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排序方式: 共有113条查询结果,搜索用时 15 毫秒
1.
Tagouegni Senghor Fotsa-Ngaffo Fernande Kenfack-Jiotsa Aurélien 《Optical and Quantum Electronics》2022,54(3):1-57
Optical and Quantum Electronics - In the past few decades, the academic research and industrial synergy is dramatically accelerating to conceptualize high data rate services. The congestion in the... 相似文献
2.
Dr. Marvin Langlais Dr. Nicolas Baulu Dr. Séverin Dronet Dr. Charlotte Dire Dr. François Jean-Baptiste-dit-Dominique Dr. David Albertini Dr. Franck D'Agosto Dr. Damien Montarnal Dr. Christophe Boisson 《Angewandte Chemie (International ed. in English)》2023,62(41):e202310437
Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR-b-PE diblock copolymers were synthesized using the {Me2Si(C13H8)2Nd(BH4)2Li(THF)}2 complex in combination with n-butyl,n-octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi-crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl-1,5-di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization-driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers. 相似文献
3.
Cedric Samuel Yvan Chalamet Fernande Boisson Jean‐Charles Majesté Frédéric Becquart Etienne Fleury 《Journal of polymer science. Part A, Polymer chemistry》2014,52(4):493-503
A one‐step process is reported to directly synthesize blends of poly(trimethylene carbonate) (PTMC) with a modified granular starch. Trimethylene Carbonate (TMC) ring‐opening polymerization is performed in the presence of native starch particles in bulk conditions at 150 °C and the efficiency of metal‐free organic catalysts (TBD and phosphazene superbases P1‐t‐Oct, P2‐t‐bu, and P4‐t‐bu) are investigated to replace the organo‐metallic stannous octanoate initiator. TMC monomer is successively converted into PTMC and the robustness of organic catalysts is highlighted with significant activities at very low concentrations (<100 ppm), where stannous octanoate is inefficient. Reactivity of starch toward TMC ROP is deeply investigated by NMR techniques and a starch‐graft‐PTMC is indirectly evidenced. Starch substitution degree reaches 0.9% indicating that PTMC grafting only occurs at the surface of swollen granular starch. PTMC graft length from the starch surface remained low in the range 2–12 and model ROP reactions highlight the role of TMC hydrolysis on PTMC graft length. Despite low PTMC grafts, a fine dispersion of intact starch particles into the PTMC matrix is evidenced. Consequently, metal‐free organic catalysts at low concentrations are promising candidates for synthesizing blends of PTMC with high loadings of surface‐modified starch (32% by weight) in 2 min within a one‐step process. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 493–503 相似文献
4.
A. Kourta B. Michel H. C. Boisson P. Gajan A. Strzelecki 《Flow, Turbulence and Combustion》2013,91(1):157-175
An unsteady RANS model is developed in order to simulate the complex situations involving both free and bounded flows. This model tuned to catch coherent flow structures is developed both in the k-ε and k-l approaches. The full 3D geometry of a round jet exiting from a reservoir into a pipe has been computed. Periodic conditions are applied in order to compare with an experiments consisting of eight jets exiting in a cross pipe flow. Improvement has been obtained with this URANS turbulence model compared to RANS and good agreement compared with experiment has been obtained. Unsteady phenomena are reproduced by the model and provide more insight into the physical properties of the flow and of the transport of a passive scalar. 相似文献
5.
6.
Marie‐France Llauro Julien Loiseau Fernande Boisson Frdric Delolme Catherine Ladavire J. Claverie 《Journal of polymer science. Part A, Polymer chemistry》2004,42(21):5439-5462
Low‐molecular‐weight poly(acrylic acid) (PAA) was synthesized by reversible addition fragmentation chain transfer polymerization with a trithiocarbonate as chain‐transfer agent (CTA). With a combination of NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, the PAA end‐groups of the polymer were analyzed before and after neutralization by sodium hydroxide. The polymer prior to neutralization is made up of the expected trithiocarbonate chain‐ends and of the H‐terminated chains issued from a reaction of transfer to solvent. After neutralization, the trithiocarbonates are transformed into thiols, disulfides, thiolactones, and additional H‐terminated chains. By quantifying the different end‐groups, it was possible to demonstrate that fragmentation is the rate limiting step in the transfer reaction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5439–5462, 2004 相似文献
7.
