Search Results (3,637)

Shield tunnels are the primary structural form of subway tunnels. Under the influence of sulfate ions and stray currents, the internal bars in shield tunnels will corrode rapidly, affecting the safe operation of the subway. In this paper, a numerical calculation model was developed to simulate rebar corrosion in shield tunnels under coupled electric and chemical field effects, the accuracy of the numerical calculation model was verified using a model test. Based on this model, the migration patterns of sulfate ions within the tunnel under stray current conditions are investigated, as well as the corrosion mechanisms of tunnel rebars. Results show that under the coupled effects of stray currents and sulfate ions, the corrosion area in a segment rebar gradually spreads from the arch waist area of a tunnel. Compared to bilateral leakage, both the migration rate of sulfate ions and the corrosion rate of rebar were higher than those in the unilateral leakage condition. Changes in the input voltage at the top of the ballast did not alter the shape of the distribution curves for the voltage and corrosion current density of segmental rebar. When the input voltage increased from 1 V to 5 V, the voltage at the mid-section of the rebar increased by 5.2 times under a bilateral leakage condition, and the voltage at the mid-section of the rebar increased by 8.2 times under a unilateral leakage condition. Compared to the bilateral leakage case, the amplitude of fluctuations in the curve was significantly reduced under unilateral leakage, but the corrosion current density increased proportionally with increasing leakage voltage in both cases. The research conclusions provide a theoretical basis for the safety assessment and disease treatment of shield tunnel structures. Full article

Soil Moisture (SM) represents the temporary storage of water within the shallow layers of the Earth’s upper surface and plays a key role in a wide range of applications, including hydrological processes, numerical weather prediction models and landslide prediction. This study evaluates the comparability of multiple satellite- and model-based SM products against in situ volumetric water content (VWC) measurements collected by a regional monitoring network in Liguria, Italy. The analyzed dataset comprises satellite-based products from the SMAP mission and the ASCAT sensors, as well as modelled Soil Moisture outputs from the HTESSEL land surface model and the Root Zone Soil Moisture (RZ SM) estimates from the continuous, distributed and physically based hydrological model Continuum. Aiming to reduce the systematic differences between the SM products and the ground network measurements, Soil Water Index (SWI) filtering and various rescaling techniques are applied and evaluated. Finally, the agreement between the rescaled SM products and the in situ measurements was assessed using standard performance scores aggregated into a single multi-objective function. Within the specific context of the study area, results suggest that rescaled model-based soil moisture products generally outperform satellite-derived surface soil moisture in reproducing in situ observations. Furthermore, among the tested rescaling techniques, Cumulative Distribution Function (CDF) matching and linear regression provide the best performance in mitigating systematic biases. Additionally, the optimization of the characteristic time length (τ) for satellite-derived SWI significantly enhances the agreement with in situ root-zone dynamics. Full article

Background: Intra-abdominal pressure (IAP) has recently been recognized as a new vital sign in critically ill patients. Microwave reflectometry has been proposed as a potential approach for non-invasive IAP measurement. However, systematic investigation on how individual anatomical and geometric factors influence changes in the microwave reflection response of the abdominal compartment is limited. Complementary information regarding illumination frequency and specific absorption rate (SAR) also warrants consideration. Objective: This study aimed to advance the current knowledge on using microwave radar-based sensors in IAP monitoring by studying the most influencing factors. The penetration depth and spot size versus radiation frequency is studied as well. Information on energy deposition due to radio-frequency exposure is investigated too. Methods: Numerical simulations were performed using abdominal models adjusted to represent different IAP levels. Reflection signal features were analyzed in relation to IAP-induced changes, and SAR was calculated using human models. Subsequently, a radar sensor prototype was tested on a benchtop abdominal phantom. Lin’s concordance correlation analysis was used to evaluate absolute agreement between radar-estimated IAP and reference IAP. Additional statistical analyses assessed bias, precision, concordance, and risk levels. Results: Sagittal abdominal diameter was the dominant factor affecting the microwave reflection response. Reflection amplitude showed a periodic trend consistent with abdominal displacement corresponding to multiples of half-wavelength values of the applied electromagnetic waves. Numerical SAR simulations showed increasing SAR with frequency while remaining below the applicable exposure limits under the investigated conditions. The radar sensor showed a bias of 0.43 mmHg and a precision of 2.55 mmHg. Concordance analysis among the paired changes remaining after application of the predefined exclusion criteria showed agreement in the direction of IAP change. Conclusion: The present study should be considered a preliminary proof of concept. Clinically, the technology is currently more suitable for early warning and trend monitoring than for precise absolute IAP measurement, and it does not yet replace standard intravesical measurements. Its ability to support clinical decision-making, including guiding fluid therapy, requires prospective validation in patients. Full article

