Search Results (804)

The Huainan Mining Area features extensively developed, fragmented-soft and low-permeability coal seams, characterized by low porosity and permeability, complex geological structures, and significant difficulty in coalbed methane (CBM) drainage. Horizontal wells with staged fracturing in the coal seam roof have become a key method for regional gas control. To further enhance the volume fracturing stimulation effect and single-well gas production, this study targets the horizontal well group in the roof of the No. 8 coal seam in the Huainan Mining Area as the research object. A saturated volume fracturing technology for horizontal wells in the coal seam roof, centered on the concept of a high pump rate (18–20 m³/min) and a high proppant volume (>250 m³/stage), is proposed. This study investigates the fracture propagation mechanisms and fracturing parameter optimization of this technology, and conducts engineering application to verify its stimulation effect. Increasing the fracturing pump rate improves the proppant-carrying capacity of the fracturing fluid, successfully enabling high-rate and high-volume proppant placement. Optimization of the perforation parameters—12 holes per m per cluster and a cluster spacing of 15–25 m—utilizes high perforation friction and moderate stress interference to promote balanced initiation and propagation of multiple fractures within a stage. The optimized ‘saturated’ injection mode, with a single-stage fluid volume exceeding 2400 m³, a single-stage proppant volume exceeding 250 m³, and a maximum sand ratio exceeding 20%, combined with a multi-size proppant mixture, enables full propping of both main and branch fractures. Microseismic monitoring shows that the hydraulic fracture extension length increased by approximately 50% compared to conventional wells, significantly enlarging the stimulated reservoir volume (SRV). Saturated fracturing achieved stable gas production of 2000 to 3000 m³/d, with average production ramp-up rates of 21.47–26.40 m³/d (five times higher than the 5.34 m³/d of the conventional well), and the stable plateau period was notably extended from 36 days to over 150 days. The saturated volume fracturing technology proposed in this study provides an important reference for efficient CBM extraction and surface gas control in mining areas with similar geological conditions. Full article

Gas Electron Multiplier (GEM) detectors have become an indispensable component of modern tracking systems. The heart of a GEM detector is a thin polyimide foil (∼50 µm) clad with copper (∼5 µm) on both sides and containing an array of regularly spaced holes (typically diameter of ∼70 µm and pitch of ∼140 µm) fabricated using photolithographic techniques. The presence of the dielectric substrate (polyimide) within the amplification region introduces a time dependent response when the detector is exposed to external irradiation, a phenomenon commonly referred to as the charging-up effect. This effect arises from the accumulation of charge on the insulating polyimide surfaces, leading to a gradual modification of the local electric field configuration inside the GEM holes and, consequently, a variation in the detector gain over time. The charging-up behaviour has been systematically investigated for triple GEM chamber prototypes using an Fe-55 radioactive source (5.9 keV X-rays) with an activity of ∼20 mCi. The characteristic charging-up time constant has been extracted, and its dependence on detector gain and irradiation rate has been examined. In addition, the uniformity of detector performance in terms of count rate, gain, and energy resolution has been studied both before and after the charging-up process. In this review article, the experimental setup, data acquisition methodology, and analysis procedures developed and carried out by our group are summarised. The key findings reported by other groups, relevant Monte Carlo simulation efforts, and future outlook for the charging-up investigation on GEM based detectors are also discussed in this article. The investigations and their outcomes reviewed here provide valuable insight into the charging-up dynamics of GEM detectors and their dependence on operational parameters. Full article

