bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Potsdam sandstone on the trace element signatures of some 19th‐century American and Canadian glass: Redwood, Redford, Mallorytown, and Como–Hudson
Authors: Owen J. Victor , Greenough John D.
Published: August 2008

Potsdam sandstone from quarries and outcrops near 19th‐century glassworks sites in Redwood, NY, and Saranac, NY, Mallorytown, ON, and Como and Hudson, QC, commonly contains _97% silica, so in terms of its purity can compete with other historical producers of silica sand (e.g., Cheshire quartzite, MA; southern New Jersey sand). Exploratory analysis of trace element data using multidimensional scaling (MDS) shows that geographically distinct sources of Potsdam sandstone can be distinguished from one another and from competing sources of silica sand, particularly in terms of high field strength elements (e.g., Nb, Y, Ti, Zr), the rare earth elements, and radioactive elements (U, Th), and this geochemical signature is carried through to the glass it was used to manufacture. Other trace elements (e.g., Ba, Sr, Rb) are concentrated in various batch ingredients (e.g., limestone, alkali fluxes). The Hf/Nb, La/Ce, Nb/Th, and La/Zr ratios for each type of glass and nearby Potsdam sandstone sources cluster together in distinct fields on MDS plots. These data confirm the use of Potsdam sandstone in these important historical glassworks, and show that except for material sampled from neighboring communities (Mallorytown and Redwood), trace elements can be used to identify specific sources of silica historically used by the glassmaking industry. © 2008 Wiley Periodicals, Inc.
Long‐term population‐based risks of breast cancer after childhood cancer
Authors: Reulen Raoul C. , Taylor Aliki J. , Winter David L. , Stiller Charles A. , Frobisher Clare , Lancashire Emma R. , McClanahan Fabienne M. , Sugden Elaine M. , Hawkins Mike M. ,   on behalf of the British Childhood Cancer Survivor Study
Published: August 2008

Previous studies have reported substantially increased risks of breast cancer among survivors of childhood cancer at 10–20 years posttreatment. Whether these excess risks are sustained beyond 40 years of age when general population incidence of breast cancer begins its steep increase is largely unknown. We quantified the risk of breast cancer in adult female survivors with considerably more survivors followed‐up beyond 40 years of age than previously available. Standardized Incidence Ratios (SIR), Excess Absolute Risks (EAR), and cumulative incidence were calculated within a population‐based cohort of 8,093 female survivors of childhood cancer. Poisson regression models were used to model SIRs and EARs in a multivariable setting. Eighty‐one survivors developed a primary breast cancer, where 37.5 were expected (SIR= 2.2, 95% CI: 1.7–2.7). SIRs decreased significantly with increasing attained age (ptrend < 0.001) to an SIR of 0.9 (95% CI: 0.5–1.8) at ages beyond 50 years; EARs increased significantly to about 40 years of age (ptrend < 0.001) but then plateau. Between 30 and 49 years of age survivors experienced approximately 1 extra breast cancer per 1,000 survivors per year. Overall, 3% developed breast cancer by the age of 50. The substantially increased relative risks of breast cancer observed at 10–20 years postdiagnosis are not sustained into ages at which the risk of breast cancer in the general population becomes substantial. Among women who survived to an age of at least 50 years there is currently no evidence of an increased risk of breast cancer. © 2008 Wiley‐Liss, Inc.
Review: Biological relevance of disseminated tumor cells in cancer patients
Authors: Riethdorf Sabine , Wikman Harriet , Pantel Klaus
Published: August 2008

The prognosis of cancer patients is largely determined by the occurrence of distant metastases. In patients with primary tumors, this relapse is mainly due to clinically occult micrometastasis present in secondary organs at primary diagnosis but not detectable even with high resolution imaging procedures. Sensitive and specific immunocytochemical and molecular assays enable the detection and characterization of disseminated tumor cells (DTC) at the single cell level in bone marrow (BM) as the common homing site of DTC and circulating tumor cells (CTC) in peripheral blood. Because of the high variability of results in DTC and CTC detection, there is an urgent need for standardized methods. In this review, we will focus on BM and present currently available methods for the detection and characterization of DTC. Furthermore, we will discuss data on the biology of DTC and the clinical relevance of DTC detection. While the prognostic impact of DTC in BM has clearly been shown for primary breast cancer patients, less is known about the clinical relevance of DTC in patients with other carcinomas. Current findings suggest that DTC are capable to survive chemotherapy and persist in a dormant nonproliferating state over years. To what extent these DTC have stem cell properties is subject of ongoing investigations. Further characterization is required to understand the biology of DTC and to identify new targets for improved risk prevention and tailoring of therapy. Our review will focus on breast, colon, lung, and prostate cancer as the main tumor entities in Europe and the United States. © 2008 Wiley‐Liss, Inc.
Perturbation of the chromosomal binding of RCC1, Mad2 and survivin causes spindle assembly defects and mitotic catastrophe
Authors: Ho Chin‐Yee , Wong Chi‐Hang , Li Hoi‐Yeung
Published: August 2008

