Search Results (2,648)

This paper investigates the asymptotic stability of a one-dimensional porous elastic system subject to a single boundary control of the fractional derivative type. The system consists of two coupled hyperbolic equations describing the displacement of an elastic solid and the volume fraction, with boundary conditions that include a generalized Caputo fractional derivative of order $\alpha \in (0,1)$ at $x=L$. This configuration has not been previously addressed in the literature. Using semigroup theory, we first reformulate the system as an abstract Cauchy problem and prove that the associated operator generates a $C_0$-semigroup of contractions on a suitable energy space, establishing global well-posedness. Under explicit and generic conditions on the physical parameters and the length L, we prove strong stability via the Arendt–Batty criterion, showing that all solutions tend to zero in the energy norm as $t\to \infty$. The main result is a polynomial decay rate: there exists $c>0$ such that $\parallel S_{\mathcal{A}}\left(t\right)U_0{\parallel }_{\mathcal{H}}\le c{t}^{-1/6}{\parallel U_0\parallel }_{D\left(\mathcal{A}\right)}$ for all initial data in the domain of the generator. The proof relies on the Borichev–Tomilov theorem and a detailed contradiction argument based on asymptotic expansions of the resolvent operator. Notably, the decay rate is independent of any relation between the wave propagation speeds, which distinguishes our result from many previous studies on porous elastic or Timoshenko systems. Full article

Optimizing the structural stability of foundations is challenging in modern geotechnical engineering. This study investigated the mechanism of geocell-reinforced foundations through discrete element modeling based on transparent soil model tests. A three-dimensional particle flow code (PFC^3D) model was developed to investigate the micromechanical soil–geocell interactions in both unreinforced and geocell-reinforced foundations under strip loading. Particle displacement, contact force distribution, and structural deformation within the foundation system were analyzed to quantify the performance of geocell reinforcement. The results show that geocell inclusion enhances structural performance by 2.1 times compared to an unreinforced foundation, increasing the bearing capacity from 60.6 to 126.8 kPa at a defined bearing capacity criterion. The geocell walls act as rigid physical boundaries that microscopically intercept the lateral migration and horizontal extrusion of soil particles. The kinematic trajectories of soil particles beneath the loading plate are forced into a downward realignment, decreasing the displacement vector rotation angle from 42° in the unreinforced soil to 27° in the reinforced soil and effectively mitigating the heave of adjacent surfaces. Furthermore, the quasi-rigid three-dimensional network completely interrupts the continuous steep contact force chains inherent in unreinforced foundations. Concentrated vertical stresses are converted into horizontal components through interfacial friction and mechanical interlocking, resulting in the lateral redistribution of the applied load by a distance of approximately 0.06 m. The geocell–soil composite considered as a flexible raft foundation extends load dispersion and reduces average subsoil pressure. A coupled tension and compression stress state in the horizontal plane is developed within the geocell structure. Forces are channeled along rigid paths by elevated bending moments and stress concentrations at the cell junctions. These findings provide micromechanical insights into the performance of geocell-reinforced-foundation systems. Full article

The Chang 8 tight oil reservoir in the Xifeng area of the Ordos Basin is characterized by poor reservoir properties, making conventional water flooding ineffective for efficient reservoir development. CO₂ flooding is therefore considered an important approach for enhancing oil recovery in tight reservoirs. However, suitable development strategies for direct CO₂ injection in undeveloped reservoir areas remain insufficiently understood. In this study, compositional numerical simulation combined with a single-factor sensitivity analysis was employed to investigate the effects of key parameters, including well pattern configuration, fracturing parameters, injection–production strategy, and gas injection modes. The results indicate that an inverted nine-spot well pattern with vertical well injection and vertical well production, a well spacing of 500 m, and a row spacing of 200 m can achieve relatively favorable areal and vertical sweep performance. A fracture half-length of 80 m, fracture widths of 0.003–0.005 m, and fracturing treatment before initial production help balance early-stage productivity and gas channeling control. Maintaining an injection rate of 0.03–0.04 PV/a, an oil production rate of 2–3 m³/d, and a bottomhole flowing pressure of 13–14 MPa is beneficial for maintaining reservoir energy and stabilizing displacement-front propagation. Based on neighboring field development experience, switching from continuous CO₂ injection to water–alternating–gas (WAG) injection during the mid-development stage can improve mobility control and enlarge the CO₂ swept volume. Under the current geological model and simulation conditions, the recommended development strategy predicts a recovery factor of 35.43% over a 30-year production period. The results provide reasonable parameter ranges and an engineering reference for direct CO₂ flooding development in the Chang 8 tight oil reservoir and similar reservoirs. Full article