To improve the directional propagation of blasting-induced cracks in sandstone and reduce over-excavation, under-excavation, and surrounding-rock damage caused by conventional circular blastholes, circular and V-shaped slotted blasthole models were established in LS-DYNA. The ALE fluid–solid coupling algorithm was adopted to investigate the effects of slot angle on the effective stress field, crack propagation pattern, and crack control index. The stress field theory at the tip of the V-shaped slot was further used to explain the directional cracking mechanism. On this basis, a two-hole V-slotted blasting model is established to analyze the influence of hole spacing on crack penetration. The results show that the V-shaped slot can form an obvious stress concentration at the tip, which changes the crack from approximately isotropic extension to directional extension along the direction of the slots. Under the present two-dimensional homogeneous sandstone model with simultaneous initiation, the 60° slot angle corresponds to the highest peak effective stress and crack control index. For the synchronized two-hole model, when the hole spacing is 70–90 cm, namely the ratio of hole spacing to blasthole diameter is approximately 14–18, the inter-hole crack penetration effect is better, and the proportion of effective cracks along the slot direction is about 80%. These results provide baseline numerical references for sandstone-controlled blasting parameter design under the modeling conditions of this study. Full article

Accurate identification of flooded layers by cased-hole logging is a critical challenge for fine-scale development and enhanced oil recovery in water-flooded oil fields at medium to high water-cut stages. Conventional methods based on single-series logging or two-dimensional crossplot techniques are inadequate for the fine-scale interpretation of complex low-permeability reservoirs. This paper proposes a novel flooded layer identification method through the deep integration of dynamic and static data. The proposed approach organically couples static open-hole logging data (porosity, resistivity, etc.) with dynamic cased-hole logging data (pulsed neutron macroscopic capture cross-section Σ and carbon–oxygen ratio, C/O) within a three-dimensional (3D) crossplot framework. A multidimensional feature parameter space is constructed, and a spatial distance-ratio model is established to quantitatively calculate the flooding index Fw for continuous evaluation of flood level (non-flooded, weakly flooded, moderately flooded, and strongly flooded). Field application in Well X of a low-permeability oil field successfully identified two ambiguous apparent water layers as weakly flooded layers, previously indistinguishable using traditional 2D methods, with interpretation results highly consistent with subsequent production tests. The identification accuracy reached over 90.7%, providing a scalable technical framework for cased-hole flooded layer evaluation in medium-to-low-permeability complex reservoirs. Full article

Against the backdrop of global energy transition and the widespread adoption of Hydrogen-Blended Natural Gas (HBNG), the safety of urban gas pipeline networks faces severe challenges. This paper systematically reviews the research progress of numerical simulation in the field of natural gas pipeline safety, focusing on its core supporting roles throughout the “Leakage–Dispersion–Evolution–Consequence” disaster chain. First, it analyzes the kinetic modeling of high-pressure leakage holes and property corrections based on real gas equations of state, elaborating on the numerical characterization of HBNG multi-component transport. Second, it compares the dispersion mechanisms and environmental coupling modeling methods in typical scenarios such as buried porous media, confined spaces in utility tunnels, underwater environments, and urban building clusters. Third, it reviews leakage monitoring technologies based on physical field simulation and data-driven approaches (e.g., Convolutional Neural Network, Long Short-Term Memory), emphasizing the value of numerical simulation in constructing digital twin training sets. Furthermore, it explores the dynamic evolution of explosion flame–shock wave interactions and the evaluation models for secondary disaster consequences. Finally, the current research status of grid-based risk pre-warning and emergency response strategies is summarized. In conclusion, numerical simulation is not only a robust method for precisely quantifying and characterizing complex physical mechanisms but also a critical technological foundation for building smart and resilient energy cities. Future research should focus on the deep coupling of multi-physics fields, physics-informed learning, and the development of system-level integrated defense systems. Full article

