Solving some special cases of monomial ratio equations appearing frequently in physical and engineering problems

We first show that monomial ratio equations are not only very common in Physics and Engineering, but the natural type of equations in many practical problems. More precisely, in the case of models involving scale variables if the used formulas are not of this type they are not physically valid. The consequence is that when estimating the model parameters we are faced with systems of monomial ratio equations that are nonlinear and difficult to solve. In this paper, we provide an original algorithm to obtain the unique solutions of systems of equations made of linear combinations of monomial ratios whose coefficient matrix has a proper null space with low dimension that permits solving the problem in a simple way. Finally, we illustrate the proposed methods by their application to two practical problems from the hydraulic and structural fields.Peer ReviewedPostprint (published version

Analysis of measurement and simulation errors in structural system identification by observability techniques

This is the peer reviewed version of the following article: [Lei, J., Lozano-Galant, J. A., Nogal, M., Xu, D., and Turmo, J. (2017) Analysis of measurement and simulation errors in structural system identification by observability techniques. Struct. Control Health Monit., 24: . doi: 10.1002/stc.1923.], which has been published in final form at http://onlinelibrary.wiley.com/wol1/doi/10.1002/stc.1923/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.During the process of structural system identification, errors are unavoidable. This paper analyzes the effects of measurement and simulation errors in structural system identification based on observability techniques. To illustrate the symbolic approach of this method a simply supported beam is analyzed step-by-step. This analysis provides, for the very first time in the literature, the parametric equations of the estimated parameters. The effects of several factors, such as errors in a particular measurement or in the whole measurement set, load location, measurement location or sign of the errors, on the accuracy of the identification results are also investigated. It is found that error in a particular measurement increases the errors of individual estimations, and this effect can be significantly mitigated by introducing random errors in the whole measurement set. The propagation of simulation errors when using observability techniques is illustrated by two structures with different measurement sets and loading cases. A fluctuation of the observed parameters around the real values is proved to be a characteristic of this method. Also, it is suggested that a sufficient combination of different load cases should be utilized to avoid the inaccurate estimation at the location of low curvature zones.Peer ReviewedPostprint (author's final draft

Community manager, una nueva salida profesional para el periodismo digital

El extraordinario auge que han experimentado las redes sociales también ha generado nuevas profesiones y oficios 2.0 que a menudo discurren por distintas áreas del saber, como los community manager, asociados a la publicidad, el marketing, la informática, la documentación y el periodismo. En los últimos años ha aumentado de manera vertiginosa la demanda de estos profesionales, al tiempo que los periodistas, acechados por la crisis del sector de la información, manifiestan su interés esta profesión emergente. El objetivo de esta comunicación es analizar el perfil profesional del community manager en un entorno inestable y cambiante y reflexionar acerca del papel que puede desempeñar el periodista digital en la configuración y desempeño profesional de las funciones propias de este oficio.The extraordinary boom experienced by social networks has also encouraged new professions and profiles 2.0 that often run through different areas of knowledge. This is the case of a new professional profile, the community manager, associated to Advertising, Marketing, Computer Science, Documentation and Journalism. The demand of those professionals has increased in recent years at a rapid pace, while journalists, stalked by the crisis of journalism and media, express interest in this emerging profession. The aim of this paper is to analyze the professional profile of community manager in a changing and unstable context and to think about the role that digital journalists can play in shaping and designing the duties and tasks of this office

