Search Results (1,779)

The corrosion behavior of N80 steel in a simulated coalbed–methane environment was investigated in a high-temperature, high-pressure autoclave. Uniform corrosion and maximum pit depth were quantified by weight-loss measurements and ultra-depth-of-field three-dimensional microscopy, respectively, while SEM, EDS, and XRD were used to characterize the morphology, elemental composition, and crystalline phases of the surface corrosion products. A one-factor-at-a-time design was applied at a constant total pressure of 10 MPa to evaluate the effects of nominal CO₂ partial pressure (0.10–1.00 MPa), nominal O₂ partial pressure (0–0.40 MPa), Cl⁻ concentration (3–187 g/L), and temperature (40–75 °C). Increasing the nominal CO₂ partial pressure raised the uniform corrosion rate from 0.712 to 0.930 mm/a but reduced the maximum pitting corrosion rate from 1.691 to 0.280 mm/a, while FeCO₃-containing surface coverage increased. Increasing the nominal O₂ partial pressure intensified both corrosion modes; at 0.40 MPa, the uniform and maximum pitting corrosion rates reached 1.446 and 2.202 mm/a, respectively, and the corrosion-product layer exhibited extensive cracking and spallation. Increasing the Cl⁻ concentration reduced the uniform corrosion rate from 1.078 to 0.839 mm/a but increased the maximum pitting corrosion rate from 0.474 to 1.807 mm/a, indicating a shift in the principal damage risk from average metal loss to localized penetration. The uniform corrosion rate reached a maximum of 1.516 mm/a at 60 °C, whereas the maximum pitting corrosion rate increased continuously to 2.202 mm/a at 75 °C. XRD identified Fe, FeCO₃, Fe₂O₃, Fe₃O₄, and FeOOH. The persistent Fe substrate reflections, interpreted together with the SEM observations, revealed spatially heterogeneous corrosion-product coverage. These results show that the protective contribution of FeCO₃-containing products depends on their surface coverage and visible integrity rather than on phase presence alone. The findings support stringent oxygen-ingress control, targeted pitting protection in high-salinity environments, and enhanced corrosion surveillance of intermediate- and high-temperature well sections. Full article

Tight reservoirs commonly exhibit low permeability and pronounced lithological heterogeneity, resulting in complex interactions among far-field stress, local structural weakness, and fluid-driven fracture propagation. In this study, four non-replicated 2 m × 2 m × 1 m physical-model specimens representing tight glutenite, tight sandstone, and No. 3 coal rock from the Huabei Oilfield were investigated using an ultra-large true-triaxial hydraulic-fracturing system. Surface-fracture observations, microseismic monitoring, and high-frequency wellhead-pressure measurements were integrated to compare fracture responses under lithology-specific combinations of injection rate, fluid viscosity, perforation configuration, and stress state. The tested glutenite cases exhibited branched or localized fracture patterns depending on the combined treatment configuration; the sandstone case was dominated by a throughgoing main fracture approximately aligned with the principal-stress direction; and the coal-rock case showed extensive participation of bedding and cleat systems. These morphological differences were accompanied by distinct pressure and microseismic signatures, indicating different pathways of hydraulic-energy redistribution and fracture activation. For the two glutenite cases, the combined change from a single-perforation configuration at 0.5 m³/min to three helical perforations at 120° and 0.7 m³/min was associated with a 42.2% larger microseismic-derived stimulated reservoir volume (SRV). Taken together, these responses indicate a shift from stronger far-field-stress-controlled localization in the comparatively uniform sandstone to progressively greater local structural control by heterogeneous interfaces in glutenite and by bedding/cleat discontinuities in coal rock. Because each configuration was represented by a single specimen and several experimental variables changed simultaneously among cases, the observed differences are interpreted as case-specific mechanistic trends rather than statistically established universal relationships. The results show the value of combining fracture morphology, microseismic spatial evolution, and pressure dynamics for interpreting lithology-dependent fracture propagation in ultra-large physical models and for developing qualitative, lithology-adapted hydraulic-fracturing concepts. Full article