This paper focuses on the significant potential of specific optical non-invasive methods, such as digital holographic microscopy, digital speckle pattern interferometry, and digital holographic interferometry, as scientific and technological tools for retrieving physical and biomechanical parameters embedded in the optical phase of laser-illuminated biomedical samples. These techniques take advantage of the laser speckle phenomena observed when non-specular surfaces are illuminated, enabling whole-field measurements and reconstruction of 3D images. Their versatility in implementation and application has led to advances in various fields of research and has broadened our understanding in both the basic and applied sciences. In clinical environments, the aforementioned quantitative optical studies are particularly valuable for understanding the behavior of biological samples, as they allow precise characterization of deformations, displacements, stress, strain, refractive index, and morphological features. Applications presented span from soft to hard tissues at both micro- and macro-scales, with results obtained from vocal cords, skin tissues, melanoma cells, and teeth. Furthermore, this overview provides a general perspective of some current speckle-based approaches and their growing relevance in biomedical research. Full article

This study investigates a 2D fractional order generalized thermoelastic problem in a homogeneous and isotropic thermoelastic hollow sphere. The sphere is exposed to a decaying heat source, and the governing equations are derived using a refined fractional-order Lord–Shulman (LS) model of generalized thermoelasticity. The Laplace transform technique is used to convert time-dependent PDEs into simpler ODEs in the Laplace domain. Its numerical inversion method is used to revert to the time domain. Numerical simulations are carried out to investigate the distributions of temperature, displacement, and stress fields within the hollow sphere. The obtained results reveal that both the fractional-order parameter and the variable thermal conductivity strongly affect the thermoelastic response, particularly the propagation characteristics of thermal waves, stress intensity, and relaxation behavior. In addition, the curvature of the hollow geometry plays an important role in modifying the radial and circumferential stress distributions and their attenuation throughout the medium. Full article

Typhoons and extreme rainfall significantly exacerbate engineering risks during deep excavation construction. Based on an asymmetric deep excavation project in Hainan under the influence of Super Typhoon Yagi, this study analyzes the evolution of Soil Mixing Wall (SMW) pile deformation and prestressed anchor cable axial forces through field monitoring. PLAXIS 3D 2023.2.0.1059 finite element software is employed to investigate the deformation response of the supporting structure under the coupled effects of excavation and extreme rainfall, revealing the optimal design for embedment depth under such adverse conditions. The results indicate that the presence of existing buildings leads to asymmetric deformation and pronounced corner effects. The synergistic action between the capping beam and the waler transforms the pile displacement profile from a cantilever mode to a bow-shaped distribution. Parametric analysis determines the optimal embedment depth to be 10.6 m and the critical safety embedment depth to be 7.6 m. Under a 400 mm/d typhoon rainfall condition, the maximum horizontal displacement of the supporting structure increases by 1.6–2.0 mm compared to non-rainfall conditions. With a 3.5 m water head, increasing the embedment depth from 6.1 m to 10.6 m reduces the maximum horizontal displacements on the east, south, and west sides by 98%, 42%, and 10%, respectively. This study provides a theoretical basis and practical reference for embedment depth optimization in typhoon-prone regions. Full article

Patient-specific implants (PSIs) in orthognathic surgery offer optimal intraoperative accuracy. However, evidence regarding their postoperative skeletal stability, specifically comparing distinct fixation designs and segmentation patterns, remains limited. We present a retrospective cohort study that evaluated 64 adult patients undergoing customized maxillary orthognathic surgery between January 2020 and June 2025. The primary predictor variables were fixation design (conventional customized plates vs. minimally invasive plates) and maxillary segmentation (monoblock vs. multisegmental). The outcome variable was 3D skeletal stability, measured as linear displacement between preoperative planning and 6-month postoperative imaging. Non-parametric tests compared displacements and clinical instability rates (defined as ≥2.0 mm). Mann–Whitney tests compared landmark displacements, Fisher’s exact tests compared proportions with ≥2.0 mm displacement, and ORs with 95% CIs were computed (α = 0.05). Analysis of 64 patients revealed that median displacement across landmarks ranged from 0.7 to 4.28 mm and 28.1% exhibited displacement ≥ 2.0 mm, primarily in molar and canine regions. While overall instability rates did not differ significantly between single-segment and multisegmental osteotomies (p = 0.28), multisegmental cases showed significantly higher displacement at the left canine (p = 0.027). Plate design was not associated with skeletal instability (p = 0.88), suggesting that minimally invasive plates provide comparable stability to conventional designs. Customized maxillary plates provide reliable postoperative stability with median displacements within clinically acceptable limits (<2 mm). Minimally invasive PSI designs offer stability comparable to conventional extended designs. However, localized instability in multisegmental cases suggests a need for careful biomechanical management regardless of the fixation method used. Full article

