Molecular modeling of particle reinforcement in elastomers: Effect of particle radius and volume fraction

Monte-Carlo simulations of the configurations of polymer chains in reinforced elastomers reveal extensive wrapping of the chains around particle clusters. The resulting increase in chain entanglement density leads to a 3.5 power law dependence of modulus on particle loading, in perfect agreement with experimental observation. Our model also gives a consistent molecular explanation of the Payne effect and the associated energy dissipation in strained reinforced elastomers.     

Evidence of sidewall covalent functionalization of single-walled carbon nanotubes and its advantages for composite processing

Single-walled carbon nanotubes (SWCNTs) were functionalized in a three-step procedure. The first step is a radical reaction creating a covalent bond between the carbon nanotube surface and grafted p-methoxyphenyl functional groups. In a second step, a deprotection of the methoxy functions generates free alcohol groups and in the final step an esterification is done in order to install a double bond for further polymerization. Evidence that functionalization has actually occurred on the SWCNT sidewalls is furnished through investigations involving several complementary techniques (visual dispersion tests, transmission electron microscopy, thermal gravimetric analysis and adsorption volumetry). We show that surface properties of SWCNTs are changed throughout the chemical treatments and that the obtained level of functionalization is low. Incorporation of functionalized SWCNTs in a polymer (poly(methyl methacrylate)) matrix was done through an in situ polymerization process. Observations of the obtained composites using scanning and transmission electron microscopy illustrate that interactions between the SWCNT surface and the polymer matrix are improved.     

Model of Water Application under Pivot Sprinkler. I: Theoretical Grounds

A model describing the application pattern produced by a single sprinkler is proposed. Based on calibrated statistical distributions and free from any ballistic consideration, this model uses a mixture of beta probability distributions in which parameters are first estimated with water application data measured in zero wind condition. Data measured in field conditions are then used to assess the wind effect on the shift of the center of gravity of the irrigated area, on the range of the sprinkler in various directions, and on the values of the beta distributions' parameters. The computation of the water application amounts at any point of the irrigated area is finally resolved in the use of a single equation, which can be easily implemented in a software package to simulate application patterns under a series of sprinklers attached to a center pivot or moving lateral irrigation machine.     

水性闪光底漆的制备与性能研究

采用水性聚丙烯酸或水性聚氨酯作为成膜基料,与水性闪光颜料、各种涂料添加剂等配制底漆。讨论了树脂和助剂的种类及其配比对颜料颗粒取向的影响。对涂膜的机械性能、闪光效果以及视觉丰满度、流平性、稳定性等的检测结果表明,漆膜具有良好的性能。     

Thermal aggregation of whey proteins in the presence of buttermilk concentrate

The objective of this study was to assess the impact of adding buttermilk concentrate to the denaturation and microparticulation process of cheese whey protein concentrate. For this purpose, the two concentrates were mixed and co-denatured (pH 4.6, 90 °C,) and homogenized. The presence of buttermilk significantly increased aggregation yield and decreased water-holding capacity of aggregates up to a buttermilk:whey protein ratio of 75:25. Modification of rheological properties suggests that denatured whey protein interacted with casein. A thiol blocker, N-ethylmaleimide, was added before heating to measure the role of disulphide bond formation in the aggregation process. Results showed that both covalent and non-covalent interactions were involved in aggregate formation. Ultrasound treatment was applied during denaturation process and was shown to influence aggregate formation. It appeared that under increased turbulence and cavitation conditions, aggregation yield was increased and water-holding capacity decreased.     

Tribological properties of fluid phase phospholipid bilayers

Our recent studies showed that solid phase phospholipid bilayers play an important role in joint lubrication mechanism. We investigate the tribological properties of fluid phase bilayers depending on various experimental parameters. Bilayers containing a fluorescent lipid with a large head-group and surfaces covered with only one bilayer poorly lubricate meaning that the slip plane during shear is located in the thin aqueous layer between the bilayers. Lubrication and resistance to normal and tangential stresses are greatly improved in buffered saline solution. Bilayers prepared by vesicle fusion method improve the tribological properties of even very rough substrates by smoothing their topographical defects.     

Microoptical elements for single mode fibre arrays free-space interconnections

The purpose of this paper is to investigate the performance of microoptics for telecommunication systems using free-space interconnects. This concerns mainly distribution or switching and routing tasks. In order to evaluate the interconnection capability of free-space microoptics, we impose severe conditions on the interconnects. These conditions correspond to the use of single mode fibre arrays at both the input and the output systems. This point is shown to become very critical when dealing with optical switches involving reconfigu-rable links. These points are illustrated by two examples : one with fixed and the other with reconfigurable interconnects but both using arrays of microoptical elements.