arXiv subjects

Chunyan Li

Publications and source records attributed to Chunyan Li.

At least 19 recordsLinked to original sources

arXiv2026

Determining Meteorological Tidal Transport through a Channel on the Coast

Transient weather systems are often associated with alternating warm and cold advections of air masses and changing wind directions, which drive coastal ocean and estuarine waters to oscillate quasi-periodically. Quantifying water transport under these meteorological oscillations between inland waterways and the coastal ocean helps interpret land-ocean interactions and the impact of migrating weather systems. The challenge lies in the difficulty of obtaining continuous, long-term direct measurements of transport due to logistical constraints. Here, we apply a method to determine the meteorological tide-induced volume transport of water through an intensive survey, correlating transport values measured by a boat-mounted ADCP with vertically averaged velocities from a bottom-mounted ADCP, which recorded a much longer time series. The correlation is then used to compute transport over the period of the bottom-mounted ADCP deployment. Observations were conducted at Belle Pass, Port Fourchon. The transport data revealed the impact of weather systems, including four cold fronts. A model of volume transport, accounting for rotary cold front wind variations, was applied, where both along-channel and along-coastline wind components contribute to the remote wind effect, leading to a more complex response to passing weather systems. The local wind effect is much smaller than the remote wind effect, and transport is primarily controlled by water level fluctuations resulting from open boundary input. Finally, the channel orientation relative to the coastline is found to be critical in determining both the magnitude and phase of the transport.

physics.ao-ph↗

arXiv2026

Logarithmic Aging Diffusion from a Multiplicative Event Clock: Rare Event Statistics, Ultraslow Transport, and Ensemble-Time Inequivalence

Logarithmic time dependences occur in many aging materials, but neither a $\ln t$ relaxation law nor a $1/t$ event rate uniquely identifies the underlying stochastic mechanism. We examine a specific log-aging process defined by iterating the age-conditioned forward-recurrence law after every event. This rule makes the event times multiplicative: the logarithmic ratios $U_n=\ln(T_{n+1}/T_n)$ are independent and identically distributed with an explicit non-exponential density. Consequently, both the mean and the variance of the event count grow linearly with $\ln(t/t_0)$, while the density of the $n$th event time has a log-normal central sector and a fixed-$n$ algebraic far tail. These clock statistics generate logarithmic drift and spreading, an Einstein relation under local detailed balance, and ultraslow transit and target-survival laws. They also separate trajectory reproducibility from ensemble--time equivalence: the relative scatter of the time-averaged mean-square displacement decays as $1/\ln(T/t_0)$, although its mean does not converge to the ensemble lag MSD. We distinguish the exact event-level construction from its diffusion-limit generalized Fokker--Planck and random-clock subordination representations, and from a generalized-Langevin closure that can match selected responses and covariances but need not reproduce event counts or rare-duration statistics. The proposed clock is therefore tested not by a single logarithmic curve, but by the joint, no-refitting consistency of multiplier, count, transport, first-passage, and finite-window observables.

cond-mat.stat-mech↗

arXiv2026

The Proudman Resonance Modified: Forced Waves in Shallow Water -- the Suppression of Resonance by Nonlinearity

Storms and severe weather are often associated with atmospheric low-pressure systems. A moving low atmospheric pressure system produces storm surge that is dependent on the wave Froude number (F) or the ratio between the speed of the storm and the shallow water wave propagation speed. Proudman's resonance for such a problem goes to infinity at F=1. This work revisits the problem by presenting a nonlinear exact solution. The first order approximation goes back to Proudman's solution. The second order approximation provides a finite solution including at resonance. The solution shows that the nonlinear advection can significantly suppress the resonance. At resonance, although the solution is finite, it bifurcates into two branches, a condition linked to chaos in theoretical fluid dynamics and many nonlinear systems. Although Proudman's solution does not provide any limit to the atmospheric pressure system, it is not without any condition. The solution exists for all low-pressure systems but has only limited validity for a moving atmospheric high-pressure system induced forced waves: at low moving speed, the solution under a high-pressure system can exist for a range of high-pressure variability but quickly become invalid as the system's speed increases. The closer F is to 1 (resonance), the easier for the solution to be invalidated for a high-pressure system. This study also found that Proudman's solution is most accurate only under subcritical conditions with small low-pressure variability and has much larger error under supercritical conditions.

