Computational Fluid Mechanics for Civil Engineering Applications

Scientific conference (2012, May 23)

Computational Homogenization for Laminated Ferromagnetic Cores in Magnetodynamics

in IEEE Transactions on Magnetics (2013), 49(5), 2049-2052

In this paper, we investigate the modeling of ferromagnetic multiscale materials. We propose a computational homogenization technique based on the heterogeneous multiscale method (HMM) that includes both ... [more ▼]

In this paper, we investigate the modeling of ferromagnetic multiscale materials. We propose a computational homogenization technique based on the heterogeneous multiscale method (HMM) that includes both eddy-current and hysteretic losses at the mesoscale. The HMM comprises: 1) a macroscale problem that captures the slow variations of the overall solution; 2) many mesoscale problems that allow to determine the constitutive law at the macroscale. As application example, a laminated iron core is considered. [less ▲]

A Computational Homogenization Method for the Evaluation of Eddy Current in Nonlinear Soft Magnetic Composites

in Proceeding of the 9th International Symposium on Electric and Magnetic Fields, EMF 2013 (2013, April 23)

The use of the soft magnetic composite (SMC) in electric devices has increased in recent years. These materials made from a metallic powder compacted with a dielectric binder are a good alternative to ... [more ▼]

The use of the soft magnetic composite (SMC) in electric devices has increased in recent years. These materials made from a metallic powder compacted with a dielectric binder are a good alternative to laminated ferromagnetic structures as their granular mesoscale structure allows to significantly reduce the eddy current losses. Furthermore unlike the laminated ferromagnetic structures, SMC exhibit isotropic magnetic properties what makes them good candidates for manufacturing machines with 3D flux paths. The isotropy of the thermal conductivity also allows for a more efficient heat dissipation. The use of classical numerical methods such as the finite element method to study the behavior of SMC is computational very expensive. Indeed a very fine mesh would be required in order to capture fine scale variations i.e. variations at level of metallic grains whence the use of multiscale methods for modelling SMC. The application of multiscale method to study the behaviour of SMC is relatively recent. In (A. Bordianu et al “A Multiscale Approach to Predict Classical Losses in Soft Magnetic Composites”, IEEE Trans. Mag., vol. 48, no. 4, 2012.), the authors used a homogenization technique to compute electrical and magnetic constitutive laws on a representative volume element (RVE). These laws were then used in finite element computations. Herein, the RVE has been chosen to account for the grain- grain contact that can occur in a actual SMC structure due to the compaction process and that can lead to the appearance of macroscale eddy currents. In this paper, we will extend the computational homogenization method success- fully used for modelling the behaviour of laminated ferromagnetic cores in mag- netodynamics (I. Niyonzima et al “Computational Homogenization for Laminated Ferromagnetic Cores in Magnetodynamics”, in Proc. of the 15th Biennal Confer- ence on Electromagnetic Field Computation, 2012) to the case of SMC. The method is based on the heterogeneous multiscale method (HMM) and couples two types of problems: a macroscale problem that captures the slow variations of the overall so- lution and many microscale problems that allow to determine the constitutive laws at the macroscale. The choice of RVE will also be discussed. [less ▲]

Computational investigation and experimental considerations for the classical implementation of a full adder on SO2 by optical pump-probe schemes

in Journal of Chemical Physics (2008), 128(19),

Following the scheme recently proposed by Remacle and Levine [Phys. Rev. A 73, 033820 (2006)], we investigate the concrete implementation of a classical full adder on two electronic states ((X) over tilde ... [more ▼]

Following the scheme recently proposed by Remacle and Levine [Phys. Rev. A 73, 033820 (2006)], we investigate the concrete implementation of a classical full adder on two electronic states ((X) over tilde (1)A(1) and (C) over tilde B-1(2)) of the SO2 molecule by optical pump-probe laser pulses using intuitive and counterintuitive (stimulated Raman adiabatic passage) excitation schemes. The resources needed for providing the inputs and reading out are discussed, as well as the conditions for achieving robustness in both the intuitive and counterintuitive pump-dump sequences. The fidelity of the scheme is analyzed with respect to experimental noise and two kinds of perturbations: The coupling to the neighboring rovibrational states and a finite rotational temperature that leads to a mixture for the initial state. It is shown that the logic processing of a full addition cycle can be realistically experimentally implemented on a picosecond time scale while the readout takes a few nanoseconds. (c) 2008 American Institute of Physics. [less ▲]

Computational modeling in tissue engineering

Book published by Springer - 1 (2013)

One of the major challenges in tissue engineering is the translation of biological knowledge on complex cell and tissue behavior into a predictive and robust engineering process. Mastering this complexity ... [more ▼]

