Graph Variogram: A novel tool to measure spatial stationarity

Irregularly sampling a spatially stationary random field does not yield a graph stationary signal in general. Based on this observation, we build a definition of graph stationarity based on intrinsic stationarity, a less restrictive definition of classical stationarity. We introduce the concept of graph variogram, a novel tool for measuring spatial intrinsic stationarity at local and global scales for irregularly sampled signals by selecting subgraphs of local neighborhoods. Graph variograms are extensions of variograms used for signals defined on continuous Euclidean space. Our experiments with intrinsically stationary signals sampled on a graph, demonstrate that graph variograms yield estimates with small bias of true theoretical models, while being robust to sampling variation of the space.Comment: Submitted to IEEE Global Conference on Signal and Information Processing 2018 (IEEE GlobalSIP 2018), Nov 2018, Anaheim, CA, United States. (https://2018.ieeeglobalsip.org/

Design, Optimization, and Analysis of Supersonic Radial Turbines

[EN] New compact engine architectures such as pressure gain combustion require ad hoc turbomachinery to ensure an adequate range of operation with high performance. A critical factor for supersonic turbines is to ensure the starting of the flow passages, which limits the flow turning and airfoil thickness. Radial outflow turbines inherently increase the cross section along the flow path, which holds great potential for high turning of supersonic flow with a low stage number and guarantees a compact design. First, the preliminary design space is described. Afterward a differential evolution multi-objective optimization with 12 geometrical design parameters is deducted. With the design tool autoblade 10.1, 768 geometries were generated and hub, shroud, and blade camber line were designed by means of Bezier curves. Outlet radius, passage height, and axial location of the outlet were design variables as well. Structured meshes with around 3.7 x 10(6) cells per passage were generated. Steady three-dimensional (3D) Reynolds-averaged Navier-Stokes (RANS) simulations, enclosed by the k-omega shear stress transport turbulence model were solved by the commercial solver CFD++. The geometry was optimized toward low entropy and high-power output. To prove the functionality of the new turbine concept and optimization, a full wheel unsteady RANS simulation of the optimized geometry exposed to a nozzled rotating detonation combustor (RDC) has been performed and the advantageous flow patterns of the optimization were also observed during transient operation.National Energy Technology Laboratory (Faculty Research Participation Program) (Funder ID: 10.13039/100013165). Spanish Ministry of Economy and Competitiveness (Grant No. TRA2016-7918-R). Universitat Politecnica de Valencia (Travel Grant). U.S. Department of Energy (Part-Time Faculty Appointment, Funder ID: 10.13039/100000015)Inhestern, LB.; Braun, J.; Paniagua, G.; Serrano, J. (2020). Design, Optimization, and Analysis of Supersonic Radial Turbines. Journal of Engineering for Gas Turbines and Power. 142(3):1-12. https://doi.org/10.1115/1.4044972S1121423Sousa, J., Braun, J., & Paniagua, G. (2017). Development of a fast evaluation tool for rotating detonation combustors. Applied Mathematical Modelling, 52, 42-52. doi:10.1016/j.apm.2017.07.019Heiser, W. H., & Pratt, D. T. (2002). Thermodynamic Cycle Analysis of Pulse Detonation Engines. Journal of Propulsion and Power, 18(1), 68-76. doi:10.2514/2.5899Braun, J., Saracoglu, B. H., & Paniagua, G. (2017). Unsteady Performance of Rotating Detonation Engines with Different Exhaust Nozzles. Journal of Propulsion and Power, 33(1), 121-130. doi:10.2514/1.b36164Nakagami, S., Matsuoka, K., Kasahara, J., Kumazawa, Y., Fujii, J., Matsuo, A., & Funaki, I. (2017). Experimental Visualization of the Structure of Rotating Detonation Waves in a Disk-Shaped Combustor. Journal of Propulsion and Power, 33(1), 80-88. doi:10.2514/1.b36084Zhou, R., & Wang, J.-P. (2013). Numerical investigation of shock wave reflections near the head ends of rotating detonation engines. Shock Waves, 23(5), 461-472. doi:10.1007/s00193-013-0440-0Fievisohn, R. T., & Yu, K. H. (2017). Steady-State Analysis of Rotating Detonation Engine Flowfields with the Method of Characteristics. Journal of Propulsion and Power, 33(1), 89-99. doi:10.2514/1.b36103Paniagua, G., Iorio, M. C., Vinha, N., & Sousa, J. (2014). Design and analysis of pioneering high supersonic axial turbines. International Journal of Mechanical Sciences, 89, 65-77. doi:10.1016/j.ijmecsci.2014.08.014Sousa, J., Paniagua, G., & Collado Morata, E. (2017). Thermodynamic analysis of a gas turbine engine with a rotating detonation combustor. Applied Energy, 195, 247-256. doi:10.1016/j.apenergy.2017.03.045Liu, Z., Braun, J., & Paniagua, G. (2018). Characterization of a Supersonic Turbine Downstream of a Rotating Detonation Combustor. Journal of Engineering for Gas Turbines and Power, 141(3). doi:10.1115/1.4040815Paniagua, G., Yasa, T., de la Loma, A., Castillon, L., & Coton, T. (2008). Unsteady Strong Shock Interactions in a Transonic Turbine: Experimental and Numerical Analysis. Journal of Propulsion and Power, 24(4), 722-731. doi:10.2514/1.34774Verstraete, T., Alsalihi, Z., & Van den Braembussche, R. A. (2010). Multidisciplinary Optimization of a Radial Compressor for Microgas Turbine Applications. Journal of Turbomachinery, 132(3). doi:10.1115/1.3144162Braun, J., Sousa, J., & Pekardan, C. (2017). Aerodynamic Design and Analysis of the Hyperloop. AIAA Journal, 55(12), 4053-4060. doi:10.2514/1.j055634Anand, V., & Gutmark, E. (2018). Rotating Detonation Combustor Research at the University of Cincinnati. Flow, Turbulence and Combustion, 101(3), 869-893. doi:10.1007/s10494-018-9934-

