Search Results (146)

Accurate and interpretable learning diagnosis is increasingly required in AI-enabled educational assessment. Existing cognitive diagnostic models typically represent item attributes with a binary Q-matrix and infer mastered or not mastered knowledge states. Although polytomous extensions allow graded mastery, item attributes rarely encode theory-aligned cognitive-process demands, which limits pedagogical interpretation of diagnosed profiles. This study aims to operationalize revised Bloom’s taxonomy at the exercise–knowledge level by constructing an Exercise–Knowledge–Cognition tensor and to develop RLDM-EKC as a DINA-type cognitive diagnosis model that infers ordered knowledge–cognition profiles. The model defines EKC-based ideal responses, estimates slip and guess parameters with an Expectation–Maximization procedure, and derives learner profiles using Maximum A Posteriori inference with uncertainty summaries. We validate the approach on synthetic data and on TIMSS 2007 Grade 4 mathematics data, comparing against classical CDMs including DINA, PA-DINA, and pG-DINA. In simulation, RLDM-EKC attains a PMR of 81.7% and an AAMR of 91.6%, and in empirical data, it yields theory-aligned multi-level cognitive profiles with transparent uncertainty reporting. These properties support actionable, human-in-the-loop feedback for teachers and learners under realistic deployment constraints. Full article

Background: The plantaris muscle (PM) shows substantial variability in its proximal belly attachments. Although often deemed vestigial, specific variants may narrow or reshape the popliteal corridor and contribute to vascular (popliteal artery entrapment syndromes, PAES) and neural conflict (TN, CPN, sural nerves). Despite abundant anatomical descriptions of the plantaris, its contribution to neurovascular compression has not been organised into a classification-linked, imaging-integrated framework. Objective: To synthesise adult and foetal anatomical data with clinical–radiological evidence into a classification-linked framework that stratifies vascular and neural compression risk by proximal PM variants, and to propose an integrated risk matrix and variant-directed diagnostic/operative pathway. Methods: Narrative, classification-centred review centred on the Olewnik schema (Types I–VI) and multi-headed/accessory variants. We mapped variant geometry to (1) physiological compromise on provoked Doppler US and (2) anatomical correlates on MRI/MR angiography (MRA) (axial “band sign”), deriving graded risk for vascular and neural axes and an integrated, action-oriented grade per limb. Results: Baseline risk is low for canonical/compact footprints (Type I–IA, Type V), moderate for capsular-junction patterns (Types II/III), and potentially higher-risk for lateral linkage (Type IV; iliotibial band (ITB)/Kaplan fibres continuity) and multi-headed configurations (duplication, bifurcation, ≥3–4 heads; accessory proximal slips). The integrated matrix upgrades risk for a clear band sign, reproducible compromise on provoked Doppler US, or multi-headed/Type IV anatomy and downgrades when rigorous provocation is negative and muscle volume is small. We provide a variant-indexed imaging checklist, common pitfalls (e.g., Type IV misread as ITB thickening; multi-headed variants misread as cyst/tumour), and operative checkpoints to target capsular clefts, lateral bands, tunnels, and accessory slips. Conclusions: A classification-linked, imaging-integrated approach clarifies which proximal PM variants are plausibly associated with neurovascular entrapment (based on case-level evidence) and aligns work-up with targeted decompression and may improve diagnostic precision and inform surgical planning. Clinical relevance: The framework operationalises variant naming in reports, standardises dynamic provocation and axial mapping, and prioritises variants considered higher risk (Type IV; multi-headed) for early multidisciplinary review. Given that most clinical signals derive from case reports/series (Level IV), these recommendations are inferential and should be applied with clinical judgement. Full article

