The objective of this work is to establish a generic continuum-based computational concept for finite growth of living biological tissues. The underlying idea is the introduction of an incompatible growth configuratio...
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The objective of this work is to establish a generic continuum-based computational concept for finite growth of living biological tissues. The underlying idea is the introduction of an incompatible growth configuration which naturally introduces a multiplicative decomposition of the deformation gradient into an elastic and a growth part. The two major challenges of finite growth are the kinematic characterization of the growth tensor and the identification of mechanical driving forces for its evolution. Motivated by morphological changes in cell geometry, we illustrate a micromechanically motivated ansatz for the growth tensor for cardiac tissue that can capture both strain-driven ventricular dilation and stress-driven wall thickening. Guided by clinical observations, we explore three distinct pathophysiological cases: athlete's heart, cardiac dilation, and cardiac wall thickening. We demonstrate the computational solution of finite growth within a fully implicit incremental iterative Newton-Raphson based finite element solution scheme. The features of the proposed approach are illustrated and compared for the three different growth pathologies in terms of a generic bi-ventricular heart model. (C) 2010 Elsevier Ltd. All rights reserved.
The main purpose of this paper is to perform a sensitivity analysis where we quantify and analyse the effects on the mean of the profit on an Income Protection policy and two risk measures of changing the values of th...
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The main purpose of this paper is to perform a sensitivity analysis where we quantify and analyse the effects on the mean of the profit on an Income Protection policy and two risk measures of changing the values of the transition intensities. All the calculations carried out are based on a multiple state model for Income Protection proposed in Continuous Mortality Investigation Committee (Continuous Mortality Investigation Reports 1991;12). Within this model, we derive a formula for the mean of the profit, which enables to evaluate it more efficiently. In order to calculate the two risk measures we use the numerical algorithms for the calculation of the moments of the profit proposed by Waters (Insurance: Mathematics and Economics 1990;9:101-113). We carry out the sensitivity analysis considering two different situations: in the first situation, we update the premium rates used to calculate the moments of the profit, according to the changes in the values of the transition intensities;in the second one, we do not update the premium rates. Both analyses are of practical interest to insurance companies selling Income Protection policies. Copyright (C) 2009 John Wiley & Sons, Ltd.
THIS Engineering Note follows a previous paper in which Avanzini [1] presented a transverse-eccentricity-vector-based algorithm to solve the classical Lambert problem: that is, the determination of a transfer orbit ha...
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THIS Engineering Note follows a previous paper in which Avanzini [1] presented a transverse-eccentricity-vector-based algorithm to solve the classical Lambert problem: that is, the determination of a transfer orbit having a specified flight time and connecting two position vectors [2]. In Avanzini's [1] paper, the eccentricity vector of the transfer orbit can be decomposed into a constant component parallel to the chord connecting the two points and a variable transverse component in the direction perpendicular to it on the orbit plane. Given the two fixed position vectors, the transfer time can be expressed as a function of the transverse eccentricity e(T). Compared with the elegant Battin's method, the derivation of this simple Lambert algorithm seems to be considerably less demanding from the mathematical standpoint and physically more intuitive [1]. However, with the only consideration of direct-transfer arcs, neither the explicit expression of the derivative of the transfer time with respect to the transverse eccentricity nor the multiple-revolution solutions based on the novel method were given in [1].
This paper deals with the prediction of the overall behavior of a class of two-phase elasto-viscoplastic composites, based on mean-field homogenization. For this, important improvements are made to the recently-propos...
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This paper deals with the prediction of the overall behavior of a class of two-phase elasto-viscoplastic composites, based on mean-field homogenization. For this, important improvements are made to the recently-proposed affine formulation. The latter theory linearizes the rate-dependent inelastic constitutive equations of each phase's material and transforms them into fictitious linear thermo-elastic relations in the Laplace-Carson domain. The main contributions of the present work are threefold. Firstly, complete mathematical developments including a full treatment of internal variables are carried out, enabling the modeling of the response under unloading and cyclic histories. Secondly, robust and accurate computational algorithms are proposed. Thirdly, an extensive validation of the predictions against reference unit cell finite element results is conducted for a variety of materials and loadings. A good agreement between predictions and reference results is observed. (c) 2005 Elsevier Ltd. All rights reserved.
Structure-preserving numerical techniques for computation of stable deflating subspaces, with applications in control systems design, are presented. The techniques use extended skew-Hamiltonian/Hamiltonian matrix penc...
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Structure-preserving numerical techniques for computation of stable deflating subspaces, with applications in control systems design, are presented. The techniques use extended skew-Hamiltonian/Hamiltonian matrix pencils, and specialized algorithms to exploit their structure: the symplectic URV decomposition, periodic QZ algorithm, solution of periodic Sylvester-like equations, etc. The structure-preserving approach has the potential to avoid the numerical difficulties which are encountered for a traditional, non-structured solution, returned by the currently available software tools.
In this paper we discuss the one dimensional heat equation and the wave equation subject to nonlocal conditions. We use the method of Laplace transforms. Finally, we obtain the solution by using a numerical technique ...
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In this paper we discuss the one dimensional heat equation and the wave equation subject to nonlocal conditions. We use the method of Laplace transforms. Finally, we obtain the solution by using a numerical technique for inverting the Laplace transforms.
The control of complex forming processes (e.g. glass forming processes) is a challenging topic due to the mostly strongly nonlinear behavior and the spatial distributed nature of the process. In this paper a new appro...
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The control of complex forming processes (e.g. glass forming processes) is a challenging topic due to the mostly strongly nonlinear behavior and the spatial distributed nature of the process. In this paper a new approach for the real-time control of a spatial distributed temperature profile of an industrial glass forming process is presented. As the temperature in the forming zone cannot be measured directly, it is estimated by the numerical solution of the partial differential equation for heat transfer by a finite element scheme. As the dimension of the state space model, which is yield by the FE algorithm, is too large for real-time optimization, a model reduction concept has been developed. The numerical solution of the optimization problem is performed by the solver HQP (Huge Quadratic Programming). Results of the NMPC concept are compared with conventional PI control results. It is shown that NMPC stabilizes the temperature of the forming zone much better than PI control. The proposed NMPC scheme is robust against model mismatch of the disturbance model. Furthermore, the allowed parameter settings for a real-time application (i.e. control horizon, sampling period) have been determined. The approach can easily be adapted to other forming processes where the temperature profile shall be controlled.
Phase change problems are of practical importance and can be found in a wide range of engineering applications. In the present paper, two proposed numerical algorithms are developed;the first one is general for phase ...
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Phase change problems are of practical importance and can be found in a wide range of engineering applications. In the present paper, two proposed numerical algorithms are developed;the first one is general for phase change problems, while the second one is for ablation problems. The boundary elements method is used as a mathematical tool in conjunction with the proposed algorithms. Two test examples were solved and the results agree with the physics of the problems. (C) 2009 Elsevier Ltd. All rights reserved.
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