Horizontal Disc Research Articles

Air-cushioning effect and Kelvin-Helmholtz instability before the slamming of a disk on water

The macroscopic dynamics of a droplet impacting a solid is crucially determined by the intricate air dynamics occurring at the vanishingly small length scale between droplet and substrate prior to direct contact. Here we investigate the inverse problem, namely the role of air for the impact of a horizontal flat disk onto a liquid surface, and find an equally significant effect. Using an in-house experimental technique, we measure the free surface deflections just before impact, with a precision of a few micrometers. Whereas stagnation pressure pushes down the surface in the center, we observe a lift-up under the edge of the disk, which sets in at a later stage, and which we show to be consistent with a Kelvin-Helmholtz instability of the water-air interface.

Optic disc morphometry using spectral domain optical coherence tomography in a Nigerian population.

To assess morphological optic disc dimensions using spectral-domain optical coherence tomography (OCT) in a Nigerian population. Good quality SD-OCT scans of the optic disc of 147 eyes of 88 participants were selected, enrolled, and retrospectively reviewed. All subjects had optic nerve head and retinal nerve fibre layer OCT imaging, as well as analysis, done using the Topcon 3D OCT-1 Maestro®. The age, sex, and some OCT-generated optic disc dimensions namely disc area (DA), vertical disc diameter (VDD), horizontal disc diameter (HDD) were retrieved from the database and analyzed. The mean age of the study subjects was 52.6±20.9 years with a range of 8-90 years; male to female ratio was 1:1.3. The right eye and left eye accounted for 75 and 72 of the 147 scans respectively. The mean DA, VDD, and HDD were 2.54 ± 0.48 mm2, 1926.5 ± 189.6 μm and 1673.9 ± 173.9 μm, respectively. Males had significantly larger DA than females (2.56 ± 0.53 mm2 vs 2.51 ± 0.44 mm2, p = 0.043). The mean DA and VDD of eyes of subjects aged 21-40 years were significantly higher compared to subjects aged 60 years and more (p = 0.008 and 0.001, respectively). The mean optic disc area and diameters are larger than those reported in similar studies involving blacks and other races. The mean disc area reduces with increasing age.

Теоретическое обоснование параметров рабочих органов разбрасывателя центробежного типа

The processes of movement of granules of solid mineral fertilizers on the surface of the spreading disc blade are described, and the main parameters at the moment of their descent from the blades are determined. It was found that the main factors that determine the speed of a fertilizer particle when it moves along a horizontal disc along a rectilinear blade are the blade length and the angular velocity of the spreading disc.

Correlation between optic disc deformation and retinal vasculature in non-pathological high myopia.

The aim of the current study was to investigate the correlation between optic disc deformation and retinal vasculature in high myopia. A total of 130 eyes with non-pathological high myopia were included in the current cross-sectional study. β-zone parapapillary atrophy (β-PPA), optic disc tilt ratio, and horizontal and vertical disc diameters were analyzed using fundus color photography. A 3x3 mm grid and a 4.5x4.5 mm grid were used to scan parafoveal and peripapillary regions, respectively, using optical coherence tomography angiography. Vessel flow density (VFD) and fractal dimension of the retina, as well as the foveal avascular zone (FAZ), were analyzed and quantified using en face projection images. Optic disc parameters that were associated with vascular changes were determined using multiple linear regression analysis. The results from the multivariate analysis revealed that β-PPA was negatively correlated with the VFD of the superficial retinal plexus (R=-2.805; P=0.006), deep retinal plexus (R=-2.801; P=0.006), radial parapapillary capillaries (R=-3.936; P<0.001) and enhanced-depth imaging of the fovea (R=-2.161; P=0.034). Additionally, FAZ was not significantly correlated with any factors in the current study. Age was negatively correlated with the VFD of the retina (R=-4.234; P<0.001), while the optic tilt ratio (R=-2.291; P=0.025) was negatively correlated with three sectors in the deep layer. Overall, the present results demonstrated that optic disc deformation was negatively correlated with the retinal microvasculature in non-pathological high myopia, particularly in the radial peripapillary capillaries and the deep retinal plexus. Therefore, optic disc deformation may be used to predict the retinal vasculature in high myopia.

