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M. Zhou

Publications and source records attributed to M. Zhou.

At least 19 recordsLinked to original sources

AIMBio-Mat: An AI-Native FAIR Platform for Closed-Loop Materials Discovery and Biomedical Translation

Materials discovery and biomedical translation increasingly require models that can reason across composition, processing, structure, biological response, manufacturability, safety, and governance constraints. Existing materials and biomedical data ecosystems are powerful but remain poorly coupled for AI-guided discovery. Here we present AIMBio, a conceptual framework for an AI-native, FAIR, and governance-aware decision layer that links materials provenance, biomedical context, knowledge graphs, uncertainty-aware machine learning, and human-in-the-loop active learning. The framework formulates biomedical-materials discovery as constrained multi-objective optimization under uncertainty and introduces practical requirements for metadata, model documentation, risk-tiered governance, evaluation metrics, and phased implementation. To make the roadmap testable, we add a minimum viable prototype specification and a worked pilot for AI-guided nanomaterials for drug delivery. AIMBio is positioned as exploratory and preclinical discovery infrastructure, not as clinical decision-support software; any clinical or regulated-device use would require separate validation, change control, and regulatory review. The central contribution is a publishable platform blueprint for converting fragmented materials and biomedical records into auditable, experimentally actionable, and translationally responsible discovery workflows.

physics.app-ph

Building a Regional Data-Centric Materials Science Ecosystem for Processing-Rich Materials Innovation in the Great Plains

Data-centric materials science is changing how materials are discovered, optimized, manufactured, and qualified, yet many deployment-limiting materials problems still depend on experimental, processing-rich, device-level, and field-relevant data that are difficult to capture in conventional materials databases. This perspective argues that the Great Plains and adjacent interior research corridor can make a distinctive national contribution by organizing distributed experimental assets into a trusted regional materials-data ecosystem. The proposed model emphasizes FAIR metadata, provenance, persistent sample identifiers, uncertainty-aware modeling, semi-closed-loop workflows, stackable workforce training, and tiered governance for academic, public, controlled-access, and industry-protected data. We identify five coupled barriers -- fragmented data, weak algorithm--laboratory translation, uneven access to cyberinfrastructure and technical staff, workforce gaps at the materials--data interface, and insufficient incentives for sharing and reuse -- and propose a staged roadmap for addressing them. A high-purity germanium pilot illustrates how regional strengths can be converted into reusable datasets, benchmark models, trained personnel, and decision-improving workflows. The broader message is that regional leadership in data-centric materials science will depend less on geographic concentration than on trustworthy data practices, interoperable infrastructure, cross-trained people, and application-driven materials challenges.

cond-mat.mtrl-sci

Sustained interpenetrating plasma flows for the investigation of late time kinetic instability evolution

Sustained collisionless interpenetrating plasma flows have been generated on the OMEGA laser facility to enable direct investigation of nonlinear evolution of fields generated by electromagnetic kinetic instabilities. FLASH simulations and Thomson scattering measurements are used to determine the plasma conditions achieved. Interpenetrating flows are observed to remain collisionless for at least 11 ns, longer than any prior OMEGA experiment, supporting the growth and nonlinear saturation of the Weibel instability. Resulting magnetic fields are measured using proton radiography. This work establishes a unique platform for late-time filament evolution measurements.

physics.plasm-ph

First look at Vela X-1 with XRISM: A simultaneous campaign with XMM-Newton and NuSTAR

High-Mass X-ray Binaries (HMXBs) serve as useful laboratories for exploring the behaviour of accreted matter onto compact objects and for probing the complex wind environments of massive stars. These investigations are essential for understanding stellar life cycles and the dynamics of the Milky Way, and they are prominent topics in the science cases for XRISM and NewAthena. We report, for the first time, a XRISM observation of the HMXB Vela X-1, conducted during the first cycle of the XRISM general observer programme and complemented by simultaneous XMM-Newton and NuSTAR coverage. This campaign targeted a critical orbital phase -- when the neutron star is in inferior conjunction -- during which significant changes in absorption are expected. We performed absorption-resolved spectral analyses during two time intervals of interest: the soft and hard hardness ratio (HR) intervals, as it is strongly correlated with absorption variability. We observed a sudden transition in the HR from a soft to a hard state, coinciding with an increase in the absorption column density. This is likely attributed to the onset of the accretion structure crossing our line of sight. With XRISM/Resolve, we also investigated the Fe K region, and we report for the first time the presence of a Fe K$\alpha$ doublet in the spectrum of Vela X-1, together with the presence of already known Fe K$\beta$ and Ni K$\alpha$ lines that are produced in cold clumps embedded in the hot ionised wind. The measured line velocities of the order of $10^2 \ \mathrm{km\,s^{-1}}$ are consistent with production sites in the vicinity of the neutron star. This precursor study with Vela X-1 shows the potential of XRISM in studying in unprecedented details the spectral evolution of wind-accreting X-ray binaries.