Background and Clinical Significance: Children may experience substantial listening difficulty (LiD) despite clinically normal pure-tone thresholds. The longitudinal course of LiD in children initially referred for speech sound disorder (SSD) is not well documented. Case Presentation: We retrospectively reviewed two individuals first evaluated during the preschool years for SSD and followed through adolescence or adulthood. Available preschool records showed air-conduction thresholds no poorer than 20 dB HL. Tympanometry showed type C1 in the right ear and type A in the left ear in Case 1 and bilateral type-A tympanograms in Case 2; bone-conduction thresholds and objective auditory tests were not documented in the reviewed records. Both cases later showed reduced word recognition in speech noise relative to their good performance in quiet, although the quiet and noise presentation levels were not identical in Case 2. A Japanese mishearing checklist yielded 6/60 in Case 1 and 24/60 by caregiver report and 45/60 by self-report in Case 2. Preschool and school-age assessments identified broader phonological, language, memory, or sequential-processing weaknesses. Serial Auditory Processing Test (APT) findings were heterogeneous. Original numerical source data were retrieved for all four serial APT assessments: Case 1 at ages 11 and 14 years and Case 2 at ages 16 and 20 years. All APT findings are interpreted descriptively, not as evidence of improvement or a diagnosis of auditory processing disorder (APD). Both cases received speech–language intervention. Case 1 later received school accommodations, whereas Case 2 continued to require compensatory strategies and adjustments in educational and workplace settings. Conclusions: These cases describe the co-occurrence of early speech-language difficulties and later clinically significant LiD but do not establish causality, predictive markers, or an APD diagnosis. Their value is descriptive: they show how functional listening needs and support requirements changed across development in two selected clinical cases. Full article

The left-to-right spatial representation of time is reflected in faster responses when past-related concepts are associated with the left side of space and future-related concepts with the right. Most research has examined this time–space congruency effect using general temporal concepts, leaving unclear whether it also characterizes personally relevant temporal contents. The present study investigated whether the time–space congruency effect extends to self-referential negative events referring to the past and the future, and whether its expression is related to individual differences in maladaptive negative thinking. Forty-seven adults categorized individually generated words referring to past or future negative personal events, as well as neutral temporal words, by making left- or right-hand responses. A significant time–space congruency effect was observed for both self-referential and neutral words. The congruency effect was numerically smaller for self-referential words, and its strength was significantly and inversely related to anxiety sensitivity, whereas no such association was found for neutral words. These findings extend the mental timeline account to personally relevant negative events and provide initial evidence that individual differences in anxiety sensitivity are related to the spatial representation of such events. Psychological distance may represent a plausible mechanism underlying this association, a possibility that warrants direct testing in future research. Full article

