1,721,005 research outputs found
A correction method for dynamic analysis of linear continuous systems
No full textA method to improve the dynamic response analysis of continuous classically damped linear system is proposed. As in fact usually, following a classical approach, a reduced number of eigenfunctions are accounted for and the response is evaluated by integrating the uncoupled differential equations of motion in modal space, neglecting the contribution of high frequency modes (truncation procedure). Here, starting from the given system, it is proposed to set up two differential equations governing the motion of two new continuous systems: the first one contains only the first m non-zero eigenvalues of the given system and the second one contains the remainder non-zero infinity - m eigenvalues. By summing up the response of the two aforementioned systems it is proven that the global response is recovered. Then, the response of the first system is evaluated by classical dynamic methods (Duhamell integral or step-by-step integration procedures), while the particular solution of the second one is obtained in series form that is shown to converge quickly
Primi rinvenimenti in Italia del virus dell’accartocciamento fogliare giallo del pomodoro in coltivazioni di fagiolo in serra.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Technical and economic analysis of EV high-power recharging pools equipped with storage
No full textA comprehensive network of high-power recharging points will be fundamental to enable long-distance travel for electric vehicles. However, the distribution grid may not be always capable to provide such high levels of power in every area. From this prospect, recharging pools equipped with battery storage system provide the opportunity to limit the maximum power request to the grid, avoiding the need for an upgrade to the grid connection. This solution can be implemented by means of various configuration depending on the storage system size and the relative energy management, leading to different costs. This paper carries out a technical and economic analysis of a high-power recharging pool connected to the low voltage distribution network and equipped with a stationary storage system. A simulation model developed in Modelica language is used to compare three different storage configurations. Results indicate that a peak shaving BESS is the most feasible solution. It is also observed that a reduced size would improve the profitability of the investment, supporting the EV recharge with a reasonable additional waiting time
Famiglia inMigrazione
No full textMuovendo da differenti prospettive disciplinari (demografia, sociologia ed economia), i contributi raccolti in questo volume documentano come la famiglia sia centrale in ogni fase del processo migratorio, dalla scelta di emigrare, ai suoi sviluppi e alle sue problematicità, con una particolare attenzione al complesso delle relazioni tra famiglia e migrazione nel contesto della società italiana del nostro tempo. I temi affrontati spaziano dall’inquadramento demografico delle famiglie straniere in Italia (Livia Ortensi), alla questione sociologica delle seconde generazioni (Stefania G. Meda), alla valutazione di matrice economica dell’impatto del cambiamento nel modello migratorio femminile sulle rimesse bilaterali internazionali (Sara Salomone). Conclude il volume uno studio socio-demografico sulle famiglie immigrate in Abruzzo, Molise e Puglia e su esperienze virtuose di accoglienza delle famiglie migranti nel Sud Italia (Isabella Cordisco
Experimental investigation of the modal response of a rail span during and after wheel passage
No full textThis paper examines the vibrations of a rail span (rail section between two consecutive sleepers) during and after the passage of a rail car’s wheel as well as under impact hammer excitation. In literature, the dynamic response of railway tracks under moving loads has been studied extensively. Many of these studies focus on the responses in relation to displacement/force-time histories and wave propagation parameters. These responses are investigated for the time instants when rail car wheels transverse over the rail spans of interest. In this context, an investigation of responses in relation to modal parameters during and after moving loads might provide additional information. Such information can be used to examine how the loading and additional masses induced by the moving wheels affect the dynamic responses. To this end, field tests were carried out at Transportation Technology Center Inc. (TTCI) facility in Colorado, U.S. First, to find the flexural modes of a rail span under no loading, data was collected from three accelerometers placed on the span under vertical impact hammer excitation. Next, the accelerometers were placed underneath the rail span, and data was collected while a rail car traveled over the span. The signal segments corresponding to during and after a wheel passage were analyzed for the identification of modal parameters. The comparison of the results demonstrated that the frequencies of the rail span increased as the loading induced by the wheel increased
Redox-flow batteries for high energy-to-power ratio storage: A preliminary experimental study
No full textIn conjunction with the worldwide interest in the safeguard of the environment, the possibility of storing electricity to allow larger renewable energy source penetration is increasingly getting ground. In this framework, among all the potential stationary energy storage systems, Redox Flow Batteries (RFBs) appear as one of the most promising solutions. This is because of their several advantages, such as the unique capability to decouple energy content from power, which makes them well adaptable at different network services and installation locations. This paper aims to display the RFBs scenario inside the global stationary storage situation. The principle of operation of these batteries is illustrated and the current landscape described. Some preliminary experimental results of an existing commercial solution of a vanadium RFB (VRFB) are presented, highlighting strengths and weaknesses points of this category. Charge and discharge experimental tests under realistic grid-interconnection scenario are performed, measuring the VRFB under study global efficiency, by an estimation of its internal losses: shunt currents, self-discharge rate and auxiliary system power consumption. Considering all these losses, the results display an overall VRFB efficiency around 50%, against the typical values taken from literature, that range between 70% to 90%
Identification of Bending Modes of Vibration in Rails by a Laser Doppler Vibrometer on a Moving Platform
No full textThis paper introduces a method to identify the bending modes of vibration of railway tracks by using a laser Doppler vibrometer (LDV) mounted on a moving platform. Two sets of experiments were conducted at Transportation Technology Center Inc. (TTCI) in Pueblo Colorado, in order to validate the proposed method. First, the bending vibration modes were identified using the signals collected from a rail span (rail section between two consecutive sleepers) by accelerometers under moving car excitation. Then, vibration measurements from rail spans were obtained by using an LDV mounted on the moving railcar. All tests were carried out at four different rail car speeds: 8 km/h (5 mph), 16 km/h (10 mph), 35 km/h (22 mph), and 45 km/h (28 mph). To find LDV signal segments corresponding to rail spans, a novel approach based on the sleeper passing frequency is introduced. Comparison of the results from both sets of tests demonstrated good agreement for all speeds
On the investigation of energy efficient torque distribution strategies through a comprehensive powertrain model
Get PDFIn electric vehicles with multiple motors, the torque at each wheel can be controlled independently, offering significant opportunities for enhancing vehicle dynamics behaviour and system efficiency. This paper investigates energy efficient torque distribution strategies for improving the operational efficiency of electric vehicles with multiple motors. The proposed strategies are based on the minimisation of power losses, considering the powertrain efficiency characteristics, and are easily implementable in real-time. A longitudinal dynamics vehicle model is developed in Simulink/Simscape environment, including energy models for the electrical machines, the converter, and the energy storage system. The energy efficient torque distribution strategies are compared with simple distribution schemes under different standardised driving cycles. The effect of the different strategies on the powertrain elements, such as the electric machine and the energy storage system, are analysed. Simulation results show that the optimal torque distribution strategies provide a reduction in energy consumption of up to 5.5% for the case-study vehicle compared to simple distribution strategies, also benefiting the battery state of charge
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