Optical Multicore Fiber Shape Sensors. A numerical and experimental performance assessment

[EN] Structural Health Monitoring (SHM) is a discipline that quantitatively assesses the integrity and performance of infrastructures, relying on sensors, and support the development of efficient Maintenance and Rehabilitation (M&R) plans. Optical Multicore Fiber (MCF) Shape Sensors offer an innovative alternative to traditional methods and enable the reconstruction of the deformed shape of structures directly and in real-time, with no need of computation models or visual contact and exploiting all the advantages of Optical Fiber Sensors (OFS) technology. Despite the intense research efforts centered on this topic by research groups worldwide, a comprehensive investigation on the parameters that influence the performance of these sensors has not been conducted yet. The first part of the thesis presents a numerical study that examines the effects of strain measurement accuracy and core position errors on the performance of optical multicore fiber shape sensors in sensing three-dimensional curvature, which is at the basis of shape reconstruction. The analysis reproduces the strain measurement process using Monte Carlo Method (MCM) and identifies several parameters which play a key role in the phenomenon, including core spacing (distance between outer cores and sensor axis), number of cores and curvature measured. Finally, a set of predictive models were calibrated, by fitting the results of the simulations, to predict the sensors performance. Afterward, an experimental study is proposed to evaluate the performance of optical multicore fiber in sensing shape, with particular focus on the influence of strain sensors length. Two shape sensors were fabricated, by inscribing long (8.0 mm) and short (1.5 mm) Fiber Bragg Gratings (FBG) into the cores of a multicore seven-core fiber. Thus, the performance of the two sensors was assessed and compared, at all the necessary phases for shape reconstruction: strain sensing, curvature calculation and shape reconstruction. To conclude, an innovative approach, based on the Saint-Venant's Torsion Theory, is presented to determine the twisting of multicore fiber and to compensate the errors due to twisting during shape reconstruction. The efficiency of the theoretical approach was then corroborated performing a series of twisting tests on a shape sensor, fabricated by inscribing FBGs sensors into an optical spun multicore seven-core fiber. The investigation of the mechanical behavior of multicore optical shape sensors has synergically involved diverse disciplines: Solid Mechanics, Photonics, Statistics and Data Analysis. Such multidisciplinary research has arisen from the prolific cooperation between the Institutes of the Institute of Science and Technology of Concrete (ICITECH) and the Institute of Telecommunications and Multimedia Applications (iTEAM) - Photonics Research Labs (PRL) - of Universitat Politècnica de València (UPV), in addition to valuable collaboration with other members of the European ITN-FINESSE project, to which this work belongs. This research work aims to enhance the performance optical multicore fiber shape sensors and support the development of new sensor geometries, with great potential for structural health monitoring applications.[ES] La Monitorización de la Salud Estructural (MSE) evalúa cuantitativamente la integridad y el comportamiento de las infraestructuras y permite desarrollar planes eficaces de Mantenimiento y Rehabilitación (M&R), utilizando los datos de los sensores. Sensores de forma basados en fibra óptica multinúcleo ofrecen una alternativa a los métodos tradicionales y permiten la reconstrucción de la deformada de estructuras de forma directa y en tiempo real, sin necesidad de modelos de cálculo o contacto visual y con todas las ventajas de la tecnología de los Sensores de Fibra Óptica (SFO). A pesar de los grandes esfuerzos en la investigación centrada en este tema por parte de los grupos de investigación de todo el mundo, todavía no se ha realizado una investigación exhaustiva que estudie los parámetros que influyen en el comportamiento de estos sensores. En la primera parte de la tesis se presenta un estudio numérico en el que se examinan los efectos de la precisión de la medición de la tensión y los errores de posición del núcleo en el comportamiento de los sensores de forma basados en fibra óptica multinúcleo para definir la curvatura tridimensional, que es la base de la reconstrucción de la forma. El análisis reproduce el proceso de medición de la tensión utilizando el método de Monte Carlo (MC) e identifica una serie de parámetros que desempeñan un papel en el proceso, entre ellos la separación del núcleo (distancia entre los núcleos exteriores y el eje del sensor), el número de núcleos y la curvatura medida. Por último, se calibró un conjunto de modelos de predicción ajustando los resultados de las simulaciones para predecir el comportamiento de los sensores. A continuación, se propone un estudio experimental para evaluar el comportamiento de los sensores de forma basado en fibra óptica multinúcleo, con especial atención en la influencia de la longitud de los sensores de deformación. Se fabricaron dos sensores de forma, inscribiendo Fiber Bragg Gratings (FBG) con longitudes de 8,0 mm