bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct numerical simulation of roll waves on landslide mudflow
Authors: Yu Boyuan , Chu Vincent H.
Published: December 2024

Roll waves on landslide muds are nonlinear instabilities on non-Newtonian laminar free-surface flow. Existing theories of the roll waves on the mudflow have been developed using long-wavelength approximations and different rheological models. The differences in the approximations and models have led to vastly different parameterizations and expressions for describing the waves. In this paper, we analyze rheological data of landslide mud and conduct direct numerical simulations (DNS) of the roll waves to reconcile the limitations and differences between existing theories. The DNS identifies for the first time the existence of a leading wave emerging as a “front runner” in mudflow instability development. Depending on the Froude and Reynolds numbers, the front runner can be a smooth or breaking wave. For comparison, we also conduct shallow-layer simulation for the instability using a two-equation depth-averaged model. We analyze temporal and spatial instabilities using two rheological models: the Herschel–Bulkley (HB) and power-law models. While HB and PL models have different rheological parameters, they produce the same roll waves on the landslide mudflow. The DNS shows the limitation of the widely used long-wavelength approximations for the dependence of the wave and instability on the Froude and Reynolds numbers. We find universality in the celerity–amplitude relationship in the nonlinear development of roll waves. The amplitude dispersion of the roll waves on the non-Newtonian mudflow follows a linear relationship remarkably similar to roll waves on laminar and turbulent flows of Newtonian fluid.
Direct numerical simulation of distributed roughness induced transition in a supersonic boundary layer
Authors: Huang Hexia , Liu Zaijie , Liu Mengying , Tan Huijun
Published: December 2024

Supersonic boundary layer transition induced by distributed roughness elements is studied via direct numerical simulation. Sinusoidal roughness patterns with different roughness heights are considered. Results show that the sinusoidal roughness pattern generates two types of counter-rotating streamwise vortex pairs in the wake. The stronger one is composed of two vortexes passing through the lateral portion of the last row of sinusoidal humps, and the weaker one is formed by the two vortexes shedding from the center of the sinusoidal humps. The roughness patch with a higher roughness height can induce the complete laminar breakdown to transition. Power spectral and flow stability analysis further identifies several types of instability modes, and the symmetric mode related to the lateral counter-rotating vortex pair is dominant and has a higher frequency. At a lower roughness height, no transition behavior is observed, and the low-frequency antisymmetric mode around each counter-rotating vortex pair becomes dominant and has a much lower growth rate.
Recasting the wobbling-in-a-cone model for the rotational anisotropy of phenylselenocyanate in poly(methyl methacrylate): Effect of internal bond rotation and polymer segmental motion
Authors: Palchowdhury Sourav , Mondal Saptarsi , Kwak Kyungwon , Cho Minhaeng
Published: December 2024

The rotational anisotropy of a molecule in a constrained environment is modeled by wobbling-in-a-cone (WIAC) motion, which describes the angular space sampled by the molecule. Recent polarization-selective IR pump–probe measurements have applied this model to phenylselenocyanate in amorphous polymers, aiming to probe the surrounding free volume. A faster rotational timescale was hypothesized to reflect the angular space within the static voids of the polymer matrix, while a slower timescale relates to constraint release by the polymer backbones. To better quantify the contributions of internal bond rotation and polymer segmental motion, we conduct molecular dynamics simulations on two phenylselenocyanate variants with different internal rotational barriers, as well as on p-chlorobenzonitrile, which lacks such internal rotational freedom, within a polymer matrix. Our analyses reveal that the faster (∼10 ps) component of the cyano group’s anisotropy decay arises from concurrent angular sampling due to internal bond rotation and WIAC motion. Conversely, polymer segmental motion was found to have a minimal influence on the slow (∼200 ps) anisotropy component. Based on these findings, we refine the WIAC model to better link rotational diffusion with the distinct free volume elements accessed by the probe molecule. This revised model allows the quantification of free volume elements associated with both internal bond rotation and wobbling motion within the polymer cage.
Effects of higher-order interactions and impulsive vaccination for rumor propagation
Authors: Liu Shijie , Zhao Donghua , Sun Yongzheng
Published: December 2024

This paper introduces a rumor propagation model with saturation incidence, based on hypergraph theory. Hypergraphs can capture the higher-order interactions between nodes in a social network, where the node degree is substituted with hyperdegree. First, the threshold for rumor spreading model is obtained, the global asymptotically stable of the rumor-free equilibrium, and the global attractive and global asymptotically stable of the rumor-prevailing equilibrium are proved. Then, we incorporate impulsive vaccination into the model to represent the guided effect, simulating the periodic educational activities organized by official institutions to counteract rumor dissemination. By employing the comparison theorem, the paper demonstrates the global attractiveness of the rumor-free periodic solution and the persistence of the model. Finally, through numerical simulations, the paper compares the effects of higher-order and pairwise interactions on rumor spreading, validating the theoretical conclusions. The results indicate that higher-order interactions can promote rumor spreading, while impulsive vaccination can effectively decrease the scale of rumor spreading.
Numerical investigation on motion responses of high-speed self-propelled submersible subject to internal solitary wave
Authors: Wang Junrong , Chang Qiangbo , He Zhenyang , Wu Wenbin
Published: December 2024

