Steady-Sensitivity Distributed Acoustic Sensors

Distributed acoustic sensors (DAS) based on phase-sensitive optical time-domain reflectometry (phiOTDR) have demonstrated interesting performance for many applications ranging from seismology to pipeline protection. However, the sensitivity of traditional DAS relying on coherent detection is strongly dependent on the system noise and trace fading points, offering poor reliability of the results in the spatial dimension. In this manuscript, we evaluate the statistical performance of a recently proposed DAS technique, namely, chirped-pulse phiOTDR, in terms of sensitivity and signal-to-noise ratio (SNR). Our results show behavioral trends that significantly differ from those of traditional DAS. In particular, the acoustic SNR distribution in chirped-pulse DAS is notably narrower than that in the traditional case, allowing to ensure a large system dynamic range across all the points of the optical trace. Hence, chirped-pulse phiOTDR offers localized perturbation detection with very high reliability, almost independent of trace fading points, along the complete reachable range of the sensor.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

Monitoring of remote seismic events in metropolitan area fibers using distributed acoustic sensing (DAS) and spatio-temporal signal processing

Este documento se considera que es una ponencia de congresos en lugar de un capítulo de libro.Optical Fiber Communication Conference (OFC) 2019, San Diego, California, USA, 3-7 March 2019Remote seismic activity is monitored with DAS using a pre-existent fiber installation in an urban area. Background noise, which greatly exceeds the amplitude of the monitored seismic signals, is eliminated via 2D (spatio-temporal) signal processing

Extending the Measurement of True Dynamic Strain via Chirped-Pulse Phase-Sensitive Optical Time Domain Reflectometry to 100's of Microstrains

26ª edición del congreso internacional Optical Fiber Sensors (OFS26), 24/09/2018-28/09/2018, Lausanne, Suiza.It is experimentally demonstrated that a chirped pulse phase-sensitive OTDR can measure large and fast dynamic strains (~100’s of µε, ~100’s of Hz) with SNR of ≥ 24dB. Signal smoothing and impact of error accumulation are also discussed.European Commissio

Distributed detection of hydrogen and deuterium diffusion into a single-mode optical fiber with chirped-pulse phase-sensitive optical time-domain reflectometry

For some infrastructures like oil and gas extraction boreholes or radioactive waste repositories, where distributed optical fiber sensors are employed to grant the safety of the facilities, the presence of gas species such as hydrogen or deuterium is one more relevant parameter to monitor. The possibility of employing the same kind of sensors for this purpose is of special interest, reducing the cost by employing a single interrogator, able to measure more than one parameter by simply employing an adequate sensing fiber. To meet this goal, we present here a sensor based on Chirped Pulse Phase sensitive Optical Time Domain Reflectometry, which is able to detect these species while they diffuse into the silica fiber core. Its ability to measure the induced change of its refractive index with a sensitivity around 10 8 has allowed determining hydrogen concentration in the silica core with precision in the order of 10 3 mol/m3 and spatial resolution ~6 m, while also providing an indirect measurement of the solubility of deuterium in a standard telecom-grade optical fiber.Commission of the European Communities JointMinisterio de Economía y CompetitividadMinisterio de Ciencia, Innovación y UniversidadesComunidad de Madri

A Comparison of Photoelastic and Finite Elements Analysis in Internal Connection and Bone Level Dental Implants

This study is a contribution to our understanding of the mechanical behaviour of dental implants through the use of the finite element and the photoelastic methods. Two internal connection and bone level dental implants with different design have been analysed (M-12 by Oxtein S.L., Zaragoza, Spain, and ASTRA, from Dentsply Sirona, Charlotte, NC, USA), evaluating the stress distribution produced by axial stresses and a comparison has been established between them, as well as between the two methods used, in order to validate the adopted hypotheses and correlate the numerical modelling performed with experimental tests. To load the implant in laboratory testing, a column was placed, such that the loading point was about 9.3 mm from the upper free surface of the resin plate. This column connects the implant with the weights used to define the test load. In turn, support for both plates was achieved by two 6 mm bolts 130 mm apart and located on a parallel line with the resin (flush with the maximum level of the implant), at a depth of 90 mm. The results obtained with both methods used were similar enough. The comparison of results is fundamentally visual, but ensures that, at least in the range of forces used, both methods are similar. Therefore, the photoelastic method can be used to confirm in a real way the virtual conditions of the finite element models, with the implications in the investigation of dental implants that this entails

