Speed Of Grains Research Articles

Flow rate in 2D silo discharge of binary granular mixtures: the role of ordering in monosized systems

A long-standing debate regarding the dynamics of silo discharge revolves around the use of mono-dispersed circular or spherical grains in simplified two-dimensional models. It is well-known that granular systems composed of particles of the same size can generate crystal or quasi-crystal domains with specific structural and dynamic behaviors. Can this ordering affect the flow rate to an extent that monosized systems cannot be good models for realistic materials? In this work, we present simulations of the discharge of two-dimensional silos filled with binary mixtures of circular grains that conserve the same mean particle size. We address the question of how ordering affects the mass flow rate, in particular considering the limit of mono-sized systems. We find that the typical hexagonal order observed does not affect the flow rate significantly. However, the flow rate does exhibit a weak, nonmonotonic dependence on packing bidispersity that correlates with changes in the outpouring speed of grains in the vicinity of the orifice.

谷子、荞麦籽粒离心式碰撞试验装置设计及试验

This critical collision damage force of millet and sweet buckwheat grain and the shelling force of shelled granular materials are important basic data for research of threshing and shelling technology and equipment. In order to master the linear velocity and collision force of grain with different moisture content when collision damage occurs, a centrifugal collision test device is designed. Based on the dynamic and kinematic analysis of grain in the centrifugal rotary table, the collision force between grain and steel plate was measured by PVDF piezoelectric pressure sensor and data acquisition system. The results showed that: under the same moisture content, the higher the rotational speed, the higher the grain crushing rate; at the same rotational speed, with the increase of moisture content, the crushing rate first decreased and then increased. When the moisture content of Jingu-21 and Yuqiao-4 is 19.7% and 17.8%, respectively, the grain crushing rate was the lowest. In terms of the anti-collision ability of grain, the optimum moisture content of threshing is between 19.7% and 21% for millet. For sweet buckwheat, the optimum moisture content of threshing is 17.8% ~19%, while the optimum moisture content of shelling by centrifugal sheller is about 11%. The faster the rotational speed of centrifugal rotary table is, the greater the linear speed of grain is, and the greater the collision force is. When the linear velocity of grain was 8.32 m/s and 11.30 m/s respectively, the millet grain moisture content was 11.1% and 20.9% respectively, damage began to appear, and the corresponding collision force was about 5.51 N and 10.6 N, respectively. When the linear velocity of grain was 8.32 m/s and 11.30m/s respectively, and the moisture content was 11.1% and 22.8% of the sweet buckwheat grain respectively, damage began to appear, the corresponding collision force was about 8.92 N and 12.79 N, respectively. When the rotating speed of rotary table was 910 r/min, the linear speed of grain was 27.05 m/s, the crushing rate of millet and sweet buckwheat grain in harvest period were 56.30% and 63.76%, respectively, and the crushing rate of millet and buckwheat grain with 11.1% moisture content were 86.27% and 89.4%, respectively. The research results can provide theoretical basis for design and optimization of millet and sweet buckwheat combine harvester, threshing device and shelling device.

Factors Determining Genotypic Variation in the Speed of Rice Germination

Rapid germination is important for both direct seeded rice in the field and for the production of germinated brown rice for healthy food. This study aims to evaluate genotypic differences in germination speed and identify characteristics that determine germination speed. Seven experiments were conducted to determine (i) the impact of dehulling on water absorption and germination, (ii) variety consistency in germination speed across crops grown in three years, and (iii) the effect of grain size. Germination speed in both paddy rice and dehulled brown rice was significantly correlated with grain moisture content at early stages of soaking, however significant interaction of genotype and grain type (paddy and brown rice) existed and varieties differed in their response to dehulling. Germination speed of grain from crops exposed to water deficit in the field was slightly slower than those with higher water supply. Sherpa/IRAT109 genotypes with smaller grain size tended to germinate faster than larger grain, however no significant effect of grain size existed among diversity set varieties. It was concluded that genotype ranking in germination speed was consistent across years and water availability conditions, and that barriers to water absorption in hull and pericarp were important determinants of germination speed. The existence of genotypic variation in germination speed has management implications for both field crop establishment and paddy germination in food processing.

