With the continuous miniaturization and integration of electronic and optoelectronic nanodevices, Moore's Law faces huge challenges from the demands of devices with multifunctional and high-performance characteristics. With several recent reports of the successful synthesis of nanomaterials such as nanoparticles, quantum dots, nanowires, and twodimensional layered materials, the utilization of such materials for the fabrication of electronic and optoelectronic nanodevices has demonstrated potential for realizing multifunctional and high-performance nanodevices in the future. In particular, owing to their excellent electrical, thermal, mechanical, and optical properties, atomically two-dimensional layered materials have emerged as the most promising materials for nanodevices to solve the bottleneck problems of traditional silicon-based devices. Two-dimensional semiconductor materials have been widely applied in many aspects of functional modules, including pn junctions, field effect transistors, rectifiers, photodetectors, and even solar cells. To provide a strong foundation for the development of high-performance and multifunctional nanodevices in the future, this review summarizes the recent advances in electronic and optoelectronic nanodevices based on novel two-dimensional semiconductor materials. We begin the review with a brief introduction of existing two-dimensional materials, including graphene, transition-metal dichalcogenide materials, black phosphorus, hexagonal boron nitride, and van der Waals heterostructures. The atom structure features, electronic and optical properties, and major applications in devices are discussed. The semiconductor materials are suitable for device channels, while graphene and hexagonal boron nitride can be used as electrodes, encapsulating materials, and components of van der Waals heterostructures for channel of field effect transistors. Next, we mainly discuss the advances in electronic and optoelectronic nanodevices based on transition-metal dichalcogenide materials, black phosphorus, and van der Waals heterostructures. In the context of electronic nanodevices, we introduce field effect transistors and other important functional devices, such as sensors, memristors, and integrated circuits. The mobility, on-off ratio, rectification ratio, and other properties of electronic devices are mentioned. In addition, we describe the potential applications of optoelectronic nanodevices for photodetectors, lasers, light-emitting diodes, photovoltaic devices, and so on. The metrics of devices performance such as responsivity, response time, and spectrum response range are compared. Finally, we summarize and compare the advantages and disadvantages of nanodevices based on different materials. Manufacturing comprehensive and high-performance nanodevices will be a promising direction in the future. In addition, the methods for improving the performance of devices are classified. This review will serve as an important reference for the development of future multifunctional and high-perfor...
The doubly fed induction generator with super capacitor is helpful to enhance the system inertia. At the same time, its structural characteristics are more suitable for the power grid topology without communication lines. However, the change of its topology also brings some problems. In this paper, when SCESS-DFIG is participating in frequency regulation, DC bus voltage fluctuation caused by power imbalance of multiple converters is studied. The dynamic power response of super capacitor with DC-DC converter is a step load for grid side converter. The load of DC bus is nonlinear and random, so the balance and stability of the original system will change accordingly. Because of the complex topology and system composition of the doubly fed induction generator with super capacitor, the conventional feed-forward compensation control strategy can not be used to improve its dynamic response speed. Therefore, this paper designs a control strategy which is applied for DC bus voltage fluctuation of the doubly fed induction generator with super capacitor. The theory proposed in this paper is verified by simulation model and experiment.
Nano-manipulation technology, as a kind of “bottom-up” tool, has exhibited an excellent capacity in the field of measurement and fabrication on the nanoscale. Although variety manipulation methods based on probes and microscopes were proposed and widely used due to locating and imaging with high resolution, the development of non-contacted schemes for these methods is still indispensable to operate small objects without damage. However, optical manipulation, especially near-field trapping, is a perfect candidate for establishing brilliant manipulation systems. This paper reports about simulations on the electric and force fields at the tips of metallic probes irradiated by polarized laser outputted coming from a scanning near-field optical microscope probe. Distributions of electric and force field at the tip of a probe have proven that the polarized laser can induce nanoscale evanescent fields with high intensity, which arouse effective force to move nanoparticles. Moreover, schemes with dual probes are also presented and discussed in this paper. Simulation results indicate that different combinations of metallic probes and polarized lasers will provide diverse near-field and corresponding optical force. With the suitable direction of probes and polarization direction, the dual probe exhibits higher trapping force and wider effective wavelength range than a single probe. So, these results give more novel and promising selections for realizing optical manipulation in experiments, so that distinguished multi-functional manipulation systems can be developed.
The enhanced phase-locked loop (EPLL) adds an amplitude estimate to the conventional phaselocked loop (PLL), which solves the problem of double-frequency disturbance in the Phase-Locked Loop mathematical model at steady state. However, there are few researches on disturbance resistance design of EPLL in complicated grid environment. Therefore, periodic disturbances of different frequencies are introduced into frequency estimation and amplitude estimation of EPLL when the grid voltage has DC offset, three-phase unbalance, high-order harmonic disturbance and sub-synchronous oscillation (SSO). This will interfere with the frequency and amplitude estimation performance of the EPLL, and then affect the closedloop control and frequency tracking of the converter. In order to improve disturbance rejection of the EPLL. Firstly, the mathematical model of the disturbance in the frequency and amplitude loop is deduced and analyzed. Then the active disturbance rejection control (ADRC) is used to improve the EPLL. Through the simulation model of MATLAB/Simulink, the parameters of the ADRC and the ESO are compared and validated. The proposed EPLL based on ADRC is verified experimentally for the tracking performance under the frequency stability or drop in complicated power grid environment.INDEX TERMS Complicated power grid environment, enhanced phase-locked loop, active disturbance rejection control, extended state observer.
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