Microcanonical black hole statistics and the finite infinite range Heisenberg model
Aste, Andreas
2015-01-01
The Gelfand pattern of the reduction of the N-fold tensor product of the fundamental representation of the special unitary group SU(2) by itself is studied in the framework of a finite Heisenberg model with infinite range, where N spins couple to each other with the same strength. A speculative comment relates the present findings to the microstatistics of black holes for illustrative purposes.
Quasi-long-range ordering in a finite-size 2D Heisenberg model
Kapikranian, O; Holovatch, Yu; Berche, Bertrand; Holovatch, Yurij; Kapikranian, Oleksandr
2006-01-01
We analyse the low-temperature behaviour of the Heisenberg model on a two-dimensional lattice of finite size. Presence of a residual magnetisation in a finite-size system enables us to use the spin wave approximation, which is known to give reliable results for the XY model at low temperatures T. For the system considered, we find that the spin-spin correlation function decays as 1/r^eta(T) for large separations r bringing about presence of a quasi-long-range ordering. We give analytic estimates for the exponent eta(T) in different regimes and support our findings by Monte Carlo simulations of the model on lattices of different sizes at different temperatures.
A Hybrid Finite Element/Helmholtz-Kirchhoff-Integral Model for Shooting Range Sound Prediction
Nijhof, M.J.J.; Eerden, F.J.M. van der
2013-01-01
National legislation enforces a limit on the Sound Levels of outdoor military shooting ranges observed in nearby residential areas. These restrictions directly influence the number of shots that may be fired at a specific shooting range, which may conflict with the required/ scheduled training capac
The Efimov effect with finite range interactions
Platter, Lucas
2017-01-01
Systems of strongly interacting atoms are receiving a lot of attention because of their interesting features in the few- and many-body sector. Strong interactions are frequently obtained in experiment by using a Feshbach resonance to tune the scattering to large values. A striking feature of three-body systems with a large scattering is the emergence of a discrete scaling symmetry that is also known as the Efimov effect. The Efimov effect has been observed through the measurement of loss rates in experiments with ultracold atoms. It is, however, also relevant to nuclear physics where the three-nucleon bound state and some halo nuclei are considered to be examples of Efimov states. Such systems can be modeled conveniently with the zero-range limit, however, in many of such experiments the finite range of the interaction leads to significant corrections that need to be taken into account. I will discuss how a finite effective range can be included in calculations for three-body systems that display the Efimov effect and how this leads to novel universal relations. Applications to experiments with homonuclear and heteronuclear ultracold atomic gases are discussed. National Science Foundation PHY-1516077, PHY-1555030.
Resonant invisibility with finite range interacting fermions
Energy Technology Data Exchange (ETDEWEB)
Nguenang, Jean-Pierre, E-mail: nguenang@yahoo.com [Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden (Germany); Fundamental Physics Laboratory: Group of Nonlinear Physics and Complex Systems, Department of Physics, University of Douala, P.O. Box 24157, Douala (Cameroon); Flach, Sergej, E-mail: flach@pks.mpg.de [Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden (Germany); Khomeriki, Ramaz, E-mail: khomeriki@hotmail.com [Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden (Germany); Department of Physics, Tbilisi State University, 3 Chavchavadze, 0128 Tbilisi, Georgia (United States)
2012-01-09
We study the eigenstates of two opposite spin fermions on a one-dimensional lattice with finite range interaction. The eigenstates are projected onto the set of Fock eigenstates of the noninteracting case. We find antiresonances for symmetric eigenstates, which eliminate the interaction between two symmetric Fock states when satisfying a corresponding selection rule. -- Highlights: ► We seek the eigenstates of two opposite spin fermions on a one-dimensional lattice with finite range interaction. ► The eigenstates are projected onto the set of Fock eigenstates of the noninteracting case. ► We find antiresonances for symmetric eigenstates when satisfying a corresponding selection rule.
Energy Technology Data Exchange (ETDEWEB)
Kapetanakis, D. (Technische Univ. Muenchen, Garching (Germany). Physik Dept.); Mondragon, M. (Technische Univ. Muenchen, Garching (Germany). Physik Dept.); Zoupanos, G. (National Technical Univ., Athens (Greece). Physics Dept.)
1993-09-01
We present phenomenologically viable SU(5) unified models which are finite to all orders before the spontaneous symmetry breaking. In the case of two models with three families the top quark mass is predicted to be 178.8 GeV. (orig.)
Finite mathematics models and applications
Morris, Carla C
2015-01-01
Features step-by-step examples based on actual data and connects fundamental mathematical modeling skills and decision making concepts to everyday applicability Featuring key linear programming, matrix, and probability concepts, Finite Mathematics: Models and Applications emphasizes cross-disciplinary applications that relate mathematics to everyday life. The book provides a unique combination of practical mathematical applications to illustrate the wide use of mathematics in fields ranging from business, economics, finance, management, operations research, and the life and social sciences.
Zero modes in finite range magnetic fields
Adam, C; Nash, C
2000-01-01
We find a class of Fermion zero modes of Abelian Dirac operators in three dimensional Euclidean space where the gauge potentials and the related magnetic fields are nonzero only in a finite space region.
Efimov Physics with a Finite-Range Parameter
Gattobigio, M.; Kievsky, A.
2015-12-01
Results obtained by the authors in recent works on the exploration of universality in systems living inside the Efimov window are critically analyzed. We discuss how to take into account finite-range corrections by introducing a finite-range parameter necessary to make comparisons to the universal predictions of the Efimov zero-range theory. Firstly we apply our analysis to two different calculations published by other authors. The first one has been used with success to describe ultracold Cs atoms close to a Feshbach resonance and the second one describes a four 4He atom system with a realistic interaction. Finally we use the finite-range parameter to analyze recombination data in experiments with ultracold 7Li atoms. The three selected cases support the introduction of the finite-range parameter as a valuable tool to extend the use of the zero-range theory to describe systems having finite-range interactions.
Monthus, Cécile
2016-04-01
The finite temperature dynamics of the Dyson hierarchical classical spins models is studied via real-space renormalization rules concerning the couplings and the relaxation times. For the ferromagnetic model involving long-ranged coupling J(r)\\propto {{r}-1-σ} in the region 1/2mean-field-like thermal ferromagnetic-paramagnetic transition, the RG flows are explicitly solved: the characteristic relaxation time τ (L) follows the critical power-law τ (L)\\propto {{L}{{z\\text{c}}(σ )}} at the phase transition and the activated law \\ln τ (L)\\propto {{L}\\psi} with \\psi =1-σ in the ferromagnetic phase. For the spin-glass model involving random long-ranged couplings of variance \\overline{{{J}2}(r)}\\propto {{r}-2σ} in the region 2/3mean-field-like thermal spin-glass-paramagnetic transition, the coupled RG flows of the couplings and of the relaxation times are studied numerically: the relaxation time τ (L) follows some power-law τ (L)\\propto {{L}{{z\\text{c}}(σ )}} at criticality and the activated law \\ln τ (L)\\propto {{L}\\psi} in the spin-glass phase with the dynamical exponent \\psi =1-σ =θ coinciding with the droplet exponent governing the flow of the couplings J(L)\\propto {{L}θ} .
Towards selecting a finite-range regularization scale
Young, Ross D; Leinweber, Derek B
2009-01-01
Extensive studies have demonstrated that finite-range regularization (FRR) offers significantly improved chiral extrapolations for lattice QCD. These studies have typically relied on selecting the finite-regularization scale based upon phenomenological input. Here we report on a preliminary investigation of a procedure to determine a preferred range of FRR scale based on nonperturbative lattice results -- without any phenomenological prejudice.
Partial wave decomposition of finite-range effective tensor interaction
Davesne, D; Pastore, A; Navarro, J
2016-01-01
We perform a detailed analysis of the properties of the finite-range tensor term associated with the Gogny and M3Y effective interactions. In particular, by using a partial wave decomposition of the equation of state of symmetric nuclear matter, we show how we can extract their tensor parameters directly from microscopic results based on bare nucleon-nucleon interactions. Furthermore, we show that the zero-range limit of both finite-range interactions has the form of the N3LO Skyrme pseudo-potential, which thus constitutes a reliable approximation in the density range relevant for finite nuclei. Finally, we use Brueckner-Hartree-Fock results to fix the tensor parameters for the three effective interactions.
Generalized similarity in finite range solar wind magnetohydrodynamic turbulence.
Chapman, S C; Nicol, R M
2009-12-11
Extended or generalized similarity is a ubiquitous but not well understood feature of turbulence that is realized over a finite range of scales. The ULYSSES spacecraft solar polar passes at solar minimum provide in situ observations of evolving anisotropic magnetohydrodynamic turbulence in the solar wind under ideal conditions of fast quiet flow. We find a single generalized scaling function characterizes this finite range turbulence and is insensitive to plasma conditions. The recent unusually inactive solar minimum--with turbulent fluctuations down by a factor of approximately 2 in power--provides a test of this invariance.
Continuum Random Phase Approximation with finite-range interactions
Energy Technology Data Exchange (ETDEWEB)
Co' , Giampaolo [Universita del Salento, Dipartimento di Fisica ' ' E. De Giorgi' ' , Lecce (Italy); INFN, Sezione di Lecce, Lecce (Italy); De Donno, Viviana [Universita del Salento, Dipartimento di Fisica ' ' E. De Giorgi' ' , Lecce (Italy); Anguiano, Marta; Lallena, Antonio M. [Universidad de Granada, Departamento de Fisica Atomica, Molecular y Nuclear, Granada (Spain)
2016-05-15
We rewrite the Random Phase Approximation secular equations in a form which allows the treatment of the continuum part of the single-particle spectrum without approximations. Within this formalism finite-range interactions can be used without restrictions. We present some results, obtained with Gogny interactions, where the role of the continuum is relevant. (orig.)
A Unified View of Finite Range Effects in Efimov Trimers
Platter, Lucas; Ji, Chen; Braaten, Eric; Phillips, Daniel
2015-05-01
Three-body recombination in ultracold atoms is a process that can demonstrate the appearance of discrete scale invariance due to the Efimov effect. Different features in the scattering length dependent recombination rate are related by universal relations in the so-called zero-range limit. However, experiments are usually carried out with systems that display non-neglible corrections due to the finite range of interatomic interaction. We explain the origin of recently constructed universal relations for systems of three identical bosons interacting through a large scattering length. Range corrected universal relations are calculated using first order perturbation theory and are benchmarked against microcopic calculations that by construction contain finite range effects. We relate our results to work done in other frameworks and explain differences and similarities. We present also relations that are crucial for analyzing experiments in the future.
Finite Range Effects in Energies and Recombination Rates of Three Identical Bosons
DEFF Research Database (Denmark)
Sørensen, Peder Klokmose; V. Fedorov, D.; S. Jensen, A.;
2013-01-01
is large. The models are built on contact potentials which take into account finite range effects; one is a two-channel model and the other is an effective range expansion model implemented through the boundary condition on the three-body wave function when two of the particles are at the same point...... in space. We compare the results with the results of the ubiquitous single-parameter zero-range model where only the scattering length is taken into account. Both finite range models predict variations of the well-known geometric scaling factor 22.7 that arises in Efimov physics. The threshold value...... at negative scattering length for creation of a bound trimer moves to higher or lower values depending on the sign of the effective range compared to the location of the threshold for the single-parameter zero-range model. Large effective ranges, corresponding to narrow resonances, are needed...
Approximate particle number projection for finite range density dependent forces
Valor, A; Robledo, L M
1996-01-01
The Lipkin-Nogami method is generalized to deal with finite range density dependent forces. New expressions are derived and realistic calculations with the Gogny force are performed for the nuclei ^{164}Er and ^{168}Er. The sharp phase transition predicted by the mean field approximation is washed out by the Lipkin-Nogami approach; a much better agreement with the experimental data is reached with the new approach than with the Hartree-Fock_Bogoliubov one, specially at high spins.
Short range correlations between nucleons in finite nuclei
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; MA Wei-Xing
2008-01-01
The short-range correlation between nucleons in finite nuclei is investigated in high energy protonnucleus and α-nucleus elastic scattering in the framework of Glauber multiple scattering theory without any free parameters. The effects on the p-4He and 4He-12C elastic scattering, and in particular on the proton elastic scattering off hallo-like nuclei, 6,8He, are estimated. Our calculations show that the short-range correlations play an important role in reproducing experimental data and could be also thought of as being possible origin and nature of halo-like phenomena in the nuclear structure. More accurate calculations along this line are needed.
Strictly finite-range potential for light and heavy nuclei
Salamon, P.; Lovas, R. G.; Betan, R. M. Id; Vertse, T.; Balkay, L.
2014-05-01
Strictly finite-range (SFR) potentials are exactly zero beyond their finite range. Single-particle energies and densities, as well as S-matrix pole trajectories, are studied in a few SFR potentials suited for the description of neutrons interacting with light and heavy nuclei. The SFR potentials considered are the standard cutoff Woods-Saxon (CWS) potentials and two potentials approaching zero smoothly: the SV potential introduced by Salamon and Vertse [Phys. Rev. C 77, 037302 (2008), 10.1103/PhysRevC.77.037302] and the SS potential of Sahu and Sahu [Int. J. Mod. Phys. E 21, 1250067 (2012), 10.1142/S021830131250067X]. The parameters of these latter potentials were set so that the potentials may be similar to the CWS shape. The range of the SV and SS potentials scales with the cube root of the mass number of the core like the nuclear radius itself. For light nuclei a single term of the SV potential (with a single parameter) is enough for a good description of the neutron-nucleus interaction. The trajectories are compared with a benchmark for which the starting points (belonging to potential depth zero) can be determined independently. Even the CWS potential is found to conform to this benchmark if the range is identified with the cutoff radius. For the CWS potentials some trajectories show irregular shapes, while for the SV and SS potentials all trajectories behave regularly.
Ciofi degli Atti, Claudio; Mezzetti, Chiara Benedetta; Morita, Hiko
2017-04-01
Background: Two-nucleon (2 N ) short-range correlations (SRC) in nuclei have been recently thoroughly investigated, both theoretically and experimentally and the study of three-nucleon (3 N ) SRC, which could provide important information on short-range hadronic structure, is underway. Novel theoretical ideas concerning 2 N and 3 N SRC are put forward in the present paper. Purpose: The general features of a microscopic one-nucleon spectral function which includes the effects of both 2 N and 3 N SRC and its comparison with ab initio spectral functions of the three-nucleon systems are illustrated. Methods: A microscopic and parameter-free one-nucleon spectral function expressed in terms of a convolution integral involving ab initio relative and center-of-mass (c.m.) momentum distributions of a 2 N pair and aimed at describing two- and three-nucleon short-range correlations, is obtained by using: (i) the two-nucleon momentum distributions obtained within ab initio approaches based upon nucleon-nucleon interactions of the Argonne family; (ii) the exact relation between one- and two-nucleon momentum distributions; (iii) the fundamental property of factorization of the nuclear wave function at short internucleon ranges. Results: The comparison between the ab initio spectral function of 3He and the one based upon the convolution integral shows that when the latter contains only two-nucleon short-range correlations the removal energy location of the peaks and the region around them exhibited by the ab initio spectral function are correctly predicted, unlike the case of the high and low removal energy tails; the inclusion of the effects of three-nucleon correlations brings the convolution model spectral function in much better agreement with the ab initio one; it is also found that whereas the three-nucleon short-range correlations dominate the high energy removal energy tail of the spectral function, their effects on the one-nucleon momentum distribution are almost one
One spatial dimensional finite volume three-body interaction for a short-range potential
Guo, Peng
2016-01-01
In this work, we use McGuire's model to describe scattering of three spinless identical particles in one spatial dimension, we first present analytic solutions of Faddeev's equation for scattering of three spinless particles in free space. The three particles interaction in finite volume is derived subsequently, and the quantization conditions by matching wave functions in free space and finite volume are presented in terms of two-body scattering phase shifts. The quantization conditions obtained in this work for short range interaction are L\\"uscher's formula like and consistent with Yang's results in \\cite{Yang:1967bm}.
Infinite matter properties and zero-range limit of nonrelativistic finite-range interactions
Davesne, D; Pastore, A; Navarro, J
2016-01-01
We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin-orbit terms from the spin-isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin-orbit of the M3Y interaction is not compatible with local gauge invariance. Finally, we show that the zero-range limit of both families of interactions coincides with the specific form of the zero-range N3LO Skyrme interaction and we emphasize from this analogy the benefits of N3LO.
Infinite matter properties and zero-range limit of non-relativistic finite-range interactions
Davesne, D.; Becker, P.; Pastore, A.; Navarro, J.
2016-12-01
We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin-orbit terms from the spin-isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin-orbit of the M3Y interaction is not compatible with local gauge invariance. Finally, we show that the zero-range limit of both families of interactions coincides with the specific form of the zero-range Skyrme interaction extended to higher momentum orders and we emphasize from this analogy its benefits.
Infinite matter properties and zero-range limit of non-relativistic finite-range interactions
Energy Technology Data Exchange (ETDEWEB)
Davesne, D. [Université de Lyon, Université Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire de Lyon, UMR 5822, F-69622 Villeurbanne cedex (France); Becker, P., E-mail: pbecker@ipnl.in2p3.fr [Université de Lyon, Université Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire de Lyon, UMR 5822, F-69622 Villeurbanne cedex (France); Pastore, A. [Department of Physics, University of York, Heslington, York, Y010 5DD (United Kingdom); Navarro, J. [IFIC (CSIC-Universidad de Valencia), Apartado Postal 22085, E-46.071-Valencia (Spain)
2016-12-15
We discuss some infinite matter properties of two finite-range interactions widely used for nuclear structure calculations, namely Gogny and M3Y interactions. We show that some useful informations can be deduced for the central, tensor and spin–orbit terms from the spin–isospin channels and the partial wave decomposition of the symmetric nuclear matter equation of state. We show in particular that the central part of the Gogny interaction should benefit from the introduction of a third Gaussian and the tensor parameters of both interactions can be deduced from special combinations of partial waves. We also discuss the fact that the spin–orbit of the M3Y interaction is not compatible with local gauge invariance. Finally, we show that the zero-range limit of both families of interactions coincides with the specific form of the zero-range Skyrme interaction extended to higher momentum orders and we emphasize from this analogy its benefits.
Universalities for the Efimov-favored system with finite-range interactions
Wu, Meng-Shan; Han, Hui-Li; Shi, Ting-Yun
2016-06-01
Universal properties of Efimov states for some triatomic systems composed by one light and two heavy atoms are investigated using the finite-range model potentials. We have successfully obtained accurate values of binding energies and sizes for three successive Efimov states. Compared with the predicted scaling constants of the zero-range theory, the ground Efimov states are found to have the largest finite-range corrections. There exists a universal size-binding momentum relation for Efimov states which can be described by the formula Rn*kn*=√{(1 +s02)/3 } derived with zero-range approximation. It is found that for the Efimov states that have large scaled sizes, their size-binding momentum relations follow the universal formula well. Our calculations demonstrate that size is an important characteristic in determining the universalities of Efimov states.
On a Finite Range Decomposition of the Resolvent of a Fractional Power of the Laplacian
Mitter, P. K.
2016-06-01
We prove the existence as well as regularity of a finite range decomposition for the resolvent G_{α } (x-y,m^2) = ((-Δ )^{α over 2} + m2)^{-1} (x-y) , for 0<α <2 and all real m, in the lattice {Z}d as well as in the continuum {R}d for dimension d≥ 2. This resolvent occurs as the covariance of the Gaussian measure underlying weakly self- avoiding walks with long range jumps (stable Lévy walks) as well as continuous spin ferromagnets with long range interactions in the long wavelength or field theoretic approximation. The finite range decomposition should be useful for the rigorous analysis of both critical and off-critical renormalisation group trajectories. The decomposition for the special case m=0 was known and used earlier in the renormalisation group analysis of critical trajectories for the above models below the critical dimension d_c =2α.
Finite element modeling methods for photonics
Rahman, B M Azizur
2013-01-01
The term photonics can be used loosely to refer to a vast array of components, devices, and technologies that in some way involve manipulation of light. One of the most powerful numerical approaches available to engineers developing photonic components and devices is the Finite Element Method (FEM), which can be used to model and simulate such components/devices and analyze how they will behave in response to various outside influences. This resource provides a comprehensive description of the formulation and applications of FEM in photonics applications ranging from telecommunications, astron
Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems.
Yang, Ge; Wang, Jun; Fang, Wen
2015-04-01
In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.
Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems
Energy Technology Data Exchange (ETDEWEB)
Yang, Ge; Wang, Jun [School of Science, Beijing Jiaotong University, Beijing 100044 (China); Fang, Wen, E-mail: fangwen@bjtu.edu.cn [School of Economics and Management, Beijing Jiaotong University, Beijing 100044 (China)
2015-04-15
In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.
Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems
Yang, Ge; Wang, Jun; Fang, Wen
2015-04-01
In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.
Finite element modeling of corneal strip extensometry
CSIR Research Space (South Africa)
Botha, N
2012-12-01
Full Text Available numerically modelled in several studies, this study focusses on accurately modelling the strip extensiometry test. Two methods were considered to simulate the experimental conditions namely, a single phase and a two phase method. A finite element model...
Directory of Open Access Journals (Sweden)
John Affisco
2008-04-01
Full Text Available We study the impact of the efforts aimed at reducing the lead-time variability in a quality-adjusted stochastic inventory model. We assume that each lot contains a random number of defective units. More specifically, a logarithmic investment function is used that allows investment to be made to reduce lead-time variability. Explicit results for the optimal values of decision variables as well as optimal value of the variance of lead-time are obtained. A series of numerical exercises is presented to demonstrate the use of the models developed in this paper. Initially the lead-time variance reduction model (LTVR is compared to the quality-adjusted model (QA for different values of initial lead-time over uniformly distributed lead-time intervals from one to seven weeks. In all cases where investment is warranted, investment in lead-time reduction results in reduced lot sizes, variances, and total inventory costs. Further, both the reduction in lot-size and lead-time variance increase as the lead-time interval increases. Similar results are obtained when lead-time follows a truncated normal distribution. The impact of proportion of defective items was also examined for the uniform case resulting in the finding that the total inventory related costs of investing in lead-time variance reduction decrease significantly as the proportion defective decreases. Finally, the results of sensitivity analysis relating to proportion defective, interest rate, and setup cost show the lead-time variance reduction model to be quite robust and representative of practice.
A Finite Model Property for Intersection Types
Directory of Open Access Journals (Sweden)
Rick Statman
2015-03-01
Full Text Available We show that the relational theory of intersection types known as BCD has the finite model property; that is, BCD is complete for its finite models. Our proof uses rewriting techniques which have as an immediate by-product the polynomial time decidability of the preorder <= (although this also follows from the so called beta soundness of BCD.
Combinatorial Properties of Finite Models
Hubicka, Jan
2010-01-01
We study countable embedding-universal and homomorphism-universal structures and unify results related to both of these notions. We show that many universal and ultrahomogeneous structures allow a concise description (called here a finite presentation). Extending classical work of Rado (for the random graph), we find a finite presentation for each of the following classes: homogeneous undirected graphs, homogeneous tournaments and homogeneous partially ordered sets. We also give a finite presentation of the rational Urysohn metric space and some homogeneous directed graphs. We survey well known structures that are finitely presented. We focus on structures endowed with natural partial orders and prove their universality. These partial orders include partial orders on sets of words, partial orders formed by geometric objects, grammars, polynomials and homomorphism orders for various combinatorial objects. We give a new combinatorial proof of the existence of embedding-universal objects for homomorphism-defined...
Combinatorial Properties of Finite Models
Hubicka, Jan
2010-09-01
We study countable embedding-universal and homomorphism-universal structures and unify results related to both of these notions. We show that many universal and ultrahomogeneous structures allow a concise description (called here a finite presentation). Extending classical work of Rado (for the random graph), we find a finite presentation for each of the following classes: homogeneous undirected graphs, homogeneous tournaments and homogeneous partially ordered sets. We also give a finite presentation of the rational Urysohn metric space and some homogeneous directed graphs. We survey well known structures that are finitely presented. We focus on structures endowed with natural partial orders and prove their universality. These partial orders include partial orders on sets of words, partial orders formed by geometric objects, grammars, polynomials and homomorphism orders for various combinatorial objects. We give a new combinatorial proof of the existence of embedding-universal objects for homomorphism-defined classes of structures. This relates countable embedding-universal structures to homomorphism dualities (finite homomorphism-universal structures) and Urysohn metric spaces. Our explicit construction also allows us to show several properties of these structures.
Finite element modeling of the human pelvis
Energy Technology Data Exchange (ETDEWEB)
Carlson, B.
1995-11-01
A finite element model of the human pelvis was created using a commercial wire frame image as a template. To test the final mesh, the model`s mechanical behavior was analyzed through finite element analysis and the results were displayed graphically as stress concentrations. In the future, this grid of the pelvis will be integrated with a full leg model and used in side-impact car collision simulations.
Non-linear finite element modeling
DEFF Research Database (Denmark)
Mikkelsen, Lars Pilgaard
The note is written for courses in "Non-linear finite element method". The note has been used by the author teaching non-linear finite element modeling at Civil Engineering at Aalborg University, Computational Mechanics at Aalborg University Esbjerg, Structural Engineering at the University...... on the governing equations and methods of implementing....
Identifying interacting pairs of sites in infinite range Ising models
Galves, Antonio; Takahashi, Daniel Yasumasa
2010-01-01
We consider Ising models (pairwise interaction Gibbs probability measures) in $\\Z^d$ with an infinite range potential. We address the problem of identifying pairs of interacting sites from a finite sample of independent realisations of the Ising model. The sample contains only the values assigned by the Ising model to a finite set of sites in $\\Z^d$. Our main result is an upperbound for the probability with our estimator to misidentify the pairs of interacting sites in this finite set.
Essays on Finite Mixture Models
A. van Dijk (Bram)
2009-01-01
textabstractFinite mixture distributions are a weighted average of a ¯nite number of distributions. The latter are usually called the mixture components. The weights are usually described by a multinomial distribution and are sometimes called mixing proportions. The mixture components may be the
Essays on Finite Mixture Models
A. van Dijk (Bram)
2009-01-01
textabstractFinite mixture distributions are a weighted average of a ¯nite number of distributions. The latter are usually called the mixture components. The weights are usually described by a multinomial distribution and are sometimes called mixing proportions. The mixture components may be the sam
Finite Memory Model for Haptic Recognition
1991-12-01
Slot 4 bu f fer s hort- term storel Slot N Long- ’erm store The model of memory proposed by Atkinson and Shiffrin . Primary memory here is as rehearsal...7 NAVAL POSTGRADUATE SCHOOL Monterey, Califormia AD-A245 342 THESIS Finite Memory Model for Haptic Recognition by Philip G. Beieri December 1991...ELEMEN1 No.) NO. No. ACCESSION NO. I1. TITLE (include Securitn Classification) FINITE MEMORY MODEL FOR HAPTIC RECOGNITION’ 12. PERSONALEAUTHOR(S) Philip
The contact in the BCS–BEC crossover for finite range interacting ultracold Fermi gases
Energy Technology Data Exchange (ETDEWEB)
Caballero-Benítez, Santiago F., E-mail: scaballero@fisica.unam.mx; Paredes, Rosario; Romero-Rochín, Víctor
2013-10-15
Using mean-field theory for the Bardeen–Cooper–Schriefer (BCS) to the Bose–Einstein condensate (BEC) crossover we investigate the ground state thermodynamic properties of an interacting homogeneous Fermi gas. The interatomic interactions modelled through a finite range potential allows us to calculate the thermodynamic behaviour as a function of the potential parameters in the whole crossover region. We concentrate in studying the Contact variable, the thermodynamic conjugate of the inverse of the s-wave scattering length. Our analysis leads to predict a quantum phase transition – like in the case of large potential range. This finding is a direct consequence of the k-dependent energy gap.
Finite Feedback Cycling in Structural Equation Models
Hayduk, Leslie A.
2009-01-01
In models containing reciprocal effects, or longer causal loops, the usual effect estimates assume that any effect touching a loop initiates an infinite cycling of effects around that loop. The real world, in contrast, might permit only finite feedback cycles. I use a simple hypothetical model to demonstrate that if the world permits only a few…
Finiteness of PST self-dual models
Monteiro del Cima, O; Sarandy, M S; Cima, Oswaldo M. Del; Piguet, Olivier; Sarandy, Marcelo S.
2001-01-01
The Pasti-Sorokin-Tonin model for describing chiral forms is considered at the quantum level. We study the ultraviolet and infrared behaviour of the model in two, four and six dimensions in the framework of algebraic renormalization. The absence of anomalies, as well as the finiteness, up to non-physical renormalizations, are shown in all dimensions analyzed.
Finiteness in SU(3){sup 3} models
Energy Technology Data Exchange (ETDEWEB)
Heinemeyer, S. [Instituto de Fisica de Cantabria (CSIC-UC), Santander (Spain); Ma, E. [Physics Department, University of California, Riverside, California 92521 (United States); Mondragon, M. [Instituto de Fisica, Universidad Nacional Autonoma de Mexico (IF-UNAM), Mexico D.F. (Mexico); Zoupanos, G. [Physics Department, National Technical University, 157 80 Zografou, Athens (Greece)
2010-07-15
We consider N = 1 supersymmetric gauge theories based on the group SU(N){sub 1} x SU(N){sub 2} x {sub ...} x SU(N){sub k} with matter content (N, N{sup *}, 1, {sub ...}, 1)+(1, N, N{sup *}, {sub ...}, 1) + {sub ...} + (N{sup *}, 1, 1, {sub ...}, N), which are finite if and only if there are exactly three generations. We study in particular two models with SU(3){sup 3} as gauge group, an all-loop and a two-loop finite model, and we examine their predictions concerning the third generation quark masses. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Weidinger, Lukas; Bauer, Florian; von Delft, Jan
2017-01-01
We introduce an equilibrium formulation of the functional renormalization group (fRG) for inhomogeneous systems capable of dealing with spatially finite-ranged interactions. In the general third-order truncated form of fRG, the dependence of the two-particle vertex is described by O (N4) independent variables, where N is the dimension of the single-particle system. In a previous paper [Bauer et al., Phys. Rev. B 89, 045128 (2014), 10.1103/PhysRevB.89.045128], the so-called coupled-ladder approximation (CLA) was introduced and shown to admit a consistent treatment for models with a purely onsite interaction, reducing the vertex to O (N2) independent variables. In this work, we introduce an extended version of this scheme, called the extended coupled ladder approximation (eCLA), which includes a spatially extended feedback between the individual channels, measured by a feedback length L , using O (N2L2) independent variables for the vertex. We apply the eCLA in a static approximation and at zero temperature to three types of one-dimensional model systems, focusing on obtaining the linear response conductance. First, we study a model of a quantum point contact (QPC) with a parabolic barrier top and on-site interactions. In our setup, where the characteristic length lx of the QPC ranges between approximately 4-10 sites, eCLA achieves convergence once L becomes comparable to lx. It also turns out that the additional feedback stabilizes the fRG flow. This enables us, second, to study the geometric crossover between a QPC and a quantum dot, again for a one-dimensional model with on-site interactions. Third, the enlarged feedback also enables the treatment of a finite-ranged interaction extending over up to L sites. Using a simple estimate for the form of such a finite-ranged interaction in a QPC with a parabolic barrier top, we study its effects on the conductance and the density. We find that for low densities and sufficiently large interaction ranges the conductance
Thermal properties of hot and dense matter with finite range interactions
Constantinou, Constantinos; Prakash, Madappa; Lattimer, James M
2015-01-01
We explore the thermal properties of hot and dense matter using a model that reproduces the empirical properties of isospin symmetric and asymmetric bulk nuclear matter, optical model fits to nucleon-nucleus scattering data, heavy-ion flow data in the energy range 0.5-2 GeV/A, and the largest well-measured neutron star mass of 2 $\\rm{M}_\\odot$. Results of this model which incorporates finite range interactions through Yukawa type forces are contrasted with those of a zero-range Skyrme model that yields nearly identical zero-temperature properties at all densities for symmetric and asymmetric nucleonic matter and the maximum neutron star mass, but fails to account for heavy-ion flow data due to the lack of an appropriate momentum dependence in its mean field. Similarities and differences in the thermal state variables and the specific heats between the two models are highlighted. Checks of our exact numerical calculations are performed from formulas derived in the strongly degenerate and non-degenerate limits....
Finite element modelling of SAW correlator
Tikka, Ajay C.; Al-Sarawi, Said F.; Abbott, Derek
2007-12-01
Numerical simulations of SAW correlators so far are limited to delta function and equivalent circuit models. These models are not accurate as they do not replicate the actual behaviour of the device. Manufacturing a correlator to specifically realise a different configuration is both expensive and time consuming. With the continuous improvement in computing capacity, switching to finite element modelling would be more appropriate. In this paper a novel way of modelling a SAW correlator using finite element analysis is presented. This modelling approach allows the consideration of different code implementation and device structures. This is demonstrated through simulation results for a 5×2-bit Barker sequence encoded SAW correlator. These results show the effect of both bulk and leaky modes on the device performance at various operating frequencies. Moreover, the ways in which the gain of the correlator can be optimised though variation of design parameters will also be outlined.
Wang, Guochao; Wang, Jun
2017-01-01
We make an approach on investigating the fluctuation behaviors of financial volatility duration dynamics. A new concept of volatility two-component range intensity (VTRI) is developed, which constitutes the maximal variation range of volatility intensity and shortest passage time of duration, and can quantify the investment risk in financial markets. In an attempt to study and describe the nonlinear complex properties of VTRI, a random agent-based financial price model is developed by the finite-range interacting biased voter system. The autocorrelation behaviors and the power-law scaling behaviors of return time series and VTRI series are investigated. Then, the complexity of VTRI series of the real markets and the proposed model is analyzed by Fuzzy entropy (FuzzyEn) and Lempel-Ziv complexity. In this process, we apply the cross-Fuzzy entropy (C-FuzzyEn) to study the asynchrony of pairs of VTRI series. The empirical results reveal that the proposed model has the similar complex behaviors with the actual markets and indicate that the proposed stock VTRI series analysis and the financial model are meaningful and feasible to some extent.
Finite element modeling of permanent magnet devices
Brauer, J. R.; Larkin, L. A.; Overbye, V. D.
1984-03-01
New techniques are presented for finite element modeling of permanent magnets in magnetic devices such as motors and generators. These techniques extend a previous sheet-current permanent magnet model that applies only for straight line B-H loops and rectangular-shaped magnets. Here Maxwell's equations are used to derive the model of a permanent magnet having a general curved B-H loop and any geometric shape. The model enables a nonlinear magnetic finite element program to use Newton-Raphson iteration to solve for saturable magnetic fields in a wide variety of devices containing permanent magnets and steels. The techniques are applied to a brushless dc motor with irregular-shaped permanent magnets. The calculated motor torque agrees well with measured torque.
Scaling functions of two-neutron separation energies of $^{20}C$ with finite range potentials
Shalchi, M A; Yamashita, M T; Tomio, Lauro; Frederico, T
2015-01-01
The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus $^{20}C$.
Scaling functions of two-neutron separation energies of 20C with finite range potentials
Shalchi, M. A.; Hadizadeh, M. R.; Yamashita, M. T.; Tomio, Lauro; Frederico, T.
2016-03-01
The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus 20C.
Scaling functions of two-neutron separation energies of 20C with finite range potentials
Directory of Open Access Journals (Sweden)
Shalchi M. A.
2016-01-01
Full Text Available The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus 20C.
Finite element model of needle electrode sensitivity
Høyum, P.; Kalvøy, H.; Martinsen, Ø. G.; Grimnes, S.
2010-04-01
We used the Finite Element (FE) Method to estimate the sensitivity of a needle electrode for bioimpedance measurement. This current conducting needle with insulated shaft was inserted in a saline solution and current was measured at the neutral electrode. FE model resistance and reactance were calculated and successfully compared with measurements on a laboratory model. The sensitivity field was described graphically based on these FE simulations.
Finite Time Blowup in a Realistic Food-Chain Model
Parshad, Rana
2013-05-19
We investigate a realistic three-species food-chain model, with generalist top predator. The model based on a modified version of the Leslie-Gower scheme incorporates mutual interference in all the three populations and generalizes several other known models in the ecological literature. We show that the model exhibits finite time blowup in certain parameter range and for large enough initial data. This result implies that finite time blowup is possible in a large class of such three-species food-chain models. We propose a modification to the model and prove that the modified model has globally existing classical solutions, as well as a global attractor. We reconstruct the attractor using nonlinear time series analysis and show that it pssesses rich dynamics, including chaos in certain parameter regime, whilst avoiding blowup in any parameter regime. We also provide estimates on its fractal dimension as well as provide numerical simulations to visualise the spatiotemporal chaos.
The finite element modeling of spiral ropes
Institute of Scientific and Technical Information of China (English)
Juan Wu
2014-01-01
Accurate understanding the behavior of spiral rope is complicated due to their complex geometry and complex contact conditions between the wires. This study proposed the finite element models of spiral ropes subjected to tensile loads. The parametric equations developed in this paper were implemented for geometric modeling of ropes. The 3D geometric models with different twisting manner, equal diameters of wires were generated in details by using Pro/ENGINEER software. The results of the present finite element analysis were on an acceptable level of accuracy as compared with those of theoretical and experimental data. Further development is ongoing to analysis the equivalent stresses induced by twisting manner of cables. The twisting manner of wires was important to spiral ropes in the three wire layers and the outer twisting manner of wires should be contrary to that of the second layer, no matter what is the first twisting manner of wires.
A finite element parametric modeling technique of aircraft wing structures
Institute of Scientific and Technical Information of China (English)
Tang Jiapeng; Xi Ping; Zhang Baoyuan; Hu Bifu
2013-01-01
A finite element parametric modeling method of aircraft wing structures is proposed in this paper because of time-consuming characteristics of finite element analysis pre-processing. The main research is positioned during the preliminary design phase of aircraft structures. A knowledge-driven system of fast finite element modeling is built. Based on this method, employing a template parametric technique, knowledge including design methods, rules, and expert experience in the process of modeling is encapsulated and a finite element model is established automatically, which greatly improves the speed, accuracy, and standardization degree of modeling. Skeleton model, geometric mesh model, and finite element model including finite element mesh and property data are established on parametric description and automatic update. The outcomes of research show that the method settles a series of problems of parameter association and model update in the pro-cess of finite element modeling which establishes a key technical basis for finite element parametric analysis and optimization design.
Multiphase Transformer Modelling using Finite Element Method
Directory of Open Access Journals (Sweden)
Nor Azizah Mohd Yusoff
2015-03-01
Full Text Available In the year of 1970 saw the starting invention of the five-phase motor as the milestone in advanced electric motor. Through the years, there are many researchers, which passionately worked towards developing for multiphase drive system. They developed a static transformation system to obtain a multiphase supply from the available three-phase supply. This idea gives an influence for further development in electric machines as an example; an efficient solution for bulk power transfer. This paper highlighted the detail descriptions that lead to five-phase supply with fixed voltage and frequency by using Finite-Element Method (FEM. Identifying of specification on a real transformer had been done before applied into software modeling. Therefore, Finite-Element Method provides clearly understandable in terms of visualize the geometry modeling, connection scheme and output waveform.
FINITE-ELEMENT MODELING OF SALT TECTONICS
Directory of Open Access Journals (Sweden)
Natalia Bakhova
2012-09-01
Full Text Available The two-dimensional thermal model of graben structure in the presence of salt tectonics on the basis of a finite elements method is constructed. The analysis of the thermal field is based on the solution of stationary equation of heat conductivity with variable boundary conditions. The high precision of temperatures distribution and heat flows is received. The decision accuracy is no more than 0,6 %.
EXODUS II: A finite element data model
Energy Technology Data Exchange (ETDEWEB)
Schoof, L.A.; Yarberry, V.R.
1994-09-01
EXODUS II is a model developed to store and retrieve data for finite element analyses. It is used for preprocessing (problem definition), postprocessing (results visualization), as well as code to code data transfer. An EXODUS II data file is a random access, machine independent, binary file that is written and read via C, C++, or Fortran library routines which comprise the Application Programming Interface (API).
Finite element modeling for materials engineers using Matlab
Oluwole, Oluleke
2014-01-01
Finite Element Modeling for Materials Engineers Using MATLAB® combines the finite element method with MATLAB to offer materials engineers a fast and code-free way of modeling for many materials processes.
Spin Foam Models with Finite Groups
Directory of Open Access Journals (Sweden)
Benjamin Bahr
2013-01-01
Full Text Available Spin foam models, loop quantum gravity, and group field theory are discussed as quantum gravity candidate theories and usually involve a continuous Lie group. We advocate here to consider quantum gravity-inspired models with finite groups, firstly as a test bed for the full theory and secondly as a class of new lattice theories possibly featuring an analogue diffeomorphism symmetry. To make these notes accessible to readers outside the quantum gravity community, we provide an introduction to some essential concepts in the loop quantum gravity, spin foam, and group field theory approach and point out the many connections to the lattice field theory and the condensed-matter systems.
Spin foam models with finite groups
Bahr, Benjamin; Ryan, James P
2011-01-01
Spin foam models, loop quantum gravity and group field theory are discussed as quantum gravity candidate theories and usually involve a continuous Lie group. We advocate here to consider quantum gravity inspired models with finite groups, firstly as a test bed for the full theory and secondly as a class of new lattice theories possibly featuring an analogue diffeomorphism symmetry. To make these notes accessible to readers outside the quantum gravity community we provide an introduction to some essential concepts in the loop quantum gravity, spin foam and group field theory approach and point out the many connections to lattice field theory and condensed matter systems.
Consistent description of 12C and 16O using finite range three-body interaction
Itagaki, N
2016-01-01
Consistent description of 12C and 16O has been a long standing problem of microscopic alpha cluster models, where the wave function is fully antisymmetrized and the effective interaction is applied not between alpha clusters but between nucleons. When the effective interaction is designed to reproduce the binding energy of 16O (four alpha), the binding energy of 12C (three alpha) becomes underbound by about 10 MeV. In the present study, by taking into account the coupling with the jj-coupling shell model components and utilizing Tohsaki interaction, which is phenomenological but has finite-range three-body interaction terms, we show that consistent understanding of these nuclei can be achieved. The original Tohsaki interaction gives small overbound of about 3 MeV for 16O, and this is improved by slightly modifying three-body Majorana exchange parameter. Also, the coupling with the jj-coupling shell model wave function strongly contributes to the increase of the binding energy of 12C. So far the application of...
Finite Element Model of Cardiac Electrical Conduction.
Yin, John Zhihao
1994-01-01
In this thesis, we develop mathematical models to study electrical conduction of the heart. One important pattern of wave propagation of electrical excitation in the heart is reentry which is believed to be the underlying mechanism of some dangerous cardiac arhythmias such as ventricular tachycardia and ventricular fibrillation. We present in this thesis a new ionic channel model of the ventricular cardiac cell membrane to study the microscopic electrical properties of myocardium. We base our model on recent single channel experiment data and a simple physical diffusion model of the calcium channel. Our ionic channel model of myocardium has simpler differential equations and fewer parameters than previous models. Further more, our ionic channel model achieves better results in simulating the strength-interval curve when we connect the membrane patch model to form a one dimensional cardiac muscle strand. We go on to study a finite element model which uses multiple states and non-nearest neighbor interactions to include curvature and dispersion effects. We create a generalized lattice randomization to overcome the artifacts generated by the interaction between the local dynamics and the regularities of the square lattice. We show that the homogeneous model does not display spontaneous wavefront breakup in a reentrant wave propagation once the lattice artifacts have been smoothed out by lattice randomization with a randomization scale larger than the characteristic length of the interaction. We further develop a finite 3-D 3-state heart model which employs a probability interaction rule. This model is applied to the simulation of Body Surface Laplacian Mapping (BSLM) using a cylindrical volume conductor as the torso model. We show that BSLM has a higher spatial resolution than conventional mapping methods in revealing the underlying electrical activities of the heart. The results of these studies demonstrate that mathematical modeling and computer simulation are very
Finite Element Modeling, Simulation, Tools, and Capabilities at Superform
Raman, Hari; Barnes, A. J.
2010-06-01
Over the past thirty years Superform has been a pioneer in the SPF arena, having developed a keen understanding of the process and a range of unique forming techniques to meet varying market needs. Superform’s high-profile list of customers includes Boeing, Airbus, Aston Martin, Ford, and Rolls Royce. One of the more recent additions to Superform’s technical know-how is finite element modeling and simulation. Finite element modeling is a powerful numerical technique which when applied to SPF provides a host of benefits including accurate prediction of strain levels in a part, presence of wrinkles and predicting pressure cycles optimized for time and part thickness. This paper outlines a brief history of finite element modeling applied to SPF and then reviews some of the modeling tools and techniques that Superform have applied and continue to do so to successfully superplastically form complex-shaped parts. The advantages of employing modeling at the design stage are discussed and illustrated with real-world examples.
Maximum likelihood estimation of finite mixture model for economic data
Phoong, Seuk-Yen; Ismail, Mohd Tahir
2014-06-01
Finite mixture model is a mixture model with finite-dimension. This models are provides a natural representation of heterogeneity in a finite number of latent classes. In addition, finite mixture models also known as latent class models or unsupervised learning models. Recently, maximum likelihood estimation fitted finite mixture models has greatly drawn statistician's attention. The main reason is because maximum likelihood estimation is a powerful statistical method which provides consistent findings as the sample sizes increases to infinity. Thus, the application of maximum likelihood estimation is used to fit finite mixture model in the present paper in order to explore the relationship between nonlinear economic data. In this paper, a two-component normal mixture model is fitted by maximum likelihood estimation in order to investigate the relationship among stock market price and rubber price for sampled countries. Results described that there is a negative effect among rubber price and stock market price for Malaysia, Thailand, Philippines and Indonesia.
Finite-Element Modelling of Biotransistors
Directory of Open Access Journals (Sweden)
Selvaganapathy PR
2010-01-01
Full Text Available Abstract Current research efforts in biosensor design attempt to integrate biochemical assays with semiconductor substrates and microfluidic assemblies to realize fully integrated lab-on-chip devices. The DNA biotransistor (BioFET is an example of such a device. The process of chemical modification of the FET and attachment of linker and probe molecules is a statistical process that can result in variations in the sensed signal between different BioFET cells in an array. In order to quantify these and other variations and assess their importance in the design, complete physical simulation of the device is necessary. Here, we perform a mean-field finite-element modelling of a short channel, two-dimensional BioFET device. We compare the results of this model with one-dimensional calculation results to show important differences, illustrating the importance of the molecular structure, placement and conformation of DNA in determining the output signal.
Finite element modeling of retinal prosthesis mechanics
Basinger, B. C.; Rowley, A. P.; Chen, K.; Humayun, M. S.; Weiland, J. D.
2009-10-01
Epiretinal prostheses used to treat degenerative retina diseases apply stimulus via an electrode array fixed to the ganglion cell side of the retina. Mechanical pressure applied by these arrays to the retina, both during initial insertion and throughout chronic use, could cause sufficient retinal damage to reduce the device's effectiveness. In order to understand and minimize potential mechanical damage, we have used finite element analysis to model mechanical interactions between an electrode array and the retina in both acute and chronic loading configurations. Modeling indicates that an acute tacking force distributes stress primarily underneath the tack site and heel edge of the array, while more moderate chronic stresses are distributed more evenly underneath the array. Retinal damage in a canine model chronically implanted with a similar array occurred in correlating locations, and model predictions correlate well with benchtop eyewall compression tests. This model provides retinal prosthesis researchers with a tool to optimize the mechanical electrode array design, but the techniques used here represent a unique effort to combine a modifiable device and soft biological tissues in the same model and those techniques could be extended to other devices that come into mechanical contact with soft neural tissues.
Measuring finite-range phase coherence in an optical lattice using Talbot interferometry
Santra, Bodhaditya; Baals, Christian; Labouvie, Ralf; Bhattacherjee, Aranya B.; Pelster, Axel; Ott, Herwig
2017-06-01
One of the important goals of present research is to control and manipulate coherence in a broad variety of systems, such as semiconductor spintronics, biological photosynthetic systems, superconducting qubits and complex atomic networks. Over the past decades, interferometry of atoms and molecules has proven to be a powerful tool to explore coherence. Here we demonstrate a near-field interferometer based on the Talbot effect, which allows us to measure finite-range phase coherence of ultracold atoms in an optical lattice. We apply this interferometer to study the build-up of phase coherence after a quantum quench of a Bose-Einstein condensate residing in a one-dimensional optical lattice. Our technique of measuring finite-range phase coherence is generic, easy to adopt and can be applied in practically all lattice experiments without further modifications.
Finite element models applied in active structural acoustic control
Oude Nijhuis, Marco H.H.; Boer, de André; Rao, Vittal S.
2002-01-01
This paper discusses the modeling of systems for active structural acoustic control. The finite element method is applied to model structures including the dynamics of piezoelectric sensors and actuators. A model reduction technique is presented to make the finite element model suitable for controll
ALTERNATING DIRECTION FINITE ELEMENT METHOD FOR SOME REACTION DIFFUSION MODELS
Institute of Scientific and Technical Information of China (English)
江成顺; 刘蕴贤; 沈永明
2004-01-01
This paper is concerned with some nonlinear reaction - diffusion models. To solve this kind of models, the modified Laplace finite element scheme and the alternating direction finite element scheme are established for the system of patrical differential equations. Besides, the finite difference method is utilized for the ordinary differential equation in the models. Moreover, by the theory and technique of prior estimates for the differential equations, the convergence analyses and the optimal L2- norm error estimates are demonstrated.
Adaptive finite difference for seismic wavefield modelling in acoustic media.
Yao, Gang; Wu, Di; Debens, Henry Alexander
2016-08-05
Efficient numerical seismic wavefield modelling is a key component of modern seismic imaging techniques, such as reverse-time migration and full-waveform inversion. Finite difference methods are perhaps the most widely used numerical approach for forward modelling, and here we introduce a novel scheme for implementing finite difference by introducing a time-to-space wavelet mapping. Finite difference coefficients are then computed by minimising the difference between the spatial derivatives of the mapped wavelet and the finite difference operator over all propagation angles. Since the coefficients vary adaptively with different velocities and source wavelet bandwidths, the method is capable to maximise the accuracy of the finite difference operator. Numerical examples demonstrate that this method is superior to standard finite difference methods, while comparable to Zhang's optimised finite difference scheme.
Model Predictive Control based on Finite Impulse Response Models
DEFF Research Database (Denmark)
Prasath, Guru; Jørgensen, John Bagterp
2008-01-01
We develop a regularized l2 finite impulse response (FIR) predictive controller with input and input-rate constraints. Feedback is based on a simple constant output disturbance filter. The performance of the predictive controller in the face of plant-model mismatch is investigated by simulations...
Intra Plate Stresses Using Finite Element Modelling
Directory of Open Access Journals (Sweden)
Jayalakshmi S.
2016-10-01
Full Text Available One of the most challenging problems in the estimation of seismic hazard is the ability to quantify seismic activity. Empirical models based on the available earthquake catalogue are often used to obtain activity of source regions. The major limitation with this approach is the lack of sufficient data near a specified source. The non-availability of data poses difficulties in obtaining distribution of earthquakes with large return periods. Such events recur over geological time scales during which tectonic processes, including mantle convection, formation of faults and new plate boundaries, are likely to take place. The availability of geometries of plate boundaries, plate driving forces, lithospheric stress field and GPS measurements has provided numerous insights on the mechanics of tectonic plates. In this article, a 2D finite element model of Indo-Australian plate is developed with the focus of representing seismic activity in India. The effect of large scale geological features including sedimentary basins, fold belts and cratons on the stress field in India is explored in this study. In order to address long term behaviour, the orientation of stress field and tectonic faults of the present Indo-Australian plate are compared with a reconstructed stress field from the early Miocene (20 Ma.
Ultralong-range order in the Fermi-Hubbard model with long-range interactions
van Loon, Erik G. C. P.; Katsnelson, Mikhail I.; Lemeshko, Mikhail
2015-08-01
We use the dual boson approach to reveal the phase diagram of the Fermi-Hubbard model with long-range dipole-dipole interactions. By using a large-scale finite-temperature calculation on a 64 ×64 square lattice we demonstrate the existence of a novel phase, possessing an "ultralong-range" order. The fingerprint of this phase—the density correlation function—features a nontrivial behavior on a scale of tens of lattice sites. We study the properties and the stability of the ultralong-range-ordered phase, and show that it is accessible in modern experiments with ultracold polar molecules and magnetic atoms.
