Fluorescence tracer method for analysis of droplet deposition pattern characteristics of the sprays applied via unmanned aerial vehicle

With the development of agricultural aviation technologies and their application in agricultural production, plant protection unmanned aerial vehicle (UAV) has been widely used to control pests and diseases of crops. The high speed rotation of the rotor in the UAV produces a powerful downwash affecting the distribution of pesticide droplets on the ground. Understanding spatial distribution of these droplets on the ground is important to evaluate application quality of the pesticides and plays an important role in improving the spray system in UAV and optimizing its operating parameters. Current methods for measuring the droplet deposition distributions use a number of collectors placed regularly on the ground to receive the droplets and measured their sizes; it is difficult for them to effectively obtain the deposition of all droplets resultdue to the downwash of UAV. This paper presents a new method to resolve this problem by improving accuracy and spatial continuity of pesticide droplets measurement applied by an unmanned helicopter. The flying parameters of a 3WQF–80–10 unmanned helicopter used to spray pesticides were obtained from the high–precision Beidou navigation system, and the RQT–C–3 fluorescent whitening tracer with mass fraction of 1.0% was used as the proxy for the pesticides. Two droplet collection methods: one used continuous strip paper and the other one used individual water sensitive paper, were used to measure the droplets deposition distribution. We divided the experimental field into three areas, with Areas 1 and 2 spaced 3 m apart, and Areas 2 and 3 spaced 1m apart. A metal bracket 8 m log and 0.5 m away from the ground was placed in each area. Prior to the experiment, a paper tape was fixed on the surface of the bracket and the water–sensitive paper cards were placed evenly in the area 0.5 m away from the paper tape. There were one paper tape and 15 water sensitive papers in each area, and a total of six spray tests were performed based on pro–designed flight parameters. The combinations of flight speed and flight height were: 2 m/s and 3 m, 2 m/s and 6 m, 2 m/s and 9 m, 3 m/s and 3 m, 3 m/s and 6 m, and 4 m/s and 9 m. The paper tape was detected by fluorescence spectroscopy analysis, and the water sensitive papers were scanned using an image processing software to obtain droplet deposition coverage rate. The results showed that distribution curves of the coverage rate obtained by the paper tape method coupled with the fluorescence spectrum tracer were consistent with that obtained from the images of the water sensitive paper method, with the R2 being 0.88~0.96. Because not all fine droplets fell on the water sensitive papers due to the effect of the high speed rotating rotor, the coverage rate curve measured by the continuous fluorescence method had multiple peaks and the value of its coverage rate was higher than that measured from the water sensitive paper method. When the unmanned helicopter flew at speed of 2 m/s and height of 3 m, the coverage ratio obtained from the continuous fluorescence method was up 16.92% compared to that sampled from the individual water–sensitive paper method, while when the flight speed was 4 m/s at height of 9 m, the coverage ratio in the latter was 97.77% higher than in the former. In terms of the impacts of unmanned helicopter operating conditions on coverage rate, when the helicopter flew at 2 m/ s and height of 3 m, the coverage rate of the droplets obtained from the two methods were the highest, being 8.34% for the continuous fluorescence method and 7.14% for the individual paper method. With the flight height and speed increasing, the spatial coverage rate of the droplets decreased. In summary, the high–speed rotor of UAV generates a downwash, making the droplets of pesticides move in different directions and resulting in a large spatial difference in their deposition on the ground. Therefore, the continuous sampling method is more adequate to evaluate the spatial distribution of the droplets. This study has implication for study on detecting deposition of pesticides and other agrochemicals applied by UAV

Identification and modulation of electronic band structures of single-phase B-(AlxGa1-x)2O3 alloys grown by laser molecular beam epitaxy

