bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation of nonclassical waves for immiscible three‐phase flow in heterogeneous porous media
Authors: Abreu Eduardo 
Published: March 2008

AbstractIn this paper we present accurate two‐dimensional numerical results, based on a new fractional time‐step method, for the numerical solution of a highly nonlinear system of partial differential equations modeling three‐phase immiscible water‐gasoil flow problems in heterogeneous petroleum reservoirs.The new numerical procedure was used to extend theoretical results for one‐dimensional three‐phase flow available in the literature by providing numerical evidence of the existence of nonclassical transitional shock in heterogeneous twodimensional three‐phase flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical procedures for the determination of the leading coefficient a (x)
Authors: Azari Hossein 
Published: March 2008

AbstractThe aim of this paper is to study the parabolic inverse problem of determination of the leading coefficient in the heat equation with an extra condition at the terminal. After introducing a new variable, we reformulate the problem as a nonclassical parabolic equation along with the initial and boundary conditions. The finite difference methods, backward Euler and Crank–Nicolson schemes are studied. The results of a numerical example are presented, which demonstrate the efficiency and rapid convergence of the methods. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Configurational forces in a micro‐cracked body
Authors: Boma Malika Bongué , Brocato Maurizio 
Published: March 2008

AbstractA framework to model micro‐cracked bodies based on the theory of continua with microstructure is presented: assuming a crack embedded in each material element, a field is considered characterising size and orientation of the crack, in addition to the usual placement in the Euclidian space. To deal with crack evolutions, we call upon configurational forces which, in the present case, occur at the level of the microstructure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The eigen‐structure of the Jacobian in multi‐class Lighthill‐Whitham‐Richards traffic flow models
Authors: Donat R. , Mulet P. 
Published: March 2008

AbstractCharacteristic‐based High Resolution Shock Capturing schemes for hyperbolic systems of conservation laws require, in their basic design structure, knowledge on the complete eigen‐decomposition of the Jacobian matrix of the system. For the Multi‐Class Lighthill‐Witham‐Richards (MCLWR) Traffic flow model considered in [4], there is no explicit formula for the eigenvalues of the Jacobian matrix, which can only be determined numerically. However, once they are determined, the eigen‐vectors are easily computed and straightforward formulas can be obtained by exploiting the specific structure of the Jacobian matrix in these models. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multilevel regularization for image deblurring problems
Authors: Donatelli M. 
Published: March 2008

AbstractWe consider the de‐blurring problem of noisy and blurred signals/images in the case of space invariant point spread functions. The use of appropriate boundary conditions leads to linear systems with structured coefficient matrices related to space invariant operators like Toeplitz, circulants, trigonometric matrix algebras etc. We combine an algebraic multigrid (which is designed ad hoc for structured matrices) with the low‐pass projectors typical of the classical geometrical multigrid for elliptic partial differential equations. The smoother is any iterative regularizing method, while the projector is chosen in order to maintain the same algebraic structure at each recursion level and having a low‐pass filter property, which is very useful in order to reduce the noise effects. In this way, we obtain a better restored image with a flatter restoration error curve and also in less time than the auxiliary method used as smoother. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical modelling of the hydrodynamic field coupled to the transport of chemical species through the finite‐element method
Authors: Anjos G. R. dos , Mangiavacchi N. , Pontes J. , Soares C. B. P. 
Published: March 2008

AbstractWe describe the main features of a numerical simulator currently under development for studying water physico‐chemical properties during the flooding of hydroelectric plants reservoirs. The work is sponsored by the brazilian Electric Energy National Agency ANEEL and conducted in a joint work of brazilian universities rearchers, with Furnas Centrais Elétricas S. A., the leading brazilian power utility company. An overview of the simulator requirements and of the involved partners is given. The software modules and engineering solutions are briefly discussed, including the finite element based transport module. Some results, future steps and partnerships are presented and discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Global properties of time‐delayed feedback control in electronic circuits
Authors: Höhne Klaus , Benner Hartmut 
Published: March 2008

AbstractGlobal properties play an important role in real life applications of time‐delayed feedback control of chaos. The success of control is not only determined by the change of the local stability of some unstable periodic state embedded in the chaotic attractor, but also related to a basin of attraction large enough to capture the chaotic trajectory within a reasonable time. We report on electronic circuit experiments where the control performance is essentially affected by the type of bifurcations limiting the control regime and their respective global properties. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive linearized models for optimization of gas networks
Authors: Kolb Oliver , Lang Jens , Bales Pia 
Published: March 2008