physics.ao-ph↗

arXiv2026

Anomalous Topological Bloch Oscillations under Non-Abelian Gauge Fields

Topological Bloch oscillations are a hallmark of quantum transport phenomenon in which wavepackets undergo oscillatory motion driven by the interplay between an external force and topological edge states and serve as a powerful dynamical probe for the geometric properties of topological bands. Spin-orbit coupling (SOC) has also emerged as a crucial ingredient for manipulating quantum states in materials, with the corresponding gauge fields arising from the Rashba and Dresselhaus interactions. In this work, we investigate the propagation of spinor wavepackets in a honeycomb Zeeman lattice governed by the Gross-Pitaevskii equation. By tuning the relative strengths of Rashba and Dresselhaus SOC, we engineer a non-Abelian gauge field that drives anomalous topological Bloch oscillations (ATBOs). Unlike conventional topological Bloch oscillation (TBOs), these ATBOs exhibit asymmetric motion, including a freezing effect in one half of the oscillation cycle, which can be tuned by the SOC parameters and external forces. Our findings establish SOC-based non-Abelian gauge fields as a powerful mechanism controlling topological quantum dynamics, with implications for spintronic devices and quantum data processing.

cond-mat.quant-gas↗

arXiv2025

Non-Inductive Current Start-Up Using Multi-Harmonic Electron Cyclotron Wave and Current Ramp-Up Through Combined Electron Cyclotron Wave and Ohmic Heating in EXL-50U Spherical Torus

The non-inductive current start-up by multi-harmonic electron cyclotron wave has been systematically investigated in the EXL-50U spherical torus. Significant enhancements of the driven current with increasing number of resonance layers have been demonstrated by variation of the number of harmonic resonance layers of the ECW through adjustment of the magnetic field or plasma cross section. The critical role of multi-harmonic ECW in enhancing the driven current has been experimentally verified for the first time. To explain the related experimental observations, a physical mechanism involving multi-harmonic heating, multiple reflections, and multi-pass absorption - leading to the generation of high-energy electrons via X-mode wave or electron Bernstein wave has been proposed. The current drive capacity of the first harmonic extraordinary mode of the ECW has also been experimentally confirmed for the first time. After the application of Ohmic heating during the current ramp-up phase, the current drive efficiency of ECW is further enhanced. Leveraging the synergistic effect between ECW and Ohmic heating, EXL-50U achieved a plasma current of 1 MA, with the non-inductively driven current fraction reaching 70%.

physics.plasm-ph↗

arXiv2025

The origin of B-type runaway stars based on kinematics

Runaway stars depart their birthplaces with high peculiar velocities. Two mechanisms are commonly invoked to explain their origin, the binary supernova scenario (BSS) and the dynamical ejection scenario (DES). Investigating the kinematic properties of runaway stars is key to understanding their origins.We intend to investigate the origins of 39 B-type runaway stars from LAMOST using orbital traceback analysis. From the catalog of LAMOST, we selected 39 B-type runaway stars and determined their spectral subtypes from key absorption lines. We then derived atmospheric parameters for each star using the Stellar Label Machine (SLAM), which is trained on TLUSTY synthetic spectra computed under the non-local thermodynamic equilibrium (NLTE) assumption. Using the derived atmospheric parameters as input, we estimated stellar masses and ages with a machine learning model trained on PARSEC evolutionary tracks. We finally performed orbital traceback with GALPY to analyze their origins. Through orbital traceback, we find that 29 stars have trajectories entirely within the Galactic disk, whereas 10 are disk-passing yet still trace back to the disk. Two stars have trajectories that intersect those of known clusters. Their orbits show similar morphologies in both the $X-Y$ and $R-Z$ planes, and their [M/H] values are comparable, suggesting possible cluster origins. However, definitive confirmation will require additional evidence. In addition, the $V_{\rm Sp} - v\sin{i}$ plane shows that runaway stars with low peculiar space velocities but high $v\sin{i}$ remain on the Galactic disk, whereas those with high peculiar space velocities but low $v\sin{i}$ pass through the disk, possibly reflecting two distinct origins.