Benchmarking deep learning forecasters against classical and physically based numerical baselines remains uncommon in the time-series forecasting literature. Meteorological station networks offer an under-exploited evaluation environment, uniquely providing a physically based climate-model comparator alongside standard baselines. We evaluated eight forecasting approaches—climatology, SARIMA, Random Forest, and five deep learning architectures (TFT, N-HiTS, PatchTST, TiDE, xLSTM)—against bias-corrected output from a five-member CMIP6 ensemble, on 100 meteorological stations across four Western Balkan countries (monthly temperature and precipitation, 1961–2020), using non-parametric significance testing, a rolling-origin backtest (five windows, 2011–2020), and a five-seed robustness check. For temperature, all five deep learning architectures achieved lower MAE than the classical baselines (p < 10⁻⁹⁹), though PatchTST’s advantage over climatology was not significant; the best-performing architecture varied across seeds and evaluation windows, so we characterise a leading cluster (N-HiTS, TFT, TiDE, PatchTST) rather than a single winner. The primary temperature advantage was geographically broad-based, while the comparison against the physical-model baseline was robust to the choice of comparator GCM. For precipitation, by contrast, a simple climatological-mean baseline outperformed all five deep learning architectures with no exception across all five rolling-origin windows. The deep learning advantage over classical and physical baselines is thus variable-specific rather than universal. Meteorological station networks, combined with a physically based climate-model comparator, constitute a well-suited evaluation environment for the broader time series forecasting community. Full article

Octet lattice cylindrical shell combines the stretching-dominated load transfer of Octet lattices with the geometric characteristics of the cylindrical shell, but the effects of different density gradients under different compression directions remain unclear. Uniform and three-layer graded 316L Octet LCSs were evaluated using quasi-static compression tests and validated finite element simulations. The results demonstrate that relative density is the primary factor controlling the overall stiffness, strength, and energy-absorption capacity of Octet LCSs. Under vertical compression, rearranging the density layers at a fixed average relative density regulates the yielding sequence and collapse path, enabling more controllable multistage energy absorption but with reduced stiffness and absolute SEA compared with uniform structures. Under transverse compression, the response is governed mainly by cross-sectional flattening, strut bending and local contact, and thus, the influence of layer arrangement on global load-bearing capacity is limited. The validated numerical model agrees well with the experiments and provides insights into the layer-sequence design of lightweight lattice cylindrical shells for protective and energy-absorbing applications. Full article

Cells of higher organisms express numerous cell surface proteins, and their spectrum and level of expression are directly related to cells’ functions. The technology of mass cell selection based on the surface protein expression levels may be highly important both for basic research and cell therapy applications. We have previously developed a method of magnetic selection of cells differing in surface marker expression levels, which we term here MACS-MEL (Magnetic-Assisted Cell Selection by Marker Expression Levels). The method demonstrated its effectiveness in the artificial model system, namely retrovirally transduced NIH 3T3 cells. However, whether it was also applicable to complex natural cell populations remained unclear. In the current study, we validated the MACS-MEL approach by separating mouse bone marrow (BM) cells into fractions according to the expression of pan-hematopoietic marker CD45. In the basic protocol, two-stage fractionation of CD45⁺ cells from BM was performed using selection of cells consecutively with 2 μL and 8 μL of anti-CD45 magnetic beads, resulting in isolation of CD45^high and CD45^int cell populations. To explore in full the potential of the method, the extended protocol was also tested, where a third selection stage with 30 μL of anti-CD45 beads was added. The isolated cell fractions were analyzed by flow cytometry for CD45 expression, as well for CD11b, Gr-1, CD117, CD115 and CD19 markers, while their in vitro progenitor function was assessed by quantitating colony-forming units (CFUs) in methyl cellulose. The results of analysis demonstrate that the isolated cell fractions significantly differed both in their surface phenotypes and CFU potential. In particular, cell fractions with progressively reduced CD45 expression were characterized by decreasing expression of myeloid differentiation markers CD11b and Gr-1, as well as B-lymphoid marker CD19. The expression of stem/progenitor cell marker CD117, on the contrary, significantly increased. The CFU frequency also strongly correlated with decrease in CD45 expression, while the differentiation potential of CFUs differed substantially in various cell fractions. In general, our results demonstrate that less differentiated hematopoietic cells in mouse BM studied using in vitro tests are characterized by lower CD45 expression levels, in full accordance with data obtained in human system. Successful validation of the MACS-MEL in a BM system, characterized by existence of multiple cell types and high phenotypic and functional heterogeneity, demonstrated the effectiveness, simplicity and affordability of this method. The MACS-MEL approach can be applied for mass selection of cells based on differential marker expression and may yield cell subsets suitable for advanced cell therapy applications. Full article