Home range analysis using a mechanistic home range model
Energy Technology Data Exchange (ETDEWEB)
Moorcroft, P.R. (Princeton Univ., NJ (United States). Dept. of Ecology and Evolutionary Biology); Lewis, M.A. (Univ. of Utah, Salt Lake City, UT (United States). Dept. of Mathematics) Crabtree, R.L. (Univ. of Idaho, Moscow, ID (United States). Dept. of Fish and Wildlife Resources)
1999-07-01
The traditional models used to characterize animal home ranges have no mechanistic basis underlying their descriptions of space use, and as a result, the analysis of animal home ranges has primarily been a descriptive endeavor. In this paper, the authors characterize coyote (Canis latrans) home range patterns using partial differential equations for expected space use that are formally derived from underlying descriptions of individual movement behavior. To the authors' knowledge, this is the first time that mechanistic models have been used to characterize animal home ranges. The results provide empirical support for a model formulation of movement response to scent marks, and suggest that having relocation data for individuals in adjacent groups is necessary to capture the spatial arrangement of home range boundaries. The authors then show how the model fits can be used to obtain predictions for individual movement and scent marking behavior and to predict changes in home range patterns. More generally, the findings illustrate how mechanistic models permit the development of a predictive theory for the relationship between movement behavior and animal spatial distribution.
Accurate finite element modeling of acoustic waves
Idesman, A.; Pham, D.
2014-07-01
In the paper we suggest an accurate finite element approach for the modeling of acoustic waves under a suddenly applied load. We consider the standard linear elements and the linear elements with reduced dispersion for the space discretization as well as the explicit central-difference method for time integration. The analytical study of the numerical dispersion shows that the most accurate results can be obtained with the time increments close to the stability limit. However, even in this case and the use of the linear elements with reduced dispersion, mesh refinement leads to divergent numerical results for acoustic waves under a suddenly applied load. This is explained by large spurious high-frequency oscillations. For the quantification and the suppression of spurious oscillations, we have modified and applied a two-stage time-integration technique that includes the stage of basic computations and the filtering stage. This technique allows accurate convergent results at mesh refinement as well as significantly reduces the numerical anisotropy of solutions. We should mention that the approach suggested is very general and can be equally applied to any loading as well as for any space-discretization technique and any explicit or implicit time-integration method.
Nuclear response functions with finite-range Gogny force: Tensor terms and instabilities
De Pace, A.; Martini, M.
2016-08-01
A fully antisymmetrized random phase approximation calculation employing the continued fraction technique is performed to study nuclear matter response functions with the finite-range Gogny force. The most commonly used parameter sets of this force, as well as some recent generalizations that include the tensor terms, are considered and the corresponding response functions are shown. The calculations are performed at first and second order in the continued fraction expansion and the explicit expressions for the second-order tensor contributions are given. Comparisons between first- and second-order continued fraction expansion results are provided. The differences between the responses obtained at the two orders turn out to be more pronounced for the forces including tensor terms than for the standard Gogny ones. In the vector channels the responses calculated with Gogny forces including tensor terms are characterized by a large heterogeneity, reflecting the different choices for the tensor part of the interaction. For the sake of comparison the response functions obtained considering a G -matrix-based nuclear interaction are also shown. As a first application of the present calculation, the possible existence of spurious finite-size instabilities of the Gogny forces with or without tensor terms has been investigated. The positive conclusion is that all the Gogny forces but the GT2 one are free of spurious finite-size instabilities. In perspective, the tool developed in the present paper can be inserted in the fitting procedure to construct new Gogny-type forces.
Modeling software with finite state machines a practical approach
Wagner, Ferdinand; Wagner, Thomas; Wolstenholme, Peter
2006-01-01
Modeling Software with Finite State Machines: A Practical Approach explains how to apply finite state machines to software development. It provides a critical analysis of using finite state machines as a foundation for executable specifications to reduce software development effort and improve quality. This book discusses the design of a state machine and of a system of state machines. It also presents a detailed analysis of development issues relating to behavior modeling with design examples and design rules for using finite state machines. This volume describes a coherent and well-tested fr
Universality in the neutron$-^{19}$C scattering using finite range separable interactions
Shalchi, M A; Hadizadeh, M R; Frederico, T; Tomio, Lauro
2016-01-01
We report a study on the low-energy properties of the elastic $s-$wave scattering of a neutron ($n$) in the carbon isotope $^{19}$C near the critical condition for the occurrence of an excited Efimov state in the three-body $n-n-^{18}$C system. For the separation energy of the two halo neutrons in $^{20}$C we use the available experimental data. We also investigate to which extent the universal scaling laws, strictly valid in the zero-range limit, will survive when using finite-range interactions. By allowing to vary the $n-^{18}$C binding energy, a scaling behavior for the real and imaginary parts of the $s-$wave phase-shift $\\delta_0$ is verified, emerging some universal characteristics given by the pole-position of $k\\cot(\\delta_0^R)$ and effective-range parameters.
Finite element model updating using bayesian framework and modal properties
CSIR Research Space (South Africa)
Marwala, T
2005-01-01
Full Text Available Finite element (FE) models are widely used to predict the dynamic characteristics of aerospace structures. These models often give results that differ from measured results and therefore need to be updated to match measured results. Some...
Finite element analysis to model complex mitral valve repair.
Labrosse, Michel; Mesana, Thierry; Baxter, Ian; Chan, Vincent
2016-01-01
Although finite element analysis has been used to model simple mitral repair, it has not been used to model complex repair. A virtual mitral valve model was successful in simulating normal and abnormal valve function. Models were then developed to simulate an edge-to-edge repair and repair employing quadrangular resection. Stress contour plots demonstrated increased stresses along the mitral annulus, corresponding to the annuloplasty. The role of finite element analysis in guiding clinical practice remains undetermined.
FINITE VOLUME METHOD OF MODELLING TRANSIENT GROUNDWATER FLOW
Directory of Open Access Journals (Sweden)
N. Muyinda
2014-01-01
Full Text Available In the field of computational fluid dynamics, the finite volume method is dominant over other numerical techniques like the finite difference and finite element methods because the underlying physical quantities are conserved at the discrete level. In the present study, the finite volume method is used to solve an isotropic transient groundwater flow model to obtain hydraulic heads and flow through an aquifer. The objective is to discuss the theory of finite volume method and its applications in groundwater flow modelling. To achieve this, an orthogonal grid with quadrilateral control volumes has been used to simulate the model using mixed boundary conditions from Bwaise III, a Kampala Surburb. Results show that flow occurs from regions of high hydraulic head to regions of low hydraulic head until a steady head value is achieved.
Modeling Dislocations and Disclinations with Finite Micropolar Elastoplasticity
2006-02-01
proposed three-term multiplicative decompositions for continuum elastoplasticity exclusive of damage , although each within a slightly different context...Modeling Dislocations and Disclinations With Finite Micropolar Elastoplasticity by John D. Clayton, David L. McDowell, and Douglas J. Bammann...and Disclinations With Finite Micropolar Elastoplasticity John D. Clayton Weapons and Materials Research Directorate, ARL David L. McDowell
Parallel direct solver for finite element modeling of manufacturing processes
DEFF Research Database (Denmark)
Nielsen, Chris Valentin; Martins, P.A.F.
2017-01-01
The central processing unit (CPU) time is of paramount importance in finite element modeling of manufacturing processes. Because the most significant part of the CPU time is consumed in solving the main system of equations resulting from finite element assemblies, different approaches have been...
A locally finite model for gravity
't Hooft, G.
2008-01-01
Matter interacting classically with gravity in 3+1 dimensions usually gives rise to a continuum of degrees of freedom, so that, in any attempt to quantize the theory, ultraviolet divergences are nearly inevitable. Here, we investigate matter of a form that only displays a finite number of degrees of
Finite-size effects in the spherical model of finite thickness
Chamati, H.
2008-09-01
A detailed analysis of the finite-size effects on the bulk critical behaviour of the d-dimensional mean spherical model confined to a film geometry with finite thickness L is reported. Along the finite direction different kinds of boundary conditions are applied: periodic (p), antiperiodic (a) and free surfaces with Dirichlet (D), Neumann (N) and a combination of Neumann and Dirichlet (ND) on both surfaces. A systematic method for the evaluation of the finite-size corrections to the free energy for the different types of boundary conditions is proposed. The free energy density and the equation for the spherical field are computed for arbitrary d. It is found, for 2 finite-size scaling form at the bulk critical temperature only for (p) and (a). For the remaining boundary conditions the standard finite-size scaling hypothesis is not valid. At d = 3, the critical amplitude of the singular part of the free energy (related to the so-called Casimir amplitude) is estimated. We obtain Δ(p) = -2ζ(3)/(5π) = -0.153 051..., Δ(a) = 0.274 543... and Δ(ND) = 0.019 22..., implying a fluctuation-induced attraction between the surfaces for (p) and repulsion in the other two cases. For (D) and (N) we find a logarithmic dependence on L.
A FINITE ELEMENT MODEL FOR SEISMICITY INDUCED BY FAULT INTERACTION
Institute of Scientific and Technical Information of China (English)
Chen Huaran; Li Yiqun; He Qiaoyun; Zhang Jieqing; Ma Hongsheng; Li Li
2003-01-01
On ths basis of interaction between faults, a finite element model for Southwest China is constructed, and the stress adjustment due to the strong earthquake occurrence in this region was studied. The preliminary results show that many strong earthquakes occurred in the area of increased stress in the model. Though the results are preliminary, the quasi-3D finite element model is meaningful for strong earthquake prediction.
A FINITE ELEMENT MODEL FOR SEISMICITY INDUCED BY FAULT INTERACTION
Institute of Scientific and Technical Information of China (English)
ChenHuaran; LiYiqun; HeQiaoyun; ZhangJieqing; MaHongsheng; LiLi
2003-01-01
On ths basis of interaction between faults, a finite element model for Southwest China is constructed, and the stress adjustment due to the strong earthquake occurrence in this region was studied. The preliminary results show that many strong earthquakes occurred in the are a of increased stress in the model. Though the results are preliminary, the quasi-3D finite element model is meaningful for strong earthquake prediction.
The Theory of Finite Models without Equal Sign
Institute of Scientific and Technical Information of China (English)
Li Bo LUO
2006-01-01
In this paper, it is the first time ever to suggest that we study the model theory of all finite structures and to put the equal sign in the same situtation as the other relations. Using formulas of infinite lengths we obtain new theorems for the preservation of model extensions, submodels, model homomorphisms and inverse homomorphisms. These kinds of theorems were discussed in Chang and Keisler's Model Theory, systematically for general models, but Gurevich obtained some different theorems in this direction for finite models. In our paper the old theorems manage to survive in the finite model theory. There are some differences between into homomorphisms and onto homomorphisms in preservation theorems too. We also study reduced models and minimum models. The characterization sentence of a model is given, which derives a general result for any theory T to be equivalent to a set of existential-universal sentences. Some results about completeness and model completeness are also given.
Neutron$-^{19}$C scattering: emergence of universal properties in a finite range potential
Shalchi, M A; Hadizadeh, M R; Frederico, T; Tomio, Lauro
2016-01-01
The low-energy properties of the elastic $s-$wave scattering for the $n-^{19}$C are studied near the critical condition for the occurrence of an excited Efimov state in $n-n-^{18}$C. It is established to which extent the universal scaling laws, strictly valid in the zero-range limit, survive when finite range potentials are considered. By fixing the two-neutrons separation energy in $^{20}$C with available experimental data, it is studied the scaling of the real ($\\delta_0^R$) and imaginary parts of the $s-$wave phase-shift with the variation of the $n-^{18}$C binding energy. We obtain some universal characteristics given by the pole-position of $k\\cot(\\delta_0^R)$ and effective-range parameters. By increasing the $n-^{18}$C binding energy, it was verified that the excited state of $^{20}$C goes to a virtual state, resembling the neutron-deuteron behavior in the triton. It is confirmed that the analytical structure of the unitary cut is not affected by the range of the potential or mass asymmetry of the three...
Neutron-19C scattering: Emergence of universal properties in a finite range potential
Shalchi, M. A.; Yamashita, M. T.; Hadizadeh, M. R.; Frederico, T.; Tomio, Lauro
2017-01-01
The low-energy properties of the elastic s-wave scattering for the n-19C are studied near the critical condition for the occurrence of an excited Efimov state in n-n-18C. It is established to which extent the universal scaling laws, strictly valid in the zero-range limit, survive when finite range potentials are considered. By fixing the two-neutrons separation energy in 20C with available experimental data, it is studied the scaling of the real (δ0R) and imaginary parts of the s-wave phase-shift with the variation of the n-18C binding energy. We obtain some universal characteristics given by the pole-position of kcot (δ0R) and effective-range parameters. By increasing the n-18C binding energy, it was verified that the excited state of 20C goes to a virtual state, resembling the neutron-deuteron behavior in the triton. It is confirmed that the analytical structure of the unitary cut is not affected by the range of the potential or mass asymmetry of the three-body system.
Neutron-19C scattering: Emergence of universal properties in a finite range potential
Directory of Open Access Journals (Sweden)
M.A. Shalchi
2017-01-01
Full Text Available The low-energy properties of the elastic s-wave scattering for the n-19C are studied near the critical condition for the occurrence of an excited Efimov state in n–n-18C. It is established to which extent the universal scaling laws, strictly valid in the zero-range limit, survive when finite range potentials are considered. By fixing the two-neutrons separation energy in 20C with available experimental data, it is studied the scaling of the real (δ0R and imaginary parts of the s-wave phase-shift with the variation of the n-18C binding energy. We obtain some universal characteristics given by the pole-position of kcot(δ0R and effective-range parameters. By increasing the n-18C binding energy, it was verified that the excited state of 20C goes to a virtual state, resembling the neutron–deuteron behavior in the triton. It is confirmed that the analytical structure of the unitary cut is not affected by the range of the potential or mass asymmetry of the three-body system.
Cluster decay half-lives of trans-lead nuclei based on a finite-range nucleon–nucleon interaction
Energy Technology Data Exchange (ETDEWEB)
Adel, A., E-mail: aa.ahmed@mu.edu.sa [Physics Department, Faculty of Science, Cairo University, Giza (Egypt); Physics Department, College of Science, Majmaah University, Zulfi (Saudi Arabia); Alharbi, T. [Physics Department, College of Science, Majmaah University, Zulfi (Saudi Arabia)
2017-02-15
Nuclear cluster radioactivity is investigated using microscopic potentials in the framework of the Wentzel–Kramers–Brillouin approximation of quantum tunneling by considering the Bohr–Sommerfeld quantization condition. The microscopic cluster–daughter potential is numerically constructed in the well-established double-folding model. A realistic M3Y-Paris NN interaction with the finite-range exchange part as well as the ordinary zero-range exchange NN force is considered in the present work. The influence of nuclear deformations on the cluster decay half-lives is investigated. Based on the available experimental data, the cluster preformation factors are extracted from the calculated and the measured half lives of cluster radioactivity. Some useful predictions of cluster emission half-lives are made for emissions of known clusters from possible candidates, which may guide future experiments.
Cluster decay half-lives of trans-lead nuclei based on a finite-range nucleon-nucleon interaction
Adel, A.; Alharbi, T.
2017-02-01
Nuclear cluster radioactivity is investigated using microscopic potentials in the framework of the Wentzel-Kramers-Brillouin approximation of quantum tunneling by considering the Bohr-Sommerfeld quantization condition. The microscopic cluster-daughter potential is numerically constructed in the well-established double-folding model. A realistic M3Y-Paris NN interaction with the finite-range exchange part as well as the ordinary zero-range exchange NN force is considered in the present work. The influence of nuclear deformations on the cluster decay half-lives is investigated. Based on the available experimental data, the cluster preformation factors are extracted from the calculated and the measured half lives of cluster radioactivity. Some useful predictions of cluster emission half-lives are made for emissions of known clusters from possible candidates, which may guide future experiments.
Refining personality disorder subtypes and classification using finite mixture modeling.
Yun, Rebecca J; Stern, Barry L; Lenzenweger, Mark F; Tiersky, Lana A
2013-04-01
The current Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic system for Axis II disorders continues to be characterized by considerable heterogeneity and poor discriminant validity. Such problems impede accurate personality disorder (PD) diagnosis. As a result, alternative assessment tools are often used in conjunction with the DSM. One popular framework is the object relational model developed by Kernberg and his colleagues (J. F. Clarkin, M. F. Lenzenweger, F. Yeomans, K. N. Levy, & O. F. Kernberg, 2007, An object relations model of borderline pathology, Journal of Personality Disorders, Vol. 21, pp. 474-499; O. F. Kernberg, 1984, Severe Personality Disorders, New Haven, CT: Yale University Press; O. F. Kernberg & E. Caligor, 2005, A psychoanalytic theory of personality disorders, in M. F. Lenzenweger & J. F. Clarkin, Eds., Major Theories of Personality Disorder, New York, NY: Guilford Press). Drawing on this model and empirical studies thereof, the current study attempted to clarify Kernberg's (1984) PD taxonomy and identify subtypes within a sample with varying levels of personality pathology using finite mixture modeling. Subjects (N = 141) were recruited to represent a wide range of pathology. The finite mixture modeling results indicated that 3 components were harbored within the variables analyzed. Group 1 was characterized by low levels of antisocial, paranoid, and aggressive features, and Group 2 was characterized by elevated paranoid features. Group 3 revealed the highest levels across the 3 variables. The validity of the obtained solution was then evaluated by reference to a variety of external measures that supported the validity of the identified grouping structure. Findings generally appear congruent with previous research, which argued that a PD taxonomy based on paranoid, aggressive, and antisocial features is a viable supplement to current diagnostic systems. Our study suggests that Kernberg's object relational model offers a
Finite element modelling of solidification phenomena
Indian Academy of Sciences (India)
K N Seetharamu; R Paragasam; Ghulam A Quadir; Z A Zainal; B Sathya Prasad; T Sundararajan
2001-02-01
The process of solidification process is complex in nature and the simulation of such process is required in industry before it is actually undertaken. Finite element method is used to simulate the heat transfer process accompanying the solidification process. The metal and the mould along with the air gap formation is accounted in the heat transfer simulation. Distortion of the casting is caused due to non-uniform shrinkage associated with the process. Residual stresses are induced in the final castings. Simulation of the shrinkage and the thermal stresses are also carried out using finite element methods. The material behaviour is considered as visco-plastic. The simulations are compared with available experimental data and the comparison is found to be good. Special considerations regarding the simulation of solidification process are also brought out.
Breakup and finite-range effects on the 8B(d,n)9C reaction
Fukui, Tokuro; Yahiro, Masanobu
2014-01-01
The astrophysical factor of 8B(p,{\\gamma})9C at zero energy, S18(0), is determined by a three-body coupled-channels analysis of the transfer reaction 8B(d,n)9C at 14.4 MeV/nucleon. Effects of the breakup channels of deuteron are investigated with the continuum-discretized coupled-channels method (CDCC). It is found that the transfer process through the deuteron breakup states, its interference with that through the deuteron ground state in particular, gives a large increase in the transfer cross section. The finite-range effects with respect to the proton- neutron relative coordinate are found to be less than 5%. As a result of the present analysis, S18(0) = 33 +/- 10 eVb is obtained that is smaller than the result of the previous DWBA analysis by about 26%.
Nuclear response functions with finite range Gogny force: tensor terms and instabilities
De Pace, A
2016-01-01
A fully-antisymmetrized random phase approximation calculation employing the continued fraction technique is performed to study nuclear matter response functions with the finite range Gogny force. The most commonly used parameter sets of this force, as well as some recent generalizations that include the tensor terms are considered and the corresponding response functions are shown. The calculations are performed at the first and second order in the continued fraction expansion and the explicit expressions for the second order tensor contributions are given. Comparison between first and second order continued fraction expansion results are provided. The differences between the responses obtained at the two orders turn to be more pronounced for the forces including tensor terms than for the standard Gogny ones. In the vector channels the responses calculated with Gogny forces including tensor terms are characterized by a large heterogeneity, reflecting the different choices for the tensor part of the interacti...
Continuum and Symmetry-Conserving Effects in Drip-line Nuclei Using Finite-range Forces
Schunck, N
2007-01-01
We report the first calculations of nuclear properties near the drip-lines using the spherical Hartree-Fock-Bogoliubov mean-field theory with a finite-range force supplemented by continuum and particle number projection effects. Calculations were carried out in a basis made of the eigenstates of a Woods-Saxon potential computed in a box, thereby garanteeing that continuum effects were properly taken into account. Projection of the self-consistent solutions on good particle number was carried out after variation, and an approximation of the variation after projection result was used. We give the position of the drip-lines and examine neutron densities in neutron-rich nuclei. We discuss the sensitivity of nuclear observables upon continuum and particle-number restoration effects.
Finite Element Models for Electron Beam Freeform Fabrication Process Project
National Aeronautics and Space Administration — This Small Business Innovation Research proposal offers to develop the most accurate, comprehensive and efficient finite element models to date for simulation of the...
Multipartite geometric entanglement in finite size XY model
Energy Technology Data Exchange (ETDEWEB)
Blasone, Massimo; Dell' Anno, Fabio; De Siena, Silvio; Giampaolo, Salvatore Marco; Illuminati, Fabrizio, E-mail: blasone@sa.infn.i [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy)
2009-06-01
We investigate the behavior of the multipartite entanglement in the finite size XY model by means of the hierarchical geometric measure of entanglement. By selecting specific components of the hierarchy, we study both global entanglement and genuinely multipartite entanglement.
Integration of geometric modeling and advanced finite element preprocessing
Shephard, Mark S.; Finnigan, Peter M.
1987-01-01
The structure to a geometry based finite element preprocessing system is presented. The key features of the system are the use of geometric operators to support all geometric calculations required for analysis model generation, and the use of a hierarchic boundary based data structure for the major data sets within the system. The approach presented can support the finite element modeling procedures used today as well as the fully automated procedures under development.
Finite element based model of parchment coffee drying
Directory of Open Access Journals (Sweden)
Preeda Prakotmak
2015-03-01
Full Text Available Heat and mass transfer in the parchment coffee during convective drying represents a complicated phenomena since it is important to consider not only the transport phenomena during drying but also the various changes of the drying materials. In order to describe drying of biomaterials adequately, a suitable mathematical model is needed. The aim of the present study was to develop a 3-D finite element model to simulate the transport of heat and mass within parchment coffee during the thin layer drying. Thin layer drying experiments of coffee bean and parchment coffee were conducted in the temperature range of 40-60o C, the relative humidity ranged from 14 to 28% and drying air velocity of 1.4 m/s. The moisture diffusivities in different coffee’s components (parchment and coffee bean were determined by minimizing the RMSE between the predicted and the experimental data of moisture contents. The simulated results showed that the moisture diffusivities of coffee bean were three orders of magnitude higher than those of the parchment. Moisture diffusivities of coffee components were found to significantly increase (P<0.05 with the increase in drying air temperature and were expressed by Arrhenius-type equations. Moreover, the model was also used to predict the moisture gradient in coffee bean during drying. The model simulates the moisture contents in different components of parchment coffee well and it provides a better understanding of the transport processes in the different components of the parchment coffee
Finite Element Model Updating Using Response Surface Method
Marwala, Tshilidzi
2007-01-01
This paper proposes the response surface method for finite element model updating. The response surface method is implemented by approximating the finite element model surface response equation by a multi-layer perceptron. The updated parameters of the finite element model were calculated using genetic algorithm by optimizing the surface response equation. The proposed method was compared to the existing methods that use simulated annealing or genetic algorithm together with a full finite element model for finite element model updating. The proposed method was tested on an unsymmetri-cal H-shaped structure. It was observed that the proposed method gave the updated natural frequen-cies and mode shapes that were of the same order of accuracy as those given by simulated annealing and genetic algorithm. Furthermore, it was observed that the response surface method achieved these results at a computational speed that was more than 2.5 times as fast as the genetic algorithm and a full finite element model and 24 ti...
A finite element model of ultrasonic extrusion
Energy Technology Data Exchange (ETDEWEB)
Lucas, M [Department of Mechanical Engineering, University of Glasgow, G12 8QQ (United Kingdom); Daud, Y, E-mail: m.lucas@mech.gla.ac.u [College of Science and Technology, UTM City Campus, Kuala Lumpur (Malaysia)
2009-08-01
Since the 1950's researchers have carried out investigations into the effects of applying ultrasonic excitation to metals undergoing elastic and plastic deformation. Experiments have been conducted where ultrasonic excitation is superimposed in complex metalworking operations such as wire drawing and extrusion, to identify the benefits of ultrasonic vibrations. This study presents a finite element analysis of ultrasonic excitation applied to the extrusion of a cylindrical aluminium bar. The effects of friction on the extrusion load are reported for the two excitation configurations of radially and axially applied ultrasonic vibrations and the results are compared with experimental data reported in the literature.
A finite element model of ultrasonic extrusion
Lucas, M.; Daud, Y.
2009-08-01
Since the 1950's researchers have carried out investigations into the effects of applying ultrasonic excitation to metals undergoing elastic and plastic deformation. Experiments have been conducted where ultrasonic excitation is superimposed in complex metalworking operations such as wire drawing and extrusion, to identify the benefits of ultrasonic vibrations. This study presents a finite element analysis of ultrasonic excitation applied to the extrusion of a cylindrical aluminium bar. The effects of friction on the extrusion load are reported for the two excitation configurations of radially and axially applied ultrasonic vibrations and the results are compared with experimental data reported in the literature.
Mixed finite elements for global tide models
Cotter, Colin J
2014-01-01
We study mixed finite element methods for the linearized rotating shallow water equations with linear drag and forcing terms. By means of a strong energy estimate for an equivalent second-order formulation for the linearized momentum, we prove long-time stability of the system without energy accumulation -- the geotryptic state. A priori error estimates for the linearized momentum and free surface elevation are given in $L^2$ as well as for the time derivative and divergence of the linearized momentum. Numerical results confirm the theoretical results regarding both energy damping and convergence rates.
Towards Finite-Gap Integration of the Inozemtsev Model
Directory of Open Access Journals (Sweden)
Kouichi Takemura
2007-03-01
Full Text Available The Inozemtsev model is considered to be a multivaluable generalization of Heun's equation. We review results on Heun's equation, the elliptic Calogero-Moser-Sutherland model and the Inozemtsev model, and discuss some approaches to the finite-gap integration for multivariable models.
A wide-range programmable frequency synthesizer based on a finite state machine filter
Alser, Mohammed H.; Assaad, Maher M.; Hussin, Fawnizu A.
2013-11-01
In this article, an FPGA-based design and implementation of a fully digital wide-range programmable frequency synthesizer based on a finite state machine filter is presented. The advantages of the proposed architecture are that, it simultaneously generates a high frequency signal from a low frequency reference signal (i.e. synthesising), and synchronising the two signals (signals have the same phase, or a constant difference) without jitter accumulation issue. The architecture is portable and can be easily implemented for various platforms, such as FPGAs and integrated circuits. The frequency synthesizer circuit can be used as a part of SERDES devices in intra/inter chip communication in system-on-chip (SoC). The proposed circuit is designed using Verilog language and synthesized for the Altera DE2-70 development board, with the Cyclone II (EP2C35F672C6) device on board. Simulation and experimental results are included; they prove the synthesizing and tracking features of the proposed architecture. The generated clock signal frequency of a range from 19.8 MHz to 440 MHz is synchronized to the input reference clock with a frequency step of 0.12 MHz.
COHESIVE ZONE FINITE ELEMENT-BASED MODELING OF HYDRAULIC FRACTURES
Institute of Scientific and Technical Information of China (English)
Zuorong Chen; A.P. Bunger; Xi Zhang; Robert G. Jeffrey
2009-01-01
Hydraulic fracturing is a powerful technology used to stimulate fluid production from reservoirs. The fully 3-D numerical simulation of the hydraulic fracturing process is of great importance to the efficient application of this technology, but is also a great challenge because of the strong nonlinear coupling between the viscous flow of fluid and fracture propagation. By taking advantage of a cohesive zone method to simulate the fracture process, a finite element model based on the existing pore pressure cohesive finite elements has been established to investigate the propagation of a penny-shaped hydraulic fracture in an infinite elastic medium. The effect of cohesive material parameters and fluid viscosity on the hydraulic fracture behaviour has been investigated. Excellent agreement between the finite element results and analytical solutions for the limiting case where the fracture process is dominated by rock fracture toughness demonstrates the ability of the cohesive zone finite element model in simulating the hydraulic fracture growth for this case.
Concomitant variables in finite mixture models
Wedel, M
The standard mixture model, the concomitant variable mixture model, the mixture regression model and the concomitant variable mixture regression model all enable simultaneous identification and description of groups of observations. This study reviews the different ways in which dependencies among
Substructure System Identification for Finite Element Model Updating
Craig, Roy R., Jr.; Blades, Eric L.
1997-01-01
This report summarizes research conducted under a NASA grant on the topic 'Substructure System Identification for Finite Element Model Updating.' The research concerns ongoing development of the Substructure System Identification Algorithm (SSID Algorithm), a system identification algorithm that can be used to obtain mathematical models of substructures, like Space Shuttle payloads. In the present study, particular attention was given to the following topics: making the algorithm robust to noisy test data, extending the algorithm to accept experimental FRF data that covers a broad frequency bandwidth, and developing a test analytical model (TAM) for use in relating test data to reduced-order finite element models.
Experimentally validated finite element model of electrocaloric multilayer ceramic structures
Energy Technology Data Exchange (ETDEWEB)
Smith, N. A. S., E-mail: nadia.smith@npl.co.uk, E-mail: maciej.rokosz@npl.co.uk, E-mail: tatiana.correia@npl.co.uk; Correia, T. M., E-mail: nadia.smith@npl.co.uk, E-mail: maciej.rokosz@npl.co.uk, E-mail: tatiana.correia@npl.co.uk [National Physical Laboratory, Hampton Road, TW11 0LW Middlesex (United Kingdom); Rokosz, M. K., E-mail: nadia.smith@npl.co.uk, E-mail: maciej.rokosz@npl.co.uk, E-mail: tatiana.correia@npl.co.uk [National Physical Laboratory, Hampton Road, TW11 0LW Middlesex (United Kingdom); Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom)
2014-07-28
A novel finite element model to simulate the electrocaloric response of a multilayer ceramic capacitor (MLCC) under real environment and operational conditions has been developed. The two-dimensional transient conductive heat transfer model presented includes the electrocaloric effect as a source term, as well as accounting for radiative and convective effects. The model has been validated with experimental data obtained from the direct imaging of MLCC transient temperature variation under application of an electric field. The good agreement between simulated and experimental data, suggests that the novel experimental direct measurement methodology and the finite element model could be used to support the design of optimised electrocaloric units and operating conditions.
Detecting Housing Submarkets using Unsupervised Learning of Finite Mixture Models
DEFF Research Database (Denmark)
Ntantamis, Christos
framework. The global form of heterogeneity is incorporated in a Hedonic Price Index model that encompasses a nonlinear function of the geographical coordinates of each dwelling. The local form of heterogeneity is subsequently modeled as a Finite Mixture Model for the residuals of the Hedonic Index...
Transmission function models of finite population genetic algorithms
Kemenade, C.H.M. van; Kok, J.N.; La Poutré, J.A.; Thierens, D.
1998-01-01
Infinite population models show a deterministic behaviour. Genetic algorithms with finite populations behave non-deterministicly. For small population sizes, the results obtained with these models differ strongly from the results predicted by the infinite population model. When the population size i
Finite element modeling for volume phantom in Electrical Impedance Tomography
Directory of Open Access Journals (Sweden)
I. O. Rybina
2011-10-01
Full Text Available Using surface phantom, "shadows" of currents, which flow below and under surface tomographic lays, include on this lay, that is cause of adding errors in reconstruction image. For processing modeling in studied object volume isotropic finite elements should be used. Cube is chosen for finite element modeling in this work. Cube is modeled as sum of six rectangular (in the base pyramids, each pyramid consists of four triangular pyramids (with rectangular triangle in the base and hypotenuse, which is equal to cube rib to provide its uniformity and electrical definition. In the case of modeling on frequencies higher than 100 kHz biological tissue resistivities are complex. In this case weight coefficient k will be complex in received cube electrical model (inverse conductivity matrix of the cube finite element.
Nonstandard Finite Difference Method Applied to a Linear Pharmacokinetics Model
Directory of Open Access Journals (Sweden)
Oluwaseun Egbelowo
2017-05-01
Full Text Available We extend the nonstandard finite difference method of solution to the study of pharmacokinetic–pharmacodynamic models. Pharmacokinetic (PK models are commonly used to predict drug concentrations that drive controlled intravenous (I.V. transfers (or infusion and oral transfers while pharmacokinetic and pharmacodynamic (PD interaction models are used to provide predictions of drug concentrations affecting the response of these clinical drugs. We structure a nonstandard finite difference (NSFD scheme for the relevant system of equations which models this pharamcokinetic process. We compare the results obtained to standard methods. The scheme is dynamically consistent and reliable in replicating complex dynamic properties of the relevant continuous models for varying step sizes. This study provides assistance in understanding the long-term behavior of the drug in the system, and validation of the efficiency of the nonstandard finite difference scheme as the method of choice.
Corsetti, Fabiano
2014-01-01
The implementation of the orbital minimization method (OMM) for solving the self-consistent Kohn-Sham (KS) problem for electronic structure calculations in a basis of non-orthogonal numerical atomic orbitals of finite-range is reported. We explore the possibilities for using the OMM as an exact cubic-scaling solver for the KS problem, and compare its performance with that of explicit diagonalization in realistic systems. We analyze the efficiency of the method depending on the choice of line search algorithm and on two free parameters, the scale of the kinetic energy preconditioning and the eigenspectrum shift. The results of several timing tests are then discussed, showing that the OMM can achieve a noticeable speedup with respect to diagonalization even for minimal basis sets for which the number of occupied eigenstates represents a significant fraction of the total basis size (>15%). We investigate the hard and soft parallel scaling of the method on multiple cores, finding a performance equal to or better ...
Straightened cervical lordosis causes stress concentration: a finite element model study.
Wei, Wei; Liao, Shenhui; Shi, Shiyuan; Fei, Jun; Wang, Yifan; Chen, Chunyue
2013-03-01
In this study, we propose a finite element analysis of the complete cervical spine with straightened and normal physiological curvature by using a specially designed modelling system. An accurate finite element model is established to recommend plausible approaches to treatment of cervical spondylosis through the finite element analysis results. There are few reports of biomechanics influence of the straightened cervical curve. It is difficult to measure internal responses of cervical spine directly. However, the finite element method has been reported to have the capability to quantify both external and internal responses to mechanical loading, such as the strain and stress distribution of spinal components. We choose a subject with a straightened cervical spine from whom to collect the CT scan data, which formed the basis of the finite element analysis. By using a specially designed modelling system, a high quality finite element model of the complete cervical spine with straightened curvature was generated, which was then mapped to reconstruct a normal physiological curvature model by a volumetric mesh deformation method based on discrete differential properties. Then, the same boundary conditions were applied to do a comparison. The result demonstrated that the active movement range of straightened cervical spine decreased by 24-33 %, but the stress increased by 5-95 %. The stress was concentrated at the facet joint cartilage, uncovertebral joint and the disk. The results suggest that cervical lordosis may have a direct impact on cervical spondylosis treatment. These results may be useful for clinical treatment of cervical spondylosis with straightened curvature.
The Finite Element Numerical Modelling of 3D Magnetotelluric
Directory of Open Access Journals (Sweden)
Ligang Cao
2014-01-01
Full Text Available The ideal numerical simulation of 3D magnetotelluric was restricted by the methodology complexity and the time-consuming calculation. Boundary values, the variation of weighted residual equation, and the hexahedral mesh generation method of finite element are three major causes. A finite element method for 3D magnetotelluric numerical modeling is presented in this paper as a solution for the problem mentioned above. In this algorithm, a hexahedral element coefficient matrix for magnetoelluric finite method is developed, which solves large-scale equations using preconditioned conjugate gradient of the first-type boundary conditions. This algorithm is verified using the homogeneous model, and the positive landform model, as well as the low resistance anomaly model.
Different radiation impedance models for finite porous materials
DEFF Research Database (Denmark)
Nolan, Melanie; Jeong, Cheol-Ho; Brunskog, Jonas;
2015-01-01
coupled to the transfer matrix method (TMM). These methods are found to yield comparable results when predicting the Sabine absorption coefficients of finite porous materials. Discrepancies with measurement results can essentially be explained by the unbalance between grazing and non-grazing sound field...... the infinite case. Thus, in order to predict the Sabine absorption coefficients of finite porous samples, one can incorporate models of the radiation impedance. In this study, different radiation impedance models are compared with two experimental examples. Thomasson’s model is compared to Rhazi’s method when...
Fiber optic displacement measurement model based on finite reflective surface
Li, Yuhe; Guan, Kaisen; Hu, Zhaohui
2016-10-01
We present a fiber optic displacement measurement model based on finite reflective plate. The theoretical model was derived, and simulation analysis of light intensity distribution, reflective plate width, and the distance between fiber probe and reflective plate were conducted in details. The three dimensional received light intensity distribution and the characteristic curve of light intensity were studied as functions of displacement of finite reflective plate. Experiments were carried out to verify the established model. The physical fundamentals and the effect of operating parameters on measuring system performance were revealed in the end.
FINITE ELEMENT MODELING OF THIN CIRCULAR SANDWICH PLATES DEFLECTION
Directory of Open Access Journals (Sweden)
K. S. Kurachka
2014-01-01
Full Text Available A mathematical model of a thin circular sandwich plate being under the vertical load is proposed. The model employs the finite element method and takes advantage of an axisymmetric finite element that leads to the small dimension of the resulting stiffness matrix and sufficient accuracy for practical calculations. The analytical expressions for computing local stiffness matrices are found, which can significantly speed up the process of forming the global stiffness matrix and increase the accuracy of calculations. A software is under development and verification. The discrepancy between the results of the mathematical model and those of analytical formulas for homogeneous thin circularsandwich plates does not exceed 7%.
Solutions manual to accompany finite mathematics models and applications
Morris, Carla C
2015-01-01
A solutions manual to accompany Finite Mathematics: Models and Applications In order to emphasize the main concepts of each chapter, Finite Mathematics: Models and Applications features plentiful pedagogical elements throughout such as special exercises, end notes, hints, select solutions, biographies of key mathematicians, boxed key principles, a glossary of important terms and topics, and an overview of use of technology. The book encourages the modeling of linear programs and their solutions and uses common computer software programs such as LINDO. In addition to extensive chapters on pr
Air Gun Launch Simulation Modeling and Finite Element Model Sensitivity Analysis
2006-01-01
Air Gun Launch Simulation Modeling and Finite Element Model Sensitivity Analysis by Mostafiz R. Chowdhury and Ala Tabiei ARL-TR-3703...Adelphi, MD 20783-1145 ARL-TR-3703 January 2006 Air Gun Launch Simulation Modeling and Finite Element Model Sensitivity Analysis...GRANT NUMBER 4. TITLE AND SUBTITLE Air Gun Launch Simulation Modeling and Finite Element Model Sensitivity Analysis 5c. PROGRAM
Finite Population Correction for Two-Level Hierarchical Linear Models.
Lai, Mark H C; Kwok, Oi-Man; Hsiao, Yu-Yu; Cao, Qian
2017-03-16
The research literature has paid little attention to the issue of finite population at a higher level in hierarchical linear modeling. In this article, we propose a method to obtain finite-population-adjusted standard errors of Level-1 and Level-2 fixed effects in 2-level hierarchical linear models. When the finite population at Level-2 is incorrectly assumed as being infinite, the standard errors of the fixed effects are overestimated, resulting in lower statistical power and wider confidence intervals. The impact of ignoring finite population correction is illustrated by using both a real data example and a simulation study with a random intercept model and a random slope model. Simulation results indicated that the bias in the unadjusted fixed-effect standard errors was substantial when the Level-2 sample size exceeded 10% of the Level-2 population size; the bias increased with a larger intraclass correlation, a larger number of clusters, and a larger average cluster size. We also found that the proposed adjustment produced unbiased standard errors, particularly when the number of clusters was at least 30 and the average cluster size was at least 10. We encourage researchers to consider the characteristics of the target population for their studies and adjust for finite population when appropriate. (PsycINFO Database Record (c) 2017 APA, all rights reserved).
Finite lifetime fragment model for synchronic band formation in dust tails of comets
Energy Technology Data Exchange (ETDEWEB)
Nishioka, Kimihiko; Watanabe, Junichi (Olympus Optical Co., Ltd., Tokyo (Japan) National Astronomical Observatory, Mitaka (Japan))
1990-10-01
Synchronic band (SYB) formation in comet dust tails is explained on the basis of a finite lifetime fragment model. Parent particles ejected from the comet nucleus break up at various times, and fragments with a finite lifetime are produced. The observed SYB is produced by the new fragments; it is formed within the lifetime. The model has been applied to SYBs in three comets, and the SYB particle lifetime was found to range from 25 to 70 days. The model describes well the shape of a SYB of Comet West. 14 refs.
Language Model Combination and Adaptation Using Weighted Finite State Transducers
Liu, X.; Gales, M. J. F.; Hieronymus, J. L.; Woodland, P. C.
2010-01-01
In speech recognition systems language model (LMs) are often constructed by training and combining multiple n-gram models. They can be either used to represent different genres or tasks found in diverse text sources, or capture stochastic properties of different linguistic symbol sequences, for example, syllables and words. Unsupervised LM adaption may also be used to further improve robustness to varying styles or tasks. When using these techniques, extensive software changes are often required. In this paper an alternative and more general approach based on weighted finite state transducers (WFSTs) is investigated for LM combination and adaptation. As it is entirely based on well-defined WFST operations, minimum change to decoding tools is needed. A wide range of LM combination configurations can be flexibly supported. An efficient on-the-fly WFST decoding algorithm is also proposed. Significant error rate gains of 7.3% relative were obtained on a state-of-the-art broadcast audio recognition task using a history dependently adapted multi-level LM modelling both syllable and word sequences
Finite-temperature corrections in the dilated chiral quark model
Kim, Y; Rho, M; Kim, Youngman; Lee, Hyun Kyu; Rho, Mannque
1995-01-01
We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense {\\it and} hot matter. We obtain the scaling law, \\frac{f_{\\pi}(T)}{f_{\\pi}} = \\frac{m_Q (T)}{m_Q} \\simeq \\frac{m_{\\sigma}(T)}{m_{\\sigma}} while we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense {\\it and} hot matter) and the RHIC experiments (hot and dilute matter) will ``see" different hadron...
Analytic regularization of the Yukawa model at finite temperature
Malbouisson, A P C; Svaiter, N F
1996-01-01
We analyse the one-loop fermionic contribution for the scalar effective potential in the temperature dependent Yukawa model. In order to regularize the model a mix between dimensional and analytic regularization procedures is used. We find a general expression for the fermionic contribution in arbitrary spacetime dimension. It is found that in D=3 this contribution is finite.
Hyperelastic Modelling and Finite Element Analysing of Rubber Bushing
Directory of Open Access Journals (Sweden)
Merve Yavuz ERKEK
2015-03-01
Full Text Available The objective of this paper is to obtain stiffness curves of rubber bushings which are used in automotive industry with hyperelastic finite element model. Hyperelastic material models were obtained with different material tests. Stress and strain values and static stiffness curves were determined. It is shown that, static stiffness curves are nonlinear. The level of stiffness affects the vehicle dynamics behaviour.
Finite element modelling of fibre-reinforced brittle materials
Kullaa, J.
1997-01-01
The tensile constitutive behaviour of fibre-reinforced brittle materials can be extended to two or three dimensions by using the finite element method with crack models. The three approaches in this study include the smeared and discrete crack concepts and a multi-surface plasticity model. The tensi
Modeling of composite piezoelectric structures with the finite volume method.
Bolborici, Valentin; Dawson, Francis P; Pugh, Mary C
2012-01-01
Piezoelectric devices, such as piezoelectric traveling- wave rotary ultrasonic motors, have composite piezoelectric structures. A composite piezoelectric structure consists of a combination of two or more bonded materials, at least one of which is a piezoelectric transducer. Piezoelectric structures have mainly been numerically modeled using the finite element method. An alternative approach based on the finite volume method offers the following advantages: 1) the ordinary differential equations resulting from the discretization process can be interpreted directly as corresponding circuits; and 2) phenomena occurring at boundaries can be treated exactly. This paper presents a method for implementing the boundary conditions between the bonded materials in composite piezoelectric structures modeled with the finite volume method. The paper concludes with a modeling example of a unimorph structure.
Excitation Gaps of Finite-Sized Systems from Optimally Tuned Range-Separated Hybrid Functionals.
Kronik, Leeor; Stein, Tamar; Refaely-Abramson, Sivan; Baer, Roi
2012-05-08
Excitation gaps are of considerable significance in electronic structure theory. Two different gaps are of particular interest. The fundamental gap is defined by charged excitations, as the difference between the first ionization potential and the first electron affinity. The optical gap is defined by a neutral excitation, as the difference between the energies of the lowest dipole-allowed excited state and the ground state. Within many-body perturbation theory, the fundamental gap is the difference between the corresponding lowest quasi-hole and quasi-electron excitation energies, and the optical gap is addressed by including the interaction between a quasi-electron and a quasi-hole. A long-standing challenge has been the attainment of a similar description within density functional theory (DFT), with much debate on whether this is an achievable goal even in principle. Recently, we have constructed and applied a new approach to this problem. Anchored in the rigorous theoretical framework of the generalized Kohn-Sham equation, our method is based on a range-split hybrid functional that uses exact long-range exchange. Its main novel feature is that the range-splitting parameter is not a universal constant but rather is determined from first principles, per system, based on satisfaction of the ionization potential theorem. For finite-sized objects, this DFT approach mimics successfully, to the best of our knowledge for the first time, the quasi-particle picture of many-body theory. Specifically, it allows for the extraction of both the fundamental and the optical gap from one underlying functional, based on the HOMO-LUMO gap of a ground-state DFT calculation and the lowest excitation energy of a linear-response time-dependent DFT calculation, respectively. In particular, it produces the correct optical gap for the difficult case of charge-transfer and charge-transfer-like scenarios, where conventional functionals are known to fail. In this perspective, we overview
Li, Jianying; Li, Haiyan; Fok, Alex S L; Watts, David C
2012-09-01
The aim of this study was to numerically evaluate the effects of filler contents and resin properties on the material properties of dental composites utilizing realistic 3D micromechanical finite element models. 3D micromechanical finite element models of dental composites containing irregular fillers with non-uniform sizes were created based on a large-scale, surrogate mixture fabricated from irregularly shaped stones and casting resin. The surrogate mixture was first scanned with a micro-CT scanner, and the images reassembled to produce a 3D finite element model. Different filler fractions were achieved by adjusting the matrix volume while keeping the fillers unchanged. Polymerization shrinkage, Young's modulus, Poisson's ratio and viscosity of the model composites were predicted using the finite element models, and their dependence on the filler fraction and material properties of the resin matrix were considered. Comparison of the numerical predictions with available experimental data and analytical models from the literature was performed. Increased filler fraction resulted in lower material shrinkage, higher Young's modulus, lower Poisson's ratio and higher viscosity in the composite. Predicted shrinkage and Young's modulus agreed well with the experimental data and analytical predictions. The McGee-McCullough model best fit the shrinkage and Young's modulus predicted by the finite element method. However, a new parameter, used as the exponent of the filler fraction, had to be introduced to the McGee-McCullough model to better match the predicted viscosity and Poisson's ratio with those from the finite element analysis. Realistic micro-structural finite element models were successfully applied to study the effects of filler fraction and matrix properties on a wide range of mechanical properties of dental composites with irregular fillers. The results can be used to direct the design of such materials to achieve the desired mechanical properties. Published by
Three dimensional mathematical model of tooth for finite element analysis
Directory of Open Access Journals (Sweden)
Puškar Tatjana
2010-01-01
Full Text Available Introduction. The mathematical model of the abutment tooth is the starting point of the finite element analysis of stress and deformation of dental structures. The simplest and easiest way is to form a model according to the literature data of dimensions and morphological characteristics of teeth. Our method is based on forming 3D models using standard geometrical forms (objects in programmes for solid modeling. Objective. Forming the mathematical model of abutment of the second upper premolar for finite element analysis of stress and deformation of dental structures. Methods. The abutment tooth has a form of a complex geometric object. It is suitable for modeling in programs for solid modeling SolidWorks. After analyzing the literature data about the morphological characteristics of teeth, we started the modeling dividing the tooth (complex geometric body into simple geometric bodies (cylinder, cone, pyramid,.... Connecting simple geometric bodies together or substricting bodies from the basic body, we formed complex geometric body, tooth. The model is then transferred into Abaqus, a computational programme for finite element analysis. Transferring the data was done by standard file format for transferring 3D models ACIS SAT. Results. Using the programme for solid modeling SolidWorks, we developed three models of abutment of the second maxillary premolar: the model of the intact abutment, the model of the endodontically treated tooth with two remaining cavity walls and the model of the endodontically treated tooth with two remaining walls and inserted post. Conclusion Mathematical models of the abutment made according to the literature data are very similar with the real abutment and the simplifications are minimal. These models enable calculations of stress and deformation of the dental structures. The finite element analysis provides useful information in understanding biomechanical problems and gives guidance for clinical research.
[Three dimensional mathematical model of tooth for finite element analysis].
Puskar, Tatjana; Vasiljević, Darko; Marković, Dubravka; Jevremović, Danimir; Pantelić, Dejan; Savić-Sević, Svetlana; Murić, Branka
2010-01-01
The mathematical model of the abutment tooth is the starting point of the finite element analysis of stress and deformation of dental structures. The simplest and easiest way is to form a model according to the literature data of dimensions and morphological characteristics of teeth. Our method is based on forming 3D models using standard geometrical forms (objects) in programmes for solid modeling. Forming the mathematical model of abutment of the second upper premolar for finite element analysis of stress and deformation of dental structures. The abutment tooth has a form of a complex geometric object. It is suitable for modeling in programs for solid modeling SolidWorks. After analysing the literature data about the morphological characteristics of teeth, we started the modeling dividing the tooth (complex geometric body) into simple geometric bodies (cylinder, cone, pyramid,...). Connecting simple geometric bodies together or substricting bodies from the basic body, we formed complex geometric body, tooth. The model is then transferred into Abaqus, a computational programme for finite element analysis. Transferring the data was done by standard file format for transferring 3D models ACIS SAT. Using the programme for solid modeling SolidWorks, we developed three models of abutment of the second maxillary premolar: the model of the intact abutment, the model of the endodontically treated tooth with two remaining cavity walls and the model of the endodontically treated tooth with two remaining walls and inserted post. Mathematical models of the abutment made according to the literature data are very similar with the real abutment and the simplifications are minimal. These models enable calculations of stress and deformation of the dental structures. The finite element analysis provides useful information in understanding biomechanical problems and gives guidance for clinical research.
Model refinements of transformers via a subproblem finite element method
Dular, Patrick; Kuo-Peng, Patrick; Ferreira Da Luz, Mauricio,; Krähenbühl, Laurent
2015-01-01
International audience; A progressive modeling of transformers is performed via a subproblem finite element method. A complete problem is split into subproblems with different adapted overlapping meshes. Model refinements are performed from ideal to real flux tubes, 1-D to 2-D to 3-D models, linear to nonlinear materials, perfect to real materials, single wire to volume conductor windings, and homogenized to fine models of cores and coils, with any coupling of these changes. The proposed unif...
Finite Element Modeling of Airflow During Phonation
Directory of Open Access Journals (Sweden)
Šidlof P.
2010-07-01
Full Text Available In the paper a mathematical model of airflow in human vocal folds is presented. The geometry of the glottal channel is based on measurements of excised human larynges. The airflow is modeled by nonstationary incompressible Navier-Stokes equations in a 2D computational domain, which is deformed in time due to vocal fold vibration. The paper presents numerical results and focuses on flow separation in glottis. Quantitative data from numerical simulations are compared to results of measurements by Particle Image Velocimetry (PIV, performed on a scaled self-oscillating physical model of vocal folds.