The aim of this paper is to investigate dynamic adjustment of the in situ stress field and the stability of main faults in the Zhangbei strong seismic region. Firstly, we utilized in situ stress measurement and monitoring data to discuss the dynamic adjustment process of the in situ stress field. Subsequently, the Fault Slip Potential (FSP) v.1.0 software package was employed to calculate the fault slip potential of the main faults. Finally, the potential hazard of fault activity was assessed. The conclusions are as follows. (1) Since November 2015, the in situ stress field has been primarily influenced by NEE compressive tectonic action, with a slight enhancement in the near SN compressive tectonic action. (2) In the initial stage, NE-trending faults exhibited the highest stress accumulation levels, with near-EW-trending faults the lowest. Influenced by the enhanced near-SN-trending compressive action, as of 19 October 2020, near-EW-trending faults displayed the highest stress accumulation, followed by NW-trending faults, with NE-trending faults showing the least accumulation. (3) From November 2015 to October 2020, the in situ stress field was in a continuous accumulation process. Using the Shangyi–Pingquan fault as a boundary, fault activity in the southern part of the strong seismic region is more hazardous than that in the northern part. Full article

Advancing hydropower development is crucial for supporting China’s “Dual Carbon” strategy and ensuring energy security. A key safety challenge in this endeavor is the stability of arch dam abutments under the combined action of high in situ stress and reservoir water loads. This study addresses this issue by proposing an integrated methodology that links detailed geological characterization, in situ stress quantification, and mechanical stability analysis. Using the Guxue high-arch dam as a case study, we first established a three-dimensional geological model to identify controlling discontinuities and delineate potential sliding blocks. A finite difference model was then developed to simulate the in situ geo-stress field and operational water pressures. Through stress tensor transformation, the stress state on potential slip surfaces was accurately determined, and safety factors were calculated based on the Mohr–Coulomb strength criterion. The results show that the critical left and right abutment rock blocks exhibit safety factors of 1.30 and 1.24, respectively, meeting design specifications while indicating a relatively lower safety margin on the right bank. The proposed approach, grounded in precise stress analysis, provides a reliable framework for assessing abutment stability under complex loading conditions, offering practical support for the safety evaluation and targeted reinforcement of high-arch dam projects in similar geological settings. Full article

Taking the Daliang Tunnel of the Lanzhou–Xinjiang High-speed Railway crossing a reverse strike-slip fault as the engineering background, seismic damage investigations of the Daliang Tunnel and other cross-fault tunnels under earthquake action were conducted. Using 1:50 meso-scale model tests, experimental analyses were carried out on the lining strain response, internal crack development and failure, and surrounding rock pressure variation during fault dislocation. The failure modes and mechanisms of tunnels crossing reverse strike-slip faults were thoroughly explored. Meanwhile, a three-dimensional numerical model of the Daliang Tunnel was established to investigate the influence of dislocation modes with structural zonation within the fault zone on the surrounding rock response. The results indicate that the damage and strain response of the tunnel lining are mainly distributed within the fracture zone, predominantly characterized by combined oblique shear and compression failure. Due to the displacement of the lining induced by strong surrounding rock movement, surrounding rock pressure exhibits considerable variation at the boundaries of the fracture zone, accompanied by certain void detachment phenomena. The overall deformation of the tunnel crossing the reverse strike-slip fault presents an “S”-shaped pattern, which is consistent with the numerical simulations. The compression and dislocation morphology of the sidewalls within the rupture surface is in good agreement with the point cloud plan view. The compressive deformation and strain of the surrounding rock are most significant within the rupture surface. Meanwhile, the soft-to-hard transition segments between the new fracture zone and the rupture surface, as well as between the rupture surface and the influence zone, exhibit a trend of first decreasing and then increasing. Full article

