On the spectral analysis of many-body systems

We describe the essential spectrum and prove the Mourre estimate for quantum particle systems interacting through k-body forces and creation-annihilation processes which do not preserve the number of particles. For this we compute the “Hamiltonian algebra” of the system, i.e. the C^∗-algebra C generated by the Hamiltonians we want to study, and show that, as in the N-body case, it is graded by a semilattice. Hilbert C^∗-modules graded by semilattices are involved in the construction of C. For example, if we start with an N-body system whose Hamiltonian algebra is CN and then we add field type couplings between subsystems, then the many-body Hamiltonian algebra C is the imprimitivity algebra of a graded Hilbert CN-module.     

Structure of Hydrogen and Hydrophobically Bonded Amphiphilic Copolymer with Poly(methacrylic acid) Complexes as Revealed by Small Angle Neutron Scattering

We study by SANS the structure of intermolecular complexes formed through hydrogen bonding and hydrophobic interactions between poly(methacrylic acid) (PMA) and a neutral copolymer surfactant (PEO-PPO-PEO). The contrast variation method enables us to probe the structure factor of each polymer in the complex and their cross structure factor. The number of copolymer chains, which results from the cooperative action of hydrogen bonding and hydrophobic interactions increases as the charge of the polyacid decreases. The aggregation preserves the micellar core-corona organization of the copolymer and shrinks the polyacid chains which adopt a similar compact structure. Finally, the structure of the aggregates is compared to that of PEO-PMA homopolymer complex observed by SANS.     

Damaged-bone remodeling theory: Thermodynamical approach

The bone remodeling process is generally viewed as bone material response to functional demands and muscle attachments by continual process of growth, reinforcement and resorption which occur in living situation. Everyday activities damage bone, and this damage is normally repaired in a continuous process. When an imbalance in this remodeling process occurs, Bones may become more susceptible to fracture. An attempt to establish a relationship between induced microdamage and adaptive bone remodeling is proposed. A thermodynamic theoretical framework is provided as basis for a consistent formulation of bone remodeling involving a chemical reaction and mass transfer between two constituents in presence of microtracks.     

Dual-channel spectral subtraction algorithms based speech enhancement dedicated to a bilateral cochlear implant

In this paper, two speech enhancement algorithms (SEAs) based on spectral subtraction (SS) principle have been evaluated for bilateral cochlear implant (BCI) users. Specifically, dual-channel noise power spectral estimation algorithm using power spectral densities (PSD) and cross power spectral density (CPSD) of the observed signals was studied. The enhanced speech signals were obtained using either Dual Channel Non Linear Spectral Subtraction ‘DC-NLSS’ or Dual-Channel Multi-Band Spectral Subtraction ‘DC-MBSS’ algorithms. For performance evaluation, some objective speech assessment tests relying on Perceptual Evaluation of Speech Quality (PESQ) score and speech Itakura-Saito (IS) distortion measurement were performed to fix the optimal number of frequency band needed in DC-MBSS algorithm. In order to evaluate the speech intelligibility, subjective listening tests were assessed with 50 normal hearing listeners using a specific BCI simulator and with three deafened BCI patients. Experimental results, obtained using French Lafon database corrupted by an additive babble noise at different Signal-to-Noise Ratios (SNR), showed that DC-MBSS algorithm improves speech understanding better than DC-NLSS algorithm for single and multiple interfering noise sources.     

Finite dynamic deformations of a hyperelastic,anisotropic, incompressible and prestressed tube. Applications to in vivo arteries

In this paper, we study the mechanical behavior of a prestressed tube subjected to finite dynamic deformations. The tube is assumed to be made of a hyperelastic, anisotropic and incompressible material. The analysis is carried out by using a Mooney–Rivlin stored energy function augmented with fiber reinforcements in four unidimensional orientations. A semi-analytical solution is proposed to study the radial dynamic mechanical response of an artery by using in vivo data. The optimal model parameters describing the mechanical characteristics of arterial wall microconstituents are obtained by minimizing the difference between computed and measured inner pressures over the cardiac cycle using a nonlinear regression. Theoretical and experimental results on rat carotid elastic arteries are compared in order to assess the validity of the approach by estimating differences of the model parameters and wall stresses with aging.     

