An aerosol deposition based MEMS piezoelectric accelerometer for low noise measurement

Potentially applied in low-noise applications such as structural health monitoring(SHM),a 1-axis piezoelectric MEMS accelerometer based on aerosol deposition is designed,fabricated,simulated,and measured in this study.It is a cantilever beam structure with a tip proof mass and PZT sensing layer.To figure out whether the design is suitable for SHM,working bandwidth and noise level are obtained via simulation.For the first time,we use aerosol deposition method to deposit thick PZT flm during the fabrication process to achieve high sensitivity.In performance measurement,we obtain the charge sensitivity,natural frequency,working bandwidth and noise equivalent acceleration of 22.74 pC/g,867.4 Hz,10-200 Hz(within±5%deviation)and 5.6μg/√Hz(at 20 Hz).To demonstrate its feasibility for real applications,vibrations of a fan are measured by our designed sensor and a commercial piezoelectric accelerometer,and the results match well with each other.Moreover,shaker vibration measurement with ADXL1001 indicates that the fabricated sensor has a much lower noise level.In the end,we show that our designed accelerometer has good performance compared to piezoelectric MEMS accelerometers in relevant studies and great potential for low-noise applications compared to low-noise capacitive MEMS accelerometers.

Optimizing water-saving irrigation schemes for rice(Oryza sativa L.)using DSSAT-CERES-Rice model

Rice is one of the major crops in China,and enhancing the rice yield and water use efficiency is critical to ensuring food security in China.Determining how to optimize a scientific and efficient irrigation and drainage scheme by combining existing technology is currently a hot topic.Crop growth models can be used to assess actual or proposed water management regimes intended to increase water use efficiency and mitigate water shortages.In this study,a CERES-Rice model was calibrated and validated using a two-year field experiment.Four irrigation and drainage treatments were designed for the experiment:alternate wetting and drying(AWD),controlled drainage(CD),controlled irrigation and drainage for a low water level(CID1),and controlled irrigation and drainage for a high water level(CID2).According to the indicators normalized root mean square error(NRMSE)and index of agreement(d),the calibrated CERES-Rice model accurately predicted grain yield(NRMSE=6.67%,d=0.77),,shoot biomass(NRMSE=3.37%,d=0.77),actual evapotranspiration(ETa)(NRMSE=3.83%,d=0.74),irrigation volume(NRMSE=15.56%,d=0.94),and leaf area index(NRMSE=9.69%,d=0.98)over 2 a.The calibrated model was subsequently used to evaluate rice production in response to the four treatments(AWD,CD,CID1,and CID2)under 60 meteorological scenarios which were divided into wet years(22 a),normal years(16 a),and dry years(22 a).Results showed that the yield of AWD was the largest among four treatments in different hydrological years.Relative to that of AWD,the yield of CD,CID1,and CID2 were respectively reduced by 5.7%,2.6%,8.7%in wet years,9.2%,2.3%,8.6% in normal years,and 9.2%,3.8%,3.9% in dry years.However,rainwater use efficiency and irrigation water use efficiency were the greatest for CID2 in different hydrological years.The entropy-weighting TOPSIS model was used to optimize the four water-saving irrigation schemes in terms of water-saving,labor-saving and high-yield,based on the simulation results of the CERES-Rice model in the past 60 a.These results showed that CID1 and AWD were optimal in the wet years,CID1 and CID2 were optimal in the normal and dry years.These results may provide a strong scientific basis for the optimization of water-saving irrigation technology for rice.

Multi-GNSS products and services at iGMAS Wuhan Innovation Application Center:strategy and evaluation

Over the past years the International Global Navigation Satellite System(GNSS)Monitoring and Assessment System(iGMAS)Wuhan Innovation Application Center(IAC)dedicated to exploring the potential of multi-GNSS signals and providing a set of products and services.This contribution summarizes the strategies,achievements,and innovations of multi-GNSS orbit/clock/bias determination in iGMAS Wuhan IAC.Both the precise products and Real-Time Services(RTS)are evaluated and discussed.The precise orbit and clock products have comparable accuracy with the precise products of the International GNSS Service(IGS)and iGMAS.The multi-frequency code and phase bias products for Global Positioning System(GPS),BeiDou Navigation Satellite System(BDS),Galileo navigation satellite system(Galileo),and GLObal NAvigation Satellite System(GLONASS)are provided to support multi-GNSS and multi-frequency Precise Point Positioning(PPP)Ambiguity Resolution(AR).Compared with dual-frequency PPP AR,the time to first fix of triple-frequency solution is improved by 30%.For RTS,the proposed orbit prediction strategy improves the three dimensional accuracy of predicted orbit by 1 cm.The multi-thread strategy and high-performance matrix library are employed to accelerate the real-time orbit and clock determination.The results with respect to the IGS precise products show the high accuracy of RTS orbits and clocks,4–9 cm and 0.1–0.2 ns,respectively.Using real-time satellite corrections,real-time PPP solutions achieve satisfactory performance with horizontal and vertical positioning errors within 2 and 4 cm,respectively,and convergence time of 16.97 min.