Search Results (271)

The hole expansion process of high-strength steel is influenced by multiple factors, including the deformation path, UTS/YS ratio, uniform elongation, sheet anisotropy, sheet thickness, strain rate, material micro-defects and the work hardening exponent. Based on forming limit curves or instability criteria, the prediction of the hole expansion ratio (HER) often requires extensive initial boundary conditions that complicate the result. In this study, V-Nb bainitic steel was subjected to hot continuous rolling and underwent water quenching with different coiling temperatures, then subsequently followed by thermal simulation and mechanical testing to fit the work hardening exponent (n) and to obtain the necking deformation instability curve. The radial displacement at the hole edge during simulation was predicted with the ratio of ultimate tensile strength to fracture strength. Furthermore, based on the tensile fracture failure criterion, the HER was predicted with the true fracture strain derived from uniaxial tensile tests. Comparison between the simulated results and actual hole expansion tests shows that the crack resistance in the post-uniform stage, strain hardening capacity and deformation compatibility between the microstructure and matrix are critical factors. And the proposed model achieves a prediction accuracy of over 85% for the V-Nb bainitic high-strength steel. Full article

In light of frequently occurring wellbore instability such as wellbore collapse and sand production that often occur in drilling and the completion of shale oil and gas development, we propose one-run shape memory thermosensitive screen technology that can expand spontaneously at a specific temperature to help strengthen the formation. Based on the theory of thermal expansion and large deformation of shape memory materials, the expansion process of the thermosensitive screen is calculated by the finite element method. After expanding to the wellbore wall, the effects of the screen squeezing force on the formation production parameters are evaluated theoretically. The analysis shows that the radial compressive stress of the thermosensitive screen decreases with the increase in the radial distance, but as the original outer diameter of the thermosensitive screen is greater than the wellbore diameter, it can provide extrusion force for the wellbore wall. According to the in situ stress model, the extrusion force after the screen contacts the wellbore can effectively improve the stress distribution near the wellbore and reduce the impact of sand production caused by formation instability. Moreover, in shale oil and gas completion, it can effectively increase the bottom hole flowing pressure and drawdown pressure. Full article

Roof damage caused by hurricanes and other storms needs to be rapidly identified and repaired to help communities recover from catastrophic events and support the well-being of residents. Traditional, ground-based inspections are time-consuming but have recently been expedited via manual interpretation of remote sensing imagery. To potentially accelerate the process, automated methods involving artificial intelligence (i.e., deep learning) can be applied. Here, we present an end-to-end workflow for training and evaluating deep learning image segmentation models that detect and delineate two classes of post-storm roof damage: roof decking and roof holes. Mask2Former models were trained using 2500 roof decking and 2500 roof hole samples from drone RGB orthomosaics (0.02–0.08 m ground sample distance [GSD]) captured in Sint Maarten and Dominica following Hurricanes Irma and Maria in 2017. The trained models were evaluated using 1440 reference samples from 10 test images, including eight drone orthomosaics (0.03–0.08 m GSD) acquired outside of the training areas in Sint Maarten and Dominica, one drone orthomosaic (0.05 m GSD) from the Bahamas, and one orthomosaic (0.15 m GSD) captured in the US Virgin Islands with a crewed aircraft and different sensor. Accuracies increased with a single-class modeling approach (instead of training one dual-class model) and expansion of the training datasets with 500 roof decking and 500 roof hole samples from external areas in the Bahamas and US Virgin Islands. The best-performing models reached overall F1 scores of 0.88 (roof decking) and 0.80 (roof hole). In this study, we provide: our end-to-end deep learning workflow; a detailed accuracy assessment organized by modeling approach, damage class, and test location; discussion of implications, limitations, and future research; and access to all data, tools, and trained models. Full article

