bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the equivalence of the Schrödinger and the quantum Liouville equations
Authors: Markowich Peter A. , Neunzert H. 
Published: August 2005

AbstractWe present a semigroup analysis of the quantum Liouville equation, which models the temporal evolution of the (quasi) distribution of an electron ensemble under the action of a scalar potential. By employing the density matrix formulation of quantum physics we prove that the quantum Liouville operator generates a unitary group on L2 if the corresponding Hamiltonian is essentially self‐adjoint.Also, we analyse the existence and non‐negativity of the particale density and prove that the solutions of the quantum Liouville equation converge to weak solutions of the classical Liouville equation as the Planck constant tends to zero (assuming that the potential is sufficiently smooth).
Stationary solutions of the linearized Boltzmann equation in a half‐space
Authors: Golse F. , Poupaud F. , Neunzert H. 
Published: August 2005

AbstractStationary half‐space solutions of the linearized Boltzmann equation are studied by energy estimates methods. We extend the results of Bardos, Caflisch and Nicolaenko for a gas of hard spheres to a general potential. Asymptotic behaviour is obtained for hard as well as soft potentials and compared to the case of hard spheres.
On the instability of resonances in parallel‐plane waveguides under local perturbations of the boundary
Authors: Morgenröther K. , Werner P. 
Published: August 2005

AbstractWe study the large‐time asymptotics for solutions u(x, t) of the wave equation with Dirichlet boundary data, generated by a time‐harmonic force distribution of frequency ω, in a class of domains with non‐compact boundaries and show that the results obtained in [11] for a special class of local perturbations of Ω0 ≔ ℝ2 × (0,1) can be extended to arbitrary smooth local perturbations Ω of Ω0. In particular, we prove that u is bounded as t → ∞ if Ω does not allow admissible standing waves of frequency ω in the sense of [8]. This implies in connection with [8]. Theorem 3.1 that the logarithmic resonances of the unperturbed domain Ω0 at the frequencies ω = πk (k = 1, 2,…) observed in [14] can be simultaneously removed by small perturbations of the boundary. As a main step of our analysis, the determination of admissible solutions of the boundary value problem ΔU + κ2U = − f in Ω, U = 0 on ∂Ω is reduced to a compact operator equation.
Dense sets and the projection theorem for acoustic harmonic waves in a homogeneous finite depth ocean
Authors: Gilbert R. P. , Xu Yongzhi 
Published: August 2005

AbstractThe scattering of a ‘plane wave’ off a submerged body situated in an ocean of finite depth is investigated. The index of refraction is considered to be depth‐independent. It is shown that the far field is not unique; hence, the problem of determining the shape of an object from its far field is not well‐posed. If solutions are sought among a restricted class of problems the ‘dense set’ property implies that the problem can be made well‐posed.
On a free boundary problem in electrostatics
Authors: Philippin G. A. 
Published: August 2005

AbstractLet Ωi ⊂ ℝN, i = 0, 1, be two bounded separately star‐shaped domains such that \documentclass{article}\pagestyle{empty}\begin{document}$ \Omega _0 \supset \bar \Omega _1 $\end{document}. We consider the electrostatic potential u defined in \documentclass{article}\pagestyle{empty}\begin{document}$ \Omega : = \Omega _0 \backslash \bar \Omega _1 $\end{document}:

The geometry of the two boundary components Γ0 and Γ1 is not given, but instead the electrostatic potential u is supposed to satisfy the further boundary conditions
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Using a best possible maximum principle, we show that this free boundary problem has a unique solution which is radially symmetric.
On the numerical treatment of an integral equation arising from a cruciform crack problem
Authors: Monegato G. , Prössdorf S. 
Published: August 2005

AbstractWe consider the following two integral equations
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the latter subject to the condition ∫v(y)dy = 0, arising from the same problem of determining the distribution of stress in a thin elastic plate in the vicinity of a cruciform crack. In particular, we prove existence and uniqueness of the solutions of the two equations above in C[0, 1]. We also analyse the behaviour of ϕ(x) near the end‐point x = 0.The therotical result obtained in the first part are then used in the last section to derive optimal rates of convergence for numerical methods, such as Galerkin, collocation and Nyström, applied to equation (1).
On a problem in condensed two‐phase combustion
Authors: Primicerio Mario , Xie Weiqing , Shu Muzeng 
Published: August 2005

