Efficient fault diagnosis of helicopter gearboxes

Application of a diagnostic system to a helicopter gearbox is presented. The diagnostic system is a nonparametric pattern classifier that uses a multi-valued influence matrix (MVIM) as its diagnostic model and benefits from a fast learning algorithm that enables it to estimate its diagnostic model from a small number of measurement-fault data. To test this diagnostic system, vibration measurements were collected from a helicopter gearbox test stand during accelerated fatigue tests and at various fault instances. The diagnostic results indicate that the MVIM system can accurately detect and diagnose various gearbox faults so long as they are included in training

Διερεύνηση συνθηκών στερεομεταφοράς και κυματικής διαταραχής στο εσωτερικό διατάξεων μαρινών

177 σ.Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Επιστήμη και Τεχνολογία Υδατικών Πόρων”Θέμα της διπλωματικής εργασίας είναι η διερεύνηση του σχεδιασμού μιας μαρίνας σε σχέση με την κυματική διαταραχή και τη στερεομεταφορά στο εσωτερικό της λιμενολεκάνης της. Το κυματικό καθεστώς στο εσωτερικό μικρών λιμένων και μαρινών είναι ένας σημαντικός παράγοντας για την ομαλή και ασφαλή λειτουργία τους και είναι ένα θέμα που χρήζει ιδιαίτερης προσοχής κατά τον σχεδιασμό τους. Ταυτόχρονα, η προωθούμενη ενέργεια στο εσωτερικό λιμενολεκανών επηρεάζει σημαντικά τις διαδικασίες στερεομεταφοράς στο εσωτερικό της. Στόχος της παρούσας εργασίας είναι σε πρώτο στάδιο να διερευνηθούν οι κυματικές συνθήκες στο εσωτερικό διαφορετικών διατάξεων μαρινών και να εξεταστεί αν είναι ασφαλείς και λειτουργικές με βάση διεθνείς κανονισμούς. Σε δεύτερο στάδιο, και με βάση τα συμπεράσματα του πρώτου σταδίου και στοιχεία που αφορούν τη στερεομεταφορά κοντά στην είσοδο της κάθε διάταξης, θα διερευνηθεί αν υπάρχει ευκολία εγκλωβισμού και μετακίνηση ιζημάτων στο εσωτερικό των εξεταζόμενων διατάξεων. Για την εκπόνηση της εργασίας χρησιμοποιήθηκε το υπολογιστικό πακέτο Mike DHI 2011 και συγκεκριμένα, χρησιμοποιήθηκε το MIKE21 ΒW. Γενικά, συμπεραίνεται κατ’ αρχάς ότι η διάταξη, ο προσανατολισμός και η προστασία της εισόδου σε σχέση με τους επικρατούντες κυματισμούς παίζουν καθοριστικό ρόλο στην διαμόρφωση ήπιου και ασφαλούς κυματικού κλίματος στο εσωτερικό και στην είσοδο λιμενολεκανών μικρών σκαφών. Διατάξεις με την είσοδο με προσανατολισμό προς τα «ανοιχτά» όπως επίσης και διατάξεις με μη προστατευμένη είσοδο παρουσιάζουν, όπως αναμενόταν, έντονη κυματική διαταραχή στο εσωτερικό τους και μη ασφαλείς συνθήκες για τον ελλιμενισμό μικρών σκαφών. Εν αντιθέσει, λιμενολεκάνες με είσοδο προστατευμένη που τοποθετείται στο υπήνεμο τμήμα τους είναι σαφώς πιο προστατευμένες και παρουσιάζουν καλύτερες συνθήκες. Σε ότι αφορά την κίνηση των ιζημάτων, σημαντικό ρόλο διαδραματίζει η τοπική ταχύτητα των υδάτων κοντά στη είσοδο της μαρίνας, καθώς σε μεγάλες ταχύτητες το ίζημα κινείται και καθιζάνει σε μικρότερο βαθμό. Συνεπώς, πολύ μεγάλες ταχύτητες στην είσοδο του έργου μπορεί να διατηρήσουν τα ιζήματα σε κίνηση και να δράσουν αποτρεπτικά σε σχέση με την καθίζηση αυτών. Διατάξεις με μεγάλη διαφορά πεδίου ταχυτήτων στην είσοδο και στο εσωτερικό της λιμενολεκάνης, έχουν μεγαλύτερη πιθανότητα να εισέλθουν ιζήματα στο εσωτερικό τους και να εγκλωβιστούν εκεί. Από την άλλη πλευρά, σε λιμενολεκάνες που επικρατούν στην είσοδο και στο εσωτερικό τους έντονοι κυματισμοί, δύναται να δημιουργηθούν συνθήκες μετακίνησης των ιζημάτων που θα αποτεθούν εντός της λιμενολεκάνης και για το λόγο αυτό διερευνήθηκαν στο δεύτερο στάδιο. Λαμβάνοντας υπόψη το συνδυασμό κριτηρίων κυματικής διαταραχής, στερεοματαφοράς και εγκλωβισμού ιζημάτων στη λιμενολεκάνη, αξίζει να σημειωθεί ότι σε γενικές γραμμές, μικρές μαρίνες, προτείνεται να σχεδιάζονται την είσοδός τους στην υπήνεμη πλευρά, προστατευμένη από τους προσπίπτοντες κυματισμούς και το έργο να σχεδιάζεται με καμπύλα στοιχεία ώστε να παρατηρείται μείωση στην ένταση των στροβίλων που δημιουργούνται στις ασυνέχειες της διαδρομής των προσπιπτόντων ρευμάτων και στη συνεπαγόμενη ένταση της στερεομεταφοράς εξωτερικά της μαρίνας.The subject of this study is to investigate how the geometry and the location of the entrance of a small harbor (marina), can affect the wave climate and sediment transport rates inside the harbor and the entrance. The wave climate inside the basin is a very important factor that should taken into serious consideration in the design of marinas for small craft. Additionally, the sediment transport inside the harbor is affected by the height of the wave and the wave energy, which impinge on the marina. The first aim of the study is to examine the impact of the marina geometry and the entrance location to the wave climate inside the given basins. The second aim though, is to examine the possibility of sedimentations movement inside the basin . In the present study, the computational model Mike21BW by DHI was used to calculate the wave heights and velocities. The study shows also that the entrance of the marina should be designed as far as possible protected. It is proposed that the entrance should be constructed on the lee side of the structure, in order to avoid a strong wave climate inside the basin. Μoreover, marinas layouts with entrances looking directly to the open sea, are more vulnerable to the waves, impinging inside the basin and effecting the docking conditions of the small crafts along the quays. Even when, the entrance is located leeward should be properly protected from the prevailing waves. Marinas, such as layout 5, that have a windward breakwaters that does not protect the entrance adequately, are not a safe haven for the berthing and protection of vessels. Marinas located on the coast often have sediment deposited near the entrance from alongshore sediment transport. Sediment accumulation within the basin happens when outside the entrance occur high wave velocities, while inside the basin the velocity field is low. Although, it is possible that the wave conditions inside basins with exposed entrances, may cause velocities near the bed that could actuate the sediments on the seabed. Taking into account the above, it should be noted that as far as the wave climate inside the basin and the sediments are concerned, small marinas, proposed to be designed with entrances located on the lee side of the harbor, in order to achieve significantly low wave height inside the basin and low sedimentation rate both outside and near the entrance of the marina.Δανάη Σ. Σοφιαδέλ

