arXiv subjects

Y. Liao

Publications and source records attributed to Y. Liao.

10 recordsLinked to original sources

arXiv2026

3D Imaging of Complex Skyrmion and Hopf Topologies in an Extended Sample

Spin textures are key for emergent magnetic phenomena such as topological protection and underpin novel spintronic device paradigms based on racetrack memory, logic gates, and neuromorphic computing. Using a coherent diffractive imaging technique called vector ptycho-tomography, in combination with algorithms that are robust to noise, we image the 3D magnetic texture of skyrmion and Hopf topologies with no prior assumptions about the sample. This directly reveals experimentally for the first time an extended 3D skyrmion lattice, including the domain wall shape, topological charge, helicity, and Hopf index. Our findings demonstrate experimentally that dipole stabilized skyrmions in Fe/Gd multilayers exhibit barrel-shaped skyrmion tubes with a twisted helicity, transitioning from N$\'e$el-type winding at the surfaces to both clockwise and counterclockwise Bloch-type winding in the bulk, that can also be described as fractional hopfions. We image a lattice of 24 skyrmions with topological charge 1, average depth-dependent domain wall width of 23 to 40 nm, depth-dependent twisted helicity from $\pm$155$\deg$ to $\pm$30$\deg$, and fractional Hopf index of $\pm$0.3. Over 10 TB of data were analyzed to yield a fully-resolved 3D reconstruction over a >0.4 $\mu$m$^3$ volume, with high fidelity down to the Nyquist limit of 8 nm. This method fills a key gap in the current landscape of magnetic imaging by enabling high-resolution, element-specific 3D reconstructions of full-field extended spin textures - offering a new route for exploring the topological complexity of magnetic materials in three dimensions.

cond-mat.mtrl-sci↗

arXiv2025

The calibration house in JUNO

As an auxiliary system within the calibration system of the Jiangmen Underground Neutrino Observatory, a calibration house is designed to provide interfaces for connecting the central detector and accommodating various calibration sub-systems. Onsite installation has demonstrated that the calibration house interfaces are capable of effectively connecting to the central detector and supporting the installation of complex and sophisticated calibration sub-systems. Additionally, controlling the levels of radon and oxygen within the calibration house is critical. Radon can increase the experimental background, while oxygen can degrade the quality of the liquid scintillator. The oxygen concentration can be maintained at levels below 10 parts per million, and the radon concentration can be kept below 15 mBq/m$^{3}$. This paper will provide detailed information on the calibration house and its methods for radon and oxygen concentration control.

physics.ins-det↗

arXiv2024

Quantum degeneracy in mesoscopic matter: Casimir effect and Bose-Einstein condensation

The ground-state phonon pressure is an analogue to the famous Casimir pressure of vacuum produced by zero-point photons. The acoustic Casimir forces are, however, many orders of magnitude weaker than the electromagnetic Casimir forces, as the typical speed of sound is 100 000 times smaller than the speed of light. Because of its weakness, zero-point acoustic Casimir pressure was never observed, although the pressure of artificially introduced sound noise on a narrow aperture has been reported. However, the magnitude of Casimir pressure increases as $1/L^3$ with the decrease of the sample size $L$, and reaches picoNewtons in the sub-micron scales. We demonstrate and measure the acoustic Casimir pressure induced by zero-point phonons in solid helium adsorbed on a carbon nanotube. We have also observed Casimir-like "pushing out" thermal phonons with the decreasing temperature or the length. We also show that all thermodynamic quantities are size-dependent, and therefore in the mesoscopic range $L\lesssim\hbar{c}/(k_BT)$ quadruple points are possible on the phase diagram where four different phases coexist. Due to the smallness of solid helium sample, temperature of Bose-Einstein condensation (BEC) of vacancies is relatively high, $10-100$ mK. This allowed us to experimentally discover the BEC in a system of zero-point vacancies, predicted more than 50 years ago.

cond-mat.mes-hall↗

arXiv2024

SEDAC: A CVAE-Based Data Augmentation Method for Security Bug Report Identification

