Quadrature error and offset error suppression circuitry for silicon micro-gyroscope

The reasons for inducing quadrature error and offset error are analyzed and the expressions of quadrature error and offset error are induced. The open-loop system analysis indicates that, in order to avoid the appearance of harmonic peaks, the frequency difference δf between drive mode and sense mode must be less than 1/（2Qy）. In order to eliminate the effects of the quadrature error and the offset error, as well as the inherent non- linearity in the capacitance-type sensors, a closed-loop feedback control circuit with quadrature correction is designed. The experimental results indicate that the quadrature error and offset error are corrected. By comparing with open-loop detection, the closed-loop feedback control circuit with quadrature correction decreases the non-linearity of the scale factor from 16. 02% to 0. 35 %, widens the maximum rate capability from ± 270 （°）/s to ± 370 （°）/s and increases the stability of zero bias from 155. 2 （°）/h to 60. 6 （°）/h.

A novel closed-loop vacuum silicon microgyroscope

A novel closed-loop control strategy of a silicon microgyroscope （SMG） is proposed. The SMG is sealed in metal can package in drive and sense modes and works under the air pressure of 10 Pa. Its quality factor reaches greater than l0 000. Self-oscillating and closed-loop methods based on electrostatic force feedback are adopted in both measure and control circuits. Both single side driving and sensing methods are used to simplify the drive circuit. These dual channel decomposition and reconstruction closed loops are applied in sense modes. The testing results demonstrate that useful signals and guadrature signals do not interact with each other because of the decoupling of their phases. Under the condition of a scale factor of 9. 6 mV/（（°） .s）, in a full measurement range of±300 （°）/s, the zero bias stability reaches 28 （°）/h with a nonlinear coefficient of 400 × 10^-6 and a simulated bandwidth of more than 100 Hz. The overall performance is improved by two orders of magnitude in comparison to that at atmospheric pressure.

Environmental application and ecological significance of nano-zero valent iron

Toxicity studies considering both the bare and stabilized forms of zero valent iron nanoparticles（nZVI） could be timely, given that ecological risks identified are minimized through modification or with substitution of approaches in the synthesis, development and environmental application of the nanoparticles before succeeding to volume production.This review is focused on the fate, transport and toxicological implications of the bare nZVI and surface modified particles used for environmental applications.

Interaction between Cu^(2+) and different types of surface-modified nanoscale zero-valent iron during their transport in porous media

This study investigated the interaction between Cu^2＋and nano zero-valent iron（NZVI）coated with three types of stabilizers（i.e., polyacrylic acid [PAA], Tween-20 and starch） by examining the Cu^2＋ uptake, colloidal stability and mobility of surface-modified NZVI（SM-NZVI） in the presence of Cu^2＋. The uptake of Cu^2＋ by SM-NZVI and the colloidal stability of the Cu-bearing SM-NZVI were examined in batch tests. The results showed that NZVI coated with different modifiers exhibited different affinities for Cu^2＋, which resulted in varying colloidal stability of different SM-NZVI in the presence of Cu^2＋. The presence of Cu^2＋ exerted a slight influence on the aggregation and settling of NZVI modified with PAA or Tween-20. However, the presence of Cu^2＋caused significant aggregation and sedimentation of starch-modified NZVI, which is due to Cu^2＋complexation with the starch molecules coated on the surface of the particles. Column experiments were conducted to investigate the co-transport of Cu^2＋ in association with SM-NZVI in water-saturated quartz sand. It was presumed that a physical straining mechanism accounted for the retention of Cu-bearing SM-NZVI in the porous media. Moreover, the enhanced aggregation of SM-NZVI in the presence of Cu^2＋ may be contributing to this straining effect.