Search Results (2,159)

The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, and mechanical performance of PLA-based materials produced via fused deposition modeling (FDM), with a focus on identifying filler-dependent behavior under different loading conditions. In this study, polylactic acid (PLA) composites reinforced with 0.5 wt.% graphene (Gr) and 0.5 wt.% silver (Ag) nanoparticles, added separately, were produced using fused deposition modeling (FDM) and comparatively investigated. Each nanofiller was incorporated individually into PLA-based filaments, and standard test specimens were fabricated via 3D printing. Structural, thermal, and mechanical properties were evaluated using tensile, compressive, and three-point bending tests, along with SEM, EDS, XRD, FTIR, DSC, and TGA analyses. The results showed that pure PLA exhibited typical brittle behavior and a single-stage thermal degradation profile. The tensile strength of pure PLA was 41.93 MPa, and the flexural strength was 70.76 MPa. The addition of 0.5 wt.% graphene led to noticeable improvements, particularly in flexural properties, while only a minimal (almost negligible) increase was observed in tensile strength, with tensile strength increasing to 42.24 MPa (+0.74%) and flexural strength increasing to 110.78 MPa (+56.6%). In contrast, 0.5 wt.% Ag exhibited mixed and load-dependent mechanical behavior, with slight improvements in flexural strength but reductions in tensile and compressive properties, where tensile strength decreased to 22.13 MPa (−47.2%) while flexural strength increased to 112.06 MPa (+58.3%). Structural and thermal analyses indicated that both nanofillers did not significantly alter the PLA matrix chemically, while contributing to controlled changes in material properties primarily through physical interactions. The novelty of this work lies in the comparative evaluation of graphene and silver nanoparticle reinforcement at a fixed low loading level within FDM-processed PLA, combined with a comprehensive and correlated analysis of mechanical, structural, and thermal behavior on the same specimen sets, enabling a clearer understanding of filler-dependent performance mechanisms in additively manufactured nanocomposites. Overall, it was concluded that low-rate nanofiller additions, when properly dispersed, may lead to selective improvements in the performance of PLA-based composites depending on filler type and loading mode, and show potential for advanced engineering applications such as lightweight structural components, functional sensors, and additive-manufactured parts requiring tailored mechanical performance and multifunctionality. Full article

The application of continuous carbon fiber (CCF) can reinforce the mechanical properties of 3D-printed parts, but the effect of reinforcement layer distribution on composite performance remains unclear. This study investigates the effect of concentrated and separated distributions of CCF layers with different numbers of reinforcement layers. Tensile and flexural tests are conducted in accordance with ASTM D5083 and ASTM D790, respectively. Under the conditions of a solid-filled matrix (Onyx) and 0° CCF deposition, both concentrated and separated CCF layers improve several mechanical properties. Compared with pure Onyx, one-layer CCF increases the tensile modulus by about six times and more than doubles the tensile strength. Increasing the CCF volume leads to further increases in these properties. With concentrated three-layer CCF, the tensile modulus and tensile strength reach 7.153 ± 0.090 GPa and 109.045 ± 5.124 MPa, respectively. For flexural properties, separated two- and three-layer CCFs significantly improve the tangent modulus of elasticity from 0.467 ± 0.106 GPa for pure Onyx to 2.246 ± 0.333 GPa and 3.394 ± 0.081 GPa, respectively. This study also compares the tensile and flexural strength-to-weight ratio of all specimen groups and analyzes the failure mechanisms based on macroscopic fracture appearance. The results can provide guidance for selecting appropriate CCF layer distribution strategies to reinforce composites in different applications. Full article

