Search Results (187)

The impact mechanism of long-term creep in gas-containing coal on coal and gas outbursts has not been fully elucidated and remains insufficiently understood for the purpose of disaster engineering control. This investigation conducted triaxial creep experiments on raw coal specimens under controlled confining pressures, axial stresses, and gas pressures. Through systematic analysis of coal’s physical responses across different loading conditions, we developed and validated a novel creep damage constitutive model for gas-saturated coal through laboratory data calibration. The key findings reveal three characteristic creep regimes: (1) a decelerating phase dominates under low stress conditions, (2) progressive transitions to combined decelerating–steady-state creep with increasing stress, and (3) triphasic decelerating–steady–accelerating behavior at critical stress levels. Comparative analysis shows that gas-free specimens exhibit lower cumulative strain than the 0.5 MPa gas-saturated counterparts, with gas presence accelerating creep progression and reducing the time to failure. Measured creep rates demonstrate stress-dependent behavior: primary creep progresses at 0.002–0.011%/min, decaying exponentially to secondary creep rates below 0.001%/min. Steady-state creep rates follow a power law relationship when subject to deviatoric stress (R² = 0.96). Through the integration of Burgers viscoelastic model with the effective stress principle for porous media, we propose an enhanced constitutive model, incorporating gas adsorption-induced dilatational stresses. This advancement provides a theoretical foundation for predicting time-dependent deformation in deep coal reservoirs and informs monitoring strategies concerning gas-bearing strata stability. This study contributes to the theoretical understanding and engineering monitoring of creep behavior in deep coal rocks. Full article

Carbon nanotube (CNT) fiber research focuses on developing functional fabrics with dual or multifunctional capabilities. This study investigates CNT fibers fabricated via dielectrophoresis (DEP) with the incorporation of 10 wt.% carbide-derived carbon (CDC), referred to as CNTCDC fibers. The linear actuation behavior of the CNT and the CNTCDC fibers is compared using identical electrolyte concentrations in both a polar aprotic solvent (propylene carbonate, PC) and a polar protic solvent (aqueous solution, aq). Electromechanical deformation (EMD) is studied through cyclic voltammetry and chronoamperometry. The CNTCDC fiber outperformed the pristine CNT fiber, exhibiting primary expansion during discharge in PC (stress: 1.64 kPa, strain: 0.1%) and during charge in water (stress: 1.32 kPa, strain: 0.047%). By contrast, the pristine CNT fibers showed mixed actuation responses in both solvents, resulting in diminished net stress and strain. Chronopotentiometric measurements indicated that the CNTCDC fibers achieved their highest specific capacitance in aqueous media, reaching 223 ± 17 F g⁻¹ at ±0.8 A g⁻¹, with a capacity retention of 94.2% at ±32 A g⁻¹. Fundamental characterization techniques, including scanning electron microcopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy, are employed to analyze fiber morphology and composition. The dual functionality of CNTCDC fibers, as both actuators and energy storage elements, is demonstrated. Full article

Background: Over the past decade, few echocardiographic investigations have assessed myocardial strain parameters in women with a history of hypertensive disorders of pregnancy (HDP), and their findings have been inconsistent. Moreover, no study has comprehensively evaluated deformation indices of all biventricular and biatrial chambers in women post-HDP. This study aimed to examine the structural and functional myocardial properties of all cardiac chambers in a cohort of women with prior HDP at six years after delivery. Methods: We analyzed a consecutive cohort of women with previous HDP and compared them with a control group of normotensive healthy women matched for age and body mass index (BMI). Both groups underwent standard transthoracic echocardiography (TTE) supplemented by a detailed speckle tracking echocardiography (STE) evaluation of biventricular and biatrial myocardial deformation, along with carotid ultrasound, at six years postpartum. The primary endpoint was subclinical myocardial dysfunction, defined by impaired left ventricular global longitudinal strain (LV-GLS < 20%), while the secondary endpoint was early carotid atherosclerosis, defined by common carotid artery intima-media thickness (CCA-IMT) ≥ 0.7 mm. Results: The study included 31 women with previous HDP (mean age 42.3 ± 5.9 years) and 30 matched controls without HDP history (mean age 40.8 ± 5.0 years). The average follow-up duration was 6.1 ± 1.3 years postpartum. Despite preserved and comparable systolic function on conventional TTE, most myocardial strain and strain rate measures in both ventricles and atria were significantly reduced in the HDP group compared to controls. Subclinical myocardial dysfunction was detected in 58.1% of women with prior HDP, and 67.7% exhibited increased CCA-IMT (≥0.7 mm). A history of pre-eclampsia (PE) was independently associated with subclinical myocardial dysfunction (HR 4.01, 95% CI 1.05–15.3, p = 0.03). Both third-trimester BMI (HR 1.21, 95% CI 1.07–1.38, p = 0.003) and PE (HR 6.38, 95% CI 1.50–27.2, p = 0.01) independently predicted early carotid atherosclerosis. Notably, a third-trimester BMI above 27 kg/m² showed optimal sensitivity and specificity for identifying the secondary outcome. Conclusions: A history of PE is independently associated with a higher risk of subclinical myocardial dysfunction and early carotid atherosclerosis at six years postpartum. Full article