Understanding the band structure evolution of (AlxGa1x)2O3 alloys is of fundamental importance for developing Ga2O3-based power electronic devices and vacuum ultraviolet super-radiation hard detectors. Here, we report on the bandgap engineering of b-(AlxGa1x)2O3 thin films and the identification of compositionally dependent electronic band structures by a combination of absorption spectra analyses and density functional theory calculations. Single-monoclinic b-phase (AlxGa1x)2O3 (0 x 0.54) films with a preferred (201) orientation were grown by laser molecular beam epitaxy with tunable bandgap ranging from 4.5 to 5.5 eV. The excellent fitting of absorption spectra by the relation of (ah) 1/2 / (h-E) unambiguously identifies that b-(AlxGa1x)2O3 alloys are indirect bandgap semiconductors. Theoretical calculations predict that the indirect nature of b-(AlxGa1x)2O3 becomes more pronounced with increased Al composition due to the increased eigenvalue energy gap between M and U points in the valence band. The experimentally determined indirect bandgap exhibits almost a linear relationship with Al composition, which is consistent with the theoretical calculation and indicates a small bowing effect and a good miscibility. The identification and modulation of (AlxGa1x)2O3 band structures allows rational design of ultra-wide bandgap oxide heterostructures for the applications in power electronics and solar-blind or X-ray detection.This research was supported by the National Key Research and Development Project (Grant No. 2017YFB0403003), the National Natural Science Foundation of China (Grant Nos. 61774081, 61322403, and 11227904), the Natural Science Foundation of Jiangsu Province (Grant Nos. BK20130013 and BK20161401), the Six Talent Peaks Project in Jiangsu Province (2014XXRJ001), the Fundamental Research Funds for the Central Universities (021014380093 and 021014380085) and the Australian Research Council. The computational part of this research was undertaken with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government under the NCRIS program

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Mechanical Performance of Methane Hydrate–Coal Mixture

Understanding mechanical behaviors of a methane hydrate–coal mixture are important for its associated application in coal and gas outburst prevention. A triaxial compression apparatus for a specimen of the methane hydrate–coal mixture was developed to measure its strength and deformation properties. Triaxial compression tests were performed on coal briquette samples under different confining pressures and methane hydrate saturation. Strain softening behavior of the methane hydrate–coal mixture can be identified for all the specimens under various conditions. The larger the methane hydrate saturation or confining pressure, the larger the peak strength, elastic modulus and peak strain. Mathematical relationships for correlating the peak strength with the methane hydrate saturation or confining pressure were also proposed

Monitor Cotton Budding Using SVM and UAV Images

Monitoring the cotton budding rate is important for growers so that they can replant cotton in a timely fashion at locations at which cotton density is sparse. In this study, a true-color camera was mounted on an unmanned aerial vehicle (UAV) and used to collect images of young cotton plants to estimate the germination of cotton plants. The collected images were preprocessed by stitching them together to obtain the single orthomosaic image. The support-vector machine method and maximum likelihood classification method were conducted to identify the cotton plants in the image. The accuracy evaluation indicated the overall accuracy of the classification for SVM is 96.65% with the Kappa coefficient of 93.99%, while for maximum likelihood classification, the accuracy is 87.85% with a Kappa coefficient of 80.67%. A method based on the morphological characteristics of cotton plants was proposed to identify and count the overlapping cotton plants in this study. The analysis showed that the method can improve the detection accuracy by 6.3% when compared to without it. The validation based on visual interpretation indicated that the method presented an accuracy of 91.13%. The study showed that the minimal resolution of no less than 1.2 cm/pixel in practice for image collection is necessary in order to recognize cotton plants accurately

Algorithm for Extracting the 3D Pose Information of <i>Hyphantria cunea</i> (Drury) with Monocular Vision

Currently, the robustness of pest recognition algorithms based on sample augmentation with two-dimensional images is negatively affected by moth pests with different postures. Obtaining three-dimensional (3D) posture information of pests can provide information for 3D model deformation and generate training samples for deep learning models. In this study, an algorithm of the 3D posture information extraction method for Hyphantria cunea (Drury) based on monocular vision is proposed. Four images of every collected sample of H. cunea were taken at 90° intervals. The 3D pose information of the wings was extracted using boundary tracking, edge fitting, precise positioning and matching, and calculation. The 3D posture information of the torso was obtained by edge extraction and curve fitting. Finally, the 3D posture information of the wings and abdomen obtained by this method was compared with that obtained by Metrology-grade 3D scanner measurement. The results showed that the relative error of the wing angle was between 0.32% and 3.03%, the root mean square error was 1.9363, and the average relative error of the torso was 2.77%. The 3D posture information of H. cunea can provide important data support for sample augmentation and species identification of moth pests

