bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuzzy random vibration of multi‐degree‐of‐freedom hysteretic systems subjected to earthquakes
Authors: Wang Guang‐Yuan , Ou Jin‐Ping
Published: March 2007

Earthquake excitation not only has evident randomness but also has strong fuzziness owing to the uncertainties in the definition of earthquake intensity and site soil classification. In this paper, the seismic ground motion is simulated as a stationary filtered white noise with fuzzy parameters, an analytical procedure is proposed to analyse the fuzzy random vibration of multi‐degree‐of‐freedom (MDOF) hysteretic systems, and the covariance matrix of the fuzzy random responses is derived by the equivalent linearization technique. Finally, some numerical results for a two‐storey shear hysteretic frame are presented to demonstrate the validity and effectiveness of the procedure proposed.
Validation of new equations for dynamic analyses of tall frame‐type structures
Authors: Kerr Arnold D. , El‐Sibaie Magdy A.
Published: March 2007

The accuracy of the new equations for long frame‐type structures, derived by Kerr and Zarembski, and extended recently by Kerr and Accorsi also to dynamic analyses, is investigated. At first, the natural frequencies of a tall frame‐type structure, with twenty floors, are determined using the new equations, and then they are compared with the corresponding results calculated using the finite element method and the common shear‐building analysis. The found agreement with the finite element analysis is close.

To check further the accuracy of the new equations, small scale models are tested on a shake table. The natural frequencies recorded in the tests are then compared with those determined from the new equations, for a wide range of geometrical parameters. The agreement with the test data is good.

The presented study indicates that the new equations are well suited for analyzing the dynamic response of tall frame‐type structures.
Random vibrations of the baltic drilling platform subjected to wind loads and water waves
Authors: Jesień Wojciech
Published: March 2007

This paper presents random vibrations of the Baltic drilling platform subjected to water waves and wind loads. The platform structure is discretized by the finite element method. Linear beam or truss elements can be used. The structure parameters (i.e. mass, damping and stiffness) are assumed as deterministic. Soil is modelled as an elastic half‐space that possesses deterministic or random parameters. Soil–structure interaction is idealized as a system of spring–dashpot elements connecting the structure and subsoil. The parameters of these elements can be random or deterministic. The sea surface is described by the one‐dimensional wave spectrum that was proposed by Striekalov and Massel24 for inland seas. It is suitable for the Baltic Sea. The wind velocity is described by the well‐known Davenport spectrum. The water and wind loads are treated as stationary ergodic processes. Gaussian distributions and zero means of these processes are assumed. In addition to this, waves and wind loads are considered as independent. Such an assumption corresponds to the situation when the storm sea is fully developed. A frequency‐domain random‐vibration approach is utilized to obtain the dynamic response of the platform. The equations of motion of the problem were solved using modal reduction. The numerical calculations were made with a specially written computer program. From the results obtained, it is concluded that the wind influence on the response of the platform can be neglected. If random parameters are assumed for the subsoil, then the response of the system describes in a more realistic way the dynamic behaviour of the platform. The velocity coupling due to soil and hydrodynamical damping is negligible. This paper is a condensation of the author's Ph.D. thesis presented at the Technical University of Gdańsk in July 1985.
Fuel Cell or Battery: Electric Cars are the Future
Authors: Van Mierlo J. , Maggetto G.
Published: March 2007

Battery and hybrid vehicles are today's sustainable mobility solutions, preparing a future shared with a hydrogen economy. The summary report of the EU High Level Group for Hydrogen and Fuel Cells, presented in June 2003, develops a vision on the contribution that hydrogen and fuel cells could make to the realization of sustainable energy systems in the future [1].

However, it seems necessary to emphasize that, as it is a long‐term vision (2000‐2050), there is a need to take strong action in the short‐ and medium‐term in order to address current environmental and energy concerns.

As stated in the Commission's November 2000 Green Paper on security of supply [2], in 1998 energy consumption in the transport sector was responsible for 28% of the emissions of CO2, the main greenhouse gas. According to the latest estimates, current CO2 emissions from transport are expected to increase by around 50%.

It is both an ecological necessity and a technological challenge to reduce the dependence on oil, from the current level of 98%, by using alternative fuels and improving the energy efficiency of the various methods of transport [3]. It is planned that the hydrogen economy will only start around 2020, at the earliest, and to be established around 2050. Fortunately, many of the electric drive technologies common with hydrogen drive systems are already in development today and implemented in battery or hybrid electric vehicles.

Two transport technologies are ready to play a significant role in this context: the battery electric vehicle and the thermal hybrid electric vehicle. They are the missing link with a future hydrogen transportation economy. It is an established fact that, from a well to wheel emission point of view, the results are positive and in favour of battery electric vehicles [4]. Important and recent studies on the environmental balance of battery electric vehicles show substantial emission and primary energy benefits, and thus CO2 reduction, when compared with conventional cars [4, 5].

