Study on Advanced Spray-Guided Gasoline Direct Injection Systems

Resumen Los sistemas de inyección directa han sido uno de los principales puntos focales de la investigación en motores, particularmente en sistemas Diésel, donde la geometría interna, movimiento de aguja y comportamiento del flujo afectan el spray externo y por tanto determinan completamente el proceso de combustión dentro del motor. Debido a regulaciones medioambientales y al potencial de los (más ineficientes) motores "Otto", grandes esfuerzos se están aportando en investigación sobre sistemas de inyección directa de gasolina. Los motores GDi tienen el potencial de incrementar sustancialmente la economía de combustible y cumplir con las regulaciones de gases contaminantes y de efecto invernadero, aunque aún existen muchos desafíos por delante. Esta tesis estudia en detalle una moderna tobera GDi que fue específicamente diseñada para el grupo de investigación conocido como Engine Combustion Network (ECN). Con metodologías punteras, este inyector ha sido usado en un amplio abanico de instalaciones experimentales para caracterizar el flujo interno y varias características clave de geometría y funcionamiento, y aplicarlo para evaluar cómo se relaciona con los efectos observados del comportamiento del chorro externo. Para la caracterización interna del flujo, el objetivo ha sido determinar la geometría de la tobera y el desplazamiento de aguja, caracterizar la tasa de inyección y el flujo de cantidad de movimiento, y evaluar el flujo cercano. Algunas metodologías nunca antes habían sido empleadas en inyectores GDi, y muchas otras lo han sido solo eventualmente. Para la geometría interna, el levantamiento de aguja y el flujo cercano, varias técnicas avanzadas con rayos-x fueron aplicadas en las instalaciones de Argonne National Laboratory. Para la tasa de inyección y flujo de cantidad de movimiento, las técnicas disponibles en el departamento han sido adaptadas desde Diésel y aplicadas en inyectores GDi multiorificio. Dado lo novedoso de las técnicas aplicadas, las particularidades de las metodologías han sido discutidas en detalle en el documento. Aún con la elevada turbulencia del flujo interno, el inyector se comporta de forma consistente inyección a inyección, incluso cuando el estudio se centra en la variabilidad orificio a orificio. Esto ha sido atribuido al comportamiento repetitivo de la aguja, evaluado en los experimentos. También fue observado que el flujo estabilizado tiene una variación de alta frecuencia que no pude ser explicado por el movimiento de la aguja, sino por el particular diseño de las toberas. El análisis de geometría interna realizado a ocho toberas nominalmente iguales resultó en la obtención de un punto vista único en la construcción de toberas y la variabilidad de dimensiones clave. Las medidas de tasa de inyección permitieron estudiar la respuesta hidráulica del inyector a varias variables como la presión de inyección, presión de descarga, temperatura de combustible y la duración de la señal de comando. Estas medidas fueron combinadas con medidas de flujo de cantidad de movimiento para estudiar el bajo valor del coeficiente de descarga, el cual fue atribuido al bajo levantamiento de aguja y coeficiente L/D de los orificios. Por otro lado, el estudio del spray externo resultó en la identificación de un importante fenómeno específico a este particular hardware, el colapso del spray. Las extensivas campañas experimentales, utilizando Schlieren e iluminación trasera difusa (DBI) permitieron identificar y describir las características macroscópicas del spray y las condiciones bajo las que el colapso ocurre. El colapso del spray se forma por una combinación de interacción de las diferentes plumas (causado por el flujo interno) y determinadas condiciones ambiente que promueven evaporación y entrada de aire. Fue determinado que a niveles de densidad y temperatura moderados se desarrolla el colapso, modificando completamente el comportamiento esperaAbstract Fuel injection systems have been one of the main focal points of engine research, particularly in Diesel engines, where the internal geometry, needle lift and flow behavior are known to affect the external spray an in turn completely determine the combustion process inside engines. Because of environmental regulation and the potential development of the more inefficient Otto engines, a lot of research efforts are currently focused into gasoline direct injection systems. GDi engines have the potential to greatly increase fuel economy and comply with pollutant and greenhouse gases emissions limits, although many challenges still remain. The current thesis studies in detail a modern type of GDi nozzle that was specifically developed for the international research group known as the Engine Combustion Network (ECN). With the objective of employing state-of-the-art techniques, this hardware has been used in a wide range of experimental facilities in order to characterize the internal flow and several geometrical and constructive aspects like needle lift; and assess how it relates to the effects seen external spray. For the internal flow characterization, the goal was to determine the nozzle geometry and needle displacement, to characterize the rate of injection and rate of momentum, and evaluate the near-nozzle flow. Some methodologies applied here have never been applied to a GDi injector before, and many have only been applied rarely. For the internal geometry, needle lift and near-nozzle flow, several advanced x-rays techniques were used at Argonne National Laboratory. For the rate of injection and rate of momentum measurements, the techniques available in CMT-Motores Térmicos have been adapted from Diesel spray research and brought to multi-hole GDi injectors. Given the novelty of the techniques used, the particular