bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete Element Method in der Geotechnik
Authors: Heesen E. , Kreuzer E.
Published: December 2008

In der Discrete Element Method (DEM) werden Böden als Granulat betrachtet, das aus einem System einzelner Partikel besteht, dieüber Kontaktkräfte miteinander in Wechselwirkung stehen und sich gegeneinander verschieben können. In dem hier verwendeten zweidimensionalen Modell werden die Partikel als konvexe unregelmäßige Polygone modelliert. Untersucht wird die Bodenmechanik im Nahfeld der Pfahlinstallation, das Fernfeld wird nicht modelliert. Es wird eine Randbedingung vorgestellt, die das Verhalten der Fernfelds adäquat wiedergibt. Bei der Modellierung zeigt sich, dass es zu deutlichen Spannungsreduktionen im umgebenden Boden kommt. Am Pfahlmantel kommt es zu starken Auflockerungen des Bodens, während andere Bodenbereiche verdichtet werden. Das Verschiebungsfeld während der Pfahlinstallation ist sehr inhomogen und instabil. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Viscosity in discontinuous Galerkin methods
Authors: Kessler Manuel
Published: December 2008

The Discontinuous Galerkin (DG) discretisation technique proposes a higher order alternative to current state of the art Finite Volume (FV) methods of second order accuracy in space. DG features higher order on unstructured grids without reconstruction, highly local data access patterns and excellent parallelisation properties. However, viscosity does not fit seamlessly into DG, but is indispensable for nearly every technical aeronautical simulation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of constrained mechanical systems
Authors: Koutsovasilis Panagiotis , Beitelschmidt Michael
Published: December 2008

Motion equations of constrained mechanical Multi Body Systems (MBS) are described by differential and algebraic equations (DAE). Various modeling methods are implemented, while the simulation is based on commercial DAE‐solvers. A comparison study concerning the quality of their results is presented. Issues, such as the importance of DAE‐index, finding a consistent set of initial conditions, the drift‐off phenomenon as well as the application of projection and stabilization techniques are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Role of PBPK modeling in drug discovery: opportunities and limitations
Authors: Poirier A. , Funk C. , Lavé T.
Published: December 2008

During drug discovery, considerable resources are required to assess the pharmacokinetic properties of potential drug candidates in vivo in animals and there is interest in optimizing the use of such testing by applying simulation. Physiologically based pharmacokinetic (PBPK) models take in vitro and in silico data inputs to predict concentration versus time profiles before any in vivo experiment is performed. If sufficiently reliable, such simulations could decrease the turnaround time for delivery of information to medicinal chemists during the optimization phase and could also be used to prioritize compounds for the more costly in vivo testing. The mechanistic framework provided by a PBPK model can integrate most of the available predictive data on a compound and provide mechanistic insights into compound properties. Such integrative capabilities and mechanistic insights are not provided by the more commonly used non compartmental or compartmental analysis. However, there are still important processes missing in the models, such as active transport processes, which are the subject of intensive investigation. Thus, mechanistic models integrating active transport processes were developed and are currently being validated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Iterated hard‐thresholding for linear inverse problems with sparsity constraints
Authors: Lorenz Dirk , Bredies Kristian
Published: December 2008

We describe an iterative algorithm for the minimization of Tikhonov type functionals which involve sparsity constraints in form of ℓp ‐penalties which have been proposed recently for the regularization of ill‐posed problems.

In contrast to the well‐known algorithm considered by Daubechies, Defrise and De Mol, it uses hard instead of soft thresholding. This hard thresholding algorithm is based on the generalized conditional gradient method. General results on the convergence of the generalized conditional gradient method enable us to prove strong convergence of the iterates. Furthermore we are able to establish convergence rates of O (n–1/2) and O (λn) for p = 1 and 1 < p ≤ 2 respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A software engineering for numerical simulation of 2D non‐stationary real MGD flows
Authors: Maglione L. S. , Elaskar S. A. , Brito H. H. , Dean R. A. , Lifschitz1 L. A.
Published: December 2008

