A data-mining approach for wind turbine fault detection based on scada data analysis using artificial neural networks

Wind energy has shown significant growth in terms of installed power in the last decade. However, one of the most critical problems for a wind farm is represented by Operation and Maintenance (O&M) costs, which can represent 20-30% of the total costs related to power generation. Various monitoring methodologies targeted to the identification of faults, such as vibration analysis or analysis of oils, are often used. However, they have the main disadvantage of involving additional costs as they usually entail the installation of other sensors to provide real-time control of the system. In this paper, we propose a methodology based on machine learning techniques using data from SCADA systems (Supervisory Control and Data Acquisition). Since these systems are generally already implemented on most wind turbines, they provide a large amount of data without requiring extra sensors. In particular, we developed models using Artificial Neural Networks (ANN) to characterize the behavior of some of the main components of the wind turbine, such as gearbox and generator, and predict operating anomalies. The proposed method is tested on real wind turbines in Italy to verify its effectiveness and applicability, and it was demonstrated to be able to provide significant help for the maintenance of a wind farm

The BeppoSAX WFC X-ray source catalogue

We present the catalogue of X-ray sources detected by the two Wide Field Cameras (WFCs) in complete observations on board BeppoSAX during its 6 years of operational lifetime, between April 1996 and April 2002. The BeppoSAX WFCs were coded mask instruments sensitive in the 2-28 keV energy band with a 40x40 square degree fields of view, pointing in opposite directions and perpendicularly to the BeppoSAX Narrow Field Instruments (NFI). The WFCs were usually operated simultaneously to NFI observations, each lasting up to several days. WFCs observed thus the entire sky several times with a typical sensitivity of 2 to 10 mCrab. A systematic analysis of all WFC observations in the BeppoSAX archive has been carried out using the latest post-mission release of the WFC analysis software and calibrations. The catalogue includes 253 distinct sources, obtained from a total sample of 8253 WFC detections. We describe the basic statistical properties of the sample and present a six-year history of two celestial calibration X-ray sources.Comment: 15 pages, 11 figures, Catalogue, Accepted for publication on A&

Incidence of Anagrus obscurus (Hymenoptera: Mymaridae) egg parasitism on Calopteryx haemorrhoidalis and Platycnemis pennipes (Odonata: Calopterygidae, Platycnemididae) in Italy

Very little is known about the incidence of egg parasitoids in odonates, perhaps because Odonata eggs are well protected in stems or leaves, sometimes below water. In Central Italy (Pontecorvo, Frosinone province) two damselflies, Calopteryx haemorrhoidalis and Platycnemis pennipes occur at high densities. In August 2007 we collected 30 stems of the aquatic plant Potamogeton sp. used as substrate for oviposition and incubated eggs in the laboratory. Most stems (24 for C. haemorrhoidalis and 23 for P. pennipes) contained odonata eggs. Parasitoids emerged from 12 stems, with a mean parasitism of 2% for C. haemorrhoidalis and 6% for P. pennipes, and a maximum of 14% and 50%, respectively. Furthermore, we observed egg-laying of 19 females of C. haemorrhoidalis and 11 of P. pennipes, and marked the stems where oviposition was observed. Clutches remained in the river for 5 days and were then collected and incubated. Parasitoids emerged from 11 stems out of 30, with an average parasitism of 8% for C. haemorrhoidalis and 3% for P. pennipes (maximum of 50% and 29%, respectively). All parasitoids belonged to the family Mymaridae, and were identified as Anagrus (Anagrus) obscurus Förster, 1861, sensu Soyka, 1955. This is the first time that such species is described as an egg parasitoid of odonates, and that an egg parasitoid of C. haemorrhoidalis and P. pennipes is identified. Our data suggest that egg parasitism might be a significant selective factor for both odonates in the studied locality, affecting female oviposition behaviour

Design of a Database of Case Studies and Technologies to Increase the Diffusion of Low-Temperature Waste Heat Recovery in the Industrial Sector

