Numerical simulation of evolutionary erodible bedforms using the particle finite element method

NASA Astrophysics Data System (ADS)

Bravo, Rafael; Becker, Pablo; Ortiz, Pablo

2017-07-01

This paper presents a numerical strategy for the simulation of flows with evolutionary erodible boundaries. The fluid equations are fully resolved in 3D, while the sediment transport is modelled using the Exner equation and solved with an explicit Lagrangian procedure based on a fixed 2D mesh. Flow and sediment are coupled in geometry by deforming the fluid mesh in the vertical direction and in velocities with the experimental sediment flux computed using the Meyer Peter Müller model. A comparison with real experiments on channels is performed, giving good agreement.

Fully implicit moving mesh adaptive algorithm

NASA Astrophysics Data System (ADS)

Chacon, Luis

2005-10-01

In many problems of interest, the numerical modeler is faced with the challenge of dealing with multiple time and length scales. The former is best dealt with with fully implicit methods, which are able to step over fast frequencies to resolve the dynamical time scale of interest. The latter requires grid adaptivity for efficiency. Moving-mesh grid adaptive methods are attractive because they can be designed to minimize the numerical error for a given resolution. However, the required grid governing equations are typically very nonlinear and stiff, and of considerably difficult numerical treatment. Not surprisingly, fully coupled, implicit approaches where the grid and the physics equations are solved simultaneously are rare in the literature, and circumscribed to 1D geometries. In this study, we present a fully implicit algorithm for moving mesh methods that is feasible for multidimensional geometries. A crucial element is the development of an effective multilevel treatment of the grid equation.ootnotetextL. Chac'on, G. Lapenta, A fully implicit, nonlinear adaptive grid strategy, J. Comput. Phys., accepted (2005) We will show that such an approach is competitive vs. uniform grids both from the accuracy (due to adaptivity) and the efficiency standpoints. Results for a variety of models 1D and 2D geometries, including nonlinear diffusion, radiation-diffusion, Burgers equation, and gas dynamics will be presented.

Multigrid Method for Modeling Multi-Dimensional Combustion with Detailed Chemistry

NASA Technical Reports Server (NTRS)

Zheng, Xiaoqing; Liu, Chaoqun; Liao, Changming; Liu, Zhining; McCormick, Steve

1996-01-01

A highly accurate and efficient numerical method is developed for modeling 3-D reacting flows with detailed chemistry. A contravariant velocity-based governing system is developed for general curvilinear coordinates to maintain simplicity of the continuity equation and compactness of the discretization stencil. A fully-implicit backward Euler technique and a third-order monotone upwind-biased scheme on a staggered grid are used for the respective temporal and spatial terms. An efficient semi-coarsening multigrid method based on line-distributive relaxation is used as the flow solver. The species equations are solved in a fully coupled way and the chemical reaction source terms are treated implicitly. Example results are shown for a 3-D gas turbine combustor with strong swirling inflows.

Numerical MHD codes for modeling astrophysical flows

NASA Astrophysics Data System (ADS)

Koldoba, A. V.; Ustyugova, G. V.; Lii, P. S.; Comins, M. L.; Dyda, S.; Romanova, M. M.; Lovelace, R. V. E.

2016-05-01

We describe a Godunov-type magnetohydrodynamic (MHD) code based on the Miyoshi and Kusano (2005) solver which can be used to solve various astrophysical hydrodynamic and MHD problems. The energy equation is in the form of entropy conservation. The code has been implemented on several different coordinate systems: 2.5D axisymmetric cylindrical coordinates, 2D Cartesian coordinates, 2D plane polar coordinates, and fully 3D cylindrical coordinates. Viscosity and diffusivity are implemented in the code to control the accretion rate in the disk and the rate of penetration of the disk matter through the magnetic field lines. The code has been utilized for the numerical investigations of a number of different astrophysical problems, several examples of which are shown.

A harmonic polynomial cell (HPC) method for 3D Laplace equation with application in marine hydrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Yan-Lin, E-mail: yanlin.shao@dnvgl.com; Faltinsen, Odd M.

2014-10-01

We propose a new efficient and accurate numerical method based on harmonic polynomials to solve boundary value problems governed by 3D Laplace equation. The computational domain is discretized by overlapping cells. Within each cell, the velocity potential is represented by the linear superposition of a complete set of harmonic polynomials, which are the elementary solutions of Laplace equation. By its definition, the method is named as Harmonic Polynomial Cell (HPC) method. The characteristics of the accuracy and efficiency of the HPC method are demonstrated by studying analytical cases. Comparisons will be made with some other existing boundary element based methods,more » e.g. Quadratic Boundary Element Method (QBEM) and the Fast Multipole Accelerated QBEM (FMA-QBEM) and a fourth order Finite Difference Method (FDM). To demonstrate the applications of the method, it is applied to some studies relevant for marine hydrodynamics. Sloshing in 3D rectangular tanks, a fully-nonlinear numerical wave tank, fully-nonlinear wave focusing on a semi-circular shoal, and the nonlinear wave diffraction of a bottom-mounted cylinder in regular waves are studied. The comparisons with the experimental results and other numerical results are all in satisfactory agreement, indicating that the present HPC method is a promising method in solving potential-flow problems. The underlying procedure of the HPC method could also be useful in other fields than marine hydrodynamics involved with solving Laplace equation.« less

Two-component dark-bright solitons in three-dimensional atomic Bose-Einstein condensates.

PubMed

Wang, Wenlong; Kevrekidis, P G

2017-03-01

In the present work, we revisit two-component Bose-Einstein condensates in their fully three-dimensional (3D) form. Motivated by earlier studies of dark-bright solitons in the 1D case, we explore the stability of these structures in their fully 3D form in two variants. In one the dark soliton is planar and trapping a planar bright (disk) soliton. In the other case, a dark spherical shell soliton creates an effective potential in which a bright spherical shell of atoms is trapped in the second component. We identify these solutions as numerically exact states (up to a prescribed accuracy) and perform a Bogolyubov-de Gennes linearization analysis that illustrates that both structures can be dynamically stable in suitable intervals of sufficiently low chemical potentials. We corroborate this finding theoretically by analyzing the stability via degenerate perturbation theory near the linear limit of the system. When the solitary waves are found to be unstable, we explore their dynamical evolution via direct numerical simulations which, in turn, reveal wave forms that are more robust. Finally, using the SO(2) symmetry of the model, we produce multi-dark-bright planar or shell solitons involved in pairwise oscillatory motion.

Multigrid methods for flow transition in three-dimensional boundary layers with surface roughness

NASA Technical Reports Server (NTRS)

Liu, Chaoqun; Liu, Zhining; Mccormick, Steve

1993-01-01

The efficient multilevel adaptive method has been successfully applied to perform direct numerical simulations (DNS) of flow transition in 3-D channels and 3-D boundary layers with 2-D and 3-D isolated and distributed roughness in a curvilinear coordinate system. A fourth-order finite difference technique on stretched and staggered grids, a fully-implicit time marching scheme, a semi-coarsening multigrid method associated with line distributive relaxation scheme, and an improved outflow boundary-condition treatment, which needs only a very short buffer domain to damp all order-one wave reflections, are developed. These approaches make the multigrid DNS code very accurate and efficient. This allows us not only to be able to do spatial DNS for the 3-D channel and flat plate at low computational costs, but also to do spatial DNS for transition in the 3-D boundary layer with 3-D single and multiple roughness elements, which would have extremely high computational costs with conventional methods. Numerical results show good agreement with the linear stability theory, the secondary instability theory, and a number of laboratory experiments. The contribution of isolated and distributed roughness to transition is analyzed.

Assessment of critical path analyses of the relationship between permeability and electrical conductivity of pore networks

NASA Astrophysics Data System (ADS)

Skaggs, Todd H.

2011-10-01

Critical path analysis (CPA) is a method for estimating macroscopic transport coefficients of heterogeneous materials that are highly disordered at the micro-scale. Developed originally to model conduction in semiconductors, numerous researchers have noted that CPA might also have relevance to flow and transport processes in porous media. However, the results of several numerical investigations of critical path analysis on pore network models raise questions about the applicability of CPA to porous media. Among other things, these studies found that (i) in well-connected 3D networks, CPA predictions were inaccurate and became worse when heterogeneity was increased; and (ii) CPA could not fully explain the transport properties of 2D networks. To better understand the applicability of CPA to porous media, we made numerical computations of permeability and electrical conductivity on 2D and 3D networks with differing pore-size distributions and geometries. A new CPA model for the relationship between the permeability and electrical conductivity was found to be in good agreement with numerical data, and to be a significant improvement over a classical CPA model. In sufficiently disordered 3D networks, the new CPA prediction was within ±20% of the true value, and was nearly optimal in terms of minimizing the squared prediction errors across differing network configurations. The agreement of CPA predictions with 2D network computations was similarly good, although 2D networks are in general not well-suited for evaluating CPA. Numerical transport coefficients derived for regular 3D networks of slit-shaped pores were found to be in better agreement with experimental data from rock samples than were coefficients derived for networks of cylindrical pores.

A novel 2.5D finite difference scheme for simulations of resistivity logging in anisotropic media

NASA Astrophysics Data System (ADS)

Zeng, Shubin; Chen, Fangzhou; Li, Dawei; Chen, Ji; Chen, Jiefu

2018-03-01

The objective of this study is to develop a method to model 3D resistivity well logging problems in 2D formation with anisotropy, known as 2.5D modeling. The traditional 1D forward modeling extensively used in practice lacks the capability of modeling 2D formation. A 2.5D finite difference method (FDM) solving all the electric and magnetic field components simultaneously is proposed. Compared to other previous 2.5D FDM schemes, this method is more straightforward in modeling fully anisotropic media and easy to be implemented. Fourier transform is essential to this FDM scheme, and by employing Gauss-Legendre (GL) quadrature rule the computational time of this step can be greatly reduced. In the numerical examples, we first demonstrate the validity of the FDM scheme with GL rule by comparing with 1D forward modeling for layered anisotropic problems, and then we model a complicated 2D formation case and find that the proposed 2.5D FD scheme is much more efficient than 3D numerical methods.

Numerical Validation of the N3S-NATUR Code for Supersonic Nozzles and Afterbody Flows

NASA Astrophysics Data System (ADS)

Perrot, Y.; Hadjadj, A.

2005-02-01

A numerical investigation was conducted to assess the ability of the three-dimensional Navier-Stokes solver, N3S-Natur [1], using the k-ω SST turbulence model when computing nozzle-afterbody flows with propulsive jets. Three nozzle configurations were selected as test cases for the computational method: the first is the ONERA TIC nozzle, the second is an axisymmetric boat-tailed afterbody configuration and the third is a fully 3D transonic nozzle. In most situations, internal and external flow-field regions are modeled. The obtained results are carefully analyzed and compared to the experimental data. A three-dimensional computation was done to make evidence of 3D phenomena which are not negligible. A particular attention was payed to the appearance of a recirculation zone on the afterbody.

UT simulation using a fully automated 3D hybrid model: Application to planar backwall breaking defects inspection

NASA Astrophysics Data System (ADS)

Imperiale, Alexandre; Chatillon, Sylvain; Darmon, Michel; Leymarie, Nicolas; Demaldent, Edouard

2018-04-01

The high frequency models gathered in the CIVA software allow fast computations and provide satisfactory quantitative predictions in a wide range of situations. However, the domain of validity of these models is limited since they do not accurately predict the ultrasound response in configurations involving subwavelength complex phenomena. In addition, when modelling backwall breaking defects inspection, an important challenge remains to capture the propagation of the creeping waves that are generated at the critical angle. Hybrid models combining numerical and asymptotic methods have already been shown to be an effective strategy to overcome these limitations in 2D [1]. However, 3D simulations remain a crucial issue for industrial applications because of the computational cost of the numerical solver. A dedicated three dimensional high order finite element model combined with a domain decomposition method has been recently proposed to tackle 3D limitations [2]. In this communication, we will focus on the specific case of planar backwall breaking defects, with an adapted coupling strategy in order to efficiently model the propagation of creeping waves. Numerical and experimental validations will be proposed on various configurations.

Methods in the study of discrete upper hybrid waves

NASA Astrophysics Data System (ADS)

Yoon, P. H.; Ye, S.; Labelle, J.; Weatherwax, A. T.; Menietti, J. D.

2007-11-01

Naturally occurring plasma waves characterized by fine frequency structure or discrete spectrum, detected by satellite, rocket-borne instruments, or ground-based receivers, can be interpreted as eigenmodes excited and trapped in field-aligned density structures. This paper overviews various theoretical methods to study such phenomena for a one-dimensional (1-D) density structure. Among the various methods are parabolic approximation, eikonal matching, eigenfunction matching, and full numerical solution based upon shooting method. Various approaches are compared against the full numerical solution. Among the analytic methods it is found that the eigenfunction matching technique best approximates the actual numerical solution. The analysis is further extended to 2-D geometry. A detailed comparative analysis between the eigenfunction matching and fully numerical methods is carried out for the 2-D case. Although in general the two methods compare favorably, significant differences are also found such that for application to actual observations it is prudent to employ the fully numerical method. Application of the methods developed in the present paper to actual geophysical problems will be given in a companion paper.

Scalar transport in inline mixers with spatially periodic flows

NASA Astrophysics Data System (ADS)

Baskan, Ozge; Rajaei, Hadi; Speetjens, Michel F. M.; Clercx, Herman J. H.

2017-01-01

Spatially persisting patterns form during the downstream evolution of passive scalars in three-dimensional (3D) spatially periodic flows due to the coupled effect of stretching and folding mechanisms of the flow field. This has been investigated in many computational and theoretical studies of 2D time-periodic and 3D spatially periodic flow fields. However, experimental studies, to date, have mainly focused on flow visualization with streaks of dye rather than fully 3D scalar field measurements. Our study employs 3D particle tracking velocimetry and 3D laser-induced fluorescence to analyze the evolution of 3D flow and scalar fields and the correlation between the coherent flow/scalar field structures in a representative inline mixer, the Quatro static mixer. For this purpose an experimental setup that consists of an optically accessible test section with transparent internal elements accommodating a pressure-driven pipe flow has been built. The flow and scalar fields clearly underline the complementarity of the experimental results with numerical simulations and provide validation of the periodicity assumption needed in numerical studies. The experimental procedure employed in this investigation, which allows studying the scalar transport in the advective limit, demonstrates the suitability of the present method for exploratory mixing studies of a variety of mixing devices, beyond the Quatro static mixer.

Rapid Gradient-Echo Imaging

PubMed Central

Hargreaves, Brian

2012-01-01

Gradient echo sequences are widely used in magnetic resonance imaging (MRI) for numerous applications ranging from angiography to perfusion to functional MRI. Compared with spin-echo techniques, the very short repetition times of gradient-echo methods enable very rapid 2D and 3D imaging, but also lead to complicated “steady states.” Signal and contrast behavior can be described graphically and mathematically, and depends strongly on the type of spoiling: fully balanced (no spoiling), gradient spoiling, or RF-spoiling. These spoiling options trade off between high signal and pure T1 contrast while the flip angle also affects image contrast in all cases, both of which can be demonstrated theoretically and in image examples. As with spin-echo sequences, magnetization preparation can be added to gradient-echo sequences to alter image contrast. Gradient echo sequences are widely used for numerous applications such as 3D perfusion imaging, functional MRI, cardiac imaging and MR angiography. PMID:23097185

Comparative 1D and 3D numerical investigation of open-channel junction flows and energy losses

NASA Astrophysics Data System (ADS)

Luo, Hao; Fytanidis, Dimitrios K.; Schmidt, Arthur R.; García, Marcelo H.

2018-07-01

The complexity of open channel confluences stems from flow mixing, secondary circulation, post-confluence flow separation, contraction and backwater effects. These effects in turn result in a large number of parameters required to adequately quantify the junction induced hydraulic resistance and describe mean flow pattern and turbulent flow structures due to flow merging. The recent development in computing power advances the application of 3D Computational Fluid Dynamics (CFD) codes to visualize and understand the Confluence Hydrodynamic Zone (CHZ). Nevertheless, 1D approaches remain the mainstay in large drainage network or waterway system modeling considering computational efficiency and data availability. This paper presents (i) a modified 1D nonlinear dynamic model; (ii) a fully 3D non-hydrostatic, Reynolds-averaged Navier-Stokes Equations (RANS)-based, Computational Fluid Dynamics (CFD) model; (iii) an analysis of changing confluence hydrodynamics and 3D turbulent flow structure under various controls; (iv) a comparison of flow features (i.e. upstream water depths, energy losses and post-confluence contraction) predicted by 1D and 3D models; and (v) parameterization of 3D flow characteristics in 1D modeling through the computation of correction coefficients associated with contraction, energy and momentum. The present comprehensive 3D numerical investigation highlights the driving mechanisms for junction induced energy losses. Moreover, the comparative 1D and 3D study quantifies the deviation of 1D approximations and associated underlying assumptions from the 'true' resultant flow field. The study may also shed light on improving the accuracy of the 1D large network modeling through the parameterization of the complex 3D feature of the flow field and correction of interior boundary conditions at junctions of larger angles and/or with substantial lateral inflows. Moreover, the enclosed numerical investigations may enhance the understanding of the primary mechanisms contributing to hydraulic structure induced turbulent flow behavior and increased hydraulic resistance.

Fully implicit Particle-in-cell algorithms for multiscale plasma simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacon, Luis

The outline of the paper is as follows: Particle-in-cell (PIC) methods for fully ionized collisionless plasmas, explicit vs. implicit PIC, 1D ES implicit PIC (charge and energy conservation, moment-based acceleration), and generalization to Multi-D EM PIC: Vlasov-Darwin model (review and motivation for Darwin model, conservation properties (energy, charge, and canonical momenta), and numerical benchmarks). The author demonstrates a fully implicit, fully nonlinear, multidimensional PIC formulation that features exact local charge conservation (via a novel particle mover strategy), exact global energy conservation (no particle self-heating or self-cooling), adaptive particle orbit integrator to control errors in momentum conservation, and canonical momenta (EM-PICmore » only, reduced dimensionality). The approach is free of numerical instabilities: ω peΔt >> 1, and Δx >> λ D. It requires many fewer dofs (vs. explicit PIC) for comparable accuracy in challenging problems. Significant CPU gains (vs explicit PIC) have been demonstrated. The method has much potential for efficiency gains vs. explicit in long-time-scale applications. Moment-based acceleration is effective in minimizing N FE, leading to an optimal algorithm.« less

An immersed boundary method for simulating vesicle dynamics in three dimensions

NASA Astrophysics Data System (ADS)

Seol, Yunchang; Hu, Wei-Fan; Kim, Yongsam; Lai, Ming-Chih

2016-10-01

We extend our previous immersed boundary (IB) method for 3D axisymmetric inextensible vesicle in Navier-Stokes flows (Hu et al., 2014 [17]) to general three dimensions. Despite a similar spirit in numerical algorithms to the axisymmetric case, the fully 3D numerical implementation is much more complicated and is far from straightforward. A vesicle membrane surface is known to be incompressible and exhibits bending resistance. As in 3D axisymmetric case, instead of keeping the vesicle locally incompressible, we adopt a modified elastic tension energy to make the vesicle surface patch nearly incompressible so that solving the unknown tension (Lagrange multiplier for the incompressible constraint) can be avoided. Nevertheless, the new elastic force derived from the modified tension energy has exactly the same mathematical form as the original one except the different definitions of tension. The vesicle surface is discretized on a triangular mesh where the elastic tension and bending force are calculated on each vertex (Lagrangian marker in the IB method) of the triangulation. A series of numerical tests on the present scheme are conducted to illustrate the robustness and applicability of the method. We perform the convergence study for the immersed boundary forces and the fluid velocity field. We then study the vesicle dynamics in various flows such as quiescent, simple shear, and gravitational flows. Our numerical results show good agreements with those obtained in previous theoretical, experimental and numerical studies.

Numerical Study of Magnetic Damping During Unidirectional Solidification

NASA Technical Reports Server (NTRS)

Li, Ben Q.

1997-01-01

A fully 3-D numerical model is developed to represent magnetic damping of complex fluid flow, heat transfer and electromagnetic field distributions in a melt cavity. The model is developed based on our in-house finite element code for the fluid flow, heat transfer and electromagnetic field calculations. The computer code has been tested against benchmark test problems that are solved by other commercial codes as well as analytical solutions whenever available. The numerical model is tested against numerical and experimental results for water reported in literature. With the model so tested, various numerical simulations are carried out for the Sn-35.5% Pb melt convection and temperature distribution in a cylindrical cavity with and without the presence of a transverse magnetic field. Numerical results show that magnetic damping can be effectively applied to reduce turbulence and flow levels in the melt undergoing solidification and over a certain threshold value a higher magnetic field resulted in a higher velocity reduction. It is found also that for a fully 3-D representation of the magnetic damping effects, the electric field induced in the melt by the applied DC magnetic field does not vanish, as some researchers suggested, and must be included even for molten metal and semiconductors. Also, for the study of the melt flow instability, a long enough time has to be applied to ensure the final fluid flow recirculation pattern. Moreover, our numerical results suggested that there seems to exist a threshold value of applied magnetic field, above which magnetic damping becomes possible and below which the convection in the melt is actually enhanced. Because of the limited financial resource allocated for the project, we are unable to carry out extensive study on this effect, which should warrant further theoretical and experimental study. In that endeavor, the developed numerical model should be very useful; and the model should serve as a useful tool for exploring necessary design parameters for planning magnetic damping experiments and interpreting the experimental results.

Fully implicit moving mesh adaptive algorithm

NASA Astrophysics Data System (ADS)

Serazio, C.; Chacon, L.; Lapenta, G.

2006-10-01

In many problems of interest, the numerical modeler is faced with the challenge of dealing with multiple time and length scales. The former is best dealt with with fully implicit methods, which are able to step over fast frequencies to resolve the dynamical time scale of interest. The latter requires grid adaptivity for efficiency. Moving-mesh grid adaptive methods are attractive because they can be designed to minimize the numerical error for a given resolution. However, the required grid governing equations are typically very nonlinear and stiff, and of considerably difficult numerical treatment. Not surprisingly, fully coupled, implicit approaches where the grid and the physics equations are solved simultaneously are rare in the literature, and circumscribed to 1D geometries. In this study, we present a fully implicit algorithm for moving mesh methods that is feasible for multidimensional geometries. Crucial elements are the development of an effective multilevel treatment of the grid equation, and a robust, rigorous error estimator. For the latter, we explore the effectiveness of a coarse grid correction error estimator, which faithfully reproduces spatial truncation errors for conservative equations. We will show that the moving mesh approach is competitive vs. uniform grids both in accuracy (due to adaptivity) and efficiency. Results for a variety of models 1D and 2D geometries will be presented. L. Chac'on, G. Lapenta, J. Comput. Phys., 212 (2), 703 (2006) G. Lapenta, L. Chac'on, J. Comput. Phys., accepted (2006)

Intermittency, coherent structures and dissipation in plasma turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, M.; Matthaeus, W. H.; Parashar, T. N.

Collisionless dissipation in turbulent plasmas such as the solar wind and the solar corona has been an intensively studied subject recently, with new insights often emerging from numerical simulation. Here we report results from high resolution, fully kinetic simulations of plasma turbulence in both two (2D) and three (3D) dimensions, studying the relationship between intermittency and dissipation. The simulations show development of turbulent coherent structures, characterized by sheet-like current density structures spanning a range of scales. An approximate dissipation measure is employed, based on work done by the electromagnetic field in the local electron fluid frame. This surrogate dissipation measuremore » is highly concentrated in small subvolumes in both 2D and 3D simulations. Fully kinetic simulations are also compared with magnetohydrodynamics (MHD) simulations in terms of coherent structures and dissipation. The interesting result emerges that the conditional averages of dissipation measure scale very similarly with normalized current density J in 2D and 3D particle-in-cell and in MHD. To the extent that the surrogate dissipation measure is accurate, this result implies that on average dissipation scales as ∼J{sup 2} in turbulent kinetic plasma. Multifractal intermittency is seen in the inertial range in both 2D and 3D, but at scales ∼ion inertial length, the scaling is closer to monofractal.« less

The Thistle Field - Analysis of its past performance and optimisation of its future development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayat, M.G.; Tehrani, D.H.

1985-01-01

The Thistle Field geology and its reservoir performance over the past six years have been reviewed. The latest reservoir simulation study of the field, covering the performance history-matching, and the conclusions of various prediction cases are reported. The special features of PORES, Britoil in-house 3D 3-phase fully implicit numerical simulator and its modeling aids as applied to the Thistle Field are presented.

Variational formulation of hybrid problems for fully 3-D transonic flow with shocks in rotor

NASA Technical Reports Server (NTRS)

Liu, Gao-Lian

1991-01-01

Based on previous research, the unified variable domain variational theory of hybrid problems for rotor flow is extended to fully 3-D transonic rotor flow with shocks, unifying and generalizing the direct and inverse problems. Three variational principles (VP) families were established. All unknown boundaries and flow discontinuities (such as shocks, free trailing vortex sheets) are successfully handled via functional variations with variable domain, converting almost all boundary and interface conditions, including the Rankine Hugoniot shock relations, into natural ones. This theory provides a series of novel ways for blade design or modification and a rigorous theoretical basis for finite element applications and also constitutes an important part of the optimal design theory of rotor bladings. Numerical solutions to subsonic flow by finite elements with self-adapting nodes given in Refs., show good agreement with experimental results.

Simulating Water Flow in Variably Saturated Soils - Exploring the Advantage of Three-dimensional Models

NASA Astrophysics Data System (ADS)

Hopp, L.; Ivanov, V. Y.

2010-12-01

There is still a debate in rainfall-runoff modeling over the advantage of using three-dimensional models based on partial differential equations describing variably saturated flow vs. models with simpler infiltration and flow routing algorithms. Fully explicit 3D models are computationally demanding but allow the representation of spatially complex domains, heterogeneous soils, conditions of ponded infiltration, and solute transport, among others. Models with simpler infiltration and flow routing algorithms provide faster run times and are likely to be more versatile in the treatment of extreme conditions such as soil drying but suffer from underlying assumptions and ad-hoc parameterizations. In this numerical study, we explore the question of whether these two model strategies are competing approaches or if they complement each other. As a 3D physics-based model we use HYDRUS-3D, a finite element model that numerically solves the Richards equation for variably-saturated water flow. As an example of a simpler model, we use tRIBS+VEGGIE that solves the 1D Richards equation for vertical flow and applies Dupuit-Forchheimer approximation for saturated lateral exchange and gravity-driven flow for unsaturated lateral exchange. The flow can be routed using either the D-8 (steepest descent) or D-infinity flow routing algorithms. We study lateral subsurface stormflow and moisture dynamics at the hillslope-scale, using a zero-order basin topography, as a function of storm size, antecedent moisture conditions and slope angle. The domain and soil characteristics are representative of a forested hillslope with conductive soils in a humid environment, where the major runoff generating process is lateral subsurface stormflow. We compare spatially integrated lateral subsurface flow at the downslope boundary as well as spatial patterns of soil moisture. We illustrate situations where both model approaches perform equally well and identify conditions under which the application of a fully-explicit 3D model may be required for a realistic description of the hydrologic response.

Parallel numerical modeling of hybrid-dimensional compositional non-isothermal Darcy flows in fractured porous media

NASA Astrophysics Data System (ADS)

Xing, F.; Masson, R.; Lopez, S.

2017-09-01

This paper introduces a new discrete fracture model accounting for non-isothermal compositional multiphase Darcy flows and complex networks of fractures with intersecting, immersed and non-immersed fractures. The so called hybrid-dimensional model using a 2D model in the fractures coupled with a 3D model in the matrix is first derived rigorously starting from the equi-dimensional matrix fracture model. Then, it is discretized using a fully implicit time integration combined with the Vertex Approximate Gradient (VAG) finite volume scheme which is adapted to polyhedral meshes and anisotropic heterogeneous media. The fully coupled systems are assembled and solved in parallel using the Single Program Multiple Data (SPMD) paradigm with one layer of ghost cells. This strategy allows for a local assembly of the discrete systems. An efficient preconditioner is implemented to solve the linear systems at each time step and each Newton type iteration of the simulation. The numerical efficiency of our approach is assessed on different meshes, fracture networks, and physical settings in terms of parallel scalability, nonlinear convergence and linear convergence.

Modeling of power transmission and stress grading for corona protection

NASA Astrophysics Data System (ADS)

Zohdi, T. I.; Abali, B. E.

2017-11-01

Electrical high voltage (HV) machines are prone to corona discharges leading to power losses as well as damage of the insulating layer. Many different techniques are applied as corona protection and computational methods aid to select the best design. In this paper we develop a reduced-order model in 1D estimating electric field and temperature distribution of a conductor wrapped with different layers, as usual for HV-machines. Many assumptions and simplifications are undertaken for this 1D model, therefore, we compare its results to a direct numerical simulation in 3D quantitatively. Both models are transient and nonlinear, giving a possibility to quickly estimate in 1D or fully compute in 3D by a computational cost. Such tools enable understanding, evaluation, and optimization of corona shielding systems for multilayered coils.

Implementation of a kappa-epsilon turbulence model to RPLUS3D code

NASA Technical Reports Server (NTRS)

Chitsomboon, Tawit

1992-01-01

The RPLUS3D code has been developed at the NASA Lewis Research Center to support the National Aerospace Plane (NASP) project. The code has the ability to solve three dimensional flowfields with finite rate combustion of hydrogen and air. The combustion process of the hydrogen-air system are simulated by an 18 reaction path, 8 species chemical kinetic mechanism. The code uses a Lower-Upper (LU) decomposition numerical algorithm as its basis, making it a very efficient and robust code. Except for the Jacobian matrix for the implicit chemistry source terms, there is no inversion of a matrix even though a fully implicit numerical algorithm is used. A k-epsilon turbulence model has recently been incorporated into the code. Initial validations have been conducted for a flow over a flat plate. Results of the validation studies are shown. Some difficulties in implementing the k-epsilon equations to the code are also discussed.

Implementation of a kappa-epsilon turbulence model to RPLUS3D code

NASA Astrophysics Data System (ADS)

Chitsomboon, Tawit

1992-02-01

The RPLUS3D code has been developed at the NASA Lewis Research Center to support the National Aerospace Plane (NASP) project. The code has the ability to solve three dimensional flowfields with finite rate combustion of hydrogen and air. The combustion process of the hydrogen-air system are simulated by an 18 reaction path, 8 species chemical kinetic mechanism. The code uses a Lower-Upper (LU) decomposition numerical algorithm as its basis, making it a very efficient and robust code. Except for the Jacobian matrix for the implicit chemistry source terms, there is no inversion of a matrix even though a fully implicit numerical algorithm is used. A k-epsilon turbulence model has recently been incorporated into the code. Initial validations have been conducted for a flow over a flat plate. Results of the validation studies are shown. Some difficulties in implementing the k-epsilon equations to the code are also discussed.

Ultra-low loss fully-etched grating couplers for perfectly vertical coupling compatible with DUV lithography tools

NASA Astrophysics Data System (ADS)

Dabos, G.; Pleros, N.; Tsiokos, D.

2016-03-01

Hybrid integration of VCSELs onto silicon-on-insulator (SOI) substrates has emerged as an attractive approach for bridging the gap between cost-effective and energy-efficient directly modulated laser sources and silicon-based PICs by leveraging flip-chip (FC) bonding techniques and silicon grating couplers (GCs). In this context, silicon GCs, should comply with the process requirements imposed by the complimentary-metal-oxide-semiconductor manufacturing tools addressing in parallel the challenges originating from the perfectly vertical incidence. Firstly, fully etched GCs compatible with deep-ultraviolet lithography tools offering high coupling efficiencies are imperatively needed to maintain low fabrication cost. Secondly, GC's tolerance to VCSEL bonding misalignment errors is a prerequisite for practical deployment. Finally, a major challenge originating from the perfectly vertical coupling scheme is the minimization of the direct back-reflection to the VCSEL's outgoing facet which may destabilize its operation. Motivated from the above challenges, we used numerical simulation tools to design an ultra-low loss, bidirectional VCSEL-to-SOI optical coupling scheme for either TE or TM polarization, based on low-cost fully etched GCs with a Si-layer of 340 nm without employing bottom reflectors or optimizing the buried-oxide layer. Comprehensive 2D Finite-Difference-Time- Domain simulations have been performed. The reported GC layout remains fully compatible with the back-end-of-line (BEOL) stack associated with the 3D integration technology exploiting all the inter-metal-dielectric (IMD) layers of the CMOS fab. Simulation results predicted for the first time in fully etched structures a coupling efficiency of as low as -0.87 dB at 1548 nm and -1.47 dB at 1560 nm with a minimum direct back-reflection of -27.4 dB and -14.2 dB for TE and TM polarization, respectively.

Forward Monte Carlo Computations of Polarized Microwave Radiation

NASA Technical Reports Server (NTRS)

Battaglia, A.; Kummerow, C.

2000-01-01

Microwave radiative transfer computations continue to acquire greater importance as the emphasis in remote sensing shifts towards the understanding of microphysical properties of clouds and with these to better understand the non linear relation between rainfall rates and satellite-observed radiance. A first step toward realistic radiative simulations has been the introduction of techniques capable of treating 3-dimensional geometry being generated by ever more sophisticated cloud resolving models. To date, a series of numerical codes have been developed to treat spherical and randomly oriented axisymmetric particles. Backward and backward-forward Monte Carlo methods are, indeed, efficient in this field. These methods, however, cannot deal properly with oriented particles, which seem to play an important role in polarization signatures over stratiform precipitation. Moreover, beyond the polarization channel, the next generation of fully polarimetric radiometers challenges us to better understand the behavior of the last two Stokes parameters as well. In order to solve the vector radiative transfer equation, one-dimensional numerical models have been developed, These codes, unfortunately, consider the atmosphere as horizontally homogeneous with horizontally infinite plane parallel layers. The next development step for microwave radiative transfer codes must be fully polarized 3-D methods. Recently a 3-D polarized radiative transfer model based on the discrete ordinate method was presented. A forward MC code was developed that treats oriented nonspherical hydrometeors, but only for plane-parallel situations.

Real-time segmentation in 4D ultrasound with continuous max-flow

NASA Astrophysics Data System (ADS)

Rajchl, M.; Yuan, J.; Peters, T. M.

2012-02-01

We present a novel continuous Max-Flow based method to segment the inner left ventricular wall from 3D trans-esophageal echocardiography image sequences, which minimizes an energy functional encoding two Fisher-Tippett distributions and a geometrical constraint in form of a Euclidean distance map in a numerically efficient and accurate way. After initialization the method is fully automatic and is able to perform at up to 10Hz making it available for image-guided interventions. Results are shown on 4D TEE data sets from 18 patients with pathological cardiac conditions and the speed of the algorithm is assessed under a variety of conditions.

Multigrid direct numerical simulation of the whole process of flow transition in 3-D boundary layers

NASA Technical Reports Server (NTRS)

Liu, Chaoqun; Liu, Zhining

1993-01-01

A new technology was developed in this study which provides a successful numerical simulation of the whole process of flow transition in 3-D boundary layers, including linear growth, secondary instability, breakdown, and transition at relatively low CPU cost. Most other spatial numerical simulations require high CPU cost and blow up at the stage of flow breakdown. A fourth-order finite difference scheme on stretched and staggered grids, a fully implicit time marching technique, a semi-coarsening multigrid based on the so-called approximate line-box relaxation, and a buffer domain for the outflow boundary conditions were all used for high-order accuracy, good stability, and fast convergence. A new fine-coarse-fine grid mapping technique was developed to keep the code running after the laminar flow breaks down. The computational results are in good agreement with linear stability theory, secondary instability theory, and some experiments. The cost for a typical case with 162 x 34 x 34 grid is around 2 CRAY-YMP CPU hours for 10 T-S periods.

A curvilinear, fully implicit, conservative electromagnetic PIC algorithm in multiple dimensions

DOE PAGES

Chacon, L.; Chen, G.

2016-04-19

Here, we extend a recently proposed fully implicit PIC algorithm for the Vlasov–Darwin model in multiple dimensions (Chen and Chacón (2015) [1]) to curvilinear geometry. As in the Cartesian case, the approach is based on a potential formulation (Φ, A), and overcomes many difficulties of traditional semi-implicit Darwin PIC algorithms. Conservation theorems for local charge and global energy are derived in curvilinear representation, and then enforced discretely by a careful choice of the discretization of field and particle equations. Additionally, the algorithm conserves canonical-momentum in any ignorable direction, and preserves the Coulomb gauge ∇ • A = 0 exactly. Anmore » asymptotically well-posed fluid preconditioner allows efficient use of large cell sizes, which are determined by accuracy considerations, not stability, and can be orders of magnitude larger than required in a standard explicit electromagnetic PIC simulation. We demonstrate the accuracy and efficiency properties of the algorithm with numerical experiments in mapped meshes in 1D-3V and 2D-3V.« less

A curvilinear, fully implicit, conservative electromagnetic PIC algorithm in multiple dimensions

NASA Astrophysics Data System (ADS)

Chacón, L.; Chen, G.

2016-07-01

We extend a recently proposed fully implicit PIC algorithm for the Vlasov-Darwin model in multiple dimensions (Chen and Chacón (2015) [1]) to curvilinear geometry. As in the Cartesian case, the approach is based on a potential formulation (ϕ, A), and overcomes many difficulties of traditional semi-implicit Darwin PIC algorithms. Conservation theorems for local charge and global energy are derived in curvilinear representation, and then enforced discretely by a careful choice of the discretization of field and particle equations. Additionally, the algorithm conserves canonical-momentum in any ignorable direction, and preserves the Coulomb gauge ∇ ṡ A = 0 exactly. An asymptotically well-posed fluid preconditioner allows efficient use of large cell sizes, which are determined by accuracy considerations, not stability, and can be orders of magnitude larger than required in a standard explicit electromagnetic PIC simulation. We demonstrate the accuracy and efficiency properties of the algorithm with numerical experiments in mapped meshes in 1D-3V and 2D-3V.

A curvilinear, fully implicit, conservative electromagnetic PIC algorithm in multiple dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacon, L.; Chen, G.

Here, we extend a recently proposed fully implicit PIC algorithm for the Vlasov–Darwin model in multiple dimensions (Chen and Chacón (2015) [1]) to curvilinear geometry. As in the Cartesian case, the approach is based on a potential formulation (Φ, A), and overcomes many difficulties of traditional semi-implicit Darwin PIC algorithms. Conservation theorems for local charge and global energy are derived in curvilinear representation, and then enforced discretely by a careful choice of the discretization of field and particle equations. Additionally, the algorithm conserves canonical-momentum in any ignorable direction, and preserves the Coulomb gauge ∇ • A = 0 exactly. Anmore » asymptotically well-posed fluid preconditioner allows efficient use of large cell sizes, which are determined by accuracy considerations, not stability, and can be orders of magnitude larger than required in a standard explicit electromagnetic PIC simulation. We demonstrate the accuracy and efficiency properties of the algorithm with numerical experiments in mapped meshes in 1D-3V and 2D-3V.« less

Fully anisotropic 3-D EM modelling on a Lebedev grid with a multigrid pre-conditioner

NASA Astrophysics Data System (ADS)

Jaysaval, Piyoosh; Shantsev, Daniil V.; de la Kethulle de Ryhove, Sébastien; Bratteland, Tarjei

2016-12-01

We present a numerical algorithm for 3-D electromagnetic (EM) simulations in conducting media with general electric anisotropy. The algorithm is based on the finite-difference discretization of frequency-domain Maxwell's equations on a Lebedev grid, in which all components of the electric field are collocated but half a spatial step staggered with respect to the magnetic field components, which also are collocated. This leads to a system of linear equations that is solved using a stabilized biconjugate gradient method with a multigrid preconditioner. We validate the accuracy of the numerical results for layered and 3-D tilted transverse isotropic (TTI) earth models representing typical scenarios used in the marine controlled-source EM method. It is then demonstrated that not taking into account the full anisotropy of the conductivity tensor can lead to misleading inversion results. For synthetic data corresponding to a 3-D model with a TTI anticlinal structure, a standard vertical transverse isotropic (VTI) inversion is not able to image a resistor, while for a 3-D model with a TTI synclinal structure it produces a false resistive anomaly. However, if the VTI forward solver used in the inversion is replaced by the proposed TTI solver with perfect knowledge of the strike and dip of the dipping structures, the resulting resistivity images become consistent with the true models.

Numerical and experimental investigation of the 3D free surface flow in a model Pelton turbine

NASA Astrophysics Data System (ADS)

Fiereder, R.; Riemann, S.; Schilling, R.

2010-08-01

This investigation focuses on the numerical and experimental analysis of the 3D free surface flow in a Pelton turbine. In particular, two typical flow conditions occurring in a full scale Pelton turbine - a configuration with a straight inlet as well as a configuration with a 90 degree elbow upstream of the nozzle - are considered. Thereby, the effect of secondary flow due to the 90 degree bending of the upstream pipe on the characteristics of the jet is explored. The hybrid flow field consists of pure liquid flow within the conduit and free surface two component flow of the liquid jet emerging out of the nozzle into air. The numerical results are validated against experimental investigations performed in the laboratory of the Institute of Fluid Mechanics (FLM). For the numerical simulation of the flow the in-house unstructured fully parallelized finite volume solver solver3D is utilized. An advanced interface capturing model based on the classic Volume of Fluid method is applied. In order to ensure sharp interface resolution an additional convection term is added to the transport equation of the volume fraction. A collocated variable arrangement is used and the set of non-linear equations, containing fluid conservation equations and model equations for turbulence and volume fraction, are solved in a segregated manner. For pressure-velocity coupling the SIMPLE and PISO algorithms are implemented. Detailed analysis of the observed flow patterns in the jet and of the jet geometry are presented.

Multidimensional, fully implicit, exactly conserving electromagnetic particle-in-cell simulations

NASA Astrophysics Data System (ADS)

Chacon, Luis

2015-09-01

We discuss a new, conservative, fully implicit 2D-3V particle-in-cell algorithm for non-radiative, electromagnetic kinetic plasma simulations, based on the Vlasov-Darwin model. Unlike earlier linearly implicit PIC schemes and standard explicit PIC schemes, fully implicit PIC algorithms are unconditionally stable and allow exact discrete energy and charge conservation. This has been demonstrated in 1D electrostatic and electromagnetic contexts. In this study, we build on these recent algorithms to develop an implicit, orbit-averaged, time-space-centered finite difference scheme for the Darwin field and particle orbit equations for multiple species in multiple dimensions. The Vlasov-Darwin model is very attractive for PIC simulations because it avoids radiative noise issues in non-radiative electromagnetic regimes. The algorithm conserves global energy, local charge, and particle canonical-momentum exactly, even with grid packing. The nonlinear iteration is effectively accelerated with a fluid preconditioner, which allows efficient use of large timesteps, O(√{mi/me}c/veT) larger than the explicit CFL. In this presentation, we will introduce the main algorithmic components of the approach, and demonstrate the accuracy and efficiency properties of the algorithm with various numerical experiments in 1D and 2D. Support from the LANL LDRD program and the DOE-SC ASCR office.

Full three-dimensional isotropic carpet cloak designed by quasi-conformal transformation optics.

PubMed

Silva, Daniely G; Teixeira, Poliane A; Gabrielli, Lucas H; Junqueira, Mateus A F C; Spadoti, Danilo H

2017-09-18

A fully three-dimensional carpet cloak presenting invisibility in all viewing angles is theoretically demonstrated. The design is developed using transformation optics and three-dimensional quasi-conformal mapping. Parametrization strategy and numerical optimization of the coordinate transformation deploying a quasi-Newton method is applied. A discussion about the minimum achievable anisotropy in the 3D transformation optics is presented. The method allows to reduce the anisotropy in the cloak and an isotropic medium could be considered. Numerical simulations confirm the strategy employed enabling the design of an isotropic reflectionless broadband carpet cloak independently of the incident light direction and polarization.

Comparing a quasi-3D to a full 3D nearshore circulation model: SHORECIRC and ROMS

USGS Publications Warehouse

Haas, Kevin A.; Warner, John C.

2009-01-01

Predictions of nearshore and surf zone processes are important for determining coastal circulation, impacts of storms, navigation, and recreational safety. Numerical modeling of these systems facilitates advancements in our understanding of coastal changes and can provide predictive capabilities for resource managers. There exists many nearshore coastal circulation models, however they are mostly limited or typically only applied as depth integrated models. SHORECIRC is an established surf zone circulation model that is quasi-3D to allow the effect of the variability in the vertical structure of the currents while maintaining the computational advantage of a 2DH model. Here we compare SHORECIRC to ROMS, a fully 3D ocean circulation model which now includes a three dimensional formulation for the wave-driven flows. We compare the models with three different test applications for: (i) spectral waves approaching a plane beach with an oblique angle of incidence; (ii) monochromatic waves driving longshore currents in a laboratory basin; and (iii) monochromatic waves on a barred beach with rip channels in a laboratory basin. Results identify that the models are very similar for the depth integrated flows and qualitatively consistent for the vertically varying components. The differences are primarily the result of the vertically varying radiation stress utilized by ROMS and the utilization of long wave theory for the radiation stress formulation in vertical varying momentum balance by SHORECIRC. The quasi-3D model is faster, however the applicability of the fully 3D model allows it to extend over a broader range of processes, temporal, and spatial scales.

Comparing a quasi-3D to a full 3D nearshore circulation model: SHORECIRC and ROMS

USGS Publications Warehouse

Haas, K.A.; Warner, J.C.

2009-01-01

Predictions of nearshore and surf zone processes are important for determining coastal circulation, impacts of storms, navigation, and recreational safety. Numerical modeling of these systems facilitates advancements in our understanding of coastal changes and can provide predictive capabilities for resource managers. There exists many nearshore coastal circulation models, however they are mostly limited or typically only applied as depth integrated models. SHORECIRC is an established surf zone circulation model that is quasi-3D to allow the effect of the variability in the vertical structure of the currents while maintaining the computational advantage of a 2DH model. Here we compare SHORECIRC to ROMS, a fully 3D ocean circulation model which now includes a three dimensional formulation for the wave-driven flows. We compare the models with three different test applications for: (i) spectral waves approaching a plane beach with an oblique angle of incidence; (ii) monochromatic waves driving longshore currents in a laboratory basin; and (iii) monochromatic waves on a barred beach with rip channels in a laboratory basin. Results identify that the models are very similar for the depth integrated flows and qualitatively consistent for the vertically varying components. The differences are primarily the result of the vertically varying radiation stress utilized by ROMS and the utilization of long wave theory for the radiation stress formulation in vertical varying momentum balance by SHORECIRC. The quasi-3D model is faster, however the applicability of the fully 3D model allows it to extend over a broader range of processes, temporal, and spatial scales. ?? 2008 Elsevier Ltd.

Recent advancements in mechanical characterisation of 3D woven composites

NASA Astrophysics Data System (ADS)

Saleh, Mohamed Nasr; Soutis, Constantinos

2017-12-01

Three dimensional (3D) woven composites have attracted the interest of academia and industry thanks to their damage tolerance characteristics and automated fabric manufacturing. Although much research has been conducted to investigate their out-of-plane "through thickness" properties, still their in-plane properties are not fully understood and rely on extensive experimentation. To date, the literature lacks an inclusive summary of the mechanical characterisation for 3D woven composites. Therefore, the objective of this paper is to provide a comprehensive review of the available research studies on 3D woven composites mechanical characterisation, with less emphasis on the out-of-plane response, but an in-depth review of the in-plane response "un-notched vs. notched". The paper highlights the knowledge gap in the literature of 3D woven composites, suggesting opportunities for future research in this field and a room for improvement in utilising Non-Destructive Techniques (NDT), such as Digital Image Correlation (DIC), Acoustic Emission (AE) and X-ray Computed Tomography (CT), for observing damage initiation and evolution in 3D woven composites that could be used to calibrate and evaluate analytical and numerical models.

Landslide/reservoir interaction: 3D numerical modelling of the Vajont rockslide and generated water wave

NASA Astrophysics Data System (ADS)

Crosta, G.; Imposimato, S.; Roddeman, D.; Frattini, P.

2012-04-01

Fast moving landslides can be originated along slopes in mountainous terrains with natural and artificial lakes, or fjords at the slope foot. This landslides can reach extremely high speed and the impact with the immobile reservoir water can be influenced by the local topography and the landslide mass profile. The impact can generate large impulse waves and landslide tsunami. Initiation, propagation and runup are the three phases that need to be considered. The landslide evolution and the consequent wave can be controlled by the initial mass position (subaerial, partially or completely submerged), the landslide speed, the type of material, the subaerial and subaqueous slope geometry, the landslide depth and length at the impact, and the water depth. Extreme events have been caused by subaerial landslides: the 1963 Vajont rockslide (Italy), the 1958 Lituya Bay event (Alaska), the Tafjord and the Loen multiple events event (Norway), also from volcanic collapses (Hawaii and Canary islands). Various researchers completed a systematic experimental work on 2D and 3D wave generation and propagation (Kamphuis and Bowering, 1970; Huber, 1980; Müller, 1995; Huber and Hager, 1997; Fritz, 2002; Zweifel, 2004; Panizzo et al., 2005; Heller, 2007; Heller and Kinnear, 2010; Sælevik et al., 2009), using both rigid blocks and deformable granular" masses. Model data and results have been used to calibrate and validate numerical modelling tools (Harbitz, 1992; Jiang and LeBlond, 1993; Grilli et al., 2002; Grilli and Watts, 2005; Lynett and Liu, 2005; Tinti et al., 2006; Abadie et al., 2010) generally considering simplified rheologies (e.g. viscous rheologies) for subaerial subaqueous spreading. We use a FEM code (Roddeman, 2011; Crosta et al., 2006, 2009, 2010, 2011) adopting an Eulerian-Lagrangian approach to give accurate results for large deformations. We model both 2D and fully 3D events considering different settings. The material is considered as a fully deformable elasto-plastic continuum and water as nearly incompressible. In particular we modeled the Vajont rockslide both in 2D and 3D considering the landslide water interaction. More simulations have been performed to validate the model against 2D and 3D tank experiments considering different slope geometries and water depth.

Numerical Simulation of the Vortex-Induced Vibration of A Curved Flexible Riser in Shear Flow

NASA Astrophysics Data System (ADS)

Zhu, Hong-jun; Lin, Peng-zhi

2018-06-01

A series of fully three-dimensional (3D) numerical simulations of flow past a free-to-oscillate curved flexible riser in shear flow were conducted at Reynolds number of 185-1015. The numerical results obtained by the two-way fluid-structure interaction (FSI) simulations are in good agreement with the experimental results reported in the earlier study. It is further found that the frequency transition is out of phase not only in the inline (IL) and crossflow (CF) directions but also along the span direction. The mode competition leads to the non-zero nodes of the rootmean- square (RMS) amplitude and the relatively chaotic trajectories. The fluid-structure interaction is to some extent reflected by the transverse velocity of the ambient fluid, which reaches the maximum value when the riser reaches the equilibrium position. Moreover, the local maximum transverse velocities occur at the peak CF amplitudes, and the values are relatively large when the vibration is in the resonance regions. The 3D vortex columns are shed nearly parallel to the axis of the curved flexible riser. As the local Reynolds number increases from 0 at the bottom of the riser to the maximum value at the top, the wake undergoes a transition from a two-dimensional structure to a 3D one. More irregular small-scale vortices appeared at the wake region of the riser, undergoing large amplitude responses.

Convergence Acceleration for Multistage Time-Stepping Schemes

NASA Technical Reports Server (NTRS)

Swanson, R. C.; Turkel, Eli L.; Rossow, C-C; Vasta, V. N.

2006-01-01

The convergence of a Runge-Kutta (RK) scheme with multigrid is accelerated by preconditioning with a fully implicit operator. With the extended stability of the Runge-Kutta scheme, CFL numbers as high as 1000 could be used. The implicit preconditioner addresses the stiffness in the discrete equations associated with stretched meshes. Numerical dissipation operators (based on the Roe scheme, a matrix formulation, and the CUSP scheme) as well as the number of RK stages are considered in evaluating the RK/implicit scheme. Both the numerical and computational efficiency of the scheme with the different dissipation operators are discussed. The RK/implicit scheme is used to solve the two-dimensional (2-D) and three-dimensional (3-D) compressible, Reynolds-averaged Navier-Stokes equations. In two dimensions, turbulent flows over an airfoil at subsonic and transonic conditions are computed. The effects of mesh cell aspect ratio on convergence are investigated for Reynolds numbers between 5.7 x 10(exp 6) and 100.0 x 10(exp 6). Results are also obtained for a transonic wing flow. For both 2-D and 3-D problems, the computational time of a well-tuned standard RK scheme is reduced at least a factor of four.

The influence of computational strategy on prediction of mechanical stress in carotid atherosclerotic plaques: comparison of 2D structure-only, 3D structure-only, one-way and fully coupled fluid-structure interaction analyses.

PubMed

Huang, Yuan; Teng, Zhongzhao; Sadat, Umar; Graves, Martin J; Bennett, Martin R; Gillard, Jonathan H

2014-04-11

Compositional and morphological features of carotid atherosclerotic plaques provide complementary information to luminal stenosis in predicting clinical presentations. However, they alone cannot predict cerebrovascular risk. Mechanical stress within the plaque induced by cyclical changes in blood pressure has potential to assess plaque vulnerability. Various modeling strategies have been employed to predict stress, including 2D and 3D structure-only, 3D one-way and fully coupled fluid-structure interaction (FSI) simulations. However, differences in stress predictions using different strategies have not been assessed. Maximum principal stress (Stress-P1) within 8 human carotid atherosclerotic plaques was calculated based on geometry reconstructed from in vivo computerized tomography and high resolution, multi-sequence magnetic resonance images. Stress-P1 within the diseased region predicted by 2D and 3D structure-only, and 3D one-way FSI simulations were compared to 3D fully coupled FSI analysis. Compared to 3D fully coupled FSI, 2D structure-only simulation significantly overestimated stress level (94.1 kPa [65.2, 117.3] vs. 85.5 kPa [64.4, 113.6]; median [inter-quartile range], p=0.0004). However, when slices around the bifurcation region were excluded, stresses predicted by 2D structure-only simulations showed a good correlation (R(2)=0.69) with values obtained from 3D fully coupled FSI analysis. 3D structure-only model produced a small yet statistically significant stress overestimation compared to 3D fully coupled FSI (86.8 kPa [66.3, 115.8] vs. 85.5 kPa [64.4, 113.6]; p<0.0001). In contrast, one-way FSI underestimated stress compared to 3D fully coupled FSI (78.8 kPa [61.1, 100.4] vs. 85.5 kPa [64.4, 113.7]; p<0.0001). A 3D structure-only model seems to be a computationally inexpensive yet reasonably accurate approximation for stress within carotid atherosclerotic plaques with mild to moderate luminal stenosis as compared to fully coupled FSI analysis. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Evaluation of an operational water cycle prediction system for the Laurentian Great Lakes and St. Lawrence River

NASA Astrophysics Data System (ADS)

Fortin, Vincent; Durnford, Dorothy; Smith, Gregory; Dyck, Sarah; Martinez, Yosvany; Mackay, Murray; Winter, Barbara

2017-04-01

Environment and Climate Change Canada (ECCC) is implementing new numerical guidance products based on fully coupled numerical models to better inform the public as well as specialized users on the current and future state of various components of the water cycle, including stream flow and water levels. Outputs from this new system, named the Water Cycle Prediction System (WCPS), have been available for the Great Lakes and St. Lawrence River watershed since June 2016. WCPS links together ECCC's weather forecasting model, GEM, the 2-D ice model C-ICE, the 3-D lake and ocean model NEMO, and a 2-D hydrological model, WATROUTE. Information concerning the water cycle is passed between the models at intervals varying from a few minutes to one hour. It currently produces two forecasts per day for the next three days of the complete water cycle in the Great Lakes region, the largest freshwater lake system in the world. Products include spatially-varying precipitation, evaporation, river discharge, water level anomalies, surface water temperatures, ice coverage, and surface currents. These new products are of interest to water resources and management authority, flood forecasters, hydroelectricity producers, navigation, environmental disaster managers, search and rescue teams, agriculture, and the general public. This presentation focuses on the evaluation of various elements forecasted by the system, and weighs the advantages and disadvantages of running the system fully coupled.

Accelerated 1 H MRSI using randomly undersampled spiral-based k-space trajectories.

PubMed

Chatnuntawech, Itthi; Gagoski, Borjan; Bilgic, Berkin; Cauley, Stephen F; Setsompop, Kawin; Adalsteinsson, Elfar

2014-07-30

To develop and evaluate the performance of an acquisition and reconstruction method for accelerated MR spectroscopic imaging (MRSI) through undersampling of spiral trajectories. A randomly undersampled spiral acquisition and sensitivity encoding (SENSE) with total variation (TV) regularization, random SENSE+TV, is developed and evaluated on single-slice numerical phantom, in vivo single-slice MRSI, and in vivo three-dimensional (3D)-MRSI at 3 Tesla. Random SENSE+TV was compared with five alternative methods for accelerated MRSI. For the in vivo single-slice MRSI, random SENSE+TV yields up to 2.7 and 2 times reduction in root-mean-square error (RMSE) of reconstructed N-acetyl aspartate (NAA), creatine, and choline maps, compared with the denoised fully sampled and uniformly undersampled SENSE+TV methods with the same acquisition time, respectively. For the in vivo 3D-MRSI, random SENSE+TV yields up to 1.6 times reduction in RMSE, compared with uniform SENSE+TV. Furthermore, by using random SENSE+TV, we have demonstrated on the in vivo single-slice and 3D-MRSI that acceleration factors of 4.5 and 4 are achievable with the same quality as the fully sampled data, as measured by RMSE of reconstructed NAA map, respectively. With the same scan time, random SENSE+TV yields lower RMSEs of metabolite maps than other methods evaluated. Random SENSE+TV achieves up to 4.5-fold acceleration with comparable data quality as the fully sampled acquisition. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc. © 2014 Wiley Periodicals, Inc.

NEUTRINO-DRIVEN TURBULENT CONVECTION AND STANDING ACCRETION SHOCK INSTABILITY IN THREE-DIMENSIONAL CORE-COLLAPSE SUPERNOVAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdikamalov, Ernazar; Ott, Christian D.; Radice, David

2015-07-20

We conduct a series of numerical experiments into the nature of three-dimensional (3D) hydrodynamics in the postbounce stalled-shock phase of core-collapse supernovae using 3D general-relativistic hydrodynamic simulations of a 27 M{sub ⊙} progenitor star with a neutrino leakage/heating scheme. We vary the strength of neutrino heating and find three cases of 3D dynamics: (1) neutrino-driven convection, (2) initially neutrino-driven convection and subsequent development of the standing accretion shock instability (SASI), and (3) SASI-dominated evolution. This confirms previous 3D results of Hanke et al. and Couch and Connor. We carry out simulations with resolutions differing by up to a factor ofmore » ∼4 and demonstrate that low resolution is artificially favorable for explosion in the 3D convection-dominated case since it decreases the efficiency of energy transport to small scales. Low resolution results in higher radial convective fluxes of energy and enthalpy, more fully buoyant mass, and stronger neutrino heating. In the SASI-dominated case, lower resolution damps SASI oscillations. In the convection-dominated case, a quasi-stationary angular kinetic energy spectrum E(ℓ) develops in the heating layer. Like other 3D studies, we find E(ℓ) ∝ℓ{sup −1} in the “inertial range,” while theory and local simulations argue for E(ℓ) ∝ ℓ{sup −5/3}. We argue that current 3D simulations do not resolve the inertial range of turbulence and are affected by numerical viscosity up to the energy-containing scale, creating a “bottleneck” that prevents an efficient turbulent cascade.« less

Fully compressible solutions for early stage Richtmyer–Meshkov instability

DOE PAGES

Margolin, Len G.; Reisner, Jon Michael

2016-10-27

Here, we will consider the effects of compressibility and viscosity on the early dynamics of the Richtmyer–Meshkov instability (RMI). In particular, we will combine theory, scaling, and high resolution simulation of RMI to probe the details of the initial compression and the subsequent viscous damping as a shock interacts with a density discontinuity. We will propose a refinement of the classic 1D model for the linear regime of RMI that, for small initial perturbation wavelengths, more accurately reproduces the 2D dynamics of a fully resolved numerical simulation.

Augmented Articles: The Future of Peer-Reviewed Publications?

NASA Astrophysics Data System (ADS)

Madura, Thomas Ignatius; Clementel, Nicola; Gull, Theodore R.

2015-08-01

The predominance of 2D figures and animations in the literature is clearly driven by the need to display data in a classic paper-journal format. However, there is no real reason that researchers should be limited to 2D graphics when presenting their results in peer-reviewed publications. This is especially true since all major astrophysical journals are now published online. So-called ‘augmented articles’ are possible, in which 3D interactive models, images, sound, and video can be included directly within an Adobe Portable Document Format (PDF) article. The inclusion of 3D interactive models in the astrophysics literature is slowly becoming popular, and several journals now fully support the inclusion of 3D interactive figures and movies. I present examples of recently published augmented articles in astronomy (e.g. Madura et al. 2015, arXiv:1503.00716) and discuss their perceived benefits and limitations. Such articles may become the norm in astronomy as data and numerical simulations increasingly become multidimensional (see http://www.technologyreview.com/view/535796/astronomers-create-3-d-printed-model-of-colliding-stellar-winds/).

Homogenization Issues in the Combustion of Heterogeneous Solid Propellants

NASA Technical Reports Server (NTRS)

Chen, M.; Buckmaster, J.; Jackson, T. L.; Massa, L.

2002-01-01

We examine random packs of discs or spheres, models for ammonium-perchlorate-in-binder propellants, and discuss their average properties. An analytical strategy is described for calculating the mean or effective heat conduction coefficient in terms of the heat conduction coefficients of the individual components, and the results are verified by comparison with those of direct numerical simulations (dns) for both 2-D (disc) and 3-D (sphere) packs across which a temperature difference is applied. Similarly, when the surface regression speed of each component is related to the surface temperature via a simple Arrhenius law, an analytical strategy is developed for calculating an effective Arrhenius law for the combination, and these results are verified using dns in which a uniform heat flux is applied to the pack surface, causing it to regress. These results are needed for homogenization strategies necessary for fully integrated 2-D or 3-D simulations of heterogeneous propellant combustion.

A 1D radiative transfer benchmark with polarization via doubling and adding

NASA Astrophysics Data System (ADS)

Ganapol, B. D.

2017-11-01

Highly precise numerical solutions to the radiative transfer equation with polarization present a special challenge. Here, we establish a precise numerical solution to the radiative transfer equation with combined Rayleigh and isotropic scattering in a 1D-slab medium with simple polarization. The 2-Stokes vector solution for the fully discretized radiative transfer equation in space and direction derives from the method of doubling and adding enhanced through convergence acceleration. Updates to benchmark solutions found in the literature to seven places for reflectance and transmittance as well as for angular flux follow. Finally, we conclude with the numerical solution in a partially randomly absorbing heterogeneous medium.

Experimental search for Exact Coherent Structures in turbulent small aspect ratio Taylor-Couette flow

NASA Astrophysics Data System (ADS)

Crowley, Christopher J.; Krygier, Michael; Grigoriev, Roman O.; Schatz, Michael F.

2017-11-01

Recent theoretical and experimental work suggests that the dynamics of turbulent flows are guided by unstable nonchaotic solutions to the Navier-Stokes equations. These solutions, known as exact coherent structures (ECS), play a key role in a fundamentally deterministic description of turbulence. In order to quantitatively demonstrate that actual turbulence in 3D flows is guided by ECS, high resolution, 3D-3C experimental measurements of the velocity need to be compared to solutions from direct numerical simulation of the Navier-Stokes equations. In this talk, we will present experimental measurements of fully time resolved, velocity measurements in a volume of turbulence in a counter-rotating, small aspect ratio Taylor-Couette flow. This work is supported by the Army Research Office (Contract # W911NF-16-1-0281).

Reactive Transport Modeling of Induced Calcite Precipitation Reaction Fronts in Porous Media Using A Parallel, Fully Coupled, Fully Implicit Approach

NASA Astrophysics Data System (ADS)

Guo, L.; Huang, H.; Gaston, D.; Redden, G. D.; Fox, D. T.; Fujita, Y.

2010-12-01

Inducing mineral precipitation in the subsurface is one potential strategy for immobilizing trace metal and radionuclide contaminants. Generating mineral precipitates in situ can be achieved by manipulating chemical conditions, typically through injection or in situ generation of reactants. How these reactants transport, mix and react within the medium controls the spatial distribution and composition of the resulting mineral phases. Multiple processes, including fluid flow, dispersive/diffusive transport of reactants, biogeochemical reactions and changes in porosity-permeability, are tightly coupled over a number of scales. Numerical modeling can be used to investigate the nonlinear coupling effects of these processes which are quite challenging to explore experimentally. Many subsurface reactive transport simulators employ a de-coupled or operator-splitting approach where transport equations and batch chemistry reactions are solved sequentially. However, such an approach has limited applicability for biogeochemical systems with fast kinetics and strong coupling between chemical reactions and medium properties. A massively parallel, fully coupled, fully implicit Reactive Transport simulator (referred to as “RAT”) based on a parallel multi-physics object-oriented simulation framework (MOOSE) has been developed at the Idaho National Laboratory. Within this simulator, systems of transport and reaction equations can be solved simultaneously in a fully coupled, fully implicit manner using the Jacobian Free Newton-Krylov (JFNK) method with additional advanced computing capabilities such as (1) physics-based preconditioning for solution convergence acceleration, (2) massively parallel computing and scalability, and (3) adaptive mesh refinements for 2D and 3D structured and unstructured mesh. The simulator was first tested against analytical solutions, then applied to simulating induced calcium carbonate mineral precipitation in 1D columns and 2D flow cells as analogs to homogeneous and heterogeneous porous media, respectively. In 1D columns, calcium carbonate mineral precipitation was driven by urea hydrolysis catalyzed by urease enzyme, and in 2D flow cells, calcium carbonate mineral forming reactants were injected sequentially, forming migrating reaction fronts that are typically highly nonuniform. The RAT simulation results for the spatial and temporal distributions of precipitates, reaction rates and major species in the system, and also for changes in porosity and permeability, were compared to both laboratory experimental data and computational results obtained using other reactive transport simulators. The comparisons demonstrate the ability of RAT to simulate complex nonlinear systems and the advantages of fully coupled approaches, over de-coupled methods, for accurate simulation of complex, dynamic processes such as engineered mineral precipitation in subsurface environments.

Generalized thick strip modelling for vortex-induced vibration of long flexible cylinders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bao, Y., E-mail: ybao@sjtu.edu.cn; Department of Aeronautics, Imperial College London, South Kensington Campus, London; Palacios, R., E-mail: r.palacios@imperial.ac.uk

2016-09-15

We propose a generalized strip modelling method that is computationally efficient for the VIV prediction of long flexible cylinders in three-dimensional incompressible flow. In order to overcome the shortcomings of conventional strip-theory-based 2D models, the fluid domain is divided into “thick” strips, which are sufficiently thick to locally resolve the small scale turbulence effects and three dimensionality of the flow around the cylinder. An attractive feature of the model is that we independently construct a three-dimensional scale resolving model for individual strips, which have local spanwise scale along the cylinder's axial direction and are only coupled through the structural modelmore » of the cylinder. Therefore, this approach is able to cover the full spectrum for fully resolved 3D modelling to 2D strip theory. The connection between these strips is achieved through the calculation of a tensioned beam equation, which is used to represent the dynamics of the flexible body. In the limit, however, a single “thick” strip would fill the full 3D domain. A parallel Fourier spectral/hp element method is employed to solve the 3D flow dynamics in the strip-domain, and then the VIV response prediction is achieved through the strip–structure interactions. Numerical tests on both laminar and turbulent flows as well as the comparison against the fully resolved DNS are presented to demonstrate the applicability of this approach.« less

The impacts of the axial-to-radial airflow quantity ratio and suction distance on air curtain dust control in a fully mechanized coal face.

PubMed

Wang, Hao; Cheng, Weimin; Sun, Biao; Yu, Haiming; Jin, Hu

2018-03-01

To understand the impacts of the axial-to-radial airflow quantity ratio (denoted as R) and the suction distance (denoted as D s ) on air curtain dust control in a fully mechanized coal face, the 3 down 610 coal face in Jiangzhuang coal mine was numerically simulated in this study. A mathematic model was established to describe the airflow migration and dust diffusion in a coal face, and a scaled physical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the airflow migration and dust diffusion at various R and D s are analyzed using Ansys CFD. The results show that a reduction of R and D s is conducive to the formation of an effective axial dust control air curtain; the dust diffusion distance decreases with the decrease of both R and D s . By analyzing the simulation results, the optimal parameter for air curtain dust control in the 3 down 610 coal face and those faces with similar production conditions is determined as R = 1/9 and D s  = 2 m. Under the optimal parameter condition, the high-concentration dust can be confined in front of the mining driver within a space 5.8 m away from the coal face.

A fully defined and scalable 3D culture system for human pluripotent stem cell expansion and differentiation

NASA Astrophysics Data System (ADS)

Lei, Yuguo; Schaffer, David V.

2013-12-01

Human pluripotent stem cells (hPSCs), including human embryonic stem cells and induced pluripotent stem cells, are promising for numerous biomedical applications, such as cell replacement therapies, tissue and whole-organ engineering, and high-throughput pharmacology and toxicology screening. Each of these applications requires large numbers of cells of high quality; however, the scalable expansion and differentiation of hPSCs, especially for clinical utilization, remains a challenge. We report a simple, defined, efficient, scalable, and good manufacturing practice-compatible 3D culture system for hPSC expansion and differentiation. It employs a thermoresponsive hydrogel that combines easy manipulation and completely defined conditions, free of any human- or animal-derived factors, and entailing only recombinant protein factors. Under an optimized protocol, the 3D system enables long-term, serial expansion of multiple hPSCs lines with a high expansion rate (∼20-fold per 5-d passage, for a 1072-fold expansion over 280 d), yield (∼2.0 × 107 cells per mL of hydrogel), and purity (∼95% Oct4+), even with single-cell inoculation, all of which offer considerable advantages relative to current approaches. Moreover, the system enabled 3D directed differentiation of hPSCs into multiple lineages, including dopaminergic neuron progenitors with a yield of ∼8 × 107 dopaminergic progenitors per mL of hydrogel and ∼80-fold expansion by the end of a 15-d derivation. This versatile system may be useful at numerous scales, from basic biological investigation to clinical development.

Numerical and Experimental Study on Hydrodynamic Performance of A Novel Semi-Submersible Concept

NASA Astrophysics Data System (ADS)

Gao, Song; Tao, Long-bin; Kou, Yu-feng; Lu, Chao; Sun, Jiang-long

2018-04-01

Multiple Column Platform (MCP) semi-submersible is a newly proposed concept, which differs from the conventional semi-submersibles, featuring centre column and middle pontoon. It is paramount to ensure its structural reliability and safe operation at sea, and a rigorous investigation is conducted to examine the hydrodynamic and structural performance for the novel structure concept. In this paper, the numerical and experimental studies on the hydrodynamic performance of MCP are performed. Numerical simulations are conducted in both the frequency and time domains based on 3D potential theory. The numerical models are validated by experimental measurements obtained from extensive sets of model tests under both regular wave and irregular wave conditions. Moreover, a comparative study on MCP and two conventional semi-submersibles are carried out using numerical simulation. Specifically, the hydrodynamic characteristics, including hydrodynamic coefficients, natural periods and motion response amplitude operators (RAOs), mooring line tension are fully examined. The present study proves the feasibility of the novel MCP and demonstrates the potential possibility of optimization in the future study.

A numerical method for simulating the dynamics of 3D axisymmetric vesicles suspended in viscous flows

NASA Astrophysics Data System (ADS)

Veerapaneni, Shravan K.; Gueyffier, Denis; Biros, George; Zorin, Denis

2009-10-01

We extend [Shravan K. Veerapaneni, Denis Gueyffier, Denis Zorin, George Biros, A boundary integral method for simulating the dynamics of inextensible vesicles suspended in a viscous fluid in 2D, Journal of Computational Physics 228(7) (2009) 2334-2353] to the case of three-dimensional axisymmetric vesicles of spherical or toroidal topology immersed in viscous flows. Although the main components of the algorithm are similar in spirit to the 2D case—spectral approximation in space, semi-implicit time-stepping scheme—the main differences are that the bending and viscous force require new analysis, the linearization for the semi-implicit schemes must be rederived, a fully implicit scheme must be used for the toroidal topology to eliminate a CFL-type restriction and a novel numerical scheme for the evaluation of the 3D Stokes single layer potential on an axisymmetric surface is necessary to speed up the calculations. By introducing these novel components, we obtain a time-scheme that experimentally is unconditionally stable, has low cost per time step, and is third-order accurate in time. We present numerical results to analyze the cost and convergence rates of the scheme. To verify the solver, we compare it to a constrained variational approach to compute equilibrium shapes that does not involve interactions with a viscous fluid. To illustrate the applicability of method, we consider a few vesicle-flow interaction problems: the sedimentation of a vesicle, interactions of one and three vesicles with a background Poiseuille flow.

Effects of perturbations and radial profiles on ignition of inertial confinement fusion hotspots

NASA Astrophysics Data System (ADS)

Taylor, S.; Chittenden, J. P.

2014-06-01

Perturbations of inertial confinement fusion hotspots from spherical symmetry cause an increase in the implosion velocity required for ignition, as investigated analytically by [R. Kishony and D. Shvarts, Phys. Plasmas 8, 4925 (2001)] and in numerical studies by many authors. In this paper, we analyse the mechanisms behind this effect by comparing fully 3D fluid simulations of National Ignition Facility targets to a novel analytic model of the thermal energy balance of the hotspot. The analytic model takes into account the radial variation of the state variables within the hotspot and provides an accurate relationship between the hotspot's 0D parameters (ρc, Tc, R , uR, and q) and its heating and cooling rates. The dominant effect of perturbations appears to be an increase in the inflow velocity at the hotspot's surface due to transverse flow of material between perturbation structures, causing premature thermalisation of kinetic energy before the hotspot is fully compressed. In hotspots with a broad perturbation spectrum, thermalisation of energy is inhibited by nonradial motion introduced by mode-mode interaction, reducing the yield further.

Numerical Analysis of AHSS Fracture in a Stretch-bending Test

NASA Astrophysics Data System (ADS)

Luo, Meng; Chen, Xiaoming; Shi, Ming F.; Shih, Hua-Chu

2010-06-01

Advanced High Strength Steels (AHSS) are increasingly used in the automotive industry due to their superior strength and substantial weight reduction advantage. However, their limited ductility gives rise to numerous manufacturing issues. One of them is the so-called `shear fracture' often observed on tight radii during stamping processes. Since traditional approaches, such as the Forming Limit Diagram (FLD), are unable to predict this type of fracture, efforts have been made to develop failure criteria that can predict shear fractures. In this paper, a recently developed Modified Mohr-Coulomb (MMC) ductile fracture criterion[1] is adopted to analyze the failure behavior of a Dual Phase (DP) steel sheet during stretch bending operations. The plasticity and ductile fracture of the present sheet are fully characterized by the Hill'48 orthotropic model and the MMC fracture model respectively. Finite Element models with three different element types (3D, shell and plane strain) were built for a Stretch Forming Simulator (SFS) test and numerical simulations with four different R/t ratios (die radius normalized by sheet thickness) were performed. It has been shown that the 3D and shell element models can accurately predict the failure location/mode, the upper die load-displacement responses as well as the wall stress and wrap angle at the onset of fracture for all R/t ratios. Furthermore, a series of parametric studies were conducted on the 3D element model, and the effects of tension level (clamping distance) and tooling friction on the failure modes/locations were investigated.

Using computed tomography and 3D printing to construct custom prosthetics attachments and devices.

PubMed

Liacouras, Peter C; Sahajwalla, Divya; Beachler, Mark D; Sleeman, Todd; Ho, Vincent B; Lichtenberger, John P

2017-01-01

The prosthetic devices the military uses to restore function and mobility to our wounded warriors are highly advanced, and in many instances not publically available. There is considerable research aimed at this population of young patients who are extremely active and desire to take part in numerous complex activities. While prosthetists design and manufacture numerous devices with standard materials and limb assemblies, patients often require individualized prosthetic design and/or modifications to enable them to participate fully in complex activities. Prosthetists and engineers perform research and implement digitally designs in collaboration to generate equipment for their patient's rehabilitation needs. 3D printing allows for these devices to be manufactured from an array of materials ranging from plastic to titanium alloy. Many designs require form fitting to a prosthetic socket or a complex surface geometry. Specialty items can be scanned using computed tomography and digitally reconstructed to produce a virtual 3D model the engineer can use to design the necessary features of the desired prosthetic, device, or attachment. Completed devices are tested for fit and function. Numerous custom prostheses and attachments have been successfully translated from the research domain to clinical reality, in particular, those that feature the use of computed tomography (CT) reconstructions. The purpose of this project is to describe the research pathways to implementation for the following clinical designs: sets of bilateral hockey skates; custom weightlifting prosthetic hands; and a wine glass holder. This article will demonstrate how to incorporate CT imaging and 3D printing in the design and manufacturing process of custom attachments and assistive technology devices. Even though some of these prosthesis attachments may be relatively simple in design to an engineer, they have an enormous impact on the lives of our wounded warriors.

