Search Results (775)

The loss of sand foundation often induces differential settlement in immersed tunnel segments, potentially causing structural damage and reducing structural resilience. Accurately assessing the damage characteristics and their effects on resilience during sand foundation loss is essential for ensuring tunnel safety. This study adopts a typical immersed tunnel project as a case study. Long-term structural deformation data acquired by distributed optical fiber sensing technology and sand foundation detection data are adopted to analyze the response characteristics and damage state of the tunnel. A refined three-dimensional tunnel–stratum interaction model is established and validated against monitoring data to investigate mechanical response characteristics, including deformation and bending moment distributions. A redundancy factor is proposed as a quantitative index for tunnel resilience under foundation loss, and a multi-level resilience grading framework is established accordingly. Furthermore, the evolution of tunnel resilience under various displacement recovery ratios, which represent the extent of differential settlement remediation, is investigated using the refined numerical model. Field detection results show that over 50% of the foundation area is affected by loosening or voids. These defects are highly consistent with regions of abnormal structural deformation, leading to a bending–torsional deformation mode, with a maximum joint differential settlement of 106.7 mm. Stress concentration occurs in the tunnel floor above denser sand zones, with a maximum crack width of 0.43 mm. The tunnel is classified as severely damaged (low resilience) based on the proposed standard, with a redundancy factor of 1.59. Bending-torsional deformation and stress concentration are gradually mitigated as the displacement recovery ratio increases. The redundancy factor exhibits a parabolic relationship with the recovery ratio, indicating that tunnel resilience can be restored to a relatively high level when the displacement recovery ratio exceeds 70%. The proposed redundancy factor and grading framework provide quantitative guidance for designing and optimizing resilience improvement strategies following sand foundation loss. Full article

Mode veering is a modal-interaction phenomenon found in vibration systems. For inertially coupled structures, the combined influence of coupling delay, nonlinear restoring force, and stochastic coupling perturbation remain insufficiently understood. This work analyzes an inertially coupled two-coordinate prototype in which a discrete delay, a delayed cubic stiffness, and positive multiplicative stochastic modulation all enter through the same relative-coordinate coupling channel. We formulate the delayed linear spectrum through a quasi-polynomial characteristic equation. We also characterize the veering by the two positive-frequency characteristic-root branches descending from the mechanical modes. Coupling delay shifts the veering center, alters the minimum frequency gap, and moves the tracked rightmost roots toward the stability boundary. An analytical imaginary-axis-crossing criterion is derived to determine the delay-induced stability boundary of the deterministic linearized system, and the resulting boundary is independently validated by direct multi-start characteristic-root searches and Chebyshev-collocation approximation of the DDE generator. A fixed-reference modal-coordinate representation identifies the off-diagonal modal terms associated with branch exchange while retaining the full delayed characteristic equation. A first-harmonic treatment of the delayed cubic term can yield an amplitude-dependent nonlinear veering backbone. For the stochastic problem, frozen lognormal coupling samples and a time-dependent Ornstein–Uhlenbeck-driven multiplier are constructed from the same unit-mean positive lognormal marginal law. The former is used to quantify realization-wise spectral broadening, whereas the latter retains temporal correlation and is used to evaluate finite-time branch residence and pathwise delayed-work statistics. The pathwise energy balance reveals that the delayed relative-coordinate work rate is sign-indefinite. This provides a common energy-transfer mechanism through which delay, nonlinearity, and stochastic modulation reshape mode veering in the inertially coupled system. Full article

Calcium silicate-based cements are hydraulic biomaterials that form a calcium silicate hydrate (C-S-H) gel during hydration, a process fundamental to their setting and progressive physicochemical development. Although these materials are widely used in vital pulp therapy, evidence regarding the effects of adhesive strategy and restoration timing on bonding performance, particularly for newer premixed formulations, remains limited. This study evaluated the effects of cement type, adhesive strategy, and restoration timing on the shear bond strength (SBS) of resin composite bonded to MTA Angelus and Well-Root PT. A total of 270 specimens were distributed across two cement types, three adhesive strategies, and three restoration intervals (45 min, 24 h, and 7 days). After thermocycling, SBS and failure modes were assessed. SBS data were analyzed using three-way ANOVA, whereas failure-mode distributions were evaluated using chi-square or Fisher’s exact tests (α = 0.05). Cement type, adhesive strategy, restoration timing, and their interactions significantly influenced SBS (p < 0.001). Well-Root PT exhibited higher early bond strength than MTA Angelus. The two-step etch-and-rinse adhesive produced the highest SBS values, whereas the universal adhesive produced the lowest. Restoration after 24 h significantly increased SBS compared with restoration after 45 min, with no additional improvement observed at 7 days. Within the limitations of this in vitro study, bonding performance was influenced by cement type, adhesive strategy, and restoration timing. The time-dependent increase in SBS is consistent with continued hydration and development of the C-S-H gel-based cement matrix, although the specific microstructural changes underlying this behavior were not directly characterized. Full article

