A new shared AWG-based OCDMA scheme implemented with time-spreading and wavelength-group-hopping embedded M-sequence code

This paper exploits the inherent cyclic and periodic free-spectral-range (FSR) properties of arrayed-waveguide grating (AWG) routers to construct a two-dimensional (2D) time-spreading and wavelength-group-hopping embedded M-sequence code for optical multiple-access networks. In the proposed codecs (encoder/decoder), a fine arrayed-waveguide grating (AWG) is used to generate an M-sequence code pattern, which is then spread in the wavelength domain by multiple coarse AWGs. The signals produced at the output ports of the coarse AWGs are then spread in the time domain using optical delay lines. The 2D code is evaluated in terms of its correlation, bit-error-rate (BER) and cardinality characteristics. It is shown that the TS/GH embedded M-sequence code yields a significant improvement in both the BER and cardinality performance of the optical multiple-access networks compared to that obtained using conventional prime-hop code (PHC), modified prime-hop code (MPHC), Barker and Walsh-based bipolar–bipolar sequence.     

Unsupervised regions based segmentation using object discovery

We present a new unsupervised algorithm to discovery and segment out common objects from multiple images. Compared with previous cosegmentation methods, our algorithm performs well even when the appearance variations in the foregrounds are more substantial than those in some areas of the backgrounds. Our algorithm mainly includes two parts: the foreground object discovery scheme and the iterative region allocation algorithm. Two terms, a region-saliency prior and a region-repeatness measure, are introduced in the foreground object discovery scheme to detect the foregrounds without any supervisory information. The iterative region allocation algorithm searches the optimal solution for the final segmentation with the constraints from a maximal spanning tree, and an effective color-based model is utilized during this process. The comparative experimental results show that the proposed algorithm matches or outperforms several previous methods on several standard datasets.     

Numerical Study of Interaction Efficiency for a 170GHz Megawatt-Level Coaxial-Gyrotron

The beam-wave interaction efficiency of a 170 GHz megawatt-level corrugated coaxial-gyrotron operating with TE31,12 mode was studied numerically.According to the self-consistent nonlinear theory,the efficiencies of two types of coaxial resonator were calculated and compared.Taking into account electronic velocity spread and cavity wall resistivity,the beam-wave interactions of improved cavity were investigated.The relationships between efficiency and magnetic field,voltage,current,beam radius,velocity ratio,and parameters of groove are presented.The results show that the voltage and magnetic field have great influence on efficiency,but the current and velocity spread do slightly.The optimized geometry parameters can improve efficiency,reduce the impact of velocity spread on efficiency,and achieve around 48.6％ electronic efficiency and 1.7MW output power at 5％ velocity spread and 6.896×10-8Ωm resistivity.     

Fading channel modelling using single-hidden layer feedforward neural networks

Due to the complexity and extensive application of wireless systems, fading channel modeling is of great importance for designing a mobile network, especially for high speed environments. High mobility challenges the speed of channel estimation and model optimization. In this study, we propose a single-hidden layer feedforward neural network (SLFN) approach to modelling fading channels, including large-scale attenuation and small-scale variation. The arrangements of SLFN in path loss (PL) prediction and fading channel estimation are provided, and the information in both of them is trained with extreme learning machine (ELM) algorithm and a faster back-propagation (BP) algorithm called Levenberg-Marquardt algorithm. Computer simulations show that our proposed SLFN estimators could obtain PL prediction and the instantaneous channel transfer function of sufficient accuracy. Furthermore, compared with BP algorithm, the ability of ELM to provide millisecond-level learning makes it very suitable for fading channel modelling in high speed scenarios.     

A traffic-camera assisted cache-and-relay routing for live video stream delivery in vehicular ad hoc networks

With the development of the Internet of Things, installation of smart mobile terminal in vehicle has become more and more popular, and consequently, how to provide services for the public utilizing vehicular ad hoc networks has aroused great interest in research and industrial areas. Among them, the kind of services supported by live video streaming attracts more attention because of its advantages. However, due to the high vehicular speed, frequent disconnection and dynamic topology, it’s difficult to guarantee the low-delay delivery of real-time video data, and there is hardly any scheme that can deliver such kind of data with satisfied quality. In this paper, we take fully advantage of the existing wireless enabled traffic cameras, and propose a novel traffic-camera assisted routing for video delivery, which can deliver live video stream to mobile target vehicle with minimal start-up delay while satisfying the required visual quality and playback performance through optimal buffering points selection and intelligent relay among them. The trace-driven simulations demonstrate that our strategy outperforms existing solutions greatly.     

Efficient fluorescent white organic light-emitting diodes using co-host/emitter dual-role possessed di(triphenyl-amine)-1,4-divinyl-naphthalene

Efficient fluorescent white organic light-emitting diodes with low carrier-injection barriers were fabricated with device structure of indium tin oxide/N,N′-bis-(1-naphthy)-N,N′-diphenyl-1,1′-biphenyl-4-4′-diamine/white emission layer/1,3,5-tris(N-phenyl-benzimidazol-2-yl)benzene/lithium fluoride/aluminium. By blending in the blue host of 1-butyl-9,10-naphthalene-anthracene in the emissive layer an efficient electro-luminescent greenish-blue co-host of di(triphenyl-amine)-1,4-divinyl-naphthalene, with the doping of a trace amount of red dye of 4-(dicyano-methylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran, bright and colour-stable white emission with high power-efficiency of 14.6 lm/W at 100 cd/m² or current efficiency of 19.2 cd/A at 300 cd/m² or 18.7 cd/A at 10,000 cd/m² was obtained. The resulted synergistic increase in brightness and efficiency may be attributed to the presence of cascading new routes with comparatively lower electron injection barrier.     

Planar mirrors for image-based robot localization and 3-D reconstruction

Planar catadioptric vision sensors consist of a pinhole camera observing a scene being reflected on two (or more) planar mirrors. These systems have recently received an increasing attention because, unlike stereo cameras, can capture two views of the same scene without the need of hardware multi-camera synchronization and calibration. In this paper we explore the original scenario in which a robot manipulator, equipped with a pinhole camera on its end-effector, observes an unknown 3-D scene both directly and reflected through multiple mirrors. We present new multiple-view properties for this scenario and, based on these theoretical results, we present new image-based camera localization and new 3-D scene reconstruction algorithms. Extensive simulation and real-data experiments illustrate the theory and show the effectiveness of the proposed designs.     

Do social media literacy skills help in combating fake news spread? Modelling the moderating role of social media literacy skills in the relationship between rational choice factors and fake news sharing behaviour

This study modelled the rational factors that predict fake news sharing behaviour. It also tested the moderating role of social media literacy skills. The focus was on social media users in Nigeria. An online survey was conducted to gather the responses from participants across Nigerian geopolitical zones. Structural equation modelling (SEM) Smart PLS 3.6 was used to analyse the data. We found that information sharing, the news finds me perception, trust in social media and status-seeking lead to fake news sharing among social media users in Nigeria. Specifically, trust in social media and status-seeking had a greater effect on fake news sharing behaviour. We also found that social media literacy skills significantly moderate the relationship between information sharing, status-seeking, the news finds me perception, trust in social media and fake news sharing in such a way that the effects/relationships are stronger among those with low social media literacy skills. This outcome contributes to theory and practice which was highlighted in the concluding aspect of this study.