SVD-based Preisach hysteresis identification and composite control of piezo actuators

In this paper, the singular value decomposition (SVD) based identification and compensation of the hysteretic phenomenon in piezo actuators are addressed using a Preisach model. First, this paper presents an SVD-based least squares algorithm and a revision approach of the identification through updating the SVD. With the identified parameters and a log of the memory curve, a Preisach-based inversion compensator is constructed which is complemented with a feedback controller to address the inevitable and residual modeling errors. Experimental results are furnished for both the identification and compensation approaches. The Preisach-based feedforward controller significantly improves the tracking performance and reduces the root-mean-square (RMS) tracking error of a PID controller by 76.7% and 89% at 1 Hz and 25 Hz, respectively. With the proposed composite controller, the percent-RMS errors at 1 Hz and 25 Hz are reduced to 0.035% and 0.31%, respectively.     

A novel digital predistorter technique using an adaptive neuro-fuzzy inference system

This letter presents a novel digital predistorter technique using an adaptive neuro-fuzzy inference system (ANFIS). The proposed approach employs real-time input and output signals of a nonlinear power amplifier as inputs to the ANFIS, so as to approximate the inverse functions of the power amplifier. The antecedent and consequent parameters of the FIS constructed by the ANFIS are tuned using backpropagation and least squares algorithms. Simulation shows that this novel technique has improved the linearity of a WCDMA signal by a further 4 dBc compared to a conventional look-up table (secant) approach. Moreover, this proposed technique is capable of adapting to instantaneous variation in the power amplifier response through time, which is a topic often omitted by researchers in this area.     

Zero-quantised discrete cosine transform prediction technique for video encoding

A new analytical model to eliminate redundant discrete cosine transform (DCT) and quantisation (Q) computations in block-based video encoders is proposed. The dynamic ranges of the quantised DCT coefficients are analysed, then a threshold scheme is derived to determine whether the DCT and Q computations can be skipped without video quality degradation. In addition, fast DCT/inverse DCT (IDCT) algorithms are presented to implement the proposed analytical model. The proposed analytical model is compared with other comparable analytical models reported in the literature. Both the theoretical analysis and experimental results demonstrate that the proposed analytical model can greatly reduce the computational complexity of video encoding without any performance degradation and outperforms other analytical models     

Minimizing hydrogen content in silicon oxynitride by thermal oxidation of silicon-rich silicon nitride

This work reports a detailed study of the re-oxidation effects on the hydrogen content and optical properties of silicon oxynitride films grown by plasma enhanced chemical vapor deposition (PECVD) with N₂O, NH₃ and SiH₄ as the precursors. Results showed that the silicon oxynitride deposited with gas flow rates of NH₃/N₂O/SiH₄ = 20/500/20 (sccm) has favorable properties for integrated waveguide applications. The refractive index of this layer is about 1.57 at 632.8 nm wavelength and the layer has a comparative low density of NH bonds. With a high temperature re-oxidation of the as-deposited film, the hydrogen content of the oxynitride film was reduced from 2.255 × 10²² to 6.98 × 10²⁰ cm⁻³ which is attributed to the removal of excess silicon oxidation and hydrogen bonds.     

Performance enhancement in organic photovoltaic devices using plasma-polymerized fluorocarbon-modified Ag nanoparticles

In this work, Ag nanoparticles were modified by an ultra-thin plasma-polymerized fluorocarbon film (CF_X) to form a composite CF_X-modified Ag nanoparticles/indium tin oxide (ITO) anode for application in organic photovoltaic (OPV) devices. A CF_X-modified Ag nanoparticles/ITO anode exhibited a superior surface work function of 5.4 eV suited for application in OPV devices. The performance of zinc phthalocyanine:fullerene-based OPV devices showed a significant improvement when the structural identical cells are made with the CF_X-modified Ag nanoparticles/ITO. This work yielded a promising power conversion efficiency of 3.5 ± 0.1%, notably higher than that with a bare ITO anode (2.7 ± 0.1%).     

Influence of multi-finger layout on the subthreshold behavior of nanometer MOS transistors

This work studies the effects of number of gate finger on the DC subthreshold characteristics of multi-finger nanoscale MOS transistors. We found in not optimally-tempered nanoscale (gate length = 90 nm) MOS transistors that the significantly deteriorated subthreshold characteristics can be effectively improved by increasing the number of gate finger. This observation was explained with a modified subthreshold slope model based on voltage-doping transformation theory. Hence, the multi-finger structure does not only enhance the operation frequency, it also improves the subthreshold DC characteristics of the nanoscale MOS transistors.     

Degradation behaviors of GaN light-emitting diodes under high-temperature and high-current stressing

A number of commercially available multiple-quantum well (MQW) InGaN/GaN blue LEDs with wavelengths of about 460 nm and a power of 1 mW were stressed at temperatures ranging from 25 to 120 °C at several accelerated DC currents. Both the forward and reverse current voltage characteristics as well as the electroluminescent spectra of the LEDs were monitored. These effects also resulted in the pronounced degradation of light efficiency and device operation lifetime. We found that the degradation of photonic characteristics, correlated very well with the generation-recombination current which is governed by the defect density. The device degradation is much faster at high temperatures. At nominal operation current and at room temperature, the light intensity degradation reaches a saturation level before the light dyes out. These results shed new lights upon the design and lifetime specifications for the emerging commercial solid-state lighting devices.     

Peer-to-peer electricity trading system: smart contracts based proof-of-benefit consensus protocol

Wireless Networks - Nowadays, people trade electricity through centralized companies or organizations which is vulnerable to cyber attacks and incapable of coping with increasing demands from...