Automatic Modulation Classification (AMC) is essential for waveform-level signal characterization. It supports spectrum sensing, signal identification, and adaptive resource allocation in cognitive radio and next-generation wireless systems. However, channel impairments such as multipath propagation, frequency offset, fast fading, and noise degrade modulation signatures, making reliable AMC challenging. Existing deep learning-based approaches often rely on purely data-driven learning, leading to insufficient modeling of modulation-relevant features, loss of transient characteristics, and limited exploitation of hierarchical relationships among modulation types. To address these issues, this paper proposes PHM-Net, a physics-informed hierarchical multi-scale network for robust AMC. The model employs a hierarchical backbone with residual encoder blocks. A Transient Feature Gating (TFG) module enhances modulation-relevant representations, a Cross-Resolution Signal Aggregation (CRSA) module fuses multi-stage features, and a Physics-Informed Hierarchical Loss (PI-HL) enforces consistency between coarse- and fine-grained predictions. Experimental results on three benchmark datasets (RML2016.10a, RML2016.10b, and RML2018.01a) show that PHM-Net consistently achieves the highest average accuracy among all compared models. On RML2018.01a, which contains 1024-sample sequences and 24 classes, PHM-Net achieves an average accuracy of 64.59% and a best-case accuracy of 98.42%, surpassing AMC_Net by 11.14 and 17.09 percentage points and CNN-Transformer by 9.43 and 11.15 percentage points, respectively. PHM-Net provides a robust and interpretable solution for AMC under complex channel conditions. Full article

Currently, data-driven fault diagnosis methods have achieved remarkable progress. However, in industrial scenarios, acquiring a sufficient amount of fault data poses a challenge, thereby leading to the issue of imbalanced data in intelligent fault diagnosis. Furthermore, manual recording and instrument measurement errors will introduce label noise, which significantly impacts diagnosis performance. To address these problems, this paper proposes a safe-domain generative adversarial network with Swin Transformer (SDGAN-ST). A safe domain selection method is utilized to eliminate noisy samples and construct a pure dataset that poses no risk to the GAN training process. Consequently, GAN can generate high-quality minority samples to rebalance the original dataset. Additionally, the Swin Transformer is employed as a classifier to capture global information for each fault sample, thereby achieving high diagnostic accuracy. Experiments on the CWRU dataset and a real-world oxygen compressor bearing dataset demonstrate the effectiveness of the proposed method. On the CWRU dataset, SDGAN-ST achieves accuracies of 98.88%, 97.63%, and 97.50% under imbalance ratios of 1:10, 1:20, and 1:30, respectively. On the real-world dataset, SDGAN-ST achieves 100% accuracy under all three imbalance ratios. Additional experiments under noise ratios of 20%, 30%, and 40% show that SDGAN-ST maintains stable diagnostic performance and is more robust to label noise than ordinary WGAN-GP-based methods. Full article

Additively manufactured cellular architectures frequently exhibit brittle failure under impact due to layer-induced stress concentrations. Through the programming of architectural and material design, specifically combining Fused Deposition Modeling (FDM) lattice topology with hyperelastic polyurea infiltration, this study achieves active control over the macroscopic transition from catastrophic structural fragmentation to stable progressive collapse. To evaluate this, auxetic and honeycomb specimens printed with ABS and glass-fiber-reinforced polyamide (PA-GF) were evaluated in unreinforced and polyurea-infiltrated states under quasi-static compression, three-point bending, and Charpy impact loading. Results show that the compressive response depends primarily on cellular topology; the pure auxetic (A-A) configuration provided the highest stiffness and energy absorption. Polyurea infiltration did not significantly alter elastic stiffness but increased post-yield stability, leading to a 96.6% elastic recovery in PA-GF A-A structures. In flexure, the base polymer governed stiffness, with ABS structures measuring 68% stiffer than PA-GF. Unreinforced ABS achieved 34% higher specific energy absorption (SEA) than PA-GF under compression, with the A-H topology maximizing SEA. Under dynamic impact, PA-GF absorbed an average of 70% more energy than ABS, and the H-A configuration recorded the highest impact resistance. The addition of polyurea shifted the failure mode from brittle fragmentation to stable elastomeric deformation, increasing absorbed impact energy by 52% for ABS and over 30% for PA-GF, preventing catastrophic structural failure. Integrating topological sequencing with elastomeric confinement provides a direct method to control energy dissipation and damage tolerance in 3D-printed cellular composites. Full article

