay Kumar
2006-01-01
Accuracy of a simulation strongly depends on the grid quality. Here, quality means orthogonality at the boundaries and quasi-orthogonality within the critical regions, smoothness, bounded aspect ratios and solution adaptive behaviour. It is not recommended to refine the parts of the domain where the solution shows little variation. It is desired to concentrate grid points and cells in the part of the domain where the solution shows strong gradients or variations. We present a simple, effective and computationally efficient approach for quadrilateral mesh adaptation. Several numerical examples are presented for supporting our claim.
Bluetooth Low Energy Mesh Networks: A Survey.
Darroudi, Seyed Mahdi; Gomez, Carles
2017-06-22
Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues.
Mesh networking optimized for robotic teleoperation
Hart, Abraham; Pezeshkian, Narek; Nguyen, Hoa
2012-06-01
Mesh networks for robot teleoperation pose different challenges than those associated with traditional mesh networks. Unmanned ground vehicles (UGVs) are mobile and operate in constantly changing and uncontrollable environments. Building a mesh network to work well under these harsh conditions presents a unique challenge. The Manually Deployed Communication Relay (MDCR) mesh networking system extends the range of and provides non-line-of-sight (NLOS) communications for tactical and explosive ordnance disposal (EOD) robots currently in theater. It supports multiple mesh nodes, robots acting as nodes, and works with all Internet Protocol (IP)-based robotic systems. Under MDCR, the performance of different routing protocols and route selection metrics were compared resulting in a modified version of the Babel mesh networking protocol. This paper discusses this and other topics encountered during development and testing of the MDCR system.
MPDATA error estimator for mesh adaptivity
Szmelter, Joanna; Smolarkiewicz, Piotr K.
2006-04-01
In multidimensional positive definite advection transport algorithm (MPDATA) the leading error as well as the first- and second-order solutions are known explicitly by design. This property is employed to construct refinement indicators for mesh adaptivity. Recent progress with the edge-based formulation of MPDATA facilitates the use of the method in an unstructured-mesh environment. In particular, the edge-based data structure allows for flow solvers to operate on arbitrary hybrid meshes, thereby lending itself to implementations of various mesh adaptivity techniques. A novel unstructured-mesh nonoscillatory forward-in-time (NFT) solver for compressible Euler equations is used to illustrate the benefits of adaptive remeshing as well as mesh movement and enrichment for the efficacy of MPDATA-based flow solvers. Validation against benchmark test cases demonstrates robustness and accuracy of the approach.
Bluetooth Low Energy Mesh Networks: A Survey
Darroudi, Seyed Mahdi; Gomez, Carles
2017-01-01
Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues. PMID:28640183
Tarjuelo-Gutierrez, J; Rodriguez-Vila, B; Pierce, D M; Fastl, T E; Verbrugghe, P; Fourneau, I; Maleux, G; Herijgers, P; Holzapfel, G A; Gomez, E J
2014-02-01
In order to perform finite element (FE) analyses of patient-specific abdominal aortic aneurysms, geometries derived from medical images must be meshed with suitable elements. We propose a semi-automatic method for generating conforming hexahedral meshes directly from contours segmented from medical images. Magnetic resonance images are generated using a protocol developed to give the abdominal aorta high contrast against the surrounding soft tissue. These data allow us to distinguish between the different structures of interest. We build novel quadrilateral meshes for each surface of the sectioned geometry and generate conforming hexahedral meshes by combining the quadrilateral meshes. The three-layered morphology of both the arterial wall and thrombus is incorporated using parameters determined from experiments. We demonstrate the quality of our patient-specific meshes using the element Scaled Jacobian. The method efficiently generates high-quality elements suitable for FE analysis, even in the bifurcation region of the aorta into the iliac arteries. For example, hexahedral meshes of up to 125,000 elements are generated in less than 130 s, with 94.8 % of elements well suited for FE analysis. We provide novel input for simulations by independently meshing both the arterial wall and intraluminal thrombus of the aneurysm, and their respective layered morphologies.
Design of electrospinning mesh devices
Russo, Giuseppina; Peters, Gerrit W. M.; Solberg, Ramon H. M.; Vittoria, Vittoria
2012-07-01
This paper describes the features of new membranes that can act as local biomedical devices owing to their peculiar shape in the form of mesh structure. These materials are designed to provide significant effects to reduce local inflammations and improve the tissue regeneration. Lamellar Hydrotalcite loaded with Diclofenac Sodium (HTLc-DIK) was homogenously dispersed inside a polymeric matrix of Poly-caprolactone (PCL) to manufacture membranes by electrospinning technique. The experimental procedure and the criteria employed have shown to be extremely effective at increasing potentiality and related applications. The employed technique has proved to be very useful to manufacture polymeric fibers with diameters in the range of nano-micro scale. In this work a dedicated collector based on a proprietary technology of IME Technologies and Eindhoven University of Technology (TU/e) was used. It allowed to obtain devices with a macro shape of a 3D-mesh. Atomic Force Microscopy (AFM) highlights a very interesting texture of the electrospun fibers. They show a lamellar morphology that is only slightly modified by the inclusion of the interclay embedded in the devices to control the drug release phenomena.
Conformal refinement of unstructured quadrilateral meshes
Energy Technology Data Exchange (ETDEWEB)
Garmella, Rao [Los Alamos National Laboratory
2009-01-01
We present a multilevel adaptive refinement technique for unstructured quadrilateral meshes in which the mesh is kept conformal at all times. This means that the refined mesh, like the original, is formed of only quadrilateral elements that intersect strictly along edges or at vertices, i.e., vertices of one quadrilateral element do not lie in an edge of another quadrilateral. Elements are refined using templates based on 1:3 refinement of edges. We demonstrate that by careful design of the refinement and coarsening strategy, we can maintain high quality elements in the refined mesh. We demonstrate the method on a number of examples with dynamically changing refinement regions.
Chambers, David W
2005-01-01
Groups naturally promote their strengths and prefer values and rules that give them an identity and an advantage. This shows up as generational tensions across cohorts who share common experiences, including common elders. Dramatic cultural events in America since 1925 can help create an understanding of the differing value structures of the Silents, the Boomers, Gen Xers, and the Millennials. Differences in how these generations see motivation and values, fundamental reality, relations with others, and work are presented, as are some applications of these differences to the dental profession.
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.
Mesh Exposure and Associated Risk Factors in Women Undergoing Transvaginal Prolapse Repair with Mesh
Directory of Open Access Journals (Sweden)
Elizabeth A. Frankman
2013-01-01
Full Text Available Objective. To determine frequency, rate, and risk factors associated with mesh exposure in women undergoing transvaginal prolapse repair with polypropylene mesh. Methods. Retrospective chart review was performed for all women who underwent Prolift Pelvic Floor Repair System (Gynecare, Somerville, NJ between September 2005 and September 2008. Multivariable logistic regression was performed to identify risk factors for mesh exposure. Results. 201 women underwent Prolift. Mesh exposure occurred in 12% (24/201. Median time to mesh exposure was 62 days (range: 10–372. When mesh was placed in the anterior compartment, the frequency of mesh exposure was higher than that when mesh was placed in the posterior compartment (8.7% versus 2.9%, P=0.04. Independent risk factors for mesh exposure were diabetes (AOR = 7.7, 95% CI 1.6–37.6; P=0.01 and surgeon (AOR = 7.3, 95% CI 1.9–28.6; P=0.004. Conclusion. Women with diabetes have a 7-fold increased risk for mesh exposure after transvaginal prolapse repair using Prolift. The variable rate of mesh exposure amongst surgeons may be related to technique. The anterior vaginal wall may be at higher risk of mesh exposure as compared to the posterior vaginal wall.
Tensile Behaviour of Welded Wire Mesh and Hexagonal Metal Mesh for Ferrocement Application
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.
Dahlgaard, Katja; Raposo, Alexandre A.S.F.; Niccoli, Teresa; St Johnston, Daniel
2007-01-01
Summary Mutants in the actin nucleators Cappuccino and Spire disrupt the polarized microtubule network in the Drosophila oocyte that defines the anterior-posterior axis, suggesting that microtubule organization depends on actin. Here, we show that Cappuccino and Spire organize an isotropic mesh of actin filaments in the oocyte cytoplasm. capu and spire mutants lack this mesh, whereas overexpressed truncated Cappuccino stabilizes the mesh in the presence of Latrunculin A and partially rescues spire mutants. Spire overexpression cannot rescue capu mutants, but prevents actin mesh disassembly at stage 10B and blocks late cytoplasmic streaming. We also show that the actin mesh regulates microtubules indirectly, by inhibiting kinesin-dependent cytoplasmic flows. Thus, the Capu pathway controls alternative states of the oocyte cytoplasm: when active, it assembles an actin mesh that suppresses kinesin motility to maintain a polarized microtubule cytoskeleton. When inactive, unrestrained kinesin movement generates flows that wash microtubules to the cortex. PMID:17925229
Quadrilateral mesh fitting that preserves sharp features based on multi-normals for Laplacian energy
Directory of Open Access Journals (Sweden)
Yusuke Imai
2014-04-01
Full Text Available Because the cost of performance testing using actual products is expensive, manufacturers use lower-cost computer-aided design simulations for this function. In this paper, we propose using hexahedral meshes, which are more accurate than tetrahedral meshes, for finite element analysis. We propose automatic hexahedral mesh generation with sharp features to precisely represent the corresponding features of a target shape. Our hexahedral mesh is generated using a voxel-based algorithm. In our previous works, we fit the surface of the voxels to the target surface using Laplacian energy minimization. We used normal vectors in the fitting to preserve sharp features. However, this method could not represent concave sharp features precisely. In this proposal, we improve our previous Laplacian energy minimization by adding a term that depends on multi-normal vectors instead of using normal vectors. Furthermore, we accentuate a convex/concave surface subset to represent concave sharp features.
Directory of Open Access Journals (Sweden)
Marcio Eduardo de Melo Viveiros
2008-12-01
Full Text Available OBJETIVO: Analisamos retrospectivamente os resultados de 21 casos de síndrome cubital tratados cirurgicamente com a técnica da epicondilectomia parcial medial. MÉTODOS: No período de fevereiro de 2001 a outubro de 2006, 21 pacientes com síndrome do canal cubital foram tratados pela técnica da epicondilectomia parcial medial do cotovelo associada à neurólise do nervo ulnar. Destes, 12 (57,1% eram do sexo masculino. O lado direito foi o acometido em 15 (71,4% pacientes. A média da idade dos pacientes foi de 51,6 anos. Pela graduação de McGowan, seis (28,6% pacientes encontravam-se no grau I, 11 (52,3%, no grau II e quatro (19,1%, no grau III do período pré-operatório. RESULTADOS: O tempo médio de acompanhamento pós-operatório foi de 25,7 meses. No pós-operatório, os pacientes foram avaliados conforme a escala de pontos de Bishop, sendo que nove (42,8% apresentavam resultados excelentes, sete (33,3%, bons, três (14,2%, regulares e dois (9,5%, ruins. Nesta série, não se encontraram como complicações a instabilidade em valgo residual, a lesão permanente do nervo ulnar, a recidiva da compressão ou a subluxação do nervo ulnar. As complicações encontradas foram perda do arco de movimento em um (4,7% caso, infecção superficial em um (4,7% e um (4,7% com dor residual. CONCLUSÃO: Os resultados apresentados permitem concluir que a epicondilectomia parcial medial do cotovelo associada à neurólise do nervo ulnar é eficiente e segura para o tratamento da síndrome do canal cubital.OBJECTIVE: The authors made a retrospective analysis of the results of 21 cases of cubital syndrome that were surgically treated with the partial medial epicondylectomy. METHODS: From February 2001 to October 2006, 21 patients with cubital tunnel syndrome were treated with the technique of elbow partial medial epicondylectomy associated to neurolysis of the ulnar nerve. Of these patients, 12 (57.1% were male. The right side was involved in 15 (71
Institute of Scientific and Technical Information of China (English)
贾科锋; 丁实; 翟丽东; 袁武; 刘庚辰; 李云生
2011-01-01
目的 为治疗肘管综合症的原位松解术提供解剖学依据.方法 14例福尔马林固定的成年肘部标本,11例行大体解剖观察肘管特点,3例分别制成1mm厚的水平、冠状和矢状位火棉胶切片.并利用水平切片的图像对肘管等结构进行三维重建.结果 肘管的底南肘关节囊和尺侧副韧带前、后及横束构成,顶由肘管支持带或滑车上肘肌和尺侧腕屈肌的肱尺两头之间的筋膜构成.滑车上肘肌起白内上髁,其上部以筋膜止于鹰嘴内侧缘;中下部分直接止于鹰嘴内侧缘.在尺神经沟水平,有一筋膜蒂将尺神经连于底的后外侧部分.结论 对于滑车上肘肌引起的尺神经卡压者,合理切除此肌肉可以达到理想的治疗效果.筋膜蒂可能有防止尺神经过度运动以及半脱位的作用.%Objective To explore anatomic features of cubital tunnel, and provide reference for the decompression treatment of the cubital tunnel syndrome. Methods 14 formalin-fixed adult elbow specimens were used in this study. 11 of them were dissected to reveal anatomic features of the cubital tunnel, other 3 were embedded by celloidin and performed successive horizontal, coronal and sagittal section with the thickness of 1mm, followed by the cubital tunnel reconstruction adopting successive horizontal sectional images. Results The floor of cubital tunnel was formed by the capsule of elbow and all the three bundles of medial collateral ligament (MCL). The roof of this tunnel was composed of cubital tunnel retinaculum or epitrochleo-anconeus (EA) and the fascia between the two heads of flexor carpi ulnaris muscle. Epitrochleo-anconeus originated from the medial epicondyle. The upper portion of this muscle inserted to the medial margin of the olecranon through a fascia while the lower 2/3 portion directly to it. A fascial pedicle was identified at the level of the retrocondylar groove. It connected the ulnar nerve to the posterolateral portion of the
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.
Mesh refinement strategy for optimal control problems
Paiva, L. T.; Fontes, F. A. C. C.
2013-10-01
Direct methods are becoming the most used technique to solve nonlinear optimal control problems. Regular time meshes having equidistant spacing are frequently used. However, in some cases these meshes cannot cope accurately with nonlinear behavior. One way to improve the solution is to select a new mesh with a greater number of nodes. Another way, involves adaptive mesh refinement. In this case, the mesh nodes have non equidistant spacing which allow a non uniform nodes collocation. In the method presented in this paper, a time mesh refinement strategy based on the local error is developed. After computing a solution in a coarse mesh, the local error is evaluated, which gives information about the subintervals of time domain where refinement is needed. This procedure is repeated until the local error reaches a user-specified threshold. The technique is applied to solve the car-like vehicle problem aiming minimum consumption. The approach developed in this paper leads to results with greater accuracy and yet with lower overall computational time as compared to using a time meshes having equidistant spacing.
7th International Meshing Roundtable '98
Energy Technology Data Exchange (ETDEWEB)
Eldred, T.J.
1998-10-01
The goal of the 7th 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 past, the Roundtable has enjoyed significant participation from each of these groups from a wide variety of countries.
Laparoscopic Pelvic Floor Repair Using Polypropylene Mesh
Directory of Open Access Journals (Sweden)
Shih-Shien Weng
2008-09-01
Conclusion: Laparoscopic pelvic floor repair using a single piece of polypropylene mesh combined with uterosacral ligament suspension appears to be a feasible procedure for the treatment of advanced vaginal vault prolapse and enterocele. Fewer mesh erosions and postoperative pain syndromes were seen in patients who had no previous pelvic floor reconstructive surgery.
3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes.
Zhong, Zichun; Guo, Xiaohu; Cai, Yiqi; Yang, Yin; Wang, Jing; Jia, Xun; Mao, Weihua
2016-01-01
By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT) scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs) are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs) of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.
3D-2D Deformable Image Registration Using Feature-Based Nonuniform Meshes
Directory of Open Access Journals (Sweden)
Zichun Zhong
2016-01-01
Full Text Available By using prior information of planning CT images and feature-based nonuniform meshes, this paper demonstrates that volumetric images can be efficiently registered with a very small portion of 2D projection images of a Cone-Beam Computed Tomography (CBCT scan. After a density field is computed based on the extracted feature edges from planning CT images, nonuniform tetrahedral meshes will be automatically generated to better characterize the image features according to the density field; that is, finer meshes are generated for features. The displacement vector fields (DVFs are specified at the mesh vertices to drive the deformation of original CT images. Digitally reconstructed radiographs (DRRs of the deformed anatomy are generated and compared with corresponding 2D projections. DVFs are optimized to minimize the objective function including differences between DRRs and projections and the regularity. To further accelerate the above 3D-2D registration, a procedure to obtain good initial deformations by deforming the volume surface to match 2D body boundary on projections has been developed. This complete method is evaluated quantitatively by using several digital phantoms and data from head and neck cancer patients. The feature-based nonuniform meshing method leads to better results than either uniform orthogonal grid or uniform tetrahedral meshes.
Characteristics of Mesh Wave Impedance in FDTD Non-Uniform Mesh
Institute of Scientific and Technical Information of China (English)
REN Wu; LIU Bo; GAO Ben-qing
2005-01-01
In order to increase the evaluating precision of mesh reflection wave, the mesh wave impedance(MWI) is extended to the non-uniform mesh in 1-D and 2-D cases for the first time on the basis of the Yee's positional relation for electromagnetic field components. Lots of characteristics are obtained for different mesh sizes and frequencies. Then the reflection coefficient caused by the non-uniform mesh can be calculated according to the theory of equivalent transmission line. By comparing it with that calculated by MWI in the uniform mesh, it is found that the evaluating error can be largely reduced and is in good agreement with that directly computed by FDTD method. And this extension of MWI can be used in the error analysis of complex mesh.
Energy Technology Data Exchange (ETDEWEB)
Wienke, B.R.; O' Dell, R.D.
1976-12-01
ESECT and EMAP are subroutines which provide a computer algorithm for mapping arbitrary meshes onto rectangular meshes in cylindrical (r,z) geometry. Input consists of the lines defining the rectangular mesh and the coordinates of the arbitrary mesh, which are assumed to be joined by straight lines. Output consists of the intersection volumes with designation of common mesh zones. The ESECT and EMAP routines do not comprise a ''free-standing'' code but, instead, are intended for inclusion in existing codes for which one mesh structure (typically Lagrangian) needs to be mapped onto an Eulerian mesh. Such mappings are of interest in coupled hydrodynamic and neutronic calculations. Exact expressions for the volumes of rotation (about z-axis) generated by the planar mesh intersection areas are used. Intersection points of the two meshes are computed and mapped onto corresponding regions on the rectangular mesh. Intersection points with the same regional indices are recorded into multilaterals, and the multilaterals are triangulated to facilitate computation of the intersection volumes. Dimension statements within ESECT/EMAP presently allow for rectangular and arbitrary meshes of 10k and 3.6k grid points. Scaling of all arrays to suit individual applications is easily effected. Computations of intersection volumes generated by overlapping 10k rectangular and 2.2k radial meshes require an average of 18 s computer time, while computation times for the same meshes scaled by a factor of /sup 1///sub 4/ in number of grid points average 3 s on the CDC 7600. Generally, cases of small cell rectangular meshes overlaid on large cell arbitrary meshes require the longer running times. 10 figures, 2 tables.