The study of flows in which an electrically conducting gas moves in a magnetic field is known as magnetogasdynamics or MGD for short. Computational MGD represents one of the most promising interdisciplinary computational technologies for aerospace design. At the present, in Argentina, an ablative magnetoplasmadynamic thruster (AMPD) is being developed as a native propulsion option for satellite and, particularly, microsatellite orbit and/or attitude control. A MGD model is generally based on the assumption that plasma can be regarded as a continuum and thus may be characterized by relatively few macroscopic quantities. A model for a flow affected by electromagnetic forces includes the full set of Maxwell's equations coupled with the Navier‐Stokes equations. The real MGD equations constitute a parabolic‐hyperbolic partial differential system. In addition the ideal part of the MGD equations is nonconvex and as consequence the wave structure is more complicated than for the Euler equations. A software tool was developed which by using structured meshes solves 2D, time‐dependent, viscous and resistive MGD flows. In this case, the numerical approach consists of an approximate Riemann solver coupled with the TVD scheme proposed by Yee. The eigensystem introduced by Powell and the normalization of the eigenvectors presented by Zarachay et al. have also been used. To check accuracy, the computational code has been applied in the simulation of a Riemann problem introduced by Brio and Wu. Also results in the simulation of the Hartmann flow are shown. The results obtained are in good agreement with those reported by other authors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of the material symmetries with anisotropic damage evolution due to a growing mixed‐mode crack
Authors: Molla‐Abbasi K. , Schuette H.
Published: December 2008

A numerical study of a growing mixed‐mode internal crack in a unit cell was undertaken with the help of a finite element simulation. The model enables us to measure the components of the elastic compliance tensor modified by damage as the crack grows, showing the evolution of the anisotropic damage and the evolution of the type of material symmetries. The evolution of the elasticity tensor shows that the damage associated with a growing elliptical crack changes the virgin isotropic properties into orthotropic ones and by crack growth the axes of orthotropic symmetry, initially aligned with the local coordinates of the crack, rotate towards the principle loading axes. Crack propagation is simulated using the stepwise method, which consists of the succession of straight segments and crack growth is governed by the principle of maximum driving force which is a direct consequence of the variational principle of a cracked body in equilibrium and considers the effect of all three stress intensity factors. Without any ad hoc assumption, the crack growth rate is calculated using its thermodynamic duality with the local maximum driving force. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient reconstruction of functions on the sphere from scattered data
Authors: Keiner Jens , Kunis Stefan , Potts Daniel
Published: December 2008

Motivated by the fact that most data collected over the surface of the earth is available at scattered nodes only, the least squares approximation and interpolation of such data has attracted much attention, see e.g. [1, 2, 5]. The most prominent approaches rely on so‐called zonal basis function methods [16] or on finite expansions into spherical harmonics [12, 14]. We focus on the latter, i.e., the use of spherical polynomials since these allow for the application of the fast spherical Fourier transform, see for example [8, 9] and the references therein. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Representation of the linear viscoelastic behaviour of wood with a constitutive theory based on fractional time derivatives
Authors: Ranz T. , Lion A.
Published: December 2008

Like many other materials used in mechanical and civil engineering, wood shows a pronounced history‐dependent mechanical material behaviour. Due to its anisotropy its rheological behaviour is strongly dependent on the direction. In this research project, the material behaviour is represented with a phenomenological theory of anisotropic fractional viscoelasticity. In order to identify the material functions and parameters, the time‐dependent creep compliances are measured in three orthogonal directions under tension and shear. As a result of the developed constitutive approach, the experimentally observed creep data is described by several power functions. In the second part of the presentation, some differences between classical models of viscoelasticity which are based on Kelvin‐Voigt or Maxwell elements and the fractional approach are presented. The assets and drawbacks with respect to wood are discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations of yield stress in ferrofluids with a stress controlled rheometer
Authors: Shahnazian H. , Odenbach S.
Published: December 2008

One of the most important properties of ferrofluids is the strong change of viscosity when subject to an applied magnetic field – the so called magnetoviscous effect. The rheological experiments as well as theoretical studies correlate this effect with the appearance of chain‐like structures of magnetic particles due to the strong interparticle interaction in presence of a magnetic field. Furthermore, viscoelastic effects or other non‐Newtonian features, like yield stress in ferrofluids, can theoretically be described with these structures under the influence of the magnetic field. In earlier experiments, when a shear rate controlled rheometer has been used, yield stress could not be investigated directly. A field dependent yield stress could only be estimated in ferrofluids. For direct yield stress investigations, a dedicated stress controlled rheometer is needed, so that the yield stress and its dependence on the magnetic field can be investigated directly. This paper presents investigations of yield stress and its dependence on the magnetic field strength as well as on volume concentration of large magnetic particles. In order to get more information about the structure formed by the particles, variation of gap thickness of the shear cell for the yield stress experiments has been used. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Well‐posedness, stability and numerical results for the thermoelastic behavior of a coupled joint‐beam PDE‐ODE system modeling the transverse motions of the antennas of a space structure
Authors: Cliff Eugene M. , Herdman Terry L. , Liu Zhuangyi , Spies Ruben D.
Published: December 2008