AbstractAn exothermic binary chemical reaction of first order is studied, assuming that one of the reactants can undergo a change of phase. In the limit of low activation energy, a one‐dimensional problem is considered and the well‐posedness of the corresponding system of two parabolic equations with a free boundary is proved in a classical sense.
Time stepping procedures for the non‐stationary Stokes equations
Authors: Varnhorn Werner 
Published: August 2005

AbstractWe consider first and second‐order implicit time stepping procedures for the non‐stationary Stokes equations in bounded domains of ℝ3. Using energy estimates we prove the optimal convergence properties in the Sobolev spaces Hm(G)(m = 0, 1, 2) uniformly in time, provided that the Stokes solution has a certain degree of regularity. Here in the case of the second‐order scheme (method of Crank–Nicholson) the Stokes solution has to satisfy a non‐local compatibility condition at the initial time t = O, which can be satisfied by a special initial construction.
Properties of solutions to the initial‐boundary value problem for a porous media‐type equation
Authors: Goncerzewicz Jan 
Published: August 2005

AbstractThe initial‐boundary value problem in a semi‐infinite strip (0, ∞)×(0, T) for a degenerate parabolic equation of the form u, t= φ(u)xx + b(x)φ(u)x is considered. The properties of solutions in the case where the initial function is compactly supported and for constant initial and boundary data are investigated.
One gauge‐invariant system for two‐dimensional relativistic fields: Global solutions, integrability
Authors: Łada Andrzej 
Published: August 2005

AbstractThe system originating from the theory of two‐dimensional hyperbolic chiral fields and the theory of self‐dual Yang‐Mills fields over ℝ2 + 2 is studied. The existence of global solutions for the Cauchy problem is established. It is observed that the system is completely integrable and one method of construction of a new solution is presented.
A remark on a compactness result in electromagnetic theory
Authors: Witsch Karl J. 
Published: August 2005

AbstractCalderon's extension theorem is a crucial tool in the proof of the compactneσs of the resolvent for the Maxwell operator, and whence this result is proved for domains with the strict cone property. However, the proof only requires an extension operator that extends W2,2‐functions compactly as W1,2‐functions. It is shown that this can be achieved under weaker regularity conditions on the domain: the cone may be replaced by some cusp of an appropriate order.
127I NQR in some iodic acid compunds
Authors: Balicheva T. G. , Grechishkin V. S. , Petrova G. A. , Shishkin V. A. 
Published: August 2005

Abstract127I NQR frequencies have been measured in 20 compounds including iodates, chromate‐iodates and tri‐iodates. Quadrupole coupling constants and asymmetry parameters have been calculated at 77°K. Lines have been assigned by the two‐frequency method. NQR data show the presence of covalent bonds in iodates and tri‐iodates. In chromate‐iodates the large value of the asymmetry parameter is due to the non‐equivalence of an oxygen atom in the IO3− ion.
Heterocycles contenant du phosphore‐XXI. Etude par RMP de déeriveés de l'oxazaphospholane‐l,3,2: I‐Analyse des spectres des composksés non substitués en 4 et 5.
Authors: Devillers Jean , Roussel Jean , Navech Jacques , Burgada Ramon 
Published: August 2005

AbstractLes dérivés de l'oxazaphospholane‐1,3,3 du titre donnent des spectres de RMP du type ABKLX. L'analyse sous‐spectrale d'un tel système montre qu'on a le choix entre huit solutions. Des expériences d'INDOR permettent d'établir le diagramme d'énergie et de choisir la bonne soultion.
The effects of chemically induced polarisation in the cage recombination products of the methyl radical
Authors: Kessenikh A. V. , Ignatenko A. V. , Rykov S. V. , Shteinshneider A. Ya. 
Published: August 2005

