During the last two decades, III-nitride-based quantum dots (QDs) have attracted great attentions for optoelectronic applications due to their unique electronic properties. In this paper, we first present an overview on the techniques of fabrication for III-nitride-based QDs. Then various optoelectronic devices such as QD lasers, QD light-emitting diodes (LEDs), QD infrared photodetectors (QDIPs) and QD intermediate band (QDIB) solar cells (SCs) are discussed. Finally, we focus on the future research directions and how the challenges can be overcome.

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Active-type dynamic vibration absorbers (ADVA) is a kind of damping system, installed an actuators in the dynamic vibration absorbers (DVA). According to the actual needs, vibration energy of the structure is transferred to vibration absorbers actively in the process of structural vibration for the effect of external excitation. Therefore, the energy is decayed or transferred quickly and the structural vibration is controlled. If the nature frequency of additional system is the same as external excitation frequency of the original system, actuators doesn’t start and the whole system behaves the property of DVA (passive damping) .Otherwise, actuators starts, which makes the energy of original structure transfer to the vibration absorbers actively, achieving the purpose of energy consumed and vibration reduced. In this paper the concept of ADVA is proposed, and the working principle of ADVA is theoretically analyzed, furthermore the expressions of the system vibration response and active control coefficient are deduced. The curves of active control force and structure amplitude against incentive frequency are plotted respectively by examples.

The dynamic control equations are derived for the mechanical model with two degrees of freedom that the soften spring is considered in the dynamic vibration absorber. In order to facilitate the computation to the equations, through the integral of the dynamic control equations which became a four order ordinary differential equation. The amplitude frequency response curves of the primary structure excited by a harmonic force were drawn with harmonic balance method, the influence of the dynamic characteristics of primary structure about this kind of nonlinear dynamic vibration absorber was discussed.