Theoretical infrared line shapes of H‐bonds within the strong anharmonic coupling theory and Fermi resonances effects

In this article, we extend a previous work toward presenting a theoretical study of the effects of Fermi resonances and the fundamental anharmonic coupling parameter α between the high‐frequency mode and the H‐bond bridge. The model incorporates (i) both intrinsic anharmonicities of the fast mode (double well potential) and the H‐bond Bridge (Morse potential), (ii) strong anharmonic coupling theory, (iii) Fermi resonances by the aid of an anharmonic coupling between the fast mode and one or several harmonic bending modes, (iv) quadratic modulation of both the angular frequency and the equilibrium position of the X? …Y stretching mode on the intermonomer ? H… motions, and (v) the quantum direct (fast and bending modes) and indirect dampings (slow mode). The IR spectral density is obtained by Fourier transform of the autocorrelation function of the transition dipole moment operator of the X? H bond. The numerical calculation shows that Fermi resonances generate very complicated profiles with multisubstructure and also provide a direct evidence of Fermi resonances which were predicted to be a major feature of H‐bonds. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Photocatalytic degradation of an azo reactive dye,Reactive Yellow 84, in water using an industrial titanium dioxide coated media

The photocatalytic degradation of an azo reactive dye, Reactive Yellow 84 (RY84), in aqueous solutions using industrial titanium dioxide coated non-woven paper was studied. The experiments were carried out to investigate the factors that influence the dye photocatalytic degradation, such as adsorption, initial concentration of dye, temperature, and solution pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetics constant of degradation. The photocatalytic degradation rate was favored by a high concentration of solution in respect to Langmuir–Hinshelwood model. The degradation was enhanced by the temperature and was favored in acidic pH range.     

A nonlocal Levinson beam model for free vibration analysis of zigzag single-walled carbon nanotubes including thermal effects

A nonlocal Levinson beam model is developed to study the free vibrations of a zigzag single-walled carbon nanotube (SWCNT) in thermal environments. The equivalent Young’s modulus and shear modulus for a zigzag SWCNT are derived using an energy-equivalent model. The present study illustrates that the vibration characteristics of an SWCNT are strongly dependent on the temperature change and on the chirality of a zigzag carbon nanotube. The investigation of the chirality and temperature effects on free vibration of carbon nanotubes may be used as a useful reference for the application and the design of nanoelectronic and nanodrive devices, nano-oscillators, and nanosensors, in which carbon nanotubes act as basic elements.     

Averaging and periodic solutions in the plane and parametrically excited pendulum

We first approximate the solutions of the nonautonomous oscillating suspension point pendulum equation by the solutions of a second order autonomous differential equation. Using the strict monotonicity of the periodic solutions of the approximating equation, we prove the existence of a large number of subharmonic periodic solutions of the plane pendulum when its point of suspension is excited parametrically.     

Continuum modeling for the modulated vibration modes of large repetitive structuresModèle continu pour les modes de vibrations modulés des longues structures répétitives

By homogenization theory, one can predict the vibrations of long repetitive structures in the low frequency range. Beyond this range, many modes have a modulated shape. Based on a multiple scale analysis, a continuum model is presented, that is able to account for this class of modes. This model involves a real coefficient that can be computed from the finite element resolution of problems defined on a few basic cells. An application in 2D elasticity is presented. To cite this article: E.M. Daya et al., C. R. Mecanique 330 (2002) 333–338.     

Antifungal activity and phytochemical screening of extracts from Phoenix dactylifera L. cultivars

In this study, the rachis extracts of eight date palm Phoenix dactylifera L. cultivars were analysed by phytochemical screening and bioautography on Fusarium oxysporum f. sp. albedinis (Foa). The choice of cultivars was based on their reaction to Foa (resistant, tolerant and sensitive). Phytochemical screening was realised for flavonoids, tannins, alkaloids and coumarins. Antifungal effects were mostly represented by dichloromethanic extracts (seven out of nine inhibition zones). The best results were represented by the dichloromethanic extract of the cultivar 'Bent-Cherk' rachis (6.50?±?1.41?mm) and the ethyl acetate extract of the cultivar 'Rotbi' rachis (6.00?±?1.41?mm). The date palm cultivars presented some similarities concerning phytochemical screening results related to their resistance or sensibility to Foa. From the correlation between phytochemical screening and bioautography, it was observed that the majority of bioactive compounds against Foa seem to be polyphenols. Thus, the natural defence mechanism in vivo against Foa is probably related to the action of polyphenols. The difference between resistant, tolerant and sensitive cultivars is related to their mechanism of action.     

Enterprise security economics: A self‐defense versus cyber‐insurance dilemma

We propose a model that optimizes enterprise investments in cybersecurity using expected utility theory. The model allows computing (a) investment in self‐defense to reduce the risk of security breaches, (b) investment in cyber insurance to transfer the residual risk to insurance companies, and (c) investment in forensic readiness to make the insured firms capable of generating provable insurance claims about security breaches. A three‐phase–based model of vulnerability rate evolution over time is proposed and used to estimate the different planned security expenditures throughout the investment horizon. At the starting time of investment, a decision maker invests to cover the existing risk of breach and periodically spends to cover the additional risk observed due to the release of new vulnerabilities. In this work, the intermediate tranches are determined while considering three different attitudes of decision makers, namely, optimistic, pessimistic, and realistic. An analysis is conducted to assess the performance of the proposed models.     

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.     

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.     

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.