methodologies and setups are discussed in detail. Despite the high turbulence of the flow, it was seen that the injector behaves consistently injection to injection, even when studying variation in individual holes. This is attributed to the repetitive behavior of the needle that was observed in the experiments. It was also observed that the stabilized flow has a high frequency variability that could not be explained by random movement of the needle, but rather by the particular design of the nozzle. The geometrical analysis done to eight, nominally equal nozzles, allowed a unique view into the construction of the nozzle and provided insights about the variability of key dimensions. The rate of injection measurements allowed to study the hydraulic response of the injector to the main variables like rail pressure, discharge pressure, fuel temperature and command signal duration. These measurements were combined with the rate of momentum measurements to study the low value of the discharge coefficient, that ultimately was attributed to the low needle lift and low L/D ratio of the orifices. On the other hand, the study of the external spray yielded the identification of very important phenomena specific to this particular hardware, the spray collapse. The extensive experimental campaigns featuring shadowgraph (Schlieren) and Diffused Back Illumination (DBI) visualization techniques allowed identifying and describing the macroscopic characteristics of the spray and the conditions under which the collapse occurs. The spray collapse engenders from a combination of the internal flow that creates plume interaction, and ambient conditions that promote air entrainment and evaporation. At moderate density and temperature levels the collapse develops, completely modifying the expected trends in the behavior of the plumes.Resum Els sistemes d'injecció directa han sigut un dels principals punts focals de la investigació en motors, particularment en sistemes dièsel, en què la geometria interna, el moviment de l'agulla i el comportament del flux afecten l'esprai extern i per tant determinen completament el procés de combustió dins del motor. Degut a regulacions mediambientals i al potencial dels (més ineficients) motors "Otto", grans esforços s'estan aportant en investigació sobre sistemes d'injecció directa de gasolina. Els motors GDi tenen el potencial d'incrementar substancialment l'economia del combustible i complir les regulacions de gasos contaminants i d'efecte hivernacle, encara que existeixen molts desafiaments per davant. Esta tesi estudia en detall una moderna tovera GDi que va ser especialment dissenyada per al grup d'investigació conegut com a ECN. Amb l'objectiu de desenvolupar metodologies punteres, este injector ha sigut usat en un ampli ventall d'instal·lacions experimentals per tal de caracteritzar el flux intern i diverses característiques clau de la seua geometria i funcionament, per tal d'avaluar com es relacionen amb els efectes observats del comportament de l'esprai extern. Per a la caracterització interna del flux, l'objectiu ha sigut determinar la geometria de la tovera i el desplaçament de l'agulla, caracteritzar la taxa d'injecció i el flux de quantitat de moviment, i avaluar el flux proper. Algunes metodologies no s'havien empleat abans en injectors GDi, i moltes altres ho han sigut únicament de manera eventual. Per a la geometria interna, l'alçament de l'agulla i el flux proper, s'han aplicat diverses tècniques avançades amb raigsx a les instal·lacions d'Argonne National Laboratory. Per a la taxa d'injecció i el flux de quantitat de moviment, les tècniques disponibles al departament han sigut adaptades des de Dièsel i aplicades a injectors GDi multi-orifici. Considerant la novetat de les tècniques aplicades, les particularitats de les metodologies es discuteixen en detall al document. A pesar de l'elevada turbulència del flux intern, l'injector es comporta de manera consistent injecció a injecció, inclús quan l'estudi se centra en la variabilitat orifici a orifici. Aquest fet s'ha atribuït al comportament repetitiu de l'agulla, avaluat als experiments. També es va observar que el flux estabilitzat té una variació d'altra freqüència que no pot ser explicat pel moviment de l'agulla, sinó pel particular disseny de les toveres. L'anàlisi de la geometria interna realitzat a vuit toveres nominalment iguals va permetre obtenir un punt de vista únic en la construcció de toveres i la variabilitat de dimensions clau. Les mesures de taxa d'injecció van permetre estudiar la resposta hidràulica de l'injector a diverses variables com la pressió d'injecció, la pressió de descàrrega, la temperatura del combustible i la duració de la senyal de comandament. Estes mesures van ser combinades amb mesures de flux de quantitat de moviment per tal d'estudiar el baix valor del coeficient de descàrrega, el qual va ser atribuït al baix alçament de l'agulla i al coeficient L/D dels orificis. D'altra banda, l'estudi de l'esprai extern va permetre identificar un important fenomen específic d'aquest hardware particular: el col·lapse de l'esprai. Les extensives campanyes experimentals, utilitzant Schlieren i il·luminació darrera difusa (DBI) van permetre identificar i descriure les característiques macroscòpiques de l'esprai i les condicions sota les quals el col·lapse té lloc. El col·lapse de l'esprai es forma per una combinació d'interacció de les diverses plomes (causat pel flux intern) i determinades condicions ambient que promouen evaporació i entrada d'aire. Es va determinar a quins nivells de densitat i temperatura moderats es desenvolupa el col·lapse, modificant completament el comportament esperat de l'esprai.Vaquerizo Sánchez, D. (2018). Study on Advanced Spray-Guided Gasoline Direct Injection Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/99568TESI

