bluuebunny/crossref_metadata_2025 huggingface dataset:
Außenraumaufgaben in der linearen Elastizitätstheorie
Authors: Leis R.
Published: March 2007

The paper starts with a short survey of the treatment of initial‐boundary‐value problems in temperature‐free linear elasticity with unisotropic media. The main part of the paper is concerned with exterior initial‐boundary‐value problems in thermoelasticity. In this case the underlying differential operator A is no longer selfadjoint. Thus the spectrum of A has to be discussed. In 2.1 it is shown that all λ with Re λ < 0 belong to the resolvent set. In 2.2 the case G = R3 with homogeneous isotropic media is considered. Let Λ be the essential spectrum in this case. In 2.3 Λ depending on the thermic coupling parameter is discussed. 2.4 treats the spectrum of A assuming the medium to be homogeneous and isotrop outside a large ball. In this case Λ is the essential spectrum for A too. Radiation conditions are formulated. Finally 2.5 presents a short treatment of the time dependent case with Laplace‐transformation.
The positivity principle in Boltzmann‐type equations
Authors: Ebersoldt F. , Leis R.
Published: March 2007

Classical theorems about matrices with non‐negative elements can be generalized for application in eigenvalue problems of integro‐differential form appearing in the description of stationary particle transport. In this way the existence and unicity of positive L1‐eigensolutions of the m‐quasi‐completely‐continuous transport operator can be deduced. These solutions can be realized by a method of successive approximation.
Elektrodynamik mit Spin
Authors: Petry W. , Leis R.
Published: March 2007

Atomistic equations of the electromagnetic field for a particle with spin are derived from a Lagrangian. These equations are consistent with the equations of motion for such a particle. The resulting phenomenological equations are the well‐known equations of Maxwell for the electromagnetic field in matter. The atomistic field equations for a particle with spin and magnetic moment give a dipole field. This result and the corresponding quantum mechanics for a particle with spin are applied to compute the hyperfine structure of the hydrogen atom by perturbation theory.
Zur Abhängigkeit der Lösung von ut + (h(u))x = 0 von ihren Anfangswerten
Authors: Wick J. , Leis R.
Published: March 2007

The above equation has some remarkable properties. In general a global solution exists in a weak sense only, and this solution is not reversible in time. Furthermore it is known, that the solutions for different initial values can coincide for all t ⩾ t0 > 0, and the set of the initial values with this property is convex. Conditions assuring that this set contains only one element are given. This means a weak form of time‐reversibility.

As a global solution exists only in the weak sense, the classical question concerning dependence of the solution on the initial values needs some modification. This problem is dealt with in suitable L1‐norms. It is shown, that the L1‐norm of the difference of two weak solutions with respect to the space variable does not increase in time.
Ghosts in tomography – the null space of the radon transform
Authors: Louis A. K. , Törnig W.
Published: March 2007

Let ω0, …, ωp−1 ϵ S1 be p distinct directions and let R denote the Radon transform. The functions f with support in the unit disc and with Rf(s, ωj) = 0 for s ϵ [−1, 1] and j = 0, …, p − 1 are given. „Ghosts”︁ are constructed, i.e. functions in the null space that pretend not existent tumors. Methods to avaoid such ghosts are indicated.
A model equation for Non‐Newtonian fluids
Authors: Niggemann M. , Kirchgässner K.
Published: March 2007

A one‐dimensional model for the equations of motion of a “simple fluid” according to Noll is proposed. An exterior problem for the model equation is solved by means of a transform method.
On the classical solutions of the initial value problem for the unmodified non‐linear Vlasov equation I general theory
Authors: Horst E. , Neunzert H.
Published: March 2007

We study existence and uniqueness of classical solutions of the initial value problem for Vlasov's equation with an unmodified Newtonian or Coulomb force. We give a necessary and sufficient condition for the existence of a solution on an interval I.
Necessary and sufficient conditions for the existence of shock curves of hyperbolic 1‐conservation laws
Authors: Chang P. H. , van der Vooren A. I.
Published: March 2007

We present three conditions for the existence of shock curves of hyperbolic 1‐conservation laws. If at least two of the conditions hold, then shock curves exist uniquely in the classical sense. We present an example (Example 2, Section 4) for which two of the conditions do not hold and a new kind of singularity occurs. In Remark 1 we present two other conditions similar to the above three conditions which also imply the existence of shock curves.
Local energy decay of solutions of linearized shallow‐water equations
Authors: Geveci T. , Kok B. , Kreiss H.‐O.
Published: March 2007

We prove the local decay of the energy of the solution to a mixed initial boundary value problem for the linearized shallow‐water equations with constant coefficients, where the domain is a half‐plane, a certain dissipative boundary condition is prescribed and the initial data have compact support contained in the open half‐plane.
Stable solutions of some ill‐posed problems
Authors: Ramm A. G. , Meister E.
Published: March 2007

Stable solutions of equations of the first kind and equations of the second kind at a characteristic value are given. Iterative processes for solutions are constructed. Extension of operators is used to turn an ill‐posed problem into a well‐posed one.
Condition number of matrices derived from two classes of integral equations
Authors: Christiansen S. , Meister E.
Published: March 2007

We investigate some integral equations, i. a. the so‐called Kupradze functional equations, where the two variables of the kernel belong to two different point sets. An extensive survey of the literature shows the various applications of these equations.