Finite Element Study on Micro Cutting Process of Guide Abrasive Wear

Two-dimensional finite element model is established by ABAQUS Explicit finite element analysis in this paper. It includes abrasive wear micro cutting process between pair of guide. Johnson-cook constitutive model is used to simulate the guide material deformation of wear process. Based on different sizes and different speed of grain, loading, cutting and unloading process are simulated by finite element, guide surface stress distribution and deformation condition are studied in the guide rail pair wear process. The simulation data is obtained by central composite experiments and regression model is gotten by MATLAB. The influence law of the particle radius and speed to guide residual compressive stress and deformation are gotten by the prediction model.

Predicting the relationship between grain-combine travel, cylinder speed and harvesting losses by applying artificial neural networks

Seed corn is one of the most sensitive crops during harvesting operation. Due to its high economic value and in order to decrease the amount of losses, harvesting operation of this crop should be done precisely. There are several factors which can affect grain combine harvesting losses. In order to find and predict the relationship between cylinder and travel speed of grain combine and seed corn harvesting losses, various Artificial Neural Networks (ANNs) were developed. For this purpose, data were collected from seed corn farms during harvesting operation in different levels of grain combine cylinder and travel speed. The developed ANN was a multilayer perceptron (MLP) with two neurons in the input layer, one and two hidden layers of various numbers of neurons and one neuron in the output layer. Results showed that the ANN model with 2-7-10-1 topology can predict the harvesting losses value well. For the optimal model, the coefficient of determination (R2), the mean absolute error (MAE) and the root mean square error (RMSE) was calculated as 0.93, 15.48 and 17.00, respectively. Finally, sensitivity analysis revealed that cylinder speed is the most significant parameter in seed corn harvesting losses.

Model Predictive Control of the Grain Drying Process

Drying plays an important role in the postharvesting process of grain. To ensure the quality of the dried grain and improve the intelligent level in drying process, a digital simulation of corn drying machine system based on a virtual instrument was established for 5HSZ dryer, automatically control the air temperature, and predict the discharging speed of grain and so forth. Finally, an online measurement and automated control software of grain parameters were developed to provide the changes of moisture, temperature, humidity, and germination rate in the process of drying. The study carried out in the actual processing showed that it can meet the requirements of the actual drying operation, effectively control the stability of the grain moisture, and keep the dry food quality.

Galileo long-term dust monitoring in the jovian magnetosphere

The Galileo spacecraft was launched in 1989, and—between 1995 and 2003—was the first spacecraft in orbit about Jupiter. The in-situ dust instrument on board was a highly sensitive impact-ionisation dust detector which measured the speed, mass and impact direction of dust particles hitting a metal target. It provided a unique 12-year record of cosmic dust in interplanetary and circumjovian space. Degradation of the instrument electronics caused by the harsh radiation environment in the inner jovian magnetosphere was recognised in various ways: the sensitivity for dust detection dropped by a factor of 7.5 between 1996 and 2003 while the noise sensitivity decreased by up to a factor of 100. Shifts in the parameters measured during dust impacts and noise events (charge amplitudes and signal rise times, etc.) required a time-dependent algorithm for noise identification. After noise removal a total of 21 224 complete data sets for dust impacts (i.e. impact charges, signal rise times, impact direction, etc.) is available from the entire Galileo mission between 1989 and 2003 (18 340 data sets from the Jupiter mission after 1996). This homogeneous data set has been used in many investigations of jovian dust published already or ongoing. Electronics degradation prevents the application of the mass and speed calibration to data obtained after 2000. Only in cases where the impact speed of grains is known by other means can grain masses be derived for later measurements. The drop of the detection sensitivity also required a time-dependent correction for fluxes of jovian dust streams, reaching a factor of 20 in 2002. We use the derived homogeneous noise-removed data set for long-term monitoring of the jovian dust streams with Galileo. The derived fluxes of dust stream particles were highly variable by about five orders of magnitude, between 3 × 10 - 3 and 6 × 10 2 m - 2 s - 1 and exhibited strong orbit-to-orbit variability. This extensive and valuable data set is available for further detailed investigations.

