bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectral filtering for ultra‐fast mode‐locking in the normal dispersive regime
Authors: Bale Brandon G. , Kutz J Nathan 
Published: October 2008

AbstractA theoretical model is developed which characterizes the physical process responsible for generating ultra‐short, high‐energy, mode‐locked pulses in a normal GVD laser cavity with spectral filtering. Two physical parameters are critical to achieving optimal performance: the ratio of the filter bandwidth to the gain bandwidth and the placement of the output coupler in the laser cavity. The spectral filtering allows for the high‐energy of typical normal GVD laser cavities to be maintained while the pulse intensity doubles and the FWHM reduces by an order of magnitude. This phenomenon is generic and ubiquitous to normal GVD mode‐locking. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SPSA vs Simplex in statistical machine translation optimization
Authors: Lambert Patrik , Banchs Rafael E. 
Published: October 2008

AbstractMost statistical machine translation systems are combinations of various models and tuning scaling factors is an important step. However, this optimisation problem is hard because the objective function has many local minima and the available algorithms cannot achieve a global optimum. Consequently, optimisations starting from different initial settings can converge to fairly different solutions. We present tuning experiments with the Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm, and compare them with the widely used downhill simplex method. With IWSLT 2005 Chinese‐English data, both methods showed similar performance, but SPSA was more robust to the choice of initial settings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On some topological and variational properties of a model for reconstructing three‐dimensional transparent images with self‐occlusions
Authors: Bellettini Giovanni 
Published: October 2008

AbstractWe discuss a variational model for reconstructing an image taking into account the depth of the various objects in the threedimensional space, based on the properties of the apparent contour. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mortar method for thermomechanically coupled problems
Authors: Berend E. , Wriggers P. , Nackenhorst U. 
Published: October 2008

AbstractIn the foundry industry a reliable prediction of quality defects of the products like residual stresses or size alterations requires detailed constitutive material equations along with a precise modelling of the cast/mould interaction. In this contribution we focus on the description of a contact‐dependent heat transfer between the metal and the mould. Within this approach the contact formulation is based on the mortar finite element scheme. This strategy has turned out to be more stable for contact problems than other schemes like node‐to‐segment discretizations, see e.g.[1]. Due to the significant difference in the stiffness of the mould and the cast in the liquid or semi‐solid state a formulation is proposed that works without additional parameters like a penalty parameter or Lagrange multipliers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Updating preconditioners for permuted non‐symmetric linear systems
Authors: Birken Philipp , Tebbens Jurjen Duintjer , Meister Andreas , Tuma Miroslav 
Published: October 2008

AbstractWe consider the solution of a sequence of nonsymmetric linear systems arising from a supersonic model problem by exploiting triangular preconditioner updates. In addition, we demonstrate how the power of the updates can be enhanced by permuting the entire sequence beforehand with a physically motivated reordering of unknowns. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional continuum mechanical modeling of the Portevin‐Le Châtelier effect
Authors: Bondár G. , Böhlke T. , Estrin Y. 
Published: October 2008

AbstractIn many Al, Cu, Fe and Ni based alloys jerky flow associated with the Portevin‐Le Châtelier (PLC) effect occurs within a specific range of temperatures and strain‐rates. This effect which reduces the ductility and the surface quality of sheet materials is caused by dynamic interaction of mobile dislocations with solute atoms [1]. A three‐dimensional continuum mechanical model of this effect, also known as dynamic strain ageing, is presented. Furthermore, the predictions of the three‐dimensional model are compared with experimental data. Special emphasis is put on the determination of the instability region in the strain and strain‐rate space [2]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of the incompressible Navier‐Stokes equations with explicit integration of the pressure term
Authors: Bonfigli G. 
Published: October 2008

AbstractWe propose a formulation of the incompressible Navier‐Stokes equations considering a Poisson equation with Neumann boundary conditions for the pressure, and innovative boundary conditions for the velocity. Numerical tests show that the proposed formulation ensures solenoidality of the velocity field. If the initial condition is not divergence‐free, exponential decay is observed in time for the error in the fulfillment of the continuity equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of scattering problems using pseudo‐differential impedance operators
Authors: Calvo David C. , Soukup Raymond J. 
Published: October 2008