Rapid Bactericidal Activity of Daptomycin against Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Peritonitis in Mice as Measured with Bioluminescent Bacteria

The rising rates of antibiotic resistance accentuate the critical need for new antibiotics. Daptomycin is a new antibiotic with a unique mode of action and a rapid in vitro bactericidal effect against gram-positive organisms. This study examined the kinetics of daptomycin's bactericidal action against peritonitis caused by methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) in healthy and neutropenic mice and compared this activity with those of other commonly used antibiotics. CD-1 mice were inoculated intraperitoneally with lethal doses of MSSA (Xen-29) or MRSA (Xen-1), laboratory strains transformed with a plasmid containing the lux operon, which confers bioluminescence. One hour later, the animals were given a single dose of daptomycin at 50 mg/kg of body weight subcutaneously (s.c.), nafcillin at 100 mg/kg s.c., vancomycin at 100 mg/kg s.c., linezolid at 100 mg/kg via gavage (orally), or saline (10 ml/kg s.c.). The mice were anesthetized hourly, and photon emissions from living bioluminescent bacteria were imaged and quantified. The luminescence in saline-treated control mice either increased (neutropenic mice) or remained relatively unchanged (healthy mice). In contrast, by 2 to 3 h postdosing, daptomycin effected a 90% reduction of luminescence of MSSA or MRSA in both healthy and neutropenic mice. The activity of daptomycin against both MSSA and MRSA strains was superior to those of nafcillin, vancomycin, and linezolid. Against MSSA peritonitis, daptomycin showed greater and more rapid bactericidal activity than nafcillin or linezolid. Against MRSA peritonitis, daptomycin showed greater and more rapid bactericidal activity than vancomycin or linezolid. The rapid decrease in the luminescent signal in the daptomycin-treated neutropenic mice underscores the potency of this antibiotic against S. aureus in the immune-suppressed host

脉宽调制变量控制喷头雾化性能及风洞环境雾滴沉积特性

Pulse width modulation (PWM) technology is an important means to achieve variable spray, and is attracting more and more researchers' attention due to its short reaction time, fast response, large flow adjustment range and good spray characteristics using conventional nozzles. But during the actual spraying process, its working parameters and environmental conditions could influence the spray accuracy seriously. In order to investigate the atomization and deposition characteristics of the PWM variable-rate nozzle, a pulse width modulation variable spraying system was designed to study the spraying atomization and deposition characteristics of TR80-005C hollow cone spray nozzle commonly used in agricultural application. In order to maintain a stable environmental condition to produce setting wind speed, the experiments were carried out in the type IEA-II wind tunnel designed by Agricultural Intelligent Equipment Technology Research Center. A dot matrix placement capacitive droplet deposition monitoring sensor was used to detect spray deposition in real time. To effectively evaluate the ground deposition properties of the wind tunnel environment, deposition evaluation index (DEIX) was deduced based on drift potional index (DIX). DEIX is inversely proportional to DIX, the smaller the DEIX value, the smaller the potential of droplet deposition, which means that the possibility of drift loss is greater. The Spraytec droplet size meter was sued to test the droplet volume median diameter (VMD) and the relative span of the droplets (RS) to determine the relationship between duty cycle and spraying atomization performance. The experiment was carried out at the Xiaotangshan National Precision Agriculture Research Station in Changping district of Beijing city. The test devices were mainly composed of PWM variable-rate spraying system, IEA-II conventional-speed wind tunnel, laser particle size analyzer and deposition measurement sensor network system. Before tests, all systems were powered on and warm up for 30 minutes. In the droplet size tests, the nozzle was placed 0.5 m directly above the droplet size analyzer, the test pressure was set to 0.4 MPa, the PWM frequency was set to 1 Hz, and the duty cycle was set to 10%-60% at the interval of 10%. Tap water was used as the spraying solution, and each setting repeated 5 times. For the droplet deposition characteristic tests, droplet deposition sensor was arranged at the bottom of the wind tunnel, the sensors were arranged in 5 rows (1 m spacing) and 3 columns (0.55 m spacing) on the vertical wind direction, and were numbered 1 to 15 starting from the upper side to the bottom of the upper side. The nozzle was fixed at the top of the wind tunnel, and the height of the relative deposition sensor was set to 1and 1.5 m respectively, and the horizontal distance between the nozzle and the first column deposition sensor was 1.3 m, the wind speed was set to 1-5 m/s, PWM frequency was set to 1 Hz and duty cycle was 10%-60%, spraying time was set as 10 s, the spraying pressure was set as 0.4 MPa. At the beginning of the test, the sensors saved datas in real time and transmitted it back to the computer. The test results showed that when the duty cycle was between 10%-40%, the VMD decreased with the increases of duty cycle, VMD was 122.3 μm at 60% duty cycle, which increased by 1.8 μm compared with that of at 40% duty cycle. When the PWM duty cycle was 60%, the RS was the smallest, compared with that of duty cycle at 20%, the RS decreased by 9.52%, that means that the droplet spectrum was the narrowest, and droplet size distribution was the most concentrated. In the deposition test, under the condition of wind speed at 1 m/s, droplets were mainly deposited within 3.3 m from the nozzle, which accounted for 95.7% of the total deposition. When the wind speed exceeded 3 m/s, the droplet settling distance increased under the action of the airflow, which may increase the possibility of spray drift. With increase of the duty cycle, DEIX value decreased and the drift rate of the droplets increased. Under the same working conditions, the larger the wind speed and the nozzle height, the smaller the DEIX and the easier spray drift. This study provides a basis for the practical application of pulse width modulation variable application techniques and PWM working condition parameters selection in agricultural field production, and provides a theoretical basis for further optimization of PWM variable adjustment devices

