Dynamic stability and bifurcation in a bundle flow

In roll draft operation mechanisms, the behavior of floating fibers is known to cause the thickness variation in output fiber bundles. Despite the significance of this phenomenon, few studies have sought to explain the underlying mechanism theoretically. We analyzed the dynamic characteristics of bundle flow in roll draft systems, based on a model of bundle flow. By applying both linear stability and phase plane analyses, we investigated an occurrence of draft waves. Our results suggest that the principles of linear stability can be applied to analyze bundle flow dynamics. The nonlinearity of bundle flow, however, reveals that the stable fixed point disappears when draft ratio changes, which in turn implies that the topological structure of the phase portrait changes as the process parameter is varied: a bifurcation property. As the process parameter increases above certain critical values, fixed points are destroyed and oscillations within the limit cycle occur. Also the system oscillates at a critical draw ratio harmonically, indicating the onset of a Hopf bifurcation, which corresponds to the draft wave. The phase portrait converges to a shell-shaped curve if the process parameter increases further. The results of this study also show that there is a specific draft ratio below which flow is always stable.     

Identification of a novel series of alkylitaconic acids in wood cultures of Ceriporiopsis subvermispora by gas chromatography/mass spectrometry.

A novel series of long-chain unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C-3 position of itaconic acid has been identified by gas chromatography/mass spectrometry during in vitro decay of eucalypt wood by the white-rot basidiomycete Ceriporiopsis subvermispora. The major compounds were identified as tetradecyl-, 7-hexadecenyl- and hexadecylitaconic acids by their mass fragmentation patterns. Other members of the same compound series, identified as dodecanyl-, tridecanyl-, tetradecenyl-, pentadecanyl-, octadecenyl- and octadecanylitaconic acids, were present in very minor amounts or traces. Whereas hexadecenylitaconic acid has already been reported in cultures of C. subvermispora, to our knowledge this is the first report of the presence of the other alkylitaconic acids in fungal cultures. These new alkylitaconic-type metabolites may constitute a source for peroxidizable lipids involved in lignin degradation during wood decay by C. subvermispora and other white-rot basidiomycetes.     

Solutions faibles H2 pour un modèle de fluide non newtonien

This Note is devoted to the study a non-linear system modelling a flow of a non-Newtonian fluid, namely aqueous polymer solutions. In the present work, we prove a theorem on the existence of weak solutions for the steady-state problem in a bounded or exterior plane domain. A first difficulty is due to the fact that we search these solutions in the natural space given by the energy inequalities. The second difficulty stems from the fact that the non-linear term involves a third-order derivative, whereas its elliptic term is only a Laplace operator. To cite this article: C. Amrouche, E.-H. Ouazar, C. R. Acad. Sci. Paris, Ser. I 341 (2005).     

Synthesis,crystal structure,magnetic properties and second harmonic generation of a new noncentrosymmetric coordination compound:Triaqua(4-amino-6-methoxypyrimidine) cuprate(Ⅱ)sulfate

The chemical preparation, crystal structure and infrared spectroscopic characterization of the triaqua(4-amino-6-methoxypyrimidine) cuprate(II) sulfate, [Cu(C_5H_7N_3)(H_2O)_3]SO_4, is reported. The compound crystallizes in the noncentrosymmetric orthorhombic space group P2_12_12_1 with lattice parameters a = 7.9025(3), b = 11.1189(4), c = 12.9720(4) , V = 1139.81(7) ~3 and Z = 4. The Cu(II) cation is fivecoordinated, in an early half-way between square pyramidal and trigonal bipyramidal fashion, by two nitrogen atoms of the 4-amino-6-methoxypyrimidine ligand and three water oxygen atoms. In the atomic arrangement, the organic ligands and the 5-connected Cu centers are linked with each other to give a 1-D corrugated hybrid chain running along the b-axis direction. The chains are interconnected by the SO_4~(2-) anions via O–H...O, O–H...S, C–H...O and N–H...O hydrogen bonds to form layers spreading parallel to the(011) plane. The vibrational absorption bands were identified by infrared spectroscopy. Quantitative measurements of the second harmonic generation(SHG) of a powdered sample at 1064 nm were performed and a relative efficiency of 5.2 times the KDP standard was observed. Magnetic properties were also defined to characterize the complex. Magnetic measurements revealed that this material had a onedimensional antiferromagnetic character. The magnetic parameters were g = 2.11 and 2J/k B = -36 K.     