Direction-of-arrival (DOA) estimation of cyclostationary signals is an important problem in array signal processing, especially in sensor-limited and underdetermined scenarios. Sparse arrays and cyclostationary statistics can improve virtual degrees of freedom and target selectivity, but incomplete difference coarray information caused by missing lags may degrade virtual covariance reconstruction and reduce the reliability of DOA estimation in closely spaced, coherent, and interference-contaminated environments. To address this issue, this paper proposes a cyclostationary DOA estimation method based on an augmented extended coprime array (AECA), SVT-based hole recovery, and weighted atomic norm minimization (ANM). The proposed method first constructs the cyclic correlation matrix at the target cyclic frequency and maps it into the AECA-based virtual coarray domain. Redundant lag observations are then aggregated, and an iterative hole recovery procedure is applied to obtain an initial structured virtual covariance matrix. On this basis, a weighted ANM-based covariance refinement model is introduced, where directly observed lags and SVT-recovered hole entries are assigned different confidence levels. The final DOA estimates are obtained using MUSIC on the refined virtual covariance matrix. Simulation results under the considered underdetermined, closely spaced, coherent-source, and interference-contaminated scenarios show that the proposed method achieves lower RMSE and clearer spectral responses than the selected baseline methods. Additional ablation, parameter sensitivity, cyclic frequency mismatch, non-Gaussian noise, and runtime analyses further clarify the contribution, robustness range, and computational cost of the proposed framework. Full article

Numerous factors influence the formation of blasting craters in engineering blasting. Based on the actual parameters of the Daye Iron Mine, this study established six sets of single-hole blasting crater numerical models with different borehole diameters using ANSYS(19.0)/LS-DYNA(R13) software. The variation in blasting crater volume with the scaled depth was analyzed to determine the optimum scaled depth for each borehole diameter, and a functional relationship between the optimum scaled depth and borehole diameter was derived through curve fitting. Furthermore, using a borehole diameter of 0.076 m as a case study, a double-hole blasting crater was developed to investigate the effect of varying hole spacing on blasting crater volume and to determine the optimal hole spacing. The blasting parameters were optimized based on the numerical simulation results. The results show that within the range of borehole diameters considered, the blasting crater volume initially increases and then decreases with increasing scaled depth of the explosive charge. The fitted relationship between the optimum scaled depth and borehole diameter is y = −180.7197x³ + 86.3754x² − 9.5504x + 1.0782. For a borehole diameter of 0.076 m, the optimum scaled depth is 0.7278 m/kg^1/3, and the optimal hole spacing is 0.52 m. Based on blasting similarity theory, the calculated optimum burial depth of the explosive charge is 0.59 m, the critical burial depth is 1.1 m, and the recommended row spacing ranges from 0.95 m to 1.18 m. The findings of this study provide a theoretical basis for optimizing blasting parameters at the Daye Iron Mine and similar mining operations. Full article

Black-hole accretion systems exhibit a characteristic coexistence of activities: broad-band X-ray variability, hot coronae, wide-angle winds, and both steady and discrete jets. This coexistence suggests a persistently time-dependent magnetic background in which noisy fluctuations and explosive release are both essential. In this paper, we connect them all to the storage, organization, and intermittent reconnection-mediated release of magnetic energy, and we propose a Synchronized Spin Model (SSM) in which multiple local dynamos in a rotating accretion flow are represented as interacting macro-spins. Their synchronization, partial synchronization, excursion, and reversal define a compact set of collective variables that organize both timing statistics and large-scale morphology. In this picture, multiscale magnetic reconnection converts stored magnetic energy into coronal heating, flares, intermittent outflows, and discrete jet activity, while the same synchronization dynamics produce amplitude modulation and demodulation, providing a route to 1/f-like variability, rms–flux/Taylor-like scaling, and approximately log-normal statistics of the demodulated envelope. We further argue that, although the continuous flux distribution in black-hole systems is more naturally discussed in multiplicative or log-normal terms, broader event-catalog statistics remain useful for describing suitably defined burst hierarchies, particularly by analogy with solar and stellar flare systems. The hard/soft cycle of X-ray binaries is then interpreted as motion through magnetic state space. Full article

