Abstract Every computation presents a small chance that an unexpected phenomenon ruins or modifies its output. Computers are prone to errors that, although may be very unlikely, are hard, expensive or simply impossible to avoid. In the exascale, with thousands of processors involved in a single computation, those errors are especially harmful because they can corrupt or distort the results, wasting human and material resources. In the present work, we study the effect of ionizing radiation on several pieces of commercial hardware, very common in modern supercomputers. Aiming to reproduce the natural radiation that could arise, CPUs (Xeon, EPYC) and GPUs (A100, V100, T4) are subject to a known flux of neutrons coming from two radioactive sources, namely $$^{252}$$ 252 Cf and $$^{241}$$ 241 Am-Be, in a special irradiation facility. The working hardware is irradiated under supervision to quantify any appearing error. Once the hardware response is characterised, we are able to scale down the radiation intensity and to estimate the effects on standard data centres. This can help administrators and researchers to develop their contingency plans and protocols.

A number of applications of wheeled robots, including planetary exploration rovers and rescue missions, require that the vehicle operates in a non-structured environment. Optimizing the vehicle mobility is of key importance in such applications. Reduced mobility can limit the ability of the robot to achieve the mission goals, or even render it immobile in extreme cases. In this paper, the effect of normal contact forces on mobility is reported. A performance indicator based on the force distribution is defined and used to compare different vehicle configurations. The validity of this indicator was assessed using both simulation and experimental results obtained for a six-wheel rover prototype. Results suggest that modifying the robot configuration to alter the normal force distribution can lead to increased traction force available at the wheel-terrain interfaces, thus improving the mobility.

The solid state transformer is an emerging technology which aims at replacing the conventional low-frequency power transformer by means of a high-frequency transformer driven by a proper AC/AC power electronics conversion system, at both transformer sides. In comparison with the conventional power transformer, the solid state transformer provides extended and enhanced operating capabilities that can be achieved with an appropriate controller design for the power electronics converters. In this work, the interaction of the solid state transformer with a distribution system is analyzed under different operating conditions. Bidirectional active power flow, full reactive power control, low-voltage side current unbalance management and high-voltage side low-voltage ride-through are achieved with the proposed control approach.

In this work, a multibody dynamics model of a wheeled mobile robot is developed to characterize the terrain reaction forces in terms of the physical and control parameters of the system. A common strategy for simulating the motion of mobile robots on soft soil is to compute the soil reaction forces using terramechanics models and to solve a forward dynamics problem by considering the soil reactions as a set of forces applied to the system. This intends to provide an accurate computation of the forces involved in the wheel-soil interaction; however, a series of factors such as the sensitivity of reaction forces to soil parameters limits the applicability of the existing terramechanics models in unstructured environments. We propose an alternative approach which does not rely on the soil properties, but at the same time does not intend to provide an exact computation of wheel-soil interaction forces. The main objective of this approach is to estimate the effect of changes in control and design parameters on the performance of the system, using the information provided by the dynamics model of the vehicle. To this end, the reaction forces for the wheel-terrain interaction in the ideal limit case of pure rolling and no penetration are obtained upon the specification of the motion at the contact points, via kinematic constraints. The validity of the analysis results obtained using the proposed paradigm is verified by simulation runs and experiments. The experimental results suggest that this approach is successful in predicting the variation of a set of important performance indicators in terms of the changes in the parameters of the system.

The authors provide an accurate scheme for generating the excitation sequence in multipulse speech coding. The method is based on spiky deconvolution techniques, which take advantage of the sparse character of the multipulse sequence. It is shown how a threshold deconvolution procedure, formerly developed by some of the authors, can be extended to deal with all-pole filters, and, consequently, how the multipulse sequence can be estimated on every frame of speech data. Quantization procedures for coding the multipulse sequence are also discussed in order to achieve a bit rate transmission lower than 6.5 kb/s.>