Multi-Class AdaBoost to Detect Sleep Apnea-Hypopnea Syndrome Severity from Oximetry Recordings Obtained at Home

Producción CientíficaThis paper aims at evaluating a novel multi-class methodology to establish Sleep Apnea-Hypopnea Syndrome (SAHS) severity by the use of single-channel at-home oximetry recordings. The study involved 320 participants derived to a specialized sleep unit due to SAHS suspicion. These were assigned to one out of the four SAHS severity degrees according to the apnea-hypopnea index (AHI): no-SAHS (AHI<5 events/hour), mild-SAHS (5≤AHI<15 e/h), moderate-SAHS (15≤AHI<30 e/h), and severe-SAHS (AHI≥30 e/h). A set of statistical, spectral, and non-linear features were extracted from blood oxygen saturation (SpO2) signals to characterize SAHS. Then, an optimum set among these features were automatically selected based on relevancy and redundancy analyses. Finally, a multi-class AdaBoost model, built with the optimum set of features, was obtained from a training set (60%) and evaluated in an independent test set (40%). Our AdaBoost model reached 0.386 Cohen’s kappa in the four-class classification task. Additionally, it reached accuracies of 89.8%, 85.8%, and 74.8% when evaluating the AHI thresholds 5 e/h, 15 e/h, and 30 e/h, respectively, outperforming the classic oxygen desaturation index. Our results suggest that SpO2 obtained at home, along with multi-class AdaBoost, are useful to detect SAHS severity.Junta de Castilla y León (project VA059U13)Pneumology and Thoracic Surgery Spanish Society (265/2012

Libro de Actas de la "I Jornada para Alumnos de Trabajo Fin de Grado y Trabajo Fin de Máster: Uso Efectivo de Herramientas TIC"