astro-ph.HE

Electron Acceleration via Trapping inside Ion Mirror-mode Structures within A Large-scale Magnetic Flux Rope

Fermi acceleration is believed as a crucial process for the acceleration of energetic electrons within flux ropes (FRs) during magnetic reconnection. However, in finite-length FRs with a large core field, the finite contracting and the escaping of electrons along the axis can significantly limit the efficiency of Fermi acceleration. Using observations from the Magnetospheric Multiscale mission in the magnetotail, we demonstrate that magnetic mirror structures inside the FR can effectively prevent the escape of energetic electrons and overcome the limitation of finite contraction. Energetic electrons were produced and formed a power-law energy distribution in these mirror structures. By evaluating the acceleration rates, we show that these energetic electrons can be continuously accelerated within the mirror structures near the central region of the FR. These results unveil a novel mechanism that is universally applicable to electron acceleration within FRs in space, laboratory, and astrophysical plasmas.

physics.space-ph

Dimming GRS 1915+105 observed with NICER and Insight--HXMT

The black hole X-ray binary GRS 1915+105 was bright for 26 years since its discovery and is well-known for its disk instabilities, quasi-periodic oscillations, and disk wind signatures. We report a long-term spectral-timing tracing of this source from mid-2017 until the onset of the "obscured state", based on the complete data from the Neutron Star Interior Composition Explorer (NICER) and the Insight--Hard X-ray Modulation Telescope (HXMT), whose hard coverage decisively informs the modeling at lower energies. In the soft state predating 2018, we observed highly ionized winds. However, in the hard state shortly before transitioning into the "obscured state" on May 14, 2019 (MJD 58617), the winds exhibited a discernible reduction in ionization degree ($\log \xi$), decreasing from above 4 to approximately 3. Our analysis involves the measurement of the frequencies of the quasi-periodic oscillations and the estimation of the properties of the ionized winds and the intensities of different spectral components through spectroscopy during the decay phase. We delve into the origin of these infrequently observed warm outflows in the hard state. It is found that the launching radius of the winds in the hard decay phase is similar to that in the soft state, indicating the launching mechanism of those winds in both states is likely the same. The presence of the ionized winds is preferentially dependent on the periphery of the accretion disk, but not directly related to the corona activities in the center of the binary system.

astro-ph.HE

Variable structures in the stellar wind of the HMXB Vela X-1

Strong stellar winds are an important feature in wind-accreting high-mass X-ray binary (HMXB) systems, providing insights into stellar evolution and their impact on surrounding environments. However, the long-term evolution and temporal variability of these winds are not fully understood. This work probes the archetypal wind-accreting HMXB Vela X-1 using MAXI observations over 14 years, focusing on orbit-to-orbit absorption variability in the 2-10 keV band. Additionally, the relation between hardness ratio trends in binary orbits and neutron star spin states is investigated. We calculate hardness ratios to track absorption variability, comparing flux changes across energy bands, as the effect of absorption on the flux is energy-dependent. Variability is analyzed by comparing hardness ratio trends across binary orbits to the MAXI long-term averaged evolution. The long-term averaged hardness ratio evolution displays a stable pattern. Yet, individual binary orbits reveal different hardness ratio evolutions between consecutive orbits with no evident periodicity. Less than half of the binary orbits align with the long-term evolution. Moreover, neutron star spin-up episodes exhibit harder-than-average hardness trends compared to spin-down episodes, although their distributions overlap considerably. The long-term averaged hardness ratio dispersion is consistent with absorption column densities reported in literature from shorter observations, suggesting that heterogeneous wind structures, including accretion wakes and wind clumps, drive observed variations. The orbit-to-orbit variability indicates that pointed X-ray observations provide limited insight into wind structure. The link between neutron star spin states and hardness trends underscores the influence of accretion on absorption, with variability tied to stellar wind density fluctuations.

astro-ph.HE

Spin measurement of 4U 1543-47 with Insight-HXMT and NICER from its 2021 outburst: A test of accretion disk models at high luminosities

