Reactivity of CO2 traps in aerogel–wollastonite composites

Synthetic wollastonite has been used as the active phase embedded into two different silica aerogel composites. These composites are different in respect of the route used for the synthesis of the wollastonite powder. Texture and composition of both types of composite have been characterized. In addition, several factors (pH, reaction time, CO₂ saturation, etc.) that could help to optimize the carbonation process at room temperature and pressure have been studied. Under the same conditions, both composites confirm previous results showing efficiencies as CO₂ sequesters between 80% and 100% in only 15 min of gas flow. The textural characteristics of the aerogel, together with the grain size of the synthetic wollastonite powder, not only increase the speed of the reaction, but also inhibit the appearance of a passivating layer on the surface of the wollastonite grains attacked by the CO₂. This is an outstanding feature as it insists on a cutting-edge challenge of the CO₂ research: its economical availability.     

Lipschitz stability in determining density and two Lamé coefficients

We consider an inverse problem of determining spatially varying density and two Lamé coefficients in a non-stationary isotropic elastic equation by a single measurement of data on the whole lateral boundary. We prove the Lipschitz stability provided that initial data are suitably chosen. The proof is based on a Carleman estimate which can be obtained by the decomposition of the Lamé system into the rotation and the divergence components.     

Classical and quantum orthogonal polynomials in one variable

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The no-response approach and its relation to non-iterative methods for the inverse scattering

This paper addresses the inverse obstacle scattering problem. In the recent years several non-iterative methods have been proposed to reconstruct obstacles (penetrable or impenetrable) from near or far field measurements. In the chronological order, we cite among others the linear sampling method, the factorization method, the probe method and the singular sources method. These methods use differently the measurements to detect the unknown obstacle and they require the use of many incident fields (i.e. the full or a part of the far field map). More recently, two other approaches have been added. They are the no-response test and the range test. Both of them use few incident fields to detect some informations about the scatterer. All the mentioned methods are based on building functions depending on some parameter. These functions share the property that their behaviors with respect to the parameter change drastically. The surface of the obstacle is located at most in the interface where these functions become large. The goal of this work is to investigate the relation between some of the non-iterative reconstruction schemes regarding the convergence issue. A given method is said to be convergent if it reconstructs a part or the entire obstacle by using few or many incident fields respectively. For simplicity we consider the obstacle reconstruction problem from far field data for the Helmholtz equation. Gen Nakamura is partially supported by Grant-in-Aid for Scientific research (B)(2)(N.14340038) of Japan Society for Promotion of Science. Mourad Sini is supported by Japan Society for Promotion of Science.     

Generalized performance evaluation of low Earth orbit satellitesystems

A novel three-dimensional distribution traffic is proposed for low Earth orbit (LEO) satellite systems. The effect of the traffic geographical nonuniformity on the performance of these satellite systems is discussed     

Unique continuation for the elastic transversely isotropic dynamical systems and its application

In this paper we prove the unique continuation property of the solution for the elastic transversely isotropic dynamical systems with smooth coefficients satisfying some conditions and apply it to extending the Dirichlet to Neumann map. The proof is based on the localized Fourier-Gauss transformation and Carleman type estimate.     

Structural study by X-ray diffraction and Mössbauer spectroscopy of a new synthetic iron phosphate: K4MgFe3(PO4)5

A new iron phosphate K₄MgFe₃(PO₄)₅ has been synthesized by the flux method and characterized by single-crystal X-ray diffraction and Mössbauer spectroscopy. It crystallizes in the tetragonal system with the space group and the unit cell parameters a=9.714(3) Å and c=9.494(5) Å. The crystal structure is of a new type. It exhibits a three-dimensional framework built up from corner-sharing MO₅ (M=0.75Fe+0.25Mg) trigonal bipyramids and PO₄ tetrahedra. The K⁺ ions are occupying large eight-sided tunnels running along c. A room temperature Mössbauer study confirmed the +3 valence state of iron and its five-coordination.     

Analytics of heteroclinic bifurcation in a 3:1 subharmonic resonance

Analytical approximation of heteroclinic bifurcation in a 3:1 subharmonic resonance is given in this paper. The system we consider that produces this bifurcation is a harmonically forced and self-excited nonlinear oscillator. This bifurcation mechanism, resulting from the disappearance of a stable slow flow limit cycle at the bifurcation point, gives rise to a synchronization phenomenon near the 3:1 resonance. The analytical approach used in this study is based on the collision criterion between the slow flow limit cycle and the three saddles involved in the bifurcation. The amplitudes of the 3:1 subharmonic response and of the slow flow limit cycle are approximated and the collision criterion is applied leading to an explicit analytical condition of heteroclinic connection. Numerical simulations are performed and compared to the analytical finding for validation.