AbstractDirect numerical solutions of scattering problems based on boundary‐integral equations are computationally costly at high frequencies. A numerical method is presented that efficiently computes accurate approximations to unknown surface quantities given known surface data (an approximate Dirichlet‐to‐Neumann map). The method is based on a pseudo‐differential impedance operator (PIO) numerically implemented using rational approximations. An example of a PIO is the so‐called on‐surface radiation condition (OSRC) method. For a convex obstacle, the method can be viewed as applying a parabolic equation directly on the surface of a scatterer. In contrast to past OSRCs, the use of rational approximations provides accuracy for wide scattering angles which is needed for grazing angles of incidence. Generalization to impedance operators for two‐dimensional acoustic scatterers with concave parts is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time series modelling of the Singapore population data
Authors: Cheang Wai Kwong 
Published: October 2008

AbstractTrends in population have important implications for a government in formulating its manpower‐related policies. A business may also need to adjust its long‐term market strategies according to these trends. This paper analyses the Singapore population data using time series regression model with autoregressive error term. In addition to a linear trend, other regressors included in the model are (i) a seasonal component of period 12 to account for the effect of the auspicious “dragon” years in the Chinese calendar; (ii) level‐shift interventions to account for the effect of the government campaigns on family planning. Two methods of estimating the autoregressive parameter are considered: maximum likelihood (ML) and restricted maximum likelihood (REML). For a time series of short or moderate sample length, it is shown in Cheang and Reinsel (2000) that the REML estimator is generally much less biased than the ML estimator. Consequently, the REML approach leads to more accurate inferences for the regression parameters. This paper compares the ML and REML estimation results, and examines the implications for the nature of nonstationarity (deterministic or stochastic trend component) exhibited by the Singapore population data series. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Challenges for mathematical and statistical modelling for metrology
Authors: Cox Maurice G , Forbes Alistair B , Harris Peter M 
Published: October 2008

AbstractThere are challenges in disseminating information concerning mathematical and statistical modelling for metrology. We specify these challenges and consider ways they are being met. In addition to journal papers, the value of supporting software and other aspects are indicated. Relevant work in the UK Software Support for Metrology programme is outlined. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical solution of 3D free surface flows using implicit methods
Authors: Oishi Cassio M. , Cuminato José A. , Tomé Murilo F. 
Published: October 2008

AbstractThis work presents an implicit technique for simulating three‐dimensional unsteady low Reynolds number free surface flows of non‐Newtonian fluids. It is based on the Marker‐and‐Cell technique and it employs finite differences on a staggered grid. Validation results and the numerical simulation of complex free surface flows are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of exit times and positions for Brownian motions and Diffusions
Authors: Deaconu Madalina , Lejay Antoine 
Published: October 2008

AbstractWe present in this note some variations of the Monte Carlo method for the random walk on spheres which allow to solve many elliptic and parabolic problems involving the Laplace operator or second‐order differential operators. In these methods, the spheres are replaced by rectangles or parallelepipeds. Our first method constructs the exit time and the exit position of a rectangle for a Brownian motion. The second method exhibits a variance reduction technique. The main point is to reduce the problem only to the use of some distributions related to the standard one‐dimensional Brownian motion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computing the radiating source term in the system of radiation magnetohydrodynamics
Authors: Dedner Andreas 
Published: October 2008

AbstractIn this paper we present results for the extended short‐characteristics method (ESC) for computing the radiation source term Qrad with special focus on using this method in combination with a finite‐volume scheme for solving the equations of radiation magnetohydrodynamics (RMHD). Since the approximation of the radiation source term takes up a large amount of the computational cost, the efficiency of this part of the numerical scheme is an essential consideration. We compare this method with other methods from the literature with respect to their computational efficiency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mixed‐integer models for topology optimization in sheet metal design
Authors: Fügenschuh Armin , Martin Alexander 
Published: October 2008

AbstractTopology optimization lies at the heart of many design tasks in mechanical engineering. For those sheet metal products that consist of a bundle of separate channels (such as conduits) we formulate the design task as a linear mixed‐integer optimization problem. The design goal is to find a topology where each channel has a given cross section area, using a minimum amount of sheet met al. In addition to a light‐weight design, stiffness should also be taken into account. The entire approach is demonstrated in the design of a conduit with five separate channels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient distance algorithm for interval‐based octree‐encoded CSG objects with time‐space coherence utilization
Authors: Dyllong Eva , Grimm Cornelius 
Published: October 2008

AbstractIn this paper, a new distance algorithm for octree‐encoded CSG objects is presented. Interval vectors are used to describe the nodes of the octree for a reliable and efficient realization of the hierarchical data structure. The algorithm yields the lower bounds of the distance between the objects and is based on accurate algorithms that have been shown in [1], but involves interval arithmetic for reliable handling of rounding errors. Furthermore, time‐space coherence is utilized to increase the efficiency of sequential distance calculations. Experiments validate the approach and show its range of applicability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A globally well‐posed nonlinear nonlocal diffusion
Authors: Guidotti Patrick 
Published: October 2008

