[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Fractional Differential Equations

Fast Fourier Transform

Graphene plasmons were predicted to possess ultra-strong field confinement and very low damping at the same time, enabling new classes of devices for deep subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. While all of these great prospects require low damping, thus far strong plasmon damping was observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this letter we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine dispersion and particularly plasmon damping in real space. We find unprecedented low plasmon damping combined with strong field confinement, and identify the main damping channels as intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key for the development of graphene nano-photonic and nano-optoelectronic devices.

Highly confined low-loss plasmons in graphene-boron nitride heterostructures

Metallic structures with nanogap features have proven highly effective as building blocks for plasmonic systems, as they can provide a wide tuning range of operating frequencies and large near-field enhancements. Recent work has shown that quantum mechanical effects such as electron tunnelling and nonlocal screening become important as the gap distances approach the subnanometre length-scale. Such quantum effects challenge the classical picture of nanogap plasmons and have stimulated a number of theoretical and experimental studies. This review outlines the findings of many groups into quantum mechanical effects in nanogap plasmons, and discusses outstanding challenges and future directions.

/pdf/quantum-mechanical-effects-in-plasmonic-structures-with-1xv8cyrx1x.pdf

Quantum mechanical effects in plasmonic structures with subnanometre gaps.

This paper focuses on modeling and oscillatory stability analysis of a wind turbine with doubly fed induction generator (DFIG). A detailed mathematical model of DFIG wind turbine with vector-control loops is developed, based on which the loci of the system Jacobian's eigenvalues have been analyzed, showing that, without appropriate controller tuning a Hopf bifurcation can occur in such a system due to various factors, such as wind speed. Subsequently, eigenvalue sensitivity with respect to machine and control parameters is performed to assess their impacts on system stability. Moreover, the Hopf bifurcation boundaries of the key parameters are also given. They can be used to guide the tuning of those DFIG parameters to ensure stable operation in practice. The computer simulations are conducted to validate the developed model and to verify the theoretical analysis.

/pdf/oscillatory-stability-and-eigenvalue-sensitivity-analysis-of-3rzhq1182u.pdf

Oscillatory Stability and Eigenvalue Sensitivity Analysis of A DFIG Wind Turbine System

A new transformerless buck–boost converter with simple structure is proposed in this study. Compared with the traditional buck–boost converter, the proposed buck–boost converter’s voltage gain is squared times of the former’s and its output voltage polarity is positive. These advantages enable it to work in a wider range of positive output. The two power switches of the proposed buck–boost converter operate synchronously. In the continuous conduction mode (CCM), two inductors are magnetized and two capacitors are discharged during the switch-on period, while two inductors are demagnetized and two capacitors are charged during the switch-off period. The operating principles, the steady-state analyses, and the small-signal model for the proposed buck–boost converter operating in CCM are presented in detail. The power electronics simulator (PSIM) and the circuit experiments are provided to validate the effectiveness of the proposed buck–boost converter.

A New Transformerless Buck–Boost Converter With Positive Output Voltage

This paper presents an active sliding mode control method for synchronizing two chaotic systems with parametric uncertainty. And a sufficient condition is drawn for the robust stability of the error dynamics, and is applied to guiding the design of the controllers. Finally, numerical results are used to show the robustness and effectiveness of the proposed control strategy.

Synchronization of chaotic systems with parametric uncertainty using active sliding mode control

This paper presents an active control method for Synchronizing two uncertain chaotic systems with parameters perturbation and generalizes it to general uncertain chaotic systems. And a sufficient condition is drawn for the stability of the error dynamics, and is applied to guiding the design of the controllers. Finally, numerical simulations are used to show the robustness and effectiveness of the proposed control strategy.

Synchronization of uncertain chaotic systems with parameters perturbation via active control

This paper presents a novel active backstepping control approach for controlling hyperchaotic Rossler system to a steady state as well as tracking of any desire trajectory to be achieved in a systematic way. The proposed method is a systematic design approach and consists in a recursive procedure that interlaces the choice of a Lyapunov function with the design of active control. Numerical results show that the controller is singularity free and the closed-loop system is stable globally. Especially, the main feature of this technique is that it gives the flexibility to construct a control law. Finally, numerical experiments verify the feasibility and effectiveness of the proposed control technique.

Xikui Ma

Papers

Oscillatory Stability and Eigenvalue Sensitivity Analysis of A DFIG Wind Turbine System

A New Transformerless Buck–Boost Converter With Positive Output Voltage

Synchronization of chaotic systems with parametric uncertainty using active sliding mode control

Synchronization of uncertain chaotic systems with parameters perturbation via active control

Controlling and tracking hyperchaotic Rössler system via active backstepping design