National University of Defense Technology

About: National University of Defense Technology is a education organization based out in Changsha, China. It is known for research contribution in the topics: Computer science & Radar. The organization has 39430 authors who have published 40181 publications receiving 358979 citations. The organization is also known as: Guófáng Kēxuéjìshù Dàxué & NUDT.

Optimal network topology for structural robustness based on natural connectivity

Abstract: The structural robustness of the infrastructure of various real-life systems, which can be represented by networks, is of great importance. Thus we have proposed a tabu search algorithm to optimize the structural robustness of a given network by rewiring the links and fixing the node degrees. The objective of our algorithm is to maximize a new structural robustness measure, natural connectivity, which provides a sensitive and reliable measure of the structural robustness of complex networks and has lower computation complexity. We initially applied this method to several networks with different degree distributions for contrast analysis and investigated the basic properties of the optimal network. We discovered that the optimal network based on the power-law degree distribution exhibits a roughly “eggplant-like” topology, where there is a cluster of high-degree nodes at the head and other low-degree nodes scattered across the body of “eggplant”. Additionally, the cost to rewire links in practical applications is considered; therefore, we optimized this method by employing the assortative rewiring strategy and validated its efficiency.

High-power coherent beam polarization combination of fiber lasers: progress and prospect [Invited]

Abstract: Coherent polarization beam combining (CPBC) of fiber lasers has the potential to scale the output total power while simultaneously maintaining good beam quality. In this paper, we will present the very recent technical advance in a single-channel coherently combinable linearly polarized narrow-linewidth fiber amplifier and high-power CPBC system. The noise property of a recently developed near 2 kW fiber amplifier and its feasibility in a CPBC system, CPBC of four 500-W-level fiber amplifiers and two kilowatt fiber amplifiers are demonstrated for the first time, which is also the first result for a 2 kW CPBC system. We have also performed numerical analysis on the performance scaling of CPBC, and deduced handy design guidelines for CPBC of a 64-element high-power system.

Gaussian Signalling for Covert Communications

Abstract: In this paper, we examine the optimality of Gaussian signalling for covert communications with an upper bound on $\mathcal {D}(p_{_{1}}||p_{_{0}})$ or $\mathcal {D}(p_{_{0}}||p_{_{1}})$ as the covertness constraint, where $\mathcal {D}(p_{_{1}}||p_{_{0}})$ and $\mathcal {D}(p_{_{0}}||p_{_{1}})$ are different due to the asymmetry of Kullback–Leibler divergence, $p_{_{0}}(y)$ and $p_{_{1}}(y)$ are the likelihood functions of the observation ${y}$ at the warden under the null hypothesis (no covert transmission) and alternative hypothesis (a covert transmission occurs), respectively. Considering additive white Gaussian noise at both the receiver and the warden, we prove that the Gaussian signalling is optimal in terms of maximizing the mutual information of transmitted and received signals for covert communications with an upper bound on $\mathcal {D}(p_{_{1}}||p_{_{0}})$ as the constraint. More interestingly, we also prove that the Gaussian signalling is not optimal for covert communications with an upper bound on $\mathcal {D}(p_{_{0}}||p_{_{1}})$ as the constraint, for which as we explicitly show skew-normal signalling can outperform the Gaussian signalling in terms of achieving higher mutual information. Finally, we prove that, for Gaussian signalling, an upper bound on $\mathcal {D}(p_{_{1}}||p_{_{0}})$ is a tighter covertness constraint in that it leads to lower mutual information than the same upper bound on $\mathcal {D}(p_{_{0}}||p_{_{1}})$ , by proving $\mathcal {D}(p_{_{0}}||p_{_{1}}) \leq \mathcal {D}(p_{_{1}}||p_{_{0}})$ .

An Auditory-Tactile Visual Saccade-Independent P300 Brain-Computer Interface.

Abstract: Most P300 event-related potential (ERP)-based brain-computer interface (BCI) studies focus on gaze shift-dependent BCIs, which cannot be used by people who have lost voluntary eye movement. However, the performance of visual saccade-independent P300 BCIs is generally poor. To improve saccade-independent BCI performance, we propose a bimodal P300 BCI approach that simultaneously employs auditory and tactile stimuli. The proposed P300 BCI is a vision-independent system because no visual interaction is required of the user. Specifically, we designed a direction-congruent bimodal paradigm by randomly and simultaneously presenting auditory and tactile stimuli from the same direction. Furthermore, the channels and number of trials were tailored to each user to improve online performance. With 12 participants, the average online information transfer rate (ITR) of the bimodal approach improved by 45.43% and 51.05% over that attained, respectively, with the auditory and tactile approaches individually. Importantly, the average online ITR of the bimodal approach, including the break time between selections, reached 10.77 bits/min. These findings suggest that the proposed bimodal system holds promise as a practical visual saccade-independent P300 BCI.