A decision theoretic framework for reliability-based optimal wind turbine selection

© 2022. Elsevier. This document is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the accepted version of a published work that appeared in final form in Reliability Engineering & System SafetyThe problem of choosing the optimal wind turbine for a specific site is of special importance in the design process of wind farm. Manifestly, the selection of the optimal wind turbine should depend on a certain criteria. In this paper, optimal wind turbine selection is studied in terms of the capacity factor of wind turbine generator and the Expected Energy not Supplied which is one of the most commonly used reliability indices for power systems. The latter one considers the load profile of the system and is suitable to compare different wind farm compositions while the former one completely ignores the load profile of the system. This paper presents general theoretical results that are helpful to compare performance of wind turbines and wind farms without data collection and further numerical assessment. In particular, the conditions on wind turbine characteristics and availability values of wind turbines are determined to compare wind turbines and wind farms in terms of the capacity factor and Expected Energy not Supplied

Plasmonic Nanoslit Array Enhanced Metal-Semiconductor-Metal Optical Detectors

Cataloged from PDF version of article.Metallic nanoslit arrays integrated on germanium metal–semiconductor–metal photodetectors show many folds of absorption enhancement for transverse-magnetic polarization in the telecommunication C-band. Such high enhancement is attributed to resonant interference of surface plasmon modes at the metal–semiconductor interface. Horizontal surface plasmon modes were reported earlier to inhibit photodetector performance. We computationally show, however, that horizontal modes enhance the efficiency of surface devices despite reducing transmitted light in the far field

Brain-like associative learning using a nanoscale non-volatile phase change synaptic device array

Recent advances in neuroscience together with nanoscale electronic device technology have resulted in huge interests in realizing brain-like computing hardwares using emerging nanoscale memory devices as synaptic elements. Although there has been experimental work that demonstrated the operation of nanoscale synaptic element at the single device level, network level studies have been limited to simulations. In this work, we demonstrate, using experiments, array level associative learning using phase change synaptic devices connected in a grid like configuration similar to the organization of the biological brain. Implementing Hebbian learning with phase change memory cells, the synaptic grid was able to store presented patterns and recall missing patterns in an associative brain-like fashion. We found that the system is robust to device variations, and large variations in cell resistance states can be accommodated by increasing the number of training epochs. We illustrated the tradeoff between variation tolerance of the network and the overall energy consumption, and found that energy consumption is decreased significantly for lower variation tolerance.Comment: Original article can be found here: http://journal.frontiersin.org/Journal/10.3389/fnins.2014.00205/abstrac

A discrete MMAP for analysing the behaviour of a multi-state complex dynamic system subject to multiple events.

A complex multi-state system subject to different types of failures, repairable and/or nonrepairable, external shocks and preventive maintenance is modelled by considering a discrete Markovian arrival process with marked arrivals (D-MMAP). The internal performance of the system is composed of several degradation states partitioned into minor and major damage states according to the risk of failure. Random external events can produce failures throughout the system. If an external shock occurs, there may be an aggravation of the internal degradation, cumulative external damage or extreme external failure. The internal performance and the cumulative external damage are observed by random inspection. If major degradation is observed, the unit goes to the repair facility for preventive maintenance. If a repairable failure occurs then the system goes to corrective repair with different time distributions depending on the failure state. Time distributions for corrective repair and preventive maintenance depend on the failure state. Rewards and costs depending on the state at which the device failed or was inspected are introduced. The system is modelled and several measures of interest are built into transient and stationary regimes. A preventive maintenance policy is shown to determine the effectiveness of preventive maintenance and the optimum state of internal and cumulative external damage at which preventive maintenance should be taken into account. A numerical example is presented, revealing the efficacy of the model. Correlations between the numbers of different events over time and in non-overlapping intervals are calculated. The results are expressed in algorithmic-matrix form and are implemented computationally with Matlab.Junta de Andalucía, Spain, under the grant FQM307Ministerio de Economía y Competitividad, España, MTM2017-88708-PEuropean Regional Development Fund (ERDF