AbstractWe are interested in simulation and optimization of gas networks. Usually, a gas network consists of various components like compressors and valves connected by pipes. The aim is to run the network cost efficiently whereas demands of consumers have to be satisfied. This results in a complex nonlinear mixed integer problem. We address this task with methods provided by discrete optimization. Therefore, the gas dynamics in all pipes and at compressors must be described by piecewise linear constraints. We introduce an adaptive approach for the linearization process to handle the complexity on the one hand and the aimed accuracy on the other and present numerical simulation and optimization results based on our model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite volume element method for the incompressible miscible displacement problems in porous media
Authors: Kumar Sarvesh , Nataraj Neela , Pani Amiya K. 
Published: March 2008

AbstractWe present the finite volume element method (FVEM) for incompressible miscible displacement problems in porous media. Optimal error estimates in L∞(L2) are derived for velocity and concentration. Numerical experiments are also presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An embedding method for simulation of immobilized enzyme kinetics and transport in sessile hydrogel drops
Authors: Wong Chao‐Jen , Nadim Ali 
Published: March 2008

AbstractA newly‐developed embedding method for simulating enzyme kinetics and transport occurring within axisymmetric 3D domains is presented. The physical problem is pertinent to gel‐pad microarrays for assessment of enzymatic activity. An enzyme is immobilized uniformly within a hydrogel which is spotted onto a solid surface in the form of a sessile drop, taking on a spherical cap shape. An aqueous solution containing substrate flows slowly past the porous drop. The substrate diffuses into the drop and is converted to product with the help of the enzyme. The product accumulates in and diffuses out of the drop and is taken away by the flow. Spatiotemporal distribution of the product, monitored via fluorescence, can be used to quantify the enzyme kinetics. This process is described by a system of nonlinear reaction‐diffusion partial differential equations, modeling the diffusive transport and enzymatic reaction. The computational domain contains both the hydrogel drop and the bulk fluid phases. The embedding method is a computational technique that enables the use of finite differences on a regular Cartesian grid for simulation of multiphase problems with complex interfaces/boundaries. It uses a volume‐fraction‐based approach, similar to the volume‐of‐fluid (VOF) method, to implement the boundary conditions that must be applied at the interface between the phases. The main advantage of the embedding method is its simplicity, which results in code generation that can be highly optimized. In the present work, we apply the embedding method to the aforementioned two‐phase reaction‐diffusion problem and validate the results by comparing to a number of exact solutions available in simpler geometries and to results obtained using a finite‐volume method on an unstructured body‐fitted mesh. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The multiple intermediate configuration approach and its influence on DIRK/MLNA finite element procedures
Authors: Quint Karsten J. , Hartmann Stefan 
Published: March 2008

AbstractThis article treats the solution of evolutionary equations based on two plastic intermediate configurations which arise in large plastic deformations within the finite element context. For this purpose high order time integration methods, diagonallyimplicit Runge‐Kutta methods (DIRK), in combination with the Multilevel‐Newton algorithm (MLNA) are used. To preserve plastic incompressibility a projection method is applied and its influence is studied. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physical aspect of mathematical description of the Doppler effect
Authors: Gawinecki Jerzy August , Rafa Józef 
Published: March 2008

AbstractWe present the Doppler effect as a solution to a wave equation concerning waves generated by a moving in space source of the wave that periodically changes it's signal in time. The solution has been reached by basing on the Cagniard‐de Hoop's method. The reached conclusion of the analysis proves that the Doppler effect presents the change in the frequency of the received signal as well as the change of it's phase. In conclusion these changes are inhomogeitic and anisotropic. This research has been successfully applied in telecommunication and in locating sources of radiation of electromagnetic waves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The use of an hourglass stabilized solid‐shell finite element in forming simulations — theoretical aspects and first industrial applications
Authors: Schwarze Marco , Reese Stefanie 
Published: March 2008

AbstractThe method of reduced integration with hourglass stabilization is one of the most powerful techniques in the field of finite element technology. Caused by the use of a reduced number of integration points it leads to very efficient finite element formulations. To avoid the appearance of non‐physical zero‐energy modes an hourglass stabilization is necessary. This paper presents an adaptive hourglass stabilization strategy motivated by the hyperelastic formulation of finite inelasticity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential geometry and the red blood cell
Authors: Vayo Westcott 
Published: March 2008

AbstractThe usual mathematical expressions for the shape of the red blood cell, whether in rectangular or polar coordinates, are very complicated and difficult to use analytically. We have found that by using parametric equations and Jacobean elliptic functions to describe the cell things are much easier. The usual differential geometric concepts can be adapted to find interesting new formulas for ideas like Fick's Law, etc. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advances in math search
Authors: Youssef Abdou 
Published: March 2008

