Nonlinear friction dynamics on fibrous materials,application to the characterization of surface quality. Part I: global characterization of phase spaces

The diversity and the complexity of fibrous materials (woven fabrics, nonwovens or knitted fabrics) make the control of surface qualities very difficult. The control and the comprehension of the tribological phenomena generated by a dynamic friction are of major importance. Whereas the traditional investigations such as measurements of average parameters like roughness or friction coefficient quickly find their limits on such deformable, heterogeneous and flexible fibrous surfaces with very heterogeneous relief, this series of two publications proposes a new manner of observing the interactions of friction. Our laboratory has developed a patented method of measurements, called MODALSENS, which aims at rubbing a very fine and flexible blade on the analyzed surface. Dynamic friction with the contact generates nonlinear vibrations, and the response of the sensor is analyzed in its phase space using the tools of nonlinear analysis of time series. Then, when the evaluated surfaces change, this first part endeavors to characterize the portraits of phases related to the nonlinear vibrations of MODALSENS in a global way, by quantifying its invariants such as dimensions, Shannon entropies, diameters of attractors and largest Lyapunov exponents. From this first part, a classification of studied fibrous surfaces is built and is expected to give rise to new estimators for the surface quality analysis of fibrous media.     

Structure of near wall turbulence downstream of a wall mounted protrusion: an interesting Reynolds stress suppression phenomena

A local suppression in the generation of near wall Reynolds stress is achieved by modifying the buffer region and sublayer (y ⁺ <30) of a turbulent pipe flow with a 16.4 wall unit high wall mounted protrusion. Multi-component, multi-point, time resolved laser Doppler velocimetry measurements are made in the undisturbed and modified ARL/PSU glycerin tunnel pipe flow at a Reynolds number of approximately 10000. A downstream converging flow field is produced by the divergence of the approaching mean flow around the protrusion. A pair of counter-rotating vortices, 15 wall units in diameter with common flow down, are generated by the protrusion and also contribute to the wall directed flow convergence. The convergence region is 15 wall units high and more than 100 wall units long and appears to decouple the near wall region from the outer turbulent wall layer. Locally, turbulent velocity fluctuations in the form of Reynolds stress producing events, sweeps and ejections, are retarded within this region. This results in a reduction in near wall uv Reynolds stress and local wall shear. Interestingly, the counter-rotating vortices act to increase turbulent diffusion in a manner which is uncorrelated with Reynolds stress generation.     

Thermotropic Luminescent Clustomesogen Showing a Nematic Phase: A Combination of Experimental and Molecular Simulation Studies

Octahedral Mo₆ nanoclusters are functionalized with two organic ligands containing cyanobiphenyl (CB) units, giving luminescent hybrid liquid crystals (LC). Although the mesogenic density around the bulky inorganic core is constant, the two hybrids show different LC properties. Interestingly, one of them shows a nematic phase, which is particularly rare for this kind of supermolecular system. This surprising result is explained by using large‐scale molecular dynamic simulations.     

Radiation induced synthesis of silver nanoshells formed onto organic micelles

Synthesis of metal nanoshells around organic micelles is achieved through radiolysis of aqueous solutions of surfactant self-assembled in spherical micelles and metal ions. The formation of the metal nanoshells is evidenced by UV-visible spectroscopy and Small Angle X-ray Scattering.     

Assessment of PBE0 for evaluating the absorption spectra of carbonyl molecules

Using the parameter‐free PBE0 hybrid functional, we compute the UV/Vis spectra of a series of solvated compounds presenting a carbonyl chromophoric unit linked to a carbon–carbon double bond. It turns out that PBE0 is extremely efficient for accurately reproducing experimental values, with a mean unsigned error of 7 nm for an extended set of compounds, although no fitting or statistical treatments are performed. PBE0 has a predictive efficiency comparable to the well‐known Woodward–Fieser empirical formula, and can therefore be used to extend these rules without requiring additional experimental results. Consequently, the UV/Vis spectra of several compounds that have not yet been synthesized are predicted. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Characterization by X-ray diffraction and electron microscopy of GaInAs and GaAsN single layers and quantum wells grown on GaAs

Experiments were performed on thick GaInAs and GaAsN layers and on GaInAs quantum wells grown on (1 1 1)B and (0 0 1) GaAs substrates. The aim of this work is to develop an experimental procedure in order to evaluate the chemical compositions and relaxation state of the samples at global as well as nanometre scale. Chemical analyses (EDS, RBS, etc.), X-ray diffraction (reciprocal space map, sin²ψ, etc.) and XTEM were carried out.The validity of the sin²ψ method on the above mentioned thin layers has been tested. Good accuracy is obtained for In and N composition but more work has to be done in order to optimize the determination of the relaxation state. Coupling TEM observations to these calculations gives valuable information on the relaxation mechanisms (misfit dislocations, stacking faults, microtwins, etc.).     

32 Phase X 32 amplitude optical arbitrary waveform generation

We describe the precise shaping and mode-resolved amplitude and phase characterization of optical arbitrary waveforms by using a 20 GHz optical frequency comb and integrated 64 x 20 GHz channel arrayed waveguide grating pair. Complex waveforms with large variations in phase and amplitude between adjacent modes were generated and characterized.     

Synthesis of ω‐phosphonated poly(ethylene oxide)s through the combination of kabachnik–fields reaction and “click” chemistry

The synthesis of new ω‐phosphonic acid‐terminated poly(ethylene oxide) (PEOs) monomethyl ethers was investigated by the combination of Atherton–Todd or Kabachnik–Fields reactions and the “click” copper‐catalyzed 1,3‐dipolar cycloaddition of azides and terminal alkynes. The Atherton–Todd route fails to give the corresponding phosphonic acid‐terminated PEOs due to competitive cleavage of the P? N bond during the dealkylation step. In contrast, the Kabachnik–Fields route leads with very good yields to ω‐phosphonic acid‐PEO through “click” reaction of azido‐PEO onto dimethyl aminopropargyl phosphonate prepared by Kabachnik–Fields reaction between propargylbenzylimine and dimethyl phosphonate, followed by acidic hydrolysis. The reported methodology, precluding the use of anionic polymerization of ethylene oxide, leads to novel well‐defined phosphonic acid‐terminated PEOs from commercially available products in good yields. Moreover, such a strategy can be adapted to anchor phosphonic acid functionality onto a wide range of polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013