Location of Parapapillary Gamma Zone and Vertical Fovea Location. The Beijing Eye Study 2011.

PurposeTo assess the spatial relationship between the locations of the parapapillary gamma zone and the fovea.MethodsIn a non-glaucomatous subgroup of the population-based Beijing Eye Study population, we measured the mean angle between the optic disc–fovea line and the horizontal (disc–fovea angle), the vertical distance of the fovea from the horizontal through the optic disc center (fovea vertical distance), and the location and width of the widest part of parapapillary gamma zone.ResultsThe study included 203 individuals (203 eyes; mean axial length, 24.4 ± 1.5 mm; range, 22.03–28.87 mm). The widest gamma zone part was located most often temporal horizontally (51.7%), then inferiorly (43.8%), superiorly (2.5%), and nasally (2.0%). The disc–fovea angle (mean, 7.50° ± 4.00°; range, –6.30° to –23.25°) was significantly higher (P = 0.003; i.e., fovea located more inferiorly) in eyes with the widest gamma zone inferiorly (8.46° ± 4.37°) than in eyes with the widest gamma zone temporally (6.71° ± 3.46°) and in eyes with the widest gamma zone temporally, superiorly, or nasally combined (6.75° ± 3.53°; P = 0.003). The fovea vertical distance (mean, 0.65 ± 0.33 mm; range, –0.20 to 1.67 mm) was longer (P = 0.001; i.e., fovea located more inferiorly) in eyes with the widest gamma zone inferiorly (0.73 ± 0.33 mm) than in eyes with the widest gamma zone temporally (0.58 ± 0.30 mm) and in eyes with a temporal, superior, or nasal gamma zone combined (0.58 ± 0.31 mm; P = 0.001). The fovea vertical distance increased (multivariate analysis) with the widest gamma zone location inferiorly (β = 0.25; P = 0.001) and wider width of the gamma zone (β = 0.19; P = 0.01).ConclusionsAn inferior fovea location is associated with a wider inferior gamma zone and vice versa, supporting the notion of an inferior shifting of Bruch's membrane as the cause for an inferior gamma zone.

The Natural History of Bruch’s Membrane Calcification in Pseudoxanthoma Elasticum

PurposeTo describe the natural history of Bruch’s membrane (BM) calcification in patients with pseudoxanthoma elasticum (PXE).DesignRetrospective cohort study.ParticipantsBoth eyes of 120 PXE patients younger than 50 years, 78 of whom had follow-up imaging after more than 1 year.MethodsAll patients underwent multimodal imaging, including color fundus photography, near-infrared reflectance (NIR) imaging, and late phase indocyanine green angiography (ICGA). We determined the distance from the optic disc to the central and temporal border of peau d’orange on NIR, expressed in horizontal optic disc diameter (ODD). The length of the longest angioid streak was classified into 5 zones.Main Outcome MeasuresAge-specific changes of peau d’orange, angioid streaks, and ICGA hypofluorescence as surrogate markers for the extent of BM calcification.ResultsIn cross-sectional analysis, longer angioid streaks were associated with increasing age (P < 0.001 for trend). The temporal border of peau d’orange showed a weak association with increasing age (β = 0.02; 95% confidence interval [CI], 0.00–0.04), whereas the central border showed a strong association (β = 0.12; 95% CI, 0.09–0.15). Longitudinal analysis revealed a median shift of the central border to the periphery of 0.08 ODD per year (interquartile range [IQR], 0.00–0.17; P < 0.001). This shift was more pronounced in patients younger than 20 years (0.12 ODD per year [IQR, 0.08–0.28]) than in patients older than 40 years (0.07 ODD per year [IQR, –0.05 to 0.15]). The temporal border did not shift during follow-up (P = 0.69). New or growing angioid streaks were detected in 39 of 156 eyes (25%). The hypofluorescent area on ICGA was visible only in the fourth or fifth decade and correlated with longer angioid streaks.ConclusionsIn PXE patients, the speckled BM calcification slowly confluences during life. The location of the temporal border of peau d’orange remains rather constant, whereas the central border shifts to the periphery. This suggests the presence of a predetermined area for BM calcification. A larger ICGA hypofluorescent area correlates with older age and longer angioid streaks, which implies that it depends on the degree of BM calcification.

