2,404 research outputs found
Application of the SAFT-Îł Mie group contribution equation of state to fluids of relevance to the oil and gas industry
Calculated data for all the figures presented in publication
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Modeling the martian atmosphere with the LMD global climate model
Introduction: For several years we have been developing a 3D Global Climate Model (GCM) for Mars derived from the models used on Earth for weather forecasting or climate changes studies [1]. The purpose of such a project is ambitious: we wish to build a 'Mars simulator' based only on physical equations, with no tailor-made forcing, but able to reproduce all the available observations of the Martian climate (temperatures, winds, but also clouds, dust, ices, chemical species, etc...).
The GCM is constantly evolving, thanks to a contnuous collaboration between several teams based in France (LMD, SA), the UK (The Open University, University of Oxford) and Spain (Instituto de Astrofisica de Andalucia), and with the support of ESA and CNES.
We are currently working on an improved version of the model. Several new parametrisation are included in the heart of the model (radiative transfer, surface and subsurface processes, dynamics) and the applications of the GCM are in contnuous development (Water, dust, CO2, radon cycles, photochemistry, thermosphere, ionosphere, etc...
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The latest (version 4.3) Mars Climate Database
Introduction: The Mars Climate Database (MCD) is a database of meteorological fields derived from General Circulation Model (GCM) numerical simulations of the Martian atmosphere and validated using available observational data. The MCD includes complementary post-processing schemes such as high spatial resolution interpolation of environmental data and means of reconstructing the variability thereof. The GCM is developed at Laboratoire de Météorologie Dynamique du CNRS (Paris, France) [1,2] in collaboration with the Open University (UK), the Oxford University (UK) and the Instituto de Astrofisica de Andalucia (Spain) with support from the European Space Agency (ESA) and the Centre National
d'Etudes Spatiales (CNES)
Modelling the fluid phase behaviour of aqueous mixtures of multifunctional alkanolamines and carbon dioxide using transferable parameters with the SAFT-VR approach
Efficacy of different antifouling treatments for seawater cooling systems
In an industrial seawater cooling system, the effects of three different antifouling treatments, viz. sodium
hypochlorite (NaClO), aliphatic amines (Mexel1432) and UV radiation, on the characteristics of the fouling formed
were evaluated. For this study a portable pilot plant, as a side-stream monitoring system and seawater cooling
system, was employed. The pilot plant simulated a power plant steam condenser, having four titanium tubes under
different treatment patterns, where fouling progression could be monitored. The nature of the fouling obtained was
chiefly inorganic, showing a clear dependence on the antifouling treatment employed. After 72 days the tubes under
treatment showed a reduction in the heat transfer resistance (R) of around 70% for NaClO, 48% for aliphatic
amines and 55% for UV, with respect to the untreated tube. The use of a logistic model was very useful for
predicting the fouling progression and the maximum asymptotic value of the increment in the heat transfer
resistance (DRmax). The apparent thermal conductivity (l) of the fouling layer showed a direct relationship with the
percentage of organic matter in the collected fouling. The characteristics and mode of action of the different
treatments used led to fouling with diverse physicochemical properties
Intertwining relations of non-stationary Schr\"odinger operators
General first- and higher-order intertwining relations between non-stationary
one-dimensional Schr\"odinger operators are introduced. For the first-order
case it is shown that the intertwining relations imply some hidden symmetry
which in turn results in a -separation of variables. The Fokker-Planck and
diffusion equation are briefly considered. Second-order intertwining operators
are also discussed within a general approach. However, due to its complicated
structure only particular solutions are given in some detail.Comment: 18 pages, LaTeX20
Resonant states in an attractive one dimensional cusp potential
We solve the two-component Dirac equation in the presence of a spatially one
dimensional symmetric attractive cusp potential. The components of the spinor
solution are expressed in terms of Whittaker functions. We compute the bound
states solutions and show that, as the potential amplitude increases, the
lowest energy state sinks into the Dirac sea becoming a resonance. We
characterize and compute the lifetime of the resonant state with the help of
the phase shift and the Breit-Wigner relation. We discuss the limit when the
cusp potential reduces to a delta point interaction.Comment: 11 pages. To appear in Physica Script
The Absence of Positive Energy Bound States for a Class of Nonlocal Potentials
We generalize in this paper a theorem of Titchmarsh for the positivity of
Fourier sine integrals. We apply then the theorem to derive simple conditions
for the absence of positive energy bound states (bound states embedded in the
continuum) for the radial Schr\"odinger equation with nonlocal potentials which
are superposition of a local potential and separable potentials.Comment: 23 page
Predictive models for the phase behaviour and solution properties of weak electrolytes: nitric, sulfuric and carbonic acid
The distribution of ionic species in electrolyte systems is important in many fields of science and engineering, ranging from the study of degradation mechanisms to the design of systems for electrochemical energy storage. Often, other phenomena closely related to the ionic speciation, such as ion pairing, clustering and hydrogen bonding, which are difficult to investigate experimentally, are also of interest. Here, we develop an accurate molecular approach, accounting for reactions as well as association and ion pairing, to deliver a predictive framework that helps validate experiment and guides future modelling of speciation phenomena of weak electrolytes. We extend the SAFT-VRE Mie equation of state [D. K. Eriksen et al., Mol. Phys., 2016, 114, 2724–2749] to study aqueous solutions of nitric, sulphuric and carbonic acid, considering complete and partially dissociated models. In order to incorporate the dissociation equilibria, correlations to experimental data for the relevant thermodynamic equilibrium constants of the dissociation reactions are taken from the literature and are imposed as a boundary condition in the calculations. The models for water, the hydronium ion, and carbon dioxide are treated as transferable and are taken from our previous work. Here we present new molecular models for nitric acid, and the nitrate, bisulfate, sulfate, and bicarbonate anions. The resulting framework is used to predict a range of phase behaviour and solution properties of the aqueous acids over wide ranges of concentration and temperature, including the degree of dissociation, as well as the activity coefficients of the ionic species, and the activity of water and osmotic coefficient, density, and vapour pressure of the solutions. The SAFT-VRE Mie models obtained in this manner provide a means of elucidating the mechanisms of association and ion pairing in the systems studied, complementing the experimental observations reported in the literature
Harmonic states for the free particle
Different families of states, which are solutions of the time-dependent free
Schr\"odinger equation, are imported from the harmonic oscillator using the
Quantum Arnold Transformation introduced in a previous paper. Among them,
infinite series of states are given that are normalizable, expand the whole
space of solutions, are spatially multi-localized and are eigenstates of a
suitably defined number operator. Associated with these states new sets of
coherent and squeezed states for the free particle are defined representing
traveling, squeezed, multi-localized wave packets. These states are also
constructed in higher dimensions, leading to the quantum mechanical version of
the Hermite-Gauss and Laguerre-Gauss states of paraxial wave optics. Some
applications of these new families of states and procedures to experimentally
realize and manipulate them are outlined.Comment: 21 pages, 3 figures. Title changed, content added, references adde
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