The battery electric vehicles and thermal hybrid electric vehicles are considered as the bridge to the future hydrogen transport economy. In any case, the hydrogen and electricity vectors should be used in the most appropriate and effective way to ensure, for the various applications, the optimum mix of the primary energy sources at a European level.
Spatial memory and hippocampal volume in humans with unilateral vestibular deafferentation
Authors: Hüfner Katharina , Hamilton Derek A. , Kalla Roger , Stephan Thomas , Glasauer Stefan , Ma Jun , Brüning Roland , Markowitsch Hans J. , Labudda Kirsten , Schichor Christian , Strupp Michael , Brandt Thomas
Published: March 2007

Patients with acquired chronic bilateral vestibular loss were recently found to have a significant impairment in spatial memory and navigation when tested with a virtual Morris water task. These deficits were associated with selective and bilateral atrophy of the hippocampus, which suggests that spatial memory and navigation also rely on vestibular input. In the present study 16 patients with unilateral vestibular deafferentation due to acoustic neurinoma were examined 5‐ to 13‐yrs post‐surgery. Volumetry of the hippocampus was performed in patients and age‐ and sex‐matched healthy controls by manually tracing the structure and by an evaluator‐independent voxel‐based morphometry. Spatial memory and navigation were assessed with a virtual Morris water task. No significant deficits in spatial memory and navigation could be demonstrated in the patients with left vestibular failure, whereas patients with right vestibular loss showed a tendency to perform worse on the respective tests. Impairment was significant only for one computed measure (heading error). The subtle deficiencies with right vestibular loss are compatible with the recently described dominance of the right labyrinth and the vestibular cortex in the right hemisphere. Volumetry did not reveal any atrophy of the hippocampus in either patient group. © 2007 Wiley‐Liss, Inc.
Tumor‐targeting Salmonella typhimurium improves cyclophosphamide chemotherapy at maximum tolerated dose and low‐dose metronomic regimens in a murine melanoma model
Authors: Jia Li‐Jun , Wei Dong‐Ping , Sun Qi‐Ming , Jin Guang‐Hui , Li Shu‐Feng , Huang Yan , Hua Zi‐Chun
Published: March 2007

Chemotherapy for cancer is partly limited by the inability of drugs to act on poorly vascularized or avascularized areas of tumors. Tumor‐targeting bacteria are capable of preferentially replicating in these poorly perfused regions. Some strains have been combined with chemotherapeutic agents and the results have been promising. However, no systematic work has been carried out to test the effect of bacteria on clinical modes of chemotherapy, such as standard maximum tolerated dose (MTD) and novel low‐dose metronomic (LDM) chemotherapy. Here Salmonella typhimurium VNP20009 was combined with cyclophosphamide (CTX) at both MTD and LDM schedules in a murine melanoma model. The results showed that VNP20009 significantly improved the effects of all forms of CTX treatments. The combination of VNP20009 and CTX led to a more significant decrease in tumor microvessel density and serum vascular endothelial growth factor (VEGF) level, compared with either treatment alone. Furthermore, combination therapy remarkably increased the number of bacteria within tumors when compared with bacteria treatment alone. These findings suggest that tumor‐targeting bacteria, in conjunction with CTX at standard MTD and LDM regimens, might be of clinical value for the treatment of melanoma. © 2007 Wiley‐Liss, Inc.
Identification of cytotoxic T‐lymphocyte epitope(s) and its agonist epitope(s) of a novel target for vaccine therapy (PAGE4)
Authors: Yokokawa Junko , Bera Tapan K. , Palena Claudia , Cereda Vittore , Remondo Cinzia , Gulley James L. , Arlen Philip M. , Pastan Ira , Schlom Jeffrey , Tsang Kwong Y.
Published: March 2007

PAGE4 is an X chromosome‐linked cancer testis antigen and is a potential new tumor‐associated antigen that is overexpressed in prostate and uterine cancers. The purpose of this study was to identify a human CTL epitope and a corresponding agonist epitope of PAGE4 to determine if PAGE4 is a potential target for vaccine‐mediated immunotherapy against PAGE4‐expressing tumors. A class I PAGE4 epitope was identified with a high level of binding to HLA‐A2. PAGE4 peptide‐pulsed dendritic cells were then used to generate human PAGE4‐specific T‐cell lines. Further studies demonstrated the generation of an enhancer agonist epitope. Compared with the native peptide, the agonist (i) bound to HLA‐A2 molecules at lower peptide concentrations, (ii) demonstrated a higher stability of the peptide HLA‐A2 complex, (iii) induced higher levels of production of IFN‐γ, Granzyme B, TNF‐α, IL‐2 and lymphotactin by PAGE4‐specific T‐cell lines and (iv) T‐cell lines generated against the agonist peptide were more efficient to lyse HLA‐A2 human tumor cells expressing native PAGE4. The studies reported here are the first to describe a PAGE4 CTL epitope and its agonist epitope, and thus identify PAGE4 as a potentially useful target for vaccine‐mediated therapy of prostate cancer. © 2007 Wiley‐Liss, Inc.
Special sets of the Hermitian surface and indicator sets
Authors: Cossidente Antonio , Marino Giuseppe , Polverino Olga
Published: March 2007

An interesting connection between special sets of the Hermitian surface of PG(3,q2), q odd, (after Shult 13) and indicator sets of line‐spreads of the three‐dimensional projective space is provided. Also, the CP‐type special sets are characterized. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 18–24, 2008
The recognition of symmetric latin squares
Authors: Ihrig Edwin C. , Ihrig Benjamin M.
Published: March 2007