astro-ph.SR↗

arXiv2025

Data-Driven Modeling of Spatiotemporal Dynamics Using Multimodal Imaging Data

Understanding how biological systems evolve across space and time remains a fundamental challenge, particularly when dynamic processes vary substantially across individuals. We present a personalized graph-based dynamical modeling framework for characterizing spatiotemporal biological dynamics from longitudinal multimodal imaging data. The framework constructs individualized brain graphs from MRI and PET measurements and learns patient-specific dynamical parameters governing regional structural and molecular changes. Applied to 1,891 participants from the Alzheimer's Disease Neuroimaging Initiative, the model captures the coordinated evolution of amyloid-$\beta$, tau, neurodegeneration, and cognition and accurately predicts their future trajectories, outperforming established clinical and neuroimaging benchmarks. Patient-specific dynamical parameters reveal distinct patterns of biological progression and provide improved prediction of future cognitive decline compared with standard biomarkers. Sensitivity analysis further identifies regional network features associated with the propagation of pathological and structural changes, recovering known temporolimbic and frontal vulnerability patterns. These results demonstrate how data-driven dynamical modeling can integrate multimodal longitudinal measurements to uncover individualized spatiotemporal patterns and latent mechanisms of biological change. The framework provides a quantitative approach for studying complex biological dynamics across heterogeneous individuals and establishes a foundation for personalized modeling of progressive biological processes.

q-bio.NC↗

arXiv2025

A catalog of new blue stragglers in open clusters with Gaia DR3

The high-precision {\it Gaia} data release 3 (DR3) enables the discovery of numerous open clusters in the Milky Way, providing an excellent opportunity to search for blue straggler stars in open clusters and investigate their formation and evolution in these environments. Using the member stars from literature open cluster catalogs, we visually inspected the color-magnitude diagram (CMD) of each cluster and selected cluster candidates that potentially host blue stragglers. We then reassessed cluster memberships using the {\tt pyUPMASK} algorithm with {\it Gaia} DR3 and performed isochrone fitting to derive physical parameters for each cluster, including age, distance modulus, mean reddening, and metallicity. Finally, we empirically identified straggler stars based on their positions relative to the best-fitting isochrone, zero-age main sequence (ZAMS), and equal-mass binary sequence on the CMD. In total, we identified 272 new straggler stars in 99 open clusters, comprising 153 blue stragglers, 98 probable blue stragglers, and 21 yellow stragglers. Compared to the reported blue straggler catalogs based on earlier {\it Gaia} data, our results increase the number of open clusters with stragglers in the Milky Way by 22.2\%, and the total number of blue stragglers by 11.2\%.

astro-ph.SR↗

arXiv2025

BMGQ: A Bottom-up Method for Generating Complex Multi-hop Reasoning Questions from Semi-structured Data

Building training-ready multi-hop question answering (QA) datasets that truly stress a model's retrieval and reasoning abilities remains highly challenging recently. While there have been a few recent evaluation datasets that capture the characteristics of hard-to-search but easy-to-verify problems -- requiring the integration of ambiguous, indirect, and cross-domain cues -- these data resources remain scarce and are mostly designed for evaluation, making them unsuitable for supervised fine-tuning (SFT) or reinforcement learning (RL). Meanwhile, manually curating non-trivially retrievable questions -- where answers cannot be found through a single direct query but instead require multi-hop reasoning over oblique and loosely connected evidence -- incurs prohibitive human costs and fails to scale, creating a critical data bottleneck for training high-capability retrieval-and-reasoning agents. To address this, we present BMGQ, a bottom-up automated method for generating high-difficulty, training-ready multi-hop questions from semi-structured knowledge sources. The BMGQ system (i) grows diverse, logically labeled evidence clusters through Natural Language Inference (NLI)-based relation typing and diversity-aware expansion; (ii) applies reverse question construction to compose oblique cues so that isolated signals are underinformative but their combination uniquely identifies the target entity; and (iii) enforces quality with a two-step evaluation pipeline that combines multi-model consensus filtering with structured constraint decomposition and evidence-based matching. The result is a scalable process that yields complex, retrieval-resistant yet verifiable questions suitable for SFT/RL training as well as challenging evaluation, substantially reducing human curation effort while preserving the difficulty profile of strong evaluation benchmarks.