The performance of ultra-high-performance fiber-reinforced concrete (UHPFRC) under repeated low-velocity impacts, particularly in the context of nominally fixed boundaries relevant to protective structures, remains underexplored. In practice, protective components made of UHPFRC, such as falling object barriers and vehicle parapet systems, are exposed to foreseeable repeated low-velocity impacts; however, no standardized design provisions or residual capacity assessment methods exist for such members, particularly under nominally fixed boundary conditions. This study presents an integrated experimental and numerical investigation into the progressive damage and failure mechanisms of a 50 mm thick UHPFRC plate with nominally fixed (bolted clamping) boundaries subjected to sequential low-velocity impacts. A custom drop-weight test setup was used for impact loading, while high-speed 3D digital image correlation (3D-DIC) captured the quarter-field transient kinematics, which were reconstructed back to the full field based on verified test symmetry and complemented by traditional accelerometer and strain gauge measurements. The results demonstrate a distinct progression of damage. Initial low-energy impacts (196 J/drop) caused negligible damage, highlighting the material’s tolerance. Subsequent higher-energy impacts induced a transition from flexural cracking to a combined flexural–punching shear failure mode. The model-assisted nominal secant stiffness indicator decreased by 5.3% over the repeated 0.5 m drops and fell by 50.8% after the 2.0 m drop, quantifying the transition in structural behavior. A finite element (FE) model, incorporating the concrete damaged plasticity (CDP) model with an energy-based degradation law, was developed and evaluated against the experimental data. This model replicated both the quantitative dynamic responses (with model-to-test ratios of peak acceleration, strain, and displacement between 0.86 and 1.30 across three energy levels) and the qualitative damage evolution. The model thus evaluated enabled a model-derived reconstruction of the critical impact force–time history, revealing the evolution of structural degradation toward the exhaustion of the plate’s global flexural resistance and the transition to a punching shear mechanism. Full article

Internal steel-core damage hidden within aluminum conductor steel-reinforced (ACSR) compression components may threaten the mechanical integrity of ultra-high-voltage transmission lines. This laboratory study evaluates metal magnetic memory testing (MMMT) responses to artificial discontinuities in seven-strand ACSR steel cores under four nominal lift-off distances, two nominal orthogonal specimen orientations, and a simplified aluminum-tube-covered condition. One intact specimen and five artificially damaged 1 m specimens were preloaded to 16 kN for 2 min, unloaded, and scanned using the normal magnetic-field component recorded by Channel 1 of a TSC-1M-4 detector. Quantitative descriptors included peak-to-peak amplitude, abnormal-field width, maximum gradient, and short-term within-specimen repeatability. At 5 mm lift-off, peak-to-peak amplitudes ranged from 18.7 to 91.4 A/m. Across three repeated repositioning scans, amplitude coefficients of variation ranged from 0.83% to 8.04%. Relative to 5 mm, the descriptive mean amplitude loss reached 66.3%, 81.9%, and 89.8% at 20, 30, and 40 mm, respectively. Orientation changed signal polarity and amplitude in a specimen-dependent manner. Anomalies remained visible under the aluminum-tube configuration, although covering and effective lift-off effects could not be separated. The results provide preliminary laboratory evidence for further evaluation of MMMT as a screening approach; the reported feature values are not field detection thresholds. Full article

Gob-side entry retaining by roof cutting and pressure relief (CRRE) eliminates coal pillar waste and mitigates mining-induced stress concentration. Although widely applied in mines shallower than 1000 m, systematic research on asymmetric deformation mechanisms and matched control technologies under ultra-deep conditions (>1000 m, σH > 60 MPa) remains limited. This study investigates the 5307 working face of Anju Coal Mine (burial depth: 1127–1195 m) using theoretical analysis, FLAC3D numerical simulation, and 480 m of field monitoring. The stress evolution, deviatoric stress field response, and asymmetric deformation mechanisms of the surrounding rock under ultra-deep mining conditions are systematically analyzed, based on which a targeted collaborative control technology is proposed. The key findings indicate that (1) CRRE significantly attenuates advanced abutment pressure compared with conventional pillar retention, with an average stress reduction of 20.1 ± 1.2% (95% CI: 17.8–22.4%, p < 0.01). (2) During the advanced mining stage, the second invariant of deviatoric stress exhibits a saddle-shaped distribution with a pronounced concentration at the mid-rib, identifying this as the dominant zone for rib bulging failure. (3) In the post-mining entry-forming stage, the roof deviatoric stress field demonstrates marked asymmetric evolution, with the distortion energy on the solid-coal side substantially exceeding that on the gob side; moreover, the low-position roof strata exhibit high distortion and poor stability, rendering them prone to bending fractures. Grounded in these mechanisms, a full-cycle differentiated surrounding rock control technology is developed, integrating pre-mining directional roof pre-splitting, active tough support reinforcement, post-mining temporary roof control and pressure relief, and gangue retaining with rib collaborative protection. The key parameters include a roof cutting height of 7 m, a cutting angle of 15°, NPR constant-resistance anchor cables with W-steel belts, and temporary support extending 300 m behind the working face. Field monitoring reveals staged deformation evolution, with stabilization achieved 250 m behind the working face. Maximum roof subsidence, floor heave, and total roof-floor convergence were 180 mm, 329 mm, and 422 mm, respectively, below the 500 mm allowable threshold for ultra-deep retained entries. Full article

