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After many large earthquakes aftershocks activity can reach depths greater than the base of the seismogenic zone that is defined by background seismic activity. This observation is generally explained by strain rate induced embrittlement associated with the increase of post-mainshock strain rate, which favors a transition from ductile to brittle behavior. However, the underlying physical processes are not well understood. Here we integrate geological and geophysical data for the 2016–2017 Central Italy seismic sequence with laboratory experiments to provide a geological and physical interpretation for the post-mainshock transient deepening of the base of the seismogenic zone.The base of the seismogenic zone in the central-northern Apennines is set typically at 9-10 kilometers and corresponds to the top of the phyllitic basement. Structural studies on exhumed basement rocks highlight a heterogeneous basement fabric consisting of competent, 10 to 200 m wide, quartz-rich lenses surrounded by an interconnected and frictionally weak phyllosilicate-rich matrix. The matrix controls the overall rheology of the basement due to its interconnectivity, and promotes aseismic deformation because its rate-strengthening behavior.Following each major (Mw > 5.5) event of the 2016–2017 sequence, a dramatic and abrupt increase in seismic rate is observed below 10 km, hence within the basement. Here we document the presence of seismicity clusters made of more than 4 earthquakes and characterized by small magnitude (Mw < 2.5), small dimensions (< 500 meters), small temporal duration (< 14 days) and a swarm-like behavior. Furthermore, these clusters are often represented by multiple or repeating earthquakes with a cross correlation coefficient higher than 0.7 for all the three components. These observations suggest that the increase of shear stressing rate within the basement is responsible for deepening of seismicity. To further explore this idea, we performed laboratory experiments on rocks from exhumed outcrops of basement rocks. We found that shear stressing rate promotes accelerated creep on the phyllosilicate-rich matrix and dynamic instabilities on the quartz-rich gouge belonging to the lenses. Our integrated analysis suggests that the mainshocks of the 2016-2017 seismic sequence promoted an increase of shear stressing rate within the basement allowing the phyllosilicate-rich matrix to creep faster hence favoring the loading and the repeated failures of locked seismogenic patches represented by the quartz-rich lenses.

Faults can be reactivated by fluid injection and pore pressure increase in the rock volumes surrounding the fault zone. Induced earthquakes represent only one of the possible responses of active faults to pore pressure perturbations, since other strain transients characterize the spectrum of fault-slip behavior. A series of fluid injection experiments, designed and undertaken in the framework of the ERC Fault Activation and Earthquake Ruptures (FEAR) project, will be conducted in the Bedretto Underground Laboratory for Geosciences and Geoenergies (BULGG, Switzerland) to understand fault reactivation processes on a target well-identified fault zone. Small and accessible faults are to be instrumented to monitor deformation and seismicity during both fluid injection and fault reactivation.The mineralogical, microstructural, and hydraulic properties of the target fault zone are investigated to characterize the fault-slip behavior. Characterization of the frictional response is achieved through a suite of laboratory rock-deformation experiments using both double-direct and rotary experimental apparatuses. Fault stimulation by fluid pressurization was also simulated in laboratory by using an injection protocol reliable for the in-situ hydraulic stimulation and consisting of stepwise pore fluid pressure increase. Experiments undertaken at low velocity with the double-direct apparatus (BRAVA) suggest that the selected fault, composed of mixed phyllosilicate-granular materials, is frictionally stable but yet can be dynamically reactivated by hydraulic stimulation.Experiments were also performed on the fault gouge from the target fault with the rotary experimental apparatus (SHIVA). First, we apply half of the stresses measured at depth in the underground laboratory to accomplish the operating capability of the apparatus: 12 MPa normal stress, 7.5 MPa confining pressure and 1.5 MPa pore fluid pressure. Second, we imposed a slip rate of 10-5 m/s for 0.01 m to have an equally compacted and textured layer. Third, we applied a shear stress so that an equivalent slip tendency of 0.35 is achieved (ca. 2.7 MPa), and kept it constant. We then increased stepwise the pore fluid pressure by 0.1 MPa every 150 s. This allows the spontaneous nucleation of slip events. After fault reactivation, the maximum slip velocity was set to 0.1 m/s. The fluid injection sequence results in a first reactivation (R1). Thanks to the nominally infinite slip available in SHIVA we run a second injection sequence up to a reactivation (R2).Our experiments show two different styles of reactivation between R1 and R2. R1 reactivation is abrupt, with slip rate accelerating up to 0.1 m/s. Instead, R2 has a stage in which slip rate oscillates (0.5-3 mm/s) just before the last step of pore pressure increase leads to acceleration to 0.1 m/s. This would suggest a role for the shear fabric developed during the first reactivation, in which extensive grain size reduction might have led to stiffening of the fault, responsible of the oscillatory slip. This frictional behavior suggests the importance of considering the effect of texture development during multiple cycles of seismic slip. The generalization of our data and observations will contribute to shed light on the mechanics of faults and induced earthquakes by fluid pressure increase.

