An unconditionally stable staggered algorithm for transient finite element analysis of coupled thermoelastic problems

An unconditionally stable second order accurate implicit-implicit staggered procedure for the finite element solution of fully coupled thermoelasticity transient problems is proposed. The procedure is stabilized with a semi-algebraic augmentation technique. A comparative cost analysis reveals the superiority of the proposed computational strategy to other conventional staggered procedures. Numerical examples of one and two-dimensional thermomechanical coupled problems demonstrate the accuracy of the proposed numerical solution algorithm

Computational methods and software systems for dynamics and control of large space structures

Two key areas of crucial importance to the computer-based simulation of large space structures are discussed. The first area involves multibody dynamics (MBD) of flexible space structures, with applications directed to deployment, construction, and maneuvering. The second area deals with advanced software systems, with emphasis on parallel processing. The latest research thrust in the second area involves massively parallel computers

BDDC and FETI-DP under Minimalist Assumptions

The FETI-DP, BDDC and P-FETI-DP preconditioners are derived in a particulary simple abstract form. It is shown that their properties can be obtained from only on a very small set of algebraic assumptions. The presentation is purely algebraic and it does not use any particular definition of method components, such as substructures and coarse degrees of freedom. It is then shown that P-FETI-DP and BDDC are in fact the same. The FETI-DP and the BDDC preconditioned operators are of the same algebraic form, and the standard condition number bound carries over to arbitrary abstract operators of this form. The equality of eigenvalues of BDDC and FETI-DP also holds in the minimalist abstract setting. The abstract framework is explained on a standard substructuring example.Comment: 11 pages, 1 figure, also available at http://www-math.cudenver.edu/ccm/reports

Finite Volume/Element Discretization on Unstructured Meshes of the Multiscale Formulation of the Large Eddy Simulation Method and Application to Vortex Shedding

A finite volume/element discretization on tetrahedral meshes of the variation- al multiscale formulation of large eddy simulations is proposed for turbulent compressible flows. This discretization features an economical procedure based on agglomeration for separating a priori the scales, a corresponding projector for eliminating the small scales from the system of equations, and an effective control of the numerical dissipation induced by upwinding. The resulting LES method is validated with the three-dimensional numerical simulation of a low-speed flow past a square cylinder at M_¥ = 0.1 and Re = 22,000, and various comparisons with experimental data

Finite Volume/Element Discretization on Unstructured Meshes of the Multiscale Formulation of the Large Eddy Simulation Method and Application to Vortex Shedding

A finite volume/element discretization on tetrahedral meshes of the variation- al multiscale formulation of large eddy simulations is proposed for turbulent compressible flows. This discretization features an economical procedure based on agglomeration for separating a priori the scales, a corresponding projector for eliminating the small scales from the system of equations, and an effective control of the numerical dissipation induced by upwinding. The resulting LES method is validated with the three-dimensional numerical simulation of a low-speed flow past a square cylinder at M_¥ = 0.1 and Re = 22,000, and various comparisons with experimental data

Tunable Graphene Antennas for Selective Enhancement of THz-Emission

In this paper, we will introduce THz graphene antennas that strongly enhance the emission rate of quantum systems at specific frequencies. The tunability of these antennas can be used to selectively enhance individual spectral features. We will show as an example that any weak transition in the spectrum of coronene can become the dominant contribution. This selective and tunable enhancement establishes a new class of graphene-based THz devices, which will find applications in sensors, novel light sources, spectroscopy, and quantum communication devices

Perception against COVID-19 Threat Affecting the Behavior of Indonesia People Three Months after the Outbreak

BACKGROUND: In Indonesia, a new behavior has been introduced in the community to prevent COVID-19 transmission following 3 months of the COVID-19 outbreak. The Ministry of Health, Republic of Indonesia, names this new concept as “the adaptation of new behavior.” However, preventive measures and health protocols encouraged by the government have not yet yielded a significant impact on reducing the COVID-19 positivity rate. This unsuccessful outcome indicates that infective circulation is still occurring caused by incompliant to the health protocol. AIM: This study aimed to measure community perceptions against COVID-19 at the individual level. METHODS: A cross-sectional study with a total of 1687 respondents was performed. Questionnaires distributed thru sharing online links which contain questions on perception of vulnerability and severity of COVID-19. Chi-square test used in analysis to determine the difference in perception with respondents’ behavior. RESULTS: A total of 81.7% of respondents who had a perception of “susceptible to contract” performed behavior suited to recommendations and 81.2% study population had a perception of “COVID-19 is severe” executed behavior suited to the recommendation. CONCLUSION: This study demonstrated the establishment of government recommendations for COVID-19 infection did not guarantee the actual health practice/behavior in the community. The existing misconception of the perspective of seriousness/severity and susceptibility would prevent the country from flattening the curve

Vortex-type elastic structured media and dynamic shielding

The paper addresses a novel model of metamaterial structure. A system of spinners has been embedded into a two-dimensional periodic lattice system. The equations of motion of spinners are used to derive the expression for the chiral term in the equations describing the dynamics of the lattice. Dispersion of elastic waves is shown to possess innovative filtering and polarization properties induced by the vortextype nature of the structured media. The related homogenised effective behavior is obtained analytically and it has been implemented to build a shielding cloak around an obstacle. Analytical work is accompanied by numerical illustrations.Comment: 24 pages, 13 figure

A FETI method with a mesh independent condition number for the iteration matrix

We introduce a framework for FETI methods using ideas from the decomposition via Lagrange multipliers of H1 0 (Ω) derived by Raviart-Thomas [22] P.-A. Raviart, J.-M. Thomas, Primal Hybrid Finite Element Metho and complemented with the detailed work on polygonal domains developed by Grisvard [17] P. Grisvard, Singularities in Boundary value problems. Recherches en Mathématiques Appliquées, 22. Masson, 1992.. We compute the action of the Lagrange multipliers using the natural H 1/2 00 scalar product, therefore no consistency error appears. As a byproduct, we obtain that the condition number for the iteration matrix is independent of the mesh size and there is no need for preconditioning. This result improves the standard asymptotic bound for this condition number shown by Mandel-Tezaur in [19] J. Mandel, R. Tezaur, Convergence of a substructuring method with Lagrange multipliers. Numer. Math., 73 (1996), 473–487. Numerical results that confirm our theoretical analysis are presented.Nous proposons une nouvelle approche des méthodes FETI: la décomposition de domaine fait appel aux multiplicateurs de Lagrange tels qu’introduits par Raviart-Thomas [22] P.-A. Raviart, J.-M. Thomas, Primal Hybrid Finite Element Methods for second order eliptic equations. Math. Comp., 31 (1977), 391-413 et au traitement des domaines polygonaux dù á Grisvard [17] P. Grisvard, Singularities in Boundary value problems. Recherches en Mathématiques Appliquées, 22. Masson, 1992. Ces multiplicateurs utilisent le produit scalaire de H 1/2 00, de sorte qu’aucune erreur de consistance n’apparaît. En outre, nous prouvons que le nombre de condition de la matrice liée à chaque itération est indépendant de la taille du maillage, ce qui améliore le résultat de Mandel-Tezaur [19] J. Mandel, R. Tezaur, Convergence of a substructuring method with Lagrange multipliers. Numer. Math., 73 (1996), 473–487; par suite, aucun préconditionnement n’est nécessaire. Nous présentons des expériences numériques qui confirment notre analyse.Ministerio de Educación y Cienci