Understanding intermittency, a ubiquitous behavior in flows of packed grains, is pivotal for establishing the rheology of granular matter. A straightforward explanation has been missing despite the long development of theories at various levels of abstraction. Here, we propose the use of a Stribeck-Hertz model that starts with the classic Coulomb friction but takes into account the interparticle tribology, i.e., the reduction of friction coefficient with sliding speed as is commonly observed. Our numerical experiments reveal a state diagram that covers a wide range of packing fractions and show that incorporating the tribology enables the occurrence of quaking intermittency in the midrange of a dimensionless shear rate, consistent with prior experimental observations. Further study of the discontinuities in the evolution of the mean contact number leads to our discovery of two types of quaking that are distinguished by the abrupt increase or decrease of neighboring contacts and reveal different pathways of microstructural change underlying these discrete events. In contrast to the prevailing paradigm in which shear is believed to promote jamming at intermediate densities, our study demonstrates that shear can also unjam a granular system, and this occurrence depends on the shear rate.

Background/Objectives: Top badminton players must carefully schedule tournaments to perform well and improve their rankings. This study examines how players plan their tournament participation and whether their scheduling strategies affect their rankings and performance, especially during Olympic and non-Olympic years. Methods: Data were extracted from the Badminton World Federation (BWF) ranking system for the top 50 men’s and women’s singles players from May 2014 to May 2019. A computer-based simulation model and cluster analysis were applied to analyze tournament participation patterns, recovery intervals, and performance trends. Statistical analyses were conducted to identify correlations between these variables and ranking outcomes. Results: Top-ranked players participated in more tournaments during Olympic years, with those competing in more than nine tournaments achieving better results. Players performing well in higher-graded tournaments tended to take longer recovery breaks, whereas lower-performing players entered more tournaments. Cluster analysis revealed two distinct performance groups, with the top 20 men’s and top 12 women’s singles players adopting different strategies compared to lower-ranked counterparts. Conclusions: Strategic scheduling of tournaments, including balancing participation frequency and recovery intervals, is vital for optimizing performance and achieving sustained ranking success. These findings emphasize the importance of high-graded tournament selection and tailored schedules for elite players.

Understanding intermittency, an ubiquitous behavior in flows of packed grains, is pivotal for establishing the rheology of granular matter. A straightforward explanation has been missing despite the long development of theories at various levels of abstraction. Here, we propose the use of a Stribeck-Hertz model that starts with the classic Coulomb friction but takes into account the inter-particle tribology, i.e. the reduction of friction coefficient with sliding speed as is commonly observed. Our numerical experiments reveal a state diagram that covers a wide range of packing fractions and show that incorporating the tribology enables the occurrence of quaking intermittency in the mid-range of a newly established dimensionless shear rate, in consistence with prior experimental observations. Further study of the discontinuities in the evolution of mean contact number leads to our discovery of two types of quaking, that are distinguished by the abrupt increase or decrease of neighboring contacts and reveal different pathways of microstructural change underlying these discrete events. In contrast to the prevailing paradigm in which shear is believed to promote jamming at intermediate densities, our study demonstrates that shear can also unjam a granular system, and this occurrence depends on the shear rate.

Compressed cylindrical shells are common in our daily life, such as rolled-up sleeves and a retreated package of drinking straws. The deformations on these cylindrical shells with a rigid core are often random and unpredictable. In contrast, compressed beer can exhibit uniform arrays of diamonds, called the Yoshimura pattern. To elucidate the difference between these systems, we combine molecular dynamics simulations and experiments to study the deformation on a compressed cylindrical shell with a rigid core. By thoroughly exploring different material parameters, we are able to pin down the mode diagram.

Why do milk cartons and aluminum cans crumple differently from paper? Besides distinct elasticity and plasticity, their unique geometric structures also play a role. Over the past few decades, crumpled sheets have been widely studied for their fascinating mechanical, energetic, and statistical properties. These include the power-law relationship between the volume density of crumpled balls and pressure, the ratio of bending to stretching energies, and statistics on the number and length of deformations. Since these conclusions were primarily derived from studies on flat sheets, verifying whether they can be safely applied to the 3D hollow objects we encounter daily is important. A cubical box, with its sides forming flat sheets, is an ideal subject for comparison. The crumpling properties of such boxes have been examined through molecular dynamics simulations and experiments. By systematically dismantling the sides of the box, we clarified the roles of sides, corners, and open/closed boundaries. This knowledge allowed us to identify corners as the key factor causing deviations from the crumpling properties of flat sheets. One significant difference is that the power-law relationship between compaction and pressure is missing, replaced by a bump characteristic of the buckling transition. Different types of corners are found to be equally important, whether they are sharp at a singular point (as in boxes), along a curve (as in aluminum cans), or rounded (as in balls and vehicles). Special attention has been given to explaining why the vertices on the surface of a crumpled ball do not buckle, allowing them to retain the properties of a flat sheet despite their 3D appearance.