4U 1543--47 is one of a handful of known black hole candidates located in the Milky Way Galaxy, and has undergone a very bright outburst in 2021, reaching a total of $\sim$9 Crab, as observed by the Monitor of All-sky Image (MAXI), and exceeding twice its Eddington luminosity. The unprecedented bright outburst of 4U 1543--47 provides a unique opportunity to test the behavior of accretion disk models at high luminosities and accretion rates. In addition, we explore the possibility of constraining the spin of the source at high accretion rates, given that previous spin measurements of 4U 1543--47 have been largely inconsistent with each other. We measure the spectral evolution of the source throughout its outburst as observed by Insight-HXMT, and compare the behavior of both the thin disk model kerrbb2, as well as the slim disk model slimbh up to the Eddington limit for two different values of disk $\alpha$-viscosity. In addition, given the behavior of these two models, we identify two `golden' epochs for which it is most suitable to measure the spin with continuum fitting.

astro-ph.HE

Observing the onset of the accretion wake in Vela X-1

High-Mass X-ray Binaries (HMXBs) offer a unique opportunity for the investigation of accretion onto compact objects and of wind structure in massive stars. A key source for such studies is the bright neutron star HMXB Vela X-1 whose convenient physical and orbital parameters facilitate the analysis and in particular enable studies of the wind structure in HMXBs. Here, we analyse simultaneous XMM-Newton and NuSTAR observations at $\phi_{\mathrm{orb}} \approx$ 0.36-0.52 and perform time-resolved spectral analysis down to the pulse period of the neutron star, based on our previous NuSTAR-only results. For the first time, we are able to trace the onset of the wakes in a broad 0.5-78 keV range with a high-time resolution of $\sim$283 s and compare to theoretical predictions. We observe a clear rise of the absorption column density of the stellar wind $N_{\mathrm{H,1}}$ starting at orbital phase $\sim$0.44, corresponding to the wake structure entering our line of sight towards the neutron star, together with local extrema throughout the observation possibly associated with clumps or other structures in the wind. Periods of high absorption reveal the presence of multiple fluorescent emission lines of highly ionised species, mainly in the soft X-ray band between 0.5 and 4 keV, indicating photoionisation of the wind.

astro-ph.HE

Monte-Carlo simulations on possible collimation effects of outflows to fan-beamed emission of ultraluminous accreting X-ray pulsars

Pulsating ultraluminous X-ray sources (PULXs) are accreting pulsars with apparent X-ray luminosity exceeding $10^{39}\, \rm erg\ s^{-1}$. We perform Monte-Carlo simulations to investigate whether high collimation effect (or strong beaming effect) is dominant in the presence of accretion outflows, for the fan beam emission of the accretion column of the neutron stars in PULXs. We show that the three nearby PULXs (RX J0209.6$-$7427, Swift J0243.6+6124 and SMC X-3), namely the three musketeers here, have their main pulsed emission not strongly collimated even if strong outflows exist. This conclusion can be extended to the current sample of extragalactic PULXs, if accretion outflows are commonly produced from them. This means that the observed high luminosity of PULXs is indeed intrinsic, which can be used to infer the existence of very strong surface magnetic fields of $\sim10^{13-14}$ G, possibly multipole fields. However, if strong outflows are launched from the accretion disks in PULXs as a consequence of disk spherization by radiation pressure, regular dipole magnetic fields of $\sim10^{12}$ G may be required, comparable to that of the three musketeers, which have experienced large luminosity changes from well below their Eddington limit ($2\times10^{38}\, \rm erg\ s^{-1}$ for a NS) to super-Eddington and their maximum luminosity fills the luminosity gap between Galactic pulsars and extragalactic PULXs.

astro-ph.HE

The spectral-timing analysis of Cygnus X-1 with Insight-HXMT

Cygnus X-1, as the first discovered black hole binary, is a key source for understanding the mechanisms of state transitions, and the scenarios of accretion in extreme gravity fields. We present a spectral-timing analysis of observations taken with the Insight-HXMT mission, focusing on the spectral-state dependent timing properties in the broad energy range of 1--150 keV, thus extending previous RXTE-based studies to both lower and higher energies. Our main results are the following: a) We successfully use a simple empirical model to fit all spectra, confirming that the reflection component is stronger in the soft state than in the hard state; b) The evolution of the total fractional root mean square (rms) depends on the selected energy band and the spectral shape, which is a direct result of the evolution of the power spectral densities (PSDs); c) In the hard/intermediate state, we see clear short-term variability features and a positive correlation between central frequencies of the variability components and the soft photon index $\Gamma_1$, also at energies above 15 keV. The power spectrum is dominated by red noise in the soft state instead. These behaviors can be traced to at least 90 keV; d) The coherence and the phase-lag spectra show different behaviors dependent on different spectral shapes.

