In this paper, we develop a novel non-parametric online actor-critic reinforcement learning (RL) algorithm to solve optimal regulation problems for a class of continuous-time affine nonlinear dynamical systems. To deal with the value function approximation (VFA) with inherent nonlinear and unknown structure, a reproducing kernel Hilbert space (RKHS)-based kernelized method is designed through online sparsification, where the dictionary size is fixed and consists of updated elements. In addition, the linear independence check condition, i.e., an online criteria, is designed to determine whether the online data should be inserted into the dictionary. The RHKS-based kernelized VFA has a variable structure in accordance with the online data collection, which is different from classical parametric VFA methods with a fixed structure. Furthermore, we develop a sparse online kernelized actor-critic learning RL method to learn the unknown optimal value function and the optimal control policy in an adaptive fashion. The convergence of the presented kernelized actor-critic learning method to the optimum is provided. The boundedness of the closed-loop signals during the online learning phase can be guaranteed. Finally, a simulation example is conducted to demonstrate the effectiveness of the presented kernelized actor-critic learning algorithm.
Two-dimensional layers of metal dichalcogenides have attracted much attention because of their ultrathin thickness and potential applications in electronics and optoelectronics.Monolayer SnS2,with a band gap of ~2.6 eV,has an octahedral lattice made of two atomic layers of sulfur and one atomic layer of tin.Till date,there have been limited reports on the growth of large-scale and high quality SnS2 atomic layers and the investigation of their properties as a semiconductor.Here,we report the chemical vapor deposition (CVD) growth of atomic-layer SnS2 with a large crystal size and uniformity.In addition,the number of layers can be changed from a monolayer to few layers and to bulk by changing the growth time.Scanning transmission electron microscopy was used to analyze the atomic structure and demonstrate the 2H stacking poly-type of different layers.The resultant SnS2 crystals is used as a photodetector with external quantum efficiency as high as 150%,suggesting promise for optoelectronic applications. 相似文献
This study presents the synergistic effects of graphene nanosheets (GNSs) and carbon fibers (CFs) additions on the electrical and electromagnetic shielding properties of GNS/CF/polypropylene (PP) composites. These composites were fabricated by the melt blending of different ratios of GNSs and CFs (20:0, 15:5, 10:10, 5:15 and 0:20 wt/wt%) into a PP polymer matrix using a Brabender mixer. Besides, the chemical and crystalline structures and the thermal stability of the resultant GNS/CF/PP composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). FT-IR and XRD showed that with the addition of GNSs content, transmittances at 1373.4?cm?1 and 1454.4?cm?1 became smaller and the characteristic peak at 26.82° became stronger. TGA showed that the GNS/CF/PP composite can be used at high temperature below 456°C. Blending 10?wt% CFs and 10?wt% GNSs into the PP polymer resulted in excellent conductivity (0.397 S/cm), which indicated the occurrence of the critical percolation threshold phenomenon, and also reached the maximum electromagnetic shielding effectiveness (EMSE) of 20?dB at 1.28–2.00?GHz. Laminated with five layers of composites, its EMSE achieved 25–38?dB at 0.3–3.0?GHz, corresponding to blocking of 94.38–98.74% electromagnetic waves. 相似文献