By a discretization of the integral equations they are replaced by systems of linear algebraic equations. The condition number of the corresponding matrices is investigated, analytically and numerically. It is thereby quantitatively found in which way the condition of the matrices deteriorates when the two point sets are moved away from each other.
Asymptotic analysis of the linear Boltzmann equation
Authors: Borysiewicz M. , Mika J. , Spiga G. , Neunzert H.
Published: March 2007

The stiff boundary value problem for the time‐independent linear Boltzmann equation is considered in the variational formulation in terms of the coercive symmetric bilinear form. It is shown that it is asymptotically equivalent to the related variational diffusion problem when the stiffness parameter tends to zero. Higher order perturbations are also discussed.
Partial asymptotic stability via limiting equations
Authors: Bondi P. , Fergola P. , Gambardella L. , Tenneriello C. , Hagedorn P.
Published: March 2007

In this paper the limiting equations approach is applied to study the stability properties with respect to a part of the state variables for nonautonomous dynamical systems. Sufficient conditions are given for uniform asymptotic eventual strongly partial stability and for uniform asymptotic partial stability. An application of the results is given.
Solvability of some overdetermined elliptic system in a domain with corners π/n
Authors: Zajaczkowski W. M. , Piskorek A.
Published: March 2007

In the paper we prove the existence and uniqueness of solutions of the overdetermined elliptic system

where b, ω are given functions, in a domain Ω C R3 with corners π/n, n = 2, 3, … The proof is divided on two steps, we construct a solution for the Laplace equation in a dihedral angle π/n, using the method of reflection and we get an estimate in the norms of the Sobolev spaces in some neighbourhood of the edge. In the dihedral angle system (A) reduces to the Dirichlet and Neumann problems for the Laplace equation. In the next step we prove the existence of solutions in the Sobolev spaces Wpl(Ω) using the existence of generalized solutions of (A).
The sommerfeld half‐plane problem revisited I: The solution of a pair of coupled Wiener‐Hopf integral equations
Authors: Heins Albert. E. , Meister E.
Published: March 2007

A study and the solution of an extension of the classical Sommerfeld half‐plane problem which leads to a pair of integral equations of the Wiener‐Hopf type is given. The method of solution is function theoretic in character and employs a combination of the ideas of Wiener and Hopf and Carleman.
A discontinuous nonlinear eigenvalue/Free boundary problem
Authors: Alexander Roger , Rabinowitz P. H.
Published: March 2007

We study the problem

(H is the Heaviside unit step function) in spherical domains Ω of arbitrary dimension. When g = 0, there are two branches of radial solutions; for small nonzero g there are solutions near the corresponding radial solution. Moreover, the set where μ = 1 is in all cases an analytic hypersurface.
On the convergence of the multigroup approximations for submultiplying slab media
Authors: Nelson P. , Victory H. D. , Neunzert H.
Published: March 2007

The stability, convergence, and consistency properties of the steady‐state multigroup model are investigated for submultiplying slab media. These concepts are defined in a Banach space setting in which the norm of the angular flux is the collision density integrated over phase space. It is shown that the multigroup approximations are stable and are both consistent with, and convergent to, the transport equation under the conditions that the maximum fluctuations in the total cross section and in the expected number of secondary particles, arising from each energy level, tend to zero as the energy mesh becomes finer. A concluding discussion deals with pathologies of the multigroup approximation for situations in which these fluctuations do not tend to zero as the norms of the energy partitions. The results in this paper complement the time‐dependent results of Belleni‐Morante and Busoni for isotropic slabs and the results of Nelson for steady‐state rod media.
Subsonic irrotational flows in multiply connected domains
Authors: Feistauer Miloslav , Meister E.
Published: March 2007

The solvability of a boundary value problem for a nonlinar elliptic partial differential equation in a plane, bounded, multiply connected domain is investigated. The solution of the problem is equal to unknown constants on inner components of the boundary. We want to determine these constants so that the solution satisfies the so‐called trailing conditions. The results have immediate applications in hydrodynamics.
Spectral properties of certain stiff problems in elasticity and acoustics
Authors: Geymonat G. , Lobo‐Hidalgo M. , Sanchez‐Palencia E. , Roach G. F.
Published: March 2007

We consider two vibration problems containing a small parameter → 0: a) Vibration of an elastic, slightly compressible body, and b) acoustic vibration of a slightly viscous compressible barotropic fluid in a vessel.