A latin squareSis isotopic to another latin squareS′ ifS′ can be obtained fromSby permuting the row indices, the column indices and the symbols inS. Because the three permutations used above may all be different, a latin square which is isotopic to a symmetric latin square need not be symmetric. We call the problem of determining whether a latin square is isotopic to a symmetric latin square the symmetry recognition problem. It is the purpose of this article to give a solution to this problem. For this purpose we will introduce a cocycle corresponding to a latin square which transforms very simply under isotopy, and we show this cocycle contains all the information needed to determine whether a latin square is isotopic to a symmetric latin square. Our results relate to 1‐factorizations of the complete graph onn + 1 vertices,Kn + 1. There is a well known construction which can be used to make ann × nlatin square from a 1‐factorization onn + 1 vertices. The symmetric idempotent latin squares are exactly the latin squares that result from this construction. The idempotent recognition problem is simple for symmetric latin squares, so our results enable us to recognize exactly which latin squares arise from 1‐factorizations ofKn + 1. As an example we show that the patterned starter 1‐factorization for the groupGgives rise to a latin square which is in the main class of the Cayley latin square forGif and only ifGis abelian. Hence, every non‐abelian group gives rise to two latin squares in different main classes. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 291–300, 2008
The Freud‐1/CC2D1A family: Transcriptional regulators implicated in mental retardation
Authors: Rogaeva Anastasia , Galaraga Kimberly , Albert Paul R.
Published: March 2007

The CC2D1A gene family consists of two homologous genes, Freud‐1/CC2D1A and Freud‐2/CC2D1B, that share conserved domains, including several DM14 domains that are specific to this protein family, a C‐terminal helix‐loop‐helix domain, and a C2 calcium‐dependent phospholipid binding domain. Although the function of Freud‐2 is unknown, Freud‐1 has been shown to function as a transcriptional repressor of the serotonin‐1A receptor gene that binds to a novel DNA element (FRE, 5′‐repressor element). The DNA binding and repressor activities of Freud‐1 are inhibited by calcium‐calmodulin‐dependent protein kinase. Recently, a deletion in the CC2D1A gene has been linked to nonsyndromic mental retardation. This deletion results in the truncation of the helix‐loop‐helix DNA binding and the C2 domains, crucial for Freud‐1 repressor activity, and hence is predicted to generate an inactive or weakly dominant negative protein. The possible mechanisms by which inactivation of Freud‐1 could lead to abnormal cortical development and cognitive impairment and the potential roles of Freud‐1 gene targets are discussed. © 2007 Wiley‐Liss, Inc.
Anion channel blockers attenuate delayed neuronal cell death induced by transient forebrain ischemia
Authors: Inoue Hana , Ohtaki Hirokazu , Nakamachi Tomoya , Shioda Seiji , Okada Yasunobu
Published: March 2007

Chloride efflux is known to be involved in the progression of apoptosis in various cell types. We have recently shown that the volume‐sensitive outwardly rectifying (VSOR) anion channel serves as the pathway for apoptotic chloride efflux in some cells. In the present study, we tested the neuroprotective effects of drugs that can block the VSOR anion channel, on delayed neuronal death (DND) induced by transient forebrain ischemia. The functional expression of the VSOR anion channel was first examined in hippocampal neurons in both primary culture and hippocampal slice preparations, by the whole‐cell patch‐clamp technique. We then tested the channel's sensitivity to an anion channel blocker, 4,4′‐diisothiocyanatostilbene‐2,2′‐disulfonic acid (DIDS), and a tyrosine kinase blocker, genistein. By histological examinations and cytochrome c release assessments, the protective effects of these drugs on the DND of hippocampal CA1 neurons in mice subjected to transient ischemia were examined. Drugs were administered via the jugular vein prior to ischemic treatment and into the peritoneal cavity after reperfusion. Hippocampal neurons were found to express the volume‐sensitive Cl– channel, which exhibits outward rectification and is sensitive to DIDS and genistein. Administration of DIDS or genistein reduced cytochrome c release and the number of damaged neurons in the CA1 region after transient forebrain ischemia. This fact suggests that the DND induction mechanism involves the activity of the VSOR anion channel and that this channel may provide a therapeutic target for the treatment of stroke. © 2007 Wiley‐Liss, Inc.
Lösungen der poissongleichung und harmonische vektorfelder in unbeschränkten gebieten
Authors: Mäulen J. , Werner P.
Published: March 2007

In the first part of this paper we consider generalised solutions of the Poisson equation ΔU=Fin open subsets ofRn(n⩾ 3) with Dirichlet or Neumann boundary data. We prove existence and uniqueness theorems, not only for the corresponding interior and exterior problems, but also for domains with boundaries extending to infinity. In the second part we discuss generalised harmonic fields in open subsets ofR3with vanishing Dirichlet or Neumann boundary condition.
Global topological perturbations of nonlinear elliptic eigenvalue problems
Authors: Peitgen H. O. , Schmitt K. , Kirchgassner K.
Published: March 2007

