A magnetically coupled regenerative turn-on and turn-off snubberconfiguration

This paper presents a magnetically coupled regenerative turn-on and turn-off snubber configuration applied to a boost converter, which operates in continuous conduction mode (CCM). In addition to reducing the stresses in the switch, providing soft transitions in its turn-off voltage and turn-on current, it transfers the energy stored in the snubber capacitor to the load. This is achieved by using a coupled inductor mounted on the main inductor of the converter, which resets the capacitor voltage at each switching period. Design equations, as well as experimental results are presented, showing the high performance of the boost converter using the proposed snubber     

Power limits for secondary devices operating on TV white spaces

The use of TV white spaces as an alternative to overcome spectrum scarcity is a huge opportunity for new telecommunication systems and services. While being attractive for its desirable propagation characteristics, this part of the spectrum imposes a major difficulty from design and regulatory perspectives: how to optimize the use of spectrum and to ensure the protection of primary users, TV systems for example, at the same time. This paper discusses strategies to be adopted by geo-location database operators to calculate adaptive maximum permitted power levels for secondary devices, according to permissible levels of interference into the digital terrestrial television primary system.     

A distributed data storage protocol for heterogeneous wireless sensor networks with mobile sinks

This paper presents ProFlex, a distributed data storage protocol for large-scale Heterogeneous Wireless Sensor Networks (HWSNs) with mobile sinks. ProFlex guarantees robustness in data collection by intelligently managing data replication among selected storage nodes in the network. Contrarily to related protocols in the literature, ProFlex considers the resource constraints of sensor nodes and constructs multiple data replication structures, which are managed by more powerful nodes. Additionally, ProFlex takes advantage of the higher communication range of such powerful nodes and uses the long-range links to improve data distribution by storage nodes. When compared with related protocols, we show through simulation that Proflex has an acceptable performance under message loss scenarios, decreases the overhead of transmitted messages, and decreases the occurrence of the energy hole problem. Moreover, we propose an improvement that allows the protocol to leverage the inherent data correlation and redundancy of wireless sensor networks in order to decrease even further the protocol’s overhead without affecting the quality of the data distribution by storage nodes.     

Influence of the deposition parameters on the growth of SiGe nanocrystals embedded in Al2O3 matrix

Si_1−xGe_x nanocrystals (NCs), embedded in Al₂O₃ matrix, were fabricated on Si (100) substrates by RF-magnetron sputtering technique with following annealing procedure at 800 °C, in nitrogen atmosphere. The presence of Si_1−xGe_x NCs was confirmed by grazing incidence X-ray diffraction (GIXRD), grazing incidence small angle X-ray scattering (GISAXS) and Raman spectroscopy. The influence of the growth conditions on the structural properties and composition of Si_1−xGe_x NCs inside the alumina matrix was analyzed. Optimal conditions to grow Si_1−xGe_x (x∼ 0.8) NCs sized between 3 and 4 nm in Al₂O₃ matrix were established.     

Analog circuits optimization based on evolutionary computation techniques

This paper presents a new design automation tool, based on a modified genetic algorithm kernel, in order to improve efficiency on the analog IC design cycle. The proposed approach combines a robust optimization with corner analysis, machine learning techniques and distributed processing capability able to deal with multi-objective and constrained optimization problems. The resulting optimization tool and the improvement in design productivity is demonstrated for the design of CMOS operational amplifiers.     

Gate sizing using geometric programming

A two-step transistor sizing optimization method based on geometric programming for delay/area minimization is presented. In the first step, Elmore delay is minimized using only minimum and maximum transistor size constraints. In the second step, the minimized delay found in the previous step is used as a constraint for area minimization. In this way, our method can target simultaneously both delay and area reduction. Moreover, by relaxing the minimized delay, one may further reduce area with small delay penalty. Gate sizing may be accomplished through transistor sizing tying each transistor inside a cell to a same scale factor. This reduces the solution space, but also improves runtime as less variables are necessary. To analyze this tradeoff between execution time and solution quality a comparison between gate sizing and transistor sizing is presented. In order to qualify our approach, the ISCAS??85 benchmark circuits are mapped to a 45?nm technology using a typical standard cell library. Gate sizing and transistor sizing are performed considering delay minimization. Gate sizing is able to reduce delay in 21?%, on average, for the same area and power values of the sizing provided by standard-cells library. Then, the transistor sizing is executed and delay can be reduced in 40.4?% and power consumption in 2.9?%, on average, compared to gate sizing. However, the transistor sizing takes about 23 times longer to be computed, on average, using a number of variables twice higher than gate sizing. Gate sizing optimizing area is executed considering a delay constraint. Three delay constraints are considered, the minimum delay given by delay optimization and delay 1 and 5?% higher than minimum delay. An energy/delay gain (EDG) metric is used to quantify the most efficient tradeoff. Considering the minimum delay, area (power) is reduced in 28.2?%, on average. Relaxing delay by just 1?%, area (power) is reduced in 41.7?% and the EDG metric is 41.7. Area can be reduced in 51?%, on average, relaxing delay by 5?% and EDG metric is 10.2.     

