Worst cases for an one-hop high frequency link

The characterisation of a HF channel by means of monthly electron density profiles can be complemented with a detailed study of radio propagation «worst cases» on situations with extremes conditions of radiopropagation for a given period. These «worst cases» correspond to conditions that can be identified by means of cumulative distributions of the key parameter f0F2. In this paper, the main parameters of the HF channel: time delay, apogee, elevation angle and transmission frequency with mean and extreme conditions are analysed. The method used to characterise the ionospheric channel is based on ray-tracing techniques

Experimental Characterization of Real Driving Cycles in a Light-Duty Diesel Engine under Different Dynamic Conditions

[EN] This paper studies the behavior of a Euro 6 diesel engine tested under dynamic conditions corresponding to different real driving emissions (RDE) scenarios. RDE cycles have been performed in an engine test bench by simulating its operation in a long van application. A computer tool has been designed to define the cycle accounting for different dynamic characteristics and driver behaviors to study their influence on CO2 and pollutant emissions, particularly CO, THC, and NOX. Different dynamic parameters have been established in terms of power, torque, engine speed, or vehicle speed. Additionally, a tool to estimate the emission of an RDE cycle from steady-state maps has been developed, helping to identify emission trends in a clearer way. Finally, the conclusions suggest that driving patterns characterized by lower engine speeds lead to fewer emissions. In addition, the analysis of RDE cycles from stationary maps helps to estimate the final tailpipe emissions of CO2 and NOX, offering the possibility to rely on tests carried out on engine test bench, dynamometer, or on the road.FundingThis research has been supported by Grant PID2020-114289RB-I00 funded by MCIN/AEI/10.13039/501100011033.Luján, JM.; Piqueras, P.; De La Morena, J.; Redondo-Puelles, F. (2022). Experimental Characterization of Real Driving Cycles in a Light-Duty Diesel Engine under Different Dynamic Conditions. Applied Sciences. 12(5):1-20. https://doi.org/10.3390/app1205247212012

Numerical analysis of flow characteristics in diesel injectors nozzles with convergent-divergent orifices

[EN] The geometry of diesel injector nozzles is known to significantly affect the characteristic spray behavior and emissions formation. In this paper, a novel nozzle concept, consisting of orifices with a convergent-divergent shape, is investigated through Computational Fluid Dynamics techniques. Three of these nozzles, characterized by different degrees of conicity, are compared to a nozzle with cylindrical orifices, which acts as a baseline. A homogeneous equilibrium model, validated against experimental data in previous works by the authors, is used to calculate the eventual cavitation formation inside these orifices. Additionally, the characteristics of the flow at the orifice outlet are analyzed for the four aforementioned nozzles in terms of their steady-state mass flow, effective outlet velocity and area coefficient. The results show that convergent-divergent nozzles exhibit a high cavitation intensity, located in the transition between the convergent and the divergent sections. This high cavitation intensity tends to compensate for the expected velocity decrease induced by the divergent shape, producing effective velocity values similar to those achieved by the cylindrical nozzle in many of the simulated conditions. The characteristics of the flow, together with the higher spray opening angles expected due to the divergent section of the nozzle, may improve atomization and fuel-air mixing processes.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Ministerio de Economia y Competitividad, of the Spanish Government, Project 'Estudio de la interaccion chorro-pared en condiciones realistas de motor' (Grant Number TRA2015-67679-c2-1-R). The PhD studies of David Jaramillo have been funded by "Conselleria d'Educacio Cultura i Esports" of "Generalitat Valenciana", Spain, by means of "Programa Vali+d per a personal investigador en formacio" (reference ACIF/2015/040).Salvador, FJ.; De La Morena, J.; Carreres, M.; Jaramillo-Císcar, D. (2017). Numerical analysis of flow characteristics in diesel injectors nozzles with convergent-divergent orifices. Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering. 231(14):1935-1944. https://doi.org/10.1177/0954407017692220S193519442311

Measurements and estimation of the columnar optical depth of tropospheric aerosols in the UV spectral region

International audienceWe report values of the columnar tropospheric aerosol optical depth at UV wavelengths based on experimental measurements of the direct spectral irradiances carried out by a commercial spectroradiometer (Li1800 of Licor company) covering the range from 300?1100 nm at two stations with different climate characteristics in Spain. The first station is located in a rural site in north central Spain with continental climate. The data extend from March to the end of October of 1995. The other station is a coastal site in the Gulf of Cádiz (southwest Spain) of maritime climate type. This study is mainly focused on the capability of estimating aerosol optical depth values in the UV region based on the extracted information in the visible and near infrared ranges. A first method has been used based on the Ångström turbidity parameters. However, since this method requires detailed spectral information, a second method has also been used, based on the correlation between wavelengths. A correlation has been established between the experimental aerosol optical depth values at 350 nm and 500 nm wavelengths. Although the type of aerosol seems to be the key factor that determines the quality of these estimations, the evaluation of the associated error is necessary to know the behaviour of these estimations in each area of study