Internal solitary waves (ISWs) pose a significant threat to underwater submersibles. Unlike low-speed submersibles in the ISW field, the high-speed submersibles form a large pitching angle, which is more dangerous for submersible maneuverability. However, the mechanisms behind the interaction between ISWs and high-speed submersibles still remain unexplored. In this work, the three-dimensional numerical model for ISW–structure interaction is used to investigate the motion response characteristics of high-speed submersibles in the ISW field. Based on the extended Korteweg–de Vries (eKdV) theory, the ISW is generated in a two-layer numerical tank by enforcing velocity inlet boundaries. The ISW evolution is obtained by solving the Navier–Stokes equations. The motion of the self-propelled submersible is simulated by solving the equation of motion of the submersible. Using this model, numerical investigation on the ISW and high-speed submersible interaction is performed. The effects of submersible depth, self-recovery stiffness, and ISW amplitude on the motion response of the high-speed submersible are analyzed systematically. When the initial position of the submersible is above the ISW trough and the initial depth is close to the trough depth, the submersible may pierce through the ISW surface, which further results in the formation of a large pitching angle, motion stall and “falling deep.” It is difficult for the submersibles with the low recovery stiffness to maintain or control the navigation trajectory. They would undergo the large pitching angle and even impact on the seabed.
Flow control treatment for shock wave/boundary layer interaction of transonic shrouded rotors
Authors: Ma Jianci , Yu Jia , Shi Guanghao , Ji Lucheng , Li Jiabin
Published: December 2024

The shock wave/boundary layer interaction at the tip of transonic shrouded rotor blades usually leads to severe flow separation, which seriously affects aerodynamic performance. In this paper, the effect of part-shroud treatment on the shock wave/boundary layer interaction was numerically investigated. The part-shroud treatment suppresses the shock wave/boundary layer interaction-induced flow separation by introducing the tip leakage vortex at an optimal location. Parametric studies reveal that positioning the tip leakage vortex onset upstream the shock wave effectively reduces flow separation on the suction side, with the best outcomes achieved when the onset is slightly upstream of the shock wave. Based on these findings, the optimal shroud range extends from the leading edge to just upstream of the shock wave under a near stall condition. In National Aeronautics and Space Administration Rotor 35, the 30% shrouded rotors demonstrate a 2.4% improvement in the stall margin over 100% shrouded rotors with little reduction in peak efficiency.
Geometry mediated spin relaxation in ZnFe2O4 spinel ferrite nanostructures
Authors: Sarkar Sourav , Saha Priyanka , Kundu Mily , Rakhshit Rupali , Mandal Kalyan
Published: December 2024

Spin-glass and superparamagnetic behavior of different spinel ferrites is well-studied by the researchers in basic as well as applied science domains. However, this study investigates how geometry variation can mediate different spin dynamics in the ZnFe2O4 spinel ferrite system. Detailed characterization techniques such as DC and AC magnetic studies and magnetic memory effect measurements have been employed to analyze the effect of size and morphology on the types of relaxations involved. Superparamagnetic relaxation is more dominant in solid nanoparticles. On the other hand, the nanohollowspheres of the same material exhibit a behavior closer to spin cluster-glass. Frustration is one of the key factors that cause spin-glass relaxation. The work, essentially, shows that higher degree frustration can be realized through geometry modification to induce spin-glass behavior in ZnFe2O4.
Effect of rudder efficiency of high-speed aircraft subject to high-energy jet
Authors: Zhou Yi , Luo Zhenbing , Liu Qiang , Zhou Yan , Xie Wei
Published: December 2024

High maneuverability is required for high-speed aircraft. However, the traditional control method with mechanical rudder surface deflection has some defects such as weak control ability and long response time. In this paper, numerical simulations analyze the ability of high-energy jet to improve the control efficiency of X-51A aircraft. The deflection angle of the rudder is 0°–18°, and the high-energy jet is applied to the head of the aircraft and the windward side of the rudder surface. The control effects of the two control methods are compared and analyzed. The results show that within the range of the rudder deflection angle mentioned in this paper, applying high-energy jet control on the head of the aircraft will weaken the rudder surface control efficiency of the X-51A-like aircraft, while applying high-energy jet control on the wind-side of the rudder surface can enhance the rudder surface control efficiency of the aircraft by 13.78%. In this study, numerical simulations were used to analyze the effect of applying high-energy jets at different positions to enhance the efficiency of the rudder surface of a high-speed aircraft. This paper offers a novel concept for employing active flow control methods to enhance the efficiency of high-speed aircraft's rudder surfaces, thereby improving the application potential of such aircraft. These findings can serve as a reference for future research on the efficiency of rudder surfaces in high-speed aircraft.
A robust Jacobian-free Newton–Krylov method for turbomachinery simulations
Authors: Zhang Jianshe , Zhang Ziqing , Dong Xu , Yuan Hang , Zhang Yanfeng , Lu Xingen
Published: December 2024

