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The fluid velocity inside the tank of agricultural sprayers is an indicator of the quality of the mixture. This study aims to formulate the best generalized linear mixed model to infer the fluid velocity inside a tank under specific operational parameters of the agitation system, such as liquid level, circuit pressures, and number of active nozzles. A complex model was developed that included operational parameters as fixed effects (FE) and the section of the tank as the random effect. The goodness of fit of the model was evaluated by considering the lowest values of Akaike&rsquo, s information criteria and Bayesian information criterion, and by estimating the residual variance. The gamma distribution and log-link function enhanced the goodness of fit of the best model. The Toeplitz structure was chosen as the structure of the covariance matrix. SPSS and SAS software were used to compute the model. The analysis showed that the greatest influence on the fluid velocity was exerted by the liquid level in the tank, followed by the circuit pressure and, finally, the number of active nozzles. The development presented here could serve as a guide for formulating models to evaluate the efficiency of the agitation system of agricultural sprayers.

A computational fluid dynamics (CFD) model for simulating the air flow produced by an air-assisted sprayer can be developed according to any one of several sets of criteria and for various specific applications. Thus far, most CFD models have focused on the characterization of the air flow generated by the sprayer. However, such models may not be the best when assessing the effectiveness of air-assisted sprayers adapted to crop geometry, such as those used in vineyards. In this study, the air flow produced by an air-assisted sprayer adapted to the geometry of a vineyard was simulated using four CFD models: Model 1 was designed to simulate air velocity measurements at the outlets; Model 2 was designed to simulate air velocity measurements at a certain distance from the outlets; Model 3 was dedicated to the modelling of the internal geometry of the air ducts rather than the characterization of the air flows generated by the sprayer; and Model 4, which was developed as a variant of Model 3, was created to perform the same calculation in several stages. The models were validated with actual measurements of the air velocity near the sprayer outlets. The results showed that although Models 1 and 2 (both of which have been used in most existing studies) simplified the calculation, they are impractical for simulating different air flows. By contrast, Models 3 and 4 provided complex meshes that complicate the convergence of the calculation and require a suitable treatment of both the viscosity and the flow near the walls. Model 3 showed the smallest error (16%) in the air velocity estimated in the treatment plane. Model 4 showed potential for future implementation of the dispersed phase and crop-air interaction because it mitigated the problems arising from the complexity of the meshes. It should also be noted that there are errors inherent to the implementation of the CFD model, errors related to inaccuracies in the geometry of the air ducts, inaccuracies related to the measurement of the air velocities, inaccuracies in the quantification of the air flow, and simplifications linked to the turbulent model. Objectius de Desenvolupament Sostenible::12 - Producció i Consum Responsables Objectius de Desenvolupament Sostenible::13 - Acció per al Clima Objectius de Desenvolupament Sostenible::8 - Treball Decent i Creixement Econòmic

El Real Decreto 1702/2011, de 18 de noviembre, de inspecciones periodicas de los equipos de aplicacion de productos fitosanitarios, establece que las CCAA son las encargadas del “control y aplicacion del programa de inspecciones que se lleven a cabo en su ambito territorial”, para dar cumplimiento a la obligacion que la Directiva 2009/128/CE de uso sostenible de plaguicidas impuso a todos los paises miembros de la UE. Para poder llevar a cabo dicha encomienda la mayoria de las CCAA (trece) promulgaron decretos u ordenes autonomicos, donde se regula lo relativo al establecimiento y funcionamiento del sistema necesario para poder realizar la inspeccion periodica de los equipos de aplicacion de fitosanitarios (EAF), desde el proceso de autorizacion de las entidades inspectoras (ITEAF) hasta los mecanismos de control de la calidad de la propia actividad inspectora y de los procesos relativos a la gestion de los resultados de las inspecciones realizadas en su ambito territorial. El resto de las autonomias, cuyo numero de equipos a inspeccionar es muy reducido, decidieron que fuesen los servicios del Departamento competente los que se encargaran de realizar la inspeccion de las maquinas y las instalaciones. En este articulo se analiza la configuracion actual del sistema completo, en el que estan implicadas las ITEAF autorizadas, los Organos Competentes de las CCAA y la Direccion General de Medios de Produccion del MAPA. Se describe el modelo establecido y las herramientas con las que se ha dotado a los agentes implicados. Asimismo, se determinan las fortalezas y debilidades del sistema de gestion, una vez que se encuentra en la fase final del proceso de implantacion del Plan Nacional de inspeccion obligatoria de todos los equipos de aplicacion de productos fitosanitarios, independientemente de que la aplicacion se realice con equipos moviles o aeronaves a cultivos en campo abierto, con equipos fijos y semimoviles en el interior de instalaciones para cultivos bajo cubierta o mediante equipos fijos.