AbstractA study of the CIDNP effects on methyl protons was carried out for the cage recombination products formed during the thermal decomposition reactions of peracetyls and peracetylcarbonates. The increase of both the cage recombination product yield and the enhancement of CIDNP on the CH3 protons is shown to be connected with the RCO2 radical lifetime, where R is an alkyl or alkoxy radical. A general theory of CIDNP is presented and the calculated data prove to be in satisfactory agreement with the experimental results.
The influence of N‐protected amino acid residues on the cis/trans isomerism of proline moieties in peptides
Authors: Voelter Wolfgang , Oster Oskar 
Published: August 2005

Abstract13C NMR spectroscopy is an excellent tool for studying the influence of N‐protecting groups on the cis/trans isomerism of proline residues in proline peptides. This communication demonstrates the usefulness of 13C NMR spectroscopy in investigating conformational problems in protein and peptide chemistry.
Association of increased type I collagen expression and relative stromal overgrowth in mouse epididymis neonatally exposed to diethylstilbestrol
Authors: Yamazaki Koji , Fukata Hideki , Adachi Tetsuya , Tainaka Hitoshi , Kohda Masao , Yamazaki Masashi , Kojima Kensuke , Chiba Kan , Mori Chisato , Komiyama Masatoshi 
Published: August 2005

AbstractThe aim of this study was to investigate the molecular changes that underlie morphological changes in the epididymis following neonatal exposure to potent synthetic estrogen, namely diethylstilbestrol (DES). Newborn male mice were subcutaneously injected with DES or endogenous estrogen, namely 17 β‐estradiol (E2) (5 µg/mouse/day), for the first 5 days. At the age of 2, 4, and 8 weeks, epididymides of the mice were dissected. Characteristic morphological abnormality, such as relative stromal overgrowth, was observed at the age of 2 weeks in the epididymis of DES‐treated mice, but not in E2‐treated mice. Microarray and real‐time RT‐PCR analyses revealed that the expression levels of procollagen type I alpha 1 (col1a1) and col1a2 genes were markedly upregulated at the age of 2 weeks in the epididymis of DES‐treated mice in comparison with the control. Western blot analysis revealed that type I collagen protein expression level in epididymis of DES‐treated mice was elevated at the age of 2 weeks. In situ hybridization analysis revealed that the signals of col1a1 mRNA were detected similarly throughout the stromal tissue of epididymis at the age of 2 weeks in control and DES‐ and E2‐treated mice. The gene expression level of epididymal type III collagen (col3a1), which is found in many stromal connective tissues as well as type I collagen, did not change at the age of 2 weeks in all groups. These results suggest that the increased type I collagen expression is associated with the relative stromal overgrowth in the epididymis of DES‐treated mice. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Electromagnetic perspective on the operation of RF coils at 1.5–11.7 Tesla
Authors: Ibrahim Tamer S. , Mitchell Chad , Schmalbrock Petra , Lee Robert , Chakeres Donald W. 
Published: August 2005

AbstractIn this work experimental and numerical studies of the MR signal were performed at frequencies ranging from 64 MHz to 485 MHz, utilizing three different MRI coils: a single‐strut transverse electromagnetic (TEM)‐based coil, a TEM resonator, and a high‐pass birdcage coil. The experimental analyses were conducted using 1.5 and 8 Tesla whole‐body systems and volume RF head coils. The simulation data were obtained utilizing an in‐house‐developed finite difference time domain (FDTD) model. Pertinent data from the numerical and experimental setups were compared, and a remarkable agreement between the two methods was found that clearly demonstrates the effectiveness of the FDTD method when it is applied rigorously. The numerical and experimental studies demonstrate the complexity of the electromagnetic (EM) fields and their role in the MR signal. These studies also reveal unique similarities and differences between the transmit and receive field distributions at various field strengths. Finally, for ultra high‐field operations, it was demonstrated mathematically, numerically, and experimentally that highly asymmetric inhomogeneous images can be acquired even for linear excitation, symmetrical load geometries, and symmetrical load positioning within the coil. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Simulation of anisotropic growth of low‐grade gliomas using diffusion tensor imaging
Authors: Jbabdi Saâd , Mandonnet Emmanuel , Duffau Hugues , Capelle Laurent , Swanson Kristin Rae , Pélégrini‐Issac Mélanie , Guillevin Rémy , Benali Habib 
Published: August 2005

