bluuebunny/crossref_metadata_2025_split huggingface dataset:
A source density function
Authors: Lehnigk Siegfried H. , Roach G. F. 
Published: August 2005

AbstractThe delta function initial condition solution of the generalized Feller equation gives rise to a four‐parameter class of one‐sided probability source density functions. Because of this origin, each of these functions represents the instantaneous density of an autonomous Markov diffusion process. As the source location parameter approaches zero the density class to be investigated here reduces to the hyper‐Gamma class. Because of the immense flexibility in shape (as compared with the hyper‐Gamma class) the source density class offers itself to a wide variety of applications in physics and statistics, especially if the observations are far removed from zero. Relative to applications, the natural and paramount concern must be directed toward the parameter estimation problem. This paper provides the analytical foundation for a numerical approach to its solution. The log‐likelihood function for the source density class will be established. Based on it the maximum‐likelihood equations will be derived. For practical numerical reasons, direct maximization of the log‐likelihood function may be more successful than an attempt to solve the (three) maximum‐likelihood equations. Therefore, the analytical properties of the log‐likelihood function will be discussed, as they are essential in the implementation of any numerical optimization routine.
The electric field in the conductive half space as a model in mining and petroleum prospecting
Authors: Goldman Y. , Joly P. , Kern M. , Nedelec J. C. 
Published: August 2005

AbstractWe present a formulation of Maxwell's equations in a conductive medium, in the time domain. In order to restrict the equations to the conductive half space, the solution in the air is represented by an integral boundary operator on the interface. The problem admits a variational formulation, allowing a finite element solution. A mathematical analysis is described for 2D and 3D models, and numerical results are presented.
A penalty approximation for a unilateral contact problem in non‐linear elasticity
Authors: Gwinner J. , Brosowski B. 
Published: August 2005

AbstractUsing Ball's approach to non‐linear elasticity, and in particular his concept of polyconvexity, we treat a unilateral three‐dimensional contact problem for a hyperelastic body under volume and surface forces. Here the unilateral constraint is described by a sublinear function which can model the contact with a rigid convex cone. We obtain a solution to this generally non‐convex, semicoercive Signorinin problem as a limit of solutions of related energy minimization problems involving friction normal to the contact surface where the friction coefficient goes to infinity. Thus we extend an approximation result of Duvaut and Lions for linear‐elastic unilateral contact problems to finite deformations and to a class of non‐linear elastic materials including the material models of Ogden and of Mooney‐Rivlin for rubberlike materials.Moreover, the underlying penalty method is shown to be exact, that is a sufficiently large friction coefficient in the auxiliary energy minimization problems suffices to produce a solution of the original unilateral problem, provided a Lagrange multiplier to the unilateral constraint exists.
Boundary control of a vibrating plate with internal damping
Authors: Leugering Günter , Schmidt E. J. P. Georg , Meister E. 
Published: August 2005

AbstractIt is shown that finite energy states of a vibrating viscoelastic plate of the Kelvin–Voigt type are, in general, not exactly controllable by L2‐boundary controls. Accordingly, we present a result on approximative controllability. The method is general.
Surface gradients and continuity properties for some integral operators in classical scattering theory
Authors: Kirsch A. , Hsiao G. C. 
Published: August 2005

AbstractThe surface gradients of some of the most important boundary integral operators for the time‐harmonic Helmholtz and Maxwell equations are computed. These results are used to give new and elementary proofs of the continuity properties of these boundary operators in Sobolev and Hölder spaces of arbitrary order.
Some decomposition theorems and their application to non‐linear potential theory and Hodge theory
Authors: Picard Rainer 
Published: August 2005

AbstractThe paper considers Dirichlet (or Neumann type) boundary value problems of generalized potential theory

on Lipschitz manifolds with boundary. Here ϵ denotes a permissible non‐linearity. The existence theory is developed in the framework of monotone operators. The approach covers a variety of applications including fluid dynamics and electro‐ and magneto‐statics. Only fairly weak regularity assumptions are required (e.g. Lipschitz boundary, L∞‐coefficients). As a by‐product we obtain a non‐linear Hodge theorem generalizing a result by L. M. Sibner and R. J. Sibner (‘A non‐linear Hodge‐DeRham theorem’, Acta Math., 125, 57–73 (1970)).
Examples of embedded eigenvalues for the Dirichlet Laplacian in perturbed waveguides
Authors: Witsch K. J. 
Published: August 2005

