bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of correlation‐based watermarking systems
Authors: Ejima Masataka , Miyazaki Akio 
Published: May 2003

AbstractWith recent advances in digital technology, it is now easy to copy digital content. As a result, unauthorized copying of content is widespread and copyright protection has become a serious issue. One solution to this problem is electronic watermarking, for which various techniques have been proposed. However, since no method of evaluation of the robustness of electronic watermarking methods has been established, it is difficult to compare various methods. This paper presents an analysis of the correlation‐based electronic watermarking method in which a pseudo‐random sequence is embedded as a watermark into the transform coefficients of the image and watermarking is detected by correlation. A method of evaluation is also proposed. Based on the proposed method, an electronic watermarking method using discrete wavelet transforms is proposed. Finally, based on the results, methods for improving the performance of the watermarking method are discussed. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(11): 1–12, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10093
Physical model for dynamic analysis of structures with FPS isolators
Authors: Almazán José L. , Llera Juan C. De la 
Published: May 2003

AbstractThis article presents a physical model for frictional pendulum isolators (FPS) that is ready to be implemented in most commercial software. The model is capable of accounting for effects such as large deformations, sticking, and uplift and impact by sensing the normal loads in the isolators through a gap element. Sticking has been incorporated into the model by extending the Park–Wen hysteretic model to the case of large deformations. The proposed model has been tested against a theoretically ‘exact’ formulation leading to essentially identical results. To facilitate its use, the physical FPS model has been cast into a typical non‐linear structural element format, i.e. with deformation as input and restoring force as output. Examples of a building and a bridge have been chosen to show the potential of the element and to provide further insight into the earthquake response of structures with FPS isolators; in particular, in aspects such as the orientation in placement of the isolator, sticking, P− Δ, and other large deformation effects. Copyright © 2003 John Wiley & Sons, Ltd.
Hybrid platform for vibration control of high‐tech equipment in buildings subject to ground motion. Part 1: experiment
Authors: Xu Y. L. , Liu H. J. , Yang Z. C. 
Published: May 2003

AbstractThis paper presents an experimental study, while a companion paper addresses an analytical study, to explore the possibility of using a hybrid platform to mitigate vibration of a batch of high‐tech equipment installed in a building subject to nearby traffic‐induced ground motion. A three‐storey building model and a hybrid platform model are designed and manufactured. The hybrid platform is mounted on the building floor through passive mounts composed of leaf springs and oil dampers and controlled actively by an electromagnetic actuator with velocity feedback control strategy. The passive mounts are designed in such a way that the stiffness and damping ratio of the platform can be changed. A series of shaking table tests are then performed on the building model without the platform, with the passive platform of different parameters, and with the hybrid platform. The experimental results demonstrate that the hybrid platform is very effective in reducing the velocity response of a batch of high‐tech equipment in the building subject to nearby traffic‐induced ground motion if dynamic properties of the platform and control feedback gain are selected appropriately. Copyright © 2003 John Wiley & Sons, Ltd.
Hybrid platform for vibration control of high‐tech equipment in buildings subject to ground motion. Part 2: analysis
Authors: Yang Z. C. , Xu Y. L. , Chen J. , Liu H. J. 
Published: May 2003

AbstractThe experimental results of using a hybrid platform to mitigate vibration of a batch of high‐tech equipment installed in a building subject to nearby traffic‐induced ground motion have been presented and discussed in the companion paper. Based on the identified dynamic properties of both the building and the platform, this paper first establishes an analytical model for hybrid control of the building‐platform system subject to ground motion in terms of the absolute co‐ordinate to facilitate the absolute velocity feedback control strategy used in the experiment. The traffic‐induced ground motion used in the experiment is then employed as input to the analytical model to compute the dynamic response of the building‐platform system. The computed results are compared with the measured results, and the comparison is found to be satisfactory. Based on the verified analytical model, coupling effects between the building and platform are then investigated. A parametric study is finally conducted to further assess the performance of both passive and hybrid platforms at microvibration level. The analytical study shows that the dynamic interaction between the building and platform should be taken into consideration. The hybrid control is effective in reducing both velocity response and drift of the platform/high‐tech equipment at microvibration level with reasonable control force. Copyright © 2003 John Wiley & Sons, Ltd.
Inelastic displacement ratios for evaluation of existing structures
Authors: Ruiz‐García Jorge , Miranda Eduardo 
Published: May 2003