To enhance critical infrastructure protection against low-cost UAV impacts, this study proposes a novel ring lattice sandwich structure (RLSS) fabricated via an economical interlocking-assembly-brazing method. Its quasi-static compressive behavior is systematically investigated through experiments, numerical simulations, and theoretical analysis. Theoretical models for relative density and initial yield stress are validated against experiments, with errors of 7.1% and 6.6%, respectively. Quasi-static tests show that the one-layer RLSS exhibits a specific energy absorption (SEA) of 8.67 J/g, while the two-layer structure drops to 5.66 J/g due to inter-layer torsional instability. SHPB impact tests at strain rates of 750–1369 s⁻¹ demonstrate a pronounced strain-rate effect, with dynamic increase factors ranging from 1.14 to 1.43. Numerical simulations accurately reproduce the experimental deformation modes and reveal that multi-layer (2–5 layers) RLSSs reduce SEA by 46.9% compared with the one-layer simulated value of 9.43 J/g. Adding a 0.3-mm inner panel in simulations restores the crushing mode and raises the SEA of the two-layer structure to 7.19 J/g, surpassing the non-panel counterpart (6.03 J/g). Hybrid core configurations provide additional advantages: Mode I (ring–pyramid with inner panel) enhances total energy absorption with a limited ring-layer count, while Mode II (alternating layers) achieves minimal plateau stress fluctuation (PSF = 0.09). These findings confirm that the proposed RLSS, especially when optimized with thin inner panels or hybrid designs, offers great potential as protective cladding against impact and blast threats. Full article

The aim was to evaluate, in vitro, the fracture load of single-rooted teeth restored using post-and-core techniques combining short fiber-reinforced composite (SFRC) and polyethylene fiber (PEF) compared with the conventional technique of post-and-core buildup using fiberglass posts (FGPs). Thirty-six single-rooted anterior teeth (12 mm root length) were assigned to three groups (n = 12): Group 1 (FGP + conventional composite resin), Group 2 (SFRC), and Group 3 (PEF + SFRC). All specimens received composite resin crowns, were subjected to 1,000,000 mechanical cycles (100 N, 45°), and were then tested for fracture resistance. Failure mode was assessed visually. After mechanical cycling, no fractures, chipping, cracks, or restoration displacement were observed in any specimen. According to the Kruskal–Wallis test and Dunn’s post hoc test with Bonferroni correction, Group 2 (946 N) showed the highest fracture load, with no significant difference from Group 3 (820 N) (p > 0.05). The lowest median was observed in Group 1 (513 N), which differed significantly from the other two groups (p < 0.05). Irreparable failures occurred in Group 1 (75%), Group 2 (50%) and Group 3 (59%). It was concluded that post-and-core technique using SFRC, either alone or in combination with PEF, is a viable and mechanically superior alternative to FGP for rehabilitating single-rooted teeth without a ferrule. Full article

Achieving an acceptable adhesive interface is necessary for the long-term success of composite restorations in primary teeth. This study compared the three-dimensional internal adaptation of composite restorations in primary second molars among four prespecified universal adhesive product–application protocol combinations using micro-computed tomography (micro-CT). Seventy-six extracted primary second molars were randomly allocated to four experimental groups (n = 19): G2-BOND Universal/self-etch, G2-BOND Universal/selective enamel etching, G-Premio Bond/self-etch, and G-Premio Bond/selective enamel etching. Following restoration and thermocycling (5000 cycles), whole-cavity interfacial gap volume percentages were quantified using micro-CT. Data were analyzed using the Kruskal–Wallis test followed by Dunn–Bonferroni-adjusted pairwise comparisons. An overall difference was detected among the four experimental groups (p = 0.016). Following adjustment for multiple comparisons, the G2-BOND Universal self-etch group showed a lower whole-cavity interfacial gap volume percentage than the corresponding selective enamel-etching group (adjusted p = 0.013). No other adjusted pairwise comparison reached statistical significance. Within the limitations of this laboratory study, these findings are restricted to the tested product–application protocol combinations and do not demonstrate an interaction between adhesive system and application mode. Full article