The accurate estimation of forest aboveground biomass (AGB) typically relies on extensive field surveys, which are highly time-consuming and cost-prohibitive. While unmanned aerial vehicle (UAV) Light Detection and Ranging (LiDAR) provides ultra-high point densities capable of reliable individual-tree analysis, its limited flight coverage restricts large-scale applications. Conversely, regional airborne laser scanning (ALS) offers broad spatial coverage, but its relatively low point cloud density makes individual-tree level analysis unreliable. To bridge this scale and data gap, this study develops a scale-consistent framework that integrates UAV-LiDAR, three-dimensional simulation, multisource remote sensing, and machine learning for Chinese fir (Cunninghamia lanceolata) plantation AGB estimation. High-density UAV-LiDAR data were first used to construct individual-tree AGB models, and the predicted tree-level biomass was aggregated to generate spatially representative “agent plots” for stand-scale modeling. A three-dimensional (3D) radiative transfer simulation framework was further employed to reproduce airborne LiDAR observations under different point densities, enabling the evaluation of structural information loss caused by LiDAR sparsity. Structural features derived from simulated LiDAR and spectral information from Sentinel-2 imagery were integrated using the Tabular Prior-data Fitted Network (TabPFN). Model reliability was assessed through 10-fold spatial block cross-validation and Monte Carlo simulations, which quantified spatial generalization and uncertainty propagation from individual-tree estimation to stand-level prediction. Feature interpretation using SHapley Additive exPlanations (SHAP) revealed that the LiDAR-derived vertical canopy structure provided the primary constraints for biomass estimation, whereas Sentinel-2 shortwave infrared features supplied complementary information related to canopy conditions. The optimal TabPFN model achieved a stand-level accuracy of R² = 0.88 and RMSE = 9.23 Mg·ha⁻¹ using LiDAR combined with Sentinel-2 data. Uncertainty analysis further demonstrated the robustness of the proposed framework under propagated errors, highlighting its potential for scalable and reliable forest biomass estimation in data-limited subtropical ecosystems. Full article

Primordial black holes (PBHs) in the asteroid-mass range, with typical masses ${10}^{17}\mathrm{g}\lesssim M\lesssim {10}^{23}\mathrm{g}$, have drawn significant recent attention as viable dark matter candidates. The peak frequencies of photons emitted via Hawking radiation from asteroid-mass PBHs range from infrared to $\gamma$-ray bands. We calculate expected local transit rates for extended PBH mass distributions that could comprise all dark matter. We evaluate prospects for detecting Hawking-radiated photons from local PBH transits through the inner Solar System and from PBH explosions in the far outer edges of the Solar System. We consider several existing and proposed ground-based and space-based instruments sensitive to photons from the radio band to ultrahigh-energy $\gamma$-rays. We find that the proposed instruments, such as the All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) satellite, can reliably detect PBH transits within $\mathcal{O}\left(0.1\mathrm{AU}\right)$ of the Earth, while the High Altitude Water Cherenkov (HAWC) observatory and Large High Altitude Air Shower Observatory (LHAASO) are both sensitive to PBH explosions out to $\mathcal{O}\left(0.1\mathrm{pc}\right)$ and $\mathcal{O}\left(0.5\mathrm{pc}\right)$, respectively. We conclude by specifically considering potential companion electromagnetic signatures in the case of a PBH explosion about ${10}^3\mathrm{AU}$ from Earth, which has been suggested as a potential source for the ∼220 PeV ultrahigh-energy KM3-230213A neutrino event observed by the KM3NeT collaboration in 2023. Whereas we find that the recent KM3NeT event would not have yielded detectable electromagnetic signals—due to its location on the sky, proposed distance from Earth, and the offline status of the HAWC observatory at that time—we demonstrate that future PBH explosions at comparable distances could yield electromagnetic signals measurable from Earth, depending on the alignment of the PBH burst with detector fields of view. Full article

