Modeling and Detection of Hotspot in Shaded Photovoltaic Cells

In this paper, we address the problem of modeling the thermal behavior of photovoltaic (PV) cells undergoing a hotspot condition. In case of shading, PV cells may experience a dramatic temperature increase, with consequent reduction of the provided power. Our model has been validated against experimental data, and has highlighted a counter-intuitive PV cell behavior, that should be considered to improve the energy efficiency of PV arrays. Then, we propose a hotspot detection scheme, enabling to identify the PV module that is under hotspot condition. Such a scheme can be used to avoid the permanent damage of the cells under hotspot, thus their drawback on the power efficiency of the entire PV system

Faults Affecting Energy-Harvesting Circuits of Self-Powered Wireless Sensors and Their Possible Concurrent Detection

We analyze the effects of faults on an energy-harvesting circuit (EHC) providing power to a wireless biomedical multisensor node. We show that such faults may prevent the EHC from producing the power supply voltage level required by the multisensor node. Then, we propose a low-cost (in terms of power consumption and area overhead) additional circuit monitoring the voltage level produced by the EHC continuously, and concurrently with the normal operation of the device. Such a monitor gives an error indication if the generated voltage falls below the minimum value required by the sensor node to operate correctly, thus allowing the activation of proper recovery actions to guarantee system fault tolerance. The proposed monitor is self-checking with regard to the internal faults that can occur during its in-field operation, thus providing an error signal when affected by faults itself

Low-Cost On-Chip Clock Jitter Measurement Scheme

In this paper, we present a low-cost, on-chip clock jitter digital measurement scheme for high performance microprocessors. It enables in situ jitter measurement during the test or debug phase. It provides very high measurement resolution and accuracy, despite the possible presence of power supply noise (representing a major source of clock jitter), at low area and power costs. The achieved resolution is scalable with technology node and can in principle be increased as much as desired, at low additional costs in terms of area overhead and power consumption. We show that, for the case of high performance microprocessors employing ring oscillators (ROs) to measure process parameter variations (PPVs), our jitter measurement scheme can be implemented by reusing part of such ROs, thus allowing to measure clock jitter with a very limited cost increase compared with PPV measurement only, and with no impact on parameter variation measurement resolution

La costruzione dei modelli di quattro architetture di Pier Luigi Nervi

L\u2019attivit\ue0 di ricerca ha avuto come obiettivo la costruzione di quattro modelli architettonici di opere scelte di Pier Luigi Nervi: il progetto dello stadio comunale Giovanni Berta di Firenze (1929-32), il progetto dello stadio Flaminio di Roma (1956-59), il progetto della tribuna dello stadio di Swindon (progetto non realizzato del 1963-66) e il progetto dello stadio Kuwait Sport Center (progetto non realizzato del 1968-69) . L\u2019intento \ue8 quello di mettere in evidenza gli aspetti strutturali e geometrici formali delle opere selezionate, in relazione a specifiche fasi progettuali ritenute rilevanti. In particolare per i progetti realizzati dello stadio Flaminio e dello stadio Berta, i modelli in mostra riportano alcune interpretazioni che non rappresentano la loro configurazione attuale ma si riferiscono a scelte progettuali deducibili dai materiali originali conservati negli archivi del MAXXI di Roma, dello CSAC di Parma e dell\u2019Archivio Storico Comunale di Firenze. La metodologia adottata per la costruzione dei modelli si \ue8 articolata in tre fasi principali. La prima fase, la costruzione dei disegni digitali, \ue8 consistita nella redazione dei disegni 2D necessari alla costruzione del modello tridimensionale. Il ridisegno di piante, sezioni e prospetti dei vari progetti ha comportato un\u2019attenta lettura dei materiali d\u2019archivio. I disegni originali, non sempre coerenti fra di loro poich\ue9 riportano fasi progettuali diverse, presentano alcune mancanze che sono state colmate attraverso un\u2019analisi delle immagini d\u2019epoca. La seconda fase, la costruzione del modello matematico, \ue8 consistita nella costruzione di modelli tridimensionali NURBS. La rappresentazione matematica digitale adottata \ue8 in grado di descrivere in modo accurato le forme geometriche ideate da Nervi, come l\u2019uso frequente di superfici rigate. Infine la terza fase \ue8 consistita nella costruzione del modello fisico. I modelli esposti sono il frutto di un lavoro che ha comportato l\u2019utilizzo di diversi metodi e tecniche costruttive, da quelle tradizionali alle lavorazioni CNC e prototipazione rapida 3