cs.AI↗

arXiv2025

SHREC 2025: Protein surface shape retrieval including electrostatic potential

This SHREC 2025 track dedicated to protein surface shape retrieval involved 9 participating teams. We evaluated the performance in retrieval of 15 proposed methods on a large dataset of 11,555 protein surfaces with calculated electrostatic potential (a key molecular surface descriptor). The performance in retrieval of the proposed methods was evaluated through different metrics (Accuracy, Balanced accuracy, F1 score, Precision and Recall). The best retrieval performance was achieved by the proposed methods that used the electrostatic potential complementary to molecular surface shape. This observation was also valid for classes with limited data which highlights the importance of taking into account additional molecular surface descriptors.

cs.CV↗

arXiv2025

Energy Dissipation Rate Guided Adaptive Sampling for Physics-Informed Neural Networks: Resolving Surface-Bulk Dynamics in Allen-Cahn Systems

We introduce the Energy Dissipation Rate guided Adaptive Sampling (EDRAS) strategy, a novel method that substantially enhances the performance of Physics-Informed Neural Networks (PINNs) in solving thermodynamically consistent partial differential equations (PDEs) over arbitrary domains. EDRAS leverages the local energy dissipation rate density as a guiding metric to identify and adaptively re-sample critical collocation points from both the interior and boundary of the computational domain. This dynamical sampling approach improves the accuracy of residual-based PINNs by aligning the training process with the underlying physical structure of the system. In this study, we demonstrate the effectiveness of EDRAS using the Allen-Cahn phase field model in irregular geometries, achieving up to a sixfold reduction in the relative mean square error compared to traditional residual-based adaptive refinement (RAR) methods. Moreover, we compare EDRAS with other residual-based adaptive sampling approaches and show that EDRAS is not only computationally more efficient but also more likely to identify high-impact collocation points. Through numerical solutions of the Allen-Cahn equation with both static (Neumann) and dynamic boundary conditions in 2D disk- and ellipse-shaped domains solved using PINN coupled with EDRAS, we gain significant insights into how dynamic boundary conditions influence bulk phase evolution and thermodynamic behavior. The proposed approach offers an effective, physically informed enhancement to PINN frameworks for solving thermodynamically consistent models, making PINN a robust and versatile computational tool for investigating complex thermodynamic processes in arbitrary geometries.

math.NA↗

arXiv2025

Identification of BHB stars using Synthetic SkyMapper colors from Gaia XP spectra

Blue horizontal-branch (BHB) stars are ideal tracers for mapping the structure of Galactic stellar halo. Traditionally, BHB sample stars are built from large-scale spectroscopic surveys utilizing their spectral features, however, the resulting sample sizes have been quite limited. In this paper, we construct a catalog of BHB stars based on synthetic colors $(u-v)_{0}$ and $(g-i)_{0}$ in SkyMapper photometric systems, which are convolved from Gaia XP spectra. A total of 49,733 BHB stars are selected from nearly the entire sky (excluding regions of low Galactic latitudes $|b| \le 8^{\circ}$ with heavy reddening), with a completeness and purity exceeding 90\%. Using member stars of globular clusters with precise distance determinations, we carefully calibrate the relationship between the $g$-band absolute magnitude and $(g-i)_{0}$, achieving a precision of 0.11\,mag, which corresponds to a 5\% uncertainty in distance. This relation is applied to derive distances for all BHB stars in the constructed sample. Given current capabilities of Gaia XP observations, the constructed BHB sample is primarily located within 20 kpc, enabling detailed mapping of the inner stellar halo. To extend this depth to the outer halo or even the edge of our Galaxy, we explore the potential of the Chinese Space Station Telescope (CSST) and its broad-band photometry for detecting BHB stars. Using mock data from synthetic spectra, we find that it is feasible to distinguish BHB stars from blue stragglers (BS) stars using CSST near-ultraviolet bands ($NUV, u$) photometry. Thanks to the deep limiting magnitude of CSST, its data will provide a groundbreaking perspective on our Galaxy, particularly regarding the outer halo, in an unprecedented volume.

