POMPE DI VUOTO PER IMPIANTI DI DEGASAGGIO D‘ACCIAIO

Da molti anni negli impianti di degasaggio degli acciai in vuoto sono impiegate due tipi di pompe, gli eiettori di vapore e le pompe meccaniche secche del tipo ROOTS. Gli eiettori di vapore sono trasportatori di gas ricco di polvere. Purtroppo l’esperienza industriale ha dimostrato che il trasporto di gas non filtrato produce dei depositi che diminuiscono la capacità aspirativa, obbliga a frequenti interventi di pulizia e allo smaltimento del residuo come rifiuto speciale pericoloso. La capacità aspirativa normalmente riscontrata più alta negli impianti ad eiettori di vapore, rispetto ad altre soluzioni poi di seguito illustrate, è dovuta al sovradimensionamento dell’impianto necessario a compensare la quantità di polvere contenuta nei gas e l’ostruzione dovuta ai depositi da essa generati. Le pompe meccaniche sono invece trasportatrici di volume di gas preventivamente filtrato e non sono influenzate dalle condizioni climatiche e dalla densità del gas, purché questo sia esente da polvere e sia sufficientemente freddo. A tal fine sono previsti dei sistemi molto efficienti d’abbattimento della polvere, come i cicloni, i filtri a maniche e gli scambiatori di calore. Le pompe meccaniche richiedono poco spazio e offrono la disponibilità istantanea del vuoto. Grazie alla filtrazione preventiva delle polveri contenute nei gas, esse mantengono le loro caratteristiche costanti nel tempo e hanno un costo operativo molto più basso rispetto agli altri sistemi di degasaggio. La potenza elettrica installata, i consumi d’energia e dei fluidi sono inferiori rispetto a quanto richiesto dalla tecnologia degli eiettori di vapore, come pure la manutenzione richiesta

Dynamical system analysis and forecasting of deformation produced by an earthquake fault

We present a method of constructing low-dimensional nonlinear models describing the main dynamical features of a discrete 2D cellular fault zone, with many degrees of freedom, embedded in a 3D elastic solid. A given fault system is characterized by a set of parameters that describe the dynamics, rheology, property disorder, and fault geometry. Depending on the location in the system parameter space we show that the coarse dynamics of the fault can be confined to an attractor whose dimension is significantly smaller than the space in which the dynamics takes place. Our strategy of system reduction is to search for a few coherent structures that dominate the dynamics and to capture the interaction between these coherent structures. The identification of the basic interacting structures is obtained by applying the Proper Orthogonal Decomposition (POD) to the surface deformations fields that accompany strike-slip faulting accumulated over equal time intervals. We use a feed-forward artificial neural network (ANN) architecture for the identification of the system dynamics projected onto the subspace (model space) spanned by the most energetic coherent structures. The ANN is trained using a standard back-propagation algorithm to predict (map) the values of the observed model state at a future time given the observed model state at the present time. This ANN provides an approximate, large scale, dynamical model for the fault.Comment: 30 pages, 12 figure

Numerical Simulation of a Passive Control of the Flow Around an Aerofoil Using a Flexible, Self Adaptive Flaplet

© 2018 The Author(s) Self-activated feathers are used by almost all birds to adapt their wing characteristics to delay stall or to moderate its adverse effects (e.g., during landing or sudden increase in angle of attack due to gusts). Some of the feathers are believed to pop up as a consequence of flow separation and to interact with the flow and produce beneficial modifications of the unsteady vorticity field. The use of self adaptive flaplets in aircrafts, inspired by birds feathers, requires the understanding of the physical mechanisms leading to the mentioned aerodynamic benefits and the determination of the characteristics of optimal flaps including their size, positioning and ideal fabrication material. In this framework, this numerical study is divided in two parts. Firstly, in a simplified scenario, we determine the main characteristics that render a flap mounted on an aerofoil at high angle of attack able to deliver increased lift and improved aerodynamic efficiency, by varying its length, position and its natural frequency. Later on, a detailed direct numerical simulation analysis is used to understand the origin of the aerodynamic benefits introduced by the flaplet movement induced by the interaction with the flow field. The parametric study that has been carried out, reveals that an optimal flap can deliver a mean lift increase of about 20% on a NACA0020 aerofoil at an incidence of 20 o degrees. The results obtained from the direct numerical simulation of the flow field around the aerofoil equipped with the optimal flap at a chord Reynolds number of 2 × 10 4 shows that the flaplet movement is mainly induced by a cyclic passage of a large recirculation bubble on the aerofoil suction side. In turns, when the flap is pushed downward, the induced plane jet displaces the trailing edge vortices further downstream, away from the wing, moderating the downforce generated by those vortices and regularising the shedding cycle that appears to be much more organised when the optimal flaplet configuration is selected