Speech enhancement in dual-microphone mobile phones using Kalman filter

In this paper, a dual-microphone speech enhancement algorithm for the mobile phones is proposed. The adopted method exploits the coherence function algorithm and the Kalman filter. This algorithm has a simple implementation that does not need a prediction of interfering signals statistics. In addition, this algorithm can be used in small devices with so closely distance between the two microphones. Moreover, the use of such algorithm allows reducing multiple noise sources at many azimuths positions. Finally, the new algorithm proves its performances referring to the perceptual evaluation of speech quality and the time domain waveforms.     

Solubility of some phenolic compounds in aqueous alkali metal nitrate solutions from (293.15 to 318.15) K

This paper is continuation of the study concerning the solubility-temperature dependence data for some phenolic compounds (PhC), contained in olive mill wastewater (OMWW), in two nitrate salts (KNO₃ and NaNO₃) aqueous solutions. The solubilities of PhC were determined in the temperature ranging from (293.15 to 318.15) K. It has been observed that the solubility, in aqueous nitrate solutions, increases with increasing temperature. Results showed that alkali metal nitrate has a salting-out effect on the solubility of PhC. The effect of the anion of the electrolyte on the solubility of PhC is observed by comparing these results with values reported in the previous papers for the effect of LiCl, NaCl and KCl. For each cation, the solubilites of the phenolic compounds are higher with nitrate anion than with chloride anion. Results were interpreted in terms of the salt hydration shells and the ability of the solute to form hydrogen-bond with water. The solubility data were accurately correlated by a semi empirical equation. The standard molar Gibbs free energies of transfer of PhC (Δ_trG^°) from pure water to aqueous solutions of the nitrate salts have been calculated from the solubility data. The decrease in solubility is correlated to the positive Δ_trG^° value which is mainly of enthalpic origin.     

Synthesis and characterization of a new monophosphate (C<Subscript>6</Subscript>H<Subscript>16</Subscript>N<Subscript>2</Subscript>)(H<Subscript>2</Subscript>PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Chemical preparation, crystal structure, and NMR spectroscopy of a new trans-2,5-dimethylpiperazinium monophosphate are given. This new compound crystallizes in the triclinic system, with the space group P-1 and the following parameters: a = 6.5033(3), b = 7.6942(4), c = 8.1473(5) Å, α = 114.997(3), β = 92.341(3), γ = 113.136(3), V = 329.14(3) ų, Z = 1, and D_x = 1.565 g cm^?3. The crystal structure has been determined and refined to R = 0.030 and R _w(F ²) = 0.032 using 1558 independent reflections. The structure can be described as infinite [H₂PO₄] _n ^n? chains with (C₆H₁₆N₂)²⁺ organic cations anchored between adjacent polyanions to form columns of anions and cations running along the b axis. This compound has also been investigated by IR, thermal, and solid-state, ¹³C and ³¹P MAS NMR spectroscopies and Ab initio calculations.     

Study of charge transport in P3HT:SiNW-based photovoltaic devices

Hybrid devices based on silicon nanowires (SiNWs) dispersed in a conjugated polymer poly(3-hexylthiophene) P3HT thin films have been realized. The carrier transport mechanism in inorganic/organic hybrid nancocomposites consisting of SiNW dispersed in P3HT layer was investigated by using I?CV characteristics and impedance spectroscopy measurements. The conduction mechanism in these hybrid nanocomposites has been identified to be thermionic emission at the interfaces. The electrical parameters of the structure have been investigated by modelization of the I?CV characteristics using an electrical equivalent circuit and have been extracted for the different SiNW volume ratios. The barrier height, the series resistance and the shunt resistance values of the diodes have been calculated as about 0.9 eV, several k?? and several M??, respectively. The diode behaves as non-ideal one because of the series resistance and the Donor/Acceptor interface layer. The impedance spectroscopy study, in the frequency range 100 Hz?C100 kHz, shows a typical behavior of disordered materials and indicative of a hopping transport in the investigated temperature range. The dc conductivity follows the Arrhenius law with an activation energy transition from 8.4 to 55.8?meV at about 294 K.