Some special environments, such as closed or harsh spaces, require contactless and real-time humidity monitoring. A flexible 920 MHz antenna sensor with vertical graphene (VG) as a sensitive film is proposed, which can measure humidity and transmit data wirelessly in real time. When the humidity changes, the number of H2O molecules absorbed by the graphene film will vary, which affects the permittivity of the antenna patch, and results in shifts in the resonant frequency. Remote humidity monitoring can be realized by analyzing the frequency response at the receiver. By depositing vertical graphene film on the antenna patch, the sensitivity can be improved from 16.3 to 32.6 kHz/% RH (linear range: 0. 57% RH) and from 145 to 290.5 kHz/% RH (57.90% RH). During humidity change, the radiation direction of the VG-based antenna sensor remains stable, and the maximum wireless transmission distance reaches 100 m. For the first time, the model of the antenna sensor is established. Furthermore, the flexible sensor can conform to various installation shapes. The experimental results show that the wireless VG-based antenna sensor is a good candidate for remote humidity monitoring and the Internet of Things.

We investigate the dynamics of a discrete-time predator-prey system. Firstly, we give necessary and sufficient conditions of the existence and stability of the fixed points. Secondly, we show that the system undergoes a flip bifurcation and a Neimark-Sacker bifurcation by using center manifold theorem and bifurcation theory. Furthermore, we present numerical simulations not only to show the consistence with our theoretical analysis, but also to exhibit the complex but interesting dynamical behaviors, such as the period-6, -11, -16, -18, -20, -21, -24, -27, and -37 orbits, attracting invariant cycles, quasi-periodic orbits, nice chaotic behaviors, which appear and disappear suddenly, coexisting chaotic attractors, etc. These results reveal far richer dynamics of the discrete-time predator-prey system. Finally, we have stabilized the chaotic orbits at an unstable fixed point using the feedback control method.

The dynamics of a discrete-time predator-prey system is investigated in detail in this paper. It is shown that the system undergoes flip bifurcation and Hopf bifurcation by using center manifold theorem and bifurcation theory. Furthermore, Marotto's chaos is proved when some certain conditions are satisfied. Numerical simulations are presented not only to illustrate our results with the theoretical analysis, but also to exhibit the complex dynamical behaviors, such as the period-6, 7, 8, 10, 14, 18, 24, 36, 50 orbits, attracting invariant cycles, quasi-periodic orbits, nice chaotic behaviors which appear and disappear suddenly, coexisting chaotic attractors, etc. These results reveal far richer dynamics of the discrete-time predator-prey system. Specifically, we have stabilized the chaotic orbits at an unstable fixed point using the feedback control method.