Read by QxMD icon Read

discrete element method

Saba Eshraghi, Ibrahim Esat, Amir A Mohagheghi
BACKGROUND: Hallux Valgus (HV) is the most common fore-foot deformity, which causes foot pain and limited motion that are encountered in podiatric and orthopedic practices. The purpose of this study is to develop a reliable pattern recognition method to identify the presence of HV based on plantar force measurements. METHOD: Forces at five discrete metatarsal regions are measured at discrete time intervals under the right foot. Under this method, it is hypothesized that force measurement at a given time interval is related to the forces at a previous time interval by using Markovian transition matrix (T matrix)...
March 11, 2018: Gait & Posture
Zhibing Yang, Ruben Juanes
Pore fluid pressure in a fault zone can be altered by natural processes (e.g., mineral dehydration and thermal pressurization) and industrial operations involving subsurface fluid injection and extraction for the development of energy and water resources. However, the effect of pore pressure change on the stability and slip motion of a preexisting geologic fault remains poorly understood; yet, it is critical for the assessment of seismic hazard. Here, we develop a micromechanical model to investigate the effect of pore pressure on fault slip behavior...
February 2018: Physical Review. E
M P A van den Ende, G Marketos, A R Niemeijer, C J Spiers
Intergranular pressure solution creep is an important deformation mechanism in the Earth's crust. The phenomenon has been frequently studied and several analytical models have been proposed that describe its constitutive behavior. These models require assumptions regarding the geometry of the aggregate and the grain size distribution in order to solve for the contact stresses and often neglect shear tractions. Furthermore, analytical models tend to overestimate experimental compaction rates at low porosities, an observation for which the underlying mechanisms remain to be elucidated...
January 2018: Journal of Geophysical Research. Solid Earth
Hao Li, Yidu Yang
This paper is devoted to the adaptive Morley element algorithms for a biharmonic eigenvalue problem in [Formula: see text] ([Formula: see text]). We combine the Morley element method with the shifted-inverse iteration including Rayleigh quotient iteration and the inverse iteration with fixed shift to propose multigrid discretization schemes in an adaptive fashion. We establish an inequality on Rayleigh quotient and use it to prove the efficiency of the adaptive algorithms. Numerical experiments show that these algorithms are efficient and can get the optimal convergence rate...
2018: Journal of Inequalities and Applications
Mengyuan Xu, Jing Yan, Yingsan Geng, Kun Zhang, Chao Sun
An innovative array of magnetic coils (the discrete Rogowski coil-RC) with the advantages of flexible structure, miniaturization and mass producibility is investigated. First, the mutual inductance between the discrete RC and circular and rectangular conductors are calculated using the magnetic vector potential (MVP) method. The results are found to be consistent with those calculated using the finite element method, but the MVP method is simpler and more practical. Then, the influence of conductor section parameters, inclination, and eccentricity on the accuracy of the discrete RC is calculated to provide a reference...
March 13, 2018: Sensors
Oleksandr Zelyak, B Gino Fallone, Joel St-Aubin
Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion...
March 12, 2018: Physics in Medicine and Biology
Domenico Ninno, Giovanni Cantele, Fabio Trani
We show that the central finite difference formula for the first and the second derivative of a function can be derived, in the context of quantum mechanics, as matrix elements of the momentum and kinetic energy operators on discrete coordinate eigenkets |xn〉 defined on a uniform grid. Starting from the discretization of integrals involving canonical commutations, simple closed-form expressions of the matrix elements are obtained. A detailed analysis of the convergence toward the continuum limit with respect to both the grid spacing and the derivative approximation order is presented...
March 8, 2018: Journal of Computational Chemistry
Sean T Hunt, Yuriy Román-Leshkov
Conspecuts Commercial and emerging renewable energy technologies are underpinned by precious metal catalysts, which enable the transformation of reactants into useful products. However, the noble metals (NMs) comprise the least abundant elements in the lithosphere, making them prohibitively scarce and expensive for future global-scale technologies. As such, intense research efforts have been devoted to eliminating or substantially reducing the loadings of NMs in various catalytic applications. These efforts have resulted in a plethora of heterogeneous NM catalyst morphologies beyond the traditional supported spherical nanoparticle...