Containing aggressive behavior is an ongoing challenge in modern society. Aggressiveness is a multi-level construct that can be driven by emotions (reactive aggression) or can be "cold-blooded" and goal-directed (proactive). Aggressive behavior could arise because of a misjudgment of others' intentions or can follow frontal brain lesions leading to a reduction of impulse control and emotion regulation. In the last few years, interventional and basic research studies adopting Non-Invasive Brain Stimulation (NIBS) have significantly risen. Those techniques have been used both in healthy people, to better understand the role of certain brain regions in psychological processes, and in aggressive subjects to improve their symptoms. From an overview of the literature, focusing on the paper that uses transcranial direct current stimulation (tDCS) to reduce aggressiveness, it emerges that tDCS can (i) enhance facial emotion expression recognition, (ii) improve impulses control, and (iii) affect approach/withdrawal motivation. The current work shows the strengths and weaknesses of tDCS intervention on aggressive individuals, suggesting that this instrument could be adopted on violent people, and paves the way for intervention in some applied settings such as prison.

The aim of this paper is to predict the electromagnetic behavior of a permanent-magnet electric motor with a spoke rotor geometry for motorsport applications. Radial-flux spoke permanent-magnet machines are designed to achieve high torque with reduced volume and weight. However, for this type of machines, three-dimensional (3-D) rotor leakage effects are considerable and need to be assessed at the very early stage of the design process. In this study, analyses have been carried out using a new two-dimensional (2-D) modified model allowing to take into account the 3-D rotor leakage effects. The leakage has been predicted in relation to motor attributes through an easy and accessible formulation that has been validated against 3-D simulations and experimental results. Using the 2-D proposed model, motor performances have been evaluated over the Le Mans driving cycle, without recurring to 3-D models.

This paper investigates the influence of number of layers and conductor size of hairpin windings of electric motors for electric vehicle applications. Firstly, the hairpin winding technology for electric motors is reviewed and key design rules are introduced. Based on these design rules, a traction motor with hairpin winding technology is modelled in a finite element analysis (FEA) software. The influence of the hairpin winding layers on the DC and the AC copper losses is investigated, based on the results obtained considering different operating points and drive cycles. The results indicate that using a higher number of winding layers does not always lead to higher efficiency. The trade-off between DC and AC losses under different operating points and drive cycles must be considered when designing for the optimal number of winding layers. Furthermore, using a larger conductor and higher fill factor for hairpin winding not necessarily lead to higher efficiency. In this study, the optimal conductor size for electric motors with hairpin windings is identified by carrying out optimizations considering drive cycle efficiency.

This work aims to analyze and compare the electromagnetic and thermal behavior of two commonly used electrical machines in the automotive field: an induction motor and a brushless permanent magnet one, here equipped with slot water jacket cooling systems. The same stator design, drive management, and winding layout, with hairpin conductors, are adopted for both machines. Four different slot cooling system design arrangements are investigated, keeping the same overall machine volume. Both motors are simulated with the proposed cooling system arrangements. Loss analyses are carried out to evaluate the impact of the different channel positioning inside the slot and their effects on the electromagnetic performance. In the end, the best cooling solution is identified for each machine, highlighting the main differences between the two machines' behavior, in addition to proving the cooling system topology goodness for hairpin windings machines in the automotive sector.

This paper focuses on the alternative current (AC) losses in hairpin winding variation due to the skin and proximity effects in synchronous brushless permanent magnet machines when supplied from a pulse width modulation (PWM) inverter. Based on a motor used in a 200kW electrical drive unit, three main methodologies are investigated to demonstrate the importance of these additional losses and how it is possible to take them into account when modeling the electrical machine performance. A more rigorous approach and two more time-efficient ones are utilized for the purpose, showing powerful ways of taking into consideration the pulse width modulation induced eddy currents losses in stator conductors since the early stages of the design process. A reduction ratio of 30:1 in computation time gives the proposed methodologies great merit not only in modeling single operating points, but over the full torque-speed characteristic, efficiency maps, and drive/duty-cycles analyses.