AbstractIt is shown that there exist domains Ω ⊂ ℝN, which outside of some ball coincide with the strip ℝN − 1 × (0, π) and for which the Dirichlet Laplacian – Δ has eigenvalues within the subinterval (1, 4) of the essential spectrum (1, ∞).
On the exponential convergence of theh–pversion for boundary element Galerkin methods on polygons
Authors: Babuška I. , Guo B. Q. , Stephan E. P. 
Published: August 2005

AbstractThis paper applies the technique of theh–pversion to the boundary element method for boundary value problems on non‐smooth, plane domains with piecewise analytic boundary and data. The exponential rate of convergence of the boundary element Galerkin solution is proved when a geometric mesh refinement towards the vertices is used.
Steady states in plasma physics—the Vlasov–Fokker–Planck equation
Authors: Dressler Klaus 
Published: August 2005

AbstractIn this paper we investigate the non‐linear Vlasov–Fokker–Planck (VFP) equation, a both physically and mathematically interesting modification of Vlasov's equation, which describes a plasma in a thermal bath. We prove existence, uniqueness and representation results for steady states of the VFP equation both in the case of a mollified interaction potential and for the VFP–Poisson system. The uniqueness and representation results are of special interest since they distinguish special solutions of the Vlasov equation.
Convergence analysis for a multiplicatively relaxed EM algorithm
Authors: Iusem Alfredo N. 
Published: August 2005

AbstractThe expectation maximization (EM) algorithm is an iterative procedure used to determine maximum likelihood estimators in situations of incomplete data. In the case of independent Poisson variables it converges to a solution of a problem of the form min ∑[〈ai,x〉 −bilog 〈ai,x〉] such thatx⩾0. Thus, it can be used to solve systems of the formAx=b,x⩾0 (withAstochastic andbpositive.) It converges to a feasible solution if it exists and to an approximate one otherwise (the one that minimizesd(b,Ax), wheredis the Kullback–Leibler information divergence). We study the convergence of the multiplicatively relaxed version proposed by Tanaka for use in positron emission tomography. We prove global convergence in the underrelaxed and unrelaxed cases. In the overrelaxed case we present a local convergence theorem together with two partial global results: the sequence generated by the algorithm is bounded and, if it converges, its limit point is a solution of the aforementioned problem.
Scattering theory for hyperbolic equations of order 2m
Authors: Pickett Douglas 
Published: August 2005

AbstractGiven self‐adjoint operators Hj, on Hilbert spaces ℋ︁j, j = 0,l, and J ∈ ℬ︁ (ℋ︁0, ℋ︁1) (where ℬ︁ (ℋ︁0 ℋ︁1)	denotes the set of bounded linear operators from ℋ︁0to ℋ︁1), define the wave operators magnified image where P0 is the projection onto the subspace for absolute continuity for H0. We use (i) to study the scattering problem associated with a pair of equations each of the form magnified image where L is a positive, self‐adjoint operator on a Hilbert space X, m is a positive integer and the αj are distinct positive constants. Methods patterned after those of Kato are used to study two equations (that is for L = L0 and L = Ll) each of the form (ii). We show that they are equivalent to equations of the form magnified image where each Ĥk is a self‐adjoint operator on an associated Hilbert space ℋ︁k. Now suppose∼he‐wave operators W±,(L1 L0) exist and are complete. Then we can find a J ∈ ℬ︁(H1 H0) such that W+(Ĥl, Ĥ0,J) exists. In the case where Lo and L1 have the same domain, ℋ︁1 and ℋ︁0 are equal as vector spaces, and under certain conditions (on Li, i = 0, 1) ℋ︁0 and ℋ︁1 have equivalent norms. Assuming these conditions, let J'∈ ℬ︁(ℋ︁1' ℋ︁0) be the identity map. We show that (with an additional assumption on L0 and L1) W+(Ĥ1Ĥ0,J) exists andisequal to W+(Ĥl,Ĥ0, J).
Attenuation correction in positron emission tomography
Authors: Natterer F. , Herzog H. 
Published: August 2005