Efficient Finite Element Modelling of Elastodynamic Scattering
Velichko, A.; Wilcox, P. D.
2010-02-01
A robust and efficient technique for predicting the complete scattering behavior for an arbitrarily-shaped defect is presented that can be implemented in a commercial FE package. The spatial size of the modeling domain around the defect is as small as possible to minimize computational expense and a minimum number of models are executed. Example results for 2D and 3D scattering in isotropic material and guided wave scattering are presented.
Finite State Transducers Approximating Hidden Markov Models
Kempe, A
1999-01-01
This paper describes the conversion of a Hidden Markov Model into a sequential transducer that closely approximates the behavior of the stochastic model. This transformation is especially advantageous for part-of-speech tagging because the resulting transducer can be composed with other transducers that encode correction rules for the most frequent tagging errors. The speed of tagging is also improved. The described methods have been implemented and successfully tested on six languages.
Finite Nuclei in the Quark-Meson Coupling Model.
Stone, J R; Guichon, P A M; Reinhard, P G; Thomas, A W
2016-03-04
We report the first use of the effective quark-meson coupling (QMC) energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the nonrelativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having a clear physics basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist, however, multiple Skyrme parameter sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF set of fewer parameters, derived in this work, is not open to such variation, chosen set being applied, without adjustment, to both the properties of finite nuclei and nuclear matter.
Zhebel, E.; Minisini, S.; Kononov, A.; Mulder, W.A.
2013-01-01
With the rapid developments in parallel compute architectures, algorithms for seismic modeling and imaging need to be reconsidered in terms of parallelization. The aim of this paper is to compare scalability of seismic modeling algorithms: finite differences, continuous mass-lumped finite elements
Zhebel, E.; Minisini, S.; Kononov, A.; Mulder, W.A.
2013-01-01
With the rapid developments in parallel compute architectures, algorithms for seismic modeling and imaging need to be reconsidered in terms of parallelization. The aim of this paper is to compare scalability of seismic modeling algorithms: finite differences, continuous mass-lumped finite elements a
Finite element modelling of vocal tract changes after voice therapy
Directory of Open Access Journals (Sweden)
Vampola T.
2011-06-01
Full Text Available Two 3D finite element (FE models were constructed, based on CT measurements of a subject phonating on [a:] before and after phonation into a tube. Acoustic analysis was performed by exciting the models with acoustic flow velocity at the vocal folds. The generated acoustic pressure of the response was computed in front of the mouth and inside the vocal tract for both FE models. Average amplitudes of the pressure oscillations inside the vocal tract and in front of the mouth were compared to display the cost-efficiency of sound energy transfer at different formant frequencies. The formants F1–F3 correspond to classical vibration modes also solvable by 1D vocal tract model. However, for higher formants, there occur more complicated transversal modes which require 3D modelling. A special attention is given to the higher frequency range (above 3.5 Hz where transversal modes exist between piriform sinuses and valleculae. Comparison of the pressure oscillation inside and outside the vocal tract showed that formants differ in their efficiency, F4 (at about 3.5 kHz, i.e. at the speaker’s or singer’s formant region being the most effective. The higher formants created a clear formant cluster around 4 kHz after the vocal exercise with the tube. Since the human ear is most sensitive to frequencies between 2 and 4 kHz concentration of sound energy in this frequency region (F4–F5 is effective for communication. The results suggest that exercising using phonation into tubes help in improving the vocal economy.
FINITE ELEMENT MODELING OF PROBLEMS OF GEOMECHANICS AND GEOPHYSICS
Directory of Open Access Journals (Sweden)
Vlasov Alexander Nikolaevich
2012-10-01
Full Text Available In the article, the authors consider some classes of problems of geomechanics that are resolved through the application of SIMULIA ABAQUS software. The tasks associated with the assessment of the zone of influence of structures produced on surrounding buildings and structures in the dense urban environment, as well as the tectonic and physical simulation of rifts with the purpose of identification of deformations of the Earth surface and other defects of lithospheric plates. These seemingly different types of tasks can be grouped together on the basis of common characteristics due to the complexity of numerical modeling problems of geomechanics and geophysics. Non-linearity of physical processes, complexity of the geological structure and variable thickness of layers, bed thinning layers, lenses, as well as singular elements, make it hard to consolidate different elements (for example, engineering and geological elements and associated structures of buildings in a single model. In this regard, software SIMULIA ABAQUS looks attractive, since it provides a highly advanced finite-element modeling technique, including a convenient hexahedral mesh generator, a wide range of models of elastic and plastic strain of materials, and the ability to work with certain geometric areas that interrelate through the mechanism of contacting surface pairs that have restrictions. It is noteworthy that the research also facilitates development of personal analytical methods designated for the assessment of physical and mechanical properties of heterogeneous materials as well as new solutions applicable in the vicinity of singular elements of the area that may be used in modeling together with ABAQUS software.
Finite element modeling of plasmon based single-photon sources
DEFF Research Database (Denmark)
Chen, Yuntian; Gregersen, Niels; Nielsen, Torben Roland;
2011-01-01
A finite element method (FEM) approach of calculating a single emitter coupled to plasmonic waveguides has been developed. The method consists of a 2D model and a 3D model: (I) In the 2D model, we have calculated the spontaneous emission decay rate of a single emitter into guided plasmonic modes...... waveguides with different geometries, as long as only one guided plasmonic mode is predominantly excited....
An autonomous DNA model for finite state automata.
Martinez-Perez, Israel M; Zimmermann, Karl-Heinz; Ignatova, Zoya
2009-01-01
In this paper we introduce an autonomous DNA model for finite state automata. This model called sticker automaton model is based on the hybridisation of single stranded DNA molecules (stickers) encoding transition rules and input data. The computation is carried out in an autonomous manner by one enzyme which allows us to determine whether a resulting double-stranded DNA molecule belongs to the automaton's language or not.
Finite Element Modeling for Ultrasonic Transducers (Preprint)
1998-02-27
virtual prototyping of transducers . Fig. 18 shows a 3D model of a Tonpilz device for low frequency sensing in air. This classical design is usually used...coupled Tonpilz transducer . A thick, flexible matching layer is bonded to the face of the conical head-mass. 7. CONCLUSIONS This paper was intended as a...This is a preprint of a paper published in Proc. SPIE Int. Symp. Medical Imaging 1998, San Diego, Feb 21-27, 1998 Ultrasonic Transducer Engineering
Symmetries of preon interactions modeled as a finite group
Bellinger, James N.
1997-07-01
I model preon interactions as a finite group. Treating the elements of the group as the bases of a vector space, I examine those linear mappings under which the transformed bases may be treated as members of a group isomorphic to the original. In some cases these mappings are continuous Lie groups.
Symmetries of preon interactions modeled as a finite group
Energy Technology Data Exchange (ETDEWEB)
Bellinger, J.N. [University of Wisconsin at Madison, Madison, Wisconsin 53706 (United States)
1997-07-01
I model preon interactions as a finite group. Treating the elements of the group as the bases of a vector space, I examine those linear mappings under which the transformed bases may be treated as members of a group isomorphic to the original. In some cases these mappings are continuous Lie groups. {copyright} {ital 1997 American Institute of Physics.}
Parallel finite element modeling of earthquake ground response and liquefaction
Institute of Scientific and Technical Information of China (English)
Jinchi Lu(陆金池); Jun Peng(彭军); Ahmed Elgamal; Zhaohui Yang(杨朝晖); Kincho H. Law
2004-01-01
Parallel computing is a promising approach to alleviate the computational demand in conducting large-scale finite element analyses. This paper presents a numerical modeling approach for earthquake ground response and liquefaction using the parallel nonlinear finite element program, ParCYCLIC, designed for distributed-memory message-passing parallel computer systems. In ParCYCLIC, finite elements are employed within an incremental plasticity, coupled solid-fluid formulation. A constitutive model calibrated by physical tests represents the salient characteristics of sand liquefaction and associated accumulation of shear deformations. Key elements of the computational strategy employed in ParCYCLIC include the development of a parallel sparse direct solver, the deployment of an automatic domain decomposer, and the use of the Multilevel Nested Dissection algorithm for ordering of the finite element nodes. Simulation results of centrifuge test models using ParCYCLIC are presented. Performance results from grid models and geotechnical simulations show that ParCYCLIC is efficiently scalable to a large number of processors.
Finiteness of the EPRL/FK spin foam model
Mikovic, Aleksandar
2011-01-01
We show that the EPRL/FK spin foam model of quantum gravity can be made finite by dividing the vertex amplitude with an appropriate power $p$ of the product of dimensions of the vertex spins and intertwiners. This power is independent of the spin foam and we find a lower bound for $p$ which makes the state sum absolutely convergent.
Finite size scaling in the planar Lebwohl-Lasher model
Mondal, Enakshi; Roy, Soumen Kumar
2003-06-01
The standard finite size scaling method for second order phase transition has been applied to Monte Carlo data obtained for a planar Lebwohl-Lasher lattice model using the Wolff cluster algorithm. We obtain Tc and the exponents γ, ν, and z and the results are different from those obtained by other investigators.
Finite petri nets as models for recursive causal behaviour
Goltz, Ursula; Rensink, Arend
1994-01-01
Goltz (1988) discussed whether or not there exist finite Petri nets (with unbounded capacities) modelling the causal behaviour of certain recursive CCS terms. As a representative example, the following term is considered: B=(a.nil | b.B)+c.nil. We will show that the answer depends on the chosen
Accountability Analysis of Electronic Commerce Protocols by Finite Automaton Model
Institute of Scientific and Technical Information of China (English)
Xie Xiao-yao; Zhang Huan-guo
2004-01-01
The accountability of electronic commerce protocols is an important aspect to insures security of electronic transaction. This paper proposes to use Finite Automaton (FA) model as a new kind of framework to analyze the trans action protocols in the application of electronic commerce.
A Finite Element Approach to Modeling Abrasive Wear Modes
Woldman, M.; Heide, van der E.; Tinga, T.; Masen, M.A.
2016-01-01
Machine components operating in sandy environments will wear because of the abrasive interaction with sand particles. In this work, a method is derived to predict the amount of wear caused by such abrasive action, in order to improve the maintenance concept of the components. A finite element model
THE TWO-LEVEL MODEL AT FINITE-TEMPERATURE
Energy Technology Data Exchange (ETDEWEB)
Goodman, A.L.
1980-07-01
The finite-temperature HFB cranking equations are solved for the two-level model. The pair gap, moment of inertia and internal energy are determined as functions of spin and temperature. Thermal excitations and rotations collaborate to destroy the pair correlations. Raising the temperature eliminates the backbending effect and improves the HFB approximation.
Complex spectrum of spin models for finite-density QCD
Nishimura, Hiromichi; Pangeni, Kamal
2016-01-01
We consider the spectrum of transfer matrix eigenvalues associated with Polyakov loops in lattice QCD at strong coupling. The transfer matrix at finite density is non-Hermitian, and its eigenvalues become complex as a manifestation of the sign problem. We show that the symmetry under charge conjugation and complex conjugation ensures that the eigenvalues are either real or part of a complex conjugate pair, and the complex pairs lead to damped oscillatory behavior in Polyakov loop correlation functions, which also appeared in our previous phenomenological models using complex saddle points. We argue that this effect should be observable in lattice simulations of QCD at finite density.
Model Reduction in Dynamic Finite Element Analysis of Lightweight Structures
DEFF Research Database (Denmark)
Flodén, Ola; Persson, Kent; Sjöström, Anders
2012-01-01
The application of wood as a construction material when building multi-storey buildings has many advantages, e.g., light weight, sustainability and low energy consumption during the construction and lifecycle of the building. However, compared to heavy structures, it is a greater challenge to build...... lightweight structures without noise and disturbing vibrations between storeys and rooms. The dynamic response of floor and wall structures may be investigated using finite element models with three-dimensional solid elements [1]. In order to analyse the global response of complete buildings, finite element...
Convergence of a finite difference method for combustion model problems
Institute of Scientific and Technical Information of China (English)
YING; Long'an
2004-01-01
We study a finite difference scheme for a combustion model problem. A projection scheme near the combustion wave, and the standard upwind finite difference scheme away from the combustion wave are applied. Convergence to weak solutions with a combustion wave is proved under the normal Courant-Friedrichs-Lewy condition. Some conditions on the ignition temperature are given to guarantee the solution containing a strong detonation wave or a weak detonation wave. Convergence to strong detonation wave solutions for the random projection method is also proved.
Finite Element Modeling of Dynamic Properties of Power Supply for an Industrial Application
2014-01-01
In this thesis, the dynamic properties of the mechanic structure of Power Supply for an Industrial Application, an Alstom company product, are considered. A finite element model of the Power Supply mechanic structure have been generated with the aid of the MSC Marc software. Based on the FE model; modal analysis have been carried out and the eigenfrequencies and eigenmodes for the FE model have been calculated in a suitable frequency range. Relevant frequency response functions for the FE mod...
Phase transitions in a one-dimensional multibarrier potential of finite range
Bar, D
2002-01-01
We have previously studied properties of a one-dimensional potential with $N$ equally spaced identical barries in a (fixed) finite interval for both finite and infinite $N$. It was observed that scattering and spectral properties depend sensitively on the ratio $c$ of spacing to width of the barriers (even in the limit $N \\to \\infty$). We compute here the specific heat of an ensemble of such systems and show that there is critical dependence on this parameter, as well as on the temperature, strongly suggestive of phase transitions.
Finite difference computing with exponential decay models
Langtangen, Hans Petter
2016-01-01
This text provides a very simple, initial introduction to the complete scientific computing pipeline: models, discretization, algorithms, programming, verification, and visualization. The pedagogical strategy is to use one case study – an ordinary differential equation describing exponential decay processes – to illustrate fundamental concepts in mathematics and computer science. The book is easy to read and only requires a command of one-variable calculus and some very basic knowledge about computer programming. Contrary to similar texts on numerical methods and programming, this text has a much stronger focus on implementation and teaches testing and software engineering in particular. .
Trew, Mark L; Smaill, Bruce H; Bullivant, David P; Hunter, Peter J; Pullan, Andrew J
2005-12-01
A generalized finite difference (GFD) method is presented that can be used to solve the bi-domain equations modeling cardiac electrical activity. Classical finite difference methods have been applied by many researchers to the bi-domain equations. However, these methods suffer from the limitation of requiring computational meshes that are structured and orthogonal. Finite element or finite volume methods enable the bi-domain equations to be solved on unstructured meshes, although implementations of such methods do not always cater for meshes with varying element topology. The GFD method solves the bi-domain equations on arbitrary and irregular computational meshes without any need to specify element basis functions. The method is useful as it can be easily applied to activation problems using existing meshes that have originally been created for use by finite element or finite difference methods. In addition, the GFD method employs an innovative approach to enforcing nodal and non-nodal boundary conditions. The GFD method performs effectively for a range of two and three-dimensional test problems and when computing bi-domain electrical activation moving through a fully anisotropic three-dimensional model of canine ventricles.
Viscoelastic models with consistent hypoelasticity for fluids undergoing finite deformations
Altmeyer, Guillaume; Rouhaud, Emmanuelle; Panicaud, Benoit; Roos, Arjen; Kerner, Richard; Wang, Mingchuan
2015-08-01
Constitutive models of viscoelastic fluids are written with rate-form equations when considering finite deformations. Trying to extend the approach used to model these effects from an infinitesimal deformation to a finite transformation framework, one has to ensure that the tensors and their rates are indifferent with respect to the change of observer and to the superposition with rigid body motions. Frame-indifference problems can be solved with the use of an objective stress transport, but the choice of such an operator is not obvious and the use of certain transports usually leads to physically inconsistent formulation of hypoelasticity. The aim of this paper is to present a consistent formulation of hypoelasticity and to combine it with a viscosity model to construct a consistent viscoelastic model. In particular, the hypoelastic model is reversible.
On the fate of the Standard Model at finite temperature
Rose, Luigi Delle; Urbano, Alfredo
2015-01-01
In this paper we revisit and update the computation of thermal corrections to the stability of the electroweak vacuum in the Standard Model. At zero temperature, we make use of the full two-loop effective potential, improved by three-loop beta functions with two-loop matching conditions. At finite temperature, we include one-loop thermal corrections together with resummation of daisy diagrams. We solve numerically---both at zero and finite temperature---the bounce equation, thus providing an accurate description of the thermal tunneling. We find that at finite temperature the instability bound excludes values of the top mass $M_t \\gtrsim 173.6$ GeV, assuming $M_h \\simeq 125$ GeV and including uncertainties on the strong coupling. We discuss the validity and temperature-dependence of this bound in the early Universe, with a special focus on the reheating phase after inflation.
Material models and properties in the finite element analysis of knee ligaments: a literature review
Directory of Open Access Journals (Sweden)
Fabio eGalbusera
2014-11-01
Full Text Available Knee ligaments are elastic bands of soft tissue with a complex microstructure and biomechanics which are critical to determine the kinematics as well as the stress bearing behavior of the knee joint. Their correct implementation in terms of material models and properties is therefore necessary in the development of finite element models of the knee, which has been performed for decades for the investigation of both its basic biomechanics and the development of replacement implants and repair strategies for degenerative and traumatic pathologies. Indeed, a wide range of element types and material models has been used to represent knee ligaments, ranging from elastic unidimensional elements to complex hyperelastic three-dimensional structures with anatomically realistic shapes. This paper systematically reviews literature studies which described finite element models of the knee, and summarizes the approaches which have been used to model the ligaments highlighting their strengths and weaknesses.
Material Models and Properties in the Finite Element Analysis of Knee Ligaments: A Literature Review
Galbusera, Fabio; Freutel, Maren; Dürselen, Lutz; D’Aiuto, Marta; Croce, Davide; Villa, Tomaso; Sansone, Valerio; Innocenti, Bernardo
2014-01-01
Knee ligaments are elastic bands of soft tissue with a complex microstructure and biomechanics, which are critical to determine the kinematics as well as the stress bearing behavior of the knee joint. Their correct implementation in terms of material models and properties is therefore necessary in the development of finite element models of the knee, which has been performed for decades for the investigation of both its basic biomechanics and the development of replacement implants and repair strategies for degenerative and traumatic pathologies. Indeed, a wide range of element types and material models has been used to represent knee ligaments, ranging from elastic unidimensional elements to complex hyperelastic three-dimensional structures with anatomically realistic shapes. This paper systematically reviews literature studies, which described finite element models of the knee, and summarizes the approaches, which have been used to model the ligaments highlighting their strengths and weaknesses. PMID:25478560
Closed Loop Finite Element Modeling of Piezoelectric Smart Structures
Directory of Open Access Journals (Sweden)
Guang Meng
2006-01-01
Full Text Available The objective of this paper is to develop a general design and analysis scheme for actively controlled piezoelectric smart structures. The scheme involves dynamic modeling of a smart structure, designing control laws and closed-loop simulation in a finite element environment. Based on the structure responses determined by finite element method, a modern system identification technique known as Observer/Kalman filter Identification (OKID technique is used to determine the system Markov parameters. The Eigensystem Realization Algorithm (ERA is then employed to develop an explicit state space model of the equivalent linear system for control law design. The Linear Quadratic Gaussian (LQG control law design technique is employed to design a control law. By using ANSYS parametric design language (APDL, the control law is incorporated into the ANSYS finite element model to perform closed loop simulations. Therefore, the control law performance can be evaluated in the context of a finite element environment. Finally, numerical examples have demonstrated the validity and efficiency of the proposed design scheme. Without any further modifications, the design scheme can be readily applied to other complex smart structures.
DEFF Research Database (Denmark)
Marodi, M.; D'ovidio, Francesco; Vicsek, T.
2002-01-01
Synchronization in a lattice of a finite population of phase oscillators with algebraically decaying, non-normalized coupling is studied by numerical simulations. A critical level of decay is found, below which full locking takes place if the population contains a sufficiently large number of ele...
Finite element model calibration using frequency responses with damping equalization
Abrahamsson, T. J. S.; Kammer, D. C.
2015-10-01
Model calibration is a cornerstone of the finite element verification and validation procedure, in which the credibility of the model is substantiated by positive comparison with test data. The calibration problem, in which the minimum deviation between finite element model data and experimental data is searched for, is normally characterized as being a large scale optimization problem with many model parameters to solve for and with deviation metrics that are nonlinear in these parameters. The calibrated parameters need to be found by iterative procedures, starting from initial estimates. Sometimes these procedures get trapped in local deviation function minima and do not converge to the globally optimal calibration solution that is searched for. The reason for such traps is often the multi-modality of the problem which causes eigenmode crossover problems in the iterative variation of parameter settings. This work presents a calibration formulation which gives a smooth deviation metric with a large radius of convergence to the global minimum. A damping equalization method is suggested to avoid the mode correlation and mode pairing problems that need to be solved in many other model updating procedures. By this method, the modal damping of a test data model and the finite element model is set to be the same fraction of critical modal damping. Mode pairing for mapping of experimentally found damping to the finite element model is thus not needed. The method is combined with model reduction for efficiency and employs the Levenberg-Marquardt minimizer with randomized starts to achieve the calibration solution. The performance of the calibration procedure, including a study of parameter bias and variance under noisy data conditions, is demonstrated by two numerical examples.
Test of modified BCS model at finite temperature
Ponomarev, V Yu
2005-01-01
A recently suggested modified BCS (MBCS) model has been studied at finite temperature. We show that this approach does not allow the existence of the normal (non-superfluid) phase at any finite temperature. Other MBCS predictions such as a negative pairing gap, pairing induced by heating in closed-shell nuclei, and ``superfluid -- super-superfluid'' phase transition are discussed also. The MBCS model is tested by comparing with exact solutions for the picket fence model. Here, severe violation of the internal symmetry of the problem is detected. The MBCS equations are found to be inconsistent. The limit of the MBCS applicability has been determined to be far below the ``superfluid -- normal'' phase transition of the conventional FT-BCS, where the model performs worse than the FT-BCS.
Finite element modelling of the 1969 Portuguese tsunami
Guesmia, M.; Heinrich, Ph.; Mariotti, C.
1996-03-01
On the 28 th February 1969, the coasts of Portugal, Spain and Morocco were affected by water waves generated by a submarine earthquake (Ms=7.3) with epicenter located off Portugal. The propagation of this tsunami has been simulated by a finite element numerical model solving the Boussinesq equations. These equations have been discretized using the finite element Galerkin method and a Crank-Nicholson scheme in time. The 2-D simulation of the 1969 tsunami is carried out using the hydraulic source calculated from the geophysical model of Okada and seismic parameters of Fukao. The modeled waves are compared with the recorded waves with respect to the travel times, the maximum amplitudes, the periods of the signal. Good agreement is found for most of the studied gauges. The comparison between Boussinesq and shallow-water models shows that the effects of frequency dispersion are minor using Fukao's seismic parameters.
Constitutive modeling and computational implementation for finite strain plasticity
Reed, K. W.; Atluri, S. N.
1985-01-01
This paper describes a simple alternate approach to the difficult problem of modeling material behavior. Starting from a general representation for a rate-tpe constitutive equation, it is shown by example how sets of test data may be used to derive restrictions on the scalar functions appearing in the representation. It is not possible to determine these functions from experimental data, but the aforementioned restrictions serve as a guide in their eventual definition. The implications are examined for hypo-elastic, isotropically hardening plastic, and kinematically hardening plastic materials. A simple model for the evolution of the 'back-stress,' in a kinematic-hardening plasticity theory, that is entirely analogous to a hypoelastic stress-strain relation is postulated and examined in detail in modeling finitely plastic tension-torsion test. The implementation of rate-type material models in finite element algorithms is also discussed.
Finite element based model of parchment coffee drying
Preeda Prakotmak
2015-01-01
Heat and mass transfer in the parchment coffee during convective drying represents a complicated phenomena since it is important to consider not only the transport phenomena during drying but also the various changes of the drying materials. In order to describe drying of biomaterials adequately, a suitable mathematical model is needed. The aim of the present study was to develop a 3-D finite element model to simulate the transport of heat and mass within parchment coffee during the thin laye...
Finite Element Modeling of Metasurfaces with Generalized Sheet Transition Conditions
Sandeep, Srikumar; Caloz, Christophe
2016-01-01
A modeling of metasurfaces in the finite element method (FEM) based on generalized sheet transition conditions (GSTCs) is presented. The discontinuities in electromagnetic fields across a metasurface as represented by the GSTC are modeled by assigning nodes to both sides of the metasurface. The FEM-GSTC formulation in both 1D and 2D domains is derived and implemented. The method is extended to handle more general bianistroptic metasurfaces. The formulations are validated by several illustrative examples.
Nanoscale Continuum Modelling of Carbon Nanotubes by Polyhedral Finite Elements
Directory of Open Access Journals (Sweden)
Logah Perumal
2016-01-01
Full Text Available As the geometry of a cell of carbon nanotube is hexagonal, a new approach is presented in modelling of single-walled carbon nanotubes using polyhedral finite elements. Effect of varying length, diameter, and thickness of carbon nanotubes on Young’s modulus is studied. Both armchair and zigzag configurations are modelled and simulated in Mathematica. Results from current approach found good agreement with the other published data.
Interacting steps with finite-range interactions: Analytical approximation and numerical results
Jaramillo, Diego Felipe; Téllez, Gabriel; González, Diego Luis; Einstein, T. L.
2013-05-01
We calculate an analytical expression for the terrace-width distribution P(s) for an interacting step system with nearest- and next-nearest-neighbor interactions. Our model is derived by mapping the step system onto a statistically equivalent one-dimensional system of classical particles. The validity of the model is tested with several numerical simulations and experimental results. We explore the effect of the range of interactions q on the functional form of the terrace-width distribution and pair correlation functions. For physically plausible interactions, we find modest changes when next-nearest neighbor interactions are included and generally negligible changes when more distant interactions are allowed. We discuss methods for extracting from simulated experimental data the characteristic scale-setting terms in assumed potential forms.
Kang, K.-T.; Kim, K.-Y.; Jung, H.-J.; Lee, H.-Y.; Chun, H.-J.; Lee, H.-M.; Moon, S.-H.; Kim, H.-J.
2010-03-01
The aim of this study is to evaluate the biomechanical changes after Spinous Process Osteotomy (SPO) with different amounts of facetectomy of the lumbar spine and to compare the models with SPO and intact models using finite element models. Intact spine models and one decompression models (L3-4) with SPO were developed. SPO models included three different amounts of facetectomy (25%, 50%, and 75%). After validation of the models, finite element analyses were performed to investigate the ranges of motion and disc stresses at each corresponding level among three SPO models and intact lumbar spine models. The ranges of motion in the SPO models were increased more than the intact models. According to increase of amounts of facetectomy, ranges of motion were also increased. Similar to range of motion, the von Mises stress of disc in the SPO models was higher than that of intact models. Moreover, with the increase of amount of facetectomy, the disc stress increased at each segments under various moments. The decompression procedures using spinous process osteotomy has been reported to provide better postoperative stability compared to the conventional laminectomy. However, facetectomy over 50 % is likely to attenuate this advantage.
Nonlinear structural finite element model updating and uncertainty quantification
Ebrahimian, Hamed; Astroza, Rodrigo; Conte, Joel P.
2015-04-01
This paper presents a framework for nonlinear finite element (FE) model updating, in which state-of-the-art nonlinear structural FE modeling and analysis techniques are combined with the maximum likelihood estimation method (MLE) to estimate time-invariant parameters governing the nonlinear hysteretic material constitutive models used in the FE model of the structure. The estimation uncertainties are evaluated based on the Cramer-Rao lower bound (CRLB) theorem. A proof-of-concept example, consisting of a cantilever steel column representing a bridge pier, is provided to verify the proposed nonlinear FE model updating framework.
Integration of Dynamic Models in Range Operations
Bardina, Jorge; Thirumalainambi, Rajkumar
2004-01-01
This work addresses the various model interactions in real-time to make an efficient internet based decision making tool for Shuttle launch. The decision making tool depends on the launch commit criteria coupled with physical models. Dynamic interaction between a wide variety of simulation applications and techniques, embedded algorithms, and data visualizations are needed to exploit the full potential of modeling and simulation. This paper also discusses in depth details of web based 3-D graphics and applications to range safety. The advantages of this dynamic model integration are secure accessibility and distribution of real time information to other NASA centers.
Universal Finite Size Corrections and the Central Charge in Non-solvable Ising Models
Giuliani, Alessandro; Mastropietro, Vieri
2013-11-01
We investigate a non-solvable two-dimensional ferromagnetic Ising model with nearest neighbor plus weak finite range interactions of strength λ. We rigorously establish one of the predictions of Conformal Field Theory (CFT), namely the fact that at the critical temperature the finite size corrections to the free energy are universal, in the sense that they are exactly independent of the interaction. The corresponding central charge, defined in terms of the coefficient of the first subleading term to the free energy, as proposed by Affleck and Blote-Cardy-Nightingale, is constant and equal to 1/2 for all and λ 0 a small but finite convergence radius. This is one of the very few cases where the predictions of CFT can be rigorously verified starting from a microscopic non solvable statistical model. The proof uses a combination of rigorous renormalization group methods with a novel partition function inequality, valid for ferromagnetic interactions.
Building relativistic mean field models for finite nuclei and neutron stars
Chen, Wei-Chia
2014-01-01
Background: Theoretical approaches based on density functional theory provide the only tractable method to incorporate the wide range of densities and isospin asymmetries required to describe finite nuclei, infinite nuclear matter, and neutron stars. Purpose: A relativistic energy density functional (EDF) is developed to address the complexity of such diverse nuclear systems. Moreover, a statistical perspective is adopted to describe the information content of various physical observables. Methods: We implement the model optimization by minimizing a suitably constructed chi-square objective function using various properties of finite nuclei and neutron stars. The minimization is then supplemented by a covariance analysis that includes both uncertainty estimates and correlation coefficients. Results: A new model, FSUGold2, is created that can well reproduce the ground-state properties of finite nuclei, their monopole response, and that accounts for the maximum neutron star mass observed up to date. In particul...
A finite element model for residual stress in repair welds
Energy Technology Data Exchange (ETDEWEB)
Feng, Z. [Edison Welding Inst., Columbus, OH (United States); Wang, X.L.; Spooner, S.; Goodwin, G.M.; Maziasz, P.J.; Hubbard, C.R.; Zacharia, T. [Oak Ridge National Lab., TN (United States)
1996-03-28
This paper describes a three-dimensional finite element model for calculation of the residual stress distribution caused by repair welding. Special user subroutines were developed to simulate the continuous deposition of filler metal during welding. The model was then tested by simulating the residual stress/strain field of a FeAl weld overlay clad on a 2{1/4}Cr-1 Mo steel plate, for which neutron diffraction measurement data of the residual strain field were available. It is shown that the calculated residual stress distribution was consistent with that determined with neutron diffraction. High tensile residual stresses in both the longitudinal and transverse directions were observed around the weld toe at the end of the weld. The strong spatial dependency of the residual stresses in the region around the weld demonstrates that the common two-dimensional cross-section finite element models should not be used for repair welding analysis.
A finite element model of ferroelectric/ferroelastic polycrystals
Energy Technology Data Exchange (ETDEWEB)
HWANG,STEPHEN C.; MCMEEKING,ROBERT M.
2000-02-17
A finite element model of polarization switching in a polycrystalline ferroelectric/ferroelastic ceramic is developed. It is assumed that a crystallite switches if the reduction in potential energy of the polycrystal exceeds a critical energy barrier per unit volume of switching material. Each crystallite is represented by a finite element with the possible dipole directions assigned randomly subject to crystallographic constraints. The model accounts for both electric field induced (i.e. ferroelectric) switching and stress induced (i.e. ferroelastic) switching with piezoelectric interactions. Experimentally measured elastic, dielectric, and piezoelectric constants are used consistently, but different effective critical energy barriers are selected phenomenologically. Electric displacement versus electric field, strain versus electric field, stress versus strain, and stress versus electric displacement loops of a ceramic lead lanthanum zirconate titanate (PLZT) are modeled well below the Curie temperature.
Three-body recombination at finite energy within an optical model
DEFF Research Database (Denmark)
Sørensen, Peder Klokmose; V. Fedorov, D.; S. Jensen, A.;
2013-01-01
We investigate three-boson recombination of equal mass systems as function of (negative) scattering length, mass, finite energy, and finite temperature. An optical model with an imaginary potential at short distance reproduces experimental recombination data and allows us to provide a simple...... parametrization of the recombination rate as function of scattering length and energy. Using the two-body van der Waals length as unit we find that the imaginary potential range and also the potential depth agree to within thirty percent for Lithium and Cesium atoms. As opposed to recent studies suggesting...
A blended continuous-discontinuous finite element method for solving the multi-fluid plasma model
Sousa, E. M.; Shumlak, U.
2016-12-01
The multi-fluid plasma model represents electrons, multiple ion species, and multiple neutral species as separate fluids that interact through short-range collisions and long-range electromagnetic fields. The model spans a large range of temporal and spatial scales, which renders the model stiff and presents numerical challenges. To address the large range of timescales, a blended continuous and discontinuous Galerkin method is proposed, where the massive ion and neutral species are modeled using an explicit discontinuous Galerkin method while the electrons and electromagnetic fields are modeled using an implicit continuous Galerkin method. This approach is able to capture large-gradient ion and neutral physics like shock formation, while resolving high-frequency electron dynamics in a computationally efficient manner. The details of the Blended Finite Element Method (BFEM) are presented. The numerical method is benchmarked for accuracy and tested using two-fluid one-dimensional soliton problem and electromagnetic shock problem. The results are compared to conventional finite volume and finite element methods, and demonstrate that the BFEM is particularly effective in resolving physics in stiff problems involving realistic physical parameters, including realistic electron mass and speed of light. The benefit is illustrated by computing a three-fluid plasma application that demonstrates species separation in multi-component plasmas.
Ruiz-Baier, Ricardo; Lunati, Ivan
2016-10-01
We present a novel discretization scheme tailored to a class of multiphase models that regard the physical system as consisting of multiple interacting continua. In the framework of mixture theory, we consider a general mathematical model that entails solving a system of mass and momentum equations for both the mixture and one of the phases. The model results in a strongly coupled and nonlinear system of partial differential equations that are written in terms of phase and mixture (barycentric) velocities, phase pressure, and saturation. We construct an accurate, robust and reliable hybrid method that combines a mixed finite element discretization of the momentum equations with a primal discontinuous finite volume-element discretization of the mass (or transport) equations. The scheme is devised for unstructured meshes and relies on mixed Brezzi-Douglas-Marini approximations of phase and total velocities, on piecewise constant elements for the approximation of phase or total pressures, as well as on a primal formulation that employs discontinuous finite volume elements defined on a dual diamond mesh to approximate scalar fields of interest (such as volume fraction, total density, saturation, etc.). As the discretization scheme is derived for a general formulation of multicontinuum physical systems, it can be readily applied to a large class of simplified multiphase models; on the other, the approach can be seen as a generalization of these models that are commonly encountered in the literature and employed when the latter are not sufficiently accurate. An extensive set of numerical test cases involving two- and three-dimensional porous media are presented to demonstrate the accuracy of the method (displaying an optimal convergence rate), the physics-preserving properties of the mixed-primal scheme, as well as the robustness of the method (which is successfully used to simulate diverse physical phenomena such as density fingering, Terzaghi's consolidation
Can sigma models describe finite temperature chiral transitions?
Kocic, Aleksandar; Aleksandar KOCIC; John KOGUT
1995-01-01
Large-N expansions and computer simulations indicate that the universality class of the finite temperature chiral symmetry restoration transition in the 3D Gross-Neveu model is mean field theory. This is a counterexample to the standard 'sigma model' scenario which predicts the 2D Ising model universality class. We trace the breakdown of the standard scenario (dimensional reduction and universality) to the absence of canonical scalar fields in the model. We point out that our results could be generic for theories with dynamical symmetry breaking, such as Quantum Chromodynamics.
Inflation from the Finite Scale Gauged Nambu-Jona-Lasinio Model
Inagaki, Tomohiro; Sakamoto, Hiroki
2016-01-01
The possibility to construct an inflationary universe scenario for the finite-scale gauged Nambu-Jona-Lasinio model is investigated. This model can be described by the Higgs-Yukawa type interaction model with the corresponding compositeness scale. Therefore, the one-loop Higgs-Yukawa effective potential is used with the compositeness condition for the study of inflationary dynamics. We evaluate the fluctuations in the cosmic microwave background for the model with a finite compositeness scale in the slow-roll approximation. We find the remarkable dependence on the gauge group and the number of fermion flavors. It is also proved that the model has similar behavior with the $\\phi^{4n}$ chaotic inflation and the Starobinsky model at the flat and steep limits, respectively. It is demonstrated that realistic inflation consistent with Planck data is possible for a range of theory parameters.
Finite elements modeling of delaminations in composite laminates
DEFF Research Database (Denmark)
Gaiotti, m.; Rizzo, C.M.; Branner, Kim;
2011-01-01
The application of composite materials in many structures poses to engineers the problem to create reliable and relatively simple methods, able to estimate the strength of multilayer composite structures. Multilayer composites, like other laminated materials, suffer from layer separation, i.e., d...... by finite elements using different techniques. Results obtained with different finite element models are compared and discussed.......The application of composite materials in many structures poses to engineers the problem to create reliable and relatively simple methods, able to estimate the strength of multilayer composite structures. Multilayer composites, like other laminated materials, suffer from layer separation, i...... of the buckling strength of composite laminates containing delaminations. Namely, non-linear buckling and post-buckling analyses are carried out to predict the critical buckling load of elementary composite laminates affected by rectangular delaminations of different sizes and locations, which are modelled...
Finite element model of reinforcement corrosion in concrete
Institute of Scientific and Technical Information of China (English)
Jin-xia XU; Lin-hua JIANG; Qi WANG
2009-01-01
A nonlinear finite element model (FEM) of the corrosion of steel reinforcement in concrete has been successfully developed on the basis of mathematical analysis of the electrochemical process of steel corrosion in concrete. The influences of the area ratio and the Tafel constants of the anode and cathode on the potential and corrosion current density have been examined with the model. It has been found that the finite element calculation is more suitable for assessing the corrosion condition of steel reinforcement than ordinary electrochemical techniques due to the fact that FEM can obtain the distributions of potential and corrosion current density on the steel surface. In addition, the local corrosion of steel reinforcement in concrete is strengthened with the decrease of both the area ratio and the Tafel constants. These results provide valuable information to the researchers who investigate steel corrosion.
Mitter, P. K.
2017-09-01
In previous papers, Mitter (J Stat Phys 163:1235-1246, 2016; Erratum: J Stat Phys 166:453-455, 2017; On a finite range decomposition of the resolvent of a fractional power of the Laplacian, http://arxiv.org/abs/1512.02877), we proved the existence as well as regularity of a finite range decomposition for the resolvent G_{α } (x-y,m^2) = ((-Δ )^{α \\over 2} + m2)^{-1} (x-y) , for 0<α <2 and all real m, in the lattice Zd for dimension d≥ 2. In this paper, which is a continuation of the previous one, we extend those results by proving the existence as well as regularity of a finite range decomposition for the same resolvent but now on the lattice torus Zd/L^{N+1}Zd for d≥ 2 provided m≠ 0 and 0<α <2. We also prove differentiability and uniform continuity properties with respect to the resolvent parameter m2. Here L is any odd positive integer and N≥ 2 is any positive integer.
Calibration of a finite element composite delamination model by experiments
DEFF Research Database (Denmark)
Gaiotti, M.; Rizzo, C.M.; Branner, Kim;
2013-01-01
distinct sub-laminates. The work focuses on experimental validation of a finite element model built using the 9-noded MITC9 shell elements, which prevent locking effects and aiming to capture the highly non linear buckling features involved in the problem. The geometry has been numerically defined...... modes related to the production methods is presented in this paper. A microscopic analysis of the fracture surfaces was carried out in order to better understand the failure mechanisms. © 2013 Taylor & Francis Group....
Landau parameters for energy density functionals generated by local finite-range pseudopotentials
Idini, Andrea; Dobaczewski, Jacek
2016-01-01
In Landau theory of Fermi liquids, the particle-hole interaction near the Fermi energy in different spin-isospin channels is probed in terms of an expansion over the Legendre polynomials. This provides a useful and efficient way to constrain properties of nuclear energy density functionals in symmetric nuclear matter and finite nuclei. In this study, we present general expressions for Landau parameters corresponding to a two-body central local regularized pseudopotential. We also show results obtained for two recently adjusted NLO and N$^2$LO parametrizations. Such pseudopotentials will be used to determine mean-field and beyond-mean-field properties of paired nuclei across the entire nuclear chart.
Friedberg-Lee model at finite temperature and density
Mao, Hong; Yao, Minjie; Zhao, Wei-Qin
2008-06-01
The Friedberg-Lee model is studied at finite temperature and density. By using the finite temperature field theory, the effective potential of the Friedberg-Lee model and the bag constant B(T) and B(T,μ) have been calculated at different temperatures and densities. It is shown that there is a critical temperature TC≃106.6 MeV when μ=0 MeV and a critical chemical potential μ≃223.1 MeV for fixing the temperature at T=50 MeV. We also calculate the soliton solutions of the Friedberg-Lee model at finite temperature and density. It turns out that when T⩽TC (or μ⩽μC), there is a bag constant B(T) [or B(T,μ)] and the soliton solutions are stable. However, when T>TC (or μ>μC) the bag constant B(T)=0 MeV [or B(T,μ)=0 MeV] and there is no soliton solution anymore, therefore, the confinement of quarks disappears quickly.
The Friedberg-Lee model at finite temperature and density
Mao, Hong; Zhao, Wei-Qin
2007-01-01
The Friedberg-Lee model is studied at finite temperature and density. By using the finite temperature field theory, the effective potential of the Friedberg-Lee model and the bag constant $B(T)$ and $B(T,\\mu)$ have been calculated at different temperatures and densities. It is shown that there is a critical temperature $T_{C}\\simeq 106.6 \\mathrm{MeV}$ when $\\mu=0 \\mathrm{MeV}$ and a critical chemical potential $\\mu \\simeq 223.1 \\mathrm{MeV}$ for fixing the temperature at $T=50 \\mathrm{MeV}$. We also calculate the soliton solutions of the Friedberg-Lee model at finite temperature and density. It turns out that when $T\\leq T_{C}$ (or $\\mu \\leq \\mu_C$), there is a bag constant $B(T)$ (or $B(T,\\mu)$) and the soliton solutions are stable. However, when $T>T_{C}$ (or $\\mu>\\mu_C$) the bag constant $B(T)=0 \\mathrm{MeV}$ (or $B(T,\\mu)=0 \\mathrm{MeV}$) and there is no soliton solution anymore, therefore, the confinement of quarks disappears quickly.
2D - Finite element model of a CIGS module
Energy Technology Data Exchange (ETDEWEB)
Janssen, G.J.M.; Slooff, L.H.; Bende, E.E. [ECN Solar Energy, Petten (Netherlands)
2012-09-15
The performance of thin-film CIGS modules is often limited due to inhomogeneities in CIGS layers. A 2-dimensional Finite Element Model for CIGS modules is demonstrated that predicts the impact of such inhomogeneities on the module performance. Results are presented of a module with a region of poor diode characteristics. It is concluded that according to this model the effects of poor diodes depend strongly on their location in the module and on their dispersion over the module surface. Due to its generic character the model can also be applied to other series connections of photovoltaic cells.
Constitutive modeling of shape memory alloys at finite strain
Energy Technology Data Exchange (ETDEWEB)
Pethoe, A. [Technical Univ. Budapest (Hungary). Dept. of Applied Mechanics
2001-07-01
A new model which is able to reproduce the basic responses of shape memory materials on both micro- and macrostructural aspects is presented. The model is based on a local finite strain continuum description and uses a multiplicative decomposition of the total deformation gradient which involves elastic, plastic and microstructurally given phase transitional parts. For the elastic behavior of the material a coupled hyper-hypoelastic model is used based on a recently developed logarithmic rate. A complex constitutive equation is presented which consists of the kinetics of phase change process given by thermodynamical basis. Finally a simple one dimensional example is also shown. (orig.)
Investigation of perpetual pavement using finite element modelling
Directory of Open Access Journals (Sweden)
Monireh Zokaei
2016-06-01
Full Text Available With considering numerous failures which exist in flexible pavements, a huge amount of money is spending on treatment and reconstructing pavements. Many researches have been performed to with improving pavement quality, increased the performance and pavements life. One type of long lasting pavements is perpetual pavement. In this research ABAQUS software is used to simulate pavement. . Materials are modelled as visco-elastic type and loading wheel is assumed to be moving. After gaining results, the effects of different parameters on pavements function is assessed. Modelling movements of loading wheel is very effective in viscoelastic condition, increase more accuracy of the finite-element model.
Modelling discrete longitudinal data using acyclic probabilistic finite automata
DEFF Research Database (Denmark)
Anantharama Ankinakatte, Smitha; Edwards, David
2015-01-01
Acyclic probabilistic finite automata (APFA) constitute a rich family of models for discrete longitudinal data. An APFA may be represented as a directed multigraph, and embodies a set of context-specific conditional independence relations that may be read off the graph. A model selection algorithm...... to minimize a penalized likelihood criterion such as AIC or BIC is described. This algorithm is compared to one implemented in Beagle, a widely used program for processing genomic data, both in terms of rate of convergence to the true model as the sample size increases, and a goodness-of-fit measure assessed...
Liu, Chang; Zhu, Xian-chun; Zhang, Xing; Tai, Yin-xia; Yan, Sen
2011-02-01
To build the physical model of four suturae which are related to the growth of maxilla in the three-dimensional finite-element model of maxillofacial bones. A 16 years old volunteer with individual normal occlusion, good periodontium health condition and without diseases of temporomandibular joint was chosen to be the material of modeling. The three-dimensional finite-element model of the volunteer's maxillofacial bones was built using the CT scan and the finite-element modeling method. Finally we built the physical model of four suturae which were related to the growth of maxilla in the model of maxillofacial bones. The model of maxillofacial bones with 86,575 nodes and 485,915 elements was generated. This model contained four suturae including sutura frontomaxillaris, sutura zygomaticomaxillaris, sutura temporozygomatica and sutura pterygopalatine. A three-dimensional finite-element model of maxillofacial bones with good biological similarity was developed.
Model order reduction techniques with applications in finite element analysis
Qu, Zu-Qing
2004-01-01
Despite the continued rapid advance in computing speed and memory the increase in the complexity of models used by engineers persists in outpacing them. Even where there is access to the latest hardware, simulations are often extremely computationally intensive and time-consuming when full-blown models are under consideration. The need to reduce the computational cost involved when dealing with high-order/many-degree-of-freedom models can be offset by adroit computation. In this light, model-reduction methods have become a major goal of simulation and modeling research. Model reduction can also ameliorate problems in the correlation of widely used finite-element analyses and test analysis models produced by excessive system complexity. Model Order Reduction Techniques explains and compares such methods focusing mainly on recent work in dynamic condensation techniques: - Compares the effectiveness of static, exact, dynamic, SEREP and iterative-dynamic condensation techniques in producing valid reduced-order mo...
Kim, H. Alicia; Hardie, Robert; Yamakov, Vesselin; Park, Cheol
2015-01-01
This paper is the second part of a two-part series where the first part presents a molecular dynamics model of a single Boron Nitride Nanotube (BNNT) and this paper scales up to multiple BNNTs in a polymer matrix. This paper presents finite element (FE) models to investigate the effective elastic and piezoelectric properties of (BNNT) nanocomposites. The nanocomposites studied in this paper are thin films of polymer matrix with aligned co-planar BNNTs. The FE modelling approach provides a computationally efficient way to gain an understanding of the material properties. We examine several FE models to identify the most suitable models and investigate the effective properties with respect to the BNNT volume fraction and the number of nanotube walls. The FE models are constructed to represent aligned and randomly distributed BNNTs in a matrix of resin using 2D and 3D hollow and 3D filled cylinders. The homogenisation approach is employed to determine the overall elastic and piezoelectric constants for a range of volume fractions. These models are compared with an analytical model based on Mori-Tanaka formulation suitable for finite length cylindrical inclusions. The model applies to primarily single-wall BNNTs but is also extended to multi-wall BNNTs, for which preliminary results will be presented. Results from the Part 1 of this series can help to establish a constitutive relationship for input into the finite element model to enable the modeling of multiple BNNTs in a polymer matrix.
Finite-Source Modeling of the South Napa Earthquake
Dreger, D. S.; Huang, M. H.; Wooddell, K. E.; Taira, T.; Luna, B.
2014-12-01
On August 24 2014 an Mw 6.0 earthquake struck south-southwest of the city of Napa, California. As part of the Berkeley Seismological Laboratory (BSL) Alarm Response a seismic moment tensor solution and preliminary finite-source model were estimated. The preliminary finite-source model used high quality three-component strong motion recordings, instrument corrected and integrated to displacement, from 8 stations of the BSL BK network for stations located between 30 to 200 km. The BSL focal mechanism (strike=155, dip=82, rake=-172), and a constant rise time and rupture velocity were assumed. The GIL7 plane-layered velocity model was used to compute Green's functions using a frequency wave-number integration approach. The preliminary model from these stations indicates the rupture was unilateral to the NNW, and up dip with a average slip of 42 cm and peak slip of 102 cm. The total scalar moment was found to be 1.15*1025 dyne cm giving a Mw 6.0.The strong directivity from the rupture likely leads to the observed elevated local strong ground motions and the extensive damage to buildings in Napa and surrounding residential areas. In this study we will reevaluate the seismic moment tensor of the mainshock and larger aftershocks, and incorporate local strong motion waveforms, GPS, and InSAR deformation data to better constrain the finite-source model. While the hypocenter and focal parameters used in the preliminary model are consistent with the mapped surface trace of the west Napa fault, the mapped surface slip lies approximately 2 km to the west. Furthermore there is a pronounced change in strike of the mapped surface offsets at the northern end. We will investigate the location of the fault model and the fit to the joint data set as well as examine the possibility of multi-segmented fault models to account for these apparently inconsistent observations.
Robbins, Joshua; Voth, Thomas E.
2007-12-01
The eXtended Finite Element Method (X-FEM) is a finite-element based discretization technique developed originally to model dynamic crack propagation [1]. Since that time the method has been used for modeling physics ranging from static meso-scale material failure to dendrite growth. Here we adapt the recent advances of Vitali and Benson [2] and Song et al. [3] to model dynamic loading of a polycrystalline material. We use demonstration problems to examine the method's efficacy for modeling the dynamic response of polycrystalline materials at the meso-scale. Specifically, we use the X-FEM to model grain boundaries. This approach allows us to i) eliminate ad-hoc mixture rules for multi-material elements and ii) avoid explicitly meshing grain boundaries.
Finite Element Modeling of the Buckling Response of Sandwich Panels
Rose, Cheryl A.; Moore, David F.; Knight, Norman F., Jr.; Rankin, Charles C.
2002-01-01
A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.
Robbins, Joshua; Voth, Thomas
2007-06-01
The eXtended Finite Element Method (X-FEM) is a finite element based discretization technique developed originally to model dynamic crack propagation [1]. Since that time the method has been used for modeling physics ranging from static mesoscale material failure to dendrite growth. Here we adapt the recent advances of Benson et al. [2] and Belytchko et al. [3] to model shock loading of polycrystalline material. Through several demonstration problems we evaluate the method for modeling the shock response of polycrystalline materials at the mesoscale. Specifically, we use the X-FEM to model grain boundaries. This approach allows us to i) eliminate ad-hoc mixture rules for multi-material elements and ii) avoid explicitly meshing grain boundaries. ([1] N. Moes, J. Dolbow, J and T. Belytschko, 1999,``A finite element method for crack growth without remeshing,'' International Journal for Numerical Methods in Engineering, 46, 131-150. [2] E. Vitali, and D. J. Benson, 2006, ``An extended finite element formulation for contact in multi-material arbitrary Lagrangian-Eulerian calculations,'' International Journal for Numerical Methods in Engineering, 67, 1420-1444. [3] J-H Song, P. M. A. Areias and T. Belytschko, 2006, ``A method for dynamic crack and shear band propagation with phantom nodes,'' International Journal for Numerical Methods in Engineering, 67, 868-893.)
