An ultra-fast protection scheme for normally-on wide bandgap devices

Here, an ultra-fast protection scheme that is dedicated to depletion-mode (d-mode) devices is proposed. The key to the d-mode device gate drive design is the negative supply and overcurrent protection, due to the safety concern for d-mode devices when a failure happens in power conversion applications. This work evaluates specific requirement of d-mode devices, such as the isolated negative power supply and short-circuit protection. Normally-on d-mode GaN devices have lower on-resistance and minimal dead time in comparison with enhancement-mode (e-mode) GaN devices, which can further reduce the switching loss and conduction loss. Both simulation and experimental verification are conducted in this work to evaluate the performance of the proposed protection scheme. The proposed desaturation scheme can wipe out the overcurrent event within 341 ns. Furthermore, the proposed negative power supply scheme can sustain its output for 60.5 ms, providing sufficient action time for the control unit to isolate the converter

Analysis of 1.2kV GaN polarisation superjunction diode surge current capability

Surge current capability of power diodes is one of the essential parameters that needs to be considered for high power density operations in power electronic applications. Gallium Nitride (GaN) is emerging as the next generation of power semiconductor devices due to its superior material characteristics. This work presents the device working principle, characteristics, and the surge capability of 1200V GaN polarisation superjunction (PSJ) hybrid diodes. The experimental results show that the GaN PSJ diode can withstand a surge current of 60A which is around 8 times its rated current and a surge energy of 5.4J. Additionally, despite having a merged PiN and Schottky structure, no bipolar current flow due to the activation of p-doped GaN can be observed until breakdown. This can also be confirmed through the device forward characteristic which shows a unique saturation behaviour at about 76A without any bipolar region

Sheffield students win US rocket competition

Viktor Fedun reports on success for SunrIde, a team of students from the University of Sheffield who designed and built a rocket

Estimated marine fish landings (in tonnes)in India during 2002 and 2003

Estimated marine fishing landing in India during 2002 and 2003 is 2.59 and 2.58 millon tonnes respectively. Gear wise landing were also estimated during this period

Marine Fish Calendar. 4 Cochin

The article provides details about the marine fish landing at Cochin fisheries harbour, Kerala during the period 1981-1985. It was found that the majority of the landing was contributed by purse seine followed by trawlers, drift gill nets, boat seines, hooks and lines etc

Short Nylon-6 Fibre/Rubber-Toughened Polystyrene Composites

The thesis describes studies on development of short Nylon-6 fibre composites based on rubber-toughened polystyrene (PS). Toughening was done using natural rubber (NR), styrene-butadiene rubber (SBR) and whole tyre reclaim (WTR). The composites were prepared by melt mixing in an internal mixer at 170 oC. It was found that the optimum blend ratio was 85/15 for PS/NR, 90/10 for PS/SBR and 90/22 for PS/WTR blends. The effect of dynamic vulcanisation on 85/15 PS/NR and 90/10 PS/SBR blends using dicumyl peroxide (DCP) at various concentrations were also studied. The dynamic crosslinking improved the tensile properties, flexural properties, impact strength and dynamic mechanical properties of both the blends. The effect of unmodified and resorcinol formaldehyde latex (RFL)-coated short Nylon-6 fibres on the mechanical properties, morphology and dynamic mechanical properties of 85/15 PS/NR, 90/10 PS/SBR and 90/22 PS/WTR blends were studied. Fibre loading was varied from 0 to 3 wt.%. For 85/15 PS/NR blend, there was a significant enhancement in tensile properties, flexural properties and impact strength with 1 wt.% of both unmodified and RFL-coated fibres. Dynamic mechanical analysis revealed that the storage modulus at room temperature was maximum at 1 wt.% fiber loading for both composites. The surface functionality of the fiber was improved by giving alkali treatment. Maleic anhydride-grafted-polystyrene (MA-g-PS) was prepared and used as a compatibiliser. The effect of MA-g-PS on the composites was investigated with respect to mechanical properties, morphology and dynamic mechanical properties. The compatibiliser loading was varied from 0 to 2 wt.%. The properties were enhanced significantly in the case of treated and untreated fibre composites at a compatibiliser loading of 0.75 wt.%. SEM analysis confirmed better bonding between the fibre and the matrix. Dynamic mechanical studies showed that the storage modulus at room temperature improved for treated fibre composites in the presence of compatibiliser. In the case of 90/10 PS/SBR composites, the addition of short Nylon-6 fibres at 1 wt.% loading improved the tensile modulus, flexural properties and impact strength while the tensile strength was marginally reduced. The surface treated fibers along with compatibiliser at 0.5 wt.% improved the tensile properties, flexural properties and impact strength. DMA reveale that the storage modulus at room temperature was better for composites containing untreated fibre and the compatibiliser. In the case of 90/22 PS/WTR blends, 1 wt.% unmodified fibre and 0.5 wt.% RFL-coated fibres improved tensile modulus, flexural properties and impact strength. Tensile strength was improved marginally. The surface treatment of Nylon fibre and the addition of compatibiliser at 0.5 wt.% enhanced the tensile properties, flexural properties and impact strength. The dynamic mechanical analysis showed that the storage modulus at room temperature was better for untreated fibre composites in conjunction with the compatibiliser. The thermal stability of PS/NR was studied by TGA. Thermal stability of the blends improved with dynamic vulcanisation and with the incorporation of RFL-coated Nylon fibres. The untreated and partially hydrolyzed fibre composites in conjunction with the compatibiliser enhanced the thermal stability. Kinetic studies showed that the degradation of the blends and the composites followed first order kinetics.Cochin University of Science and TechnologyDepartment of Polymer Science and Rubber Technology, Cochin University of Science and Technolog

Sheffield University Nova Rocket Innovative Design Engineering (SUNRIDE)

Sheffield University Nova Rocket Innovation Design Engineering (SunrIde) was the first ever student-led rocketry team from the UK to participate in Spaceport America Cup (SA Cup) 2018, the largest space industry backed annual rocketry engineering competition in the world. The main objective of the SunrIde was to design and build a high-power reusable rocket in the 10,000 ft above ground level (AGL) category with commercial-off-the-shelf (COTS) solid propulsion system. The rocket should reach the projected apogee within the smallest margin possible while carrying either a dead weight 3-unit CubeSat payload or a scientific experiment, both weighing no less than 8.8 lb (4 kg), with a 5% allowance. The University of Sheffield team launched and recovered a self-designed rocket that reached an altitude of 10,017 ft (3,053 m) above ground level (AGL). It won the James Barrowman Award for Flight Dynamics with the most accurate altitude prediction at 99.83%. This success sets an important precedent for aspiring STEM students across the UK by encouraging them to expand their engineering skills through practical projects and increases the UKs high-power rocketry presence

Not Available

Not AvailableEstimated marine fishing landing in India during 2002 and 2003 is 2.59 and 2.58 millon tonnes respectively. Gear wise landing were also estimated during this period.Not Availabl