This paper is concerned with bifurcation from infinity for nonlinear elliptic equations, which are not necessarily linearizable at infinity. The methods employed are global perturbation techniques by means of which one obtains access to continua of positive solutions bifurcating from infinity via continua bifurcating from trivial solutions.
Galerkin approximations for the one‐dimensional vlasov‐poisson equation
Authors: Cooper J. , Neunzert H.
Published: March 2007

By taking Fourier series in the space variable, and truncating, we construct a Galerkin scheme for approximate solutions to the one dimensional Vlasov‐Poisson equation. Existence is proved for the approximate solutions and they are shown to converge to an exact solution in a weak sense.
Variational derivatives and p‐gradients of functionals on spaces of continuously differentiable functions
Authors: Hamilton E. P. , Nashed M. Z. , Brosowski B.
Published: March 2007

The purpose of this paper is to introduce and study a new type of derivative – the variational gradient – for a functional on Cn[a, b]. Local and global versions of this concept are analyzed. This notion provides a natural approach to variational derivatives on Cn[a, b] under rather mild smoothness assumptions on the functional. When applied in the context of the Calculus of Variations, the notion of the variational gradient captures the natural boundary conditions (as well as the Euler‐Lagrange equations) under weaker smoothness assumptions than those usually required using Gǎteaux variations.

Conditions are established for the existence of the variational derivative and an integral representation for the Gǎteaux variation in terms of the variational derivative is derived. Conditions for the variational derivative to be differentiable are also established.
Ein resonanzphänomen in der theorie akustischer und elektromagnetischer wellen
Authors: Werner P.
Published: March 2007

We discuss the asymptotic behaviour of acoustic and electromagnetic waves, generated by given time‐harmonic exterior forces with frequency ω, in the unbounded region between the parallel planes X3 = 0 and X3 = 1, and show that the principle of limiting amplitude is violated if ω = πn(n = 1, 2,…). For these values of the frequency, forces with compact support can be chosen such that the amplitudes of the waves increase with a logarithmic rate as t → ∞.
On the transmission problem of the helmholtz equation for quadrants
Authors: Latz N. , Meister E.
Published: March 2007

The plane transmission problem of the Helmholtz equation for quadrants is characterized by a one‐dimensional singular integral equation, which refers to the Fourier transform of the normal derivative of the solution along the x‐axis. It is derived by solving the transmission problem for the upper and the lower half‐plane involving a Neumann condition at y = 0. This is done by a two‐dimensional Laplace transform technique. The inverse Laplace transform with respect to the second cartesian coordinate and the restriction of this one to y = 0 then lead to the integral equation. Thereby the transmission conditions of the original problem at y = 0 have to be taken into account. The resulting integral equation is of generalized Wiener‐Hopf‐type. It is solved via the contraction theorem imposing restricting conditions on the wave numbers.
Thin elastic and periodic plates
Authors: Caillerie D. , Nedelec J. C.
Published: March 2007

This paper is devoted to the study of a three dimensional model of elastic periodic plate when the thickness e of the plate and the size ω of the periods are small. In the three studied limits (e → 0 then ω → 0), (ω → 0 then e → 0) and lately (e and ω → 0 together) the three dimensional equation of elasticity are approached by the two dimensional general equations of a linear anisotropic plate, the stretching and bending being coupled. This study points out the importance of the ratio of the two small parameters, indeed the moduli occuring in the two dimensional equations are different in the three limits. In each case a convergence proof is carried out.
An existence theorem for compressible viscous and heat conducting fluids
Authors: Łukaszewicz G. , Piskorek A.
Published: March 2007

We consider an initial‐boundary value problem of a flow of a viscous and heat‐conducting gas in a bounded domain D ⊂ R3. We assume that the boundary S of D consists of two disjoint surfaces S1 and S2 of class C2, and that the gas enters D through the surface S1 and leaves D through the surface S2.

Our aim is to prove the existence (locally in time) of a solution of the problem in anisotropic Sobolev spaces.
Exact and chapman‐enskog solutions for the carleman model
Authors: Palczewski A. , Neunzert H.
Published: March 2007

The Chapman‐Enskog procedure is applied to the Carleman model of the Boltzmann equation. It has been proved that the Carleman equations possess a solution on the time interval on which a smooth solution of the fluid‐like equation exists. The calculations have been performed up to the first order i.e., to the Navier‐Stokes‐like equation. It has been shown that in this case a difference between an exact solution and the Chapman‐Enskog solution is of order ϵ2. Extension of the results to higher orders is also possible. This gives a justification of the Chapman‐Enskog procedure as an asymptotic expansion method.
On the geometric form of free boundaries satisfying a bernoulli condition
Authors: Acker A. , Payne L. E.
Published: March 2007

In the x–y plane, let Ω denote an annular domain bounded by the simple closed curves ⌜ and ⌜*, such that the capacity potential U in Ω satisfies ∣ ▽ U∣ = 1 on ⌜. Assuming ⌜* to be known, we obtain qualitative properties of ⌜. For example, the number of local maxima or minima of the y‐co‐ordinate relative to ⌜ cannot exceed the corresponding number for ⌜*.
An error analysis of the tau method for a class of singularly perturbed problems for differential equations
Authors: Ortiz E. L. , Pham‐Ngoc‐Dinh A. , Törnig W.
Published: March 2007

By using classical results of Poincaré and Birkhoff we discuss the existence and uniqueness of solution for a class of singularly perturbed problems for differential equations. The Tau method formulation of Ortiz [6] is applied to the construction of approximate solutions of these problems. Sharp error bounds are deduced.