Hermann, Verena; Käser, Martin; Castro, Cristóbal E.
2011-02-01
We present a Discontinuous Galerkin finite element method using a high-order time integration technique for seismic wave propagation modelling on non-conforming hybrid meshes in two space dimensions. The scheme can be formulated to achieve the same approximation order in space and time and avoids numerical artefacts due to non-conforming mesh transitions or the change of the element type. A point-wise Gaussian integration along partially overlapping edges of adjacent elements is used to preserve the schemes accuracy while providing a higher flexibility in the problem-adapted mesh generation process. We describe the domain decomposition strategy of the parallel implementation and validate the performance of the new scheme by numerical convergence test and experiments with comparisons to independent reference solutions. The advantage of non-conforming hybrid meshes is the possibility to choose the mesh spacing proportional to the seismic velocity structure, which allows for simple refinement or coarsening methods even for regular quadrilateral meshes. For particular problems of strong material contrasts and geometrically thin structures, the scheme reduces the computational cost in the sense of memory and run-time requirements. The presented results promise to achieve a similar behaviour for an extension to three space dimensions where the coupling of tetrahedral and hexahedral elements necessitates non-conforming mesh transitions to avoid linking elements in form of pyramids.
Proceedings of the 20th International Meshing Roundtable
2012-01-01
This volume contains the articles presented at the 20th International Meshing Roundtable (IMR) organized, in part, by Sandia National Laboratories and was held in Paris, France on Oct 23-26, 2011. This is the first year the IMR was held outside the United States territory. Other sponsors of the 20th IMR are Systematic Paris Region Systems & ICT Cluster, AIAA, NAFEMS, CEA, and NSF. The Sandia National Laboratories started the first IMR in 1992, and the conference has been held annually since. Each year the IMR brings together researchers, developers, and application experts, from a variety of disciplines, to present and discuss ideas on mesh generation and related topics. The topics covered by the IMR have applications in numerical analysis, computational geometry, computer graphics, as well as other areas, and the presentations describe novel work ranging from theory to application. .
Kinetic mesh-free method for flutter prediction in turbomachines
Indian Academy of Sciences (India)
V Ramesh; S M Deshpande
2014-02-01
The present paper deals with the development and application of a kinetic theory-based mesh-free method for unsteady flows. The method has the capability to compute on any arbitrary distribution of moving nodes. In general, computation of unsteady flow past multiple moving boundaries using conventional finite volume solvers are quite involved. They invariably require repeated grid generation or an efficient grid movement strategy. This approach becomes more difficult when there are many moving boundaries. In the present work, we propose a simple and an effective node movement strategy for the mesh-free solver. This can tackle the unsteady problems with moving boundaries in a much easier way. Using the present method we have computed unsteady flow in oscillating turbomachinery blades. A simple energy method has been used to predict flutter using the unsteady computations. The results compare well with the available experiments and other computations.
Security Routing Protocol For The Wireless Mesh Networks (WMNs)
Institute of Scientific and Technical Information of China (English)
王五妹; 赵彩丹; 黄联芬; 姚彦
2008-01-01
The pretty promising Wireless Mesh Networking technique, which is regarded as the next generation wireless Internet, not only possesses the normal features of wireless networks, but also has the advantages of multi-hop, self-organizing, etc. However, the great strength of the Mesh Networks also lead to a serious problem in the perspective of network security. This paper starts with the security issue of WMN routing and puts forward the corresponding solutions to the two kinds of routings’ security, such as adding the public/private (Pi/Si) key to the AODV to solve the problem of black hole and adding the credit value of nodes to the DSR to improve the security.
Automatic off-body overset adaptive Cartesian mesh method based on an octree approach
Energy Technology Data Exchange (ETDEWEB)
Peron, Stephanie, E-mail: stephanie.peron@onera.fr [ONERA - The French Aerospace Lab, F-92322 Chatillon (France); Benoit, Christophe, E-mail: christophe.benoit@onera.fr [ONERA - The French Aerospace Lab, F-92322 Chatillon (France)
2013-01-01
This paper describes a method for generating adaptive structured Cartesian grids within a near-body/off-body mesh partitioning framework for the flow simulation around complex geometries. The off-body Cartesian mesh generation derives from an octree structure, assuming each octree leaf node defines a structured Cartesian block. This enables one to take into account the large scale discrepancies in terms of resolution between the different bodies involved in the simulation, with minimum memory requirements. Two different conversions from the octree to Cartesian grids are proposed: the first one generates Adaptive Mesh Refinement (AMR) type grid systems, and the second one generates abutting or minimally overlapping Cartesian grid set. We also introduce an algorithm to control the number of points at each adaptation, that automatically determines relevant values of the refinement indicator driving the grid refinement and coarsening. An application to a wing tip vortex computation assesses the capability of the method to capture accurately the flow features.
1990-03-01
Bezier , B-Splines). the general form of 3-D elliptic grid generation equations can be used taking into account the constraints represented by Eqs.(2...has its maximum slope where the curvature of u(x) has its maximum curva - ture and its minimum slope where the curvature of u(x) is also minimal The...Among the many techniques available, we mention: analytic definition (for simple geometries), Bezier -patches, and transfinite mappings. Our experience
Quadratically consistent projection from particles to mesh
Duque, Daniel
2016-01-01
The advantage of particle Lagrangian methods in computational fluid dynamics is that advection is accurately modeled. However, this complicates the calculation of space derivatives. If a mesh is employed, it must be updated at each time step. On the other hand, fixed mesh, Eulerian, formulations benefit from the mesh being defined at the beginning of the simulation, but feature non-linear advection terms. It therefore seems natural to combine the two approaches, using a fixed mesh to perform calculations related to space derivatives, and using the particles to advect the information with time. The idea of combining Lagrangian particles and a fixed mesh goes back to Particle-in-Cell methods, and is here considered within the context of the finite element method (FEM) for the fixed mesh, and the particle FEM (pFEM) for the particles. Our results, in agreement with recent works, show that interpolation ("projection") errors, especially from particles to mesh, are the culprits of slow convergence of the method if...
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.
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.
Osteoblast functions in functionally graded Ti-6Al-4 V mesh structures.
Nune, K C; Kumar, A; Misra, R D K; Li, S J; Hao, Y L; Yang, R
2016-03-01
We describe here the combined efforts of engineering and biological sciences as a systemic approach to fundamentally elucidate osteoblast functions in functionally graded Ti-6Al-4 V mesh structures in relation to uniform/monolithic mesh arrays. First, the interconnecting porous architecture of functionally graded mesh arrays was conducive to cellular functions including attachment, proliferation, and mineralization. The underlying reason is that the graded fabricated structure with cells seeded from the large pore size side provided a channel for efficient transfer of nutrients to other end of the structure (small pore size), leading to the generation of mineralized extracellular matrix by differentiating pre-osteoblasts. Second, a comparative and parametric study indicated that gradient mesh structure had a pronounced effect on cell adhesion and mineralization, and strongly influenced the proliferation phase. High intensity and near-uniform distribution of proteins (actin and vinculin) on struts of the gradient mesh structure (cells seeded from large pore side) implied signal transduction during cell adhesion and was responsible for superior cellular activity, in comparison to the uniform mesh structure and non-porous titanium alloy. Cells adhered to the mesh struts by forming a sheet, bridging the pores through numerous cytoplasmic extensions, in the case of porous mesh structures. Intercellular interaction in porous structures provided a pathway for cells to communicate and mature to a differentiated phenotype. Furthermore, the capability of cells to migrate through the interconnecting porous architecture on mesh structures led to colonization of the entire structure. Cells were embedded layer-by-layer in the extracellular matrix as the matrix mineralized. The outcomes of the study are expected to address challenges associated with the treatment of segmental bone defects and bone-remodeling through favorable modulation of cellular response. Moreover, the study
Automatic mesh adaptivity for CADIS and FW-CADIS neutronics modeling of difficult shielding problems
Energy Technology Data Exchange (ETDEWEB)
Ibrahim, A. M.; Peplow, D. E.; Mosher, S. W.; Wagner, J. C.; Evans, T. M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Wilson, P. P.; Sawan, M. E. [University of Wisconsin-Madison, 1500 Engineering Dr., Madison, WI 53706 (United States)
2013-07-01
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)
Xin, Qin; Yao, Xiaolan; Engelstad, Paal E.
2010-09-01
Wireless Mesh Networking is an emerging communication paradigm to enable resilient, cost-efficient and reliable services for the future-generation wireless networks. We study here the minimum-latency communication primitive of gossiping (all-to-all communication) in multi-hop ad-hoc Wireless Mesh Networks (WMNs). Each mesh node in the WMN is initially given a message and the objective is to design a minimum-latency schedule such that each mesh node distributes its message to all other mesh nodes. Minimum-latency gossiping problem is well known to be NP-hard even for the scenario in which the topology of the WMN is known to all mesh nodes in advance. In this paper, we propose a new latency-efficient approximation scheme that can accomplish gossiping task in polynomial time units in any ad-hoc WMN under consideration of Large Interference Range (LIR), e.g., the interference range is much larger than the transmission range. To the best of our knowledge, it is first time to investigate such a scenario in ad-hoc WMNs under LIR, our algorithm allows the labels (e.g., identifiers) of the mesh nodes to be polynomially large in terms of the size of the WMN, which is the first time that the scenario of large labels has been considered in ad-hoc WMNs under LIR. Furthermore, our gossiping scheme can be considered as a framework which can be easily implied to the scenario under consideration of mobility-related issues since we assume that the mesh nodes have no knowledge on the network topology even for its neighboring mesh nodes.
Adaptive meshing technique applied to an orthopaedic finite element contact problem.
Roarty, Colleen M; Grosland, Nicole M
2004-01-01
Finite element methods have been applied extensively and with much success in the analysis of orthopaedic implants. Recently a growing interest has developed, in the orthopaedic biomechanics community, in how numerical models can be constructed for the optimal solution of problems in contact mechanics. New developments in this area are of paramount importance in the design of improved implants for orthopaedic surgery. Finite element and other computational techniques are widely applied in the analysis and design of hip and knee implants, with additional joints (ankle, shoulder, wrist) attracting increased attention. The objective of this investigation was to develop a simplified adaptive meshing scheme to facilitate the finite element analysis of a dual-curvature total wrist implant. Using currently available software, the analyst has great flexibility in mesh generation, but must prescribe element sizes and refinement schemes throughout the domain of interest. Unfortunately, it is often difficult to predict in advance a mesh spacing that will give acceptable results. Adaptive finite-element mesh capabilities operate to continuously refine the mesh to improve accuracy where it is required, with minimal intervention by the analyst. Such mesh adaptation generally means that in certain areas of the analysis domain, the size of the elements is decreased (or increased) and/or the order of the elements may be increased (or decreased). In concept, mesh adaptation is very appealing. Although there have been several previous applications of adaptive meshing for in-house FE codes, we have coupled an adaptive mesh formulation with the pre-existing commercial programs PATRAN (MacNeal-Schwendler Corp., USA) and ABAQUS (Hibbit Karlson and Sorensen, Pawtucket, RI). In doing so, we have retained several attributes of the commercial software, which are very attractive for orthopaedic implant applications.
H(curl) Auxiliary Mesh Preconditioning
Energy Technology Data Exchange (ETDEWEB)
Kolev, T V; Pasciak, J E; Vassilevski, P S
2006-08-31
This paper analyzes a two-level preconditioning scheme for H(curl) bilinear forms. The scheme utilizes an auxiliary problem on a related mesh that is more amenable for constructing optimal order multigrid methods. More specifically, we analyze the case when the auxiliary mesh only approximately covers the original domain. The latter assumption is important since it allows for easy construction of nested multilevel spaces on regular auxiliary meshes. Numerical experiments in both two and three space dimensions illustrate the optimal performance of the method.
Engagement of Metal Debris into Gear Mesh
handschuh, Robert F.; Krantz, Timothy L.
2010-01-01
A series of bench-top experiments was conducted to determine the effects of metallic debris being dragged through meshing gear teeth. A test rig that is typically used to conduct contact fatigue experiments was used for these tests. Several sizes of drill material, shim stock and pieces of gear teeth were introduced and then driven through the meshing region. The level of torque required to drive the "chip" through the gear mesh was measured. From the data gathered, chip size sufficient to jam the mechanism can be determined.
Application of mesh network radios to UGS
Calcutt, Wade; Jones, Barry; Roeder, Brent
2008-04-01
During the past five years McQ has been actively pursuing integrating and applying wireless mesh network radios as a communications solution for unattended ground sensor (UGS) systems. This effort has been rewarded with limited levels of success and has ultimately resulted in a corporate position regarding the use of mesh network radios for UGS systems. A discussion into the background of the effort, the challenges of implementing commercial off-the-shelf (COTS) mesh radios with UGSs, the tradeoffs involved, and an overview of the future direction is presented.
Mesh Optimization for Ground Vehicle Aerodynamics
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...
Rigidity Constraints for Large Mesh Deformation
Institute of Scientific and Technical Information of China (English)
Yong Zhao; Xin-Guo Liu; Qun-Sheng Peng; Hu-Jun Bao
2009-01-01
It is a challenging problem of surface-based deformation to avoid apparent volumetric distortions around largely deformed areas. In this paper, we propose a new rigidity constraint for gradient domain mesh deformation to address this problem. Intuitively the proposed constraint can be regarded as several small cubes defined by the mesh vertices through mean value coordinates. The user interactively specifies the cubes in the regions which are prone to volumetric distortions, and the rigidity constraints could make the mesh behave like a solid object during deformation. The experimental results demonstrate that our constraint is intuitive, easy to use and very effective.
SURFACE MESH PARAMETERIZATION WITH NATURAL BOUNDARY
Institute of Scientific and Technical Information of China (English)
Ye Ming; Zhu Xiaofeng; Wang Chengtao
2003-01-01
Using the projected curve of surface mesh boundary as parameter domain border, linear mapping parameterization with natural boundary is realized. A fast algorithm for least squares fitting plane of vertices in the mesh boundary is proposed. After the mesh boundary is projected onto the fitting plane, low-pass filtering is adopted to eliminate crossovers, sharp corners and cavities in the projected curve and convert it into an eligible convex parameter domain boundary. In order to facilitate quantitative evaluations of parameterization schemes, three distortion-measuring formulae are presented.
Charged particle tracking through electrostatic wire meshes using the finite element method
Devlin, L. J.; Karamyshev, O.; Welsch, C. P.
2016-06-01
Wire meshes are used across many disciplines to accelerate and focus charged particles, however, analytical solutions are non-exact and few codes exist which simulate the exact fields around a mesh with physical sizes. A tracking code based in Matlab-Simulink using field maps generated using finite element software has been developed which tracks electrons or ions through electrostatic wire meshes. The fields around such a geometry are presented as an analytical expression using several basic assumptions, however, it is apparent that computational calculations are required to obtain realistic values of electric potential and fields, particularly when multiple wire meshes are deployed. The tracking code is flexible in that any quantitatively describable particle distribution can be used for both electrons and ions as well as other benefits such as ease of export to other programs for analysis. The code is made freely available and physical examples are highlighted where this code could be beneficial for different applications.
Acquiring Plausible Predications from MEDLINE by Clustering MeSH Annotations.
Miñarro-Giménez, Jose Antonio; Kreuzthaler, Markus; Bernhardt-Melischnig, Johannes; Martínez-Costa, Catalina; Schulz, Stefan
2015-01-01
The massive accumulation of biomedical knowledge is reflected by the growth of the literature database MEDLINE with over 23 million bibliographic records. All records are manually indexed by MeSH descriptors, many of them refined by MeSH subheadings. We use subheading information to cluster types of MeSH descriptor co-occurrences in MEDLINE by processing co-occurrence information provided by the UMLS. The goal is to infer plausible predicates to each resulting cluster. In an initial experiment this was done by grouping disease-pharmacologic substance co-occurrences into six clusters. Then, a domain expert manually performed the assignment of meaningful predicates to the clusters. The mean accuracy of the best ten generated biomedical facts of each cluster was 85%. This result supports the evidence of the potential of MeSH subheadings for extracting plausible medical predications from MEDLINE.
Note: Radial-thrust combo metal mesh foil bearing for microturbomachinery.
Park, Cheol Hoon; Choi, Sang Kyu; Hong, Doo Euy; Yoon, Tae Gwang; Lee, Sung Hwi
2013-10-01
This Note proposes a novel radial-thrust combo metal mesh foil bearing (MMFB). Although MMFBs have advantages such as higher stiffness and damping over conventional air foil bearings, studies related to MMFBs have been limited to radial MMFBs. The novel combo MMFB is composed of a radial top foil, thrust top foils, and a ring-shaped metal mesh damper--fabricated by compressing a copper wire mesh--with metal mesh thrust pads for the thrust bearing at both side faces. In this study, the combo MMFB was fabricated in half-split type to support the rotor for a micro gas turbine generator. The manufacture and assembly process for the half-split-type combo MMFB is presented. In addition, to verify the proposed combo MMFB, motoring test results up to 250,000 rpm and axial displacements as a function of rotational speed are presented.
Charged particle tracking through electrostatic wire meshes using the finite element method
Energy Technology Data Exchange (ETDEWEB)
Devlin, L. J.; Karamyshev, O.; Welsch, C. P., E-mail: carsten.welsch@cockcroft.ac.uk [The Cockcroft Institute, Daresbury Laboratory, Warrington (United Kingdom); Department of Physics, University of Liverpool, Liverpool (United Kingdom)
2016-06-15
Wire meshes are used across many disciplines to accelerate and focus charged particles, however, analytical solutions are non-exact and few codes exist which simulate the exact fields around a mesh with physical sizes. A tracking code based in Matlab-Simulink using field maps generated using finite element software has been developed which tracks electrons or ions through electrostatic wire meshes. The fields around such a geometry are presented as an analytical expression using several basic assumptions, however, it is apparent that computational calculations are required to obtain realistic values of electric potential and fields, particularly when multiple wire meshes are deployed. The tracking code is flexible in that any quantitatively describable particle distribution can be used for both electrons and ions as well as other benefits such as ease of export to other programs for analysis. The code is made freely available and physical examples are highlighted where this code could be beneficial for different applications.
