Infecciones más comunes en el paciente trasplantado

Organ transplantation has become one of the most important areas of medical research and, at present, is still the only therapeutical tool for several diseases. However, there are a number of factors related to transplantation, like immunosuppression and prolonged neutropenia that affect the incidence of infection. These infections are somehow peculiar to trasplant recipients. In fact, there are infectious diseases that only occur in immunodepression situations and, moreover, clinical expression of these infectious diseases can be quite different from that in immunocompetent patients. Besides these aspects, some infections, due to the high prevalence described, must be considered for prevention strategies because they continue to be a principal cause of morbidity and mortality, either due to direct effects or to their implication in the pathogenesis of rejection. These strategies commence before trasplantation by active immunization through vaccine administration to the patient and to people in the milieu and continue after trasplantation with prophylaxis or pre-emptive therapy. The importance of infectious diseases in the evolution and prognosis of trasplant recipients gives a special meaning to the understanding of associated infections, their clinical expression and ways of prevention and treatment

Twin-entry turbine losses: An analysis using CFD data

This is the author's version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/14680874211007647[EN] The current paper presents a computational fluid dynamics (CFD) flow behaviour and losses analysis of twin-entry radial turbines in terms of its Mass Flow Ratio (MFR, the ratio between the flow passing through one of its intake ports and its total mass flow), focusing on the mixing phenomena in the unequal admission conditions cases. The CFD simulations are first validated with experimental data. Then, the losses mechanisms are analysed and quantified in the different parts of the twin-entry turbine in terms of the MFR value. A sudden expansion is found at the junction of both branches in the interspace between volutes and rotor for unequal and partial admission cases. Tracking the flow coming from each of the turbine intake ports, it has been observed that both flow branches do not fully mix with each other within the rotor. Another source of losses has been identified in the contact between both flow branches due to their momentum exchange that depends on the difference between both flow branches velocities. These losses have not been considered before, and they should be included in mean line loss-based models for twin-entry turbine since they are very significant for unequal admission conditions.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Nicolas Medina is partially supported through contract FPU17/02803 of Programa de Formacion de Profesorado Universitario of Spanish Ministerio de Ciencia, Innovacion y Universidades. This work has been partially supported by the 'Ayuda a Primeros Proyectos de Investigacion' (PAID-06-18), Vicerrectorado de Investigacion, Innovacion y Transferencia de la Universitat Politecnica de Valencia (UPV), Valencia, Spain.Galindo, J.; Serrano, J.; García-Cuevas González, LM.; Medina, N. (2022). Twin-entry turbine losses: An analysis using CFD data. International Journal of Engine Research. 23(7):1180-1200. https://doi.org/10.1177/146808742110076471180120023

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

A Robust Adiabatic Model for a Quasi-Steady Prediction of Far-Off Non-Measured Performance in Vaneless Twin-Entry or Dual-Volute Radial Turbines

[EN] The current investigation describes in detail a mass flow oriented model for extrapolation of reduced mass flow and adiabatic efficiency of double entry radial inflow turbines under any unequal and partial flow admission conditions. The model is based on a novel approach, which proposes assimilating double entry turbines to two variable geometry turbines (VGTs) using the mass flow ratio ( MFR ) between the two entries as the discriminating parameter. With such an innovative approach, the model can extrapolate performance parameters to non-measured MFR s, blade-to-jet speed ratios, and reduced speeds. Therefore, the model can be used in a quasi-steady method for predicting double entry turbines performance instantaneously. The model was validated against a dataset from two different double entry turbine types: a twin-entry symmetrical turbine and a dual-volute asymmetrical turbine. Both were tested under steady flow conditions. The proposed model showed accurate results and a coherent set of fitting parameters with physical meaning, as discussed in this paper. The obtained parameters showed very similar figures for the aforementioned turbine types, which allows concluding that they are an adequate set of values for initializing the fitting procedure of any type of double entry radial turbine.Vishnu Samala is partially supported through contract FPI-2017-S2-1256 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia. This work was partially funded by the 'Ayuda a Primeros Proyectos de Investigacion' (PAID-06-18), Vicerrectorado de Investigacion, Innovacion y Transferencia de la Universitat Politecnica de Valencia (UPV), Valencia, Spain.Serrano, J.; Arnau Martínez, FJ.; García-Cuevas González, LM.; Samala, V. (2020). A Robust Adiabatic Model for a Quasi-Steady Prediction of Far-Off Non-Measured Performance in Vaneless Twin-Entry or Dual-Volute Radial Turbines. 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Energy Conversion and Management, 81, 270-281. doi:10.1016/j.enconman.2014.01.043Serrano, J. R., Arnau, F. J., Dolz, V., Tiseira, A., & Cervelló, C. (2008). A model of turbocharger radial turbines appropriate to be used in zero- and one-dimensional gas dynamics codes for internal combustion engines modelling. Energy Conversion and Management, 49(12), 3729-3745. doi:10.1016/j.enconman.2008.06.031Serrano, J. R., Arnau, F. J., García-Cuevas, L. M., Dombrovsky, A., & Tartoussi, H. (2016). Development and validation of a radial turbine efficiency and mass flow model at design and off-design conditions. Energy Conversion and Management, 128, 281-293. doi:10.1016/j.enconman.2016.09.032Serrano, J. R., Arnau, F. J., García-Cuevas, L. M., & Inhestern, L. B. (2019). An innovative losses model for efficiency map fitting of vaneless and variable vaned radial turbines extrapolating towards extreme off-design conditions. Energy, 180, 626-639. doi:10.1016/j.energy.2019.05.062Chiong, M. 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Computational Study of the Propeller Position Effects in Wing-Mounted, Distributed Electric Propulsion with Boundary Layer Ingestion in a 25 kg Remotely Piloted Aircraft