Lead-based alloy has received widespread attention as a coolant in nuclear reactors. However, there is limited research on pure lead after solidification. In this study, a systematic investigation was conducted on the long-term evolution of the microstructure and physical properties of pure lead samples solidified under different cooling rates, with a comparative analysis against of lead–bismuth eutectic (LBE). Microscopic detection (using optical and electron microscopes), density measurement, and compressive mechanical testing were carried out. The study results show that during the long-term evolution process after solidification (at room temperature of 27 °C), pure lead samples spontaneously undergo recovery and recrystallization, with larger grain size and more uniform microstructure. The density of samples remains within a stable range. The yield strength of samples after solidification will gradually decrease over time. For example, after 180 days of evolution, the yield strength of the rapidly cooled sample (10 K/min) decreased from 4.879 MPa to 3.766 MPa. Full article

Recently there has been notable interest in the reduction in emissions of the shipping industry via the substitution of the currently used fossil fuels with alternative green fuels. One such alternative studied presently could be the use of pure vegetable oils, which are cheaper and easier to produce than other proposed fuels. In this study, pure vegetable oils were tested in a constant volume combustion chamber to assess their ignition quality via the measurement of their Estimated Cetane Number (ECN) and to compare it with that of heavy fuel oils (HFOs). Moreover, the effect of vegetable oil composition on ignition quality was investigated. It was found that all the vegetable oils tested possessed significantly higher ignition quality than standard heavy fuel oils. Vegetable oil ignition quality was found to be most impacted by their degree of unsaturation. The results of the present study indicate that from the point of view of ignition quality, vegetable oils are a viable alternative to fossil fuels, being expected to lead to an increase in the ignition quality of standard heavy fuel oils. Full article

We develop an analytical framework to describe the impact of in-plane strain on the electronic and transport properties of graphene. Starting from a strain-modified nearest-neighbor tight-binding model, we derive the energy spectrum and group velocities, explicitly incorporating bond-dependent hopping renormalization. A dimensionless anisotropy parameter, derived from velocity fluctuations, is introduced to quantify directional transport imbalance. We show that this parameter admits a closed-form expression entirely determined by the strain tensor, linking lattice deformation directly to measurable transport quantities. In the small-strain regime, a compact expression is obtained, $\eta \approx ϵ\left(1+\nu \right)\cos \left(2\theta \right)$, revealing an angular dependence controlled solely by the orientation of the applied deformation. This establishes that strain acts as a purely geometric control parameter, separating magnitude and orientation effects. Within the semiclassical Boltzmann framework, the same parameter fully determines the conductivity tensor, leading to simple expressions for the longitudinal components ${\sigma }_{x,y}={\sigma }_0\left(1\mp \eta \right)$ and a clear identification of the preferred transport direction. Importantly, the total conductivity remains constant, while strain redistributes transport between orthogonal directions. These results provide a transparent and predictive description of strain-induced transport anisotropy, demonstrating that the directional electronic response can be tuned without modifying the material composition, offering a practical route to control electronic response in graphene through purely mechanical means. Full article

Land capitalization has become one of the central issues in contemporary China’s economic development and land system reform. Existing scholarship has predominantly approached this topic from the perspectives of effects, governance, and property rights, while a spatial analytical lens remains conspicuously absent. This study draws on the theoretical perspective of the production of space (spatial politics) and selects Xunliao Bay, a coastal tourism destination currently undergoing rapid land capitalization, as a typical case. Based on qualitative methods, including three-phase, five-time interviews and non-participatory observation conducted in Xunliao Bay, it investigates the spatial logic and restructuring processes of land capitalization in coastal tourism areas. The findings reveal that: (1) Land capitalization in coastal tourism destinations is essentially a process of the spatialization of capital, following a logical sequence of “spatial occupation–spatial planning–spatial production.” (2) In Xunliao Bay, land capitalization has generated multifaceted spatial consequences, leading to the reconfiguration of land property rights, land functional attributes, and land morphology. (3) Far from being a purely economic value-adding endeavor, land capitalization in coastal tourism destinations constitutes a spatial political process fraught with power struggles, interest negotiations, and conflicts. In this process, capital forges “growth coalitions” with local governments to complete land consolidation and property rights restructuring, subsequently redefines land attributes through planning mechanisms to safeguard its own interests, and ultimately engages in selective land use to carry out landscape construction and spatial production, thereby profoundly reshaping the local socio-spatial fabric. This study extends the spatial perspective and tourism context within land capitalization research and deepens the theoretical understanding of land capitalization as a socio-spatial and political process. Full article

