1,721,090 research outputs found
Ultrasound-clinical correlations in the assessment of the newborn at risk for brain damage.
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A novel predictive power flow control strategy for hydrogen city rail train
No full textHydrogen-based vehicular traction has already reached a mature technological level and can replace the more polluting diesel engines. The adoption of this technology can also alleviate the carbon footprint issue of the rail trains running on non-electrified lines. This study presents a model and a numerical performance analysis of an electric hybrid train in an urban context. The train uses hydrogen as fuel and operates over non-electrified lines with zero local emission. The electric traction motors of the train are fed by a hybrid power unit consisting of several hydrogen fuel cell stacks operating independently in on/off mode and a set of flywheel energy storage devices. Each component of the power train is modeled separately and its operating limits are chosen on the base of technical literature. An innovative predictive logic to manage power flows is defined and proposed with the aim to minimize the fuel consumption. Furthermore, this approach uses a regenerative electrical braking and eliminates dissipative devices, like rheostats, which are commonly utilized onboard electric trains. This predictive approach is based on the optimal management of the power unit components according to the advanced knowledge of the data of the rail vehicle, the characteristics of path, drive cycle and payload for an established route. The fuel cell stacks operate accordingly to the average traction power requirement in each railway line section, whereas the flywheel energy storage system manages the dynamic power. A parametric model of the system and a respective software tool have been developed; this implementation, that incorporates many tunable parameters of the train and rail path, is able to simulate the rail train operating on a specific railway path by implementing the novel control strategy. An existing single track non-electrified line, designed again for urban service, has been selected as a case study to evaluate the performance of the proposed system. The specific fuel consumptions obtained with the novel control strategy and with a single fuel cell system operating at constant power are compared under the same operating conditions. The results highlight that significant fuel savings can be achieved
A novel optimal power control for a city transit hybrid bus equipped with a partitioned hydrogen fuel cell stack
Full text linkThe development of more sustainable and zero-emissions collective transport solutions could play a very important measure in the near future within smart city policies. This paper tries to give a contribution to this aim, proposing a novel approach to fuel cell vehicle design and operation. Traditional difficulties experienced in fuel cell transient operation are, in fact, normally solved in conventional vehicle prototypes, through the hybridization of the propulsion system and with the complete fulfillment of transients in road energy demand through a high-capacity onboard energy storage device. This makes it normally necessary to use Li-ion battery solutions, accepting their restrictions in terms of weight, costs, energy losses, limited lifetime, and environmental constraints. The proposed solution, instead, introduces a partitioning of the hydrogen fuel cell (FC) and novel optimal power control strategy, with the aim of limiting the capacity of the energy storage, still avoiding FC transient operation. The limited capacity of the resulting energy storage systems which, instead, has to answer higher power requests, makes it possible to consider the utilization of a high-speed flywheel energy storage system (FESS) in place of high energy density Li-ion batteries. The proposed control strategy was validated by vehicle simulations based on a modular and parametric model; input data were acquired experimentally on an operating electric bus in real traffic conditions over an urban bus line. Simulation results highlight that the proposed control strategy makes it possible to obtain an overall power output for the FC stacks which better follows road power demands, and a relevant downsizing of the FESS device
ECOENCEFALOGRAFIA INTRAOPERATORIA IN NEUROCHIRURGIA
No full textIntraoperative ultrasonography with real time sonographic imaging equipment is widely used and, in the neurosurgical operating room, has been really successfull, initially in the brain and subsequently in the spinal cord as well. Its main applications i.e. accurate needle biopsies, localization of intracerebral masses, placement of ventricular and cyst shunts, can diminish the amount of potential damage to normal brain tissue. Moreover results of tumor resection may be intraoperatively confirmed and the end results are more accurate. No intraoperative complications and no postoperative infections result from use of ultrasound in the operating room. No evidence is given that the small amount of mechanical vibration emitted by the transducer damages the brain or the spinal cord.Surgical procedures, as a result, are faster, safer and better planned by virtue of informations obtained by ultrasonographic intraoperative examination, instead of simple preoperative imaging procedures.Intraoperative ultrasonography with real time sonographic imaging equipment is widely used and, in the neurosurgical operating room has been really successful, initially in the brain and subsequently in the spinal cord as well. Its main applications i.e. accurate needle biopsies, localization of intracerebral masses, placement of ventricular and cyst shunts, can diminish the amount of potential damage to normal brain tissue. Moreover the results of tumor resection may be intraoperatively confirmed and the end results are more accurate. No intraoperative complications and no postoperative infections result from use of ultrasound in the operating room. No evidence is given that the small amount of mechanical vibration emitted by the transducer damages the brain or the spinal cord. Surgical procedures, as a result, are faster, safer and better planned by virtue of infomations obtained by ultrasonographic intraoperative examination, instead of simple preoperative imaging procedures
Effect analysis of payload variation on energy consumption of a hydrogen powered light urban train
No full textIn this study a light hybrid rail train hydrogen powered is considered and the influence of the payload factor variation on traction energy consumption is investigated. For this purpose, a parametric software has been developed to simulate the train running over a railway path by varying the payload factor. As simulated system, an existing non-electrified single-track line has been taken into consideration and the traction energy requirement has been evaluated as function of the pay load factor. The specific fuel consumptions of a similar Diesel train have been compared under the same operating conditions. The results highlight that a significant fuel saving to be achieved
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