AbstractAs digital libraries of mathematical and scientific contents become available, it is essential to have math‐aware search systems. The search systems must understand math symbols and structures, and allow users to enter queries that involve not only text keywords but also mathematical expressions and fragments of expressions. In addition, the search results must be presented in a way that enables the user to find the desired information rapidly. This short paper gives a quick overview of the state of the art of math search, and focuses on the math search system that the author has developed for the Digital Library of Mathematical Functions (DLMF) project of the National Institute of Standards and Technology. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the discrete compactness of hp edge finite elements
Authors: Boffi Daniele 
Published: March 2008

AbstractWe investigate the relationship between Discrete Compactness Property and the conditions introduced in [1] for the convergence of eigenvalue problems in mixed form; we shall show that both aspects can be put in the same unified framework. As a corollary of our theory, we can show that the hp version of rectangular Raviart–Thomas elements can be successfully applied to the approximation of Laplace eigenmodes in mixed form. This follows from the analogous result for edge elements presented in [2]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fructose‐induced N‐terminal glycation of enkephalins and related peptides
Authors: Jakas Andreja , Vinković Marijana , Smrečki Vilko , Šporec Maja , Horvat Štefica 
Published: March 2008

AbstractThe formation of glycation products in model systems consisting of fructose and the endogenous opioid peptides not containing lysine residue, such as Leu‐enkephalin (Tyr‐Gly‐Gly‐Phe‐Leu) and Met‐enkephalin (Tyr‐Gly‐Gly‐Phe‐Met), or of their fragments, Tyr‐Gly‐Gly‐Phe and Tyr‐Gly‐Gly, was examined. N‐(2‐Deoxy‐aldos‐2‐yl)‐peptides (Heyns compounds) as well as diastereoisomeric imidazolidinone compounds were identified as reaction products of N‐terminal amino group glycation for each of the peptides studied. The structure of the glycation products and relative configuration of C‐2 substituents on the imidazolidinone ring in diastereoisomers were determined by NMR experiments. The chemical and enzymatic stability of the fructose‐derived glycated products of Leu‐ and Met‐enkephalin was studied in phosphate‐buffered saline (pH 7.4) and in human serum at 37 °C. The obtained results revealed that glycation increases the stability of the parent peptide to enzymatic degradation. As a result of different configuration at the newly formed stereogenic center, large stability differences in the 2S* and 2R* isomers of the imidazolidinone compounds were observed. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
n and k testing of magnetic heads with imaging spectroscopic ellipsometry
Authors: Vaupel M. , Yunfeng Song , Zhimin Yuan 
Published: March 2008

AbstractThe method of imaging spectroscopic ellipsometry is applied on magnetic read/write heads of hard disks. By means of spectroscopic ellipsometry, an optical model of the TiC/Al2O3 substrate including surface roughness and concentration gradient of TiC in the alumina substrate is generated. Surface roughness is measured with both ellipsometry and atomic force microscopy (AFM). The granular structure of TiC/Al2O3 is investigated in micrographs of n and k. It is discussed how Delta mapping of the magnetic pole area of the head can be used to measure DLC coating thickness and the variation of chemical constitution of the metal substrate. Repeatability of measurements of Delta is optimized in a one µm2 region of interest (ROI) on a metal stripe of the magnetic pole. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarization optics of interfaces and thin films
Authors: Azzam R. M. A. 
Published: March 2008

AbstractThe differential reflection of p‐ and s‐polarized light by interfaces and thin films is central to the theory and applications of ellipsometry. It is also the basis of a wide variety of optical devices for the control and analysis of polarized light such as polarizers, polarizing and polarization‐preserving beam splitters, and quarter‐wave and half‐wave retarders. New insight into the correlation between optical properties of film and substrate materials and reflection properties is emphasized. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometry study of thin diffusion barriers of TaN and Ta for Cu interconnects in integrated circuits
Authors: Rudra S. , Wächtler T. , Friedrich M. , Louis S. J. , Himcinschi C. , Zimmermann S. , Schulz S. E. , Silaghi S. , Cobet C. , Esser N. , Gessner T. , Zahn D. R. T. 
Published: March 2008

AbstractThe objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV–visible range. Single layers of tantalum nitride and bilayer films of Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73–8.7 eV and the dielectric functions were simulated using Drude–Lorentz model and effective medium approximation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the β‐phase of Ta, it turned out to be a mixture of α‐ and β‐phases with higher contribution of the α‐phase. It is shown that even a very small intermixture of two different phases of Ta can be determined accurately using ellipsometry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Si1–xGex:H thin films with graded composition and structure by real time spectroscopic ellipsometry
Authors: Podraza N. J. , Li Jing , Wronski C. R. , Dickey E. C. , Horn M. W. , Collins R. W. 
Published: March 2008