To clarify the influence of reinforcement corrosion on the mechanical performance of road tunnel linings, localized tests on reinforcement-induced concrete expansion are conducted to identify cracking patterns and their effects on load-bearing behavior. Refined three-dimensional finite element models of localized concrete and the entire tunnel are developed using the concrete damaged plasticity model and the extended finite element method and validated against experimental results. The mechanical response and crack evolution of the lining under corrosion are analyzed. Results show that in single-reinforcement specimens, cracks propagate perpendicular to the reinforcement axis, whereas in multiple-reinforcement specimens, interacting cracks coalesce to form a π-shaped pattern. The cover-layer crack width exhibits a linear relationship with the corrosion rate. Corrosion leads to a reduction in the stiffness and load-bearing capacity of the local concrete. At the tunnel scale, however, its influence remains highly localized, and the additional deflection exhibits little correlation with the initial deflection. Local corrosion causes a decrease in bending moment and an increase in axial force in adjacent linings; when the corrosion rate exceeds about 15%, stiffness damage and internal force distribution tend to stabilize. Damage and cracks initiate around corroded reinforcement holes, extend toward the cover layer, and connect longitudinally, forming potential spalling zones. Full article

This study focuses on the high-precision microhole machining of 304 stainless steel and explores a backwater-assisted picosecond laser trepanning technique. The laser used is a 30 W green picosecond laser with a wavelength of 532 nm, a repetition rate of 1000 kHz, and a pulse width of less than 15 ps. Experiments were conducted under both water-based and non-water-based laser processing environments to systematically investigate the effects of laser power and scanning cycles on hole roundness, taper, and overall hole quality. The experimental results further confirm the advantages of the backwater-assisted technique in reducing slag accumulation, minimizing roundness variation, and improving hole uniformity. In addition, thermal effects during the machining process were analyzed, showing that the water-based environment effectively suppresses the expansion of the heat-affected zone and mitigates recast layer formation, thereby enhancing hole wall quality. Compared with conventional non-water-based methods, the backwater-assisted approach demonstrates superior processing stability, better hole morphology, and more efficient thermal management. This work provides a reliable technical route and theoretical foundation for precision microhole machining of stainless steel and exhibits strong potential for engineering applications. Full article

Background: Early hematoma expansion is a major determinant of poor outcomes after spontaneous intracerebral hemorrhage (ICH). Identifying reliable predictors of hematoma expansion may facilitate risk stratification and timely interventions. This study aimed to evaluate clinical, laboratory, and radiological factors associated with early hematoma expansion within 24 h. Methods: We retrospectively analyzed consecutive patients with spontaneous ICH admitted to a tertiary hospital in Korea between 2009 and 2021. Inclusion criteria were aged ≥ 18 years, primary spontaneous ICH, baseline non-contrast CT (NCCT), and follow-up CT within 24 h. Clinical, laboratory, and medication histories were collected, and NCCT/CT angiography (CTA) imaging markers (spot sign, blend sign, hypodensity, swirl sign, black hole sign, island sign, mean hematoma density) were evaluated. Early hematoma expansion was defined as an absolute volume increase ≥6 cm³ or a relative increase ≥33% on follow-up CT. Multivariate logistic regression identified independent predictors. Results: Among 899 screened patients, 581 met inclusion criteria (mean age 61.6 years; 59.7% male). Seventy-eight patients (13.4%) experienced early hematoma expansion. Independent predictors included CTA spot sign (adjusted OR 9.001, 95% CI 4.414–18.354), blend sign (OR 3.054, 95% CI 1.349–6.910), mean hematoma density <60 HU (OR 2.432, 95% CI 1.271–4.655), male sex (OR 2.902, 95% CI 1.419–5.935), and statin use (OR 2.990, 95% CI 1.149–7.782). Prior antiplatelet therapy was associated with a reduced risk of hematoma expansion (OR 0.118, 95% CI 0.014–0.981). Conclusions: Early hematoma expansion occurred in 13.4% of patients and was predicted by a combination of CTA and NCCT markers, as well as clinical and pharmacological factors. Spot sign remained the strongest predictor, while NCCT features such as blend sign and low hematoma density also provided practical prognostic value. These findings underscore the multifactorial pathophysiology of ICH expansion and highlight the importance of integrating imaging, clinical, and therapeutic variables into prediction models to improve early risk stratification and guide targeted interventions. Full article

