arXiv subjects

Xiaolong Yang

Publications and source records attributed to Xiaolong Yang.

At least 37 records · Page 2Linked to original sources

arXiv2026

A Privacy-Preserving Localization Scheme with Node Selection in Mobile Networks

Localization in mobile networks has been widely applied in many scenarios. However, an entity responsible for location estimation exposes both the target and anchors to potential location leakage at any time, creating serious security risks. Although existing studies have proposed privacy-preserving localization algorithms, they still face challenges of insufficient positioning accuracy and excessive communication overhead. In this article, we propose a privacy-preserving localization scheme, named PPLZN. PPLZN protects protects the location privacy of both the target and anchor nodes in crowdsourced localization. Simulation results validate the effectiveness of PPLZN. Evidently, it can achieve accurate position estimation without location leakage and outperform state-of-the-art approaches in both positioning accuracy and communication overhead. In addition, PPLZN significantly reduces computational and communication overhead in large-scale deployments, making it well-fitted for practical privacy-preserving localization in resource-constrained networks.

cs.CR↗

arXiv2025

Jet reorientation revealed by intermittent jet activity in radio galaxy 0954+556

Intermittent jet activity of AGNs is a common phenomenon, whereas significant jet reorientation during episodic jet activity in relatively young radio galaxies are rarely reported. The quasar 0954+556 at redshift of 0.903 is an intriguing source exhibiting an unusual radio jet structure with significantly different jet directions at kpc and pc scales. At kpc scales, images from the VLA exhibit a bright core, a linear jet extending 24 kpc to the northwest, and a discrete jet component 16 kpc to the northeast. At pc scales, images from the VLBA show a two-component structure with a projected separation of 360 pc in the north-south direction. The peculiar structure of 0954+556 might result from jet reorientation. Here, our aim was to investigate the possible mechanism via multiscale and multifrequency deep radio images. We performed VLA and VLBA observations of 0954+556. Together with some existing data in the NRAO data archive, we made multiple VLA images at 1.4-22 GHz and VLBA images at 1.7-43 GHz for various image analyses of the jet structure. We identified the location of the radio core at pc scales, detected the faint counter-jets at both pc and kpc scales for the first time, and revealed a diffuse emission region connecting pc and kpc scale forward jets. Our spectral index distribution and spectral aging analysis indicate that 0954+556 might undergo at least two episodes of jet activity during the current AGN phase. Moreover, pc scale polarization maps display a well-resolved spine-sheath polarization structure. It seems that the jet direction of 0954+556 changed significantly during intermittent jet activity. This may explain the different jet orientations and spectral ages observed from kpc to pc scales. The research provides a strong case that AGN jet direction might change rapidly on timescales of one million years.

astro-ph.HE↗

arXiv2025

Phonon-Dominated Thermal Transport and Large Violation of the Wiedemann-Franz Law in Topological Semimetal CoSi

The Wiedemann-Franz (WF) law, relating the electronic thermal conductivity ($κ_{\rm e}$) to the electrical conductivity, is vital in numerous applications such as in the design of thermoelectric materials and in the experimental determination of the lattice thermal conductivity ($κ_{\rm L}$). While the WF law is generally robust, violations are frequently observed, typically manifesting in a reduced Lorenz number ($L$) relative to the Sommerfeld value ($L_0$) due to inelastic scattering. Here, we report a pronounced departure from the WF law in the topological semimetal CoSi, where the electronic Lorenz number ($L_{\rm e}$) instead rises up to $\sim40\%$ above $L_0$. We demonstrate that this anomaly arises from strong bipolar diffusive transport, enabled by topological band-induced electron-hole compensation, which allows electrons and holes to flow cooperatively and additively enhance the heat current. Concurrently, we unveil that the lattice contribution to thermal conductivity is anomalously large and becomes the dominant component below room temperature. As a result, if $κ_{\rm L}$ is assumed negligible -- as conventional in metals, the resulting $L$ from the total thermal conductivity ($κ_{\rm tot}=κ_{\rm L}+κ_{\rm e}$) deviates from $L_0$ by more than a factor of three. Our work provides deeper insight into the unconventional thermal transport physics in topological semimetals.

cond-mat.mtrl-sci↗

arXiv2025

Anharmonicity-driven phonon avoided crossing and anomalous thermal transport in nodal-line semimetal ZrSiS

