Identification of arches in 2D granular packings

We identify arches in a bed of granular disks generated by a molecular dynamic-type simulation. We use the history of the deposition of the particles to identify the supporting contacts of each particle. Then, arches are defined as sets of mutually stable disks. Different packings generated through tapping are analyzed. The possibility of identifying arches from the static structure of a deposited bed, without any information on the history of the deposition, is discussed.Comment: 12 pages, 7 figure

A Framework for Generating HTTP Adaptive Streaming Traffic in ns-3

Accepted short paperInternational audienceVideo streaming is today one of the most relevant service in mobile Internet, which represents around 50% of total mobile data traffic. Consequently, researchers perform huge efforts to design and propose new mechanisms and archi-tectures to improve video streaming in mobile networks. In this regard, simulation is a relevant step to test and validate those new mechanisms and models. ns-3 is one models of the most widely used network simulator due to its rich library of network and its vast user community. Despite of its relevance, ns-3 lacks of realistic traffic source. This paper presents a HTTP Adaptive Streaming traffic generator framework for mobile networks in ns-3. Its design and validation are presented, as well as some possible evolution directions and future works

Role of vibrations in the jamming and unjamming of grains discharging from a silo

We present experimental results of the jamming of non-cohesive particles discharged from a flat bottomed silo subjected to vertical vibration. When the exit orifice is only a few grain diameter wide, the flow can be arrested due to the formation of blocking arches. Hence, an external excitation is needed to resume the flow. The use of a continuous gentle vibration is a usual technique to ease the flow in such situations. Even though jamming is less frequent, it is still an issue in vibrated silos. There are, in principle, two possible mechanisms through which vibrations may facilitate the flow: (i) a decrease in the probability of the formation of blocking arches, and (ii) the breakage of blocking arches once they have been formed. By measuring the time intervals inside an avalanche during which no particles flow through the outlet, we are able to estimate the probability of breaking a blocking arch by vibrations. The result agrees with the prediction of a bivariate probabilistic model in which the formation of blocking arches is equally probable in vibrated and non-vibrated silos. This indicates that the second aforementioned mechanism is the main responsible for improving the flowability in gently vibrated silos

Celo inter manus pontificum tradidit spiritum. The ideology surrounding royal deaths in the light of the Latin castilian-leonese chronicles (twelfth and thirteenth centuries)

The death of a king in the medieval chronicles is an incomparable historiographical locus from which to examine this phenomenon. Historiographical texts written at the Castilian-Leonese court during the twelfth century and first half of the thirteenth century, in addition to offering first hand information on royal deaths and the accompanying ceremonies and funeral rites, fully reflect the ideological conceptions and propagandistic constructs surrounding such exceptional events, as will be seen in the first section of this article. In a second section, attention will be paid to the narrative and literary treatment given to the death of a king, as on a formal plane this is also considered to be an event of notable importance.This article is framed in the Migravit and Sepultus Research Projects financed by the Ministerio de Ciencia, Innovación y Universidades and the Casa de Velázquez [ref.: HAR2016-74846-P]

Modeling particle-fluid interaction in a coupled CFD-DEM framework

In this work, we present an alternative methodology to solve the particle-fluid interaction in the resolved CFDEM coupling framework. This numerical approach consists of coupling a Discrete Element Method (DEM) with a Computational Fluid Dynamics (CFD) scheme, solving the motion of immersed particles in a fluid phase. As a novelty, our approach explicitly accounts for the body force acting on the fluid phase when computing the local momentum balance equations. Accordingly, we implement a fluid-particle interaction computing the buoyant and drag forces as a function of local shear strain and pressure gradient. As a benchmark, we study the Stokesian limit of a single particle. The validation is performed comparing our outcomes with the ones provided by a previous resolved methodology and the analytical prediction. In general, we find that the new implementation reproduces with very good accuracy the Stokesian dynamics. Complementarily, we study the settling terminal velocity of a sphere under confined conditions

The Accounts Auditing for Public Interest Entities: Analysis of the Companies Listed on the Madrid Stock Exchange

Resumen: Este trabajo tiene como finalidad última describir algunas de las principales cuestiones que sirven para definir la situación actual del mercado de auditoría de EIP en España, a través del análisis de la información presentada en diversos tipos de informes anuales de las empresas cotizadas en la Bolsa de Madrid. Como objetivo general, se pretende determinar en qué medida sus prácticas en materia de auditoría se ajustan, no sólo a la legislación del país, sino a las recomendaciones publicadas por las autoridades competentes. Haciendo uso de la información disponible tanto en la página Web de la CNMV como en las de las propias empresas, se elabora una base de datos con información relativa a cuestiones como el Informe de auditoría, honorarios y la Comisión de Auditoría, entre otras. Entre los principales resultados obtenidos, destaca el dominio de las Big-4 en variables como el número de auditorías, los honorarios, el incumplimiento de determinadas exigencias normativas como el período de contratación y la escasa diversidad de género en la composición de las Comisiones de Auditoría. Este estudio puede resultar de utilidad, entre otros colectivos, al Instituto de Contabilidad y Auditoría de Cuentas y a las Corporaciones representativas de los profesionales del sector, como comprobación del alcance de sus medidas; a los stakeholders, a los auditores y a las propias empresas auditadas, como baremo para determinar su posición en el mercado; y a la sociedad en general, para seguir creando conciencia sobre la relevancia de la función pública que tiene la auditoría. Abstract: The purpose of this paper is to describe some of the main issues that serve to define the current situation of the EIP audit market in Spain, through the analysis of the information presented in various types of annual reports of companies listed on the Madrid Stock Exchange. As a general objective, it is intended to determine the extent to which its audit practices are adjusted, not only to the country's legislation, but also to the recommendations published by the competent authorities. Making use of the information available both on the website of the CNMV and those of the companies themselves, a database is created with information on issues such as the Audit Report, fees and the Audit Committee, among others. Among the main results obtained, highlights the Big-4 domain in variables such as the number of audits, fees, non- compliance with certain regulatory requirements such as the recruitment period and the low gender diversity in the composition of the Audit Commissions. This study can be useful, among other groups, to the Institute of Accounting and Auditing of Accounts and to the representative Corporations of the professionals of the sector, as a check of the scope of their measures; to the stakeholders, the auditors and the audited companies themselves, as a basis for determining their position in the market; and to society in general, to continue creating awareness about the relevance of the public function of the audit.Grado en Administración y Dirección de Empresa