Search results for "numerical [methods]"
showing 10 items of 500 documents
Electronic properties of carbon nanotubes under torsion
2012
A computationally-effective approach for calculating the electromechanical behavior of SWNTs and MWNTs of the dimensions used in nano-electronic devices has been developed. It is a mixed finite element-tight-binding code carefully designed to realize significant time saving in calculating deformation-induced changes in electrical transport properties of the nanotubes. The effect of the MWNT diameter and chirality on the conductance after mechanical deformation was investigated. In case of torsional deformation results revealed the conductance of MWNTs to depend strongly on the diameter, since bigger MWNTs reach much earlier the buckling load under torsion their electrical conductivity chang…
Numerical modeling and validation of hydrothermal liquefaction of a lignin particle for biocrude production
2021
Abstract Lignin liquefaction process under catalyst-free conditions in a temperature range from 573 K to 647 K is investigated with this mathematical model. Based on the theoretical understanding of the physical and chemical processes of the liquefaction process in subcritical temperatures, a comprehensive mathematical model for the decomposition of lignin by hydrolysis reaction pathway is developed on the results of a series of batch experiments. The model consists of four main sections. They are liquefaction of lignin particle, oily film, and inorganic (ash) layer formation behavior during the liquefaction, kinetic model to model further liquefaction process of initial products, and the l…
An Improved Thermal Lamination Model for Analysis of Heat Transfer in Composite Structures
2002
A new thermal lamination model and its associated finite element model are presented for analysis of heat transfer in laminated composite structures. The form of the present model closely resembles that of recent zig-zag sublaminate structural laminate theories. The through-thickness distribution of temperature is assumed to vary linearly within each ply, and continuity of transverse flux at ply interfaces is enforced analytically. Thus, the number of computational degrees-offreedom (DOFs) is made independent of the number of plies in the sublaminate. In its present form, the model contains only two computational DOFs in each sublaminate–the temperature at the top and bottom surface of the…
Numerical 2D And 3D Simulations of a Spherical Fabry–Pérot Resonator for Application as a Reference Cavity for Laser Frequency Stabilisation
2015
Abstract We report on the results of a numerical study of deformations of a spherical Fabry-Pérot cavity that can be used for laser frequency stabilisation. It is demonstrated that for a precise simulation of the cavity deformations a 3D model has to be used instead of a simpler 2D model, which employs simulation on the symmetry plane of the cavity. To lower the sensitivity to environmental perturbations, it is suggested to use a material with a low density and a high Young’s modulus. We also show that the mechanical resonance frequencies of the cavity are mainly determined by the size of the cavity.
Numerical analysis of light soaking phenomenon in Ruthenium based Dye Sensitized Solar Cells
2017
Dye Sensitized Solar Cells (DSSCs) are widely considered one of the most promising third generation photovoltaic devices, especially thanks to their relatively low cost if compared to conventional solar cells. An interesting phenomenon affecting such devices is the so-called light soaking effect, consisting in the increase of cell main electrical parameters after the exposition to solar light. In this work, starting from the experimental characterization carried out on Ruthenium-based DSSCs, we report on a series of numerical analysis performed to better describe the above-mentioned light soaking effect in order to show the relationship between such phenomenon and the main physical paramete…
Nonlinear Structural Mechanics Based Modeling of Carbon Nanotube Deformation
2003
A nonlinear structural mechanics based approach for modeling the structure and the deformation of single-wall and multiwall carbon nanotubes (CNTs) is presented. Individual tubes are modeled using shell finite elements, where a specific pairing of elastic properties and mechanical thickness of the tube wall is identified to enable successful modeling with shell theory. The effects of van der Waals forces are simulated with special interaction elements. This new CNT modeling approach is verified by comparison with molecular dynamics simulations and high-resolution micrographs available in the literature. The mechanics of wrinkling of multiwall CNTs are studied, demonstrating the role of the …
Numerical Modeling Approaches of FRCMs/SRG Confined Masonry Columns
2019
The Fabric Reinforced Cementitious Matrices (FRCMs) and Steel Reinforced Grout (SRG) are a promising strengthening solution for existing masonry since inorganic matrix is considerably compatible with historical substrates. The present paper is focused on a Finite Element (FE) analysis of masonry columns confined with FRCM composites developed by Abaqus-code. The masonry columns were modelled using a macro model approach. The model was performed by using the following functions Concrete Damage Plasticity (CDP) and the Plastic (P) in order to describe the constitutive laws of material for masonry columns and external reinforcement, respectively. Typical failures of FRCM-systems are slippage o…
DEGENERATE MATRIX METHOD FOR SOLVING NONLINEAR SYSTEMS OF DIFFERENTIAL EQUATIONS
1998
Degenerate matrix method for numerical solving nonlinear systems of ordinary differential equations is considered. The method is based on an application of special degenerate matrix and usual iteration procedure. The method, which is connected with an implicit Runge‐Kutta method, can be simply realized on computers. An estimation for the error of the method is given. First Published Online: 14 Oct 2010
Numerical model of macro-segregation during directional crystallization process
1998
Abstract In the paper the mathematical model of macro-segregation proceeding during the directional crystallization process is presented. The boundary-initial problem considered is discussed. Next the numerical approximation constructed on the basis of the boundary element method supplemented by a procedure called the artificial heat source method is described. The boundary condition on the solidification front resulting from the alloy component balance is introduced, while in finally the practical aspects of computations concerning the course of the process are discussed.
Functional A Posteriori Error Estimates for Time-Periodic Parabolic Optimal Control Problems
2015
This article is devoted to the a posteriori error analysis of multiharmonic finite element approximations to distributed optimal control problems with time-periodic state equations of parabolic type. We derive a posteriori estimates of the functional type, which are easily computable and provide guaranteed upper bounds for the state and co-state errors as well as for the cost functional. These theoretical results are confirmed by several numerical tests that show high efficiency of the a posteriori error bounds. peerReviewed