Politecnio die Bari - Catalogo di prodotti della Ricerca
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Doppler Effect Estimation and Compensation for Satellite Systems in Geolocation Problems
Get PDFThe framework of the article is a theoretical investigation of the Doppler effect on electromagnetic signals. The target application is relevant to satellite missions with resource-constrained systems based on low-cost hardware platforms and the innovation of the paper is on the error compensation strategy and on the proposal of an approximate polynomial model. In particular, the scenario of interest considers a non-cooperative emitter of electromagnetic waves on the surface of the Earth and a receiver able to perform Angle of Arrival measurements embarked on a satellite in Low Earth Orbit. Assuming the problem of geolocation is solved, and starting from the kinematics of the satellite and its relative motion with respect to the emitter, the correction on the frequency is derived with respect to the orbital parameters, which is a common representation of data for satellite systems. The purpose of the paper is not only to provide a reference model to predict the necessary correction on the frequency of the signal due to the Doppler effect, but also to present a real-time strategy for compensation in the pipeline of signal processing after its geolocation. The main goal of the paper is to give real-time estimation and compensation strategy for the Doppler factor considering only the current instantaneous kinematic information, without the information on the history of the signal over time. Furthermore, data fitted from simulations show that a first degree polynomial model has a maximum error prediction on the order of less than 0.01 percent around Nadir pointing and can be appealing for fast computation of this correction with low-cost hardware based on Field Programmable Gate Array
Study of WH production through vector boson scattering and extraction of the relative sign of the W and Z couplings to the Higgs boson in proton-proton collisions at s=13TeV
No full textA search for the production of a W boson and a Higgs boson through vector boson scattering (VBS) is presented, using CMS data from proton-proton collisions at s=13TeV collected from 2016 to 2018. The integrated luminosity of the data sample is 138fb−1. Selected events must be consistent with the presence of two jets originating from VBS, the leptonic decay of the W boson to an electron or muon, possibly also through an intermediate τ lepton, and a Higgs boson decaying into a pair of b quarks, reconstructed as either a single merged jet or two resolved jets. A measurement of the process as predicted by the standard model (SM) is performed alongside a study of beyond-the-SM (BSM) scenarios. The SM analysis sets an observed (expected) 95% confidence level upper limit of 14.3 (9.9) on the ratio of the measured VBS WH cross section to that expected by the SM. The BSM analysis, conducted within the so-called κ framework, excludes all scenarios with λWZ<0 that are consistent with current measurements, where λWZ=κW/κZ and κW and κZ are the HWW and HZZ coupling modifiers, respectively. The significance of the exclusion is beyond 5 standard deviations, and it is consistent with the SM expectation of λWZ=1
Development of additive manufacturing processes for multi-material metal components
No full textThis thesis reports on all applications developed and published in the field of multi-material additive manufacturing with metal powders. The topics covered include several widely used technologies in the field of Additive Manufacturing (AM), such as Direct Energy Deposition (DED) and Laser Powder Bed Fusion (LPBF). The knowledge available in the literature on these categories of processes has served as a basis for the development of innovative studies and, in particular, for the optimisation, production and characterisation of artefacts consisting of metallic materials of different natures used simultaneously in the same process.
The text of the thesis has been divided into the following application categories:
1) Experiments using the LPBF process
a) Case studies where the transition between different materials is immediate (clear);
b) Case studies where the transition between different materials in gradual (cFGM).
2) Case studies using the DED process.
The most rigorous scientific methods available in the literature and the most advanced investigation techniques in powder metallurgy and laser processes were used in all phases of the experiments. In fact, it is possible to list the instruments used by subdividing them as shown below:
In the design phase of the experiment, various tools and methods are used. Bibliographic research is the first step to gather relevant information, followed by the use of statistical methods for Design of Experiments (DOE). Additionally, numerical simulations are conducted to model and predict the behavior of the system.
During the setup phase, the functionality and calibration of the equipment and instruments are checked to ensure they are ready for the experiment. Then, the necessary process parameters are set to perform the tests.