March 6, 2018: Accounts of Chemical Research
Alexander Maslowski, Adam Wang, Mingshan Sun, Todd Wareing, Ian Davis, Josh Star-Lack
PURPOSE: To describe Acuros® CTS, a new software tool for rapidly and accurately estimating scatter in x-ray projection images by deterministically solving the linear Boltzmann transport equation (LBTE). METHODS: The LBTE describes the behavior of particles as they interact with an object across spatial, energy, and directional (propagation) domains. Acuros CTS deterministically solves the LBTE by modeling photon transport associated with an x-ray projection in three main steps: 1) Ray tracing photons from the x-ray source into the object where they experience their first scattering event and form scattering sources...
March 6, 2018: Medical Physics
Jacquelynn F Duron
Prosecution of child sexual abuse cases is an important aspect of a community's response for holding perpetrators accountable and protecting children. Differences in charging rates across jurisdictions may reflect considerations made in prosecutors' decision-making process. This mixed-methods, multiphase study used data from a Children's Advocacy Center in a suburban county in the Southern United States to explore the factors associated with child sexual abuse cases that are accepted for prosecution and the process followed by prosecutors...
March 2, 2018: Child Abuse & Neglect
Nan Ji, Tiantian Liu, Jingjie Xu, Longzhu Q Shen, Benzhuo Lu
Membrane channel proteins control the diffusion of ions across biological membranes. They are closely related to the processes of various organizational mechanisms, such as: cardiac impulse, muscle contraction and hormone secretion. Introducing a membrane region into implicit solvation models extends the ability of the Poisson-Boltzmann (PB) equation to handle membrane proteins. The use of lateral periodic boundary conditions can properly simulate the discrete distribution of membrane proteins on the membrane plane and avoid boundary effects, which are caused by the finite box size in the traditional PB calculations...
February 28, 2018: International Journal of Molecular Sciences
Rastin Matin, Marek Krzysztof Misztal, Anier Hernández-García, Joachim Mathiesen
The lattice Boltzmann method has become one of the standard techniques for simulating a wide range of fluid flows. However, the intrinsic coupling of momentum and space discretization restricts the traditional lattice Boltzmann method to regular lattices. Alternative off-lattice Boltzmann schemes exist for both single- and multiphase flows that decouple the velocity discretization from the underlying spatial grid. The current study extends the applicability of these off-lattice methods by introducing a finite element formulation that enables simulating contact line dynamics for partially wetting fluids...
January 2018: Physical Review. E
Josefina Nordström, Göran Alderborn, Göran Frenning
Compressibility and tablet forming ability (compactibility) of bimodal mixtures of differently sized granules formed from microcrystalline cellulose were studied experimentally and numerically with the discrete element method (DEM). Compression data was analysed using the Kawakita equation. A multi-body contact law that accounts for contact dependence resulting from plastic incompressibility/geometric hardening was used in the DEM simulations. The experimental Kawakita a and 1/b parameters both depended non-monotonically on composition (weight fraction of large particles)...
February 6, 2018: International Journal of Pharmaceutics
Huan Huan Zhang, Wei E I Sha, Zhi Xiang Huang, Guang Ming Shi
Thermal management and simulation are becoming increasingly important in many areas of engineering applications. There are three cooling routes for thermal management, namely thermal conduction, thermal convection and thermal radiation, among which the first two approaches have been widely studied and applied, while the radiation cooling has not yet attracted much attention in terrestrial environment because it usually contributes less to the total amount of thermal dissipation. Thus the simulation method for radiation cooling was also seldom noticed...