La velocidad del fluido en el interior de un pulverizador agrícola, necesaria para la mezcla homogénea de la materia activa, está determinada por el sistema de agitación interna, de tipo hidráulico en la mayoría de los casos. Esta velocidad varía según (a) algunos parámetros de trabajo: presión, número de boquillas y llenado del depósito; y (b) la geometría de la cuba: altura, anchura, tipología de la sección y presencia de obstáculos e irregularidades en el interior del depósito.Se ha realizado un ensayo en el depósito de un pulverizador hidroneumático en el que se ha medido la velocidad del fluido (cm/s) con un velocímetro acústico Doppler 3D, en 32 puntos repartidos en varias posiciones, y variando la presión del sistema de agitación (8, 10, 12 bar), el número de boquillas activas (2, 4), y el nivel de llenado de la cuba (1000, 2000, 3000 L).Este trabajo persigue ajustar y describir un modelo mixto lineal generalizado apropiado para el análisis de la influencia que cada variable (geométricas y de regulación del sistema de agitación) ejerce sobre la velocidad interior del fluido. Teniendo en cuenta que estos modelos permiten que la variable dependiente no tenga una distribución normal, que las observaciones estén correlacionadas y que tenga una relación lineal con las variables independientes y covariables a través de una función de enlace determinada.Se han obtenido diferencias significativas entre los niveles de llenado del depósito, de modo que cuanto más llena está, la velocidad es significativamente menor; entre la presión del sistema de agitación: a mayor presión mayor velocidad; entre el número de boquillas activas, (cuantas menos activas mayor es la velocidad) y entre las secciones (zona de medida) del depósito.

En Aragon, en los anos 2016 y 2017, se han producido 295 y 464 incendios respectivamente, afectando a una superficie total de 915 y 908 ha. De dichos incendios, un 12% de los ocurridos en 2016 y un 7% de los que tuvieron lugar en 2017 fueron debidos a motores y maquinas, mayormente producidos por cosechadoras. El proposito de este trabajo ha sido investigar las zonas criticas de las cosechadoras asociadas al riesgo de incendio a traves de la realizacion de una encuesta dirigida a propietarios de cosechadoras en Aragon. Se ha recabado informacion tanto sobre caracteristicas tecnicas de las maquinas (marca, potencia, antiguedad de la maquina, hectareas cosechadas, etc.) como, en su caso, de las caracteristicas de los incendios producidos (cultivo cosechado, utilizacion de sistema de picado, zona de la maquina donde se origino el incendio, etc.). En las 275 respuestas obtenidas se han referido 75 casos de incendio. En base a los datos facilitados en la encuesta, se ha analizado si existe alguna relacion entre las caracteristicas de la maquina y la produccion de un incendio, y se han comparado las zonas de la cosechadora en la que se ha originado el incendio con informacion facilitada por una compania de seguros. Se ha podido concluir que solo existe una relacion estadisticamente significativa de los incendios con el numero de hectareas cosechadas (vida util de la cosechadora), siendo especialmente alto el riesgo para maquinas con mas de 6000 ha acumuladas. Por otra parte, un 32% de los incendios tuvieron su origen en la zona del motor, frente a un 31% en la barra de corte y un 18% en los rodamientos y correas. El uso del picador no favorecio el origen del incendio en ninguna zona concreta de la maquina. El estudio se ha completado con medidas de temperatura in situ realizadas sobre varias maquinas en el verano de 2018, registrandose temperaturas superiores a 300 °C en el colector de escape, y superiores a 400 °C en la barra de corte cuando la cuchilla trabajaba en condiciones de rozamiento.