Power batteries used in electric-powered vessels, new-energy tractors or construction machinery typically require prolonged, continuous operation at high power levels, which can lead to significant heat buildup and pose serious threats to battery safety, cycle life, and operational stability. Traditional air-cooled and liquid-cooled systems struggle to meet the requirements for efficient heat dissipation under heavy loads. Phase change materials (PCMs) are ideal for passive battery thermal management due to their high latent heat but are severely limited by low thermal conductivity and liquid leakage. In this study, nitrogen-doped carbon nanotubes@SiO₂ (PNT@SiO₂) were synthesized and further fabricated into oriented porous aerogels by directional freeze-drying using cellulose-based materials as the skeleton. Polyethylene glycol-8000 (PEG-8000) was loaded via vacuum impregnation to obtain the PSAP composite PCM. The optimized composite exhibits a thermal conductivity of 0.93 W/m·K, 3.2 times that of pure PEG, with 96% PEG loading and a phase change enthalpy of 158 J/g. Battery thermal management tests demonstrate its excellent temperature control and heat suppression performance. This study provides a high-performance and feasible thermal management solution for power batteries used in relevant fields. Full article

With the advancement of energy storage technology, there have been significantly increased demands for the storage performance and operating temperature of capacitor dielectric materials. As a high-temperature resistant polymer, polyimide (PI) shows great potential for application as a dielectric material. In this study, binary PI composite films with various contents of yttria-stabilized zirconia particles (YZPs) were prepared via in situ polymerization. The results demonstrated that the incorporation of YZPs enhanced the breakdown resistance compared to pure PI films. Specifically, at a YZP content of 8 wt%, the breakdown strength (BDS) of the composite films reached 566 kV·mm⁻¹. Although the mechanical strength exhibited a slight reduction, the dielectric properties remained stable, leading to an overall improvement in energy storage performance. Overall, 2 wt% YZPs/PI (with 5 mol% Y₂O₃, ZPb2) film is optimal in terms of its mechanical and dielectric properties. This research establishes a solid foundation for the engineering development and industrial implementation of high-performance PI-based polymer dielectric materials. Full article

This study aimed to analyze the effect of various phenolic acids introduced into pectin films on their ability to inhibit microorganisms. The antimicrobial activity of six phenolic acids—gallic, protocatechuic, caffeic, sinapic, coumaric, and ferulic acids—was verified against Bacillus subtilis bacteria. No inhibitory effect was observed when the acids were introduced into the substrates with the films, as the polysaccharide films served as a breeding ground for microorganisms. Bacterial growth was inhibited when pure acid was introduced to the substrate. Gallic and caffeic acid, at concentrations of 50 and 75 mM/dm³, respectively, completely inhibited bacterial growth. However, studies on pears have shown that such concentrations of phenolic acids are unsuitable for fruit coatings, as they lead to cloudiness and impaired visual appeal. Consequently, the lowest effective concentration was applied to fruit, reducing the total bacterial count from 2.59 ± 0.04 to 1.88 ± 0.22 log CFU/mL and mold and yeast counts from 2.11 ± 0.09 to 1.63 ± 0.10 log CFU/mL. The coating produced with the lowest tested concentration of gallic acid reduced the pears’ respiration rate. The amount of CO₂ released by coated fruit was approximately 4 mg/kg·h lower than that of uncoated pears, and the level of ethylene released was approximately 6 ppm lower. The addition of gallic acid at a concentration of 15 mM/dm³ to the coating reduced the growth of bacteria, yeasts, and molds. After 12 days of pear storage, the number of microorganisms in coated fruit was approximately 0.71 log CFU/mL lower for bacterial cells and 0.48 log CFU/mL lower for yeasts and molds. Full article

