Search

© 2018 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works., [EN] This work presents a finite-element study of the Debye memory in piezoelectric devices. The memory dependence is due to the spontaneous polarization of the electric dipoles, and it can be understood as a transient viscosity-like effect. The formulation assumes a small strain and rotation hypothesis, and the main contribution is the inclusion of the time-dependent constitutive behavior. For this purpose, a unique numerical formulation that uses convolution integrals is developed to solve the time-dependent electric constitutive equation. A consistent and monolithic finite-element formulation is then obtained and implemented. Finally, a commercial piezoelectric device is simulated for two operational modes, an actuator and a sensor. Several important conclusions on the coupled mechanical and electric fields are reported, and the stability of the time integration scheme is tested by representing the time evolution of the electromechanic energy.

Marek’s disease (MD) is a highly contagious pathogenic and oncogenic disease primarily affecting chickens. However, the mechanisms of genetic resistance for MD are complex and not fully understood. MD-resistant line 63 and MD-susceptible line 72 are two highly inbred progenitor lines of White Leghorn. Recombinant Congenic Strains (RCS) were developed from these two lines, which show varied susceptibility to MD. We investigated genetic structure and genomic signatures across the genome, including the line 63 and line 72, six RCSs, and two reciprocally crossed flocks between the lines 63 and 72 (F1 63 × 72 and F1 72 × 63) using Affymetrix® Axiom® HD 600 K genotyping array. We observed 18 chickens from RCS lines were specifically clustered into resistance sub-groups distributed around line 63. Additionally, homozygosity analysis was employed to explore potential genetic components related to MD resistance, while runs of homozygosity (ROH) are regions of the genome where the identical haplotypes are inherited from each parent. We found several genes including SIK, SOX1, LIG4, SIK1 and TNFSF13B were contained in ROH region identified in resistant group (line 63 and RCS), and these genes have been reported that are contribute to immunology and survival. Based on FST based population differential analysis, we also identified important genes related to cell death and anti-apoptosis, including AKT1, API5, CDH13, CFDP and USP15, which could be involved in divergent selection during inbreeding process. Our findings offer valuable insights for understanding the genetic mechanism of resistance to MD and the identified genes could be considered as candidate biomarkers in further evaluation.

This dissertation presents the formulation and validation of a new 3d mixed cable element that is based on a two-field variational formulation and is suitable for the nonlinear static and dynamic analysis of cable structures.The new cable element is derived in general curvilinear coordinates under finite deformations, and identifies conjugate strain and stress measures for the nonlinear catenary problem. The formulation uses the weak form of the strain-displacement relation and the principle of virtual work to propose two numerical implementations of the element, one with a continuous axial force distribution and one with a discontinuous one.This dissertation also proposes a new filtered energy-momentum conserving algorithm for obtaining the dynamic response of cable structures in time. This new algorithm exactly conserves the Hamiltonian structure of the two-field mixed catenary problem for any {non\-linear} elastic complementary energy, and provides a consistent time integration in the case of inelastic material response. A postprocessing Savitzky-Golay filter is included to address the high-frequency contributions that appear in cables with a large sag-to-span ratio, without jeopardizing the desired conserving properties.The new element and the consistent time integration scheme are first validated under nonlinear elastic material response with several benchmark problems from the literature. In these examples, the mixed cable element obtains very accurate results for coarse meshes, and displays especially accurate axial force distributions compared to other models. For cables with a small sag-to-span ratio, the energy-conserving scheme and the Newmark method yield nearly identical results, while in the case of cables with a large sag-to-span ratio, for which the Newmark time integrator diverges, the new scheme gives accurate results and exactly conserves the total energy of the system.The proposed formulations are also validated under viscoelastic material respon

This paper presents a family of finite elements for the nonlinear static and dynamic analysis of cables based on a mixed variational formulation in curvilinear coordinates and finite deformations. This formulation identifies stress measures, in the form of axial forces, and conjugate deformation measures for the nonlinear catenary problem. The continuity requirements lead to two distinct implementations: one with a continuous axial force distribution and one with a discontinuous. Two examples from the literature on nonlinear cable analysis are used to validate the proposed formulation for St VenantKirchhoff elastic materials. These studies show that displacements and axial forces are captured with high accuracy for both the static and the dynamic case.

This paper proposes a general finite-element procedure for the nonlinear analysis of cables based on a mixed variational formulation in curvilinear coordinates with finite deformations. The formulation accounts for nonlinear elasticity and inelasticity, overcoming the limitation of recent numerical approaches which integrate explicitly the global balance of linear momentum for a linear elastic material with infinitesimal deformations. The formulation uses a weak form of the catenary problem and of the strain-displacement relation to derive a new family of cable finite elements with a continuous or discontinuous axial force field. Several examples from the literature on nonlinear cable analysis are used to validate the proposed formulation for St. Venant-Kirchhoff elastic materials and neo-Hookean materials. These studies show that the proposed formulation captures the displacements and the axial force distribution with high accuracy using a small number of finite elements., Peer Reviewed, Postprint (author's final draft)