Synchronization algorithms for modern aeronautical ground communications

The task covered by the this thesis has been to develop and implement the synchronization algorithms for the physical layer of an aeronautical communication system for both the forward link and the reverse link

Energy Efficient Control and Fault Detection for HVAC Systems

The interest in HVAC (Heating, Ventilation and Air-Conditioning) technology has rapidly increased in the last years. HVAC systems have become important in the design of medium-large buildings in order to ensure thermal comfort in the environments with respect to the temperature and humidity of the air. Control, optimisation and maintenance procedures are fundamental in HVAC systems in order to guarantee people comfort and energy efficient solutions in their management. Two different topics are covered in this thesis. Energy Efficient Control of Ice Thermal Energy Storage Systems HVAC plants have recently begun to be matched with thermal energy storage systems. If properly designed, installed, and maintained, these systems can be used to store energy when its cost is low and exploiting it when the price increases. In particular, in HVAC cooling systems, a common thermal storage medium is ice. From a control and optimisation point of view, a cooling plant with ice storage proves to be a complex system. Standard control strategies seem not to be able to achieve the right trade-off between energy efficiency and demand satisfaction. In this thesis, in order to design efficient control strategies for storage systems, a HVAC model with ice storage is developed in a simulation environment. The thermal behaviour of the HVAC system is derived from the mass and energy conservation equations; in particular the ice storage is considered a hybrid system, thus taking into consideration both sensible and latent heat. Three standard control methods are compared with a non-linear predictive control strategy. The simulations results show that the implemented non-linear predictive control strategy provides the best control for the efficient energy management of ice storage systems. Fault Detection in HVAC Systems Operating problems associated with degraded equipment, poor maintenance, and improperly implemented controls, plague many HVAC systems. Fault detection methods can therefore play a key role in monitoring complex HVAC plants, detecting anomalous behaviours in such a way as to keep the systems in their best operational conditions with minimum costs. In this thesis, fault detection and diagnosis methods on variable air volume (VAV) systems are first designed. To this aim, a VAV system model with two zones is developed; the control of system is obtained with a direct feedback linearisation technique. Supervised classification methods are used to detect and diagnose the simulated faults in the model. The simulations results show the good performances of the classification in the detection and diagnosis of the most common faults in VAV systems. Detection methods are then developed for the most relevant faults affecting chillers. To this aim, data collected in the research project 1043-RP promoted by ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) are used. In this project experimental studies were conducted on a centrifugal water-cooled chiller in order to collect data in both normal and faulty situations. The developed technique is based on one-class classification methods with a novelty detection approach, where only normal data are used to characterize the correct system behaviour. The classification results confirm the effectiveness of the proposed method for the detection of the most common faults in chillers

The miR-144/451 locus is required for erythroid homeostasis.

The process of erythropoiesis must be efficient and robust to supply the organism with red bloods cells both under condition of homeostasis and stress. The microRNA (miRNA) pathway was recently shown to regulate erythroid development. Here, we show that expression of the locus encoding miR-144 and miR-451 is strictly dependent on Argonaute 2 and is required for erythroid homeostasis. Mice deficient for the miR-144/451 cluster display a cell autonomous impairment of late erythroblast maturation, resulting in erythroid hyperplasia, splenomegaly, and a mild anemia. Analysis of gene expression profiles from wild-type and miR-144/451-deficient erythroblasts revealed that the miR-144/451 cluster acts as a "tuner" of gene expression, influencing the expression of many genes. MiR-451 imparts a greater impact on target gene expression than miR-144. Accordingly, mice deficient in miR-451 alone exhibited a phenotype indistinguishable from miR-144/451-deficient mice. Thus, the miR-144/451 cluster tunes gene expression to impart a robustness to erythropoiesis that is critical under conditions of stress

Intestinal region-specific Wnt signalling profiles reveal interrelation between cell identity and oncogenic pathway activity in cancer development.