Impact of three-dimensional endoanal ultrasound on the outcome of anal fistula surgery: a prospective cohort study.

PubMed

Ding, J-H; Bi, L-X; Zhao, K; Feng, Y-Y; Zhu, J; Zhang, B; Yin, S-H; Zhao, Y-J

2015-12-01

The aim of the study was to evaluate the impact of three-dimensional endoanal ultrasound (3D-EAUS) on postoperative outcome in patients with anal fistula. This prospective study compared clinical and functional outcomes of patients with and without preoperative 3D-EAUS examination 1 year after anal fistula surgery. Patients were prospectively followed and evaluated by a standardized protocol including physical examination, the Wexner Incontinence Score (WIS) and anorectal manometry, at baseline and 1 year after surgery. A total of 196 patients were enrolled. There were no significant differences in demographic and operative parameters, except for operation time, between the two groups. At 1 year follow-up, the overall recurrence rates were 8.8% (9/102) in the 3D-EAUS group and 13.8% (13/94) in the examination under anaesthesia (EUA) group. In the subgroup of patients with complex fistulae, the recurrence rate was numerically lower in the 3D-EAUS group (12.8% vs 22.5%; P = 0.26). The WIS in the EUA group significantly worsened (0.35 ± 0.94 vs 1.07 ± 1.59; P = 0.003) with a decreased the number of fully continent patients (82.5% vs 55%; P = 0.008) while neither the WIS nor the proportion of fully continent patients changed in the 3D-EAUS group. Fewer patients in the 3D-EAUS group developed incontinence postoperatively (6.7% vs 33.3%; P = 0.012) and they had better maximum resting pressure and maximum squeeze pressure than the EUA group. Preoperative use of 3D-EAUS had a favourable impact on the outcome of surgical treatment for anal fistulae, especially in those with complex anal fistula. It should be routinely used in the clinical setting. Colorectal Disease © 2015 The Association of Coloproctology of Great Britain and Ireland.

Novel fully integrated computer system for custom footwear: from 3D digitization to manufacturing

NASA Astrophysics Data System (ADS)

Houle, Pascal-Simon; Beaulieu, Eric; Liu, Zhaoheng

1998-03-01

This paper presents a recently developed custom footwear system, which integrates 3D digitization technology, range image fusion techniques, a 3D graphical environment for corrective actions, parametric curved surface representation and computer numerical control (CNC) machining. In this system, a support designed with the help of biomechanics experts can stabilize the foot in a correct and neutral position. The foot surface is then captured by a 3D camera using active ranging techniques. A software using a library of documented foot pathologies suggests corrective actions on the orthosis. Three kinds of deformations can be achieved. The first method uses previously scanned pad surfaces by our 3D scanner, which can be easily mapped onto the foot surface to locally modify the surface shape. The second kind of deformation is construction of B-Spline surfaces by manipulating control points and modifying knot vectors in a 3D graphical environment to build desired deformation. The last one is a manual electronic 3D pen, which may be of different shapes and sizes, and has an adjustable 'pressure' information. All applied deformations should respect a G1 surface continuity, which ensure that the surface can accustom a foot. Once the surface modification process is completed, the resulting data is sent to manufacturing software for CNC machining.

Numerical developments for short-pulsed Near Infra-Red laser spectroscopy. Part I: direct treatment

NASA Astrophysics Data System (ADS)

Boulanger, Joan; Charette, André

2005-03-01

This two part study is devoted to the numerical treatment of short-pulsed laser near infra-red spectroscopy. The overall goal is to address the possibility of numerical inverse treatment based on a recently developed direct model to solve the transient radiative transfer equation. This model has been constructed in order to incorporate the last improvements in short-pulsed laser interaction with semi-transparent media and combine a discrete ordinates computing of the implicit source term appearing in the radiative transfer equation with an explicit treatment of the transport of the light intensity using advection schemes, a method encountered in reactive flow dynamics. The incident collimated beam is analytically solved through Bouger Beer Lambert extinction law. In this first part, the direct model is extended to fully non-homogeneous materials and tested with two different spatial schemes in order to be adapted to the inversion methods presented in the following second part. As a first point, fundamental methods and schemes used in the direct model are presented. Then, tests are conducted by comparison with numerical simulations given as references. In a third and last part, multi-dimensional extensions of the code are provided. This allows presentation of numerical results of short pulses propagation in 1, 2 and 3D homogeneous and non-homogeneous materials given some parametrical studies on medium properties and pulse shape. For comparison, an integral method adapted to non-homogeneous media irradiated by a pulsed laser beam is also developed for the 3D case.

Untangling Slab Dynamics Using 3-D Numerical and Analytical Models

NASA Astrophysics Data System (ADS)

Holt, A. F.; Royden, L.; Becker, T. W.

2016-12-01

Increasingly sophisticated numerical models have enabled us to make significant strides in identifying the key controls on how subducting slabs deform. For example, 3-D models have demonstrated that subducting plate width, and the related strength of toroidal flow around the plate edge, exerts a strong control on both the curvature and the rate of migration of the trench. However, the results of numerical subduction models can be difficult to interpret, and many first order dynamics issues remain at least partially unresolved. Such issues include the dominant controls on trench migration, the interdependence of asthenospheric pressure and slab dynamics, and how nearby slabs influence each other's dynamics. We augment 3-D, dynamically evolving finite element models with simple, analytical force-balance models to distill the physics associated with subduction into more manageable parts. We demonstrate that for single, isolated subducting slabs much of the complexity of our fully numerical models can be encapsulated by simple analytical expressions. Rates of subduction and slab dip correlate strongly with the asthenospheric pressure difference across the subducting slab. For double subduction, an additional slab gives rise to more complex mantle pressure and flow fields, and significantly extends the range of plate kinematics (e.g., convergence rate, trench migration rate) beyond those present in single slab models. Despite these additional complexities, we show that much of the dynamics of such multi-slab systems can be understood using the physics illuminated by our single slab study, and that a force-balance method can be used to relate intra-plate stress to viscous pressure in the asthenosphere and coupling forces at plate boundaries. This method has promise for rapid modeling of large systems of subduction zones on a global scale.

Inkjet-/3D-/4D-printed autonomous wearable RF modules for biomonitoring, positioning and sensing applications

NASA Astrophysics Data System (ADS)

Bito, Jo; Bahr, Ryan; Hester, Jimmy; Kimionis, John; Nauroze, Abdullah; Su, Wenjing; Tehrani, Bijan; Tentzeris, Manos M.

2017-05-01

In this paper, numerous inkjet-/3D-/4D-printed wearable flexible antennas, RF electronics, modules and sensors fabricated on paper and other polymer (e.g. LCP) substrates are introduced as a system-level solution for ultra-low-cost mass production of autonomous Biomonitoring, Positioning and Sensing applications. This paper briefly discusses the state-of-the-art area of fully-integrated wearable wireless sensor modules on paper or flexible LCP and show the first ever 4D sensor module integration on paper, as well as numerous 3D and 4D multilayer paper-based and LCP-based RF/microwave, flexible and wearable structures, that could potentially set the foundation for the truly convergent wireless sensor ad-hoc "on-body networks of the future with enhanced cognitive intelligence and "rugged" packaging. Also, some challenges concerning the power sources of "nearperpetual" wearable RF modules, including flexible miniaturized batteries as well as power-scavenging approaches involving electromagnetic and solar energy forms are discuessed. The final step of the paper will involve examples from mmW wearable (e.g. biomonitoring) antennas and RF modules, as well as the first examples of the integration of inkjet-printed nanotechnology-based (e.g.CNT) sensors on paper and organic substrates for Internet of Things (IoT) applications. It has to be noted that the paper will review and present challenges for inkjetprinted organic active and nonlinear devices as well as future directions in the area of environmentally-friendly "green") wearable RF electronics and "smart-skin conformal sensors.

Ultrasound SIV measurement of helical valvular flow behind the great saphenous vein

NASA Astrophysics Data System (ADS)

Park, Jun Hong; Kim, Jeong Ju; Lee, Sang Joon; Yeom, Eunseop; Experimental Fluid Mechanics Laboratory Team; LaboratoryMicrothermal; Microfluidic Measurements Collaboration

2017-11-01

Dysfunction of venous valve and induced secondary abnormal flow are closely associated with venous diseases. Thus, detailed analysis of venous valvular flow is invaluable from biological and medical perspectives. However, most previous studies on venous perivalvular flows were based on qualitative analyses. On the contrary, quantitative analysis on the perivalvular flows has not been fully understood yet. In this study, 3D valvular flows under in vitro and in vivo conditions were experimentally investigated using ultrasound speckle image velocimetry (SIV) for analyzing their flow characteristics. The results for in vitro model obtained by the SIV technique were compared with those derived by numerical simulation and color Doppler method to validate its measurement accuracy. Then blood flow in the human great saphenous vein was measured using the SIV with respect to the dimensionless index, helical intensity. The results obtained by the SIV method are well matched well with those obtained by the numerical simulation and color Doppler method. The hemodynamic characteristics of 3D valvular flows measured by the validated SIV method would be helpful in diagnosis of valve-related venous diseases. None.

Approaches to Numerical Relativity

NASA Astrophysics Data System (ADS)

d'Inverno, Ray

2005-07-01

Introduction Ray d'Inverno; Preface C. J. S. Clarke; Part I. Theoretical Approaches: 1. Numerical relativity on a transputer array Ray d'Inverno; 2. Some aspects of the characteristic initial value problem in numerical relativity Nigel Bishop; 3. The characteristic initial value problem in general relativity J. M. Stewart; 4. Algebraic approachs to the characteristic initial value problem in general relativity Jõrg Frauendiener; 5. On hyperboidal hypersurfaces Helmut Friedrich; 6. The initial value problem on null cones J. A. Vickers; 7. Introduction to dual-null dynamics S. A. Hayward; 8. On colliding plane wave space-times J. B. Griffiths; 9. Boundary conditions for the momentum constraint Niall O Murchadha; 10. On the choice of matter model in general relativity A. D. Rendall; 11. A mathematical approach to numerical relativity J. W. Barrett; 12. Making sense of the effects of rotation in general relativity J. C. Miller; 13. Stability of charged boson stars and catastrophe theory Franz E. Schunck, Fjodor V. Kusmartsev and Eckehard W. Mielke; Part II. Practical Approaches: 14. Numerical asymptotics R. Gómez and J. Winicour; 15. Instabilities in rapidly rotating polytropes Scott C. Smith and Joan M. Centrella; 16. Gravitational radiation from coalescing binary neutron stars Ken-Ichi Oohara and Takashi Nakamura; 17. 'Critical' behaviour in massless scalar field collapse M. W. Choptuik; 18. Goudunov-type methods applied to general relativistic gravitational collapse José Ma. Ibánez, José Ma. Martí, Juan A. Miralles and J. V. Romero; 19. Astrophysical sources of gravitational waves and neutrinos Silvano Bonazzola, Eric Gourgoulhon, Pawel Haensel and Jean-Alain Marck; 20. Gravitational radiation from triaxial core collapse Jean-Alain Marck and Silvano Bonazzola; 21. A vacuum fully relativistic 3D numerical code C. Bona and J. Massó; 22. Solution of elliptic equations in numerical relativity using multiquadrics M. R. Dubal, S. R. Oliveira and R. A. Matzner; 23. Self-gravitating thin disks around rotating black holes A. Lanza; 24. An ADI and causal reconnection Gabrielle D. Allen and Bernard F. Schutz; 25. Time-symmetric ADI and causal reconnection Miguel Alcubierre and Bernard F. Schutz; 26. The numerical study of topological defects E. P. S. Shellard; 27. Computations of bubble growth during the cosmological quark-hadron transition J. C. Miller and O. Pantano; 28. Initial data of axisymmetric gravitational waves with a cosmological constant Ken-Ichi Nakao, Kei-Ichi Maeda, Takashi Nakamura and Ken-Ichi Oohara.

Comparison of 2D numerical models for river flood hazard assessment: simulation of the Secchia River flood in January, 2014

NASA Astrophysics Data System (ADS)

Shustikova, Iuliia; Domeneghetti, Alessio; Neal, Jeffrey; Bates, Paul; Castellarin, Attilio

2017-04-01

Hydrodynamic modeling of inundation events still brings a large array of uncertainties. This effect is especially evident in the models run for geographically large areas. Recent studies suggest using fully two-dimensional (2D) models with high resolution in order to avoid uncertainties and limitations coming from the incorrect interpretation of flood dynamics and an unrealistic reproduction of the terrain topography. This, however, affects the computational efficiency increasing the running time and hardware demands. Concerning this point, our study evaluates and compares numerical models of different complexity by testing them on a flood event that occurred in the basin of the Secchia River, Northern Italy, on 19th January, 2014. The event was characterized by a levee breach and consequent flooding of over 75 km2 of the plain behind the dike within 48 hours causing population displacement, one death and economic losses in excess of 400 million Euro. We test the well-established TELEMAC 2D, and LISFLOOD-FP codes, together with the recently launched HEC-RAS 5.0.3 (2D model), all models are implemented using different grid size (2-200 m) based on the 1 m digital elevation model resolution. TELEMAC is a fully 2D hydrodynamic model which is based on the finite-element or finite-volume approach. Whereas HEC-RAS 5.0.3 and LISFLOOD-FP are both coupled 1D-2D models. All models are calibrated against observed inundation extent and maximum water depths, which are retrieved from remotely sensed data and field survey reports. Our study quantitatively compares the three modeling strategies highlighting differences in terms of the ease of implementation, accuracy of representation of hydraulic processes within floodplains and computational efficiency. Additionally, we look into the different grid resolutions in terms of the results accuracy and computation time. Our study is a preliminary assessment that focuses on smaller areas in order to identify potential modeling schemes that would be efficient for simulating flooding scenarios for large and very large floodplains. This research aims at contributing to the reduction of uncertainties and limitations in hazard and risk assessment.

3D Simulation of Multiple Simultaneous Hydraulic Fractures with Different Initial Lengths in Rock

NASA Astrophysics Data System (ADS)

Tang, X.; Rayudu, N. M.; Singh, G.

2017-12-01

Hydraulic fracturing is widely used technique for extracting shale gas. During this process, fractures with various initial lengths are induced in rock mass with hydraulic pressure. Understanding the mechanism of propagation and interaction between these induced hydraulic cracks is critical for optimizing the fracking process. In this work, numerical results are presented for investigating the effect of in-situ parameters and fluid properties on growth and interaction of multi simultaneous hydraulic fractures. A fully coupled 3D fracture simulator, TOUGH- GFEM is used for simulating the effect of different vital parameters, including in-situ stress, initial fracture length, fracture spacing, fluid viscosity and flow rate on induced hydraulic fractures growth. This TOUGH-GFEM simulator is based on 3D finite volume method (FVM) and partition of unity element method (PUM). Displacement correlation method (DCM) is used for calculating multi - mode (Mode I, II, III) stress intensity factors. Maximum principal stress criteria is used for crack propagation. Key words: hydraulic fracturing, TOUGH, partition of unity element method , displacement correlation method, 3D fracturing simulator

Higher-Order Neural Networks Applied to 2D and 3D Object Recognition

NASA Technical Reports Server (NTRS)

Spirkovska, Lilly; Reid, Max B.

1994-01-01

A Higher-Order Neural Network (HONN) can be designed to be invariant to geometric transformations such as scale, translation, and in-plane rotation. Invariances are built directly into the architecture of a HONN and do not need to be learned. Thus, for 2D object recognition, the network needs to be trained on just one view of each object class, not numerous scaled, translated, and rotated views. Because the 2D object recognition task is a component of the 3D object recognition task, built-in 2D invariance also decreases the size of the training set required for 3D object recognition. We present results for 2D object recognition both in simulation and within a robotic vision experiment and for 3D object recognition in simulation. We also compare our method to other approaches and show that HONNs have distinct advantages for position, scale, and rotation-invariant object recognition. The major drawback of HONNs is that the size of the input field is limited due to the memory required for the large number of interconnections in a fully connected network. We present partial connectivity strategies and a coarse-coding technique for overcoming this limitation and increasing the input field to that required by practical object recognition problems.

2D OR NOT 2D: THE EFFECT OF DIMENSIONALITY ON THE DYNAMICS OF FINGERING CONVECTION AT LOW PRANDTL NUMBER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garaud, Pascale; Brummell, Nicholas

2015-12-10

Fingering convection (otherwise known as thermohaline convection) is an instability that occurs in stellar radiative interiors in the presence of unstable compositional gradients. Numerical simulations have been used in order to estimate the efficiency of mixing induced by this instability. However, fully three-dimensional (3D) computations in the parameter regime appropriate for stellar astrophysics (i.e., low Prandtl number) are prohibitively expensive. This raises the question of whether two-dimensional (2D) simulations could be used instead to achieve the same goals. In this work, we address this issue by comparing the outcome of 2D and 3D simulations of fingering convection at low Prandtlmore » number. We find that 2D simulations are never appropriate. However, we also find that the required 3D computational domain does not have to be very wide: the third dimension only needs to contain a minimum of two wavelengths of the fastest-growing linearly unstable mode to capture the essentially 3D dynamics of small-scale fingering. Narrow domains, however, should still be used with caution since they could limit the subsequent development of any large-scale dynamics typically associated with fingering convection.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thurgood, Jonathan O.; McLaughlin, James A.; Pontin, David I., E-mail: jonathan.thurgood@northumbria.ac.uk

Here we detail the dynamic evolution of localized reconnection regions about 3D magnetic null points using numerical simulation. We demonstrate for the first time that reconnection triggered by the localized collapse of a 3D null point that is due to an external magnetohydrodynamic (MHD) wave involves a self-generated oscillation, whereby the current sheet and outflow jets undergo a reconnection reversal process during which back-pressure formation at the jet heads acts to prise open the collapsed field before overshooting the equilibrium into an opposite-polarity configuration. The discovery that reconnection at fully 3D nulls can proceed naturally in a time-dependent and periodicmore » fashion suggests that oscillatory reconnection mechanisms may play a role in explaining periodicity in astrophysical phenomena associated with magnetic reconnection, such as the observed quasi-periodicity of solar and stellar flare emission. Furthermore, we find that a consequence of oscillatory reconnection is the generation of a plethora of freely propagating MHD waves that escape the vicinity of the reconnection region.« less

Disparity profiles in 3DV applications: overcoming the issue of heterogeneous viewing conditions in stereoscopic delivery

NASA Astrophysics Data System (ADS)

Boisson, Guillaume; Chamaret, Christel

2012-03-01

More and more numerous 3D movies are released each year. Thanks to the current spread of 3D-TV displays, these 3D Video (3DV) contents are about to enter massively the homes. Yet viewing conditions determine the stereoscopic features achievable for 3DV material. Because the conditions at home - screen size and distance to screen - differ significantly from a theater, 3D Cinema movies need to be repurposed before broadcast and replication on 3D Blu-ray Discs for being fully enjoyed at home. In that paper we tackle that particular issue of how to handle the variety of viewing conditions in stereoscopic contents delivery. To that extend we first investigate what is basically at stake for granting stereoscopic viewers' comfort, through the well-known - and sometimes dispraised - vergence-accommodation conflict. Thereby we define a set of basic rules that can serve as guidelines for 3DV creation. We propose disparity profiles as new requirements for 3DV production and repurposing. Meeting proposed background and foreground constraints prevents from visual fatigue, and occupying the whole depth budget available grants optimal 3D effects. We present an efficient algorithm for automatic disparity-based 3DV retargeting depending on the viewing conditions. Variants are proposed depending on the input format (stereoscopic binocular content or depth-based format) and the level of complexity achievable.

Electron acceleration in the Solar corona - 3D PiC code simulations of guide field reconnection

NASA Astrophysics Data System (ADS)

Alejandro Munoz Sepulveda, Patricio

2017-04-01

The efficient electron acceleration in the solar corona detected by means of hard X-ray emission is still not well understood. Magnetic reconnection through current sheets is one of the proposed production mechanisms of non-thermal electrons in solar flares. Previous works in this direction were based mostly on test particle calculations or 2D fully-kinetic PiC simulations. We have now studied the consequences of self-generated current-aligned instabilities on the electron acceleration mechanisms by 3D magnetic reconnection. For this sake, we carried out 3D Particle-in-Cell (PiC) code numerical simulations of force free reconnecting current sheets, appropriate for the description of the solar coronal plasmas. We find an efficient electron energization, evidenced by the formation of a non-thermal power-law tail with a hard spectral index smaller than -2 in the electron energy distribution function. We discuss and compare the influence of the parallel electric field versus the curvature and gradient drifts in the guiding-center approximation on the overall acceleration, and their dependence on different plasma parameters.

Seismic Wave Propagation in Fully Anisotropic Axisymmetric Media: Applications and Practical Considerations

NASA Astrophysics Data System (ADS)

van Driel, Martin; Nissen-Meyer, Tarje; Stähler, Simon; Waszek, Lauren; Hempel, Stefanie; Auer, Ludwig; Deuss, Arwen

2014-05-01

We present a numerical method to compute high-frequency 3D elastic waves in fully anisotropic axisymmetric media. The method is based on a decomposition of the wavefield into a series of uncoupled 2D equations, for which the dependence of the wavefield on the azimuth can be solved analytically. The remaining 2D problems are then solved using a spectral element method (AxiSEM). AxiSEM was recently published open-source (Nissen-Meyer et al. 2014) as a production ready code capable to compute global seismic wave propagation up to frequencies of ~2Hz. It accurately models visco-elastic dissipation and anisotropy (van Driel et al., submitted to GJI) and runs efficiently on HPC resources using up to 10K cores. At very short period, the Fresnel Zone of body waves is narrow and sensitivity is focused around the geometrical ray. In cases where the azimuthal variations of structural heterogeneity exhibit long spatial wavelengths, so called 2.5D simulations (3D wavefields in 2D models) provide a good approximation. In AxiSEM, twodimensional variations in the source-receiver plane are effectively modelled as ringlike structures extending in the out-of-plane direction. In contrast to ray-theory, which is widely used in high-frequency applications, AxiSEM provides complete waveforms, thus giving access to frequency dependency, amplitude variations, and peculiar wave effects such as diffraction and caustics. Here we focus on the practical implications of the inherent axisymmetric geometry and show how the 2.5D-features of our method method can be used to model realistic anisotropic structures, by applying it to problems such as the D" region and the inner core.

Nonlinear three-dimensional verification of the SPECYL and PIXIE3D magnetohydrodynamics codes for fusion plasmas

NASA Astrophysics Data System (ADS)

Bonfiglio, D.; Chacón, L.; Cappello, S.

2010-08-01

With the increasing impact of scientific discovery via advanced computation, there is presently a strong emphasis on ensuring the mathematical correctness of computational simulation tools. Such endeavor, termed verification, is now at the center of most serious code development efforts. In this study, we address a cross-benchmark nonlinear verification study between two three-dimensional magnetohydrodynamics (3D MHD) codes for fluid modeling of fusion plasmas, SPECYL [S. Cappello and D. Biskamp, Nucl. Fusion 36, 571 (1996)] and PIXIE3D [L. Chacón, Phys. Plasmas 15, 056103 (2008)], in their common limit of application: the simple viscoresistive cylindrical approximation. SPECYL is a serial code in cylindrical geometry that features a spectral formulation in space and a semi-implicit temporal advance, and has been used extensively to date for reversed-field pinch studies. PIXIE3D is a massively parallel code in arbitrary curvilinear geometry that features a conservative, solenoidal finite-volume discretization in space, and a fully implicit temporal advance. The present study is, in our view, a first mandatory step in assessing the potential of any numerical 3D MHD code for fluid modeling of fusion plasmas. Excellent agreement is demonstrated over a wide range of parameters for several fusion-relevant cases in both two- and three-dimensional geometries.

Nonlinear three-dimensional verification of the SPECYL and PIXIE3D magnetohydrodynamics codes for fusion plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonfiglio, Daniele; Chacon, Luis; Cappello, Susanna

2010-01-01

With the increasing impact of scientific discovery via advanced computation, there is presently a strong emphasis on ensuring the mathematical correctness of computational simulation tools. Such endeavor, termed verification, is now at the center of most serious code development efforts. In this study, we address a cross-benchmark nonlinear verification study between two three-dimensional magnetohydrodynamics (3D MHD) codes for fluid modeling of fusion plasmas, SPECYL [S. Cappello and D. Biskamp, Nucl. Fusion 36, 571 (1996)] and PIXIE3D [L. Chacon, Phys. Plasmas 15, 056103 (2008)], in their common limit of application: the simple viscoresistive cylindrical approximation. SPECYL is a serial code inmore » cylindrical geometry that features a spectral formulation in space and a semi-implicit temporal advance, and has been used extensively to date for reversed-field pinch studies. PIXIE3D is a massively parallel code in arbitrary curvilinear geometry that features a conservative, solenoidal finite-volume discretization in space, and a fully implicit temporal advance. The present study is, in our view, a first mandatory step in assessing the potential of any numerical 3D MHD code for fluid modeling of fusion plasmas. Excellent agreement is demonstrated over a wide range of parameters for several fusion-relevant cases in both two- and three-dimensional geometries.« less

Landau-Zener-Stückelberg-Majorana interference in a 3D transmon driven by a chirped microwave

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Ming; Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045; Zhou, Yu

2016-03-14

By driving a 3D transmon with microwave fields, we generate an effective avoided energy-level crossing. Then we chirp microwave frequency, which is equivalent to driving the system through the avoided energy-level crossing by sweeping the avoided crossing. A double-passage chirp produces Landau-Zener-Stückelberg-Majorana (LZSM) interference that agree well with the numerical results, especially with the initial state being an eigen-energy state in the center of an avoided level crossing. A time-resolved state tomography measurement is performed in the evolution of LZSM interference, showing an experimental evidence for the dynamical evolution of quantum state. Our method is fully applicable to other quantummore » systems that contain no intrinsic avoided level crossing, providing an alternative approach for quantum control and quantum simulation.« less

A novel 3D micron-scale DPTV (Defocused Particle Tracking Velocimetry) and its applications in microfluidic devices

NASA Astrophysics Data System (ADS)

Roberts, John

2005-11-01

The rapid advancements in micro/nano biotechnology demand quantitative tools for characterizing microfluidic flows in lab-on-a-chip applications, validation of computational results for fully 3D flows in complex micro-devices, and efficient observation of cellular dynamics in 3D. We present a novel 3D micron-scale DPTV (defocused particle tracking velocimetry) that is capable of mapping out 3D Lagrangian, as well as 3D Eulerian velocity flow fields at sub-micron resolution and with one camera. The main part of the imaging system is an epi-fluorescent microscope (Olympus IX 51), and the seeding particles are fluorescent particles with diameter range 300nm - 10um. A software package has been developed for identifying (x,y,z,t) coordinates of the particles using the defocused images. Using the imaging system, we successfully mapped the pressure driven flow fields in microfluidic channels. In particular, we measured the Laglangian flow fields in a microfluidic channel with a herring bone pattern at the bottom, the later is used to enhance fluid mixing in lateral directions. The 3D particle tracks revealed the flow structure that has only been seen in numerical computation. This work is supported by the National Science Foundation (CTS - 0514443), the Nanobiotechnology Center at Cornell, and The New York State Center for Life Science Enterprise.

A Numerical Multiscale Framework for Modeling Patient-Specific Coronary Artery Bypass Surgeries

NASA Astrophysics Data System (ADS)

Ramachandra, Abhay B.; Kahn, Andrew; Marsden, Alison

2014-11-01

Coronary artery bypass graft (CABG) surgery is performed to revascularize diseased coronary arteries, using arterial, venous or synthetic grafts. Vein grafts, used in more than 70% of procedures, have failure rates as high as 50% in less than 10 years. Hemodynamics is known to play a key role in the mechano-biological response of vein grafts, but current non-invasive imaging techniques cannot fully characterize the hemodynamic and biomechanical environment. We numerically compute hemodynamics and wall mechanics in patient-specific 3D CABG geometries using stabilized finite element methods. The 3D patient-specific domain is coupled to a 0D lumped parameter circulatory model and parameters are tuned to match patient-specific blood pressures, stroke volumes, heart rates and heuristic flow-split values. We quantify differences in hemodynamics between arterial and venous grafts and discuss possible correlations to graft failure. Extension to a deformable wall approximation will also be discussed. The quantification of wall mechanics and hemodynamics is a necessary step towards coupling continuum models in solid and fluid mechanics with the cellular and sub-cellular responses of grafts, which in turn, should lead to a more accurate prediction of the long term outcome of CABG surgeries, including predictions of growth and remodeling.

Numerical Simulation of rivulet build up via lubrication equations

NASA Astrophysics Data System (ADS)

Suzzi, N.; Croce, G.

2017-11-01

A number of engineering problems involve the evolution of a thin layer of liquid over a non-wettable substrate. For example, CO2 chemical absorption is carried out in packed columns, where post-combustion CO2 flows up while liquid solvent falls down through a collection of corrugated sheets. Further application include, among others, in-flight icing simulations, moisture condensation on de-humidifier fins, fogging build up and removal. Here, we present a development of an in-house code solving numerically the 2D lubrication equation for a film flowing down an inclined plate. The disjoining pressure approach is followed, in order to model both the contact line discontinuity and the surface wettability. With respect to the original implementation, the full modeling of capillary pressure terms according to Young- Laplace relation allows to investigate contact angles close to π/2. The code is thus validated with literature numerical results, obtained by a fully 3D approach (VOF), showing satisfying agreement despite a strong reduction in terms of computational cost. Steady and unsteady wetting dynamics of a developing rivulet are investigated (and validated) under different load conditions and for different values of the contact angles.

Interface- and discontinuity-aware numerical schemes for plasma 3-T radiation diffusion in two and three dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, William W., E-mail: dai@lanl.gov; Scannapieco, Anthony J.

2015-11-01

A set of numerical schemes is developed for two- and three-dimensional time-dependent 3-T radiation diffusion equations in systems involving multi-materials. To resolve sub-cell structure, interface reconstruction is implemented within any cell that has more than one material. Therefore, the system of 3-T radiation diffusion equations is solved on two- and three-dimensional polyhedral meshes. The focus of the development is on the fully coupling between radiation and material, the treatment of nonlinearity in the equations, i.e., in the diffusion terms and source terms, treatment of the discontinuity across cell interfaces in material properties, the formulations for both transient and steady states,more » the property for large time steps, and second order accuracy in both space and time. The discontinuity of material properties between different materials is correctly treated based on the governing physics principle for general polyhedral meshes and full nonlinearity. The treatment is exact for arbitrarily strong discontinuity. The scheme is fully nonlinear for the full nonlinearity in the 3-T diffusion equations. Three temperatures are fully coupled and are updated simultaneously. The scheme is general in two and three dimensions on general polyhedral meshes. The features of the scheme are demonstrated through numerical examples for transient problems and steady states. The effects of some simplifications of numerical schemes are also shown through numerical examples, such as linearization, simple average of diffusion coefficient, and approximate treatment for the coupling between radiation and material.« less

Fully nonlinear development of the most unstable goertler vortex in a three dimensional boundary layer

NASA Technical Reports Server (NTRS)

Otto, S. R.; Bassom, Andrew P.

1992-01-01

The nonlinear development is studied of the most unstable Gortler mode within a general 3-D boundary layer upon a suitably concave surface. The structure of this mode was first identified by Denier, Hall and Seddougui (1991) who demonstrated that the growth rate of this instability is O(G sup 3/5) where G is the Gortler number (taken to be large here), which is effectively a measure of the curvature of the surface. Previous researchers have described the fate of the most unstable mode within a 2-D boundary layer. Denier and Hall (1992) discussed the fully nonlinear development of the vortex in this case and showed that the nonlinearity causes a breakdown of the flow structure. The effect of crossflow and unsteadiness upon an infinitesimal unstable mode was elucidated by Bassom and Hall (1991). They demonstrated that crossflow tends to stabilize the most unstable Gortler mode, and for certain crossflow/frequency combinations the Gortler mode may be made neutrally stable. These vortex configurations naturally lend themselves to a weakly nonlinear stability analysis; work which is described in a previous article by the present author. Here we extend the ideas of Denier and Hall (1992) to the three-dimensional boundary layer problem. It is found that the numerical solution of the fully nonlinear equations is best conducted using a method which is essentially an adaption of that utilized by Denier and Hall (1992). The influence of crossflow and unsteadiness upon the breakdown of the flow is described.

Theoretical Analysis of the Accuracy and Safety of MRI-Guided Transurethral 3-D Conformal Ultrasound Prostate Therapy

NASA Astrophysics Data System (ADS)

Burtnyk, Mathieu; Chopra, Rajiv; Bronskill, Michael

2009-04-01

MRI-guided transurethral ultrasound therapy is a promising new approach for the treatment of localized prostate cancer. Several studies have demonstrated the feasibility of producing large regions of thermal coagulation adequate for prostate therapy; however, the quantitative assessment of shaping these regions to complex 3-D human prostate geometries has not been fully explored. This study used numerical simulations and twenty manually-segmented pelvic anatomical models derived from high-quality MR images of prostate cancer patients to evaluate the treatment accuracy and safety of 3-D conformal MRI-guided transurethral ultrasound therapy. The simulations incorporated a rotating multi-element planar dual-frequency ultrasound transducer (seventeen 4×3 mm elements) operating at 4.7/9.7 MHz and 10 W/cm2 maximum acoustic power. Results using a novel feedback control algorithm which modulated the ultrasound frequency, power and device rate of rotation showed that regions of thermal coagulation could be shaped to predefined prostate volumes within 1.0 mm across the vast majority of these glands. Treatment times were typically 30 min and remained below 60 min for large 60 cc prostates. With a rectal cooling temperature of 15° C, the rectal wall did not exceed 30EM43 in half of the twenty patient models with only a few 1 mm3 voxels above this threshold in the other cases. At 4.7 MHz, heating of the pelvic bone can become significant when it is located less than 10 mm from the prostate. Numerical simulations show that MRI-guided transurethral ultrasound therapy can thermally coagulate whole prostate glands accurately and safely in 3-D.

Accuracy of 1D microvascular flow models in the limit of low Reynolds numbers.

PubMed

Pindera, Maciej Z; Ding, Hui; Athavale, Mahesh M; Chen, Zhijian

2009-05-01

We describe results of numerical simulations of steady flows in tubes with branch bifurcations using fully 3D and reduced 1D geometries. The intent is to delineate the range of validity of reduced models used for simulations of flows in microcapillary networks, as a function of the flow Reynolds number Re. Results from model problems indicate that for Re less than 1 and possibly as high as 10, vasculatures may be represented by strictly 1D Poiseuille flow geometries with flow variation in the axial dimensions only. In that range flow rate predictions in the different branches generated by 1D and 3D models differ by a constant factor, independent of Re. When the cross-sectional areas of the branches are constant these differences are generally small and appear to stem from an uncertainty of how the individual branch lengths are defined. This uncertainty can be accounted for by a simple geometrical correction. For non-constant cross-sections the differences can be much more significant. If additional corrections for the presence of branch junctions and flow area variations are not taken into account in 1D models of complex vasculatures, the resultant flow predictions should be interpreted with caution.

Empirical Reconstruction and Numerical Modeling of the First Geoeffective Coronal Mass Ejection of Solar Cycle 24

NASA Astrophysics Data System (ADS)

Wood, B. E.; Wu, C.-C.; Howard, R. A.; Socker, D. G.; Rouillard, A. P.

2011-03-01

We analyze the kinematics and morphology of a coronal mass ejection (CME) from 2010 April 3, which was responsible for the first significant geomagnetic storm of solar cycle 24. The analysis utilizes coronagraphic and heliospheric images from the two STEREO spacecraft, and coronagraphic images from SOHO/LASCO. Using an empirical three-dimensional (3D) reconstruction technique, we demonstrate that the CME can be reproduced reasonably well at all times with a 3D flux rope shape, but the case for a flux rope being the correct interpretation is not as strong as some events studied with STEREO in the past, given that we are unable to infer a unique orientation for the flux rope. A model with an orientation angle of -80° from the ecliptic plane (i.e., nearly N-S) works best close to the Sun, but a model at 10° (i.e., nearly E-W) works better far from the Sun. Both interpretations require the cross section of the flux rope to be significantly elliptical rather than circular. In addition to our empirical modeling, we also present a fully 3D numerical MHD model of the CME. This physical model appears to effectively reproduce aspects of the shape and kinematics of the CME's leading edge. It is particularly encouraging that the model reproduces the amount of interplanetary deceleration observed for the CME during its journey from the Sun to 1 AU.

Numerical implementation, verification and validation of two-phase flow four-equation drift flux model with Jacobian-free Newton–Krylov method

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2016-08-24

This study presents a numerical investigation on using the Jacobian-free Newton–Krylov (JFNK) method to solve the two-phase flow four-equation drift flux model with realistic constitutive correlations (‘closure models’). The drift flux model is based on Isshi and his collaborators’ work. Additional constitutive correlations for vertical channel flow, such as two-phase flow pressure drop, flow regime map, wall boiling and interfacial heat transfer models, were taken from the RELAP5-3D Code Manual and included to complete the model. The staggered grid finite volume method and fully implicit backward Euler method was used for the spatial discretization and time integration schemes, respectively. Themore » Jacobian-free Newton–Krylov method shows no difficulty in solving the two-phase flow drift flux model with a discrete flow regime map. In addition to the Jacobian-free approach, the preconditioning matrix is obtained by using the default finite differencing method provided in the PETSc package, and consequently the labor-intensive implementation of complex analytical Jacobian matrix is avoided. Extensive and successful numerical verification and validation have been performed to prove the correct implementation of the models and methods. Code-to-code comparison with RELAP5-3D has further demonstrated the successful implementation of the drift flux model.« less

Automated 3D structure composition for large RNAs

PubMed Central

Popenda, Mariusz; Szachniuk, Marta; Antczak, Maciej; Purzycka, Katarzyna J.; Lukasiak, Piotr; Bartol, Natalia; Blazewicz, Jacek; Adamiak, Ryszard W.

2012-01-01

Understanding the numerous functions that RNAs play in living cells depends critically on knowledge of their three-dimensional structure. Due to the difficulties in experimentally assessing structures of large RNAs, there is currently great demand for new high-resolution structure prediction methods. We present the novel method for the fully automated prediction of RNA 3D structures from a user-defined secondary structure. The concept is founded on the machine translation system. The translation engine operates on the RNA FRABASE database tailored to the dictionary relating the RNA secondary structure and tertiary structure elements. The translation algorithm is very fast. Initial 3D structure is composed in a range of seconds on a single processor. The method assures the prediction of large RNA 3D structures of high quality. Our approach needs neither structural templates nor RNA sequence alignment, required for comparative methods. This enables the building of unresolved yet native and artificial RNA structures. The method is implemented in a publicly available, user-friendly server RNAComposer. It works in an interactive mode and a batch mode. The batch mode is designed for large-scale modelling and accepts atomic distance restraints. Presently, the server is set to build RNA structures of up to 500 residues. PMID:22539264

The development of a revised version of multi-center molecular Ornstein-Zernike equation

NASA Astrophysics Data System (ADS)

Kido, Kentaro; Yokogawa, Daisuke; Sato, Hirofumi

2012-04-01

Ornstein-Zernike (OZ)-type theory is a powerful tool to obtain 3-dimensional solvent distribution around solute molecule. Recently, we proposed multi-center molecular OZ method, which is suitable for parallel computing of 3D solvation structure. The distribution function in this method consists of two components, namely reference and residue parts. Several types of the function were examined as the reference part to investigate the numerical robustness of the method. As the benchmark, the method is applied to water, benzene in aqueous solution and single-walled carbon nanotube in chloroform solution. The results indicate that fully-parallelization is achieved by utilizing the newly proposed reference functions.

Viscous wing theory development. Volume 1: Analysis, method and results

NASA Technical Reports Server (NTRS)

Chow, R. R.; Melnik, R. E.; Marconi, F.; Steinhoff, J.

1986-01-01

Viscous transonic flows at large Reynolds numbers over 3-D wings were analyzed using a zonal viscid-inviscid interaction approach. A new numerical AFZ scheme was developed in conjunction with the finite volume formulation for the solution of the inviscid full-potential equation. A special far-field asymptotic boundary condition was developed and a second-order artificial viscosity included for an improved inviscid solution methodology. The integral method was used for the laminar/turbulent boundary layer and 3-D viscous wake calculation. The interaction calculation included the coupling conditions of the source flux due to the wing surface boundary layer, the flux jump due to the viscous wake, and the wake curvature effect. A method was also devised incorporating the 2-D trailing edge strong interaction solution for the normal pressure correction near the trailing edge region. A fully automated computer program was developed to perform the proposed method with one scalar version to be used on an IBM-3081 and two vectorized versions on Cray-1 and Cyber-205 computers.

Status and future of the 3D MAFIA group of codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebeling, F.; Klatt, R.; Krawzcyk, F.

1988-12-01

The group of fully three dimensional computer codes for solving Maxwell's equations for a wide range of applications, MAFIA, is already well established. Extensive comparisons with measurements have demonstrated the accuracy of the computations. A large numer of components have been designed for accelerators, such as kicker magnets, non cyclindrical cavities, ferrite loaded cavities, vacuum chambers with slots and transitions, etc. The latest additions to the system include a new static solver that can calculate 3D magneto- and electrostatic fields, and a self consistent version of the 2D-BCI that solves the field equations and the equations of motion in parallel.more » Work on new eddy current modules has started, which will allow treatment of laminated and/or solid iron cores excited by low frequency currents. Based on our experience with the present releases 1 and 2, we have started a complete revision of the whole user interface and data structure, which will make the codes even more user-friendly and flexible.« less

Nonlinear interaction between underwater explosion bubble and structure based on fully coupled model

NASA Astrophysics Data System (ADS)

Zhang, A. M.; Wu, W. B.; Liu, Y. L.; Wang, Q. X.

2017-08-01

The interaction between an underwater explosion bubble and an elastic-plastic structure is a complex transient process, accompanying violent bubble collapsing, jet impact, penetration through the bubble, and large structural deformation. In the present study, the bubble dynamics are modeled using the boundary element method and the nonlinear transient structural response is modeled using the explicit finite element method. A new fully coupled 3D model is established through coupling the equations for the state variables of the fluid and structure and solving them as a set of coupled linear algebra equations. Based on the acceleration potential theory, the mutual dependence between the hydrodynamic load and the structural motion is decoupled. The pressure distribution in the flow field is calculated with the Bernoulli equation, where the partial derivative of the velocity potential in time is calculated using the boundary integral method to avoid numerical instabilities. To validate the present fully coupled model, the experiments of small-scale underwater explosion near a stiffened plate are carried out. High-speed imaging is used to capture the bubble behaviors and strain gauges are used to measure the strain response. The numerical results correspond well with the experimental data, in terms of bubble shapes and structural strain response. By both the loosely coupled model and the fully coupled model, the interaction between a bubble and a hollow spherical shell is studied. The bubble patterns vary with different parameters. When the fully coupled model and the loosely coupled model are advanced with the same time step, the error caused by the loosely coupled model becomes larger with the coupling effect becoming stronger. The fully coupled model is more stable than the loosely coupled model. Besides, the influences of the internal fluid on the dynamic response of the spherical shell are studied. At last, the case that the bubble interacts with an air-backed stiffened plate is simulated. The associated interesting physical phenomenon is obtained and expounded.

Static and quasi-static analysis of lobed-pumpkin balloon

NASA Astrophysics Data System (ADS)

Nakashino, Kyoichi; Sasaki, Makoto; Hashimoto, Satoshi; Saito, Yoshitaka; Izutsu, Naoki

The present study is motivated by the need to improve design methodology for super pressure balloon with 3D gore design concept, currently being developed at the Scientific Balloon Center of ISAS/JAXA. The distinctive feature of the 3-D gore design is that the balloon film has excess materials not only in the circumferential direction but also in the meridional direction; the meridional excess is gained by attaching the film boundaries to the corresponding tendons of a shorter length with a controlled shortening rate. The resulting balloon shape is a pumpkin-like shape with large bulges formed between adjacent tendons. The balloon film, when fully inflated, develops wrinkles in the circumferential direction over its entire region, so that the stresses in the film are limited to a small amount of uniaxial tension in the circumferential direction while the high meridional loads are carried by re-enforced tendons. Naturally, the amount of wrinkling in the film is dominated by the shortening rate between the film boundaries and the tendon curve. In the 3-D gore design, as a consequence, the shortening rate becomes a fundamental design parameter along with the geometric parameters of the gore. In view of this, we have carried out a series of numerical study of the lobed-pumpkin balloon with varying gore geometry as well as with varying shortening rate. The numerical simula-tions were carried out with a nonlinear finite element code incorporating the wrinkling effect. Numerical results show that there is a threshold value for the shortening rate beyond which the stresses in the balloon film increases disproportionately. We have also carried out quasi-static simulations of the inflation process of the lobed-pumpkin balloon, and have obtained asymmetric deformations when the balloon films are in uniaxial tension state.

Lensfree diffractive tomography for the imaging of 3D cell cultures

NASA Astrophysics Data System (ADS)

Berdeu, Anthony; Momey, Fabien; Dinten, Jean-Marc; Gidrol, Xavier; Picollet-D'hahan, Nathalie; Allier, Cédric

2017-02-01

New microscopes are needed to help reaching the full potential of 3D organoid culture studies by gathering large quantitative and systematic data over extended periods of time while preserving the integrity of the living sample. In order to reconstruct large volumes while preserving the ability to catch every single cell, we propose new imaging platforms based on lens-free microscopy, a technic which is addressing these needs in the context of 2D cell culture, providing label-free and non-phototoxic acquisition of large datasets. We built lens-free diffractive tomography setups performing multi-angle acquisitions of 3D organoid cultures embedded in Matrigel and developed dedicated 3D holographic reconstruction algorithms based on the Fourier diffraction theorem. Nonetheless, holographic setups do not record the phase of the incident wave front and the biological samples in Petri dish strongly limit the angular coverage. These limitations introduce numerous artefacts in the sample reconstruction. We developed several methods to overcome them, such as multi-wavelength imaging or iterative phase retrieval. The most promising technic currently developed is based on a regularised inverse problem approach directly applied on the 3D volume to reconstruct. 3D reconstructions were performed on several complex samples such as 3D networks or spheroids embedded in capsules with large reconstructed volumes up to 25 mm3 while still being able to identify single cells. To our knowledge, this is the first time that such an inverse problem approach is implemented in the context of lens-free diffractive tomography enabling to reconstruct large fully 3D volumes of unstained biological samples.

Fast carotid artery MR angiography with compressed sensing based three-dimensional time-of-flight sequence.

PubMed

Li, Bo; Li, Hao; Dong, Li; Huang, Guofu

2017-11-01

In this study, we sought to investigate the feasibility of fast carotid artery MR angiography (MRA) by combining three-dimensional time-of-flight (3D TOF) with compressed sensing method (CS-3D TOF). A pseudo-sequential phase encoding order was developed for CS-3D TOF to generate hyper-intense vessel and suppress background tissues in under-sampled 3D k-space. Seven healthy volunteers and one patient with carotid artery stenosis were recruited for this study. Five sequential CS-3D TOF scans were implemented at 1, 2, 3, 4 and 5-fold acceleration factors for carotid artery MRA. Blood signal-to-tissue ratio (BTR) values for fully-sampled and under-sampled acquisitions were calculated and compared in seven subjects. Blood area (BA) was measured and compared between fully sampled acquisition and each under-sampled one. There were no significant differences between the fully-sampled dataset and each under-sampled in BTR comparisons (P>0.05 for all comparisons). The carotid vessel BAs measured from the images of CS-3D TOF sequences with 2, 3, 4 and 5-fold acceleration scans were all highly correlated with that of the fully-sampled acquisition. The contrast between blood vessels and background tissues of the images at 2 to 5-fold acceleration is comparable to that of fully sampled images. The images at 2× to 5× exhibit the comparable lumen definition to the corresponding images at 1×. By combining the pseudo-sequential phase encoding order, CS reconstruction, and 3D TOF sequence, this technique provides excellent visualizations for carotid vessel and calcifications in a short scan time. It has the potential to be integrated into current multiple blood contrast imaging protocol. Copyright © 2017. Published by Elsevier Inc.

On the local well-posedness and a Prodi-Serrin-type regularity criterion of the three-dimensional MHD-Boussinesq system without thermal diffusion

NASA Astrophysics Data System (ADS)

Larios, Adam; Pei, Yuan

2017-07-01

We prove a Prodi-Serrin-type global regularity condition for the three-dimensional Magnetohydrodynamic-Boussinesq system (3D MHD-Boussinesq) without thermal diffusion, in terms of only two velocity and two magnetic components. To the best of our knowledge, this is the first Prodi-Serrin-type criterion for such a 3D hydrodynamic system which is not fully dissipative, and indicates that such an approach may be successful on other systems. In addition, we provide a constructive proof of the local well-posedness of solutions to the fully dissipative 3D MHD-Boussinesq system, and also the fully inviscid, irresistive, non-diffusive MHD-Boussinesq equations. We note that, as a special case, these results include the 3D non-diffusive Boussinesq system and the 3D MHD equations. Moreover, they can be extended without difficulty to include the case of a Coriolis rotational term.

Numerical Study of Richtmyer-Meshkov Instability with Re-Shock

NASA Astrophysics Data System (ADS)

Wong, Man Long; Livescu, Daniel; Lele, Sanjiva

2017-11-01

The interaction of a Mach 1.45 shock wave with a perturbed planar interface between two gases with an Atwood number 0.68 is studied through 2D and 3D shock-capturing adaptive mesh refinement (AMR) simulations with physical diffusive and viscous terms. The simulations have initial conditions similar to those in the actual experiment conducted by Poggi et al. [1998]. The development of the flow and evolution of mixing due to the interactions with the first shock and the re-shock are studied together with the sensitivity of various global parameters to the properties of the initial perturbation. Grid resolutions needed for fully resolved and 2D and 3D simulations are also evaluated. Simulations are conducted with an in-house AMR solver HAMeRS built on the SAMRAI library. The code utilizes the high-order localized dissipation weighted compact nonlinear scheme [Wong and Lele, 2017] for shock-capturing and different sensors including the wavelet sensor [Wong and Lele, 2016] to identify regions for grid refinement. First and third authors acknowledge the project sponsor LANL.

Finite Element Modeling of Magnetically-Damped Convection during Solidification

NASA Technical Reports Server (NTRS)

deGroh, H. C.; Li, B. Q.; Lu, X.

1998-01-01

A fully 3-D, transient finite element model is developed to represent the magnetic damping effects on complex fluid flow, heat transfer and electromagnetic field distributions in a Sn- 35.5%Pb melt undergoing unidirectional solidification. The model is developed based on our in- house finite element code for the fluid flow, heat transfer and electromagnetic field calculations. The numerical model is tested against numerical and experimental results for water as reported in literature. Various numerical simulations are carried out for the melt convection and temperature distribution with and without the presence of a transverse magnetic field. Numerical results show that magnetic damping can be effectively applied to stabilize melt flow, reduce turbulence and flow levels in the melt and over a certain threshold value a higher magnetic field resulted in a greater reduction in velocity. Also, for the study of melt flow instability, a long enough running time is needed to ensure the final fluid flow recirculation pattern. Moreover, numerical results suggest that there seems to exist a threshold value of applied magnetic field, above which magnetic damping becomes possible and below which the 0 convection in the melt is actually enhanced.

A 3D, fully Eulerian, VOF-based solver to study the interaction between two fluids and moving rigid bodies using the fictitious domain method

NASA Astrophysics Data System (ADS)

Pathak, Ashish; Raessi, Mehdi

2016-04-01

We present a three-dimensional (3D) and fully Eulerian approach to capturing the interaction between two fluids and moving rigid structures by using the fictitious domain and volume-of-fluid (VOF) methods. The solid bodies can have arbitrarily complex geometry and can pierce the fluid-fluid interface, forming contact lines. The three-phase interfaces are resolved and reconstructed by using a VOF-based methodology. Then, a consistent scheme is employed for transporting mass and momentum, allowing for simulations of three-phase flows of large density ratios. The Eulerian approach significantly simplifies numerical resolution of the kinematics of rigid bodies of complex geometry and with six degrees of freedom. The fluid-structure interaction (FSI) is computed using the fictitious domain method. The methodology was developed in a message passing interface (MPI) parallel framework accelerated with graphics processing units (GPUs). The computationally intensive solution of the pressure Poisson equation is ported to GPUs, while the remaining calculations are performed on CPUs. The performance and accuracy of the methodology are assessed using an array of test cases, focusing individually on the flow solver and the FSI in surface-piercing configurations. Finally, an application of the proposed methodology in simulations of the ocean wave energy converters is presented.

Automation and Preclinical Evaluation of a Dedicated Emission Mammotomography System for Fully 3-D Molecular Breast Imaging

DTIC Science & Technology

2009-10-01

molecular breast imaging, with the ability to dynamically contour any sized breast, will improve detection and potentially in vivo characterization of...Having flexible 3D positioning about the breast yielded minimal RMSD differences, which is important for high resolution molecular emission imaging. This...TITLE: Automation and Preclinical Evaluation of a Dedicated Emission Mammotomography System for Fully 3-D Molecular Breast Imaging PRINCIPAL

Optical stent inspection of surface texture and coating thickness

NASA Astrophysics Data System (ADS)

Bermudez, Carlos; Laguarta, Ferran; Cadevall, Cristina; Matilla, Aitor; Ibañez, Sergi; Artigas, Roger

2017-02-01

Stent quality control is a critical process. Coronary stents have to be inspected 100% so no defective stent is implanted into a human body. We have developed a high numerical aperture optical stent inspection system able to acquire both 2D and 3D images. Combining a rotational stage, an area camera with line-scan capability and a triple illumination arrangement, unrolled sections of the outer, inner, and sidewalls surfaces are obtained with high resolution. During stent inspection, surface roughness and coating thickness uniformity is of high interest. Due to the non-planar shape of the surface of the stents, the thickness values of the coating need to be corrected with the 3D surface local slopes. A theoretical model and a simulation are proposed, and a measurement with white light interferometry is shown. Confocal and spectroscopic reflectometry showed to be limited in this application due to stent surface roughness. Due to the high numerical aperture of the optical system, only certain parts of the stent are in focus, which is a problem for defect detection, specifically on the sidewalls. In order to obtain fully focused 2D images, an extended depth of field algorithm has been implemented. A comparison between pixel variance and Laplacian filtering is shown. To recover the stack image, two different methods are proposed: maximum projection and weighted intensity. Finally, we also discuss the implementation of the processing algorithms in both the CPU and GPU, targeting real-time 2-Million pixel image acquisition at 50 frames per second.

Fiber-chip edge coupler with large mode size for silicon photonic wire waveguides.

PubMed

Papes, Martin; Cheben, Pavel; Benedikovic, Daniel; Schmid, Jens H; Pond, James; Halir, Robert; Ortega-Moñux, Alejandro; Wangüemert-Pérez, Gonzalo; Ye, Winnie N; Xu, Dan-Xia; Janz, Siegfried; Dado, Milan; Vašinek, Vladimír

2016-03-07

Fiber-chip edge couplers are extensively used in integrated optics for coupling of light between planar waveguide circuits and optical fibers. In this work, we report on a new fiber-chip edge coupler concept with large mode size for silicon photonic wire waveguides. The coupler allows direct coupling with conventional cleaved optical fibers with large mode size while circumventing the need for lensed fibers. The coupler is designed for 220 nm silicon-on-insulator (SOI) platform. It exhibits an overall coupling efficiency exceeding 90%, as independently confirmed by 3D Finite-Difference Time-Domain (FDTD) and fully vectorial 3D Eigenmode Expansion (EME) calculations. We present two specific coupler designs, namely for a high numerical aperture single mode optical fiber with 6 µm mode field diameter (MFD) and a standard SMF-28 fiber with 10.4 µm MFD. An important advantage of our coupler concept is the ability to expand the mode at the chip edge without leading to high substrate leakage losses through buried oxide (BOX), which in our design is set to 3 µm. This remarkable feature is achieved by implementing in the SiO 2 upper cladding thin high-index Si 3 N 4 layers. The Si 3 N 4 layers increase the effective refractive index of the upper cladding near the facet. The index is controlled along the taper by subwavelength refractive index engineering to facilitate adiabatic mode transformation to the silicon wire waveguide while the Si-wire waveguide is inversely tapered along the coupler. The mode overlap optimization at the chip facet is carried out with a full vectorial mode solver. The mode transformation along the coupler is studied using 3D-FDTD simulations and with fully-vectorial 3D-EME calculations. The couplers are optimized for operating with transverse electric (TE) polarization and the operating wavelength is centered at 1.55 µm.

Towards a new multiscale air quality transport model using the fully unstructured anisotropic adaptive mesh technology of Fluidity (version 4.1.9)

NASA Astrophysics Data System (ADS)

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.

Grounding line dynamics inferred from a 3D full-Stokes model solving the contact problem

NASA Astrophysics Data System (ADS)

Favier, Lionel; Gagliardini, Olivier; Durand, Gael; Zwinger, Thomas

2010-05-01

The mass balance of marine ice-sheets, such as the West Antarctic Ice Sheet, is mostly controlled by their grounding line dynamics. Most numerical models simulating marine ice-sheets involve simplifications and do not include all the stress gradients. First results obtained with a 3D full-Stokes model for the grounded ice-sheet / floating ice-shelf transition, using the finite-element code Elmer/Ice, are presented. The initial geometry, which takes into account a dome and a calving front, has been laterally extruded from a previously investigated 2D flowline geometry. The grounding line migration is computed by solving the contact problem between the ice and the rigid downward sloping bedrock, where a non linear friction law is applied in the two horizontal directions. The evolutions of the sea-air and sea-ice interfaces are determined by the solution of a local transport equation. The consistency between the 3D model and the analogous results of the flowline model is shown by comparing the results in the basic extruded case, with no normal flux through lateral boundaries. Thereafter, spatially non uniform perturbations are introduced, to simulate the grounding line dynamics under fully three-dimensional perturbations.

The LS-STAG immersed boundary/cut-cell method for non-Newtonian flows in 3D extruded geometries

NASA Astrophysics Data System (ADS)

Nikfarjam, F.; Cheny, Y.; Botella, O.

2018-05-01

The LS-STAG method is an immersed boundary/cut-cell method for viscous incompressible flows based on the staggered MAC arrangement for Cartesian grids, where the irregular boundary is sharply represented by its level-set function, results in a significant gain in computer resources (wall time, memory usage) compared to commercial body-fitted CFD codes. The 2D version of LS-STAG method is now well-established (Cheny and Botella, 2010), and this paper presents its extension to 3D geometries with translational symmetry in the z direction (hereinafter called 3D extruded configurations). This intermediate step towards the fully 3D implementation can be applied to a wide variety of canonical flows and will be regarded as the keystone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this stage of development. The LS-STAG method is then applied to various Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion) for which benchmark results and experimental data are available. The purpose of these investigations are (a) to investigate the formal order of accuracy of the LS-STAG method, (b) to assess the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows) (c) to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods).

Investigation of Fully Three-Dimensional Helical RF Field Effects on TWT Beam/Circuit Interaction

NASA Technical Reports Server (NTRS)

Kory, Carol L.

2000-01-01

A fully three-dimensional (3D), time-dependent, helical traveling wave-tube (TWT) interaction model has been developed using the electromagnetic particle-in-cell (PIC) code MAFIA. The model includes a short section of helical slow-wave circuit with excitation fed by RF input/output couplers, and electron beam contained by periodic permanent magnet (PPM) focusing. All components of the model are simulated in three dimensions allowing the effects of the fully 3D helical fields on RF circuit/beam interaction to be investigated for the first time. The development of the interaction model is presented, and predicted TWT performance using 2.5D and 3D models is compared to investigate the effect of conventional approximations used in TWT analyses.

Two dimensional model for coherent synchrotron radiation

NASA Astrophysics Data System (ADS)

Huang, Chengkun; Kwan, Thomas J. T.; Carlsten, Bruce E.

2013-01-01

Understanding coherent synchrotron radiation (CSR) effects in a bunch compressor requires an accurate model accounting for the realistic beam shape and parameters. We extend the well-known 1D CSR analytic model into two dimensions and develop a simple numerical model based on the Liénard-Wiechert formula for the CSR field of a coasting beam. This CSR numerical model includes the 2D spatial dependence of the field in the bending plane and is accurate for arbitrary beam energy. It also removes the singularity in the space charge field calculation present in a 1D model. Good agreement is obtained with 1D CSR analytic result for free electron laser (FEL) related beam parameters but it can also give a more accurate result for low-energy/large spot size beams and off-axis/transient fields. This 2D CSR model can be used for understanding the limitation of various 1D models and for benchmarking fully electromagnetic multidimensional particle-in-cell simulations for self-consistent CSR modeling.

Temporary Shell Proof-of-Concept Technique: Digital-Assisted Workflow to Enable Customized Immediate Function in Two Visits in Partially Edentulous Patients

PubMed

Pozzi, Alessandro; Arcuri, Lorenzo; Moy, Peter K

2018-03-01

The growing interest in minimally invasive implant placement and delivery of a prefabricated provisional prosthesis immediately, thus minimizing "time to teeth," has led to the development of numerous 3-dimensional (3D) planning software programs. Given the enhancements associated with fully digital workflows, such as better 3D soft-tissue visualization and virtual tooth rendering, computer-guided implant surgery and immediate function has become an effective and reliable procedure. This article describes how modern implant planning software programs provide a comprehensive digital platform that enables efficient interplay between the surgical and restorative aspects of implant treatment. These new technologies that streamline the overall digital workflow allow transformation of the digital wax-up into a personalized, CAD/CAM-milled provisional restoration. Thus, collaborative digital workflows provide a novel approach for time-efficient delivery of a customized, screw-retained provisional restoration on the day of implant surgery, resulting in improved predictability for immediate function in the partially edentate patient.

Clustering of vertically constrained passive particles in homogeneous isotropic turbulence.

PubMed

De Pietro, Massimo; van Hinsberg, Michel A T; Biferale, Luca; Clercx, Herman J H; Perlekar, Prasad; Toschi, Federico

2015-05-01

We analyze the dynamics of small particles vertically confined, by means of a linear restoring force, to move within a horizontal fluid slab in a three-dimensional (3D) homogeneous isotropic turbulent velocity field. The model that we introduce and study is possibly the simplest description for the dynamics of small aquatic organisms that, due to swimming, active regulation of their buoyancy, or any other mechanism, maintain themselves in a shallow horizontal layer below the free surface of oceans or lakes. By varying the strength of the restoring force, we are able to control the thickness of the fluid slab in which the particles can move. This allows us to analyze the statistical features of the system over a wide range of conditions going from a fully 3D incompressible flow (corresponding to the case of no confinement) to the extremely confined case corresponding to a two-dimensional slice. The background 3D turbulent velocity field is evolved by means of fully resolved direct numerical simulations. Whenever some level of vertical confinement is present, the particle trajectories deviate from that of fluid tracers and the particles experience an effectively compressible velocity field. Here, we have quantified the compressibility, the preferential concentration of the particles, and the correlation dimension by changing the strength of the restoring force. The main result is that there exists a particular value of the force constant, corresponding to a mean slab depth approximately equal to a few times the Kolmogorov length scale η, that maximizes the clustering of the particles.

A 3D staggered-grid finite difference scheme for poroelastic wave equation

NASA Astrophysics Data System (ADS)

Zhang, Yijie; Gao, Jinghuai

2014-10-01

Three dimensional numerical modeling has been a viable tool for understanding wave propagation in real media. The poroelastic media can better describe the phenomena of hydrocarbon reservoirs than acoustic and elastic media. However, the numerical modeling in 3D poroelastic media demands significantly more computational capacity, including both computational time and memory. In this paper, we present a 3D poroelastic staggered-grid finite difference (SFD) scheme. During the procedure, parallel computing is implemented to reduce the computational time. Parallelization is based on domain decomposition, and communication between processors is performed using message passing interface (MPI). Parallel analysis shows that the parallelized SFD scheme significantly improves the simulation efficiency and 3D decomposition in domain is the most efficient. We also analyze the numerical dispersion and stability condition of the 3D poroelastic SFD method. Numerical results show that the 3D numerical simulation can provide a real description of wave propagation.

Ab initio analytical Raman intensities for periodic systems through a coupled perturbed Hartree-Fock/Kohn-Sham method in an atomic orbital basis. II. Validation and comparison with experiments

NASA Astrophysics Data System (ADS)

Maschio, Lorenzo; Kirtman, Bernard; Rérat, Michel; Orlando, Roberto; Dovesi, Roberto

2013-10-01

In this work, we validate a new, fully analytical method for calculating Raman intensities of periodic systems, developed and presented in Paper I [L. Maschio, B. Kirtman, M. Rérat, R. Orlando, and R. Dovesi, J. Chem. Phys. 139, 164101 (2013)]. Our validation of this method and its implementation in the CRYSTAL code is done through several internal checks as well as comparison with experiment. The internal checks include consistency of results when increasing the number of periodic directions (from 0D to 1D, 2D, 3D), comparison with numerical differentiation, and a test of the sum rule for derivatives of the polarizability tensor. The choice of basis set as well as the Hamiltonian is also studied. Simulated Raman spectra of α-quartz and of the UiO-66 Metal-Organic Framework are compared with the experimental data.

Multigrid methods for numerical simulation of laminar diffusion flames

NASA Technical Reports Server (NTRS)

Liu, C.; Liu, Z.; Mccormick, S.

1993-01-01

This paper documents the result of a computational study of multigrid methods for numerical simulation of 2D diffusion flames. The focus is on a simplified combustion model, which is assumed to be a single step, infinitely fast and irreversible chemical reaction with five species (C3H8, O2, N2, CO2 and H2O). A fully-implicit second-order hybrid scheme is developed on a staggered grid, which is stretched in the streamwise coordinate direction. A full approximation multigrid scheme (FAS) based on line distributive relaxation is developed as a fast solver for the algebraic equations arising at each time step. Convergence of the process for the simplified model problem is more than two-orders of magnitude faster than other iterative methods, and the computational results show good grid convergence, with second-order accuracy, as well as qualitatively agreement with the results of other researchers.

An advanced constitutive model in the sheet metal forming simulation: the Teodosiu microstructural model and the Cazacu Barlat yield criterion

NASA Astrophysics Data System (ADS)

Alves, J. L.; Oliveira, M. C.; Menezes, L. F.

2004-06-01

Two constitutive models used to describe the plastic behavior of sheet metals in the numerical simulation of sheet metal forming process are studied: a recently proposed advanced constitutive model based on the Teodosiu microstructural model and the Cazacu Barlat yield criterion is compared with a more classical one, based on the Swift law and the Hill 1948 yield criterion. These constitutive models are implemented into DD3IMP, a finite element home code specifically developed to simulate sheet metal forming processes, which generically is a 3-D elastoplastic finite element code with an updated Lagrangian formulation, following a fully implicit time integration scheme, large elastoplastic strains and rotations. Solid finite elements and parametric surfaces are used to model the blank sheet and tool surfaces, respectively. Some details of the numerical implementation of the constitutive models are given. Finally, the theory is illustrated with the numerical simulation of the deep drawing of a cylindrical cup. The results show that the proposed advanced constitutive model predicts with more exactness the final shape (medium height and ears profile) of the formed part, as one can conclude from the comparison with the experimental results.

Impurity bound states in d-wave superconductors with subdominant order parameters

NASA Astrophysics Data System (ADS)

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica

Single magnetic impurity induces intra-gap bound states in conventional s-wave superconductors (SCs) but, in d-wave SCs only virtual bound states can be induced. However, in small cuprate islands a fully gapped spectrum has recently been discovered. In this work, we investigate the real bound states due to potential and magnetic impurities in the two candidate fully gapped states for this system: the topologically trivial d + is -wave state and the topologically non-trivial d + id' -wave (chiral d-wave state). Using the analytic T-matrix formalism and self-consistent numerical tight-binding lattice calculations, we show that potential and magnetic impurities create entirely different intra-gap bound states in d + is -wave and chiral d-wave SCs. Therefore, our results suggest that the bound states mainly depend on the subdominant order parameter. Considering that recent experiments have demonstrated an access to adjustable coupling J, impurities thus offer an intriguing way to clearly distinguish between the chiral d-wave and topologically trivial d + is -wave state. This work was supported by Swedish Research Council, Swedish Foundation for Strategic Research, the Wallenberg Academy Fellows program and the Göran Gustafsson Foundation. The computations were performed on resources provided by SNIC at LUNARC.

Meshless deformable models for 3D cardiac motion and strain analysis from tagged MRI.

PubMed

Wang, Xiaoxu; Chen, Ting; Zhang, Shaoting; Schaerer, Joël; Qian, Zhen; Huh, Suejung; Metaxas, Dimitris; Axel, Leon

2015-01-01

Tagged magnetic resonance imaging (TMRI) provides a direct and noninvasive way to visualize the in-wall deformation of the myocardium. Due to the through-plane motion, the tracking of 3D trajectories of the material points and the computation of 3D strain field call for the necessity of building 3D cardiac deformable models. The intersections of three stacks of orthogonal tagging planes are material points in the myocardium. With these intersections as control points, 3D motion can be reconstructed with a novel meshless deformable model (MDM). Volumetric MDMs describe an object as point cloud inside the object boundary and the coordinate of each point can be written in parametric functions. A generic heart mesh is registered on the TMRI with polar decomposition. A 3D MDM is generated and deformed with MR image tagging lines. Volumetric MDMs are deformed by calculating the dynamics function and minimizing the local Laplacian coordinates. The similarity transformation of each point is computed by assuming its neighboring points are making the same transformation. The deformation is computed iteratively until the control points match the target positions in the consecutive image frame. The 3D strain field is computed from the 3D displacement field with moving least squares. We demonstrate that MDMs outperformed the finite element method and the spline method with a numerical phantom. Meshless deformable models can track the trajectory of any material point in the myocardium and compute the 3D strain field of any particular area. The experimental results on in vivo healthy and patient heart MRI show that the MDM can fully recover the myocardium motion in three dimensions. Copyright © 2014. Published by Elsevier Inc.

Meshless deformable models for 3D cardiac motion and strain analysis from tagged MRI

PubMed Central

Wang, Xiaoxu; Chen, Ting; Zhang, Shaoting; Schaerer, Joël; Qian, Zhen; Huh, Suejung; Metaxas, Dimitris; Axel, Leon

2016-01-01

Tagged magnetic resonance imaging (TMRI) provides a direct and noninvasive way to visualize the in-wall deformation of the myocardium. Due to the through-plane motion, the tracking of 3D trajectories of the material points and the computation of 3D strain field call for the necessity of building 3D cardiac deformable models. The intersections of three stacks of orthogonal tagging planes are material points in the myocardium. With these intersections as control points, 3D motion can be reconstructed with a novel meshless deformable model (MDM). Volumetric MDMs describe an object as point cloud inside the object boundary and the coordinate of each point can be written in parametric functions. A generic heart mesh is registered on the TMRI with polar decomposition. A 3D MDM is generated and deformed with MR image tagging lines. Volumetric MDMs are deformed by calculating the dynamics function and minimizing the local Laplacian coordinates. The similarity transformation of each point is computed by assuming its neighboring points are making the same transformation. The deformation is computed iteratively until the control points match the target positions in the consecutive image frame. The 3D strain field is computed from the 3D displacement field with moving least squares. We demonstrate that MDMs outperformed the finite element method and the spline method with a numerical phantom. Meshless deformable models can track the trajectory of any material point in the myocardium and compute the 3D strain field of any particular area. The experimental results on in vivo healthy and patient heart MRI show that the MDM can fully recover the myocardium motion in three dimensions. PMID:25157446

3D lens-free time-lapse microscopy for 3D cell culture

NASA Astrophysics Data System (ADS)

Berdeu, Anthony; Momey, Fabien; Laperrousaz, Bastien; Bordy, Thomas; Gidrol, Xavier; Dinten, Jean-Marc; Picollet-D'hahan, Nathalie; Allier, Cédric

2017-07-01

We propose a new imaging platform based on lens-free time-lapse microscopy for 3D cell culture and its dedicated algorithm lying on a fully 3D regularized inverse problem approach. First 3D+t results are presented

Objective and subjective comparison of standard 2-D and fully 3-D reconstructed data on a PET/CT system.

PubMed

Strobel, Klaus; Rüdy, Matthias; Treyer, Valerie; Veit-Haibach, Patrick; Burger, Cyrill; Hany, Thomas F

2007-07-01

The relative advantage of fully 3-D versus 2-D mode for whole-body imaging is currently the focus of considerable expert debate. The nature of 3-D PET acquisition for FDG PET/CT theoretically allows a shorter scan time and improved efficiency of FDG use than in the standard 2-D acquisition. We therefore objectively and subjectively compared standard 2-D and fully 3-D reconstructed data for FDG PET/CT on a research PET/CT system. In a total of 36 patients (mean 58.9 years, range 17.3-78.9 years; 21 male, 15 female) referred for known or suspected malignancy, FDG PET/CT was performed using a research PET/CT system with advanced detector technology with improved sensitivity and spatial resolution. After 45 min uptake, a low-dose CT (40 mAs) from head to thigh was performed followed by 2-D PET (emission 3 min per field) and 3-D PET (emission 1.5 min per field) with both seven slices overlap to cover the identical anatomical region. Acquisition time was therefore 50% less (seven fields; 21 min vs. 10.5 min). PET data was acquired in a randomized fashion, so in 50% of the cases 2-D data was acquired first. CT data was used for attenuation correction. 2-D (OSEM) and 3-D PET images were iteratively reconstructed. Subjective analysis of 2-D and 3-D images was performed by two readers in a blinded, randomized fashion evaluating the following criteria: sharpness of organs (liver, chest wall/lung), overall image quality and detectability and dignity of each identified lesion. Objective analysis of PET data was investigated measuring maximum standard uptake value with lean body mass (SUV(max,LBM)) of identified lesions. On average, per patient, the SUV(max) was 7.86 (SD 7.79) for 2-D and 6.96 (SD 5.19) for 3-D. On a lesion basis, the average SUV(max) was 7.65 (SD 7.79) for 2-D and 6.75 (SD 5.89) for 3-D. The absolute difference on a paired t-test of SUV 3-D-2-D based on each measured lesion was significant with an average of -0.956 (P=0.002) and an average of -0.884 on a patient base (P<0.05). With 3-D the SUV(max) decreased by an average of 5.2% for each lesion, and an average of 6.0% for each patient. Subjective analysis showed fair inter-observer agreement regarding detectability (kappa=0.24 for 3-D; 0.36 for 3-D) and dignity (kappa=0.44 for 3-D and 0.4 for 2-D) of the lesions. There was no significant diagnostic difference between 3-D and 2-D. Only in one patient, a satellite liver metastasis of a colon cancer was missed in 3-D and detected only in 2-D. On average, the overall image quality for 3-D images was equal (in 24%) or inferior (in 76%) compared to 2-D. A possible major advantage of 3-D data acquisition is the faster patient throughput with a 50% reduction in scan time. The fully 3-D reconstruction technique has overcome the technical drawbacks of current 3-D imaging technique. In our limited number of patients there was no significant diagnostic difference between 2-D and fully 3-D.

Numerical and analytical modelling of the MHD buoyancy-driven flow in a Bridgman crystal growth configuration

NASA Astrophysics Data System (ADS)

Davoust, L.; Moreau, R.; Cowley, M. D.; Tanguy, P. A.; Bertrand, F.

1997-10-01

We present analytical and numerical models of magnetohydrodynamic(MHD) buoyancy-driven flow within the liquid pool of a horizontal Bridgman crystal growth furnace, under the influence of a uniform vertical magnetic field B0. A horizontal differentially heated cylinder, whose aspect ratio (radius to length) is small enough for a fully developed regime to be established in the central core, is considered. With Hartmann layers remaining electrically inactive, a modified Rayleigh number RaG, which is the ration of the ordinary Rayleigh number to the square of the Hartmann number, is found to control the MHD reorganisation of the flow. This modified Rayleigh number is a measure of the importance of thermal convection relative to diffusion if velocity is estimated from the balance between the torques of buoyancy and the Laplace force. When RaG is much smaller than unity (quasi-diffusive regime), an analytical modelling of the flow, based on a power series of RaG, demonstrates that this balance requires secondary vortices within vertical mid-planes of the cylinder, both within the core flow and near the end walls. A 3-D numerical calculation of the flow provides evidence of the transition from a convective MHD flow (when RaG is still of the order of unity) to the quasi-diffusive flow, analytically studied. Indeed, this transition takes the form of a rather complex 3-D MHD organisation of the flow which is due to the nonuniformity of the axial temperature gradient along the cylinder.

Large-scale 3D inversion of marine controlled source electromagnetic data using the integral equation method

NASA Astrophysics Data System (ADS)

Zhdanov, M. S.; Cuma, M.; Black, N.; Wilson, G. A.