Constructing a meridian for a given motion of a particle on a surface rotating around a vertical axis

The article deals with the design of a surface of rotation, which is reduced to finding its meridian according to specified conditions. These conditions are the nature of the particle's motion on the inner surface when it rotates around a vertical axis. The absolute motion of a particle is formed from the ratio of the rotational motion of the surface and the relative motion (sliding) of the particle on the surface. Classical examples of such motion are the motion of a particle inside a vertical cone rotating with a constant angular velocity around its axis, as well as the special case when the angle of inclination of the cone's constituent parts is zero and it turns into a horizontal disk. The meridian curve can be given by an explicit equation or by parametric equations as a function of the independent variable. In this article, we consider the case when the meridian of a surface of rotation is given by parametric equations as a function of time. This makes it possible to compose a differential equation of motion of a particle in which all dependencies are functions of time. These dependencies need to be found from the compiled differential equation of motion of the particle. When a particle hits a surface, it starts to slide along it, describing a curved trajectory. Taking into account the rotational motion of the surface, the absolute trajectory is found. The first derivative of its length in time gives the absolute velocity, and the second gives the absolute acceleration, the expression of which includes the unknown functions describing the meridian. The differential equation of motion is written in projections on the three axes of the Cartesian coordinate system. The system of three equations includes four unknown functions: two equations describing the meridian, the dependence of the angular velocity of the particle sliding, and the surface reaction. To solve the equation, the number of unknown functions must be reduced to three. To do this, we define one dependence. This approach leads to special cases, one of which is the movement of a particle on a horizontal disk rotating around a vertical axis. A specific example is considered and a meridian curve is constructed as a result of numerical solution of the equations, provided that the particle inside the surface rises upward with a constant given speed.

Estimation of dimensional and qualitative parameters of disk spreader with electric drive

Purpose. Experimental methods to estimate the flight range of mineral fertilizer granules, to determine the shape of the fertilizer scattering torch, to compare the results of practical research with theoretical calculations of the flight range. Methods. Full-scale experimental studies of a mock-up sample of a fertilizer spreader. Results. To improve the quality of sieving, a multi-disc device for sifting mineral fertilizers over the field surface is proposed. It is proposed to make the device in the form of independent, functionally independent modules. Each module consists of three independent units: a fertilizer tank with an agitator; horizontal disc dispenser with calibration holes; a horizontal spreader plate. Each of the modules is equipped with its own electric drive, allowing them to be individually adjusted to a specific operating mode. As a result of studies of a prototype dispenser with active forced-batch dosing of bulk mineral fertilizers, its satisfactory performance was obtained. This makes it possible to regulate the dosage of fertilizers on the spreading disc within the specified limits, and the range of spreading the fertilizers through the individual setting of a certain number of rotational speed of the spreading disc. This arrangement does not limit their number and attachment points on the frame, and the working width of the unit will be regulated only by their number and the range of fertilizer spreading by each individual block. Conclusions. The flight range of mineral fertilizer granules depends on the frequency of rotation of the spreading disc, its height above the surface of the field, and the coefficient of windage of the fertilizers. With a change in the location of the spreading disc height from 0.2 to 1 m, at a spreading disc speed of 46.6; 33.3; 50 s-1, the spreading range for granular superphosphate (double) varies from 1.56 to 7.65 m, granular superphosphate from 1.54 to 7.24 m, granular ammonium nitrate from 1.46 to 6 m. The flight ranges of pellets obtained by practical and theoretical methods coincide within the limits of the requirements. The shape of the resulting spreading spot of fertilizer granules allows, in the case of installing several spreading modules in a line, to obtain fertilizer spreading in the form of an elongated ellipse. Keywords: mineral fertilizers, scatter torch, granules, spreading disc, rotation frequency, flight range.

