Kainmueller, Dagmar
2014-01-01
? Segmentation of anatomical structures in medical image data is an essential task in clinical practice. Dagmar Kainmueller introduces methods for accurate fully automatic segmentation of anatomical structures in 3D medical image data. The author's core methodological contribution is a novel deformation model that overcomes limitations of state-of-the-art Deformable Surface approaches, hence allowing for accurate segmentation of tip- and ridge-shaped features of anatomical structures. As for practical contributions, she proposes application-specific segmentation pipelines for a range of anatom
Automated hexahedral meshing of anatomic structures using deformable registration.
Grosland, Nicole M; Bafna, Ritesh; Magnotta, Vincent A
2009-02-01
This work introduces a novel method of automating the process of patient-specific finite element (FE) model development using a mapped mesh technique. The objective is to map a predefined mesh (template) of high quality directly onto a new bony surface (target) definition, thereby yielding a similar mesh with minimal user interaction. To bring the template mesh into correspondence with the target surface, a deformable registration technique based on the FE method has been adopted. The procedure has been made hierarchical allowing several levels of mesh refinement to be used, thus reducing the time required to achieve a solution. Our initial efforts have focused on the phalanx bones of the human hand. Mesh quality metrics, such as element volume and distortion were evaluated. Furthermore, the distance between the target surface and the final mapped mesh were measured. The results have satisfactorily proven the applicability of the proposed method. PMID:18688764
Lenz, F; Doll, S; Sohn, C; Brocker, K A
2013-10-01
Purpose: Polypropylene mesh implants are frequently used for pelvic floor reconstruction in women. Yet they vary in size and fixation. The purpose of this study is to compare four mesh products with regard to their anatomical positioning and functionality within the pelvic floor, to determine whether each mesh fits equally well in a female cadaver. Methods: One female pelvis was dissected, opening the retropubic space exposing the endopelvic fascia and demonstrating the arcus tendineus fasciae pelvis (ATFP). Anatomical parameters were measured before and after implanting four meshes via the transobturator approach. Results: The anterior fixation of the ATFP was found to be 5 mm lateral to the symphysis in this cadaver. The endopelvic fascia covered 54.6 cm(2). The obturator nerve was located 35 mm from the white line. The distance of the proximal and lateral points of mesh fixation from the ischial spine or ATFP varied from 0 to 25 mm. The meshes varied in size and anatomical positioning. Conclusion: These observations demonstrate the necessity of developing optimally sized meshes and appropriate introducer techniques that can provide sufficient vaginal support. Surgeons, furthermore, need profound knowledge of anatomy, the patient's pelvic floor defect and the meshes available on the market. PMID:24771893
Accurate solution of the Dirac equation on Lagrange meshes
Baye, Daniel; Godefroid, Michel
2014-01-01
The Lagrange-mesh method is an approximate variational method taking the form of equations on a grid because of the use of a Gauss quadrature approximation. With a basis of Lagrange functions involving associated Laguerre polynomials related to the Gauss quadrature, the method is applied to the Dirac equation. The potential may possess a $1/r$ singularity. For hydrogenic atoms, numerically exact energies and wave functions are obtained with small numbers $n+1$ of mesh points, where $n$ is the principal quantum number. Numerically exact mean values of powers $-2$ to 3 of the radial coordinate $r$ can also be obtained with $n+2$ mesh points. For the Yukawa potential, a 15-digit agreement with benchmark energies of the literature is obtained with 50 mesh points or less.
Accurately simulating anisotropic thermal conduction on a moving mesh
Kannan, Rahul; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark
2015-01-01
We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretisation stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the co...
Accurately simulating anisotropic thermal conduction on a moving mesh
Kannan, Rahul; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark
2016-05-01
We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretization stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the conductive heat transport in galaxy clusters, the evolution of supernova remnants, or the distribution of heat from black hole-driven jets into the intracluster medium.
Rumple, Christopher; Krane, Michael; Richter, Joseph; Craven, Brent
2013-11-01
The mammalian nose is a multi-purpose organ that houses a convoluted airway labyrinth responsible for respiratory air conditioning, filtering of environmental contaminants, and chemical sensing. Because of the complexity of the nasal cavity, the anatomy and function of these upper airways remain poorly understood in most mammals. However, recent advances in high-resolution medical imaging, computational modeling, and experimental flow measurement techniques are now permitting the study of respiratory airflow and olfactory transport phenomena in anatomically-accurate reconstructions of the nasal cavity. Here, we focus on efforts to manufacture an anatomically-accurate transparent model for stereoscopic particle image velocimetry (SPIV) measurements. Challenges in the design and manufacture of an index-matched anatomical model are addressed. PIV measurements are presented, which are used to validate concurrent computational fluid dynamics (CFD) simulations of mammalian nasal airflow. Supported by the National Science Foundation.
Augustin, Christoph M.; Neic, Aurel; Liebmann, Manfred; Prassl, Anton J.; Niederer, Steven A.; Haase, Gundolf; Plank, Gernot
2016-01-01
Electromechanical (EM) models of the heart have been used successfully to study fundamental mechanisms underlying a heart beat in health and disease. However, in all modeling studies reported so far numerous simplifications were made in terms of representing biophysical details of cellular function and its heterogeneity, gross anatomy and tissue microstructure, as well as the bidirectional coupling between electrophysiology (EP) and tissue distension. One limiting factor is the employed spatial discretization methods which are not sufficiently flexible to accommodate complex geometries or resolve heterogeneities, but, even more importantly, the limited efficiency of the prevailing solver techniques which is not sufficiently scalable to deal with the incurring increase in degrees of freedom (DOF) when modeling cardiac electromechanics at high spatio-temporal resolution. This study reports on the development of a novel methodology for solving the nonlinear equation of finite elasticity using human whole organ models of cardiac electromechanics, discretized at a high para-cellular resolution. Three patient-specific, anatomically accurate, whole heart EM models were reconstructed from magnetic resonance (MR) scans at resolutions of 220 μm, 440 μm and 880 μm, yielding meshes of approximately 184.6, 24.4 and 3.7 million tetrahedral elements and 95.9, 13.2 and 2.1 million displacement DOF, respectively. The same mesh was used for discretizing the governing equations of both electrophysiology (EP) and nonlinear elasticity. A novel algebraic multigrid (AMG) preconditioner for an iterative Krylov solver was developed to deal with the resulting computational load. The AMG preconditioner was designed under the primary objective of achieving favorable strong scaling characteristics for both setup and solution runtimes, as this is key for exploiting current high performance computing hardware. Benchmark results using the 220 μm, 440 μm and 880 μm meshes demonstrate
Creation of Anatomically Accurate Computer-Aided Design (CAD) Solid Models from Medical Images
Stewart, John E.; Graham, R. Scott; Samareh, Jamshid A.; Oberlander, Eric J.; Broaddus, William C.
1999-01-01
Most surgical instrumentation and implants used in the world today are designed with sophisticated Computer-Aided Design (CAD)/Computer-Aided Manufacturing (CAM) software. This software automates the mechanical development of a product from its conceptual design through manufacturing. CAD software also provides a means of manipulating solid models prior to Finite Element Modeling (FEM). Few surgical products are designed in conjunction with accurate CAD models of human anatomy because of the difficulty with which these models are created. We have developed a novel technique that creates anatomically accurate, patient specific CAD solids from medical images in a matter of minutes.
Rumple, C.; Richter, J.; Craven, B. A.; Krane, M.
2012-11-01
A summary of the research being carried out by our multidisciplinary team to better understand the form and function of the nose in different mammalian species that include humans, carnivores, ungulates, rodents, and marine animals will be presented. The mammalian nose houses a convoluted airway labyrinth, where two hallmark features of mammals occur, endothermy and olfaction. Because of the complexity of the nasal cavity, the anatomy and function of these upper airways remain poorly understood in most mammals. However, recent advances in high-resolution medical imaging, computational modeling, and experimental flow measurement techniques are now permitting the study of airflow and respiratory and olfactory transport phenomena in anatomically-accurate reconstructions of the nasal cavity. Here, we focus on efforts to manufacture transparent, anatomically-accurate models for stereo particle image velocimetry (SPIV) measurements of nasal airflow. Challenges in the design and manufacture of index-matched anatomical models are addressed and preliminary SPIV measurements are presented. Such measurements will constitute a validation database for concurrent computational fluid dynamics (CFD) simulations of mammalian respiration and olfaction. Supported by the National Science Foundation.
Parallelization of a high-order accurate unstructured mesh finite-volume solver
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A generic solver eliminates the need to write new finite-volume codes for each type of physics. By separating the physics from the numerics of the solver, a modular design is achieved. New physics modules can easily be written with a minimal knowledge of the finite-volume method. A parallel solver allows simulation of complex physics on intricate domains in a timely manner by using numerous processors simultaneously. In this paper we describe the steps needed to adapt a high-order accurate unstructured mesh generic finite-volume solver to a parallel architecture. A message-passing approach is used which allows the solver to operate on a distributed memory system, such as a cluster of workstations. The reconstruction stencil is determined at the preprocessing stage and an appropriate parallel data structure for the solution is formed. Fluxes for faces on the partition boundary are evaluated by communicating the reconstruction coefficients to the adjacent processor. Good performance scalability is achieved for second and fourth-order accurate solutions on cell and vertex centered meshes. (authors)
Lee, Dongwook
2013-01-01
In this paper, we extend the unsplit staggered mesh scheme (USM) for 2D magnetohydrodynamics (MHD) (Lee and Deane, 2009) to a full 3D MHD scheme. The scheme is a finite-volume Godunov method consisting of a constrained transport (CT) method and an efficient and accurate single-step, directionally unsplit multidimensional data reconstruction-evolution algorithm, which extends the original 2D corner transport upwind (CTU) method (Colella, 1990). We present two types of data reconstruction-evolution algorithms for 3D: (1) a reduced CTU scheme and (2) a full CTU scheme. The reduced 3D CTU scheme is a variant of a simple 3D extension of the 2D CTU method by Colella (1990) and is considered as a direct extension from the 2D USM scheme. The full 3D CTU scheme is our primary 3D solver which includes all multidimensional cross-derivative terms for stability. The latter method is logically analogous to the 3D unsplit CTU method by Saltzman. The major novelties in our algorithms are twofold. First, we extend the reduced...
O'Halloran, M.; Lohfeld, S.; Ruvio, G.; Browne, J.; Krewer, F.; Ribeiro, C. O.; Inacio Pita, V. C.; Conceicao, R. C.; Jones, E.; Glavin, M.
2014-05-01
Breast cancer is one of the most common cancers in women. In the United States alone, it accounts for 31% of new cancer cases, and is second only to lung cancer as the leading cause of deaths in American women. More than 184,000 new cases of breast cancer are diagnosed each year resulting in approximately 41,000 deaths. Early detection and intervention is one of the most significant factors in improving the survival rates and quality of life experienced by breast cancer sufferers, since this is the time when treatment is most effective. One of the most promising breast imaging modalities is microwave imaging. The physical basis of active microwave imaging is the dielectric contrast between normal and malignant breast tissue that exists at microwave frequencies. The dielectric contrast is mainly due to the increased water content present in the cancerous tissue. Microwave imaging is non-ionizing, does not require breast compression, is less invasive than X-ray mammography, and is potentially low cost. While several prototype microwave breast imaging systems are currently in various stages of development, the design and fabrication of anatomically and dielectrically representative breast phantoms to evaluate these systems is often problematic. While some existing phantoms are composed of dielectrically representative materials, they rarely accurately represent the shape and size of a typical breast. Conversely, several phantoms have been developed to accurately model the shape of the human breast, but have inappropriate dielectric properties. This study will brie y review existing phantoms before describing the development of a more accurate and practical breast phantom for the evaluation of microwave breast imaging systems.
The Quick Measure of a Nurbs Surface Curvature for Accurate Triangular Meshing
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Kniat Aleksander
2014-04-01
Full Text Available NURBS surfaces are the most widely used surfaces for three-dimensional models in CAD/ CAE programs. When a model for FEM calculation is prepared with a CAD program it is inevitable to mesh it finally. There are many algorithms for meshing planar regions. Some of them may be used for meshing surfaces but it is necessary to take the curvature of the surface under consideration to avoid poor quality mesh. The mesh must be denser in the curved regions of the surface. In this paper, instead of analysing a surface curvature, the method to assess how close is a mesh triangle to the surface to which its vertices belong, is presented. The distance between a mesh triangle and a parallel tangent plane through a point on a surface is the measure of the triangle quality. Finding the surface point whose projection is located inside the mesh triangle and which is the tangency point to the plane parallel to this triangle is an optimization problem. Mathematical description of the problem and the algorithm to find its solution are also presented in the paper.
Streett, Craig L.; Venkatachari, Balaji Shankar; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung
2016-01-01
Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.
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Background: Numbering of the thoracic spine on MRI can be tedious if C2 and L5-S1 are not included and may lead to errors in lesion level. Purpose: To determine whether anatomic landmarks or external markers are reliable as an aid for accurate numbering of thoracic vertebrae on MRI. Material and Methods: Sixty-seven thoracic spine MR studies of 67 patients (30 males, 37 females, age range 18-83 years) were studied, composed of 52 consecutive MR studies and an additional 15 MRI in which vitamin E markers were placed over the skin. In the 52 thoracic MR examinations potential numbering aids such as the level of the sternal apex, pulmonary artery, aortic arch, and osseous or disc abnormalities were numbered on both cervical localizer (standard of reference) and thoracic sagittal images. The additional 15 examinations in which vitamin E markers were placed over the skin were evaluated for consistency in the level of the markers on different sequences in the same exam. Results: The sternal apex level ranged from T2 to T5 [T3 in 28/51 patients (55%), T2 in 10/51 (20%)]. The aortic arch level ranged from T2 to T4 [T4 in 18/48 (38%) and T3 in 17 (35%)]. Pulmonary artery level ranged from T4 to T6-7 disc [T5 in 20/52 patients (38%) and T6 in 14/52 (27%)]. In 3 of 12 patients who had abnormalities in a vertebral body or disc as definite point reference, the non-localizer image mislabelled the level. In 11/15 (73%) patients with vitamin E markers that were placed over the upper thoracic spine, the results showed consistency in the level of the markers in relation to the reference points or consistent inter-marker gap between the sequences. Conclusion: There are only two reliable ways to accurately define the levels if no landmarking feature is available on the magnet. The first is by including C2 in the thoracic sequence of a diagnostic quality, and the second is by using an abnormality in the discs or vertebral bodies as a point of reference
New approach based on tetrahedral-mesh geometry for accurate 4D Monte Carlo patient-dose calculation
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In the present study, to achieve accurate 4D Monte Carlo dose calculation in radiation therapy, we devised a new approach that combines (1) modeling of the patient body using tetrahedral-mesh geometry based on the patient’s 4D CT data, (2) continuous movement/deformation of the tetrahedral patient model by interpolation of deformation vector fields acquired through deformable image registration, and (3) direct transportation of radiation particles during the movement and deformation of the tetrahedral patient model. The results of our feasibility study show that it is certainly possible to construct 4D patient models (= phantoms) with sufficient accuracy using the tetrahedral-mesh geometry and to directly transport radiation particles during continuous movement and deformation of the tetrahedral patient model. This new approach not only produces more accurate dose distribution in the patient but also replaces the current practice of using multiple 3D voxel phantoms and combining multiple dose distributions after Monte Carlo simulations. For routine clinical application of our new approach, the use of fast automatic segmentation algorithms is a must. In order to achieve, simultaneously, both dose accuracy and computation speed, the number of tetrahedrons for the lungs should be optimized. Although the current computation speed of our new 4D Monte Carlo simulation approach is slow (i.e. ∼40 times slower than that of the conventional dose accumulation approach), this problem is resolvable by developing, in Geant4, a dedicated navigation class optimized for particle transportation in tetrahedral-mesh geometry. (paper)
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Background and purpose: Low contrast in the cone-beam computed tomography (CBCT) scans hampers fast online evaluation of interfractional changes in the lymph node position on a daily basis. In this study we have investigated whether high-contrast anatomical landmarks in the vicinity of the nodes may be used as surrogates for the lymph node positions. Materials and methods: Forty lung cancer patients were treated with an online CBCT-based setup strategy involving soft-tissue match on the primary tumor. One hundred and sixteen lymph nodes were delineated separately on the planning-CT scans and categorized according to the lymph node stations. Five anatomical landmarks were selected as surrogate structures and assigned to the individual nodes. In addition, the carina was delineated. Registrations between the planning-CT and the daily CBCTs were performed retrospectively and positional deviations between the nodes and the surrogate structures or the carina were registered. Results: The mean displacement between lymph nodes and surrogate structures was 1.6 mm with systematic/random errors of 0.7/0.7 mm, significantly smaller than the mean displacement between nodes and the carina. Conclusions: The position of the lymph nodes can be evaluated using selected anatomical landmarks on a daily basis using CBCT
GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
Hopkins, Philip F
2014-01-01
We present and study two new Lagrangian numerical methods for solving the equations of hydrodynamics, in a systematic comparison with moving-mesh, SPH, and non-moving grid methods. The new methods are designed to capture many advantages of both smoothed-particle hydrodynamics (SPH) and grid-based or adaptive mesh refinement (AMR) schemes. They are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a Riemann solver acting over the volume 'overlap.' We implement and test a parallel, second-order version of the method with coupled self-gravity & cosmological integration, in the code GIZMO: this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods we study; does not require 'artificial diffusion' terms; and allows fluid elements to move with the flow so resolution is automatically adaptive. We consider a large suite of test problems, and find that on all problems the new methods a...
Hepburn, I; Chen, W; De Schutter, E
2016-08-01
Spatial stochastic molecular simulations in biology are limited by the intense computation required to track molecules in space either in a discrete time or discrete space framework, which has led to the development of parallel methods that can take advantage of the power of modern supercomputers in recent years. We systematically test suggested components of stochastic reaction-diffusion operator splitting in the literature and discuss their effects on accuracy. We introduce an operator splitting implementation for irregular meshes that enhances accuracy with minimal performance cost. We test a range of models in small-scale MPI simulations from simple diffusion models to realistic biological models and find that multi-dimensional geometry partitioning is an important consideration for optimum performance. We demonstrate performance gains of 1-3 orders of magnitude in the parallel implementation, with peak performance strongly dependent on model specification. PMID:27497550
Hepburn, I.; Chen, W.; De Schutter, E.
2016-08-01
Spatial stochastic molecular simulations in biology are limited by the intense computation required to track molecules in space either in a discrete time or discrete space framework, which has led to the development of parallel methods that can take advantage of the power of modern supercomputers in recent years. We systematically test suggested components of stochastic reaction-diffusion operator splitting in the literature and discuss their effects on accuracy. We introduce an operator splitting implementation for irregular meshes that enhances accuracy with minimal performance cost. We test a range of models in small-scale MPI simulations from simple diffusion models to realistic biological models and find that multi-dimensional geometry partitioning is an important consideration for optimum performance. We demonstrate performance gains of 1-3 orders of magnitude in the parallel implementation, with peak performance strongly dependent on model specification.
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This paper proposes an alternative approach to enhance localization accuracy of MEG and EEG focal sources. The proposed approach assumes anatomically constrained spatio-temporal dipoles, initial positions of which are estimated from local peak positions of distributed sources obtained from a pre-execution of distributed source reconstruction. The positions of the dipoles are then adjusted on the cortical surface using a novel updating scheme named cortical surface scanning. The proposed approach has many advantages over the conventional ones: (1) as the cortical surface scanning algorithm uses spatio-temporal dipoles, it is robust with respect to noise; (2) it requires no a priori information on the numbers and initial locations of the activations; (3) as the locations of dipoles are restricted only on a tessellated cortical surface, it is physiologically more plausible than the conventional ECD model. To verify the proposed approach, it was applied to several realistic MEG/EEG simulations and practical experiments. From the several case studies, it is concluded that the anatomically constrained dipole adjustment (ANACONDA) approach will be a very promising technique to enhance accuracy of focal source localization which is essential in many clinical and neurological applications of MEG and EEG
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Lei Zhang
2015-01-01
Full Text Available Background: Food and Drug Administration announcements have highlighted the standard rate of mesh-related complications. We aimed to report the short-term results and complications of tension-free polypropylene mesh (PROSIMA™ surgical repair of pelvic organ prolapse (POP using the standard category (C, timing (T, and site (S classification system. Methods: A prospective cohort study of 48 patients who underwent PROSIMA™ mesh kit-related surgical repairs were followed for two years at Peking Union Medical College Hospital. Recurrence was defined as symptomatic POP quantification (POP-Q Stage II or higher (leading edge ≥ −1 cm. The Patient Global Impression of Change Questionnaire, the Chinese version of the Pelvic Floor Impact Questionnaire short-form-7 and POP/Urinary Incontinence Sexual Questionnaire short-form-12 were used to evaluate the self-perception and sexual function of each patient. Mesh-related complications conformed to the International Urogynecological Association/International Continence Society joint terminology. The paired-sample t-test, one-way analysis of variance, Fisher′s exact test, Kaplan-Meier survival analysis and log-rank test were used to analyze data. Results: All patients were followed up for ≥12 months; 30 (62.5% patients completed the 24 months study. We observed a 93.8% (45/48 positive anatomical outcome rate at 12 months and 90.0% (27/30 at 24 months. Recurrence most frequently involved the anterior compartment (P < 0.05. Pelvic symptoms improved significantly from baseline (P < 0.05, although the patients′ impressions of change and sexual function were not satisfying. Vaginal complication was the main complication observed (35.4%, 17/48. The survival analysis did not identify any relationship between vaginal complication and anatomical recurrent prolapse (POP-Q ≥ Stage II (P = 0.653. Conclusions: Tension-free polypropylene mesh (PROSIMA™ -related surgical repair of POP has better short
Institute of Scientific and Technical Information of China (English)
Lei Zhang; Lan Zhu; Juan Chen; Tao Xu; Jing-He Lang
2015-01-01
Background:Food and Drug Administration announcements have highlighted the standard rate of mesh-related complications.We aimed to report the short-term results and complications of tension-free polypropylene mesh (PROSIMATM) surgical repair of pelvic organ prolapse (POP) using the standard category (C),timing (T),and site (S) classification system.Methods:A prospective cohort study of 48 patients who underwent PROSIMATM mesh kit-related surgical repairs were followed for two years at Peking Union Medical College Hospital.Recurrence was defined as symptomatic POP quantification (POP-Q) Stage Ⅱ or higher (leading edge ≥-1 cm).The Patient Global Impression of Change Questionnaire,the Chinese version of the Pelvic Floor Impact Questionnaire short-form-7 and POP/Urinary Incontinence Sexual Questionnaire short-form-12 were used to evaluate the self-perception and sexual function of each patient.Mesh-related complications conformed to the International Urogynecological Association/International Continence Society joint terminology.The paired-sample t-test,one-way analysis of variance,Fisher's exact test,Kaplan-Meier survival analysis and log-rank test were used to analyze data.Results:All patients were followed up for≥1 2 months; 30 (62.5％) patients completed the 24 months study.We observed a 93.8％ (45/48) positive anatomical outcome rate at 12 months and 90.0％ (27/30) at 24 months.Recurrence most frequently involved the anterior compartment (P ＜ 0.05).Pelvic symptoms improved significantly from baseline (P ＜ 0.05),although the patients' impressions of change and sexual function were not satisfying.Vaginal complication was the main complication observed (35.4％,17/48).The survival analysis did not identify any relationship between vaginal complication and anatomical recurrent prolapse (POP-Q ≥ Stage Ⅱ) (P =0.653).Conclusions:Tension-free polypropylene mesh (PROSIMATM)-related surgical repair of POP has better short-term anatomical outcomes at the
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The aortic valve exhibits complex three-dimensional (3D) anatomy and heterogeneity essential for the long-term efficient biomechanical function. These are, however, challenging to mimic in de novo engineered living tissue valve strategies. We present a novel simultaneous 3D printing/photocrosslinking technique for rapidly engineering complex, heterogeneous aortic valve scaffolds. Native anatomic and axisymmetric aortic valve geometries (root wall and tri-leaflets) with 12–22 mm inner diameters (ID) were 3D printed with poly-ethylene glycol-diacrylate (PEG-DA) hydrogels (700 or 8000 MW) supplemented with alginate. 3D printing geometric accuracy was quantified and compared using Micro-CT. Porcine aortic valve interstitial cells (PAVIC) seeded scaffolds were cultured for up to 21 days. Results showed that blended PEG-DA scaffolds could achieve over tenfold range in elastic modulus (5.3±0.9 to 74.6±1.5 kPa). 3D printing times for valve conduits with mechanically contrasting hydrogels were optimized to 14 to 45 min, increasing linearly with conduit diameter. Larger printed valves had greater shape fidelity (93.3±2.6, 85.1±2.0 and 73.3±5.2% for 22, 17 and 12 mm ID porcine valves; 89.1±4.0, 84.1±5.6 and 66.6±5.2% for simplified valves). PAVIC seeded scaffolds maintained near 100% viability over 21 days. These results demonstrate that 3D hydrogel printing with controlled photocrosslinking can rapidly fabricate anatomical heterogeneous valve conduits that support cell engraftment. (paper)
ACCURATE BENDING STRENGTH ANALYSIS OF ASYMMETRIC GEARS USING THE NOVEL ES-PIM WITH TRIANGULAR MESH
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G. Y. Zhang
2011-12-01
Full Text Available This paper extends the edge-based smoothed point interpolation method (ES-PIM to bending strength analysis of asymmetric gears with complex outlines. Five sets of asymmetric gears with pressure angles of 20°/20°, 25°/20°, 30°/20°, 35°/20° and 40°/20° were generated by a specially designed rack cutter. Four key factors, e.g. accuracy, convergence, the convergence rate and the computational efficiency of the present ES-PIM were checked in great detail on these five models, and the distributions of bending stresses at the fillet of the drive side were carefully investigated. The finite element method (FEM was also used to calculate the abovementioned factors to stress the advantages of ES-PIM. The numerical results indicate that ES-PIM can provide more efficient and accurate solutions in the stress field than the FEM, and is very suitable for stress analysis of complicated asymmetric gears.
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There is a need for accurate surface area measurement of internal anatomical structures in order to define light dosimetry in adjunctive intraoperative photodynamic therapy (AIOPDT). The authors investigated whether computer-assisted triangulation of serial sections generated by computed tomography (CT) scanning can give an accurate assessment of the surface area of the walls of the true pelvis after anterior resection and before colorectal anastomosis. They show that the technique of paper density tessellation is an acceptable method of measuring the surface areas of phantom objects, with a maximum error of 0.5%, and is used as the gold standard. Computer-assisted triangulation of CT images of standard geometric objects and accurately-constructed pelvic phantoms gives a surface area assessment with a maximum error of 2.5% compared with the gold standard. The CT images of 20 patients' pelves have been analysed by computer-assisted triangulation and this shows the surface area of the walls varies from 143 cm2 to 392 cm2. (Author)
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Bache, Steven T.; Juang, Titania; Belley, Matthew D. [Duke University Medical Physics Graduate Program, Durham, North Carolina 27705 (United States); Koontz, Bridget F.; Yoshizumi, Terry T.; Kirsch, David G.; Oldham, Mark, E-mail: mark.oldham@duke.edu [Duke University Medical Center, Durham, North Carolina 27710 (United States); Adamovics, John [Rider University, Lawrenceville, New Jersey 08648 (United States)
2015-02-15
Purpose: Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1–15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm{sup 3}) optical computed tomography (optical-CT) dose read-out. Methods: Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180
International Nuclear Information System (INIS)
Purpose: Sophisticated small animal irradiators, incorporating cone-beam-CT image-guidance, have recently been developed which enable exploration of the efficacy of advanced radiation treatments in the preclinical setting. Microstereotactic-body-radiation-therapy (microSBRT) is one technique of interest, utilizing field sizes in the range of 1–15 mm. Verification of the accuracy of microSBRT treatment delivery is challenging due to the lack of available methods to comprehensively measure dose distributions in representative phantoms with sufficiently high spatial resolution and in 3 dimensions (3D). This work introduces a potential solution in the form of anatomically accurate rodent-morphic 3D dosimeters compatible with ultrahigh resolution (0.3 mm3) optical computed tomography (optical-CT) dose read-out. Methods: Rodent-morphic dosimeters were produced by 3D-printing molds of rodent anatomy directly from contours defined on x-ray CT data sets of rats and mice, and using these molds to create tissue-equivalent radiochromic 3D dosimeters from Presage. Anatomically accurate spines were incorporated into some dosimeters, by first 3D printing the spine mold, then forming a high-Z bone equivalent spine insert. This spine insert was then set inside the tissue equivalent body mold. The high-Z spinal insert enabled representative cone-beam CT IGRT targeting. On irradiation, a linear radiochromic change in optical-density occurs in the dosimeter, which is proportional to absorbed dose, and was read out using optical-CT in high-resolution (0.5 mm isotropic voxels). Optical-CT data were converted to absolute dose in two ways: (i) using a calibration curve derived from other Presage dosimeters from the same batch, and (ii) by independent measurement of calibrated dose at a point using a novel detector comprised of a yttrium oxide based nanocrystalline scintillator, with a submillimeter active length. A microSBRT spinal treatment was delivered consisting of a 180
Zhang, Bin; Liang, Chunlei
2015-08-01
This paper presents a simple, efficient, and high-order accurate sliding-mesh interface approach to the spectral difference (SD) method. We demonstrate the approach by solving the two-dimensional compressible Navier-Stokes equations on quadrilateral grids. This approach is an extension of the straight mortar method originally designed for stationary domains [7,8]. Our sliding method creates curved dynamic mortars on sliding-mesh interfaces to couple rotating and stationary domains. On the nonconforming sliding-mesh interfaces, the related variables are first projected from cell faces to mortars to compute common fluxes, and then the common fluxes are projected back from the mortars to the cell faces to ensure conservation. To verify the spatial order of accuracy of the sliding-mesh spectral difference (SSD) method, both inviscid and viscous flow cases are tested. It is shown that the SSD method preserves the high-order accuracy of the SD method. Meanwhile, the SSD method is found to be very efficient in terms of computational cost. This novel sliding-mesh interface method is very suitable for parallel processing with domain decomposition. It can be applied to a wide range of problems, such as the hydrodynamics of marine propellers, the aerodynamics of rotorcraft, wind turbines, and oscillating wing power generators, etc.
Chang, Chau-Lyan; Venkatachari, Balaji Shankar; Cheng, Gary
2013-01-01
With the wide availability of affordable multiple-core parallel supercomputers, next generation numerical simulations of flow physics are being focused on unsteady computations for problems involving multiple time scales and multiple physics. These simulations require higher solution accuracy than most algorithms and computational fluid dynamics codes currently available. This paper focuses on the developmental effort for high-fidelity multi-dimensional, unstructured-mesh flow solvers using the space-time conservation element, solution element (CESE) framework. Two approaches have been investigated in this research in order to provide high-accuracy, cross-cutting numerical simulations for a variety of flow regimes: 1) time-accurate local time stepping and 2) highorder CESE method. The first approach utilizes consistent numerical formulations in the space-time flux integration to preserve temporal conservation across the cells with different marching time steps. Such approach relieves the stringent time step constraint associated with the smallest time step in the computational domain while preserving temporal accuracy for all the cells. For flows involving multiple scales, both numerical accuracy and efficiency can be significantly enhanced. The second approach extends the current CESE solver to higher-order accuracy. Unlike other existing explicit high-order methods for unstructured meshes, the CESE framework maintains a CFL condition of one for arbitrarily high-order formulations while retaining the same compact stencil as its second-order counterpart. For large-scale unsteady computations, this feature substantially enhances numerical efficiency. Numerical formulations and validations using benchmark problems are discussed in this paper along with realistic examples.
International Nuclear Information System (INIS)
The clinical differentiation between typical idiopathic Parkinson's disease (IPD) and atypical parkinsonian disorders such as multiple system atrophy (MSA) is complicated by the presence of signs and symptoms common to both forms. The goal of this study was to re-evaluate the contribution of brain perfusion single-photon emission tomography (SPET) with anatomical standardisation and automated analysis in the differentiation of IPD and MSA. This was achieved by discriminant analysis in comparison with a large set of age- and gender-matched healthy volunteers. Technetium-99m ethyl cysteinate dimer SPET was performed on 140 subjects: 81 IPD patients (age 62.6±10.2 years; disease duration 11.0±6.4 years; 50 males/31 females), 15 MSA patients (61.5±9.2 years; disease duration 3.0±2.2 years; 9 males/6 females) and 44 age- and gender-matched healthy volunteers (age 59.2±11.9 years; 27 males/17 females). Patients were matched for severity (Hoehn and Yahr stage). Automated predefined volume of interest (VOI) analysis was carried out after anatomical standardisation. Stepwise discriminant analysis with cross-validation using the leave-one-out method was used to determine the subgroup of variables giving the highest accuracy for this differential diagnosis. Between MSA and IPD, the only regions with highly significant differences in uptake after Bonferroni correction were the putamen VOIs. Comparing MSA versus normals and IPD, with putamen VOI values as discriminating variables, cross-validated performance showed correct classification of MSA patients with a sensitivity of 73.3%, a specificity of 84% and an accuracy of 83.6%. Additional input from the right caudate head and the left prefrontal and left mesial temporal cortex allowed 100% discrimination even after cross-validation. Discrimination between the IPD group alone and healthy volunteers was accurate in 94% of the cases after cross-validation, with a sensitivity of 91.4% and a specificity of 100%. The three
Dumbser, Michael; Loubère, Raphaël
2016-08-01
In this paper we propose a simple, robust and accurate nonlinear a posteriori stabilization of the Discontinuous Galerkin (DG) finite element method for the solution of nonlinear hyperbolic PDE systems on unstructured triangular and tetrahedral meshes in two and three space dimensions. This novel a posteriori limiter, which has been recently proposed for the simple Cartesian grid case in [62], is able to resolve discontinuities at a sub-grid scale and is substantially extended here to general unstructured simplex meshes in 2D and 3D. It can be summarized as follows: At the beginning of each time step, an approximation of the local minimum and maximum of the discrete solution is computed for each cell, taking into account also the vertex neighbors of an element. Then, an unlimited discontinuous Galerkin scheme of approximation degree N is run for one time step to produce a so-called candidate solution. Subsequently, an a posteriori detection step checks the unlimited candidate solution at time t n + 1 for positivity, absence of floating point errors and whether the discrete solution has remained within or at least very close to the bounds given by the local minimum and maximum computed in the first step. Elements that do not satisfy all the previously mentioned detection criteria are flagged as troubled cells. For these troubled cells, the candidate solution is discarded as inappropriate and consequently needs to be recomputed. Within these troubled cells the old discrete solution at the previous time tn is scattered onto small sub-cells (Ns = 2 N + 1 sub-cells per element edge), in order to obtain a set of sub-cell averages at time tn. Then, a more robust second order TVD finite volume scheme is applied to update the sub-cell averages within the troubled DG cells from time tn to time t n + 1. The new sub-grid data at time t n + 1 are finally gathered back into a valid cell-centered DG polynomial of degree N by using a classical conservative and higher order
Augustin, C. M.; Swart, P. K.; Broad, K.
2014-12-01
Geologic carbon capture and storage (CCS) is a feasible solution to the international greenhouse gas (GHG) emissions problem and it has recently been called a "vital" mitigation tool by the International Energy Agency. However, there exists uncertainty concerning the terminal fate of stored carbon dioxide (CO2.) In this regard, reliable monitoring, verification and accounting (MVA) technologies are essential for making CCS publicly acceptable. Chiefly, MVA addresses safety and environmental concerns by providing a warning system to prevent or alleviate CO2 leakages. A secondary purpose of MVA technologies is to prove compliance with CO2 reduction standards through inventory verification. A key MVA tool for tracking CO2 leakages is surface (atmospheric) monitoring. Demonstrating its value, industry actors feel an impetus to invest in surface monitoring as a low-risk, high-value technology to mitigate liability in cases of potential leakages. Despite how necessary this tool is, to date, all surface monitoring mesh designs and best practices have been proposed locally, without discussion of standardization or optimization on a regional, national or international level. We identify the fundamental problem of surface monitoring mesh design as locating the monitoring sites to record CO2 levels over the designated geographic area at lowest cost with maximum impact. We approach this problem from both an operations research (OR) perspective and atmospheric dispersion perspective. From an OR perspective, we approach mesh design using multiobjective optimization models - we specify the relative placement of candidate sites, observation time interval, and optimality criteria. In the second approach, we model CO2 leakage scenarios to test the effectiveness of proposed mesh design from the first approach. We use atmospheric dispersion modeling softwares AERMOD and SCREEN3 - both tools developed by the United States Environmental Protection Agency and codified into law - for
Scandalously Parallelizable Mesh Generation
Bortz, David
2011-01-01
We propose a novel approach which employs random sampling to generate an accurate non-uniform mesh for numerically solving Partial Differential Equation Boundary Value Problems (PDE-BVP's). From a uniform probability distribution U over a 1D domain, we sample M discretizations of size N where M>>N. The statistical moments of the solutions to a given BVP on each of the M ultra-sparse meshes provide insight into identifying highly accurate non-uniform meshes. Essentially, we use the pointwise mean and variance of the coarse-grid solutions to construct a mapping Q(x) from uniformly to non-uniformly spaced mesh-points. The error convergence properties of the approximate solution to the PDE-BVP on the non-uniform mesh are superior to a uniform mesh for a certain class of BVP's. In particular, the method works well for BVP's with locally non-smooth solutions. We present a framework for studying the sampled sparse-mesh solutions and provide numerical evidence for the utility of this approach as applied to a set of e...
On Optimal Bilinear Quadrilateral Meshes
Energy Technology Data Exchange (ETDEWEB)
D' Azevedo, E.
1998-10-26
The novelty of this work is in presenting interesting error properties of two types of asymptotically optimal quadrilateral meshes for bilinear approximation. The first type of mesh has an error equidistributing property where the maximum interpolation error is asymptotically the same over all elements. The second type has faster than expected super-convergence property for certain saddle-shaped data functions. The super-convergent mesh may be an order of magnitude more accurate than the error equidistributing mesh. Both types of mesh are generated by a coordinate transformation of a regular mesh of squares. The coordinate transformation is derived by interpreting the Hessian matrix of a data function as a metric tensor. The insights in this work may have application in mesh design near known corner or point singularities.
On Optimal Bilinear Quadrilateral Meshes
Energy Technology Data Exchange (ETDEWEB)
D' Azevedo, E
2000-03-17
The novelty of this work is in presenting interesting error properties of two types of asymptotically ''optimal'' quadrilateral meshes for bilinear approximation. The first type of mesh has an error equidistributing property where the maximum interpolation error is asymptotically the same over all elements. The second type has faster than expected ''super-convergence'' property for certain saddle-shaped data functions. The ''superconvergent'' mesh may be an order of magnitude more accurate than the error equidistributing mesh. Both types of mesh are generated by a coordinate transformation of a regular mesh of squares. The coordinate transformation is derived by interpreting the Hessian matrix of a data function as a metric tensor. The insights in this work may have application in mesh design near corner or point singularities.
International Nuclear Information System (INIS)
Finite element (FE) methods are widely used in electrical impedance tomography (EIT) to enable rapid image reconstruction of different tissues based on their electrical conductivity. For EIT of brain function, anatomically-accurate (head-shaped) FE meshes have been shown to improve the quality of the reconstructed images. Unfortunately, given the lack of a computational protocol to generate patient-specific meshes suitable for EIT, production of such meshes is currently ad hoc and therefore very time consuming. Here we describe a robust protocol for rapid generation of patient-specific FE meshes from MRI or CT scan data. Most of the mesh generation process is automated and uses freely available user-friendly software. Other necessary custom scripts are provided as supplementary online data and are fully documented. The patient scan data is segmented into four surfaces: brain, cerebrospinal fluid, skull and scalp. The segmented surfaces are then triangulated and used to generate a global mesh of tetrahedral elements. The resulting meshes exhibit high quality when tested with different criteria and were validated in computational simulations. The proposed protocol provides a rapid and practicable method for generation of patient-specific FE meshes of the human head that are suitable for EIT. This method could eventually be extended to other body regions and might confer benefits with other imaging techniques such as optical tomography or EEG inverse source imaging. (paper)
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
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.
A Lightweight Model for Gear Mesh Dynamics Incorporating Variable Mesh Stiffness
Directory of Open Access Journals (Sweden)
Fokas Nikolaos
2015-01-01
Full Text Available Variable stiffness of the gear tooth mesh for a pair of spur gears is computed using an accurate lightweight mathematical formulation. This is used to simulate gear dynamic behavior. Gear eigenfrequencies are calculated for the SDOF system and correlated with gear physical properties and the effect of stiffness variation during a mesh cycle is studied.
Applications of automatic mesh generation and adaptive methods in computational medicine
Energy Technology Data Exchange (ETDEWEB)
Schmidt, J.A.; Macleod, R.S. [Univ. of Utah, Salt Lake City, UT (United States); Johnson, C.R.; Eason, J.C. [Duke Univ., Durham, NC (United States)
1995-12-31
Important problems in Computational Medicine exist that can benefit from the implementation of adaptive mesh refinement techniques. Biological systems are so inherently complex that only efficient models running on state of the art hardware can begin to simulate reality. To tackle the complex geometries associated with medical applications we present a general purpose mesh generation scheme based upon the Delaunay tessellation algorithm and an iterative point generator. In addition, automatic, two- and three-dimensional adaptive mesh refinement methods are presented that are derived from local and global estimates of the finite element error. Mesh generation and adaptive refinement techniques are utilized to obtain accurate approximations of bioelectric fields within anatomically correct models of the heart and human thorax. Specifically, we explore the simulation of cardiac defibrillation and the general forward and inverse problems in electrocardiography (ECG). Comparisons between uniform and adaptive refinement techniques are made to highlight the computational efficiency and accuracy of adaptive methods in the solution of field problems in computational medicine.
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.
O'Hara, Ryan P.; Chand, Arpita; Vidiyala, Sowmya; Arechavala, Stacie M.; Mitsouras, Dimitrios; Rudin, Stephen; Ionita, Ciprian N.
2016-03-01
Complex vascular anatomies can cause the failure of image-guided endovascular procedures. 3D printed patient-specific vascular phantoms provide clinicians and medical device companies the ability to preemptively plan surgical treatments, test the likelihood of device success, and determine potential operative setbacks. This research aims to present advanced mesh manipulation techniques of stereolithographic (STL) files segmented from medical imaging and post-print surface optimization to match physiological vascular flow resistance. For phantom design, we developed three mesh manipulation techniques. The first method allows outlet 3D mesh manipulations to merge superfluous vessels into a single junction, decreasing the number of flow outlets and making it feasible to include smaller vessels. Next we introduced Boolean operations to eliminate the need to manually merge mesh layers and eliminate errors of mesh self-intersections that previously occurred. Finally we optimize support addition to preserve the patient anatomical geometry. For post-print surface optimization, we investigated various solutions and methods to remove support material and smooth the inner vessel surface. Solutions of chloroform, alcohol and sodium hydroxide were used to process various phantoms and hydraulic resistance was measured and compared with values reported in literature. The newly mesh manipulation methods decrease the phantom design time by 30 - 80% and allow for rapid development of accurate vascular models. We have created 3D printed vascular models with vessel diameters less than 0.5 mm. The methods presented in this work could lead to shorter design time for patient specific phantoms and better physiological simulations.
