Analisi delle funzionalità e delle prestazioni di un casello autostradale mediante un modello di coda multiclasse

Riguarda la realizzazione di un modello per l'analisi prestazionale di un casello autostradale, in grado di valutare performance e livello di qualità erogato all'utenza in relazione al rapporto esistente tra domanda e offerta di servizio. Trattandosi di un varco autostradale si tratterà di analizzare un problema relativo ad un certo numero di veicoli in attesa di ricevere un servizio caratterizzato da tempi e modalità diverse a seconda della tipologia veicolare e della tipologia di esazione utilizzata. Il problema viene affrontato tramite la teoria delle code che permette la valutazione dei relativi parametri prestazionali. Partendo dallo studio dei casi più semplici di coda M/M/1 vengono fatte valutazioni sui tempi di servizio arrivando a identificare il modello M/G/1 come più appropriato per un tale problema. Viene poi illustrata l'impostazione del modello con input e output relativi. Il modello viene infine applicato a una stazione reale della rete per evidenziare le valutazioni che è possibile ottenere da un modello così realizzato.

Hydraulic evaluation of the gyro electric wave energy converter

Motivation Thanks for a scholarship offered by ALma Mater Studiorum I could stay in Denmark for six months during which I could do physical tests on the device Gyro PTO at the Departmet of Civil Engineering of Aalborg University. Aim The goal of my thesis is an hydraulic evaluation of the device: Gyro PTO, a gyroscopic device for conversion of mechanical energy in ocean surface waves to electrical energy. The principle of the system is the application of the gyroscopic moment of flywheels equipped on a swing float excited by waves. The laboratory activities were carried out by: Morten Kramer, Jan Olsen, Irene Guaraldi, Morten Thøtt, Nikolaj Holk. The main purpose of the tests was to investigate the power absorption performance in irregular waves, but testing also included performance measures in regular waves and simple tests to get knowledge about characteristics of the device, which could facilitate the possibility of performing numerical simulations and optimizations. Methodology To generate the waves and measure the performance of the device a workstation was created in the laboratory. The workstation consist of four computers in each of wich there was a different program. Programs have been used : Awasys6, LabView, Wave lab, Motive optitrack, Matlab, Autocad Main Results Thanks to the obtained data with the tank testing was possible to make the process of wave analisys. We obtained significant wave height and period through a script Matlab and then the values of power produced, and energy efficiency of the device for two types of waves: regular and irregular. We also got results as: physical size, weight, inertia moments, hydrostatics, eigen periods, mooring stiffness, friction, hydrodynamic coefficients etc. We obtained significant parameters related to the prototype in the laboratory after which we scale up the results obtained for two future applications: one in Nissun Brending and in the North Sea. Conclusions The main conclusion on the testing is that more focus should be put into ensuring a stable and positive power output in a variety of wave conditions. In the irregular waves the power production was negative and therefore it does not make sense to scale up the results directly. The average measured capture width in the regular waves was 0.21 m. As the device width is 0.63 m this corresponds to a capture width ratio of: 0.21/0.63 * 100 = 33 %. Let’s assume that it is possible to get the device to produce as well in irregular waves under any wave conditions, and lets further assume that the yearly absorbed energy can be converted into electricity at a PTO-efficiency of 90 %. Under all those assumptions the results in table are found, i.e. a Nissum Bredning would produce 0.87 MWh/year and a North Sea device 85 MWh/year.

Proposta di traduzione parziale dal cinese di "Le avventure del topolino senza coda: Le uova decorate venute dal cielo". Un racconto di Liu Haiqi.

Il presente elaborato ha l'obiettivo di mostrare una proposta di traduzione dal cinese dei primi due capitoli di "Le avventure del topolino senza coda: le uova decorate venute dal cielo", terzo e ultimo episodio della serie scritta da Liu Haiqi, pubblicata nel 2012 dalla Jieli editrice. La prima parte è dedicata alle informazioni sull'autore, sulla serie, sul libro e sul contesto letterario in cui si inserisce, nonché alla presentazione della proposta di traduzione, il cui testo originale si trova in appendice. La seconda parte contiene l'analisi, il commento e i temi emersi dalla lettura del testo.

Riparazione del trave di coda di un Cessna Super Skymaster 337A danneggiato

Il presente elaborato ha lo scopo di descrivere le fasi di riparazione del trave di coda di un Cessna Super Skymaster 337A danneggiatosi durante le fasi di rimessaggio in hangar. Per prima cosa andremo ad analizzare le normative in materia di manutenzione degli aeromobili, in particolare la circolare 13 del RAI (Metodi accettabili per la manutenzione degli aeromobili) e la circolare 43.13-1A delle FAA (Acceptable methods, techniques, and practices-Aircraft ispection and repair). Verificheremo poi la tipologia del danno subito dal velivolo e, rifacendoci anche al Service Manual del costruttore, andremo a progettare la riparazione. Riparazioni estese a rivestimenti resistenti su strutture a guscio, infatti, devono preferibilmente essere fatte seguendo le specifiche raccomandazioni del costruttore dell’aeromobile. In molti casi, soprattutto se il danno non è esteso, le parti della riparazione possono essere progettate, e ne può essere dimostrata l’adeguata resistenza, senza calcolare i carichi e le sollecitazioni di progetto, considerando nel modo dovuto il materiale e le dimensioni delle parti originali e dei giunti chiodati. La cosa importante è che la parte riparata dovrà risultare pari all’originale per quanto riguarda la robustezza in relazione a tutti i tipi di carichi e alla rigidezza generale. Nel nostro caso andremo comunque a effettuare un’analisi strutturale per verificare l’effettiva correttezza dei principi contenuti nel manuale di manutenzione. Una volta verificato questo, procederemo con la realizzazione della riparazione soffermandoci sulle caratteristiche dei materiali utilizzati e sulle metodologie utilizzate durante la lavorazione. A lavoro ultimato trarremo poi le dovute conclusioni.