Mitotic catastrophe is a form of cell death that results from aberrant mitosis. Currently, the mechanisms involved in this form of cell death remain poorly understood. We found that actinomycin D induces mitotic catastrophe with severe spindle assembly defects. We have studied the nature of three groups of chromosome binding proteins in mitotic cells treated with actinomycin D. We found that actinomycin D reduced the binding affinity of RCC1 to the mitotic chromosome, which led to a reduction of RanGTP level. In addition, Mad2 was not concentrated at the kinetochores, indicating that the mitotic spindle checkpoint was affected. Furthermore, the localization of survivin was altered in cells. These data suggested that chromosomal binding of the mitotic regulators such as RCC1, Mad2 and survivin is essential for mitotic progression. Mitotic chromosomes not only carry the genetic material needed for the newly synthesized daughter cells, but also serve as docking sites for some of the mitotic regulators. Perturbation of their binding to the mitotic chromosome by actinomycin D could affect their functions in regulating mitotic progression thus leading to severe spindle defects and mitotic catastrophe. J. Cell. Biochem. 105: 835–846, 2008. © 2008 Wiley‐Liss, Inc.
Lopinavir impairs protein synthesis and induces eEF2 phosphorylation via the activation of AMP‐activated protein kinase
Authors: Hong‐Brown Ly Q. , Brown C. Randell , Huber Danuta S. , Lang Charles H.
Published: August 2008

HIV anti‐retroviral drugs decrease protein synthesis, although the underlying regulatory mechanisms of this process are not fully established. Therefore, we investigated the effects of the HIV protease inhibitor lopinavir (LPV) on protein metabolism. We also characterized the mechanisms that mediate the effects of this drug on elongation factor‐2 (eEF2), a key component of the translational machinery. Treatment of C2C12 myocytes with LPV produced a dose‐dependent inhibitory effect on protein synthesis. This effect was observed at 15 min and was maintained for at least 4 h. Mechanistically, LPV increased the phosphorylation of eEF2 and thereby decreased the activity of this protein. Increased phosphorylation of eEF2 was associated with increased activity of its upstream regulators AMP‐activated protein kinase (AMPK) and eEF2 kinase (eEF2K). Both AMPK and eEF2K directly phosphorylated eEF2 in an in vitro kinase assay suggesting two distinct paths lead to eEF2 phosphorylation. To verify this connection, myocytes were treated with the AMPK inhibitor compound C. Compound C blocked eEF2K and eEF2 phosphorylation, demonstrating that LPV affects eEF2 activity via an AMPK‐eEF2K dependent pathway. In contrast, incubation of myocytes with rottlerin suppressed eEF2K, but not eEF2 phosphorylation, suggesting that eEF2 can be regulated independent of eEF2K. Finally, LPV did not affect PP2A activity when either eEF2 or peptide was used as the substrate. Collectively, these results indicate that LPV decreases protein synthesis, at least in part, via inhibition of eEF2. This appears regulated by AMPK which can act directly on eEF2 or indirectly via the action of eEF2K. J. Cell. Biochem. 105: 814–823, 2008. © 2008 Wiley‐Liss, Inc.
Ozonation of chloronitrobenzenes in aqueous solution: kinetics and mechanism
Authors: Li Bingzhi , Xu Xiangyang , Zhu Liang
Published: August 2008

BACKGROUND: Chloronitrobenzenes (ClNBs) are a family of toxic and bio‐resistant organic compounds. Ozone treatment is specifically suitable for partial or complete oxidation of non‐biodegradable components. However, few studies on the decomposition of ClNBs by ozone are available, and kinetics and mechanisms of ClNBs ozonation have not been thoroughly investigated. The kinetics and mechanism of ozonation degradation of ClNBs in aqueous solution were investigated, and the contribution of both molecular ozone and hydroxyl radicals was also evaluated.

RESULTS: The results demonstrated that the decomposition of ClNBs was a pseudo‐first‐order reaction with respect to the pollutant concentration and the overall rate constant increased with an increase in pH. It declined, however, with an increase in pollutant and radical scavenger concentration. Furthermore, TOC removal rate was significantly lower than that of ClNBs, but the same order o‐ClNB < m‐ClNB < p‐ClNB was followed. Ozonation could not reduce TOC significantly, p‐chlorophenol, p‐nitrophenol, 2‐chloro‐5‐nitrophenol and 5‐chloro‐2‐nitrophenol were detected as primary degradation intermediates in ozonation of p‐ClNB. Rate constants of the direct reaction between ozone and ClNBs at 25 °C had been found to be lower than 1 M−1S−1. More than 95% of ClNBs removal was due to hydroxyl radical oxidation at pH ≥ 7.

