bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of Electrohydrodynamic Flow in a Circular Cylindrical Conduit
Authors: McKee S. , Watson R. , Cuminato J. A. , Caldwell J. , Chen M. S. 
Published: May 2007

AbstractThe electrohydrodynamic flow of a fluid in an “ion drag” configuration in a circular cylindrical conduit is governed by a non‐linear second‐order ordinary differential equation. The degree of non‐linearity in this equation is determined by a nondimensional parameter α and the equation can be approximated by two different linear equations for very small or very large values of α respectively. Perturbation solutions of the fluid velocities for α ≪ 1 and α ≫ 1 are developed. A Gauss‐Newton finite‐difference solver combined with the continuation method and a Runge‐Kutta shooting method are used to provide numerical results for the fluid velocity over a large range of values of α. Both numerical and analytical results are compared in order to establish the range of validity for the perturbation solutions.
The Volume Fraction Concept in the Porous Media Theory
Authors: Bluhm J. , De Boer R. 
Published: May 2007

AbstractIn this paper the volume fraction concept in the porous media theory is considered. First, the historical development of this important concept is traced. Thereupon, the concept of volume fractions is formulated and the transport theorems, which govern the transformations of volume elements from one placement to another, are derived. An essential feature is the incorporation of the effect of incompressibility into the transport theorems. This is only possible by the introduction of a new multiplicative decomposition of the deformation gradients of the constituents into parts describing the deformations of the realistic (true) materials and parts including the changes of the pores.
Finite‐Elemente‐Analyse gummiartiger inkompressibler Elastomere unter großen Verzerrungen und Kontaktwechselwirkungen
Authors: Itskov M. 
Published: May 2007

AbstractIn der vorliegenden Arbeit wird das Problem der Finite‐Elemente‐Analyse gummiartiger, strikt inkompressibler Elastomere unter großen Verzerrungen und Kontaktwechselwirkungen behandelt. Die Inkompressibilitätsbedingungen werden durch Ausschließung in expliziter Form eines Teiles von Komponenten des Verschiebungsfeldes aus dem globalen FE‐Gleichungssystem erfüllt. Numerische Aspekte dieser Vorgehensweise werden ausführlich besprochen. Zur Modellierung der reibungslosen Kontaktwechselwirkung von Oberflächen eines modellierten Körpers miteinander und mit festen Anschlägen wird die Penalty‐Methode angewandt. Numerische Beispiele und experimentelle Ergebnisse werden angeführt und verglichen.
On Tensor Functions of Second‐Order Tensors and Vectors Under N‐Gonal Classes Dnh
Authors: Zheng Q.‐S. 
Published: May 2007

AbstractIn three‐dimensional space there are seven series of classes, i,e., 𝒟nh, 𝒟n, 𝒟nd, 𝒞nv, 𝒞nh, 𝒞n, and 𝒞ni in general n‐gonal systems for n = integer ⩾ 1. The classes 𝒟nh are of most practical interest, they not only cover the usual orthotropy 𝒟2h, tetratropy 𝒟4h, and hexatropy 𝒟6h, but they contain the other six series of classes, too. Furthermore, one may refer to the overall material symmetry of a fibre‐reinforced composite with fibre reinforcements equivalently in the 0, π/s, 2π/s,…,(s – 1) π/s directions for s ⩾ 3 as the symmetry 𝒟2sh, and this kind of composite is known as a quasiisotropic material since its planar linear elasticity is isotropic. In this paper we establish the complete and irreducible representation for scalar‐valued, vector‐valued, and second‐order tensor‐valued functions of any finite number of second‐order tensors and vectors with respect to the infinitely many classes 𝒟nh, in supplement to the known representation with respect to the orthotropy 𝒟2h. These results allow for a general invariant formulation of constitutive equations for crystals in the tetragonal, trigonal, and hexagonal systems, as well as quasi‐isotropic fibre‐reinforced composites.
The Eigenfunctions of the Stokes Operator in Special Domains. I
Authors: Rummler B. 
Published: May 2007

AbstractWe consider the eigenvalue problem of the Stokes operator in a bounded cylindrical domain of ℝ3 with homogeneous Dirichlet boundary conditions on the curved part of the boundary and periodical conditions in the main stream direction. We deduce by separation the corresponding systems of ordinary differential equations and solve them explicitly looking for bounded, solenoidal vector fields fulfilling the boundary conditions. The investigation of possible cases yields either the explicit eigenfunctions and eigenvalues, or equations for the determination of the eigenvalues, and a general representation of the eigenfunctions.
Elastic Wave Scattering on a Thin‐Walled Inclusion
Authors: Lavrov N. A. 
Published: May 2007

