Ultrastable Shear-Jammed Granular Material

Abstract

World models have demonstrated superiority in autonomous driving, particularly in the generation of multi-view driving videos. However, significant challenges still exist in generating customized driving videos. In this paper, we propose DriveDreamer-2, which builds upon the framework of DriveDreamer and incorporates a Large Language Model (LLM) to generate user-defined driving videos. Specifically, an LLM interface is initially incorporated to convert a user's query into agent trajectories. Subsequently, a HDMap, adhering to traffic regulations, is generated based on the trajectories. Ultimately, we propose the Unified Multi-View Model to enhance temporal and spatial coherence in the generated driving videos. DriveDreamer-2 is the first world model to generate customized driving videos, it can generate uncommon driving videos (e.g., vehicles abruptly cut in) in a user-friendly manner. Besides, experimental results demonstrate that the generated videos enhance the training of driving perception methods (e.g., 3D detection and tracking). Furthermore, video generation quality of DriveDreamer-2 surpasses other state-of-the-art methods, showcasing FID and FVD scores of 11.2 and 55.7, representing relative improvements of ∼30% and ∼50%.

Shear hardening in frictionless amorphous solids near the jamming transition

“…Shear hardening has been directly observed in previous studies [15,25,36,37]. Simulations report a hardening regime on the stress-strain curve, following elastic and softening regimes [25,36].…”

“…Finally, it would be interesting to examine the effect of friction on shear hardening. Recent progress in producing ultra-stable granular materials makes an experimental investigation of frictional shear hardening feasible [15,48]. It is expected that the critical exponents are non-universal with different friction coefficients [48].…”

“…This behavior (observed with a fixed volume) is equivalent to the well-known dilatancy effect [8,9] under pressure-controlled conditions, initially demonstrated by Reynolds more than 100 years ago [10]. The vestige of shear hardening in the unjammed phase is the phenomenon of shear jamming, observed in many experiments [11][12][13][14][15] and simulations [16? -28].…”

Shear jamming and fragility in fractal suspensions under confinement

“…Controlling fractal dimension in these systems by tuning the inter-particle interactions and observing the resulting flow behaviour can shed light on the sharp rise in stressinduced contact formation or contact proliferation. Exploring the stability properties of SJ state in fractal suspensions using a similar approach used for dry granular materials 37 can be an interesting future direction to explore. We hope that our study will motivate further experimental and theoretical studies of SJ in suspensions of fractal particles.…”

Microscopic reversibility and emergent elasticity in ultrastable granular systems

“…The stability of shearjammed states, however, remains at best partially understood. In a recent experiment [1], the stability of shear-jammed states in a frictional granular system was systematically examined by monitoring their evolution under small-amplitude, volumeconserving cyclic shear. Many shear-jammed packings relaxed to a stress-free, diffusive steady state under cyclic strain amplitude as small as 1%.…”