A mathematical model for both axial and transverse motions of two beams with cylindrical cross‐sections coupled through a joint is presented and analyzed. The motivation for this problem comes from the need to accurately model damping and joint dynamics for the next generation of inflatable/rigidizable space structures. Thermo‐elastic damping is included in the two beams and the motions are coupled through a joint which includes an internal moment. Thermal response in each beam is modeled by two temperature fields. The first field describes the circumferentially averaged temperature along the beam, and is linked to the axial deformation of the beam. The second describes the circumferential variation and is coupled to transverse bending. The resulting equations of motion consist of four, second‐order in time, partial differential equations, four, first‐order in time, partial differential equations, four second order ordinary differential equations, and certain compatibility boundary conditions. The system is written as an abstract differential equation in an appropriate Hilbert space, consisting of function spaces describing the distributed beam deflections and temperature fields, and a finite‐dimensional space that projects important features at the joint boundary. Semigroup theory is used to prove that the system is well‐posed, and that with positive damping parameters the resulting semigroup is exponentially stable. Steady states are characterized and several numerical approximation results are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exact controllability of a semilinear thermoelastic system with control and nonlinearity in thermal component only
Authors: Tomar Nutan Kumar , Sukavanam N.
Published: December 2008

A result concerning the exact controllability of semilinear thermoelastic system, in which the control and nonlinear term occurs solely in the thermal equation, is derived under the influence of rotational inertia and Lipschitz nonlinearity, subject to the clamped/Dirichlet boundary conditions. In the proof we make use the result given by Avalos G. [Differential and Integral Equations, 13 (2000), 613‐630] which states that the corresponding linear system is exact controllable. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Undergraduate computational science and engineering education: A SIAM Working Group Report
Authors: Turner Peter R , Vakalis Ignatios
Published: December 2008

Computational Science and Engineering (CSE) is a rapidly growing multidisciplinary area with connections ot the sciences, engineering, mathematics and computer science. CSE is a legitimate and important academic enterprise, even if it is yet to be formally recognized by a number of institutions. The undergraduate arena is the most important segment of the educational pipeline, since it prepares teachers for the high school environment, invigorates students to pursue graduate studies in cutting edgetechnical fields, and produces a vast number of future employees for industry and the “knowledge‐based” economy. Thus it is critical that CSE curricula and programs are a viable option for every undergraduate student. This presentation introduces the SIAM Working Group report on undergraduate CSE education. The particular focus here is on background and the varying nature of programs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Re‐entrant corner flow of Phan‐Thien‐Tanner fluids
Authors: Evans J.D. , Sibley D.N.
Published: December 2008

Results are described for the planar flow of Phan‐Thien‐Tanner (PTT) fluids around re‐entrant corners. A stress singularity similar to the Upper Convected Maxwell (UCM) model is obtained, namely O (r–2(1–α)) where r is the radial distance from the corner and π /α the corner angle. However, the stream function vanishes at the slower rate O (r(1+α)α ) compared to O (r(3–α)α ) for UCM – this feature being a consequence of the shear thinning property of the PTT model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An efficient HOC scheme for transient convection‐diffusion‐reaction equations with discontinuous coefficients and singular source terms
Authors: Ray Rajendra K , Kalita Jiten C , Dass Anoop K
Published: December 2008

In this paper, we propose a new methodology for numerically solving one‐dimensional (1D) transient convection‐diffusion‐reaction equations with discontinuous coefficients and singular source terms on nonuniform space grids. This Higher Order Compact (HOC) formulation is at least third order accurate at regular grid points and exactly third order accurate at points just next to the discontinuity. We conduct numerous numerical studies on a number of problems and compare our results with those obtained with immersed interface and other well‐known methods. In all cases our formulation is found to produce better results on relatively coarser grids. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subgroup structure of bifurcation equations with crystallographic group symmetry
Authors: Makeev Oleg , Loginov Boris
Published: December 2008

For stationary and Andronov‐Hopf bifurcation with symmetry of highest crystalline classes of basic syngonies of symmorphic crystallographic groups as semidirect products of translations on basic directions and point symmetry of lattice the subgroup structure of relevant bifurcation equations and bifurcating solutions dual to subgroup structure of such symmetry is investigated. Applications to phase transitions in physics are considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ein Ansatz zur Beschreibung der dreidimensionalen Topographiedynamik bei Bremsvorgängen
Authors: Müller M. , Ostermeyer G.‐P.
Published: December 2008

Die Dynamik in der Grenzschicht zwischen Bremsbelag und Bremsscheibe ist während eines Bremsvorganges durch eine komplexe Wechselwirkung zwischen Reibung und Verschleiß charakterisiert. Um explizite Aussagen über globale Verschleißraten oder laterale Anregungsmechanismen zu erhalten, ist ein Modell eines Zellulären Automaten auf eine dreidimensionale Topographiebeschreibung erweitert worden. Zur Verifizierung und Quantifizierung werden identische Bremssysteme mit unterschiedlicher Belastungsgeschichte optisch untersucht. Die daraus gewonnenen Daten der Oberflächentopographie werden in diesem Paper den Ergebnissen aus der Simulation gegenübergestellt und interpretiert. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Bogolubov generating functional method in statistical physics and the Wigner transform (Poster Presentation)
Authors: Prykarpatsky Anatoliy K. , Bogolubov Nikolai N.
Published: December 2008

