Search results for "Potential"
showing 10 items of 3348 documents
MAST solution of advection problems in irrotational flow fields
2007
Abstract A new numerical–analytical Eulerian procedure is proposed for the solution of convection-dominated problems in the case of existing scalar potential of the flow field. The methodology is based on the conservation inside each computational elements of the 0th and 1st order effective spatial moments of the advected variable. This leads to a set of small ODE systems solved sequentially, one element after the other over all the computational domain, according to a MArching in Space and Time technique. The proposed procedure shows the following advantages: (1) it guarantees the local and global mass balance; (2) it is unconditionally stable with respect to the Courant number, (3) the so…
Near zero energy islands in the Mediterranean: Supporting policies and local obstacles
2014
Abstract Based on a recent technical–economical analysis on the island of Pantelleria, a policy feasibility study for a complete upgrading of the energy system of this Mediterranean Island is carried out. Pantelleria, situated between Sicily and Africa, owns a large potential in terms of renewable energy resources, although there are some obstacles in turning it into a Near Zero Energy system. Starting from a deep energy system audit, the study proposes the project for a near zero energy island, through the efficient transformation of the different existing natural energy resources into electrical energy and heat: the solar, the wind-based and the geothermal systems. In this way, the island…
Mapping evapotranspiration on vineyards: A comparison between Penman-Monteith and energy balance approaches for operational purposes
2012
Estimation of evapotranspiration (ET) in Sicilian vineyard is an emerging issue since these agricultural systems are more and more converted from rainfed to irrigated conditions, with significant impacts on the management of the scarce water resources of the region. The choice of the most appropriate methodology for assessing water use in these systems is still an issue of debating, due to the complexity of canopy and root systems and for their high spatial fragmentation. In vineyards, quality and quantity of the final product are dependent on the controlled stress conditions to be set trough irrigation. This paper reports an application of the well-known Penman-Monteith approach, applied i…
A new resonance in thee-H2-scattering
1969
A short-lived compound state of the systeme-H2 in the energy region from 13.5 to 15 eV has been investigated. It desintegrates preferably into theC 1 π u v=0, 1, 2, 3,... vibrational states of H2. Excitation functions and angular dependences of these states have been measured. The H2 vibrational levels are situated at 13.63, 13.93, 14.20, 14.70, 14.92,... eV. The shape of the potential energy curve and the internuclear distance of the compound state should be very similar to that of theC 1 π u resp.D 1 π u state ofH 2.
A theoretical study of the addition of CH3MgCl to chiral α-alkoxy carbonyl compounds
1998
Abstract A theoretical characterisation of the addition of CH 3 MgCl to the carbonyl group of 2-hydroxypropanal and 3,4-di- O -methyl-1- O -trimethylsilyl- l -erythrulose has been carried out. The PM3 semiempirical procedure and the ab initio method at HF level of theory with the 3–21G and 6–31G ∗ basis sets have been applied to identify the stationary points on the potential energy surface. The correlation effects have been included by using the MP2/6–31G ∗ method, as well as by means of MP3/6–31G ∗ // MP2/6–31G ∗ and MP4/6–31G ∗ //MP2/6–31G ∗ single point calculations. The geometry, harmonic vibrational frequencies, transition vector and electronic structure of the transition structures h…
Natural light in the architectural interior: Fake news on the Caravaggio of Palermo
2022
The paper investigates the mystery of a painting, Caravaggio’s The Nativity, and the scope of certain design devices implied in the interior/exterior relationship and described as a function of recognisable physical elements. For a long time, it was believed that this painting, placed on the altar of the oratory of San Lorenzo, was made in Palermo. It is a piece of fake news detected by interpreting and examining an architectural interior. Here, the value of natural light emerges, and we glimpse an irrefutable truth and therefore achieve an understanding of what happens when observing The Nativity and the oratory. What is the difference between recognising and identifying the arche, that is…
Comparison of spike parameters from optically identified GABAergic and glutamatergic neurons in sparse cortical cultures
2015
We are pleased to note that our publication “Comparison of spike parameters from optically identified GABAergic and glutamatergic neurons in sparse cortical cultures” by Weir et al. (2015) raised some discussion on the feasibility of solely electrophysiological discrimination of distinct neuronal subpopulations in vitro. We agree with Becchetti and Wanke (2015) that their report and our study on the same question were conducted with different technical approaches and that this may explain the observed differences between both studies. Although we obviously recorded a reduced spontaneous neuronal activity under our sparse culture conditions, these conditions were necessary to enable the uneq…
Quantum chemistry of the excited state: 2005 overview
2005
The present contribution contains an overview of quantum-chemical methods and strategies to compute and interpret spectroscopic and photochemical phenomena in molecular systems. The state of the art for the quantum chemistry of the excited state is reviewed, focusing in the advantages and disadvantages of the most commonly employed computational methods, from the single configurational procedures like CI-Singles (CIS), propagator approaches, and Coupled-Cluster (CC) techniques, to the more sophisticated multiconfigurational treatments, with particular emphasis on perturbation theory, the CASPT2 approach. Also, a short summary on the performance, lights, and shadows of the popular TDDFT meth…
Fall of Potential Measurement of the Earth Resistance in Urban Environments: Accuracy Evaluation
2019
Both Standards EN 50522 and IEEE 81 propose the fall of potential method (FPM) to carry out the measurement of the resistance to earth ( $R_{\text{ES}}$ ) of an earthing system (ES). However, in urban areas, the recommended distances between the ES and auxiliary electrodes are not easy to respect, due to the presence of buildings and tarmac. Furthermore, unknown buried metallic parts and interconnections among ESs could modify the earth potential profile of the area, affecting the measurement results. In this paper, the key-issues that influence the measured $R_{\text{ES}}$ when the FPM is used in an urban environment are presented. A parametric analysis, carried out with Comsol Multiphysic…
Nonlinear response theory for Markov processes: simple models for glassy relaxation.
2012
The theory of nonlinear response for Markov processes obeying a master equation is formulated in terms of time-dependent perturbation theory for the Green's functions and general expressions for the response functions up to third order in the external field are given. The nonlinear response is calculated for a model of dipole reorientations in an asymmetric double well potential, a standard model in the field of dielectric spectroscopy. The static nonlinear response is finite with the exception of a certain temperature $T_0$ determined by the value of the asymmetry. In a narrow temperature range around $T_0$, the modulus of the frequency-dependent cubic response shows a peak at a frequency …