Ca impurity in small mixed 4^4He-3^3He clusters

The structure of small mixed helium clusters doped with one calcium atom has been determined within the diffusion Monte Carlo framework. The results show that the calcium atom sits at the $^4$He-$^3$He interface. This is in agreement with previous studies, both experimental and theoretical, performed for large clusters. A comparison between the results obtained for the largest cluster we have considered for each isotope shows a clear tendency of the Ca atom to reside in a deep dimple at the surface of the cluster for $^4$He clusters, and to become fully solvated for $^3$He clusters. We have calculated the absorption spectrum of Ca around the $4s4p \leftarrow 4s^2$ transition and have found that it is blue-shifted from that of the free-atom transition by an amount that depends on the size and composition of the cluster.Comment: 24 pages, 11 figures. Accepted on Journal of Chemical Physic

Microscopic study of the He2-SF6 trimers

The He2-SF6 trimers, in their different He isotopic combinations, are studied both in the framework of the correlated Jastrow approach and of the Correlated Hyperspherical Harmonics expansion method. The energetics and structure of the He-SF6 dimers are analyzed, and the existence of a characteristic rotational band in the excitation spectrum is discussed, as well as the isotopic differences. The binding energies and the spatial properties of the trimers, in their ground and lowest lying excited states, obtained by the Jastrow ansatz are in excellent agreement with the results of the converged CHH expansion. The introduction of the He-He correlation makes all trimers bound by largely suppressing the short range He-He repulsion. The structural properties of the trimers are qualitatively explained in terms of the shape of the interactions, Pauli principle and masses of the constituents.Comment: 17 pages, 5 figures. Submitted to PR

System for Detection of Malicious Wireless Device Patterns

The research within presents the use of Hidden Markov Models (HMM) for the detection of wireless devices in highly noisy environments using their unintended electromagnetic emissions (UEE). All electromagnetic devices emit such radiation that is unique to the electronics, housing, and other device attributes. This pattern recognition system can provide continuous detection analysis and can provide ideal information regarding the distance to an unknown device. An experiment was performed where UEE of a device was detected by a spectrum analyzer. Experimental result shows that our model can accurately detect if there is a device nearby emitting UEE or not

Solidification of small para-H2 clusters at zero temperature

We have determined the ground-state energies of para-H$_2$ clusters at zero temperature using the diffusion Monte Carlo method. The liquid or solid character of each cluster is investigated by restricting the phase through the use of proper importance sampling. Our results show inhomogeneous crystallization of clusters, with alternating behavior between liquid and solid phases up to N=55. From there on, all clusters are solid. The ground-state energies in the range N=13--75 are established and the stable phase of each cluster is determined. In spite of the small differences observed between the energy of liquid and solid clusters, the corresponding density profiles are significantly different, feature that can help to solve ambiguities in the determination of the specific phase of H$_2$ clusters.Comment: 17 pages, accepted for publication in J. Phys. Chem.

In-cylinder pressure based model for exhaust temperature estimation in internal combustion engines

[EN] Exhaust temperature is a valuable parameter for engine control. However, measurement conditions at the engine exhaust and the slow dynamic response of temperature sensors difficult the determination of the instantaneous exhaust temperature. The present paper proposes a methodology for estimating the exhaust temperature exclusively relying in-cylinder pressure signal, engine speed and exhaust lambda.The presented methodology can replace or actualize widespread look-up table models for correcting calibration offsets, due to ageing, sensor bias or disturbances associated with the engine operation. The method uses the existence of resonant modes in the in-cylinder pressure for inferring the trapped mass and the in-cylinder temperature. An isentropic expansion of the gasses through the valves is assumed for estimating the cylinder outlet temperature of the gases, and the gas temperature drop along the exhaust runner and manifold is modelled through a nodal thermal model. The method was compared with current models under steady and transient conditions in a four stroke CI engine. Variations of injection, EGR, intake pressure and rail pressure were performed under steady operation and the transient response of the method was validated under specific transient test and at the WLTP cycle. A time invariant first order model was used for comparing the estimated temperature with that provided by the experimental sensors. (C) 2016 Elsevier Ltd. All rights reserved.This research has been partially financed by the Spanish Ministerio de Economia Competitividad, through project TRA2013-40853-R "Desarrollo de nuevas tecnicas de limitation de la perdida de presion en DPFs para reducir las emisiones y el consumo de los motores diesel (PRELIMIT)".Guardiola, C.; Olmeda, P.; Plá Moreno, B.; Bares-Moreno, P. (2017). In-cylinder pressure based model for exhaust temperature estimation in internal combustion engines. Applied Thermal Engineering. 115:212-220. https://doi.org/10.1016/j.applthermaleng.2016.12.092S21222011