Implicit methods are widely used in computational fluid dynamics numerical simulations of turbomachinery to accelerate convergence speed. However, simplified implicit nonlinear iterative algorithms, such as lower-upper symmetric-Gauss–Seidel method, will suffer from convergence slowdown or even divergence when dealing with off-design operations. In this study, a fast implicit Jacobian-Free Newton–Krylov finite volume method is developed to alleviate convergence difficulties of turbomachinery simulations. Based on the generalized minimal residual method, a matrix free solution for large sparse linear system is implemented, which avoids expensive and complex explicitly assembly of high-order Jacobian matrix. And a low-order Jacobian matrix assembled by graph coloring and finite difference method is adopted as preconditioning matrix. The nonlinear iterations are divided in two stages: startup stage and Newton stage. In the startup stage, an approximate Jacobian linear system is coupled with adaptive Courant–Friedrichs–Lewy number algorithm, solution update strategy and preconditioning lagging method to drive the nonlinear iteration with high computational efficiency. Once the residual is low enough, the Newton stage will be switched with an infinite time step to achieve rapid convergence. The robustness, accuracy and high efficiency of the applied nonlinear solver for different conditions was demonstrated by three test cases: a compressor cascade, a turbine cascade, and an axial compressor rotor. The potentiality of the method to enhance computational robustness of turbomachinery aerodynamic simulation for wide operation range is confirmed.
Aerodynamic characterization of leading-edge tubercles bionic airfoils with different configurations at high Reynolds number
Authors: Guo Xiangying , Xu Jie , Huang Yongchang , Cao Dongxing
Published: December 2024

Leading-edge tubercles have consistently been a key focus in aerodynamic biomimetics. A leading-edge tubercled wing model, based on the ONERA (Office National d'Études et de Recherches Aérospatiales) M6 wing, was examined at high Reynolds numbers to analyze the effects of the tubercles. First, six distinct parameter configurations were employed to analyze the aerodynamic characteristics of the tubercled wing, comprising three conventional single-equation configurations and three modified two-equation superimposed configurations. Numerical results indicate that the tubercled wing exhibits reduced performance at low angles of attack but improved performance at high angles of attack. Among the tested configurations, the single-equation model A06R26 achieved the best performance, with a maximum lift coefficient increase of 16.7% and a maximum lift-to-drag ratio improvement of 9%. Subsequent analysis, including shock vortex plots, reveals that the tubercled wing generates localized shocks at the troughs of the tubercles and causes early airflow separation at low angles while suppressing separation at high angles. Additionally, surface flow analysis reveals two primary flow modes on the surface of the tubercled wing at high Reynolds numbers, which are the main contributors to its superior performance. Finally, the performance of the tubercled wing configured with a single-equation model is compared to that of a two-equation model. The analysis shows that integrating advantageous configurations from the single-equation model into the multi-equation model allows the latter to inherit favorable performance characteristics, such as lift-to-drag ratio. This provides valuable recommendations for the continued development of tubercled wings in complex and realistic scenarios.
Investigation into unsteady inter-blade vortex in Francis turbines: Insight from unit speed effect and alleviation strategy
Authors: Sun Longgang , Zhang Qian , Wang Zhaoning , Xu Zhuofei , Guo Pengcheng
Published: December 2024

Inter-blade vortex is a special cavitation vortex within the Francis turbine runner, which can trigger high-amplitude pressure fluctuations, significantly limiting the flexible regulation capability. This paper numerically investigates the impact of attack angle variations on the evolution of inter-blade vortices by varying the unit speed. The cavitation volume, indicating vortex intensity, initially decreases sharply, then diminishes before rising swiftly with volume pulsations. Two types of inter-blade vortices emerge: type A is observed at low unit speed, attaching at the intersection of blade leading edge and runner crown, and type B, attaching at the mid-crown blade channel at high unit speed. The variational mode decomposition technology identifies vortex frequencies, type A at approximately 5.0fn and type B at around 1.0fn. Hydraulic instability, primarily driven by pressure fluctuations from inter-blade vortices, is more influenced by type B during transient simulations. Furthermore, an optimization approach including multi-objective and multi-condition was developed to reduces the vortex strength, improving hydraulic efficiency by 1.63% and 3.84%, decreasing cavitation volumes by 88.91% and 70.19%, with maximum pressure fluctuation amplitudes reduced by 57.7% and 82.6% for type A and type B inter-blade vortices, respectively. These findings enhance turbine stability across a wide operating range.
Hydrodynamic mechanisms implicit in the transition from surface standing-and-walking to standing-and-turning behavior in robotic dolphins
Authors: Lei Ming , Gai Qingyuan , Li Zhihan , Luo Xiang , Xia Dan
Published: December 2024

In order to overcome the operational challenges faced by traditional underwater robots at the water surface and improve their surface maneuverability, this study adopts the dolphin as a biological model to investigate its hydrodynamic performance during the transition from standing-and-walking (SAW) to standing-and-turning (SAT) behaviors on the water surface. The research leverages the compound motion of the body, caudal fin, and pectoral fins in a three-dimensional dolphin physical model to realize three novel SAT modes based on the SAW, respectively: different amplitude (DA), different frequency (DF), and different phase (DP). Through a series of numerical simulations, the time-varying patterns of key parameters during the transition process were described, and the mapping relationships between kinematic parameters and hydrodynamic performance for each mode were quantitatively analyzed, revealing the transient evolution of the flow field around the dolphin model. The results showed that the proposed SAT modes could simultaneously generate vertical and horizontal thrusts, along with torque around the body's longitudinal axis, enabling the transition from SAW to SAT behavior. Among the three turning modes, the DF mode exhibited the most stable maneuverability. Notably, under specific conditions, the turning radius of the DP mode can reach 0.014 m, effectively achieving in-place SAT behavior, which is challenging for traditional underwater robots. This work provides a novel approach to addressing the surface operation challenges faced by traditional underwater robots, significantly enhancing their maneuverability on the water surface.
Representation of a perceptual bias in the prefrontal cortex
Authors: Serrano-Fernández Luis , Beirán Manuel , Romo Ranulfo , Parga Néstor
Published: December 2024