CONCLUSION: Advanced oxidation processes may be the preferred choice for the elimination of ClNBs from the environment. Copyright © 2008 Society of Chemical Industry
Enteral nutrition in adult Crohn's disease: Present status and perspectives
Authors: Dupont Benoît , Dupont Claire , Justum Anne‐Marie , Piquet Marie‐Astrid , Reimund Jean‐Marie
Published: August 2008

Enteral nutrition has long been a therapeutic alternative often used in adult Crohn's disease patients to obtain remission or clinical response, especially in those not responding to conventional therapy such as corticosteroids. However, the increasing use of immunosuppressors (6‐mercaptopurine and azathioprine, methotrexate,etc.), and the advent of biotherapies (especially anti‐tumor necrosis factor‐alpha (TNF‐α) antibodies), decreased its use in adult Crohn's disease. Nevertheless, enteral nutrition remains of interest in patients presenting concomitant malnutrition (in particular in nonobstructed patients needing surgery), or in those intolerant or who failed to other therapeutics. In addition, recent studies provide data indicating its potential interest in maintenance therapy in selected patients groups. Finally, future research (in particular in the field of immuno‐ or pharmaconutrition) could lead to enteral formula's improvement, with better tolerance and acceptability, as well as increased efficacy.
Dynamic optimization and event location in atmospheric chemistry
Authors: Caboussat Alexandre , Landry Chantal
Published: August 2008

A model coupling differential equations and an optimization problem with equality and inequality constraints is described. The first order optimality conditions are coupled with the differential equations to form a differential‐algebraic system. Inequality constraints for the optimization variables induce discontinuities in the first derivatives of the solution in time. Tracking techniques based on sensitivity analysis and second order multistep methods are proposed to locate the discontinuities. Application to the dynamics of organic atmospheric aerosol particles is given to illustrate the detection of the activation of constraints. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Solving generalized complex‐symmetric eigenvalue problems arising from resonant MEMS simulations with PETSc
Authors: Koyamaname Tsuyoshi , Govindjee Sanjay
Published: August 2008

In the operation of high frequency resonators in micro electromechanical systems(MEMS), there is a strong need to be able to accurately determine the energy loss rates or alternatively the quality of resonance. The resonance quality is directly related to a designers ability to assemble a high fidelity system response for signal filtering, for example. This has implications on robustness and quality of electronic communication and also strongly influences overall rates of power consumption in such devices – i.e. battery life. An index of the quality of resonance Q is inversely proportional to the amount of energy loss existing in the system, and can be defined in terms of the complex‐valued eigenvalues ω of the system as, . In this presentation, we examine methods for accurately simulating energy loss using the direct modeling of acoustic radiation via perfectly matched layer (PML) technology for 3‐D structures, which results in complex‐symmetric mass and stiffness matrices. Thus it is crucial that one is able to accurately compute eigenvalues of a complex‐symmetric system. 3‐D modeling increases the number of degrees of freedom and complexity in obtaining the solution, resulting in a requirement for more computing power and memory which can only be supplied by parallel computing methods. The simulations are conducted through the MEMS simulation software HiQLab in combination with the parallel numerical libraries PETSc and Trilinos. A modified smoothed aggregation algebraic multigrid method for solving a linear system of equations is combined with a Jacobi‐Davidson method to solve for desired eigenvalues. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The nullspace method for the three‐dimensional Stokes problem
Authors: Le Borne Sabine , Kriemann Ronald
Published: August 2008

In this paper, we present the preconditioned nullspace method for the iterative solution of the three‐dimensional Stokes problem. In the nullspace method, the original saddle point system is reduced to a positive definite problem by representing the solution with respect to a basis of discretely divergence free vectors. The exact, explicit computation of such a basis typically has non‐optimal (storage and computational) complexity. There exist some algorithms that exploit the sparsity of the matrix and work well for two dimensional problems but fail for three dimensions. Here, we will exploit an implicit representation of the nullspace basis which can be computed efficiently also in a three‐dimensional setting, possibly only as an approximation. We will present some numerical results to illustrate the performance of the resulting solution method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Halley and Newton are one step apart
Authors: Gundersen Geir , Steihaug Trond
Published: August 2008

One of the central problems of scientific computation is the efficient numerical solution of the system of n equations in n unknowns F (x) = 0 where F: Rn → Rn is sufficiently smooth. While Newton's method is usually used for solving such systems, third order methods will in general use fewer iterations than a second order method to reach the same accuracy. However, the number of arithmetic operations per iteration is higher for third order methods than second order methods. In this note we will consider the case where F = ∇f, where f is three times continuously differentiable. We will show that for a large class of sparse problems the ratio of the number of arithmetic operations of a third order method and Newton's method is constant per iteration. It is shown that

equation image

when the structure of the tensor is induced by a general sparse structured Hessian matrix which gives no fill‐ins when we use a direct method to solve a system of linear equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stochastic modeling of non‐equilibrium multiphase flow in porous media
Authors: Tyagi Manav , Jenny Patrick , Tchelepi Hamdi A.
Published: August 2008