y 1,5 mm en los núcleos de una fibra multinúcleo de siete núcleos. Así, se evaluó y comparó el comportamiento de los dos sensores en todas las fases necesarias para la reconstrucción de la forma, incluyendo la medición de la tensión, el cálculo de la curvatura y la reconstrucción de la forma. Para concluir, se presenta un enfoque innovador, basado en la Teoría de la Torsión de Saint-Venant, para determinar la torsión de la fibra multinúcleo y compensar los errores debidos a la torsión durante la reconstrucción de la forma. La eficiencia del enfoque teórico fue verificada realizando una serie de pruebas de torsión en un sensor de forma, fabricado inscribiendo los sensores de FBGs en una fibra óptica multinúcleo torcida y siete núcleos. La investigación del comportamiento mecánico de los sensores ópticos de forma multinúcleo ha involucrado sinérgicamente diversas disciplinas: Mecánica del sólido, Fotónica, Estadística y Análisis de datos. Esta investigación multidisciplinaria ha surgido de la prolífica cooperación entre el Instituto de Ciencia y Tecnología del Hormigón (ICITECH) y el Instituto de Telecomunicaciones y Aplicaciones Multimedia (iTEAM) - Laboratorio de Investigación Fotónica (LIF) - de la Universidad Politécnica de Valencia (UPV), además de la valiosa colaboración con otros miembros del proyecto europeo ITN-FINESSE, al que pertenece este trabajo. Este trabajo de investigación puede permitir mejorar el comportamiento de los sensores de forma basados en fibra óptica multinúcleo y apoyar el desarrollo de nuevas geometrías de sensores, con un gran potencial para aplicaciones de control de la salud estructural.[CA] Structural Health Monitoring (SHM) avalua quantitativament la integritat i el comportament de les infraestructures i permet desenrotllar plans eficaços de Maintenance and Rehabilitation (M&R), utilitzant les dades dels sensors. Optical Multicore Fiber (MCF) Shape Sensors oferixen una alternativa als mètodes tradicionals i permeten la reconstrucció de la forma de la deformació de les estructures de forma directa i en temps real, sense necessitat de models de càlcul o contacte visual i amb tots els avantatges de l'Optical Fiber Sensors (OFS) Technology. A pesar dels grans esforços en la investigació centrada en aquest tema per part dels grups d'investigació de tot el món, encara no s'ha realitzat una investigació exhaustiva que estudie els paràmetres que influïxen en el comportament d'aquestos sensors. En la primera part de la tesi es presenta un estudi numèric en què s'examinen els efectes de la precisió del mesurament de la tensió i els errors de posició del nucli en el comportament dels sensors de forma basats en fibra òptica multinucli per a definir la curvatura tridimensional, que és la base de la reconstrucció de la forma. L'anàlisi reproduïx el procés de mesurament de la tensió utilitzant el mètode de Monte Carlo (MC) i identifica una sèrie de paràmetres que exercixen un paper en el procés, entre ells la separació del nucli (distància entre els nuclis exteriors i l'eix del sensor), el nombre de nuclis i la mesura de la curvatura. Finalment, es va calibrar un conjunt de models de predicció ajustant els resultats de les simulacions per a predir el comportament dels sensors. A continuació, es proposa un estudi experimental per a avaluar el comportament dels sensors de forma basat en fibra òptica multinucli, amb especial atenció en la influència de la longitud dels sensors de deformació. Es van fabricar dos sensors de forma, inscrivint Fiber Bragg Gratings (FBG) amb longituds de 8,0 mm i 1,5 mm en els nuclis d'una fibra multinucli de set nuclis. Així, es va avaluar i es va comparar el comportament dels dos sensors en totes les fases necessàries per a la reconstrucció de la forma, incloent el mesurament de la tensió, el càlcul de la curvatura i la reconstrucció de la forma. Per a concloure, es presenta un enfocament innovador, basat en la Teoria de la Torsió de Saint-Venant, per a determinar la torsió de la fibra multinucli i compensar els errors deguts a la torsió durant la reconstrucció de la forma. L'eficiència de l'enfocament teòric va ser verificada realitzant una sèrie de proves de torsió en un sensor de forma, fabricat inscrivint els sensors de FBGs en una fibra òptica de set nuclis de filat múltiple. La investigació del comportament mecànic dels sensors òptics de forma multinucli ha involucrat sinèrgicament diverses disciplines: Mecànica del sòlid, Fotónica, Estadística i Anàlisi de dades. Aquesta investigació multidisciplinària ha sorgit de la prolífica cooperació entre l'Institut de Ciència i Tecnologia del Formigó (ICITECH) i l'Institut de Telecomunicacions i Aplicacions Multimèdia (iTEAM) - Laboratori de investigación fotònica (LIF) - de la Universitat Politècnica de València (UPV), a més de la valuosa col·laboració amb altres membres del projecte europeu ITN- FINESSE, al qual pertany aquest treball. Aquest treball d'investigació pot permetre millorar el comportament dels sensors de forma basats en fibra òptica multinucli i ajudar al desenrotllament de noves geometries de sensors, amb un gran potencial per a aplicacions de control de la salut estructural.Floris, I. (2020). Optical Multicore Fiber Shape Sensors. A numerical and experimental performance assessment [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/148715TESI