The asymptotics of eigenvalues for problem a) is studied by using a uniformly convergent expansion of the stiff type. After a re‐scaling of the spectral parameter, the problem b) reduces to an analogous problem, and we prove that, as ε → 0, infinitely many eigenvalues converge to 0 (which is an eigenvalue of infinite multiplicity of the corresponding inviscid acoustic problem).
Spline methods in geodetic approximation problems
Authors: Freeden Willi , Törnig W.
Published: March 2007

This paper is concerned with spline methods in a reproducing kernel Hilbert space consisting of functions defined and harmonic in the outer space of a regular surface (e.g. sphere, ellipsoid, telluroid, geoid, (regularized) earth's surface). Spline methods are used to solve interpolation and smoothing problems with respect to a (fundamental) system of linear functional giving information about earth's gravity field. Best approximations to linear functionals are discussed. The spline of interpolation is characterized as the spline of best approximation in the sense of an appropriate (energy) norm.
Akustische wellen in Gebieten, die von zwei lokal gestorten parallelen ebenen begrenzt sind
Authors: Faulhaber Markus , Werner P.
Published: March 2007

We consider acoustic waves in domains with boundaries, coinciding with two parallel planes outside a sufficiently large sphere. Several results on spectral properties of the Laplace operator in such domains are derived and used to prove uniqueness and existence of a solution of the Dirichlet boundary value problem for the reduced wave equation under additional restrictions. In particular, a class of domains is described for which no eigenvalues are present.
A minimax principle for nonlinear eigenvalue problems with applications to nonoverdamped systems
Authors: Voss H. , Werner B. , Hadeler K. P.
Published: March 2007

The theory of Rayleigh functionals for non‐linear eigenvalue problems T(λ) u = 0 is extended to cases where the functional is defined only on a proper subset. The theory applies to problems which do not satisfy an overdamping condition and yields a minimax characterization of eigenvalues. Applications to damped free vibrations of an elastic body are discussed.
Applications of bloch expansion to periodic elastic and viscoelastic media
Authors: Turbe N. , Wilcox C.
Published: March 2007

We consider an unbounded, elastic non homogeneous material with periodic structure. It is shown that the solution of the equations of motion can be expanded in eigenfunctions of periodic operators. The Bloch expansion is used to prove that when the wave‐length is long compared to the period of the structure (related to a small parameter ϵ), the first term of the exact solution expansion, in powers of ϵ, is the solution of the equations obtained in homogenization theory. The case of a long memory linear viscoelastic material is then studied.
A‐posteriori error analysis and adaptive finite element methods for singularly perturbed convection‐diffusion equations
Authors: Reinhardt Hans‐Jürgen , Wendland W.
Published: March 2007

For singularly perturbed one‐dimensional convection‐diffusion equations, finite element approximations are constructed based on a so‐called approximate symmetrization of the given unsymmetric problem. Local a‐posteriori error estimates are established with respect to an appropriate energy norm where the bounds are proved to be realistic. The local bounds, called error indicators, provide a basis for a self‐adaptive mesh refinement. For a model problem numerical results are presented showing that the adaptive method detects and resolves the boundary layer.
Finite‐element method for time‐dependent euler equation
Authors: Saiac J. H. , Nedelec J.C.
Published: March 2007

This paper presents finite element methods to approximate inviscid incompressible flow problems.

First we emphasize the conservation properties of these problems, and we show that finite element methods appear as a very natural way to find conservative schemes such as Arakawa's scheme. We give convergence theorems and an error analysis of finite element discretization schemes. We turn then to the time differencing problem. We derive stability and convergence results for a second‐order semi‐implicit scheme and for the leap‐frog scheme.
The emergence of solitons of the korteweg‐de vries equation from arbitrary initial conditions
Authors: Eckhaus W. , Schuur P.
Published: March 2007

We study the solution u(x, t) of the Korteweg‐de Vries equation ut − 6uux + uxxx = 0 with arbitrary initial conditions u(x, 0) = u0(x), u0(x) decaying sufficiently rapidly as |ξ|→∞. Using the method of the inverse scattering transformation we analyse the Gel'fand‐Levitan equation in all coordinate systems moving to the right and give a complete and rigorous description of the emergence of solitons.
Ein Hodge‐Satz für Mannigfaltigkeiten mit nicht‐glattem Rand
Authors: Picard R. , Leis R.
Published: March 2007

In this paper the question of determining the dimension of the space of harmonic Dirichlet and Neumann differential forms on a Riemannian manifold with non‐smooth boundary is answered for a wide class of boundaries. The admissible boundaries can be characterized using a generalized “global segment property”. The well‐known relation between the Betti numbers and the dimension of these spaces is established in this more general case, too. Bounded and non‐bounded manifolds are treated (“exterior and interior domains”).
Approximate inversion of the 3 D radon transform
Authors: Louis A. K. , Töring W.
Published: March 2007

The nuclear magnetic resonance (NMR) zeugmatography, a new technology in diagnostic medicine, leads to the problem of inverting the Radon transform in three dimensions. In contrast to even dimensions in odd dimensions the inversion formula is local. In three dimensions it consists of a backprojection operator, which brings no problems for the implementation, and taking the second derivative of the data. This is usually approximated by the central difference quotient. Here the effect of this approximate inversion operator is studied, error estimates for this ill‐posed problem are given and a stepsize is computed which minimizes the sum of discretization and data error.
The coupling of boundary integral and finite element methods for the bidimensional exterior steady stokes problem
Authors: Sequeira A. , Nedelec J.C.
Published: March 2007