AbstractNonlinear diffusions have successfully been employed to perform a variety of tasks in image processing. In the context of denoising, the Perona‐Malik equation is a particularly successful example. In spite of its cherished qualities, it is mathematically ill‐posed and has some practical short‐comings. In this short paper a new nonlocal nonlinear diffusion is reported upon, which is globally well‐posed and shares with Perona‐Malik all its qualities even improving on its weaknesses. It can be viewed as a new kind of regularization. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Well modeling in the multi‐scale finite‐volume context
Authors: Jenny Patrick , Lunati Ivan 
Published: October 2008

AbstractAn extension of the multi‐scale finite‐volume (MSFV) method is devised, which allows to simulate flow and transport in reservoirs with complex well configurations. The new framework fits nicely into the data structure of the original MSFV method and it has the important property that no large patches covering the whole well are required. For each well, an additional degree of freedom is introduced. While the treatment of pressure‐constraint wells is trivial, since the well‐bore reference pressure is explicitly specified, additional equations have to be solved to obtain the unknown pressure values of rate‐constraint wells. Numerical simulations of a difficult test case with multiple complex wells demonstrate the ability of the new framework to capture the interference between the various wells and the reservoir accurately. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on the convergence behavior of algorithms via reachable set analysis
Authors: Jordan J. 
Published: October 2008

AbstractMany iterative algorithms can be interpreted as discrete‐time control systems evolving on manifolds. Here, shift parameters act as control inputs. The Adherence structure of the reachable sets provides fundamental limitations on the possible convergence behavior of the algorithm.We analyse the reachable sets of inverse iteration schemes and rational iteration schemes. In particular we show a necessary conditions for the existence of local convergent shift strategies for inverse iteration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Invariant manifolds and the interplanetary superhighway
Authors: Lo Martin W. 
Published: October 2008

AbstractWe propose a different model to study the Solar System by considering it as a series of Three Body Problems (Sun‐Planet‐Infinitesimal Body). The invariant manifolds of each Three Body System intersect in space to provide a transport mechanism spanning the entire Solar System which is popularly called the “Interplanetary Superhighway”. This concept is useful for designing space missions and for understanding the motions of minor bodies in the Solar System. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Parareal in time approximation of the Korteveg‐deVries‐Burgers' equations
Authors: MahmoudKaber Sidi , Maday Yvon 
Published: October 2008

AbstractThe parareal in time algorithm is a predictor corrector method that allows to get parallelisation through the time. It consists in segmenting the interval of time integration into slabs, then propose iteratively seed values at the left hand side of each of the slabs. The derivation of the seed values is done sequentially and involves propagator that should mimic the equation to be solved but should be very cheap and parallel accurate propagations of each seed value over each slab. Various approaches have been proposed to get the coarse propagator, in this paper, we use the averaging approach developed by Barenblatt and Chorin for the Korteveg‐deVries‐Burgers' equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Stefan problem related to a non‐equilibrium shrinking unreacted core model with fast reaction for the sphere
Authors: Muntean Adrian 
Published: October 2008

AbstractThe problem studied in this note refers to a substantial part of a larger system of partial differential equations modeling diffusion and fast reaction of a gaseous species A in a reactive spherical porous region. We report on the local existence and uniqueness of weak solutions to the corresponding moving‐boundary system containing two coupled mass‐balance equations in a moving annulus. Since the system incorporates an explicit description of the velocity of the moving boundary, our formulation resembles to the one‐phase Stefan‐like problem with kinetic condition. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulation of building evacuation in emergency conditions
Authors: Camarena Alicia Guadalupe Ortega 
Published: October 2008

AbstractIn the present work, pedestrian behaviour in crowds is assumed to be a coupled phenomena. Therefore, the use of continuousand individual‐models in different regions according to its local density is suggested. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A geometrical multiscale approach to the evaluation of hemodynamic risk factors for internal carotid artery aneurysm development.
Authors: Passerini Tiziano , Veneziani Alessandro 
Published: October 2008

AbstractIn this work we address morphological and fluid‐mechanical features of Internal Carotid Artery (ICA) which can be possibly related to the presence and the rupture of cerebral aneurysms. A classification is presented, based on geometrical characteristics (ICA radius and curvature). Fluid dynamics analyses of blood flow in vessels belonging to different classes show significant differences in mechanical behaviour, being the risk of rupture (a dramatic event) potentially quite different among the classes. Classification could have therefore a significant predictive role. Multiscale models can be exploited to take into account the mechanical effects of the circulatory system embodying the pathological vascular district. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards the computational homogenization of discrete microstructures
Authors: Ricker Sarah , Menzel Andreas , Steinmann Paul 
Published: October 2008