These error bounds are applied to the discussions of a model problem, a simple one‐dimensional analogue of Navier‐Stokes equation, which has been considered recently by several authors (see [2], [3], [8], [10]). Numerical results for this problem [8] show that the Tau method leads to more accurate approximations than specially designed finite difference or finite element schemes.
Exact bounds for the radially symmetric shape of confined plasma in the unit circle
Authors: Hoffmann K.‐H. , Sprekels J. , Hsiao G.
Published: March 2007

The method of “cone iteration”; is used to obtain exact bounds for the solutions of a class of nonlinear operator equations. The general theory is applied to the problem of finding radially symmetric solutions of the plasma problem in the unit circle. Existence and uniqueness results are obtained at the same time. Some numerical examples demonstrate the method's high degree of accuracy.
Local validity of the boltzmann equation
Authors: Shinbrot M. , Neunzert H.
Published: March 2007

The validity of the Boltzmann equation is proved, locally in time, by showing that its solution is a limit of solutions of the BBGKY hierarchy.
Finite elements for the eigenvalue problem of differential operators in unbounded intervals
Authors: Höhn W. , Törnig W.
Published: March 2007

The eigenvalue problem for one‐dimensional differential operators with a possible essential spectrum is discretized with finite elements defined on a bounded interval together with a fundamental system of the differential equation outside of the interval. A non‐pollution property of the discrete spectra is proved and the error in the approximation of isolated eigenvalues and corresponding eigenvectors is estimated. The convergence of some numerical algorithms for the solution of the subsequent discrete nonlinear eigenvalue problem is proved. The method is tested in some numerical examples.
A fast solver for riemann problems
Authors: Halter E. , Martensen E.
Published: March 2007

An efficient algorithm is presented for solving the Riemann problem for a polytropic gas. It enables the user to compute the solution for all physically reasonable data. The convergence of the algorithm is proved. The accuracy of the solution is limited only by the accuracy of the computer. There is an a‐priori estimation of the required number of iterations. The rate of convergence turns out to be much higher than that of the usual fixed point iteration scheme.
Unrestricted lower bounds for eigenvalues for classes of elliptic equations and systems of equations with applications to problems in elasticity
Authors: Levine H. A. , Protter M. H. , Payne L. E.
Published: March 2007

Lower bounds for the eigenvalues of some elliptic equations and elliptic systems over bounded regions are obtained. The bounds are universal in that they depend only upon the volume of the region. Specific applications include the clamped plate, the buckling problem for the clamped plate and the equations of linear elasticity.

Our results are consequences of extensions of the methods of Li and Yau (Comm. Mat. Phys. 88 (1983) 309–318) who obtained such results for the eigenvalues of the fixed membrane problem.
On a free boundary value problem of physical geodesy, I (uniqueness)
Authors: Witsch Karl J. , Leis R.
Published: March 2007

The determination of the figure of the earth is considered as a local free boundary value problem of potential theory: the shape of a slowly rotating heavy body has to be found from the boundary data of the attracting force and its potential outside of the body, provided that an approximation to the solution is already known. In this paper a uniqueness result is proved which is local with respect to theC1‐topology.
A note on the solvability of Boltzmann's equation via comparison methods
Authors: Wieser W. , Neunzert H.
Published: March 2007

We consider the Cauchyproblem for the space‐inhomogeneous Boltzmann equation. For the so‐called soft‐interaction case we prove unique local solvability, analogous to a result of Palczewski [1]. However, since in our proof a comparison argument is used rather than the familiar contraction mapping principle, we are able to extend the previously known time‐interval of existence. In a final section the two main difficulties in generalizing the result are discussed in some detail.
Relative influence of two small parameters in non uniformly elliptic homogenization problems
Authors: Paulin J. Saint Jean , Eckhaus W.
Published: March 2007

We study three elliptic problems depending on two small parameters (ϵ = homogenization parameter and δ = perturbation parameter which causes non uniform ellipticity). In each case, the homogenized operator corresponding to the second order operator is independent of the way (ϵ, δ) → (0, 0), but the convergence results and the limit solution do depend on the relative size of ϵ and δ; the relevant parameter is δϵ−2.
Examples involving the geometric form of level curves of harmonic functions
Authors: Acker A. , Payne L.
Published: March 2007

In the x‐y plane, we give, for example, a Jordan curve Γ containing exactly one local maximum and one local minimum in the y‐direction, such that some level curve of the capacity potential in the exterior complement of Γ has at least n local maxima and n local minima in the y‐direction, n being any prescribed number.
Optimal bounds for bilinear forms associated with linear equations
Authors: Mika J. , Pack D. C. , Cole R. J. , Roach G. F.
Published: March 2007

