23 research outputs found
Wake losses optimization of offshore wind farms with moveable floating wind turbines
In the future, floating wind turbines could be used to harvest energy in deep offshore areas where higher
wind mean speeds are observed. Currently, several floating turbine concepts are being designed and
tested in small scale projects; in particular, one concept allows the turbine to move after installation. This
article presents a novel layout optimization framework for wind farms composed of moveable floating
turbines. The proposed framework uses an evolutionary optimization strategy in a nested configuration
which simultaneously optimizes the anchoring locations and the wind turbine position within the mooring
lines for each individual wind direction. The results show that maximum energy production is
obtained when moveable wind turbines are deployed in an optimized layout. In conclusion, the framework
represents a new design optimization tool for future offshore wind farms composed of moveable
floating turbines
Electrical control of glass-like dynamics in vanadium dioxide for data storage and processing
Metalâoxideâsemiconductor junctions are the building blocks of modern electronics and can provide a variety of functionalities, from memory to computing. The technology, however, faces constraints in terms of further miniaturization and compatibility with postâvon Neumann computing architectures. Manipulation of structuralârather than electronicâstates could provide a path to ultrascaled low-power functional devices, but the electrical control of such states is challenging. Here we report electronically accessible long-lived structural states in vanadium dioxide that can provide a scheme for data storage and processing. The states can be arbitrarily manipulated on short timescales and tracked beyond 10,000âs after excitation, exhibiting features similar to glasses. In two-terminal devices with channel lengths down to 50ânm, sub-nanosecond electrical excitation can occur with an energy consumption as small as 100âfJ. These glass-like functional devices could outperform conventional metalâoxideâsemiconductor electronics in terms of speed, energy consumption and miniaturization, as well as provide a route to neuromorphic computation and multilevel memories
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4D printing roadmap
Four-dimensional (4D) printing is an advanced manufacturing technology that has rapidly emerged as a transformative tool with the capacity to reshape various research domains and industries. Distinguished by its integration of time as a dimension, 4D printing allows objects to dynamically respond to external stimuli, setting it apart from conventional 3D printing. This roadmap has been devised, by contributions of 44 active researchers in this field from 32 affiliations world-wide, to navigate the swiftly evolving landscape of 4D printing, consolidating recent advancements and making them accessible to experts across diverse fields, ranging from biomedicine to aerospace, textiles to electronics. The roadmapâs goal is to empower both experts and enthusiasts, facilitating the exploitation of 4D printingâs transformative potential to create intelligent, adaptive objects that are not only feasible but readily attainable. By addressing current and future challenges and proposing advancements in science and technology, it sets the stage for revolutionary progress in numerous industries, positioning 4D printing as a transformative tool for the future
Near-junction heat spreaders for hot spot thermal management of high power density electronic devices
Many high power (opto-) electronic devices such as transistors, diodes, and lasers suffer from significant hot spot temperature rises due to the high heat fluxes generated in their active area, which limits their performance, reliability, and lifetime. Employing high thermal conductivity materials near the heat source, known as near-junction heat spreaders, offers a low-cost and effective thermal management approach. Here, we present analytical heat spreader models and a methodology to evaluate their performance. Experimental demonstration of near-junction diamond heat spreaders on vertical GaN PiN diodes revealed significantly reduced spreading resistances, along with very low temperature gradients across the device. The findings in this work provide design guidelines and demonstrate excellent prospects, especially for the devices on low thermal conductivity substrates. The theoretical analysis of optimized diamond heat spreaders shows an 86% reduction of spreading resistance for GaN devices and 98% for Ga2O3 devices. In addition, our results show that a 3âÎŒm-thick layer of high-quality CVD-deposited diamond heat spreaders on GaN-on-Si devices can provide better heat spreading than GaN-on-SiC devices and perform similar to GaN-on-diamond devices, highlighting the significant potential of heat spreaders as an effective and low-cost thermal management approach. INTRODUCTIO
Highly selective and responsive ultra-violet detection using an improved phototransistor
An ultra-violet (UV) phototransistor with 700x200 lm2 gate area decorated with vertically aligned Zinc Oxide (ZnO) nanorods to enhance UV responsivity is designed and manufactured. Spectral responsivity of the device was measured for wavelengths ranged from 200 to 1100 nm of the electromagnetic spectrum in different transistor working regions. The best responsivity was achieved at sub-threshold and very weak inversion region. In order to enhance UV range selectivity, oxygen plasma has been employed on the nanorods, and consequently, nearly 3-fold improvement in its relative sensitivity at 375 nm was achieved. The final manufactured phototransistor shows a highly selective response of 24 kA/W in the UV range.MicroelectronicsElectrical Engineering, Mathematics and Computer Scienc