Surface-acoustic-wave counterflow micropumps for on-chip liquid motion control in two-dimensional microchannel arrays

Fully controlled liquid injection and flow in hydrophobic polydimethylsiloxane (PDMS) two-dimensional microchannel arrays based on on-chip integrated, low-voltage-driven micropumps are demonstrated. Our architecture exploits the surface-acoustic-wave (SAW) induced counterflow mechanism and the effect of nebulization anisotropies at crossing areas owing to lateral propagating SAWs. We show that by selectively exciting single or multiple SAWs, fluids can be drawn from their reservoirs and moved towards selected positions of a microchannel grid. Splitting of the main liquid flow is also demonstrated by exploiting multiple SAW beams. As a demonstrator, we show simultaneous filling of two orthogonal microchannels. The present results show that SAW micropumps are good candidates for truly integrated on-chip fluidic networks allowing liquid control in arbitrarily shaped two-dimensional microchannel arrays.

Chest pulse-wave velocity: a novel approach to assess arterial stiffness

Pulse-wave velocity (PWV) is considered as the gold-standard method to assess arterial stiffness, an independent predictor of cardiovascular morbidity and mortality. Current available devices that measure PWV need to be operated by skilled medical staff, thus, reducing the potential use of PWV in the ambulatory setting. In this paper, we present a new technique allowing continuous, unsupervised measurements of pulse transit times (PTT) in central arteries by means of a chest sensor. This technique relies on measuring the propagation time of pressure pulses from their genesis in the left ventricle to their later arrival at the cutaneous vasculature on the sternum. Combined thoracic impedance cardiography and phonocardiography are used to detect the opening of the aortic valve, from which a pre-ejection period (PEP) value is estimated. Multichannel reflective photoplethysmography at the sternum is used to detect the distal pulse-arrival time (PAT). A PTT value is then calculated as PTT = PAT - PEP. After optimizing the parameters of the chest PTT calculation algorithm on a nine-subject cohort, a prospective validation study involving 31 normo- and hypertensive subjects was performed. 1/chest PTT correlated very well with the COMPLIOR carotid to femoral PWV (r = 0.88, p < 10 (-9)). Finally, an empirical method to map chest PTT values onto chest PWV values is explored.

Assessment of right ventricular systolic function: Comparison between cardiac magnetic resonance derived ejection fraction and pulsed-wave tissue Doppler imaging of the tricuspid annulus

Systolic right ventricular (RV) function is an important predictor in the course of various congenital and acquired heart diseases. Its practical determination by echocardiography remains challenging. We compared routine assessment of lateral tricuspid annular systolic motion velocity (TV(lat), cm/s) using pulsed-wave tissue Doppler imaging from the apical 4-chamber view with cardiac magnetic resonance (CMR) as reference method.

Intermittent spike-wave dynamics in a heterogeneous, spatially extended neural mass model

Generalised epileptic seizures are frequently accompanied by sudden, reversible transitions from low amplitude, irregular background activity to high amplitude, regular spike-wave discharges (SWD) in the EEG. The underlying mechanisms responsible for SWD generation and for the apparently spontaneous transitions to SWD and back again are still not fully understood. Specifically, the role of spatial cortico-cortical interactions in ictogenesis is not well studied. We present a macroscopic, neural mass model of a cortical column which includes two distinct time scales of inhibition. This model can produce both an oscillatory background and a pathological SWD rhythm. We demonstrate that coupling two of these cortical columns can lead to a bistability between out-of-phase, low amplitude background dynamics and in-phase, high amplitude SWD activity. Stimuli can cause state-dependent transitions from background into SWD. In an extended local area of cortex, spatial heterogeneities in a model parameter can lead to spontaneous reversible transitions from a desynchronised background to synchronous SWD due to intermittency. The deterministic model is therefore capable of producing absence seizure-like events without any time dependent adjustment of model parameters. The emergence of such mechanisms due to spatial coupling demonstrates the importance of spatial interactions in modelling ictal dynamics, and in the study of ictogenesis.

Excitability and recruitment patterns of spinal motoneurons in human sleep as assessed by F-wave recordings

This study examines the excitability and recruitment of spinal motoneurons in human sleep. The main objective was to assess whether supraspinal inhibition affects the different subpopulations of the compound spinal motoneuron pool in the same way or rather in a selective fashion in the various sleep stages. To this end, we studied F-conduction velocities (FCV) and F-tacheodispersion alongside F-amplitudes and F-persistence in 22 healthy subjects in sleep stages N2, N3 (slow-wave sleep), REM and in wakefulness. Stimuli were delivered on the ulnar nerve, and F-waves were recorded from the first dorsal interosseus muscle. Repeated sets of stimuli were stored to obtain at least 15 F-waves for each state of vigilance. F-tacheodispersion was calculated based on FCVs using the modified Kimura formula. Confirming the only previous study, excitability of spinal motoneurons was generally decreased in all sleep stages compared with wakefulness as indicated by significantly reduced F-persistence and F-amplitudes. More importantly, F-tacheodispersion showed a narrowed range of FCV in all sleep stages, most prominently in REM. In non-REM, this narrowed range was associated with a shift towards significantly decreased maximal FCV and mean FCV as well as with a trend towards lower minimal FCV. In REM, the lowering of mean FCV was even more pronounced, but contrary to non-REM sleep without a shift of minimal and maximal FCV. Variations in F-tacheodispersion between sleep stages suggest that different supraspinal inhibitory neuronal circuits acting on the spinal motoneuron pool may contribute to muscle hypotonia in human non-REM sleep and to atonia in REM sleep.