AbstractWe describe a mathematical method for computing the attenuation distribution from Positron emission tomography (PET) data. The method renders possible the correction of PET data for attenuation without a transmission scan. It can be applied if the attenuation distribution is sufficiently simple (abdomen and bead). We give the results for computer‐generated data and for data on patients.
Spatially localized free vibrations for a non‐linear string model
Authors: Feireisl Eduard 
Published: August 2005

AbstractWe prove the existence of infinitely many non‐zero time‐periodic solutions (breathers) to the dispersive wave equation of the form magnified image which are localized in the spatial variable, that is magnified imageThe main tool employed is the concentration compactness principle of P. L. Lions.
Multicriteria optimization in antenna design
Authors: Angell T. S. , Kirsch A. 
Published: August 2005

AbstractWe formulate certain problems in the optimal design of radiating structures such as multicriteria optimization problems. We review the basic background of such problems, prove the existence of Pareto optimal points, and give necessary conditions. We apply the latter to the numerical computation of optimal surface currents for the problem of simultaneously optimizing both the quality factor and the signal‐to‐noise ratio of a conformal antenna.
Boundary integral solution of the two‐dimensional heat equation
Authors: Hsiao George C. , Saranen J. 
Published: August 2005

AbstractHere we consider initial boundary value problems for the heat equation by using the heat potential representation for the solution. Depending on the choice of the representation we are led to a solution of the various boundary integral equations. We discuss the solvability of these equations in anisotropic Sobolev spaces. It turns out that the double‐layer heat potential D and its spatial adjoint D′ have smoothing properties similar to the single‐layer heat operator. This yields compactness of the operators D and D′. In addition, for any constant c ≠ 0, cI + D′ and cI + D′ are isomorphisms. Based on the coercivity of the single‐layer heat operator and the above compactness we establish the coerciveness of the hypersingular heat operator. Moreover, we show an equivalence between the weak solution and the various boundary integral solutions. As a further application we describe a coupling procedure for an exterior initial boundary value problem for the non‐homogeneous heat equation.
The NMR spectra and conformations of cyclic compounds–VIII. Car‐3‐ene
Authors: Abraham R. J. , Cooper M. A. , Whittaker D. 
Published: August 2005

AbstractThe 220 MHz PMR spectrum of car‐3‐ene (3,7,7‐trimethylbicyclo[4,1,0]hept‐3‐ene) is interpreted and a conformation deduced. In contrast to previous work, which has discussed a highly buckled structure for the 6 membered ring, the present work finds this ring to be essentially planar.
Stéréochimie de β‐diols et de leurs dérivés cycliques–VI. Calcul empirique des déplacements chimiques en série dioxannique. Détermination et discussion des incréments de calcul
Authors: Maroni Pierre , Cazaux Louis , Gorrichon Jean‐Pierre , Tisnes Pierre , Wolf Jean‐Gérard 
Published: August 2005

AbstractAfin de calculer empiriquement les déplacements chimiques des protons de dioxannes‐1,3 méthylés, nous avons tout d'abord dégagé les valeurs de base du déplacement chimique de chaque proton du dioxanne‐1,3. ensuite, en utilisant des dérivés méthylés en conformation chaise, nous avons établi une systématique effets Δδ des groupes méthyles en position quelconque.Pour certaines molécules, présentant notamment des interaction gauches, ces divers effts peuvent être modifiés, et nous avons é ces perturbations. L'analogie de Δδ entre les deux séries dioxannique et cyclohexanique a été rapprochée d'une similitude de gémétrie des cycles. Cependant la présence des atomes d'oxygène introduit des différnces parfois importantes.
Stéréochimie de β‐diols et de leurs dérivés cycliques—VII. Calcul empirique des déplacements chimiques en série dioxannique. Application a l'analyse conformationnelle de dérivés alkyles
Authors: Maroni P. , Cazaux L. , Gorrichon J. P. , Tisnes P. , Wolf J. G. 
Published: August 2005