astro-ph.HE

Fan beamed X-ray emission from 1 keV to above 130 keV from the ultraluminous X-ray pulsar RX J0209.6-7427 in the Small Magellanic Cloud

We present detailed timing and spectral analyses of the transient X-ray pulsar RX J0209.6$-$7427 in the Small Magellanic Cloud during its 2019 giant outburst. With a better known distance than most galactic X-ray pulsars, its peak luminosity is determined to be $(1.11\pm0.06)\times 10^{39}\, \rm erg\ s^{-1}$; it is thus a {\it bonda fide} pulsating ultraluminous X-ray source (PULX). Owing to the broad energy band of \textit{Insight}-HXMT, its pulsed X-ray emission was detected from 1 keV up to the 130$-$180 keV band, which is the highest energy emission detected from any PULXs outside the Milky Way. This allows us to conclude that its main pulsed X-ray emission is from the "fan beam" of the accretion column, and its luminosity is thus intrinsic. We also estimate its magnetic field of (4.8$-$8.6)$\times10^{12}$ G or (1.7$-$2.2)$\times10^{13}$ G, from its spin evolution or transition in the accretion column structure during the outburst; we suggest that the two values of the magnetic field strength correspond to the dipole and multipole magnetic fields of the neutron star, similar to the recent discovery in the Galactic PULX Swift J0243.6+6124. Therefore, the nature of the neutron star and its ULX emission can be understood within the current theoretical frame of accreting neutron stars. This may have implications for understanding the nature of those farther away extragalactic PULXs.

astro-ph.HE

A multi-cubic-kilometre neutrino telescope in the western Pacific Ocean

Next-generation neutrino telescopes with significantly improved sensitivity are required to pinpoint the sources of the diffuse astrophysical neutrino flux detected by IceCube and uncover the century-old puzzle of cosmic ray origins. A detector near the equator will provide a unique viewpoint of the neutrino sky, complementing IceCube and other neutrino telescopes in the Northern Hemisphere. Here we present results from an expedition to the north-eastern region of the South China Sea, in the western Pacific Ocean. A favorable neutrino telescope site was found on an abyssal plain at a depth of $\sim$ 3.5km. At depths below 3km, the sea current speed, water absorption and scattering lengths for Cherenkov light, were measured to be $v_{\mathrm{c}}<$10cm/s, $\lambda_{\mathrm{abs} }\simeq$ 27m and $\lambda_{\mathrm{sca} }\simeq$ 63m, respectively. Accounting for these measurements, we present the design and expected performance of a next-generation neutrino telescope, TRopIcal DEep-sea Neutrino Telescope (TRIDENT). With its advanced photon-detection technology and large dimensions, TRIDENT expects to observe the IceCube steady source candidate NGC 1068 with 5$\sigma$ significance within 1 year of operation. This level of sensitivity will open a new arena for diagnosing the origin of cosmic rays and probing fundamental physics over astronomical baselines.

astro-ph.HE

Majorization-type cluster robust bounds for block filters and eigensolvers

Convergence analysis of block iterative solvers for Hermitian eigenvalue problems and the closely related research on properties of matrix-based signal filters are challenging, and attract increasing attention due to their recent applications in spectral data clustering and graph-based signal processing. We combine majorization-based techniques pioneered for investigating the Rayleigh-Ritz method in [SIAM J. Matrix Anal. Appl., 31 (2010), pp. 1521-1537] with tools of classical analysis of the block power method by Rutishauser [Numer. Math., 13 (1969), pp. 4-13] to derive convergence rate bounds of an abstract block iteration, wherein tuples of tangents of principal angles or relative errors of Ritz values are bounded using majorization in terms of arranged partial sums and tuples of convergence factors. Our novel bounds are robust in presence of clusters of eigenvalues, improve some previous results, and are applicable to most known block iterative solvers and matrix-based filters, e.g., to block power, Chebyshev, and Lanczos methods combined with shift-and-invert approaches and polynomial filtering.

math.NA

Game Theory and Machine Learning in UAVs-Assisted Wireless Communication Networks: A Survey

