arXiv subjects

Rui Guo

Publications and source records attributed to Rui Guo.

At least 55 records · Page 3Linked to original sources

arXiv2024

LiDAR-based Quadrotor for Slope Inspection in Dense Vegetation

This work presents a LiDAR-based quadrotor system for slope inspection in dense vegetation environments. Cities like Hong Kong are vulnerable to climate hazards, which often result in landslides. To mitigate the landslide risks, the Civil Engineering and Development Department (CEDD) has constructed steel flexible debris-resisting barriers on vulnerable natural catchments to protect residents. However, it is necessary to carry out regular inspections to identify any anomalies, which may affect the proper functioning of the barriers. Traditional manual inspection methods face challenges and high costs due to steep terrain and dense vegetation. Compared to manual inspection, unmanned aerial vehicles (UAVs) equipped with LiDAR sensors and cameras have advantages such as maneuverability in complex terrain, and access to narrow areas and high spots. However, conducting slope inspections using UAVs in dense vegetation poses significant challenges. First, in terms of hardware, the overall design of the UAV must carefully consider its maneuverability in narrow spaces, flight time, and the types of onboard sensors required for effective inspection. Second, regarding software, navigation algorithms need to be designed to enable obstacle avoidance flight in dense vegetation environments. To overcome these challenges, we develop a LiDAR-based quadrotor, accompanied by a comprehensive software system. The goal is to deploy our quadrotor in field environments to achieve efficient slope inspection. To assess the feasibility of our hardware and software system, we conduct functional tests in non-operational scenarios. Subsequently, invited by CEDD, we deploy our quadrotor in six field environments, including five flexible debris-resisting barriers located in dense vegetation and one slope that experienced a landslide. These experiments demonstrated the superiority of our quadrotor in slope inspection.

cs.RO↗

arXiv2024

Schwarzschild Modeling of Barred S0 Galaxy NGC 4371

We apply the barred Schwarzschild method developed by Tahmasebzadeh et al. (2022) to a barred S0 galaxy, NGC 4371, observed by IFU instruments from the TIMER and ATLAS3D projects. We construct the gravitational potential by combining a fixed black hole mass, a spherical dark matter halo, and stellar mass distribution deprojected from $3.6$ $μ$m S$^4$G image considering an axisymmetric disk and a triaxial bar. We independently modelled kinematic data from TIMER and ATLAS3D. Both models fit the data remarkably well. We find a consistent bar pattern speed from the two sets of models with $Ω_{\rm p} = 23.6 \pm 2.8 \hspace{.08cm} \mathrm{km \hspace{.04cm} s^{-1} \hspace{.04cm} kpc^{-1} }$ and $Ω_{\rm p} = 22.4 \pm 3.5 \hspace{.08cm} \mathrm{km \hspace{.04cm} s^{-1} \hspace{.04cm} kpc^{-1} }$, respectively. The dimensionless bar rotation parameter is determined to be $ 1.88 \pm 0.37$, indicating a likely slow bar in NGC 4371. Additionally, our model predicts a high amount of dark matter within the bar region ($M_{\rm DM}/ M_{\rm total}$ $\sim 0.51 \pm 0.06$), which, aligned with the predictions of cosmological simulations, indicates that fast bars are generally found in baryon-dominated disks. Based on the best-fitting model, we further decompose the galaxy into multiple 3D orbital structures, including a BP/X bar, a classical bulge, a nuclear disk, and a main disk. The BP/X bar is not perfectly included in the input 3D density model, but BP/X-supporting orbits are picked through the fitting to the kinematic data. This is the first time a real barred galaxy has been modelled utilizing the Schwarzschild method including a 3D bar.

astro-ph.GA↗

arXiv2024

Inverse scattering transform for the discrete nonlocal PT symmetric nonlinear Schrödinger equation with nonzero boundary conditions