Shale gas reservoirs are characterized by low permeability, nanoscale pore structures, and complex fracture networks. Multistage fractured horizontal wells are an important technology for commercial shale gas development. However, many shale gas productivity models primarily emphasize gas transport within the reservoir and fracture system, while pressure variations caused by frictional losses along the horizontal wellbore are often simplified or treated separately. To address this issue, this study develops a fully coupled multiscale dual-porosity numerical model that integrates the shale matrix, hydraulic fractures, and horizontal wellbore within a unified simulation framework. The model incorporates key physical mechanisms governing shale gas transport, including Knudsen diffusion, Langmuir adsorption–desorption, stress sensitivity, and non-Darcy flow in fractures. Meanwhile, the Darcy–Weisbach equation is introduced to describe wellbore frictional pressure losses. The reliability of the proposed model is validated through history matching with field production data from the Changning shale gas reservoir. The results demonstrate that neglecting wellbore friction losses leads to a 30–50% overestimation of horizontal well productivity, indicating that wellbore friction has a significant impact on fracture flow distribution and productivity prediction. Furthermore, an exponent factor r is introduced to characterize and evaluate non-uniform fracture placement patterns. The results show that toe-dense fracture placement can increase cumulative gas production by approximately 37.8% compared with uniform fracture placement when r = 1.10, which yields the highest cumulative gas production among the tested cases. However, the additional production benefit becomes substantially smaller after the initial increase and remains relatively stable as r further increases. This study improves the understanding of friction-induced heel-to-toe effects and provides an effective numerical approach for productivity prediction and fracture placement design in shale gas horizontal wells. Full article

This study develops an analytical model for a mid-deep U-shaped borehole heat exchanger (UBHE) based on the segmented finite line source method, integrating geothermal gradient, five-layer geological stratification, and groundwater seepage within a unified framework. The injection, horizontal, and extraction sections are represented by independent local coordinates and coupled through the position- and time-dependent unit-length heat-transfer rate $q_l\left(s_n,t\right)$. Validation against the benchmark results of Bao et al. yields a mean absolute error of 0.87 °C and a mean relative error of 1.6%. Numerical-independence tests identify a 1 h time step and 100/50 m vertical/horizontal segment lengths as the adopted settings, and the iterative residual reaches 10⁻⁴ °C within eight iterations for the representative case. In a homogeneous, no-seepage limiting case, the model agrees with the classical finite line-source solution with an MAE of 0.012 °C and a maximum relative-error magnitude of 0.41%. The extraction-well fluid-temperature peak occurs at 600–800 m depth, whereas the local heat-transfer direction changes near 1600 m. For the investigated 2500–650–2500 m geometry, the highest cycle-averaged outlet temperature is obtained at an insulation length of 1600 m. Sensitivity analyses further quantify the effects of seepage velocity, equivalent thermal conductivity, geothermal gradient, and the validation insulation-length assumption. Full article

Most existing creep studies on NEPE propellant focus on room and high temperatures, lacking systematic investigation into low-temperature creep damage. In this work, uniaxial creep tests at −10 °C, −30 °C and −50 °C under three stress levels were conducted. All specimens show complete three-stage creep behavior. Higher stress accelerates interface debonding and shortens rupture life, while low temperature restricts molecular chain movement and suppresses damage growth. Combined with continuum damage mechanics and strain-equivalence hypothesis, a modified time-hardening creep model embedded with the Kachanov damage-evolution equation is established. All fitting coefficients of determination exceed 0.989. A FORTRAN UMAT subroutine is developed on ABAQUS (version 2024) for numerical simulation, using SDV1 and SDV8 to output creep strain and damage variables respectively. Simulation strain curves match experimental data well and reproduce full-range creep evolution. Damage remains low for most of the service time and surges only in the final 5–10% of the lifetime. The proposed model and subroutine accurately characterize the low-temperature creep and damage evolution of NEPE propellant, supporting grain structural integrity analysis and long-term storage life prediction. Full article