This paper proposes a single-stage common-ground series-capacitor-compensated buck–boost inverter (CG-SCC-BBI) for wide-input DC–AC applications. Featuring a common-ground neutral and a series-blocking film capacitor, the topology inherently suppresses high-frequency common-mode leakage-current excitation and blocks the structural DC offset. To counteract frequency-dependent voltage attenuation caused by the output network, a fundamental-frequency equivalent model is derived to pre-scale the modulation reference and fully restore output voltage amplitude. The four-switch power stage operates with single-active-leg PWM, confining high-frequency switching to a single half-bridge at any instant to significantly reduce the switching-loss budget. Furthermore, by eliminating the conventional line-frequency output filter choke and utilizing film capacitors exclusively, the topology completely avoids electrolytic capacitors, thereby enhancing long-term operational reliability and lifespan. The proposed inverter supports seamless transition between boost and buck operating modes across the entire input-voltage range. Its operating principles are validated through time-domain simulations, and these were experimentally verified on a 300 W SiC MOSFET standalone laboratory prototype. Experimental results confirm correct operation from 95 V to 400 V DC input, achieving maximum measured efficiencies of 96.79% at the rated 300 W under low-input operation and 97.66% at the rated 300 W under high-input operation, while maintaining an output-current total harmonic distortion (THD) below 2.5%. Full article

Background: Right-to-left shunting through a patent foramen ovale (PFO) is an underrecognized yet potentially reversible cause of refractory hypoxemia, particularly in patients with right ventricular dysfunction. This case report describes heart-rate-dependent right-to-left shunting through a PFO causing refractory hypoxemia in a patient with inflammatory cardiomyopathy and severe right ventricular dysfunction, presumably arising from biventricular output mismatch. Case Presentation: We report the case of a 41-year-old male with inflammatory cardiomyopathy and a recently implanted single-chamber pacemaker (VVI mode, lower rate limit 50 bpm), admitted for decompensated heart failure. After initial clinical improvement with guideline-directed therapy, the patient’s intrinsic heart rate declined, and ventricular pacing at 50 bpm became the dominant rhythm. He subsequently developed refractory hypoxemia unresponsive to mechanical ventilation. Systematic hemodynamic assessment was performed using transthoracic echocardiography and thoracic electrical bioimpedance (TEB) monitoring at different pacing rates. Results: Echocardiographic evaluation revealed dynamic interatrial shunting through a PFO with the following characteristics: left-to-right at a pacing rate of 80 bpm and right-to-left at 50 bpm. Hemodynamic and echocardiographic data suggested that bradycardia induced biventricular output mismatch—left ventricular outflow tract velocity–time integral (VTI) increased by approximately 38% (from 17.5 cm to 24.1 cm), whereas right ventricular outflow tract VTI increased by only approximately 4% (13.3 cm vs. 13.8 cm). This mismatch likely resulted in relative elevation of right atrial pressure, thereby driving right-to-left shunting through the PFO. Increasing the pacing rate to 80 bpm reversed the shunt direction, normalized oxygenation, and facilitated successful extubation. Conclusions: This case suggests that in patients with severe right ventricular dysfunction, bradycardia may induce biventricular output mismatch with substantially greater left than right ventricular stroke volume augmentation, and presumably relative elevation of right atrial pressure, potentially leading to dynamic right-to-left shunting through a PFO. For such patients with unexplained hypoxemia, the possibility of dynamic PFO shunting should be considered. Appropriately increasing the pacing rate may help restore biventricular output matching, reverse shunt direction, and improve oxygenation; individualized heart rate management strategies warrant clinical consideration. Full article

Mobile-phone overuse and attention fragmentation have become pressing societal and public-health concerns. Cyberpsychology research highlights addictive engagement loops driven by intermittent rewards, persuasive design, and habit formation. In this article we synthesize current evidence on mobile-phone addiction and propose “Digital White Spaces” (DWSs), a socio-technical framework that combines privacy-preserving monitoring, AI-driven detection of addictive loops, device-mode interventions, and physical signal-limited zones to restore user autonomy. Full article