AbstractThe main objective of the current work is the extension of a computational homogenization scheme towards the simulation of discrete micro‐structures. On the micro‐level so‐called multiple particle systems (MPS) are introduced for which a continuization scheme, resulting in a formulation analogous to a homogenization scheme, is developed. Furthermore, three types of constitutive behavior are applied to these particle systems and their influence on the overall macro‐structure is studied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of surfactant on bubble and thread dynamics
Authors: Booty M.R. , Siegel M. 
Published: October 2008

AbstractTwo examples from the dynamics of surfactant‐laden interfacial flow are considered. In the first example, a bubble is rapidly stretched by an imposed flow to form a dumb‐bell shape, then the imposed flow is relaxed, so that the bubble evolves solely under the action of surfactant‐modified surface tension. In the second example, a surfactant‐coated bubble is continually stretched by a steady extensional flow. At sufficiently small strain rates, steady bubble shapes are found, whereas at larger strain rates a long‐wave model of the dynamics predicts behavior that is reminiscent of experimentally observed tip‐streaming. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coupled system of Korteweg‐de Vries equation‐type in domains with oscillatory moving boundaries
Authors: Vera Octavio , Sepúlveda Mauricio , Bisognin Vanilde 
Published: October 2008

AbstractWe consider the initial‐boundary value problem in a bounded domain with oscillatory moving boundaries and nonhomogeneous boundary conditions for the coupled system of equations of KdV type modelling strong interactions between internal solitary waves. We give a result of global existence and uniqueness for strong solutions for the coupled system of equations of Korteweg – de Vries type as well as the exponential decay of small solutions in asymptotically cylindrical domains. We present a numerical examples based in semi‐implicit finite differences showing the numerical effect of the oscillatory moving boundaries for this kind of systems. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A positive and conservative second order finite volume scheme applied to a phosphor cycle in canals with sediment
Authors: Benz Joachim , Meister Andreas , Zardo Philipp Andrea 
Published: October 2008

AbstractThis paper is devoted to the description of a higher order finite volume scheme for the 2D shallow water equation with a specific focus on a complex phosphor cycle describing processes in lakes and rivers. The scheme guarantees the unconditional positivity and mass conservation of respectively modelled quantities, which are crucial properties for meaningful computed results in biochemical contexts. It works on secondary unstructured meshes which enables the application to arbitrary complex geometries. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Straight chains of interconnected mass points under the action of non‐symmetric dry friction
Authors: Zeidis I. , Zimmermann K. , Pivovarov M. 
Published: October 2008

AbstractThe motion of a chain of interconnected equal material points placed on a rough straight line and connected by equal kinematical constraints is considered. It is supposed that the system experiences a small non‐symmetric Coulomb dry frictional force acting from the line side upon each mass point and opposite to the direction of motion. The magnitude of this force depends on the direction of motion. To the equation of motion the procedure of averaging is applied. The expression for the stationary “on the average” velocity of the motion of the system as a single whole is found. The obtained theoretical results can be used for the design of worm‐like vibration robots. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cointegration applied to purchasing‐power analysis of mean Ukrainian total wages
Authors: Bardadym Tamara , Emmenegger Jean‐François 
Published: October 2008

AbstractThe main purpose of this study is to propose Johansen's [6] methodology of linear cointegration analysis as a tool to measure the purchasing power of the Ukrainian mean total wages (MTW) within the period of November 1993 to December 2004 expressed in terms of prices of some basic food products or of the Consumer Price Index (CPI). Nineteen monthly price time series of basic food products, the CPI and MTW published by the State Committee of Statistics of Ukraine (Derzhkomstat) have been selected. Preliminary studies of stationarity are undertaken to establish their degree of integratedness with a battery of adequate unit root tests. A cointegration analysis of couples of one of these price time series of some basic food products, respectively the CPI and the MTW time series are realised, yielding linear functions between both selected series, establishing tentative long‐run equilibrium relations for subperiods shorter than the interval 1993 to 2004. The results show that the purchasing power of the MTW, expressed in terms of the prices of some basic food products, respectively the CPI, gradually increased from 1993 to 2004. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of anisotropic atomic motions in biological macromolecules
Authors: Burden C. J. , Formont L. , Oakley A. J. 
Published: October 2008

AbstractA compact and convenient graphical technique for assessing agreement between spatial atomic distributions in large molecules determined from alternate sources is presented. The procedure is available as downloadable software. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)