To elucidate the coupling characteristics between unsteady flow and hydrodynamic loads in the guide vane region of a pump–turbine under runaway conditions, a model pump–turbine of a high-head pumped storage power station was selected as the research object. A combined approach of model experiments and three-dimensional unsteady numerical simulations was employed to investigate the guide vane hydraulic torque, flow field structures, pressure distribution, and pressure fluctuation characteristics under different pre-opening guide vane conditions. In the experiments, the hydraulic torque of guide vanes was measured using a guide vane shaft strain testing method at five guide vane openings of 19 mm, 25 mm, 33 mm, 41 mm, and 45 mm. In the numerical simulations, a full-passage unsteady computational model was established based on the SST k-ω turbulence model, and the reliability of the numerical model was validated against experimental results. The results indicate that the guide vane hydraulic torque under runaway conditions exhibits pronounced periodic fluctuations, and the dominant period in the time domain is consistent with the blade passing frequency, demonstrating that rotor–stator interaction between the runner wake and guide vanes is the primary mechanism inducing unsteady hydraulic loads. As the guide vane opening decreases, the flow passage area in the guide vane region is reduced, and the high-speed swirling flow at the runner outlet generates significant jet impingement and local shear layers near the guide vane inlet, resulting in enhanced circumferential non-uniformity of the flow field and a substantial increase in the pressure difference across the guide vane surfaces. Among all operating conditions, the hydraulic torque fluctuation at a₀ = 19 mm is the most severe. Under small-opening conditions, flow separation, wake accumulation, and local backflow structures are prone to occur in the vicinity of the guide vanes, accompanied by pronounced high-frequency pressure disturbances and local impulsive pressure peaks. With increasing guide vane opening, the flow attachment behavior and flow field continuity are gradually improved, and the pressure fluctuations evolve from random oscillations to regular periodic pulsations, indicating a significant enhancement in flow stability. The study demonstrates that small guide vane opening conditions produce hydrodynamic load characteristics—specifically, higher-amplitude and more intermittent torque fluctuations, as well as lower minimum pressures—that are indicative of conditions conducive to increased vibration, fatigue accumulation, and cavitation risk; however, direct structural or two-phase cavitation analyses are required to confirm these implications. The present results can provide a theoretical basis for the optimal design of guide vane mechanisms and the safe operation of pump–turbines under runaway conditions, and quantitative coupling analysis reveals that the cross-correlation between inlet pressure and torque decreases from R = 0.87 at a₀ = 19 mm to R = 0.72 at a₀ = 45 mm, confirming that the flow–load coupling weakens substantially with increasing opening. Full article

This study presents a systematic investigation into the mechanical responses of two tungsten-based alloys—84W–11.2Ni–4.8Fe and 88W–8.4Ni–3.6Fe—fabricated via selective laser melting (SLM). Quasi-static compression tests using a universal testing machine and dynamic impact experiments employing a split Hopkinson pressure bar (SHPB) were conducted over a temperature range of 298–598 K and strain rates spanning from 1 × 10⁻³ s⁻¹ to 2.3 × 10³ s⁻¹. Both alloys exhibited significant strain-rate hardening and thermal softening effects. Based on the experimental data, a Johnson–Cook (J–C) constitutive model was established. The fidelity of the calibrated model for the 84W alloy was rigorously validated through pulsed X-ray radiography and static armor penetration tests. The SLM-fabricated 84W-shaped charge liner produced a well-collimated jet with a tip velocity of 5101.5 m/s and achieved a penetration depth of 87 mm into rolled homogeneous armor (RHA)-equivalent steel targets. Numerical simulations using the developed J–C model showed close agreement with experimental measurements, with a maximum discrepancy of only 9.19%, thereby confirming the predictive capability of the constitutive model. These results demonstrate that the proposed J–C model can reliably characterize the large-deformation behavior of SLM-processed 84W and 88W liners under the extreme thermomechanical conditions characteristic of shaped charge jet formation—namely high temperature, high pressure, and ultra-high strain rate. Collectively, this work establishes a foundational framework for the application of SLM technology to shaped charge liner design and provides a critical basis for further research into jet formation physics and penetration mechanics of tungsten-based alloys. Full article

