Generation of H₂ on Board Lng Vessels for Consumption in the Propulsion System

[Abstract] At present, LNG vessels without reliquefaction plants consume the BOG (boil-off gas) in their engines and the excess is burned in the gas combustion unit without recovering any of its energy content. Excess BOG energy could be captured to produce H₂, a fuel with high energy density and zero emissions, through the installation of a reforming plant. Such H₂ production would, in turn, require on-board storage for its subsequent consumption in the propulsion plant when navigating in areas with stringent anti-pollution regulations, thus reducing CO₂ and SOₓ emissions. This paper presents a review of the different H₂ storage systems and the methods of burning it in propulsion engines, to demonstrate the energetic viability thereof on board LNG vessels. Following the analysis, it is identified that a pressurised and cooled H₂ storage system is the best suited to an LNG vessel due to its simplicity and the fact that it does not pose a safety hazard. There are a number of methods for consuming the H₂ generated in the DF engines that comprise the propulsión plant, but the use of a mixture of 70% CH₄-30% H₂ is the most suitable as it does not require any modifications to the injection system. Installation of an on-board reforming plant and H₂ storage system generates sufficient H₂ to allow for almost 3 days’ autonomy with a mixture of 70%CH₄-30%H₂. This reduces the engine consumption of CH₄ by 11.38%,thus demonstrating that the system is not only energy-efficient, but lends greater versatility to the vessel

Pressure dependence of the melting mechanism at the limit of overheating in Lennard-Jones crystals

We study the pressure dependence of the melting mechanism of a surface free Lennard-Jones crystal by constant pressure Monte Carlo simulation. The difference between the overheating temperature($T_{OH}$) and the thermodynamical melting point($T_M$) increase for increasing pressure. When particles move into the repulsive part of the potential the properties at $T_{OH}$ change. There is a crossover pressure where the volume jump becomes pressure-independent. The overheating limit is pre-announced by thermal excitation of big clusters of defects. The temperature zone where the system is dominated by these big clusters of defects increases with increasing pressure. Beyond the crossover pressure we find that excitation of defects and clusters of them start at the same temperature scale related with $T_{OH}$.Comment: 6 pages, 5 figures. Accepted for publication in Physical Review

The granites of Galicia used as industrial rock

[Resumen] Se han estudiado todos los tipos de rocas graníticas de la Comunidad Autónoma de Galicia para su utilización como roca industrial: áridos y piedra natural. El mercado de los áridos y la industria de la Piedra Natural son dos subsectores mineros de primer orden, tanto en Galicia como en el resto de España, con producciones globales en granitoides de 10 Mt (millones de toneladas) y un valor anual cercano a los 31.000 Mpts (millones de pesetas) para Galicia. Los tipos litológicos beneficiados son: granitoides inhomogéneos, granitos de dos micas, granitos biot1ticos y ortogneises, cuyas diferencias petrológicas, texturales y mineralógicas van a condicionar su nivel de calidad en uno y otro mercado.[Abstract] We have studied aH the types of granitic rocks of the region of Galicia, for their use as an industrial rock in aggregates and natural stone. The aggregate market and the natural stone industry are very important mining subsection, as much in Galicia as in the rest of Spain, with general granite productions of 10 Mt (millions of tonnes) and 31.000 Mpts (miHions of pesetas) as the annual value in Galicia. The types of mining rocks are: inhomogeneous granite, two mica granite, biotite granite and granite gneiss, whose petrological, textural and mineralogical differences determine their quality level in both uses

Analytic description of the scattering of electrons by molecules

The scattering of electrons by molecules is considered. The structure of the molecule is described in terms of the vibron model, which is an algebraic approach to the description of rotational and vibrational molecular excitations. The dynamics of electron-molecule collision is discussed in terms of coupled-channel calculations, where we assume an isocentrifugal approximation. In the sudden limit, where the excitation energies of the molecule are neglected, the coupled-channel system decouples into eigenchannels. The scattering amplitudes of the eigenchannels, characterized by 1/r2 potentials, are obtained analytically. The resulting probabilities of excitation of the molecular states and the limiting values of the quasielastic cross sections are evaluated in the U(3) and the O(4) limits. A comparison of the results for the differential cross sections with experimental data and other calculations is made for LiF and KI.Dirección General de Investigación Científica y Técnica PB92-06

Three-body continuum discretization in a basis of transformed harmonic oscillator states

The inclusion of the continuum in the study of weakly-bound three-body systems is discussed. A transformed harmonic oscillator basis is introduced to provide an appropriate discrete and finite basis for treating the continuum part of the spectrum. As examples of the application of the method the strength functions corresponding to several operators that couple the ground state to the continuum are investigated, for 6He, and compared with previous calculations. It is found that the energy moments of these distributions are accurately reproduced with a small basis set.Comment: 12 figures, submitted to PR

Transformaciones de haz mediante microlentes selfoc activas

[EN]: In this paper light propagation in an active selfoc microlens with complex refractive index and gradient parameter are examined. The ray-transfer matrix of an active material regarded as a diffraction-free first order optical system is presented to describe the beam transformations in active selfoc microlenses. Results concerning Gaussian beam transformationsand on-axis irradiance through the active selfoc microlens are discussed and commented. © Sociedad Española de Óptica.[ES]: En este trabajo se estudia la propagación de la luz a través de una microlente selfoc activa con un índice de refracción y parámetro de gradiente complejos. La matriz de transferencia de rayos, vista como un sistema óptico de primer orden libre de efectos de difracción, es introducida para describir las transformaciones que puede sufrir un haz en microlentes selfoc activas. Por último se presentan y comentan los resultados correspondientes a las transformaciones de haces Gaussianos y a la irradiancia en eje a través de la microlente selfoc activa.This work has been sponsored by Xunta de Galicia/Feder (INCITE08PXIB206013PR), Ministerio de Ciencia e Innovación (MAT2010-18519) and CDTI (SURFALUX SOL-00030930), Spain. Besides, Ana I. Gomez-Varela wants to acknowledge the financial support from the FPU (Formación de Profesorado Universitario) grant 2009 (Ministerio de Educación, Spain).Peer Reviewe