Precise respiration assessment is crucial for heart rate variability (HRV) interpretation as respiratory components—particularly respiratory sinus arrhythmia (RSA)—provide essential information on vagally mediated regulation. Conventional single-lead electrocardiogram-derived respiration (EDR) methods measure the amplitude modulation of the QRS-waveform caused by respiratory chest movements. This causes a displacement of the electrical heart axis in relation to the ECG lead axis, typically within the 2D frontal plane of the Einthoven electrode montage. Another approach is based on heartbeat acceleration and deceleration during respective inspiration and expiration causing RR interval modulation. However, interval-based methods depend on the complexity of sympathovagal factors that affect RSA. The present feasibility study accounts for the 3D rotational movement of the electrical heart axis during the respiratory cycle and avoids non-respiratory neuromodulatory confounds. The beat-to-beat cardiac rotation was extracted from Frank-XYZ coordinates reconstructed via a four-electrode EASI device. In a pilot study with data from 19 healthy adults performing acoustically paced breathing (6–18 bpm), three surrogates (${\mathrm{RR-Interval}}_{\mathrm{EDR}}$, ${\mathrm{R-Amplitude}}_{\mathrm{EDR}}$, ${\mathrm{Heartmovement}}_{\mathrm{EDR}}$) were compared using a unified Python 3.11.13 pipeline (3D VCG R-peak detection, multivariate Mahalanobis artifact correction, wavelet-based analysis) against a synthetic reference derived from the instructed breathing schedule. The results demonstrated a consistently lower estimation error and higher reference-based signal-to-noise ratio (refSNR), measuring spectral alignment with the paced-breathing trajectory for ${\mathrm{Heartmovement}}_{\mathrm{EDR}}$ and achieving a mean refSNR of 6.01 dB (vs. 4.62 dB for ${\mathrm{RR-Interval}}_{\mathrm{EDR}}$ and 3.20 dB for ${\mathrm{R-Amplitude}}_{\mathrm{EDR}}$) and a mean absolute estimation error of 0.016 Hz (vs. 0.050 Hz and 0.032 Hz, respectively). Notably, ${\mathrm{Heartmovement}}_{\mathrm{EDR}}$ and ${\mathrm{R-Amplitude}}_{\mathrm{EDR}}$ performance slightly improved at higher heart rates, consistent with the interpretation that higher cardiac sampling density benefits spectral resolution for chest movement-based methods, whereas ${\mathrm{RR-Interval}}_{\mathrm{EDR}}$ showed no significant heart rate dependence. Furthermore, ${\mathrm{Heartmovement}}_{\mathrm{EDR}}$ was compared with the EDR results obtained by applying the Kubios-HRV Premium software (version 3.5.0). Kubios-EDR yielded higher precision at elevated breathing frequencies, whereas ${\mathrm{Heartmovement}}_{\mathrm{EDR}}$ outperformed Kubios-EDR at breathing rates below 10 bpm—a range that is particularly relevant for vagally activating slow breathing protocols or treatments. Future work should validate this method using a direct respiration measurement under spontaneous natural breathing conditions. Full article