Understanding thermal and electrical transport in topological materials is essential for advancing their applications in quantum technologies and energy conversion. Herein, we employ first-principles calculations to systematically investigate phonon and charge transport in the prototypical nodal-line semimetal ZrSiS. The results unveil that anharmonic phonon renormalization results in the pronounced softening of heat-carrying phonons and suppressed lattice thermal conductivity ($κ_{\rm L}$). Crucially, anharmonic effects are found to noticeably weaken Zr-S interactions, triggering avoided-crossing behavior of low-frequency optical phonons. The combination of phonon softening and avoided crossing synergistically reduces phonon group velocities, yielding a 16\% suppression in $κ_{\rm L}$ along the $c$-axis at room temperature. Contrary to conventional metals, we discover that the lattice contribution to thermal conductivity in ZrSiS is abnormally large, even dominating heat conduction along the $c$-axis. This unusual behavior results in a substantial deviation of the Lorenz number from the Sommerfeld value -- exceeding it by up to threefold -- thereby challenging the validation of standard Wiedemann-Franz law for thermal conductivity estimation. Moreover, our calculations demonstrate that ZrSiS exhibits exceptional electrical conductivity, attributed to its topological electronic Dirac states that account for both high Fermi velocities and weak electron-phonon coupling. This study provides critical insights into the electrical and thermal transport mechanisms in ZrSiS and highlights the importance of anharmonic effects in the lattice dynamics and thermal transport of metallic materials.

cond-mat.mtrl-sci↗

arXiv2025

PEEL: A Poisoning-Exposing Encoding Theoretical Framework for Local Differential Privacy

Local Differential Privacy (LDP) is a widely adopted privacy-protection model in the Internet of Things (IoT) due to its lightweight, decentralized, and scalable nature. However, it is vulnerable to poisoning attacks, and existing defenses either incur prohibitive resource overheads or rely on domain-specific prior knowledge, limiting their practical deployment. To address these limitations, we propose PEEL, a Poisoning-Exposing Encoding theoretical framework for LDP, which departs from resource- or prior-dependent countermeasures and instead leverages the inherent structural consistency of LDP-perturbed data. As a non-intrusive post-processing module, PEEL amplifies stealthy poisoning effects by re-encoding LDP-perturbed data via sparsification, normalization, and low-rank projection, thereby revealing both output and rule poisoning attacks through structural inconsistencies in the reconstructed space. Theoretical analysis proves that PEEL, integrated with LDP, retains unbiasedness and statistical accuracy, while being robust to expose both output and rule poisoning attacks. Moreover, evaluation results show that LDP-integrated PEEL not only outperforms four state-of-the-art defenses in terms of poisoning exposure accuracy but also significantly reduces client-side computational costs, making it highly suitable for large-scale IoT deployments.

cs.CR↗

arXiv2025

From Quarter to All: Accelerating Speculative LLM Decoding via Floating-Point Exponent Remapping and Parameter Sharing

Large language models achieve impressive performance across diverse tasks but exhibit high inference latency due to their large parameter sizes. While quantization reduces model size, it often leads to performance degradation compared to the full model. Speculative decoding remains lossless but typically incurs extra overheads. We propose SPEQ, an algorithm-hardware co-designed speculative decoding method that uses part of the full-model weight bits to form a quantized draft model, thereby eliminating additional training or storage overhead. A reconfigurable processing element array enables efficient execution of both the draft and verification passes. Experimental results across 15 LLMs and tasks demonstrate that SPEQ achieves speedups of 2.07x, 1.53x, and 1.45x compared over FP16, Olive, and Tender, respectively.

cs.AR↗

arXiv2025

MoBiLE: Efficient Mixture-of-Experts Inference on Consumer GPU with Mixture of Big Little Experts

Mixture-of-Experts (MoE) models have recently demonstrated exceptional performance across a diverse range of applications. The principle of sparse activation in MoE models facilitates an offloading strategy, wherein active experts are maintained in GPU HBM, while inactive experts are stored in CPU DRAM. The efficacy of this approach, however, is fundamentally constrained by the limited bandwidth of the CPU-GPU interconnect. To mitigate this bottleneck, existing approaches have employed prefetching to accelerate MoE inference. These methods attempt to predict and prefetch the required experts using specially trained modules. Nevertheless, such techniques are often encumbered by significant training overhead and have shown diminished effectiveness on recent MoE models with fine-grained expert segmentation. In this paper, we propose MoBiLE, a plug-and-play offloading-based MoE inference framework with \textit{mixture of big-little experts}. It reduces the number of experts for unimportant tokens to half for acceleration while maintaining full experts for important tokens to guarantee model quality. Further, a dedicated fallback and prefetching mechanism is designed for switching between little and big experts to improve memory efficiency. We evaluate MoBiLE on four typical modern MoE architectures and challenging generative tasks. Our results show that MoBiLE achieves a speedup of 1.60x to 1.72x compared to the baseline on a consumer GPU system, with negligible degradation in accuracy.