Dust on the Outskirts of the Jovian System

The outer region of the jovian system between ∼50 and 300 jovian radii from the planet is found to be the host of a previously unknown dust population. We used the data from the dust detector aboard the Galileo spacecraft collected from December 1995 to April 2001 during Galileo's numerous traverses of the outer jovian system. Analyzing the ion amplitudes, calibrated masses and speeds of grains, and impact directions, we found about 100 individual events fully compatible with impacts of grains moving around Jupiter in bound orbits. These grains have moderate eccentricities and a wide range of inclinations—from prograde to retrograde ones. The radial number density profile of the micrometer-sized dust is nearly flat between about 50 and 300 jovian radii. The absolute number density level (∼10 km−3 with a factor of 2 or 3 uncertainty) surpasses by an order of magnitude that of the interplanetary background. We identify the sources of the bound grains with outer irregular satellites of Jupiter. Six outer tiny moons are orbiting the planet in prograde and fourteen in retrograde orbits. These moons are subject to continuous bombardment by interplanetary micrometeoroids. Hypervelocity impacts create ejecta, nearly all of which get injected into circumjovian space. Our analytic and numerical study of the ejecta dynamics shows that micrometer-sized particles from both satellite families, although strongly perturbed by solar tidal gravity and radiation pressure, would stay in bound orbits for hundreds of thousands of years as do a fraction of smaller grains, several tenths of a micrometer in radius, ejected from the prograde moons. Different-sized ejecta remain confined to spheroidal clouds embracing the orbits of the parent moons, with appreciable asymmetries created by the radiation pressure and solar gravity perturbations. Spatial location of the impacts, mass distribution, speeds, orbital inclinations, and number density of dust derived from the data are all consistent with the dynamical model.

Simulation of Eolian Saltation

Saltation is important in the transport of sand-sized granular material by wind and in the ejection of dust from the bed both on Earth and on Mars. The evolution of the saltating population and all its characteristic profiles is calculated from inception by pure aerodynamic entrainment through to steady state. Results of numerical simulations of single-grain impacts into granular beds are condensed into analytic expressions for the number and speeds of grains rebounding or rejected (splashed) from the bed. A model is combined with (i) this numerical representation, (ii) an expression for the aerodynamic entrainment rate, and (iii) the modification of the wind velocity profile by saltating grains. Calculated steady state mass fluxes are within the range of mass fluxes measured in wind tunnel experiments; mass flux is nonlinearly dependent on the shear velocity. Aerodynamically entrained grains in the system are primarily seeding agents; at steady state, aerodynamic entrainment is rare. The time for the entire system to reach steady state is roughly 1 second, or several long-trajectory hop times.

Saltation and suspension trajectories of solid grains in a water stream

This paper continues the investigation of the motion of solitary grains in a water stream, reported by Francis (1973)- The trajectories of solid grains are photographed by a multi-exposure technique as they are propelled by water streams along the bed of a laboratory channel. Many thousands of photographs were taken and analysed to determine the positions, velocities and accelerations of the grain. The technique does not take into account the possible effect, in multi-grain transport, of intergranular collisions. The three different modes of transport of grains were all observed — rolling, saltation and suspension, and the proportion of each found for a variety of transport stage w*/w*0. The development of suspension is much less rapid than the development of saltation from rolling, but even at the highest stage used, about 3.0, there is still a small amount of rolling. The trajectory dimensions and geometry are shown in relation to the stage which uniquely determines the geometry. Experiments where the grain is suddenly entrained from a stationary position show that several features of the subsequent trajectory are the same as those of a trajectory with a prior history of movement: thus it is inferred that the start of a trajectory is by way of hydrodynamic forces rather than by the conservation of momentum of previous trajectories. Impacts and trajectories were analysed for the coefficient of friction tan cc and for the height of the effective thrust. While tan a is shown to be rather larger than has been suspected in the past, the variation of yn throws light upon predominance of slow fluid near the bed rather than high speed inrushes of fast fluid. Better information is now available for finding the mean forward speed of grains compared to that presented in the earlier paper. There are grounds for believing the existence of a * shear-drift ’ force on grains when they are in a velocity gradient, giving a force opposing gravity: but there is no evidence of a proximity effect of the bed independent of the velocity gradient.

Photographic Effects of Electron and Positive Hole Traps in Silver Halide Emulsion Grains

AbstractExaminations were made on the photographic effects of various electron and positive hole traps including sensitivity specks of chemical sensitizations, metal ions, and various dyes, showing that the photographic elfecls were markedly dependent upon the natures of the traps and emulsion grains used. It was indicated that photographic speed of grains was increased by traps only under the specific condition that the traps could be helpful for the increase of the efficiency of latent image formation at the surface of the grains.

