Studio del protocollo SIP in presenza di collegamenti satellitari

In questo lavoro è stato affrontato il problema della segnalazione SIP su link satellitare, con particolare attenzione all'interazione tra i timer SIP e i gli elevati ritardi del link satellitare. Sono state analizzate le prestazioni in termini di CSD(Call setup delay), percentuali di sessioni fallite e throughput

Analisi delle performance di sistemi di Mixed Reality cooperativi in rete locale

Siamo sempre stati abituati fin dal principio ad interagire con l’ambiente che ci circonda, utilizzando gli oggetti fisici presenti attorno a noi per soddisfare le nostre esigenze, ma se esistesse di più di questo? Se fosse possibile avere attorno a noi oggetti che non sono propriamente corpi fisici, ma che hanno un comportamento coerente con l’ambiente circostante e non venisse percepita la differenza tra essi e un vero e proprio oggetto? Ci si sta riferendo a quella che oggi viene chiamata Mixed Reality, una realtà mista resa visibile tramite appositi dispositivi, in cui è possibile interagire contemporaneamente con oggetti fisici e oggetti digitali che vengono chiamati ologrammi. Un aspetto fondamentale che riguarda questa tipologia di sistemi è sicuramente la collaborazione. In questa tesi viene esaminato il panorama delle tecnologie allo stato dell'arte che permettono di vivere esperienze di Collaborative Mixed Reality, ma soprattutto ci si concentra sulla progettazione di una vera e propria architettura in rete locale che consenta la realizzazione di un sistema condiviso. Successivamente all'applicazione di varie strategie vengono valutati i risultati ottenuti da rigorose misurazioni, per determinare scientificamente le prestazioni dell'architettura progettata e poter trarre delle conclusioni, considerando analogie e differenze rispetto ad altre possibili soluzioni

Optimization of WAAM Deposition Patterns for T-crossing Features

AbstractAmong emerging additive manufacturing technologies for metallic components, WAAM (Wire and Arc Additive Manufacturing) is one of the most promising. It is an arc based technology characterized by high productivity, high energy efficiency and low raw material cost. Anyway, it has some drawbacks limiting its diffusion in the industry. One is the open issue about the layer deposition strategy that must be manually optimized in order to reduce as possible the residual stress and strains, efficiently matching the geometrical characteristics of the component to build and assure a constant height for each layer. This work deals with the definition of deposition paths for WAAM. The choice of a path must be carried out as a compromise between productivity and material usage efficiency. In the present paper, the process to select an optimized strategy for the manufacturing of T-crossing features will be shown

Editorial of Special Issue "Embolization Techniques: State of the Art and Future Perspectives"

Embolization is one of the most important applications in interventional radiology which can be mainly performed using an endovascular approach [...]

Selection of Optimal Process Parameters for Wire Arc Additive Manufacturing

Abstract This paper is about the optimal selection of process parameters for Wire Arc Additive Manufacturing technology, an emerging solution for additive production of metal parts. In particular, the selection of the process parameters is based on the evolution of the microstructure and on the mechanical properties of the final samples obtained through the successive deposition weld beads of a ER70S-6 steel, according to the AWS legislation. The feed rate and the heat input during the deposition of the weld beads have been varied, in order to understand how the temperature reached by the samples can affect the final product mechanical characteristics. The final cooling has been carried in calm air at room temperature and between the deposition of a weld bead and the following one it has been imposed a pause of 60s. The tests on mechanical properties carried out have been: A full experimental campaign that includes: macrographic observations, micrographic observations and Vickers microhardness. The analysis of these tests has highligthed that by varying the process parameters, the samples do not have substantial differences between them. Instead, a microstructure that evolves from pearlitic-ferritic grains until bainitic lamellae along the vertical direction of the samples has been observed by micrographic analysis and confirmed by microhardness measurements

Transcatheter Aortic Valve Implantation (TAVI) Planning with Dual-Layer Spectral CT Using Virtual Monoenergetic Image (VMI) Reconstructions and 20 mL of Contrast Media

Transcatheter aortic valve implantation (TAVI) is a less invasive alternative to surgical implantation and its implementation is progressively increasing worldwide. We routinely perform pre-procedural aortic angiography CT to assess aortic dimensions and vascular anatomy. This study aims to evaluate the image quality of CTA for TAVI planning using dual-layer spectral CT, with virtual monoenergetic image reconstructions at 40 keV. Thirty-one patients underwent a CTA protocol with the injection of 20 mL of contrast media. Image quality was assessed by measuring the mean density in Hounsfield Units (HU), the signal-to-noise ratio, and the contrast-to-noise ratio in VMI reconstructions. Additionally, a blinded subjective analysis was conducted by two observers. The results showed significant enhancement at all sampled vascular levels with a gradual decrease in HU from proximal to distal regions. Favourable subjective ratings were given for all parameters, with greater variability in the evaluation of iliac axes. A significant negative correlation (p < 0.05) was observed between BMI and CA at all vascular levels, indicating reduced contrast enhancement with increasing BMI. Spectral CT, along with reducing iodine load, allows for obtaining high-quality images without a significant increase in noise. The reduction in iodine load can have positive implications in clinical practice, improving patient safety and resource efficiency