Perception is influenced by sensory stimulation, prior knowledge, and contextual cues, which collectively contribute to the emergence of perceptual biases. However, the precise neural mechanisms underlying these biases remain poorly understood. This study aims to address this gap by analyzing neural recordings from the prefrontal cortex (PFC) of monkeys performing a vibrotactile frequency discrimination task. Our findings provide empirical evidence supporting the hypothesis that perceptual biases can be reflected in the neural activity of the PFC. We found that the state-space trajectories of PFC neuronal activity encoded a warped representation of the first frequency presented during the task. Remarkably, this distorted representation of the frequency aligned with the predictions of its Bayesian estimator. The identification of these neural correlates expands our understanding of the neural basis of perceptual biases and highlights the involvement of the PFC in shaping perceptual experiences. Similar analyses could be employed in other delayed comparison tasks and in various brain regions to explore where and how neural activity reflects perceptual biases during different stages of the trial.
Leukemia inhibitory factor (LIF) receptor amplifies pathogenic activation of fibroblasts in lung fibrosis
Authors: Nguyen Hung N. , Jeong Yunju , Kim Yunhye , Kamiya Mari , Kim Yaunghyun , Athar Humra , Castaldi Peter J. , Hersh Craig P. , Menon Jaivardhan A. , Wong Jessie , Chan Ian , Oldham William M. , Padera Robert F. , Sharma Nirmal S. , Sholl Lynette M. , Vivero Marina , Watts Gerald F. M. , Knipe Rachel S. , Black Katharine E. , Hariri Lida P. , Yun Jeong H. , Merriam Louis T. , Yuan Ke , Kim Edy Y. , Brenner Michael B.
Published: December 2024

Fibrosis drives end-organ damage in many diseases. However, clinical trials targeting individual upstream activators of fibroblasts, such as TGFβ, have largely failed. Here, we target the leukemia inhibitory factor receptor (LIFR) as an “autocrine master amplifier” of multiple upstream activators of lung fibroblasts. In idiopathic pulmonary fibrosis (IPF), the most common fibrotic lung disease, we found that lung myofibroblasts had high LIF expression, and the fibroblasts in fibroblastic foci coexpressed LIF and LIFR. In IPF, fibroblastic foci are the “leading edge” of fibrosis and a key site of disease pathogenesis. TGFβ1, one of the principal drivers of fibrosis, up-regulated LIF expression in IPF fibroblasts. We found that TGFβ1, IL-4, and IL-13 stimulations of fibroblasts require the LIF-LIFR axis to evoke a strong fibrogenic effector response in fibroblasts. In vitro antibody blockade of LIFR on IPF lung fibroblasts reduced the induction of profibrotic genes after TGFβ1 stimulation. Silencing LIF and LIFR reduced profibrotic fibroblast activation following TGFβ1, IL-4, and IL-13 stimulations. We also demonstrated that LIFR amplified profibrotic stimuli in precision-cut lung slices from IPF patients. These LIFR signals were transduced via JAK2, and STAT1 in IPF lung fibroblasts. Together, we find that LIFR drives an autocrine circuit that amplifies and sustains pathogenic activation of IPF fibroblasts. Targeting a single, downstream master amplifier on fibroblasts, like LIFR, is an alternative therapeutic strategy that simultaneously attenuates the profibrotic effects of multiple upstream stimuli.
Inertia-induced mixing and reaction maximization in laminar porous media flows
Authors: Chen Michael A. , Lee Sang Hyun , Kang Peter K.
Published: December 2024

Solute transport and biogeochemical reactions in porous and fractured media flows are controlled by mixing, as are subsurface engineering operations such as contaminant remediation, geothermal energy production, and carbon sequestration. Porous media flows are generally regarded as slow, so the effects of fluid inertia on mixing and reaction are typically ignored. Here, we demonstrate through microfluidic experiments and numerical simulations of mixing-induced reaction that inertial recirculating flows readily emerge in laminar porous media flows and dramatically alter mixing and reaction dynamics. An optimal Reynolds number that maximizes the reaction rate is observed for individual pore throats of different sizes. This reaction maximization is attributed to the effects of recirculation flows on reactant availability, mixing, and reaction completion, which depend on the topology of recirculation relative to the boundary of the reactants or mixing interface. Recirculation enhances mixing and reactant availability, but a further increase in flow velocity reduces the residence time in recirculation, leading to a decrease in reaction rate. The reaction maximization is also confirmed in a flow channel with grain inclusions and randomized porous media. Interestingly, the domain-wide reaction rate shows a dramatic increase with increasing Re in the randomized porous media case. This is because fluid inertia induces complex three-dimensional flows in randomized porous media, which significantly increases transverse spreading and mixing. This study shows how inertial flows control reaction dynamics at the pore scale and beyond, thus having major implications for a wide range of environmental systems.
Simultaneous visualization of membrane fluidity and morphology defines adhesion signatures of cancer cells
Authors: Matsuzaki Takahisa , Fujii Mai , Noro Hayata , Togo Shodai , Watanabe Mami , Suganuma Masami , Sharma Shivani , Kobayashi Naritaka , Kawamura Ryuzo , Nakabayashi Seiichiro , Yoshikawa Hiroshi Y.
Published: December 2024