A License-Based Search Engine

International audienceThe reuse of licensed resources to produce new ones is very common and encouraged on the Web. But producing resources whose licenses are compliant with all reused resource licenses is not easy. It is necessary to know (1) the set of licenses with which the license of the produced resource is compliant and (2) what are the available resources whose licenses are part of this set. With CaLi, we provide an answer to the first concern. CaLi is a lattice-based model that partially orders licenses in terms of compatibility and compliance. In this demonstration, we illustrate the usability of CaLi through a prototype for the second concern. That is, based on a CaLi ordering of licenses we implement a license-based search engine which can answer questions such as "find licensed resources that can be reused under a given license" or "find licensed resources that can reuse a resource that has a particular license"

Laser fetoscopy ablation for twin–twin transfusion syndrome may reduce the risk of ROP

Profesor contratado doctor con plaza vinculada al Hospital Universitario San Cecilio de Granada Grupo de Investigación RICORS Enfermedades Inflamatorias; RD21/0002/0011,Purpose: Twin–twin transfusion syndrome (TTTS) is a condition wherein monochorionic twins share a common placenta with placental anastomoses between the two foetal circulations. Most infants who survive TTTS are born prematurely. This study aimed to determine whether fetoscopic laser ablation (FLA) can reduce the risk of retinopathy of prematurity (ROP) and whether TTTS was a risk factor for ROP. Methods: This single-centre, retrospective, comparative study included 32 monochorionic twins with TTTS matched for gestational age, birthweight and sex to premature twins and singletons without TTTS (n = 68; twins, n = 34; and singletons, n = 34) born between 2003 and 2022. A single ophthalmologist recorded the fundus findings. FLA was performed using Solomon's technique to separate the vascular systems of the twins with TTTS. Results: The gestational age and weight of premature infants with TTTS treated with FLA were significantly higher than those of untreated infants (p = 0.001 and p = 0.001, respectively); however, the hyaline membrane grade was lower (p = 0.004). A significant increase in weight (g/day) (p = 0.002) and lesser avascular area in the peripheral temporal retina (p = 0.045) was observed at postnatal week 4. The risk of ROP in the FLA group was 2.6 times (13.3% vs. 35.3%) lower than that in the non-FLA group; however, this difference was not significant. The incidence of any stage of ROP (25% vs. 18%) and treatment for ROP type 1 (6.25% vs. 5.9%) did not differ significantly between monochorionic twins with TTTS and premature infants without TTTS. Conclusion: The gestational age of premature infants with TTTS treated with FLA was higher than that of untreated infants. Moreover, a reduction in complications of prematurity was also observed. Laser fetoscopy in twin–twin transfusion syndrome may reduce the risk of ROP, but the difference was not statistically significant in this small study.Universidad de Granada aporta fondos para publicación del artículo en acceso abierto (Funding for open access charge): Universidad de Granada /CBUA. Acuerdo Universidad de Granada con Wiley 2023

Gestión de cuentas por cobrar de la Empresa Distribuidora Ferretera Sullón SAC. Chepén, 2021