Mathematical Modelling and Computer Simulation of the Flow in Thin Gap Channel due to Alternating Volumetric Mass Forces

The mathematical modelling and computer simulation are presented for the complex flow in thin gap channel due to alternating volumetrically distributed mass forces. The flow equations and obtained analytical solutions for limit cases are considered in the cylindrical coordinate system with the axis directed along the channel, which is rotating around its axis. The channel is placed inside the cylinder on the edge of the circular horizontal disk, which is rotating around vertical axis in its centre. The two rotations around different perpendicular axes create complex unknown features in a flow due to the alternating centrifugal and Coriolis forces, which substantially vary by the angle. The centrifugal force from the disk rotation is directed to its edge, while the centrifugal force due to rotation of the channel is acting by the channel’s radius. As a result, the two different centrifugal forces are directed counter currently in one side of the channel and vary by the angle up to adding of the two of them in the same direction in the opposite side of the channel. The conditions may fit to the strong cavitation regime inside the volume of fluid flow due to a stretching of the liquid in some locations.

Technological working process of the centrifugal pneumatic apparatus for spraying mineral fertilizers and their mixtures

The object of research is the process of centrifugal disk pneumomechanical apparatus for smooth application of mineral fertilizers and their mixtures on the field surface. When mineral fertilizers or their mixtures are sown in the field, the process of separation of grains into fractions is observed. This process takes place after they are thrown from the apparatus, that is, in space motion. This means that the quality control of mineral fertilizers is a factor independent of the technological process of the centrifugal disk apparatus. A pneumatic-mechanical hardware scheme was developed using the method of analysis of technological processes of centrifugal devices in existing and patent information materials and the combination of structural elements for high-quality spraying of fertilizer mixtures in them. The pneumomechanical apparatus consists of a horizontal disc with a diameter of 600 mm, 4 logarithmic coil-shaped blades on the disc, and 4 additional air-generating devices under each disc under the disc. The centrifugal pneumomechanical device has two functions at the same time, the first is to spray mineral fertilizers, and the second is to create an additional air flow and direct it behind the discarded fertilizer grains, which ensures even spraying of component fertilizers of different sizes, shapes and densities.

Numerical description of axisymmetric blue whirls over liquid-fuel pools

This numerical investigation is focused on determining the structures of blue whirls, recently found to occur in laboratory investigations of fire whirls when the circulation becomes sufficiently large to produce a vortex breakdown that drastically shortens the fire whirl and correspondingly reduces residence times, so that the yellow flames turn blue. The computations address axisymmetric configurations for round pools of liquid fuels flush with and at the center of a larger solid horizontal disc, at the outer edge of which vanes of adjustable angles cause the entrained air to enter with a controllable azimuthal component of velocity. The nondimensionlized conservation equations employed include realistic Lewis numbers with temperature-dependent transport coefficients and a one-step chemical-kinetic approximation that correctly reproduces laminar burning velocities. Buoyancy and radiant energy transport from the flames to the liquid surface are both taken into account, the latter being found to be essential for the blue whirl. Along with the vaporization-equilibrium and energy-conservation boundary conditions at the fuel surface, inflow boundary conditions are provided by a recently developed solution for the boundary-layer flow over the solid disc, while zero-gradient outflow conditions are applied above the whirl. Controlling nondimensional parameters, besides Reynolds, Damköhler, and Froude numbers, are a ratio of radiant to convective energy flux and a ratio of azimuthal to inward radial flow velocity in the boundary layer at the edge of the disc. The computed conditions for the onset of the blue whirl, as well as the computed structure of the whirl itself, bear close resemblance to what was found experimentally.