With the continuous expansion of deep-sea resource exploration, marine environmental monitoring, and underwater operations, Autonomous Underwater Vehicles (AUVs) have been increasingly widely applied. Aiming at the demand for high-performance main propulsion systems of Autonomous Underwater Vehicles (AUVs), this paper conducts research on the structural design and hydrodynamic performance of a 30 kW rim-driven thruster (RDT) and its coupling mechanism with AUVs. By combining computational fluid dynamics (CFD) simulations and experimental methods, the influence of the advance coefficient on the open-water performance of the thruster is revealed. An integrated coupling simulation model of the AUV and RDT is established to analyze the performance attenuation law of the thruster and the characteristics of the coupled flow field under wake flow conditions, and to clarify the two-way interaction mechanism between the thruster and AUV. Towing tank tests were carried out at sailing speeds ranging from 1 to 4 kn, which verifies the reliability of the numerical simulation model and the matching performance between the thruster and AUV. The results show that the open-water efficiency of the thruster reaches a peak value of 0.536 at the advance coefficient $\mathrm{J}=0.8$, which is close to the optimal efficiency range with good matching performance of the propulsion system Under wake flow conditions, the attenuation range of the thrust coefficient of the thruster is 12.45–16.53% with the increase in advance coefficient. The main reasons are the uneven inflow velocity and unstable flow field pressure distribution caused by the non-uniform wake flow at the AUV stern. At the ship speeds of 2 kn, 3 kn and 4 kn, the self-propulsion rotational speeds obtained from test fitting are in good agreement with the simulation results, with all relative errors less than 8%. This study provides a theoretical basis and technical reference for the engineering design of medium and high-power rim-driven thrusters as well as the matching optimization of AUV-thruster systems. Full article

To address the insufficient load-bearing capacity and overall stiffness of timber truss roofs in brick–timber and earth–timber structures in rural areas, as well as the requirements for preserving traditional architectural characteristics, a steel–timber composite roof system was proposed. The system was developed through rational integration of timber and steel components to enhance the overall mechanical performance of the structure. At the joint level, flexural performance tests were conducted on cramp-iron joint, gusset–plate joint, and steel–timber joint. The moment–rotation relationships, failure modes, and ductility characteristics of the three joint types were systematically investigated. Based on the experimental results, a trilinear moment–rotation model was established. Furthermore, a finite element model of the roof structure was established using SAP2000 (26.2.0), and the stress distribution and load–displacement responses under horizontal static loading were analyzed through numerical simulation. The influence of different joint configurations on the mechanical performance of the roof structure was evaluated from an overall structural perspective. The results demonstrated that the peak bending moment of the steel–timber joint was increased by approximately 163.50% and 3.74% compared with those of the cramp-iron joint and gusset–plate joint, respectively. The ductility coefficient was enhanced by approximately 9.33% and 62.91%, respectively. In the finite element model of the roof structure, the peak load of the roof system with the steel–timber joint was increased by approximately 114.96% and 9.54%, while the corresponding displacement capacity was improved by approximately 76.62% and 43.41%, compared with the other two roof systems, respectively. Future studies will focus on further evaluating the seismic performance of steel–timber composite roof systems through cyclic loading experiments, dynamic response analysis, and full-scale structural validation, thereby providing a more comprehensive understanding of their long-term applicability in earthquake-prone rural buildings. Full article