La presente investigación tiene como objetivo principal: “Determinar el impacto que tiene la gestión de cuentas por cobrar en la empresa distribuidora ferretera Sullón SAC. Chepén, 2021”. La población motivo de estudio comprende los estados financieros de los años 2020 y 2021, cuya muestra fue, el estado financiero correspondiente al año 2021. En el presente trabajo utilizaremos dos técnicas con sus respectivos instrumentos, la primera técnica a utilizar es la entrevista, la misma que se, efectuará al jefe del departamento de ventas, quién está encargado del proceso total de una venta; para ello se dispondrá de una guía de entrevista como instrumento, para que la recolección de la información sea de forma ordenada, a fin de tener claridad en la obtención de datos. La segunda técnica que se aplicará, es él análisis documental, llámese, estados financieros y reportes de ventas al crédito; donde se utilizará como instrumento una guía documental. Según los resultados de la investigación se concluye que la Gestión de cuentas por cobrar, se está ejecutando incorrectamente, acompañado de políticas de ventas inadecuadas que hacen difícil su recuperación.Trabajo de investigaciónGestión empresarial y emprendimient

Contribution to Tip Leakage Loss Modeling in Radial Turbines Based on 3D Flow Analysis and 1D Characterization

[EN] The characterization of tip leakage flow plays an important role for one-dimesional loss modeling and design in radial turbine research. Tip leakage losses can be expressed as function of fluid momentum and mass flow passing through the tip gap. Friction-driven flow and contrariwise oriented pressure gradient-driven flow are highly coupled. However, these numbers are mostly unknown and dependent on tip gap geometry and turbine running condition. Based on a commonly used definition of a non-dimensional tip leakage momentum ratio, a novel correlation has been derived. This allows a consistent characterization for variable tip gap sizes over a wide range of operating conditions. The correlation has been validated by means of CFD data with high variety in reduced speed tip gap geometry and expansion ratios. Results of the novel number show significant improvements of quantitative and qualitative results over a wide range of running conditions in comparison to existing correlations. Furthermore, correlations for tip leakage velocities, that can easily be used in one-dimensional models, have been derived. Finally, it has been demonstrated, that the influence of inlet flow momentum on the tip leakage flow can be analyzed with presented correlations.The work has been partially supported by FEDER and the Spanish Ministry of Economy and Competitiveness through grant number TRA2016-79185-R. The authors would also like to acknowledge the Research and Development Aid Program PAID-01-16 of the Universitat Politecnica de Valencia, Spain.Serrano, J.; Navarro, R.; García-Cuevas González, LM.; Inhestern, LB. (2019). Contribution to Tip Leakage Loss Modeling in Radial Turbines Based on 3D Flow Analysis and 1D Characterization. International Journal of Heat and Fluid Flow. 78. https://doi.org/10.1016/j.ijheatfluidflow.2019.108423S7

Turbocharger turbine rotor tip leakage loss and mass flow model valid up to extreme off-design conditions with high blade to jet speed ratio

[EN] Due to the power consumption restriction of the turbocharger compressor, common turbine maps are rather narrow. To extrapolate them, reliable physical submodels are needed that are valid for broad ranges. Plenty of research has been done referring to tip leakage losses in axial and traditional radial turbomachinery. However, less effort has been put into the tip leakage analysis of radial turbocharger turbines, whose characteristics including high rotational speed and geometry are rather different. Commonly developed tip leakage loss models in radial turbines are mainly based on correlations with the rotational speed, while in axial turbomachinery they are mainly based on blade loading assumptions. Wide range computational fluid dynamics (CFD) data of a medium sized automotive turbine have been used to analyze tip leakage mass flow under extremely diverse running conditions. To be able to fit a model in a broad range of the map, blade loading and rotational speed have to be considered. A novel tip clearance model has been derived from the Navier Stokes Equations. The model owns a dependency on the rotational speed and the blade loading. With this approach CFD data have been fitted in a very good quality to model the tip leakage mass flow rate and tip leakage losses.The work has been partially supported by FEDER and the Spanish Ministry of Economy and Competitiveness through grant number TRA2016-79185-R.Serrano, J.; Navarro, R.; García-Cuevas González, LM.; Inhestern, LB. (2018). Turbocharger turbine rotor tip leakage loss and mass flow model valid up to extreme off-design conditions with high blade to jet speed ratio. Energy. 147:1299-1310. https://doi.org/10.1016/j.energy.2018.01.083S1299131014

Speech and Speaker Recognition for Home Automation: Preliminary Results

International audienceIn voice controlled multi-room smart homes ASR and speaker identification systems face distance speech conditionswhich have a significant impact on performance. Regarding voice command recognition, this paper presents an approach whichselects dynamically the best channel and adapts models to the environmental conditions. The method has been tested on datarecorded with 11 elderly and visually impaired participants in a real smart home. The voice command recognition error ratewas 3.2% in off-line condition and of 13.2% in online condition. For speaker identification, the performances were below veryspeaker dependant. However, we show a high correlation between performance and training size. The main difficulty was the tooshort utterance duration in comparison to state of the art studies. Moreover, speaker identification performance depends on the sizeof the adapting corpus and then users must record enough data before using the system