astro-ph.GA↗

arXiv2025

Rare-Event-Induced Ergodicity Breaking in Logarithmic Aging Systems

Ergodicity breaking and aging effects are fundamental challenges in out-of-equilibrium systems. Various mechanisms have been proposed to understand the non-ergodic and aging phenomena, possibly related to observations in systems ranging from structural glass and Anderson glasses to biological systems and mechanical systems. While anomalous diffusion described by Levy statistics efficiently captures ergodicity breaking, the origin of aging and ergodicity breaking in systems with ultraslow dynamics remain unclear. Here, we report a novel mechanism of ergodicity breaking in systems exhibiting log-aging diffusion. This mechanism, characterized by increasingly infrequent rare events with aging, yields statistics deviating significantly from Levy distribution, breaking ergodicity as shown by unequal time- and ensemble-averaged mean squared displacements and two distinct asymptotic probability distribution functions. Notably, although these rare events contribute negligibly to statistical averages, they dramatically change the system's characteristic time. This work lays the groundwork for microscopic understanding of out-of-equilibrium systems and provides new perspectives on glasses and Griffiths-McCoy singularities.

cond-mat.dis-nn↗

arXiv2025

Census of Blue Straggler Stars in Distant Open Clusters and Maximum Fractional Mass Excess of OC BSS

We identified blue straggler stars (BSSs) in 53 open clusters utilizing data from Gaia DR3. Most of these clusters are situated in the outer regions of the Galactic disc, encompassing structures such as the warp and the Outer arm. We analyzed their astrometric parameters and determined that 48 of them demonstrate high reliability in radial density profile. Furthermore, through manual isochrone fitting and visual inspection, we confirmed 119 BSS candidates and identified 328 additional possible candidates within these clusters. Our results contribute to a 46% increase in the sample size of BSSs in open clusters for regions of the Galactic disc where Rgc > 12 kpc. We observed that the new samples are fainter compared to those identified in the past. Additionally, we investigated the maximum fractional mass excess (Me) of the BSSs in open clusters, including previously published BSS samples. Our findings indicate a strong correlation between the capability to produce highest-Me BSSs and the mass of their host clusters. This observation appears to reinforce a fundamental principle whereby an increase in the mass of a star cluster correlates with a higher likelihood of stellar mergers. In contrast, we observe minimal correlation between maximum-Me and the cluster age. Among clusters containing BSSs, younger clusters (0.5 to 1 Gyr) display a scarcity of high-Me BSSs. This scarcity may be attributed to the absence of more massive clusters within this age range.