Accurate wellbore-pressure prediction is essential for safe drilling and pressure management in ultra-deep wells, where high temperature and pressure strongly alter drilling-fluid rheology. Existing rheological-parameter models are often calibrated for specific fluids and narrow temperature–pressure ranges, limiting their use in ultra-deep-well hydraulics. We measured three water-based drilling fluids at temperatures and pressures up to 210 °C and 206.5 MPa, compared seven rheological models, and developed a multidimensional evaluation method considering global fitting accuracy, extreme-condition performance, low-shear-rate representation, absolute shear-stress deviation, and model complexity. Using ambient-condition Herschel–Bulkley (H-B) parameters as baselines, we proposed a temperature–pressure (T-P)-coupled correction model requiring fluid-specific calibration to predict H-B parameters over the tested range. The fluids exhibited temperature-induced thinning, pressure-induced thickening, and shear-thinning behavior. The H-B model showed the best overall performance, with mean R² values above 0.997 and mean absolute percentage errors below 2.5% for all fluids. Substituting the corrected parameters into the H-B equation yielded mean shear-stress errors no greater than 4.04%. Field validation showed that the T-P-coupled model reduced the mean circulating-pressure-loss error from 2.72% to 0.78%. This approach provides practical inputs for rheology estimation and circulating-pressure calculation in ultra-deep wells under wide temperature and pressure conditions. Full article

A hybrid metasurface absorber (MSA) based on a central-bar-coupled split-disk dimer is proposed and numerically investigated for high-resolution refractive-index sensing in the near-infrared spectral region. The metasurface consists of silicon nitride dielectric resonators integrated with a gold plasmonic layer, enabling strong electromagnetic confinement, enhanced light–matter interaction, and ultra-narrow resonant features within the 1000–1400 nm wavelength range. The optimized structure supports multiple resonant modes under both x- and y-polarized excitation, producing sharp reflection dips with full-width-at-half-maximum values as low as 0.58 nm and quality factors reaching 2007. Refractive-index sensing performance was evaluated by varying the aqueous superstrate refractive index from 1.33 to 1.35, resulting in bulk sensitivities up to 860 nm/RIU under normal incidence. The angular response was further analyzed for incidence angles up to 5°, revealing polarization-dependent resonance splitting and the emergence of additional high-Q resonant branches under oblique excitation. Several angularly induced resonances exhibit narrower linewidths than those observed at normal incidence while preserving high refractive-index sensitivity up to 870 nm/RIU. Electric-field distributions confirm strong field localization near the dielectric boundaries and coupling regions, validating the hybrid resonant mechanism responsible for the enhanced spectral selectivity and sensing performance. The proposed MSA provides a promising platform for compact and ultrasensitive biosensing applications. Full article

Extreme biomimetics represents a novel multidisciplinary direction within classical biomimetics and bioinspired materials science that draws inspiration from extremophiles and extreme natural habitats to create unusual approaches for the design of next-generation materials, including composites never reported or predicted before. This review is divided into several sections covering achievements and fundamental challenges in the following fields: sources of inspiration—organisms and locations; biological materials for extreme biomimetics based on examples of biosilica, cellulose, chitin, and structural proteins (collagen, byssus, silk, keratin). Additionally, conchixes of molluscan shell origin, fish scales, and spongin as a skeletal biocomposite of industrial sponge origin are represented and discussed from the viewpoint of extreme biomimetics. Finally, scientifically based but daring experimental decisions in modern extreme biomimetics, taking the examples of extreme carbonization of naturally pre-structured biomaterials, galvanobiomimetics, in-flame biomimetics, pyro-biomimetics, and ultra-high pressure mimetics are represented for the first time as current trends with challenging goals. Full article

Upper-loss and lower-kick (UL–LK) events may occur in ultra-deep fractured carbonate formations when gas enters from a lower high-pressure zone while drilling fluid is lost to an upper low-pressure fracture. Because both flows can continue after shut-in, the wellbore remains incompletely closed. This study develops a transient wellbore-formation pressure model based on phase mass conservation and global volume balance, and introduces an effective gas–liquid partition coefficient to represent phase separation at the fracture inlet. The model shows that circulation loss limits bottomhole-pressure recovery, allowing gas influx to persist after shut-in. Relative to kick-only conditions, UL–LK conditions have a lower initial shut-in casing pressure (SICP) but a steeper subsequent buildup. A smaller partition coefficient, corresponding to preferential liquid loss, leaves more free gas in the wellbore and further increases the SICP buildup rate. A surface-pressure-based screening method was developed from contrasting SICP and shut-in drillpipe pressure (SIDPP) responses. When applied to five field cases, the method correctly identified three UL–LK cases and two kick-only cases. Its outcomes for five field cases agreed with the field interpretations. This framework supports post-shut-in pressure prediction and rapid screening without dedicated downhole measurements. Full article