Institute of Scientific and Technical Information of China (English)
郑旖; 张为民
2012-01-01
Based on the mathematical expression is the 3D Model of the gear surface established in MAT-LAB.The method of object -oriented programming is applied to the establishment .The average distributed knots of the finite elements are generated at the curve of the tooth surface , which is based on the modular model .And the knots are the Basis of the generation of triangle elements of the tooth surface .% 在 MATLAB 中根据数学解析式建立齿轮齿面的三维模型，并且将面向对象的编程方法运用到数学模型的建立中。在模块化的齿面模型基础上，在齿面曲线上生成平均分布的有限元网格节点，并以生成的节点为基础建立齿面的三角形网格单元。
Salo, Zoryana; Beek, Maarten; Whyne, Cari Marisa
2012-08-01
Robust generation of pelvic finite element models is necessary to understand variation in mechanical behaviour resulting from differences in gender, aging, disease and injury. The objective of this study was to apply and evaluate mesh morphing and mapping techniques to facilitate the creation and structural analysis of specimen-specific finite element (FE) models of the pelvis. A specimen-specific pelvic FE model (source mesh) was generated following a traditional user-intensive meshing scheme. The source mesh was morphed onto a computed tomography scan generated target surface of a second pelvis using a landmarked-based approach, in which exterior source nodes were shifted to target surface vertices, while constrained along a normal. A second copy of the morphed model was further refined through mesh mapping, in which surface nodes of the initial morphed model were selected in patches and remapped onto the surfaces of the target model. Computed tomography intensity-based material properties were assigned to each model. The source, target, morphed and mapped models were analyzed under axial compression using linear static FE analysis, and their strain distributions were evaluated. Morphing and mapping techniques were effectively applied to generate good quality and geometrically complex specimen-specific pelvic FE models. Mapping significantly improved strain concurrence with the target pelvis FE model.
Assignment of fields from particles to mesh
Duque, Daniel
2016-01-01
In Computational Fluid Dynamics there have been many attempts to combine the power of a fixed mesh on which to carry out spatial calculations with that of a set of particles that moves following the velocity field. These ideas indeed go back to Particle-in-Cell methods, proposed about 60 years ago. Of course, some procedure is needed to transfer field information between particles and mesh. There are many possible choices for this "assignment", or "projection". Several requirements may guide this choice. Two well-known ones are conservativity and stability, which apply to volume integrals of the fields. An additional one is here considered: preservation of information. This means that mesh interpolation, followed by mesh assignment, should leave the field values invariant. The resulting methods are termed "mass" assignments due to their strong similarities with the Finite Element Method. We test several procedures, including the well-known FLIP, on three scenarios: simple 1D convection, 2D convection of Zales...
Shape space exploration of constrained meshes
Yang, Yongliang
2011-01-01
We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc.
LR: Compact connectivity representation for triangle meshes
Energy Technology Data Exchange (ETDEWEB)
Gurung, T; Luffel, M; Lindstrom, P; Rossignac, J
2011-01-28
We propose LR (Laced Ring) - a simple data structure for representing the connectivity of manifold triangle meshes. LR provides the option to store on average either 1.08 references per triangle or 26.2 bits per triangle. Its construction, from an input mesh that supports constant-time adjacency queries, has linear space and time complexity, and involves ordering most vertices along a nearly-Hamiltonian cycle. LR is best suited for applications that process meshes with fixed connectivity, as any changes to the connectivity require the data structure to be rebuilt. We provide an implementation of the set of standard random-access, constant-time operators for traversing a mesh, and show that LR often saves both space and traversal time over competing representations.
Shape space exploration of constrained meshes
Yang, Yongliang
2011-12-12
We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.
Spacetime Meshing for Discontinuous Galerkin Methods
Thite, Shripad Vidyadhar
2008-01-01
Spacetime discontinuous Galerkin (SDG) finite element methods are used to solve such PDEs involving space and time variables arising from wave propagation phenomena in important applications in science and engineering. To support an accurate and efficient solution procedure using SDG methods and to exploit the flexibility of these methods, we give a meshing algorithm to construct an unstructured simplicial spacetime mesh over an arbitrary simplicial space domain. Our algorithm is the first spacetime meshing algorithm suitable for efficient solution of nonlinear phenomena in anisotropic media using novel discontinuous Galerkin finite element methods for implicit solutions directly in spacetime. Given a triangulated d-dimensional Euclidean space domain M (a simplicial complex) and initial conditions of the underlying hyperbolic spacetime PDE, we construct an unstructured simplicial mesh of the (d+1)-dimensional spacetime domain M x [0,infinity). Our algorithm uses a near-optimal number of spacetime elements, ea...
Metal Mesh Filters for Terahertz Receivers Project
National Aeronautics and Space Administration — The technical objective of this SBIR program is to develop and demonstrate metal mesh filters for use in NASA's low noise receivers for terahertz astronomy and...
Adaptive sampling for mesh spectrum editing
Institute of Scientific and Technical Information of China (English)
ZHAO Xiang-jun; ZHANG Hong-xin; BAO Hu-jun
2006-01-01
A mesh editing framework is presented in this paper, which integrates Free-Form Deformation (FFD) and geometry signal processing. By using simplified model from original mesh, the editing task can be accomplished with a few operations. We take the deformation of the proxy and the position coordinates of the mesh models as geometry signal. Wavelet analysis is employed to separate local detail information gracefully. The crucial innovation of this paper is a new adaptive regular sampling approach for our signal analysis based editing framework. In our approach, an original mesh is resampled and then refined iteratively which reflects optimization of our proposed spectrum preserving energy. As an extension of our spectrum editing scheme,the editing principle is applied to geometry details transferring, which brings satisfying results.
Mesh Processing in Medical Image Analysis
DEFF Research Database (Denmark)
The following topics are dealt with: mesh processing; medical image analysis; interactive freeform modeling; statistical shape analysis; clinical CT images; statistical surface recovery; automated segmentation; cerebral aneurysms; and real-time particle-based representation....
Obtuse triangle suppression in anisotropic meshes
Sun, Feng
2011-12-01
Anisotropic triangle meshes are used for efficient approximation of surfaces and flow data in finite element analysis, and in these applications it is desirable to have as few obtuse triangles as possible to reduce the discretization error. We present a variational approach to suppressing obtuse triangles in anisotropic meshes. Specifically, we introduce a hexagonal Minkowski metric, which is sensitive to triangle orientation, to give a new formulation of the centroidal Voronoi tessellation (CVT) method. Furthermore, we prove several relevant properties of the CVT method with the newly introduced metric. Experiments show that our algorithm produces anisotropic meshes with much fewer obtuse triangles than using existing methods while maintaining mesh anisotropy. © 2011 Elsevier B.V. All rights reserved.
Gear Mesh Loss-of-Lubrication Experiments and Analytical Simulation
Handschuh, Robert F.; Polly, Joseph; Morales, Wilfredo
2011-01-01
An experimental program to determine the loss-of-lubrication (LOL) characteristics of spur gears in an aerospace simulation test facility has been completed. Tests were conducted using two different emergency lubricant types: (1) an oil mist system (two different misted lubricants) and (2) a grease injection system (two different grease types). Tests were conducted using a NASA Glenn test facility normally used for conducting contact fatigue. Tests were run at rotational speeds up to 10000 rpm using two different gear designs and two different gear materials. For the tests conducted using an air-oil misting system, a minimum lubricant injection rate was determined to permit the gear mesh to operate without failure for at least 1 hr. The tests allowed an elevated steady state temperature to be established. A basic 2-D heat transfer simulation has been developed to investigate temperatures of a simulated gear as a function of frictional behavior. The friction (heat generation source) between the meshing surfaces is related to the position in the meshing cycle, the load applied, and the amount of lubricant in the contact. Experimental conditions will be compared to those from the 2-D simulation.
A novel partitioning method for block-structured adaptive meshes
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.
MHD simulations on an unstructured mesh
Energy Technology Data Exchange (ETDEWEB)
Strauss, H.R. [New York Univ., NY (United States); Park, W.; Belova, E.; Fu, G.Y. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Longcope, D.W. [Univ. of Montana, Missoula, MT (United States); Sugiyama, L.E. [Massachusetts Inst. of Tech., Cambridge, MA (United States)
1998-12-31
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.
Mesh Processing in Medical Image Analysis
DEFF Research Database (Denmark)
The following topics are dealt with: mesh processing; medical image analysis; interactive freeform modeling; statistical shape analysis; clinical CT images; statistical surface recovery; automated segmentation; cerebral aneurysms; and real-time particle-based representation.......The following topics are dealt with: mesh processing; medical image analysis; interactive freeform modeling; statistical shape analysis; clinical CT images; statistical surface recovery; automated segmentation; cerebral aneurysms; and real-time particle-based representation....
Vector field processing on triangle meshes
De Goes, Fernando; Desbrun, Mathieu; Tong, Yiying
2015-01-01
While scalar fields on surfaces have been staples of geometry processing, the use of tangent vector fields has steadily grown in geometry processing over the last two decades: they are crucial to encoding directions and sizing on surfaces as commonly required in tasks such as texture synthesis, non-photorealistic rendering, digital grooming, and meshing. There are, however, a variety of discrete representations of tangent vector fields on triangle meshes, and each approach offers different tr...
Mesh geometry impact on Micromegas performance with an Exchangeable Mesh prototype
Energy Technology Data Exchange (ETDEWEB)
Kuger, F., E-mail: fabian.kuger@cern.ch [CERN, Geneva (Switzerland); Julius-Maximilians-Universität, Würzburg (Germany); Bianco, M.; Iengo, P. [CERN, Geneva (Switzerland); Sekhniaidze, G. [CERN, Geneva (Switzerland); Universita e INFN, Napoli (Italy); Veenhof, R. [Uludağ University, Bursa (Turkey); Wotschack, J. [CERN, Geneva (Switzerland)
2016-07-11
The reconstruction precision of gaseous detectors is limited by losses of primary electrons during signal formation. In addition to common gas related losses, like attachment, Micromegas suffer from electron absorption during its transition through the micro mesh. This study aims for a deepened understanding of electron losses and their dependency on the mesh geometry. It combines experimental results obtained with a novel designed Exchangeable Mesh Micromegas (ExMe) and advanced microscopic-tracking simulations (ANSYS and Garfield++) of electron drift and mesh transition.
Denner, Fabian; van Wachem, Berend G. M.
2015-10-01
Total variation diminishing (TVD) schemes are a widely applied group of monotonicity-preserving advection differencing schemes for partial differential equations in numerical heat transfer and computational fluid dynamics. These schemes are typically designed for one-dimensional problems or multidimensional problems on structured equidistant quadrilateral meshes. Practical applications, however, often involve complex geometries that cannot be represented by Cartesian meshes and, therefore, necessitate the application of unstructured meshes, which require a more sophisticated discretisation to account for their additional topological complexity. In principle, TVD schemes are applicable to unstructured meshes, however, not all the data required for TVD differencing is readily available on unstructured meshes, and the solution suffers from considerable numerical diffusion as a result of mesh skewness. In this article we analyse TVD differencing on unstructured three-dimensional meshes, focusing on the non-linearity of TVD differencing and the extrapolation of the virtual upwind node. Furthermore, we propose a novel monotonicity-preserving correction method for TVD schemes that significantly reduces numerical diffusion caused by mesh skewness. The presented numerical experiments demonstrate the importance of accounting for the non-linearity introduced by TVD differencing and of imposing carefully chosen limits on the extrapolated virtual upwind node, as well as the efficacy of the proposed method to correct mesh skewness.
Discrete differential geometry: the nonplanar quadrilateral mesh.
Twining, Carole J; Marsland, Stephen
2012-06-01
We consider the problem of constructing a discrete differential geometry defined on nonplanar quadrilateral meshes. Physical models on discrete nonflat spaces are of inherent interest, as well as being used in applications such as computation for electromagnetism, fluid mechanics, and image analysis. However, the majority of analysis has focused on triangulated meshes. We consider two approaches: discretizing the tensor calculus, and a discrete mesh version of differential forms. While these two approaches are equivalent in the continuum, we show that this is not true in the discrete case. Nevertheless, we show that it is possible to construct mesh versions of the Levi-Civita connection (and hence the tensorial covariant derivative and the associated covariant exterior derivative), the torsion, and the curvature. We show how discrete analogs of the usual vector integral theorems are constructed in such a way that the appropriate conservation laws hold exactly on the mesh, rather than only as approximations to the continuum limit. We demonstrate the success of our method by constructing a mesh version of classical electromagnetism and discuss how our formalism could be used to deal with other physical models, such as fluids.
Hybrid Surface Mesh Adaptation for Climate Modeling
Institute of Scientific and Technical Information of China (English)
Ahmed Khamayseh; Valmor de Almeida; Glen Hansen
2008-01-01
Solution-driven mesh adaptation is becoming quite popular for spatial error control in the numerical simulation of complex computational physics applications, such as climate modeling. Typically, spatial adaptation is achieved by element subdivision (h adaptation) with a primary goal of resolving the local length scales of interest. A second, lesspopular method of spatial adaptivity is called "mesh motion" (r adaptation); the smooth repositioning of mesh node points aimed at resizing existing elements to capture the local length scales. This paper proposes an adaptation method based on a combination of both element subdivision and node point repositioning (rh adaptation). By combining these two methods using the notion of a mobility function, the proposed approach seeks to increase the flexibility and extensibility of mesh motion algorithms while providing a somewhat smoother transition between refined regions than is pro-duced by element subdivision alone. Further, in an attempt to support the requirements of a very general class of climate simulation applications, the proposed method is de-signed to accommodate unstructured, polygonal mesh topologies in addition to the most popular mesh types.
Hydrodynamic simulations on a moving Voronoi mesh
Springel, Volker
2011-01-01
At the heart of any method for computational fluid dynamics lies the question of how the simulated fluid should be discretized. Traditionally, a fixed Eulerian mesh is often employed for this purpose, which in modern schemes may also be adaptively refined during a calculation. Particle-based methods on the other hand discretize the mass instead of the volume, yielding an approximately Lagrangian approach. It is also possible to achieve Lagrangian behavior in mesh-based methods if the mesh is allowed to move with the flow. However, such approaches have often been fraught with substantial problems related to the development of irregularity in the mesh topology. Here we describe a novel scheme that eliminates these weaknesses. It is based on a moving unstructured mesh defined by the Voronoi tessellation of a set of discrete points. The mesh is used to solve the hyperbolic conservation laws of ideal hydrodynamics with a finite volume approach, based on a second-order Godunov scheme with an exact Riemann solver. A...
Unstructured Mesh Movement and Viscous Mesh Generation for CFD-Based Design Optimization Project
National Aeronautics and Space Administration — The innovations proposed by ResearchSouth are: 1) a robust method to automatically insert high quality anisotropic prismatic (viscous boundary layer) cells into any...
Fire performance of basalt FRP mesh reinforced HPC thin plates
DEFF Research Database (Denmark)
Hulin, Thomas; Hodicky, Kamil; Schmidt, Jacob Wittrup;
2013-01-01
An experimental program was carried out to investigate the influence of basalt FRP (BFRP) reinforcing mesh on the fire behaviour of thin high performance concrete (HPC) plates applied to sandwich elements. Samples with BFRP mesh were compared to samples with no mesh, samples with steel mesh...
Meshing Highly Regular Structures: The Case of Super Carbon Nanotubes of Arbitrary Order
Directory of Open Access Journals (Sweden)
Christian Schröppel
2015-01-01
Full Text Available Mesh generation is an important step in many numerical methods. We present the “Hierarchical Graph Meshing” (HGM method as a novel approach to mesh generation, based on algebraic graph theory. The HGM method can be used to systematically construct configurations exhibiting multiple hierarchies and complex symmetry characteristics. The hierarchical description of structures provided by the HGM method can be exploited to increase the efficiency of multiscale and multigrid methods. In this paper, the HGM method is employed for the systematic construction of super carbon nanotubes of arbitrary order, which present a pertinent example of structurally and geometrically complex, yet highly regular, structures. The HGM algorithm is computationally efficient and exhibits good scaling characteristics. In particular, it scales linearly for super carbon nanotube structures and is working much faster than geometry-based methods employing neighborhood search algorithms. Its modular character makes it conducive to automatization. For the generation of a mesh, the information about the geometry of the structure in a given configuration is added in a way that relates geometric symmetries to structural symmetries. The intrinsically hierarchic description of the resulting mesh greatly reduces the effort of determining mesh hierarchies for multigrid and multiscale applications and helps to exploit symmetry-related methods in the mechanical analysis of complex structures.
Finite element model for linear-elastic mixed mode loading using adaptive mesh strategy
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
An adaptive mesh finite element model has been developed to predict the crack propagation direction as well as to calculate the stress intensity factors (SIFs), under linear-elastic assumption for mixed mode loading application. The finite element mesh is generated using the advancing front method. In order to suit the requirements of the fracture analysis, the generation of the background mesh and the construction of singular elements have been added to the developed program. The adaptive remeshing process is carried out based on the posteriori stress error norm scheme to obtain an optimal mesh. Previous works of the authors have proposed techniques for adaptive mesh generation of 2D cracked models. Facilitated by the singular elements, the displacement extrapolation technique is employed to calculate the SIF. The fracture is modeled by the splitting node approach and the trajectory follows the successive linear extensions of each crack increment. The SIFs values for two different case studies were estimated and validated by direct comparisons with other researchers work.
Complete Multiple Description Mesh-Based Video Coding Scheme and Its Performance
Institute of Scientific and Technical Information of China (English)
Yang-Li Wang; Cheng-Ke Wu
2005-01-01
This paper proposes a multiple description (MD) mesh-based motion coding method, which generates two descriptions for mesh-based motion by subsampling the nodes of a right-angled triangular mesh and dividing them into two groups. Motion vectors associated with the mesh nodes in each group are transmitted over distinct channels. With the nodes in each group, two other regular triangular meshes besides the original one can be constructed, and three different prediction images can be reconstructed according to descriptions available. The proposed MD mesh-based motion coding method is then combined with the pairwise correlating transform (PCT), and a complete MD video coding scheme is proposed. Further measures are taken to reduce the mismatch between the encoder and decoder that occurs when only one description is received and the decoder reconstruction is different from the encoder. The performance of the proposed scheme is evaluated using computer simulations, and the results show, compared to Reibman's MD transform coding (MDTC) method, the proposed scheme achieves better redundancy rate distortion (RRD) performance. In packet loss scenario, the proposed scheme outperforms the MDTC method.
Multi-Dimensional, Compressible Viscous Flow on a Moving Voronoi Mesh
Muñoz, Diego; Marcus, Robert; Vogelsberger, Mark; Hernquist, Lars
2012-01-01
Numerous formulations of finite volume schemes for the Euler and Navier-Stokes equations exist, but in the majority of cases they have been developed for structured and stationary meshes. In many applications, more flexible mesh geometries that can dynamically adjust to the problem at hand and move with the flow in a (quasi) Lagrangian fashion would, however, be highly desirable, as this can allow a significant reduction of advection errors and an accurate realization of curved and moving boundary conditions. Here we describe a novel formulation of viscous continuum hydrodynamics that solves the equations of motion on a Voronoi mesh created by a set of mesh-generating points. The points can move in an arbitrary manner, but the most natural motion is that given by the fluid velocity itself, such that the mesh dynamically adjusts to the flow. Owing to the mathematical properties of the Voronoi tessellation, pathological mesh-twisting effects are avoided. Our implementation considers the full Navier-Stokes equat...
