The Hughes model for pedestrian dynamics and congestion modelling

In this paper we present a numerical study of some variations of the Hughes model for pedestrian flow under different types of congestion effects. The general model consists of a coupled non-linear PDE system involving an eikonal equation and a first order conservation law, and it intends to approximate the flow of a large pedestrian group aiming to reach a target as fast as possible, while taking into account the congestion of the crowd. We propose an efficient semi-Lagrangian scheme (SL) to approximate the solution of the PDE system and we investigate the macroscopic effects of different penalization functions modelling the congestion phenomena.Comment: 6 page

Rediscover Rosarito: a public diplomacy initiative for the local community in Rosarito Beach, Baja Mexico

Rediscover Rosarito is a cross-cultural public affairs graduate class initiative started in February 2008. That year, 28 graduate Communication Management (CM) students from diverse backgrounds and nationalities, taught by Dr. Gregory Payne of the Communication Studies Department, reached out to elected governmental leaders, public officials, citizens and expatriates of Rosarito Beach in Baja Mexico. Together, they launched a public affairs campaign that stressed the importance of grassroots public diplomacy as a major strategy. The goal of the program then and now is to develop and implement an ongoing campaign to help restore the image of this heavily tourism dependent beach community, which had been devastated by a drastic drop in visitor levels as a result of Mexican President Jose Caledron’s ‘war on drugs,’ a violent reaction from the drug cartels against this action, as well as biased media coverage regarding the crisis from sources on both sides of the border, which reflect the all too often proclivity of the media to sensationalize such stores in the effort to secure readershi

El crédito comercial y la crisis crediticia: un análisis descriptivo en Europa; Reino Unido y España

El uso de crédito comercial como forma de financiar el corto plazo ha aumentando en los últimos años, las grandes empresas utilizan más días del que necesitan para realizar los pagos a las pequeñas empresas, lo que provoca fatales consecuencias financieras para los proveedores. Estos problemas financieros no son nuevos, pero con la restricción pronunciada del crédito los problemas se agudizan debido a que el uso masivo del crédito comercial repercute negativamente en los proveedores cuya insolvencia y riesgo de quiebra aumentan. En este trabajo se revisan de forma descriptiva el uso del crédito comercial en la crisis crediticia. Las principales contribuciones de la ponencia son dos. En primer lugar, mostrar las consecuencias financieras por la utilización del crédito comercial y, concretamente, en la crisis crediticia, y cómo el gobierno de Reino Unido desarrolla políticas públicas de pago para reducir el efecto negativo de los impagados. En segundo lugar, estudiar y comparar la situación de los países europeos en términos de pago a los proveedores y, en particular, el caso de Reino Unido, pero también el caso Español.The use of trade credit as a short-term financing is increasing in the last years; large firms use more days to pay small firms than they need, which causes financial fatal consequences to suppliers. These financial problems are not new, but with the credit crunch they are coming up because the massive use of the trade credit impacts negatively on suppliers whose insolvency and bankruptcy risks increase. In this paper we review in a descriptive way the use of trade credit in the credit crunch. The main contributions of the paper are two. Firstly, we show the financial consequences of the use of trade credit, and specifically in credit crisis, and how UK government develop public payment policies to reduce the negative effect of delete payments. Secondly, we study and compare the situation of European countries in terms of payment to suppliers, and in particular the case of UK, but also Spanish case

The role of market-implied severity modeling for credit VaR

En este trabajo proponemos el uso de mixturas de distribciones beta para modelizar la severidad impícita en el mercado. En nuestro análisis extraemos las tasas de recuperación de la cotización de los credit default swaps (CDS) en lugar de utilizar bonos que han impagado. La principal ventaja de obtener la estructura temporal implícita de tasas de recuperación de los CDS en lugar de utilizar los bonos impagados es que nos permite identificar tasas de recuperación para empresas con baja probabilidad de impago. Del análisis empírico se obtienen resultados que no permiten aceptar que una única distribución beta sea capaz de representar las tasas de recuperación implícitas mientras que la propuesta basada en mixturas de distribuciones beta si que es aceptada. Además, hay que destacar la importancia de utilizar esta metodología de ajuste por su importancia para una correcta estimación del Valor en Riesgo de crédito.In this paper we propose to use beta-component mixtures to model the market-implied severity. In our analysis we extract and identify recovery rates from credit default swaps instead of using defaulted bonds. The main advantage of extracting implied, endogenous and dynamic functions of recovery rates from credit default swaps versus using defaulted bonds is that it allows to identify recovery rates of low probability of default companies. We carry out an empirical analysis and our results show that a single beta distribution is rejected as a correct specification for implied recovery rates while a beta-component mixture is accepted. Futhermore, we highlight the importance of this modeling approach by focusing on its role for credit VaR

Vector-like Quarks at the Origin of Light Quark Masses and Mixing

We show how a novel fine-tuning problem present in the Standard Model can be solved through the introduction of a single flavour symmetry G, together with three $Q = - 1/3$ quarks, three $Q = 2/3$ quarks, as well as a complex singlet scalar. The symmetry G is extended to the additional fields and it is an exact symmetry of the Lagrangian, only spontaneously broken by the vacuum. Specific examples are given and a phenomenological analysis of the main features of the model is presented. It is shown that even for vector-like quarks with masses accessible at the LHC, one can have realistic quark masses and mixing, while respecting the strict constraints on process arising from flavour changing neutral currents (FCNC). The vector-like quark decay channels are also described.Comment: 25 pages, no figure

Plasmids in the aphid endosymbiont Buchnera aphidicola with the smallest genomes. A puzzling evolutionary story.

Buchnera aphidicola, the primary endosymbiont of aphids, has undergone important genomic and biochemical changes as an adaptation to intracellular life. The most important structural changes include a drastic genome reduction and the amplification of genes encoding key enzymes for the biosynthesis of amino acids by their translocation to plasmids. Molecular characterization through different aphid subfamilies has revealed that the genes involved in leucine and tryptophan biosynthesis show a variable fate, since they can be located on plasmids or on the chromosome in different lineages. This versatility contrasts with the genomic stasis found in three distantly related B. aphidicola strains already sequenced. We present the analysis of three B. aphidicola strains (BTg, BCt and BCc) belonging to aphids from different tribes of the subfamily Lachninae, that was estimated to harbour the bacteria with the smallest genomes. The presence of both leucine and tryptophan plasmids in BTg, a chimerical leucine-tryptophan plasmid in BCt, and only a leucine plasmid in BCc, indicates the existence of many recombination events in a recA minus bacterium. In addition, these B. aphidicola plasmids are the simplest described in this species, indicating that plasmids are also involved in the genome shrinkage process

Evolving Material Porosity on an Additive Manufacturing Simulation with the Generalized Method of Cells

The effect of material porosity on final part distortion and residual stresses in a selective laser sintering manufacturing simulation is presented here. A time-dependent thermomechanical model is used with the open-source FEA software CalculiX. Effective homogenized material properties for Inconel 625 are precomputed using NASAs Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC). The evolving porosity of the material is estimated with each pass of the laser beam during simulation runtime. A comparison with a homogenous model and the evolving model shows that the evolving porous model predicts larger distortions with greater residual stresses

On the Asymptotic Nature of First Order Mean Field Games

For a class of finite horizon first order mean field games and associated N-player games, we give a simple proof of convergence of symmetric N-player Nash equilibria in distributed open-loop strategies to solutions of the mean field game in Lagrangian form. Lagrangian solutions are then connected with those determined by the usual mean field game system of two coupled first order PDEs, and convergence of Nash equilibria in distributed Markov strategies is established