AbstractSilicon‐germanium (Si1−x Gex:H) thin films have been prepared by plasma enhanced chemical vapor deposition of SiH4 and GeH4 and measured during growth using real time spectroscopic ellipsometry. A two‐layer virtual interface analysis has been applied to study the structural evolution of Si1−x Gex:H films that initially nucleate in the amorphous (a) phase, but evolve to the microcrystalline (μc) phase with accumulated thickness. The compositional evolution of alloy‐graded a‐Si1−x Gex:H has been studied as well using similar methods. Both types of films are of interest for Si‐based photovoltaic devices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A FEM‐based application for numerical calculations of ellipsometric data
Authors: Wiklund H. , Arwin H. , Järrendahl K. 
Published: March 2008

AbstractFor modeling of advanced optical structures there is a need for stronger and more flexible modeling tools. Our aim is to develop and verify an application tool for calculations based on the Finite Element Method (FEM) of optical structures. To be able to understand which effects in the results that arises from limitations in the model, we begin by verifying the application tool for the most basic surface structures and gradually increase the complexity of the structures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhancement in ellipsometric thin film sensitivity near surface plasmon resonance conditions
Authors: Arwin H. , Poksinski M. , Johansen K. 
Published: March 2008

AbstractEllipsometry used in internal reflection mode exhibits enhanced thin film sensitivity if operated close to surface plasmon resonance conditions. Compared to conventional ellipsometry, the changes in the ellipsometric parameter Δ are several orders of magnitude larger. Here, the origin of this large sensitivity is discussed by analysing thin film approximations of the complex reflectance ratio. It is found that the thickness sensitivity in Δ is proportional to the inverse of the difference between the intrinsic and the radiation‐induced damping of the surface plasmons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The optical Hall effect
Authors: Hofmann T. , Herzinger C. M. , Krahmer C. , Streubel K. , Schubert M. 
Published: March 2008

AbstractClassic electrical Hall effect measurements are standard for electrical characterization of free charge carriers in semiconductor layer structures. We demonstrate that magnetooptic generalized ellipsometry at long wavelengths when applied to conducting or semiconducting multilayer or nanoscopically in‐homogeneous structures can yield equivalent and even much increased information. We term this new method optical Hall effect, because it finds simple explanation within the model described by E. H. Hall for the occurrence of the transverse and longitudinal voltages augmented by non‐locality of the charge response in time. Transverse and longitudinal birefringence cause magnificent anisotropic polarization responses unraveling rich information on free charge properties of complex‐structured samples due to external magnetic fields and collective movement of bound and unbound charge carriers. We demonstrate that with our technique density, type, mobility, effective mass including anisotropy can be measured without any electrical contact in buried structures, and which may have been inaccessible to any true electrical evaluation thus far. We predict a realm of applications for the optical Hall effect in future materials research and engineering. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
PIII nitriding of fcc‐alloys containing Ni and Cr
Authors: Lutz Johanna , Gerlach Jürgen W. , Mändl Stephan 
Published: March 2008

AbstractFace‐centred cubic (fcc) alloys such as austenitic stainless steel, Ni base alloys and Co base alloys are important materials with a high corrosion resistance. Nitrogen insertion by PIII into all these alloys at moderate temperatures leads to the formation of an expanded austenite structure. A similar activation energy for the thermally assisted diffusion of about 0.75 eV was found for steel and CoCr alloys with CrN precipitates beyond 400 °C in both systems. However, a double layer structure was observed for CoCr, similar to Ni alloys, in contrast to a single layer for austenitic steel. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Production of nitrogen‐containing carbon plasma using shunting arc discharge for carbon nitride films preparation
Authors: Takaki K. , Imanishi K. , Murakami T. , Mukaigawa S. , Fujiwara T. , Suda Y. , Yukimura K. 
Published: March 2008

AbstractA magnetically driven carbon‐shunting arc discharge was generated in nitrogen gas circumstance and amorphous carbon nitride (a‐CNx) films were prepared. A silicon substrate was immersed into the plasma, and a series of pulse voltage was applied to the substrate synchronizing with ignition of the shunting arc with a peak current of 1.7 kA. The ambient nitrogen gas pressure was varied in wide range. The shunting arc plasma was successfully produced and was accelerated along carbon rails. Heating energy to generate the shunting arc had minimum value for variation of the ambient gas pressure. A spectroscopic measurement from the plasma light emission showed that the produced plasma contained nitrogen particles in ambient nitrogen gas circumstance. X‐ray photoelectron spectroscopy (XPS) analysis showed that the prepared carbon films contained nitrogen and was obtained to be N/C ratio of 0.35 at 2 Pa nitrogen gas pressure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)