In this paper, we represent a new numerical method for solving the steady‐state Stokes equations in an unbounded plane domain. The technique consists in coupling the boundary integral and the finite element methods. An artificial smooth boundary is introduced separating an interior inhomogeneous region from an exterior one. The solution in the exterior domain is represented by an integral equation over the artificial boundary. This integral equation is incorporated into a velocitypressure formulation for the interior region, and a finite element method is used to approximate the resulting variational problem. This is studied by means of an abstract framework, well adapted to the model problem, in which convergence results and optimal error estimates are derived. Computer results will be discussed in a forthcoming paper.
Solvability of an initial boundary value problem for the euler equations in twodimensional domain with corners
Authors: Zajaczkowski W. M. , Piskorek A.
Published: March 2007

The aim of this paper is to prove the existence and uniqueness of local solutions of some initial boundary value problems for the Euler equations of an incompressible fluid in a bounded domain Ω ⊂ R2 with corners. We consider two cases of a nonvanishing normal component of velocity on the boundary. In three‐dimensional case such problems have been considered in papers [12], [13], [14]. Similar problems in domains without corners have been considered in [2]–[6], [11]. In this paper the relation between the maximal corner angle of the boundary and the smoothness of the solutions is shown. The paper consists of four sections. In section 1 two initial boundary value problems for the Euler equations are formulated. In section 2 the existence and uniqueness of solutions of the Laplace equation in twodimensional domain with corners for the Dirichlet and Neumann problems is proved in the Sobolev spaces. In sections 3 and 4 we prove the existence and uniqueness of solutions of problems formulated in section 1, using the method of successive approximations.
Integral formulation for a steady‐state transport process with general boundary conditions
Authors: Busoni G. , Frosali G. , Neunzert H.
Published: March 2007

A linear equation for a particle steady‐state transport process in a homogeneous slab of finite thickness with boundary conditions of general type is derived. This equation differs from the well‐known integral equation for no‐reentry boundary conditions because of the presence of a per‐turbance linear operator which describes the effect of the re‐emission of the particles incident at the wall. The properties of the resulting operator are investigated. The dependence of the first positive eigenvalue on physical parameters is studies in detail. The results obtained are enough to discuss the existence of a critical strictly positive solution of the physical problems which motivated this research.
Functional differential equations with certain monotonicity properties
Authors: Mierczyński J.
Published: March 2007

The present paper is concerned with the study of retarded differential equations in n‐space, which satisfy some monotonicity properties. Sufficient conditions are given guaranteeing that solutions are contained in the probability (n – 1)‐simplex. Existence and uniqueness of constant solutions are proved. It is also shown that every solution converges to a constant as t → ∞.
Continuous dependence on geometry for the backward heat equation
Authors: Crooke P. S. , Payne L. E.
Published: March 2007

In this paper we are concerned with the development of criteria for stabilizing inherently unstable initial‐boundary value problems under small errors in the geometry of the underlying domain. We consider in particular the initial‐boundary‐value problem for the backward heat equation assuming that some error has been made in characterizing the geometry of the domain under consideration. It is shown that solutions which belong to an appropriately defined constraint set depend continuously in L2 on errors in the geometry.
On the swelling of a glassy polymer in contact with a well‐stirred solvent
Authors: Comparini E. , Ricci R. , Neunzert H.
Published: March 2007

We consider a free boundary problem arising from a model for sorption of solvent by polymers.

Existence and uniqueness of the solution are proved and some results about the asymptotic behaviour are established.
On the asymptotic behaviour and stability of the solution for the Broadwell model of the Boltzmann equation in three dimensions
Authors: Toscani G. , Neunzert H.
Published: March 2007

The initial value problem for the full Broadwell model, in gas kinetic theory, is investigated. By means of a fixed point theorem an upper estimate for the solution is derived, provided that the initial values satisfy suitable a priori conditions. Since this estimate is function of the time, the asymptotic behaviour of the global solution is determined.
On the existence of optimum large amplitude hydrofoil propulsion II
Authors: Urbach H. P. , van de Vooren A. I.
Published: March 2007

The possibility of optimum thrust‐production by means of a flexible profile is discussed using a linearized theory. By applying the theory of trace theorems and Rellich's lemma, it is shown that there exists an optimum path for the profile in every class which consists of paths having uniformly bounded amplitudes and slopes.
Wall effects on the slow steady motion of a particle in a viscous incompressible fluid
Authors: Fischer T. M. , Wendland W.
Published: March 2007

In this paper, asymptotic expansions with respect to small Reynolds numbers are proved for the slow steady motion of an arbitrary particle in a viscous, incompressible fluid past a single plane wall. The flow problem is modelled by a certain boundary value problem for the stationary, nonlinear Navier‐Stokes equations. The coefficients of these expansions are the solutions of various, linear Stokes problems which can be constructed by single layer potentials and corresponding boundary integral equations on the boundary surface of the particle. Furthermore, some asymptotic estimates at small Reynolds numbers are presented for the slow steady motion of an arbitrary particle in a viscous, incompressible fluid between two parallel, plane walls and in an infinitely long, rectilinear cylinder of arbitrary cross section.