On Wave-Induced Elastic Deformations of a Submerged Wave Energy Device

Structural integrity has remained a challenge for design and analysis of wave energy devices. A difficulty in assessment of the structural integrity is often laid in the accurate determination of the wave-induced loads on the wave energy devices and the repones of the structure. Decoupled hydroelastic response of a submerged, oscillating wave energy device to extreme nonlinear wave loads is studied here. The submerged wave energy device consists of an oscillating horizontal disc attached to a direct-drive power take-off system. The structural frame of the wave energy device is fixed on the seafloor in shallow water. Several extreme wave conditions are considered in this study. The nonlinear wave loads on members of the submerged structure are obtained by use of the level I Green-Naghdi equations and Morison’s equation for cylindrical members. Distribution of Von Mises stresses and the elastic response of the structure to the extreme wave loads are determined by use of a finite element method. The decoupled hydroelastic analysis of the structure is carried out for devices built by four different materials, namely stainless steel, concrete, aluminium alloy, and titanium alloy. The elastic response of these devices is studied and results are compared with each other. Points of maximum stress and deformations are determined and the structural integrity under the extreme conditions is assessed. It is shown that the proposed approaches provide invaluable information about the structural integrity of wave energy devices.

Deformation and stress in hydrothermal regions: The case of a disk-shaped inclusion in a half-space

Hydrothermal regions are affected by a wide variety of phenomena, including ground inflation and deflation episodes. Among them, calderas offer the opportunity to study the complex interactions between magmatic processes at depth and permeable rocks saturated with fluids in the upper sedimentary layers. One of such regions is the Campi Flegrei caldera in southern Italy, where several source models have been applied over the years to reproduce the ground displacement and seismicity observed during the most recent phase of major unrest (1982–1984). The present work aims at introducing a new source model consisting of a thermo-poro-elastic inclusion embedded in a homogeneous poroelastic half-space. The inclusion is meant to represent a permeable rock layer stressed and strained by hot and pressurized volatiles released upward by an underlying magmatic reservoir and is modeled as a thin horizontal disk inside which a sudden change of temperature and pore pressure occurs. We provide semi-analytical solutions for the displacement and stress fields both within and outside the source and check them by comparison with those obtained through a fully numerical approach. Results provided by our model are compared with two other deformation source models often used to describe volcanic environments in terms of pressurized cavities describing a spherical magma chamber (Mogi source) or a sill-like magma intrusion (Fialko source). For the Campi Flegrei 1982–84 unrest, our model provides a better reproduction of ground deformation data and manages to explain the widespread presence of compressive focal mechanisms, since the stress field promoted both inside and outside the thermo-poro-elastic inclusion is very different from pressurized cavities.

Association between morphological characteristics of the optic disc and other anatomical features of the fundus in highly myopic eyes

To investigate associated factors with optic disc characteristics in high myopia patients. According to the meta-analysis of pathologic myopia study, patients were divided into groups from categories 1 (C1) to C4. The diameters, tilt ratio, and rotation degree of optic disc, and the diameters of parapapillary atrophy were measured among other morphometric variables. Totally 147 eyes (84 patients) were included. Longer horizontal optic disc diameter was associated with smaller tilt ratio (p < 0.001, unstandardized regression coefficient B: -0.59), greater rotation degree (p < 0.001, B: 0.01), and longer horizontal delta zone diameter (p < 0.001, B: 0.09). Longer vertical optic disc diameter was associated with smaller rotation degree (p < 0.001, B: 0.01), longer vertical delta zone diameter (p < 0.001, B: 0.16), and longer disc-fovea distance (DFD; p < 0.024, B: 0.14). Generally, the horizontal optic disc diameter of C3 and C4 groups was smaller than C1 and C2, while vertical diameter and tilt ratio was greater than in C1 and C2. After setting axial length (AL) as an independent variable, horizontal diameters and tilt ratio still showed significant differences, while vertical diameters did not show significant differences. Axial elongation was associated with an increase of vertical optic disc diameter that was correlated with an reduction of optic disc rotation degree. By contrast, horizontal optic disc diameter elongation was correlated with an reduction of optic disc tilt ratio and an increase of optic disc rotation degree, which was independent of axial elongation.