Liu, Rong
2009-01-01
Polygonal meshes are ubiquitous in geometric modeling. They are widely used in many applications, such as computer games, computer-aided design, animation, and visualization. One of the important problems in mesh processing and analysis is segmentation, where the goal is to partition a mesh into segments to suit the particular application at hand. In this thesis we study structural-level mesh segmentation, which seeks to decompose a given 3D shape into parts according to human intuition. We t...
SUPERFISH accuracy dependence on mesh size
Merson, J. L.; Boicourt, G. P.
1989-02-01
The RF cavity code SUPERFISH is extensively used for the design of drift-tube linac (DTL), radio-frequency quadrupole (RFQ), and coupled-cavity linac (CCL) structures. It has been known for some time that considerably finer meshes are required near the nose of a drift tube to ensure accurate calculation of the resonant frequency and related secondary quantities. This paper discusses the results of numerical experiments designed to provide rules to set proper mesh sizes for DTL, RFQ, and CCL problems. During this work, SUPERFISH problems involving more than 100,000 mesh points were solved.
Anatomic Total Shoulder System
Full Text Available GLOBAL AP ANATOMIC TOTAL SHOULDER SYSTEM METHODIST HOSPITAL PHILADELPHIA, PA April 17, 2008 00:00:10 ANNOUNCER: ... you'll be able to watch a live global AP anatomic total shoulder surgery from Methodist Hospital ...
Namiot, Dmitry
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...
Grid adaptation using chimera composite overlapping meshes
Kao, Kai-Hsiung; Liou, Meng-Sing; Chow, Chuen-Yen
1994-01-01
The objective of this paper is to perform grid adaptation using composite overlapping meshes in regions of large gradient to accurately capture the salient features during computation. The chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using trilinear interpolation. Application to the Euler equations for shock reflections and to shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well-resolved.
Grid adaption using Chimera composite overlapping meshes
Kao, Kai-Hsiung; Liou, Meng-Sing; Chow, Chuen-Yen
1993-01-01
The objective of this paper is to perform grid adaptation using composite over-lapping meshes in regions of large gradient to capture the salient features accurately during computation. The Chimera grid scheme, a multiple overset mesh technique, is used in combination with a Navier-Stokes solver. The numerical solution is first converged to a steady state based on an initial coarse mesh. Solution-adaptive enhancement is then performed by using a secondary fine grid system which oversets on top of the base grid in the high-gradient region, but without requiring the mesh boundaries to join in any special way. Communications through boundary interfaces between those separated grids are carried out using tri-linear interpolation. Applications to the Euler equations for shock reflections and to a shock wave/boundary layer interaction problem are tested. With the present method, the salient features are well resolved.
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...
Pertel, Michael J.
1992-01-01
A table of useful summation formulae are derived, together with a Mathematica package for producing them. The distance distribution in mesh routing networks is derived. The mean and variance of the distance distribution are computed. A program for computing the distance distribution of any mesh is presented.
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.
Urogynecologic Surgical Mesh Implants
... be used for urogynecologic procedures, including repair of pelvic organ prolapse (POP) and stress urinary incontinence (SUI). It is ... associated with surgical mesh for transvaginal repair of pelvic organ prolapse 513(e) Proposed Order for Reclassification of Surgical ...
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.
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,
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
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.
3D harmonic phase tracking with anatomical regularization.
Zhou, Yitian; Bernard, Olivier; Saloux, Eric; Manrique, Alain; Allain, Pascal; Makram-Ebeid, Sherif; De Craene, Mathieu
2015-12-01
This paper presents a novel algorithm that extends HARP to handle 3D tagged MRI images. HARP results were regularized by an original regularization framework defined in an anatomical space of coordinates. In the meantime, myocardium incompressibility was integrated in order to correct the radial strain which is reported to be more challenging to recover. Both the tracking and regularization of LV displacements were done on a volumetric mesh to be computationally efficient. Also, a window-weighted regression method was extended to cardiac motion tracking which helps maintain a low complexity even at finer scales. On healthy volunteers, the tracking accuracy was found to be as accurate as the best candidates of a recent benchmark. Strain accuracy was evaluated on synthetic data, showing low bias and strain errors under 5% (excluding outliers) for longitudinal and circumferential strains, while the second and third quartiles of the radial strain errors are in the (-5%,5%) range. In clinical data, strain dispersion was shown to correlate with the extent of transmural fibrosis. Also, reduced deformation values were found inside infarcted segments. PMID:26363844
Algebraic mesh quality metrics
Energy Technology Data Exchange (ETDEWEB)
KNUPP,PATRICK
2000-04-24
Quality metrics for structured and unstructured mesh generation are placed within an algebraic framework to form a mathematical theory of mesh quality metrics. The theory, based on the Jacobian and related matrices, provides a means of constructing, classifying, and evaluating mesh quality metrics. The Jacobian matrix is factored into geometrically meaningful parts. A nodally-invariant Jacobian matrix can be defined for simplicial elements using a weight matrix derived from the Jacobian matrix of an ideal reference element. Scale and orientation-invariant algebraic mesh quality metrics are defined. the singular value decomposition is used to study relationships between metrics. Equivalence of the element condition number and mean ratio metrics is proved. Condition number is shown to measure the distance of an element to the set of degenerate elements. Algebraic measures for skew, length ratio, shape, volume, and orientation are defined abstractly, with specific examples given. Combined metrics for shape and volume, shape-volume-orientation are algebraically defined and examples of such metrics are given. Algebraic mesh quality metrics are extended to non-simplical elements. A series of numerical tests verify the theoretical properties of the metrics defined.
Numerical modeling of seismic waves using frequency-adaptive meshes
Hu, Jinyin; Jia, Xiaofeng
2016-08-01
An improved modeling algorithm using frequency-adaptive meshes is applied to meet the computational requirements of all seismic frequency components. It automatically adopts coarse meshes for low-frequency computations and fine meshes for high-frequency computations. The grid intervals are adaptively calculated based on a smooth inversely proportional function of grid size with respect to the frequency. In regular grid-based methods, the uniform mesh or non-uniform mesh is used for frequency-domain wave propagators and it is fixed for all frequencies. A too coarse mesh results in inaccurate high-frequency wavefields and unacceptable numerical dispersion; on the other hand, an overly fine mesh may cause storage and computational overburdens as well as invalid propagation angles of low-frequency wavefields. Experiments on the Padé generalized screen propagator indicate that the Adaptive mesh effectively solves these drawbacks of regular fixed-mesh methods, thus accurately computing the wavefield and its propagation angle in a wide frequency band. Several synthetic examples also demonstrate its feasibility for seismic modeling and migration.
Anatomic Total Shoulder System
Full Text Available GLOBAL AP ANATOMIC TOTAL SHOULDER SYSTEM METHODIST HOSPITAL PHILADELPHIA, PA April 17, 2008 00:00:10 ANNOUNCER: DePuy Orthopedics is continually advancing the standard of orthopedic patient care. In a few ...
Anatomic Total Shoulder System
Full Text Available ... Orthopedics is continually advancing the standard of orthopedic patient care. In a few moments, you'll be ... and version variability which allows adaptability to a patient's unique anatomical makeup. Dr. Gerald R. Williams, Jr., ...
Anatomic Total Shoulder System
Full Text Available ... to a patient's unique anatomical makeup. Dr. Gerald R. Williams, Jr., a shoulder specialist from the Rothman ... That might help. Could you raise the O.R. table, please? 00:28:35 WOMAN: Can you ...
Anatomic Total Shoulder System
Full Text Available GLOBAL AP ANATOMIC TOTAL SHOULDER SYSTEM METHODIST HOSPITAL PHILADELPHIA, PA April 17, 2008 00:00:10 ANNOUNCER: DePuy Orthopedics is continually advancing the standard of orthopedic patient ...
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.
Mizoguchi, Tomohiro; Kanai, Satoshi
Along with the rapid growth of industrial X-ray CT scanning systems, it is now possible to non-destructively acquire the entire meshes of assemblies consisting of a set of parts. For the advanced inspections of the assemblies, such as estimation of their assembling errors or examinations of their behaviors in the motions, based on their CT scanned meshes, it is necessary to accurately decompose the mesh and to extract a set of partial meshes each of which correspond to a part. Moreover it is required to create models which can be used for the real-product based simulations. In this paper, we focus on CT scanned meshes of gear assemblies as examples and propose beneficial methods for establishing such advance inspections of the assemblies. We first propose a method that accurately decomposes the mesh into partial meshes each of which corresponds to a gear based on periodicity recognitions. The key idea is first to accurately recognize the periodicity of each gear and then to extract the partial meshes as sets of topologically connected mesh elements where periodicities are valid. Our method can robustly and accurately recognize periodicities from noisy scanned meshes. In contrast to previous methods, our method can deal with single-material CT scanned meshes and can estimate the correct boundaries of neighboring parts with no previous knowledge. Moreover it can efficiently extract the partial meshes from large scanned meshes containing about one million triangles in a few minutes. We also propose a method for creating simulation models which can be used for a gear teeth contact evaluation using extracted partial meshes and their periodicities. Such an evaluation of teeth contacts is one of the most important functions in kinematic simulations of gear assemblies for predicting the power transmission efficiency, noise and vibration. We demonstrate the effectiveness of our method on a variety of artificial and CT scanned meshes.
Badal, Andreu; Kyprianou, Iacovos; Badano, Aldo; Sempau, Josep; Myers, Kyle J.
2007-03-01
X-ray imaging system optimization increases the benefit-to-cost ratio by reducing the radiation dose to the patient while maximizing image quality. We present a new simulation tool for the generation of realistic medical x-ray images for assessment and optimization of complete imaging systems. The Monte Carlo code simulates radiation transport physics using the subroutine package PENELOPE, which accurately simulates the transport of electrons and photons within the typical medical imaging energy range. The new code implements a novel object-oriented geometry package that allows simulations with homogeneous objects of arbitrary shapes described by triangle meshes. The flexibility of this code, which uses the industry standard PLY input-file format, allows the use of detailed anatomical models developed using computer-aided design tools applied to segmented CT and MRI data. The use of triangle meshes highly simplifies the ray-tracing algorithm without reducing the generality of the code, since most surface models can be tessellated into triangles while retaining their geometric details. Our algorithm incorporates an octree spatial data structure to sort the triangles and accelerate the simulation, reaching execution speeds comparable to the original quadric geometry model of PENELOPE. Coronary angiograms were simulated using a tessellated version of the NURBS-based Cardiac-Torso (NCAT) phantom. The phantom models 330 objects, comprised in total of 5 million triangles. The dose received by each organ and the contribution of the different scattering processes to the final image were studied in detail.
Difference schemes on non-uniform mesh and their application
Institute of Scientific and Technical Information of China (English)
MA Yanwen; GAO Hui; FU Dexun; LI Xinliang
2004-01-01
High order accurate schemes are needed to simulate the multi-scale complex flow fields to get fine structures in simulation of the complex flows with large gradient of fluid parameters near the wall, and schemes on non-uniform mesh are desirable for many CFD (computational fluid dynamics) workers. The construction methods of difference approximations and several difference approximations on non-uniform mesh are presented. The accuracy of the methods and the influence of stretch ratio of the neighbor mesh increment on accuracy are discussed. Some comments on these methods are given, and comparison of the accuracy of the results obtained by schemes based on both non-uniform mesh and coordinate transformation is made, and some numerical examples with non-uniform mesh are presented.
Personalized identification of abdominal wall hernia meshes on computed tomography.
Pham, Tuan D; Le, Dinh T P; Xu, Jinwei; Nguyen, Duc T; Martindale, Robert G; Deveney, Clifford W
2014-01-01
An abdominal wall hernia is a protrusion of the intestine through an opening or area of weakness in the abdominal wall. Correct pre-operative identification of abdominal wall hernia meshes could help surgeons adjust the surgical plan to meet the expected difficulty and morbidity of operating through or removing the previous mesh. First, we present herein for the first time the application of image analysis for automated identification of hernia meshes. Second, we discuss the novel development of a new entropy-based image texture feature using geostatistics and indicator kriging. Third, we seek to enhance the hernia mesh identification by combining the new texture feature with the gray-level co-occurrence matrix feature of the image. The two features can characterize complementary information of anatomic details of the abdominal hernia wall and its mesh on computed tomography. Experimental results have demonstrated the effectiveness of the proposed study. The new computational tool has potential for personalized mesh identification which can assist surgeons in the diagnosis and repair of complex abdominal wall hernias. PMID:24184112
Volume-conserving mesh smoothing for front-tracking methods
International Nuclear Information System (INIS)
Among the various direct numerical simulation (DNS) methods dedicated to multiphase flow, the front-tracking methods that use a Lagrangian mesh to describe explicitly the interfaces are generally considered as a very accurate and complex method. In this family of methods, while a fine Lagrangian mesh is desirable for a better representation of the interfacial area, the surface forces and the bubble or droplet volume, one cannot arbitrarily choose the Lagrangian mesh size. Indeed, the Lagrangian mesh displacement algorithm is unstable if the number of Lagrangian degrees of freedom does not match the number of involved Eulerian velocity points. As a consequence, in traditional front-tracking implementations, an accurate description of the interfaces is expensive in terms of Eulerian mesh cells. We demonstrate that a front-tracking interface smoothing (FTIS) method can reduce the constraints on the mesh sizes. It consists in damping the highest spatial frequency components of the Lagrangian mesh to compensate for the lack of Eulerian velocity points. The test case of fundamental proper frequency of a bubble proves the validity of the FTIS method. An example of a 3D-bubble rising shows the interest and the potential applications of the FTIS method. (authors)
Seismic Wave Simulation for Complex Rheologies on Unstructured Meshes
de la Puente, Josep
2008-01-01
The possibility of using accurate numerical methods to simulate seismic wavefields on unstructured meshes for complex rheologies is explored. In particular, the Discontinuous Galerkin (DG) finite element method for seismic wave propagation is extended to the rheological types of viscoelasticity, anisotropy and poroelasticity. First is presented the DG method for the elastic isotropic case on tetrahedral unstructured meshes. Then an extension to viscoelastic wave propagation based upon a Gener...
Mesh generation technology for nuclear reactor simulation; barriers and opportunities
International Nuclear Information System (INIS)
Mesh generation in support of nuclear reactor simulation has much in common with the requirements of other application areas, such as computational fluid dynamics (CFD). Indeed, fluid dynamics analysis of the coolant behavior inside the reactor core is an internal flow problem that requires the resolution of spatial and temporal variations in the flow caused by complex component configurations, fluids/structure interaction, turbulence, and thermal heating of the coolant. Typical concerns of meshing complex geometries; the use of hexahedral vs. tetrahedral elements, element geometric quality, mesh smoothness, use of anisotropic elements in the thermal boundary layer, etc., are all considerations important to the reactor meshing problem. Reactor meshing begins to become more specialized as the need to employ reactor simulation as a predictive design and safety analysis capability grows in importance. First, a predictive capability will require more precise physical models to be included, and these models will need to be supported by a computational science framework that will allow them to be accurately approximated both spatially and temporally during the reactor core analysis. Both the multiphysical nature of the composite reactor model and details of the physics algorithms themselves will place new requirements on the meshing process needed to support multidimensional reactor simulation. This article discusses the current state of meshing technology applied to reactor simulation and examines a set of issues that are important in the generation of high-quality reactor meshes today and in the future
Wang, Xinheng
2008-01-01
Wireless telemedicine using GSM and GPRS technologies can only provide low bandwidth connections, which makes it difficult to transmit images and video. Satellite or 3G wireless transmission provides greater bandwidth, but the running costs are high. Wireless networks (WLANs) appear promising, since they can supply high bandwidth at low cost. However, the WLAN technology has limitations, such as coverage. A new wireless networking technology named the wireless mesh network (WMN) overcomes some of the limitations of the WLAN. A WMN combines the characteristics of both a WLAN and ad hoc networks, thus forming an intelligent, large scale and broadband wireless network. These features are attractive for telemedicine and telecare because of the ability to provide data, voice and video communications over a large area. One successful wireless telemedicine project which uses wireless mesh technology is the Emergency Room Link (ER-LINK) in Tucson, Arizona, USA. There are three key characteristics of a WMN: self-organization, including self-management and self-healing; dynamic changes in network topology; and scalability. What we may now see is a shift from mobile communication and satellite systems for wireless telemedicine to the use of wireless networks based on mesh technology, since the latter are very attractive in terms of cost, reliability and speed. PMID:19047448
Anatomic Total Shoulder System
Full Text Available ... AP ANATOMIC TOTAL SHOULDER SYSTEM METHODIST HOSPITAL PHILADELPHIA, PA April 17, 2008 00:00:10 ANNOUNCER: DePuy ... you don't make a bunch of small passes at the lesser tuberosity and make it a ...
Anatomic Total Shoulder System
Full Text Available ... Anatomic Total Shoulder surgery, which featured the latest innovation in shoulder surgery from DePuy Orthopedics. OR-Live makes it easy for you to learn more. Just click on the "Request Information" button on your webcast screen and open the door to informed medical care. 01:21: ...
Anatomic Total Shoulder System
Full Text Available ... advancing the standard of orthopedic patient care. In a few moments, you'll be able to watch a live global AP anatomic total shoulder surgery from Methodist Hospital in Philadelphia. A revolution in shoulder orthopedics, the Global AP gives ...
Anatomic Total Shoulder System
Full Text Available ... by almost ten years, is shoulders. So by definition, the average shoulder-replacement patient is almost ten ... Anatomic Total Shoulder surgery, which featured the latest innovation in shoulder surgery from DePuy Orthopedics. OR-Live ...
Identification of anatomical terminology in medical text.
Sneiderman, C. A.; Rindflesch, T. C.; Bean, C. A.
1998-01-01
We report on an experiment to use the natural language processing tools being developed in the SPECIALIST system to accurately identify terminology associated with the coronary arteries as expressed in coronary catheterization reports. The ultimate goal is to map from any anatomically-oriented medical text to online images, using the UMLS as an intermediate knowledge source. We describe some of the problems encountered when processing coronary artery terminology and report on the results of a...
Anatomically Plausible Surface Alignment and Reconstruction
DEFF Research Database (Denmark)
Paulsen, Rasmus R.; Larsen, Rasmus
2010-01-01
With the increasing clinical use of 3D surface scanners, there is a need for accurate and reliable algorithms that can produce anatomically plausible surfaces. In this paper, a combined method for surface alignment and reconstruction is proposed. It is based on an implicit surface representation...... energy that has earlier proved to be particularly well suited for human surface scans. The method has been tested on full cranial scans of ten test subjects and on several scans of the outer human ear....
Notes on the Mesh Handler and Mesh Data Conversion
International Nuclear Information System (INIS)
At the outset of the development of the thermal-hydraulic code (THC), efforts have been made to utilize the recent technology of the computational fluid dynamics. Among many of them, the unstructured mesh approach was adopted to alleviate the restriction of the grid handling system. As a natural consequence, a mesh handler (MH) has been developed to manipulate the complex mesh data from the mesh generator. The mesh generator, Gambit, was chosen at the beginning of the development of the code. But a new mesh generator, Pointwise, was introduced to get more flexible mesh generation capability. An open source code, Paraview, was chosen as a post processor, which can handle unstructured as well as structured mesh data. Overall data processing system for THC is shown in Figure-1. There are various file formats to save the mesh data in the permanent storage media. A couple of dozen of file formats are found even in the above mentioned programs. A competent mesh handler should have the capability to import or export mesh data as many as possible formats. But, in reality, there are two aspects that make it difficult to achieve the competence. The first aspect to consider is the time and efforts to program the interface code. And the second aspect, which is even more difficult one, is the fact that many mesh data file formats are proprietary information. In this paper, some experience of the development of the format conversion programs will be presented. File formats involved are Gambit neutral format, Ansys-CFX grid file format, VTK legacy file format, Nastran format and CGNS
Serial and parallel dynamic adaptation of general hybrid meshes
Kavouklis, Christos
The Navier-Stokes equations are a standard mathematical representation of viscous fluid flow. Their numerical solution in three dimensions remains a computationally intensive and challenging task, despite recent advances in computer speed and memory. A strategy to increase accuracy of Navier-Stokes simulations, while maintaining computing resources to a minimum, is local refinement of the associated computational mesh in regions of large solution gradients and coarsening in regions where the solution does not vary appreciably. In this work we consider adaptation of general hybrid meshes for Computational Fluid Dynamics (CFD) applications. Hybrid meshes are composed of four types of elements; hexahedra, prisms, pyramids and tetrahedra, and have been proven a promising technology in accurately resolving fluid flow for complex geometries. The first part of this dissertation is concerned with the design and implementation of a serial scheme for the adaptation of general three dimensional hybrid meshes. We have defined 29 refinement types, for all four kinds of elements. The core of the present adaptation scheme is an iterative algorithm that flags mesh edges for refinement, so that the adapted mesh is conformal. Of primary importance is considered the design of a suitable dynamic data structure that facilitates refinement and coarsening operations and furthermore minimizes memory requirements. A special dynamic list is defined for mesh elements, in contrast with the usual tree structures. It contains only elements of the current adaptation step and minimal information that is utilized to reconstruct parent elements when the mesh is coarsened. In the second part of this work, a new parallel dynamic mesh adaptation and load balancing algorithm for general hybrid meshes is presented. Partitioning of a hybrid mesh reduces to partitioning of the corresponding dual graph. Communication among processors is based on the faces of the interpartition boundary. The distributed
Early fetal anatomical sonography.
LENUS (Irish Health Repository)
Donnelly, Jennifer C
2012-10-01
Over the past decade, prenatal screening and diagnosis has moved from the second into the first trimester, with aneuploidy screening becoming both feasible and effective. With vast improvements in ultrasound technology, sonologists can now image the fetus in greater detail at all gestational ages. In the hands of experienced sonographers, anatomic surveys between 11 and 14 weeks can be carried out with good visualisation rates of many structures. It is important to be familiar with the normal development of the embryo and fetus, and to be aware of the major anatomical landmarks whose absence or presence may be deemed normal or abnormal depending on the gestational age. Some structural abnormalities will nearly always be detected, some will never be and some are potentially detectable depending on a number of factors.
Reference Man anatomical model
Energy Technology Data Exchange (ETDEWEB)
Cristy, M.
1994-10-01
The 70-kg Standard Man or Reference Man has been used in physiological models since at least the 1920s to represent adult males. It came into use in radiation protection in the late 1940s and was developed extensively during the 1950s and used by the International Commission on Radiological Protection (ICRP) in its Publication 2 in 1959. The current Reference Man for Purposes of Radiation Protection is a monumental book published in 1975 by the ICRP as ICRP Publication 23. It has a wealth of information useful for radiation dosimetry, including anatomical and physiological data, gross and elemental composition of the body and organs and tissues of the body. The anatomical data includes specified reference values for an adult male and an adult female. Other reference values are primarily for the adult male. The anatomical data include much data on fetuses and children, although reference values are not established. There is an ICRP task group currently working on revising selected parts of the Reference Man document.
Standardized anatomic space for abdominal fat quantification
Tong, Yubing; Udupa, Jayaram K.; Torigian, Drew A.
2014-03-01
The ability to accurately measure subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) from images is important for improved assessment and management of patients with various conditions such as obesity, diabetes mellitus, obstructive sleep apnea, cardiovascular disease, kidney disease, and degenerative disease. Although imaging and analysis methods to measure the volume of these tissue components have been developed [1, 2], in clinical practice, an estimate of the amount of fat is obtained from just one transverse abdominal CT slice typically acquired at the level of the L4-L5 vertebrae for various reasons including decreased radiation exposure and cost [3-5]. It is generally assumed that such an estimate reliably depicts the burden of fat in the body. This paper sets out to answer two questions related to this issue which have not been addressed in the literature. How does one ensure that the slices used for correlation calculation from different subjects are at the same anatomic location? At what anatomic location do the volumes of SAT and VAT correlate maximally with the corresponding single-slice area measures? To answer these questions, we propose two approaches for slice localization: linear mapping and non-linear mapping which is a novel learning based strategy for mapping slice locations to a standardized anatomic space so that same anatomic slice locations are identified in different subjects. We then study the volume-to-area correlations and determine where they become maximal. We demonstrate on 50 abdominal CT data sets that this mapping achieves significantly improved consistency of anatomic localization compared to current practice. Our results also indicate that maximum correlations are achieved at different anatomic locations for SAT and VAT which are both different from the L4-L5 junction commonly utilized.
VPN Mesh in Industrial Networking
Berndtsson, Andreas
2013-01-01
This thesis report describes the process and present the results gained while evaluating available VPN mesh solutions and equipment for integration into Industrial systems. The task was divided into several sub steps; summarize the previous work done in the VPN mesh area, evaluate the available VPN mesh solutions, verify that the interesting equipment comply with the criteria set by ABB and lastly verify that the equipment can be integrated transparently into already running systems. The resu...
Papadakis, A. P.; Georghiou, G. E.; Metaxas, A. C.
2008-12-01
A new adaptive mesh generator has been developed and used in the analysis of high-pressure gas discharges, such as avalanches and streamers, reducing computational times and computer memory needs significantly. The new adaptive mesh generator developed, uses normalized error indicators, varying from 0 to 1, to guarantee optimal mesh resolution for all carriers involved in the analysis. Furthermore, it uses h- and r-refinement techniques such as mesh jiggling, edge swapping and node addition/removal to develop an element quality improvement algorithm that improves the mesh quality significantly and a fast and accurate algorithm for interpolation between meshes. Finally, the mesh generator is applied in the characterization of the transition from a single electron to the avalanche and streamer discharges in high-voltage, high-pressure gas discharges for dc 1 mm gaps, RF 1 cm point-plane gaps and parallel-plate 40 MHz configurations, in ambient atmospheric air.
Energy Technology Data Exchange (ETDEWEB)
Papadakis, A P [Department of Electrical Engineering, Frederick University Cyprus, 7 Y Frederickou Street, Palouriotissa, Nicosia 1036 (Cyprus); Georghiou, G E [Department of Electrical and Computer Engineering, University of Cyprus, 75 Kallipoleos, PO Box 20577, 1678, Nicosia (Cyprus); Metaxas, A C [St John' s College, University of Cambridge, Cambridge, CB2 1TP (United Kingdom)], E-mail: eng.ap@frederick.ac.cy, E-mail: geg@ucy.ac.cy, E-mail: acm33@cam.ac.uk
2008-12-07
A new adaptive mesh generator has been developed and used in the analysis of high-pressure gas discharges, such as avalanches and streamers, reducing computational times and computer memory needs significantly. The new adaptive mesh generator developed, uses normalized error indicators, varying from 0 to 1, to guarantee optimal mesh resolution for all carriers involved in the analysis. Furthermore, it uses h- and r-refinement techniques such as mesh jiggling, edge swapping and node addition/removal to develop an element quality improvement algorithm that improves the mesh quality significantly and a fast and accurate algorithm for interpolation between meshes. Finally, the mesh generator is applied in the characterization of the transition from a single electron to the avalanche and streamer discharges in high-voltage, high-pressure gas discharges for dc 1 mm gaps, RF 1 cm point-plane gaps and parallel-plate 40 MHz configurations, in ambient atmospheric air.
Solving the resonating-group equation on a Lagrange mesh
Hesse, M; Baye, D
2002-01-01
The resonating-group method allows treating reactions in a fully microscopic way. The non-local resonating-group equation can be accurately solved on a Lagrange mesh involving few mesh points. This mesh technique is combined with either the R-matrix method or the Hulthen-Kohn method. The forbidden states can be eliminated by a special treatment. The accuracy of the technique of solution is illustrated on a solvable non-local potential. Phase shifts for the alpha+n and alpha+p scatterings are calculated with both variants of the resonating-group method on a Lagrange mesh and a comparison is performed between them and the equivalent generator-coordinate method.
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 ...
Mesh quality improvement for SciDAC applications
International Nuclear Information System (INIS)
Accurate and efficient numerical solution of partial differential equations requires well-formed meshes that are non-inverted, smooth, well-shaped, oriented, and size-adapted. The Mesquite mesh quality improvement toolkit is a software library that applies optimization algorithms to create well-formed meshes via node movement. Mesquite can be run standalone using drivers or called directly from an application code. Mesquite can play an essential role in the SLAC accelerator design program as a component in automatic shape optimization software and in manufacturing defect-correction studies to smoothly deform meshes in response to geometric domain deformations guided by the optimization of design parameters. Mesquite has also been applied to problems in fusion, biology, and propellant burn studies
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.
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.
h-Adaptive Mesh Generation using Electric Field Intensity Value as a Criterion (in Japanese)
Toyonaga, Kiyomi; Cingoski, Vlatko; Kaneda, Kazufumi; Yamashita, Hideo
1994-01-01
Finite mesh divisions are essential to obtain accurate solution of two dimensional electric field analysis. It requires the technical knowledge to generate a suitable fine mesh divisions. In electric field problem, analysts are usually interested in the electric field intensity and its distribution. In order to obtain electric field intensity with high-accuracy, we have developed and adaptive mesh generator using electric field intensity value as a criterion.
Anatomical imaging for radiotherapy
Energy Technology Data Exchange (ETDEWEB)
Evans, Philip M [Joint Physics Department, Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey SM2 5PT (United Kingdom)], E-mail: phil.evans@icr.ac.uk
2008-06-21
The goal of radiation therapy is to achieve maximal therapeutic benefit expressed in terms of a high probability of local control of disease with minimal side effects. Physically this often equates to the delivery of a high dose of radiation to the tumour or target region whilst maintaining an acceptably low dose to other tissues, particularly those adjacent to the target. Techniques such as intensity modulated radiotherapy (IMRT), stereotactic radiosurgery and computer planned brachytherapy provide the means to calculate the radiation dose delivery to achieve the desired dose distribution. Imaging is an essential tool in all state of the art planning and delivery techniques: (i) to enable planning of the desired treatment, (ii) to verify the treatment is delivered as planned and (iii) to follow-up treatment outcome to monitor that the treatment has had the desired effect. Clinical imaging techniques can be loosely classified into anatomic methods which measure the basic physical characteristics of tissue such as their density and biological imaging techniques which measure functional characteristics such as metabolism. In this review we consider anatomical imaging techniques. Biological imaging is considered in another article. Anatomical imaging is generally used for goals (i) and (ii) above. Computed tomography (CT) has been the mainstay of anatomical treatment planning for many years, enabling some delineation of soft tissue as well as radiation attenuation estimation for dose prediction. Magnetic resonance imaging is fast becoming widespread alongside CT, enabling superior soft-tissue visualization. Traditionally scanning for treatment planning has relied on the use of a single snapshot scan. Recent years have seen the development of techniques such as 4D CT and adaptive radiotherapy (ART). In 4D CT raw data are encoded with phase information and reconstructed to yield a set of scans detailing motion through the breathing, or cardiac, cycle. In ART a set of
Anatomical imaging for radiotherapy
International Nuclear Information System (INIS)
The goal of radiation therapy is to achieve maximal therapeutic benefit expressed in terms of a high probability of local control of disease with minimal side effects. Physically this often equates to the delivery of a high dose of radiation to the tumour or target region whilst maintaining an acceptably low dose to other tissues, particularly those adjacent to the target. Techniques such as intensity modulated radiotherapy (IMRT), stereotactic radiosurgery and computer planned brachytherapy provide the means to calculate the radiation dose delivery to achieve the desired dose distribution. Imaging is an essential tool in all state of the art planning and delivery techniques: (i) to enable planning of the desired treatment, (ii) to verify the treatment is delivered as planned and (iii) to follow-up treatment outcome to monitor that the treatment has had the desired effect. Clinical imaging techniques can be loosely classified into anatomic methods which measure the basic physical characteristics of tissue such as their density and biological imaging techniques which measure functional characteristics such as metabolism. In this review we consider anatomical imaging techniques. Biological imaging is considered in another article. Anatomical imaging is generally used for goals (i) and (ii) above. Computed tomography (CT) has been the mainstay of anatomical treatment planning for many years, enabling some delineation of soft tissue as well as radiation attenuation estimation for dose prediction. Magnetic resonance imaging is fast becoming widespread alongside CT, enabling superior soft-tissue visualization. Traditionally scanning for treatment planning has relied on the use of a single snapshot scan. Recent years have seen the development of techniques such as 4D CT and adaptive radiotherapy (ART). In 4D CT raw data are encoded with phase information and reconstructed to yield a set of scans detailing motion through the breathing, or cardiac, cycle. In ART a set of
Ye, Dexin; Lu, Ling; Joannopoulos, John D; Soljačić, Marin; Ran, Lixin
2016-03-01
A solid material possessing identical electromagnetic properties as air has yet to be found in nature. Such a medium of arbitrary shape would neither reflect nor refract light at any angle of incidence in free space. Here, we introduce nonscattering corrugated metallic wires to construct such a medium. This was accomplished by aligning the dark-state frequencies in multiple scattering channels of a single wire. Analytical solutions, full-wave simulations, and microwave measurement results on 3D printed samples show omnidirectional invisibility in any configuration. This invisible metallic mesh can improve mechanical stability, electrical conduction, and heat dissipation of a system, without disturbing the electromagnetic design. Our approach is simple, robust, and scalable to higher frequencies. PMID:26884208
A discretization of the multigroup PN radiative transfer equation on general meshes
Hermeline, F.
2016-05-01
We propose and study a finite volume method of discrete duality type for discretizing the multigroup PN approximation of radiative transfer equation on general meshes. This method is second order-accurate on a very large variety of meshes, stable under a Courant-Friedrichs-Lewy condition and it preserves naturally the diffusion asymptotic limit.
Rich: Open Source Hydrodynamic Simulation on a Moving Voronoi Mesh
Yalinewich, Almog; Sari, Re'em
2014-01-01
We present here RICH, a state of the art 2D hydrodynamic code based on Godunov's method, on an unstructured moving mesh (the acronym stands for Racah Institute Computational Hydrodynamics). This code is largely based on the code AREPO. It differs from AREPO in the interpolation and time advancement scheme as well as a novel parallelization scheme based on Voronoi tessellation. Using our code we study the pros and cons of a moving mesh (in comparison to a static mesh). We also compare its accuracy to other codes. Specifically, we show that our implementation of external sources and time advancement scheme is more accurate and robust than AREPO's, when the mesh is allowed to move. We performed a parameter study of the cell rounding mechanism (Llyod iterations) and it effects. We find that in most cases a moving mesh gives better results than a static mesh, but it is not universally true. In the case where matter moves in one way, and a sound wave is traveling in the other way (such that relative to the grid the...
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.
Transoral Surgery: An Anatomic Study
Rock, Jack P.; Tomecek, Frank J.; Ross, Lawrence
1993-01-01
The transoral approaches have become commonplace in modern neurosurgical practice for treatment of ventral midline lesions of the clivus and upper cervical spine. Although the standard technique of transoral surgery is conceptually simple, anatomic relationships are not so readily appreciated. The present study was undertaken in an effort to define more clearly the midline anatomic relationships as they pertain to the standard transoral and transpalatine operations. The anatomic relationships...
21 CFR 878.3300 - Surgical mesh.
2010-04-01
... GENERAL AND PLASTIC SURGERY DEVICES Prosthetic Devices § 878.3300 Surgical mesh. (a) Identification... acetabular and cement restrictor mesh used during orthopedic surgery. (b) Classification. Class II....
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...
Tetrahedral mesh for needle insertion
Syvertsen, Rolf Anders
2007-01-01
This is a Master’s thesis in how to make a tetrahedral mesh for use in a needle insertion simulator. It also describes how it is possible to make the simulator, and how to improve it to make it as realistic as possible. The medical simulator uses a haptic device, a haptic scene graph and a FEM for realistic soft tissue deformation and interaction. In this project a tetrahedral mesh is created from a polygon model, and then the mesh has been loaded into the HaptX haptic scene graph. The object...
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.
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
Directory of Open Access Journals (Sweden)
Shuo Liang
2015-01-01
Full Text Available Background: Although repair augmented with mesh has been proved its priority in anatomical and functional recovery after anterior compartment reconstruction, the data about posterior compartment are scarce. The aim of this study was to compare bowel functional outcome of posterior vaginal compartment repair with and without mesh in patients with pelvic organ prolapse (POP. Methods: This was a prospective, double-blind, clinical pilot study of 22 postmenopausal women with symptomatic POP (overall POP-quantification [POP-Q] Stage III-IV who underwent total pelvic floor reconstruction. Patients were grouped according to the use of mesh for posterior vaginal compartment repair: A mesh group and a nonmesh group. POP-Q stage, the pelvic floor impact questionnaire short form-7 (PFIQ-7 and anorectal manometry were evaluated before and 3 months after surgery. Anatomical success was defined as POP-Q Stage II or less. A t-test was used to compare preoperative with postoperative data in the two groups. Results: Totally, 17 (71% were available for the follow-up. POP-Q measurements improved significantly compared to baseline (P 0.05. Compared with baseline, the nonmesh group exhibited a statistically significant decrease in anal residual pressure, a significant increase in the anorectal pressure difference during bowel movement, and a reduced rate of dyssynergia defecation pattern (P < 0.05. Conclusions: Provided there is sufficient support for the anterior wall and apex of vagina with mesh, posterior compartment repair without mesh may be as effective as repair with mesh for anatomical recovery while providing better anorectal motor function.
Medical Image Processing for Fully Integrated Subject Specific Whole Brain Mesh Generation
Directory of Open Access Journals (Sweden)
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 Study on the Efficient Mesh Generation for Finite Element Analysis of Electric Machinery
Energy Technology Data Exchange (ETDEWEB)
Kim, Jin Tae [Hangul and Computer Co.,Ltd. (Korea); Chung, Tae Kyung [Chungang University (Korea); Kim, Hyeong Seok [Soonchunhyang University (Korea)
1999-04-01
To obtain more accurate result in the finite element analysis for electric machinery, it is important to have a mesh being of good quality. This paper describes a new technique of mesh generation for the finite element method. When the list of points defining the region of analysis is given, an appropriate distribution of interior points is generated first. Secondly the points are connected to form the triangles. Finally the connectivity data are used to reposition the interior points using laplacian smoothing and mesh relaxation technique. In this paper, a mesh searching technique of Lawson which modifies the start mesh is proposed in addition to the above three steps. This algorithm is simple and produces the meshes being of good quality with high speed in comparison with the existing one. (author). 16 refs., 10 figs., 2 tabs.
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. PMID:15959688
Generic Mesh Refinement On GPU
Boubekeur, Tamy; Schlick, Christophe
2005-01-01
International audience Many recent publications have shown that a large variety of computation involved in computer graphics can be moved from the CPU to the GPU, by a clever use of vertex or fragment shaders. Nonetheless there is still one kind of algorithms that is hard to translate from CPU to GPU: mesh refinement techniques. The main reason for this, is that vertex shaders available on current graphics hardware do not allow the generation of additional vertices on a mesh stored in grap...
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.
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.
INCISIONAL HERNIA - ONLAY VS SUBLAY MESH HERNIOPLAS T Y
Directory of Open Access Journals (Sweden)
Ravi Kamal Kumar
2015-04-01
Full Text Available 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 better one. METHODS : A prospective study was conducted of 37 ca ses of incisional hernia admitted in Govt. General Hospital Guntur from Jan 2012 to Dec 2013. 20 of the cases underwent open mesh repair by onlay method whereas 17 cases underwent open mesh repair by the sublay i . e . retrorectus placement of the mesh. Obser vations were made regarding time taken for both types of repairs, post - operative complications like flap necrosis, wound seroma, wound infecton, postoperative ileus etc., after discharge from the hospital the cases were followed up in the OPD upto Dec . 201 4 and any complications and recurrences were noted. OBSERVATIONS AND RESULTS: Most of the cases (75% were female and the incisional hernias were in the lower abdomen. The time taken for the surgery is more in the sublay group and the postoperative pain score is also more in the sublay group. But the wound complications like wound infection and flap necrosis were more (25 - 30% in the onlay group. Also one case (5% developed recurrence. Though the time taken for the surgery and the skill needed is more fo r the sublay group the wound complications are acceptable in the sublay group. Also there are no recurrences observed in the sublay group. But no statistically significant difference (p<0 . 7 is detected when all the post - operative complications are taken t ogether between the sublay and onlay repair techniques . CONCLUSIONS: Although it can be argued, theoretically and by the wound complication rate, in favour of
Tracking in anatomic pathology.
Pantanowitz, Liron; Mackinnon, Alexander C; Sinard, John H
2013-12-01
Bar code-based tracking solutions, long present in clinical pathology laboratories, have recently made an appearance in anatomic pathology (AP) laboratories. Tracking of AP "assets" (specimens, blocks, slides) can enhance laboratory efficiency, promote patient safety, and improve patient care. Routing of excess clinical material into research laboratories and biorepositories are other avenues that can benefit from tracking of AP assets. Implementing tracking is not as simple as installing software and turning it on. Not all tracking solutions are alike. Careful analysis of laboratory workflow is needed before implementing tracking to assure that this solution will meet the needs of the laboratory. Such analysis will likely uncover practices that may need to be modified before a tracking system can be deployed. Costs that go beyond simply that of purchasing software will be incurred and need to be considered in the budgeting process. Finally, people, not technology, are the key to assuring quality. Tracking will require significant changes in workflow and an overall change in the culture of the laboratory. Preparation, training, buy-in, and accountability of the people involved are crucial to the success of this process. This article reviews the benefits, available technology, underlying principles, and implementation of tracking solutions for the AP and research laboratory. PMID:23634908
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.
Optimal Cache-Oblivious Mesh Layouts
Bender, Michael A.; Kuszmaul, Bradley C.; Teng, Shang-Hua; Wang, Kebin
2007-01-01
A mesh is a graph that divides physical space into regularly-shaped regions. Meshes computations form the basis of many applications, e.g. finite-element methods, image rendering, and collision detection. In one important mesh primitive, called a mesh update, each mesh vertex stores a value and repeatedly updates this value based on the values stored in all neighboring vertices. The performance of a mesh update depends on the layout of the mesh in memory. This paper shows how to find a memory...
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.
User Manual for the PROTEUS Mesh Tools
International Nuclear Information System (INIS)
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 MTMeshToMesh.x and the MTRadialLattice.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.
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.
Performance of a mixed-mesh Godunov-based flood inundation model
Kim, B.; Sanders, B. F.; Kim, H.; Famiglietti, J. S.
