Sound Transmission Loss Analysis of a Double Plate-Acoustic Cavity Coupling System with In-Plane Functionally Graded Materials

In this paper, the isogeometric analysis (IGA) is employed to develop an acoustic radiation model for a double plate-acoustic cavity coupling system, with a focus on analyzing the sound transmission loss (STL). The functionally graded (FG) plate exhibits a different material properties in-plane, and the power-law rule is adopted as the governing principle for material mixing. To validate the harmonic response and demonstrate the accuracy and convergence of the isogeometric modeling, ANASYS is utilized to compare with numerical examples. A plane wave serves as the acoustic excitation, and the Rayleigh integral is applied to discretize the radiated plate. The STL results are compared with the literature, confirming the reliability of the coupling system. Finally, the investigation is conducted to study impact of cavity depth and power-law parameter on the STL.

Isolation and Preliminary Identification of Broad-spectrum Bacteriocin-producing Lactobacillus Strain CW3

[ Objective] This study aimed to screen and preliminarily identify LactobaciUus strain CW3. [ Method] Oxford cup double-plate method was used for preliminary screening of broad-spectrum bacteriacin-producing LactobaciUus strain; after eliminating the interference of organic acid and hydrogen peroxide, antibac- terial substances containing protein properties produced by the screened strain were detected; finally, the obtained strain was identified. [ Result] After elimination of interference factors such as organic acid and hydrogen peroxide, the fermentation supernatant of strain CW3 could stil｜ inhibit the growth of indicator strains; the antibacterial activity of fermentation broth was significantly reduced after treatment with trypsase and pepsase, which indicated that the produced antibacterial sub- stances were bacteriocins. Results of physiological and biochemical identification showed that strain CW3 belonged to Lactobacillus plantarum. [ Conclusion] CW3 is a broad-spectrum bacteriocin-producing LactobaciUus plantarum strain.

Influence of vibration on the grain flow sensor during the harvest and the difference elimination method

The grain yield data collected by the intelligent yield measurement system of the combine harvester is generated into a field plot yield distribution map,which is of great significance for guiding agricultural production.However,in the process of drawing the yield map,the combine harvester is affected by vibration during operation and the generated error data in the process of collecting data which will cause the drawing results to be inaccurate.This study researched two factors that cause errors,then,the influence of vibration interference on the measurement signal was eliminated by filtering,vibration isolation,and designing a double-plates differential grain flow sensor.Three methods were taken to eliminate random errors,gross errors and systematic errors,including using the arithmetic average value to replace the true value,the 3σcriterion,and removing the filling time data and the delaying time data.Finally,the grain yield distribution map was obtained through Matlab and Excel.The results showed that the interference frequency above 50 Hz could be eliminated by filtering,but it was difficult to filter the low-frequency signal which was close to the grain impact frequency.The vibration amplitude was reduced to 14.29%by adding a vibration isolation plate,and the SNR was increased from−4.67 dB to 29.21 dB by combining low-pass filtering and damping vibration isolation.When the grain feeding rate was 2 kg/s,the natural vibration amplitude of the sensor after difference was about 0.02 V and evenly distributed around the zero voltage 0.2 V.The influence of positive and negative offset on the average value of grain impact signal could be ignored,and the signal-to-noise ratio was increased from 29.21 dB to 62.49 dB.The results of field experiments showed that the yield map drawn can clearly display the yield value of the harvest area,which is used to guide agricultural production.