Analysis of disturbance-induced "virtual" perturbations in chirped pulse φ-OTDR

When a disturbance acts on a fiber it induces a change in the local refractive index that influences the fiber backscattering trace. If a chirped pulse φ-OTDR setup is used to interrogate the fiber, this refractive index change appears as a local shift of the received trace, linear to the acting perturbation. However, the refractive index change influences the round trip time of all the backscattering components generated by further fiber sections as well. Due to the high sensitivity of chirped pulse φ-OTDR, the change in the round trip time of the backscattering components, which is usually negligible, may appear as a virtual perturbation in certain conditions. In this letter we derive a mathematical model for the virtual perturbation induced by a disturbance acting on the fiber, when the measurement is performed by a chirped pulse φ-OTDR. We experimentally validate the model by inducing a temperatura change on a known span of fiber while monitoring its effects in a further fiber section kept at rest. The experimental results are then analyzed and compared with the theoretical ones.European CommissionMinisterio de Economía y CompetitividadMinisterio de Ciencia, Innovación y UniversidadesComunidad de Madri

Photonic Seismology

International Photonics and OptoElectronics Meetings 2019, OFDA, 11/11/2019-14/11/2019, Wuhan, ChinaOne of the greatest outstanding challenges in seismology is the sparsity of instrumentation across the Earth, particularly in the oceans. In this work we show that optical fiberbased distributed acoustic sensors (DAS) can represent a low-cost solution (basically inexistent so far) for monitoring seismicity in remote areas of the ocean. This solution can retrofit existing telecommunication optical fiber cables lying in the ocean and transform them (with no basic change in the cable itself) into powerful seismic sensing arrays. With a single optoelectronic unit in the end of the cable (onshore), a full span of 50-100 km can be monitored, with thousands of measuring points interrogated.Commission of the European Communities JointMinisterio de Economía y CompetitividadMinisterio de Ciencia, Innovación y UniversidadesComunidad de Madri

Monitorización de actividad sísmica usando sensores distribuidos en fibra basados en φOTDR y pulsos con chirp

XI Reunión Española de Optoelectrónica (OPTOEL 2019), 03/07/2019-05/07/2019, Zaragoza, España.Actualmente, los sistemas de comunicaciones ópticas de larga distancia se basan en una extensa red de fibra óptica que se encuentra instalada alrededor del globo. En este trabajo, presentamos cómo esta red de fibra puede ser empleada para un uso alternativo: el análisis de movimientos sísmicos del planeta. Para ello, se ha utilizado la fibra como elemento sensor en un sistema de sensado distribuido basado en OTDR sensible a fase (φOTDR) usando pulsos con chirp con el que se ha detectado un terremoto de grado 8,2 ocurrido el pasado agosto en las Islas Fiji. Este terremoto se ha detectado en dos localizaciones diferentes, un entorno metropolitano en la ciudad de Pasadena (California, EEUU) y un entorno submarino en la costa de Bélgica. Usando técnicas de procesado lineales se ha podido ex-traer información del terremoto del ruido ambiente. Los resultados aquí mostrados muestran el gran potencial de la red de fibra ya instalada para su uso como sismógrafo distribuido.Ministerio de Economía y CompetitividadComunidad de MadridEuropean Commissio

Subscapular and triceps skinfolds reference values of Hispanic American children and adolescents and their comparison with the reference of Centers for Disease Control and Prevention (CDC)

Introduction: the assessment of the skinfold thickness is an objective measure of adiposity. Therefore, it is a useful tool for nutritional diagnosis and prevention of metabolic risk associated with excess fat in chilhood and adolescence. Objective: to provide percentiles of subscapular and triceps skinfolds for Hispanic American schoolchildren and compare them with those published by the Centers for Disease Control and Prevention (CDC) from United States, that it have been commonly used as a reference in most of these countries. Methods: subscapular and triceps skinfolds were measured in 9.973 schoolchildren 4-19 aged from Spain, Argentina, Cuba, Venezuela and Mexico with Holtain caliper with 0.2 mm accuracy. Percentiles were obtained with the LMS statistical method and were presented in tables divided in stages of 6 months and in curves graphics. The difference between Hispanic American and CDC mean values were provided for P3, P50 and P97 in mm and also were graphically represented. Results: skinfolds measurements obviously increased with age in both sexes but, in boys, this increase is much more marked in highest percentiles between 8 and 13 years; this maximum is reached earlier than what occurs in CDC reference. In both sexes, all percentiles analized in Hispanic American schoolchildren were higher than the CDC reference except P97 up to 10 or 13 years that was notably smaller. Conclusions: the skinfolds percentiles of Hispanic American children and adolescents differ from CDC that are usually used as reference. The values of subscapular and triceps skinfolds provided in this study, could be applied to populations of a similar ethnic background, especially in comparative studies of body composition