2009-12-01

The marine controlled source electromagnetic (MCSEM) method has become widely used in offshore oil and gas exploration. Interpretation of MCSEM data is still a very challenging problem, especially if one would like to take into account the realistic 3D structure of the subsurface. The inversion of MCSEM data is complicated by the fact that the EM response of a hydrocarbon-bearing reservoir is very weak in comparison with the background EM fields generated by an electric dipole transmitter in complex geoelectrical structures formed by a conductive sea-water layer and the terranes beneath it. In this paper, we present a review of the recent developments in the area of large-scale 3D EM forward modeling and inversion. Our approach is based on using a new integral form of Maxwell’s equations allowing for an inhomogeneous background conductivity, which results in a numerically effective integral representation for 3D EM field. This representation provides an efficient tool for the solution of 3D EM inverse problems. To obtain a robust inverse model of the conductivity distribution, we apply regularization based on a focusing stabilizing functional which allows for the recovery of models with both smooth and sharp geoelectrical boundaries. The method is implemented in a fully parallel computer code, which makes it possible to run large-scale 3D inversions on grids with millions of inversion cells. This new technique can be effectively used for active EM detection and monitoring of the subsurface targets.

Overview of Edge Simulation Laboratory (ESL)

NASA Astrophysics Data System (ADS)

Cohen, R. H.; Dorr, M.; Hittinger, J.; Rognlien, T.; Umansky, M.; Xiong, A.; Xu, X.; Belli, E.; Candy, J.; Snyder, P.; Colella, P.; Martin, D.; Sternberg, T.; van Straalen, B.; Bodi, K.; Krasheninnikov, S.

2006-10-01

The ESL is a new collaboration to build a full-f electromagnetic gyrokinetic code for tokamak edge plasmas using continuum methods. Target applications are edge turbulence and transport (neoclassical and anomalous), and edge-localized modes. Initially the project has three major threads: (i) verification and validation of TEMPEST, the project's initial (electrostatic) edge code which can be run in 4D (neoclassical and transport-timescale applications) or 5D (turbulence); (ii) design of the next generation code, which will include more complete physics (electromagnetics, fluid equation option, improved collisions) and advanced numerics (fully conservative, high-order discretization, mapped multiblock grids, adaptivity), and (iii) rapid-prototype codes to explore the issues attached to solving fully nonlinear gyrokinetics with steep radial gradiens. We present a brief summary of the status of each of these activities.

Modulation of cortical activity in 2D versus 3D virtual reality environments: an EEG study.

PubMed

Slobounov, Semyon M; Ray, William; Johnson, Brian; Slobounov, Elena; Newell, Karl M

2015-03-01

There is a growing empirical evidence that virtual reality (VR) is valuable for education, training, entertaining and medical rehabilitation due to its capacity to represent real-life events and situations. However, the neural mechanisms underlying behavioral confounds in VR environments are still poorly understood. In two experiments, we examined the effect of fully immersive 3D stereoscopic presentations and less immersive 2D VR environments on brain functions and behavioral outcomes. In Experiment 1 we examined behavioral and neural underpinnings of spatial navigation tasks using electroencephalography (EEG). In Experiment 2, we examined EEG correlates of postural stability and balance. Our major findings showed that fully immersive 3D VR induced a higher subjective sense of presence along with enhanced success rate of spatial navigation compared to 2D. In Experiment 1 power of frontal midline EEG (FM-theta) was significantly higher during the encoding phase of route presentation in the 3D VR. In Experiment 2, the 3D VR resulted in greater postural instability and modulation of EEG patterns as a function of 3D versus 2D environments. The findings support the inference that the fully immersive 3D enriched-environment requires allocation of more brain and sensory resources for cognitive/motor control during both tasks than 2D presentations. This is further evidence that 3D VR tasks using EEG may be a promising approach for performance enhancement and potential applications in clinical/rehabilitation settings. Copyright © 2014 Elsevier B.V. All rights reserved.

On the performance of a high head Francis turbine at design and off-design conditions

NASA Astrophysics Data System (ADS)

Aakti, B.; Amstutz, O.; Casartelli, E.; Romanelli, G.; Mangani, L.

2015-01-01

In the present paper, fully 360 degrees transient and steady-state simulations of a Francis turbine were performed at three operating conditions, namely at part load (PL), best efficiency point (BEP), and high load (HL), using different numerical approaches for the pressure-velocity coupling. The simulation domain includes the spiral casing with stay and guide vanes, the runner and the draft tube. The main target of the investigations is the numerical prediction of the overall performance of the high head Francis turbine model as well as local and integral quantities of the complete machine in different operating conditions. All results were compared with experimental data published by the workshop organization. All CFD simulations were performed at model scale with a new in-house, 3D, unstructured, object-oriented finite volume code within the framework of the open source OpenFOAM library. The novel fully coupled pressure-based solver is designed to solve the incompressible RANS- Equations and is capable of handling multiple references of frame (MRF). The obtained results show that the overall performance is well captured by the simulations. Regarding the local flow distributions within the inlet section of the draft-tube, the axial velocity is better estimated than the circumferential component.

Microscopic description of fission dynamics: Toward a 3D computation of the time dependent GCM equation

NASA Astrophysics Data System (ADS)

Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.

2017-09-01

Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r-process to fuel cycle optimization in nuclear energy. The need for a predictive theory applicable where no data is available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. One of the most promising theoretical frameworks is the time dependent generator coordinate method (TDGCM) applied under the Gaussian overlap approximation (GOA). However, the computational cost of this method makes it difficult to perform calculations with more than two collective degree of freedom. Meanwhile, it is well-known from both semi-phenomenological and fully microscopic approaches that at least four or five dimensions may play a role in the dynamics of fission. To overcome this limitation, we develop the code FELIX aiming to solve the TDGCM+GOA equation for an arbitrary number of collective variables. In this talk, we report the recent progress toward this enriched description of fission dynamics. We will briefly present the numerical methods adopted as well as the status of the latest version of FELIX. Finally, we will discuss fragments yields obtained within this approach for the low energy fission of major actinides.

The Initialization of the Divergent Component of the Horizontal Wind in Mesoscale Numerical Weather Prediction Models and Its Effect on Initial Precipitation Rates.

DTIC Science & Technology

1979-05-01

jets in barotropic channel and hemispheric models. He used the following initializations: (1) geostrophic, (2) mass field in balance with the fully...equation. Operating on (2.12) with V x yields I__ + V . + Vx.V4 + V .f + V Vf + + fD + D (2.16) -x az + k.VZ x -i + kV7 x - V x Fr =0 With (2.6g), (2.15) can

Effect of Freeze-Thaw Cycles on Soil Nitrogen Reactive Transport in a Polygonal Arctic Tundra Ecosystem at Barrow AK Using 3-D Coupled ALM-PFLOTRAN

NASA Astrophysics Data System (ADS)

Yuan, F.; Wang, G.; Painter, S. L.; Tang, G.; Xu, X.; Kumar, J.; Bisht, G.; Hammond, G. E.; Mills, R. T.; Thornton, P. E.; Wullschleger, S. D.

2017-12-01

In Arctic tundra ecosystem soil freezing-thawing is one of dominant physical processes through which biogeochemical (e.g., carbon and nitrogen) cycles are tightly coupled. Besides hydraulic transport, freezing-thawing can cause pore water movement and aqueous species gradients, which are additional mechanisms for soil nitrogen (N) reactive-transport in Tundra ecosystem. In this study, we have fully coupled an in-development ESM(i.e., Advanced Climate Model for Energy, ACME)'s Land Model (ALM) aboveground processes with a state-of-the-art massively parallel 3-D subsurface thermal-hydrology and reactive transport code, PFLOTRAN. The resulting coupled ALM-PFLOTRAN model is a Land Surface Model (LSM) capable of resolving 3-D soil thermal-hydrological-biogeochemical cycles. This specific version of PFLOTRAN has incorporated CLM-CN Converging Trophic Cascade (CTC) model and a full and simple but robust soil N cycle. It includes absorption-desorption for soil NH4+ and gas dissolving-degasing process as well. It also implements thermal-hydrology mode codes with three newly-modified freezing-thawing algorithms which can greatly improve computing performance in regarding to numerical stiffness at freezing-point. Here we tested the model in fully 3-D coupled mode at the Next Generation Ecosystem Experiment-Arctic (NGEE-Arctic) field intensive study site at the Barrow Environmental Observatory (BEO), AK. The simulations show that: (1) synchronous coupling of soil thermal-hydrology and biogeochemistry in 3-D can greatly impact ecosystem dynamics across polygonal tundra landscape; and (2) freezing-thawing cycles can add more complexity to the system, resulting in greater mobility of soil N vertically and laterally, depending upon local micro-topography. As a preliminary experiment, the model is also implemented for Pan-Arctic region in 1-D column mode (i.e. no lateral connection), showing significant differences compared to stand-alone ALM. The developed ALM-PFLOTRAN coupling codes embeded within ESM will be used for Pan-Arctic regional evaluation of climate change-caused ecosystem responses and their feedbacks to climate system at various scales.

Fermi acceleration in time-dependent billiards: theory of the velocity diffusion in conformally breathing fully chaotic billiards

NASA Astrophysics Data System (ADS)

Batistić, Benjamin; Robnik, Marko

2011-09-01

We study aspects of the Fermi acceleration (the unbounded growth of the energy) in a certain class of time-dependent 2D billiards. Specifically, we look at the conformally breathing billiards (periodic oscillation of the boundary which preserves the shape of the billiard at all times), which are fully chaotic as static (frozen) billiards, and we show that for large velocities around v0 and for not too long times, we observe just normal diffusion of the velocity as a function of the physical (continuous) time, around v0. However, the diffusion is not homogeneous, as the diffusion constant D depends on v0 as a power law D∝1/v30. Taking this into account, we show that to the leading order the average velocity v(n) as a function of the number of collisions n obeys a power law v∝n1/6 thus, the Fermi acceleration exponent is β = 1/6, which is in excellent agreement with the numerical calculations of the fully chaotic oval billiard, the Sinai billiard and the cardioid billiard. The error of the velocity estimates is of the order 1/v2. Thus, the higher the velocity, the better our analytic approximation. Moreover, we derive the underlying universal equation of the velocity dynamics of the time-dependent conformally breathing billiards, correct up to and including the order 1/v in the regime of the large velocity of the particle v. This universal equation does not depend on the dynamical properties of the system (integrability, ergodicity, chaoticity). We present the results of the numerical simulations for three billiards in complete agreement with the theory. We believe that this is a first step towards theoretical understanding of the power law growth and the Fermi acceleration exponents in 2D billiards, although our theory is so far specialized to the conformally breathing fully chaotic billiards.

Whole lung morphometry with 3D multiple b-value hyperpolarized gas MRI and compressed sensing.

PubMed

Chan, Ho-Fung; Stewart, Neil J; Parra-Robles, Juan; Collier, Guilhem J; Wild, Jim M

2017-05-01

To demonstrate three-dimensional (3D) multiple b-value diffusion-weighted (DW) MRI of hyperpolarized 3 He gas for whole lung morphometry with compressed sensing (CS). A fully-sampled, two b-value, 3D hyperpolarized 3 He DW-MRI dataset was acquired from the lungs of a healthy volunteer and retrospectively undersampled in the k y and k z phase-encoding directions for CS simulations. Optimal k-space undersampling patterns were determined by minimizing the mean absolute error between reconstructed and fully-sampled 3 He apparent diffusion coefficient (ADC) maps. Prospective three-fold, undersampled, 3D multiple b-value 3 He DW-MRI datasets were acquired from five healthy volunteers and one chronic obstructive pulmonary disease (COPD) patient, and the mean values of maps of ADC and mean alveolar dimension (Lm D ) were validated against two-dimensional (2D) and 3D fully-sampled 3 He DW-MRI experiments. Reconstructed undersampled datasets showed no visual artifacts and good preservation of the main image features and quantitative information. A good agreement between fully-sampled and prospective undersampled datasets was found, with a mean difference of +3.4% and +5.1% observed in mean global ADC and Lm D values, respectively. These differences were within the standard deviation range and consistent with values reported from healthy and COPD lungs. Accelerated CS acquisition has facilitated 3D multiple b-value 3 He DW-MRI scans in a single breath-hold, enabling whole lung morphometry mapping. Magn Reson Med 77:1916-1925, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Recursive regularization step for high-order lattice Boltzmann methods

NASA Astrophysics Data System (ADS)

Coreixas, Christophe; Wissocq, Gauthier; Puigt, Guillaume; Boussuge, Jean-François; Sagaut, Pierre

2017-09-01

A lattice Boltzmann method (LBM) with enhanced stability and accuracy is presented for various Hermite tensor-based lattice structures. The collision operator relies on a regularization step, which is here improved through a recursive computation of nonequilibrium Hermite polynomial coefficients. In addition to the reduced computational cost of this procedure with respect to the standard one, the recursive step allows to considerably enhance the stability and accuracy of the numerical scheme by properly filtering out second- (and higher-) order nonhydrodynamic contributions in under-resolved conditions. This is first shown in the isothermal case where the simulation of the doubly periodic shear layer is performed with a Reynolds number ranging from 104 to 106, and where a thorough analysis of the case at Re=3 ×104 is conducted. In the latter, results obtained using both regularization steps are compared against the Bhatnagar-Gross-Krook LBM for standard (D2Q9) and high-order (D2V17 and D2V37) lattice structures, confirming the tremendous increase of stability range of the proposed approach. Further comparisons on thermal and fully compressible flows, using the general extension of this procedure, are then conducted through the numerical simulation of Sod shock tubes with the D2V37 lattice. They confirm the stability increase induced by the recursive approach as compared with the standard one.

Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

PubMed Central

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

2017-01-01

Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

Data-Driven Modeling of Solar Corona by a New 3d Path-Conservative Osher-Solomon MHD Odel

NASA Astrophysics Data System (ADS)

Feng, X. S.; Li, C.

2017-12-01

A second-order path-conservative scheme with Godunov-type finite volume method (FVM) has been implemented to advance the equations of single-fluid solar wind plasma magnetohydrodynamics (MHD) in time. This code operates on the six-component composite grid system in 3D spherical coordinates with hexahedral cells of quadrilateral frustum type. The generalized Osher-Solomon Riemann solver is employed based on a numerical integration of the path-dependentdissipation matrix. For simplicity, the straight line segment path is used and the path-integral is evaluated in a fully numerical way by high-order numerical Gauss-Legendre quadrature. Besides its closest similarity to Godunov, the resulting scheme retains the attractive features of the original solver: it is nonlinear, free of entropy-fix, differentiable and complete in that each characteristic field results in a different numerical viscosity, due to the full use of the MHD eigenstructure. By using a minmod limiter for spatial oscillation control, the pathconservative scheme is realized for the generalized Lagrange multiplier (GLM) and the extended generalized Lagrange multiplier (EGLM) formulation of solar wind MHD systems. This new model of second-order in space and time is written in FORTRAN language with Message Passing Interface (MPI) parallelization, and validated in modeling time-dependent large-scale structure of solar corona, driven continuously by the Global Oscillation Network Group (GONG) data. To demonstrate the suitability of our code for the simulation of solar wind, we present selected results from October 9th, 2009 to December 29th, 2009 , & Year 2008 to show its capability of producing structured solar wind in agreement with the observations.

PIXIE3D: A Parallel, Implicit, eXtended MHD 3D Code

NASA Astrophysics Data System (ADS)

Chacon, Luis

2006-10-01

We report on the development of PIXIE3D, a 3D parallel, fully implicit Newton-Krylov extended MHD code in general curvilinear geometry. PIXIE3D employs a second-order, finite-volume-based spatial discretization that satisfies remarkable properties such as being conservative, solenoidal in the magnetic field to machine precision, non-dissipative, and linearly and nonlinearly stable in the absence of physical dissipation. PIXIE3D employs fully-implicit Newton-Krylov methods for the time advance. Currently, second-order implicit schemes such as Crank-Nicolson and BDF2 (2^nd order backward differentiation formula) are available. PIXIE3D is fully parallel (employs PETSc for parallelism), and exhibits excellent parallel scalability. A parallel, scalable, MG preconditioning strategy, based on physics-based preconditioning ideas, has been developed for resistive MHD, and is currently being extended to Hall MHD. In this poster, we will report on progress in the algorithmic formulation for extended MHD, as well as the the serial and parallel performance of PIXIE3D in a variety of problems and geometries. L. Chac'on, Comput. Phys. Comm., 163 (3), 143-171 (2004) L. Chac'on et al., J. Comput. Phys. 178 (1), 15- 36 (2002); J. Comput. Phys., 188 (2), 573-592 (2003) L. Chac'on, 32nd EPS Conf. Plasma Physics, Tarragona, Spain, 2005 L. Chac'on et al., 33rd EPS Conf. Plasma Physics, Rome, Italy, 2006

EBM regeneration and changes in EBM component mRNA expression in stromal cells after corneal injury

PubMed Central

Santhanam, Abirami; Marino, Gustavo K.; Torricelli, Andre A. M.

2017-01-01

Purpose To investigate the production of the epithelial basement membrane (EBM) component mRNAs at time points before lamina lucida and lamina densa regeneration in anterior stromal cells after corneal injury that would heal with and without fibrosis. Methods Rabbit corneas were removed from 2 to 19 days after −4.5D or −9.0D photorefractive keratectomy (PRK) with the VISX S4 IR laser. Corneas were evaluated with transmission electron microscopy (TEM) for full regeneration of the lamina lucida and the lamina densa. Laser capture microdissection (LCM) based quantitative real-time (RT)–PCR was used to quantitate the expression of mRNAs for laminin α-3 (LAMA3), perlecan, nidogen-1, and nidogen-2 in the anterior stroma. Results After −4.5D PRK, EBM was found to be fully regenerated at 8 to 10 days after surgery. At 4 days after PRK, the nidogen-2 and LAMA3 mRNAs levels were detected at statistically significantly lower levels in the anterior stroma of the −9.0D PRK corneas (where the EBM would not fully regenerate) compared to the −4.5D PRK corneas (where the EBM was destined to fully regenerate). At 7 days after PRK, nidogen-2 and LAMA3 mRNAs continued to be statistically significantly lower in the anterior stroma of the −9.0D PRK corneas compared to their expression in the anterior stroma of the −4.5D PRK corneas. Conclusions Key EBM components LAMA3 and nidogen-2 mRNAs are expressed at higher levels in the anterior stroma during EBM regeneration in the −4.5D PRK corneas where the EBM is destined to fully regenerate and no haze developed compared to the −9.0D PRK corneas where the EBM will not fully regenerate and myofibroblast-related stromal fibrosis (haze) will develop. PMID:28275314

Implementation of a 3d numerical model of a folded multilayer carbonate aquifer

NASA Astrophysics Data System (ADS)

Di Salvo, Cristina; Guyennon, Nicolas; Romano, Emanuele; Bruna Petrangeli, Anna; Preziosi, Elisabetta

2016-04-01

The main objective of this research is to present a case study of the numerical model implementation of a complex carbonate, structurally folded aquifer, with a finite difference, porous equivalent model. The case study aquifer (which extends over 235 km2 in the Apennine chain, Central Italy) provides a long term average of 3.5 m3/s of good quality groundwater to the surface river network, sustaining the minimum vital flow, and it is planned to be exploited in the next years for public water supply. In the downstream part of the river in the study area, a "Site of Community Importance" include the Nera River for its valuable aquatic fauna. However, the possible negative effects of the foreseen exploitation on groundwater dependent ecosystems are a great concern and model grounded scenarios are needed. This multilayer aquifer was conceptualized as five hydrostratigraphic units: three main aquifers (the uppermost unconfined, the central and the deepest partly confined), are separated by two locally discontinuous aquitards. The Nera river cuts through the two upper aquifers and acts as the main natural sink for groundwater. An equivalent porous medium approach was chosen. The complex tectonic structure of the aquifer requires several steps in defining the conceptual model; the presence of strongly dipping layers with very heterogeneous hydraulic conductivity, results in different thicknesses of saturated portions. Aquifers can have both unconfined or confined zones; drying and rewetting must be allowed when considering recharge/discharge cycles. All these characteristics can be included in the conceptual and numerical model; however, being the number of flow and head target scarce, the over-parametrization of the model must be avoided. Following the principle of parsimony, three steady state numerical models were developed, starting from a simple model, and then adding complexity: 2D (single layer), QUASI -3D (with leackage term simulating flow through aquitards) and fully-3D (with aquitards simulated explicitly and transient flow represented by 3D governing equations). At first, steady state simulation were run under average seasonal recharge. To overcome dry-cell problems in the FULL-3D model, the Newton-Raphson formulation for MODFLOW-2005 was invoked. Steady state calibration was achieved mainly using annual average flow along four streambed's Nera River springs and average water level data available only in two observation wells. Results show that a FULL-3D zoned model was required to match the observed distribution of river base flow. The FULL-3D model was then run in transient conditions (1990-2013) by using monthly spatially distributed recharge estimated using the Thornthwaite-Mather method based on 60 years of climate data. The monitored flow of one spring, used for public water supply, was used as proxy data for reconstruct Nera River hydrogram; proxy-based hydrogram was used for calibration of storage coefficients and further model's parameters adjustment. Once calibrated, the model was run under different aquifer management scenario (i.e., pumping wells planned to be active for water supply); the related risk of depletion of spring discharge and groundwater-surface water interaction was evaluated.

Does fluid infiltration affect the motion of sediment grains? - A 3-D numerical modelling approach using SPH

NASA Astrophysics Data System (ADS)

Bartzke, Gerhard; Rogers, Benedict D.; Fourtakas, Georgios; Mokos, Athanasios; Canelas, Ricardo B.; Huhn, Katrin

2017-04-01

With experimental techniques it is difficult to measure flow characteristics, e.g. the velocity of pore water flow in sediments, at a sufficient resolution and in a non-intrusive way. As a result, the effect of fluid flow at the surface and in the interior of a sediment bed on particle motion is not yet fully understood. Numerical models may help to overcome these problems. In this study Smoothed Particle Hydrodynamics (SPH) was chosen since it is ideally suited to simulate flows in sediment beds, at a high temporal and spatial resolution. The solver chosen is DualSPHysics 4.0 (www.dual.sphysics.org), since this is validated for a range of flow conditions. For the present investigation a 3D numerical flow channel was generated with a length of 15.0 cm, a width of 0.5 cm and a height of 4.0 cm. The entire domain was flooded with 8 million fluid particles, while 400 mobile sediment particles were deposited under applied gravity (grain diameter D50=10 mm) to generate randomly packed beds. Periodic boundaries were applied to the sidewalls to mimic an endless flow. To drive the flow, an acceleration perpendicular to the bed was applied to the fluid, reaching a target value of 0.3 cm/s, simulating 12 seconds of real time. Comparison of the model results to the law of the wall showed that flow speeds decreased logarithmically from the top of the domain towards the surface of the beds, indicating a fully developed boundary layer. Analysis of the fluid surrounding the sediment particles revealed critical threshold velocities, subsequently resulting in the initiation of motion due to drag. Sediment flux measurements indicated that with increasing simulation time a larger quantity of sediment particles was transported at the direct vicinity of the bed, whereas the amount of transported particles along with flow speed values, within the pore spaces, decreased with depth. Moreover, sediment - sediment particle collisions at the sediment surface lead to the opening of new pore spaces. As a result, higher quantities of fluid particles infiltrated through the larger interstices between the sediment particles, which successively increased the potential for the initiation of motion of sediment particles located in the deeper horizons. This effect has been underestimated in prior studies and highlights the importance of sediment - sediment particle collision and fluid infiltration as an important characteristic that can eventually help to better understand the development of the shear layer but also various sediment morphological features.

Elastohydrodynamic lubrication of point contacts. Ph.D. Thesis - Leeds Univ.

NASA Technical Reports Server (NTRS)

Hamrock, B. J.

1976-01-01

A procedure for the numerical solution of the complete, isothermal, elastohydrodynamic lubrication problem for point contacts is given. This procedure calls for the simultaneous solution of the elasticity and Reynolds equations. By using this theory the influence of the ellipticity parameter and the dimensionless speed, load, and material parameters on the minimum and central film thicknesses was investigated. Thirty-four different cases were used in obtaining the fully flooded minimum- and central-film-thickness formulas. Lubricant starvation was also studied. From the results it was possible to express the minimum film thickness for a starved condition in terms of the minimum film thickness for a fully flooded condition, the speed parameter, and the inlet distance. Fifteen additional cases plus three fully flooded cases were used in obtaining this formula. Contour plots of pressure and film thickness in and around the contact have been presented for both fully flooded and starved lubrication conditions.

Direct numerical simulation of human phonation

NASA Astrophysics Data System (ADS)

Saurabh, Shakti; Bodony, Daniel

2016-11-01

A direct numerical simulation study of the generation and propagation of the human voice in a full-body domain is conducted. A fully compressible fluid flow model, anatomically representative vocal tract geometry, finite deformation model for vocal fold (VF) motion and a fully coupled fluid-structure interaction model are employed. The dynamics of the multi-layered VF tissue with varying stiffness are solved using a quadratic finite element code. The fluid-solid domains are coupled through a boundary-fitted interface and utilize a Poisson equation-based mesh deformation method. A new inflow boundary condition, based upon a quasi-1D formulation with constant sub-glottal volume velocity, linked to the VF movement, has been adopted. Simulations for both child and adult phonation were performed. Acoustic characteristics obtained from these simulation are consistent with expected values. A sensitivity analysis based on VF stiffness variation is undertaken and sound pressure level/fundamental frequency trends are established. An evaluation of the data against the commonly-used quasi-1D equations suggest that the latter are not sufficient to model phonation. Phonation threshold pressures are measured for several VF stiffness variations and comparisons to clinical data are carried out. Supported by the National Science Foundation (CAREER Award Number 1150439).

Experimental and numerical investigation of a scalable modular geothermal heat storage system

NASA Astrophysics Data System (ADS)

Nordbeck, Johannes; Bauer, Sebastian; Beyer, Christof

2017-04-01

Storage of heat will play a significant role in the transition towards a reliable and renewable power supply, as it offers a way to store energy from fluctuating and weather dependent energy sources like solar or wind power and thus better meet consumer demands. The focus of this study is the simulation-based design of a heat storage system, featuring a scalable and modular setup that can be integrated with new as well as existing buildings. For this, the system can be either installed in a cellar or directly in the ground. Heat supply is by solar collectors, and heat storage is intended at temperatures up to about 90°C, which requires a verification of the methods used for numerical simulation of such systems. One module of the heat storage system consists of a helical heat exchanger in a fully water saturated, high porosity cement matrix, which represents the heat storage medium. A lab-scale storage prototype of 1 m3 volume was set up in a thermally insulated cylinder equipped with temperature and moisture sensors as well as flux meters and temperature sensors at the inlet and outlet pipes in order to experimentally analyze the performance of the storage system. Furthermore, the experimental data was used to validate an accurate and spatially detailed high-resolution 3D numerical model of heat and fluid flow, which was developed for system design optimization with respect to storage efficiency and environmental impacts. Three experiments conducted so far are reported and analyzed in this work. The first experiment, consisting of cooling of the fully loaded heat storage by heat loss across the insulation, is designed to determine the heat loss and the insulation parameters, i.e. heat conductivity and heat capacity of the insulation, via inverse modelling of the cooling period. The average cooling rate experimentally found is 1.2 °C per day. The second experiment consisted of six days of thermal loading up to a storage temperature of 60°C followed by four days of heat extraction. The experiment was performed for the determination of heat losses during a complete thermal loading and extraction cycle. The storage could be charged with 54 kWh of heat energy during thermal loading. 36 kWh could be regained during the extraction period, which translates to a heat loss of 33% during the 10 days of operation. Heat exchanger fluid flow rates and supply temperature were measured during the experiment and used as input for the 3D finite element model. Numerically simulated temperature distribution in the storage, return temperature and heat balances were compared to the measured data and showed that the 3D model accurately reflects the storage behavior. Also the third experiment, consisting of six days of cyclic operation after five days of continuous thermal loading, a good agreement between observed and modelled heat storage behavior is found. In addition to determining the storage performance during cyclic operation, the experiment will also be used to further validate the numerical model. This abstract will present the laboratory setup as well as the experimental data obtained from the experiment. It will also present the modelling approach chosen for the numerical representation of the experiment and give a comparison between measured and modelled temperatures and heat balances for the modular heat storage system.

Fully resolved simulations of expansion waves propagating into particle beds

NASA Astrophysics Data System (ADS)

Marjanovic, Goran; Hackl, Jason; Annamalai, Subramanian; Jackson, Thomas; Balachandar, S.

2017-11-01

There is a tremendous amount of research that has been done on compression waves and shock waves moving over particles but very little concerning expansion waves. Using 3-D direct numerical simulations, this study will explore expansion waves propagating into fully resolved particle beds of varying volume fractions and geometric arrangements. The objectives of these simulations are as follows: 1) To fully resolve all (1-way coupled) forces on the particles in a time varying flow and 2) to verify state-of-the-art drag models for such complex flows. We will explore a range of volume fractions, from very low ones that are similar to single particle flows, to higher ones where nozzling effects are observed between neighboring particles. Further, we will explore two geometric arrangements: body centered cubic and face centered cubic. We will quantify the effects that volume fraction and geometric arrangement plays on the drag forces and flow fields experienced by the particles. These results will then be compared to theoretical predictions from a model based on the generalized Faxen's theorem. This work was supported in part by the U.S. Department of Energy under the Predictive Science Academic Alliance Program, under Contract No. DE-NA0002378.

Finite-element 3D simulation tools for high-current relativistic electron beams

NASA Astrophysics Data System (ADS)

Humphries, Stanley; Ekdahl, Carl

2002-08-01

The DARHT second-axis injector is a challenge for computer simulations. Electrons are subject to strong beam-generated forces. The fields are fully three-dimensional and accurate calculations at surfaces are critical. We describe methods applied in OmniTrak, a 3D finite-element code suite that can address DARHT and the full range of charged-particle devices. The system handles mesh generation, electrostatics, magnetostatics and self-consistent particle orbits. The MetaMesh program generates meshes of conformal hexahedrons to fit any user geometry. The code has the unique ability to create structured conformal meshes with cubic logic. Organized meshes offer advantages in speed and memory utilization in the orbit and field solutions. OmniTrak is a versatile charged-particle code that handles 3D electric and magnetic field solutions on independent meshes. The program can update both 3D field solutions from the calculated beam space-charge and current-density. We shall describe numerical methods for orbit tracking on a hexahedron mesh. Topics include: 1) identification of elements along the particle trajectory, 2) fast searches and adaptive field calculations, 3) interpolation methods to terminate orbits on material surfaces, 4) automatic particle generation on multiple emission surfaces to model space-charge-limited emission and field emission, 5) flexible Child law algorithms, 6) implementation of the dual potential model for 3D magnetostatics, and 7) assignment of charge and current from model particle orbits for self-consistent fields.

Decomposed direct matrix inversion for fast non-cartesian SENSE reconstructions.

PubMed

Qian, Yongxian; Zhang, Zhenghui; Wang, Yi; Boada, Fernando E

2006-08-01

A new k-space direct matrix inversion (DMI) method is proposed here to accelerate non-Cartesian SENSE reconstructions. In this method a global k-space matrix equation is established on basic MRI principles, and the inverse of the global encoding matrix is found from a set of local matrix equations by taking advantage of the small extension of k-space coil maps. The DMI algorithm's efficiency is achieved by reloading the precalculated global inverse when the coil maps and trajectories remain unchanged, such as in dynamic studies. Phantom and human subject experiments were performed on a 1.5T scanner with a standard four-channel phased-array cardiac coil. Interleaved spiral trajectories were used to collect fully sampled and undersampled 3D raw data. The equivalence of the global k-space matrix equation to its image-space version, was verified via conjugate gradient (CG) iterative algorithms on a 2x undersampled phantom and numerical-model data sets. When applied to the 2x undersampled phantom and human-subject raw data, the decomposed DMI method produced images with small errors (< or = 3.9%) relative to the reference images obtained from the fully-sampled data, at a rate of 2 s per slice (excluding 4 min for precalculating the global inverse at an image size of 256 x 256). The DMI method may be useful for noise evaluations in parallel coil designs, dynamic MRI, and 3D sodium MRI with fixed coils and trajectories. Copyright 2006 Wiley-Liss, Inc.

Towards full-Braginskii implicit extended MHD

NASA Astrophysics Data System (ADS)

Chacon, Luis

2009-05-01

Recently, viable algorithms have been proposed for the scalable, fully-implicit temporal integration of 3D resistive MHD and cold-ion extended MHD models. While significant, these achievements must be tempered by the fact that such models lack predictive capabilities in regimes of interest for magnetic fusion. Short of including kinetic closures, a natural evolution path towards predictability starts by considering additional terms as described in Braginskii's fluid closures in the collisional regime. Here, we focus on the inclusion of two fundamental elements of relevance for fusion plasmas: anisotropic parallel electron transport, and warm-ion physics (i.e., ion finite Larmor radius effects, included via gyroviscosity). Both these elements introduce significant numerical difficulties, due to the strong anisotropy in the former, and the presence of dispersive waves in the latter. In this presentation, we will discuss progress in our fully implicit algorithmic formulation towards the inclusion of both these elements. L. Chac'on, Phys. Plasmas, 15, 056103 (2008) L. Chac'on, J. Physics: Conf. Series, 125, 012041 (2008)

Adaptive temporal refinement in injection molding

NASA Astrophysics Data System (ADS)

Karyofylli, Violeta; Schmitz, Mauritius; Hopmann, Christian; Behr, Marek

2018-05-01

Mold filling is an injection molding stage of great significance, because many defects of the plastic components (e.g. weld lines, burrs or insufficient filling) can occur during this process step. Therefore, it plays an important role in determining the quality of the produced parts. Our goal is the temporal refinement in the vicinity of the evolving melt front, in the context of 4D simplex-type space-time grids [1, 2]. This novel discretization method has an inherent flexibility to employ completely unstructured meshes with varying levels of resolution both in spatial dimensions and in the time dimension, thus allowing the use of local time-stepping during the simulations. This can lead to a higher simulation precision, while preserving calculation efficiency. A 3D benchmark case, which concerns the filling of a plate-shaped geometry, is used for verifying our numerical approach [3]. The simulation results obtained with the fully unstructured space-time discretization are compared to those obtained with the standard space-time method and to Moldflow simulation results. This example also serves for providing reliable timing measurements and the efficiency aspects of the filling simulation of complex 3D molds while applying adaptive temporal refinement.

Jump events in a 3D Edwards-Anderson spin glass

NASA Astrophysics Data System (ADS)

Mártin, Daniel A.; Iguain, José Luis

2017-11-01

The statistical properties of infrequent particle displacements, greater than a certain distance, are known as jump dynamics in the context of structural glass formers. We generalize the concept of a jump to the case of a spin glass, by dividing the system into small boxes, and considering the infrequent cooperative spin flips in each box. Jumps defined this way share similarities with jumps in structural glasses. We perform numerical simulations for the 3D Edwards-Anderson model, and study how the properties of these jumps depend on the waiting time after a quench. Similar to the results for structural glasses, we find that while jump frequency depends strongly on time, the jump duration and jump length are roughly stationary. At odds with some results reported on studies of structural glass formers, at long enough times, the rest time between jumps varies as the inverse of jump frequency. We give a possible explanation for this discrepancy. We also find that our results are qualitatively reproduced by a fully-connected trap model.

A Laminar Flow-Based Microfluidic Tesla Pump via Lithography Enabled 3D Printing.

PubMed

Habhab, Mohammed-Baker; Ismail, Tania; Lo, Joe Fujiou

2016-11-23

Tesla turbine and its applications in power generation and fluid flow were demonstrated by Nicholas Tesla in 1913. However, its real-world implementations were limited by the difficulty to maintain laminar flow between rotor disks, transient efficiencies during rotor acceleration, and the lack of other applications that fully utilize the continuous flow outputs. All of the aforementioned limits of Tesla turbines can be addressed by scaling to the microfluidic flow regime. Demonstrated here is a microscale Tesla pump designed and fabricated using a Digital Light Processing (DLP) based 3D printer with 43 µm lateral and 30 µm thickness resolutions. The miniaturized pump is characterized by low Reynolds number of 1000 and a flow rate of up to 12.6 mL/min at 1200 rpm, unloaded. It is capable of driving a mixer network to generate microfluidic gradient. The continuous, laminar flow from Tesla turbines is well-suited to the needs of flow-sensitive microfluidics, where the integrated pump will enable numerous compact lab-on-a-chip applications.

AxiSEM3D: a new fast method for global wave propagation in 3-D Earth models with undulating discontinuities

NASA Astrophysics Data System (ADS)

Leng, K.; Nissen-Meyer, T.; van Driel, M.; Al-Attar, D.

2016-12-01

We present a new, computationally efficient numerical method to simulate global seismic wave propagation in realistic 3-D Earth models with laterally heterogeneous media and finite boundary perturbations. Our method is a hybrid of pseudo-spectral and spectral element methods (SEM). We characterize the azimuthal dependence of 3-D wavefields in terms of Fourier series, such that the 3-D equations of motion reduce to an algebraic system of coupled 2-D meridional equations, which can be solved by a 2-D spectral element method (based on www.axisem.info). Computational efficiency of our method stems from lateral smoothness of global Earth models (with respect to wavelength) as well as axial singularity of seismic point sources, which jointly confine the Fourier modes of wavefields to a few lower orders. All boundary perturbations that violate geometric spherical symmetry, including Earth's ellipticity, topography and bathymetry, undulations of internal discontinuities such as Moho and CMB, are uniformly considered by means of a Particle Relabeling Transformation.The MPI-based high performance C++ code AxiSEM3D, is now available for forward simulations upon 3-D Earth models with fluid outer core, ellipticity, and both mantle and crustal structures. We show novel benchmarks for global wave solutions in 3-D mantle structures between our method and an independent, fully discretized 3-D SEM with remarkable agreement. Performance comparisons are carried out on three state-of-the-art tomography models, with seismic period going down to 5s. It is shown that our method runs up to two orders of magnitude faster than the 3-D SEM for such settings, and such computational advantage scales favourably with seismic frequency. By examining wavefields passing through hypothetical Gaussian plumes of varying sharpness, we identify in model-wavelength space the limits where our method may lose its advantage.

DNS study of dependence of bulk consumption velocity in a constant-density reacting flow on turbulence and mixture characteristics

NASA Astrophysics Data System (ADS)

Yu, Rixin; Lipatnikov, Andrei N.

2017-06-01

3D Direct Numerical Simulation (DNS) study of propagation of a single-reaction wave in forced, statistically stationary, homogeneous, isotropic, and constant-density turbulence was performed in order to evaluate both developing UTt and fully developed UTs bulk turbulent consumption velocities by independently varying a ratio of 0.5 ≤u'/SL≤ 90 of the r.m.s. turbulent velocity to the laminar wave speed and a ratio of 0.39 ≤L11/δF≤ 12.5 of the longitudinal integral length scale of the turbulence to the laminar wave thickness. Accordingly, the Damköhler D a =(L11SL ) /(u'δF ) and Karlovitz K a =δF/(SLτη ) numbers were varied from 0.01 to 24.7 and from 0.36 to 587, respectively. Here, τη is the Kolmogorov time scale. The obtained DNS data show that, at sufficiently low Da, the fully developed ratio of UTs/u' is mainly controlled by Da and scales as √{D a }. However, such a scaling should not be extrapolated to high Da. The higher Da (or the lower Ka), the less pronounced dependence of UTs/u' on a ratio of L11/δF. Moreover, scaling laws UT∝u'αSL1 -α(L11/δF ) β are substantially different for developing UTt and fully developed UTs, i.e., the scaling exponents α and, especially, β depend on the wave-development time. Furthermore, α and, especially, β depend on a method used to evaluate the developing UTt. Such effects can contribute to significant scatter of expressions for UT or ST as a function of {u', SL, L11, δF}, obtained by parameterizing various experimental databases.

Electrode-shaping for the excitation and detection of permitted arbitrary modes in arbitrary geometries in piezoelectric resonators.

PubMed

Pulskamp, Jeffrey S; Bedair, Sarah S; Polcawich, Ronald G; Smith, Gabriel L; Martin, Joel; Power, Brian; Bhave, Sunil A

2012-05-01

This paper reports theoretical analysis and experimental results on a numerical electrode shaping design technique that permits the excitation of arbitrary modes in arbitrary geometries for piezoelectric resonators, for those modes permitted to exist by the nonzero piezoelectric coefficients and electrode configuration. The technique directly determines optimal electrode shapes by assessing the local suitability of excitation and detection electrode placement on two-port resonators without the need for iterative numerical techniques. The technique is demonstrated in 61 different electrode designs in lead zirconate titanate (PZT) thin film on silicon RF micro electro-mechanical system (MEMS) plate, beam, ring, and disc resonators for out-of-plane flexural and various contour modes up to 200 MHz. The average squared effective electromechanical coupling factor for the designs was 0.54%, approximately equivalent to the theoretical maximum value of 0.53% for a fully electroded length-extensional mode beam resonator comprised of the same composite. The average improvement in S(21) for the electrode-shaped designs was 14.6 dB with a maximum improvement of 44.3 dB. Through this piezoelectric electrodeshaping technique, 95% of the designs showed a reduction in insertion loss.

Three dimensional numerical prediction of icing related power and energy losses on a wind turbine

NASA Astrophysics Data System (ADS)

Sagol, Ece

Regions of Canada experience harsh winter conditions that may persist for several months. Consequently, wind turbines located in these regions are exposed to ice accretion and its adverse effects, from loss of power to ceasing to function altogether. Since the weather-related annual energy production loss of a turbine may be as high as 16% of the nominal production for Canada, estimating these losses before the construction of a wind farm is essential for investors. A literature survey shows that most icing prediction methods and codes are developed for aircraft, and, as this information is mostly considered corporate intellectual property, it is not accessible to researchers in other domains. Moreover, aircraft icing is quite different from wind turbine icing. Wind turbines are exposed to icing conditions for much longer periods than aircraft, perhaps for several days in a harsh climate, whereas the maximum length of exposure of an aircraft is about 3-4 hours. In addition, wind turbine blades operate at subsonic speeds, at lower Reynolds numbers than aircraft, and their physical characteristics are different. A few icing codes have been developed for wind turbine icing nevertheless. However, they are either in 2D, which does not consider the 3D characteristics of the flow field, or they focus on simulating each rotation in a time-dependent manner, which is not practical for computing long hours of ice accretion. Our objective in this thesis is to develop a 3D numerical methodology to predict rime ice shape and the power loss of a wind turbine as a function of wind farm icing conditions. In addition, we compute the Annual Energy Production of a sample turbine under both clean and icing conditions. The sample turbine we have selected is the NREL Phase VI experimental wind turbine installed on a wind farm in Sweden, the icing events at which have been recorded and published. The proposed method is based on computing and validating the clean performance of the turbine, and then computing the ice shape and iced blade performance, under icing conditions. The first step is to compute the performance of the NREL Phase VI using the commercial ANSYSFLUENT computational fluid dynamics (CFD) tool. In order to reduce the computational cost, we use a rotating reference frame model which computes the flow properties as time-averaged quantities. A grid sensitivity study has been performed to eliminate the effect of mesh on the results. Of the existing models for characterizing turbulence, we have selected the two-equation SST k-pi model. In general, the computed pressure coefficients and bending moment have shown good agreement with the experimental data, particularly at pre-stall speeds. Although the torque deviates from the experimental data, the trend with respect to the wind speed is similar. After the clean power curve has been computed, collection efficiency, which is directly proportional to the rate of icing of a surface, is analyzed. A multiphase analysis, for the air and water phases, is necessary to compute the rate of accumulation of the droplets on the blade surfaces. We study two different approaches that are found in the literature -- Eulerian and Lagrangian -- and determine the most suitable one for our study case. The former applies the governing equations to the liquid phase, while the latter computes the trajectory of each droplet present in the air. We eventually decided on the Eulerian model for our study, as it can be adapted to handle large and complex meshes better than the Lagrangian model. This step is validated on a NACA 0012 airfoil, as experimental data for 3D flows are not available in the literature. The ice accretion on the sample wind turbine blades is computed using both a Quasi-3D and a Fully-3D method, which have a similar theoretical background, but a different order of modeling. In the former, all the steps are carried out in 2D and the overall power is computed using the Blade Element Momentum method, while the latter performs all the steps in the 3D domain. The Fully-3D method yields more accurate predictions for a clean blade. For icing conditions, a validation is not possible, owing to the lack of experimental data. However, the two methods produce quite different results for the performance of the ice shape and the iced blade. A critical analysis of the results shows that, although the computational cost of the Fully-3D method is much higher, icing analyses in 2D may lack accuracy, because the ice shape and the related power loss are compromised by not considering the 3D features of rotational flow. While performing the CFD computations on the iced blade, the rough surface of the ice is smoothed to a degree, in order to prevent numerical instability and to keep the mesh size within a reasonable limit. However, roughness effects cannot be excluded altogether, as they contribute significantly to performance reduction. We consider roughness through a modification in the CFD code, and assess its effect on performance for the clean blade.

A Numerical Study of Displacement Body and Curvature Effects on Incompressible and Compressible Laminar Boundary Layers. Ph.D. Thesis - Va. Polytechnic Inst.

NASA Technical Reports Server (NTRS)

Wornom, S. F.

1971-01-01

This technique has been applied to study such effects on incompressible flow around cylinders at moderate to low Reynolds numbers and for compression ramps at hypersonic Mach numbers by employing a finite difference method to obtain numerical solutions. The results indicate that the technique can be applied successfully in both regimes and does predict the correct trend in regions of large curvature and displacement body effects. It was concluded that curvature corrections should only be attempted in cases where all displacement effects can be fully accounted for.

Externally Calibrated Parallel Imaging for 3D Multispectral Imaging Near Metallic Implants Using Broadband Ultrashort Echo Time Imaging

PubMed Central

Wiens, Curtis N.; Artz, Nathan S.; Jang, Hyungseok; McMillan, Alan B.; Reeder, Scott B.

2017-01-01

Purpose To develop an externally calibrated parallel imaging technique for three-dimensional multispectral imaging (3D-MSI) in the presence of metallic implants. Theory and Methods A fast, ultrashort echo time (UTE) calibration acquisition is proposed to enable externally calibrated parallel imaging techniques near metallic implants. The proposed calibration acquisition uses a broadband radiofrequency (RF) pulse to excite the off-resonance induced by the metallic implant, fully phase-encoded imaging to prevent in-plane distortions, and UTE to capture rapidly decaying signal. The performance of the externally calibrated parallel imaging reconstructions was assessed using phantoms and in vivo examples. Results Phantom and in vivo comparisons to self-calibrated parallel imaging acquisitions show that significant reductions in acquisition times can be achieved using externally calibrated parallel imaging with comparable image quality. Acquisition time reductions are particularly large for fully phase-encoded methods such as spectrally resolved fully phase-encoded three-dimensional (3D) fast spin-echo (SR-FPE), in which scan time reductions of up to 8 min were obtained. Conclusion A fully phase-encoded acquisition with broadband excitation and UTE enabled externally calibrated parallel imaging for 3D-MSI, eliminating the need for repeated calibration regions at each frequency offset. Significant reductions in acquisition time can be achieved, particularly for fully phase-encoded methods like SR-FPE. PMID:27403613

3D Tensorial Elastodynamics for Isotropic Media on Vertically Deformed Meshes

NASA Astrophysics Data System (ADS)

Shragge, J. C.

2017-12-01

Solutions of the 3D elastodynamic wave equation are sometimes required in industrial and academic applications of elastic reverse-time migration (E-RTM) and full waveform inversion (E-FWI) that involve vertically deformed meshes. Examples include incorporating irregular free-surface topography and handling internal boundaries (e.g., water bottom) directly into the computational meshes. In 3D E-RTM and E-FWI applications, the number of forward modeling simulations can number in the tens of thousands (per iteration), which necessitates the development of stable, accurate and efficient 3D elastodynamics solvers. For topographic scenarios, most finite-difference solution approaches use a change-of-variable strategy that has a number of associated computational challenges, including difficulties in handling of the free-surface boundary condition. In this study, I follow a tensorial approach and use a generalized family of analytic transforms to develop a set of analytic equations for 3D elastodynamics that directly incorporates vertical grid deformations. Importantly, this analytic approach allows for the specification of an analytic free-surface boundary condition appropriate for vertically deformed meshes. These equations are both straightforward and efficient to solve using a velocity-stress formulation with finite-difference (MFD) operators implemented on a fully staggered grid. Moreover, I demonstrate that the use of mimetic finite difference (MFD) methods allows stable, accurate, and efficient numerical solutions to be simulated for typical topographic scenarios. Examples demonstrate that high-quality elastic wavefields can be generated for topographic surfaces exhibiting significant topographic relief.

Groping for quantitative digital 3-D image analysis: an approach to quantitative fluorescence in situ hybridization in thick tissue sections of prostate carcinoma.

PubMed

Rodenacker, K; Aubele, M; Hutzler, P; Adiga, P S

1997-01-01

In molecular pathology numerical chromosome aberrations have been found to be decisive for the prognosis of malignancy in tumours. The existence of such aberrations can be detected by interphase fluorescence in situ hybridization (FISH). The gain or loss of certain base sequences in the desoxyribonucleic acid (DNA) can be estimated by counting the number of FISH signals per cell nucleus. The quantitative evaluation of such events is a necessary condition for a prospective use in diagnostic pathology. To avoid occlusions of signals, the cell nucleus has to be analyzed in three dimensions. Confocal laser scanning microscopy is the means to obtain series of optical thin sections from fluorescence stained or marked material to fulfill the conditions mentioned above. A graphical user interface (GUI) to a software package for display, inspection, count and (semi-)automatic analysis of 3-D images for pathologists is outlined including the underlying methods of 3-D image interaction and segmentation developed. The preparative methods are briefly described. Main emphasis is given to the methodical questions of computer-aided analysis of large 3-D image data sets for pathologists. Several automated analysis steps can be performed for segmentation and succeeding quantification. However tumour material is in contrast to isolated or cultured cells even for visual inspection, a difficult material. For the present a fully automated digital image analysis of 3-D data is not in sight. A semi-automatic segmentation method is thus presented here.

Influence of a white noise at channel inlet on the parallel and wavy convective instabilities of Poiseuille-Rayleigh-Bénard flows

NASA Astrophysics Data System (ADS)

Nicolas, Xavier; Zoueidi, Noussaiba; Xin, Shihe

2012-08-01

The present paper concerns Poiseuille-Rayleigh-Bénard mixed convection flows in horizontal rectangular air-filled channels of large spanwise aspect ratio (W/H ≥ 10) and it focuses on the primary and secondary thermoconvective instabilities made of steady longitudinal and unsteady wavy rolls for 100 ≤ Re ≤ 200, 3000 < Ra < 15 000, Pr = 0.7, and W/H = 10. Time linear stability analysis of longitudinal rolls and 3D nonlinear numerical simulations using a specially tailored finite difference code is performed for this purpose. A bibliographical review, linear stability analysis and 3D numerical simulations allow establishing the full stability diagram for Re ≤ 300 and Ra ≤ 20 000. The linear stability analysis indicates that the critical Rayleigh number Ra≈*(Re) of the neutral curve between longitudinal and wavy rolls for W/H = 10 is increased at least by a factor of 1.5 in comparison with infinite W/H. The numerical study shows that the usual definitions of growth lengths for longitudinal rolls are inappropriate and it explains the discrepancies observed on wall Nusselt numbers in the literature between experimental and numerical results for the fully developed longitudinal rolls: Nusselt number decreasing at Ra > 8000 is due to spanwise oscillations of thermoconvective rolls that favor a bulk temperature homogenization. Because they are a convective instability, wavy rolls and their space and time development are studied numerically by maintaining at channel inlet, a permanent random excitation: it is designed to cover all the modes and allows detecting the wavy roll modes that are naturally amplified by the flow and those that are damped. Wavy roll patterns are characterized with respect to its three control parameters: Re, the relative distance ɛ to the critical Rayleigh number Ra≈*, and the excitation magnitude Aexc. The growth length of the wavy rolls is shown to correlate with ɛ-0.72 and Log(Aexc). The frequency, wave number, and phase velocity of the most amplified mode, the wall averaged Nusselt number and the spanwise displacements of the wavy rolls are independent of Aexc in the fully developed zone, but depend a lot on ɛ for ɛ < 2 and nearly stabilize for ɛ > 2 (i.e., Ra > 3Ra≈*). Correlation laws as a function of Re, ɛ, and Aexc are proposed for most of the exploited quantities. Numerical simulations performed are in a good agreement with experimental results on the wavy rolls obtained by Pabiou et al. ["Wavy secondary instability of longitudinal rolls in Rayleigh-Bénard-Poiseuille flows," J. Fluid Mech. 542, 175 (2005), 10.1017/S0022112005006154]. Finally, wavy roll characteristics are shown to be potentially interesting to better homogenize the vapor depositions in the horizontal rectangular chemical vapor deposition reactors used to make thin coatings on heated substrates from gaseous components.

A multi-dimensional nonlinearly implicit, electromagnetic Vlasov-Darwin particle-in-cell (PIC) algorithm

NASA Astrophysics Data System (ADS)

Chen, Guangye; Chacón, Luis; CoCoMans Team

2014-10-01

For decades, the Vlasov-Darwin model has been recognized to be attractive for PIC simulations (to avoid radiative noise issues) in non-radiative electromagnetic regimes. However, the Darwin model results in elliptic field equations that renders explicit time integration unconditionally unstable. Improving on linearly implicit schemes, fully implicit PIC algorithms for both electrostatic and electromagnetic regimes, with exact discrete energy and charge conservation properties, have been recently developed in 1D. This study builds on these recent algorithms to develop an implicit, orbit-averaged, time-space-centered finite difference scheme for the particle-field equations in multiple dimensions. The algorithm conserves energy, charge, and canonical-momentum exactly, even with grid packing. A simple fluid preconditioner allows efficient use of large timesteps, O (√{mi/me}c/veT) larger than the explicit CFL. We demonstrate the accuracy and efficiency properties of the of the algorithm with various numerical experiments in 2D3V.

Partitioned coupling of advection-diffusion-reaction systems and Brinkman flows

NASA Astrophysics Data System (ADS)

Lenarda, Pietro; Paggi, Marco; Ruiz Baier, Ricardo

2017-09-01

We present a partitioned algorithm aimed at extending the capabilities of existing solvers for the simulation of coupled advection-diffusion-reaction systems and incompressible, viscous flow. The space discretisation of the governing equations is based on mixed finite element methods defined on unstructured meshes, whereas the time integration hinges on an operator splitting strategy that exploits the differences in scales between the reaction, advection, and diffusion processes, considering the global system as a number of sequentially linked sets of partial differential, and algebraic equations. The flow solver presents the advantage that all unknowns in the system (here vorticity, velocity, and pressure) can be fully decoupled and thus turn the overall scheme very attractive from the computational perspective. The robustness of the proposed method is illustrated with a series of numerical tests in 2D and 3D, relevant in the modelling of bacterial bioconvection and Boussinesq systems.

Gestures in an Intelligent User Interface

NASA Astrophysics Data System (ADS)

Fikkert, Wim; van der Vet, Paul; Nijholt, Anton

In this chapter we investigated which hand gestures are intuitive to control a large display multimedia interface from a user's perspective. Over the course of two sequential user evaluations, we defined a simple gesture set that allows users to fully control a large display multimedia interface, intuitively. First, we evaluated numerous gesture possibilities for a set of commands that can be issued to the interface. These gestures were selected from literature, science fiction movies, and a previous exploratory study. Second, we implemented a working prototype with which the users could interact with both hands and the preferred hand gestures with 2D and 3D visualizations of biochemical structures. We found that the gestures are influenced to significant extent by the fast paced developments in multimedia interfaces such as the Apple iPhone and the Nintendo Wii and to no lesser degree by decades of experience with the more traditional WIMP-based interfaces.

Development of a Top-View Numeric Coding Teaching-Learning Trajectory within an Elementary Grades 3-D Visualization Design Research Project

ERIC Educational Resources Information Center

Sack, Jacqueline J.

2013-01-01

This article explicates the development of top-view numeric coding of 3-D cube structures within a design research project focused on 3-D visualization skills for elementary grades children. It describes children's conceptual development of 3-D cube structures using concrete models, conventional 2-D pictures and abstract top-view numeric…

Partial differential equations of 3D boundary layer and their numerical solutions in turbomachinery

NASA Astrophysics Data System (ADS)

Zhang, Guoqing; Hua, Yaonan; Wu, Chung-Hua

1991-08-01

This paper studies the 3D boundary layer equations (3DBLE) and their numerical solutions in turbomachinery: (1) the general form of 3DBLE in turbomachines with rotational and curvature effects are derived under the semiorthogonal coordinate system, in which the normal pressure gradient is not equal to zero; (2) the method of solution of the 3DBLE is discussed; (3) the 3D boundary layers on the rotating blade surface, IGV endwall, rotor endwall (with a relatively moving boundary) are numerically solved, and the predicted data correlates well with the measured data; and (4) the comparison is made between the numerical results of 3DBLE with and without normal pressure gradient.

Novel and simple route to fabricate fully biocompatible plasmonic mushroom arrays adhered on silk biopolymer

NASA Astrophysics Data System (ADS)

Park, Joonhan; Choi, Yunkyoung; Lee, Myungjae; Jeon, Heonsu; Kim, Sunghwan

2014-12-01

A fully biocompatible plasmonic quasi-3D nanostructure is demonstrated by a simple and reliable fabrication method using strong adhesion between gold and silk fibroin. The quasi-3D nature gives rise to complex photonic responses in reflectance that are prospectively useful in bio/chemical sensing applications. Laser interference lithography is utilized to fabricate large-area plasmonic nanostructures.A fully biocompatible plasmonic quasi-3D nanostructure is demonstrated by a simple and reliable fabrication method using strong adhesion between gold and silk fibroin. The quasi-3D nature gives rise to complex photonic responses in reflectance that are prospectively useful in bio/chemical sensing applications. Laser interference lithography is utilized to fabricate large-area plasmonic nanostructures. Electronic supplementary information (ESI) available: The incident angle dependence of reflectance spectra and the atomic force microscopy image of the Au nanoparticle array on a silk film after 1 hour of ultrasonication. See DOI: 10.1039/c4nr05172f

Optical Linear Algebra for Computational Light Transport

NASA Astrophysics Data System (ADS)

O'Toole, Matthew

Active illumination refers to optical techniques that use controllable lights and cameras to analyze the way light propagates through the world. These techniques confer many unique imaging capabilities (e.g. high-precision 3D scanning, image-based relighting, imaging through scattering media), but at a significant cost; they often require long acquisition and processing times, rely on predictive models for light transport, and cease to function when exposed to bright ambient sunlight. We develop a mathematical framework for describing and analyzing such imaging techniques. This framework is deeply rooted in numerical linear algebra, and models the transfer of radiant energy through an unknown environment with the so-called light transport matrix. Performing active illumination on a scene equates to applying a numerical operator on this unknown matrix. The brute-force approach to active illumination follows a two-step procedure: (1) optically measure the light transport matrix and (2) evaluate the matrix operator numerically. This approach is infeasible in general, because the light transport matrix is often much too large to measure, store, and analyze directly. Using principles from optical linear algebra, we evaluate these matrix operators in the optical domain, without ever measuring the light transport matrix in the first place. Specifically, we explore numerical algorithms that can be implemented partially or fully with programmable optics. These optical algorithms provide solutions to many longstanding problems in computer vision and graphics, including the ability to (1) photo-realistically change the illumination conditions of a given photo with only a handful of measurements, (2) accurately capture the 3D shape of objects in the presence of complex transport properties and strong ambient illumination, and (3) overcome the multipath interference problem associated with time-of-flight cameras. Most importantly, we introduce an all-new imaging regime---optical probing---that provides unprecedented control over which light paths contribute to a photo.

Novel and simple route to fabricate fully biocompatible plasmonic mushroom arrays adhered on silk biopolymer.

PubMed

Park, Joonhan; Choi, Yunkyoung; Lee, Myungjae; Jeon, Heonsu; Kim, Sunghwan

2015-01-14

A fully biocompatible plasmonic quasi-3D nanostructure is demonstrated by a simple and reliable fabrication method using strong adhesion between gold and silk fibroin. The quasi-3D nature gives rise to complex photonic responses in reflectance that are prospectively useful in bio/chemical sensing applications. Laser interference lithography is utilized to fabricate large-area plasmonic nanostructures.

Computational Astrophysical Magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Norman, M. L.

1994-05-01

Cosmic magnetic fields have intrigued and vexed astrophysicists seeking to understand their complex dynamics in a wide variety of astronomical settings. Magnetic fields are believed to play an important role in regulating star formation in molecular clouds, providing an effective viscosity in accretion disks, accelerating astrophysical jets, and influencing the large scale structure of the ISM of disk galaxies. Radio observations of supernova remnants and extragalactic radio jets prove that magnetic fields are are fundamentally linked to astrophysical particle acceleration. Magnetic fields exist on cosmological scales as shown by the existence of radio halos in clusters of galaxies. Theoretical investigation of these and other phenomena require numerical simulations due to the inherent complexity of MHD, but until now neither the computer power nor the numerical algorithms existed to mount a serious attack on the most important problems. That has now changed. Advances in parallel computing and numerical algorithms now permit the simulation of fully nonlinear, time-dependent astrophysical MHD in 2D and 3D. In this talk, I will describe the ZEUS codes for astrophysical MHD developed at the Laboratory for Computational Astrophysics (LCA) at the University of Illinois. These codes are now available to the national community. The numerical algorithms and test suite used to validate them are briefly discussed. Several applications of ZEUS to topics listed above are presented. An extension of ZEUS to model ambipolar diffusion in weakly ionized plasmas is illustrated. I discuss how continuing exponential growth in computer power and new numerical algorithms under development will allow us to tackle two grand challenges: compressible MHD turbulence and relativistic MHD. This work is partially supported by grants NSF AST-9201113 and NASA NAG 5-2493.

Decentralized Quasi-Newton Methods

NASA Astrophysics Data System (ADS)

Eisen, Mark; Mokhtari, Aryan; Ribeiro, Alejandro

2017-05-01

We introduce the decentralized Broyden-Fletcher-Goldfarb-Shanno (D-BFGS) method as a variation of the BFGS quasi-Newton method for solving decentralized optimization problems. The D-BFGS method is of interest in problems that are not well conditioned, making first order decentralized methods ineffective, and in which second order information is not readily available, making second order decentralized methods impossible. D-BFGS is a fully distributed algorithm in which nodes approximate curvature information of themselves and their neighbors through the satisfaction of a secant condition. We additionally provide a formulation of the algorithm in asynchronous settings. Convergence of D-BFGS is established formally in both the synchronous and asynchronous settings and strong performance advantages relative to first order methods are shown numerically.

Non-reciprocal elastic wave propagation in 2D phononic membranes with spatiotemporally varying material properties

NASA Astrophysics Data System (ADS)

Attarzadeh, M. A.; Nouh, M.

2018-05-01

One-dimensional phononic materials with material fields traveling simultaneously in space and time have been shown to break elastodynamic reciprocity resulting in unique wave propagation features. In the present work, a comprehensive mathematical analysis is presented to characterize and fully predict the non-reciprocal wave dispersion in two-dimensional space. The analytical dispersion relations, in the presence of the spatiotemporal material variations, are validated numerically using finite 2D membranes with a prescribed number of cells. Using omnidirectional excitations at the membrane's center, wave propagations are shown to exhibit directional asymmetry that increases drastically in the direction of the material travel and vanishes in the direction perpendicular to it. The topological nature of the predicted dispersion in different propagation directions are evaluated using the computed Chern numbers. Finally, the degree of the 2D non-reciprocity is quantified using a non-reciprocity index (NRI) which confirms the theoretical dispersion predictions as well as the finite simulations. The presented framework can be extended to plate-type structures as well as 3D spatiotemporally modulated phononic crystals.

Numerical modelling techniques of soft soil improvement via stone columns: A brief review

NASA Astrophysics Data System (ADS)

Zukri, Azhani; Nazir, Ramli

2018-04-01

There are a number of numerical studies on stone column systems in the literature. Most of the studies found were involved with two-dimensional analysis of the stone column behaviour, while only a few studies used three-dimensional analysis. The most popular software utilised in those studies was Plaxis 2D and 3D. Other types of software that used for numerical analysis are DIANA, EXAMINE, ZSoil, ABAQUS, ANSYS, NISA, GEOSTUDIO, CRISP, TOCHNOG, CESAR, GEOFEM (2D & 3D), FLAC, and FLAC 3. This paper will review the methodological approaches to model stone column numerically, both in two-dimensional and three-dimensional analyses. The numerical techniques and suitable constitutive model used in the studies will also be discussed. In addition, the validation methods conducted were to verify the numerical analysis conducted will be presented. This review paper also serves as a guide for junior engineers through the applicable procedures and considerations when constructing and running a two or three-dimensional numerical analysis while also citing numerous relevant references.

Increasing Range and Lethality of Extended-Range Munitions (ERMS) using Numerical Weather Prediction (NWP) and the AUV Workbench to Compute a Ballistic Correction (BALCOR)

DTIC Science & Technology

2006-12-01

2 D . APPROACH TAKEN......................................................................................3 E...7 d . FORCEnet.................................................................................8 D . HISTORY OF LONG-RANGE PROJECTILES (LRPS...46 D . NUMERICAL WEATHER MODELING CENTERS...............................47 1. Fleet Numerical Meteorological

Consistency between 2D-3D Sediment Transport models

NASA Astrophysics Data System (ADS)

Villaret, Catherine; Jodeau, Magali

2017-04-01

Sediment transport models have been developed and applied by the engineering community to estimate transport rates and morphodynamic bed evolutions in river flows, coastal and estuarine conditions. Environmental modelling systems like the open-source Telemac modelling system include a hierarchy of models from 1D (Mascaret), 2D (Telemac-2D/Sisyphe) and 3D (Telemac-3D/Sedi-3D) and include a wide range of processes to represent sediment flow interactions under more and more complex situations (cohesive, non-cohesive and mixed sediment). Despite some tremendous progresses in the numerical techniques and computing resources, the quality/accuracy of model results mainly depend on the numerous choices and skills of the modeler. In complex situations involving stratification effects, complex geometry, recirculating flows… 2D model assumptions are no longer valid. A full 3D turbulent flow model is then required in order to capture the vertical mixing processes and to represent accurately the coupled flow/sediment distribution. However a number of theoretical and numerical difficulties arise when dealing with sediment transport modelling in 3D which will be high-lighted : (1) Dependency of model results to the vertical grid refinement and choice of boundary conditions and numerical scheme (2) The choice of turbulence model determines also the sediment vertical distribution which is governed by a balance between the downward settling term and upward turbulent diffusion. (3) The use of different numerical schemes for both hydrodynamics (mean and turbulent flow) and sediment transport modelling can lead to some inconsistency including a mismatch in the definition of numerical cells and definition of boundary conditions. We discuss here those present issues and present some detailed comparison between 2D and 3D simulations on a set of validation test cases which are available in the Telemac 7.2 release using both cohesive and non-cohesive sediments.

Direct numerical simulation of turbulent pipe flow using the lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Peng, Cheng; Geneva, Nicholas; Guo, Zhaoli; Wang, Lian-Ping

2018-03-01

In this paper, we present a first direct numerical simulation (DNS) of a turbulent pipe flow using the mesoscopic lattice Boltzmann method (LBM) on both a D3Q19 lattice grid and a D3Q27 lattice grid. DNS of turbulent pipe flows using LBM has never been reported previously, perhaps due to inaccuracy and numerical stability associated with the previous implementations of LBM in the presence of a curved solid surface. In fact, it was even speculated that the D3Q19 lattice might be inappropriate as a DNS tool for turbulent pipe flows. In this paper, we show, through careful implementation, accurate turbulent statistics can be obtained using both D3Q19 and D3Q27 lattice grids. In the simulation with D3Q19 lattice, a few problems related to the numerical stability of the simulation are exposed. Discussions and solutions for those problems are provided. The simulation with D3Q27 lattice, on the other hand, is found to be more stable than its D3Q19 counterpart. The resulting turbulent flow statistics at a friction Reynolds number of Reτ = 180 are compared systematically with both published experimental and other DNS results based on solving the Navier-Stokes equations. The comparisons cover the mean-flow profile, the r.m.s. velocity and vorticity profiles, the mean and r.m.s. pressure profiles, the velocity skewness and flatness, and spatial correlations and energy spectra of velocity and vorticity. Overall, we conclude that both D3Q19 and D3Q27 simulations yield accurate turbulent flow statistics. The use of the D3Q27 lattice is shown to suppress the weak secondary flow pattern in the mean flow due to numerical artifacts.

A continuous mixing model for pdf simulations and its applications to combusting shear flows

NASA Technical Reports Server (NTRS)

Hsu, A. T.; Chen, J.-Y.

1991-01-01

The problem of time discontinuity (or jump condition) in the coalescence/dispersion (C/D) mixing model is addressed in this work. A C/D mixing model continuous in time is introduced. With the continuous mixing model, the process of chemical reaction can be fully coupled with mixing. In the case of homogeneous turbulence decay, the new model predicts a pdf very close to a Gaussian distribution, with finite higher moments also close to that of a Gaussian distribution. Results from the continuous mixing model are compared with both experimental data and numerical results from conventional C/D models.

Deep convolutional neural network and 3D deformable approach for tissue segmentation in musculoskeletal magnetic resonance imaging.

PubMed

Liu, Fang; Zhou, Zhaoye; Jang, Hyungseok; Samsonov, Alexey; Zhao, Gengyan; Kijowski, Richard

2018-04-01

To describe and evaluate a new fully automated musculoskeletal tissue segmentation method using deep convolutional neural network (CNN) and three-dimensional (3D) simplex deformable modeling to improve the accuracy and efficiency of cartilage and bone segmentation within the knee joint. A fully automated segmentation pipeline was built by combining a semantic segmentation CNN and 3D simplex deformable modeling. A CNN technique called SegNet was applied as the core of the segmentation method to perform high resolution pixel-wise multi-class tissue classification. The 3D simplex deformable modeling refined the output from SegNet to preserve the overall shape and maintain a desirable smooth surface for musculoskeletal structure. The fully automated segmentation method was tested using a publicly available knee image data set to compare with currently used state-of-the-art segmentation methods. The fully automated method was also evaluated on two different data sets, which include morphological and quantitative MR images with different tissue contrasts. The proposed fully automated segmentation method provided good segmentation performance with segmentation accuracy superior to most of state-of-the-art methods in the publicly available knee image data set. The method also demonstrated versatile segmentation performance on both morphological and quantitative musculoskeletal MR images with different tissue contrasts and spatial resolutions. The study demonstrates that the combined CNN and 3D deformable modeling approach is useful for performing rapid and accurate cartilage and bone segmentation within the knee joint. The CNN has promising potential applications in musculoskeletal imaging. Magn Reson Med 79:2379-2391, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Numerical study on non-locally reacting behavior of nacelle liners incorporating drainage slots

NASA Astrophysics Data System (ADS)

Chen, Chao; Li, Xiaodong; Thiele, Frank

2018-06-01

For acoustic liners used in current commercial nacelles, in order to prevent any liquid accumulating in the resonators, drainage slots are incorporated on the partition walls between closely packed cavities. Recently, an experimental study conducted by Busse-Gerstengarbe et al. shown that the cell interaction introduced by drainage slots causes an additional dissipation peak which increases with the size of the slot. However, the variation of damping process due to drainage slots is still not fully understood. Therefore, a numerical study based on computational aeroacoustic methods is carried out to investigate the mechanism of the changed attenuation characteristics due to drainage slots in presence of grazing incident sound waves with low or high intensities. Different slot configurations are designed based on the generic non-locally reacting liner model adopted in the experimental investigation. Both 2-D and 3-D numerical simulations of only slit resonators are carried out. Numerical results indicate that the extra peak is a result of a resonance excited in the second cavity at specific frequency. Under high sound pressure level incoming waves, the basic characteristics of the acoustic performance remain. However, vortex shedding transpires at the resonances around both the slits and the drainage slot. Vorticity contours show that the connection of two coupled cavities decreases the strength of vortex shedding around the basic Helmholtz resonance due to a higher energy reflection. Meanwhile, the cell interaction significantly increases the vorticity magnitude near the extra resonant frequency. Finally, a semi-empirical model is derived to predict the extra attenuation peak frequency.

Externally calibrated parallel imaging for 3D multispectral imaging near metallic implants using broadband ultrashort echo time imaging.

PubMed

Wiens, Curtis N; Artz, Nathan S; Jang, Hyungseok; McMillan, Alan B; Reeder, Scott B

2017-06-01

To develop an externally calibrated parallel imaging technique for three-dimensional multispectral imaging (3D-MSI) in the presence of metallic implants. A fast, ultrashort echo time (UTE) calibration acquisition is proposed to enable externally calibrated parallel imaging techniques near metallic implants. The proposed calibration acquisition uses a broadband radiofrequency (RF) pulse to excite the off-resonance induced by the metallic implant, fully phase-encoded imaging to prevent in-plane distortions, and UTE to capture rapidly decaying signal. The performance of the externally calibrated parallel imaging reconstructions was assessed using phantoms and in vivo examples. Phantom and in vivo comparisons to self-calibrated parallel imaging acquisitions show that significant reductions in acquisition times can be achieved using externally calibrated parallel imaging with comparable image quality. Acquisition time reductions are particularly large for fully phase-encoded methods such as spectrally resolved fully phase-encoded three-dimensional (3D) fast spin-echo (SR-FPE), in which scan time reductions of up to 8 min were obtained. A fully phase-encoded acquisition with broadband excitation and UTE enabled externally calibrated parallel imaging for 3D-MSI, eliminating the need for repeated calibration regions at each frequency offset. Significant reductions in acquisition time can be achieved, particularly for fully phase-encoded methods like SR-FPE. Magn Reson Med 77:2303-2309, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Fully automated, real-time 3D ultrasound segmentation to estimate first trimester placental volume using deep learning.

PubMed

Looney, Pádraig; Stevenson, Gordon N; Nicolaides, Kypros H; Plasencia, Walter; Molloholli, Malid; Natsis, Stavros; Collins, Sally L

2018-06-07

We present a new technique to fully automate the segmentation of an organ from 3D ultrasound (3D-US) volumes, using the placenta as the target organ. Image analysis tools to estimate organ volume do exist but are too time consuming and operator dependant. Fully automating the segmentation process would potentially allow the use of placental volume to screen for increased risk of pregnancy complications. The placenta was segmented from 2,393 first trimester 3D-US volumes using a semiautomated technique. This was quality controlled by three operators to produce the "ground-truth" data set. A fully convolutional neural network (OxNNet) was trained using this ground-truth data set to automatically segment the placenta. OxNNet delivered state-of-the-art automatic segmentation. The effect of training set size on the performance of OxNNet demonstrated the need for large data sets. The clinical utility of placental volume was tested by looking at predictions of small-for-gestational-age babies at term. The receiver-operating characteristics curves demonstrated almost identical results between OxNNet and the ground-truth). Our results demonstrated good similarity to the ground-truth and almost identical clinical results for the prediction of SGA.

Experimental And Numerical Investigation Of Aerothermal Characteristics Of The IXV Hypersonic Vehicle

NASA Astrophysics Data System (ADS)

Paris, S.; Charbonnier, D.; Tran, D.

2011-05-01

The main results of the aerothermodynamic hypersonic characterization of Intermediate eXperimental Vehicle (IXV), by means of both CFD simulations and wind tunnel measurements, have been reported and analyzed. In the framework of ESA FLPP Program, the VKI (Von Karman Institute) was in charge of an experimental test campaign for the consolidation of the aerothermal database in cold hypersonic regime. The tests campaign has been carried out at VKI Free Piston Longshot wind tunnel at mach 14. The numerical simulations have been performed for VKI wind tunnel conditions by CFSE with the in-house NSMB flow solver (Navier-Stokes Multi-Blocks 3D), the goal being to support the procedure of extrapolation-to-flight of the measurements and the general aerothermal characterization. Laminar, transitional and fully turbulent flows have been computed, with air considered as an ideal gas, for the wind tunnel tests numerical rebuilding. A detailed comparison of all measured and predicted hypersonic relevant phenomena and parameters (surface pressure and heat flux) is reported in the paper, together with a detailed description of configuration, freestream conditions, model attitude effects and flap deflection effect. The detailed analyze of the experimental and numerical data gives information on the nature of the flow on the body and on the flaps for the most critical configuration

3D image processing architecture for camera phones

NASA Astrophysics Data System (ADS)

Atanassov, Kalin; Ramachandra, Vikas; Goma, Sergio R.; Aleksic, Milivoje

2011-03-01

Putting high quality and easy-to-use 3D technology into the hands of regular consumers has become a recent challenge as interest in 3D technology has grown. Making 3D technology appealing to the average user requires that it be made fully automatic and foolproof. Designing a fully automatic 3D capture and display system requires: 1) identifying critical 3D technology issues like camera positioning, disparity control rationale, and screen geometry dependency, 2) designing methodology to automatically control them. Implementing 3D capture functionality on phone cameras necessitates designing algorithms to fit within the processing capabilities of the device. Various constraints like sensor position tolerances, sensor 3A tolerances, post-processing, 3D video resolution and frame rate should be carefully considered for their influence on 3D experience. Issues with migrating functions such as zoom and pan from the 2D usage model (both during capture and display) to 3D needs to be resolved to insure the highest level of user experience. It is also very important that the 3D usage scenario (including interactions between the user and the capture/display device) is carefully considered. Finally, both the processing power of the device and the practicality of the scheme needs to be taken into account while designing the calibration and processing methodology.

Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime

NASA Astrophysics Data System (ADS)

Cowan, B. M.; Kalmykov, S. Y.; Beck, A.; Davoine, X.; Bunkers, K.; Lifschitz, A. F.; Lefebvre, E.; Bruhwiler, D. L.; Shadwick, B. A.; Umstadter, D. P.; Umstadter

2012-08-01

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100-terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined. First, the Cartesian code vorpal (Nieter, C. and Cary, J. R. 2004 VORPAL: a versatile plasma simulation code. J. Comput. Phys. 196, 538) using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while keeping the usage of computational resources modest. The second way to reduce the simulation load is using reduced-geometry codes. In our case, the quasi-cylindrical code calder-circ (Lifschitz, A. F. et al. 2009 Particle-in-cell modelling of laser-plasma interaction using Fourier decomposition. J. Comput. Phys. 228(5), 1803-1814) uses decomposition of fields and currents into a set of poloidal modes, while the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the interaction allows using just two modes, reducing the computational load to roughly that of a planar Cartesian simulation while preserving the 3D nature of the interaction. This significant economy of resources allows using fine resolution in the direction of propagation and a small time step, making numerical dispersion vanishingly small, together with a large number of particles per cell, enabling good particle statistics. Quantitative agreement of two simulations indicates that these are free of numerical artefacts. Both approaches thus retrieve the physically correct evolution of the plasma bubble, recovering the intrinsic connection of electron self-injection to the nonlinear optical evolution of the driver.

Study of Electron-scale Dissipation near the X-line During Magnetic Reconnection in a Laboratory Plasma

NASA Astrophysics Data System (ADS)

Ji, H.; Yoo, J.; Dorfman, S. E.; Jara-Almonte, J.; Yamada, M.; Swanson, C.; Daughton, W. S.; Roytershteyn, V.; Kuwahata, A.; Ii, T.; Inomoto, M.; Ono, Y.; von Stechow, A.; Grulke, O.; Phan, T.; Mozer, F.; Bale, S. D.

2013-12-01

Despite its disruptive influences on the large-scale structures of space and solar plasmas, the crucial topological changes and associated dissipation during magnetic reconnection take place only near an X-line within thin singular layers. In the modern collisionless models where electrons and ions are allowed to move separately, it has been predicted that ions exhaust efficiently through a thicker, ion-scale dissipative layer while mobile electrons can evacuate through a thinner, electron-scale dissipation layer, allowing for efficient release of magnetic energy. While ion dissipation layers have been frequently detected, the existence of election layers near the X-line and the associated dissipation structures and mechanisms are still an open question, and will be a main subject of the coming MMS mission. In this presentation, we will summarize our efforts in the past a few years to study electron-scale dissipation in a well-controlled and well-diagnosed reconnecting current sheet in a laboratory plasma, with close comparisons with the state-of-the-art, 2D and 3D fully kinetic simulations. Key results include: (1) positive identification of electromagnetic waves detected at the current sheet center as long wave-length, lower-hybrid drift instabilities (EM-LHDI), (2) however, there is strong evidence that this EM-LHDI cannot provide the required force to support the reconnection electric field, (3) detection of 3D flux-rope-like magnetic structures during impulsive reconnection events, and (4) electrons are heated through non-classical mechanisms near the X-line with a small but clear temperature anisotropy. These results, unfortunately, do not resolve the outstanding discrepancies on electron layer thickness between best available experiments and fully kinetic simulations. To make further progress, we are continuously pushing in the both experimental and numerical frontiers. Experimentally, we started investigations on EM-LHDI and electron heating as a function of guide field strength and symmetry of reconnection geometry, with new attempts to measure non-thermal electrons and higher frequency fluctuations. Numerically, we started investigations of kinetic simulations at realistic ratios of electron plasma frequency to cyclotron frequency, and also at realistic ratios of ion mass to electron mass. The most updated results of these new projects will be presented with discussions on the relevance to space observations.

Determination of Paleoseismic Ground Motions from Inversion of Block Failures in Masonry Structures

NASA Astrophysics Data System (ADS)

Yagoda-Biran, G.; Hatzor, Y. H.

2010-12-01

Accurate estimation of ground motion parameters such as expected peak ground acceleration (PGA), predominant frequency and duration of motion in seismically active regions, is crucial for hazard preparedness and sound engineering design. The best way to estimate quantitatively these parameters would be to investigate long term recorded data of past strong earthquakes in a studied region. In some regions of the world however recorded data are scarce due to lack of seismic network infrastructure, and in all regions the availability of recorded data is restricted to the late 19th century and onwards. Therefore, existing instrumental data are hardly representative of the true seismicity of a region. When recorded data are scarce or not available, alternative methods may be applied, for example adopting a quantitative paleoseismic approach. In this research we suggest the use of seismically damaged masonry structures as paleoseismic indicators. Visitors to archeological sites all over the world are often struck by structural failure features which seem to be "seismically driven", particularly when inspecting old masonry structures. While it is widely accepted that no other loading mechanism can explain the preserved damage, the actual driving mechanism remains enigmatic even now. In this research we wish to explore how such failures may be triggered by earthquake induced ground motions and use observed block displacements to determine the characteristic parameters of the paleoseismic earthquake motion, namely duration, frequency, and amplitude. This is performed utilizing a 3D, fully dynamic, numerical analysis performed with the Discontinuous Deformation Analysis (DDA) method. Several case studies are selected for 3D numerical analysis. First we study a simple structure in the old city of L'Aquila, Italy. L'Aquila was hit by an earthquake on April 6th, 2009, with over 300 casualties and many of its medieval buildings damaged. This case study is an excellent opportunity to validate our method, since in the case of L'Aquila, both the damaged structure and the ground motions are recorded. The 3D modeling of the structure is rather complicated, and is performed by first modeling the structure with CAD software and later "translating" the model to the numerical code used. In the future, several more case studies will be analyzed, such as Kedesh and Avdat in Israel, and in collaboration with Hugh and Bilham the Temple of Shiva at Pandrethan, Kashmir. Establishing a numerical 3D dynamic analysis for back analysis of stone displacement in masonry structures as a paleoseismic tool can provide much needed data on ground motion parameters in regions where instrumental data are scarce, or are completely absent.

Numerical simulation of MPD thruster flows with anomalous transport

NASA Technical Reports Server (NTRS)

Caldo, Giuliano; Choueiri, Edgar Y.; Kelly, Arnold J.; Jahn, Robert G.

1992-01-01

Anomalous transport effects in an Ar self-field coaxial MPD thruster are presently studied by means of a fully 2D two-fluid numerical code; its calculations are extended to a range of typical operating conditions. An effort is made to compare the spatial distribution of the steady state flow and field properties and thruster power-dissipation values for simulation runs with and without anomalous transport. A conductivity law based on the nonlinear saturation of lower hybrid current-driven instability is used for the calculations. Anomalous-transport simulation runs have indicated that the resistivity in specific areas of the discharge is significantly higher than that calculated in classical runs.

Uncertainty Propagation for Turbulent, Compressible Flow in a Quasi-1D Nozzle Using Stochastic Methods

NASA Technical Reports Server (NTRS)

Zang, Thomas A.; Mathelin, Lionel; Hussaini, M. Yousuff; Bataille, Francoise

2003-01-01

This paper describes a fully spectral, Polynomial Chaos method for the propagation of uncertainty in numerical simulations of compressible, turbulent flow, as well as a novel stochastic collocation algorithm for the same application. The stochastic collocation method is key to the efficient use of stochastic methods on problems with complex nonlinearities, such as those associated with the turbulence model equations in compressible flow and for CFD schemes requiring solution of a Riemann problem. Both methods are applied to compressible flow in a quasi-one-dimensional nozzle. The stochastic collocation method is roughly an order of magnitude faster than the fully Galerkin Polynomial Chaos method on the inviscid problem.

Nonlinear 3D visco-resistive MHD modeling of fusion plasmas: a comparison between numerical codes

NASA Astrophysics Data System (ADS)

Bonfiglio, D.; Chacon, L.; Cappello, S.

2008-11-01

Fluid plasma models (and, in particular, the MHD model) are extensively used in the theoretical description of laboratory and astrophysical plasmas. We present here a successful benchmark between two nonlinear, three-dimensional, compressible visco-resistive MHD codes. One is the fully implicit, finite volume code PIXIE3D [1,2], which is characterized by many attractive features, notably the generalized curvilinear formulation (which makes the code applicable to different geometries) and the possibility to include in the computation the energy transport equation and the extended MHD version of Ohm's law. In addition, the parallel version of the code features excellent scalability properties. Results from this code, obtained in cylindrical geometry, are compared with those produced by the semi-implicit cylindrical code SpeCyl, which uses finite differences radially, and spectral formulation in the other coordinates [3]. Both single and multi-mode simulations are benchmarked, regarding both reversed field pinch (RFP) and ohmic tokamak magnetic configurations. [1] L. Chacon, Computer Physics Communications 163, 143 (2004). [2] L. Chacon, Phys. Plasmas 15, 056103 (2008). [3] S. Cappello, Plasma Phys. Control. Fusion 46, B313 (2004) & references therein.

Numerical relativity for D dimensional axially symmetric space-times: Formalism and code tests

NASA Astrophysics Data System (ADS)

Zilhão, Miguel; Witek, Helvi; Sperhake, Ulrich; Cardoso, Vitor; Gualtieri, Leonardo; Herdeiro, Carlos; Nerozzi, Andrea

2010-04-01

The numerical evolution of Einstein’s field equations in a generic background has the potential to answer a variety of important questions in physics: from applications to the gauge-gravity duality, to modeling black hole production in TeV gravity scenarios, to analysis of the stability of exact solutions, and to tests of cosmic censorship. In order to investigate these questions, we extend numerical relativity to more general space-times than those investigated hitherto, by developing a framework to study the numerical evolution of D dimensional vacuum space-times with an SO(D-2) isometry group for D≥5, or SO(D-3) for D≥6. Performing a dimensional reduction on a (D-4) sphere, the D dimensional vacuum Einstein equations are rewritten as a 3+1 dimensional system with source terms, and presented in the Baumgarte, Shapiro, Shibata, and Nakamura formulation. This allows the use of existing 3+1 dimensional numerical codes with small adaptations. Brill-Lindquist initial data are constructed in D dimensions and a procedure to match them to our 3+1 dimensional evolution equations is given. We have implemented our framework by adapting the Lean code and perform a variety of simulations of nonspinning black hole space-times. Specifically, we present a modified moving puncture gauge, which facilitates long-term stable simulations in D=5. We further demonstrate the internal consistency of the code by studying convergence and comparing numerical versus analytic results in the case of geodesic slicing for D=5, 6.

Laser printing of 3D metallic interconnects

NASA Astrophysics Data System (ADS)

Beniam, Iyoel; Mathews, Scott A.; Charipar, Nicholas A.; Auyeung, Raymond C. Y.; Piqué, Alberto

2016-04-01

The use of laser-induced forward transfer (LIFT) techniques for the printing of functional materials has been demonstrated for numerous applications. The printing gives rise to patterns, which can be used to fabricate planar interconnects. More recently, various groups have demonstrated electrical interconnects from laser-printed 3D structures. The laser printing of these interconnects takes place through aggregation of voxels of either molten metal or of pastes containing dispersed metallic particles. However, the generated 3D structures do not posses the same metallic conductivity as a bulk metal interconnect of the same cross-section and length as those formed by wire bonding or tab welding. An alternative is to laser transfer entire 3D structures using a technique known as lase-and-place. Lase-and-place is a LIFT process whereby whole components and parts can be transferred from a donor substrate onto a desired location with one single laser pulse. This paper will describe the use of LIFT to laser print freestanding, solid metal foils or beams precisely over the contact pads of discrete devices to interconnect them into fully functional circuits. Furthermore, this paper will also show how the same laser can be used to bend or fold the bulk metal foils prior to transfer, thus forming compliant 3D structures able to provide strain relief for the circuits under flexing or during motion from thermal mismatch. These interconnect "ridges" can span wide gaps (on the order of a millimeter) and accommodate height differences of tens of microns between adjacent devices. Examples of these laser printed 3D metallic bridges and their role in the development of next generation electronics by additive manufacturing will be presented.

Turbulence and deterministic chaos. [computational fluid dynamics

NASA Technical Reports Server (NTRS)

Deissler, Robert G.

1992-01-01

Several turbulent and nonturbulent solutions of the Navier-Stokes equations are obtained. The unaveraged equations are used numerically in conjunction with tools and concepts from nonlinear dynamics, including time series, phase portraits, Poincare sections, largest Liapunov exponents, power spectra, and strange attractors. Initially neighboring solutions for a low Reynolds number fully developed turbulence are compared. Several flows are noted: fully chaotic, complex periodic, weakly chaotic, simple periodic, and fixed-point. Of these, only fully chaotic is classified as turbulent. Besides the sustained flows, a flow which decays as it becomes turbulent is examined. For the finest grid, 128(exp 3) points, the spatial resolution appears to be quite good. As a final note, the variation of the velocity derivatives skewness of a Navier-Stokes flow as the Reynolds number goes to zero is calculated numerically. The value of the skewness is shown to become small at low Reynolds numbers, in agreement with intuitive arguments that nonlinear terms should be negligible.

Exploring time-resolved photoluminescence for nanowires using a three-dimensional computational transient model.

PubMed

Ren, Dingkun; Scofield, Adam C; Farrell, Alan C; Rong, Zixuan; Haddad, Michael A; Laghumavarapu, Ramesh B; Liang, Baolai; Huffaker, Diana L

2018-04-26

Time-resolved photoluminescence (TRPL) has been implemented experimentally to measure the carrier lifetime of semiconductors for decades. For the characterization of nanowires, the rich information embedded in TRPL curves has not been fully interpreted and meaningfully mapped to the respective material properties. This is because their three-dimensional (3-D) geometries result in more complicated mechanisms of carrier recombination than those in thin films and analytical solutions cannot be found for those nanostructures. In this work, we extend the intrinsic power of TRPL by developing a full 3-D transient model, which accounts for different material properties and drift-diffusion, to simulate TRPL curves for nanowires. To show the capability of the model, we perform TRPL measurements on a set of GaAs nanowire arrays grown on silicon substrates and then fit the measured data by tuning various material properties, including carrier mobility, Shockley-Read-Hall recombination lifetime, and surface recombination velocity at the GaAs-Si heterointerface. From the resultant TRPL simulations, we numerically identify the lifetime characteristics of those material properties. In addition, we computationally map the spatial and temporal electron distributions in nanowire segments and reveal the underlying carrier dynamics. We believe this study provides a theoretical foundation for interpretation of TRPL measurements to unveil the complex carrier recombination mechanisms in 3-D nanostructured materials.

A Spectral Element Ocean Model on the Cray T3D: the interannual variability of the Mediterranean Sea general circulation

NASA Astrophysics Data System (ADS)

Molcard, A. J.; Pinardi, N.; Ansaloni, R.

A new numerical model, SEOM (Spectral Element Ocean Model, (Iskandarani et al, 1994)), has been implemented in the Mediterranean Sea. Spectral element methods combine the geometric flexibility of finite element techniques with the rapid convergence rate of spectral schemes. The current version solves the shallow water equations with a fifth (or sixth) order accuracy spectral scheme and about 50.000 nodes. The domain decomposition philosophy makes it possible to exploit the power of parallel machines. The original MIMD master/slave version of SEOM, written in F90 and PVM, has been ported to the Cray T3D. When critical for performance, Cray specific high-performance one-sided communication routines (SHMEM) have been adopted to fully exploit the Cray T3D interprocessor network. Tests performed with highly unstructured and irregular grid, on up to 128 processors, show an almost linear scalability even with unoptimized domain decomposition techniques. Results from various case studies on the Mediterranean Sea are shown, involving realistic coastline geometry, and monthly mean 1000mb winds from the ECMWF's atmospheric model operational analysis from the period January 1987 to December 1994. The simulation results show that variability in the wind forcing considerably affect the circulation dynamics of the Mediterranean Sea.

Parameterized code SHARM-3D for radiative transfer over inhomogeneous surfaces.

PubMed

Lyapustin, Alexei; Wang, Yujie

2005-12-10

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima-Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom.

Parameterized code SHARM-3D for radiative transfer over inhomogeneous surfaces

NASA Astrophysics Data System (ADS)

Lyapustin, Alexei; Wang, Yujie

2005-12-01

The code SHARM-3D, developed for fast and accurate simulations of the monochromatic radiance at the top of the atmosphere over spatially variable surfaces with Lambertian or anisotropic reflectance, is described. The atmosphere is assumed to be laterally uniform across the image and to consist of two layers with aerosols contained in the bottom layer. The SHARM-3D code performs simultaneous calculations for all specified incidence-view geometries and multiple wavelengths in one run. The numerical efficiency of the current version of code is close to its potential limit and is achieved by means of two innovations. The first is the development of a comprehensive precomputed lookup table of the three-dimensional atmospheric optical transfer function for various atmospheric conditions. The second is the use of a linear kernel model of the land surface bidirectional reflectance factor (BRF) in our algorithm that has led to a fully parameterized solution in terms of the surface BRF parameters. The code is also able to model inland lakes and rivers. The water pixels are described with the Nakajima-Tanaka BRF model of wind-roughened water surface with a Lambertian offset, which is designed to model approximately the reflectance of suspended matter and of a shallow lake or river bottom.

SIMULATIONS OF 2D AND 3D THERMOCAPILLARY FLOWS BY A LEAST-SQUARES FINITE ELEMENT METHOD. (R825200)

EPA Science Inventory

Numerical results for time-dependent 2D and 3D thermocapillary flows are presented in this work. The numerical algorithm is based on the Crank-Nicolson scheme for time integration, Newton's method for linearization, and a least-squares finite element method, together with a matri...

Electronic holography using binary phase modulation

NASA Astrophysics Data System (ADS)

Matoba, Osamu

2014-06-01

A 3D display system by using a phase-only distribution is presented. Especially, binary phase distribution is used to reconstruct a 3D object for wide viewing zone angle. To obtain the phase distribution to be displayed on a phase-mode spatial light modulator, both of experimental and numerical processes are available. In this paper, we present a numerical process by using a computer graphics data. A random phase distribution is attached to all polygons of an input 3D object to reconstruct a 3D object well from the binary phase distribution. Numerical and experimental results are presented to show the effectiveness of the proposed system.

Real-time 3-D space numerical shake prediction for earthquake early warning

NASA Astrophysics Data System (ADS)

Wang, Tianyun; Jin, Xing; Huang, Yandan; Wei, Yongxiang

2017-12-01

In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.

An online-coupled NWP/ACT model with conserved Lagrangian levels

NASA Astrophysics Data System (ADS)

Sørensen, B.; Kaas, E.; Lauritzen, P. H.

2012-04-01

Numerical weather and climate modelling is under constant development. Semi-implicit semi-Lagrangian (SISL) models have proven to be numerically efficient in both short-range weather forecasts and climate models, due to the ability to use long time steps. Chemical/aerosol feedback mechanism are becoming more and more relevant in NWP as well as climate models, since the biogenic and anthropogenic emissions can have a direct effect on the dynamics and radiative properties of the atmosphere. To include chemical feedback mechanisms in the NWP models, on-line coupling is crucial. In 3D semi-Lagrangian schemes with quasi-Lagrangian vertical coordinates the Lagrangian levels are remapped to Eulerian model levels each time step. This remapping introduces an undesirable tendency to smooth sharp gradients and creates unphysical numerical diffusion in the vertical distribution. A semi-Lagrangian advection method is introduced, it combines an inherently mass conserving 2D semi-Lagrangian scheme, with a SISL scheme employing both hybrid vertical coordinates and a fully Lagrangian vertical coordinate. This minimizes the vertical diffusion and thus potentially improves the simulation of the vertical profiles of moisture, clouds, and chemical constituents. Since the Lagrangian levels suffer from traditional Lagrangian limitations caused by the convergence and divergence of the flow, remappings to the Eulerian model levels are generally still required - but this need only be applied after a number of time steps - unless dynamic remapping methods are used. For this several different remapping methods has been implemented. The combined scheme is mass conserving, consistent, and multi-tracer efficient.

A hierarchy of models for simulating experimental results from a 3D heterogeneous porous medium

NASA Astrophysics Data System (ADS)

Vogler, Daniel; Ostvar, Sassan; Paustian, Rebecca; Wood, Brian D.

2018-04-01

In this work we examine the dispersion of conservative tracers (bromide and fluorescein) in an experimentally-constructed three-dimensional dual-porosity porous medium. The medium is highly heterogeneous (σY2 = 5.7), and consists of spherical, low-hydraulic-conductivity inclusions embedded in a high-hydraulic-conductivity matrix. The bimodal medium was saturated with tracers, and then flushed with tracer-free fluid while the effluent breakthrough curves were measured. The focus for this work is to examine a hierarchy of four models (in the absence of adjustable parameters) with decreasing complexity to assess their ability to accurately represent the measured breakthrough curves. The most information-rich model was (1) a direct numerical simulation of the system in which the geometry, boundary and initial conditions, and medium properties were fully independently characterized experimentally with high fidelity. The reduced-information models included; (2) a simplified numerical model identical to the fully-resolved direct numerical simulation (DNS) model, but using a domain that was one-tenth the size; (3) an upscaled mobile-immobile model that allowed for a time-dependent mass-transfer coefficient; and, (4) an upscaled mobile-immobile model that assumed a space-time constant mass-transfer coefficient. The results illustrated that all four models provided accurate representations of the experimental breakthrough curves as measured by global RMS error. The primary component of error induced in the upscaled models appeared to arise from the neglect of convection within the inclusions. We discuss the necessity to assign value (via a utility function or other similar method) to outcomes if one is to further select from among model options. Interestingly, these results suggested that the conventional convection-dispersion equation, when applied in a way that resolves the heterogeneities, yields models with high fidelity without requiring the imposition of a more complex non-Fickian model.

NOTE: An innovative phantom for quantitative and qualitative investigation of advanced x-ray imaging technologies

NASA Astrophysics Data System (ADS)

Chiarot, C. B.; Siewerdsen, J. H.; Haycocks, T.; Moseley, D. J.; Jaffray, D. A.

2005-11-01

Development, characterization, and quality assurance of advanced x-ray imaging technologies require phantoms that are quantitative and well suited to such modalities. This note reports on the design, construction, and use of an innovative phantom developed for advanced imaging technologies (e.g., multi-detector CT and the numerous applications of flat-panel detectors in dual-energy imaging, tomosynthesis, and cone-beam CT) in diagnostic and image-guided procedures. The design addresses shortcomings of existing phantoms by incorporating criteria satisfied by no other single phantom: (1) inserts are fully 3D—spherically symmetric rather than cylindrical; (2) modules are quantitative, presenting objects of known size and contrast for quality assurance and image quality investigation; (3) features are incorporated in ideal and semi-realistic (anthropomorphic) contexts; and (4) the phantom allows devices to be inserted and manipulated in an accessible module (right lung). The phantom consists of five primary modules: (1) head, featuring contrast-detail spheres approximate to brain lesions; (2) left lung, featuring contrast-detail spheres approximate to lung modules; (3) right lung, an accessible hull in which devices may be placed and manipulated; (4) liver, featuring conrast-detail spheres approximate to metastases; and (5) abdomen/pelvis, featuring simulated kidneys, colon, rectum, bladder, and prostate. The phantom represents a two-fold evolution in design philosophy—from 2D (cylindrically symmetric) to fully 3D, and from exclusively qualitative or quantitative to a design accommodating quantitative study within an anatomical context. It has proven a valuable tool in investigations throughout our institution, including low-dose CT, dual-energy radiography, and cone-beam CT for image-guided radiation therapy and surgery.

Fractally Fourier decimated homogeneous turbulent shear flow in noninteger dimensions.

PubMed

Fathali, Mani; Khoei, Saber

2017-02-01

Time evolution of the fully resolved incompressible homogeneous turbulent shear flow in noninteger Fourier dimensions is numerically investigated. The Fourier dimension of the flow field is extended from the integer value 3 to the noninteger values by projecting the Navier-Stokes equation on the fractal set of the active Fourier modes with dimensions 2.7≤d≤3.0. The results of this study revealed that the dynamics of both large and small scale structures are nontrivially influenced by changing the Fourier dimension d. While both turbulent production and dissipation are significantly hampered as d decreases, the evolution of their ratio is almost independent of the Fourier dimension. The mechanism of the energy distribution among different spatial directions is also impeded by decreasing d. Due to this deficient energy distribution, turbulent field shows a higher level of the large-scale anisotropy in lower Fourier dimensions. In addition, the persistence of the vortex stretching mechanism and the forward spectral energy transfer, which are three-dimensional turbulence characteristics, are examined at changing d, from the standard case d=3.0 to the strongly decimated flow field for d=2.7. As the Fourier dimension decreases, these forward energy transfer mechanisms are strongly suppressed, which in turn reduces both the small-scale intermittency and the deviation from Gaussianity. Besides the energy exchange intensity, the variations of d considerably modify the relative weights of local to nonlocal triadic interactions. It is found that the contribution of the nonlocal triads to the total turbulent kinetic energy exchange increases as the Fourier dimension increases.

LES-based filter-matrix lattice Boltzmann model for simulating fully developed turbulent channel flow

NASA Astrophysics Data System (ADS)

Zhuo, Congshan; Zhong, Chengwen

2016-11-01

In this paper, a three-dimensional filter-matrix lattice Boltzmann (FMLB) model based on large eddy simulation (LES) was verified for simulating wall-bounded turbulent flows. The Vreman subgrid-scale model was employed in the present FMLB-LES framework, which had been proved to be capable of predicting turbulent near-wall region accurately. The fully developed turbulent channel flows were performed at a friction Reynolds number Reτ of 180. The turbulence statistics computed from the present FMLB-LES simulations, including mean stream velocity profile, Reynolds stress profile and root-mean-square velocity fluctuations greed well with the LES results of multiple-relaxation-time (MRT) LB model, and some discrepancies in comparison with those direct numerical simulation (DNS) data of Kim et al. was also observed due to the relatively low grid resolution. Moreover, to investigate the influence of grid resolution on the present LES simulation, a DNS simulation on a finer gird was also implemented by present FMLB-D3Q19 model. Comparisons of detailed computed various turbulence statistics with available benchmark data of DNS showed quite well agreement.

Agricultural Recharge Practices for Managing Nitrate in Regional Groundwater: Time-Resolution Assessment of Numerical Modeling Approach

NASA Astrophysics Data System (ADS)

Bastani, M.; Harter, T.

2017-12-01

Intentional recharge practices in irrigated landscapes are promising options to control and remediate groundwater quality degradation with respect to nitrate. To better understand the effect of these practices, a fully 3D transient heterogeneous transport model simulation is developed using MODFLOW and MT3D. The model is developed for a long-term study of nitrate improvements in an alluvial groundwater basin in Eastern San Joaquin Valley, CA. Different scenarios of agricultural recharge strategies including crop type change and winter flood flows are investigated. Transient simulations with high spatio-temporal resolutions are performed. We then consider upscaling strategies that would allow us to simplify the modeling process such that it can be applied at a very large basin-scale (1000s of square kilometers) for scenario analysis. We specifically consider upscaling of time-variant boundary conditions (both internal and external) that have significant influence on calculation cost of the model. We compare monthly transient stresses to upscaled annual and further upscaled average steady-state stresses on nitrate transport in groundwater under recharge scenarios.

A Laminar Flow-Based Microfluidic Tesla Pump via Lithography Enabled 3D Printing

PubMed Central

Habhab, Mohammed-Baker; Ismail, Tania; Lo, Joe Fujiou

2016-01-01

Tesla turbine and its applications in power generation and fluid flow were demonstrated by Nicholas Tesla in 1913. However, its real-world implementations were limited by the difficulty to maintain laminar flow between rotor disks, transient efficiencies during rotor acceleration, and the lack of other applications that fully utilize the continuous flow outputs. All of the aforementioned limits of Tesla turbines can be addressed by scaling to the microfluidic flow regime. Demonstrated here is a microscale Tesla pump designed and fabricated using a Digital Light Processing (DLP) based 3D printer with 43 µm lateral and 30 µm thickness resolutions. The miniaturized pump is characterized by low Reynolds number of 1000 and a flow rate of up to 12.6 mL/min at 1200 rpm, unloaded. It is capable of driving a mixer network to generate microfluidic gradient. The continuous, laminar flow from Tesla turbines is well-suited to the needs of flow-sensitive microfluidics, where the integrated pump will enable numerous compact lab-on-a-chip applications. PMID:27886051

Non-thermal electron distribution functions through 3D magnetic reconnection instabilities in the solar wind

NASA Astrophysics Data System (ADS)

Alejandro Munoz Sepulveda, Patricio; Buechner, Joerg

2017-04-01

The effects of kinetic instabilities on the solar wind electron velocity distribution functions (eVDFs) are mostly well understood under local homogeneous and stationary conditions. But the solar wind also contains current sheets, which affect the local properties of instabilities, turbulence and thus the observed non-maxwellian features in the eVDFs. Those processes are vastly unexplored. Therefore, we aim to investigate the influence of self-consistently generated turbulence via electron-scale instabilities in reconnecting current sheets on the formation of suprathermal features in the eVDFs. For this sake, we carry out 3D fully-kinetic Particle-in-Cell code numerical simulations of force free current sheets with a guide magnetic field. We find extended tails, anisotropic plateaus and non-gyrotropic features in the eVDFs, correlated with the locations and time where micro-turbulence is enhanced in the current sheet due to current-aligned streaming instabilities. We also discuss the influence of the plasma parameters, such as the ion to electron temperature ratio, on the excitation of current sheet instabilities and their effect on the properties of the eVDFs.

3D visualization of solar wind ion data from the Chang'E-1 exploration

NASA Astrophysics Data System (ADS)

Zhang, Tian; Sun, Yankui; Tang, Zesheng

2011-10-01

Chang'E-1 (abbreviation CE-1), China's first Moon-orbiting spacecraft launched in 2007, carried equipment called the Solar Wind Ion Detector (abbreviation SWID), which sent back tens of gigabytes of solar wind ion differential number flux data. These data are essential for furthering our understanding of the cislunar space environment. However, to fully comprehend and analyze these data presents considerable difficulties, not only because of their huge size (57 GB), but also because of their complexity. Therefore, a new 3D visualization method is developed to give a more intuitive representation than traditional 1D and 2D visualizations, and in particular to offer a better indication of the direction of the incident ion differential number flux and the relative spatial position of CE-1 with respect to the Sun, the Earth, and the Moon. First, a coordinate system named Selenocentric Solar Ecliptic (SSE) which is more suitable for our goal is chosen, and solar wind ion differential number flux vectors in SSE are calculated from Geocentric Solar Ecliptic System (GSE) and Moon Center Coordinate (MCC) coordinates of the spacecraft, and then the ion differential number flux distribution in SSE is visualized in 3D space. This visualization method is integrated into an interactive visualization analysis software tool named vtSWIDs, developed in MATLAB, which enables researchers to browse through numerous records and manipulate the visualization results in real time. The tool also provides some useful statistical analysis functions, and can be easily expanded.

Convective Dynamics and Disequilibrium Chemistry in the Atmospheres of Giant Planets and Brown Dwarfs

NASA Astrophysics Data System (ADS)

Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

2018-02-01

Disequilibrium chemical processes significantly affect the spectra of substellar objects. To study these effects, dynamical disequilibrium has been parameterized using the quench and eddy diffusion approximations, but little work has been done to explore how these approximations perform under realistic planetary conditions in different dynamical regimes. As a first step toward addressing this problem, we study the localized, small-scale convective dynamics of planetary atmospheres by direct numerical simulation of fully compressible hydrodynamics with reactive tracers using the Dedalus code. Using polytropically stratified, plane-parallel atmospheres in 2D and 3D, we explore the quenching behavior of different abstract chemical species as a function of the dynamical conditions of the atmosphere as parameterized by the Rayleigh number. We find that in both 2D and 3D, chemical species quench deeper than would be predicted based on simple mixing-length arguments. Instead, it is necessary to employ length scales based on the chemical equilibrium profile of the reacting species in order to predict quench points and perform chemical kinetics modeling in 1D. Based on the results of our simulations, we provide a new length scale, derived from the chemical scale height, that can be used to perform these calculations. This length scale is simple to calculate from known chemical data and makes reasonable predictions for our dynamical simulations.

Convergence Acceleration of Runge-Kutta Schemes for Solving the Navier-Stokes Equations

NASA Technical Reports Server (NTRS)

Swanson, Roy C., Jr.; Turkel, Eli; Rossow, C.-C.

2007-01-01

The convergence of a Runge-Kutta (RK) scheme with multigrid is accelerated by preconditioning with a fully implicit operator. With the extended stability of the Runge-Kutta scheme, CFL numbers as high as 1000 can be used. The implicit preconditioner addresses the stiffness in the discrete equations associated with stretched meshes. This RK/implicit scheme is used as a smoother for multigrid. Fourier analysis is applied to determine damping properties. Numerical dissipation operators based on the Roe scheme, a matrix dissipation, and the CUSP scheme are considered in evaluating the RK/implicit scheme. In addition, the effect of the number of RK stages is examined. Both the numerical and computational efficiency of the scheme with the different dissipation operators are discussed. The RK/implicit scheme is used to solve the two-dimensional (2-D) and three-dimensional (3-D) compressible, Reynolds-averaged Navier-Stokes equations. Turbulent flows over an airfoil and wing at subsonic and transonic conditions are computed. The effects of the cell aspect ratio on convergence are investigated for Reynolds numbers between 5:7 x 10(exp 6) and 100 x 10(exp 6). It is demonstrated that the implicit preconditioner can reduce the computational time of a well-tuned standard RK scheme by a factor between four and ten.

Advanced numerical methods for three dimensional two-phase flow calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toumi, I.; Caruge, D.

1997-07-01

This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses anmore » extension of Roe`s method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations.« less

Direct Numerical Simulation of Turbulent Couette-Poiseuille Flow With Zero Skin Friction

NASA Technical Reports Server (NTRS)

Coleman, Gary N.; Spalart, Philippe R.

2015-01-01

The near-wall scaling of mean velocity U(yw) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to the square root of yw in the region just above the wall at which the mean shear dU=dy = 0.

A viscous flow study of shock-boundary layer interaction, radial transport, and wake development in a transonic compressor

NASA Technical Reports Server (NTRS)

Hah, Chunill; Reid, Lonnie

1991-01-01

A numerical study based on the 3D Reynolds-averaged Navier-Stokes equation has been conducted to investigate the detailed flow physics inside a transonic compressor. 3D shock structure, shock-boundary layer interaction, flow separation, radial mixing, and wake development are all investigated at design and off-design conditions. Experimental data based on laser anemometer measurements are used to assess the overall quality of the numerical solution. An additional experimental study to investigate end-wall flow with a hot-film was conducted, and these results are compared with the numerical results. Detailed comparison with experimental data indicates that the overall features of the 3D shock structure, the shock-boundary layer interaction, and the wake development are all calculated very well in the numerical solution. The numerical results are further analyzed to examine the radial mixing phenomena in the transonic compressor. A thin sheet of particles is injected in the numerical solution upstream of the compressor. The movement of particles is traced with a 3D plotting package. This numerical survey of tracer concentration reveals the fundamental mechanisms of radial transport in this transonic compressor.

A numerical method for solving the 3D unsteady incompressible Navier Stokes equations in curvilinear domains with complex immersed boundaries

NASA Astrophysics Data System (ADS)

Ge, Liang; Sotiropoulos, Fotis

2007-08-01

A novel numerical method is developed that integrates boundary-conforming grids with a sharp interface, immersed boundary methodology. The method is intended for simulating internal flows containing complex, moving immersed boundaries such as those encountered in several cardiovascular applications. The background domain (e.g. the empty aorta) is discretized efficiently with a curvilinear boundary-fitted mesh while the complex moving immersed boundary (say a prosthetic heart valve) is treated with the sharp-interface, hybrid Cartesian/immersed-boundary approach of Gilmanov and Sotiropoulos [A. Gilmanov, F. Sotiropoulos, A hybrid cartesian/immersed boundary method for simulating flows with 3d, geometrically complex, moving bodies, Journal of Computational Physics 207 (2005) 457-492.]. To facilitate the implementation of this novel modeling paradigm in complex flow simulations, an accurate and efficient numerical method is developed for solving the unsteady, incompressible Navier-Stokes equations in generalized curvilinear coordinates. The method employs a novel, fully-curvilinear staggered grid discretization approach, which does not require either the explicit evaluation of the Christoffel symbols or the discretization of all three momentum equations at cell interfaces as done in previous formulations. The equations are integrated in time using an efficient, second-order accurate fractional step methodology coupled with a Jacobian-free, Newton-Krylov solver for the momentum equations and a GMRES solver enhanced with multigrid as preconditioner for the Poisson equation. Several numerical experiments are carried out on fine computational meshes to demonstrate the accuracy and efficiency of the proposed method for standard benchmark problems as well as for unsteady, pulsatile flow through a curved, pipe bend. To demonstrate the ability of the method to simulate flows with complex, moving immersed boundaries we apply it to calculate pulsatile, physiological flow through a mechanical, bileaflet heart valve mounted in a model straight aorta with an anatomical-like triple sinus.

Three dimensional Lagrangian structures in the Antarctic Polar Vortex.

NASA Astrophysics Data System (ADS)

Mancho, Ana M.; Garcia-Garrido, Victor J.; Curbelo, Jezabel; Niang, Coumba; Mechoso, Carlos R.; Wiggins, Stephen

2017-04-01

Dynamical systems theory has supported the description of transport processes in fluid dynamics. For understanding trajectory patterns in chaotic advection the geometrical approach by Poincaré seeks for spatial structures that separate regions corresponding to qualitatively different types of trajectories. These structures have been referred to as Lagrangian Coherent Structures (LCS), which typically in geophysical flows are well described under the approach of incompressible 2D flows. Different tools have been used to visualize LCS. In this presentation we use Lagrangian Descriptors [1,2,3,4] (function M) for visualizing 3D Lagrangian structures in the atmosphere, in particular in the Antarctic Polar Vortex. The function M is computed in a fully 3D incompressible flow obtained from data provided by the European Centre for Medium-Range Weather Forecast and it is represented in 2D surfaces. We discuss the findings during the final warming that took place in the spring of 1979 [5]. This research is supported by MINECO grant MTM2014-56392-R. Support is acknowledged also from CSIC grant COOPB20265, U.S. NSF grant AGS-1245069 and ONR grant No. N00014- 01-1-0769. C. Niang acknowledges Fundacion Mujeres por Africa and ICMAT Severo Ochoa project SEV-2011-0087 for financial support. [1] C. Mendoza, A. M. Mancho. The hidden geometry of ocean flows. Physical Review Letters 105 (2010), 3, 038501-1-038501-4. [2] A. M. Mancho, S. Wiggins, J. Curbelo, C. Mendoza. Lagrangian Descriptors: A Method for Revealing Phase Space Structures of General Time Dependent Dynamical Systems. Communications in Nonlinear Science and Numerical Simulation. 18 (2013) 3530-3557. [3] C. Lopesino, F. Balibrea-Iniesta, S. Wiggins and A. M. Mancho. Lagrangian descriptors for two dimensional, area preserving autonomous and nonautonomous maps. Communications in Nonlinear Science and Numerical Simulations, 27 (2015) (1-3), 40-51. [4] C. Lopesino, F. Balibrea-Iniesta, V. J. García-Garrido, S. Wiggins, and A. M. Mancho, A. M. A theoretical framework for lagrangian descriptors. International Journal of Bifurcation and Chaos (2017) to appear. [5] The three-dimensional Lagrangian geometry of the Antarctic Polar Vortex circulation. Preprint.

Landslide Spreading, Impulse Water Waves and Modelling of the Vajont Rockslide

NASA Astrophysics Data System (ADS)

Crosta, Giovanni B.; Imposimato, Silvia; Roddeman, Dennis

2016-06-01

Landslides can occur in different environments and can interact with or fall into water reservoirs or open sea with different characteristics. The subaerial evolution and the transition from subaerial to subaqueous conditions can strongly control the landslide evolution and the generated impulse waves, and consequently the final hazard zonation. We intend to model the landslide spreading, the impact with the water surface and the generation of the impulse wave under different 2D and 3D conditions and settings. We verify the capabilities of a fully 2D and 3D FEM ALE approach to model and analyse near-field evolution. To this aim we validate the code against 2D laboratory experiments for different Froude number conditions (Fr = 1.4, 3.2). Then the Vajont rockslide (Fr = 0.26-0.75) and the consequent impulse wave are simulated in 2D and 3D. The sliding mass is simulated as an elasto-plastic Mohr-Coulomb material and the lake water as a fully inviscid low compressibility fluid. The rockslide model is validated against field observations, including the total duration, the profile and internal geometry of the final deposit, the maximum water run-up on the opposite valley flank and on the rockslide mass. 2D models are presented for both the case of a dry valley and that of the impounded lake. The set of fully 3D simulations are the first ones available and considering the rockslide evolution, propagation and interaction with the water reservoir. Advantages and disadvantages of the modelling approach are discussed.

Generating 3D and 3D-like animations of strongly uneven surface microareas of bloodstains from small series of partially out-of-focus digital SEM micrographs.

PubMed

Hortolà, Policarp

2010-01-01

When dealing with microscopic still images of some kinds of samples, the out-of-focus problem represents a particularly serious limiting factor for the subsequent generation of fully sharp 3D animations. In order to produce fully-focused 3D animations of strongly uneven surface microareas, a vertical stack of six digital secondary-electron SEM micrographs of a human bloodstain microarea was acquired. Afterwards, single combined images were generated using a macrophotography and light microscope image post-processing software. Subsequently, 3D animations of texture and topography were obtained in different formats using a combination of software tools. Finally, a 3D-like animation of a texture-topography composite was obtained in different formats using another combination of software tools. By one hand, results indicate that the use of image post-processing software not concerned primarily with electron micrographs allows to obtain, in an easy way, fully-focused images of strongly uneven surface microareas of bloodstains from small series of partially out-of-focus digital SEM micrographs. On the other hand, results also indicate that such small series of electron micrographs can be utilized for generating 3D and 3D-like animations that can subsequently be converted into different formats, by using certain user-friendly software facilities not originally designed for use in SEM, that are easily available from Internet. Although the focus of this study was on bloodstains, the methods used in it well probably are also of relevance for studying the surface microstructures of other organic or inorganic materials whose sharp displaying is difficult of obtaining from a single SEM micrograph.

3D modeling based on CityEngine

NASA Astrophysics Data System (ADS)

Jia, Guangyin; Liao, Kaiju

2017-03-01

Currently, there are many 3D modeling softwares, like 3DMAX, AUTOCAD, and more populous BIM softwares represented by REVIT. CityEngine modeling software introduced in this paper can fully utilize the existing GIS data and combine other built models to make 3D modeling on internal and external part of buildings in a rapid and batch manner, so as to improve the 3D modeling efficiency.

Numerical Study on the Tensile Behavior of 3D Four Directional Cylindrical Braided Composite Shafts

NASA Astrophysics Data System (ADS)

Zhao, Guoqi; Wang, Jiayi; Hao, Wenfeng; Liu, Yinghua; Luo, Ying

2017-10-01

The tensile behavior of 3D four directional cylindrical braided composite shafts was analyzed with the numerical method. The unit cell models for the 3D four directional cylindrical braided composite shafts with various braiding angles were constructed with ABAQUS. Hashin's failure criterion was used to analyze the tensile strength and the damage evolution of the unit cells. The influence of the braiding angle on the tensile behavior of the 3D four directional cylindrical braided composite shafts was analyzed. The numerical results showed that the tensile strength along the braiding direction increased as the braiding angle decreased. These results should play an integral role in the design of braiding composites shafts.

Positive contrast of SPIO-labeled cells by off-resonant reconstruction of 3D radial half-echo bSSFP.

PubMed

Diwoky, Clemens; Liebmann, Daniel; Neumayer, Bernhard; Reinisch, Andreas; Knoll, Florian; Strunk, Dirk; Stollberger, Rudolf

2015-01-01

This article describes a new acquisition and reconstruction concept for positive contrast imaging of cells labeled with superparamagnetic iron oxides (SPIOs). Overcoming the limitations of a negative contrast representation as gained with gradient echo and fully balanced steady state (bSSFP), the proposed method delivers a spatially localized contrast with high cellular sensitivity not accomplished by other positive contrast methods. Employing a 3D radial bSSFP pulse sequence with half-echo sampling, positive cellular contrast is gained by adding artificial global frequency offsets to each half-echo before image reconstruction. The new contrast regime is highlighted with numerical intravoxel simulations including the point-spread function for 3D half-echo acquisitions. Furthermore, the new method is validated on the basis of in vitro cell phantom measurements on a clinical MRI platform, where the measured contrast-to-noise ratio (CNR) of the new approach exceeds even the negative contrast of bSSFP. Finally, an in vivo proof of principle study based on a mouse model with a clear depiction of labeled cells within a subcutaneous cell islet containing a cell density as low as 7 cells/mm(3) is presented. The resultant isotropic images show robustness to motion and a high CNR, in addition to an enhanced specificity due to the positive contrast of SPIO-labeled cells. Copyright © 2014 John Wiley & Sons, Ltd.

The InterFrost benchmark of Thermo-Hydraulic codes for cold regions hydrology - first inter-comparison results

NASA Astrophysics Data System (ADS)

Grenier, Christophe; Roux, Nicolas; Anbergen, Hauke; Collier, Nathaniel; Costard, Francois; Ferrry, Michel; Frampton, Andrew; Frederick, Jennifer; Holmen, Johan; Jost, Anne; Kokh, Samuel; Kurylyk, Barret; McKenzie, Jeffrey; Molson, John; Orgogozo, Laurent; Rivière, Agnès; Rühaak, Wolfram; Selroos, Jan-Olof; Therrien, René; Vidstrand, Patrik

2015-04-01

The impacts of climate change in boreal regions has received considerable attention recently due to the warming trends that have been experienced in recent decades and are expected to intensify in the future. Large portions of these regions, corresponding to permafrost areas, are covered by water bodies (lakes, rivers) that interact with the surrounding permafrost. For example, the thermal state of the surrounding soil influences the energy and water budget of the surface water bodies. Also, these water bodies generate taliks (unfrozen zones below) that disturb the thermal regimes of permafrost and may play a key role in the context of climate change. Recent field studies and modeling exercises indicate that a fully coupled 2D or 3D Thermo-Hydraulic (TH) approach is required to understand and model the past and future evolution of landscapes, rivers, lakes and associated groundwater systems in a changing climate. However, there is presently a paucity of 3D numerical studies of permafrost thaw and associated hydrological changes, and the lack of study can be partly attributed to the difficulty in verifying multi-dimensional results produced by numerical models. Numerical approaches can only be validated against analytical solutions for a purely thermic 1D equation with phase change (e.g. Neumann, Lunardini). When it comes to the coupled TH system (coupling two highly non-linear equations), the only possible approach is to compare the results from different codes to provided test cases and/or to have controlled experiments for validation. Such inter-code comparisons can propel discussions to try to improve code performances. A benchmark exercise was initialized in 2014 with a kick-off meeting in Paris in November. Participants from USA, Canada, Germany, Sweden and France convened, representing altogether 13 simulation codes. The benchmark exercises consist of several test cases inspired by existing literature (e.g. McKenzie et al., 2007) as well as new ones. They range from simpler, purely thermal cases (benchmark T1) to more complex, coupled 2D TH cases (benchmarks TH1, TH2, and TH3). Some experimental cases conducted in cold room complement the validation approach. A web site hosted by LSCE (Laboratoire des Sciences du Climat et de l'Environnement) is an interaction platform for the participants and hosts the test cases database at the following address: https://wiki.lsce.ipsl.fr/interfrost. The results of the first stage of the benchmark exercise will be presented. We will mainly focus on the inter-comparison of participant results for the coupled cases (TH1, TH2 & TH3). Further perspectives of the exercise will also be presented. Extensions to more complex physical conditions (e.g. unsaturated conditions and geometrical deformations) are contemplated. In addition, 1D vertical cases of interest to the Climate Modeling community will be proposed. Keywords: Permafrost; Numerical modeling; River-soil interaction; Arctic systems; soil freeze-thaw

Numerical Investigation of T-joints with 3D Four Directional Braided Composite Fillers Under Tensile Loading

NASA Astrophysics Data System (ADS)

Li, Xiao-kang; Liu, Zhen-guo; Hu, Long; Wang, Yi-bo; Lei, Bing; Huang, Xiang

2017-02-01

Numerical studied on T-joints with three-dimensional four directional (3D4D) braided composite fillers was presented in this article. Compared with conventional unidirectional prepreg fillers, the 3D braided composite fillers have excellent ability to prevent crack from penetrating trigone fillers, which constantly occurred in the conventional fillers. Meanwhile, the 3D braided composite fillers had higher fiber volume fraction and eliminated the fiber folding problem in unidirectional prepreg fillers. The braiding technology and mechanical performance of 3D4D braided fillers were studied. The numerical model of carbon fiber T-joints with 3D4D braided composite fillers was built by finite element analysis software. The damage formation, extension and failing process of T-joints with 3D4D braided fillers under tensile load were investigated. Further investigation was extended to the effect of 3D4D braided fillers with different braiding angles on mechanical behavior of the T-joints. The study results revealed that the filling area was the weakest part of the T-joints where the damage first appeared and the crack then rapidly spread to the glue film around the filling area and the interface between over-laminate and soleplate. The 3D4D braided fillers were undamaged and the braiding angle change induced a little effect on the bearing capacity of T-joints.

Simulation of dilute polymeric fluids in a three-dimensional contraction using a multiscale FENE model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griebel, M., E-mail: griebel@ins.uni-bonn.de, E-mail: ruettgers@ins.uni-bonn.de; Rüttgers, A., E-mail: griebel@ins.uni-bonn.de, E-mail: ruettgers@ins.uni-bonn.de

The multiscale FENE model is applied to a 3D square-square contraction flow problem. For this purpose, the stochastic Brownian configuration field method (BCF) has been coupled with our fully parallelized three-dimensional Navier-Stokes solver NaSt3DGPF. The robustness of the BCF method enables the numerical simulation of high Deborah number flows for which most macroscopic methods suffer from stability issues. The results of our simulations are compared with that of experimental measurements from literature and show a very good agreement. In particular, flow phenomena such as a strong vortex enhancement, streamline divergence and a flow inversion for highly elastic flows are reproduced.more » Due to their computational complexity, our simulations require massively parallel computations. Using a domain decomposition approach with MPI, the implementation achieves excellent scale-up results for up to 128 processors.« less

COLLABORATIVE RESEARCH AND DEVELOPMENT (CR&D) Delivery Order 0043: Deformation and Texture Development During Hot Working of Titanium

DTIC Science & Technology

2008-04-01

Hot Working of Titanium 5a. CONTRACT NUMBER F33615-03-D-5801-0043 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 61202F 6 . AUTHOR(S) A.A...micrographs and thus to correlate microstructural features and texture data [3- 6 ]. For instance, Germain, et al. [3, 4 ] linked local orientations...microstructures can be developed in alpha/beta titanium alloys by TMP [2- 4 ], namely, fully lamellar, fully equiaxed, and duplex (bi-modal). A mixture

A Parallel Numerical Algorithm To Solve Linear Systems Of Equations Emerging From 3D Radiative Transfer

NASA Astrophysics Data System (ADS)

Wichert, Viktoria; Arkenberg, Mario; Hauschildt, Peter H.

2016-10-01

Highly resolved state-of-the-art 3D atmosphere simulations will remain computationally extremely expensive for years to come. In addition to the need for more computing power, rethinking coding practices is necessary. We take a dual approach by introducing especially adapted, parallel numerical methods and correspondingly parallelizing critical code passages. In the following, we present our respective work on PHOENIX/3D. With new parallel numerical algorithms, there is a big opportunity for improvement when iteratively solving the system of equations emerging from the operator splitting of the radiative transfer equation J = ΛS. The narrow-banded approximate Λ-operator Λ* , which is used in PHOENIX/3D, occurs in each iteration step. By implementing a numerical algorithm which takes advantage of its characteristic traits, the parallel code's efficiency is further increased and a speed-up in computational time can be achieved.

Towards dense volumetric pancreas segmentation in CT using 3D fully convolutional networks

NASA Astrophysics Data System (ADS)

Roth, Holger; Oda, Masahiro; Shimizu, Natsuki; Oda, Hirohisa; Hayashi, Yuichiro; Kitasaka, Takayuki; Fujiwara, Michitaka; Misawa, Kazunari; Mori, Kensaku

2018-03-01

Pancreas segmentation in computed tomography imaging has been historically difficult for automated methods because of the large shape and size variations between patients. In this work, we describe a custom-build 3D fully convolutional network (FCN) that can process a 3D image including the whole pancreas and produce an automatic segmentation. We investigate two variations of the 3D FCN architecture; one with concatenation and one with summation skip connections to the decoder part of the network. We evaluate our methods on a dataset from a clinical trial with gastric cancer patients, including 147 contrast enhanced abdominal CT scans acquired in the portal venous phase. Using the summation architecture, we achieve an average Dice score of 89.7 +/- 3.8 (range [79.8, 94.8])% in testing, achieving the new state-of-the-art performance in pancreas segmentation on this dataset.

Toward the holistic, reference, and extendable atlas of the human brain, head, and neck.

PubMed

Nowinski, Wieslaw L

2015-06-01

Despite numerous efforts, a fairly complete (holistic) anatomical model of the whole, normal, adult human brain, which is required as the reference in brain studies and clinical applications, has not yet been constructed. Our ultimate objective is to build this kind of atlas from advanced in vivo imaging. This work presents the taxonomy of our currently developed brain atlases and addresses the design, content, functionality, and current results in the holistic atlas development as well as atlas usefulness and future directions. We have developed to date 35 commercial brain atlases (along with numerous research prototypes), licensed to 63 companies and institutions, and made available to medical societies, organizations, medical schools, and individuals. These atlases have been applied in education, research, and clinical applications. Hundreds of thousands of patients have been treated by using our atlases. Based on this experience, the first version of the holistic and reference atlas of the brain, head, and neck has been developed and made available. The atlas has been created from multispectral 3 and 7 Tesla and high-resolution CT in vivo scans. It is fully 3D, scalable, interactive, and highly detailed with about 3,000 labeled components. This atlas forms a foundation for the development of a multi-level molecular, cellular, anatomical, physiological, and behavioral brain atlas platform.

3D model assisted fully automated scanning laser Doppler vibrometer measurements

NASA Astrophysics Data System (ADS)

Sels, Seppe; Ribbens, Bart; Bogaerts, Boris; Peeters, Jeroen; Vanlanduit, Steve

2017-12-01

In this paper, a new fully automated scanning laser Doppler vibrometer (LDV) measurement technique is presented. In contrast to existing scanning LDV techniques which use a 2D camera for the manual selection of sample points, we use a 3D Time-of-Flight camera in combination with a CAD file of the test object to automatically obtain measurements at pre-defined locations. The proposed procedure allows users to test prototypes in a shorter time because physical measurement locations are determined without user interaction. Another benefit from this methodology is that it incorporates automatic mapping between a CAD model and the vibration measurements. This mapping can be used to visualize measurements directly on a 3D CAD model. The proposed method is illustrated with vibration measurements of an unmanned aerial vehicle

Effects of compressibility on turbulent relative particle dispersion

NASA Astrophysics Data System (ADS)

Shivamoggi, Bhimsen K.

2016-08-01

In this paper, phenomenological developments are used to explore the effects of compressibility on the relative particle dispersion (RPD) in three-dimensional (3D) fully developed turbulence (FDT). The role played by the compressible FDT cascade physics underlying this process is investigated. Compressibility effects are found to lead to reduction of RPD, development of the ballistic regime and particle clustering, corroborating the laboratory experiment and numerical simulation results (Cressman J. R. et al., New J. Phys., 6 (2004) 53) on the motion of Lagrangian tracers on a surface flow that constitutes a 2D compressible subsystem. These formulations are developed from the scaling relations for compressible FDT and are validated further via an alternative dimensional/scaling development for compressible FDT similar to the one given for incompressible FDT by Batchelor and Townsend (Surveys in Mechanics (Cambridge University Press) 1956, p. 352). The rationale for spatial intermittency effects is legitimized via the nonlinear scaling dependence of RPD on the kinetic-energy dissipation rate.

Magneto-thermo-elastokinetics of Geometrically Nonlinear Laminated Composite Plates. Part 1: Foundation of the Theory

NASA Technical Reports Server (NTRS)

Hasanyan, Davresh; Librescu, Liviu; Qin, Zhanming; Ambur, Damodar R.

2006-01-01

A fully coupled magneto-thermo-elastokinetic model of laminated composite, finitely electroconductive plates incorporating geometrical nonlinearities and subjected to a combination of magnetic and thermal fields, as well as carrying an electrical current is developed, In this context. the first-order transversely shearable plate theory in conjunction with von-Karman geometrically nonlinear strain concept is adopted. Related to the distribution of electric and magnetic field disturbances within the plate, the assumptions proposed by Ambartsumyan and his collaborators are adopted. Based on the electromagnetic equations (i.e. the ones by Faraday, Ampere, Ohm, Maxwell and Lorentz), the modified Fourier's law of heat conduction and on the elastokinetic field equations, the 3-D coupled problem is reduced to an equivalent 2- D one. The theory developed herein provides a foundation for the investigation, both analytical and numerical, of the interacting effects among the magnetic, thermal and elastic fields in multi-layered thin plates made of anisotropic materials.

BISON Theory Manual The Equations behind Nuclear Fuel Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hales, J. D.; Williamson, R. L.; Novascone, S. R.

2016-09-01

BISON is a finite element-based nuclear fuel performance code applicable to a variety of fuel forms including light water reactor fuel rods, TRISO particle fuel, and metallic rod and plate fuel. It solves the fully-coupled equations of thermomechanics and species diffusion, for either 2D axisymmetric or 3D geometries. Fuel models are included to describe temperature and burnup dependent thermal properties, fission product swelling, densification, thermal and irradiation creep, fracture, and fission gas production and release. Plasticity, irradiation growth, and thermal and irradiation creep models are implemented for clad materials. Models are also available to simulate gap heat transfer, mechanical contact,more » and the evolution of the gap/plenum pressure with plenum volume, gas temperature, and fission gas addition. BISON is based on the MOOSE framework and can therefore efficiently solve problems using standard workstations or very large high-performance computers. This document describes the theoretical and numerical foundations of BISON.« less

Fast implementations of reconstruction-based scatter compensation in fully 3D SPECT image reconstruction

NASA Astrophysics Data System (ADS)

Kadrmas, Dan J.; Frey, Eric C.; Karimi, Seemeen S.; Tsui, Benjamin M. W.

1998-04-01

Accurate scatter compensation in SPECT can be performed by modelling the scatter response function during the reconstruction process. This method is called reconstruction-based scatter compensation (RBSC). It has been shown that RBSC has a number of advantages over other methods of compensating for scatter, but using RBSC for fully 3D compensation has resulted in prohibitively long reconstruction times. In this work we propose two new methods that can be used in conjunction with existing methods to achieve marked reductions in RBSC reconstruction times. The first method, coarse-grid scatter modelling, significantly accelerates the scatter model by exploiting the fact that scatter is dominated by low-frequency information. The second method, intermittent RBSC, further accelerates the reconstruction process by limiting the number of iterations during which scatter is modelled. The fast implementations were evaluated using a Monte Carlo simulated experiment of the 3D MCAT phantom with tracer, and also using experimentally acquired data with tracer. Results indicated that these fast methods can reconstruct, with fully 3D compensation, images very similar to those obtained using standard RBSC methods, and in reconstruction times that are an order of magnitude shorter. Using these methods, fully 3D iterative reconstruction with RBSC can be performed well within the realm of clinically realistic times (under 10 minutes for image reconstruction).

EPE analysis of sub-N10 BEoL flow with and without fully self-aligned via using Coventor SEMulator3D

NASA Astrophysics Data System (ADS)

Franke, Joern-Holger; Gallagher, Matt; Murdoch, Gayle; Halder, Sandip; Juncker, Aurelie; Clark, William

2017-03-01

During the last few decades, the semiconductor industry has been able to scale device performance up while driving costs down. What started off as simple geometrical scaling, driven mostly by advances in lithography, has recently been accompanied by advances in processing techniques and in device architectures. The trend to combine efforts using process technology and lithography is expected to intensify, as further scaling becomes ever more difficult. One promising component of future nodes are "scaling boosters", i.e. processing techniques that enable further scaling. An indispensable component in developing these ever more complex processing techniques is semiconductor process modeling software. Visualization of complex 3D structures in SEMulator3D, along with budget analysis on film thicknesses, CD and etch budgets, allow process integrators to compare flows before any physical wafers are run. Hundreds of "virtual" wafers allow comparison of different processing approaches, along with EUV or DUV patterning options for defined layers and different overlay schemes. This "virtual fabrication" technology produces massively parallel process variation studies that would be highly time-consuming or expensive in experiment. Here, we focus on one particular scaling booster, the fully self-aligned via (FSAV). We compare metal-via-metal (mevia-me) chains with self-aligned and fully-self-aligned via's using a calibrated model for imec's N7 BEoL flow. To model overall variability, 3D Monte Carlo modeling of as many variability sources as possible is critical. We use Coventor SEMulator3D to extract minimum me-me distances and contact areas and show how fully self-aligned vias allow a better me-via distance control and tighter via-me contact area variability compared with the standard self-aligned via (SAV) approach.

Autocorrelation exponent of conserved spin systems in the scaling regime following a critical quench.

PubMed

Sire, Clément

2004-09-24

We study the autocorrelation function of a conserved spin system following a quench at the critical temperature. Defining the correlation length L(t) approximately t(1/z), we find that for times t' and t satisfying L(t')infinity limit, we show that lambda(')(c)=d+2 and phi=z/2. We give a heuristic argument suggesting that this result is, in fact, valid for any dimension d and spin vector dimension n. We present numerical simulations for the conserved Ising model in d=1 and d=2, which are fully consistent with the present theory.

Use of natural user interfaces in water simulations

NASA Astrophysics Data System (ADS)

Donchyts, G.; Baart, F.; van Dam, A.; Jagers, B.

2013-12-01

Conventional graphical user interfaces, used to edit input and present results of earth science models, have seen little innovation for the past two decades. In most cases model data is presented and edited using 2D projections even when working with 3D data. The emergence of 3D motion sensing technologies, such as Microsoft Kinect and LEAP Motion, opens new possibilities for user interaction by adding more degrees of freedom compared to a classical way using mouse and keyboard. Here we investigate how interaction with hydrodynamic numerical models can be improved using these new technologies. Our research hypothesis (H1) states that properly designed 3D graphical user interface paired with the 3D motion sensor can significantly reduce the time required to setup and use numerical models. In this work we have used a LEAP motion controller combined with a shallow water flow model engine D-Flow Flexible Mesh. Interacting with numerical model using hands

A novel fully-humanised 3D skin equivalent to model early melanoma invasion

PubMed Central

Hill, David S; Robinson, Neil D P; Caley, Matthew P; Chen, Mei; O’Toole, Edel A; Armstrong, Jane L; Przyborski, Stefan; Lovat, Penny E

2015-01-01

Metastatic melanoma remains incurable, emphasising the acute need for improved research models to investigate the underlying biological mechanisms mediating tumour invasion and metastasis, and to develop more effective targeted therapies to improve clinical outcome. Available animal models of melanoma do not accurately reflect human disease and current in vitro human skin equivalent models incorporating melanoma cells are not fully representative of the human skin microenvironment. We have developed a robust and reproducible, fully-humanised 3D skin equivalent comprising a stratified, terminally differentiated epidermis and a dermal compartment consisting of fibroblast-generated extracellular matrix. Melanoma cells incorporated into the epidermis were able to invade through the basement membrane and into the dermis, mirroring early tumour invasion in vivo. Comparison of our novel 3D melanoma skin equivalent with melanoma in situ and metastatic melanoma indicates this model accurately recreates features of disease pathology, making it a physiologically representative model of early radial and vertical growth phase melanoma invasion. PMID:26330548

A Quantitative Evaluation of SCEC Community Velocity Model Version 3.0

NASA Astrophysics Data System (ADS)

Chen, P.; Zhao, L.; Jordan, T. H.

2003-12-01

We present a systematic methodology for evaluating and improving 3D seismic velocity models using broadband waveform data from regional earthquakes. The operator that maps a synthetic waveform into an observed waveform is expressed in the Rytov form D(ω ) = {exp}[{i} ω δ τ {p}(ω ) - ω δ τ {q}(ω )]. We measure the phase delay time δ τ p(ω ) and the amplitude reduction time δ τ q(ω ) as a function of frequency ω using Gee & Jordan's [1992] isolation-filter technique, and we correct the data for frequency-dependent interference and frequency-independent source statics. We have applied this procedure to a set of small events in Southern California. Synthetic seismograms were computed using three types of velocity models: the 1D Standard Southern California Crustal Model (SoCaL) [Dreger & Helmberger, 1993], the 3D SCEC Community Velocity Model, Version 3.0 (CVM3.0) [Magistrale et al., 2000], and a set of path-averaged 1D models (A1D) extracted from CVM3.0 by horizontally averaging wave slownesses along source-receiver paths. The 3D synthetics were computed using K. Olsen's finite difference code. More than 1000 measurements were made on both P and S waveforms at frequencies ranging from 0.2 to 1 Hz. Overall, the 3D model provided a substantially better fit to the waveform data than either laterally homogeneous or path-dependent 1D models. Relative to SoCaL, CVM3.0 provided a variance reduction of about 64% in δ τ p, and 41% in δ τ q. Relative to A1D, the variance reduction is about 46% and 20%, respectively. The same set of measurements can be employed to invert for both seismic source properties and seismic velocity structures. Fully numerical methods are being developed to compute the Fréchet kernels for these measurements [L. Zhao et. al., this meeting]. This methodology thus provides a unified framework for regional studies of seismic sources and Earth structure in Southern California and elsewhere.

Unconventional pairing symmetry of interacting Dirac fermions on a π -flux lattice

NASA Astrophysics Data System (ADS)

Guo, Huaiming; Khatami, Ehsan; Wang, Yao; Devereaux, Thomas P.; Singh, Rajiv R. P.; Scalettar, Richard T.

2018-04-01

The pairing symmetry of interacting Dirac fermions on the π -flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s*- (i.e., extended s -) and d -wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional d s* -wave phase consisting of alternating stripes of s*- and d -wave phases. A complementary mean-field analysis shows that while the s*- and d -wave symmetries individually have nodes in the energy spectrum, the d s* channel is fully gapped. The results represent a new realization of pairing in Dirac systems, connected to the problem of chiral d -wave pairing on the honeycomb lattice, which might be more readily accessed by cold-atom experiments.

A Thermo-Hydro-Mechanical coupled Numerical modeling of Injection-induced seismicity on a pre-existing fault

NASA Astrophysics Data System (ADS)

Kim, Jongchan; Archer, Rosalind

2017-04-01

In terms of energy development (oil, gas and geothermal field) and environmental improvement (carbon dioxide sequestration), fluid injection into subsurface has been dramatically increased. As a side effect of these operations, a number of injection-induced seismic activities have also significantly risen. It is known that the main causes of induced seismicity are changes in local shear and normal stresses and pore pressure as well. This mechanism leads to increase in the probability of earthquake occurrence on permeable pre-existing fault zones predominantly. In this 2D fully coupled THM geothermal reservoir numerical simulation of injection-induced seismicity, we investigate the thermal, hydraulic and mechanical behavior of the fracture zone, considering a variety of 1) fault permeability, 2) injection rate and 3) injection temperature to identify major contributing parameters to induced seismic activity. We also calculate spatiotemporal variation of the Coulomb stress which is a combination of shear stress, normal stress and pore pressure and lastly forecast the seismicity rate on the fault zone by computing the seismic prediction model of Dieterich (1994).

Numerical solutions of Navier-Stokes equations for compressible turbulent two/three dimensional flows in terminal shock region of an inlet/diffuser

NASA Technical Reports Server (NTRS)

Liu, N. S.; Shamroth, S. J.; Mcdonald, H.

1983-01-01

The multidimensional ensemble averaged compressible time dependent Navier Stokes equations in conjunction with mixing length turbulence model and shock capturing technique were used to study the terminal shock type of flows in various flight regimes occurring in a diffuser/inlet model. The numerical scheme for solving the governing equations is based on a linearized block implicit approach and the following high Reynolds number calculations were carried out: (1) 2 D, steady, subsonic; (2) 2 D, steady, transonic with normal shock; (3) 2 D, steady, supersonic with terminal shock; (4) 2 D, transient process of shock development and (5) 3 D, steady, transonic with normal shock. The numerical results obtained for the 2 D and 3 D transonic shocked flows were compared with corresponding experimental data; the calculated wall static pressure distributions agree well with the measured data.

A hybrid experimental-numerical technique for determining 3D velocity fields from planar 2D PIV data

NASA Astrophysics Data System (ADS)

Eden, A.; Sigurdson, M.; Mezić, I.; Meinhart, C. D.

2016-09-01

Knowledge of 3D, three component velocity fields is central to the understanding and development of effective microfluidic devices for lab-on-chip mixing applications. In this paper we present a hybrid experimental-numerical method for the generation of 3D flow information from 2D particle image velocimetry (PIV) experimental data and finite element simulations of an alternating current electrothermal (ACET) micromixer. A numerical least-squares optimization algorithm is applied to a theory-based 3D multiphysics simulation in conjunction with 2D PIV data to generate an improved estimation of the steady state velocity field. This 3D velocity field can be used to assess mixing phenomena more accurately than would be possible through simulation alone. Our technique can also be used to estimate uncertain quantities in experimental situations by fitting the gathered field data to a simulated physical model. The optimization algorithm reduced the root-mean-squared difference between the experimental and simulated velocity fields in the target region by more than a factor of 4, resulting in an average error less than 12% of the average velocity magnitude.

Fourier rebinning and consistency equations for time-of-flight PET planograms

PubMed Central

Li, Yusheng; Defrise, Michel; Matej, Samuel; Metzler, Scott D

2016-01-01

Due to the unique geometry, dual-panel PET scanners have many advantages in dedicated breast imaging and on-board imaging applications since the compact scanners can be combined with other imaging and treatment modalities. The major challenges of dual-panel PET imaging are the limited-angle problem and data truncation, which can cause artifacts due to incomplete data sampling. The time-of-flight (TOF) information can be a promising solution to reduce these artifacts. The TOF planogram is the native data format for dual-panel TOF PET scanners, and the non-TOF planogram is the 3D extension of linogram. The TOF planograms is five-dimensional while the objects are three-dimensional, and there are two degrees of redundancy. In this paper, we derive consistency equations and Fourier-based rebinning algorithms to provide a complete understanding of the rich structure of the fully 3D TOF planograms. We first derive two consistency equations and John's equation for 3D TOF planograms. By taking the Fourier transforms, we obtain two Fourier consistency equations and the Fourier-John equation, which are the duals of the consistency equations and John's equation, respectively. We then solve the Fourier consistency equations and Fourier-John equation using the method of characteristics. The two degrees of entangled redundancy of the 3D TOF data can be explicitly elicited and exploited by the solutions along the characteristic curves. As the special cases of the general solutions, we obtain Fourier rebinning and consistency equations (FORCEs), and thus we obtain a complete scheme to convert among different types of PET planograms: 3D TOF, 3D non-TOF, 2D TOF and 2D non-TOF planograms. The FORCEs can be used as Fourier-based rebinning algorithms for TOF-PET data reduction, inverse rebinnings for designing fast projectors, or consistency conditions for estimating missing data. As a byproduct, we show the two consistency equations are necessary and sufficient for 3D TOF planograms. Finally, we give numerical examples of implementation of a fast 2D TOF planogram projector and Fourier-based rebinning for a 2D TOF planograms using the FORCEs to show the efficacy of the Fourier-based solutions. PMID:28255191

Fourier rebinning and consistency equations for time-of-flight PET planograms.

PubMed

Li, Yusheng; Defrise, Michel; Matej, Samuel; Metzler, Scott D

2016-01-01

Due to the unique geometry, dual-panel PET scanners have many advantages in dedicated breast imaging and on-board imaging applications since the compact scanners can be combined with other imaging and treatment modalities. The major challenges of dual-panel PET imaging are the limited-angle problem and data truncation, which can cause artifacts due to incomplete data sampling. The time-of-flight (TOF) information can be a promising solution to reduce these artifacts. The TOF planogram is the native data format for dual-panel TOF PET scanners, and the non-TOF planogram is the 3D extension of linogram. The TOF planograms is five-dimensional while the objects are three-dimensional, and there are two degrees of redundancy. In this paper, we derive consistency equations and Fourier-based rebinning algorithms to provide a complete understanding of the rich structure of the fully 3D TOF planograms. We first derive two consistency equations and John's equation for 3D TOF planograms. By taking the Fourier transforms, we obtain two Fourier consistency equations and the Fourier-John equation, which are the duals of the consistency equations and John's equation, respectively. We then solve the Fourier consistency equations and Fourier-John equation using the method of characteristics. The two degrees of entangled redundancy of the 3D TOF data can be explicitly elicited and exploited by the solutions along the characteristic curves. As the special cases of the general solutions, we obtain Fourier rebinning and consistency equations (FORCEs), and thus we obtain a complete scheme to convert among different types of PET planograms: 3D TOF, 3D non-TOF, 2D TOF and 2D non-TOF planograms. The FORCEs can be used as Fourier-based rebinning algorithms for TOF-PET data reduction, inverse rebinnings for designing fast projectors, or consistency conditions for estimating missing data. As a byproduct, we show the two consistency equations are necessary and sufficient for 3D TOF planograms. Finally, we give numerical examples of implementation of a fast 2D TOF planogram projector and Fourier-based rebinning for a 2D TOF planograms using the FORCEs to show the efficacy of the Fourier-based solutions.

Effects of the approximations of light propagation on quantitative photoacoustic tomography using two-dimensional photon diffusion equation and linearization

NASA Astrophysics Data System (ADS)

Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya

2017-12-01

Quantitative photoacoustic tomography (QPAT) employing a light propagation model will play an important role in medical diagnoses by quantifying the concentration of hemoglobin or a contrast agent. However, QPAT by the light propagation model with the three-dimensional (3D) radiative transfer equation (RTE) requires a huge computational load in the iterative forward calculations involved in the updating process to reconstruct the absorption coefficient. The approximations of the light propagation improve the efficiency of the image reconstruction for the QPAT. In this study, we compared the 3D/two-dimensional (2D) photon diffusion equation (PDE) approximating 3D RTE with the Monte Carlo simulation based on 3D RTE. Then, the errors in a 2D PDE-based linearized image reconstruction caused by the approximations were quantitatively demonstrated and discussed in the numerical simulations. It was clearly observed that the approximations affected the reconstructed absorption coefficient. The 2D PDE-based linearized algorithm succeeded in the image reconstruction of the region with a large absorption coefficient in the 3D phantom. The value reconstructed in the phantom experiment agreed with that in the numerical simulation, so that it was validated that the numerical simulation of the image reconstruction predicted the relationship between the true absorption coefficient of the target in the 3D medium and the reconstructed value with the 2D PDE-based linearized algorithm. Moreover, the the true absorption coefficient in 3D medium was estimated from the 2D reconstructed image on the basis of the prediction by the numerical simulation. The estimation was successful in the phantom experiment, although some limitations were revealed.

Large-Scale 3D Printing: The Way Forward

NASA Astrophysics Data System (ADS)

Jassmi, Hamad Al; Najjar, Fady Al; Ismail Mourad, Abdel-Hamid

2018-03-01

Research on small-scale 3D printing has rapidly evolved, where numerous industrial products have been tested and successfully applied. Nonetheless, research on large-scale 3D printing, directed to large-scale applications such as construction and automotive manufacturing, yet demands a great a great deal of efforts. Large-scale 3D printing is considered an interdisciplinary topic and requires establishing a blended knowledge base from numerous research fields including structural engineering, materials science, mechatronics, software engineering, artificial intelligence and architectural engineering. This review article summarizes key topics of relevance to new research trends on large-scale 3D printing, particularly pertaining (1) technological solutions of additive construction (i.e. the 3D printers themselves), (2) materials science challenges, and (3) new design opportunities.

3D Transient Hydraulic Tomography (3DTHT): An Efficient Field and Modeling Method for High-Resolution Estimation of Aquifer Heterogeneity

NASA Astrophysics Data System (ADS)

Barrash, W.; Cardiff, M. A.; Kitanidis, P. K.

