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discrete element method

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https://www.readbyqxmd.com/read/28297998/splash-detail-due-to-a-single-grain-incident-on-a-granular-bed
#1
Takahiro Tanabe, Takashi Shimada, Nobuyasu Ito, Hiraku Nishimori
Using the discrete element method, we study the splash processes induced by the impact of a grain on a randomly packed bed. Good correspondence is obtained between our numerical results and the findings of previous experiments for the movement of ejected grains. Furthermore, the distributions of the ejection angle and ejection speed for individual grains vary depending on the relative timing at which the grains are ejected after the initial impact. Obvious differences are observed between the distributions of grains ejected during the earlier and later splash periods: the form of the vertical ejection-speed distribution varies from a power-law form to a lognormal form with time; this difference may determine grain trajectory after ejection...
February 2017: Physical Review. E
https://www.readbyqxmd.com/read/28294574/phase-field-boundary-conditions-for-the-voxel-finite-cell-method-surface-free-stress-analysis-of-ct-based-bone-structures
#2
L H Nguyen, S K F Stoter, T Baum, J S Kirschke, M Ruess, Z Yosibash, D Schillinger
The voxel finite cell method employs unfitted finite element meshes and voxel quadrature rules to seamlessly transfer CT data into patient-specific bone discretizations. The method, however, still requires the explicit parametrization of boundary surfaces to impose traction and displacement boundary conditions, which constitutes a potential roadblock to automation. We explore a phase-field based formulation for imposing traction and displacement constraints in a diffuse sense. Its essential component is a diffuse geometry model generated from metastable phase-field solutions of the Allen-Cahn problem that assumes the imaging data as initial condition...
March 11, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28289574/digital-morphing-wing-active-wing-shaping-concept-using-composite-lattice-based-cellular-structures
#3
Benjamin Jenett, Sam Calisch, Daniel Cellucci, Nick Cramer, Neil Gershenfeld, Sean Swei, Kenneth C Cheung
We describe an approach for the discrete and reversible assembly of tunable and actively deformable structures using modular building block parts for robotic applications. The primary technical challenge addressed by this work is the use of this method to design and fabricate low density, highly compliant robotic structures with spatially tuned stiffness. This approach offers a number of potential advantages over more conventional methods for constructing compliant robots. The discrete assembly reduces manufacturing complexity, as relatively simple parts can be batch-produced and joined to make complex structures...
March 1, 2017: Soft Robotics
https://www.readbyqxmd.com/read/28280517/mixed-total-variation-and-l-1-regularization-method-for-optical-tomography-based-on-radiative-transfer-equation
#4
Jinping Tang, Bo Han, Weimin Han, Bo Bi, Li Li
Optical tomography is an emerging and important molecular imaging modality. The aim of optical tomography is to reconstruct optical properties of human tissues. In this paper, we focus on reconstructing the absorption coefficient based on the radiative transfer equation (RTE). It is an ill-posed parameter identification problem. Regularization methods have been broadly applied to reconstruct the optical coefficients, such as the total variation (TV) regularization and the L(1) regularization. In order to better reconstruct the piecewise constant and sparse coefficient distributions, TV and L(1) norms are combined as the regularization...
2017: Computational and Mathematical Methods in Medicine
https://www.readbyqxmd.com/read/28269628/development-of-an-open-source-cosimulation-method-of-the-knee
#5
Anne Schmitz, Davide Piovesan
Rigid body dynamics and soft tissue loads are solved simultaneously in a cosimulation framework to couple musculoskeletal dynamics and tissue mechanics. The goal of this work was to implement a validated, open-source cosimulation framework of the knee to determine how this coupling affects computed cartilage loads. The kinematic knee joint of a generic whole body model in the open-source software OpenSim was replaced by a previously developed discrete element knee model that consisted of a six degree of freedom (dof) tibiofemoral joint and one dof patellofemoral joint...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28268867/fea-modeling-and-fluid-flow-simulation-of-human-rectum-with-inserted-bowel-catheters
#6
Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman
In this project, fluid flow and fluid-structure interaction are studied for the human lower gastrointestinal (GI) region. The study consists of two steps. First, we apply meshing methods to discretize both the human lower GI model and the catheter model at sufficient resolution suitable for importing into a Finite Element Analysis (FEA) tool. For model discretization, 3D models of the colon reconstructed from human MRI slices are used to obtain the valid inlet and outlet boundary surfaces. To resolve the viscous boundary layer in flow studies, a special structure of the near-wall volumetric mesh is built by triangular prisms that construct quasi-structured, multiple near-boundary sub-layers...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28249103/a-hybrid-computational-model-to-explore-the-topological-characteristics-of-epithelial-tissues
#7
Ismael González-Valverde, José Manuel García Aznar
Epithelial tissues show a particular topology where cells resemble a polygon-like shape, but some biological processes can alter this tissue topology. During cell proliferation, mitotic cell dilation deforms the tissue and modifies the tissue topology. Additionally, cells are reorganized in the epithelial layer and these rearrangements also alter the polygon distribution. We present here a computer-based hybrid framework focused on the simulation of epithelial layer dynamics that combines discrete and continuum numerical models...