AbstractThe dynamic three‐dimensional problem of interaction between an elastic wave and a thin‐walled elastic inclusion is considered. The incident wave length is comparable to the large linear size of the inclusion. Integral equations of motion are obtained by means of the asymptotic approach proposed. The deflections of a circular plate and a fragment of a spherical shell embedded in the medium are calculated in the case of axial symmetry.
Domain Decomposition with Nonmatching Grids and Mixed Formulation in the Spaces W, p(Ω), W(Ω)
Authors: Pousin J. , Sassi T. 
Published: May 2007

AbstractIn this note, we deal with the domain decomposition method with nonmatching grids for the Laplace operator in the Sobolev space W(Ω) for 2 < p < ∞. Expressing the problem by a mixed formulation, the Brezzi‐Babuška theorem applies (see for example [18]), and we prove that the problem is well posed. A priori error estimates for Lagrangean finite elements of first order are given. Note that the approximate problem can be solved by elimination. This result is straightforwardly extended to the plane linearized elasticity model (see remark 4). This is important when one intents to solve plane nonlinear elasticity problems by using the domain decomposition method with nonmatching grids combined with an adaptive finite element technique based on a posteriori error estimates (see [15]). Please note that the right functional setting for stating nonlinear elasticity problems in the Sobolev space W1,p with 2 < p.
The Eigenfunctions of the Stokes Operator in Special Domains. II
Authors: Rummler B. 
Published: May 2007

AbstractWe investigate the eigenvalue problem of the Stokes operator in an open bounded rectangular parallelepiped of the ℝ3 supplemented with homogeneous Dirichlet boundary conditions on two face to face lying lateral surfaces and periodical conditions in the directions orthogonal to the other faces. By separation we deduce a corresponding system of ordinary differential equations. We look for solutions as solenoidal vector fields satifying the boundary conditions. The investigation of possible cases yields either the explicit eigenfunctions and eigenvalues or equations for determining the eigenvalues and a general deduced form of the eigenfunctions. In the appendix we give an example of the first eigenvalues of the Stokes operator for fixed l = 2.69.
Acoustic Field in a Shallow, Stratified Ocean with a Poro‐Elastic Seabed
Authors: Gilbert R. P. , Lin Z. 
Published: May 2007

AbstractIn this paper we investigate the propagating solutions of the acoustic equation in a stratified shallow ocean with a poroelastic, semi‐infinite seabed. The ocean‐seabed system is first Hankel transformed. Then the method of transmutation is used to generate the transformed solutions in the water column; whereas, the modal seabed equations are solved using the computer algebra Macsyma. In the water column the transformed solutions are first decomposed using the Mittag‐Leffler expansion for the discrete spectrum. Both the discrete and continuous spectrum are then used to give a spectral representation of the solution, from which we develop a numerical scheme. Some numerical examples are given to illustrate the method.
Stability of a Viscoelastic Pipe Filled with a Moving Fluid
Authors: Drozdov A. D. 
Published: May 2007

AbstractSufficient stability conditions are derived for transversal oscillations of a thin‐walled viscoelastic pipe filled with a moving fluid. By using two different approaches, explicit expressions are developed for the critical flow velocities. In particular, steady flow and time‐periodic flow are considered. The effect of material and geometrical parameters on the critical velocity is studied numerically.
Stress Distribution in a Long Circular Cylinder Containing an Elliptical Crack
Authors: Lee Doo‐Sung 
Published: May 2007

AbstractThis paper deals with the three dimensional analysis of the stress distribution in a long circular cylinder containing an elliptical crack. The surface of the crack is perpendicular to the axis of the cylinder and is subjected to a constant pressure. The equations of the classical theory of elasticity are solved in terms of an unknown function which is then shown to be the solution of an integro‐differential equation. Numerical solution of the integro‐differential equation is obtained. The resultant stress intensity magnification factors for the elliptical crack in the cylinder are presented in graphical forms for various crack aspect ratios and proximity ratios.
Informationsverlust, abstrakte Entropie und die mathematische Beschreibung des zweiten Hauptsatzes der Thermodynamik
Authors: Ansorge R. , Sonar Th. 
Published: May 2007