La Degradazione dei manufatti lignei causata da insetti

The chief coleopters and isopters which attack wooden articles are reported, with particular reference to pest identification for adequate control measures. Bio-ethologycal information useful for pest diagnosis are supplied, as well as predisposing factors and control techniques

Appunti sulla situazione apistica in Sardegna: 1. il censimento

The results are reported of two studies effected at an interval of 5 years. A comparison of beekeeper characteristics, apiary organization, rearing techinques and hygenic conditions showed the development of a more rational apiculture

Agonistic interactions between the honeybee (<i>Apis mellifera ligustica</i>) and the European wasp (<i>Vespula germanica</i>) reveal context-dependent defense strategies

Predator–prey relationships between sympatric species allow the evolution of defense behaviors, such as honeybee colonies defending their nests against predatory wasps. We investigated the predator–prey relationship between the honeybee (Apis mellifera ligustica) and the European wasp (Vespula germanica) by evaluating the effectiveness of attack and defense behaviors, which have coevolved in these sympatric species, as well as the actual damage and disturbance caused to the colonies under attack. Attack and defense behaviors were recorded in front of the hive to observe attacks at the hive entrance (68 attacks in 279 h) and at ground level on isolated and weakened honeybees close to the hive (465 attacks in 32 h). We found that V. germanica attacked the hive entrance infrequently due to the low success rate of this strategy and instead preferred a specialized attack method targeting adult honeybees at ground level, demonstrating opportunistic scavenger behavior. Individual honeybees usually responded effectively to an attack by recruiting an average of two nestmates, causing the wasp to flee, whereas collective balling behavior was only observed on four occasions. V. germanica does not appear to disrupt the foraging activity of the colonies under attack. We found that agonistic events supported by other nestmates were typically the most intense ones, involving physical combat and prolonged attacks at the entrance to the hive. These observations support the hypothesis that A. mellifera ligustica can adapt its behavior to match the severity of the threat and the context of the attack

Design of a High-Speed Ferrite-based Brushless DC Machine for Electric Vehicles

In the present paper an analytic procedure for the preliminary design of a High-Speed ferrite-based Brushless DC Machine (HS-BLDC) has been proposed. In particular, mechanical and electromagnetic modeling have been developed in order to take into account their mutual influence in the definition of the geometry of the electrical machine. In addition, suitable design targets have been imposed in accordance with electric vehicle application requirements. Hence, several mechanical and electromagnetic constraints have been introduced in order to comply with high-speed operation, preventing demagnetization issues of ferrite magnets as well. Subsequently, an HS-BLDC characterized by an inner rotor configuration has been designed in accordance with the proposed methodology. The analytical procedure and the corresponding results have been reported and validated by means of Finite Element Analyses (FEAs), highlighting the effectiveness of the proposed configuration and design solutions

Effects of core position uncertainty on optical shape sensor accuracy

[EN] Optical fiber sensors are now widely recognized as extremely reliable instruments to sense strain. Optical shape sensors consist of multiple single-core optical fibers or multicore optical fibers capable of sensing bending direction and curvature by comparing the longitudinal strain of different cores in an instrumented section and reconstructing the sensor shape. This paper describes a study on the effects of core position errors on the precision of optical shape sensors when measuring strain, bending direction and curvature, and identifies the role of measured curvature and core spacing (distance between section center and external cores), considering 7, 4, and 3-core fiber geometries, three of those most widely employed for sensing applications. The Monte Carlo technique was utilized to reproduce the measurement process. Forty-five simulations, including 3.10(6) trials, were carried out for each geometry with the aim of investigating the law of uncertainty propagation. The results of the analysis, applicable to both multiple single-core fibers and multicore optical sensors equipped with distributed or quasi-distributed strain-sensors, show the effects of core position uncertainty and will be useful for new sensor designs and user options by predicting the achievable performance of these devices.This work was carried out within the ITN-FINESSE framework, funded by the European Union's Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Action Grant Agreement No 722509. It was also supported by the Ministry of Economy and Competitiveness of Spain under the project DIMENSION TEC2017-88029-R.Floris, I.; Calderón García, PA.; Sales Maicas, S.; Adam, JM. (2019). Effects of core position uncertainty on optical shape sensor accuracy. Measurement. 139:21-33. https://doi.org/10.1016/j.measurement.2019.03.031S213313

POPULATION DYNAMICS AND SEASONAL ABUNDANCE OF THAUMASTOCORISPEREGRINUSIN EUCALYPTUSPLANTATIONS IN SARDINIA (ITALY)

