CFD analysis of the fuel-air mixture formation process in passive prechambers for use in a high-pressure direct injection (HPDI) Two-stroke engine

The research on two-stroke engines has been focused lately on the development of direct injection systems for reducing the emissions of hydrocarbons by minimizing the fuel shortcircuiting. Low temperature combustion (LTC) may be the next step to further improve emissions and fuel consumption; however, LTC requires unconventional ignition systems. Jet ignition, i.e., the use of prechambers to accelerate the combustion process, turned out to be an effective way to perform LTC. The present work aims at proving the feasibility of adopting passive prechambers in a high-pressure, direct injection, two-stroke engine through non-reactive computational fluid dynamics analyses. The goal of the analysis is the evaluation of the prechamber performance in terms of both scavenging efficiency of burnt gases and fuel/air mixture formation inside the prechamber volume itself, in order to guarantee the mixture ignitability. Two prechamber geometries, featuring different aspect ratios and orifice numbers, were investigated. The analyses were replicated for two different locations of the injection and for three operating conditions of the engine in terms of revolution speed and load. Upon examination of the results, the effectiveness of both prechambers was found to be strongly dependent on the injection setup

La salute “intelligente”: eHealth, consenso informato e principio di non-discriminazione

L’intelligenza artificiale medica, branca avanguardistica della sanità digitale, promette di diventare, nel prossimo futuro, un valido sostegno per il professionista sanitario, ma pone (almeno) un duplice ordine di problemi di natura costituzionale, strettamente connessi: da un lato, spinge a interrogarsi sulla configurabilità di un obbligo in capo al medico di informare il paziente dell’uso di tali tecnologie nel processo diagnostico e terapeutico, quale espressione del principio del consenso informato, anche alla luce dei diversi rischi di bias che interessano la macchina; dall’altro, impone una riflessione sull’impatto proprio di questi bias sul godimento del diritto alla salute. Sommario: 1. Introduzione. L’impatto dell’eHealth sul diritto costituzionale alla salute: la prospettiva di analisi. – 2. Le radici costituzionali del consenso informato come proiezione dell’autodeterminazione terapeutica. – 3. L’intelligenza artificiale a supporto della diagnosi: quale impatto sul consenso informato? – 3.1. Il contenuto dell’obbligo informativo in capo al medico in contesti clinici tradizionali. – 3.2. Sull’esistenza di un obbligo di informare il paziente dell’utilizzo di intelligenza artificiale per la diagnosi e la proposta di terapia. – 4. Applicazioni medico-sanitarie dell’intelligenza artificiale e (rischi di) discriminazione. – 5. (Segue.) Oltre la “neutralità” degli strumenti digitali.“Intelligent” health: eHealth, informed consent and principle of non-discrimination. Medical AI, one of the emerging areas encompassed by eHealth, promises to offer valuable support to healthcare professionals in the near future, but it poses (at least) two sets of closely related constitutional problems: on the one hand, the issue of informed consent must be addressed, determining whether a legal obligation exists to disclose AI/ML usage for diagnostic or therapeutic purposes, especially in light of the very real risks of algorithmic bias; on the other hand, further reflection on the potential impact of precisely these biases on (the enjoyment of) the right to health is certainly required

Low-speed preconditioning for strongly coupled integration of Reynolds-averaged Navier–Stokes equations and two-equation turbulence models

Computational fluid dynamics codes using the density-based compressible flow formulation of the Navier–Stokes equations have proven to be very successful for the analysis of high-speed flows. However, solution accuracy degradation and, for explicit solvers, reduction of the residual convergence rates occur as the local Mach number decreases below the threshold of 0.1. This performance impairment worsens remarkably in the presence of flow reversals at wall boundaries and unbounded high-vorticity flow regions. These issues can be resolved using low-speed preconditioning, but there exists an outstanding problem regarding the use of this technology in the strongly coupled integration of the Reynolds-averaged Navier–Stokes equations and two-equation turbulence models, such as the k − ω shear stress transport model. It is not possible to precondition only the RANS equations without altering parts of the governing equations, and there did not exist an approach for preconditioning both the RANS and the SST equations. This study solves this problem by introducing a turbulent low-speed preconditioner of the RANS and SST equations that does not require any alteration of the governing equations. The approach has recently been shown to significantly improve convergence rates in the case of a one-equation turbulence model. The study focuses on the explicit multigrid integration of the governing equations, but most algorithms are applicable also to implicit integration methods. The paper provides all algorithms required for implementing the presented turbulent preconditioner in other computational fluid dynamics codes. The new method is applicable to all low- and mixed-speed aeronautical and propulsion flow problems, and is demonstrated by analyzing the flow field of a Darrieus wind turbine rotor section at two operating conditions, one of which is characterized by significant blade/vortex interaction. Verification and further validation of the new method is also based on the comparison of the results obtained with the developed density-based code and those obtained with a commercial pressure-based code

Precision-based exercise as a new therapeutic option for children and adolescents with haematological malignancies

Children and adolescents with haematological malignancies (pedHM) are characterized by a severe loss of exercise ability during cancer treatment, lasting throughout their lives once healed and impacting their social inclusion prospects. The investigation of the effect of a precision-based exercise program on the connections between systems of the body in pedHM patients is the new frontier in clinical exercise physiology. This study is aimed at evaluating the effects of 11 weeks (3 times weekly) of combined training (cardiorespiratory, resistance, balance and flexibility) on the exercise intolerance in PedHM patients. Two-hundred twenty-six PedHM patients were recruited (47% F). High or medium frequency participation (HAd and MAd) was considered when a participant joined; > 65% or between 30% and < 64% of training sessions, respectively. The \u201cup and down stairs\u2019\u2019 test (TUDS), \u201c6 min walking\u201d test (6MWT), the \u201c5 Repetition Maximum strength\u201d leg extension and arm lateral raise test (5RM-LE and 5RM-ALR), flexibility (stand and reach), and balance (stabilometry), were performed and evaluated before and after training. The TUDS, the 5RM-LE and 5RM-ALR, and the flexibility exercises showed an increase in HAd and MAd groups (P < 0.05), while the 6MWT and balance tests showed improvement only in HAd group (P < 0.0001). these results support the ever\u2010growing theory that, in the case of the treatment of PedHM, \u2018exercise is medicine\u2019 and it has the potential to increase the patient\u2019s chances of social inclusion

A Geological Itinerary Through the Southern Apennine Thrust-Belt (Basilicata—Southern Italy)

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