Computation of Exterior Acoustics Problems in Two Dimensions by Trefftz-Type Finite Elements

2015 ◽  
Vol 712 ◽  
pp. 17-22
Author(s):  
Małgorzata Stojek
Keyword(s):  
Finite Elements ◽  
Cross Section ◽  
Radiation Condition ◽  
Two Dimensions ◽  
Least Square ◽  
Fe Method ◽  
Complete Set ◽  
Least Square Procedure

The paper deals with the application of the so-called T-type finite elements [1] to the calculation of the exterior acoustic problems in two dimensions. The method is based on the use of asuitably truncated T-complete set of Trefftz functions over individual subdomains linked by means ofa least square procedure. The vertex singularities and the Sommerfeld radiation condition are readilyincorporated in the trial functions. In order to show the performance of the approach two examples ofcomputations for infinite cylinders (of circular and square cross section) are presented and comparedwith those obtained by means of h-adaptive FE method [2].

scholarly journals Material parameter identification using finite elements with time-adaptive higher-order time integration and experimental full-field strain information

2021 ◽  
Author(s):  
Stefan Hartmann ◽  
Rose Rogin Gilbert
Keyword(s):  
Experimental Data ◽  
Finite Elements ◽  
Parameter Identification ◽  
Material Parameter ◽  
Measurement Data ◽  
Least Square ◽  
Image Correlation ◽  
Field Strain ◽  
Material Parameter Identification ◽  
Full Field

AbstractIn this article, we follow a thorough matrix presentation of material parameter identification using a least-square approach, where the model is given by non-linear finite elements, and the experimental data is provided by both force data as well as full-field strain measurement data based on digital image correlation. First, the rigorous concept of semi-discretization for the direct problem is chosen, where—in the first step—the spatial discretization yields a large system of differential-algebraic equation (DAE-system). This is solved using a time-adaptive, high-order, singly diagonally-implicit Runge–Kutta method. Second, to study the fully analytical versus fully numerical determination of the sensitivities, required in a gradient-based optimization scheme, the force determination using the Lagrange-multiplier method and the strain computation must be provided explicitly. The consideration of the strains is necessary to circumvent the influence of rigid body motions occurring in the experimental data. This is done by applying an external strain determination tool which is based on the nodal displacements of the finite element program. Third, we apply the concept of local identifiability on the entire parameter identification procedure and show its influence on the choice of the parameters of the rate-type constitutive model. As a test example, a finite strain viscoelasticity model and biaxial tensile tests applied to a rubber-like material are chosen.

scholarly journals Import Flows of Bangladesh: Gravity Model Approach under Panel Data Methodology

2012 ◽  
Vol 60 (2) ◽  
pp. 153-157 ◽  
Author(s):  
Mili Roy ◽  
Md. Israt Rayhan
Keyword(s):  
Panel Data ◽  
Gravity Model ◽  
Cross Section ◽  
Time Series Data ◽  
Random Effect ◽  
Least Square ◽  
Series Data ◽  
Ordinary Least Square ◽  
Extended Gravity ◽  
Trading Partners

In counterpoint to export growth, Bangladesh import growth has remained much less strong, despite impressive progress in import liberalization. This study gives an overview of different methodologies related to gravity model analysis in Bangladesh’s import flow. A pooled cross section and time series data were analyzed to incorporate the country specific heterogeneity in country pair trading partners. The import flows are justified by the basic gravity model since Bangladesh’s imports are positively significant by the economy size and inversely related to trade barrier. Accordingly, we have analyzed pooled ordinary least square, fixed effect, random effect. This study also explores extended gravity model using several variables in the light of gravity model panel data approach. Bangladesh’s import is determined by the home and foreign country’s gross domestic product and exchange rate. In addition, Cross section results show that regional trade arrangement which is South Asian Association for Regional Co-operation and border are significant for Bangladesh’s importimplies that Bangladesh should import more from intra regional country and also should import from India.DOI: http://dx.doi.org/10.3329/dujs.v60i2.11485 Dhaka Univ. J. Sci. 60(2): 153-157, 2012 (July)  

Strain field determination in III–V heteroepitaxy coupling finite elements with experimental and theoretical techniques at the nanoscale

2017 ◽  
Vol 26 (1-2) ◽  
pp. 1-8
Author(s):  
Nikoletta Florini ◽  
George P. Dimitrakopulos ◽  
Joseph Kioseoglou ◽  
Nikos T. Pelekanos ◽  
Thomas Kehagias
Keyword(s):  
Finite Elements ◽  
Strain Field ◽  
Strain Distribution ◽  
Elastic Strain ◽  
Growth Direction ◽  
Current Status ◽  
Interface Plane ◽  
Fe Method ◽  
Semiconductor Nanostructure

AbstractWe are briefly reviewing the current status of elastic strain field determination in III–V heteroepitaxial nanostructures, linking finite elements (FE) calculations with quantitative nanoscale imaging and atomistic calculation techniques. III–V semiconductor nanostructure systems of various dimensions are evaluated in terms of their importance in photonic and microelectronic devices. As elastic strain distribution inside nano-heterostructures has a significant impact on the alloy composition, and thus their electronic properties, it is important to accurately map its components both at the interface plane and along the growth direction. Therefore, we focus on the determination of the stress-strain fields in III–V heteroepitaxial nanostructures by experimental and theoretical methods with emphasis on the numerical FE method by means of anisotropic continuum elasticity (CE) approximation. Subsequently, we present our contribution to the field by coupling FE simulations on InAs quantum dots (QDs) grown on (211)B GaAs substrate, either uncapped or buried, and GaAs/AlGaAs core-shell nanowires (NWs) grown on (111) Si, with quantitative high-resolution transmission electron microscopy (HRTEM) methods and atomistic molecular dynamics (MD) calculations. Full determination of the elastic strain distribution can be exploited for band gap tailoring of the heterostructures by controlling the content of the active elements, and thus influence the emitted radiation.

scholarly journals Multi-group cross section library generation for HTGR lattice physics code XPZ

2021 ◽  
Vol 2048 (1) ◽  
pp. 012028
Author(s):  
Lerui Zhang ◽  
Ding She ◽  
Lei Shi ◽  
Richard Chambon ◽  
Alain Hébert
Keyword(s):  
Data Processing ◽  
Cross Section ◽  
Nuclear Data ◽  
Automatic Generation ◽  
Detailed Data ◽  
Processing Scheme ◽  
Processing Module ◽  
Complete Set ◽  
Evaluated Nuclear Data ◽  
High Temperature Gas

Abstract The XPZ code was previously developed for the lattice physics computation in High Temperature Gas-cooled Reactors (HTGRs), which adopted the multi-group cross section library converted from the existing open-source DRAGON library. In this paper, a new format of multi-group cross section library named XPZLIB has been implemented in XPZ code. XPZLIB is designed in binary and HDF5 formats, including detailed data contents for resonance, transport and depletion calculations. A new data-processing module named XPZR is developed based on NJOY-2016 to generate nuclide dependent XPZLIB from the most recent evaluated nuclear data, and besides, the PyNjoy-2016 system is developed for automatic generation of integrated XPZLIB including a complete set of nuclides. The new generated XPZLIB is presented with the XPZ code. Numerical results demonstrate the accuracy of the new library XPZLIB and the reliability of the data processing scheme. Moreover, the influence of different versions of ENDF/B data is investigated.

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