Glass fiber reinforced polypropylene composite plates have gradually attracted more attention because of their repeated molding, higher toughness, higher durability, and fatigue resistance compared to glass fiber reinforced thermosetting composites. In practical engineering applications, composite plates have to undergo bending effect at different angles in corrosive environment of concrete, including bending bars from 0~90°, and stirrups of 90°, which may lead to long-term performance degradation. Therefore, it is important to evaluate the long-term performance of glass fiber reinforced polypropylene composite bending plates in an alkali environment. In the current paper, a new bending device is developed to prepare glass fiber reinforced polypropylene bending plates with the bending angles of 60° and 90°. It should be pointed out that the above two bending angles are simulated typical bending bars and stirrups, respectively. The plate is immersed in the alkali solution environment for up to 90 days for long-term exposure. Mechanical properties (tensile properties and shear properties), thermal properties (dynamic mechanical properties and thermogravimetric analysis) and micro-morphology analysis (surface morphology analysis) were systematically designed to evaluate the influence mechanism of bending angle and alkali solution immersion on the long-term mechanical properties. The results show the bending effect leads to the continuous failure of fibers, and the outer fibers break under tension, and the inner fibers buckle under compression, resulting in debonding of the fiber–matrix interface. Alkali solution (OH⁻ ions) corrode the surface of glass fiber to form soluble silicate, which is proved by the mass fraction of glass fiber decreased obviously from 79.9% to 73.65% from thermogravimetric analysis. This contributes to the highest degradation ratio of tensile strength was 71.6% (60° bending) and 65.6% (90° bending), respectively, compared to the plate with bending angles of 0°. A high curvature bending angle (such as 90°) leads to local buckling of fibers and plastic deformation of the matrix, forming microcracks and fiber–resin interface bonding at the bending area, which accelerates the chemical erosion and debonding process in the interface area, bringing about an additional maximum 10.56% degradation rate of the shear strength. In addition, the alkali immersion leads to the obvious degradation of storage modulus and thermal decomposition temperature of composite plate. Compared with the other works on the long-term mechanical properties of glass fiber reinforced polypropylene, it can be found that the long-term performance of glass fiber reinforced polypropylene composites is controlled by the corrosive media type, bending angle and immersion time. The research results will provide durability data for glass fiber reinforced polypropylene composites used in concrete as stirrups. Full article

Progressive damage evolution in rock masses serves as the fundamental mechanism driving geological hazards by controlling deformation patterns and failure predictability. To address the critical challenge of predicting fracture behaviors in heterogeneous geological media, this study pioneers the integration of real-time computed tomography (CT) scanning and acoustic emission (AE) monitoring to investigate self-organized criticality and fracture predictability in Cretaceous sandstone under uniaxial compression. By systematically analyzing internal structural evolution and damage parameters, this established a multiparameter framework to characterize self-organized processes and critical phase transitions during progressive fracturing. Key findings include the following: (1) Distinct critical thresholds emerge during yield-stage self-organization, marked by abrupt transitions in AE signals and crack metrics—from microdamage coalescence initiating volumetric expansion (first critical point) to macrocrack nucleation preceding peak strength (second critical point). (2) AE-crack evolution follows power–law statistics, where elevated scaling exponents (r > 0.85) correlate with intensified nonlinear damage, accelerated localization, and progressive rate enhancement. Yield-stage power–law acceleration provides quantifiable failure precursors. (3) Yield-stage damage patterns exhibit 85% similarity with terminal failure configurations, confirming yield-stage as the definitive precursor with critical temporal signatures for failure prediction. A conceptual framework integrating multiparameter responses (AE signals, crack metrics) was developed to decipher self-organized critical phase transitions during deformation-failure processes. This work establishes methodological foundations for investigating damage mechanisms and predictive strategies in heterogeneous rock systems. Full article