The recovery of waste heat is a fundamental means of achieving the ambitious medium- and long-term targets set by European and international directives. Despite the large availability of waste heat, especially at low temperatures (<250 degrees C), the implementation rate of heat recovery interventions is still low, mainly due to non-technical barriers. To overcome this limitation, this work aims to develop two distinct databases containing waste heat recovery case studies and technologies as a novel tool to enhance knowledge transfer in the industrial sector. Through an in-depth analysis of the scientific literature, the two databases' structures were developed, defining fields and information to collect, and then a preliminary population was performed. Both databases were validated by interacting with companies which operate in the heat recovery technology market and which are possible users of the tools. Those proposed are the first example in the literature of databases completely focused on low-temperature waste heat recovery in the industrial sector and able to provide detailed information on heat exchange and the technologies used. The tools proposed are two key elements in supporting companies in all the phases of a heat recovery intervention: from identifying waste heat to choosing the best technology to be adopted

Private hospital energy performance benchmarking using energy audit data: an Italian case study

The increased focus on energy efficiency, both at the national and international levels, has fostered the diffusion and development of specific energy consumption benchmarks for most relevant economic sectors. In this context, energy-intensive facilities, such as hospitals and health structures, represent a unique case. Indeed, despite the high energy consumption of these structures, scientific literature lacks the presence of adequate energy performance benchmarks, especially in regard to the European context. Thus, this study aimed at defining energy benchmark indicators for the Italian private healthcare sector using data collected from the Italian mandatory energy audits according to Art.8 EU Directive 27/2012. The benchmark indicators’ definition was made using a methodology proposed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). This methodology provided the calculation of specific energy performance indicators (EnPIs) by considering the global energy consumption of the different sites and the sector’s relevant variables. The results obtained were compared with those obtained from a consolidated but more complex methodology: the one envisaged by the Environmental Protection Agency. The results obtained allowed us to validate the reliability of the proposed methodology, as well as the validity and future usability of the calculated indicators. Relying on a significant database containing actual data from recent energy audits, this study was thus able to provide an up-to-date and reliable benchmark for the private healthcare sector

Elevated alanine aminotransferase in blood donors: role of different factors and multiple viral infections.

Many different aetiological agents stimulate alanine aminotransferase (ALT) production. Viral markers and other aetiologies were investigated in 2166 individuals, randomly selected from 10 000 consecutive blood donors. Elevation of ALT was found in 10.8% of subjects. Grouping donors according to ALT level and correlating with, respectively, hepatitis B core antibody (HBcAb), cytomegalovirus antibody alone, or associated with HBcAb, showed similar findings (high ALT 11.1%, normal 11.6%; high 85.4%, normal 81.4%; high 10.2%, normal 11.0%, respectively). Hepatitis C virus (HCV) antibody was found to be significantly associated with elevated ALT levels (high 1.7%, normal 0.26%). Other causes of ALT elevation were alcohol abuse (17%), obesity (25%) and dyslipidaemia (38%), but in 11% there was no obvious aetiology. Although HCV is a rare cause of elevated ALT in blood donors, it seems to be the only virus, among those tested, to account for liver damage. This may be due to the non-protective role of HCV antibody, the low specificity of ALT, or the pathogenic role of uninvestigated viruses

What kind of hepatitis

Finding one major hepatotropic virus may not be enough to identify the aetiology of liver disease when risk factors are present, particularly in patients with past or present infection with other viral agents, or chronic liver disease. The pathogenic process in these cases is often complex. In the five cases we report, acute hepatitis (initiated by halothane, cytomegalovirus or Epstein-Barr virus) preceded the reactivation of hepatitis B infection, and these events occurred in patients with chronic hepatitis C infection. Each case demonstrates how several viruses can be implicated in the development of hepatitis, either as single agents or via cross-activation of T cells. The nosography of hepatitis, therefore, and the optimum therapeutic choices, can puzzle the clinical team

