Search Results (812)

Major earthquakes often induce multi-structural rupture styles, which serve as a crucial basis for understanding stress partitioning and strain adjustment within tectonic systems, as well as for constructing regional deformation models. The 1927 M 8.0 Gulang earthquake in the northeastern Tibetan Plateau exemplifies this phenomenon. This rare event, characterized by a single mainshock triggering multiple structural ruptures, resulted in approximately 40,000 casualties and numerous missing persons. In this study, we integrate interpretations of satellite remote sensing imagery, field observations of surface ruptures, and analyses of regional tectonic–geomorphic deformations to reconstruct the coseismic processes of the Gulang earthquake. Our findings reveal that the coseismic surface ruptures exhibit distinct mechanical characteristics driven by complex stress fields. Survey and analysis results indicate that regional tectonic compression oriented from SSW–SW to NNE–NE triggered the mainshock rupture. This stress regime caused nearly E–W folding of strata north of the Huangcheng–Shuangta Fault (HSF), alongside sinistral strike-slip motion in the central-eastern section and thrusting at the eastern end of the Southern Wuwei Basin Fault (SWBF). Blocked by the rigid Alxa Block to the north, comprehensive evidence—including the Late Holocene gravelly clay folded strata formed by north-to-south compression in the Liutiao Lake area, the geomorphic deformation characterized by higher northern and lower southern terraces on both sides of the east–west-trending fault, and the clockwise rotational tectonic surfaces developed at the eastern end of the HSF zone in Shuixiakou—indicates that the coseismic tectonic movement and energy transfer within the meizoseismal area underwent a rapid clockwise rotation from NE to S. This strain rotation induced N–S tensional rupturing along the southern branch of the eastern HSF and nearly E–W thrusting along the NNW-trending Wuwei–Gulang Fault (WGF). Furthermore, this intense and rapid clockwise rotation generated a transient extensional environment characterized by rapid E–W to SE stretching, leading to the formation of a newly identified, NNE-trending, high-angle dextral strike-slip normal fault (hereafter referred to as the NNEF). This process also triggered localized activity at the junctions between the NNEF and the Lenglongling Fault (LLLF), and between the WGF and the nearly E–W-trending Gulang Fault (GLF). We conclude that the seismogenic structure of the 1927 Gulang mainshock comprises three primary components: (1) a fault–fold belt consisting of the SWBF and the nearly E–W fold system north of the HSF; (2) the southern branch of the eastern HSF; and (3) the WGF. The observed segmental activities of the GLF and LLLF are attributed to local strain adjustments. By identifying the newly formed NNEF and characterizing these segmental activations, this study provides new insights into the mechanisms of local strain adjustment within the tectonic systems of the northeastern Tibetan Plateau. Full article

Dielectric elastomer actuators (DEAs) are attracting much attention as candidates for next-generation flexible actuation. Among various DE matrices, polyacrylate rubber (AR) is especially promising owing to their intrinsically high dielectric constant (ε_r) and good mechanical performance. In particular, its mechanical behavior is close to that of porcine bladder tissue, making it a potentially good material for soft biomedical actuators for artificial bladder constructs. To achieve high actuated strain, which requires high ε_r, high breakdown strength, and low elastic modulus, an AR DE composite filled with silane-functionalized TiO₂ was fabricated, exhibiting good electromechanical performance enabled by strengthened interfacial polarization. To improve compatibility between TiO₂ and AR matrix, TiO₂ was preferentially modified with a silane coupling agent (CA) that features a double bond as its functional group, which can be introduced on TiO₂ surface and participate in vulcanization with AR, thereby forming co-crosslinking bridges that strengthen interfacial bonding, improve filler dispersion, and increase interfacial polarizability within the matrix. As a result, at relatively low filler loadings, the composite exhibits a significantly increased ε_r, while maintaining low modulus, low dielectric loss and high elasticity. The 10 CA@TiO₂/AR composite exhibits a maximal actuated strain of 7.9% at 31.9 kV/mm without pre-stretch, which is 1.48 times that of pure AR and 1.32 times that of the 10 TiO₂/AR composite. Full article

