Distribució batimètrica dels peixos litorals de substract rocós a l'illa de Cabrera

La ictiofauna que es troba sobre fons rocosos litorals de l'illa de Cabrera ha estat estudiada, mitjançant la tècnica de comptatges visuals, en transsectes fixos de 50 x 5 m, situats a -6, -30 i -45 m de fondària. En total han estat observades 46 espècies, pertanyents a 19 famílies, entre les quals dominen clarament els làbrids i els espàrids. La fondària és el principal factor que determina les diferències qualitatives i quantitatives observades al llarg de l'estudi. El segon factor sembla ser degut a la diferència en l'heterogeneïtat del substrat, i a l'existència a absència d'algues frondoses. En fondària hom observa una certa disminució del nombre d'espècies de làbrids i espàrids. L'ampli marge de fondàries estudiades i l'extrema polarització de les mostres en les comunitats bentòniques de Cabrera permet definir dues associacions de peixos litorals: una de superficial, carateritzada sobretot per Symphodus roissali, Symphodus ocellatus, Thalassoma pavo, i Parablennius rouxij i una de fonda, caracteritzada, entre d'altres per Anthias anthias, Labrus bimaculatus, Symphodus melanocercus i Gobius vittatus. Amb tot, més que una zonació en sentit estricte, hom postula l'existència d'un continuum, on les diferències quantitatives són gairebé tan importants com les qualitatives, i on unes espècies succeeixen les altres de forma gradual. En un treball subsidiari, hom estudia amb més detall la distribució en fondària de dues espècies simpàtriques, Serranus cabrilla i Serranus scriba, entre les quals es produeix, més que una competència per l'espai, un cas de compartimentació espacial. Les pautes de distribució en fondària d'aquestes dues espècies poden ser paradigmàtiques del que ocorre en molts altres casos.The coastal fish fauna from Cabrera island rocky bottoms has been studied by visual censuses along 50 x 5 m strip transects sitted at -6, -30 and -45 m depth. 46 fish species have been recorded, belonging to 19 families dominated by Labridae (11 species) and Sparidae (9 species). Depth is the main environmental factor affecting qualitative and quantitative fish distribution, being bottom heterogenity (hole size and presence or absence of frondose algae) the second one. A decrease of Labridae and Sparidae species has been found with depth. Two rocky fish assemblages have been distinguished attending to their depth distribution ranks: a shallow one, characterized by Symphodus roissali, Symphodus ocellatus, Thalassoma pavo and Parablennius rouxij and a deep one, characterized mainly by Anthias anthias, Labrus bimaculatus, Symphodus melanocercus and Gobius vittatus. However, there is a continuum change of species with depth instead of critical discontinuities between the two fish assemblages. Depth patterns of two sympatric species (Serranus cabrilla and Serranus scribal has been studied as an example of this continuos depth fish distribution

On the Torelli problem and Jacobian Nullwerte in genus three

We give a closed formula for recovering a non-hyperelliptic genus three curve from its period matrix, and derive some identities between Jacobian Nullwerte in dimension three

Design and FDM/FFF Implementation of a Compact Omnidirectional Wheel for a Mobile Robot and Assessment of ABS and PLA Printing Materials

This paper proposes the design and 3D printing of a compact omnidirectional wheel optimized to create a small series of three-wheeled omnidirectional mobile robots. The omnidirectional wheel proposed is based on the use of free-rotating passive wheels aligned transversally to the center of the main wheel and with a constant separation gap. This paper compares a three inner-passive wheels design based on mass-produced parts and 3D printed elements. The inner passive wheel that better combines weight, cost, and friction is implemented with a metallic ball bearing fitted inside a 3D printed U-grooved ring that holds a soft toric joint. The proposed design has been implemented using acrylonitrile butadiene styrene (ABS) and tough polylactic acid (PLA) as 3D printing materials in order to empirically compare the deformation of the weakest parts of the mechanical design. The conclusion is that the most critical parts of the omnidirectional wheel are less prone to deformation and show better mechanical properties if they are printed horizontally (with the axes that hold the passive wheels oriented parallel to the build surface), with an infill density of 100% and using tough PLA rather than ABS as a 3D printing material