[Establishment of 3-dimensional finite element model of human knee joint and its biomechanics].
Yuan, Ping; Wang, Wanchun
2010-01-01
To establish a 3-dimensional (3-D) finite element knee model in healthy Chinese males, to verify the validity of the model, and to analyze the biomechanics of this model under axial load, flexion moment, varus/valgus torque, and internal/external axial torque. A set of consecutive transectional computerized tomography images of normal male knee joints in upright weight-bearing position was selected. With image processing and inversion technology, the 3-D finite element model of the normal knee joint was established through the software ABAQOUS/STANDARD Version-6.5.Biomechanical analysis of this model was processed under axial load, flexion moment, varus/valgus torque, and internal/external axial torque. A 3-D finite element model of healthy Chinese males was successfully established. The ranges of motion of varus and valgus were both small and the difference between them has no statistical significance (P>0.05). The motion of internal and external rotation of the knee took place only in flexion situation.The range of motion of external rotation was larger than that of internal rotation in the same knee (Pknee resembles the actual knee segments. It can imitate the knee response to different loads. This model could be used for further study on knee biomechanics.
DEFF Research Database (Denmark)
Rohde, John; Toftegaard, Thomas Skjødeberg
2012-01-01
Novel parametric finite-element models are provided for discrete SMD capacitors and inductors in the frequency range 100 MHz to 4 GHz. The aim of the models is to facilitate performance optimization and analysis of RF PCB designs integrating these SMD components with layout geometries...... such as antennas and PCB traces. The models presented are benchmarked against real-life measurements and conventional circuit models. Furthermore, two example parallel-resonance circuits are designed based on interpolation of the results and validated by measurements in order to demonstrate the accuracy...... of the presented modelling approach....
Morshed, Monjur; Ingalls, Brian; Ilie, Silvana
2017-01-01
Sensitivity analysis characterizes the dependence of a model's behaviour on system parameters. It is a critical tool in the formulation, characterization, and verification of models of biochemical reaction networks, for which confident estimates of parameter values are often lacking. In this paper, we propose a novel method for sensitivity analysis of discrete stochastic models of biochemical reaction systems whose dynamics occur over a range of timescales. This method combines finite-difference approximations and adaptive tau-leaping strategies to efficiently estimate parametric sensitivities for stiff stochastic biochemical kinetics models, with negligible loss in accuracy compared with previously published approaches. We analyze several models of interest to illustrate the advantages of our method.
The Einstein specific heat model for finite systems
Boscheto, E.; de Souza, M.; López-Castillo, A.
2016-06-01
The theoretical model proposed by Einstein to describe the phononic specific heat of solids as a function of temperature consists of the very first application of the concept of energy quantization to describe the physical properties of a real system. Its central assumption lies in the consideration of a total energy distribution among N (in the thermodynamic limit N → ∞) non-interacting oscillators vibrating at the same frequency (ω). Nowadays, it is well-known that most materials behave differently at the nanoscale, having thus some cases physical properties with potential technological applications. Here, a version of the Einstein model composed of a finite number of particles/oscillators is proposed. The main findings obtained in the frame of the present work are: (i) a qualitative description of the specific heat in the limit of low-temperatures for systems with nano-metric dimensions; (ii) the observation that the corresponding chemical potential function for finite solids becomes null at finite temperatures as observed in the Bose-Einstein condensation and; (iii) emergence of a first-order like phase transition driven by varying N.
Finite element modeling of consolidation of composite laminates
Institute of Scientific and Technical Information of China (English)
Xiangqiao Yan
2006-01-01
Advanced fiber reinforced polymer composites have been increasingly applied to various structural corn-ponents.One of the important processes to fabricate high performance laminated composites is an autoclave assisted prepreg lay-up.Since the quality of laminated composites is largely affected by the cure cycle,selection of an appropriate cure cycle for each application is important and must be opti-mized.Thus.some fundamental model of the consolidation and cure processes is necessary for selecting suitable param-eters for a specific application.This article is concerned with the "flow-compaction" model during the autoclave process-ing of composite materials.By using a weighted residual method,two-dimensional finite element formulation for the consolidation process of thick thermosetting composites is presented and the corresponding finite element code is developed.Numerical examples.including comparison of the present numerical results with one-dimensional and two-dimensional analytical solutions,are given to illustrate the accuracy and effectiveness of the proposed finite element formulation.In addition,a consolidation simulation of As4/3501-6 graphite/epoxy laminate is carried out and compared with the experimental results available in the literature.
Dynamical effects of a one-dimensional multibarrier potential of finite range
Bar, D
2002-01-01
We discuss the properties of a large number N of one-dimensional (bounded) locally periodic potential barriers in a finite interval. We show that the transmission coefficient, the scattering cross section $\\sigma$, and the resonances of $\\sigma$ depend sensitively upon the ratio of the total spacing to the total barrier width. We also show that a time dependent wave packet passing through the system of potential barriers rapidly spreads and deforms, a criterion suggested by Zaslavsky for chaotic behaviour. Computing the spectrum by imposing (large) periodic boundary conditions we find a Wigner type distribution. We investigate also the S-matrix poles; many resonances occur for certain values of the relative spacing between the barriers in the potential.
A finite element model for protein transport in vivo
Directory of Open Access Journals (Sweden)
Montas Hubert J
2007-06-01
Full Text Available Abstract Background Biological mass transport processes determine the behavior and function of cells, regulate interactions between synthetic agents and recipient targets, and are key elements in the design and use of biosensors. Accurately predicting the outcomes of such processes is crucial to both enhancing our understanding of how these systems function, enabling the design of effective strategies to control their function, and verifying that engineered solutions perform according to plan. Methods A Galerkin-based finite element model was developed and implemented to solve a system of two coupled partial differential equations governing biomolecule transport and reaction in live cells. The simulator was coupled, in the framework of an inverse modeling strategy, with an optimization algorithm and an experimental time series, obtained by the Fluorescence Recovery after Photobleaching (FRAP technique, to estimate biomolecule mass transport and reaction rate parameters. In the inverse algorithm, an adaptive method was implemented to calculate sensitivity matrix. A multi-criteria termination rule was developed to stop the inverse code at the solution. The applicability of the model was illustrated by simulating the mobility and binding of GFP-tagged glucocorticoid receptor in the nucleoplasm of mouse adenocarcinoma. Results The numerical simulator shows excellent agreement with the analytic solutions and experimental FRAP data. Detailed residual analysis indicates that residuals have zero mean and constant variance and are normally distributed and uncorrelated. Therefore, the necessary and sufficient criteria for least square parameter optimization, which was used in this study, were met. Conclusion The developed strategy is an efficient approach to extract as much physiochemical information from the FRAP protocol as possible. Well-posedness analysis of the inverse problem, however, indicates that the FRAP protocol provides insufficient
The Instanton-Dyon Liquid Model III: Finite Chemical Potential
Liu, Yizhuang; Zahed, Ismail
2016-01-01
We discuss an extension of the instanton-dyon liquid model that includes light quarks at finite chemical potential in the center symmetric phase. We develop the model in details for the case of SU_c(2)\\times SU_f(2) by mapping the theory on a 3-dimensional quantum effective theory. We analyze the different phases in the mean-field approximation. We extend this analysis to the general case of SU_c(N_c)\\times SU_f(N_f) and note that the chiral and diquark pairings are always comparable.
Automorphisms and Generalized Involution Models of Finite Complex Reflection Groups
Marberg, Eric
2010-01-01
We prove that a finite complex reflection group has a generalized involution model, as defined by Bump and Ginzburg, if and only if each of its irreducible factors is either $G(r,p,n)$ with $\\gcd(p,n)=1$; $G(r,p,2)$ with $r/p$ odd; or $G_{23}$, the Coxeter group of type $H_3$. We additionally provide explicit formulas for all automorphisms of $G(r,p,n)$, and construct new Gelfand models for the groups $G(r,p,n)$ with $\\gcd(p,n)=1$.
Optimal policies for a finite-horizon batching inventory model
Al-Khamis, Talal M.; Benkherouf, Lakdere; Omar, Mohamed
2014-10-01
This paper is concerned with finding an optimal inventory policy for the integrated replenishment-production batching model of Omar and Smith (2002). Here, a company produces a single finished product which requires a single raw material and the objective is to minimise the total inventory costs over a finite planning horizon. Earlier work in the literature considered models with linear demand rate function of the finished product. This work proposes a general methodology for finding an optimal inventory policy for general demand rate functions. The proposed methodology is adapted from the recent work of Benkherouf and Gilding (2009).
Small velocity and finite temperature variations in kinetic relaxation models
Markowich, Peter
2010-01-01
A small Knuden number analysis of a kinetic equation in the diffusive scaling is performed. The collision kernel is of BGK type with a general local Gibbs state. Assuming that the flow velocity is of the order of the Knudsen number, a Hilbert expansion yields a macroscopic model with finite temperature variations, whose complexity lies in between the hydrodynamic and the energy-transport equations. Its mathematical structure is explored and macroscopic models for specific examples of the global Gibbs state are presented. © American Institute of Mathematical Sciences.
Artificial emotional model based on finite state machine
Institute of Scientific and Technical Information of China (English)
MENG Qing-mei; WU Wei-guo
2008-01-01
According to the basic emotional theory, the artificial emotional model based on the finite state machine(FSM) was presented. In finite state machine model of emotion, the emotional space included the basic emotional space and the multiple emotional spaces. The emotion-switching diagram was defined and transition function was developed using Markov chain and linear interpolation algorithm. The simulation model was built using Stateflow toolbox and Simulink toolbox based on the Matlab platform.And the model included three subsystems: the input one, the emotion one and the behavior one. In the emotional subsystem, the responses of different personalities to the external stimuli were described by defining personal space. This model takes states from an emotional space and updates its state depending on its current state and a state of its input (also a state-emotion). The simulation model realizes the process of switching the emotion from the neutral state to other basic emotions. The simulation result is proved to correspond to emotion-switching law of human beings.
A vortex model for Darrieus turbine using finite element techniques
Energy Technology Data Exchange (ETDEWEB)
Ponta, Fernando L. [Universidad de Buenos Aires, Dept. de Electrotecnia, Grupo ISEP, Buenos Aires (Argentina); Jacovkis, Pablo M. [Universidad de Buenos Aires, Dept. de Computacion and Inst. de Calculo, Buenos Aires (Argentina)
2001-09-01
Since 1970 several aerodynamic prediction models have been formulated for the Darrieus turbine. We can identify two families of models: stream-tube and vortex. The former needs much less computation time but the latter is more accurate. The purpose of this paper is to show a new option for modelling the aerodynamic behaviour of Darrieus turbines. The idea is to combine a classic free vortex model with a finite element analysis of the flow in the surroundings of the blades. This avoids some of the remaining deficiencies in classic vortex models. The agreement between analysis and experiment when predicting instantaneous blade forces and near wake flow behind the rotor is better than the one obtained in previous models. (Author)
Digital Waveguides versus Finite Difference Structures: Equivalence and Mixed Modeling
Directory of Open Access Journals (Sweden)
Karjalainen Matti
2004-01-01
Full Text Available Digital waveguides and finite difference time domain schemes have been used in physical modeling of spatially distributed systems. Both of them are known to provide exact modeling of ideal one-dimensional (1D band-limited wave propagation, and both of them can be composed to approximate two-dimensional (2D and three-dimensional (3D mesh structures. Their equal capabilities in physical modeling have been shown for special cases and have been assumed to cover generalized cases as well. The ability to form mixed models by joining substructures of both classes through converter elements has been proposed recently. In this paper, we formulate a general digital signal processing (DSP-oriented framework where the functional equivalence of these two approaches is systematically elaborated and the conditions of building mixed models are studied. An example of mixed modeling of a 2D waveguide is presented.
Motion analysis study on sensitivity of finite element model of the cervical spine to geometry.
Zafarparandeh, Iman; Erbulut, Deniz U; Ozer, Ali F
2016-07-01
Numerous finite element models of the cervical spine have been proposed, with exact geometry or with symmetric approximation in the geometry. However, few researches have investigated the sensitivity of predicted motion responses to the geometry of the cervical spine. The goal of this study was to evaluate the effect of symmetric assumption on the predicted motion by finite element model of the cervical spine. We developed two finite element models of the cervical spine C2-C7. One model was based on the exact geometry of the cervical spine (asymmetric model), whereas the other was symmetric (symmetric model) about the mid-sagittal plane. The predicted range of motion of both models-main and coupled motions-was compared with published experimental data for all motion planes under a full range of loads. The maximum differences between the asymmetric model and symmetric model predictions for the principal motion were 31%, 78%, and 126% for flexion-extension, right-left lateral bending, and right-left axial rotation, respectively. For flexion-extension and lateral bending, the minimum difference was 0%, whereas it was 2% for axial rotation. The maximum coupled motions predicted by the symmetric model were 1.5° axial rotation and 3.6° lateral bending, under applied lateral bending and axial rotation, respectively. Those coupled motions predicted by the asymmetric model were 1.6° axial rotation and 4° lateral bending, under applied lateral bending and axial rotation, respectively. In general, the predicted motion response of the cervical spine by the symmetric model was in the acceptable range and nonlinearity of the moment-rotation curve for the cervical spine was properly predicted.
Panczak, Tim; Ring, Steve; Welch, Mark
1999-01-01
Thermal engineering has long been left out of the concurrent engineering environment dominated by CAD (computer aided design) and FEM (finite element method) software. Current tools attempt to force the thermal design process into an environment primarily created to support structural analysis, which results in inappropriate thermal models. As a result, many thermal engineers either build models "by hand" or use geometric user interfaces that are separate from and have little useful connection, if any, to CAD and FEM systems. This paper describes the development of a new thermal design environment called the Thermal Desktop. This system, while fully integrated into a neutral, low cost CAD system, and which utilizes both FEM and FD methods, does not compromise the needs of the thermal engineer. Rather, the features needed for concurrent thermal analysis are specifically addressed by combining traditional parametric surface based radiation and FD based conduction modeling with CAD and FEM methods. The use of flexible and familiar temperature solvers such as SINDA/FLUINT (Systems Improved Numerical Differencing Analyzer/Fluid Integrator) is retained.
Hussein Rappel; Aghil Yousefi-Koma; Jalil Jamali; Ako Bahari
2014-01-01
This paper presents a numerical model of lamb wave propagation in a homogenous steel plate using elastodynamic finite integration technique (EFIT) as well as its validation with analytical results. Lamb wave method is a long range inspection technique which is considered to have unique future in the field of structural health monitoring. One of the main problems facing the lamb wave method is how to choose the most appropriate frequency to generate the waves for adequate transmission capab...
Validation of a finite element model of the human metacarpal.
Barker, D S; Netherway, D J; Krishnan, J; Hearn, T C
2005-03-01
Implant loosening and mechanical failure of components are frequently reported following metacarpophalangeal (MCP) joint replacement. Studies of the mechanical environment of the MCP implant-bone construct are rare. The objective of this study was to evaluate the predictive ability of a finite element model of the intact second human metacarpal to provide a validated baseline for further mechanical studies. A right index human metacarpal was subjected to torsion and combined axial/bending loading using strain gauge (SG) and 3D finite element (FE) analysis. Four different representations of bone material properties were considered. Regression analyses were performed comparing maximum and minimum principal surface strains taken from the SG and FE models. Regression slopes close to unity and high correlation coefficients were found when the diaphyseal cortical shell was modelled as anisotropic and cancellous bone properties were derived from quantitative computed tomography. The inclusion of anisotropy for cortical bone was strongly influential in producing high model validity whereas variation in methods of assigning stiffness to cancellous bone had only a minor influence. The validated FE model provides a tool for future investigations of current and novel MCP joint prostheses.
Finite-dimensional attractors for the Kirchhoff models
Zhijian, Yang
2010-09-01
The paper studies the existence of the finite-dimensional global attractor and exponential attractor for the dynamical system associated with the Kirchhoff models arising in elasto-plastic flow utt-div{|∇u|m -1∇u}-Δut+Δ2u+h(ut)+g(u)=f(x). By using the method of ℓ-trajectories and the operator technique, it proves that under subcritical case, 1≤m
Wave Transformation Modeling with Effective Higher-Order Finite Elements
Directory of Open Access Journals (Sweden)
Tae-Hwa Jung
2016-01-01
Full Text Available This study introduces a finite element method using a higher-order interpolation function for effective simulations of wave transformation. Finite element methods with a higher-order interpolation function usually employ a Lagrangian interpolation function that gives accurate solutions with a lesser number of elements compared to lower order interpolation function. At the same time, it takes a lot of time to get a solution because the size of the local matrix increases resulting in the increase of band width of a global matrix as the order of the interpolation function increases. Mass lumping can reduce computation time by making the local matrix a diagonal form. However, the efficiency is not satisfactory because it requires more elements to get results. In this study, the Legendre cardinal interpolation function, a modified Lagrangian interpolation function, is used for efficient calculation. Diagonal matrix generation by applying direct numerical integration to the Legendre cardinal interpolation function like conducting mass lumping can reduce calculation time with favorable accuracy. Numerical simulations of regular, irregular and solitary waves using the Boussinesq equations through applying the interpolation approaches are carried out to compare the higher-order finite element models on wave transformation and examine the efficiency of calculation.
Finite time singularities in a class of hydrodynamic models
Ruban, V P; Rasmussen, J J
2001-01-01
Models of inviscid incompressible fluid are considered, with the kinetic energy (i.e., the Lagrangian functional) taking the form ${\\cal L}\\sim\\int k^\\alpha|{\\bf v_k}|^2d^3{\\bf k}$ in 3D Fourier representation, where $\\alpha$ is a constant, $0<\\alpha< 1$. Unlike the case $\\alpha=0$ (the usual Eulerian hydrodynamics), a finite value of $\\alpha$ results in a finite energy for a singular frozen-in vortex filament. This property allows us to study the dynamics of such filaments without necessity in some regularization procedure. The linear analysis of small symmetrical deviations from a stationary solution is performed for a pair of anti-parallel vortex filaments and an analog of the Crow instability is found at small wave-numbers. A local approximate Hamiltonian is obtained for nonlinear long-scale dynamics of this system. Self-similar solutions of the corresponding equations are found analytically, which describe finite time singularity formation with all length scales decreasing like $(t^*-t)^{1/(2-\\alph...
The Blended Finite Element Method for Multi-fluid Plasma Modeling
2016-07-01
Briefing Charts 3. DATES COVERED (From - To) 07 June 2016 - 01 July 2016 4. TITLE AND SUBTITLE The Blended Finite Element Method for Multi-fluid Plasma ...BLENDED FINITE ELEMENT METHOD FOR MULTI-FLUID PLASMA MODELING Éder M. Sousa1, Uri Shumlak2 1ERC INC., IN-SPACE PROPULSION BRANCH (RQRS) AIR FORCE RESEARCH...MULTI-FLUID PLASMA MODEL 2 BLENDED FINITE ELEMENT METHOD Blended Finite Element Method Nodal Continuous Galerkin Modal Discontinuous Galerkin Model
Finite difference methods for coupled flow interaction transport models
Directory of Open Access Journals (Sweden)
Shelly McGee
2009-04-01
Full Text Available Understanding chemical transport in blood flow involves coupling the chemical transport process with flow equations describing the blood and plasma in the membrane wall. In this work, we consider a coupled two-dimensional model with transient Navier-Stokes equation to model the blood flow in the vessel and Darcy's flow to model the plasma flow through the vessel wall. The advection-diffusion equation is coupled with the velocities from the flows in the vessel and wall, respectively to model the transport of the chemical. The coupled chemical transport equations are discretized by the finite difference method and the resulting system is solved using the additive Schwarz method. Development of the model and related analytical and numerical results are presented in this work.
Finite element model calibration of a nonlinear perforated plate
Ehrhardt, David A.; Allen, Matthew S.; Beberniss, Timothy J.; Neild, Simon A.
2017-03-01
This paper presents a case study in which the finite element model for a curved circular plate is calibrated to reproduce both the linear and nonlinear dynamic response measured from two nominally identical samples. The linear dynamic response is described with the linear natural frequencies and mode shapes identified with a roving hammer test. Due to the uncertainty in the stiffness characteristics from the manufactured perforations, the linear natural frequencies are used to update the effective modulus of elasticity of the full order finite element model (FEM). The nonlinear dynamic response is described with nonlinear normal modes (NNMs) measured using force appropriation and high speed 3D digital image correlation (3D-DIC). The measured NNMs are used to update the boundary conditions of the full order FEM through comparison with NNMs calculated from a nonlinear reduced order model (NLROM). This comparison revealed that the nonlinear behavior could not be captured without accounting for the small curvature of the plate from manufacturing as confirmed in literature. So, 3D-DIC was also used to identify the initial static curvature of each plate and the resulting curvature was included in the full order FEM. The updated models are then used to understand how the stress distribution changes at large response amplitudes providing a possible explanation of failures observed during testing.
Finite element modeling of nanotube structures linear and non-linear models
Awang, Mokhtar; Muhammad, Ibrahim Dauda
2016-01-01
This book presents a new approach to modeling carbon structures such as graphene and carbon nanotubes using finite element methods, and addresses the latest advances in numerical studies for these materials. Based on the available findings, the book develops an effective finite element approach for modeling the structure and the deformation of grapheme-based materials. Further, modeling processing for single-walled and multi-walled carbon nanotubes is demonstrated in detail.
Noise modeling for MOAs and ranges
Lucas, Michael J.; Lee, Robert A.
Whenever there is a reallocation of DOD fixed- or rotary-wing aircraft or a change in the use of the airspace requirements, either an Environmental Assessment or an Environmental Impact Statement must be prepared. These environmental studies require an analysis of the noise impacts resulting from aircraft operations surrounding the airports and under Military Training Routes (MTR's), Military Operating Areas (MOA's), and Ranges. NOISEMAP and ROUTEMAP were developed for the purpose of estimating the noise levels around military airports and under MTR's. Neither of these programs is suitable for estimating noise levels under MOA's or Ranges. MR NMAP is a PC-based computer model that has been developed to calculate the noise levels under MOA's and ranges. The program calculates L(sub dn), CNEL, L(sub eq), SEL, L(sub max), and where appropriate L(sub dnmr). The program output is a tabular form or in graphics suitable for inclusion in reports. The computer program is designed for use by environmental planning personnel who are familiar with MOA and range operations and with noise, but are not necessarily expert. The program will be widely distributed to DOD planners and contractors that have a requirement to make noise estimates. A companion graphical user interface (GUI) computer program called MR OPS has been developed that allows the user to draw the airspace, specify areas of high/medium/low activity, and draw the specific flight tracks for bombing runs and military training routes. MR OPS writes an ASCII file that is read by MR NMAP. Contained in this ASCII file is the operation data and keywords that control the computational features in MR NMAP. MR NMAP is written in FORTRAN; executable versions are available under DOS, Windows, and Windows NT. MR OPS is written in the C programming language and will run under Windows and Windows NT.
Vortices in gauge models at finite density with vector condensates
Gorbar, E V; Miransky, V A; Jia, Junji
2006-01-01
There exists a class of gauge models incorporating a finite density of matter in which the Higgs mechanism is provided by condensates of gauge (or gauge and scalar) fields, i.e., there are vector condensates in this case. We describe vortex solutions in the simplest model in this class, the gauged $SU(2)\\times U(1)_Y$ $\\sigma$-model with the chemical potential for hypercharge $Y$, in which the gauge symmetry is completely broken. It is shown that there are three types of topologically stable vortices in the model, connected either with photon field or hypercharge gauge field, or with both of them. Explicit vortex solutions are numerically found and their energy per unit length are calculated. The relevance of these solutions for the gluonic phase in the dense two-flavor QCD is discussed.
Model Reduction in Dynamic Finite Element Analysis of Lightweight Structures
DEFF Research Database (Denmark)
Flodén, Ola; Persson, Kent; Sjöström, Anders
2012-01-01
. The objective of the analyses presented in this paper is to evaluate methods for model reduction of detailed finite element models of floor and wall structures and to investigate the influence of reducing the number of degrees of freedom and computational cost on the dynamic response of the models in terms....... The drawback of component mode synthesis compared to modelling with structural elements is the increased computational cost, although the number of degrees of freedom is small in comparison, as a result of the large bandwidth of the system matrices.......The application of wood as a construction material when building multi-storey buildings has many advantages, e.g., light weight, sustainability and low energy consumption during the construction and lifecycle of the building. However, compared to heavy structures, it is a greater challenge to build...
Strongly Interacting Matter at Finite Chemical Potential: Hybrid Model Approach
Srivastava, P. K.; Singh, C. P.
2013-06-01
Search for a proper and realistic equation of state (EOS) for strongly interacting matter used in the study of the QCD phase diagram still appears as a challenging problem. Recently, we constructed a hybrid model description for the quark-gluon plasma (QGP) as well as hadron gas (HG) phases where we used an excluded volume model for HG and a thermodynamically consistent quasiparticle model for the QGP phase. The hybrid model suitably describes the recent lattice results of various thermodynamical as well as transport properties of the QCD matter at zero baryon chemical potential (μB). In this paper, we extend our investigations further in obtaining the properties of QCD matter at finite value of μB and compare our results with the most recent results of lattice QCD calculation.
Development of simplified finite element models for welded joints
Energy Technology Data Exchange (ETDEWEB)
Song, Seong Il; Ahn, Sung Wook; Kim, Young Geul; Kim, Hyun Gyu [Dept. of Mechanical and Automotive Engineering, Seoul National University of Science and Technology, Seoul (Korea, Republic of)
2015-11-15
In this paper, we develop simplified finite element (FE) models for butt-, lap- and T-welded joints by performing numerical and experimental experiments. Three-point bending tests of butt- and lap-welded specimens are performed to obtain the stiffness of the specimens and the strains at points near the welding beads. Similarly the stiffness and strains of T-welded specimen are measured by applying a point load at the end of the specimen. To develop simplified FE models, we consider the shape parameters of width, thickness and the angle of weld elements in the numerical simulations. The shape parameters of the simplified FE models are determined by building linear regression models for the experimental data sets.
Development of Simplified Finite Element Models for Welded Joints
Energy Technology Data Exchange (ETDEWEB)
Song, Seong Il; Ahn, Sung Wook; Kim, Young Geul; Kim, Hyun Gyu [Seoul National Univ. of Sci. and Tech., Seoul (Korea, Republic of)
2015-11-15
In this paper, we develop simplified finite element (FE) models for butt-, lap- and T-welded joints by performing numerical and experimental experiments. Three-point bending tests of butt- and lap-welded specimens are performed to obtain the stiffness of the specimens and the strains at points near the welding beads. Similarly the stiffness and strains of T-welded specimen are measured by applying a point load at the end of the specimen. To develop simplified FE models, we consider the shape parameters of width, thickness and the angle of weld elements in the numerical simulations. The shape parameters of the simplified FE models are determined by building linear regression models for the experimental data sets.
Assessment of stochastically updated finite element models using reliability indicator
Hua, X. G.; Wen, Q.; Ni, Y. Q.; Chen, Z. Q.
2017-01-01
Finite element (FE) model updating techniques have been a viable approach to correcting an initial mathematical model based on test data. Validation of the updated FE models is usually conducted by comparing model predictions with independent test data that have not been used for model updating. This approach of model validation cannot be readily applied in the case of a stochastically updated FE model. In recognizing that structural reliability is a major decision factor throughout the lifecycle of a structure, this study investigates the use of structural reliability as a measure for assessing the quality of stochastically updated FE models. A recently developed perturbation method for stochastic FE model updating is first applied to attain the stochastically updated models by using the measured modal parameters with uncertainty. The reliability index and failure probability for predefined limit states are computed for the initial and the stochastically updated models, respectively, and are compared with those obtained from the 'true' model to assess the quality of the two models. Numerical simulation of a truss bridge is provided as an example. The simulated modal parameters involving different uncertainty magnitudes are used to update an initial model of the bridge. It is shown that the reliability index obtained from the updated model is much closer to true reliability index than that obtained from the initial model in the case of small uncertainty magnitude; in the case of large uncertainty magnitude, the reliability index computed from the initial model rather than from the updated model is closer to the true value. The present study confirms the usefulness of measurement-calibrated FE models and at the same time also highlights the importance of the uncertainty reduction in test data for reliable model updating and reliability evaluation.
Lipkin-Meshkov-Glick model at finite temperature
Storozhenko, A N; Vdovin, A I
1997-01-01
The Lipkin-Meshkov-Glick model is used to examine the validity of some approximate methods in a many-body theory at finite temperatures. Namely, the thermal random phase approximation (TRPA) and the thermal renormalized random phase approximation (TRRPA) are studied. An average energy of the system, an average quasispin projection and a particle number variance are calculated within these approximation and exactly with the grand canonical ensemble partition function. On the whole the results of TRRPA are found to be in better agreement with the exact ones. The validity of the both approximation becomes better with increasing temperature as well as particle number.
Finite element modelling of a rotating piezoelectric ultrasonic motor.
Frangi, A; Corigliano, A; Binci, M; Faure, P
2005-10-01
The evaluation of the performance of ultrasonic motors as a function of input parameters such as the driving frequency, voltage input and pre-load on the rotor is of key importance to their development and is here addressed by means of a finite element three-dimensional model. First the stator is simulated as a fully deformable elastic body and the travelling wave dynamics is accurately reproduced; secondly the interaction through contact between the stator and the rotor is accounted for by assuming that the rotor behaves as a rigid surface. Numerical results for the whole motor are finally compared to available experimental data.
A finite element model investigation of gunshot injury.
Raul, Jean-Sébastien; Deck, Caroline; Meyer, Franck; Geraut, Annie; Willinger, Rémy; Ludes, Bertrand
2007-03-01
Multiple gunshot suicide can be a controversial subject mainly because of wrong opinions concerning immediate incapacitation or alleged backwards hurling. For the last 20 years, experts in medicine and physics have tried to demonstrate what really happens during a gunshot wound. Different methods have been used to achieve this aim such as basic physics or the use of empirical evidence. In this paper, using a finite element model of the human head, we demonstrate that no incapacitation or backwards hurling can occur from a gunshot fired between the eyes which did not enter the cerebrum.
Modelling the viscoelasticity of ceramic tiles by finite element
Pavlovic, Ana; Fragassa, Cristiano
2016-05-01
This research details a numerical method aiming at investigating the viscoelastic behaviour of a specific family of ceramic material, the Grès Porcelain, during an uncommon transformation, known as pyroplasticity, which occurs when a ceramic tile bends under a combination of thermal stress and own weight. In general, the theory of viscoelasticity can be considered extremely large and precise, but its application on real cases is particularly delicate. A time-depending problem, as viscoelasticity naturally is, has to be merged with a temperature-depending situation. This paper investigates how the viscoelastic response of bending ceramic materials can be modelled by commercial Finite Elements codes.
Long Range Strategic Planning. An Applied Model.
1983-06-01
should be long term analysis aimed at efficient stewardship of this nation’s finite resources. Strategic relationships , however, are "as much psycho...South Africa. "Oi’.r forefathers believed, and we still believe today, that God himself made the diversity of peoples on earth ... Interracial ...the Koeberg nuclear power stations. The relationship between the South African decisions .’>.’; to pursue an enrichment capability, build light
Leukocyte deformability: finite element modeling of large viscoelastic deformation.
Dong, C; Skalak, R
1992-09-21
An axisymmetric deformation of a viscoelastic sphere bounded by a prestressed elastic thin shell in response to external pressure is studied by a finite element method. The research is motivated by the need for understanding the passive behavior of human leukocytes (white blood cells) and interpreting extensive experimental data in terms of the mechanical properties. The cell at rest is modeled as a sphere consisting of a cortical prestressed shell with incompressible Maxwell fluid interior. A large-strain deformation theory is developed based on the proposed model. General non-linear, large strain constitutive relations for the cortical shell are derived by neglecting the bending stiffness. A representation of the constitutive equations in the form of an integral of strain history for the incompressible Maxwell interior is used in the formulation of numerical scheme. A finite element program is developed, in which a sliding boundary condition is imposed on all contact surfaces. The mathematical model developed is applied to evaluate experimental data of pipette tests and observations of blood flow.
A schematic model for QCD at finite temperature
Lerma, S; Hess, P O; Civitarese, O; Reboiro, M
2002-01-01
The simplest version of a class of toy models for QCD is presented. It is a Lipkin-type model, for the quark-antiquark sector, and, for the gluon sector, gluon pairs with spin zero are treated as elementary bosons. The model restricts to mesons with spin zero and to few baryonic states. The corresponding energy spectrum is discussed. We show that ground state correlations are essential to describe physical properties of the spectrum at low energies. Phase transitions are described in an effective manner, by using coherent states. The appearance of a Goldstone boson for large values of the interaction strength is discussed, as related to a collective state. The formalism is extended to consider finite temperatures. The partition function is calculated, in an approximate way, showing the convenience of the use of coherent states. The energy density, heat capacity and transitions from the hadronic phase to the quark-gluon plasma are calculated.
A Finite element model of tactile flow for softness perception.
Battaglia, Edoardo; Bianchi, Matteo; D'Angelo, Maria Laura; D'Imperio, Mariapaola; Cannella, Ferdinando; Scilingo, Enzo P; Bicchi, Antonio
2015-01-01
Touch is an extremely dynamic sense. To take into account this aspect, it has been hypothesized that there are mechanisms in the brain that specialize in processing dynamic tactile stimuli, in a way not too dissimilar from what happens for optical flow in dynamic vision. The concept of tactile flow, related to the rate of expansion of isostrain volumes in the human fingerpad, was used to explain some perceptual illusions as well as mechanisms of human softness perception. In this paper we describe a computational model of tactile flow, and apply it to a finite element model of interaction between deformable bodies. The shape and material properties of the bodies are modeled from those of a human fingertip interacting with specimens with different softness properties. Results show that the rate of expansion of isostrain volumes can be used to discriminate different materials in terms of their softness characteristics.
Surface photovoltage measurements and finite element modeling of SAW devices.
Energy Technology Data Exchange (ETDEWEB)
Donnelly, Christine
2012-03-01
Over the course of a Summer 2011 internship with the MEMS department of Sandia National Laboratories, work was completed on two major projects. The first and main project of the summer involved taking surface photovoltage measurements for silicon samples, and using these measurements to determine surface recombination velocities and minority carrier diffusion lengths of the materials. The SPV method was used to fill gaps in the knowledge of material parameters that had not been determined successfully by other characterization methods. The second project involved creating a 2D finite element model of a surface acoustic wave device. A basic form of the model with the expected impedance response curve was completed, and the model is ready to be further developed for analysis of MEMS photonic resonator devices.
Finite element modeling of electrically rectified piezoelectric energy harvesters
Wu, P. H.; Shu, Y. C.
2015-09-01
Finite element models are developed for designing electrically rectified piezoelectric energy harvesters. They account for the consideration of common interface circuits such as the standard and parallel-/series-SSHI (synchronized switch harvesting on inductor) circuits, as well as complicated structural configurations such as arrays of piezoelectric oscillators. The idea is to replace the energy harvesting circuit by the proposed equivalent load impedance together with the capacitance of negative value. As a result, the proposed framework is capable of being implemented into conventional finite element solvers for direct system-level design without resorting to circuit simulators. The validation based on COMSOL simulations carried out for various interface circuits by the comparison with the standard modal analysis model. The framework is then applied to the investigation on how harvested power is reduced due to fabrication deviations in geometric and material properties of oscillators in an array system. Remarkably, it is found that for a standard array system with strong electromechanical coupling, the drop in peak power turns out to be insignificant if the optimal load is carefully chosen. The second application is to design broadband energy harvesting by developing array systems with suitable interface circuits. The result shows that significant broadband is observed for the parallel (series) connection of oscillators endowed with the parallel-SSHI (series-SSHI) circuit technique.
One-electron singular spectral features of the 1D Hubbard model at finite magnetic field
Carmelo, J. M. P.; Čadež, T.
2017-01-01
The momentum, electronic density, spin density, and interaction dependences of the exponents that control the (k , ω)-plane singular features of the σ = ↑ , ↓ one-electron spectral functions of the 1D Hubbard model at finite magnetic field are studied. The usual half-filling concepts of one-electron lower Hubbard band and upper Hubbard band are defined in terms of the rotated electrons associated with the model Bethe-ansatz solution for all electronic density and spin density values and the whole finite repulsion range. Such rotated electrons are the link of the non-perturbative relation between the electrons and the pseudofermions. Our results further clarify the microscopic processes through which the pseudofermion dynamical theory accounts for the one-electron matrix elements between the ground state and excited energy eigenstates.
Building relativistic mean field models for finite nuclei and neutron stars
Chen, Wei-Chia; Piekarewicz, J.
2014-10-01
Background: Theoretical approaches based on density functional theory provide the only tractable method to incorporate the wide range of densities and isospin asymmetries required to describe finite nuclei, infinite nuclear matter, and neutron stars. Purpose: A relativistic energy density functional (EDF) is developed to address the complexity of such diverse nuclear systems. Moreover, a statistical perspective is adopted to describe the information content of various physical observables. Methods: We implement the model optimization by minimizing a suitably constructed χ2 objective function using various properties of finite nuclei and neutron stars. The minimization is then supplemented by a covariance analysis that includes both uncertainty estimates and correlation coefficients. Results: A new model, "FSUGold2," is created that can well reproduce the ground-state properties of finite nuclei, their monopole response, and that accounts for the maximum neutron-star mass observed up to date. In particular, the model predicts both a stiff symmetry energy and a soft equation of state for symmetric nuclear matter, suggesting a fairly large neutron-skin thickness in Pb208 and a moderate value of the nuclear incompressibility. Conclusions: We conclude that without any meaningful constraint on the isovector sector, relativistic EDFs will continue to predict significantly large neutron skins. However, the calibration scheme adopted here is flexible enough to create models with different assumptions on various observables. Such a scheme—properly supplemented by a covariance analysis—provides a powerful tool to identify the critical measurements required to place meaningful constraints on theoretical models.
Finite element model selection using Particle Swarm Optimization
Mthembu, Linda; Friswell, Michael I; Adhikari, Sondipon
2009-01-01
This paper proposes the application of particle swarm optimization (PSO) to the problem of finite element model (FEM) selection. This problem arises when a choice of the best model for a system has to be made from set of competing models, each developed a priori from engineering judgment. PSO is a population-based stochastic search algorithm inspired by the behaviour of biological entities in nature when they are foraging for resources. Each potentially correct model is represented as a particle that exhibits both individualistic and group behaviour. Each particle moves within the model search space looking for the best solution by updating the parameters values that define it. The most important step in the particle swarm algorithm is the method of representing models which should take into account the number, location and variables of parameters to be updated. One example structural system is used to show the applicability of PSO in finding an optimal FEM. An optimal model is defined as the model that has t...
Viscoelastic Finite Difference Modeling Using Graphics Processing Units
Fabien-Ouellet, G.; Gloaguen, E.; Giroux, B.
2014-12-01
Full waveform seismic modeling requires a huge amount of computing power that still challenges today's technology. This limits the applicability of powerful processing approaches in seismic exploration like full-waveform inversion. This paper explores the use of Graphics Processing Units (GPU) to compute a time based finite-difference solution to the viscoelastic wave equation. The aim is to investigate whether the adoption of the GPU technology is susceptible to reduce significantly the computing time of simulations. The code presented herein is based on the freely accessible software of Bohlen (2002) in 2D provided under a General Public License (GNU) licence. This implementation is based on a second order centred differences scheme to approximate time differences and staggered grid schemes with centred difference of order 2, 4, 6, 8, and 12 for spatial derivatives. The code is fully parallel and is written using the Message Passing Interface (MPI), and it thus supports simulations of vast seismic models on a cluster of CPUs. To port the code from Bohlen (2002) on GPUs, the OpenCl framework was chosen for its ability to work on both CPUs and GPUs and its adoption by most of GPU manufacturers. In our implementation, OpenCL works in conjunction with MPI, which allows computations on a cluster of GPU for large-scale model simulations. We tested our code for model sizes between 1002 and 60002 elements. Comparison shows a decrease in computation time of more than two orders of magnitude between the GPU implementation run on a AMD Radeon HD 7950 and the CPU implementation run on a 2.26 GHz Intel Xeon Quad-Core. The speed-up varies depending on the order of the finite difference approximation and generally increases for higher orders. Increasing speed-ups are also obtained for increasing model size, which can be explained by kernel overheads and delays introduced by memory transfers to and from the GPU through the PCI-E bus. Those tests indicate that the GPU memory size
Eigenvectors and scalar products for long range interacting spin chains II: the finite size effects
Serban, D
2013-01-01
In this note, we study the eigenvectors and the scalar products the integrable long-range deformation of a XXX spin chain which is solved exactly by algebraic Bethe ansatz, and it coincides in the bulk with the Inozemtsev spin chain. At the closing point it contains a defect which effectively removes the wrapping interactions. Here we concentrate on determining the defect term for the first non-trivial order in perturbation in the deformation parameter and how it affects the Bethe ansatz equations. Our study is motivated by the relation with the dilatation operator of the N = 4 gauge theory in the su(2) sector.
An Application of Finite Element Modelling to Pneumatic Artificial Muscle
Directory of Open Access Journals (Sweden)
R. Ramasamy
2005-01-01
Full Text Available The purpose of this article was to introduce and to give an overview of the Pneumatic Artificial Muscles (PAMs as a whole and to discuss its numerical modelling, using the Finite Element (FE Method. Thus, more information to understand on its behaviour in generating force for actuation was obtained. The construction of PAMs was mainly consists of flexible, inflatable membranes which having orthotropic material behaviour. The main properties influencing the PAMs will be explained in terms of their load-carrying capacity and low weight in assembly. Discussion on their designs and capacity to function as locomotion device in robotics applications will be laid out, followed by FE modelling to represent PAMs overall structural behaviour under any potential operational conditions.
NON-LINEAR FINITE ELEMENT MODELING OF DEEP DRAWING PROCESS
Directory of Open Access Journals (Sweden)
Hasan YILDIZ
2004-03-01
Full Text Available Deep drawing process is one of the main procedures used in different branches of industry. Finding numerical solutions for determination of the mechanical behaviour of this process will save time and money. In die surfaces, which have complex geometries, it is hard to determine the effects of parameters of sheet metal forming. Some of these parameters are wrinkling, tearing, and determination of the flow of the thin sheet metal in the die and thickness change. However, the most difficult one is determination of material properties during plastic deformation. In this study, the effects of all these parameters are analyzed before producing the dies. The explicit non-linear finite element method is chosen to be used in the analysis. The numerical results obtained for non-linear material and contact models are also compared with the experiments. A good agreement between the numerical and the experimental results is obtained. The results obtained for the models are given in detail.
Finite Temperature Casimir Effect in Randall-Sundrum Models
Rypestøl, Marianne
2009-01-01
The finite temperature Casimir effect for a scalar field in the bulk region of the two Randall-Sundrum models, RSI and RSII, is studied. We calculate the Casimir energy and the Casimir force for two parallel plates with separation $a$ on the visible brane in the RSI model. High-temperature and low-temperature cases are covered. Attractiveness versus repulsiveness of the temperature correction to the force is discussed in the typical special cases of Dirichlet-Dirichlet, Neumann-Neumann, and Dirichlet-Neumann boundary conditions at low temperature. The Abel-Plana summation formula is made use of, as this turns out to be most convenient. Some comments are made on the related contemporary literature.
Lower extremity finite element model for crash simulation
Energy Technology Data Exchange (ETDEWEB)
Schauer, D.A.; Perfect, S.A.
1996-03-01
A lower extremity model has been developed to study occupant injury mechanisms of the major bones and ligamentous soft tissues resulting from vehicle collisions. The model is based on anatomically correct digitized bone surfaces of the pelvis, femur, patella and the tibia. Many muscles, tendons and ligaments were incrementally added to the basic bone model. We have simulated two types of occupant loading that occur in a crash environment using a non-linear large deformation finite element code. The modeling approach assumed that the leg was passive during its response to the excitation, that is, no active muscular contraction and therefore no active change in limb stiffness. The approach recognized that the most important contributions of the muscles to the lower extremity response are their ability to define and modify the impedance of the limb. When nonlinear material behavior in a component of the leg model was deemed important to response, a nonlinear constitutive model was incorporated. The accuracy of these assumptions can be verified only through a review of analysis results and careful comparison with test data. As currently defined, the model meets the objective for which it was created. Much work remains to be done, both from modeling and analysis perspectives, before the model can be considered complete. The model implements a modeling philosophy that can accurately capture both kinematic and kinetic response of the lower limb. We have demonstrated that the lower extremity model is a valuable tool for understanding the injury processes and mechanisms. We are now in a position to extend the computer simulation to investigate the clinical fracture patterns observed in actual crashes. Additional experience with this model will enable us to make a statement on what measures are needed to significantly reduce lower extremity injuries in vehicle crashes. 6 refs.
Finite Elements Modeling in Diagnostics of Small Closed Pneumothorax.
Lorkowski, J; Mrzygłód, M; Grzegorowska, O
2015-01-01
Posttraumatic pneumothorax still remains to be a serious clinical problem and requires a comprehensive diagnostic and monitoring during treatment. The aim of this paper is to present a computer method of modeling of small closed pneumothorax. Radiological images of 34 patients of both sexes with small closed pneumothorax were taken into consideration. The control group consisted of X-rays of 22 patients treated because of tension pneumothorax. In every single case the model was correlated with the clinical manifestations. The procedure of computational rapid analysis (CRA) for in silico analysis of surgical intervention was introduced. It included implementation of computerize tomography images and their automatic conversion into 3D finite elements model (FEM). In order to segmentize the 3D model, an intelligent procedure of domain recognition was used. In the final step, a computer simulation project of fluid-structure interaction was built, using the ANSYS\\Workbench environment of multi-physics analysis. The FEM model and computer simulation project were employed in the analysis in order to optimize surgical intervention. The model worked out well and was compatible with the clinical manifestations of pneumothorax. We conclude that the created FEM model is a promising tool for facilitation of diagnostic procedures and prognosis of treatment in the case of small closed pneumothorax.
Design Through Manufacturing: The Solid Model - Finite Element Analysis Interface
Rubin, Carol
2003-01-01
State-of-the-art computer aided design (CAD) presently affords engineers the opportunity to create solid models of machine parts which reflect every detail of the finished product. Ideally, these models should fulfill two very important functions: (1) they must provide numerical control information for automated manufacturing of precision parts, and (2) they must enable analysts to easily evaluate the stress levels (using finite element analysis - FEA) for all structurally significant parts used in space missions. Today's state-of-the-art CAD programs perform function (1) very well, providing an excellent model for precision manufacturing. But they do not provide a straightforward and simple means of automating the translation from CAD to FEA models, especially for aircraft-type structures. The research performed during the fellowship period investigated the transition process from the solid CAD model to the FEA stress analysis model with the final goal of creating an automatic interface between the two. During the period of the fellowship a detailed multi-year program for the development of such an interface was created. The ultimate goal of this program will be the development of a fully parameterized automatic ProE/FEA translator for parts and assemblies, with the incorporation of data base management into the solution, and ultimately including computational fluid dynamics and thermal modeling in the interface.
3D finite element model for treatment of cleft lip
Jiao, Chun; Hong, Dongming; Lu, Hongbing; Wang, Jianqi; Lin, Qin; Liang, Zhengrong
2009-02-01
Cleft lip is a congenital facial deformity with high occurrence rate in China. Surgical procedure involving Millard or Tennison methods is usually employed for treatment of cleft lip. However, due to the elasticity of the soft tissues and the mechanical interaction between skin and maxillary, the occurrence rate of facial abnormality or dehisce is still high after the surgery, leading to multiple operations of the patient. In this study, a framework of constructing a realistic 3D finite element model (FEM) for the treatment of cleft lip has been established. It consists of two major steps. The first one is the reconstruction of a 3D geometrical model of the cleft lip from scanning CT data. The second step is the build-up of a FEM for cleft lip using the geometric model, where the material property of all the tetrahedrons was calculated from the CT densities directly using an empirical curve. The simulation results demonstrated (1) the deformation procedure of the model step-by-step when forces were applied, (2) the stress distribution inside the model, and (3) the displacement of all elements in the model. With the computer simulation, the minimal force of having the cleft be repaired is predicted, as well as whether a given force sufficient for the treatment of a specific individual. It indicates that the proposed framework could integrate the treatment planning with stress analysis based on a realistic patient model.
Energy Technology Data Exchange (ETDEWEB)
Aristovich, K Y; Khan, S H, E-mail: kirill.aristovich.1@city.ac.u [School of Engineering and Mathematical Sciences, City University London, Northampton Square, London EC1V 0HB (United Kingdom)
2010-07-01
Realistic computer modelling of biological objects requires building of very accurate and realistic computer models based on geometric and material data, type, and accuracy of numerical analyses. This paper presents some of the automatic tools and algorithms that were used to build accurate and realistic 3D finite element (FE) model of whole-brain. These models were used to solve the forward problem in magnetic field tomography (MFT) based on Magnetoencephalography (MEG). The forward problem involves modelling and computation of magnetic fields produced by human brain during cognitive processing. The geometric parameters of the model were obtained from accurate Magnetic Resonance Imaging (MRI) data and the material properties - from those obtained from Diffusion Tensor MRI (DTMRI). The 3D FE models of the brain built using this approach has been shown to be very accurate in terms of both geometric and material properties. The model is stored on the computer in Computer-Aided Parametrical Design (CAD) format. This allows the model to be used in a wide a range of methods of analysis, such as finite element method (FEM), Boundary Element Method (BEM), Monte-Carlo Simulations, etc. The generic model building approach presented here could be used for accurate and realistic modelling of human brain and many other biological objects.
On the fate of the Standard Model at finite temperature
Energy Technology Data Exchange (ETDEWEB)
Rose, Luigi Delle; Marzo, Carlo [Università del Salento, Dipartimento di Matematica e Fisica “Ennio De Giorgi' ,Via Arnesano, 73100 Lecce (Italy); INFN - Sezione di Lecce,via Arnesano, 73100 Lecce (Italy); Urbano, Alfredo [SISSA - International School for Advanced Studies,via Bonomea 256, 34136 Trieste (Italy)
2016-05-10
In this paper we revisit and update the computation of thermal corrections to the stability of the electroweak vacuum in the Standard Model. At zero temperature, we make use of the full two-loop effective potential, improved by three-loop beta functions with two-loop matching conditions. At finite temperature, we include one-loop thermal corrections together with resummation of daisy diagrams. We solve numerically — both at zero and finite temperature — the bounce equation, thus providing an accurate description of the thermal tunneling. Assuming a maximum temperature in the early Universe of the order of 10{sup 18} GeV, we find that the instability bound excludes values of the top mass M{sub t}≳173.6 GeV, with M{sub h}≃125 GeV and including uncertainties on the strong coupling. We discuss the validity and temperature-dependence of this bound in the early Universe, with a special focus on the reheating phase after inflation.
The Three-Dimensional Finite-Volume Non-Hydrostatic Icosahedral Model (NIM)
Lee, J. L.; MacDonald, A. E.
2014-12-01
A multi-scales Non-hydrostatic Icosahedral Model (NIM) has been developed at Earth System Research Laboratory (ESRL) to meet NOAA's future prediction mission ranging from mesoscale short-range, high-impact weather forecasts to longer-term intra-seasonal climate prediction. NIM formulates the latest numerical innovation of the three-dimensional finite-volume control volume on the quasi-uniform icosahedral grid suitable for ultra-high resolution simulations. NIM is designed to utilize the state-of-art computing architecture such as Graphic Processing Units (GPU) processors to run globally at kilometer scale resolution to explicitly resolve convective storms and complex terrains. The novel features of NIM numerical design include: 1.1. A local coordinate system upon which finite-volume integrations are undertaken. The use of a local Cartesian coordinate greatly simplifies the mathematic formulation of the finite-volume operators and leads to the finite-volume integration along straight lines on the plane, rather than along curved lines on the spherical surface. 1.2. A general indirect addressing scheme developed for modeling on irregular grid. It arranges the icosahedral grid with a one-dimensional vector loop structure, table specified memory order, and an indirect addressing scheme that yields very compact code despite the complexities of this grid. 1.3. Use of three-dimensional finite-volume integration over control volumes constructed on the height coordinates. Three-dimensional finite-volume integration accurately represents the Newton Third Law over terrain and improves pressure gradient force over complex terrain. 1.4. Use of the Runge-Kutta 4th order conservative and positive-definite transport scheme 1.5. NIM dynamical solver has been implemented on CPU as well as GPU. As one of the potential candidates for NWS next generation models, NIM dynamical core has been successfully verified with various benchmark test cases including those proposed by DCMIP
Modeling of contact surface morphology and dust particles by using finite element method
Institute of Scientific and Technical Information of China (English)
WANG Dong; XU Liang-jun
2007-01-01
The effect of dust particles on electric contacts and a hazardous size range of hard dust particles using a rigid model were discussed before. As further research, elastic-plastic model of finite element analysis was established in this work, which is closer to real condition. In this work, the behavior of large size and small size particles, and the influence of particles hardness were investigated. The calculating result of small-size particles presents a general hazardous size coefficient for different contact surface morphology; for large-size particles, it presents a hazardous size coefficient for complicated composition of the dust. And the effect of the dust shape is also discussed.