La enseñanza del metabolismo: retos y oportunidades

En el marco del Proyecto de Innovación Educativa de la Universidad de Málaga PIE15-163, cuya descripción y resultados incluimos, decidimos que esta era una excelente oportunidad para reflexionar acerca de la enseñanza del metabolismo y de poner por escrito dichas reflexiones en un libro. Quisimos y pudimos contar con la colaboración de buena parte de los compañeros del Departamento de Biología Molecular y Bioquímica que apoyaron con su firma el proyecto PIE15-163 y extendimos nuestra invitaciones a otros compañeros de dentro y fuera de la Universidad de Málaga. Del Departamento de Biología Molecular y Bioquímica de la Universidad de Málaga hemos recibido aportaciones de los catedráticos Victoriano Valpuesta Fernández, Ana Rodríguez Quesada y Antonio Heredia Bayona, los profesores titulares María Josefa Pérez Rodríguez, José Luis Urdiales Ruiz e Ignacio Fajardo Paredes y la investigadora postdoctoral y profesora sustituta interina Beatriz Martínez Poveda. De otros departamentos de la Universidad de Málaga hemos contado con las aportaciones de la catedrática del Departamento de Especialidades Quirúrgicas, Bioquímica e Inmunología Pilar Morata Losa, del catedrático del Departamento de Lenguajes y Ciencias de la Computación José Francisco Aldana Montes y los componentes de su grupo de investigación Khaos Ismael Navas Delgado, María Jesús García Godoy, Esteban López Camacho y Maciej Rybinski, del catedrático Ángel Blanco López, del Área de Conocimiento de Didáctica de las Ciencias Experimentales y del Doctor en Ciencias Químicas y actual doctorando del Programa de Doctorado "Educación y Comunicación Social" Ángel Luis García Ponce. De fuera de la Universidad de Málaga, hemos contado con las aportaciones del catedrático de la Universidad de La Laguna Néstor V. Torres Darias, de la catedrática de la Universitat de les Illes Balears Pilar Roca Salom y de sus compañeros los profesores Jorge Sastre Serra y Jordi Oliver, de los catedráticos de la Universidad de Granada Rafael Salto González y María Dolores Girón González y su colaborador el Dr. José Dámaso Vílchez Rienda, del profesor titular de la Universidad de Alcalá Ángel Herráez, del investigador postdoctoral de la Universidad de Erlangen (Alemania) Guido Santos y del investigador postdoctoral de la empresa Brain Dynamics Carlos Rodríguez Caso.Hemos estructurado los contenidos del libro en diversas secciones. La primera presenta el Proyecto en cuyo marco se ha gestado la iniciativa que ha conducido a la edición del presente libro. La segunda sección la hemos titulado "¿Qué metabolismo?" e incluye diversas aportaciones personales que reflexionan acerca de qué metabolismo debe conocer un graduado en Bioquímica, en Biología, en Química, en Farmacia o en Medicina, así como una aportación acerca de qué bioquímica estructural y enzimología son útiles y necesarias para un estudiante que vaya a afrontar el estudio del metabolismo. La tercera sección, "Bases conceptuales", analiza las aportaciones del aprendizaje colaborativo, el contrato de aprendizaje y el aprendizaje basado en la resolución de casos prácticos a la mejora del proceso enseñanza-aprendizaje dentro del campo de la Bioquímica y Biología Molecular, más concretamente en el estudio del metabolismo. La cuarta sección se titula "Herramientas", es la más extensa e incluye las diversas aportaciones centradas en propuestas concretas de aplicación relevantes y útiles para la mejora de la docencia-aprendizaje del metabolismo. Sigue una sección dedicada a presentar de forma resumida los "Resultados" del proyecto PIE15-163. El libro concluye con una "coda final" en la que se reflexiona acerca del aprendizaje de la Química a la luz de la investigación didáctica.Patrocinado por el Proyecto de Innovación Educativa de la Universidad de Málaga PIE15-16