arXiv subjects

Biqin Dong

Publications and source records attributed to Biqin Dong.

3 recordsLinked to original sources

arXiv2026

Boson peak and medium-range elastic heterogeneity in calcium silicate hydrate probed by terahertz spectroscopy and low-temperature calorimetry

The boson peak (BP), a universal vibrational anomaly of disordered solids, has been predicted but not systematically characterized in calcium silicate hydrate (C-S-H), the binding phase of hardened cement. Building on a preliminary terahertz survey, we characterize the BP across five Ca/Si ratios (0.5-1.7) using terahertz time-domain spectroscopy (THz-TDS) and low-temperature calorimetry, two probes of vibrational dynamics that complement the static picture of conventional structural methods. After Bruggeman correction for crystalline impurities, both probes locate the BP near 1 THz; they agree on frequency but diverge in intensity. The terahertz integrated spectral weight and the calorimetric Cp/T3 peak both fall monotonically with Ca/Si, whereas the apparent terahertz peak height is maximal at Ca/Si = 1.0, where damping is low and oscillator strength still substantial. This decoupling marks a structural crossover between silicate-chain depolymerization and interlayer calcium filling. From the BP we obtain a medium-range dynamical correlation length of order 1 nm (0.3-2 nm) and a coherent-potential elastic-heterogeneity parameter that decreases from gamma = 0.98 to 0.48 as Ca/Si rises; the Debye-normalized BP frequency (nu_BP/nu_D = 0.15-0.17) places C-S-H within the range reported for silicate glasses. Because gamma governs the distribution of energy barriers for local structural rearrangements, it provides a quantitative, composition-resolved descriptor relevant to the intrinsic creep and thermal transport of C-S-H, linking nanoscale vibrational dynamics to the macroscopic durability of concrete. The dual-probe boson-peak approach is transferable to other amorphous solids, including the supplementary cementitious materials of low-carbon cements.

cond-mat.mtrl-sci↗

arXiv2026

A Contrastive Pre-trained Foundation Model for Deciphering Imaging Noisomics across Modalities

Characterizing imaging noise is notoriously data-intensive and device-dependent, as modern sensors entangle physical signals with complex algorithmic artifacts. Current paradigms struggle to disentangle these factors without massive supervised datasets, often reducing noise to mere interference rather than an information resource. Here, we introduce "Noisomics", a framework shifting the focus from suppression to systematic noise decoding via the Contrastive Pre-trained (CoP) Foundation Model. By leveraging the manifold hypothesis and synthetic noise genome, CoP employs contrastive learning to disentangle semantic signals from stochastic perturbations. Crucially, CoP breaks traditional deep learning scaling laws, achieving superior performance with only 100 training samples, outperforming supervised baselines trained on 100,000 samples, thereby reducing data and computational dependency by three orders of magnitude. Extensive benchmarking across 12 diverse out-of-domain datasets confirms its robust zero-shot generalization, demonstrating a 63.8% reduction in estimation error and an 85.1% improvement in the coefficient of determination compared to the conventional training strategy. We demonstrate CoP's utility across scales: from deciphering non-linear hardware-noise interplay in consumer photography to optimizing photon-efficient protocols for deep-tissue microscopy. By decoding noise as a multi-parametric footprint, our work redefines stochastic degradation as a vital information resource, empowering precise imaging diagnostics without prior device calibration.

cs.CV↗

arXiv2015

Ultrafast All-optical Modulation Exploiting the Vibrational Dynamic of Metallic Meta-atoms

Optical control over elementary molecular vibration establishes fundamental capabilities for exploiting the broad range of optical linear and nonlinear phenomena. However, experimental demonstration of the coherently driven molecular vibration remains a challenge task due to the weak optical force imposed on natural materials. Here we report the design of "meta-atom" that exhibits giant artificial optical nonlinearity. These "meta-atoms" support co-localized magnetic resonance at optical frequency and vibration resonance at GHz frequency with a deep-sub-diffraction-limit spatial confinement ($λ^2/100$). The coherent coupling of those two distinct resonances manifests a strong optical force, which is fundamentally different from the commonly studied form of radiation forces, the gradient forces, or photo-thermal induced deformation. It results in a giant third-order susceptibility $χ^{(3)}$ of $10^{-13}$ $m^2$/$V^2$, which is more than six orders of magnitude larger than that found in natural materials. The all-optical modulation at the frequency well above 1 GHz has thus been demonstrated experimentally.

physics.optics↗