In the case of the flow problem with a single plane wall, the paper is based on a thesis, which the author has written under the guidance of Professor Dr. Wolfgang L. Wendland.
Absorbing boundary conditions for the linearized shallow water equations
Authors: Warsaw H. Kołakowski , Piskorek A.
Published: March 2007

A mixed problem imitating the Cauchy problem for the linearized shallow water equations is considered. This problem is also a mixed problem with perfectly absorbing conditions (cp. [1], [3]). An exact formula for the conditions has been given.
On an exterior boundary‐value problem for the time‐harmonic maxwell equations with boundary conditions for the normal components of the electric and magnetic field
Authors: Kress R. , Leis R.
Published: March 2007

We treat the time‐harmonic Maxwell equations with the boundary condition (ν, E) = (ν, H) = 0 in an exterior multiply connected domain. A uniqueness result by Yee for the case of a simply connected domain is extended to multiply connected domains and existence is obtained by a boundary integral equation approach.
A note on the nonlinear stability of a spatially symmetric vlasov‐possion flow
Authors: Marchioro C. , Pulvirenti M. , Neunzert H.
Published: March 2007

We give sufficient conditions for the nonlinear stability of a, possibly non‐smooth, spatially homogeneous Vlasov‐Poisson flow.

Research partially supported by Italian CNR and Ministero della Pubblica Istruzione.
Evolution of two concentrated vortices in a two‐dimensional bounded domain
Authors: Marchioro Carlo , Pagani Enrico , Neunzert H.
Published: March 2007

We prove that two initially concentrated vortices with opposite vorticity of an incompressible ideal fluid moving in a two‐dimensional bounded domain, remain concentrated during the time. The motion of their centers converges to the solution of the point vortex model with the corresponding initial conditions.
Microstrip‐fed monopole dumbbell‐shaped antenna for UWB application
Authors: Tseng Ching‐Fang , Huang Cheng‐Liang
Published: March 2007

The monopole dumbbell‐shaped antenna fed by a 50 Ω microstrip line for ultrawideband (UWB) application is studied. By tuning the dumbbell‐shaped radiator and height of the feed gap (D), the monopole antenna has a 2:1 VSWR (return loss < 10 dB) from 2.89 to more than 15 GHz. The bandwidth covered 3.1–10.6 GHz, which has approved by the Federal Communications Commission as a commercial UWB band. Moreover, the antenna features near omnidirectional characteristics in the operation range and good radiation efficiency. The UWB, monopole characteristics of the antenna are confirmed experimentally. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1470–1473, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22404
Small area right angle bends fabricated with hybrid conventional and interference lithography
Authors: Zhou Yaling , Tan Hua , Klotzkin David J.
Published: March 2007

A technique to fabricate high‐resolution, photonic features in selected areas aligned to large features such as waveguides, sources, or detectors without e‐beam lithography is demonstrated. This low‐cost parallel technique can be readily extended to produce resonant cavities and photonic‐crystals integrated into conventional waveguide structures. A right‐angle bend using integrated Bragg reflectors is designed and characterized. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1300–1303, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22408
Spatial diversity antenna for WLAN application
Authors: Shin Yong‐Sun , Park Seong‐Ook
Published: March 2007

This article presents a novel printed diversity planar monopole antenna integrated on a PCMCIA network card with minimized the mutual coupling for WLAN application at the 5 GHz bands (5150–5350 and 5725–5875 MHz). The proposed diversity antenna is printed on FR‐4 substrate and small size enough to be embedded in the laptop computer. Optimizing the separation distance and antenna parameters with use of two slots on a ground, the good isolation performance (less than −20 dB) between the two printed monopole antennas is achieved. The proposed diversity antenna has an impedance bandwidth of 2360 MHz ranging from 4520 to 6889 MHz (S11 < −10 dB). There is a good agreement between the simulated and measured results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1290–1294, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22414
Optical labeling using carrier suppressed second harmonic subcarrier label
Authors: Cho Jeong‐Sik , Won Yong‐Hyub
Published: March 2007

A carrier‐suppressed second harmonic subcarrier‐multiplexed labeling technique for optical label switching network is demonstrated. It provides frequency doubling for optical subcarrier label so that requirement for high bandwidth optical or electrical components can be reduced. The results of two‐span transmission of 10‐Gb/s payload with 1.244‐Gb/s subcarrier label show improved performance of the labeling technique. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1468–1470, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22418
A 40‐Gb/s SCM optical communication system based on an integrated CMOS transceiver
Authors: Chen Jinghong , Saibi Fadi , Sackinger Edward , Othmer Joe , Yu Mark , Huang Titus , Liu Ting‐Ping , Azadet Kamran
Published: March 2007

In this letter, the feasibility of a 40‐Gb/s subcarrier multiplexed optical transmission system using low‐cost optical electronic components and CMOIS IC technology is studied. A test chip and its measurement results are reported. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1272–1274, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22433
Simultaneous negative‐ and positive‐phase‐velocity propagation in an isotropic chiral medium
Authors: Mackay Tom G. , Lakhtakia Akhlesh
Published: March 2007

The phase velocity of plane waves propagating in an isotropic chiral medium can be simultaneously positive for left‐circularly polarized light and negative for right‐circularly polarized light (or vice versa). The constitutive parameter regimes supporting this phenomenon are established for nondissipative and dissipative mediums. The boundary between positive‐ and negative‐phase velocity is characterized by infinite phase velocity. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1245–1246, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22434
Design and fabrication of the circularly polarized microstrip patch antenna
Authors: Hyeonjin Lee , Jung Jinwoo , Yeongseog Lim
Published: March 2007