2011-12-01
Godunov-based finite volume models for solving the shallow-water equations, which are seeing increasing use in hydrology for flood inundation modeling, have almost exclusively adopted either structured meshes of quadrilateral cells or unstructured meshes of triangular cells but have not focused on mixing quadrilateral and triangular cells as is common with finite element models. Triangular meshing is advantageous in complex topography arising from channel junctions, meandering channels, and artificial structures because powerful Delaunay mesh generators easily accommodate internal and external boundary constraints while retaining mesh quality attributes such as area and angle properties. On the other hand, quadrilateral meshing is advantages in the absence of boundary constraints because efficient and low-overhead mesh designs such as Cartesian grids can be used. Motivated by the need for efficient and accurate modeling of flood inundation including channel flows, overbank flows, and overtopping processes, a mixed-mesh version of the BreZo flood inundation model is presented and its ease-of-use and performance in a series of laboratory and field scale test problems is examined in comparison to versions that use either triangular or quadrilateral cells exclusively. We find that mixed meshes are not as easily prepared as triangular meshes for commonly encountered study-site geometries, but execution times and memory requirements for a similar level of accuracy are reduced. The challenges of designing high quality meshes for flood modeling highlights the need for a new class of mesh generators that can scan high resolution topographic data (e.g., lidar) for critical features (e.g., channels and levees) and automate mixed-mesh generation and parameterization.
CCD Photometry of bright stars using objective wire mesh
International Nuclear Information System (INIS)
Obtaining accurate photometry of bright stars from the ground remains problematic due to the danger of overexposing the target and/or the lack of suitable nearby comparison stars. The century-old method of using objective wire mesh to produce multiple stellar images seems promising for the precise CCD photometry of such stars. Furthermore, our tests on β Cep and its comparison star, differing by 5 mag, are very encouraging. Using a CCD camera and a 20 cm telescope with the objective covered by a plastic wire mesh, in poor weather conditions, we obtained differential photometry with a precision of 4.5 mmag per two minute exposure. Our technique is flexible and may be tuned to cover a range as big as 6-8 mag. We discuss the possibility of installing a wire mesh directly in the filter wheel.
Adaptive anisotropic meshing for steady convection-dominated problems
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Hoa [Tulane University; Gunzburger, Max [Florida State University; Ju, Lili [University of South Carolina; Burkardt, John [Florida State University
2009-01-01
Obtaining accurate solutions for convection–diffusion equations is challenging due to the presence of layers when convection dominates the diffusion. To solve this problem, we design an adaptive meshing algorithm which optimizes the alignment of anisotropic meshes with the numerical solution. Three main ingredients are used. First, the streamline upwind Petrov–Galerkin method is used to produce a stabilized solution. Second, an adapted metric tensor is computed from the approximate solution. Third, optimized anisotropic meshes are generated from the computed metric tensor by an anisotropic centroidal Voronoi tessellation algorithm. Our algorithm is tested on a variety of two-dimensional examples and the results shows that the algorithm is robust in detecting layers and efficient in avoiding non-physical oscillations in the numerical approximation.
CCD Photometry of bright stars using objective wire mesh
Energy Technology Data Exchange (ETDEWEB)
Kamiński, Krzysztof; Zgórz, Marika [Astronomical Observatory Institute, Faculty of Physics, A. Mickiewicz University, Słoneczna 36, 60-286 Poznań (Poland); Schwarzenberg-Czerny, Aleksander, E-mail: chrisk@amu.edu.pl [Copernicus Astronomical Centre, ul. Bartycka 18, PL 00-716 Warsaw (Poland)
2014-06-01
Obtaining accurate photometry of bright stars from the ground remains problematic due to the danger of overexposing the target and/or the lack of suitable nearby comparison stars. The century-old method of using objective wire mesh to produce multiple stellar images seems promising for the precise CCD photometry of such stars. Furthermore, our tests on β Cep and its comparison star, differing by 5 mag, are very encouraging. Using a CCD camera and a 20 cm telescope with the objective covered by a plastic wire mesh, in poor weather conditions, we obtained differential photometry with a precision of 4.5 mmag per two minute exposure. Our technique is flexible and may be tuned to cover a range as big as 6-8 mag. We discuss the possibility of installing a wire mesh directly in the filter wheel.
Relativistic polarizabilities with the Lagrange-mesh method
Filippin, Livio; Baye, Daniel
2016-01-01
Relativistic dipolar to hexadecapolar polarizabilities of the ground state and some excited states of hydrogenic atoms are calculated by using numerically exact energies and wave functions obtained from the Dirac equation with the Lagrange-mesh method. This approach is an approximate variational method taking the form of equations on a grid because of the use of a Gauss quadrature approximation. The partial polarizabilities conserving the absolute value of the quantum number $\\kappa$ are also numerically exact with small numbers of mesh points. The ones where $|\\kappa|$ changes are very accurate when using three different meshes for the initial and final wave functions and for the calculation of matrix elements. The polarizabilities of the $n=2$ excited states of hydrogenic atoms are also studied with a separate treatment of the final states that are degenerate at the nonrelativistic approximation. The method provides high accuracies for polarizabilities of a particle in a Yukawa potential and is applied to a...
Anatomical variations of paranasal sinuses at multislice computed tomography: what to look for
Energy Technology Data Exchange (ETDEWEB)
Miranda, Christiana Maia Nobre Rocha de; Maranhao, Carol Pontes de Miranda [Clinica de Medicina Nuclear e Radiologia de Maceio (Medradius), Maceio, AL (Brazil). Setor de Tomografia Computadorizada; Arraes, Fabiana Maia Nobre Rocha [Clinica Sinus, Maceio, AL (Brazil); Padilha, Igor Gomes; Farias, Lucas de Padua Gomes de; Jatoba, Mayara Stephanie de Araujo; Andrade, Anna Carolina Mendonca de; Padilha, Bruno Gomes [Universidade Federal de Alagoas (UFAL), Maceio, AL (Brazil)
2011-07-15
Multislice computed tomography is currently the imaging modality of choice for evaluating paranasal sinuses and adjacent structures. Such a method has been increasingly utilized in the assessment of anatomical variations, allowing their accurate identification with high anatomical details. Some anatomical variations may predispose to sinusal diseases, constituting areas of high risk for injuries and complications during surgical procedures. Therefore, the recognition of such variations is critical in the preoperative evaluation for endoscopic surgery. (author)
Geostrophic balance preserving interpolation in mesh adaptive shallow-water ocean modelling
Maddison, James R; Farrell, Patrick E
2010-01-01
The accurate representation of geostrophic balance is an essential requirement for numerical modelling of geophysical flows. Significant effort is often put into the selection of accurate or optimal balance representation by the discretisation of the fundamental equations. The issue of accurate balance representation is particularly challenging when applying dynamic mesh adaptivity, where there is potential for additional imbalance injection when interpolating to new, optimised meshes. In the context of shallow-water modelling, we present a new method for preservation of geostrophic balance when applying dynamic mesh adaptivity. This approach is based upon interpolation of the Helmholtz decomposition of the Coriolis acceleration. We apply this in combination with a discretisation for which states in geostrophic balance are exactly steady solutions of the linearised equations on an f-plane; this method guarantees that a balanced and steady flow on a donor mesh remains balanced and steady after interpolation on...
A coarse-mesh nodal method-diffusive-mesh finite difference method
International Nuclear Information System (INIS)
Modern nodal methods have been successfully used for conventional light water reactor core analyses where the homogenized, node average cross sections (XSs) and the flux discontinuity factors (DFs) based on equivalence theory can reliably predict core behavior. For other types of cores and other geometries characterized by tightly-coupled, heterogeneous core configurations, the intranodal flux shapes obtained from a homogenized nodal problem may not accurately portray steep flux gradients near fuel assembly interfaces or various reactivity control elements. This may require extreme values of DFs (either very large, very small, or even negative) to achieve a desired solution accuracy. Extreme values of DFs, however, can disrupt the convergence of the iterative methods used to solve for the node average fluxes, and can lead to a difficulty in interpolating adjacent DF values. Several attempts to remedy the problem have been made, but nothing has been satisfactory. A new coarse-mesh nodal scheme called the Diffusive-Mesh Finite Difference (DMFD) technique, as contrasted with the coarse-mesh finite difference (CMFD) technique, has been developed to resolve this problem. This new technique and the development of a few-group, multidimensional kinetics computer program are described in this paper
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.
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...
Computational mesh generation for vascular structures with deformable surfaces
International Nuclear Information System (INIS)
Computational blood flow and vessel wall mechanics simulations for vascular structures are becoming an important research tool for patient-specific surgical planning and intervention. An important step in the modelling process for patient-specific simulations is the creation of the computational mesh based on the segmented geometry. Most known solutions either require a large amount of manual processing or lead to a substantial difference between the segmented object and the actual computational domain. We have developed a chain of algorithms that lead to a closely related implementation of image segmentation with deformable models and 3D mesh generation. The resulting processing chain is very robust and leads both to an accurate geometrical representation of the vascular structure as well as high quality computational meshes. The chain of algorithms has been tested on a wide variety of shapes. A benchmark comparison of our mesh generation application with five other available meshing applications clearly indicates that the new approach outperforms the existing methods in the majority of cases. (orig.)
Zheng, J.; Zhu, J.; Wang, Z.; Fang, F.; Pain, C. C.; Xiang, J.
2015-06-01
A new anisotropic hr-adaptive mesh technique has been applied to modelling of multiscale transport phenomena, which is based on a discontinuous Galerkin/control volume discretization on unstructured meshes. Over existing air quality models typically based on static-structured grids using a locally nesting technique, the advantage of the anisotropic hr-adaptive model has the ability to adapt the mesh according to the evolving pollutant distribution and flow features. That is, the mesh resolution can be adjusted dynamically to simulate the pollutant transport process accurately and effectively. To illustrate the capability of the anisotropic adaptive unstructured mesh model, three benchmark numerical experiments have been setup for two-dimensional (2-D) transport phenomena. Comparisons have been made between the results obtained using uniform resolution meshes and anisotropic adaptive resolution meshes.
Gosselin, Marie-Christine; Neufeld, Esra; Moser, Heidi; Huber, Eveline; Farcito, Silvia; Gerber, Livia; Jedensjö, Maria; Hilber, Isabel; Di Gennaro, Fabienne; Lloyd, Bryn; Cherubini, Emilio; Szczerba, Dominik; Kainz, Wolfgang; Kuster, Niels
2014-09-01
The Virtual Family computational whole-body anatomical human models were originally developed for electromagnetic (EM) exposure evaluations, in particular to study how absorption of radiofrequency radiation from external sources depends on anatomy. However, the models immediately garnered much broader interest and are now applied by over 300 research groups, many from medical applications research fields. In a first step, the Virtual Family was expanded to the Virtual Population to provide considerably broader population coverage with the inclusion of models of both sexes ranging in age from 5 to 84 years old. Although these models have proven to be invaluable for EM dosimetry, it became evident that significantly enhanced models are needed for reliable effectiveness and safety evaluations of diagnostic and therapeutic applications, including medical implants safety. This paper describes the research and development performed to obtain anatomical models that meet the requirements necessary for medical implant safety assessment applications. These include implementation of quality control procedures, re-segmentation at higher resolution, more-consistent tissue assignments, enhanced surface processing and numerous anatomical refinements. Several tools were developed to enhance the functionality of the models, including discretization tools, posing tools to expand the posture space covered, and multiple morphing tools, e.g., to develop pathological models or variations of existing ones. A comprehensive tissue properties database was compiled to complement the library of models. The results are a set of anatomically independent, accurate, and detailed models with smooth, yet feature-rich and topologically conforming surfaces. The models are therefore suited for the creation of unstructured meshes, and the possible applications of the models are extended to a wider range of solvers and physics. The impact of these improvements is shown for the MRI exposure of an adult
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...
Application of the VOF method based on unstructured quadrilateral mesh
Institute of Scientific and Technical Information of China (English)
JI Chun-ning; SHI Ying
2008-01-01
To simulate two-dimensional free-surface flows with complex boundaries directly and accurately, a novel VOF (Volume-of-fluid) method based on unstructured quadrilateral mesh is presented. Without introducing any complicated boundary treatment or artificial diffusion, this method treated curved boundaries directly by utilizing the inherent merit of unstructured mesh in fitting curves. The PLIC (Piecewise Linear Interface Calculation) method was adopted to obtain a second-order accurate linearized reconstruction approximation and the MLER (Modified Lagrangian-Eulerian Re-map) method was introduced to advect fluid volumes on unstructured mesh. Moreover, an analytical relation for the interface's line constant vs. the volume clipped by the interface was developed so as to improve the method's efficiency. To validate this method, a comprehensive series of large straining advection tests were performed. Numerical results provide convincing evidences for the method's high volume conservative accuracy and second-order shape error convergence rate. Also, a dramatic improvement on computational accuracy over its unstructured triangular mesh counterpart is checked.
Compressive VOF method with skewness correction to capture sharp interfaces on arbitrary meshes
Denner, Fabian; van Wachem, Berend G. M.
2014-12-01
The accurate and efficient modelling of two-phase flows is at present mostly limited to structured, unskewed meshes, due to the additional topological and numerical complexity of arbitrary, unstructured meshes. Compressive VOF methods which discretize the interface advection with algebraic differencing schemes are computationally efficient and inherently applicable to arbitrary meshes. However, compressive VOF methods evidently suffer severely from numerical diffusion on meshes with topological skewness. In this paper we present a compressive VOF method using a state-of-the-art donor-acceptor advection scheme which includes novel modifications to substantially reduce numerical diffusion on arbitrary meshes without adding computational complexity. The new methodology accurately captures evolving interfaces on any arbitrary, non-overlapping mesh and conserves mass within the limits of the applied solver tolerance. A thorough validation of the presented methods is conducted, examining the pure advection of the interface indicator function as well as the application to evolving interfaces with surface tension. Crucially, the results on equidistant Cartesian and arbitrary tetrahedral meshes are shown to be comparable and accurate.
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...
Directory of Open Access Journals (Sweden)
Watanabe,Toyohiko
2012-02-01
Full Text Available Polypropylene mesh implants for the correction of pelvic organ prolapse (POP are now available in Japan. We developed an innovative approach for correcting POP by placing polypropylene mesh transvaginally with laparoscopic assistance. From June 2007 through March 2010, sixteen consecutive patients with symptomatic stage 2 or 3 pelvic organ prolapse underwent the laparoscopic-assisted tension-free vaginal mesh procedure at Okayama University Hospital. All patients were evaluated before and at 1, 3, 6, and 12 months after surgery. Female sexual function was also evaluated with the Female Sexual Function Index (FSFI. The procedure was performed successfully without significant complications. Fifteen of 16 patients were considered anatomically cured (93.8% at 12 months postoperatively. One patient with a recurrent stage 3 vaginal vault prolapse required sacral colpopexy six months postoperatively. Total FSFI scores improved significantly from 10.3±1.3 at baseline to 18.0±1.2 at 12 months after surgery. The laparoscopic-assisted trans-vaginal mesh is a safe, effective, and simple procedure for POP repairs. The procedure not only restores anatomic relationships but also improves sexual function.
ANATOMICAL PROPERTIES OF PLANTAGO ARENARIA
Nicoleta IANOVICI; SINITEAN, Adrian; Aurel FAUR
2011-01-01
Psammophytes are marked by a number of adaptations that enable them to exist in the hard environmental conditions of the sand habitats. In this study, the anatomical characteristics of Plantago arenaria were examined. Studies were conducted to assess the diversity of anatomical adaptations of vegetative organs in this taxa. Results are presented with original photographs. The analysis of leaf anatomy in P. arenaria showed that the leaves contained a contained xeromorphic traits. Arbuscular my...
Multiple scale mesh free analysis
International Nuclear Information System (INIS)
Recent developments of mesh free and multi-scale methods and their applications in applied mechanics are surveyed. Three major methodologies are reviewed. First, smoothed particle hydrodynamics (SPH) is discussed as a representative of a non-local kernel, strong form collocation approach. Second, mesh-free Galerkin methods, which have been active research area in recent years, are reviewed. Third, some applications of molecular dynamics (MD) in applied mechanics are discussed. The emphases of this survey are placed on simulations of finite deformations, fracture, shear bands, multi-scale methods, and nano-scale mechanics. Refs. 13 (author)
DISCO: A 3D Moving-Mesh Magnetohydrodynamics Code Designed for the Study of Astrophysical Disks
Duffell, Paul C
2016-01-01
This work presents the publicly available moving-mesh magnetohydrodynamics code DISCO. DISCO is efficient and accurate at evolving orbital fluid motion in two and three dimensions, especially at high Mach number. DISCO employs a moving-mesh approach utilizing a dynamic cylindrical mesh that can shear azimuthally to follow the orbital motion of the gas. The moving mesh removes diffusive advection errors and allows for longer timesteps than a static grid. Magnetohydrodynamics is implemented in DISCO using an HLLD Riemann solver and a novel constrained transport scheme which is compatible with the mesh motion. DISCO is tested against a wide variety of problems, which are designed to test its stability, accuracy and scalability. In addition, several magnetohydrodynamics tests are performed which demonstrate the accuracy and stability of the new constrained transport approach, including two tests of the magneto-rotational instability (MRI); one testing the linear growth rate and the other following the instability...
A Numerical Study of Blowup in the Harmonic Map Heat Flow Using the MMPDE Moving Mesh Method
Haynes, R.D.; Huang, W.; Zegeling, P.A.
2013-01-01
The numerical solution of the harmonic heat map flow problems with blowup in finite or infinite time is considered using an adaptive moving mesh method. A properly chosen monitor function is derived so that the moving mesh method can be used to simulate blowup and produce accurate blowup profiles wh
Development and verification of unstructured adaptive mesh technique with edge compatibility
International Nuclear Information System (INIS)
In the design study of the large-sized sodium-cooled fast reactor (JSFR), one key issue is suppression of gas entrainment (GE) phenomena at a gas-liquid interface. Therefore, the authors have been developed a high-precision CFD algorithm to evaluate the GE phenomena accurately. The CFD algorithm has been developed on unstructured meshes to establish an accurate modeling of JSFR system. For two-phase interfacial flow simulations, a high-precision volume-of-fluid algorithm is employed. It was confirmed that the developed CFD algorithm could reproduce the GE phenomena in a simple GE experiment. Recently, the authors have been developed an important technique for the simulation of the GE phenomena in JSFR. That is an unstructured adaptive mesh technique which can apply fine cells dynamically to the region where the GE occurs in JSFR. In this paper, as a part of the development, a two-dimensional unstructured adaptive mesh technique is discussed. In the two-dimensional adaptive mesh technique, each cell is refined isotropically to reduce distortions of the mesh. In addition, connection cells are formed to eliminate the edge incompatibility between refined and non-refined cells. The two-dimensional unstructured adaptive mesh technique is verified by solving well-known lid-driven cavity flow problem. As a result, the two-dimensional unstructured adaptive mesh technique succeeds in providing a high-precision solution, even though poor-quality distorted initial mesh is employed. In addition, the simulation error on the two-dimensional unstructured adaptive mesh is much less than the error on the structured mesh with a larger number of cells. (author)
[Sigismund Laskowski and his anatomical preparations technique].
Gryglewski, Ryszard W
2015-01-01
Fixation of the entire bodies or individual organs, and later as well tissues and cellular structures, was and still is often a challenge for anatomists and histologists. Technique that combines extensive knowledge of natural sciences, as well as technical skills, was by those best researchers as Frederik Ruysch, brought to perfection. Preparations, if done with care and talent, are really propelling progress in anatomical studies and determining the quality of education for medical students and young physicians. And as it is true for many of today's medical disciplines and natural sciences, the nineteenth century was in many ways a breaking point for preparatory techniques in the realm of anatomy and histology. Among those who have achieved success, earning notoriety during their lifetime and often going into the annals of European most distinguished scholars were some Polish names: Louis Maurice Hirschfeld, whose preparations of the nervous system earned him well-deserved, international fame, Louis Charles Teichmann, who was the very first so precisely describing the lymphatic system and a creator of unique injection mass, Henry Kadyi, known for his outstanding preparations, especially of vascular system. Henry Frederick Hoyer sen., who was one of the first to use formalin regularly for accurate microscopic preparations, is seen by many as the founder of the Polish histology. In this group of innovators and precursors of modern preparation techniques place should be reserved for Zygmunt (Sigismund) Laskowski, Polish patriot, fighting in January Uprising, later an immigrant, a professor at the university sequentially Paris and Geneva. Acclaimed author of anatomical tables and certainly creator of one of the groundbreaking techniques in anatomical preparations. Based after many years of research on the simple glycerine-phenol mixture achieved excellent results both in fixation of entire bodies and organs or tissues. Quality of those preparations was as high and
International Nuclear Information System (INIS)
Numerical solution of the diffusion equation plays a key role in the study of inertial confinement fusion (ICF). In this paper, based on the global support operator method, a flux-based scheme is proposed. The scheme has local stencil with second-order accuracy both in space and time. For strongly distorted meshes, a procedure of normal direction fix is adopted with proper methods for the computation of corner volume weights, which obtains accurate discretization of the face flux. Numerical experiments show that the scheme can obtain accurate solution for linear problems on non-convex meshes. The method has second-order spatial and temporal accuracy on non-smooth meshes. The method can also preserve the symmetry well and can be extended to the three dimensional unstructured meshes. (authors)
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.
Damiani, G R; Riva, D; Pellegrino, A; Gaetani, M; Tafuri, S; Turoli, D; Croce, P; Loverro, G
2016-04-01
117 women with severe pelvic organ prolapse (POP; stage > 2) were enrolled to elucidate a 24-month outcome of POP surgery, using conventional or mesh repair with 3 techniques. 59 patients underwent conventional repair and 58 underwent mesh repair. Two types of mesh were used: a trocar-guided transobturator polypropylene (Avaulta, Bard Inc.) and a porcine dermis mesh (Pelvisoft, Bard Inc.). Women with recurrences, who underwent previous unsuccessful conventional repair, were randomised. Primary outcome was the evaluation of anatomic failures (prolapse stage > 1) in treated and untreated compartments. Anatomic failure was observed in 11 of 58 patients (19%; CI 8.9-29) in the mesh group and in 16 of 59 patients (27.1%; p value = 0.3) in the conventional group. 9 of 11 failures in the mesh group (15.5%; CI 6.2-24.8) were observed in the untreated compartment (de novo recurrences), 14.3% in Pelvisoft and 16.7% in Avaulta arm, while only 1 recurrence in the untreated compartment (1.7%) was observed in the conventional group (odds ratio 10.6, p = 0.03). PMID:26492359
On-line residual capacity estimation for resource allocation in wireless mesh networks
Sarıkaya, Yunus; Sarikaya, Yunus
2008-01-01
Contention-based multi access scheme of 802.11 based wireless mesh networks imposes difficulties in achieving predictable service quality in multi-hop networks. In order to offer effective advanced network services such as flow admission control or load balancing, the residual capacity of the wireless links should be accurately estimated. In this work, we propose and validate an algorithm for the residual bandwidth of wireless mesh network. By collecting transmission statistics from the nearb...
ANATOMICAL PROPERTIES OF PLANTAGO ARENARIA
Directory of Open Access Journals (Sweden)
Nicoleta IANOVICI
2011-01-01
Full Text Available Psammophytes are marked by a number of adaptations that enable them to exist in the hard environmental conditions of the sand habitats. In this study, the anatomical characteristics of Plantago arenaria were examined. Studies were conducted to assess the diversity of anatomical adaptations of vegetative organs in this taxa. Results are presented with original photographs. The analysis of leaf anatomy in P. arenaria showed that the leaves contained a contained xeromorphic traits. Arbuscular mycorrhizal symbiosis seems to be critical for their survival.
Feature-preserving mesh denoising via normal guided quadric error metrics
Yu, Jinze; Wei, Mingqiang; Qin, Jing; Wu, Jianhuang; Heng, Pheng-Ann
2014-11-01
While modern optical and laser 3D scanners can generate high accuracy mesh models, to largely avoid their introducing noise which prohibits practical applications still results in high cost. Thus, optimizing noisy meshes while preserving their geometric details is necessary for production, which still remains as challenging work. In this paper we propose a novel and efficient two-stage feature-preserving mesh denoising framework which can remove noise while preserving fine features of a surface mesh. We improve the capability of feature preservation of our vertex updating scheme by employing an extension of the quadric error metrics (QEM), which can track and minimize updating errors and hence well preserve the overall shape as well as detailed features of a mesh. We further leverage vertex normals to guide the vertex updating process, as the normal field of a mesh reflects the geometry of the underlying surface. In addition, to obtain a more accurate normal field to guide vertex updating, we develop an improved normal filter by integrating advantages of existing filters. Compared with traditional gradient descent based schemes, our method performs better on challenging regions with rich geometric features. Moreover, a local entropy metric is proposed to measure stability of a mesh and the effectiveness of vertex updating algorithms. Qualitative and quantitative experiments demonstrate that our approach can effectively remove noise from noisy meshes while preserving or recovering geometrical features of original objects.
Simple mesh stent placement for treating intracranial aneurysm: progress in research
International Nuclear Information System (INIS)
Treatment of an aneurysm with a mesh stent alone becomes an emerging technique. The mechanism involves the mesh stents, when it crosses the neck of an aneurysm could change the internal circulation and induce the formation of stable thrombus and in turn assists the growth of neointima for anatomical healing of the aneurysmal neck. The mesh stent technique aimed at vascular reconstruction with expected curing effect for aneurysm together as a simple and safe way to keep the patency of the small arterial branches, just contrary to the covered stent. This technique couldn't be carried out practically in wide scale because of immaturity, therefore we give a comprehesive review in the progress of this field. (authors)
[Antique anatomical collections for contemporary museums].
Nesi, Gabriella; Santi, Raffaella
2013-01-01
Anatomy and Pathology Museum collections display a great biological value and offer unique samples for research purposes. Pathological specimens may be investigated by means of modern radiological and molecular biology techniques in order to provide the etiological background of disease, with relevance to present-day knowledge. Meanwhile, historical resources provide epidemiologic data regarding the socio-economic conditions of the resident populations, the more frequently encountered illnesses and dietary habits. These multidisciplinary approaches lead to more accurate diagnoses also allowing new strategies in cataloguing and musealization of anatomical specimens. Further, once these data are gathered, they may constitute the basis of riedited Museum catalogues feasible to be digitalized and displayed via the Web. PMID:25807710
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.
22nd International Meshing Roundtable
Staten, Matthew
2014-01-01
This volume contains the articles presented at the 22nd International Meshing Roundtable (IMR) organized, in part, by Sandia National Laboratories and was held on Oct 13-16, 2013 in Orlando, Florida, 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.
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.
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.
ROAMing terrain (Real-time Optimally Adapting Meshes)
Energy Technology Data Exchange (ETDEWEB)
Duchaineau, M.; Wolinsky, M.; Sigeti, D.E.; Miller, M.C.; Aldrich, C.; Mineev, M.
1997-07-01
Terrain visualization is a difficult problem for applications requiring accurate images of large datasets at high frame rates, such as flight simulation and ground-based aircraft testing using synthetic sensor stimulation. On current graphics hardware, the problem is to maintain dynamic, view-dependent triangle meshes and texture maps that produce good images at the required frame rate. We present an algorithm for constructing triangle meshes that optimizes flexible view-dependent error metrics, produces guaranteed error bounds, achieves specified triangle counts directly, and uses frame-to-frame coherence to operate at high frame rates for thousands of triangles per frame. Our method, dubbed Real-time Optimally Adapting Meshes (ROAM), uses two priority queues to drive split and merge operations that maintain continuous triangulations built from pre-processed bintree triangles. We introduce two additional performance optimizations: incremental triangle stripping and priority-computation deferral lists. ROAM execution time is proportionate to the number of triangle changes per frame, which is typically a few percent of the output mesh size, hence ROAM performance is insensitive to the resolution and extent of the input terrain. Dynamic terrain and simple vertex morphing are supported.
Bercea, Gheorghe-Teodor; McRae, Andrew T. T.; Ham, David A.; Mitchell, Lawrence; Rathgeber, Florian; Nardi, Luigi; Luporini, Fabio; Kelly, Paul H. J.
2016-01-01
We present a generic algorithm for numbering and then efficiently iterating over the data values attached to an extruded mesh. An extruded mesh is formed by replicating an existing mesh, assumed to be unstructured, to form layers of prismatic cells. Applications of extruded meshes include, but are not limited to, the representation of 3D high aspect ratio domains employed by geophysical finite element simulations. These meshes are structured in the extruded direction. The algorithm presented ...
Adaptive Mesh Refinement in CTH
International Nuclear Information System (INIS)
This paper reports progress on implementing a new capability of adaptive mesh refinement into the Eulerian multimaterial shock- physics code CTH. The adaptivity is block-based with refinement and unrefinement occurring in an isotropic 2:1 manner. The code is designed to run on serial, multiprocessor and massive parallel platforms. An approximate factor of three in memory and performance improvements over comparable resolution non-adaptive calculations has-been demonstrated for a number of problems
Mesh networked unattended ground sensors
Colling, Kent; Calcutt, Wade; Winston, Mark; Jones, Barry
2006-05-01
McQ has developed a family of low cost unattended ground sensors that utilize self-configured, mesh network communications for wireless sensing. Intended for use in an urban environment, the area monitored by the sensor system poses a communication challenge. A discussion into the sensor's communication performance and how it affects sensor installation and the operation of the system once deployed is presented.
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.
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.
Directory of Open Access Journals (Sweden)
Paulo Palma
2010-04-01
Full Text Available PURPOSE: This prospective study was performed to achieve visualization of the reestablishment of anatomy after reconstructive surgery in the different pelvic compartments with non-absorbable radiopaque meshes, providing valuable anatomic information for surgeons implanting meshes. MATERIALS AND METHODS: A total of 30 female patients with stress urinary incontinence (SUI, anterior and posterior vaginal wall prolapse, or both underwent surgical repair using radiopaque meshes after written informed consent. Patients with SUI underwent five different surgeries. Patients with anterior vaginal prolapse underwent a procedure using a combined pre-pubic and transobturator mesh, and those with posterior vaginal prolapse underwent posterior slingplasty. Three-dimensional reconstruction using helical CT was performed four weeks postoperatively. RESULTS: In all cases, the mesh was clearly visualized. Transobturator slings were shown at the midurethra, and the anchoring tails perforated the obturator foramen at the safety region. Mini-slings were in the proper place, and computed angiography revealed that the anchoring system was away from the obturator vessels. In patients undergoing procedure for anterior vaginal prolapse, both pre-pubic armpit and obturator slings were clearly seen and the mesh was in the proper position, supporting the bladder base and occluding the distal part of the urogenital hiatus. Transcoccygeal sacropexy revealed indirectly a well-supported "neo rectovaginal fascia" and the anchoring tails at the level of ischial spines. CONCLUSION: Three-dimensional helical tomography images of the female pelvis using radiopaque meshes have a potential role in improving our understanding of pelvic floor reconstructive surgeries. These radiopaque meshes might be the basis of a new investigative methodology.
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.
Optimizing the geometrical accuracy of curvilinear meshes
Toulorge, Thomas; Remacle, Jean-François
2015-01-01
This paper presents a method to generate valid high order meshes with optimized geometrical accuracy. The high order meshing procedure starts with a linear mesh, that is subsequently curved without taking care of the validity of the high order elements. An optimization procedure is then used to both untangle invalid elements and optimize the geometrical accuracy of the mesh. Standard measures of the distance between curves are considered to evaluate the geometrical accuracy in planar two-dimensional meshes, but they prove computationally too costly for optimization purposes. A fast estimate of the geometrical accuracy, based on Taylor expansions of the curves, is introduced. An unconstrained optimization procedure based on this estimate is shown to yield significant improvements in the geometrical accuracy of high order meshes, as measured by the standard Haudorff distance between the geometrical model and the mesh. Several examples illustrate the beneficial impact of this method on CFD solutions, with a part...
Adaptive mesh generation for image registration and segmentation
DEFF Research Database (Denmark)
Fogtmann, Mads; Larsen, Rasmus
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...
Biologic mesh for abdominal wall reconstruction
Directory of Open Access Journals (Sweden)
King KS
2014-11-01
Full Text Available Kathryn S King,1 Frank P Albino,2 Parag Bhanot3 1School of Medicine, Georgetown University Hospital, Washington, DC, USA; 2Department of Plastic Surgery, 3Department of General Surgery, Georgetown University Hospital, Washington, DC, USA Background: Mesh reinforcement significantly decreases rates of recurrence following ventral hernia repair. Historically, biologic mesh was touted as superior in the setting of infection; however, selecting the appropriate mesh for a given clinical scenario is often a matter of debate. The purpose of this review is to highlight a number of the more commonly used biologic mesh products with a review of outcomes from the current literature. Methods: Outcomes following abdominal wall reconstruction using biologic mesh were reviewed for acellular cadaveric human dermis, cross-linked porcine dermis, non-cross-linked porcine dermis, porcine small intestine submucosa, acellular bovine pericardial, and acellular bovine dermal mesh. Studies with rigorous methods, adequate patient samples, and sufficient follow-up were selected for review. Results: Hernia recurrence rates following biologic mesh reinforcement vary widely. Porcine small intestine submucosa and bovine pericardium were associated with the lowest hernia recurrence rates. Porcine cross-linked dermal mesh products resulted in higher rates of adhesion formation and lower rates of tissue incorporation compared to non-cross-linked porcine mesh. Conclusion: Successful ventral hernia repair can be achieved with acceptable complications rates for each of the reviewed mesh products. Biologic meshes have an advantage over synthetic mesh in contaminated wounds but their use may not be cost-effective in all patient populations. Those with and/or at high risk for wound complications may also undergo repair with biologic mesh. Keywords: biologic mesh, ventral hernia repair, acellular dermal matrix
Automatic mesh adaptivity for CADIS and FW-CADIS neutronics modeling of difficult shielding problems
International Nuclear Information System (INIS)
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)
Low-diffusivity scalar transport using a WENO scheme and dual meshing
Kubrak, B; Herlina, H; Greve, F; Wissink, JG
2013-01-01
Interfacial mass transfer of low-diffusive substances in an unsteady flow environment is marked by a very thin boundary layer at the interface and other regions with steep concentration gradients. A numerical scheme capable of resolving accurately most details of this process is presented. In this scheme, the fifth-order accurate WENO method developed by [13] was implemented on a non-uniform staggered mesh to discretize the scalar convection while for the scalar diffusion a fourth-order accur...
Nonlinear Analyses of Adobe Masonry Walls Reinforced with Fiberglass Mesh
Directory of Open Access Journals (Sweden)
Vincenzo Giamundo
2014-02-01
Full Text Available Adobe constructions were widespread in the ancient world, and earth was one of the most used construction materials in ancient times. Therefore, the preservation of adobe structures, especially against seismic events, is nowadays an important structural issue. Previous experimental tests have shown that the ratio between mortar and brick mechanical properties (i.e., strength, stiffness and elastic modulus influences the global response of the walls in terms of strength and ductility. Accurate analyses are presented in both the case of unreinforced and reinforced with fiberglass mesh when varying the mechanical properties of the materials composing the adobe masonry structure. The main issues and variability in the behavior of seismic resisting walls when varying the mechanical properties are herein highlighted. The aim of the overall research activity is to improve the knowledge about the structural behavior of adobe structural members unreinforced and reinforced with fiberglass mesh inside horizontal mortar joints.
Anisotropic Diffusion in Mesh-Free Numerical Magnetohydrodynamics
Hopkins, Philip F
2016-01-01
We extend recently-developed mesh-free Lagrangian methods for numerical magnetohydrodynamics (MHD) to arbitrary anisotropic diffusion equations, including: passive scalar diffusion, Spitzer-Braginskii conduction and viscosity, cosmic ray diffusion/streaming, anisotropic radiation transport, non-ideal MHD (Ohmic resistivity, ambipolar diffusion, the Hall effect), and turbulent 'eddy diffusion.' We study these as implemented in the code GIZMO for both new meshless finite-volume Godunov schemes (MFM/MFV) as well as smoothed-particle hydrodynamics (SPH). We show the MFM/MFV methods are accurate and stable even with noisy fields and irregular particle arrangements, and recover the correct behavior even in arbitrarily anisotropic cases. They are competitive with state-of-the-art AMR/moving-mesh methods, and can correctly treat anisotropic diffusion-driven instabilities (e.g. the MTI and HBI, Hall MRI). We also develop a new scheme for stabilizing anisotropic tensor-valued fluxes with high-order gradient estimators ...
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.
The moving mesh code Shadowfax
Vandenbroucke, Bert; De Rijcke, Sven
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 ...
Digital photography in anatomical pathology
Leong F; Leong A
2004-01-01
Digital imaging has made major inroads into the routine practice of anatomical pathology and replaces photographic prints and Kodachromes for reporting and conference purposes. More advanced systems coupled to computers allow greater versatility and speed of turnaround as well as lower costs of incorporating macroscopic and microscopic pictures into pathology reports and publications. Digital images allow transmission to remote sites via the Internet for consultation, quality assurance and ed...
Development of a pregnant woman phantom using polygonal mesh, for dosimetric evaluations
International Nuclear Information System (INIS)
Due to the embryo/fetus radiosensitivity the accurate estimation of the absorbed dose distribution in the abdominal area is an additional problem caused by the exposure of pregnant women to ionizing radiation in medical applications. This paper reports the construction and insertion of a fetal representation in a female geometry by means of 3D modeling techniques. In order to characterize an ECM the Grupo de Dosimetria Numerica (GDN) is using, mainly, simulators emitting gamma sources and voxel phantoms coupled to a MC code. The phantoms are predominantly constructed from stacks of magnetic resonance images (MRI), computed tomography (CT) (obtained from scans of real patients) or from 3D modeling techniques. Due to the difficulty of obtaining medical images of pregnant women, 3D objects in several formats (.obj, .max, .blend, etc.) were acquired for anatomical representation of a non-pregnant adult. To construct a fetal representation, the 3D modeling technique called Poly Modeling (polygon mesh) was used inside of the software Autodesk 3ds Max 2014 (free student version). Information about the radiosensibility of organs included in the abdominal area will be used to fit and use the pregnant phantom in numerical dosimetry. For this, the phantom will be voxelized and the masses of organs of interest will be adjusted according to data provided by International Commission on Radiological Protection (ICRP). Finally, the phantom will be coupled to a MC code creating a MCE that will serve as base for the construction of several other models involving pregnant women submitted to ionizing radiation. (author)
Development of a pregnant woman phantom using polygonal mesh, for dosimetric evaluations
Energy Technology Data Exchange (ETDEWEB)
Cabral, Manuela O.M.; Vieira, Jose W., E-mail: manuela.omc@gmail.com [Universidade Federal de Pernambuco (DEN/UFPE), Recife, PE (Brazil). Departamento de Energia Nuclear; Leal Neto, Viriato, E-mail: viriatoleal@yahoo.com.br [Instituto Federal de Educacao, Ciencia e Tecnologia de Pernambuco (IFPE), Recife, PE (Brazil); Lima, Fernando R.A., E-mail: falima@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil)
2014-07-01
Due to the embryo/fetus radiosensitivity the accurate estimation of the absorbed dose distribution in the abdominal area is an additional problem caused by the exposure of pregnant women to ionizing radiation in medical applications. This paper reports the construction and insertion of a fetal representation in a female geometry by means of 3D modeling techniques. In order to characterize an ECM the Grupo de Dosimetria Numerica (GDN) is using, mainly, simulators emitting gamma sources and voxel phantoms coupled to a MC code. The phantoms are predominantly constructed from stacks of magnetic resonance images (MRI), computed tomography (CT) (obtained from scans of real patients) or from 3D modeling techniques. Due to the difficulty of obtaining medical images of pregnant women, 3D objects in several formats (.obj, .max, .blend, etc.) were acquired for anatomical representation of a non-pregnant adult. To construct a fetal representation, the 3D modeling technique called Poly Modeling (polygon mesh) was used inside of the software Autodesk 3ds Max 2014 (free student version). Information about the radiosensibility of organs included in the abdominal area will be used to fit and use the pregnant phantom in numerical dosimetry. For this, the phantom will be voxelized and the masses of organs of interest will be adjusted according to data provided by International Commission on Radiological Protection (ICRP). Finally, the phantom will be coupled to a MC code creating a MCE that will serve as base for the construction of several other models involving pregnant women submitted to ionizing radiation. (author)
Sierra toolkit computational mesh conceptual model
International Nuclear Information System (INIS)
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.
Improved AFEM algorithm for bioluminescence tomography based on dual-mesh alternation strategy
Institute of Scientific and Technical Information of China (English)
Wei Li; Heng Zhao; Xiaochao Qu; Yanbin Hou; Xueli Chen; Duofang Chen; Xiaowei He; Qitan Zhang; Jimin Liang
2012-01-01
Adaptive finite element method (AFEM) is broadly adopted to recover the internal source in biological tissues.In this letter,a novel dual-mesh alternation strategy (dual-mesh AFEM) is developed for bioluminescence tomography.By comprehensively considering the error estimation of the finite element method solution on each mesh,two different adaptive strategies based on the error indicator of the reconstructed source and the photon flux density are used alternately in the process.Combined with the constantly adjusted permissible region in the adaptive process,the new algorithm can achieve a more accurate source location compared with the AFEM in the previous experiments.%Adaptive finite element method (AFEM) is broadly adopted to recover the internal source in biological tissues. In this letter, a novel dual-mesh alternation strategy (dual-mesh AFEM) is developed for biolumi-nescence tomography. By comprehensively considering the error estimation of the finite element method solution on each mesh, two different adaptive strategies based on the error indicator of the reconstructed source and the photon flux density are used alternately in the process. Combined with the constantly adjusted permissible region in the adaptive process, the new algorithm can achieve a more accurate source location compared with the AFEM in the previous experiments.
Towards Perceptual Quality Evaluation of Dynamic Meshes
Torkhani, Fakhri; Wang, Kai; Montanvert, Annick
2011-01-01
In practical applications, it is common that a 3D mesh undergoes some lossy operations. Since the end users of 3D meshes are often human beings, it is thus important to derive metrics that can faithfully assess the perceptual distortions induced by these operations. Like in the case of image quality assessment, metrics based on mesh geometric distances (e.g. Hausdorff distance and root mean squared error) cannot correctly predict the visual quality degradation. Recently, several perceptually-...
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.
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
International Nuclear Information System (INIS)
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
Association Discovery Protocol for Hybrid Wireless Mesh Networks
Adjih, Cédric; Cho, Song Yean; Jacquet, Philippe
2006-01-01
Wireless mesh networks (WMNs) consist of two kinds of nodes: mesh routers which form the backbones of WMNs and mesh clients which associate with mesh routers to access networks. Because of the discrepancy between mesh routers and mesh clients, WMNs have a hybrid structure. Their hybrid structure presents an opportunity to integrate WMNs with different networks such as wireless LAN, Bluetooth and sensor networks through bridging functions in mesh routers. Because of the ability to integrate va...
