Optimised wavelength interleaved radio-over-fibre system based on highly birefringent fibre Bragg gratings

A new scheme, based on Bragg gratings written in highly birefringent fibre that allows both increasing the channel density and relaxing the filter bandwidth requirements in future radio-over-fibre wavelength interleaved distribution networks, is presented and tested.     

Thermal-lens and photo-acoustic methods for the determination of SiC thermal properties

In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρc_p, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (c_p) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments.     

Intrusion Detection System for Wireless Sensor Networks Using Danger Theory Immune-Inspired Techniques

An IDS framework inspired in the Human Immune System to be applied in the wireless sensor network context is proposed. It uses an improved decentralized and customized version of the Dendritic Cell Algorithm, which allows nodes to monitor their neighborhood and collaborate to identify an intruder. The work was implemented and tested both in simulation and in real sensor platform scenarios, comparing them to each other and was also compared to a Negative Selection Theory implementation in order to demonstrate its efficiency in detecting a denial-of-sleep attack and in energy consumption. Results demonstrated the success of the proposal.     

基于重叠正交变换的自适应图像水印

本文提出了一种基于重叠正交变换（LOT）的自适应图像水印算法,给出了水印嵌簇检测的详细算法设计,数字图像水印是最近发展起来的一项新技术,它为图像的版权保护问题提供了一种新的解决思路,本文首次在水印算法中采用了LOT以代替传统的离散余弦变换（DCT),从而有效地避免了DCT的块效应,同时,本文还利用人的视觉系统（HVS）特性,在对图像块进行分类的基础上完成水印的自适应嵌入,实验结果表明,本文所提出的图像水印算法有效地提高了水印的鲁棒性和透明性。     

有机半导体电注入激光器

有机半导体激光器实现了从光泵浦到电泵浦。回顾了有机半导体激光器从光泵浦到电流入的发展过程。概述了有机半导体材料产生激光的特性,介绍了贝尔实验室第一个有机固态电注入型激光器的工作原理,提出了在器件结构上的一些新设想。     

A visible-light and infrared video database for performance evaluation of video/image fusion methods

Multidimensional Systems and Signal Processing - In general, the fusion of visible-light and infrared images produces a composite representation where both data are pictured in a single image. The...     

基于AFM的微结构加工实验研究

本文建立了微动工作台和原子力显微镜相结合的微加工系统，在该系统上采用金刚石针尖进行微加工实验，与SPI系统本身的刻划软件刻划出的图形进行了比较分析，得出这个系统适合微结构的加工；并给出了采用该方法加工的1111面及多边形面微结构；还分析了金刚石针尖几何角度及SPM和工作台的相关参数对加工的影响。     

Dynamical diseases of brain systems: different routes to epileptic seizures

In this overview, we consider epilepsies as dynamical diseases of brain systems since they are manifestations of the property of neuronal networks to display multistable dynamics. To illustrate this concept we may assume that at least two states of the epileptic brain are possible: the interictal state characterized by a normal, apparently random, steady-state electroencephalography (EEG) ongoing activity, and the ictal state, that is characterized by paroxysmal occurrence of synchronous oscillations and is generally called, in neurology, a seizure. The transition between these two states can either occur: 1) as a continuous sequence of phases, like in some cases of mesial temporal lobe epilepsy (MTLE); or 2) as a sudden leap, like in most cases of absence seizures. In the mathematical terminology of nonlinear systems, we can say that in the first case the system's attractor gradually deforms from an interictal to an ictal attractor. The causes for such a deformation can be either endogenous or external. In this type of ictal transition, the seizure possibly may be anticipated in its early, preclinical phases. In the second case, where a sharp critical transition takes place, we can assume that the system has at least two simultaneous interictal and ictal attractors all the time. To which attractor the trajectories converge, depends on the initial conditions and the system's parameters. An essential question in this scenario is how the transition between the normal ongoing and the seizure activity takes place. Such a transition can occur either due to the influence of external or endogenous factors or due to a random perturbation and, thus, it will be unpredictable. These dynamical changes may not be detectable from the analysis of the ongoing EEG, but they may be observable only by measuring the system's response to externally administered stimuli. In the special cases of reflex epilepsy, the leap between the normal ongoing attractor and the ictal attractor is caused by a well-defined external perturbation. Examples from these different scenarios are presented and discussed.     

Directed diffusion for wireless sensor networking

Advances in processor, memory, and radio technology enable small and cheap nodes capable of sensing, communication, and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. We explore the directed diffusion paradigm for such coordination. Directed diffusion is data-centric in that all communication is for named data. All nodes in a directed-diffusion-based network are application aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network (e.g., data aggregation). We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network analytically and experimentally. Our evaluation indicates that directed diffusion can achieve significant energy savings and can outperform idealized traditional schemes (e.g., omniscient multicast) under the investigated scenarios.     

分布式光纤拉曼放大器的增益平坦设计

介绍了在波分复用（WDM）系统中分布式光纤拉曼放大器（FRA）的理论分析模型。在此基础上，对增益平坦设计所需考虑的因素进行了分析；最后通过试验证明了它的有效性。