112,477 research outputs found
Vibrational Energy Transfer in CO+N 2 Collisions: A Database for V-V and V-T/R Quantum-Classical Rate Coefficients
No full textKnowledge of energy exchange rate constants in inelastic collisions is critically required for accurate characterization and simulation of several processes in gaseous environments, including planetary atmospheres, plasma, combustion, etc. Determination of these rate constants requires accurate potential energy surfaces (PESs) that describe in detail the full interaction region space and the use of collision dynamics methods capable of including the most relevant quantum effects. In this work, we produce an extensive collection of vibration-to-vibration (V–V) and vibration-to-translation/rotation (V–T/R) energy transfer rate coefficients for collisions between CO and N2 molecules using a mixed quantum-classical method and a recently introduced (A. Lombardi, F. Pirani, M. Bartolomei, C. Coletti, and A. Laganà, Frontiers in chemistry, 7, 309 (2019)) analytical PES, critically revised to improve its performance against ab initio and experimental data of different sources. The present database gives a good agreement with available experimental values of V–V rate coefficients and covers an unprecedented number of transitions and a wide range of temperatures. Furthermore, this is the first database of V–T/R rate coefficients for the title collisions. These processes are shown to often be the most probable ones at high temperatures and/or for highly excited molecules, such conditions being relevant in the modeling of hypersonic flows, plasma, and aerospace applications
[rec. di] I. Bonomi, V. Coletti, "L'italiano della musica nel mondo", Firenze, Accademia della Crusca-goWare, 2015-2016
No full textBook review:
I. Bonomi, V. Coletti, "L'italiano della musica nel mondo", Firenze, Accademia della Crusca-goWare, 2015-2016, 203 pp.
(«La lingua italiana nel mondo», Nuova serie e-book)
ISBN 978-88-6797-423-
Salophen and salen oxo vanadium complexes as catalysts of sulfides oxidation with H2O2: Mechanistic insights
No full textThe application of V(V) catalysts in oxidation of sulfides with peroxides offers an efficient procedure, that
is compatible with different functional groups, and leads to good yields and selectivities. However, the
understanding of the factors affecting the reactivity of different catalysts is still far to be complete. An
experimental and theoretical study on a series of V(V) complexes containing variously substituted salen
and salophen ligands is reported with the aim to correlate the activity of the catalysts with the electronic
character of the vanadium center. The results obtained indicate that steric factors play a major role in
determining the outcome of the reaction, often overcoming the electronic effects. Theoretical results
suggest the intervention in the catalytic cycle of an hydroperoxo vanadium species
d-Dimensional Kepler–Coulomb Sturmians and Hyperspherical Harmonics as Complete Orthonormal Atomic and Molecular Orbitals
No full textSturmian basis sets are increasingly finding applications to the description of atomic and molecular structure, because of their mathematical properties and their flexibility regarding the ability to describe features of specific physical problems. However, their nature and properties have not been fully exploited in quantum chemistry. In this work we present a classification of Kepler-Coulomb Sturmian sets, where notations, symmetry properties, useful formulae, and relationships are described in detail, so to provide support for their applications to physical problems. The mathematical solution of Schrodinger equation is given for these sets both in configuration and momentum space, where Sturmian eigenfunctions coincide with hyperspherical harmonics and connections between different sets manifestly appear as elements of angular momentum algebra. Applications of the considered sets and some of their generalizations are also briefly accounted for
Vibrational Energy Transfer in CO+N<sub>2</sub> Collisions: A Database for V–V and V–T/R Quantum-Classical Rate Coefficients
No full textKnowledge of energy exchange rate constants in inelastic collisions is critically required for accurate characterization and simulation of several processes in gaseous environments, including planetary atmospheres, plasma, combustion, etc. Determination of these rate constants requires accurate potential energy surfaces (PESs) that describe in detail the full interaction region space and the use of collision dynamics methods capable of including the most relevant quantum effects. In this work, we produce an extensive collection of vibration-to-vibration (V–V) and vibration-to-translation/rotation (V–T/R) energy transfer rate coefficients for collisions between CO and N2 molecules using a mixed quantum-classical method and a recently introduced (A. Lombardi, F. Pirani, M. Bartolomei, C. Coletti, and A. Laganà, Frontiers in chemistry, 7, 309 (2019)) analytical PES, critically revised to improve its performance against ab initio and experimental data of different sources. The present database gives a good agreement with available experimental values of V–V rate coefficients and covers an unprecedented number of transitions and a wide range of temperatures. Furthermore, this is the first database of V–T/R rate coefficients for the title collisions. These processes are shown to often be the most probable ones at high temperatures and/or for highly excited molecules, such conditions being relevant in the modeling of hypersonic flows, plasma, and aerospace applications
Efficient and sustainable V-catalyzed oxidative desulfurization of fuels assisted by ionic liquids
No full textFuel desulfurization is an appealing topic for the chemical industry since severe environmental regulations regarding SO2 emissions have been legislated in many countries. In order to reduce the amount of sulfur-containing compounds in fuels, responsible for high SOx emission levels, a green chemistry approach is compulsory. In this paper, vanadium salen and salophen complexes were used in the oxidation of a model aromatic sulfide, such as dibenzothiophene (DBT), in the presence of H2O2 as green oxidant. The oxidative process was successfully coupled with the extraction of the oxidized compounds by ionic liquids. The system resulted highly selective for sulfide oxidation, showing poor reactivity toward the oxidation of alkenes and allowing a significant reduction of S content in a model benzine. To note, the use of microwave in place of standard heating allowed to obtain 98% of DBT oxidation and almost complete sulfur extraction in the model fuel in 1000 s. For these reasons, this system was considered an easy, rapid and clean process to achieve fuel desulfurization
A view on conditional measures through local representability of binary relations
No full textWe consider binary relations <= admitting a conditional measure of uncertainty phi (precisely plausibility, possibility and their dual functions), which locally represents <=: for every pair A <= B, the measure phi(.C) almost represents for any hypothesis C D A V B, and represents <= under the most specific hypothesis C = A V B. (C) 2007 Published by Elsevier Inc
A dual Stage ion engine for high impulse missions
No full textIn this paper, the applicability of dual stage ion optics and in particular of the so-called dual stage ion engine to high power, high specific impulse missions will be evaluated. First, the performance limits of conventional two gridded ion engines (GIE) will be discussed and the advantages provided by dual stage ion engines reported. The limits of applicability of a dual stage ion engine will be analyzed analytically and the results confirmed numerically. The lifetime and performance of a three gridded dual stage ion engine (DS3G) will be numerically investigated and compared to those of a conventional GIE assessing for the first time in the open literature under what condition dual stage ion optics provide performance improvements over conventional GIEs and what is its impact on the thruster lifetime. Dual stage ion engines have been found to be capable of providing higher thrust density and longer lifetime with respect to conventional gridded ion engines
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