Ab-Initio Studies on Carburization of Fe3Al Based Alloys

AbstractFe-Al based alloys exhibit excellent properties but suffer metal dusting in carburizing atmospheres. Surface composition can be a determinant factor in the solution of this problem. We calculate in this work the C adsorption energies in the L21 Fe2AlX (X=Ti,V,Nb) structures and we study the influence of surface covering. Our results show the beneficial effect of Ti, suggesting that there could exist an activation energy to promote the incorporation of C in the subsurface layers when the surface is covered enoug

C–H activation and metalation at electrode surfaces: 2,3-dimethyl-1,4-dihydroxybenzene on Pd(pc) and Pd(111) studied by TLE, HREELS and DFT

Previous studies, based on thin-layer electrochemistry (TLE), in situ scanning tunneling microscopy (EC-STM), high-resolution electron energy loss spectroscopy (HREELS) and density functional theory (DFT) computations, on the chemical adsorption of hydroquinone from aqueous solutions onto atomically smooth Pd (and Pt) electrode surfaces indicated two modes of attachment that depended upon the solution concentration. At low activities, the diphenol was oxidatively chemisorbed as benzoquinone in a flat orientation, suggestive of a Pd(2,3,5,6-η-C_6H_4O_2) surface complex; at higher concentrations, vertical chemisorption was effected via two C–H bond activations (or metalations) at the 2 and 3 ring positions, evocative of an o-phenylene organopalladium compound. We have extended the work to 2,3-dimethyl-1,4-dihydroxybenzene on Pd(pc) and Pd(111) electrodes to probe the effect of two methyl substituents on only one side of the diphenol ring. Surface coverage and adsorbed-molecule cross section data from TLE and HREELS measurements revealed non-random concentration-dependent adsorbate orientations similar to the oxidative chemisorption of hydroquinone: flat at low concentrations and edgewise at elevated concentrations. The DFT results suggested that, for the flat structure, surface coordination is via the two double bonds of the quinone ring as in [Pd(2,3,5,6-η)-2,3-dimethyl-p-quinone]. For the edge-vertical orientation, a structure analogous to an o-phenylene compound is generated in which C–H bonds at the 5 and 6 ring positions are activated and then metalated. DFT-simulated HREELS spectra helped identify the observed peaks that distinguish the surface-coordinated quinone from the surface-metalated diphenol

Unveiling the interaction of reactions and phase transition during thermal abuse of Li-ion batteries

Safety considerations have always accompanied the development of new battery chemistries; this holds especially for the Li-ion battery with its highly reactive components. An overall assessment and decrease of risks of catastrophic failures such as during thermal runaway, requires an in-depth and quantitative understanding of the ongoing processes and their interaction. This can be provided by predictive mathematical models. Thus, we developed a thermal runaway model that focuses on rigorous modelling of thermodynamic properties and reactions of each component within a Li-ion battery. Moreover, the presented model considers vapour–liquid equilibria of a binary solvent mixture for the first time. Simulations show a fragile equilibrium between endothermic and exothermic reactions, such as LiPF$_{6}$ and LEDC decomposition, in the early phases of self-heating. Further, an autocatalytic cycle involving the production of HF and the SEI component Li$_{2}$CO$_{3}$ could be revealed. Additionally, the unpredictability of the thermal runaway could be directly correlated to availability of LEDC or contaminants such as water. Also, solvent boiling can have a significant influence on the self-heating phase of a Li-ion battery, due to its endothermic nature. Further analysis revealed that the rising pressure, stemming from gassing reactions, can suppress solvent boiling until the thermal runaway occurs

On the complexity of computing the kk-restricted edge-connectivity of a graph

The \emph{$k$-restricted edge-connectivity} of a graph $G$, denoted by $\lambda_k(G)$, is defined as the minimum size of an edge set whose removal leaves exactly two connected components each containing at least $k$ vertices. This graph invariant, which can be seen as a generalization of a minimum edge-cut, has been extensively studied from a combinatorial point of view. However, very little is known about the complexity of computing $\lambda_k(G)$. Very recently, in the parameterized complexity community the notion of \emph{good edge separation} of a graph has been defined, which happens to be essentially the same as the $k$-restricted edge-connectivity. Motivated by the relevance of this invariant from both combinatorial and algorithmic points of view, in this article we initiate a systematic study of its computational complexity, with special emphasis on its parameterized complexity for several choices of the parameters. We provide a number of NP-hardness and W[1]-hardness results, as well as FPT-algorithms.Comment: 16 pages, 4 figure

Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf3+

This work proposes a new methodology to build interaction potentials between a highly charged metal cation and water molecules. These potentials, which can be used in classical computer simu- lations, have been fitted to reproduce quantum mechanical interaction energies (MP2 and BP86) for a wide range of [M(H2O)n]m+(H2O)l clusters (n going from 6 to 10 and l from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the cation-water potential. The simultaneous consideration of poly-hydrated clusters and the polarizability of the interacting particles allows the inclusion of the most important many-body effects in the new polarizable potential. Applications have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solution. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulations of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaion structure with coordination number close to 8 and average RCf–O in the range 2.43–2.48 Å, whereas the fourth one is closer to 9 with RCf–O = 2.54 Å. Simulated EXAFS spectra derived from the structural Monte Carlo distribution compares fairly well with the available experimental spectrum for the simulations bearing 8 water molecules. An angular distribution similar to that of a square antiprism is found for the octa-coordination.Ministerio de Ciencia e Innovación CTQ2011-2593

Efectos del tráfico del tractor sobre la distribución de la compactación del suelo y los rendimientos de trigo en España

395-403The general objective of this paper was to quantify the changes in the physical properties of an Aridisol soil and the effect on wheat yield due to agricultural tractors traffic in the Vélez Blanco District, Almería Spain. Parameters measured were cone index (CI) in the 0-600 mm depth profile, bulk density (BD) and rut depth; the variable wheat yields (WY) was measured too. The traffic treatments applied were: 0 (control plot), 1, 3, 5, and 7 tractor passes in the same tracks. Each experimental plot was trafficked with two tractors, one light (60 kN) and one heavy (80 kN). In topsoil (0-200 mm), up to five passes of the heavy (HT) and light tractors (LT), as in one and three passes, the BD and CI values responded to the ground pressure being higher in absolute value for LT. For the 200 to 400 mm depth range HT caused higher CI (1,570 to 2,200 kPa) and BD (1.38 to 1.68 Mg m-3) values than LT. Eight months later, WY was evaluated in tractor's track areas and decreases in the range of 18-38 percent, were measured. For seven passes the applications of total loads of 80 and 60 kN increased BD up to 1.5 Mg m-3 at depths of 200-600 mm. Although soil had high bulk density prior to traffic treatments, a significant increment of subsoil compaction still occurred due to the high traffic intensities applied

Efectos del tráfico del tractor sobre la distribución de la compactación del suelo y los rendimientos de trigo en España

The general objective of this paper was to quantify the changes in the physical properties of an Aridisol soil and the effect on wheat yield due to agricultural tractors traffic in the Vélez Blanco District, Almería Spain. Parameters measured were cone index (CI) in the 0-600 mm depth profile, bulk density (BD) and rut depth; the variable wheat yields (WY) was measured too. The traffic treatments applied were: 0 (control plot), 1, 3, 5, and 7 tractor passes in the same tracks. Each experimental plot was trafficked with two tractors, one light (60 kN) and one heavy (80 kN). In topsoil (0-200 mm), up to five passes of the heavy (HT) and light tractors (LT), as in one and three passes, the BD and CI values responded to the ground pressure being higher in absolute value for LT. For the 200 to 400 mm depth range HT caused higher CI (1,570 to 2,200 kPa) and BD (1.38 to 1.68 Mg m-3) values than LT. Eight months later, WY was evaluated in tractor's track areas and decreases in the range of 18-38%, were measured. For seven passes the applications of total loads of 80 and 60 kN increased BD up to 1.5 Mg m-3 at depths of 200-600 mm. Although soil had high bulk density prior to traffic treatments, a significant increment of subsoil compaction still occurred due to the high traffic intensities applied.El objetivo general del estudio fue cuantificar los cambios producidos en las propiedades físicas de un suelo Aridisol y los efectos sobre el rendimiento del trigo debido al tráfico de tractores agrícolas en Vélez Blanco, Almería, España. Los parámetros analizados fueron índice de cono (IC) a una profundidad de 0-600 mm, densidad aparente (DA) y profundidad de huella; también se analizó la variable rendimiento del trigo (RT). Los tratamientos de tráfico aplicados fueron: cero (parcela testigo), y uno, tres, cinco, y siete pasadas de tractor sobre la misma huella. En cada parcela experimental se utilizaron dos tractores, uno ligero (60 kN) y uno pesado (80 kN). En el horizonte superficial (0-200 mm), hasta las cinco pasadas de los tractores pesados (TP) y ligeros (TL), los valores de DA y de IC respondieron a la presión en el área de contacto, siendo más alto en valor absoluto para TL cuando pasó una y tres veces. Para el rango de profundidad 200-400 mm, TP causó valores más altos de IC (1.570 a 2.200 kPa) y DA (1,38 a 1,68 Mg m-3) que TL. RT se evaluó ocho meses después sobre el área pisada, observándose una disminución en un rango de 18-38%. Las cargas totales aplicadas de 80 y 60 kN, con siete pasadas, aumentaron DA hasta 1,5 Mg m-3 en el rango 200-600 mm. A pesar de que el suelo presentó una alta DA antes de aplicar los tratamientos, se observó un incremento significativo de la compactación del subsuelo por las altas intensidades de tráfico aplicadas.Facultad de Ciencias Agrarias y Forestale