Innovación EducativaEste libro de resúmenes engloba los trabajos presentados en la “I Jornada para alumnos de Trabajo Fin de Grado (TFG) y Trabajo Fin de Máster (TFM). Uso efectivo de herramientas TIC”, celebrada en Valladolid el 21 de marzo de 2019. Los trabajos aceptados tienen como autores a alumnos de TFG o TFM que han presentado su tema de estudio de TFG/TFM y los principales resultados obtenidos hasta el momento de acuerdo con los requisitos formales de la Jornada. Estos resúmenes cubren un amplio rango de temáticas, incluyendo el procesado de señales e imágenes o el diseño de dispositivos y redes de comunicaciones, entre otros. Todos los trabajos han seguido un proceso de revisión riguroso, siendo evaluados en profundidad por los miembros del Comité Organizador. Los editores del libro de resúmenes de la “I Jornada para alumnos de Trabajo Fin de Grado (TFG) y Trabajo Fin de Máster (TFM). Uso efectivo de herramientas TIC” agradecen enormemente a todos los alumnos, profesores y ponentes su participación en la Jornada, ya que su contribución ha sido imprescindible para la celebración de este evento.Vicerrectorado de Docencia de la Universidad de Valladolid (PID Nº 55: “Nuevas propuestas en la tutorización de Trabajos Fin de Grado y Trabajos Fin de Máster con el apoyo de entornos virtuales de aprendizaje colaborativo"

Implementación de un Kernel LINUX sobre un procesador tipo software utilizando una FPGA

En el mercado existen multitud de microprocesadores capaz de realizar multitud de tareas muy variadas, sin embargo, todos ellos tienen una limitación, el hardware, ya que éste no puede ser modificado una vez se fabrica la placa. En este aspecto, las FPGA tienen mucho que decir al respecto, dado que gracias a lo que se conoce como softcore, es posible diseñar un microprocesador en lenguaje VHDL capaz de comportarse de la forma deseada, incluyendo en este diseño los periféricos y utilidades deseadas como memoria caché, unidad de gestión de memoria, coma flotante, etc. Además, cuando se emplea el termino FPGA, normalmente se piensa en un sistema embebido, capaz de ejecutar una aplicación una y otra vez a una velocidad elevadísima, aquí es donde entra en juego el softcore Microblaze, diseñado por Xilinx, ya que permite añadir a una simple FPGA la capacidad e ejecutar un sistema operativo como puede ser Linux. Este proyecto se centra en el diseño de un softcore capaz de ejecutar un kernel Linux y los periféricos asociados al mismo, pasando para ello por diferentes puntos del diseño, que van desde la creación del procesador propiamente dicho, pasando por la inclusión de periféricos de utilidad, y la creación de un sistema operativo muy básico capaz de ser cargado en la memoria RAM de la FPGA y ejecutado para tener un sistema operativo completamente funcional, que finalmente ejecute una aplicación de control sobre los diferentes periféricos

Study of liquid and vapor phase behavior on Diesel sprays for heavy duty engine nozzles

A lot of effort has been put in the past years into the understanding of the delivery and development of diesel sprays in engine-like conditions as it has been proved to be a very important step for the design of better and cleaner commercial engines. Due to the bigger share of passenger cars engines over heavy duty engines, the research has been mainly focused on the investigation using small nozzles. This paper studies two nozzles with diameters representative of those that can be encountered in heavy duty engines, with the objective of corroborating the conclusions gathered for small nozzles representative of passenger car engines. The experimental data have been acquired by state-of-the-art techniques and equipment, and serves two purposes: further the understanding of the physics involved in the injection event and spray evaporation; and provide a dataset to CFD models that can accurately predict the behavior of the injection event. The tests were performed in a constant pressure flow vessel that allows to simulate engine-like conditions (1000 K and 15 Mpa) with continuous flow. The injection system tested is a novel, common-rail, solenoid-actuated injector for heavy duty applications which operates up to 220 Mpa. All experiments were performed in non-reacting conditions. The extended test matrix allowed to determine the influence of several parameters such as rail pressure, gas temperature, gas density, and nozzle geometry on the air-fuel mixing and evaporation process, by analyzing the spray penetration and spreading angle. Mie scattering and double-pass Schlieren optical configurations have been used to measure global liquid and vapor penetration, respectively. The data proves that spray penetration at low temperature can be up to 15% faster than spray penetration at high temperature conditions at the same density for the nozzles experi-mented, which limits the usability of low temperature experiments to infer the behavior of the injector at high temperature conditions. The data also shows that the nozzle with the biggest diameter provided the highest value of stabilized liquid length as expected. Also, when vapor phase is reached, the temperature has negligible effect on the global diesel spray morphology, and no influence on the tip penetration or on the spreading angle.This work was sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Estudio de la interaction chorro-pared en condiciones realistas de motor (SPRAY WALL)" reference TRA2015-67679-c2-1-R. Daniel Vaquerizo is partially supported through contract FPI-S2-2015-1069 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia.Payri, R.; Gimeno, J.; Bracho Leon, G.; Vaquerizo, D. (2016). Study of liquid and vapor phase behavior on Diesel sprays for heavy duty engine nozzles. Applied Thermal Engineering. 107:365-378. doi:10.1016/j.applthermaleng.2016.06.159S36537810

