Numerical Implementation of a Critical State Model for Soft Rocks

This paper details the basic tasks for the numerical implementation of a simple elasto-plastic critical state model for bonded materials (i.e. soft rocks-hard soils) into the finite element program SNAC developed at the University of Newcastle in Australia. The first task described focusses on the derivation of the incremental constitutive relationships used to represent the mechanical response of a bonded/cemented material under saturated conditions. The second task presents how these stress-strain relations can be numerically integrated using an explicit substepping scheme with automatic error control. The third task concentrates on the verification of the substepping algorithm proposed. The model used to represent the saturated mechanical response of a bonded material combines the modified Cam clay with the constitutive relationships for cemented materials proposed in Gens & Nova (1993), but incorporates some flexibility on the degradation law adopted. The role of suction and other relevant aspects of unsaturated behaviour are also discussed at the end of the paper

Security in networks of unmanned aerial vehicles for surveillance with an agent-based approach inspired by the principles of blockchain

Unmanned aerial vehicles (UAVs) can support surveillance even in areas without network infrastructure. However, UAV networks raise security challenges because of its dynamic topology. This paper proposes a technique for maintaining security in UAV networks in the context of surveillance, by corroborating information about events from different sources. In this way, UAV networks can conform peer-to-peer information inspired by the principles of blockchain, and detect compromised UAVs based on trust policies. The proposed technique uses a secure asymmetric encryption with a pre-shared list of official UAVs. Using this technique, the wrong information can be detected when an official UAV is physically hijacked. The novel agent based simulator ABS-SecurityUAV is used to validate the proposed approach. In our experiments, around 90% of UAVs were able to corroborate information about a person walking in a controlled area, while none of the UAVs corroborated fake information coming from a hijacked UAV

Physical Sensors for Precision Aquaculture: A Review

(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this[EN] Aquaculture is presented as a sustainable method to provide fish, although in reality, it is far from being sustainable. Its negative impacts on the environment can be prevented and corrected by the use of sensors, developing precision aquaculture. Sensors are widely used in terrestrial applications, but in underwater environments, their use is constrained by a variety of issues. The aim of this paper is to describe the state-of-the-art of the underwater sensors for water quality monitoring. First, the requirements and challenges of underwater sensors for aquaculture monitoring are discussed in detail. The main challenges are the need of a waterproof isolation or the need to avoid corrosion and biofouling, among others. Second, there are some advantages compared with the terrestrial applications, such as no need of minimized systems or the fact that such systems only require low accuracy. Subsequently, we evaluated the different options available to sense each variable, related to the needs of the aquaculture sensors. For temperature monitoring, thermistors, thermocouples or RTC seem to offer similar advantages. In contrast, for dissolved oxygen monitoring, the optical method seems to be the best option. For turbidity, optical methods are the most employed ones, while for conductivity measurements, the inductive coils are a promising option.This work was supported by the pre-doctoral student grant "Ayudas para contratos predoctorales de Formacion del Profesorado Universitario FPU (Convocatoria 2014)" with reference: FPU14/02953 by the Ministerio de Educacion, Cultura y Deporte.Parra-Boronat, L.; Lloret Mauri, G.; Lloret, J.; Rodilla, M. (2018). Physical Sensors for Precision Aquaculture: A Review. IEEE Sensors Journal. 18(10):3915-3923. https://doi.org/10.1109/JSEN.2018.2817158S39153923181