We present experimental results of the effect of the hopper angle on the clogging of grains discharged from a two-dimensional silo under gravity action. We observe that the probability of clogging can be reduced by three orders of magnitude by increasing the hopper angle. In addition, we find that for very large hopper angles, the avalanche size (〈s〉) grows with the outlet size (D) stepwise, in contrast to the case of a flat-bottom silo for which 〈s〉 grows smoothly with D. This surprising effect is originated from the static equilibrium requirement imposed by the hopper geometry to the arch that arrests the flow. The hopper angle sets the bounds of the possible angles of the vectors connecting consecutive beads in the arch. As a consequence, only a small and specific portion of the arches that jam a flat-bottom silo can survive in hoppers.
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http://dx.doi.org/10.1103/PhysRevE.99.032901 | DOI Listing |
Insects
November 2024
State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Seventeen species of the -group of (Hymenoptera: Aphelinidae) are reviewed worldwide, including three new species, and five previously described species in China. The -group was defined by a combination of characters: head and body dark with parts of metasoma pale; fore wing with a complete row of setae inside the linea calva, or also only with a few setae in the angle between the linea and marginal vein; legs with mesocoxae, metacoxae and metatibia dark, metafemur pale. In this paper, three new species, Wang & Huang, , Wang & Huang, and Wang & Huang, , are described and illustrated, with notes on one species, Hopper & Woolley, new to China.
View Article and Find Full Text PDFTeff, which is surged in other continent and a cornerstone Ethiopian grain used as injera, suffers from low yield due to outdated sowing practices and minimal use of modern fertilizers. The traditional method is inefficient, squandering seeds and fertilizer, and relying on a large number of animals for trampling. Researchers addressed this challenge by creating a new machine that combines a seedbed compactor with a tool that sows both teff seeds and fertilizer.
View Article and Find Full Text PDFPlast Reconstr Surg
June 2024
From the Craniofacial Center, Divisions of Plastic and Craniofacial Surgery and Oral and Maxillofacial Surgery, Seattle Children's Hospital.
J Morphol
May 2024
Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, UK.
Using finite element analysis on the astragali of five macropodine kangaroos (extant and extinct hoppers) and three sthenurine kangaroos (extinct proposed bipedal striders) we investigate how the stresses experienced by the ankle in similarly sized kangaroos of different hypothesized/known locomotor strategy compare under different simulation scenarios, intended to represent the moment of midstance at different gaits. These tests showed a clear difference between the performance of sthenurines and macropodines with the former group experiencing lower stress in simulated bipedal strides in all species compared with hopping simulations, supporting the hypothesis that sthenurines may have utilized this gait. The Pleistocene macropodine Protemnodon also performed differently from all other species studied, showing high stresses in all simulations except for bounding.
View Article and Find Full Text PDFMaterials (Basel)
April 2024
Department of Organization of Transport, Traffic and Transport Operations, L. N. Gumilyov Eurasian National University, Satbaev 2, Astana 010000, Kazakhstan.
Centrifugal disk dispensers are widely used in various tasks of dosing bulk, dispersed materials. The design of the disk depends on the physical and mechanical characteristics of the dosing medium. The work discusses the development of an analytical model of the movement of a material particle along a conical centrifugal disk depending on the kinematic characteristics of the dosing process and the characteristics of the dosing material, as well as experimental confirmation of the theoretical model, which is relevant for the calculation and design of working elements of this type.
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