Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

Security enhancement for NOMA-UAV networks

Owing to its distinctive merits, non-orthogonal multiple access (NOMA) techniques have been utilized in unmanned aerial vehicle (UAV) enabled wireless base stations to provide effective coverage for terrestrial users. However, the security of NOMA-UAV systems remains a challenge due to the line-of-sight air-to-ground channels and higher transmission power of weaker users in NOMA. In this paper, we propose two schemes to guarantee the secure transmission in UAV-NOMA networks. When only one user requires secure transmission, we derive the hovering position for the UAV and the power allocation to meet rate threshold of the secure user while maximizing the sum rate of remaining users. This disrupts the eavesdropping towards the secure user effectively. When multiple users require secure transmission, we further take the advantage of beamforming via multiple antennas at the UAV to guarantee their secure transmission. Due to the non-convexity of this problem, we convert it into a convex one for an iterative solution by using the second order cone programming. Finally, simulation results are provided to show the effectiveness of the proposed scheme

Inferring Affective Meanings of Words from Word Embedding

Affective lexicon is one of the most important resource in affective computing for text. Manually constructed affective lexicons have limited scale and thus only have limited use in practical systems. In this work, we propose a regression-based method to automatically infer multi-dimensional affective representation of words via their word embedding based on a set of seed words. This method can make use of the rich semantic meanings obtained from word embedding to extract meanings in some specific semantic space. This is based on the assumption that different features in word embedding contribute differently to a particular affective dimension and a particular feature in word embedding contributes differently to different affective dimensions. Evaluation on various affective lexicons shows that our method outperforms the state-of-the-art methods on all the lexicons under different evaluation metrics with large margins. We also explore different regression models and conclude that the Ridge regression model, the Bayesian Ridge regression model and Support Vector Regression with linear kernel are the most suitable models. Comparing to other state-of-the-art methods, our method also has computation advantage. Experiments on a sentiment analysis task show that the lexicons extended by our method achieve better results than publicly available sentiment lexicons on eight sentiment corpora. The extended lexicons are publicly available for access

Studies on the effect of Celastrus orbiculatus (Celastraceae) extract on chemosensitivity of liver cancer cells via Wnt/β-catenin pathway

Purpose: To examine the efficacy of Celastrus orbiculatus extract (COE) on the chemosensitivity of liver cancer (LC) cells and its mechanism of action.Methods: Hep G2/ADM cells in the logarithmic growth phase were assigned to a control group (no treatment for cell culture medium only) and a study group (120 μg/ml COE added to the culture medium). After 48 h of incubation, the biological responses were compared. The study group wasdivided into groups A and B, while control group was divided into groups C and D, with 1 μmol/L XAV939 added in groups A and C. Cell proliferation, cell invasion, cell apoptosis rate, and apoptosis protein in the four groups were evaluated.Results: The study group showed significantly lower values in terms of cell proliferation and cell invasiveness (p < 0.05) and a higher apoptotic rate than the control group (p < 0.05)). The study group also demonstrated an elevated pro-apoptotic protein Bax level and a declined anti-apoptotic protein Bcl-2  level. In contrast to group B, the proliferation and invasiveness of Hep G2/ADM cells in group A treated with the inhibitor, XAV939, were significantly lower (p < 0.05), while the apoptotic rate exhibited a significant increase (p < 0.05). There was a rise in the level of pro-apoptotic protein, Bax, and a fall in the anti-apoptotic protein Bcl-2 level in group A. Lower levels of β-catenin, c-Myc, and cyclin D1 protein were observed in the study group compared with the control group (p < 0.05). Compared with other groups, the multiplication capacity and invasiveness of cells in group A treated with COE and inhibitor XAV939 significantly declined, while the apoptotic rate increased (p < 0.05).Conclusion: COE reverses drug resistance in chemotherapy by inhibiting the expression of Wnt/β-catenin pathway in LC cells. Therefore, COE has potentials for use along with chemotherapeutic agents in the management of liver cancer