Review on Automatic Variable-Rate Spraying Systems Based on Orchard Canopy Characterization

Pesticide consumption and environmental pollution in orchards can be greatly decreased by combining variable-rate spray treatments with proportional control systems. Nowadays, farmers can use variable-rate canopy spraying to apply weed killers only where they are required which provides environmental friendly and cost-effective crop protection chemicals. Moreover, restricting the use of pesticides as Plant Protection Products (PPP) while maintaining appropriate canopy deposition is a serious challenge. Additionally, automatic sprayers that adjust their application rates to the size and shape of orchard plantations has indicated a significant potential for reducing the use of pesticides. For the automatic spraying, the existing research used an Artificial Intelligence and Machine Learning. Also, spraying efficiency can be increased by lowering spray losses from ground deposition and off-target drift. Therefore, this study involves a thorough examination of the existing variable-rate spraying techniques in orchards. In addition to providing examples of their predictions and briefly addressing the influences on spraying parameters, it also presents various alternatives to avoiding pesticide overuse and explores their advantages and disadvantages

INKJET PRINTING: FACING CHALLENGES AND ITS NEW APPLICATIONS IN COATING INDUSTRY

This study is devoted to some of the most important issues for advancing inkjet printing for possible application in the coating industry with a focus on piezoelectric droplet on demand (DOD) inkjet technology. Current problems, as embodied in liquid filament breakup along with satellite droplet formation and reduction in droplet sizes, are discussed and then potential solutions identified. For satellite droplets, it is shown that liquid filament break-up behavior can be predicted by using a combination of two pi-numbers, including the Weber number, We and the Ohnesorge number, Oh, or the Reynolds number, Re, and the Weber number, We. All of these are dependent only on the ejected liquid properties and the velocity waveform at the print-head inlet. These new criteria are shown to have merit in comparison to currently used criteria for identifying filament physical features such as length and diameter that control the formation of subsequent droplets. In addition, this study performs scaling analyses for the design and operation of inkjet printing heads. Because droplet sizes from inkjet nozzles are typically on the order of nozzle dimensions, a numerical simulation is carried out to provide insight into how to reduce droplet sizes by employing a novel input waveform impressed on the print-head liquid inflow without changing the nozzle geometry. A regime map for characterizing the generation of small droplets based on We and a non-dimensional frequency, Ω is proposed and discussed. In an attempt to advance inkjet printing technology for coating purposes, a prototype was designed and then tested numerically. The numerical simulation successfully proved that the proposed prototype could be useful for coating purposes by repeatedly producing mono-dispersed droplets with controllable size and spacing. Finally, the influences of two independent piezoelectric characteristics - the maximum head displacement and corresponding frequency, was investigated to examine the quality of filament breakup quality and favorable piezoelectric displacements and frequencies were identified

Developing paper-based devices for mapping agricultural pesticides and environmental contaminants