2012-12-01

The distribution of hydraulic conductivity (K) is a major control on groundwater flow and contaminant transport. Our limited ability to determine 3D heterogeneous distributions of K is a major reason for increased costs and uncertainties associated with virtually all aspects of groundwater contamination management (e.g., site investigations, risk assessments, remediation method selection/design/operation, monitoring system design/operation). Hydraulic tomography (HT) is an emerging method for directly estimating the spatially variable distribution of K - in a similar fashion to medical or geophysical imaging. Here we present results from 3D transient field-scale experiments (3DTHT) which capture the heterogeneous K distribution in a permeable, moderately heterogeneous, coarse fluvial unconfined aquifer at the Boise Hydrogeophysical Research Site (BHRS). The results are verified against high-resolution K profiles from multi-level slug tests at BHRS wells. The 3DTHT field system for well instrumentation and data acquisition/feedback is fully modular and portable, and the in-well packer-and-port system is easily assembled and disassembled without expensive support equipment or need for gas pressurization. Tests are run for 15-20 min and the aquifer is allowed to recover while the pumping equipment is repositioned between tests. The tomographic modeling software developed uses as input observations of temporal drawdown behavior from each of numerous zones isolated in numerous observation wells during a series of pumping tests conducted from numerous isolated intervals in one or more pumping wells. The software solves for distributed K (as well as storage parameters Ss and Sy, if desired) and estimates parameter uncertainties using: a transient 3D unconfined forward model in MODFLOW, the adjoint state method for calculating sensitivities (Clemo 2007), and the quasi-linear geostatistical inverse method (Kitanidis 1995) for the inversion. We solve for K at >100,000 sub-m3 (1m x 1m x 0.6m) locations in a 60m x 60m x 18m modeled volume of the BHRS, with the primary investigated volume approximately 12m x 8m x 16m. Computing times are reasonable on high-end desktop computers or small clusters; we are investigating additional efficiency improvements with massive parallelization. Results from complete coverage (1m-length zones) in one pumping well and five observation wells provide a basis for evaluating method resolution capabilities by comparing K statistics from solutions with all tests and observations against partial test and observation coverage, and against independent K measurements at wells with multi-level slug tests. From these analyses we show that 3DTHT compares well with slug test results, and high-resolution information on heterogeneity is lost rapidly with reduction in test or observation coverage.

Development of new two-dimensional spectral/spatial code based on dynamic cyclic shift code for OCDMA system

NASA Astrophysics Data System (ADS)

Jellali, Nabiha; Najjar, Monia; Ferchichi, Moez; Rezig, Houria

2017-07-01

In this paper, a new two-dimensional spectral/spatial codes family, named two dimensional dynamic cyclic shift codes (2D-DCS) is introduced. The 2D-DCS codes are derived from the dynamic cyclic shift code for the spectral and spatial coding. The proposed system can fully eliminate the multiple access interference (MAI) by using the MAI cancellation property. The effect of shot noise, phase-induced intensity noise and thermal noise are used to analyze the code performance. In comparison with existing two dimensional (2D) codes, such as 2D perfect difference (2D-PD), 2D Extended Enhanced Double Weight (2D-Extended-EDW) and 2D hybrid (2D-FCC/MDW) codes, the numerical results show that our proposed codes have the best performance. By keeping the same code length and increasing the spatial code, the performance of our 2D-DCS system is enhanced: it provides higher data rates while using lower transmitted power and a smaller spectral width.

Numerical investigations on cavitation intensity for 3D homogeneous unsteady viscous flows

NASA Astrophysics Data System (ADS)

Leclercq, C.; Archer, A.; Fortes-Patella, R.

2016-11-01

The cavitation erosion remains an industrial issue. In this paper, we deal with the cavitation intensity which can be described as the aggressiveness - or erosive capacity - of a cavitating flow. The estimation of this intensity is a challenging problem both in terms of modelling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a model was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. An intensity model based on pressure and void fraction derivatives was developped and applied to a NACA 65012 hydrofoil tested at LMH-EPFL (École Polytechnique Fédérale de Lausanne) [1]. 2D and 3D unsteady cavitating simulations were performed using a homogeneous model with void fraction transport equation included in Code_Saturne with cavitating module [2]. The article presents a description of the numerical code and the physical approach considered. Comparisons between 2D and 3D simulations, as well as between numerical and experimental results obtained by pitting tests, are analyzed in the paper.

Enhancement of 3D guide field magnetic reconnection by self-generated kinetic turbulence

NASA Astrophysics Data System (ADS)

Alejandro Munoz Sepulveda, Patricio; Buechner, Joerg

2017-04-01

Kinetic plasma turbulence is ubiquitous in magnetic reconnection in laboratory, space and astrophysical plasmas. Most of previous investigations focused on the role of low-frequency/Alfvénic turbulence in homogeneous plasmas. High-frequency/electron-scale turbulence in the reconnecting current sheets, however, have been rarely addressed. Our aim is to investigate the role of this self-generated turbulence via kinetic instabilities in 3D magnetic reconnection. For this sake, we carried out 3D fully-kinetic Particle-in-Cell (PiC) code numerical simulations of force free current sheets with a guide magnetic field, a common situation in the plasmas of interest. We show that the dynamically evolving kinetic turbulence spectra is broadband, with a power-law spectrum between the lower hybrid and up to the electron frequencies with a spectral index near 2.7 at the reconnection site. This result is directly in the frequency-domain, without change of frame of reference assuming Taylor's hypothesis. The evolution of the turbulence correlates with the growth and rate of magnetic reconnection and can be explained by unstable waves caused by (kinetic) streaming instabilities driven by electron current. This provides a plausible explanation for the enhancement of magnetic reconnection due to turbulence observed in laboratory experiments like MRX, VTF and VINETA-II, as well as of in-situ measurements in the Earth's magnetosphere by the MMS spacecraft.

Simulating emissions of 1,3-dichloropropene after soil fumigation under field conditions.

PubMed

Yates, S R; Ashworth, D J

2018-04-15

Soil fumigation is an important agricultural practice used to produce many vegetable and fruit crops. However, fumigating soil can lead to atmospheric emissions which can increase risks to human and environmental health. A complete understanding of the transport, fate, and emissions of fumigants as impacted by soil and environmental processes is needed to mitigate atmospheric emissions. Five large-scale field experiments were conducted to measure emission rates for 1,3-dichloropropene (1,3-D), a soil fumigant commonly used in California. Numerical simulations of these experiments were conducted in predictive mode (i.e., no calibration) to determine if simulation could be used as a substitute for field experimentation to obtain information needed by regulators. The results show that the magnitude of the volatilization rate and the total emissions could be adequately predicted for these experiments, with the exception of a scenario where the field was periodically irrigated after fumigation. In addition, the timing of the daily peak 1,3-D emissions was not accurately predicted for these experiments due to the peak emission rates occurring during the night or early-morning hours. This study revealed that more comprehensive mathematical models (or adjustments to existing models) are needed to fully describe emissions of soil fumigants from field soils under typical agronomic conditions. Published by Elsevier B.V.

CFD determination of flow perturbation boundary conditions for seal rotordynamic modeling

NASA Astrophysics Data System (ADS)

Venkatesan, Ganesh

2002-09-01

A new approach has been developed and utilized to determine the flow field perturbations (i.e. disturbance due to rotor eccentricity and/or motion) upstream of and within a non-contacting seal. The results are proposed for use with bulk-flow perturbation and CFD-perturbation seal rotordynamic models, as well as in fully 3-D CFD models, to specify approximate boundary conditions for the first-order variables at the computational domain inlet. The perturbation quantities were evaluated by subtracting the numerical flow field solutions corresponding to the concentric rotor position from that for an eccentric rotor position. The disturbance pressure quantities predicted from the numerical solutions were validated by comparing with previous pressure measurements. A parametric study was performed to understand the influence of upstream chamber height, seal clearance, shaft speed, whirl speed, zeroth-order streamwise and swirl velocities, and downstream pressure on the distribution of the first-order quantities in the upstream chamber, seal inlet and seal exit regions. Radially bulk-averaged first-order quantities were evaluated in the upstream chamber, as well as at the seal inlet and exit. The results were finally presented in the form of generalized dimensionless boundary condition correlations so that they can be applied to seal rotordynamic models over a wide range of operating conditions and geometries. To examine the effect of the proposed, approximate first-order boundary conditions on the solutions of the fully 3-D CFD rotordynamic models, the first-order boundary condition correlations for the upstream chamber were used to adjust the circumferential distribution of domain inlet values. The benefit of the boundary condition expressions was assessed for two previously measured test cases, one for a gas seal and the other for a liquid seal. For the gas seal case, a significant improvement in the prediction of the cross-coupled stiffness, when including the proposed first-order inlet boundary values, was found. In the case of liquid seals the tangential impedance values obtained with boundary condition adjustments showed a very slight improvement for a range of whirl speeds over those obtained without them. The radial impedance values obtained with the new adjustments showed a significant improvement over those obtained without them.

Development of a High-Order Navier-Stokes Solver Using Flux Reconstruction to Simulate Three-Dimensional Vortex Structures in a Curved Artery Model

NASA Astrophysics Data System (ADS)

Cox, Christopher

Low-order numerical methods are widespread in academic solvers and ubiquitous in industrial solvers due to their robustness and usability. High-order methods are less robust and more complicated to implement; however, they exhibit low numerical dissipation and have the potential to improve the accuracy of flow simulations at a lower computational cost when compared to low-order methods. This motivates our development of a high-order compact method using Huynh's flux reconstruction scheme for solving unsteady incompressible flow on unstructured grids. We use Chorin's classic artificial compressibility formulation with dual time stepping to solve unsteady flow problems. In 2D, an implicit non-linear lower-upper symmetric Gauss-Seidel scheme with backward Euler discretization is used to efficiently march the solution in pseudo time, while a second-order backward Euler discretization is used to march in physical time. We verify and validate implementation of the high-order method coupled with our implicit time stepping scheme using both steady and unsteady incompressible flow problems. The current implicit time stepping scheme is proven effective in satisfying the divergence-free constraint on the velocity field in the artificial compressibility formulation. The high-order solver is extended to 3D and parallelized using MPI. Due to its simplicity, time marching for 3D problems is done explicitly. The feasibility of using the current implicit time stepping scheme for large scale three-dimensional problems with high-order polynomial basis still remains to be seen. We directly use the aforementioned numerical solver to simulate pulsatile flow of a Newtonian blood-analog fluid through a rigid 180-degree curved artery model. One of the most physiologically relevant forces within the cardiovascular system is the wall shear stress. This force is important because atherosclerotic regions are strongly correlated with curvature and branching in the human vasculature, where the shear stress is both oscillatory and multidirectional. Also, the combined effect of curvature and pulsatility in cardiovascular flows produces unsteady vortices. The aim of this research as it relates to cardiovascular fluid dynamics is to predict the spatial and temporal evolution of vortical structures generated by secondary flows, as well as to assess the correlation between multiple vortex pairs and wall shear stress. We use a physiologically (pulsatile) relevant flow rate and generate results using both fully developed and uniform entrance conditions, the latter being motivated by the fact that flow upstream of a curved artery may not have sufficient straight entrance length to become fully developed. Under the two pulsatile inflow conditions, we characterize the morphology and evolution of various vortex pairs and their subsequent effect on relevant haemodynamic wall shear stress metrics.

A parallel domain decomposition-based implicit method for the Cahn–Hilliard–Cook phase-field equation in 3D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Xiang; Yang, Chao; State Key Laboratory of Computer Science, Chinese Academy of Sciences, Beijing 100190

2015-03-15

We present a numerical algorithm for simulating the spinodal decomposition described by the three dimensional Cahn–Hilliard–Cook (CHC) equation, which is a fourth-order stochastic partial differential equation with a noise term. The equation is discretized in space and time based on a fully implicit, cell-centered finite difference scheme, with an adaptive time-stepping strategy designed to accelerate the progress to equilibrium. At each time step, a parallel Newton–Krylov–Schwarz algorithm is used to solve the nonlinear system. We discuss various numerical and computational challenges associated with the method. The numerical scheme is validated by a comparison with an explicit scheme of high accuracymore » (and unreasonably high cost). We present steady state solutions of the CHC equation in two and three dimensions. The effect of the thermal fluctuation on the spinodal decomposition process is studied. We show that the existence of the thermal fluctuation accelerates the spinodal decomposition process and that the final steady morphology is sensitive to the stochastic noise. We also show the evolution of the energies and statistical moments. In terms of the parallel performance, it is found that the implicit domain decomposition approach scales well on supercomputers with a large number of processors.« less

PIXIE3D: A Parallel, Implicit, eXtended MHD 3D Code.

NASA Astrophysics Data System (ADS)

Chacon, L.; Knoll, D. A.

2004-11-01

We report on the development of PIXIE3D, a 3D parallel, fully implicit Newton-Krylov extended primitive-variable MHD code in general curvilinear geometry. PIXIE3D employs a second-order, finite-volume-based spatial discretization that satisfies remarkable properties such as being conservative, solenoidal in the magnetic field, non-dissipative, and stable in the absence of physical dissipation.(L. Chacón , phComput. Phys. Comm.) submitted (2004) PIXIE3D employs fully-implicit Newton-Krylov methods for the time advance. Currently, first and second-order implicit schemes are available, although higher-order temporal implicit schemes can be effortlessly implemented within the Newton-Krylov framework. A successful, scalable, MG physics-based preconditioning strategy, similar in concept to previous 2D MHD efforts,(L. Chacón et al., phJ. Comput. Phys). 178 (1), 15- 36 (2002); phJ. Comput. Phys., 188 (2), 573-592 (2003) has been developed. We are currently in the process of parallelizing the code using the PETSc library, and a Newton-Krylov-Schwarz approach for the parallel treatment of the preconditioner. In this poster, we will report on both the serial and parallel performance of PIXIE3D, focusing primarily on scalability and CPU speedup vs. an explicit approach.

A 3D network of helicates fully assembled by pi-stacking interactions.

PubMed

Vázquez, Miguel; Taglietti, Angelo; Gatteschi, Dante; Sorace, Lorenzo; Sangregorio, Claudio; González, Ana M; Maneiro, Marcelino; Pedrido, Rosa M; Bermejo, Manuel R

2003-08-07

The neutral dinuclear dihelicate [Cu2(L)2] x 2CH3CN (1) forms a unique 3D network in the solid state due to pi-stacking interactions, which are responsible for intermolecular antiferromagnetic coupling between Cu(II) ions.

Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

NASA Astrophysics Data System (ADS)

Lei, Qinghua; Wang, Xiaoguang; Xiang, Jiansheng; Latham, John-Paul

2017-12-01

A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a "through-going" joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.

Symmetry-plane model of 3D Euler flows: Mapping to regular systems and numerical solutions of blowup

NASA Astrophysics Data System (ADS)

Mulungye, Rachel M.; Lucas, Dan; Bustamante, Miguel D.

2014-11-01

We introduce a family of 2D models describing the dynamics on the so-called symmetry plane of the full 3D Euler fluid equations. These models depend on a free real parameter and can be solved analytically. For selected representative values of the free parameter, we apply the method introduced in [M.D. Bustamante, Physica D: Nonlinear Phenom. 240, 1092 (2011)] to map the fluid equations bijectively to globally regular systems. By comparing the analytical solutions with the results of numerical simulations, we establish that the numerical simulations of the mapped regular systems are far more accurate than the numerical simulations of the original systems, at the same spatial resolution and CPU time. In particular, the numerical integrations of the mapped regular systems produce robust estimates for the growth exponent and singularity time of the main blowup quantity (vorticity stretching rate), converging well to the analytically-predicted values even beyond the time at which the flow becomes under-resolved (i.e. the reliability time). In contrast, direct numerical integrations of the original systems develop unstable oscillations near the reliability time. We discuss the reasons for this improvement in accuracy, and explain how to extend the analysis to the full 3D case. Supported under the programme for Research in Third Level Institutions (PRTLI) Cycle 5 and co-funded by the European Regional Development Fund.

Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases

NASA Astrophysics Data System (ADS)

Grenier, Christophe; Anbergen, Hauke; Bense, Victor; Chanzy, Quentin; Coon, Ethan; Collier, Nathaniel; Costard, François; Ferry, Michel; Frampton, Andrew; Frederick, Jennifer; Gonçalvès, Julio; Holmén, Johann; Jost, Anne; Kokh, Samuel; Kurylyk, Barret; McKenzie, Jeffrey; Molson, John; Mouche, Emmanuel; Orgogozo, Laurent; Pannetier, Romain; Rivière, Agnès; Roux, Nicolas; Rühaak, Wolfram; Scheidegger, Johanna; Selroos, Jan-Olof; Therrien, René; Vidstrand, Patrik; Voss, Clifford

2018-04-01

In high-elevation, boreal and arctic regions, hydrological processes and associated water bodies can be strongly influenced by the distribution of permafrost. Recent field and modeling studies indicate that a fully-coupled multidimensional thermo-hydraulic approach is required to accurately model the evolution of these permafrost-impacted landscapes and groundwater systems. However, the relatively new and complex numerical codes being developed for coupled non-linear freeze-thaw systems require verification. This issue is addressed by means of an intercomparison of thirteen numerical codes for two-dimensional test cases with several performance metrics (PMs). These codes comprise a wide range of numerical approaches, spatial and temporal discretization strategies, and computational efficiencies. Results suggest that the codes provide robust results for the test cases considered and that minor discrepancies are explained by computational precision. However, larger discrepancies are observed for some PMs resulting from differences in the governing equations, discretization issues, or in the freezing curve used by some codes.

Spacecraft Observations of Oblique Electron Beams Breaking the Frozen-In Law During Asymmetric Reconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egedal, J.; Le, Ari; Daughton, William

Fully kinetic simulations of asymmetric magnetic reconnection reveal the presence of magnetic-field-aligned beams of electrons flowing toward the topological magnetic x line. Within the ~ 6d e electron-diffusion region, the beams become oblique to the local magnetic field, providing a unique signature of the electron-diffusion region where the electron frozen-in law is broken. These numerical predictions are confirmed by in situ Magnetospheric Multiscale spacecraft observations during asymmetric reconnection at Earth’s dayside magnetopause.

Spacecraft Observations of Oblique Electron Beams Breaking the Frozen-In Law During Asymmetric Reconnection

DOE PAGES

Egedal, J.; Le, Ari; Daughton, William; ...

2018-01-29

Fully kinetic simulations of asymmetric magnetic reconnection reveal the presence of magnetic-field-aligned beams of electrons flowing toward the topological magnetic x line. Within the ~ 6d e electron-diffusion region, the beams become oblique to the local magnetic field, providing a unique signature of the electron-diffusion region where the electron frozen-in law is broken. These numerical predictions are confirmed by in situ Magnetospheric Multiscale spacecraft observations during asymmetric reconnection at Earth’s dayside magnetopause.

Direct numerical simulation of two-dimensional wall-bounded turbulent flows from receptivity stage.

PubMed

Sengupta, T K; Bhaumik, S; Bhumkar, Y G

2012-02-01

Deterministic route to turbulence creation in 2D wall boundary layer is shown here by solving full Navier-Stokes equation by dispersion relation preserving (DRP) numerical methods for flow over a flat plate excited by wall and free stream excitations. Present results show the transition caused by wall excitation is predominantly due to nonlinear growth of the spatiotemporal wave front, even in the presence of Tollmien-Schlichting (TS) waves. The existence and linear mechanism of creating the spatiotemporal wave front was established in Sengupta, Rao and Venkatasubbaiah [Phys. Rev. Lett. 96, 224504 (2006)] via the solution of Orr-Sommerfeld equation. Effects of spatiotemporal front(s) in the nonlinear phase of disturbance evolution have been documented by Sengupta and Bhaumik [Phys. Rev. Lett. 107, 154501 (2011)], where a flow is taken from the receptivity stage to the fully developed 2D turbulent state exhibiting a k(-3) energy spectrum by solving the Navier-Stokes equation without any artifice. The details of this mechanism are presented here for the first time, along with another problem of forced excitation of the boundary layer by convecting free stream vortices. Thus, the excitations considered here are for a zero pressure gradient (ZPG) boundary layer by (i) monochromatic time-harmonic wall excitation and (ii) free stream excitation by convecting train of vortices at a constant height. The latter case demonstrates neither monochromatic TS wave, nor the spatiotemporal wave front, yet both the cases eventually show the presence of k(-3) energy spectrum, which has been shown experimentally for atmospheric dynamics in Nastrom, Gage and Jasperson [Nature 310, 36 (1984)]. Transition by a nonlinear mechanism of the Navier-Stokes equation leading to k(-3) energy spectrum in the inertial subrange is the typical characteristic feature of all 2D turbulent flows. Reproduction of the spectrum noted in atmospheric data (showing dominance of the k(-3) spectrum over the k(-5/3) spectrum in Nastrom et al.) in laboratory scale indicates universality of this spectrum for all 2D turbulent flows. Creation of universal features of 2D turbulence by a deterministic route has been established here for the first time by solving the Navier-Stokes equation without any modeling, as has been reported earlier in the literature by other researchers.

Highly stable aptamers selected from a 2'-fully modified fGmH RNA library for targeting biomaterials.

PubMed

Friedman, Adam D; Kim, Dongwook; Liu, Rihe

2015-01-01

When developed as targeting ligands for the in vivo delivery of biomaterials to biological systems, RNA aptamers immediately face numerous obstacles, in particular nuclease degradation and post-selection 2' modification. This study aims to develop a novel class of highly stable, 2'-fully modified RNA aptamers that are ideal for the targeted delivery of biomaterials. We demonstrated the facile transcription of a fGmH (2'-F-dG, 2'-OMe-dA/dC/dU) RNA library with unexpected hydrophobicity, the direct selection of aptamers from a fGmH RNA library that bind Staphylococcus aureus Protein A (SpA) as a model target, and the superior nuclease and serum stability of these aptamers compared to 2'-partially modified RNA variants. Characterizations of fGmH RNA aptamers binding to purified SpA and to endogenous SpA present on the surface of S. aureus cells demonstrate fGmH RNA aptamer selectivity and stability. Significantly, fGmH RNA aptamers were able to functionalize, stabilize, and specifically deliver aggregation-prone silver nanoparticles (AgNPs) to S. aureus with SpA-dependent antimicrobial effects. This study describes a novel aptamer class with considerable potential to improve the in vivo applicability of nucleic acid-based affinity molecules to biomaterials.

Fully 3D modeling of tokamak vertical displacement events with realistic parameters

NASA Astrophysics Data System (ADS)

Pfefferle, David; Ferraro, Nathaniel; Jardin, Stephen; Bhattacharjee, Amitava

2016-10-01

In this work, we model the complex multi-domain and highly non-linear physics of Vertical Displacement Events (VDEs), one of the most damaging off-normal events in tokamaks, with the implicit 3D extended MHD code M3D-C1. The code has recently acquired the capability to include finite thickness conducting structures within the computational domain. By exploiting the possibility of running a linear 3D calculation on top of a non-linear 2D simulation, we monitor the non-axisymmetric stability and assess the eigen-structure of kink modes as the simulation proceeds. Once a stability boundary is crossed, a fully 3D non-linear calculation is launched for the remainder of the simulation, starting from an earlier time of the 2D run. This procedure, along with adaptive zoning, greatly increases the efficiency of the calculation, and allows to perform VDE simulations with realistic parameters and high resolution. Simulations are being validated with NSTX data where both axisymmetric (toroidally averaged) and non-axisymmetric induced and conductive (halo) currents have been measured. This work is supported by US DOE Grant DE-AC02-09CH11466.

Numerical study on 3D composite morphing actuators

NASA Astrophysics Data System (ADS)

Oishi, Kazuma; Saito, Makoto; Anandan, Nishita; Kadooka, Kevin; Taya, Minoru

2015-04-01

There are a number of actuators using the deformation of electroactive polymer (EAP), where fewer papers seem to have focused on the performance of 3D morphing actuators based on the analytical approach, due mainly to their complexity. The present paper introduces a numerical analysis approach on the large scale deformation and motion of a 3D half dome shaped actuator composed of thin soft membrane (passive material) and EAP strip actuators (EAP active coupon with electrodes on both surfaces), where the locations of the active EAP strips is a key parameter. Simulia/Abaqus Static and Implicit analysis code, whose main feature is the high precision contact analysis capability among structures, are used focusing on the whole process of the membrane to touch and wrap around the object. The unidirectional properties of the EAP coupon actuator are used as input data set for the material properties for the simulation and the verification of our numerical model, where the verification is made as compared to the existing 2D solution. The numerical results can demonstrate the whole deformation process of the membrane to wrap around not only smooth shaped objects like a sphere or an egg, but also irregularly shaped objects. A parametric study reveals the proper placement of the EAP coupon actuators, with the modification of the dome shape to induce the relevant large scale deformation. The numerical simulation for the 3D soft actuators shown in this paper could be applied to a wider range of soft 3D morphing actuators.

A Lagrangian model of Copepod dynamics in turbulent flows

NASA Astrophysics Data System (ADS)

Ardeshiri, Hamidreza; Benkeddad, Ibtissem; Schmitt, Francois G.; Souissi, Sami; Toschi, Federico; Calzavarini, Enrico

2016-04-01

Planktonic copepods are small crustaceans that have the ability to swim by quick powerful jumps. Such an aptness is used to escape from high shear regions, which may be caused either by flow perturbations, produced by a large predator such as fish larave, or by the inherent highly turbulent dynamics of the ocean. Through a combined experimental and numerical study, we investigate the impact of jumping behaviour on the small-scale patchiness of copepods in a turbulent environment. Recorded velocity tracks of copepods displaying escape response jumps in still water are used to define and tune a Lagrangian Copepod (LC) model. The model is further employed to simulate the behaviour of thousands of copepods in a fully developed hydrodynamic turbulent flow obtained by direct numerical simulation of the Navier-Stokes equations. First, we show that the LC velocity statistics is in qualitative agreement with available experimental observations of copepods in turbulence. Second, we quantify the clustering of LC, via the fractal dimension D2. We show that D2 can be as low as 2.3, corresponding to local sheetlike aggregates, and that it critically depends on the shear-rate sensitivity of the proposed LC model. We further investigate the effect of jump intensity, jump orientation and geometrical aspect ratio of the copepods on the small-scale spatial distribution. Possible ecological implications of the observed clustering on encounter rates and mating success are discussed.

3-D parallel program for numerical calculation of gas dynamics problems with heat conductivity on distributed memory computational systems (CS)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sofronov, I.D.; Voronin, B.L.; Butnev, O.I.

1997-12-31

The aim of the work performed is to develop a 3D parallel program for numerical calculation of gas dynamics problem with heat conductivity on distributed memory computational systems (CS), satisfying the condition of numerical result independence from the number of processors involved. Two basically different approaches to the structure of massive parallel computations have been developed. The first approach uses the 3D data matrix decomposition reconstructed at temporal cycle and is a development of parallelization algorithms for multiprocessor CS with shareable memory. The second approach is based on using a 3D data matrix decomposition not reconstructed during a temporal cycle.more » The program was developed on 8-processor CS MP-3 made in VNIIEF and was adapted to a massive parallel CS Meiko-2 in LLNL by joint efforts of VNIIEF and LLNL staffs. A large number of numerical experiments has been carried out with different number of processors up to 256 and the efficiency of parallelization has been evaluated in dependence on processor number and their parameters.« less

Spontaneous development of arcuate single-sided subduction in global 3-D mantle convection models with a free surface

NASA Astrophysics Data System (ADS)

Crameri, Fabio; Tackley, Paul

2014-05-01

The work presented aims at a better understanding of plate tectonics, a crucial dynamical feature within the global framework of mantle convection. Special focus is given to the interaction of subduction-related mantle flow and surface topography. Thereby, the application of a numerical model with two key functional requirements is essential: an evolution over a long time period to naturally model mantle flow and a physically correct topography calculation. The global mantle convection model presented in Crameri et al. (2012a) satisfies both of these requirements. First, it is efficiently calculated by the finite-volume code Stag-YY (e.g., Tackley 2008) using a multi-grid method on a fully staggered grid. Second, it applies the sticky-air method (Matsumoto and Tomoda 1983; Schmeling et al, 2008) and thus approximates a free surface when the sticky-air parameters are chosen carefully (Crameri et al., 2012b). This leads to dynamically self-consistent mantle convection with realistic, single-sided subduction. New insights are thus gained into the interplay of obliquely sinking plates, toroidal mantle flow and the arcuate shape of slabs and trenches. Numerous two-dimensional experiments provide optimal parameter setups that are applied to three-dimensional models in Cartesian and fully spherical geometries. Features observed and characterised in the latter experiments give important insight into the strongly variable behaviour of subduction zones along their strike. This includes (i) the spontaneous development of arcuate trench geometry, (ii) regional subduction polarity reversals and slab tearing, and the newly discovered features (iii) 'slab tunnelling' and (iv) 'back-slab spiral flow'. Overall, this study demonstrates the strong interaction between surface topography and mantle currents and highlights the variability of subduction zones and their individual segments. REFERENCES Crameri, F., P. J. Tackley, I. Meilick, T. V. Gerya, and B. J. P. Kaus (2012a), A free plate surface and weak oceanic crust produce single-sided subduction on Earth, Geophys. Res. Lett., 39(3), L03,306. Crameri, F., H. Schmeling, G. J. Golabek, T. Duretz, R. Orendt, S. J. H. Buiter, D. A. May, B. J. P. Kaus, T. V. Gerya, and P. J. Tackley (2012b), A comparison of numerical surface topography calculations in geodynamic modelling: an evaluation of the 'sticky air' method, Geophys. J. Int., 189(1), 38-54. Matsumoto, T., and Y. Tomoda (1983), Numerical simulation of the initiation of subduction at the fracture zone, J. Phys. Earth, 31(3), 183-194. Schmeling, H., A. Babeyko, A. Enns, C. Faccenna, F. Funiciello, T. Gerya, G. Golabek, S. Grigull, B. Kaus, G. Morra, S. Schmalholz, and J. van Hunen (2008), A benchmark comparison of spontaneous subduction models-Towards a free surface, Phys. Earth Planet. Int., 171(1-4), 198-223. Tackley, P. J. (2008), Modelling compressible mantle convection with large viscosity contrasts in a three-dimensional spherical shell using the yin-yang grid, Phys. Earth Planet. Int., 171(1-4), 7-18.

Fully Resolved Simulations of 3D Printing

NASA Astrophysics Data System (ADS)

Tryggvason, Gretar; Xia, Huanxiong; Lu, Jiacai

2017-11-01

Numerical simulations of Fused Deposition Modeling (FDM) (or Fused Filament Fabrication) where a filament of hot, viscous polymer is deposited to ``print'' a three-dimensional object, layer by layer, are presented. A finite volume/front tracking method is used to follow the injection, cooling, solidification and shrinking of the filament. The injection of the hot melt is modeled using a volume source, combined with a nozzle, modeled as an immersed boundary, that follows a prescribed trajectory. The viscosity of the melt depends on the temperature and the shear rate and the polymer becomes immobile as its viscosity increases. As the polymer solidifies, the stress is found by assuming a hyperelastic constitutive equation. The method is described and its accuracy and convergence properties are tested by grid refinement studies for a simple setup involving two short filaments, one on top of the other. The effect of the various injection parameters, such as nozzle velocity and injection velocity are briefly examined and the applicability of the approach to simulate the construction of simple multilayer objects is shown. The role of fully resolved simulations for additive manufacturing and their use for novel processes and as the ``ground truth'' for reduced order models is discussed.

Performance of fully-coupled algebraic multigrid preconditioners for large-scale VMS resistive MHD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, P. T.; Shadid, J. N.; Hu, J. J.

Here, we explore the current performance and scaling of a fully-implicit stabilized unstructured finite element (FE) variational multiscale (VMS) capability for large-scale simulations of 3D incompressible resistive magnetohydrodynamics (MHD). The large-scale linear systems that are generated by a Newton nonlinear solver approach are iteratively solved by preconditioned Krylov subspace methods. The efficiency of this approach is critically dependent on the scalability and performance of the algebraic multigrid preconditioner. Our study considers the performance of the numerical methods as recently implemented in the second-generation Trilinos implementation that is 64-bit compliant and is not limited by the 32-bit global identifiers of themore » original Epetra-based Trilinos. The study presents representative results for a Poisson problem on 1.6 million cores of an IBM Blue Gene/Q platform to demonstrate very large-scale parallel execution. Additionally, results for a more challenging steady-state MHD generator and a transient solution of a benchmark MHD turbulence calculation for the full resistive MHD system are also presented. These results are obtained on up to 131,000 cores of a Cray XC40 and one million cores of a BG/Q system.« less

Performance of fully-coupled algebraic multigrid preconditioners for large-scale VMS resistive MHD

DOE PAGES

Lin, P. T.; Shadid, J. N.; Hu, J. J.; ...

2017-11-06

Here, we explore the current performance and scaling of a fully-implicit stabilized unstructured finite element (FE) variational multiscale (VMS) capability for large-scale simulations of 3D incompressible resistive magnetohydrodynamics (MHD). The large-scale linear systems that are generated by a Newton nonlinear solver approach are iteratively solved by preconditioned Krylov subspace methods. The efficiency of this approach is critically dependent on the scalability and performance of the algebraic multigrid preconditioner. Our study considers the performance of the numerical methods as recently implemented in the second-generation Trilinos implementation that is 64-bit compliant and is not limited by the 32-bit global identifiers of themore » original Epetra-based Trilinos. The study presents representative results for a Poisson problem on 1.6 million cores of an IBM Blue Gene/Q platform to demonstrate very large-scale parallel execution. Additionally, results for a more challenging steady-state MHD generator and a transient solution of a benchmark MHD turbulence calculation for the full resistive MHD system are also presented. These results are obtained on up to 131,000 cores of a Cray XC40 and one million cores of a BG/Q system.« less

Triggering the volume phase transition of core-shell Au nanorod-microgel nanocomposites with light

NASA Astrophysics Data System (ADS)

Rodríguez-Fernández, Jessica; Fedoruk, Michael; Hrelescu, Calin; Lutich, Andrey A.; Feldmann, Jochen

2011-06-01

We have coated gold nanorods (NRs) with thermoresponsive microgel shells based on poly(N-isopropylacrylamide) (pNIPAM). We demonstrate by simultaneous laser-heating and optical extinction measurements that the Au NR cores can be simultaneously used as fast optothermal manipulators (switchers) and sensitive optical reporters of the microgel state in a fully externally controlled and reversible manner. We support our results with optical modeling based on the boundary element method and 3D numerical analysis on the temperature distribution. Briefly, we show that due to the sharp increase in refractive index resulting from the optothermally triggered microgel collapse, the longitudinal plasmon band of the coated Au NRs is significantly red-shifted. The optothermal control over the pNIPAM shell, and thereby over the optical response of the nanocomposite, is fully reversible and can be simply controlled by switching on and off a NIR heating laser. In contrast to bulk solution heating, we demonstrate that light-triggering does not compromise colloidal stability, which is of primary importance for the ultimate utilization of these types of nanocomposites as remotely controlled optomechanical actuators, for applications spanning from drug delivery to photonic crystals and nanoscale motion.

Tensor numerical methods in quantum chemistry: from Hartree-Fock to excitation energies.

PubMed

Khoromskaia, Venera; Khoromskij, Boris N

2015-12-21

We resume the recent successes of the grid-based tensor numerical methods and discuss their prospects in real-space electronic structure calculations. These methods, based on the low-rank representation of the multidimensional functions and integral operators, first appeared as an accurate tensor calculus for the 3D Hartree potential using 1D complexity operations, and have evolved to entirely grid-based tensor-structured 3D Hartree-Fock eigenvalue solver. It benefits from tensor calculation of the core Hamiltonian and two-electron integrals (TEI) in O(n log n) complexity using the rank-structured approximation of basis functions, electron densities and convolution integral operators all represented on 3D n × n × n Cartesian grids. The algorithm for calculating TEI tensor in a form of the Cholesky decomposition is based on multiple factorizations using algebraic 1D "density fitting" scheme, which yield an almost irreducible number of product basis functions involved in the 3D convolution integrals, depending on a threshold ε > 0. The basis functions are not restricted to separable Gaussians, since the analytical integration is substituted by high-precision tensor-structured numerical quadratures. The tensor approaches to post-Hartree-Fock calculations for the MP2 energy correction and for the Bethe-Salpeter excitation energies, based on using low-rank factorizations and the reduced basis method, were recently introduced. Another direction is towards the tensor-based Hartree-Fock numerical scheme for finite lattices, where one of the numerical challenges is the summation of electrostatic potentials of a large number of nuclei. The 3D grid-based tensor method for calculation of a potential sum on a L × L × L lattice manifests the linear in L computational work, O(L), instead of the usual O(L(3) log L) scaling by the Ewald-type approaches.

Probing the universality of synchronised hair around rotating black holes with Q-clouds

NASA Astrophysics Data System (ADS)

Herdeiro, Carlos; Kunz, Jutta; Radu, Eugen; Subagyo, Bintoro

2018-04-01

Recently, various families of black holes (BHs) with synchronised hair have been constructed. These are rotating BHs surrounded, as fully non-linear solutions of the appropriate Einstein-matter model, by a non-trivial bosonic field in synchronised rotation with the BH horizon. Some families bifurcate globally from a bald BH (e.g. the Kerr BH), whereas others bifurcate only locally from a bald BH (e.g. the D = 5 Myers-Perry BH). It would be desirable to understand how generically synchronisation allows hairy BHs to bifurcate from bald ones. However, the construction and scanning of the domain of existence of the former families of BHs can be a difficult and time consuming (numerical) task. Here, we first provide a simple perturbative argument to understand the generality of the synchronisation condition. Then, we observe that the study of Q-clouds is a generic tool to establish the existence of BHs with synchronised hair bifurcating (globally or locally) from a given bald BH without having to solve the fully non-linear coupled system of Einstein-matter equations. As examples, we apply this tool to establish the existence of synchronised hair around D = 6 Myers-Perry BHs, D = 5 black rings and D = 4 Kerr-AdS BHs, where D is the spacetime dimension. The black rings case provides an example of BHs with synchronised hair beyond spherical horizon topology, further establishing the generality of the mechanism.

Transport and Deposition of Nanoparticles in the Pore Network of a Reservoir Rock: Effects of Pore Surface Heterogeneity and Radial Diffusion

NASA Astrophysics Data System (ADS)

Pham, Ngoc; Papavassiliou, Dimitrios

2014-03-01

In this study, transport behavior of nanoparticles under different pore surface conditions of consolidated Berea sandstone is numerically investigated. Micro-CT scanning technique is applied to obtain 3D grayscale images of the rock sample geometry. Quantitative characterization, which is based on image analysis is done to obtain physical properties of the pore network, such as the pore size distribution and the type of each pore (dead-end, isolated, and fully connected pore). Transport of water through the rock is simulated by employing a 3D lattice Boltzmann method. The trajectories of nanopaticles moving under convection in the simulated flow field and due to molecular diffusion are monitored in the Lagrangian framework. It is assumed in the model that the particle adsorption on the pore surface, which is modeled as a pseudo-first order adsorption, is the only factor hindering particle propagation. The effect of pore surface heterogeneity to the particle breakthrough is considered, and the role of particle radial diffusion is also addressed in details. The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.

A scalable nonlinear fluid-structure interaction solver based on a Schwarz preconditioner with isogeometric unstructured coarse spaces in 3D

NASA Astrophysics Data System (ADS)

Kong, Fande; Cai, Xiao-Chuan

2017-07-01

Nonlinear fluid-structure interaction (FSI) problems on unstructured meshes in 3D appear in many applications in science and engineering, such as vibration analysis of aircrafts and patient-specific diagnosis of cardiovascular diseases. In this work, we develop a highly scalable, parallel algorithmic and software framework for FSI problems consisting of a nonlinear fluid system and a nonlinear solid system, that are coupled monolithically. The FSI system is discretized by a stabilized finite element method in space and a fully implicit backward difference scheme in time. To solve the large, sparse system of nonlinear algebraic equations at each time step, we propose an inexact Newton-Krylov method together with a multilevel, smoothed Schwarz preconditioner with isogeometric coarse meshes generated by a geometry preserving coarsening algorithm. Here "geometry" includes the boundary of the computational domain and the wet interface between the fluid and the solid. We show numerically that the proposed algorithm and implementation are highly scalable in terms of the number of linear and nonlinear iterations and the total compute time on a supercomputer with more than 10,000 processor cores for several problems with hundreds of millions of unknowns.

3D-optical measurement system using a new vignetting aperture procedure

NASA Astrophysics Data System (ADS)

Hofbauer, Engelbert; Rascher, Rolf; Wühr, Konrad; Friedke, Felix; Stubenrauch, Thomas; Pastötter, Benjamin; Schleich, Sebastian; Zöcke, Christine

2014-05-01

A newly developed measuring procedure uses vignetting to evaluate angles and angle changes, independently from the measurement distance. Further on, the same procedure enables the transmission of a digital readout and therefore a better automation of the electronic signal evaluation, for use as an alignment telescope. The fully extended readout by a simple 3-D reflector will provide the user with a measurement result with six degrees of freedom. The vignetting field stop procedure will be described. Firstly, considering artificial vignetting, the theoretical basics from geometric-optical view are represented. Secondly, the natural vignetting with photometric effects will be considered. The distribution of intensity in the image plane light spot, the so-called V-SPOT, is analytically deduced as a function of differently measured variables. Intensity shifts within the V-Spot are examined independently from different effects by numeric simulation. On these basics, the theoretical research regarding accuracy, linearity as well as results in 2 dimensional surface reconstruction on precision optical mirrors and also three dimensional measurements in mechanical engineering are examined. Effects and deviations will be discussed. The project WiPoVi is sponsored by "Ingenieur Nachwuchs - Qualifizierung von Ingenieurnachwuchs an Fachhochschulen" by Bavarian State Ministry of Education, Science and the Arts.

Spatial and size distributions of garnets grown in a pseudotachylyte generated during a lower crust earthquake

NASA Astrophysics Data System (ADS)

Clerc, Adriane; Renard, François; Austrheim, Håkon; Jamtveit, Bjørn

2018-05-01

In the Bergen Arc, western Norway, rocks exhumed from the lower crust record earthquakes that formed during the Caledonian collision. These earthquakes occurred at about 30-50 km depth under granulite or amphibolite facies metamorphic conditions. Coseismic frictional heating produced pseudotachylytes in this area. We describe pseudotachylytes using field data to infer earthquake magnitude (M ≥ 6.6), low dynamic friction during rupture propagation (μd < 0.1) and laboratory analyses to infer fast crystallization of microlites in the pseudotachylyte, within seconds of the earthquake arrest. High resolution 3D X-ray microtomography imaging reveals the microstructure of a pseudotachylyte sample, including numerous garnets and their corona of plagioclase that we infer have crystallized in the pseudotachylyte. These garnets 1) have dendritic shapes and are surrounded by plagioclase coronae almost fully depleted in iron, 2) have a log-normal volume distribution, 3) increase in volume with increasing distance away from the pseudotachylyte-host rock boundary, and 4) decrease in number with increasing distance away from the pseudotachylyte -host rock boundary. These characteristics indicate fast mineral growth, likely within seconds. We propose that these new quantitative criteria may assist in the unambiguous identification of pseudotachylytes in the field.

A scalable nonlinear fluid–structure interaction solver based on a Schwarz preconditioner with isogeometric unstructured coarse spaces in 3D

DOE PAGES

Kong, Fande; Cai, Xiao-Chuan

2017-03-24

Nonlinear fluid-structure interaction (FSI) problems on unstructured meshes in 3D appear many applications in science and engineering, such as vibration analysis of aircrafts and patient-specific diagnosis of cardiovascular diseases. In this work, we develop a highly scalable, parallel algorithmic and software framework for FSI problems consisting of a nonlinear fluid system and a nonlinear solid system, that are coupled monolithically. The FSI system is discretized by a stabilized finite element method in space and a fully implicit backward difference scheme in time. To solve the large, sparse system of nonlinear algebraic equations at each time step, we propose an inexactmore » Newton-Krylov method together with a multilevel, smoothed Schwarz preconditioner with isogeometric coarse meshes generated by a geometry preserving coarsening algorithm. Here ''geometry'' includes the boundary of the computational domain and the wet interface between the fluid and the solid. We show numerically that the proposed algorithm and implementation are highly scalable in terms of the number of linear and nonlinear iterations and the total compute time on a supercomputer with more than 10,000 processor cores for several problems with hundreds of millions of unknowns.« less

Edge gyrokinetic theory and continuum simulations

NASA Astrophysics Data System (ADS)

Xu, X. Q.; Xiong, Z.; Dorr, M. R.; Hittinger, J. A.; Bodi, K.; Candy, J.; Cohen, B. I.; Cohen, R. H.; Colella, P.; Kerbel, G. D.; Krasheninnikov, S.; Nevins, W. M.; Qin, H.; Rognlien, T. D.; Snyder, P. B.; Umansky, M. V.

2007-08-01

The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five-dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential and mirror ratio, and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the plateau regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL.

TRIM—3D: a three-dimensional model for accurate simulation of shallow water flow

USGS Publications Warehouse

Casulli, Vincenzo; Bertolazzi, Enrico; Cheng, Ralph T.

1993-01-01

A semi-implicit finite difference formulation for the numerical solution of three-dimensional tidal circulation is discussed. The governing equations are the three-dimensional Reynolds equations in which the pressure is assumed to be hydrostatic. A minimal degree of implicitness has been introduced in the finite difference formula so that the resulting algorithm permits the use of large time steps at a minimal computational cost. This formulation includes the simulation of flooding and drying of tidal flats, and is fully vectorizable for an efficient implementation on modern vector computers. The high computational efficiency of this method has made it possible to provide the fine details of circulation structure in complex regions that previous studies were unable to obtain. For proper interpretation of the model results suitable interactive graphics is also an essential tool.

A fully integrated direct-conversion digital satellite tuner in 0.18 μm CMOS

NASA Astrophysics Data System (ADS)

Si, Chen; Zengwang, Yang; Mingliang, Gu

2011-04-01

A fully integrated direct-conversion digital satellite tuner for DVB-S/S2 and ABS-S applications is presented. A broadband noise-canceling Balun-LNA and passive quadrature mixers provided a high-linearity low noise RF front-end, while the synthesizer integrated the loop filter to reduce the solution cost and system debug time. Fabricated in 0.18 μm CMOS, the chip achieves a less than 7.6 dB noise figure over a 900-2150 MHz L-band, while the measured sensitivity for 4.42 MS/s QPSK-3/4 mode is -91 dBm at the PCB connector. The fully integrated integer-N synthesizer operating from 2150 to 4350 MHz achieves less than 1 °C integrated phase error. The chip consumes about 145 mA at a 3.3 V supply with internal integrated LDOs.

Stability and instability towards delocalization in many-body localization systems

NASA Astrophysics Data System (ADS)

De Roeck, Wojciech; Huveneers, François

2017-04-01

We propose a theory that describes quantitatively the (in)stability of fully many-body localization (MBL) systems due to ergodic, i.e., delocalized, grains, that can be, for example, due to disorder fluctuations. The theory is based on the ETH hypothesis and elementary notions of perturbation theory. The main idea is that we assume as much chaoticity as is consistent with conservation laws. The theory describes correctly—even without relying on the theory of local integrals of motion (LIOM)—the MBL phase in one dimension at strong disorder. It yields an explicit and quantitative picture of the spatial boundary between localized and ergodic systems. We provide numerical evidence for this picture. When the theory is taken to its extreme logical consequences, it predicts that the MBL phase is destabilised in the long time limit whenever (1) interactions decay slower than exponentially in d =1 and (2) always in d >1 . Finer numerics is required to assess these predictions.

A numerical investigation of the effects of the spanwise length on the 3-D wake of a circular cylinder

NASA Astrophysics Data System (ADS)

Labbé, D. F. L.; Wilson, P. A.

2007-11-01

The numerical prediction of vortex-induced vibrations has been the focus of numerous investigations to date using tools such as computational fluid dynamics. In particular, the flow around a circular cylinder has raised much attention as it is present in critical engineering problems such as marine cables or risers. Limitations due to the computational cost imposed by the solution of a large number of equations have resulted in the study of mostly 2-D flows with only a few exceptions. The discrepancies found between experimental data and 2-D numerical simulations suggested that 3-D instabilities occurred in the wake of the cylinder that affect substantially the characteristics of the flow. The few 3-D numerical solutions available in the literature confirmed such a hypothesis. In the present investigation the effect of the spanwise extension of the solution domain on the 3-D wake of a circular cylinder is investigated for various Reynolds numbers between 40 and 1000. By assessing the minimum spanwise extension required to predict accurately the flow around a circular cylinder, the infinitely long cylinder is reduced to a finite length cylinder, thus making numerical solution an effective way of investigating flows around circular cylinders. Results are presented for three different spanwise extensions, namely πD/2, πD and 2πD. The analysis of the force coefficients obtained for the various Reynolds numbers together with a visualization of the three-dimensionalities in the wake of the cylinder allowed for a comparison between the effects of the three spanwise extensions. Furthermore, by showing the different modes of vortex shedding present in the wake and by analysing the streamwise components of the vorticity, it was possible to estimate the spanwise wavelengths at the various Reynolds numbers and to demonstrate that a finite spanwise extension is sufficient to accurately predict the flow past an infinitely long circular cylinder.

Numerical simulations of thermo-compositional global convection with generation of proto-continental crust

NASA Astrophysics Data System (ADS)

Rozel, A. B.; Golabek, G.; Gerya, T.; Jain, C.; Tackley, P. J.

2017-12-01

We study the creation of primordial continental crust (TTG rocks) employing fully self-consistent numerical models of thermo-chemical convection on a global scale at the Archean. We use realistic rheological parameters [1] in 2D spherical annulus geometry using the convection code StagYY [2] for a one billion years period. Starting from a pyrolytic composition and an initially warm core, our simulations first generate mafic crust and depleted mantle in the upper mantle. The basaltic material can be both erupted (cold) and/or intruded (warm) at the base of the crust following a predefined partitioning. At all times, water concentration is considered fully saturated in the top 10 km of the domain, and it simply advected with the deforming material elsewhere. We track the pressure-temperature conditions of the newly formed hydrated basalt and check if it matches the conditions necessary for the formation of proto-continental crust [3]. We systematically test the influence of volcanism (eruption, also called "heat pipe") and plutonism (intrusive magmatism) on the time-dependent geotherm in the lithosphere. We show that the "heat-pipe" model (assuming 100% eruption) suggested to be the main heat loss mechanism during the Archean epoch [4] is not able to produce continental crust since it forms a too cold lithosphere. We also systematically test various friction coefficients and show that an intrusion fraction higher than 60% (in agreement with [5]) combined with a friction coefficient larger than 0.1 produces the expected amount of the three main petrological TTG compositions previously reported [3]. This result seems robust as the amount of TTG rocks formed vary over orders of magnitude. A large eruption over intrusion ratio can result in up to 100 times less TTG felsic crust production than a case where plutonism dominates. This study represents a major step towards the production of self-consistent convection models able to generate the continental crust of the Earth.[1] Lourenço D. et al. (2016) Earth Plan. Sci. Lett. 438, 18-28. [2] Tackley P.J. (2008) Phys. Earth Plan. Int. 171, 7-18. [3] Moyen J.-F. (2011) Lithos 123, 21-36. [4] Moore, W. and Webb, A. (2013) Nature, 501, 501-505. [5] Crisp, J. A. (1984) Journ. Volc. Geoth. Res., 20, 177-211.

Computational modeling of fully-ionized, magnetized plasmas using the fluid approximation

NASA Astrophysics Data System (ADS)

Schnack, Dalton

2005-10-01

Strongly magnetized plasmas are rich in spatial and temporal scales, making a computational approach useful for studying these systems. The most accurate model of a magnetized plasma is based on a kinetic equation that describes the evolution of the distribution function for each species in six-dimensional phase space. However, the high dimensionality renders this approach impractical for computations for long time scales in relevant geometry. Fluid models, derived by taking velocity moments of the kinetic equation [1] and truncating (closing) the hierarchy at some level, are an approximation to the kinetic model. The reduced dimensionality allows a wider range of spatial and/or temporal scales to be explored. Several approximations have been used [2-5]. Successful computational modeling requires understanding the ordering and closure approximations, the fundamental waves supported by the equations, and the numerical properties of the discretization scheme. We review and discuss several ordering schemes, their normal modes, and several algorithms that can be applied to obtain a numerical solution. The implementation of kinetic parallel closures is also discussed [6].[1] S. Chapman and T.G. Cowling, ``The Mathematical Theory of Non-Uniform Gases'', Cambridge University Press, Cambridge, UK (1939).[2] R.D. Hazeltine and J.D. Meiss, ``Plasma Confinement'', Addison-Wesley Publishing Company, Redwood City, CA (1992).[3] L.E. Sugiyama and W. Park, Physics of Plasmas 7, 4644 (2000).[4] J.J. Ramos, Physics of Plasmas, 10, 3601 (2003).[5] P.J. Catto and A.N. Simakov, Physics of Plasmas, 11, 90 (2004).[6] E.D. Held et al., Phys. Plasmas 11, 2419 (2004)

A fully covariant mean-field dynamo closure for numerical 3 + 1 resistive GRMHD

NASA Astrophysics Data System (ADS)

Bucciantini, N.; Del Zanna, L.

2013-01-01

The powerful high-energy phenomena typically encountered in astrophysics invariably involve physical engines, like neutron stars and black hole accretion discs, characterized by a combination of highly magnetized plasmas, strong gravitational fields and relativistic motions. In recent years, numerical schemes for general relativistic magnetohydrodynamics (GRMHD) have been developed to model the multidimensional dynamics of such systems, including the possibility of evolving space-time. Such schemes have been also extended beyond the ideal limit including the effects of resistivity, in an attempt to model dissipative physical processes acting on small scales (subgrid effects) over the global dynamics. Along the same lines, the magnetic field could be amplified by the presence of turbulent dynamo processes, as often invoked to explain the high values of magnetization required in accretion discs and neutron stars. Here we present, for the first time, a further extension to include the possibility of a mean-field dynamo action within the framework of numerical 3 + 1 (resistive) GRMHD. A fully covariant dynamo closure is proposed, in analogy with the classical theory, assuming a simple α-effect in the comoving frame. Its implementation into a finite-difference scheme for GRMHD in dynamical space-times (the x-echo code by Bucciantini & Del Zanna) is described, and a set of numerical test is presented and compared with analytical solutions wherever possible.

Scaling properties of the two-dimensional randomly stirred Navier-Stokes equation.

PubMed

Mazzino, Andrea; Muratore-Ginanneschi, Paolo; Musacchio, Stefano

2007-10-05

We inquire into the scaling properties of the 2D Navier-Stokes equation sustained by a force field with Gaussian statistics, white noise in time, and with a power-law correlation in momentum space of degree 2 - 2 epsilon. This is at variance with the setting usually assumed to derive Kraichnan's classical theory. We contrast accurate numerical experiments with the different predictions provided for the small epsilon regime by Kraichnan's double cascade theory and by renormalization group analysis. We give clear evidence that for all epsilon, Kraichnan's theory is consistent with the observed phenomenology. Our results call for a revision in the renormalization group analysis of (2D) fully developed turbulence.

4D numerical observer for lesion detection in respiratory-gated PET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorsakul, Auranuch; Li, Quanzheng; Ouyang, Jinsong

2014-10-15

Purpose: Respiratory-gated positron emission tomography (PET)/computed tomography protocols reduce lesion smearing and improve lesion detection through a synchronized acquisition of emission data. However, an objective assessment of image quality of the improvement gained from respiratory-gated PET is mainly limited to a three-dimensional (3D) approach. This work proposes a 4D numerical observer that incorporates both spatial and temporal informations for detection tasks in pulmonary oncology. Methods: The authors propose a 4D numerical observer constructed with a 3D channelized Hotelling observer for the spatial domain followed by a Hotelling observer for the temporal domain. Realistic {sup 18}F-fluorodeoxyglucose activity distributions were simulated usingmore » a 4D extended cardiac torso anthropomorphic phantom including 12 spherical lesions at different anatomical locations (lower, upper, anterior, and posterior) within the lungs. Simulated data based on Monte Carlo simulation were obtained using GEANT4 application for tomographic emission (GATE). Fifty noise realizations of six respiratory-gated PET frames were simulated by GATE using a model of the Siemens Biograph mMR scanner geometry. PET sinograms of the thorax background and pulmonary lesions that were simulated separately were merged to generate different conditions of the lesions to the background (e.g., lesion contrast and motion). A conventional ordered subset expectation maximization (OSEM) reconstruction (5 iterations and 6 subsets) was used to obtain: (1) gated, (2) nongated, and (3) motion-corrected image volumes (a total of 3200 subimage volumes: 2400 gated, 400 nongated, and 400 motion-corrected). Lesion-detection signal-to-noise ratios (SNRs) were measured in different lesion-to-background contrast levels (3.5, 8.0, 9.0, and 20.0), lesion diameters (10.0, 13.0, and 16.0 mm), and respiratory motion displacements (17.6–31.3 mm). The proposed 4D numerical observer applied on multiple-gated images was compared to the conventional 3D approach applied on the nongated and motion-corrected images. Results: On average, the proposed 4D numerical observer improved the detection SNR by 48.6% (p < 0.005), whereas the 3D methods on motion-corrected images improved by 31.0% (p < 0.005) as compared to the nongated method. For all different conditions of the lesions, the relative SNR measurement (Gain = SNR{sub Observed}/SNR{sub Nongated}) of the 4D method was significantly higher than one from the motion-corrected 3D method by 13.8% (p < 0.02), where Gain{sub 4D} was 1.49 ± 0.21 and Gain{sub 3D} was 1.31 ± 0.15. For the lesion with the highest amplitude of motion, the 4D numerical observer yielded the highest observer-performance improvement (176%). For the lesion undergoing the smallest motion amplitude, the 4D method provided superior lesion detectability compared with the 3D method, which provided a detection SNR close to the nongated method. The investigation on a structure of the 4D numerical observer showed that a Laguerre–Gaussian channel matrix with a volumetric 3D function yielded higher lesion-detection performance than one with a 2D-stack-channelized function, whereas a different kind of channels that have the ability to mimic the human visual system, i.e., difference-of-Gaussian, showed similar performance in detecting uniform and spherical lesions. The investigation of the detection performance when increasing noise levels yielded decreasing detection SNR by 27.6% and 41.5% for the nongated and gated methods, respectively. The investigation of lesion contrast and diameter showed that the proposed 4D observer preserved the linearity property of an optimal-linear observer while the motion was present. Furthermore, the investigation of the iteration and subset numbers of the OSEM algorithm demonstrated that these parameters had impact on the lesion detectability and the selection of the optimal parameters could provide the maximum lesion-detection performance. The proposed 4D numerical observer outperformed the other observers for the lesion-detection task in various lesion conditions and motions. Conclusions: The 4D numerical observer shows substantial improvement in lesion detectability over the 3D observer method. The proposed 4D approach could potentially provide a more reliable objective assessment of the impact of respiratory-gated PET improvement for lesion-detection tasks. On the other hand, the 4D approach may be used as an upper bound to investigate the performance of the motion correction method. In future work, the authors will validate the proposed 4D approach on clinical data for detection tasks in pulmonary oncology.« less

3-D numerical simulations of earthquake ground motion in sedimentary basins: testing accuracy through stringent models

NASA Astrophysics Data System (ADS)

Chaljub, Emmanuel; Maufroy, Emeline; Moczo, Peter; Kristek, Jozef; Hollender, Fabrice; Bard, Pierre-Yves; Priolo, Enrico; Klin, Peter; de Martin, Florent; Zhang, Zhenguo; Zhang, Wei; Chen, Xiaofei

2015-04-01

Differences between 3-D numerical predictions of earthquake ground motion in the Mygdonian basin near Thessaloniki, Greece, led us to define four canonical stringent models derived from the complex realistic 3-D model of the Mygdonian basin. Sediments atop an elastic bedrock are modelled in the 1D-sharp and 1D-smooth models using three homogeneous layers and smooth velocity distribution, respectively. The 2D-sharp and 2D-smooth models are extensions of the 1-D models to an asymmetric sedimentary valley. In all cases, 3-D wavefields include strongly dispersive surface waves in the sediments. We compared simulations by the Fourier pseudo-spectral method (FPSM), the Legendre spectral-element method (SEM) and two formulations of the finite-difference method (FDM-S and FDM-C) up to 4 Hz. The accuracy of individual solutions and level of agreement between solutions vary with type of seismic waves and depend on the smoothness of the velocity model. The level of accuracy is high for the body waves in all solutions. However, it strongly depends on the discrete representation of the material interfaces (at which material parameters change discontinuously) for the surface waves in the sharp models. An improper discrete representation of the interfaces can cause inaccurate numerical modelling of surface waves. For all the numerical methods considered, except SEM with mesh of elements following the interfaces, a proper implementation of interfaces requires definition of an effective medium consistent with the interface boundary conditions. An orthorhombic effective medium is shown to significantly improve accuracy and preserve the computational efficiency of modelling. The conclusions drawn from the analysis of the results of the canonical cases greatly help to explain differences between numerical predictions of ground motion in realistic models of the Mygdonian basin. We recommend that any numerical method and code that is intended for numerical prediction of earthquake ground motion should be verified through stringent models that would make it possible to test the most important aspects of accuracy.

Integrated modeling of high βN steady state scenario on DIII-D

DOE PAGES

Park, Jin Myung; Ferron, J. R.; Holcomb, Christopher T.; ...

2018-01-10

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with β N > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state ( d/dt = 0) solutions and reproduces most features of DIII-D high β N discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high q min > 2 scenario achieves stable operation at β N as high as 5 by using a very broadmore » current density profile to improve the ideal-wall stabilization of low- n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high β N steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.« less

Integrated modeling of high βN steady state scenario on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jin Myung; Ferron, J. R.; Holcomb, Christopher T.

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with β N > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state ( d/dt = 0) solutions and reproduces most features of DIII-D high β N discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high q min > 2 scenario achieves stable operation at β N as high as 5 by using a very broadmore » current density profile to improve the ideal-wall stabilization of low- n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high β N steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.« less

Integrated modeling of high βN steady state scenario on DIII-D

NASA Astrophysics Data System (ADS)

Park, J. M.; Ferron, J. R.; Holcomb, C. T.; Buttery, R. J.; Solomon, W. M.; Batchelor, D. B.; Elwasif, W.; Green, D. L.; Kim, K.; Meneghini, O.; Murakami, M.; Snyder, P. B.

2018-01-01

Theory-based integrated modeling validated against DIII-D experiments predicts that fully non-inductive DIII-D operation with βN > 4.5 is possible with certain upgrades. IPS-FASTRAN is a new iterative numerical procedure that integrates models of core transport, edge pedestal, equilibrium, stability, heating, and current drive self-consistently to find steady-state (d/dt = 0) solutions and reproduces most features of DIII-D high βN discharges with a stationary current profile. Projecting forward to scenarios possible on DIII-D with future upgrades, the high qmin > 2 scenario achieves stable operation at βN as high as 5 by using a very broad current density profile to improve the ideal-wall stabilization of low-n instabilities along with confinement enhancement from low magnetic shear. This modeling guides the necessary upgrades of the heating and current drive system to realize reactor-relevant high βN steady-state scenarios on DIII-D by simultaneous optimization of the current and pressure profiles.

Two-Phase Flow Model and Experimental Validation for Bubble Augmented Waterjet Propulsion Nozzle

NASA Astrophysics Data System (ADS)

Choi, J.-K.; Hsiao, C.-T.; Wu, X.; Singh, S.; Jayaprakash, A.; Chahine, G.

2011-11-01

The concept of thrust augmentation through bubble injection into a waterjet has been the subject of many patents and publications over the past several decades, and there are simplified computational and experimental evidence of thrust increase. In this work, we present more rigorous numerical and experimental studies which aim at investigating two-phase water jet propulsion systems. The numerical model is based on a Lagrangian-Eulerian method, which considers the bubbly mixture flow both in the microscopic level where individual bubble dynamics are tracked and in the macroscopic level where bubbles are collectively described by the local void fraction of the mixture. DYNAFLOW's unsteady RANS solver, 3DYNAFS-Vis is used to solve the macro level variable density mixture medium, and a fully unsteady two-way coupling between this and the bubble dynamics/tracking code 3DYNAFS-DSM is utilized. Validation studies using measurements in a half 3-D experimental setup composed of divergent and convergent sections are presented. Visualization of the bubbles, PIV measurements of the flow, bubble size and behavior are observed, and the measured flow field data are used to validate the models. Thrust augmentation as high as 50% could be confirmed both by predictions and by experiments. This work was supported by the Office of Naval Research under the contract N00014-07-C-0427, monitored by Dr. Ki-Han Kim.

Numerical and Experimental Study of Transport Phenomena in Directional Solidification of Succinonitrile

NASA Technical Reports Server (NTRS)

de Groh, Henry C., III; Yao, Minwu

1994-01-01

A numerical and experimental study of the growth of succinonitrile (SCN) using a horizontal Bridginan furnace and transparent glass ampoule was conducted. Two experiments were considered: one in which the temperature profile was fixed relative to the ampoule (no-growth case); and a second in which the thermal profile was translated at a constant rate (steady growth case). Measured temperature profiles on the outer surface of the ampoule were used as thermal boundary conditions for the modelling. The apparent heat capacity formulation combined with the variable viscositymeth was used to model the phase change in SeN. Both 2-D and 3-D models were studied and numerical solutions obtained using the commercial finite element code, FIDAP1. Comparison of the numerical results to experimental data showed excellent agreement. The complex 3-D shallow-cavity flow in the melt, differences between 2-D and 3-D models, effects of natural convection on the thermal gradient and shape of the solid/liquid interface, and the sensitivity of simulations to specific assumptions, are also discussed.

Critical percolation clusters in seven dimensions and on a complete graph

NASA Astrophysics Data System (ADS)

Huang, Wei; Hou, Pengcheng; Wang, Junfeng; Ziff, Robert M.; Deng, Youjin

2018-02-01

We study critical bond percolation on a seven-dimensional hypercubic lattice with periodic boundary conditions (7D) and on the complete graph (CG) of finite volume (number of vertices) V . We numerically confirm that for both cases, the critical number density n (s ,V ) of clusters of size s obeys a scaling form n (s ,V ) ˜s-τn ˜(s /Vdf*) with identical volume fractal dimension df*=2 /3 and exponent τ =1 +1 /df*=5 /2 . We then classify occupied bonds into bridge bonds, which includes branch and junction bonds, and nonbridge bonds; a bridge bond is a branch bond if and only if its deletion produces at least one tree. Deleting branch bonds from percolation configurations produces leaf-free configurations, whereas deleting all bridge bonds leads to bridge-free configurations composed of blobs. It is shown that the fraction of nonbridge (biconnected) bonds vanishes, ρn ,CG→0 , for large CGs, but converges to a finite value, ρn ,7 D=0.006 193 1 (7 ) , for the 7D hypercube. Further, we observe that while the bridge-free dimension dbf*=1 /3 holds for both the CG and 7D cases, the volume fractal dimensions of the leaf-free clusters are different: dlf,7 D *=0.669 (9 ) ≈2 /3 and dlf,CG *=0.3337 (17 ) ≈1 /3 . On the CG and in 7D, the whole, leaf-free, and bridge-free clusters all have the shortest-path volume fractal dimension dmin*≈1 /3 , characterizing their graph diameters. We also study the behavior of the number and the size distribution of leaf-free and bridge-free clusters. For the number of clusters, we numerically find the number of leaf-free and bridge-free clusters on the CG scale as ˜lnV , while for 7D they scale as ˜V . For the size distribution, we find the behavior on the CG is governed by a modified Fisher exponent τ'=1 , while for leaf-free clusters in 7D, it is governed by Fisher exponent τ =5 /2 . The size distribution of bridge-free clusters in 7D displays two-scaling behavior with exponents τ =4 and τ'=1 . The probability distribution P (C1,V ) d C1 of the largest cluster of size C1 for whole percolation configurations is observed to follow a single-variable function P ¯(x ) d x , with x ≡C1/Vdf* for both CG and 7D. Up to a rescaling factor for the variable x , the probability functions for CG and 7D collapse on top of each other within the entire range of x . The analytical expressions in the x →0 and x →∞ limits are further confirmed. Our work demonstrates that the geometric structure of high-dimensional percolation clusters cannot be fully accounted for by their complete-graph counterparts.

Additive Manufacturing in the Marine Corps

DTIC Science & Technology

2015-06-01

commonly referred to as 3D printing. This thesis answers the question of how additive manufacturing can improve the effectiveness of Marine Corps...analysis of current and future 3D -printing processes, examination of several civilian and military examples, and examination of the impact across...fully integrating 3D printers, such as the lack of certification and qualification standards, unreliable end product results, and determining ownership

Motion compensation for fully 4D PET reconstruction using PET superset data

NASA Astrophysics Data System (ADS)

Verhaeghe, J.; Gravel, P.; Mio, R.; Fukasawa, R.; Rosa-Neto, P.; Soucy, J.-P.; Thompson, C. J.; Reader, A. J.

2010-07-01

Fully 4D PET image reconstruction is receiving increasing research interest due to its ability to significantly reduce spatiotemporal noise in dynamic PET imaging. However, thus far in the literature, the important issue of correcting for subject head motion has not been considered. Specifically, as a direct consequence of using temporally extensive basis functions, a single instance of movement propagates to impair the reconstruction of multiple time frames, even if no further movement occurs in those frames. Existing 3D motion compensation strategies have not yet been adapted to 4D reconstruction, and as such the benefits of 4D algorithms have not yet been reaped in a clinical setting where head movement undoubtedly occurs. This work addresses this need, developing a motion compensation method suitable for fully 4D reconstruction methods which exploits an optical tracking system to measure the head motion along with PET superset data to store the motion compensated data. List-mode events are histogrammed as PET superset data according to the measured motion, and a specially devised normalization scheme for motion compensated reconstruction from the superset data is required. This work proceeds to propose the corresponding time-dependent normalization modifications which are required for a major class of fully 4D image reconstruction algorithms (those which use linear combinations of temporal basis functions). Using realistically simulated as well as real high-resolution PET data from the HRRT, we demonstrate both the detrimental impact of subject head motion in fully 4D PET reconstruction and the efficacy of our proposed modifications to 4D algorithms. Benefits are shown both for the individual PET image frames as well as for parametric images of tracer uptake and volume of distribution for 18F-FDG obtained from Patlak analysis.

Motion compensation for fully 4D PET reconstruction using PET superset data.

PubMed

Verhaeghe, J; Gravel, P; Mio, R; Fukasawa, R; Rosa-Neto, P; Soucy, J-P; Thompson, C J; Reader, A J

2010-07-21

Fully 4D PET image reconstruction is receiving increasing research interest due to its ability to significantly reduce spatiotemporal noise in dynamic PET imaging. However, thus far in the literature, the important issue of correcting for subject head motion has not been considered. Specifically, as a direct consequence of using temporally extensive basis functions, a single instance of movement propagates to impair the reconstruction of multiple time frames, even if no further movement occurs in those frames. Existing 3D motion compensation strategies have not yet been adapted to 4D reconstruction, and as such the benefits of 4D algorithms have not yet been reaped in a clinical setting where head movement undoubtedly occurs. This work addresses this need, developing a motion compensation method suitable for fully 4D reconstruction methods which exploits an optical tracking system to measure the head motion along with PET superset data to store the motion compensated data. List-mode events are histogrammed as PET superset data according to the measured motion, and a specially devised normalization scheme for motion compensated reconstruction from the superset data is required. This work proceeds to propose the corresponding time-dependent normalization modifications which are required for a major class of fully 4D image reconstruction algorithms (those which use linear combinations of temporal basis functions). Using realistically simulated as well as real high-resolution PET data from the HRRT, we demonstrate both the detrimental impact of subject head motion in fully 4D PET reconstruction and the efficacy of our proposed modifications to 4D algorithms. Benefits are shown both for the individual PET image frames as well as for parametric images of tracer uptake and volume of distribution for (18)F-FDG obtained from Patlak analysis.

PDF turbulence modeling and DNS

NASA Technical Reports Server (NTRS)

Hsu, A. T.

1992-01-01

The problem of time discontinuity (or jump condition) in the coalescence/dispersion (C/D) mixing model is addressed in probability density function (pdf). A C/D mixing model continuous in time is introduced. With the continuous mixing model, the process of chemical reaction can be fully coupled with mixing. In the case of homogeneous turbulence decay, the new model predicts a pdf very close to a Gaussian distribution, with finite higher moments also close to that of a Gaussian distribution. Results from the continuous mixing model are compared with both experimental data and numerical results from conventional C/D models. The effect of Coriolis forces on compressible homogeneous turbulence is studied using direct numerical simulation (DNS). The numerical method used in this study is an eight order compact difference scheme. Contrary to the conclusions reached by previous DNS studies on incompressible isotropic turbulence, the present results show that the Coriolis force increases the dissipation rate of turbulent kinetic energy, and that anisotropy develops as the Coriolis force increases. The Taylor-Proudman theory does apply since the derivatives in the direction of the rotation axis vanishes rapidly. A closer analysis reveals that the dissipation rate of the incompressible component of the turbulent kinetic energy indeed decreases with a higher rotation rate, consistent with incompressible flow simulations (Bardina), while the dissipation rate of the compressible part increases; the net gain is positive. Inertial waves are observed in the simulation results.

Neutron and X-ray total scattering study of hydrogen disorder in fully hydrated hydrogrossular, Ca3Al2(O4H4)3

NASA Astrophysics Data System (ADS)

Keen, David A.; Keeble, Dean S.; Bennett, Thomas D.

2018-04-01

The structure of fully hydrated grossular, or katoite, contains an unusual arrangement of four O-H bonds within each O4 tetrahedra. Neutron and X-ray total scattering from a powdered deuterated sample have been measured to investigate the local arrangement of this O4D4 cluster. The O-D bond length determined directly from the pair distribution function is 0.954 Å, although the Rietveld-refined distance between average O and D positions was slightly smaller. Reverse Monte Carlo refinement of supercell models to the total scattering data show that other than the consequences of this correctly determined O-D bond length, there is little to suggest that the O4D4 structure is locally significantly different from that expected based on the average structure determined solely from Bragg diffraction.

Automatic bladder segmentation from CT images using deep CNN and 3D fully connected CRF-RNN.

PubMed

Xu, Xuanang; Zhou, Fugen; Liu, Bo

2018-03-19

Automatic approach for bladder segmentation from computed tomography (CT) images is highly desirable in clinical practice. It is a challenging task since the bladder usually suffers large variations of appearance and low soft-tissue contrast in CT images. In this study, we present a deep learning-based approach which involves a convolutional neural network (CNN) and a 3D fully connected conditional random fields recurrent neural network (CRF-RNN) to perform accurate bladder segmentation. We also propose a novel preprocessing method, called dual-channel preprocessing, to further advance the segmentation performance of our approach. The presented approach works as following: first, we apply our proposed preprocessing method on the input CT image and obtain a dual-channel image which consists of the CT image and an enhanced bladder density map. Second, we exploit a CNN to predict a coarse voxel-wise bladder score map on this dual-channel image. Finally, a 3D fully connected CRF-RNN refines the coarse bladder score map and produce final fine-localized segmentation result. We compare our approach to the state-of-the-art V-net on a clinical dataset. Results show that our approach achieves superior segmentation accuracy, outperforming the V-net by a significant margin. The Dice Similarity Coefficient of our approach (92.24%) is 8.12% higher than that of the V-net. Moreover, the bladder probability maps performed by our approach present sharper boundaries and more accurate localizations compared with that of the V-net. Our approach achieves higher segmentation accuracy than the state-of-the-art method on clinical data. Both the dual-channel processing and the 3D fully connected CRF-RNN contribute to this improvement. The united deep network composed of the CNN and 3D CRF-RNN also outperforms a system where the CRF model acts as a post-processing method disconnected from the CNN.

Numerical simulation of deformation and failure processes of a complex technical object under impact loading

NASA Astrophysics Data System (ADS)

Kraus, E. I.; Shabalin, I. I.; Shabalin, T. I.

2018-04-01

The main points of development of numerical tools for simulation of deformation and failure of complex technical objects under nonstationary conditions of extreme loading are presented. The possibility of extending the dynamic method for construction of difference grids to the 3D case is shown. A 3D realization of discrete-continuum approach to the deformation and failure of complex technical objects is carried out. The efficiency of the existing software package for 3D modelling is shown.

ALEX neutral beam probe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pourrezaei, K.

1982-01-01

A neutral beam probe capable of measuring plasma space potential in a fully 3-dimensional magnetic field geometry has been developed. This neutral beam was successfully used to measure an arc target plasma contained within the ALEX baseball magnetic coil. A computer simulation of the experiment was performed to refine the experimental design and to develop a numerical model for scaling the ALEX neutral beam probe to other cases of fully 3-dimensional magnetic field. Based on this scaling a 30 to 50 keV neutral cesium beam probe capable of measuring space potential in the thermal barrier region of TMX Upgrade wasmore » designed.« less

X-ray fluorescence holography studies for a Cu3Au crystal

NASA Astrophysics Data System (ADS)

Dąbrowski, K. M.; Dul, D. T.; Jaworska-Gołąb, T.; Rysz, J.; Korecki, P.