Dependence of Sensitizing and Desensitizing Effects of Dyes upon Sizes of Silver Bromide Grains

The photographic effects of phenosafranine (1) which acts as an electron trap and of 9methyl-thiacarbocyanine (2) which acts as a positive hole trap were examined by use of three kinds of silver bromide grains with different sizes. The blue speed of all grains studied were decreased by (1). While (2) decreased the blue speed of the coarse grain (O.5m), but it increased that of the fine grain (O.17m). lt is considered that the recombination is faster at the surface of the fine grain than at the surface of the coarse grain, as suggested in an earlier paper. The obtained result can be thus understood by the view that (2) causes the recombination process at the surface of the cearse grain, and prevents the rapid reeombination at the surface of the fine grain, acting as a positive hole trap which can be a weak recombination center. These results also suggest that there are two kinds of desensitization caused by dyes.

Photographic Effects of Hexachlororhodate (III)

The mechanism of photographic effects of hexachlororhodate (III)[1] at AgBr and AgBrl grain surfaces was studied. Compound [1] markedly decreased both surface and internal speeds of AgBr grains. By bathing coated emulsions in the aqueous solution of [1] before and after exposure to light, it was confirmed that the above desensitizing phenomenon resulted mainly from the depression of latent image formation by [1]. The desensitization by [1] was competitive with that by phenosafranine, which is known to act as a trap for photo-electrons in silver halides. Although [1] decreased photographic speeds of the grains in which the ratio of internal speed to surface one was small (primitive AgBr), [1] increased those of the grains in which the ratio was large (primitive AgBrl). The effect of [1] upon the electronic process in AgBr grains was confirmed by observing that the emission of the grains at about 600 nm at liquid nitrogen temperature was markedly quenched by [1]. The above-mentioned results support the consideration that (1) acts as a trap for photo-electrons causing photographic sensitizing and desensitizing phenomena at the surface of AgBr and AgBrI grains.

Protein, lysine and feed intake level effects on pig growth. III. Regression analysis and economic aspects

SUMMARYData from the experiment described in the first paper of this series were subjected to regression analysis. Lean meat and live-weight gain response to both lysine and crude protein intake was almost linear in period 1 but in later periods little response was evident. Response of live-weight gain to increased energy was continuous though diminishing in the later periods. In periods 1 and 2 lean gains showed positive though diminishing response to energy.In a multivariate regression analysis it was clear especially for younger pigs that the response to dietary lysine for both live-weight and lean meat gains is influenced by the dietary level of crude protein and the energy intake. Separate multivariate analysis for each sex indicated that females are more efficient converters of lysine and energy into live weight and lean meat. Also an interaction between sex and dietary lysine level was suggested.A methodology for an economic analysis taking the joint objectives of total cost of production, speed of grain and quality of gain is established as a basis for design of high profit system of production.

キルン内の原料移動および温度分布

In the previous paper we described the installation of a multi-purpose 46 m long kiln with 6 sampling holes and the method of taking samples from a reducing kiln while it is in operation, then showed some results of measuring works.In this paper we discuss the travel of material and distribution of its temperature. Many literatures are found which investigate the transportation of raw materials, through a rotary kiln in the field of cement industry. From the viewpoint of roasting reaction, the material is composed of a single element for a cement kiln; however, it is always a mixture of 2 elements 'which consist of reducing agent and substrate for a reducing kiln. Then if segregation occurs between 2 elements, it means an interruption of reducing reaction in the kiln.So the segregation of material is one of the most important facts in the reducing kiln.After various experiments, researches and observations, we reach the following conclusions;(1) Segregation occurs because of different repose angles of material grain.(2) Travelling speed of grain through the rotary kiln is decided by the filling ratio of charge and its local position in the bed.(3) The grain of iron sand is so fine, and the reducing agent is not so fine, and as the result, the reducing agent has tendency to segregate outside of bed. We call it belt type segregation.(4) Belt type segregation grows into rippling distribution across the axis of kiln, we call it striped segregation.It is necessary for reductive roasting with kiln to control the grain size of charge material. In the future reports we shall analyse the segregation quantitatively again.Generally, a reductive kiln has three zones by the name of drying, heating and reducing zone. Measured distribution of material temperature is almost linear throughout its length, and the rate of heat transfer in the last zone by means of improvement on heat transmission and prevention of segregation in charge material.