This work explores several cooling system topologies for permanent magnet machines with hairpin winding configurations in automotive traction applications. A common cooling system such as a housing water jacket is initially utilized and subsequently compared to a slot water jacket one. Four different in-slot cooling arrangements are considered, leading to four different stator designs, keeping the same machine volume. The impact of the different loss components on the machine performance both electromagnetically and thermally is analyzed. The work aims to show and prove the goodness of the slot water jacket for hairpin windings in addition to the selection of the optimal solution among the proposed ones.

This paper deals with the design of a high power-density, high efficiency and low torque ripple propulsion motor for electric aircraft. The proposed design procedure resulted in a high-performance propulsion motor intended for a direct-drive solution on an 8–12 passenger commercial aircraft with a range up to 1000 miles. The electromagnetic design is firstly addressed and then the thermal management is discussed. A set of design development steps are investigated and validated through finite-element software, involving studies for the optimal selection of the of air gap diameter and the slot/pole combination, followed by improving the efficiency by suitable material selection and methods for losses mitigation. Finally, in order to prove the enhancement of power density and efficiency through this feasibility design study, the designed propulsion motor performance is compared to the state-of-the-art motors of similar direct-drive aircraft propulsion systems.

Winding losses in Brushless Permanent Magnet (BPM) machines are typically, one of the largest loss contributions, especially in high speed applications such as e-chargers, compressors and traction. For this purpose, it is crucial to predict and take into account also the AC winding loss component, in order to reduce the total amount of stator winding losses. In this paper, a comparative study of aluminum and copper windings is conducted with the aim of mitigating the effect of the winding losses. The study is carried out considering two high speed machines. The first one is the main motor of an electric powertrain, developed for a fully electric motorsport application, whereas the second one is a high-speed turbocharger for an electric vehicle power boost application.

This work deals with the AC winding losses calculation in electrical machines used in modern automotive traction applications; considering both hybrid and fully electric vehicles. The research is carried out estimating the AC winding losses amount for various configurations, through the use of detailed finite element analysis (FEA) and of a new hybrid analytical-FEA calculation method. A comparison of the obtained results by the two methods is carried out, in order to prove the proposed methodology effectiveness and to evaluate the winding losses impact on the overall design performance.

The aim of this paper is to present a study regarding the thermal management of a high performance electrical machine designed for motorsport application. The electrical machine under examination is a radial flux permanent magnet machine able to run up to 12000rpm and equipped with three different cooling systems: housing cooling jacket, direct slot cooling and liquid-cooled rotor. The thermal behaviour of the machine is studied considering the electrical machine involved in a real race drive cycle like Le Mans circuit. The machine losses, during the race, are calculated with electromagnetic simulations, whose results are then used for the thermal study of the machine behaviour, with the aim of optimising its cooling systems. Special attention is given to the high frequency losses occurring in the winding.

This paper investigates proximity and skin effects winding losses in a high performance and high frequency brushless permanent magnet machine designed for electric sport racing application, where such losses have a relevant impact. A detailed finite element analysis (FEA), with all conductors per slot modelled, is performed for various winding configurations, with single and multiple strands-in-hand, considering random conductors placement within the stator slots. A new hybrid analytical-FEA method is proposed for speeding up the losses calculation and then validated against pure FEA method. The proposed method can be further used in accurate and fast estimation of the motor performance and in optimization procedures, avoiding heavy computational burden of full FEA simulations.

Fans are commonly used to cool electric motors. They can be mounted directly on the electric motor shaft providing a simple and inexpensive cooling system. The fan sizing is crucial to ensure safe operating temperatures of the electric motor. Referring to the self-ventilated motors, in this paper a numerical model has been developed and validated for a given radial fan. Afterwards, numerical analyses have been done in order to assess the performance of fans characterized by different shapes. Dimensionless characteristic curves have been calculated varying the wheel aspect ratio and the number of blades. Calculations show that, for a given blade number, the dimensionless flow capacity depends on the aspect ratio of the impeller. Furthermore, for a given geometry, there is an optimal number of blades that maximizes the flow rate processed by the fan. Results allow to obtain relationships useful to the right choice or sizing of such fluid machines.