In recent years, Unmanned Aerial Vehicles (UAVs) have been used in fields such as architecture, business delivery, military and civilian theaters, and many others. With increased applications comes the increased demand for advanced algorithms for resource allocation and energy management. As is well known, game theory and machine learning are two powerful tools already widely used in the wireless communication field and there are numerous surveys of game theory and machine learning usage in wireless communication. Existing surveys however focus either on game theory or machine learning and due to this fact, the current article surveys both game-theoretic and machine learning algorithms for use by UAVs in Wireless Communication Networks (U-WCNs). We also discuss how to combine game theory and machine learning for solving problems in U-WCNs and identify several future research directions.

cs.MA

Radio morphology of southern narrow-line Seyfert 1 galaxies with Very Large Array observations

We present the results of new radio observations carried out with the Karl G. Jansky Very Large Array C-configuration at 5.5 GHz for a sample of southern narrow-line Seyfert 1 galaxies (NLS1s). This work increases the number of known radio-detected NLS1s in the southern hemisphere, and confirms that the radio emission of NLS1s is mainly concentrated in a central region at kpc-scale and only a few sources show diffuse emission. In radio-quiet NLS1s, the radio luminosity tends to be higher in steep-spectrum sources and be lower in flat-spectrum sources, which is opposite to radio-loud NLS1s. This may be because the radio emission of steep NLS1s is dominated by misaligned jets, AGN-driven outflows, or star formation superposing on a compact core. Instead the radio emission of flat NLS1s may be produced by a central core which has not yet developed radio jets and outflows. We discover new NLS1s harboring kpc-scale radio jets and confirm that a powerful jet does not require a large-mass black hole to be generated. We also find sources dominated by star formation. These NLS1s could be new candidates in investigating the radio emission of different mechanisms.

astro-ph.GA

WLAN Indoor Intrusion Detection Based on Deep Signal Feature Fusion and Minimized-MKMMD Transfer Learning

Indoor intrusion detection technology has been widely utilized in network security monitoring, smart city, entertainment games, and other fields. Most existing indoor intrusion detection methods directly exploit the Received Signal Strength (RSS) data collected by Monitor Points (MPs) and do not consider the instability of WLAN signals in the complex indoor environments. In response to this urgent problem, this paper proposes a novel WLAN indoor intrusion detection method based on deep signal feature fusion and Minimized Multiple Kernel Maximum Mean Discrepancy (Minimized-MKMMD). Firstly, the multi-branch deep convolutional neural network is used to conduct the dimensionality reduction and feature fusion of the RSS data, and the tags are obtained according to the features of the offline and online RSS fusion features that are corresponding to the silence and intrusion states, and then based on this, the source domain and target domain are constructed respectively. Secondly, the optimal transfer matrix is constructed by minimizing MKMMD. Thirdly, the transferred RSS data in the source domain is utilized for training the classifiers that are applying in getting the classification of the RSS fusion features in the target domain in the same shared subspace. Finally, the intrusion detection of the target environment is realized by iteratively updating the process above until the algorithm converges. The experimental results show that the proposed method can effectively improve the accuracy and robustness of the intrusion detection system.

eess.SP

Universality of lower hybrid waves at Earth's magnetopause

Waves around the lower hybrid frequency are frequently observed at Earth's magnetopause, and readily reach very large amplitudes. Determining the properties of lower hybrid waves is crucial because they are thought to contribute to electron and ion heating, cross-field particle diffusion, anomalous resistivity, and energy transfer between electrons and ions. All these processes could play an important role in magnetic reconnection at the magnetopause and the evolution of the boundary layer. In this paper, the properties of lower hybrid waves at Earth's magnetopause are investigated using the Magnetospheric Multiscale (MMS) mission. For the first time, the properties of the waves are investigated using fields and direct particle measurements. The highest-resolution electron moments resolve the velocity and density fluctuations of lower hybrid waves, confirming that electrons remain approximately frozen in at lower hybrid wave frequencies. Using fields and particle moments the dispersion relation is constructed and the wave-normal angle is estimated to be close to $90^{\circ}$ to the background magnetic field. The waves are shown to have a finite parallel wave vector, suggesting that they can interact with parallel propagating electrons. The observed wave properties are shown to agree with theoretical predictions, the previously used single-spacecraft method, and four-spacecraft timing analyses. These results show that single-spacecraft methods can accurately determine lower hybrid wave properties.

physics.space-ph