Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental...Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental equation of earth moving mechanics for calculating the soil passive reaction acting on a rotating fiat disc blade as used on a zero-till single disc seeder. The study considers the effects of disc variable depth of cut, sweep and tilt angles, free rotation and a scrubbing reaction at the beveled edge. This paper outlines the modeling approach and prediction results for a fixed circular blade operating at 90° sweep angle over a range of speeds and at two tilt angles. To account for the varying depth across the circular disc shape width, elemental wide blade force reactions acting on wide blade segments of elemental width were integrated across the disc working width. By including inertia forces due to speed as well as additional bulldozing forces due to the loose soil accumulation in front of the blade the draught and upward vertical forces acting on the vertical disc blade were predicted with a deviation of 6%-19% and 1.5%-14% from measured data, respectively. The model was able to predict the effect of increasing the tilt angle from 0° to 20° on reducing both draught and upward vertical forces. Further development and validation of the model will be described in subsequent papers, reflecting a step by step approach of increasing complexity to model a disc blade as used on a zero-till single disc seeding system.展开更多
In order to evaluate the effect of subsoiling on the soil physical properties and wheat yield in dry land conditions, this research was conducted in Mamassani area of Fars province in Iran. The experiment was laid dow...In order to evaluate the effect of subsoiling on the soil physical properties and wheat yield in dry land conditions, this research was conducted in Mamassani area of Fars province in Iran. The experiment was laid down in the form of a complete block experimental design with four treatments and four replications for three years. Treatments included： （1） conventional tillage without using subsoiler which was control treatment （So）; （2） using subsoiler with the shank space of 40 cm which was equal to the subsoiling depth （SO; （3） using subsoiler with the shank space of 60 cm which was 1.5 times of the subsoiling depth （S2）; and （4） using subsoiler with the shank space of 80 cm which was 2 times of the subsoiling depth （S3）. Subsoiling depth was set at 40 cm which was the lower limit of the hard pan depth in the soil. Soil cone index, soil bulk density, soil moisture content, wheat yield, and yield components were measured in this study and SAS software was used to analyze the collected data. Results showed that subsoiling decreased the soil bulk density and cone index, and increased water retention of the soil. Results also revealed that applying subsoiler increased wheat yield and yield components in our dry land conditions. Since subsoiling improved soil physical conditions and increases wheat yield, applying subsoiler in such a dry land conditions is therefore recommended. Results of this study also showed that subsoiling with the shank space of 40 cm and 60 cm had better performance compared to the shank space of 80 cm. On the other hand, shank space of 40 cm reduced the subsoiler effective working width and consequently effective field capacity. Therefore, subsoiler with a shank space of 60 cm is recommended for application in dry land soils of our type.展开更多
This study proposes a new auxetic-shaped steel plate shear walls(simply referred to as ASSPSWs)consisting of boundary members and built-in perforated infill plates.The connection type between the boundary members is a...This study proposes a new auxetic-shaped steel plate shear walls(simply referred to as ASSPSWs)consisting of boundary members and built-in perforated infill plates.The connection type between the boundary members is a hinge joint.The hole forms on the infill plates include orthogonal ellipse-shaped(ASSPSW-OE)and orthogonal peanutshaped(ASSPSW-OP).This paper studied the hysteretic performance of two steel plate shear walls’types based on the finite element analysis method.Within the study context,a parametric analysis was carried out to investigate the influence of various factors,such as hole size and hole distance,on the seismic performance of steel plate shear walls(SPSWs).The results indicated that reducing the the ratio of the ligament thickness to ellipse major axis(t/D)in orthogonal ellipse-shaped SPSWs can effectively increase the porosity while reducing the bearing and energy dissipation capacities.Under the condition with the t/D unchanged,increasing the ratio of the major to minor axis of the ellipse(d/D)raises the porosity and does not significantly reduce the bearing capacity and energy dissipation capacity of the SPSWs.For orthogonal peanut-shaped SPSWs,the holes’geometrical parameters significantly influence the hysteretic performance.Particularly,with the increase in the radial ratio of large to small circles in a peanut-shaped hole(R/r),the spacing between cells decreases.When drift exceeds 2%,the equivalent viscous damping ratio decreases sharply.Unlike the orthogonal ellipse-shaped SPSWs,changing the arrangement angle of peanut-shaped cells has no significant effect on orthogonal peanut-shaped SPSWs.However,the larger the angle,the greater the out-of-plane buckling of orthogonal ellipse-shaped SPSWs;thus,the energy dissipation capacity is reduced.The similarities lie in that the larger cell arrangement angle will make the steel plates have a complete stress field,and the bearing capacity will be slightly improved.When the cell arrangement angle(θ)is 45°,the SPSWs can develop high initial stiffness.展开更多
Structural relaxation and glass transition in binary hard-spherical particle mixtures have been reported to exhibit unusual features depending on the size disparity and composition. However, the mechanism by which the...Structural relaxation and glass transition in binary hard-spherical particle mixtures have been reported to exhibit unusual features depending on the size disparity and composition. However, the mechanism by which the mixing effects lead to these features and whether these features are universal for particles with anisotropic geometries remains unclear. Here, we employ event-driven molecular dynamics simulation to investigate the dynamical and structural properties of binary two-dimensional hard-ellipse mixtures. We find that the relaxation dynamics for translational degrees of freedom exhibit equivalent trends as those observed in binary hard-spherical mixtures. However, the glass transition densities for translational and rotational degrees of freedom present different dependencies on size disparity and composition. Furthermore,we propose a mechanism based on structural properties that explain the observed mixing effects and decoupling behavior between translational and rotational motions in binary hard-ellipse systems.展开更多
文摘Previous soil-disc force prediction models have considered spherical and concave blades, as used on disc ploughs and harrows, with many simplifying assumptions. This study proposes an approach applying the fundamental equation of earth moving mechanics for calculating the soil passive reaction acting on a rotating fiat disc blade as used on a zero-till single disc seeder. The study considers the effects of disc variable depth of cut, sweep and tilt angles, free rotation and a scrubbing reaction at the beveled edge. This paper outlines the modeling approach and prediction results for a fixed circular blade operating at 90° sweep angle over a range of speeds and at two tilt angles. To account for the varying depth across the circular disc shape width, elemental wide blade force reactions acting on wide blade segments of elemental width were integrated across the disc working width. By including inertia forces due to speed as well as additional bulldozing forces due to the loose soil accumulation in front of the blade the draught and upward vertical forces acting on the vertical disc blade were predicted with a deviation of 6%-19% and 1.5%-14% from measured data, respectively. The model was able to predict the effect of increasing the tilt angle from 0° to 20° on reducing both draught and upward vertical forces. Further development and validation of the model will be described in subsequent papers, reflecting a step by step approach of increasing complexity to model a disc blade as used on a zero-till single disc seeding system.
