arXiv subjects

Qing Tong

Publications and source records attributed to Qing Tong.

9 recordsLinked to original sources

arXiv2026

Twistsonics: engineering acoustic topological textures in moire sound lattices

Moire superlattices formed by twisting periodic systems provide a powerful platform for emergent topological phenomena, but their use for programming real-space topology in acoustic wave fields remains largely unexplored. Here we report a phase-controlled spoof surface acoustic wave platform for constructing moire topological textures in the acoustic particle-velocity field. On a perforated acoustic metasurface, two twisted skyrmion lattices are synthesized and superposed, yielding acoustic skyrmion bags with controllable topological numbers and geometries. The twist angle and rotation center control the scale and configuration of the bags, enabling deterministic reshaping of the composite texture. We further introduce controlled defects to assess the defect tolerance of the moire skyrmion bags. The skyrmion bags retain their composite topology over a finite range of defect densities, and comparison with an untwisted single-layer skyrmion lattice suggests enhanced stability of the enclosed skyrmion cluster relative to the single-layer reference at higher defect densities. The same programmable platform also supports transitions from skyrmion lattices to meron lattices and enables twist-induced meron clusters. These findings establish acoustic moire superlattices as a reconfigurable platform for engineering robust real-space topological textures, with potential applications in topology-guided acoustic manipulation and information encoding.

physics.app-ph↗

arXiv2025

Acoustic helical dichroism enhanced by chiral quasi-bound states in the continuum

Acoustic helical dichroism (HD) arises from the interaction between vortex beams carrying orbital angular momentum (OAM) and chiral media, yet such chiral sound-matter interactions are typically weak. Here, we employ quasi-bound states in the continuum (QBICs) in acoustic meta-cavities composed of coupled Helmholtz resonators to enhance acoustic HD. We design both achiral and chiral meta-cavities that support QBICs in the form of vortex states with high Q-factors. Using full-wave numerical simulations, we show that the QBICs in the achiral meta-cavities cannot enhance acoustic HD due to the absence of a chiral wavefront. In contrast, the chiral meta-cavity exhibits a pronounced HD enhancement through the QBICs with a 3D helical wavefront, which can be excited by incident waves either with or without OAM. Our work identifies two essential requirements for enhancing acoustic HD effect via QBICs: a high Q-factor of the states and 3D chirality of the state fields, which usually compromise each other in conventional acoustic resonators. The findings open new avenues for achieving strong chiral sound-matter interactions, with potential applications in acoustic chiral sensing and acoustic OAM manipulation.

physics.app-ph↗

arXiv2025

Advancing Mathematical Reasoning in Language Models: The Impact of Problem-Solving Data, Data Synthesis Methods, and Training Stages

Mathematical reasoning remains a challenging area for large language models (LLMs), prompting the development of math-specific LLMs such as LLEMMA, DeepSeekMath, and Qwen2-Math, among others. These models typically follow a two-stage training paradigm: pre-training with math-related corpora and post-training with problem datasets for supervised fine-tuning (SFT). Despite these efforts, the improvements in mathematical reasoning achieved through continued pre-training (CPT) are often less significant compared to those obtained via SFT. This study addresses this discrepancy by exploring alternative strategies during the pre-training phase, focusing on the use of problem-solving data over general mathematical corpora. We investigate three primary research questions: (1) Can problem-solving data enhance the model's mathematical reasoning capabilities more effectively than general mathematical corpora during CPT? (2) Are synthetic data from the same source equally effective, and which synthesis methods are most efficient? (3) How do the capabilities developed from the same problem-solving data differ between the CPT and SFT stages, and what factors contribute to these differences? Our findings indicate that problem-solving data significantly enhances the model's mathematical capabilities compared to general mathematical corpora. We also identify effective data synthesis methods, demonstrating that the tutorship amplification synthesis method achieves the best performance. Furthermore, while SFT facilitates instruction-following abilities, it underperforms compared to CPT with the same data, which can be partially attributed to its poor learning capacity for more challenging problem-solving data. These insights provide valuable guidance for optimizing the mathematical reasoning capabilities of LLMs, culminating in our development of a powerful mathematical base model called MathGPT-8B.

cs.CL↗

arXiv2024

DiReDi: Distillation and Reverse Distillation for AIoT Applications

Typically, the significant efficiency can be achieved by deploying different edge AI models in various real world scenarios while a few large models manage those edge AI models remotely from cloud servers. However, customizing edge AI models for each user's specific application or extending current models to new application scenarios remains a challenge. Inappropriate local training or fine tuning of edge AI models by users can lead to model malfunction, potentially resulting in legal issues for the manufacturer. To address aforementioned issues, this paper proposes an innovative framework called "DiReD", which involves knowledge DIstillation & REverse DIstillation. In the initial step, an edge AI model is trained with presumed data and a KD process using the cloud AI model in the upper management cloud server. This edge AI model is then dispatched to edge AI devices solely for inference in the user's application scenario. When the user needs to update the edge AI model to better fit the actual scenario, the reverse distillation (RD) process is employed to extract the knowledge: the difference between user preferences and the manufacturer's presumptions from the edge AI model using the user's exclusive data. Only the extracted knowledge is reported back to the upper management cloud server to update the cloud AI model, thus protecting user privacy by not using any exclusive data. The updated cloud AI can then update the edge AI model with the extended knowledge. Simulation results demonstrate that the proposed "DiReDi" framework allows the manufacturer to update the user model by learning new knowledge from the user's actual scenario with private data. The initial redundant knowledge is reduced since the retraining emphasizes user private data.

