Improved control strategy of DFIG-based wind turbines using direct torque and direct power control techniques

This paper presents different control strategies for a variable-speed wind energy conversion system (WECS), based on a doubly fed induction generator. Direct Torque Control (DTC) with Space-Vector Modulation is used on the rotor side converter. This control method is known to reduce the fluctuations of the torque and flux at low speeds in contrast to the classical DTC, where the frequency of switching is uncontrollable. The reference for torque is obtained from the maximum power point tracking technique of the wind turbine. For the grid-side converter, a fuzzy direct power control is proposed for the control of the instantaneous active and reactive power. Simulation results of the WECS are presented to compare the performance of the proposed and classical control approaches.Peer reviewedFinal Accepted Versio

Board gender diversity and corporate environmental performance: the moderating role of family and dual class majority ownership structures

While prior work has investigated the impact of (a) ownership structure and (b) board gender diversity separately on corporate environmental performance, researchers have not studied the potentially important relationship between ownership control and female board diversity in influencing corporate environmental performance jointly. We do so in the context of majority ownership in family controlled and dual class firms whose motives and influence are theoretically different from that of the firm’s minority shareholders. Drawing on resource dependency, socio-emotional wealth theory, and secondary agency theory, we hypothesize that majority family owners and dual class owners likely choose women directors to help advance their personal preferences for environmental CSR. Our empirical tests utilizing 2755 US firmyears over the 2010-2015 show that, as hypothesized, these two majority ownership types interact with board gender diversity to positively influence corporate environmental performance

Performance of Er:YAG laser ablation of hard bone under different irrigation water cooling conditions

The biological applicability of the Erbium-doped Yttrium Aluminum Garnet (Er:YAG) laser in surgical processes is so far limited to hard dental tissues. Using the Er:YAG laser for bone ablation is being studied since it has shown good performance for ablating dental hard tissues at the wavelength 2.94 μm, which coincides with the absorption peak of water, one of the main components of hard tissue, like teeth and bone. To obtain a decent performance of the laser in the cutting process, we aim at examining the influence of sequenced water jet irrigation on both, the ablation rate and the prevention of carbonization while performing laser ablation of bone with fixed laser parameters. An Er:YAG laser at 2.94 μm wavelength, 940 mJ energy per pulse, 400 μs pulse width, and 10 Hz repetition rate is used for the ablation of a porcine femur bone under different pulsed water jet irrigation conditions. We used micro-computed tomography (micro-CT) scans to determine the geometry of the ablated areas. In addition, scanning electron microscopy (SEM) is used for qualitative observations for the presence of carbonization and micro-fractures on the ablated surfaces. We evaluate the performance of the laser ablation process for the different water jet conditions in terms of the ablation rate, quantified by the ablated volume per second and the ablation efficiency, calculated as the ablated volume per pulse energy. We provide an optimized system for laser ablation which delivers the appropriate amount of water to the bone and consequently, the bone is ablated in the most efficient way possible without carbonization

Recommendation on Measures to Safeguard Freedom of Expression and Undistorted Competition in EU Trade Mark Law

Whatever the protection afforded to trade marks, it must always be balanced against general interests, in particular the fundamental freedom of expression and the guarantee of undistorted competition, as reflected in the Lisbon Treaty, the Charter of Fundamental Rights and the European Convention on Human Rights. The need for an appropriate balance is inherent in trade mark law. It is an issue of particular importance in the light of ongoing technological, economic and social developments, and of considerable complexity because of the diversity of legitimate interests of trade mark proprietors, consumers, competitors and the public at large. Against this background, the Recommendation provides guidance on how to offer sufficient room for freedom of expression and freedom of competition in the envisaged new EU trade mark legislation. It addresses measures to be taken by legislators, trade mark registration offices and the courts at various stages: from the grant of trade mark rights and the analysis of trade mark infringement to limitations of trade mark protection and the appropriate distribution of the burden of proof

Validation of collaborative cyberspace virtual reality oculometry enhanced with near real-time spatial audio

Abstract Currently, most medical image data, such as optical coherence tomography (OCT) images, are displayed in two dimensions on a computer screen. Advances in computer information technology have contributed to the growing storage of these data in electronic form. However, the data are usually processed only locally on site. To overcome such hurdles, a cyberspace virtual reality (csVR) application was validated, in which interactive OCT data were presented simultaneously to geographically distant sites (Lucerne, London, and Barcelona) where three graders independently measured the ocular csVR OCT diameters. A total of 109 objects were measured, each three times, resulting in a total of 327 csVR measurements. A minor mean absolute difference of 5.3 µm was found among the 3 measurements of an object (standard deviation 4.2 µm, coefficient of variation 0.3% with respect to the mean object size). Despite the 5 h of online work, csVR was well tolerated and safe. Digital high-resolution OCT data can be remotely and collaboratively processed in csVR. With csVR, measurements and actions enhanced with spatial audio communication can be made consistently in near real time, even if the users are situated geographically far apart. The proposed visuo-auditory framework has the potential to further boost the convenience of digital medicine toward csVR precision and collaborative medicine