Thaumastocoris peregrinusis a eucalyptus pest native to Australia. It is currently the only species belonging to theThaumastocoridae family in Europe. In Italy, it was reported for the first time in Latium in 2011, whereas in Sardinia itwas detected in January 2015 on a Eucalyptus camaldulensis plantation located in the south of the island. Our researchteam carried out a monitoring program for two-years in order to verify its geographical distribution, the main periods ofinfestation, the flight peaks of the adults and to also detect the presence of unhatched eggs on leaves. During the firstyear, the occurrence of adults of T. peregrinuswas verified by yellow sticky traps placed in twelve areas distributedthroughout the island where Eucalyptus plantations were located. In the second year, the population dynamics and theoccurrence of eggs on leaves were evaluated only in three representative study areas, already included in the previousmonitoring program, located in the north, centre and south of the island, respectively. Field surveys showed thepresence of T. peregrinusin all the monitored locations. The highest adult population was observed from late summer toinitial autumn, with a significant increase in adults caught by yellow sticky traps from August, which reached its peakin September and gradually decreased in the following months. The presence of eggs of T. peregrinuson leaves fromJune to December also indicates that the insect is currently well established in the region

PRELIMINARY RESULTS ON THE SPATIO-TEMPORAL VARIABILITYOF GLYCASPIS BRIMBLECOMBEI(HEMIPTERA PSYLLIDAE) POPULATIONSFROM A THREE-YEAR MONITORING PROGRAM IN SARDINIA (ITALY)

The red gum lerp psyllid Glycaspis brimblecombeiis an invasive insect species worldwide. Prolonged attacksby this psyllid may cause both direct and indirect damages to Eucalyptustrees, such as plant weakening, developmentalreductions and phylloptosis, resulting in death within 2-3 years. After the first report in Campania (Italy) in 2010 onEucalyptus camaldulensis trees, it quickly spread to all surrounding central-southern regions of Italy. In Sardinia, G.brimblecombeiwas first recorded in 2011, and is currently found throughout the island. From 2013 to 2015 amonitoring program was carried out in 11 locations throughout Sardinia in order to estimate the density pattern of bothits adults and preimaginal stages, as well as the general population trend of G. brimblecombeiover the years. Ananalysis of G. brimblecombei population abundance showed an almost stable level of infestation over the years, and aseasonal pattern with a population peak in the summer. However, an earlier peak of population abundance was detectedin 2015 compared to the previous years. A spatial heterogeneity of the level of infestation was observed throughout theisland, highlighting the potential effects of environmental conditions in regulating the populations of both G.brimblecombeiand its natural enemies

Measurement uncertainty of multicore optical fiber sensors used to sense curvature and bending direction

[EN] This paper describes a study of the influence of strain measurement uncertainty on sensing curvature and bending direction, considering one of the most widely used fiber geometries for sensing applications (7-core Multicore Fiber) with different core spacings (distance between outer cores and fiber axis). The Monte Carlo method was proposed to simulate the real measurement process and 33 simulations with 106 iterations were performed to determine the laws of propagation of strain measurement uncertainty in calculating curvature and bending direction. The outcomes, which show the strong influence of strain uncertainty and core spacing on the precision of Multicore Fiber sensors, can be used to support the design of new sensors or new fiber geometry and to predict their achievable performance.This work was carried out within the ITN-FINESSE framework, funded by the European Union's Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Action Grant Agreement No 722509. It was also supported by the Ministry of Economy and Competitiveness of Spain under the project DIMENSION TEC-2017-88029-R.Floris, I.; Sales Maicas, S.; Calderón García, PA.; Adam, JM. (2019). Measurement uncertainty of multicore optical fiber sensors used to sense curvature and bending direction. Measurement. 132:35-46. https://doi.org/10.1016/j.measurement.2018.09.033S354613

INSECT PESTS OF EUCALYPTUSPLANTATIONS IN SARDINIA (ITALY)

In Sardinia (Italy), Eucalyptusplantations cover approximately 23,000 hectares, above all in the southern part ofthe island. There is a complex of phytophagous insect pests that is threatening the health status of Eucalyptustrees. Themost recent invasions include the sap-suckers, Glycaspis brimblecombei, Blastopsylla occidentalis, and the bronze bug,Thaumastocoris peregrinus. Other pest species have also been reported, including the gall wasps, Ophelimus maskelliand Leptocybe invasa, the longhorn beetles, Phoracantha semipunctataand P. recurva, and the weevils, Gonipterusscutellatusand Polydrusus(= Metallites) parallelus. Defoliation caused by the gypsy moth, Lymantria dispar, have alsobeen frequently observed in various Eucalyptus-planted areas of Sardinia