Offshore reinforced concrete (RC) structures, such as bridges and high-piled wharves, are frequently subjected to the coupled action of steel corrosion and ship collision loads. However, existing studies lack systematic quantification and in-depth revelation of the synergistic degradation mechanism under this coupling effect, resulting in an insufficient scientific basis for engineering design and reinforcement. To address this gap, this study established a refined three-dimensional numerical model of drop hammer-reinforced concrete beams based on ABAQUS, comprehensively considering the strain rate effects of steel and concrete, steel–concrete bond–slip behavior, and the trilinear constitutive model of corroded steel. After validating the model’s reliability against experimental data from the existing literature, parametric simulations were conducted to investigate the coupled effects of different corrosion rates and drop heights (0.25–1.5 m). Key findings include: (1) corrosion reduces the peak impact force by 9.7–58.9% and increases the maximum mid-span displacement by 6.6–35.7%, with this effect amplified by higher drop heights; (2) shear performance degradation (16.14–35.19%) is significantly more severe than flexural performance degradation (13.28–28.93%), confirming that shear performance is more sensitive to corrosion; (3) corrosion causes cracks to propagate from a localized distribution to a global distribution, while higher drop heights accelerate structural evolution toward brittle failure; (4) the synergistic degradation law of “corrosion exacerbates impact damage, and impact amplifies corrosion defects” is revealed. By quantifying the corrosion–impact coupling effect, this study advances research in the field and provides critical technical support for damage assessment and service life prediction for offshore RC structures. In engineering practice, it is recommended that offshore structures in high-corrosion environments prioritize shear resistance enhancement and adopt targeted protective measures for high-impact-risk areas to mitigate the risk of brittle failure. Full article

This paper proposes a reinforcement learning (RL)-based control method for robust path tracking of a 4-wheel independent steering (4WIS) mobile robot in outdoor rough terrain environments. Traditional wheeled robots typically suffer from limitations including mobility constraints in narrow spaces, path deviations caused by ground slip, and reduced traction on rough terrain. To address these challenges, we designed a 4WIS mobile robot and implemented an architecture that independently controls the steering and driving of each wheel. The RL state space is defined by look-ahead path information, robot pose, velocity, and tracking errors, while the action space consists of target angular velocity and steering angle. To ensure robust performance, we applied random path and terrain generation and implemented domain randomization for sensors and actuators based on empirical GPS and motor data. The proposed controller was validated against the Pure Pursuit algorithm through dynamic simulations and real-world experiments. In simulations mimicking outdoor terrain, the controller reduced lateral and heading RMSE by 6.32% and 16.00%, respectively. In actual outdoor environments, it reduced these errors by 21.54% and 4.78%, respectively. These results demonstrate that the proposed controller provides superior robust tracking performance in unstructured outdoor environments. Full article

We present a covariant geometric extension of General Relativity formulated within a controlled effective field theory framework. The gravitational action is supplemented by curvature-dependent operators parametrized by three coefficients $\alpha$, $\beta$, and $\gamma$, chosen such that the resulting field equations remain second order in time derivatives and free of Ostrogradsky instabilities. In a homogeneous and isotropic cosmological background, the modified dynamics generically replaces the classical Big Bang singularity with a smooth, nonsingular bounce driven by a repulsive curvature core proportional to $a^{-6}$. A distinctive feature of the framework is the presence of a geometric slip term proportional to $\dot{H}$, which encodes curvature-memory effects at the level of the background evolution without introducing additional propagating degrees of freedom. This term dynamically correlates the expansion rate with its temporal variation, leading to effective ultraviolet damping and enhanced dynamical stability across the high-curvature regime. As a consequence, the cosmological solutions admit the definition of an intrinsic relational time variable that is strictly monotonic throughout the evolution, including across the bounce. The emergent temporal ordering arises purely from geometric dynamics and does not rely on matter clocks, nonlocality, or fundamental violations of time-reversal or CPT symmetry. We discuss the consistency of the framework within its effective field theory domain of validity and comment on its implications for the conceptual problems of singularity resolution and the emergence of time in cosmology. Full article

The effective bending stiffness formula for cross-sections of timber–concrete composite (TCC) beams was derived under semi-sinusoidal loading condition in Eurocode 5; however, this formula does not account for the non-uniform distribution of bending stiffness along the span. This limitation prevents it from characterizing the mechanical behavior under real loading conditions, which could potentially compromise the safety and serviceability of the structural design. To investigate the distribution pattern of bending stiffness, differential segment analysis was conducted, incorporating interfacial slip effects. A governing differential equation for curvature was established, and the resulting curvature distribution was used to compute deflections by means of the conjugate beam method. The results demonstrate that the bending stiffness distribution depends critically on shear connector arrangement and loading conditions. Under third-point loading, the bending stiffness monotonically decreases from the mid-span to the load application points and increases toward the supports. Under uniform loads, bending stiffness peaks at the mid-span and declines gradually toward the supports. Reducing shear connector spacing enhances composite action while amplifying bending stiffness non-uniformity. Experimental validation confirms that both the conjugate beam method (using analytical curvature solutions) and the simplified approach in Eurocode 5 achieve 99% average accuracy in predicting the mid-span deflection of TCC beams. In addition, careful attention must be paid to the deflection values at loading points, particularly when the loading position is close to the supports. Full article