Constrained observability method in static structural system identification

This is the peer reviewed version of the following article: [Lei J, Nogal M, Lozano-Galant JA, Xu D, Turmo J. Constrained observability method in static structural system identification. Struct Control Health Monit. 2018;25:e2040. https://doi.org/10.1002/stc.2040], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/stc.2040/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Identifiability of parameters in structural system identification (SSI) is of primary importance in any SSI method. It depends on the number and the location of the measurements, which is linked with sensor configuration. In this paper, under the framework of SSI by observability method (OM), the number of necessary measurements to identify all parameters of structural system was clarified first. Then, an example was solved step by step to show the lacking constraints among unknowns in SSI by OM. In a frame example, it was found that no measurement set having as many measurements as the number of unknowns was able to identify all parameters. To further understand this phenomenon, the observability of a simply supported beam was analyzed in an exhaustive way using 252 possible measurement sets. Three quarters of these sets were not able to identify all the parameters. In order to solve this issue, for the very first time, SSI by constrained observability method (COM), which appends the nonlinear constraints to SSI by OM, was proposed. With SSI by COM applied, the observability of the structural parameters with respect to the 252 sets was greatly improved. Finally, the efficacy of SSI by COM was verified by a 13-story frame building.Peer ReviewedPostprint (author's final draft

La narratividad digital ante la lecto-escritura esquizofrénica: un desplazamiento hermenéutico

El artículo plantea la aparición de un nuevo género periodístico en la prensa digital que convierte el texto en discurso, debido a la apropiación del mismo realizada por los comentarios "inmediatos". Estos nuevos lecto-escritores despliegan la intencionalidad del autor, desarrollando exploraciones del contexto y el paratexto. Los nuevos textos se convierten en parte del original, dando lugar a una lecto-escritura esquizofrénica, donde el periodista es sometido a una disociación entre lo que dijo y lo que los lecto-escritores piensan que dijo. Los nuevos lectores, ven convertido el texto original en sólo el preámbulo de los comentarios - la lectura más apasionante - que desplazan el sentido original, lo obvian o lo despliegan en infinitas posibilidades. El productor original es deglutido y termina convertido en un lecto-escritor más que lucha por imponer un sentido a su propio texto

Novel swirl flow-focusing microfluidic device for the production of monodisperse microbubbles

A novel swirl flow-focusing microfluidic axisymmetric device for the generation of monodisperse microbubbles at high production rates to be used as in-line contrast agents for medical applications is presented. The swirl effect is induced upstream of the discharge orifice by a circular array of microblades which form a given angle with the radial direction. The induced vortical component on the focusing liquid stabilizes the gas meniscus by the vorticity amplification due to vortex stretching as the liquid is forced through the discharge orifice. The stabilized meniscus tapers into a steady gas ligament that breaks into monodisperse microbubbles. A reduction up to 57% in the microbubble diameter is accomplished when compared to conventional axisymmetric flow-focusing microdevices. An exhaustive experimental study is performed for various blade angles and numerous gas to liquid flow rate ratios, validating previous VoF numerical simulations. The microbubbles issued from the stabilized menisci verify prior scaling law of flow-focusing