Endotoxin receptor CD14 in PiZ α-1-antitrypsin deficiency individuals

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Informed Switching Strongly Decreases the Prevalence of Antibiotic Resistance in Hospital Wards

Antibiotic resistant nosocomial infections are an important cause of mortality and morbidity in hospitals. Antibiotic cycling has been proposed to contain this spread by a coordinated use of different antibiotics. Theoretical work, however, suggests that often the random deployment of drugs (“mixing”) might be the better strategy. We use an epidemiological model for a single hospital ward in order to assess the performance of cycling strategies which take into account the frequency of antibiotic resistance in the hospital ward. We assume that information on resistance frequencies stems from microbiological tests, which are performed in order to optimize individual therapy. Thus the strategy proposed here represents an optimization at population-level, which comes as a free byproduct of optimizing treatment at the individual level. We find that in most cases such an informed switching strategy outperforms both periodic cycling and mixing, despite the fact that information on the frequency of resistance is derived only from a small sub-population of patients. Furthermore we show that the success of this strategy is essentially a stochastic phenomenon taking advantage of the small population sizes in hospital wards. We find that the performance of an informed switching strategy can be improved substantially if information on resistance tests is integrated over a period of one to two weeks. Finally we argue that our findings are robust against a (moderate) preexistence of doubly resistant strains and against transmission via environmental reservoirs. Overall, our results suggest that switching between different antibiotics might be a valuable strategy in small patient populations, if the switching strategies take the frequencies of resistance alleles into account

Alarmins MRP8 and MRP14 Induce Stress Tolerance in Phagocytes under Sterile Inflammatory Conditions

Hyporesponsiveness by phagocytes is a well-known phenomenon in sepsis that is frequently induced by low-dose endotoxin stimulation of Toll-like receptor 4 (TLR4) but can also be found under sterile inflammatory conditions. We now demonstrate that the endogenous alarmins MRP8 and MRP14 induce phagocyte hyporesponsiveness via chromatin modifications in a TLR4-dependent manner that results in enhanced survival to septic shock in mice. During sterile inflammation, polytrauma and burn trauma patients initially present with high serum concentrations of myeloid-related proteins (MRPs). Human neonatal phagocytes are primed for hyporesponsiveness by increased peripartal MRP concentrations, which was confirmed in murine neonatal endotoxinemia in wild-type and MRP14(-/-) mice. Our data therefore indicate that alarmin-triggered phagocyte tolerance represents a regulatory mechanism for the susceptibility of neonates during systemic infections and sterile inflammation

Performance of the QuickVue Influenza A+B Rapid Test for Pandemic H1N1 (2009) Virus Infection in Adults

To investigate the diagnostic accuracy of the QuickVue® Influenza A+B rapid test we conducted a prospective observational study in which this rapid test was compared with a real-time reverse transcription polymerase chain reaction (RT-PCR) for pandemic influenza A H1N1 (2009) infection in Austrian adults. The sensitivity, specificity, and positive and negative predictive values of the QuickVue test compared with the RT-PCR were 26% (95% CI 18–35), 98% (95% CI 92–100), 94% (95% CI 80–99) and 50% (95% CI 42–58), respectively. The prevalence of pandemic H1N1 (2009) virus infection among the 209 patients included in the study was 57%. Our data suggest that a positive QuickVue test provides considerable information for the diagnosis of pandemic influenza A H1N1 (2009) virus infection in young adults but that a negative QuickVue test result should, if relevant for patient management or public health measures, be verified using PCR