Search results for "position"
showing 10 items of 6771 documents
Multi-Resolution error analysis of predicted absorption coefficients. Method and application to the infrared spectrum of methane at high temperature.
2010
La version V2 inclut les modifications proposées par les reviewers.; International audience; A general method for the estimation of the confidence interval of molecular absorption coefficients is presented. Statistical numerical experiments are implemented to quantify the propagation of errors from line parameters to absorption coefficients or cross-sections as a function of the resolution. The method uses line parameter predictions (position and intensity) with estimated uncertainties derived from global polyad models. This work is especially intended to provide expert information for applications requiring theoretical predictions for which the present state of the art of line by line high…
D2 and H2 adsorption capacity and selectivity in CHA zeolites: Effect of Si/Al ratio, cationic composition and temperature
2020
International audience; The work deals with the effect of composition of CHA zeolites on the adsorption and separation of H2 and D2 under cryogenic temperatures. In the first part of this work the effect of Si/Al ratio and cationic composition on single gas adsorption of H2 and D2 was studied at 77.4 K. It was found that the adsorption capacities increase with Al content up to Si/Al = 2.1. Unexpectedly, Na-CHA zeolite with the highest Al content (Si/Al = 1.1) adsorbs only negligible amount because of the collapse of the zeolite structure upon dehydration at 400°C. The Na-and Li-containing chabazites with Si/Al = 2.1 possess similar adsorption capacities. In contrast, progressive replacement…
Interfacial Modification for High-Efficiency Vapor-Phase-Deposited Perovskite Solar Cells Based on a Metal Oxide Buffer Layer.
2018
Vacuum deposition is one of the most technologically relevant techniques for the fabrication of perovskite solar cells. The most efficient vacuum-based devices rely on doped organic contacts, compromising the long-term stability of the system. Here, we introduce an inorganic electron-transporting material to obtain power conversion efficiencies matching the best performing vacuum-deposited devices, with open-circuit potential close to the thermodynamic limit. We analyze the leakage current reduction and the interfacial recombination improvement upon use of a thin (<10 nm) interlayer of C60, as well as a more favorable band alignment after a bias/ultraviolet light activation process. This wo…
Peak capacity estimation in isocratic elution.
2008
Peak capacity (i.e. maximal number of resolved peaks that fit in a chromatographic window) is a theoretical concept with growing interest, but based on a situation rarely met in practice. Real chromatograms tend to have uneven distributions, with overlapped peaks and large gaps. The number of resolved compounds should, therefore, be known from estimations. Several equations have been reported for this purpose based on three perspectives, namely, the intuitive approach (peak capacity as the size of the retention time window measured in peak width units), which assumes peaks with the same width, and the outlines of Giddings and Grushka, which consider changes in peak width with retention time…
Spinodal decomposition of a two-dimensional model alloy with mobile vacancies
1991
Abstract Monte Carlo simulations are performed for the initial stages of phase separation in a model binary alloy (AB), where unmixing is caused by a repulsive energy between atoms of different kind ( e AA = e BB = e ), and a small fraction c v of mobile vacancies is present (typically c v = 0.04.) Unlike previous work, where interdiffusion was modelled in an unrealistic way by direct interchange of A and B atoms for c v = 0, were use the vacancy mechanism of diffusion: A-atoms may jump to vacant sites with a rate Γ A and B-atoms may jump to vacant sites with a rate Γ B , no direct A–B interchange being permitted. It is shown that the overall time-scale on which phase separation proceeds ty…
Phase separation of an asymmetric binary fluid mixture confined in a nanoscopic slit pore: Molecular-dynamics simulations
2008
As a generic model system of an asymmetric binary fluid mixture, hexadecane dissolved in carbon dioxide is considered, using a coarse-grained bead-spring model for the short polymer, and a simple spherical particle with Lennard-Jones interactions for the carbon dioxide molecules. In previous work, it has been shown that this model reproduces the real phase diagram reasonable well, and also the initial stages of spinodal decomposition in the bulk following a sudden expansion of the system could be studied. Using the parallelized simulation package ESPResSo on a multiprocessor supercomputer, phase separation of thin fluid films confined between parallel walls that are repulsive for both types…
Subamorphous thermal conductivity of crystalline half-Heusler superlattices
2021
The quest to improve the thermoelectric figure of merit has mainly followed the roadmap of lowering the thermal conductivity while keeping unaltered the power factor of the material. Ideally an electron-crystal phonon-glass system is desired. In this work, we report an extraordinary reduction of the cross-plane thermal conductivity in crystalline (TiNiSn):(HfNiSn) half-Heusler superlattices (SLs). We create SLs with thermal conductivities below the effective amorphous limit, which is kept in a large temperature range (120–300 K). We measured thermal conductivity at room temperature values as low as 0.75 W m−1 K−1, the lowest thermal conductivity value reported so far for half-Heusler compou…
Dynamics of Polymer Melts above the Glass Transition: Monte Carlo Studies of the Bond Fluctuation Model
1997
The bond fluctuation model on the simple cubic lattice with a bond-length dependent potential energy favoring long bonds exhibits a glassy freezing in as the temperature is lowered, many properties being qualitatively similar to experiment. The present paper studies the dynamical properties of the model (as they result from the random hopping algorithm), using configurations of undercooled polymer melts that have been carefully equilibrated by the slithering snake algorithm. In this way quantitatively reliable data can be obtained for distinctly lower temperatures than in the previous work on the dynamics of this model that used the random hopping algorithm for equilibration as well. If var…
A mathematical tool for describing the behaviour of a dense effluent discharge
2009
In many cases a dense effluent has to be discharged in the environment with possible harmful consequences. The preferred design for the relevant discharge unit is that of a simple or multi-port diffuser issuing jets at a given inclination above the horizontal. This work presents the follow-on developments of a model previously proposed to predict the behaviour of inclined dense jets issuing in a stagnant environment. It consists of a set of three ordinary differential equations that can be solved by standard numerical methods. Model outputs include information on the trajectory, spreading and dilution of inclined dense jets, return point position and concentration. Interestingly the model a…
Ageing of isotactic polypropylene due to morphology evolution, experimental limitations of realtime density measurements with a gradient column
2006
Abstract Ageing in crystalline polymers is responsible for the deterioration of physical properties leading, for example, to a decrease in toughness and to dimensional changes that are to some extent responsible for warpage and scrap production in injection molding. Since, it depends on the mutual transformation of stable and metastable phases, being always related to changes in morphological organization, it is here preferred to call it ‘Morphological ageing’. Although, one would expect the ageing regime to be determined by the complex morphology with amorphous phases of different mobility and eventually multiple crystalline phases, transformed into each other at an associated transition, …