Electrostatic spraying application is adopted in crop protection to prevent pest infestation,to improve product quality and to maximize yield.It involves a superposition of charges to pesticide spray droplets to attra...Electrostatic spraying application is adopted in crop protection to prevent pest infestation,to improve product quality and to maximize yield.It involves a superposition of charges to pesticide spray droplets to attract substrate ions at obscured surfaces.The droplets wraparound effect reduces off-target deposition,enhances on-target spray and invariably improves spray efficiency.Electrostatic spraying system works effectively at optimum parameters in combination with charging voltages,application pressures,spraying height regimes,flow rate,travel speed,electrode material,and nozzle orientation.Many combinations of the system parameter settings have been systematically used by researchers for the electrostatic application,but there are unknown specific optimum parameters combinations for pesticide spraying.Since droplets chargeability influences the effectiveness of electrostatic spraying system,the parameters that produce ideal charge to mass ratio determine the functionality of the spraying deposition,retention and surface coverage.This article,therefore,analyses electrostatic system parameters that produce suitably charged droplets characteristics for effective impacting behavior of pesticides on substrates.Increasing applied voltages consequently maximizes charge-mass ratio to optimum and starts declining upon further increase in voltages beyond a critical point.This review further proposes the selection of an optimum electrostatic parameters combination that yields optimum droplets chargeability in pesticide application.Also,it is necessary to investigate the charge property of substrates prior to pesticide application in order to superpose the right opposite charge on spray droplets at rupture time during electrostatic spraying system.展开更多
Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments.Transient talking activities characterize...Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments.Transient talking activities characterized by low(0.2 L/s),medium(0.9 L/s),and high(1.6 L/s)airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics(CFD)simulations based on a real human airway model.SST k-ωmodel was chosen to predict the airflow field,and the discrete phase model(DPM)was used to calculate the trajectories of droplets within the respiratory tract.The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet,and bronchi,larynx,and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords,and among which,over 90%of droplets over 5μm released from vocal cords deposited at the larynx and pharynx-larynx junction.Generally,droplets’deposition fraction increased with their size,and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate.This threshold size for droplets released from the vocal folds was 10-20μm,while that for droplets released from the bronchi was 5-20μm under various airflow rates.Besides,successive syllables pronounced at low airflow rates promoted the escape of small droplets,but do not significantly affect the droplet threshold diameter.This study indicates that droplets larger than 20μm may entirely originate from the oral cavity,where viral loads are lower;it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.展开更多
基金The authors would like to appreciate the financial support from the funds of the National Key Research and Development Plan of China(grant number 2016YFD0200700)the National Natural Science Foundation of China(grant number 51475215,31601676)the Advanced Talent Research Funding of Jiangsu University(grant number 5501200004).
文摘Electrostatic spraying application is adopted in crop protection to prevent pest infestation,to improve product quality and to maximize yield.It involves a superposition of charges to pesticide spray droplets to attract substrate ions at obscured surfaces.The droplets wraparound effect reduces off-target deposition,enhances on-target spray and invariably improves spray efficiency.Electrostatic spraying system works effectively at optimum parameters in combination with charging voltages,application pressures,spraying height regimes,flow rate,travel speed,electrode material,and nozzle orientation.Many combinations of the system parameter settings have been systematically used by researchers for the electrostatic application,but there are unknown specific optimum parameters combinations for pesticide spraying.Since droplets chargeability influences the effectiveness of electrostatic spraying system,the parameters that produce ideal charge to mass ratio determine the functionality of the spraying deposition,retention and surface coverage.This article,therefore,analyses electrostatic system parameters that produce suitably charged droplets characteristics for effective impacting behavior of pesticides on substrates.Increasing applied voltages consequently maximizes charge-mass ratio to optimum and starts declining upon further increase in voltages beyond a critical point.This review further proposes the selection of an optimum electrostatic parameters combination that yields optimum droplets chargeability in pesticide application.Also,it is necessary to investigate the charge property of substrates prior to pesticide application in order to superpose the right opposite charge on spray droplets at rupture time during electrostatic spraying system.
基金supported by the National Natural Science Foundation of China(No.51808488,No.52178092)。
文摘Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments.Transient talking activities characterized by low(0.2 L/s),medium(0.9 L/s),and high(1.6 L/s)airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics(CFD)simulations based on a real human airway model.SST k-ωmodel was chosen to predict the airflow field,and the discrete phase model(DPM)was used to calculate the trajectories of droplets within the respiratory tract.The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet,and bronchi,larynx,and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords,and among which,over 90%of droplets over 5μm released from vocal cords deposited at the larynx and pharynx-larynx junction.Generally,droplets’deposition fraction increased with their size,and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate.This threshold size for droplets released from the vocal folds was 10-20μm,while that for droplets released from the bronchi was 5-20μm under various airflow rates.Besides,successive syllables pronounced at low airflow rates promoted the escape of small droplets,but do not significantly affect the droplet threshold diameter.This study indicates that droplets larger than 20μm may entirely originate from the oral cavity,where viral loads are lower;it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.