G-CREWE: Graph CompREssion With Embedding for Network Alignment

Network alignment is useful for multiple applications that require increasingly large graphs to be processed. Existing research approaches this as an optimization problem or computes the similarity based on node representations. However, the process of aligning every pair of nodes between relatively large networks is time-consuming and resource-intensive. In this paper, we propose a framework, called G-CREWE (Graph CompREssion With Embedding) to solve the network alignment problem. G-CREWE uses node embeddings to align the networks on two levels of resolution, a fine resolution given by the original network and a coarse resolution given by a compressed version, to achieve an efficient and effective network alignment. The framework first extracts node features and learns the node embedding via a Graph Convolutional Network (GCN). Then, node embedding helps to guide the process of graph compression and finally improve the alignment performance. As part of G-CREWE, we also propose a new compression mechanism called MERGE (Minimum dEgRee neiGhbors comprEssion) to reduce the size of the input networks while preserving the consistency in their topological structure. Experiments on all real networks show that our method is more than twice as fast as the most competitive existing methods while maintaining high accuracy.Comment: 10 pages, accepted at the 29th ACM International Conference onInformation and Knowledge Management (CIKM 20

Adipocyte lipid synthesis coupled to neuronal control of thermogenic programming

BACKGROUND: The de novo biosynthesis of fatty acids (DNL) through fatty acid synthase (FASN) in adipocytes is exquisitely regulated by nutrients, hormones, fasting, and obesity in mice and humans. However, the functions of DNL in adipocyte biology and in the regulation of systemic glucose homeostasis are not fully understood. METHODS and RESULTS: Here we show adipocyte DNL controls crosstalk to localized sympathetic neurons that mediate expansion of beige/brite adipocytes within inguinal white adipose tissue (iWAT). Induced deletion of FASN in white and brown adipocytes of mature mice (iAdFASNKO mice) enhanced glucose tolerance, UCP1 expression, and cAMP signaling in iWAT. Consistent with induction of adipose sympathetic nerve activity, iAdFASNKO mice displayed markedly increased neuronal tyrosine hydroxylase (TH) and neuropeptide Y (NPY) content in iWAT. In contrast, brown adipose tissue (BAT) of iAdFASNKO mice showed no increase in TH or NPY, nor did FASN deletion selectively in brown adipocytes (UCP1-FASNKO mice) cause these effects in iWAT. CONCLUSIONS: These results demonstrate that downregulation of fatty acid synthesis via FASN depletion in white adipocytes of mature mice can stimulate neuronal signaling to control thermogenic programming in iWAT