The construction of upper and lower bounds to the bilinear quantity g0, f, where f is the solution of an operator equation Tf = f0, requires either an approximation for f or one for T−1. In this paper the question of “best” approximation of T−1 by an operator of the form B = βI, where β is a real constant, is investigated for linear operators that are either self‐adjoint or can be related by suitable manipulations to others that are. Particular attention is paid to a special operator, previously studied by Robinson, of importance in predicting the dynamic polarisabilities of quantum‐mechanical systems.
An optimal design problem for submerged bodies
Authors: Angell T. S. , Hsiao G. C. , Kleinman R. E.
Published: March 2007

The problem of finding the shape of a smooth body submerged in a fluid of finite depth which minimizes added mass or damping is considered. The optimal configuration is sought in a suitably constrained class so as to be physically meaningful and for which the mathematical problem of a submerged body with linearized free surface condition is uniquely solvable. The problem is formulated as a constrained optimization problem whose cost functional (e.g. added mass) is a domain functional. Continuity of the solution of the boundary value problem with respect to variations of the boundary is established in an appropriate function space setting and this is used to establish existence of an optimal solution. A variational inequality is derived for the optimal shape and it is shown how finite dimensional approximate solutions may be found.
The two‐dimensional, linear, orthotropic plate: The traction problem
Authors: Gilbert R. P. , Schneider M.
Published: March 2007

In [13] we extended the analysis of Ciarlet and Destuynder [5] to the clamped orthotropic plate. For the present paper we shall apply these methods to the orthotropic plate under traction. In particular, we shall be considering the type of problem posed in Friedrichs and Dressler [10] for the isotropic plate and make use of the fact that the variational problem will split just as was the case for the partial differential equation formulation. With the present approach we shall be able to produce a proper convergence analysis for the formal asymptotics used in Friedrichs and Dressler.
On the computer implementation of a coupled boundary and finite element method for the bidimensional exterior steady stokes problem
Authors: Sequeira Adélia , Lisboa  , Palaiseau  , Nedelec J. C.
Published: March 2007

A numerical technique based on the coupling of boundary and finite element methods has been developed by the author for the steady Stokes problem in an unbounded domain. The present paper deals with the implementation of the coupled program in the two‐dimensional case. Computational results are given for a particular problem which can be seen as a good test case for the accuracy of the method.
On optimal shape design of systems governed by mixed Dirichlet‐Signorini boundary value problems
Authors: Haslinger J. , Neittaanmäki P. , Meister E.
Published: March 2007

A problem for finding optimal shape for systems governed by the mixed unilateral boundary value problem of Dirichlet‐Signorini‐type is considered. Conditions for the solvability of the problem are stated when a variational inequality formulation and when a penalty method is used for solving the state problem in question. The asymptotic relation of design problems based on these two formulations is presented. The optimal shape design problem is discretized by means of finite element method. The convergence results for the approximation are proved. The discretized versions are then formulated as a non‐linear programming problem. Results of practical computations of the problem in question are reported.
Functional spaces for norton‐hoff materials
Authors: Geymonat G. , Suquet P. , Nedelec J. C.
Published: March 2007

Some specific functional spaces are required for the study of Norton‐Hoff materials. For this purpose we establish here a Korn's inequality and miscellaneous results of duality, traces, density and orthogonality.
Periodic solutions of quasilinear non‐autonomous systems with impulses
Authors: Hristova S. G. , Bainov D. D. , Roach G. F.
Published: March 2007

The paper considers a system of differential equations with impulse perturbations at fixed moments in time of the formmagnified imagewhere x ϵ Rn, ε is a small parameter,

Sufficient conditions have been found for existence of the periodic solution of the given system in the critical and non‐critical cases.
On the determination of the worst sampling error in a communication system for pulse‐amplitude‐modulated signals by solving an approximation problem
Authors: Krabs W. , Meister E.
Published: March 2007

A communication system for pulse‐amplitude‐modulated signals is considered whose impulse response is bandlimited. For a certain class of sampling errors the worst case is investigated where the sampling error of the system is such that the least mean square transmission error achieved by a suitable choice of the impulse response becomes maximal. This problem is dualized in the sense of two person game theory and thereby transferred to an equivalent approximation problem for whose solution a necessary and sufficient condition is given and applied to special cases.
The influence of a geographical barrier on the balance of selection and migration
Authors: van der Meer J. J. E. , Roach G. F.
Published: March 2007

In biology, a cline is defined as a usually gradual change in gene frequency or phenotype of a population in equilibrium, from one place to another.

We define a cline as a nonconstant stable steady state solution. However, for the model studied in this paper, these two definitions coincide: a nonconstant stable steady state solution is necessarily monotone. It is proved that for small values of the penetrability of the barrier, exactly two clines exist.

