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In this paper, we investigate the secrecy outage performance of a typical cooperative downlink non-orthogonal multiple access (NOMA) system over Nakagami-m fading channel, in which the base station transmits a superimposed signal to two users via a relay. First, the secrecy outage behavior of the considered system over Nakagami-m fading channel under three wiretapping cases, e.g., one eavesdropper (Eve), non-colluding and colluding eavesdroppers, are studied, and both analytical and asymptotic expressions for the secrecy outage probability are derived. Next, by considering the availability of Eves' channel state information, we adopt the two-stage relay selection (RS) strategy to improve the system's secrecy outage performance. Finally, simulation results are provided to corroborate the accuracy of our derived expressions. The results show that: 1) there exists secrecy performance floor for cooperative NOMA system, and it was determined by the weak user's secrecy requirement and the channel conditions of the Eves; 2) the two-stage RS scheme can increase the secrecy outage performance significantly under three wiretapping cases; 3) the secrecy performance of cooperative NOMA network is superior to that of orthogonal multiple access network on the condition of low and medium signal-to-noise ratio regions.

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Solution synthesis of MoS2 precursor followed by direct printing could be an effective way to make printed electronic devices. A linear MoS2 pattern was obtained by an electrohydrodynamic (EHD)-jet printer with a sol-gel system without chemical vapor deposition. The morphology of the MoS2 after a transfer process was maintained without wrinkles or cracking, resulting in a smooth surface compared with that of spin-coated films. EHD-jet printed MoS2 was transferred onto high-k dielectric Al2O3 and used as a semiconductor layer in thin film transistor (TFT) devices. The printed MoS2 TFT has relatively good electrical characteristics, such as a linear field effect mobility, current ratio, and low subthreshold swing of 47.64  ±  2.99 cm2 V−1 s−1, 7.39  ±  0.12 × 106, and 0.7  ±  0.05 V decade−1, respectively. This technique may have promise for future applications.

Background subtraction is one of the most fundamental and challenging tasks in computer vision. Many background subtraction algorithms work well under the assumption that the backgrounds are static over short time periods but degrade dramatically in dynamic scenes, such as swaying trees, rippling water, and waving curtains. In this paper, we propose an effective background subtraction method to address these difficulties by combining color features with texture features in the ViBe framework. Specifically, we present a novel local compact binary count (LCBC) feature that can capture local binary gray-scale difference information and totally discard the local binary structural information. The effective fusion of color and LCBC information significantly improves the performance of the ViBe model, making it very robust to background variations while still highlighting the moving objects. We further embed the total variation (TV) norm regularization technique into the proposed method, which can enhance the spatial smoothness of foreground objects, thereby further improving the accuracy of the method. We evaluate the proposed method against ten sequences containing dynamic backgrounds and show that our method outperforms many state-of-the-art methods in reducing the false positives without compromising the reasonable foreground definitions. The experimental results on challenging well-known data sets demonstrate that the proposed method works effectively on a wide range of dynamic background scenes.INDEX TERMS Foreground detection, nonparametric background modeling, local compact binary count, dynamic background, video signal processing.