At present, research on the long-term stability of multi-cavern coordinated injection–production operations for salt cavern compressed air energy storage (CAES) remains limited. Large-capacity energy storage utilizing multiple interconnected salt caverns has become an inevitable development trend for modern CAES power stations, highlighting the necessity and importance of stability evaluation and design optimization for underground salt cavern storage clusters. Based on the Anning 350 MW CAES demonstration project, this paper takes the abandoned salt caverns of the project as research objects. A three-dimensional geological and cavern model is established using the FLAC3D numerical simulation method, and stability analysis is carried out under static conditions and three long-term gas injection and production scenarios (the pressure conditions are provided by ground-based equipment). The characteristics of the plastic zone, displacement, stress distribution, and volume shrinkage of the caverns are systematically investigated. The results show that under static conditions, the internal pressure significantly controls the development of the plastic zone, and the caverns are generally stable at pressures above 4 MPa. During long-term operation, the plastic zones of each cavern gradually expand, displacements accumulate continuously, and stresses tend to stabilize after an initial accumulation period. After 30 years of operation, no through-going plastic zones appear in any cavern, and all volume shrinkage rates are below 30%. Among the three cases, Case 1 exhibits the best stability, while enhanced monitoring is required for local high-stress regions in Case 3. This study verifies that the salt cavern development for the Anning CAES project is safe and controllable during long-term operation. The layout spacing of caverns is reasonably designed and fully satisfies the stability requirements of salt cavern CAES power stations. The research results can provide a technical guarantee for the construction of the first CAES power station in Yunnan Province and also offer a reliable reference for the design and construction of similar multi-cavity salt cavern CAES projects. Full article

To characterize the transport of the mining-induced sediment plume in the Clarion–Clipperton Zone (CCZ) nodule area, this study introduces a particle relative dispersion (RD) to assess material dispersion in 2D and 3D. In 2D, forward and backward RD results show clear sub-regional differences in particle aggregation and diffusion. Forward RD reaches a maximum ridge value of 40 km in regions of strong shear and strain. Backward RD effectively identifies upstream source regions and convergence pathways. High RD values align closely with strong strain-rate gradients, indicating that particle separation and mixing are primarily driven by transition regions between flow structures rather than uniform high- or low-strain areas. In the 3D, the vertical domain was limited to the 4500–4600 m depth range above the seabed. The overall RD patterns remain broadly consistent with the 2D results, while the maximum RD increases to approximately 80 km due to the inclusion of vertical displacement and local vertical shear effects. Within the 4500–4600 m depth range, horizontal transport remains dominant, whereas vertical variations are comparatively weak, and particle trajectories exhibit only minor local differences. Compared with the 2D case, the deep-layer 3D RD distribution exhibits lower skewness values, suggesting a more spatially balanced particle separation pattern with reduced directional asymmetry. Multi scale quasi-3D RD analysis provides essential insights into material dispersion and convergence patterns, offering valuable information for evaluating transport pathways, potential pollutant spread, and ecological risks associated with deep-sea mining. Full article

Image registration accuracy is strongly influenced by imaging geometry, yet this effect has not been explicitly characterized in a closed-form expression under practical plane-based image registration conditions. This paper establishes a geometry-induced lower bound on the image registration error within a plane-based image registration framework. While prior work has primarily focused on improving accuracy through algorithmic advancements, we show that the residual registration error under practical 2D registration conditions is fundamentally influenced by imaging geometry and height variation, regardless of the image registration performance. A closed-form expression of the lower bound is derived as a function of imaging geometry and height offset. The formulation explicitly characterizes how geometric configuration governs displacement in the reference image space or registration plane. The analysis reveals that, even under reliable matching conditions, residual errors may persist due to the inherent coupling between viewing geometry and elevation variation. The derived bound is validated using multiple image pairs acquired under different geometric configurations. The experimental results show that the formulation captures the dominant geometric effect. The proposed formulation provides a practical and interpretable geometric reference for analyzing registration accuracy under varying imaging configurations. Full article

With the rapid expansion of urban underground space in China, anti-floating has become a critical challenge, and uplift piles are a key solution. Previous studies on composite anchor-cable uplift piles have primarily focused on small-diameter single-pipe types (≤600 mm), often simplifying the pile as an integral component, leaving the multi-interface stress transfer mechanisms of large-diameter piles inadequately understood. This study proposes a back-analysis method based on orthogonal experiments, implemented using Abaqus 3D finite element software, to determine interfacial mechanical parameters for three critical contact pairs (strand-grout, grout-steel pipe, steel pipe-concrete) in large-diameter multi-pipe composite anchor-cable uplift piles. These parameters are then implemented in a refined 3D finite element model to simulate the load-deformation behavior of such piles. Quantitative results show that the back-calculated parameters are highly reliable, with maximum simulation errors for pile head displacement limited to 13.0% and 9.6% for fully bonded and semi-bonded piles, respectively. Unlike conventional piles, stress and strain in this new pile type transfer progressively from the inner steel strands outward and from the top downward, resulting in reduced pile-soil displacement mismatch, fuller mobilization of side interfacial strength, and effective mitigation of concrete cracking. This study provides a systematic parameter-calibration framework and numerical platform, offering theoretical and technical support for optimized design and engineering application of large-diameter composite uplift piles. Full article