AbstractWe intend to discuss the relations between the more abstract notion of entropy and the ideas of information using nonlinear partial differential equations as an example. Hyperbolic equations of the first order, where vanishing of the characteristics in a discontinuity may be interpreted as loss of initial information, will serve as illustration. The problem of non‐physical rarefaction shocks in discussed, and with Lax′ shock condition a first entropy condition is introduced. The approximation of a physical problem with friction by an inviscid problem leads to a demand for an entropy inequality characterizing the solutions of the model with friction in the limit, when friction vanishes. This demand for an additional condition, namely for an entropy inequality as mathematical pendant to the second fundamental law also dominates the numerics of the presented equations. It is only the fulfilment of a discrete entropy condition — i.e. of a discretized form of the second fundamental law — that provides for the convergence of finite difference procedures.
Energetic Estimates and Asymptotics for Electro‐Reaction‐Diffusion Systems
Authors: Glitzky A. , Hünlich R. 
Published: May 2007

AbstractIn this paper we deal with equations modelling the transport of electrically charged species in heterostructures by diffusion, drift and reaction processes. We show that for such models the free energy decays monotonously and exponentially to its equilibrium value. For this purpose we prove an estimate of the free energy from above by the corresponding dissipation rate. Exactly the same results are obtained for the fully implicit discrete‐time scheme.
On the Cauchy Problem for Some Elliptic Systems in a Spherical Shell in Rn
Authors: Shlapunov A. A. 
Published: May 2007

AbstractSolvability conditions and a formula for solutions of the Cauchy problem for the Laplace equation, matrix factorizations of the Laplace operator and the Lamé type system in a shell D in Rn (n ≧ 2) are obtained in terms of spherical harmonics. More exactly, we consider a situation where the Cauchy data are given on the exterior surface S of a shell D the interior surface of which is a sphere in Rn.
On the Convergence of Discretizations for Set Valued Operator Equations
Authors: Lei J. 
Published: May 2007

AbstractThis paper is concerned with the theory of the convergence of discretizations for set‐valued operator equations. It is a continuation of investigations in [2], [7], [5], some results for one‐valued operators have been generalized herein. As an application, two examples for set‐valued differential equations are discussed.
Creeping Flow past a Solid Sphere in a Porous Medium
Authors: Ganapathy R. 
Published: May 2007

AbstractThis paper reports an analytical study of the creeping flow past a solid sphere in an unbounded sparsely‐packed porous medium assuming the validity of the Brinkman model. A closed form solution is obtained for the flow field and streamlines are drawn to demonstrate its evolution. No separation flow occurs near the rear stagnation point. In the case of low permeability media, there is an overshoot in the tangential component of velocity in the vicinity of the sphere and the total drag on the sphere is found to increase with a decrease in the value of the permeability parameter. Heat transfer due to this forced convection has been exemplified.
A Spline Difference Scheme on a Piecewise Equidistant Grid
Authors: Surla K. , Uzelac Z. 
Published: May 2007

AbstractWe consider singularly perturbed boundary value problems of reaction‐diffusion type and their discretization via quadratic spline difference schemes on a piecewise equidistant mesh of the Shishkin type. On such a mesh we prove that a solution to the discretisation is almost second order accurate in the discrete maximum norm, uniformly in the perturbation parameter. Numerical results are presented, which verify this rate of convergence.
The Thin‐Walled Rod of an Open Cross‐Section as an Element of a 3D‐Structure
Authors: Anisimov D. N. , Goldshtein Yu. B. 
Published: May 2007

AbstractThe relation for a rectilinear thin‐walled rod of an open cross‐section is established between displacements and corresponding forces applied at the ends of the rod. The problem is solved in a linear setting, taking into account a flexure, a uniform and nonuniform warping, and also an axial deformation. The calculation is conducted in the deformed configuration. Coefficients of the thin‐walled rod relation form a matrix of rigidity of this rod that allows to include a thinwalled rod of an open cross‐section in a library of a finite element method.
Speech Sound Representation in the Auditory Nerve: Computer Simulation Studies on Inner Ear Mechanisms
Authors: Rattay F. , Lutter P. 
Published: May 2007