Managing excessive water production in oil fields during primary, secondary, or enhanced recovery remains challenging. It increases costs and reduces hydrocarbon recovery, particularly in reservoirs with high-conductivity pathways such as high-permeability zones and fractures. Hydrogels are commonly used for water blocking and retention; however, their effectiveness diminishes at higher flow rates due to mechanical weaknesses and structural limitations. These problems are intensified under harsh environmental conditions, including high temperatures, salinity, and hardness. In this study, we investigate how altering the molecular suprastructure of preformed particle gel (PPG) can improve its effectiveness in shear-responsive water-blockage treatments, particularly when traditional PPGs cannot control rising flow rates. We enhance the shear-responsive mechanical properties of a composite PPG by increasing the density and diversity of intermolecular interactions. We use two different strategies: first, incorporating cationic groups into the polymer backbone to form a polyampholyte network with stronger electrostatic interactions; second, adding a linear anionic polymer to generate a secondary interpenetrating network that can undergo a coil–stretch transition under thermal and shear stimuli, thereby enhancing its own solvation and whole-network expansion. Molecular simulations provide an interpretation of the experimentally observed shear-thickening response and enhanced disproportionate permeability reduction at high flow rates. The water residual resistance factor of the improved PPGs deviates from the typical shear-thinning power-law behavior (n < 1) observed in conventional PPG, showing shear-thickening (n > 1). Tests reveal a strong ability to preferentially reduce water flow over oil, with Disproportionate Permeability Reduction increasing from 8 to 117 in the high-flow-rate zone. The enhanced strength and thermal stability also improve resistance to washout under high-pressure gradients. This research provides a novel approach to tailoring the microscopic architecture of PPGs to achieve selective, robust water blockage, offering a high-efficiency solution for complex reservoir environments. Full article

Bioelectricity plays a vital role in regulating cellular behavior. During the process of tissue repair and regeneration, surface electrical signals provided by biomaterials are found to be helpful. The characteristics of these electrical signals typically vary depending on the specific tissue repair requirements. In this study, zinc oxide nanorod (ZNR) arrays were loaded onto a poly(vinylidene fluoride-trifluoroethylene) (PVTF) substrate via the hydrothermal method. The nanorods were subsequently tilted by uniaxial stretching to form a ZNR/PVTF composite film with in-plane, horizontally aligned ZNRs along the stretching direction on the surface. The distribution of ZNRs created a heterogeneous potential across the PVTF substrate. Under ultraviolet (UV) irradiation, the surface potential of the ZNRs increased by approximately 76 mV due to a photoelectric response, enabling the formation of an adjustable millivolt-level surface potential. After corona polarization, the dipoles within the PVTF were aligned to achieve piezoelectric properties. The existence of oriented surface ZNRs enhanced the piezoelectric response of the ZNR/PVTF film, allowing for volt-level dynamic electrical signals through a force-voltage coupling mechanism. The output voltage increased from 1.32 V (PVTF) to 2.42 V (ZNR/PVTF) under the same 30° bending condition. Moreover, the ZNR/PVTF film exhibited excellent short-term biocompatibility toward bone marrow stem cells (BMSCs). Overall, this work presents an effective strategy for generating multiscale electrical signals through external field applications, demonstrating strong potential for tissue repair and regeneration. Full article

