1,721,404 research outputs found
Electrical storage for the enhancement of energy and cost efficiency of urban railroad systems
No full textToday's city traffic is often congested, because of the large amount of vehicles in comparison to the available space. Moreover road transportation contributes to the urban pollution and greenhouse gas emissions. One solution in the urban environment is the use of tramways. The most important bonus comes from the inherent reversibility of electric drives: energy can be sent back to the electricity source, while braking the vehicle. This can be done by installing some storage device on-board trains, or installing them in one or more points of the supply network. This paper therefore draws some results about when these systems can be useful and how they can be controlled. In general, storage systems with the following variants can be considered: • Stationary supercapacitors. • Stationary high-power lithium batteries. When the storage system is constituted by a supercapacitor, it is mandatory to interpose between it and the line a DC/DC converter. When, on the contrary, it is constituted by a lithium battery, the presence of the converter can be avoided. This paper provides an evaluation of the variant based on stationary high power lithium batteries, in a realistic case study. Some rather general conclusions will be drawn from the proposed analysis. © Civil-Comp Press, 2014
Direct bone effects of calcimimetics in chronic kidney disease?
No full textCalcimimetics are widely used in patients on dialysis to treat secondary hyperparathyroidism. Our current view is that bone effects are only indirect through parathyroid hormone suppression. However, because bone cells express the calcium-sensing receptor, direct calcium-sensing receptor–mediated effects are also possible. New experimental data demonstrate direct anabolic bone actions of calcimimetics, independent of parathyroid hormone suppression. Because these effects could be clinically useful, further studies are necessary to confirm the validity of this observation
Impact of innovative ILHYPOS supercapacitors on a fuel cell vehicle
No full textElectrochemical capacitors (SC) are receiving increasing attention as possible enabling technologies in applications where high power is required for short times, such as in hybrid vehicles (HEV) and uninterruptible power systems (UPS). Moreover, there are some applications using fuel cells (FC) as power generators, whose energy efficiency is greatly reduced whenever FC power variations are significant. In 2005 the European Commission (EC) funded the ILHYPOS project, mainly aimed at the research and development of innovative SCs with highly improved specific performances (specific energy and power), and based on environmentally acceptable materials, such as ionic liquids, a novel electrolyte class of materials, with a working voltage in excess of 5 V. The improvements of SC performances were pursued also studying new electrode materials and/or cell designs: specific energy in excess of 40 Wh/kg, based only on active material weights have been estimated, in configurations with electronic conducting polymers or activated carbons in asymmetric configurations. As part of the Project ILHYPOS, the possible impact of the studied SCs has been evaluated by means of simulations in defined applications, such as those in fuel cell vehicles (FCV) and UPS, powered by fuel cells. The simulations for vehicle applications have been performed by using conventional standardized and real duty cycles. The sizing of the ILHYPOS SCs has been carried out with developed mathematical models and applied to a FC hybrid electric van, a test prototype developed by an Italian small enterprise. This paper first highlights the most recent achievements of the ILHYPOS Project and, then, presents the impacts of the developed SCs with respect to commercial SCs and a drivetrain with and without SCs. © 2009 AVERE
Regulation strategy of an Ultracapacitor storage model for a gantry crane
No full textThis paper presents, for a system consisting of a gantry crane, the regulation strategy of an Ultracapacitor (UC) based storage system, and its performance test using a simulated model of the system © 2013 IEEE
Experimental Analysis of NMC Lithium Cells Aging for Second Life Applications
No full textNowadays the electric power system is facing new challenges related to the integration of renewable sources, more and more frequently combined with energy storage systems. The use of these technologies is very promising, although it requires sophisticated control architectures in order to successfully balance the intermittence and unpredictability of renewables, and provide the power grid with new services. The presence of a storage state estimator is absolutely required to correctly identify the storage performance and present conditions, in terms of stored energy, aging or possible failures; this is crucial to assess the real exploitability of the battery, both during its first or second life application. This paper focuses in particular on aging mechanisms, describing and comparing three possible models and their deployment procedures. Flexibility of implementation, accuracy in aging determination, and ease of use of each technique have been deeply analysed and compared. İ 2018 IEEE
Use of electrochemical storage in substations to enhance energy and cost efficiency of tramways
No full textThis paper evaluates, in a case study with real data, the advantages of using regenerative braking in a tram line, both in case of non-reversible substations and substations equipped with battery energy storage. It shows that the addition of storage enhances energy efficiency a lot, and therefore this is a very cost-effective solution. © 2013 AEIT
A geometrically exact formulation of thin laminated composite shells
No full textA geometrically exact approach is employed to formulate the equations of motion of thin multi-layered composite shells subject to excitations that cause large strains, displacements, and rotations. Ad hoc truncated kinematic approximations of the obtained semi-intrinsic theory delivers, as a by-product, the kinematics of the Koiter and the Naghdi theories of shells, respectively. Numerical simulations are carried out both for cylindrical and spherical shells: nonlinear equilibrium paths are constructed considering a quasi-static load increase. The comparisons between the results furnished by the geometrically exact theory and those obtained by Koiter and Naghdi theories show the high accuracy of the proposed nonlinear approach. Classical theories become increasingly inaccurate at deflection amplitudes of the order of the shell thickness, evidencing that significant misrepresentations of the system behavior are possible if reduced-order kinematics are taken into account
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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