Since we prove that the Ω‐limit set of any initial condition is a steady state solution, the information thus obtained yields a rather complete understanding of the qualitative behaviour of the solutions of the evolution problem under consideration.
Existence and uniqueness of a rayleigh surface wave propagating along the free boundary of a transversely isotropic elastic half space
Authors: Guillot J. C. , Nedelec J. C.
Published: March 2007

In this article the existence and the uniqueness of a Rayleigh surface wave propagating along the free boundary of a transversely isotropic elastic half space are proved by a spectral method.
Formulation variationnelle espace‐temps pour le calcul par potentiel retardé de la diffraction d'une onde acoustique (I)
Authors: et T. Ha Duong A. Bamberger , Nedelec J. C.
Published: March 2007

We give here a space‐time variational formula to the problem of the transient acoustic scattering by a free (pressure release) surface, using the retarded potential technique. From this formula, we obtain new schemes for the calculation of the potential density. We prove stability and convergence of such schemes: these are as far as we know, the first results in that direction for such problem. The case of a hard obstacle will be treated in the second part of the paper.
The low frequency limit for time‐harmonic acoustic waves
Authors: Picard R. , Leis R.
Published: March 2007

The question of convergence of the solution of the exterior Dirichlet boundary value problem of the first order system of linearized acoustics as the frequency ω tends to zero is considered. The particular difficulty of having zero as an eigenvalue is handled by introducing certain scalar characteristics that — if prescribed — imply uniqueness in the limit case ω = 0. Convergence to the static solution in a weighted L2‐space is shown. Eventually the convergence result obtained can be extended to a larger class of boundary value problems of Mathematical Physics due to the structure of the argument.
An algorithm for tracing the boundary curves of mushy regions in some degenerate diffusion problems
Authors: de Mottoni P. , Santi E. , Hadeler K.‐P.
Published: March 2007

We present an algorithm for approximating the solution of the degenerate diffusion problem ut = (ϕ(u))xx in (0,1) × R+ (with zero Dirichlet boundary conditions, and nonnegative initial datum u0), where ϕ(u) = min {ku1} for some ϰ > 0. The algorithm also provides an approximation for the interface curves which represent the boundary of the Mushy Region 𝔐 = {(x, t): ϕ (u(x, t)) = 1}. The convergence of the algorithm is proved.
On the simulation source technique for exterior problems in acoustics
Authors: Kress R. , Mohsen A. , Brosowski B.
Published: March 2007

For the solution of the exterior Dirichlet problem for the Helmholtz equation we propose to seek the solution in the form of an acoustic single‐layer potential with a distribution extended over an internal surface. This leads to an ill‐posed integral equation of the first kind which can be approximately solved by the Tikhonov regularization technique.
Formulation variationnelle pour le calcul de la diffraction d'une onde acoustique par une surface rigide
Authors: et T. Ha Duong A. Bamberger , Nedelec J. C.
Published: March 2007

This work is a continuation of [1]. We give a space‐time variational formula to the problem of the scattered acoutic wave by a hard body, using the double layer retarded potential technique. New schemes are constructed from this variationnal formula, for which we prove the stability and errors estimates.
A boundary integral equation method for three‐dimensional crack problems in elasticity
Authors: Stephan E. P. , Wendland W. L.
Published: March 2007

This paper presents a solution procedure for three‐dimensional crack problems via first kind boundary integral equations on the crack surface. The Dirichlet (Neumann) problem is reduced to a system of integral equations for the jump of the traction (of the field) across the crack surface. The calculus of pseudodifferential operators is used to derive existence and regularity of the solutions of the integral equations. With the concept of the principal symbol and the Wiener‐Hopf technique we derive the explicit behavior of the densities of the integral equations near the edge of the crack surface. Based on the detailed regularity results we show how to improve the boundary element Galerkin method for our integral equations. Quasi‐optimal asymptotic estimates for the Galerkin error are given.
High velocity particles in a collisionless plasma
Authors: Glassey R. T. , Strauss W. A. , Neunzert H.
Published: March 2007

We prove that smooth solutions of the relativistic Vlasov‐Maxwell equations exist for all time provided the kinetic energy density is uniformly bounded.
On the convergence of the spline collocation with discontinuous data
Authors: Saranen J. , Wendland W.
Published: March 2007

In this article we study the convergence of the collocation method in the case where the smoothest splines are used as trial functions. The given data is allowed to be piecewise continuous. Our model problem is stated by means of an explicit Fourier representation in the space of periodic functions. Thus the results are applicable e.g. to differential operators and to classical integral operators of the convolutional type. Error estimates are given for a class of Sobolev norms. An application to the single layer potential is discussed.
Resonances and standing waves
Authors: Morgenröther K. , Werner P.
Published: March 2007

Recent investigations on aperiodic waves, which are generated by time‐harmonic forces in waveguides, indicate a close relationship between resonances and certain time‐harmonic solutions of homogeneous boundary value problems for the wave equation (“standing waves”). This paper is motivated by the observation that, in all known cases, standing waves are connected with resonances if and only if they are subject to suitable asymptotic restrictions as |x| → ∞. These asymptotic properties are used to introduce a class of “admissible” standing waves. We prove that admissible standing waves do not exist in a certain class of local perturbations Ω of the n‐dimensional domain Ω0 bounded by the hyperplanes xn = 0 and xn = π. This extends a result of M. Faulhaber on the absence of eigenvalues. As we shall show in a subsequent paper, absence of admissible standing waves implies absence of resonances.
Blow‐up of solutions of the gain‐term‐only Boltzmann equation
Authors: Illner R. , Shinbrot M. , Neunzert H.
Published: March 2007

It is shown that the Boltzmann equation with no loss term cannot have a global solution when the mean free path is small, even with initial data describing a cloud of gas released in an infinite vacuum.
The Helmholtz equation in disturbed half‐spaces
Authors: Willers A. , Werner P.
Published: March 2007