Accuracy of tree stem circumference estimation using close range photogrammetry: Does point-based stem disk thickness matter?

There is an increase in the use of photogrammetric point clouds for tree attribute mensuration. Stem diameter and circumference can be estimated from point clouds using stem disks of varying thicknesses along the bole. However, there is a dearth of information on the effect of the thickness of point cloud-based stem disks on the accuracy of diameter and circumference estimations. In this study, we outlined a GIS-based procedure for analysing Structure from Motion-derived photogrammetric point clouds with a view to providing an optimal disk thickness for accurate circumference estimates. Geo-referenced point clouds were created from photographs of 30 trees belonging to five savanna species. For each tree, 20 horizontal stem disks, with increasing thicknesses of 1 to 20 mm were made at breast height using the open source QGIS software. The resulting cross-sections were manually delineated and digitised. The difference between reference (manually measured) and point cloud-based circumferences at breast height was expressed as mean absolute percent error (MAPE) and compared across tree species, size and disk thickness. We found significant effects of species identity, tree size and disk thickness on MAPE. A stem disk of 7 mm in thickness provided consistently lower MAPE values (< 6%). This suggests that the accuracy of tree stem circumference estimations from photogrammetric point clouds depends on stem disk thickness.

Long term change of the optic disc and OCT parameters during myopic shift in children with large cup to disc ratio.

PurposeThis observational case series was to determine long term optic disc changes in eyes with large cup to disc ratio (CDR) and compare the changes induced by myopic shift during childhood with normal control eyes.MethodsChildren under 15 years of age who developed myopia with serial optic disc photographs and spectral domain (SD)-optical coherence tomography (OCT) images with a minimal interval of three years were evaluated. Children with average CDR ≥ 0.6 on SD-OCT were classified as having large CDR. The ratios of vertical disc diameter (VDD), horizontal disc diameter (HDD), and maximum peripapillary atrophy (PPA) width (PPW) were measured to quantify morphologic changes of optic discs and SD-OCT parameters, such as peripapillary retinal nerve fiber layer (RNFL) thickness and macular ganglion cell and inner plexiform layer (GCIPL) thickness were measured.ResultsOf the 82 eyes (82 patients) analyzed, 42 eyes had large CDR and 40 eyes were normal controls. The mean age and refractive error at initial examination were not different between groups (P = 0.33, P = 0.76, respectively). The changes in HDD/VDD and PPW/VDD ratios during follow-up showed no significant difference among the groups (P = 0.45, P = 0.62, respectively). No statistical significance was found in changes in RNFL and GCIPL thickness between the two groups (P = 0.74, P = 0.79, respectively).ConclusionsChildren with enlarged CDR showed changes in optic disc morphology and RNFL/GCIPL thickness similar to normal children during myopic shift.

COMPARATIVE PERFORMANCE OF SCREEN AND SHEET CATHODES IN DECOLORIZATION OF ACID RED 14 BY ELECTROCOAGULATION

This study investigated the efficiency of decolorization of Acid Red 14 dye solution using screen cathode and compare the results with sheet cathode by electrocoagulation. A simple electrochemical cell was performed with horizontal mild steel iron disc anode and vertical stainless steel cylindrical cathodes (screen or sheet). Process duration, agitation speed, current density, initial dye concentration and electrolyte NaCl concentrations were the variables studied. It was found that screen cathode was more effective than sheet cathode. . For dye solution with 50 ppm and agitation speed 100 rpm after 18 min, 86 % color removal was achieved on using screen cathode, while 77 % color removal was achieved on using sheet cathode. The higher efficiency of screen cathode is attributed to the fact that screen acts as turbulence promoter and generate high turbulence intensity.