In this article, circularly polarized microstrip patch antenna with a 5.8 GHz frequency for the Industrial Scientific Medical is designed and fabricated. The proposed modified cross‐slots antenna composed four separate slots by removing the intersection of the cross‐slot in conventional structure. The proposed antenna improved characteristics of the gain, radiation pattern, and impedance bandwidth than the conventional cross‐slots antenna. As a result, the proposed antenna obtains impedance bandwidth of 240 MHz (VSWR < 1.5) and maximal gain of 5 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1415–1418, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22441
A 24‐GHz power‐efficient MMIC pulse oscillator for UWB radar applications
Authors: Kim Deokhwan , Kim Dong‐Wook , Hong Songcheol
Published: March 2007

A 24‐GHz power‐efficient pulse oscillator for ultrawideband (UWB) radar applications implemented with InGaP HBT MMIC technology is proposed. The oscillator uses a common base inductive feedback topology without output buffers. The bias current is switched on by a pulse‐control voltage. The oscillator consumes power only when the 24‐GHz pulse is generated, allowing high power efficiency to be obtained. A high output power of 8 dBm and a low phase noise of −120 dBc/Hz at 1 MHz offset frequency are obtained in continuous wave (CW) mode. While in pulse‐mode operation, the oscillator shows a 1‐ns pulse width with only 5 ps of phase jitter. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1412–1415, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22456
Simple method for a K‐band SIW filter with dual‐mode quasi‐elliptic function response
Authors: Huang Tsung‐Hui , Chang Chin‐Sheng , Chen Han‐Jan , Chen Lih‐Shan , Horng Jui‐Hong , Wang Yeong‐Her , Houng Mau‐Phon
Published: March 2007

A simple method for a K‐band substrate integrated waveguide (SIW) filter with dual‐mode response quasi‐elliptic function response is designed, fabricated, and measured around 20 GHz. By using an orthogonal input and output (I/O) feed‐line and adjusting a perturbation, the proposed filter with two transmission‐zeros are so close to the passband that the selectivity and out‐of‐band rejection of the filter are significantly increased. The designed filter demonstrates the superior passband characteristics with a measured central frequency fo = 20 GHz, the insertion loss S21 = −2.9 dB, the return loss S11 = −23.5 dB. Experimental results of the fabricated filter measured by network analyzer are well agreed with the simulation results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1246–1249, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22465
Equivalent circuit model of a tri‐resonance wideband dielectric resonator antenna
Authors: Ruan Yu‐Feng , Guo Yong‐Xin , Shi Xiang‐Quan
Published: March 2007

An equivalent circuit model of a tri‐resonance wideband dielectric resonator antenna is presented to give a physical insight into the wideband behavior of the antenna. The well‐known Levenberg–Marquardt algorithm is employed to improve the convergence characteristics of the curve fitting method used for finding the complex equivalent circuit model values having three resonators. The equivalent circuit models with various combinations of the antenna parameters such as dielectric constant, probe length, excitation position, and air‐gap are provided to verify that the proposed equivalent circuit model can give a good description of the antenna wideband behavior. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1427–1433, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22470
Wavelength‐switchable fiber laser
Authors: Medendorp Zachari , Valiunas Jonas , Das Gautam
Published: March 2007

A simple and novel technique to produce a switchable erbium‐doped fiber laser is proposed and demonstrated. The wavelength switching is achieved by changing the input pump power. The lasing lines are stable for more than an hour at room temperatures. The effects of separation between the lasing lines and the length of the erbium‐doped fiber on switching are explored. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1231–1233, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22477
Liver receptor homologue‐1 (LRH‐1) activates the promoter of brain aromatase (cyp19a2) in a teleost fish, the medaka, Oryzias latipes
Authors: Ohmuro‐Matsuyama Yuki , Okubo Kataaki , Matsuda Masaru , Ijiri Shigeho , Wang Deshou , Guan Guijun , Suzuki Taiga , Matsuyama Makoto , Morohashi Ken‐ichiro , Nagahama Yoshitaka
Published: March 2007

The medaka, Oryzias latipes, like other fish, have two distinct aromatase genes, the ovarian (cyp19a1) and brain (cyp19a2) forms. We previously reported that Ad4BP/SF‐1, a member of the NR5A subfamily, plays an important role in the regulation of cyp19a1 expression in medaka ovarian follicles during vitellogenesis. In the present study, we investigated whether liver receptor homologue‐1 (LRH‐1), another NR5A subfamily member, is involved in the regulation of cyp19a2 expression in the medaka brain. In situ hybridization analysis revealed that LRH‐1 was expressed in the hypothalamus, where it colocalized with aromatase (cyp19a2). We then showed by transient transfection assays that LRH‐1 was able to increase expression of a cyp19a2 reporter gene in various mammalian cell lines, and that mutation of a putative LRH‐1 binding site within the cyp19a2 promoter abolished this effect. Taken together, these findings suggest that LRH‐1 plays a role in regulating cyp19a2 expression in the medaka brain. This is the first to demonstrate in vitro the activation of brain aromatase by LRH‐1 in the vertebrate brain. Mol. Reprod. Dev. 74: 1065–1071, 2007. © 2007 Wiley‐Liss, Inc.
The split delivery vehicle routing problem: Applications, algorithms, test problems, and computational results
Authors: Chen Si , Golden Bruce , Wasil Edward
Published: March 2007