In this paper, the inverse scattering transform for the integrable discrete nonlocal PT symmetric nonlinear Schrödinger equation with nonzero boundary conditions is presented. According to the two different signs of symmetry reduction and two different values of the phase difference between plus and minus infinity, we discuss four cases with significant differences about analytical regions, symmetry, asymptotic behavior and the presence or absence of discrete eigenvalues, namely, the existence or absence of soliton solutions. Therefore, in all cases, we study the direct scattering and inverse scattering problem, separately. The Riemann-Hilbert problem is constructed and solved as well as the reconstruction formula of potential is derived, respectively. Finally, combining the time evolution, we provide the dark, bright, dark-bright soliton solutions on the nonzero background in difference cases under the reflectionless condition.

math-ph↗

arXiv2024

QUB-Cirdan at "Discharge Me!": Zero shot discharge letter generation by open-source LLM

The BioNLP ACL'24 Shared Task on Streamlining Discharge Documentation aims to reduce the administrative burden on clinicians by automating the creation of critical sections of patient discharge letters. This paper presents our approach using the Llama3 8B quantized model to generate the "Brief Hospital Course" and "Discharge Instructions" sections. We employ a zero-shot method combined with Retrieval-Augmented Generation (RAG) to produce concise, contextually accurate summaries. Our contributions include the development of a curated template-based approach to ensure reliability and consistency, as well as the integration of RAG for word count prediction. We also describe several unsuccessful experiments to provide insights into our pathway for the competition. Our results demonstrate the effectiveness and efficiency of our approach, achieving high scores across multiple evaluation metrics.

cs.CL↗

arXiv2024

The Riemann-Hilbert approach for the nonlocal derivative nonlinear Schrödinger equation with nonzero boundary conditions

In this paper, the nonlocal reverse space-time derivative nonlinear Schrödinger equation under nonzero boundary conditions is investigated using the Riemann-Hilbert (RH) approach. The direct scattering problem focuses on the analyticity, symmetries, and asymptotic behaviors of the Jost eigenfunctions and scattering matrix functions, leading to the construction of the corresponding RH problem. Then, in the inverse scattering problem, the Plemelj formula is employed to solve the RH problem. So the reconstruction formula, trace formulae, $θ$ condition, and exact expression of the single-pole and double-pole solutions are obtained. Furthermore, dark-dark solitons, bright-dark solitons, and breather solutions of the reverse space-time derivative nonlinear Schrödinger equation are presented along with their dynamic behaviors summarized through graphical simulation.

nlin.SI↗

arXiv2024

Simultaneous Deep Learning of Myocardium Segmentation and T2 Quantification for Acute Myocardial Infarction MRI

In cardiac Magnetic Resonance Imaging (MRI) analysis, simultaneous myocardial segmentation and T2 quantification are crucial for assessing myocardial pathologies. Existing methods often address these tasks separately, limiting their synergistic potential. To address this, we propose SQNet, a dual-task network integrating Transformer and Convolutional Neural Network (CNN) components. SQNet features a T2-refine fusion decoder for quantitative analysis, leveraging global features from the Transformer, and a segmentation decoder with multiple local region supervision for enhanced accuracy. A tight coupling module aligns and fuses CNN and Transformer branch features, enabling SQNet to focus on myocardium regions. Evaluation on healthy controls (HC) and acute myocardial infarction patients (AMI) demonstrates superior segmentation dice scores (89.3/89.2) compared to state-of-the-art methods (87.7/87.9). T2 quantification yields strong linear correlations (Pearson coefficients: 0.84/0.93) with label values for HC/AMI, indicating accurate mapping. Radiologist evaluations confirm SQNet's superior image quality scores (4.60/4.58 for segmentation, 4.32/4.42 for T2 quantification) over state-of-the-art methods (4.50/4.44 for segmentation, 3.59/4.37 for T2 quantification). SQNet thus offers accurate simultaneous segmentation and quantification, enhancing cardiac disease diagnosis, such as AMI.

eess.IV↗

arXiv2024

Are High $Σ_1$ Massive Blue Spiral Galaxies Rejuvenated Systems?

