Search results for "surface"
showing 10 items of 9345 documents
Urban runoff modelling uncertainty: Comparison among Bayesian and pseudo-Bayesian methods
2009
Urban stormwater quality modelling plays a central role in evaluation of the quality of the receiving water body. However, the complexity of the physical processes that must be simulated and the limited amount of data available for calibration may lead to high uncertainty in the model results. This study was conducted to assess modelling uncertainty associated with catchment surface pollution evaluation. Eight models were compared based on the results of a case study in which there was limited data available for calibration. Uncertainty analysis was then conducted using three different methods: the Bayesian Monte Carlo method, the GLUE pseudo-Bayesian method and the GLUE method revised by m…
Atmospheric dry deposition processes of particles on urban and suburban surfaces: Modelling and validation works
2019
Abstract Dry deposition process is one of the important pathways for the removal of particles from atmosphere. It is the result of a combination of different environmental and physical factors as atmospheric conditions, particle properties, characteristics of the canopy. For this latter factor, urban canopy represents unevenly combinations of different types of surface elements that increases the complexity of deposition process phenomena. Therefore, particle dry deposition on urban surfaces is not easy to configure and, although empirical or semi-empirical models in literature have been developed to address this aspect, there is not standardized and commonly accepted criteria, especially f…
Urban Surface Energy Balance Models: Model Characteristics and Methodology for a Comparison Study
2009
Many urban surface energy balance models now exist. These vary in complexity from simple schemes that represent the city as a concrete slab, to those which incorporate detailed representations of momentum and energy fluxes distributed within the atmospheric boundary layer. While many of these schemes have been evaluated against observations, with some models even compared with the same data sets, such evaluations have not been undertaken in a controlled manner to enable direct comparison. For other types of climate model, for instance the Project for Intercomparison of Land-Surface Parameterization Schemes (PILPS) experiments (Henderson-Sellers et al., 1993), such controlled comparisons hav…
Effects of simulated environmental changes on growth and growth form in a late snowbed population of pohlia wahlenbergii (Web. et Mohr) Andr
2003
In a factorial field experiment we increased the temperature (Open Top Chambers) and nutrients (nitrogen, phosphorus, and potassium [NPK]) to simulate predicted future climate changes and studied the growth response of the acrocarpous bryophyte Pohlia wahlenbergii (Bryaceae) in a wet snowbed environment. The species shows a positive growth-length response to added nutrients and increased temperature. The stronger response to nutrients indicates a strong limitation of nutrients in the snowbed environment. There was an immediate response to nutrient treatment, whereas the temperature response was delayed. The growth response shows a clear interaction between temperature and nutrients. The imm…
Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation
2014
International audience; This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ∼ 6 and ∼ 0.2 k BP in Eu-rope. We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthro-pogenic land use (deforestation) from the HYDE3.1 (History Database of the Global Environment) scenario (V + H3.1), and (iii) potential vegetation with anthropogenic land …
Chemical effect on the XPS spectra of the valence band and on O KLL and Pd MNN Auger spectra in pumice-supported catalysts
1992
X-ray photoelectron spectra of the valence band and X-ray-excited O KLL Auger transition of pumice-supported Pd and Pt catalysts have been obtained and compared to the corresponding spectra of pumice (a naturally occurring amorphous aluminosilicate). The changes observed indicate interaction between metal and support. The valence region of the catalysts consists of three large peaks: one due to the d band of the metals and the other to the O 2p non-bonding orbitals and bonding-type orbitals formed by a mixing of the atomic orbitals (O 2p, Si 3s and Si 3p) of oxygen and silicon from the support. The intensity decrease of the component due to the bonding orbitals, observed in the catalyst spe…
Spin Switching in Molecular Quantum Cellular Automata Based on Mixed-Valence Tetrameric Units
2016
In this article we focus on the study of spin effects in a single square-planar mixed-valence cell comprising two electrons and in coupled molecular cells for quantum cellular automata. Using the vibronic model we demonstrate that the polarizabilities of the cell are different in spin-singlet and spin-triplet states of the electronic pair. Based on this inference the concept of spin switching in molecular quantum cellular automata is proposed, and the conditions under which this effect is feasible are derived. In order to reveal these conditions we have performed a series of quantum-mechanical calculations of the vibronic energy levels of the isolated cell and of the cell subjected to the e…
Photomagnetic effect in a cyanide-bridged mixed-valence {FeII2FeIII2} molecular square
2012
The self-assembly of [Fe(III)(Tp)(CN)(3)](-) and [Fe(II)(bik)(2)(S)(2)](2+) affords the cyanide-bridged mixed valence {Fe(III)(2)Fe(II)(2)}(2+) molecular square, which exhibits a photomagnetic effect under laser light irradiation at low temperature and also shows thermal spin-state conversion near ambient temperature.
When Does Gold Behave as a Halogen? Predicted Uranium Tetraauride and Other MAu4 Tetrahedral Species, (M = Ti, Zr, Hf, Th)
2003
Quantum chemical calculations suggest that a series of molecules with the general formula MAu4 are stable, where M = U, Th, and a group-4 atom. They correspond to Au in the formal valence state -1 and indicate that gold can act as a ligand similar to the halogen series. Of the MAu4 species studied, UAu4, the first predicted mixed gold uranium compound, has a short M-Au bond distance, 2.71 A, which would locate Au between Br and I from the bond length point of view in the U-tetrahalide series. Energetically, the U-Au bond is weaker than the corresponding U-Br and U-I bonds.
Spin-resolved low-energy and hard x-ray photoelectron spectroscopy of off-stoichiometric Co2MnSi Heusler thin films exhibiting a record TMR
2015
Half-metallic Co2MnSi-based Heusler compounds have attracted attention because they yield very high tunnelling magnetoresistance (TMR) ratios. Record TMR ratios of 1995% (at 4.2 K) are obtained from off-stoichiometric Co2MnSi-based magnetic tunnel junctions. This work reports on a combination of band structure calculations and spin-resolved and photon-polarisation-dependent photoelectron spectroscopy for off-stoichiometric Heusler thin films with the composition Co2Mn1.30Si0.84. Co and Mn are probed by magnetic dichroism in angle-resolved photoelectron spectroscopy at the 2p core level. In contrast to the delocalised Co 3d states, a pronounced localisation of the Mn 3d states is deduced fro…