Size and cost reduction are among the main issues of electric motor design and fabrication. This paper proposes an original layout for an axial flux permanent-magnet motor with printed circuit board (PCB) winding. In contrast to other axial flux motors of the same type, which are generally made with a three-phase fractional slot winding, the proposed motor has a two-phase wave winding printed on either side of the PCB. This configuration allows increasing the number of pole pairs and the supply frequency so to reduce the stator and rotor core widths. The winding is also characterized by a large copper percentage on the board, which improves the torque density of the motor. The results of the mathematical analysis, of the numerical simulation and of the experiments are compared. A method for the computation of the phase inductances is also proposed and validated. The main dimensions of the magnets are optimized via the finite-element method. The experimental comparison shows the advantages of the proposed motor in comparison to the traditional shaded pole motor for household applications.

The objective of this paper is to introduce a new high performance electric motor for a high speed and torque motor sport application. A compact radial flux machine, with double layer concentrated winding and interior permanent magnets has been designed to achieve high torque with a low weight. The motor is made with 18 copper coils, 6 per phase, pre-wound and placed in the slots, which are directly cooled by forced oil. The motor is also equipped with a shaft spiral groove cooling system for magnet temperature control.

With the increase in the production of electric and hybrid vehicles, testing electric drivetrains for performance assessment has become a key factor in the automotive industry. An alternative to the installation of the drivetrain on the real vehicle, is represented by the emulation of performances with a real-time controlled test bench. The paper proposes a test rig for half a bus, which is able to reproduce the real operating conditions of driving during a driving cycle. The test rig is able to emulate slope, adhesion conditions, weather conditions by suitably commanding a load generator/motor drive. The paper explains the test rig architecture and the software implemented in the real time data acquisition and control platform. The drivetrain of an electric bus is tested using the proposed test bench. The results compare the performances of the selected drivetrain for the electric bus in different road/wheel adhesion conditions.

A method is being developed to employ TERFENOL to optimize the shapes of wings for minimum drag during transonic cruise. Potential advantages include enhanced UAV attack and surveillance capabilities through increased dash speed, longer loiter, and extended range as well as decreased fuel expenditures for transport aircraft. Two smart-wing concepts were compared: an adaptive wing with the capability to change the shape of the wing box and a smart trailing edge that modifies camber while maintaining a smooth upper surface. While the adaptive wing provides the most capability to change the structural shape to minimize shock- induced drag, when actuator- and structural-weight penalties were considered as well as reliability and maintenance, it was determined that the smart trailing edge is the better concept. Numerical optimization of a simplified smart trailing edge determined the optimum configuration and optimum deflections for minimum drag. The system has the potential to extend the range of a small-fuselage large-wing UAV bomber by 9% and increase its loiter time by 11%. Magnetic and electronic design improvements to the TERFENOL linear-wave motor have been identified that will enable us to miniaturized it for UAV applications while doubling its actuation force and speed, and halving its power.

This paper deals with the design of a scalable 200kW/ 370Nm or 75kW/ 200Nm, induction machines for electrical vehicles traction system. Two configurations are considered as low cost rare-earth free magnet electric motor alternatives: inner rotor and outer rotor. Both designs allow mass production while providing higher performance compared to current technologies. The electromagnetic, thermal and mechanical constraints are considered throughout the machine design, from the specifications to the optimization. Rotor die-casting, oil spray cooling and hairpin stator winding are used in the analyzed solutions. Analytical and numerical methods are used for electromagnetic and continuous thermal performance calculation over the full speed range of the machine, along with the mechanical limits from a stress and modal point of view.

This paper deals with the design of a 200kW, 20krpm machine for an electric vehicle application. The aim of the research is to design a low cost, rare-earth free magnet electric motor while ensuring mass production feasibility and providing higher performance than currently available technologies. Electromagnetic, thermal and mechanical constraints are considered throughout the machine design process, from the specification to the optimization. Rotor die-casting, oil spray cooling and hairpin winding are among the solutions investigated to fulfill the project requirements. Analytical and numerical methods are adopted for electromagnetic and continuous performance calculations over the machine's full speed range, taking into account the mechanical limits from a stress and modal point of view.

Exact analytical solutions, by an inverse type of method, are derived for the motion of a particle under a central Newtonian gravitational force and an atmospheric drag force proportional to the square of the speed. In these solutions a form of the orbit is assumed, and the corresponding required atmospheric density, as a function of height, is determined. Some simple specific examples are furnished to illustrate such exact solutions for the entire motion of a satellite including both its orbital decay phase and its planetary entry phase. In one of these examples the required atmospheric density distribution closely approximates, at least in the orbital decay phase, isothermal models frequently assumed for actual planetary atmospheres. (Author)