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Liquid hydrocarbons conversion into hydrogen rich gas is a central process step in fuel processors for auxiliary power units (APUs) for naval applications. Diesel, together with gasoline, is the preferred fuel for these applications. The CNR-ITAE has developed an hydrogen generator based on steam reforming (SR) of n-dodecane (n-C 12 H 26 ) as surrogate of diesel, designed for a maximum hydrogen production of 1.5 Nm 3 /h. The prototype consists of an integrated catalytic reactor coupled with heat exchanger, static mixer, water–dodecane and recycle reservoirs, manual/automatic valves, pressure regulators/transducers, flow meters, and ancillaries. The unit has been engineered, focusing every single component and the system integration, to meet the requirements of small size and volume, improving thermal/mass transfer and system efficiency. This study reports the performance of the hydrogen generator with a commercial Rh-based catalyst, packed on the steam reforming reactor. Experimental tests were carried out at a molar ratio steam to carbon (S/C) of 2.5, under a gas hourly space velocity (GHSV) of 3500 h −1 , as derived from preliminary investigations in laboratory scale. Total conversion of n-dodecane and absence of carbon deposition phenomena, were observed. The syngas produced (H 2 /CO = 4.7) was adequate to feed a Solid Oxide Fuel Cell (SOFC). [ABSTRACT FROM AUTHOR]

Abstract: A hash function is a mapping from a key universe U to a range of integers, i.e., , where m is the range''s size. A perfect hash function for some set is a hash function that is one-to-one on S, where . A minimal perfect hash function for some set is a perfect hash function with a range of minimum size, i.e., . This paper presents a construction for (minimal) perfect hash functions that combines theoretical analysis, practical performance, expected linear construction time and nearly optimal space consumption for the data structure. For n keys and m=n the space consumption ranges from to bits, and for it ranges from to bits. This is within a small constant factor from the theoretical lower bounds of bits for m=n and bits for . We combine several theoretical results into a practical solution that has turned perfect hashing into a very compact data structure to solve the membership problem when the key set S is static and known in advance. By taking into account the memory hierarchy we can construct (minimal) perfect hash functions for over a billion keys in 46min using a commodity PC. An open source implementation of the algorithms is available at http://cmph.sf.net under the GNU Lesser General Public License (LGPL). [Copyright &y& Elsevier]

In this work we consider the scalar field model with a false vacuum proposed by Avelar et al. (2008) [27]. The model depends on a parameter s > 0. The model has unstable nontopological lump solutions with a bell shape for small s , acquiring a flat plateau around the maximum for large s. For s → ∞ the ϕ 4 model is recovered. We show that for s ≳ 2 the lump is metastable with the only negative mode very close to zero. Metastable lumps can propagate and survive long enough to produce dynamical effects. Due to their simplicity, they can be an alternative to the procedure of stabilization which requires, for instance, a complex scalar field to construct nontopological solitons. We study lump-lump collisions in this model, describing the main characteristics of the scattering products at their dependence on s and the initial velocity modulus of each lump. [ABSTRACT FROM AUTHOR]

In this work we consider a model where the potential has two topological sectors connecting three adjacent minima, as occurs with the ϕ 6 model. In each topological sector, the potential is symmetric around the local maximum. For ϕ > 0 there is a linear map between the model and the λ ϕ 4 model. For ϕ < 0 the potential is reflected. Linear stability analysis of kink and antikink lead to discrete and continuum modes related by a linear coordinate transformation to those known analytically for the λ ϕ 4 model. Fixing one topological sector, the structure of antikink-kink scattering is related to the observed in the λ ϕ 4 model. For kink-antikink collisions a new structure of bounce windows appear. Depending on the initial velocity, one can have oscillations of the scalar field at the center of mass even for one bounce, or a change of topological sector. We also found a structure of one-bounce, with secondary windows corresponding to the changing of the topological sector accumulating close to each one-bounce windows. The kink-kink collisions are characterized by a repulsive interaction and there is no possibility of forming a bound state. [ABSTRACT FROM AUTHOR]

A new approach for the direct conversion of syngas into methanol has been proposed as alternative to the conventional process requiring WGS and/or PSA clean-up steps for syngas upgrading. A comparative thermodynamic equilibrium analysis of biogas reforming processes (dry reforming, steam reforming and oxy-steam reforming) has been performed using the Gibbs free energy minimization method. The calculations have been carried out under different biogas composition (CH 4 /CO 2 = 1–2.3), reaction temperature (400–900 °C), S/CH 4 (0.0–3.0) and O 2 /CH 4 (0.0–0.2) molar ratios. The effects of process variables on the reforming performances as well as on the syngas quality, in term of CH 4 and CO 2 conversion, H 2 /CO and H 2 /CO 2 ratios, coke deposition and energetic consumption, has been examined. Subsequently, methanol synthesis has been studied using the same mathematical approach, with the aim to identify the most adequate operating conditions for the direct conversion of the syngas obtained from reforming process into methanol. The simulations suggested that steam reforming of biogas, with high methane content, is the most appropriate route to produce a syngas quality suitable for the new proposed approach. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of a Solid Oxide Fuel Cell (SOFC) was investigated by feeding a reformate of n-dodecane. Experiments were carried out at 800 °C by using a commercial-type cell with a composition Ni-YSZ/YSZ/YDC/LSFC and a chemical processor operating under Steam Reforming (SR) conditions at 800 °C, S/C equal to 2.5, and GHSV equal to 16,000 h −1 in the presence of a commercial type catalyst based on Rh-CeO 2 -ZrO 2 . The composition of reformate gas was determined by gas-chromatography before the SOFC cell. An electrochemical lifetime test of 500 h for the coupled reformer-SOFC system demonstrated a good stability. EIS and polarizations curves were carried out during the endurance test. The catalyst of the chemical processor was analysed post-operation showing a negligible amount of carbon, whereas the discharged cell showed an increase of Ni particle size caused by the electrochemical ageing. A similar test was carried out under practical conditions with a large area SOFC showing a good stability characteristics and promising scale-up properties. [ABSTRACT FROM AUTHOR]

In this work we examine kink-antikink collisions in two distinct hyperbolic models. The models depend on a deformation parameter, which controls two main characteristics of the potential with two degenerate minima: the height of the barrier and the values of the minima. In particular, the rest mass of the kinks decreases monotonically as the deformation parameter increases, and we identify the appearance of a gradual suppression of two bounce windows in the kink scattering and the production of long lived oscillons. The two effects are reported in connection to the presence of more than one vibrational state in the stability potential. [ABSTRACT FROM AUTHOR]