AbstractAcoustical signals are represented in the auditory nerve both by place‐rate information and by the fine structure of the time differences in the spiking pattern. For those parts of human speech which are quite aperiodic the place‐rate information is very poor, because the mechanical tuning process needs time. Computer simulation of inner ear mechanics shows that the onset of a signal moves all parts of the basilar membrane. Plenty of fibers coming from all regions will be stimulated by the first pressure wave. Because of the rapid neural adaptation process even fibers with high characteristic frequencies are systematically activated by low frequency speech components. The time structure of the firing pattern seems to be of much higher significance than previously assumed. It is also of importance for the quasiperiodic parts of speech. Irregularities in speech and sound level are the reasons, why signal processing is not governed by the sharp tuning properties of auditory fibers which are known from stimulations with pure periodic signals of low level.
On New Hydrodynamic Conservation Laws Related to the Particle Relabeling Symmetry
Authors: Albert H.‐F. 
Published: May 2007

AbstractPure particle relabeling symmetry is a special orthogonal Lie group of transformations of the labeling coordinates of Lagrangian hydrodynamics. In reversible hydrodynamics it leaves the corresponding Lagrangian function invariant. Via Noether's theory it generates a conservation law not discussed before. It not only allows to generalize the concepts of helicity and enstrophy but also yields Ertel's and Hollmann's vorticity conservation theorems. This new conservation theorem may be regarded as the base of the whole vorticity theory. A generalization to irreversible motion of arbitrary fluid is discussed briefly. Some secondary consequences are: The baroclinic fluid is isotropic only if the isentropic surfaces are spherical (§ 3); for a stationary motion the vorticity conservation theorems are special reformulations of the Bernoulli equation (end of § 4). A scaling symmetry which is the superposition of a special particle relabeling symmetry and a certain scaling of time and distance from center of gravitation is also discussed. The physical meaning of the corresponding conservation law is not completely investigated.
Point Symmetries for Lagrangian Fluid Dynamics
Authors: Albert H.‐F. 
Published: May 2007

AbstractAlthough it is very difficult to find the whole symmetry group of the Lagrangian hydrodynamic equations of a Newtonian fluid, we are able to present all of the point symmetries of the dynamics of a non‐viscous and non‐heat conducting perfect gas in the Lagrangian (co‐moving) frame of reference. The latter possesses the structure of a Hamiltonian dynamics for which one can discuss not only Lie, but also Noether symmetries. New results are found for some kind of particle relabeling symmetry. Consequences of these symmetries, as conservation laws and invariant solutions, are discussed elsewhere. Most of the calculations have been carried out with the computer algebraic system REDUCE.
Microwave roasting and positional distribution of fatty acids of phospholipids in soybeans (Glycine max L.)
Authors: Yoshida Hiromi , Takagi Sachiko 
Published: May 2007

AbstractWhole soybeans were exposed to microwave roasting for 6, 12, and 20 min at a frequency of 2,450 MHz and were studied not only for phospholipid composition but also for positional distribution of the fatty acids. During microwave roasting, the greatest rate of phospholipid losses (P<0.05) was observed in phosphatidylethanolamine (PE), followed by phosphatidylcholine (PC) and phosphatidylinositol (PI), respectively. Therefore, the effects of microwave roasting on the composition and positional distribution of the fatty acids are likely clearer in PE than in PC or PI. However, the principal characteristics for the positional distribution of fatty acids are still retained during microwave roasting: unsaturated fatty acids, especially linoleic, are predominantly concentrated in the 2‐position, and saturated fatty acids, especially palmitic, primarily occupy the 1‐position after 12 or 20 min of roasting. The results suggest that unsaturated fatty acids located in the 2‐position are significantly protected from microwave roasting.
Location of deep‐sea shark (Centrophorus squamosus) glycerol ether lipid double bonds by nitric oxide chemical ionization mass spectrometry
Authors: Sellier Nicole M. , Bordier Catherine G. 
Published: May 2007

AbstractChemical ionization mass spectrometry with nitric oxide as the reactant gas has proved to be an efficient tool for locating the double bond in monoalkenylglycerols of type HO‐CH2‐CHOH‐CH2‐O‐(CH2)n‐1‐CH=CH‐(CH2)n‐2‐CH3. These monoalkenylglycerols were extracted from the liver oil of the shark Centrophorus squamosus, which lives at depths ranging from 1000 m and deeper. The presence of characteristic acylium ions R1CO+ and/or R2CO+ allowed location of the double‐bond position.
Stereospecific analysis of triacylglycerols from vegetable oils by two procedures—II: Normal and high‐oleic sunflower oils
Authors: Damiani P. , Cossignani L. , Simonetti M. S. , Santinelli F. , Monotti M. 
Published: May 2007