One of the major challenges in tissue engineering is the translation of biological knowledge on complex cell and tissue behavior into a predictive and robust engineering process. Mastering this complexity is an essential step towards clinical applications of tissue engineering. This volume discusses computational modeling tools that allow studying the biological complexity in a more quantitative way. More specifically, computational tools can help in: (i) quantifying and optimizing the tissue engineering product, e.g. by adapting scaffold design to optimize micro-environmental signals or by adapting selection criteria to improve homogeneity of the selected cell population; (ii) quantifying and optimizing the tissue engineering process, e.g. by adapting bioreactor design to improve quality and quantity of the final product; and (iii) assessing the influence of the in vivo environment on the behavior of the tissue engineering product, e.g. by investigating vascular ingrowth. The book presents examples of each of the above mentioned areas of computational modeling. The underlying tissue engineering applications will vary from blood vessels over trachea to cartilage and bone. For the chapters describing examples of the first two areas, the main focus is on (the optimization of) mechanical signals, mass transport and fluid flow encountered by the cells in scaffolds and bioreactors as well as on the optimization of the cell population itself. In the chapters describing modeling contributions in the third area, the focus will shift towards the biology, the complex interactions between biology and the micro-environmental signals and the ways in which modeling might be able to assist in investigating and mastering this complexity. The chapters cover issues related to (multiscale/multiphysics) model building, training and validation, but also discuss recent advances in scientific computing techniques that are needed to implement these models as well as new tools that can be used to experimentally validate the computational results. [less ▲]

Computational modelling of calcium mediated bone regeneration

Poster (2010, November 26)

Computational modelling of peri-implant healing

in Middleton, J.; Jones, M. L.; Shrive, N. (Eds.) Proceedings of the 8th interantional symposium on Computer Methods in Biomechanics and Biomedical Engineering (2008)

Computational Study Of Lipid-Destabilizing Protein Fragments: Towards A Comprehensive View Of Tilted Peptides

in Proteins-Structure Function and Genetics (2001), 44(4), 435-47

Tilted peptides are short sequence fragments (10-20 residues long) that possess an asymmetric hydrophobicity gradient along their sequence when they are helical. Due to this gradient, they adopt a tilted ... [more ▼]

Tilted peptides are short sequence fragments (10-20 residues long) that possess an asymmetric hydrophobicity gradient along their sequence when they are helical. Due to this gradient, they adopt a tilted orientation towards a single lipid/water interface and destabilize the lipids. We have detected those peptides in many different proteins with various functions. While being all tilted-oriented at a single lipid/water interface, no consensus sequence can be evidenced. In order to better understand the relationships between their lipid-destabilizing activity and their properties, we used IMPALA to classify the tilted peptides. This method allows the study of interactions between a peptide and a modeled lipid bilayer using simple restraint functions designed to mimic some of the membrane properties. We predict that tilted peptides have access to a wide conformational space in membranes, in contrast to transmembrane and amphipathic helices. In agreement with previous studies, we suggest that those metastable configurations could lead to the perturbation of the acyl chains organization and could be a general mechanism for lipid destabilization. Our results further suggest that tilted peptides fall into two classes: those from proteins acting on membrane behave differently than destabilizing fragments from interfacial proteins. While the former have equal access to the two layers of the membrane, the latter are confined within a single lipid layer. This could be in relation with the organization of lipid substrate on which the peptides physiologically act. [less ▲]

Computational study of the error distribution in right-censored and selection-biased regression models

Conference (2010, May 18)

Consider the regression model Y = m(X) + σ(X) Ɛ where m(X) =E [Y|X] and σ²(X) = Var [Y|X] are unknown smooth functions and the error Ɛ, with unknown distribution, is independent of X. The pair (X,Y) is ... [more ▼]

Consider the regression model Y = m(X) + σ(X) Ɛ where m(X) =E [Y|X] and σ²(X) = Var [Y|X] are unknown smooth functions and the error Ɛ, with unknown distribution, is independent of X. The pair (X,Y) is subject to generalized selection bias and the response to right censoring. We construct a new estimator for the cumulative distribution function of the error Ɛ, and develop a bootstrap technique to select the smoothing parameter involved in the procedure. The estimator is studied via extended simulations and applied to real unemployment data. [less ▲]

Computational treatment of the error distribution in nonparametric regression with right-censored and selection-biased data

Conference (2010, August 24)

Consider the regression model Y = m(X) + σ(X) Ɛ , where m(X) = E[Y|X] and σ²(X) = Var[Y|X] are unknown smooth functions and the error Ɛ (with unknown distribution) is independent of X. The pair (X;Y) is ... [more ▼]

Consider the regression model Y = m(X) + σ(X) Ɛ , where m(X) = E[Y|X] and σ²(X) = Var[Y|X] are unknown smooth functions and the error Ɛ (with unknown distribution) is independent of X. The pair (X;Y) is subject to generalized selection bias and the response to right censoring. We construct a new estimator for the cumulative distribution function of the error Ɛ , and develop a bootstrap technique to select the smoothing parameter involved in the procedure. The estimator is studied via extended simulations and applied to real unemployment data. [less ▲]