Determination of thermal conductivity and diffusivity of soaked steels using the “Mirage effect” method

In this work, we intend to study the thermal properties of the soaked steels like XC48 and their evolution according to the heating temperature and for different soaking media, using the “Mirage effect” method which permits the simultaneous determination of thermal conductivity and diffusivity. We have observed a discontinuity of thermal conductivity and diffusivity at the temperature of the ferro-paramagnetic transition.     

Oscillations spatio-temporelles engendrees par un automate cellulaire

We study a planar cellular automaton which is a simple model of a reaction-diffusion mechanism in excitable media; we are especially interested in the spatio-temporal organization which it generates. Under suitable assumptions, the sequence of the states of the plan is ultimately either stationary or periodic. In the latter case, we prove that there exists only one admissible period which is independent of the initial conditions and that a spatial organization of the plan appears, consisting of parallel equidistant target-wave-fronts growing with constant speed.     

Cohomology Rings of Aspherical Groups

It is shown by construction that the only restriction on theintegral cohomology ring of a finitely presented asphericalgroup is that it has dimension at most 2.     

Interaction of acetic acid with solid water

The interaction of acetic acid (AA, CH(3)COOH), with solid water, deposited on metals, tungsten and gold, at 80 K, was investigated. We have prepared acid/water interfaces at 80 K, namely, acid layers on thin films of solid water and H(2)O adlayers on thin acid films; they were annealed between 80 and 200 K. Metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy UPS(HeII) were utilized to obtain information on the electronic structure of the outermost surface from the study of the electron emission from the weakest bound MOs of the acids, and of the molecular water. Temperature-programmed desorption (TPD) provided information on the desorption kinetics, and Fourier-transformed infrared spectroscopy (FTIR) provided information on the identification of the adsorbed species as well as on the water and acid crystallization. The results are compatible with the finding of ref 1 (preceding paper), made on the basis of DFT calculations, that AA adsorbs on ice as cyclic dimers. Above 120 K, a rearrangement of the AA dimers is suggested by a sharpening of the spectral features in the IR spectra and by spectral changes in MIES and UPS; this is attributed to the glass transition in AA around 130 K. Above 150 K the spectra transform into those characteristic for polycrystalline polymer chains. This structure is stable up to about 180 K; desorption of water takes place from underneath the AA film, and practically all water has desorbed through the AA film before AA desorption starts. There is no indication of water-induced deprotonation of the acid molecules. For the interaction of H(2)O molecules adsorbed on amorphous AA films, the comparison of MIES with the DFT results of ref 1 shows that the initial phase of exposure does not lead to the formation of a top-adsorbed closed water film at 80 K. Rather, the H(2)O molecules become attached to or incorporated into the preexisting AA network by H bonding; no water network is formed in the initial stage of the water adsorption. Also under these conditions no deprotonation of the acid can be detected.     

Dynamic and acoustic response of bidirectionally stiffened plates with eccentric stiffeners subject to airborne and structure-borne excitations

An analytical method based on the modal expansion technique was developed to predict the vibro-acoustic response of both unidirectionally and bidirectionally stiffened flat panel. This paper presents the response to diffuse acoustic field (DAF) and turbulent boundary layer (TBL) excitations in terms of their joint acceptance. Numerical results for the dynamic and acoustic responses are compared with finite element method (FEM) and boundary element (BEM) results for stiffened panel with complex and eccentrically shaped stiffeners subject to point force excitation. A theoretical prediction of the transmission loss (TL) is also compared with laboratory measurements conducted on flat panels representing aircraft models as well as with hybrid statistical energy analysis (SEA)-FEM periodic model. The results confirm that the stiffened panel has the same acoustic response as the skin without stiffeners at frequencies where the structural wavelengths are equal to the spacing between the stiffeners. In addition, the transmission loss is lowered by the presence of the stiffeners at some particular region of frequencies below the critical frequency with respect to the unstiffened panel.     

Expressions of dissipated powers and stored energies in poroelastic media modeled by {u,U} and {u,P} formulations

This paper is devoted to the rigorous obtention of the energy balance in porous materials. The wave propagation in the porous media is described by Biot-Allard's {u,U} and {u,P} formulations. The paper derives the expressions for stored kinetic and strain energies together with dissipated energies. It is shown that, in the case of mixed formulations, these expressions do not correspond to the real and imaginary parts of the variational formulations. A quantitative convergence analysis of finite element scheme is then undertaken with the help of these indicators. It is shown that the order of convergence of these indicators for linear finite-element is one and that they are then well fitted to check the validity of finite-element models.     

Novel synthesis of 3-cyano-2-pyridones derivatives catalyzed by Au–Co/TiO2

Research on Chemical Intermediates - The current work described a new and highly selective method for the synthesis of substituted 3-cyano-2-pyridones scaffolds using gold-cobalt supported on TiO2...     

Theoretical and experimental investigations of complexation with BF3.Et2O effects on electronic structures,energies and photophysical properties of Anil and tetraphenyl (hydroxyl) imidazol

The novel compounds (E)‐2‐(((4‐hydroxyphenyl)imino)methyl)phenol, Tetraphenyl (hydroxyl) imidazole and their corresponding Boron difluoride complexes were synthesized and characterized by spectroscopic techniques. Density functional theory calculations at B3LYP‐D3/6–311++G (d, p) level of theory were performed for the geometric parameters. The MEP surface studies were used to understand the behavior of molecules in terms of charge transfer and to determine how these molecules interact. We used the GIAO and the B3LYP‐D3 with a 6–311++ G (d, p) basis set to simulate the (¹H‐NMR and ¹⁹F‐NMR) and the IR spectra, respectively. The corresponding calculated results are in good agreement with the experimental data. The stability of the molecule arising from hyperconjugation interaction and charge delocalization were analyzed using NBO analysis. FMOs revealed the occurrence of charge transfer within the molecule. The complexation using BF₃.Et₂O was also found to have remarkable effects on the electrochemical properties of the studied molecules, where (b) and (d) present lower chemical stability, higher reactivity and higher polarizability than (a) and (c), respectively. Moreover, the energy gap of (a) and (c) decreased after complexation using BF₃.Et₂O, indicating the reliability of the electrochemical evaluation of LUMO and HOMO energy levels. These values are the factors explaining the possible charge transfer interaction within the molecule. The absorption and emission spectra of the model compound were also simulated and compared to experimental observations in the DMF solvent. The results of DFT calculations supported the structural and spectroscopic data and confirmed the structure modification of frontier molecular orbitals for BF₂ complexes as well as tunable potentials and energy levels.     

Chitosan-Based Materials for the Removal of Nickel Ions from Aqueous Solutions

Russian Journal of Physical Chemistry A - Sorption of Ni(II) ions from liquid effluents utilizing chemically modified chitosan; (vanillin, polymer I) and (ortho-vanillin, polymer II) is studied...