Transport of phase space densities through tetrahedral meshes using discrete flow mapping
Bajars, Janis; Sondergaard, Niels; Tanner, Gregor
2016-01-01
Discrete flow mapping was recently introduced as an efficient ray based method determining wave energy distributions in complex built up structures. Wave energy densities are transported along ray trajectories through polygonal mesh elements using a finite dimensional approximation of a ray transfer operator. In this way the method can be viewed as a smoothed ray tracing method defined over meshed surfaces. Many applications require the resolution of wave energy distributions in three-dimensional domains, such as in room acoustics, underwater acoustics and for electromagnetic cavity problems. In this work we extend discrete flow mapping to three-dimensional domains by propagating wave energy densities through tetrahedral meshes. The geometric simplicity of the tetrahedral mesh elements is utilised to efficiently compute the ray transfer operator using a mixture of analytic and spectrally accurate numerical integration. The important issue of how to choose a suitable basis approximation in phase space whilst m...
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.
Converting skeletal structures to quad dominant meshes
DEFF Research Database (Denmark)
Bærentzen, Jakob Andreas; Misztal, Marek Krzysztof; Welnicka, Katarzyna
2012-01-01
We propose the Skeleton to Quad-dominant polygonal Mesh algorithm (SQM), which converts skeletal structures to meshes composed entirely of polar and annular regions. Both types of regions have a regular structure where all faces are quads except for a single ring of triangles at the center of each...... polar region. The algorithm produces high quality meshes which contain irregular vertices only at the poles or where several regions join. It is trivial to produce a stripe parametrization for the output meshes which also lend themselves well to polar subdivision. After an initial description of SQM, we...
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
Mesh Migration Into Urinary Bladder After Open Ventral Herniorrhaphy With Mesh: A Case Report
Su, Yann-Rong; Chan, Pei-Hui
2014-01-01
Ventral hernia repair with mesh products is of increasing popularity. The long-term results of mesh repair of ventral hernia are superior to primary suture repair. However, occasional complications may still present. We report on a 77-year-old man who underwent ventral hernia repair with a mesh 5 years ago with complication of mesh migration into the urinary bladder and enterovesical fistula. The patient presented with lower urinary tract symptoms initially. By urinalysis, persistent hematuri...
MeshLab: an open-source 3D mesh processing system
Cignoni, Paolo; Corsini, Massimiliano; Ranzuglia, Guido
2008-01-01
MeshLab is a free and open-source general-purpose mesh processing system designed to assist in the management of not-so-small, unstructured 3D models that typically occur in the pipeline when processing 3D scanned data in the context of Cultural Heritage. MeshLab provides a set of tools for editing, cleaning, healing, inspecting, rendering and converting the resulting meshes
Pattern recognition of anatomical shapes in CT scans
International Nuclear Information System (INIS)
In medical image processing pattern recognition has become of major value in anatomical analysis and in computer aided information processing. Specifically, pattern recognition techniques simplify software development by means of which clinicians can manipulate anatomical relationships. As part of an overall CT pattern recognition system, a sequential edge tracking routine was devised together with a normalized Fourier descriptor analysis of identified shapes. A collection of shapes were extracted from CT scans of two patients and entered into an anatomic shape dictionary. This dictionary was employed in pattern matching experiments and in three-dimensional anatomical reconstruction. A sequential-edge tracking algorithm of high reliability, consistency, and image invariance, capable of utilizing heuristic and statistical rules, was demonstrated. Tests of pattern matching algorithms based on Fourier descriptors provided rapid and accurate body organ recognition of shapes extracted from de novo images using the shape dictionary. Results indicate that automated contour extraction and object recognition from cross-sectional images of human anatomy can be performed effectively, reliably, and rapidly. This abstract discusses an image processing environment that circumvents manual and subjective shape extraction, by substituting automatic and quantitative shape extraction, pattern matching and object recognition
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.
Mesh Geometric Editing Approach Based on Gpu Texture
Directory of Open Access Journals (Sweden)
Guiping Qian
2012-09-01
Full Text Available This paper presents a novel interactive mesh editing approach based on GPU texture mapping. The main feature is that it copies 2D surface geometry information to GPU frame buffer. The planar mesh information is transformed into GPU texture and placed on apposite position of target mesh. 3D information is retrieved after stitching two mesh components from the primitive vertex coordinates. When running real-time mesh cloning operator, our mesh editing approach can copy arbitrary irregular geometric features from source mesh to target mesh. Experimental results indicate that our method can outperform previous related mesh editing techniques.
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.
CDCC calculations with the Lagrange-mesh technique
International Nuclear Information System (INIS)
We apply the Lagrange-mesh technique to the Continuum Discretized Coupled Channel (CDCC) theory. The CDCC equations are solved with the R-matrix method, using Lagrange functions as variational basis. The choice of Lagrange functions is shown to be efficient and accurate for elastic scattering as well as for breakup reactions. We describe the general formalism for two-body projectiles, and apply it to the d+58Ni collision at Ed=80 MeV. Various numerical and physical aspects are discussed. Benchmark calculations on elastic scattering and breakup are presented.
Optimal Point Placement for Mesh Smoothing
Amenta, Nina; Bern, Marshall; Eppstein, David
1998-01-01
We study the problem of moving a vertex in an unstructured mesh of triangular, quadrilateral, or tetrahedral elements to optimize the shapes of adjacent elements. We show that many such problems can be solved in linear time using generalized linear programming. We also give efficient algorithms for some mesh smoothing problems that do not fit into the generalized linear programming paradigm.
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.
Anatomically based lower limb nerve model for electrical stimulation
Directory of Open Access Journals (Sweden)
Soboleva Tanya K
2007-12-01
Full Text Available Abstract Background Functional Electrical Stimulation (FES is a technique that aims to rehabilitate or restore functionality of skeletal muscles using external electrical stimulation. Despite the success achieved within the field of FES, there are still a number of questions that remain unanswered. One way of providing input to the answers is through the use of computational models. Methods This paper describes the development of an anatomically based computer model of the motor neurons in the lower limb of the human leg and shows how it can be used to simulate electrical signal propagation from the beginning of the sciatic nerve to a skeletal muscle. One-dimensional cubic Hermite finite elements were used to represent the major portions of the lower limb nerves. These elements were fit to data that had been digitised using images from the Visible Man project. Nerves smaller than approximately 1 mm could not be seen in the images, and thus a tree-branching algorithm was used to connect the ends of the fitted nerve model to the respective skeletal muscle. To simulate electrical propagation, a previously published mammalian nerve model was implemented and solved on the anatomically based nerve mesh using a finite difference method. The grid points for the finite difference method were derived from the fitted finite element mesh. By adjusting the tree-branching algorithm, it is possible to represent different levels of motor-unit recruitment. Results To illustrate the process of a propagating nerve stimulus to a muscle in detail, the above method was applied to the nerve tree that connects to the human semitendinosus muscle. A conduction velocity of 89.8 m/s was obtained for a 15 μm diameter nerve fibre. This signal was successfully propagated down the motor neurons to a selected group of motor units in the muscle. Conclusion An anatomically and physiologically based model of the posterior motor neurons in the human lower limb was developed. This
Adaptive radial basis function mesh deformation using data reduction
Gillebaart, T.; Blom, D. S.; van Zuijlen, A. H.; Bijl, H.
2016-09-01
Radial Basis Function (RBF) mesh deformation is one of the most robust mesh deformation methods available. Using the greedy (data reduction) method in combination with an explicit boundary correction, results in an efficient method as shown in literature. However, to ensure the method remains robust, two issues are addressed: 1) how to ensure that the set of control points remains an accurate representation of the geometry in time and 2) how to use/automate the explicit boundary correction, while ensuring a high mesh quality. In this paper, we propose an adaptive RBF mesh deformation method, which ensures the set of control points always represents the geometry/displacement up to a certain (user-specified) criteria, by keeping track of the boundary error throughout the simulation and re-selecting when needed. Opposed to the unit displacement and prescribed displacement selection methods, the adaptive method is more robust, user-independent and efficient, for the cases considered. Secondly, the analysis of a single high aspect ratio cell is used to formulate an equation for the correction radius needed, depending on the characteristics of the correction function used, maximum aspect ratio, minimum first cell height and boundary error. Based on the analysis two new radial basis correction functions are derived and proposed. This proposed automated procedure is verified while varying the correction function, Reynolds number (and thus first cell height and aspect ratio) and boundary error. Finally, the parallel efficiency is studied for the two adaptive methods, unit displacement and prescribed displacement for both the CPU as well as the memory formulation with a 2D oscillating and translating airfoil with oscillating flap, a 3D flexible locally deforming tube and deforming wind turbine blade. Generally, the memory formulation requires less work (due to the large amount of work required for evaluating RBF's), but the parallel efficiency reduces due to the limited
Mesh deformation based on artificial neural networks
Stadler, Domen; Kosel, Franc; Čelič, Damjan; Lipej, Andrej
2011-09-01
In the article a new mesh deformation algorithm based on artificial neural networks is introduced. This method is a point-to-point method, meaning that it does not use connectivity information for calculation of the mesh deformation. Two already known point-to-point methods, based on interpolation techniques, are also presented. In contrast to the two known interpolation methods, the new method does not require a summation over all boundary nodes for one displacement calculation. The consequence of this fact is a shorter computational time of mesh deformation, which is proven by different deformation tests. The quality of the deformed meshes with all three deformation methods was also compared. Finally, the generated and the deformed three-dimensional meshes were used in the computational fluid dynamics numerical analysis of a Francis water turbine. A comparison of the analysis results was made to prove the applicability of the new method in every day computation.
Resolution of the Gross-Pitaevskii equation with the imaginary-time method on a Lagrange mesh.
Baye, D; Sparenberg, J-M
2010-11-01
The Lagrange-mesh method is an approximate variational calculation which has the simplicity of a mesh calculation. Combined with the imaginary-time method, it is applied to the iterative resolution of the Gross-Pitaevskii equation. Two variants of a fourth-order factorization of the exponential of the Hamiltonian and two types of mesh (Lagrange-Hermite and Lagrange-sinc) are employed and compared. The accuracy is checked with the help of these comparisons and of the virial theorem. The Lagrange-Hermite mesh provides very accurate results with short computing times for values of the dimensionless parameter of the nonlinear term up to 10⁴. For higher values up to 10⁷, the Lagrange-sinc mesh is more efficient. Examples are given for anisotropic and nonseparable trapping potentials. PMID:21230613
Digital imaging in anatomic pathology.
O'Brien, M J; Sotnikov, A V
1996-10-01
Advances in computer technology continue to bring new innovations to departments of anatomic pathology. This article briefly reviews the present status of digital optical imaging, and explores the directions that this technology may lead over the next several years. Technical requirements for digital microscopic and gross imaging, and the available options for image archival and retrieval are summarized. The advantages of digital images over conventional photography in the conference room, and the usefulness of digital imaging in the frozen section suite and gross room, as an adjunct to surgical signout and as a resource for training and education, are discussed. An approach to the future construction of digital histologic sections and the computer as microscope is described. The digital technologic applications that are now available as components of the surgical pathologist's workstation are enumerated. These include laboratory information systems, computerized voice recognition, and on-line or CD-based literature searching, texts and atlases and, in some departments, on-line image databases. The authors suggest that, in addition to these resources that are already available, tomorrow's surgical pathology workstation will include network-linked digital histologic databases, on-line software for image analysis and 3-D image enhancement, expert systems, and ultimately, advanced pattern recognition capabilities. In conclusion, the authors submit that digital optical imaging is likely to have a significant and positive impact on the future development of anatomic pathology. PMID:8853053
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.
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.
A moving mesh unstaggered constrained transport scheme for magnetohydrodynamics
Mocz, Philip; Pakmor, Rüdiger; Springel, Volker; Vogelsberger, Mark; Marinacci, Federico; Hernquist, Lars
2016-08-01
We present a constrained transport (CT) algorithm for solving the 3D ideal magnetohydrodynamic (MHD) equations on a moving mesh, which maintains the divergence-free condition on the magnetic field to machine-precision. Our CT scheme uses an unstructured representation of the magnetic vector potential, making the numerical method simple and computationally efficient. The scheme is implemented in the moving mesh code AREPO. We demonstrate the performance of the approach with simulations of driven MHD turbulence, a magnetized disc galaxy, and a cosmological volume with primordial magnetic field. We compare the outcomes of these experiments to those obtained with a previously implemented Powell divergence-cleaning scheme. While CT and the Powell technique yield similar results in idealized test problems, some differences are seen in situations more representative of astrophysical flows. In the turbulence simulations, the Powell cleaning scheme artificially grows the mean magnetic field, while CT maintains this conserved quantity of ideal MHD. In the disc simulation, CT gives slower magnetic field growth rate and saturates to equipartition between the turbulent kinetic energy and magnetic energy, whereas Powell cleaning produces a dynamically dominant magnetic field. Such difference has been observed in adaptive-mesh refinement codes with CT and smoothed-particle hydrodynamics codes with divergence-cleaning. In the cosmological simulation, both approaches give similar magnetic amplification, but Powell exhibits more cell-level noise. CT methods in general are more accurate than divergence-cleaning techniques, and, when coupled to a moving mesh can exploit the advantages of automatic spatial/temporal adaptivity and reduced advection errors, allowing for improved astrophysical MHD simulations.
Constrained CVT Meshes and a Comparison of Triangular Mesh Generators
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Hoa [Florida State University; Burkardt, John [Florida State University; Gunzburger, Max [Florida State University; Ju, Lili [University of South Carolina; Saka, Yuki [Florida State University
2009-01-01
Mesh generation in regions in Euclidean space is a central task in computational science, and especially for commonly used numerical methods for the solution of partial differential equations, e.g., finite element and finite volume methods. We focus on the uniform Delaunay triangulation of planar regions and, in particular, on how one selects the positions of the vertices of the triangulation. We discuss a recently developed method, based on the centroidal Voronoi tessellation (CVT) concept, for effecting such triangulations and present two algorithms, including one new one, for CVT-based grid generation. We also compare several methods, including CVT-based methods, for triangulating planar domains. To this end, we define several quantitative measures of the quality of uniform grids. We then generate triangulations of several planar regions, including some having complexities that are representative of what one may encounter in practice. We subject the resulting grids to visual and quantitative comparisons and conclude that all the methods considered produce high-quality uniform grids and that the CVT-based grids are at least as good as any of the others.
Method of modifying a volume mesh using sheet extraction
Borden, Michael J.; Shepherd, Jason F.
2007-02-20
A method and machine-readable medium provide a technique to modify a hexahedral finite element volume mesh using dual generation and sheet extraction. After generating a dual of a volume stack (mesh), a predetermined algorithm may be followed to modify the volume mesh of hexahedral elements. The predetermined algorithm may include the steps of determining a sheet of hexahedral mesh elements, generating nodes for merging, and merging the nodes to delete the sheet of hexahedral mesh elements and modify the volume mesh.
International Nuclear Information System (INIS)
A high-precision simulation method for gas-liquid two-phase flows on unstructured meshes has been developed as a part of numerical studies on a gas entrainment phenomenon in the sodium-cooled fast reactor (JSFR). In this study, a two-dimensional unstructured adaptive mesh algorithm is developed because an adaptive mesh technique is necessary to simulate the local gas entrainment phenomenon accurately in large size JSFR. In a proposed two-dimensional adaptive mesh algorithm, each cell is isotropically subdivided to reduce distortions of the mesh. In addition, a connection cell is formed to eliminate the edge incompatibility between a refined and a non-refined cells. When forming connection cells, patterns of each connection cell is determined by subdivision condisions of neighboring cells. After checking the developed two-dimensional unstructured adaptive mesh manipulations (subdivision and merging of cells and construction of connection cells), the present adaptive mesh algorithm is verified by solving well-kwon driven cavity problem. As the result, the present unstructed adaptive mesh algorithm succeeds in reproducing vortical flow field in the cavity using relatively small cell number. (author)
Adaptive mesh refinement and automatic remeshing in crystal plasticity finite element simulations
International Nuclear Information System (INIS)
In finite element simulations dedicated to the modelling of microstructure evolution, the mesh has to be fine enough to: (i) accurately describe the geometry of the constituents; (ii) capture local strain gradients stemming from the heterogeneity in material properties. In this paper, 3D polycrystalline aggregates are discretized into unstructured meshes and a level set framework is used to represent the grain boundaries. The crystal plasticity finite element method is used to simulate the plastic deformation of these aggregates. A mesh sensitivity analysis based on the deformation energy distribution shows that the predictions are, on average, more sensitive near grain boundaries. An anisotropic mesh refinement strategy based on the level set description is introduced and it is shown that it offers a good compromise between accuracy requirements on the one hand and computation time on the other hand. As the aggregates deform, mesh distortion inevitably occurs and ultimately causes the breakdown of the simulations. An automatic remeshing tool is used to periodically reconstruct the mesh and appropriate transfer of state variables is performed. It is shown that the diffusion related to data transfer is not significant. Finally, remeshing is performed repeatedly in a highly resolved 500 grains polycrystal subjected to about 90% thickness reduction in rolling. The predicted texture is compared with the experimental data and with the predictions of a standard Taylor model
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.
Mesh Surgery for Anterior Vaginal Wall Prolapse: A Meta-analysis.
Juliato, Cássia Raquel Teatin; Santos Júnior, Luiz Carlos do; Haddad, Jorge Milhem; Castro, Rodrigo Aquino; Lima, Marcelo; Castro, Edilson Benedito de
2016-07-01
Purpose Pelvic organ prolapse (POP) is a major health issue worldwide, affecting 6-8% of women. The most affected site is the anterior vaginal wall. Multiple procedures and surgical techniques have been used, with or without the use of vaginal meshes, due to common treatment failure, reoperations, and complication rates in some studies. Methods Systematic review of the literature and meta-analysis regarding the use of vaginal mesh in anterior vaginal wall prolapse was performed. A total of 115 papers were retrieved after using the medical subject headings (MESH) terms: 'anterior pelvic organ prolapse OR cystocele AND surgery AND (mesh or colporrhaphy)' in the PubMed database. Exclusion criteria were: follow-up shorter than 1 year, use of biological or absorbable meshes, and inclusion of other vaginal wall prolapses. Studies were put in a data chart by two independent editors; results found in at least two studies were grouped for analysis. Results After the review of the titles by two independent editors, 70 studies were discarded, and after abstract assessment, 18 trials were eligible for full text screening. For final screening and meta-analysis, after applying the Jadad score (> 2), 12 studies were included. Objective cure was greater in the mesh surgery group (odds ratio [OR] = 1,28 [1,07-1,53]), which also had greater blood loss (mean deviation [MD] = 45,98 [9,72-82,25]), longer surgery time (MD = 15,08 [0,48-29,67]), but less prolapse recurrence (OR = 0,22 [01,3-0,38]). Dyspareunia, symptom resolution and reoperation rates were not statistically different between groups. Quality of life (QOL) assessment through the pelvic organ prolapse/urinary incontinence sexual questionnaire (PISQ-12), the pelvic floor distress inventory (PFDI-20), the pelvic floor impact questionnaire (PFIQ-7), and the perceived quality of life scale (PQOL) was not significantly different. Conclusions Anterior vaginal prolapse mesh surgery has greater anatomic
4D cone-beam CT reconstruction using multi-organ meshes for sliding motion modeling
Zhong, Zichun; Gu, Xuejun; Mao, Weihua; Wang, Jing
2016-02-01
A simultaneous motion estimation and image reconstruction (SMEIR) strategy was proposed for 4D cone-beam CT (4D-CBCT) reconstruction and showed excellent results in both phantom and lung cancer patient studies. In the original SMEIR algorithm, the deformation vector field (DVF) was defined on voxel grid and estimated by enforcing a global smoothness regularization term on the motion fields. The objective of this work is to improve the computation efficiency and motion estimation accuracy of SMEIR for 4D-CBCT through developing a multi-organ meshing model. Feature-based adaptive meshes were generated to reduce the number of unknowns in the DVF estimation and accurately capture the organ shapes and motion. Additionally, the discontinuity in the motion fields between different organs during respiration was explicitly considered in the multi-organ mesh model. This will help with the accurate visualization and motion estimation of the tumor on the organ boundaries in 4D-CBCT. To further improve the computational efficiency, a GPU-based parallel implementation was designed. The performance of the proposed algorithm was evaluated on a synthetic sliding motion phantom, a 4D NCAT phantom, and four lung cancer patients. The proposed multi-organ mesh based strategy outperformed the conventional Feldkamp-Davis-Kress, iterative total variation minimization, original SMEIR and single meshing method based on both qualitative and quantitative evaluations.
An adaptive mesh finite volume method for the Euler equations of gas dynamics
Mungkasi, Sudi
2016-06-01
The Euler equations have been used to model gas dynamics for decades. They consist of mathematical equations for the conservation of mass, momentum, and energy of the gas. For a large time value, the solution may contain discontinuities, even when the initial condition is smooth. A standard finite volume numerical method is not able to give accurate solutions to the Euler equations around discontinuities. Therefore we solve the Euler equations using an adaptive mesh finite volume method. In this paper, we present a new construction of the adaptive mesh finite volume method with an efficient computation of the refinement indicator. The adaptive method takes action automatically at around places having inaccurate solutions. Inaccurate solutions are reconstructed to reduce the error by refining the mesh locally up to a certain level. On the other hand, if the solution is already accurate, then the mesh is coarsened up to another certain level to minimize computational efforts. We implement the numerical entropy production as the mesh refinement indicator. As a test problem, we take the Sod shock tube problem. Numerical results show that the adaptive method is more promising than the standard one in solving the Euler equations of gas dynamics.
Anatomic consideration for preventive implantation.
Denissen, H W; Kalk, W; Veldhuis, H A; van Waas, M A
1993-01-01
The aim of preventive implant therapy is to prevent or delay loss of alveolar ridge bone mass. For use in an anatomic study of 60 mandibles, resorption of the alveolar ridge was classified into four preventive stages: (1) after extraction of teeth; (2) after initial resorption; (3) when the ridge has atrophied to a knife-edge shape; and (4) when only basal bone remains. Implantation in stage 3 necessitates removal of the knife-edge ridge to create space for cylindrical implants. Therefore, implantation in stage 2 is advocated to prevent the development of stage 3. The aim of implantation in stage 4 is to prevent total loss of function of the atrophic mandible. PMID:8359876
Polygonal Prism Mesh in the Viscous Layers for the Polyhedral Mesh Generator, PolyGen
International Nuclear Information System (INIS)
Polyhedral mesh has been known to have some benefits over the tetrahedral mesh. Efforts have been made to set up a polyhedral mesh generation system with open source programs SALOME and TetGen. The evaluation has shown that the polyhedral mesh generation system is promising. But it is necessary to extend the capability of the system to handle the viscous layers to be a generalized mesh generator. A brief review to the previous works on the mesh generation for the viscous layers will be made in section 2. Several challenging issues for the polygonal prism mesh generation will be discussed as well. The procedure to generate a polygonal prism mesh will be discussed in detail in section 3. Conclusion will be followed in section 4. A procedure to generate meshes in the viscous layers with PolyGen has been successfully designed. But more efforts have to be exercised to find the best way for the generating meshes for viscous layers. Using the extrusion direction of the STL data will the first of the trials in the near future
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.
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.
Evaluation of Different Meshing Techniques for the Case of a Stented Artery.
Lotfi, Azadeh; Simmons, Anne; Barber, Tracie
2016-03-01
The formation and progression of in-stent restenosis (ISR) in bifurcated vessels may vary depending on the technique used for stenting. This study evaluates the effect of a variety of mesh styles on the accuracy and reliability of computational fluid dynamics (CFD) models in predicting these regions, using an idealized stented nonbifurcated model. The wall shear stress (WSS) and the near-stent recirculating vortices are used as determinants. The meshes comprise unstructured tetrahedral and polyhedral elements. The effects of local refinement, as well as higher-order elements such as prismatic inflation layers and internal hexahedral core, have also been examined. The uncertainty associated with individual mesh style was assessed through verification of calculations using the grid convergence index (GCI) method. The results obtained show that the only condition which allows the reliable comparison of uncertainty estimation between different meshing styles is that the monotonic convergence of grid solutions is in the asymptotic range. Comparisons show the superiority of a flow-adaptive polyhedral mesh over the commonly used adaptive and nonadaptive tetrahedral meshes in terms of resolving the near-stent flow features, GCI value, and prediction of WSS. More accurate estimation of hemodynamic factors was obtained using higher-order elements, such as hexahedral or prismatic grids. Incorporating these higher-order elements, however, was shown to introduce some degrees of numerical diffusion at the transitional area between the two meshes, not necessarily translating into high GCI value. Our data also confirmed the key role of local refinement in improving the performance and accuracy of nonadaptive mesh in predicting flow parameters in models of stented artery. The results of this study can provide a guideline for modeling biofluid domain in complex bifurcated arteries stented in regards to various stenting techniques. PMID:26784359
Numerical simulation of H2/air detonation using unstructured mesh
Togashi, Fumiya; Löhner, Rainald; Tsuboi, Nobuyuki
2009-06-01
To explore the capability of unstructured mesh to simulate detonation wave propagation phenomena, numerical simulation of H2/air detonation using unstructured mesh was conducted. The unstructured mesh has several adv- antages such as easy mesh adaptation and flexibility to the complicated configurations. To examine the resolution dependency of the unstructured mesh, several simulations varying the mesh size were conducted and compared with a computed result using a structured mesh. The results show that the unstructured mesh solution captures the detailed structure of detonation wave, as well as the structured mesh solution. To capture the detailed detonation cell structure, the unstructured mesh simulations required at least twice, ideally 5times the resolution of structured mesh solution.
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....
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.
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.
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.
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.
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...
Bosmans, Lode; Valente, Giordano; Wesseling, Mariska; Van Campen, Anke; De Groote, Friedl; De Schutter, Joris; Jonkers, Ilse
2015-07-16
Scaled generic musculoskeletal models are commonly used to drive dynamic simulations of motions. It is however, acknowledged that not accounting for variability in musculoskeletal geometry and musculotendon parameters may confound the simulation results, even when analysing control subjects. This study documents the three-dimensional anatomical variability of musculotendon origins and insertions of 33 lower limb muscles determined based on magnetic resonance imaging in six subjects. This anatomical variability was compared to the musculotendon point location in a generic musculoskeletal model. Furthermore, the sensitivity of muscle forces during gait, calculated using static optimization, to perturbations of the musculotendon point location was analyzed with a generic model. More specific, a probabilistic approach was used: for each analyzed musculotendon point, the three-dimensional location was re-sampled with a uniform Latin hypercube method within the anatomical variability and the static optimization problem was then re-solved for all perturbations. We found that musculotendon point locations in the generic model showed only variable correspondences with the anatomical variability. The anatomical variability of musculotendon point location did affect the calculated muscle forces: muscles most sensitive to perturbations within the anatomical variability are iliacus and psoas. Perturbation of the gluteus medius anterior, iliacus and psoas induces the largest concomitant changes in muscle forces of the unperturbed muscles. Therefore, when creating subject-specific musculoskeletal models, these attachment points should be defined accurately. In addition, the size of the anatomical variability of the musculotendon point location was not related to the sensitivity of the calculated muscle forces. PMID:25979383
Automatic Assignment of Non-Leaf MeSH Terms to Biomedical Articles.
Kavuluru, Ramakanth; Rios, Anthony
2015-01-01
Assigning labels from a hierarchical vocabulary is a well known special case of multi-label classification, often modeled to maximize micro F1-score. However, building accurate binary classifiers for poorly performing labels in the hierarchy can improve both micro and macro F1-scores. In this paper, we propose and evaluate classification strategies involving descendant node instances to build better binary classifiers for non-leaf labels with the use-case of assigning Medical Subject Headings (MeSH) to biomedical articles. Librarians at the National Library of Medicine tag each biomedical article to be indexed by their PubMed information system with terms from the MeSH terminology, a biomedical conceptual hierarchy with over 27,000 terms. Human indexers look at each article's full text to assign a set of most suitable MeSH terms for indexing it. Several recent automated attempts focused on using the article title and abstract text to identify MeSH terms for the corresponding article. Despite these attempts, it is observed that assigning MeSH terms corresponding to certain non-leaf nodes of the MeSH hierarchy is particularly challenging. Non-leaf nodes are very important as they constitute one third of the total number of MeSH terms. Here, we demonstrate the effectiveness of exploiting training examples of descendant terms of non-leaf nodes in improving the performance of conventional classifiers for the corresponding non-leaf MeSH terms. Specifically, we focus on reducing the false positives (FPs) caused due to descendant instances in traditional classifiers. Our methods are able to achieve a relative improvement of 7.5% in macro-F1 score while also increasing the micro-F1 score by 1.6% for a set of 500 non-leaf terms in the MeSH hierarchy. These results strongly indicate the critical role of incorporating hierarchical information in MeSH term prediction. To our knowledge, our effort is the first to demonstrate the role of hierarchical information in improving
Doing the twist: diagonal meshes are isomorphic to twisted toroidal Meshes
Pearlmutter, Barak A
1996-01-01
We show that a k x n diagonal mesh is isomorphic to a n+k/2 x n+k/2 - nk/2 twisted toroidal mesh, i.e., a network similar to a standard n+k/2 x n-k/2 toroidal mesh, but with opposite handed twists of n-k/2 in the two directions, which results in a loss of (n-k/2)2 nodes.
Gamra: Simple Meshes for Complex Earthquakes
Landry, Walter; Barbot, Sylvain
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 discontinui...
MHD simulations on an unstructured mesh
International Nuclear Information System (INIS)
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....
Massively parallel computation on anisotropic meshes
Digonnet, Hugues; Silva, Luisa; Coupez, Thierry
2013-01-01
In this paper, we present developments done to obtain efficient parallel computations on supercomputers up to 8192 cores. While most massively parallel computation are shown using regular grid it is less common to see massively parallel computation using anisotropic adapted unstructured meshes. We will present here two mains components done to reach very large scale calculation up to 10 billions unknowns using a muligrid method over unstructured mesh running on 8192 cores. We firstly focus on...
Brain Morphometry Using Anatomical Magnetic Resonance Imaging
Bansal, Ravi; Gerber, Andrew J.; Peterson, Bradley S.
2008-01-01
The efficacy of anatomical magnetic resonance imaging (MRI) in studying the morphological features of various regions of the brain is described, also providing the steps used in the processing and studying of the images. The ability to correlate these features with several clinical and psychological measures can help in using anatomical MRI to…
Mesh geometry impact on Micromegas performance with an Exchangeable Mesh prototype
Kuger, F.; Bianco, M.; Iengo, P.; Sekhniaidze, G.; Veenhof, R.; Wotschack, J.
2016-07-01
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.
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)...
How to model wireless mesh networks topology
International Nuclear Information System (INIS)
The specification of network connectivity model or topology is the beginning of design and analysis in Computer Network researches. Wireless Mesh Networks is an autonomic network that is dynamically self-organised, self-configured while the mesh nodes establish automatic connectivity with the adjacent nodes in the relay network of wireless backbone routers. Researches in Wireless Mesh Networks range from node deployment to internetworking issues with sensor, Internet and cellular networks. These researches require modelling of relationships and interactions among nodes including technical characteristics of the links while satisfying the architectural requirements of the physical network. However, the existing topology generators model geographic topologies which constitute different architectures, thus may not be suitable in Wireless Mesh Networks scenarios. The existing methods of topology generation are explored, analysed and parameters for their characterisation are identified. Furthermore, an algorithm for the design of Wireless Mesh Networks topology based on square grid model is proposed in this paper. The performance of the topology generated is also evaluated. This research is particularly important in the generation of a close-to-real topology for ensuring relevance of design to the intended network and validity of results obtained in Wireless Mesh Networks researches
MHD simulations on an unstructured mesh
International Nuclear Information System (INIS)
We describe work on a full MHD code using an unstructured mesh. MH3D++ is an extension of the PPPL MH3D resistive full MHD code. MH3D++ replaces the structured mesh and finite difference / fourier discretization of MH3D with an unstructured mesh and finite element / fourier discretization. Low level routines which perform differential operations, solution of PDEs such as Poisson's equation, and graphics, are encapsulated in C++ objects to isolate the finite element operations from the higher level code. The high level code is the same, whether it is run in structured or unstructured mesh versions. This allows the unstructured mesh version to be benchmarked against the structured mesh version. As a preliminary example, disruptions in DIIID reverse shear equilibria are studied numerically with the MH3D++ code. Numerical equilibria were first produced starting with an EQDSK file containing equilibrium data of a DIII-D L-mode negative central shear discharge. Using these equilibria, the linearized equations are time advanced to get the toroidal mode number n = 1 linear growth rate and eigenmode, which is resistively unstable. The equilibrium and linear mode are used to initialize 3D nonlinear runs. An example shows poloidal slices of 3D pressure surfaces: initially, on the left, and at an intermediate time, on the right
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...
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.
Accurate Finite Difference Algorithms
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Recommendation for maximum allowable mesh size for plant combustion analyses with CFD codes
International Nuclear Information System (INIS)
Highlights: ► Used mesh size has to be small enough to resolve all pressure waves relevant for the structural response analyses. ► Maximum allowable mesh size for a combustion pressure load calculation decreases with increasing relevant natural frequency of the structure. ► Maximum allowable mesh size for a combustion pressure load calculation increases with increasing of the speed of the sound in the gas mixture. ► Maximum allowable mesh size can be calculated from the developed analytical formula. - Abstract: The selection of the maximum allowable mesh size for a fluid dynamic calculation with Computational Fluid Dynamic (CFD) codes is essential for the reliability of the results assuming suitable physical and numerical models are used. Calculations with CFD codes are necessary for the assessment of the consequences of pressure loads on containment structures due to possible hydrogen combustion in nuclear power plants in a severe accident and on piping system due to pressure wave propagation in case of a pipe break accident or fast closing of a valve in a pipe with forced flow. CFD simulations of the transport and distribution of the released hydrogen/steam as well as the possible combustion during the transient in the containment require an appropriate mesh size to resolve the relevant phenomena and loads. The determination of the mesh size has to take into account: •adequate delineation of the containment geometry for accurate hydrogen distribution calculations, •sufficient conservative resolution of the combustion phenomena for the determination of pressure wave propagation and pressure loads, •no loss of pressure wave loads with relevant frequencies for the structural response analysis of the containment during the combustion calculation. In this paper, it is found that the accuracy of the calculated pressure wave associated with its frequency depends on the mesh size and a simple and easily useable analytical formula for the determination of
Recommendation for maximum allowable mesh size for plant combustion analyses with CFD codes
Energy Technology Data Exchange (ETDEWEB)
Movahed-Shariat-Panahi, M.A., E-mail: Mohammad-Ali.Movahed@areva.com [AREVA GmbH Offenbach (Germany)
2012-12-15
Highlights: Black-Right-Pointing-Pointer Used mesh size has to be small enough to resolve all pressure waves relevant for the structural response analyses. Black-Right-Pointing-Pointer Maximum allowable mesh size for a combustion pressure load calculation decreases with increasing relevant natural frequency of the structure. Black-Right-Pointing-Pointer Maximum allowable mesh size for a combustion pressure load calculation increases with increasing of the speed of the sound in the gas mixture. Black-Right-Pointing-Pointer Maximum allowable mesh size can be calculated from the developed analytical formula. - Abstract: The selection of the maximum allowable mesh size for a fluid dynamic calculation with Computational Fluid Dynamic (CFD) codes is essential for the reliability of the results assuming suitable physical and numerical models are used. Calculations with CFD codes are necessary for the assessment of the consequences of pressure loads on containment structures due to possible hydrogen combustion in nuclear power plants in a severe accident and on piping system due to pressure wave propagation in case of a pipe break accident or fast closing of a valve in a pipe with forced flow. CFD simulations of the transport and distribution of the released hydrogen/steam as well as the possible combustion during the transient in the containment require an appropriate mesh size to resolve the relevant phenomena and loads. The determination of the mesh size has to take into account: Bullet adequate delineation of the containment geometry for accurate hydrogen distribution calculations, Bullet sufficient conservative resolution of the combustion phenomena for the determination of pressure wave propagation and pressure loads, Bullet no loss of pressure wave loads with relevant frequencies for the structural response analysis of the containment during the combustion calculation. In this paper, it is found that the accuracy of the calculated pressure wave associated with its
International Nuclear Information System (INIS)
The existing studies concerning image-free navigated implantation of hip resurfacing arthroplasty are based on analysis of the accuracy of conventional biplane radiography. Studies have shown that these measurements in biplane radiography are imprecise and that precision is improved by use of three-dimensional (3D) computer tomography (CT) scans. To date, the accuracy of image-free navigation devices for hip resurfacing has not been investigated using CT scans, and anteversion accuracy has not been assessed at all. Furthermore, no study has tested the reliability of the navigation software concerning the automatically calculated implant position. The purpose of our study was to analyze the accuracy of varus-valgus and anteversion using an image-free hip resurfacing navigation device. The reliability of the software-calculated implant position was also determined. A total of 32 femoral hip resurfacing components were implanted on embalmed human femurs using an image-free navigation device. In all, 16 prostheses were implanted with the proposed position generated by the navigation software; the 16 prostheses were inserted in an optimized valgus position. A 3D CT scan was undertaken before and after operation. The difference between the measured and planned varus-valgus angle averaged 1 deg (mean±standard deviation (SD): group I, 1 deg±2 deg; group II, 1 deg±1 deg). The mean±SD difference between femoral neck anteversion and anteversion of the implant was 4 deg (group I, 4 deg±4 deg; group II, 4 deg±3 deg). The software-calculated implant position differed 7 deg±8 deg from the measured neck-shaft angle. These measured accuracies did not differ significantly between the two groups. Our study proved the high accuracy of the navigation device concerning the most important biomechanical factor: the varus-valgus angle. The software calculation of the proposed implant position has been shown to be inaccurate and needs improvement. Hence, manual adjustment of the implant position in the software-planning step is frequently required. (author)
Relativistic Vlasov-Maxwell modelling using finite volumes and adaptive mesh refinement
Wettervik, Benjamin Svedung; Siminos, Evangelos; Fülöp, Tünde
2016-01-01
The dynamics of collisionless plasmas can be modelled by the Vlasov-Maxwell system of equations. An Eulerian approach is needed to accurately describe processes that are governed by high energy tails in the distribution function, but is of limited efficiency for high dimensional problems. The use of an adaptive mesh can reduce the scaling of the computational cost with the dimension of the problem. Here, we present a relativistic Eulerian Vlasov-Maxwell solver with block-structured adaptive mesh refinement in one spatial and one momentum dimension. The discretization of the Vlasov equation is based on a high-order finite volume method. A flux corrected transport algorithm is applied to limit spurious oscillations and ensure the physical character of the distribution function. We demonstrate a speed-up by a factor of five, because of the use of an adaptive mesh, in a typical scenario involving laser-plasma interaction in the self-induced transparency regime.
Detecting Translation Errors in CAD Surfaces and Preparing Geometries for Mesh Generation
Energy Technology Data Exchange (ETDEWEB)
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.
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
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...
Ultrasound appearances after mesh implantation-evidence of mesh contraction or folding?
Czech Academy of Sciences Publication Activity Database
Švabík, K.; Martan, A.; Mašata, J.; Haddad El, R.; Hubka, P.; Pavlíková, Markéta
2011-01-01
Roč. 22, č. 5 (2011), s. 529-533. ISSN 0937-3462 Grant ostatní: GA MZd(CZ) NR9216 Institutional research plan: CEZ:AV0Z10300504 Keywords : prolift anterior * mesh shrinking * mesh retraction * vaginal ultrasound * vaginal surgery Subject RIV: FK - Gynaecology, Childbirth Impact factor: 1.832, year: 2011
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. PMID:26577253
Cartesian anisotropic mesh adaptation for compressible flow
International Nuclear Information System (INIS)
Simulating transient compressible flows involving shock waves presents challenges to the CFD practitioner in terms of the mesh quality required to resolve discontinuities and prevent smearing. This paper discusses a novel two-dimensional Cartesian anisotropic mesh adaptation technique implemented for compressible flow. This technique, developed for laminar flow by Ham, Lien and Strong, is efficient because it refines and coarsens cells using criteria that consider the solution in each of the cardinal directions separately. In this paper the method will be applied to compressible flow. The procedure shows promise in its ability to deliver good quality solutions while achieving computational savings. The convection scheme used is the Advective Upstream Splitting Method (Plus), and the refinement/ coarsening criteria are based on work done by Ham et al. Transient shock wave diffraction over a backward step and shock reflection over a forward step are considered as test cases because they demonstrate that the quality of the solution can be maintained as the mesh is refined and coarsened in time. The data structure is explained in relation to the computational mesh, and the object-oriented design and implementation of the code is presented. Refinement and coarsening algorithms are outlined. Computational savings over uniform and isotropic mesh approaches are shown to be significant. (author)
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.
Verification of Unstructured Mesh Capabilities in MCNP6 for Reactor Physics Problems
Energy Technology Data Exchange (ETDEWEB)
Burke, Timothy P. [Los Alamos National Laboratory; Martz, Roger L. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory
2012-08-22
New unstructured mesh capabilities in MCNP6 (developmental version during summer 2012) show potential for conducting multi-physics analyses by coupling MCNP to a finite element solver such as Abaqus/CAE[2]. Before these new capabilities can be utilized, the ability of MCNP to accurately estimate eigenvalues and pin powers using an unstructured mesh must first be verified. Previous work to verify the unstructured mesh capabilities in MCNP was accomplished using the Godiva sphere [1], and this work attempts to build on that. To accomplish this, a criticality benchmark and a fuel assembly benchmark were used for calculations in MCNP using both the Constructive Solid Geometry (CSG) native to MCNP and the unstructured mesh geometry generated using Abaqus/CAE. The Big Ten criticality benchmark [3] was modeled due to its geometry being similar to that of a reactor fuel pin. The C5G7 3-D Mixed Oxide (MOX) Fuel Assembly Benchmark [4] was modeled to test the unstructured mesh capabilities on a reactor-type problem.
Directory of Open Access Journals (Sweden)
Jose Tadeu Nunes Tamanini
2013-07-01
Full Text Available Objective To compare the use of polypropylene mesh (PM and the traditional anterior vaginal wall colporraphy in women with anterior vaginal wall prolapse (AVWP using objective and subjective tests and evaluation of quality of life (QoL. Materials and Methods One hundred women were randomly distributed in two preoperatory groups. The first group (mesh (n = 45 received a PM implant and the control group (n = 55 was submitted to traditional colporraphy. Postoperatory follow-up was done after 12 months. The primary objective was the correction of the Ba point ≤ -2 POP-Q (Pelvic Organ Prolapse Quantification System and the secondary objective was the improvement of vaginal symptoms and QoL through ICIQ-VS (International Consultation on Incontinence Questionnaire - Vaginal Symptoms. Complications related to the use of PM or not were also described. Results There was a significant difference between all POP-Q measures of pre- and postoperatory periods of each group in particular. There was a significant difference of the Ba point of the postoperatory period between the Mesh and Control group. The mean of Ba point in the Mesh group was statistically lower than of the Control group, depicting the better anatomical result of the first group. Both techniques improved vaginal symptoms and QoL. The most frequent complication of the Mesh group was prepubic hematoma in the perioperative period. In 9.3% of the cases treated with mesh it was observed PM exposition at the anterior vaginal wall after 12 months, being most of them treated clinically. Conclusion The treatment of AVWP significantly improved the Ba point in the Mesh group in comparison to the Control group. There were no differences of the vaginal symptoms and QoL between the two groups after 12 months. There were few and low grade complications on both groups.