Application of a one-dimensional spray model to teach diffusion flame fundamentals for engineering students

[EN] This study presents the application of an existing interactive application for teaching spray dynamics in engineering degrees. The model is based on spray momentum conservation and can be used to evaluate both fuel-air mixing characteristics in inert conditions as well as diffusion flame performance once combustion takes place. During a dedicated computer-lab session, the students perform parametric studies regarding the influence of the nozzle outlet diameter, the combustion chamber density and the spray cone opening angle on the mixing process, characterized by the maximum stoichiometric length. Later on, the effect of the combustion reaction on the mixing field is evaluated. The results are analyzed taking as a reference to the theoretical development made by Spalding and Schlichting for diffusion gas jets. The outcomes of several years using this technique are reported.García-Oliver, JM.; García Martínez, A.; De La Morena, J.; Monsalve-Serrano, J. (2019). Application of a one-dimensional spray model to teach diffusion flame fundamentals for engineering students. Computer Applications in Engineering Education. 27(5):1202-1216. https://doi.org/10.1002/cae.22146S12021216275Aleiferis, P. G., Behringer, M. K., & Malcolm, J. S. (2016). Integral Length Scales and Time Scales of Turbulence in an Optical Spark-Ignition Engine. Flow, Turbulence and Combustion, 98(2), 523-577. doi:10.1007/s10494-016-9775-9Battin-Leclerc, F. (2008). Detailed chemical kinetic models for the low-temperature combustion of hydrocarbons with application to gasoline and diesel fuel surrogates. Progress in Energy and Combustion Science, 34(4), 440-498. doi:10.1016/j.pecs.2007.10.002Burke, R. D., De Jonge, N., Avola, C., & Forte, B. (2017). A virtual engine laboratory for teaching powertrain engineering. Computer Applications in Engineering Education, 25(6), 948-960. doi:10.1002/cae.21847Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Briceño, F. J. (2014). An experimental analysis on the evolution of the transient tip penetration in reacting Diesel sprays. Combustion and Flame, 161(8), 2137-2150. doi:10.1016/j.combustflame.2014.01.022Desantes, J. M., Pastor, J. V., García-Oliver, J. M., & Pastor, J. M. (2009). A 1D model for the description of mixing-controlled reacting diesel sprays. Combustion and Flame, 156(1), 234-249. doi:10.1016/j.combustflame.2008.10.008Dumouchel, C., Cousin, J., & Triballier, K. (2005). On the role of the liquid flow characteristics on low-Weber-number atomization processes. Experiments in Fluids, 38(5), 637-647. doi:10.1007/s00348-005-0944-1Edmonds, E. (1980). Where Next in Computer Aided Learning? British Journal of Educational Technology, 11(2), 97-104. doi:10.1111/j.1467-8535.1980.tb00396.xFansler, T. D., & Parrish, S. E. (2014). Spray measurement technology: a review. Measurement Science and Technology, 26(1), 012002. doi:10.1088/0957-0233/26/1/012002Gutiérrez-Romero, J. E., Zamora-Parra, B., & Esteve-Pérez, J. A. (2016). Acquisition of offshore engineering design skills on naval architecture master courses through potential flow CFD tools. Computer Applications in Engineering Education, 25(1), 48-61. doi:10.1002/cae.21778IPCC. Intergovernmental Panel on Climate Change Working Group I. Climate Change 2013: The Physical Science Basis.Long‐term Climate Change: Projections Commitments and Irreversibility  Cambridge University Press New York NY  2013:1029–136.https://doi.org/10.1017/CBO9781107415324.024W. Kirchstetter, T., Harley, R. A., Kreisberg, N. M., Stolzenburg, M. R., & Hering, S. V. (1999). On-road measurement of fine particle and nitrogen oxide emissions from light- and heavy-duty motor vehicles. Atmospheric Environment, 33(18), 2955-2968. doi:10.1016/s1352-2310(99)00089-8K. BenNaceur L.Cozzi andT.Gould.World Energy Outlook 2016.2016.https://doi.org/10.1787/weo‐2016‐enM.Nesbitet al. Comparative Study on the differences between the EU and US legislation on emissions in the automotive sector.2016.PASTOR, J., JAVIERLOPEZ, J., GARCIA, J., & PASTOR, J. (2008). A 1D model for the description of mixing-controlled inert diesel sprays. Fuel, 87(13-14), 2871-2885. doi:10.1016/j.fuel.2008.04.017PAYRI, R., GARCIA, J., SALVADOR, F., & GIMENO, J. (2005). Using spray momentum flux measurements to understand the influence of diesel nozzle geometry on spray characteristics. Fuel, 84(5), 551-561. doi:10.1016/j.fuel.2004.10.009Payri, R., Salvador, F. J., Gimeno, J., & Novella, R. (2011). Flow regime effects on non-cavitating injection nozzles over spray behavior. International Journal of Heat and Fluid Flow, 32(1), 273-284. doi:10.1016/j.ijheatfluidflow.2010.10.001Perumal, K., & Ganesan, R. (2015). CFD modeling for the estimation of pressure loss coefficients of pipe fittings: An undergraduate project. Computer Applications in Engineering Education, 24(2), 180-185. doi:10.1002/cae.21695Regueiro, A., Patiño, D., Míguez, C., & Cuevas, M. (2017). A practice for engineering students based on the control and monitoring an experimental biomass combustor using labview. Computer Applications in Engineering Education, 25(3), 392-403. doi:10.1002/cae.21806Sick, V., Drake, M. C., & Fansler, T. D. (2010). High-speed imaging for direct-injection gasoline engine research and development. Experiments in Fluids, 49(4), 937-947. doi:10.1007/s00348-010-0891-3SPALDING, D. B. (1979). The stability of steady exothermic chemical reactions in simple non-adiabatic systems. Combustion and Mass Transfer, 399-406. doi:10.1016/b978-0-08-022106-9.50025-5Weilenmann, M., Soltic, P., Saxer, C., Forss, A.-M., & Heeb, N. (2005). Regulated and nonregulated diesel and gasoline cold start emissions at different temperatures. Atmospheric Environment, 39(13), 2433-2441. doi:10.1016/j.atmosenv.2004.03.081www.upv.es. Universitat Politècnica de València.Zhao, H., & Ladommatos, N. (1998). Optical diagnostics for soot and temperature measurement in diesel engines. Progress in Energy and Combustion Science, 24(3), 221-255. doi:10.1016/s0360-1285(97)00033-

