1,721,060 research outputs found
Effect of Blade Design and Control Strategies on Levelized Cost of Energy of Tidal Stream Turbines
No full textOptimization of a floating offshore wind turbine platform and mooring lines according to an innovative wind farm wake control technique
No full textThe floating offshore wind resource has a very large expected impact on the overall energy production scenario. Regardless, the exploitation of such valuable resource remains a technological challenge due to the harsh environment in which they operate and higher costs of installation and maintenance. A crucial component of a floating offshore wind turbine is represented by the floating platform, which provides the hydrostatic stability and absorbs the loads coming from both sea-waves and by wind acting on the turbine. While often seen as a disadvantage of the floating offshore wind turbines, the possibility of enhancing the floater motion can be exploited to control the evolution of the wake structure behind the wind turbine rotors, re-energizing the flow in the wake and increasing in this way the power production of rotors set behind the upstream turbine. Designing the floater and mooring lines configuration to enhance yaw oscillations at a certain frequency is expected to increase this behaviour. In this work we apply a simulation-based approach with the aim of designing a floating platform and mooring lines configuration optimized for their integration within this new control strategy based on wake-mixing in wind farms. The optimization process is applied to the DTU 10MW reference wind turbine supported by a semi-submersible floater composed of three spars ("Triple Spar" concept). The modification of the floating platform spar arrangement and mooring lines properties allowed to tune the yaw natural frequency of the system in accordance with the excitation frequency of the wake control technique, while controlling the deviation of operational constraints and costs from baseline configuration
The effect of Ginkgo Biloba in isolated ischemic/ reperfused rat heart. Alink between vitaminE preservation and prostaglandin biosynthesis
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Validation of the Compatibility Between a Porous Silicon-Based Gas Sensor Technology and Standard Microelectronic Process
No full textThe compatibility of a recently proposed porous silicon
formation procedure for gas sensor integration with a commercial
microelectronic process is analyzed. Porous silicon-based
gas sensors have been produced on a test chip by means of a postprocessing
approach that enables silicon anodization in selected
areas. The effects of the post-processing procedure on electronic
circuits, integrated on the test chip as the sensors, have been investigated
by electrical measurements. Critical electrical parameters of
purposely-designed high-performance analog cells have been measured
on several post-processed and not post-processed samples.
Experimental outcomes demonstrate the actual compatibility of
the post-processing procedure for porous silicon formation with
commercial microelectronic processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Addressing Reliability and Degradation of Chemitransistor Sensors by Electrical Tuning of the Sensitivity
No full textTuning of the sensitivity of porous silicon JFET gas sensors
No full textIn this work, electrical tuning of the sensitivity of an integrated solid-state gas sensor is demonstrated. The sensor, namely PSJFET - Porous Silicon Junction Field Effect Transistor, consists of a p-channel JFET with an additional PS sensing gate on its top. The sensor current value is proportional to the NO(2) concentration in the environment, that is I(DS)=S center dot[NO(2)], at least in the range investigated (between 100 ppb and 500 ppb). Interestingly, and differently from most of gas sensors reported in the literature, the normalized sensor sensitivity S=dI(DS)/(I(DS0)center dot d[NO(2)]) can be effectively tuned by changing the voltage value of the electrical gate terminal of the JFET device. This feature allows the fabrication of gas sensors with superior performances: for example, it can be exploited to compensate for aging-induced degradation of the sensitivity during the sensor life-time. It is worthy of mentioning that, such an effect can be obtained without any increase of the sensor power dissipation, due to the high impedance of the gate terminal of the PSJFET
Short-term prevention of thromboembolic complications in patients with atrial fibrillation with aspirin plus clopidogrel: the Clopidogrel-Aspirin Atrial Fibrillation (CLAAF) pilot study
No full textBackground We evaluated the short-term safety and efficacy of aspirin-plus-clopidogrel as antithrombotic therapy in nonvalvular atrial fibrillation (AF). Methods and results Thirty patients (11 women, 45 to 75 years of age) with non-high-risk permanent (n = 12) or persistent AF awaiting cardioversion (n = 18) underwent transesophageal echocardiography to exclude left heart thrombi and were then randomly assigned to receive warfarin (international normalized ratio, 2 to 3 for 3 weeks) or aspirin (100 mg/d alone for 1 week)-plus-clopidogrel (75 mg/d added to aspirin for 3 weeks). Bleeding time and serum thromboxane B2 were measured at entry and at 3 weeks. Bleeding time, not affected by warfarin, was prolonged by 71% by aspirin (P < .05) and further, by 144%, by adding clopidogrel (P < .01 vs aspirin alone; +319%, P < .01, vs baseline). Thromboxane B2, not affected by warfarin, was reduced by aspirin (-98%, P < .01) but not further by clopidogrel. No thrombi or dense spontaneous echo-contrast were found at the 3-week transesophageal echocardiography. Seven of 9 patients receiving warfarin and 7 of 9 patients receiving aspirin-plus-clopidogrel, undergoing electrical cardioversion, achieved sinus rhythm. No thromboembolic or hemorrhagic events occurred in both arms throughout the 3-week treatment and a further 3-month follow-up. Conclusions Aspirin-plus-clopidogrel and warfarin were equally safe and effective in preventing thromboembolism in this small group of patients with non-high-risk AF
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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