A Cross-Sectional Study of Dietary and Genetic Predictors of Blood Folate Levels in Healthy Young Adults

Since 1998, the U.S. has mandated folic acid (FA) fortification of certain grain products to reduce the risk of neural tube defects. Folate intake and red blood cell (RBC) folate concentrations increased substantially post-intervention, although recent studies raise concerns about the level of ongoing benefit. This study investigated blood folate level determinants in healthy young adults, including intake of naturally occurring food folate, synthetic FA, and the interaction of naturally occurring food folate with a common missense variant in the FOLH1 gene thought to affect absorption. Participants (n = 265) completed the Diet History Questionnaire II, RBC folate testing, and were genotyped for the 484T>C FOLH1 variant. Men reported significantly greater intake of all folate sources except for supplemental FA, but RBC folate levels did not significantly differ by sex. Synthetic FA was a stronger predictor of RBC folate than naturally occurring food folate. In the largest racial group, synthetic FA and the interaction of FOLH1 genotype with naturally occurring food folate significantly predicted RBC folate, with the overall model accounting for 13.8% of the variance in RBC folate levels. Blood folate levels rely on a complex interaction of natural and synthetic folate intake as well as FOLH1 genotype

Long term survival after coronary endarterectomy in patients undergoing combined coronary and valvular surgery – a fifteen year experience

<p>Abstract</p> <p>Background</p> <p>Coronary Endarterectomy (CE) in patients undergoing coronary artery bypass graft (CABG) surgery has been shown to be beneficial in those with diffuse coronary artery disease. There are no published data on its role and benefit in patients undergoing more complex operations. We present our experience with CE in patients undergoing valve surgery with concomitant CABG.</p> <p>Materials and methods</p> <p>Between 1989 and 2003, 237 patients underwent CABG with valve surgery under a single surgeon at our institution. Of these, 41 patients needed CE. Data was retrospectively obtained from hospital records and database. Further follow-up was obtained by telephone interview. All variables were analyzed by univariate analysis for significant factors relating to hospital mortality. Morbidity and long term survival was also studied. There were 29 males and 12 females with a mean age of 67.4 ± 8.1 and body mass index of 26.3 ± 3.3. Their mean euroscore was 7.6 ± 3.2 and the log euro score was 12.2 ± 16.1.</p> <p>Results</p> <p>Thirty-two patients were discharged from the intensive therapy unit within 48 hours after surgery. Average hospital stay was 12.7 ± 10.43 days. Thirty day mortality was 9.8%. Six late deaths occurred during the 14 year follow up. Ten year survival was 57.2% (95% CL 37.8%–86.6%). Three of the survivors had Class II symptoms, with one requiring nitrates. None required further percutaneous or surgical intervention. We compared the result with the available mortality figure from the SCTS database.</p> <p>Conclusion</p> <p>Compared to the SCTS database for these patients, we have observed that CE does not increase the mortality in combined procedures. By accomplishing revascularization in areas deemed ungraftable, we have shown an added survival benefit in this group of patients.</p

Tailoring microstructure and phase segregation for low friction carbon-based nanocomposite coatings

Friction has a direct relation with the energy efficiency and environmental cleanliness in all moving mechanical systems. To develop low friction coatings is extremely beneficial for preserving not only our limited energy resources but also the earth’s environment. This study proposes a new design for low friction carbon-based nanocomposite coatings by tailoring the microstructure and phase segregation,and thereby it contributes to better controlling the mechanical and tribological properties. Experimental findings and theoretical calculations reveal that high-hardness (18.2 GPa), high-adhesion strength (28 N) as well as low-internal stress (-0.8 GPa) can be achieved by a nanocrystallite/amorphous microstructure architecture for the nc-WC/a-C(Al) carbon-based nanocomposite coating;in particular low friction (~0.05) can be acquired by creating a strong thermodynamic driving force to promote phase segregation of graphitic carbon from the a-C structure so as to form a low shear strength graphitic tribo-layer on the friction contact surfaces. This design concept is general and has been successfully employed to fabricate a wide class of low friction carbon-based nanocomposite coating