Four-body continuum-discretized coupled-channels calculations using a transformed harmonic oscillator basis

The scattering of a weakly bound three-body system by a target is discussed. A transformed harmonic oscillator basis is used to provide an appropriate discrete and finite basis for treating the continuum part of the spectrum of the projectile. The continuum-discretized coupled channels framework is used for the scattering calculations. The formalism is applied to different reactions, 6He+12C at 229.8 MeV, 6He+64Zn at 10 and 13.6 MeV, and 6He+208Pb at 22 MeV, induced by the Borromean nucleus 6He. Both the Coulomb and nuclear interactions with a target are taken into account.Comment: Published in Phys. Rev.

Photocatalytic activity of nitrogen-doped and undoped titanium dioxide sputtered thin films

In the present work titanium dioxide (TiO2) thin films were grown by d.c. reactive magnetron sputtering process, systematically varying the Ar/O2 ratio in the gas mixture, in order to study the influence of the oxygen partial pressure on the crystallographic structure and photocatalytic activity of the TiO2 thin films. After the sputtering process the TiO2 coatings were nitrided in a microwave (f= 2.45 GHz) Electron Cyclotron Resonance (ECR) plasma discharge in pure nitrogen, to compare the photocatalytic activity of undoped and nitrogen-doped TiO2 thin films. The crystal structure of the TiO2 grown samples was studied by x-ray diffraction (XRD) and the presence of the anatase phase in these films were corroborated by Raman spectroscopy. On the other hand, X-ray photoelectron spectroscopy (XPS) measurements carried out in the nitrogen-doped TiO2 samples, showed that the nitrogen was incorporated to the films with an average concentration of 18 at% of N. The UV-Vis optical spectroscopy allowed calculating the band gap. A narrowing of the optical band gap from 3.2 eV for the undoped films to 2.5 eV for the N-doped films was observed. Photocatalytic activity tests were done using a methylene blue (MB) dye solution. The irradiation of the films in the MB dye solution was carried out with an emission lamp in the UV and in the visible range for undoped and N-doped TiO2 films, respectively. The results showed that the N-doped TiO2 films had a higher photocalytic activity in the visible range, reaching a greater MB degradation in comparison with undoped samples, which were subjected to a higher energy radiation.Fil: Franco Arias, Lina Maria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad del Valle; ColombiaFil: Zambrano, G.. Universidad del Valle; ColombiaFil: Gómez, M. E.. Universidad del Valle; ColombiaFil: Camps, E.. Instituto Nacional de Investigaciones Nucleares; MéxicoFil: Escobar Alarcón, L.. Instituto Nacional de Investigaciones Nucleares; Méxic

Structural and optical characterisation of planar waveguides obtained via sol-gel

8 páginas, 6 figuras, 1 tabla.-- Trabajo presentado a la "International Conference on Applications of Optics and Photonics" celebrada en Braga (Portugal) en Mayo del 2011.Planar waveguides of SiO2:TiO2 (multilayer structure) and SiO2:CeO2 (thick layer) were prepared onto commercial glass substrates using a sol-gel technique combined with dip-coating. These glassy coatings were structural characterised by Transmission Electron Microscopy (TEM) Energy Dispersive X-ray analysis and by Confocal Microscopy. Thicknesses of 1230 nm and 4,15 μm and refractive indices of 1.59 and 1.48 for SiO2:TiO2 (70:30) and SiO2:CeO2 (95:5) waveguides were obtained, respectively, by Spectroscopic Ellypsometry. Losses of 0.8 dB/cm were measured by double prism method in the SiO2:CeO2 system.The authors acknowledge funding from MICINN (TEC2006-10469, CEN 2007-2014, SURFALUX SOL-00030930 and MAT2010-18519), from DGA (Group of Excellence in Laser Material Processing and Characterisation) and XUNTA DE GALICIA (INCITE08PXIB206013PR).Peer reviewe

Sex-Specific Effects of Early Life Stress on Brain Mitochondrial Function, Monoamine Levels and Neuroinflammation

Sex differences have been reported in the susceptibility to early life stress and its neurobiological correlates in humans and experimental animals. However, most of the current research with animal models of early stress has been performed mainly in males. In the present study, prolonged maternal separation (MS) paradigm was applied as an animal model to resemble the effects of adverse early experiences in male and female rats. Regional brain mitochondrial function, monoaminergic activity, and neuroinflammation were evaluated as adults. Mitochondrial energy metabolism was greatly decreased in MS females as compared with MS males in the prefrontal cortex, dorsal hippocampus, and the nucleus accumbens shell. In addition, MS males had lower serotonin levels and increased serotonin turnover in the prefrontal cortex and the hippocampus. However, MS females showed increased dopamine turnover in the prefrontal cortex and increased norepinephrine turnover in the striatum, but decreased dopamine turnover in the hippocampus. Sex differences were also found for pro-inflammatory cytokine levels, with increased levels of TNF-α and IL-6 in the prefrontal cortex and hippocampus of MS males, and increased IL-6 levels in the striatum of MS females. These results evidence the complex sex- and brain region-specific long-term consequences of early life stress.This work was supported by grants PSI 2017-83038-P to HGP and NC, PSI 2017-90806-REDT to JLA, PSI 2017-83893-R to JLA (Ministry of Economy and Competitiveness, Spain)