cs.LG↗

arXiv2024

Topological Dark Spots of Electric Near Field in Metal Structures

Electric dark spots are point singularities at which the electric field amplitude vanishes. These singularities usually emerge in real space accidentally and are unstable due to the vectorial property of the electric field. In this paper, we show that topologically protected electric dark spots can emerge in metal scatterers under external excitation. The material property of metal imposes a boundary condition that reduces the vectorial electric field on the metal surface to a scalar field. The phase singularity of this scalar field has zero amplitude and carries a well-defined topological charge corresponding to an electric dark spot. The topological electric dark spots give rise to the superoscillation phenomenon with a divergent local wavenumber. We uncover the global charge conservation property of the dark spots on the scatterers' surfaces and demonstrate their stability under different perturbations. We also demonstrate the manipulation of the dark spots' topological charge and spatial location. The results open a new avenue for nanophotonic near-field manipulations and may find applications in optical metrology, optical sensing, and super-resolution imaging.

physics.optics↗

arXiv2024

Sculpturing sound fields with real-space topology

Artificial structures have been widely used to manipulate sound fields. Most properties of these structures derive from the material and geometry. Few are explicitly related to the structural topology in the real space. Here, we discover a fundamental connection between the real-space topology of acoustic structures and the topological properties of sound fields. We find that the genus of acoustic cavities can protect the birth of singularities in velocity polarization and isopressure line fields. The total topological index of the surface singularities is equal to the cavities' Euler characteristic. This intriguing relationship is rooted in the Poincare-Hopf theorem and is irrelevant to the specific material, geometric details, or excitation properties. The isopressure line singularities lead to acoustic hotspots and quiet zones. The velocity polarization singularities give rise to nontrivial polarization Mobius strips and skyrmion textures. The results enable sound sculpturing with structural topology and can find applications in acoustic communications, acoustic sensing, and noise control.

physics.app-ph↗

arXiv2023

Acoustic circular dichroism in a three-dimensional chiral metamaterial

Circular dichroism (CD) is an intriguing chiroptical phenomenon associated with the interaction of chiral structures with circularly polarized lights. Although the CD effect has been extensively studied in optics, it has not yet been demonstrated in acoustic systems. Here, we demonstrate the acoustic CD effect in a three-dimensional chiral metamaterial supporting circularly polarized transverse sound. We find that the effect is negligible in the lossy metamaterial possessing $C_4$ rotational symmetry but can be strongly enhanced in the $C_2$-symmetric system with inhomogeneous loss. The phenomena can be understood based on the properties of the metamaterial's complex band structure and the quality factors of its eigenmodes. We show that the enhanced CD in the $C_2$-symmetric system is attributed to the polarization bandgaps and the non-Hermitian exceptional points appearing near the Brillouin-zone center and boundaries. The results contribute to the understanding of chiral sound-matter interactions and can find applications in acoustic sensing of chiral structures and sound manipulations based on its vector properties.

physics.app-ph↗

arXiv2021

Acoustic helical dichroism in a one-dimensional lattice of chiral resonators

Circular dichroism and helical dichroism are intriguing chiroptical phenomena with broad applications in optical sensing and imaging. Here, we generalize one of the phenomena-helical dichroism-to acoustics. We show that a one-dimensional lattice of chiral resonators with loss can induce differential absorption of helical sounds (i.e. acoustic vortices) carrying opposite orbital angular momentum (OAM). This acoustic helical dichroism strongly depends on the rotation symmetry of the chiral resonators. A breaking of the $C_4$ rotation symmetry can induce coupling between the opposite chiral dipole modes of the resonators. This leads to OAM bandgaps and non-Hermitian exceptional points near the Brillouin-zone center and boundaries, which together give rise to significantly enhanced helical dichroism. The underlying physics can be well captured by an effective Hamiltonian that quantitatively reproduces the complex band structures. The acoustic helical dichroism can find important applications in acoustic OAM manipulations and chiral sound-matter interactions.

physics.app-ph↗

arXiv2021

Spin-orbit interactions of transverse sound

Spin-orbit interactions (SOIs) endow light with intriguing properties and applications such as photonic spin-Hall effects and spin-dependent vortex generations. However, it is counterintuitive that SOIs can exist for sound, which is a longitudinal wave that carries no intrinsic spin. Here, we theoretically and experimentally demonstrate that airborne sound can possess artificial transversality in an acoustic micropolar metamaterial and thus carry both spin and orbital angular momentum. This enables the realization of acoustic SOIs with rich phenomena beyond those in conventional acoustic systems. We demonstrate that acoustic activity of the metamaterial can induce coupling between the spin and linear crystal momentum k, which leads to negative refraction of the transverse sound. In addition, we show that the scattering of the transverse sound by a dipole particle can generate spin-dependent acoustic vortices via the geometric phase effect. The acoustic SOIs can provide new perspectives and functionalities for sound manipulations beyond the conventional scalar degree of freedom and may open an avenue to the development of spin-orbit acoustics.

physics.app-ph↗