2015-12-01

In this work we show that performing a numerical correction for beam attenuation and indirect excitation allows one to fully restore element sensitivity in the three-dimensional reconstruction of the atomic structure. This is exemplified by a comparison of atomic images reconstructed from holograms measured for ordered and disordered phases of a Cu3Au crystal that clearly show sensitivity to changes in occupancy of the atomic sites. Moreover, the numerical correction, which is based on quantitative methods of X-ray fluorescence spectroscopy, was extended to take into account the influence of a disturbed overlayer in the sample.

Elastic Differential Cross Sections

NASA Technical Reports Server (NTRS)

Werneth, Charles M.; Maung, Khin M.; Ford, William P.; Norbury, John W.; Vera, Michael D.

2014-01-01

The eikonal, partial wave (PW) Lippmann-Schwinger, and three-dimensional Lippmann-Schwinger (LS3D) methods are compared for nuclear reactions that are relevant for space radiation applications. Numerical convergence of the eikonal method is readily achieved when exact formulas of the optical potential are used for light nuclei (A less than or equal to 16) and the momentum-space optical potential is used for heavier nuclei. The PW solution method is known to be numerically unstable for systems that require a large number of partial waves, and, as a result, the LS3D method is employed. The effect of relativistic kinematics is studied with the PW and LS3D methods and is compared to eikonal results. It is recommended that the LS3D method be used for high energy nucleon- nucleus reactions and nucleus-nucleus reactions at all energies because of its rapid numerical convergence and stability.

Nuclear Cross Sections for Space Radiation Applications

NASA Technical Reports Server (NTRS)

Werneth, C. M.; Maung, K. M.; Ford, W. P.; Norbury, J. W.; Vera, M. D.

2015-01-01

The eikonal, partial wave (PW) Lippmann-Schwinger, and three-dimensional Lippmann-Schwinger (LS3D) methods are compared for nuclear reactions that are relevant for space radiation applications. Numerical convergence of the eikonal method is readily achieved when exact formulas of the optical potential are used for light nuclei (A = 16) and the momentum-space optical potential is used for heavier nuclei. The PW solution method is known to be numerically unstable for systems that require a large number of partial waves, and, as a result, the LS3D method is employed. The effect of relativistic kinematics is studied with the PW and LS3D methods and is compared to eikonal results. It is recommended that the LS3D method be used for high energy nucleon-nucleus reactions and nucleus-nucleus reactions at all energies because of its rapid numerical convergence and stability for both non-relativistic and relativistic kinematics.

Three-dimensional finite amplitude electroconvection in dielectric liquids

NASA Astrophysics Data System (ADS)

Luo, Kang; Wu, Jian; Yi, Hong-Liang; Tan, He-Ping

2018-02-01

Charge injection induced electroconvection in a dielectric liquid lying between two parallel plates is numerically simulated in three dimensions (3D) using a unified lattice Boltzmann method (LBM). Cellular flow patterns and their subcritical bifurcation phenomena of 3D electroconvection are numerically investigated for the first time. A unit conversion is also derived to connect the LBM system to the real physical system. The 3D LBM codes are validated by three carefully chosen cases and all results are found to be highly consistent with the analytical solutions or other numerical studies. For strong injection, the steady state roll, polygon, and square flow patterns are observed under different initial disturbances. Numerical results show that the hexagonal cell with the central region being empty of charge and centrally downward flow is preferred in symmetric systems under random initial disturbance. For weak injection, the numerical results show that the flow directly passes from the motionless state to turbulence once the system loses its linear stability. In addition, the numerically predicted linear and finite amplitude stability criteria of different flow patterns are discussed.

Fully kinetic particle simulations of high pressure streamer propagation

NASA Astrophysics Data System (ADS)

Rose, David; Welch, Dale; Thoma, Carsten; Clark, Robert

2012-10-01

Streamer and leader formation in high pressure devices is a dynamic process involving a hierarchy of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. We have performed 2D and 3D fully EM implicit particle-in-cell simulation model of gas breakdown leading to streamer formation under DC and RF fields. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm [D. R. Welch, et al., J. Comp. Phys. 227, 143 (2007)] that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge. These models are being applied to the analysis of high-pressure gas switches [D. V. Rose, et al., Phys. Plasmas 18, 093501 (2011)] and gas-filled RF accelerator cavities [D. V. Rose, et al. Proc. IPAC12, to appear].

3D Cryo-Imaging: A Very High-Resolution View of the Whole Mouse

PubMed Central

Roy, Debashish; Steyer, Grant J.; Gargesha, Madhusudhana; Stone, Meredith E.; Wilson, David L.

2009-01-01

We developed the Case Cryo-imaging system that provides information rich, very high-resolution, color brightfield, and molecular fluorescence images of a whole mouse using a section-and-image block-face imaging technology. The system consists of a mouse-sized, motorized cryo-microtome with special features for imaging, a modified, brightfield/ fluorescence microscope, and a robotic xyz imaging system positioner, all of which is fully automated by a control system. Using the robotic system, we acquired microscopic tiled images at a pixel size of 15.6 µm over the block face of a whole mouse sectioned at 40 µm, with a total data volume of 55 GB. Viewing 2D images at multiple resolutions, we identified small structures such as cardiac vessels, muscle layers, villi of the small intestine, the optic nerve, and layers of the eye. Cryo-imaging was also suitable for imaging embryo mutants in 3D. A mouse, in which enhanced green fluorescent protein was expressed under gamma actin promoter in smooth muscle cells, gave clear 3D views of smooth muscle in the urogenital and gastrointestinal tracts. With cryo-imaging, we could obtain 3D vasculature down to 10 µm, over very large regions of mouse brain. Software is fully automated with fully programmable imaging/sectioning protocols, email notifications, and automatic volume visualization. With a unique combination of field-of-view, depth of field, contrast, and resolution, the Case Cryo-imaging system fills the gap between whole animal in vivo imaging and histology. PMID:19248166

Insights from 3D numerical simulations on the dynamics of the India-Asia collision zone

NASA Astrophysics Data System (ADS)

Pusok, A. E.; Kaus, B.; Popov, A.

2013-12-01

The dynamics of the India-Asia collision zone remains one of the most remarkable topics of the current research interest: the transition from subduction to collision and uplift, followed by the rise of the abnormally thick Tibetan plateau, and the deformation at its Eastern and Western syntaxes, are processes still not fully understood. Models that have addressed this topic include wholescale underthrusting of Indian lithospheric mantle under Tibet, distributed homogeneous shortening or the thin-sheet model, slip-line field model for lateral extrusion or lower crustal flow models for the exhumation of the Himalayan units and lateral spreading of the Tibetan plateau. Of these, the thin-sheet model has successfully illustrated some of the basic physics of continental collision and has the advantage of a 3D model being reduced to 2D, but one of its major shortcomings is that it cannot simultaneously represent channel flow and gravitational collapse of the mantle lithosphere, since these mechanisms require the lithosphere to interact with the underlying mantle, or to have a vertically non-homogeneous rheology. As a consequence, 3D models are emerging as powerful tools to understand the dynamics of coupled systems. However, because of yet recent developments and various complexities, the current 3D models simulating the dynamics of continent collision zones have relied on certain explicit assumptions, such as replacing part of the asthenosphere with various types of boundary conditions that mimic the effect of mantle flow, in order to focus on the lithospheric/crustal deformation. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We present qualitative results on lithospheric and upper-mantle scale simulations in which the Indian lithosphere is subducted and/or indented into Asia. We investigate the way deep processes affect continental tectonics at convergent margins, addressing the role the continent subduction and indentation plays on the development of continental tectonics during convergence and we discuss the implications these offer for the Asian tectonics. Acknowledgements: Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on MOGON (ZDV Mainz computing center) and JUQUEEN (Jülich high-performance computing center).

A Novel Method for Dynamic Short-Beam Shear Testing of 3D Woven Composites

DTIC Science & Technology

2011-08-11

specimen was homogenized as an orthotropic elastic material with properties given in Table 1 [38]. The use of fully elastic model removes any material...impact event however after approximately 0.5 mm of deflection, equilibrium is reached. It is observed from Fig. 4(d) that equilibrium is never fully ...The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing

A Unit-Cell Model for Predicting the Elastic Constants of 3D Four Directional Cylindrical Braided Composite Shafts

NASA Astrophysics Data System (ADS)

Hao, Wenfeng; Liu, Ye; Huang, Xinrong; Liu, Yinghua; Zhu, Jianguo

2018-06-01

In this work, the elastic constants of 3D four directional cylindrical braided composite shafts were predicted using analytical and numerical methods. First, the motion rule of yarn carrier of 3D four directional cylindrical braided composite shafts was analyzed, and the horizontal projection of yarn motion trajectory was obtained. Then, the geometry models of unit-cells with different braiding angles and fiber volume contents were built up, and the meso-scale models of 3D cylindrical braided composite shafts were obtained. Finally, the effects of braiding angles and fiber volume contents on the elastic constants of 3D braided composite shafts were analyzed theoretically and numerically. These results play a crucial role in investigating the mechanical properties of 3D 4-directional braided composites shafts.

Polarimetric Calibration and Assessment of GF-3 Images in Steppe

NASA Astrophysics Data System (ADS)

Chang, Y.; Yang, J.; Li, P.; Shi, L.; Zhao, L.

2018-04-01

The GaoFen-3 (GF-3) satellite is the first fully polarimetric synthetic aperture radar (PolSAR) satellite in China. It has three fully polarimetric imaging modes and is available for many applications. The system has been taken on several calibration experiments after the launch in Inner Mongolia by the Institute of Electronics, Chinese Academy of Sciences (IECAS), and the polarimetric calibration (PolCAL) strategy of GF-3 are also improved. Therefore, it is necessary to assess the image quality before any further applications. In this paper, we evaluated the polarimetric residual errors of GF-3 images that acquired in July 2017 in a steppe site. The results shows that the crosstalk of these images varies from -36 dB to -46 dB, and the channel imbalance varies from -0.43 dB to 0.55 dB with angle varying from -1.6 to 3.6 degree. We also made a PolCAL experiment to restrain the polarimetric distortion afterwards, and the polarimetric quality of the image got better after the PolCAL processing.

Computational Challenges of 3D Radiative Transfer in Atmospheric Models

NASA Astrophysics Data System (ADS)

Jakub, Fabian; Bernhard, Mayer

2017-04-01

The computation of radiative heating and cooling rates is one of the most expensive components in todays atmospheric models. The high computational cost stems not only from the laborious integration over a wide range of the electromagnetic spectrum but also from the fact that solving the integro-differential radiative transfer equation for monochromatic light is already rather involved. This lead to the advent of numerous approximations and parameterizations to reduce the cost of the solver. One of the most prominent one is the so called independent pixel approximations (IPA) where horizontal energy transfer is neglected whatsoever and radiation may only propagate in the vertical direction (1D). Recent studies implicate that the IPA introduces significant errors in high resolution simulations and affects the evolution and development of convective systems. However, using fully 3D solvers such as for example MonteCarlo methods is not even on state of the art supercomputers feasible. The parallelization of atmospheric models is often realized by a horizontal domain decomposition, and hence, horizontal transfer of energy necessitates communication. E.g. a cloud's shadow at a low zenith angle will cast a long shadow and potentially needs to communication through a multitude of processors. Especially light in the solar spectral range may travel long distances through the atmosphere. Concerning highly parallel simulations, it is vital that 3D radiative transfer solvers put a special emphasis on parallel scalability. We will present an introduction to intricacies computing 3D radiative heating and cooling rates as well as report on the parallel performance of the TenStream solver. The TenStream is a 3D radiative transfer solver using the PETSc framework to iteratively solve a set of partial differential equation. We investigate two matrix preconditioners, (a) geometric algebraic multigrid preconditioning(MG+GAMG) and (b) block Jacobi incomplete LU (ILU) factorization. The TenStream solver is tested for up to 4096 cores and shows a parallel scaling efficiency of 80-90% on various supercomputers.

Numerical modeling techniques for flood analysis

NASA Astrophysics Data System (ADS)

Anees, Mohd Talha; Abdullah, K.; Nawawi, M. N. M.; Ab Rahman, Nik Norulaini Nik; Piah, Abd. Rahni Mt.; Zakaria, Nor Azazi; Syakir, M. I.; Mohd. Omar, A. K.

2016-12-01

Topographic and climatic changes are the main causes of abrupt flooding in tropical areas. It is the need to find out exact causes and effects of these changes. Numerical modeling techniques plays a vital role for such studies due to their use of hydrological parameters which are strongly linked with topographic changes. In this review, some of the widely used models utilizing hydrological and river modeling parameters and their estimation in data sparse region are discussed. Shortcomings of 1D and 2D numerical models and the possible improvements over these models through 3D modeling are also discussed. It is found that the HEC-RAS and FLO 2D model are best in terms of economical and accurate flood analysis for river and floodplain modeling respectively. Limitations of FLO 2D in floodplain modeling mainly such as floodplain elevation differences and its vertical roughness in grids were found which can be improve through 3D model. Therefore, 3D model was found to be more suitable than 1D and 2D models in terms of vertical accuracy in grid cells. It was also found that 3D models for open channel flows already developed recently but not for floodplain. Hence, it was suggested that a 3D model for floodplain should be developed by considering all hydrological and high resolution topographic parameter's models, discussed in this review, to enhance the findings of causes and effects of flooding.

Controllable growth of porous structures from co-continuous polymer blend

NASA Astrophysics Data System (ADS)

Zhang, Wei

To enable controllable generation of porous structures, a set of new fabrication techniques utilizing the annealing kinetics of co-continuous polymer blends were proposed and investigated. As the first step towards the creation of an organized porous material, a new technique based on regulating the thermal boundary conditions to controllably grow gradient porous structures was developed. In this technique, specially designed thermal boundaries were used to generate a well-defined temperature field inside a co-continuous polymer blend with fine phase structure. Because of the temperature dependency of zero-shear viscosity and its influence on phase coarsening rate, a graded phase size distribution was generated by this temperature field. After one component was selectively dissolved, a gradient porous structure was produced. To demonstrate the versatility of this technique, three different gradient porous structures were created. After the effectiveness of thermal boundary condition in developing organized porous materials was verified, the possibility of utilizing kinematic and dynamic boundary conditions to obtain extra controllability was investigated. Two types of kinematic boundary conditions, no-slip wall and 1D hard wall confinement were tested separately. It was found that no-slip wall could greatly slow down the phase coarsening rate of the nearby polymer blend. When a no-slip wall and a fully slip wall were applied at each side of a molten co-continuous blend, a pore size gradient was generated in the direction perpendicular to the wall surface with smaller pores near the no-slip wall. One directional hard wall confinement formed by a pair of fully slip parallel walls led to the formation of an aligned phase structure oriented in the vertical direction to the walls. Experiments regarding the effect of dynamic boundary condition were conducted by imposing different chemical potentials at the surface of molten blend. Fully dense surface and completely open surface were generated when high energy metallic surface and low energy PTFE (polytetrafluoroethylene) were applied respectively. In addition to the creation of polymeric porous materials, the generation of organized porous nanocomposite with high nanoparticle loading was also explored to incorporate unique properties seldom appearing in polymeric materials. The influence of blending procedure was first studied to secure the required co-continuous phase morphology for making porous nanocomposite. It was found that one had to simultaneously introduce all ingredients for mixing to minimize the change in viscosity ratio and produce the initial co-continuous structures. Because of the high nanoparticle loading, most of the formed pores were crowded with aggregates from particles originally located in the dissolved phase. To obtain the desired high permeability, a technique based on small strain oscillation was developed to facilitate rapid migration of these nanoparticles out of the sacrificial component. The effectiveness of this method was confirmed by a parametric experimental study. In addition, it was found that the migration rate of the nanoparticle could be predicted by combining the Einstein-Stokes diffusion model with the Cox-Merz rule. To create porous material with desired geometries for different application needs, a new molding technique capable of creating precise micropatterned porous structures was developed and examined. In this new technique, hot embossing and in-mold quiescent annealing were applied successively to a co-continuous polymer blend to pattern the blend into expected geometries and in the same time produce the desired bulk microstructures. The effectiveness of this molding protocol was confirmed by experimental results in which devices with different micropatterns, average pore sizes, pore size distributions, and pore alignments were created. For cases where fully open surface is required, a criterion for choosing a proper molding condition was provided. Other than these experimental efforts, a new numerical simulation approach was developed to obtain better control for growing complex gradient porous structures. First, rheological characterization was combined with CFD (computational fluid dynamics) to simulate the quiescent annealing process. According to experimental results from other researchers, there is a simple relation between 2D and 3D coarsening rates for a co-continuous polymer blend. If a similar relation could be obtained between 2D and 3D simulation, the computational cost could be greatly reduced. To verify the existence of the aforementioned relation, the 2D and 3D coarsening rates were calculated through simulation on a simplified 3D model. With 2D simulation, both the initiation linear growth region and the later stage plateau were predicted, and these findings agreed with experimental results from literature. Non-isothermal temperature field was also incorporated in the model to predict the phase size distribution. Finally, the experimental conditions used in the creations of 1D and 2D gradient porous structures were applied in numerical simulations. The simulation results closely matched the experimental results. (Abstract shortened by UMI.)

Distribution of aerosolized particles in healthy and emphysematous rat lungs: comparison between experimental and numerical studies.

PubMed

Oakes, Jessica M; Marsden, Alison L; Grandmont, Céline; Darquenne, Chantal; Vignon-Clementel, Irene E

2015-04-13

In silico models of airflow and particle deposition in the lungs are increasingly used to determine the therapeutic or toxic effects of inhaled aerosols. While computational methods have advanced significantly, relatively few studies have directly compared model predictions to experimental data. Furthermore, few prior studies have examined the influence of emphysema on particle deposition. In this work we performed airflow and particle simulations to compare numerical predictions to data from our previous aerosol exposure experiments. Employing an image-based 3D rat airway geometry, we first compared steady flow simulations to coupled 3D-0D unsteady simulations in the healthy rat lung. Then, in 3D-0D simulations, the influence of emphysema was investigated by matching disease location to the experimental study. In both the healthy unsteady and steady simulations, good agreement was found between numerical predictions of aerosol delivery and experimental deposition data. However, deposition patterns in the 3D geometry differed between the unsteady and steady cases. On the contrary, satisfactory agreement was not found between the numerical predictions and experimental data for the emphysematous lungs. This indicates that the deposition rate downstream of the 3D geometry is likely proportional to airflow delivery in the healthy lungs, but not in the emphysematous lungs. Including small airway collapse, variations in downstream airway size and tissue properties, and tracking particles throughout expiration may result in a more favorable agreement in future studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Anomalous Lower Crustal and Surface Features as a Result of Plume-induced Continental Break-up: Inferences from Numerical Models

NASA Astrophysics Data System (ADS)

Beniest, A.; Koptev, A.; Leroy, S. D.

2016-12-01

Anomalous features along the South American and African rifted margins at depth and at the surface have been recognised with gravity and magnetic modelling. They include high velocity/high density bodies at lower crustal level and topography variations that are usually interpreted as aborted rifts. We present fully-coupled lithosphere-scale numerical models that permit us to explain both features in a relatively simple framework of an interaction between rheologically stratified continental lithosphere and an active mantle plume. We used 2D and 3D numerical models to investigate the impact of thermo-rheological structure of the continental lithosphere and initial plume position on continental rifting and breakup processes. Based on the results of our 2D experiments, three main types of continental break-up are revealed: A) mantle plume-induced break-up, directly located above the centre of the mantle anomaly, B) mantle plume-induced break-up, 50 to 250 km displaced from the initial plume location and C) self-induced break-up due to convection and/or slab-subduction/delamination, considerably shifted (300 to 800 km) from the initial plume position. With our 3D, laterally homogenous initial setup, we show that a complex system, with the axis of continental break-up 100's of km's shifted from the original plume location, can arise spontaneously from simple and perfectly symmetric preliminary settings. Our modelling demonstrates that fragments of a laterally migrating plume head become glued to the base of the lithosphere and remain at both sides of the newly-formed oceanic basin after continental break-up. Underplated plume material soldered into lower parts of lithosphere can be interpreted as the high-velocity/high density magmatic bodies at lower crustal levels. In the very early stages of rifting, first impingement of the vertically upwelled mantle plume to the lithospheric base leads to surface topographic variations. Given the shifted position of the final spreading centre with respect to initial plume position, these topographic variations resemble aborted rifts that are observed on passive margins. Lastly, after continuous extension and transition to the spreading state, strain rate relocalizations develop that can be interpreted as ridge jumps that are commonly observed in nature.

A unified Fourier theory for time-of-flight PET data

PubMed Central

Li, Yusheng; Matej, Samuel; Metzler, Scott D

2016-01-01

Fully 3D time-of-flight (TOF) PET scanners offer the potential of previously unachievable image quality in clinical PET imaging. TOF measurements add another degree of redundancy for cylindrical PET scanners and make photon-limited TOF-PET imaging more robust than non-TOF PET imaging. The data space for 3D TOF-PET data is five-dimensional with two degrees of redundancy. Previously, consistency equations were used to characterize the redundancy of TOF-PET data. In this paper, we first derive two Fourier consistency equations and Fourier-John equation for 3D TOF PET based on the generalized projection-slice theorem; the three partial differential equations (PDEs) are the dual of the sinogram consistency equations and John's equation. We then solve the three PDEs using the method of characteristics. The two degrees of entangled redundancy of the TOF-PET data can be explicitly elicited and exploited by the solutions of the PDEs along the characteristic curves, which gives a complete understanding of the rich structure of the 3D X-ray transform with TOF measurement. Fourier rebinning equations and other mapping equations among different types of PET data are special cases of the general solutions. We also obtain new Fourier rebinning and consistency equations (FORCEs) from other special cases of the general solutions, and thus we obtain a complete scheme to convert among different types of PET data: 3D TOF, 3D non-TOF, 2D TOF and 2D non-TOF data. The new FORCEs can be used as new Fourier-based rebinning algorithms for TOF-PET data reduction, inverse rebinnings for designing fast projectors, or consistency conditions for estimating missing data. Further, we give a geometric interpretation of the general solutions—the two families of characteristic curves can be obtained by respectively changing the azimuthal and co-polar angles of the biorthogonal coordinates in Fourier space. We conclude the unified Fourier theory by showing that the Fourier consistency equations are necessary and sufficient for 3D X-ray transform with TOF measurement. Finally, we give numerical examples of inverse rebinning for a 3D TOF PET and Fourier-based rebinning for a 2D TOF PET using the FORCEs to show the efficacy of the unified Fourier solutions. PMID:26689836

A unified Fourier theory for time-of-flight PET data.

PubMed

Li, Yusheng; Matej, Samuel; Metzler, Scott D

2016-01-21

Fully 3D time-of-flight (TOF) PET scanners offer the potential of previously unachievable image quality in clinical PET imaging. TOF measurements add another degree of redundancy for cylindrical PET scanners and make photon-limited TOF-PET imaging more robust than non-TOF PET imaging. The data space for 3D TOF-PET data is five-dimensional with two degrees of redundancy. Previously, consistency equations were used to characterize the redundancy of TOF-PET data. In this paper, we first derive two Fourier consistency equations and Fourier-John equation for 3D TOF PET based on the generalized projection-slice theorem; the three partial differential equations (PDEs) are the dual of the sinogram consistency equations and John's equation. We then solve the three PDEs using the method of characteristics. The two degrees of entangled redundancy of the TOF-PET data can be explicitly elicited and exploited by the solutions of the PDEs along the characteristic curves, which gives a complete understanding of the rich structure of the 3D x-ray transform with TOF measurement. Fourier rebinning equations and other mapping equations among different types of PET data are special cases of the general solutions. We also obtain new Fourier rebinning and consistency equations (FORCEs) from other special cases of the general solutions, and thus we obtain a complete scheme to convert among different types of PET data: 3D TOF, 3D non-TOF, 2D TOF and 2D non-TOF data. The new FORCEs can be used as new Fourier-based rebinning algorithms for TOF-PET data reduction, inverse rebinnings for designing fast projectors, or consistency conditions for estimating missing data. Further, we give a geometric interpretation of the general solutions--the two families of characteristic curves can be obtained by respectively changing the azimuthal and co-polar angles of the biorthogonal coordinates in Fourier space. We conclude the unified Fourier theory by showing that the Fourier consistency equations are necessary and sufficient for 3D x-ray transform with TOF measurement. Finally, we give numerical examples of inverse rebinning for a 3D TOF PET and Fourier-based rebinning for a 2D TOF PET using the FORCEs to show the efficacy of the unified Fourier solutions.

Separation of Evans and Hiro currents in VDE of tokamak plasma

NASA Astrophysics Data System (ADS)

Galkin, Sergei A.; Svidzinski, V. A.; Zakharov, L. E.

2014-10-01

Progress on the Disruption Simulation Code (DSC-3D) development and benchmarking will be presented. The DSC-3D is one-fluid nonlinear time-dependent MHD code, which utilizes fully 3D toroidal geometry for the first wall, pure vacuum and plasma itself, with adaptation to the moving plasma boundary and accurate resolution of the plasma surface current. Suppression of fast magnetosonic scale by the plasma inertia neglecting will be demonstrated. Due to code adaptive nature, self-consistent plasma surface current modeling during non-linear dynamics of the Vertical Displacement Event (VDE) is accurately provided. Separation of the plasma surface current on Evans and Hiro currents during simulation of fully developed VDE, then the plasma touches in-vessel tiles, will be discussed. Work is supported by the US DOE SBIR Grant # DE-SC0004487.

Unconventional pairing symmetry of interacting Dirac fermions on a π -flux lattice

DOE PAGES

Guo, Huaiming; Khatami, Ehsan; Wang, Yao; ...

2018-04-20

The pairing symmetry of interacting Dirac fermions on the π-flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s*- (i.e., extended s-) and d-wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional ds*-wave phase consisting of alternating stripes of s*- and d-wave phases. A complementary mean-field analysis shows that while the s*- and d-wave symmetries individually have nodes in the energy spectrum, the ds* channel is fully gapped. The results represent amore » new realization of pairing in Dirac systems, connected to the problem of chiral d-wave pairing on the honeycomb lattice, which might be more readily accessed by cold-atom experiments.« less

Stochastic process of pragmatic information for 2D spiral wave turbulence in globally and locally coupled Alief-Panfilov oscillators

NASA Astrophysics Data System (ADS)

Kuwahara, Jun; Miyata, Hajime; Konno, Hidetoshi

2017-09-01

Recently, complex dynamics of globally coupled oscillators have been attracting many researcher's attentions. In spite of their numerous studies, their features of nonlinear oscillator systems with global and local couplings in two-dimension (2D) are not understood fully. The paper focuses on 2D states of coherent, clustered and chaotic oscillation especially under the effect of negative global coupling (NGC) in 2D Alief-Panfilov model. It is found that the tuning NGC can cause various new coupling-parameter dependency on the features of oscillations. Then quantitative characterization of various states of oscillations (so called spiral wave turbulence) is examined by using the pragmatic information (PI) which have been utilized in analyzing multimode laser, solar activity and neuronal systems. It is demonstrated that the dynamics of the PI for various oscillations can be characterized successfully by the Hyper-Gamma stochastic process.

Anibamine and its Analogues as Novel Anti Prostate Cancer Agents

DTIC Science & Technology

2010-06-01

PC- 3, and DU-145 has been conducted continuously to evaluate the efficacy of more ligands. A molecular modeling study (3D QSAR ) protocol has been... Toxicology at Virginia Commonwealth University. Both the PI’s lab and Dr. 10 Selley’s lab have fully functional binding assay facility. The assays is...pursue the docking study and 3D QSAR study. 5.3 3D QSAR (Quantitative Structure-Activity Relationships) Study As proposed in our proposal, we will

Three-dimensional analysis of flow-chemical interaction within a single square channel of a lean NO x trap catalyst.

PubMed

Fornarelli, Francesco; Dadduzio, Ruggiero; Torresi, Marco; Camporeale, Sergio Mario; Fortunato, Bernardo

2018-02-01

A fully 3D unsteady Computational Fluid Dynamics (CFD) approach coupled with heterogeneous reaction chemistry is presented in order to study the behavior of a single square channel as part of a Lean [Formula: see text] Traps. The reliability of the numerical tool has been validated against literature data considering only active BaO site. Even though the input/output performance of such catalyst has been well known, here the spatial distribution within a single channel is investigated in details. The square channel geometry influences the flow field and the catalyst performance being the flow velocity distribution on the cross section non homogeneous. The mutual interaction between the flow and the active catalyst walls influences the spatial distribution of the volumetric species. Low velocity regions near the square corners and transversal secondary flows are shown in several cross-sections along the streamwise direction at different instants. The results shed light on the three-dimensional characteristic of both the flow field and species distribution within a single square channel of the catalyst with respect to 0-1D approaches.

Fully automatic three-dimensional visualization of intravascular optical coherence tomography images: methods and feasibility in vivo

PubMed Central

Ughi, Giovanni J; Adriaenssens, Tom; Desmet, Walter; D’hooge, Jan

2012-01-01

Intravascular optical coherence tomography (IV-OCT) is an imaging modality that can be used for the assessment of intracoronary stents. Recent publications pointed to the fact that 3D visualizations have potential advantages compared to conventional 2D representations. However, 3D imaging still requires a time consuming manual procedure not suitable for on-line application during coronary interventions. We propose an algorithm for a rapid and fully automatic 3D visualization of IV-OCT pullbacks. IV-OCT images are first processed for the segmentation of the different structures. This also allows for automatic pullback calibration. Then, according to the segmentation results, different structures are depicted with different colors to visualize the vessel wall, the stent and the guide-wire in details. Final 3D rendering results are obtained through the use of a commercial 3D DICOM viewer. Manual analysis was used as ground-truth for the validation of the segmentation algorithms. A correlation value of 0.99 and good limits of agreement (Bland Altman statistics) were found over 250 images randomly extracted from 25 in vivo pullbacks. Moreover, 3D rendering was compared to angiography, pictures of deployed stents made available by the manufacturers and to conventional 2D imaging corroborating visualization results. Computational time for the visualization of an entire data sets resulted to be ~74 sec. The proposed method allows for the on-line use of 3D IV-OCT during percutaneous coronary interventions, potentially allowing treatments optimization. PMID:23243578

Numerical conformal mapping: Methods, applications, and theory. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeLillo, T.K.

1995-11-01

Section 1 of this report, briefly summarizes research performed under this grant during the first two years 1992 to 1994 and makes some overall remarks. Section 2, summarizes research performed during the final year from September, 1994 through May 31, 1995, more fully. The main achievement of the last period has been the application of numerical conformed mapping to the solution of the biharmonic equation. Section 3, summarizes travel, meetings, and other expenses supported by this grant during the final year.

Development of discrete gas kinetic scheme for simulation of 3D viscous incompressible and compressible flows

NASA Astrophysics Data System (ADS)

Yang, L. M.; Shu, C.; Wang, Y.; Sun, Y.

2016-08-01

The sphere function-based gas kinetic scheme (GKS), which was presented by Shu and his coworkers [23] for simulation of inviscid compressible flows, is extended to simulate 3D viscous incompressible and compressible flows in this work. Firstly, we use certain discrete points to represent the spherical surface in the phase velocity space. Then, integrals along the spherical surface for conservation forms of moments, which are needed to recover 3D Navier-Stokes equations, are approximated by integral quadrature. The basic requirement is that these conservation forms of moments can be exactly satisfied by weighted summation of distribution functions at discrete points. It was found that the integral quadrature by eight discrete points on the spherical surface, which forms the D3Q8 discrete velocity model, can exactly match the integral. In this way, the conservative variables and numerical fluxes can be computed by weighted summation of distribution functions at eight discrete points. That is, the application of complicated formulations resultant from integrals can be replaced by a simple solution process. Several numerical examples including laminar flat plate boundary layer, 3D lid-driven cavity flow, steady flow through a 90° bending square duct, transonic flow around DPW-W1 wing and supersonic flow around NACA0012 airfoil are chosen to validate the proposed scheme. Numerical results demonstrate that the present scheme can provide reasonable numerical results for 3D viscous flows.

Stellar models with calibrated convection and temperature stratification from 3D hydrodynamics simulations

NASA Astrophysics Data System (ADS)

Mosumgaard, Jakob Rørsted; Ball, Warrick H.; Aguirre, Víctor Silva; Weiss, Achim; Christensen-Dalsgaard, Jørgen

2018-06-01

Stellar evolution codes play a major role in present-day astrophysics, yet they share common simplifications related to the outer layers of stars. We seek to improve on this by the use of results from realistic and highly detailed 3D hydrodynamics simulations of stellar convection. We implement a temperature stratification extracted directly from the 3D simulations into two stellar evolution codes to replace the simplified atmosphere normally used. Our implementation also contains a non-constant mixing-length parameter, which varies as a function of the stellar surface gravity and temperature - also derived from the 3D simulations. We give a detailed account of our fully consistent implementation and compare to earlier works, and also provide a freely available MESA-module. The evolution of low-mass stars with different masses is investigated, and we present for the first time an asteroseismic analysis of a standard solar model utilising calibrated convection and temperature stratification from 3D simulations. We show that the inclusion of 3D results have an almost insignificant impact on the evolution and structure of stellar models - the largest effect are changes in effective temperature of order 30 K seen in the pre-main sequence and in the red-giant branch. However, this work provides the first step for producing self-consistent evolutionary calculations using fully incorporated 3D atmospheres from on-the-fly interpolation in grids of simulations.

Numerical Optimization Strategy for Determining 3D Flow Fields in Microfluidics

NASA Astrophysics Data System (ADS)

Eden, Alex; Sigurdson, Marin; Mezic, Igor; Meinhart, Carl

2015-11-01

We present a hybrid experimental-numerical method for generating 3D flow fields from 2D PIV experimental data. An optimization algorithm is applied to a theory-based simulation of an alternating current electrothermal (ACET) micromixer in conjunction with 2D PIV data to generate an improved representation of 3D steady state flow conditions. These results can be used to investigate mixing phenomena. Experimental conditions were simulated using COMSOL Multiphysics to solve the temperature and velocity fields, as well as the quasi-static electric fields. The governing equations were based on a theoretical model for ac electrothermal flows. A Nelder-Mead optimization algorithm was used to achieve a better fit by minimizing the error between 2D PIV experimental velocity data and numerical simulation results at the measurement plane. By applying this hybrid method, the normalized RMS velocity error between the simulation and experimental results was reduced by more than an order of magnitude. The optimization algorithm altered 3D fluid circulation patterns considerably, providing a more accurate representation of the 3D experimental flow field. This method can be generalized to a wide variety of flow problems. This research was supported by the Institute for Collaborative Biotechnologies through grant W911NF-09-0001 from the U.S. Army Research Office.

Modelling the dynamo in fully convective M-stars

NASA Astrophysics Data System (ADS)

Yadav, Rakesh Kumar; Christensen, Ulrich; Morin, Julien; Wolk, Scott; Poppenhaeger, Katja; Reiners, Ansgar; gastine, Thomas

2017-05-01

M-stars are among the most active and numerous stars in our galaxy. Their activity plays a fundamentally important role in shaping the exoplanetary biosphere since the habitable zones are very close to these stars. Therefore, modeling M-star activity has become a focal point in habitability studies. The fully convective members of the M-star population demand more immediate attention due to the discovery of Earth-like exoplanets around our stellar neighbors Proxima Centauri and TRAPPIST-1 which are both fully convective. The activity of these stars is driven by their convective dynamo, which may be fundamentally different from the solar dynamo due the absence of radiative cores. We model this dynamo mechanism using high-resolution 3D anelastic MHD simulations. To understand the evolution of the dynamo mechanism we simulate two cases, one with a fast enough rotation period to model a star in the `saturated' regime of the rotation-activity realtionship and the other with a slower period to represent cases in the `unsaturated' regime. We find the rotation period fundamentally controls the behavior of the dynamo solution: faster rotation promotes strong magnetic fields (of order kG) on both small and large length scales and the dipolar component of the magnetic field is dominant and stable, however, slower rotation leads to weaker magnetic fields which exhibit cyclic behavior. In this talk, I will present the simulation results and discuss how we can use them to interpret several observed features of the M-star activity.

Course Design and Student Responses to an Online PBL Course in 3D Modelling for Mining Engineers

ERIC Educational Resources Information Center

McAlpine, Iain; Stothard, Phillip

2005-01-01

To enhance a course in 3D Virtual Reality (3D VR) modelling for mining engineers, and to create the potential for off campus students to fully engage with the course, a problem based learning (PBL) approach was applied to the course design and all materials and learning activities were provided online. This paper outlines some of the theoretical…

Effect of Material Property Variations at Near Critical Thermodynamic Conditions on Pipe Flow Heat Transfer

NASA Astrophysics Data System (ADS)

Barney, Rebecca; Nourgaliev, Robert; Delplanque, Jean-Pierre; McCallen, Rose

2017-11-01

Heat transfer is quantified and contrasted for the Poiseuille flow of a fluid at both subcritical and supercritical thermodynamic conditions in a circular pipe subject to a uniform wall heat flux. The conditions considered are relevant to Supercritical Water Reactor (SCWR) applications. In the supercritical thermodynamic regime, a fluid can exhibit large density variations of density, thermal conductivity, and viscosity, which will affect flow and heat transfer characteristics significantly. An advanced equation of state for supercritical water was implemented in a 2D and 3D Arbitrary Lagrangian-Eurlerian multi-physics simulation tool called ALE3D developed at Lawrence Livermore National Laboratory. A newly developed, robust, high-order in space and time, fully implicit reconstructed discontinuous Galerkin (rDG) method is used to enable the numerical simulation of convective heat transfer with supercritical water. Results demonstrate the capability of this approach to accurately capture the non-linear behavior and enhanced heat transfer with supercritical water. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Information management release number LLNL-ABS-736004. Work is supported by the Integrated University Program Graduate Fellowship. Opinions, findings, conclusions or recommendations expressed are of the authors and do not necessarily reflect the views of DOE office of NE.

Continuum Edge Gyrokinetic Theory and Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, X Q; Xiong, Z; Dorr, M R

The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regimemore » with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear electrostatic gyrokinetic equations that are for both neoclassical and turbulence simulations.« less

3D printed electromagnetic transmission and electronic structures fabricated on a single platform using advanced process integration techniques

NASA Astrophysics Data System (ADS)

Deffenbaugh, Paul Issac

3D printing has garnered immense attention from many fields including in-office rapid prototyping of mechanical parts, outer-space satellite replication, garage functional firearm manufacture, and NASA rocket engine component fabrication. 3D printing allows increased design flexibility in the fabrication of electronics, microwave circuits and wireless antennas and has reached a level of maturity which allows functional parts to be printed. Much more work is necessary in order to perfect the processes of 3D printed electronics especially in the area of automation. Chapter 1 shows several finished prototypes of 3D printed electronics as well as newly developed techniques in fabrication. Little is known about the RF and microwave properties and applications of the standard materials which have been developed for 3D printing. Measurement of a wide variety of materials over a broad spectrum of frequencies up to 10 GHz using a variety of well-established measurement methods is performed throughout chapter 2. Several types of high frequency RF transmission lines are fabricated and valuable model-matched data is gathered and provided in chapter 3 for future designers' use. Of particular note is a fully 3D printed stripline which was automatically fabricated in one process on one machine. Some core advantages of 3D printing RF/microwave components include rapid manufacturing of complex, dimensionally sensitive circuits (such as antennas and filters which are often iteratively tuned) and the ability to create new devices that cannot be made using standard fabrication techniques. Chapter 4 describes an exemplary fully 3D printed curved inverted-F antenna.

Nucleon-nucleon scattering from fully dynamical lattice QCD.

PubMed

Beane, S R; Bedaque, P F; Orginos, K; Savage, M J

2006-07-07

We present results of the first fully dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1S0 channel and 3S1 - 3D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with a lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions.

Global Dynamic Numerical Simulations of Plate Tectonic Reorganizations

NASA Astrophysics Data System (ADS)

Morra, G.; Quevedo, L.; Butterworth, N.; Matthews, K. J.; Müller, D.

2010-12-01

We use a new numerical approach for global geodynamics to investigate the origin of present global plate motion and to identify the causes of the last two global tectonic reorganizations occurred about 50 and 100 million years ago (Ma) [1]. While the 50 Ma event is the most well-known global plate-mantle event, expressed by the bend in the Hawaiian-Emperor volcanic chain, a prominent plate reorganization at about 100 Ma, although presently little studied, is clearly indicated by a major bend in the fracture zones in the Indian Ocean and by a change in Pacific plate motion [2]. Our workflow involves turning plate reconstructions into surface meshes that are subsequently employed as initial conditions for global Boundary Element numerical models. The tectonic setting that anticipates the reorganizations is processed with the software GPlates, combining the 3D mesh of the paleo-plate morphology and the reconstruction of paleo-subducted slabs, elaborated from tectonic history [3]. All our models involve the entire planetary system, are fully dynamic, have free surface, are characterized by a spectacular computational speed due to the simultaneous use of the multi-pole algorithm and the Boundary Element formulation and are limited only by the use of sharp material property variations [4]. We employ this new tool to unravel the causes of plate tectonic reorganizations, producing and comparing global plate motion with the reconstructed ones. References: [1] Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, VOL. 46, RG3004, 44 PP., 2008 [2] Wessel, P. and Kroenke, L.W. Pacific absolute plate motion since 145 Ma: An assessment of the fixed hot spot hypothesis. Journal of Geophysical Research, Vol 113, B06101, 2008 [3] L. Quevedo, G. Morra, R. D. Mueller. Parallel Fast Multipole Boundary Element Method for Crustal Dynamics, Proceeding 9th World Congress and 4th Asian Pacific Congress on Computational Mechanics, July 2010, iopscience.iop.org/1757-899X/10/1/012012. [4] G. Morra, P. Chatelain, P. Tackley and P. Koumoutzakos, 2007, Large scale three-dimensional boundary element simulation of subduction, in Proceeding International Conference on Computational Science - Part III, LNCS 4489, pp. 1122-1129. Interaction between two subducting slabs.

Processing And Display Of Medical Three Dimensional Arrays Of Numerical Data Using Octree Encoding

NASA Astrophysics Data System (ADS)

Amans, Jean-Louis; Darier, Pierre

1986-05-01

imaging modalities such as X-Ray computerized Tomography (CT), Nuclear Medecine and Nuclear Magnetic Resonance can produce three-dimensional (3-D) arrays of numerical data of medical object internal structures. The analysis of 3-D data by synthetic generation of realistic images is an important area of computer graphics and imaging.

Explicit filtering in large eddy simulation using a discontinuous Galerkin method

NASA Astrophysics Data System (ADS)

Brazell, Matthew J.

The discontinuous Galerkin (DG) method is a formulation of the finite element method (FEM). DG provides the ability for a high order of accuracy in complex geometries, and allows for highly efficient parallelization algorithms. These attributes make the DG method attractive for solving the Navier-Stokes equations for large eddy simulation (LES). The main goal of this work is to investigate the feasibility of adopting an explicit filter in the numerical solution of the Navier-Stokes equations with DG. Explicit filtering has been shown to increase the numerical stability of under-resolved simulations and is needed for LES with dynamic sub-grid scale (SGS) models. The explicit filter takes advantage of DG's framework where the solution is approximated using a polyno- mial basis where the higher modes of the solution correspond to a higher order polynomial basis. By removing high order modes, the filtered solution contains low order frequency content much like an explicit low pass filter. The explicit filter implementation is tested on a simple 1-D solver with an initial condi- tion that has some similarity to turbulent flows. The explicit filter does restrict the resolution as well as remove accumulated energy in the higher modes from aliasing. However, the ex- plicit filter is unable to remove numerical errors causing numerical dissipation. A second test case solves the 3-D Navier-Stokes equations of the Taylor-Green vortex flow (TGV). The TGV is useful for SGS model testing because it is initially laminar and transitions into a fully turbulent flow. The SGS models investigated include the constant coefficient Smagorinsky model, dynamic Smagorinsky model, and dynamic Heinz model. The constant coefficient Smagorinsky model is over dissipative, this is generally not desirable however it does add stability. The dynamic Smagorinsky model generally performs better, especially during the laminar-turbulent transition region as expected. The dynamic Heinz model which is based on an improved model, handles the laminar-turbulent transition region well while also showing additional robustness.

The solar exposure time required for vitamin D3 synthesis in the human body estimated by numerical simulation and observation in Japan.

PubMed

Miyauchi, Masaatsu; Hirai, Chizuko; Nakajima, Hideaki

2013-01-01

Although the importance of solar radiation for vitamin D3 synthesis in the human body is well known, the solar exposure time required to prevent vitamin D deficiency has not been determined in Japan. This study attempted to identify the time of solar exposure required for vitamin D3 synthesis in the body by season, time of day, and geographic location (Sapporo, Tsukuba, and Naha) using both numerical simulations and observations. According to the numerical simulation for Tsukuba at noon in July under a cloudless sky, 3.5 min of solar exposure are required to produce 5.5 μg vitamin D3 per 600 cm2 skin corresponding to the area of a face and the back of a pair of hands without ingestion from foods. In contrast, it took 76.4 min to produce the same quantity of vitamin D3 at Sapporo in December, at noon under a cloudless sky. The necessary exposure time varied considerably with the time of the day. For Tsukuba at noon in December, 22.4 min were required, but 106.0 min were required at 09:00 and 271.3 min were required at 15:00 for the same meteorological conditions. Naha receives high levels of ultraviolet radiation allowing vitamin D3 synthesis almost throughout the year.

Quasi-3D Modeling and Efficient Simulation of Laminar Flows in Microfluidic Devices.

PubMed

Islam, Md Zahurul; Tsui, Ying Yin

2016-10-03

A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found.

Quasi-3D Modeling and Efficient Simulation of Laminar Flows in Microfluidic Devices

PubMed Central

Islam, Md. Zahurul; Tsui, Ying Yin

2016-01-01

A quasi-3D model has been developed to simulate the flow in planar microfluidic systems with low Reynolds numbers. The model was developed by decomposing the flow profile along the height of a microfluidic system into a Fourier series. It was validated against the analytical solution for flow in a straight rectangular channel and the full 3D numerical COMSOL Navier-Stokes solver for flow in a T-channel. Comparable accuracy to the full 3D numerical solution was achieved by using only three Fourier terms with a significant decrease in computation time. The quasi-3D model was used to model flows in a micro-flow cytometer chip on a desktop computer and good agreement between the simulation and the experimental results was found. PMID:27706104

3D critical layers in fully-developed turbulent flows

NASA Astrophysics Data System (ADS)

Saxton-Fox, Theresa; McKeon, Beverley

2016-11-01

Recent work has shown that 3D critical layers drive self-sustaining behavior of exact coherent solutions of the Navier-Stokes equations (Wang et al. 2007; Hall and Sherwin 2010; Park and Graham 2015). This study investigates the role of 3D critical layers in fully-developed turbulent flows. 3D critical layer effects are identified in instantaneous snapshots of turbulent boundary layers in both experimental and DNS data (Wu et al. 2014). Additionally, a 3D critical layer effect is demonstrated to appear using only a few resolvent response modes from the resolvent analysis of McKeon and Sharma 2010, with phase relationships appropriately chosen. Connections are sought to the thin shear layers observed in turbulent boundary layers (Klewicki and Hirschi 2004; Eisma et al. 2015) and to amplitude modulation observations (Mathis et al. 2009; Duvvuri and McKeon 2014). This research is made possible by the Department of Defense through the National Defense & Engineering Graduate Fellowship (NDSEG) Program and by the Air Force Office of Scientific Research Grant # FA9550-12-1-0060. The support of the Center for Turbulence Research (CTR) summer program at Stanford is gratefully acknowledged.

Automated design of infrared digital metamaterials by genetic algorithm

NASA Astrophysics Data System (ADS)

Sugino, Yuya; Ishikawa, Atsushi; Hayashi, Yasuhiko; Tsuruta, Kenji

2017-08-01

We demonstrate automatic design of infrared (IR) metamaterials using a genetic algorithm (GA) and experimentally characterize their IR properties. To implement the automated design scheme of the metamaterial structures, we adopt a digital metamaterial consisting of 7 × 7 Au nano-pixels with an area of 200 nm × 200 nm, and their placements are coded as binary genes in the GA optimization process. The GA combined with three-dimensional (3D) finite element method (FEM) simulation is developed and applied to automatically construct a digital metamaterial to exhibit pronounced plasmonic resonances at the target IR frequencies. Based on the numerical results, the metamaterials are fabricated on a Si substrate over an area of 1 mm × 1 mm by using an EB lithography, Cr/Au (2/20 nm) depositions, and liftoff process. In the FT-IR measurement, pronounced plasmonic responses of each metamaterial are clearly observed near the targeted frequencies, although the synthesized pixel arrangements of the metamaterials are seemingly random. The corresponding numerical simulations reveal the important resonant behavior of each pixel and their hybridized systems. Our approach is fully computer-aided without artificial manipulation, thus paving the way toward the novel device design for next-generation plasmonic device applications.

Highly Stable Aptamers Selected from a 2′-Fully Modified fGmH RNA Library for Targeting Biomaterials

PubMed Central

Friedman, Adam D.; Kim, Dongwook; Liu, Rihe

2014-01-01

When developed as targeting ligands for the in vivo delivery of biomaterials to biological systems, RNA aptamers immediately face numerous obstacles, in particular nuclease degradation and post-selection 2′ modification. This study aims to develop a novel class of highly stable, 2′-fully modified RNA aptamers that are ideal for the targeted delivery of biomaterials. We demonstrated the facile transcription of a fGmH (2′-F-dG, 2′-OMe-dA/dC/dU) RNA library with unexpected hydrophobicity, the direct selection of aptamers from a fGmH RNA library that bind Staphylococcus aureus Protein A (SpA) as a model target, and the superior nuclease and serum stability of these aptamers compared to 2′-partially modified RNA variants. Characterizations of fGmH RNA aptamers binding to purified SpA and to endogenous SpA present on the surface of S. aureus cells demonstrate fGmH RNA aptamer selectivity and stability. Significantly, fGmH RNA aptamers were able to functionalize, stabilize, and further deliver aggregation-prone silver nanoparticles (AgNPs) to S. aureus with SpA-dependent antimicrobial effects. This study describes a novel aptamer class with considerable potential to improve the in vivo applicability of nucleic acid-based affinity molecules to biomaterials. PMID:25443790

Numerical taxonomy on data: Experimental results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cohen, J.; Farach, M.

1997-12-01

The numerical taxonomy problems associated with most of the optimization criteria described above are NP - hard [3, 5, 1, 4]. In, the first positive result for numerical taxonomy was presented. They showed that if e is the distance to the closest tree metric under the L{sub {infinity}} norm. i.e., e = min{sub T} [L{sub {infinity}} (T-D)], then it is possible to construct a tree T such that L{sub {infinity}} (T-D) {le} 3e, that is, they gave a 3-approximation algorithm for this problem. We will refer to this algorithm as the Single Pivot (SP) heuristic.

3D deeply supervised network for automated segmentation of volumetric medical images.

PubMed

Dou, Qi; Yu, Lequan; Chen, Hao; Jin, Yueming; Yang, Xin; Qin, Jing; Heng, Pheng-Ann

2017-10-01

While deep convolutional neural networks (CNNs) have achieved remarkable success in 2D medical image segmentation, it is still a difficult task for CNNs to segment important organs or structures from 3D medical images owing to several mutually affected challenges, including the complicated anatomical environments in volumetric images, optimization difficulties of 3D networks and inadequacy of training samples. In this paper, we present a novel and efficient 3D fully convolutional network equipped with a 3D deep supervision mechanism to comprehensively address these challenges; we call it 3D DSN. Our proposed 3D DSN is capable of conducting volume-to-volume learning and inference, which can eliminate redundant computations and alleviate the risk of over-fitting on limited training data. More importantly, the 3D deep supervision mechanism can effectively cope with the optimization problem of gradients vanishing or exploding when training a 3D deep model, accelerating the convergence speed and simultaneously improving the discrimination capability. Such a mechanism is developed by deriving an objective function that directly guides the training of both lower and upper layers in the network, so that the adverse effects of unstable gradient changes can be counteracted during the training procedure. We also employ a fully connected conditional random field model as a post-processing step to refine the segmentation results. We have extensively validated the proposed 3D DSN on two typical yet challenging volumetric medical image segmentation tasks: (i) liver segmentation from 3D CT scans and (ii) whole heart and great vessels segmentation from 3D MR images, by participating two grand challenges held in conjunction with MICCAI. We have achieved competitive segmentation results to state-of-the-art approaches in both challenges with a much faster speed, corroborating the effectiveness of our proposed 3D DSN. Copyright © 2017 Elsevier B.V. All rights reserved.

High-Order Implicit-Explicit Multi-Block Time-stepping Method for Hyperbolic PDEs

NASA Technical Reports Server (NTRS)

Nielsen, Tanner B.; Carpenter, Mark H.; Fisher, Travis C.; Frankel, Steven H.

2014-01-01

This work seeks to explore and improve the current time-stepping schemes used in computational fluid dynamics (CFD) in order to reduce overall computational time. A high-order scheme has been developed using a combination of implicit and explicit (IMEX) time-stepping Runge-Kutta (RK) schemes which increases numerical stability with respect to the time step size, resulting in decreased computational time. The IMEX scheme alone does not yield the desired increase in numerical stability, but when used in conjunction with an overlapping partitioned (multi-block) domain significant increase in stability is observed. To show this, the Overlapping-Partition IMEX (OP IMEX) scheme is applied to both one-dimensional (1D) and two-dimensional (2D) problems, the nonlinear viscous Burger's equation and 2D advection equation, respectively. The method uses two different summation by parts (SBP) derivative approximations, second-order and fourth-order accurate. The Dirichlet boundary conditions are imposed using the Simultaneous Approximation Term (SAT) penalty method. The 6-stage additive Runge-Kutta IMEX time integration schemes are fourth-order accurate in time. An increase in numerical stability 65 times greater than the fully explicit scheme is demonstrated to be achievable with the OP IMEX method applied to 1D Burger's equation. Results from the 2D, purely convective, advection equation show stability increases on the order of 10 times the explicit scheme using the OP IMEX method. Also, the domain partitioning method in this work shows potential for breaking the computational domain into manageable sizes such that implicit solutions for full three-dimensional CFD simulations can be computed using direct solving methods rather than the standard iterative methods currently used.

Ultra-wideband Ge-rich silicon germanium integrated Mach-Zehnder interferometer for mid-infrared spectroscopy.

PubMed

Vakarin, Vladyslav; Ramírez, Joan Manel; Frigerio, Jacopo; Ballabio, Andrea; Le Roux, Xavier; Liu, Qiankun; Bouville, David; Vivien, Laurent; Isella, Giovanni; Marris-Morini, Delphine

2017-09-01

This Letter explores the use of Ge-rich Si 0.2 Ge 0.8 waveguides on graded Si 1-x Ge x substrate for the demonstration of ultra-wideband photonic integrated circuits in the mid-infrared (mid-IR) wavelength range. We designed, fabricated, and characterized broadband Mach-Zehnder interferometers fully covering a range of 3 μm in the mid-IR band. The fabricated devices operate indistinctly in quasi-TE and quasi-TM polarizations, and have an extinction ratio higher than 10 dB over the entire operating wavelength range. The obtained results are in good correlation with theoretical predictions, while numerical simulations indicate that the device bandwidth can reach one octave with low additional losses. This Letter paves the way for further realization of mid-IR integrated spectrometers using low-index-contrast Si 1-x Ge x waveguides with high germanium concentration.

Airway reopening: Steadily propagating bubbles in buckled elastic tubes

NASA Astrophysics Data System (ADS)

Heil, Matthias; Hazel, Andrew L.

2001-11-01

Many pulmonary diseases result in the collapse and occlusion of parts of the lung by viscous fluid. The subsequent airway reopening is generally assumed to occur via the propagation of an air finger into the collapsed, fluid-filled part of the airway. The problem has some similarity to the scenario of the `first breath' when air has to enter the fluid-filled lungs of a newborn baby for the first time. We have developed the first three-dimensional computational model of airway reopening, based on a finite-element solution of the free-surface Stokes equations, fully coupled to the equations of large-displacement shell theory. Following a brief discussion of the numerical method, we will present results that illustrate the 3D flow field by which the steadily propagating air finger reopens the non-axisymmetrically collapsed airway. Finally, we will contrast the system's behaviour to predictions from earlier two-dimensional models.

Development and Application of Agglomerated Multigrid Methods for Complex Geometries

NASA Technical Reports Server (NTRS)

Nishikawa, Hiroaki; Diskin, Boris; Thomas, James L.

2010-01-01

We report progress in the development of agglomerated multigrid techniques for fully un- structured grids in three dimensions, building upon two previous studies focused on efficiently solving a model diffusion equation. We demonstrate a robust fully-coarsened agglomerated multigrid technique for 3D complex geometries, incorporating the following key developments: consistent and stable coarse-grid discretizations, a hierarchical agglomeration scheme, and line-agglomeration/relaxation using prismatic-cell discretizations in the highly-stretched grid regions. A signi cant speed-up in computer time is demonstrated for a model diffusion problem, the Euler equations, and the Reynolds-averaged Navier-Stokes equations for 3D realistic complex geometries.

A hybrid method for flood simulation in small catchments combining hydrodynamic and hydrological techniques

NASA Astrophysics Data System (ADS)

Bellos, Vasilis; Tsakiris, George

2016-09-01

The study presents a new hybrid method for the simulation of flood events in small catchments. It combines a physically-based two-dimensional hydrodynamic model and the hydrological unit hydrograph theory. Unit hydrographs are derived using the FLOW-R2D model which is based on the full form of two-dimensional Shallow Water Equations, solved by a modified McCormack numerical scheme. The method is tested at a small catchment in a suburb of Athens-Greece for a storm event which occurred in February 2013. The catchment is divided into three friction zones and unit hydrographs of 15 and 30 min are produced. The infiltration process is simulated by the empirical Kostiakov equation and the Green-Ampt model. The results from the implementation of the proposed hybrid method are compared with recorded data at the hydrometric station at the outlet of the catchment and the results derived from the fully hydrodynamic model FLOW-R2D. It is concluded that for the case studied, the proposed hybrid method produces results close to those of the fully hydrodynamic simulation at substantially shorter computational time. This finding, if further verified in a variety of case studies, can be useful in devising effective hybrid tools for the two-dimensional flood simulations, which are lead to accurate and considerably faster results than those achieved by the fully hydrodynamic simulations.

Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases

DOE PAGES

Grenier, Christophe; Anbergen, Hauke; Bense, Victor; ...

2018-02-26

In high-elevation, boreal and arctic regions, hydrological processes and associated water bodies can be strongly influenced by the distribution of permafrost. Recent field and modeling studies indicate that a fully-coupled multidimensional thermo-hydraulic approach is required to accurately model the evolution of these permafrost-impacted landscapes and groundwater systems. However, the relatively new and complex numerical codes being developed for coupled non-linear freeze-thaw systems require verification. Here in this paper, this issue is addressed by means of an intercomparison of thirteen numerical codes for two-dimensional test cases with several performance metrics (PMs). These codes comprise a wide range of numerical approaches, spatialmore » and temporal discretization strategies, and computational efficiencies. Results suggest that the codes provide robust results for the test cases considered and that minor discrepancies are explained by computational precision. However, larger discrepancies are observed for some PMs resulting from differences in the governing equations, discretization issues, or in the freezing curve used by some codes.« less

Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grenier, Christophe; Anbergen, Hauke; Bense, Victor

In high-elevation, boreal and arctic regions, hydrological processes and associated water bodies can be strongly influenced by the distribution of permafrost. Recent field and modeling studies indicate that a fully-coupled multidimensional thermo-hydraulic approach is required to accurately model the evolution of these permafrost-impacted landscapes and groundwater systems. However, the relatively new and complex numerical codes being developed for coupled non-linear freeze-thaw systems require verification. Here in this paper, this issue is addressed by means of an intercomparison of thirteen numerical codes for two-dimensional test cases with several performance metrics (PMs). These codes comprise a wide range of numerical approaches, spatialmore » and temporal discretization strategies, and computational efficiencies. Results suggest that the codes provide robust results for the test cases considered and that minor discrepancies are explained by computational precision. However, larger discrepancies are observed for some PMs resulting from differences in the governing equations, discretization issues, or in the freezing curve used by some codes.« less

Flow above and within granular media composed of spherical and non-spherical particles - using a 3D numerical model

NASA Astrophysics Data System (ADS)

Bartzke, Gerhard; Kuhlmann, Jannis; Huhn, Katrin

2016-04-01

The entrainment of single grains and, hence, their erosion characteristics are dependent on fluid forcing, grain size and density, but also shape variations. To quantitatively describe and capture the hydrodynamic conditions around individual grains, researchers commonly use empirical approaches such as laboratory flume tanks. Nonetheless, it is difficult with such physical experiments to measure the flow velocities in the direct vicinity or within the pore spaces of sediments, at a sufficient resolution and in a non-invasive way. As a result, the hydrodynamic conditions in the water column, at the fluid-porous interface and within pore spaces of a granular medium of various grain shapes is not yet fully understood. For that reason, there is a strong need for numerical models, since these are capable of quantifying fluid speeds within a granular medium. A 3D-SPH (Smooth Particle Hydrodynamics) numerical wave tank model was set up to provide quantitative evidence on the flow velocities in the direct vicinity and in the interior of granular beds composed of two shapes as a complementary method to the difficult task of in situ measurement. On the basis of previous successful numerical wave tank models with SPH, the model geometry was chosen in dimensions of X=2.68 [m], Y=0.48 [m], and Z=0.8 [m]. Three suites of experiments were designed with a range of particle shape models: (1) ellipsoids with the long axis oriented in the across-stream direction, (2) ellipsoids with the long axis oriented in the along-stream direction, and (3) spheres. Particle diameters ranged from 0.04 [m] to 0.08 [m]. A wave was introduced by a vertical paddle that accelerated to 0.8 [m/s] perpendicular to the granular bed. Flow measurements showed that the flow velocity values into the beds were highest when the grains were oriented across the stream direction and lowest in case when the grains were oriented parallel to the stream, indicating that the model was capable to simulate simultaneously the flow into and within a granular medium composed of spherical and non-spherical shapes under wave forcing. It is concluded that variations in grain shape orientation within a bed appear to control the amount of flow that can be accumulated by the pores, which was illustrated in a conceptual model.

Microsphere-assisted super-resolution imaging with enlarged numerical aperture by semi-immersion

NASA Astrophysics Data System (ADS)

Wang, Fengge; Yang, Songlin; Ma, Huifeng; Shen, Ping; Wei, Nan; Wang, Meng; Xia, Yang; Deng, Yun; Ye, Yong-Hong

2018-01-01

Microsphere-assisted imaging is an extraordinary simple technology that can obtain optical super-resolution under white-light illumination. Here, we introduce a method to improve the resolution of a microsphere lens by increasing its numerical aperture. In our proposed structure, BaTiO3 glass (BTG) microsphere lenses are semi-immersed in a S1805 layer with a refractive index of 1.65, and then, the semi-immersed microspheres are fully embedded in an elastomer with an index of 1.4. We experimentally demonstrate that this structure, in combination with a conventional optical microscope, can clearly resolve a two-dimensional 200-nm-diameter hexagonally close-packed (hcp) silica microsphere array. On the contrary, the widely used structure where BTG microsphere lenses are fully immersed in a liquid or elastomer cannot even resolve a 250-nm-diameter hcp silica microsphere array. The improvement in resolution through the proposed structure is due to an increase in the effective numerical aperture by semi-immersing BTG microsphere lenses in a high-refractive-index S1805 layer. Our results will inform on the design of microsphere-based high-resolution imaging systems.

Coupling MAST-1D, a sediment routing model for channel-floodplain complexes, with channel migration relationships to predict reach-averaged river morphodynamics. Preliminary results

NASA Astrophysics Data System (ADS)

Viparelli, E.; Eke, E. C.; Lauer, J. W.

2017-12-01

Sediment exchange between the channel and floodplain can occur via meander migration, overbank deposition or erosion, and changes in channel geometry. Depending on channel and floodplain history, floodplains can act either as sources or sinks of bed material and/or wash load. Here we present preliminary modeling results that explicitly account for the feedbacks between the changes in floodplain geometry and sediment size distribution and the changes in channel geometry and migration. These results are obtained by coupling the Morphodynamics And Sediment Tracers in 1D (MAST-1D) program with the results of meander migration studies linking the bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. MAST-1D is a numerical model built to describe grain size specific transport of sediment and tracers and the long-term - i.e. decadal and longer - evolution of channel floodplain complexes. MAST-1D differs from other 1D numerical models because it allows for 1) uneven exchange of sediment and tracers between the river channel and the floodplain, 2) temporal changes in channel geometry, bed elevation and floodplain thickness, which result in changes in the channel hydraulic capacity, and 3) temporal changes of size distribution and tracer content in the floodplain, in the load and in the underlying substrate. Under conditions of constant base level, water and sediment supply, the system evolves toward a steady state wherein the amount of sediment deposited through point bar deposition and overbank sedimentation is balanced by the erosion of sediment from the floodplain through lateral migration. The current formulation couples MAST-1D with empirical channel migration relationships that link bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. Future development of this preliminary work will involve a fully coupled MAST-1D model with a standard meander migration model that will allow for the building of floodplain stratigraphy and tracking of the position of the meandering channel in space and time.

FacetModeller: Software for manual creation, manipulation and analysis of 3D surface-based models

NASA Astrophysics Data System (ADS)

Lelièvre, Peter G.; Carter-McAuslan, Angela E.; Dunham, Michael W.; Jones, Drew J.; Nalepa, Mariella; Squires, Chelsea L.; Tycholiz, Cassandra J.; Vallée, Marc A.; Farquharson, Colin G.

2018-01-01

The creation of 3D models is commonplace in many disciplines. Models are often built from a collection of tessellated surfaces. To apply numerical methods to such models it is often necessary to generate a mesh of space-filling elements that conforms to the model surfaces. While there are meshing algorithms that can do so, they place restrictive requirements on the surface-based models that are rarely met by existing 3D model building software. Hence, we have developed a Java application named FacetModeller, designed for efficient manual creation, modification and analysis of 3D surface-based models destined for use in numerical modelling.

Evaluation of a Fully 3-D Bpf Method for Small Animal PET Images on Mimd Architectures

NASA Astrophysics Data System (ADS)

Bevilacqua, A.

Positron Emission Tomography (PET) images can be reconstructed using Fourier transform methods. This paper describes the performance of a fully 3-D Backprojection-Then-Filter (BPF) algorithm on the Cray T3E machine and on a cluster of workstations. PET reconstruction of small animals is a class of problems characterized by poor counting statistics. The low-count nature of these studies necessitates 3-D reconstruction in order to improve the sensitivity of the PET system: by including axially oblique Lines Of Response (LORs), the sensitivity of the system can be significantly improved by the 3-D acquisition and reconstruction. The BPF method is widely used in clinical studies because of its speed and easy implementation. Moreover, the BPF method is suitable for on-time 3-D reconstruction as it does not need any sinogram or rearranged data. In order to investigate the possibility of on-line processing, we reconstruct a phantom using the data stored in the list-mode format by the data acquisition system. We show how the intrinsically parallel nature of the BPF method makes it suitable for on-line reconstruction on a MIMD system such as the Cray T3E. Lastly, we analyze the performance of this algorithm on a cluster of workstations.

A Variational Reduction and the Existence of a Fully Localised Solitary Wave for the Three-Dimensional Water-Wave Problem with Weak Surface Tension

NASA Astrophysics Data System (ADS)

Buffoni, Boris; Groves, Mark D.; Wahlén, Erik

2017-12-01

Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3} ) has recently been given. In this article we present an existence theory for the physically more realistic case {0 < β < 1/3} . A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.

A Variational Reduction and the Existence of a Fully Localised Solitary Wave for the Three-Dimensional Water-Wave Problem with Weak Surface Tension

NASA Astrophysics Data System (ADS)

Buffoni, Boris; Groves, Mark D.; Wahlén, Erik

2018-06-01

Fully localised solitary waves are travelling-wave solutions of the three- dimensional gravity-capillary water wave problem which decay to zero in every horizontal spatial direction. Their existence has been predicted on the basis of numerical simulations and model equations (in which context they are usually referred to as `lumps'), and a mathematically rigorous existence theory for strong surface tension (Bond number {β} greater than {1/3}) has recently been given. In this article we present an existence theory for the physically more realistic case {0 < β < 1/3}. A classical variational principle for fully localised solitary waves is reduced to a locally equivalent variational principle featuring a perturbation of the functional associated with the Davey-Stewartson equation. A nontrivial critical point of the reduced functional is found by minimising it over its natural constraint set.

45° sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co3FeN/MnN bilayers.

PubMed

Hajiri, T; Yoshida, T; Filianina, M; Jaiswal, S; Borie, B; Asano, H; Zabel, H; Kläui, M

2017-12-05

We report an unusual angular-dependent exchange bias effect in ferromagnet/antiferromagnet bilayers, where both ferromagnet and antiferromagnet are epitaxially grown. Numerical model calculations predict an approximately 45° period for the sign switching of the exchange-bias field, depending on the ratio between magnetocrystalline anisotropy and exchange-coupling constant. The switching of the sign is indicative of a competition between a fourfold magnetocrystalline anisotropy of the ferromagnet and a unidirectional anisotropy field of the exchange coupling. This predicted unusual angular-dependent exchange bias and its magnetization switching process are confirmed by measurements on fully epitaxial Co 3 FeN/MnN bilayers by longitudinal and transverse magneto-optic Kerr effect magnetometry. These results provide a deeper understanding of the exchange coupling phenomena in fully epitaxial bilayers with tailored materials and open up a complex switching energy landscape engineering by anisotropies.

45° sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co3FeN/MnN bilayers

NASA Astrophysics Data System (ADS)

Hajiri, T.; Yoshida, T.; Filianina, M.; Jaiswal, S.; Borie, B.; Asano, H.; Zabel, H.; Kläui, M.

2018-01-01

We report an unusual angular-dependent exchange bias effect in ferromagnet/antiferromagnet bilayers, where both ferromagnet and antiferromagnet are epitaxially grown. Numerical model calculations predict an approximately 45° period for the sign switching of the exchange-bias field, depending on the ratio between magnetocrystalline anisotropy and exchange-coupling constant. The switching of the sign is indicative of a competition between a fourfold magnetocrystalline anisotropy of the ferromagnet and a unidirectional anisotropy field of the exchange coupling. This predicted unusual angular-dependent exchange bias and its magnetization switching process are confirmed by measurements on fully epitaxial Co3FeN/MnN bilayers by longitudinal and transverse magneto-optic Kerr effect magnetometry. These results provide a deeper understanding of the exchange coupling phenomena in fully epitaxial bilayers with tailored materials and open up a complex switching energy landscape engineering by anisotropies.

Impact of two chemistry mechanisms fully coupled with mesoscale model on the atmospheric pollutants distribution

NASA Astrophysics Data System (ADS)

Arteta, J.; Cautenet, S.; Taghavi, M.; Audiffren, N.

Air quality models (AQM) consist of many modules (meteorology, emission, chemistry, deposition), and in some conditions such as: vicinity of clouds or aerosols plumes, complex local circulations (mountains, sea breezes), fully coupled models (online method) are necessary. In order to study the impact of lumped chemical mechanisms in AQM simulations, we examine the ability of both different chemical mechanisms: (i) simplified: Condensed Version of the MOdèle de Chimie Atmosphérique 2.2 (CV-MOCA2.2), and (ii) reference: Regional Atmospheric Chemistry Model (RACM), which are coupled online with the Regional Atmospheric Modeling Systems (RAMS) model, on the distribution of pollutants. During the ESCOMPTE experiment (Expérience sur Site pour COntraindre les Modèles de Pollution et de Transport d'Emissions) conducted over Southern France (including urban and industrial zones), Intensive observation periods (IOP) characterized by various meteorological and mixed chemical conditions are simulated. For both configurations of modeling, numerical results are compared with surface measurements (75 stations) for primary (NO x) and secondary (O 3) species. We point out the impact of the two different chemical mechanisms on the production of species involved in the oxidizing capacity such as ozone and radicals within urban and industrial areas. We highlight that both chemical mechanisms produce very similar results for the main pollutants (NO x and O 3) in three-dimensional (3D) distribution, despite large discrepancies in 0D modeling. For ozone concentration, we found sometimes small differences (5-10 ppb) between the mechanisms under study according to the cases (polluted or not). The relative difference between the two mechanisms over the whole domain is only -7% for ozone from CV-MOCA 2.2 versus RACM. When the order of magnitude is needed rather than an accurate estimate, a reduced mechanism is satisfactory. It has the advantage of running faster (four times less than CPU time on SGI 3800 with 30 processors). Simplified mechanisms are really important to study cases for which an online coupling is necessary between meso-scale and chemistry models (clouds or aerosols plumes impacts, highly variable meteorology).

Nanocellulosic materials as bioinks for 3D bioprinting.

PubMed

Piras, Carmen C; Fernández-Prieto, Susana; De Borggraeve, Wim M

2017-09-26

3D bioprinting is a new developing technology with lots of promise in tissue engineering and regenerative medicine. Being biocompatible, biodegradable, renewable and cost-effective, cellulosic nanomaterials have recently captured the attention of researchers due to their applicability as inks for 3D bioprinting. Although a number of cellulose-based bioinks have been reported, the potential of cellulose nanofibrils and nanocrystals has not been fully explored yet. This minireview aims at highlighting the use of nanocellulosic materials for 3D bioprinting as an emerging, promising, new research field.

Conjunction of 2D and 3D modified flow solvers for simulating spatio-temporal wind induced hydrodynamics in the Caspian Sea

NASA Astrophysics Data System (ADS)

Zounemat-Kermani, Mohammad; Sabbagh-Yazdi, Saeed-Reza

2010-06-01

The main objective of this study is the simulation of flow dynamics in the deep parts of the Caspian Sea, in which the southern and middle deep regions are surrounded by considerable areas of shallow zones. To simulate spatio-temporal wind induced hydrodynamics in deep waters, a conjunctive numerical model consisting of a 2D depth average model and a 3D pseudo compressible model is proposed. The 2D model is applied to determine time dependent free surface oscillations as well as the surface velocity patterns and is conjunct to the 3D flow solver for computing three-dimensional velocity and pressure fields which coverage to steady state for the top boundary condition. The modified 2D and 3D sets of equations are conjunct considering interface shear stresses. Both sets of 2D and 3D equations are solved on unstructured triangular and tetrahedral meshes using the Galerkin Finite Volume Method. The conjunctive model is utilized to investigate the deep currents affected by wind, Coriolis forces and the river inflow conditions of the Caspian Sea. In this study, the simulation of flow field due to major winds as well as transient winds in the Caspian Sea during a period of 6 hours in the winter season has been conducted and the numerical results for water surface level are then compared to the 2D numerical results.

Solution of the 2-D steady-state radiative transfer equation in participating media with specular reflections using SUPG and DG finite elements

NASA Astrophysics Data System (ADS)

Le Hardy, D.; Favennec, Y.; Rousseau, B.

2016-08-01

The 2D radiative transfer equation coupled with specular reflection boundary conditions is solved using finite element schemes. Both Discontinuous Galerkin and Streamline-Upwind Petrov-Galerkin variational formulations are fully developed. These two schemes are validated step-by-step for all involved operators (transport, scattering, reflection) using analytical formulations. Numerical comparisons of the two schemes, in terms of convergence rate, reveal that the quadratic SUPG scheme proves efficient for solving such problems. This comparison constitutes the main issue of the paper. Moreover, the solution process is accelerated using block SOR-type iterative methods, for which the determination of the optimal parameter is found in a very cheap way.

Quantifying the errors due to the superposition of analytical deformation sources

NASA Astrophysics Data System (ADS)

Neuberg, J. W.; Pascal, K.

2012-04-01

The displacement field due to magma movement in the subsurface is often modelled using a Mogi point source or a dislocation Okada source embedded in a homogeneous elastic half-space. When the magmatic system cannot be modelled by a single source it is often represented by several sources, their respective deformation fields are superimposed. However, in such a case the assumption of homogeneity in the half-space is violated and the interaction between sources in an elastic medium is neglected. In this investigation we have quantified the effects of neglecting the interaction between sources on the surface deformation field. To do so, we calculated the vertical and horizontal displacements for models with adjacent sources and we tested them against the solutions of corresponding numerical 3D finite element models. We implemented several models combining spherical pressure sources and dislocation sources, varying the pressure or dislocation of the sources and their relative position. We also investigated three numerical methods to model a dike as a dislocation tensile source or as a pressurized tabular crack. We found that the discrepancies between simple superposition of the displacement field and a fully interacting numerical solution depend mostly on the source types and on their spacing. The errors induced when neglecting the source interaction are expected to vary greatly with the physical and geometrical parameters of the model. We demonstrated that for certain scenarios these discrepancies can be neglected (<5%) when the sources are separated by at least 4 radii for two combined Mogi sources and by at least 3 radii for juxtaposed Mogi and Okada sources

Lagrangian model of copepod dynamics: Clustering by escape jumps in turbulence

NASA Astrophysics Data System (ADS)

Ardeshiri, H.; Benkeddad, I.; Schmitt, F. G.; Souissi, S.; Toschi, F.; Calzavarini, E.

