Mechanistic-empirical pavement design guide : características y elementos distintivos

[Abstract] This paper is aimed at describing the most distinctive features of the pavement design method known as Mechanistic-Empirical Pavement Design Guide and to compare it with other renowned methodologies, while emphasizing its advantages and disadvantages. The MEPDG can accurately predict damage evolution, thus helping to choose the most appropriate design for new pavements or to schedule the conservation of the already existing ones. After analyzing different pavement design and management methods, the MEPDG stands out as the most comprehensive one as it takes into account and properly combines the greatest number of factors that affect the pavement. Therefore, some countries outside the USA have already imported and calibrated this method, what, at the same time, allows the scientific community to carry out comparative studies and improve its small deficiencies.[Resumen] El objetivo de este artículo es describir los rasgos más característicos del método de diseño de firmes conocido como Mechanistic-Empirical Pavement Design Guide, así como compararlo con otras metodologías de renombre, destacando sus ventajas y desventajas. El MEPDG puede predecir con precisión la evolución de los deterioros, ayudando por tanto a elegir el diseño más adecuado para el caso de firmes de nueva construcción, o a programar la conservación de los ya existentes. Tras analizar diferentes métodos de diseño y gestión de firmes, el MEPDG destaca como el más completo al ser el que tiene en cuenta un mayor número de factores que afectan al firme. Por ello algunos países fuera de EEUU ya han importado y calibrado este método, lo que al mismo tiempo permite a la comunidad científica llevar a cabo estudios comparativos y mejorar sus pequeñas deficiencias

Autonomous driving: a bird's eye view

[Abstract:] The introduction of autonomous vehicles (AV) will represent a milestone in the evolution of transportation and personal mobility. AVs are expected to significantly reduce accidents and congestion, while being economically and environmentally beneficial. However, many challenges must be overcome before reaching this ideal scenario. This study, which results from on-site visits to top research centres and a comprehensive literature review, provides an overall state-of-the-practice on the subject and identifies critical issues to succeed. For example, although most of the required technology is already available, ensuring the robustness of AVs under all boundary conditions is still a challenge. Additionally, the implementation of AVs must contribute to the environmental sustainability by promoting the usage of alternative energies and sustainable mobility patterns. Electric vehicles and sharing systems are suitable options, although both require some refinement to incentivise a broader range of customers. Other aspects could be more difficult to resolve and might even postpone the generalisation of automated driving. For instance, there is a need for cooperation and management strategies geared towards traffic efficiency. Also, for transportation and land-use planning to avoid negative territorial and economic impacts. Above all, safe and ethical behaviour rules must be agreed upon before AVs hit the road.Ministerio de Economía y Competitividad; TRA2016-79019-R/COO

A simple algorithm for the estimation of road traffic space mean speeds from data available to most management centres

[Abstract:] The control of the evolution of road traffic streams is highly related to productivity, safety, sustainability and, even, comfort. Although, nowadays, the findings from research efforts and the development of new technologies enable accurate traffic forecasts in almost any conditions, these calculations are usually limited by the data and the equipment available. Most traffic management centres depend on the data provided, at best, by double-loop detectors. These loops supply time means over different aggregation periods, which are indiscriminately used as the bases for subsequent estimations. Since space mean speeds are those needed in most applications (note the fundamental relationship between flow and density in traffic flow theory), most current practice begins with an error. This paper introduces a simple algorithm that the allows estimation of space mean speeds from the data provided by the loops without the need for any additional financial outlay, as long as the traffic in each time interval of aggregation is stationary and its speed distribution is log-normal. Specifically, it is focused on the calculation of the variance of the speeds with regard to the time mean, thus making possible to use the relationship between time mean speeds and space mean speeds defined by Rakha (2005). The results obtained with real data show that the algorithm behaves well if the calculation conditions help fulfil the initial hypotheses. The primary difficulties arise with transient traffic and, in this case, other specific methodologies should be used. Data fusion seems promising in this regard. Nevertheless, it cannot be denied that the improvement provided by the algorithm turns out to be highly beneficial both when used alone in the case of stationarity or as a part of a fusion