Revisiting the Least-squares Procedure for Gradient Reconstruction on Unstructured Meshes
Mavriplis, Dimitri J.; Thomas, James L. (Technical Monitor)
2003-01-01
The accuracy of the least-squares technique for gradient reconstruction on unstructured meshes is examined. While least-squares techniques produce accurate results on arbitrary isotropic unstructured meshes, serious difficulties exist for highly stretched meshes in the presence of surface curvature. In these situations, gradients are typically under-estimated by up to an order of magnitude. For vertex-based discretizations on triangular and quadrilateral meshes, and cell-centered discretizations on quadrilateral meshes, accuracy can be recovered using an inverse distance weighting in the least-squares construction. For cell-centered discretizations on triangles, both the unweighted and weighted least-squares constructions fail to provide suitable gradient estimates for highly stretched curved meshes. Good overall flow solution accuracy can be retained in spite of poor gradient estimates, due to the presence of flow alignment in exactly the same regions where the poor gradient accuracy is observed. However, the use of entropy fixes has the potential for generating large but subtle discretization errors.
A study on the dependency between turbulent models and mesh configurations of CFD codes
Energy Technology Data Exchange (ETDEWEB)
Bang, Jungjin; Heo, Yujin; Jerng, Dong-Wook [CAU, Seoul (Korea, Republic of)
2015-10-15
This paper focuses on the analysis of the behavior of hydrogen mixing and hydrogen stratification, using the GOTHIC code and the CFD code. Specifically, we examined the mesh sensitivity and how the turbulence model affects hydrogen stratification or hydrogen mixing, depending on the mesh configuration. In this work, sensitivity analyses for the meshes and the turbulence models were conducted for missing and stratification phenomena. During severe accidents in a nuclear power plants, the generation of hydrogen may occur and this will complicate the atmospheric condition of the containment by causing stratification of air, steam, and hydrogen. This could significantly impact containment integrity analyses, as hydrogen could be accumulated in local region. From this need arises the importance of research about stratification of gases in the containment. Two computation fluid dynamics code, i.e. GOTHIC and STAR-CCM+ were adopted and the computational results were benchmarked against the experimental data from PANDA facility. The main findings observed through the present work can be summarized as follows: 1) In the case of the GOTHIC code, it was observed that the aspect ratio of the mesh was found more important than the mesh size. Also, if the number of the mesh is over 3,000, the effects of the turbulence models were marginal. 2) For STAR-CCM+, the tendency is quite different from the GOTHIC code. That is, the effects of the turbulence models were small for fewer number of the mesh, however, as the number of mesh increases, the effects of the turbulence models becomes significant. Another observation is that away from the injection orifice, the role of the turbulence models tended to be important due to the nature of mixing process and inducted jet stream.
SU-E-T-437: Dosimetric Assessment of Brass Mesh Bolus for Postmastectomy Chest Wall Irradiation
Energy Technology Data Exchange (ETDEWEB)
Manger, R; Paxton, A; Cervino, L [University of California, San Diego, La Jolla, CA (United States)
2014-06-01
Purpose: It has been suggested that the use of a brass mesh bolus for chest wall irradiation sufficiently increases surface dose while having little effect on the dose at depth. This work quantified the increase in surface dose when using a brass mesh bolus in postmastectomy chest wall radiotherapy compared to tissue-equivalent bolus and assessed its effect on dose at depth. Methods: Percent depth doses with brass bolus, 5mm tissue-equivalent bolus, and no bolus were determined for a 6 MV photon beam in a solid water phantom using a parallel plate ionization chamber. Gafchromic film was used to determine the surface dose for the same three experimental setups. For comparison to a realistic treatment setup, gafchromic film and OSLDs were used to determine the surface dose over the irradiated area of a 6 MV chest wall plan with tangential beams delivered to a heterogeneous thorax phantom. The plan was generated using a CT of the phantom and delivered using brass mesh bolus, 5mm tissue-equivalent bolus, and no bolus. Results: For the en face beam, the central surface dose increased to 90% of maximum with the tissue-equivalent bolus, but to only 62% of maximum with the brass mesh. Using tangential beams on the thorax phantom, the surface dose increased from 40–72% to 75–110% of prescribed dose, with the brass mesh, and to 85–109% with the tissue-equivalent bolus. At depths beyond dmax in the plastic water phantom, the dose with and without brass mesh bolus differed by less than 0.5%. Conclusion: A brass mesh may be considered as a substitute for tissue-equivalent bolus to increase the superficial dose of 6 MV chest wall tangent plans. The brass mesh does not significantly change the dose at depth, so a non-bolus plan could be used for bolus and non-bolus treatments.
Venkatachari, Balaji Shankar; Chang, Chau-Lyan
2016-11-01
The focus of this study is scale-resolving simulations of the canonical normal shock- isotropic turbulence interaction using unstructured tetrahedral meshes and the space-time conservation element solution element (CESE) method. Despite decades of development in unstructured mesh methods and its potential benefits of ease of mesh generation around complex geometries and mesh adaptation, direct numerical or large-eddy simulations of turbulent flows are predominantly carried out using structured hexahedral meshes. This is due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for unstructured meshes that can resolve multiple physical scales and flow discontinuities simultaneously. The CESE method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to accurately simulate turbulent flows using tetrahedral meshes. As part of the study, various regimes of the shock-turbulence interaction (wrinkled and broken shock regimes) will be investigated along with a study on how adaptive refinement of tetrahedral meshes benefits this problem. The research funding for this paper has been provided by Revolutionary Computational Aerosciences (RCA) subproject under the NASA Transformative Aeronautics Concepts Program (TACP).
Directory of Open Access Journals (Sweden)
K.Senthamil Selvan
2013-04-01
Full Text Available Wireless mesh networking has transpired as a gifted technology for potential broadband wireless access.In a communication network, wireless mesh network plays a vital role in transmission and are structured ina mesh topology. The coordination of mesh routers and mesh clients forms the wireless mesh networkswhich are routed through the gateways. Wireless mesh networks uses IEEE 802.11 standards and has itswide applications broadband home networking and enterprise networking deployment such as Microsoftwireless mesh and MIT etc. A professional Qos provisioning in intra cluster packet level resourceallocation for WMN approach takes power allocation, sub carrier allocation and packet scheduling. Thisapproach combines the merits of a Karush-Kuhn-Tucker (KKT algorithm and a genetic algorithm (GAbased approach. The KKT algorithm uses uniform power allocation over all the subcarriers, based on theoptimal allocation criterion. The genetic algorithm is used to generate useful solutions to optimization andsearch problems and it is also used for search problems. By combining the intrinsic worth of both theapproaches, it facilitates effective QOS provisioning at the packet level. It is concluded that, this approachachieves a preferred stability between system implementation and computational convolution.
Institute of Scientific and Technical Information of China (English)
王纯; 刘艳梅; 周涛; 余兴刚; 谢诞梅
2012-01-01
网格的划分是对工程问题进行数值模拟的重要环节,网格质量的高低直接影响计算结果的精度.在对汽轮机叶片周围流场的数值模拟过程中,较高质量的网格是基础要求,但由于汽轮机末级叶片结构非常复杂,这就加大了其网格划分过程中的难度.为了进一步提高ICEM CFD对汽轮机叶片周围流场网格划分的质量,并针对避免产生“负体积”的问题.提出了一种可以得到高质量网格的方法,并阐述了在实际操作中应该注意的事项.%The mesh generation is an important part of the numerical simulation of engineering problems. Ihe quality ot the grid directly affects the accuracy of the calculation result. The last stage turbine blade has a very complicated structure, which increase the difficulty in the process of grids partition. However,the flow field computation around the steam turbine blade needs higher quality grid. In order to improve the grid quality of the flow field around steam turbine blades with ICEM CFD and to avoid "negative volume" , this paper puts forward a method which can generate high-quality grids . What' s more,it illustrates what matters should be paid attention to in practice.
Multiple Staggered Mesh Ewald: Boosting the Accuracy of the Smooth Particle Mesh Ewald Method
Wang, Han; Fang, Jun
2016-01-01
The smooth particle mesh Ewald (SPME) method is the standard method for computing the electrostatic interactions in the molecular simulations. In this work, the multiple staggered mesh Ewald (MSME) method is proposed to boost the accuracy of the SPME method. Unlike the SPME that achieves higher accuracy by refining the mesh, the MSME improves the accuracy by averaging the standard SPME forces computed on, e.g. $M$, staggered meshes. We prove, from theoretical perspective, that the MSME is as accurate as the SPME, but uses $M^2$ times less mesh points in a certain parameter range. In the complementary parameter range, the MSME is as accurate as the SPME with twice of the interpolation order. The theoretical conclusions are numerically validated both by a uniform and uncorrelated charge system, and by a three-point-charge water system that is widely used as solvent for the bio-macromolecules.
Conservative interpolation between general spherical meshes
Directory of Open Access Journals (Sweden)
E. Kritsikis
2015-06-01
Full Text Available An efficient, local, explicit, second-order, conservative interpolation algorithm between spherical meshes is presented. The cells composing the source and target meshes may be either spherical polygons or longitude–latitude quadrilaterals. Second-order accuracy is obtained by piecewise-linear finite volume reconstruction over the source mesh. Global conservation is achieved through the introduction of a supermesh, whose cells are all possible intersections of source and target cells. Areas and intersections are computed exactly to yield a geometrically exact method. The main efficiency bottleneck caused by the construction of the supermesh is overcome by adopting tree-based data structures and algorithms, from which the mesh connectivity can also be deduced efficiently. The theoretical second-order accuracy is verified using a smooth test function and pairs of meshes commonly used for atmospheric modelling. Experiments confirm that the most expensive operations, especially the supermesh construction, have O(NlogN computational cost. The method presented is meant to be incorporated in pre- or post-processing atmospheric modelling pipelines, or directly into models for flexible input/output. It could also serve as a basis for conservative coupling between model components, e.g. atmosphere and ocean.
Conservative interpolation between general spherical meshes
Kritsikis, Evaggelos; Aechtner, Matthias; Meurdesoif, Yann; Dubos, Thomas
2017-01-01
An efficient, local, explicit, second-order, conservative interpolation algorithm between spherical meshes is presented. The cells composing the source and target meshes may be either spherical polygons or latitude-longitude quadrilaterals. Second-order accuracy is obtained by piece-wise linear finite-volume reconstruction over the source mesh. Global conservation is achieved through the introduction of a supermesh, whose cells are all possible intersections of source and target cells. Areas and intersections are computed exactly to yield a geometrically exact method. The main efficiency bottleneck caused by the construction of the supermesh is overcome by adopting tree-based data structures and algorithms, from which the mesh connectivity can also be deduced efficiently.The theoretical second-order accuracy is verified using a smooth test function and pairs of meshes commonly used for atmospheric modelling. Experiments confirm that the most expensive operations, especially the supermesh construction, have O(NlogN) computational cost. The method presented is meant to be incorporated in pre- or post-processing atmospheric modelling pipelines, or directly into models for flexible input/output. It could also serve as a basis for conservative coupling between model components, e.g., atmosphere and ocean.
Karipineni, Farah; Joshi, Priya; Parsikia, Afshin; Dhir, Teena; Joshi, Amit R T
2016-03-01
Laparoscopic-assisted ventral hernia repair (LAVHR) with mesh is well established as the preferred technique for hernia repair. We sought to determine whether primary fascial closure and/or overlap of the mesh reduced recurrence and/or complications. We conducted a retrospective review on 57 LAVHR patients using polyester composite mesh between August 2010 and July 2013. They were divided into mesh-only (nonclosure) and primary fascial closure with mesh (closure) groups. Patient demographics, prior surgical history, mesh overlap, complications, and recurrence rates were compared. Thirty-nine (68%) of 57 patients were in the closure group and 18 (32%) in the nonclosure group. Mean defect sizes were 15.5 and 22.5 cm(2), respectively. Participants were followed for a mean of 1.3 years [standard deviation (SD) = 0.7]. Recurrence rates were 2/39 (5.1%) in the closure group and 1/18 (5.6%) in the nonclosure group (P = 0.947). There were no major postoperative complications in the nonclosure group. The closure group experienced four (10.3%) complications. This was not a statistically significant difference (P = 0.159). The median mesh-to-hernia ratio for all repairs was 15.2 (surface area) and 3.9 (diameter). Median length of stay was 14.5 hours (1.7-99.3) for patients with nonclosure and 11.9 hours (6.9-90.3 hours) for patients with closure (P = 0.625). In conclusion, this is one of the largest series of LAVHR exclusively using polyester dual-sided mesh. Our recurrence rate was about 5 per cent. Significant mesh overlap is needed to achieve such low recurrence rates. Primary closure of hernias seems less important than adequate mesh overlap in preventing recurrence after LAVHR.
Combining 3d Volume and Mesh Models for Representing Complicated Heritage Buildings
Tsai, F.; Chang, H.; Lin, Y.-W.
2017-08-01
This study developed a simple but effective strategy to combine 3D volume and mesh models for representing complicated heritage buildings and structures. The idea is to seamlessly integrate 3D parametric or polyhedral models and mesh-based digital surfaces to generate a hybrid 3D model that can take advantages of both modeling methods. The proposed hybrid model generation framework is separated into three phases. Firstly, after acquiring or generating 3D point clouds of the target, these 3D points are partitioned into different groups. Secondly, a parametric or polyhedral model of each group is generated based on plane and surface fitting algorithms to represent the basic structure of that region. A "bare-bones" model of the target can subsequently be constructed by connecting all 3D volume element models. In the third phase, the constructed bare-bones model is used as a mask to remove points enclosed by the bare-bones model from the original point clouds. The remaining points are then connected to form 3D surface mesh patches. The boundary points of each surface patch are identified and these boundary points are projected onto the surfaces of the bare-bones model. Finally, new meshes are created to connect the projected points and original mesh boundaries to integrate the mesh surfaces with the 3D volume model. The proposed method was applied to an open-source point cloud data set and point clouds of a local historical structure. Preliminary results indicated that the reconstructed hybrid models using the proposed method can retain both fundamental 3D volume characteristics and accurate geometric appearance with fine details. The reconstructed hybrid models can also be used to represent targets in different levels of detail according to user and system requirements in different applications.
Connectivity editing for quad-dominant meshes
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.
Retrofitting Masonry Walls with Carbon Mesh
Directory of Open Access Journals (Sweden)
Patrick Bischof
2014-01-01
Full Text Available Static-cyclic shear load tests and tensile tests on retrofitted masonry walls were conducted at UAS Fribourg for an evaluation of the newly developed retrofitting system, the S&P ARMO-System. This retrofitting system consists of a composite of carbon mesh embedded in a specially adapted high quality spray mortar. It can be applied with established construction techniques using traditional construction materials. The experimental study has shown that masonry walls reinforced by this retrofitting system reach a similar strength and a higher ductility than retrofits by means of bonded carbon fiber reinforced polymer sheets. Hence, the retrofitting system using carbon fiber meshes embedded in a high quality mortar constitutes a good option for static or seismic retrofits or reinforcements for masonry walls. However, the experimental studies also revealed that the mechanical anchorage of carbon mesh may be delicate depending on its design.
Mesh saliency with adaptive local patches
Nouri, Anass; Charrier, Christophe; Lézoray, Olivier
2015-03-01
3D object shapes (represented by meshes) include both areas that attract the visual attention of human observers and others less or not attractive at all. This visual attention depends on the degree of saliency exposed by these areas. In this paper, we propose a technique for detecting salient regions in meshes. To do so, we define a local surface descriptor based on local patches of adaptive size and filled with a local height field. The saliency of mesh vertices is then defined as its degree measure with edges weights computed from adaptive patch similarities. Our approach is compared to the state-of-the-art and presents competitive results. A study evaluating the influence of the parameters establishing this approach is also carried out. The strength and the stability of our approach with respect to noise and simplification are also studied.
Performance of a streaming mesh refinement algorithm.
Energy Technology Data Exchange (ETDEWEB)
Thompson, David C.; Pebay, Philippe Pierre
2004-08-01
In SAND report 2004-1617, we outline a method for edge-based tetrahedral subdivision that does not rely on saving state or communication to produce compatible tetrahedralizations. This report analyzes the performance of the technique by characterizing (a) mesh quality, (b) execution time, and (c) traits of the algorithm that could affect quality or execution time differently for different meshes. It also details the method used to debug the several hundred subdivision templates that the algorithm relies upon. Mesh quality is on par with other similar refinement schemes and throughput on modern hardware can exceed 600,000 output tetrahedra per second. But if you want to understand the traits of the algorithm, you have to read the report!
Greene, Patrick T.; Schofield, Samuel P.; Nourgaliev, Robert
2017-04-01
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. 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.
Software tools for manipulating fe mesh, virtual surgery and post-processing
Directory of Open Access Journals (Sweden)
Milašinović Danko Z.
2009-01-01
Full Text Available This paper describes a set of software tools which we developed for the calculation of fluid flow through cardiovascular organs. Our tools work with medical data from a CT scanner, but could be used with any other 3D input data. For meshing we used a Tetgen tetrahedral mesh generator, as well as a mesh re-generator that we have developed for conversion of tetrahedral elements into bricks. After adequate meshing we used our PAKF solver for calculation of fluid flow. For human-friendly presentation of results we developed a set of post-processing software tools. With modification of 2D mesh (boundary of cardiovascular organ it is possible to do virtual surgery, so in a case of an aorta with aneurism, which we had received from University Clinical center in Heidelberg from a multi-slice 64-CT scanner, we removed the aneurism and ran calculations on both geometrical models afterwards. The main idea of this methodology is creating a system that could be used in clinics.
Generation and Adaptive Modification of Anisotropic Meshes Project
National Aeronautics and Space Administration — The ability to quickly and reliably simulate high-speed flows over a wide range of geometrically complex configurations is critical to many of NASA's missions....
Mesh Generation via Local Bisection Refinement of Triangulated Grids
2015-06-01
tb [Maubach 1995, Theorem 5.1]. This is exploited in the recursive algorithm RefineTriangle (Algorithm 2) to com- patibly refine a given triangle; the... recursion depth of RefineTriangle is bounded by the maximum level of refinement in T [Maubach 1995]. RefineTriangle calls itself repeatedly on a... sequence of triangles until a compatibly divisible triangle is found. This sequence of triangles is then bisected in reverse order to preserve
Generation and Adaptive Modification of Anisotropic Meshes Project
National Aeronautics and Space Administration — The ability to quickly and reliably simulate high-speed flows over a wide range of geometrically complex configurations is critical to many of NASA's missions....
Open preperitoneal groin hernia repair with mesh
DEFF Research Database (Denmark)
Andresen, Kristoffer; Rosenberg, Jacob
2017-01-01
A systematic review was conducted and reported according to the PRISMA statement. PubMed, Cochrane library and Embase were searched systematically. Studies were included if they provided clinical data with more than 30 days follow up following repair of an inguinal hernia with an open preperitoneal mesh......Background For the repair of inguinal hernias, several surgical methods have been presented where the purpose is to place a mesh in the preperitoneal plane through an open access. The aim of this systematic review was to describe preperitoneal repairs with emphasis on the technique. Data sources...
Adaptive mesh refinement for storm surge
Mandli, Kyle T.
