arXiv subjects

Cheng-En Tsai

Publications and source records attributed to Cheng-En Tsai.

6 recordsLinked to original sources

arXiv2025

Internal motion of soft granular particles under circular shearing: Rate-dependent quaking and its spatial structure

Tightly packed granular particles under shear often exhibit intriguing intermittencies, specifically, sudden stress drops that we refer to as quaking. To probe the nature of this phenomenon, we prototype a circular shear cell that is capable of imposing a uniform and unlimited shear strain under quasi-static cyclic driving. Spherical PDMS(polydimethylsiloxane) particles, immersed in fluid, are driven in a fixed total volume at a wide range of shear rates, with particle trajectories captured in 3D space via refraction-index-matched fluorescent tomography. Statistics on the magnitude of fluctuating displacements of individual particles shows distinct dependence on the shear rate. Particle motions are smooth at high shear rates. At intermediate shear rates, quaking emerges with clusters of particles exhibiting relatively large displacements. At low shear rates, a cluster can span the entire system. and the cluster exhibits substructures in view of localized particle movements. Overall, we have confirmed that the quaking phenomena in the current setup are consistent with our previous work [Phys. Rev. Lett.,126, 128001 (2021)], and that the dimensionless shear rate that we have proposed [Phys. Rev. Research 6, 023065 (2024)] is indeed a good parameter for unifying the transitions observed in different experimental geometries.

cond-mat.soft↗

arXiv2024

Qsyn: A Developer-Friendly Quantum Circuit Synthesis Framework for NISQ Era and Beyond

In this paper, we introduce a new quantum circuit synthesis (QCS) framework, Qsyn, for developers to research, develop, test, experiment, and then contribute their QCS algorithms and tools to the framework. Our framework is more developer-friendly than other modern QCS frameworks in three aspects: (1) We design a rich command-line interface so that developers can easily design various testing scenarios and flexibly conduct experiments on their algorithms. (2) We offer detailed access to many data representations on different abstract levels of quantum circuits so that developers can optimize their algorithms to the extreme. (3) We define a rigid developing flow and environment so that developers can ensure their development qualities with the best modern software engineering practices. We illustrate the friendliness of our framework with a showcase of developing a T-Count Optimization algorithm and demonstrate our performance superiority with fair comparisons to other modern QCS frameworks.

quant-ph↗

arXiv2024

Two types of quaking and shear unjamming: state diagram for soft granular particles under shear

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.

cond-mat.soft↗

arXiv2023

Dynamical force measurements for contacting soft surfaces upon steady sliding: Fixed-depth tribology

The tribology between surfaces can have a profound impact on the response of a mechanical system, such as how granular particles are driven to flow. In this work, we perform experiments that time-resolve the tangential and normal components of the force between two semi-cylindrical PDMS (polydimethylsiloxane) samples immersed in fluid, as they slide against each other in a range of controlled speeds. The time-averaged friction force shows a non-monotonic dependence on the sliding speed over four decades, which is consistent to the paradigmatic Stribeck diagram and three dynamical regimes associated with it. Our specially designed fixed-depth setup allows us to study the fluctuation of force that exhibits strong stick-slip patterns in one of the regimes. Data from repetitive experiments reveal that both the "onset speed" for the stick-slip patterns and its spatial location along the sample change gradually during the course of our experiments, indicating changes on the sample surfaces. In addition, we conduct counterpart experiments by using spherical samples rubbing against each other, to make a direct connection of the inter-particle tribology to the granular flow reported in our previous work [Phys. Rev. Lett. 126,128001 (2021)].

cond-mat.soft↗

arXiv2023

Evidence for spontaneous arrangement of two-way flow in water bridge via particle image velocimetry

By revisiting the century-old problem of water bridge, we demonstrate that it is in fact dynamic and comprises of two coaxial water currents that carry different charges and flow in opposite directions. This spontaneous separation is triggered by the different stages to construct the water bridge. Initially, a flow is facilitated by the cone jet that is powered by H+ and flows out of the positive-electrode beaker. An opposing cone-jet from negative beaker is established later and forced to take the outer route. This spontaneous arrangement of two-way flow is revealed by using fluorescein and carbon powder as tracers, and the Particle Image Velocimetry, These two opposing flows are found to carry non-equal flux that results in a net transport of water to the negative beaker. We manage to estimate the flow speed and cross-sectional area of these co-axial flows as a function of time and applied voltage. Note that the water on the outer layer functions as a millimeter tube that confines and interacts strongly with the flow inside. This provides a first natural and yet counter example to the recently reported near-frictionless flow in an equally miniatureized soft wall made from ferrofluid.

cond-mat.soft↗

arXiv2020

Rate-dependent Stick-slips in Steady Shearing: Signature of Transition between Granular Solid and Fluid

Despite extensive studies on either smooth granular-fluid flow or the solid-like deformation at the slow limit, the change between these two extremes remains largely unexplored. By systematically investigating the fluctuations of tightly packed grains under steady shearing, we identify a transition zone with prominent stick-slip avalanches. We establish a state diagram, and propose a new dimensionless shear rate based on the speed dependence of inter-particle friction and particle size. With fluid-immersed particles confined in a fixed volume and forced to "flow" at viscous numbers $J$ decades below reported values, we answer how a granular system can transition to the regime sustained by solid-to-solid friction that goes beyond existing paradigms based on suspension rheology.

cond-mat.soft↗