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Soil erosion by water is a main form of land degradation worldwide. The problem has been addressed, among others, in the United Nations Sustainability Goals. However, for mitigation of erosion consequences and adequate management of affected areas, reliable information on the magnitude and spatial patterns of erosion is needed. Although such need is often addressed by erosion modelling, precise erosion monitoring is necessary for the calibration and validation of erosion models and to study erosion patterns in landscapes. Conventional methods for quantification of rill erosion are based on labour-intensive field measurements. In contrast, remote sensing techniques promise fast, non-invasive, systematic and larger-scale surveying. Thus, the main objective of this study was to develop and evaluate automated and transferable methodologies for mapping the spatial extent of erosion rills from a single acquisition of remote sensing data. Data collected by an uncrewed aerial vehicle was used to deliver a highly detailed digital elevation model (DEM) of the analysed area. Rills were classified by two methods with different settings. One approach was based on a series of decision rules applied on DEM-derived geomorphological terrain attributes. The second approach utilized the random forest machine learning algorithm. The methods were tested on three agricultural fields representing different erosion patterns and vegetation covers. Our study showed that the proposed methods can ensure recognition of rills with accuracies between 80 and 90% depending on rill characteristics. In some cases, however, the methods were sensitive to very small rill incisions and to similar geometry of rills to other features. Additionally, their performance was influenced by the vegetation structure and cover. Besides these challenges, the introduced approach was capable of mapping rills fully automatically at the field scale and can, therefore, support a fast and flexible assessment of erosion magnitudes.

We present an anharmonic approach for molecule-surface vibrations that employs rigid body coordinates, based on the Rodrigues rotation formula, to describe curvilinear displacements (rotations and translations) of the molecule along normal modes. These displacements are used to calculate energy data points from which one-dimensional polynomial potentials are fitted using cubic splines. In these potentials, for each of the six rigid body modes separately, one-dimensional Schrödinger equations are solved with harmonic oscillator or Fourier functions (for pure rotations) as basis sets. The anharmonic vibrational energies obtained are used to calculate partition functions and from them enthalpies, entropies, and Gibbs free energies of adsorption. Our numerical implementation has been successfully tested for Morse and cosine potentials with known analytical solutions. The methods have been applied to adsorption of CH

A hybrid QM:QM method (MP2:(PBE+D2) + ΔCCSD(T)) is employed that reaches chemical accuracy (±4 kJ mol−1) for periodic systems. Three mechanisms are considered and evidence is produced that cracking proceeds via protonation of a C C bond at the Bronsted acid site. For H-FER, H-MFI, and H-CHA, the deviations between predictions (uncertainty ± 4 kJ mol−1) and experiment (error ± 5 kJ mol−1) are between −3 and +8 kJ mol−1. The predicted apparent enthalpy barriers for H-FER, H-MFI, H-CHA, and H-FAU at 650 K are 153, 153, 160, and 182 kJ mol−1, respectively. Their variation with the pore size is dominated by the adsorption enthalpies (−55, −47, −40, and −29 kJ mol−1, respectively), whereas the intrinsic enthalpy barriers vary within a narrow range of 10 kJ mol−1 only. Routine PBE+D2 calculations show large errors, −16 to −20 and −40 to −60 kJ mol−1 for adsorption enthalpies and enthalpy barriers, respectively.

We use a chemically accurate (4 kJ/mol) hybrid MP2:(PBE+D2) + ΔCCSD(T) method to determine relative stabilities of all possible π-complexes, alkoxides, and carbenium ions formed from propene, buten...

The dependence of deprotonation energies of zeolitic Bronsted acid sites on the dielectric constants of these materials is investigated using quantum chemical calculations. The deprotonation energy decreases as the reciprocal value of average static dielectric constant of the zeolite framework increases with a correlation coefficient R2 equal to 0.74 (252 data points for 19 zeolite frameworks). We decompose the deprotonation energy of these nanoporous materials into an intrinsic deprotonation energy and a proton “solvation” energy within zeolites which is the origin of the observed 1/e dependence. The intrinsic deprotonation energy is shown to be a superior acidity descriptor. In agreement with experiments, it indicates that two-dimensional zeolites (nanosheets) are not more acidic than three-dimensional ones (bulk materials). We use our large data set to examine the dependence of the intrinsic deprotonation energy on structure parameters (Al O Si bond angle, O H bond distance, confinement coefficient) and on the structure relaxation energy but for none of them a correlation has been found.

