Numerical Application (numerical + application)

Distribution by Scientific Domains


Selected Abstracts


Large displacement behaviour of a structural model with foundation uplift under impulsive and earthquake excitations

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2003
Giuseppe Oliveto
Abstract This paper considers the dynamical behaviour of a structural model with foundation uplift. The equations of motion of the system considered are derived for large displacements thus allowing for the eventual overturning of the system. The transition conditions between successive phases of motion, derived in terms of the specific Lagrangian co-ordinates used in the formulation of the equations of motion, present innovative aspects which resolve some previously inexplicable behaviour in the structural response reported in the literature. The dynamical behaviour of the model is considered under impulsive and long-duration ground motions. The minimum horizontal acceleration impulses for the uplift and the overturning of the system are evaluated in analytical form. The sensitivity of the model to uplifting and to overturning under impulsive excitations is established as a function of few significant structural parameters. Numerical applications have been performed changing either the structural parameters or the loading parameter, in order to analyse several dynamical behaviours and also to validate the analytical results. For earthquake ground motions the results, reported in the form of response spectra, show that linearized models generally underestimate, sometimes significantly, the structural response. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Non-parametric,parametric model for random uncertainties in non-linear structural dynamics: application to earthquake engineering

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2004
Christophe Desceliers
Abstract This paper deals with the transient response of a non-linear dynamical system with random uncertainties. The non-parametric probabilistic model of random uncertainties recently published and extended to non-linear dynamical system analysis is used in order to model random uncertainties related to the linear part of the finite element model. The non-linearities are due to restoring forces whose parameters are uncertain and are modeled by the parametric approach. Jayne's maximum entropy principle with the constraints defined by the available information allows the probabilistic model of such random variables to be constructed. Therefore, a non-parametric,parametric formulation is developed in order to model all the sources of uncertainties in such a non-linear dynamical system. Finally, a numerical application for earthquake engineering analysis is proposed concerning a reactor cooling system under seismic loads. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Combining policy instruments to curb greenhouse gas emissions

ENVIRONMENTAL POLICY AND GOVERNANCE, Issue 3 2001
Olivier Bahn
The Kyoto Protocol has set greenhouse gas emission reduction targets for selected countries. To comply with these reduction requirements, decision-makers may use market-based instruments on a national or international basis. This paper advocates the combining of national emission taxes with international trade of emission permits. As a numerical application, this paper analyses macro-economic impacts of such a strategy for Switzerland. Copyright © 2001 John Wiley & Sons, Ltd and ERP Environment [source]


A Maslov-propagator seismogram for weakly anisotropic media

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002
Georg Rümpker
Summary We introduce a formalism to calculate shear-wave seismograms for weakly-anisotropic and inhomogeneous media. The method is based on the combination of the forward-propagator method, which accounts for shear-wave interaction along a single reference ray, and the Maslov ray-summation, which incorporates amplitude and phase information from neighbouring rays to account for waveform and diffraction effects at caustics and in shadow regions. The approach is based on the assumption that the multiply split shear waves, on the way to a given receiver, travel along a common ray path that can by obtained from ray tracing in an isotropic reference medium (i.e. the common-ray approximation). The forward propagator and the Maslov amplitude are expressed with respect to radial and transverse coordinates (perpendicular to the ray propagation direction) that are defined uniquely by the initial conditions. Local polarizations and slownesses of the fast and slow shear-waves in the direction of propagation are obtained from the eikonal equation. The Maslov-propagator phase is given by the average shear-wave traveltime along the reference ray. Phase advances and delays of individual shear wave components are accounted for by the propagator. The geometrical-spreading information required for the Maslov integration is supplied by dynamic ray tracing in the isotropic reference medium. In the high-frequency limit effective phase functions are defined to assess the validity of the Maslov propagator phase information. For a homogeneous isotropic reference medium, we find good agreement with exact Maslov phase functions for anisotropic perturbations of up to 20 per cent. As a numerical application we consider effects of inhomogeneous anisotropy in a shear-wave cross-hole survey. The variations of the transversely-isotropic medium require 2-D slowness integrals. The method can handle discontinuities of the fast polarization along the ray path and also for neighbouring rays which is important for the slowness integration. Smooth transitions between isotropic and anisotropic regions along the ray path can be accounted for without the need to switch between numerical formulations. [source]


Spatial foundation structures over no tension soil

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2005
A. Baratta
Abstract The problem of the stress distribution induced in the soil by a single circular foundation structure is approached in a three-dimensional analysis. Since the soil is typically made by not-cohesive materials, its behaviour is modelled by means of the not resisting tension (NRT) hypothesis, thus assuming that its very low resistance to tensile stresses can be completely neglected and that it keeps linearly elastic under pure compression. After developing the problem from a theoretical point of view on the basis of an energetic approach, a numerical application,which is able to reproduce the stress distribution induced by a circular foundation on the soil,is performed. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Dairy disaggregation and joint production in an economy-wide model,

