Abstract
The direction of arrival of sound waves has been extensively used for passive acoustic tracking of underwater sound sources, such as marine mammals or ultrasonic electronic tags attached to animals or submerged equipment. This process can be automated by measuring the time difference of arrival (TDOA) of the sound wave arriving to two or more hydrophones and then calculating the relative direction of the acoustic source using those time differences. Although the generalized cross-correlation between the received signals is a common technique for determining the TDOA, the underwater environment introduces several distortions in amplitude and phase of the received sound waves due to reflections and reverberation, particularly in confined spaces. This is aggravated by the variation of the sound propagation speed with temperature, pressure and salinity. Because of this, the use of the cross-correlation method not effective to determine the TDOA especially when using single frequency pulses as the transmitted signal. In this work we propose an alternative method to calculate the TDOA, consisting in the analysis of the initial part of the received signals to discover a series of similar zero-crossing periods to identify their beginning, and then calculating the time difference between them. We have implemented this technique in a reconfigurable system-on-chip, attaching to an embedded ARM processor a custom designed digital signal processing system. This has been tested in a test tank and in outside environment. This system is capable of computing in real-time the 2D direction of an underwater acoustic transmitter, and combining the different directions resulting from the relative movement between transmitter and receiver it is possible to estimate the relative position of the acoustic source.

Abstract
Atmospheric Electric Potential Gradient (PG) measurements were carried out in three sites forming a triangular array in Southern Portugal. The campaign was performed during the summer, characterized by Saharan dust outbreaks; 16th-17th July 2014 dust event is considered. Short time-scale oscillations of the PG at two of the stations and a mid time-scale suppression of the PG in the three stations are found. Results are interpreted as evidencing long-range dust electrification; attributed to the air-Earth electrical current creating a bipolar charge distribution inside of the dust layer. The relevance of using arrays of sensors, instead of single sited, is highlighted.

Abstract
Our goal is the provide a tour of recent progress towards rendering Kalman filters suitable for driving astronomical adaptive optics with increasing numbers of degrees of freedom and discuss the prospects to port them to the foreseen real-time architectures.

Abstract
Novel input modalities such as touch, tangibles or gestures try to exploit human's innate skills rather than imposing new learning processes. However, no work has been reported that systematically evaluates how these interfaces influence users' performance, that is, assesses if one interface can be more or less appropriate for interaction regarding: (1) different age groups; and (2) different basic tasks, as content insertion or manipulation. This work presents itself as an exploratory evaluation about whether or not the users' efficiency is indeed influenced by different input modalities and age. We conducted a usability evaluation with 60 subjects to understand how different interfaces may influence the speed and accuracy of three specific age groups (children, young adults and older-adults) when dealing with a basic content insertion task. Four input modalities were considered to perform the task (keyboard, touch, tangibles and gestures) and the methodology was based on usability testing (speed, accuracy and user preference). Overall, results show that there is a statistically significant difference in speed of task completion between the age groups, and there may be indications that the type of interface that is used can indeed influence efficiency in insertion tasks, and not so much other factors like age. Also, the study raises new issues regarding the "old" mouse input versus the "new" input modalities.

Abstract

Abstract
A fundamental problem in the management of an automated guided vehicle system (AGVS) is the determination of the load to be transported and the vehicle to transport it. The time for the loading and unloading of pallets must be specified as soon as possible. Typical objectives are minimization of travel times and costs by the reduction of the number of vehicles required to fulfill a given transportation order. This article presents a methodology for the estimation the minimum number of AGVs (considering all the available ones at the shop floor level) required to execute a given transportation order within a specific time-window. A comparison is made between the algorithms Shortest Job First and meta-heuristic Tabu Search (applied to an initial solution) for a task assignment. An enhanced Dijkstra algorithm is used for the conflict-free routing task. The number of vehicles is estimated so as to provide an efficient distribution of tasks and reduce the operational costs of the materials handling system. Simulation results of two typical industrial warehouse shop floor scenarios are provided. Although the study focuses on pre-planning of order fulfillment of materials handling, the proposed methodology can also be utilized as an important tool for investment analysis of the warehouse layout design and for estimating the ideal number of AGVs.