Investigations on the Use of the Power Transistor Source Inductance to Mitigate the Electromagnetic Emission of Switching Power Circuits

With power designers always demanding for faster power switches, electromagnetic interference has become an issue of primary concern. As known, the commutation of power transistors is the main cause of the electromagnetic noise, which can be worsened by the presence of unwanted oscillations superimposed onto the switching waveforms. This work proposes a solution to mitigate the oscillations caused by the turn-on of a power transistor by exploiting its source inductance plus an external one. In this context, an optimization method is proposed to find the optimal value of the source inductance as a trade-off between oscillation damping and power dissipation. The experimental results performed on a prototyped power converter assess the proposed technique as the spectrum of the conducted emission is attenuated by 20 dB at the oscillation frequency. With respect to traditional solution based on snubbers, the proposed solution results in a similar oscillation damping, but with a 0.5% higher power efficiency

An Adaptive Method to Reduce Undershoots and Overshoots in Power Switching Transistors Through a Low Complexity Active Gate Driver

Active gate drivers lend themselves well to reducing over- and under- voltages during the commutations of hard switched power transistors, as well as to damping resonances. However, their control strategy is a major challenge, as it should account for variations of operating condition, parameter spread, and non linearities of the driven transistor. This paper proposes an effective control method to reduce overshoots and undershoots in a power transistor driven by an active gate driver. The modulation pattern is modified on-the-fly and none a-priori characterization is required. The presented method modifies the timing parameter to attain almost zero over- and under- voltages with the lowest power losses. This is achieved by combining a low complexity active gate driver with the measurements of peak values of the drain-source voltage. The technique was experimentally assessed for a 48-12 V DC-DC converter, and resulted in better switching performance than standard solutions and open loop control

Critical Upper Limb Ischemia Due to Brachial Tourniquet in Misdiagnosed Thoracic Outlet Syndrome after Carpal Tunnel Decompression: A Case Report

We present the case of a 68-year-old woman, referred to our department for critical upper limb ischemia, which had occurred a few days after homolateral surgical ligamentotomy for carpal tunnel syndrome, diagnosed and confirmed by electromyography, and performed with a brachial tourniquet. The patient was later admitted for subsequent progressive necrosis of the first three fingers of the left hand, accompanied by signs of upper limb ischemia. An accessory cervical rib was identified, completely obliterating the subclavian artery distally at the origin of the suprascapular artery. A complete humeral artery occlusion was also found at the middle third of the humerus. The accessory rib was resected and the subclavian artery recanalized. A few days later, necrosis of the distal third of the first two fingers appeared and surgical resection was performed. Despite this chronic condition, the acute occlusion of collateral circles was probably induced by the brachial tourniquet. This represents a rare event, never previously reported in the literature: a case of critical upper limb ischemia due to a brachial tourniquet in a patient with misdiagnosed thoracic outlet syndrome. Until specific electrophysiological criteria for this syndrome can be found, attention should focus on history and clinical examination in patients with suspected carpal tunnel syndrome

From Radio to In-Pipe Acoustic Communication for Smart Water Networks in Urban Environments: Design Challenges and Future Trends

The smart management of water resources is an increasingly important topic in today’s society. In this context, the paradigm of Smart Water Grids (SWGs) aims at a constant monitoring through a network of smart nodes deployed over the water distribution infrastructure. This facilitates a continuous assessment of water quality and the state of health of the pipeline infrastructure, enabling early detection of leaks and water contamination. Acoustic-wave-based technology has arisen as a viable communication technique among the nodes of the network. Such technology can be suitable for replacing traditional wireless networks in SWGs, as the acoustic channel is intrinsically embedded in the water supply network. However, the fluid-filled pipe is one of the most challenging media for data communication. Existing works proposing in-pipe acoustic communication systems are romising, but a comparison between the different implementations and their performance has not yet been reported. This paper reviews existing works dealing with acoustic-based ommunication networks in real large-scale urban water supply networks. For this purpose, an overview of the characteristics, trends and design challenges of existing works is provided in he present work as a guideline for future research

A Baseband Wireless VNA for the Characterization of Multi-Port Distributed Systems

Frequency characterization of spatially-large structures has become increasingly required, mostly in the fields of Structural Health Monitoring and Communication Systems based on non conventional media. When the ports of the system under measurement are far apart, methods based on traditional wired instruments become unattractive for field applications, due to the increased complexity, cost and signal integrity related issues. Aiming towards removing the wired connection from the ports of the system under test and the elaboration unit, the main issue to be dealt with is the time-synchronization of measurements at the ports. This contribution proposes a solution to such an issue by presenting a Wireless Vector Network Analyzer, suitable for the characterization of distributed systems. For this purpose, a wireless synchronization scheme is proposed, which is based on the disciplining of the signal sampling clock from the 1-Pulse-Per-Second reference signal. The proposed synchronization method reduces clock jitter at different ports at 1.13 μs over a 300 s observation interval. The hardware and software implementation of the system are detailed and experimental results proving its operation are provided

A Wireless Communication System for Urban Water Supply Networks Based on Guided Acoustic Waves

The structural complexity of real-world pipeline networks makes it difficult to derive physics-based models of acoustic propagation. This work deals with the design of a communication system based on the propagation of acoustic waves in water-filled pipes. A method based on the experimental characterization of the communication channel is proposed. This approach is applied to an urban water distribution pipeline, and a black-box model representing its frequency response is obtained. The derived two-port model is used for the simulation of a complete communication system, comprising transmitter and receiver models, with the aim of using the water pipe as a wireless communication channel. It is shown that the choice of modulation parameters is critical in order to deal with issues such as the frequency selectivity of the channel and multipath wave propagation. A communication system is presented and the experimental results of the communicated data are provided

Report on the Deliberative Panel of the Market‐based Solutions for the Extreme Poor Programme

This report describes the discussions held by a deliberative panel on disability in Uganda. The panel formed part of a wider research project on ‘market‐based solutions for the extreme poor’ funded by the Rockefeller Foundation. The Foundation was interested in how market activity (broadly defined) could reach and potentially benefit the very poorest and most marginalised people. The research team proposed that this issue was looked at through the lens of disability, since persons with disabilities account for around 20 per cent of the population in Uganda, and persons with disabilities are usually among the poorest. The research focuses on two localities: the urban location of Kawempe on the outskirts of Kampala, and the rural neighbourhood of Gulu.The Rockefeller Foundatio

Dissipative DNA nanotechnology

DNA nanotechnology has emerged as a powerful tool to precisely design and control molecular circuits, machines and nanostructures. A major goal in this field is to build devices with life-like properties, such as directional motion, transport, communication and adaptation. Here we provide an overview of the nascent field of dissipative DNA nanotechnology, which aims at developing life-like systems by combining programmable nucleic-acid reactions with energy-dissipating processes. We first delineate the notions, terminology and characteristic features of dissipative DNA-based systems and then we survey DNA-based circuits, devices and materials whose functions are controlled by chemical fuels. We emphasize how energy consumption enables these systems to perform work and cyclical tasks, in contrast with DNA devices that operate without dissipative processes. The ability to take advantage of chemical fuel molecules brings dissipative DNA systems closer to the active molecular devices that exist in nature