February 8, 2018: Scientific Reports
Kewei Li, Ray W Ogden, Gerhard A Holzapfel
Recently, micro-sphere-based methods derived from the angular integration approach have been used for excluding fibres under compression in the modelling of soft biological tissues. However, recent studies have revealed that many of the widely used numerical integration schemes over the unit sphere are inaccurate for large deformation problems even without excluding fibres under compression. Thus, in this study, we propose a discrete fibre dispersion model based on a systematic method for discretizing a unit hemisphere into a finite number of elementary areas, such as spherical triangles...
January 2018: Journal of the Royal Society, Interface
Axel Målqvist, Anna Persson
We use the local orthogonal decomposition technique introduced in Målqvist and Peterseim (Math Comput 83(290):2583-2603, 2014) to derive a generalized finite element method for linear and semilinear parabolic equations with spatial multiscale coefficients. We consider nonsmooth initial data and a backward Euler scheme for the temporal discretization. Optimal order convergence rate, depending only on the contrast, but not on the variations of the coefficients, is proven in the [Formula: see text]-norm. We present numerical examples, which confirm our theoretical findings...
2018: Numerische Mathematik
M Jake Pushie, Andrew Crawford, Nicole J Sylvain, Huishu Hou, Mark J Hackett, Graham N George, Michael E Kelly
Stroke exacts a heavy financial and economic burden, is a leading cause of death, and the leading cause of long term disability in those who survive. The penumbra surrounds the ischemic core of the stroke lesion and is comprised of metabolically stressed cells that may become part of the growing infarct or can potentially recover. Preserving the penumbra to promote functional recovery is a central goal in stroke research. Using synchrotron-based X-ray fluorescence imaging the elemental changes in brain tissue following ischemic stroke can be visualized...
January 25, 2018: ACS Chemical Neuroscience
Yingying Guo, Pengfei Yuan, Jianan Zhang, Yongfeng Hu, Ibrahim Saana Amiinu, Xin Wang, Jigang Zhou, Huicong Xia, Zhibo Song, Qun Xu, Shichun Mu
Structural and compositional engineering atomic-scaled metal-N-C catalysts is important yet challenging in boosting their performance for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Here, a boron (B)-doped Co-N-C active sites confined in hierarchical porous carbon sheets (denoted as Co-N,B-CSs) were obtained by soft template self-assembly pyrolysis method. Significantly, the introduced B element gives an electron deficient site, that can actives the electron transfer around the Co-N-C sites, strength the interaction with oxygenated species, and thus accelerate reaction kinetics in the 4e- processed oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)...
January 23, 2018: ACS Nano
Sandip Mandal, D V Khakhar
We report a transition from a disordered state to an ordered state in the flow of nearly monodisperse granular matter flowing in an inclined channel with planar slide walls and a bumpy base, using discrete element method simulations. For low particle-sidewall friction coefficients, the flowing particles are disordered, however, for high sidewall friction, an ordered state is obtained, characterized by a layering of the particles and hexagonal packing of the particles in each layer. The extent of ordering, quantified by the local bond-orientational order parameter, varies in the cross section of the channel, with the highest ordering near the sidewalls...
November 2017: Physical Review. E
Arman Pazouki, Michał Kwarta, Kyle Williams, William Likos, Radu Serban, Paramsothy Jayakumar, Dan Negrut
We summarize and numerically compare two approaches for modeling and simulating the dynamics of dry granular matter. The first one, the discrete-element method via penalty (DEM-P), is commonly used in the soft matter physics and geomechanics communities; it can be traced back to the work of Cundall and Strack [P. Cundall, Proc. Symp. ISRM, Nancy, France 1, 129 (1971); P. Cundall and O. Strack, Geotechnique 29, 47 (1979)GTNQA80016-850510.1680/geot.1979.29.1.47]. The second approach, the discrete-element method via complementarity (DEM-C), considers the grains perfectly rigid and enforces nonpenetration via complementarity conditions; it is commonly used in robotics and computer graphics applications and had two strong promoters in Moreau and Jean [J...
October 2017: Physical Review. E
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"