BACKGROUND: Cancer results from the accumulation of mutations leading to the acquisition of cancer promoting characteristics such as increased proliferation and resistance to cell death. In colorectal cancer, an early mutation leading to such features usually occurs in the APC or CTNNB1 genes, thereby activating Wnt signalling. However, substantial phenotypic differences between cancers originating within the same organ, such as molecular subtypes, are not fully reflected by differences in mutations. Indeed, the phenotype seems to result from a complex interplay between the cell-intrinsic features and the acquired mutations, which is difficult to disentangle when established tumours are studied. METHODS: We use a 3D in vitro organoid model to study the early phase of colorectal cancer development. From three different murine intestinal locations we grow organoids. These are transformed to resemble adenomas after Wnt activation through lentiviral transduction with a stable form of β-Catenin. The gene expression before and after Wnt activation is compared within each intestinal origin and across the three locations using RNA sequencing. To validate and generalize our findings, we use gene expression data from patients. RESULTS: In reaction to Wnt activation we observe downregulation of location specific genes and differentiation markers. A similar effect is seen in patient data, where genes with significant differential expression between the normal left and right colon are downregulated in the cancer samples. Furthermore, the signature of Wnt target genes differs between the three intestinal locations in the organoids. The location specific Wnt signatures are dominated by genes which have been lowly expressed in the tissue of origin, and are the targets of transcription factors that are activated following enhanced Wnt signalling. CONCLUSION: We observed that the region-specific cell identity has a substantial effect on the reaction to Wnt activation in a simple intestinal adenoma model. These findings provide a way forward in resolving the distinct biology between left- and right-sided human colon cancers with potential clinical relevance

Control of intestinal stem cell function and proliferation by mitochondrial pyruvate metabolism.

Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells

The reproducibility of biomedical research: sleepers awake!

There is increasing concern about the reliability of biomedical research, with recent articles suggesting that up to 85% of research funding is wasted. This article argues that an important reason for this is the inappropriate use of molecular techniques, particularly in the field of RNA biomarkers, coupled with a tendency to exaggerate the importance of research findings