astro-ph.SR↗

arXiv2024

Unveiling the Binary Nature of NGC 2323

As a well-known open cluster, NGC 2323 (also called M50) has been widely investigated for over a hundred years and has always been considered a classical single cluster. In this work, with the help of Gaia DR3, we study the binary structure nature of this cluster. Although indistinguishable in the spatial space, the small but undeniable difference in the proper motion indicates that they may be two individual clusters. After investigating the properties of the two clusters, it is found that they have very close positions (three-dimensional $\Delta$pos = 12.3 pc, $\sigma_{\Delta \mathrm{pos}} = 3.4$ pc) and similar tangential velocities (two-dimensional $\Delta$V = 2.2 km s$^{-1}$, $\sigma_{\Delta \mathrm{V}} = 0.02$ km s$^{-1}$), indicating the existence of their physical association. Moreover, the best isochrone fitting ages of the two clusters are the same (158 Myr), further proving their possibly common origin. To comprehensively understand the formation and evolution of this binary cluster, we employ the PETAR $N$-body code to trace back their birthplace and deduce their dynamical evolutionary fate. With observational mean cluster properties, the simulations suggest that they may form together, and then orbit each other as a binary cluster for over 200 Myr. After that, because of their gradual mass loss, the two clusters will eventually separate and evolve into two independent clusters. Meanwhile, the numerical $N$-body simulation suggests that the less massive cluster is unlikely to be the cluster tidal tails created by the differential rotation of the Milky Way.

astro-ph.GA↗

arXiv2024

Towards Cross-Modal Text-Molecule Retrieval with Better Modality Alignment

Cross-modal text-molecule retrieval model aims to learn a shared feature space of the text and molecule modalities for accurate similarity calculation, which facilitates the rapid screening of molecules with specific properties and activities in drug design. However, previous works have two main defects. First, they are inadequate in capturing modality-shared features considering the significant gap between text sequences and molecule graphs. Second, they mainly rely on contrastive learning and adversarial training for cross-modality alignment, both of which mainly focus on the first-order similarity, ignoring the second-order similarity that can capture more structural information in the embedding space. To address these issues, we propose a novel cross-modal text-molecule retrieval model with two-fold improvements. Specifically, on the top of two modality-specific encoders, we stack a memory bank based feature projector that contain learnable memory vectors to extract modality-shared features better. More importantly, during the model training, we calculate four kinds of similarity distributions (text-to-text, text-to-molecule, molecule-to-molecule, and molecule-to-text similarity distributions) for each instance, and then minimize the distance between these similarity distributions (namely second-order similarity losses) to enhance cross-modal alignment. Experimental results and analysis strongly demonstrate the effectiveness of our model. Particularly, our model achieves SOTA performance, outperforming the previously-reported best result by 6.4%.

cs.IR↗

arXiv2024

The route of random process to ultraslow aging phenomena

Logarithmic aging phenomena are prevalent in various systems, including electronic materials and biological structures. This study utilizes a generalized continuous time random walk (CTRW) framework to investigate the mechanisms behind the logarithmic aging phenomena. By incorporating non-Markovian jump processes with significant memory effects, we modify traditional diffusion models to exhibit logarithmic decay in both survival and return probabilities. In addition, we analyze the impact of aging on autocorrelation functions, illustrating how long-term memory behaviors affect the temporal evolution of physical properties. These results connect microscopic models to macroscopic manifestations in real-world systems, advancing the understanding of ultraslow dynamics in disordered systems.

cond-mat.stat-mech↗

arXiv2024

Existence and Stability of Dissipative Solitons in a Dual-Waveguide Lattice with Linear Gain and Nonlinear Losses

In this study, we investigate the existence and stability of in-phase and out-of-phase dissipative solitons in a dual-waveguide lattice with linear localized gain and nonlinear losses under both focusing and defocusing nonlinearities. Numerical results reveal that both types of dissipative solitons bifurcate from the linear amplified modes, and their nonlinear propagation constant changes to a real value when nonlinearity, linear localized gain, and nonlinear losses coexist. We find that increasing the linear gain coefficient leads to an increase in the power and propagation constant of both types of dissipative solitons. For defocusing nonlinearity, in-phase solitons are stable across their entire existence region, while focusing nonlinearity confines them to a small stable region near the lower cutoff value in the propagation constant. In contrast, out-of-phase solitons have a significantly larger stable region under focusing nonlinearity compared to defocusing nonlinearity. The stability regions of both types of dissipative solitons increase with increasing nonlinear losses coefficient. Additionally, we validate the results of linear stability analysis for dissipative solitons using propagation simulations, showing perfect agreement between the two methods.

physics.optics↗