We show that the N.N. Bogolubov generating functional method is a very effective tool for studying distribution functions of both equilibrium and non equilibrium states of classical many‐particle dynamical systems. In some cases the Bogolubov generating functionals can be represented by means of infinite Ursell‐Mayer diagram expansions, whose convergence holds under some additional constraints on statistical system. The classical Bogolubov idea [1] to use the Wigner density operator transformation for studying the non equilibrium distribution functions is developed and new analytic non‐stationary solution to the classical N.N. Bogolubov evolution functional equation is constructed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mathematical notation and the use of functions (Poster Presentation)
Authors: Thielemann Henning
Published: December 2008

In contrast to natural languages, mathematical notation is accepted as being exceptionally precise. It shall make mathematical statements unambiguous, it shall allow formal manipulation, it is model for programming languages, computer algebra systems and machine provers. However, what is traditional notation and is it indeed as precise as expected?

We discuss some examples of notation which require caution. How are they adapted in computer algebra systems? Can we improve them somehow? What can we learn from functional programming? (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Olga Taussky, a torchbearer for mathematics and teacher of mathematicians
Authors: Uhlig Frank
Published: December 2008

Olga Taussky‐Todd's mathematical and personal life (1906‐1995), her achievements and obstacles, her scientific reasoning and teaching all have served as inspiration to many mathematicians. We describe her role in the mathematics world of the previous century as a torchbearer for mathematics and mathematicians, bearing the “torch of scientific truth” that burns inside of mathematics and its applications. Besides her many deep math contributions – too many to elaborate – she excelled at distilling and presenting mathematical concepts and ideas in her work and gave us many visionary papers and math talks. By sharing her mathematical vision freely she has inspired many of us. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Prediction of bond ratings using statistical and neural networks techniques
Authors: Alam S.
Published: December 2008

Quantitative models have been developed to predict bond ratings of firms in the Indian manufacturing sector, using financial leverage, profitability, asset management ability, stability and market sensitivity of the firm, which totally involved 16 variables. These 16 independent variables are first reduced to seven orthogonal variables using principal component analysis. Then these variables are used to build three types of models, namely Multiple Discriminant Analysis (MDA), Multinomial Logistic Regression (MLR) and Artificial Neural Networks (ANN). Based on both in‐sample classification and out‐sample validation it is found that both MLR and ANN models are superior to MDA, with little difference in performance between themselves. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Teaching computational science with computer algebra
Authors: Gander Walter
Published: December 2008

Computer algebra systems can be used to generate algorithms for numerical computations. We have computed and shown examples in [1] and more recently in [2]. In this paper we emphasize the teaching aspect and use essentially the capability of computer algebra system to construct and manipulate the interpolating polynomial and to compute a series expansion of a function. We automatically generate formulas for integration with error terms and also generate multi‐step methods for integrating differential equations. Furthermore we discuss the use of multiple precision. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regularization of diffusion tensor MRI via local coordinates
Authors: Gur Yaniv , Pasternak Ofer , Sochen Nir
Published: December 2008

We propose a novel framework for regularization of symmetric positive‐definite (SPD) tensors (e.g., diffusion tensors). This framework is based on differential geometry. The space of SPD matrices, Pn, is described as a Riemannian manifold that is parameterized via the Iwasawa coordinate system. Then, distances on Pn are measured in terms of a natural GL (n)‐invariant Riemannian metric. Using the Beltrami framework we construct a set of coupled geometric PDEs with respect to the Iwasawa coordinates. Then, by means of the gradient descent method these equations define the regularization flow over Pn. It appears to be that the local coordinate approach via that coordinate system results in very simple numerics that leads to fast convergence of the algorithm. We demonstrate the efficiency of this algorithm on real volumetric DTI datasets. Results of fibers tractography before and afterthe regularization process arepresented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the Lagrangian formulation of a Lane‐Emden‐type equation and double reduction
Authors: Khalique C Masood , Ntsime Pauline
Published: December 2008

We classify all Noether point symmetries of the Lane‐Emden‐type equation x y ″ + n y ′ + xνf (y) = 0 with respect to the standard Lagrangian L = 1/2 xny ′2 – xn +ν –1 ∫ f (y)dy for various functions f (y). We then obtain first integrals of the various cases which admit Noether point symmetries and obtain reduction to quadratures for these cases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence and iterative approximation of solutions of some systems of variational inequalities and inclusions
Authors: Khan Syed Huzoorul H. , Kazmi K.R.
Published: December 2008

In 1968, Brézis [Ann. Inst. Fourier (Grenoble), 18(1) (1968) 115‐175] initiated the study of the existence theory of a class of variational inequalities later known as variational inclusions, using proximal‐point mappings due to Moreau [Bull. Soc. Math. France, 93 (1965) 273‐299]. Variational inclusions include variational, quasi‐variational, variational‐like inequalities as special cases.

