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Elements Used (element + used)

Distribution by Scientific Domains
Engineering57%
Physics and Astronomy28%

Selected Abstracts

Lower and upper bound estimation of isotropic and orthotropic fracture mechanics problems using elements with rotational degrees of freedom

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2008
Antoinette de Klerk
Abstract We use Rice's path-independent J integral, as well as its dual, the I* integral, to estimate lower and upper bounds of the stress intensity factor K in linear elastic fracture mechanics problems. The elements used contain rotational degrees of freedom, and are derived from the correct energy principles to guarantee path independence of the integrals. That is, the displacement-based elements used in calculating the J integral are derived from the principle of potential energy; the assumed stress elements used in calculating the I* integral are derived from complementary energy principles. For lower bound estimation in particular, elements with drilling degrees of freedom are advantageous, due to their superior accuracy. Numerical results are presented for isotropic and orthotropic mode I and mode II fracture mechanics problems. In addition, we reflect on suitable finite element integration schemes, and applicable values for the problem dependent penalty parameter , which is used in deriving the elements. Copyright © 2006 John Wiley & Sons, Ltd. [source]

3-D nested eigenanalysis on finite element grids

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2006
Giorgio Pini
Abstract The computation of several of the leftmost eigenpairs of generalized symmetric eigenproblems in 3-D finite element (FE) discretizations is addressed using the nested iteration deflation accelerated conjugate gradient (NI-DACG) method previously studied and improved by the authors in a 2-D framework. Numerical results from the flow (diffusion type) equation integrated over tetrahedral FE shows speed-ups relative to DACG ranging between 2 up to more than 10 depending on the aspect ratio of the elements used. NI-DACG also compares favourably with the performance of IRAM, i.e. the implicit restarted Arnoldi method, implemented in the eigenvalue package ARPACK. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Platinum group elements in impactites of the ICDP Chicxulub drill core Yaxcopoil-1: Are there traces of the projectile?

METEORITICS & PLANETARY SCIENCE, Issue 6 2004
Roald Tagle
These are the main elements used for projectile identification. They were determined by nickel sulfide fire assay combined with inductively coupled plasma mass spectrometry. The concentration of PGE in the samples are low. The concentration patterns of the suevite samples resemble the pattern of the continental crust. We conclude that any meteoritic fraction in these samples is below 0.05%. A syn- and post-impact modification of the PGE pattern from meteoritic toward a continental crust pattern is very unlikely. The globally distributed fallout at the Cretaceous-Tertiary (K/T) boundary, however, has high PGE concentrations. Therefore, the lack of a significant meteoritic PGE signature in the crater is not an argument for a PGE-poor impactor. Taking the results of three-dimensional numerical simulations of the Chicxulub event into account, the following conclusions are drawn: 1) The main fraction of the impactor was ejected into and beyond the stratosphere, distributed globally, and deposited in the K/T boundary clay; and 2) the low amount of projectile contamination in the Yax-1 lithologies may reflect an oblique impact. However, the role of volatiles in the mixing process between projectile and target is not well-understood and may also have played a fundamental role. [source]

Positioning the learning asset portfolio as a key component in an organization's enterprise risk management strategy

PERFORMANCE IMPROVEMENT, Issue 6 2009
Peter J. McAliney
This article presents a process for valuing a portfolio of learning assets used by line executives across industries to value traditional business assets. Embedded within the context of enterprise risk management, this strategic asset allocation process is presented step by step, providing readers the operational considerations to implement this program within their organization to enhance performance improvement. At the individual initiative level, readers will recognize elements used in developing retrospective return on investments (ROIs) for learning programs. [source]

Theoretical analysis of optical gain in PbSe/Pb1,xSrxSe quantum well lasers

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2009
Y. H. Sun
Abstract In this article, theoretical calculation of optical gain has been performed for IV,VI lead salt PbSe/Pb1,xSrxSe quantum well lasers emitting at about 4,6,µm by using an analytic gain expression. The reduced density of states and interband transition matrix elements used in the calculation were derived in the framework of the k·p model. Peak optical gain as a function of carrier concentration and radiative current density was calculated. The material parameters and laser structures that affect device performance were analyzed in details. [source]

Numerische Modellierung von Holz und Verbindungselementen in Holz-Beton-Verbundkonstruktionen

BAUTECHNIK, Issue 6 2005
Marco Grosse Dipl.-Ing.
Durch die Anwendung der FEM können auch komplexe Strukturen berechnet werden, die sich nicht mehr als Stab- oder Flächentragwerke abbilden lassen. Es ist daher naheliegend, auch das Tragverhalten von Bauteilen oder Bauteilkomponenten in Abhängigkeit von verschiedenen Einflußparametern mit Hilfe von FE-Modellen zu simulieren. Um dabei aber Versagensmechanismen abbilden zu können, ist es notwendig, das Materialverhalten der Baustoffe im Nachbruchbereich zu berücksichtigen. Es wird ein konstitutives Materialmodell für den Werkstoff Holz vorgestellt, welches das räumlich anisotrope und vom Beanspruchungsmodus abhängige, nichtlineare Tragverhalten einbezieht. Durch die Kombination mit einem leistungsfähigen Betonmodell ist es möglich, Holz-Beton-Verbundkonstruktionen zu untersuchen. Anhand der Simulationen von Scherversuchen mit verschiedenen Schubverbindungselementen soll die Leistungsfähigkeit solcher numerischer Modelle verdeutlicht werden. Numerical modelling of timber and connection elements used in timber-concrete composite structures. Complex load carrying structures that can not be reproduced as framework ore simple surface models can be calculated using the Finite Element Method. Therefore it seems desirable to simulate the structural behaviour of members or components considering several influence parameters with the help of FE-models too. However, to model the failure mechanism it is necessary to take into account the material behaviour in the critical and post critical range. An adequate numerical model for timber that considers the specific anisotropic and load dependent strength and degradation behaviour is introduced. In combination with an capable model for concrete it is possible to examine timber concrete composite structures. The effectiveness of such models is verified by simulations of shear tests with several fastener elements. [source]