Beihang University

About: Beihang University is a education organization based out in Beijing, China. It is known for research contribution in the topics: Computer science & Control theory. The organization has 67002 authors who have published 73507 publications receiving 975691 citations. The organization is also known as: Beijing University of Aeronautics and Astronautics.

Path Following of a Surface Vessel With Prescribed Performance in the Presence of Input Saturation and External Disturbances

Abstract: This paper presents a path following controller of a surface vessel with a prescribed performance in the presence of input saturation and external disturbances. Based on the three degrees-of-freedom model of the surface vessel, the designed backstepping control scheme features three functional parts, namely, guidance, attitude control, and velocity control. To guarantee that the position errors are confined within the prescribed convergence rates and maximum overshoot, a performance constrained guidance law is formulated with an error transformed function. Command filters are incorporated in the control subsections to limit the magnitude of the virtual controls and simultaneously avoid arduous computations involving their time derivatives. Subsequently, auxiliary systems that are governed by smooth switching functions are developed in an unprecedented manner to compensate for the saturation constraints on actuators. Nonlinear disturbance observers are concurrently introduced to estimate the unknown external disturbances for increasing system's robustness. It is demonstrated that under the proposed control, the prescribed transient and steady tracking performance bounds are never violated, and all closed-loop signals remain uniformly ultimately bounded, despite the presence of input saturation and disturbances. Results from a comparative simulation study illustrate the effectiveness and advantages of the proposed method.

Polymer-composite with high dielectric constant and enhanced absorption properties based on graphene–CuS nanocomposites and polyvinylidene fluoride

Abstract: Novel reduced graphene oxide (RGO)/CuS nanocomposites, featuring CuS microspheres embedded in reduced graphene oxide (RGO) layers, are successfully fabricated by using an in situ growth approach in the presence of cexadecyl trimethyl ammonium bromide (CTAB) under mild wet-chemical conditions (140 °C). Characterization of the nanocomposites indicates that the CuS complex microspheres with relatively uniform size are embedded in the RGO layers to form unique core–shell nanostructures. A simple hot-press process is employed to synthesize the RGO/CuS/PVDF composites. With a filler loading of 15 wt%, the dielectric constant of the composites can reach 36 at 2 GHz, which is 10 times higher than that of pure PVDF. The composites with a filler loading of 5 wt% exhibit high values of reflection loss and the maximum loss is 32.7 dB at 10.7 GHz when the thickness is just 2.5 mm, and it can be adjusted by the thickness. The enhanced mechanism is also explained based on the Debye dipolar relaxation of the composites. The composite with a high dielectric constant is a promising material in high capacitance, while the composite with enhanced absorption can decrease the environmental pollution caused by microwave irradiation.

Au/TiO2/Au as a Plasmonic Coupling Photocatalyst

Abstract: The enhanced near-field amplitude of localized surface plasmon resonance in the proximity of metal nanoparticles can boost the photocatalytic activity of the neighboring semiconductor, which has been proven and has attracted wide interest recently. Since the plasmon resonance energy strongly depends on the metal particle size and shape, interparticle spacing, and dielectric property of the surrounding medium, it is available to improve the photocatalytic activity of the neighboring semiconductor by designing and synthesizing targeted metal nanoparticles or assembled nanostructures. In this paper, we propose a Au/TiO2/Au nanostructure with the thickness of the middle layer TiO2 nanosheets around 5 nm, which satisfies the distance needed for the coupling effect between the opposite and nearly touching Au nanoparticles, and thus, it can be used as a “plasmonic coupling photocatalyst”. Compared with the bare TiO2 nanosheet films, the photocurrent density of this favorable nanostructure exhibited a significant...