In the split delivery vehicle routing problem (SDVRP), a customer's demand can be split among several vehicles. In this article, we review applications of the SDVRP including the routing of helicopters in the North Sea and solution methods such as integer programming and tabu search. We develop a new heuristic that combines a mixed integer program and a record‐to‐record travel algorithm. Our heuristic produces high‐quality solutions to six benchmark problems that have 50–199 customers and generally performs much better than tabu search. On five other problems for which lower bounds exist, our heuristic obtains solutions within 5.85%, on average. Finally, we generate 21 new test problems that have 8–288 customers. A near‐optimal solution can be visually estimated for each problem. We apply our heuristic to these new problems and report our computational results. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 49(4), 318–329 2007
Maximum‐norm superapproximation of the gradient for the trilinear block finite element
Authors: Liu Jinghong , Zhu Qiding
Published: March 2007

For a model elliptic boundary value problem in three dimensions, we give the weak estimate of the first type for trilinear block elements and the estimate for W1,1‐seminorm of the discrete derivative Green's function over rectangular partitions of the domain, from which we obtain maximum‐norm superapproximation of the gradient for the trilinear block finite element approximation. Furthermore, utilizing this superapproximation, we can also obtain maximum‐norm superconvergence of the gradient. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Identification and determination of the major constituents in traditional Chinese medicinal plant Polygonum multiflorum thunb by HPLC coupled with PAD and ESI/MS
Authors: Yi Tao , Leung Kelvin S. Y. , Lu Guang‐Hua , Zhang Hao , Chan Kelvin
Published: March 2007

An HPLC–PAD–MS method has been developed for the qualitative and quantitative analysis of the major chemical constituents in Polygonum multiflorum Thunb. Chromatographic separation was conducted on an Alltima C18 column using water:acetonitrile:acetic acid as the mobile phase. Altogether nine compounds of various classes, including stilbene glucosides, anthraquinone glucosides and anthraquinone derivates, were identified by online ESI/MS. Their identities were ascertained by comparison with data derived from the literature and/or standard compounds. Five components were quantified by HPLC–PAD and the method was fully validated. All the linear regressions were acquired with R2 > 0.99 and the quantification limits (with a signal‐to‐noise ratio of 3) ranged from 0.63 and 1.57 ng. Repeatability was evaluated by intra‐ and inter‐day assays and RSD value was within 2.47%. Recovery studies for the quantified compounds were found to be within the range 96.32–102.53% with RSD less than 2.35%. The overall procedure is rapid and reproducible and is considered suitable for qualitative and quantitative analysis of a large number of samples. Copyright © 2007 John Wiley & Sons, Ltd.
Structural control of rubber modified thermoplastic as produced by the mass process
Authors: Freeguard Graham F.
Published: March 2007

Commercially important polyblends can be produced by a mass process which proceeds via the dispersion of a rubber solution phase. During the process several distinct stages can be identified and structural variation of the final polymer is achieved by controlled agitation. The relationship between the nature and structure of the dispersed phase and the mechanical properties of the polyblend are illustrated and discussed in the light of current theories of impact enhancement.
Preparation and properties of polymer lattices polymerised without surfactants
Authors: Ono Hiroshi , Saeki Hideo
Published: March 2007

Series of polystyrene and polymethyl methacrylate latex dispersions have been prepared in the absence of any surfactant using potassium persulphate as an initiator. The latex particles are stabilised by the electrical repulsion generated by the sulphate groups which are covalently linked to the polymer molecules and are not removed by dialysis. The effects of polymerisation temperature, monomer concentration and initiator concentration on the ultimate particle size and conversion were investigated for these two series of lattices. The modal diameters of these lattices were found to be in the range of 530 to 1550 nm for polystyrene lattices, and 140 to 270 nm for polymethyl methacrylate lattices. The surface charge densities were calculated from conductometric titration results for polymethyl methacrylate lattices and were found to increase almost linearly with increase of the concentration of potassium persulphate used.
Assessment of the high temperature performance of phenolic—phosphate resin composites
Authors: Hodd Kenneth A. , Reader Alan L. , Redfarn Cyril A.
Published: March 2007

The thermal stability of a phenolic‐phosphate resin, prepared by the transesterification of triphenyl phosphate and resorcinol and cured with hexamethylene tetraamine, has been compared with that of a conventional phenolic resin. Thermogravimetric analysis (TGA) of the resins, in air, demonstrated that the phenolic‐phosphate resin had the superior thermal resistance. Accordingly, to assess the performance of phenolic‐phosphate resins as thermally stable binders in composites, long‐term heating ageing studies at 250°C were carried out on asbestos‐filled moulded test specimens. The results of these tests were less welldefined than the TGA results, for the phenolic composite had the higher flexural strength (108.5 MNm−2) initially compared with 56.7 MNm−2 for the phenolic‐phosphate composite. However, after 1000 h heating at 250°C neither system retained a useful level of flexural strength, although the phenolic‐phosphate composite (18.35 MNm−2) was stronger than the phenolic composite (5.4 MNm−2).
A light scattering study of some solutions of triblock copolymers
Authors: Brown Bernar D. L.
Published: March 2007