We developed an advanced optical microscope for the simultaneous visualization of membrane fluidity and morphology to define cell adhesion signatures. This microscope combines ratiometric spectral imaging of membrane fluidity and interferometric imaging of membrane morphology. As a preliminary demonstration, we simultaneously visualized the interface between a giant unilamellar vesicle (GUV) and a glass substrate at different temperatures. We identified more fluid regions of the membrane and membrane adhesion sites (conversely, low-fluidic, ordered membrane domains correlate with nonadhered regions). This microscopic system was applied to human breast cancer cell lines with different malignancies; then, we identified adhesion signature of cancer cells: 1) low-fluidic, ordered membrane domains at the cell periphery and 2) large fluidic deviation at the nonadhered region. Inhibition of the cholesterol synthesis pathway suppresses the ordered membrane domains at the cancer cell periphery; thus, high level of cholesterol supports the appearance. Furthermore, an inhibitor of the unsaturated lipid synthesis pathway suppressed the large fluidic deviation at the nonadhered region; variation of unsaturated lipids contributes to heterogeneity of the cancer membrane. Therefore, our advanced optical microscopy enables us to couple membrane physical properties with cell adhesion, leading to definition of adhesion signatures of broad cell types, not just for cancer cells, that regulate life phenomena.
Human DBR1 deficiency impairs stress granule–dependent PKR antiviral immunity
Authors: Ru Shuo , Tang Sisi , Xu Hui , Yin Jiahao , Guo Yan , Song Liuping , Jin Zhenyu , Lee Danyel , Chan Yi-Hao , Chen Xingyao , Buerer Luke , Fairbrother William , Jia Weidong , Casanova Jean-Laurent , Zhang Shen-Ying , Gao Daxing
Published: December 2024

The molecular mechanism by which inborn errors of the human RNA lariat–debranching enzyme 1 (DBR1) underlie brainstem viral encephalitis is unknown. We show here that the accumulation of RNA lariats in human DBR1-deficient cells interferes with stress granule (SG) assembly, promoting the proteasome degradation of at least G3BP1 and G3BP2, two key components of SGs. In turn, impaired assembly of SGs, which normally recruit PKR, impairs PKR activation and activity against viruses, including HSV-1. Remarkably, the genetic ablation of PKR abolishes the corresponding antiviral effect of DBR1 in vitro. We also show that Dbr1Y17H/Y17H mice are susceptible to similar viral infections in vivo. Moreover, cells and brain samples from Dbr1Y17H/Y17H mice exhibit decreased G3BP1/2 expression and PKR phosphorylation. Thus, the debranching of RNA lariats by DBR1 permits G3BP1/2- and SG assembly-mediated PKR activation and cell-intrinsic antiviral immunity in mice and humans. DBR1-deficient patients are prone to viral disease because of intracellular lariat accumulation, which impairs G3BP1/2- and SG assembly-dependent PKR activation.
Cindy Ma: Science is often not black and white, and the answer usually lies in the grey
Authors: Cols Montserrat
Published: December 2024

Professor Cindy Ma heads the Human Immune Disorders Laboratory at the Garvan Institute of Medical Research. She is a member of the Garvan Faculty, holds a conjoint appointment with UNSW Sydney (School of Clinical Medicine, Faculty of Medicine and Health), and is an NHMRC of Australia Investigator Grant Fellow (L1). Her research interests lie in the study of human diseases of the immune system such as primary immunodeficiencies due to inborn errors of immunity (IEI), resulting from disease-causing monogenic germline variants. Another area of research her laboratory is perusing is the pathways that cause severe allergies and atopic diseases such as atopic dermatitis and food anaphylaxis.
Non-local structured adaptive dictionary learning method for seismic waveform inversion
Authors: Qi Hongyu , Fu Zhenwu , Li Yang , Han Bo
Published: December 2024

Full waveform inversion (FWI) is a technique used to estimate subsurface model parameters by minimizing the difference between observed and calculated seismic data. Sparsity-promoting regularization are useful tools for traditional FWI methods to tackle complex subsurface structures. Since the traditional regularization techniques can only impose some fixed priors, it is necessary to develop a regularization strategy to obtain more flexible priors. In this way, we develop a structural sparse representation method that exploits the non-local self-similarity prior of the model, which is achieved by grouping similar patches using graph matching operators and a dynamic group selection strategy. A group-based dictionary is trained with the aim of providing the best sparse representation of complex features and variations in the entire model perturbation. The dynamic selection strategy of the training method can balance computational efficiency and inversion accuracy by constantly updating and retaining groups during the processing. In addition, two loop algorithm framework is utilized to enhance the robustness and the efficiency of the proposed method. Numerical experiments are presented to demonstrate that the proposed method outperforms the total variation regularization method and the adaptive dictionary learning with non-local self-similarity in terms of robustness and resolution. This structural sparsity-promoting regularization is incorporated into the FWI problem through a two-loop algorithm framework, enhancing the robustness and efficiency of FWI results.
Boron modification of AuRh mesoporous nanotubes for electro-reduction of nitrogen to ammonia
Authors: Yang Guanghui , Song Jiale , Li Xinmiao , Deng Kai , Yu Hongjie , Xu You , Wang Hongjing , Wang Ziqiang , Wang Liang
Published: December 2024

