Minimum ignition energy of methanol-air mixtures

A method for computing minimum ignition energies for gaseous fuel mixtures with detailed and reduced chemistry, by numerical integration of time-dependent conservation equations in a spherically symmetrical configuration, is presented and discussed, testing its general characteristics and accuracy. The method is applied to methanol-air mixtures described by a 38-step Arrhenius chemistry description and by an 8-step chemistry description based on steady-state approximations for reaction intermediaries. Comparisons of predictions with results of available experimental measurements produced reasonable agreements and supported both the robustness of the computational method and the usefulness of the 8-step reduction in achieving accurate predictions.This work was supported by the Spanish MCINN through Projects # CSD2010-00011, ENE2012-33213 and ENE2015-65852-C2-1-R

A multipurpose reduced chemical-kinetic mechanism for methanol combustion

A multipurpose reduced chemical-kinetic mechanism for methanol combustion comprising 8 overall reactions and 11 reacting chemical species is presented. The development starts by investigating the minimum set of elementary reactions needed to describe methanol combustion with reasonable accuracy over a range of conditions of temperature, pressure, and composition of interest in combustion. Starting from a 27-step mechanism that has been previously tested and found to give accurate predictions of ignition processes for these conditions, it is determined that the addition of 11 elementary reactions taken from its basis (San Diego) mechanism extends the validity of the description to premixed-flame propagation, strain-induced extinction of non-premixed flames, and equilibrium composition and temperatures, giving results that compare favourably with experimental measurements and also with computations using the 247-step detailed San Diego mechanism involving 50 reactive species. Specifically, premixed-flame propagation velocities and extinction strain rates for non-premixed counterflow flames calculated with the 38-step mechanism show departures from experimental measurements and detailed-chemistry computations that are roughly on the order of 10%, comparable with expected experimental uncertainties. Similar accuracy is found in comparisons of autoignition times over the range considered, except at very high temperatures, under which conditions the computations tend to overpredict induction times for all of the chemistry descriptions tested. From this 38-step mechanism, the simplification is continued by introducing steady-state approximations for the intermediate species CH3, CH4, HCO, CH3O, CH2OH, and O, leading to an 8-step reduced mechanism that provides satisfactory accuracy for all conditions tested.This work was supported by the Spanish MCINN [projects numbers CSD2010-00011, ENE2012-33213 and ENE2015-65852-C2-1-R

Non-Boussinesq stability analysis of natural-convection gaseous flow on inclined hot plates

The buoyancy-driven boundary-layer flow that develops over a semi-infinite inclined hot plate is known to become unstable at a finite distance from the leading edge, characterized by a critical value of the Grashof number Gr based on the local boundary-layer thickness. The nature of the resulting instability depends on the inclination angle /, measured from the vertical direction. For values of / below a critical value /c the instability is characterized by the appearance of spanwise traveling waves, whereas for/ > /c the bifurcated flow displays Görtler-like streamwise vortices. The Boussinesq approximation, employed in previous linear stability analyses, ceases to be valid for gaseous flow when the wall-to- ambient temperature ratio Hw is not close to unity. The corresponding non-Boussinesq analysis is pre- sented here, accounting also for the variation with temperature of the different transport properties. A temporal stability analysis including nonparallel effects of the base flow is used to determine curves of neutral stability, which are then employed to delineate the dependences of the critical Grashof number and of its associated wave length on the inclination angle / and on the temperature ratio Hw for the two instability modes, giving quantitative information of interest for configurations with Hw 1 1. The analysis provides in particular the predicted dependence of the crossover inclination angle /c on Hw , indicating that for gaseous flow with Hw 1 1 spanwise traveling waves are predominant over a range of inclination angles 0 6 / 6 /c that is significantly wider than that predicted in the Boussinesq approximation

Influence of the structural components of artificial turf systems on impact attenuation in amateur football players