AbstractA recent computational model of brain tumor growth, developed to better describe how gliomas invade through the adjacent brain parenchyma, is based on two major elements: cell proliferation and isotropic cell diffusion. On the basis of this model, glioma growth has been simulated in a virtual brain, provided by a 3D segmented MRI atlas. However, it is commonly accepted that glial cells preferentially migrate along the direction of fiber tracts. Therefore, in this paper, the model has been improved by including anisotropic extension of gliomas. The method is based on a cell diffusion tensor derived from water diffusion tensor (as given by MRI diffusion tensor imaging). Results of simulations have been compared with two clinical examples demonstrating typical growth patterns of low‐grade gliomas centered around the insula. The shape and the kinetic evolution are better simulated with anisotropic rather than isotropic diffusion. The best fit is obtained when the anisotropy of the cell diffusion tensor is increased to greater anisotropy than the observed water diffusion tensor. The shape of the tumor is also influenced by the initial location of the tumor. Anisotropic brain tumor growth simulations provide a means to determine the initial location of a low‐grade glioma as well as its cell diffusion tensor, both of which might reflect the biological characteristics of invasion. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Penetration calculations and measurements for a layered soil target
Authors: Byers Rupert K. , Chabai Albert J. 
Published: August 2005

AbstractA tow‐dimensional finite difference wave propagation code was used to analyse the impact of a rigid, ogival‐nosed penetrator with a target consisting of thin alternating layers of silt, sand, and clay. The response of the idealized target was described with an elastic‐plastic constitutive model depending upon two stress invariants and the history of plastic deformation. Interfacial friction between the penetrator and target was assumed to be negligible.Comparisons are made of calculated results and those of nominally similar experiments conducted at the Watching Hill test site in Alberta, Canada. Analysis of these comparisons reveals that numerical methods like the one employed in this study can yield insight into penomena, as well as suggesting possible improvements in the calculation technique.
Methods for the numerical solution of the equations of viscoelasticity
Authors: Booker J. R. , Small J. C. 
Published: August 2005

AbstractIn this paper a finite element formulation for a linear viscoelastic ageing material is developed. It is shown that these equations can be solved in the from of an eigenvalue expansion thus reducing the problem to the solution of a set of Volterra Integral equations. An alternative method of solution based on expansion in terms of an operator related to Poisson's ratio is also developed and this solution method is found to significantly reduce the computational effort necessary in the solution of aproblem.
Mathematical modelling of monotonic and cyclic undrained clay behaviour
Authors: Prévost Jean‐Hervé 
Published: August 2005

AbstractThe proposed general analytical model describes the anisotropic, elasto‐plastic, path‐dependent, stress‐strain‐strength properties of inviscid saturated clays under undrained loading conditions. The model combines properties of isotropic and kinematic plasticity by introducing the concept of a field of plastic moduli which is defined in stress space by the relative configuration of yield surfaces. For any loading (or unloading) history, the instantaneous configuration is determined by calculating the translation and contraction (or expansion) of each yield surface. The stress‐strain behaviour of clays can thus be determined for complex loading paths and in particular for cyclic loadings. The stress‐strain relationships are provided for use in finite element analyses. The model parameters required to characterize the behaviour of any given clay can be derived entirely from conventional triaxial or simple shear soil test results. The model's extreme versatility is demonstrated by using it to formulate the behaviour of the Drammen clay under both monotonic and cyclic loading conditions. The parameters are determined by using solely the results from monotonic and cyclic strain‐controlled simple shear experimental tests, and the model's accuracy is evaluated by applying it to predict the results of other tests such as (1) cyclic stress‐controlled simple shear tests, (2) monotonic triaxial loading compression and unloading extension tests, and (3) cyclic stress‐ and strain‐controlled triaxial tests on, this same clay. The theoretical predictions are found to agree extremely well with the experimental test results.
On the time‐dependent effects in advancing tunnels
Authors: Ghaboussi Jamshid , Gioda Giancarlo 
Published: August 2005