An agricultural implement for underground application of rodenticide bait to control the Mediterranean pocket gopher (Microtus Duodecimcostatus) in fruit orchards has been designed and tested. The main objective of this research was to design and test the implement by using the finite element method (FEM) and considering a range of loads generated on most commonly used furrow openers in agricultural implements. As a second step, the prototype was tested in the field by analysing the effects of forward speed and application depth on the mechanical behaviour of the implement structure. The FEM was used in the design phase and a prototype was manufactured. The structural strains on the prototype chassis under working conditions were tested by using strain gauges to validate the design phase. Three forward speeds (4.5, 5.5, and 7.0 km/h), three application depths (0.12, 0.15, and 0.17 m), and two types of soil (clayey-silty-loam and clayey-silty-sandy) were considered. The prototype was validated successfully by analysing the information obtained from the strain gauges. The Von Mises stresses indicated a safety coefficient of 1.9 for the most critical load case. Although both forward speed and application depth had a significant effect on the stresses generated on the chassis, the latter parameter critically affected the structural behaviour of the implement. The effects of the application depth on the strains were linear such that strains increased with depth. In contrast, strains remained roughly constant regardless of variation in the forward speed.

A computational fluid dynamics (CFD) model of the fluid velocities generated by the agitation system of an air-assisted sprayer was developed and validated by practical experiments in a laboratory. The model was developed considering different settings of the agitation system: Three water levels in the tank (1000, 2000, and 3000 L), two different numbers of active nozzles (2 or 4), and three working pressures of the agitation circuit (8, 10, or 12 bar). Actual measurements of the fluid velocity into the tank were taken using an acoustic Doppler velocimeter (ADV). CFD simulations made it possible to estimate fluid velocities at 38% of the measuring points with relative errors of less than 30%. Additionally, the CFD models have allowed the correct prediction of the general behavior of the fluid in the tank considering mean velocities depending on the setting parameters of the agitation system (water level in the tank, hydraulic circuit pressure, and number of active nozzles).

The suitability of using 3-D laser technology to assess the performance of a twin disc centrifugal fertiliser spreader was analysed. A static test with an Amazone ZA-M twin disc fertiliser spreader distributing di-ammonium sulphate was developed. The spreader was adjusted to spread the fertiliser at a distance of 12 m at three different rates. The test was conducted inside a building; 64 sample boxes were installed on the floor within a 2 m × 2 m frame. Considering the static test, for each spreading rate, five consecutive measurements were made using a Leica HDS6000 3D laser scanner. The information supplied by the laser scanner was correlated with the weight of the fertiliser collected in the boxes using linear regression equations. Each regression model was obtained for one particular and specific spreading configuration. This reduces the applicability of the method because for each spreader setting requires a new surface distribution to be measured to establish a new regression model. A field test was conducted to obtain a fertiliser distribution curve, with the machine set at 41.1 kg min −1 , while the tractor was progressing at 8 km h −1 . This information was used to validate the laser technology by comparing the real distribution curve with the simulated curve. The correlation coefficient (adjusted R 2 ) was 0.86. The information provided by the scanner also enabled the surface distribution of the product, the maximum spreading distance, the spreading symmetry on both sides of the machine and the trajectory of the grains of fertiliser to be analysed.

The use of plant protection products such as pesticides to protect crops against attacks by fungi, insects and weeds is a common agricultural practice. The affected areas have to be treated uniformly and with the appropriate concentration. This is achieved by the use of agricultural machinery such as air-assisted sprayers. The most common air-assisted sprayers have only one fan on the rear. This implies that the airflow generated around the machine is not symmetrical. Consequently, it is not possible to ensure the same quality of treatment for all trees. The installation of a second fan and the increase in tank capacity in the machines have resulted in machines with greater dimensions. These machines have to support higher loads compared to traditional air-assisted sprayers. The development of these new designs of air-assisted sprayers requires optimization of their chassis in order to ensure the proper operation of these agricultural implements. The main objective of this study is the design and optimization of a chassis for an air-assisted sprayer equipped with a 4000 l tank and two axial fans.

An air-assisted sprayer equipped with two reversed rotation fans was evaluated in a peach orchard. The effects on the spray deposition of the forward speed, the air volumetric flow rate, and the number of activated fans were analyzed. Spray mixtures contained manganese chelate as a tracer. Spray deposition was evaluated qualitatively through visual estimation of water-sensitive papers and quantitatively by analysis of filter papers using an atomic absorption spectrometer. Deposition and canopy penetration increased when the air volumetric flow was increased for most of the sampling points. The forward speed had no significant effect on the deposition and canopy penetration for most of the sampling points. The effect of the number of activated fans on the spray deposition was significant with increased deposition for the case of two activated fans.