2014-03-01
An approach to utilizing adaptive mesh refinement algorithms for storm surge modeling is proposed. Currently numerical models exist that can resolve the details of coastal regions but are often too costly to be run in an ensemble forecasting framework without significant computing resources. The application of adaptive mesh refinement algorithms substantially lowers the computational cost of a storm surge model run while retaining much of the desired coastal resolution. The approach presented is implemented in the GeoClaw framework and compared to ADCIRC for Hurricane Ike along with observed tide gauge data and the computational cost of each model run. © 2014 Elsevier Ltd.
Relativistic MHD with Adaptive Mesh Refinement
Anderson, M; Liebling, S L; Neilsen, D; Anderson, Matthew; Hirschmann, Eric; Liebling, Steven L.; Neilsen, David
2006-01-01
We solve the relativistic magnetohydrodynamics (MHD) equations using a finite difference Convex ENO method (CENO) in 3+1 dimensions within a distributed parallel adaptive mesh refinement (AMR) infrastructure. In flat space we examine a Balsara blast wave problem along with a spherical blast wave and a relativistic rotor test both with unigrid and AMR simulations. The AMR simulations substantially improve performance while reproducing the resolution equivalent unigrid simulation results. We also investigate the impact of hyperbolic divergence cleaning for the spherical blast wave and relativistic rotor. We include unigrid and mesh refinement parallel performance measurements for the spherical blast wave.
Laparoscopic rectocele repair using polyglactin mesh.
Lyons, T L; Winer, W K
1997-05-01
We assessed the efficacy of laparoscopic treatment of rectocele defect using a polyglactin mesh graft. From May 1, 1995, through September 30, 1995, we prospectively evaluated 20 women (age 38-74 yrs) undergoing pelvic floor reconstruction for symptomatic pelvic floor prolapse, with or without hysterectomy. Morbidity of the procedure was extremely low compared with standard transvaginal and transrectal approaches. Patients were followed at 3-month intervals for 1 year. Sixteen had resolution of symptoms. Laparoscopic application of polyglactin mesh for the repair of the rectocele defect is a viable option, although long-term follow-up is necessary.
Adaptive Mesh Refinement for Storm Surge
Mandli, Kyle T
2014-01-01
An approach to utilizing adaptive mesh refinement algorithms for storm surge modeling is proposed. Currently numerical models exist that can resolve the details of coastal regions but are often too costly to be run in an ensemble forecasting framework without significant computing resources. The application of adaptive mesh refinement algorithms substantially lowers the computational cost of a storm surge model run while retaining much of the desired coastal resolution. The approach presented is implemented in the \\geoclaw framework and compared to \\adcirc for Hurricane Ike along with observed tide gauge data and the computational cost of each model run.
Energy Technology Data Exchange (ETDEWEB)
Ibrahim, Ahmad M., E-mail: ibrahimam@ornl.gov [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Wilson, Paul P. [University of Wisconsin-Madison, 1500 Engineering Dr., Madison, WI 53706 (United States); Sawan, Mohamed E., E-mail: sawan@engr.wisc.edu [University of Wisconsin-Madison, 1500 Engineering Dr., Madison, WI 53706 (United States); Mosher, Scott W.; Peplow, Douglas E.; Grove, Robert E. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States)
2014-10-15
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.
Directory of Open Access Journals (Sweden)
J.R. Martínez-Méndez
2008-09-01
Full Text Available Las lesiones del plexo braquial son una de las patologías más graves y con mayor número de secuelas del miembro superior. En el momento actual las transferencias nerviosas se encuentran en primera línea del armamento terapéutico para reconstruir funciones proximales del miembro superior. En el estudio que presentamos se realizaron 20 transferencias nerviosas al nervio cubital del gato común, tomando bien el nervio accesorio del espinal (10 casos o bien el nervio toracodorsal (10 casos. Como grupo control se utilizó el lado contralateral al intervenido. Durante el año siguiente, se evaluó la reinervación mediante estudios electromiográficos, histológicos de nervio y músculo, así como histoquímicos de médula espinal. Tras el análisis de los resultados encontramos que las motoneuronas de ambos nervios donantes son capaces de conseguir reinervaciones parciales del territorio cubital.A brachial plexus injury is one of the most severe pathologies of the upper limb, and also has severe sequels. In the actual state of the art, nerve transfers are being used as first line of therapeutic approach in the reconstruction of proximal functions of the upper limb. In this study 20 nerve transfers were made to the ulnar nerve of the cat, using the spinal accessory nerve (10 cases or the thoracodorsal nerve (10 cases. The opposite side was used as control. During next year, reinnervation was assessed by electromyography, nerve and muscle histology and histochemical evaluation of the spinal cord. We found that motoneurons of both donor nerves are able to make partial reinervation of the ulnar nerve territory.
Institute of Scientific and Technical Information of China (English)
王家桢; 马良; 张惠珍
2015-01-01
Euclidean Steiner minimum tree problem , a classical NP-hard problem in combination optimization , has been widely studied in many fields .Euclidean Steiner minimal tree problem in 3-space is the generalization of Euclidean Steiner minimum tree problem in 2-space .The research results on Euclidean Steiner minimal tree problem in 3-space have been rarely published because of their difficulties .In this paper , a hybrid intelligent method is designed by using Delaunay tetrahedron mesh generation technology to solve the Euclidean Steiner min -imal tree problem in 3-space , which can not only avoid falling into local optima , but also has good effects in solving large scale problems .Promising results are obtained by using this hybrid method coded in MATLAB to solve series of Euclidean Steiner minimum tree problem instances in 3-space .%Steiner最小树问题是组合优化中经典的NP难题，在许多实际问题中有着广泛的应用，而三维欧氏Stei-ner最小树问题是对二维欧氏Steiner最小树问题的推广。由于三维欧氏Steiner树问题的求解非常困难，至今为止的相关成果较为少见。本文针对该问题，利用Delaunay四面体网格剖分技术，提出了一种混合型智能求解方法，不仅可以尽量避免拓扑结构陷入局部最优，且对较大规模的问题求解亦有良好的效果。算法在Matlab环境下编程实现，经实例测试，获得了满意的效果。
MeshEZW: an image coder using mesh and finite elements
Landais, Thomas; Bonnaud, Laurent; Chassery, Jean-Marc
2003-08-01
In this paper, we present a new method to compress the information in an image, called MeshEZW. The proposed approach is based on the finite elements method, a mesh construction and a zerotree method. The zerotree method is an adaptive of the EZW algorithm with two new symbols for increasing the performance. These steps allow a progressive representation of the image by the automatic construction of a bitstream. The mesh structure is adapted to the image compression domain and is defined to allow video comrpession. The coder is described and some preliminary results are discussed.
A Hamiltonian Particle-Mesh Method for the Rotating Shallow Water Equations
Frank, J.E.; Gottwald, G.A.; Reich, S.; Griebel, M.; Schweitzer, M.A.
2003-01-01
A new particle-mesh method is proposed for the rotating shallow-water equations. The spatially truncated equations are Hamiltonian and satisfy a Kelvin circulation theorem. The generation of non-smooth components in the layer-depth is avoided by applying a smoothing operator similar to what has rece
Constrained and joint inversion on unstructured meshes
Doetsch, J.; Jordi, C.; Rieckh, V.; Guenther, T.; Schmelzbach, C.
2015-12-01
Unstructured meshes allow for inclusion of arbitrary surface topography, complex acquisition geometry and undulating geological interfaces in the inversion of geophysical data. This flexibility opens new opportunities for coupling different geophysical and hydrological data sets in constrained and joint inversions. For example, incorporating geological interfaces that have been derived from high-resolution geophysical data (e.g., ground penetrating radar) can add geological constraints to inversions of electrical resistivity data. These constraints can be critical for a hydrogeological interpretation of the inversion results. For time-lapse inversions of geophysical data, constraints can be derived from hydrological point measurements in boreholes, but it is difficult to include these hard constraints in the inversion of electrical resistivity monitoring data. Especially mesh density and the regularization footprint around the hydrological point measurements are important for an improved inversion compared to the unconstrained case. With the help of synthetic and field examples, we analyze how regularization and coupling operators should be chosen for time-lapse inversions constrained by point measurements and for joint inversions of geophysical data in order to take full advantage of the flexibility of unstructured meshes. For the case of constraining to point measurements, it is important to choose a regularization operator that extends beyond the neighboring cells and the uncertainty in the point measurements needs to be accounted for. For joint inversion, the choice of the regularization depends on the expected subsurface heterogeneity and the cell size of the parameter mesh.
Hash functions and triangular mesh reconstruction*1
Hrádek, Jan; Kuchař, Martin; Skala, Václav
2003-07-01
Some applications use data formats (e.g. STL file format), where a set of triangles is used to represent the surface of a 3D object and it is necessary to reconstruct the triangular mesh with adjacency information. It is a lengthy process for large data sets as the time complexity of this process is O( N log N), where N is number of triangles. Triangular mesh reconstruction is a general problem and relevant algorithms can be used in GIS and DTM systems as well as in CAD/CAM systems. Many algorithms rely on space subdivision techniques while hash functions offer a more effective solution to the reconstruction problem. Hash data structures are widely used throughout the field of computer science. The hash table can be used to speed up the process of triangular mesh reconstruction but the speed strongly depends on hash function properties. Nevertheless the design or selection of the hash function for data sets with unknown properties is a serious problem. This paper describes a new hash function, presents the properties obtained for large data sets, and discusses validity of the reconstructed surface. Experimental results proved theoretical considerations and advantages of hash function use for mesh reconstruction.
Particle Collection Efficiency for Nylon Mesh Screens.
Cena, Lorenzo G; Ku, Bon-Ki; Peters, Thomas M
Mesh screens composed of nylon fibers leave minimal residual ash and produce no significant spectral interference when ashed for spectrometric examination. These characteristics make nylon mesh screens attractive as a collection substrate for nanoparticles. A theoretical single-fiber efficiency expression developed for wire-mesh screens was evaluated for estimating the collection efficiency of submicrometer particles for nylon mesh screens. Pressure drop across the screens, the effect of particle morphology (spherical and highly fractal) on collection efficiency and single-fiber efficiency were evaluated experimentally for three pore sizes (60, 100 and 180 μm) at three flow rates (2.5, 4 and 6 Lpm). The pressure drop across the screens was found to increase linearly with superficial velocity. The collection efficiency of the screens was found to vary by less than 4% regardless of particle morphology. Single-fiber efficiency calculated from experimental data was in good agreement with that estimated from theory for particles between 40 and 150 nm but deviated from theory for particles outside this size range. New coefficients for the single-fiber efficiency model were identified that minimized the sum of square error (SSE) between the values estimated with the model and those determined experimentally. Compared to the original theory, the SSE calculated using the modified theory was at least one order of magnitude lower for all screens and flow rates with the exception of the 60-μm pore screens at 2.5 Lpm, where the decrease was threefold.
Functionalized Nanofiber Meshes Enhance Immunosorbent Assays.
Hersey, Joseph S; Meller, Amit; Grinstaff, Mark W
2015-12-01
Three-dimensional substrates with high surface-to-volume ratios and subsequently large protein binding capacities are of interest for advanced immunosorbent assays utilizing integrated microfluidics and nanosensing elements. A library of bioactive and antifouling electrospun nanofiber substrates, which are composed of high-molecular-weight poly(oxanorbornene) derivatives, is described. Specifically, a set of copolymers are synthesized from three 7-oxanorbornene monomers to create a set of water insoluble copolymers with both biotin (bioactive) and triethylene glycol (TEG) (antifouling) functionality. Porous three-dimensional nanofiber meshes are electrospun from these copolymers with the ability to specifically bind streptavidin while minimizing the nonspecific binding of other proteins. Fluorescently labeled streptavidin is used to quantify the streptavidin binding capacity of each mesh type through confocal microscopy. A simplified enzyme-linked immunosorbent assay (ELISA) is presented to assess the protein binding capabilities and detection limits of these nanofiber meshes under both static conditions (26 h) and flow conditions (1 h) for a model target protein (i.e., mouse IgG) using a horseradish peroxidase (HRP) colorimetric assay. Bioactive and antifouling nanofiber meshes outperform traditional streptavidin-coated polystyrene plates under flow, validating their use in future advanced immunosorbent assays and their compatibility with microfluidic-based biosensors.
Mesh Optimization for Ground Vehicle Aerodynamics
Directory of Open Access Journals (Sweden)
Adrian Gaylard
2010-04-01
Full Text Available
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 limited memory environment and in a reasonable amount of time but without compromising the accuracy of results. The study was further extended to take into account the car model size effect. Three car model sizes have been investigated and compared with MIRA scale wind tunnel results. Parameters that lead to drag value closer to experiment with less memory and computational time have been identified. Scaling the optimized mesh size with the length of car model was successfully used to predict the drag of the other car sizes with reasonable accuracy. This investigation was carried out using STARCCM+ commercial software package, however the findings can be applied to any other CFD package.
Details of tetrahedral anisotropic mesh adaptation
Jensen, Kristian Ejlebjerg; Gorman, Gerard
2016-04-01
We have implemented tetrahedral anisotropic mesh adaptation using the local operations of coarsening, swapping, refinement and smoothing in MATLAB without the use of any for- N loops, i.e. the script is fully vectorised. In the process of doing so, we have made three observations related to details of the implementation: 1. restricting refinement to a single edge split per element not only simplifies the code, it also improves mesh quality, 2. face to edge swapping is unnecessary, and 3. optimising for the Vassilevski functional tends to give a little higher value for the mean condition number functional than optimising for the condition number functional directly. These observations have been made for a uniform and a radial shock metric field, both starting from a structured mesh in a cube. Finally, we compare two coarsening techniques and demonstrate the importance of applying smoothing in the mesh adaptation loop. The results pertain to a unit cube geometry, but we also show the effect of corners and edges by applying the implementation in a spherical geometry.
Drag reduction properties of superhydrophobic mesh pipes
Geraldi, Nicasio R.; Dodd, Linzi E.; Xu, Ben B.; Wells, Gary G.; Wood, David; Newton, Michael I.; McHale, Glen
2017-09-01
Even with the recent extensive study into superhydrophobic surfaces, the fabrication of such surfaces on the inside walls of a pipe remains challenging. In this work we report a convenient bi-layered pipe design using a thin superhydrophobic metallic mesh formed into a tube, supported inside another pipe. A flow system was constructed to test the fabricated bi-layer pipeline, which allowed for different constant flow rates of water to be passed through the pipe, whilst the differential pressure was measured, from which the drag coefficient (ƒ) and Reynolds numbers (Re) were calculated. Expected values of ƒ were found for smooth glass pipes for the Reynolds number (Re) range 750-10 000, in both the laminar and part of the turbulent regimes. Flow through plain meshes without the superhydrophobic coating were also measured over a similar range (750 superhydrophobic coating, ƒ was found for 4000 superhydrophobic mesh can support a plastron and provide a drag reduction compared to a plain mesh, however, the plastron is progressively destroyed with use and in particular at higher flow rates.
Performance Evaluation of Coded Meshed Networks
DEFF Research Database (Denmark)
Krigslund, Jeppe; Hansen, Jonas; Pedersen, Morten Videbæk;
2013-01-01
of the former to enhance the gains of the latter. We first motivate our work through measurements in WiFi mesh networks. Later, we compare state-of-the-art approaches, e.g., COPE, RLNC, to CORE. Our measurements show the higher reliability and throughput of CORE over other schemes, especially, for asymmetric...
Mesh Currents and Josephson Junction Arrays
1995-01-01
A simple but accurate mesh current analysis is performed on a XY model and on a SIMF model to derive the equations for a Josephson junction array. The equations obtained here turn out to be different from other equations already existing in the literature. Moreover, it is shown that the two models come from an unique hidden structure
Deconstructing six dimensional gauge theories with strongly coupled moose meshes
Gregoire, T; Gregoire, Thomas; Wacker, Jay G.
2002-01-01
It has recently been realized that five dimensional theories can be generated dynamically from asymptotically free, QCD-like four dimensional dynamics via ``deconstruction.'' In this paper we generalize this construction to six dimensional theories using a moose mesh with alternating weak and strong gauge groups. A new ingredient is the appearance of self couplings between the higher dimensional components of the gauge fields that appear as a potential for pseudo-Goldstone bosons in the deconstructed picture. We show that, in the limit where the weak gauge couplings are made large, such potentials are generated with appropriate size from finite one loop correction. Our construction has a number of applications, in particular to the constructions of ``little Higgs'' models of electroweak symmetry breaking.
Contingency-Constrained Unit Commitmentin Meshed Isolated Power Systems
DEFF Research Database (Denmark)
Sokoler, Leo Emil; Vinter, Peter; Bærentsen, Runi
2015-01-01
is kept above a predefined limit in the event of a contingency. The minimum frequency constraints are formulated using novel sufficient conditions that take into account the system inertia and the dynamics of the power generators. The proposed sufficient conditions are attractive from both a computational......This paper presents a mixed-integer linear optimization problem for unit commitment and economic dispatch of power generators in a meshed isolated power system. The optimization problem is referred to as the optimal reserve planning problem (ORPP). The ORPP guarantees that the system frequency...... and a modelling point of view. We compare the ORPP to a unit commitment problem that only considers the stationary behavior of the frequency. Simulations based on a Faroe Islands case study show that, without being overly conservative, potential blackouts and power outages can be avoided using the ORPP...
Moving mesh cosmology: the hydrodynamics of galaxy formation
Sijacki, Debora; Keres, Dusan; Springel, Volker; Hernquist, Lars
2011-01-01
We present a detailed comparison between the well-known SPH code GADGET and the new moving-mesh code AREPO on a number of hydrodynamical test problems. Through a variety of numerical experiments we establish a clear link between test problems and systematic numerical effects seen in cosmological simulations of galaxy formation. Our tests demonstrate deficiencies of the SPH method in several sectors. These accuracy problems not only manifest themselves in idealized hydrodynamical tests, but also propagate to more realistic simulation setups of galaxy formation, ultimately affecting gas properties in the full cosmological framework, as highlighted in papers by Vogelsberger et al. (2011) and Keres et al. (2011). We find that an inadequate treatment of fluid instabilities in GADGET suppresses entropy generation by mixing, underestimates vorticity generation in curved shocks and prevents efficient gas stripping from infalling substructures. In idealized tests of inside-out disk formation, the convergence rate of g...
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.
Szmelter, J.; Marchant, M. J.; Evans, A.; Weatherill, N. P.
A cell vertex finite volume Jameson scheme is used to solve the 2D compressible, laminar, viscous fluid flow equations on locally embedded multiblock meshes. The proposed algorithm is applicable to both the Euler and Navier-Stokes equations. It is concluded that the adaptivity method is very successful in efficiently improving the accuracy of the solution. Both the mesh generator and the flow equation solver which are based on a quadtree data structure offer good flexibility in the treatment of interfaces. It is concluded that methods under consideration lead to accurate flow solutions.
Institute of Scientific and Technical Information of China (English)
Weitao LIU; Changchuan XIE; Michel Bellet; Hervé Combeau
2009-01-01
In order to improve the prediction accuracy of macrosegregation channel, an algorithm for dynamic remeshing is proposed. The basic idea is to generate fine elements near the liquidus isotherm. The norm of the gradient of solid fraction is used for piloting the remeshing in the mushy zone; whereas, the objective mesh size in the liquid is considered as a function of the distance to the liquidus isotherm. The efficiency of mesh adaptation is demonstrated by prediction of macrosegregation channel in a case of unidirectional solidification.