AbstractLe calcul empirique des déplacements chimiques de méthyl dioxannes‐1,3 conduit à des résultats cohérents. L'écart avec la valeur expérimentale a pu être corrélé à la déformation du cycle dioxannique. La méthode a été étendue aux substituants éthyle, isopropyle et tertibutyle en position 4 ou 6 sur ce cycle.En l'bsence de substituant en 5, le groupe tertiobutyle n'induit pas plus de déformation du cycle en position 4 qu'en 2 ou 5. Les interactions particulières de ce groupement avec un ou deux méthyles en 5 sont mises en relief.
Solvent effects on the proton magnetic resonance spectra of p‐substituted phenyltin chlorides
Authors: Matsubayashi Gen‐Etsu , Koezuka Hiroshi , Tanaka Toshio 
Published: August 2005

AbstractA PMR study of solvent effects on some p‐substituted phenyltin chlorides (substituents = CH3, (CH3)3C, CH3O) is reported. Co‐ordination of solvent molecules to the tin atom leads to an unusual low field shift of the o‐ring protons. The results for p‐tolytin trichloride have been compared with those for p‐tolylsilyl trichloride and discussed. In o‐, m‐ and p‐tolyltin trichlorides long range spin‐spin couplings between the ring methyl protons and the tin atom have been observed. The order of magnitude is o‐ > p‐ > m‐methyl protons.
Non‐empirical calculations of NMR indirect spin–spin coupling constants. Part 13: configurational assignment of aminosulfonylamidines
Authors: Krivdin Leonid B. , Larina Lyudmila I. , Chernyshev Kirill A. , Rozentsveig Igor B. 
Published: August 2005

AbstractCarbon–carbon coupling constants have been experimentally measured using the INADEQUATE pulse sequence in the series of N‐[1,2‐bis(dialkylamino)‐2‐arylethylidene]arylsulfonamides obtained from N‐(1‐aryl‐2,2,2‐trichloroethyl)amides of arylsulfonic acids. Comparison of the experimental J(C,C) in this series with those calculated at the SOPPA (Second‐Order Polarization Propagator Approach) level in the model aminosulfonylamidine provided an unambiguous assignment at the CN bond of the eight‐title aminosulfonylamidines to E‐configuration, while the unknown J(C,C) couplings in their inaccessible diverse Z isomers have been predicted with high reliability. The established marked difference between J(C,C) of the corresponding carbon–carbon bonds in cis and trans orientations to the nitrogen lone pair in aminosulfonylamidines provides a powerful tool in the configurational assignment at the CN bond in a wide series of the related systems containing the CNSO2R moiety. Copyright © 2005 John Wiley & Sons, Ltd.
Variable‐density one‐shot fourier velocity encoding
Authors: DiCarlo Julie C. , Hargreaves Brian A. , Nayak Krishna S. , Hu Bob S. , Pauly John M. , Nishimura Dwight G. 
Published: August 2005

AbstractIn areas of highly pulsatile and turbulent flow, real‐time imaging with high temporal, spatial, and velocity resolution is essential. The use of 1D Fourier velocity encoding (FVE) was previously demonstrated for velocity measurement in real time, with fewer effects resulting from off‐resonance. The application of variable‐density sampling is proposed to improve velocity measurement without a significant increase in readout time or the addition of aliasing artifacts. Two sequence comparisons are presented to improve velocity resolution or increase the velocity field of view (FOV) to unambiguously measure velocities up to 5 m/s without aliasing. The results from a tube flow phantom, a stenosis phantom, and healthy volunteers are presented, along with a comparison of measurements using Doppler ultrasound (US). The studies confirm that variable‐density acquisition of kz‐kv space improves the velocity resolution and FOV of such data, with the greatest impact on the improvement of FOV to include velocities in stenotic ranges. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Analytical approach to the MR signal
Authors: Ibrahim Tamer S. 
Published: August 2005

