The Covid-19 pandemic has brought about new challenges to educational institutions around the world, as there has been a sudden interest in distancelearning solutions in the offering of disciplines, including the science and technology ones. Distance-learning will have a direct impact on the training of professionals that will develop the bespoke Internet of Things (IoT) solutions that homes, offices, companies, and cities are increasingly dependent on.Regardless, the training for IoT needs to consider the particularities of wireless communications, as it is essential to guarantee communication in any IoT solution. However, this training is hindered by the difficulty of conducting remote experiments that reproduce the wireless channel behavior. Besides, learning the main theoretical concepts of wireless connectivity would be facilitated by the adoption of practical methods centered on the student, the socalled inductive training methods. This paper presents a remote, low cost, open-source network emulation environment capable of reproducing the behavior of nonguided, low-power links under different configurations. The emulation environment incorporates inductive approaches in the experimentation with wireless connectivity while following a consolidated project methodology. This environment was offered at a postgraduate course in the first semester of 2020. An end of course survey with the students indicated that the environment contributed to the comprehension of the principles governing the over-the-air connectivity. The evidence suggests that this remote environment is a useful tool for academic investigations of the particularities of low-power wireless channels.
The IEEE 802.15.4 network standard is being used as a suitable solution for wireless sensor networks in many environments and areas of expertise. They differ from other types of wireless networks because of its specific features. This work intends to analyse the mobility impact on IEEE 802.15.4 networks. For this reason it was developed a simulation platform with the requirements necessary to evaluate and compare environments with and without mobility. The results show that the mobility of elements in the scenarios evaluated caused signal degradation at short distances, but improvement in the rate of transmission for distances between 30 and 40 meters, as well as at distances greater than 60 meters. This is due to the fact that at intermediate distances the network presents high rate of collisions, making the technique CSMA/CA improve network performance in environments with more variability of the signal.
This paper reports impedance data and high voltage plasma photographic plates of high dilutions of sodium chloride in water submitted to the homeopathic dilution and succession up to 30cH. Extremely low concentrations of the original salt, even beyond Avogadro number, clearly differ from 'pure' water and; the action of sodium chloride on the electrical properties of water is inverted at high dilution.
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