Abstract
A neodymium-doped glass waveguide laser based on a new structure employing two core layers is reported. This double-layer structure allows a photosensitive layer to be integrated with an efficient gain layer. Singlemode operation was obtained with a lasing threshold of 93 mW and an efficiency of 0.6%.

Abstract
The extraction of relevant objects (foreground) from a background is an important first step in many applications. We propose a technique that tackles this problem using a cascade of change detection tests, including noise-induced, illumination variation and structural changes. An objective comparison of pixel-wise modelling methods is first presented. Given its best relation performance/complexity, the mixture of Gaussians was chosen to be used in the proposed method to detect structural changes. Experimental results show that the cascade technique consistently outperforms the commonly used mixture of Gaussians, without additional post-processing and without the expense of processing overheads. ©2007 IEEE.

Abstract
Purpose - The purpose of this paper is to determine the state probabilities for a float system when overhauls are performed periodically. Design/methodology/approach - First, a model is developed to express the relationship between the rate of occurrence of failure and time interval between overhauls. Then, a methodology is defined to develop differential equations for each system state in order to calculate corresponding system state probabilities. Findings - Since it is considered that units requiring an overhaul stay in operation until replacement, the possibility of failure of those units has to be included. Then, the determination of system state probabilities has to be done iteratively. Practical implications - The methodology proposed in this paper enables comparison of different designs for a float system submitted to periodic overhauls through some different performance measures. System state probabilities can also be used to determine the idle time of units, which is essential to obtain the cost of production loss and, therefore, the system maintenance cost. Originality/value - This paper considers simultaneously three different factors that influence maintenance float system performance: the number of spare units and the number of maintenance crews (which mean minimising the downtime effect) and the overhaul frequency (which means decreasing the number of failures). © Emerald Group Publishing Limited.

Abstract
The problem of simultaneous localization and mapping has been studied by the mobile robotics scientific community over the last two decades. Most solutions for this problem are based on probabilistic theory in order to represent the uncertainty in robot perception and action. One of the most efficient probabilistic methods is the Extended Kalman Filter (EKF). However, the EKF demands a considerable amount of computing power and is usually processed by high-end laptops coupled to the robots. In this work, we present an implementation of the EKF targeting an embedded system based on an FPGA device. In order to improve performance, our approach combines a softcore processor with customized hardware. We present experiments with four different FPGA implementations, being the first purely based on software, the second using custom instruction logic directly connected to the processor's ALU, the third using hardware accelerators connected to the processor's data bus, and finally the fourth combining those two hardware/software solutions. For the experiments conducted, the results obtained with a small addition of hardware resources permitted to increase from 2x to 4x the performance of the global system.

Abstract

Abstract
Hybrid materials produced by the hydrolytic sol-gel process reveal strong absorption in the spectral region of 1550 nm, mainly due to the high concentration of OH groups. This characteristic constitutes an obstacle to the application of these materials, in particular to telecom integrated optical devices. A simple thermal treatment applied to the device does not contribute to increase the transparency. The real-time influence of temperature and environment humidity on the optical transmission properties of sot-gel organic-inorganic raised channel waveguides is analyzed in order to achieve an understanding of the OH group's behaviour in the materials. We demonstrate that the level of the optical losses at 1550 nm can significantly be decreased at high temperature. Cooling the sample in dry atmosphere makes it possible to reach a better transparency, which can be useful to improve the performance of hybrid sol-gel optical devices.