Search results for "Thermodynamics"
showing 10 items of 2774 documents
N2-, O2- and air-broadened half-widths and line shifts for transitions in the nu3 band of methane in the 2726- to 3200-cm-1 spectral region
2008
International audience; Complex Robert-Bonamy calculations of the pressure-broadened half-width and the pressure-induced line shift are made for some 4000 transitions in the [nu]3 band of methane with N2, O2, and air as the perturbing gases. This work focuses on A and F symmetry transitions in the spectral range 2726 to 3200 cm-1. More work is needed on the intermolecular potential before calculations can be made for the E-symmetry transitions. The calculations are made at 225 and 296 K in order to determine the temperature dependence of the half-width. The calculations are compared with measurements. These data are to support remote sensing of the Earth and Titan atmospheres.
Mechanism of aluminium incorporation into C–S–H from ab initio calculations
2014
Blended cements have great potential to reduce the CO2 footprint due to cement production. C(alcium)–S(ilicate)–H(ydrate) in these novel materials is known to incorporate a considerable amount of Al. We have for the first time applied large-scale first principles calculations to address the mechanism of Al incorporation into low C/S ratio C–S–H. In agreement with state-of-the-art NMR information, our calculations show that Al substitutes Si in bridging tetrahedra only, and that substitutions in pairing tetrahedra are strongly disfavoured in a wide range of conditions. In broad terms, the energy penalty for having an Al atom in a pairing position is of about 20 kcal mol−1. Al in bridging tet…
Estimating the temperature evolution of foodstuffs during freezing with a 3D meshless numerical method
2015
Abstract Freezing processes are characterised by sharp changes in specific heat capacity and thermal conductivity for temperatures close to the freezing point. This leads to strong nonlinearities in the governing PDE that may be difficult to resolve using traditional numerical methods. In this work we present a meshless numerical method, based on a local Hermite radial basis function collocation approach in finite differencing mode, to allow the solution of freezing problems. By introducing a Kirchhoff transformation and solving the governing equations in Kirchhoff space, the strength of nonlinearity is reduced while preserving the structure of the heat equation. In combination with the hig…
Dynamic reliability indices for k-out-of-n multi-state system
2005
A multi-state system k-out-of-n is one of basic models in reliability analysis. In this system, k is the minimum number of n components that must work for the system to work and both the system and its components can have more than two states. A structure function declares relation between system and component states uniquely. New algorithm for reliability analysis of the k-out-of-n multi-state system is proposed in this paper. We use two tools for examine this system: (a) structure function for the system description; (b) direct partial logic derivatives for analysis this system. New algorithm for reliability analysis of the multi-state system k-out-of-n is allowed to calculate the probabi…
Observable Streaming Potential in Membranes
2003
Theories describing the electrokinetic processes in membranes usually involve nonobservable variables. One of these phenomena is the streaming potential, i.e., the electric potential generated by a pressure difference imposed across the membrane system. In this work the streaming potential is successfully described by using observable variables in the framework of thermodynamics of irreversible processes. The observable electric potential is the central quantity of the transport equations. The relaxation with time of this electric potential difference is well explained by the solute flux in these transport equations. The fluxes and forces defined in the formulation permit one to analyze the…
Design of carborane molecular architectures via electronic structure computations
2009
10 pags, 9 figs
Combined effect of solvent content, temperature and pH on the chromatographic behaviour of ionisable compounds.
2008
The organic solvent content and the pH in the mobile phase are the usual main factors in reversed-phase liquid chromatographic separations, owing to their strong effects on retention and/or selectivity. Temperature is often neglected. However, even in cases where the impact of this factor on selectivity is minor, the reduction in analysis time is still an interesting reason to consider it. In addition, ionisable compounds may exhibit selectivity changes, owing to the interaction of organic solvent and/or temperature with pH. The separation of ionisable compounds (nine diuretics: bendroflumethiazide, benzthiazide, bumetanide, chlorthalidone, furosemide, piretanide, probenecid, trichloromethi…
Non-uniform Sediment Transport Estimation in Non-equilibrium Situations: Case Studies
2014
Abstract Quantitative estimate of sediment transport in alluvial channels is one of the most important task in river engineering. Even today, numerical models of sediment transport processes are confronted with some difficulties, often of conceptual nature. One of these difficulties is the simulation of non-uniform sediment transport in non-equilibrium situations, which requires the characterization of the ability of the alluvial system to immediately overcome the variations of the sediment boundary conditions. In this work a 1-D numerical model, which includes a new expression of the so-called “adaptation coefficient”, has been applied to test its capability to simulate the transient bed p…
Thermodynamics of small systems embedded in a reservoir: a detailed analysis of finite size effects
2012
International audience; We present a detailed study on the finite size scaling behaviour of thermodynamic properties for small systems of particles embedded in a reservoir. Previously, we derived that the leading finite size effects of thermodynamic properties for small systems scale with the inverse of the linear length of the small system, and we showed how this can be used to describe systems in the thermodynamic limit [Chem. Phys. Lett. 504, 199 (2011)]. This approach takes into account an effective surface energy, as a result of the non-periodic boundaries of the small embedded system. Deviations from the linear behaviour occur when the small system becomes very small, i.e. smaller tha…
Structural, energetic and kinetic database of catalytic reactions: Benzyl alcohol to benzaldehyde oxidation on MnOx clusters
2021
Abstract Data here reported are connected with the research article “Benzyl Alcohol to Benzaldehyde Oxidation on MnO x Clusters: Unraveling Atomistic Features” Gueci et al. [1] . This work described and discussed structural and energetic results, calculated by Density Functional Theory (DFT). In order to get kinetic information, DFT results were refined by an original approach, which will be shortly described in the following article. The crossed analysis of experimental and computational energetic and kinetic data allowed to (i) reconstruct the complicated lattice that connects the primary and secondary mechanisms of the reaction and (ii) identify alternative process pathways capable of by…