AbstractResults of a detailed statistical study of constant relative strength inelastic displacement ratios to estimate maximum lateral inelastic displacement demands on existing structures from maximum lateral elastic displacement demands are presented. These ratios were computed for single‐degree‐of‐freedom systems with different levels of lateral strength normalized to the strength required to remain elastic when subjected to a relatively large ensemble of recorded earthquake ground motions. Three groups of soil conditions with shear wave velocities higher than 180m/s are considered. The influence of period of vibration, level of lateral yielding strength, site conditions, earthquake magnitude, distance to the source, and strain‐hardening ratio are evaluated and discussed. Mean inelastic displacement ratios and those associated with various percentiles are presented. A special emphasis is given to the dispersion of these ratios. It is concluded that distance to the source has a negligible influence on constant relative strength inelastic displacement ratios. However, for periods smaller than 1s earthquake magnitude and soil conditions have a moderate influence on these ratios. Strain hardening decreases maximum inelastic displacement at a fairly constant rate depending on the level of relative strength for periods of vibration longer than about 1.0s while it decreases maximum inelastic displacement non‐linearly as the period of vibration shortens and as the relative‐strength ratio increases for periods of vibration shorter than 1.0s. Finally, results from non‐linear regression analyses are presented that provide a simplified expression to be used to approximate mean inelastic displacement ratios during the evaluation of existing structures built on firm sites. Copyright © 2003 John Wiley & Sons, Ltd.
Seismic risk evaluation of RC bridge structures
Authors: Lupoi A. , Franchin P. , Schotanus M. 
Published: May 2003

AbstractIn this work a probabilistic methodology, recently developed by Cornell and co‐workers for seismic risk assessment of moment‐resisting steel frames, is investigated for possible applications to RC bridge structures. The basic theory is first illustrated; it is characterized by a remarkably simple but accurate mathematical formulation and by a light computational effort to estimate the risk. A simple extension to account for uncertainties in the mechanical parameters is then proposed. The methodology is applied to an existing RC bridge. The study has confirmed the robustness of the methodology with respect to the simplifying assumptions on which it is based, in particular to the reduced number of accelerograms required for a stable and accurate estimate of risk, and demonstrates the applicability to the case of RC bridges. Copyright © 2003 John Wiley & Sons, Ltd.
An efficient finite difference scheme for free‐surface flows in narrow rivers and estuaries
Authors: Chen XinJian 
Published: May 2003

AbstractThis paper presents a free‐surface correction (FSC) method for solving laterally averaged, 2‐D momentum and continuity equations. The FSC method is a predictor–corrector scheme, in which an intermediate free surface elevation is first calculated from the vertically integrated continuity equation after an intermediate, longitudinal velocity distribution is determined from the momentum equation. In the finite difference equation for the intermediate velocity, the vertical eddy viscosity term and the bottom‐ and sidewall friction terms are discretized implicitly, while the pressure gradient term, convection terms, and the horizontal eddy viscosity term are discretized explicitly. The intermediate free surface elevation is then adjusted by solving a FSC equation before the intermediate velocity field is corrected. The finite difference scheme is simple and can be easily implemented in existing laterally averaged 2‐D models. It is unconditionally stable with respect to gravitational waves, shear stresses on the bottom and side walls, and the vertical eddy viscosity term. It has been tested and validated with analytical solutions and field data measured in a narrow, riverine estuary in southwest Florida. Model simulations show that this numerical scheme is very efficient and normally can be run with a Courant number larger than 10. It can be used for rivers where the upstream bed elevation is higher than the downstream water surface elevation without any problem. Copyright © 2003 John Wiley & Sons, Ltd.
Chebyshev super spectral viscosity solution of a two‐dimensional fluidized‐bed model
Authors: Sarra Scott A. 
Published: May 2003

