Search results for "solu"
showing 10 items of 7577 documents
Enhanced calculation of optimal gradient programs in reversed-phase liquid chromatography
2003
Abstract The resolution of a mixture of 16 β-blockers under gradient elution was optimised using both isocratic and gradient training sets, with a reversed-phase column and acetonitrile–water eluents. Error theory was applied to measure the information extracted from different gradient experimental designs. This allows checking the expected accuracy when gradient predictions exceed the initial solvent concentrations tested in the training set. This work applies the results on modelling found in a previous study [J. Chromatogr. A 1018 (2003) 169] where the performance of several retention models was compared. Enhanced retention predictions were applied to the optimisation of gradient program…
Exact 3D solution for static and damped harmonic response of simply supported general laminates
2014
International audience; The state-space method is adapted to obtain three dimensional exact solutions for the static and damped dynamic behaviors of simply supported general laminates. The state-space method is written in a general form that permits to handle both cross-ply and antisymmetric angle-ply laminates. This general form also permits to obtain exact solutions for general laminates, albeit with some constraints. For the general case and for the static behavior, either an additive term is added to the load to simulate simply supported boundary conditions, or the plate bends in a particular way. For the dynamic behavior, the general case leads to pairs of natural frequencies for each …
Nonexistence Results for Higher Order Fractional Differential Inequalities with Nonlinearities Involving Caputo Fractional Derivative
2021
Higher order fractional differential equations are important tools to deal with precise models of materials with hereditary and memory effects. Moreover, fractional differential inequalities are useful to establish the properties of solutions of different problems in biomathematics and flow phenomena. In the present work, we are concerned with the nonexistence of global solutions to a higher order fractional differential inequality with a nonlinearity involving Caputo fractional derivative. Namely, using nonlinear capacity estimates, we obtain sufficient conditions for which we have no global solutions. The a priori estimates of the structure of solutions are obtained by a precise analysis …
Integro-differential equation modelling heat transfer in conducting, radiating and semitransparent materials
1998
In this work we analyse a model for radiative heat transfer in materials that are conductive, grey and semitransparent. Such materials are for example glass, silicon, water and several gases. The most important feature of the model is the non-local interaction due to exchange of radiation. This, together with non-linearity arising from the well-known Stefan-Boltzmann law, makes the resulting heat equation non-monotone. By analysing the terms related to heat radiation we prove that the operator defining the problem is pseudomonotone. Hence, we can prove the existence of weak solution in the cases where coercivity can be obtained. In the general case, we prove the solvability of the system us…
Numerical modelling of the electrochemical behaviour of 316 stainless steel based upon static and dynamic experimental microcapillary-based technique…
2008
objective of this work was to determine the parameters that affect the mass transport and the distribution of species in microcapillaries close to the specimen surface. Local experiments were carried out under static and flow conditions on type 316L stainless steel in 1.7 M NaCl, pH = 3, by means of the electrochemical microcell and the scanning droplet cell technique. The polarisation behaviour of pure iron (used as a model system) in an aqueous environment was calculated adopting a finite element approach and was compared to the experimental results. The corrosion system consists of three parallel electrochemical reactions: the oxygen reduction reaction (ORR), the hydrogen evolution react…
Inverse prediction of local interface temperature during electromagnetic pulse welding via precipitate kinetics
2019
Abstract Interface temperature of electromagnetic pulse welding is difficult to measure by insitu methods. Here, the local temperature rise is investigated using the kinetics of precipitates and dispersoids (transformation or dissolution) at the interface zone (IZ) and affected zone (AZ) of three welds. This fine scale analysis allows estimating of local temperature range for AZ that reaches between 250 and 360 °C on both sides of narrow IZ, while the IZ itself experiences between 360 and 500 °C or even beyond 500 °C. The interface temperature increases with the increasing impact intensity. The current work estimated thermal field based on the precipitate transformations, which occur during…
Effect of mechanical stirring and temperature on dynamic hydrothermal synthesis of titanate nanotubes
2017
Abstract In the late century, it has been clearly demonstrated that titanate nanotubes (TNTs) are attractive nanomaterials with various potential applications due to their interesting properties. In this work, an essential reaction parameter, rarely considered in the literature, has been studied: stirring during hydrothermal synthesis. For this purpose, an intermittent mechanical stirring, ranging from 0 to 20 min/h, has been applied during the TNTs synthesis using a new dynamic hydrothermal reactor. It was proved that a long stirring cycle (more than 10 min/h) at 150 °C and an overall reaction time of 16 h promotes nanoribbons synthesis instead of nanotubes. In this context, a detailed mor…
Linear versus Three-Arm Star Polybutadiene: Effects of Polymer Architecture on the Thermodynamic Solution Behavior
2012
The interaction of linear and of three-arm star polybutadiene (PB) with THF was studied in the temperature range between 25 and 55 °C. Information for dilute solution rests on light scattering experiments; Flory–Huggins interaction parameter χ stem from vapor pressure measurements as a function of φ, the volume fraction of polymer. Despite the minute divergence in the architecture, the second osmotic virial coefficients of the two PBs differ noticeably. The present work demonstrates that these disparities become much more pronounced as φ increases and that they depend strongly on temperature. These findings are interpreted on the basis of an approach accounting for the effects of chain conn…
A Promising New Method to Estimate Drug-Polymer Solubility at Room Temperature
2016
The established methods to predict drug-polymer solubility at room temperature either rely on extrapolation over a long temperature range or are limited by the availability of a liquid analogue of the polymer. To overcome these issues, this work investigated a new methodology where the drug-polymer solubility is estimated from the solubility of the drug in a solution of the polymer at room temperature using the shake-flask method. Thus, the new polymer in solution method does not rely on temperature extrapolations and only requires the polymer and a solvent, in which the polymer is soluble, that does not affect the molecular structure of the drug and polymer relative to that in the solid st…
Magnetic Ion Exchange Interactions in NiO—MgO Solid Solutions
2006
In this work, a review of recent experimental data and their interpretation for NicMg1−c O solid solutions is given. In particular, the influence of exchange interactions between Ni2+ ions on the structural, optical, magnetic, and vibrational properties is discussed.