In 1985, Pang [Math. Prog. 31 (1985) 206‐219] showed that a variety of equilibrium models can be uniformly modelled as a variational inequality defined on the product sets equivalent to a system of variational inequalities and discuss the convergence of method of decomposition for system of variational inequalities.

Motivated by the recent research work in this directions, we consider some systems of variational (‐like) inequalities and inclusions; develop the iterative algorithms for finding the approximate solutions and discuss their convergence criteria. Further, we study the sensitivity analysis of solution of the system of variational inclusions. The techniques and results presented here improve the corresponding techniques and results for the variational inequalities and inclusions in the literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Boundary value problems in the theory of binary mixtures
Authors: Svanadze Merab
Published: December 2008

In this paper, the boundary value problems of steady oscillation (vibration) of the linear theory of thermoelasticity for binary mixtures are investigated by means of the boundary integral equation method (potential method). The uniqueness and existence theorems of solutions of the exterior boundary value problems by means potential method and multidimensional singular integral equations are proved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic limits of compressible Euler‐Maxwell system in plasma physics
Authors: Wang Shu
Published: December 2008

In this talk we will discuss asymptotic limit of compressible Euler‐Maxwell system in plasma physics. Some recent results about the convergence of compressible Euler‐Maxwell system to the incompressible Euler equations or incompressible e‐MHD equations will be given via the quasi‐neutral regime. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Connectedness of number theoretical tilings (dual tilings generated by Pisot units of degree 3 and 4)
Authors: Akiyama Shigeki , Gjini Nertila
Published: December 2008

We study the connectedness of Pisot dual tilings. It is shown that each tile generated by a Pisot unit of degree 3 is arcwise connected. However surprisingly, we found families of disconnected Pisot dual tiles of degree 4 which have infinitely many connected components. Also we give a simple necessary and sufficient condition for the connectedness of the Pisot dual tiles of degree 4. As a byproduct, we give a complete classification of the β expansion of 1 for quartic Pisot units. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of the R‐functions method to the solution of elliptic PDEs (Poster Presentation)
Authors: Gladkov Svyatoslav , Svendsen Bob
Published: December 2008

In the current work, the basics of the theory of R‐functions have been presented. Applications of this theory were shown on two model problems – Poisson equation and biharmonic equation – in complex two‐dimensional domains both with homogeneous Dirichlet boundary conditions. The solution is performed in conjunction with the Bubnov‐Galerkin method. As the basis for approximation tensor products of monomials were taken. The convergence study includes the comparison of current results with the standard finite element solution and the dependence of the number of coordinate functions on the relative error in the maximum‐norm. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear mathematical model for intensive steel quenching and its analytical solution in closed form
Authors: Guseynov Sh.E.
Published: December 2008

In the present paper the nonlinear mathematical model for intensive steel quenching processes is considered. This model involves the hyperbolic heat conduction equation, the initial conditions and the Newton type nonlinear boundary conditions characterizing the boiling process on quenchant surface. The reduction of the original problem to the Volterra type nonlinear integral equation is the essence of offered approach. Besides, in the present work some analytical procedure for solving of obtained nonlinear equation is proposed. It is proved that this analytical procedure permits finding the unique solution of the original nonlinear model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical approach for some classes of coefficient inverse problems
Authors: Guseynov Sh.E.
Published: December 2008

In present work we consider some class of homogeneous one‐dimensional on spatial variable coefficient linear inverse problems of thermal conductivity in the bounded domain under. Offered approach allows reducing this class of inverse problems to the problems for the solving of the first kind Volterra linear integral equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The numerical analysis and experimental researches of influence of triangular asperity's outline deviations after turning on the burnished product's technological quality
Authors: Kulakowska Agnieszka , Kukielka Leon
Published: December 2008