[EN] Distributed electric propulsion and boundary layer ingestion are two attractive technologies to reduce the power consumption of fixed wing aircraft. Through careful distribution of the propulsive system elements, higher aerodynamic and propulsive efficiency can be achieved, as well as a lower risk of total loss of aircraft due to foreign object damage. When used on the wing, further reductions of the bending moment on the wing root can even lead to reductions of its structural weight, thus mitigating the expected increase of operating empty weight due to the extra components needed. While coupling these technologies in fixed-wing aircraft is being actively studied in the big aircraft segment, it is also an interesting approach for increasing the efficiency even for aircraft with maximum take-off masses as low as 25 kg, such as the A3 open subcategory for civil drones from EASA. This paper studies the effect of changing the propellers' position in the aerodynamic performance parameters of a distributed electric propulsion with boundary layer ingestion system in a 25 kg fixed-wing aircraft, as well as in the performance of the propellers. The computational results show the trade-offs between the aerodynamic efficiency and the propeller efficiency when the vertical position is varied.This research was funded by the Agencia Estatal de Investigacion of Spain through grant number PID2020-119468RA-I00/AEI/10.13039/501100011033.Serrano, J.; Tiseira, A.; García-Cuevas González, LM.; Varela-Martínez, P. (2021). Computational Study of the Propeller Position Effects in Wing-Mounted, Distributed Electric Propulsion with Boundary Layer Ingestion in a 25 kg Remotely Piloted Aircraft. Drones. 5(3):1-18. https://doi.org/10.3390/drones5030056S1185

Thermo-economic analysis of an oxygen production plant powered by an innovative energy recovery system

[EN] Oxy-fuel combustion is considered an attractive alternative to reduce pollutant emissions, which uses high-purity oxygen mixed instead of air for combustion processes. However, purchasing large amounts of high-purity oxygen may be unprofitable for certain industrial sectors, discouraging its implementation. Considering this, the potential of an oxygen production cycle for factories using oxy-fuel combustion is studied by performing a thermo-economic analysis where high-purity oxygen, electricity, and natural gas prices are considered. Oxygen is produced by membrane means, where mixed ionic-electronic conducting membranes are used, which require high temperatures and pressure gradients to work properly. A set of turbochargers is implemented, chosen by scaling an off-the-shelf model, what introduces an innovative way of waste energy recovering for improving the performance of the cycle. The whole cycle is powered by waste heat from high temperature flue gases, and it is sized for a ceramic manufacturing factory. In this work, two cases are analysed, differentiated by considering additional heating and the vacuum generation method in the oxygen line. The first case exhibits smaller production levels, although better profitability (31¿€t¿1), whereas the second case displays higher production levels and production costs (33¿€t¿1). Both cases are competitive concerning the average price of high-purity oxygen, supposing an average of 50¿€t¿1 in wholesale markets, proving the potential of the proposed alternative for oxygen production.This research work has been supported by Grant PDC2021120821-I00 funded by MCIN/AEI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. This work has also been supported by Grant UPV-SOLGEN-79674 funded by the Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia (PAID-11-21). The authors want to acknowledge the institution "Conselleria d'Educacio, Investigaci o, Cultura i Esport de la Generalitat Valenciana" and its grant program "Subvenciones para la contratacion de personal investigador de caracter predoctoral" for doctoral studies (ACIF/2020/246) funded by The European Union. Also, this work is part of grant number INNVA1/2021/38 funded by "Agencia Valenciana de la Innovacion (AVI)" and by "ERDF A way of making Europe".Serrano, J.; Arnau Martínez, FJ.; García-Cuevas González, LM.; Gutierrez, FA. (2022). Thermo-economic analysis of an oxygen production plant powered by an innovative energy recovery system. Energy. 255:1-18. https://doi.org/10.1016/j.energy.2022.12441911825