Quiescent galaxies generally possess denser cores than star-forming galaxies with similar mass. As a measurement of the core density, the central stellar mass surface density within a radius of 1 kpc ($Σ_1$) was thus suggested to be closely related to galaxy quenching. Massive star-forming galaxies with high $Σ_1$ do not fit into this picture. To understand the origin of such galaxies, we compare the spatially-resolved stellar population and star formation properties of massive ($ > 10^{10.5}{\rm M}_{\odot}$) blue spiral galaxies with high and low $Σ_1$, divided by $Σ_1 = 10^{9.4} M_\odot \, {\rm kpc}^{-2}$, based on the final release of MaNGA IFU data. We find that both high $Σ_1$ and low $Σ_1$ blue spirals show large diversities in stellar population and star formation properties. Despite the diversities, high $Σ_1$ blue spirals are statistically different from the low $Σ_1$ ones. Specifically, the radial profiles of the luminosity-weighted age and Mgb/${\rm \langle Fe \rangle}$ show that high $Σ_1$ blue spirals consist of a larger fraction of galaxies with younger and less $α$-element enhanced centers than their low $Σ_1$ counterparts, $\sim 55\%$ versus $\sim 30\%$. The galaxies with younger centers mostly have higher central specific star formation rates, which still follow the spaxel-based star formation main sequence relation though. Examinations of the H$α$ velocity field and the optical structures suggest that galactic bars or galaxy interactions should be responsible for the rejuvenation of these galaxies. The remaining $\sim 45\% $ of high $Σ_1$ blue spirals are consistent with the inside-out growth scenario.

astro-ph.GA↗

arXiv2024

The semi-discrete complex modified Korteweg-de Vries equation with zero and non-zero boundary conditions: Riemann-Hilbert approach and N-soliton solutions

We focus on the semi-discrete complex modified Korteweg-de Vries (DcmKdV) equation in this paper. The direct and inverse scattering theory is developed with zero and non-zero boundary conditions (BCs) of the potential. For direct problem, the properties of the eigenfunctions and the scattering matrix, including analyticity, asymptotics and symmetries, are investigated, which facilitates the establishment of the Riemann-Hilbert (RH) problems. By solving the RH problems in the inverse problem part, the reconstruction potential formulas are obtained, which allows us to derive the N-soliton solutions in the reflectionless case. Meanwhile, the trace formulas are derived by means of studying the corresponding RH problems. Furthermore, the dynamic characteristics of the 1-soliton and 2-soliton with zero and non-zero boundary are demonstrated by graphical simulation.

nlin.SI↗

arXiv2024

Analytical and numerical studies for integrable and non-integrable fractional discrete modified Korteweg-de Vries hierarchies

Under investigation in this paper is the fractional integrable and non-integrable discrete modified Korteweg-de Vries hierarchies. The linear dispersion relations, completeness relations, inverse scattering transform, and fractional soliton solutions of the fractional integrable discrete modified Korteweg-de Vries hierarchy will be explored. The inverse scattering problem will be solved accurately by using Gel'fand-Levitan-Marchenko (GLM) equations and Riemann-Hilbert (RH) problem. The peak velocity of fractional soliton solutions will be analyzed. The numerical solutions of the non-integrable fractional averaged discrete modified Korteweg-de Vries equation which has a simpler form than the integrable one will be obtained by a split-step fourier method.

nlin.SI↗

arXiv2024

North-South asymmetries in the Galactic thin disk associated with the vertical phase spiral as seen using LAMOST-Gaia stars

