Active control of micro-vibration in sandwich panels for space applications

LAUREA MAGISTRALELe presenti e future missioni spaziali presenteranno requisiti da soddisfare sempre più stringenti. In particolare quelli legati al precision pointing. Essi sono talmente stringenti che anche il minimo tremolio indotto sul payload potrebbe compromettere le performance dell'intera missione. Una delle cause di tali effetti negativi è rappresentata dalle cosiddette micro-vibrations. Esse sono piccole vibrazioni indotte sulle strutture ove è situato il payload. Tale fenomeno è inevitabile poichè queste vibrazioni sono generate da dispositivi essenziali per la missione, come ad esempio reaction wheels, oppure da fenomeni come il cosiddetto propellant sloshing. Dunque, agire sulle strutture di supporto del payload con l'obiettivo di attenuare le suddette micro-vibrazioni ha già iniziato ad essere considerata parte rilevante e importante durante la fase di sviluppo di un progetto per una missione spaziale. L'obiettivo di questa tesi è fornire una prova di fattibilità riguardo un dispositivo semplice e affidabile da poter essere montato sulle strutture interessate da questo problema. Lo scopo di tale dispositivo è quello di controllare attivamente la struttura per minimizzare lo spostamento, e quindi il tremolio, nei punti in cui è montato il payload grazie alla local direct velocity feedback control law (una legge di controllo per cui l'attuatore agisce in base alla velocità nel punto in cui è montato). In aggiunta a ciò, la struttura di supporto considerata nel presente lavoro è un pannello sandwich, dato il sempre maggiore impiego di tali strutture nel settore aerospaziale.Present and future space missions need always more stringent requirements about precision pointing. They are so stringent that even the minimum jitter induced to the payload could significantly degradate the performances of the mission. One of the causes of such detrimental effects on the mission's performances is represented by micro-vibrations induced on the spacecraft's structure where the payload is installed. Such phenomenon is unavoidable because it is generated by essential devices, such as reaction wheels, or other phenomena taking place during the mission as propellant sloshing, for instance. Therefore, acting on the supporting structures for micro-vibration attenuation has become a relevant part in current project life cycle. The purpose of this thesis is to provide a proof of concept relative to a simple and reliable device to be mounted on the affected structure. The aim of such device is to actively control the structure to minimise the displacement at payload location by means of a local direct velocity feedback control law. Furthermore, the considered supporting structure is a sandwich panel because of the increasing employment of such structures in the aerospace sector

Optimal dry port configuration for container terminals: A non-linear model for sustainable decision making

In recent years the maritime freight transport has rapidly increased, causing congestion in many port areas. In some cases, in order to improve the capacity and the reliability of the temporary storage, a solution, recommended by industry officials, is the expansion of the terminal capacity. When this solution is not available, the ‘dry port’ area represents an effective alternative. The adoption of a dry port, if on one hand leads to benefits on terminal congestion, on the other hand requires resources and investments due to the transport of the container from port to dry port and vice versa. In the evaluation of the strategy to be adopted different aspects shall be evaluated to estimate time required for the container handling inside and outside the terminal on the basis of the congestion degree. In this paper, to support decision makers in identifying the best strategy to be adopted, a mathematical model allowing to identify the number of containers to be stocked in port and/or in dry port is defined considering the intra-/inter-terminal handling of the containers, in order to minimize the overall running costs and of the carbon footprint. The model, based on a computational algorithm for non-linear programming, is able to provide the number of containers to be stocked in port and/or in dry port, ensuring an effective strategy dependent on ‘road’ and ‘non-road' material handling equipment adopted, on the number and size of containers, as well as on the distance from port to dry port. Results obtained from numerical experiments show that, on the basis of the running cost and the carbon footprint of the container handling activities, it is possible to identify the most economic and eco-friendly container handling configuration. The case study of the Port of Bari (Italy) is investigated. In this case, given the overall number of containers to be stocked and the distance between port and dry port, the solutions found by the model identify a configuration able to ensure a reduction of 7% and 11% of the running cost and of the carbon footprint, respectively, when compared to the configuration in which all containers are stored in the port

A Control Strategy for Smart Energy Charging of Warehouse Material Handling Equipment

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An analytical framework for assessing cognitive capacity and processing speed of operators in industry 4.0

Abstract The fourth industrial revolution introduced a new paradigm in manufacturing systems. The digital network is at the basis of the smart manufacturing and the physical context is strictly related to the artificial intelligence. This new manufacturing context drastically changed the role of the operator since the increasing adoption of innovative devices in manufacturing process modified the work activities and the operator is employed in more cognitive than physical tasks. Therefore, the purpose of this paper consists in developing an analytical framework to assess the human cognitive capacity occupancy and the human processing time of correct information known as the quality performance. The analytical framework presented allows to assess the human mental workload imposed by the task and how the processing speed of correct information changes when quality performance varies

Life Cycle Assessment Of Production And Assembly Lines: A Research Agenda

As one of the largest consumers of energy and raw materials, manufacturing is responsible for a significant share of global greenhouse gas emissions, pollution, and resource depletion. However, it also holds the potential to lead the transition towards a more sustainable economy by adopting cleaner technologies, improving energy efficiency, and embracing circular economy practices. The impact of manufacturing systems needs to be assessed through methods able to detect the main emission hotspots and areas of inefficiency that are responsible of negative environmental impacts. Among the extant methodologies, Life Cycle Assessment (LCA) has been detected as the most promising one to play this role. Nevertheless, currently, conceptual models are missing in literature to effectively support the practical and tailored implementation of the LCA methodology in manufacturing. To ground the basis to build such model, through a systematic literature review, the aim of this paper is to investigate which are the theoretical and empirical gaps and limitations related to the application of LCA for evaluating the environmental impact of assembly or production plants. The analysis allowed to define which type of issues are related with the different types of production systems and LCA phases, supporting researchers and practitioners in the definition of the main requirements and functionalities that an LCA-based model should possess in manufacturing

Does Adiponectin Act as an Antiangiogenic Factor in B-Cell Chronic Lymphocytic Leukemia?

Angiogenesis is involved in the pathogenesis of B-cell chronic lymphocytic leukemia (CLL), and high microvascular density has been found in CLL to be associated with a poor prognosis. In this study, we assessed serum levels of adiponectin in 69 patients with Binet stage A B-CLL, and these values were retrospectively correlated with bone marrow (BM) microvessel area and serum levels of vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), angiogenin, PECAM-1 (CD31), matrix metalloproteinase-9 (MMP-9), interleukin-8 (IL-8), syndecan-1, and the percentage of CD38+ or ZAP-70+ CLL cells. The positive correlation between serum levels of adiponectin and VEGF (P = .03) does not translate into an increase of the extent of BM angiogenesis (P = .404), FGF-2 (P = .348), angiogenin (P = .402), and CD31 (P = .248) serum concentrations. Accordingly, IL-8 (P = .175), syndecan-1 (P = .06), and MMP-9 (P = .144) circulating levels were not likely to reflect adiponectin concentration. Furthermore, patients with higher levels of adiponectin had a more favorable biological profile as defined by a lower number of both CD38− (r = −0.294; P = .02) and ZAP-70+ (r = −0.285; P = .04). Finally, we evaluated the presence of adiponectin in B-CLL cells at gene expression level. RMA intensity values for adiponectin gene transcript denote a homogeneous low expression in B-CLL cells, whereas VEGF transcript was highly expressed with a degree of interpatient variability. Overall, these data seem to indicate that adiponectin could be involved as an antiangiogenic factor in B-CLL