ECN Spray G External Spray Visualization and Spray Collapse Description through Penetration and Morphology Analysis

[EN] Inside a DISI engine, a wide range of pressure and temperature conditions are possible, and with the current evolution of the systems, many of the conditions are subject to be encountered at the moment of injection. Given the great differences between Diesel injectors and GDi fuel injectors, the effects of such conditions on the development of the fuel injected can cause phenomena like flash boiling and spray collapse that fundamentally change the behavior of sprays. In this work, the Spray G injector developed by Delphi for the Engine Combustion Network (ECN) group has been tested in a High Pressure High Temperature Constant Pressure Flow Rig (HPHT - CPFR) in a wide range of experimental conditions capturing the liquid and vapor phases of the spray by means of DBI and Schlieren imaging. The work presents the results obtained by spray visualization through comparisons of parametric variations with special focus on the collapse of the spray that occurs under high ambient temperature and density conditions. Spray collapse has been described by showing the direct increase that can cause in spray penetration and the great closing effect that can produce to the aperture of the spray (spray angle). Several contour comparisons using the raw images and the detected contours have been discussed in order to support and further explain the observed trends. (C) 2016 Elsevier Ltd. All rights reserved.This work was sponsored by "Ministerio de Economia y Competitividad" in the frame of the project "Estudio de la interaccion chorro-pared en condiciones realistas de motor (SPRAY WALL)" reference TRA2015-67679-C2-1-R. Daniel Vaquerizo is partially supported through contract FPI-S2-2015-1069 of "Programa de Apoyo para la Investigacion y Desarrollo (PAID)" of Universitat Politecnica de Valencia.Payri, R.; Salvador, FJ.; Marti-Aldaravi, P.; Vaquerizo, D. (2017). ECN Spray G External Spray Visualization and Spray Collapse Description through Penetration and Morphology Analysis. Applied Thermal Engineering. 112:304-316. https://doi.org/10.1016/j.applthermaleng.2016.10.023S30431611

Nocturnal Oximetry-based Evaluation of Habitually Snoring Children

Rationale: The vast majority of children around the world undergoing adenotonsillectomy for obstructive sleep apnea–hypopnea syndrome (OSA) are not objectively diagnosed by nocturnal polysomnography because of access availability and cost issues. Automated analysis of nocturnal oximetry (nSpO2), which is readily and globally available, could potentially provide a reliable and convenient diagnostic approach for pediatric OSA. Methods: DeidentifiednSpO2 recordings froma total of 4,191 children originating from13 pediatric sleep laboratories around the worldwere prospectively evaluated after developing and validating an automated neural network algorithm using an initial set of single-channel nSpO2 recordings from 589 patients referred for suspected OSA. Measurements and Main Results: The automatically estimated apnea–hypopnea index (AHI) showed high agreement with AHI from conventional polysomnography (intraclass correlation coefficient, 0.785) when tested in 3,602 additional subjects. Further assessment on the widely used AHI cutoff points of 1, 5, and 10 events/h revealed an incremental diagnostic ability (75.2, 81.7, and 90.2% accuracy; 0.788, 0.854, and 0.913 area under the receiver operating characteristic curve, respectively). Conclusions: Neural network–based automated analyses of nSpO2 recordings provide accurate identification of OSA severity among habitually snoring children with a high pretest probability of OSA. Thus, nocturnal oximetry may enable a simple and effective diagnostic alternative to nocturnal polysomnography, leading to more timely interventions and potentially improved outcomes.Supported in part by project VA037 U16 from the Consejer´ıa de Educacio´ n de la Junta de Castilla y Leo´ n and the European Regional Development Fund (FEDER), project RTC-2015-3446-1 from the Ministerio de Econom´ıa y Competitividad and FEDER, and project 153/2015 of the Sociedad Espan˜ ola de Neumolog´ıa y Cirug´ıa Tora´ cica (SEPAR). L.K.-G. is supported by NIH grant 1R01HL130984. M.F.P. was supported by a Fellowship Educational grant award from the Kingdom of Saudi Arabia. D.´A. was in receipt of a Juan de la Cierva grant from the Ministerio de Econom´ıa y Competitividad. The funders played no role in the study design, data collection, data analysis, interpretation, and writing of the manuscript