Non‐equilibrium phenomena arising from the pore scale dynamics can have considerable effect on the large scale dynamics of multiphase flow in porous media. In such cases, the relative permeabilities and capillary pressure curves are not just simple functions of phase saturations, rather are dynamic functions of space and time. The present work proposes a stochastic approach in which particle mobility can be modelled based on the actual conductance of fluid volume inside a pore space. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Portfolio Improvement by Using the Sharpe Rule and Value‐at‐Risk
Authors: Yu Kwok Wai , Yang Xiao Qi , Wong Heung
Published: August 2008

This study discusses the applications of the Sharpe rule in portfolio measurement and management. It proposes that a portion of the portfolio value should be invested in some other assets for portfolio improvement. By applying the Sharpe rule, it can be determined that new stocks are worthy of adding to the old portfolio if they satisfy a condition, in which the average return rate of these stocks is greater than the return rate of the old portfolio multiplied by the sum of the elasticity of the VaR and 1. One attraction of our approach is diversification. A numerical example in the Hong Kong stock market is presented for illustration. Some experimental results show that a new portfolio with the 'highest' Sharpe ratio can be obtained by adding only a few new assets. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐reflecting boundary conditions for the compressible Euler and Navier‐Stokes equations in the finite volume method
Authors: Kyncl Martin , Pelant Jaroslav , Felcman Jiří
Published: August 2008

The paper is concerned with the numerical implementation of the inlet and outlet boundary conditions in the finite volume method for the solution of the 3D Euler and Navier‐Stokes equations. The explicit time marching procedure is described. The classical Riemann problem is modified for physically relevant boundary conditions with the aim to keep conservation laws. This technique was used in [2]. The initial condition in the Riemann problem is replaced by the suitable one‐sided boundary condition. This results in the acceleration of the numerical method itself. On the inlet the pressure and the density and the angle of attack or velocity vector and the entropy are prescribed. On the outlet the pressure or normal component of the velocity or temperature or mass flow are investigated in such a way to obtain the unique solution of the modified Riemann problem. Various combinations of inlet and outlet boundary conditions are investigated. This results in the sufficiently precise approximation of real flow boundary conditions. Numerical examples illustrating the usefulness of the proposed approach for cascade flow are presented. Another numerical example is shown in [3]. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computation of static‐equivalent load sets for bone remodeling simulation
Authors: Lutz André , Nackenhorst Udo
Published: August 2008

Theories and related computational techniques for the prediction of bone mass loss, for example caused by endoprosthetic treatment, have been under discussion for more than 20 years. Today, numerical aspects and constitutive modeling of stress adaptive bone remodeling seem to be sufficiently solved. However there is an open question about the description of the loading conditions in the framework of quasi‐static approaches (see e.g. [1]). Due to the complexity of the subject only a limited data base is available on measured and computed joint and muscle forces for typical movements. To close this gap, an inverse simulation approach on the identification of static‐equivalent load sets related to measured bone mass density distributions will be presented in this contribution. Based on a first order approach of bone remodeling, these load sets are computed by an hierarchic genetic‐gradient algorithm and lead to the original bone mass distribution obtained by high resolution imaging techniques. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The application of the FDEM program package with error estimate to industrial problems
Authors: Adolph Torsten , Schönauer Willi
Published: August 2008

The Finite Difference Element Method (FDEM) program package is a robust and efficient black‐box solver that solves arbitrary nonlinear systems of elliptic and parabolic partial differential equations under arbitrary nonlinear boundary conditions on arbitrary domains in 2‐D and 3‐D. FDEM is an unprecedented generalization of the finite difference method on unstructured finite element meshes. From the difference of formulas of different order, we get an easy access to the discretization error. By the knowledge of this error, the mesh may be refined locally to reduce the error to a prescribed relative tolerance. The error estimate is a unique property for such a general black‐box. In addition, the FDEMprogram package is efficiently parallelized on distributed memory parallel computers.

