Controlled synthesis of crosslinked polyamide 6 using a bis-monomer derived from cyclized lysine

The controlled synthesis of polyamide 6 chemical networks by anionic ring-opening copolymerization of ε-caprolactam (CL) with synthesized bis-ε-caprolactam derived from α-amino-ε-caprolactam, i.e. N-functionalized α-amino-ε-caprolactam bis-monomers, using sodium ε-caprolactamate as an initiator and hexamethylene-1,6-dicarbamoylcaprolactam as di-functional fast activator was examined in bulk at 140 °C. An urea-based bis-monomer and CL were first shown to copolymerize with a decreasing polymerization rate due to side reactions. On the contrary, quantitative copolymerization of CL with various amounts of bis-N(2-oxo-3-azepanyl)-1,6-tetramethylenediamide, an amide-based bis-monomer, leads to fast kinetics similar to the homopolymerization of CL. Crosslinked PA6 with network exhibiting elastic or viscoelastic behaviors, depending on the amount of crosslinker, were observed and characterized by swelling in hexafluoroisopropanol, dynamic mechanical analysis and rheology measurements. Crystallinity and swelling were shown to decrease with the increasing content of the crosslinking agent.     

In situ characterization of floc morphology by image analysis in a turbulent Taylor–Couette reactor

Flocculation of bentonite was performed in a turbulent Taylor–Couette reactor under various shear rates. Image processing enabled to determine various morphological characteristics of individual flocs. Not only their mean values but also their distributions were studied under various hydrodynamic conditions. Relevant properties were selected. The temporal evolution of radius of gyration and circularity distributions was monitored during the flocculation process. Although size and shape are obviously correlated, this article points out that their dependency to hydrodynamics is different, showing that flocs of similar sizes produced under different hydrodynamic conditions exhibit different shapes. The sizes are calibrated by the turbulence as the double radius of gyration is close to Kolmogorov microscale, whereas the circularity seems correlated to the rotation speed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2389–2403, 2014     

High energy resolution five-crystal spectrometer for high quality fluorescence and absorption measurements on an x-ray absorption spectroscopy beamline

Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1-2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.     

Flexible‐elastic copolymerized polyurethane‐tannin foams

Open cell foams obtained by the simultaneous coreaction of condensed flavonoid tannins with an alkoxylated fatty amine and polymeric diphenylmethane isocyanate yielded highly flexible/elastic polyurethane foams. Copolymerized amine/isocyanate/tannin oligomers were identified by ¹³C NMR and MALDI‐TOF spectroscopy. In general, between 30% and 50% of natural tannins is added to the components used to obtain polymerisation of the polyurethane. The characteristic of these new, partially biosourced polyurethanes is that the tannin present slows down burning, some of them can be made flame self‐extinguishing and if burning they neither flow nor asperge flaming material around, contrary to what occurs with normal polyurethanes. This limits the possibility of transmitting fire to other materials in the same environment. Cyclic compression tests were carried out showing that after 50 cycles foam recovery was in excess of 80%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40499.     

Contribution to understanding parabolic oxidation kinetics of dilute alloys. Part II: Oxides with metal deficit or oxygen excess

Concerning the parabolic oxidation of alloys with a low content of a different valence element it is shown that the Wagner-Hauffe valence approach contains some inaccuracies. This paper is devoted to the growth of an oxide MO with metal deficit or oxygen excess. The case is developed where the doping is high enough to modify the defect concentrations over the entire oxide scale. It is shown that lower-valence metal additions decrease the scaling constant and modify the influence of oxygen pressure. For additions of higher-valence metals, as long as electronic conductivity remains over the whole scale, the limiting step might be the diffusion of ionic defects under only an electric field, with an increase of the scaling constant. When the conductivity becomes essentially ionic over the whole scale the limiting step might be the diffusion of electron holes, and the scaling constant will decrease with an increase in the doping level. Globally the parabolic constant might therefore increase and pass through a maximum before decreasing.     

Dynamic characterization of machining systems

In the working space model of machining, an experimental procedure is implemented to determine the elastic behaviour of the machining system. In this paper, a dynamic characterization and vibration analysis has long been used for the detection and identification of the machine tool condition. The natural frequencies of the lathe machining system are required (Ernault HN400??France) according to three different situations with no cutting process are acquired. The system modal analysis is used to identify the natural frequencies. These frequencies are then compared to the ones obtained on the spindle numerical model by finite element method. This work is validated by experimental tests based on measures of the lathe machine tool frequencies domain. The main objective is to identify a procedure giving the natural frequency values for the machine tool components, in order to establish a better condition in the cutting process of the machine tool.     

Finite element model of the contact between a vibrating conductor and a suspension clamp

Aeolian vibrations may lead to failure of the overhead conductors of electrical transmission lines. Damages are caused by fretting fatigue at the attachment position of pieces of hardware. This phenomenon depends much on contact mechanics. The contact between a wire and a suspension clamp, a critical location, was modelled using the finite element method. Results from strain measurements on vibrating conductors served as input. The numerical results gave estimates of stresses and slip amplitudes. We can use these results to compute crack initiation criteria. The Ruiz and Chen criterion was chosen here and results compared well with experimental data.     

驱动LED串的DCM升压转换器简化分析（2）——实际考虑

固定频率升压转换器采用不连续导电模式（DCM）工作,能够有效地用于快速调光操作,提供比采用连续导电模式（CCM）工作的竞争器件更优异的瞬态响应,这种转换器非常适合于以恒流模式驱动LED串。但驱动LED的升压转换器的交流分析,跟使用标准电阻型负载的升压转换器的交流分析不同,在推导最终的传递函数时必须非常审慎。本文分为两个单元：⑴理论分析,介绍如何推导驱动LED串的升压转换器的小信号响应;⑵实际考虑,深入研究实施方案,并验证经验结果及与理论推导比较。     

Electron spin resonance measurement of nitroxy probes mobility,attached to a polymer through a spacer arm

Summary Stable nitroxide radical probes are attached to styrene-divinylbenzene gel type resins through spacer arms, the length of which being 1 to 7 methylene groups. Results of electron spin resonance analysis which allows to estimate the local viscosity are discussed. Mobility of the nitroxide probes generally increases with the number of CH₂ groups, the effect being compared to a decrease of cross-linking density.     

Effects of the “pays de bray” fault on fluid paleocirculations in the Paris basin dogger reservoir, France

Clay fractions and fluid inclusions were studied in the Aulnay sous Bois and Cerneux (CER-1 and CER-P6) wells located 10 km, 1.3 and 0.6 km, respectively, from the “Pays de Bray” fault (Paris Basin, France). It was shown that a connection was probably established between the Dogger and Triassic reservoirs during the active period of the fault. Chemical and heat transfers have locally modified the diagenesis conditions in the Dogger formation, inducing an overmaturation of clay minerals. These effects, although attenuated, are still identifiable in the Aulnay and CER-1 wells. A maximum temperature of about 90°C was maintained in CER-P6 site even during the uplift stage of the basin.