In this paper, we analyze the agegraphic dark energy from the entropy of the anti-de Sitter black hole using the age of the universe as the IR cutoff. We constrain its parameter with the Pantheon+ Type Ia supernova sample and observational Hubble parameter data, finding that the Akaike Information Criterion cannot effectively distinguish this model from the standard $\Lambda$CDM model. The present value of Hubble constant $H_0$ and the model parameter $b^2$ are constrained to $H_0=67.7\pm 1.8$ and $b^2=0.{303}_{-0.024}^{+0.019}$. This model realizes the whole evolution of the universe, including the late-time accelerated expansion. Although it asymptotically approaches the standard $\Lambda$CDM model in the future, statefinder analysis shows that late-time deviations allow the two models to be distinguished. Full article

We present a quantitative theory of contraction and expansion cycles within the Quantum Memory Matrix (QMM) cosmology. In this framework, spacetime consists of finite-capacity Hilbert cells that store quantum information. Each non-singular bounce adds a fixed increment of imprint entropy, defined as the cumulative quantum information written irreversibly into the matrix and distinct from coarse-grained thermodynamic entropy, thereby providing an intrinsic, monotonic cycle counter. By calibrating the geometry–information duality, inferring today’s cumulative imprint from CMB, BAO, chronometer, and large-scale-structure constraints, and integrating the modified Friedmann equations with imprint back-reaction, we find that the Universe has already completed $N_{\mathrm{past}}=3.6\pm 0.4$ cycles. The finite Hilbert capacity enforces an absolute ceiling: propagating the holographic write rate and accounting for instability channels implies only $N_{\mathrm{future}}=7.8\pm 1.6$ additional cycles before saturation halts further bounces. Integrating Kodama-vector proper time across all completed cycles yields a total cumulative age $t_{\mathrm{QMM}}=62.0\pm 2.5\mathrm{Gyr}$, compared to the $13.8\pm 0.2\mathrm{Gyr}$ of the current expansion usually described by $\mathrm{\Lambda }$CDM. The framework makes concrete, testable predictions: an enhanced faint-end UV luminosity function at $z\gtrsim 12$ observable with JWST, a stochastic gravitational-wave background with $f^{2/3}$ scaling in the LISA band from primordial black-hole mergers, and a nanohertz background with slope $\alpha \simeq 2/3$ accessible to pulsar-timing arrays. These signatures provide near-term opportunities to confirm, refine, or falsify the cyclical QMM chronology. Full article

We reconstructed the morphology of holes using silicone replication technology, and inverted the hole parameters to reveal the law of high-pressure water jet (HPWJ) hole formation under multi-field coupling. The results show that under the multi-field coupling effects, the evolution of the hole exhibits stage-wise characteristics; in the rapid expansion phase, the hole extends rapidly and deeply, forming a “wedge” pattern, and in the stabilization adjustment phase, the rate of hole expansion slows down, and the hole morphology shifts towards an “elliptical” or “teardrop-shaped” form. However, an increase in confining pressure inhibits the transformation of the hole morphology, and as a result, the “wedge-shaped” characteristics of the hole become more pronounced. With constant confining pressure, increased jet pressure significantly enhances both hole depth and volumetric average extension rate, exhibiting a positive correlation. Conversely, with constant jet pressure, increased confining pressure significantly decreases both hole depth and volumetric average extension rate, exhibiting a negative correlation. Based on silicone replication technology, we established a mapping relationship between ‘pore morphology-jet flow and environmental parameters’ which can be used to evaluate the pressure relief and permeability enhancement effects in deep low-permeability coal seams. By optimizing jet parameters, we can expand the scope of pressure relief and permeability improvement in coal seams, thereby enhancing gas drainage efficiency. Full article