In this paper we demonstrate the usefulness of the FDEM program package by its application to several industrial problems. This gives completely new results as up to now people have solved these problems blindly, unaware of the error of their solution. The first problem is the numerical simulation of a microreactor where we have one chemical component entering through the main channel and one chemical component entering through a side channel so that there is a reaction of the components. We want to examine the flow field and the behaviour of the chemical components. The second problem is the heat conduction in a high pressure Diesel injection pump. This problem is based on a preceding fluid‐structure interaction problem, and we now compute the temperature distribution in the injection pump additionally. Finally, we simulate the distribution of the temperature in a DC/AC converter module with six power‐MOSFETs heated with uniform power. At the bottom of the module air cooling is applied. In contrast to the first two elliptic problems, this is a 3‐D parabolic problem. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of skin‐stiffener debonding in stiffened carbon/epoxy panels
Authors: Balzani Claudio , Wagner Werner
Published: August 2008

Aircraft fuselage structures are typically composed of a curved skin connected to longitudinal stiffeners. They are nowadays made of carbon/epoxy laminates. Skin‐stiffener debonding can lead to a significant reduction of their compressive loadcarrying capacity in the postbuckling range of response. This work examines this effect in the framework of the finite element method. A zero‐thickness interface element written in terms of cohesive tractions and relative displacements is derived which is inserted between skin and stiffener. A special cohesive law already presented in [1, 2] describes the softening behavior of the interface while taking into account contact conditions. A numerical example shows the applicability of the model. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Empirical study of the rate of convergence of some fixed point iterative methods
Authors: Berinde Vasile , Păcurar Mădălina
Published: August 2008

An approach for the empirical study of the rate of convergence of fixed point iterative methods is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adaptive least‐squares finite element approximations to transonic‐flow problems
Authors: Chang Shin‐Perng , Chen Tsu‐Fen
Published: August 2008

This work concerns solutions of compressible potential flow problems based on weighted least‐squares finite element approximations. The model problem considered is that of the potential flow past a circular cylinder. To capture the transonic flow region, an adaptive algorithm based on mesh redistribution with local mesh refinement and smoothing is developed for suitably weighted least‐squares approximations. Numerical results for the model problem are given for the transonic case with shocks. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An adaptive level set method for shock‐driven fluid‐structure interaction
Authors: Deiterding Ralf
Published: August 2008

The fluid‐structure interaction simulation of shock‐ and detonation‐loaded structures requires numerical methods that can cope with large deformations as well as local topology changes. A robust, level‐set‐based shock‐capturing fluid solver is described that allows coupling to any solid mechanics solver. As computational example, the elastic response of a thin steel panel, modeled with both shell and beam theory, to a shock wave in air is considered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Displacement field analysis of the topology optimized structure
Authors: Kutylowski Ryszard
Published: August 2008

In this paper for the topology optimization process the minimum compliance approach is used with FEM as very useful method for numerical realization of the problem. During the optimization process homogenized domain changes into discrete structure which means the final structure consists of the many optimal placed bars. The analysis of the deformed structure and the deformed finite elements is done from the displacement field point of view. It can be noticed, some of the finite elements reduce their size, some of them increase their size. It depends on the element status (void‐empty, stressed or not stressed). The question arises: is the topology optimization process cause of the negative Poisson ratio for some parts of the structure? (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of pharmacokinetic uncertainty generated by irregular drug intake: A stochastic modeling approach
Authors: Nekka Fahima , Gohore Bi Denis , Fenneteau Frédérique , Li Jun
Published: August 2008

In this paper, we have translated, in mathematical terms, a largely reported swine feeding behaviour and assessed its impact on pharmacokinetics of the chosen antibiotic. This mechanistic‐based approach allowed us to delineate the role of different feeding patterns, to quantify the pharmacokinetic variability induced by feeding behaviour and to learn about random features of the pharmacokinetic variation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A quadrature free convergent method for the numerical solution of linear Fredholm integral equations based on Hermite‐spline interpolation
Authors: Shahmorad S. , Abdollahi A.
Published: August 2008

In this paper we use the Hermite‐spline interpolation in a special form for the numerical solution of linear Fredholm integral equations. We prove the convergence of this method as a main part of the paper. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some results on coupled linear wave equations
Authors: Eden Alp , Erbay Saadet , Hacinliyan Irma
Published: August 2008

In the present study, we consider a generalized Davey‐Stewartson (GDS) system consisting of a nonlinear Schrödinger (NLS) type equation and two asymmetrically coupled linear wave equations. We obtain integral representation of solutions to the coupled linear wave equations. As applications, we present some localized solutions to the GDS system for a special choice of parameters and find some estimates of the solutions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the moving boundary formulation for parabolic problems on unbounded domains
Authors: Fazio Riccardo , Iacono Salvatore
Published: August 2008

A parabolic problem defined on unbounded domains and admitting invariance property to Lie group of scalings can be transformed into an equivalent boundary value problem governed by an ODE defined on an infinite interval. A free boundary formulation and a convergence theorem for this kind of transformed problems are available in [Fazio, SIAM J. Numer. Anal., 33 (1996), pp. 1473‐1484]. Depending on its scaling invariance properties, the free boundary problem is then solved numerically using either an iterative or a non‐iterative method. Finally, the solution of the parabolic problem is retrieved applying the inverse map of similarity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of cold‐formed thin‐walled beams with application of an expert system
Authors: Kasperska R. , Ostwald M. , Mikolajewski D.
Published: August 2008