Interacting with image hierarchies for fast and accurate object segmentation
Beard, David V.; Eberly, David H.; Hemminger, Bradley M.; Pizer, Stephen M.; Faith, R. E.; Kurak, Charles; Livingston, Mark
1994-05-01
Object definition is an increasingly important area of medical image research. Accurate and fairly rapid object definition is essential for measuring the size and, perhaps more importantly, the change in size of anatomical objects such as kidneys and tumors. Rapid and fairly accurate object definition is essential for 3D real-time visualization including both surgery planning and Radiation oncology treatment planning. One approach to object definition involves the use of 3D image hierarchies, such as Eberly's Ridge Flow. However, the image hierarchy segmentation approach requires user interaction in selecting regions and subtrees. Further, visualizing and comprehending the anatomy and the selected portions of the hierarchy can be problematic. In this paper we will describe the Magic Crayon tool which allows a user to define rapidly and accurately various anatomical objects by interacting with image hierarchies such as those generated with Eberly's Ridge Flow algorithm as well as other 3D image hierarchies. Preliminary results suggest that fairly complex anatomical objects can be segmented in under a minute with sufficient accuracy for 3D surgery planning, 3D radiation oncology treatment planning, and similar applications. Potential modifications to the approach for improved accuracy are summarized.
International Nuclear Information System (INIS)
Hexagonal coarse mesh methods in three dimensional diffusion theory programme have been examined for calculating in detail nuclear characteristics of fast breeder reactors composed of hexagonal fuel assemblies, comparing with more accurate triangular fine mesh method. The fast breeder reactors considered here are LMFBRs with different core configurations including heterogeneous core and GCFRs in different burnup states. The nuclear characteristics investigated in the comparative study are effective multiplication factor, power and neutron flux distributions, breeding ratio, reactivity effects and control rod reactivity worth. The comparative study indicates that the conventional coarse mesh method is not adeguate to detailed evaluation on nuclear characteristics of fast breeder reactors, and that the improved coarse mesh method developed by T. Takeda et al. is very useful for this purpose, though some problems exists in evaluation of power distribution and breeding ratio of the extremely composite fast breeder reactors, such as the radially heterogeneous core LMFBR. (author)
Interactive graphical tools for three-dimensional mesh redistribution
Energy Technology Data Exchange (ETDEWEB)
Dobbs, L.A.
1996-03-01
Three-dimensional meshes modeling nonlinear problems such as sheet metal forming, metal forging, heat transfer during welding, the propagation of microwaves through gases, and automobile crashes require highly refined meshes in local areas to accurately represent areas of high curvature, stress, and strain. These locally refined areas develop late in the simulation and/or move during the course of the simulation, thus making it difficult to predict their exact location. This thesis is a systematic study of new tools scientists can use with redistribution algorithms to enhance the solution results and reduce the time to build, solve, and analyze nonlinear finite element problems. Participatory design techniques including Contextual Inquiry and Design were used to study and analyze the process of solving such problems. This study and analysis led to the in-depth understanding of the types of interactions performed by FEM scientists. Based on this understanding, a prototype tool was designed to support these interactions. Scientists participated in evaluating the design as well as the implementation of the prototype tool. The study, analysis, prototype tool design, and the results of the evaluation of the prototype tool are described in this thesis.
Automatic Tooth Segmentation of Dental Mesh Based on Harmonic Fields.
Liao, Sheng-hui; Liu, Shi-jian; Zou, Bei-ji; Ding, Xi; Liang, Ye; Huang, Jun-hui
2015-01-01
An important preprocess in computer-aided orthodontics is to segment teeth from the dental models accurately, which should involve manual interactions as few as possible. But fully automatic partition of all teeth is not a trivial task, since teeth occur in different shapes and their arrangements vary substantially from one individual to another. The difficulty is exacerbated when severe teeth malocclusion and crowding problems occur, which is a common occurrence in clinical cases. Most published methods in this area either are inaccurate or require lots of manual interactions. Motivated by the state-of-the-art general mesh segmentation methods that adopted the theory of harmonic field to detect partition boundaries, this paper proposes a novel, dental-targeted segmentation framework for dental meshes. With a specially designed weighting scheme and a strategy of a priori knowledge to guide the assignment of harmonic constraints, this method can identify teeth partition boundaries effectively. Extensive experiments and quantitative analysis demonstrate that the proposed method is able to partition high-quality teeth automatically with robustness and efficiency. PMID:26413507
Automatic Tooth Segmentation of Dental Mesh Based on Harmonic Fields
Directory of Open Access Journals (Sweden)
Sheng-hui Liao
2015-01-01
Full Text Available An important preprocess in computer-aided orthodontics is to segment teeth from the dental models accurately, which should involve manual interactions as few as possible. But fully automatic partition of all teeth is not a trivial task, since teeth occur in different shapes and their arrangements vary substantially from one individual to another. The difficulty is exacerbated when severe teeth malocclusion and crowding problems occur, which is a common occurrence in clinical cases. Most published methods in this area either are inaccurate or require lots of manual interactions. Motivated by the state-of-the-art general mesh segmentation methods that adopted the theory of harmonic field to detect partition boundaries, this paper proposes a novel, dental-targeted segmentation framework for dental meshes. With a specially designed weighting scheme and a strategy of a priori knowledge to guide the assignment of harmonic constraints, this method can identify teeth partition boundaries effectively. Extensive experiments and quantitative analysis demonstrate that the proposed method is able to partition high-quality teeth automatically with robustness and efficiency.
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.
Ultrasound Anatomical Visualization of the rabbit liver
Kamelia Dimcheva Stamatova-Yovcheva; Rosen Dimitrov; David Yovchev; Krassimira Uzunova; Rumen Binev
2014-01-01
The topic was to investigate the anatomical features of the rabbit liver by two- and three-dimensional ultrasonography. Eighteen sexually mature healthy clinically New Zealand rabbits aged eight months were studied. Two-dimensional ultarsonographic anatomical image of the rabbit liver presented it in the cranial abdominal region as a relatively hypoechoic finding. Its contours were regular and in close contact with the hyperechoic diaphragm. Liver parenchyma was heterogeneous. The gall bladde...
Cardiovascular and lung mesh generation based on centerlines.
Marchandise, E; Geuzaine, C; Remacle, J F
2013-06-01
We present a fully automatic procedure for the mesh generation of tubular geometries such as blood vessels or airways. The procedure is implemented in the open-source Gmsh software and relies on a centerline description of the input geometry. The presented method can generate different type of meshes: isotropic tetrahedral meshes, anisotropic tetrahedral meshes, and mixed hexahedral/tetrahedral meshes. Additionally, a multiple layered arterial wall can be generated with a variable thickness. All the generated meshes rely on a mesh size field and a mesh metric that is based on centerline descriptions, namely the distance to the centerlines and a local reference system based on the tangent and the normal directions to the centerlines. Different examples show that the proposed method is very efficient and robust and leads to high quality computational meshes. PMID:23606344
Stochastic domain decomposition for time dependent adaptive mesh generation
Bihlo, Alexander; Walsh, Emily J
2015-01-01
The efficient generation of meshes is an important component in the numerical solution of problems in physics and engineering. Of interest are situations where global mesh quality and a tight coupling to the solution of the physical partial differential equation (PDE) is important. We consider parabolic PDE mesh generation and present a method for the construction of adaptive meshes in two spatial dimensions using stochastic domain decomposition that is suitable for an implementation in a multi- or many-core environment. Methods for mesh generation on periodic domains are also provided. The mesh generator is coupled to a time dependent physical PDE and the system is evolved using an alternating solution procedure. The method uses the stochastic representation of the exact solution of a parabolic linear mesh generator to find the location of an adaptive mesh along the (artificial) subdomain interfaces. The deterministic evaluation of the mesh over each subdomain can then be obtained completely independently us...
[Establishment of anatomical terminology in Japan].
Shimada, Kazuyuki
2008-12-01
The history of anatomical terminology in Japan began with the publication of Waran Naikei Ihan-teimŏ in 1805 and Chŏtei Kaitai Shinsho in 1826. Although the establishment of Japanese anatomical terminology became necessary during the Meiji era when many western anatomy books imported into Janan were translated, such terminology was not unified during this period and varied among translators. In 1871, Tsukumo Ono's Kaibŏgaku Gosen was published by the Ministry of Education. Although this book is considered to be the first anatomical glossary terms in Japan, its contents were incomplete. Overseas, the German Anatomical Society established a unified anatomical terminology in 1895 called the Basle Nomina Anatomica (B.N.A.). Based on this development, Kaibŏgaku Meishŭ which follows the BNA, by Buntarŏ Suzuki was published in 1905. With the subsequent establishment in 1935 of Jena Nomina Anatomica (J.N.A.), the unification of anatomical terminology was also accelerated in Japan, leading to the further development of terminology. PMID:19108488
MUSIC: a mesh-unrestricted simulation code
International Nuclear Information System (INIS)
A general formalism to solve the G-group neutron diffusion equation is described. The G-group flux is represented by complementing an ''asymptotic'' mode with (G-1) ''transient'' modes. A particular reduction-to-one-group technique gives a high computational efficiency. MUSIC, a 2-group code using the above formalism, is presented. MUSIC is demonstrated on a fine-mesh calculation and on 2 coarse-mesh core calculations: a heavy-water reactor (HWR) problem and the 2-D lightwater reactor (LWR) IAEA benchmark. Comparison is made to finite-difference results
Multigrid solution strategies for adaptive meshing problems
Mavriplis, Dimitri J.
1995-01-01
This paper discusses the issues which arise when combining multigrid strategies with adaptive meshing techniques for solving steady-state problems on unstructured meshes. A basic strategy is described, and demonstrated by solving several inviscid and viscous flow cases. Potential inefficiencies in this basic strategy are exposed, and various alternate approaches are discussed, some of which are demonstrated with an example. Although each particular approach exhibits certain advantages, all methods have particular drawbacks, and the formulation of a completely optimal strategy is considered to be an open problem.
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.
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.
Flow Simulation in Engine Cylinder with Spring Mesh
Directory of Open Access Journals (Sweden)
M. H. Shojaeefard
2008-01-01
Full Text Available This investigation presents results from numerical simulation of the air flow in Spark Ignition Engine (SI engine cylinder. Accurate modeling of the flow in cylinder is a key part of successful combustion simulation. The most usual numerical method in Computational Fluid Dynamics (CFD is finite volume. In this investigation an important, common fluid flow patterns in CFD simulations, namely, Tumble motion typical in automotive engines and RNG k-ε turbulence model were used. The air flow in a two-valve engine cylinder during 720 degree of crank angle was investigated by using a CFD code which is basis on finite volume and codes which were written in visual C++ environment. Dynamic Mesh and Moving Boundary capability were used for this model. The comparison results with previous researches results, Kiva-3v and PIV experimental, show good agreement.
Local mesh refinement for incompressible fluid flow with free surfaces
Energy Technology Data Exchange (ETDEWEB)
Terasaka, H.; Kajiwara, H.; Ogura, K. [Tokyo Electric Power Company (Japan)] [and others
1995-09-01
A new local mesh refinement (LMR) technique has been developed and applied to incompressible fluid flows with free surface boundaries. The LMR method embeds patches of fine grid in arbitrary regions of interest. Hence, more accurate solutions can be obtained with a lower number of computational cells. This method is very suitable for the simulation of free surface movements because free surface flow problems generally require a finer computational grid to obtain adequate results. By using this technique, one can place finer grids only near the surfaces, and therefore greatly reduce the total number of cells and computational costs. This paper introduces LMR3D, a three-dimensional incompressible flow analysis code. Numerical examples calculated with the code demonstrate well the advantages of the LMR method.
Directory of Open Access Journals (Sweden)
Ting-Chen Chang
2015-01-01
Full Text Available Objective. To evaluate the clinical outcomes and urodynamic effects of tailored anterior transvaginal mesh surgery (ATVM and tailored posterior transvaginal mesh surgery (PTVM. Methods. We developed ATVM for the simultaneous correction of cystocele and stress urinary incontinence and PTVM for the simultaneous correction of enterocoele, uterine prolapse, vaginal stump prolapse, and rectocele. Results. A total of 104 women enrolled. The median postsurgical follow-up was 25.5 months. The anatomic cure rate was 98.1% (102/104. Fifty-eight patients underwent urodynamic studies before and after surgeries. The pad weight decreased from 29.3 ± 43.1 to 6.4 ± 20.9 g at 3 months. Among the 20 patients with ATVM, 13 patients had objective stress urinary incontinence (SUI at baseline while 8 patients came to have no demonstrated SUI (NDSUI, and 2 improved after surgery. Among the 38 patients who underwent ATVM and PTVM, 24 had objective SUI at baseline while 18 came to have NDSUI, and 2 improved after surgery. Mesh extrusion (n = 4, vaginal hematoma (n = 3, and voiding difficulty (n = 2 were noted postoperatively. Quality of life was substantially improved. Conclusions. Our findings document the advantages of these two novel pelvic reconstructive surgeries for pelvic organ prolapse, which had a positive impact on quality of life. ATVM surgery additionally provided an anti-incontinence effect. This clinical trial is registered at ClinicalTrials.gov (NCT02178735.
Energy Technology Data Exchange (ETDEWEB)
Van de Velde, Joris, E-mail: joris.vandevelde@ugent.be [Department of Anatomy, Ghent University, Ghent (Belgium); Department of Radiotherapy, Ghent University, Ghent (Belgium); Audenaert, Emmanuel [Department of Physical Medicine and Orthopedic Surgery, Ghent University, Ghent (Belgium); Speleers, Bruno; Vercauteren, Tom; Mulliez, Thomas [Department of Radiotherapy, Ghent University, Ghent (Belgium); Vandemaele, Pieter; Achten, Eric [Department of Radiology, Ghent University, Ghent (Belgium); Kerckaert, Ingrid; D' Herde, Katharina [Department of Anatomy, Ghent University, Ghent (Belgium); De Neve, Wilfried [Department of Radiotherapy, Ghent University, Ghent (Belgium); Van Hoof, Tom [Department of Anatomy, Ghent University, Ghent (Belgium)
2013-11-15
Purpose: To develop contouring guidelines for the brachial plexus (BP) using anatomically validated cadaver datasets. Magnetic resonance imaging (MRI) and computed tomography (CT) were used to obtain detailed visualizations of the BP region, with the goal of achieving maximal inclusion of the actual BP in a small contoured volume while also accommodating for anatomic variations. Methods and Materials: CT and MRI were obtained for 8 cadavers positioned for intensity modulated radiation therapy. 3-dimensional reconstructions of soft tissue (from MRI) and bone (from CT) were combined to create 8 separate enhanced CT project files. Dissection of the corresponding cadavers anatomically validated the reconstructions created. Seven enhanced CT project files were then automatically fitted, separately in different regions, to obtain a single dataset of superimposed BP regions that incorporated anatomic variations. From this dataset, improved BP contouring guidelines were developed. These guidelines were then applied to the 7 original CT project files and also to 1 additional file, left out from the superimposing procedure. The percentage of BP inclusion was compared with the published guidelines. Results: The anatomic validation procedure showed a high level of conformity for the BP regions examined between the 3-dimensional reconstructions generated and the dissected counterparts. Accurate and detailed BP contouring guidelines were developed, which provided corresponding guidance for each level in a clinical dataset. An average margin of 4.7 mm around the anatomically validated BP contour is sufficient to accommodate for anatomic variations. Using the new guidelines, 100% inclusion of the BP was achieved, compared with a mean inclusion of 37.75% when published guidelines were applied. Conclusion: Improved guidelines for BP delineation were developed using combined MRI and CT imaging with validation by anatomic dissection.
International Nuclear Information System (INIS)
Purpose: To develop contouring guidelines for the brachial plexus (BP) using anatomically validated cadaver datasets. Magnetic resonance imaging (MRI) and computed tomography (CT) were used to obtain detailed visualizations of the BP region, with the goal of achieving maximal inclusion of the actual BP in a small contoured volume while also accommodating for anatomic variations. Methods and Materials: CT and MRI were obtained for 8 cadavers positioned for intensity modulated radiation therapy. 3-dimensional reconstructions of soft tissue (from MRI) and bone (from CT) were combined to create 8 separate enhanced CT project files. Dissection of the corresponding cadavers anatomically validated the reconstructions created. Seven enhanced CT project files were then automatically fitted, separately in different regions, to obtain a single dataset of superimposed BP regions that incorporated anatomic variations. From this dataset, improved BP contouring guidelines were developed. These guidelines were then applied to the 7 original CT project files and also to 1 additional file, left out from the superimposing procedure. The percentage of BP inclusion was compared with the published guidelines. Results: The anatomic validation procedure showed a high level of conformity for the BP regions examined between the 3-dimensional reconstructions generated and the dissected counterparts. Accurate and detailed BP contouring guidelines were developed, which provided corresponding guidance for each level in a clinical dataset. An average margin of 4.7 mm around the anatomically validated BP contour is sufficient to accommodate for anatomic variations. Using the new guidelines, 100% inclusion of the BP was achieved, compared with a mean inclusion of 37.75% when published guidelines were applied. Conclusion: Improved guidelines for BP delineation were developed using combined MRI and CT imaging with validation by anatomic dissection
Laparoscopic preperitoneal mesh repair using a novel self-adhesive mesh
Nik Kosai; Paul Anthony Sutton; Jonathan Evans; Joseph Varghese
2011-01-01
Prosthetic mesh is now used routinely in inguinal hernia repairs, although its fixation is thought to be a potential cause of chronic groin pain. The Parietene ProGrip™ (TYCO Healthcare) mesh, which is semi-resorbable and incorporates self-fixing properties, has been shown to provide satisfactory repair in open surgery. We describe the use of this mesh in TAPP hernia repair, which has not previously been reported in the literature. A prospective study of 29 patients showed a mean operative ti...
Performance of the hybrid wireless mesh protocol for wireless mesh networks
DEFF Research Database (Denmark)
Boye, Magnus; Staalhagen, Lars
2010-01-01
Wireless mesh networks offer a new way of providing end-user access and deploying network infrastructure. Though mesh networks offer a price competitive solution to wired networks, they also come with a set of new challenges such as optimal path selection, channel utilization, and load balancing....... These challenges must first be overcome before satisfactory network stability and throughput can be achieved. This paper studies the performance of the Hybrid Wireless Mesh Protocol, the proposed routing protocol for the upcoming IEEE 802.11s standard. HWMP supports two modes of path selection: reactive...
Institute of Scientific and Technical Information of China (English)
Tomosato Takada; Kazuo Kashiyama
2008-01-01
This paper presents an urban modeling system using CAD/GIS data for atmosphere environ- mental simulation, such as wind flow and contaminant spread in urban area. The CAD data is used for the shape modeling for the high-storied buildings and civil structures with complicated shape since the data for that is not included in the 3D-GIS data accurately. The unstructured mesh based on the tetrahedron element is employed in order to express the urban structures with complicated shape accurately. It is difficult to un- derstand the quality of shape model and mesh by the conventional visualization technique. In this paper, the stereoscopic visualization using virtual reality (VR) technology is employed for the vedfication of the quality of shape model and mesh. The present system is applied to the atmosphere environmental simulation in ur- ban area and is shown to be an useful planning and design tool to investigate the atmosphere environmental problem.
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
A semi-automated vertical feature terrain extraction algorithm is described and applied to a two-dimensional, depth-integrated, shallow water equation inundation model. The extracted features describe what are commonly sub-mesh scale elevation details (ridge and valleys), which may be ignored in standard practice because adequate mesh resolution cannot be afforded. The extraction algorithm is semi-automated, requires minimal human intervention, and is reproducible. A lidar-derived digital elevation model (DEM) of coastal Mississippi and Alabama serves as the source data for the vertical feature extraction. Unstructured mesh nodes and element edges are aligned to the vertical features and an interpolation algorithm aimed at minimizing topographic elevation error assigns elevations to mesh nodes via the DEM. The end result is a mesh that accurately represents the bare earth surface as derived from lidar with element resolution in the floodplain ranging from 15 m to 200 m. To examine the influence of the inclusion of vertical features on overland flooding, two additional meshes were developed, one without crest elevations of the features and another with vertical features withheld. All three meshes were incorporated into a SWAN+ADCIRC model simulation of Hurricane Katrina. Each of the three models resulted in similar validation statistics when compared to observed time-series water levels at gages and post-storm collected high water marks. Simulated water level peaks yielded an R2 of 0.97 and upper and lower 95% confidence interval of ∼ ± 0.60 m. From the validation at the gages and HWM locations, it was not clear which of the three model experiments performed best in terms of accuracy. Examination of inundation extent among the three model results were compared to debris lines derived from NOAA post-event aerial imagery, and the mesh including vertical features showed higher accuracy. The comparison of model results to debris lines demonstrates that additional
Development of 5- and 10-year-old pediatric phantoms based on polygon mesh surfaces
International Nuclear Information System (INIS)
Purpose: The purpose of this study is the development of reference pediatric phantoms for 5- and 10-year-old children to be used for the calculation of organ and tissue equivalent doses in radiation protection. Methods: The study proposes a method for developing anatomically highly sophisticated pediatric phantoms without using medical images. The 5- and 10-year-old male and female phantoms presented here were developed using 3D modeling software applied to anatomical information taken from atlases and textbooks. The method uses polygon mesh surfaces to model body contours, the shape of organs as well as their positions, and orientations in the human body. Organ and tissue masses comply with the corresponding data given by the International Commission on Radiological Protection (ICRP) for the 5- and 10-year-old reference children. Bones were segmented into cortical bone, spongiosa, medullary marrow, and cartilage to allow for the use of micro computer tomographic (μCT) images of trabecular bone for skeletal dosimetry. Results: The four phantoms, a male and a female for each age, and their organs are presented in 3D images and their organ and tissue masses in tables which show the compliance of the ICRP reference values. Dosimetric data, calculated for the reference pediatric phantoms by Monte Carlo methods were compared with corresponding data from adult mesh phantoms and pediatric stylized phantoms. The comparisons show reasonable agreement if the anatomical differences between the phantoms are properly taken into account. Conclusions: Pediatric phantoms were developed without using medical images of patients or volunteers for the first time. The models are reference phantoms, suitable for regulatory dosimetry, however, the 3D modeling method can also be applied to medical images to develop patient-specific phantoms.
Development of 5- and 10-year-old pediatric phantoms based on polygon mesh surfaces
Energy Technology Data Exchange (ETDEWEB)
Melo Lima, V. J. de; Cassola, V. F.; Kramer, R.; Oliveira Lira, C. A. B. de; Khoury, H. J.; Vieira, J. W. [Department of Anatomy, Federal University of Pernambuco, Avenida Professor Moraes Rego 1235, CEP 50670-901, Recife, Pernambuco (Brazil); Department of Nuclear Energy, Federal University of Pernambuco, Avenida Professor Luiz Freire 1000, CEP 50740-540, Recife, Pernambuco (Brazil); Federal Institute of Education, Science and Technology of Pernambuco, Avenida Professor Luiz Freire 500, CEP 50740-540, Recife, Pernambuco, Brazil and Polytechnic School of Pernambuco, University of Pernambuco, Rua Benfica 455, CEP 50751-460, Recife, Pernambuco (Brazil)
2011-08-15
Purpose: The purpose of this study is the development of reference pediatric phantoms for 5- and 10-year-old children to be used for the calculation of organ and tissue equivalent doses in radiation protection. Methods: The study proposes a method for developing anatomically highly sophisticated pediatric phantoms without using medical images. The 5- and 10-year-old male and female phantoms presented here were developed using 3D modeling software applied to anatomical information taken from atlases and textbooks. The method uses polygon mesh surfaces to model body contours, the shape of organs as well as their positions, and orientations in the human body. Organ and tissue masses comply with the corresponding data given by the International Commission on Radiological Protection (ICRP) for the 5- and 10-year-old reference children. Bones were segmented into cortical bone, spongiosa, medullary marrow, and cartilage to allow for the use of micro computer tomographic ({mu}CT) images of trabecular bone for skeletal dosimetry. Results: The four phantoms, a male and a female for each age, and their organs are presented in 3D images and their organ and tissue masses in tables which show the compliance of the ICRP reference values. Dosimetric data, calculated for the reference pediatric phantoms by Monte Carlo methods were compared with corresponding data from adult mesh phantoms and pediatric stylized phantoms. The comparisons show reasonable agreement if the anatomical differences between the phantoms are properly taken into account. Conclusions: Pediatric phantoms were developed without using medical images of patients or volunteers for the first time. The models are reference phantoms, suitable for regulatory dosimetry, however, the 3D modeling method can also be applied to medical images to develop patient-specific phantoms.
Highly Symmetric and Congruently Tiled Meshes for Shells and Domes
Rasheed, Muhibur; Bajaj, Chandrajit
2016-01-01
We describe the generation of all possible shell and dome shapes that can be uniquely meshed (tiled) using a single type of mesh face (tile), and following a single meshing (tiling) rule that governs the mesh (tile) arrangement with maximal vertex, edge and face symmetries. Such tiling arrangements or congruently tiled meshed shapes, are frequently found in chemical forms (fullerenes or Bucky balls, crystals, quasi-crystals, virus nano shells or capsids), and synthetic shapes (cages, sports domes, modern architectural facades). Congruently tiled meshes are both aesthetic and complete, as they support maximal mesh symmetries with minimal complexity and possess simple generation rules. Here, we generate congruent tilings and meshed shape layouts that satisfy these optimality conditions. Further, the congruent meshes are uniquely mappable to an almost regular 3D polyhedron (or its dual polyhedron) and which exhibits face-transitive (and edge-transitive) congruency with at most two types of vertices (each type transitive to the other). The family of all such congruently meshed polyhedra create a new class of meshed shapes, beyond the well-studied regular, semi-regular and quasi-regular classes, and their duals (platonic, Catalan and Johnson). While our new mesh class is infinite, we prove that there exists a unique mesh parametrization, where each member of the class can be represented by two integer lattice variables, and moreover efficiently constructable.
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...
Markov Random Fields on Triangle Meshes
DEFF Research Database (Denmark)
Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jakob Andreas;
2010-01-01
In this paper we propose a novel anisotropic smoothing scheme based on Markov Random Fields (MRF). Our scheme is formulated as two coupled processes. A vertex process is used to smooth the mesh by displacing the vertices according to a MRF smoothness prior, while an independent edge process labels...
Multi-level coarse-mesh rebalance
International Nuclear Information System (INIS)
A multi-level coarse-mesh rebalance method is developed and applied to the acceleration of the nodal diffusion equations. The resulting method is demonstrated for the IAEA Light Water Reactor Benchmark problems. A new organization of data in disk and main storage is developed and evaluated with respect to large computers, minicomputers, and parallel microprocessors. (Auth.)
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.
Generating quality tetrahedral meshes from binary volumes
DEFF Research Database (Denmark)
Hansen, Mads Fogtmann; Bærentzen, Jakob Andreas; Larsen, Rasmus
2010-01-01
use these measures to generate high quality meshes from signed distance maps. This paper also describes an approach for computing (smooth) signed distance maps from binary volumes as volumetric data in many cases originate from segmentation of objects from imaging techniques such as CT, MRI, etc. The...
Constrained-Transport Magnetohydrodynamics with Adaptive-Mesh-Refinement in CHARM
Miniati, Francesco; Martin, Daniel F.
2011-01-01
We present the implementation of a three-dimensional, second order accurate Godunov-type algorithm for magneto-hydrodynamic (MHD), in the adaptive-mesh-refinement (AMR) cosmological code {\\tt CHARM}. The algorithm is based on the full 12-solve spatially unsplit Corner-Transport-Upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the Piecewise-Parabolic-Method (PPM), while the magnetic field variables are face-centered and are evolved through application of the St...
A free surface finite element model for low Froude number mould filling problems on fixed meshes
Coppola Owen, Ángel H.; Codina, Ramon
2011-01-01
The simulation of low Froude number mould filling problems on fixed meshes presents significant difficulties. As the Froude number decreases, the coupling between the position of the interface and the resulting flow field increases. The usual two-phase flow model provides poor results for such flow. In order to overcome the difficulties, a free surface model that applies boundary conditions at the interface accurately is used. Moreover, the use of wall laws on curved boundaries also fails in ...
A Patch-based Partitioner for Structured Adaptive Mesh Refinement : Implementation and Evaluation
Vakili, Abbas
2008-01-01
To increase the speed of computer simulations we solve partial differential equations (PDEs) using structured adaptive mesh refinement (SAMR). During the execution of an SAMR-application, finer grids are superimposed dynamically on coarser grids where a more accurate solution is needed in the computation area. To further decrease the computation time, we use parallel computers and divide the computational work between the processors. This gives rise to challenging load balancing problem. The ...
A first collision source method for ATTILA, an unstructured tetrahedral mesh discrete ordinates code
Energy Technology Data Exchange (ETDEWEB)
Wareing, T.A.; Morel, J.E.; Parsons, D.K.
1998-12-01
A semi-analytic first collision source method is developed for the transport code, ATTILA, a three-dimensional, unstructured tetrahedral mesh, discrete-ordinates code. This first collision source method is intended to mitigate ray effects due to point sources. The method is third-order accurate, which is the same order of accuracy as the linear-discontinuous spatial differencing scheme used in ATTILA. Numerical results are provided to demonstrate the accuracy and efficiency of the first collision source method.
Laparoscopic preperitoneal mesh repair using a novel self-adhesive mesh
Directory of Open Access Journals (Sweden)
Nik Kosai
2011-01-01
Full Text Available Prosthetic mesh is now used routinely in inguinal hernia repairs, although its fixation is thought to be a potential cause of chronic groin pain. The Parietene ProGrip™ (TYCO Healthcare mesh, which is semi-resorbable and incorporates self-fixing properties, has been shown to provide satisfactory repair in open surgery. We describe the use of this mesh in TAPP hernia repair, which has not previously been reported in the literature. A prospective study of 29 patients showed a mean operative time to be 47.6 min, with 96% of patients discharged home on the day of surgery or the day after. Visual analog pain scales (out of 10 reduced from 4 preoperatively to 0 at 6 months, and only 1 patient suffered a minor wound complication. The use of this mesh in transabdominal preperitoneal hernia repair is therefore feasible, safe, and may reduce postoperative pain.
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.
Lateral laryngopharyngeal diverticulum: anatomical and videofluoroscopic study
Energy Technology Data Exchange (ETDEWEB)
Costa, Milton Melciades Barbosa [Universidade Federal do Rio de Janeiro ICB/CCS/UFRJ, Laboratorio de Motilidade Digestiva e Imagem, S. F1-008, Departamento de Anatomia, Rio de Janeiro (Brazil); Koch, Hilton Augusto [Universidade Federal do Rio de Janeiro ICB/CCS/UFRJ, Departamento de Radiologia, Rio de Janeiro (Brazil)
2005-07-01
The aims were to characterize the anatomical region where the lateral laryngopharyngeal protrusion occurs and to define if this protrusion is a normal or a pathological entity. This protrusion was observed on frontal contrasted radiographs as an addition image on the upper portion of the laryngopharynx. We carried out a plane-by-plane qualitative anatomical study through macroscopic and mesoscopic surgical dissection on 12 pieces and analyzed through a videofluoroscopic method on frontal incidence the pharyngeal phase of the swallowing process of 33 patients who had a lateral laryngopharyngeal protrusion. The anatomical study allowed us to identify the morphological characteristics that configure the high portion of the piriform recess as a weak anatomical point. The videofluoroscopic study allowed us to observe the laryngopharyngeal protrusion and its relation to pharyngeal repletion of the contrast medium. All kinds of the observed protrusions could be classified as ''lateral laryngopharyngeal diverticula.'' The lateral diverticula were more frequent in older people. These lateral protrusions can be found on one or both sides, usually with a small volume, without sex or side prevalence. This formation is probably a sign of a pharyngeal transference difficulty associated with a deficient tissue resistance in the weak anatomical point of the high portion of the piriform recess. (orig.)
Development of newborn and 1-year-old reference phantoms based on polygon mesh surfaces
International Nuclear Information System (INIS)
The purpose of this study is the development of paediatric reference phantoms for newborn and 1-year-old infants to be used for the calculation of organ and tissue equivalent doses in radiation protection. The study proposes a method for developing anatomically highly sophisticated paediatric phantoms without using medical images. The newborn and 1-year-old hermaphrodite phantoms presented here were developed using three-dimensional (3D) modelling software applied to anatomical information taken from atlases, textbooks and images provided by the Department of Anatomy of the Federal University of Pernambuco, Brazil. The method uses polygon mesh surfaces to model body contours, the shape of organs as well as their positions and orientations in the human body. Organ and tissue masses agree with corresponding data given by the International Commission on Radiological Protection for newborn and 1-year-old reference children. Bones were segmented into cortical bone, spongiosa, medullary marrow and cartilage to allow for the use of μCT images of trabecular bone for skeletal dosimetry. Anatomical results show 3D images of the phantoms’ surfaces, organs and skeletons, as well as tables with organ and tissue masses or skeletal tissue volumes. Dosimetric results present comparisons of organ and tissue absorbed doses or specific absorbed fractions between the newborn and 1-year-old phantoms and corresponding data for other paediatric stylised or voxel phantoms. Most differences were found to be below 10%. (paper)
Moving mesh generation with a sequential approach for solving PDEs
DEFF Research Database (Denmark)
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 a......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 of...... 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....
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.
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.
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.
Simple optimization method for EMI mesh pattern design
Alpman, Mehmet Erhan; Senger, Tolga
2014-05-01
Metallic mesh coatings are used on visible and infrared windows and domes widely to provide shielding from EMI (Electromagnetic Interference). In this paper, different EMI mesh geometries are compared with each other regarding various performance parameters. But to decide the best fitting EMI mesh geometry to particular optic system is a little bit complicated issue. Therefore, we try to find a simple optimization methodology to decide best EMI mesh geometry design that fits our particular high performance ISR (Intelligence, Surveillance and Reconnaissance) systems.
Problem-adapted mesh generation with FEM-features
Werner, Horst; Weber, Christian; Schilke, Martin
2000-01-01
Today automatic meshing of CAD geometry is the most common method of FEM mesh generation. However, to get results of acceptable accuracy with universal meshing algorithms it is necessary to use rather small-sized elements which leads to high memory and CPU time consumption. Furthermore, the irregularity of automatically generatated meshes makes it difficult to create well-defined local areas with different material properties. A solution for this problem is the application of predefined build...
Zheng, J.; Zhu, J.; Wang, Z.; Fang, F.; Pain, C. C.; Xiang, J.
2015-10-01
An integrated method of advanced anisotropic hr-adaptive mesh and discretization numerical techniques has been, for first time, applied to modelling of multiscale advection-diffusion problems, which is based on a discontinuous Galerkin/control volume discretization on unstructured meshes. Over existing air quality models typically based on static-structured grids using a locally nesting technique, the advantage of the anisotropic hr-adaptive model has the ability to adapt the mesh according to the evolving pollutant distribution and flow features. That is, the mesh resolution can be adjusted dynamically to simulate the pollutant transport process accurately and effectively. To illustrate the capability of the anisotropic adaptive unstructured mesh model, three benchmark numerical experiments have been set up for two-dimensional (2-D) advection phenomena. Comparisons have been made between the results obtained using uniform resolution meshes and anisotropic adaptive resolution meshes. Performance achieved in 3-D simulation of power plant plumes indicates that this new adaptive multiscale model has the potential to provide accurate air quality modelling solutions effectively.
Congenital neck masses: embryological and anatomical perspectives
Directory of Open Access Journals (Sweden)
Zahida Rasool
2013-08-01
Full Text Available Neck masses are a common problem in paediatric age group. They tend to occur frequently and pose a diagnostic dilemma to the ENT surgeons. Although the midline and lateral neck masses differ considerably in their texture and presentation but the embryological perspective of these masses is not mostly understood along with the fundamental anatomical knowledge. The article tries to correlate the embryological, anatomical and clinical perspectives for the same. [Int J Res Med Sci 2013; 1(4.000: 329-332
Algorithms to automatically quantify the geometric similarity of anatomical surfaces
Boyer, D; Clair, E St; Puente, J; Funkhouser, T; Patel, B; Jernvall, J; Daubechies, I
2011-01-01
We describe new approaches for distances between pairs of 2-dimensional surfaces (embedded in 3-dimensional space) that use local structures and global information contained in inter-structure geometric relationships. We present algorithms to automatically determine these distances as well as geometric correspondences. This is motivated by the aspiration of students of natural science to understand the continuity of form that unites the diversity of life. At present, scientists using physical traits to study evolutionary relationships among living and extinct animals analyze data extracted from carefully defined anatomical correspondence points (landmarks). Identifying and recording these landmarks is time consuming and can be done accurately only by trained morphologists. This renders these studies inaccessible to non-morphologists, and causes phenomics to lag behind genomics in elucidating evolutionary patterns. Unlike other algorithms presented for morphological correspondences our approach does not requir...
Directory of Open Access Journals (Sweden)
Ralf Joukhadar
2015-01-01
Full Text Available Introduction. Sacropexy is a generally applied treatment of prolapse, yet there are known possible complications of it. An essential need exists for better alloplastic materials. Methods. Between April 2013 and June 2014, we performed a modified laparoscopic bilateral sacropexy (MLBS in 10 patients using a MRI-visible PVDF mesh implant. Selected patients had prolapse POP-Q stages II-III and concomitant OAB. We studied surgery-related morbidity, anatomical and functional outcome, and mesh-visibility in MRI. Mean follow-up was 7.4 months. Results. Concomitant colporrhaphy was conducted in 1/10 patients. Anatomical success was defined as POP-Q stage 0-I. Apical success rate was 100% and remained stable. A recurrent cystocele was seen in 1/10 patients during follow-up without need for intervention. Out of 6 (6/10 patients with preoperative SUI, 5/6 were healed and 1/6 persisted. De-novo SUI was seen in 1/10 patients. Complications requiring a relaparoscopy were seen in 2/10 patients. 8/10 patients with OAB were relieved postoperatively. The first in-human magnetic resonance visualization of a prolapse mesh implant was performed and showed good quality of visualization. Conclusion. MLBS is a feasible and safe procedure with favorable anatomical and functional outcome and good concomitant healing rates of SUI and OAB. Prospective data and larger samples are required.
Partitioning of unstructured meshes for load balancing
International Nuclear Information System (INIS)
Many large-scale engineering and scientific calculations involve repeated updating of variables on an unstructured mesh. To do these types of computations on distributed memory parallel computers, it is necessary to partition the mesh among the processors so that the load balance is maximized and inter-processor communication time is minimized. This can be approximated by the problem, of partitioning a graph so as to obtain a minimum cut, a well-studied combinatorial optimization problem. Graph partitioning algorithms are discussed that give good but not necessarily optimum solutions. These algorithms include local search methods recursive spectral bisection, and more general purpose methods such as simulated annealing. It is shown that a general procedure enables to combine simulated annealing with Kernighan-Lin. The resulting algorithm is both very fast and extremely effective. (authors) 23 refs., 3 figs., 1 tab
Gamra: Simple meshing for complex earthquakes
Landry, Walter; Barbot, Sylvain
2016-05-01
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 (Leveque and Li, 1994), 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 modeling. 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.
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.
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.
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.
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.
Motion Editing for Time-Varying Mesh
Xu, Jianfeng; Yamasaki, Toshihiko; Aizawa, Kiyoharu
2008-12-01
Recently, time-varying mesh (TVM), which is composed of a sequence of mesh models, has received considerable interest due to its new and attractive functions such as free viewpoint and interactivity. TVM captures the dynamic scene of the real world from multiple synchronized cameras. However, it is expensive and time consuming to generate a TVM sequence. In this paper, an editing system is presented to reuse the original data, which reorganizes the motions to obtain a new sequence based on the user requirements. Hierarchical motion structure is observed and parsed in TVM sequences. Then, the representative motions are chosen into a motion database, where a motion graph is constructed to connect those motions with smooth transitions. After the user selects some desired motions from the motion database, the best paths are searched by a modified Dijkstra algorithm to achieve a new sequence. Our experimental results demonstrate that the edited sequences are natural and smooth.
Motion Editing for Time-Varying Mesh
Directory of Open Access Journals (Sweden)
Kiyoharu Aizawa
2008-08-01
Full Text Available Recently, time-varying mesh (TVM, which is composed of a sequence of mesh models, has received considerable interest due to its new and attractive functions such as free viewpoint and interactivity. TVM captures the dynamic scene of the real world from multiple synchronized cameras. However, it is expensive and time consuming to generate a TVM sequence. In this paper, an editing system is presented to reuse the original data, which reorganizes the motions to obtain a new sequence based on the user requirements. Hierarchical motion structure is observed and parsed in TVM sequences. Then, the representative motions are chosen into a motion database, where a motion graph is constructed to connect those motions with smooth transitions. After the user selects some desired motions from the motion database, the best paths are searched by a modified Dijkstra algorithm to achieve a new sequence. Our experimental results demonstrate that the edited sequences are natural and smooth.
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.
Electrostatic PIC with adaptive Cartesian mesh
Kolobov, Vladimir; Arslanbekov, Robert
2016-05-01
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.
Towards a large-scale scalable adaptive heart model using shallow tree meshes
Krause, Dorian; Dickopf, Thomas; Potse, Mark; Krause, Rolf
2015-10-01
Electrophysiological heart models are sophisticated computational tools that place high demands on the computing hardware due to the high spatial resolution required to capture the steep depolarization front. To address this challenge, we present a novel adaptive scheme for resolving the deporalization front accurately using adaptivity in space. Our adaptive scheme is based on locally structured meshes. These tensor meshes in space are organized in a parallel forest of trees, which allows us to resolve complicated geometries and to realize high variations in the local mesh sizes with a minimal memory footprint in the adaptive scheme. We discuss both a non-conforming mortar element approximation and a conforming finite element space and present an efficient technique for the assembly of the respective stiffness matrices using matrix representations of the inclusion operators into the product space on the so-called shallow tree meshes. We analyzed the parallel performance and scalability for a two-dimensional ventricle slice as well as for a full large-scale heart model. Our results demonstrate that the method has good performance and high accuracy.
Directory of Open Access Journals (Sweden)
Knutson Gary A
2005-07-01
Full Text Available Abstract Background Leg-length inequality is most often divided into two groups: anatomic and functional. Part I of this review analyses data collected on anatomic leg-length inequality relative to prevalence, magnitude, effects and clinical significance. Part II examines the functional "short leg" including anatomic-functional relationships, and provides an outline for clinical decision-making. Methods Online database – Medline, CINAHL and MANTIS – and library searches for the time frame of 1970–2005 were done using the term "leg-length inequality". Results and Discussion Using data on leg-length inequality obtained by accurate and reliable x-ray methods, the prevalence of anatomic inequality was found to be 90%, the mean magnitude of anatomic inequality was 5.2 mm (SD 4.1. The evidence suggests that, for most people, anatomic leg-length inequality does not appear to be clinically significant until the magnitude reaches ~ 20 mm (~3/4". Conclusion Anatomic leg-length inequality is near universal, but the average magnitude is small and not likely to be clinically significant.
