Principle and Experimental Verification of Caudal-fin-type Piezoelectric-stack Pump with Variable-cross-section Oscillating Vibrator

In the traditional flow-resistance-differential (FRD) type valve-less piezoelectric pump,the generated outflow and pressure are discontinuous because of the inherent periodicity and fluctuation of the pump.To overcome these drawbacks,utilizing the bending vibration of piezoelectric bimorph to drive fluid was conducted.However,our investigation on the current status of this piezoelectric bimorph pump shows that larger driving force and vibration amplitude are required for fluid pumping;the pumping can be realized through the centrifugal force;and the mechanism of fluid pumping is no longer further studied.Based on these cases,the paper designed a piezoelectric-stack pump with variable-cross-section oscillating (VCSO) vibrator by imitating the swing of the caudal-fin of tuna,and the pump is neither the rotating type nor the volumetric type according to the taxonomy.The interaction between the oscillating vibrator and the fluid parcel is firstly analyzed from the viewpoint of momentum conservation,and the analytical expression of pump flow rate is obtained.Then the modal and harmonic response analyses on the vibrator immerged in water are carried out.From the analyses the first two orders resonance frequencies are 832 Hz and 1 939 Hz,respectively,and the peak value of the tip amplitude is 0.6 mm.Laser Doppler vibrometer is used to measure both the frequency and vibration amplitude,and the determined first two orders resonance frequencies are 617 Hz and 1 356 Hz,respectively.The measured tip amplitude reaches to the peak value of 0.3 mm.At last,experimental measurement for the flow rates with different driving frequencies is conducted.The results show that the flow rate can reach 560 mL/min at 1 370 Hz when the pump runs under the backpressure of 30 mm water column.And the flow rate is as much as 560% of that of experiment results carried out by researchers from Brazil.The proposed pump innovates in both theory and taxonomy;in addition,the pump overcomes the drawbacks such as large flow fluctuation and low flow rate in the traditional FRD type pumps,which will help to broaden the application of the valve-less piezoelectric pump.

Effect of cooling rate on MC carbide in directionally solidified nickel-based superalloy under high thermal gradient

A series of directional solidification experiments have been performed to study the effect of cooling rate on the precipitation behavior of MC carbide in nickel-based superalloy under the temperature gradient of 500 K·s-1.Results reveal that the morphology of MC carbide changes from coarse block to fine strip,then to Chinese-script,and their sizes reduce gradually with the increasing of cooling rate from 2.53 K·s-1 to 36.4 K·s-1.At low cooling rates,most of these carbides are found to be located at the grain boundary and interdendritic regions,while the coupled growth of some carbides and γ matrix in the center of γ grains is occurred at high cooling rate.The main elements forming MC carbide are Ta,W,and Hf.

Recognition of cotton growth period for precise spraying based on convolution neural network

Dynamic acquisition of crop morphology is beneficial to real-time variable decision of precise spraying operations in fields.However,the existing spraying quantity regulation has high tolerance on the statistical characteristics of regional morphology,so expensive LiDAR and ultrasonic radar can’t make full use of their high accuracy,and can reduce decision speed because of too much detail of branches and leaves.Therefore,designing a novel recognition system embedded machine learning with low-cost monocular vision is more feasible,especially in China,where the agricultural implements are medium sizes and cost-sensitive.In addition,we found that the growth period of crops is an important reference index for guiding spraying.So,taking cotton as a case study,a cotton morphology acquisition by a single camera is established,and a cotton growth period recognition algorithm based on Convolution Neural Network(CNN)is proposed in this paper.Through the optimization process based on confusion matrix and recognition efficiency,an optimized CNN model structure is determined from 9 different model structures,and its reliability was verified by changing training sets and test sets many times based on the idea of kfold test.The accuracy,precision,recall,F1-score and recognition speed of this CNN model are 93.27%,95.39%,94.31%,94.76%and 71.46 ms per image,respectively.In addition,compared with the performance of VGG16 and AlexNet,the convolution neural network model proposed in this paper has better performance.Finally,in order to verify the reliability of the designed recognition system and the feasibility of the spray decision-making algorithm based on CNN,spraying deposition experiments were carried out with 3 different growthperiods of cotton.The experiments’results validate that after the optimal spray parameters were applied at different growth periods respectively,the average optimum index in 3 growth periods was 42.29%,which was increased up to 62.24%than the operations without distinguishing growth periods.

From agricultural engineering and forestry engineering to biomechinfotronic engineering

The deterioration of global environment,decreasing of biological diversity,increasing of natural disasters,exhausting of biological resources and acceleration of desertification emphasize the need to provide the human-beings with the suitable environments.Nowadays,precision agriculture and precision forestry have been emphasized to obtain the maximum output with minimum input and the least impact on the environment,so agricultural and forestry engineering systems require multi-disciplinary design groups to deal with some common interests and the concept of biomechinfotronics is needed.The word“biomechinfotronic”is introduced to describe the multidisciplinary aspects of this complex system.In the paper,the prospects,mission analysis,education system,research areas of biomechinfotronics are studied.The particular characteristics of biomechinfotronics are the synergistic integration of biological engineering with mechatronics,bioinformatics,infotronics,bioelectronics and intelligent computer systems for conducting common research and development and for recruiting and training students with wide specialties.