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FAOD (Malattie ossidazione degli acidi grassi): Indagini Biochimiche e Genetico-Molecolari in ambito di un programma di Screening Neonatale
No full textLa ricerca si è resa possibile grazie al conferimento della borsa di studio -Anno 2011/2012- da parte della Fondazione Achille Lattuc
Analysis of Heat Transfer Characteristics of Supercritical Fuels in Rocket Cooling Systems by a Space Marching Numerical Technique
No full textMethane and Liquefied Natural Gas (LNG) have been recently considered both for launch and for in-space applications because of several advantages they present if compared with other commonly used fuels. In particular, several studies are dedicated at the use of methane in liquid rocket engines with turbopumb fed systems. In this framework, the present study focuses on the use of methane or LNG as coolant in regenerative cooling systems. The study has two main purposes. The first is to understand what are the differences between using pure methane or LNG in a cooling system. The second purpose is to investigate on the heat transfer deterioration which is a thermodynamic phenomenon that could affect methane or LNG in cooling channels. The idea is to fulfill these objectives by numerical studies. The test cases that have to be analyzed are straight channels with circular cross section, a length of the order of the meter and a diameter of the order of the millimeter. The Reynolds number is of the order of 10^5 − 10^6 , which implies that the flow is turbulent. The coolant enters the channels with a supercritical pressure (∼10 MPa) and a subcritical temperature (∼ 110 K), which correspond to a very low compressibility. As a consequence, the inlet Mach number are very low (∼ 0.01). High heat fluxes up to 10 MW/m^2 are enforced along the channel. The temperature variations along the channel cause a change in all the thermophysical properties that strongly nfluence the coolant behavior.
Thermophysical properties of real fluids and mixtures of real fluids are used to carry out the present investigations. An equation of state based on the Helmholtz free energy is used for the thermodynamic properties. Transport property models are based on the extended corresponding states approach used in combination with accurate models for the transport properties of each considered species. A numerical code is developed pecifically to deal with the test cases of interest. It is based on parabolized Navier Stokes equations which can be solved with a space marching approach. The numerical model, used together with the selected thermophysical models, is validated against experimental data. Finally the developed code is used to obtain the desired results. First a comparison between LNG and pure methane behavior is carried out which permits to emphasize their different properties. In particular, the influence of the LNG composition on the coolant flow is analyzed.
Subsequently, study of the deterioration of the heat transfer is addressed both with
methane and LNG. Parametric studies permit to understand what are the main parameters involved in the phenomenon and how it can be handled
Romania, l’attuale situazione economica e le difficili prospettive di superamento della crisi
No full textPaper restoration and protection by using Gellan-gum gel
No full textTraditional wet restoration methods for librarian and archival artifacts - such as cleaning by immersion - present lots of limitations that are primarily due to the uncontrolled release of water to the paper supports.
An approach able to provide a more gradual release of water to the supports is needed. Using Gellan gum as gelling agent to optimise the presence of water and minimise the impact on the paper supports during cleaning treatments, this method was developed. The Gellan gum method can be used also for deacidification as well as for reductive bleaching pourposes.
Different analyses were carried out to assess the suitability and the effectiveness of cleaning treatments of paper artifacts. Some of these were conducted by water immersion, some others by cellulose ethers contact or by Gellan gum rigid gels contact. In particular, colourimetric analysis was performed to quantify colour modification. Microscopy investigations (including SEM) were employed to observe the structural modification possibly occurred on the paper surface. In order to compare the effectiveness of chemical stabilisation treatments, pH and alkaline reserve measurements were performed.
During the experiment, modern paper samples and original artifacts - considered "expendable" - are used.
Based on the acquired experience, results on three cases of studies are also presented.
Results show that the treatment by contact (Gellan gum) is a viable alternative to traditional methods of restoration in terms of effectiveness and safety. Moreover, Gellan gum gel is manageable, easy to use, inexpensive and respectful of the unique characteristics of the archival and librarian artifacts.
Concerning deacification and reductive bleaching, better results were obtained using Gellan gum as carrier for aqueous solutions with calcium propionate and borane terz-butylamine complex. This method provides an increase of pH values comparable to that achieved by immersion. Furthermore, it leaves an appreciable amount of alkaline reserve on the paper support.
The result obtained on the three case of studies show the same trend, in terms of color changes
A Reinforcement Learning based Cognitive Approach for Quality of Experience Management in the Future Internet
No full textThis thesis aims at providing an innovative contribution to the definition of the Future Internet Core Platform, in the frame of the "La Sapienza" University research activities on the EU FP7 FI-WARE project. The thesis introduces and designs an innovative "Cognitive Application Interface" in charge of deriving key parameters driving the Network Control elements to meet personalised Application Quality of Experience Requirements. The thesis proposes the innovative concept of a dynamic association between Applications and Classes of Service. A Reinforcement Learning based approach is followed. A solution based on a standard Q-learning algorithm is proposed. Simulation results obtained using the OPNET simulation tool are described. Preliminary work on an alternative solution based on a Foe Q-Learning algorithm is also illustrated. The proposed framework is very flexible, allows QoE personalization, requires low processing capabilities and entails a very limited signalling overhead
Energy Saving in IP over WDM Backbone Networks
No full textThe energy consumption of the Internet is exploding due to the increase of the number of devices connected to it as well as the increase of traffic volume that is estimated in about 50% per year fuelled by mobile data and video applications; consequently, it is crucial to improve network efficiency to prevent the Internet from being throttled by an energy bottleneck. This PhD dissertation deals with the energy efficiency of telecommunication networks and specifically faces the problem of saving energy in the backbone section of the network. The main contributions concern the definition of algorithms and mechanisms that integrate and exploit the knowledge of the network topology, the carried traffic and the power behaviour of network devices to achieve energy efficiency in the network. Three novel contributions are presented which are related to three different saving strategies.
The first faced problem concerns the design of energy efficient virtual topologies in two-layers IP over WDM networks. The problem is formalized as a Mixed Integer Linear Programming (MILP) problem and a novel heuristic algorithm, named Start-Single Hop and ReRoute, is proposed and compared with the optimal solution and another heuristic solution proposed in the literature. Results obtained through extended simulations demonstrate that the proposed solution is able to reduce the network energy consumption with respect to other solutions and to perform close to the optimal solution.
Another key aspect faced in the dissertation is related to the possibility of saving energy in presence of variable traffic exploiting traffic engineering strategies that aim at aggregating the traffic on a subset of network elements in order to put in sleeping unused devices. Concerning this point, an Energy Aware Traffic Engineering mechanism, named DAISIES, is proposed. Besides achieving good level of energy efficiency, the proposed solution overcome many practical issues rising from the adaptation of link switch-off mechanism, such as packet loss, out-of-order packet delivering and routing instabilities.
The last faced problem concerns the energy efficiency of the optical network layer. In this area a two different solutions are proposed. The first one is based on an iterative greedy algorithm that a posteriori tries to aggregate lightpaths on a subset of optical fibres links, re-optimizing the network when the traffic decreases. The second one, instead, directly works on lightpaths provisioning, exploiting a Power Aware Routing and Wavelength Assignment (PA-RWA) algorithm that tries to set up lightpaths in such a way that the total consumed energy is minimized. Specifically, the performance of the proposed PA-RWA algorithm is evaluated and compared with other solutions proposed in the literature showing better performance both in terms of energy efficiency and blocking probability.
In summary, this dissertation makes important contributions to the networking research community providing new methods and approaches for the definition of energy efficient networking techniques