Reflexiones en torno a la prensa tradicional ante la competencia digital

Cada día resultan más comunes los estudios y encuentros encaminados a analizar los avances, las virtudes y los defectos del periodismo digital. En este contexto, hablar de la prensa tradicional, investigar su tendencia, su desarrollo y, en definitiva, su desenvolvimiento en un mundo dominado por lo tecnológico parece haberse convertido en algo obsoleto, falto de interés. Pero no debemos olvidar que la prensa escrita sigue entre nosotros, y en España somos todavía muy numerosos los ciudadanos que permanecemos fieles a nuestros diarios impresos para informarnos de la actualidad política, económica, social, etc. Nos encontramos, pues, en un momento de la historia periodística española caracterizada por la convivencia de ambos tipos de periodismo: el tradicional y el digital. Tanto es así, que cada día resulta más frecuente encontrarnos con noticias mixtas, es decir, con noticias impresas que nos remiten a su versión digital para completar nuestro conocimiento de los hechos acaecidos. Por ello, no debemos cerrar tan rápido el capítulo dedicado a investigar la prensa tradicional y, en especial, la repercusión de los medios electrónicos en la misma: en qué ha cambiado y en qué debe cambiar para resistir, si es lo que deseamos, al envite electrónico. En esta comunicación analizaremos, a partir de la exploración de algunos diarios nacionales y locales españoles, las nuevas tendencias de la prensa de nuestro país, centrándonos, en esta ocasión, en tres indicadores de calidad: tipo de discurso periodístico predominante; profundidad de tratamiento de las informaciones, y preservación y defensa de los valores tradicionales del documento periodístico. El estudio de tales indicadores nos permitirá comprobar si los diarios impresos se están esforzando por incrementar en lo posible la calidad de sus productos informativos para ser competitivos frente a los medios digitales.Researches and meetings focused on digital journalism are the more and more common. However, to research and discuss about the traditional press – its trends and development in a digital and technological era – seems to be out- dated or lacking of interest. But we should not forget that the written press is still very alive among us and there are many people who are still faithful to keep informed. This current moment in history of journalism in Spain is marked by the coexistence of both types of press: traditional and digital. Actually, it is quite usual nowadays to find mixed news – printed news that direct readers to the digital version for more in-depth information. Therefore, we should not leave the research on printed press, most of all on the effects of digital media on the traditional one: how this has changed and how it should change to resist. In this paper, we analyse, exploring several national and local Spanish newspapers, the new trends in the Spanish press, focusing on three press quality indicators: the predominant type of journalistic discourse, the depth of news coverage and the preservation and defence of traditional journalistic values. The study of these indicators will let us to check if printed newspapers are making an effort to increase the quality of their news to be competitive versus digital media

Comparison among different structural system identification methods

The observability techniques have been proposed to deal with structural system identification under static loading tests. Up to now, this method has only been analyzed from a symbolical point of view. Despite the elegance of this approach, this mathematic analysis is far from being applicable in actual structures. To fill this gap, this paper presents a new observability procedure that combines both a symbolical and a numerical approach. To illustrate the potential of the proposed method, the observability technique is compared with two alternative methods presented in the literature. This comparison shows that, unlike to other analyzed methods, no information from the undamaged structure is required. Furthermore, the number of measurements required to be measured for damage detection is significantly reduced.Postprint (published version

Comparison among different structural system identification methods

The observability techniques have been proposed to deal with structural system identification under static loading tests. Up to now, this method has only been analyzed from a symbolical point of view. Despite the elegance of this approach, this mathematic analysis is far from being applicable in actual structures. To fill this gap, this paper presents a new observability procedure that combines both a symbolical and a numerical approach. To illustrate the potential of the proposed method, the observability technique is compared with two alternative methods presented in the literature. This comparison shows that, unlike to other analyzed methods, no information from the undamaged structure is required. Furthermore, the number of measurements required to be measured for damage detection is significantly reduced

Dealing with the peculiarities of the structural system identification of cable-stayed bridges by observability techniques

Traditionally, the structural response of a bridge is modelled by simplistic physics-based models in which the mechanical and geometrical properties are assumed as known. Nevertheless, this is not the case in most actual structures where the values of the actual properties are unknown due to uncertainties in the materials, in the construction methods or in the stress state. In some cases, a calibration of the computer models using monitoring information of the actual structure is required to improve the accuracy of the predicted structural response. To carry out this task Structural System Identification (SSI) methods can be used. Recently, the authors proposed a promising static SSI method based on observability techniques. This method addressed the problems appearing when unknown parameters are assumed into the stiffness matrix of a structure. The observability method was efficiently applied to deal with simple structures, such as single and multiple span beams. Nevertheless, the presented works did not address the peculiarities appearing in complex structures with different load-bearing elements, such as cable-stayed bridges. To fill this gap, this paper proposes the first application of observability techniques to deal with the SSI of cable-stayed bridges. This work enables to define which set of deflections or rotations should be measured on site to identify a certain set of unknown mechanical properties in the deck, the pylon and the stay cables. A set of academic examples, of growing complexity, are used to explain the role that the inclination and cracking of the load-bearing elements of a cable-stayed bridge plays in the SSI by observability techniques. The results obtained in these academic structures are validated by more complex models of real cable-stayed bridges