Analisi dei sistemi radar passivi con segnali satellitari Inmarsat

L’obiettivo di questo lavoro di tesi è l’analisi delle forme d’onda emesse dal sistema di comunicazione satellitare Inmarsat e vedere se sono adatte ad essere sfruttate come illuminatori di opportunità in un sistema radar passivo. Per prima cosa ci siamo dedicati allo studio dei principi di funzionamento dei sistemi radar bistatici, cercando di evidenziare pregi e difetti di tale architettura studiandone la geometria e mettendo in luce le differenze con il caso monostatico. Il radar passivo è un sensore che non trasmette un normale segnale radar, ma sfrutta le emissioni elettromagnetiche di trasmettitori non cooperanti, come ad esempio stazioni TV, stazioni radio FM, basestation GSM, UMTS, o ancora radar spaziali e satelliti. Per queste ragioni il radar passivo si presenta come valida alternativa ai normali radar, in quanto potenzialmente meno ingombrante e più economico grazie alla mancanza del trasmettitore. La capacità di un radar passivo di individuare target dipende dalla potenza dell’illuminatore utilizzato. Infatti, radar passivi che sfruttano illuminatori broadcast di tipo terrestre possono coprire un area limitata, invece l‟impiego di un trasmettitore di tipo satellitare garantirebbe una copertura a livello globale. L‟utilizzo della rete di comunicazione satellitare Inmarsat presenta una nuova opportunità nell’impiego di questi segnali come illuminatori di opportunità per applicazioni di radar passivo. Quindi abbiamo studiato le caratteristiche dei segnali Inmarsat:tipo di modulazione,l’ampiezza della banda e le potenze dei sistemi di trasmissione. Lo studio di questi segnali ha rafforzato la loro candidatura come possibili illuminatori di opportunità. Ci siamo dedicati ad individuare le capacità di copertura del sistema radar passivo utilizzante il suddetto illuminatore di opportunità. Analizzata l’equazione bistatica del radar e individuato il volume spaziale in cui calcolare la copertura, è stato simulato il diagramma di irradiazione dei sistemi di antenna e sono state stabilite le caratteristiche dei possibili ricevitori. I valori ottenuti dai diagrammi di copertura rappresentano valide indicazioni del livello di potenza che si otterrebbero operando in presenza dei diversi tipi di illuminatore. Infine l’attenzione è stata incentrata sullo studio della sua funzione di ambiguità. Questo strumento analitico viene utilizzato per lo studio delle performance in termini di risoluzione in range e doppler. L’analisi è stata effettuata su un dato reale. In particolare il sistema di acquisizione è composto da una scheda USRP2 equipaggiata con una daughterboard DBSRX che lavora su una determinata banda alle frequenze di interesse . I risultati ottenuti hanno provato la fattibilità del sistema radar passivo basato su un illuminatore di opportunità staellitare inmarsat

cis-acting sequences and trans-acting factors in the localization of mRNA for mitochondrial ribosomal proteins

mRNA localization is a conserved post-transcriptional process crucial for a variety of systems. Although several mechanisms have been identified, emerging evidence suggests that most transcripts reach the protein functional site by moving along cytoskeleton elements. We demonstrated previously that mRNA for mitochondrial ribosomal proteins are asymmetrically distributed in the cytoplasm, and that localization in the proximity of mitochondria is mediated by the 3′-UTR. Here we show by biochemical analysis that these mRNA transcripts are associated with the cytoskeleton through the microtubule network. Cytoskeleton association is functional for their intracellular localization near the mitochondrion, and the 3′-UTR is involved in this cytoskeleton-dependent localization. To identify the minimal elements required for localization, we generated DNA constructs containing, downstream from the GFP gene, deletion mutants of mitochondrial ribosomal protein S12 3′-UTR, and expressed them in HeLa cells. RT-PCR analysis showed that the localization signals responsible for mRNA localization are located in the first 154 nucleotides. RNA pulldown assays, mass spectrometry, and RNP immunoprecipitation assay experiments, demonstrated that mitochondrial ribosomal protein S12 3′-UTR interacts specifically with TRAP1 (tumor necrosis factor receptor-associated protein1), hnRNPM4 (heterogeneous nuclear ribonucleoprotein M4), Hsp70 and Hsp60 (heat shock proteins 70 and 60), and α-tubulin in vitro and in vivo