This paper investigates the role of solvable and nilpotent Lie algebras in the domains of cryptography and steganography, emphasizing their potential in enhancing security protocols and covert communication methods. In the context of cryptography, we explore their application in public-key infrastructure, secure data verification, and the resolution of commutator-based problems that underpin data protection strategies. In steganography, we examine how the algebraic properties of solvable Lie algebras can be leveraged to embed confidential messages within multimedia content, such as images and video, thereby reinforcing secure communication in dynamic environments. We introduce a key exchange protocol founded on the structural properties of solvable Lie algebras, offering an alternative to traditional number-theoretic approaches. The proposed Lie Exponential Diffie–Hellman Problem (LEDHP) introduces a novel cryptographic challenge based on Lie group structures, offering enhanced security through the complexity of non-commutative algebraic operations. The protocol utilizes the non-commutative nature of Lie brackets and the computational difficulty of certain algebraic problems to ensure secure key agreement between parties. A detailed security analysis is provided, including resistance to classical attacks and discussion of post-quantum considerations. The algebraic complexity inherent to solvable Lie algebras presents promising potential for developing cryptographic protocols resilient to quantum adversaries, positioning these mathematical structures as candidates for future-proof security systems. Additionally, we propose a method for secure message embedding using the Lie algebra in combination with frame deformation techniques in animated objects, offering a novel approach to steganography in motion-based media. Full article

This article aims to clarify the applicability of He’s two-scale fractal dimension transform by replacing $t^{\mathsf{\alpha }}$ with $\mathsf{\tau }$. It demonstrates the potential to capture the influence of the fractal parameter on the system’s damping frequency, particularly when the viscoelastic term (damping) does not equal half of the fractional inertia force term. The analysis examines the elastomer materials’ dynamic fractal amplitude–time response, considering the viscohyperelastic effects related to the material’s energy dissipation capacity. To determine the amplitude of oscillations for the nonlinear equation of motion of a body supported by a viscohyperelastic elastomer subjected to uniaxial stretching, the harmonic balance perturbation method, combined with the two-scale fractal dimension transform and Ross’s formula, is employed. Numerical calculations demonstrate the effectiveness of He’s two-scale fractal transformation in capturing fractal phenomena associated with the fractional time derivative of deformation. This is due to a correlation between the fractional rate of viscoelasticity and the fractal structure of media in elastomer materials, which is reflected in the oscillation amplitude decay. Furthermore, the approach introduced by El-Dib to replace the original fractional equation of motion with an equivalent linear oscillator with integer derivatives is used to further assess the qualitative and quantitative performance of our derived solution. The proposed approach elucidates the applicability of He’s two-scale fractal calculus for determining the amplitude of oscillations in viscohyperelastic systems, where the fractal derivative order of the inertia and damping terms varies. Full article

This study examines the dynamic response of bottom-sitting steel shell structures subjected to underwater shock waves. A computational framework integrating the Arbitrary Lagrangian Eulerian (ALE) method was implemented in finite-element analysis to simulate three-dimensional interactions between shock waves and curved shell geometries (hemispherical and cylindrical configurations). An analysis of the impacts of shock-wave propagation media, explosive distance, charge equivalence, hydrostatic pressure, and shell thickness on the dynamic response of these bottom-sitting shell structures is conducted. The findings reveal that the deformation of semi-spherical steel shells subjected to underwater shock waves is significantly greater than that of shells subjected to air shock waves, with effective stress reaching up to 831.4 MPa underwater. The mechanical deformation of curved steel shells exhibits a gradual increase with increasing explosive equivalents. The center displacement of the hemispherical shell at 800 kg equivalent is 6 times that at 50 kg equivalent. Within the range of 0 to 2.0092 MPa, hydrostatic pressure leads to an approximate 26.34% increase in the center vertical displacement of the semi-cylindrical shell compared with 0 MPa, while restricting horizontal convex deformation. Increasing thickness from 0.025 m to 0.05 m results in a reduction of approximately 60% in the center vertical displacement of the semi-cylindrical shell. These quantitative correlations provide critical benchmarks for enhancing the blast resilience of underwater foundation systems. Full article