Growth of carbon nanotubes and microfibers over stainless steel mesh by cracking of methane
2008-01-01
The ${La}_{2}{NiO}_{4}$ film was synthesized on the 304 stainless steel (SS) mesh. The hydrogen reduction of La2NiO4 generated homogeneous nanocatalyst particles (probably ${Ni}/{La}_2{O}_{3}$) over which methane was cracked, producing carbon notubes/microfibers and hydrogen. The carbon nanotubes/microfibers were strongly bonded to the SS mesh. It was observed that the methane conversion always reached its maximum at the cracking temperature of 750 °C regardless of its concentration varying f...
Oxidation and degradation of polypropylene transvaginal mesh.
Talley, Anne D; Rogers, Bridget R; Iakovlev, Vladimir; Dunn, Russell F; Guelcher, Scott A
2017-04-01
Polypropylene (PP) transvaginal mesh (TVM) repair for stress urinary incontinence (SUI) has shown promising short-term objective cure rates. However, life-altering complications have been associated with the placement of PP mesh for SUI repair. PP degradation as a result of the foreign body reaction (FBR) has been proposed as a contributing factor to mesh complications. We hypothesized that PP oxidizes under in vitro conditions simulating the FBR, resulting in degradation of the PP. Three PP mid-urethral slings from two commercial manufacturers were evaluated. Test specimens (n = 6) were incubated in oxidative medium for up to 5 weeks. Oxidation was assessed by Fourier Transform Infrared Spectroscopy (FTIR), and degradation was evaluated by scanning electron microscopy (SEM). FTIR spectra of the slings revealed evidence of carbonyl and hydroxyl peaks after 5 weeks of incubation time, providing evidence of oxidation of PP. SEM images at 5 weeks showed evidence of surface degradation, including pitting and flaking. Thus, oxidation and degradation of PP pelvic mesh were evidenced by chemical and physical changes under simulated in vivo conditions. To assess changes in PP surface chemistry in vivo, fibers were recovered from PP mesh explanted from a single patient without formalin fixation, untreated (n = 5) or scraped (n = 5) to remove tissue, and analyzed by X-ray photoelectron spectroscopy. Mechanical scraping removed adherent tissue, revealing an underlying layer of oxidized PP. These findings underscore the need for further research into the relative contribution of oxidative degradation to complications associated with PP-based TVM devices in larger cohorts of patients.
Wireless Mesh Network Routing Under Uncertain Demands
Wellons, Jonathan; Dai, Liang; Chang, Bin; Xue, Yuan
Traffic routing plays a critical role in determining the performance of a wireless mesh network. Recent research results usually fall into two ends of the spectrum. On one end are the heuristic routing algorithms, which are highly adaptive to the dynamic environments of wireless networks yet lack the analytical properties of how well the network performs globally. On the other end are the optimal routing algorithms that are derived from the optimization problem formulation of mesh network routing. They can usually claim analytical properties such as resource use optimality and throughput fairness. However, traffic demand is usually implicitly assumed as static and known a priori in these problem formulations. In contrast, recent studies of wireless network traces show that the traffic demand, even being aggregated at access points, is highly dynamic and hard to estimate. Thus, to apply the optimization-based routing solution in practice, one must take into account the dynamic and uncertain nature of wireless traffic demand. There are two basic approaches to address the traffic uncertainty in optimal mesh network routing (1) predictive routing that infers the traffic demand with maximum possibility based in its history and optimizes the routing strategy based on the predicted traffic demand and (2) oblivious routing that considers all the possible traffic demands and selects the routing strategy where the worst-case network performance could be optimized. This chapter provides an overview of the optimal routing strategies for wireless mesh networks with a focus on the above two strategies that explicitly consider the traffic uncertainty. It also identifies the key factors that affect the performance of each routing strategy and provides guidelines towards the strategy selection in mesh network routing under uncertain traffic demands.
Randomized clinical trial of self-gripping mesh versus sutured mesh for Lichtenstein hernia repair
DEFF Research Database (Denmark)
Jorgensen, L N; Sommer, T; Assaadzadeh, S;
2012-01-01
between the groups in postoperative complications (33·7 versus 40·4 per cent; P = 0·215), rate of recurrent hernia within 1 year (1·2 per cent in both groups) or quality of life. CONCLUSION: The avoidance of suture fixation using a self-gripping mesh was not accompanied by a reduction in chronic symptoms......BACKGROUND: Many patients develop discomfort after open repair of a groin hernia. It was hypothesized that suture fixation of the mesh is a cause of these symptoms. METHODS: This patient- and assessor-blinded randomized multicentre clinical trial compared a self-gripping mesh (Parietene Progrip......(®) ) and sutured mesh for open primary repair of uncomplicated inguinal hernia by the Lichtenstein technique. Patients were assessed before surgery, on the day of operation, and at 1 and 12 months after surgery. The primary endpoint was moderate or severe symptoms after 12 months, including a combination...
Pournoury, M.; Zamiri, A.; Kim, T. Y.; Yurlov, V.; Oh, K.
2016-03-01
Capacitive touch sensor screen with the metal materials has recently become qualified for substitution of ITO; however several obstacles still have to be solved. One of the most important issues is moiré phenomenon. The visibility problem of the metal-mesh, in touch sensor module (TSM) is numerically considered in this paper. Based on human eye contract sensitivity function (CSF), moiré pattern of TSM electrode mesh structure is simulated with MATLAB software for 8 inch screen display in oblique view. Standard deviation of the generated moiré by the superposition of electrode mesh and screen image is calculated to find the optimal parameters which provide the minimum moiré visibility. To create the screen pixel array and mesh electrode, rectangular function is used. The filtered image, in frequency domain, is obtained by multiplication of Fourier transform of the finite mesh pattern (product of screen pixel and mesh electrode) with the calculated CSF function for three different observer distances (L=200, 300 and 400 mm). It is observed that the discrepancy between analytical and numerical results is less than 0.6% for 400 mm viewer distance. Moreover, in the case of oblique view due to considering the thickness of the finite film between mesh electrodes and screen, different points of minimum standard deviation of moiré pattern are predicted compared to normal view.
INCISIONAL HERNIA - ONLAY VS SUBLAY MESH HERNIOPLAS T Y
Ravi Kamal Kumar; Chandrakumar; Vijayalaxmi,; Thokala; Venkat Ramana
2015-01-01
BACKGROUND : Incisional hernia is a common surgical problem. Anatomical repair of hernia is now out of vogue. Polypropylene mesh repair has now become accepted. In open mesh repair of incisional hernia cases the site of placement of mesh is still debated. Some surgeo ns favour the onlay repair and others use sublay or retro - rectus plane for deployment of the mesh. AIM: The aim of the study is to examine the pros and cons of both the techniques and find the bett...
Explicit inverse distance weighting mesh motion for coupled problems
Witteveen, J.A.S.; Bijl, H.
2009-01-01
An explicit mesh motion algorithm based on inverse distance weighting interpolation is presented. The explicit formulation leads to a fast mesh motion algorithm and an easy implementation. In addition, the proposed point-by-point method is robust and flexible in case of large deformations, hanging nodes, and parallelization. Mesh quality results and CPU time comparisons are presented for triangular and hexahedral unstructured meshes in an airfoil flutter fluid-structure interaction problem.
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.
Selective separation of oil and water with mesh membranes by capillarity
Yu, Yuanlie
2016-05-29
The separation of oil and water from wastewater generated in the oil-production industries, as well as in frequent oil spillage events, is important in mitigating severe environmental and ecological damage. Additionally, a wide arrange of industrial processes require oils or fats to be removed from aqueous systems. The immiscibility of oil and water allows for the wettability of solid surfaces to be engineered to achieve the separation of oil and water through capillarity. Mesh membranes with extreme, selective wettability can efficiently remove oil or water from oil/water mixtures through a simple filtration process using gravity. A wide range of different types of mesh membranes have been successfully rendered with extreme wettability and applied to oil/water separation in the laboratory. These mesh materials have typically shown good durability, stability as well as reusability, which makes them promising candidates for an ever widening range of practical applications. © 2016 Elsevier B.V.
Zhang, Bo; Peng, Bo; Huang, Jingfang; Pitsianis, Nikos P.; Sun, Xiaobai; Lu, Benzhuo
2015-05-01
We present PAFMPB, an updated and parallel version of the AFMPB software package for fast calculation of molecular solvation-free energy. The new version has the following new features: (1) The adaptive fast multipole method and the boundary element methods are parallelized; (2) A tool is embedded for automatic molecular VDW/SAS surface mesh generation, leaving the requirement for a mesh file at input optional; (3) The package provides fast calculation of the total solvation-free energy, including the PB electrostatic and nonpolar interaction contributions. PAFMPB is implemented in C and Fortran programming languages, with the Cilk Plus extension to harness the computing power of both multicore and vector processing. Computational experiments demonstrate the successful application of PAFMPB to the calculation of the PB potential on a dengue virus system with more than one million atoms and a mesh with approximately 20 million triangles.
A nonlinear equivalent circuit method for analysis of passive intermodulation of mesh reflectors
Directory of Open Access Journals (Sweden)
Jiang Jie
2014-08-01
Full Text Available Passive intermodulation (PIM has gradually become a serious electromagnetic interference due to the development of high-power and high-sensitivity RF/microwave communication systems, especially large deployable mesh reflector antennas. This paper proposes a field-circuit coupling method to analyze the PIM level of mesh reflectors. With the existence of many metal–metal (MM contacts in mesh reflectors, the contact nonlinearity becomes the main reason for PIM generation. To analyze these potential PIM sources, an equivalent circuit model including nonlinear components is constructed to model a single MM contact so that the transient current through the MM contact point induced by incident electromagnetic waves can be calculated. Taking the electric current as a new electromagnetic wave source, the far-field scattering can be obtained by the use of electromagnetic numerical methods or the communication link method. Finally, a comparison between simulation and experimental results is illustrated to verify the validity of the proposed method.
Wang, Tianyang; Chu, Fulei; Han, Qinkai
2017-03-01
Identifying the differences between the spectra or envelope spectra of a faulty signal and a healthy baseline signal is an efficient planetary gearbox local fault detection strategy. However, causes other than local faults can also generate the characteristic frequency of a ring gear fault; this may further affect the detection of a local fault. To address this issue, a new filtering algorithm based on the meshing resonance phenomenon is proposed. In detail, the raw signal is first decomposed into different frequency bands and levels. Then, a new meshing index and an MRgram are constructed to determine which bands belong to the meshing resonance frequency band. Furthermore, an optimal filter band is selected from this MRgram. Finally, the ring gear fault can be detected according to the envelope spectrum of the band-pass filtering result.
A new anisotropic mesh adaptation method based upon hierarchical a posteriori error estimates
Huang, Weizhang; Kamenski, Lennard; Lang, Jens
2010-03-01
A new anisotropic mesh adaptation strategy for finite element solution of elliptic differential equations is presented. It generates anisotropic adaptive meshes as quasi-uniform ones in some metric space, with the metric tensor being computed based on hierarchical a posteriori error estimates. A global hierarchical error estimate is employed in this study to obtain reliable directional information of the solution. Instead of solving the global error problem exactly, which is costly in general, we solve it iteratively using the symmetric Gauß-Seidel method. Numerical results show that a few GS iterations are sufficient for obtaining a reasonably good approximation to the error for use in anisotropic mesh adaptation. The new method is compared with several strategies using local error estimators or recovered Hessians. Numerical results are presented for a selection of test examples and a mathematical model for heat conduction in a thermal battery with large orthotropic jumps in the material coefficients.
Soghrati, Soheil; Xiao, Fei; Nagarajan, Anand
2016-12-01
A Conforming to Interface Structured Adaptive Mesh Refinement (CISAMR) technique is introduced for the automated transformation of a structured grid into a conforming mesh with appropriate element aspect ratios. The CISAMR algorithm is composed of three main phases: (i) Structured Adaptive Mesh Refinement (SAMR) of the background grid; (ii) r-adaptivity of the nodes of elements cut by the crack; (iii) sub-triangulation of the elements deformed during the r-adaptivity process and those with hanging nodes generated during the SAMR process. The required considerations for the treatment of crack tips and branching cracks are also discussed in this manuscript. Regardless of the complexity of the problem geometry and without using iterative smoothing or optimization techniques, CISAMR ensures that aspect ratios of conforming elements are lower than three. Multiple numerical examples are presented to demonstrate the application of CISAMR for modeling linear elastic fracture problems with intricate morphologies.
Selective separation of oil and water with mesh membranes by capillarity.
Yu, Yuanlie; Chen, Hua; Liu, Yun; Craig, Vincent S J; Lai, Zhiping
2016-09-01
The separation of oil and water from wastewater generated in the oil-production industries, as well as in frequent oil spillage events, is important in mitigating severe environmental and ecological damage. Additionally, a wide arrange of industrial processes require oils or fats to be removed from aqueous systems. The immiscibility of oil and water allows for the wettability of solid surfaces to be engineered to achieve the separation of oil and water through capillarity. Mesh membranes with extreme, selective wettability can efficiently remove oil or water from oil/water mixtures through a simple filtration process using gravity. A wide range of different types of mesh membranes have been successfully rendered with extreme wettability and applied to oil/water separation in the laboratory. These mesh materials have typically shown good durability, stability as well as reusability, which makes them promising candidates for an ever widening range of practical applications.
Directory of Open Access Journals (Sweden)
Licandro Francesco
2007-01-01
Full Text Available Current video-surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper is to present an experience of implementation of a large-scale video-surveillance system based on a wireless mesh network infrastructure, discussing architecture, protocol, and implementation issues. More specifically, the paper proposes an architecture for a video-surveillance system, and mainly centers its focus on the routing protocol to be used in the wireless mesh network, evaluating its impact on performance at the receiver side. A wireless mesh network was chosen to support a video-surveillance application in order to reduce the overall system costs and increase scalability and performance. The paper analyzes the performance of the network in order to choose design parameters that will achieve the best trade-off between video encoding quality and the network traffic generated.
Directory of Open Access Journals (Sweden)
Francesco Licandro
2007-03-01
Full Text Available Current video-surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper is to present an experience of implementation of a large-scale video-surveillance system based on a wireless mesh network infrastructure, discussing architecture, protocol, and implementation issues. More specifically, the paper proposes an architecture for a video-surveillance system, and mainly centers its focus on the routing protocol to be used in the wireless mesh network, evaluating its impact on performance at the receiver side. A wireless mesh network was chosen to support a video-surveillance application in order to reduce the overall system costs and increase scalability and performance. The paper analyzes the performance of the network in order to choose design parameters that will achieve the best trade-off between video encoding quality and the network traffic generated.
On Reducing Delay in Mesh-Based P2P Streaming: A Mesh-Push Approach
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.
Yokoi, Naoyuki; Manabe, Kengo; Tenjimbayashi, Mizuki; Shiratori, Seimei
2015-03-04
Inspired by naturally occurring superhydrophobic surfaces such as "lotus leaves", a number of approaches have been attempted to create specific surfaces having nano/microscale rough structures and a low surface free energy. Most importantly, much attention has been paid in recent years to the improvement of the durability of highly transparent superhydrophobic surfaces. In this report, superhydrophobic surfaces are fabricated using three steps. First, chemical and morphological changes are generated in the polyester mesh by alkaline treatment of NaOH. Second, alkaline treatment causes hydrophobic molecules of 1H,1H,2H,2H-perfluorodecyltrichlorosilane to react with the hydroxyl groups on the fiber surfaces forming covalent bonds by using the chemical vapor deposition method. Third, hydrophobicity is enhanced by treating the mesh with SiO2 nanoparticles modified with 1H,1H,2H,2H-perfluorooctyltriethoxysilane using a spray method. The transmittance of the fabricated superhydrophobic mesh is approximately 80% in the spectral range of 400-1000 nm. The water contact angle and the water sliding angle remain greater than 150° and lower than 25°, respectively, and the transmittance remains approximately 79% after 100 cycles of abrasion under approximately 10 kPa of pressure. The mesh surface exhibits a good resistance to acidic and basic solutions over a wide range of pH values (pH 2-14), and the surface can also be used as an oil/water separation material because of its mesh structure.
A testing preocedure for the evaluation of directional mesh bias
Slobbe, A.T.; Hendriks, M.A.N.; Rots, J.G.
2013-01-01
This paper presents a dedicated numerical test that enables to assess the directional mesh bias of constitutive models in a systematic way. The test makes use of periodic boundary conditions, by which strain localization can be analyzed for different mesh alignments with preservation of mesh uniform
Multiphase flow of immiscible fluids on unstructured moving meshes
DEFF Research Database (Denmark)
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam
2012-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization op...
21 CFR 870.3650 - Pacemaker polymeric mesh bag.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Pacemaker polymeric mesh bag. 870.3650 Section 870...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Prosthetic Devices § 870.3650 Pacemaker polymeric mesh bag. (a) Identification. A pacemaker polymeric mesh bag is an implanted device used to hold a...
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
Tetrahedral-Mesh Simulation of Turbulent Flows with the Space-Time Conservative Schemes
Chang, Chau-Lyan; Venkatachari, Balaji; Cheng, Gary C.
2015-01-01
Direct numerical simulations of turbulent flows are predominantly carried out using structured, hexahedral meshes despite decades of development in unstructured mesh methods. Tetrahedral meshes offer ease of mesh generation around complex geometries and the potential of an orientation free grid that would provide un-biased small-scale dissipation and more accurate intermediate scale solutions. However, due to the lack of consistent multi-dimensional numerical formulations in conventional schemes for triangular and tetrahedral meshes at the cell interfaces, numerical issues exist when flow discontinuities or stagnation regions are present. The space-time conservative conservation element solution element (CESE) method - due to its Riemann-solver-free shock capturing capabilities, non-dissipative baseline schemes, and flux conservation in time as well as space - has the potential to more accurately simulate turbulent flows using unstructured tetrahedral meshes. To pave the way towards accurate simulation of shock/turbulent boundary-layer interaction, a series of wave and shock interaction benchmark problems that increase in complexity, are computed in this paper with triangular/tetrahedral meshes. Preliminary computations for the normal shock/turbulence interactions are carried out with a relatively coarse mesh, by direct numerical simulations standards, in order to assess other effects such as boundary conditions and the necessity of a buffer domain. The results indicate that qualitative agreement with previous studies can be obtained for flows where, strong shocks co-exist along with unsteady waves that display a broad range of scales, with a relatively compact computational domain and less stringent requirements for grid clustering near the shock. With the space-time conservation properties, stable solutions without any spurious wave reflections can be obtained without a need for buffer domains near the outflow/farfield boundaries. Computational results for the
Terrain-driven unstructured mesh development through semi-automatic vertical feature extraction
Bilskie, Matthew V.; Coggin, David; Hagen, Scott C.; Medeiros, Stephen C.
