Research On Acoustic Properties And Growth Characteristics Of Certain Plant Seeds Under Ultrasound

The human food supply comes mainly from the seeds of crops.However,the long growth cycle of seeds and the low survival rate are still the serious problems in increasing grain output.Understanding the characteristics of plant seeds is helpful in increasing grain yield,so the study on the characteristics of plant seeds is extremely important.Ultrasound,as a form of physical energy,is widely used in agricultural production with good directivity and penetration characteristics.Therefore,the acoustic and growth characteristics of some plant seeds are studied under ultrasonic conditions.In this paper,the study on the characteristics of plant seeds under ultrasonic conditions was mainly divided into two aspects:First,the acoustic parameters of generalized plant seeds were measured;Second,the ultrasound parameters that make the plant seeds exhibit the best growth characteristics were studied through theoretical derivation and experimental verification.The former analyzed the ultrasonic echo signals and determined the acoustic characteristic parameters reflecting the characteristics of plant seeds.The latter mainly changed the ultrasonic field where plant seeds were located by adjusting parameters such as ultrasonic frequency and waveform,and determined the most suitable ultrasonic parameters for plant seeds.The following conclusions were researched in this paper based on the theoretical and experimental research:1.Based on the shape and structural characteristics of some plant seeds,the generalized plant seeds were equivalent to the hierarchical spherical medium structure,and a five-layer medium hierarchical structure model was established for ultrasound on plant seed system.The acoustic transmission coefficient of the model was deduced using the theory of layered medium model.The results showed that the acoustic transmission coefficient spectrum was a periodic oscillation function that takes extreme values at a range of specific frequency values.2.According to the acoustic transmission coefficient expression of the five-layer medium hierarchical structure model,the acoustic transmission coefficient spectrum was obtained by MATLAB simulation,the influence of the cortex layer thickness on the acoustic transmission coefficient spectrum of mung bean seeds was studied and the study resonant fundamental frequency of different seeds were obtained.The study found that the changes of the cortex layer thickness had no effect on the resonant fundamental frequency,but with the decrease of the cortex layer thickness,the sound energy transmitted through the seed was increased.3.The sound pressure distributions of different waves of circular planar transducers were analyzed and compared by MATLAB,the found that the fluctuation range of the pulse wave sound field was much smaller than the single frequency continuous wave.4.The transfer matrix method was used to analyze the transducer band range of ultrasound on plant seed system and the forbidden band frequency range of plant seed hierarchical structure model was determined.5.The different experiments were respectively designed based on the influence of the cortex layer thickness on the acoustic transmission coefficient spectrum,resonant fundamental frequency of ultrasound on plant seed system,sound pressure distributions of single-frequency continuous wave and circularly-wave circular planar transducers.The results showed that the plant seeds exhibited the best growth characteristics when the plant seeds without cortex were radiated by pulsed ultrasonic waves with a frequency equal to the resonant fundamental frequency.