AbstractTriacylglycerol stereospecific analysis of normal (NOS) and high‐oleic sunflower (HOS) oils was carried out by two procedures to study the influence of variety and growing conditions. Four cultural varieties, two NOS and two HOS, were grown in seven different places of Italy. Three of the four varieties were grown both in dry conditions and with irrigation. Concerning the triacylglycerol fatty acid compositions, the results showed no significant differences between irrigated and nonirrigated samples (P>0.05), between the two NOS, and between the two HOS varieties. Between NOS and HOS varieties, only stearic acid showed no significant differences (P>0.05). The fatty acid compositions of the sn‐2 position of NOS and HOS samples showed different percentage abundances (P<0.01), especially for oleic and linoleic acids. Fatty acid distributions in the sn‐1 and sn‐3 positions indicated a certain asymmetry. The relationships between the percentage intrapositional content of each acid (one sn‐position at a time) and its percentage content in the original triacylglycerol matrix were studied. A general regression model was used to verify if the content of each acid at the three stereospecific positions changed at the same rate as the content in the intact triacylglycerols. The interpositional compositions of all varieties of NOS and HOS oils showed analogous trends for each acid.
A simple and rapid method for concurrent determination of petroselinic and oleic acids in oils
Authors: Santinelli F. , Damiani P. 
Published: May 2007

AbstractA procedure to determine the petroselinic acid/oleic acid ratio in oils is described. The method is based on transesterification of the constituent fatty acids to methyl esters. An aliquot of the solution of the esters is then analyzed by capillary gas chromatography; another aliquot is used for epoxidation of the double bonds with 3‐chloroperoxybenzoic acid and subsequent opening of the oxirane ring with hydrochloric acid to obtain the chlorohydrin derivatives. The hydroxy groups are then silanized, and the reaction mixture is analyzed by high‐resolution gas chromatography‐mass spectrometry. The procedure is precise, rapid, and reproducible, and several samples can be analyzed in one working day.
Determination of iodine value of palm oil by differential scanning calorimetry
Authors: Haryati T. , Che Man Y. B. , Asbi A. , Ghazali H. M. , Buana L. 
Published: May 2007

AbstractIodine value (IV) is used as a parameter in process control as well as a quality parameter in traded palm oil products. IV measures the number of double bonds in the molecular structure of an oil. To form a double bond, carbon requires more energy (615 kJ/mol) than to form a single bond (350 kJ/mol). Therefore, the thermal behavior of an oil could reflect its iodine value. This study was conducted to demonstrate the use of a differential scanning calorimeter (DSC) to determine the IV of palm oil and its products as an attempt to reduce the use of chemicals in the analysis. The DSC thermograms of palm oil showed a clear separation of the substances that have low melting points (low‐T), consisting of triunsaturated, monosaturated and disaturated triglycerides, from the high ones (high‐T), consisting of trisaturated triglycerides. Regression analysis showed that the peak characteristics, namely, area and height of the low‐T group and height of the high‐T group in the heating thermogram and also the height of the high‐T group in the cooling thermogram, can predict the IV of palm oil with R2 higher than 0.99. This study concludes that DSC can be used to determine the IV of palm oil and its products.
Separation and quantitation of cholesterol oxides by HPLC with an evaporative light scattering detector in a model system
Authors: Lakritz L. , Jones K. C. 
Published: May 2007

AbstractA method to analyze cholesterol and 10 of its oxidation products, ranging from the weakly polar cholest‐4‐ene‐3,6‐dione to moderately polar cholest‐5‐ene‐3β,7α‐diol, in a single run is described. The separation was achieved by normal‐phase gradient high‐performance liquid chromatography with an evaporative light‐scattering detector. This universal mass detector does not detect changes in solvent composition; this makes it possible to employ gradients, an essential technique whenever a wide range of compounds with diverse characteristics is to be separated. Standards at concentrations from 0.1–1.0 µg were separated within 37 min on an alumina/silica column with a gradient elution system that contained dichloromethane, acetonitrile, and water.