Papers by Author: Zhi Zheng Wu

Abstract: The tracking servo control has played an important role in the data storage servo systems. In the next generation optical data storage systems, i.e. the near-field recording system, the tracking error of the servo system should be below 10 nanometers under various unknown situations. However, higher data transfer rate and higher data density make it difficult to maintain the desired tracking precision during normal disk operation. It is proposed in this paper to use an adaptive regulation approach to maintain the tracking error below its desired value, despite unknown track eccentricity and external force disturbance. The performance of the proposed control approach is analyzed and simulation results are presented to illustrate the capability of the proposed adaptive regulator to achieve and maintain the desired tracking precision.

Abstract: Recently, magnetic fluid deformable mirrors (MFDMs) were proposed as a novel type of wavefront correctors for adaptice optics (AO) systems, which offer cost and performance advantages over existing wavefront correctors. These mirrors are developed by coating the free surface of a magnetic fluid with a thin reflective film of nano-particles. The reflective surface of the mirrors can be deformed using a locally applied magnetic field and thus serves as a wavefront corrector. In this paper, the working principle of MFDMs is first presented, then the perspectives of MFDMs that will have to be addressed before they can be finally used practically in AO applications are discussed.

Abstract: Efficient assembly of nanowires or nanotubes into functional nanodevices is one of the keys for practical application of the promising nanotechnology. Generally there are two ways for the assembly of nanowires or nanotubes: directed assembly during growth and post-growth assembly. The post-growth assembly technique is advantageous in some aspects comparatively for it puts little limitation on the nanowire or nanotube materials involved, and it can produce large nanowire arrays with better consistency. So this paper reviewed post-growth nanowire assembly techniques and discussed their advantages and shortcomings.

Abstract: In this paper, the design for a new piezoelectrically transduced hybrid resonator with robust resonance frequency is proposed. The frequency stability problem is improved by two compensation methods for the resonator. One is to use two different thin films with a negative and positive temperature coefficient of sound velocity respectively to construct the vibrating structure by the SiO2 and ZnO thin films, and the other is to use the feedback technology to compensate the frequency shift by adjusting the electric stiffness of the resonator.

Abstract: In this paper, the design for a new piezoelectrically transduced hybrid resonator is proposed. The frequency stability problem is improved by using two different thin films with a negative and positive temperature coefficient of sound velocity, respectively, where the main vibrating structure is constructed by the SiO₂ and ZnO thin films. This new hybrid resonator combines the advantages of piezoelectric and capacitive resonators together and can be implemented by the simple fabrication technique utilizing surface micromachining.