A hybrid of high level and low level quantum mechanics (QM) methods has been employed to predict intrinsic and apparent energy barriers for the direct proton exchange mechanism of methane, ethane, propane, n-butane, and i-butane on Brønsted sites of H-MFI. The specific hybrid MP2:PBE+D2 + ΔCC implementation used is known to yield the so-called "chemical accuracy" (±4 kJ/mol). Whereas the apparent enthalpy barriers decrease with increasing C number from 104 to 63 kJ/mol, in line with the decreasing heat of adsorption, the intrinsic enthalpy barriers are constant within 124-127 kJ/mol at 500 K. For methane, ethane, propane, and n-butane, we find the expected agreement of apparent barriers with activation energies from batch recirculation reactor experiments. The activation energies derived from NMR experiments (103-113 kJ/mol) are similarly constant as the predicted intrinsic barriers but systematically lower. For i-butane the predicted intrinsic and apparent barriers for the direct proton exchange step are the same as for n-butane with deviations of 2-5 kJ/mol, while the experiments yield values that are 50-60 kJ/mol lower, far outside the estimated range of combined experimental and computational uncertainty (±14 kJ/mol). A change to the indirect proton exchange mechanism, in which a hydride ion is transferred between the alkane and a tert-butyl carbenium ion can be excluded, because we confirm previous findings that the barrier for dehydrogenation that would create a tert-butyl cation from i-butane is much too high, 188 and 132 kJ/mol for the intrinsic and apparent enthalpy barriers, respectively, at 500 K. The possible role of extraframework- and framework-bound alumina species is discussed.

This study uses time-series Sentinel-1(S-1) synthetic aperture radar images to evaluate the impact of multi-temporal polarimetric processing on land-cover classification. Various polarimetr...

This study uses the ray tracing method to simulate synthetic aperture radar (SAR) images of urban areas. The images are constructed for polarisations: horizontal-horizontal (HH) and vertical-vertic...

Post-processing is the last and often optional stage of land cover (LC) classification from satellite images. In the traditional approach, it is usually applied to remove the effect of “salt and pepper” from the classified image and also to standardize the image details according to the defined minimum mapping unit (MMU). The proposed post-processing method presented in this paper, has been used in the Sentinel-2 Global Land Cover (S2GLC) project. Its main goal is to remove or minimize typical classification errors that can appear in the classification output. Therefore, a set of functions that are able to improve the result of LC classifications has been developed. These include relatively simply defined rules that operate based on predefined threshold values of selected spectral channels, spectral indexes or auxiliary data. Additionally, logical relations between certain LC classes have been implemented. The proposed post-processing has been applied to the classification results of the S2GLC project and helped to improve LC classification in all test sites representing different parts of the globe.

Supervised classification of satellite images is performed based on utilization of reference training data. Therefore, the availability and quality of reference data highly influences the results and the course of the entire classification process. In the Sentinel-2 Global Land Cover (S2GLC) project Sentinel-2 images are classified using Random Forest (RF) algorithm powered by training points selected from existing low resolution land cover databases. This approach allows to perform the classification process in a highly automatic manner without much intervention of an operator. An alternative method for creating training dataset has been developed in order to ensure the implementation of the S2GLC classification in case of limited access to the required land cover databases or their low quality. The proposed method is a semi-automatic process initiated by an operator, who by a visual interpretation, indicates only several starting samples for the classes of interest. Afterwards, utilizing this limited set of initial training samples, hundreds or thousands of training samples with similar spectral characteristics are automatically selected from the image. Such a set of data, can be further used as an alternative source of training data for land cover classification on much greater scale. Comparing to the traditional approach, in which all samples or training areas are manually indicated, the developed method is very effective and also allows for processing data more rapidly. The semi-automatic training can be used as an alternative or supplement the training dataset applied in the S2GLC classification approach.

Agricultural land cover is characterized by fast changes within time. The phenological dynamic of plants can deliver crucial information for crop classifications. To enhance a crop classification multi-temporal indices are proposed. They are calculated based on the time series of coherence matrices and parameters of H/α decomposition derived from dual polarimetric synthetic aperture radar images (Sentinel-1). The study shows that the use of multi-temporal indices increases the accuracy of crop classification by 9% in comparison to classification based only on the time series of coherence matrices.

The general aim of this work was to elaborate efficient and reliable aggregation method that could be used for creating a land cover map at a global scale from multitemporal satellite imagery. The study described in this paper presents methods for combining results of land cover/land use classifications performed on single-date Sentinel-2 images acquired at different time periods. For that purpose different aggregation methods were proposed and tested on study sites spread on different continents. The initial classifications were performed with Random Forest classifier on individual Sentinel-2 images from a time series. In the following step the resulting land cover maps were aggregated pixel by pixel using three different combinations of information on the number of occurrences of a certain land cover class within a time series and the posterior probability of particular classes resulting from the Random Forest classification. From the proposed methods two are shown superior and in most cases were able to reach or outperform the accuracy of the best individual classifications of single-date images. Moreover, the aggregations results are very stable when used on data with varying cloudiness. They also enable to reduce considerably the number of cloudy pixels in the resulting land cover map what is significant advantage for mapping areas with frequent cloud coverage.

All the pre-processing algorithms are being improved constantly. The biggest challenge for the multitemporal analysis is to deal with errors caused directly by the chain of pre-processing of raw Sentinel-2 data to the level L1C - misregistration of pixels. Another problem to overcome while aggregating a series of classifications is the incorrect mask of clouds over artificial structures resulting from atmospheric correction performed with Sen2Cor software. Presented errors have direct influence on the overall accuracy of classifications performed in S2GLC project which are going to be implemented as a fully automatic process.