AbstractIn this work, an analytical evaluation of the MR signal is presented using the principle of reciprocity for any transmit and receive probe(s) with general geometrical structure(s). It is shown that the excitation of the spins cannot be explained using the principle of reciprocity in its standard form due to the asymmetry in the permeability tensor of the transverse magnetization. In the reception problem, the standard form of the principle of reciprocity is then utilized to calculate the NMR signal. As expected, the analysis shows that the strength of the NMR signal is a function of the receive coil's (fictitious) circularly polarized component of the field that poses an opposite sense of rotation to that corresponding with the excitation field, produced by the same coil, if it were to be used for excitation. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Selective excitation of myelin water using inversion–recovery‐based preparations
Authors: Travis Adam R. , Does Mark D. 
Published: August 2005

AbstractT1 and T2 relaxation of excised frog sciatic nerve water was characterized at 7 T. Based on these findings, optimal timings for multiple inversion–recovery magnetization preparations were determined to selectively excite the so‐called myelin–water T2 component. Subsequent double inversion–recovery and triple inversion–recovery preparations were used in combination with CPMG acquisitions to experimentally determine optimal timings and effect of the preparation. Using double inversion–recovery, optimal timings were found to excite magnetization that is predominantly (≈93%) derived from the myelin–water component. Greater selectivity (≈96%) was found by extending the preparation to triple inversion–recovery, at the price of decreasing SNR by a factor of ≈ 2. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Evaluation of Nørsett methods for integrating differential equations in time
Authors: Smith I. M. , Siemieniuch J. L. , Gladwell I. 
Published: August 2005

AbstractSome recently developed implicit time discretizations are discussed whose main application is to solving ordinary differential equations arising from finite element approximations to partial differential equations. Their theoretical properties, computer implementation and numerical behaviour, as observed in tests on simple examples, are compared with well‐known discretizations such as the Crank‐Nicholson method.
Numerical performance of some finite element schemes for analysis of seepage in porous elastic media
Authors: Sandhu Ranbir S. , Liu Honho , Singh Kamar J. 
Published: August 2005

AbstractSeveral finite element schemes for analysis of seepage in porous elastic media, based on different spatial and temporal discretization, were implemented in computer programs. Their numerical performance is evaluated by comparison with the exact solution for Terzaghi's problem of one‐dimensional consolidation.
Time‐dependent multilaminate model of rocks—a numerical study of deformation and failure of rock masses
Authors: Zienkiewicz O. C. , Pande G. N. 
Published: August 2005

AbstractA new model for rocks and rock‐like material with multiple planes of weakness is proposed. The behaviour of the assembly applies tensile and Mohr‐Coulomb shear limits on each such plane with possible strain dependence of frictional properties. The visco‐plastic algorithm which allows the incorporation of time effects is used to obtain static solutions.The model is illustrated in actual context by applications to stability of rock slopes and behaviour of tunnels.A generalization of the model to include arbitrary three‐dimensional distribution of laminae in ‘quasi‐plane strain’ is included. The effect of various flow rules adopted for plastic straining is indicated.
Large strain analysis of some geomechanics problems by the finite element method
Authors: Yamada Yoshiaki , Wifi Abdalla S. 
Published: August 2005

AbstractThis paper presents a rational approach to the finite strain analysis of elastic‐plastic materials. An updated incremental finite element technique was applied to problems of shallow foundations of homogeneous as well as multilayer soils. This was based on a variational principle which is suitable for such problems.
A mathematical model for predicting coupled heat and water movement in unsaturated soil
Authors: Dempsey Barry J. 
Published: August 2005

AbstractAn investigation was conducted to develop a comprehensive moisture model for predicting non‐isothermal moisture conditions in soils. An extensive literature review indicated that a model based on the Philip and de Vries equations for non‐isothermal moisture movement and heat conduction would give the best results. By using numerical methods, the implicit finite difference approximations to the moisture movement and heat‐transfer equations were programmed for computer solution of water content and temperature in the soil with time.Validation studies indicate that the moisture model can be used to predict accurately moisture conditions in the soil. The model was validated by using hydraulic data from laboratory studies conducted on soil columns compacted with AASHO A‐3 and AASHO A‐4 soil.The application of the moisture model to the study of non‐isothermal moisture movement in the field is demonstrated. The influence of parameters such as water table depth, precipitation, and soil hydraulic properties on soil moisture content are shown by use of the moisture model. The model is shown to be applicable to a wide range of boundary conditions and that it predicts the moisture‐temperature regime with time in soils utilizing climatic input data.