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Background: in patients with heart failure (HF) and atrial fibrillation (AF), AF ablation improves left ventricular ejection fraction (LVEF), along with prognosis, in a variable percentage of patients. We aimed to investigate the predictors of LVEF recovery after AF ablation and to develop a prediction model for individualized assessment. Methods: we conducted an observational, retrospective, single-centre study on 111 consecutive patients with AF and HF with impaired LVEF (

We explore the application of some recent results in exponential analysis and sparse interpolation to underwater acoustics, in a joint effort from marine engineers and computational mathematicians. The fact that, in practice, the sampling rate used for the recording of an echoed signal is often a multiple of the Nyquist rate, is regarded as a constraint on the cost and performance of echo sounding devices. Here we illustrate how the latter can be overcome, using a new regular sampling scheme, that can even go well below the Nyquist rate. In the numerical examples an average of 20-25 % of the Nyquist rate is amply sufficient to reliably recognize and reconstruct the echo. The sparse sub-Nyquist method under consideration allows to recover from possible aliasing introduced by the subsampling. The technique does not need newly designed hardware, has low computational complexity and uses a small number of samples.

High pressures on the soil surface by action of heavy machinery and tillage process cause soil compaction and hardpan layers formation. De-compaction is a energy demanding operation applied to break deeply compacted soil for agricultural uses. Three dimensional simulations of soil decompaction are presented based on a soil-tool interaction model implemented in DEMeter software. Formulation of soil-soil and soil-tool interaction are combined into an elastic-plastic particle based model for soil deformation and evaluated in different tension states among soil particles; The macromechanical input parameters include: adhesion, friction, Young’s modulus, Poisson’s coefficient, elastic limit, plastic limit and soil density. Compression triaxial tests and shear box tests were carried out in order to obtain the required mechanical properties for a tropical clay soil. Simulations of unconfined compression tests using different particle sizes and inter-particle tension were used to calibrate the model to experimental stress-strain curves. The performance of complex tillage tools geometries is tested with 3D simulations and evaluated based on the reaction force on the tool as a function of time and displacement. The results show qualitative and quantitative adjusts of real patter of soil behaviour.

We describe a multiscale method to simulate the deformation of plant tissue. At the cellular scale we use a combination of Smoothed Particle Hydrodynamics (SPH) and discrete elements to model the geometrical structure and basic properties of individual plant cells. At the coarse level, the material is described by the standard continuum approach without explicitly constructing a constitutive equation. Instead, the coarse scale finite element model uses simulations with the fine (cellular) scale model in small subdomains, called Representative Volume Elements (RVEs), to determine the necessary coarse scale variables; such as the stress and the elasticity and viscosity tensors. We present an implicit time integration scheme for the coarse finite element model allowing much larger time steps than possible with explicit methods. Computation of the Cauchy stress from an RVE is straightforward by volume averaging over the RVE. In this work, we use forward finite differencing of the objective Truesdell stress rate to estimate both the fourth order elasticity and viscosity tensors. These tensors are then used to construct the coarse scale stiffness and damping matrices, required for implicit integration. ispartof: TW Reports nrpages: 15 status: published

We present a multiscale method for the simulation of large viscoelastic deformations and show its applicability to biological tissue such as plant tissue. At the microscopic level we use a particle method to model the geometrical structure and basic properties of individual cells. The cell fluid, modeled as a viscoelastic fluid by means of Smoothed Particle Hydrodynamics (SPH) is enclosed in an elastic cell wall, modeled by discrete elements. The macroscopic equation and stress tensor are derived from the SPH model by means of the Generalized Mathematical Homogenization technique. The macroscopic domain is discretized using standard finite elements, where the stress tensor is evaluated from microscopic simulations in small sub-domains, called Representative Volume Elements (RVEs). Our emphasis is on reconstructing the microscopic state inside the RVE for given macroscopic deformation and velocity gradient. We propose a scheme to initialize the RVE consistently not only with the macroscopic variables, but also with the microscopic dynamics. ispartof: TW Reports nrpages: 21 status: published

ispartof: Proceedings of the 4th SPHERIC workshop vol:4 ispartof: 4th SPHERIC Workshop location:Nantes date:26 May - 29 May 2009 status: published

We present a micro-macro method for the simulation of large elastic deformations of plant tissue. At the microscopic level we use a discrete element model to describe the geometrical structure and basic properties of individual plant cells. The macroscopic domain is discretized using standard finite elements, in which the unknown macroscopic material properties (the stress-strain relation) are computed using the microscopic model in small sub-domains, called representative volume elements (RVEs), centered around the macroscopic quadrature points. The boundary conditions for these RVEs are derived from the macroscopic deformation gradient. The computation of the macroscopic stress tensor is based on the definition of virial stress, as defined in molecular dynamics. The anisotropic Eulerian elasticity tensor is estimated using a forward finite difference approximation for the Truesdell rate of the Cauchy stress tensor. We investigate the influence of the size of the RVE and the boundary conditions via numerical experiments. We show that the multi-scale method converges to the solution of the full microscopic simulation, both for globally and adaptively refined finite element meshes and achieves a significant speed-up compared with the full microscopic simulation. ispartof: TW Reports nrpages: 21 status: published

Humidification of the cooling air during long term storage of horticultural products helps to prevent moisture and quality losses. High pressure fogging is one of the few systems that can be used in ultra low oxygen storage rooms. The method relies on the efficient evaporation of the microdrops in the spray. A three-dimensional computational fluid dynamics (CFD) model was developed, validated and applied to predict the storage room air velocity, temperature and humidity distributions, and fate of the water droplets that were sprayed for humidifying the storage room. An Eulerian-Lagrangian multiphase flow model was used. The model takes into account two-way coupling with turbulent dispersion and droplet evaporation. The droplet diameter distribution was measured and used as an input to the model. The product loaded in boxes in a stack was considered as a porous medium, where the loss coefficients to the three orthogonal directions were determined from a combined discrete element–CFD simulation. The dynamic behaviour of the fan and the cooler was also taken into account. Humidification increased the room relative humidity and the cooling rate. Decreasing the application pressure increased the amount of droplets deposited on the top of the stack. Good agreement was found between predicted and measured results. ispartof: AgEng 2008 ispartof: AgEng 2008 location:Crete date:23 Jun - 25 Jun 2008 status: published