Radial Basis Functions (RBFs), since their inception in the 1960s, have emerged as a key tool in digital engineering applications. As interpolators in multidimensional spaces, RBFs play a crucial role both in generic data science problems and in 3D space manipulation. Their ability to represent large 3D datasets in a mesh-free manner has established them as the standard approach for data mapping and mesh deformation. A fast implementation of RBFs is essential to fully exploit this mathematical approach in digital engineering applications. This paper provides an overview of fast RBF methods in digital engineering and presents practical applications in the field of Computer-Aided Engineering (CAE), highlighting the role of RBFs in the development of a digital twin capable of real-time interaction with 3D structural components; after detailing the workflow for a simple plate with a hole, the method is demonstrated for the structural redesign of a scooter engine connecting rod and for the interactive conceptual design of a CubeSat. Full article

The Event Horizon Telescope (EHT) imaging of M87* and Sgr A* provides a unique opportunity to test spacetime geometries in the strong-field regime. Motivated by this, we systematically investigate the optical characteristics for three types of nonsingular black holes (BHs) with a Minkowski core and constrain the quantum gravity effect parameter $\alpha$ and the regularization parameter n using EHT observational data. Utilizing the observed shadow sizes of M87* and Sgr A*, we conduct a detailed comparison of the constraints on $\alpha$ for the three BH types. Our analysis reveals significant differences among them: Type I BHs exhibit the largest upper limit, whereas Type III BHs show the smallest upper limit. Furthermore, the constraints derived from M87* observations are tighter than those from Sgr A*, reflecting the close dependence of these limits on current observational precision. Subsequently, we simulate BH images at the current EHT resolution using a Gaussian filter. Although the photon ring and lensed ring features cannot be resolved, variations in shadow size and brightness distribution are clearly detectable. Within the parameter space allowed by EHT observations, the shadow size and total intensity exhibit a distinct monotonic hierarchy: Type I BHs display the largest shadow and highest total intensity, while Type III BHs show the opposite trend. Finally, we find that increasing $\alpha$ leads to shadow contraction and dimming, whereas increasing n causes the shadow to expand while making the optical characteristics of the three BH types increasingly indistinguishable. Consequently, the three BH types become more readily distinguishable only when n is small or $\alpha$ is large. Full article

We extended the higher-dimensional quantum Oppenheimer–Snyder model to the case with a cosmological constant. For the AdS case, we discuss its thermodynamic properties in extended phase space formalism and make a comparison with classical black holes. For quantum-corrected small black holes in AdS spacetime, the temperature no longer diverges but tends to zero. Additionally, the heat capacity exhibits characteristic behavior indicative of an extra phase transition induced by quantum corrections, highlighting the profound impact of quantum effects on black hole thermodynamics. Full article

Microscale physical cues at the cell–extracellular matrix adhesion interface are increasingly being recognized as important regulators of cellular behavior. B16-F10 melanoma-derived cells retain melanogenic activity, including microphthalmia-associated transcription factor (MITF) expression and inducible melanin production, and are widely used for studies of melanogenesis and pigmentation-associated cellular responses. Melanocytic cells are sensitive to the physical characteristics of the surrounding microenvironment, including adhesion-dependent mechanical cues. However, the mechanism by which physical cues derived from the adhesion interface regulate melanoma cell function remains incompletely understood. In this study, we investigated the mechanism by which defined micropatterned substrates modulate melanoma cell morphology, migration, nuclear architecture, and melanogenic activity. Polydimethylsiloxane substrates with pillar- and hole-shaped microstructures (5, 10, and 50 µm diameters and spacings; 10 µm height or depth) were fabricated and coated with fibronectin. B16-F10 melanoma cells cultured on narrow pillar patterns (5 and 10 µm) exhibited restricted cell spreading, shortened protrusions, suppressed migration, and pronounced nuclear deformation compared with flat substrates. These mechanical constraints were accompanied by significant reductions in melanin production and downregulation of melanogenesis-related genes (Mitf, Tyr, and Tyrp1). Comparable trends were observed for Matrigel-coated substrates, indicating that microscale topography exerted consistent effects on B16-F10 melanoma cell responses across the tested extracellular matrix conditions. Collectively, our results demonstrate that surface topography with narrow pillar microstructures is associated with topography-dependent changes in cell behavior and melanogenic activity, providing insights into how microscale topographic confinement influences melanoma cell morphology and melanogenic activity. Full article