2016-04-01

Planktonic copepods are small crustaceans that have the ability to swim by quick powerful jumps. Such an aptness is used to escape from high shear regions, which may be caused either by flow perturbations, produced by a large predator (i.e., fish larvae), or by the inherent highly turbulent dynamics of the ocean. Through a combined experimental and numerical study, we investigate the impact of jumping behavior on the small-scale patchiness of copepods in a turbulent environment. Recorded velocity tracks of copepods displaying escape response jumps in still water are here used to define and tune a Lagrangian copepod (LC) model. The model is further employed to simulate the behavior of thousands of copepods in a fully developed hydrodynamic turbulent flow obtained by direct numerical simulation of the Navier-Stokes equations. First, we show that the LC velocity statistics is in qualitative agreement with available experimental observations of copepods in turbulence. Second, we quantify the clustering of LC, via the fractal dimension D2. We show that D2 can be as low as ˜2.3 and that it critically depends on the shear-rate sensitivity of the proposed LC model, in particular it exhibits a minimum in a narrow range of shear-rate values. We further investigate the effect of jump intensity, jump orientation, and geometrical aspect ratio of the copepods on the small-scale spatial distribution. At last, possible ecological implications of the observed clustering on encounter rates and mating success are discussed.

Two-dimensional vocal tracts with three-dimensional behavior in the numerical generation of vowels.

PubMed

Arnela, Marc; Guasch, Oriol

2014-01-01

Two-dimensional (2D) numerical simulations of vocal tract acoustics may provide a good balance between the high quality of three-dimensional (3D) finite element approaches and the low computational cost of one-dimensional (1D) techniques. However, 2D models are usually generated by considering the 2D vocal tract as a midsagittal cut of a 3D version, i.e., using the same radius function, wall impedance, glottal flow, and radiation losses as in 3D, which leads to strong discrepancies in the resulting vocal tract transfer functions. In this work, a four step methodology is proposed to match the behavior of 2D simulations with that of 3D vocal tracts with circular cross-sections. First, the 2D vocal tract profile becomes modified to tune the formant locations. Second, the 2D wall impedance is adjusted to fit the formant bandwidths. Third, the 2D glottal flow gets scaled to recover 3D pressure levels. Fourth and last, the 2D radiation model is tuned to match the 3D model following an optimization process. The procedure is tested for vowels /a/, /i/, and /u/ and the obtained results are compared with those of a full 3D simulation, a conventional 2D approach, and a 1D chain matrix model.

Testing a 1-D Analytical Salt Intrusion Model and the Predictive Equation in Malaysian Estuaries

NASA Astrophysics Data System (ADS)

Gisen, Jacqueline Isabella; Savenije, Hubert H. G.

2013-04-01

Little is known about the salt intrusion behaviour in Malaysian estuaries. Study on this topic sometimes requires large amounts of data especially if a 2-D or 3-D numerical models are used for analysis. In poor data environments, 1-D analytical models are more appropriate. For this reason, a fully analytical 1-D salt intrusion model, based on the theory of Savenije in 2005, was tested in three Malaysian estuaries (Bernam, Selangor and Muar) because it is simple and requires minimal data. In order to achieve that, site surveys were conducted in these estuaries during the dry season (June-August) at spring tide by moving boat technique. Data of cross-sections, water levels and salinity were collected, and then analysed with the salt intrusion model. This paper demonstrates a good fit between the simulated and observed salinity distribution for all three estuaries. Additionally, the calibrated Van der Burgh's coefficient K, Dispersion coefficient D0, and salt intrusion length L, for the estuaries also displayed a reasonable correlations with those calculated from the predictive equations. This indicates that not only is the salt intrusion model valid for the case studies in Malaysia but also the predictive model. Furthermore, the results from this study describe the current state of the estuaries with which the Malaysian water authority in Malaysia can make decisions on limiting water abstraction or dredging. Keywords: salt intrusion, Malaysian estuaries, discharge, predictive model, dispersion

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

NASA Astrophysics Data System (ADS)

Rose, D. V.; Welch, D. R.; Clark, R. E.; Thoma, C.; Zimmerman, W. R.; Bruner, N.; Rambo, P. K.; Atherton, B. W.

2011-09-01

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF6.

Using 3-D Numerical Weather Data in Piloted Simulations

NASA Technical Reports Server (NTRS)

Daniels, Taumi S.

2016-01-01

This report describes the process of acquiring and using 3-D numerical model weather data sets in NASA Langley's Research Flight Deck (RFD). A set of software tools implement the process and can be used for other purposes as well. Given time and location information of a weather phenomenon of interest, the user can download associated numerical weather model data. These data are created by the National Oceanic and Atmospheric Administration (NOAA) High Resolution Rapid Refresh (HRRR) model, and are then processed using a set of Mathworks' Matlab(TradeMark) scripts to create the usable 3-D weather data sets. Each data set includes radar re ectivity, water vapor, component winds, temperature, supercooled liquid water, turbulence, pressure, altitude, land elevation, relative humidity, and water phases. An open-source data processing program, wgrib2, is available from NOAA online, and is used along with Matlab scripts. These scripts are described with sucient detail to make future modi cations. These software tools have been used to generate 3-D weather data for various RFD experiments.

DYNA3D: A computer code for crashworthiness engineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hallquist, J.O.; Benson, D.J.

1986-09-01

A finite element program with crashworthiness applications has been developed at LLNL. DYNA3D, an explicit, fully vectorized, finite deformation structural dynamics program, has four capabilities that are critical for the efficient and realistic modeling crash phenomena: (1) fully optimized nonlinear solid, shell, and beam elements for representing a structure; (2) a broad range of constitutive models for simulating material behavior; (3) sophisticated contact algorithms for impact interactions; (4) a rigid body capability to represent the bodies away from the impact region at a greatly reduced cost without sacrificing accuracy in the momentum calculations. Basic methodologies of the program are brieflymore » presented along with several crashworthiness calculations. Efficiencies of the Hughes-Liu and Belytschko-Tsay shell formulations are considered.« less

3D SPH numerical simulation of the wave generated by the Vajont rockslide

NASA Astrophysics Data System (ADS)

Vacondio, R.; Mignosa, P.; Pagani, S.

2013-09-01

A 3D numerical modeling of the wave generated by the Vajont slide, one of the most destructive ever occurred, is presented in this paper. A meshless Lagrangian Smoothed Particle Hydrodynamics (SPH) technique was adopted to simulate the highly fragmented violent flow generated by the falling slide in the artificial reservoir. The speed-up achievable via General Purpose Graphic Processing Units (GP-GPU) allowed to adopt the adequate resolution to describe the phenomenon. The comparison with the data available in literature showed that the results of the numerical simulation reproduce satisfactorily the maximum run-up, also the water surface elevation in the residual lake after the event. Moreover, the 3D velocity field of the flow during the event and the discharge hydrograph which overtopped the dam, were obtained.

Coupling Hydrodynamic and Wave Propagation Codes for Modeling of Seismic Waves recorded at the SPE Test.

NASA Astrophysics Data System (ADS)

Larmat, C. S.; Rougier, E.; Delorey, A.; Steedman, D. W.; Bradley, C. R.

2016-12-01

The goal of the Source Physics Experiment (SPE) is to bring empirical and theoretical advances to the problem of detection and identification of underground nuclear explosions. For this, the SPE program includes a strong modeling effort based on first principles calculations with the challenge to capture both the source and near-source processes and those taking place later in time as seismic waves propagate within complex 3D geologic environments. In this paper, we report on results of modeling that uses hydrodynamic simulation codes (Abaqus and CASH) coupled with a 3D full waveform propagation code, SPECFEM3D. For modeling the near source region, we employ a fully-coupled Euler-Lagrange (CEL) modeling capability with a new continuum-based visco-plastic fracture model for simulation of damage processes, called AZ_Frac. These capabilities produce high-fidelity models of various factors believed to be key in the generation of seismic waves: the explosion dynamics, a weak grout-filled borehole, the surrounding jointed rock, and damage creation and deformations happening around the source and the free surface. SPECFEM3D, based on the Spectral Element Method (SEM) is a direct numerical method for full wave modeling with mathematical accuracy. The coupling interface consists of a series of grid points of the SEM mesh situated inside of the hydrodynamic code's domain. Displacement time series at these points are computed using output data from CASH or Abaqus (by interpolation if needed) and fed into the time marching scheme of SPECFEM3D. We will present validation tests with the Sharpe's model and comparisons of waveforms modeled with Rg waves (2-8Hz) that were recorded up to 2 km for SPE. We especially show effects of the local topography, velocity structure and spallation. Our models predict smaller amplitudes of Rg waves for the first five SPE shots compared to pure elastic models such as Denny &Johnson (1991).

Numerical Simulation of Floating Bodies in Extreme Free Surface Waves

NASA Astrophysics Data System (ADS)

Hu, Zheng Zheng; Causon, Derek; Mingham, Clive; Qiang, Ling

2010-05-01

A task of the EPSRC funded research project 'Extreme Wave loading on Offshore Wave Energy Devices: a Hierarchical Team Approach' is to investigate the survivability of two wave energy converter (WEC) devices Pelamis and the Manchester Bobber using different CFD approaches. Both devices float on the water surface, generating the electricity from the motion of the waves. In this paper, we describe developments of the AMAZON-SC 3D numerical wave tank (NWT) to study extreme wave loading of a fixed or floating (in Heave motion) structure. The extreme wave formulation as an inlet condition is due to Dalzell (1999) and Ning et. al. (2009) in which a first or second-order Stokes focused wave can be prescribed. The AMAZON-SC 3D code (see e.g. Hu et al. (2009)) uses a cell centred finite volume method of the Godunov-type for the space discretization of the Euler and Navier Stokes equations. The computational domain includes both air and water regions with the air/water boundary captured as a discontinuity in the density field thereby admitting the break up and recombination of the free surface. Temporal discretisation uses the artificial compressibility method and a dual time stepping strategy to maintain a divergence free velocity field. Cartesian cut cells are used to provide a fully boundary-fitted gridding capability on an regular background Cartesian grid. Solid objects are cut out of the background mesh leaving a set of irregularly shaped cells fitted to the boundary. The advantages of the cut cell approach have been outlined previously by Causon et al. (2000, 2001) including its flexibility for dealing with complex geometries whether stationary or in relative motion. The field grid does not need to be recomputed globally or even locally for moving body cases; all that is necessary is to update the local cut cell data at the body contour for as long as the motion continues. The handing of numerical wave paddles and device motion in a NWT is therefore straightforward and efficient. Firstly, extreme design wave conditions are generated in an empty NWT and compared with physical experiments as a precursor to calculations to investigate the survivability of the Bobber device operating in a challenging wave climate. Secondly, we consider a bench-mark test case involving in a first order regular wave maker acting on a fixed cylinder and Pelamis. Finally, a floating Bobber has been simulated under extreme wave conditions. These results will be reported at the meeting. Causon D.M., Ingram D.M., Mingham C.G., Yang G. Pearson R.V. (2000). Calculation of shallow water flows using a Cartesian cut cell approach. Advances in Water resources, 23: 545-562. Causon D.M., Ingram D.M., Mingham C.G. (2000). A Cartesian cut cell method for shallow water flows with moving boundaries. Advances in Water resources, 24: 899-911. Dalzell J.F. 1999 A note on finite depth second-order wave-wave interactions. Appl. Ocean Res. 21, 105-111. Ning D.Z., Zang J., Liu S.X. Eatock Taylor R. Teng B. & Taylor P.H. 2009 Free surface and wave kinematics for nonlinear focused wave groups. J. Ocean Engineering. Accepted. Hu Z.Z., Causon D.M., Mingham C.M. and Qian L.(2009). Numerical wave tank study of a wave energy converter in heave. Proceedlings 19th ISOPE conference, Osaka, Japan Qian L., Causon D.M. & Mingham C.G., Ingram D.M. 2006 A free-surface capturing method for two fluid flows with moving bodies. Proc. Roy. Soc. London, Vol. A 462 21-42.

The agreement between 3D, standard 2D and triplane 2D speckle tracking: effects of image quality and 3D volume rate.

PubMed

Trache, Tudor; Stöbe, Stephan; Tarr, Adrienn; Pfeiffer, Dietrich; Hagendorff, Andreas

2014-12-01

Comparison of 3D and 2D speckle tracking performed on standard 2D and triplane 2D datasets of normal and pathological left ventricular (LV) wall-motion patterns with a focus on the effect that 3D volume rate (3DVR), image quality and tracking artifacts have on the agreement between 2D and 3D speckle tracking. 37 patients with normal LV function and 18 patients with ischaemic wall-motion abnormalities underwent 2D and 3D echocardiography, followed by offline speckle tracking measurements. The values of 3D global, regional and segmental strain were compared with the standard 2D and triplane 2D strain values. Correlation analysis with the LV ejection fraction (LVEF) was also performed. The 3D and 2D global strain values correlated good in both normally and abnormally contracting hearts, though systematic differences between the two methods were observed. Of the 3D strain parameters, the area strain showed the best correlation with the LVEF. The numerical agreement of 3D and 2D analyses varied significantly with the volume rate and image quality of the 3D datasets. The highest correlation between 2D and 3D peak systolic strain values was found between 3D area and standard 2D longitudinal strain. Regional wall-motion abnormalities were similarly detected by 2D and 3D speckle tracking. 2DST of triplane datasets showed similar results to those of conventional 2D datasets. 2D and 3D speckle tracking similarly detect normal and pathological wall-motion patterns. Limited image quality has a significant impact on the agreement between 3D and 2D numerical strain values.

Fully Coupled 3D Finite Element Model of Hydraulic Fracturing in a Permeable Rock Formation

NASA Astrophysics Data System (ADS)

Salimzadeh, S.; Paluszny, A.; Zimmerman, R. W.

2015-12-01

Hydraulic fracturing in permeable rock formations is a complex three-dimensional multi-physics phenomenon. Numerous analytical models of hydraulic fracturing processes have been proposed that typically simplify the physical processes, or somehow reduce the problem from three dimensions to two dimensions. Moreover, although such simplified models are able to model the growth of a single hydraulic fracture into an initially intact, homogeneous rock mass, they are generally not able to model fracturing of heterogeneous rock formations, or to account for interactions between multiple induced fractures, or between an induced fracture and pre-existing natural fractures. We have developed a numerical finite-element model for hydraulic fracturing that does not suffer from any of the limitations mentioned above. The model accounts for fluid flow within a fracture, the propagation of the fracture, and the leak-off of fluid from the fracture into the host rock. Fluid flow through the permeable rock matrix is modelled using Darcy's law, and is coupled with the laminar flow within the fracture. Fractures are discretely modelled in the three-dimensional mesh. Growth of a fracture is modelled using the concepts of linear elastic fracture mechanics (LEFM), with the onset and direction of growth based on stress intensity factors that are computed for arbitrary tetrahedral meshes. The model has been verified against several analytical solutions available in the literature for plane-strain (2D) and penny-shaped (3D) fractures, for various regimes of domination: viscosity, toughness, storage and leak-off. The interaction of the hydraulically driven fracture with pre-existing fractures and other fluid-driven fractures in terms of fluid leak-off, stress interaction and fracture arrest is investigated and the results are presented. Finally, some preliminary results are presented regarding the interaction of a hydraulically-induced fracture with a set of pre-existing natural fractures.

The program FANS-3D (finite analytic numerical simulation 3-dimensional) and its applications

NASA Technical Reports Server (NTRS)

Bravo, Ramiro H.; Chen, Ching-Jen

1992-01-01

In this study, the program named FANS-3D (Finite Analytic Numerical Simulation-3 Dimensional) is presented. FANS-3D was designed to solve problems of incompressible fluid flow and combined modes of heat transfer. It solves problems with conduction and convection modes of heat transfer in laminar flow, with provisions for radiation and turbulent flows. It can solve singular or conjugate modes of heat transfer. It also solves problems in natural convection, using the Boussinesq approximation. FANS-3D was designed to solve heat transfer problems inside one, two and three dimensional geometries that can be represented by orthogonal planes in a Cartesian coordinate system. It can solve internal and external flows using appropriate boundary conditions such as symmetric, periodic and user specified.

Three-D Flow Analysis of the Alternate SSME HPOT TAD

NASA Technical Reports Server (NTRS)

Kubinski, Cheryl A.

1993-01-01

This paper describes the results of numerical flow analyses performed in support of design development of the Space Shuttle Main Engine Alternate High Pressure Oxidizer Turbine Turn-around duct (TAD). The flow domain has been modeled using a 3D, Navier-Stokes, general purpose flow solver. The goal of this effort is to achieve an alternate TAD exit flow distribution which closely matches that of the baseline configuration. 3D Navier Stokes CFD analyses were employed to evaluate numerous candidate geometry modifications to the TAD flowpath in order to achieve this goal. The design iterations are summarized, as well as a description of the computational model, numerical results and the conclusions based on these calculations.

Summary of Documentation for DYNA3D-ParaDyn's Software Quality Assurance Regression Test Problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zywicz, Edward

The Software Quality Assurance (SQA) regression test suite for DYNA3D (Zywicz and Lin, 2015) and ParaDyn (DeGroot, et al., 2015) currently contains approximately 600 problems divided into 21 suites, and is a required component of ParaDyn’s SQA plan (Ferencz and Oliver, 2013). The regression suite allows developers to ensure that software modifications do not unintentionally alter the code response. The entire regression suite is run prior to permanently incorporating any software modification or addition. When code modifications alter test problem results, the specific cause must be determined and fully understood before the software changes and revised test answers can bemore » incorporated. The regression suite is executed on LLNL platforms using a Python script and an associated data file. The user specifies the DYNA3D or ParaDyn executable, number of processors to use, test problems to run, and other options to the script. The data file details how each problem and its answer extraction scripts are executed. For each problem in the regression suite there exists an input deck, an eight-processor partition file, an answer file, and various extraction scripts. These scripts assemble a temporary answer file in a specific format from the simulation results. The temporary and stored answer files are compared to a specific level of numerical precision, and when differences are detected the test problem is flagged as failed. Presently, numerical results are stored and compared to 16 digits. At this accuracy level different processor types, compilers, number of partitions, etc. impact the results to various degrees. Thus, for consistency purposes the regression suite is run with ParaDyn using 8 processors on machines with a specific processor type (currently the Intel Xeon E5530 processor). For non-parallel regression problems, i.e., the two XFEM problems, DYNA3D is used instead. When environments or platforms change, executables using the current source code and the new resource are created and the regression suite is run. If differences in answers arise, the new answers are retained provided that the differences are inconsequential. This bootstrap approach allows the test suite answers to evolve in a controlled manner with a high level of confidence. Developers also run the entire regression suite with (serial) DYNA3D. While these results normally differ from the stored (parallel) answers, abnormal termination or wildly different values are strong indicators of potential issues.« less

Numerical analysis of laminar and turbulent incompressible flows using the finite element Fluid Dynamics Analysis Package (FIDAP)

NASA Technical Reports Server (NTRS)

Sohn, Jeong L.

1988-01-01

The purpose of the study is the evaluation of the numerical accuracy of FIDAP (Fluid Dynamics Analysis Package). Accordingly, four test problems in laminar and turbulent incompressible flows are selected and the computational results of these problems compared with other numerical solutions and/or experimental data. These problems include: (1) 2-D laminar flow inside a wall-driven cavity; (2) 2-D laminar flow over a backward-facing step; (3) 2-D turbulent flow over a backward-facing step; and (4) 2-D turbulent flow through a turn-around duct.

Using high-order polynomial basis in 3-D EM forward modeling based on volume integral equation method

NASA Astrophysics Data System (ADS)

Kruglyakov, Mikhail; Kuvshinov, Alexey

2018-05-01

3-D interpretation of electromagnetic (EM) data of different origin and scale becomes a common practice worldwide. However, 3-D EM numerical simulations (modeling)—a key part of any 3-D EM data analysis—with realistic levels of complexity, accuracy and spatial detail still remains challenging from the computational point of view. We present a novel, efficient 3-D numerical solver based on a volume integral equation (IE) method. The efficiency is achieved by using a high-order polynomial (HOP) basis instead of the zero-order (piecewise constant) basis that is invoked in all routinely used IE-based solvers. We demonstrate that usage of the HOP basis allows us to decrease substantially the number of unknowns (preserving the same accuracy), with corresponding speed increase and memory saving.

Spectral-element Seismic Wave Propagation on CUDA/OpenCL Hardware Accelerators

NASA Astrophysics Data System (ADS)

Peter, D. B.; Videau, B.; Pouget, K.; Komatitsch, D.

2015-12-01

Seismic wave propagation codes are essential tools to investigate a variety of wave phenomena in the Earth. Furthermore, they can now be used for seismic full-waveform inversions in regional- and global-scale adjoint tomography. Although these seismic wave propagation solvers are crucial ingredients to improve the resolution of tomographic images to answer important questions about the nature of Earth's internal processes and subsurface structure, their practical application is often limited due to high computational costs. They thus need high-performance computing (HPC) facilities to improving the current state of knowledge. At present, numerous large HPC systems embed many-core architectures such as graphics processing units (GPUs) to enhance numerical performance. Such hardware accelerators can be programmed using either the CUDA programming environment or the OpenCL language standard. CUDA software development targets NVIDIA graphic cards while OpenCL was adopted by additional hardware accelerators, like e.g. AMD graphic cards, ARM-based processors as well as Intel Xeon Phi coprocessors. For seismic wave propagation simulations using the open-source spectral-element code package SPECFEM3D_GLOBE, we incorporated an automatic source-to-source code generation tool (BOAST) which allows us to use meta-programming of all computational kernels for forward and adjoint runs. Using our BOAST kernels, we generate optimized source code for both CUDA and OpenCL languages within the source code package. Thus, seismic wave simulations are able now to fully utilize CUDA and OpenCL hardware accelerators. We show benchmarks of forward seismic wave propagation simulations using SPECFEM3D_GLOBE on CUDA/OpenCL GPUs, validating results and comparing performances for different simulations and hardware usages.

The stochastic dynamics of intermittent porescale particle motion

NASA Astrophysics Data System (ADS)

Dentz, Marco; Morales, Veronica; Puyguiraud, Alexandre; Gouze, Philippe; Willmann, Matthias; Holzner, Markus

2017-04-01

Numerical and experimental data for porescale particle dynamics show intermittent patterns in Lagrangian velocities and accelerations, which manifest in long time intervals of low and short durations of high velocities [1, 2]. This phenomenon is due to the spatial persistence of particle velocities on characteristic heterogeneity length scales. In order to systematically quantify these behaviors and extract the stochastic dynamics of particle motion, we focus on the analysis of Lagrangian velocities sampled equidistantly along trajectories [3]. This method removes the intermittency observed under isochrone sampling. The space-Lagrangian velocity series can be quantified by a Markov process that is continuous in distance along streamline. It is fully parameterized in terms of the flux-weighted Eulerian velocity PDF and the characteristic pore-length. The resulting stochastic particle motion describes a continuous time random walk (CTRW). This approach allows for the process based interpretation of experimental and numerical porescale velocity, acceleration and displacement data. It provides a framework for the characterization and upscaling of particle transport and dispersion from the pore to the Darcy-scale based on the medium geometry and Eulerian flow attributes. [1] P. De Anna, T. Le Borgne, M. Dentz, A.M. Tartakovsky, D. Bolster, and P. Davy, "Flow intermittency, dispersion, and correlated continuous time random walks in porous media," Phys. Rev. Lett. 110, 184502 (2013). [2] M. Holzner, V. L. Morales, M. Willmann, and M. Dentz, "Intermittent Lagrangian velocities and accelerations in three- dimensional porous medium flow," Phys. Rev. E 92, 013015 (2015). [3] M. Dentz, P. K. Kang, A. Comolli, T. Le Borgne, and D. R. Lester, "Continuous time random walks for the evolution of Lagrangian velocities," Phys. Rev. Fluids (2016).

Fully Nonlinear Modeling and Analysis of Precision Membranes

NASA Technical Reports Server (NTRS)

Pai, P. Frank; Young, Leyland G.

2003-01-01

High precision membranes are used in many current space applications. This paper presents a fully nonlinear membrane theory with forward and inverse analyses of high precision membrane structures. The fully nonlinear membrane theory is derived from Jaumann strains and stresses, exact coordinate transformations, the concept of local relative displacements, and orthogonal virtual rotations. In this theory, energy and Newtonian formulations are fully correlated, and every structural term can be interpreted in terms of vectors. Fully nonlinear ordinary differential equations (ODES) governing the large static deformations of known axisymmetric membranes under known axisymmetric loading (i.e., forward problems) are presented as first-order ODES, and a method for obtaining numerically exact solutions using the multiple shooting procedure is shown. A method for obtaining the undeformed geometry of any axisymmetric membrane with a known inflated geometry and a known internal pressure (i.e., inverse problems) is also derived. Numerical results from forward analysis are verified using results in the literature, and results from inverse analysis are verified using known exact solutions and solutions from the forward analysis. Results show that the membrane theory and the proposed numerical methods for solving nonlinear forward and inverse membrane problems are accurate.

Numerical simulation of the generation, propagation, and diffraction of nonlinear waves in a rectangular basin: A three-dimensional numerical wave tank

NASA Astrophysics Data System (ADS)

Darwiche, Mahmoud Khalil M.

The research presented herein is a contribution to the understanding of the numerical modeling of fully nonlinear, transient water waves. The first part of the work involves the development of a time-domain model for the numerical generation of fully nonlinear, transient waves by a piston type wavemaker in a three-dimensional, finite, rectangular tank. A time-domain boundary-integral model is developed for simulating the evolving fluid field. A robust nonsingular, adaptive integration technique for the assembly of the boundary-integral coefficient matrix is developed and tested. A parametric finite-difference technique for calculating the fluid- particle kinematics is also developed and tested. A novel compatibility and continuity condition is implemented to minimize the effect of the singularities that are inherent at the intersections of the various Dirichlet and/or Neumann subsurfaces. Results are presented which demonstrate the accuracy and convergence of the numerical model. The second portion of the work is a study of the interaction of the numerically-generated, fully nonlinear, transient waves with a bottom-mounted, surface-piercing, vertical, circular cylinder. The numerical model developed in the first part of this dissertation is extended to include the presence of the cylinder at the centerline of the basin. The diffraction of the numerically generated waves by the cylinder is simulated, and the particle kinematics of the diffracted flow field are calculated and reported. Again, numerical results showing the accuracy and convergence of the extended model are presented.

pyGIMLi: An open-source library for modelling and inversion in geophysics

NASA Astrophysics Data System (ADS)

Rücker, Carsten; Günther, Thomas; Wagner, Florian M.

2017-12-01

Many tasks in applied geosciences cannot be solved by single measurements, but require the integration of geophysical, geotechnical and hydrological methods. Numerical simulation techniques are essential both for planning and interpretation, as well as for the process understanding of modern geophysical methods. These trends encourage open, simple, and modern software architectures aiming at a uniform interface for interdisciplinary and flexible modelling and inversion approaches. We present pyGIMLi (Python Library for Inversion and Modelling in Geophysics), an open-source framework that provides tools for modelling and inversion of various geophysical but also hydrological methods. The modelling component supplies discretization management and the numerical basis for finite-element and finite-volume solvers in 1D, 2D and 3D on arbitrarily structured meshes. The generalized inversion framework solves the minimization problem with a Gauss-Newton algorithm for any physical forward operator and provides opportunities for uncertainty and resolution analyses. More general requirements, such as flexible regularization strategies, time-lapse processing and different sorts of coupling individual methods are provided independently of the actual methods used. The usage of pyGIMLi is first demonstrated by solving the steady-state heat equation, followed by a demonstration of more complex capabilities for the combination of different geophysical data sets. A fully coupled hydrogeophysical inversion of electrical resistivity tomography (ERT) data of a simulated tracer experiment is presented that allows to directly reconstruct the underlying hydraulic conductivity distribution of the aquifer. Another example demonstrates the improvement of jointly inverting ERT and ultrasonic data with respect to saturation by a new approach that incorporates petrophysical relations in the inversion. Potential applications of the presented framework are manifold and include time-lapse, constrained, joint, and coupled inversions of various geophysical and hydrological data sets.

Dynamic coupling of three hydrodynamic models

NASA Astrophysics Data System (ADS)

Hartnack, J. N.; Philip, G. T.; Rungoe, M.; Smith, G.; Johann, G.; Larsen, O.; Gregersen, J.; Butts, M. B.

2008-12-01

The need for integrated modelling is evidently present within the field of flood management and flood forecasting. Engineers, modellers and managers are faced with flood problems which transcend the classical hydrodynamic fields of urban, river and coastal flooding. Historically the modeller has been faced with having to select one hydrodynamic model to cover all the aspects of the potentially complex dynamics occurring in a flooding situation. Such a single hydrodynamic model does not cover all dynamics of flood modelling equally well. Thus the ideal choice may in fact be a combination of models. Models combining two numerical/hydrodynamic models are becoming more standard, typically these models combine a 1D river model with a 2D overland flow model or alternatively a 1D sewer/collection system model with a 2D overland solver. In complex coastal/urban areas the flood dynamics may include rivers/streams, collection/storm water systems along with the overland flow. The dynamics within all three areas is of the same time scale and there is feedback in the system across the couplings. These two aspects dictate a fully dynamic three way coupling as opposed to running the models sequentially. It will be shown that the main challenges of the three way coupling are time step issues related to the difference in numerical schemes used in the three model components and numerical instabilities caused by the linking of the model components. MIKE FLOOD combines the models MIKE 11, MIKE 21 and MOUSE into one modelling framework which makes it possible to couple any combination of river, urban and overland flow fully dynamically. The MIKE FLOOD framework will be presented with an overview of the coupling possibilities. The flood modelling concept will be illustrated through real life cases in Australia and in Germany. The real life cases reflect dynamics and interactions across all three model components which are not possible to reproduce using a two-way coupling alone. The models comprise 2D inundation modelling, river networks with multiple structures (pumps, weirs, culverts), urban drainage networks as well as dam break modelling. The models were used to quantify the results of storm events or failures (dam break, pumping failures etc) coinciding with high discharge in river system and heavy rainfall. The detailed representation of the flow path through the city allowed a direct assessment of flood risk Thus it is found that the three-way coupled model is a practical and useful tool for integrated flood management.

Can Computational Sediment Transport Models Reproduce the Observed Variability of Channel Networks in Modern Deltas?

NASA Astrophysics Data System (ADS)

Nesvold, E.; Mukerji, T.

2017-12-01

River deltas display complex channel networks that can be characterized through the framework of graph theory, as shown by Tejedor et al. (2015). Deltaic patterns may also be useful in a Bayesian approach to uncertainty quantification of the subsurface, but this requires a prior distribution of the networks of ancient deltas. By considering subaerial deltas, one can at least obtain a snapshot in time of the channel network spectrum across deltas. In this study, the directed graph structure is semi-automatically extracted from satellite imagery using techniques from statistical processing and machine learning. Once the network is labeled with vertices and edges, spatial trends and width and sinuosity distributions can also be found easily. Since imagery is inherently 2D, computational sediment transport models can serve as a link between 2D network structure and 3D depositional elements; the numerous empirical rules and parameters built into such models makes it necessary to validate the output with field data. For this purpose we have used a set of 110 modern deltas, with average water discharge ranging from 10 - 200,000 m3/s, as a benchmark for natural variability. Both graph theoretic and more general distributions are established. A key question is whether it is possible to reproduce this deltaic network spectrum with computational models. Delft3D was used to solve the shallow water equations coupled with sediment transport. The experimental setup was relatively simple; incoming channelized flow onto a tilted plane, with varying wave and tidal energy, sediment types and grain size distributions, river discharge and a few other input parameters. Each realization was run until a delta had fully developed: between 50 and 500 years (with a morphology acceleration factor). It is shown that input parameters should not be sampled independently from the natural ranges, since this may result in deltaic output that falls well outside the natural spectrum. Since we are interested in studying the patterns occurring in nature, ideas are proposed for how to sample computer realizations that match this distribution. By establishing a link between surface based patterns from the field with the associated subsurface structure from physics-based models, this is a step towards a fully Bayesian workflow in subsurface simulation.

Kindergartners’ Fluent Processing of Symbolic Numerical Magnitude is Predicted by Their Cardinal Knowledge and Implicit Understanding of Arithmetic Two Years Earlier

PubMed Central

Moore, Alex M.; vanMarle, Kristy; Geary, David C.

2016-01-01

Fluency in first graders’ processing of the magnitudes associated with Arabic numerals, collections of objects, and mixtures of objects and numerals predicts current and future mathematics achievement. The quantitative competencies that support the development of fluent processing of magnitude are not fully understood, however. At the beginning and end of preschool (M = 3 years, 9 months at first assessment; range 3 years, 3 months to 4years, 3 months), 112 (51 boys) children completed tasks measuring numeral recognition and comparison, acuity of the approximate number system, and knowledge of counting principles, cardinality, and implicit arithmetic, and completed a magnitude processing task (number sets test) in kindergarten. Use of Bayesian and linear regression techniques revealed that two measures of preschoolers’ cardinal knowledge and their competence at implicit arithmetic predicted later fluency of magnitude processing, controlling domain general factors, preliteracy skills, and parental education. The results help to narrow the search for the early foundation of children’s emerging competence with symbolic mathematics and provide direction for early interventions. PMID:27236038

Kindergartners' fluent processing of symbolic numerical magnitude is predicted by their cardinal knowledge and implicit understanding of arithmetic 2years earlier.

PubMed

Moore, Alex M; vanMarle, Kristy; Geary, David C

2016-10-01

Fluency in first graders' processing of the magnitudes associated with Arabic numerals, collections of objects, and mixtures of objects and numerals predicts current and future mathematics achievement. The quantitative competencies that support the development of fluent processing of magnitude, however, are not fully understood. At the beginning and end of preschool (M=3years 9months at first assessment, range=3years 3months to 4years 3months), 112 children (51 boys) completed tasks measuring numeral recognition and comparison, acuity of the approximate number system, and knowledge of counting principles, cardinality, and implicit arithmetic and also completed a magnitude processing task (number sets test) in kindergarten. Use of Bayesian and linear regression techniques revealed that two measures of preschoolers' cardinal knowledge and their competence at implicit arithmetic predicted later fluency of magnitude processing, controlling domain-general factors, preliteracy skills, and parental education. The results help to narrow the search for the early foundation of children's emerging competence with symbolic mathematics and provide direction for early interventions. Copyright © 2016 Elsevier Inc. All rights reserved.

The Sedimentation of Particles under Orthogonal Shear in Viscoelastic Fluids

NASA Astrophysics Data System (ADS)

Murch, William L.; Krishnan, Sreenath; Shaqfeh, Eric S. G.

2016-11-01

Many engineering applications, including oil and gas recovery, require the suspension of particles in viscoelastic fluids during fluid transport and processing. A topic of specific importance involves such particle suspensions experiencing an applied shear flow in a direction perpendicular to gravity (referred to as orthogonal shear). Previously, it has been shown that particle sedimentation coupled with an orthogonal shear flow can reduce the particle settling rate in elastic fluids. The underlying mechanism of this enhanced coupling drag is not fully understood, particularly at finite Weissenberg numbers. This talk examines the role of fluid elasticity on a single, non-Brownian, rigid sphere settling in orthogonal shear using experiments and numerical simulations. New experiments were performed in a Taylor-Couette flow cell using Boger fluids to study the coupling drag as a function of the shear and sedimentation Weissenberg numbers as well as particle confinement. The elastic effect was also studied with fully 3D simulations of flow past a rigid sphere, using the FENE-P constitutive model to describe the polymeric fluid rheology. These simulations show good agreement with the experiments and allow for further insight into the mechanism of elasticity-enhanced drag. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship.

Formation and Reconnection of Three-Dimensional Current Sheets in the Solar Corona

NASA Technical Reports Server (NTRS)

Edmondson, J. K.; Antiochos, S. K.; DeVore, C. R.; Zurbuchen, T. H.

2010-01-01

Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun s corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional magnetohydrodynamic (3D MHD) simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to apply directly the vast body of knowledge gained from the many studies of 2D reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet- Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona. Subject Headings: Sun: corona Sun: magnetic fields Sun: reconnection

3D numerical modeling of India-Asia-like collision

NASA Astrophysics Data System (ADS)

-Erika Püsök, Adina; Kaus, Boris; Popov, Anton

2013-04-01

One of the most striking features of plate tectonics and lithospheric deformation is the India-Asia collision zone, which formed when the Indian continent collided with Eurasia, around 50 million years ago. The rise of the abnormally thick Tibetan plateau, the deformation at its Eastern and Western syntaxes, the transition from subduction to collision and uplift and the interaction of tectonics and climate are processes not fully understood. Though various geophysical methods have been employed to shed light on the present structure of the Indian-Asian lithosphere, the driving mechanisms that uplifted the Tibetan plateau remain highly controversial and different hypotheses imply contradictory scenarios. Models for double crustal thickness include: wholescale underthrusting of Indian lithospheric mantle under Tibet (Argand model), distributed homogeneous shortening or the thin-sheet model (England and Houseman, 1986), slip-line field model to also explain extrusion of Eastern side of Tibet away from Indian indentor (Tapponier and Molnar, 1976) or lower crustal flow models for the exhumation of the Himalayan units and lateral spreading of the Tibetan plateau (Royden et al., 1998, Beaumont et al., 2004). The thin-sheet model has emerged as a more successful (or at least more widely used) model, but one of its major shortcomings is that it cannot simultaneously represent channel flow and gravitational collapse of the mantle lithosphere (Lechmann et al., 2011), since these mechanisms require the lithosphere to interact with the underlying mantle, or to have a vertically non-homogeneous rheology. Of those who favour a layered structure of the lithosphere beneath Tibet, some attribute the lack of substantial seismicity underneath the Moho as evidence that all the strength of the lithosphere resides in the upper crust and the mantle is weak - the crème brulée model (Jackson, 2002), while others point out that some processes can be well explained if the crust resides above a strong mantle lithosphere - the jelly sandwich model (Burov and Watts, 2006). 3D models are thus needed to investigate these hypotheses. However, fully 3D models of the dynamics of continent collision zones have only been developed very recently, and presently most research groups have relied on certain explicit assumptions for their codes. Here, we employ the parallel 3D code LaMEM (Lithosphere and Mantle Evolution Model), with a finite difference staggered grid solver, which is capable of simulating lithospheric deformation while simultaneously taking mantle flow and a free surface into account. We here report on first lithospheric and upper-mantle scale simulations in which the Indian lithosphere is indented into Asia. Acknowledgements. Funding was provided by the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Grant agreement #258830. Numerical computations have been performed on JUQUEEN of the Jülich high-performance computing center. • Beaumont, C., Jamieson, R.A., Nguyen, M.H., Medvedev, S.E., 2004. Crustal channel flows: 1. Numerical models with applications to the tectonics of the Himalayan-Tibetan orogeny. J. Geophys. Res. 109, B06406. • Burov, E. & Watts, W.S., 2006. The long-term strength of continental lithosphere: "jelly sandwich" or "crème brûlée"?. GSA Today, 16, doi: 10.1130/1052-5173(2006)1016<1134:TLTSOC>1132.1130.CO;1132. • England P., Houseman, G., 1986. Finite strain calculations of continental deformation. 2. Comparison with the India-Asia collision zone. J. Geophys. Res.- Solid Earth and Planets 91 (B3), 3664-3676. • Jackson, J., 2002. Strength of the continental lithosphere: time to abandon the jelly sandwich?. GSA Today, September, 4-10. • Lechmann, S.M., May, D.A., Kaus, B.J.P., Schmalholz, S.M., 2011. Comparing thin-sheet models with 3D multilayer models for continental collision. Geophy. Int. J. doi: 10.1111/j.1365-246X.2011.05164.x • Royden, L.H., Burchfiel, B.C., King, R.W., Wang, E., Chen, Z.L., Shen, F., Liu, Y.P., 1997. Surface deformation and lower crustal flow in eartern Tibet. Science 276 (5313), 788-790. • Tapponier, P., Molnar, P., 1976. Slip-line field-theory and large-scale continental tectonics. Nature 264 (5584), 319-324.

Transthoracic 3D echocardiographic left heart chamber quantification in patients with bicuspid aortic valve disease.

PubMed

van den Hoven, Allard T; Mc-Ghie, Jackie S; Chelu, Raluca G; Duijnhouwer, Anthonie L; Baggen, Vivan J M; Coenen, Adriaan; Vletter, Wim B; Dijkshoorn, Marcel L; van den Bosch, Annemien E; Roos-Hesselink, Jolien W

2017-12-01

Integration of volumetric heart chamber quantification by 3D echocardiography into clinical practice has been hampered by several factors which a new fully automated algorithm (Left Heart Model, (LHM)) may help overcome. This study therefore aims to evaluate the feasibility and accuracy of the LHM software in quantifying left atrial and left ventricular volumes and left ventricular ejection fraction in a cohort of patients with a bicuspid aortic valve. Patients with a bicuspid aortic valve were prospectively included. All patients underwent 2D and 3D transthoracic echocardiography and computed tomography. Left atrial and ventricular volumes were obtained using the automated program, which did not require manual contour detection. For comparison manual and semi-automated measurements were performed using conventional 2D and 3D datasets. 53 patients were included, in four of those patients no 3D dataset could be acquired. Additionally, 12 patients were excluded based on poor imaging quality. Left ventricular end-diastolic and end-systolic volumes and ejection fraction calculated by the LHM correlated well with manual 2D and 3D measurements (Pearson's r between 0.43 and 0.97, p < 0.05). Left atrial volume (LAV) also correlated significantly although LHM did estimate larger LAV compared to both 2DE and 3DE (Pearson's r between 0.61 and 0.81, p < 0.01). The fully automated software works well in a real-world setting and helps to overcome some of the major hurdles in integrating 3D analysis into daily practice, as it is user-independent and highly reproducible in a group of patients with a clearly defined and well-studied valvular abnormality.

An Integrative, Multi-Scale Computational Model of a Swimming Lamprey Fully Coupled to Its Fluid Environment and Incorporating Proprioceptive Feedback

NASA Astrophysics Data System (ADS)

Hamlet, C. L.; Hoffman, K.; Fauci, L.; Tytell, E.

2016-02-01

The lamprey is a model organism for both neurophysiology and locomotion studies. To study the role of sensory feedback as an organism moves through its environment, a 2D, integrative, multi-scale model of an anguilliform swimmer driven by neural activation from a central pattern generator (CPG) is constructed. The CPG in turn drives muscle kinematics and is fully coupled to the surrounding fluid. The system is numerically evolved in time using an immersed boundary framework producing an emergent swimming mode. Proprioceptive feedback to the CPG based on experimental observations adjust the activation signal as the organism interacts with its environment. Effects on the speed, stability and cost (metabolic work) of swimming due to nonlinear dependencies associated with muscle force development combined with proprioceptive feedback to neural activation are estimated and examined.

Fluid preconditioning for Newton–Krylov-based, fully implicit, electrostatic particle-in-cell simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, G., E-mail: gchen@lanl.gov; Chacón, L.; Leibs, C.A.

2014-02-01

A recent proof-of-principle study proposes an energy- and charge-conserving, nonlinearly implicit electrostatic particle-in-cell (PIC) algorithm in one dimension [9]. The algorithm in the reference employs an unpreconditioned Jacobian-free Newton–Krylov method, which ensures nonlinear convergence at every timestep (resolving the dynamical timescale of interest). Kinetic enslavement, which is one key component of the algorithm, not only enables fully implicit PIC as a practical approach, but also allows preconditioning the kinetic solver with a fluid approximation. This study proposes such a preconditioner, in which the linearized moment equations are closed with moments computed from particles. Effective acceleration of the linear GMRES solvemore » is demonstrated, on both uniform and non-uniform meshes. The algorithm performance is largely insensitive to the electron–ion mass ratio. Numerical experiments are performed on a 1D multi-scale ion acoustic wave test problem.« less

Dissipative particle dynamics: Effects of thermostating schemes on nano-colloid electrophoresis

NASA Astrophysics Data System (ADS)

Hassanzadeh Afrouzi, Hamid; Moshfegh, Abouzar; Farhadi, Mousa; Sedighi, Kurosh

2018-05-01

A novel fully explicit approach using dissipative particle dynamics (DPD) method is introduced in the present study to model the electrophoretic transport of nano-colloids in an electrolyte solution. Slater type charge smearing function included in 3D Ewald summation method is employed to treat electrostatic interaction. Performance of various thermostats are challenged to control the system temperature and study the dynamic response of colloidal electrophoretic mobility under practical ranges of external electric field (0 . 072 < E < 0 . 361 v/nm) covering linear to non-linear response regime, and ionic salt concentration (0.049 < SC < 0 . 69 [M]) covering weak to strong Debye screening of the colloid. System temperature and electrophoretic mobility both show a direct and inverse relationships respectively with electric field and colloidal repulsion; although they each respectively behave direct and inverse trends with salt concentration under various thermostats. Nosé-Hoover-Lowe-Andersen and Lowe-Andersen thermostats are found to function more effectively under high electric fields (E > 0 . 145[v/nm ]) while thermal equilibrium is maintained. Reasonable agreements are achieved by benchmarking the system radial distribution function with available EW3D modellings, as well as comparing reduced mobility against conventional Smoluchowski and Hückel theories, and numerical solution of Poisson-Boltzmann equation.

Anderson localization of electrons in single crystals: LixFe7Se8

PubMed Central

Ying, Tianping; Gu, Yueqiang; Chen, Xiao; Wang, Xinbo; Jin, Shifeng; Zhao, Linlin; Zhang, Wei; Chen, Xiaolong

2016-01-01

Anderson (disorder-induced) localization, proposed more than half a century ago, has inspired numerous efforts to explore the absence of wave diffusions in disordered media. However, the proposed disorder-induced metal-insulator transition (MIT), associated with the nonpropagative electron waves, has hardly been observed in three-dimensional (3D) crystalline materials, let alone single crystals. We report the observation of an MIT in centimeter-size single crystals of LixFe7Se8 induced by lattice disorder. Both specific heat and infrared reflectance measurements reveal the presence of considerable electronic states in the vicinity of the Fermi level when the MIT occurs, suggesting that the transition is not due to Coulomb repulsion mechanism. The 3D variable range hopping regime evidenced by electrical transport measurements at low temperatures indicates the localized nature of the electronic states on the Fermi level. Quantitative analyses of carrier concentration, carrier mobility, and simulated density of states (DOS) fully support that LixFe7Se8 is an Anderson insulator. On the basis of these results, we provide a unified DOS picture to explain all the experimental results, and a schematic diagram for finding other potential Anderson insulators. This material will thus serve as a rich playground for both theoretical and experimental investigations on MITs and disorder-induced phenomena. PMID:26989781

A numerical study of attraction/repulsion collective behavior models: 3D particle analyses and 1D kinetic simulations

NASA Astrophysics Data System (ADS)

Vecil, Francesco; Lafitte, Pauline; Rosado Linares, Jesús

2013-10-01

We study at particle and kinetic level a collective behavior model based on three phenomena: self-propulsion, friction (Rayleigh effect) and an attractive/repulsive (Morse) potential rescaled so that the total mass of the system remains constant independently of the number of particles N. In the first part of the paper, we introduce the particle model: the agents are numbered and described by their position and velocity. We identify five parameters that govern the possible asymptotic states for this system (clumps, spheres, dispersion, mills, rigid-body rotation, flocks) and perform a numerical analysis on the 3D setting. Then, in the second part of the paper, we describe the kinetic system derived as the limit from the particle model as N tends to infinity; we propose, in 1D, a numerical scheme for the simulations, and perform a numerical analysis devoted to trying to recover asymptotically patterns similar to those emerging for the equivalent particle systems, when particles originally evolved on a circle.

Three-Dimensional Simulations of Electron Beams Focused by Periodic Permanent Magnets

NASA Technical Reports Server (NTRS)

Kory, Carol L.

1999-01-01

A fully three-dimensional (3D) model of an electron beam focused by a periodic permanent magnet (PPM) stack has been developed. First, the simulation code MAFIA was used to model a PPM stack using the magnetostatic solver. The exact geometry of the magnetic focusing structure was modeled; thus, no approximations were made regarding the off-axis fields. The fields from the static solver were loaded into the 3D particle-in-cell (PIC) solver of MAFIA where fully 3D behavior of the beam was simulated in the magnetic focusing field. The PIC solver computes the time-integration of electromagnetic fields simultaneously with the time integration of the equations of motion of charged particles that move under the influence of those fields. Fields caused by those moving charges are also taken into account; thus, effects like space charge and magnetic forces between particles are fully simulated. The electron beam is simulated by a number of macro-particles. These macro-particles represent a given charge Q amounting to that of several million electrons in order to conserve computational time and memory. Particle motion is unrestricted, so particle trajectories can cross paths and move in three dimensions under the influence of 3D electric and magnetic fields. Correspondingly, there is no limit on the initial current density distribution of the electron beam, nor its density distribution at any time during the simulation. Simulation results including beam current density, percent ripple and percent transmission will be presented, and the effects current, magnetic focusing strength and thermal velocities have on beam behavior will be demonstrated using 3D movies showing the evolution of beam characteristics in time and space. Unlike typical beam optics models, this 3D model allows simulation of asymmetric designs such as non- circularly symmetric electrostatic or magnetic focusing as well as the inclusion of input/output couplers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zegadlo, Krzysztof B., E-mail: zegadlo@if.pw.edu.pl; Karpierz, Miroslaw A.; Wasak, Tomasz

We report results of the analysis for families of one-dimensional (1D) trapped solitons, created by competing self-focusing (SF) quintic and self-defocusing (SDF) cubic nonlinear terms. Two trapping potentials are considered, the harmonic-oscillator (HO) and delta-functional ones. The models apply to optical solitons in colloidal waveguides and other photonic media, and to matter-wave solitons in Bose-Einstein condensates loaded into a quasi-1D trap. For the HO potential, the results are obtained in an approximate form, using the variational and Thomas-Fermi approximations, and in a full numerical form, including the ground state and the first antisymmetric excited one. For the delta-functional attractive potential,more » the results are produced in a fully analytical form, and verified by means of numerical methods. Both exponentially localized solitons and weakly localized trapped modes are found for the delta-functional potential. The most essential conclusions concern the applicability of competing Vakhitov-Kolokolov (VK) and anti-VK criteria to the identification of the stability of solitons created under the action of the competing SF and SDF terms.« less

Stabilization of solitons under competing nonlinearities by external potentials

NASA Astrophysics Data System (ADS)

Zegadlo, Krzysztof B.; Wasak, Tomasz; Malomed, Boris A.; Karpierz, Miroslaw A.; Trippenbach, Marek

2014-12-01

We report results of the analysis for families of one-dimensional (1D) trapped solitons, created by competing self-focusing (SF) quintic and self-defocusing (SDF) cubic nonlinear terms. Two trapping potentials are considered, the harmonic-oscillator (HO) and delta-functional ones. The models apply to optical solitons in colloidal waveguides and other photonic media, and to matter-wave solitons in Bose-Einstein condensates loaded into a quasi-1D trap. For the HO potential, the results are obtained in an approximate form, using the variational and Thomas-Fermi approximations, and in a full numerical form, including the ground state and the first antisymmetric excited one. For the delta-functional attractive potential, the results are produced in a fully analytical form, and verified by means of numerical methods. Both exponentially localized solitons and weakly localized trapped modes are found for the delta-functional potential. The most essential conclusions concern the applicability of competing Vakhitov-Kolokolov (VK) and anti-VK criteria to the identification of the stability of solitons created under the action of the competing SF and SDF terms.

Higher-order compositional modeling of three-phase flow in 3D fractured porous media based on cross-flow equilibrium

NASA Astrophysics Data System (ADS)

Moortgat, Joachim; Firoozabadi, Abbas

2013-10-01

Numerical simulation of multiphase compositional flow in fractured porous media, when all the species can transfer between the phases, is a real challenge. Despite the broad applications in hydrocarbon reservoir engineering and hydrology, a compositional numerical simulator for three-phase flow in fractured media has not appeared in the literature, to the best of our knowledge. In this work, we present a three-phase fully compositional simulator for fractured media, based on higher-order finite element methods. To achieve computational efficiency, we invoke the cross-flow equilibrium (CFE) concept between discrete fractures and a small neighborhood in the matrix blocks. We adopt the mixed hybrid finite element (MHFE) method to approximate convective Darcy fluxes and the pressure equation. This approach is the most natural choice for flow in fractured media. The mass balance equations are discretized by the discontinuous Galerkin (DG) method, which is perhaps the most efficient approach to capture physical discontinuities in phase properties at the matrix-fracture interfaces and at phase boundaries. In this work, we account for gravity and Fickian diffusion. The modeling of capillary effects is discussed in a separate paper. We present the mathematical framework, using the implicit-pressure-explicit-composition (IMPEC) scheme, which facilitates rigorous thermodynamic stability analyses and the computation of phase behavior effects to account for transfer of species between the phases. A deceptively simple CFL condition is implemented to improve numerical stability and accuracy. We provide six numerical examples at both small and larger scales and in two and three dimensions, to demonstrate powerful features of the formulation.

Lossy to lossless object-based coding of 3-D MRI data.

PubMed

Menegaz, Gloria; Thiran, Jean-Philippe

2002-01-01

We propose a fully three-dimensional (3-D) object-based coding system exploiting the diagnostic relevance of the different regions of the volumetric data for rate allocation. The data are first decorrelated via a 3-D discrete wavelet transform. The implementation via the lifting steps scheme allows to map integer-to-integer values, enabling lossless coding, and facilitates the definition of the object-based inverse transform. The coding process assigns disjoint segments of the bitstream to the different objects, which can be independently accessed and reconstructed at any up-to-lossless quality. Two fully 3-D coding strategies are considered: embedded zerotree coding (EZW-3D) and multidimensional layered zero coding (MLZC), both generalized for region of interest (ROI)-based processing. In order to avoid artifacts along region boundaries, some extra coefficients must be encoded for each object. This gives rise to an overheading of the bitstream with respect to the case where the volume is encoded as a whole. The amount of such extra information depends on both the filter length and the decomposition depth. The system is characterized on a set of head magnetic resonance images. Results show that MLZC and EZW-3D have competitive performances. In particular, the best MLZC mode outperforms the others state-of-the-art techniques on one of the datasets for which results are available in the literature.

Rubber Impact on 3D Textile Composites

NASA Astrophysics Data System (ADS)

Heimbs, Sebastian; Van Den Broucke, Björn; Duplessis Kergomard, Yann; Dau, Frederic; Malherbe, Benoit

2012-06-01

A low velocity impact study of aircraft tire rubber on 3D textile-reinforced composite plates was performed experimentally and numerically. In contrast to regular unidirectional composite laminates, no delaminations occur in such a 3D textile composite. Yarn decohesions, matrix cracks and yarn ruptures have been identified as the major damage mechanisms under impact load. An increase in the number of 3D warp yarns is proposed to improve the impact damage resistance. The characteristic of a rubber impact is the high amount of elastic energy stored in the impactor during impact, which was more than 90% of the initial kinetic energy. This large geometrical deformation of the rubber during impact leads to a less localised loading of the target structure and poses great challenges for the numerical modelling. A hyperelastic Mooney-Rivlin constitutive law was used in Abaqus/Explicit based on a step-by-step validation with static rubber compression tests and low velocity impact tests on aluminium plates. Simulation models of the textile weave were developed on the meso- and macro-scale. The final correlation between impact simulation results on 3D textile-reinforced composite plates and impact test data was promising, highlighting the potential of such numerical simulation tools.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mermigkis, Panagiotis G.; Tsalikis, Dimitrios G.; Institute of Chemical Engineering and High Temperature Chemical Processes, GR 26500 Patras

A kinetic Monte Carlo (kMC) simulation algorithm is developed for computing the effective diffusivity of water molecules in a poly(methyl methacrylate) (PMMA) matrix containing carbon nanotubes (CNTs) at several loadings. The simulations are conducted on a cubic lattice to the bonds of which rate constants are assigned governing the elementary jump events of water molecules from one lattice site to another. Lattice sites belonging to PMMA domains of the membrane are assigned different rates than lattice sites belonging to CNT domains. Values of these two rate constants are extracted from available numerical data for water diffusivity within a PMMA matrixmore » and a CNT pre-computed on the basis of independent atomistic molecular dynamics simulations, which show that water diffusivity in CNTs is 3 orders of magnitude faster than in PMMA. Our discrete-space, continuum-time kMC simulation results for several PMMA-CNT nanocomposite membranes (characterized by different values of CNT length L and diameter D and by different loadings of the matrix in CNTs) demonstrate that the overall or effective diffusivity, D{sub eff}, of water in the entire polymeric membrane is of the same order of magnitude as its diffusivity in PMMA domains and increases only linearly with the concentration C (vol. %) in nanotubes. For a constant value of the concentration C, D{sub eff} is found to vary practically linearly also with the CNT aspect ratio L/D. The kMC data allow us to propose a simple bilinear expression for D{sub eff} as a function of C and L/D that can describe the numerical data for water mobility in the membrane extremely accurately. Additional simulations with two different CNT configurations (completely random versus aligned) show that CNT orientation in the polymeric matrix has only a minor effect on D{sub eff} (as long as CNTs do not fully penetrate the membrane). We have also extensively analyzed and quantified sublinear (anomalous) diffusive phenomena over small to moderate times and correlated them with the time needed for penetrant water molecules to explore the available large, fast-diffusing CNT pores before Fickian diffusion is reached.« less

Determination of the effective diffusivity of water in a poly (methyl methacrylate) membrane containing carbon nanotubes using kinetic Monte Carlo simulations.

PubMed

Mermigkis, Panagiotis G; Tsalikis, Dimitrios G; Mavrantzas, Vlasis G

2015-10-28

A kinetic Monte Carlo (kMC) simulation algorithm is developed for computing the effective diffusivity of water molecules in a poly(methyl methacrylate) (PMMA) matrix containing carbon nanotubes (CNTs) at several loadings. The simulations are conducted on a cubic lattice to the bonds of which rate constants are assigned governing the elementary jump events of water molecules from one lattice site to another. Lattice sites belonging to PMMA domains of the membrane are assigned different rates than lattice sites belonging to CNT domains. Values of these two rate constants are extracted from available numerical data for water diffusivity within a PMMA matrix and a CNT pre-computed on the basis of independent atomistic molecular dynamics simulations, which show that water diffusivity in CNTs is 3 orders of magnitude faster than in PMMA. Our discrete-space, continuum-time kMC simulation results for several PMMA-CNT nanocomposite membranes (characterized by different values of CNT length L and diameter D and by different loadings of the matrix in CNTs) demonstrate that the overall or effective diffusivity, D(eff), of water in the entire polymeric membrane is of the same order of magnitude as its diffusivity in PMMA domains and increases only linearly with the concentration C (vol. %) in nanotubes. For a constant value of the concentration C, D(eff) is found to vary practically linearly also with the CNT aspect ratio L/D. The kMC data allow us to propose a simple bilinear expression for D(eff) as a function of C and L/D that can describe the numerical data for water mobility in the membrane extremely accurately. Additional simulations with two different CNT configurations (completely random versus aligned) show that CNT orientation in the polymeric matrix has only a minor effect on D(eff) (as long as CNTs do not fully penetrate the membrane). We have also extensively analyzed and quantified sublinear (anomalous) diffusive phenomena over small to moderate times and correlated them with the time needed for penetrant water molecules to explore the available large, fast-diffusing CNT pores before Fickian diffusion is reached.

Higher Rank ABJM Wilson Loops from Matrix Models

NASA Astrophysics Data System (ADS)

Cookmeyer, Jonathan; Liu, James; Zayas, Leopoldo

2017-01-01

We compute the expectation values of 1/6 supersymmetric Wilson Loops in ABJM theory in higher rank representations. Using standard matrix model techniques, we calculate the expectation value in the rank m fully symmetric and fully antisymmetric representation where m is scaled with N. To leading order, we find agreement with the classical action of D6 and D2 branes in AdS4 ×CP3 respectively. Further, we compute the first subleading order term, which, on the AdS side, makes a prediction for the one-loop effective action of the corresponding D6 and D2 branes. Supported by the National Science Foundation under Grant No. PHY 1559988 and the US Department of Energy under Grant No. DE-SC0007859.

Hyperbolic reformulation of a 1D viscoelastic blood flow model and ADER finite volume schemes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montecinos, Gino I.; Müller, Lucas O.; Toro, Eleuterio F.

2014-06-01

The applicability of ADER finite volume methods to solve hyperbolic balance laws with stiff source terms in the context of well-balanced and non-conservative schemes is extended to solve a one-dimensional blood flow model for viscoelastic vessels, reformulated as a hyperbolic system, via a relaxation time. A criterion for selecting relaxation times is found and an empirical convergence rate assessment is carried out to support this result. The proposed methodology is validated by applying it to a network of viscoelastic vessels for which experimental and numerical results are available. The agreement between the results obtained in the present paper and thosemore » available in the literature is satisfactory. Key features of the present formulation and numerical methodologies, such as accuracy, efficiency and robustness, are fully discussed in the paper.« less

3D numerical simulations of multiphase continental rifting

NASA Astrophysics Data System (ADS)

Naliboff, J.; Glerum, A.; Brune, S.

2017-12-01

Observations of rifted margin architecture suggest continental breakup occurs through multiple phases of extension with distinct styles of deformation. The initial rifting stages are often characterized by slow extension rates and distributed normal faulting in the upper crust decoupled from deformation in the lower crust and mantle lithosphere. Further rifting marks a transition to higher extension rates and coupling between the crust and mantle lithosphere, with deformation typically focused along large-scale detachment faults. Significantly, recent detailed reconstructions and high-resolution 2D numerical simulations suggest that rather than remaining focused on a single long-lived detachment fault, deformation in this phase may progress toward lithospheric breakup through a complex process of fault interaction and development. The numerical simulations also suggest that an initial phase of distributed normal faulting can play a key role in the development of these complex fault networks and the resulting finite deformation patterns. Motivated by these findings, we will present 3D numerical simulations of continental rifting that examine the role of temporal increases in extension velocity on rifted margin structure. The numerical simulations are developed with the massively parallel finite-element code ASPECT. While originally designed to model mantle convection using advanced solvers and adaptive mesh refinement techniques, ASPECT has been extended to model visco-plastic deformation that combines a Drucker Prager yield criterion with non-linear dislocation and diffusion creep. To promote deformation localization, the internal friction angle and cohesion weaken as a function of accumulated plastic strain. Rather than prescribing a single zone of weakness to initiate deformation, an initial random perturbation of the plastic strain field combined with rapid strain weakening produces distributed normal faulting at relatively slow rates of extension in both 2D and 3D simulations. Our presentation will focus on both the numerical assumptions required to produce these results and variations in 3D rifted margin architecture arising from a transition from slow to rapid rates of extension.

Efficient generation of hPSC-derived midbrain dopaminergic neurons in a fully defined, scalable, 3D biomaterial platform

PubMed Central

Adil, Maroof M.; Rodrigues, Gonçalo M. C.; Kulkarni, Rishikesh U.; Rao, Antara T.; Chernavsky, Nicole E.; Miller, Evan W.; Schaffer, David V.

2017-01-01

Pluripotent stem cells (PSCs) have major potential as an unlimited source of functional cells for many biomedical applications; however, the development of cell manufacturing systems to enable this promise faces many challenges. For example, there have been major recent advances in the generation of midbrain dopaminergic (mDA) neurons from stem cells for Parkinson’s Disease (PD) therapy; however, production of these cells typically involves undefined components and difficult to scale 2D culture formats. Here, we used a fully defined, 3D, thermoresponsive biomaterial platform to rapidly generate large numbers of action-potential firing mDA neurons after 25 days of differentiation (~40% tyrosine hydroxylase (TH) positive, maturing into 25% cells exhibiting mDA neuron-like spiking behavior). Importantly, mDA neurons generated in 3D exhibited a 30-fold increase in viability upon implantation into rat striatum compared to neurons generated on 2D, consistent with the elevated expression of survival markers FOXA2 and EN1 in 3D. A defined, scalable, and resource-efficient cell culture platform can thus rapidly generate high quality differentiated cells, both neurons and potentially other cell types, with strong potential to accelerate both basic and translational research. PMID:28091566

Semantic Building FAÇADE Segmentation from Airborne Oblique Images

NASA Astrophysics Data System (ADS)

Lin, Y.; Nex, F.; Yang, M. Y.

2018-05-01

With the introduction of airborne oblique camera systems and the improvement of photogrammetric techniques, high-resolution 2D and 3D data can be acquired in urban areas. This high-resolution data allows us to perform detailed investigations on building roofs and façades which can contribute to LoD3 city modeling. Normally, façade segmentation is achieved from terrestrial views. In this paper, we address the problem from aerial views by using high resolution oblique aerial images as the data source in urban areas. In addition to traditional image features, such as RGB and SIFT, normal vector and planarity are also extracted from dense matching point clouds. Then, these 3D geometrical features are projected back to 2D space to assist façade interpretation. Random forest is trained and applied to label façade pixels. Fully connected conditional random field (CRF), capturing long-range spatial interactions, is used as a post-processing to refine our classification results. Its pairwise potential is defined by a linear combination of Gaussian kernels and the CRF model is efficiently solved by mean field approximation. Experiments show that 3D features can significantly improve classification results. Also, fully connected CRF performs well in correcting noisy pixels.

The Wadden Sea in transition - consequences of sea level rise

NASA Astrophysics Data System (ADS)

Becherer, Johannes; Hofstede, Jacobus; Gräwe, Ulf; Purkiani, Kaveh; Schulz, Elisabeth; Burchard, Hans

2018-01-01

The impact of sea level rise (SLR) on the future morphological development of the Wadden Sea (North Sea) is investigated by means of extensive process-resolving numerical simulations. A new sediment and morphodynamic module was implemented in the well-established 3D circulation model GETM. A number of different validations are presented, ranging from an idealized 1D channel over a semi-idealized 2D Wadden Sea basin to a fully coupled realistic 40-year hindcast without morphological amplification of the Sylt-Rømøbight, a semi-enclosed subsystem of the Wadden Sea. Based on the results of the hindcast, four distinct future scenarios covering the period 2010-2100 are simulated. While these scenarios differ in the strength of SLR and wind forcing, they also account for an expected increase of tidal range over the coming century. The results of the future projections indicate a transition from a tidal-flat-dominated system toward a lagoon-like system, in which large fractions of the Sylt-Rømøbight will remain permanently covered by water. This has potentially dramatic implications for the unique ecosystem of the Wadden Sea. Although the simulations also predict an increased accumulation of sediment in the back-barrier basin, this accumulation is far too weak to compensate for the rise in mean sea level.

Active remote sensing of snow using NMM3D/DMRT and comparison with CLPX II airborne data

USGS Publications Warehouse

Xu, X.; Liang, D.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.; Lettenmaier, D.P.; Cline, D.W.; Yueh, S.H.

2010-01-01

We applied the Numerical Maxwell Model of three-dimensional simulations (NMM3D) in the Dense Media Radiative Theory (DMRT) to calculate backscattering coefficients. The particles' positions are computer-generated and the subsequent Foldy-Lax equations solved numerically. The phase matrix in NMM3D has significant cross-polarization, particularly when the particles are densely packed. The NMM3D model is combined with DMRT in calculating the microwave scattering by dry snow. The NMM3D/DMRT equations are solved by an iterative solution up to the second order in the case of small to moderate optical thickness. The numerical results of NMM3D/DMRT are illustrated and compared with QCA/DMRT. The QCA/DMRT and NMM3D/DMRT results are also applied to compare with data from two specific datasets from the second Cold Land Processes Experiment (CLPX II) in Alaska and Colorado. The data are obtained at the Ku-band (13.95 GHz) observations using airborne imaging polarimetric scatterometer (POLSCAT). It is shown that the model predictions agree with the field measurements for both co-polarization and cross-polarization. For the Alaska region, the average snow depth and snow density are used as the inputs for DMRT. The grain size, selected from within the range of the ground measurements, is used as a best-fit parameter within the range. For the Colorado region, we use the Variable Infiltration Capacity Model (VIC) to obtain the input snow profiles for NMM3D/DMRT. ?? 2010 IEEE.

Solving phase appearance/disappearance two-phase flow problems with high resolution staggered grid and fully implicit schemes by the Jacobian-free Newton–Krylov Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2016-04-01

The phase appearance/disappearance issue presents serious numerical challenges in two-phase flow simulations. Many existing reactor safety analysis codes use different kinds of treatments for the phase appearance/disappearance problem. However, to our best knowledge, there are no fully satisfactory solutions. Additionally, the majority of the existing reactor system analysis codes were developed using low-order numerical schemes in both space and time. In many situations, it is desirable to use high-resolution spatial discretization and fully implicit time integration schemes to reduce numerical errors. In this work, we adapted a high-resolution spatial discretization scheme on staggered grid mesh and fully implicit time integrationmore » methods (such as BDF1 and BDF2) to solve the two-phase flow problems. The discretized nonlinear system was solved by the Jacobian-free Newton Krylov (JFNK) method, which does not require the derivation and implementation of analytical Jacobian matrix. These methods were tested with a few two-phase flow problems with phase appearance/disappearance phenomena considered, such as a linear advection problem, an oscillating manometer problem, and a sedimentation problem. The JFNK method demonstrated extremely robust and stable behaviors in solving the two-phase flow problems with phase appearance/disappearance. No special treatments such as water level tracking or void fraction limiting were used. High-resolution spatial discretization and second- order fully implicit method also demonstrated their capabilities in significantly reducing numerical errors.« less

Investigation of surface wave amplitudes in 3-D velocity and 3-D Q models

NASA Astrophysics Data System (ADS)

Ruan, Y.; Zhou, Y.

2010-12-01

It has been long recognized that seismic amplitudes depend on both wave speed structures and anelasticity (Q) structures. However, the effects of lateral heterogeneities in wave speed and Q structures on seismic amplitudes has not been well understood. We investigate the effects of 3-D wave speed and 3-D anelasticity (Q) structures on surface-wave amplitudes based upon wave propagation simulations of twelve globally-distributed earthquakes and 801 stations in Earth models with and without lateral heterogeneities in wave speed and anelasticity using a Spectral Element Method (SEM). Our tomographic-like 3-D Q models are converted from a velocity model S20RTS using a set of reasonable mineralogical parameters, assuming lateral perturbations in both velocity and Q are due to temperature perturbations. Surface-wave amplitude variations of SEM seismograms are measured in the period range of 50--200 s using boxcar taper, cosine taper and Slepian multi-tapers. We calculate ray-theoretical predictions of surface-wave amplitude perturbations due to elastic focusing, attenuation, and anelastic focusing which respectively depend upon the second spatial derivative (''roughness'') of perturbations in phase velocity, 1/Q, and the roughness of perturbations in 1/Q. Both numerical experiments and theoretical calculations show that (1) for short-period (~ 50 s) surface waves, the effects of amplitude attenuation due to 3-D Q structures are comparable with elastic focusing effects due to 3-D wave speed structures; and (2) for long-period (> 100 s) surface waves, the effects of attenuation become much weaker than elastic focusing; and (3) elastic focusing effects are correlated with anelastic focusing at all periods due to the correlation between velocity and Q models; and (4) amplitude perturbations are depend on measurement techniques and therefore cannot be directly compared with ray-theoretical predictions because ray theory does not account for the effects of measurement techniques. We calculate 3-D finite-frequency sensitivity of surface-wave amplitude to perturbations in wave speed and anelasticity (Q) which fully account for the effects of elastic focusing, attenuation, anelastic focusing as well as measurement techniques. We show that amplitude perturbations calculated using wave speed and Q sensitivity kernels agree reasonably well with SEM measurements and therefore the sensitivity kernels can be used in a joint inversion of seismic phase delays and amplitudes to simultaneously image high resolution 3-D wave speed and 3-D Q structures in the upper mantle.

Gis-Based Smart Cartography Using 3d Modeling

NASA Astrophysics Data System (ADS)

Malinverni, E. S.; Tassetti, A. N.

2013-08-01

3D City Models have evolved to be important tools for urban decision processes and information systems, especially in planning, simulation, analysis, documentation and heritage management. On the other hand existing and in use numerical cartography is often not suitable to be used in GIS because not geometrically and topologically correctly structured. The research aim is to 3D structure and organize a numeric cartography for GIS and turn it into CityGML standardized features. The work is framed around a first phase of methodological analysis aimed to underline which existing standard (like ISO and OGC rules) can be used to improve the quality requirement of a cartographic structure. Subsequently, from this technical specifics, it has been investigated the translation in formal contents, using an owner interchange software (SketchUp), to support some guide lines implementations to generate a GIS3D structured in GML3. It has been therefore predisposed a test three-dimensional numerical cartography (scale 1:500, generated from range data captured by 3D laser scanner), tested on its quality according to the previous standard and edited when and where necessary. Cad files and shapefiles are converted into a final 3D model (Google SketchUp model) and then exported into a 3D city model (CityGML LoD1/LoD2). The GIS3D structure has been managed in a GIS environment to run further spatial analysis and energy performance estimate, not achievable in a 2D environment. In particular geometrical building parameters (footprint, volume etc.) are computed and building envelop thermal characteristics are derived from. Lastly, a simulation is carried out to deal with asbestos and home renovating charges and show how the built 3D city model can support municipal managers with risk diagnosis of the present situation and development of strategies for a sustainable redevelop.

3-D FDTD simulation of shear waves for evaluation of complex modulus imaging.

PubMed

Orescanin, Marko; Wang, Yue; Insana, Michael

2011-02-01

The Navier equation describing shear wave propagation in 3-D viscoelastic media is solved numerically with a finite differences time domain (FDTD) method. Solutions are formed in terms of transverse scatterer velocity waves and then verified via comparison to measured wave fields in heterogeneous hydrogel phantoms. The numerical algorithm is used as a tool to study the effects on complex shear modulus estimation from wave propagation in heterogeneous viscoelastic media. We used an algebraic Helmholtz inversion (AHI) technique to solve for the complex shear modulus from simulated and experimental velocity data acquired in 2-D and 3-D. Although 3-D velocity estimates are required in general, there are object geometries for which 2-D inversions provide accurate estimations of the material properties. Through simulations and experiments, we explored artifacts generated in elastic and dynamic-viscous shear modulus images related to the shear wavelength and average viscosity.

Comprehensive study of numerical anisotropy and dispersion in 3-D TLM meshes

NASA Astrophysics Data System (ADS)

Berini, Pierre; Wu, Ke

1995-05-01

This paper presents a comprehensive analysis of the numerical anisotropy and dispersion of 3-D TLM meshes constructed using several generalized symmetrical condensed TLM nodes. The dispersion analysis is performed in isotropic lossless, isotropic lossy and anisotropic lossless media and yields a comparison of the simulation accuracy for the different TLM nodes. The effect of mesh grading on the numerical dispersion is also determined. The results compare meshes constructed with Johns' symmetrical condensed node (SCN), two hybrid symmetrical condensed nodes (HSCN) and two frequency domain symmetrical condensed nodes (FDSCN). It has been found that under certain circumstances, the time domain nodes may introduce numerical anisotropy when modelling isotropic media.

Basic and Advanced Numerical Performances Relate to Mathematical Expertise but Are Fully Mediated by Visuospatial Skills

ERIC Educational Resources Information Center

Sella, Francesco; Sader, Elie; Lolliot, Simon; Cohen Kadosh, Roi

2016-01-01

Recent studies have highlighted the potential role of basic numerical processing in the acquisition of numerical and mathematical competences. However, it is debated whether high-level numerical skills and mathematics depends specifically on basic numerical representations. In this study mathematicians and nonmathematicians performed a basic…

Automatic pedicles detection using convolutional neural network in a 3D spine reconstruction from biplanar radiographs

NASA Astrophysics Data System (ADS)

Bakhous, Christine; Aubert, Benjamin; Vazquez, Carlos; Cresson, Thierry; Parent, Stefan; De Guise, Jacques

2018-02-01

The 3D analysis of the spine deformities (scoliosis) has a high potential in its clinical diagnosis and treatment. In a biplanar radiographs context, a 3D analysis requires a 3D reconstruction from a pair of 2D X-rays. Whether being fully-/semiautomatic or manual, this task is complex because of the noise, the structure superimposition and partial information due to a limited projections number. Being involved in the axial vertebra rotation (AVR), which is a fundamental clinical parameter for scoliosis diagnosis, pedicles are important landmarks for the 3D spine modeling and pre-operative planning. In this paper, we focus on the extension of a fully-automatic 3D spine reconstruction method where the Vertebral Body Centers (VBCs) are automatically detected using Convolutional Neural Network (CNN) and then regularized using a Statistical Shape Model (SSM) framework. In this global process, pedicles are inferred statistically during the SSM regularization. Our contribution is to add a CNN-based regression model for pedicle detection allowing a better pedicle localization and improving the clinical parameters estimation (e.g. AVR, Cobb angle). Having 476 datasets including healthy patients and Adolescent Idiopathic Scoliosis (AIS) cases with different scoliosis grades (Cobb angles up to 116°), we used 380 for training, 48 for testing and 48 for validation. Adding the local CNN-based pedicle detection decreases the mean absolute error of the AVR by 10%. The 3D mean Euclidian distance error between detected pedicles and ground truth decreases by 17% and the maximum error by 19%. Moreover, a general improvement is observed in the 3D spine reconstruction and reflected in lower errors on the Cobb angle estimation.