To investigate the cyclic behavior of FRP-reinforced steel fiber reinforced concrete (SFRC) composite walls, this paper proposes a section-based finite spring calculation method (FSCM) to reliably predict the cyclic response of such walls under seismic loads. The proposed model accounts for the bond-slip effect of FRP bars and the confining action of transverse reinforcement in the boundary elements. Numerical calculations were conducted on six composite wall specimens with varying longitudinal bar types, fiber volume fractions, concrete strengths, and axial compression ratios. The results indicate that the established calculation method efficiently characterizes the “pinching” effect induced by the linear-elastic properties of FRP bars, and the obtained hysteretic curves are in good agreement with experimental data. Furthermore, the model accurately predicts the load-bearing capacity and residual displacements of the FRP-reinforced SFRC composite walls. Specifically, the average error of peak load calculation for all specimens ranges from −3.36% to 7.36%, and the predicted residual displacements correlate well with the experimental data. These findings demonstrate the applicability of the proposed model for key seismic performance indicators and provide a reliable basis for the research and engineering application of FRP-reinforced SFRC composite walls. Full article

Subsoiling is a highly effective deep tillage method used to mitigate soil compaction in orchard rows, a condition frequently resulting from repeated passes of agricultural machinery. This compaction can reduce water infiltration into deeper soil layers, leading to excessive surface water stagnation and a subsequent reduction in soil fertility. Subsoiling restores the structure of compacted soil by creating a vertical cut and lifting the ground without inverting the soil layers. This action promotes stable soil porosity and enhanced drainage, effectively eliminating the plough sole, and consequently improving root growth and nutrient absorption. Despite its benefits, subsoiling is an energy-intensive practice. Vibrating subsoilers can significantly reduce the high traction force required by conventional subsoilers, thereby enabling the use of smaller, less powerful tractors. This study investigated the performance of a single-shank subsoiler equipped with an innovative oscillating working tool, focusing on its dynamic-energy requirements, tillage quality, and the whole-body vibrations (WBV) transmitted to the tractor driver. Comparative tests were conducted in a compacted poplar grove using two 4WD tractors of different power and mass, with the subsoiler’s oscillating tool alternately activated and deactivated. The results demonstrated that the oscillating tool reduced draft force, traction power requirement, fuel consumption, and tractor slip, while maintaining tillage efficiency, displacing a greater mass of soil. However, a comparison of the measured vibrations indicated that their level reached a hazardous condition for the driver of the lower-power, lower-mass tractor when the oscillating tool was active. Full article

The micromechanisms “slip transfer, slip irreversibility, microplasticity, and fatigue cracking” in titanium alloys are reviewed, with a special emphasis on near-α and α + β alloys. As the interplay between slip activity, microplasticity, and fatigue cracking governs both the microscale and macroscale mechanical response, we reveal how the slip irreversibility and localized dislocation activity at the grain boundaries (GBs) and α/β interfaces generate dislocation pile-ups and strain localization, subsequently driving fatigue crack initiation and propagation. The review highlights the favorable crack initiation along basal planes and the roles of α grain orientations, slip transfer barriers, and the β phase in governing fatigue cracking, while addressing unresolved questions about localized interactions and texture effects. It also explores the complex interactions that govern the effects of microstructures, textures, and defects on fatigue cracking. Ultimately, the review provides a unified framework for linking slip events to microplasticity and to fatigue failure, offering actionable insights for alloy design and fatigue prediction. Full article

