A Bionic Fish Cilia Median-Low Frequency Three-Dimensional Piezoresistive MEMS Vector Hydrophone

A bionic fish cilia median-low frequency three-dimensional MEMS vector hydrophone is reported in this paper. The piezoresistive reasonable position was obtained through finite element analysis by ANSYS and the structure was formed by MEMS processes including lithography, ion implantation, PECVD and etching,etc. The standing wave barrel results show that the lowest sensitivity of the hydrophone is-200 d B and reach up to-160 d B(in which the voltage amplification factor is 300). It has a good frequency response characteristics in 25 Hz ～ 1500 Hz band. Directivity tests displayed that the hydrophone has a good "8"-shaped directivity,in which the resolution is not less than 30 d B, and asymmetry of the maximum axial sensitivity value is less than 1.2 d B.

Refocusing and locating effect of fluorescence scattering field

Optical imaging deep inside scattering medium has always been one of the challenges in the field of bioimaging,which significantly drawbacks the employment of con-focal microscopy system.Although a variety of feedback techniques,such as acoustic or nonlinear fluorescence-based schemes have realized the refocusing of the coherent light,the problems of non-invasively refocusing and locating of linearly-excited fluorescent beads inside the scattering medium have not been thoroughly explored.In this paper,we linearly excited the fluorescent beads inside a scattering medium by using our homemade optical con-focal system,collected the fluorescence scattering light as the optimized target,and established a theoretical model of target contrast enhancement,which is consistent with the experimental data.By improving both the cost function and variation rate within the genetic algorithm,we could refocus the fluorescence scattering field while improving the contrast enhancement factor to 12.8 dB.Then,the positions of the fluorescent beads are reconstructed by subpixel accuracy centroid localization algorithm,and the corresponding error is no more than 4.2μm with several fluorescent beads within the field of view.Finally,the main factors such as the number of fluorescent beads,the thickness of the scattering medium,the modulating parameter,the experimental noise and the system long-term stability are analyzed and discussed in detail.This study proves the feasibility of reconstructing fluorescent labeled cells inside biological tissues,which provides certain reference value for deep imaging of biological tissues.

Simulation Study on the Controllable Dielectrophoresis Parameters of Graphene

The method of using dielectrophoresis （DEP） to assemble graphene between micro-electrodes has been proven to be simple and efficient. We present an optimization method for the kinetic formula of graphene DEP, and discuss the simulation of the graphene assembly process based on the finite element method. The simulated results illustrate that the accelerated motion of graphene is in agreement with the distribution of the electric field squared gradient. We also conduct research on the controllable parameters of the DEP assembly such as the alternating current （AC） frequency, the shape of micro-electrodes, and the ratio of the gap between electrodes to the characteristic/geometric length of graphene （λ）. The simulations based on the Clausius-Mossotti factor reveal that both graphene velocity and direction are influenced by the AC frequency. When graphene is close to the electrodes, the shape of micro-electrodes will exert great influence on the velocity of graphene. Also, λ has a great influence on the velocity of graphene. Generally, the velocity of graphene would be greater when λ is in the range of 0.4 0.6. The study is of a theoretical guiding significance in improving the precision and efficiency of the graphene DEP assembly.

Synergetic effect of BiOCl/Bi12O17Cl2 and MoS2: in situ DRIFTS investigation on photocatalytic NO oxidation pathway

The BiOCl/Bi12O17Cl2@MoS2(BOC-MS)composites were successfully synthesized by a facile method at room temperature.The physicochemical properties of the as-obtained samples were characterized by X-ray diffractometer(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),ultraviolet–visible diffuse reflection spectra(UV–Vis DRS),photoluminescence(PL),Brunauer–Emmett–Teller–Barrett–Joyner–Halenda(BET–BJH),and electron spin resonance(ESR)in detail.Moreover,the in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)was applied to elucidate the adsorption and photocatalytic reaction mechanism.The optimized BOC-MS-1.0 composites exhibited excellent visible light photocatalytic capability(51.1%)and photochemical stability for removal of NO.Based on the DMPOESR spin trapping,the·O2-radicals andáOH radicals were identified as the main active species generated from BOCMS-1.0 under visible light irradiation.The enhanced photocatalytic performance can be ascribed to the positive synergetic effect of the MoS2 and the effective carrier separation ability.

A fast integral sliding mode controller with an extended state observer for position control of permanent magnet synchronous motor servo systems

Permanent magnet synchronous motor(PMSM)has been widely used in position control applications.Its performance is not satisfactory due to internal uncertainties and external load disturbances.To enhance the control performance of PMSM systems,a new method that has fast response and good robustness is proposed in this study.First,a modified integral terminal sliding mode controller is developed,which has a fast-sliding surface and a continuous reaching law.Then,an extended state observer is applied to measure the internal and external disturbances.Therefore,the disturbances can be compensated for in a feedforward manner.Compared with other sliding mode methods,the proposed method has faster response and better robustness against system disturbances.In addition,the position tracking error can converge to zero in a finite time.Simulation and experimental results reveal that the proposed control method has fast response and good robustness,and enables high-precision control.