cs.CL↗

arXiv2025

Impact of Thermal Effects on the Current-Tunable Electrical Transport in the Ferrimagnetic Semiconductor Mn$_3$Si$_2$Te$_6$

In the ferrimagnetic semiconductor Mn$_3$Si$_2$Te$_6$, a colossal magnetoresistance (CMR) is observed only when a magnetic field is applied along the magnetic hard axis ($\mathbf{H}\parallel c$). This phenomenon suggests an unconventional CMR mechanism potentially driven by the interplay between magnetism, topological band structure, and/or chiral orbital currents (COC). By comparing electrical resistance measurements using continuous direct currents and pulse currents, we found that the current-induced insulator-metal transition, supporting the COC-driven CMR mechanism, is likely a consequence of Joule heating effects. First-principles calculations reveal a pronounced band gap reduction upon tilting the magnetic moments toward the $c$-axis, accompanied by increased carrier concentration and Fermi velocity. Combining spin orientation-dependent electronic structure with Boltzmann transport theory, the calculated electrical resistance closely reproduces the CMR observed experimentally. These findings suggest that the CMR in Mn$_3$Si$_2$Te$_6$ stems primarily from band gap reduction induced by partial polarization of magnetic moments along the magnetic hard axis.

cond-mat.mtrl-sci↗

arXiv2025

Lunar Orbital VLBI Experiment: motivation, scientific purposes and status

The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang'E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 2024 March 20, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequency standard, and VLBI data formatting and acquisition electronics. Several components of the QueQiao-2 nominal onboard instrumentation, such as the 4.2-meter antenna, the data storage device, and the downlink communication system, contribute to the overall spaceborne VLBI instrumentation. This allows us to form a space radio telescope capable of co-observing with Earth-based radio telescopes in VLBI mode. In this space VLBI system, the length of the baseline extends up to approximately 380,000 km. This paper presents the LOVEX scientific objectives, architecture, instrumentation, pre-launch tests, in-flight verification and calibration, and the first in-flight detections of interferometric response (''fringes'') achieved through observations of the quasar AO 0235+164 and the Chang'E-6 orbital module, positioned at the Sun-Earth Lagrange point L2. These initial results demonstrate the successful performance of LOVEX, verifying its capability for both astronomical and spacecraft tracking observations at ultra-long VLBI baselines.

astro-ph.IM↗

arXiv2025

Symmetry-breaking strain drives significant reduction in lattice thermal conductivity: A case study of boron arsenide

Recent research has revealed that cubic boron arsenide (BAs) exhibits a non-monotonic pressure dependence of lattice thermal conductivity ($κ_{\rm L}$) under isotropic strain. Here, through rigorous first-principles calculations, we unveil that uniaxial tensile strain induces a monotonic reduction in the $κ_{\rm L}$ of BAs -- a striking contrast to the isotropic scenario. The results show that applying uniaxial (100) strain leads to the lifting of phonon band degeneracy, accompanied by an overall softening of the phonon spectrum. These modifications significantly increase phonon-phonon scattering channels by facilitating the fulfillment of selection rules, resulting in a concurrent increase in both three- and four-phonon scattering rates. Consequently, $κ_{\rm L}$ exhibits a dramatic suppression of nearly 80\% under large tension at room temperature. Meanwhile, we unexpectedly observe that the uniaxial strain suppresses $κ_{\rm L}$ much more strongly in the direction perpendicular to the strain than along the stretching direction. This work establishes the fundamental understanding of the thermal conductivity behavior of BAs under uniaxial strain and opens a promising avenue for manipulating solid-state heat transport by tuning crystal symmetry.

cond-mat.mtrl-sci↗

arXiv2025

Electrochemistry-Enhanced Dynamic Paths Sampling Unveiling Nuclear Quantum Effects in Electrocatalysis