Solutions of NaCl, MgCl2 and CaCl2 in methanol–water mixtures have been investigated by the molecular dynamics simulations. Special attention has been paid to the OH stretching frequencies and hydrogen bonds of the water and methanol molecules in the subsystems; the coordination shells of the ions and the bulk solvent. The influence of the ions on the properties of the solvent molecules is limited to the first coordination shells and it depends on the ion charge density. Thus all cations affect the intramolecular bonds, valence angles, and the dipole moment and the Cl− ion influences only the length and vibrations of the nearest OH bond of the water molecules, but it does not affect the properties of the methanol molecules. Though the influence of the cations on the solvent molecules is strong, the interactions between the solvent molecules enhance the molecular polarization. In consequence the induced dipole moment and the OH frequencies of the water and methanol molecules in the cation shells depend also on the methanol mole fraction. The shift of the OH stretching frequency correlates linearly with the induced dipole moment, but it does not correlate with the strength of the hydrogen bonds.

The near-surface structural properties of epitaxial Fe(1 1 0) films on W(1 1 0) were studied using quantitative low-energy electron diffraction analysis. A discernible, up to 1%, relaxation of the outermost atomic layers was found, in contrast to the bulk Fe(1 1 0) surface, which shows almost no relaxation.

The growth of one and two atomic layers of iron on a W(110) substrate was followed by low-energy electron microscopy. The near-surface structural properties of the perfectly flat pseudomorphic films were studied by quantitative low-energy electron diffraction analysis from areas of uniform thickness as well as by the density functional theory. A strong relaxation of the outermost atomic layers was found in Fe mono- and bilayers on W(110). By calculating the phonon dispersion relations and phonon density of states, the stability of the pseudomorphic iron bilayer on a tungsten substrate has been addressed. To complete the physical picture, an iron trilayer has also been analyzed in order to identify the source of instability for its pseudomorphic phase. Our results show that the surface instability originates from the softening of the in-plane surface modes along the [110] direction, although the soft modes were not observed. The enhanced magnetic moments calculated within the density functional theory are in good agreement with experimental findings reported for these systems.

Molecular dynamics simulations of MgCl 2 solutions in methanol–water mixtures, over the whole range of the methanol mole fraction at room temperature have been performed. The methanol and water molecules have been modeled as flexible three-site bodies. Solvation of the magnesium ions has been discussed on the basis of the radial and angular distribution functions, the orientation of the solvent molecules and their geometrical arrangement in the coordination shells. Analysis of the H-bonds of the solvent molecules coordinated by Mg 2+ has been based on a geometric criterion of the H-bond. Persistence of the primary and secondary shell has been estimated. In all studied solutions Mg 2+ is six-coordinated and the solvent molecules form an octahedron. The antidipole orientation of the molecules favours the water molecules as H-donors in the first shell and the methanol molecules as H-acceptor in the second shell. Thus an excess of water and an excess of methanol has been observed in the first and the second shells of Mg 2+ . An exchange of the solvent molecules between the primary and secondary shells occur. The persistence of the second shell is longer than the shells of monovalent ions.

Molecular dynamics simulations of CaCl2 solutions in water and methanol-water mixtures, with methanol concentrations of 5, 10, 50, and 90 mol %, at room temperature, have been performed. The methanol and water molecules have been modeled as flexible three-site bodies. Solvation of the calcium ions has been discussed on the basis of the radial and angular distribution functions, the orientation of the solvent molecules, and their geometrical arrangement in the coordination shells. Analysis of the H-bonds of the solvent molecules coordinated by Ca2+ has been done. Residence time of the solvent molecules in the coordination shell has been calculated. The preferential hydration of the calcium ions has been found over the whole range of the mixture composition. The water concentration in the first and second coordination shells of Ca2+ significantly exceeds the water content in the solution, despite the very similar interaction energy of the calcium ion with water and methanol. In aqueous solution and methanol-water mixtures, the first coordination shell of Ca2+ is irregular and long-living. The solvent molecules prefer the anti-dipole arrangement, but, in aqueous solutions and water-rich mixtures, the water molecules in the primary shell have only one H-bonded neighbor.

Sodium, calcium and magnesium ions are essential for the biological activity of many polyelectrolytes. This activity depends on a condensation of the metal ions. There are several clues, which suggest that interactions between the polyelectrolyte and metal ions depend on a hydration of the ion. This accounts for the great interest in the hydration of metal ions, particularly in the systems containing hydrophobic groups. In aqueous solutions the hydration of Na+, Mg2+ and Ca2+ differs. The first hydration shells of Na+ and Mg2+ consists of six water molecules and have octahedral symmetry (Dietz et al, 1982; Hawlicka & Swiatla-Wojcik, 1995). The first shell of Ca2+ is larger; it contains eight or more water molecules and does not show any regularity (Owczarek et al., 2007). X-ray diffraction studies (Tamura et al., 1992, Megyes et al., 2004) have suggested that all these cations are sixcoordinated in methanolic solutions thus their shells are octahedral.