Three samples of polystyrene‐polybutadiene‐polystyrene block copolymers have been studied by means of the light scattering technique in several solvents. The light scattering measurements indicate the degree of heterogeneity of the samples. Further measurements which were made on the least heterogeneous of the samples in a solvent closely matching the refractive index of the centre block suggest that the two types of polymer are largely separate. In this case the angular intensity variation of the light scattering can be interpreted in terms of the scattering obtained from a “dumb‐bell” configuration.
Mechanical properties and wear behaviour of plastics in relation to their use in prostheses
Authors: Atkinson John R.
Published: March 2007

The mechanisms of wear in plastics are reviewed and the properties required for high wear resistance derived. The importance of determining relevant mechanical properties at meaningful temperatures and strain rates is discussed. The particular advantages of high molecular weight polyethylene for prostheses are outlined and a typical wear test on this material described.
Some aspects of the emulsion polymerisation of vinyl acetate
Authors: Stannett Vivian , Klein Andrew , Litt Morton
Published: March 2007

The present status of work on the mechanism of the emulsion polymerisation of vinyl acetate initiated by potassium persulphate is critically reviewed. In addition, some new data illustrating the effect of adding electrolytes is presented. The polymerisation proceeds by a mechanism different from that of most vinyl monomers. In particular, the rates are approximately zero order on monomer from 20 to 85% conversion with only a minor dependence on the soap concentration and the number of particles. The dependence of the rate on the initiator concentration varies with different investigators from 0.5–1.0 order. The results are discussed in terms of various current theories and an attempt is made to rationalise them in a reasonable way.
Chloromodified ethylene propylene diene polymers
Authors: Schoen Löwhardt A. A. , van Raaijen Wim , van'T Wout Johan W. F.
Published: March 2007

The heterogeneous gas/solid chlorination of various ethylene propylene diene polymers has been studied at temperatures between 0 and 75°C at conditions which are unfavourable for free radical reactions. The structure of the chloromodified polymers has been cleared by n.m.r. and from these data a chlorination mechanism has been proposed. An equation for the diffusion controlled chlorination rate has also been given as well as some cure characteristics and mechanical properties of allylic chlorine containing chloromodified ethylene propylene dicyclopentadiene polymers.
Electroinitiated emulsion polymerisation of vinyl acetate. I. The mechanism of initiation
Authors: Tidswell Bryan M. , Train Andrew W.
Published: March 2007

Vinyl acetate has been shown to polymerise during the electrolysis of its aqueous acidified emulsion. The stabilisation of the emulsion is difficult and sodium salts of ethoxylated fatty alcohols have been used as emulsifier. Polymerisation occurs only within a narrow, low pH range. Percentage conversion and molecular weight show a maximum at about pH = 1. Below this value, acid hydrolysis of monomer interferes with the polymerisation whilst at higher values a change in the electrode process may occur. Polymerisation is considered to occur through the presence of hydrogen radicals adsorbed on the mercury cathode.
Electroinitiated emulsion polymerisation of vinyl monomers. III. Homopolymerisation and copolymerisation with vinyl acetate
Authors: Tidswell Bryan M. , Train Andrew W.
Published: March 2007

Of the monomers studied, vinyl acetate and vinyl n‐caproate are the only ones capable of electroinitiated homopolymerisation in aqueous acidic emulsion. Water solubility does not appear to be the overriding consideration. Activity of the radical would seem to be most important. Copolymerisation with monomers not undergoing homopolymerisation in this system produces good yields of copolymers low in vinyl acetate concentration.
Dynamic mechanical properties of polypentenamers with pendant ionic groups and their hydrogenated derivatives
Authors: Sanui K. , Macknight William J.
Published: March 2007

Dynamic mechanical properties of substituted polypentenamers having thioglycolate side groups and their hydrogenated derivatives have been studied. Methyl esters, acids and salts were investigated at two concentrations, 5.5 mole (%) and 9.2 mole (%). In the un‐hydrogenated derivatives one principal relaxation, labelled β, exists in the temperature range from‐160 to 100°C. This relaxation arises from microbrownian segmental motion accompanying the glass transition. Its temperature is affected by the concentration of substituent but not the chemical nature of the substituent. A ‘rubbery plateau’ region exists in the acid and salt derivatives and in the latter the salt groups act as reinforcing fillers in this plateau region, consistent with the ionic domain model for their structures.

In the hydrogenated derivatives, three relaxations occur in the temperature range from −160 to 120°C and these are labelled α, β, and γ in order of decreasing temperature. The α relaxation arises from motions associated with the crystal phase except in the case of the 9.2 mole (%) sodium salt derivatives where it arises from motions occurring within ionic domains. The β relaxation arises from microbrownian segmental motions accompanying the glass transition, and the γ relaxation arises from localised motions which may involve both amorphous and crystalline phase components.