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...
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 and...... samples displaying a full sandwich structure. Final results confirmed the bond loss between concrete and BFRP mesh with temperature. The available void where the epoxy burnt away allowed the concrete matrix to release pressure and limit pore stresses, delaying spalling. It also reduced the mechanical...
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.
Mini-mesh repair for femoral hernia
Hakan Kulacoglu
2014-01-01
INTRODUCTION: Femoral hernia consists only 4% of all primary groin hernias. It is described as “the Bête Noire of Hernias” because of its nature and anatomy which is difficult to understand for the surgeons and tendency to recurrence. Although there is some large series of femoral hernia in the literature, few studies prospectively comparing repair techniques especially for this type of hernia has been published. A new technique named mini-mesh repair is described here. PRESENTATION OF CAS...
Titanium mesh cages (TMC) in spine surgery
Grob, Dieter; Daehn, Sylvia; Mannion, Anne F.
2004-01-01
The introduction of the titanium mesh cage (TMC) in spinal surgery has opened up a variety of applications that are realizable as a result of the versatility of the implant. Differing applications of TMCs in the whole spine are described in a series of 150 patients. Replacement and reinforcement of the anterior column represent the classic use of cylindrical TMCs. The TMC as a multisegmental concave support in kyphotic deformities and as a posterior interlaminar spacer or lamina replacement a...
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.
Symmetries and the coarse-mesh method
International Nuclear Information System (INIS)
This report approaches the basic problem of the coarse-mesh method from a new side. Group theory is used for the determination of the space dependency of the flux. The result is a method called ANANAS after the analytic-analytic solution. This method was tested on two benchmark problems: one given by Melice and the IAEA benchmark. The ANANAS program is an experimental one. The method was intended for use in hexagonal geometry. (Auth.)
Nonconforming finite element methods on quadrilateral meshes
Hu, Jun; Zhang, Shangyou
2013-01-01
It is well-known that it is comparatively difficult to design nonconforming finite elements on quadrilateral meshes by using Gauss-Legendre points on each edge of triangulations. One reason lies in that these degrees of freedom associated to these Gauss-Legendre points are not all linearly independent for usual expected polynomial spaces, which explains why only several lower order nonconforming quadrilateral finite elements can be found in literature. The present paper proposes two families ...
Deploying rural community wireless mesh networks
Ishmael, J; Bury, S.; Pezaros, D.; Race, N. J. P.
2008-01-01
Inadequate Internet access is widening the digital divide between town and countryside, degrading both social communication and business advancements in rural areas. Wireless mesh networking can provide an excellent framework for delivering broadband services to such areas. With this in mind, Lancaster University deployed a WMN in the rural village of Wray over a three-year period, providing the community with Internet service that exceeds many urban offerings. The project gave researchers...
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.
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.
Report of a rare anatomic variant
DEFF Research Database (Denmark)
De Brucker, Y; Ilsen, B; Muylaert, C;
2015-01-01
We report the CT findings in a case of partial anomalous pulmonary venous return (PAPVR) from the left upper lobe in an adult. PAPVR is an anatomic variant in which one to three pulmonary veins drain into the right atrium or its tributaries, rather than into the left atrium. This results in a lef...
Evolution of the Anatomical Theatre in Padova
Macchi, Veronica; Porzionato, Andrea; Stecco, Carla; Caro, Raffaele
2014-01-01
The anatomical theatre played a pivotal role in the evolution of medical education, allowing students to directly observe and participate in the process of dissection. Due to the increase of training programs in clinical anatomy, the Institute of Human Anatomy at the University of Padova has renovated its dissecting room. The main guidelines in…
Magnetic resonance angiography: infrequent anatomic variants
International Nuclear Information System (INIS)
We studied through RM angiography (3D TOF) with high magnetic field equipment (1.5 T) different infrequent intracerebral vascular anatomic variants. For their detection we emphasise the value of post-processed images obtained after conventional angiographic sequences. These post-processed images should be included in routine protocols for evaluation of the intracerebral vascular structures. (author)
HPV Vaccine Effective at Multiple Anatomic Sites
A new study from NCI researchers finds that the HPV vaccine protects young women from infection with high-risk HPV types at the three primary anatomic sites where persistent HPV infections can cause cancer. The multi-site protection also was observed at l
Handbook of anatomical models for radiation dosimetry
Eckerman, Keith F
2010-01-01
Covering the history of human model development, this title presents the major anatomical and physical models that have been developed for human body radiation protection, diagnostic imaging, and nuclear medicine therapy. It explores how these models have evolved and the role that modern technologies have played in this development.
Adaptive mesh refinement and adjoint methods in geophysics simulations
Burstedde, Carsten
2013-04-01
It is an ongoing challenge to increase the resolution that can be achieved by numerical geophysics simulations. This applies to considering sub-kilometer mesh spacings in global-scale mantle convection simulations as well as to using frequencies up to 1 Hz in seismic wave propagation simulations. One central issue is the numerical cost, since for three-dimensional space discretizations, possibly combined with time stepping schemes, a doubling of resolution can lead to an increase in storage requirements and run time by factors between 8 and 16. A related challenge lies in the fact that an increase in resolution also increases the dimensionality of the model space that is needed to fully parametrize the physical properties of the simulated object (a.k.a. earth). Systems that exhibit a multiscale structure in space are candidates for employing adaptive mesh refinement, which varies the resolution locally. An example that we found well suited is the mantle, where plate boundaries and fault zones require a resolution on the km scale, while deeper area can be treated with 50 or 100 km mesh spacings. This approach effectively reduces the number of computational variables by several orders of magnitude. While in this case it is possible to derive the local adaptation pattern from known physical parameters, it is often unclear what are the most suitable criteria for adaptation. We will present the goal-oriented error estimation procedure, where such criteria are derived from an objective functional that represents the observables to be computed most accurately. Even though this approach is well studied, it is rarely used in the geophysics community. A related strategy to make finer resolution manageable is to design methods that automate the inference of model parameters. Tweaking more than a handful of numbers and judging the quality of the simulation by adhoc comparisons to known facts and observations is a tedious task and fundamentally limited by the turnaround times
Tetrahedral Mesh Improvement Using Multi-face Retriangulation
DEFF Research Database (Denmark)
Misztal, Marek Krzysztof; Bærentzen, Jakob Andreas; Anton, Francois; Erleben, Kenny
In this paper we propose a simple technique for tetrahedral mesh improvement without inserting Steiner vertices, concentrating mainly on boundary conforming meshes. The algorithm makes local changes to the mesh to remove tetrahedra which are poor according to some quality criterion. While the...... on tetrahedral mesh improvement, our algorithm makes local changes to the mesh to reduce an energy measure which reflects the quality criterion. The addition of our new local operation allows us to advance the mesh to a lower energy state in cases where no other local change would lead to a reduction....... We also make use of the edge collapse operation in order to reduce the size of the mesh while improving its quality. With these operations, we demonstrate that it is possible to obtain a significantly greater improvement to the worst dihedral angles than using the operations from the previous works...
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.
Oral, intestinal, and skin bacteria in ventral hernia mesh implants
Langbach, Odd; Kristoffersen, Anne Karin; Abesha-Belay, Emnet; Enersen, Morten; Røkke, Ola; Olsen, Ingar
2016-01-01
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 serve as sources for the
O'Hara, P.; Hollkamp, J.; Duarte, C. A.; Eason, T.
2016-01-01
This paper presents a two-scale extension of the generalized finite element method (GFEM) which allows for static fracture analyses as well as fatigue crack propagation simulations on fixed, coarse hexahedral meshes. The approach is based on the use of specifically-tailored enrichment functions computed on-the-fly through the use of a fine-scale boundary value problem (BVP) defined in the neighborhood of existing mechanically-short cracks. The fine-scale BVP utilizes tetrahedral elements, and thus offers the potential for the use of a highly adapted fine-scale mesh in the regions of crack fronts capable of generating accurate enrichment functions for use in the coarse-scale hexahedral model. In this manner, automated hp-adaptivity which can be used for accurate fracture analyses, is now available for use on coarse, uniform hexahedral meshes without the requirements of irregular meshes and constrained approximations. The two-scale GFEM approach is verified and compared against alternative approaches for static fracture analyses, as well as mixed-mode fatigue crack propagation simulations. The numerical examples demonstrate the ability of the proposed approach to deliver accurate results even in scenarios involving multiple discontinuities or sharp kinks within a single computational element. The proposed approach is also applied to a representative panel model similar in design and complexity to that which may be used in the aerospace community.
International Nuclear Information System (INIS)
In an attempt to automatically produce high-quality all-hex meshes, we investigated a mesh improvement strategy: given an initial poor-quality all-hex mesh, we iteratively changed the element connectivity, adding and deleting elements and nodes, and optimized the node positions. We found a set of hex reconnection primitives. We improved the optimization algorithms so they can untangle a negative-Jacobian mesh, even considering Jacobians on the boundary, and subsequently optimize the condition number of elements in an untangled mesh. However, even after applying both the primitives and optimization we were unable to produce high-quality meshes in certain regions. Our experiences suggest that many boundary configurations of quadrilaterals admit no hexahedral mesh with positive Jacobians, although we have no proof of this
Kyoung-Sik Park
2009-01-01
Objective : This study was carried to identify the anatomical component of FTMM(Foot Taeyang Meridian Muscle) in human lower limb, and further to help the accurate application to real acupuncture. Methods : FTM at the surface of the lower limb was labelled with latex. And cadaver was stripped off to demonstrate muscles, nerves and the others and to display the internal structures of FTMM, being divided into outer, middle, and inner layer. Results : FTMM in human lower limb is composed o...
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
Historical evolution of anatomical terminology from ancient to modern.
Sakai, Tatsuo
2007-06-01
The historical development of anatomical terminology from the ancient to the modern can be divided into five stages. The initial stage is represented by the oldest extant anatomical treatises by Galen of Pergamon in the Roman Empire. The anatomical descriptions by Galen utilized only a limited number of anatomical terms, which were essentially colloquial words in the Greek of this period. In the second stage, Vesalius in the early 16th century described the anatomical structures in his Fabrica with the help of detailed magnificent illustrations. He coined substantially no anatomical terms, but devised a system that distinguished anatomical structures with ordinal numbers. The third stage of development in the late 16th century was marked by innovation of a large number of specific anatomical terms especially for the muscles, vessels and nerves. The main figures at this stage were Sylvius in Paris and Bauhin in Basel. In the fourth stage between Bauhin and the international anatomical terminology, many anatomical textbooks were written mainly in Latin in the 17th century, and in modern languages in the 18th and 19th centuries. Anatomical terms for the same structure were differently expressed by different authors. The last stage began at the end of the 19th century, when the first international anatomical terminology in Latin was published as Nomina anatomica. The anatomical terminology was revised repeatedly until the current Terminologia anatomica both in Latin and English. PMID:17585563
CAD and mesh repair with Radial Basis Functions
Marchandise, E.; Piret, C.; Remacle, J.-F.
2012-03-01
In this paper we present a process that includes both model/mesh repair and mesh generation. The repair algorithm is based on an initial mesh that may be either an initial mesh of a dirty CAD model or STL triangulation with many errors such as gaps, overlaps and T-junctions. This initial mesh is then remeshed by computing a discrete parametrization with Radial Basis Functions (RBF's). We showed in [1] that a discrete parametrization can be computed by solving Partial Differential Equations (PDE's) on an initial correct mesh using finite elements. Paradoxically, the meshless character of the RBF's makes it an attractive numerical method for solving the PDE's for the parametrization in the case where the initial mesh contains errors or holes. In this work, we implement the Orthogonal Gradients method to be described in [2], as a RBF solution method for solving PDE's on arbitrary surfaces. Different examples show that the presented method is able to deal with errors such as gaps, overlaps, T-junctions and that the resulting meshes are of high quality. Moreover, the presented algorithm can be used as a hole-filling algorithm to repair meshes with undesirable holes. The overall procedure is implemented in the open-source mesh generator Gmsh [3].
A software package using a mesh-grid method for simulating HPGe detector efficiencies
Energy Technology Data Exchange (ETDEWEB)
Gritzo, Russell E [Los Alamos National Laboratory; Jackman, Kevin R [REMOTE SENSING LAB; Biegalski, Steven R [UT AUSTIN
2009-01-01
Traditional ways of determining the absolute full-energy peak efficiencies of high-purity germanium (HPGe) detectors are often time consuming, cost prohibitive, or not feasible. A software package, KMESS (Kevin's Mesh Efficiency Simulator Software), was developed to assist in predicting these efficiencies. It uses a semiempirical mesh-grid method and works for arbitrary source shapes and counting geometries. The model assumes that any gamma-ray source shape can be treated as a large enough collection of point sources. The code is readily adaptable, has a web-based graphical front-end. and could easily be coupled to a 3D scanner. As will be shown. this software can estimate absolute full-energy peak efficiencies with good accuracy in reasonable computation times. It has applications to the field of gamma-ray spectroscopy because it is a quick and accurate way to assist in performing quantitative analyses using HPGe detectors.
DISCONTINUITY-CAPTURING FINITE ELEMENT COMPUTATION OF UNSTEADY FLOW WITH ADAPTIVE UNSTRUCTURED MESH
Institute of Scientific and Technical Information of China (English)
DONG Genjin; LU Xiyun; ZHUANG Lixian
2004-01-01
A discontinuity-capturing scheme of finite element method (FEM) is proposed. The unstructured-grid technique combined with a new type of adaptive mesh approach is developed for both compressible and incompressible unsteady flows, which exhibits the capability of capturing the shock waves and/or thin shear layers accurately in an unsteady viscous flow at high Reynolds number.In particular, a new testing variable, i.e., the disturbed kinetic energy E, is suggested and used in the adaptive mesh computation, which is universally applicable to the capturing of both shock waves and shear layers in the inviscid flow and viscous flow at high Reynolds number. Based on several calculated examples, this approach has been proved to be effective and efficient for the calculations of compressible and incompressible flows.
A novel approach in formulation of special transition elements: Mesh interface elements
Sarigul, Nesrin
1991-01-01
The objective of this research program is in the development of more accurate and efficient methods for solution of singular problems encountered in various branches of mechanics. The research program can be categorized under three levels. The first two levels involve the formulation of a new class of elements called 'mesh interface elements' (MIE) to connect meshes of traditional elements either in three dimensions or in three and two dimensions. The finite element formulations are based on boolean sum and blending operators. MEI are being formulated and tested in this research to account for the steep gradients encountered in aircraft and space structure applications. At present, the heat transfer and structural analysis problems are being formulated from uncoupled theory point of view. The status report: (1) summarizes formulation for heat transfer and structural analysis; (2) explains formulation of MEI; (3) examines computational efficiency; and (4) shows verification examples.
Estimation Normal Vector of Triangular Mesh Vertex by Angle and Centroid Weights and its Application
Directory of Open Access Journals (Sweden)
Yueping Chen
2013-04-01
Full Text Available To compute vertex normal of triangular meshes more accurately, this paper presents an improved algorithm based on angle and centroid weights. Firstly, four representational algorithms are analyzed by comparing their weighting characteristics such as angles, areas and centroids. The drawbacks of each algorithm are discussed. Following that, an improved algorithm is put forward based on angle and centroid weights. Finally, by taking the deviation angle between the nominal normal vector and the estimated one as the error evaluation standard factor, the triangular mesh models of spheres, ellipsoids, paraboloids and cylinders are used to analyze the performance of all these estimation algorithms. The machining and inspection operations of one mould part are conducted to verify the improved algorithm. Experimental results demonstrate that the algorithm is effective.
Integrating anatomical pathology to the healthcare enterprise.
Daniel-Le Bozec, Christel; Henin, Dominique; Fabiani, Bettina; Bourquard, Karima; Ouagne, David; Degoulet, Patrice; Jaulent, Marie-Christine
2006-01-01
For medical decisions, healthcare professionals need that all required information is both correct and easily available. We address the issue of integrating anatomical pathology department to the healthcare enterprise. The pathology workflow from order to report, including specimen process and image acquisition was modeled. Corresponding integration profiles were addressed by expansion of the IHE (Integrating the Healthcare Enterprise) initiative. Implementation using respectively DICOM Structured Report (SR) and DICOM Slide-Coordinate Microscopy (SM) was tested. The two main integration profiles--pathology general workflow and pathology image workflow--rely on 13 transactions based on HL7 or DICOM standard. We propose a model of the case in anatomical pathology and of other information entities (orders, image folders and reports) and real-world objects (specimen, tissue samples, slides, etc). Cases representation in XML schemas, based on DICOM specification, allows producing DICOM image files and reports to be stored into a PACS (Picture Archiving and Communication System. PMID:17108550
ANATOMIC RESEARCH OF SUPERIOR CLUNIAL NERVE TRAUMA
Institute of Scientific and Technical Information of China (English)
无
1999-01-01
In order to find the mechanism of superior clunial nerve (SCN) trauma, we dissected and revealed SCN from 12 corpses (24 sides). Combining 100 sides of SCN trauma, we inspected the course of SCN, the relation between SCN and it's neighbour tissues with the situation of SCN when being subjected to force. We found that the following special anatomic characteristics and mechanical elements such as the course of SCN, it's turning angles, the bony fibrous tube at the iliac crest, the posterior layer of the lumbodorsal fascia and SCN neighbour adipose tissue, are the causes of external force inducing SCN trauma. The anatomic revealment is the guidance of SCN trauma treatment with edged needle.
Sub-micrometer anatomical models of the sarcolemma of cardiac myocytes based on confocal imaging.
Sachse, Frank B; Savio-Galimberti, Eleonora; Goldhaber, Joshua I; Bridge, John H B
2008-01-01
We describe an approach to develop anatomical models of cardiac cells. The approach is based on confocal imaging of living ventricular myocytes with submicrometer resolution, digital image processing of three-dimensional stacks with high data volume, and generation of dense triangular surface meshes representing the sarcolemma including the transverse tubular system. The image processing includes methods for deconvolution, filtering and segmentation. We introduce and visualize models of the sarcolemma of whole ventricular myocytes and single transversal tubules. These models can be applied for computational studies of cell and sub-cellular physical behavior and physiology, in particular cell signaling. Furthermore, the approach is applicable for studying effects of cardiac development, aging and diseases, which are associated with changes of cell anatomy and protein distributions. PMID:18229702
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.
Parameterization of triangular meshes for texture mapping
Leksell, Mats
2008-01-01
A parameterization of a three-dimensional triangular mesh M to a two dimensional parameter domain is a invertibel PM : S - R, where is the set of all points on the surface. one of the use for such a mapping is for mapping an image from the parameter space D-R onto S. thesis evalutes several apporaches for creating such a mapping. for this purpos , the optimal mapping is an isomtry, i.e. a mapping that preserves the length of all the edges. Such a mapping is however often impossible or somputa...
Improving Multicast Communications Over Wireless Mesh Networks
Keegan, Brian
2010-01-01
In wireless mesh networks (WMNs) the traditional approach to shortest path tree based multicasting is to cater for the needs of the poorest performingnode i.e. the maximum permitted multicast line rate is limited to the lowest line rate used by the individual Child nodes on a branch. In general, this meansfixing the line rate to its minimum value and fixing the transmit power to its maximum permitted value. This simplistic approach of applying a single multicast rate for all nodes in the mult...
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.
Shadowfax: Moving mesh hydrodynamical integration code
Vandenbroucke, Bert
2016-05-01
Shadowfax simulates galaxy evolution. Written in object-oriented modular C++, it evolves 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. For the hydrodynamical integration, it makes use of a (co-) moving Lagrangian mesh. The code has a 2D and 3D version, contains utility programs to generate initial conditions and visualize simulation snapshots, and its input/output is compatible with a number of other simulation codes, e.g. Gadget2 (ascl:0003.001) and GIZMO (ascl:1410.003).
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.
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.
Anatomical basis for impotence following haemorrhoid sclerotherapy.
Pilkington, S. A.; Bateman, A C; Wombwell, S.; Miller, R
2000-01-01
Impotence has been reported as a rare but important complication of sclerotherapy for haemorrhoids. The relationship between the anterior wall of the rectum and the periprostatic parasympathetic nerves responsible for penile erection was studied to investigate a potential anatomical explanation for this therapeutic complication. A tissue block containing the anal canal, rectum and prostate was removed from each of six male cadaveric subjects. The dimensions of the components of the rectal wal...
Quantifying anatomical shape variations in neurological disorders.
Singh, Nikhil; Fletcher, P Thomas; Preston, J Samuel; King, Richard D; Marron, J S; Weiner, Michael W; Joshi, Sarang
2014-04-01
We develop a multivariate analysis of brain anatomy to identify the relevant shape deformation patterns and quantify the shape changes that explain corresponding variations in clinical neuropsychological measures. We use kernel Partial Least Squares (PLS) and formulate a regression model in the tangent space of the manifold of diffeomorphisms characterized by deformation momenta. The scalar deformation momenta completely encode the diffeomorphic changes in anatomical shape. In this model, the clinical measures are the response variables, while the anatomical variability is treated as the independent variable. To better understand the "shape-clinical response" relationship, we also control for demographic confounders, such as age, gender, and years of education in our regression model. We evaluate the proposed methodology on the Alzheimer's Disease Neuroimaging Initiative (ADNI) database using baseline structural MR imaging data and neuropsychological evaluation test scores. We demonstrate the ability of our model to quantify the anatomical deformations in units of clinical response. Our results also demonstrate that the proposed method is generic and generates reliable shape deformations both in terms of the extracted patterns and the amount of shape changes. We found that while the hippocampus and amygdala emerge as mainly responsible for changes in test scores for global measures of dementia and memory function, they are not a determinant factor for executive function. Another critical finding was the appearance of thalamus and putamen as most important regions that relate to executive function. These resulting anatomical regions were consistent with very high confidence irrespective of the size of the population used in the study. This data-driven global analysis of brain anatomy was able to reach similar conclusions as other studies in Alzheimer's disease based on predefined ROIs, together with the identification of other new patterns of deformation. The
Anatomic Landmarks for the First Dorsal Compartment
Hazani, Ron; Engineer, Nitin J.; Cooney, Damon; Wilhelmi, Bradon J.
2009-01-01
Objective: Knowledge of anatomic landmarks for the first dorsal compartment can assist clinicians with management of de Quervain's disease. The radial styloid, the scaphoid tubercle, and Lister's tubercle can be used as superficial landmarks for the first dorsal compartment. Methods: Thirty-two cadaveric wrists were dissected, and measurements were taken from the predetermined landmarks to the extensor retinaculum. The compartments were also inspected for variability of the abductor pollicis ...
Microstructure and Anatomical Characteristics of Daemonorops margaritae
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Daemonorops margaritae is among the most important commercial rattan in South China. Its microstructure and basic anatomical characteristics as well as variation were investigated. Results show that: 1)The variation along the height is small, while the variation along the radial direction is significant; 2) The fibre length, fibre ratio and distribution density of the vascular bundles in the cross section decrease from cortex to core, while the fibre width, vessel element length and width, parenchyma ratio,...
Pure endoscopic endonasal odontoidectomy: anatomical study
Messina, Andrea; Bruno, Maria Carmela; Decq, Philippe; Coste, Andre; Cavallo, Luigi Maria; de Divittis, Enrico; Cappabianca, Paolo; Tschabitscher, Manfred
2007-01-01
Different disorders may produce irreducible atlanto-axial dislocation with compression of the ventral spinal cord. Among the surgical approaches available for a such condition, the transoral resection of the odontoid process is the most often used. The aim of this anatomical study is to demonstrate the possibility of an anterior cervico-medullary decompression through an endoscopic endonasal approach. Three fresh cadaver heads were used. A modified endonasal endoscopic approach was made in al...
ACCESSORY SPLEEN: A CLINICALLY RELEVANT ANATOMIC ANOMALY
Prachi Saffar; Amit Kumar; Ankur
2016-01-01
The purpose of our study is to emphasize on the clinical relevance of the presence of accessory spleen. It is not only a well-documented anatomic anomaly, it holds special significance in the differential diagnosis of intra-abdominal tumours and lymphadenopathy. MATERIALS AND METHODS Thirty male cadavers from North Indian population above the age of 60 yrs. were dissected in the Anatomy Department of FMHS, SGT University, Gurgaon, over a period of 5 yrs. (Sep 2010-Aug 2015) and presence...
Adjoint Sensitivity Computations for an Embedded-Boundary Cartesian Mesh Method and CAD Geometry
Nemec, Marian; Aftosmis,Michael J.
2006-01-01
Cartesian-mesh methods are perhaps the most promising approach for addressing the issues of flow solution automation for aerodynamic design problems. In these methods, the discretization of the wetted surface is decoupled from that of the volume mesh. This not only enables fast and robust mesh generation for geometry of arbitrary complexity, but also facilitates access to geometry modeling and manipulation using parametric Computer-Aided Design (CAD) tools. Our goal is to combine the automation capabilities of Cartesian methods with an eficient computation of design sensitivities. We address this issue using the adjoint method, where the computational cost of the design sensitivities, or objective function gradients, is esseutially indepeudent of the number of design variables. In previous work, we presented an accurate and efficient algorithm for the solution of the adjoint Euler equations discretized on Cartesian meshes with embedded, cut-cell boundaries. Novel aspects of the algorithm included the computation of surface shape sensitivities for triangulations based on parametric-CAD models and the linearization of the coupling between the surface triangulation and the cut-cells. The objective of the present work is to extend our adjoint formulation to problems involving general shape changes. Central to this development is the computation of volume-mesh sensitivities to obtain a reliable approximation of the objective finction gradient. Motivated by the success of mesh-perturbation schemes commonly used in body-fitted unstructured formulations, we propose an approach based on a local linearization of a mesh-perturbation scheme similar to the spring analogy. This approach circumvents most of the difficulties that arise due to non-smooth changes in the cut-cell layer as the boundary shape evolves and provides a consistent approximation tot he exact gradient of the discretized abjective function. A detailed gradient accurace study is presented to verify our approach
Exploring brain function from anatomical connectivity
Directory of Open Access Journals (Sweden)
Gorka Zamora-López
2011-06-01
Full Text Available The intrinsic relationship between the architecture of the brain and the range of sensory and behavioral phenomena it produces is a relevant question in neuroscience. Here, we review recent knowledge gained on the architecture of the anatomical connectivity by means of complex network analysis. It has been found that corticocortical networks display a few prominent characteristics: (i modular organization, (ii abundant alternative processing paths and (iii the presence of highly connected hubs. Additionally, we present a novel classification of cortical areas of the cat according to the role they play in multisensory connectivity. All these properties represent an ideal anatomical substrate supporting rich dynamical behaviors, as-well-as facilitating the capacity of the brain to process sensory information of different modalities segregated and to integrate them towards a comprehensive perception of the real world. The result here exposed are mainly based in anatomical data of cats’ brain, but we show how further observations suggest that, from worms to humans, the nervous system of all animals might share fundamental principles of organization.
Anatomical MRI with an atomic magnetometer
Savukov, I
2012-01-01
Ultra-low field (ULF) MRI is a promising method for inexpensive medical imaging with various additional advantages over conventional instruments such as low weight, low power, portability, absence of artifacts from metals, and high contrast. Anatomical ULF MRI has been successfully implemented with SQUIDs, but SQUIDs have the drawback of cryogen requirement. Atomic magnetometers have sensitivity comparable to SQUIDs and can be in principle used for ULF MRI to replace SQUIDs. Unfortunately some problems exist due to the sensitivity of atomic magnetometers to magnetic field and gradients. At low frequency, noise is also substantial and a shielded room is needed for improving sensitivity. In this paper, we show that at 85 kHz, the atomic magnetometer can be used to obtain anatomical images. This is the first demonstration of any use of atomic magnetometers for anatomical MRI. The demonstrated resolution is 1.1x1.4 mm2 in about six minutes of acquisition with SNR of 10. Some applications of the method are discuss...
Anatomic variation of cranial parasympathetic ganglia
Directory of Open Access Journals (Sweden)
Selma Siéssere
2008-06-01
Full Text Available Having broad knowledge of anatomy is essential for practicing dentistry. Certain anatomical structures call for detailed studies due to their anatomical and functional importance. Nevertheless, some structures are difficult to visualize and identify due to their small volume and complicated access. Such is the case of the parasympathetic ganglia located in the cranial part of the autonomic nervous system, which include: the ciliary ganglion (located deeply in the orbit, laterally to the optic nerve, the pterygopalatine ganglion (located in the pterygopalatine fossa, the submandibular ganglion (located laterally to the hyoglossus muscle, below the lingual nerve, and the otic ganglion (located medially to the mandibular nerve, right beneath the oval foramen. The aim of this study was to present these structures in dissected anatomic specimens and perform a comparative analysis regarding location and morphology. The proximity of the ganglia and associated nerves were also analyzed, as well as the number and volume of fibers connected to them. Human heads were dissected by planes, partially removing the adjacent structures to the point we could reach the parasympathetic ganglia. With this study, we concluded that there was no significant variation regarding the location of the studied ganglia. Morphologically, our observations concur with previous classical descriptions of the parasympathetic ganglia, but we observed variations regarding the proximity of the otic ganglion to the mandibular nerve. We also observed that there were variations regarding the number and volume of fiber bundles connected to the submandibular, otic, and pterygopalatine ganglia.
Piriformis Fossa – An Anatomical and Orthopedics Consideration
Lakhwani, O. P.; Mittal, P.S.; D. C. Naik
2014-01-01
Introduction: Piriformis fossa is an important anatomical landmark having significant clinical value in orthopedic surgery; but its location and anatomical relationship with surrounding structures are not clearly defined. Hence it is necessary to clearly describe it in respect to anatomical and orthopedic aspect.
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.
Algebraic turbulence modeling for unstructured and adaptive meshes
Mavriplis, Dimitri J.
1990-01-01
An algebraic turbulence model based on the Baldwin-Lomax model, has been implemented for use on unstructured grids. The implementation is based on the use of local background structured turbulence meshes. At each time-step, flow variables are interpolated from the unstructured mesh onto the background structured meshes, the turbulence model is executed on these meshes, and the resulting eddy viscosity values are interpolated back to the unstructured mesh. Modifications to the algebraic model were required to enable the treatment of more complicated flows, such as confluent boundary layers and wakes. The model is used in conjuction with an efficient unstructured multigrid finite-element Navier-Stokes solver in order to compute compressible turbulent flows on fully unstructured meshes. Solutions about single and multiple element airfoils are obtained and compared with experimental data.
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,...
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.
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.
Li, Jichun
2014-12-02
For decades, the widely used finite difference method on staggered grids, also known as the marker and cell (MAC) method, has been one of the simplest and most effective numerical schemes for solving the Stokes equations and Navier–Stokes equations. Its superconvergence on uniform meshes has been observed by Nicolaides (SIAM J Numer Anal 29(6):1579–1591, 1992), but the rigorous proof is never given. Its behavior on non-uniform grids is not well studied, since most publications only consider uniform grids. In this work, we develop the MAC scheme on non-uniform rectangular meshes, and for the first time we theoretically prove that the superconvergence phenomenon (i.e., second order convergence in the (Formula presented.) norm for both velocity and pressure) holds true for the MAC method on non-uniform rectangular meshes. With a careful and accurate analysis of various sources of errors, we observe that even though the local truncation errors are only first order in terms of mesh size, the global errors after summation are second order due to the amazing cancellation of local errors. This observation leads to the elegant superconvergence analysis even with non-uniform meshes. Numerical results are given to verify our theoretical analysis.
Accurate, meshless methods for magnetohydrodynamics
Hopkins, Philip F.; Raives, Matthias J.
2016-01-01
Recently, we explored new meshless finite-volume Lagrangian methods for hydrodynamics: the `meshless finite mass' (MFM) and `meshless finite volume' (MFV) methods; these capture advantages of both smoothed particle hydrodynamics (SPH) and adaptive mesh refinement (AMR) schemes. We extend these to include ideal magnetohydrodynamics (MHD). The MHD equations are second-order consistent and conservative. We augment these with a divergence-cleaning scheme, which maintains nabla \\cdot B≈ 0. We implement these in the code GIZMO, together with state-of-the-art SPH MHD. We consider a large test suite, and show that on all problems the new methods are competitive with AMR using constrained transport (CT) to ensure nabla \\cdot B=0. They correctly capture the growth/structure of the magnetorotational instability, MHD turbulence, and launching of magnetic jets, in some cases converging more rapidly than state-of-the-art AMR. Compared to SPH, the MFM/MFV methods exhibit convergence at fixed neighbour number, sharp shock-capturing, and dramatically reduced noise, divergence errors, and diffusion. Still, `modern' SPH can handle most test problems, at the cost of larger kernels and `by hand' adjustment of artificial diffusion. Compared to non-moving meshes, the new methods exhibit enhanced `grid noise' but reduced advection errors and diffusion, easily include self-gravity, and feature velocity-independent errors and superior angular momentum conservation. They converge more slowly on some problems (smooth, slow-moving flows), but more rapidly on others (involving advection/rotation). In all cases, we show divergence control beyond the Powell 8-wave approach is necessary, or all methods can converge to unphysical answers even at high resolution.
Mesh Plug Repair of Inguinal Hernia; Single Surgeon Experience
Ahmet Serdar Karaca
2013-01-01
Aim: Mesh repair of inguinal hernia repairs are shown to be an effective and reliable method. In this study, a single surgeon%u2019s experience with plug-mesh method performs inguinal hernia repair have been reported. Material and Method: 587 patients with plug-mesh repair of inguinal hernia, preoperative age, body / mass index, comorbid disease were recorded in terms of form. All of the patients during the preoperative and postoperative hernia classification of information, duration of oper...
Adaptive Mesh Redistibution Method Based on Godunov's Scheme
Azarenok, Boris N.; Ivanenko, Sergey A.; Tang, Tao
2003-01-01
In this work, a detailed description for an efficent adaptive mesh redistribution algorithm based on the Godunov's scheme is presented. After each mesh iteration a second-order finite-volume flow solver is used to update the flow parameters at the new time level directly without using interpolation. Numerical experiments are perfomed to demonstrate the efficency and robustness of the proposed adaptive mesh algorithm in one and two dimensions.
Silhouette smoothing for real-time rendering of mesh surfaces
Wang, L.; Tu, C.; W. Wang; Meng, X.; Chan, B; Yan, D.
2008-01-01
Coarse piecewise linear approximation of surfaces causes undesirable polygonal appearance of silhouettes. We present an efficient method for smoothing the silhouettes of coarse triangle meshes using efficient 3D curve reconstruction and simple local re-meshing. It does not assume the availability of a fine mesh and generates only moderate amount of additional data at run time. Furthermore, polygonal feature edges are also smoothed in a unified framework. Our method is based on a novel interpo...
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.
A thread-parallel algorithm for anisotropic mesh adaptation
Rokos, Georgios; Gorman, Gerard J.; Southern, James; Kelly, Paul H. J.
2013-01-01
Anisotropic mesh adaptation is a powerful way to directly minimise the computational cost of mesh based simulation. It is particularly important for multi-scale problems where the required number of floating-point operations can be reduced by orders of magnitude relative to more traditional static mesh approaches. Increasingly, finite element and finite volume codes are being optimised for modern multi-core architectures. Typically, decomposition methods implemented through the Message Passin...
An Anonymous Authentication and Communication Protocol for Wireless Mesh Networks
Sen, Jaydip
2011-01-01
Wireless mesh networks (WMNs) have emerged as a key technology for next generation wireless broadband networks showing rapid progress and inspiring numerous compelling applications. A WMN comprises of a set of mesh routers (MRs) and mesh clients (MCs), where MRs are connected to the Internet backbone through the Internet gateways (IGWs). The MCs are wireless devices and communicate among themselves over possibly multi-hop paths with or without the involvement of MRs. User privacy and security...
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...
Towards Unstructured Mesh Generation Using the Inverse Poisson Problem
Bunin, Guy
2008-01-01
A novel approach to unstructured quadrilateral mesh generation for planar domains is presented. Away from irregular vertices, the resulting meshes have the properties of nearly conformal grids. The technique is based on a theoretical relation between the present problem, and the inverse Poisson (IP) problem with point sources. An IP algorithm is described, which constructs a point-source distribution, whose sources correspond to the irregular vertices of the mesh. Both the background theory a...
An Efficient Bandwidth Estimation Schemes used in Wireless Mesh Networks
A.Sandeep Kumar ,Second Author
2012-01-01
wireless mesh networks (WMNs) has been widely used for the new generation wireless network. The capability of self-organization in WMNs reduces the complexity of wireless network deployment and maintenance. So, the perfect estimation of the bandwidth available of the mesh nodes is the required to admission control mechanism which provides QOs confirmation in wireless mesh networks. The bandwidth estimation of schemes do not give clear output. Here we are proposing bandwidth scheme estimation ...
Multiphase flow of immiscible fluids on unstructured moving meshes
Misztal, Marek Krzysztof; Erleben, Kenny; Bargteil, Adam; Fursund, Jens; Christensen , Brian Bunch; Bærentzen, Jakob Andreas; Bridson, Robert
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 operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between ...
Conversion of Performance Mesh Animation into Cage-based Animation
Savoye, Yann; Franco, Jean-Sébastien
2010-01-01
Markerless highly-detailed performance capture is an emerging technology in vision-based graphics and 3D video. For instance, a framework for generating mesh animations from multi-view silhouettes is presented in [Vlasic et al. 2008]. Achieving inverse animation by approximating dynamic mesh using rigid skinning has inspired researchers to convert video-based reconstructed mesh sequence into rigid kinematic parameters as seen in [de Aguiar et al. 2008]. In contrast with previous techniques us...
Lim, Hong-Chul; Yoon, Yong-Cheol; Wang, Joon-Ho; Bae, Ji-Hoon
2012-01-01
Background The purpose of this study was to compare the initial stability of anatomical and non-anatomical single bundle anterior cruciate ligament (ACL) reconstruction and to determine which would better restore intact knee kinematics. Our hypothesis was that the initial stability of anatomical single bundle ACL reconstruction would be superior to that of non-anatomical single bundle ACL reconstruction. Methods Anterior tibial translation (ATT) and internal rotation of the tibia were measure...
Secure Routing in Wireless Mesh Networks
Sen, Jaydip
2011-01-01
Wireless mesh networks (WMNs) have emerged as a promising concept to meet the challenges in next-generation networks such as providing flexible, adaptive, and reconfigurable architecture while offering cost-effective solutions to the service providers. Unlike traditional Wi-Fi networks, with each access point (AP) connected to the wired network, in WMNs only a subset of the APs are required to be connected to the wired network. The APs that are connected to the wired network are called the Internet gateways (IGWs), while the APs that do not have wired connections are called the mesh routers (MRs). The MRs are connected to the IGWs using multi-hop communication. The IGWs provide access to conventional clients and interconnect ad hoc, sensor, cellular, and other networks to the Internet. However, most of the existing routing protocols for WMNs are extensions of protocols originally designed for mobile ad hoc networks (MANETs) and thus they perform sub-optimally. Moreover, most routing protocols for WMNs are des...
Finding regions of interest on toroidal meshes
Energy Technology Data Exchange (ETDEWEB)
Wu Kesheng; Sinha, Rishi R; Shoshani, Arie [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Jones, Chad; Ma, Kwan-Liu [University of California, Davis, CA (United States); Ethier, Stephane [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Klasky, Scott [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Winslett, Marianne, E-mail: kwu@lbl.gov [University of Illinois, Urbana-Champaign, IL (United States)
2011-01-15
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is under way to turn this aspiration into a reality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large number of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is hundreds of times faster than a recently published method based on Cartesian coordinates.
Finding Regions of Interest on Toroidal Meshes
International Nuclear Information System (INIS)
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is underway to turn this aspiration intoreality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large amount of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is 100s of times faster than a recently published method based on Cartesian coordinates.
Finding regions of interest on toroidal meshes
International Nuclear Information System (INIS)
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is under way to turn this aspiration into a reality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large number of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is hundreds of times faster than a recently published method based on Cartesian coordinates.
Finding Regions of Interest on Toroidal Meshes
Energy Technology Data Exchange (ETDEWEB)
Wu, Kesheng; Sinha, Rishi R; Jones, Chad; Ethier, Stephane; Klasky, Scott; Ma, Kwan-Liu; Shoshani, Arie; Winslett, Marianne
2011-02-09
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is underway to turn this aspiration intoreality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinementfusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large amount of data are produced,the careful study of ``interesting'' parts of the data is critical to gain understanding. In this paper, we present an efficient approach forfinding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce acompact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructingregions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with bothcomputational complexity analysis and experimental measurements. Furthermore, this new approach is 100s of times faster than a recentlypublished method based on Cartesian coordinates.
Mesh-based parallel code coupling interface
Energy Technology Data Exchange (ETDEWEB)
Wolf, K.; Steckel, B. (eds.) [GMD - Forschungszentrum Informationstechnik GmbH, St. Augustin (DE). Inst. fuer Algorithmen und Wissenschaftliches Rechnen (SCAI)
2001-04-01
MpCCI (mesh-based parallel code coupling interface) is an interface for multidisciplinary simulations. It provides industrial end-users as well as commercial code-owners with the facility to combine different simulation tools in one environment. Thereby new solutions for multidisciplinary problems will be created. This opens new application dimensions for existent simulation tools. This Book of Abstracts gives a short overview about ongoing activities in industry and research - all presented at the 2{sup nd} MpCCI User Forum in February 2001 at GMD Sankt Augustin. (orig.) [German] MpCCI (mesh-based parallel code coupling interface) definiert eine Schnittstelle fuer multidisziplinaere Simulationsanwendungen. Sowohl industriellen Anwender als auch kommerziellen Softwarehersteller wird mit MpCCI die Moeglichkeit gegeben, Simulationswerkzeuge unterschiedlicher Disziplinen miteinander zu koppeln. Dadurch entstehen neue Loesungen fuer multidisziplinaere Problemstellungen und fuer etablierte Simulationswerkzeuge ergeben sich neue Anwendungsfelder. Dieses Book of Abstracts bietet einen Ueberblick ueber zur Zeit laufende Arbeiten in der Industrie und in der Forschung, praesentiert auf dem 2{sup nd} MpCCI User Forum im Februar 2001 an der GMD Sankt Augustin. (orig.)
Fully implicit adaptive mesh refinement MHD algorithm
Philip, Bobby
2005-10-01
In the macroscopic simulation of plasmas, the numerical modeler is faced with the challenge of dealing with multiple time and length scales. The former results in stiffness due to the presence of very fast waves. The latter requires one to resolve the localized features that the system develops. Traditional approaches based on explicit time integration techniques and fixed meshes are not suitable for this challenge, as such approaches prevent the modeler from using realistic plasma parameters to keep the computation feasible. We propose here a novel approach, based on implicit methods and structured adaptive mesh refinement (SAMR). Our emphasis is on both accuracy and scalability with the number of degrees of freedom. To our knowledge, a scalable, fully implicit AMR algorithm has not been accomplished before for MHD. As a proof-of-principle, we focus on the reduced resistive MHD model as a basic MHD model paradigm, which is truly multiscale. The approach taken here is to adapt mature physics-based technologyootnotetextL. Chac'on et al., J. Comput. Phys. 178 (1), 15- 36 (2002) to AMR grids, and employ AMR-aware multilevel techniques (such as fast adaptive composite --FAC-- algorithms) for scalability. We will demonstrate that the concept is indeed feasible, featuring optimal scalability under grid refinement. Results of fully-implicit, dynamically-adaptive AMR simulations will be presented on a variety of problems.
