•The role of Al2O3 inclusions in the pitting corrosion initiation stage in a marine environment was studied.•A high dislocation density region existed around Al2O3 inclusions in the cold rolling ...Q460NH steel.•A mechanism different from the galvanic coupling was used to explain the selective dissolution of matrix around inclusions.•Al2O3 clusters had a more negative effect on the corrosion behaviour of the Q460NH steel analysed than single inclusions.
The influence of Al2O3 inclusions on the localized corrosion behaviour of Q460NH steel was investigated in a simulated marine environment. According to the current sensing atomic force microscopy (CS-AFM) result, there was no galvanic couple between Al2O3 inclusions and the adjacent steel. Therefore, a different mechanism from that traditionally used (considering the galvanic coupling between inclusions and matrix) to explain the selective dissolution of the matrix around inclusions, dominated the pit initiation and propagation process in this system. Electron backscattered diffraction (EBSD) analysis showed a region of high dislocation density around the inclusions. Both microcrevices and the high dislocation density region around inclusions can easily induce localized corrosion. The catalytic-occluded cells and oxygen-concentration cell could accelerate the propagation of the pits. Furthermore, inclusion clusters had a larger negative effect than single inclusions on the corrosion resistance of the steel. Scanning vibrating electrode technique (SVET) measurements confirmed that inclusions play a key role in the corrosion process.
Maintenance work orders are commonly used to document information about wind turbine operation and maintenance. This includes details about proactive and reactive wind turbine downtimes, such as ...preventative and corrective maintenance. However, the information contained in maintenance work orders is often unstructured and difficult to analyze, presenting challenges for decision-makers wishing to use it for optimizing operation and maintenance. To address this issue, this work compares three different approaches to calculating reliability key performance indicators from maintenance work orders. The first approach involves manual labeling of the maintenance work orders by domain experts, using the schema defined in an industrial guideline to assign the label accordingly. The second approach involves the development of a model that automatically labels the maintenance work orders using text classification methods. Through this method, we are able to achieve macro average and weighted average F1-scores of 0.75 and 0.85 respectively. The third technique uses an AI-assisted tagging tool to tag and structure the raw maintenance information, together with a novel rule-based approach for extracting relevant maintenance work orders for failure rate calculation. In our experiments, the AI-assisted tool leads to an 88% drop in tagging time in comparison to the other two approaches, while expert labeling and text classification are more accurate in KPI extraction. Overall, our findings make extracting maintenance information from maintenance work orders more efficient, enable the assessment of reliability key performance indicators, and therefore support the optimization of wind turbine operation and maintenance.
Display omitted
•Al graded Mg-Al thin films were synthesized via combinatorial magnetron sputtering.•Al graded Mg-Al thin films were analyzed via in-situ electrochemistry.•The Mg-Al solid solution ...corrosion resistance increases with the Al concentration.•Exceeding cAl ∼ 4 wt% causes a distinct anodic current density decrease.•Exceeding cAl ∼ 4 wt% causes a predominant cathodic partial reaction on the surface.
The effect of varying Al concentrations on the electrochemical corrosion resistance of binary Mg-Al solid solutions thin films under alkaline immersion conditions was investigated via a combination of in-situ flow-cell, scanning vibrating electrode technique and microscopy analysis. These spatially resolving characterization techniques are employed along the Al concentration gradient of the combinatorically grown thin films enabling efficient screening of the Al concentration dependent electrochemical corrosion behaviour. The analysis revealed an increasing corrosion resistance with increasing Al concentration, as a consequence of Al induced hydroxide reinforcement. Specifically, the addition of >4 wt.% Al decreases the corrosion current density in the range of 70–90 % compared to pure Mg.
With the background of numerous wind turbines phasing out of fixed feed‐in tariffs in the following years and an increasing share of negative electricity market prices on the spot market, the ...availability definitions of “time‐based” and “production‐based” availability are possibly no longer suitable for assessing the overall performance of a wind turbine. This paper introduces a novel definition: the “monetary‐based” availability. The differences between the established definitions and the “monetary‐based” availability are highlighted by comparing the measures on an empirical data set. Furthermore, results on the impact of scheduling planned downtimes towards a monetary‐based optimum show that revenues can be increased. By shifting only a small share of the annual downtime to an optimum to maximize the revenue from electricity, a strong increase in additional earnings and thereby an increasment of the monetary‐based availability can be achieved.
Abstract
Maintenance data of wind turbines is an important information source for calculating key performance indicators. Also, it can be used for developing models for early fault detection. Both ...activities aim for supporting informed decisions in operation and maintenance. However, such data is rarely available in a structured and standardized format which hinders the interoperability of different enterprises. Consequently, maintenance information is often unused or only usable with considerable personnel effort. To digitalize wind farm maintenance, a digitalization workflow is developed and presented in this paper. The workflow consists of the steps optical character recognition, information extraction and text classification. The workflow is applied on real-world wind turbine service reports and invoices. First results for each step show good performance metrics and potential for further real-world application of the proposed method.
•A method for autoencoder-based anomaly root cause analysis (ARCANA) is introduced.•The method provides human interpretable explanations for anomalies.•The explanations help to identify the ...underlying root causes.•The applicability of ARCANA is demonstrated on wind turbine sensor data.•Validation of the explanations is shown with failure data.