Electrocatalytic nitrogen reduction reaction (NRR) is a prospective tactics for ammonia synthesis. However, the development of highly active NRR electrocatalysts is still challenging owing to the difficult activation of nitrogen and competitive hydrogen evolution reaction (HER). Here, we synthesized boron-doped AuRh mesoporous nanotubes (B-AuRh MNTs) via dual-template method coupled with boron doping. The mesoporous nanotube structure has high specific surface area and excellent surface permeability. Thereby, the B-AuRh MNTs exhibit NH3 yield of 13.3 μg h−1 mg−1
cat and Faraday efficiency of 22.5% under 0.1 M Na2SO4. The doping of boron with weak hydrogen adsorption can generate electronic effect, thus stimulating the activation of N2 molecules and effectively inhibiting HER. This study proposes a universal method for the preparation of boron-doped Au-based catalysts, which is beneficial to improve the NRR performance.
E-beam fluorinated CVD graphene: in-situ XPS study on stability and NH3 adsorption doping effect
Authors: Malesys V , Duan T , Denys E , Li Hu , Leifer K , Simon L
Published: December 2024

Graphene exhibits promise in gas detection applications despite its limited selectivity. Functionalization with fluorine atoms offers a potential solution to enhance selectivity, particularly towards ammonia (NH+) molecules. This article presents a study on electron-beam fluorinated graphene (FG) and its integration into gas sensor platforms. We begin by characterizing the thermal stability of fluorographene, demonstrating its resilience up to 450 °C. Subsequently, we investigate the nature of NH3 interaction with FG, exploring distinct adsorption energies to address preferential adsorption concerns. Notably, we introduce an innovative approach utilizing x-ray photoelectron spectroscopy cartography for simultaneous analysis of fluorinated and pristine graphene, offering enhanced insights into their properties and interactions. This study contributes to advancing the understanding and application of FG in gas sensing technologies.
Theory-based integrated modelling of tungsten transport in ITER plasmas
Authors: Fajardo D , Angioni C , Kim S H , Koechl F , Fable E , Loarte A , Polevoi A , Tardini G ,   the ASDEX Upgrade Team
Published: December 2024

A wide variety of ITER plasmas are investigated using a recently-developed integrated modelling framework, with particular emphasis on the transport and effects of tungsten (W) motivated by ITER’s new full-W walls. This workflow is entirely based on theoretical transport models and it has been recently validated against experimental data. Simulations in L-mode and H-mode are performed at different plasma currents and heating powers to assess the maximum W concentrations that allow access and sustainment of H-mode operation, as well as dynamical simulations of the ramp-up, from the limiter to the diverted phase, finding maximum tolerable W concentrations to avoid a radiative collapse of the plasma. A simple physical parameter is shown to order the ratio of W neoclassical to turbulent transport magnitudes for all considered ITER plasmas as well as previously simulated ASDEX Upgrade experiments.
Anisotropic in-plane field angle dependence of critical current in commercial REBCO tapes and its impact on toroidal field magnet for compact tokamak fusion device
Authors: Zhou Benzhe , Zhang Zili , Liu Quanyue , Zhang Xiaolong , Strickland Nicholas , Suo Hongli , Wang Lei , Liu Jianhua , Wang Qiuliang
Published: December 2024

The critical current (I
c) of commercial rare-earth barium copper oxide (REBCO) tapes is generally assumed to exhibit isotropic behavior with respect to the magnetic field angle applied within the tape’s basal plane (in-plane). This paper investigates the field angle dependence of critical current, both in-plane and out-of-plane, for commercial REBCO tapes manufactured by SuperOX, under fields ranging from 0 T to 8 T at 20 K. Remarkably, the in-plane field angle dependence of I
c shows significant anisotropy, with the minimum I
c no longer occurring at the traditional 90° (parallel to the ab-plane), but instead shifting to approximately 130°, a phenomenon reported for the first time. This novel anisotropic in-plane field angle dependence of I
c can substantially affect the performance of toroidal field magnets for compact tokamak fusion devices. Simulations indicate that considering versus neglecting the anisotropic in-plane field angle dependence of I
c can lead to I
c variations of up to 19.58% within the D-shaped coils of the toroidal field magnets. The locations of maximum deviation vary across different double-pancake coils within the D-shaped winding packs. This study highlights the complexity of I
c distribution in toroidal field magnets for compact fusion applications, urging further consideration of anisotropic in-plane field angle dependence of I
c of commercial REBCO tapes in fusion magnet design.
Physics-driven lumped-element modelling for impedance simulations of superconducting accelerator magnets
Authors: Janitschke M , Bednarek M , Ravaioli E , Verweij A P , Willering G , van Rienen U
Published: December 2024