We select 1,052,469 (754,635) thin disk stars from {\it Gaia} eDR3 and LAMOST DR7 in the range of Galactocentric radius $R$ (guiding center radius $R_\mathrm{g}$) from 8 to 11\,kpc to investigate the asymmetries between the North and South of the disk midplane. More specifically we analyze the vertical velocity dispersion profiles ($σ_{v_{z}}(z$)) in different bins of $R$ ($R_\mathrm{g}$) and $[\mathrm{Fe/H}]$. We find troughs in the profiles of $σ_{v_{z}}(z)$ located in both the North ($z \sim 0.7$\,kpc) and South ($z \sim -0.5$\,kpc) of the disk at all radial and chemical bins studied. The difference between the Northern and Southern vertical velocity dispersion profiles ($Δσ_{v_{z}}(|z|)$) shows a shift between curves of different $R$ and $R_\mathrm{g}$. A similar shift exists in these NS asymmetry profiles further divided into different $[\mathrm{Fe/H}]$ ranges. The sample binned with $R_\mathrm{g}$ more clearly displays the features in the velocity dispersion profiles. The shift in the peaks of the $Δσ_{v_{z}}$ profiles and the variation in the phase spiral shape binned by metallicity indicate the variation of the vertical potential profiles and the radial metallicity gradient. The wave-like signal in NS asymmetry of $σ_{v_{z}}(z)$ largely originates from phase spiral; while the NS asymmetry profiles of [Fe/H] only display a weak wave-like feature near solar radius. We perform a test particle simulation to qualitatively reproduce the observed results. A quantitative explanation of the NS asymmetry in the metallicity profile needs careful consideration of the spiral shape and the perturbation model, and we leave this for future work.

astro-ph.GA↗

arXiv2023

Watertightization of Trimmed Surfaces at Intersection Boundary

This paper introduces a watertight technique to deal with the boundary representation of surface-surface intersection in CAD. Surfaces play an important role in today's geometric design. The mathematical model of non-uniform rational B-spline surfaces (NURBS) is the mainstream and ISO standard. In the situation of surface-surface intersection, things are a little complicated, for some parts of surfaces may be cut-off, so called trimmed surfaces occur, which is the central topic in the past decades in CAD community of both academia and industry. The main problem is that the parametric domain of the trimmed surface generally is not the standard square or rectangle, and rather, typically, bounded by curves, based on point inverse of the intersection points and interpolated. The existence of gaps or overlaps at the intersection boundary makes hard the preprocessing of CAE and other downstream applications. The NURBS are in this case hard to keep a closed form. In common, a special data structure of intersection curves must be affiliated to support downstream applications, while the data structure of the whole CAD system is not unified, and the calculation is not efficient. In terms of Bezier surface, a special case of NURBS, this paper designs a reparameterization or normalization to transform the trimmed surface into a group of Bezier surface patches in standard parametric domain [0,1]X[0,1]. And then the boundary curve of normalized Bezier surface patch can be replaced by the intersection curve to realize watertight along the boundary. In this way, the trimmed surface is wiped out, the "gap" between CAD and CAE is closed.

cs.GR↗

arXiv2023

Dissecting the Runtime Performance of the Training, Fine-tuning, and Inference of Large Language Models

Large Language Models (LLMs) have seen great advance in both academia and industry, and their popularity results in numerous open-source frameworks and techniques in accelerating LLM pre-training, fine-tuning, and inference. Training and deploying LLMs are expensive as it requires considerable computing resources and memory, hence many efficient approaches have been developed for improving system pipelines as well as operators. However, the runtime performance can vary significantly across hardware and software stacks, which makes it difficult to choose the best configuration. In this work, we aim to benchmark the performance from both macro and micro perspectives. First, we benchmark the end-to-end performance of pre-training, fine-tuning, and serving LLMs in different sizes , i.e., 7, 13, and 70 billion parameters (7B, 13B, and 70B) on three 8-GPU platforms with and without individual optimization techniques, including ZeRO, quantization, recomputation, FlashAttention. Then, we dive deeper to provide a detailed runtime analysis of the sub-modules, including computing and communication operators in LLMs. For end users, our benchmark and findings help better understand different optimization techniques, training and inference frameworks, together with hardware platforms in choosing configurations for deploying LLMs. For researchers, our in-depth module-wise analyses discover potential opportunities for future work to further optimize the runtime performance of LLMs.

cs.PF↗

arXiv2023

Machine learning approach to analyze heavy quark diffusion coefficient in relativistic heavy-ion collisions

