Search results for "Gibbs"
showing 10 items of 164 documents
Propan-2-ol dehydration on H-ZSM-5 and H-Y zeolite: a DFT study
2012
The catalytic dehydration of propan-2-ol over H-Y and H-ZMS-5 aluminated zeolite models, mimicking both internal cavities and external surfaces, was studied by DFT calculations to investigate the reaction mechanism. After the adsorption of propan-2-ol on the zeolite, the dehydration mechanism starts with alcohol protonation, occurring by one acidic –OH group of the zeolite fragment, followed by a concerted β-elimination to give propene. The catalytic activity is affected by the size of the zeolite cavity, which is larger in the H-Y than in the H-ZMS-5 zeolite. The adsorption energy of the reagent, as an example, decreases in the order: H-Y cavity ≃ H-ZMS-5 surface > H-ZMS-5 cavity, pointing…
Pd-catalyzed hydrodehalogenation of chlorinated olefins: Theoretical insights to the reaction mechanism
2012
Abstract Density functional theory calculations are applied to study energetics of trichloroethene (TCE) hydrodechlorination over pure Pd(1 1 1), chlorine-covered Pd(1 1 1), and Pd island supported by Au(1 1 1). Our results show that in all cases C Cl bond breakings take place more readily than C H bond formations and that TCE dechlorinates fully producing CCH precursors for the hydrogenations. The reaction pathway through radical-like species provides a possible explanation to the experimental product distributions that show a nominal amount of lesser chlorinated species in the presence of excess hydrogen. The surface chlorine resulted from the TCE decomposition weakens the binding of the …
From CO2 to dimethyl carbonate with dialkyldimethoxystannanes: the key role of monomeric species.
2011
International audience; The formation of dimethyl carbonate (DMC) from CO(2) and methanol with the dimer [n-Bu(2)Sn(OCH(3))(2)](2) was investigated by experimental kinetics in support of DFT calculations. Under the reaction conditions (357-423 K, 10-20 MPa), identical initial rates are observed with three different reacting mixtures, CO(2)/toluene, supercritical CO(2), and CO(2)/methanol, and are consistent with the formation of monomeric di-n-butyltin(iv) species. An intramolecular mechanism is, therefore, proposed with an Arrhenius activation energy amounting to 104 ± 10 kJ mol(-1) for DMC synthesis. DFT calculations on the [(CH(3))(2)Sn(OCH(3))(2)](2)/CO(2) system show that the exothermi…
Application of reverse electrodialysis to site-specific types of saline solutions: A techno-economic assessment
2019
Abstract Salinity gradients are a non-conventional source of renewable energy based on the recovery of the Gibbs free energy related to the mixing of solutions at different concentrations. Reverse Electrodialysis is a promising and innovative technology able to convert this energy directly into electric current. The worldwide availability of salinity gradients is limited to those locations where water bodies at different salinity levels are present. The present work analyses a number of different scenarios worldwide, in locations where salinity gradients are naturally available or generated by anthropogenic activities. A techno-economic model of the Reverse Electrodialysis process is presen…
Techno-economic evaluation of Reverse Electrodialysis process in different real environments
2018
Salinity Gradient Power is a promising renewable energy source based on the recovery of the chemical potential released from the mixing of solutions at different concentrations. Natural salinity gradients are extensively available worldwide in natural reservoirs. Reverse Electrodialysis is an innovative technology able to perform a direct conversion of the energy of mixing into electricity. Salinity gradients coming from natural resources or from human activities are worldwide available. In the present work a number of different scenarios, including natural resources (e.g. rivers, seas, lakes and salt ponds), industrial/urban wastes (e.g. brine and treated wastewaters) are analysed. The aim…
Polynomial mapped bases: theory and applications
2022
Abstract In this paper, we collect the basic theory and the most important applications of a novel technique that has shown to be suitable for scattered data interpolation, quadrature, bio-imaging reconstruction. The method relies on polynomial mapped bases allowing, for instance, to incorporate data or function discontinuities in a suitable mapping function. The new technique substantially mitigates the Runge’s and Gibbs effects.
Porous silicon based photoluminescence immunosensor for rapid and highly-sensitive detection of Ochratoxin A.
2017
A rapid and low cost photoluminescence (PL) immunosensor for the determination of low concentrations of Ochratoxin A (OTA) has been developed. This immunosensor was based on porous silicon (PSi) and modified by antibodies against OTA (anti-OTA). PSi layer was fabricated by metal-assisted chemical etching (MACE) procedure. Main structural parameters (pore size, layer thickness, morphology and nanograins size) and composition of PSi were investigated by means of X-Ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. PL-spectroscopy of PSi was performed at room temperature and showed a wide emission band centered at 680 ± 20nm. Protein A was covalently immobilized …
Determinants of spatial intensity of stop locations on cruise passengers tracking data
2021
This paper aims at analyzing the spatial intensity in the distribution of stop locations of cruise passengers during their visit at the destination through a stochastic point process modelling approach on a linear network. Data collected through the integration of GPS tracking technology and questionnaire-based survey on cruise passengers visiting the city of Palermo are used, to identify the main determinants which characterize their stop locations pattern. The spatial intensity of stop locations is estimated through a Gibbs point process model, taking into account for both individual-related variables, contextual-level information, and for spatial interaction among stop points. The Berman…
Poisson Regression with Change-Point Prior in the Modelling of Disease Risk around a Point Source
2003
Bayesian estimation of the risk of a disease around a known point source of exposure is considered. The minimal requirements for data are that cases and populations at risk are known for a fixed set of concentric annuli around the point source, and each annulus has a uniquely defined distance from the source. The conventional Poisson likelihood is assumed for the counts of disease cases in each annular zone with zone-specific relative risk and parameters and, conditional on the risks, the counts are considered to be independent. The prior for the relative risk parameters is assumed to be piecewise constant at the distance having a known number of components. This prior is the well-known cha…
Statistical inference and Monte Carlo algorithms
1996
This review article looks at a small part of the picture of the interrelationship between statistical theory and computational algorithms, especially the Gibbs sampler and the Accept-Reject algorithm. We pay particular attention to how the methodologies affect and complement each other.