Model for thermal behavior of shaded photovoltaic cells under hot-spot condition

We address the problem of modeling the thermal behavior of photovoltaic (PV) cells that, due to their being exposed to shading, may experience a dramatic temperature increase (a phenomenon referred to as hot-spot) with consequent reduction of the provided power. Our proposed model has been validated against experimental data, and constitutes a first preliminary step towards the development of shading-tolerant approaches, while also highlighting a counterintuitive PV cell behavior useful to energy efficient PC array design. © 2011 IEEE

Secure communication protocol for wireless sensor networks

We propose a new communication protocol for wireless sensor networks, allowing to make them secure with respect to malicious attacks. Compared to standard secure protocols (e.g., the IEEE 802.15.4 and the ZigBee), the one we propose allows to increase security significantly, at negligible impact on node complexity. A possible hardware scheme to implement our protocol is also proposed. © 2010 IEEE

Novel organometallic building blocks for molecular crystal engineering. Part 4. Synthesis and characterization of mono- and bis-amido derivatives of [CoIII(h5-C5H4COOH)2]+ and their utilization as ligands.

The synthesis and structural characterization of the hexafluorophosphate salts of the substituted bis-amido mol. complexes [CoIII(h5-C5H4CONHC4H3N2)2]+ (1), [CoIII(h5-C5H4CONHCH2C5H4N)2]+ (2), [CoIII(h5-C5H4CON(C5H4N)2)2]+ (3), and of the amido-carboxyl complexes [CoIII(h5-C5H4CON(C5H4N)2)(h5-C5H4COOH)]+ (4), and [CoIII(h5-C5H4CONHC2N3(C5H4N)2)(h5-C5H4COOH)]+ (5) are reported. The pyridyl and pyrazine substituted amido ligands on the sandwich cores have been chosen because they allow both coordination to metal centers and participation in hydrogen bonding. The hydrogen bonding interactions established by the family of complexes in the solid state has been investigated. The utilization of complex 5 for the prepn. of the complex of complexes [Cd(NO3)2{CoIII(h5-C5H4CONHC2N3(C5H4N)(C5H4NH))(h5-C5H4COOH)}2]6+ (6) is reported as a first example of the potential of the substituted mono-and bis-amides as ligands. The isolation and structural characterization of the carbonyl chloride cation [CoIII(h5-C5H4COCl)2]+ (7) as its tetrachloro cobaltate anion salt is also described

Mechanochemical and solution preparation of the coordination polymers Ag[N(CH2CH2)3N]2[CH3COO].5H2O and Zn[N(CH2CH2)3N]Cl2.

The coordination polymer Ag[N(CH2CH2)3N]2[CH3COO].5H2O was obtained by co-grinding in the solid state and in the air of a stoichiometric amt. of AgOAc and of [N(CH2CH2)3N] (1,4-diazabicyclooctane). Single crystals suitable for x-ray diffraction were obtained from a water-MeOH soln. and used to compare calcd. and exptl. x-ray powder diffractograms. When ZnCl2 was used instead of AgOAc in the equimolar reaction with [N(CHCH2)3N], the soln. and solid-state treatments afford different products. Single crystals of the Zn-based coordination polymer Zn[N(CHCH2)3N]Cl2 were obtained by layering a soln. of ZnCl2 in MeOH over a soln. of [N(CH2CH2)3N] in CH2Cl2. The product of the co-grinding, identified only from x-ray powder diffraction, converts, on prolonged grinding, into the cryst. material obtained from the reaction in soln., anhyd. Zn[N(CH2CH2)3N]Cl2

Studio clinico-statistico sull’erisipela negli anni 1991-1996.

viene presentata una revisione della casistica realtiva alle infezioni di erisipel

Il “grande simulatore” si veste di Kaposi.

Vengono descritti peculiari aspetti clinici del Morbo di Kapos