arXiv subjects

Shuai Yao

Publications and source records attributed to Shuai Yao.

18 recordsLinked to original sources

arXiv2026

Pulsed heterodyne detection enables fiber-compatible, high-specificity Brillouin biomechanics in intact tissue and the living brain

Brillouin microscopy provides label-free, three-dimensional mechanical characterization of biological specimens, but current dispersive detection imposes two limits: the fiber background folds onto the sample spectrum, precluding single-fiber operation, and a ~250 MHz dispersion-induced instrumental broadening blurs mechanically distinct components within a focal volume. Here, we introduce pulsed heterodyne Brillouin detection (PHBD), which retrieves the spectrum electronically from temporal beat notes, overcoming both limitations. The fiber background beats outside the detection band and is rejected; elimination of dispersive broadening yields 25-MHz spectrometer resolution. Pulsed excitation reaches Brillouin-signal-shot-noise-limited detection, attaining 9.0-MHz shift precision in 3 ms at 30 mW in water with 53-fold improvement in energy efficiency over continuous-wave excitation. Through a bare 125-um fiber, PHBD resolves regional contrast along a 4-mm insertion track in the living mouse brain; in free space, it resolves distinct Brillouin components from the cell wall and adjacent cytoplasm in strongly scattering Arabidopsis root tips with epi-mode.

physics.optics↗

arXiv2026

Quasi-stationary Slice Detection-Based Robust Respiration Rate Estimation under Large-scale Random Body Movement

Radar-based non-contact respiration rate (RR) measurement has become increasingly popular due to its convenience, non-intrusiveness, and low cost. However, it is still quite challenging to accurately acquire vital signs estimation in complex measurement scenarios with large-scale random body movements (RBM), particularly for RR estimation due to strong low-frequency interferences. To cope with the RBM challenge in RR estimation, we propose a novel two-stage RR estimation scheme involving detecting the portion of signals, called as quasi-stationary slices, exhibiting the quasi-stationary pattern. At the detection stage, an enhanced deep neural network framework incorporating the dynamic snake convolution is exploited to detect the quasi-stationary slices in the micro-Doppler spectra. At the estimation stage, we mitigate RBM interferences and achieve accurate RR estimation by only using the portion of ridges consistent with the location of detected quasi-stationary slice. Extensive experimental results demonstrate that our proposed scheme can accurately detect quasi-stationary slices under normal scenarios with large-scale RBM, thereby reducing the error of subsequent RR estimation.

eess.SP↗

arXiv2026

Yet Even Less Is Even Better For Agentic, Reasoning, and Coding LLMs

Training effective software engineering agents requires large volumes of task-specific trajectories, incurring substantial data construction costs. Inspired by the "Less-Is-More" hypothesis in mathematical reasoning, we investigate its extension to agentic scenarios and propose an end-to-end training framework that achieves superior agentic capabilities with fewer but higher-quality training trajectories. This is achieved via STITCH (Sliding-memory Trajectory Inference and Task Chunking Heuristic), a coarse-to-fine mechanism that filters low-value noise and retains decision-critical tokens to maximize training signal quality. We conduct experiments across multiple agent frameworks (e.g., mini-SWE-agent, MSWE-agent), model scales (30B to 355B), and multilingual settings (Python, Java, and ArkTS). On SWE-bench Verified, models trained with STITCH achieve up to 63.16% relative improvement over base models. On Multi-SWE-bench (Java), MiniMax-M2.5-STITCH achieves 43.75% with our CodeArts Agent scaffold (+16.67%). On HarmonyOS (ArkTS), GLM-4.7-STITCH improves the compilation pass rate to 61.31% (+43.34%) with less than 1K training trajectories. Our results confirm that the "Less-Is-More" paradigm generalizes effectively to complex agentic tasks across diverse languages and model scales.

cs.SE↗

arXiv2026

mmWave-Diffusion:A Novel Framework for Respiration Sensing Using Observation-Anchored Conditional Diffusion Model

Millimeter-wave (mmWave) radar enables contactless respiratory sensing,yet fine-grained monitoring is often degraded by nonstationary interference from body micromotions.To achieve micromotion interference removal,we propose mmWave-Diffusion,an observation-anchored conditional diffusion framework that directly models the residual between radar phase observations and the respiratory ground truth,and initializes sampling within an observation-consistent neighborhood rather than from Gaussian noise-thereby aligning the generative process with the measurement physics and reducing inference overhead. The accompanying Radar Diffusion Transformer (RDT) is explicitly conditioned on phase observations, enforces strict one-to-one temporal alignment via patch-level dual positional encodings, and injects local physical priors through banded-mask multi-head cross-attention, enabling robust denoising and interference removal in just 20 reverse steps. Evaluated on 13.25 hours of synchronized radar-respiration data, mmWave-Diffusion achieves state-of-the-art waveform reconstruction and respiratory-rate estimation with strong generalization. Code repository:https://github.com/goodluckyongw/mmWave-Diffusion.

