4,851 research outputs found

    Travel stories and travelers. Transdisciplinary approaches and proposals for a history of Europe

    Get PDF
    The article proposes the theme of the history of travel and travelers for a comprehensive approach to teaching and learning history for active citizenship education. In particular, we analyze briefly on the historical ways: itineraries, routes, and cultures. From the routes of faith to the itineraries and routes of trade to the routes of conflict (European explorations and conquests in the Americas, from the crusades to the world wars) and their participants; your travel and trade

    Evaluation of the hydro - Mechanical efficiency of external gear pumps

    Get PDF
    This paper proposes and describes a model for evaluating the hydro-mechanical efficiency of external gear machines. The model is built considering and evaluating the main friction losses in the machines, including the viscous friction losses at the tooth tip gap, at the bearing blocks-gears gaps, at the journal bearings, and the meshing loss. To calculate the shear stress at each gap interface, the geometry of the gap has to be known. For this reason, the actual position of the gears inside the pump casing and consequent radial pressure distribution are numerically calculated to evaluate the gap height at the tooth tips. Moreover, the variation of the tilt and reference height of the lateral gaps between the gears and the pump bushings are considered. The shear stresses within the lateral gaps are estimated, for different lateral heights and tilt values. At the journal bearings gaps, the half Sommerfeld solution has been applied. The meshing loss has been calculated according to the suggestion of the International Standards. The hydro-mechanical efficiency results are then discussed with reference to commercial pumps experimentally characterized by the authors in a previous work. The average percentage deviation from experimental data was around 2%, without considering the most critical operating conditions (high delivery pressure, low rotational speed). The limits of this approach are also explained. Finally, the role of each source of loss is discussed, considering different operating conditions and two values of fluid viscosity. Lateral gap losses and meshing loss are much more relevant in determining the hydro-mechanical efficiency variation in the pump's operating range, especially at a low delivery pressure. Moreover, while lateral gap losses increase with the rotational speed, the meshing loss shows the opposite behavior. The tooth tip gap losses are never as relevant, but they increase at high pressure. The journal bearings losses become comparable with the lateral and meshing ones at high delivery pressure values. Considering the pumps analyzed and the operating range of delivery pressure values and rotational speed values, the meshing loss made the mechanical efficiency vary in a percentage range of ±7%, with lateral losses in the range of about the ±15%, when also considering the extreme operating points (low speed, high pressure; high speed, low pressure). The weight of the lateral losses slightly reduced when we analyzed the higher temperature results, while the meshing losses slightly increased

    Modelling of hydrostatic bearings for servo-cylinders

    Get PDF
    Hydraulic servo cylinders are widely used in versatile industrial applications such as machine tools, industrial robots, autonomous manufacturing systems and special applications in laboratories. To reduce friction and allow smooth and controllable displacement of the actuator, hydrostatic journal bearings are used at the ends of the rod. The design and manufacturing of this elements is challenging since the good operation relays on the very small tolerances required to bear the load on the cylinder and to reduce leakages. In this work, a virtual design and test tool for hydrostatic journal bearing with pockets, developed in OpenModelica environment, is presented. The influence of eccentricity and manufacturing tolerances is then studied and discussed. The model proposed has the aim to explore the extreme and critical operating conditions of the servo-cylinder and to help and/or improve the design phase

    Ketorolac vs. morfina nel trattamento del dolore acuto in pazienti traumatizzati: un’analisi di minimizzazione dei costi

    Get PDF
    Aim of this study is to develop an economic valuation comparing ketorolac vs. morphine for the treatment of sharp pain caused by heavy limb injury, in traumatology ward and in first aid ward. As cost minimization analysis, this economic valuation has been based on clinical results of Rainer et al. (2000). Ketorolac and morphine have the same efficacy in calming the pain; the greatest difference in the clinical outcomes is about the morphine side effects (nausea, vomiting and phlebitis). Assuming the hospital point of view with a differential costs perspective, the ketorolac patients showed two consequences than could generate lower resources consumption: less side effects and the reduction of time permanence in first aid ward. Considering the drug cost, the administration cost and the side effects treatment costs, the expenditure for every single morphine patient is L. 23.385, vs L. 4.875 for a ketorolac patient, with a difference of L. 18.510

    Health financing at district level in Malawi: an analysis of the distribution of funds at two points in time.

    Get PDF
    There is growing attention to tracking country level resource flows to health, but limited evidence on the sub-national allocation of funds. We examined district health financing in Malawi in 2006 and 2011, and equity in the allocation of funding, together with the association between financing and under five and neonatal mortality. We explored the process for receiving and allocating different funding sources at district level. We obtained domestic and external financing data from the Integrated Financial Management Information System (2006-11) and AidData (2000-12) databases. Out-of-pocket payment data came from two rounds of integrated household budget surveys (2005; 2010). Mortality data came from the Multiple Indicator Cluster Survey (2006) and Demographic and Health Survey (2010). We described district level health funding by source, ran correlations between funding and outcomes and generated concentration curves and indices. 41 semi-structured interviews were conducted at the national level and in 10 districts with finance and health managers. Per capita spending from all sources varied substantially across districts and doubled between 2006 and 2011 from 7181 Kwacha to 15 312 Kwacha. In 2011, external funding accounted for 74% of funds, with domestic funding accounting for 19% of expenditure, and out of pocket (OOP) funding accounting for 7%. All funding sources were concentrated among wealthier districts, with OOP being the most pro-rich, followed by domestic expenditure and external funding. Districts with higher levels of domestic and external funding had lower levels of post-neonatal mortality, and those with higher levels of out-of-pocket payments had higher levels of 1-59 month mortality in 2006. There was no association between changes in financing and outcomes. Districts reported delayed receipt of lower-than-budgeted funds, forcing them to scale-down activities and rely on external funding. Governments need to track how resources are allocated sub-nationally to maximize equity and ensure allocations are commensurate to health need

    A Pixel Vertex Tracker for the TESLA Detector

    Get PDF
    In order to fully exploit the physics potential of a e+e- linear collider, such as TESLA, a Vertex Tracker providing high resolution track reconstruction is required. Hybrid Silicon pixel sensors are an attractive sensor technology option due to their read-out speed and radiation hardness, favoured in the high rate TESLA environment, but have been so far limited by the achievable single point space resolution. A novel layout of pixel detectors with interleaved cells to improve their spatial resolution is introduced and the results of the characterisation of a first set of test structures are discussed. In this note, a conceptual design of the TESLA Vertex Tracker, based on hybrid pixel sensors is presentedComment: 20 pages, 11 figure
    • …
    corecore