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

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

Blog as a teaching and learning of languages

Resumen tomado de la publicaciónTítulo, resumen y palabras clave también en inglésLas actuales corrientes pedagógicas proponen un enfoque constructivista (teorías de Vigotsky [Ivic, 1994]) y un aprendizaje colaborativo (Ausubel y Novak [Daley, 2010]); por lo que las analogías con la Web 2.0 son evidentes, pues ésta se basa en la creación de conocimiento compartido. El término Web 2.0 está asociado con aplicaciones web para compartir información y una de las herramientas utilizadas es el blog. Se pretende familiarizar al profesorado y al alumnado implicado con esta herramienta. Respecto al aprendizaje de la lengua en sí misma, se persigue una mejora de las cuatro destrezas comunicativas. Se utiliza la herramienta en el aula, pero se fomenta el aprendizaje autónomo, método especialmente útil en este tipo de centros. No se utiliza el blog como una simple bitácora, sino que se transforma en un medio para crear una interacción entre el alumnado, promoviendo así el aprendizaje colaborativo. Se propone el uso de los blogs como un elemento adicional a las clases, bien como un refuerzo o como profundización y ampliación de conocimientos lingüísticos y culturales, pero nunca como un sustituto de éstas.ES

The sphaleron energy for SU(2)-Higgs from cooling

The cooling algorithm for saddle points presented in ref. [1] is generalized to obtain static classical solutions of the SU(2)-Higgs field theory in the limit of infinite Higgs self-coupling. The sphaleron energy obtained via this algorithm is ${\cal E}_{\rm sph}= 5.08(7)\,M_W/\alpha_W$ to be compared with 5.0707 obtained in the variational approach [2].Comment: 3 pages, uuencoded compressed PostScript file. Contribution to Lattice '94, 27 Sep - 1 Oct 1994, Bielefeld, German

Topology by improved cooling: susceptibility and size distributions

We use a cooling algorithm based on an improved action with scale invariant instanton solutions, which needs no monitoring or calibration and has a inherent cut off for dislocations. We present results for SU(2) Yang-Mills theory where the method provides good susceptibility data and physical size distributions of instantons.Comment: 3 pages, 4 figures. Talk presented at LATTICE96(topology

Perturbative contributions to Wilson loops in twisted lattice boxes and reduced models

We compute the perturbative expression of Wilson loops up to order $g^4$ for SU($N$) lattice gauge theories with Wilson action on a finite box with twisted boundary conditions. Our formulas are valid for any dimension and any irreducible twist. They contain as a special case that of the 4-dimensional Twisted Eguchi-Kawai model for a symmetric twist with flux $k$. Our results allow us to analyze the finite volume corrections as a function of the flux. In particular, one can quantify the approach to volume independence at large $N$ as a function of flux $k$. The contribution of fermion fields in the adjoint representation is also analyzed.Comment: pdflatex 57 pages, 9 figures, 4 appendice

Improved cooling algorithm for gauge theories

We propose and study a ``gold-washing" - type of algorithm which smooths out the short range fluctuations but leaves invariant instantons above a certain size. The algorithm needs no monitoring or calibration.Comment: Latex file, 4 pages, 4 figures in uuencoded compressed tar file. Contribution to Lattice 9

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

Uso de modelos econométricos en aseguramiento de portafolios

El aseguramiento de portafolio trae consigo unos costos de transacción asociados que son reconocidos por la teoría financiera pero que no han sido objeto de estudio de muchas aproximaciones empíricas. Mediante modelos econométricos de series de tiempo se puede pronosticar el número de rebalanceos necesarios para mantener un portafolio asegurado, así como el tiempo que debe transcurrir entre cada uno de estos. Para tal fin se usan modelos de Datos de Cuenta de Poisson Autorregresivos (ACP) modificados para captar las características de la serie y modelos de Duración Autorregresivos (ACD). Los modelos capturan la autocorrelación de las series y pronostican adecuadamente el costo de transacción asociado a los rebalanceos.Portfolio insurance and delta hedging involves transaction costs that are recognized in finance theory but have not been studied in many empirical applications. Econometric time series models can be used to forecast the number of recompositions of an insured portfolio, and the time between each recomposition. We forecast these variables using modified autoregressive conditional Poisson models (ACP) and autoregressive conditional duration models (ACD) The model are successful in capturing the series’ autocorrelation, and provide sensible estimates of the transaction cost associated with the recompositions