Tratamiento de salmueras de fermentación de aceitunas verdes

The paper studies the characteristics of the several procedures that might be used to regenerate green table olive fermentation brines with the aim of reusing them in other stages of the elaboration process and specially for the final packaging of these fruits. The reuse may considerably reduce the waste water pollution of the canning industry as brines make up about 80% of the organic pollutant lead of its waste waters. The two most interesting methods are: adsorption with activated carbon, followed by a cross filtration to separate the adsorbent; and ultrafiltration. The former, should be GA activated carbon, which is the most efficient, in a proportion ranging between 5 and 10 g per litre. For the second, a polysulphone 1.000 daltons molecular weight cut membrane at 18 bars pressure should be used. A previous treatment of brines with bentonite (2 g/l), a range of temperatures between 30 and 45°C as well as low suspended solids and polyphenol contents, increases efficiency notably. In principle, an approximate study of costs shows that regenerated brines are obtained, using either of the two procedures, at slightly lower prices than fresh brines prepared from their ingredients.El trabajo compara las características de los diversos tratamientos de regeneración aplicables a las salmueras de fermentación de aceitunas verdes estilo sevillano para poderlas reutilizar en otras operaciones dentro del proceso productivo, en especial en el envasado final de los frutos. Con ello, se reduciría el vertido de estas soluciones que son las responsables de la carga contaminante del efluente de estas industrias. Los dos métodos más interesantes son: adsorción con carbón activo, seguido de una filtración tangencial para separar el absorbente; y la ultrafiltración. En el primer caso, el tipo de carbón activo más eficaz es el denominado GA, que necesita ser utilizado en una proporción entre 5 y 10 g por litro. En el segundo una membrana de polisulfona de 1.000 daltons de corte molecular es lo más adecuado, trabajando a una presión de 18 bars. Un pretratamiento con bentonita (2 g/l), temperatura entre 30 y 45°G y la menor concentración inicial de polifenoles y sólidos en suspensión aumentan el rendimiento de forma considerable. En principio, un estudio económico aproximado de costes indica que la regeneración por cualquiera de los dos sistemas daría una salmuera regenerada a un precio algo inferior al obtenido al preparar el líquido de gobierno para envasar a partir de sus componentes

Efectos del tráfico del tractor sobre la distribución de la compactación del suelo y los rendimientos de trigo en España

The general objective of this paper was to quantify the changes in the physical properties of an Aridisol soil and the effect on wheat yield due to agricultural tractors traffic in the Vélez Blanco District, Almería Spain. Parameters measured were cone index (CI) in the 0-600 mm depth profile, bulk density (BD) and rut depth; the variable wheat yields (WY) was measured too. The traffic treatments applied were: 0 (control plot), 1, 3, 5, and 7 tractor passes in the same tracks. Each experimental plot was trafficked with two tractors, one light (60 kN) and one heavy (80 kN). In topsoil (0-200 mm), up to five passes of the heavy (HT) and light tractors (LT), as in one and three passes, the BD and CI values responded to the ground pressure being higher in absolute value for LT. For the 200 to 400 mm depth range HT caused higher CI (1,570 to 2,200 kPa) and BD (1.38 to 1.68 Mg m-3) values than LT. Eight months later, WY was evaluated in tractor's track areas and decreases in the range of 18-38%, were measured. For seven passes the applications of total loads of 80 and 60 kN increased BD up to 1.5 Mg m-3 at depths of 200-600 mm. Although soil had high bulk density prior to traffic treatments, a significant increment of subsoil compaction still occurred due to the high traffic intensities applied.El objetivo general del estudio fue cuantificar los cambios producidos en las propiedades físicas de un suelo Aridisol y los efectos sobre el rendimiento del trigo debido al tráfico de tractores agrícolas en Vélez Blanco, Almería, España. Los parámetros analizados fueron índice de cono (IC) a una profundidad de 0-600 mm, densidad aparente (DA) y profundidad de huella; también se analizó la variable rendimiento del trigo (RT). Los tratamientos de tráfico aplicados fueron: cero (parcela testigo), y uno, tres, cinco, y siete pasadas de tractor sobre la misma huella. En cada parcela experimental se utilizaron dos tractores, uno ligero (60 kN) y uno pesado (80 kN). En el horizonte superficial (0-200 mm), hasta las cinco pasadas de los tractores pesados (TP) y ligeros (TL), los valores de DA y de IC respondieron a la presión en el área de contacto, siendo más alto en valor absoluto para TL cuando pasó una y tres veces. Para el rango de profundidad 200-400 mm, TP causó valores más altos de IC (1.570 a 2.200 kPa) y DA (1,38 a 1,68 Mg m-3) que TL. RT se evaluó ocho meses después sobre el área pisada, observándose una disminución en un rango de 18-38%. Las cargas totales aplicadas de 80 y 60 kN, con siete pasadas, aumentaron DA hasta 1,5 Mg m-3 en el rango 200-600 mm. A pesar de que el suelo presentó una alta DA antes de aplicar los tratamientos, se observó un incremento significativo de la compactación del subsuelo por las altas intensidades de tráfico aplicadas.Facultad de Ciencias Agrarias y Forestale