2015-12-01
validation techniques are necessary for state-of-the-art flood inundation models. In addition, the semi-automated, unstructured mesh generation process presented herein increases the overall accuracy of simulated storm surge across the floodplain without reliance on hand digitization or sacrificing computational cost.
Aliyazicioglu, Tolga; Yalti, Tunc; Kabaoglu, Burcak
2017-08-01
Approximately one fifth of patients suffer from inguinal pain after laparoscopic total extraperitoneal (TEP) inguinal hernia repair. There is existing literature suggesting that the staples used to fix the mesh can cause postoperative inguinal pain. In this study, we describe our experience with laparoscopic TEP inguinal hernia surgery using 3-dimensional mesh without mesh fixation, in our institution. A total of 300 patients who had undergone laparoscopic TEP inguinal hernia repair with 3-dimensional mesh in VKV American Hospital, Istanbul from November 2006 to November 2015 were studied retrospectively. Using the hospital's electronic archive, we studied patients' selected parameters, which are demographic features (age, sex), body mass index, hernia locations and types, duration of operations, preoperative and postoperative complications, duration of hospital stays, cost of surgery, need for analgesics, time elapsed until returning to daily activities and work. A total of 300 patients underwent laparoscopic TEP hernia repair of 437 inguinal hernias from November 2006 to November 2015. Of the 185 patients, 140 were symptomatic. Mean duration of follow-up was 48 months (range, 6 to 104 mo). The mean duration of surgery was 55 minutes for bilateral hernia repair, and 38 minutes for unilateral hernia repair. The mean duration of hospital stay was 0.9 day. There was no conversion to open surgery. In none of the cases the mesh was fixated with either staples or fibrin glue. Six patients (2%) developed seroma that were treated conservatively. One patient had inguinal hernia recurrence. One patient had preperitoneal hematoma. One patient operated due to indirect right-sided hernia developed right-sided hydrocele. One patient had wound dehiscence at the umbilical port entry site. Chronic pain developed postoperatively in 1 patient. Ileus developed in 1 patient. Laparoscopic TEP inguinal repair with 3-dimensional mesh without mesh fixation can be performed as safe as
Meshed split skin graft for extensive vitiligo
Directory of Open Access Journals (Sweden)
Srinivas C
2004-05-01
Full Text Available A 30 year old female presented with generalized stable vitiligo involving large areas of the body. Since large areas were to be treated it was decided to do meshed split skin graft. A phototoxic blister over recipient site was induced by applying 8 MOP solution followed by exposure to UVA. The split skin graft was harvested from donor area by Padgett dermatome which was meshed by an ampligreffe to increase the size of the graft by 4 times. Significant pigmentation of the depigmented skin was seen after 5 months. This procedure helps to cover large recipient areas, when pigmented donor skin is limited with minimal risk of scarring. Phototoxic blister enables easy separation of epidermis thus saving time required for dermabrasion from recipient site.
Variational mesh segmentation via quadric surface fitting
Yan, Dongming
2012-11-01
We present a new variational method for mesh segmentation by fitting quadric surfaces. Each component of the resulting segmentation is represented by a general quadric surface (including plane as a special case). A novel energy function is defined to evaluate the quality of the segmentation, which combines both L2 and L2 ,1 metrics from a triangle to a quadric surface. The Lloyd iteration is used to minimize the energy function, which repeatedly interleaves between mesh partition and quadric surface fitting. We also integrate feature-based and simplification-based techniques in the segmentation framework, which greatly improve the performance. The advantages of our algorithm are demonstrated by comparing with the state-of-the-art methods. © 2012 Elsevier Ltd. All rights reserved.
Capacity estimation of wireless mesh networks
2005-01-01
Resumo: Este trabalho apresenta uma estimação da capacidade das redes sem fio tipo Mesh. As redes deste tipo têm topologias e padrões de tráfego únicos que as diferenciam das redes sem fio convencionais. Nas redes sem fio tipo mesh os nós atuam como clientes e como servidores e o tráfego e encaminhado para uma ou várias gateways em um modo multi-salto. A estimação da capacidade é baseada em estudos da Camada Física e MAC. Efeitos da propagação do canal são avaliados Abstract: This work add...
Nondispersive optical activity of meshed helical metamaterials.
Park, Hyun Sung; Kim, Teun-Teun; Kim, Hyeon-Don; Kim, Kyungjin; Min, Bumki
2014-11-17
Extreme optical properties can be realized by the strong resonant response of metamaterials consisting of subwavelength-scale metallic resonators. However, highly dispersive optical properties resulting from strong resonances have impeded the broadband operation required for frequency-independent optical components or devices. Here we demonstrate that strong, flat broadband optical activity with high transparency can be obtained with meshed helical metamaterials in which metallic helical structures are networked and arranged to have fourfold rotational symmetry around the propagation axis. This nondispersive optical activity originates from the Drude-like response as well as the fourfold rotational symmetry of the meshed helical metamaterials. The theoretical concept is validated in a microwave experiment in which flat broadband optical activity with a designed magnitude of 45° per layer of metamaterial is measured. The broadband capabilities of chiral metamaterials may provide opportunities in the design of various broadband optical systems and applications.
Energy-efficient wireless mesh networks
CSIR Research Space (South Africa)
Ntlatlapa, N
2007-06-01
Full Text Available deficient areas such as rural areas in Africa. Index Terms—Energy efficient design, Wireless Mesh networks, Network Protocols I. INTRODUCTION The objectives of this research group are the application and adaptation of existing wireless local area... networks, especially those based on 802.11 standard, for the energyefficient wireless mesh network (EEWMN) architectures, protocols and controls. In addition to the WMN regular features of self...
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.
Electrostatic PIC with adaptive Cartesian mesh
Kolobov, Vladimir I
2016-01-01
We describe an initial implementation of an electrostatic Particle-in-Cell (ES-PIC) module with adaptive Cartesian mesh in our Unified Flow Solver framework. Challenges of PIC method with cell-based adaptive mesh refinement (AMR) are related to a decrease of the particle-per-cell number in the refined cells with a corresponding increase of the numerical noise. The developed ES-PIC solver is validated for capacitively coupled plasma, its AMR capabilities are demonstrated for simulations of streamer development during high-pressure gas breakdown. It is shown that cell-based AMR provides a convenient particle management algorithm for exponential multiplications of electrons and ions in the ionization events.
Overlay Share Mesh for Interactive Group Communication with High Dynamic
Institute of Scientific and Technical Information of China (English)
WU Yan-hua; CAI Yun-ze; XU Xiao-ming
2007-01-01
An overlay share mesh infrastructure is presented for high dynamic group communication systems, such as distributed interactive simulation (DIS) and distributed virtual environments (DVE). Overlay share mesh infrastructure can own better adapting ability for high dynamic group than tradition multi-tree multicast infrastructure by sharing links among different groups. The mechanism of overlay share mesh based on area of interest (AOI) was discussed in detail in this paper. A large number of simulation experiments were done and the permance of mesh infrastructure was studied. Experiments results proved that overlay mesh infrastructure owns better adaptability than traditional multi-tree infrastructure for high dynamic group communication systems.
Diffusive mesh relaxation in ALE finite element numerical simulations
Energy Technology Data Exchange (ETDEWEB)
Dube, E.I.
1996-06-01
The theory for a diffusive mesh relaxation algorithm is developed for use in three-dimensional Arbitary Lagrange/Eulerian (ALE) finite element simulation techniques. This mesh relaxer is derived by a variational principle for an unstructured 3D grid using finite elements, and incorporates hourglass controls in the numerical implementation. The diffusive coefficients are based on the geometric properties of the existing mesh, and are chosen so as to allow for a smooth grid that retains the general shape of the original mesh. The diffusive mesh relaxation algorithm is then applied to an ALE code system, and results from several test cases are discussed.
Effects of mesh resolution on hypersonic heating prediction
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
Aeroheating prediction is a challenging and critical problem for the design and optimization of hypersonic vehicles.One challenge is that the solution of the Navier-Stokes equations strongly depends on the computational mesh.In this letter,the effect of mesh resolution on heat flux prediction is studied.It is found that mesh-independent solutions can be obtained using fine mesh,whose accuracy is confirmed by results from kinetic particle simulation.It is analyzed that mesh-induced numerical error comes m...
Wireless experiments on a Motorola mesh testbed.
Energy Technology Data Exchange (ETDEWEB)
Riblett, Loren E., Jr.; Wiseman, James M.; Witzke, Edward L.
2010-06-01
Motomesh is a Motorola product that performs mesh networking at both the client and access point levels and allows broadband mobile data connections with or between clients moving at vehicular speeds. Sandia National aboratories has extensive experience with this product and its predecessors in infrastructure-less mobile environments. This report documents experiments, which characterize certain aspects of how the Motomesh network performs when obile units are added to a fixed network infrastructure.
Airbag Mapped Mesh Auto-Flattening Method
Institute of Scientific and Technical Information of China (English)
ZHANG Jinhuan; MA Chunsheng; BAI Yuanli; HUANG Shilin
2005-01-01
Current software cannot easily model an airbag to be flattened without wrinkles. This paper improves the modeling efficiency using the initial metric method to design a mapped mesh auto-flattening algorithm. The element geometric transformation matrix was obtained using the theory of computer graphics. The algorithm proved to be practical for modeling a passenger-side airbag model. The efficiency and precision of modeling airbags are greatly improved by this method.
Solid Mesh Registration for Radiotherapy Treatment Planning
DEFF Research Database (Denmark)
Noe, Karsten Østergaard; Sørensen, Thomas Sangild
2010-01-01
We present an algorithm for solid organ registration of pre-segmented data represented as tetrahedral meshes. Registration of the organ surface is driven by force terms based on a distance field representation of the source and reference shapes. Registration of internal morphology is achieved usi...... to complete. The proposed method has many potential uses in image guided radiotherapy (IGRT) which relies on registration to account for organ deformation between treatment sessions....
Performance Evaluation of Coded Meshed Networks
DEFF Research Database (Denmark)
Krigslund, Jeppe; Hansen, Jonas; Pedersen, Morten Videbæk
2013-01-01
of the former to enhance the gains of the latter. We first motivate our work through measurements in WiFi mesh networks. Later, we compare state-of-the-art approaches, e.g., COPE, RLNC, to CORE. Our measurements show the higher reliability and throughput of CORE over other schemes, especially, for asymmetric...... and/or high loss probabilities. We show that a store and forward scheme outperforms COPE under some channel conditions, while CORE yields 3dB gains....
Particle Mesh Hydrodynamics for Astrophysics Simulations
Chatelain, Philippe; Cottet, Georges-Henri; Koumoutsakos, Petros
We present a particle method for the simulation of three dimensional compressible hydrodynamics based on a hybrid Particle-Mesh discretization of the governing equations. The method is rooted on the regularization of particle locations as in remeshed Smoothed Particle Hydrodynamics (rSPH). The rSPH method was recently introduced to remedy problems associated with the distortion of computational elements in SPH, by periodically re-initializing the particle positions and by using high order interpolation kernels. In the PMH formulation, the particles solely handle the convective part of the compressible Euler equations. The particle quantities are then interpolated onto a mesh, where the pressure terms are computed. PMH, like SPH, is free of the convection CFL condition while at the same time it is more efficient as derivatives are computed on a mesh rather than particle-particle interactions. PMH does not detract from the adaptive character of SPH and allows for control of its accuracy. We present simulations of a benchmark astrophysics problem demonstrating the capabilities of this approach.
Mesh Learning for Classifying Cognitive Processes
Ozay, Mete; Öztekin, Uygar; Vural, Fatos T Yarman
2012-01-01
The major goal of this study is to model the encoding and retrieval operations of the brain during memory processing, using statistical learning tools. The suggested method assumes that the memory encoding and retrieval processes can be represented by a supervised learning system, which is trained by the brain data collected from the functional Magnetic Resonance (fMRI) measurements, during the encoding stage. Then, the system outputs the same class labels as that of the fMRI data collected during the retrieval stage. The most challenging problem of modeling such a learning system is the design of the interactions among the voxels to extract the information about the underlying patterns of brain activity. In this study, we suggest a new method called Mesh Learning, which represents each voxel by a mesh of voxels in a neighborhood system. The nodes of the mesh are a set of neighboring voxels, whereas the arc weights are estimated by a linear regression model. The estimated arc weights are used to form Local Re...
Parallel object-oriented adaptive mesh refinement
Energy Technology Data Exchange (ETDEWEB)
Balsara, D.; Quinlan, D.J.
1997-04-01
In this paper we study adaptive mesh refinement (AMR) for elliptic and hyperbolic systems. We use the Asynchronous Fast Adaptive Composite Grid Method (AFACX), a parallel algorithm based upon the of Fast Adaptive Composite Grid Method (FAC) as a test case of an adaptive elliptic solver. For our hyperbolic system example we use TVD and ENO schemes for solving the Euler and MHD equations. We use the structured grid load balancer MLB as a tool for obtaining a load balanced distribution in a parallel environment. Parallel adaptive mesh refinement poses difficulties in expressing both the basic single grid solver, whether elliptic or hyperbolic, in a fashion that parallelizes seamlessly. It also requires that these basic solvers work together within the adaptive mesh refinement algorithm which uses the single grid solvers as one part of its adaptive solution process. We show that use of AMR++, an object-oriented library within the OVERTURE Framework, simplifies the development of AMR applications. Parallel support is provided and abstracted through the use of the P++ parallel array class.
Mesh deployable antenna mechanics testing method
Jiang, Li
Rapid development in spatial technologies and continuous expansion of astronautics applications require stricter and stricter standards in spatial structure. Deployable space structure as a newly invented structural form is being extensively adopted because of its characteristic (i.e. deployability). Deployable mesh reflector antenna is a kind of common deployable antennas. Its reflector consists in a kind of metal mesh. Its electrical properties are highly dependent on its mechanics parameters (including surface accuracy, angle, and position). Therefore, these mechanics parameters have to be calibrated. This paper presents a mesh antenna mechanics testing method that employs both an electronic theodolite and a laser tracker. The laser tracker is firstly used to measure the shape of radial rib deployable antenna. The measurement data are then fitted to a paraboloid by means of error compensation. Accordingly, the focus and the focal axis of the paraboloid are obtained. The following step is to synchronize the coordinate systems of the electronic theodolite and the measured antenna. Finally, in a microwave anechoic chamber environment, the electromechanical axis is calibrated. Testing results verify the effectiveness of the presented method.
Data-Parallel Mesh Connected Components Labeling and Analysis
Energy Technology Data Exchange (ETDEWEB)
Harrison, Cyrus; Childs, Hank; Gaither, Kelly
2011-04-10
We present a data-parallel algorithm for identifying and labeling the connected sub-meshes within a domain-decomposed 3D mesh. The identification task is challenging in a distributed-memory parallel setting because connectivity is transitive and the cells composing each sub-mesh may span many or all processors. Our algorithm employs a multi-stage application of the Union-find algorithm and a spatial partitioning scheme to efficiently merge information across processors and produce a global labeling of connected sub-meshes. Marking each vertex with its corresponding sub-mesh label allows us to isolate mesh features based on topology, enabling new analysis capabilities. We briefly discuss two specific applications of the algorithm and present results from a weak scaling study. We demonstrate the algorithm at concurrency levels up to 2197 cores and analyze meshes containing up to 68 billion cells.
Data-Parallel Mesh Connected Components Labeling and Analysis
Energy Technology Data Exchange (ETDEWEB)
Harrison, Cyrus; Childs, Hank; Gaither, Kelly
2011-04-10
We present a data-parallel algorithm for identifying and labeling the connected sub-meshes within a domain-decomposed 3D mesh. The identification task is challenging in a distributed-memory parallel setting because connectivity is transitive and the cells composing each sub-mesh may span many or all processors. Our algorithm employs a multi-stage application of the Union-find algorithm and a spatial partitioning scheme to efficiently merge information across processors and produce a global labeling of connected sub-meshes. Marking each vertex with its corresponding sub-mesh label allows us to isolate mesh features based on topology, enabling new analysis capabilities. We briefly discuss two specific applications of the algorithm and present results from a weak scaling study. We demonstrate the algorithm at concurrency levels up to 2197 cores and analyze meshes containing up to 68 billion cells.
Institute of Scientific and Technical Information of China (English)
王战业; 曹洪弘; 夏炳兰
2014-01-01
Objective To explore the diagnostic value of ultrasonography for carpal tunnel and cubital tunnel syndrome. Method Twenty-five healthy subjects were enrolled as control group and 35 patients with suspected carpal tunnel syndrome and 22 patients with suspected ulnar nerve compression were enrolled as disease group. The median nerve was examined by ultrasonography. The cross sectional area (CSA) at peas bone level and anteroposterior diameters (D1), anteroposterior diameters at hook bone level (D2) and distal level (D3) of median nerve, and CSA of the elbow ulnar nerve were measured. The difference values between D1 and D2 (D), D3 and D2 (d) were calculated. The ultrasonography findings in lesion group were compared with those observed during operation. Results Ultrasonography can display the morphological changes of median and ulnar nerves after compression. The CSA of median and ulnar nerves、D、d in lesion group were bigger than those in control group (P<0.03). The diagnostic accurate rates of ultrasonography for carpal tunnel and cubital tunnel syndromes were 97.9%and 95.4%, respectively. Conclusion High-frequency ultrasonography can diagnose carpal tunnel and cubital tunnel syndromes effectively.%目的：探讨超声对腕管综合征、肘管综合征的诊断价值。方法25例体检健康者为对照组，临床疑诊35例腕管综合征和22例尺神经卡压患者为病变组，超声探查正中神经豌豆骨水平横断面积及其前后径（D1）、钩骨勾水平前后径（D2）、钩骨勾水平远端前后径（D3），肘部尺神经横断面积，计算D1与D2差值（D），D3与D2差值（d），将病变组超声检查结果与术中所见进行比较。结果超声可显示正中神经、尺神经卡压后的形态变化，病变组正中神经横断面积、D、d及尺神经横断面积均大于对照组（P＜0．03）。与术中所见比较，超声诊断腕管综合征、肘管综合征准确率分别为97．9％、95．4％。结
Oral, intestinal, and skin bacteria in ventral hernia mesh implants
Directory of Open Access Journals (Sweden)
Odd Langbach
2016-07-01
Full Text Available Background: In ventral hernia surgery, mesh implants are used to reduce recurrence. Infection after mesh implantation can be a problem and rates around 6–10% have been reported. Bacterial colonization of mesh implants in patients without clinical signs of infection has not been thoroughly investigated. Molecular techniques have proven effective in demonstrating bacterial diversity in various environments and are able to identify bacteria on a gene-specific level. Objective: The purpose of this study was to detect bacterial biofilm in mesh implants, analyze its bacterial diversity, and look for possible resemblance with bacterial biofilm from the periodontal pocket. Methods: Thirty patients referred to our hospital for recurrence after former ventral hernia mesh repair, were examined for periodontitis in advance of new surgical hernia repair. Oral examination included periapical radiographs, periodontal probing, and subgingival plaque collection. A piece of mesh (1×1 cm from the abdominal wall was harvested during the new surgical hernia repair and analyzed for bacteria by PCR and 16S rRNA gene sequencing. From patients with positive PCR mesh samples, subgingival plaque samples were analyzed with the same techniques. Results: A great variety of taxa were detected in 20 (66.7% mesh samples, including typical oral commensals and periodontopathogens, enterics, and skin bacteria. Mesh and periodontal bacteria were further analyzed for similarity in 16S rRNA gene sequences. In 17 sequences, the level of resemblance between mesh and subgingival bacterial colonization was 98–100% suggesting, but not proving, a transfer of oral bacteria to the mesh. Conclusion: The results show great bacterial diversity on mesh implants from the anterior abdominal wall including oral commensals and periodontopathogens. Mesh can be reached by bacteria in several ways including hematogenous spread from an oral site. However, other sites such as gut and skin may also
Research on meshing theory of noninvolute beveloid gears
Institute of Scientific and Technical Information of China (English)
李瑰贤; 温建民; 李笑; 刘福利; 刘宇
2003-01-01
A mathematical model has been developed using the space engagement theory and the differential ge-ometry for the line contact of noninvolute beveloid gears with intersecting axes with their tooth profile equationsand engagement equations established for the first time and their meshing theory analysed. It can be seen fromthe fact that the tooth profile equation finally derived is no longer a standard involute helicoid and standard invo-lute beveloid gears with intersecting axes have no way to satisfy the line contact requirement. However, the non-invdute beveloid gears derived in this paper satisfy the line contact requirement very well. All these work willinevitably facilitate further investigations into gear tooth generation, stiffness, backlash and efficiency of trans-mission.