The conventional fault-control strategy for fiber-optic communication failures in modular multilevel converters (MMCs) directly bypasses faulty submodules (SMs). However, once communication is restored, the bypassed SMs cannot be reintegrated, and the converter must shut down when redundancy is exhausted. This paper establishes a fault-propagation model and proposes a long-timescale non-bypass fault-tolerant control strategy that avoids unnecessary SM bypassing and improves system reliability. First, a mathematical fault-propagation model is developed for downlink command loss and uplink status-feedback interruption. The model reveals a positive correlation between modulation-index deviation and current fluctuation during downlink faults and derives the coupling mechanism between switching states and DC-voltage fluctuation during uplink faults. On this basis, a non-bypass fault-tolerant control method is developed in which a faulty SM switches to a local constant-voltage closed-loop mode. This mode preserves the SM’s electrical connection and voltage stability while enabling rapid resynchronization and recommissioning after fiber-optic communication is restored. Hardware-in-the-loop (HIL) results show that the proposed strategy limits current fluctuations to within 0.1% under transient faults and DC-voltage fluctuations to within ±1% under permanent faults while substantially improving system availability compared with the conventional bypass scheme. The proposed method provides a cost-effective and practically implementable approach to maintaining uninterrupted operation of VSC-HVDC MMCs under communication-link failures. Full article

The increasing integration of power electronic converters in hybrid AC/DC microgrids introduces significant challenges in maintaining DC-link voltage stability during mode transitions, where uncoordinated actions cause large voltage deviations. This paper proposes a coordinated hierarchical control strategy incorporating a supervisory finite state machine (FSM) and a slew-rate-limited reference shaping mechanism to ensure smooth transitions in a microgrid interfaced through a bidirectional DC–DC converter and a three-level T-type inverter. The supervisory layer coordinates the sequencing of subsystem activation and routes all mode changes through a dedicated transition state in which the power reference is gradually shaped to suppress DC-link disturbances, while a dedicated resynchronization state manages reconnection to the grid after a sustained outage. The strategy is validated through detailed switching-level simulations across five operating scenarios, including islanded load energization, grid blackout, discharging-to-charging transitions, state-of-charge limit management, and grid restoration through reclosing and resynchronization, and is further compared against a droop-based coordination scheme. Simulation results demonstrate that the proposed approach reduces the transient DC-link voltage deviation from approximately 18–20% to below 7%, and to as low as 2.6%, without introducing steady-state error, confirming its effectiveness in enhancing the dynamic stability of the system during mode transitions. Full article

Dry-connected prefabricated composite walls have been increasingly used in steel structures owing to the development of building industrialization and the demand for rapid and efficient construction. However, the respective influences of dry-connection configuration and wall panel material on the seismic response of prefabricated composite walls require further clarification. To address this issue, full-scale quasi-static tests, continuum damage mechanics (CDM) analysis, and finite element simulations were conducted. Six specimens were tested under low-cycle reversed loading. The influence of connection type was evaluated by comparing MRC walls with U-type and Z-type connections, whereas the influence of wall panel material was evaluated by comparing MRC and SFC walls under U-type connections. For the tested MRC walls, the deformation capacity of the connections strongly influenced the failure mode. The U-type rigid connections provided limited deformation buffering, resulting in stress concentration at the wall ends, initial cracking at displacements of 8–10 mm, rapid crack propagation, and semi-brittle failure. In contrast, the Z-type flexible connections released deformation demand through the slip and rotation mechanisms of the slotted holes. The maximum tested displacements of the Z-type specimens were approximately 2.58–2.78 times the ultimate displacements of the corresponding U-type specimens. The Z-type specimens maintained stable load-carrying behavior with limited panel damage throughout the tested displacement range. Furthermore, a restoring-force calculation method was established based on CDM theory, and the predicted peak loads were generally consistent with the experimental results. This study identifies the load-transfer, deformation, and energy-dissipation characteristics of the tested connection–panel configurations and provides comparative evidence for the further development of prefabricated composite wall systems. Full article