eess.IV↗

arXiv2026

Impact of refractive index heterogeneity on stimulated Brillouin scattering microscopy: a quantitative analysis

Stimulated Brillouin scattering (SBS) microscopy enables label-free biomechanical imaging, with Brillouin gain serving as a critical contrast parameter for quantitative analysis. However, the influence of sample-induced refractive index (RI) heterogeneity on gain measurements remains poorly understood. Here, we quantitatively investigate, how RI mismatch affects SBS microscopy using finite element simulations and experiments on a phantom sample comprising polydimethylsiloxane beads embedded in agarose gel. We demonstrate that RI heterogeneity induces focal field distortion that reduce pump-probe beam overlap, resulting in attenuated Brillouin gain and degraded shift precision at material interfaces. Crucially, we establish that fiber-coupling efficiency, commonly used for system alignment, cannot serve as a linear proxy for Brillouin gain due to its heightened sensitivity to focal field distortion.

physics.optics↗

arXiv2026

Uniqueness of Ground State Solutions for a Defocusing Hartree Equation via Inverse Optimal Problems

We study a generalized defocusing Hartree equation with nonlocal exchange potential and repulsive Hartree--Fock interaction. Using an inverse optimal problem (IOP) approach, we prove the existence and uniqueness of ground state solutions. Additionally, we establish the existence of principal solutions, their continuous dependence on parameters, and a dual variational formulation. The IOP method provides a systematic framework for addressing inverse problems in nonlocal Schrödinger operators and offers new insights into the structure of solutions for defocusing Hartree-type equations.

math.AP↗

arXiv2025

On planar Schrodinger-Poisson systems with repulsive interactions in the mass supercritical regime

In this paper, we investigate solutions with prescribed $L^{2}$-norm (i.e., prescribed mass) for the planar Schrödinger-Poisson (SP) equation% \begin{equation*} -Δu+λu+α\left( \log |\cdot |\ast |u|^{2}\right) u=|u|^{p-2}u,\ \text{in}\ Ω_{R} , \end{equation*}% where $λ\in \mathbb{R}$ is unknown, $α<0,p>4$ and $Ω_{R} \subseteq \mathbb{R}^{2}$ is a domain. First, we prove that the energy functional $J$ corresponding to the SP equation in $\mathbb{R}^{2}$ is unbounded both above and below on the Pohozaev manifold $\mathcal{P}$; this explains the reason why the minimax level of $J$ is difficult to determine, as referenced in [Cingolani and Jeanjean, SIAM J. Math. Anal., 2019]. Second, we establish the existence of a ground state and a high-energy solution, both with positive energy in a large bounded domain $Ω_{R} $, which is a substantial advancement in addressing an open problem proposed in [Cingolani and Jeanjean, SIAM J. Math. Anal., 2019]. Finally, we analyze the asymptotic behavior of solutions as the domain $Ω_{R} $ is extended to the entire space $\mathbb{R}^{2}$.

math.AP↗

arXiv2025

Normalized solutions for the NLS equation with potential in higher dimension: the purely Sobolev critical case

We study normalized solutions for the nonlinear Schrodinger (NLS) equation with potential and Sobolev critical nonlinearity. By establishing suitable assumptions on the potential, together with new techniques, we find a mountain-pass type solution for N>=6, which solves an open problem presented in a recent paper [Verzini and Yu, arXiv:2505.05357v1]. Moreover, we also find a local minimizer with negative energy for N>=3, which improves the results in [Verzini and Yu, arXiv:2505.05357v1].

math.AP↗

arXiv2025

Three bound states with prescribed angular momentum to the cubic-quintic NLS equations in $\mathbb{R}^{3}$

In this paper, we investigate bound states with prescribed angular momentum and mass for the nonlinear Schrödinger equations (NLS) with the cubic-quintic nonlinearity in dimensions three. We demonstrate that there exist three solutions for the double constrained problem: a local minimizer, a mountain pass type solution, and a global minimizer. Moreover, by means of the minimax method, we construct a new mountain pass path and further obtain the geometric link among the three solutions as well as a comparison of their energy levels. This seems to be the first paper concerning three solutions, with the method also being applicable to the single constraint problem.