Superconducting magnets in particle accelerators are subject to various forces, radiation, high voltages, or thermal gradients. These can cause failures such as inter-turn shorts, which can be very challenging to detect after the magnets are installed in the accelerator. Measurements in the time- and frequency domain can pinpoint outlier magnets or precursors of such failures. Interpretable, physics-driven simulations can facilitate this by studying if manufacturing tolerances cause the observed behaviour or if it can be correctly classified as an outlier. An equivalent circuit model is proposed to simulate superconducting accelerator magnets’ impedances. The physics-driven model includes various coupled, non-linear effects in the superconductors, such as superconducting filament magnetisation, inter-filament and inter-strand coupling currents, eddy currents in the strands’ copper and various magnet components, and stray capacitances. The model is validated against a wide range of available time- and frequency-domain measurements performed at the Large Hadron Collider at CERN. A very good agreement is achieved across the different measurements and domains. The network model is computationally very inexpensive while still preserving good accuracy and interpretability. The model can hence be used to reproduce impedances of superconducting magnets accurately for performance evaluations and to investigate the impact of failures.
Magnetic imaging of Abrikosov vortices trapped near moats in the niobium thin film
Authors: Pan Yinping , Wu Guangting , Zhang Denghui , Fan Xinxin , Wang Yue , Liu Xu , Niu Minghui , Zhang Lu , Ren Jie , Wang Zhen , Chen Lei
Published: December 2024

Abrikosov vortices trapped in superconducting circuits can reduce their operation margin and, in some cases, even lead to failure. Moats have been introduced to reduce the impact of Abrikosov vortices by providing a favorable location for trapping them at a distance from the circuit. However, the distribution mechanism of vortices near moats driven by applied magnetic fields and currents remains unclear. In this study, we used multiple moats to construct square-shaped areas in the niobium (Nb) thin film and employed magnetic force microscopy to observe the distribution of vortices induced by applied magnetic fields and currents near these areas. The moats effectively prevented vortices from entering the square-shaped area, particularly when the spacing between two moats was <550 nm. Furthermore, we discovered that the edges of moats generated new vortices with polarities opposite to those entering from both the edges of the Nb film under applied current. These vortices attracted each other and annihilated in pairs. These findings provide more insights into designing the layouts of superconducting integrated circuits.
Effect of sulfur doping on superconductivity and charge density wave order in Kagome metal CsV3(Sb1−xSx)5
Authors: Song Fei , Ke Chuan , Liu Yutong , Weng Tianqi , Hsieh Chun-Chang , Cheng Cui Hua , Chen Yongliang , Zhao Yong
Published: December 2024

Recently, the coexistence and competition of superconductivity (SC) and charge density wave (CDW) have emerged in Kagome superconductor AV3Sb5 (A = K, Rb, Cs) under pressure, which has aroused widespread interest. Here, chemical substitution is used to introduce chemical pressure to further investigate the coexistence and competition between CDW and SC states. By preparing CsV3(Sb1−x
S
x
)5 series single crystals and studying their crystal structure, chemical valence states, SC, and electronic transport behavior, it is found that S doping causes significant chemical pressure that is similar to axial mechanical pressure, resulting in suppression on the CDW and enhancement on SC. The T
c−x relationship exhibits a double dome SC, similar to the behavior observed in the CsV3Sb5 under mechanical pressure. In addition, a negative correlation between T
CDW and the disorder degree (measured by residual resistivity) is observed. This correlation is consistent with the observed translational jump in the ρ(T) curve before and after the CDW transition, that is, the temperature coefficient of resistivity does not change before and after the CDW phase transition, but only the resistivity curve shifts to a certain value. This phenomenon reveals that disorder is an important factor affecting the CDW transition of the system. Further, S doping also induces hole band filling effect that results in a decrease in the DOS at E
F and consequently counterbalances the T
c enhancement effect from chemical pressure to a certain extent. The electronic phase diagram of the CsV3(Sb1−x
S
x
)5 system is accordingly established, which demonstrates the correlation between the SC, CDW, disorder degree, and other electronic nature of the system.
Gen TSO: A General JWST Simulator for Exoplanet Times-series Observations
Authors: Cubillos Patricio E.
Published: December 2024

Gen TSO is a noise calculator specifically tailored to simulate James Webb Space Telescope (JWST) time-series observations of exoplanets. Gen TSO enables the estimation of signal-to-noise ratios (S/Ns) for transit or eclipse depths through an interactive graphical interface, similar to the JWST Exposure Time Calculator (ETC). This interface leverages the ETC by combining its noise simulator, Pandeia, with additional exoplanet resources from the NASA Exoplanet Archive, the Gaia DR3 catalog of stellar sources, and the TrExoLiSTS database of JWST programs. The initial release of Gen TSO allows users to calculate S/Ns for all JWST instruments for the spectroscopic time-series modes available as of the Cycle 4 GO call. Additionally, Gen TSO allows users to simulate target acquisition on the science targets or, when needed, on nearby stellar targets within the visit splitting distance. This article presents an overview of Gen TSO and its main functionalities. Gen TSO has been designed to provide both an intuitive graphical interface and a modular API to access the resources mentioned above, facilitating planing and simulation of JWST exoplanet time-series observations. Gen TSO is available for installation via the Python Package Index and its documentation can be found at pcubillos.github.io/gen_tso.
Transition from random self-propulsion to rotational motion in a non-Markovian microswimmer
Authors: Adersh F , Muhsin M , Sahoo M
Published: December 2024