The paper concerns determination dependence of preparing inaccuracy surface after previous treatment on the state and properties of burnished article's surface layer (SL). The researches were realized in two stages. In the first one numerical analysis were made, and in the second one experimental verification of receiving results. The application in ANSYS was elaborated. It makes possible to analyze the influence of outline deviations of triangular asperity after turning on the surface roughness and the state of strains and stresses in SL after burnishing rolling. The variables in calculations are: height deviation of triangular asperity after turning Δht = 0.01 ÷ 0.04 [mm], and its distance deviation Δst = 0.05 ÷ 0.2 [mm] as well as the depth of burnishing a = 0.03 ÷ 0.39 [mm]. The results of experimental researches and numerical analysis cover in 5% confidence interval. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduction problems in multi‐scale systems dynamics
Authors: Kuzmina Lyudmila K.
Published: December 2008

The paper is devoted to the different aspects of mathematical modelling and qualitative analysis in dynamics of complex multi‐scale systems that are generated by applied problems of engineering practice. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear and linear instability of the Rossby‐Haurwitz wave
Authors: Skiba Yuri N.
Published: December 2008

As is known, the large‐scale dynamics of barotropic atmosphere can approximately be described by the nonlinear barotropic vorticity equation. It is also well known that the Rossby‐Haurwitz (RH) waves, being exact solutions to this equation, represent one of the main features of meteorological fields. Therefore the stability properties of the RH wave are of considerable interest for deeper understanding of the low‐frequency variability of the atmosphere. Many works has been devoted to the barotropic instability of flows on a beta‐plane and a sphere. However, mathematically, the nonlinear stability problem of the RH wave is still far from its complete solution. Indeed, some of the stability results have been obtained numerically, and hence, contain calculation errors. Severe truncation of perturbations used in the spectral stability analysis, though leads to interesting and useful conclusions, does not allow obtaining comprehensive results. The weak point of some analytical nonlinear instability studies consists in using inappropriate norms for perturbations. It should also be noted that a necessary condition for the linear instability of the RH wave was obtained only recently (Skiba, 2000).

In the present work, the nonlinear stability of the RH wave in an ideal incompressible fluid on a rotating sphere is analytically studied. Let H(n) be a subspace of homogeneous spherical polynomials of degree n. Mathematically, a RH wave of degree n is the sum of a super‐rotating flow of subspace H(1) and a homogeneous spherical polynomial of subspace H(n). First, we derive a conservation law for arbitrary RH‐wave perturbations which asserts that any perturbation evolves in such a way that its kinetic energy E(t) and enstrophy q(t) decrease, remain constant or increase simultaneously. The law is used to divide all the perturbations into three invariant sets depending on the value of their mean spectral number k(t)=q(t)/E(t) introduced by Fjortoft (1953). These sets are denoted as M where k(t)¡n(n+1) (large‐scale perturbations), N where k(t)¿n(n+1) (small‐scale perturbations), and Z where k(t)=n(n+1) (boundary surface between the sets M and N). Note that Z includes one more invariant set, namely, the subspace H(n). The existence of invariant sets of perturbations allows us to study the RH wave instability in each set separately. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impulsive displacement of liquid in a pipe
Authors: Kleinstein Gerald G.
Published: December 2008

The solution of a viscous liquid, originally at rest in a pipe, which is set impulsively into motion by a pressure gradient is well known. Analyzing this solution shows that the displacement time – the time it takes to completely displace the liquid originally at rest in the pipe – falls primarily within an inviscid window. Assuming this result remains essentially unchanged when the displaced and displacing liquids are different we apply an inviscid analysis to determine the displacement time as a function of the density ratio of the liquids and the pressure difference. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Endangered species, real options, and forest management
Authors: Abdallah Skander Ben , Lasserre Pierre
Published: December 2008

We use a real option approach to determine optimally when a social planner has to stop or resume logging in situations where an endangered species relies on forest habitat for its survival, and that habitat evolves stochasticly. The model incorporates economic, ecological and social features, and is calibrated to generate an optimal forest management rule that balances the benefits from commercial forest exploitation with the risks of extinction facing the endangered species. For the reasonable parameters used in our application to the Rangifer tarandus caribou, an endangered species in Central Labrador (Canada), the policy of banning logging temporarily is quite attractive as it does not require long banning periods while it drastically reduces the extinction risk and increases forest value. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on the wire sawing process
Authors: Liedke T. , Ams A. , Kuna M.
Published: December 2008

The wire sawing technology plays an important role on the manufacturing of thin discs out of brittle materials and is used for example in the solar‐ and microelectronic industry. The surface of a wire sawn disc shows a characteristic geometry, which suggests the influence of oscillations during the slicing process. In order to examine the process a distinct‐element‐model is used to simulate the motion and the interaction of the abrasive particles with the moving wire and the workpiece. The simulation shows interesting phenomena like clustering of particles and reacting forces to the wire, which could be one reason for the observed oscillations in the process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Function theoretical approach to anisotropic plane elasticity
Authors: Soldatov A.
Published: December 2008

