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The protection provided by wearing masks has been a guideline worldwide to prevent the risk of COVID-19 infection. The current work presents an investigation that analyzes the effectiveness of face shields as personal protective equipment. To that end, a multiphase computational fluid dynamic study based on Eulerian–Lagrangian techniques was defined to simulate the spread of the droplets produced by a sneeze. Different scenarios were evaluated where the relative humidity, ambient temperature, evaporation, mass transfer, break up, and turbulent dispersion were taken into account. The saliva that the human body generates was modeled as a saline solution of 8.8 g per 100 mL. In addition, the influence of the wind speed was studied with a soft breeze of 7 km/h and a moderate wind of 14 km/h. The results indicate that the face shield does not provide accurate protection, because only the person who is sneezed on is protected. Moreover, with a wind of 14 km/h, none of the droplets exhaled into the environment hit the face shield, instead, they were deposited onto the neck and face of the wearer. In the presence of an airflow, the droplets exhaled into the environment exceeded the safe distance marked by the WHO. Relative humidity and ambient temperature play an important role in the lifetime of the droplets.

In this article, a control strategy approach is proposed for a system consisting of a quadrotortransporting a double pendulum. In our case, we attempt to achieve a swing free transportationof the pendulum, while the quadrotor closely follows a specific trajectory. This dynamic system ishighly nonlinear, therefore, the fulfillment of this complex task represents a demanding challenge.Moreover, achieving dampening of the double pendulum oscillations while following a precisetrajectory are conflicting goals. We apply a proportional derivative (PD) and a model predictivecontrol (MPC) controllers for this task. Transportation of a multiple pendulum with an aerial robotis a step forward in the state of art towards the study of the transportation of loads with complexdynamics. We provide the modeling of the quadrotor and the double pendulum. For MPC wedefine the cost function that has to be minimized to achieve optimal control. We report encouragingpositive results on a simulated environmentcomparing the performance of our MPC-PD controlcircuit against a PD-PD configuration, achieving a three fold reduction of the double pendulummaximum swinging angle.

Axial flow fans are broadly applied in numerous industrial applications because of their simplicity, compactness and moderately low cost, such us propulsion machines and cooling systems. Computational fluid dynamics techniques are commonly applied to investigate flow phenomena through the axial fan and the rotor dynamic performance. In the present work, a computational model of an axial fan is presented in the current study. Numerical simulations of a single stage axial fan on variable conditions have been performed to obtain the detailed flow field of the centrifugal fan. The investigation of the current work is focused on the rotor-stator configuration and the modeling of aerodynamic behavior of the blade rows. The precise prediction of axial force and efficiency has essential implication for the optimized operation of axial fan and the choice of thrust bearing. Furthermore, it can act as guide for the geometrical and structural axial fan design and the study of axial force prediction.

In the present study, a new micro-power scaled electromagnetic (EM) harvester is designed and fabricated. The device has an innovative magnetic flux varying mechanism with two cylindrical Nb magnets and a central core moving inside the magnets back and forth. The system harvest electricity from the linear oscillations by the help of a spring attached at the bottom part of the core. The device requires only one spring and a second linear-laminated core closes the flux outside of the magnets in order to lower the reluctance of the system. The device is 6 cm in length and 2.4 cm in width in cylindrical geometry as a compact and stable geometry. The experimental verifications have proven that it can generate up to U = 7.76 mV output voltage depending on the oscillation frequency. The maximal output power has been measured as P= 32 µW for 44 Hz frequency with the resistive load RL = 0.2 Ohm. The power density p = 1.17 µW/cm 3 has been obtained, experimentally.