Kinetic Solvers with Adaptive Mesh in Phase Space
Arslanbekov, Robert R; Kolobov, Vladimir I; 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-s...
STL Triangular Mesh Generation Based on SAT Model
Directory of Open Access Journals (Sweden)
Yuwei Zhang
2013-06-01
Full Text Available Mesh generation is a fundamental technique in multiple domains. In this study, a STL triangular mesh generation method based on SAT model is proposed. Two novel triangulation methods, the constrained Delaunay algorithm and the grid subtraction algorithm, are employed on the multi-loop planer regions and the curved surfaces respectively. For the use of node adjustment, the mesh nodes on the surface boundary are strictly matched, with no cracks created on the joint of model surfaces. Experiments show that the proposed solution works effectively and high quality of the mesh model is achieved.
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.
Reconfigurable lattice mesh designs for programmable photonic processors.
Pérez, Daniel; Gasulla, Ivana; Capmany, José; Soref, Richard A
2016-05-30
We propose and analyse two novel mesh design geometries for the implementation of tunable optical cores in programmable photonic processors. These geometries are the hexagonal and the triangular lattice. They are compared here to a previously proposed square mesh topology in terms of a series of figures of merit that account for metrics that are relevant to on-chip integration of the mesh. We find that that the hexagonal mesh is the most suitable option of the three considered for the implementation of the reconfigurable optical core in the programmable processor. PMID:27410130
Application of particle-mesh Ewald summation to ONIOM theory
Kobayashi, Osamu; Nanbu, Shinkoh
2015-11-01
We extended a particle mesh Ewald (PME) summation method to the ONIOM (our Own N-layered Integrated molecular Orbitals and molecular Mechanics) scheme (PME-ONIOM) to validate the simulation in solution. This took the form of a nonadiabatic ab initio molecular dynamics (MD) simulation in which the Zhu-Nakamura trajectory surface hopping (ZN-TSH) method was performed for the photoisomerization of a (Z)-penta-2,4-dieniminium cation (protonated Schiff base, PSB3) electronically excited to the S1 state in a methanol solution. We also calculated a nonadiabatic ab initio MD simulation with only minimum image convention (MI-ONIOM). The lifetime determined by PME-ONIOM-MD was 3.483 ps. The MI-ONIOM-MD lifetime of 0.4642 ps was much shorter than those of PME-ONIOM-MD and the experimentally determined excited state lifetime. The difference eminently illustrated the accurate treatment of the long-range solvation effect, which destines the electronically excited PSB3 for staying in S1 at the pico-second or the femto-second time scale.
CONSTRAINED-TRANSPORT MAGNETOHYDRODYNAMICS WITH ADAPTIVE MESH REFINEMENT IN CHARM
International Nuclear Information System (INIS)
We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.
Constrained-transport Magnetohydrodynamics with Adaptive Mesh Refinement in CHARM
Miniati, Francesco; Martin, Daniel F.
2011-07-01
We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.
A Study of Bandwidth Measurement Technique in Wireless Mesh Networks
Directory of Open Access Journals (Sweden)
Ajeet Kumar Singh
2011-09-01
Full Text Available Wireless mesh networks (WMNs have been proposed as a key technology for next generation wireless networking to provide last-mile broadband access. H ere we have given our observation and study for end to-end bandwidth estimation in WMNs. End-to-end Ban dwidth Estimation is an important metric for network management and monitoring. It can also impr ove the effectiveness of congestion control mechanism, audio/video stream adoration and dynamic overlay. In recent years, many techniques have been developed for bandwidth estimation in the wire d as well as the last-hop wireless networks, but th ey under-perform in WMNs. We investigate attributes th at can affect the bandwidth estimation in WNMs; we found existing techniques do not consider the effec t of attributes like CSMA/CA-based contending traff ic and high interference interference that leads to th e error full estimation. In this paper, we present an active bandwidth measu rement technique called Bandwidth Probe based on th e packet dispersion principle. It measures the steady state bandwidth of the system while considering th e effects of the FIFO cross and CSMA/CA-based contend ing traffic. It is also mitigating the effect of interference. We also show how to achieve the stati onary state behaviour of the system to limit the nu mber of probe packets. On simulation, Bandwidth Probe gi ves a accurate estimation of the available bandwidt h using average convergence time and lower intrusiven ess.
Anatomic atlas for computed tomography in the mesaticephalic dog: caudal abdomen and pelvis
International Nuclear Information System (INIS)
The purpose of this study was to produce a comprehensive anatomic atlas of CT anatomy of the dog for use by veterinary radiologists, clinicians, and surgeons. Whole-body CT images of two mature beagle dogs were made with the dogs supported in sternal recumbency and using a slice thickness of 13 mm. At the end of the CT session, each dog was euthanized, and while carefully maintaining the same position, the body was frozen. The body was then sectioned at 13-mm intervals, with the cuts matched as closely as possible to the CT slices. The frozen sections were cleaned, photographed, and radiographed using xeroradiography. Each CT image was studied and compared with its corresponding xeroradiograph and anatomic section to assist in the accurate identification of specific structures. Clinically relevant anatomic structures were identified and labeled in the three corresponding photographs (CT image, xeroradiograph, and anatomic section). In previous papers, the head and neck, and the thorax and cranial abdomen of the mesaticephalic (beagle) dog were presented. In this paper, the caudal part of the abdomen and pelvis of the bitch and male dog are presented
Anatomic atlas for computed tomography in the mesaticephalic dog: head and neck
International Nuclear Information System (INIS)
The purpose of this study was to produce a comprehensive anatomic atlas of CT anatomy of the dog for use by veterinary radiologists, clinicians, and surgeons. Whole-body CT images of two mature beagle dogs were made with the dogs supported in sternal recumbency and using a slice thickness of 13 mm. The head was scanned using high-resolution imaging with a slice thickness of 8 mm. At the end of the CT session, each dog was euthanized, and while carefully maintaining the same position, the body was placed in a walk-in freezer until completely frozen. The body was then sectioned at 13-mm (head at 8-mm) intervals, with the cuts matched as closely as possible to the CT slices. The forzen sections were cleaned, photographed, and radiographed using xeroradiography. Each CT image was studied and compared with its corresponding xeroradiograph and anatomic section to assist in the accurate identification of specific structures. Intact, sagittally sectioned, and disarticulated dog skulls were used as reference models. Clinically relevant anatomic structures were identified and labeled in the three corresponding photographs (CT image, xeroradiograph, and anatomic section). In this paper, the CT anatomy of the head and neck of the mesaticephalic dog is presented
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.
International Nuclear Information System (INIS)
The use of statistical parametric mapping (SPM) program has increased for the analysis of brain PET and SPECT images. Montreal neurological institute (MNI) coordinate is used in SPM program as a standard anatomical framework. While the most researchers look up Talairach atlas to report the localization of the activations detected in SPM program, there is significant disparity between MNI templates and Talairach atlas. That disparity between Talairach and MNI coordinates makes the interpretation of SPM result time consuming, subjective and inaccurate. The purpose of this study was to develop a program to provide objective anatomical information of each x-y-z position in ICBM coordinate. Program was designed to provide the anatomical information for the given x-y-z position in MNI coordinate based on the statistical probabilistic anatomical map (SPAM) images of ICBM. When x-y-z position was given to the program, names of the anatomical structures with non-zero probability and the probabilities that the given position belongs to the structures were tabulated. The program was coded using IDL and JAVA language for the easy transplantation to any operating system or platform. Utility of this program was shown by comparing the results of this program to those of SPM program. Preliminary validation study was performed by applying this program to the analysis of PET brain activation study of human memory in which the anatomical information on the activated areas are previously known. Real time retrieval of probabilistic information with 1 mm spatial resolution was archived using the programs. Validation study showed the relevance of this program: probability that the activated area for memory belonged to hippocampal formation was more than 80%. These programs will be useful for the result interpretation of the image analysis performed on MNI coordinate, as done in SPM program
TOPICAL REVIEW: Anatomical imaging for radiotherapy
Evans, Philip M.
2008-06-01
The goal of radiation therapy is to achieve maximal therapeutic benefit expressed in terms of a high probability of local control of disease with minimal side effects. Physically this often equates to the delivery of a high dose of radiation to the tumour or target region whilst maintaining an acceptably low dose to other tissues, particularly those adjacent to the target. Techniques such as intensity modulated radiotherapy (IMRT), stereotactic radiosurgery and computer planned brachytherapy provide the means to calculate the radiation dose delivery to achieve the desired dose distribution. Imaging is an essential tool in all state of the art planning and delivery techniques: (i) to enable planning of the desired treatment, (ii) to verify the treatment is delivered as planned and (iii) to follow-up treatment outcome to monitor that the treatment has had the desired effect. Clinical imaging techniques can be loosely classified into anatomic methods which measure the basic physical characteristics of tissue such as their density and biological imaging techniques which measure functional characteristics such as metabolism. In this review we consider anatomical imaging techniques. Biological imaging is considered in another article. Anatomical imaging is generally used for goals (i) and (ii) above. Computed tomography (CT) has been the mainstay of anatomical treatment planning for many years, enabling some delineation of soft tissue as well as radiation attenuation estimation for dose prediction. Magnetic resonance imaging is fast becoming widespread alongside CT, enabling superior soft-tissue visualization. Traditionally scanning for treatment planning has relied on the use of a single snapshot scan. Recent years have seen the development of techniques such as 4D CT and adaptive radiotherapy (ART). In 4D CT raw data are encoded with phase information and reconstructed to yield a set of scans detailing motion through the breathing, or cardiac, cycle. In ART a set of
Cheung, Man Yan; Almukhtar, Anas; Keeling, Andrew; Hsung, Tai-Chiu; Ju, Xiangyang; McDonald, James; Ayoub, Ashraf; Khambay, Balvinder Singh
2016-01-01
Purpose Three dimensional analysis of the face is required for the assessment of complex changes following surgery, pathological conditions and to monitor facial growth. The most suitable method may be “dense surface correspondence”. Materials and Methods This method utilizes a generic facial mesh and “conformation process” to establish anatomical correspondences between two facial images. The aim of this study was to validate the use of conformed meshes to measure simulated maxillary and mandibular surgical movements. The “simulation” was performed by deforming the actual soft tissues of the participant during image acquisition. The study was conducted on 20 volunteers and used 77 facial landmarks pre-marked over six anatomical regions; left cheek, right cheek, left upper lip, philtrum, right upper lip and chin region. Each volunteer was imaged at rest and after performing 5 different simulated surgical procedures using 3D stereophotogrammetry. The simulated surgical movement was determined by measuring the Euclidean distances and the mean absolute x, y and z distances of the landmarks making up the six regions following digitization. A generic mesh was then conformed to each of the aligned six facial 3D images. The same six regions were selected on the aligned conformed simulated meshes and the surgical movement determined by determining the Euclidean distances and the mean absolute x, y and z distances of the mesh points making up the six regions were determined. Results In all cases the mean Euclidian distance between the simulated movement and conformed region was less than 0.7mm. For the x, y and z directions the majority of differences in the mean absolute distances were less than 1.0mm except in the x-direction for the left and right cheek regions, which was above 2.0mm. Conclusions This concludes that the conformation process has an acceptable level of accuracy and is a valid method of measuring facial change between two images i.e. pre- and
Constitutional and Anatomical Characteristics of Mature Women
Institute of Scientific and Technical Information of China (English)
Vladimir NNikolenko; DmitryBNikityuk; SvetlanaVKlochkova; AnastasiaABahmet
2015-01-01
Objective To identify the constitutional and anatomical peculiarities of constitution of women of mature age.Methods There was completed comprehensive anthropometric and bio-electrical survey of 651 mature women ( relative norm) living in the Moscow region .Results The quantitative distribution of women by somatotypological affiliation was revealed;anthropometric and body component composition in representatives of different somatotypes were defined .Conclusion Thus, the performed study revealed and quantiely character-ised the distribution of women according to their constitutional types in the studied population of mature age women living in Moscow region under the relative norm conditions .
Java meshing tool for sphere arrangements
International Nuclear Information System (INIS)
A tool for meshing sphere arrangements was programmed in order to perform finite element calculations. Sphere arrangements are investigated in frame of the feasibility study of the sphere-pac nuclear fuel. One major concern of this study is the thermal conductivity of the arrangement. Further concerns are the mechanical behavior and sintering of the fuel. The thermal conductivity of the fuel was addressed with the computer code SPACON based on a unit cell approach and a radial heat flow experiment. However, a further approach using the finite element method is desirable, in order to better understanding the thermal flow through the package and to cross check with SPACON data and with experimental data. Also the mechanical behavior of the fuel could be addressed using the finite element technique. (author)
Hypersonic Flow Computations on Unstructured Meshes
Bibb, K. L.; Riley, C. J.; Peraire, J.
1997-01-01
A method for computing inviscid hypersonic flow over complex configurations using unstructured meshes is presented. The unstructured grid solver uses an edge{based finite{volume formulation. Fluxes are computed using a flux vector splitting scheme that is capable of representing constant enthalpy solutions. Second{order accuracy in smooth flow regions is obtained by linearly reconstructing the solution, and stability near discontinuities is maintained by locally forcing the scheme to reduce to first-order accuracy. The implementation of the algorithm to parallel computers is described. Computations using the proposed method are presented for a sphere-cone configuration at Mach numbers of 5.25 and 10.6, and a complex hypersonic re-entry vehicle at Mach numbers of 4.5 and 9.8. Results are compared to experimental data and computations made with established structured grid methods. The use of the solver as a screening tool for rapid aerodynamic assessment of proposed vehicles is described.
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 using...... a non-linear elastic finite element model. A key feature of the method is that the user does not need to specify boundary conditions (surface point correspondences) prior to the finite element analysis. Instead the boundary matches are found as an integrated part of the analysis. The method is...... seconds 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....
Superoleophobic Surfaces Obtained via Hierarchical Metallic Meshes.
Grynyov, Roman; Bormashenko, Edward; Whyman, Gene; Bormashenko, Yelena; Musin, Albina; Pogreb, Roman; Starostin, Anton; Valtsifer, Viktor; Strelnikov, Vladimir; Schechter, Alex; Kolagatla, Srikanth
2016-05-01
Hierarchical metallic surfaces demonstrating pronounced water and oil repellence are reported. The surfaces were manufactured with stainless-steel microporous meshes, which were etched with perfluorononanoic acid. As a result, a hierarchical relief was created, characterized by roughness at micro- and sub-microscales. Pronounced superoleophobicity was registered with regard to canola, castor, sesame, flax, crude (petroleum), and engine oils. Relatively high sliding angles were recorded for 5 μL turpentine, olive, and silicone oil droplets. The stability of the Cassie-like air trapping wetting state, established with water/ethanol solutions, is reported. The omniphobicity of the surfaces is due to the interplay of their hierarchical relief and surface fluorination. PMID:27077637
Visualization of Scalar Adaptive Mesh Refinement Data
Energy Technology Data Exchange (ETDEWEB)
VACET; Weber, Gunther; Weber, Gunther H.; Beckner, Vince E.; Childs, Hank; Ligocki, Terry J.; Miller, Mark C.; Van Straalen, Brian; Bethel, E. Wes
2007-12-06
Adaptive Mesh Refinement (AMR) is a highly effective computation method for simulations that span a large range of spatiotemporal scales, such as astrophysical simulations, which must accommodate ranges from interstellar to sub-planetary. Most mainstream visualization tools still lack support for AMR grids as a first class data type and AMR code teams use custom built applications for AMR visualization. The Department of Energy's (DOE's) Science Discovery through Advanced Computing (SciDAC) Visualization and Analytics Center for Enabling Technologies (VACET) is currently working on extending VisIt, which is an open source visualization tool that accommodates AMR as a first-class data type. These efforts will bridge the gap between general-purpose visualization applications and highly specialized AMR visual analysis applications. Here, we give an overview of the state of the art in AMR scalar data visualization research.
Parallel-In-Time For Moving Meshes
Energy Technology Data Exchange (ETDEWEB)
Falgout, R. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Manteuffel, T. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Southworth, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schroder, J. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-02-04
With steadily growing computational resources available, scientists must develop e ective ways to utilize the increased resources. High performance, highly parallel software has be- come a standard. However until recent years parallelism has focused primarily on the spatial domain. When solving a space-time partial di erential equation (PDE), this leads to a sequential bottleneck in the temporal dimension, particularly when taking a large number of time steps. The XBraid parallel-in-time library was developed as a practical way to add temporal parallelism to existing se- quential codes with only minor modi cations. In this work, a rezoning-type moving mesh is applied to a di usion problem and formulated in a parallel-in-time framework. Tests and scaling studies are run using XBraid and demonstrate excellent results for the simple model problem considered herein.
High-Order Conservative Remapping with a posteriori MOOD stabilization on polygonal meshes
Blanchard, Ghislain; Loubere, Raphael
2015-01-01
In this article we present a 2D conservative remapping method which relies on exact polygonal mesh in-tersection, high accurate polynomial reconstruction (up to degree 5) and a posteriori stabilization based onMOOD paradigm [21, 30, 31, 80]. This paradigm does not compute any sort of a priori limiter for the poly-nomial reconstructions. Instead it rather observes if the candidate solution after remapping does not fulfilluser-given validity criteria, and, in this case, locally to those so-call...
Towards accurate emergency response behavior
International Nuclear Information System (INIS)
Nuclear reactor operator emergency response behavior has persisted as a training problem through lack of information. The industry needs an accurate definition of operator behavior in adverse stress conditions, and training methods which will produce the desired behavior. Newly assembled information from fifty years of research into human behavior in both high and low stress provides a more accurate definition of appropriate operator response, and supports training methods which will produce the needed control room behavior. The research indicates that operator response in emergencies is divided into two modes, conditioned behavior and knowledge based behavior. Methods which assure accurate conditioned behavior, and provide for the recovery of knowledge based behavior, are described in detail
Verification of radiation transport codes with unstructured meshes
International Nuclear Information System (INIS)
Confidence in the results of a radiation transport code requires that the code be verified against problems with known solutions. Such verification problems may be generated by means of the method of manufactured solutions. Previously we reported the application of this method to the verification of radiation transport codes for structured meshes, in particular the SCEPTRE code. We extend this work to verification with unstructured meshes and again apply it to SCEPTRE. We report on additional complexities for unstructured mesh verification of transport codes. Refinement of such meshes for error convergence studies is more involved, particularly for tetrahedral meshes. Furthermore, finite element integrations arising from the presence of the streaming operator exhibit different behavior for unstructured meshes than for structured meshes. We verify SCEPTRE with a combination of 'exact' and 'inexact' problems. Errors in the results are consistent with the discretizations, either being limited to roundoff error or displaying the expected rates of convergence with mesh refinement. We also observe behaviors in the results that were difficult to analyze and predict from a strictly theoretical basis, thereby yielding benefits from verification activities beyond demonstrating code correctness. (author)
Vaginal Approaches Using Synthetic Mesh to Treat Pelvic Organ Prolapse
Moon, Jei Won
2016-01-01
Pelvic organ prolapse (POP) is a very common condition in elderly women. In women with POP, a sacrocolpopexy or a vaginal hysterectomy with anterior and posterior colporrhaphy has long been considered as the gold standard of treatment. However, in recent decades, the tendency to use a vaginal approach with mesh for POP surgery has been increasing. A vaginal approach using mesh has many advantages, such as its being less invasive than an abdominal approach and easier to do than a laparoscopic approach and its having a lower recurrence rate than a traditional approach. However, the advantages of a vaginal approach with mesh for POP surgery must be weighed against the disadvantages. Specific complications that have been reported when using mesh in POP procedures are mesh erosion, dyspareunia, hematomas, urinary incontinence and so on, and evidence supporting the use of transvaginal surgery with mesh is still lacking. Hence, surgeons should understand the details of the surgical pelvic anatomy, the various surgical techniques for POP surgery, including using mesh, and the possible side effects of using mesh. PMID:26962530
Lagrangian fluid dynamics using the Voronoi-Delauanay mesh
International Nuclear Information System (INIS)
A Lagrangian technique for numerical fluid dynamics is described. This technique makes use of the Voronoi mesh to efficiently locate new neighbors, and it uses the dual (Delaunay) triangulation to define computational cells. This removes all topological restrictions and facilitates the solution of problems containing interfaces and multiple materials. To improve computational accuracy a mesh smoothing procedure is employed
A Special Acknowledgement based Routing for Mesh Network
DEFF Research Database (Denmark)
Banoth, Rajkumar
2012-01-01
Within the last few years, prevalence and importance of wireless networks increased significantly. Especially, wireless mesh networks received a lot of attention in both academic research and commercial deployment. The networking performance of the mesh can degraded gradually, if a node gets...
Mesh Processing in Medical-Image Analysis-a Tutorial
DEFF Research Database (Denmark)
Levine, Joshua A.; Paulsen, Rasmus Reinhold; Zhang, Yongjie
2012-01-01
Medical-image analysis requires an understanding of sophisticated scanning modalities, constructing geometric models, building meshes to represent domains, and downstream biological applications. These four steps form an image-to-mesh pipeline. For research in this field to progress, the imaging...
Tangle-Free Finite Element Mesh Motion for Ablation Problems
Droba, Justin
2016-01-01
In numerical simulations involving boundaries that evolve in time, the primary challenge is updating the computational mesh to reflect the physical changes in the domain. In particular, the fundamental objective for any such \\mesh motion" scheme is to maintain mesh quality and suppress unphysical geometric anamolies and artifacts. External to a physical process of interest, mesh motion is an added component that determines the specifics of how to move the mesh given certain limited information from the main system. This paper develops a set of boundary conditions designed to eliminate tangling and internal collision within the context of PDE-based mesh motion (linear elasticity). These boundary conditions are developed for two- and three-dimensional meshes. The paper presents detailed algorithms for commonly occuring topological scenarios and explains how to apply them appropriately. Notably, the techniques discussed herein make use of none of the specifics of any particular formulation of mesh motion and thus are more broadly applicable. The two-dimensional algorithms are validated by an extensive verification procedure. Finally, many examples of diverse geometries in both two- and three-dimensions are shown to showcase the capabilities of the tangle-free boundary conditions.
Volume Decomposition and Feature Recognition for Hexahedral Mesh Generation
International Nuclear Information System (INIS)
Considerable progress has been made on automatic hexahedral mesh generation in recent years. Several automatic meshing algorithms have proven to be very reliable on certain classes of geometry. While it is always worth pursuing general algorithms viable on more general geometry, a combination of the well-established algorithms is ready to take on classes of complicated geometry. By partitioning the entire geometry into meshable pieces matched with appropriate meshing algorithm the original geometry becomes meshable and may achieve better mesh quality. Each meshable portion is recognized as a meshing feature. This paper, which is a part of the feature based meshing methodology, presents the work on shape recognition and volume decomposition to automatically decompose a CAD model into meshable volumes. There are four phases in this approach: (1) Feature Determination to extinct decomposition features, (2) Cutting Surfaces Generation to form the ''tailored'' cutting surfaces, (3) Body Decomposition to get the imprinted volumes; and (4) Meshing Algorithm Assignment to match volumes decomposed with appropriate meshing algorithms. The feature determination procedure is based on the CLoop feature recognition algorithm that is extended to be more general. Results are demonstrated over several parts with complicated topology and geometry
Scalable Video Streaming in Wireless Mesh Networks for Education
Liu, Yan; Wang, Xinheng; Zhao, Liqiang
2011-01-01
In this paper, a video streaming system for education based on a wireless mesh network is proposed. A wireless mesh network is a self-organizing, self-managing and reliable intelligent network, which allows educators to deploy a network quickly. Video streaming plays an important role in this system for multimedia data transmission. This new…
Development and validation of a particle-mesh method for incompressible multiphase flows
International Nuclear Information System (INIS)
A hybrid method to simulate unsteady multiphase flows in which a sharp interface separates incompressible fluids of different density and viscosity is described. One phase is represented by moving particles and the other phase is defined on stationary mesh. The flow field is discretized by a conservative finite volume approximation on the stationary mesh, and the interface is automatically captured by the distribution of particles moving through the stationary mesh. The effects of surface tension and wall adhesion are evaluated by the Continuum Surface Force (CSF) model. The different phases are treated as one fluid with variable material properties. Advection of fluid properties such as density and viscosity is done by following the motion of the particles. The method simplifies the calculation of interface interaction, enables accurate modeling of two- and three-dimensional multiphase flows and does not impose any modeling restrictions on the dynamic evolutions of fluid interfaces having surface tension. The surface tension model has been validated on both static and dynamic interfaces having surface tension. Several two-dimensional numerical simulations suggest that large simulations involving interacting interfaces are feasible. The method would be extended to many new and physically interesting problems, such as the annular-dispersed flow in BWR fuel bundle. (author)
Application of a heterogeneous coarse mesh transport method to a MOX benchmark problem
International Nuclear Information System (INIS)
Recently, a coarse mesh transport method was extended to 2-D geometry by coupling Monte Carlo response function calculations to deterministic sweeps for converging the partial currents on the coarse mesh boundaries. More extensive testing of the new method has been performed with the previously published continuous energy benchmark problem, as well as the multigroup C5G7 MOX problem. The effect of the partial current representation in space, for the MOX problem, and in space and energy, for the smaller problem, on the accuracy of the results is the focus of this paper. For the MOX problem, accurate results were obtained with the assumption that the partial currents are piecewise-constant on four spatial segments per coarse mesh interface. Specifically, the errors in the system multiplication factor and the average absolute pin power were 0.12% and 0.68%, respectively. The root mean square and the mean relative pin power errors were 1.15% and 0.56%, respectively. (authors)
Directory of Open Access Journals (Sweden)
Thái Anh Nhan
2016-01-01
Full Text Available A one-dimensional linear convection-diffusion problem with a perturbation parameter ɛ multiplying the highest derivative is considered. The problem is solved numerically by using the standard upwind scheme on special layer-adapted meshes. It is proved that the numerical solution is ɛ-uniform accurate in the maximum norm. This is done by a new proof technique in which the discrete system is preconditioned in order to enable the use of the principle where “ɛ-uniform stability plus ɛ-uniform consistency implies ɛ-uniform convergence.” Without preconditioning, this principle cannot be applied to convection-diffusion problems because the consistency error is not uniform in ɛ. At the same time, the condition number of the discrete system becomes independent of ɛ due to the same preconditioner; otherwise, the condition number of the discrete system before preconditioning increases when ɛ tends to 0. We obtained such results in an earlier paper, but only for the standard Shishkin mesh. In a nontrivial generalization, we show here that the same proof techniques can be applied to the whole class of Shishkin-type meshes.
An unstructured-mesh atmospheric model for nonhydrostatic dynamics: Towards optimal mesh resolution
Szmelter, Joanna; Zhang, Zhao; Smolarkiewicz, Piotr K.
2015-08-01
The paper advances the limited-area anelastic model (Smolarkiewicz et al. (2013) [45]) for investigation of nonhydrostatic dynamics in mesoscale atmospheric flows. New developments include the extension to a tetrahedral-based median-dual option for unstructured meshes and a static mesh adaptivity technique using an error indicator based on inherent properties of the Multidimensional Positive Definite Advection Transport Algorithm (MPDATA). The model employs semi-implicit nonoscillatory forward-in-time integrators for soundproof PDEs, built on MPDATA and a robust non-symmetric Krylov-subspace elliptic solver. Finite-volume spatial discretisation adopts an edge-based data structure. Simulations of stratified orographic flows and the associated gravity-wave phenomena in media with uniform and variable dispersive properties verify the advancement and demonstrate the potential of heterogeneous anisotropic discretisation with large variation in spatial resolution for study of complex stratified flows that can be computationally unattainable with regular grids.
Institute of Scientific and Technical Information of China (English)
Wang Wenyan; Zhu Lan; Wei Bing; Lang Jinghe
2014-01-01
Background During the past decade,graft materials have been widespread used in the vagina in order to correct pelvic organ prolapse.The aim of this study was to describe and compare the exact anatomical position of the puncture devices and their relations to the relevant anatomical structures in the ProliftTM and a modified pelvic reconstructive surgery with mesh.Methods Twelve fresh cadavers were allocated randomly to either the ProliftTM or the modified pelvic reconstructive surgery group.Each group had six fresh cadavers.Relevant distances between the puncture devices and anatomical structures were recorded in both minimally invasive puncture surgeries.Results The mean distances from the posterior puncture points of the obturator membrane to the posterior branch of obturator arteries were shorter ((0.60±0.36) cm and (0.78±0.10) cm) when compared with the distances to the anterior branch of obturator arteries ((1.53±0.46) cm and (1.86±0.51) cm) for the reconstruction of the anterior compartment in both surgeries (all P ＜0.05).The distance from the puncture points of the pelvic floor through the ischiorectal fossa to the coccygeal and inferior gluteal arteries in the ProliftTM technique ((0.88±0.10) cm) and ((1.59±0.36) cm)) were much shorter than that in the modified pelvic reconstructive surgery ((2.95±0.09) cm) and ((3.40±0.36) cm)) for the reconstruction of the middle and posterior compartments (all P ＜0.05).Conclusions Compared with the ProliftTM technique,the modified pelvic reconstructive surgery with mesh would be safer not to cause great damage to the inferior gluteal arteries and the coccygeal arteries.The posterior branch of obturator arteries would be easier to be injured than the anterior branch of obturator arteries during anterior compartment reconstruction in both surgeries.
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.
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.
Faster color conversion via lookup table mesh dimension management
Rijavec, Nenad
2008-08-01
Converting images between color spaces is a computationally very demanding task. The conversion is based on lookup tables that have an output colorspace value defined for each node in a mesh that covers the input space. If the input color value to be converted is not a mesh node, the output is computed by interpolating values in the surrounding mesh nodes. For a three dimensional input space, such as the RGB, tetrahedral and trilinear interpolations are used. If the input space is four dimensional, quadrilinear interpolation is used. This paper discusses how to reduce the complexity of lookup table implementation by exploiting the relationships between input and output color space components and using moderate lookup table expansion to achieve significant speed advantage. For example, a CMYK to K conversion, commonly implemented using quadrilinear interpolation on a 9x9x9x9 mesh can be reduced to bilinear interpolation assuming the mesh can grow from 6561 nodes to 684288 nodes.
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.
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...
Anatomic Optical Coherence Tomography of Upper Airways
Chin Loy, Anthony; Jing, Joseph; Zhang, Jun; Wang, Yong; Elghobashi, Said; Chen, Zhongping; Wong, Brian J. F.
The upper airway is a complex and intricate system responsible for respiration, phonation, and deglutition. Obstruction of the upper airways afflicts an estimated 12-18 million Americans. Pharyngeal size and shape are important factors in the pathogenesis of airway obstructions. In addition, nocturnal loss in pharyngeal muscular tone combined with high pharyngeal resistance can lead to collapse of the airway and periodic partial or complete upper airway obstruction. Anatomical optical coherence tomography (OCT) has the potential to provide high-speed three-dimensional tomographic images of the airway lumen without the use of ionizing radiation. In this chapter we describe the methods behind endoscopic OCT imaging and processing to generate full three dimensional anatomical models of the human airway which can be used in conjunction with numerical simulation methods to assess areas of airway obstruction. Combining this structural information with flow dynamic simulations, we can better estimate the site and causes of airway obstruction and better select and design surgery for patients with obstructive sleep apnea.
Navnit Jha; R. K. Mohanty; Vinod Chauhan
2014-01-01
An efficient algorithm for the numerical solution of higher (even) orders two-point nonlinear boundary value problems has been developed. The method is third order accurate and applicable to both singular and nonsingular cases. We have used cubic spline polynomial basis and geometric mesh finite difference technique for the generation of this new scheme. The irreducibility and monotone property of the iteration matrix have been established and the convergence analysis of the proposed method h...
Gangfeng Wu; Zhiguo He; Guohua Liu
2014-01-01
Based on the Godunov-type cell-centered finite volume method, this paper presents a two-dimensional well-balanced shallow water model for simulating flows over arbitrary topography with wetting and drying. The central upwind scheme is used for the computation of mass and momentum fluxes on interface. The novel aspect of the present model is a robust and accurate nonnegative water depth reconstruction method which is implemented in the unstructured mesh to achieve second-order accuracy in spac...
SIP-CESE MHD model of solar wind with adaptive mesh refinement of hexahedral meshes
Feng, Xueshang; Xiang, Changqing; Zhong, Dingkun; Zhou, Yufen; Yang, Liping; Ma, Xiaopeng
2014-07-01
Solar-interplanetary space involves many features, such as discontinuities and heliospheric current sheet, with spatial scales many orders of magnitude smaller than the system size. The scalable, massively parallel, block-based, adaptive-mesh refinement (AMR) promises to resolve different temporal and spatial scales on which solar-wind plasma occurs throughout the vast solar-interplanetary space with even less cells but can generate a good enough resolution. Here, we carry out the adaptive mesh refinement (AMR) implementation of our Solar-Interplanetary space-time conservation element and solution element (CESE) magnetohydrodynamic model (SIP-CESE MHD model) using a six-component grid system (Feng et al., 2007, 2010). The AMR realization of the SIP-CESE MHD model is naturalized directly in hexahedral meshes with the aid of the parallel AMR package PARAMESH available at http://sourceforge.net/projects/paramesh/. At the same time, the topology of the magnetic field expansion factor and the minimum angular separation (at the photosphere) between an open field foot point and its nearest coronal-hole boundary are merged into the model in order to determine the volumetric heating source terms. Our numerical results for the validation study of the solar-wind background of Carrington rotation 2060 show overall good agreements in the solar corona and in interplanetary space with the observations from the Solar and Heliospheric Observatory (SOHO) and spacecraft data from OMNI.
Rotor Airloads Prediction Using Unstructured Meshes and Loose CFD/CSD Coupling
Biedron, Robert T.; Lee-Rausch, Elizabeth M.
2008-01-01
The FUN3D unsteady Reynolds-averaged Navier-Stokes solver for unstructured grids has been modified to allow prediction of trimmed rotorcraft airloads. The trim of the rotorcraft and the aeroelastic deformation of the rotor blades are accounted for via loose coupling with the CAMRAD II rotorcraft computational structural dynamics code. The set of codes is used to analyze the HART-II Baseline, Minimum Noise and Minimum Vibration test conditions. The loose coupling approach is found to be stable and convergent for the cases considered. Comparison of the resulting airloads and structural deformations with experimentally measured data is presented. The effect of grid resolution and temporal accuracy is examined. Rotorcraft airloads prediction presents a very substantial challenge for Computational Fluid Dynamics (CFD). Not only must the unsteady nature of the flow be accurately modeled, but since most rotorcraft blades are not structurally stiff, an accurate simulation must account for the blade structural dynamics. In addition, trim of the rotorcraft to desired thrust and moment targets depends on both aerodynamic loads and structural deformation, and vice versa. Further, interaction of the fuselage with the rotor flow field can be important, so that relative motion between the blades and the fuselage must be accommodated. Thus a complete simulation requires coupled aerodynamics, structures and trim, with the ability to model geometrically complex configurations. NASA has recently initiated a Subsonic Rotary Wing (SRW) Project under the overall Fundamental Aeronautics Program. Within the context of SRW are efforts aimed at furthering the state of the art of high-fidelity rotorcraft flow simulations, using both structured and unstructured meshes. Structured-mesh solvers have an advantage in computation speed, but even though remarkably complex configurations may be accommodated using the overset grid approach, generation of complex structured-mesh systems can require
Accurate determination of antenna directivity
DEFF Research Database (Denmark)
Dich, Mikael
1997-01-01
The derivation of a formula for accurate estimation of the total radiated power from a transmitting antenna for which the radiated power density is known in a finite number of points on the far-field sphere is presented. The main application of the formula is determination of directivity from power...
S-Mesh: a Mesh-based on-chip network with separation of control and transmission
Institute of Scientific and Technical Information of China (English)
LIU Hao; ZOU Xue-cheng; JI Li-xin; CAI Meng; ZHANG Ke-feng
2009-01-01
The current network-on-chip (NoC) topology cannot predict subsequent switch node status promptly. Switch nodes have to perform various functions such as routing decision, data forwarding, packet buffering, congestion control and properties of an NoC system. Therefore, these make switch architecture far more complex. This article puts forward a separating on-chip network architecture based on Mesh (S-Mesh). S-Mesh is an on-chip network that separates routing decision flow from the switches. It consists of two types of networks: datapath network (DN) and control network (CN). The CN establishes data paths for data transferring in DN. Meanwhile, the CN also transfers instructions between different resources. This property makes switch architecture simple, and eliminates conflicts in network interface units between the resource and switch. Compared with 2D-Mesh, Torus Mesh, Fat-tree and Butterfly, the average packet latency in S-Mesh is the shortest when the packet length is more than 53 B. Compared with 2D-Mesh, the areas savings of S-Mesh is about 3%--7%, and the power dissipation is decreased by approximate 2%.
Numerical analysis on the external characteristic of torque converter based on dynamic mesh
International Nuclear Information System (INIS)
For analysis of the flow field of torque converter's start operating performance, the paper established a mathematical model and simulated the numerical value of YJ series hydrodynamic torque converter. In view of the partial impact fluid and cavitation phenomenon in processes such as multiple flow area coupling algorithms the sliding mesh method cannot achieve the flow parameters real-time transfer problems between the impellers. The model, established by dynamic mesh technology, set pump wheel and turbine blade for the rotating part of dynamic mesh, pick up each iterative step of pump wheel and turbine by the size of moment through the function, and deposited it into the text file. Through calculating the changes of text data, we can judge whether the result is stable. Take the comprehensive consideration of the stability, accuracy and efficiency during the calculation, set pressure-velocity coupling algorithm as the SIMPLE algorithm, set spatial discrete format as the first order up stream format, set turbulence model as the RNG K-ε model, and realize the turbulence flow transient calculation of the hydrodynamic torque converter. Numerical simulation by the calculation was compared with the moment data from the experiments, the results show that the model established by dynamic mesh technology is more accurate and reliable. Thereafter, the pump wheel's start-up rotate speed increased from 0 to 1000r/min gradually, then remained constant. Through the analysis, we concluded as follows: the pump wheel 's moment increased gradually, the value of the turbine's moment was small, the flow increased slowly from the positive value in the early stage. Then the turbine's moment increased gradually, the flow changed into negative value until stable
Parameterized reduced order models from a single mesh using hyper-dual numbers
Brake, M. R. W.; Fike, J. A.; Topping, S. D.
2016-06-01
In order to assess the predicted performance of a manufactured system, analysts must consider random variations (both geometric and material) in the development of a model, instead of a single deterministic model of an idealized geometry with idealized material properties. The incorporation of random geometric variations, however, potentially could necessitate the development of thousands of nearly identical solid geometries that must be meshed and separately analyzed, which would require an impractical number of man-hours to complete. This research advances a recent approach to uncertainty quantification by developing parameterized reduced order models. These parameterizations are based upon Taylor series expansions of the system's matrices about the ideal geometry, and a component mode synthesis representation for each linear substructure is used to form an efficient basis with which to study the system. The numerical derivatives required for the Taylor series expansions are obtained via hyper-dual numbers, and are compared to parameterized models constructed with finite difference formulations. The advantage of using hyper-dual numbers is two-fold: accuracy of the derivatives to machine precision, and the need to only generate a single mesh of the system of interest. The theory is applied to a stepped beam system in order to demonstrate proof of concept. The results demonstrate that the hyper-dual number multivariate parameterization of geometric variations, which largely are neglected in the literature, are accurate for both sensitivity and optimization studies. As model and mesh generation can constitute the greatest expense of time in analyzing a system, the foundation to create a parameterized reduced order model based off of a single mesh is expected to reduce dramatically the necessary time to analyze multiple realizations of a component's possible geometry.
A three-dimensional nodal method with Channel-wise Intrinsic Axial Mesh Adaptation
International Nuclear Information System (INIS)
Highlights: • CIAMA solves axial heterogeneity without iterative node re-homogenization. • CIAMA can easily resolve the control rod cusping problem. • CIAMA result shows great potential for 3-D pin-by-pin calculation. - Abstract: In a conventional coarse mesh nodal method the more accurate treatment of intra-nodal axial heterogeneity requires iterative axial node re-homogenization using axial flux profiles either reconstructed from core-wise coarse mesh solution or obtained from channel-wise axial fine mesh calculation. In this paper a new nodal method formulation, using Channel-wise Intrinsic Axial Mesh Adaptation (CIAMA), is proposed to solve this problem in a more fundamental way. For a given transverse (radial) leakage, along each axial channel a rigorous sub-node heterogeneous calculation is performed with the explicit axial heterogeneity within each coarse axial node. However, the transverse leakage between the axial channels is still calculated on the basis of coarse axial nodes, using the axially averaged radial current in each coarse axial node. Since the coupling between the axial channels is through the coarse axial nodes, it is not necessary to match the boundaries of the axial sub-nodes of neighboring axial channels in order to incorporate the axial sub-node calculation as an intrinsic part of the whole core global calculation. Therefore in the CIAMA nodal method, each axial channel is allowed to have its own sub-nodes adapting to its own axial heterogeneity variation. The CIAMA method has been implemented in the commercial code EGRET, which is used to qualify CIAMA. Excellent results of modeling fuel grid and control rod movement are presented. Application of CIAMA to three-dimensional pin-by-pin core calculation is also discussed and demonstrated to work well
Numerical analysis on the external characteristic of torque converter based on dynamic mesh
Su, H. S.; Yang, G. L.; Zhang, L. Q.; Zhang, J. F.; Li, R. N.
2013-12-01
For analysis of the flow field of torque converter's start operating performance, the paper established a mathematical model and simulated the numerical value of YJ series hydrodynamic torque converter. In view of the partial impact fluid and cavitation phenomenon in processes such as multiple flow area coupling algorithms the sliding mesh method cannot achieve the flow parameters real-time transfer problems between the impellers. The model, established by dynamic mesh technology, set pump wheel and turbine blade for the rotating part of dynamic mesh, pick up each iterative step of pump wheel and turbine by the size of moment through the function, and deposited it into the text file. Through calculating the changes of text data, we can judge whether the result is stable. Take the comprehensive consideration of the stability, accuracy and efficiency during the calculation, set pressure-velocity coupling algorithm as the SIMPLE algorithm, set spatial discrete format as the first order up stream format, set turbulence model as the RNG K-ε model, and realize the turbulence flow transient calculation of the hydrodynamic torque converter. Numerical simulation by the calculation was compared with the moment data from the experiments, the results show that the model established by dynamic mesh technology is more accurate and reliable. Thereafter, the pump wheel's start-up rotate speed increased from 0 to 1000r/min gradually, then remained constant. Through the analysis, we concluded as follows: the pump wheel 's moment increased gradually, the value of the turbine's moment was small, the flow increased slowly from the positive value in the early stage. Then the turbine's moment increased gradually, the flow changed into negative value until stable.