Background: Bonding to sclerotic dentin remains one of the most challenging procedures in restorative dentistry due to tubular occlusion and hypermineralization, which limit resin infiltration. This study evaluated the influence of adhesive system, surface treatment, storage time, and substrate position on microtensile bond strength (µTBS) to natural sclerotic dentin. Methods: Sixteen extracted human molars with sclerotic dentin were selected and randomly assigned to nine experimental groups according to the adhesive system and surface treatment. Three adhesives were tested: a two-step self-etch adhesive (Clearfil SE Bond 2, Kuraray Noritake Dental, Tokyo, Japan) and two universal adhesives, one containing 10-MDP (G-Premio Bond, GC Corp., Tokyo, Japan) and one without 10-MDP (iBond Universal, Kulzer GmbH, Hanau, Germany). Each adhesive was applied under three conditions: no pretreatment (control), Al₂O₃ air-abrasion, and Bioglass 45S5 (ProSylc^®, Velopex International, London, UK) air-abrasion. Composite build-ups were performed, and the specimens were sectioned into 1 mm² beams for microtensile testing either after 24 h or after 6 months of storage in distilled water at 37 °C of hypertonic solution. The effect of beam position (central vs. peripheral) was also analyzed. Bond strength was measured by µTBS testing, and the results were analyzed using multifactorial ANOVA and Tukey’s test (α = 0.05). Failure modes were examined under stereomicroscopy, whereas optical microscopy was used for qualitative evaluation of representative fractured interfaces. Results: Significant main effects were found for adhesive system and surface treatment (p < 0.001), with a notable interaction between them (p < 0.05). Al₂O₃ air-abrasion produced the highest bond strengths, particularly for the self-etch adhesive containing functional monomers (53.4 ± 6.1 MPa), representing a 53% increase over the untreated control. Bioglass air-abrasion did not enhance adhesion and led to irregular hybrid layers. The position of the beams affected only one universal adhesive, with higher µTBS in peripheral regions. After six months of water storage, bond strengths remained stable across most groups, indicating good hydrolytic resistance of the interfaces. Conclusions: Both the adhesive system and the surface treatment significantly influenced bonding effectiveness to sclerotic dentin. The combination of Al₂O₃ air-abrasion with an MDP-containing self-etch adhesive achieved the most durable and homogeneous bond interface. providing a clinically reliable protocol for restorative treatments in sclerotic dentin. Within the limitations of this in vitro study, this combination may represent a potentially useful strategy for improving adhesion to sclerotic dentin, although further investigations are required to confirm its clinical applicability. Full article

Post-disaster emergency communication recovery is not merely a link-repair task but a high-level planning problem constrained by service priorities, inter-object dependencies, resource budgets, and time windows. Existing restoration optimization methods generally rely on fully structured inputs, whereas direct large language model (LLM) planning may produce fluent candidates that violate encoded prerequisites, stage-order relations, budget limits, or temporal constraints. To address this challenge, we propose ICG-Restore, an intent-constrained, graph-enhanced LLM planning framework with rule-consistent minimal-edit repair. ICG-Restore transforms mixed restoration requests and structured network observations into task packages that can be checked for validator-level feasibility under an encoded high-level constraint model and evaluated by downstream abstract executors or schedulers. The framework compiles natural-language requests, structured observations, and operational rules into a task-intent object; retrieves task-relevant context from a heterogeneous scenario graph and a restoration knowledge graph; generates stage-wise restoration candidates; and applies bounded local corrections to candidates that violate encoded constraints. In this paper, “minimal-edit” is a descriptive label for a bounded local repair principle that prioritizes less disruptive corrections. Candidates accepted by the validators are evaluated and ranked by a safety-aware agent executor operating in an abstract restoration action space. Experiments on controlled abstract topologies covering three scales, four restoration tasks, and five environmental evolution modes show that ICG-Restore improves validator-level constraint satisfaction and benchmark-estimated recovery utility. Compared with Direct-LLM, it improves CSR and CRS by 1.99% and 24.56%, respectively; benchmark-specific WCTC@5 structural-alignment diagnostic increases by 38.87%. Full article

Ex situ hydrogen biomethanation represents a promising approach to converting surplus renewable electricity into CH₄-rich gas through the biological reduction in CO₂ with H₂, mediated by hydrogenotrophic methanogens. In this study, an ex situ H₂ biomethanation process was investigated in a lab-scale mesophilic anaerobic reactor operated in fed-batch mode. The system followed a cyclic operational strategy comprising sequential gas feeding, reaction, and discharge phases. Hydrogen was supplied through a pressure-controlled feeding strategy, whereas CO₂ injection maintained dissolved CO₂ concentrations at 25, 17, and 2 mg L⁻¹ during the initial, intermediate, and final stages, respectively. During early operation, volatile fatty acids (VFAs) temporarily accumulated to 3 g L⁻¹, accompanied by a decrease in pH. Progressively lowering the dissolved CO₂ target restored process stability, reduced the VFA concentration to 618 mg L⁻¹, and increased the pH to 7.6. Under stable final-stage conditions, the reactor achieved an average CH₄ concentration of 93.3%, a hydrogen utilization efficiency of 99%, and a methane evolution rate (MER) of 3.95 NL CH₄ L_VR⁻¹ d⁻¹. These results show that combining pressure-controlled hydrogen injection with dissolved CO₂ regulation enhances methane production and maintains stable ex situ biomethanation. Full article