The flow of air generated by a new design of air assisted sprayer equipped with two axial fans of reversed rotation was analyzed. For this goal, a 3D sonic anemometer has been used (accuracy: 1.5%; measurement range: 0 to 45 m/s). The study was divided into a static test and a dynamic test. During the static test, the air velocity in the working vicinity of the sprayer was measured considering the following machine configurations: (1) one activated fan regulated at three air flows (machine working as a traditional sprayer); (2) two activated fans regulated at three air flows for each fan. In the static test 72 measurement points were considered. The location of the measurement points was as follow: left and right sides of the sprayer; three sections of measurement (A, B and C); three measurement distances from the shaft of the machine (1.5 m, 2.5 m and 3.5 m); and four measurement heights (1 m, 2 m, 3 m and 4 m). The static test results have shown significant differences in the module and the vertical angle of the air velocity vector in function of the regulations of the sprayer. In the dynamic test, the air velocity was measured at 2.5 m from the axis of the sprayer considering four measurement heights (1 m, 2 m, 3 m and 4 m). In this test, the sprayer regulations were: one or two activated fans; one air flow for each fan; forward speed of 2.8 km/h. The use of one fan (back) or two fans (back and front) produced significant differences on the duration of the presence of wind in the measurement point and on the direction of the air velocity vector. The module of the air velocity vector was not affected by the number of activated fans.

There are several methods to dimension concrete slabs due to vehicle loads, most of them based on Westergaard theory. These methods have been developed for industrial vehicles (cars, trucks and forklifts). Considering agricultural buildings one of the most used vehicles is the agricultural tractor whose characteristics (tires of great dimensions but with a reduced contact surface) are different to those of the industrial vehicles. The goal of this research was to analyze the applicability of the finite element method (FEM) to estimate the stresses generated on the concrete slabs considering the loads transmitted by agricultural tractors. To achieve this objective, the effect of the loads transmitted by the rear axle tires of three agricultural tractors has been considered. In parallel, the same study has been carried out using the Westergaard theory. As a preliminary step, to validate the FEM, a numerical analysis has been made to obtain the stresses generated on a concrete slab considering three forklifts. The numerical analysis results have been compared with those obtained by mean of validated methods (Portland Cement Association) and the classical theory of Westergaard. For each agricultural tractor, the actual geometry of the contact surface of tires has been measured on a concrete slab and discretized by the FEM. As a result of the research process developed, it is possible to conclude that the FEM is a valid tool to analyze the tensions generated by the loads transmitted by the tires of agricultural tractors on concrete floors supported on the ground. En relación con el dimensionado de soleras de hormigón apoyadas sobre el suelo, existen metodologías rigurosas para el cálculo de las tensiones de trabajo, basadas en la teoría de Westergaard, pero desarrolladas para vehículos industriales (coches, camiones y carretillas elevadoras). En las soleras de edificios agrícolas, el vehículo más utilizado es el tractor agrícola, que dispone de neumáticos de elevada anchura y diámetro, pero con una superficie de contacto reducida. En este artículo se ha abordado el estudio de las tensiones generadas en las soleras de hormigón por las cargas transmitidas por los neumáticos de los tractores agrícolas utilizando el método de elementos finitos (FEM). Para ello, se han estudiado las cargas transmitidas por los neumáticos del eje trasero de tres tractores. En paralelo, se ha realizado el mismo estudio utilizando la metodología de cálculo clásica de Westergaard. Como paso previo se ha justificado la utilización del FEM realizando una validación de cálculo de soleras para vehículos tradicionales industriales (carretillas elevadoras) en comparación con métodos validados para ese tipo de vehículos (Portland Cement Association, PCA) y con la teoría clásica de Westergaard. Como resultado se puede concluir que el FEM es una herramienta válida para analizar las tensiones generadas por las cargas transmitidas por los neumáticos de los tractores agrícolas sobre soleras de hormigón apoyadas sobre el terreno.

Durante muchos años, la sociedad mexicana en su conjunto, ha hecho un gran esfuerzo para otorgarle más escolaridad al mayor número de personas posible. Por razones estructurales, este proceso se ha ido reflejando cada vez más en la escolaridad de los trabajadores , particularmente de los más jóvenes. Por la misma razón, las personas que por primera vez buscan trabajo, tienen más educación. En este trabajo se intenta responder a la pregunta ¿Cuál es el efecto sobre la distribución del ingreso de una oferta de mano de obra cada vez con más escolaridad