The steel-plate–concrete composite reinforcement method is derived from the bonded steel plate and increased-section techniques. It is employed to enhance the strength of concrete structures that require a substantial increase in load-bearing capacity. To develop a flexural deformation calculation theory that accounts for slip effects in general reinforced cross-sections with bilateral symmetry, interfacial slip and deflection equations are formulated based on the relationship between interlayer slip and the rotational angle of beams in the plane, as well as the principle of force equilibrium. A numerical method, established based on this theoretical framework, is proposed to facilitate the analytical solution and is verified to be consistent with analytical results. Furthermore, the accuracy of the calculation theory is validated through bending experiments. Finally, the influence of key parameters affecting slip on the flexural stiffness of the reinforced beam is evaluated by determining the stiffness reduction coefficient according to the theory. The results indicate that the flexural stiffness of reinforced beams is governed by three non-dimensional parameters: the boundary condition parameter (μ), composite action parameter (shear connector stiffness (βl)), and relative bending stiffness parameter (G_∞/G₀). The loading mode does not affect the flexural stiffness of the reinforced beams. As βl approaches 100 and G_∞/G₀ approaches 1, η approaches 100%. In cases where high stiffness is required, reducing interfacial slip can minimize the loss of flexural stiffness in composite structures. Conservative calculations indicate that satisfying the conditions βl ≥ 8 and G_∞/G₀ ≤ 1.6 during design can ensure that the reduction in flexural stiffness of the reinforced beam remains above 90%. Full article

In accelerated bridge construction, precast concrete girders are connected to cast-in-place concrete slab using shear transfer reinforcement across the interface plane to ensure the composite action. The steel transverse reinforcement is prone to severe corrosion due to the extensive use of de-icing salts and severe environmental conditions. As glass fiber-reinforced polymer (GFRP) reinforcement has shown to be an effective alternative to conventional steel rebars as flexural and shear reinforcement, the present research work is exploring the performance of GFRP reinforcements as shear transfer reinforcement between precast and cast-in-place concretes. Experimental testing was carried out on forty large-scale push-off specimens. Each specimen consists of two L-shaped concrete blocks cast at different times, cold joints, where GFRP reinforcement was used as shear friction reinforcement across the interface with no special treatment applied to the concrete surface at the interface. The investigated parameters included the GFRP reinforcement shape (stirrups and headed bars), reinforcement ratio, axial stiffness, and the concrete compressive strength. The relative slip, reinforcement strain, ultimate strength, and failure modes were reported. The test results showed the effectiveness and competitive shear transfer performance of GFRP compared to steel rebars. A shear friction model for predicting the shear capacity of as-cast, cold concrete joints reinforced by GFRP reinforcement is introduced. Full article

This study experimentally evaluates the structural performance of Concrete-Filled Double-Skin (CFDS) hybrid connections that are intended as key components of large-scale floating offshore wind substructures. The innovative aspect of this work lies in the direct experimental comparison of five representative connection details—Headed Stud (HS), Perfobond (PB), L-beam-joint (LJ), L-beam-spacing (LS), and Angle (AN)—with respect to multiple performance indices that are critical under harsh offshore environments. First, full-scale CFDS specimens were fabricated with identical global dimensions while varying only the connection details. The hybrid behavior of the CFDS system arises from the complementary actions of the outer steel tube, which primarily resists tensile forces, and the infilled concrete, which provides dominant compressive resistance and confinement. This composite interaction enhances the stiffness, ductility, and energy absorption capacity of the member under flexural demands, which are essential for floating offshore structures operating under complex marine loading. Second, monotonic bending tests were conducted using a 2000 kN actuator under a cantilever-type configuration, and load–displacement responses were recorded at three locations. Third, the stiffness, ductility, and energy absorption capacity (toughness) were quantified from the measured curves to clarify the deformation and failure characteristics of each connection type. The results show that the PB connection achieved the highest maximum load and exhibited stable ductile behavior with plastic energy dominating the total toughness. The LJ connection provided well-balanced stiffness and deformation capacity with low sensitivity to measurement locations, indicating high reliability for design applications. In contrast, the HS and LS connections experienced localized slip and position-dependent stiffness, while the AN connection showed the lowest load-carrying efficiency. Overall, the findings highlight that connection-level detailing has a decisive influence on the global performance of CFDS hybrid members and provide fundamental data for developing design guidelines for floating offshore structures operating under complex marine loading conditions. Full article