Multirotor motion enhancement using propeller speed measurements

Multirotor autopilots often depend on open-loop control without the feedback of propeller speeds, although they are a critical factor in determining motion characteristics. This paper proposes a system that leverages actual propeller speeds as direct feedback to the autopilot to improve the state estimation and dynamics of the multirotor. Software-in-the-Loop (SITL) and Hardware-in-the-Loop (HITL) simulations with real data, in different scenarios, are conducted to demonstrate the impact of combining propeller speeds with typical drone sensors. The results show that the drone becomes more stable with lower trajectory errors. Further, a noticeable reduction in the vehicle position median error while following a trajectory is shown, and a considerable increase in the flying duration time before crashing in case of a motor fault. These results highlight the potential of adding propeller speed feedback to increase the autopilot’s controllability which enhances drone performance in sensitive applications

Photocatalysis with Nanoparticles for Environmental Applications: Reactor Design Issues

The scale-up of photochemical or photo-catalytic processes is a hard task, requir-ing the correct definition of light distribution across the device. After a collection of examples of different photoreactor layouts adopted for water treatment, the main modelling issues are reviewed. Alternative radiation modelling approaches are compared. The reaction rate ex-pressions are presented, considering the dependence on light, catalyst and reactants distribution and including possible mass transfer limitations

Arsenic phytoextraction and hyperaccumulation by fern species Fitoextração e hiperacumulação de arsênio por espécies de samambaias

Arsenic (As) is an ubiquitous trace metalloid found in all environmental media. Its presence at elevated concentrations in soils derives from both anthropogenic and natural inputs. Arsenic is a toxic and carcinogenic element, which has caused severe environmental and health problem worldwide. Technologies currently available for the remediation of arsenic-contaminated sites are expensive, environmentally disruptive, and potentially hazardous to workers. Phytoextraction, a strategy of phytoremediation, uses plants to clean up contaminated soils and has been successfully applied to arsenic contaminated soils. It has the advantage of being cost-effective and environmentally friendly. A major step towards the development of phytoextraction of arsenic-impacted soils is the discovery of the arsenic hyper accumulation in ferns, first in Pteris vittata, which presented an extraordinary capacity to accumulate 2.3% arsenic in its biomass. Another fern, Pityrogramma calomelanos was found to exhibit the same hyperaccumulating characteristics. After that, screening experiments have revealed that the Pteris genus is really unique in that many species have the potential to be used in phytoextraction of arsenic. In general, these plants seem to have both constitutive and adaptive mechanisms for accumulating or tolerating high arsenic concentration. In the past few years, much work has been done to understand and improve the hyperaccumulating capability of these amazing plants. In particular, the field of molecular biology seems to hold the key for the future of the phytoremediation.<br>O arsênio e um metalóide traço encontrado basicamente em todos os ambientes. Elevadas concentrações de arsênio no solo podem acontecer naturalmente devido ao intemperismo de rochas ricas em arsênio, como também de atividades antropogênicas. O arsênio é um elemento tóxico e cancerígeno. Em muitas partes do mundo, a contaminação pelo arsênio tem causado problemas ambientais e de saude. As técnicas disponíveis para a remediação do arsênio são economicamente proibitivas, destroem a paisagem natural e ainda podem afetar a saúde de pessoas diretamente envolvidas no processo. A fitoextração, uma das estratégias da fitoremediação, utiliza plantas para descontaminar solos e tem sido aplicada com sucesso em solos contaminados com arsênio e outros elementos. Dentre muitas vantagens, essa técnica tem baixo custo quando comparada com as convencionais. Um ponto chave no desenvolvimento da fitoextração foi a constatação de que samambaias hiperacumulam arsênio. Primeiro, em Pteris vittata, que apresentou extraordinária capacidade para remover arsênio do solo, concentrando 2.3% do arsênio na biomassa. Em seguida, foi observado que a samambaia Pityrogramma calomelanos possui capacidade semelhante para acumular arsênio. Essa característica peculiar foi observada em outras samambaias do genero Pteris. Em geral, essas plantas parecem apresentar mecanismos constitutivos e adaptativos que permitem elevada absorção e sobrevivência em solos com altas concentrações de arsênio. Muitas pesquisas têm sido conduzidas no sentido de entender e aumentar a capacidade de aborção de arsênio dessas plantas. Em particular, a chave para a aplicação bem sucedida da fitoremediação parece estar na biologia molecular