AUSTRALIAN JOURNAL OF AGRICULTURAL & RESOURCE ECONOMICS, Issue 4 2010
Angus Charteris
We examine the impact of dairy disaggregation and joint production on trade liberalisation outcomes in an economy-wide model. Depending on parameterisation, our model includes either (i) a single dairy commodity, (ii) several dairy commodities without joint production or (iii) several dairy commodities with joint production. In a numerical application, we consider the removal of US tariffs on dairy exports from New Zealand (the world's largest dairy exporter). We show that failing to account for joint production when dairy commodities are disaggregated leads to misleading results. Our preferred dairy production function differs from those used in other applied trade models. Our analysis can be used to determine when accounting for joint production in other sectors is important. [source]


Bi-level Programming Formulation and Heuristic Solution Approach for Dynamic Traffic Signal Optimization

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2006
Dazhi Sun
Conventional methods of signal timing optimization assume given traffic flow pattern, whereas traffic assignment is performed with the assumption of fixed signal timing. This study develops a bi-level programming formulation and heuristic solution approach (HSA) for dynamic traffic signal optimization in networks with time-dependent demand and stochastic route choice. In the bi-level programming model, the upper level problem represents the decision-making behavior (signal control) of the system manager, while the user travel behavior is represented at the lower level. The HSA consists of a Genetic Algorithm (GA) and a Cell Transmission Simulation (CTS) based Incremental Logit Assignment (ILA) procedure. GA is used to seek the upper level signal control variables. ILA is developed to find user optimal flow pattern at the lower level, and CTS is implemented to propagate traffic and collect real-time traffic information. The performance of the HSA is investigated in numerical applications in a sample network. These applications compare the efficiency and quality of the global optima achieved by Elitist GA and Micro GA. Furthermore, the impact of different frequencies of updating information and different population sizes of GA on system performance is analyzed. [source]


Recovering acoustic reflectivity using Dirichlet-to-Neumann maps and left- and right-operating adjoint propagators

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2005
M. W. P. Dillen
SUMMARY Constructing an image of the Earth subsurface from acoustic wave reflections has previously been described as a recursive downward redatuming of sources and receivers. Most of the methods that have been presented involve reflectivity and propagators associated with one-way wavefield components. In this paper, we consider the reflectivity relation between two-way wavefield components, each a solution of a Helmholtz equation. To construct forward and inverse propagators, and a reflection operator, the invariant-embedding technique is followed, using Dirichlet-to-Neumann maps. Employing bilinear and sesquilinear forms, the forward- and inverse-scattering problems, respectively, are treated analogously. Through these mathematical constructs, the relationship between a causality radiation condition and symmetry, with respect to a bilinear form, is associated with the requirement of an anticausality radiation condition with respect to a sesquilinear form. Using reciprocity, sources and receivers are redatumed recursively to the reflector, employing left- and right-operating adjoint propagators. The exposition of the proposed method is formal, that is numerical applications are not derived. The key to applications lies in the explicit representation, characterization and approximation of the relevant operators (symbols) and fundamental solutions (path integrals). Existing constructive work which could be applied to the proposed method are referred to in the text. [source]


A constitutive model for the dynamic and high-pressure behaviour of a propellant-like material: Part I: Experimental background and general structure of the model

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 6 2001
Hervé Trumel
Abstract This paper is the first part of a work that aims at developing a mechanical model for the behaviour of propellant-like materials under high confining pressure and strain rate. The behaviour of a typical material is investigated experimentally. Several microstructural deformation processes are identified and correlated with loading conditions. The resulting behaviour is complex, non-linear, and characterized by multiple couplings. The general structure of a relevant model is sought using a thermodynamic framework. A viscoelastic-viscoplastic-compaction model structure is derived under suitable simplifying assumptions, in the framework of finite, though moderate, strains. Model development, identification and numerical applications are given in the companion paper. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Auxiliary functions for molecular integrals with Slater-type orbitals.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2006

Abstract Many types of molecular integrals involving Slater functions can be expressed, with the ,-function method in terms of sets of one-dimensional auxiliary integrals whose integrands contain two-range functions. After reviewing the properties of these functions (including recurrence relations, derivatives, integral representations, and series expansions), we carry out a detailed study of the auxiliary integrals aimed to facilitate both the formal and computational applications of the ,-function method. The usefulness of this study in formal applications is illustrated with an example. The high performance in numerical applications is proved by the development of a very efficient program for the calculation of two-center integrals with Slater functions corresponding to electrostatic potential, electric field, and electric field gradient. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]


On the regularity of flows with Ladyzhenskaya Shear-dependent viscosity and slip or non-slip boundary conditions,

COMMUNICATIONS ON PURE & APPLIED MATHEMATICS, Issue 4 2005
H. Beirão da Veiga
Navier-Stokes equations with shear dependent viscosity under the classical non-slip boundary condition have been introduced and studied, in the sixties, by O. A. Ladyzhenskaya and, in the case of gradient dependent viscosity, by J.-L. Lions. A particular case is the well known Smagorinsky turbulence model. This is nowadays a central subject of investigation. On the other hand, boundary conditions of slip type seems to be more realistic in some situations, in particular in numerical applications. They are a main research subject. The existence of weak solutions u to the above problems, with slip (or non-slip) type boundary conditions, is well known in many cases. However, regularity up to the boundary still presents many open questions. In what follows we present some regularity results, in the stationary case, for weak solutions to this kind of problems; see Theorems 3.1 and 3.2. The evolution problem is studied in the forthcoming paper [6]; see the remark at the end of the introduction. © 2004 Wiley Periodicals, Inc. [source]