The representation of general solutions of Lame system of plane elasticity is given with the help of so‐called Douglis analytic functions. Using integral representation of these functions the basic boundary value problems for Lame system are reduced to equivalent singular integral equations on the boundary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of double stratification on MHD free convection with Soret and Dufour effects in a Darcian porous media
Authors: Tak S.S. , Lodha Arti
Published: December 2008

The heat and mass transfer characteristics of natural convection about a vertical surface embedded in a doubly stratified saturated porous medium subjected to a magnetic field is studied, taking into account the Dufour and Soret effects. It is found that the similarity solution exists for the case of uniform surface heat and mass flux conditions when the thermal and solutal stratification of the medium are assumed to have power function form x1/3. The resulting set of ordinary coupled nonlinear differential equations is solved numerically using shooting technique. Nusselt and Sherwood numbers are tabulated for various values of the involved parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stochastic Krylov subspace methods for flow in random porous media
Authors: Klie Hector , Rodriguez Adolfo , Wheeler Mary F.
Published: December 2008

The present work establishes a comparative analysis of two different Krylov‐based methods for assessing uncertainty in porous media flow applications. They are: (1) the stochastic reduced basis method (SRBM) and the (2) Krylov‐Karhunen‐Loeve moment equation (KKLME). The former relies on the construction of an orthogonal basis from which projectors may be realized to perform the uncertainty analysis on a lower‐dimensional space. The second approach relies on the idea of expressing input and corresponding outputs in terms of stochastic and perturbative polynomial expansions. By grouping terms and moments of the same order, the original stochastic equation is replaced by successive (and parallel) solutions of a set of deterministic equations. We provide a set of numerical experiments illustrating the capabilities of SRBM and KKLME against Monte Carlo simulations (MCS) on stationary permeability cases. We show that KKLME is superior to SRBM. Furthermore, KKLME appears to be also a more efficient alternative than MCS for non‐stationary permeability field distributions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparation of hollow composite spheres with raspberry‐like structure based on hydrogen‐bonding interaction
Authors: Wang Junyou , Li Hao , Yang Xinlin
Published: December 2008

The hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd.
Simultaneous determination of three phytoecdysteroids in the roots of four medicinal plants from the genus Asparagus by HPLC
Authors: Wu Jia‐Jun , Cheng Ka‐Wing , Wang Hao , Ye Wen‐Cai , Li Edmund T. S. , Wang Mingfu
Published: December 2008

Introduction

The genus Asparagus is known to contain phytoecdysteroids that have been shown to exhibit many beneficial pharmacological properties such as improving lipid metabolism, modulating immunological responses, etc. Currently, knowledge about the contents of phytoecdysteroids in the roots of Asparagus species is limited and HPLC methods for their analyses are unsatisfactory.

Objective

To develop an HPLC method for the simultaneous determination of three phytoecdysteroids, 20‐hydroxyecdysone, ecdysone and ajugasterone C, in the roots of four Asparagus species.

Methodology

Reference standards of phytoecdysteroids were isolated from the roots of Asparagus filicinus by open column chromatography. HPLC analysis was performed on an Alltima C18 column with gradient elution using aqueous 0.2% formic acid solution containing 0.2% isopropanol and acetonitrile.

Results

All calibration curves showed good linear correlation coefficients (r2 > 0.9994) within the tested ranges. Limits of detection (S/N = 3) and quantification (S/N = 10) for the three analytes were less than 2.7 and 9.9 ng, respectively. Intra‐ and inter‐day RSDs of retention times and peak areas were less than 2.61%. The recoveries were between 93.2 and 107.5%, and the RSDs were less than 3.83% for the root samples of A. filicinus.

Conclusion

The HPLC method established is appropriate for the efficient quantitative and qualitative analyses of important phytoecdysteroids in Asparagus species. This study showed that A. filicinus is rich in phytoecdysteroids, especially 20‐hydroxyecdysone. However the three studied phytoecdysteroids were not detected in A. cochinchinensis, A. officinalis and A. setaceus. Copyright © 2008 John Wiley & Sons, Ltd.
Further examining the triangle tip: Improving support for students with emotional and behavioral needs
Authors: Kern Lee , Hilt‐Panahon Alexandra , Sokol Natalie G.
Published: December 2008

Students identified as having emotional and behavioral disorders (EBD) experience the poorest educational outcomes among any disability group. Although models of intervention and corresponding evidence‐based practices continue to advance, the promise of new approaches has failed to reach the general population of students with EBD. In this artice, we visit possible explanations for these continued poor outcomes. Breakdowns along several systems are discussed, including placement and related practices as well as the absence of individualized approaches. In addition, we offer suggestions for improvement. © 2008 Wiley Periodicals, Inc.
Compatibility of toluidine blue with laser microdissection and saturation labeling DIGE
Authors: Kirana Chandra , Ward Teresa , Jordan T. William , Rawson Pisana , Royds Janice , Shi Hong Jun , Stubbs Richard , Hood Kylie
Published: December 2008