Square-free OM computation of global integral bases

© 2022 Mathematical Sciences PublishersFor a prime p, the OM algorithm finds the p-adic factorization of an irreducible polynomial f¿Z[x]¿¿Z[¿] in polynomial time. This may be applied to construct p-integral bases in the number field K defined by f. In this paper, we adapt the OM techniques to work with a positive integer N instead of p. As an application, we obtain an algorithm to compute global integral bases in K, which does not require a previous factorization of the discriminant of f.Partially supported by grants MTM2015-66180-R and MTM2016-75980-P from the Spanish MECPeer ReviewedPostprint (author's final draft

Assessing over Time Performance of an eNose Composed of 16 Single-Type MOX Gas Sensors Applied to Classify Two Volatiles

This paper assesses the over time performance of a custom electronic nose (eNose) composed of an array of commercial low-cost and single-type miniature metal-oxide (MOX) semiconductor gas sensors. The eNose uses 16 BME680 versatile sensor devices, each including an embedded non-selective MOX gas sensor that was originally proposed to measure the total volatile organic compounds (TVOC) in the air. This custom eNose has been used previously to detect ethanol and acetone, obtaining initial promising classification results that worsened over time because of sensor drift. The current paper assesses the over time performance of different classification methods applied to process the information gathered from the eNose. The best classification results have been obtained when applying a linear discriminant analysis (LDA) to the normalized conductance of the sensing layer of the 16 MOX gas sensors available in the eNose. The LDA procedure by itself has reduced the influence of drift in the classification performance of this single-type eNose during an evaluation period of three month

Characterizing superradiant dynamics in atomic arrays via a cumulant expansion approach

Ordered atomic arrays with subwavelength lattice spacing emit light collectively. For fully inverted atomic arrays, this results in an initial burst of radiation and a fast build up of coherences between the atoms at initial times. Based on a cumulant expansion of the equations of motion, we derive exact analytical expressions for the emission properties and numerically analyze the full many-body problem resulting in the collective decay process for unprecedented system sizes of up to a few hundred atoms. We benchmark the cumulant expansion approach and show that it correctly captures the cooperative dynamics resulting in superradiance. For fully inverted arrays, this allows us to extract the scaling of the superradiant peak with particle number. For partially excited arrays where no coherences are shared among atoms, we also determine the critical number of excitations required for the emergence of superradiance in one- and two-dimensional geometries. In addition, we study the robustness of superradiance in the case of non-unit filling and position disorder.Comment: 13 pages, 7 figure

Systematic Odometry Error Evaluation and Correction in a Human-Sized Three-Wheeled Omnidirectional Mobile Robot Using Flower-Shaped Calibration Trajectories

Odometry is a simple and practical method that provides a periodic real-time estimation of the relative displacement of a mobile robot based on the measurement of the angular rotational speed of its wheels. The main disadvantage of odometry is its unbounded accumulation of errors, a factor that reduces the accuracy of the estimation of the absolute position and orientation of a mobile robot. This paper proposes a general procedure to evaluate and correct the systematic odometry errors of a human-sized three-wheeled omnidirectional mobile robot designed as a versatile personal assistant tool. The correction procedure is based on the definition of 36 individual calibration trajectories which together depict a flower-shaped figure, on the measurement of the odometry and ground truth trajectory of each calibration trajectory, and on the application of several strategies to iteratively adjust the effective value of the kinematic parameters of the mobile robot in order to match the estimated final position from these two trajectories. The results have shown an average improvement of 82.14% in the estimation of the final position and orientation of the mobile robot. Therefore, these results can be used for odometry calibration during the manufacturing of human-sized three-wheeled omnidirectional mobile robots

Application of a Single-Type eNose to Discriminate the Brewed Aroma of One Caffeinated and Decaffeinated Encapsulated Espresso Coffee Type

This paper assesses a custom single-type electronic nose (eNose) applied to differentiate the complex aromas generated by the caffeinated and decaffeinated versions of one encapsulated espresso coffee mixture type. The eNose used is composed of 16 single-type (identical) metal–oxide semiconductor (MOX) gas sensors based on microelectromechanical system (MEMS). This eNose proposal takes advantage of the small but inherent sensing variability of MOX gas sensors in order to provide a multisensorial description of volatiles or aromas. Results have shown that the information provided with this eNose processed using LDA is able to successfully discriminate the complex aromas of one caffeinated and decaffeinated encapsulated espresso coffee type