The aim of this paper is to present the problem of optimal design of selected cross section shapes of the thin‐walled coldformed beams under combined loads. The optimization problem is given as the bicriteria one, where the cross‐sectional area of the thin‐walled beam and the deflection of the beam centre are the objective functions. The work provided optimal parameters of cross‐sections of the beams, satisfying the conditions of general and local stability, strength, limiting loading capacity of the beam, structural, technological and exploitation constraints. This paper outlines the application of a knowledge‐based expert system built to assist engineers in the designing process and multicriteria optimization of cold‐formed thin‐walled beams. The paper includes some exemplary numerical results in the form of figures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sort‐Jacobi and generalizations of the symmetric eigenvalue problem
Authors: Kleinsteuber M.
Published: August 2008

In this paper, it is sketched how the Sort‐Jacobi method for the symmetric eigenvalue problem extends to the (–1)‐eigenspace of the Cartan involution on an arbitrary semisimple Lie algebra. The proposed method is independent of the representation of the underlying Lie algebra and generalizes well‐known normal form problems such as the symmetric, Hermitian, skewsymmetric, symmetric and skew‐symmetric ℝ‐Hamiltonian eigenvalue problem and the singular value decomposition. It allows a unified treatment of the above eigenvalue methods, including local convergence analysis. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A predictor‐corrector method for a class of equilibrium problems
Authors: Preda Vasile , Beldiman Miruna , Bătătorescu Anton
Published: August 2008

We consider two classes of generalized monotone functions and generalized skew symmetric functions. By applying the method of auxiliary‐principle, we propose and study a predictor‐corrector algorithm for solving mixed quasiequilibrium problems involving σ ‐pseudomonotone functions with respect to a ξ ‐skew symmetric bifunction, which are concepts introduced in this paper. We prove the convergence of the iterative sequence under generalized pseudomonotonicity and skew symmetry assumptions, improving some known results in the recent literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sufficient conditions for exact penalty in constrained optimization
Authors: Zaslavski Alexander J.
Published: August 2008

In this paper we use the penalty approach in order to study constrained minimization problems. A penalty function is said to have the exact penalty property if there is a penalty coefficient for which a solution of an unconstrained penalized problem is a solution of the corresponding constrained problem. We discuss very simple sufficient conditions for the exact penalty property. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical benchmarks for creep‐damage modeling
Authors: Altenbach Holm , Naumenko Konstantin , Gorash Yevgen
Published: August 2008

The aim of creep modeling is to reflect basis features of creep in structures including the evolution of inelastic deformations, relaxation and redistribution of stresses as well as the local reduction of material strength. A model should be able to account material deterioration processes in order to predict long term structural behavior and to analyze critical zones of creep failure. In recent years general purpose finite element codes have become the widely accepted tool for the structural analysis. To consider both the creep and the damage processes, a specific constitutive model with selected internal state variables, special types of stress and temperature functions as well as material constants identified from available experimental data should be incorporated into the commercial finite element code by writing a user defined material subroutine. To assess the reliability of the developed subroutine as well as the accuracy of the results with respect to the mesh density, type of finite element, the time step, and the iteration methods, numerical benchmark problems are required. Here we present two benchmark problems of creep‐damage mechanics which can be solved by approximate numerical methods. The reference solutions are compared with the finite element solutions by ANSYS and ABAQUS finite element codes with user creep model subroutines. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanisms for oscillations in a biological competition model
Authors: Curtu Rodica
Published: August 2008

A four‐dimensional dynamical system that models perceptual bistability in the brain is analyzed. Two variables represent the activity of two competing neural populations and they evolve in fast time; other two variables are slow and they are associated with an intrinsic negative feedback to each population. The external stimulus strength I is the bifurcation parameter. We construct the normal form and prove that oscillations occur in the system through supercritical Hopf bifurcations: as I decreases from large to moderate values a limit cycle is born; then it disappears for lower values of I. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The magic of SPSA
Authors: Gerencsér L. , Vágó Zs. , Hill Stacy D.
Published: August 2008

The basics of SPSA (simultaneous perturbation stochastic approximation) initiated and developed in [1] will be desctribed. We point out the advantages of SPSA over the finite difference stochastic approximation (FDSA) or Kiefer‐Wolfowitz (KW) method. Its applicability in noise free optimization and in discrete optimization will be also briefly described. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical modeling of compressible turbulent channel flow
Authors: Heinz Stefan
Published: August 2008