2021 Summer.Includes bibliographical references.The detection of environmental contaminants is important to ensure the health of both humans and the environment. Currently, detection is done by instrumentation like liquid or gas chromatography coupled with mass spectrometry. While sensitive and selective for multiple analytes, these instruments suffer from disadvantages like large size, high sample cost, and the need for a trained analyst to run the samples. As an alternative, microfluidic paper-based analytical devices (µPADs) are becoming more common as inexpensive, fast, easy to use devices to detect and quantify a variety of analytes. My research has been focused on developing µPADs for three different analytes: pesticides, PFAS, and heavy metals. In order to ensure proper crop protection and pest management, it is important to manage and optimize pesticide application. Currently, this is done by water-sensitive papers, which often inaccurately portray the presence of pesticide due to humidity and extraneous water droplets that are not pesticide. In Chapter 2, I have developed a method that uses filter paper to capture a fluorescent tracer dye that has been mixed with the pesticide and then sprayed over the crop. The filter papers are imaged with a lightbox and Raspberry Pi camera system and then analyzed to determine percent coverage. After optimization and validation of the method to WSP, the filter paper method was used to evaluate pesticide distribution in a citrus grove in Florida (Chapter 3). The data from these field studies was used to make recommendations for which application method is best for the different types of pesticides. Paper-based devices are inherently limited by the inability to control fluid properties like mixing. In order to incorporate mixing but also retain a small device that does not require external power to initial flow, a microfluidic device was fabricated out of two glass slides. A staggered herringbone pattern is laser ablated into the slides, and a channel is formed by double-sided adhesive (Chapter 4). Mixing was quantified using blue and yellow dyes. A reaction between horseradish peroxidase and hydrogen peroxide was used as a representative enzymatic reaction and also to determine enzyme kinetics. Since the microfluidic device is made of glass, it is also compatible with non-aqueous solvents. Paper-based devices do not work well with organic solvents because the hydrophobic wax on the paper is dissolved by the solvent. In Chapter 5, the dissertation returns to traditional µPADs for environmental contaminants. Per- and polyfluoroalkyl substances (PFAS) are class of compounds that are highly persistent, toxic, bioaccumulative, and ubiquitous. While multiple instrument-based methods exist for sensitive and selective detection in a variety of matrices, there is a huge need for a fast, inexpensive, and easy-to-use sensor for PFAS detection. This would enable widespread testing of drinking water supplies, ensuring human health. A µPAD was developed for the detection of perfluorooctane sulfonate (PFOS) where the ion-pairing of PFOS and methylene green forms a purple circle. The diameter of the purple circle can be measured by the naked eye with a ruler or with the help of a smartphone to correlate the diameter back to PFOS concentration. At a cost of cents per sample, this µPAD enables fast and inexpensive detection of PFOS to ensure safe drinking water. A common issue with environmental µPADs is the relatively high limits of detection compared to what is needed for regulatory purposes. It can be challenging to lower the limits of detection without incorporating an external pretreatment and/or preconcentration step. As µPADs are small and handle only a small volume of sample (<120 µL), there is the possibility of increasing the sample capacity of the device but without significantly increasing the device size or analysis time. By adding multiple layers of absorbent filter paper underneath radial device for heavy metal detection, the sample volume increased to 1 mL, decreasing the limit of detection for a radial copper detection card from 100 ppb to 5 ppb (Chapter 6). The research presented here achieves the goal of developing µPADs for environmental contaminants. They can be used in different ways to visualize the presence of the contaminant for monitoring and management purposes, ultimately ensuring human and environmental health

Fuel Injection

Fuel Injection is a key process characterizing the combustion development within Internal Combustion Engines (ICEs) and in many other industrial applications. State of the art in the research and development of modern fuel injection systems are presented in this book. It consists of 12 chapters focused on both numerical and experimental techniques, allowing its proper design and optimization

Charging Level and Deposition of Droplets in Electrostatic Painting

The process of electrostatic painting has become a very important method of coating in a wide range of industrial applications including those used in the automobile industry. The general principle of spray coating is to deposit liquid droplets or solid powder particles on coated targets having various shapes. The electrostatic coating process consists of three main stages: droplet formation and charging, transportation and deposition. The complication of this process is caused by various factors, such as the physical properties of the material to be used, the appropriate electrical and mechanical conditions and the target surface to be coated, which affects significantly the deposition uniformity and the finish quality, especially when it contains some sharp edges and recessed areas. In this thesis, a numerical investigation of the charging level on a spherical droplet formed out of a cylindrical ligament in an external uniform electric field is presented. The droplet charge on a single ligament was predicted for different droplet sizes, ligament lengths, ligament diameters and electrode widths. The effect of these model parameters on the charge levels was found to be significant. A mathematical approximation for the charge magnitude as a function of the droplet radius to some exponent and ligament length is also formulated. The value of the radius exponent decreases dramatically with increasing the ligament length. Also, the estimated values of the droplet charge were compared for linear and circular arrays of ligaments, which show a great influence of the geometry of the sprayer on the charge levels. A very good agreement between the experimental and numerical results in the case of a circular array of ligaments, including a specified space charge, was obtained. All numerical simulations were performed using COMSOL, a Finite Element commercial software. A further study is carried out to investigate the deposition thickness profile on a stationary and moving flat target by incorporating a numerical simulation of the industrial electrostatic coating process via ANSYS, a CFD commercial software. A modified injection pattern was suggested to achieve a closer agreement with the experimental data. The injection pattern includes 15 bands of different particle sizes (i.e. polydispersed particles) and charge to mass ratios. A combination of different injection angles and fractions of mass flow rates was suggested in each size band. A very good agreement between the experimental and numerical deposition patterns was obtained in both cases of a stationary and moving target. Also, the deposition thickness profile was calculated on a target surface with a small perturbation at the center using ANSYS numerical model. Different model parameters of a perturbed surface, such as the size of the indentation or the protrusion and the radius of the corner were investigated in this study. The numerical results reveal a very low particle concentration inside the indentation, which is caused by the Faraday cage effect and it is strongly affected by the depth of the indentation, while the edge effect, which shows the high concentration of deposited particles at the corner, increases with decreasing the radius of curvature. The predicted deposition patterns were very consistent with the calculated values of the electric field for different surface perturbations

Technical aspects of pesticide application : a literature review

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