Abstract
Underwater wireless communication systems are becoming a priority in terms of research and technological development due to the increasing demand for exploring the oceans in areas such as pharmaceutical, oil, minerals, environmental and biodiversity. This demand is increasing exponentially with the need for high data rate and near-real-time communications. In this work an underwater low power acoustic modem to operate over tens of meters, achieving a maximum data rate of 1 Mbps, is presented. This solution allows for reprogramming the digital signal processing block enabling the use of different types of digital modulations in order to improve the modem's performance. The system is based on a poly(vinylidene fluoride) PVDF ultrasonic emitter transducer which is capable of sending high quality signals needed for digital modulations with high symbol rates per carrier period. BPSK, BFSK and OOK modulations have been tested. The results registered were 3x10(-3) BER with 1 Mbps OOK, 2.3x10-5 with 512 kbps and 1x10-8 with 256 kbps.

Abstract
The reduction of carbon emission is imperative towards the Green Internet. Hence, this paper proposes and validates green routing metrics focused on improving energy efficiency of multi-hop approaches in heterogeneous wireless peoplecentric environments. The validation is carried out through discrete event simulations based on real data set traces and controlled random topologies for the specific case of AODV. Results show improvements to network lifetime without penalizing other performance metrics.

Abstract
In this work, a phase-shifted fiber Bragg grating is proposed for strain sensing at extreme temperatures. The grating structure is written in bare standard single mode fiber, using the point-by-point femtosecond laser technique. Strain measurements are performed at temperatures ranging from room temperature up to 900°C. By subjecting the sensor to such extreme conditions, the wavelength of the grating increases. © 2014 OSA.

Abstract
Over the last three decades, several despeckling filters have been developed to reduce the speckle noise inherently present in ultrasound images without losing the diagnostic information. In this paper, a new intensity and feature preservation evaluation metric for full speckle reduction evaluation is proposed based contrast and feature similarities. A comparison of the despeckling methods is done, using quality metrics and visual interpretation of images profiles to evaluate their performance and show the benefits each one can contribute to noise reduction and feature preservation. To test the methods, noise-free images and simulated B-mode ultrasound images are used. This way, the despeckling techniques can be compared using numeric metrics, taking the noise-free image as a reference. In this study, a total of seventeen different speckle reduction algorithms have been documented based on adaptive filtering, diffusion filtering and wavelet filtering, with sixteen qualitative metrics estimation.

Abstract
Rekindles and false alarms are phenomena that have a significant presence in the Portuguese forest fire management system and an important impact on suppression resources in particular and fire management resources in general. In this paper, we propose a discrete-event simulation model of a forest fire suppression system designed to analyze the joint impact of ignitions, rekindles, and false alarms on the performance of the system. The model is applied to a case study of the district of Porto, Portugal, for the critical period of the forest fire season, between July and September 2010. We study the behavior of the system's point of collapse, comparing the real base scenario with a benchmark scenario built with reference values for rekindles and false alarms, and also as a function of the number of fire incidents, considering historical variations. The results of the analysis are useful for operational decision-making and provide relevant information on the trade-off between prevention and suppression efforts.

Abstract