A Decade of GRB Follow-Up by BOOTES in Spain (2003–2013)

This article covers ten years of GRB follow-ups by the Spanish BOOTES stations: 71 follow-ups providing 23 detections. Follow-ups by BOOTES-1B from 2005 to 2008 were given in a previous article and are here reviewed and updated, and additional detection data points are included as the former articlemerely stated their existence. The all-sky cameras CASSANDRA have not yet detected any GRB optical afterglows, but limits are reported where available.The authors appreciate the auspices of INTA, IHSM-UMA/CSIC, and UMA as well as the financial support by the Junta de Andaluca and the Spanish Ministry of Economy and Competitiveness through the Research Projects P07-TIC-03094, P12-TIC2839, AYA2009-14000-C03-01, AYA 2010-39727-C03-01, and AYA-2015-71718-R. Martin Jelinek was supported by the postdoctoral fellowship of the Czech Academy of Sciences. This study was carried out in the framework of the Unidad Asociada IAA-CSIC at the Group of Planetary Science of ETSI-UPV/EHU. This work was supported by the Ikerbasque Foundation for Science. The Czech CVUT FEL team acknowledges the support by GA CR Grant 13-33324S

On the sub-micron aerosol size distribution in a coastal-rural site at El Arenosillo Station (SW – Spain)

This study focuses on the analysis of the sub-micron aerosol characteristics at El Arenosillo Station, a rural and coastal environment in South-western Spain between 1 August 2004 and 31 July 2006 (594 days). The mean total concentration (NT) was 8660 cm−3 and the mean concentrations in the nucleation (NNUC), Aitken (NAIT) and accumulation (NACC) particle size ranges were 2830 cm−3, 4110 cm−3 and 1720 cm−3, respectively. Median size distribution was characterised by a single-modal fit, with a geometric diameter, median number concentration and geometric standard deviation of 60 nm, 5390 cm−3 and 2.31, respectively. Characterisation of primary emissions, secondary particle formation, changes to meteorology and long-term transport has been necessary to understand the seasonal and annual variability of the total and modal particle concentration. Number concentrations exhibited a diurnal pattern with maximum concentrations around noon. This was governed by the concentrations of the nucleation and Aitken modes during the warm seasons and only by the nucleation mode during the cold seasons. Similar monthly mean total concentrations were observed throughout the year due to a clear inverse variation between the monthly mean NNUC and NACC. It was related to the impact of desert dust and continental air masses on the monthly mean particle levels. These air masses were associated with high values of NACC which suppressed the new particle formation (decreasing NNUC). Each day was classified according to a land breeze flow or a synoptic pattern influence. The median size distribution for desert dust and continental aerosol was dominated by the Aitken and accumulation modes, and marine air masses were dominated by the nucleation and Aitken modes. Particles moved offshore due to the land breeze and had an impact on the particle burden at noon, especially when the wind was blowing from the NW sector in the morning during summer time. This increased NNUC and NAIT by factors of 3.1 and 2.4, respectively. Nucleation events with the typical "banana" shape were characterised by a mean particle nucleation rate of 0.74 cm−3 s−1, a mean growth rate of 1.96 nm h−1 and a mean total duration of 9.25 h (starting at 10:55 GMT and ending at 20:10 GMT). They were observed for 48 days. Other nucleation events were identified as those produced by the emissions from the industrial areas located at a distance of 35 km. They were observed for 42 days. Both nucleation events were strongly linked to the marine air mass origin

Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 1: Analysis of parameter influence

The main objective of this study is to compare the erythemal UV irradiance (UVER) and spectral UV irradiances (at 305, 310 and 324 nm) from the Ozone Monitoring Instrument (OMI) onboard NASA EOS/Aura polar sun-synchronous satellite (launched in July 2004, local equator crossing time 01:45 p.m.) with ground-based measurements from the Brewer spectrophotometer #150 located at El Arenosillo (South of Spain). The analyzed period comprises more than four years, from October 2004 to December 2008. The effects of several factors (clouds, aerosols and the solar elevation) on OMI-Brewer comparisons were analyzed. The proxies used for each factor were: OMI Lambertian Equivalent Reflectivity (LER) at 360 nm (clouds), the aerosol optical depth (AOD) at 440 nm measured from the ground-based Cimel sun-photometer (<a href="http://aeronet.gsfc.nasa.gov"target="_blank">http://aeronet.gsfc.nasa.gov</a>), and solar zenith angle (SZA) at OMI overpass time. The comparison for all sky conditions reveals positive biases (OMI higher than Brewer) 12.3% for UVER, 14.2% for UV irradiance at 305 nm, 10.6% for 310 nm and 8.7% for 324 nm. The OMI-Brewer root mean square error (RMSE) is reduced when cloudy cases are removed from the analysis, (e.g., RMSE~20% for all sky conditions and RMSE smaller than 10% for cloud-free conditions). However, the biases remain and even become more significant for the cloud-free cases with respect to all sky conditions. The mentioned overestimation is partially due to aerosol extinction influence. In addition, the differences OMI-Brewer typically decrease with SZA except days with high aerosol loading, when the bias is near constant. The seasonal dependence of the OMI-Brewer difference for cloud-free conditions is driven by aerosol climatology. <br><br> To account for the aerosol effect, a first evaluation in order to compare with previous TOMS results (Antón et al., 2007) was performed. This comparison shows that the OMI bias is between +14% and +19% for UVER and spectral UV irradiances for moderately-high aerosol load (AOD>0.25). The OMI bias is decreased by a factor of 2 (the typical bias varies from +8% to +12%) under cloud-free and low aerosol load conditions (AOD<0.1). More detailed analysis of absorbing aerosols influence on OMI bias at our station is presented in a companion paper (Cachorro et al., 2010)

Diferencias en los niveles de motivación por sexo, curso y tipo de centro educativo en el aprendizaje estratégico de la lengua extranjera

This research shows an analysis of the main motivational models applied to foreign language acquisition and is aimed at identifying the motivational variables that present the highest influence in the strategic acquisition of a foreign language. The questionnaire Autoeficacia y Motivación Académica was given to a sample of 564 subjects (309 males and 254 females) who were studying 3rd (41.030%) and 4th (28.597%) of Secondary Education and 1st year of High School (30.373%) in two schools of the Comunidad de Madrid (41.7% in a public school and 58.3% in a private school). Results show that values of items related to instrumental motivation are the highest. Females obtained higher results in all factors studied in the same way as the private school with the exception of the variable Perceived Ability which was higher in the public school.La investigación realiza una revisión de los principales modelos motivacionales aplicados al aprendizaje de idiomas y se centra en la identificación de aquellas variables motivacionales que más inciden en el aprendizaje estratégico de una lengua extranjera. Para ello, se aplicó el Cuestionario de Autoeficacia y Motivación Académica a una muestra de 564 sujetos (309 varones y 254 mujeres) pertenecientes a 3.º (41,030%) y 4.º (28,597%) de ESO y 1.º de Bachillerato (30,373%) de dos centros educativos de la CM (41,7%, centro público y 58,3%, centro privado). Los resultados muestran que las puntuaciones en los ítems que indican motivación instrumental (motivos profesionales y de reconocimiento social) son los más altos. Las mujeres obtienen puntuaciones más altas en todos los factores así como el centro privado, salvo en la variable Habilidad Percibida, que es superior en el centro público