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles

[EN] Gasoline direct injection (GDI) nozzles are manufactured to meet geometric specifications with length scales on the order of a few hundred microns. The machining tolerances of these nominal dimensions are not always known due to the difficulty in accurately measuring such small length scales in a nonintrusive fashion. To gain insight into the variability of the machined dimensions as well as any effects that this variability may have on the fuel spray behavior, a series of measurements of the internal geometry and fuel mass distribution were performed on a set of eight nominally duplicate GDI “Spray G” nozzles provided by the Engine Combustion Network. The key dimensions of each of the eight nozzle holes were measured with micron resolution using full spectrum x-ray tomographic imaging at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Fuel density distributions at 2 mm downstream of the nozzle tips were obtained by performing x-ray radiography measurements for many lines of sight. The density measurements reveal nozzle-to-nozzle as well as hole-to-hole density variations. The combination of high-resolution geometry and fuel distribution datasets allows spray phenomena to be linked to specific geometric characteristics of the nozzle, such as variability in the hole lengths and counterbore diameters, and the hole inlet corner radii. This analysis provides important insight into which geometrical characteristics of the nozzles may have the greatest importance in the development of the injected sprays, and to what degree these geometric variations might account for the total spray variability. The goal of this work is then to further the understanding of the relationship between internal nozzle geometry and fuel injection, provide input to improve computational models, and ultimately aid in optimizing injector design for higher fuel efficiency and lower emissions engines.This research was performed at the 7-BM beamline of the APS at Argonne National Laboratory. Use of the APS is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-06CH11357. We gratefully acknowledge the computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. We thank Dr. Doga Gürsoy for the use of TomoPy and corresponding user support, as well as Dr. Xianghui Xiao at the APS 2-BM beamline for technical guidance in performing x-ray tomography. Argonne’s x-ray fuel injection research is sponsored by the DOE Vehicle Technologies Program under the direction of Gurpreet Singh and Leo Breton.Matusik, K.; Duke, D.; Sovis, N.; Swantek, A.; Powell, C.; Payri, R.; Vaquerizo, D.... (2017). A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 313-320. https://doi.org/10.4995/ILASS2017.2017.4766OCS31332

A Convolutional Neural Network Architecture to Enhance Oximetry Ability to Diagnose Pediatric Obstructive Sleep Apnea