Aortic dissection (AD) is a highly lethal cardiovascular emergency, and clinical studies have found that a high percentage of AD patients are hypertensive. In previous studies, the AD model was simplified, such as by treating the vessel wall as a single-layer rigid material, ignoring the complex biomechanical factors of the vascular lumen. This study elucidates key biomechanical mechanisms by which hypertension promotes primary AD progression using multiscale modeling. First, based on experimental data from longitudinal and circumferential uniaxial tensile testing of porcine aortic walls (5–7-month-old specimens), a constitutive model of the aortic wall was developed using the Holzapfel–Gasser–Ogden (HGO) framework. The material parameters were calibrated via inverse optimization in ABAQUS-ISIGHT, achieving close alignment with mechanical properties of the human aorta. Using this validated model to define the hyperelastic properties of the aortic wall, a multiphysics coupling platform was constructed in COMSOL Multiphysics 6.2, integrating computational fluid dynamics (CFD) and fluid–structure interaction (FSI) algorithms. This framework systematically quantified the effects of blood pressure (bp) fluctuations on compressive stresses, von Mises stresses, and deformation of the intimal flap within the AD lesion region. With constant blood rheology, elevated blood pressure enhances wall stresses (compressive and von Mises), and intima-media sheet deformation, this can trigger initial rupture tears, false lumen dilation, and branch arterial flow obstruction, ultimately deteriorating end-organ perfusion. Full article

Multi-functionality and high mission adaptability are important trends in the development of future aircrafts. Trans-domain aircraft, with their unique take-off and landing capabilities and cross-medium capability, have significant potential in the field of emergency rescue, marine monitoring and tourism. Trans-domain aircraft will meet various flight conditions in different domains. Therefore, the design of wing structures must consider the mechanical effects of different media on the aircraft. In the current study, a fishbone variable camber wing is proposed based on the concept of a camber morphing wing. The relationship between the actuation force and the trailing edge deflection is analyzed using the fluid–structure interaction. The flight performance of the flight conditions including cruise or climb underneath and cruise above the water can also be evaluated in the design iteration since the load-carrying capability can be satisfied and the structural deformation of the fluid loads and the actuators is taken into account. Finite element analysis is also employed for the structural verification. Finally, a structural model is manufactured, which is tested above and under water by measuring the trailing edge deflection using the digital image correlation technology. Full article

This work studies the water-exit problems of slender cylinders under various conditions through experimental investigation. An experimental platform was equipped with high-speed photography. A total of 13 experimental cases with varying head shapes (conical, spherical, and truncated cone designs), length-to-diameter ratios (5:1–7:1), ejection velocities (7.24–17.93 m/s), and elastic moduli (227.36–279.14 MPa) were conducted to capture water-exit characteristics. The investigation identified ejection velocity as the predominant parameter governing cavity morphology and stability, with higher velocities correlating to increased cavity dimensions and reduced drag coefficients by 54%. Conical head shape resulted in superior drag reduction characteristics, forming a typical cigar-shaped cavity with clear and regular boundaries. Additionally, an increased length-to-diameter ratio substantially improved drag reduction performance by 33%. Material elastic moduli proved crucial for water-exit stability, as cylinders with lower moduli experienced severe bending deformation and even trajectory changes, while higher moduli cylinders maintained their form with minimal deformation. This study illuminates the physical mechanisms of slender body water-exit under multi-factor coupling conditions, providing experimental evidence and theoretical guidance for cross-media vehicle design and underwater equipment optimization. Full article

The aim of this study was to analyze the spectrum of Candida manifestations in the orofacial region to address the lack of comprehensive data in the diverse pediatric population. This retrospective study included all positive Candida findings in patients aged 0–18 years treated between 2014 and 2023 at a university maxillofacial department in Germany and evaluated associated risk profiles, comorbidities and species distributions. Candida infection sites included oral mucosa, dental abscesses and otitis media. Candida was more frequent in children with pre-existing conditions, particularly immunosuppression, neuromuscular disorders and facial deformities. Tympanostomy tubes and recent antibiotic use were significant risk factors for Candida in otitis media. Whereas in dental abscesses, Candida had a significant proportion independent of prior antibiotic use. Non-albicans subspecies, particularly Candida parapsilosis, were notably more prevalent in the middle ear compared to oral and dental infections. Candida manifests in various forms in the orofacial region, with different characteristics and species distributions. Further investigations are needed to better understand the role of Candida as a symptom or a contributor to an underlying condition. Full article