We study the motion of an inertial microswimmer in a non-Newtonian environment with a finite memory and present the theoretical realization of an unexpected transition from random self-propulsion to rotational (circular or elliptical) motion. Further, the rotational motion of the swimmer is followed by spontaneous local directional reversal, yet with a steady-state angular diffusion. Moreover, the advent of this behaviour is observed in the oscillatory regime of the inertia-memory parameter space of the dynamics. We quantify this unconventional rotational motion of the microswimmer by measuring the time evolution of the direction of its instantaneous velocity or orientation. By solving the generalized Langevin model of non-Markovian dynamics of an inertial active Ornstein–Uhlenbeck particle, we show that the emergence of the rotational (circular or elliptical) trajectory is due to the presence of both inertial motion and memory in the environment.
Node ranking based on graph curvature and PageRank
Authors: Qu 曲 Hongbo 鸿博 , Song 宋 Yu-Rong 玉蓉 , Li 李 Ruqi 汝琦 , Li 李 Min 敏 , Jiang 蒋 Guo-Ping 国平
Published: December 2024

Identifying key nodes in complex networks is crucial for understanding and controlling their dynamics. Traditional centrality measures often fall short in capturing the multifaceted roles of nodes within these networks. The PageRank algorithm, widely recognized for ranking web pages, offers a more nuanced approach by considering the importance of connected nodes. However, existing methods generally overlook the geometric properties of networks, which can provide additional insights into their structure and functionality. In this paper, we propose a novel method named Curv-PageRank (C-PR), which integrates network curvature and PageRank to identify influential nodes in complex networks. By leveraging the geometric insights provided by curvature alongside structural properties, C-PR offers a more comprehensive measure of a node’s influence. Our approach is particularly effective in networks with community structures, where it excels at pinpointing bridge nodes critical for maintaining connectivity and facilitating information flow. We validate the effectiveness of C-PR through extensive experiments. The results demonstrate that C-PR outperforms traditional centrality-based and PageRank methods in identifying critical nodes. Our findings offer fresh insights into the structural importance of nodes across diverse network configurations, highlighting the potential of incorporating geometric properties into network analysis.
Three-dimensional simulations of RF wave propagation and power coupling in cold magnetized plasma near an ICRF antenna
Authors: Zhang 张 Lei-Yu 雷宇 , Li 李 Yi-Xuan 屹轩 , Zhang 张 Quan-Zhi 权治
Published: December 2024

The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies (ICRF) is studied based on self-developed 3DFEM-IA code. This code effectively resolves the three-dimensional (3D) geometry and the electromagnetic field using the finite element method. Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases, surface current density on the antenna straps, and background plasma density. Notably, the non-uniform surface current density on the antenna straps, resulting from the presence of induced currents, contributes to a reduction in coupling power within the edge plasma. Furthermore, the calculated coupling impedance increases with plasma density, corroborating well with experimental measurements.
Resonance of hypernuclei with complex momentum representation*
Authors: Zhang 张 Hantao 涵韬 , Chen 陈 Chao-Feng 超锋 , Zhou 周 Xian-Rong 先荣 , Ren 任 Zhongzhou 中洲
Published: December 2024

By combining the Skyrme-Hartree-Fock method with complex momentum representation (CMR), the resonant states of

O,

Ca,

Ca, and

Ni were investigated. The phase shifts for hyperon-nucleus elastic scattering were determined with continuum level density (CLD), and the scattering length as well as the resonance energy were obtained by utilizing the effective range expansion. Our method, abbreviated as CMR-CLD, exhibits good consistency with traditional approaches and provides ground work for investigating scattering and resonance problems in deformed and multi-hyperon hypernuclei.
Influence of the density gradient on turbulent heat transport at ion-scales: an inter-machine study with the gyrokinetic code stella
Authors: Thienpondt H. , García-Regaña J.M. , Calvo I. , Acton G. , Barnes M.
Published: December 2024

Efficient control of turbulent heat transport is crucial for magnetic confinement fusion reactors. This work discusses the complex interplay between density gradients and microinstabilities, shedding light on their impact on turbulent heat transport in different fusion devices. In particular, the influence of density gradients on turbulent heat transport is investigated through an extensive inter-machine study, including various stellarators such as W7-X, LHD, TJ-II and NCSX, along with the Asdex Upgrade tokamak (AUG) and the tokamak geometry of the Cyclone Base Case (CBC). Linear and nonlinear simulations are performed employing the δf-gyrokinetic code stella across a wide range of parameters to explore the effects of density gradients, temperature gradients, and kinetic electrons. A strong reduction in ion heat flux with increasing density gradients is found in NCSX and W7-X due to the stabilization of temperature-gradient-driven modes without significantly destabilizing density-gradient-driven modes. In contrast, the tokamaks exhibit an increase in ion heat flux with density gradients. Notably, the behavior of ion heat fluxes in stellarators does not align with that of linear growth rates, if only the fastest-growing mode is taken into account. Additionally, this study provides physical insights into the microinstabilities, emphasizing the dominance of trapped-electron-modes (TEMs) in CBC, AUG, TJ-II, LHD and NCSX, while both the TEM and the passing-particle-driven universal instability contribute significantly in W7-X.