The diffusion coefficient of heavy quarks in the deconfined medium is examined in this research using a deep convolutional neural network (CNN) trained with data from relativistic heavy ion collisions involving heavy flavor hadrons. The CNN is trained using observables such as the nuclear modification factor $R_{AA}$ and the elliptic flow $v_2$ of non-prompt $J/ψ$ from B-hadron decay in different centralities, where B meson evolutions are calculated using the Langevin equation and the Instantaneous Coalescence Model. The CNN outputs the parameters characterizing the temperature and momentum dependence of the heavy quark diffusion coefficient. By inputting the experimental data of non-prompt $J/ψ$ $(R_{AA}, v_2)$ from various collision centralities into multiple channels of the well-trained network, we derive the values of the diffusion coefficient parameters. Additionally, We evaluate the uncertainty in determining the diffusion coefficient by taking into account the uncertainties present in the experimental data $(R_{AA}, v_2)$, which serve as inputs to the deep neural network.

nucl-th↗

arXiv2023

Numerical analyses of the flow past a short rotating cylinder

This work studies the three-dimensional flow dynamics around a rotating circular cylinder of finite length, whose axis is positioned perpendicular to the streamwise direction. Direct numerical simulations and global stability analyses are performed within a parameter range of Reynolds number $Re=DU_\infty/ν<500$ (based on cylinder diameter $D$, uniform incoming flow velocity $U_\infty$), length-to-diameter ratio $AR=L/D\leq2$ and dimensionless rotation rate $α=DΩ/2U_\infty\leq2$ (where $Ω$ is rotation rate). By solving Nav\-ier--Sto\-kes equations, we investigated the wake patterns and explored the phase diagrams of the lift and drag coefficients. For a cylinder with $AR=1$, we found that when the rotation effect is weak ($0\leqα\lesssim0.3$), the wake pattern is similar to the unsteady wake past the non-rotating finite-length cylinder, but with a new linear unstable mode competing to dominate the saturation state of the wake. The flow becomes stable for $0.3\lesssimα\lesssim0.9$ when $Re<360$. When the rotation effect is strong ($α\gtrsim0.9$), new low-frequency wake patterns with stronger oscillations emerge. Furthermore, the stability analyses based on the time-averaged flows and on the steady solutions demonstrate the existence of multiple unstable modes undergoing Hopf bifurcation, greatly influenced by the rotation effect. The shapes of these global eigenmodes are presented and compared, as well as their structural sensitivity, visualising the flow region important for the disturbance development with rotation. This research contributes to our understanding of the complex bluff-body wake dynamics past this critical configuration.

physics.flu-dyn↗

arXiv2023

Measuring the Milky Way Vertical Potential with the Phase Snail in a Model Independent Way

The vertical phase-space spiral (snail) is a direct sign of dis-equilibrium of Milky Way's disc. Nevertheless, the wrapping of the phase snail contains information of the vertical potential. We propose a novel method to measure the vertical potential utilizing the intersections between the snail and $z$/$V_{z}$ axes, for which we know the maximum vertical heights ($Z_{max}$) or the maximum vertical velocities ($V_{z,max}$). Using a refined linear interpolation method, we directly obtain $(Z_{max},\ \frac{1}{2}V_{z,max}^{2})$ for these snail intersections to constrain the vertical potential profile empirically. Our method is model independent since no assumptions about the snail shape or the vertical potential have been made. Although the snail binned by the guiding center radius ($R_{g}$) is more prominent, it traces a vertical potential shallower than that of the snail binned by the same Galactocentric radius ($R$). We apply an empirical method to correct this difference. We measure the snail intersections in several $R_{g}$ bins within $7.5< R_{g} < 11.0$ kpc for Gaia DR3, and apply the interpolation method to deduce the potential values at several vertical heights. The potential at the snail intersections, as well as the following mass modeling are consistent with the popular Milky Way potentials in the literature. For the $R_{g}$-binned phase snail in the Solar neighborhood, the mass modeling indicates a local dark matter density of $ρ_{\rm dm}= 0.0150\pm0.0031$ $\rm M_{\odot}\,pc^{-3}$, consistent with previous works. Our method could be applied to larger radial ranges in future works, to provide independent and stronger constraints on the Milky Way's potential.

