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311.
We introduce a new iterative method for the computation of the minimal nonnegative solutionG of the matrix equation
, arising in the numerical solution of M/G/1 type Markov chains. The idea consists in applying a relaxation technique to customarily
used functional iteration formulas. The proposed method is easy to implement and outperforms, in terms of number of iterations
and execution time, the standard functional iteration techniques. 相似文献
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313.
Beatrice Ch. D. Salert Hartmut Krueger Sergey A. Bagnich Thomas Unger Frank Jaiser Mahmoud Al‐Sa'di Dieter Neher Anna Hayer Thomas Eberle 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):601-613
A new matrix system for phosphorescent organic light‐emitting diodes (OLEDs) based on an electron transporting component attached to an inert polymer backbone, an electronically neutral co‐host, and a phosphorescent dye that serves as both emitter and hole conductor are presented. The inert co‐host is used either as small molecules or covalently connected to the same chain as the electron‐transporting host. The use of a small molecular inert co‐host in the active layer is shown to be highly advantageous in comparison to a purely polymeric matrix bearing the same functionalities. Analysis of the dye phosphorescence decay in pure polymer, small molecular co‐host film, and their blend lets to conclude that dye molecules distribute mostly in the small molecular co‐host phase, where the co‐host prevents agglomeration and self‐quenching of the phosphorescence as well as energy transfer to the electron transporting units. In addition, the co‐host accumulates at the anode interface where it acts as electron blocking layer and improves hole injection. This favorable phase separation between polymeric and small molecular components results in devices with efficiencies of about 47 cd/A at a luminance of 1000 cd/m2. Investigation of OLED degradation demonstrates the presence of two time regimes: one fast component that leads to a strong decrease at short times followed by a slower decrease at longer times. Unlike the long time degradation, the efficiency loss that occurs at short times is reversible and can be recovered by annealing of the device at 180 °C. We also show that the long‐time degradation must be related to a change of the optical and electrical bulk properties. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
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Loredana Maiuolo Beatrice Russo Vincenzo Algieri Monica Nardi Maria Luisa Di Gioia Matteo Antonio Tallarida Antonio De Nino 《Tetrahedron letters》2019,60(9):672-674
A simple procedure to obtain 1,5-disubstituted 1,2,3-triazoles, using the Er(OTf)3/[mpy]OTf/H2O catalytic system is described. The reaction proceeds through an eliminative azide–olefin cycloaddition (EAOC) offering a highly regioselective approach and good yields (81–94%). The advantages of this method include simple operations of work-up and the ability of the catalytic system to be re-used five times without an evident loss in yield. The role of IL and water were speculated, invoking also a probable ionic self-assembly (ISA) effect. 相似文献
317.
Varinder K. Aggarwal Javier de Vicente Beatrice Pelotier Ian P. Holmes Roger V. Bonnert 《Tetrahedron letters》2000,41(52):2296-10331
Aldehydes can be homologated to ketones in moderate to good yields using aryldiazomethanes generated in situ from tosylhydrazones. Chiral aldehydes can be employed with almost complete retention of configuration. The tosylhydrazones can also be generated in situ from the corresponding aldehyde leading to a one-pot process for coupling two different carbonyl compounds to give ketones. 相似文献
318.
Beatrice Meini. 《Mathematics of Computation》2002,71(239):1189-1204
We propose a new quadratically convergent algorithm, having a low computational cost per step and good numerical stability properties, which allows the simultaneous approximation of the extreme solutions of the matrix equations and . The algorithm is based on the cyclic reduction method.
319.
320.
Sbaraglia G Pitzurra L Moroni B Nocentini A Vitali M Poli G Miliani C Bistoni F 《Annali di chimica》2003,93(11):889-896
The microbial activity plays an important role in the biodegradative processes implied in stonework decay. In natural environments it is not possible to separate the damage produced by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have described, as commented in the text, how fungal colonization observed on scaglia may be the result of the fine grain size of rock, whereas inhibition of growth on marble may depend on the surface characteristics of calcite grains after grinding. The extent of microbial growth clearly depends on the quantity of cations released in solution. However, fungal growth may, in turn, induce a decrease in pH, thus promoting mineral chemical attack. These observation points to selective action of fungal species in promoting weathering well evidenced by the presence of different extents of cations released in suspension from the same sample. Detailed studies are in progress in order to go into this question. 相似文献