The purpose of this research was to evaluate the infuence of the structural components of diferent 3rd generation artifcial turf football feld systems on the biomechanical response of impact attenuation in amateur football players. A total of 12 amateur football players (24.3±3.7 years, 73.5±5.5kg, 178.3±4.1cm and 13.7±4.3 years of sport experience) were evaluated on three third generation artifcial turf systems (ATS) with diferent structural components. ATS were composed of asphalt subbase and 45mm of fbre height with (ATS1) and without (ATS2) elastic layer or compacted granular sub-base, 60mm of fbre height without elastic layer (ATS3). Two triaxial accelerometers were frmly taped to the forehead and the distal end of the right tibia of each individual. The results reveal a higher force reduction on ATS3 in comparison to ATS1 (+6.24%, CI95%: 1.67 to 10.92, ES: 1.07; p<0.05) and ATS2 (+21.08%, CI95%: 16.51 to 25.66, ES: 2.98; p<0.05) elastic layer. Tibia acceleration rate was lower on ATS3 than ATS1 (−0.32, CI95%: −0.60 to −0.03, ES: 4.23; p<0.05) and ATS2 (−0.35, CI95%: −0.64 to −0.06; ES: 4.69; p<0.05) at 3.3m/s. A very large correlation (r=0.7 to 0.9; p<0.05) was found between energy restitution and fbre height in both head and tibial peak acceleration and stride time. In conclusion, structural components (fbre height, infll, sub-base and elastic layer) determine the mechanical properties of artifcial turf felds. A higher force reduction and lower energy restitution diminished the impact received by the player which could protect against injuries associated with impacts compared to harder artifcial turf surfaces

Halorubrum chaoviator sp. nov., a haloarchaeon isolated from sea salt in Baja California, Mexico, Western Australia and Naxos, Greece

hree halophilic isolates, strains Halo-G*T, AUS-1 and Naxos II, were compared. Halo-G* was isolated from an evaporitic salt crystal from Baja California, Mexico, whereas AUS-1 and Naxos II were isolated from salt pools in Western Australia and the Greek island of Naxos, respectively. Halo-G*T had been exposed previously to conditions of outer space and survived 2 weeks on the Biopan facility. Chemotaxonomic and molecular comparisons suggested high similarity between the three strains. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains clustered with Halorubrum species, showing sequence similarities of 99.2–97.1 %. The DNA–DNA hybridization values of strain Halo-G*T and strains AUS-1 and Naxos II are 73 and 75 %, respectively, indicating that they constitute a single species. The DNA relatedness between strain Halo-G*T and the type strains of 13 closely related species of the genus Halorubrum ranged from 39 to 2 %, suggesting that the three isolates constitute a different genospecies. The G+C content of the DNA of the three strains was 65.5–66.5 mol%. All three strains contained C20C20 derivatives of diethers of phosphatidylglycerol, phosphatidylglyceromethylphosphate and phosphatidylglycerolsulfate, together with a sulfated glycolipid. On the basis of these results, a novel species that includes the three strains is proposed, with the name Halorubrum chaoviator sp. nov. The type strain is strain Halo-G*T (=DSM 19316T =NCIMB 14426T =ATCC BAA-1602T)

Nueva localidad de Psilotum nudum (L.) PB.

Two naturalised taxa in the Iberian Peninsula present in west Andalusia. Plabras clave. Hibiscus, Solanum, Andalucía.Key words. Hibiscus, Solamon, Andalusia

El furtivismo arqueológico. Consideraciones legales y científicas sobre los hallazgos arqueológicos

El problema de las actuaciones arqueológicas incontroladas realizadas por no profesionales es un fenómeno social que viene desde antiguo. La proliferación de estos ‘’aficionados’’ a la Arqueología que buscan, recogen, se guardan y a menudo venden objetos arqueológicos es uno de los principales obstáculos con el que nos encontramos los arqueólogos a la hora de reconstruir los modos de vida de nuestros antepasado

Combining dimensional analysis with model based systems engineering

The model based systems engineering (MBSE) approach describes a system using consistent views to provide a holistic model as complete as possible. MBSE methodologies end with the physical architecture of the system, but a physical model is clearly incomplete without the study of its associated physical laws and phenomena related to the whole system or its parts. However, the computational demands could be excessive even for modest projects. Dimensional analysis (DA) is common in fluid dynamics and chemical engineering, but its application to systems engineering is still limited. We describe an engineering methodological process, which incorporates DA as a powerful tool to understand the physical constraints of the system without the burden of complex analytical or numerical calculations. A detailed example describing a microantenna is presented showing the benefits of this approach. The selected example describes a problem rarely covered in modern expositions of DA in order to show the wide benefit of these techniques. The information provided by this analysis is very useful to select the best physically realizable architectures, testing design, and conduct trade-off studies. The complexity of modern systems and systems of systems demands new testing procedures in order to comply with increasingly demanding requirements and regulations. This can be accomplished through research in new DA methods. Finally, this article serves as a fairly comprehensive guide to the use of DA in the context of MBSE, detailing its strengths, limitations, and controversial issues