In the execution phase of the experiment, in-situ monitoring methods are used to control key process quantities (as geometrical features) and parameters. These include optical and thermal techniques, both on-axis and off-axis, to ensure that the process proceeds under the established conditions.
Next comes the process analysis phase, where techniques such as image analysis and control charts are used to evaluate the performance and stability of the process.
The characterization of specimens involves both non-destructive testing and more detailed analyses using Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), and X-ray Diffraction (XRD). In addition to these analyses, metallographic and mechanical characterizations are performed to determine the physical properties of the samples.
Finally, in the conclusion phase of the experiment, the results are analyzed to establish a correlation between the inputs and outputs using Analysis of Variance (ANOVA). Moreover, the numerical models developed during the design phase are validated.
The experiments carried out demonstrated that multi-material components produced by additive manufacturing processes are a real option, offering significant advantages in providing the optimum properties where they are required. Ad hoc fixtures were designed and built to produce test specimens on machines not designed for this purpose. In-process monitoring methods have provided important information for process optimisation, especially when analysed with appropriate statistical and image analysis tools
Reducing the environmental impact of manufacturing processes by means of natural based lubricants
No full textCold rolling and machining processes are significant in the manufacturing of products, as they are utilized to modify the product's geometry and to influence its mechanical properties. The process of cold rolling involves a reduction in the thickness of the strip below its recrystallization temperature, resulting in an improvement in surface quality and an enhancement in strength due to the work hardening. Friction and wear are intrinsic factors that contribute to increase the energy consumption and equipment degradation. While friction is a necessary component for the proper grip of the strip, it also affects the distribution of force and can accelerate the wear of the rolls. Therefore, it is essential to utilize lubricants to minimize excessive friction. On the other hand, machining is a process that involves the controlled removal of material using computer numerical control technology. The use of metalworking fluids plays a primary role as they reduce friction at the tool/workpiece interface, thereby enhancing dimensional accuracy, surface finish and reducing the required power. Effective lubrication also facilitates an efficient chip removal, thereby optimizing the overall machining process. Mineral-based oils persist as the dominant lubricant in engineering applications due to their accessibility, cost-effectiveness and compatibility with a range of materials. However, the extensive exploitation of mineral oils results in environmental concerns due to their non-biodegradable, soil-contaminating, rapidly depleting and volatile nature. Mineral oils have the potential to persist in ecosystems, thereby contaminating groundwater for up to a century and impacting both plant growth and aquatic life. A single liter of mineral oil has the potential to pollute up to one million liters of water, making it imperative to address these environmental impacts with urgency. In addition, in the period between 2010 and 2015, approximately 33000 tons of oil were released into the environment, with 700 tons of this being the result of major spill incidents. This has led to an intensification of global environmental efforts, driven by rising petroleum prices, depletion of oil reserves and increasingly strict regulations on the use of mineral oil.
This study was conducted in collaboration with the Italian company Kimya and proposes the use of eco-friendly lubricants as a viable alternative to traditional formulations. The objective of the research is to evaluate the performance of these innovative lubricants from multiple perspectives with the aim of determining whether they can be considered a solution that is at least as effective as - or potentially more effective than - conventional lubricants.
For the cold rolling process, two formulations of eco-friendly lubricants, derived from animal and vegetable sources, were examined and evaluated in comparison with a third commercial semi-synthetic formulation. The comparison was conducted both in the industrial environment by means of a test conducted on the two-stand reversing cold mill (RCM) at the Marcegaglia plant in Ravenna, Italy, and at the laboratory scale. The industrial test revealed that the use of the green formulations exhibited advantages in terms of reduced rolling forces, decreased electrical consumption and lower work roll's wear for a wide range of coils and conditions. Results were corroborated by tribological tests conducted using the CSM high-temperature pin-on-disk tribometer (which demonstrated a reduction in the coefficient of friction CoF of approximately 10%) and the Falex tribometer (which showed a 10% improvement in extreme pressure performance and a 15% reduction in the CoF).