Aharonian F Akhperjanian AG Barres de Almeida U Bazer-Bachi AR Becherini Y Behera B Beilicke M Benbow W Bernlöhr K Boisson C Bochow A Borrel V Braun I Brion E Brucker J Brun P Bühler R Bulik T Büsching I Boutelier T Carrigan S Chadwick PM Charbonnier A Chaves RC Chounet LM Clapson AC Coignet G Costamante L Dalton M Degrange B Deil C Dickinson HJ Djannati-Ataï A Domainko W Drury LO Dubois F Dubus G Dyks J Egberts K Emmanoulopoulos D Espigat P Farnier C Feinstein F Fiasson A Förster A Fontaine G 《Physical review letters》2008,101(17):170402
In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived. 相似文献
8.
Nicolas Dargère Véronique Bounor-Legaré Fernande Boisson Philippe Cassagnau Grégory Martin Phillipe Sonntag Nicolas Garois 《Journal of Sol-Gel Science and Technology》2012,62(3):389-396
Hydridosilazane compounds containing Si–N and Si–H bonds can be used as precursors of SiOx materials. The hydrolysis-condensation reactions of tetramethyldisilazane, as a polyhydridosilazane model compound, were
investigated by 1H and 29Si liquid NMR spectroscopy. These reactions were carried out at room temperature for up to 120 min in presence of water. The
identified products are short linear siloxane species (hydride terminated polydimethylsiloxanes MHDxMH) and cyclosiloxanes. Silicon hydride persistence in the reactional mixture suggested that silazane group is more sensitive
to hydrolysis reaction than silicon hydride group. Moreover, additional experiments evidenced that the low steric hindrance
of the silicon hydride influences the silazane hydrolysis kinetic. Hence the presence of ammonia released during silazane
hydrolysis reaction was demonstrated to be a catalyst of the silicon hydride hydrolysis reaction. 相似文献
9.
Jean-Charles Boisson Laetitia Jourdan El-Ghazali Talbi Dragos Horvath 《Journal of Mathematical Modelling and Algorithms》2010,9(2):195-208
In this article, the impact of single-objective methods as intensification factors in a multi-objective approach is presented
for the flexible docking problem. Based on a novel tri-objective model, a parallel multi-objective genetic algorithm has been
designed. However, due to the high variability of the energy objective, intensification methods focused on this objective
have been also included in order to improve the convergence speed of the genetic algorithm and the quality of the results.
The corresponding approach, combining single- and multi-objective methods, has been proved efficient according to the tested
instances and the quality criterion used. 相似文献
10.
Han MK Wu YQ Kramer M Vatovez B Grandjean F Long GJ Miller GJ 《Inorganic chemistry》2006,45(26):10503-10519
Ternary rare-earth iron silicides RE(2-x)Fe4Si(14-y) (RE = Y, Gd-Lu; x approximately equal to 0.8; y approximately equal to 4.1) crystallize in the hexagonal system with a approximately equal to 3.9 A, c approximately equal to 15.3 A, Pearson symbol hP20-4.9. Their structures involve rare-earth silicide planes with approximate compositions of "RE1.2Si1.9" alternating with beta-FeSi2-derived slabs and are part of a growing class of rare-earth/transition-metal/main-group compounds based on rare-earth/main-group element planes interspersed with (distorted) fluorite-type transition-metal/main-group element layers. The rare-earth silicide planes in the crystallographic unit cells show partial occupancies of both the RE and Si sites because of interatomic distance constraints. Transmission electron microscopy reveals a 4a x 4b x c superstructure for these compounds, whereas further X-ray diffraction experiments suggest ordering within the ab planes but disordered stacking along the c direction. A 4a x 4b structural model for the rare-earth silicide plane is proposed, which provides good agreement with the electron microscopy results and creates two distinct Fe environments in a 15:1 ratio. Fe-57 M?ssbauer spectra confirm these two different iron environments in the powder samples. Magnetic susceptibilities suggest weak (essentially no) magnetic coupling between rare-earth elements, and resistivity measurements indicate poor metallic behavior with a large residual resistivity at low temperatures, which is consistent with disorder. First-principles electronic-structure calculations on model structures identify a pseudogap in the densities of states for specific valence-electron counts that provides a basis for a useful electron-counting scheme for this class of rare-earth/transition-metal/main-group compounds. 相似文献