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The purpose of this paper is to provide an overview of the sound power radiation mechanism of air-core reactors and to describe the method that is used to calculate sound power by using the electrical load. Sound power radiation of an air-core reactor is related to the alternating current harmonics, the mechanical tension stiffness and, most importantly, the breathing mode resonance. An analytical model that is based on electrical loads and mechanical properties of the air-core reactor is developed to calculate radial and axial forces caused by the radial and axial magnetic induction fields. This study employs the hemispherical spreading theory, which is a simple and common method that is used to predict sound propagation. Additionally, a numerical model is proposed. In this, the excitation of the acoustic field that surrounds the reactor is introduced by considering the radial and axial displacements of the reactor's windings, as the windings are subjected to the action of the radial and axial electromagnetic forces. Finally, a comparison is presented between analytical and numerical models and it is observed that the models are correlated.

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Flow-induced vibration of heat-exchanger tube bundles often causes serious damage, resulting in reduced efficiency and high maintenance costs. The excitation mechanism of flow-induced vibration is classified as vortex shedding, acoustical resonance, turbulent buffeting, or fluid-elastic instability. This paper aims to identify the mechanism that causes flow-induced vibration in a specific heat-exchanger tube bundle with cross-flow and proposes a solution to this problem. This case is investigated through acceleration and sound pressure level measurements. Moreover, finite-element models are developed to view the acoustic models of the cavity and vibration modes of the tubes and plates. The layout pattern of the tube array, the spacing ratio, the Strouhal number, and the flow characteristics are used to determine the excitation mechanism.

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In typical household refrigeration systems, the compressor is structurally connected to the cabinet through an assembly composed of rubber mounts and a steel support plate, usually called base-plate. This plate works as a vibration energy path from the compressor to other refrigerator components, and its dynamic behavior must be known in order to avoid the coincidence of resonances and operational frequencies , a situation in which the energy flow is maximized. One way to design a support that satisfies this requirement is to optimize the shape of the plate, locating its structural modes as far as possible from the operational frequency and first harmonics. In this work, the Finite Element Method (FEM) is used to solve the eigenvalue problem and to parameterize the optimization procedure, which is based on positioning of the nodes of a design region (the plate) in a FEM simplified model. Due to the large number of variables, a gradientbased method is adopted. The objective of the methodology is to maximize the difference between two adjacent eigenvalues near the fundamental operation frequency of the compressor, in order to obtain a large and effective bandgap. A geometrical constraint is imposed to the problem and it is represented by a maximum allowed deformation of the plate. The gradients needed are obtained using elementary stiffness and mass matrices information. The obtained results show that the procedure leads to a new shape which ensures the desired dynamic characteristics for the support plate.

This paper presents a preliminary study on the use of reinforcement learning to control the torque vectoring of a small rear wheel driven electric race car in order to improve vehicle handling and vehicle stability. The reinforcement learning algorithm used is Neural Fitted Q Iteration and the sampling of experiences is based on simulations of the vehicle behavior using the software CarMaker. The cost function is based on the position of the states on the phase-plane of sideslip angle and sideslip angular velocity. The resulting controller is able to improve the vehicle handling and stability with a significant reduction in vehicle sideslip angle.