To address the challenge of determining the borehole layout scheme in the practical application of high-pressure gas expansion rock breaking, this study takes the excavation of the safety passage at Kaixuan Road Station on the North Extension Line 2 of Chongqing Metro Line 18 as the engineering background. The rock-breaking capacity was evaluated by analyzing the damaged zone volume caused by gas expansion using FLAC3D 6.0 numerical simulation software, and vibration monitoring was conducted for the historical buildings on the surface. This study revealed the following: (1) When the borehole depth is 1.2 m and the charge length is 0.6 m, the optimal angle is 70°, with the optimal vertical and horizontal spacing between holes being 1200 mm and 2000 mm, respectively. (2) The numerical simulations indicated that by adjusting the charge density, the optimized sandstone borehole network parameters could be applied to mudstone strata, and the rock-breaking effect was similar. The difference in the volume of the damaged zones obtained in the two strata was less than 3%. (3) The vibration analysis demonstrated that the peak particle velocity generated by high-pressure gas expansion rock fracturing at the ancient building directly above was 0.06316 cm/s, which was lower than the threshold value of 0.1 cm/s and approximately 67.95% lower than that of explosive blasting. Furthermore, when the tunnel depth exceeded 29 m, the vibration velocity of surface structures remained within the safety range. The results verified the feasibility of applying the same borehole network parameters to different strata, providing theoretical support for the practical application of high-pressure gas expansion rock fracturing technology in engineering projects. Full article

Background and Purpose: Spontaneous intracerebral hemorrhage (ICH) is associated with high rates of morbidity and mortality. Early hematoma expansion (HE) is a key driver of poor outcomes, yet readily available non-contrast CT (NCCT) markers remain underused. We assessed four predefined NCCT signs—Blend Sign (BS), Black Hole Sign (BHS), Irregular Shape (IRS), and Satellite Sign (SS)—and a simple composite score (SUM_BBIS, 0–4) for their association with HE and in-hospital mortality. Methods: We retrospectively analyzed 404 consecutive adults with primary spontaneous ICH admitted to a tertiary-care center between January 2017 and December 2023. Patients with secondary causes of hemorrhage or without follow-up NCCT were excluded. Each sign was scored dichotomously by blinded readers and summed to form the SUM_BBIS. HE was defined as a >6 mL or >33% volume increase on repeat NCCT within 24–48 h. Outcomes included HE and in-hospital mortality; secondary analyses explored relationships with baseline hematoma volume, location, intraventricular extension (IVH), and comorbidities. Results: Among 404 patients, Irregular Shape was most frequent (62.1%), followed by Satellite Sign (34.9%), Black Hole Sign (31.1%), and Blend Sign (15.3%). Hematoma expansion occurred in 22.0% (89/404). Expansion was more common when ≥1 sign was present, with the Black Hole Sign showing the strongest association (56.2% vs. 23.8%; p < 0.001). In-hospital mortality rose stepwise with higher SUM_BBIS (mean 1.95 in non-survivors vs. 0.93 in survivors; p < 0.001). Conclusions: The four predefined NCCT signs, particularly BHS, identify ICH patients at increased risk of HE and in-hospital death. A simple, purely imaging-based composite (SUM_BBIS) captures cumulative radiological complexity and stratifies risk in a stepwise manner. Systematic evaluation of these markers may enhance early triage and inform timely therapeutic decisions, especially in emergency and resource-limited settings. Full article

In urban construction, the efficient demolition of concrete structures imposes high-precision requirements on blasting technology. The mesoscopic evolution mechanism of concrete blasting damage is the key to optimizing blasting parameters. In this study, a numerical model of concrete blasting is established using Particle Flow Code (PFC). By comparing it with an experimental model containing a blast hole and a horizontal single fissure, the rationality and reliability of the model in simulating blasting damage evolution are verified. On this basis, four groups of control variable schemes are designed (concrete particle size distribution, aggregate content, prefabricated fissure inclination angle, and fissure length) to systematically explore the effects of mesoscopic structures and macroscopic defects on blasting damage. The results show that larger concrete particles make it easier for damage cracks to avoid large particles, forming sparse and irregular crack networks. A higher aggregate content enhances the “obstruction-guidance” effect of aggregate distribution on damage. When the aggregate content is 40%, the vertical damage expansion is the most prominent, reaching up to 3.05 cm. Fissure inclination angle affects the damage direction by guiding the propagation path of stress waves. Fissures inclined at 30°~60° serve as preferential damage channels, while 90° vertical fissures make vertical damage more significant. An increased fissure length expands the damage range, and the damage degree is the highest for a 40 mm long fissure, being 1.29 times that of a 30 mm fissure. The research results reveal the mesoscopic evolution laws of concrete blasting damage, providing a theoretical basis for the optimization of engineering blasting parameters and safety control. Full article