Energy Efficient Control and Fault Detection for HVAC Systems

The interest in HVAC (Heating, Ventilation and Air-Conditioning) technology has rapidly increased in the last years. HVAC systems have become important in the design of medium-large buildings in order to ensure thermal comfort in the environments with respect to the temperature and humidity of the air. Control, optimisation and maintenance procedures are fundamental in HVAC systems in order to guarantee people comfort and energy efficient solutions in their management. Two different topics are covered in this thesis. Energy Efficient Control of Ice Thermal Energy Storage Systems HVAC plants have recently begun to be matched with thermal energy storage systems. If properly designed, installed, and maintained, these systems can be used to store energy when its cost is low and exploiting it when the price increases. In particular, in HVAC cooling systems, a common thermal storage medium is ice. From a control and optimisation point of view, a cooling plant with ice storage proves to be a complex system. Standard control strategies seem not to be able to achieve the right trade-off between energy efficiency and demand satisfaction. In this thesis, in order to design efficient control strategies for storage systems, a HVAC model with ice storage is developed in a simulation environment. The thermal behaviour of the HVAC system is derived from the mass and energy conservation equations; in particular the ice storage is considered a hybrid system, thus taking into consideration both sensible and latent heat. Three standard control methods are compared with a non-linear predictive control strategy. The simulations results show that the implemented non-linear predictive control strategy provides the best control for the efficient energy management of ice storage systems. Fault Detection in HVAC Systems Operating problems associated with degraded equipment, poor maintenance, and improperly implemented controls, plague many HVAC systems. Fault detection methods can therefore play a key role in monitoring complex HVAC plants, detecting anomalous behaviours in such a way as to keep the systems in their best operational conditions with minimum costs. In this thesis, fault detection and diagnosis methods on variable air volume (VAV) systems are first designed. To this aim, a VAV system model with two zones is developed; the control of system is obtained with a direct feedback linearisation technique. Supervised classification methods are used to detect and diagnose the simulated faults in the model. The simulations results show the good performances of the classification in the detection and diagnosis of the most common faults in VAV systems. Detection methods are then developed for the most relevant faults affecting chillers. To this aim, data collected in the research project 1043-RP promoted by ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) are used. In this project experimental studies were conducted on a centrifugal water-cooled chiller in order to collect data in both normal and faulty situations. The developed technique is based on one-class classification methods with a novelty detection approach, where only normal data are used to characterize the correct system behaviour. The classification results confirm the effectiveness of the proposed method for the detection of the most common faults in chillers.Negli ultimi anni l’interesse per la tecnologia HVAC (Heating, Ventilation and Air-Conditioning) è rapidamente cresciuto. I sistemi HVAC sono diventati importanti nella progettazione di edifici medio-grandi al fine di assicurare comfort termico negli ambienti rispetto alla temperatura e umidità dell’aria. Procedure di controllo, ottimizzazione e manutenzione sono fondamentali nei sistemi HVAC al fine di garantire il comfort delle persone e soluzioni energeticamente efficienti nella loro gestione. In questa tesi vengono trattati due diversi argomenti. Controllo Energeticamente Efficiente di Sistemi ad Accumulo di Energia Termica a Ghiaccio Recentemente si è cominciato ad abbinare impianti HVAC con sistemi ad accumulo di energia termica. Se adeguatamente progettati, installati e mantenuti, questi sistemi possono essere usati per accumulare energia quando il suo costo è basso e sfruttandola quando il prezzo aumenta. In particolare, nei sistemi HVAC per raffreddamento, un mezzo diffuso per accumulo termico è il ghiaccio. Da un punto di vista di controllo e ottimizzazione, un impianto per raffreddamento con accumulo a ghiaccio si dimostra essere un sistema complesso. Strategie di controllo standard non sembrano essere capaci di ottenere il giusto compromesso tra efficienza energetica e soddisfacimento della domanda. In questa tesi, al fine di progettare strategie di controllo efficiente per sistemi con accumulo, si sviluppa in un ambiente di simulazione un modello HVAC con accumulo a ghiaccio. Il comportamento termico del sistema HVAC viene derivato dalle equazioni di conservazione di massa e energia; in particolare l’accumulo a ghiaccio viene considerato un sistema ibrido, tenendo così in considerazione sia il calore sensibile sia quello latente. Tre metodi di controllo standard vengono confrontati con una strategia di controllo predittivo non-lineare. I risultati delle simulazioni mostrano che la strategia di controllo predittivo non-lineare implementata fornisce il migliore controllo per una gestione energeticamente efficiente di sistemi con accumulo a ghiaccio. Rilevamento Guasti in Sistemi HVAC Problemi di funzionamento associati ad apparati degradati, scarsa manutenzione, e controlli erroneamente implementati, affliggono molti sistemi HVAC. Metodi di rilevamento guasti possono dunque giocare un ruolo chiave nel monitorare impianti HVAC complessi, rilevando comportamenti anomali in modo da mantenere i sistemi nelle loro migliori condizioni operative a costo minimo. In questa tesi vengono dapprima progettati metodi di rilevamento e diagnosi guasti su sistemi a tutta aria a portata variabile (VAV-Variable Air Volume). A questo scopo, viene sviluppato un modello di un sistema VAV con due zone; il controllo del sistema viene ottenuto con una tecnica di direct feedback linearisation. Metodi di classificazione supervisionati vengono usati per rilevare e diagnosticare i guasti simulati nel modello. I risultati delle simulazioni mostrano le buone performance della classificazione nel rilevamento e diagnosi dei guasti più diffusi nei sistemi VAV. Vengono successivamente sviluppati metodi di rilevamento per i guasti più rilevanti che affliggono i refrigeratori di liquido (chiller). A questo scopo, vengono utilizzati i dati raccolti nel progetto di ricerca 1043-RP promosso da ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers). In questo progetto sono stati condotti studi sperimentali su un chiller centrifugo raffreddato ad acqua al fine di raccogliere dati sia in situazioni normali sia in situazioni in presenza di guasto. La tecnica sviluppata si basa su metodi di classificazione a una classe con un approccio di novelty detection, dove solamente dati normali vengono utilizzati per caratterizzare il comportamento corretto del sistema. I risultati di classificazione confermano l’efficacia del metodo proposto per il rilevamento dei guasti più diffusi nei chiller

Algoritmi per la previsione del carico in applicazioni HVAC

Il lavoro si pone come obiettivo l’applicazione di metodi e algoritmi per la previsione del carico in sistemi HVAC (Heating, Ventilating and Air Conditioning). La previsione risulta utile per il risparmio energetico durante il periodo caldo dell’anno. Infatti al fine di ridurre la richiesta di raffreddamento durante il periodo diurno e i costi energetici del sistema, è possibile utilizzare un accumulo frigorifero: questa tecnica consiste nella produzione durante il periodo notturno di tutta o di una parte dell’energia frigorifera richiesta durante il periodo diurno. L’energia frigorifera può essere accumulata sotto forma di acqua refrigerata o di ghiaccio. Per quantificare l’energia da accumulare durante il periodo notturno è necessaria una previsione del carico per le ore diurne successive. La previsione viene elaborata utilizzando principalmente tecniche di identificazione e reti neurali artificiali. Diverse prove simulative verificano la qualità della previsione ottenuta con gli algoritmi utilizzati