Directory of Open Access Journals (Sweden)
Gang-ge CHENG
2013-09-01
Full Text Available Objective To explore the clinical effect and surgical technique of the repair of large defect involving frontal, temporal, and parietal regions using digitally reconstructed titanium mesh. Methods Twenty patients with large frontal, temporal, and parietal skull defect hospitalized in Air Force General Hospital from November 2006 to May 2012 were involved in this study. In these 20 patients, there were 13 males and 7 females, aged 18-58 years (mean 39 years, and the defect size measured from 7.0cm×9.0cm to 11.5cm×14.0cm (mean 8.5cm×12.0cm. Spiral CT head scan and digital three-dimensional reconstruction of skull were performed in all the patients. The shape and geometric size of skull defect was traced based on the symmetry principle, and then the data were transferred into digital precision lathe to reconstruct a titanium mesh slightly larger (1.0-1.5cm than the skull defect, and the finally the prosthesis was perfected after pruning the border. Cranioplasty was performed 6-12 months after craniotomy using the digitally reconstructed titanium mesh. Results The digitally reconstructed titanium mesh was used in 20 patients with large frontal, temporal, parietal skull defect. The surgical technique was relatively simple, and the surgical duration was shorter than before. The titanium mesh fit to the defect of skull accurately with satisfactory molding effect, good appearance and symmetrical in shape. No related complication was found in all the patients. Conclusion Repair of large frontal, temporal, parietal skull defect with digitally reconstructed titanium mesh is more advantageous than traditional manual reconstruction, and it can improve the life quality of patients.
International Nuclear Information System (INIS)
Among computational models, voxel phantoms based on computer tomographic (CT), nuclear magnetic resonance (NMR) or colour photographic images of patients, volunteers or cadavers have become popular in recent years. Although being true to nature representations of scanned individuals, voxel phantoms have limitations, especially when walled organs have to be segmented or when volumes of organs or body tissues, like adipose, have to be changed. Additionally, the scanning of patients or volunteers is usually made in supine position, which causes a shift of internal organs towards the ribcage, a compression of the lungs and a reduction of the sagittal diameter especially in the abdominal region compared to the regular anatomy of a person in the upright position, which in turn can influence organ and tissue absorbed or equivalent dose estimates. This study applies tools developed recently in the areas of computer graphics and animated films to the creation and modelling of 3D human organs, tissues, skeletons and bodies based on polygon mesh surfaces. Female and male adult human phantoms, called FASH (Female Adult meSH) and MASH (Male Adult meSH), have been designed using software, such as MakeHuman, Blender, Binvox and ImageJ, based on anatomical atlases, observing at the same time organ masses recommended by the International Commission on Radiological Protection for the male and female reference adult in report no 89. 113 organs, bones and tissues have been modelled in the FASH and the MASH phantoms representing locations for adults in standing posture. Most organ and tissue masses of the voxelized versions agree with corresponding data from ICRP89 within a margin of 2.6%. Comparison with the mesh-based male RPIAM and female RPIAF phantoms shows differences with respect to the material used, to the software and concepts applied, and to the anatomies created.
Nomina anatomica. Anatomic terminology and the old French terminology.
Chiapas-Gasca, Karla; Passos, Luiz Fernando De Souza; Euzébio Ribeiro, Sandra Lúcia; Villaseñor-Ovies, Pablo
A surprising finding in our seminars in Latin America and Spain was that approximately half of the participants continued to use the old French anatomical nomenclature. The substance of this paper is a table in which we compare the anatomical names for the items reviewed in our seminar, in a Spanish version of the old French nomenclature and in the Spanish, Portuguese, and English versions of the currently employed anatomical terms. PMID:23228528
How to Avoid and Deal with Pelvic Mesh Litigation.
Karlovsky, Matthew E
2016-08-01
Medical malpractice as it relates to transvaginal mesh implantation adds another level of responsibility when deciding on surgical options to repair stress urinary incontinence or pelvic organ prolapse. As mesh is a viable option for repair, the informed consent process must involve a time commitment to discuss thoroughly the knowns and unknowns about mesh, and potentially must cover other aspects related to surgery: FDA classification of mesh, experience, potential off label usage, and conflicts of interest. A therapeutic alliance must be developed between physician and patient to allay possible fears about the intrinsic uncertainty of surgery. Proper risk assessment of the patient and pre-operative judgment as to when and if mesh implantation is appropriate are decisions that must be documented. Resolution of a conflict from a complication can be dealt with formally or informally. Above all, sharp skills, good communication, broad knowledge base of mesh surgeries, complication management, knowledge of guidelines, along with methodical documentation can mitigate or avert mesh-related litigation. PMID:27287606
Probabilistic analysis on fault tolerance of 3-Dimensional mesh networks
Institute of Scientific and Technical Information of China (English)
王高才; 陈建二; 王国军; 陈松乔
2003-01-01
The probability model is used to analyze the fault tolerance of mesh. To simplify its analysis, it is as-sumed that the failure probability of each node is independent. A 3-D mesh is partitioned into smaller submeshes,and then the probability with which each submesh satisfies the defined condition is computed. If each submesh satis-fies the condition, then the whole mesh is connected. Consequently, the probability that a 3-D mesh is connected iscomputed assuming each node has a failure probability. Mathematical methods are used to derive a relationship be-tween network node failure probability and network connectivity probability. The calculated results show that the 3-D mesh networks can remain connected with very high probability in practice. It is formally proved that when thenetwork node failure probability is boutded by 0.45 %, the 3-D mesh networks of more than three hundred thousandnodes remain connected with probability larger than 99 %. The theoretical results show that the method is a power-ful technique to calculate the lower bound of the connectivity probability of mesh networks.
Two Similarity Metrics for Medical Subject Headings (MeSH):
Smalheiser, Neil R.; Bonifield, Gary
2016-01-01
In the present paper, we have created and characterized several similarity metrics for relating any two Medical Subject Headings (MeSH terms) to each other. The article-based metric measures the tendency of two MeSH terms to appear in the MEDLINE record of the same article. The author-based metric measures the tendency of two MeSH terms to appear in the body of articles written by the same individual (using the 2009 Author-ity author name disambiguation dataset as a gold standard). The two metrics are only modestly correlated with each other (r = 0.50), indicating that they capture different aspects of term usage. The article-based metric provides a measure of semantic relatedness, and MeSH term pairs that co-occur more often than expected by chance may reflect relations between the two terms. In contrast, the author metric is indicative of how individuals practice science, and may have value for author name disambiguation and studies of scientific discovery. We have calculated article metrics for all MeSH terms appearing in at least 25 articles in MEDLINE (as of 2014) and author metrics for MeSH terms published as of 2009. The dataset is freely available for download and can be queried at http://arrowsmith.psych.uic.edu/arrowsmith_uic/mesh_pair_metrics.html. Handling editor: Elizabeth Workman, MLIS, PhD. PMID:27213780
Finite element simulation of impact response of wire mesh screens
Directory of Open Access Journals (Sweden)
Wang Caizheng
2015-01-01
Full Text Available In this paper, the response of wire mesh screens to low velocity impact with blunt objects is investigated using finite element (FE simulation. The woven wire mesh is modelled with homogeneous shell elements with equivalent smeared mechanical properties. The mechanical behaviour of the woven wire mesh was determined experimentally with tensile tests on steel wire mesh coupons to generate the data for the smeared shell material used in the FE. The effects of impacts with a low mass (4 kg and a large mass (40 kg providing the same impact energy are studied. The joint between the wire mesh screen and the aluminium frame surrounding it is modelled using contact elements with friction between the corresponding elements. Damage to the screen of different types compromising its structural integrity, such as mesh separation and pulling out from the surrounding frame is modelled. The FE simulation is validated with results of impact tests conducted on woven steel wire screen meshes.
Normal anatomical measurements in cervical computerized tomography
International Nuclear Information System (INIS)
Radiodiagnostically relevant normal values and variations for measurements of the cervical region, the arithmetical average and the standard deviation were determined from adequate computer tomograms on 60 healthy women and men, aged 20 to 83 years. The sagittal diameter of the prevertebral soft tissue and the lumina of the upper respiratory tract were evaluated at exactly defined levels between the hyoid bone and the incisura jugularis sterni. - The thickness of the aryepiglottic folds, the maximal sagittal and transverse diameters of the thyroid gland and the calibre of the great cervical vessels were defined. - To assess information about laryngeal function in computerized tomography, measurements of distances between the cervical spine and anatomical fixed points of the larynx and hypopharynx were made as well as of the degree of vocal cord movement during normal respiration and phonation. (orig.)
Normal anatomical measurements in cervical computerized tomography
Energy Technology Data Exchange (ETDEWEB)
Zaunbauer, W.; Daepp, S.; Haertel, M.
1985-11-01
Radiodiagnostically relevant normal values and variations for measurements of the cervical region, the arithmetical average and the standard deviation were determined from adequate computer tomograms on 60 healthy women and men, aged 20 to 83 years. The sagittal diameter of the prevertebral soft tissue and the lumina of the upper respiratory tract were evaluated at exactly defined levels between the hyoid bone and the incisura jugularis sterni. - The thickness of the aryepiglottic folds, the maximal sagittal and transverse diameters of the thyroid gland and the calibre of the great cervical vessels were defined. - To assess information about laryngeal function in computerized tomography, measurements of distances between the cervical spine and anatomical fixed points of the larynx and hypopharynx were made as well as of the degree of vocal cord movement during normal respiration and phonation.
Anatomic correlations in radiogallium imaging of the peritoneum and retroperitoneum
International Nuclear Information System (INIS)
Radiogallium (67Ga) imaging of the abdomen and pelvis has been useful not only in detecting inflammations in these regions, but in pointing out their precise anatomic localization. Once the anatomic site is determined, it is often possible to infer the source of origin of the problem (such as ruptured viscus or pancreatitis). Interpretation of the images depends on recognition of patterns that define known anatomic boundaries such as the transverse mesocolon, root of the small mesentery, perirenal space, and pararenal space, or else show diffuse peritoneal uptake. The anatomic patterns may have continued usefulness in future studies, such as when radiolabeled leukocytes are employed to localize inflammations
MRI anatomical variants of mammillary bodies.
Tagliamonte, Micaela; Sestieri, Carlo; Romani, Gian Luca; Gallucci, Massimo; Caulo, Massimo
2015-01-01
The mammillary bodies (MBs) are classically defined as a pair of small round structures located on the undersurface of the diencephalon. The systematic observation of MR brain images of patients with neurological diseases, but also of healthy subjects enrolled in research protocols, reveals, however, a greater anatomical variability. The aim of the present study was to define the spectrum of such variability using spatial normalized 3D TFE T1-weighted MR images in a group of 151 healthy right-handed young subjects (78 females, age range 16-39 years). The MBs were identified on reformatted coronal and axial images and classified according to morphological, positional and numerical criteria. On the basis of coronal images, MBs were first divided into symmetrical (86.1 %) and asymmetrical (13.9 %), depending on their respective height. Symmetrical MBs were further subdivided into three variants [type A (2.7 %), B (76.2 %), C (7.3 %)] according to the depth of the intermammillary sulcus. Two morphological variants were defined on axial images, depending on whether the MBs were circular (63.6 %) or elliptic (36.4 %). This latter group was further divided in two subgroups, depending on whether the MBs were parallel (21.9 %) or convergent (14.6 %). Finally, two subjects (1.3 %) presented a supernumeral MB. The transverse size of the third ventricle was greater in the type A compared to the type B and C groups. Gender did not significantly affect the frequency of MBs variants, except for the three symmetrical subgroups in which the variants A and C were more frequent in males than in females. These findings suggest the presence of an anatomical variability of the MBs, in contrast to their classical definition. Therefore, atypical presentation of MBs can be the expression of this variability rather than a marker of neurological disorders (i.e. cerebral malformation, mesial temporal sclerosis, Wernicke-Korsakoff syndrome). PMID:24072163
Very High Order $\\PNM$ Schemes on Unstructured Meshes for the Resistive Relativistic MHD Equations
Dumbser, Michael
2009-01-01
In this paper we propose the first better than second order accurate method in space and time for the numerical solution of the resistive relativistic magnetohydrodynamics (RRMHD) equations on unstructured meshes in multiple space dimensions. The nonlinear system under consideration is purely hyperbolic and contains a source term, the one for the evolution of the electric field, that becomes stiff for low values of the resistivity. For the spatial discretization we propose to use high order $\\PNM$ schemes as introduced in \\cite{Dumbser2008} for hyperbolic conservation laws and a high order accurate unsplit time discretization is achieved using the element-local space-time discontinuous Galerkin approach proposed in \\cite{DumbserEnauxToro} for one-dimensional balance laws with stiff source terms. The divergence free character of the magnetic field is accounted for through the divergence cleaning procedure of Dedner et al. \\cite{Dedneretal}. To validate our high order method we first solve some numerical test c...
Multirate Anypath Routing in Wireless Mesh Networks
Laufer, Rafael
2008-01-01
In this paper, we present a new routing paradigm that generalizes opportunistic routing in wireless mesh networks. In multirate anypath routing, each node uses both a set of next hops and a selected transmission rate to reach a destination. Using this rate, a packet is broadcast to the nodes in the set and one of them forwards the packet on to the destination. To date, there is no theory capable of jointly optimizing both the set of next hops and the transmission rate used by each node. We bridge this gap by introducing a polynomial-time algorithm to this problem and provide the proof of its optimality. The proposed algorithm runs in the same running time as regular shortest-path algorithms and is therefore suitable for deployment in link-state routing protocols. We conducted experiments in a 802.11b testbed network, and our results show that multirate anypath routing performs on average 80% and up to 6.4 times better than anypath routing with a fixed rate of 11 Mbps. If the rate is fixed at 1 Mbps instead, p...
Elliptic Solvers for Adaptive Mesh Refinement Grids
Energy Technology Data Exchange (ETDEWEB)
Quinlan, D.J.; Dendy, J.E., Jr.; Shapira, Y.
1999-06-03
We are developing multigrid methods that will efficiently solve elliptic problems with anisotropic and discontinuous coefficients on adaptive grids. The final product will be a library that provides for the simplified solution of such problems. This library will directly benefit the efforts of other Laboratory groups. The focus of this work is research on serial and parallel elliptic algorithms and the inclusion of our black-box multigrid techniques into this new setting. The approach applies the Los Alamos object-oriented class libraries that greatly simplify the development of serial and parallel adaptive mesh refinement applications. In the final year of this LDRD, we focused on putting the software together; in particular we completed the final AMR++ library, we wrote tutorials and manuals, and we built example applications. We implemented the Fast Adaptive Composite Grid method as the principal elliptic solver. We presented results at the Overset Grid Conference and other more AMR specific conferences. We worked on optimization of serial and parallel performance and published several papers on the details of this work. Performance remains an important issue and is the subject of continuing research work.
Fair packet scheduling in Wireless Mesh Networks
Nawab, Faisal
2014-02-01
In this paper we study the interactions of TCP and IEEE 802.11 MAC in Wireless Mesh Networks (WMNs). We use a Markov chain to capture the behavior of TCP sessions, particularly the impact on network throughput due to the effect of queue utilization and packet relaying. A closed form solution is derived to numerically determine the throughput. Based on the developed model, we propose a distributed MAC protocol called Timestamp-ordered MAC (TMAC), aiming to alleviate the unfairness problem in WMNs. TMAC extends CSMA/CA by scheduling data packets based on their age. Prior to transmitting a data packet, a transmitter broadcasts a request control message appended with a timestamp to a selected list of neighbors. It can proceed with the transmission only if it receives a sufficient number of grant control messages from these neighbors. A grant message indicates that the associated data packet has the lowest timestamp of all the packets pending transmission at the local transmit queue. We demonstrate that a loose ordering of timestamps among neighboring nodes is sufficient for enforcing local fairness, subsequently leading to flow rate fairness in a multi-hop WMN. We show that TMAC can be implemented using the control frames in IEEE 802.11, and thus can be easily integrated in existing 802.11-based WMNs. Our simulation results show that TMAC achieves excellent resource allocation fairness while maintaining over 90% of maximum link capacity across a large number of topologies.
OctMesh: un entorno de elementos finitos en Octave
Rodríguez Galván, José Rafael
2007-01-01
En este trabajo se presenta a OctMesh, un entorno de herramientas o toolbox para la resolución de ecuaciones en derivadas parciales mediante el método de los elementos finitos sobre Octave. Octave es un entorno de cálculo numérico con licencia libre que utiliza de forma nativa el lenguaje de Matlab y es altamente compatible con este. Técnicamente, OctMesh, constituye una interfaz para el acceso desde Octave a las posibilidades de libMesh, una biblioteca (también con licencia libre) para la...
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.
Robust Generation of Signed Distance Fields from Triangle Meshes
DEFF Research Database (Denmark)
Bærentzen, Jakob Andreas
A new method for robust generation of distance fields from triangle meshes is presented. Graphics hardware is used to accelerate a technique for generating layered depth images. From multiple layered depth images, a binary volume and a point representation are extracted. The point information is...... 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....
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...... operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the...
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...... operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the...
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...... operations improve element quality and avoid element inversion. In the context of multiphase flow, we guarantee that every element is occupied by a single fluid and, consequently, the interface between fluids is represented by a set of faces in the simplicial complex. This approach ensures that the...
Engagement of Metal Debris into a 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.
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.
Expected Transmission Energy Route Metric for Wireless Mesh Senor Networks
Directory of Open Access Journals (Sweden)
YanLiang Jin
2011-01-01
Full Text Available Mesh is a network topology that achieves high throughput and stable intercommunication. With great potential, it is expected to be the key architecture of future networks. Wireless sensor networks are an active research area with numerous workshops and conferences arranged each year. The overall performance of a WSN highly depends on the energy consumption of the network. This paper designs a new routing metric for wireless mesh sensor networks. Results from simulation experiments reveal that the new metric algorithm improves the energy balance of the whole network and extends the lifetime of wireless mesh sensor networks (WMSNs.
RAM: a Relativistic Adaptive Mesh Refinement Hydrodynamics Code
Energy Technology Data Exchange (ETDEWEB)
Zhang, Wei-Qun; /KIPAC, Menlo Park; MacFadyen, Andrew I.; /Princeton, Inst. Advanced Study
2005-06-06
The authors have developed a new computer code, RAM, to solve the conservative equations of special relativistic hydrodynamics (SRHD) using adaptive mesh refinement (AMR) on parallel computers. They have implemented a characteristic-wise, finite difference, weighted essentially non-oscillatory (WENO) scheme using the full characteristic decomposition of the SRHD equations to achieve fifth-order accuracy in space. For time integration they use the method of lines with a third-order total variation diminishing (TVD) Runge-Kutta scheme. They have also implemented fourth and fifth order Runge-Kutta time integration schemes for comparison. The implementation of AMR and parallelization is based on the FLASH code. RAM is modular and includes the capability to easily swap hydrodynamics solvers, reconstruction methods and physics modules. In addition to WENO they have implemented a finite volume module with the piecewise parabolic method (PPM) for reconstruction and the modified Marquina approximate Riemann solver to work with TVD Runge-Kutta time integration. They examine the difficulty of accurately simulating shear flows in numerical relativistic hydrodynamics codes. They show that under-resolved simulations of simple test problems with transverse velocity components produce incorrect results and demonstrate the ability of RAM to correctly solve these problems. RAM has been tested in one, two and three dimensions and in Cartesian, cylindrical and spherical coordinates. they have demonstrated fifth-order accuracy for WENO in one and two dimensions and performed detailed comparison with other schemes for which they show significantly lower convergence rates. Extensive testing is presented demonstrating the ability of RAM to address challenging open questions in relativistic astrophysics.
Optical breast shape capture and finite-element mesh generation for electrical impedance tomography
International Nuclear Information System (INIS)
X-ray mammography is the standard for breast cancer screening. The development of alternative imaging modalities is desirable because mammograms expose patients to ionizing radiation. Electrical impedance tomography (EIT) may be used to determine tissue conductivity, a property which is an indicator of cancer presence. EIT is also a low-cost imaging solution and does not involve ionizing radiation. In breast EIT, impedance measurements are made using electrodes placed on the surface of the patient's breast. The complex conductivity of the volume of the breast is estimated by a reconstruction algorithm. EIT reconstruction is a severely ill-posed inverse problem. As a result, noisy instrumentation and incorrect modelling of the electrodes and domain shape produce significant image artefacts. In this paper, we propose a method that has the potential to reduce these errors by accurately modelling the patient breast shape. A 3D hand-held optical scanner is used to acquire the breast geometry and electrode positions. We develop methods for processing the data from the scanner and producing volume meshes accurately matching the breast surface and electrode locations, which can be used for image reconstruction. We demonstrate this method for a plaster breast phantom and a human subject. Using this approach will allow patient-specific finite-element meshes to be generated which has the potential to improve the clinical value of EIT for breast cancer diagnosis
Balsara, Dinshaw S.; Dumbser, Michael
2015-10-01
Several advances have been reported in the recent literature on divergence-free finite volume schemes for Magnetohydrodynamics (MHD). Almost all of these advances are restricted to structured meshes. To retain full geometric versatility, however, it is also very important to make analogous advances in divergence-free schemes for MHD on unstructured meshes. Such schemes utilize a staggered Yee-type mesh, where all hydrodynamic quantities (mass, momentum and energy density) are cell-centered, while the magnetic fields are face-centered and the electric fields, which are so useful for the time update of the magnetic field, are centered at the edges. Three important advances are brought together in this paper in order to make it possible to have high order accurate finite volume schemes for the MHD equations on unstructured meshes. First, it is shown that a divergence-free WENO reconstruction of the magnetic field can be developed for unstructured meshes in two and three space dimensions using a classical cell-centered WENO algorithm, without the need to do a WENO reconstruction for the magnetic field on the faces. This is achieved via a novel constrained L2-projection operator that is used in each time step as a postprocessor of the cell-centered WENO reconstruction so that the magnetic field becomes locally and globally divergence free. Second, it is shown that recently-developed genuinely multidimensional Riemann solvers (called MuSIC Riemann solvers) can be used on unstructured meshes to obtain a multidimensionally upwinded representation of the electric field at each edge. Third, the above two innovations work well together with a high order accurate one-step ADER time stepping strategy, which requires the divergence-free nonlinear WENO reconstruction procedure to be carried out only once per time step. The resulting divergence-free ADER-WENO schemes with MuSIC Riemann solvers give us an efficient and easily-implemented strategy for divergence-free MHD on
Moore, Christopher; Hopkins, Matthew; Moore, Stan; Boerner, Jeremiah; Cartwright, Keith
2015-09-01
Simulation of breakdown is important for understanding and designing a variety of applications such as mitigating undesirable discharge events. Such simulations need to be accurate through early time arc initiation to late time stable arc behavior. Here we examine constraints on the timestep and mesh size required for arc simulations using the particle-in-cell (PIC) method with direct simulation Monte Carlo (DMSC) collisions. Accurate simulation of electron avalanche across a fixed voltage drop and constant neutral density (reduced field of 1000 Td) was found to require a timestep ~ 1/100 of the mean time between collisions and a mesh size ~ 1/25 the mean free path. These constraints are much smaller than the typical PIC-DSMC requirements for timestep and mesh size. Both constraints are related to the fact that charged particles are accelerated by the external field. Thus gradients in the electron energy distribution function can exist at scales smaller than the mean free path and these must be resolved by the mesh size for accurate collision rates. Additionally, the timestep must be small enough that the particle energy change due to the fields be small in order to capture gradients in the cross sections versus energy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Wang, Cheng; Dong, XinZhuang; Shu, Chi-Wang
2015-10-01
For numerical simulation of detonation, computational cost using uniform meshes is large due to the vast separation in both time and space scales. Adaptive mesh refinement (AMR) is advantageous for problems with vastly different scales. This paper aims to propose an AMR method with high order accuracy for numerical investigation of multi-dimensional detonation. A well-designed AMR method based on finite difference weighted essentially non-oscillatory (WENO) scheme, named as AMR&WENO is proposed. A new cell-based data structure is used to organize the adaptive meshes. The new data structure makes it possible for cells to communicate with each other quickly and easily. In order to develop an AMR method with high order accuracy, high order prolongations in both space and time are utilized in the data prolongation procedure. Based on the message passing interface (MPI) platform, we have developed a workload balancing parallel AMR&WENO code using the Hilbert space-filling curve algorithm. Our numerical experiments with detonation simulations indicate that the AMR&WENO is accurate and has a high resolution. Moreover, we evaluate and compare the performance of the uniform mesh WENO scheme and the parallel AMR&WENO method. The comparison results provide us further insight into the high performance of the parallel AMR&WENO method.
Sui, Yi; Spelt, Peter D. M.; Ding, Hang
2010-11-01
Diffuse Interface (DI) methods are employed widely for the numerical simulation of two-phase flows, even with moving contact lines. In a DI method, the interface thickness should be as thin as possible to simulate spreading phenomena under realistic flow conditions, so a fine grid is required, beyond the reach of current methods that employ a uniform grid. Here we have integrated a DI method based on a uniform mesh, to a block-based adaptive mesh refinement method, so that only the regions near the interface are resolved by a fine mesh. The performance of the present method is tested by simulations including drop deformation in shear flow, Rayleigh-Taylor instability and drop spreading on a flat surface, et al. The results show that the present method can give accurate results with much smaller computational cost, compared to the original DI method based on a uniform mesh. Based on the present method, simulation of drop spreading is carried out with Cahn number of 0.001 and the contact line region is well resolved. The flow field near the contact line, the contact line speed as well as the apparent contact angle are investigated in detail and compared with previous analytical work.
Development of a hybrid particle-mesh method for two-phase flow simulations with phase change
International Nuclear Information System (INIS)
A hybrid particle-mesh method was developed for efficient and accurate simulations of two-phase flows with phase change. In this method, the CIP/MM (constrained interpolated profile/multi-moment finite volume) method is used to calculate the main part of two-phase flows, while the finite volume particle (FVP) method is applied to represent the interface between two phases based on a Lagrangian scheme. The conservation equations are first solved by CIP/MM, and then mass, velocity and energy on the mesh grid are interpolated to numerical particles, which are distributed only on the surface of liquid phase to capture the phase interface by the FVP method. The particles are also used to calculate heat and mass transfers due to phase change on the interface. The phase of each particle is determined according to its enthalpy value interpolated from mesh grids. The mesh and particle methods are combined tightly in a single numerical solution algorithm to improve numerical accuracy and stability. Two benchmark simulations of conventional 1D Stefan problem for a vapor-liquid system and horizontal film boiling behavior demonstrate that this hybrid method is potentially applicable to two-phase flow calculations with phase change occurring at moving interface. (author)
Directory of Open Access Journals (Sweden)
Martin ePyka
2014-09-01
Full Text Available Computational models of neural networks can be based on a variety of different parameters. These parameters include, for example, the 3d shape of neuron layers, the neurons' spatial projection patterns, spiking dynamics and neurotransmitter systems. While many well-developed approaches are available to model, for example, the spiking dynamics, there is a lack of approaches for modeling the anatomical layout of neurons and their projections. We present a new method, called Parametric Anatomical Modeling (PAM, to fill this gap. PAM can be used to derive network connectivities and conduction delays from anatomical data, such as the position and shape of the neuronal layers and the dendritic and axonal projection patterns. Within the PAM framework, several mapping techniques between layers can account for a large variety of connection properties between pre- and post-synaptic neuron layers. PAM is implemented as a Python tool and integrated in the 3d modeling software Blender. We demonstrate on a 3d model of the hippocampal formation how PAM can help reveal complex properties of the synaptic connectivity and conduction delays, properties that might be relevant to uncover the function of the hippocampus. Based on these analyses, two experimentally testable predictions arose: i the number of neurons and the spread of connections is heterogeneously distributed across the main anatomical axes, ii the distribution of connection lengths in CA3-CA1 differ qualitatively from those between DG-CA3 and CA3-CA3. Models created by PAM can also serve as an educational tool to visualize the 3d connectivity of brain regions. The low-dimensional, but yet biologically plausible, parameter space renders PAM suitable to analyse allometric and evolutionary factors in networks and to model the complexity of real networks with comparatively little effort.
Directory of Open Access Journals (Sweden)
Argraves W Scott
2010-04-01
Full Text Available Abstract Background An important objective of DNA microarray-based gene expression experimentation is determining inter-relationships that exist between differentially expressed genes and biological processes, molecular functions, cellular components, signaling pathways, physiologic processes and diseases. Results Here we describe GeneMesh, a web-based program that facilitates analysis of DNA microarray gene expression data. GeneMesh relates genes in a query set to categories available in the Medical Subject Headings (MeSH hierarchical index. The interface enables hypothesis driven relational analysis to a specific MeSH subcategory (e.g., Cardiovascular System, Genetic Processes, Immune System Diseases etc. or unbiased relational analysis to broader MeSH categories (e.g., Anatomy, Biological Sciences, Disease etc.. Genes found associated with a given MeSH category are dynamically linked to facilitate tabular and graphical depiction of Entrez Gene information, Gene Ontology information, KEGG metabolic pathway diagrams and intermolecular interaction information. Expression intensity values of groups of genes that cluster in relation to a given MeSH category, gene ontology or pathway can be displayed as heat maps of Z score-normalized values. GeneMesh operates on gene expression data derived from a number of commercial microarray platforms including Affymetrix, Agilent and Illumina. Conclusions GeneMesh is a versatile web-based tool for testing and developing new hypotheses through relating genes in a query set (e.g., differentially expressed genes from a DNA microarray experiment to descriptors making up the hierarchical structure of the National Library of Medicine controlled vocabulary thesaurus, MeSH. The system further enhances the discovery process by providing links between sets of genes associated with a given MeSH category to a rich set of html linked tabular and graphic information including Entrez Gene summaries, gene ontologies
RSW Mixed Element Cell-Centered Medium Mesh
National Aeronautics and Space Administration — This RSW gridset is designed as the medium size mixed element grid for use with cell-centered unstructured meshes. UG3 : Grid File Name = rsw_med_mixedcc.b8.ugrid...
Tetrahedral mesh improvement via optimization of the element condition number
Energy Technology Data Exchange (ETDEWEB)
FREITAG,LORI A.; KNUPP,PATRICK
2000-05-22
The authors present a new shape measure for tetrahedral elements that is optimal in that it gives the distance of a tetrahedron from the set of inverted elements. This measure is constructed from the condition number of the linear transformation between a unit equilateral tetrahedron and any tetrahedron with positive volume. Using this shape measure, they formulate two optimization objective functions that are differentiated by their goal: the first seeks to improve the average quality of the tetrahedral mesh; the second aims to improve the worst-quality element in the mesh. They review the optimization techniques used with each objective function and presents experimental results that demonstrate the effectiveness of the mesh improvement methods. They show that a combined optimization approach that uses both objective functions obtains the best-quality meshes for several complex geometries.
Ultra-fast spreading on superhydrophilic fibrous mesh with nanochannels
International Nuclear Information System (INIS)
In this paper, we fabricated a TiO2 mesh with ultra-fast spreading superhydrophilic property without UV irradiation. Through electrospinning process followed by calcinations, we obtained meshes with special micropores and nanochannels composite hierarchical structures. Each fiber exhibits a bundle structure of aligned elementary filaments with nanochannels, which should be resulted from phase separation and stretch of electrostatic force during electrospinning process. The mesh shows ultra-fast spreading property within only tens of milliseconds (ms). It is concluded that the special topography offered a multi-scale 3D capillary effect that play crucial role in ultra-fast spreading superhydrophilic property of the mesh. This study provides interesting insights to design novel materials concerning liquid transport and dissipation, which may find its way in various applications.
Method of determining dynamic retention of mesh phase separator
Давыдов, Сергей Александрович
2010-01-01
In given work the engineering design procedure of dynamic retention of mesh phase’s delimiters is presented. This allows to determine functionability of means fuel continuity support in dynamic conditions at a stage of outline designing.
Self-organizing mesh network of android devices
Rui Miguel Ribeiro Archer
2013-01-01
Extension of existing android software to allow a mesh network of android devices to self-configure and start applications on top of it. Survey of current capabilities and analysis of network impact of used protocols.
Improving Performance of Wireless Mesh Network using Channel Allocation Schemes
Directory of Open Access Journals (Sweden)
Pranay Joshi, Prof. Rupesh Dubey, Prof. Harsh Goud
2013-07-01
Full Text Available One of the major advantages of wireless com-munication over wired is the flexibility when creating links between nodes. But this comes at a price as influences from outside the mesh network can distort communication between the nodes and even the nodes themselves interfere with each other. By carefully selecting channels where each link transmits data on, the interference can be minimized causing the throughput and end-to-end delay to be improved. We compares the channel allocation schemes to find the best channel selection for each link. While single radio mesh nodes operating on a single channel suffer from capacity constraints, equipping mesh routers with multiple radios using multiple non overlapping channels can significantly alleviate the capacity problem and increase the aggregate bandwidth available to the network. The goal of channel assignment algorithms in multi radio mesh networks is to minimize interference while improving the aggregate network capacity and maintaining the connectivity of the network.
Form-finding with polyhedral meshes made simple
Tang, Chengcheng
2014-07-27
We solve the form-finding problem for polyhedral meshes in a way which combines form, function and fabrication; taking care of user-specified constraints like boundary interpolation, planarity of faces, statics, panel size and shape, enclosed volume, and last, but not least, cost. Our main application is the interactive modeling of meshes for architectural and industrial design. Our approach can be described as guided exploration of the constraint space whose algebraic structure is simplified by introducing auxiliary variables and ensuring that constraints are at most quadratic. Computationally, we perform a projection onto the constraint space which is biased towards low values of an energy which expresses desirable "soft" properties like fairness. We have created a tool which elegantly handles difficult tasks, such as taking boundary-alignment of polyhedral meshes into account, planarization, fairing under planarity side conditions, handling hybrid meshes, and extending the treatment of static equilibrium to shapes which possess overhanging parts.
ARC Code TI: Middleware Using Existing SSH Hosts (Mesh)
National Aeronautics and Space Administration — Mesh is a secure, lightweight grid middleware that is based on the addition of a single sign-on capability to the built-in public key authentication mechanism of...
Design and Implementation of the MESH Services Platform
Batteram, Harold J.; Bakker, John-Luc; Verhoosel, Jack P.C.; Diakov, Nikolay K.
1999-01-01
Industry acceptance of TINA (Telecommunications Information Networking Architecture) will depend heavily on both the evaluation of working systems that implement this architecture, and on the experiences obtained during the design and implementation of these systems. During the MESH' (Multimedia ser
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.
RSW Fully Tet Coarse Cell-Centered Mesh
National Aeronautics and Space Administration — This is the RSW fully tetrahedral unstructured mesh dataset for a cell-centered code, including the viscous wind tunnel wall. UG3 : Grid File Name =...
An Investigation of Anatomical Competence in Junior Medical Doctors
Vorstenbosch, Marc A. T. M.; Kooloos, Jan G. M.; Bolhuis, Sanneke M.; Laan, Roland F. J. M.
2016-01-01
Because of a decrease of the time available for anatomy education, decisions need to be made to reduce the relevant content of the anatomy curriculum. Several expert consensus initiatives resulted in lists of structures, lacking analysis of anatomical competence. This study aims to explore the use of anatomical knowledge by medical doctors in an…
PC Assisted Anatomical Measurements in 3D Using CT Data
DEFF Research Database (Denmark)
Hvidtfeldt, Mogens; Pedersen, Steen
1999-01-01
To assess facilities and applications of a programme for a PC based CT measurements in 3D of anatomical angelse in the skeleton.......To assess facilities and applications of a programme for a PC based CT measurements in 3D of anatomical angelse in the skeleton....
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
Design methodology of the strength properties of medical knitted meshes
Mikołajczyk, Z.; Walkowska, A.
2016-07-01
One of the most important utility properties of medical knitted meshes intended for hernia and urological treatment is their bidirectional strength along the courses and wales. The value of this parameter, expected by the manufacturers and surgeons, is estimated at 100 N per 5 cm of the sample width. The most frequently, these meshes are produced on the basis of single- or double-guide stitches. They are made of polypropylene and polyester monofilament yarns with the diameter in the range from 0.6 to 1.2 mm, characterized by a high medical purity. The aim of the study was to develop the design methodology of meshes strength based on the geometrical construction of the stitch and strength of yarn. In the environment of the ProCAD warpknit 5 software the simulated stretching process of meshes together with an analysis of their geometry changes was carried out. Simulations were made for four selected representative stitches. Both on a built, unique measuring position and on the tensile testing machine the real parameters of the loops geometry of meshes were measured. Model of mechanical stretching of warp-knitted meshes along the courses and wales was developed. The thesis argument was made, that the force that breaks the loop of warp-knitted fabric is the lowest value of breaking forces of loop link yarns or yarns that create straight sections of loop. This thesis was associate with the theory of strength that uses the “the weakest link concept”. Experimental verification of model was carried out for the basic structure of the single-guide mesh. It has been shown that the real, relative strength of the mesh related to one course is equal to the strength of the yarn breakage in a loop, while the strength along the wales is close to breaking strength of a single yarn. In relation to the specific construction of the medical mesh, based on the knowledge of the density of the loops structure, the a-jour mesh geometry and the yarns strength, it is possible, with high
Cingoski, Vlatko; Yamashita, Hideo
1995-01-01
In this paper, the problem of defining the optimal mesh density for accurate computation of 3-D eddy-current distribution using first-order edge-based finite elements of mixed type is presented. The accuracy of eddy-current distribution is investigated using various finite element mesh densities both inside and outside the penetration area of eddy-current flow. All three components of eddy-current vectors were monitored by developing 3-D test model. The 3-D test model and the obtained results...
CHRONIC GROIN PAIN FOLLOWING LICHTENSTEIN MESH HERNIOPLASTY FOR INGUINAL HERNIA
Ajay; Prabir Kr
2015-01-01
AIMS AND OBJECTIVES To assess the incidence of Chronic Groin pain following Lichtenstein Mesh Hernioplasty for Inguinal Hernia. MATERIALS AND METHODS The study includes 210 patients from December 2010-November 2014 who underwent Lichtenstein Mesh Hernioplasty for Inguinal Hernia, but only 154 patients reported at three months and 147 reported at six months. Because 63 patients did not report at six months, they were finally excluded from the study. So ultimately 147 p...
OPEN PREPERITONEAL MESH REPAIR FOR INGUINAL HERNIA: A VIABLE OPTION
Suresh; Ramya
2014-01-01
BACKGROUND: Inguinal hernia still remains a significant clinical problem despite the availability of variety of surgical techniques. This study was designed to evaluate the outcome and benefit of open preperitoneal mesh repair. OBJECTIVE: To evaluate the open preperitoneal mesh repair technique regarding complications, recurrences, safety and benefit. PATIENTS AND METHODS: Between July 2013 and June 2014, a prospective study of 25 consecutive patients operated for groin he...
Intrusion Detection Systems for Community Wireless Mesh Networks
Makaroff, D.; Smith, Paul; Race, Nicholas J.P.; Hutchison, David
2008-01-01
Wireless mesh networks are being increasingly used to provide affordable network connectivity to communities where wired deployment strategies are either not possible or are prohibitively expensive. Unfortunately, computer networks (including mesh networks) are frequently being exploited by increasingly profit-driven and insidious attackers, which can affect their utility for legitimate use. In response to this, a number of countermeasures have been developed, including intrusion detection sy...
Fibrin sealant for mesh fixation in laparoscopic umbilical hernia repair
DEFF Research Database (Denmark)
Eriksen, J R; Bisgaard, T; Assaadzadeh, S;
2013-01-01
Fibrin sealant for mesh fixation has significant positive effects on early outcome after laparoscopic ventral hernia repair (LVHR) compared with titanium tacks. Whether fibrin sealant fixation also results in better long-term outcome is unknown.......Fibrin sealant for mesh fixation has significant positive effects on early outcome after laparoscopic ventral hernia repair (LVHR) compared with titanium tacks. Whether fibrin sealant fixation also results in better long-term outcome is unknown....
A Survey on Energy Efficiency for Wireless Mesh Network
Sarra Mamechaoui; Fedoua Didi; Guy Pujolle
2013-01-01
Reducing CO2 emissions is an important global environmental issue. Over the recent years, wireless and mobile communications have increasingly become popular with consumers. An increasingly popular type of wireless access is the so-called Wireless Mesh Networks (WMNs) that provide wireless connectivity through much cheaper and more flexible backhaul infrastructure compared with wired solutions. Wireless Mesh Network (WMN) is an emerging new technology which is being adopted as the wireless in...
A general boundary capability embedded in an orthogonal mesh
Energy Technology Data Exchange (ETDEWEB)
Hewett, D.W.; Yu-Jiuan Chen [Lawrence Livermore National Lab., CA (United States)
1995-07-01
The authors describe how they hold onto orthogonal mesh discretization when dealing with curved boundaries. Special difference operators were constructed to approximate numerical zones split by the domain boundary; the operators are particularly simple for this rectangular mesh. The authors demonstrated that this simple numerical approach, termed Dynamic Alternating Direction Implicit, turned out to be considerably more efficient than more complex grid-adaptive algorithms that were tried previously.
Reconstructive laparoscopic prolapse surgery to avoid mesh erosions
Directory of Open Access Journals (Sweden)
Devassy, Rajesh
2013-09-01
Full Text Available Introduction: The objective of the study is to examine the efficacy of the purely laparoscopic reconstructive management of cystocele and rectocele with mesh, to avoid the risk of erosion by the graft material, a well known complication in vaginal mesh surgery. Material and methods: We performed a prospective, single-case, non-randomized study in 325 patients who received laparoscopic reconstructive management of pelvic organe prolaps with mesh. The study was conducted between January 2004 and December 2012 in a private clinic in India. The most common prolapse symptoms were reducible vaginal lump, urinary stress incontinence, constipation and flatus incontinence, sexual dysfunction and dypareunia. The degree e of the prolaps was staged according to POPQ system. The approach was purely laparoscopic and involved the use of polypropylene (Prolene or polyurethane with activated regenerated cellulose coating (Parietex mesh. Results: The mean age was 55 (30–80 years and the most of the patients were multiparous (272/325. The patients received a plastic correction of the rectocele only (138 cases, a cystocele and rectocele (187 cases with mesh. 132 patients had a concomitant total hysterectomy; in 2 cases a laparoscopic supracervical hysterectomy was performed and 190 patients had a laparoscopic colposuspension. The mean operation time was 82.2 (60–210 minutes. The mean follow up was 3.4 (3–5 years. Urinary retention developed in 1 case, which required a new laparoscopical intervention. Bladder injury, observed in the same case was in one session closed with absorbable suture. There were four recurrences of the rectocele, receiving a posterior vaginal colporrhaphy. Erosions of the mesh were not reported or documented. Conclusion: The pure laparoscopic reconstructive management of the cystocele and rectocele with mesh seems to be a safe and effective surgical procedure potentially avoiding the risk of mesh erosions.