This study presents a novel approach to understanding fatigue and crack growth phenomena by benchmarking experimental observations with numerical simulations. We introduced controlled residual stress fields away from notch-induced crack nucleation sites and analyzed their interaction with crack nucleation and growth. Surprisingly, our findings revealed that the introduction of generally beneficial compressive residual stresses had a counter-intuitive negative impact on product fatigue life. Despite daunting challenges in applying classical fatigue principles to describe crack nucleation and growth, our numerical simulations provided valuable insights, capturing the trend of observed crack paths, albeit not their velocity. This research sheds light on the complex interplay between residual stresses and crack propagation, offering important considerations for fatigue analysis and product design. Full article

Achieving high efficiency and quality in millisecond pulsed laser drilling of metallic through-holes is contingent on precise process control. This study introduces a penetration detection-based method to determine the pulse count threshold, effectively overcoming the limitations of conventional approaches. We systematically investigated the effects of pulse energy, defocus, and beam expansion ratio on the drilling of 3 mm thick 304 stainless steel and TC4 titanium alloy. The experiments revealed that for stainless steel 304, the minimum taper angle was achieved at a pulse energy of 2.2 J, a defocus amount of −0.5 mm, and a beam expansion ratio of 2.5. Additionally, relatively high drilling efficiency was observed when the pulse energy ranged from 2.6 to 2.8 J, the defocus amount was −1 to 0 mm, and the beam expansion ratio was 3 to 4. For titanium alloy TC4, the minimum taper angle was achieved at a pulse energy of 2.6 J, a defocus amount of −0.5 mm, and a beam expansion ratio of 3.5. High drilling efficiency was recorded when the pulse energy was 2.8 J, the defocus amount was −0.5 mm, and the beam expansion ratio ranged from 2.5 to 3. When stainless steel 304 and titanium alloy TC4 were processed using the same laser parameters, the drilling efficiency of stainless steel 304 was higher than that of titanium alloy TC4 under the same conditions. This work provides a practical process control strategy and a valuable parameter database for high-quality, efficient laser drilling of these industrially important metals. Full article

In this work, we demonstrate high-efficiency 385 nm AlGaN-based near-ultraviolet micro light emitting diode (NUV-Micro LED) arrays. The epi structure is prepared using a novel AlN-inserted superlattice electrical blocking layer which enhances hole spreading in the p-type region significantly. The NUV-Micro LED arrays in this work comprise 228 chips in parallel with wavelengths at 385 nm, and each single chip size is 15 × 30 μm². Compared with conventional bulk AlGaN-based EBL structures, the NUV-Micro LED arrays that implemented the new hole spreading enhanced superlattice electrical blocking layer (HSESL-EBL) structure proposed in this work had a remarkable increase in light output power (LOP) at current density, increasing the range down from 0.02 A/cm² to as high as 97 A/cm². The array’s light output power is increased up to 1540% at the lowest current density 0.02 A/cm², and up to 58% at the highest current density 97 A/cm², measured under room temperature (RT); consequently, the WPE is increased from 13.4% to a maximum of 30.18%. This AlN-inserted HESEL-EBL design significantly enhances both the lateral expansion efficiency and the hole injection efficiency into the multi quantum well (MQW) in the arrays, improving the concentration distribution of the holes in MQW while maintaining good suppression of electron leakage. The array’s efficiency droop has also been greatly reduced. Full article