Finite Element Analysis of Patella Alta: A Patellofemoral Instability Model
Duchman, Kyle R.; Grosland, Nicole M.; Bollier, Matthew J.
2017-01-01
Abstract Background: This study aims to provide biomechanical data on the effect of patella height in the setting of medial patellofemoral ligament (MPFL) reconstruction using finite element analysis. The study will also examine patellofemoral joint biomechanics using variable femoral insertion sites for MPFL reconstruction. Methods: A previously validated finite element knee model was modified to study patella alta and baja by translating the patella a given distance to achieve each patella height ratio. Additionally, the models were modified to study various femoral insertion sites of the MPFL (anatomic, anterior, proximal, and distal) for each patella height model, resulting in 32 unique scenarios available for investigation. Results: In the setting of patella alta, the patellofemoral contact area decreased, resulting in a subsequent increase in maximum patellofemoral contact pressures as compared to the scenarios with normal patellar height. Additionally, patella alta resulted in decreased lateral restraining forces in the native knee scenario as well as following MPFL reconstruction. Changing femoral insertion sites had a variable effect on patellofemoral contact pressures; however, distal and anterior femoral tunnel malpositioning in the setting of patella alta resulted in grossly elevated maximum patellofemoral contact pressures as compared to other scenarios. Conclusions: Patella alta after MPFL reconstruction results in decreased lateral restraining forces and patellofemoral contact area and increased maximum patellofemoral contact pressures. When the femoral MPFL tunnel is malpositioned anteriorly or distally on the femur, the maximum patellofemoral contact pressures increase with severity of patella alta. Clinical Relevance: When evaluating patients with patellofemoral instability, it is important to recognize patella alta as a potential aggravating factor. Failure to address patella alta in the setting of MPFL femoral tunnel malposition may result in
Finite Element Models for Electron Beam Freeform Fabrication Process
Chandra, Umesh
2012-01-01
Electron beam freeform fabrication (EBF3) is a member of an emerging class of direct manufacturing processes known as solid freeform fabrication (SFF); another member of the class is the laser deposition process. Successful application of the EBF3 process requires precise control of a number of process parameters such as the EB power, speed, and metal feed rate in order to ensure thermal management; good fusion between the substrate and the first layer and between successive layers; minimize part distortion and residual stresses; and control the microstructure of the finished product. This is the only effort thus far that has addressed computer simulation of the EBF3 process. The models developed in this effort can assist in reducing the number of trials in the laboratory or on the shop floor while making high-quality parts. With some modifications, their use can be further extended to the simulation of laser, TIG (tungsten inert gas), and other deposition processes. A solid mechanics-based finite element code, ABAQUS, was chosen as the primary engine in developing these models whereas a computational fluid dynamics (CFD) code, Fluent, was used in a support role. Several innovative concepts were developed, some of which are highlighted below. These concepts were implemented in a number of new computer models either in the form of stand-alone programs or as user subroutines for ABAQUS and Fluent codes. A database of thermo-physical, mechanical, fluid, and metallurgical properties of stainless steel 304 was developed. Computing models for Gaussian and raster modes of the electron beam heat input were developed. Also, new schemes were devised to account for the heat sink effect during the deposition process. These innovations, and others, lead to improved models for thermal management and prediction of transient/residual stresses and distortions. Two approaches for the prediction of microstructure were pursued. The first was an empirical approach involving the
Finite mixture models for the computation of isotope ratios in mixed isotopic samples
Koffler, Daniel; Laaha, Gregor; Leisch, Friedrich; Kappel, Stefanie; Prohaska, Thomas
2013-04-01
Finite mixture models have been used for more than 100 years, but have seen a real boost in popularity over the last two decades due to the tremendous increase in available computing power. The areas of application of mixture models range from biology and medicine to physics, economics and marketing. These models can be applied to data where observations originate from various groups and where group affiliations are not known, as is the case for multiple isotope ratios present in mixed isotopic samples. Recently, the potential of finite mixture models for the computation of 235U/238U isotope ratios from transient signals measured in individual (sub-)µm-sized particles by laser ablation - multi-collector - inductively coupled plasma mass spectrometry (LA-MC-ICPMS) was demonstrated by Kappel et al. [1]. The particles, which were deposited on the same substrate, were certified with respect to their isotopic compositions. Here, we focus on the statistical model and its application to isotope data in ecogeochemistry. Commonly applied evaluation approaches for mixed isotopic samples are time-consuming and are dependent on the judgement of the analyst. Thus, isotopic compositions may be overlooked due to the presence of more dominant constituents. Evaluation using finite mixture models can be accomplished unsupervised and automatically. The models try to fit several linear models (regression lines) to subgroups of data taking the respective slope as estimation for the isotope ratio. The finite mixture models are parameterised by: • The number of different ratios. • Number of points belonging to each ratio-group. • The ratios (i.e. slopes) of each group. Fitting of the parameters is done by maximising the log-likelihood function using an iterative expectation-maximisation (EM) algorithm. In each iteration step, groups of size smaller than a control parameter are dropped; thereby the number of different ratios is determined. The analyst only influences some control
Finite element code development for modeling detonation of HMX composites
Duran, Adam V.; Sundararaghavan, Veera
2017-01-01
In this work, we present a hydrodynamics code for modeling shock and detonation waves in HMX. A stable efficient solution strategy based on a Taylor-Galerkin finite element (FE) discretization was developed to solve the reactive Euler equations. In our code, well calibrated equations of state for the solid unreacted material and gaseous reaction products have been implemented, along with a chemical reaction scheme and a mixing rule to define the properties of partially reacted states. A linear Gruneisen equation of state was employed for the unreacted HMX calibrated from experiments. The JWL form was used to model the EOS of gaseous reaction products. It is assumed that the unreacted explosive and reaction products are in both pressure and temperature equilibrium. The overall specific volume and internal energy was computed using the rule of mixtures. Arrhenius kinetics scheme was integrated to model the chemical reactions. A locally controlled dissipation was introduced that induces a non-oscillatory stabilized scheme for the shock front. The FE model was validated using analytical solutions for SOD shock and ZND strong detonation models. Benchmark problems are presented for geometries in which a single HMX crystal is subjected to a shock condition.
Three Case Studies in Finite Element Model Updating
Directory of Open Access Journals (Sweden)
M. Imregun
1995-01-01
Full Text Available This article summarizes the basic formulation of two well-established finite element model (FEM updating techniques for improved dynamic analysis, namely the response function method (RFM and the inverse eigensensitivity method (IESM. Emphasis is placed on the similarities in their mathematical formulation, numerical treatment, and on the uniqueness of the resulting updated models. Three case studies that include welded L-plate specimens, a car exhaust system, and a highway bridge were examined in some detail and measured vibration data were used throughout the investigation. It was experimentally observed that significant dynamic behavior discrepancies existed between some of the nominally identical structures, a feature that makes the task of model updating even more difficult because no unequivocal reference data exist in this particular case. Although significant improvements were obtained in all cases where the updating of the FE model was possible, it was found that the success of the updated models depended very heavily on the parameters used, such as the selection and number of the frequency points for RFM, and the selection of modes and the balancing of the sensitivity matrix for IESM. Finally, the performance of the two methods was compared from general applicability, numerical stability, and computational effort standpoints.
A finite difference model for free surface gravity drainage
Energy Technology Data Exchange (ETDEWEB)
Couri, F.R.; Ramey, H.J. Jr.
1993-09-01
The unconfined gravity flow of liquid with a free surface into a well is a classical well test problem which has not been well understood by either hydrologists or petroleum engineers. Paradigms have led many authors to treat an incompressible flow as compressible flow to justify the delayed yield behavior of a time-drawdown test. A finite-difference model has been developed to simulate the free surface gravity flow of an unconfined single phase, infinitely large reservoir into a well. The model was verified with experimental results in sandbox models in the literature and with classical methods applied to observation wells in the Groundwater literature. The simulator response was also compared with analytical Theis (1935) and Ramey et al. (1989) approaches for wellbore pressure at late producing times. The seepage face in the sandface and the delayed yield behavior were reproduced by the model considering a small liquid compressibility and incompressible porous medium. The potential buildup (recovery) simulated by the model evidenced a different- phenomenon from the drawdown, contrary to statements found in the Groundwater literature. Graphs of buildup potential vs time, buildup seepage face length vs time, and free surface head and sand bottom head radial profiles evidenced that the liquid refills the desaturating cone as a flat moving surface. The late time pseudo radial behavior was only approached after exaggerated long times.
Calibration under uncertainty for finite element models of masonry monuments
Energy Technology Data Exchange (ETDEWEB)
Atamturktur, Sezer,; Hemez, Francois,; Unal, Cetin
2010-02-01
Historical unreinforced masonry buildings often include features such as load bearing unreinforced masonry vaults and their supporting framework of piers, fill, buttresses, and walls. The masonry vaults of such buildings are among the most vulnerable structural components and certainly among the most challenging to analyze. The versatility of finite element (FE) analyses in incorporating various constitutive laws, as well as practically all geometric configurations, has resulted in the widespread use of the FE method for the analysis of complex unreinforced masonry structures over the last three decades. However, an FE model is only as accurate as its input parameters, and there are two fundamental challenges while defining FE model input parameters: (1) material properties and (2) support conditions. The difficulties in defining these two aspects of the FE model arise from the lack of knowledge in the common engineering understanding of masonry behavior. As a result, engineers are unable to define these FE model input parameters with certainty, and, inevitably, uncertainties are introduced to the FE model.
Customized Finite Element Modelling of the Human Cornea.
Directory of Open Access Journals (Sweden)
Irene Simonini
Full Text Available To construct patient-specific solid models of human cornea from ocular topographer data, to increase the accuracy of the biomechanical and optical estimate of the changes in refractive power and stress caused by photorefractive keratectomy (PRK.Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery. Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea.Patient-specific geometrical models of the cornea allow for the creation of personalized refractive maps at different levels of IOP. Thinned postoperative corneas show a higher stress gradient across the thickness and higher sensitivity of all geometrical and refractive parameters to the fluctuation of the IOP.Patient-specific numerical models of the cornea can provide accurate quantitative information on the refractive properties of the cornea under different levels of IOP and describe the change of the stress state of the cornea due to refractive surgery (PRK. Patient-specific models can be used as indicators of feasibility before performing the surgery.
Vibration Response of Multi Storey Building Using Finite Element Modelling
Chik, T. N. T.; Zakaria, M. F.; Remali, M. A.; Yusoff, N. A.
2016-07-01
Interaction between building, type of foundation and the geotechnical parameter of ground may trigger a significant effect on the building. In general, stiffer foundations resulted in higher natural frequencies of the building-soil system and higher input frequencies are often associated with other ground. Usually, vibrations transmitted to the buildings by ground borne are often noticeable and can be felt. It might affect the building and become worse if the vibration level is not controlled. UTHM building is prone to the ground borne vibration due to closed distance from the main road, and the construction activities adjacent to the buildings. This paper investigates the natural frequency and vibration mode of multi storey office building with the presence of foundation system and comparison between both systems. Finite element modelling (FEM) package software of LUSAS is used to perform the vibration analysis of the building. The building is modelled based on the original plan with the foundation system on the structure model. The FEM results indicated that the structure which modelled with rigid base have high natural frequency compare to the structure with foundation system. These maybe due to soil structure interaction and also the damping of the system which related to the amount of energy dissipated through the foundation soil. Thus, this paper suggested that modelling with soil is necessary to demonstrate the soil influence towards vibration response to the structure.
Finite-difference modeling of commercial aircraft using TSAR
Energy Technology Data Exchange (ETDEWEB)
Pennock, S.T.; Poggio, A.J.
1994-11-15
Future aircraft may have systems controlled by fiber optic cables, to reduce susceptibility to electromagnetic interference. However, the digital systems associated with the fiber optic network could still experience upset due to powerful radio stations, radars, and other electromagnetic sources, with potentially serious consequences. We are modeling the electromagnetic behavior of commercial transport aircraft in support of the NASA Fly-by-Light/Power-by-Wire program, using the TSAR finite-difference time-domain code initially developed for the military. By comparing results obtained from TSAR with data taken on a Boeing 757 at the Air Force Phillips Lab., we hope to show that FDTD codes can serve as an important tool in the design and certification of U.S. commercial aircraft, helping American companies to produce safe, reliable air transportation.
Behavioral Modeling Based on Probabilistic Finite Automata: An Empirical Study.
Tîrnăucă, Cristina; Montaña, José L; Ontañón, Santiago; González, Avelino J; Pardo, Luis M
2016-06-24
Imagine an agent that performs tasks according to different strategies. The goal of Behavioral Recognition (BR) is to identify which of the available strategies is the one being used by the agent, by simply observing the agent's actions and the environmental conditions during a certain period of time. The goal of Behavioral Cloning (BC) is more ambitious. In this last case, the learner must be able to build a model of the behavior of the agent. In both settings, the only assumption is that the learner has access to a training set that contains instances of observed behavioral traces for each available strategy. This paper studies a machine learning approach based on Probabilistic Finite Automata (PFAs), capable of achieving both the recognition and cloning tasks. We evaluate the performance of PFAs in the context of a simulated learning environment (in this case, a virtual Roomba vacuum cleaner robot), and compare it with a collection of other machine learning approaches.
OXYGEN PRESSURE REGULATOR DESIGN AND ANALYSIS THROUGH FINITE ELEMENT MODELING
Directory of Open Access Journals (Sweden)
Asterios KOSMARAS
2017-05-01
Full Text Available Oxygen production centers produce oxygen in high pressure that needs to be defused. A regulator is designed and analyzed in the current paper for medical use in oxygen production centers. This study aims to design a new oxygen pressure regulator and perform an analysis using Finite Element Modeling in order to evaluate its working principle. In the design procedure,the main elements and the operating principles of a pressure regulator are taking into account. The regulator is designed and simulations take place in order to assessthe proposed design. Stress analysis results are presented for the main body of the regulator, as well as, flow analysis to determine some important flow characteristics in the inlet and outlet of the regulator.
Finite Hypernuclei in the Latest Quark-Meson Coupling Model
Energy Technology Data Exchange (ETDEWEB)
Pierre A. M. Guichon; Anthony W. Thomas; Kazuo Tsushima
2007-12-12
The most recent development of the quark-meson coupling (QMC) model, in which the effect of the mean scalar field in-medium on the hyperfine interaction is also included self-consistently, is used to compute the properties of finite hypernuclei. The calculations for $\\Lambda$ and $\\Xi$ hypernuclei are of comparable quality to earlier QMC results without the additional parameter needed there. Even more significantly, the additional repulsion associated with the increased hyperfine interaction in-medium completely changes the predictions for $\\Sigma$ hypernuclei. Whereas in the earlier work they were bound by an amount similar to $\\Lambda$ hypernuclei, here they are unbound, in qualitative agreement with the experimental absence of such states. The equivalent non-relativistic potential felt by the $\\Sigma$ is repulsive inside the nuclear interior and weakly attractive in the nuclear surface, as suggested by the analysis of $\\Sigma$-atoms.
A Stochastic Investment Model on a Finite Time Horizon
Institute of Scientific and Technical Information of China (English)
Tao; Pang
2014-01-01
In this paper,we consider an investment optimization problem on a finite time horizon.One risky and one riskless asset are considered,and transaction costs are ignored.The risky asset prices obey a logarithmic Brownian motion,and interest rates vary according to a Vasicek interest rate model.The goal is to choose optimal investment policies to maximize the expected Hyperbolic Absolute Risk Aversion(HARA)utility of final payoff(wealth).The problem is then reduced to a 1-dimensional stochastic control problem by virtue of the Girsanov transformation.A dynamic programming principle is used to derive the dynamic programming equation(DPE).Explicit solutions are derived under certain conditions.The solutions are then used to derive the optimal investment strategy.
Maximum Likelihood in a Generalized Linear Finite Mixture Model by Using the EM Algorithm
Jansen, R.C.
A generalized linear finite mixture model and an EM algorithm to fit the model to data are described. By this approach the finite mixture model is embedded within the general framework of generalized linear models (GLMs). Implementation of the proposed EM algorithm can be readily done in statistical
Directory of Open Access Journals (Sweden)
Hussein Rappel
2014-01-01
integration technique (EFIT as well as its validation with analytical results. Lamb wave method is a long range inspection technique which is considered to have unique future in the field of structural health monitoring. One of the main problems facing the lamb wave method is how to choose the most appropriate frequency to generate the waves for adequate transmission capable of properly propagating in the material, interfering with defects/damages, and being received in good conditions. Modern simulation tools based on numerical methods such as finite integration technique (FIT, finite element method (FEM, and boundary element method (BEM may be used for modeling. In this paper, two sets of simulation are performed. In the first set, group velocities of lamb wave in a steel plate are obtained numerically. Results are then compared with analytical results to validate the simulation. In the second set, EFIT is employed to study fundamental symmetric mode interaction with a surface braking defect.
Finite Element Modeling and Analysis of Powder Stream in Low Pressure Cold Spray Process
Goyal, Tarun; Walia, Ravinderjit Singh; Sharma, Prince; Sidhu, Tejinder Singh
2016-07-01
Low pressure cold gas dynamic spray (LPCGDS) is a coating process that utilize low pressure gas (5-10 bars instead of 25-30 bars) and the radial injection of powder instead of axial injection with the particle range (1-50 μm). In the LPCGDS process, pressurized compressed gas is accelerated to the critical velocity, which depends on length of the divergent section of nozzle, the propellant gas and particle characteristics, and the diameters ratio of the inlet and outer diameters. This paper presents finite element modeling (FEM) of powder stream in supersonic nozzle wherein adiabatic gas flow and expansion of gas occurs in uniform manner and the same is used to evaluate the resultant temperature and velocity contours during coating process. FEM analyses were performed using commercial finite volume package, ANSYS CFD FLUENT. The results are helpful to predict the characteristics of powder stream at the exit of the supersonic nozzle.
Three-body recombination at finite energy within an optical model
Sørensen, P. K.; Fedorov, D. V.; Jensen, A. S.; Zinner, N. T.
2013-10-01
We investigate three-boson recombination of equal mass systems as function of (negative) scattering length, mass, finite energy, and finite temperature. An optical model with an imaginary potential at short distance reproduces experimental recombination data and allows us to provide a simple parametrization of the recombination rate as function of scattering length and energy. Using the two-body van der Waals length as unit we find that the imaginary potential range and also the potential depth agree to within 30% for lithium and cesium atoms. As opposed to recent studies suggesting universality of the threshold for bound-state formation, our results suggest that the recombination process itself could have universal features.
Finite element modelling of dielectric elastomer minimum energy structures
O'Brien, Benjamin; McKay, Thomas; Calius, Emilio; Xie, Shane; Anderson, Iain
2009-03-01
This paper presents an experimentally validated finite element model suitable for simulating the quasi-static behaviour of Dielectric Elastomer Minimum Energy Structure(s) (DEMES). A DEMES consists of a pre-stretched Dielectric Elastomer Actuator (DEA) adhered to a thin, flexible frame. The tension in the stretched membrane causes the frame to curl up, and when a voltage is applied, the frame returns to its initial planar state thus forming a useful bending actuator. The simulation method presented here incorporates a novel strain energy function suitable for simulating general DEA actuator elements. When compared against blocked force data from our previous work, the new model provides a good fit with an order of magnitude reduction in computational time. Furthermore, the model accurately matched experimental data on the free displacement of DEMES formed with non-equibiaxially pre-stretched VHB4905 membranes driven by 2500 V. Non-equibiaxially pre-stretching the membranes allowed control of effective frame stiffness and bending moment, this was exploited by using the model to optimise stroke at 2500 V in a hypothetical case study. Dielectric constant measurements for non-equibiaxially stretched VHB4905 are also presented.
Crystallographic effects during micromachining — A finite-element model
Song, Shin-Hyung; Choi, Woo Chun
2015-07-01
Mechanical micromachining is a powerful and effective way for manufacturing small sized machine parts. Even though the micromachining process is similar to the traditional machining, the material behavior during the process is much different. In particular, many researchers report that the basic mechanics of the work material is affected by microstructures and their crystallographic orientations. For example, crystallographic orientations of the work material have significant influence on force response, chip formation and surface finish. In order to thoroughly understand the effect of crystallographic orientations on the micromachining process, finite-element model (FEM) simulating orthogonal cutting process of single crystallographic material was presented. For modeling the work material, rate sensitive single crystal plasticity of face-centered cubic (FCC) crystal was implemented. For the chip formation during the simulation, element deletion technique was used. The simulation model is developed using ABAQUS/explicit with user material subroutine via user material subroutine (VUMAT). Simulations showed that variation of the specific cutting energy at different crystallographic orientations of work material shows significant anisotropy. The developed FEM model can be a useful prediction tool of micromachining of crystalline materials.
A finite element model for thermomechanical analysis in casting processes
Energy Technology Data Exchange (ETDEWEB)
Celentano, D. (International Center for Numerical Methods in Engineering, E.T.S. d' Enginyers de Camins, Canals i Ports, Univ. Politecnica de Catalunya, Barcelona (Spain)); Oller, S. (International Center for Numerical Methods in Engineering, E.T.S. d' Enginyers de Camins, Canals i Ports, Univ. Politecnica de Catalunya, Barcelona (Spain)); Onate, E. (International Center for Numerical Methods in Engineering, E.T.S. d' Enginyers de Camins, Canals i Ports, Univ. Politecnica de Catalunya, Barcelona (Spain))
1993-11-01
This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechanical model to simulate the solidification problem in casting has been developed. The model, based on a general isotropic thermoelasto-plasticity theory and formulated in a macroscopical point of view, includes generalized phase-change effects and considers the different thermomechanical behaviour of the solidifying material during its evolution from liquid to solid. For this purpose, a phase-change variable, plastic evolution equations and a temperature-dependent material constitutive law have been defined. Some relevant aspects of this model are presented here. Full thermomechanical coupling terms have been considered as well as variable thermal and mechanical boundary conditions: the first are due to air gap formation, while the second involve a contact formulation. Particular details concerning the numerical implementation of this model are also mentioned. An enhanced staggered scheme, used to solve the highly non-linear fully coupled finite element equations, is proposed. Furthermore, a proper convergence criterion to stop the iteration process is adopted and, although the quadratic convergence of Newton-Rapshon's method is not achieved, several numerical experiments demonstrate reasonable convergence rates. Finally, an experimental cylindrical casting test problem, including phase-change phenomena, temperature-dependent constitutive properties and contact effects, is analyzed. Numerical results are compared with some laboratory measurements. (orig.).
PHD TUTORIAL: Finite-temperature models of Bose Einstein condensation
Proukakis, Nick P.; Jackson, Brian
2008-10-01
The theoretical description of trapped weakly interacting Bose-Einstein condensates is characterized by a large number of seemingly very different approaches which have been developed over the course of time by researchers with very distinct backgrounds. Newcomers to this field, experimentalists and young researchers all face a considerable challenge in navigating through the 'maze' of abundant theoretical models, and simple correspondences between existing approaches are not always very transparent. This tutorial provides a generic introduction to such theories, in an attempt to single out common features and deficiencies of certain 'classes of approaches' identified by their physical content, rather than their particular mathematical implementation. This tutorial is structured in a manner accessible to a non-specialist with a good working knowledge of quantum mechanics. Although some familiarity with concepts of quantum field theory would be an advantage, key notions, such as the occupation number representation of second quantization, are nonetheless briefly reviewed. Following a general introduction, the complexity of models is gradually built up, starting from the basic zero-temperature formalism of the Gross-Pitaevskii equation. This structure enables readers to probe different levels of theoretical developments (mean field, number conserving and stochastic) according to their particular needs. In addition to its 'training element', we hope that this tutorial will prove useful to active researchers in this field, both in terms of the correspondences made between different theoretical models, and as a source of reference for existing and developing finite-temperature theoretical models.
Finite Element Model and Validation of Nasal Tip Deformation.
Manuel, Cyrus T; Harb, Rani; Badran, Alan; Ho, David; Wong, Brian J F
2017-03-01
Nasal tip mechanical stability is important for functional and cosmetic nasal airway surgery. Palpation of the nasal tip provides information on tip strength to the surgeon, though it is a purely subjective assessment. Providing a means to simulate nasal tip deformation with a validated model can offer a more objective approach in understanding the mechanics and nuances of the nasal tip support and eventual nasal mechanics as a whole. Herein we present validation of a finite element (FE) model of the nose using physical measurements recorded using an ABS plastic-silicone nasal phantom. Three-dimensional photogrammetry was used to capture the geometry of the phantom at rest and while under steady state load. The silicone used to make the phantom was mechanically tested and characterized using a linear elastic constitutive model. Surface point clouds of the silicone and FE model were compared for both the loaded and unloaded state. The average Hausdorff distance between actual measurements and FE simulations across the nose were 0.39 ± 1.04 mm and deviated up to 2 mm at the outermost boundaries of the model. FE simulation and measurements were in near complete agreement in the immediate vicinity of the nasal tip with millimeter accuracy. We have demonstrated validation of a two-component nasal FE model, which could be used to model more complex modes of deformation where direct measurement may be challenging. This is the first step in developing a nasal model to simulate nasal mechanics and ultimately the interaction between geometry and airflow.
Finite time singularities in a class of hydrodynamic models
DEFF Research Database (Denmark)
Ruban, V.P.; Podolsky, D.I.; Juul Rasmussen, J.
2001-01-01
), a finite value of alpha results in a finite energy for a singular, frozen-in vortex filament. This property allows us to study the dynamics of such filaments without the necessity of a regularization procedure for short length scales. The linear analysis of small symmetrical deviations from a stationary...... analytically. They describe the formation of a finite time singularity, with all length scales decreasing like (t*-t)(1/(2-alpha)), where t* is the singularity time....
Almeida, EDGARD S.; Spilker, ROBERT L.
1998-01-01
This two-part paper addresses finite element-based computational models for the three-dimensional (3-D) nonlinear analysis of soft hydrated tissues, such as articular cartilage in diarthrodial joints, under physiologically relevant loading conditions. A biphasic continuum description is used to represent the soft tissue as a two-phase mixture of incompressible inviscid fluid and a hyperelastic, transversely isotropic solid. Alternate mixed-penalty and velocity-pressure finite element formulations are used to solve the nonlinear biphasic governing equations, including the effects of strain-dependent permeability and a hyperelastic solid phase under finite deformation. The resulting first-order, nonlinear system of equations is discretized in time using an implicit finite difference scheme, and solved using the Newton-Raphson method. Details of the formulations were presented in Part I [1]. In Part II, the two formulations are used to develop two-dimensional (2-D) quadrilateral and triangular elements and three-dimensional (3-D) hexahedral and tetrahedral elements. Numerical examples, including those representative of soft tissue material testing and simple human joints, are used to validate the formulations and to illustrate their applications. A focus of this work is the comparison of the alternate formulations for nonlinear problems. While it is demonstrated that both formulations produce a range of converging elements, the velocity-pressure formulation is found to be more efficient computationally.
Almeida, EDGARD S.; Spilker, ROBERT L.
1997-01-01
This paper addresses finite element-based computational models for the three-dimensional, (3-D) nonlinear analysis of soft hydrated tissues, such as the articular cartilage in diarthrodial joints, under physiologically relevant loading conditions. A biphasic continuum description is used to represent the soft tissue as a two-phase mixture of incompressible, inviscid fluid and a hyperelastic solid. Alternate mixed-penalty and velocity-pressure finite element formulations are used to solve the nonlinear biphasic governing equations, including the effects of a strain-dependent permeability and a hyperelastic solid phase under finite deformation. The resulting first-order nonlinear system of equations is discretized in time using an implicit finite difference scheme, and solved using the Newton-Raphson method. Using a discrete divergence operator, an equivalence is shown between the mixed-penalty method and a penalty method previously derived by Suh et al. [1]. In Part II [2], the mixed-penalty and velocity-pressure formulations are used to develop two-dimensional (2-D) quadrilateral and triangular elements and 3-D hexahedral and tetrahedral elements. Numerical examples, including those representative of soft tissue material testing and simple human joints, are used to validate the formulations and to illustrate their applications. A focus of this work is the comparison of alternate formulations for nonlinear problems. While it is demonstrated that both formulations produce a range of converging elements, the velocity-pressure formulation is found to be more efficient computationally.
Alimonti, L.; Atalla, N.
2017-02-01
This work is concerned with the hybrid finite element-transfer matrix methodology recently proposed by the authors. The main assumption behind this hybrid method consists in neglecting the actual finite lateral extent of the acoustic treatment. Although a substantial increase of the computational efficiency can be achieved, the effect of the reflected field (i.e. finite size effects) may be sometimes important, preventing the hybrid model from giving quantitative meaningful results. For this reason, a correction to account for wave reflections at the lateral boundaries of the acoustic treatment is sought. It is shown in the present paper that the image source method can be successfully employed to retrieve such finite size effects. Indeed, such methodology is known to be effective when the response of the system is a smooth function of the frequency, like in the case of highly dissipative acoustic treatments. The main concern of this paper is to assess accuracy and feasibility of the image source method in the context of acoustic treatments modeling. Numerical examples show that the performance of the standard hybrid model can be substantially improved by the proposed correction without deteriorating excessively the computational efficiency.
A general finite element model for numerical simulation of structure dynamics
Institute of Scientific and Technical Information of China (English)
WANG Fujun; LI Yaojun; Han K.; Feng Y.T.
2006-01-01
A finite element model used to simulate the dynamics with continuum and discontinuum is presented. This new approach is conducted by constructing the general contact model. The conventional discrete element is treated as a standard finite element with one node in this new method. The one-node element has the same features as other finite elements, such as element stress and strain. Thus, a general finite element model that is consistent with the existed finite element model is set up. This new model is simple in mathematical concept and is straightforward to be combined into the existing standard finite element code. Numerical example demonstrates that this new approach is more effective to perform the dynamic process analysis in which the interactions among a large number of discrete bodies and continuum objects are included.
Energy Technology Data Exchange (ETDEWEB)
Gneiding, N., E-mail: Natalia.Gneiding@physik.uni-erlangen.de [Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg, 91052 Erlangen (Germany); Zhuromskyy, O.; Peschel, U. [Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg, 91058 Erlangen (Germany); Shamonina, E. [Department of Engineering Science, University of Oxford, Parks Road, OX1 3PJ Oxford (United Kingdom)
2014-10-28
Metamaterials are comprised of metallic structures with a strong response to incident electromagnetic radiation, like, for example, split ring resonators. The interaction of resonator ensembles with electromagnetic waves can be simulated with finite difference or finite elements algorithms, however, above a certain ensemble size simulations become inadmissibly time or memory consuming. Alternatively a circuit description of metamaterials, a well developed modelling tool at radio and microwave frequencies, allows to significantly increase the simulated ensemble size. This approach can be extended to the IR spectral range with an appropriate set of circuit element parameters accounting for physical effects such as electron inertia and finite conductivity. The model is verified by comparing the coupling coefficients with the ones obtained from the full wave numerical simulations, and used to optimize the nano-antenna design with improved radiation characteristics.
3D Finite Difference Modelling of Basaltic Region
Engell-Sørensen, L.
2003-04-01
The main purpose of the work was to generate realistic data to be applied for testing of processing and migration tools for basaltic regions. The project is based on the three - dimensional finite difference code (FD), TIGER, made by Sintef. The FD code was optimized (parallelized) by the author, to run on parallel computers. The parallel code enables us to model large-scale realistic geological models and to apply traditional seismic and micro seismic sources. The parallel code uses multiple processors in order to manipulate subsets of large amounts of data simultaneously. The general anisotropic code uses 21 elastic coefficients. Eight independent coefficients are needed as input parameters for the general TI medium. In the FD code, the elastic wave field computation is implemented by a higher order FD solution to the elastic wave equation and the wave fields are computed on a staggered grid, shifted half a node in one or two directions. The geological model is a gridded basalt model, which covers from 24 km to 37 km of a real shot line in horizontal direction and from the water surface to the depth of 3.5 km. The 2frac {1}{2}D model has been constructed using the compound modeling software from Norsk Hydro. The vertical parameter distribution is obtained from observations in two wells. At The depth of between 1100 m to 1500 m, a basalt horizon covers the whole sub surface layers. We have shown that it is possible to simulate a line survey in realistic (3D) geological models in reasonable time by using high performance computers. The author would like to thank Norsk Hydro, Statoil, GEUS, and SINTEF for very helpful discussions and Parallab for being helpful with the new IBM, p690 Regatta system.
Frontal Crash Analysis of a Fully Detailed Car Model Based on Finite Element Method
Institute of Scientific and Technical Information of China (English)
Han Shan-Ling; Zhu Ping; Lin Zhong-Qin; Shi Yu-Liang
2004-01-01
This paper sets up a highly detailed finite element model of a car for frontal crashworthiness applications, and then explains the characteristics of it. The geometry model is preprocessed by Hypermesh software. The finite element method solver program selected for the simulation is LS-DYNA. After the crash simulation is carefully analyzed, the frontal crash experiment is aimed to validate the finite element model. The simulation results are basically in agreement with the experimental results. The validation of the finite element model is crucial for the further research in optimization of the automotive structure or lightweighting of the vehicle.
Finite-frequency model reduction of continuous-time switched linear systems with average dwell time
Ding, Da-Wei; Du, Xin
2016-11-01
This paper deals with the model reduction problem of continuous-time switched linear systems with finite-frequency input signals. The objective of the paper is to propose a finite-frequency model reduction method for such systems. A finite-frequency ? performance index is first defined in frequency domain, and then a finite-frequency performance analysis condition is derived by Parseval's theorem. Combined with the average dwell time approach, sufficient conditions for the existence of exponentially stable reduced-order models are derived. An algorithm is proposed to construct the desired reduced-order models. The effectiveness of the proposed method is illustrated by a numerical example.
Finite element analysis of osteoporosis models based on synchrotron radiation
Xu, W.; Xu, J.; Zhao, J.; Sun, J.
2016-04-01
With growing pressure of social aging, China has to face the increasing population of osteoporosis patients as well as the whole world. Recently synchrotron radiation has become an essential tool for biomedical exploration with advantage of high resolution and high stability. In order to study characteristic changes in different stages of primary osteoporosis, this research focused on the different periods of osteoporosis of rats based on synchrotron radiation. Both bone histomorphometry analysis and finite element analysis were then carried on according to the reconstructed three dimensional models. Finally, the changes of bone tissue in different periods were compared quantitatively. Histomorphometry analysis showed that the structure of the trabecular in osteoporosis degraded as the bone volume decreased. For femurs, the bone volume fraction (Bone volume/ Total volume, BV/TV) decreased from 69% to 43%. That led to the increase of the thickness of trabecular separation (from 45.05μ m to 97.09μ m) and the reduction of the number of trabecular (from 7.99 mm-1 to 5.97mm-1). Simulation of various mechanical tests with finite element analysis (FEA) indicated that, with the exacerbation of osteoporosis, the bones' ability of resistance to compression, bending and torsion gradually became weaker. The compression stiffness of femurs decreased from 1770.96 Fμ m-1 to 697.41 Fμ m-1, the bending and torsion stiffness were from 1390.80 Fμ m-1 to 566.11 Fμ m-1 and from 2957.28N.m/o to 691.31 N.m/o respectively, indicated the decrease of bone strength, and it matched the histomorphometry analysis. This study suggested that FEA and synchrotron radiation were excellent methods for analysing bone strength conbined with histomorphometry analysis.
Physical Constraint Finite Element Model for Medical Image Registration.
Directory of Open Access Journals (Sweden)
Jingya Zhang
Full Text Available Due to being derived from linear assumption, most elastic body based non-rigid image registration algorithms are facing challenges for soft tissues with complex nonlinear behavior and with large deformations. To take into account the geometric nonlinearity of soft tissues, we propose a registration algorithm on the basis of Newtonian differential equation. The material behavior of soft tissues is modeled as St. Venant-Kirchhoff elasticity, and the nonlinearity of the continuum represents the quadratic term of the deformation gradient under the Green- St.Venant strain. In our algorithm, the elastic force is formulated as the derivative of the deformation energy with respect to the nodal displacement vectors of the finite element; the external force is determined by the registration similarity gradient flow which drives the floating image deforming to the equilibrium condition. We compared our approach to three other models: 1 the conventional linear elastic finite element model (FEM; 2 the dynamic elastic FEM; 3 the robust block matching (RBM method. The registration accuracy was measured using three similarities: MSD (Mean Square Difference, NC (Normalized Correlation and NMI (Normalized Mutual Information, and was also measured using the mean and max distance between the ground seeds and corresponding ones after registration. We validated our method on 60 image pairs including 30 medical image pairs with artificial deformation and 30 clinical image pairs for both the chest chemotherapy treatment in different periods and brain MRI normalization. Our method achieved a distance error of 0.320±0.138 mm in x direction and 0.326±0.111 mm in y direction, MSD of 41.96±13.74, NC of 0.9958±0.0019, NMI of 1.2962±0.0114 for images with large artificial deformations; and average NC of 0.9622±0.008 and NMI of 1.2764±0.0089 for the real clinical cases. Student's t-test demonstrated that our model statistically outperformed the other methods in
Finite element modelling of helmeted head impact under frontal loading
Indian Academy of Sciences (India)
Praveen Kumar Pinnoji; Puneet Mahajan
2007-08-01
Finite element models of the head and helmet were used to study contact forces during frontal impact of the head with a rigid surface. The ﬁnite element model of the head consists of skin, skull, cerebro-spinal ﬂuid (CSF), brain, tentorium and falx. The ﬁnite element model of the helmet consists of shell and foam liner. The foam is taken as elasto-plastic, the brain is assumed to be viscoelastic and all other components are taken as elastic. The contact forces and coup pressures with helmet on the head are much lower than in the absence of the helmet. A parametric study was performed to investigate the effect of liner thickness and density on the contact forces, pressures and energy absorption during impact. For 4 ms-1 velocity, expanded poly styrene (EPS) foam of density 24 kg m-3 gave the lowest contact forces and for the velocities considered, thickness of the foam did not affect the contact forces.
Finite element modeling of superelastic nickel-titanium orthodontic wires.
Naceur, Ines Ben; Charfi, Amin; Bouraoui, Tarak; Elleuch, Khaled
2014-11-28
Thanks to its good corrosion resistance and biocompatibility, superelastic Ni–Ti wire alloys have been successfully used in orthodontic treatment. Therefore, it is important to quantify and evaluate the level of orthodontic force applied to the bracket and teeth in order to achieve tooth movement. In this study, three dimensional finite element models with a Gibbs-potential-based-formulation and thermodynamic principles were used. The aim was to evaluate the influence of possible intraoral temperature differences on the forces exerted by NiTi orthodontic arch wires with different cross sectional shapes and sizes. The prediction made by this phenomenological model, for superelastic tensile and bending tests, shows good agreement with the experimental data. A bending test is simulated to study the force variation of an orthodontic NiTi arch wire when it loaded up to the deflection of 3 mm, for this task one half of the arch wire and the 3 adjacent brackets were modeled. The results showed that the stress required for the martensite transformation increases with the increase of cross-sectional dimensions and temperature. Associated with this increase in stress, the plateau of this transformation becomes steeper. In addition, the area of the mechanical hysteresis, measured as the difference between the forces of the upper and lower plateau, increases.
A Successive Selection Method for finite element model updating
Gou, Baiyong; Zhang, Weijie; Lu, Qiuhai; Wang, Bo
2016-03-01
Finite Element (FE) model can be updated effectively and efficiently by using the Response Surface Method (RSM). However, it often involves performance trade-offs such as high computational cost for better accuracy or loss of efficiency for lots of design parameter updates. This paper proposes a Successive Selection Method (SSM), which is based on the linear Response Surface (RS) function and orthogonal design. SSM rewrites the linear RS function into a number of linear equations to adjust the Design of Experiment (DOE) after every FE calculation. SSM aims to interpret the implicit information provided by the FE analysis, to locate the Design of Experiment (DOE) points more quickly and accurately, and thereby to alleviate the computational burden. This paper introduces the SSM and its application, describes the solution steps of point selection for DOE in detail, and analyzes SSM's high efficiency and accuracy in the FE model updating. A numerical example of a simply supported beam and a practical example of a vehicle brake disc show that the SSM can provide higher speed and precision in FE model updating for engineering problems than traditional RSM.
Finite element modeling of blast lung injury in sheep.
Gibbons, Melissa M; Dang, Xinglai; Adkins, Mark; Powell, Brian; Chan, Philemon
2015-04-01
A detailed 3D finite element model (FEM) of the sheep thorax was developed to predict heterogeneous and volumetric lung injury due to blast. A shared node mesh of the sheep thorax was constructed from a computed tomography (CT) scan of a sheep cadaver, and while most material properties were taken from literature, an elastic-plastic material model was used for the ribs based on three-point bending experiments performed on sheep rib specimens. Anesthetized sheep were blasted in an enclosure, and blast overpressure data were collected using the blast test device (BTD), while surface lung injury was quantified during necropsy. Matching blasts were simulated using the sheep thorax FEM. Surface lung injury in the FEM was matched to pathology reports by setting a threshold value of the scalar output termed the strain product (maximum value of the dot product of strain and strain-rate vectors over all simulation time) in the surface elements. Volumetric lung injury was quantified by applying the threshold value to all elements in the model lungs, and a correlation was found between predicted volumetric injury and measured postblast lung weights. All predictions are made for the left and right lungs separately. This work represents a significant step toward the prediction of localized and heterogeneous blast lung injury, as well as volumetric injury, which was not recorded during field testing for sheep.
An improved optimal elemental method for updating finite element models
Institute of Scientific and Technical Information of China (English)
Duan Zhongdong(段忠东); Spencer B.F.; Yan Guirong(闫桂荣); Ou Jinping(欧进萍)
2004-01-01
The optimal matrix method and optimal elemental method used to update finite element models may not provide accurate results. This situation occurs when the test modal model is incomplete, as is often the case in practice. An improved optimal elemental method is presented that defines a new objective function, and as a byproduct, circumvents the need for mass normalized modal shapes, which are also not readily available in practice. To solve the group of nonlinear equations created by the improved optimal method, the Lagrange multiplier method and Matlab function fmincon are employed. To deal with actual complex structures,the float-encoding genetic algorithm (FGA) is introduced to enhance the capability of the improved method. Two examples, a 7-degree of freedom (DOF) mass-spring system and a 53-DOF planar frame, respectively, are updated using the improved method.Thc example results demonstrate the advantages of the improved method over existing optimal methods, and show that the genetic algorithm is an effective way to update the models used for actual complex structures.
Gleadall, Andrew; Pan, Jingzhe; Ding, Lifeng; Kruft, Marc-Anton; Curcó, David
2015-11-01
Molecular dynamics (MD) simulations are widely used to analyse materials at the atomic scale. However, MD has high computational demands, which may inhibit its use for simulations of structures involving large numbers of atoms such as amorphous polymer structures. An atomic-scale finite element method (AFEM) is presented in this study with significantly lower computational demands than MD. Due to the reduced computational demands, AFEM is suitable for the analysis of Young's modulus of amorphous polymer structures. This is of particular interest when studying the degradation of bioresorbable polymers, which is the topic of an accompanying paper. AFEM is derived from the inter-atomic potential energy functions of an MD force field. The nonlinear MD functions were adapted to enable static linear analysis. Finite element formulations were derived to represent interatomic potential energy functions between two, three and four atoms. Validation of the AFEM was conducted through its application to atomic structures for crystalline and amorphous poly(lactide).
Finite Element Modelling of Seismic Liquefaction in Soils
Galavi, V.; Petalas, A.; Brinkgreve, R.B.J.
2013-01-01
Numerical aspects of seismic liquefaction in soils as implemented in the finite element code, PLAXIS, is described in this paper. After description of finite element equations of dynamic problems, three practical dynamic boundary conditions, namely viscous boundary tractions, tied degrees of freedom
Sparrow, Victor Ward
1990-01-01
This study has concerned the propagation of finite amplitude, i.e. weakly non-linear, acoustical blast waves from explosions over hard and porous media models of outdoor ground surfaces. The nonlinear acoustic propagation effects require a numerical solution in the time domain. To model a porous ground surface, which in the frequency domain exhibits a finite impedance, the linear phenomenological porous model of Morse and Ingard was used. The phenomenological equations are solved in the time domain for coupling with the time domain propagation solution in the air. The numerical solution is found through the method of finite differences. The second-order in time and fourth -order in space MacCormack method was used in the air, and the second-order in time and space MacCormack method was used in the porous medium modeling the ground. Two kinds of numerical absorbing boundary conditions were developed for the air propagation equations to truncate the physical domain for solution on a computer. Radiation conditions first were used on those sides of the domain where there were outgoing waves. Characteristic boundary conditions secondly are employed near the acoustic source. The numerical model agreed well with the Pestorius algorithm for the propagation of electric spark pulses in the free field, and with a result of Pfriem for normal plane reflection off a hard surface. In addition, curves of pressure amplification versus incident angle for waves obliquely incident on the hard and porous surfaces were produced which are similar to those in the literature. The model predicted that near grazing finite amplitude acoustic blast waves decay with distance over hard surfaces as r to the power -1.2. This result is consistent with the work of Reed. For propagation over the porous ground surface, the model predicted that this surface decreased the decay rate with distance for the larger blasts compared to the rate expected in the linear acoustics limit.
SU($4$) Polyakov linear-sigma model at finite temperature and density
Diab, Abdel Magied; Tawfik, Abdel Nasser; Dahab, Eiman Abou El
2016-01-01
In mean-field approximation, the SU($4$) Polyakov linear - sigma model (PLSM) is constructed in order to characterize the quark-hadron phase structure in a wide range of temperatures and densities. The chiral condensates $\\sigma_l$, $\\sigma_s$ and $\\sigma_c$ for light, strange and charm quarks, respectively, and the deconfinement order-parameters $\\phi$ and $\\phi^*$ shall be analyzed at finite temperatures and densities. We conclude that the critical temperatures corresponding to charm condensates are greater than that to strange and light ones, respectively. Thus, the charm condensates are likely not affected by the QCD phase transition. Furthermore, increasing the chemical potentials decreases the corresponding critical temperatures.
An electromechanical finite element model for piezoelectric energy harvester plates
De Marqui Junior, Carlos; Erturk, Alper; Inman, Daniel J.
2009-10-01
Vibration-based energy harvesting has been investigated by several researchers over the last decade. The goal in this research field is to power small electronic components by converting the waste vibration energy available in their environment into electrical energy. Recent literature shows that piezoelectric transduction has received the most attention for vibration-to-electricity conversion. In practice, cantilevered beams and plates with piezoceramic layers are employed as piezoelectric energy harvesters. The existing piezoelectric energy harvester models are beam-type lumped parameter, approximate distributed parameter and analytical distributed parameter solutions. However, aspect ratios of piezoelectric energy harvesters in several cases are plate-like and predicting the power output to general (symmetric and asymmetric) excitations requires a plate-type formulation which has not been covered in the energy harvesting literature. In this paper, an electromechanically coupled finite element (FE) plate model is presented for predicting the electrical power output of piezoelectric energy harvester plates. Generalized Hamilton's principle for electroelastic bodies is reviewed and the FE model is derived based on the Kirchhoff plate assumptions as typical piezoelectric energy harvesters are thin structures. Presence of conductive electrodes is taken into account in the FE model. The predictions of the FE model are verified against the analytical solution for a unimorph cantilever and then against the experimental and analytical results of a bimorph cantilever with a tip mass reported in the literature. Finally, an optimization problem is solved where the aluminum wing spar of an unmanned air vehicle (UAV) is modified to obtain a generator spar by embedding piezoceramics for the maximum electrical power without exceeding a prescribed mass addition limit.
On the Development of the SIMon Finite Element Head Model.
Takhounts, Erik G; Eppinger, Rolf H; Campbell, J Quinn; Tannous, Rabih E; Power, Erik D; Shook, Lauren S
2003-10-01
The SIMon (Simulated Injury Monitor) software package is being developed to advance the interpretation of injury mechanisms based on kinematic and kinetic data measured in the advanced anthropomorphic test dummy (AATD) and applying the measured dummy response to the human mathematical models imbedded in SIMon. The human finite element head model (FEHM) within the SIMon environment is presented in this paper. Three-dimensional head kinematic data in the form of either a nine accelerometer array or three linear CG head accelerations combined with three angular velocities serves as an input to the model. Three injury metrics are calculated: Cumulative strain damage measure (CSDM) - a correlate for diffuse axonal injury (DAI); Dilatational damage measure (DDM) - to estimate the potential for contusions; and Relative motion damage measure (RMDM) - a correlate for acute subdural hematoma (ASDH). During the development, the SIMon FEHM was tuned using cadaveric neutral density targets (NDT) data and further validated against the other available cadaveric NDT data and animal brain injury experiments. The hourglass control methods, integration schemes, mesh density, and contact stiffness penalty coefficient were parametrically altered to investigate their effect on the model's response. A set of numerical and physical parameters was established that allowed a satisfactory prediction of the motion of the brain with respect to the skull, when compared with the NDT data, and a proper separation of injury/no injury cases, when compared with the brain injury data. Critical limits for each brain injury metric were also established. Finally, the SIMon FEHM performance was compared against HIC15 through the use of NHTSA frontal and side impact crash test data. It was found that the injury metrics in the current SIMon model predicted injury in all cases where HIC15 was greater than 700 and several cases from the side impact test data where HIC15 was relatively small. Side impact was
2.5-D modeling of cross-hole electromagnetic measurement by finite element method
Institute of Scientific and Technical Information of China (English)
Shen Jinsong; Sun Wenbo
2008-01-01
A finite element method is developed for simulating frequency domain electromagnetic responses due to a dipole source in the 2-D conductive structures.Computing costs are considerably minimized by reducing the full three-dimensional problem to a series of two-dimensional problems.This is accomplished by transforming the problem into y-wave number (Ky) domain using Fourier transform and the y-axis is parallel to the structural strike.In the Ky domain,two coupled partial differential equations for magnetic field Hy and electric field Ey are derived.For a specific value of Ky,the coupled equations are solved by the finite clement method with isoparametric elements in the x-z plane.Application of the inverse Fourier transform to the Ky domain provides the electric and magnetic fields in real space.The equations derived can be applied to general complex two-dimensional structures containing either electric or magnetic dipole source in any direction.In the modeling of the electromagnetic measurement,we adopted a pseudo-delta function to distribute the dipole source current and circumvent the problem of singularity at the source point.Moreover,the suggested method used isoparametric finite elements to accommodate the complex subsurface formation.For the large scale linear system derived from the discretization of the Maxwell's equations,several iterative solvers were used and compared to select the optimal one.A quantitative test of accuracy was presented which compared the finite element results with analytic solutions for a dipole source in homogeneous space for different ranges and different wave numbers Ky.to validate the code and check its effectiveness.In addition,we addressed the effects of the distribution range τ of the pseudo-delta function on the numerical results in homogeneous medium.
A finite-volume scheme for a kidney nephron model
Directory of Open Access Journals (Sweden)
Seguin Nicolas
2012-04-01
Full Text Available We present a finite volume type scheme to solve a transport nephron model. The model consists in a system of transport equations with specific boundary conditions. The transport velocity is driven by another equation that can undergo sign changes during the transient regime. This is the main difficulty for the numerical resolution. The scheme we propose is based on an explicit resolution and is stable under a CFL condition which does not depend on the stiffness of source terms. Nous présentons un schéma numérique de type volume fini que l’on applique à un modèle de transport dans le néphron. Ce modèle consiste en un système d’équations de transport, avec des conditions aux bords spécifiques. La vitesse du transport est la solution d’un autre système d’équation et peut changer de signe au cours du régime transitoire. Ceci constitue la principale difficulté pour la résolution numérique. Le schéma proposé, basé sur une résolution explicite, est stable sous une condition CFL non restrictive.