Modeling and Experimental Validation of the Atomization Efficiency of a Rotary Atomizer for Aerial Spraying

Rotary atomizers are mainly used in agricultural manned aircrafts. Atomization characteristics at high speeds have been studied, but methods to measure the atomization efficiency have not been elucidated. The atomization efficiency of rotary atomizers under high-speed airflow was investigated using an IEA-I high-speed wind tunnel experimental installation, AU5000 rotary atomizer, and a laser diffraction particle size analyzer. Accordingly, a model equation for atomization efficiency measurements was innovatively obtained. When the flow rate, fan blade angle of the atomizer, and wind speed were used as variables, the experimental results showed that the atomization efficiency mainly depended on the fan blade angle. When the fan blade angle was 35°, the atomization efficiency was optimal, regardless of wind speed. In contrast, when the fan blade angle of the atomizer was 65°, it exhibited the worst atomization efficiency, regardless of the wind speed. The experimental data from this study can provide guidance for aerial application in fixed-wing manned aircraft, such as the flow rate, and operating speed

A new spray deposition pattern measurement system based on spectral analysis of a fluorescent tracer

To complement shortages of discrete sampling data and improve the detection accuracy of droplet deposition in unmanned aerial vehicle (UAV) spraying, we developed a new spray deposition pattern measurement system (SDPMS) based on a fluorescent tracer and spectral analysis. Then, we evaluated the system performance in two field spraying experiments in comparison with water-sensitive paper results. The system comprises a fluorescence scanner and spectral analysis program. The fluorescence scanner includes an ultraviolet light, spectrometer, far end controller, stepping motor, and sample reel. First, 1.0% fluorescent tracer solution is sprayed, and the droplets are collected on a paper strip. Then, the paper strip is scanned with the fluorescence scanner, and a set of fluorescence intensity values is collected and processed by the spectral analysis program. Finally, the spray deposition pattern is calculated. The experimental results showed that the spray deposition pattern from the SDPMS had a 0.89 correlation coefficient with that of water-sensitive paper. A linear regression model between fluorescence intensity and deposit coverage was constructed, with a coefficient of determination of 0.91 (F = 61.8845, P < 0.001). In addition, a linear regression model between fluorescence intensity and volume rate was constructed, with a coefficient of determination of 0.89 (F = 51.6639, P < 0.001). The SDPMS and field experiments offer a good foundation for the development of an improved system compatible with UAV spraying