astro-ph.GA↗

arXiv2023

Physics-Informed Supervised Residual Learning for Electromagnetic Modeling

In this study, physics-informed supervised residual learning (PhiSRL) is proposed to enable an effective, robust, and general deep learning framework for 2D electromagnetic (EM) modeling. Based on the mathematical connection between the fixed-point iteration method and the residual neural network (ResNet), PhiSRL aims to solve a system of linear matrix equations. It applies convolutional neural networks (CNNs) to learn updates of the solution with respect to the residuals. Inspired by the stationary and non-stationary iterative scheme of the fixed-point iteration method, stationary and non-stationary iterative physics-informed ResNets (SiPhiResNet and NiPhiResNet) are designed to solve the volume integral equation (VIE) of EM scattering. The effectiveness and universality of PhiSRL are validated by solving VIE of lossless and lossy scatterers with the mean squared errors (MSEs) converging to $\sim 10^{-4}$ (SiPhiResNet) and $\sim 10^{-7}$ (NiPhiResNet). Numerical results further verify the generalization ability of PhiSRL.

physics.comp-ph↗

arXiv2023

The evolution of the chiral symmetry in cesium isotopes

Following the reports of candidate chiral doublet bands observed in cesium isotopes, the possible chiral candidates and the evolution of three-dimensional rotation in $^{120-134}{\textrm{Cs}}$ are investigated within the microscopic three-dimensional tilted axis cranking covariant density functional theory (3DTAC-CDFT). By investigating the evolution of the polar angle $θ$ and azimuth angle $φ$ as a function of rotational frequency $\hbarω$, the transition from the planar rotation to the chiral rotation has been found in $^{121-133}{\textrm{Cs}}$. The corresponding critical rotational frequency $ω_{\textrm{crit}}$ of the appearance of chiral aplanar rotation decreases as neutron number increases, which can be attributed to the neutrons in $(gd)$ and $(sd)$ shells having smaller angular momentum components along both the short and long axes, and larger components along medium axis, respectively. In comparison, only planar rotation has been obtained in $^{120,134}{\textrm{Cs}}$. With these interpretations, the obtained $I\sim\hbarω$ and energy spectra as well as $B(M1)/B(E2)$ values show reasonable agreement with the available experimental data. In addition, the evolution of quadrupole deformation $β$ and triaxial deformation $γ$ are also discussed.

nucl-th↗

arXiv2023

MyoFold: rapid Myocardial tissue and movement quantification via a highly Folded sequence

Purpose: To develop and evaluate a cardiovascular magnetic resonance sequence (MyoFold) for rapid myocardial tissue and movement characterization. Method: MyoFold sequentially performs joint T1/T2 mapping and cine for one left-ventricle slice within a breathing-holding of 12 heartbeats. MyoFold uses balanced Steady-State-Free-Precession (bSSFP) with 2-fold acceleration for data readout and adopts an electrocardiogram (ECG) to synchronize the cardiac cycle. MyoFold first acquires six single-shot inversion-recovery images at the diastole of the first six heartbeats. For joint T1/T2 mapping, T2 preparation (T2-prep) adds different T2 weightings to the last three images. On the remaining six heartbeats, segmented bSSFP is continuously performed for each cardiac phase for cine. We build a neural network and trained it using the numerical simulation of MyoFold for T1 and T2 calculations. MyoFold was validated through phantom and in-vivo experiments and compared to MOLLI, SASHA, T2-prep bSSFP, and convention cine. Results: MyoFold phantom T1 had a 10% overestimation while MyoFold T2 had high accuracy. MyoFold in-vivo T1 had comparable accuracy to that of SASHA and precision to that of MOLLI. MyoFold had good agreement with T2-prep bSSFP in myocardium T2 measurement. There was no difference in the myocardium thickness measurement between the MyoFold cine and convention cine. Conclusion: MyoFold can simultaneously quantify myocardial tissue and movement, with accuracy and precision comparable to dedicated sequences, saving three-fold scan time.

physics.med-ph↗