Display omitted
A popular method to detect anomalous behaviour or specific failures in wind turbine sensor data uses a specific type of neural network called an autoencoder. These models have proven to be very successful in detecting such deviations, yet cannot show the underlying cause or failure directly. Such information is necessary for the implementation of these models in the planning of maintenance actions. In this paper we introduce a novel method: ARCANA. We use ARCANA to identify the possible root causes of anomalies detected by an autoencoder. It describes the process of reconstruction as an optimisation problem that aims to remove anomalous properties from an anomaly considerably. This reconstruction must be similar to the anomaly and thus identify only a few, but highly explanatory anomalous features, in the sense of Ockham’s razor. The proposed method is applied on an open data set of wind turbine sensor data, where an artificial error was added onto the wind speed sensor measurements to acquire a controlled test environment. The results are compared with the reconstruction errors of the autoencoder output. The ARCANA method points out the wind speed sensor correctly with a significantly higher feature importance than the other features, whereas using the non-optimised reconstruction error does not. Even though the deviation in one specific input feature is very large, the reconstruction error of many other features is large as well, complicating the interpretation of the detected anomaly. Additionally, we apply ARCANA to a set of offshore wind turbine data. Two case studies are discussed, demonstrating the technical relevance of ARCANA.
The usage of machine learning techniques is widely spread and has also been implemented in the wind industry in the last years. Many of these techniques have shown great success but need to ...constantly prove the expectation of functionality. This paper describes a new method to monitor the health of a wind turbine using an undercomplete autoencoder. To evaluate the health monitoring quality of the autoencoder, the number of anomalies before an event has happened are to be considered. The results show that around 35% of all historical events that have resulted into a failure show many anomalies. Furthermore, the wind turbine subsystems which are subject to good detectability are the rotor system and the control system. If only one third of the service duties can be planned in advance, and thereby the scheduling time can be reduced, huge cost saving potentials can be seen.
Amylin is a pancreatic β-cell hormone that produces effects in several different organ systems. One of its best-characterized effects is the reduction in eating and body weight seen in preclinical ...and clinical studies. Amylin activates specific receptors, a portion of which it shares with calcitonin gene-related peptide (CGRP). Amylin's role in the control of energy metabolism relates to its satiating effect, but recent data indicate that amylin may also affect hedonic aspects in the control of eating, including a reduction of the rewarding value of food. Recently, several amylin-based peptides have been characterized. Pramlintide (Symlin
) is currently the only one being used clinically to treat type 1 and type 2 diabetes. However other amylin analogs with improved pharmacokinetic properties are being considered as anti-obesity treatment strategies. Several other studies in obesity have shown that amylin agonists could also be useful for weight loss, especially in combination with other agents.
This review will briefly summarize amylin physiology and pharmacology and then focus on amylin's role in food reward and the effects of amylin analogs in pre-clinical testing for anti-obesity drugs.
We propose here that the effects of amylin may be homeostatic and hedonic in nature.
Liver transplant (LT) programs in Germany increasingly face a multiethnic patient population. To date no outcome data for LT in patients with a history of migration is available for Germany. This ...complicates decision-making before wait-listing such patients. We conducted a single-center cohort analysis of all primary LT between April 2007 and December 2015, stratified for the history of migration to investigate differences in the outcome. We found transplant rates resembling the proportion of persons with a history of migration in the general public in the region of our center. Differences were found concerning age at LT and prevalence of underlying diseases. Re-Transplant rates, Kaplan-Meier Estimates for overall survival, also after stratification for viral hepatitis, sex, ethnicity or presence of a language-barrier showed no statistical differences. The multivariate analysis showed no migration-related covariate associated with a negative outcome. These results stand in contrast to most of the previous evidence from North America and the UK and need to be taken into consideration during the wait-listing process of patients with a history of migration in need of a LT in centers in the Eurotransplant region.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Brainstem mechanisms of amylin-induced anorexia Potes, Catarina Soares; Lutz, Thomas Alexander
Physiology & behavior,
07/2010, Letnik:
100, Številka:
5
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Abstract Amylin is secreted by pancreatic beta-cells and is believed to be a physiological signal of satiation. Amylin's effect on eating has been shown to be mediated via a direct action at the area ...postrema (AP) via amylin receptors that are heterodimers of the calcitonin receptor core protein with a receptor activity modifying protein. Peripheral amylin leads to accumulation of cyclic guanosine monophosphate, phosphorylated extracellular-signal regulated kinase 1/2 and c-Fos protein in AP neurons. The particular amylin-activated AP neurons mediating its anorexigenic action seem to be noradrenergic. The central pathways mediating amylin's effects have been characterized by lesioning and tracing studies, identifying important connections from the AP to the nucleus of the solitary tract and lateral parabrachial nucleus. Amylin was shown to interact, probably at the brainstem, with other signals involved in the short term control of food intake, namely cholecystokinin, glucagon-like peptide 1 and peptide YY. Amylin also interacts with the adiposity signal leptin; this interaction, which is thought to involve the hypothalamus, may have important implications for the development of new and improved hormonal obesity treatments. In conclusion, amylin actions on food intake seem to reside primarily within the brainstem, and the associated mechanisms are starting to be unraveled. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior SSIB Annual Meeting in Portland, July 2009.
PDF