Proton-coupled electron transfers (PCET) are elementary steps in electrocatalysis. However, accurate calculations of PCET rates remain challenging, especially considering nuclear quantum effects (NQEs) under a constant potential condition. Statistical sampling of reaction paths is an ideal approach for rate calculations, however, is always limited by the rare-event issue. Here we develop an electrochemistry-driven quantum dynamics approach enabling realistic enhanced paths sampling under constant potentials without a priori defined reaction coordinates. We apply the method in modeling the Volmer step of the hydrogen evolution reaction, and demonstrate that the NQEs exhibit more than one order of magnitude impact on the computed rate constant, indicating an essential role of NQEs in electrochemistry.

physics.chem-ph↗

arXiv2025

Single-dislocation phonons: atomic-scale measurement and their thermal properties

Nanoscale defects such as dislocations, have a significant impact on the phonon thermal transport properties in non-metallic materials. To unravel these effects, understanding of defect phonon modes is essential. Herein, at the atomic scale, the localized phonons of individual dislocation at a Si/Ge interface are measured via monochromated electron energy loss spectroscopy in a scanning transmission electron microscope. These modes are then correlated with the local microstructure, further revealing the dislocation effects on the local thermal transport properties. The dislocation causes phonon redshift in several milli-electron-volts within about two to four nanometers of the core, where both of the strain field and Ge-segregation play roles. With the presence of dislocation, the local interfacial thermal conductance can be either enhanced or reduced, depending on the complex interaction and competition between lattice-disorder (dislocation) and element-disorder (heterointerface mixing and Ge-segregation) at the interface. These findings provide valuable insights to improve the thermal properties of thermoelectric generators and thermal management systems through proper defect engineering.

cond-mat.mtrl-sci↗

arXiv2025

PoisonCatcher: Revealing and Identifying LDP Poisoning Attacks in IIoT

Local Differential Privacy (LDP), a robust privacy-protection model, is widely adopted in the Industrial Internet of Things (IIoT) due to its lightweight, decentralized, and scalable. However, its perturbation-based privacy-protection mechanism hinders distinguishing between any two data, thereby facilitating LDP poisoning attacks. The exposed physical-layer vulnerabilities and resource-constrained prevalent at the IIoT edge not only facilitate such attacks but also render existing LDP poisoning defenses, all of which are deployed at the edge and rely on ample resources, impractical. This work proposes a LDP poisoning defense for IIoT in the resource-rich aggregator. We first reveal key poisoning attack modes occurring within the LDP-utilized IIoT data-collection process, detailing how IIoT vulnerabilities enable attacks, and then formulate a general attack model and derive the poisoned data's indistinguishability. This work subsequently analyzes the poisoning impacts on aggregated data based on industrial process correlation, revealing the distortion of statistical query results' temporal similarity and the resulting disruption of inter-attribute correlation, and uncovering the intriguing paradox that adversaries' attempts to stabilize their poisoning actions for stealth are difficult to maintain. Given these findings, we propose PoisonCatcher, a solution for identifying poisoned data, which includes time-series detectors based on temporal similarity, attribute correlation, and pattern stability metrics to detect poisoned attributes, and a latent-bias feature miner for identifying poisons. Experiments on the real-world dataset indicate that PoisonCatcher successfully identifies poisoned data, demonstrating robust identification capabilities with F2 scores above 90.7\% under various attack settings.

cs.CR↗

arXiv2025

Identification of 4876 Bent-Tail Radio Galaxies in the FIRST Survey Using Deep Learning Combined with Visual Inspection

Bent-tail radio galaxies (BTRGs) are characterized by bent radio lobes. This unique shape is mainly caused by the movement of the galaxy within a cluster, during which the radio jets are deflected by the intra-cluster medium. A combined method, which involves a deep learning-based radio source finder along with visual inspection, has been utilized to search for BTRGs from the Faint Images of the Radio Sky at Twenty-centimeters survey images. Consequently, a catalog of 4876 BTRGs has been constructed, among which 3871 are newly discovered. Based on the classification scheme of the opening angle between the two jets of the galaxy, BTRGs are typically classified as either wide-angle-tail (WAT) sources or narrow-angle-tail (NAT) sources. Our catalog comprises 4424 WATs and 652 NATs. Among these, optical counterparts are identified for 4193 BTRGs. This catalog covers luminosities in the range of $1.91\times10^{20} \leq L_{\rm 1.4\,GHz} \leq 1.45\times10^{28}$ ${\rm W\,Hz^{-1}}$ and redshifts from $z = 0.0023$ to $z = 3.43$. Various physical properties of these BTRGs and their statistics are presented. Particularly, by the nearest neighbor method, we found that 1825 BTRGs in this catalog belong to galaxy clusters reported in literature.