Furthermore, two novel methodologies based on inverse analysis were presented for the investigation of the friction condition at the roll/strip interface, utilizing experimental data obtained from the RCM. The first methodology integrates a plane strain analytical model of the process within an optimization procedure managed by the multi-objective genetic algorithm MOGA-II. The optimization loop was capable of assessing four different values of the CoF for each stand of the two passes of the RCM by minimizing the discrepancy between the experimental and analytical rolling forces. The obtained values served to confirm the capability of the green formulations to consistently minimize the contact conditions. With regard to the second methodology, the process was simulated using the commercial finite element (FE) software Abaqus/CAE. The objective was to determine the CoF values in the two stands of the first pass by minimizing the difference between the experimental and numerical values of the rolling forces and inter-stand tension. Specifically, accurate metamodels were trained on the calculated error values using interpolating algorithms and integrated into the optimization procedure managed by the MOGA-II genetic algorithm. The results demonstrated that variations in the CoF not only affect the contact pressures in the roll bite of the same stand but also affect the friction conditions in the other stand.
As part of the environmental assessment, the treatment of the emulsion was investigated in two distinct scenarios: the first involved fresh emulsions, which were treated with a powder composed of bentonite and activated carbon, and the second involved waste emulsions from the RCM. For waste emulsions, two different treatment modalities were explored: the physical and the chemical treatment. The efficacy of the treatments was demonstrated by the low chemical oxygen demand (COD) and total surfactant content in the resulting aqueous phase, which permitted its reuse for the production of new emulsions with lubricating properties comparable to those of fresh emulsions.
For the machining processes, the animal-based lubricant was comparatively investigated with a commercial semi-synthetic one in terms of environmental impact and lubricating/anti-wear performance. With regard to the former aspect, the values of non-ionic surfactants and COD in the aqueous phase obtained after the chemical breaking of the emulsions were evaluated. For the second aspect, the performance of the emulsions at different concentrations was evaluated in both laboratory scale (using the Falex tribometer) and in the industrial production (tool flank wear assessment during turning operations). The chemical breaking revealed that the aqueous phase of the natural emulsion, both fresh and after several months of use, exhibited minimal non-ionic surfactant and COD content. From the perspective of the machining processes, tribological and wear tests demonstrated that the natural emulsion consistently resulted in a reduction in tool wear compared to the semi-synthetic emulsion
Transparent Graphene-Based RIS for 6G Communications in the THz Spectrum
No full textIn the quest for sixth-generation wireless communication technology (6G), Terahertz waves represent a key technology due to their distinct advantages over microwaves and infrared radiation. Reconfigurable intelligent surfaces (RIS) emerge as a critical technology within this context. This paper presents a numerical investigation and the optimized design of a transparent graphene-based RIS operating in the THz spectrum. The aim of the paper is twofold: the former is to demonstrate the reconfigurability of the proposed RIS by exploiting two methods, referred to as "digital"and "analogical". The latter is to demonstrate the effects of the losses and of the mutual coupling among unit cells on the power flow pattern. This aspect is crucial in the design of the RIS and cannot be overlooked, differently from other papers reported in the literature which analyze the RIS as an "ideal"structure evaluating only an analytical estimation of the array factor and neglecting the interaction among the unit cells. Our results hold significant promise for improving the development of a new class of smart devices crucial for 6G wireless communication systems
Il patrimonio militare oltre la dismissione. Il progetto per la ex Caserma Magrone di Bari
No full textThe process of decommissioning military areas calls for a rethinking of large portions of the city that were previously enclosed, keeping a vast and heterogeneous built heritage. The Ministry of Defence's Caserme Verdi project expressed the need to respond to the degradation of the military heritage through investments to upgrade infrastructure of the armed forces and recover existing buildings, opening up new possibilities for urban integration of the barracks.
Bari hosts large military areas, which weave different relationships with the parts of the city where they place themselves in terms of infrastructure and urban form. Some disused barracks have already undergone transformations, which have confronted the military heritage in its material consistency but have also expressed value judgements on it through design.
The former Magrone Barracks represents a relevant case study for the future regeneration processes of military areas in Bari as its transformation responds to the need to combine the innovation of technology transfer, public administration and public space with knowledge and design for the existing heritage of the armed force, aimed at interpreting its form and characters
