1,355,479 research outputs found
Solar Position Identification on Sky Images for Photovoltaic Nowcasting applications
No full textNowcasting, i.e. very-short term forecasting, of photovoltaic (PV) production has a growing importance. A typical method to perform it, relies on sky cameras and sky images that, duly processed, can provide a forecast of sharp and fast changes in PV production. The first issue that arises while dealing with these analyses regards the identification and forecasting of the solar position in the images, especially when it is covered by clouds. In this paper, three different techniques for solar identification in sky images are proposed, analysed and compared
Photovoltaic Plant Output Power Forecast by Means of Hybrid Artificial Neural Networks
No full textThe main goal of this chapter is to show the set up a well-defined method to identify and properly train the hybrid artificial neural network both in terms of number of neurons, hidden layers and training set size in order to perform the day-ahead power production forecast applicable to any photovoltaic (PV) plant, accurately. Therefore, this chapter has been addressed to describe the adopted hybrid method (PHANN—Physic Hybrid Artificial Neural Network) combining both the deterministic clear sky solar radiation algorithm (CSRM) and the stochastic artificial neural network (ANN) method in order to enhance the day-ahead power forecast. In the previous works, this hybrid method had been tested on different PV plants by assessing the role of different training sets varying in the amount of data and number of trials, which should be included in the “ensemble forecast.” In this chapter, the main results obtained by applying the above-mentioned procedure specifically referred to the available data of the PV power production of a single PV module are presented
X-Ray Emission from the Linear Plasma of a Spherical Pinch: The Electron Distribution Function in a Strong Electric Field
No full textThe plasma generated in a spherical pinch device consists of a linear discharge along the diameter of a spherical vessel and of an implosion that compresses the linear plasma. Because the linear discharge by itself is found to emit pulses of soft X rays, this phenomenon is investigated by considering a spatially uniform plasma subjected to an electric field. With an appropriate change of variables, a one-dimensional time-independent Boltzmann Fokker-Planck equation is transformed into a confluent hypergeometric equation. The electron distribution function is then calculated in closed form together with the density current to obtain the X-ray spectra from such plasmas
C'è Vita su Marte?
No full textUna raccolta di interviste esclusive a dieci importanti personalità del mondo della scienza e dell'aerospazio, con un duplice obiettivo: da un lato, scattare una fotografia sullo stato attuale del settore spaziale, raccontandone i diversi aspetti dal punto di vista dei suoi protagonisti; dall'altro, proiettare lo sguardo del lettore verso il futuro, concentrandosi sulle prossime missioni di esplorazione planetaria, robotica e con equipaggio umano, non solo alla volta del Pianeta Rosso, ma anche della Luna e di altri corpi celesti, che vedono e vedranno l'Italia in prima fila. Attraverso il punto di vista di questo dream team spaziale, accompagnato da una bella selezione di immagini, l'Autore approfondisce alcuni fra i temi di maggior interesse e attualità, con riferimenti anche alla recente pandemia di coronavirus, all'importante ruolo della medicina spaziale e alle ricerche scientifiche in campo biomedico condotte in condizioni di microgravità sulla Stazione Spaziale Internazionale, tratteggiando un quadro in cui l'esplorazione planetaria non è che il filo conduttore, il pretesto, per intraprendere un viaggio nello spazio e nel futuro di più ampio respiro. Prefazione di Luca Parmitano. Interviste a: Piero Angela, Giorgio Bianciardi, Piero Bianucci, Walter Cugno, Giancarlo Genta, Vincenzo Giorgio, Paolo Nespoli, Linda Raimondo, Liliana Ravagnolo, Giorgio Saccoccia
The Poetic Knowledge of Shizuki Tadao Traces of Dutch Poet Jacob Cats in Early Nineteenth-Century Japan
