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The demand of wireless solutions in industrial applications increases since the early nineties. This trend is not only ongoing, it is further pushed by developments in the area of software stacks like the latest Bluetooth Low Energy Stack. It is also pushed by new chip-designs and powerful and highly integrated electronic hardware. The acceptance of wireless technologies as a possible solution for industrial applications, has overcome the entry barrier [1]. The first step to see wireless as standard for many industrial applications is almost accomplished. Nevertheless there is nearly none acceptance of wireless technology for Safety applications. One highly challenging and demanding requirement is still unsolved: The aspect safety and robustness. Those topics have been addressed in many cases but always in a similar manner. WirelessHART as an example addresses this topic with redundant so called multiple propagation paths and frequency hopping to handle with interferences and loss of network participants. So far the pure peer to peer link is rarely investigated and there are less safety solutions available. One product called LoRa™ can be seen as one possible solution to address this lack of safety within wireless links. This paper focuses on the safety performance evaluation of a modem-chip-design. The use of diverse and redundant wireless technologies like LoRa can lead to an increase acceptance of wireless in safety applications. Many measurements in real industrial application have been carried out to be able to benchmark the new chip in terms of the safety aspects. The content of this research results can help to raise the level of confidence in wireless. In this paper, the term “safety” is used for data transmission reliability.
Rubber materials are characterized by a variety of inelasticities such as softening behavior, hysteresis loops and permanent set. In order to calculate the inelastic material behavior, constitutive models, that describe rubber as a homogeneous continuum, have to make use of damping or friction elements.
On the nanoscale, there is no need to adopt such rheological models. Inelastic material behavior can be explained and simulated by a continuous rearrangement of bonds, in particular, the van der Waals interactions, and by the polymer chains transitioning between cis and trans equilibrium torsion angles. The discrete molecular dynamics simulations presented in this paper are performed in an explicit FEM environment using nonlinear but elastic force field potentials. From a structural mechanics point of view, topological changes of the polymer network can be interpreted as a sequence of local material instability problems due to negative tangential bond stiffnesses.
In order to obtain representative results within reasonable computational time, the model is optimized with respect to the number of atoms and the loading velocity. It is shown that by increasing the model size, the stress–strain curves become independent of both the atoms initial state and the strain amplitudes.