State-dependent Jastrow correlation functions for 4He nuclei

We calculate the ground-state energy for the nucleus 4He with V4 nucleon interactions, making use of a Jastrow description of the corresponding wavefunction with state-dependent correlation factors. The effect related to the state dependence of the correlation is quite important, lowering the upper bound for the ground-state energy by some 2 MeV.Comment: 10 pages, REVTeX, to be published in J. Phys. G: Nucl. Part. Phy

Model-based passive and active diagnostics strategies for diesel oxidation catalyst

[EN] This article proposes a diesel oxidation catalyst diagnostics strategy based on the exothermic process generated by exhaust gas species oxidation in the catalyst. The diagnostics strategy is designed to be applied on-board and respecting real-time electronic control unit computational limitations. Diagnostics purposes are fulfilled by means of the comparison of the passive model temperature, which represents the outlet temperature of a non-impregnated diesel oxidation catalyst, and the measurement provided by the on-board catalyst-out temperature sensor. Thus, the presented diagnostics strategy uses only two production grade temperature sensors and the measurements of air and fuel mass flows from the electronic control unit. Passive diagnostics is based on the oxidation of engine-raw emissions, whilst active diagnostics is based on the oxidation of requested post injected fuel. Post-injection strategy is also discussed for active diagnosis. Then, the diagnostics strategy is able to discern whether the diesel oxidation catalyst is able to oxidise or not. (C) 2016 Elsevier Ltd. All rights reserved.This research has been partially financed by the Spanish Ministerio de Economia y Competitividad, through project TRA2013-40853-R 'Desarrollo de nuevas tecnicas de limitacion de la perdida de presion en DPFs para reducir las emisiones y el consumo de los motores diesel (PRELIMIT)'.Guardiola, C.; Plá Moreno, B.; Piqueras, P.; Mora-Pérez, J.; Lefebvre, D. (2017). Model-based passive and active diagnostics strategies for diesel oxidation catalyst. Applied Thermal Engineering. 110:962-971. https://doi.org/10.1016/j.applthermaleng.2016.08.207S96297111

Apuntes de historia política y de los tratados (1490 á 1815) : con arreglo al programa para los exámenes de ingreso en las carreras diplomatica y consular

Port. con escudo real

Atomic kinetic energy, momentum distribution and structure of solid neon at zero-temperature

We report on the calculation of the ground-state atomic kinetic energy, $E_{k}$, and momentum distribution of solid Ne by means of the diffusion Monte Carlo method and Aziz HFD-B pair potential. This approach is shown to perform notably for this crystal since we obtain very good agreement with respect to experimental thermodynamic data. Additionally, we study the structural properties of solid Ne at densities near the equilibrium by estimating the radial pair-distribution function, Lindemann's ratio and atomic density profile around the positions of the perfect crystalline lattice. Our value for $E_{k}$ at the equilibrium density is $41.51(6)$ K, which agrees perfectly with the recent prediction made by Timms {\it et al.}, $41(2)$ K, based on their deep-inelastic neutron scattering experiments carried out over the temperature range $4 - 20$ K, and also with previous path integral Monte Carlo results obtained with the Lennard-Jones and Aziz HFD-C2 atomic pairwise interactions. The one-body density function of solid Ne is calculated accurately and found to fit perfectly, within statistical uncertainty, to a Gaussian curve. Furthermore, we analyze the degree of anharmonicity of solid Ne by calculating some of its microscopic ground-state properties within traditional harmonic approaches. We provide insightful comparison to solid $^4$He in terms of the Debye model, in order to size the relevance of anharmonic effects in Ne.Comment: 20 pages, 7 figures. To be published in Physical Review

Synchronization, Diversity, and Topology of Networks of Integrate and Fire Oscillators

We study synchronization dynamics of a population of pulse-coupled oscillators. In particular, we focus our attention in the interplay between networks topological disorder and its synchronization features. Firstly, we analyze synchronization time $T$ in random networks, and find a scaling law which relates $T$ to networks connectivity. Then, we carry on comparing synchronization time for several other topological configurations, characterized by a different degree of randomness. The analysis shows that regular lattices perform better than any other disordered network. The fact can be understood by considering the variability in the number of links between two adjacent neighbors. This phenomenon is equivalent to have a non-random topology with a distribution of interactions and it can be removed by an adequate local normalization of the couplings.Comment: 6 pages, 8 figures, LaTeX 209, uses RevTe