3D Printing and Nanotechnology: A Multiscale Alliance in Personalized Medicine

3D printing and nanotechnology have been two important tools in the development of therapeutic approaches for personalized medicine. More recently, their alliance has been improved in an effort to build innovative, versatile, multifunctional, and/or smart medical and pharmaceutical products. Therefore, an extensive review about scientific studies that ally 3D printing and nanomaterials in the development of new approaches for pharmaceutical and medical applications for the treatment and prevention of diseases is presented here. The articles are classified into five categories according to their main application: Cell growth and tissue engineering, antimicrobial, drug delivery, stimulus-response, and theranostics. Semisolid extrusion, inorganic nanoparticles, and cell growth and tissue engineering are the most reported 3D printing technique, type of nanomaterial, and application, respectively. The increase in papers dedicated to these areas is also notable, especially in the 2019 and 2020, when semisolid extrusion became the most used technique, overcoming fused deposition modelling. In fact, this review highlights that the possibility of an alliance between 3D printing and nanotechnology for the production of multiscale materials is undoubtedly a great opportunity for knowledge and innovation in the pharmaceutical and medical area.     

Deriving Efficient Porous Heteroatom‐Doped Carbon Electrocatalysts for Hydrazine Oxidation from Transition Metal Ions‐Coordinated Casein

In this work, the synthesis of high‐performance, metal ion‐imprinted, mesoporous carbon electrocatalysts for hydrazine oxidation reaction (HzOR) using casein or a family of phosphoproteins derived from cow's milk as a precursor is shown. The synthesis is made possible by mixing trace amounts of non‐noble metal ions (Fe³⁺ or Co²⁺) with casein and then producing different metal ions‐functionalized casein intermediates, which upon carbonization, followed by acid treatment, lead to metal ion‐imprinted catalytically active sites on the materials. The materials effectively electrocatalyze HzOR with low overpotentials at neutral pH and exhibit among the highest electrocatalytic performances ever reported for carbon catalysts. Their catalytic activities are also better than the corresponding control material, synthesized by carbonization of pure casein and other materials previously reported for HzOR. This work demonstrates a novel synthetic route that transforms an inexpensive protein to highly active carbon‐based electrocatalysts by modifying its surfaces with trace amounts of non‐noble metals. The types of metal ions employed in the synthesis are found to dictate the electrocatalytic activities of the materials. Notably, Fe³⁺ is found to be more effective than Co²⁺ in helping the conversion of casein into more electrocatalytically active carbon materials for HzOR.     

SDN-based architecture for providing quality of service to high-performance distributed applications

The specification of quality of service (QoS) requirements in most of the existing networks is still challenging. In part, traditional network environments are limited by their high administrative cost, although software-defined networks (SDNs), a newer network paradigm, simplify the management of the whole network infrastructure. In fact, SDN provides a simple way to effectively develop QoS provisioning mechanisms. In this sense, we explore the SDN model and its flexibility to develop a QoS provisioning architecture. Through the use of our new architecture, network operators are able to specify QoS levels in a simple way. Each individual data flow can be addressed, and the architecture we propose also negotiates the QoS requirements between the network controller and applications. On the other hand, the network controller continuously monitors the network environment. Then, it allocates network elements resources and prioritizes traffic, adjusting the network performance. We evaluate the feasibility of our QoS provisioning mechanism by presenting three experimental setups under realistic scenarios. For example, for a given scenario where we evaluate file transfers, our results indicate that the additional SDN modules present negligible overhead. Moreover, for a given setup, we observe a reduction of up to 82% in the file transfer times.     

Touch‐Interactive Flexible Sustainable Energy Harvester and Self‐Powered Smart Card

Sustainable and safe energy sources combined with cost effectiveness are major goals for society when considering the current scenario of mass production of portable and Internet of Things (IoT) devices along with the huge amount of inevitable e‐waste. The conceptual design of a self‐powered “eco‐energy” smart card based on paper promotes green and clean energy, which will bring the zero e‐waste challenge one step closer to fruition. A commercial raw filter paper is modified through a fast in situ functionalization method, resulting in a conductive cellulose fiber/polyaniline composite, which is then applied as an energy harvester based on a mechano‐responsive charge transfer mechanism through a metal/conducting polymer interface. Different electrodes are studied to optimize charge transfer based on contact energy level differences. The highest power density and current density obtained from such a paper‐based “eco‐energy” smart card device are 1.75 W m^?2 and 33.5 mA m^?2 respectively. This self‐powered smart energy card is also able to light up several commercial light‐emitting diodes, power on electronic devices, and charge capacitors.