Compensación de los errores de alineación provocados por las deflexiones de los ejes en transmisiones de engranajes cónicos espirales diseñadas con distintos tipos de huella de contacto

[SPA] En el presente trabajo se analiza una metodología para compensar los errores de alineación debidos a las deflexiones de los ejes en transmisiones de engranajes cónicos espirales cuando se transmite una carga nominal o de diseño, considerando cuatro tipos de patrones de contacto: lineal, localizado en la dirección longitudinal, localizado en la dirección del perfil, y localizado en una dirección ajustada diagonal. Para ello se determinan en primer lugar los parámetros de máquina correspondientes al proceso Cyclo-Palloid que permiten diseñar dichos patrones de contacto. A continuación se aplica un proceso iterativo en cada uno de los cuatro diseños. Este proceso iterativo requiere analizar, en cada etapa del proceso, la transmisión con ejes mediante el método de los elementos finitos, para obtener los errores de alineación debidos a la deflexión de los ejes. Los resultados muestran la eficacia de la metodología propuesta para compensar, desde el diseño de las geometrías de las superficies de contacto, las deflexiones de los ejes en los cuatro tipos de patrones de contacto, así como la mayor tolerancia de los diseños con contacto localizado en la dirección del perfil y en la dirección diagonal ajustada a variaciones de la carga de diseño. Se presentan varios ejemplos numéricos. [ENG] In this paper, a methodology to compensate alignment errors due to shaft deflections for a given design load in spiral bevel gear drives is presented, considering four types of contact pattern, linear and localized in longitudinal, profile and adjusted diagonal directions. Firstly, the machine-tool settings corresponding to a Cyclo-Palloid process are determined to design the mentioned four contact patterns. Secondly, an iterative process for each contact design is required where a finite element analysis provides the alignment errors due to shaft deflections. The results show the efficency of the proposed methodology to compensate alignment errors from the design of the gear tooth surfaces in the four types of contact pattern, and the larger tolerance in the profile and adjusted diagonal directions designs to variations of the design load. Several numerical examples are presented

Aportación al conocimiento de las algas marinas bentónicas del litoral comprendido entre el estuario del río Quejo y Punta de la Mesa, Noja, Cantabria, España

Se presenta un catálogo de la flora bentónica marina del litoral comprendido entre el estuario del río Quejo y la Punta de Mesa, Noja, Cantabria. Se aportan datos sobre el hábitat y estado reproductor de los taxones observados. El total de especies identificadas es de 146, de las cuales 95 corresponden a las Rodófitas (65%), 18 a las Clorófitas (12%) y 33 a las Feofíceas (23%). Consideramos que 20 especies (Pterocladiella melanoidea, Bonnemaisonia clavata en su fase esporofítica (Trailliella intricata), Phyllophora sicula, Gastroclonium reflexum, Aglaothamnion feldmanniae, Callithamnion corymbosum, Centroceras clavulatum, Ptilothamnion sphaericum, Drachiella minuta, Polysiphonia nigra, Polysiphonia scopulorum, Polysiphonia stricta, Streblocladia collabens, Cladophora albida, Codium decorticatum, Acinetospora crinita, Ectocarpus siliculosus, Zanardinia typus, Phyllariopsis brevipes subsp. pseudopurpurascens y Sargassum vulgare) son nuevas citas para la flora de Cantabria. Además 17 especies son segundas citas.A benthic marine algae catalogue from Noja, Cantabria is provided, including reproductive and habitat data of the distinct taxa. The total amount of species is 146, 95 of them are Rhodophyta (65%), 18 Chlorophyta (12%) and 33 Heterokontophyta (23%). We consider that 20 species (Pterocladiella melanoidea, Bonnemaisonia clavata (Trailliella intricata), Phyllophora sicula, Gastroclonium reflexum, Aglaothamnion feldmanniae, Callithamnion corymbosum, Centroceras clavulatum, Ptilothamnion sphaericum, Drachiella minuta, Polysiphonia nigra, Polysiphonia scopulorum, Polysiphonia stricta, Streblocladia collabens, Cladophora albida, Codium decorticatum, Acinetospora crinita, Ectocarpus siliculosus, Zanardinia typus, Phyllariopsis brevipes subsp. pseudopurpurascens and Sargassum vulgare) are new records for Cantabria. Moreover, 17 species are second records