AbstractA finite element study is presented of the short‐term effects that develop when a tunnel is driven in a ground showing viscous behaviour associated with the deviatoric deformations. Axisymmetric conditions around the tunnel centreline are assumed and the process of excavation is simulated by means of a step‐by‐step time incremental technique. The Kelvin's model is used to approximate the medium creep behaviour and a simple procedure is presented that allows the determination of the creep model constants from the laboratory test data. Various rates of advancing, the presence of an unsupported zone close to the tunnel face and the temporary interruption of the excavation process are considered. For the viscous model and the analytical technique used, simple, approximate relationships are presented for the displacements around the tunnel and the overexcavation volume as functions of the rate of excavation advancing.
An analytical solution for the consolidation around a driven pile
Authors: Randolph M. F. , Wroth C. P. 
Published: August 2005

AbstractField studies have shown that the driving of a displacement pile into cohesive soil generates large excess pore pressures in the vicinity of the pile. These pore pressures are often larger than the effective overburden pressure and facilitate the installation of the pile. The subsequent increase in bearing capacity of the pile is largely controlled by the dissipation of the excess pore pressures and a consequent increase in the effective stresses acting on the pile. The paper presents a closed formanalytical solution for the radial consolidation of the soil around a driven pile, assuming that the soil skeleton deforms elastically. This assumption is examined in the light of the predicted effective stress changes in the soil and is shown to lead to, a realistic model for the decay of pore pressure near the pile with time after driving. Although the solution may be applied to any initial distribution of excess pore pressure, attention is focussed on that due to the expansion of a cylindrical cavity in an ideal elastic, perfectly plastic soil. The resulting logarithmic variation of excess pore pressure with radius is considered to be close to that generated around a pile as a result of driving. In addition to giving estimates of the time needed for a driven pile to achieve its maximum strength, the solution may also be used in the analysis of pressuremeter tests to provide in‐situ measurements of the coefficient of consolidation of the soil.
A constitutive model for sand in triaxial compression
Authors: Nova R. , Wood D. M. 
Published: August 2005

AbstractAlthough there is a large number of constitutive models for sand available in the literature it is believed that a fresh approach, striking a balance between complexity and theoretical rigour, is desirable.The approach here has certain conceptual links with the Cam Clay series of elastic–plastic models, but includes the more general starting assumption that the yield function, plastic potential and failure locus should be given quite distinct mathematical expressions. Possible physical bases for the proposed forms are discussed.Ways in which the parameters required to define the model may be determined are suggested and the use of the model is then demonstrated. Firstly, it is shown that, where a limited set of experimental data is available, the model is flexible enough to be able to match the test results. Secondly, it is shown that, where a wide range of test results has been produced, it is possible to determine the model constitutive parameters from a small number of tests and proceed to make satisfactory predictionsfor other, quite different, types of test.The model is developed for sand at a single initial density, but the way in which the constitutive parameters might be expected to vary with density is discussed. The model is described for conditions of triaxial compression, and extension to more general stress states will be needed before it can be put to the test of incorporation in, for example, a finite element program.
Finite difference techniques for modelling geothermal reservoirs
Authors: Zyvoloski G. A. , O'Sullivan M. J. , Krol D. E. 
Published: August 2005

AbstractTwo finite difference algorithms suitable for long‐time simulation of the exploitation of a two‐phase geothermal reservoir are presented. One is based on the hopscotch method proposed by Saul'yev1 and analysed further by Gordon2 and Gourlay.3 The other is based on the well‐known ADI method. Both methods use a Newton–Raphson iterative technique in order to obtain accurate solutions of the non‐linear difference equations involved. Rapid convergence of the iterative schemes occurs both for single‐phase and two‐phase reservoir problems. One‐ and two‐dimensional model problems are presented.
Elastic–plastic analysis of geotechnical problems by mathematical programming
Authors: Gioda Giancarlo , de Donato Osvaldo 
Published: August 2005

AbstractA numerical technique, based on a mathematical programming algorithm, is presented for the solution of geotechnical problems where elastic‐plastic material behaviour is considered. The proposed approach can be adopted for geotechnical media characterized by any suitable yield condition, accounting, if necessary, for workhardening behaviour. The loading process is subdivided into a series of steps applied to a finite element mesh with geometry and material properties constant along each step, but with possible changes between subsequent steps. As an application some typical geotechnical problems are analysed by means of the proposed algorithm and a comparison is made between the available in situ measurements and the numerical results.