文摘In order to evaluate the effect of subsoiling on the soil physical properties and wheat yield in dry land conditions, this research was conducted in Mamassani area of Fars province in Iran. The experiment was laid down in the form of a complete block experimental design with four treatments and four replications for three years. Treatments included： （1） conventional tillage without using subsoiler which was control treatment （So）; （2） using subsoiler with the shank space of 40 cm which was equal to the subsoiling depth （SO; （3） using subsoiler with the shank space of 60 cm which was 1.5 times of the subsoiling depth （S2）; and （4） using subsoiler with the shank space of 80 cm which was 2 times of the subsoiling depth （S3）. Subsoiling depth was set at 40 cm which was the lower limit of the hard pan depth in the soil. Soil cone index, soil bulk density, soil moisture content, wheat yield, and yield components were measured in this study and SAS software was used to analyze the collected data. Results showed that subsoiling decreased the soil bulk density and cone index, and increased water retention of the soil. Results also revealed that applying subsoiler increased wheat yield and yield components in our dry land conditions. Since subsoiling improved soil physical conditions and increases wheat yield, applying subsoiler in such a dry land conditions is therefore recommended. Results of this study also showed that subsoiling with the shank space of 40 cm and 60 cm had better performance compared to the shank space of 80 cm. On the other hand, shank space of 40 cm reduced the subsoiler effective working width and consequently effective field capacity. Therefore, subsoiler with a shank space of 60 cm is recommended for application in dry land soils of our type.
基金support of the National Natural Science Foundation of China(Grant Nos.51878315,51908416).Any opinions,findings,and conclusions or recommendations provided in this paper are those of the authors and do not necessarily reflect the views of the sponsors.
文摘This study proposes a new auxetic-shaped steel plate shear walls(simply referred to as ASSPSWs)consisting of boundary members and built-in perforated infill plates.The connection type between the boundary members is a hinge joint.The hole forms on the infill plates include orthogonal ellipse-shaped(ASSPSW-OE)and orthogonal peanutshaped(ASSPSW-OP).This paper studied the hysteretic performance of two steel plate shear walls’types based on the finite element analysis method.Within the study context,a parametric analysis was carried out to investigate the influence of various factors,such as hole size and hole distance,on the seismic performance of steel plate shear walls(SPSWs).The results indicated that reducing the the ratio of the ligament thickness to ellipse major axis(t/D)in orthogonal ellipse-shaped SPSWs can effectively increase the porosity while reducing the bearing and energy dissipation capacities.Under the condition with the t/D unchanged,increasing the ratio of the major to minor axis of the ellipse(d/D)raises the porosity and does not significantly reduce the bearing capacity and energy dissipation capacity of the SPSWs.For orthogonal peanut-shaped SPSWs,the holes’geometrical parameters significantly influence the hysteretic performance.Particularly,with the increase in the radial ratio of large to small circles in a peanut-shaped hole(R/r),the spacing between cells decreases.When drift exceeds 2%,the equivalent viscous damping ratio decreases sharply.Unlike the orthogonal ellipse-shaped SPSWs,changing the arrangement angle of peanut-shaped cells has no significant effect on orthogonal peanut-shaped SPSWs.However,the larger the angle,the greater the out-of-plane buckling of orthogonal ellipse-shaped SPSWs;thus,the energy dissipation capacity is reduced.The similarities lie in that the larger cell arrangement angle will make the steel plates have a complete stress field,and the bearing capacity will be slightly improved.When the cell arrangement angle(θ)is 45°,the SPSWs can develop high initial stiffness.
基金supported by the National Natural Science Foundation of China(21474109,21674055)the International Partnership Program of Chinese Academy of Sciences(121522KYSB20160015)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2016204)
文摘Structural relaxation and glass transition in binary hard-spherical particle mixtures have been reported to exhibit unusual features depending on the size disparity and composition. However, the mechanism by which the mixing effects lead to these features and whether these features are universal for particles with anisotropic geometries remains unclear. Here, we employ event-driven molecular dynamics simulation to investigate the dynamical and structural properties of binary two-dimensional hard-ellipse mixtures. We find that the relaxation dynamics for translational degrees of freedom exhibit equivalent trends as those observed in binary hard-spherical mixtures. However, the glass transition densities for translational and rotational degrees of freedom present different dependencies on size disparity and composition. Furthermore,we propose a mechanism based on structural properties that explain the observed mixing effects and decoupling behavior between translational and rotational motions in binary hard-ellipse systems.