Producción CientíficaThis study aims at assessing the usefulness of deep learning to enhance the diagnostic ability of oximetry in the context of automated detection of pediatric obstructive sleep apnea (OSA). A total of 3196 blood oxygen saturation (SpO2) signals from children were used for this purpose. A convolutional neural network (CNN) architecture was trained using 20-min SpO2 segments from the training set (859 subjects) to estimate the number of apneic events. CNN hyperparameters were tuned using Bayesian optimization in the validation set (1402 subjects). This model was applied to three test sets composed of 312, 392, and 231 subjects from three independent databases, in which the apnea-hypopnea index (AHI) estimated for each subject (AHICNN) was obtained by aggregating the output of the CNN for each 20-min SpO2 segment. AHICNN outperformed the 3% oxygen desaturation index (ODI3), a clinical approach, as well as the AHI estimated by a conventional feature-engineering approach based on multi-layer perceptron (AHIMLP). Specifically, AHICNN reached higher four-class Cohen’s kappa in the three test databases than ODI3 (0.515 vs 0.417, 0.422 vs 0.372, and 0.423 vs 0.369) and AHIMLP (0.515 vs 0.377, 0.422 vs 0.381, and 0.423 vs 0.306). In addition, our proposal outperformed state-of-the-art studies, particularly for the AHI severity cutoffs of 5 e/h and 10 e/h. This suggests that the information automatically learned from the SpO2 signal by deep-learning techniques helps to enhance the diagnostic ability of oximetry in the context of pediatric OSA.This work was supported by 'Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación’ and ‘European Regional Development Fund (FEDER)’ under projects DPI2017-84280-R and RTC 2017 6516-1, by “European Commission” and “FEDER” under project 'Análisis y correlación entre la epigenética y la actividad cerebral para evaluar el riesgo de migraña crónica y episódica en mujeres' (‘Cooperation Programme Interreg V-A Spain-Portugal POCTEP 2014–2020’), by Sociedad Española de Neumología y Cirugía Torácica (SEPAR) under project 649/2018, by Sociedad Española de Sueño (SES) under project “Beca de Investigación SES 2019”, and by ‘Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina, (CIBER-BBN), Spain’ through ‘Instituto de Salud Carlos III’ co-funded with FEDER funds. The Childhood Adenotonsillectomy Trial (CHAT) was supported by National Institutes of Health (NIH) grants HL083075, HL083129, UL1-RR-024134, and UL1 RR024989. The National Sleep Research Resource was supported by the National Heart, Lung, and Blood Institute (R24 HL114473, 75N92019R002). F. Vaquerizo-Villar was in receipt of a ‘Ayuda para contratos predoctorales para la Formación de Profesorado Universitario (FPU)’ grant from the Ministerio de Educación, Cultura y Deporte (FPU16/02938). D. Álvarez is supported by a "Ramón y Cajal" grant (RYC2019-028566-I) from the 'Ministerio de Ciencia e Innovación - Agencia Estatal de Investigación’ co-funded by the European Social Fund (ESF). V. Barroso-García and E. Santamaría-Vazquez were in a receipt of a ‘Ayuda para financiar la contratación predoctoral de personal investigador’ grant from the Consejería de Educación de la Junta de Castilla y León and the ESF. L. Kheirandish-Gozal and D. Gozal were supported by NIH grants HL130984, HL140548, and AG061824

Wavelet analysis of overnight airflow to detect obstructive sleep apnea in children

Producción CientíficaThis study focused on the automatic analysis of the airflow signal (AF) to aid in the diagnosis of pediatric obstructive sleep apnea (OSA). Thus, our aims were: (i) to characterize the overnight AF characteristics using discrete wavelet transform (DWT) approach, (ii) to evaluate its diagnostic utility, and (iii) to assess its complementarity with the 3% oxygen desaturation index (ODI3). In order to reach these goals, we analyzed 946 overnight pediatric AF recordings in three stages: (i) DWT-derived feature extraction, (ii) feature selection, and (iii) pattern recognition. AF recordings from OSA patients showed both lower detail coefficients and decreased activity associated with the normal breathing band. Wavelet analysis also revealed that OSA disturbed the frequency and energy distribution of the AF signal, increasing its irregularity. Moreover, the information obtained from the wavelet analysis was complementary to ODI3. In this regard, the combination of both wavelet information and ODI3 achieved high diagnostic accuracy using the common OSA-positive cutoffs: 77.97%, 81.91%, and 90.99% (AdaBoost.M2), and 81.96%, 82.14%, and 90.69% (Bayesian multi-layer perceptron) for 1, 5, and 10 apneic events/hour, respectively. Hence, these findings suggest that DWT properly characterizes OSA-related severity as embedded in nocturnal AF, and could simplify the diagnosis of pediatric OSA.Ministerio de Ciencia, Innovación y Universidades, Agencia Estatal de Investigación y Fondo Europeo de Desarrollo Regional (FEDER) - (Projects DPI2017-84280-R and RTC-2017-6516-1)Comisión Europea y Fondo Europeo de Desarrollo Regional (FEDER) - (POCTEP 0702_MIGRAINEE_2_E)Instituto de Salud Carlos III y Fondo Europeo de Desarrollo Regional (FEDER) - (CIBER-BBN)Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación y Fondo Social Europeo - (grant RYC2019- 028566-I)Ministerio de Educación, Cultura y Deporte - (grant FPU16/02938)Institutes of Health - (grants HL130984, HL140548, and AG061824