Direct steam generation in parabolic trough collectors

Existing commercial parabolic trough power plants use thermal oil as a heat transfer fluid, with working temperatures in the region of 400ºC. In order to achieve more efficient generating systems, a second generation of parabolic troughs that operate at temperatures higher than 400ºC is being developed. One possibility, Abengoa Solar is assessing, it is the use of direct steam generation (DSG) inside parabolic troughs in order to achieve higher temperatures; the first stage heating up to 450 ºC and the second stage heating up to 550 ºC. There is, however, a certain degree of complexity in the use of DSG technology that has resulted in it not yet being utilized in commercial plant designs. Due to the presence of saturated steam inside the parallel loops the required control system is more complex, particularly during transitory periods of radiation. Also the higher operating pressures and temperatures in the solar field mean that the receiver tubes and interconnections between collectors are very critical components. For this reason, typical systems utilize an intermediate fluid for energy transfer. In order to overcome these challenges, Abengoa Solar has built a demonstration plant of 8 MWht. The plant is composed of an evaporator field with three parallel loops and a superheater field with two loops in order to work at 85 bar and 450ºC. The demonstration plant has been operated and evaluated for one year. During this test period, the following have been evaluated and validated: An innovative control strategy system that guarantees the stability of the plant even under transient conditions. Receiver tube design able to achieve 450ºC, analyzing the mechanical behavior, optical performance, and heat losses. Different configurations of interconnections between collectors with ball joints and flexible rotation joints. A theoretical model has been developed for commercial scale DSG plants and validated with experimental data obtained from the demonstration plant

Evolution along the sequence of S0 Hubble types induced by dry minor mergers. II - Bulge-disk coupling in the photometric relations through merger-induced internal secular evolution

Galaxy mergers are considered as questionable mechanisms for the evolution of lenticular galaxies (S0's), on the basis that even minor ones induce structural changes that are difficult to reconcile with the strong bulge-disk coupling observed in the photometric scaling relations of S0's. We check if the evolution induced onto S0's by dry intermediate and minor mergers can reproduce their photometric scaling relations, analysing the bulge-disk decompositions of the merger simulations presented in Eliche-Moral et al. (2012). The mergers induce an evolution in the photometric planes compatible with the data of S0's, even in those ones indicating a strong bulge-disk coupling. The mergers drive the formation of the observed photometric relation in some cases, whereas they induce a slight dispersion compatible with data in others. Therefore, this evolutionary mechanism tends to preserve these scaling relations. In those photometric planes where the morphological types segregate, the mergers always induce evolution towards the region populated by S0's. The structural coupling of the bulge and the disk is preserved or reinforced because the mergers trigger internal secular processes in the primary disk that induce significant bulge growth, even although these models do not induce bars. Intermediate and minor mergers can thus be considered as plausible mechanisms for the evolution of S0's attending to their photometric scaling relations, as they can preserve and even strengthen any pre-existing structural bulge-disk coupling, triggering significant internal secular evolution (even in the absence of bars or dissipational effects). This means that it may be difficult to isolate the effects of pure internal secular evolution from those of the merger-driven one in present-day early-type disks (abridged).Comment: Accepted for publication in Astronomy & Astrophysics, 13 pages, 8 figures. Definitive version after proofs. Added references and corrected typo

Blockchain-based architecture for the control of logistics activities: Pharmaceutical utilities case study

Logistics services involve a wide range of transport operations between distributors and clients. Currently, the large number of intermediaries are a challenge for this sector, as it makes all the processes more complicated. To face that problem, we propose a system that uses smart contracts to remove intermediaries and speed up logistics activities. Our new model combines smart contracts and a multi-agent system in a single platform to improve the current logistics system by increasing organization, security and getting rid of several human intermediaries to automate its processes, making distribution times significantly faster. Also, with this kind of approach, it is possible to apply penalties to parties that do not comply with the terms of using this platform.This work was developed as part of ‘Virtual Ledger Technologies DLT/Blockchain y Cripto-IOT sobre organizaciones virtuales de agentes ligeros y su aplicación en la eficiencia en el transporte de última milla’, ID SA267P18, project cofinanced by Junta Castilla y León, Consejería de Educación and FEDER funds. Also, the research work carried out by Yeray Mezquita is supported by the pre-doctoral fellowship from the University of Salamanca and Banco Santander

Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation

This is the peer-reviewed version of the following article: Fluorescence of methylated derivatives of hydroxyphenylimidazopyridine. Resolution of strongly overlapping spectra and a new ESIPT dye showing very efficient radiationless deactivation Alfonso Brenlla, Manoel Veiga, M. Carmen Ríos Rodríguez, Manuel Mosquera and Flor Rodríguez-Prieto Photochem. Photobiol. Sci., 2011, 10, 1622. DOI: 10.1039/c1pp05165b, which has been published in final form at http://pubs.rsc.org/en/content/articlelanding/2011/pp/c1pp05165b This article may be used for non-commercial purposes onlyThe ground- and excited-state behaviour of the isomeric species 2-(2′-methoxyphenyl)imidazo[4,5-b]pyridine (1-OMe) and 2-(2′-hydroxyphenyl)-4-methylimidazo[4,5-b]pyridine (1-NMe) in neutral and acid media has been studied by UV-vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The new dye 1-NMe is non-fluorescent in neutral media except in trifluoroethanol, where it shows a very weak fluorescence. 1-NMe also exhibits highly solvent-dependent fluorescence intensity in acidic media. We propose that the neutral species experiences a fast excited-state intramolecular proton transfer (ESIPT), relaxing afterwards by intramolecular twisting associated with internal charge transfer (TICT) and subsequent very fast internal conversion of the proton-transferred TICT structure. The behaviour of 1-NMe in acidic media is explained by the existence of a ground-state tautomeric equilibrium between species with intramolecular hydrogen bonds N–H⋯OH and N⋯HO. The first type of tautomers dissociates at the hydroxyl group in water and ethanol, but fluoresces in acetonitrile and trifluoroethanol due to the inability of these solvents to accept the proton. The second type of tautomers is non-emissive due to fast radiationless deactivation through an ESIPT-TICT process. The fluorescence of 1-OMe was investigated in neutral and acidic media, demonstrating the photobasic character of the pyridine nitrogen. A ground-state equilibrium between pyridinium and imidazolium cations was found for this species, showing overlapping absorption and fluorescence spectra. We devised a method to resolve the spectra by applying principal component global analysis to a series of excitation spectra taken at different emission wavelengths, which allowed estimation of the equilibrium constant between the cationsWe are indebted to the Spanish Ministry of Education and Science and the European Regional Development Fund (Grants CTQ2007-68057-C02-01/BQU and CTQ2010-17835) and the Xunta de Galicia (Grant IN845B-2010/094) for financial support of our work. A. Brenlla thanks the Fundación Segundo Gil Dávila for a postgraduate research grantS

Evolution induced by dry minor mergers onto fast-rotator S0 galaxies

We analysed collisionless N-body simulations of intermediate and minor dry mergers onto S0s to test whether these mergers can generate S0 galaxies with kinematics intermediate between fast and slow rotators. We find that minor mergers induce a lower decrease of the global rotational support than encounters of lower mass ratios, which results in S0s with properties intermediate between fast and slow rotators. The resulting remnants are intrinsically more triaxial, less flattened, and span the whole range of apparent ellipticities up to $\epsilon_\mathrm{e} \sim 0.8$. They do not show lower apparent ellipticities in random projections than initially; on the contrary, the formation of oval distortions and the disc thickening increase the percentage of projections at $0.4 < \epsilon_\mathrm{e} < 0.7$. In the experiments with S0b progenitor galaxies, minor mergers tend to spin up the bulge and to decrease slightly its intrinsic ellipticity, whereas in the cases of primary S0c galaxies they keep the rotational support of the bulge nearly constant and decrease significantly its intrinsic ellipticity. The remnant bulges remain nearly spherical ($B/A \sim C/A > 0.9$), but exhibit a wide range of triaxialities ($0.20 < T < 1.00$). In the plane of global anisotropy of velocities ($\delta$) vs. intrinsic ellipticity ($\epsilon_\mathrm{e,intr}$), some of our models extend the linear trend found in previous major merger simulations towards higher $\epsilon_\mathrm{e,intr}$ values, while others depart from it. This is consistent with the wide dispersion exhibited by real S0s in this diagram compared with ellipticals, which follow the linear trend drawn by major merger simulations. The different trends exhibited by ellipticals and S0 galaxies in the $\delta$ - $\epsilon_\mathrm{e}$ diagram may be pointing to the different role played by major mergers in the build-up of each morphological type.Comment: Corrected typos. 20 pages, 14 figures. Accepted for publishing in A&

Calibration of calculation models of wooden guardrails with Operational Modal Analysis

This study analyses the differences between two calculation models for guardrails on building sites that use wooden boards and tubular steel posts. Wood was considered an isotropic material in one model and an orthotropic material in a second model. The elastic constants of the wood were obtained with ultrasound. Frequencies and vibration modes were obtained for both models through linear analysis using the finite element method. The two models were experimentally calibrated through operational modal analysis. The results obtained show that for the three types of wood under analysis, the model which considered them as an orthotropic material fitted the experimental results better than the model which considered them as an isotropic material