math.AP↗

arXiv2025

A Framework for Spontaneous Brillouin Noise: Unveiling Fundamental Limits in Brillouin Metrology

Spontaneous Brillouin scattering (SpBS) provides a non-contact tool for probing the mechanical and thermodynamic properties of materials, enabling important applications such as distributed optical fiber sensing and high-resolution Brillouin microscopy. Achieving metrological precision in these systems relies critically on identifying fundamental noise sources. While a pioneering study three decades ago numerically investigated an intrinsic SpBS noise mechanism, this phenomenon has remained largely unexplored, particularly in the context of Brillouin metrological systems. Here, by revisiting its physical formation process and rethinking its stochastic behaviors, we develop and experimentally validate a comprehensive analytical framework on this long-overlooked noise source. Importantly, we theoretically predict, for the first time, the SpBS noise is a universal and fundamental limit that can dominate over conventional limits such as shot noise in Brillouin metrological systems like imaging, microscopy and sensing. Specifically, we experimentally demonstrate the SpBS-noise-limited regime in Brillouin imaging and sensing scenarios. This framework establishes a critical foundation for understanding and optimizing the performance bounds of current and future Brillouin-based technologies across diverse applications.

physics.optics↗

arXiv2025

Normalized multi-bump solutions for Choquard equation involving sublinear case

In this paper, we study the existence of normalized multi-bump solutions for the following Choquard equation \begin{equation*} -ε^2Δu +λu=ε^{-(N-μ)}\left(\int_{\mathbb{R}^N}\frac{Q(y)|u(y)|^p}{|x-y|^μ}dy\right)Q(x)|u|^{p-2}u, \text{in}\ \mathbb{R}^N, \end{equation*} where $N\geq3$, $μ\in (0,N)$, $ε>0$ is a small parameter and $λ\in\mathbb{R}$ appears as a Lagrange multiplier. By developing a new variational approach, we show that the problem has a family of normalized multi-bump solutions focused on the isolated part of the local maximum of the potential $Q(x)$ for sufficiently small $ε>0$. The asymptotic behavior of the solutions as $ε\rightarrow0$ are also explored. It is worth noting that our results encompass the sublinear case $p<2$, which complements some of the previous works.

math.AP↗

arXiv2025

Standing waves with prescribed mass for biharmonic NLS with positive dispersion and Sobolev critical exponent

We investigate standing waves with prescribed mass for a class of biharmonic Schrodinger equations with positive Laplacian dispersion in the Sobolev critical regime. By establishing novel energy inequalities and developing a direct minimization approach, we prove the existence of two normalized solutions for the corresponding stationary problem. The first one is a ground state with negative level, and the second one is a higher-energy solution with positive level. It is worth noting that we do not work in the space of radial functions, and do not use Palais-Smale sequences so as to avoid applying the relatively complex mini-max approach based on a strong topological argument. Finally, we explore the relationship between the ground states and the least action solutions, some asymptotic properties and dynamical behavior of solutions, such as the orbital stability and the global existence.

math.AP↗

arXiv2025

SelaFD:Seamless Adaptation of Vision Transformer Fine-tuning for Radar-based Human Activity Recognition

Human Activity Recognition (HAR) such as fall detection has become increasingly critical due to the aging population, necessitating effective monitoring systems to prevent serious injuries and fatalities associated with falls. This study focuses on fine-tuning the Vision Transformer (ViT) model specifically for HAR using radar-based Time-Doppler signatures. Unlike traditional image datasets, these signals present unique challenges due to their non-visual nature and the high degree of similarity among various activities. Directly fine-tuning the ViT with all parameters proves suboptimal for this application. To address this challenge, we propose a novel approach that employs Low-Rank Adaptation (LoRA) fine-tuning in the weight space to facilitate knowledge transfer from pre-trained ViT models. Additionally, to extract fine-grained features, we enhance feature representation through the integration of a serial-parallel adapter in the feature space. Our innovative joint fine-tuning method, tailored for radar-based Time-Doppler signatures, significantly improves HAR accuracy, surpassing existing state-of-the-art methodologies in this domain. Our code is released at https://github.com/wangyijunlyy/SelaFD.

cs.CV↗

arXiv2024

Normalized solutions for NLS equations with potential on bounded domains: Ground states and multiplicity