Multiscale Finite-Element Modeling of Sandwich Honeycomb Composite Structures
Directory of Open Access Journals (Sweden)
Yu. I. Dimitrienko
2014-01-01
Full Text Available The paper presents a developed multi-scale model of sandwich honeycomb structures. The model allows us both to calculate effective elastic-strength characteristics of honeycomb and forced covering of sandwich, and to find a 3D stress-strain state of structures using the threedimensional elastic theory for non- homogeneous media. On the basis of finite element analysis it is shown, that under four-point bending the maximal value of bending and shear stresses in the sandwich honeycomb structures are realized in the zone of applied force and plate support. Here the local stress maxima approximately 2-3 times exceed the “engineering” theoretical plate values of bending and shear stresses in the middle of panel. It is established that at tests for fourpoint bending there is a failure of the honeycomb sandwich panels because of the local adhesion failure rather than because of the covering exfoliation off the honeycomb core in the middle of panel.
A shell finite element model of the pelvic floor muscles.
d'Aulignac, D; Martins, J A C; Pires, E B; Mascarenhas, T; Jorge, R M Natal
2005-10-01
The pelvic floor gives support to the organs in the abdominal cavity. Using the dataset made public in (Janda et al. J. Biomech. (2003) 36(6), pp. 749-757), we have reconstructed the geometry of one of the most important parts of the pelvic floor, the levator ani, using NURB surfaces. Once the surface is triangulated, the corresponding mesh is used in a finite element analysis with shell elements. Based on the 3D behavior of the muscle we have constructed a shell that takes into account the direction of the muscle fibers and the incompressibility of the tissue. The constitutive model for the isotropic strain energy and the passive strain energy stored in the fibers is adapted from Humphrey's model for cardiac muscles. To this the active behavior of the skeletal muscle is added. We present preliminary results of a simulation of the levator ani muscle under pressure and with active contraction. This research aims at helping simulate the damages to the pelvic floor that can occur after childbirth.
FEMA: a Finite Element Model of Material Transport through Aquifers
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.; Huff, D.D.
1985-01-01
This report documents the construction, verification, and demonstration of a Finite Element Model of Material Transport through Aquifers (FEMA). The particular features of FEMA are its versatility and flexibility to deal with as many real-world problems as possible. Mechanisms included in FEMA are: carrier fluid advection, hydrodynamic dispersion and molecular diffusion, radioactive decay, sorption, source/sinks, and degradation due to biological, chemical as well as physical processes. Three optional sorption models are embodied in FEMA. These are linear isotherm and Freundlich and Langmuir nonlinear isotherms. Point as well as distributed source/sinks are included to represent artificial injection/withdrawals and natural infiltration of precipitation. All source/sinks can be transient or steady state. Prescribed concentration on the Dirichlet boundary, given gradient on the Neumann boundary segment, and flux at each Cauchy boundary segment can vary independently of each other. The aquifer may consist of as many formations as desired. Either completely confined or completely unconfined or partially confined and partially unconfined aquifers can be dealt with effectively. FEMA also includes transient leakage to or from the aquifer of interest through confining beds from or to aquifers lying below and/or above.
Contraction preconditioner in finite-difference electromagnetic modeling
Yavich, Nikolay; Zhdanov, Michael S.
2016-06-01
This paper introduces a novel approach to constructing an effective preconditioner for finite-difference (FD) electromagnetic modeling in geophysical applications. This approach is based on introducing an FD contraction operator, similar to one developed for integral equation formulation of Maxwell's equation. The properties of the FD contraction operator were established using an FD analog of the energy equality for the anomalous electromagnetic field. A new preconditioner uses a discrete Green's function of a 1D layered background conductivity. We also developed the formulas for an estimation of the condition number of the system of FD equations preconditioned with the introduced FD contraction operator. Based on this estimation, we have established that for high contrasts, the condition number is bounded by the maximum conductivity contrast between the background conductivity and actual conductivity. When there are both resistive and conductive anomalies relative to the background, the new preconditioner is advantageous over using the 1D discrete Green's function directly. In our numerical experiments with both resistive and conductive anomalies, for a land geoelectrical model with 1:10 contrast, the method accelerates convergence of an iterative method (BiCGStab) by factors of 2 to 2.5, and in a marine example with 1:50 contrast, by a factor of 4.6, compared to direct use of the discrete 1D Green's function as a preconditioner.
Contraction pre-conditioner in finite-difference electromagnetic modelling
Yavich, Nikolay; Zhdanov, Michael S.
2016-09-01
This paper introduces a novel approach to constructing an effective pre-conditioner for finite-difference (FD) electromagnetic modelling in geophysical applications. This approach is based on introducing an FD contraction operator, similar to one developed for integral equation formulation of Maxwell's equation. The properties of the FD contraction operator were established using an FD analogue of the energy equality for the anomalous electromagnetic field. A new pre-conditioner uses a discrete Green's function of a 1-D layered background conductivity. We also developed the formulae for an estimation of the condition number of the system of FD equations pre-conditioned with the introduced FD contraction operator. Based on this estimation, we have established that the condition number is bounded by the maximum conductivity contrast between the background conductivity and actual conductivity. When there are both resistive and conductive anomalies relative to the background, the new pre-conditioner is advantageous over using the 1-D discrete Green's function directly. In our numerical experiments with both resistive and conductive anomalies, for a land geoelectrical model with 1:10 contrast, the method accelerates convergence of an iterative method (BiCGStab) by factors of 2-2.5, and in a marine example with 1:50 contrast, by a factor of 4.6, compared to direct use of the discrete 1-D Green's function as a pre-conditioner.
Finite Element Modeling of Reheat Stretch Blow Molding of PET
Krishnan, Dwarak; Dupaix, Rebecca B.
2004-06-01
Poly (ethylene terephthalate) or PET is a polymer used as a packaging material for consumer products such as beverages, food or other liquids, and in other applications including drawn fibers and stretched films. Key features that make it widely used are its transparency, dimensional stability, gas impermeability, impact resistance, and high stiffness and strength in certain preferential directions. These commercially useful properties arise from the fact that PET crystallizes upon deformation above the glass transition temperature. Additionally, this strain-induced crystallization causes the deformation behavior of PET to be highly sensitive to processing conditions. It is thus crucial for engineers to be able to predict its performance at various process temperatures, strain rates and strain states so as to optimize the manufacturing process. In addressing these issues; a finite element analysis of the reheat blow molding process with PET has been carried out using ABAQUS. The simulation employed a constitutive model for PET developed by Dupaix and Boyce et al.. The model includes the combined effects of molecular orientation and strain-induced crystallization on strain hardening when the material is deformed above the glass transition temperature. The simulated bottles were also compared with actual blow molded bottles to evaluate the validity of the simulation.
Modulus reconstruction from prostate ultrasound images using finite element modeling
Yan, Zhennan; Zhang, Shaoting; Alam, S. Kaisar; Metaxas, Dimitris N.; Garra, Brian S.; Feleppa, Ernest J.
2012-03-01
In medical diagnosis, use of elastography is becoming increasingly more useful. However, treatments usually assume a planar compression applied to tissue surfaces and measure the deformation. The stress distribution is relatively uniform close to the surface when using a large, flat compressor but it diverges gradually along tissue depth. Generally in prostate elastography, the transrectal probes used for scanning and compression are cylindrical side-fire or rounded end-fire probes, and the force is applied through the rectal wall. These make it very difficult to detect cancer in prostate, since the rounded contact surfaces exaggerate the non-uniformity of the applied stress, especially for the distal, anterior prostate. We have developed a preliminary 2D Finite Element Model (FEM) to simulate prostate deformation in elastography. The model includes a homogeneous prostate with a stiffer tumor in the proximal, posterior region of the gland. A force is applied to the rectal wall to deform the prostate, strain and stress distributions can be computed from the resultant displacements. Then, we assume the displacements as boundary condition and reconstruct the modulus distribution (inverse problem) using linear perturbation method. FEM simulation shows that strain and strain contrast (of the lesion) decrease very rapidly with increasing depth and lateral distance. Therefore, lesions would not be clearly visible if located far away from the probe. However, the reconstructed modulus image can better depict relatively stiff lesion wherever the lesion is located.
Essentials of finite element modeling and adaptive refinement
Dow, John O
2012-01-01
Finite Element Analysis is a very popular, computer-based tool that uses a complex system of points called nodes to make a grid called a ""mesh. "" The mesh contains the material and structural properties that define how the structure will react to certain loading conditions, allowing virtual testing and analysis of stresses or changes applied to the material or component design. This groundbreaking text extends the usefulness of finite element analysis by helping both beginners and advanced users alike. It simplifies, improves, and extends both the finite element method while at the same t
Auto-Regressive Models of Non-Stationary Time Series with Finite Length
Institute of Scientific and Technical Information of China (English)
FEI Wanchun; BAI Lun
2005-01-01
To analyze and simulate non-stationary time series with finite length, the statistical characteristics and auto-regressive (AR) models of non-stationary time series with finite length are discussed and studied. A new AR model called the time varying parameter AR model is proposed for solution of non-stationary time series with finite length. The auto-covariances of time series simulated by means of several AR models are analyzed. The result shows that the new AR model can be used to simulate and generate a new time series with the auto-covariance same as the original time series. The size curves of cocoon filaments regarded as non-stationary time series with finite length are experimentally simulated. The simulation results are significantly better than those obtained so far, and illustrate the availability of the time varying parameter AR model. The results are useful for analyzing and simulating non-stationary time series with finite length.
FEWA: a Finite Element model of Water flow through Aquifers
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.; Huff, D.D.
1983-11-01
This report documents the implementation and demonstration of a Finite Element model of Water flow through Aquifers (FEWA). The particular features of FEWA are its versatility and flexibility to deal with as many real-world problems as possible. Point as well as distributed sources/sinks are included to represent recharges/pumpings and rainfall infiltrations. All sources/sinks can be transient or steady state. Prescribed hydraulic head on the Dirichlet boundaries and fluxes on Neumann or Cauchy boundaries can be time-dependent or constant. Source/sink strength over each element and node, hydraulic head at each Dirichlet boundary node, and flux at each boundary segment can vary independently of each other. Either completely confined or completely unconfined aquifers, or partially confined and partially unconfined aquifers can be dealt with effectively. Discretization of a compound region with very irregular curved boundaries is made easy by including both quadrilateral and triangular elements in the formulation. Large-field problems can be solved efficiently by including a pointwise iterative solution strategy as an optional alternative to the direct elimination solution method for the matrix equation approximating the partial differential equation of groundwater flow. FEWA also includes transient flow through confining leaky aquifers lying above and/or below the aquifer of interest. The model is verified against three simple cases to which analytical solutions are available. It is then demonstrated by two examples of how the model can be applied to heterogeneous and anisotropic aquifers with transient boundary conditions, time-dependent sources/sinks, and confining aquitards for a confined aquifer of variable thickness and for a free surface problem in an unconfined aquifer, respectively. 20 references, 25 figures, 8 tables.
Finite element modelling of the tricuspid valve: A preliminary study.
Stevanella, Marco; Votta, Emiliano; Lemma, Massimo; Antona, Carlo; Redaelli, Alberto
2010-12-01
The incomplete efficacy of current surgical repair procedures of the tricuspid valve (TV) demands a deeper comprehension of the physiological TV biomechanics. To this purpose, computational models can provide quantitative insight into TV biomechanical response and allow analysing the role of each TV substructure. We present here a three-dimensional finite element model of the tricuspid valve that takes into account most of its peculiar features. Experimental measurements were performed on human and porcine valves to obtain a more detailed TV anatomical framework. To overcome the complete lack of information on leaflets mechanical properties, we performed a sensitivity analysis on the parameters of the adopted non-linear hyperelastic constitutive model, hypothesizing three different parameter sets for three significant collagen fibre distributions. Results showed that leaflets' motion and maximum principal stress distribution were almost insensitive to the different material parameters considered. Highest stresses (about 100kPa) were located near the annulus of the anterior and septal leaflets, while the posterior leaflet experienced lower stresses (about 55kPa); stresses at the commissures were nearly zero. Conversely, changes in constitutive parameters deeply affected leaflets' strains magnitude, but not their overall pattern. Strains computed assuming that TV leaflets tissue are reinforced by a sparse and loosely arranged network of collagen fibres fitted best experimental data, thus suggesting that this may be the actual microstructure of TV leaflets. In a long-term perspective, this preliminary study aims at providing a starting point for the development of a predictive tool to quantitatively evaluate TV diseases and surgical repair procedures.
Model equation for strongly focused finite-amplitude sound beams
Kamakura; Ishiwata; Matsuda
2000-06-01
A model equation that describes the propagation of sound beams in a fluid is developed using the oblate spheroidal coordinate system. This spheroidal beam equation (SBE) is a parabolic equation and has a specific application to a theoretical prediction on focused, high-frequency beams from a circular aperture. The aperture angle does not have to be small. The theoretical background is basically along the same analytical lines as the composite method (CM) reported previously [B. Ystad and J. Berntsen, Acustica 82, 698-706 (1996)]. Numerical examples are displayed for the amplitudes of sound pressure along and across the beam axis when sinusoidal waves are radiated from the source with uniform amplitude distribution. The primitive approach to linear field analysis is readily extended to the case where harmonic generation in finite-amplitude sound beams becomes significant due to the inherent nonlinearity of the medium. The theory provides the propagation and beam pattern profiles that differ from the CM solution for each harmonic component.
Finite Element Modeling of scattered electromagnetic waves for stroke analysis.
Priyadarshini, N; Rajkumar, E R
2013-01-01
Stroke has become one of the leading causes of mortality worldwide and about 800 in every 100,000 people suffer from stroke each year. The occurrence of stroke is ranked third among the causes of acute death and first among the causes for neurological dysfunction. Currently, Neurological examinations followed by medical imaging with CT, MRI or Angiography are used to provide better identification of the location and the type of the stroke, however they are neither fast, cost-effective nor portable. Microwave technology has emerged to complement these modalities to diagnose stroke as it is sensitive to the differences between the distinct dielectric properties of the brain tissues and blood. This paper investigates the possibility of diagnosing the type of stroke using Finite Element Analysis (FEA). The object of interest is a simulated head phantom with stroke, created with its specifying material characteristics like electrical conductivity and relative permittivity. The phantom is then placed in an electromagnetic field generated by a dipole antenna radiating at 1 GHz. The FEM forward model solver computes the scattered electromagnetic field by finding the solution for the Maxwell's wave equation in the head volume. Subsequently the inverse scattering problem is solved using the Contrast Source Inversion (CSI) method to reconstruct the dielectric profile of the head phantom.
Finite element modeling of a progressively expanding shape memory stent.
Thériault, Philippe; Terriault, Patrick; Brailovski, Vladimir; Gallo, Richard
2006-01-01
Cardiovascular stents are small cylindrical devices introduced in stenosed arteries to reopen the lumen and restore blood flow. However, this treatment presents complications, including restenosis, which is the reclosing of the artery's diameter after the insertion of a stent. The structure of the prosthesis penetrates into and injures the walls of the patient's artery. There then follows a proliferation of cells and the formation of scar tissue around the injury, similar to the scarring of other organic tissues. This reaction to the trauma subjects the artery to close. The proposed solution is to develop a Nitinol stent with a progressive expansion device made of polyethylene, allowing smooth and gradual contact between the stent and the artery's wall by creep effect. The purpose of this paper is to describe the technology and methodology for the numerical study of this kind of stent through the finite element method. ANSYS 8.0 software is used to perform the analysis. The Nitinol is modeled with a superelastic law and the polyethylene with a yield hardening law. A first simulation determines the final geometry of the stent laser cut from a small tube. A second simulation examines the behavior of the prosthesis during surgery and over the 4 weeks following the operation. The results demonstrate that a compromise can be reached between a limited expansion prior the inflation of the expandable balloon and a significant expansion by creep of the polymer rings.
Finite Element Modeling of Cutaneous Electrical Stimulation for Sensory Feedback
Institute of Scientific and Technical Information of China (English)
LI Si; CHAI Guo-hong; SUI Xiao-hong; LAN Ning
2014-01-01
It is currently difficult for the amputee to perceive environmental information such as tactile pressure on the fingertip of the present upper limb prostheses. Sensory feedback induced by cutaneous electrical stimulation can be used to transmit tactile information from hand prostheses to sensory nerve of intact upper arm, thus producing the corresponding perceptions in human brain. In order to have a deeper understanding on the distribution of stimulation current within the limb, and find a better placement of the stimulating and reference electrodes, we constructed a three-dimensional upper-limb model to systematically study the effect of electrode placement on current distribution based on finite element analysis. In these simulations, the reference electrode is positioned at four different locations around and on the axial direction of the arm. The results show that with the increase of distance between reference electrode and stimulating electrode, the current density increases in the skin layer of the upper limb. When the reference electrode is on the opposite side of stimulating electrode around the arm, the current is more concentrated in the skin layer, which is in line with recent findings in psychophysiological experiments. But better spatial selectivity could be achieved when the reference electrode is closer to the stimulating electrode around the arm, and it is more obvious in comparison with that on the axial direction. These findings will provide insights for the design of electrode array used for evoking cutaneous sensory afferents.
A mixed finite element scheme for viscoelastic flows with XPP model
Institute of Scientific and Technical Information of China (English)
Xianhong Han; Xikui Li
2008-01-01
A mixed finite element formulation for viscoe-lastic flows is derived in this paper, in which the FIC (finite incremental calculus) pressure stabilization process and the DEVSS (discrete elastic viscous stress splitting) method using the Crank-Nicolson-based split are introduced within a general framework of the iterative version of the fractio-nal step algorithm. The SU (streamline-upwind) method is particularly chosen to tackle the convective terms in constitu-tive equations of viscoelastic flows. Thanks to the proposed scheme the finite elements with equal low-order interpola-tion approximations for stress-velocity-pressure variables can be successfully used even for viscoelastic flows with high Weissenberg numbers. The XPP (extended Pom-Pom) consti-tutive model for describing viscoelastic behaviors is particu-larly integrated into the proposed scheme. The numerical results for the 4:1 sudden contraction flow problem demons-trate prominent stability, accuracy and convergence rate of the proposed scheme in both pressure and stress distributions over the flow domain within a wide range of the Weissenberg number, particularly the capability in reproducing the results, which can be used to explain the "die swell" phenomenon observed in the polymer injection molding process.
Finite Element Models for Electron Beam Freeform Fabrication Process Project
National Aeronautics and Space Administration — This Small Business Innovation Research Phase II proposal offers to develop a comprehensive computer simulation methodology based on the finite element method for...
Estimation of periodontal ligament’s equivalent mechanical parameters for finite element modeling
Xia, Zeyang; Jiang, Feifei; Chen, Jie
2014-01-01
Introduction Young’s modulus (E) and Poisson’s ratio (v) of the periodontal ligament are needed in a finite element analysis for investigating the biomechanical behavior of a tooth, periodontal ligament, and bone complex. However, large discrepancies in E (0.01–1,750 MPa) and v (0.28–0.49) were reported previously. The objective of this study was to narrow the ranges and to provide equivalent E and v pairs suitable for finite element modeling of a tooth, periodontal ligament, and bone complex by using a reported crown load-displacement relationship as the criterion. Methods A 3-dimensional finite element model of a 3-tooth, periodontal ligament, and bone complex, consisting of a maxillary central incisor with 2 adjacent teeth, from a cone-beam computed tomography scan was created. The dimensions, constraints, and loading condition were kept similar to those reported in the human study. With the load applied to the crown, both v and E were adjusted independently, and the corresponding crown displacements were calculated. The resulting load-displacement curves were compared with those reported in the human study. The mean absolute displacement difference method was used to find the best fit. The E and v pairs that generated the minimum mean absolute displacement difference were identified. Results The finite element model with 1 of the 3 E and v pairs (v = 0.35, E = 0.87 MPa; v = 0.4, E = 0.71 MPa; and v = 0.45, E = 0.47 MPa) simulated the tooth, periodontal ligament, and bone complex well. The mean absolute displacement differences were 0.0135, 0.0138, and 0.0138 mm, respectively; these are less than 8% of 0.175 mm, which was the crown displacement of the tooth, periodontal ligament, and bone complex under the load of 500 cN. Conclusions The E and v values close to the 3 pairs might be used for finite element modeling of the tooth, periodontal ligament, and bone complex. PMID:23561409
Kees, C. E.; Miller, C. T.; Dimakopoulos, A.; Farthing, M.
2016-12-01
The last decade has seen an expansion in the development and application of 3D free surface flow models in the context of environmental simulation. These models are based primarily on the combination of effective algorithms, namely level set and volume-of-fluid methods, with high-performance, parallel computing. These models are still computationally expensive and suitable primarily when high-fidelity modeling near structures is required. While most research on algorithms and implementations has been conducted in the context of finite volume methods, recent work has extended a class of level set schemes to finite element methods on unstructured methods. This work considers models of three-phase flow in domains containing air, water, and granular phases. These multi-phase continuum mechanical formulations show great promise for applications such as analysis of coastal and riverine structures. This work will consider formulations proposed in the literature over the last decade as well as new formulations derived using the thermodynamically constrained averaging theory, an approach to deriving and closing macroscale continuum models for multi-phase and multi-component processes. The target applications require the ability to simulate wave breaking and structure over-topping, particularly fully three-dimensional, non-hydrostatic flows that drive these phenomena. A conservative level set scheme suitable for higher-order finite element methods is used to describe the air/water phase interaction. The interaction of these air/water flows with granular materials, such as sand and rubble, must also be modeled. The range of granular media dynamics targeted including flow and wave transmision through the solid media as well as erosion and deposition of granular media and moving bed dynamics. For the granular phase we consider volume- and time-averaged continuum mechanical formulations that are discretized with the finite element method and coupled to the underlying air
Evaluating the accuracy of finite element models at reduced length scales
Kemp, Connor
Finite element models are used frequently in both engineering and scientific research. While they can provide useful information as to the performance of materials, as length scales are decreased more sophisticated model descriptions are required. It is also important to develop methods by which existing models may be verified against experimental findings. The present study evaluates the ability of various finite element models to predict materials behaviour at length scales ranging from several microns to tens of nanometers. Considering this motivation, this thesis is provided in manuscript form with the bulk of material coming from two case studies. Following an overview of relevant literature in Chapter 2, Chapter 3 considers the nucleation of delta-zirconium hydrides in a Zircaloy-2 matrix. Zirconium hydrides are an important topic in the nuclear industry as they form a brittle phase which leads to delayed hydride cracking during reactor start-up and shut-down. Several FE models are used to compare present results with literature findings and illustrate the weaknesses of standard FE approaches. It is shown that standard continuum techniques do not sufficiently capture the interfacial effects of an inclusion-matrix system. By using nano-scale material descriptions, nucleation lattice strains are obtained which are in good agreement with previous experimental studies. The motivation for Chapter 4 stems from a recognized need to develop a method for modeling corrosion behaviour of materials. Corrosion is also an issue for reactor design and an ability to predict failure points is needed. Finite element models could be used for this purpose, provided model accuracy is verified first. In Chapter 4 a technique is developed which facilitates the extraction of sub-micron resolution strain data from correlation images obtained during in-situ tensile deformation. By comparing image correlation results with a crystal plasticity finite element code it is found that good
Gabel, R.; Lang, P. F.; Smith, L. A.; Reed, D. A.
1989-01-01
Boeing Helicopter, together with other United States helicopter manufacturers, participated in a finite element applications program to emplace in the United States a superior capability to utilize finite element analysis models in support of helicopter airframe design. The activities relating to planning and creating a finite element vibrations model of the Boeing Model 36-0 composite airframe are summarized, along with the subsequent analytical correlation with ground shake test data.
A comparison of numerical methods used for finite element modelling of soft tissue deformation
Pathmanathan, P
2009-05-01
Soft tissue deformation is often modelled using incompressible non-linear elasticity, with solutions computed using the finite element method. There are a range of options available when using the finite element method, in particular the polynomial degree of the basis functions used for interpolating position and pressure, and the type of element making up the mesh. The effect of these choices on the accuracy of the computed solution is investigated, using a selection of model problems motivated by typical deformations seen in soft tissue modelling. Model problems are set up with discontinuous material properties (as is the case for the breast), steeply changing gradients in the body force (as found in contracting cardiac tissue), and discontinuous first derivatives in the solution at the boundary, caused by a discontinuous applied force (as in the breast during mammography). It was found that the choice of pressure basis functions is vital in the presence of a material interface, higher-order schemes do not perform as well as may be expected when there are sharp gradients, and in general it is important to take the expected regularity of the solution into account when choosing a numerical scheme. © IMechE 2009.
Finite-Element Modeling of Timber Joints with Punched Metal Plate Fasteners
DEFF Research Database (Denmark)
Ellegaard, Peter
2006-01-01
The focus of this paper is to describe the idea and the theory behind a finite-element model developed for analysis of timber trusses with punched metal plate fasteners (nail plates). The finite-element model includes the semirigid and nonlinear behavior of the joints (nonlinear nail and plate...... elements) and contact between timber beams, if any (bilinear contact elements). The timber beams have linear-elastic properties. The section forces needed for design of the joints are given directly by the finite-element model, since special elements are used to model the nail groups and the nail plate...... area over the joint lines. The finite-element model is based on the Foschi model, but with further improvements. After the theory of the model is described, results from experimental tests with two types of nail plate joints are compared with predictions given by the model. The model estimates...
Song, Huimin
In the aerospace and automotive industries, many finite element analyses use lower-dimensional finite elements such as beams, plates and shells, to simplify the modeling. These simplified models can greatly reduce the computation time and cost; however, reduced-dimensional models may introduce inaccuracies, particularly near boundaries and near portions of the structure where reduced-dimensional models may not apply. Another factor in creation of such models is that beam-like structures frequently have complex geometry, boundaries and loading conditions, which may make them unsuitable for modeling with single type of element. The goal of this dissertation is to develop a method that can accurately and efficiently capture the response of a structure by rigorous combination of a reduced-dimensional beam finite element model with a model based on full two-dimensional (2D) or three-dimensional (3D) finite elements. The first chapter of the thesis gives the background of the present work and some related previous work. The second chapter is focused on formulating a system of equations that govern the joining of a 2D model with a beam model for planar deformation. The essential aspect of this formulation is to find the transformation matrices to achieve deflection and load continuity on the interface. Three approaches are provided to obtain the transformation matrices. An example based on joining a beam to a 2D finite element model is examined, and the accuracy of the analysis is studied by comparing joint results with the full 2D analysis. The third chapter is focused on formulating the system of equations for joining a beam to a 3D finite element model for static and free-vibration problems. The transition between the 3D elements and beam elements is achieved by use of the stress recovery technique of the variational-asymptotic method as implemented in VABS (the Variational Asymptotic Beam Section analysis). The formulations for an interface transformation matrix and
Effect of Modeling Range on Structural Analysis for Powerhouse of Hydroelectric Power Plant by FEM
Institute of Scientific and Technical Information of China (English)
ZHANG Qiling; WU Hegao; YANG Huaquan
2009-01-01
In this paper, three different modeling ranges were selected in the structural analysis for a hydropower house. The analysis was carried out using ABAQUS 6.6. The modeling range has a remarkable effect on finite ele-ment method(FEM)calculation result at the middle position of typical cross-sections where the concrete is rela-tively thin, and at the region close to turbine floor. If the ventilation barrel, floor slabs and columns above turbine floor are excluded from FEM model, the maximum rise difference of pedestal structure increases by about 24% compared with that of the whole model. It is indicated that different modeling ranges indeed affect FEM calculation result, and the structure above turbine floor in the FEM model should be included.
First-order phase transition in $1d$ Potts model with long-range interactions
Uzelac, K.; Glumac, Z.
1998-01-01
The first-order phase transition in the one-dimensional $q$-state Potts model with long-range interactions decaying with distance as $1/r^{1+\\sigma}$ has been studied by Monte Carlo numerical simulations for $0 2$. On the basis of finite-size scaling analysis of interface free energy $\\Delta F_L$, specific heat and Binder's fourth order cumulant, we obtain the first-order transition which occurs for $\\sigma$ below a threshold value $\\sigma_c(q)$.
Finite element model updating of concrete structures based on imprecise probability
Biswal, S.; Ramaswamy, A.
2017-09-01
Imprecise probability based methods are developed in this study for the parameter estimation, in finite element model updating for concrete structures, when the measurements are imprecisely defined. Bayesian analysis using Metropolis Hastings algorithm for parameter estimation is generalized to incorporate the imprecision present in the prior distribution, in the likelihood function, and in the measured responses. Three different cases are considered (i) imprecision is present in the prior distribution and in the measurements only, (ii) imprecision is present in the parameters of the finite element model and in the measurement only, and (iii) imprecision is present in the prior distribution, in the parameters of the finite element model, and in the measurements. Procedures are also developed for integrating the imprecision in the parameters of the finite element model, in the finite element software Abaqus. The proposed methods are then verified against reinforced concrete beams and prestressed concrete beams tested in our laboratory as part of this study.
High-Resolution Finite Volume Modeling of Wave Propagation in Orthotropic Poroelastic Media
Lemoine, Grady I; LeVeque, Randall J
2012-01-01
Poroelasticity theory models the dynamics of porous, fluid-saturated media. It was pioneered by Maurice Biot in the 1930s through 1960s, and has applications in several fields, including geophysics and modeling of in vivo bone. A wide variety of methods have been used to model poroelasticity, including finite difference, finite element, pseudospectral, and discontinuous Galerkin methods. In this work we use a Cartesian-grid high-resolution finite volume method to numerically solve Biot's equations in the time domain for orthotropic materials, with the stiff relaxation source term in the equations incorporated using operator splitting. This class of finite volume method has several useful properties, including the ability to use wave limiters to reduce numerical artifacts in the solution, ease of incorporating material inhomogeneities, low memory overhead, and an explicit time-stepping approach. To the authors' knowledge, this is the first use of high-resolution finite volume methods to model poroelasticity. T...
Ali, S Tabrez
2014-01-01
In this article, we present Defmod, a fully unstructured, two or three dimensional, parallel finite element code for modeling crustal deformation over time scales ranging from milliseconds to thousands of years. Defmod can simulate deformation due to all major processes that make up the earthquake/rifting cycle, in non-homogeneous media. Specifically, it can be used to model deformation due to dynamic and quasistatic processes such as co-seismic slip or dike intrusion(s), poroelastic rebound due to fluid flow and post-seismic or post-rifting viscoelastic relaxation. It can also be used to model deformation due to processes such as post-glacial rebound, hydrological (un)loading, injection and/or withdrawal of compressible or incompressible fluids from subsurface reservoirs etc. Defmod is written in Fortran 95 and uses PETSc's parallel sparse data structures and implicit solvers. Problems can be solved using (stabilized) linear triangular, quadrilateral, tetrahedral or hexahedral elements on shared or distribut...
Schroeter, Jens; Wunsch, Carl
1986-01-01
The paper studies with finite difference nonlinear circulation models the uncertainties in interesting flow properties, such as western boundary current transport, potential and kinetic energy, owing to the uncertainty in the driving surface boundary condition. The procedure is based upon nonlinear optimization methods. The same calculations permit quantitative study of the importance of new information as a function of type, region of measurement and accuracy, providing a method to study various observing strategies. Uncertainty in a model parameter, the bottom friction coefficient, is studied in conjunction with uncertain measurements. The model is free to adjust the bottom friction coefficient such that an objective function is minimized while fitting a set of data to within prescribed bounds. The relative importance of the accuracy of the knowledge about the friction coefficient with respect to various kinds of observations is then quantified, and the possible range of the friction coefficients is calculated.
Doorwar, Shashvat; Mohanty, Kishore K
2014-07-01
Immiscible displacement of viscous oil by water in a petroleum reservoir is often hydrodynamically unstable. Due to similarities between the physics of dielectric breakdown and immiscible flow in porous media, we extend the existing dielectric breakdown model to simulate viscous fingering patterns for a wide range of viscosity ratios (μ(r)). At low values of power-law index η, the system behaves like a stable Eden growth model and as the value of η is increased to unity, diffusion limited aggregation-like fractals appear. This model is compared with our two-dimensional (2D) experiments to develop a correlation between the viscosity ratio and the power index, i.e., η = 10(-5)μ(r)(0.8775). The 2D and three-dimensional (3D) simulation data appear scalable. The fingering pattern in 3D simulations at finite viscosity ratios appear qualitatively similar to the few experimental results published in the literature.
Solomon, S. C.
1980-01-01
The measurability of changes in plate driving or resistive forces associated with plate boundary earthquakes by laser rangefinding or VLBI is considered with emphasis on those aspects of plate forces that can be characterized by such measurements. Topics covered include: (1) analytic solutions for two dimensional stress diffusion in a plate following earthquake faulting on a finite fault; (2) two dimensional finite-element solutions for the global state of stress at the Earth's surface for possible plate driving forces; and (3) finite-element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting.
Finite element model of the Jefferson fracture: comparison with a cadaver model
Bozkus, Hakan; Karakas, Askin; Hancı, Murat; Uzan, Mustafa; Bozdag, Ergun; Sarıoglu, Ali
2001-01-01
This study tries to explain the reason why the Jefferson fracture is a burst fracture, using two different biomechanical models: a finite element model (FEM) and a cadaver model used to determine strain distribution in C1 during axial static compressive loading. For the FEM model, a three-dimensional model of C1 was obtained from a 29-year-old healthy human, using axial CT scans with intervals of 1.0 mm. The mesh model was composed of 8200 four-noded isoparametric tetrahedrons and 37,400 soli...
Finite Size Corrections to the Excitation Energy Transfer in a Massless Scalar Interaction Model
Maeda, N; Tobita, Y; Ishikawa, K
2016-01-01
We study the excitation energy transfer (EET) for a simple model in which a virtual massless scalar particle is exchanged between two molecules. If the time interval is finite, then the finite size effect generally appears in a transition amplitude through the regions where the wave nature of quanta remains. We calculated the transition amplitude for EET and obtained finite size corrections to the standard formula derived by using Fermi's golden rule. These corrections for the transition amplitude appear outside the resonance energy region. The estimation in a photosynthesis system indicates that the finite size correction could reduce the EET time considerably.
The representation of boundary currents in a finite element shallow water model
Düben, Peter D
2015-01-01
We evaluate the influence of local resolution, eddy viscosity, coastline structure, and boundary conditions on the numerical representation of boundary currents in a finite element shallow-water model. The use of finite element discretization methods offers a higher flexibility compared to finite difference and finite volume methods, that are mainly used in previous publications. This is true for the geometry of the coast lines and for the realization of boundary conditions. For our investigations we simulate steady separation of western boundary currents from idealized and realistic coast lines. The use of grid refinement allows a detailed investigation of boundary separation at reasonable numerical cost.
A new approach for modelling lattice energy in finite crystal domains
Bilotsky, Y.; Gasik, M.
2015-09-01
Evaluation of internal energy in a crystal lattice requires precise calculation of lattice sums. Such evaluation is a problem in the case of small (nano) particles because the traditional methods are usually effective only for infinite lattices and are adapted to certain specific potentials. In this work, a new method has been developed for calculation of lattice energy. The method is a generalisation of conventional geometric probability techniques for arbitrary fixed lattices in a finite crystal domain. In our model, the lattice energy for wide range of two- body central interaction potentials (including long-range Coulomb potential) has been constructed using absolutely convergent sums. No artificial cut-off potential or periodical extension of the domain (which usually involved for such calculations) have been made for calculation of the lattice energy under this approach. To exemplify the applications of these techniques, the energy of Coulomb potential has been plotted as the function of the domain size.
Adaptive grid finite element model of the tokamak scrapeoff layer
Energy Technology Data Exchange (ETDEWEB)
Kuprat, A.P.; Glasser, A.H. [Los Alamos National Lab., NM (United States)
1995-07-01
The authors discuss unstructured grids for application to transport in the tokamak edge SOL. They have developed a new metric with which to judge element elongation and resolution requirements. Using this method, the authors apply a standard moving finite element technique to advance the SOL equations while inserting/deleting dynamically nodes that violate an elongation criterion. In a tokamak plasma, this method achieves a more uniform accuracy, and results in highly stretched triangular finite elements, except near separatrix X-point where transport is more isotropic.
Finite difference modeling of sinking stage curved beam based on revised Vlasov equations
Institute of Scientific and Technical Information of China (English)
张磊; 朱真才; 沈刚; 曹国华
2015-01-01
For the static analysis of the sinking stage curved beam, a finite difference model was presented based on the proposed revised Vlasov equations. First, revised Vlasov equations for thin-walled curved beams with closed sections were deduced considering the shear strain on the mid-surface of the cross-section. Then, the finite difference formulation of revised Vlasov equations was implemented with the parabolic interpolation based on Taylor series. At last, the finite difference model was built by substituting geometry and boundary conditions of the sinking stage curved beam into the finite difference formulation. The validity of present work is confirmed by the published literature and ANSYS simulation results. It can be concluded that revised Vlasov equations are more accurate than the original one in the analysis of thin-walled beams with closed sections, and that present finite difference model is applicable in the evaluation of the sinking stage curved beam.
Institute of Scientific and Technical Information of China (English)
WANG Dian-Fu
2008-01-01
In terms of the Nambu-Jona-Lasinio mechanism, dynamical breaking of gauge symmetry for the maximally generalized Yang-Mills model is investigated. The gauge symmetry behavior at finite temperature is also investigated and it is shown that the gauge symmetry broken dynamically at zero temperature can be restored at finite temperatures.
Market segment derivation and profiling via a finite mixture model framework
Wedel, M; Desarbo, WS
2002-01-01
The Marketing literature has shown how difficult it is to profile market segments derived with finite mixture models. especially using traditional descriptor variables (e.g., demographics). Such profiling is critical for the proper implementation of segmentation strategy. we propose a new finite mix
3D GEOMETRIC MODELING AND FINITE ELEMENT ANALYSIS OF “TURBO-COOLER” SUBASSEMBLY
Directory of Open Access Journals (Sweden)
EFTIMIE Dorin
2013-06-01
Full Text Available 3D design of turbo-cooler subassembly can be optimized by using finite element analysis software NX 7.5. Finite element analysis results are useful for 3D design of this unit. Results can be easily implemented in 3D design in order to optain optimal virtual model that meets the requirements imposed.
Quantitative Validation of a Human Body Finite Element Model Using Rigid Body Impacts.
Vavalle, Nicholas A; Davis, Matthew L; Stitzel, Joel D; Gayzik, F Scott
2015-09-01
Validation is a critical step in finite element model (FEM) development. This study focuses on the validation of the Global Human Body Models Consortium full body average male occupant FEM in five localized loading regimes-a chest impact, a shoulder impact, a thoracoabdominal impact, an abdominal impact, and a pelvic impact. Force and deflection outputs from the model were compared to experimental traces and corridors scaled to the 50th percentile male. Predicted fractures and injury severity measures were compared to evaluate the model's injury prediction capabilities. The methods of ISO/TS 18571 were used to quantitatively assess the fit of model outputs to experimental force and deflection traces. The model produced peak chest, shoulder, thoracoabdominal, abdominal, and pelvis forces of 4.8, 3.3, 4.5, 5.1, and 13.0 kN compared to 4.3, 3.2, 4.0, 4.0, and 10.3 kN in the experiments, respectively. The model predicted rib and pelvic fractures related to Abbreviated Injury Scale scores within the ranges found experimentally all cases except the abdominal impact. ISO/TS 18571 scores for the impacts studied had a mean score of 0.73 with a range of 0.57-0.83. Well-validated FEMs are important tools used by engineers in advancing occupant safety.
Finite Element Model of the Knee for Investigation of Injury Mechanisms: Development and Validation
Kiapour, Ali; Kiapour, Ata M.; Kaul, Vikas; Quatman, Carmen E.; Wordeman, Samuel C.; Hewett, Timothy E.; Demetropoulos, Constantine K.; Goel, Vijay K.
2014-01-01
Multiple computational models have been developed to study knee biomechanics. However, the majority of these models are mainly validated against a limited range of loading conditions and/or do not include sufficient details of the critical anatomical structures within the joint. Due to the multifactorial dynamic nature of knee injuries, anatomic finite element (FE) models validated against multiple factors under a broad range of loading conditions are necessary. This study presents a validated FE model of the lower extremity with an anatomically accurate representation of the knee joint. The model was validated against tibiofemoral kinematics, ligaments strain/force, and articular cartilage pressure data measured directly from static, quasi-static, and dynamic cadaveric experiments. Strong correlations were observed between model predictions and experimental data (r > 0.8 and p knee joint as well as the complex, nonuniform stress and strain fields that occur in biological soft tissue. Such a model will facilitate the in-depth understanding of a multitude of potential knee injury mechanisms with special emphasis on ACL injury. PMID:24763546
Indahlastari, Aprinda; Chauhan, Munish; Schwartz, Benjamin; Sadleir, Rosalind J.
2016-12-01
Objective. In this study, we determined efficient head model sizes relative to predicted current densities in transcranial direct current stimulation (tDCS). Approach. Efficiency measures were defined based on a finite element (FE) simulations performed using nine human head models derived from a single MRI data set, having extents varying from 60%-100% of the original axial range. Eleven tissue types, including anisotropic white matter, and three electrode montages (T7-T8, F3-right supraorbital, Cz-Oz) were used in the models. Main results. Reducing head volume extent from 100% to 60%, that is, varying the model’s axial range from between the apex and C3 vertebra to one encompassing only apex to the superior cerebellum, was found to decrease the total modeling time by up to half. Differences between current density predictions in each model were quantified by using a relative difference measure (RDM). Our simulation results showed that {RDM} was the least affected (a maximum of 10% error) for head volumes modeled from the apex to the base of the skull (60%-75% volume). Significance. This finding suggested that the bone could act as a bioelectricity boundary and thus performing FE simulations of tDCS on the human head with models extending beyond the inferior skull may not be necessary in most cases to obtain reasonable precision in current density results.
van de Walle, Axel; Rouleau, Lucie; Deckers, Elke; Desmet, Wim
2015-01-01
In many engineering applications, viscoelastic treatments are used to suppress vibrations of lightly damped structures. Computational methods provide powerful tools for the design and analysis of these structures. The most commonly used method to model the dynamics of complex structures is the finite element method. Its use, however, often results in very large and computationally demanding models, especially when viscoelastic material behaviour has to be taken into account. To alleviate this...
Liao, F; Huang, Z.
2015-01-01
Open Access funded by Engineering and Physical Sciences Research Council under a Creative Commons license. A robust finite element procedure for modelling the localised fracture of reinforced concrete beams at elevated temperatures is developed. In this model a reinforced concrete beam is represented as an assembly of 4-node quadrilateral plain concrete, 3-node main reinforcing steel bar, and 2-node bond-link elements. The concrete element is subdivided into layers for considering the temp...
Micromechanical Failure Analyses for Finite Element Polymer Modeling
Energy Technology Data Exchange (ETDEWEB)
CHAMBERS,ROBERT S.; REEDY JR.,EARL DAVID; LO,CHI S.; ADOLF,DOUGLAS B.; GUESS,TOMMY R.
2000-11-01
Polymer stresses around sharp corners and in constrained geometries of encapsulated components can generate cracks leading to system failures. Often, analysts use maximum stresses as a qualitative indicator for evaluating the strength of encapsulated component designs. Although this approach has been useful for making relative comparisons screening prospective design changes, it has not been tied quantitatively to failure. Accurate failure models are needed for analyses to predict whether encapsulated components meet life cycle requirements. With Sandia's recently developed nonlinear viscoelastic polymer models, it has been possible to examine more accurately the local stress-strain distributions in zones of likely failure initiation looking for physically based failure mechanisms and continuum metrics that correlate with the cohesive failure event. This study has identified significant differences between rubbery and glassy failure mechanisms that suggest reasonable alternatives for cohesive failure criteria and metrics. Rubbery failure seems best characterized by the mechanisms of finite extensibility and appears to correlate with maximum strain predictions. Glassy failure, however, seems driven by cavitation and correlates with the maximum hydrostatic tension. Using these metrics, two three-point bending geometries were tested and analyzed under variable loading rates, different temperatures and comparable mesh resolution (i.e., accuracy) to make quantitative failure predictions. The resulting predictions and observations agreed well suggesting the need for additional research. In a separate, additional study, the asymptotically singular stress state found at the tip of a rigid, square inclusion embedded within a thin, linear elastic disk was determined for uniform cooling. The singular stress field is characterized by a single stress intensity factor K{sub a} and the applicable K{sub a} calibration relationship has been determined for both fully bonded and
Chatelain, Christophe
2014-03-01
The q-state Potts model with long-range correlated disorder is studied by means of large-scale Monte Carlo simulations for q=2, 4, 8, and 16. Evidence is given of the existence of a Griffiths phase, where the thermodynamic quantities display an algebraic finite-size scaling, in a finite range of temperatures. The critical exponents are shown to depend on both the temperature and the exponent of the algebraic decay of disorder correlations, but not on the number of states of the Potts model. The mechanism leading to the violation of hyperscaling relations is observed in the entire Griffiths phase.
An implicit discontinuous Galerkin finite element model for water waves
van der Vegt, Jacobus J.W.; Ambati, V.R.; Bokhove, Onno
2005-01-01
We discuss a new higher order accurate discontinuous Galerkin finite element method for non-linear free surface gravity waves. The algorithm is based on an arbitrary Lagrangian Eulerian description of the flow field using deforming elements and a moving mesh, which makes it possible to represent
An Eulerean finite element model for penetration in layered soil
Berg, van den Peter; Borst, de Rene; Huetink, Han
1996-01-01
An Eulerean large-strain finite element formulation is presented to simulate static soil penetration. The method is an extension of the Updated Lagrangean description to an Eulerean formulation taking into account convection of deformation-history-dependent properties as well as material properties.
Mathematical modeling of interdigitated electrode arrays in finite electrochemical cells
Guajardo, Cristian; Surareungchai, Werasak
2016-01-01
Accurate theoretical results for interdigitated array of electrodes (IDAE) in semi-infinite cells can be found in the literature. However, these results are not always applicable when using finite cells. In this study, theoretical expressions for IDAE in a finite geometry cell are presented. At known current density, transient and steady state concentration profiles were obtained as well as the response time to a current step. Concerning the diffusion limited current, a lower bound was derived from the concentration profile and an upper bound was obtained from the limiting current of the semi-infinite case. The lower bound, which is valid when Kirchhoff's current law applies to the unit cell, can be useful to ensure a minimum current level during the design of the electrochemical cell. Finally, a criterion was developed defining when the behaviors of finite and semi-infinite cells are comparable. This allows to obtain higher current levels in finite cells, approaching that of the semi-infinite case. Examples ...
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
With the consideration of slip deformation mechanism and various slip systems of body centered cubic (BCC) metals,Taylor-type and finite element polycrystai models were embedded into the commercial finite element code ABAQUS to realize crystal plasticity finte element modeling,based on the rate dependent crystal constitutive equations.Initial orientations measured by electron backscatter diffraction (EBSD) were directly input into the crystal plasticity finite element model to simulate the development of rolling texture of interstitial-flee steel (IF steel) at various reductions.The modeled results show a good agreement with the experimental results.With increasing reduction,the predicted and experimental rolling textures tend to sharper,and the results simulated by the Taylor-type model are stronger than those simulated by finite element model.Conclusions are obtained that rolling textures calculated with 48 {110}+{ 112}+{123} slip systems are more approximate to EBSD results.
Holographic zero sound at finite temperature in the Sakai-Sugimoto model
DiNunno, Brandon S; Jokela, Niko; Pedraza, Juan F
2014-01-01
In this paper, we study the fate of the holographic zero sound mode at finite temperature and non-zero baryon density in the deconfined phase of the Sakai-Sugimoto model of holographic QCD. We establish the existence of such a mode for a wide range of temperatures and investigate the dispersion relation, quasi-normal modes, and spectral functions of the collective excitations in four different regimes, namely, the collisionless quantum, collisionless thermal, and hydrodynamic regimes, as well as an intermediate crossover between the latter two. For sufficiently high temperatures, the zero sound completely disappears, and the physics is dominated by an emergent diffusive mode. We compare our findings to Landau-Fermi liquid theory and to other holographic models.
The square lattice Ising model on the rectangle I: Finite systems
Hucht, Alfred
2016-01-01
The partition function of the square lattice Ising model on the rectangle is calculated exactly for arbitrary system size $L\\times M$ and temperature. We start with the dimer method of Kasteleyn, McCoy & Wu, construct a highly symmetric block transfer matrix and derive a factorization of the involved determinant, effectively decomposing the free energy into two parts, $F(L,M)=F_{\\infty}^{\\leftrightarrow}(L,M)+F_\\mathrm{res}^{\\leftrightarrow}(L,M)$. The residual part $F_\\mathrm{res}^{\\leftrightarrow}(L,M)$ contains the nontrivial finite-size contributions and becomes exponentially small for large $L/M$ and off-critical temperatures. It is given by the determinant of a $\\frac{M}{2}\\times\\frac{M}{2}$ matrix and can be mapped onto an effective spin model with $M$ spins and long-range interactions. The relations to the Casimir potential and the Casimir force scaling functions are discussed.
Finite nuclei in relativistic models with a light chiral scalar meson
Furnstahl, R. J.; Serot, Brian D.
1993-05-01
Relativistic chiral models with a light scalar meson appear to provide an economical marriage of successful relativistic mean-field theories and chiral symmetry. The scalar meson serves as both the chiral partner of the pion and the mediator of the intermediate-range nucleon-nucleon (NN) attraction. However, while some of these models can reproduce the empirical nuclear matter saturation point, they fail to reproduce observed properties of finite nuclei, such as spin-orbit splittings, shell structure, charge densities, and surface energetics. These deficiencies imply that this realization of chiral symmetry is incorrect. An alternative scenario, which features a heavy chiral scalar and dynamical generation of the NN attraction, is discussed.
An Integrated Magnetic Circuit Model and Finite Element Model Approach to Magnetic Bearing Design
Provenza, Andrew J.; Kenny, Andrew; Palazzolo, Alan B.
2003-01-01
A code for designing magnetic bearings is described. The code generates curves from magnetic circuit equations relating important bearing performance parameters. Bearing parameters selected from the curves by a designer to meet the requirements of a particular application are input directly by the code into a three-dimensional finite element analysis preprocessor. This means that a three-dimensional computer model of the bearing being developed is immediately available for viewing. The finite element model solution can be used to show areas of magnetic saturation and make more accurate predictions of the bearing load capacity, current stiffness, position stiffness, and inductance than the magnetic circuit equations did at the start of the design process. In summary, the code combines one-dimensional and three-dimensional modeling methods for designing magnetic bearings.
Directory of Open Access Journals (Sweden)
Bin Wang
2016-01-01
Full Text Available This paper studies the application of frequency distributed model for finite time control of a fractional order nonlinear hydroturbine governing system (HGS. Firstly, the mathematical model of HGS with external random disturbances is introduced. Secondly, a novel terminal sliding surface is proposed and its stability to origin is proved based on the frequency distributed model and Lyapunov stability theory. Furthermore, based on finite time stability and sliding mode control theory, a robust control law to ensure the occurrence of the sliding motion in a finite time is designed for stabilization of the fractional order HGS. Finally, simulation results show the effectiveness and robustness of the proposed scheme.
Shear-flexible finite-element models of laminated composite plates and shells
Noor, A. K.; Mathers, M. D.
1975-01-01
Several finite-element models are applied to the linear static, stability, and vibration analysis of laminated composite plates and shells. The study is based on linear shallow-shell theory, with the effects of shear deformation, anisotropic material behavior, and bending-extensional coupling included. Both stiffness (displacement) and mixed finite-element models are considered. Discussion is focused on the effects of shear deformation and anisotropic material behavior on the accuracy and convergence of different finite-element models. Numerical studies are presented which show the effects of increasing the order of the approximating polynomials, adding internal degrees of freedom, and using derivatives of generalized displacements as nodal parameters.
Hashemi-Kia, M.; Toossi, M.