No full textIn the history of the Dutch-Japanese relations, Shizuki Tadao is recognised as an extraordinary scholar. However, his translations of European books from Dutch into Japanese only paint a partial picture of his research. In fact, he also developed valuable theories on language that allowed the Japanese to better grasp Dutch. Furthermore, he introduced European grammatical concepts and terminology in Japan. A lesser-known interest of Shizuki was poetry, evidenced by three citations from the Dutch poet Jacob Cats (1577‐1660), found in Shizuki’s works on language, by two Dutch poems attributed to him, and by an additional indirect reference to Shizuki’s knowledge on the theory of poetry. The present article aims at better understanding the figure of Shizuki as a scholar of Dutch and to add a piece to the research on the spreading of Cats’ emblems
Sistema cardiovascolare e disturbi respiratori nel sonno
No full textLa sindrome delle apnee ostruttive nel sonno ( Obstructive sleep apnea Syndrome OSAS) è caratterizzazta dall'interruzione ripetitiva della ventilazione durante il sonno causata dall'ostruzione intermittente delle alte vie aeree, associata a disturbo del sonno e ad ipossia e, non costantemente ipercapnia. Queste ultime aymentano lo sforzo respiratorio con aumento della pressione negativa intratoracica e aumento della pressione transmurale ventricolare sinistra. aumenta anche il ritorno venoso al ventricolo destro e la pressione arteriosa polmonare con aumenti del postcarico ventricolare destro. L'ipossia intermittente induce la produzione di radicali liberi, di molecole proinfiammatorie, e riduzione dell'ossido nitrico (NO) con predisposizione all'aterosclerosi e all'ipertensione arteriosa. Se l'OSAS viene riconosciuta per tempo e trattata tempestivamente le alterazioni a carico del cuore regrediscono nell'arco di alcuni mesi. E' pertanto necessario aumentare la consapevolezza dei pediatri riguardo queste patologie, spesso misconosciute dai genitori stessi dei bambin
Single-Incision Versus Standard Multiple-Incision Laparoscopic Cholecystectomy: A Meta-analysis of Experimental and Observational Studies
No full textChristopher Joby, The Dutch Language in Japan (1600-1900). A Cultural and Sociolinguistic Study of Dutch as a Contact Language in Tokugawa and Meiji Japan, Leiden, Brill, 2020, 494 pp. isbn 9789004436442
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A New Probabilistic Ensemble Method for an Enhanced Day-Ahead PV Power Forecast
No full textThe penetration of nonprogrammable renewable energy sources, namely wind and solar technology, has greatly increased in the last decades and nowadays the shift toward green energy sources represents a priority worldwide. The high variability of the primary source challenges the grid operators in ensuring the stability and reliability of the electric grid. Machine learning algorithms, and in particular artificial neural networks, are one of the most reliable methods for photovoltaic (PV) energy production forecast. This article proposes a new ensemble method based on the probabilistic distribution of the trials, the probabilistic ensemble method (PEM). The proposed method has been tested on a three-years real case study, where the available days have been clustered according to the solar irradiation forecast. The days where the worst performance, in terms of nRMSE, was recorded mostly belonged to the totally cloudy days class, that has been therefore selected for the analysis. The PEM has been compared with the ensemble based on the mean value, achieving an improvement in the nRMSE metric up to 4.79% in 2017 in the totally cloudy days class
Space distribution and energy straggling of charged particles via Fokker-Planck equation
No full textThe Fokker-Planck equation describing a beam of charged particles entering a homogeneous medium is solved here for a stationary case. Interactions are taken into account through Coulomb cross-section. Starting from the charged-particle distribution as a function of velocity and penetration depth, some important kinetic quantities are calculated, like mean velocity, range and the loss of energy per unit space. In such quantities the energy straggling is taken into account. This phenomenon is not considered in the continuous slowing-down approximation that is commonly used to obtain the range and the stopping power. Finally the well-known Bohr or Bethe formula is found as a first-order approximation of the Fokker-Planck equation. © 1996 Società Italiana di Fisica
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