The commercialization of poly(butylene succinate-co-adipate) (PBSA), a biodegradable and potentially fully biobased random copolyester, is still ongoing. Due to its high relevance as mono material or as blend component in flexible film applications, a sound understanding of compounding, further processing and film properties is necessary. In this work, PBSA, poly (lactic acid) (PLA) and blends at three different compositions thereof were processed into flat films and blown films, respectively. Investigating the films with X-ray diffraction (XRD), multivariate confocal Raman microscopy (CRM) and scanning electron microscopy (SEM) revealed the semicrystalline order as well as the blend morphology. While PBSA is semicrystalline, PLA remains amorphous after the processing step. As imaged by CRM, flat films exhibit lamellar-like domains formed during uniaxial stretching and rapid cooling, whereas blown films show no pronounced preferential orientation. Tensile tests in both the machine and transverse directions demonstrate the versatility of PBSA and its blends in spanning a wide range of mechanical strength and flexibility, covering and partly exceeding the stiffness and strength ranges typically reported for commodity polyolefins while exhibiting reduced ductility. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) provide further insights into the thermal properties of the pure and blend materials. Full article

Microplastics (MP) are transported through rivers, acting as major conduits to oceans, yet standard transport models often fail to capture polymer-specific dynamics like settling and removal. This study proposes two novel analytical frameworks to address this: a modified Advection–Dispersion Equation (ADE) incorporating first-order sinking and removal, and a multi-phase model accounting for hydrodynamic–particle coupling. We derived exact closed-form solutions for a finite pulse input and validated the baseline model against established results. Our results demonstrate that the conventional ADE significantly overestimates peak MP concentrations, while the modified ADE reveals a “stretching” effect that extends the duration of ecosystem exposure. Our analysis indicates that sinking is the primary driver of mass loss to sediments, with higher sinking rates reducing aqueous concentrations by approximately 50% compared to non-settling scenarios. However, removal employs negligible influence during the initial pulse phase but shows cumulative impact over long transport distances. The study highlights the critical need to incorporate sediment accumulation terms into risk assessments, as ignoring sinking leads to underestimating benthic pollution and overestimating marine flux. Additionally, the multi-phase formulation provides a theoretical basis for modeling dense plastic spills where particles alter flow momentum. Full article

As a pivotal hub for the northward advancement of the Belt and Road Initiative and a strategic outpost for national security, the spatial patterns of towns in the border regions of northern Inner Mongolia exert a direct impact on the region’s sustainable development and long-term prosperity. This study focuses on 141 border towns situated along the Inner Mongolia stretch of China’s northern border. By leveraging analytical tools including kernel density analysis, standard deviation ellipse method, and nearest neighbor index analysis, it explores the distinctive characteristics of their spatial distribution. Furthermore, this study applies the Geodetector method to quantify the explanatory power of key influencing factors on the spatial differentiation of these border towns. The findings can be summarized as follows: (1) The border towns along the Inner Mongolia stretch of the northern border displayed a distinct heterogeneous distribution gradient characterized by prominent regional agglomeration and formed a three-tier spatial hierarchy. Specifically, the Bayannur–Hetao Plain Town Cluster served as the primary agglomeration core, supplemented by two secondary clusters, namely the Xing’an League–Southern Greater Khingan Range Town Cluster and the Hulunbuir–Border Port Town Cluster. In contrast, the Alxa League constituted a low-density peripheral belt with sparse town distribution. (2) Factor analysis via Geodetector revealed that the spatial distribution pattern of these border towns was primarily driven by the core mechanism of port-led urbanization. This core driver was synergistically reinforced by secondary factors such as mineral resource endowments, jointly shaping a complex spatial layout that partially transcended natural geographical constraints—a stark contrast to coastal ports, where development is dominated by innate natural geographic advantages. Full article