Bug tracking systems store many bug reports, some of which are related to security. Identifying those security bug reports (SBRs) may help us predict some security-related bugs and solve security issues promptly so that the project can avoid threats and attacks. However, in the real world, the ratio of security bug reports is severely low; thus, directly training a prediction model with raw data may result in inaccurate results. Faced with the massive challenge of data imbalance, many researchers in the past have attempted to use text filtering or clustering methods to minimize the proportion of non-security bug reports (NSBRs) or apply oversampling methods to synthesize SBRs to make the dataset as balanced as possible. Nevertheless, there are still two challenges to those methods: 1) They ignore long-distance contextual information. 2) They fail to generate an utterly balanced dataset. To tackle these two challenges, we propose SEDAC, a new SBR identification method that generates similar bug report vectors to solve data imbalance problems and accurately detect security bug reports. Unlike previous studies, it first converts bug reports into individual bug report vectors with distilBERT, which are based on word2vec. Then, it trains a generative model through conditional variational auto-encoder (CVAE) to generate similar vectors with security labels, which makes the number of SBRs equal to NSBRs'. Finally, balanced data are used to train a security bug report classifier. To evaluate the effectiveness of our framework, we conduct it on 45,940 bug reports from Chromium and four Apache projects. The experimental results show that SEDAC outperforms all the baselines in g-measure with improvements of around 14.24%-50.10%.

cs.CR↗

arXiv2020

A Deep Learning Framework for Assessing Physical Rehabilitation Exercises

Computer-aided assessment of physical rehabilitation entails evaluation of patient performance in completing prescribed rehabilitation exercises, based on processing movement data captured with a sensory system. Despite the essential role of rehabilitation assessment toward improved patient outcomes and reduced healthcare costs, existing approaches lack versatility, robustness, and practical relevance. In this paper, we propose a deep learning-based framework for automated assessment of the quality of physical rehabilitation exercises. The main components of the framework are metrics for quantifying movement performance, scoring functions for mapping the performance metrics into numerical scores of movement quality, and deep neural network models for generating quality scores of input movements via supervised learning. The proposed performance metric is defined based on the log-likelihood of a Gaussian mixture model, and encodes low-dimensional data representation obtained with a deep autoencoder network. The proposed deep spatio-temporal neural network arranges data into temporal pyramids, and exploits the spatial characteristics of human movements by using sub-networks to process joint displacements of individual body parts. The presented framework is validated using a dataset of ten rehabilitation exercises. The significance of this work is that it is the first that implements deep neural networks for assessment of rehabilitation performance.

cs.LG↗

arXiv2019

Characterization of 30 $^{76}$Ge enriched Broad Energy Ge detectors for GERDA Phase II

The GERmanium Detector Array (GERDA) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double beta decay of $^{76}$Ge into $^{76}$Se+2e$^-$. GERDA has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new Ge detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the HADES underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for GERDA Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the strength of pulse shape simulation codes.

physics.ins-det↗

arXiv2014

Formal Semantic Annotations for Models Interoperability in a PLM environment

Nowadays, the need for system interoperability in or across enterprises has become more and more ubiquitous. Lots of research works have been carried out in the information exchange, transformation, discovery and reuse. One of the main challenges in these researches is to overcome the semantic heterogeneity between enterprise applications along the lifecycle of a product. As a possible solution to assist the semantic interoperability, semantic annotation has gained more and more attentions and is widely used in different domains. In this paper, based on the investigation of the context and the related works, we identify some existing drawbacks and propose a formal semantic annotation approach to support the semantics enrichment of models in a PLM environment.

cs.SE↗

arXiv2004

H/A Higgs Mixing in CP-Noninvariant Supersymmetric Theories

For large masses, the two heavy neutral Higgs bosons are nearly degenerate in many 2--Higgs doublet models, and particularly in supersymmetric models. In such a scenario the mixing between the states can be very large if the theory is CP-noninvariant. We analyze the formalism describing this configuration, and we point to some interesting experimental consequences.

hep-ph↗

arXiv2000

Higgs radiation off quarks in supersymmetric theories at e^+e^- colliders

Yukawa couplings between Higgs bosons and quarks in supersymmetric theories can be measured in the processes e^+e^- -> Q Qbar + Higgs. We have determined the cross sections of these processes in the minimal supersymmetric model including the complete set of next-to-leading order QCD corrections for all channels.

hep-ph↗

arXiv1998

Higgs Radiation off Top Quarks in e^+e^- Collisions

The strength of the Yukawa coupling of the leptons and quarks with the Higgs boson is uniquely determined by the Higgs mechanism for generating masses in the Standard Model. The top-Higgs coupling can be measured directly in the process e^+e^- --> t tbar H. This process therefore provides a fundamental test of the Higgs mechanism. Extending earlier analyses carried out in the Born approximation, we have determined the cross section for this process including QCD corrections, which turn out to be important.

hep-ph↗