乳液聚合中聚苯胺膜形成的动力学研究

以(NH4)2S2O8(APS)为氧化剂,十二烷基苯磺酸(DBSA)同时为乳化剂和掺杂剂,采用乳液聚合方法制备聚苯胺膜(PANIfilm),用石英晶体微天平(QCM)实时监测聚苯胺膜的形成过程,并对其动力学过程进行研究.结果表明,聚苯胺成膜反应对APS是0.5级,对苯胺是1级,聚苯胺膜增长速率随温度的升高而增加,而聚苯胺膜的最终沉积量却减小,表观活化能Ea=41.15kJ/mol,与均相溶液聚合成膜法的结果相近;随着DBSA浓度的增加,聚苯胺膜增长速率减小,而最终的沉积量增大.     

Consistent inlet and outlet boundary conditions for particle methods

In this paper, simple and consistent open boundary conditions are presented for the numerical simulation of viscous incompressible laminar flows. The present approach is based on an arbitrary Lagrangian-Eulerian particle method using upwind interpolation. Three kinds of inlet/outlet boundary conditions are proposed for particle methods, a pressure specified inlet/outlet condition, a velocity profile specified inlet/outlet condition, and a fully developed flow outlet condition. These inlet/outlet conditions are realized by using boundary particles and modification to the physical value such as velocity. Poiseuille flows, flows over a backward-facing step, and flows in a T-shape branch are calculated. The results are compared with those of mesh-based methods such as the finite volume method. The method presented herein exhibits accuracy and numerical stability.     

Finite deformations of a hyperelastic, compressible and fibre reinforced tube

Finite torsion and axial stretch of a long, hyperelastic, compressible and circular tube is studied for the design of a prototype of small diameter vascular prosthesis. The analysis is carried out in the context of the finite elasticity theory by using a class of Ogden strain energy function augmented with unidirectional reinforcing that is characterized by a single additional constitutive parameter for strength of reinforcement. The highly non-linear differential equations with variable coefficients governing the problem are solved numerically using a Runge–Kutta method. For different prestresses supported by the tube, the effects of the combined deformation on the stress distributions are presented.     

Essential spectra of some matrix operators and application to two-group transport operators with general boundary conditions

In this article we investigate the essential spectra of a 2×2 block operator matrix on a Banach space. Furthermore, we apply the obtained results to determine the essential spectra of two-group transport operators with general boundary conditions in the Banach space Lp([−a,a]×[−1,1])×Lp([−a,a]×[−1,1]), a>0.     

On the Stationary Navier–Stokes Problem in $$\mathbb {R}^3$$: An Approach in Weighted Sobolev Spaces

In this paper, we study the steady-state Navier–Stokes equations in \(\mathbb {R}^3\). First, we establish the existence of very weak solution in \(\varvec{L}^p(\mathbb {R}^3)\) with \(3/2< p < +\infty \) under smallness conditions on the data. A uniqueness result is also given in case the data belong to \(\mathbb {L}^r(\mathbb {R}^3)\cap \mathbb {L}^{3/2}(\mathbb {R}^3)\) with \(3/2<r<3\). We also discuss the case where the data are not necessarily small. In particular, these results enhance those obtained by Bjorland et al. (Commun Partial Differ Equ 26:216–246, 2011), and are in agreement with those obtained by Kim and Kozono (J Math Anal Appl 395(2):486–495, 2012). Second, we prove a result of existence and uniqueness of weak solution in the weighted Sobolev space \(\varvec{W}_0^{1,p}(\mathbb {R}^3)\cap \varvec{W}_0^{1,\,3/2}(\mathbb {R}^3)\) in case of small external forces given by \(\mathrm{div}\mathbb {F}\) with \(\mathbb {F} \in \mathbb {L}^p(\mathbb {R}^3)\cap \mathbb {L}^{3/2}(\mathbb {R}^3)\) and \(1<p<3\).