Residual stresses are inevitably introduced during plate manufacturing and pre-processing (e.g., quenching and pre-stretching). However, springback prediction in creep age forming (CAF) is still frequently carried out by assuming an initially stress-free blank, which may lead to biased deformation–stress histories and tool compensation errors, hindering high-accuracy forming. This study aimed to close this practical gap by quantifying how inherited residual stresses affected the CAF springback of AA2219 double-curvature thin-walled parts. In this study, a multi-step finite element (FE) process chain covering quenching, pre-stretching, and creep age forming (CAF) was developed to investigate the evolution of the initial residual stress field and its influence on CAF springback. Surface residual stresses after quenching and after pre-stretching were measured by X-ray diffraction (XRD) to validate the FE models. The results show that, after quenching, the through-thickness residual stress exhibits a characteristic ‘compressive at the surfaces and tensile in the core’ distribution, and pre-stretching markedly reduces the residual stress level. During CAF, although the initial residual stress difference is largely equilibrated during loading, it affects springback primarily through differences in accumulated creep deformation. Incorporating the initial residual stress field reduces the springback error bandwidth from 9.59 mm to 3.51 mm (a 63.4% reduction) under the original die configuration. Additional simulations under a modified die curvature (geometric deviation ≈ 6 mm) demonstrate that the springback reduction remains at the millimeter scale, indicating that the proposed FE framework maintains a consistent predictive improvement across different curvature conditions. This work provides a theoretical basis and practical guidance for high-precision creep age forming. Full article

Biological muscles generate tension from the combined contribution of the passive elastic recoil and the actively controlled contractile mechanisms. Understanding and replicating these passive and active tensions is necessary and beneficial for designing soft robotic actuators that emulate muscle-like behavior. In the current work, the aim is to develop a mathematical framework for modeling both the passive and active tensions in a biological muscle as functions of muscle length and contraction velocity. We will describe the passive tension by a nonlinear monotonically increasing function of length with threshold behavior in order to capture the experimentally observed stiffening occurring in stretched biological muscles. We will model the active tension using the superposition of Gaussian functions that relate bell-shaped tension-length with a flat plateau over the optimal length of the sarcomere. The parameters of this Gaussian representation of the active tension-length relation are determined from formulating a least-squares optimization problem, such that a Characteristic (indicator) function is approximated globally over the optimal length range of the sarcomere by summation of some Gaussian functions. The closed-form formulations for the required integrals are derived using the integral of the product of two Gaussian functions over ${\mathbb{R}}^n$ as well as the error function which enables efficient parameter identification. We will also propose a symmetric tension–velocity relation that distinguishes three phases of concentric, eccentric and isometric contractions, and is parametrized directly by measurable quantities of isometric tension and maximum shortening velocity. The passive and active tensions are finally combined into a unified comprehensive tension model in which the exponentially modeled passive tension is added up to the active contribution, formulated as the product of the activation level, a normalized length-dependent factor and a normalized velocity-dependent factor. The resulting model reproduces canonical tension-length and tension-velocity relations and provides an analytically tractable comprehensive tension model that can be embedded in the dynamics of soft and continuum robot actuators inspired by biological muscles. Full article

Despite reductions in sulphur and nitrogen emissions, lakes and streams in Europe and North America have shown only partial recovery from acidification. This study aims to assess the chemical and biological recovery of the upper stretch of the Litavka River, currently on of the most acidic stream in the Czech Republic. Water composition and macroinvertebrates were studied for 1999, 2010, and 2021, along with long-term data on hydrology and climate. Over these 22 years, concentrations of SO₄²⁻, base cations, conductivity, and toxic Al forms (Al_i) significantly decreased, but pH only increased from 4.2 to 4.3. Biological recovery was most evident during 1999–2010, with an increase in the number of taxa and the appearance of less acid-tolerant taxa such as stonefly Diura bicaudata and caddisfly Rhyacophila sp., mainly associated with decreased Al_i toxicity. Subsequently, however, despite continued chemical improvement, macroinvertebrate diversity decreased, and sensitive taxa were again absent in 2021. Average annual temperature increased by 2.4 °C over the past 50 years (1970–2020) while precipitation remained unchanged, resulting in significant aridification of the regional climate. We attribute the lack of biological recovery in 2021 to climate-related changes, including more frequent dry periods and floods. Although partial biological recovery of the river followed chemical recovery, the increasing frequency of hydrological extremes has likely become the main limiting factor. Full article

