Preserving context security in AWS IoT Core

Cloud computing platforms are widely used as enabling frameworks for the Internet of Things. Within this context, a number of peripheral devices are connected to the middleware and constantly communicate raw data in order for them to be processed. Although several countermeasures were designed (and often adopted) in order to secure the communication channel and to ensure device and back-end authentication, several deployed IoT solution are subject to context security threats, where authenticated devices act in an allowed yet unexpected way and trigger undesired processing tasks in the back-end. As AWS IoT Core is currently the most adopted middleware in this context, this paper proposes a practical solution to achieve context security in such a scenario

Towards a single-phase mixed formulation of refractory castables and structural concrete at high temperatures

Structural materials are broadly used in applications such as nuclear vessels, high-temperature processes, and civil construction. Usually, during their placing and lifespan, they may present free or chemically bonded liquid phases in their structure, demanding careful attention when exposed to high heating rates. Their behavior in such conditions is a challenging problem as it comprises numerous highly nonlinear properties (not easily measured via experimental tests), strongly coupled equations and unreliable experimental benchmarks. Nonetheless, such simulations are of great interest. This work aims to provide a numerical study, checking whether its solution indeed converges and yields reliable results. Additionally, as the model needs several input parameters, this work conducts a sensitivity analysis and also assesses its applicability to more complex scenarios, as such issues remain open in the literature. In order to do that, a simple model that can be easily adapted for mixed formulations and complex geometries was proposed. It was found out that when considering unidimensional models the choices regarding the interpolation of the sorption isotherms are not essential to the numerical stability of the system. Besides that, the permeability and thermal conductivity of the material are the most important parameters that affect the simulation results of pressure, temperature and evaporable water content profiles. Finally, the 2D mesoscale simulation of concrete with polymeric fibers (based on the mixed formulation of the problem) yielded results that agreed with experimental observations. Thus, the model proposed herein can provide a solid base for future works and also important insights towards simpler methodologies