Experimental analysis of physical magnitudes through films and its application in the classroom

En este trabajo mostramos cómo nuestros alumnos de secundaria y bachillerato han podido realizar, en los últimos 10 cursos, investigaciones sobre fenómenos o situaciones físicas de la vida cotidiana cercanas a sus intereses. El procedimiento consiste en realizar grabaciones de video digital y la posterior aplicación de un programa informático (Avimèca) que permite seguir la escena fotograma a fotograma asociando valores numéricos a cada punto elegido para poder analizar ciertas magnitudes físicas. En contra de lo que puede parecer, el procedimiento es sencillo y los elementos empleados son relativamente económicos. En cualquier caso, para facilitar la tarea a otros profesores, se agrega una guía del programa que, por otra parte, es de acceso gratuito. Además, se detalla el modo en que se hemos implementado esta actividad en el aula y enumeramos las dificultades encontradas, así como las soluciones propuestas.In this paper we show how our Secondary and High School students have been able to research phenomena or physical situation of their real lives closer to their interests in the last 10 years. The procedure is to make digital video recordings and then applying a computer program (Avimèca), which monitors the scene frame by frame and attaching numerical values to each selected point in order to analyze some physical magnitudes. Contrary to what may seem, the procedure is simple and relatively inexpensive elements are used. In any case, to make it easier for other teachers, a program guide is added which is free-access. In addition, the way in which we implemented this classroom activity is detailed, listing the difficulties encountered and the corresponding proposed solutions

Technology: a necessary but not sufficient condition for future personal mobility

Número especial: Sustainable Road Transportation Planning[Abstract:] Technological advances revolutionize industrial processes, science, communications, and our way of life. However, developed societies have reached a stage in which the fascination with technological innovations often results in their indiscriminate consumption. In this paper, road traffic is used as a line of argument to demonstrate that the random introduction of technology does not imply benefits to society. Particularly, it is analyzed why some of the potential benefits of technological progress are lost in fields such as traffic monitoring, data handling, and traffic management, or in sustainable mobility initiatives, such as the introduction of electric vehicles or the implementation vehicle sharing projects. The risks faced in the future advent of autonomous vehicles are also discussed, and ideas for improvement suggested. A critical reflection on other transportation modes that are expected to be realized in the near future is included as well. The performed analysis evidences that the potential improvement in personal mobility will not become a reality if it exclusively relies on the latest technological devices, in line with consumers’ fantasies or economic interests. This is a statement that could be generalized to many other fields. The implementation/consumption of a particular technology should not be an objective in itself, but a tool to bring benefits to society.Ministerio de Economía y Competitividad; TRA2016-79019-R/COO

Watermelon Juice: Potential Functional Drink for Sore Muscle Relief in Athletes

L-Citrulline is an excellent candidate to reduce muscle soreness, and watermelon is a fruit rich in this amino acid. This study investigated the potential of watermelon juice as a functional drink for athletes. An in vitro study of intestinal absorption of l-citrulline in Caco-2 cells was performed using unpasteurized (NW), pasteurized (80 °C for 40 s) watermelon juice (PW) and, as control, a standard of l-citrulline. l-citrulline bioavailability was greater when it was contained in a matrix of watermelon and when no heat treatment was applied. In the in vivo experiment (maximum effort test in a cycloergometer), seven athletes were supplied with 500 mL of natural watermelon juice (1.17 g of l-citrulline), enriched watermelon juice (4.83 g of l-citrulline plus 1.17 g from watermelon), and placebo. Both watermelon juices helped to reduce the recovery heart rate and muscle soreness after 24 h.Actividad Física y Deport