Springback control in Multi-Point Stretch Forming (MPSF) is significantly hindered by the computational intensity of Finite Element Analysis (FEA) and the limited predictive robustness of traditional regression methods. This study develops a hybrid GWO-CatBoost model acting as a data-driven surrogate for MPSF simulations by integrating the Grey Wolf Optimizer (GWO) with the CatBoost algorithm for high-precision springback forecasting. An FEA model of the MPSF process was initially validated through experimental comparison under a representative working condition to assess modeling accuracy. A comprehensive dataset comprising 1200 scenarios was generated via a full factorial design, incorporating key variables: curvature radius, sheet thickness, cushion thickness, and pre-stretching rate. In this study, the GWO was employed to perform automated hyperparameter tuning for CatBoost by optimizing the learning rate, tree depth, and number of iterations, thereby enabling accurate modeling of the complex nonlinear relationship between process inputs and numerical springback values. Numerical evaluations demonstrate that the GWO-CatBoost model outperforms GWO-XGBoost and GWO-Random Forest benchmarks, achieving a Coefficient of Determination (R²) of 0.9293, a root mean square error (RMSE) of 0.0274 mm and mean absolute error (MAE) of 0.0189 mm. Sensitivity analysis identifies sheet thickness as the dominant factor (46% contribution), with cushion thickness as the secondary driver (23%). This predictive framework serves as a computationally efficient auxiliary surrogate, designed to assist iterative finite element analyses and support process optimization in the manufacture of complex-curved panels. Full article

We propose a two-level theory that connects Lin-equation-based dynamical coarse-graining of the turbulence cascade with an information-theoretic selection principle in logarithmic wavenumber space. This framework places the dissipation-range spectral shape on a verifiable logical basis rather than on ad hoc fitting. At the first (dynamical) level, we formulate an autonomous conservative Fokker–Planck equation for the normalized density and probability current. Under sufficient boundary decay and a strictly positive effective diffusion, the sign-reversed Kullback–Leibler divergence is shown to be a Lyapunov functional, yielding a rigorous H-theorem and fixing the arrow of time in scale space. At the second (selection) level, the dissipation range is treated as a stationary boundary-value problem for an open system by introducing a killing term for an unnormalized scale density. A WKB (Liouville–Green) analysis restricts the admissible tail to a stretched-exponential form and links the tail exponent to the high-wavenumber scaling of the effective diffusion. The exponential prefactor is fixed by dissipation-rate consistency, and the remaining degree of freedom is determined by one-dimensional Kullback–Leibler minimization (Hyper-MaxEnt) against a globally constructed reference distribution. The resulting exponent range is validated against the high-resolution DNS spectra reported in the literature. Full article

As oil and gas well development moves towards ultra deep formations, the high temperature at the bottom of the well causes the failure of copolymer retarders, leading to increased risk of oil and gas leakage and carbon emissions during cementing operations. To further ensure the safety of high-temperature oil and gas cementing operations, the influence of N,N-dimethylacrylamide (DMAA) on the high-temperature performance of copolymer retarders was explored. DMAA was introduced into copolymer retarders to form ultra-high temperature retarders. By analyzing the micro mechanism of copolymer retarders, the regulation of high-temperature retarders on the micro hydration process of cement slurry at high temperatures was revealed. Results showed that the cement slurry containing 3.0% SH5L (Pentameric copolymer retarder-introduced DMAA) exhibits a significantly similar thickening time with 3.4% SH4L (Quaternary copolymer-retarder) at 180 °C, demonstrating superior retardation performance at a lower dosage. The ultra-high-temperature polycarboxylate retarder SH5L was prepared by introducing the DMAA, enhancing its temperature resistance and retardation performance at high temperatures. The coupling of SH5L and Ca²⁺ retards the hydration and crystallization process of the cement slurry. The combination of rigid polycyclic structures and cationic monomers weakens the chelation between anionic groups and Ca²⁺, inhibiting the curling of polymers in ionic solutions. Polymer chains stretch with increasing temperature, enhancing their ability to bind with Ca²⁺ and improving their high-temperature retardation performance. Full article

