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排序方式: 共有66条查询结果,搜索用时 31 毫秒
1.
We investigated the photoluminescence (PL) properties of carbon nitride films (CNx) deposited by rf magnetron sputtering and compared them to their microstructure depending on the target self-bias. While many of the data are compatible with ‘a-C:H like’ PL properties the observed variation of the PL efficiency η with respect to the target bias cannot be easily explained by the standard models. It is suggested that the observed variation of η is rather dominated by a change in microstructure which depends on the bombardment intensity during growth than by the concentration of non-radiative centres. 相似文献
2.
Dr. Luke D. Elliott Dr. Jonathan P. Knowles Dr. Paul J. Koovits Katie G. Maskill Michael J. Ralph Dr. Guillaume Lejeune Lee J. Edwards Richard I. Robinson Ian R. Clemens Brian Cox David D. Pascoe Guido Koch Martin Eberle Malcolm B. Berry Prof. Kevin I. Booker‐Milburn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(46):15226-15232
The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20 % lower than that of batch, whereas three‐layer reactors were 20 % more productive. Finally, the utility of flow chemistry was demonstrated in the scale‐up of the ring‐opening reaction of a potentially explosive [1.1.1] propellane with butane‐2,3‐dione. 相似文献
3.
Xavier Cattoën Achraf Noureddine Jonas Croissant Nirmalya Moitra Kristýna Bürglová Jana Hodačová Olivia de los Cobos Martine Lejeune Fabrice Rossignol Delphine Toulemon Sylvie Bégin-Colin Benoît P. Pichon Laurence Raehm Jean-Olivier Durand Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2014,70(2):245-253
The combination of the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with sol–gel processing enables the versatile preparation of sol–gel materials under different shapes with targeted functionalities through a diversity-oriented approach. In this account, the development of the CuAAC reaction under anhydrous conditions for the synthesis of sol–gel precursors and for the assembling of magnetic nanoparticles on self-assembled monolayers is related, as well as the use of the classical CuAAC methodologies for the functionalization of mesoporous silica nanoparticles and microdots arrays. Coupling CuAAC and Sol–Gel will result in simplified preparations of multifunctional materials with controlled morphologies. 相似文献
4.
Lejeune C Coelho C Bonhomme-Coury L Azaïs T Maquet J Bonhomme C 《Solid state nuclear magnetic resonance》2005,27(4):242-246
We show that it is possible to efficiently transfer magnetization from 31P to 29Si, using variable amplitude CP MAS experiment. This experiment is demonstrated by using Si5O(PO4)6, the synthesis protocol of which is described. From the obtained results, we show that the experiment allows the spectral edition of 29Si spectra from 31P→29Si CP, enabling the studies of derivatives involving Si–O–P linkages, such as phosphosilicate glasses, microporous silicoaluminophosphates (SAPO) and bioactive phosphosilicates. 相似文献
5.
Tiago P. Filomena Miguel A. Lejeune 《Journal of Optimization Theory and Applications》2014,161(1):308-329
We consider a probabilistic portfolio optimization model including fixed and proportional transaction costs. We derive a deterministic equivalent of the probabilistic model for fat-tailed portfolio returns. We develop a method which finds provably near-optimal solutions in minimal amount of time for industry-sized (up to 2000 assets) problems. To solve the mixed-integer nonlinear programming (MINLP) deterministic formulation equivalent to the stochastic problem, we design a mathematical programming-based warm-start heuristic. The tests show the computational efficiency of the heuristic which is more than an order of magnitude faster than Cplex in finding high-quality solutions. 相似文献
6.
Saladin Ducretet Lejeune Henri Moissan Jules Violle Lagrange und Hoho 《Fresenius' Journal of Analytical Chemistry》1895,34(1):176-178
Ohne Zusammenfassung 相似文献
7.
It is shown that the effective mass of nucleons in nuclear matter has a pronounced and narrow maximum near the Fermi surface, in contradistinction with previous belief that this local enhancement exists only in finite nuclei. Implications of this finding for self-consistent Hartree-Fock calculations of finite nuclei are pointed out. 相似文献
8.
9.
Barrière F Fabre B Hao E Lejeune ZM Hwang E Garno JC Nesterov EE Vicente MG 《Macromolecules》2009,42(8):2981-2987
Carborane-functionalized conducting polymer films have been electrogenerated in dichloromethane from the anodic oxidation of ortho- (1), meta- (3) and para-carborane (4) isomers linked to two 2-thienyl units. The corresponding electrochemical response was characterized by a broad reversible redox system corresponding to the p-doping/undoping of the polythiophene backbone, the formal potential of which increased in the order poly(1) < poly(3) < poly(4), from ca. 0.50 to 1.15 V vs Ag/Ag(+) 10(-2) M. From further UV-visible spectroscopy analysis, the optical band gap was estimated at 1.8, 2.0 and 2.2 eV for poly(1), poly(3) and poly(4), respectively. The more conjugated and electroconductive character of poly(1) is ascribed to a more planar conformation of the conjugated backbone resulting from an intramolecular β-β' cyclization reaction in the monomer, consequently yielding a fused conjugated polymer. Molecular modeling calculations using the DFT method support this hypothesis. The surface topography and maps of the conductive domains of the electropolymerized films were evaluated by conducting probe AFM. The three polymers exhibit fairly similar morphological characteristics and a surface roughness of ~2 nm. Current-voltage (I-V) characteristics of conducting AFM tip-carborane polymer-ITO junctions showed that poly(1) had the highest conductivity. 相似文献
10.
Miguel A. Lejeune 《Annals of Operations Research》2012,200(1):23-36
This study revisits the celebrated p-efficiency concept introduced by Prékopa (Z.?Oper. Res. 34:441?C461, 1990) and defines a p-efficient point (pLEP) as a combinatorial pattern. The new definition uses elements from the combinatorial pattern recognition field and is based on the combinatorial pattern framework for stochastic programming problems proposed in Lejeune (Stochastic programming e-print series (SPEPS) 2010-5, 2010). The approach is based on the binarization of the probability distribution, and the generation of a consistent partially defined Boolean function representing the combination (F,p) of the binarized probability distribution F and the enforced probability level p. A combinatorial pattern provides a compact representation of the defining characteristics of a pLEP and opens the door to new methods for the generation of pLEPs. We show that a combinatorial pattern representing a pLEP constitutes a strong and prime pattern and we derive it through the solution of an integer programming problem. Next, we demonstrate that the (finite) collection of pLEPs can be represented as a disjunctive normal form (DNF). We propose a mixed-integer programming formulation allowing for the construction of the DNF that is shown to be prime and irreducible. We illustrate the proposed method on a problem studied by Prékopa (Stochastic programming: handbook in operations research and management science, vol.?10, Elsevier, Amsterdam, 2003). 相似文献