With the acceleration of urbanization, surface deformation monitoring has become crucial. Existing monitoring systems face several challenges, such as data singularity, the poor nighttime monitoring quality of video surveillance, and fragmented visual data. To address these issues, this paper presents a 3D real-scene (3DRS)-enhanced GNSS/intelligent vision surface deformation monitoring system. The system integrates GNSS monitoring terminals and multi-source meteorological sensors to accurately capture minute displacements at monitoring points and multi-source Internet of Things (IoT) data, which are then automatically stored in MySQL databases. To enhance the functionality of the system, the visual sensor data are fused with 3D models through streaming media technology, enabling 3D real-scene augmented reality to support dynamic deformation monitoring and visual analysis. WebSocket-based remote lighting control is implemented to enhance the quality of video data at night. The spatiotemporal fusion of UAV aerial data with 3D models is achieved through Blender image-based rendering, while edge detection is employed to extract crack parameters from intelligent inspection vehicle data. The 3DRS model is constructed through UAV oblique photography, 3D laser scanning, and the combined use of SVSGeoModeler and SketchUp. A visualization platform for surface deformation monitoring is built on the 3DRS foundation, adopting an “edge collection–cloud fusion–terminal interaction” approach. This platform dynamically superimposes GNSS and multi-source IoT monitoring data onto the 3D spatial base, enabling spatiotemporal correlation analysis of millimeter-level displacements and early risk warning. Full article

In this article, novel methods of analysis to solve the (3+1)-dimensional generalized fractional Kadomtsev–Petviashvili equation, which plays a crucial role in the modelling of fluid dynamics, particularly wave propagation in complicated media, are presented. The fractional KP equation, a well-established mathematical model, uses fractional derivatives to more adequately describe more general types of nonlinear wave phenomena, with a richer and improved understanding of the dynamics of fluids with non-classical characteristics, such as anomalous diffusion or long-range interactions. Two efficient methods, the exponential rational function technique (ERFT) and the generalized Kudryashov technique (GKT), have been applied to find exact travelling solutions describing soliton behaviour. Solitons, localized waveforms that do not deform during propagation, are central to the dynamics of waves in fluid systems. The characteristics of the obtained results are explored in depth and presented both by three-dimensional plots and by two-dimensional contour plots. Plots provide an explicit picture of how the solitons evolve in space and time and provide insight into the underlying physical phenomena. We also added modulation instability. Our analysis of modulation instability further underscores the robustness and physical relevance of the obtained solutions, bridging theoretical advancements with observable phenomena. Full article

Rainfall is one of the major causes of geological hazards such as landslides and slope failures because it decreases shear strength along the failure surface and increases the driving force of the sliding mass due to the movement of the wetting front in the geological media. Deterministic limit equilibrium methods are typically used to evaluate the stability of slopes in terms of Factor of Safety (FoS), considering the worst-case scenario. However, a coupled flow deformation analysis procedure combined with a probabilistic method is required to consider the temporal and spatial variations in the soil properties due to water infiltration and to evaluate the probability of slope failure. The study aims to develop a probabilistic framework for evaluating the probability of failure of an earth slope using the response surface derived from sample data generated from a coupled flow–deformation finite element (FE) program considering uncertain rainfall characteristics. Finite slopes with 1.5H:1V and 2H:1V slope ratios composed of sandy soil were analyzed considering the possible variations in soil and rainfall parameters. Based on the FE results, a response surface was developed for the FoS as a function of soil and rainfall parameters. The response surface was utilized to generate random scenarios and calculate the failure probability using Monte Carlo Simulation (MCS). The results obtained from the MCS were compared using the First-Order Reliability Method (FORM). The results indicated that the total probability of failure predicted by MCS was closer to the probability of failure by FORM. The total probability of failure predicted from MSC and FORM were 0.0633 and 0.0640 for the 1.5:1 slope and 0.0249 and 0.0229 for the 2:1 slope, respectively. This level of probability of failure was deemed unsatisfactory to poor based on the criteria by the US Army Corps of Engineers. Therefore, the proposed framework provides a valuable tool from the probabilistic perspective for assessing the performance level of slopes subjected to uncertain rainfall conditions. Full article