Several questions that are relevant to turbulence modeling are addressed on the basis of recently obtained direct numerical simulation results of turbulent supersonic channel flow. In particular, this concerns the turbulence frequency production mechanism, wall damping effects on turbulence model parameters, and the relevance of compressibility effects. Limited support is found for usually applied models for the turbulence frequency production and wall damping effects. In contrast to that it is shown that turbulence frequency production mechanisms and wall damping effects may be explained very well on the basis of a frequency scaling that characterizes mean flow changes. The influence of compressibility is found to be relevant. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control of a thermomechanical model of phase transitions in steel
Authors: Hömberg Dietmar , Kern Daniela
Published: August 2008

We consider an optimal control problem concerning heat treatment of steel. The mathematical model consists of the equations of thermoelasticity coupled to a system of rate laws accounting for the phase transition kinetics. For the coupling a mixture ansatz for the different thermal expansion coefficients is used. In contrast to classical thermoelasticity this leads to residual deformations whenever the resulting phase distribution at end‐time is inhomogenous. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wavelets and splines for modelling the earth's magnetic field
Authors: Mayer Carsten
Published: August 2008

At the present time there is an unprecedented opportunity to use satellite magnetometer data, as for example Oersted and CHAMP records, to improve our knowledge of the Earth's magnetic field and its sources. These measurements contain contributions from the main magnetic field of the Earth, the crustal field as well as contributions coming from different exterior (ionospheric and magnetospheric) sources. For the mathematical analysis of the data it is critical to have in hand appropriate tools which separate these sources and which are able to analyze the different contributions independently. We present in this talk an approach in terms of (spherical) scalar and vectorial scaling functions and wavelets to handle these problems. Examples include crustal field modelling and reconstruction of ionospheric currents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An hp finite element method for singularly perturbed systems of reactiondiffusion equations
Authors: Oberbroeckling Lisa , Xenophontos Christos
Published: August 2008

We consider the approximation of a coupled system of two singularly perturbed reaction‐diffusion equations by the finite element method. The solution to such problems contains boundary layers which overlap and interact, and the numerical approximation must take this into account in order for the resulting scheme to converge uniformly with respect to the singular perturbation parameters. We present results on a high order hp finite element scheme which includes elements of size O (εp) and O (μp) near the boundary, where ε, μ are the singular perturbation parameters and p is the degree of the approximating polynomials. Under the assumption of analytic input data, the method yields exponential rates of convergence as p → ∞, independently of ε and μ. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A holistic finite element and multi‐body systems approach for the virtual product development
Authors: Barthel Corinna
Published: August 2008

This article describes the creation of a holistic modeling of a machine tool using a multi‐body‐systems approach with an integrated flexible body. This lower order model is validated by a detailed finite element model and its eigenvalues are improved by a model‐updating algorithm. The improved model is used for investigation of the machine vibration during the cutting process and the prediction of chatter. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coarse‐to‐fine partitioning of signals
Authors: Florack Luc
Published: August 2008

An empirically acquired signal can be analyzed in a multi‐scale framework. Its multi‐scale structure induces a hierarchical partitioning of the signal domain into topologically meaningful segments. A method is proposed to operationalize this using elementary results from singularity theory for certain generic solutions of the one‐dimensional heat equation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hölder continuity of minimizers for the state constrained Boza problem
Authors: Bettiol Piernicola , Frankowska Hélène
Published: August 2008

Regularity of minimizers for the Bolza optimal control problem has been extensively studied by several authors (cf. For instance [2–5] and the references contained therein). Here we give a generalization of some results of [5] by using an approach introduced in [3]. We consider a Bolza problem under state constraints and show that, if the Hamiltonian function is smooth enough and enjoys some monotonicity properties, then both the adjoint state and optimal trajectory enjoy Hölder type regularity. We also provide sufficient conditions for Hölder regularity of optimal controls. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transonic viscous inviscid interactions in narrow channels
Authors: Meyer G. , Kluwick A.
Published: August 2008

Unsteady as well as steady transonic flows through channels which are so narrow that the classical boundary layer approach fails are considered. As a consequence the properties of the inviscid core and the viscosity dominated boundary layer region can no longer be determined in subsequent steps but have to be calculated simultaneously. The resulting interaction problem for laminar flows is formulated for both perfect and dense gases under the requirement that the channel is sufficiently narrow so that the flow outside the viscous wall layers becomes one‐dimensional in the leading order approximation. The latter allows an interpretation of the flow in the core region by means of the theory of one‐dimensional transonic inviscid flow through a Laval nozzle while preserving the essential features of the interaction problem associated with the internal structure of pseudoshocks. The sensitivity of a separation bubble caused by a pseudoshock of sufficient strength to perturbations under the condition of choked flow will be demonstrated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical propagator method solutions for the linear parabolic initial boundary‐value problems
Authors: Rimshans Janis , Guseynov Sharif
Published: August 2008