We consider boundary value problems for the Helmholtz equation in domains with boundaries coinciding with a plane outside a sufficiently large sphere. As opposed to the method of Gartmeier [6] (see also [12]) our analysis leads to an integral equation of the second kind with a compact operator. In the last chapter we study the set of far field patterns which are generated by entire incident fields.
A free boundary problem for three‐dimensional harmonic vector fields
Authors: Wegmann R. , Martensen E.
Published: March 2007

We study in this paper a free boundary value problem (FB), where a region Go in R3 is determined by the condition that there exists a vector field vo in Go which satisfies div vo = eo, curl vo = go in Go and vo = E on the boundary ∂Go with a given scalar function eo and given vector fields go and E. We give two equivalent formulations for this problem. Then we characterize the solutions by a non‐linear integral equation. In order to solve the latter by a Newton method we linearize this equation. We investigate the ensuing linear integral equation. In case of axisymmetric configurations this is a singular integral equation whose index can be easily determined from the given data. We obtain a related equation, if we try to construct a field v in a region G which is on the boundary perpendicular to a given field B. Finally we use this method to investigate an astrophysical problem, which arises in the theory of pulsar magnetospheres.
An ecoepidemiological model with disease in predator: the ratio‐dependent case
Authors: Haque Mainul , Venturino Ezio
Published: March 2007

We propose a ratio‐dependent demographic predator–prey model in which also a disease spreads among predators via homogeneous mixing. Equilibria of the system are analysed, numerical evidence shows limit cycles to arise. The disease effects on the model are discussed. Comparisons of these findings with results of some related investigations allow the general conclusion that an infection in either species, prey or predator, may act as a biological control. Copyright © 2007 John Wiley & Sons, Ltd.
Analytical and numerical solution of the elastodynamic strip load problem
Authors: Verruijt A. , Brinkgreve R. B. J. , Li S.
Published: March 2007

Analytical and numerical solutions of the elastodynamic problem of an instantaneous strip load on a half space are presented and compared. The analytical solution is obtained using the De Hoop–Cagniard method, and the numerical solution is obtained using the dynamic module of the finite element package Plaxis. The purpose of the paper is to validate the numerical solution by comparison with a completely analytical solution, and to verify that the main characteristics of the analytical solution are also obtained in the numerical solution. Particular attention is paid to the magnitude, the velocity, and the shape of the Rayleigh wave disturbances. Copyright © 2007 John Wiley & Sons, Ltd.
Randomized, double‐blind, sham‐controlled evaluation of the effect of functional continuous magnetic stimulation in patients with urgency incontinence
Authors: Suzuki Tsuneki , Yasuda Kosaku , Yamanishi Tomonori , Kitahara Satoshi , Nakai Hideo , Suda Shin , Ohkawa Hiromi
Published: March 2007

Aims

To evaluate the effect of functional continuous magnetic stimulation (FCMS) on urgency incontinence in randomized, sham‐controlled manner.

Methods

Thirty‐nine patients with urgency incontinence, 16 males and 23 females (aged 66.0 ± 16.5 years), who were refractory to pelvic floor muscle training (PFMT), were randomly assigned either to the treatment schedule performing 10‐week active treatment, followed by 4‐week non‐treatment interval and then by 10‐week sham treatment (A–S, n = 20) or to that performing the sham treatment first followed by 10‐week active treatment (S–A, n = 19).

Results

At 10 weeks, the number of leaks/week, the total score of the International Consultation on Incontinence‐Questionnaire: Short Form (ICIQ‐SF), and maximum cystometric capacity (MCC) were significantly improved as compared with the initial levels (P < 0.001, P < 0.001, and P = 0.003, respectively) in the former group, but not in the latter group. Four (20.0%) patients were cured in the A–S group, while no patient was cured in the S–A group.At the end of the A–S schedule (24 weeks of study), the effect of the active treatment was still maintained at a significantly improved level, as compared with the initial level. At the end of the S–A schedule, the number of leaks/week was significantly improved as compared with the initial level and with its 10‐week level (P < 0.001 and P = 0.049, respectively), as well as ICIQ‐SF total score (P = 0.001 and P = 0.006, respectively). MCC significantly increased from its initial level (P = 0.030).

Conclusion

Magnetic stimulation was effective on urgency incontinence in comparison to sham stimulation in this small patient group. Neurourol. Urodynam. 26:767–772, 2007. © 2007 Wiley‐Liss, Inc.
Stability and error analysis for spectral Galerkin method for the Navier–Stokes equations with L2 initial data
Authors: He Yinnian
Published: March 2007

In this article we consider the spectral Galerkin method with the implicit/explicit Euler scheme for the two‐dimensional Navier–Stokes equations with the L2 initial data. Due to the poor smoothness of the solution on [0,1), we use the the spectral Galerkin method based on high‐dimensional spectral space HM and small time step Δt2 on this interval. While on [1,∞), we use the spectral Galerkin method based on low‐dimensional spectral space Hm(m = O(M1/2)) and large time step Δt. For the spectral Galerkin method, we provide the standard H2‐stability and the L2‐error analysis. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2007