AbstractThe numerical solution of a model describing a two‐dimensional fluidized bed by a Chebyshev super spectral viscosity (SSV) method is considered. The model is in the form of a hyperbolic system of conservation laws with a source term, coupled with an elliptic equation for determining a stream function. The coupled elliptic equation is solved by a finite‐difference method. The mixed SSV/finite‐difference method produces physically shaped bubbles, on a very coarse grid. Fine scale details, which were not present in previous finite‐difference solutions, are present in the solution. Copyright © 2003 John Wiley & Sons, Ltd.
A spectral/finite‐difference approach for narrow‐channel flow with inertia
Authors: Siddique Mizanur R. , Khayat Roger E. 
Published: May 2003

AbstractA hybrid spectral/finite‐difference scheme is proposed to determine the inertial flow inside narrow channels. The flow field is represented spectrally in the depthwise direction, which together with the Galerkin projection lead to a system of equations that are solved using a variable step finite difference discretization. The method is particularly effective for non‐linear flow, and its validity is here demonstrated for a flow with inertia. The problem is closely related to high‐speed lubrication flow. The validity of the spectral representation is assessed by examining the convergence of the method, and comparing with the fully two‐dimensional finite‐volume solution (FLUENT), and the widely used depth‐averaging method from shallow‐water theory. It is found that a low number of modes are usually sufficient to secure convergence and accuracy. Good agreement is obtained between the low‐order description and the finite‐volume solution at low to moderate modified Reynolds number. The depth‐averaging solution is unable to predict accurately (qualitatively and quantitatively) the high‐inertia flow. The influence of inertia is examined on the flow. Copyright © 2003 John Wiley & Sons, Ltd.
Analysis of the local truncation error in the pressure‐free projection method for incompressible flows: a new accurate expression of the intermediate boundary conditions
Authors: Iannelli P. , Denaro F. M. 
Published: May 2003

AbstractThe numerical integration of the Navier–Stokes equations for incompressible flows demands efficient and accurate solution algorithms for pressure–velocity splitting. Such decoupling was traditionally performed by adopting the Fractional Time‐Step Method that is based on a formal separation between convective–diffusive momentum terms from the pressure gradient term. This idea is strictly related to the fundamental theorem on the Helmholtz–Hodge orthogonal decomposition of a vector field in a finite domain, from which the name projection methods originates. The aim of this paper is to provide an original evaluation of the local truncation error (LTE) for analysing the actual accuracy achieved by solving the de‐coupled system. The LTE sources are formally subdivided in two categories: errors intrinsically due to the splitting of the original system and errors due to the assignment of the boundary conditions. The main goal of the present paper consists in both providing the LTE analysis and proposing a remedy for the inaccuracy of some types of intermediate boundary conditions associated with the prediction equation. Such evaluations will be directly performed in the physical space for both the time continuous formulation and the finite volume discretization along with the discrete Adams–Bashforth/Crank–Nicolson time integration. A new proposal for a boundary condition expression, congruent with the discrete prediction equation is herein derived, fulfilling the goal of accomplishing the closure of the problem with fully second order accuracy. In our knowledge, this procedure is new in the literature and can be easily implemented for confined flows. The LTE is clearly highlighted and many computations demonstrate that our proposal is efficient and accurate and the goal of adopting the pressure‐free method in a finite domain with fully second order accuracy is reached. Copyright © 2003 John Wiley & Sons, Ltd.
CFD simulation of two‐ and three‐dimensional free‐surface flow
Authors: Apsley David , Hu Wei 
Published: May 2003