The shallow water equations as a hybrid flow model for the numerical and experimental analysis of hydro power stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostermann, Lars; Seidel, Christian

2015-03-10

The numerical analysis of hydro power stations is an important method of the hydraulic design and is used for the development and optimisation of hydro power stations in addition to the experiments with the physical submodel of a full model in the hydraulic laboratory. For the numerical analysis, 2D and 3D models are appropriate and commonly used.The 2D models refer mainly to the shallow water equations (SWE), since for this flow model a large experience on a wide field of applications for the flow analysis of numerous problems in hydraulic engineering already exists. Often, the flow model is verified bymore » in situ measurements. In order to consider 3D flow phenomena close to singularities like weirs, hydro power stations etc. the development of a hybrid fluid model is advantageous to improve the quality and significance of the global model. Here, an extended hybrid flow model based on the principle of the SWE is presented. The hybrid flow model directly links the numerical model with the experimental data, which may originate from physical full models, physical submodels and in-situ measurements. Hence a wide field of application of the hybrid model emerges including the improvement of numerical models and the strong coupling of numerical and experimental analysis.« less

A self-calibrated angularly continuous 2D GRAPPA kernel for propeller trajectories

PubMed Central

Skare, Stefan; Newbould, Rexford D; Nordell, Anders; Holdsworth, Samantha J; Bammer, Roland

2008-01-01

The k-space readout of propeller-type sequences may be accelerated by the use of parallel imaging (PI). For PROPELLER, the main benefits are reduced blurring due to T2 decay and SAR reduction, while for EPI-based propeller acquisitions such as Turbo-PROP and SAP-EPI, the faster k-space traversal alleviates geometric distortions. In this work, the feasibility of calculating a 2D GRAPPA kernel on only the undersampled propeller blades themselves is explored, using the matching orthogonal undersampled blade. It is shown that the GRAPPA kernel varies slowly across blades, therefore an angularly continuous 2D GRAPPA kernel is proposed, in which the angular variation of the weights is parameterized. This new angularly continuous kernel formulation greatly increases the numerical stability of the GRAPPA weight estimation, allowing the generation of fully sampled diagnostic quality images using only the undersampled propeller data. PMID:19025911

Analytic Expressions for the Gravity Gradient Tensor of 3D Prisms with Depth-Dependent Density

NASA Astrophysics Data System (ADS)

Jiang, Li; Liu, Jie; Zhang, Jianzhong; Feng, Zhibing

2017-12-01

Variable-density sources have been paid more attention in gravity modeling. We conduct the computation of gravity gradient tensor of given mass sources with variable density in this paper. 3D rectangular prisms, as simple building blocks, can be used to approximate well 3D irregular-shaped sources. A polynomial function of depth can represent flexibly the complicated density variations in each prism. Hence, we derive the analytic expressions in closed form for computing all components of the gravity gradient tensor due to a 3D right rectangular prism with an arbitrary-order polynomial density function of depth. The singularity of the expressions is analyzed. The singular points distribute at the corners of the prism or on some of the lines through the edges of the prism in the lower semi-space containing the prism. The expressions are validated, and their numerical stability is also evaluated through numerical tests. The numerical examples with variable-density prism and basin models show that the expressions within their range of numerical stability are superior in computational accuracy and efficiency to the common solution that sums up the effects of a collection of uniform subprisms, and provide an effective method for computing gravity gradient tensor of 3D irregular-shaped sources with complicated density variation. In addition, the tensor computed with variable density is different in magnitude from that with constant density. It demonstrates the importance of the gravity gradient tensor modeling with variable density.

Dielectric Spectroscopic Detection of Early Failures in 3-D Integrated Circuits.

PubMed

Obeng, Yaw; Okoro, C A; Ahn, Jung-Joon; You, Lin; Kopanski, Joseph J

The commercial introduction of three dimensional integrated circuits (3D-ICs) has been hindered by reliability challenges, such as stress related failures, resistivity changes, and unexplained early failures. In this paper, we discuss a new RF-based metrology, based on dielectric spectroscopy, for detecting and characterizing electrically active defects in fully integrated 3D devices. These defects are traceable to the chemistry of the insolation dielectrics used in the through silicon via (TSV) construction. We show that these defects may be responsible for some of the unexplained early reliability failures observed in TSV enabled 3D devices.

Fracture network created by 3D printer and its validation using CT images

NASA Astrophysics Data System (ADS)

Suzuki, A.; Watanabe, N.; Li, K.; Horne, R. N.

2017-12-01

Understanding flow mechanisms in fractured media is essential for geoscientific research and geological development industries. This study used 3D printed fracture networks in order to control the properties of fracture distributions inside the sample. The accuracy and appropriateness of creating samples by the 3D printer was investigated by using a X-ray CT scanner. The CT scan images suggest that the 3D printer is able to reproduce complex three-dimensional spatial distributions of fracture networks. Use of hexane after printing was found to be an effective way to remove wax for the post-treatment. Local permeability was obtained by the cubic law and used to calculate the global mean. The experimental value of the permeability was between the arithmetic and geometric means of the numerical results, which is consistent with conventional studies. This methodology based on 3D printed fracture networks can help validate existing flow modeling and numerical methods.

Design and Implementation of a Self-Directed Stereochemistry Lesson Using Embedded Virtual Three-Dimensional Images in a Portable Document Format

ERIC Educational Resources Information Center

Cody, Jeremy A.; Craig, Paul A.; Loudermilk, Adam D.; Yacci, Paul M.; Frisco, Sarah L.; Milillo, Jennifer R.

2012-01-01

A novel stereochemistry lesson was prepared that incorporated both handheld molecular models and embedded virtual three-dimensional (3D) images. The images are fully interactive and eye-catching for the students; methods for preparing 3D molecular images in Adobe Acrobat are included. The lesson was designed and implemented to showcase the 3D…

Caroli formalism in near-field heat transfer between parallel graphene sheets

NASA Astrophysics Data System (ADS)

Jiang, Jia-Huei; Wang, Jian-Sheng

2017-10-01

In this work we conduct a close-up investigation into the nature of near-field heat transfer (NFHT) of two graphene sheets in parallel-plate geometry. We develop a fully microscopic and quantum approach using the nonequilibrium Green's function method. A Caroli formula for heat flux is proposed and numerically verified. We show that our near-field-to-black-body heat flux ratios generally exhibit 1 /dα dependence, with an effective exponent α ≈2.2 , at long distances exceeding 100 nm and up to one micron; in the opposite d →0 limit, the values converge to a range within an order of magnitude. We justify this feature by noting it is owing to the breakdown of local conductivity theory, which predicts a 1 /d dependence. Furthermore, from the numerical result, we find that in addition to thermal wavelength λt h a shorter distance scale ˜10 -100 nm, comparable to the graphene thermal length (ℏ vF/kBT ) or Fermi wavelength (kF-1), marks the transition point between the short- and long-distance transfer behaviors; within that point, a relatively large variation of heat flux in response to doping level becomes a typical characteristic. The emergence of such large variation is tied to relative NFHT contributions from the intra- and interband transitions. Beyond that point, scaling of thermal flux ∝1 /dα can be generally observed.

Coronal heating by the resonant absorption of Alfven waves: The effect of viscous stress tensor

NASA Technical Reports Server (NTRS)

Ofman, L.; Davila, J. M.; Steinolfson, R. S.

1994-01-01

The time-dependent linearized magnetohydrodynamics (MHD) equations for a fully compressible, low-beta, viscoresistive plasma are solved numerically using an implicit integration scheme. The full viscosity stress tensor (Braginskii 1965) is included with the five parameters eta(sub i) i = 0 to 4. In agreement with previous studies, the numerical simulations demonstrate that the dissipation on inhomogeneities in the background Alfven speed occurs in a narrow resonant layer. For an active region in the solar corona the values of eta(sub i) are eta(sub o) = 0.65 g/cm/s, eta(sub 1) = 3.7 x 10(exp -12) g/cm/s, eta(sub 2) = 4 eta(sub 1), eta(sub 3) = 1.4 x 10(exp -6) g/cm/s, eta(sub 4) = 2 eta(sub 3), with n = 10(exp 10)/cu cm, T = 2 x 10(exp 6) K, and B = 100 G. When the Lundquist number S = 10(exp 4) and R(sub 1) much greater than S (where R(sub 1) is the dimensionless shear viscous number) the width of the resistive dissipation layer d(sub r) is 0.22a (where a is the density gradient length scale) and d(sub r) approximately S(exp -1/3). When S much greater than R(sub 1) the shear viscous dissipation layer width d(sub r) scales as R(sub 1)(exp -1/3). The shear viscous and the resistive dissipation occurs in an overlapping narrow region, and the total heating rate is independent of the value of the dissipation parameters in agreement with previous studies. Consequently, the maximum values of the perpendicular velocity and perpendicular magnetic field scale as R(sub 1)(exp -1/3). It is evident from the simulations that for solar parameters the heating due to the compressive viscosity (R(sub 0) = 560) is negligible compared to the resistive and the shear viscous (R(sub 1)) dissipation and it occurs in a broad layer of order a in width. In the solar corona with S approximately equals 10(exp 4) and R(sub 1) approximately equals 10(exp 14) (as calculated from the Braginskii expressions), the shear viscous resonant heating is of comparable magnitude to the resistive resonant heating.

Can CH-53K 3D Technical Data Support the Provisioning Process

DTIC Science & Technology

2017-05-01

contain the minimum required data characteristics and elements (Appendix A) and (2) are fully anno - tated, they can be converted to 3D PDF files that...were anno - tated as part of the original model development/creation process, the time to perform an annotation would be about 50 percent (about 1.5...files, after the fact. If the models had been anno - tated at the time they were created, we estimate that the cost to implement a 3D PDF solution for

Numerical prediction of 3-D ejector flows

NASA Technical Reports Server (NTRS)

Roberts, D. W.; Paynter, G. C.

1979-01-01

The use of parametric flow analysis, rather than parametric scale testing, to support the design of an ejector system offers a number of potential advantages. The application of available 3-D flow analyses to the design ejectors can be subdivided into several key elements. These are numerics, turbulence modeling, data handling and display, and testing in support of analysis development. Experimental and predicted jet exhaust for the Boeing 727 aircraft are examined.

A semi-analytical model of a time reversal cavity for high-amplitude focused ultrasound applications

NASA Astrophysics Data System (ADS)

Robin, J.; Tanter, M.; Pernot, M.

2017-09-01

Time reversal cavities (TRC) have been proposed as an efficient approach for 3D ultrasound therapy. They allow the precise spatio-temporal focusing of high-power ultrasound pulses within a large region of interest with a low number of transducers. Leaky TRCs are usually built by placing a multiple scattering medium, such as a random rod forest, in a reverberating cavity, and the final peak pressure gain of the device only depends on the temporal length of its impulse response. Such multiple scattering in a reverberating cavity is a complex phenomenon, and optimisation of the device’s gain is usually a cumbersome process, mostly empirical, and requiring numerical simulations with extremely long computation times. In this paper, we present a semi-analytical model for the fast optimisation of a TRC. This model decouples ultrasound propagation in an empty cavity and multiple scattering in a multiple scattering medium. It was validated numerically and experimentally using a 2D-TRC and numerically using a 3D-TRC. Finally, the model was used to determine rapidly the optimal parameters of the 3D-TRC which had been confirmed by numerical simulations.

Simulation of the 3-D Evolution of Electron Scale Magnetic Reconnection - Motivated by Laboratory Experiments Predictions for MMS

NASA Astrophysics Data System (ADS)

Buechner, J.; Jain, N.; Sharma, A.

2013-12-01

The four s/c of the Magnetospheric Multiscale (MMS) mission, to be launched in 2014, will use the Earth's magnetosphere as a laboratory to study the microphysics of three fundamental plasma processes. One of them is magnetic reconnection, an essentially multi-scale process. While laboratory experiments and past theoretical investigations have shown that important processes necessary to understand magnetic reconnection take place at electron scales the MMS mission for the first time will be able to resolve these scales by in space observations. For the measurement strategy of MMS it is important to make specific predictions of the behavior of current sheets with a thickness of the order of the electron skin depth which play an important role in the evolution of collisionless magnetic reconnection. Since these processes are highly nonlinear and non-local numerical simulation is needed to specify the current sheet evolution. Here we present new results about the nonlinear evolution of electron-scale current sheets starting from the linear stage and using 3-D electron-magnetohydrodynamic (EMHD) simulations. The growth rates of the simulated instabilities compared well with the growth rates obtained from linear theory. Mechanisms and conditions of the formation of flux ropes and of current filamentation will be discussed in comparison with the results of fully kinetic simulations. In 3D the X- and O-point configurations of the magnetic field formed in reconnection planes alternate along the out-of-reconnection-plane direction with the wavelength of the unstable mode. In the presence of multiple reconnection sites, the out-of-plane magnetic field can develop nested structure of quadrupoles in reconnection planes, similar to the 2-D case, but now with variations in the out-of-plane direction. The structures of the electron flow and magnetic field in 3-D simulations will be compared with those in 2-D simulations to discriminate the essentially 3D features. We also discuss the influence of guide fields, as in the magnetopause case and show how the 3-D evolution of an electron current sheet is influenced the strength of the guide field. This is unlike the 2-D case where reconnection takes place only in a plane. This work was partially funded by the Max-Planck/Princeton Center for Plasma Physics and the National Science Foundation.

The instanton method and its numerical implementation in fluid mechanics

NASA Astrophysics Data System (ADS)

Grafke, Tobias; Grauer, Rainer; Schäfer, Tobias

2015-08-01

A precise characterization of structures occurring in turbulent fluid flows at high Reynolds numbers is one of the last open problems of classical physics. In this review we discuss recent developments related to the application of instanton methods to turbulence. Instantons are saddle point configurations of the underlying path integrals. They are equivalent to minimizers of the related Freidlin-Wentzell action and known to be able to characterize rare events in such systems. While there is an impressive body of work concerning their analytical description, this review focuses on the question on how to compute these minimizers numerically. In a short introduction we present the relevant mathematical and physical background before we discuss the stochastic Burgers equation in detail. We present algorithms to compute instantons numerically by an efficient solution of the corresponding Euler-Lagrange equations. A second focus is the discussion of a recently developed numerical filtering technique that allows to extract instantons from direct numerical simulations. In the following we present modifications of the algorithms to make them efficient when applied to two- or three-dimensional (2D or 3D) fluid dynamical problems. We illustrate these ideas using the 2D Burgers equation and the 3D Navier-Stokes equations.

Thermal cure effects on electromechanical properties of conductive wires by direct ink write for 4D printing and soft machines

NASA Astrophysics Data System (ADS)

Mu, Quanyi; Dunn, Conner K.; Wang, Lei; Dunn, Martin L.; Qi, H. Jerry; Wang, Tiejun

2017-04-01

Recent developments in soft materials and 3D printing are promoting the rapid development of novel technologies and concepts, such as 4D printing and soft machines, that in turn require new methods for fabricating conductive materials. Despite the ubiquity of silver nanoparticles (NPs) in the conducting electrodes of printed electronic devices, their potential use in stretchable conductors has not been fully explored in 4D printing and soft machines. This paper studies the effect of thermal cure conditions on conductivity and electro-mechanical behaviors of silver ink by the direct ink write (DIW) printing approach. We found that the electro-mechanical properties of silver wires can be tailored by controlling cure time and cure temperature to achieve conductivity as well as stretchability. For the silver NP ink we used in the experiments, silver wires cured at 80 °C for 10-30 min have conductivity >1% bulk silver, Young’s modulus <100 MPa, yield strain ˜9%, and can retain conductivity up to 300% strain. In addition, under stress controlled cyclic loading/unloading conditions, the resistance of these wires is only about 1.3 times the initial value after the 100th repeat cycle (7.6% maximum strain in the first cycle). Silver wires cured at 120 °C for 10-20 min are more sensitive to strain and have a yield strain of around 6%. These properties indicate that the silver ink can be used to fabricate stretchable electrodes and flex sensors. Using the DIW fabrication method, we printed silver ink patterns on the surface of 3D printed polymer parts, with the future goal of constructing fully 3D printed arbitrarily formed soft and stretchable devices and of applying them to 4D printing. We demonstrated a fully printed functional soft-matter sensor and a circuit element that can be stretched by as much as 45%.

Development of Inverse Raman Spectroscopy for Probing Rapidly Decomposing Explosives and Propellants

DTIC Science & Technology

1981-07-01

RECiPIENT’S CATALOG NUMBER TECHNICAL REPORT ARBRL-TR-02345 D -4 / .3 --- 4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED DEVELOPMENT OF...21 D . Numerical Parameters for Eq. (9) ... .......... .. 24 E. A Numerical Estimate of a ..... .............. ... 26 F. Window Damage: A...Function of Ruby Intensity ..... . 41 D . Focussing Considerations .... .............. ... 41 E. Effects of Polarization ....... ............... 40 F

Numerical modeling the formation of impact craters: Implications for the structure of Europa's ice shell

NASA Astrophysics Data System (ADS)

Silber, E. A.; Johnson, B. C.

2017-12-01

Craters produced by hypervelocity impacts are an invaluable tool for studying planetary surfaces. The observed impact crater depth-diameter (d-D) on the Galilean moon Europa exhibits three distinct transition regimes, two of which may correspond to the presence of warm convecting ice at depths of 7-8 km and a liquid ocean at 19-25 km, respectively [1]. In our study, we use iSALE2D to model formation of impact craters on Europa to investigate thickness and internal structure of its ice shell. This study is different from previous modeling studies [2,3] in that we consider the both fully conductive ice shell over ocean, as well as conductive lid overlying warm convecting ice, to discern the boundary conditions at the interface between the ice and the underlying ocean. Moreover, our model includes implementation of the full viscoelastic-plastic rheology for ice. Our results suggest that both conductive shell over ocean and conductive lid over warm convective ice are equally probable on Europa. We will discuss the implications and relevance of these results. The plausible scenarios are either a 6 - 7 km thick conductive ice lid overlying warm convecting ice at 265 K, or an 8 km completely conductive ice shell over ocean. Acknowledgements: We gratefully acknowledge the developers of iSALE-2D (www.isale-code.de), the simulation code used in our research, including G. Collins, K. Wünnermann, D. Elbeshausen, B. Ivanov and J. Melosh. References: [1] Schenk P. (2002) Nature, 417, 419-421. [2] Bray V.J. et al. (2014) Icarus, 231, 394-406. [3] Cox R. and Beuer A.W. (2015) JGR - Planets, 120(10), 1708-1719.

Evaluating implementation of methicillin-resistant Staphylococcus aureus (MRSA) prevention guidelines in spinal cord injury centers using the PARIHS framework: a mixed methods study.

PubMed

Balbale, Salva N; Hill, Jennifer N; Guihan, Marylou; Hogan, Timothy P; Cameron, Kenzie A; Goldstein, Barry; Evans, Charlesnika T

2015-09-09

To prevent methicillin-resistant Staphylococcus aureus (MRSA) in Spinal Cord Injury and Disorder (SCI/D) Centers, the "Guidelines for Implementation of MRSA Prevention Initiative in the Spinal Cord Injury Centers" were released in July 2008 in the Veterans Affairs (VA) Health Care System. The purpose of this study was to use the Promoting Action on Research Implementation in Health Systems (PARiHS) framework to evaluate the experiences of implementation of SCI/D MRSA prevention guidelines in VA SCI/D Centers approximately 2-3 years after the guidelines were released. Mixed methods were used across two phases in this study. The first phase included an anonymous, web-based cross-sectional survey administered to providers at all 24 VA SCI/D Centers. The second phase included semi-structured telephone interviews with providers at 9 SCI/D Centers. The PARiHS framework was used as the foundation of both the survey questions and semi-structured interview guide. The survey was completed by 295 SCI/D providers (43.8 % response rate) from 22 of the 24 SCI/D Centers (91.7 % participation rate). Respondents included nurses (57.3 %), therapists (24.4 %), physicians (11.1 %), physician assistants (3.4 %), and other health care professionals (3.8 %). Approximately 36 % of the SCI/D providers surveyed had not seen, did not remember seeing, or had never heard of the MRSA SCI/D guidelines, whereas 42.3 % of providers reported that the MRSA SCI/D guidelines were fully implemented in their SCI/D Center. Data revealed numerous barriers and facilitators to guideline implementation. Facilitators included enhanced leadership support and provider education, focused guideline dissemination to reach SCI/D providers, and strong perceived evidence supporting the guidelines. Barriers included lack of awareness of the guidelines among physical therapists and physician assistants and challenges in cohorting/isolating MRSA-positive patients and following contact precautions. Successful implementation of MRSA infection prevention guidelines in SCI/D settings requires (1) guideline dissemination that reaches the full range of SCI/D providers working in inpatient, outpatient, and other care settings, (2) provider education that is frequent and systematic, (3) strong leadership support, and (4) that barriers unique to the recommendations are addressed. These findings may be used to inform selection of implementation strategies and optimize infection prevention beyond MRSA as well as in other specialty care populations.

Study on the Before Cavity Interaction in a Second Harmonic Gyrotron Using 3D CFDTD PIC Simulations

NASA Astrophysics Data System (ADS)

Lin, M. C.; Illy, S.; Thumm, M.; Jelonnek, J.

2016-10-01

A computational study on before cavity interaction (BCI) in a 28 GHz second harmonic (SH) gryotron for industrial applications has been performed using a 3-D conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) method. On the contrary to the after cavity interaction (ACI), i.e. beam wave interaction in the non-linear uptaper after the cavity, which has been widely investigated, the BCI, i.e. beam wave interaction in the non-linear downtaper before the cavity connected to the beam tunnel with an entrance, is less noticed and discussed. Usually the BCI might be considered easy to be eliminated. However, this is not always the case. As the SH gyrotron had been designed for SH TE12 mode operation, the first harmonic (FH) plays the main competition. In the 3-D CFDTD PIC simulations, a port boundary has been employed for the gyro-beam entrance of the gyrotron cavity instead of a metallic short one which is not reflecting a realistic situation as an FH backward wave oscillation (BWO) is competing with the desired SH generation. A numerical instability has been found and identified as a failure of the entrance port boundary caused by an evanescent wave or mode conversion. This indicates the entrance and downtaper are not fully cut-off for some oscillations. A further study shows that the undesired oscillation is the FH TE11 BWO mode concentrated around the beam tunnel entrance and downtaper. A mitigation strategy has been found to suppress this undesired BCI and avoid possible damage to the gun region.

3D ultrasound-based patient positioning for radiotherapy

NASA Astrophysics Data System (ADS)

Wang, Michael H.; Rohling, Robert N.; Archip, Neculai; Clark, Brenda G.

2006-03-01

A new 3D ultrasound-based patient positioning system for target localisation during radiotherapy is described. Our system incorporates the use of tracked 3D ultrasound scans of the target anatomy acquired using a dedicated 3D ultrasound probe during both the simulation and treatment sessions, fully automatic 3D ultrasound-toultrasound registration, and OPTOTRAK IRLEDs for registering simulation CT to ultrasound data. The accuracy of the entire radiotherapy treatment process resulting from the use of our system, from simulation to the delivery of radiation, has been validated on a phantom. The overall positioning error is less than 5mm, which includes errors from estimation of the irradiated region location in the phantom.

A reconstruction method of intra-ventricular blood flow using color flow ultrasound: a simulation study

NASA Astrophysics Data System (ADS)

Jang, Jaeseong; Ahn, Chi Young; Jeon, Kiwan; Choi, Jung-il; Lee, Changhoon; Seo, Jin Keun

2015-03-01

A reconstruction method is proposed here to quantify the distribution of blood flow velocity fields inside the left ventricle from color Doppler echocardiography measurement. From 3D incompressible Navier- Stokes equation, a 2D incompressible Navier-Stokes equation with a mass source term is derived to utilize the measurable color flow ultrasound data in a plane along with the moving boundary condition. The proposed model reflects out-of-plane blood flows on the imaging plane through the mass source term. For demonstrating a feasibility of the proposed method, we have performed numerical simulations of the forward problem and numerical analysis of the reconstruction method. First, we construct a 3D moving LV region having a specific stroke volume. To obtain synthetic intra-ventricular flows, we performed a numerical simulation of the forward problem of Navier-Stokes equation inside the 3D moving LV, computed 3D intra-ventricular velocity fields as a solution of the forward problem, projected the 3D velocity fields on the imaging plane and took the inner product of the 2D velocity fields on the imaging plane and scanline directional velocity fields for synthetic scanline directional projected velocity at each position. The proposed method utilized the 2D synthetic projected velocity data for reconstructing LV blood flow. By computing the difference between synthetic flow and reconstructed flow fields, we obtained the averaged point-wise errors of 0.06 m/s and 0.02 m/s for u- and v-components, respectively.

Time-dependent effects of repeated THC treatment on dopamine D2/3 receptor-mediated signalling in midbrain and striatum.

PubMed

Tournier, Benjamin B; Tsartsalis, Stergios; Dimiziani, Andrea; Millet, Philippe; Ginovart, Nathalie

2016-09-15

This study examined the time-course of alterations in levels and functional sensitivities of dopamine D2/3 receptors (D2/3R) during the course and up to 6 weeks following cessation of chronic treatment with Delta(9)-Tetrahydrocannabinol (THC) in rats. THC treatment led to an increase in D2/3R levels in striatum, as assessed using [(3)H]-(+)-PHNO, that was readily observable after one week of treatment, remained stably elevated during the subsequent 2 weeks of treatment, but fully reversed within 2 weeks of THC discontinuation. THC-induced D2/3R alterations were more pronounced and longer lasting in the dopamine cell body regions of the midbrain, wherein [(3)H]-(+)-PHNO binding was still elevated at 2 weeks but back to control values at 6 weeks after THC cessation. Parallel analyses of the psychomotor effects of pre- and post-synaptic doses of quinpirole also showed a pattern of D2/3R functional supersensitivity indicative of more rapid subsidence in striatum than in midbrain following drug cessation. These results indicate that chronic THC is associated with a biochemical and functional sensitization of D2/3R signaling, that these responses show a region-specific temporal pattern and are fully reversible following drug discontinuation. These results suggest that an increased post-synaptic D2/3R function and a decreased DA presynaptic signaling, mediated by increased D2/3R autoinhibition, may predominate during distinct phases of withdrawal and may contribute both to the mechanisms leading to relapse and to cannabinoid withdrawal symptoms. The different rates of normalization of D2/3R function in striatum and midbrain may be critical information for the development of new pharmacotherapies for cannabis dependence. Copyright © 2016 Elsevier B.V. All rights reserved.

5D Tempest simulations of kinetic edge turbulence

NASA Astrophysics Data System (ADS)

Xu, X. Q.; Xiong, Z.; Cohen, B. I.; Cohen, R. H.; Dorr, M. R.; Hittinger, J. A.; Kerbel, G. D.; Nevins, W. M.; Rognlien, T. D.; Umansky, M. V.; Qin, H.

2006-10-01

Results are presented from the development and application of TEMPEST, a nonlinear five dimensional (3d2v) gyrokinetic continuum code. The simulation results and theoretical analysis include studies of H-mode edge plasma neoclassical transport and turbulence in real divertor geometry and its relationship to plasma flow generation with zero external momentum input, including the important orbit-squeezing effect due to the large electric field flow-shear in the edge. In order to extend the code to 5D, we have formulated a set of fully nonlinear electrostatic gyrokinetic equations and a fully nonlinear gyrokinetic Poisson's equation which is valid for both neoclassical and turbulence simulations. Our 5D gyrokinetic code is built on 4D version of Tempest neoclassical code with extension to a fifth dimension in binormal direction. The code is able to simulate either a full torus or a toroidal segment. Progress on performing 5D turbulence simulations will be reported.

Large-scale thermal convection of viscous fluids in a faulted system: 3D test case for numerical codes

NASA Astrophysics Data System (ADS)

Magri, Fabien; Cacace, Mauro; Fischer, Thomas; Kolditz, Olaf; Wang, Wenqing; Watanabe, Norihiro

2017-04-01

In contrast to simple homogeneous 1D and 2D systems, no appropriate analytical solutions exist to test onset of thermal convection against numerical models of complex 3D systems that account for variable fluid density and viscosity as well as permeability heterogeneity (e.g. presence of faults). Owing to the importance of thermal convection for the transport of energy and minerals, the development of a benchmark test for density/viscosity driven flow is crucial to ensure that the applied numerical models accurately simulate the physical processes at hands. The presented study proposes a 3D test case for the simulation of thermal convection in a faulted system that accounts for temperature dependent fluid density and viscosity. The linear stability analysis recently developed by Malkovsky and Magri (2016) is used to estimate the critical Rayleigh number above which thermal convection of viscous fluids is triggered. The numerical simulations are carried out using the finite element technique. OpenGeoSys (Kolditz et al., 2012) and Moose (Gaston et al., 2009) results are compared to those obtained using the commercial software FEFLOW (Diersch, 2014) to test the ability of widely applied codes in matching both the critical Rayleigh number and the dynamical features of convective processes. The methodology and Rayleigh expressions given in this study can be applied to any numerical model that deals with 3D geothermal processes in faulted basins as by example the Tiberas Basin (Magri et al., 2016). References Kolditz, O., Bauer, S., Bilke, L., Böttcher, N., Delfs, J. O., Fischer, T., U. J. Görke, T. Kalbacher, G. Kosakowski, McDermott, C. I., Park, C. H., Radu, F., Rink, K., Shao, H., Shao, H.B., Sun, F., Sun, Y., Sun, A., Singh, K., Taron, J., Walther, M., Wang,W., Watanabe, N., Wu, Y., Xie, M., Xu, W., Zehner, B., 2012. OpenGeoSys: an open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media. Environmental Earth Sciences, 67(2), 589-599. Diersch, H. J, 2014. FEFLOW Finite Element Modeling of Flow, Mass and Heat Transport in Porous and Fractured Media, Springer-Verlag Berlin Heidelberg, ISBN 978-3-642-38738-8. Gaston D., Newman C., Hansen G., Lebrun-Grandie D, 2009. MOOSE: A parallel solution framework for coupled systems of nonlinear equations. Nucl. Engrg. Design, 239, 1,768-1778 Magri, F., Möller, S., Inbar, N., Möller, P., Raggad, M., Rödiger, T., Rosenthal, E., Siebert, C., 2016. 2D and 3D coexisting modes of thermal convection in fractured hydrothermal systems - Implications for transboundary flow in the Lower Yarmouk Gorge. Marine and Petroleum Geology 78, 750-758, DOI: /10.1016/j.marpetgeo.2016.10.002 Malkovsky, V. I., Magri, F., 2016. Thermal convection of temperature-dependent viscous fluids within three-dimensional faulted geothermal systems: estimation from linear and numerical analyses, Water Resour. Res., 52, 2855-2867, DOI:10.1002/2015WR018001.

Fully porous 3D printed titanium femoral stem to reduce stress-shielding following total hip arthroplasty.

PubMed

Arabnejad, Sajad; Johnston, Burnett; Tanzer, Michael; Pasini, Damiano

2017-08-01

Current hip replacement femoral implants are made of fully solid materials which all have stiffness considerably higher than that of bone. This mechanical mismatch can cause significant bone resorption secondary to stress shielding, which can lead to serious complications such as peri-prosthetic fracture during or after revision surgery. In this work, a high strength fully porous material with tunable mechanical properties is introduced for use in hip replacement design. The implant macro geometry is based off of a short stem taper-wedge implant compatible with minimally invasive hip replacement surgery. The implant micro-architecture is fine-tuned to locally mimic bone tissue properties which results in minimum bone resorption secondary to stress shielding. We present a systematic approach for the design of a 3D printed fully porous hip implant that encompasses the whole activity spectrum of implant development, from concept generation, multiscale mechanics of porous materials, material architecture tailoring, to additive manufacturing, and performance assessment via in vitro experiments in composite femurs. We show that the fully porous implant with an optimized material micro-structure can reduce the amount of bone loss secondary to stress shielding by 75% compared to a fully solid implant. This result also agrees with those of the in vitro quasi-physiological experimental model and the corresponding finite element model for both the optimized fully porous and fully solid implant. These studies demonstrate the merit and the potential of tuning material architecture to achieve a substantial reduction of bone resorption secondary to stress shielding. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1774-1783, 2017. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Integrated Use of Remote Sensed Data and Numerical Cartography for the Generation of 3d City Models

NASA Astrophysics Data System (ADS)

Bitelli, G.; Girelli, V. A.; Lambertini, A.

2018-05-01

3D city models are becoming increasingly popular and important, because they constitute the base for all the visualization, planning, management operations regarding the urban infrastructure. These data are however not available in the majority of cities: in this paper, the possibility to use geospatial data of various kinds with the aim to generate 3D models in urban environment is investigated. In 3D modelling works, the starting data are frequently the 3D point clouds, which are nowadays possible to collect by different sensors mounted on different platforms: LiDAR, imagery from satellite, airborne or unmanned aerial vehicles, mobile mapping systems that integrate several sensors. The processing of the acquired data and consequently the obtainability of models able to provide geometric accuracy and a good visual impact is limited by time, costs and logistic constraints. Nowadays more and more innovative hardware and software solutions can offer to the municipalities and the public authorities the possibility to use available geospatial data, acquired for diverse aims, for the generation of 3D models of buildings and cities, characterized by different level of detail. In the paper two cases of study are presented, both regarding surveys carried out in Emilia Romagna region, Italy, where 2D or 2.5D numerical maps are available. The first one is about the use of oblique aerial images realized by the Municipality for a systematic documentation of the built environment, the second concerns the use of LiDAR data acquired for other purposes; in the two tests, these data were used in conjunction with large scale numerical maps to produce 3D city models.

Influence of MO/MF2 modifiers (M = Ca, Sr, Ba) on spectroscopic properties of Eu3+ ions in germanate and borate glasses

NASA Astrophysics Data System (ADS)

Zur, Lidia; Janek, Joanna; Pietrasik, Ewa; Sołtys, Marta; Pisarska, Joanna; Pisarski, Wojciech A.

2016-11-01

Series of Eu3+-doped lead-free germanate and borate glasses were synthesized. The MO glass modifiers (M = Ca, Sr or Ba) were partially or totally substituted by MF2 in chemical composition. In contrast to samples modified by CaO/CaF2 or SrO/SrF2, the germanate glass samples containing BaO and/or BaF2 are fully amorphous, while the lead-free borate glasses are fully amorphous, independently from glass modifiers. Effect of glass modifiers on spectroscopic properties of Eu3+ were systematically investigated. For that reason, excitation and emission spectra of Eu3+ ions in examined systems were registered. Based on the emission spectra, ratio of integrated luminescence intensity of the 5D0 → 7F2 transition to that of the 5D0 → 7F1 transition (R factor) was calculated. Moreover, the luminescence decay curves were collected and the luminescence lifetimes of the 5D0 excited state of Eu3+ ions were determined in function of MF2 concentration.

A new unified approach to analyze wing-body-tail configurations with control surfaces in steady, oscillatory and fully unsteady, subsonic and supersonic flows

NASA Technical Reports Server (NTRS)

Tseng, K.; Morino, L.

1975-01-01

A general formulation for the analysis of steady and unsteady, subsonic and supersonic potential aerodynamics for arbitrary complex geometries is presented. The theoretical formulation, the numerical procedure, and numerical results are included. In particular, generalized forces for fully unsteady (complex frequency) aerodynamics for an AGARD coplanar wing-tail interfering configuration in both subsonic and supersonic flows are considered.

An innovative hybrid 3D analytic-numerical model for air breathing parallel channel counter-flow PEM fuel cells.

PubMed

Tavčar, Gregor; Katrašnik, Tomaž

2014-01-01

The parallel straight channel PEM fuel cell model presented in this paper extends the innovative hybrid 3D analytic-numerical (HAN) approach previously published by the authors with capabilities to address ternary diffusion systems and counter-flow configurations. The model's core principle is modelling species transport by obtaining a 2D analytic solution for species concentration distribution in the plane perpendicular to the cannel gas-flow and coupling consecutive 2D solutions by means of a 1D numerical pipe-flow model. Electrochemical and other nonlinear phenomena are coupled to the species transport by a routine that uses derivative approximation with prediction-iteration. The latter is also the core of the counter-flow computation algorithm. A HAN model of a laboratory test fuel cell is presented and evaluated against a professional 3D CFD simulation tool showing very good agreement between results of the presented model and those of the CFD simulation. Furthermore, high accuracy results are achieved at moderate computational times, which is owed to the semi-analytic nature and to the efficient computational coupling of electrochemical kinetics and species transport.

Improving the seismic small-scale modelling by comparison with numerical methods

NASA Astrophysics Data System (ADS)

Pageot, Damien; Leparoux, Donatienne; Le Feuvre, Mathieu; Durand, Olivier; Côte, Philippe; Capdeville, Yann

2017-10-01

The potential of experimental seismic modelling at reduced scale provides an intermediate step between numerical tests and geophysical campaigns on field sites. Recent technologies such as laser interferometers offer the opportunity to get data without any coupling effects. This kind of device is used in the Mesures Ultrasonores Sans Contact (MUSC) measurement bench for which an automated support system makes possible to generate multisource and multireceivers seismic data at laboratory scale. Experimental seismic modelling would become a great tool providing a value-added stage in the imaging process validation if (1) the experimental measurement chain is perfectly mastered, and thus if the experimental data are perfectly reproducible with a numerical tool, as well as if (2) the effective source is reproducible along the measurement setup. These aspects for a quantitative validation concerning devices with piezoelectrical sources and a laser interferometer have not been yet quantitatively studied in published studies. Thus, as a new stage for the experimental modelling approach, these two key issues are tackled in the proposed paper in order to precisely define the quality of the experimental small-scale data provided by the bench MUSC, which are available in the scientific community. These two steps of quantitative validation are dealt apart any imaging techniques in order to offer the opportunity to geophysicists who want to use such data (delivered as free data) of precisely knowing their quality before testing any imaging technique. First, in order to overcome the 2-D-3-D correction usually done in seismic processing when comparing 2-D numerical data with 3-D experimental measurement, we quantitatively refined the comparison between numerical and experimental data by generating accurate experimental line sources, avoiding the necessity of geometrical spreading correction for 3-D point-source data. The comparison with 2-D and 3-D numerical modelling is based on the Spectral Element Method. The approach shows the relevance of building a line source by sampling several source points, except the boundaries effects on later arrival times. Indeed, the experimental results highlight the amplitude feature and the delay equal to π/4 provided by a line source in the same manner than numerical data. In opposite, the 2-D corrections applied on 3-D data showed discrepancies which are higher on experimental data than on numerical ones due to the source wavelet shape and interferences between different arrivals. The experimental results from the approach proposed here show that discrepancies are avoided, especially for the reflected echoes. Concerning the second point aiming to assess the experimental reproducibility of the source, correlation coefficients of recording from a repeated source impact on a homogeneous model are calculated. The quality of the results, that is, higher than 0.98, allow to calculate a mean source wavelet by inversion of a mean data set. Results obtained on a more realistic model simulating clays on limestones, confirmed the reproducibility of the source impact.

Numerical investigation on the viewing angle of a lenticular three-dimensional display with a triplet lens array.

PubMed

Kim, Hwi; Hahn, Joonku; Choi, Hee-Jin

2011-04-10

We investigate the viewing angle enhancement of a lenticular three-dimensional (3D) display with a triplet lens array. The theoretical limitations of the viewing angle and view number of the lenticular 3D display with the triplet lens array are analyzed numerically. For this, the genetic-algorithm-based design method of the triplet lens is developed. We show that a lenticular 3D display with viewing angle of 120° and 144 views without interview cross talk can be realized with the use of an optimally designed triplet lens array. © 2011 Optical Society of America

Convective Differentiation of the Earth's Mantle

NASA Astrophysics Data System (ADS)

Hansen, U.; Schmalzl, J.; Stemmer, K.

2007-05-01

The differentiation of the Earth is likely to be influenced by convective motions within the early mantle. Double- diffusive convection (d.d.c), driven by thermally and compositionally induced density differences is considered as a vital mechanism behind the dynamic differentiation of the early mantle.. We demonstrate that d.d.c can lead to layer formation on a planetary scale in the diffusive regime where composition stabilizes the system whil heat provides the destabilizing force. Choosing initial conditions in which a stable compositional gradient overlies a hot reservoir we mimic the situation of a planet in a phase after core formation. Differently from earlier studies we fixed the temperature rather than the heat flux at the lower boundary, resembling a more realistic condition for the core-mantle boundary. We have carried out extended series of numerical experiments, ranging from 2D calculations in constant viscosity fluids to fully 3D experiments in spherical geometry with strongly temperature dependent viscosity. The buoyancy ratio R and the Lewis number Le are the important dynamical parameters. In all scenarios we could identify a parameter regime where the non-layered initial structure developed into a state consisting of several, mostly two layers. Initially plumes from the bottom boundary homogenize a first layer which subsequently thickens. The bottom layer heats up and then convection is initiated in the top layer. This creates dynamically (i.e. without jump in the material behavior) a stack of separately convecting layers. The bottom layer is significantly thicker than the top layer. Strongly temperature dependent viscosity leads to a more complex evolution The formation of the bottom layer is followed by the generation of several layers on top. Finally the uppermost layer starts to convect. In general, the multilayer structure collapses into a two layer system. We employed a numerical technique, allowing for a diffusion free treatment of the compositional field. In each case a similar evolution has been observed. This indicates that a temporary formation of layered structures in planetary interiors is a typical phenomenon. Moreover, in this scenario, plate tectonics appears only in later stages of the evolution.

Changing the scale of hydrogeophysical aquifer heterogeneity characterization

NASA Astrophysics Data System (ADS)

Paradis, Daniel; Tremblay, Laurie; Ruggeri, Paolo; Brunet, Patrick; Fabien-Ouellet, Gabriel; Gloaguen, Erwan; Holliger, Klaus; Irving, James; Molson, John; Lefebvre, Rene

2015-04-01

Contaminant remediation and management require the quantitative predictive capabilities of groundwater flow and mass transport numerical models. Such models have to encompass source zones and receptors, and thus typically cover several square kilometers. To predict the path and fate of contaminant plumes, these models have to represent the heterogeneous distribution of hydraulic conductivity (K). However, hydrogeophysics has generally been used to image relatively restricted areas of the subsurface (small fractions of km2), so there is a need for approaches defining heterogeneity at larger scales and providing data to constrain conceptual and numerical models of aquifer systems. This communication describes a workflow defining aquifer heterogeneity that was applied over a 12 km2 sub-watershed surrounding a decommissioned landfill emitting landfill leachate. The aquifer is a shallow, 10 to 20 m thick, highly heterogeneous and anisotropic assemblage of littoral sand and silt. Field work involved the acquisition of a broad range of data: geological, hydraulic, geophysical, and geochemical. The emphasis was put on high resolution and continuous hydrogeophysical data, the use of direct-push fully-screened wells and the acquisition of targeted high-resolution hydraulic data covering the range of observed aquifer materials. The main methods were: 1) surface geophysics (ground-penetrating radar and electrical resistivity); 2) direct-push operations with a geotechnical drilling rig (cone penetration tests with soil moisture resistivity CPT/SMR; full-screen well installation); and 3) borehole operations, including high-resolution hydraulic tests and geochemical sampling. New methods were developed to acquire high vertical resolution hydraulic data in direct-push wells, including both vertical and horizontal K (Kv and Kh). Various data integration approaches were used to represent aquifer properties in 1D, 2D and 3D. Using relevant vector machines (RVM), the mechanical and geophysical CPT/SMR measurements were used to recognize hydrofacies (HF) and obtain high-resolution 1D vertical profiles of hydraulic properties. Bayesian sequential simulation of the low-resolution surface-based geoelectrical measurements as well as high-resolution direct-push measurements of the electrical and hydraulic conductivities provided realistic estimates of the spatial distribution of K on a 250-m-long 2D survey line. Following a similar approach, all 1D vertical profiles of K derived from CPT/SMR soundings were integrated with available 2D geoelectrical profiles to obtain the 3D distribution of K over the study area. Numerical models were developed to understand flow and mass transport and assess how indicators could constrain model results and their K distributions. A 2D vertical section model was first developed based on a conceptual representation of heterogeneity which showed a significant effect of layering on flow and transport. The model demonstrated that solute and age tracers provide key model constraints. Additional 2D vertical section models with synthetic representations of low and high K hydrofacies were also developed on the basis of CPT/SMR soundings. These models showed that high-resolution profiles of hydraulic head could help constrain the spatial distribution and continuity of hydrofacies. History matching approaches are still required to simulate geostatistical models of K using hydrogeophysical data, while considering their impact on flow and transport with constraints provided by tracers of solutes and groundwater age.

Lab-on-a-Chip Device for Rapid Measurement of Vitamin D Levels.

PubMed

Peter, Harald; Bistolas, Nikitas; Schumacher, Soeren; Laurisch, Cecilia; Guest, Paul C; Höller, Ulrich; Bier, Frank F

2018-01-01

Lab-on-a-chip assays allow rapid analysis of one or more molecular analytes on an automated user-friendly platform. Here we describe a fully automated assay and readout for measurement of vitamin D levels in less than 15 min using the Fraunhofer in vitro diagnostics platform. Vitamin D (25-hydroxyvitamin D 3 [25(OH)D 3 ]) dilution series in buffer were successfully tested down to 2 ng/mL. This could be applied in the future as an inexpensive point-of-care analysis for patients suffering from a variety of conditions marked by vitamin D deficiencies.

Fabrication and characterisation of a fully auxetic 3D lattice structure via selective electron beam melting

NASA Astrophysics Data System (ADS)

Warmuth, Franziska; Osmanlic, Fuad; Adler, Lucas; Lodes, Matthias A.; Körner, Carolin

2017-02-01

A three-dimensional fully auxetic cellular structure with negative Poisson’s ratio is presented. Samples are fabricated from Ti6Al4V powder via selective electron beam melting. The influence of the strut thickness and the amplitude of the strut on the mechanical properties and the deformation behaviour of cellular structures is studied.

3D numerical simulation of free surface shape during the crystal growth of floating zone (FZ) silicon

NASA Astrophysics Data System (ADS)

Han, Xue-Feng; Liu, Xin; Nakano, Satoshi; Harada, Hirofumi; Miyamura, Yoshiji; Kakimoto, Koichi

2018-02-01

In FZ growth processes, the stability of the free surface is important in the production of single crystal silicon with high quality. To investigate the shape of the free surface in the FZ silicon crystal growth, a 3D numerical model that included gas and liquid phases was developed. In this present study, 3D Young-Laplacian equations have been solved using the Volume of Fluid (VOF) Model. Using this new model, we predicted the 3D shape of the free surface in FZ silicon crystal growth. The effect of magnetic pressure on shape of free surface has been considered. In particular, the free surface of the eccentric growth model, which could not be previously solved using the 2D Young-Laplacian equations, was solved using the VOF model. The calculation results are validated by the experimental results.

Validation of computational code UST3D by the example of experimental aerodynamic data

NASA Astrophysics Data System (ADS)

Surzhikov, S. T.

2017-02-01

Numerical simulation of the aerodynamic characteristics of the hypersonic vehicles X-33 and X-34 as well as spherically blunted cone is performed using the unstructured meshes. It is demonstrated that the numerical predictions obtained with the computational code UST3D are in acceptable agreement with the experimental data for approximate parameters of the geometry of the hypersonic vehicles and in excellent agreement with data for blunted cone.

3D numerical simulation of transient processes in hydraulic turbines

NASA Astrophysics Data System (ADS)

Cherny, S.; Chirkov, D.; Bannikov, D.; Lapin, V.; Skorospelov, V.; Eshkunova, I.; Avdushenko, A.

2010-08-01

An approach for numerical simulation of 3D hydraulic turbine flows in transient operating regimes is presented. The method is based on a coupled solution of incompressible RANS equations, runner rotation equation, and water hammer equations. The issue of setting appropriate boundary conditions is considered in detail. As an illustration, the simulation results for runaway process are presented. The evolution of vortex structure and its effect on computed runaway traces are analyzed.

Simultaneous 3D localization of multiple MR-visible markers in fully reconstructed MR images: proof-of-concept for subsecond position tracking.

PubMed

Thörmer, Gregor; Garnov, Nikita; Moche, Michael; Haase, Jürgen; Kahn, Thomas; Busse, Harald

2012-04-01

To determine whether a greatly reduced spatial resolution of fully reconstructed projection MR images can be used for the simultaneous 3D localization of multiple MR-visible markers and to assess the feasibility of a subsecond position tracking for clinical purposes. Miniature, inductively coupled RF coils were imaged in three orthogonal planes with a balanced steady-state free precession (SSFP) sequence and automatically localized using a two-dimensional template fitting and a subsequent three-dimensional (3D) matching of the coordinates. Precision, accuracy, speed and robustness of 3D localization were assessed for decreasing in-plane resolutions (0.6-4.7 mm). The feasibility of marker tracking was evaluated at the lowest resolution by following a robotically driven needle on a complex 3D trajectory. Average 3D precision and accuracy, sensitivity and specificity of localization ranged between 0.1 and 0.4 mm, 0.5 and 1.0 mm, 100% and 95%, and 100% and 96%, respectively. At the lowest resolution, imaging and localization took ≈350 ms and provided an accuracy of ≈1.0 mm. In the tracking experiment, the needle was clearly depicted on the oblique scan planes defined by the markers. Image-based marker localization at a greatly reduced spatial resolution is considered a feasible approach to monitor reference points or rigid instruments at subsecond update rates. Copyright © 2012 Elsevier Inc. All rights reserved.

An efficient and stable hydrodynamic model with novel source term discretization schemes for overland flow and flood simulations

NASA Astrophysics Data System (ADS)

Xia, Xilin; Liang, Qiuhua; Ming, Xiaodong; Hou, Jingming

2017-05-01

Numerical models solving the full 2-D shallow water equations (SWEs) have been increasingly used to simulate overland flows and better understand the transient flow dynamics of flash floods in a catchment. However, there still exist key challenges that have not yet been resolved for the development of fully dynamic overland flow models, related to (1) the difficulty of maintaining numerical stability and accuracy in the limit of disappearing water depth and (2) inaccurate estimation of velocities and discharges on slopes as a result of strong nonlinearity of friction terms. This paper aims to tackle these key research challenges and present a new numerical scheme for accurately and efficiently modeling large-scale transient overland flows over complex terrains. The proposed scheme features a novel surface reconstruction method (SRM) to correctly compute slope source terms and maintain numerical stability at small water depth, and a new implicit discretization method to handle the highly nonlinear friction terms. The resulting shallow water overland flow model is first validated against analytical and experimental test cases and then applied to simulate a hypothetic rainfall event in the 42 km2 Haltwhistle Burn, UK.

Quinoa - Adaptive Computational Fluid Dynamics, 0.2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakosi, Jozsef; Gonzalez, Francisco; Rogers, Brandon

Quinoa is a set of computational tools that enables research and numerical analysis in fluid dynamics. At this time it remains a test-bed to experiment with various algorithms using fully asynchronous runtime systems. Currently, Quinoa consists of the following tools: (1) Walker, a numerical integrator for systems of stochastic differential equations in time. It is a mathematical tool to analyze and design the behavior of stochastic differential equations. It allows the estimation of arbitrary coupled statistics and probability density functions and is currently used for the design of statistical moment approximations for multiple mixing materials in variable-density turbulence. (2) Inciter,more » an overdecomposition-aware finite element field solver for partial differential equations using 3D unstructured grids. Inciter is used to research asynchronous mesh-based algorithms and to experiment with coupling asynchronous to bulk-synchronous parallel code. Two planned new features of Inciter, compared to the previous release (LA-CC-16-015), to be implemented in 2017, are (a) a simple Navier-Stokes solver for ideal single-material compressible gases, and (b) solution-adaptive mesh refinement (AMR), which enables dynamically concentrating compute resources to regions with interesting physics. Using the NS-AMR problem we plan to explore how to scale such high-load-imbalance simulations, representative of large production multiphysics codes, to very large problems on very large computers using an asynchronous runtime system. (3) RNGTest, a test harness to subject random number generators to stringent statistical tests enabling quantitative ranking with respect to their quality and computational cost. (4) UnitTest, a unit test harness, running hundreds of tests per second, capable of testing serial, synchronous, and asynchronous functions. (5) MeshConv, a mesh file converter that can be used to convert 3D tetrahedron meshes from and to either of the following formats: Gmsh, (http://www.geuz.org/gmsh), Netgen, (http://sourceforge.net/apps/mediawiki/netgen-mesher), ExodusII, (http://sourceforge.net/projects/exodusii), HyperMesh, (http://www.altairhyperworks.com/product/HyperMesh).« less

Numerical electromagnetic frequency domain analysis with discrete exterior calculus

NASA Astrophysics Data System (ADS)

Chen, Shu C.; Chew, Weng Cho

2017-12-01

In this paper, we perform a numerical analysis in frequency domain for various electromagnetic problems based on discrete exterior calculus (DEC) with an arbitrary 2-D triangular or 3-D tetrahedral mesh. We formulate the governing equations in terms of DEC for 3-D and 2-D inhomogeneous structures, and also show that the charge continuity relation is naturally satisfied. Then we introduce a general construction for signed dual volume to incorporate material information and take into account the case when circumcenters fall outside triangles or tetrahedrons, which may lead to negative dual volume without Delaunay triangulation. Then we examine the boundary terms induced by the dual mesh and provide a systematical treatment of various boundary conditions, including perfect magnetic conductor (PMC), perfect electric conductor (PEC), Dirichlet, periodic, and absorbing boundary conditions (ABC) within this method. An excellent agreement is achieved through the numerical calculation of several problems, including homogeneous waveguides, microstructured fibers, photonic crystals, scattering by a 2-D PEC, and resonant cavities.

Hydrodynamic characteristics of the two-phase flow field at gas-evolving electrodes: numerical and experimental studies

NASA Astrophysics Data System (ADS)

Liu, Cheng-Lin; Sun, Ze; Lu, Gui-Min; Yu, Jian-Guo

2018-05-01

Gas-evolving vertical electrode system is a typical electrochemical industrial reactor. Gas bubbles are released from the surfaces of the anode and affect the electrolyte flow pattern and even the cell performance. In the current work, the hydrodynamics induced by the air bubbles in a cold model was experimentally and numerically investigated. Particle image velocimetry and volumetric three-component velocimetry techniques were applied to experimentally visualize the hydrodynamics characteristics and flow fields in a two-dimensional (2D) plane and a three-dimensional (3D) space, respectively. Measurements were performed at different gas rates. Furthermore, the corresponding mathematical model was developed under identical conditions for the qualitative and quantitative analyses. The experimental measurements were compared with the numerical results based on the mathematical model. The study of the time-averaged flow field, three velocity components, instantaneous velocity and turbulent intensity indicate that the numerical model qualitatively reproduces liquid motion. The 3D model predictions capture the flow behaviour more accurately than the 2D model in this study.

Hydrodynamic characteristics of the two-phase flow field at gas-evolving electrodes: numerical and experimental studies.

PubMed

Liu, Cheng-Lin; Sun, Ze; Lu, Gui-Min; Yu, Jian-Guo

2018-05-01

Gas-evolving vertical electrode system is a typical electrochemical industrial reactor. Gas bubbles are released from the surfaces of the anode and affect the electrolyte flow pattern and even the cell performance. In the current work, the hydrodynamics induced by the air bubbles in a cold model was experimentally and numerically investigated. Particle image velocimetry and volumetric three-component velocimetry techniques were applied to experimentally visualize the hydrodynamics characteristics and flow fields in a two-dimensional (2D) plane and a three-dimensional (3D) space, respectively. Measurements were performed at different gas rates. Furthermore, the corresponding mathematical model was developed under identical conditions for the qualitative and quantitative analyses. The experimental measurements were compared with the numerical results based on the mathematical model. The study of the time-averaged flow field, three velocity components, instantaneous velocity and turbulent intensity indicate that the numerical model qualitatively reproduces liquid motion. The 3D model predictions capture the flow behaviour more accurately than the 2D model in this study.

Hydrodynamic characteristics of the two-phase flow field at gas-evolving electrodes: numerical and experimental studies

PubMed Central

Lu, Gui-Min; Yu, Jian-Guo

2018-01-01

Gas-evolving vertical electrode system is a typical electrochemical industrial reactor. Gas bubbles are released from the surfaces of the anode and affect the electrolyte flow pattern and even the cell performance. In the current work, the hydrodynamics induced by the air bubbles in a cold model was experimentally and numerically investigated. Particle image velocimetry and volumetric three-component velocimetry techniques were applied to experimentally visualize the hydrodynamics characteristics and flow fields in a two-dimensional (2D) plane and a three-dimensional (3D) space, respectively. Measurements were performed at different gas rates. Furthermore, the corresponding mathematical model was developed under identical conditions for the qualitative and quantitative analyses. The experimental measurements were compared with the numerical results based on the mathematical model. The study of the time-averaged flow field, three velocity components, instantaneous velocity and turbulent intensity indicate that the numerical model qualitatively reproduces liquid motion. The 3D model predictions capture the flow behaviour more accurately than the 2D model in this study. PMID:29892347

Special Issue: NextGen Materials for 3D Printing.

PubMed

Chua, Chee Kai; Yeong, Wai Yee; An, Jia

2018-04-04

Only a handful of materials are well-established in three-dimensional (3D) printing and well-accepted in industrial manufacturing applications. However, recent advances in 3D printable materials have shown potential for enabling numerous novel applications in the future. This special issue, consisting of 2 reviews and 10 research articles, intends to explore the possible materials that could define next-generation 3D printing.

Atomically thick bismuth selenide freestanding single layers achieving enhanced thermoelectric energy harvesting.

PubMed

Sun, Yongfu; Cheng, Hao; Gao, Shan; Liu, Qinghua; Sun, Zhihu; Xiao, Chong; Wu, Changzheng; Wei, Shiqiang; Xie, Yi

2012-12-19

Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat. However, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Here, a single-layer-based (SLB) composite fabricated from atomically thick single layers was proposed to optimize the thermoelectric parameters fully. Freestanding five-atom-thick Bi(2)Se(3) single layers were first synthesized via a scalable interaction/exfoliation strategy. As revealed by X-ray absorption fine structure spectroscopy and first-principles calculations, surface distortion gives them excellent structural stability and a much increased density of states, resulting in a 2-fold higher electrical conductivity relative to the bulk material. Also, the surface disorder and numerous interfaces in the Bi(2)Se(3) SLB composite allow for effective phonon scattering and decreased thermal conductivity, while the 2D electron gas and energy filtering effect increase the Seebeck coefficient, resulting in an 8-fold higher figure of merit (ZT) relative to the bulk material. This work develops a facile strategy for synthesizing atomically thick single layers and demonstrates their superior ability to optimize the thermoelectric energy harvesting.

A 3D THz image processing methodology for a fully integrated, semi-automatic and near real-time operational system

NASA Astrophysics Data System (ADS)

Brook, A.; Cristofani, E.; Vandewal, M.; Matheis, C.; Jonuscheit, J.; Beigang, R.

2012-05-01

The present study proposes a fully integrated, semi-automatic and near real-time mode-operated image processing methodology developed for Frequency-Modulated Continuous-Wave (FMCW) THz images with the center frequencies around: 100 GHz and 300 GHz. The quality control of aeronautics composite multi-layered materials and structures using Non-Destructive Testing is the main focus of this work. Image processing is applied on the 3-D images to extract useful information. The data is processed by extracting areas of interest. The detected areas are subjected to image analysis for more particular investigation managed by a spatial model. Finally, the post-processing stage examines and evaluates the spatial accuracy of the extracted information.

Benzoylated ethyl 1-thioglycosides: direct preparation from per-O-benzoylated sugars

PubMed Central

Sail, Deepak; Kováč, Pavol

2012-01-01

D-Glucose, lactose, maltose, and melibiose were benzoylated with Bz2O–Et3N reagent to give fully benzoylated β products. Under the same conditions, D-mannose produced a mixture where the β-benzoate predominated. Treatment of the foregoing compounds with EtSH at slightly elevated temperature (50– 60 °C) in the presence of BF3·Et2O as a promoter gave the corresponding ethyl 1-thio glycosides in high yields. The α-products predominated in all cases in the anomeric mixtures formed. Individual products of all reactions were isolated by chromatography, they were obtained in analytically pure state, and were fully characterized by 1H and 13C NMR data and physical constants. PMID:22739243

Benzoylated ethyl 1-thioglycosides: direct preparation from per-O-benzoylated sugars.

PubMed

Sail, Deepak; Kováč, Pavol

2012-08-01

D-Glucose, lactose, maltose, and melibiose were benzoylated with Bz(2)O-Et(3)N reagent to give fully benzoylated β products. Under the same conditions, D-mannose produced a mixture where the β-benzoate predominated. Treatment of the foregoing compounds with EtSH at slightly elevated temperature (50-60°C) in the presence of BF(3)·Et(2)O as a promoter gave the corresponding ethyl 1-thio glycosides in high yields. The α-products predominated in all cases in the anomeric mixtures formed. Individual products of all reactions were isolated by chromatography, they were obtained in analytically pure state, and were fully characterized by (1)H and (13)C NMR data and physical constants. Published by Elsevier Ltd.

Collaborative Visualization and Analysis of Multi-dimensional, Time-dependent and Distributed Data in the Geosciences Using the Unidata Integrated Data Viewer

NASA Astrophysics Data System (ADS)

Meertens, C. M.; Murray, D.; McWhirter, J.

2004-12-01

Over the last five years, UNIDATA has developed an extensible and flexible software framework for analyzing and visualizing geoscience data and models. The Integrated Data Viewer (IDV), initially developed for visualization and analysis of atmospheric data, has broad interdisciplinary application across the geosciences including atmospheric, ocean, and most recently, earth sciences. As part of the NSF-funded GEON Information Technology Research project, UNAVCO has enhanced the IDV to display earthquakes, GPS velocity vectors, and plate boundary strain rates. These and other geophysical parameters can be viewed simultaneously with three-dimensional seismic tomography and mantle geodynamic model results. Disparate data sets of different formats, variables, geographical projections and scales can automatically be displayed in a common projection. The IDV is efficient and fully interactive allowing the user to create and vary 2D and 3D displays with contour plots, vertical and horizontal cross-sections, plan views, 3D isosurfaces, vector plots and streamlines, as well as point data symbols or numeric values. Data probes (values and graphs) can be used to explore the details of the data and models. The IDV is a freely available Java application using Java3D and VisAD and runs on most computers. UNIDATA provides easy-to-follow instructions for download, installation and operation of the IDV. The IDV primarily uses netCDF, a self-describing binary file format, to store multi-dimensional data, related metadata, and source information. The IDV is designed to work with OPeNDAP-equipped data servers that provide real-time observations and numerical models from distributed locations. Users can capture and share screens and animations, or exchange XML "bundles" that contain the state of the visualization and embedded links to remote data files. A real-time collaborative feature allows groups of users to remotely link IDV sessions via the Internet and simultaneously view and control the visualization. A Jython-based formulation facility allows computations on disparate data sets using simple formulas. Although the IDV is an advanced tool for research, its flexible architecture has also been exploited for educational purposes with the Virtual Geophysical Exploration Environment (VGEE) development. The VGEE demonstration added physical concept models to the IDV and curricula for atmospheric science education intended for the high school to graduate student levels.

45^○ sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co₃FeN/MnN bilayers.

PubMed

Hajiri, Tetsuya; Yoshida, Takuya; Filianina, Mariia; Jaiswal, Samridh; Borie, Benjamin; Asano, H; Zabel, Hartmut; Klaui, Mathias

2017-11-20

We report an unusual angular-dependent exchange bias effect in ferromagnet/antiferromagnet bilayers, where both ferromagnet and antiferromagnet are epitaxially grown. Numerical model calculations predict an approximately 45$^\\circ$ period for the sign switching of the exchange-bias field, depending on the ratio between magnetocrystalline anisotropy and exchange-coupling constant. The switching of the sign is indicative of a competition between a fourfold magnetocrystalline anisotropy of the ferromagnet and a unidirectional anisotropy field of the exchange coupling. This predicted unusual angular-dependent exchange bias and its magnetization switching process are confirmed by measurements on fully epitaxial Co$_3$FeN/MnN bilayers by longitudinal and transverse magneto-optic Kerr effect magnetometry. These results provide a deeper understanding of the exchange coupling phenomena in fully epitaxial bilayers with tailored materials and open up a complex switching energy landscape engineering by anisotropies. © 2017 IOP Publishing Ltd.

Dynamic integral imaging technology for 3D applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huang, Yi-Pai; Javidi, Bahram; Martínez-Corral, Manuel; Shieh, Han-Ping D.; Jen, Tai-Hsiang; Hsieh, Po-Yuan; Hassanfiroozi, Amir

2017-05-01

Depth and resolution are always the trade-off in integral imaging technology. With the dynamic adjustable devices, the two factors of integral imaging can be fully compensated with time-multiplexed addressing. Those dynamic devices can be mechanical or electrical driven. In this presentation, we will mainly focused on discussing various Liquid Crystal devices which can change the focal length, scan and shift the image position, or switched in between 2D/3D mode. By using the Liquid Crystal devices, dynamic integral imaging have been successfully applied on 3D Display, capturing, and bio-imaging applications.

Artery and vein segmentation of the cerebral vasculature in 4D CT using a 3D fully convolutional neural network

NASA Astrophysics Data System (ADS)

Meijs, Midas; Manniesing, Rashindra

2018-02-01

Segmentation of the arteries and veins of the cerebral vasculature is important for improved visualization and for the detection of vascular related pathologies including arteriovenous malformations. We propose a 3D fully convolutional neural network (CNN) using a time-to-signal image as input and the distance to the center of gravity of the brain as spatial feature integrated in the final layers of the CNN. The method was trained and validated on 6 and tested on 4 4D CT patient imaging data. The reference standard was acquired by manual annotations by an experienced observer. Quantitative evaluation showed a mean Dice similarity coefficient of 0.94 +/- 0.03 and 0.97 +/- 0.01, a mean absolute volume difference of 4.36 +/- 5.47 % and 1.79 +/- 2.26 % for artery and vein respectively and an overall accuracy of 0.96 +/- 0.02. The average calculation time per volume on the test set was approximately one minute. Our method shows promising results and enables fast and accurate segmentation of arteries and veins in full 4D CT imaging data.

Numerical simulation of solar coronal magnetic fields

NASA Technical Reports Server (NTRS)

Dahlburg, Russell B.; Antiochos, Spiro K.; Zang, T. A.

1990-01-01

Many aspects of solar activity are believed to be due to the stressing of the coronal magnetic field by footpoint motions at the photosphere. The results are presented of a fully spectral numerical simulation which is the first 3-D time dependent simulation of footpoint stressing in a geometry appropriate for the corona. An arcade is considered that is initially current-free and impose a smooth footpoint motion that produces a twist in the field of approx 2 pi. The footprints were fixed and the evolution was followed until the field relaxes to another current-free state. No evidence was seen for any instability, either ideal or resistive and no evidence for current sheet formation. The most striking feature of the evolution is that in response to photospheric motions, the field expands rapidly upward to minimize the stress. The expansion has two important effects. First, it suppresses the development of dips in the field that could support dense, cool material. For the motions assumed, the magnetic field does not develop a geometry suitable for prominence formation. Second, the expansion inhibits ideal instabilities such as kinking. The results indicate that simple stearing of a single arcade is unlikely to lead to solar activity such as flares or prominences. Effects are discussed that might possibly lead to such activity.

Advances toward field application of 3D hydraulic tomography

NASA Astrophysics Data System (ADS)

Cardiff, M. A.; Barrash, W.; Kitanidis, P. K.

2011-12-01

Hydraulic tomography (HT) is a technique that shows great potential for aquifer characterization and one that holds the promise of producing 3D hydraulic property distributions, given suitable equipment. First suggested over 15 years ago, HT assimilates distributed aquifer pressure (head) response data collected during a series of multiple pumping tests to produce estimates of aquifer property variability. Unlike traditional curve-matching analyses, which assume homogeneity or "effective" parameters within the radius of influence of a hydrologic test, HT analysis relies on numerical models with detailed heterogeneity in order to invert for the highly resolved 3D parameter distribution that jointly fits all data. Several numerical and laboratory investigations of characterization using HT have shown that property distributions can be accurately estimated between observation locations when experiments are correctly designed - a property not always shared by other, simpler 1D characterization approaches such as partially-penetrating slug tests. HT may represent one of the best methods available for obtaining detailed 3D aquifer property descriptions, especially in deep or "hard" aquifer materials, where direct-push methods may not be feasible. However, to date HT has not yet been widely adopted at contaminated field sites. We believe that current perceived impediments to HT adoption center around four key issues: 1) A paucity in the scientific literature of proven, cross-validated 3D field applications 2) A lack of guidelines and best practices for performing field 3D HT experiments; 3) Practical difficulty and time commitment associated with the installation of a large number of high-accuracy sampling locations, and the running of a large number of pumping tests; and 4) Computational difficulty associated with solving large-scale inverse problems for parameter identification. In this talk, we present current results in 3D HT research that addresses these four issues, and thus bring HT closer to field practice. Topics to be discussed include: -Improving field efficiency through design and implementation of new modular, easily-installed equipment for 3D HT. -Validating field-scale 3D HT through application and cross-validation at the Boise Hydrogeophysical Research Site. -Developing guidelines for HT implementation based on field experience, numerical modeling, and a comprehensive literature review of the past 15 years of HT research. -Application of novel, fast numerical methods for large-scale HT data analysis. The results presented will focus on the application of 3D HT, but in general we also hope to provide insights on aquifer characterization that stimulate thought on the issue of continually updating aquifer characteristics estimates while recognizing uncertainties and providing guidance for future data collection.

A quantification method for numerical dissipation in quasi-DNS and under-resolved DNS, and effects of numerical dissipation in quasi-DNS and under-resolved DNS of turbulent channel flows

NASA Astrophysics Data System (ADS)

Komen, E. M. J.; Camilo, L. H.; Shams, A.; Geurts, B. J.; Koren, B.

2017-09-01

LES for industrial applications with complex geometries is mostly characterised by: a) a finite volume CFD method using a non-staggered arrangement of the flow variables and second order accurate spatial and temporal discretisation schemes, b) an implicit top-hat filter, where the filter length is equal to the local computational cell size, and c) eddy-viscosity type LES models. LES based on these three main characteristics is indicated as industrial LES in this paper. It becomes increasingly clear that the numerical dissipation in CFD codes typically used in industrial applications with complex geometries may inhibit the predictive capabilities of explicit LES. Therefore, there is a need to quantify the numerical dissipation rate in such CFD codes. In this paper, we quantify the numerical dissipation rate in physical space based on an analysis of the transport equation for the mean turbulent kinetic energy. Using this method, we quantify the numerical dissipation rate in a quasi-Direct Numerical Simulation (DNS) and in under-resolved DNS of, as a basic demonstration case, fully-developed turbulent channel flow. With quasi-DNS, we indicate a DNS performed using a second order accurate finite volume method typically used in industrial applications. Furthermore, we determine and explain the trends in the performance of industrial LES for fully-developed turbulent channel flow for four different Reynolds numbers for three different LES mesh resolutions. The presented explanation of the mechanisms behind the observed trends is based on an analysis of the turbulent kinetic energy budgets. The presented quantitative analyses demonstrate that the numerical errors in the industrial LES computations of the considered turbulent channel flows result in a net numerical dissipation rate which is larger than the subgrid-scale dissipation rate. No new computational methods are presented in this paper. Instead, the main new elements in this paper are our detailed quantification method for the numerical dissipation rate, the application of this method to a quasi-DNS and under-resolved DNS of fully-developed turbulent channel flow, and the explanation of the effects of the numerical dissipation on the observed trends in the performance of industrial LES for fully-developed turbulent channel flows.

Calculation of plasma dielectric response in inhomogeneous magnetic field near electron cyclotron resonance

NASA Astrophysics Data System (ADS)

Evstatiev, Evstati; Svidzinski, Vladimir; Spencer, Andy; Galkin, Sergei

2014-10-01

Full wave 3-D modeling of RF fields in hot magnetized nonuniform plasma requires calculation of nonlocal conductivity kernel describing the dielectric response of such plasma to the RF field. In many cases, the conductivity kernel is a localized function near the test point which significantly simplifies numerical solution of the full wave 3-D problem. Preliminary results of feasibility analysis of numerical calculation of the conductivity kernel in a 3-D hot nonuniform magnetized plasma in the electron cyclotron frequency range will be reported. This case is relevant to modeling of ECRH in ITER. The kernel is calculated by integrating the linearized Vlasov equation along the unperturbed particle's orbits. Particle's orbits in the nonuniform equilibrium magnetic field are calculated numerically by one of the Runge-Kutta methods. RF electric field is interpolated on a specified grid on which the conductivity kernel is discretized. The resulting integrals in the particle's initial velocity and time are then calculated numerically. Different optimization approaches of the integration are tested in this feasibility analysis. Work is supported by the U.S. DOE SBIR program.

Compressible convection in geophysical fluids: comparison of anelastic, anelastic liquid and full numerical simulations

NASA Astrophysics Data System (ADS)

Curbelo, Jezabel; Alboussiere, Thierry; Labrosse, Stephane; Dubuffet, Fabien; Ricard, Yanick

2015-11-01

In this talk we describe the numerical method implemented to study convection in a fully compressible two-dimensional model, which may be reduced to the different simplifications such as the anelastic approximation and the anelastic liquid approximation. Various equations of state are considered, from the ideal gas equation to equations related to liquid or solid condensed matter. We are particularly interested in the total value and spatial distribution of viscous dissipation. We analyze the solutions obtained with each approximation in a wide range of dimensionless parameters and compare the domain of validity of each of them. The authors are grateful to the LABEX Lyon Institute of Origins (ANR-10-LABX-0066) of the Universite de Lyon for its financial support ``Investissements d'Avenir'' (ANR-11-IDEX-0007) of the French government operated by the National Research Agency (ANR).

Experimental and Numerical Analysis of Structural Acousticcontrol Interior Noise Reduction

NASA Technical Reports Server (NTRS)

Mei, Chuh; Bevan, Jeffrey S.

1999-01-01

The research results contained in this technical report were performed under the NASA grant entitled "Experimental and Numerical Structural Acoustic Control for Interior Noise Reduction". The report is based essentially on partial progress of the Ph.D. dissertation prepared by Jeffrey S. Bevan under direct guidance of Dr. Chuh Mei. The document presents a finite element formulation and control of sound radiated from cylindrical panels embedded with piezoceramic actuators. The extended MIN6 shallow shell element is fully electrical-structural coupled. A piezoelectric modal actuator participation (PMAP) is defined which indicates the actuator performance to each of the offending modes. Genetic algorithm is also employed to validate the sensor and actuator locations determined by the PMAP criteria. The work was conducted at the Department of Aerospace Engineering, Old Dominion University. Mr. Travis L. Turner, Structural Acoustics Branch, NASA Langley Research Center is the technical monitor.

Age-of-Air, Tape Recorder, and Vertical Transport Schemes

NASA Technical Reports Server (NTRS)

Lin, S.-J.; Einaudi, Franco (Technical Monitor)

2000-01-01

A numerical-analytic investigation of the impacts of vertical transport schemes on the model simulated age-of-air and the so-called 'tape recorder' will be presented using an idealized 1-D column transport model as well as a more realistic 3-D dynamical model. By comparing to the 'exact' solutions of 'age-of-air' and the 'tape recorder' obtainable in the 1-D setting, useful insight is gained on the impacts of numerical diffusion and dispersion of numerical schemes used in global models. Advantages and disadvantages of Eulerian, semi-Lagrangian, and Lagrangian transport schemes will be discussed. Vertical resolution requirement for numerical schemes as well as observing systems for capturing the fine details of the 'tape recorder' or any upward propagating wave-like structures can potentially be derived from the 1-D analytic model.

Numerical optimization of perturbative coils for tokamaks

NASA Astrophysics Data System (ADS)

Lazerson, Samuel; Park, Jong-Kyu; Logan, Nikolas; Boozer, Allen; NSTX-U Research Team

2014-10-01

Numerical optimization of coils which apply three dimensional (3D) perturbative fields to tokamaks is presented. The application of perturbative 3D magnetic fields in tokamaks is now commonplace for control of error fields, resistive wall modes, resonant field drive, and neoclassical toroidal viscosity (NTV) torques. The design of such systems has focused on control of toroidal mode number, with coil shapes based on simple window-pane designs. In this work, a numerical optimization suite based on the STELLOPT 3D equilibrium optimization code is presented. The new code, IPECOPT, replaces the VMEC equilibrium code with the IPEC perturbed equilibrium code, and targets NTV torque by coupling to the PENT code. Fixed boundary optimizations of the 3D fields for the NSTX-U experiment are underway. Initial results suggest NTV torques can be driven by normal field spectrums which are not pitch-resonant with the magnetic field lines. Work has focused on driving core torque with n = 1 and edge torques with n = 3 fields. Optimizations of the coil currents for the planned NSTX-U NCC coils highlight the code's free boundary capability. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the U.S. Department of Energy.