The Agile Alert System For Gamma-Ray Transients

In recent years, a new generation of space missions offered great opportunities of discovery in high-energy astrophysics. In this article we focus on the scientific operations of the Gamma-Ray Imaging Detector (GRID) onboard the AGILE space mission. The AGILE-GRID, sensitive in the energy range of 30 MeV-30 GeV, has detected many gamma-ray transients of galactic and extragalactic origins. This work presents the AGILE innovative approach to fast gamma-ray transient detection, which is a challenging task and a crucial part of the AGILE scientific program. The goals are to describe: (1) the AGILE Gamma-Ray Alert System, (2) a new algorithm for blind search identification of transients within a short processing time, (3) the AGILE procedure for gamma-ray transient alert management, and (4) the likelihood of ratio tests that are necessary to evaluate the post-trial statistical significance of the results. Special algorithms and an optimized sequence of tasks are necessary to reach our goal. Data are automatically analyzed at every orbital downlink by an alert pipeline operating on different timescales. As proper flux thresholds are exceeded, alerts are automatically generated and sent as SMS messages to cellular telephones, e-mails, and push notifications of an application for smartphones and tablets. These alerts are crosschecked with the results of two pipelines, and a manual analysis is performed. Being a small scientific-class mission, AGILE is characterized by optimization of both scientific analysis and ground-segment resources. The system is capable of generating alerts within two to three hours of a data downlink, an unprecedented reaction time in gamma-ray astrophysics.Comment: 34 pages, 9 figures, 5 table

The “Far-West” of Anopheles gambiae Molecular Forms

The main Afrotropical malaria vector, Anopheles gambiae sensu stricto, is undergoing a process of sympatric ecological diversification leading to at least two incipient species (the M and S molecular forms) showing heterogeneous levels of divergence across the genome. The physically unlinked centromeric regions on all three chromosomes of these closely related taxa contain fixed nucleotide differences which have been found in nearly complete linkage disequilibrium in geographic areas of no or low M-S hybridization. Assays diagnostic for SNP and structural differences between M and S forms in the three centromeric regions were applied in samples from the western extreme of their range of sympatry, the only area where high frequencies of putative M/S hybrids have been reported. The results reveal a level of admixture not observed in the rest of the range. In particular, we found: i) heterozygous genotypes at each marker, although at frequencies lower than expected under panmixia; ii) virtually all possible genotypic combinations between markers on different chromosomes, although genetic association was nevertheless detected; iii) discordant M and S genotypes at two X-linked markers near the centromere, suggestive of introgression and inter-locus recombination. These results could be indicative either of a secondary contact zone between M and S, or of the maintenance of ancestral polymorphisms. This issue and the perspectives opened by these results in the study of the M and S incipient speciation process are discussed

Models of Individual Blue Stragglers

This chapter describes the current state of models of individual blue stragglers. Stellar collisions, binary mergers (or coalescence), and partial or ongoing mass transfer have all been studied in some detail. The products of stellar collisions retain memory of their parent stars and are not fully mixed. Very high initial rotation rates must be reduced by an unknown process to allow the stars to collapse to the main sequence. The more massive collision products have shorter lifetimes than normal stars of the same mass, while products between low mass stars are long-lived and look very much like normal stars of their mass. Mass transfer can result in a merger, or can produce another binary system with a blue straggler and the remnant of the original primary. The products of binary mass transfer cover a larger portion of the colour-magnitude diagram than collision products for two reasons: there are more possible configurations which produce blue stragglers, and there are differing contributions to the blended light of the system. The effects of rotation may be substantial in both collision and merger products, and could result in significant mixing unless angular momentum is lost shortly after the formation event. Surface abundances may provide ways to distinguish between the formation mechanisms, but care must be taking to model the various mixing mechanisms properly before drawing strong conclusions. Avenues for future work are outlined.Comment: Chapter 12, in Ecology of Blue Straggler Stars, H.M.J. Boffin, G. Carraro & G. Beccari (Eds), Astrophysics and Space Science Library, Springe