AbstractThe paper describes the implementation of moving‐mesh and free‐surface capabilities within a 3‐d finite‐volume Reynolds‐averaged‐Navier–Stokes solver, using surface‐conforming multi‐block structured meshes. The free‐surface kinematic condition can be applied in two ways: enforcing zero net mass flux or solving the kinematic equation by a finite‐difference method. The free surface is best defined by intermediate control points rather than the mesh vertices. Application of the dynamic boundary condition to the piezometric pressure at these points provides a hydrostatic restoring force which helps to eliminate any unnatural free‐surface undulations. The implementation of time‐marching methods on moving grids are described in some detail and it is shown that a second‐order scheme must be applied in both scalar‐transport and free‐surface equations if flows driven by free‐surface height variations are to be computed without significant wave attenuation using a modest number of time steps. Computations of five flows of theoretical and practical interest—forced motion in a pump, linear waves in a tank, quasi‐1d flow over a ramp, solitary wave interaction with a submerged obstacle and 3‐d flow about a surface‐penetrating cylinder—are described to illustrate the capabilities of our code and methods. Copyright © 2003 John Wiley & Sons, Ltd.
Spectral element method for viscoelastic flows in a planar contraction channel
Authors: Meng Sha , Li Xin Kai , Evans Gwynne 
Published: May 2003

AbstractA new algorithm, which combines the spectral element method with elastic viscous splitting stress (EVSS) method, has been developed for viscoelastic fluid flows in a planar contraction channel. The system of spectral element approximations to the velocity, pressure, extra stress and the rate of deformation variables is solved by a preconditioned conjugate gradient method based on the Uzawa iteration procedure. The numerical approach is implemented on a planar four‐to‐one contraction channel for a fluid governed by an Oldroyd‐B constitutive equation. The behaviour of the Oldroyd‐B fluids in the contraction channel is investigated with various Weissenberg numbers. It is shown that numerical solutions obtained here agree well with experimental measurements and other numerical predictions. Copyright © 2003 John Wiley & Sons, Ltd.
A numerical study of the propulsive efficiency of a flapping hydrofoil
Authors: Pedro G. , Suleman A. , Djilali N. 
Published: May 2003

AbstractA computational fluid dynamics study of the swimming efficiency of a two‐dimensional flapping hydrofoil at a Reynolds number of 1100 is presented. The model accounts fully for viscous effects that are particularly important when flow separation occurs. The model uses an arbitrary Lagrangian–Eulerian (ALE) method to track the moving boundaries of oscillatory and flapping bodies. A parametric analysis is presented of the variables that affect the motion of the hydrofoil as it moves through the flow along with flow visualizations in an attempt to quantify and qualify the effect that these variables have on the performance of the hydrofoil. Copyright © 2003 John Wiley & Sons, Ltd.
A theoretical Taylor–Galerkin model for first‐order hyperbolic equation
Authors: Sheu Tony W. H. , Lee P. H. 
Published: May 2003

AbstractThis paper presents a class of Taylor–Galerkin (TG) finite‐element models for solving the first‐order hyperbolic equation which admits discontinuities. Five parameters are introduced for purposes of controlling stability, monotonicity and accuracy. In this paper, the total variation diminishing concept and the theory of M‐matrix are applied to construct a monotonic TG model for capturing discontinuities. To avoid making the scheme overly diffusive, we apply a flux‐corrected transport (FCT) technique of Boris and Book to overcome the difficulty with anti‐diffusive flux. In smooth flow regions, our strategyof developing the temporal and spatial high‐order TG finite‐element model is based on modified equation analysis. In regions where discontinuity is encountered, we resort to two dispersively more accurate models to make the prediction accuracy as high as that obtained in smooth cases. These models are developed using the entropy‐increasing principle and the theory of group velocity. Guided by this theory, a slower group velocity should be used ahead of the shock. To avoid a train of post‐shocks, free parameters should be chosen properly to obtain a group velocity which takes on a larger value than the exact phase velocity. In this paper, we also apply the entropy‐increasing principle to determine free parameters introduced in the finite‐element model. Under the entropy‐increasing requirement, it is mandatory that coefficients of the even and odd derivative terms shown in the modified equation should change signs alternatively in order to avoid non‐physical wiggles. Several benchmark problems have been investigated to confirm the integrity of these proposed characteristic models. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical simulation of the unsteady behaviour of cavitating flows
Authors: Coutier‐Delgosha O. , Reboud J. L. , Delannoy Y. 
Published: May 2003