We investigate normalized solutions for a class of nonlinear Schrödinger (NLS) equations with potential $V$ and inhomogeneous nonlinearity $g(|u|)u=|u|^{q-2}u+β|u|^{p-2}u$ on a bounded domain $Ω$. Firstly, when $2+\frac{4}{N}<q<p\leq2^*:=\frac{2N}{N-2}$ and $β=-1$, under an explicit smallness assumption on $V$, we prove the existence of a global minimum solution and a high-energy solution if the mass is large enough. For this case we do not require that $Ω$ is star-shaped, which partly solves an open problem by Bartsch et al. [Math. Ann. 390 (2024) 4813--4859]. Moreover, we find that the global minimizer also exists although the nonlinearity is $L^2$-supercritical. Secondly, when $2<q<2+\frac{4}{N}<p=2^*$ and $β=1$, under the smallness and some extra assumptions on $V$, we prove the existence of a ground state and a high-energy solution if $Ω$ is star-shaped and the mass is small enough. It seems to be new in the study of normalized ground state in the context of the Brézis-Nirenberg problem, even for the autonomous case of $V(x)\equiv0$.

math.AP↗

arXiv2024

Standing waves with prescribed mass for Schrodinger equations with competing Van Der Waals type potentials

We investigate standing waves with prescribed mass for a class of Schrodinger equations with competing Van Der Waals type potentials, arising in a model of non-relativistic bosonic atoms and molecules. By developing an approach based on a direct minimization of the energy functional on a new constrained manifold, we establish the existence of two normalized solutions for the corresponding stationary problem. One is a local minimizer with positive level and the other one is a global minimizer with negative level. Moreover, we find that the global minimizer is farther away from the origin than the local minimizer. Finally, we explore the relations between the ground state solution and the least action solution, and some dynamical behavior and scattering results are presented as well.

math.AP↗

arXiv2024

Existence and dynamical behaviour of vectorial standing waves with prescribed mass for Hartree-Fock type systems

In this paper, we investigate vectorial standing waves with prescribed mass for the Hartree-Fock type system (HF system) with the double coupled feature. Such system is viewed as an approximation of the Coulomb system with two particles appeared in quantum mechanics. By exploring the interaction of the double coupled terms, we prove the exis?tence/nonexistence and symmetry of vectorial energy ground states for the corresponding stationary problem. Furthermore, we obtain the relation between vectorial energy ground states and vectorial action ground states in some cases. Finally, we establish conditions for global well-posedness and finite time blow-up to HF system with the initial data, and prove orbital stability/strong instability of standing waves.

math.AP↗

arXiv2023

The planar Schrodinger--Poisson system with exponential critical growth: The local well-posedness and standing waves with prescribed mass

In this paper, we investigate a class of planar Schrödinger-Poisson systems with critical exponential growth. We establish conditions for the local well-posedness of the Cauchy problem in the energy space, which seems innovative as it was not discussed at all in any previous results. By introducing some new ideas and relaxing some of the classical growth assumptions on the nonlinearity, we show that such system has at least two standing waves with prescribed mass, where one is a ground state standing waves with positive energy, and the other one is a high-energy standing waves with positive energy. In addition, with the help of the local well-posedness, we show that the set of ground state standing waves is orbitally stable.

math.AP↗

arXiv2023

Standing waves for the NLS equation with competing nonlocal and local nonlinearities: the double $L^{2}$-supercritical case

We investigate the NLS equation with competing Hartree-type and power-type nonlinearities \begin{equation*} \begin{array}{ll} i\partial _{t}ψ+Δψ+γ(I_{α}\ast |ψ|^{p})|ψ|^{p-2}ψ+μ|ψ|^{q-2}ψ=0, & \text{ }\forall (t,x)\in \mathbb{R\times R}^{N},% \end{array}% \end{equation*}% where $γμ<0$. We establish conditions for the local well-posedness in the energy space. Under the double $L^{2}$-supercritical case, we prove the existence and multiplicity of standing waves with prescribed mass by developing a constraint method when $γ<0,μ>0$ and $γ>0,μ<0, $ respectively. Moreover, we prove weak orbital stablility and strong instability of standing waves by considering a suitable local minimization problem and by analyzing the fibering mapping, respectively. A new analysis of the fibering mapping is performed in this work. We believe that it is innovative as it was not discussed at all in any previous results. The lower bound rate of blow-up solutions for the Cauchy problem is given as well. Due to the different \textquotedblleft strength" of the two types of nonlinearities, we find some essential differences in our results between these two competing cases. We will be dealing with two major scenarios that are totally different from each other due to their diverse geometric structure. This leads to surprising findings. Additionally, the competing pure power-type nonlinearities case can be derived from our study thanks to a good choice of the kernel of the Hartree term.

math.AP↗