Hydrodynamical Adaptive Mesh Refinement Simulations of Disk Galaxies
Gibson, Brad K; Sanchez-Blazquez, Patricia; Teyssier, Romain; House, Elisa L; Brook, Chris B; Kawata, Daisuke
2008-01-01
To date, fully cosmological hydrodynamic disk simulations to redshift zero have only been undertaken with particle-based codes, such as GADGET, Gasoline, or GCD+. In light of the (supposed) limitations of traditional implementations of smoothed particle hydrodynamics (SPH), or at the very least, their respective idiosyncrasies, it is important to explore complementary approaches to the SPH paradigm to galaxy formation. We present the first high-resolution cosmological disk simulations to redshift zero using an adaptive mesh refinement (AMR)-based hydrodynamical code, in this case, RAMSES. We analyse the temporal and spatial evolution of the simulated stellar disks' vertical heating, velocity ellipsoids, stellar populations, vertical and radial abundance gradients (gas and stars), assembly/infall histories, warps/lopsideness, disk edges/truncations (gas and stars), ISM physics implementations, and compare and contrast these properties with our sample of cosmological SPH disks, generated with GCD+. These prelim...
LOAD AWARE ADAPTIVE BACKBONE SYNTHESIS IN WIRELESS MESH NETWORKS
Institute of Scientific and Technical Information of China (English)
Yuan Yuan; Zheng Baoyu
2009-01-01
Wireless Mesh Networks (WMNs) are envisioned to support the wired backbone with a wireless Backbone Networks (BNet) for providing internet connectivity to large-scale areas.With a wide range of internet-oriented applications with different Quality of Service (QoS) requirement,the large-scale WMNs should have good scalability and large bandwidth.In this paper,a Load Aware Adaptive Backbone Synthesis (LAABS) algorithm is proposed to automatically balance the traffic flow in the WMNs.The BNet will dynamically split into smaller size or merge into bigger one according to statistic load information of Backbone Nodes (BNs).Simulation results show LAABS generates moderate BNet size and converges quickly,thus providing scalable and stable BNet to facilitate traffic flow.
Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.
2013-04-01
Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.
Open Volumetric Mesh-An Efficient Data Structure for Tetrahedral and Hexa-hedral Meshes
Institute of Scientific and Technical Information of China (English)
XIAN Chu-hua; LI Gui-qing; GAO Shu-ming
2013-01-01
This work introduces a scalable and efficient topological structure for tetrahedral and hexahedral meshes. The design of the data structure aims at maximal flexibility and high performance. It provides a high scalability by using hierarchical representa-tions of topological elements. The proposed data structure is array-based, and it is a compact representation of the half-edge data structure for volume elements and half-face data structure for volumetric meshes. This guarantees constant access time to the neighbors of the topological elements. In addition, an open-source implementation named Open Volumetric Mesh (OVM) of the pro-posed data structure is written in C++using generic programming concepts.
Schoenmaeckers, Ernst J P; van der Valk, Steef B A; van den Hout, Huib W; Raymakers, Johan F T J; Rakic, Srdjan
2009-07-01
The potential for shrinkage of intraperitoneally implanted meshes for laparoscopic repair of ventral and incisional hernia (LRVIH) remains a concern. Numerous experimental studies on this issue reported very inconsistent results. Expanded polytetrafluoroethylene (ePTFE) mesh has the unique property of being revealed by computed tomography (CT). We therefore conducted an analysis of CT findings in patients who had previously undergone LRVIH with an ePTFE mesh (DualMesh, WL Gore, Flagstaff, AZ, USA) in order to evaluate the shrinkage of implanted meshes. Of 656 LRVIH patients with DualMesh, all patients who subsequently underwent CT scanning were identified and only those with precisely known transverse diameter of implanted mesh and with CT scans made more than 3 months postoperatively were selected (n = 40). Two radiologists who were blinded to the size of the implanted mesh measured in consensus the maximal transverse diameter of the meshes by using the AquariusNET program (TeraRecon Inc., San Mateo, CA, USA). Mesh shrinkage was defined as the relative loss of transverse diameter as compared with the original transverse diameter of the mesh. The mean time from LRVIH to CT scan was 17.9 months (range 3-59 months). The mean shrinkage of the mesh was 7.5% (range 0-23.7%). For 11 patients (28%) there was no shrinkage at all. Shrinkage of 1-10% was found in 16 patients (40%), of 10-20% in 10 patients (25%), and of 20-24% in 3 patients (7.5%). No correlation was found regarding the elapsed time between LRVIH and CT, and shrinkage. There were two recurrences, one possibly related to shrinkage. Our observations indicate that shrinkage of DualMesh is remarkably lower than has been reported in experimental studies (8-51%). This study is the first to address the problem of shrinkage after intraperitoneal implantation of synthetic mesh in a clinical material.
Directory of Open Access Journals (Sweden)
Gugri Mukthinath
2016-06-01
Full Text Available Background: Inguinal hernia repair is the most frequently performed operation in any general surgical unit. The complications of using the mesh has been the rationale to examine the role of mesh in hernia repair in detail and to begin investigating the biocompatibility of different mesh modifications and to challenge old mesh concepts. Therefore the present study is undertaken to compare the lightweight mesh (Ultrapro with conventional prolene mesh in lichtenstein hernia repair. Methods: Thirty one patients with primary unilateral inguinal hernia was subjected either to lightweight mesh Lichtenstein's hernioplasty or standard prolene mesh Lichtenstein's hernioplasty. The patients were followed in the surgical OPD at 1 month, 6 months and 1 year for time taken to return to normal activities, chronic groin pain, foreign body sensation, seroma formation and recurrence. Results: Chronic pain among patients in standard prolene mesh group at 1 month, 6 month, and 1 year follow up was seen in 45.2%, 16% and 3.2% of the patients respectively, in light weight mesh group patients at 1 month, 6 month and 1 year follow up was 32.2%, 6.4% and none at one year respectively. Foreign body sensation in the light weight mesh group is significantly less compared to patients in standard prolene mesh group. Time taken to return to work was relatively shorter among patients in Light weight mesh group. There was no recurrence in both groups. Conclusion: Light weight mesh is an ideal choice in Lichenstein's hernioplasty whenever feasible. [Int J Res Med Sci 2016; 4(6.000: 2130-2134
[Meta-Mesh: metagenomic data analysis system].
Su, Xiaoquan; Song, Baoxing; Wang, Xuetao; Ma, Xinle; Xu, Jian; Ning, Kang
2014-01-01
With the current accumulation of metagenome data, it is possible to build an integrated platform for processing of rigorously selected metagenomic samples (also referred as "metagenomic communities" here) of interests. Any metagenomic samples could then be searched against this database to find the most similar sample(s). However, on one hand, current databases with a large number of metagenomic samples mostly serve as data repositories but not well annotated database, and only offer few functions for analysis. On the other hand, the few available methods to measure the similarity of metagenomic data could only compare a few pre-defined set of metagenome. It has long been intriguing scientists to effectively calculate similarities between microbial communities in a large repository, to examine how similar these samples are and to find the correlation of the meta-information of these samples. In this work we propose a novel system, Meta-Mesh, which includes a metagenomic database and its companion analysis platform that could systematically and efficiently analyze, compare and search similar metagenomic samples. In the database part, we have collected more than 7 000 high quality and well annotated metagenomic samples from the public domain and in-house facilities. The analysis platform supplies a list of online tools which could accept metagenomic samples, build taxonomical annotations, compare sample in multiple angle, and then search for similar samples against its database by a fast indexing strategy and scoring function. We also used case studies of "database search for identification" and "samples clustering based on similarity matrix" using human-associated habitat samples to demonstrate the performance of Meta-Mesh in metagenomic analysis. Therefore, Meta-Mesh would serve as a database and data analysis system to quickly parse and identify similar
Perspective on the Lagrange-Jacobi mesh
Rampho, Gaotsiwe J.
2016-07-01
This paper presents a unified treatment of the kinetic energy matrix elements related to a number of Lagrange functions associated with the Lagrange-Jacobi mesh. The matrix elements can be readily modified for application to problems requiring eigenfunction expansion with Lagrange-Legendre, Lagrange-Chebyshev, Lagrange-Gegenbauer, as well as the Lagrange-Jacobi functions. The applicability of and the accuracy attainable with the matrix elements is demonstrated with the solution to the Schrödinger equation for confining trigonometric Pöschl-Teller potentials. The results obtained are within machine accuracy when appropriate choices of the basis functions are used.
Performance of FACTS equipment in Meshed systems
Energy Technology Data Exchange (ETDEWEB)
Lerch, E.; Povh, D. [Siemens AG, Berlin (Germany)
1994-12-31
Modern power electronic devices such as thyristors and GTOs have made it possible to design controllable network elements, which will play a considerable role in ensuring reliable economic operation of transmission systems as a result of their capability to rapidly change active and reactive power. A number of FACTS elements for high-speed active and reactive power control will be described. Control of power system fluctuations in meshed systems by modulation of active and reactive power will be demonstrated using a number of examples. (author) 7 refs., 11 figs.
Corset neophallic musculoplasty with a mesh endoprosthesis
Directory of Open Access Journals (Sweden)
V. V. Mikhailichenko
2014-12-01
Full Text Available During thoracodorsal flap phalloplasty, recovered contractility of the muscular base of the neophallus may lead to its shortening that impedes introjection.To eliminate deformity and shortening of the neophallus, the authors propose the procedure of corset plasty of its muscle, which differs in that the alloplastic material – esfil mesh endoprosthesis, is used as a corset instead of fascia latum of the hip. The proposed procedure reduces surgical trauma, improves the functional characteristics of the neophallus, and accelerates sexual rehabilitation.
Corset neophallic musculoplasty with a mesh endoprosthesis
Directory of Open Access Journals (Sweden)
V. V. Mikhailichenko
2014-01-01
Full Text Available During thoracodorsal flap phalloplasty, recovered contractility of the muscular base of the neophallus may lead to its shortening that impedes introjection.To eliminate deformity and shortening of the neophallus, the authors propose the procedure of corset plasty of its muscle, which differs in that the alloplastic material – esfil mesh endoprosthesis, is used as a corset instead of fascia latum of the hip. The proposed procedure reduces surgical trauma, improves the functional characteristics of the neophallus, and accelerates sexual rehabilitation.
Relativistic MHD with adaptive mesh refinement
Energy Technology Data Exchange (ETDEWEB)
Anderson, Matthew [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States); Hirschmann, Eric W [Department of Physics and Astronomy, Brigham Young University, Provo, UT 84602 (United States); Liebling, Steven L [Department of Physics, Long Island University-C W Post Campus, Brookville, NY 11548 (United States); Neilsen, David [Department of Physics and Astronomy, Brigham Young University, Provo, UT 84602 (United States)
2006-11-22
This paper presents a new computer code to solve the general relativistic magnetohydrodynamics (GRMHD) equations using distributed parallel adaptive mesh refinement (AMR). The fluid equations are solved using a finite difference convex ENO method (CENO) in 3 + 1 dimensions, and the AMR is Berger-Oliger. Hyperbolic divergence cleaning is used to control the {nabla} . B = 0 constraint. We present results from three flat space tests, and examine the accretion of a fluid onto a Schwarzschild black hole, reproducing the Michel solution. The AMR simulations substantially improve performance while reproducing the resolution equivalent unigrid simulation results. Finally, we discuss strong scaling results for parallel unigrid and AMR runs.
Split Bregman's algorithm for three-dimensional mesh segmentation
Habiba, Nabi; Ali, Douik
2016-05-01
Variational methods have attracted a lot of attention in the literature, especially for image and mesh segmentation. The methods aim at minimizing the energy to optimize both edge and region detections. We propose a spectral mesh decomposition algorithm to obtain disjoint but meaningful regions of an input mesh. The related optimization problem is nonconvex, and it is very difficult to find a good approximation or global optimum, which represents a challenge in computer vision. We propose an alternating split Bregman algorithm for mesh segmentation, where we extended the image-dedicated model to a three-dimensional (3-D) mesh one. By applying our scheme to 3-D mesh segmentation, we obtain fast solvers that can outperform various conventional ones, such as graph-cut and primal dual methods. A consistent evaluation of the proposed method on various public domain 3-D databases for different metrics is elaborated, and a comparison with the state-of-the-art is performed.
Embedding meshes in Boolean cubes by graph decomposition
Energy Technology Data Exchange (ETDEWEB)
Ho, C.T. (IBM Almaden Research Center, San Jose, CA (US)); Johnsson, S.L. (Dept. of Computer Science and Electrical Engineering, Yale Univ., New Haven, CT (US))
1990-04-01
This paper explores the embeddings of multidimensional meshes into minimal Boolean cubes by graph decomposition. The graph decomposition technique can be used to improve the average dilation and average congestion. The graph decomposition technique combined with some particular two-dimensional embeddings allows for minimal-expansion, dilation-two, congestion-two embeddings of about 87% of all two-dimensional meshes, with a significantly lower average dilation and congestion than by modified line compression. For three-dimensional meshes the authors show that the graph decomposition technique, together with two three-dimensional mesh embeddings presented in this paper and modified line compression, yields dilation-two embeddings of more than 96% of all three dimensional meshes contained in a 512 {times} 512 {times} 512 mesh.
Investigation of Mesh Choosing Parameters in Screen Printing System
Directory of Open Access Journals (Sweden)
Ahmet AKGÜL
2012-05-01
Full Text Available The mesh, which is made by weaving of natural silk, plastic, or metal fibers, is basic material for screen-printing. Image is created on stretched on a frame in screen-printing. Mesh should be selected correctly for a high quality printing. Therefore, substrates, types of print job and mesh parameters have importance. Need to know more about to mesh, yarn type, yarn thickness, frequency of weaving, stretching tension, the kind of weaving, etc. In this study, for a high quality screen-printing, mesh variables examined in detail and optimum conditions indicated, with the aim of increase productivity, minimize to losses time, material and labor. As a result, this information’s for obtaining a high quality printing with screen-printing system have importance as a guide. Also resolution of the image, amount of print run and viscosity of the printing ink, factors affecting the selection of mesh.
MeSH Up: effective MeSH text classification for improved document retrieval
Trieschnigg, Dolf; Pezik, Piotr; Lee, Vivian; Jong, de Franciska; Kraaij, Wessel; Rebholz-Schuhmann, Dietrich
2009-01-01
Motivation: Controlled vocabularies such as the Medical Subject Headings (MeSH) thesaurus and the Gene Ontology (GO) provide an efficient way of accessing and organizing biomedical information by reducing the ambiguity inherent to free-text data. Different methods of automating the assignment of MeS
MeSH Up: Effective MeSH text classification for improved document retrieval
Trieschnigg, D.; Pezik, P.; Lee, V.; Jong, F.de; Kraaij, W.; Rebholz-Schuhmann, D.
2009-01-01
Motivation: Controlled vocabularies such as the Medical Subject Headings (MeSH) thesaurus and the Gene Ontology (GO) provide an efficient way of accessing and organizing biomedical information by reducing the ambiguity inherent to free-text data. Different methods of automating the assignment of MeS
Vertex-based diffusion for 3-D mesh denoising.
Zhang, Ying; Ben Hamza, A
2007-04-01
We present a vertex-based diffusion for 3-D mesh denoising by solving a nonlinear discrete partial differential equation. The core idea behind our proposed technique is to use geometric insight in helping construct an efficient and fast 3-D mesh smoothing strategy to fully preserve the geometric structure of the data. Illustrating experimental results demonstrate a much improved performance of the proposed approach in comparison with existing methods currently used in 3-D mesh smoothing.
Multiphase Flow of Immiscible Fluids on Unstructured Moving Meshes
DEFF Research Database (Denmark)
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam;
2013-01-01
In this paper, we present a method for animating multiphase flow of immiscible fluids using unstructured moving meshes. Our underlying discretization is an unstructured tetrahedral mesh, the deformable simplicial complex (DSC), that moves with the flow in a Lagrangian manner. Mesh optimization op...... complement and solve our optimization on the GPU. We provide the results of parameter studies as well as a performance analysis of our method, together with suggestions for performance optimization....
Deng, Meng; Gu, Yunpeng; Liu, Zhenjun; Qi, Yue; Ma, Gui E; Kang, Ning
2015-01-01
Adipose-derived stem cell (ADSC) is considered as a cell source potentially useful for angiogenesis in tissue engineering and regenerative medicine. This study investigated the growth and endothelial differentiation of human ADSCs on polyglycolic acid/polylactic acid (PGA/PLA) mesh compared to 2D plastic. Cell adhesion, viability, and distribution of hADSCs on PGA/PLA mesh were observed by CM-Dil labeling, live/dead staining, and SEM examination while endothelial differentiation was evaluated by flow cytometry, Ac-LDL/UEA-1 uptake assay, immunofluorescence stainings, and gene expression analysis of endothelial related markers. Results showed hADSCs gained a mature endothelial phenotype with a positive ratio of 21.4 ± 3.7% for CD31+/CD34- when induced in 3D mesh after 21 days, which was further verified by the expressions of a comprehensive range of endothelial related markers, whereas hADSCs in 2D induced and 2D/3D noninduced groups all failed to differentiate into endothelial cells. Moreover, compared to 2D groups, the expression for α-SMA was markedly suppressed in 3D cultured hADSCs. This study first demonstrated the endothelial differentiation of hADSCs on the PGA/PLA mesh and pointed out the synergistic effect of PGA/PLA 3D culture and growth factors on the acquisition of mature characteristic endothelial phenotype. We believed this study would be the initial step towards the generation of prevascularized tissue engineered constructs.