On the base of our numerical propagator method a new finite volume difference scheme is proposed for solution of linear initial‐boundary value problems. Stability of the scheme is investigated taking into account the obtained analytical solution of the initial‐boundary value problems. It is shown that stability restrictions for the propagator scheme become weaker in comparison to traditional semi‐implicit difference schemes. There are some regions of coefficients, for which the elaborated propagator difference scheme becomes absolutely stable. It is proven that the scheme is unconditionally monotonic. Analytical solutions, which are consistent with solubility conditions of the problem are formulated for the case of constant coefficients of parabolic equation by using Green function approach. Solubility of the linear initial‐boundary value problem with Newton boundary conditions containing lower order derivatives is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Schwarz‐type smoothers for elliptic optimal control problems
Authors: Simon René , Zulehner Walter
Published: August 2008

We present a multigrid method for elliptic optimal control problems using a patch smoother. The method allows a rigorous multigrid convergence analysis and shows good convergence properties, which are comparable with known results from literature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigation of shock wave‐loaded plates
Authors: Stoffel Marcus , Schmidt Rüdiger , Weichert Dieter
Published: August 2008

In the present paper measured and simulated vibrations of viscoplastic plates under impulsive loadings are compared to each other. The aim is to determine how accurately the measured deformations can be calculated by the chosen constitutive and structural theories. The damage growth in the plate specimens until failure is predicted by finite element simulations and compared to shock tube experiments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ergodicity, mixing and the Bernoulli property in a DNA hybridization microarray
Authors: Sturman Rob , Wiggins Stephen
Published: August 2008

Pulsed source–sink devices are an effective way of achieving dynamic hybridization in DNA microarrays. These can be modelled as linked twist maps, and in particular, basing the design on the dynamics of a hyperbolic toral automorphism allows the application of a set of techniques from ergodic theory. This gives a rigorous framework in which to discuss mixing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multiscale damage simulation
Authors: Timmel Mario , Kaliske Michael , Kolling Stefan , Mueller Ralf
Published: August 2008

Numerous materials show a softening behaviour at dynamic loading. The decrease of stress is caused by the evolution in the microscale in terms of areas where the local stiffness is reduced, e.g. due to micro‐void growth. For a numerical treatment of this material behaviour, phenomenological damage approaches are used in daily engineering practice. For a better understanding of the micromechanical process of such phenomenological models, multiscale methods are becoming increasingly important. The physical quantities that are responsible for the microstructural evolution associated with the damage process are transferred into the numerical model. In this context, the method of configurational forces will be used to describe the geometrical changes of damaged areas. With the help of homogenization, macro‐ and microscale will be coupled. In consequence, each Gaussian point of the macroscale is modelled by an own microstructure (RVE), where the microscale evolves during the loading process according to observable damage phenomena. Hereby, we present the general case of hyperelastic materials at finite strains. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On projected gradient methods for regularizing reconstruction of synchrotron radiation spectra distribution function
Authors: Wang Yanfei , Du Yonghua , Hu Tiandou
Published: August 2008

We study the numerical methods for the reconstruction of the spectral distribution function of SR by measurement of the attenuation of the SR energy spectrum. The reconstruction of the spectral distribution function of SR is an ill‐posed integral operator equation of the first kind. Therefore, robust method to overcome the ill‐posedness and to improve the computational efficiency is a major task in numerical computation. Because of the physical meaning of the problem, we study projected gradient methods in this paper. Numerical simulations are given. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical methods for inferring phylogenies
Authors: Albrecht Felipe , Borges Nelson
Published: August 2008

Molecular phylogenies describe the study of evolution relationships between living beings, protein and genetic sequences and other molecular taxons. In recent years there has been increased interest in producing large and accurate phylogenies trees using some numerical computational methods approach. One class of molecular phylogenies is the distance matrices method, with the matrix whose entries represent the distinctions between the taxons under study. To construct large and accurate trees for a large number of taxons, the computational processing increases and parallel computing can be helpful. So far we have tested some methods to solve the linear systems, being driven to important conclusions, like which is the best tested method, and having also reached some questions about communication. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic properties of microcomponents under uniaxial stress
Authors: Jöchen K. , Böhlke T.
Published: August 2008

In order to develop highly stressable microcomponents for various applications, the structural behavior of such parts has to be examined with respect to an accurate prediction of the elastic and plastic characteristics. When simulating microparts, the major challenge is to capture the significant material heterogeneities, which are the result of the small geometrical dimensions of the components being of the same order of magnitude as the grain size. For this reason, the concept of effective properties fails and apparent properties have to be considered. In this paper we examine the elastic properties of microspecimens made of gold. Therefore, various finite element simulations have been evaluated statistically in order to identify the characteristic parameters of the distribution. Polycrystals are modeled as a periodic Voronoi tesselation with a uniform distribution of crystal orientations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)