Tissue fixation and staining protocols for laser microdissection are frequently not fully compatible with subsequent proteomic analysis. We compared the effect of three common histological stains (toluidine blue (TB), hemotoxylin, and hematoxylin and eosin (HE)) on tissue visualization, protein recovery, the saturation labeling reaction, and 2‐D electrophoresis. TB provided the best visualization of colorectal tumor tissue during laser microdissection (LMD) and had a comparable effect on protein recovery and the saturation labeling reaction with hematoxylin, provided a modified 2‐D clean‐up protocol was used. Eosin inhibited both protein recovery and the saturation labeling reaction.
Preparation of C60‐functionalized magnetic silica microspheres for the enrichment of low‐concentration peptides and proteins for MALDI‐TOF MS analysis
Authors: Chen Hemei , Qi Dawei , Deng Chunhui , Yang Penyuan , Zhang Xiangmin
Published: December 2008

In this work, for the first time, a novel C60‐functionalized magnetic silica microsphere (designated C60‐f‐MS) was synthesized by radical polymerization of C60 molecules on the surface of magnetic silica microspheres. The resulting C60‐f‐MS microsphere has magnetite core and thin C60 modified silica shell, which endow them with useful magnetic responsivity and surface affinity toward low‐concentration peptides and proteins. As a result of their excellent magnetic property, the synthesized C60‐f‐MS microspheres can be easily separated from sample solution without ultracentrifuge. The C60‐f‐MS microspheres were successfully applied to the enrichment of low‐concentration peptides in tryptic protein digest and human urine via a MALDI‐TOF MS analysis. Moreover, they were demonstrated to have enrichment efficiency for low‐concentration proteins. Due to the novel materials maintaining excellent magnetic properties and admirable adsorption, the process of enrichment and desalting is very fast (only 5 min), convenient and efficient. As it has been demonstrated in the study, newly developed fullerene‐derivatized magnetic silica materials are superior to those already available in the market. The facile and low‐cost synthesis as well as the convenient and efficient enrichment process of the novel C60‐f‐MS microspheres makes it a promising candidate for isolation of low‐concentration peptides and proteins even in complex biological samples such as serum, plasma, and urine or cell lysate.
Jacketed polymers: Controlled synthesis of mesogen‐jacketed polymers and block copolymers
Authors: Gao Long‐Cheng , Fan Xing‐He , Shen Zhi‐Hao , Chen Xiaofang , Zhou Qi‐Feng
Published: December 2008

The controlled radical polymerization of mesogen‐jacketed liquid crystalline polymers has triggered great interests in synthesis of complex structures as well as well‐defined linear homopolymers with controlled molecular weight and narrow molecular weight distributions. This review highlights the synthetic strategies of controlled radical polymerization of linear homopolymers, star polymers, superbranched polymers, graft polymers, block copolymers, star block copolymers, and so on. The employed living methods include nitroxide‐mediated radical polymerization and atom transfer radical polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 319–330, 2009
Correlation of free radical copolymerization behavior and copolymer properties with the strength of π‐π stacking interactions between aromatic fluorocarbons and aromatic hydrocarbons: Comparison of the copolymerization behavior of 2,3,4,5,6‐pentafluorostyrene with styrene, 1‐vinylnaphthalene and 2‐vinylnaphthalene
Authors: Pugh Coleen , Paz‐Pazos Marta , Tang Chau N.
Published: December 2008

2,3,4,5,6‐Pentafluorostyrene (PFS) was copolymerized with 1‐vinylnaphathalene (1VN) in bulk by radical copolymerization at 25 °C (r1VNrPFS = 0.070) using t‐butylperoxy pivalate as the inititator, at 70 °C (r1VNrPFS = 0.11) using benzyol peroxide as the initiator, and at 120 °C (r1VNrPFS = 0.28) using t‐butyl peroxide as the initiator; PFS was also copolymerized with 2‐vinylnaphathalene (2VN) in bulk by radical copolymerization at 70 °C (r2VNrPFS = 0.15) under similar conditions. Their reactivity ratios were determined at low monomer conversions using the nonlinear least‐squares method of analysis, which demonstrated that both comonomer pairs tend to alternate, and that their alternating tendency increases with decreasing temperature, similar to the radical copolymerizations of PFS with styrene (St) in bulk. The glass transition temperatures determined by differential scanning calorimetry are elevated relative to their mole‐average values, with the extent of elevation being greater for the 1VN‐PFS copolymers than for the 2VN‐PFS copolymers, which is greater than that for St‐PFS copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 331–345, 2009