Mapping gene-by-gene single-nucleotide variation in 8,535 <i>Mycobacterium tuberculosis</i> genomes:a resource to support potential vaccine and drug development

Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosisMycobacterium bovi

Mining directional drug interaction effects on myopathy using the FAERS database

Mining high-order drug-drug interaction (DDI) induced adverse drug effects from electronic health record (EHR) databases is an emerging area, and very few studies have explored the relationships between high-order drug combinations. We investigate a novel pharmacovigilance problem for mining directional DDI effects on myopathy using the FDA Adverse Event Reporting System (FAERS) database. Our work provides information on the risk of myopathy associated with adding new drugs on the already prescribed medication, and visualizes the identified directional DDI patterns as user-friendly graphical representation. We utilize the Apriori algorithm to extract frequent drug combinations from the FAERS database. We use odds ratio (OR) to estimate the risk of myopathy associated with directional DDI. We create a tree-structured graph to visualize the findings for easy interpretation. Our method confirmed myopathy association with previously reported HMG-CoA reductase inhibitors like rosuvastatin, fluvastatin, simvastatin and atorvastatin. New, previously unidentified but mechanistically plausible associations with myopathy were also observed, such as the DDI between pamidronate and levofloxacin. Additional top findings are gadolinium-based imaging agents, which however are often used in myopathy diagnosis. Other DDIs with no obvious mechanism are also reported, such as that of sulfamethoxazole with trimethoprim and potassium chloride. This study shows the feasibility to estimate high-order directional DDIs in a fast and accurate manner. The results of the analysis could become a useful tool in the specialists' hands through an easy-to-understand graphic visualization

Pitfalls in Quantitative Myocardial PET Perfusion I: Myocardial Partial Volume Correction

BACKGROUND: PET quantitative myocardial perfusion requires correction for partial volume loss due to one-dimensional LV wall thickness smaller than scanner resolution. METHODS: We aimed to assess accuracy of risk stratification for death, MI, or revascularization after PET using partial volume corrections derived from two-dimensional ACR and three-dimensional NEMA phantoms for 3987 diagnostic rest-stress perfusion PETs and 187 MACE events. NEMA, ACR, and Tree phantoms were imaged with Rb-82 or F-18 for size-dependent partial volume loss. Perfusion and Coronary Flow Capacity were recalculated using different ACR- and NEMA-derived partial volume corrections compared by Kolmogorov-Smirnov statistics to standard perfusion metrics with established correlations with MACE. RESULTS: Partial volume corrections based on two-dimensional ACR rods (two equal radii) and three-dimensional NEMA spheres (three equal radii) over estimate partial volume corrections, quantitative perfusion, and Coronary Flow Capacity by 50% to 150% over perfusion metrics with one-dimensional partial volume correction, thereby substantially impairing correct risk stratification. CONCLUSIONS: ACR (2-dimensional) and NEMA (3-dimensional) phantoms overestimate partial volume corrections for 1-dimensional LV wall thickness and myocardial perfusion that are corrected with a simple equation that correlates with MACE for optimal risk stratification applicable to most PET-CT scanners for quantifying myocardial perfusion

Leveraging Graph Diffusion Models for Network Refinement Tasks

Most real-world networks are noisy and incomplete samples from an unknown target distribution. Refining them by correcting corruptions or inferring unobserved regions typically improves downstream performance. Inspired by the impressive generative capabilities that have been used to correct corruptions in images, and the similarities between "in-painting" and filling in missing nodes and edges conditioned on the observed graph, we propose a novel graph generative framework, SGDM, which is based on subgraph diffusion. Our framework not only improves the scalability and fidelity of graph diffusion models, but also leverages the reverse process to perform novel, conditional generation tasks. In particular, through extensive empirical analysis and a set of novel metrics, we demonstrate that our proposed model effectively supports the following refinement tasks for partially observable networks: T1: denoising extraneous subgraphs, T2: expanding existing subgraphs and T3: performing "style" transfer by regenerating a particular subgraph to match the characteristics of a different node or subgraph.Comment: Work in Progress. 21 pages, 7 figure