The deep to ultra-deep sandstone reservoirs of the Cretaceous Bashijiqike Formation in the Kelasu structural belt of the Kuqa Depression exhibit strong heterogeneity. This study integrates single-well stress calculation, image log fracture interpretation, thin-section petrographic analysis, and porosity–permeability testing to compare stress, fracture, and reservoir characteristics across the Dabei–Bozi cross-section. The results show that the northern stress release zone is characterized by low S_H (98 to 148 MPa) and E (9220 to 23,420 MPa), indicating weak cumulative stress, low effective fracture density (0.09 fractures/m), and primary-pore dominated reservoirs. The central stress transition zone has progressively increasing S_H (136 to 187 MPa) and E (27,450 to 33,210 MPa) from north to south, indicating strong cumulative stress, high effective fracture density (0.31 fractures/m), and mixed primary–secondary pore-fracture reservoirs. The southern stress accumulation zone shows increasing S_H but decreasing E to the south, indicating that the late-stage high stress results in low effective fracture density (0.08 fractures/m) and preserving primary pores. These results demonstrate that reservoir quality is governed by the cumulative effect of the stress field, rather than by present-day stress or peak paleo-stress alone. This reservoir distribution model could provide a theoretical basis for reservoir prediction in the foreland basin. Full article

Charge-coupled device (CCD) image sensors stand out for their high sensitivity, low noise, and strong radiation tolerance, which have established them as core components in high-end imaging fields such as astronomical observation, remote sensing, and defense and security. With increasingly stringent requirements for imaging system performance in emerging applications, including ultra-high resolution, intelligent sensing, and multimodal information fusion, CCD technology continues to evolve toward higher levels of integration and improved performance. Within a fixed sensor area, one of the most straightforward ways to raise image resolution is to shrink pixel size, that is, CCD pixel miniaturization. In this review, we provide a systematic survey of the major advances in CCD pixel miniaturization achieved in recent years. We first detail four mainstream CCD architectures—linear-array, full-frame, frame-transfer, and interline-transfer—along with several newly developed architectures, and compare their performance characteristics and application constraints. We then summarize the key technologies that enable pixel miniaturization and examine several closely related technological directions. Finally, we look at the current state of CCD pixel miniaturization and discuss its future development trends. Full article

The use of ultra-high magnetic fields, such as 11.74 T in magnetic resonance imaging (MRI), offers great potential for achieving superior image quality and enabling advanced imaging applications. The development of new field-strength systems requires an investigation into the performance of radiofrequency transmitters and receivers. Loop coils are a popular choice for MRI scanners up to 7 T, with better performance exhibited at 3 T, whereas volume coils such as birdcage coils are preferred for 1.5 T scanners. On this basis, the field strength of 11.74 T raises the question of which resonator design will provide superior performance. Dipole antennas have been proposed for many applications involving different field strengths and target organs. One of the limitations of dipole antennas is the relationship between the resonance and the length. At 11.74 T, the dipole frequency of operation is 500 MHz, which provides a dipole antenna length of approximately 28 cm, which is acceptable for an MRI scanner. This study analyzed the transmission and reception performances of dipole arrays with different radii in terms of field intensity, uniformity, SAR, effectiveness, g-factor, and field optimization. Full article

Ultra-deep Ordovician carbonates in the Tarim Basin are a major target for oil and gas exploration in China. Localized overpressure, however, creates substantial well-control risks and impairs drilling safety and exploration performance. This study investigates the Fudong Block of the Fuman Oilfield using drilling, seismic, and well-test data. We develop a high-resolution, layer-specific formation-pressure prediction workflow that integrates well and seismic data through a stress–fracture-pressure framework. The workflow combines geomechanical modeling, prediction of the in situ stress field and fracture distribution, stress-fracture matching, Biot-theory-based pressure prediction, and iterative calibration against drilling observations. The results show that: (1) overpressure is concentrated near secondary faults, branch faults, and NW-trending faults. It is jointly controlled by tectonic compression, pressure retention within fracture–vug bodies, and fluid charging. Multiple vertically separated pressure systems are common, and their marked heterogeneity is closely related to secondary-fault development and fracture–vug connectivity; (2) drilling disturbance can generate apparent overpressure and lead to erroneous pressure interpretation. Overpressured wells commonly exhibit a kick followed by lost circulation or simultaneous kick and loss. Drilling-fluid invasion into confined fracture–vug bodies causes pressure buildup; and (3) formation pressure is a key parameter in integrated geological and engineering sweet-spot evaluation and is closely linked to wellbore stability. Field applications confirm the accuracy of the proposed workflow. The method strengthens integrated geology-engineering evaluation and provides a practical basis for the safe and efficient development of ultra-deep carbonate reservoirs. Full article