March 1, 2017: International Journal for Numerical Methods in Biomedical Engineering
https://www.readbyqxmd.com/read/28227886/development-of-an-open-source-cosimulation-method-of-the-knee
#8
Anne Schmitz, Davide Piovesan, Anne Schmitz, Davide Piovesan, Anne Schmitz, Davide Piovesan
Rigid body dynamics and soft tissue loads are solved simultaneously in a cosimulation framework to couple musculoskeletal dynamics and tissue mechanics. The goal of this work was to implement a validated, open-source cosimulation framework of the knee to determine how this coupling affects computed cartilage loads. The kinematic knee joint of a generic whole body model in the open-source software OpenSim was replaced by a previously developed discrete element knee model that consisted of a six degree of freedom (dof) tibiofemoral joint and one dof patellofemoral joint...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28227065/fea-modeling-and-fluid-flow-simulation-of-human-rectum-with-inserted-bowel-catheters
#9
Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Yong Zhang, Tina VanRiper, Brian Rague, Drew Weidman, Tina VanRiper, Drew Weidman, Brian Rague, Yong Zhang
In this project, fluid flow and fluid-structure interaction are studied for the human lower gastrointestinal (GI) region. The study consists of two steps. First, we apply meshing methods to discretize both the human lower GI model and the catheter model at sufficient resolution suitable for importing into a Finite Element Analysis (FEA) tool. For model discretization, 3D models of the colon reconstructed from human MRI slices are used to obtain the valid inlet and outlet boundary surfaces. To resolve the viscous boundary layer in flow studies, a special structure of the near-wall volumetric mesh is built by triangular prisms that construct quasi-structured, multiple near-boundary sub-layers...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
https://www.readbyqxmd.com/read/28207956/application-of-network-methods-for-understanding-evolutionary-dynamics-in-discrete-habitats
#10
Gili Greenbaum, Nina H Fefferman
In populations occupying discrete habitat patches, gene flow between habitat patches may form an intricate population structure. In such structures, the evolutionary dynamics resulting from interaction of gene flow patterns with other evolutionary forces may be exceedingly complex. Several models describing gene flow between discrete habitat patches have been presented in the population genetics literature; however, these models have usually addressed relatively simple settings of habitable patches, and have stopped short of providing general methodologies for addressing non-trivial gene flow patterns...
February 16, 2017: Molecular Ecology
https://www.readbyqxmd.com/read/28183069/a-dynamic-model-of-the-piezoelectric-traveling-wave-rotary-ultrasonic-motor-stator-with-the-finite-volume-method
#11
I A Renteria Marquez, V Bolborici
This manuscript presents a method to model in detail the piezoelectric traveling wave rotary ultrasonic motor (PTRUSM) stator response under the action of DC and AC voltages. The stator is modeled with a discrete two dimensional system of equations using the finite volume method (FVM). In order to obtain accurate results, a model of the stator bridge is included into the stator model. The model of the stator under the action of DC voltage is presented first, and the results of the model are compared versus a similar model using the commercial finite element software COMSOL Multiphysics...
January 31, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28181798/shape-morphing-materials-from-stimuli-responsive-hydrogel-hybrids
#12
Seog-Jin Jeon, Adam W Hauser, Ryan C Hayward
The formation of well-defined and functional three-dimensional (3D) structures by buckling of thin sheets subjected to spatially nonuniform stresses is common in biological morphogenesis and has become a subject of great interest in synthetic systems, as such programmable shape-morphing materials hold promise in areas including drug delivery, biomedical devices, soft robotics, and biomimetic systems. Given their ability to undergo large changes in swelling in response to a wide variety of stimuli, hydrogels have naturally emerged as a key type of material in this field...
February 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28163785/efficient-estimation-of-the-maximum-metabolic-productivity-of-batch-systems
#13
Peter C St John, Michael F Crowley, Yannick J Bomble
BACKGROUND: Production of chemicals from engineered organisms in a batch culture involves an inherent trade-off between productivity, yield, and titer. Existing strategies for strain design typically focus on designing mutations that achieve the highest yield possible while maintaining growth viability. While these methods are computationally tractable, an optimum productivity could be achieved by a dynamic strategy in which the intracellular division of resources is permitted to change with time...