astro-ph.GA↗

arXiv2025

Anomalous Magnetotransport in the Paramagnetic State of a Magnetic Kagome Metal EuTi$_3$Bi$_4$

We investigate the electrical transport properties of a magnetic kagome metal EuTi$_3$Bi$_4$, which undergoes magnetic ordering below $T_\mathrm{c}=10.5$ K. Unlike typical magnets showing anomalous magnetotransport in their ordered states, EuTi$_3$Bi$_4$ exhibits unusual magnetotransport behaviors in its paramagnetic phase. Specifically, the magnetoconductivity shows a linear dependence on magnetic field at low fields below $\sim 1$ T, and the Hall conductivity undergoes a sign change below about 2 T. These behaviors resemble those observed in the charge density wave (CDW) phase of kagome metals $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs). The anomalous magnetotransport in $A$V$_3$Sb$_5$ has commonly been attributed to the possible emergence of a time-reversal symmetry breaking chiral CDW order. However, given the absence of CDW in EuTi$_3$Bi$_4$ and its manifestation exclusively in the paramagnetic state, the anomalous magnetotransport observed in EuTi$_3$Bi$_4$ is likely associated with multiband transport and/or the van Hove singularities near the Fermi level.

cond-mat.str-el↗

arXiv2024

Late-time radio brightening and emergence of a radio jet in the changing-look AGN 1ES 1927+654

We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN after an optical outburst in late 2017 and has since displayed considerable changes in X-ray emission, including the destruction and rebuilding of the X-ray corona in 2019-2020. Radio observations prior to 2023 show a faint and compact radio source typical of radio-quiet AGN. Starting in February 2023, 1ES 1927+654 began exhibiting a radio flare with a steep exponential rise, reaching a peak 60 times previous flux levels, and has maintained this higher level of radio emission for over a year to date. The 5-23 GHz spectrum is broadly similar to gigahertz-peaked radio sources, which are understood to be young radio jets less than ~1000 years old. Recent high-resolution VLBA observations at 23.5 GHz now show resolved extensions on either side of the core, with a separation of ~0.15 pc, consistent with a new and mildly relativistic bipolar outflow. A steady increase in the soft X-ray band (0.3-2 keV) concurrent with the radio may be consistent with jet-driven shocked gas, though further observations are needed to test alternate scenarios. This source joins a growing number of CL-AGN and tidal disruption events which show late-time radio activity, years after the initial outburst.

astro-ph.HE↗

arXiv2024

A Machine-Learning Accelerated Grand Canonical Sampling Framework for Nuclear Quantum Effects in Constant Potential Electrochemistry

Proton-coupled electron transfer (PCET) is the key step for energy conversion in electrocatalysis. Atomic-scale simulation acts as an indispensable tool to provide a microscopic understanding of PCET. However, consideration of the quantum nature of transferring protons under an exact grand canonical (GC) constant potential condition is a great challenge for theoretical electrocatalysis. Here, we develop a unified computational framework to explicitly treat nuclear quantum effects (NQEs) by a sufficient GC sampling, further assisted by a machine learning force field adapted for electrochemical conditions. Our work demonstrates a non-negligible impact of NQEs on PCET simulations for hydrogen evolution reaction at room temperature, and provides a physical picture that wave-like quantum characteristic of the transferring protons facilitates the particles to tunnel through classical barriers in PCET paths, leading to a remarkable activation energy reduction compared to classical simulations. Moreover, the physical insight of NQEs may reshape our fundamental understanding of other types of PCET reactions in broader scenarios of energy conversion processes.

cond-mat.mtrl-sci↗

arXiv2024

Listening for echo from the stimulated axion decay with the 21 CentiMeter Array

The axion is a hypothetical elementary particle that could solve the long-standing strong CP problem in particle physics and the dark matter mystery in the cosmos. Due to the stimulation of the ambient photons, the axion dark matter decay into photons is significantly enhanced so that its echo signal could be detected by terrestrial telescopes. As a pathfinder, we study the expected sensitivity of searching for the axion dark matter in the mass range between $0.41$ and $1.6μ\text{eV}$ with the 21 CentiMeter Array (21CMA). We aim to cover the whole 21CMA frequency range in two years by using a 1MW emitter. We find that the resulting sensitivity on the axion-photon coupling could surpass other existing limits by about one order of magnitude.

hep-ph↗