Ribosomal protein uL3 targets E2F1 and Cyclin D1 in cancer cell response to nucleolar stress

Several experimental strategies in the treatment of cancer include drug alteration of cell cycle regulatory pathways as a useful strategy. Extra-ribosomal functions of human ribosomal protein L3 (uL3) may affect DNA repair, cell cycle arrest and apoptosis. In the present study, we demonstrated that uL3 is required for the activation of G1/S transition genes. Luciferase assays established that uL3 negatively regulates the activity of E2F1 promoter. Induced ribosome-free uL3 reduces Cyclin D1 mRNA and protein levels. Using protein/protein immunoprecipitation methods, we demonstrated that uL3 physically interacts with PARP-1 affecting E2F1 transcriptional activity. Our findings led to the identification of a new pathway mediated by uL3 involving E2F1 and Cyclin D1 in the regulation of cell cycle progression

Forget-me-not: History-less Mobile Messaging

Text messaging has long been a popular activity, and today smartphone apps enable users to choose from a plethora of mobile messaging applications. While we know a lot about SMS practices, we know less about practices of messaging applications. In this paper, we take a first step to explore one ubiquitous aspect of mobile messaging – messaging history. We designed, built, and trialled a mobile messaging application without history—named forget-me-not. The two-week trial showed that history-less messaging no longer supports chit-chat as seen in e.g. WhatsApp, but is still considered conversational and more ‘engaging’. Participants expressed being lenient and relaxed about what they wrote. Removing the history allowed us to gain insights into what uses history has in other mobile messaging applications, such as planning events, allowing for distractions, and maintaining multiple conversation threads

NEW APPROACHES FOR VERY SHORT-TERM STEADY-STATE ANALYSIS OF AN ELECTRICAL DISTRIBUTION SYSTEM WITH WIND FARMS

Distribution networks are undergoing radical changes due to the high level of penetration of dispersed generation. Dispersed generation systems require particular attention due to their incorporation of uncertain energy sources, such as wind farms, and due to the impacts that such sources have on the planning and operation of distribution networks. In particular, the foreseeable, extensive use of wind turbine generator units in the future requires that distribution system engineers properly account for their impacts on the system. Many new technical considerations must be addressed, including protection coordination, steady-state analysis, and power quality issues. This paper deals with the very short-term, steady-state analysis of a distribution system with wind farms, for which the time horizon of interest ranges from one hour to a few hours ahead. Several wind-forecasting methods are presented in order to obtain reliable input data for the steady-state analysis. Both deterministic and probabilistic methods were considered and used in performing deterministic and probabilistic load-flow analyses. Numerical applications on a 17-bus, medium-voltage, electrical distribution system with various wind farms connected at different busbars are presented and discusse

Voltage stability in unbalanced power systems: A new complementarity constraints-based approach

Voltage stability has become a fundamental issue in the new, liberalized markets due to the fact that the new power systems are approaching more and more the stability limits. Then, several approaches were proposed in the relevant literature to find the critical conditions and recently the problem was faced also with reference to unbalanced three phase power systems. The unbalances, in fact, can be responsible of more critical stability conditions than in balanced power systems. Continuation power flow and optimal power flows were applied to analyze such conditions. This paper deals with voltage stability analysis in unbalanced power systems and proposes a new optimization model to determine the critical point based on the use of complementarity constraints. Different formulations, with increasing complexity, of the optimization model are proposed and tested. In particular, the maximum stability margin is calculated by a single-stage or a multi-stage procedure that accounts for the relationship between the actual operating point and the maximum loading point. In addition, the multi-stage maximum stability margin problem is formulated also in a probabilistic framework to account for the uncertainties affecting the input data (e.g., load powers). An application is presented on a test system highlighting the feasibility and the goodness of the proposed technique. Both load and line unbalances are taken into account to capture the dependence of voltage stability on the level of unbalances