2017: Biotechnology for Biofuels
https://www.readbyqxmd.com/read/28157986/fast-design-of-broadband-terahertz-diffusion-metasurfaces
#14
Jie Zhao, Qiang Cheng, Tian Qi Wang, Wei Yuan, Tie Jun Cui
A method for fast design of broadband terahertz diffusion metasurface is presented. The proposed metasurface is composed by three kinds of simply patterned elements with different resonant properties. To obtain the best broadband performance with the lowest backward reflections, a genetic algorithm is developed to manipulate the resonances for the fast determination of element geometries. An inverse discrete Fourier transform method is used to predict the scattering pattern of the metasurface with high accuracy and low time consumption, significantly enhancing the efficiency of the array-pattern design...
January 23, 2017: Optics Express
https://www.readbyqxmd.com/read/28155717/sph-dem-approach-to-numerically-simulate-the-deformation-of-three-dimensional-rbcs-in-non-uniform-capillaries
#15
Hasitha-Nayanajith Polwaththe-Gallage, Suvash C Saha, Emilie Sauret, Robert Flower, Wijitha Senadeera, YuanTong Gu
BACKGROUND: Blood continuously flows through the blood vessels in the human body. When blood flows through the smallest blood vessels, red blood cells (RBCs) in the blood exhibit various types of motion and deformed shapes. Computational modelling techniques can be used to successfully predict the behaviour of the RBCs in capillaries. In this study, we report the application of a meshfree particle approach to model and predict the motion and deformation of three-dimensional RBCs in capillaries...
December 28, 2016: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28147591/acoustic-scattering-for-3d-multi-directional-periodic-structures-using-the-boundary-element-method
#16
Mahmoud Karimi, Paul Croaker, Nicole Kessissoglou
An efficient boundary element formulation is proposed to solve three-dimensional exterior acoustic scattering problems with multi-directional periodicity. The multi-directional periodic acoustic problem is represented as a multilevel block Toeplitz matrix. By exploiting the Toeplitz structure, the computational time and storage requirements to construct and to solve the linear system of equations arising from the boundary element formulation are significantly reduced. The generalized minimal residual method is implemented to solve the linear system of equations...
January 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28133590/friction-phenomena-and-their-impact-on-the-shear-behaviour-of-granular-material
#17
Bettina Suhr, Klaus Six
In the discrete element simulation of granular materials, the modelling of contacts is crucial for the prediction of the macroscopic material behaviour. From the tribological point of view, friction at contacts needs to be modelled carefully, as it depends on several factors, e.g. contact normal load or temperature to name only two. In discrete element method (DEM) simulations the usage of Coulomb's law of friction is state of the art in modelling particle-particle contacts. Usually in Coulomb's law, for all contacts only one constant coefficient of friction is used, which needs to reflect all tribological effects...
2017: Comput Part Mech
https://www.readbyqxmd.com/read/28127720/dem-modelling-of-granule-rearrangement-and-fracture-behaviours-during-a-closed-die-compaction
#18
Ryoichi Furukawa, Kazunori Kadota, Tetsuro Noguchi, Atsuko Shimosaka, Yoshiyuki Shirakawa
The closed-die compaction behaviour of D-mannitol granules has been simulated by the discrete element method (DEM) to investigate the granule rearrangement and fracture behaviour during compaction which affects the compactibility of the tablet. The D-mannitol granules produced in a fluidized bed were modelled as agglomerates of primary particles connected by linear spring bonds. The validity of the model granule used in the DEM simulation was demonstrated by comparing to the experimental results of a uniaxial compression test...
January 26, 2017: AAPS PharmSciTech
https://www.readbyqxmd.com/read/28124766/why-granular-media-are-thermal-and-quite-normal-after-all
#19
Yimin Jiang, Mario Liu
Two approaches exist to account for granular dynamics: The athermal one takes grains as elementary, the thermal one considers the total entropy that includes microscopic degrees of freedom such as phonons and electrons. Discrete element method (DEM), granular kinetic theory and athermal statistical mechanics (ASM) belong to the first, granular solid hydrodynamics (GSH) to the second one. A discussion of the conceptual differences between both is given here, leading, among others, to the following insights: 1) While DEM and granular kinetic theory are well justified to take grains as athermal, any entropic consideration is far less likely to succeed...
January 2017: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/28114851/theoretical-and-experimental-analysis-of-amplitude-control-ablation-and-bipolar-ablation-in-creating-linear-lesion-and-discrete-lesions-for-treating-atrial-fibrillation
#20
Shengjie Yan, Xiaomei Wu, Weiqi Wang
PURPOSE: Radiofrequency (RF) energy is often used to create a linear lesion or discrete lesions for blocking the accessory conduction pathways for treating atrial fibrillation. By using finite element analysis, we study the ablation effect of amplitude control ablation mode (AcM) and bipolar ablation mode (BiM) in creating a linear lesion and discrete lesions in a 5-mm-thick atrial wall; particularly, the characteristic of lesion shape has been investigated in amplitude control ablation...
January 23, 2017: International Journal of Hyperthermia
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