1990-01-01
As a result of this work, a reduction procedure has been developed which can be applied to large finite element model of airframe type structures. This procedure, which is tailored to be used with MSC/NASTRAN finite element code, is applied to the full airframe dynamic finite element model of AH-64A Attack Helicopter. The applicability of the resulting reduced model to parametric and optimization studies is examined. Through application of the design sensitivity analysis, the viability and efficiency of this reduction technique has been demonstrated in a vibration reduction study.
Research on dynamic model of printed circuit board based on finite element method
Wei, Hui; Xu, Liangjun
2017-08-01
The vibration characteristics of printed circuit boards are related to the reliability of electronic components installed on their surface. Finite element software is a powerful tool to analyze the vibration characteristics of printed circuit boards, and the correct establishment of finite element model is very important. In this paper, the dynamic model of anisotropic printed circuit board is established by analyzing the material properties of printed circuit board. The influence of boundary condition and lumped mass on the vibration characteristics of printed circuit board is analyzed. In order to establish a more realistic printed circuit The finite element model of the plate provides the necessary basis.
A FINITE ELEMENT MODEL FOR NUMERICAL SIMULATION OF THERMO-MECHANICAL FRICTIONAL CONTACT PROBLEMS
Institute of Scientific and Technical Information of China (English)
张洪武; 韩炜; 陈金涛; 段庆林
2003-01-01
Two kinds of variational principles for numerical simulation of heat transfer and contact analyses are respectively presented. A finite element model for numerical simulation of the thermal contact problems is developed with a pressure dependent heat transfer constitutive model across the contact surface. The numerical algorithm for the finite element analysis of the thermomechanical contact problems is thus developed. Numerical examples are computed and the results demonstrate the validity of the model and algorithm developed.
Finite element model of magnetoconvection of a ferrofluid
Snyder, Suzanne M.; Cader, Tahir; Finlayson, Bruce A.
2003-06-01
Combined natural and magnetic convective heat transfer through a ferrofluid in a cubic enclosure is simulated numerically. The momentum equation includes a magnetic term that arises when a magnetic fluid is in the presence of a magnetic field gradient and a temperature gradient. In order to validate the theory, the wall temperature isotherms and Nusselt numbers are compared to experimental work of Sawada et al. (Int. J. Appl. Electromagn. Mater. 4 (1994) 329). Results are obtained using standard computational fluid dynamics codes, with modifications to account for the Langevin factor when needed. The CFD code FIDAP uses the finite element method, sometimes with a user-defined subroutine. The CFD code FEMLAB uses the finite element method with a user-supplied body force.
The quantum Ising model: finite sums and hyperbolic functions
Damski, Bogdan
2015-10-01
We derive exact closed-form expressions for several sums leading to hyperbolic functions and discuss their applicability for studies of finite-size Ising spin chains. We show how they immediately lead to closed-form expressions for both fidelity susceptibility characterizing the quantum critical point and the coefficients of the counterdiabatic Hamiltonian enabling arbitrarily quick adiabatic driving of the system. Our results generalize and extend the sums presented in the popular Gradshteyn and Ryzhik Table of Integrals, Series, and Products.
The quantum Ising model: finite sums and hyperbolic functions
Bogdan Damski
2015-01-01
We derive exact closed-form expressions for several sums leading to hyperbolic functions and discuss their applicability for studies of finite-size Ising spin chains. We show how they immediately lead to closed-form expressions for both fidelity susceptibility characterizing the quantum critical point and the coefficients of the counterdiabatic Hamiltonian enabling arbitrarily quick adiabatic driving of the system. Our results generalize and extend the sums presented in the popular Gradshteyn...
A model study on a pair of trapped particles interacting with an arbitrary effective range
Goswami, Partha
2016-01-01
We study the effects of the effective range of interaction on the eigenvalues and eigenstates of two particles confined in a three-dimensional (3D) isotropic as well as one- or quasi-one dimensional harmonic (1D) traps. For this we employ model potentials which mimic finite-range s-wave interactions over a wide range of s-wave scattering length $a_s$ including the unitarity limits $a_s \\rightarrow \\pm\\infty$. Our results show that when the range is larger than the 3D or 1D harmonic oscillator length scale, the eigenvalues and eigenstates are nearly similar to those of noninteracting two particles in the 3D or 1D trap, respectively. In case of 3D, we find that when the range goes to zero, the results of contact potential as derived by Busch {\\it et al.} [Foundations of Physics, {\\bf28}, 549 (1998)] are reproduced. However, in the case of 1D, such reproducibility does not occur as the range goes to zero. We have calculated the eigenvalues and eigenstates in 1D harmonic trap taking one-dimensional finite- range ...
On the representability of complete genomes by multiple competing finite-context (Markov models.
Directory of Open Access Journals (Sweden)
Armando J Pinho
Full Text Available A finite-context (Markov model of order k yields the probability distribution of the next symbol in a sequence of symbols, given the recent past up to depth k. Markov modeling has long been applied to DNA sequences, for example to find gene-coding regions. With the first studies came the discovery that DNA sequences are non-stationary: distinct regions require distinct model orders. Since then, Markov and hidden Markov models have been extensively used to describe the gene structure of prokaryotes and eukaryotes. However, to our knowledge, a comprehensive study about the potential of Markov models to describe complete genomes is still lacking. We address this gap in this paper. Our approach relies on (i multiple competing Markov models of different orders (ii careful programming techniques that allow orders as large as sixteen (iii adequate inverted repeat handling (iv probability estimates suited to the wide range of context depths used. To measure how well a model fits the data at a particular position in the sequence we use the negative logarithm of the probability estimate at that position. The measure yields information profiles of the sequence, which are of independent interest. The average over the entire sequence, which amounts to the average number of bits per base needed to describe the sequence, is used as a global performance measure. Our main conclusion is that, from the probabilistic or information theoretic point of view and according to this performance measure, multiple competing Markov models explain entire genomes almost as well or even better than state-of-the-art DNA compression methods, such as XM, which rely on very different statistical models. This is surprising, because Markov models are local (short-range, contrasting with the statistical models underlying other methods, where the extensive data repetitions in DNA sequences is explored, and therefore have a non-local character.
Short-Range Correlation Models in Electronic Structure Theory
Goldey, Matthew Bryant
fraction of MP2/CBS computational cost. Second, attenuated MP2 is developed within the larger aug-cc-pVTZ (aTZ) basis set for inter- and intramolecular non-bonded interactions. A single attenuation parameter is optimized on the S66 database of 66 intermolecular interactions, leading to a very large RMS error reduction by a factor of greater than 5 relative to standard MP2/aTZ. Attenuation introduces an error of opposite sign to basis set superposition error (BSSE) and overestimation of dispersion interactions in finite basis MP2. A variety of tests including the S22 set, conformer energies of peptides, alkanes, sugars, sulfate-water clusters, and the coronene dimer establish the transferability of the MP2(terfc, aTZ) model to other inter and intra-molecular interactions. Direct comparisons against attenuation in the smaller aug-cc-pVDZ basis shows that MP2(terfc, aTZ) often significantly outperforms MP2(terfc, aDZ), although at higher computational cost. MP2(terfc, aDZ) and MP2(terfc, aTZ) often outperform MP2 at the complete basis set limit. Comparison of the two attenuated MP2 models against each other and against attenuation using non-augmented basis sets gives insight into the error cancellation responsible for their remarkable success. Third, I present an improved algorithm for single-node multi-threaded computation of the correlation energy using resolution of the identity second-order Moller-Plesset perturbation theory (RI-MP2). This algorithm is based on shared memory parallelization of the rate-limiting steps and an overall reduction in the number of disk reads. The requisite fifth-order computation in RI-MP2 calculations is efficiently parallelized within this algorithm, with improvements in overall parallel efficiency as the system size increases. Fourth-order steps are also parallelized. As an application, I present energies and timings for several large, noncovalently interacting systems with this algorithm, and demonstrate that the RI-MP2 cost is still
Melis, Matthew E.
1990-01-01
COMGEN (Composite Model Generator) is an interactive FORTRAN program which can be used to create a wide variety of finite element models of continuous fiber composite materials at the micro level. It quickly generates batch or session files to be submitted to the finite element pre- and postprocessor PATRAN based on a few simple user inputs such as fiber diameter and percent fiber volume fraction of the composite to be analyzed. In addition, various mesh densities, boundary conditions, and loads can be assigned easily to the models within COMGEN. PATRAN uses a session file to generate finite element models and their associated loads which can then be translated to virtually any finite element analysis code such as NASTRAN or MARC.
Finite Temperature CPT-even Electrodynamics of the Standard Model Extension
Casana, Rodolfo; Rodrigues, Josberg S; Silva, Madson R O
2009-01-01
In this work, we examine the finite temperature properties of the non-birefringent coefficients of the CPT-even and Lorentz-invariance-violating (LIV) electrodynamics of the standard model extension, represented by the term $W_{\\alpha \
Finite Lattice Hamiltonian Computations in the P-Representation the Schwinger Model
Aroca, J M; Alvarez-Campot, G; Alvarez-Campot, Gonzalo
1999-01-01
The Schwinger model is studied in a finite lattice by means of the P-representation. The vacuum energy, mass gap and chiral condensate are evaluated showing good agreement with the expected values in the continuum limit.
Finite Lattice Hamiltonian Computations in the P-Representation: the Schwinger Model
1997-01-01
The Schwinger model is studied in a finite lattice by means of the P-representation. The vacuum energy, mass gap and chiral condensate are evaluated showing good agreement with the expected values in the continuum limit.
FINITE ELEMENT ANALYSIS OF CONCRETE BASED ON TWO SURFACE ELASTOPLASTIC MODEL
Institute of Scientific and Technical Information of China (English)
冯继玲; 王世文
1997-01-01
This paper presents finite element formulas based on two surface elastoplastic yielding model. The study also discusses the numerical procedures and develops the corresponding software. These formulas have provided accurate elastoplastic method for analysing concrete, rock and soil like materials.
The model companion of the class of pseudocomplemented semilattices is finitely axiomatizable
Adler, Joël
2012-01-01
In this paper it is shown that the class $\\mathcal{PCSL}^{ec}$ of existentially closed pseudocomplemented semilattices is finitely axiomatizable by appropriately extending the finite axiomatization of the class $\\mathcal{\\mathcal{PCSL}}^{ac}$ of algebraically closed pseudocomplemented semilattices presented in Rupp, Addler, and Schmid. Because $\\mathcal{PCSL}^{ec}$ coincides with the model companion of the class $\\mathcal{PCSL}$ of pseudocomplemented semilattices this addendum to Rupp, Addler, and Schmid solves the problem posed by Albert and Burris in the final paragraph of their paper: "Does the class of pseudocomplemented semilattices have a finitely axiomatizable model companion?"
Modeling of diffusion with partitioning in stratum corneum using a finite element model.
Barbero, Ana M; Frasch, H F
2005-09-01
Partitioning and diffusion of chemicals in skin is of interest to researchers in areas such as transdermal penetration and drug disposition, either for risk assessment or transdermal delivery. In this study a finite element method is used to model diffusion in the skin's outermost layer, the stratum corneum (SC). The SC is considered to be a finite two-dimensional composite having different diffusivity values in each medium as well as a partition coefficient at the interfaces between media. A commercial finite element package with thermal analysis capabilities is selected due to the flexibility of this software to handle irregular geometries. Partitioning is accommodated through a change of variables technique. This technique is validated by comparison of model results with analytical solutions of steady-state flux, transient concentration profiles, and time lag for diffusion in laminates. Two applications are presented. Diffusion is solved in a two-dimensional "brick and mortar" geometry that is a simplification of human stratum corneum, with a partition coefficient between corneocyte and lipid. Results are compared to the diffusion in multiple laminates to examine effects of the partition coefficient. The second application is the modeling of diffusion with partitioning through an irregular geometry which is obtained from a micrograph of hairless mouse stratum corneum.
A Computational Approach for Automated Posturing of a Human Finite Element Model
2016-07-01
following: obtaining source geometries in the posture being tested, a so- called posturing “by hand” where geometries are moved to what “looks correct ...ARL-MR-0934• JULY 2016 US Army Research Laboratory A Computational Approach for Automated Posturing of a Human Finite ElementModel by Justin McKee...Automated Posturing of a Human Finite ElementModel by Justin McKee Bennett Aerospace, Inc., Cary, NC Adam Sokolow Weapons and Materials Research
Energy Technology Data Exchange (ETDEWEB)
Patra, Anirban [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wen, Wei [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Martinez Saez, Enrique [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Tome, Carlos [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-31
This report describes the implementation of a crystal plasticity framework (VPSC) for irradiation hardening and plastic deformation in the finite element code, MOOSE. Constitutive models for irradiation hardening and the crystal plasticity framework are described in a previous report [1]. Here we describe these models briefly and then describe an algorithm for interfacing VPSC with finite elements. Example applications of tensile deformation of a dog bone specimen and a 3D pre-irradiated bar specimen performed using MOOSE are demonstrated.
FINITE ELEMENT METHOD AS A BASIS FOR THE MODELING OF ROAD SURFACE STRESS-STRAIN STATE
2011-01-01
Problem statement. Despite the fact that rigid roads with asphalt concrete pavement widespread,their design and calculation provide for approximate data with some number of hidden factors. Thepresent paper proposes to use finite element method to model stress-strain state of rigid roads withasphalt concrete pavement.Results. The use of the finite element method enables one to construct the precise model ofstress-strain state of road pavement. The calculations performed on the basis of the mod...
Finite Size Corrected Relativistic Mean-Field Model and QCD Critical End Point
Uddin, Saeed; Ahmad, Jan Shabir
2012-01-01
The effect of finite size of hadrons on the QCD phase diagram is analyzed using relativistic mean field model for the hadronic phase and the Bag model for the QGP phase. The corrections to the EOS for hadronic phase are incorporated in a thermodynamic consistent manner for Van der Waals like interaction. It is found that the effect of finite size of baryons is to shift CEP to higher chemical potential values.
Development and Full Body Validation of a 5th Percentile Female Finite Element Model.
Davis, Matthew L; Koya, Bharath; Schap, Jeremy M; Gayzik, F Scott
2016-11-01
To mitigate the societal impact of vehicle crash, researchers are using a variety of tools, including finite element models (FEMs). As part of the Global Human Body Models Consortium (GHBMC) project, comprehensive medical image and anthropometrical data of the 5th percentile female (F05) were acquired for the explicit purpose of FEM development. The F05-O (occupant) FEM model consists of 981 parts, 2.6 million elements, 1.4 million nodes, and has a mass of 51.1 kg. The model was compared to experimental data in 10 validation cases ranging from localized rigid hub impacts to full body sled cases. In order to make direct comparisons to experimental data, which represent the mass of an average male, the model was compared to experimental corridors using two methods: 1) post-hoc scaling the outputs from the baseline F05-O model and 2) geometrically morphing the model to the body habitus of the average male to allow direct comparisons. This second step required running the morphed full body model in all 10 simulations for a total of 20 full body simulations presented. Overall, geometrically morphing the model was found to more closely match the target data with an average ISO score for the rigid impacts of 0.76 compared to 0.67 for the scaled responses. Based on these data, the morphed model was then used for model validation in the vehicle sled cases. Overall, the morphed model attained an average weighted score of 0.69 for the two sled impacts. Hard tissue injuries were also assessed and the baseline F05-O model was found to predict a greater occurrence of pelvic fractures compared to the GHBMC average male model, but predicted fewer rib fractures.
Directory of Open Access Journals (Sweden)
Ibrahim Dauda Muhammad
2015-01-01
Full Text Available The single-walled zirconia nanotube is structurally modeled and its Young’s modulus is valued by using the finite element approach. The nanotube was assumed to be a frame-like structure with bonds between atoms regarded as beam elements. The properties of the beam required for input into the finite element analysis were computed by connecting energy equivalence between molecular and continuum mechanics. Simulation was conducted by applying axial tensile strain on one end of the nanotube while the other end was fixed and the corresponding reaction force recorded to compute Young’s modulus. It was found out that Young’s modulus of zirconia nanotubes is significantly affected by some geometrical parameters such as chirality, diameter, thickness, and length. The obtained values of Young’s modulus for a certain range of diameters are in agreement with what was obtained in the few experiments that have been conducted so far. This study was conducted on the cubic phase of zirconia having armchair and zigzag configuration. The optimal diameter and thickness were obtained, which will assist in designing and fabricating bulk nanostructured components containing zirconia nanotubes for various applications.
Finite size scaling analysis on Nagel-Schreckenberg model for traffic flow
Balouchi, Ashkan; Browne, Dana
2015-03-01
The traffic flow problem as a many-particle non-equilibrium system has caught the interest of physicists for decades. Understanding the traffic flow properties and though obtaining the ability to control the transition from the free-flow phase to the jammed phase plays a critical role in the future world of urging self-driven cars technology. We have studied phase transitions in one-lane traffic flow through the mean velocity, distributions of car spacing, dynamic susceptibility and jam persistence -as candidates for an order parameter- using the Nagel-Schreckenberg model to simulate traffic flow. The length dependent transition has been observed for a range of maximum velocities greater than a certain value. Finite size scaling analysis indicates power-law scaling of these quantities at the onset of the jammed phase.
Chen, Yu-Yi; Juang, Jia-Yang
2016-07-01
The standard collinear four-point probe method is an indispensable tool and has been extensively used for characterizing conductive thin films with homogeneous and isotropic electrical properties. In this paper, we conduct three-dimensional (3D) finite element simulations on conductive multilayer films to study the relationship between the reading of the four-point probe and the conductivity of the individual layers. We find that a multilayer film may be modeled as a simple equivalent circuit with multiple resistances, connected in parallel for a wide range of resistivity and thickness ratios, as long as its total thickness is smaller than approximately half of the probe spacing. As a result, we may determine the resistivity of each layer sequentially by applying the four-point probe, with the original correction factor π/ln(2), after deposition of each layer.
Finite Element Modelling Full Vehicle Side Impact with Ultrahigh Strength Hot Stamped Steels
Taylor, T.; Fourlaris, G.; Cafolla, J.
2016-10-01
"Hot stamped boron steel" 22MnB5 has been imperative in meeting the automotive industry's demand for materials exhibiting higher tensile strength in the final component. In this paper, the crash performance of three experimental grades developed for automotive hot stamping technologies, exhibiting wider tensile property ranges than 22MnB5, was validated by finite element modelling full vehicle side impact with the experimental material data applied to the B-pillar reinforcement. The superior anti-intrusive crash performance of grade 38MnB5 was demonstrated, with 11 mm less intrusion of the B-pillar reinforcement compared to 22MnB5. Moreover, the superior "impact-energy absorptive" crash performance of grade 15MnCr5 was demonstrated, with 0.15 kJ greater impact-energy absorption by the B-pillar reinforcement compared to 22MnB5.
Finite size effects on the phase diagram of the thermodynamical cluster model
Mallik, S; Chaudhuri, G
2016-01-01
The thermodynamical cluster model is known to present a first-order liquid-gas phase transition in the idealized case of an uncharged, infinitely extended medium. However, in most practical applications of this model, the system is finite and charged. In this paper we study how the phase diagram is modified by finite size and Coulomb effects. We show that the thermodynamic anomalies which are associated to the finite system counterpart of first order phase transitions, are correctly reproduced by this effective model. However, approximations in the calculation of the grandcanonical partition sum prevent obtaining the exact mapping between statistical ensembles which should be associated to finite systems. The ensemble inequivalence associated to the transition persists in the presence of Coulomb, but the phase diagram is deeply modified with respect to the simple liquid-gas phase transition characteristic of the neutral system.
Approximate solution for frequency synchronization in a finite-size Kuramoto model.
Wang, Chengwei; Rubido, Nicolás; Grebogi, Celso; Baptista, Murilo S
2015-12-01
Scientists have been considering the Kuramoto model to understand the mechanism behind the appearance of collective behavior, such as frequency synchronization (FS) as a paradigm, in real-world networks with a finite number of oscillators. A major current challenge is to obtain an analytical solution for the phase angles. Here, we provide an approximate analytical solution for this problem by deriving a master solution for the finite-size Kuramoto model, with arbitrary finite-variance distribution of the natural frequencies of the oscillators. The master solution embodies all particular solutions of the finite-size Kuramoto model for any frequency distribution and coupling strength larger than the critical one. Furthermore, we present a criterion to determine the stability of the FS solution. This allows one to analytically infer the relationship between the physical parameters and the stable behavior of networks.
Dynamic test and finite element model updating of bridge structures based on ambient vibration
Institute of Scientific and Technical Information of China (English)
2008-01-01
The dynamic characteristics of bridge structures are the basis of structural dynamic response and seismic analysis,and are also an important target of health condition monitoring.In this paper,a three-dimensional finite-element model is first established for a highway bridge over a railroad on No.312 National Highway.Based on design drawings,the dynamic characteristics of the bridge are studied using finite element analysis and ambient vibration measurements.Thus,a set of data is selected based on sensitivity analysis and optimization theory;the finite element model of the bridge is updated.The numerical and experimental results show that the updated method is more simple and effective,the updated finite element model can reflect the dynamic characteristics of the bridge better,and it can be used to predict the dynamic response under complex external forces.It is also helpful for further damage identification and health condition monitoring.
Finite Nuclei in the Quark-Meson Coupling (QMC) Model
Stone, J R; Reinhard, P G; Thomas, A W
2016-01-01
We report the first use of the effective QMC energy density functional (EDF), derived from a quark model of hadron structure, to study a broad range of ground state properties of even-even nuclei across the periodic table in the non-relativistic Hartree-Fock+BCS framework. The novelty of the QMC model is that the nuclear medium effects are treated through modification of the internal structure of the nucleon. The density dependence is microscopically derived and the spin-orbit term arises naturally. The QMC EDF depends on a single set of four adjustable parameters having clear physical basis. When applied to diverse ground state data the QMC EDF already produces, in its present simple form, overall agreement with experiment of a quality comparable to a representative Skyrme EDF. There exist however multiple Skyrme paramater sets, frequently tailored to describe selected nuclear phenomena. The QMC EDF parameter set is not open to such variation, chosen set being applied, without adjustment, to both the propert...
Finite element model analysis of thermal failure in connector
Institute of Scientific and Technical Information of China (English)
WANG Xin; XU Liang-jun
2007-01-01
Thermal analysis and thermal diagnose are important for small power connector especially in electronic devices since their structure is usually compact. In this paper thermal behavior of small power connector was investigated. It was found that the contact resistance increased due to the Joule heating, and that increased contact resistance produced more Joule heating; this mutual action causes the connector to lose efficiency. The thermal distribution in the connector was analyzed using finite element method (FEM). The failure mechanism is discussed. It provides basis for improving the structure. The conclusion was verified by experimental results.
A finite Zitterbewegung model for relativistic quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Noyes, H.P.
1990-02-19
Starting from steps of length h/mc and time intervals h/mc{sup 2}, which imply a quasi-local Zitterbewegung with velocity steps {plus minus}c, we employ discrimination between bit-strings of finite length to construct a necessary 3+1 dimensional event-space for relativistic quantum mechanics. By using the combinatorial hierarchy to label the strings, we provide a successful start on constructing the coupling constants and mass ratios implied by the scheme. Agreement with experiments is surprisingly accurate. 22 refs., 1 fig.
Finite Element Modeling Techniques for Analysis of VIIP
Feola, Andrew J.; Raykin, J.; Gleason, R.; Mulugeta, Lealem; Myers, Jerry G.; Nelson, Emily S.; Samuels, Brian C.; Ethier, C. Ross
2015-01-01
Visual Impairment and Intracranial Pressure (VIIP) syndrome is a major health concern for long-duration space missions. Currently, it is thought that a cephalad fluid shift in microgravity causes elevated intracranial pressure (ICP) that is transmitted along the optic nerve sheath (ONS). We hypothesize that this in turn leads to alteration and remodeling of connective tissue in the posterior eye which impacts vision. Finite element (FE) analysis is a powerful tool for examining the effects of mechanical loads in complex geometries. Our goal is to build a FE analysis framework to understand the response of the lamina cribrosa and optic nerve head to elevations in ICP in VIIP.
Modelling the effect of climate change on species ranges
Nagelkerke, C.J.; Alkemade, J.R.M.
2003-01-01
Three main types of models can be used to understand and predict climate-related range shifts. Equilibrium models predict potential future distributions from the current climate envelope of a species, but do not take migration constraints into account. They show that future range changes can be
Finite element model updating of natural fibre reinforced composite structure in structural dynamics
Directory of Open Access Journals (Sweden)
Sani M.S.M.
2016-01-01
Full Text Available Model updating is a process of making adjustment of certain parameters of finite element model in order to reduce discrepancy between analytical predictions of finite element (FE and experimental results. Finite element model updating is considered as an important field of study as practical application of finite element method often shows discrepancy to the test result. The aim of this research is to perform model updating procedure on a composite structure as well as trying improving the presumed geometrical and material properties of tested composite structure in finite element prediction. The composite structure concerned in this study is a plate of reinforced kenaf fiber with epoxy. Modal properties (natural frequency, mode shapes, and damping ratio of the kenaf fiber structure will be determined using both experimental modal analysis (EMA and finite element analysis (FEA. In EMA, modal testing will be carried out using impact hammer test while normal mode analysis using FEA will be carried out using MSC. Nastran/Patran software. Correlation of the data will be carried out before optimizing the data from FEA. Several parameters will be considered and selected for the model updating procedure.
Institute of Scientific and Technical Information of China (English)
R ANSARI; S ROUHI; M ARYAYI
2013-01-01
By the atomistic and continuum finite element models, the free vibration behavior of single-walled carbon nanotubes (SWCNTs) is studied. In the atomistic finite element model, the bonds and atoms are modeled by the beam and point mass elements, respectively. The molecular mechanics is linked to structural mechanics to determine the elastic properties of the mentioned beam elements. In the continuum finite element approach, by neglecting the discrete nature of the atomic structure of the nanotubes, they are modeled with shell elements. By both models, the natural frequencies of SWCNTs are computed, and the effects of the geometrical parameters, the atomic structure, and the boundary conditions are investigated. The accuracy of the utilized methods is verified in comparison with molecular dynamic simulations. The molecular structural model leads to more reliable results, especially for lower aspect ratios. The present analysis provides valuable information about application of continuum models in the investigation of the mechanical behaviors of nanotubes.
Directory of Open Access Journals (Sweden)
Martin R Langer
Full Text Available Species-range expansions are a predicted and realized consequence of global climate change. Climate warming and the poleward widening of the tropical belt have induced range shifts in a variety of marine and terrestrial species. Range expansions may have broad implications on native biota and ecosystem functioning as shifting species may perturb recipient communities. Larger symbiont-bearing foraminifera constitute ubiquitous and prominent components of shallow water ecosystems, and range shifts of these important protists are likely to trigger changes in ecosystem functioning. We have used historical and newly acquired occurrence records to compute current range shifts of Amphistegina spp., a larger symbiont-bearing foraminifera, along the eastern coastline of Africa and compare them to analogous range shifts currently observed in the Mediterranean Sea. The study provides new evidence that amphisteginid foraminifera are rapidly progressing southwestward, closely approaching Port Edward (South Africa at 31°S. To project future species distributions, we applied a species distribution model (SDM based on ecological niche constraints of current distribution ranges. Our model indicates that further warming is likely to cause a continued range extension, and predicts dispersal along nearly the entire southeastern coast of Africa. The average rates of amphisteginid range shift were computed between 8 and 2.7 km year(-1, and are projected to lead to a total southward range expansion of 267 km, or 2.4° latitude, in the year 2100. Our results corroborate findings from the fossil record that some larger symbiont-bearing foraminifera cope well with rising water temperatures and are beneficiaries of global climate change.
Langer, Martin R; Weinmann, Anna E; Lötters, Stefan; Bernhard, Joan M; Rödder, Dennis
2013-01-01
Species-range expansions are a predicted and realized consequence of global climate change. Climate warming and the poleward widening of the tropical belt have induced range shifts in a variety of marine and terrestrial species. Range expansions may have broad implications on native biota and ecosystem functioning as shifting species may perturb recipient communities. Larger symbiont-bearing foraminifera constitute ubiquitous and prominent components of shallow water ecosystems, and range shifts of these important protists are likely to trigger changes in ecosystem functioning. We have used historical and newly acquired occurrence records to compute current range shifts of Amphistegina spp., a larger symbiont-bearing foraminifera, along the eastern coastline of Africa and compare them to analogous range shifts currently observed in the Mediterranean Sea. The study provides new evidence that amphisteginid foraminifera are rapidly progressing southwestward, closely approaching Port Edward (South Africa) at 31°S. To project future species distributions, we applied a species distribution model (SDM) based on ecological niche constraints of current distribution ranges. Our model indicates that further warming is likely to cause a continued range extension, and predicts dispersal along nearly the entire southeastern coast of Africa. The average rates of amphisteginid range shift were computed between 8 and 2.7 km year(-1), and are projected to lead to a total southward range expansion of 267 km, or 2.4° latitude, in the year 2100. Our results corroborate findings from the fossil record that some larger symbiont-bearing foraminifera cope well with rising water temperatures and are beneficiaries of global climate change.
Nakamura, Keiko; Tajima, Kiyoshi; Chen, Ker-Kong; Nagamatsu, Yuki; Kakigawa, Hiroshi; Masumi, Shin-ich
2013-12-01
This study focused on the application of novel finite-element analysis software for constructing a finite-element model from the computed tomography data of a human dentulous mandible. The finite-element model is necessary for evaluating the mechanical response of the alveolar part of the mandible, resulting from occlusal force applied to the teeth during biting. Commercially available patient-specific general computed tomography-based finite-element analysis software was solely applied to the finite-element analysis for the extraction of computed tomography data. The mandibular bone with teeth was extracted from the original images. Both the enamel and the dentin were extracted after image processing, and the periodontal ligament was created from the segmented dentin. The constructed finite-element model was reasonably accurate using a total of 234,644 nodes and 1,268,784 tetrahedral and 40,665 shell elements. The elastic moduli of the heterogeneous mandibular bone were determined from the bone density data of the computed tomography images. The results suggested that the software applied in this study is both useful and powerful for creating a more accurate three-dimensional finite-element model of a dentulous mandible from the computed tomography data without the need for any other software.
A finite element model of the foot and ankle for automotive impact applications.
Shin, Jaeho; Yue, Neng; Untaroiu, Costin D
2012-12-01
A finite element (FE) model of the foot and leg was developed to improve understanding of injury mechanisms of the ankle and subtalar joints during vehicle collisions and to aid in the design of injury countermeasures. The FE model was developed based on the reconstructed geometry of a male volunteer close to the anthropometry of a 50th percentile male and a commercial anatomical database. While the forefoot bones were defined as rigid bodies connected by ligament models, the surrounding bones of the ankle and subtalar joints and the leg bones were modeled as deformable structures. The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The whole foot and leg model was validated in different loading conditions including forefoot impact, axial rotation, dorsiflexion, and combined loadings. Overall results obtained in the model validation indicated improved biofidelity relative to previous FE models. The developed model was used to investigate the injury tolerance of the ankle joint under brake pedal loading for internally and externally rotated feet. Ligament failures were predicted as the main source of injury in this loading condition. A 12% variation of failure moment was observed in the range of axial foot rotations (±15°). The most vulnerable position was the internally rotated (15°) posture among three different foot positions. Furthermore, the present foot and ankle model will be coupled together with other body region FE models into the state-of-art human FE model to be used in the field of automotive safety.
Development and validation of a 10-year-old child ligamentous cervical spine finite element model.
Dong, Liqiang; Li, Guangyao; Mao, Haojie; Marek, Stanley; Yang, King H
2013-12-01
Although a number of finite element (FE) adult cervical spine models have been developed to understand the injury mechanisms of the neck in automotive related crash scenarios, there have been fewer efforts to develop a child neck model. In this study, a 10-year-old ligamentous cervical spine FE model was developed for application in the improvement of pediatric safety related to motor vehicle crashes. The model geometry was obtained from medical scans and meshed using a multi-block approach. Appropriate properties based on review of literature in conjunction with scaling were assigned to different parts of the model. Child tensile force-deformation data in three segments, Occipital-C2 (C0-C2), C4-C5 and C6-C7, were used to validate the cervical spine model and predict failure forces and displacements. Design of computer experiments was performed to determine failure properties for intervertebral discs and ligaments needed to set up the FE model. The model-predicted ultimate displacements and forces were within the experimental range. The cervical spine FE model was validated in flexion and extension against the child experimental data in three segments, C0-C2, C4-C5 and C6-C7. Other model predictions were found to be consistent with the experimental responses scaled from adult data. The whole cervical spine model was also validated in tension, flexion and extension against the child experimental data. This study provided methods for developing a child ligamentous cervical spine FE model and to predict soft tissue failures in tension.
Keshtkar, Ahmad; Keshtkar, Asghar
2008-02-01
When the tissue is changing from normal to abnormal, the distribution of tissue liquids between intra and extra cellular space will be changed and then the measured conductivity and impedivity will also be changed. Therefore, it will cause a different current distribution inside the human bladder tissue in normal and malignant cases. By knowing the amount of electrical impedance inside the bladder tissue and the morphological parameters of the different layers of this tissue, the current distribution inside the bladder tissue (surface fluid, superficial urothelium, intermediate urothelium, basal urothelium, basement membrane, and connective tissue) was modelled and calculated in different frequencies using the finite element analysis. The model results showed that very little of the current actually flows through the urothelium and much of the injected current flows through the connective tissue beneath the urothelium (in normal cases). However, most of the current flows through the surface fluid in the low frequency range in normal tissue. Furthermore, for the high frequencies, the tight junctions are short-circuited, so the current penetrates deeper, flowing through the connective tissue beneath the urothelium, while, in the malignant cases, at least 50% of the injected current flows beneath transformed urothelium across the frequency range modelled.
Directory of Open Access Journals (Sweden)
James O’Daniel
2011-01-01
Full Text Available Simulating fragment penetration into steel involves complicated modeling of severe behavior of the materials through multiple phases of response. Penetration of a fragment-like projectile was simulated using finite element (FE and meshfree particle formulations. Extreme deformation and failure of the material during the penetration event were modeled with several approaches to evaluate each as to how well it represents the actual physics of the material and structural response. A steel Fragment Simulating Projectile (FSP – designed to simulate a fragment of metal from a weapon casing – was simulated for normal impact into a flat square plate. A range of impact velocities was used to examine levels of exit velocity ranging from relatively small to one on the same level as the impact velocity. The numerical code EPIC, used for all the simulations presented herein, contains the element and particle formulations, as well as the explicit methodology and constitutive models needed to perform these simulations. These simulations were compared against experimental data, evaluating the damage caused to the projectile and the target plates, as well as comparing the residual velocity when the projectile perforated the target.
A Study of Hardening Behavior Based on a Finite-Deformation Gradient Crystal-Plasticity Model
Pouriayevali, Habib
2016-01-01
A systematic study on the different roles of the governing components of a well-defined finite-deformation gradient crystal-plasticity model proposed by (Gurtin, 2008b) is carried out, in order to visualize the capability of the model in the prediction of a wide range of hardening behaviors as well as rate-dependent, scale-variation and Bauschinger-like responses in a single crystal. A function of accumulation rates of dislocations is employed and viewed as a measure of formation of short-range interactions which impede dislocation movements within a crystal. The model is first represented in the reference configuration for the purpose of numerical implementation, and then implemented in the FEM software ABAQUS via a user-defined subroutine (UEL). Our simulation results reveal that the dissipative gradient-strengthening is also identified as a source of isotropic-hardening behavior, which represents the effect of cold work introduced by (Gurtin and Ohno, 2011). Moreover, plastic flows in predefined slip syste...
Arya, V. K.; Kaufman, A.
1989-01-01
A description of the finite element implementation of Robinson's unified viscoplastic model into the General Purpose Finite Element Program (MARC) is presented. To demonstrate its application, the implementation is applied to some uniaxial and multiaxial problems. A comparison of the results for the multiaxial problem of a thick internally pressurized cylinder, obtained using the finite element implementation and an analytical solution, is also presented. The excellent agreement obtained confirms the correct finite element implementation of Robinson's model.
Finite Temperature Induced Fermion Number In The Nonlinear sigma Model In (2+1) Dimensions
Dunne, G V; Rao, K; Dunne, Gerald V.; Lopez-Sarrion, Justo; Rao, Kumar
2002-01-01
We compute the finite temperature induced fermion number for fermions coupled to a static nonlinear sigma model background in (2+1) dimensions, in the derivative expansion limit. While the zero temperature induced fermion number is well known to be topological (it is the winding number of the background), at finite temperature there is a temperature dependent correction that is nontopological -- this finite T correction is sensitive to the detailed shape of the background. At low temperature we resum the derivative expansion to all orders, and we consider explicit forms of the background as a CP^1 instanton or as a baby skyrmion.
Huang, Qihua; Wang, Hao
2016-08-01
The question of the effects of environmental toxins on ecological communities is of great interest from both environmental and conservational points of view. Mathematical models have been applied increasingly to predict the effects of toxins on a variety of ecological processes. Motivated by the fact that individuals with different sizes may have different sensitivities to toxins, we develop a toxin-mediated size-structured model which is given by a system of first order fully nonlinear partial differential equations (PDEs). It is very possible that this work represents the first derivation of a PDE model in the area of ecotoxicology. To solve the model, an explicit finite difference approximation to this PDE system is developed. Existence-uniqueness of the weak solution to the model is established and convergence of the finite difference approximation to this unique solution is proved. Numerical examples are provided by numerically solving the PDE model using the finite difference scheme.
Evaluation of Finite-Rate GasSurface Interaction Models for a Carbon Based Ablator
Chen, Yih-Kanq; Goekcen, Tahir
2015-01-01
Two sets of finite-rate gas-surface interaction model between air and the carbon surface are studied. The first set is an engineering model with one-way chemical reactions, and the second set is a more detailed model with two-way chemical reactions. These two proposed models intend to cover the carbon surface ablation conditions including the low temperature rate-controlled oxidation, the mid-temperature diffusion-controlled oxidation, and the high temperature sublimation. The prediction of carbon surface recession is achieved by coupling a material thermal response code and a Navier-Stokes flow code. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and Ablation Program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting full Navier-Stokes equations using Data Parallel Line Relaxation method. Recession analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities with heat fluxes ranging from 45 to 1100 wcm2 are performed and compared with data for model validation. The ablating material used in these arc-jet tests is Phenolic Impregnated Carbon Ablator. Additionally, computational predictions of surface recession and shape change are in good agreement with measurement for arc-jet conditions of Small Probe Reentry Investigation for Thermal Protection System Engineering.
Altmeyer, Guillaume; Panicaud, Benoit; Rouhaud, Emmanuelle; Wang, Mingchuan; Roos, Arjen; Kerner, Richard
2016-11-01
When constructing viscoelastic models, rate-form relations appear naturally to relate strain and stress tensors. One has to ensure that these tensors and their rates are indifferent with respect to the change of observers and to the superposition with rigid body motions. Objective transports are commonly accepted to ensure this invariance. However, the large number of transport operators developed makes the choice often difficult for the user and may lead to physically inconsistent formulation of hypoelasticity. In this paper, a methodology based on the use of the Lie derivative is proposed to model consistent hypoelasticity as an equivalent incremental formulation of hyperelasticity. Both models are shown to be reversible and completely equivalent. Extension to viscoelasticity is then proposed from this consistent model by associating consistent hypoelastic models with viscous behavior. As an illustration, Mooney-Rivlin nonlinear elasticity is coupled with Newton viscosity and a Maxwell-like material is investigated. Numerical solutions are then presented to illustrate a viscoelastic material subjected to finite deformations for a large range of strain rates.
Alimonti, Luca; Atalla, Noureddine; Berry, Alain; Sgard, Franck
2014-05-01
Modeling complex vibroacoustic systems including poroelastic materials using finite element based methods can be unfeasible for practical applications. For this reason, analytical approaches such as the transfer matrix method are often preferred to obtain a quick estimation of the vibroacoustic parameters. However, the strong assumptions inherent within the transfer matrix method lead to a lack of accuracy in the description of the geometry of the system. As a result, the transfer matrix method is inherently limited to the high frequency range. Nowadays, hybrid substructuring procedures have become quite popular. Indeed, different modeling techniques are typically sought to describe complex vibroacoustic systems over the widest possible frequency range. As a result, the flexibility and accuracy of the finite element method and the efficiency of the transfer matrix method could be coupled in a hybrid technique to obtain a reduction of the computational burden. In this work, a hybrid methodology is proposed. The performances of the method in predicting the vibroacoutic indicators of flat structures with attached homogeneous acoustic treatments are assessed. The results prove that, under certain conditions, the hybrid model allows for a reduction of the computational effort while preserving enough accuracy with respect to the full finite element solution.
Finite element modeling of electromagnetic fields and waves using NASTRAN
Moyer, E. Thomas, Jr.; Schroeder, Erwin
1989-01-01
The various formulations of Maxwell's equations are reviewed with emphasis on those formulations which most readily form analogies with Navier's equations. Analogies involving scalar and vector potentials and electric and magnetic field components are presented. Formulations allowing for media with dielectric and conducting properties are emphasized. It is demonstrated that many problems in electromagnetism can be solved using the NASTRAN finite element code. Several fundamental problems involving time harmonic solutions of Maxwell's equations with known analytic solutions are solved using NASTRAN to demonstrate convergence and mesh requirements. Mesh requirements are studied as a function of frequency, conductivity, and dielectric properties. Applications in both low frequency and high frequency are highlighted. The low frequency problems demonstrate the ability to solve problems involving media inhomogeneity and unbounded domains. The high frequency applications demonstrate the ability to handle problems with large boundary to wavelength ratios.
Finite-element modeling and analysis in nanomedicine and dentistry.
Choi, Andy H; Conway, Richard C; Ben-Nissan, Besim
2014-08-01
This article aims to provide a brief background to the current applications of finite-element analysis (FEA) in nanomedicine and dentistry. FEA was introduced in orthopedic biomechanics in the 1970s in order to assess the stresses and deformation in human bones during functional loadings and in the design and analysis of implants. Since then, it has been applied with great frequency in orthopedics and dentistry in order to analyze issues such as implant design, bone remodeling and fracture healing, the mechanical properties of biomedical coatings on implants and the interactions at the bone-implant interface. More recently, FEA has been used in nanomedicine to study the mechanics of a single cell and to gain fundamental insights into how the particulate nature of blood influences nanoparticle delivery.
Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis
S. Hosseini; MOGHANI, J. S.; Jensen, B B
2011-01-01
This paper presents an accurate modeling method that is applied to a single-sided outer-rotor transverse flux permanent magnet generator. The inductances and the induced electromotive force for a typical generator are calculated using the magnetostatic three-dimensional finite element method. A new method is then proposed that reveals the behavior of the generator under any load. Finally, torque calculations are carried out using three dimensional finite element analyses. It is shown that...
Finite Size Scaling and "perfect" actions the three dimensional Ising model
Ballesteros, H G; Martín-Mayor, V; Muñoz-Sudupe, A
1998-01-01
Using Finite-Size Scaling techniques, we numerically show that the first irrelevant operator of the lattice $\\lambda\\phi^4$ theory in three dimensions is (within errors) completely decoupled at $\\lambda=1.0$. This interesting result also holds in the Thermodynamical Limit, where the renormalized coupling constant shows an extraordinary reduction of the scaling-corrections when compared with the Ising model. It is argued that Finite-Size Scaling analysis can be a competitive method for finding improved actions.
SEMI-ANALYTICAL FINITE ELEMENT METHOD FOR FICTITIOUS CRACK MODEL IN FRACTURE MECHANICS OF CONCRETE
Institute of Scientific and Technical Information of China (English)
王承强; 郑长良
2004-01-01
Based on the Hamiltonian governing equations of plane elasticity for sectorial domain, the variable separation and eigenfunction expansion techniques were employed to develop a novel analytical finite element for the fictitious crack model in fracture mechanics of concrete. The new analytical element can be implemented into FEM program systems to solve fictitious crack propagation problems for concrete cracked plates with arbitrary shapes and loads. Numerical results indicate that the method is more efficient and accurate than ordinary finite element method.
Suvorov, A. S.; Sokov, E. M.; V'yushkina, I. A.
2016-09-01
A new method is presented for the automatic refinement of finite element models of complex mechanical-acoustic systems using the results of experimental studies. The method is based on control of the spectral characteristics via selection of the optimal distribution of adjustments to the stiffness of a finite element mesh. The results of testing the method are given to show the possibility of its use to significantly increase the simulation accuracy of vibration characteristics of bodies with arbitrary spatial configuration.
Chalupecký, Vladimír
2011-01-01
We propose a semi-discrete finite difference multiscale scheme for a concrete corrosion model consisting of a system of two-scale reaction-diffusion equations coupled with an ode. We prove energy and regularity estimates and use them to get the necessary compactness of the approximation estimates. Finally, we illustrate numerically the behavior of the two-scale finite difference approximation of the weak solution.
Finite element modelling of creep process - steady state stresses and strains
Directory of Open Access Journals (Sweden)
Sedmak Aleksandar S.
2014-01-01
Full Text Available Finite element modelling of steady state creep process has been described. Using an analogy of visco-plastic problem with a described procedure, the finite element method has been used to calculate steady state stresses and strains in 2D problems. An example of application of such a procedure have been presented, using real life problem - cylindrical pipe with longitudinal crack at high temperature, under internal pressure, and estimating its residual life, based on the C*integral evaluation.
Nonlinear dynamics of planetary gears using analytical and finite element models
Ambarisha, Vijaya Kumar; Parker, Robert G.
2007-05-01
Vibration-induced gear noise and dynamic loads remain key concerns in many transmission applications that use planetary gears. Tooth separations at large vibrations introduce nonlinearity in geared systems. The present work examines the complex, nonlinear dynamic behavior of spur planetary gears using two models: (i) a lumped-parameter model, and (ii) a finite element model. The two-dimensional (2D) lumped-parameter model represents the gears as lumped inertias, the gear meshes as nonlinear springs with tooth contact loss and periodically varying stiffness due to changing tooth contact conditions, and the supports as linear springs. The 2D finite element model is developed from a unique finite element-contact analysis solver specialized for gear dynamics. Mesh stiffness variation excitation, corner contact, and gear tooth contact loss are all intrinsically considered in the finite element analysis. The dynamics of planetary gears show a rich spectrum of nonlinear phenomena. Nonlinear jumps, chaotic motions, and period-doubling bifurcations occur when the mesh frequency or any of its higher harmonics are near a natural frequency of the system. Responses from the dynamic analysis using analytical and finite element models are successfully compared qualitatively and quantitatively. These comparisons validate the effectiveness of the lumped-parameter model to simulate the dynamics of planetary gears. Mesh phasing rules to suppress rotational and translational vibrations in planetary gears are valid even when nonlinearity from tooth contact loss occurs. These mesh phasing rules, however, are not valid in the chaotic and period-doubling regions.
Benchmarking novel approaches for modelling species range dynamics.
Zurell, Damaris; Thuiller, Wilfried; Pagel, Jörn; Cabral, Juliano S; Münkemüller, Tamara; Gravel, Dominique; Dullinger, Stefan; Normand, Signe; Schiffers, Katja H; Moore, Kara A; Zimmermann, Niklaus E
2016-08-01
Increasing biodiversity loss due to climate change is one of the most vital challenges of the 21st century. To anticipate and mitigate biodiversity loss, models are needed that reliably project species' range dynamics and extinction risks. Recently, several new approaches to model range dynamics have been developed to supplement correlative species distribution models (SDMs), but applications clearly lag behind model development. Indeed, no comparative analysis has been performed to evaluate their performance. Here, we build on process-based, simulated data for benchmarking five range (dynamic) models of varying complexity including classical SDMs, SDMs coupled with simple dispersal or more complex population dynamic models (SDM hybrids), and a hierarchical Bayesian process-based dynamic range model (DRM). We specifically test the effects of demographic and community processes on model predictive performance. Under current climate, DRMs performed best, although only marginally. Under climate change, predictive performance varied considerably, with no clear winners. Yet, all range dynamic models improved predictions under climate change substantially compared to purely correlative SDMs, and the population dynamic models also predicted reasonable extinction risks for most scenarios. When benchmarking data were simulated with more complex demographic and community processes, simple SDM hybrids including only dispersal often proved most reliable. Finally, we found that structural decisions during model building can have great impact on model accuracy, but prior system knowledge on important processes can reduce these uncertainties considerably. Our results reassure the clear merit in using dynamic approaches for modelling species' response to climate change but also emphasize several needs for further model and data improvement. We propose and discuss perspectives for improving range projections through combination of multiple models and for making these approaches
Energy Technology Data Exchange (ETDEWEB)
Kim, K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Petersson, N. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rodgers, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-10-25
Acoustic waveform modeling is a computationally intensive task and full three-dimensional simulations are often impractical for some geophysical applications such as long-range wave propagation and high-frequency sound simulation. In this study, we develop a two-dimensional high-order accurate finite-difference code for acoustic wave modeling. We solve the linearized Euler equations by discretizing them with the sixth order accurate finite difference stencils away from the boundary and the third order summation-by-parts (SBP) closure near the boundary. Non-planar topographic boundary is resolved by formulating the governing equation in curvilinear coordinates following the interface. We verify the implementation of the algorithm by numerical examples and demonstrate the capability of the proposed method for practical acoustic wave propagation problems in the atmosphere.
Inhomogeneous condensation in effective models for QCD using the finite-mode approach
Heinz, Achim; Wagner, Marc; Rischke, Dirk H
2016-01-01
We use a numerical method, the finite-mode approach, to study inhomogeneous condensation in effective models for QCD in a general framework. Former limitations of considering a specific ansatz for the spatial dependence of the condensate are overcome. Different error sources are analyzed and strategies to minimize or eliminate them are outlined. The analytically known results for $1+1$ dimensional models (such as the Gross-Neveu model and extensions of it) are correctly reproduced using the finite-mode approach. Moreover, the NJL model in $3+1$ dimensions is investigated and its phase diagram is determined with particular focus on the inhomogeneous phase at high density.
Finite element model updating for large span spatial steel structure considering uncertainties
Institute of Scientific and Technical Information of China (English)
TENG Jun; ZHU Yan-huang; ZHOU Feng; LI Hui; OU Jin-ping
2010-01-01
In order to establish the baseline finite element model for structural health monitoring,a new method of model updating was proposed after analyzing the uncertainties of measured data and the error of finite element model.In the new method,the finite element model was replaced by the multi-output support vector regression machine(MSVR).The interval variables of the measured frequency were sampled by Latin hypercube sampling method.The samples of frequency were regarded as the inputs of the trained MSVR.The outputs of MSVR were the target values of design parameters.The steel structure of National Aquatic Center for Beijing Olympic Games was introduced as a case for finite element model updating.The results show that the proposed method can avoid solving the problem of complicated calculation.Both the estimated values and associated uncertainties of the structure parameters can be obtained by the method.The static and dynamic characteristics of the updated finite element model are in good agreement with the measured data.
Vibration Analysis of Rotating Tapered Timoshenko Beams by a New Finite Element Model
Directory of Open Access Journals (Sweden)
Bulent Yardimoglu
2006-01-01
Full Text Available A new finite element model is developed and subsequently used for transverse vibrations of tapered Timoshenko beams with rectangular cross-section. The displacement functions of the finite element are derived from the coupled displacement field (the polynomial coefficients of transverse displacement and cross-sectional rotation are coupled through consideration of the differential equations of equilibrium approach by considering the tapering functions of breadth and depth of the beam. This procedure reduces the number of nodal variables. The new model can also be used for uniform beams. The stiffness and mass matrices of the finite element model are expressed by using the energy equations. To confirm the accuracy, efficiency, and versatility of the new model, a semi-symbolic computer program in MATLAB® is developed. As illustrative examples, the bending natural frequencies of non-rotating/rotating uniform and tapered Timoshenko beams are obtained and compared with previously published results and the results obtained from the finite element models of solids created in ABAQUS. Excellent agreement is found between the results of new finite element model and the other results.
Optimal implicit 2-D finite differences to model wave propagation in poroelastic media
Itzá, Reymundo; Iturrarán-Viveros, Ursula; Parra, Jorge O.