Method of calculating the shear stiffness of the flooring under the action of horizontal loads

This article deals with the issue of calculating combined plywood-metal flooring as a horizontal disk of stiffness, taking into account the structural non-linearity. An analytically obtained method calculating the shear stiffness of the flooring under the action of horizontal loads is proposed.The task was to derive a three-line correlation - relationship for the fictitious connection operation, based on the constructively nonlinear operation of the flooring. Based on the proposed analytical method of calculating the shear stiffness of the flooring under the influence of horizontal loads, the work of the flooring is modeled as part of the design scheme shown in the figure. The resulting diagram of fictitious relationships was introduced as a characteristic of nonlinear work. In manual calculation in the derivation of the analytical formulas, the compound was considered as a pure hinge. We can conclude that the proposed analytical method of calculating the shear stiffness of the flooring when it is working on a horizontal load, taking into account the structural non-linearity.

A proposed unsteady bioconvection model for transient thin film flow of rate-type nanoparticles configured by rotating disk

The revolution in nanotechnology has made new developments toward enhancement of energy resources which play a substantial role in the growth of industries and technologies. The aim of this novel investigation is to develop a mathematical model for unsteady volatile finite flow of the upper film transmitted by rate-type nanofluid due to the horizontal spinning disk in the presence of gyrotactic motile microorganisms. The most preferable subclass of rate-type fluid, namely Maxwell fluid, is utilized to predict the exclusive rheological parameters. The additional unique features like activation energy, thermal radiation and Joule heating are also included for the current flow situation. The indicated partial differential system is transformed into nonlinear ordinary differential equations using appropriate self-similar transformation. The governing equations are translated to ordinary differential equations, and later on, shooting procedure is followed to construct the numerical arrangement of the transmuted dimensionless flow problem. The value of physical limitations is shown in the plots and table tests. In contrast, wider Brownian motion and thermophoresis parameters have different intensity field features. The graphical and numerical results are drawn against different prominent parameters over velocity profile, temperature distribution, volumetric fraction, nanoparticle, density of motile microorganisms. The results revealed that the increase in buoyancy ratio parameter and Rayleigh number reduced the axial velocity, radial velocity and azimuthal distribution. A progressive temperature distribution is noted with increasing Rayleigh number and buoyancy ratio constant. It is further observed that change in unsteady parameter enhanced the concentration and motile microorganism distribution effectively.

Development of a Variable-Rate Controller for a Low-Cost Precision Planter

HighlightsA low-cost controller for variable-rate seeding was developed.The controller successfully identified management zones and changed the angular velocity of the seed metering device.The variable-rate controller maintained the actual seeding rate according to the prescribed seeding map.Abstract. The use of machines for variable-rate applications is becoming popular in modern agriculture. Due to the presence of imported and complex components, the acquisition cost of these machines is high for smallholder farmers. Several studies have been carried out using low-cost components in the development of precision agriculture machines to facilitate their adoption in low-income agriculture. Thus, the objective of this work was to develop a variable-rate controller for a low-cost precision planter. The system was developed and installed on a 1-row manual planter with a horizontal perforated disk distributor. A direct-current electric motor was used to drive the seed metering device. The angular velocity of the electric motor was controlled by a BeagleBone Black single-board computer. A program was written in Python 3.6 language, and a graphical user interface was generated by using PyQt5. Field trials were performed with maize seeds using a 28-hole disk and a prescription seeding map with four management zones. The row spacing was 0.75 m, and the planter ground speed was close to 1.0 m s-1. Field tests showed that the controller was effective at identifying the four management zones and controlling the angular velocity of the motor. By counting the number of plants germinated in the field test, it was verified that the variation in the angular velocity of the motor produced a change in the planting density. At each management zone, the planting density corresponded to the prescribed seeding map. The total cost of the parts used to assemble the controller was US$337.97, characterizing it as low cost. Successful field tests showed the potential for using low-cost components to develop variable-rate machines for smallholder farmers. Keywords: Low-income agriculture, Management zones, Precision agriculture, Single-board computer, Smallholder farmers.