Powdered organic fertilizer is crucial for sustainable agriculture, but its poor flowability and hygroscopic compaction and caking nature cause frequent blockages during mechanized strip application. While a single Johnson–Kendall–Roberts (JKR) discrete element method (DEM) model simulates powder flow well, it fails to reflect the mechanical breakage of hard caked lumps. Thus, this study established a comprehensive DEM model simultaneously simulating both powder and caked lumps. Based on coarse-graining theory, 0.147 mm particles were scaled to 2 mm spheres. Contact parameters (e.g., JKR surface energy) were calibrated using response surface methodology, yielding a repose angle simulation error of only 0.18%. The actual three-dimensional (3D) geometry of caked lumps was reconstructed via 3D scanning, and breakage mechanical parameters were accurately calibrated by combining uniaxial compression tests with a Bonding model (errors for ultimate load and displacement < 2%). Applying this model to an anti-blocking fertilizer discharge device, simulations and performance tests demonstrated an acceptable macroscopic representation of both powder flow and lump breakage. The optimized device achieved a strip application uniformity coefficient of variation of 3.87–6.40%. By simulating the complex coexistence of powder flow and lump breakage, this study provides a feasible parameter calibration method and numerical reference for optimizing anti-blocking discharge devices. Full article

Stroke-related gait impairments are frequently associated with deficits in trunk control, movement coordination, and dynamic stability. Although robotic-assisted gait rehabilitation has shown promising clinical benefits, phase-specific biomechanical adaptations following rehabilitation remain incompletely understood. This study investigated phase-specific biomechanical adaptations following robotic-assisted gait rehabilitation in individuals with stroke using sensor-derived waveform analysis. Rehabilitation was performed three times per week over approximately 5–6 weeks using treadmill-based robotic gait training under dynamic body-weight support conditions. Pre- and post-intervention kinematic data were collected using a sensor-based motion analysis system. Joint kinematics, trunk motion, and center of gravity (COG) displacement were analyzed across the normalized gait cycle using waveform-based effect size analysis, statistical parametric mapping, principal component analysis, and k-means clustering to explore inter-individual adaptation patterns. Thirteen post-stroke hemiplegia patients (10 males; age = 63.9 ± 13.8 years), including six subacute and seven chronic stroke survivors, completed 16 rehabilitation sessions. The most prominent improvements were observed in trunk lateral flexion, particularly during loading response (d = 0.47, p < 0.01), indicating enhanced frontal plane trunk stability. Trunk flexion–extension showed reduced compensatory motion, whereas hip and knee adaptations were smaller and phase-dependent. COG displacement decreased across the gait cycle, reflecting improved dynamic stability. Step length increased significantly on both hemiplegic (Δ = +5.73 cm, p = 0.024) and intact sides (Δ = +8.83 cm, p = 0.007), while cadence and load symmetry remained unchanged. Clustering analysis revealed heterogeneous adaptation profiles rather than distinct responder groups. Chronic participants demonstrated greater variability within the Principal Component Analysis space compared to subacute participants, suggesting more variable and individualized biomechanical reorganization patterns rather than clearly separable recovery categories. Overall, robotic rehabilitation induced inter-individual biomechanical adaptations, predominantly involving proximal trunk control and stabilization strategies. Full article

Gob-side roadways driven along the floor while retaining top coal in thick soft coal seams are prone to instability under strong mining-induced dynamic loading. To clarify the instability mechanism and develop an effective control method, the 1609 return airway of Jiulishan Mine was investigated using field survey, borehole imaging, FLAC3D numerical simulation, industrial testing, and field monitoring. The results show that, under the combined effects of large mining height, insufficient filling of the gob by the caved immediate roof, weak retained top coal, and low coal strength, shear failure planes tend to develop within the narrow coal pillar and extend from the gob-side roof toward the floor. Once the dominant shear plane cuts through the pillar, the overall bearing structure is destroyed, leading to shear slip, asymmetric rib deformation, roof subsidence toward the coal-pillar side, and rib–roof coupled instability. Based on a multi-index evaluation of pillar load-bearing capacity, plastic zone development, stress concentration, roadway deformation, and coal recovery, a 3 m coal pillar was determined as the rational width. A coordinated “narrow coal pillar + cross-rib anchorage” scheme was proposed, and field verification confirmed its effectiveness in controlling roof separation, roadway surface displacement, and internal surrounding-rock damage. Full article