2016-08-01
Numerical modeling of seismic waves in heterogeneous porous reservoir rocks is an important tool for the interpretation of seismic surveys in reservoir engineering. We apply globally optimal implicit staggered-grid finite differences (FD) to model 2-D wave propagation in heterogeneous poroelastic media at a low-frequency range (<10 kHz). We validate the numerical solution by comparing it to an analytical-transient solution obtaining clear seismic wavefields including fast P and slow P and S waves (for a porous media saturated with fluid). The numerical dispersion and stability conditions are derived using von Neumann analysis, showing that over a wide range of porous materials the Courant condition governs the stability and this optimal implicit scheme improves the stability of explicit schemes. High-order explicit FD can be replaced by some lower order optimal implicit FD so computational cost will not be as expensive while maintaining the accuracy. Here, we compute weights for the optimal implicit FD scheme to attain an accuracy of γ = 10-8. The implicit spatial differentiation involves solving tridiagonal linear systems of equations through Thomas' algorithm.
Asgharpour, Z; Baumgartner, D; Willinger, R; Graw, M; Peldschus, S
2014-05-01
Traumatic head injuries can result from vehicular accidents, sports, falls or assaults. The current advances in computational methods and the detailed finite element models of the human head provide a significant opportunity for biomechanical study of human head injuries. The biomechanical characteristics of the human head through head impact scenarios can be studied in detail by using the finite element models. Skull fracture is one of the most frequent occurring types of head injuries. The purpose of this study is to analyse the experimental head impacts on cadavers by means of the Strasbourg University Finite Element Head Model (SUFEHM). The results of the numerical model and experimental data are compared for validation purpose. The finite element model has also been applied to predict the skull bone fracture in frontal impacts. The head model includes the scalp, the facial bone, the skull, the cerebral spinal fluid, the meninges, the cerebrum and the cerebellum. The model is used to simulate the experimental frontal head impact tests using a cylindrical padded impactor. Results of the computational simulation shows that the model correlated well with a number of experimental data and a global fracture pattern has been predicted well by the model. Therefore the presented numerical model could be used for reconstruction of head impacts in different impact conditions also the forensic application of the head model would provide a tool for investigation of the causes and mechanism of head injuries.
Rajagopal, K. R.; Srinivasa, A. R.
2016-08-01
The aim of this paper is to develop a new unified class of 3D nonlinear anisotropic finite deformation inelasticity model that (1) exhibits rate-independent or dependent hysteretic response (i.e., response wherein reversal of the external stimuli does not cause reversal of the path in state space) with or without yield surfaces. The hysteresis persists with quasistatic loading. (2) Encompasses a wide range of different types of inelasticity models (such as Mullins effect in rubber, rock and soil mechanics, traditional metal plasticity, hysteretic behavior of shape memory materials) into a simple unified framework that is relatively easy to implement in computational schemes and (3) does not require any a priori particular notion of plastic strain or yield function. The core idea behind the approach is the development of an system of implicit rate equations that allow for the continuity of the response but with different rates along different directions. The theory, which is in purely mechanical setting, subsumes and generalizes many commonly used approaches for hypoelasticity and rate-independent plasticity. We illustrate its capability by modeling the Mullins effect which is the inelastic behavior of certain rubbery materials. We are able to simulate the entire cyclic response without the use of additional internal variables, i.e., the entire response is modeled by using an implicit function of stress and strain measures and their rates.
The Neuman Systems Model Institute: testing middle-range theories.
Gigliotti, Eileen
2003-07-01
The credibility of the Neuman systems model can only be established through the generation and testing of Neuman systems model-derived middle-range theories. However, due to the number and complexity of Neuman systems model concepts/concept interrelations and the diversity of middle-range theory concepts linked to these Neuman systems model concepts by researchers, no explicit middle-range theories have yet been derived from the Neuman systems model. This article describes the development of an organized program for the systematic study of the Neuman systems model. Preliminary work, already accomplished, is detailed, and a tentative plan for the completion of further preliminary work as well as beginning the actual research conduction phase is proposed.
Development of a Three-Dimensional Finite Element Chest Model for the 5(th) Percentile Female.
Kimpara, Hideyuki; Lee, Jong B; Yang, King H; King, Albert I; Iwamoto, Masami; Watanabe, Isao; Miki, Kazuo
2005-11-01
Several three-dimensional (3D) finite element (FE) models of the human body have been developed to elucidate injury mechanisms due to automotive crashes. However, these models are mainly focused on 50(th) percentile male. As a first step towards a better understanding of injury biomechanics in the small female, a 3D FE model of a 5(th) percentile female human chest (FEM-5F) has been developed and validated against experimental data obtained from two sets of frontal impact, one set of lateral impact, two sets of oblique impact and a series of ballistic impacts. Two previous FE models, a small female Total HUman Model for Safety (THUMS-AF05) occupant version 1.0Beta (Kimpara et al. 2002) and the Wayne State University Human Thoracic Model (WSUHTM, Wang 1995 and Shah et al. 2001) were integrated and modified for this model development. The model incorporated not only geometrical gender differences, such as location of the internal organs and structure of the bony skeleton, but also the biomechanical differences of the ribs due to gender. It includes a detailed description of the sternum, ribs, costal cartilage, thoracic spine, skin, superficial muscles, intercostal muscles, heart, lung, diaphragm, major blood vessels and simplified abdominal internal organs and has been validated against a series of six cadaveric experiments on the small female reported by Nahum et al. (1970), Kroell et al. (1974), Viano (1989), Talantikite et al. (1998) and Wilhelm (2003). Results predicted by the model were well-matched to these experimental data for a range of impact speeds and impactor masses. More research is needed in order to increase the accuracy of predicting rib fractures so that the mechanisms responsible for small female injury can be more clearly defined.
Telfer, Scott; Erdemir, Ahmet; Woodburn, James; Cavanagh, Peter R
2016-01-25
Integration of patient-specific biomechanical measurements into the design of therapeutic footwear has been shown to improve clinical outcomes in patients with diabetic foot disease. The addition of numerical simulations intended to optimise intervention design may help to build on these advances, however at present the time and labour required to generate and run personalised models of foot anatomy restrict their routine clinical utility. In this study we developed second-generation personalised simple finite element (FE) models of the forefoot with varying geometric fidelities. Plantar pressure predictions from barefoot, shod, and shod with insole simulations using simplified models were compared to those obtained from CT-based FE models incorporating more detailed representations of bone and tissue geometry. A simplified model including representations of metatarsals based on simple geometric shapes, embedded within a contoured soft tissue block with outer geometry acquired from a 3D surface scan was found to provide pressure predictions closest to the more complex model, with mean differences of 13.3kPa (SD 13.4), 12.52kPa (SD 11.9) and 9.6kPa (SD 9.3) for barefoot, shod, and insole conditions respectively. The simplified model design could be produced in 3h in the case of the more detailed model, and solved on average 24% faster. FE models of the forefoot based on simplified geometric representations of the metatarsal bones and soft tissue surface geometry from 3D surface scans may potentially provide a simulation approach with improved clinical utility, however further validity testing around a range of therapeutic footwear types is required.
Medium Range Forecast (MRF) and Nested Grid Model (NGM)
National Oceanic and Atmospheric Administration, Department of Commerce — The Nested Grid Model (NGM) and Medium Range Forecast (MRF) Archive is historical digital data set DSI-6140, archived at the NOAA National Centers for Environmental...
Lattice Boltzmann models with mid-range interactions
Falcucci, Giacomo; Bella, Gino; Shiatti, Giancarlo; Chibbaro, Sergio; Sbragaglia, M.; Succi, Sauro
2007-01-01
An extension of the standard Shan-Chen model for non ideal-fluids, catering for mid-range, soft-core and hard-core repulsion, is investigated. It is shown that the inclusion of such mid-range interactions does not yield any visible enhancement of the density jump across the dense and light phases. S
Soil Compressibility Models for a Wide Stress Range
Chong, Song-Hun
2016-03-03
Soil compressibility models with physically correct asymptotic void ratios are required to analyze situations that involve a wide stress range. Previously suggested models and other functions are adapted to satisfy asymptotic void ratios at low and high stress levels; all updated models involve four parameters. Compiled consolidation data for remolded and natural clays are used to test the models and to develop correlations between model parameters and index properties. Models can adequately fit soil compression data for a wide range of stresses and soil types; in particular, models that involve the power of the stress σ\\'β display higher flexibility to capture the brittle response of some natural soils. The use of a single continuous function avoids numerical discontinuities or the need for ad hoc procedures to determine the yield stress. The tangent stiffness-readily computed for all models-should not be mistaken for the small-strain constant-fabric stiffness. © 2016 American Society of Civil Engineers.
Finite element modeling of a 3D coupled foot-boot model.
Qiu, Tian-Xia; Teo, Ee-Chon; Yan, Ya-Bo; Lei, Wei
2011-12-01
Increasingly, musculoskeletal models of the human body are used as powerful tools to study biological structures. The lower limb, and in particular the foot, is of interest because it is the primary physical interaction between the body and the environment during locomotion. The goal of this paper is to adopt the finite element (FE) modeling and analysis approaches to create a state-of-the-art 3D coupled foot-boot model for future studies on biomechanical investigation of stress injury mechanism, foot wear design and parachute landing fall simulation. In the modeling process, the foot-ankle model with lower leg was developed based on Computed Tomography (CT) images using ScanIP, Surfacer and ANSYS. Then, the boot was represented by assembling the FE models of upper, insole, midsole and outsole built based on the FE model of the foot-ankle, and finally the coupled foot-boot model was generated by putting together the models of the lower limb and boot. In this study, the FE model of foot and ankle was validated during balance standing. There was a good agreement in the overall patterns of predicted and measured plantar pressure distribution published in literature. The coupled foot-boot model will be fully validated in the subsequent works under both static and dynamic loading conditions for further studies on injuries investigation in military and sports, foot wear design and characteristics of parachute landing impact in military.
Application of the Single Hardening Model in the Finite Element Program ABAQUS
DEFF Research Database (Denmark)
Jakobsen, Kim Parsberg
that several conceptual models, describing the non-linear and irreversible behaviour of soil, have been developed over the last three decades few of them are accessible in commercial finite element programs. In the present study the Single Hardening Model, that is a time independent elastoplastic constitutive...... or in combined deformation and flow problems. Today, many of these problems are solved using various finite element computer softwares, capable of handling both geometric and material non-linearities. The latter is especially important in soil mechanics and soil-structure interaction problems. Despite the feat...... model, developed by Lade and Kim (Kim & Lade 1988, Lade & Kim 1988a, Lade & Kim 1988b) is implemented as a user defined material module, UMAT, in the commercial finite element program, ABAQUS. The advantages of the Single Hardening Model Iie in its ability to predict elastic and plastic displacements...
Finite Element Modeling of a Fluid Filled Cylindrical Shell with Active Constrained Layer Damping
Institute of Scientific and Technical Information of China (English)
ZHANG Yi; ZHANG Zhi-yi; TONG Zong-peng; HUA Hong-xing
2005-01-01
On the basis of the piezoelectric theory, Mindlin plate theory, viscoelastic theory and ideal fluid equa tion, the finite element modeling of a fluid-filled cylindrical shell with active constrained layer damping (ACLD) was discussed. Energy methods and Lagrange's equation were used to obtain dynamic equations of the cylindrical shell with ACLD treatments, which was modeled as well with the finite element method. The GHM (Golla-Hughes-McTavish) method was applied to model the frequency dependent damping of viscoelastic material. Ideal and incompressible fluid was considered to establish the dynamic equations of the fluid-filled cylindrical shell with ACLD treatments, Numerical results obtained from the finite element analysis were compared with those from an experiment. The comparison shows that the proposed modeling method is accurate and reliable.
Hydro-mechanical modeling of impermeable discontinuity in rock by extended finite element method
Institute of Scientific and Technical Information of China (English)
郑安兴; 罗先启
2015-01-01
The extended finite element method(XFEM) is a numerical method for modeling discontinuities within the classical finite element framework. The computation mesh in XFEM is independent of the discontinuities, such that remeshing for moving discontinuities can be overcome. The extended finite element method is presented for hydro-mechanical modeling of impermeable discontinuities in rock. The governing equation of XFEM for hydraulic fracture modeling is derived by the virtual work principle of the fracture problem considering the water pressure on crack surface. The coupling relationship between water pressure gradient on crack surface and fracture opening width is obtained by semi-analytical and semi-numerical method. This method simplifies coupling analysis iteration and improves computational precision. Finally, the efficiency of the proposed method for modeling hydraulic fracture problems is verified by two examples and the advantages of the XFEM for hydraulic fracturing analysis are displayed.
The finite element method for the global gravity field modelling
Kollár, Michal; Macák, Marek; Mikula, Karol; Minarechová, Zuzana
2014-05-01
We present a finite element approach for solving the fixed gravimetric boundary-value problem on a global level. To that goal, we have defined the computational domain bounded by the real topography and a chosen satellite level. The boundary-value problem consists of the Laplace equation for the disturbing potential and the Neumann boundary condition given by the gravity disturbances applied on the bottom boundary, and the Dirichlet boundary condition given by the disturbing potential applied on the upper boundary. Afterwards, the computational domain is meshed with several different meshes chosen to avoid the problem of simple spherical meshes that contain a singularity at poles. Our aim has been to show how the right mesh can improve results as well as significantly reduce the computational time. The practical implementation has been done in the FEM software ANSYS using 3D linear elements SOLID70 and for solving the linear system of equations, the preconditioned conjugate gradients method has been chosen. The obtained disturbing potential has been applied to calculate the geopotential value W0.
Vande Geest, Jonathan P; Simon, B R; Rigby, Paul H; Newberg, Tyler P
2011-04-01
Finite element models (FEMs) including characteristic large deformations in highly nonlinear materials (hyperelasticity and coupled diffusive/convective transport of neutral mobile species) will allow quantitative study of in vivo tissues. Such FEMs will provide basic understanding of normal and pathological tissue responses and lead to optimization of local drug delivery strategies. We present a coupled porohyperelastic mass transport (PHEXPT) finite element approach developed using a commercially available ABAQUS finite element software. The PHEXPT transient simulations are based on sequential solution of the porohyperelastic (PHE) and mass transport (XPT) problems where an Eulerian PHE FEM is coupled to a Lagrangian XPT FEM using a custom-written FORTRAN program. The PHEXPT theoretical background is derived in the context of porous media transport theory and extended to ABAQUS finite element formulations. The essential assumptions needed in order to use ABAQUS are clearly identified in the derivation. Representative benchmark finite element simulations are provided along with analytical solutions (when appropriate). These simulations demonstrate the differences in transient and steady state responses including finite deformations, total stress, fluid pressure, relative fluid, and mobile species flux. A detailed description of important model considerations (e.g., material property functions and jump discontinuities at material interfaces) is also presented in the context of finite deformations. The ABAQUS-based PHEXPT approach enables the use of the available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries, nonlinear material laws, pre- and postprocessing, etc.). PHEXPT FEMs can be used to simulate the transport of a relatively large neutral species (negligible osmotic fluid flux) in highly deformable hydrated soft tissues and tissue-engineered materials.
Finite population size effects in quasispecies models with single-peak fitness landscape
Saakian, David B.; Deem, Michael W.; Hu, Chin-Kun
2012-04-01
We consider finite population size effects for Crow-Kimura and Eigen quasispecies models with single-peak fitness landscape. We formulate accurately the iteration procedure for the finite population models, then derive the Hamilton-Jacobi equation (HJE) to describe the dynamic of the probability distribution. The steady-state solution of HJE gives the variance of the mean fitness. Our results are useful for understanding the population sizes of viruses in which the infinite population models can give reliable results for biological evolution problems.
Application of a data base management system to a finite element model
Rogers, J. L., Jr.
1980-01-01
In today's software market, much effort is being expended on the development of data base management systems (DBMS). Most commercially available DBMS were designed for business use. However, the need for such systems within the engineering and scientific communities is becoming apparent. A potential DBMS application that appears attractive is the handling of data for finite element engineering models. The applications of a commercially available, business-oriented DBMS to a structural engineering, finite element model is explored. The model, DBMS, an approach to using the DBMS, advantages and disadvantages are described. Plans for research on a scientific and engineering DBMS are discussed.
Robinson, J. C.
1982-01-01
A systematic finite-element model modification technique has been applied to two small problems and a model of the main wing box of a research drone aircraft. The procedure determines the sensitivity of the eigenvalues and eigenvector components to specific structural changes, calculates the required changes and modifies the finite-element model. Good results were obtained where large stiffness modifications were required to satisfy large eigenvalue changes. Sensitivity matrix conditioning problems required the development of techniques to insure existence of a solution and accelerate its convergence. A method is proposed to assist the analyst in selecting stiffness parameters for modification.
Singular dynamics and emergence of nonlocality in long-range quantum models
Lepori, L; Vodola, D
2016-01-01
We discuss how nonlocality originates in long-range quantum systems and how it affects their dynamics at and out of the equilibrium. We focus in particular on the Kitaev chains with long-range pairings and on the quantum Ising chain with long-range antiferromagnetic coupling (both having a power-law decay with exponent \\alpha). By studying the dynamic correlation functions, we find that for every finite \\alpha two different behaviours can be identified, one typical of short-range systems and the other connected with locality violation. The latter behaviour is shown related also with the known power-law decay tails previously observed in the static correlation functions, and originated by modes, having in general energies far from the minima of the spectrum, where particular singularities develop as a consequence of the long-rangedness of the system. We refer to these modes as to "singular" modes, and as to "singular dynamics" to their dynamics. For the Kitaev model they are manifest, at finite \\alpha, in deri...
Chen, Si; Xu, Tian-min; Lou, Hang-di; Rong, Qi-guo
2012-12-01
To get individualized facial three-dimensional finite element (FE) model from transformation of a generic one to assist orthodontic analysis and prediction of treatment-related morphological change of facial soft tissue. A generic three-dimensional FE model of craniofacial soft and hard tissue was constructed based on a volunteer's spiral CT data. Seven pairs of main peri-oral muscles were constructed based on a combination of CT image and anatomical method. Individualized model could be obtained through transformation of the generic model based on selection of corresponding anatomical landmarks and radial basis functions (RBF) method. Validation was analyzed through superimposition of the transformed model and cone-beam CT (CBCT) reconstruction data. Pre- and post-treatment CBCT data of two patients were collected, which were superimposed to gain the amount of anterior teeth retraction and anterior alveolar surface remodeling that could be used as boundary condition. Different values of Poisson ratio ν and Young's modulus E were tested during simulation. Average deviation was 0.47 mm and 0.75 mm in the soft and hard tissue respectively. It could be decreased to a range of +0.29 mm and -0.21 mm after a second transformation at the lip-mouth region. The best correspondence between simulation and post-treatment result was found with elastic properties of soft tissues defined as follows. Poisson ratio ν for skin, muscle and fat being set as 0.45 while Young's modulus being set as 90.0 kPa, 6.2 kPa and 2.0 kPa respectively. Individualized three-dimensional facial FE model could be obtained through mathematical model transformation. With boundary condition defined according to treatment plan such FE model could be used to analyze the effect of orthodontic treatment on facial soft tissue.
USING A NEW FINITE SLIT PORE MODEL FOR NLDFT ANALYSIS OF CARBON PORE STRUCTURE
Energy Technology Data Exchange (ETDEWEB)
Jagiello, Jacek [Micromeritics Instrument Corporation; Kenvin, Jeffrey [Micromeritics Instrument Corporation; Oliver, James P [Micromeritics Instrument Corporation; Lupini, Andrew R [ORNL; Contescu, Cristian I [ORNL
2011-01-01
In this work, we present a model for analyzing activated carbon micropore structures based on graphene sheet walls of finite thickness and extent. This is a two-dimensional modification of the widely used infinite slit pore model that assumes graphite-like infinitely extended pore walls. The proposed model has two versions: (1) a strip pore constructed with graphene strip walls that have finite length L in the x direction and are infinite in the y direction. Strip pores are open on both sides in the x direction. (2) A channel pore is a strip pore partially closed along one edge by a perpendicularly oriented graphene wall. This more realistic model allows pore termination via both physical pore entrances and pore blockage. The model consequently introduces heterogeneity of the adsorption potential that is reduced near pore entrances and enhanced near corners of pore walls. These energetically heterogeneous structures fill with adsorbate more gradually than homogeneous pores of the same width. As a result, the calculated adsorption isotherms are smoother and less steep for the finite versus the infinite pore model. In the application of this model for carbon characterization it is necessary to make an assumption about the pore length. In this work we made this assumption based on the high resolution scanning transmission electron microscopy (STEM) results. We find the agreement between the experiment and the model significantly better for the finite than for the infinite pore model.
Triedman, John K.; Jolley, Matthew; Stinstra, Jeroen; Brooks, Dana H.; MacLeod, Rob
2008-01-01
ICD implants may be complicated by body size and anatomy. One approach to this problem has been the adoption of creative, extracardiac implant strategies using standard ICD components. Because data on safety or efficacy of such ad hoc implant strategies is lacking, we have developed image-based finite element models (FEMs) to compare electric fields and expected defibrillation thresholds (DFTs) using standard and novel electrode locations. In this paper, we review recently published studies by our group using such models, and progress in meshing strategies to improve efficiency and visualization. Our preliminary observations predict that they may be large changes in DFTs with clinically relevant variations of electrode placement. Extracardiac ICDs of various lead configurations are predicted to be effective in both children and adults. This approach may aid both ICD development and patient-specific optimization of electrode placement, but the simplified nature of current models dictates further development and validation prior to clinical or industrial utilization. PMID:18817926
Freed, Alan D.; Diethelm, Kai; Gray, Hugh R. (Technical Monitor)
2002-01-01
Fraction-order viscoelastic (FOV) material models have been proposed and studied in 1D since the 1930's, and were extended into three dimensions in the 1970's under the assumption of infinitesimal straining. It was not until 1997 that Drozdov introduced the first finite-strain FOV constitutive equations. In our presentation, we shall continue in this tradition by extending the standard, FOV, fluid and solid, material models introduced in 1971 by Caputo and Mainardi into 3D constitutive formula applicable for finite-strain analyses. To achieve this, we generalize both the convected and co-rotational derivatives of tensor fields to fractional order. This is accomplished by defining them first as body tensor fields and then mapping them into space as objective Cartesian tensor fields. Constitutive equations are constructed using both variants for fractional rate, and their responses are contrasted in simple shear. After five years of research and development, we now possess a basic suite of numerical tools necessary to study finite-strain FOV constitutive equations and their iterative refinement into a mature collection of material models. Numerical methods still need to be developed for efficiently solving fraction al-order integrals, derivatives, and differential equations in a finite element setting where such constitutive formulae would need to be solved at each Gauss point in each element of a finite model, which can number into the millions in today's analysis.
Vertical slice modelling of nonlinear Eady waves using a compatible finite element method
Yamazaki, Hiroe; Shipton, Jemma; Cullen, Michael J. P.; Mitchell, Lawrence; Cotter, Colin J.
2017-08-01
A vertical slice model is developed for the Euler-Boussinesq equations with a constant temperature gradient in the direction normal to the slice (the Eady-Boussinesq model). The model is a solution of the full three-dimensional equations with no variation normal to the slice, which is an idealised problem used to study the formation and subsequent evolution of weather fronts. A compatible finite element method is used to discretise the governing equations. To extend the Charney-Phillips grid staggering in the compatible finite element framework, we use the same node locations for buoyancy as the vertical part of velocity and apply a transport scheme for a partially continuous finite element space. For the time discretisation, we solve the semi-implicit equations together with an explicit strong-stability-preserving Runge-Kutta scheme to all of the advection terms. The model reproduces several quasi-periodic lifecycles of fronts despite the presence of strong discontinuities. An asymptotic limit analysis based on the semi-geostrophic theory shows that the model solutions are converging to a solution in cross-front geostrophic balance. The results are consistent with the previous results using finite difference methods, indicating that the compatible finite element method is performing as well as finite difference methods for this test problem. We observe dissipation of kinetic energy of the cross-front velocity in the model due to the lack of resolution at the fronts, even though the energy loss is not likely to account for the large gap on the strength of the fronts between the model result and the semi-geostrophic limit solution.
M.G. de Jong (Martijn); J-B.E.M. Steenkamp (Jan-Benedict)
2009-01-01
textabstractWe present a class of finite mixture multilevel multidimensional ordinal IRT models for large scale cross-cultural research. Our model is proposed for confirmatory research settings. Our prior for item parameters is a mixture distribution to accommodate situations where different groups
European column buckling curves and finite element modelling including high strength steels
DEFF Research Database (Denmark)
Jönsson, Jeppe; Stan, Tudor-Cristian
2017-01-01
Eurocode allows for finite element modelling of plated steel structures, however the information in the code on how to perform the analysis or what assumptions to make is quite sparse. The present paper investigates the deterministic modelling of flexural column buckling using plane shell element...
DEFF Research Database (Denmark)
Andersen, Lars Vabbersgaard; Kirkegaard, Poul Henning; Persson, K.;
2012-01-01
The paper concerns the development of a modular parametric finite-element model that can be applied to the analysis of vibro-acoustic problems in relation to multistory lightweight structures. Floors and walls can be modelled as structural elements, or substructures may be utilised for each type...
Local buckling of aluminium structures exposed to fire. Part 2: Finite element models
Maljaars, J.; Soetens, F.
2009-01-01
A test series was carried out and reported in a corresponding paper on slender aluminium alloy sections, loaded in compression at elevated temperature. This paper gives the results of simulations of these tests with a finite element model. For this purpose, a novel constitutive model for fire expose
Vermolen, F.J.; Javierre, E.
2011-01-01
A simplified finite-element model for wound healing is proposed. The model takes into account the sequential steps of dermal regeneration, wound contraction, angiogenesis and wound closure. An innovation in the present study is the combination of the aforementioned partially overlapping processes,
Finite element models for the steady state analysis of moving loads
Kok, A.W.M.
2000-01-01
The analysis of structures subjected to fast moving loads is a subject of growing interest in railway and pavement engineering. The applications of transient analyses using finite element models, however, are still very limited. The faster a load moves the more elements we need to model the structu
Shu, Jian-Jun
2014-01-01
A finite element model and its equivalent electronic analogue circuit of hydraulic transmission lines have been developed. Basic equations are approximated to be a set of ordinary differential equations that can be represented in state space form. The accuracy of the model is demonstrated by comparison with the method of characteristics.
Creating a Test Validated Structural Dynamic Finite Element Model of the X-56A Aircraft
Pak, Chan-Gi; Truong, Samson
2014-01-01
Small modeling errors in the finite element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the Multi Utility Technology Test-bed, X-56A aircraft, is the flight demonstration of active flutter suppression, and therefore in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground vibration test-validated structural dynamic finite element model of the X-56A aircraft is created in this study. The structural dynamic finite element model of the X-56A aircraft is improved using a model tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, while other properties such as center of gravity location, total weight, and offdiagonal terms of the mass orthogonality matrix were used as constraints. The end result was a more improved and desirable structural dynamic finite element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.
Creating a Test-Validated Finite-Element Model of the X-56A Aircraft Structure
Pak, Chan-Gi; Truong, Samson
2014-01-01
Small modeling errors in a finite-element model will eventually induce errors in the structural flexibility and mass, thus propagating into unpredictable errors in the unsteady aerodynamics and the control law design. One of the primary objectives of the X-56A Multi-Utility Technology Testbed aircraft is the flight demonstration of active flutter suppression and, therefore, in this study, the identification of the primary and secondary modes for the structural model tuning based on the flutter analysis of the X-56A aircraft. The ground-vibration test-validated structural dynamic finite-element model of the X-56A aircraft is created in this study. The structural dynamic finite-element model of the X-56A aircraft is improved using a model-tuning tool. In this study, two different weight configurations of the X-56A aircraft have been improved in a single optimization run. Frequency and the cross-orthogonality (mode shape) matrix were the primary focus for improvement, whereas other properties such as c.g. location, total weight, and off-diagonal terms of the mass orthogonality matrix were used as constraints. The end result was an improved structural dynamic finite-element model configuration for the X-56A aircraft. Improved frequencies and mode shapes in this study increased average flutter speeds of the X-56A aircraft by 7.6% compared to the baseline model.
Finite Time Ruin Probabilities and Large Deviations for Generalized Compound Binomial Risk Models
Institute of Scientific and Technical Information of China (English)
Yi Jun HU
2005-01-01
In this paper, we extend the classical compound binomial risk model to the case where the premium income process is based on a Poisson process, and is no longer a linear function. For this more realistic risk model, Lundberg type limiting results for the finite time ruin probabilities are derived. Asymptotic behavior of the tail probabilities of the claim surplus process is also investigated.
Real-time volumetric deformable models for surgery simulation using finite elements and condensation
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Cotin, S.
1996-01-01
This paper discusses the application of SD solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate...
Vermolen, F.J.; Javierre, E.
2011-01-01
A simplified finite-element model for wound healing is proposed. The model takes into account the sequential steps of dermal regeneration, wound contraction, angiogenesis and wound closure. An innovation in the present study is the combination of the aforementioned partially overlapping processes, w
Directory of Open Access Journals (Sweden)
Olga Izbash
2016-04-01
Full Text Available In the present paper we consider the expressibility of formulas in the provability logic $GL$ and related to it questions of the model completeness of system of formulas. We prove the absence of a finite approximation relative to model completeness in $GL$.
Hooper, Russell; Toose, E.M.; Macosko, Christopher W.; Derby, Jeffrey J.
2001-01-01
A modified boundary element method (BEM) and the DEVSS-G finite element method (FEM) are applied to model the deformation of a polymeric drop suspended in another fluid subjected to start-up uniaxial extensional flow. The effects of viscoelasticity, via the Oldroyd-B differential model, are
A circular finite-element model reconstruction in electrical impedance tomography
DEFF Research Database (Denmark)
Møsner, Lars Nordahl; Andersen, Ole Trier; Dawids, Steen
1989-01-01
A circular finite-element model utilizing triangular picture elements is constructed using a previously published reconstruction method. The model is applied to examples of simulated reconstructed pictures to illustrate its properties with regard to sensitivity, contrast and shape of the object...
Real-time volumetric deformable models for surgery simulation using finite elements and condensation
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Cotin, S.
1996-01-01
This paper discusses the application of SD solid volumetric Finite Element models to surgery simulation. In particular it introduces three new ideas for solving the problem of achieving real-time performance for these models. The simulation system we have developed is described and we demonstrate...
RESEARCH ON THE SELECTION OF FRICTION MODELS IN THE FINITE ELEMENT SIMULATION OF WARM EXTRUSION
Institute of Scientific and Technical Information of China (English)
X.B. Lin; H.S. Xiao; Z.L. Zhang
2003-01-01
During the process of finite element simulation of precision warm forging, the selec-tion of friction models has a direct effect on the precision accuracy of finite elementsimulation results. Among all the factors which influence the selection of frictionmodels, the distribution rule of normal stress at the tool-workpiece interface is a keyone. To find out the distribution rule of normal stress at the tool-workpiece inter-face, this paper has made a systematic research on three typical plastic deformationprocesses: forward extrusion, backward extrusion, and lateral extrusion by a methodof finite element simulation. Then on the base of synthesizing and correcting tradi-tional friction models, a new general friction model which is fit for warm extrusion isdeveloped at last.
A finite-element model predicts thermal damage in cutaneous contact burns.
Orgill, D P; Solari, M G; Barlow, M S; O'Connor, N E
1998-01-01
Thermal injury results from exposure of skin elements to an externally applied heat source. Finite-element analysis of heat transfer in cutaneous burns allows for an accurate prediction of tissue time-temperature relationships throughout the exposed tissue. A two-dimensional, axisymmetric, finite-element model of a contact burn was constructed, and damage integrals were calculated by applying the Arrhenius equation to the time-temperature profiles at each point. The epidermis, dermis, and subcutaneous fat were modeled as uniform elements with distinct thermal properties. Heated aluminum blocks were applied to Yorkshire pigs for 10 to 80 seconds to produce contact burns. Wound biopsies taken at 1, 24, and 48 hours were examined histologically and measured for the depth of burn. A significant deepening of the gelatinized tissue was observed in tissue taken from 1 hour to 24 hours. The finite-element prediction of cutaneous contact burn damage correlated well with histologic observations in this porcine model.
3-d finite element model development for biomechanics: a software demonstration
Energy Technology Data Exchange (ETDEWEB)
Hollerbach, K.; Hollister, A.M.; Ashby, E.
1997-03-01
Finite element analysis is becoming an increasingly important part of biomechanics and orthopedic research, as computational resources become more powerful, and data handling algorithms become more sophisticated. Until recently, tools with sufficient power did not exist or were not accessible to adequately model complicated, three-dimensional, nonlinear biomechanical systems. In the past, finite element analyses in biomechanics have often been limited to two-dimensional approaches, linear analyses, or simulations of single tissue types. Today, we have the resources to model fully three-dimensional, nonlinear, multi-tissue, and even multi-joint systems. The authors will present the process of developing these kinds of finite element models, using human hand and knee examples, and will demonstrate their software tools.
POD-Galerkin reduced-order modeling with adaptive finite element snapshots
Ullmann, Sebastian; Rotkvic, Marko; Lang, Jens
2016-11-01
We consider model order reduction by proper orthogonal decomposition (POD) for parametrized partial differential equations, where the underlying snapshots are computed with adaptive finite elements. We address computational and theoretical issues arising from the fact that the snapshots are members of different finite element spaces. We propose a method to create a POD-Galerkin model without interpolating the snapshots onto their common finite element mesh. The error of the reduced-order solution is not necessarily Galerkin orthogonal to the reduced space created from space-adapted snapshot. We analyze how this influences the error assessment for POD-Galerkin models of linear elliptic boundary value problems. As a numerical example we consider a two-dimensional convection-diffusion equation with a parametrized convective direction. To illustrate the applicability of our techniques to non-linear time-dependent problems, we present a test case of a two-dimensional viscous Burgers equation with parametrized initial data.
Vafaeian, B; Le, L H; Tran, T N H T; El-Rich, M; El-Bialy, T; Adeeb, S
2016-05-01
The present study investigated the accuracy of micro-scale finite element modeling for simulating broadband ultrasound propagation in water-saturated trabecular bone-mimicking phantoms. To this end, five commercially manufactured aluminum foam samples as trabecular bone-mimicking phantoms were utilized for ultrasonic immersion through-transmission experiments. Based on micro-computed tomography images of the same physical samples, three-dimensional high-resolution computational samples were generated to be implemented in the micro-scale finite element models. The finite element models employed the standard Galerkin finite element method (FEM) in time domain to simulate the ultrasonic experiments. The numerical simulations did not include energy dissipative mechanisms of ultrasonic attenuation; however, they expectedly simulated reflection, refraction, scattering, and wave mode conversion. The accuracy of the finite element simulations were evaluated by comparing the simulated ultrasonic attenuation and velocity with the experimental data. The maximum and the average relative errors between the experimental and simulated attenuation coefficients in the frequency range of 0.6-1.4 MHz were 17% and 6% respectively. Moreover, the simulations closely predicted the time-of-flight based velocities and the phase velocities of ultrasound with maximum relative errors of 20 m/s and 11 m/s respectively. The results of this study strongly suggest that micro-scale finite element modeling can effectively simulate broadband ultrasound propagation in water-saturated trabecular bone-mimicking structures.
Westreich, Daniel; Cole, Stephen R; Schisterman, Enrique F; Platt, Robert W
2012-08-30
Motivated by a previously published study of HIV treatment, we simulated data subject to time-varying confounding affected by prior treatment to examine some finite-sample properties of marginal structural Cox proportional hazards models. We compared (a) unadjusted, (b) regression-adjusted, (c) unstabilized, and (d) stabilized marginal structural (inverse probability-of-treatment [IPT] weighted) model estimators of effect in terms of bias, standard error, root mean squared error (MSE), and 95% confidence limit coverage over a range of research scenarios, including relatively small sample sizes and 10 study assessments. In the base-case scenario resembling the motivating example, where the true hazard ratio was 0.5, both IPT-weighted analyses were unbiased, whereas crude and adjusted analyses showed substantial bias towards and across the null. Stabilized IPT-weighted analyses remained unbiased across a range of scenarios, including relatively small sample size; however, the standard error was generally smaller in crude and adjusted models. In many cases, unstabilized weighted analysis showed a substantial increase in standard error compared with other approaches. Root MSE was smallest in the IPT-weighted analyses for the base-case scenario. In situations where time-varying confounding affected by prior treatment was absent, IPT-weighted analyses were less precise and therefore had greater root MSE compared with adjusted analyses. The 95% confidence limit coverage was close to nominal for all stabilized IPT-weighted but poor in crude, adjusted, and unstabilized IPT-weighted analysis. Under realistic scenarios, marginal structural Cox proportional hazards models performed according to expectations based on large-sample theory and provided accurate estimates of the hazard ratio.
An effective model for dynamic finite difference calculations
Energy Technology Data Exchange (ETDEWEB)
Dey, T.N.
1996-01-01
An effective stress model, which simulates the mechanical effects of pore fluids on deformation and strength of porous materials, is described. The model can directly use SESAME table equations-of-state (EOSs) for the solid and fluid components. the model assumes that undrained (no fluid flow) conditions occur. Elastic and crushing behavior of the pore space can be specified from the results of simple laboratory tests. The model fully couples deviatoric and volumetric behavior in the sense that deviatoric and tensile failure depend on the effective pressure, while volumetric changes caused by deviatoric failure are coupled back to the volumetric behavior of the material. Strain hardening and softening of the yield surface, together with a number of flow rules, can be modeled. This model has been implemented into the SMC123 and CTH codes.
3D scene modeling from multiple range views
Sequeira, Vitor; Goncalves, Joao G. M.; Ribeiro, M. Isabel
1995-09-01
This paper presents a new 3D scene analysis system that automatically reconstructs the 3D geometric model of real-world scenes from multiple range images acquired by a laser range finder on board of a mobile robot. The reconstruction is achieved through an integrated procedure including range data acquisition, geometrical feature extraction, registration, and integration of multiple views. Different descriptions of the final 3D scene model are obtained: a polygonal triangular mesh, a surface description in terms of planar and biquadratics surfaces, and a 3D boundary representation. Relevant experimental results from the complete 3D scene modeling are presented. Direct applications of this technique include 3D reconstruction and/or update of architectual or industrial plans into a CAD model, design verification of buildings, navigation of autonomous robots, and input to virtual reality systems.
Sensor modelling and camera calibration for close-range photogrammetry
Luhmann, Thomas; Fraser, Clive; Maas, Hans-Gerd
2016-05-01
Metric calibration is a critical prerequisite to the application of modern, mostly consumer-grade digital cameras for close-range photogrammetric measurement. This paper reviews aspects of sensor modelling and photogrammetric calibration, with attention being focussed on techniques of automated self-calibration. Following an initial overview of the history and the state of the art, selected topics of current interest within calibration for close-range photogrammetry are addressed. These include sensor modelling, with standard, extended and generic calibration models being summarised, along with non-traditional camera systems. Self-calibration via both targeted planar arrays and targetless scenes amenable to SfM-based exterior orientation are then discussed, after which aspects of calibration and measurement accuracy are covered. Whereas camera self-calibration is largely a mature technology, there is always scope for additional research to enhance the models and processes employed with the many camera systems nowadays utilised in close-range photogrammetry.
Model-based uncertainty in species range prediction
DEFF Research Database (Denmark)
Pearson, R. G.; Thuiller, Wilfried; Bastos Araujo, Miguel;
2006-01-01
Aim Many attempts to predict the potential range of species rely on environmental niche (or 'bioclimate envelope') modelling, yet the effects of using different niche-based methodologies require further investigation. Here we investigate the impact that the choice of model can have on predictions...... day (using the area under the receiver operating characteristic curve (AUC) and kappa statistics) and by assessing consistency in predictions of range size changes under future climate (using cluster analysis). Results Our analyses show significant differences between predictions from different models......, with predicted changes in range size by 2030 differing in both magnitude and direction (e.g. from 92% loss to 322% gain). We explain differences with reference to two characteristics of the modelling techniques: data input requirements (presence/absence vs. presence-only approaches) and assumptions made by each...
Development and validation of a weight-bearing finite element model for total knee replacement.
Woiczinski, M; Steinbrück, A; Weber, P; Müller, P E; Jansson, V; Schröder, Ch
2016-01-01
Total knee arthroplasty (TKA) is a successful procedure for osteoarthritis. However, some patients (19%) do have pain after surgery. A finite element model was developed based on boundary conditions of a knee rig. A 3D-model of an anatomical full leg was generated from magnetic resonance image data and a total knee prosthesis was implanted without patella resurfacing. In the finite element model, a restarting procedure was programmed in order to hold the ground reaction force constant with an adapted quadriceps muscle force during a squat from 20° to 105° of flexion. Knee rig experimental data were used to validate the numerical model in the patellofemoral and femorotibial joint. Furthermore, sensitivity analyses of Young's modulus of the patella cartilage, posterior cruciate ligament (PCL) stiffness, and patella tendon origin were performed. Pearson's correlations for retropatellar contact area, pressure, patella flexion, and femorotibial ap-movement were near to 1. Lowest root mean square error for retropatellar pressure, patella flexion, and femorotibial ap-movement were found for the baseline model setup with Young's modulus of 5 MPa for patella cartilage, a downscaled PCL stiffness of 25% compared to the literature given value and an anatomical origin of the patella tendon. The results of the conducted finite element model are comparable with the experimental results. Therefore, the finite element model developed in this study can be used for further clinical investigations and will help to better understand the clinical aspects after TKA with an unresurfaced patella.
Transport and dispersion of pollutants in surface impoundments: a finite element model
Energy Technology Data Exchange (ETDEWEB)
Yeh, G.T.
1980-07-01
A surface impoundment model in finite element (SIMFE) is presented to enable the simulation of flow circulations and pollutant transport and dispersion in natural or artificial lakes, reservoirs or ponds with any number of islands. This surface impoundment model consists of two sub-models: hydrodynamic and pollutant transport models. Both submodels are simulated by the finite element method. While the hydrodynamic model is solved by the standard Galerkin finite element scheme, the pollutant transport model can be solved by any of the twelve optional finite element schemes built in the program. Theoretical approximations and the numerical algorithm of SIMFE are described. Detail instruction of the application are given and listing of FORTRAN IV source program are provided. Two sample problems are given. One is for an idealized system with a known solution to show the accuracy and partial validation of the models. The other is applied to Prairie Island for a set of hypothetical input data, typifying a class of problems to which SIMFE may be applied.
Directory of Open Access Journals (Sweden)
Stephan eLau
2016-04-01
Full Text Available Magnetoencephalography (MEG signals are influenced by skull defects. However, there is a lack of evidence of this influence during source reconstruction. Our objectives are to characterize errors in source reconstruction from MEG signals due to ignoring skull defects and to assess the ability of an exact finite element head model to eliminate such errors.A detailed finite element model of the head of a rabbit used in a physical experiment was constructed from magnetic resonance and co-registered computer tomography imaging that differentiated nine tissue types. Sources of the MEG measurements above intact skull and above skull defects respectively were reconstructed using a finite element model with the intact skull and one incorporating the skull defects.The forward simulation of the MEG signals reproduced the experimentally observed characteristic magnitude and topography changes due to skull defects. Sources reconstructed from measured MEG signals above intact skull matched the known physical locations and orientations. Ignoring skull defects in the head model during reconstruction displaced sources under a skull defect away from that defect. Sources next to a defect were reoriented. When skull defects, with their physical conductivity, were incorporated in the head model, the location and orientation errors were mostly eliminated. The conductivity of the skull defect material non-uniformly modulated the influence on MEG signals.We propose concrete guidelines for taking into account conducting skull defects during MEG coil placement and modeling. Exact finite element head models can improve localization of brain function, specifically after surgery.
Jian, Wang; Xiaohong, Meng; Hong, Liu; Wanqiu, Zheng; Yaning, Liu; Sheng, Gui; Zhiyang, Wang
2017-03-01
Full waveform inversion and reverse time migration are active research areas for seismic exploration. Forward modeling in the time domain determines the precision of the results, and numerical solutions of finite difference have been widely adopted as an important mathematical tool for forward modeling. In this article, the optimum combined of window functions was designed based on the finite difference operator using a truncated approximation of the spatial convolution series in pseudo-spectrum space, to normalize the outcomes of existing window functions for different orders. The proposed combined window functions not only inherit the characteristics of the various window functions, to provide better truncation results, but also control the truncation error of the finite difference operator manually and visually by adjusting the combinations and analyzing the characteristics of the main and side lobes of the amplitude response. Error level and elastic forward modeling under the proposed combined system were compared with outcomes from conventional window functions and modified binomial windows. Numerical dispersion is significantly suppressed, which is compared with modified binomial window function finite-difference and conventional finite-difference. Numerical simulation verifies the reliability of the proposed method.
Electric field distribution in a finite-volume head model of deep brain stimulation.
Grant, Peadar F; Lowery, Madeleine M
2009-11-01
This study presents a whole-head finite element model of deep brain stimulation to examine the effect of electrical grounding, the finite conducting volume of the head, and scalp, skull and cerebrospinal fluid layers. The impedance between the stimulating and reference electrodes in the whole-head model was found to lie within clinically reported values when the reference electrode was incorporated on a localized surface in the model. Incorporation of the finite volume of the head and inclusion of surrounding outer tissue layers reduced the magnitude of the electric field and activating function by approximately 20% in the region surrounding the electrode. Localized distortions of the electric field were also observed when the electrode was placed close to the skull. Under bipolar conditions the effect of the finite conducting volume was shown to be negligible. The results indicate that, for monopolar stimulation, incorporation of the finite volume and outer tissue layers can alter the magnitude of the electric field and activating function when the electrode is deep within the brain, and may further affect the shape if the electrode is close to the skull.
PyLith: A Finite-Element Code for Modeling Quasi-Static and Dynamic Crustal Deformation
Aagaard, B.; Williams, C. A.; Knepley, M. G.
2011-12-01
We have developed open-source finite-element software for 2-D and 3-D dynamic and quasi-static modeling of crustal deformation. This software, PyLith (current release is version 1.6) can be used for quasi-static viscoelastic modeling, dynamic spontaneous rupture and/or ground-motion modeling. Unstructured and structured finite-element discretizations allow for spatial scales ranging from tens of meters to hundreds of kilometers with temporal scales in dynamic problems ranging from milliseconds to minutes and temporal scales in quasi-static problems ranging from minutes to thousands of years. PyLith development is part of the NSF funded Computational Infrastructure for Geodynamics (CIG) and the software runs on a wide variety of platforms (laptops, workstations, and Beowulf clusters). Binaries (Linux, Darwin, and Windows systems) and source code are available from geodynamics.org. PyLith uses a suite of general, parallel, graph data structures called Sieve for storing and manipulating finite-element meshes. This permits use of a variety of 2-D and 3-D cell types including triangles, quadrilaterals, hexahedra, and tetrahedra. Current PyLith features include prescribed fault ruptures with multiple earthquakes and aseismic creep, spontaneous fault ruptures with a variety of fault constitutive models, time-dependent Dirichlet and Neumann boundary conditions, absorbing boundary conditions, time-dependent point forces, and gravitational body forces. PyLith supports infinitesimal and small strain formulations for linear elastic rheologies, linear and generalized Maxwell viscoelastic rheologies, power-law viscoelastic rheologies, and Drucker-Prager elastoplastic rheologies. Current software development focuses on coupling quasi-static and dynamic simulations to resolve multi-scale deformation across the entire seismic cycle and the coupling of elasticity to heat and/or fluid flow.
CONTRIBUTIONS TO THE FINITE ELEMENT MODELING OF LINEAR ULTRASONIC MOTORS
Directory of Open Access Journals (Sweden)
Oana CHIVU
2013-05-01
Full Text Available The present paper is concerned with the main modeling elements as produced by means of thefinite element method of linear ultrasonic motors. Hence, first the model is designed and then a modaland harmonic analysis are carried out in view of outlining the main outcomes
CONTRIBUTIONS TO THE FINITE ELEMENT MODELING OF ROTARY ULTRASONIC MOTORS
Directory of Open Access Journals (Sweden)
Oana CHIVU
2013-05-01
Full Text Available The present paper is concerned with the main modeling elements as produced by means of thefinite element method of rotary ultrasonic motors. Hence, first the model is designed and then a modaland harmonic analysis are carried out in view of outlining the main outcomes
3D Finite Element Modeling of Sliding Wear
2013-12-01
Failure Modeling of Titanium 6Al-4V and Aluminum 2024-T3 With the Johnson - Cook Material Model”, Report No DOT/FAA/AR-03/57, Office of Aviation...177 1.4.3 Johnson - Cook Viscoplastic Model...178 1.4.4 Johnson - Cook Flow Rule ...................................................................179 1.4.5 Johnson - Cook Dynamic Failure
A new approach to finite element modeling, analysis and post-processing
White, Gil
1987-01-01
Recent advances in both hardware and software have opened the door to a new generation of finite element modeling systems. INTERGRAPH CORP has combined an innovative programming concept with a stand alone workstation hardware platform to produce a new standard in finite element modeling called I/FEM. The system offers the COSMIC NASTRAN user full integration between design and analysis. I/FEM not only addresses the needs of the NASTRAN user of today, it also provides for continued evolution of the COSMIC NASTRAN product.
Standard Model Extension and Casimir effect for fermions at finite temperature
Santos, A. F.; Khanna, Faqir C.
2016-11-01
Lorentz and CPT symmetries are foundations for important processes in particle physics. Recent studies in Standard Model Extension (SME) at high energy indicate that these symmetries may be violated. Modifications in the lagrangian are necessary to achieve a hermitian hamiltonian. The fermion sector of the standard model extension is used to calculate the effects of the Lorentz and CPT violation on the Casimir effect at zero and finite temperature. The Casimir effect and Stefan-Boltzmann law at finite temperature are calculated using the thermo field dynamics formalism.
Long-ranged contributions to solvation free energies from theory and short-ranged models
Remsing, Richard C.; Liu, Shule; Weeks, John D.
2016-03-01
Long-standing problems associated with long-ranged electrostatic interactions have plagued theory and simulation alike. Traditional lattice sum (Ewald-like) treatments of Coulomb interactions add significant overhead to computer simulations and can produce artifacts from spurious interactions between simulation cell images. These subtle issues become particularly apparent when estimating thermodynamic quantities, such as free energies of solvation in charged and polar systems, to which long-ranged Coulomb interactions typically make a large contribution. In this paper, we develop a framework for determining very accurate solvation free energies of systems with long-ranged interactions from models that interact with purely short-ranged potentials. Our approach is generally applicable and can be combined with existing computational and theoretical techniques for estimating solvation thermodynamics. We demonstrate the utility of our approach by examining the hydration thermodynamics of hydrophobic and ionic solutes and the solvation of a large, highly charged colloid that exhibits overcharging, a complex nonlinear electrostatic phenomenon whereby counterions from the solvent effectively overscreen and locally invert the integrated charge of the solvated object.
Cox, P G; Fagan, M J; Rayfield, E J; Jeffery, N
2011-12-01
Rodents are defined by a uniquely specialized dentition and a highly complex arrangement of jaw-closing muscles. Finite element analysis (FEA) is an ideal technique to investigate the biomechanical implications of these specializations, but it is essential to understand fully the degree of influence of the different input parameters of the FE model to have confidence in the model's predictions. This study evaluates the sensitivity of FE models of rodent crania to elastic properties of the materials, loading direction, and the location and orientation of the models' constraints. Three FE models were constructed of squirrel, guinea pig and rat skulls. Each was loaded to simulate biting on the incisors, and the first and the third molars, with the angle of the incisal bite varied over a range of 45°. The Young's moduli of the bone and teeth components were varied between limits defined by findings from our own and previously published tests of material properties. Geometric morphometrics (GMM) was used to analyse the resulting skull deformations. Bone stiffness was found to have the strongest influence on the results in all three rodents, followed by bite position, and then bite angle and muscle orientation. Tooth material properties were shown to have little effect on the deformation of the skull. The effect of bite position varied between species, with the mesiodistal position of the biting tooth being most important in squirrels and guinea pigs, whereas bilateral vs. unilateral biting had the greatest influence in rats. A GMM analysis of isolated incisor deformations showed that, for all rodents, bite angle is the most important parameter, followed by elastic properties of the tooth. The results here elucidate which input parameters are most important when defining the FE models, but also provide interesting glimpses of the biomechanical differences between the three skulls, which will be fully explored in future publications. © 2011 The Authors. Journal of