AbstractA 2D numerical model is proposed to simulate unsteady cavitating flows. The Reynolds‐averaged Navier–Stokes equations are solved for the mixture of liquid and vapour, which is considered as a single fluid with variable density. The vapourization and condensation processes are controlled by a barotropic state law that relates the fluid density to the pressure variations. The numerical resolution is a pressure‐correction method derived from the SIMPLE algorithm, with a finite volume discretization. The standard scheme is slightly modified to take into account the cavitation phenomenon. That numerical model is used to calculate unsteady cavitating flows in two Venturi type sections. The choice of the turbulence model is discussed, and the standard RNG k–εmodel is found to lead to non‐physical stable cavities. A modified k–εmodel is proposed to improve the simulation. The influence of numerical and physical parameters is presented, and the numerical results are compared to previous experimental observations and measurements. The proposed model seems to describe the unsteady cavitation behaviour in 2D geometries well. Copyright © 2003 John Wiley & Sons, Ltd.
Development of a parallel storm surge model
Authors: Davis Justin R. , Sheng Y. Peter 
Published: May 2003

AbstractA new parallel storm surge model, the Parallel Environmental Model (PEM), is developed and tested by comparisons with analytic solutions. The PEM is a 2‐D vertically averaged, wetting and drying numerical model and can be operated in explicit, semi‐implicit and fully implicit modes. In the implicit mode, the propagation, Coriolis and bottom friction terms can all be treated implicitly. The advection and diffusion terms are solved with a parallel Eulerian–Lagrangian scheme developed for this study. The model is developed specifically for use on parallel computer systems and will function accordingly in either explicit of implicit modes. Storm boundary conditions are based on a simple exponential decay of pressure from the centre of a storm. The simulated flooding caused by a major Category 5 hurricane making landfall in the Indian River Lagoon, Florida is then presented as an example application of the PEM. Copyright © 2003 John Wiley & Sons, Ltd.
The identification of trends in the utilisation of mental health services by elderly: a Dutch case register study
Authors: Pijl Ysbrand J. , Sytema Sjoerd 
Published: May 2003

AbstractObjectiveIn view of the rapid ageing of the population any changes in the use of mental health services by the elderly became increasingly important for policy development. This study aimed at the supply of information about trends in the numbers of elderly clients, the services they used and the volume and pattern of service utilisation.MethodsDetails of elderly users and their use of community‐ and hospital‐based services between 1990 and 1999 were retrieved from the Groningen case register. Developments in population size and age distribution in the register area were taken into account, as were the unit costs of mental health services.ResultsLarge age specific changes were found that caused only the expenditures on the oldest elderly to increase due to a shift from outpatient clinics to prolonged psychogeriatric day treatment and inpatient care. Comparatively young elderly used fewer inpatient services and more community care. The number of new elderly clients declined progressively. In some age groups treated prevalence also decreased, but to a lesser extent, because of a prolonged use of mental health services.ConclusionsStudy results seemed well in accordance with mental health policy as to deinstitutionalization and active ageing. Research on the effect of mental health care on life expectancy and the time lag between the intake of mental health providers and treated prevalence was proposed in order to improve the prediction of future service use by elderly. Copyright © 2003 John Wiley & Sons, Ltd.