We investigate the influence of dark matter halos surrounding supermassive black holes on the gravitational waves emitted by extreme mass ratio inspirals (EMRIs). Focusing on circular orbits, we model the orbital evolution by incorporating both gravitational-wave radiation reaction and dynamical friction induced by the dark matter distribution, including possible density spikes near the black hole. Using frequency-domain waveform analysis, we compute the phase evolution of gravitational waves and quantify the dephasing caused by different halo parameters, including slope, density, and mass ratio. We further explore the distinguishability of dark matter models with annihilation, non-annihilation, and p-wave velocity dependence, as well as the potential to differentiate between astrophysical and primordial black holes. Our results show that even small variations in the dark matter properties lead to observable phase differences over a four-year EMRI evolution, making space-based detectors such as LISA sensitive probes of central dark matter distributions. Finally, we employ the Fisher matrix formalism to estimate the precision with which key parameters, such as halo slope and density, can be constrained, demonstrating that EMRI observations provide a promising avenue to probe both the nature of dark matter and the formation history of supermassive black holes. Full article

Simulations of intermediate-mass black holes (IMBHs) in dwarf galaxies within 10 Mpc that host bright nuclear star clusters (NSCs), prime candidates for IMBH formation, using the High Angular Resolution Monolithic Optical and Near-infrared Integral (HARMONI) field spectrograph on the Extremely Large Telescope, probe black hole formation in the early universe. Our approach combines observed surface-brightness profiles from the Hubble Space Telescope (HST), synthetic stellar population spectra, and Jeans Anisotropic Modeling (JAM) for stellar dynamics. Mock HARMONI observations were generated with the HSIM simulator and analyzed in a Bayesian framework to infer IMBH masses down to 0.5% of the NSC mass. In this work, we extend these simulations by constructing improved stellar mass models using SimCADO to simulate imaging with the Multi-AO Imaging Camera for Deep Observations (MICADO). The MICADO data are jointly analyzed with HARMONI kinematics via JAM to reassess IMBH masses and uncertainties. This combined framework enables us to examine how variations in the NSC inner surface-brightness slope influence IMBH mass estimates, providing tighter constraints on low-mass black holes and advancing models for IMBH detection in NSCs. Full article

High-velocity multi-projectile impacts from accidental external debris (e.g., uncontained engine debris or runway stones) on the liquid-filled fuel tanks of modern unmanned aerial vehicles (UAVs) induce complex Fluid–Structure Interaction (FSI) and Hydrodynamic Ram (HRAM) effects, resulting in highly complex dynamic response mechanisms. This study combines high-velocity impact tests with Three-Dimensional Digital Image Correlation (3D-DIC) technology and employs FSI finite element simulations based on the Structured Arbitrary Lagrangian–Eulerian (S-ALE) algorithm to thoroughly investigate the dynamic response mechanisms of liquid-filled containers penetrated by dual projectiles under different spatial spacings and temporal intervals. The results indicate that variations in the spatiotemporal parameters of dual projectiles significantly reconstruct the fluid load field: small spacing and short temporal intervals induce strong wave interference and superposition, generating an amplified composite loading effect that causes a sharp increase in target plate impulse and deformation energy. Conversely, small spacing and long temporal intervals trigger a significant “cavity shielding” phenomenon, causing the subsequent projectile to travel through the existing cavity, which massively suppresses the effective generation of its load and energy transfer. Furthermore, fluid displacement induced by cavity intersection generates secondary pressure waves; the petal hole evolution of the rear plate is dictated by the formation of plastic hinge lines, presenting four typical deformation modes—oblique cross, normal cross, asymmetric pentagon, and hexagon—depending on the degree of spatiotemporal coupling. This study reveals the laws governing the enhanced HRAM effect of dual projectiles, providing key theoretical support for the lightweight protection design and crashworthiness evaluation of long-endurance commercial UAV fuel tanks. Full article