Relaxation and Landau-Zener experiments down to 100 mK in ferritin

Temperature-independent magnetic viscosity in ferritin has been observed from 2 K down to 100 mK, proving that quantum tunneling plays the main role in these particles at low temperature. Magnetic relaxation has also been studied using the Landau-Zener method making the system crossing zero resonant field at different rates, alpha=dH/dt, ranging from 10^{-5} to 10^{-3} T/s, and at different temperatures, from 150 mK up to the blocking temperature. We propose a new Tln(Delta H_{eff}/tau_0 alpha) scaling law for the Landau-Zener probability in a system distributed in volumes, where Delta H_{eff} is the effective width of the zero field resonance.Comment: 13 pages, 4 postscript figure

Radial turbine performance measurement under extreme off-design Conditions

[EN] During automotive urban driving conditions and future homologation cycles, automotive radial turbines experience transient conditions, whereby the same operate at very high blade speed ratios and, thus, at very low power outputs. Under those conditions, the turbine power output might not be enough to feed the mechanical power needs of the compressor. Typical fast one-dimensional full engine simulations rely on steady-state performance maps to characterize the turbocharger. Due to the restricting compressor braking power, extreme off-design measurements cannot be obtained in standard gas stands without using an external brake instead of the compressor or without using a motor attached to the turbocharger shaft. Such turbocharger assemblies cause shaft balancing issues inherent to the connection to a brake operating at high rotational speeds or need basic changes of the turbocharger geometry. This paper presents a novel approach for turbine performance map measurements at very low expansion ratio and very low mass flow without the aforementioned issues. The method uses the turbocharger compressor as a centrifugal turbine, providing mechanical power to the shaft and enabling turbine performance measurements from points of very high expansion ratio up to very low pressure ratio. It is even possible to measure at almost zero flow rate in the turbine when it consumes shaft power instead of producing it. This experimental procedure that can be applied to whatever turbocharger produces valuable information for the development and validation of turbine performance models aiming to extrapolate its behaviour at off-design conditions.The authors of this paper wish to thank M.A. Ortiz for his invaluable help during the experimental setup. The work has been partially supported by the Spanish Ministry of Economy and Competitiveness through grant number TRA2013-40853-R.Serrano, J.; Tiseira, AO.; García-Cuevas González, LM.; Inhestern, LB.; Tartoussi, H. (2017). Radial turbine performance measurement under extreme off-design Conditions. Energy. 125:72-84. https://doi.org/10.1016/j.energy.2017.02.118S728412

Experimental approach for the characterization and performance analysis of twin entry radial-inflow turbines in a gas stand and with different flow admission conditions

[EN] In an internal combustion engine, twin entry turbine operates under different unequal admission conditions by feeding the turbine with a dissimilar amount of flow in each entry for a majority of the time. Despite of the impact on turbine performance, normal characteristic maps of these turbines are usually available only for full admission conditions. The current study investigates the best way of building characteristic maps of twin entry radial inflow turbines working under different admission conditions. The mass flow conditions are varied independently for each entry and results are examined to characterize the turbine performance parameters. The new methodology provides a practical approach regarding the reduced turbine speed; mass flow ratio; pressure ratios and efficiencies of a twin entry turbine. The most important conclusion of this work is the protocol of data analysis itself, which allows systematizing the testing procedure of this type of turbines with different steady flow admission and in quasi-adiabatic conditions. By sorting the experimental data in an orderly manner through proposed analysis, the readers can get benefit of this procedure to calibrate their own quasi-steady models for both: mass flow rate and efficiency; or to build new quasi-steady models with clear merit functions for fitting.Vishnu Samala is partially supported through contract FPI-2017-S2-1256 of Programa de Apoyo para la Investigacion y Desarrollo (PAID) of Universitat Politecnica de Valencia. This work was partially funded by FEDER and Government of Spain through Project TRA2016-79185-R. The authors wish to thank M.A. Ortiz and R. Carrascosa for their invaluable work during the experimental setup and campaign.Serrano, J.; Arnau Martínez, FJ.; García-Cuevas González, LM.; Samala, V.; Smith, L. (2019). Experimental approach for the characterization and performance analysis of twin entry radial-inflow turbines in a gas stand and with different flow admission conditions. Applied Thermal Engineering. 159:1-14. https://doi.org/10.1016/j.applthermaleng.2019.113737S11415