The microbiological safety of whole wheat flour remains a critical issue due to its susceptibility to contamination by spore-forming thermophilic bacteria. In this study, two thermophilic species, Bacillus subtilis and Bacillus mesentericus, were isolated from locally produced wheat grains and used as target microorganisms to evaluate the antibacterial potential of freshly pressed cabbage juices. Juices obtained from five cabbage varieties—red cabbage, white cabbage, napa (Chinese) cabbage, broccoli, and cauliflower—were comparatively assessed using the broth dilution method to determine their minimum inhibitory and bactericidal effects (n = 3). The results revealed pronounced differences in antibacterial efficacy among the tested samples. White cabbage juice exhibited selective inhibitory activity against B. subtilis at a dilution of 1:4, whereas napa cabbage and broccoli juices demonstrated the highest antibacterial activity against both Bacillus species at a dilution of 1:3. Importantly, napa cabbage juice showed no inhibitory effect on Saccharomyces cerevisiae, indicating its compatibility with dough fermentation processes. Spectroscopic analysis of the bioactive fraction obtained from napa cabbage juice revealed characteristic absorption bands at 3422 cm⁻¹ (O–H stretching), 2907–2840 cm⁻¹ (aliphatic C–H stretching), 1740 cm⁻¹ (ester carbonyl group), and 1641 cm⁻¹ (C=C stretching). The predominance of lipophilic compounds, including fatty acid esters, terpenes, and sulfur-containing compounds (734 cm⁻¹), suggests a molecular basis for the observed antibacterial activity against Bacillus spp. Overall, these findings identify napa cabbage as a promising source of selective natural antimicrobial agents capable of enhancing the microbiological safety of whole wheat flour-based bakery products without compromising yeast activity. Full article

The emulsification of a molten fusible metal alloy in a liquid epoxy matrix with its subsequent curing is a novel way to create a highly concentrated phase-change material. However, numerous challenges have arisen. The high interfacial tension between the molten metal and epoxy resin and the difference in their viscosities hinder the stretching and breaking of metal droplets during stirring. Further, the high density of metal droplets and lack of suitable surfactants lead to their rapid coalescence and sedimentation in the non-cross-linked resin. Finally, the high differences in the thermal expansion coefficients of the metal alloy and cross-linked epoxy polymer may cause cracking of the resulting phase-change material. This work overcomes the above problems by using nanosilica-induced physical gelation to thicken the epoxy medium containing Wood’s metal, stabilize their interfacial boundary, and immobilize the molten metal droplets through the creation of a gel-like network with a yield stress. In turn, the yield stress and the subsequent low-temperature curing with diethylenetriamine prevent delamination and cracking, while the transformation of the epoxy resin as a physical gel into a cross-linked polymer gel ensures form stability. The stabilization mechanism is shown to combine Pickering-like interfacial anchoring of hydrophilic silica at the metal/epoxy boundary with bulk gelation of the epoxy phase, enabling high metal loadings. As a result, epoxy shape-stable phase-change materials containing up to 80 wt% of Wood’s metal were produced. Wood’s metal forms fine dispersed droplets in epoxy medium with an average size of 2–5 µm, which can store thermal energy with an efficiency of up to 120.8 J/cm³. Wood’s metal plasticizes the epoxy matrix and decreases its glass transition temperature because of interactions with the epoxy resin and its hardener. However, the reinforcing effect of the metal particles compensates for this adverse effect, increasing Young’s modulus of the cured phase-change system up to 825 MPa. These form-stable, high-energy-density composites are promising for thermal energy storage in building envelopes, radiation-protective shielding, or industrial heat management systems where leakage-free operation and mechanical integrity are critical. Full article