Traditional Chinese sticky rice–lime mortar, a key material for restoring historic masonry buildings, suffers significant degradation under combined salt erosion and freeze–thaw cycling. This study experimentally investigated the coupled effects of chloride, sulfate, and freeze–thaw action on sticky rice–lime mortar under simulated service conditions. Specimens prepared using traditional methods were subjected to freeze–thaw cycling in pure water, 5% Na₂SO₄ solution, 5% NaCl solution, and 5% NaCl + 5% Na₂SO₄ solution. Their mechanical properties, phase compositions, and pore structures were characterized through compressive, dynamic elastic modulus, X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) tests. After six freeze–thaw cycles, the relative dynamic elastic modulus (0.72, 0.58, 0.57, 0.55), mass loss (1.7%, 3.69%, 4.82%, 5.60%), and compressive strength loss (30.05%, 43.90%, 47.56%, 52.43%) progressively worsened from pure water to Na₂SO₄ to NaCl to compound salt conditions, indicating that under the same concentration, the deterioration induced by sodium chloride freeze–thaw is more severe than that caused by sodium sulfate, while the compound salt freeze–thaw condition leads to the most severe deterioration. Under compound salt freeze–thaw, the deterioration mechanisms include expansion due to gypsum formation, salt crystallization, ice formation, and the dissolution of cementitious phases driven by CaCl₂ attack. Furthermore, clear correlations are observed among the mass loss rate, compressive strength loss rate, and relative dynamic elastic modulus, as well as between the peak strain and secant modulus. These findings provide valuable insights for improving the durability of historic restoration mortars. Full article

Poly(L-lactic acid) (PLLA) is a biodegradable polyester that has garnered widespread attention for its potential applications as a replacement for conventional petroleum-based plastics. However, PLLA’s prolonged biodegradation is a significant limitation in its applications, particularly in single-use packaging, as it can lead to environmental accumulation and hinder the sustainability goals of reducing plastic waste. This paper examines the effect of incorporating thermoplastic chitosan (TPC) on the mechanical and biodegradation properties of PLLA. TPC was prepared using lactic acid as a plasticizer. PLLA/TPC composites were produced by thermo-mechanical processes. TPC contents of 1%, 2.5%, 5%, and 10% were investigated. The PLLA/TPC films exhibited distinct phase separation, as verified by scanning electron microscopy analysis. The incorporation of 2.5% TPC led to a 20.8% enhancement in elongation at break and a 7.4% improvement in tensile toughness relative to pure PLLA film. Nonetheless, both values diminished when the TPC content surpassed 2.5 wt%. The surface wettability of the PLLA/TPC films, assessed via water contact angle measurements and weight loss from soil burial tests, enhanced with greater TPC content. The PLLA/TPC films showed significantly greater weight loss after being buried in soil for 12 months compared to pure PLLA film. The increases in weight loss were 4, 11, 14, and 72 times greater for the TPC contents of 1%, 2.5%, 5%, and 10%, respectively. Incorporating TPC in this study improved the flexibility and biodegradability of PLLA, leading to PLLA-based composites with enhanced potential for environmentally sustainable single-use packaging. Full article

Uranium dioxide (UO₂) is the standard fuel in light water reactors, but improving its mechanical performance is essential for achieving higher burnups. This study employs first-principles density functional theory with the DFT + U approach to investigate the effect of molybdenum (Mo) substitution on the elastic properties of UO₂. Supercell models with Mo concentrations from 3.125 to 9.375 at.% are constructed, and elastic constants are calculated using the stress–strain method, complemented by Bader charge and charge density analyses. The results reveal a non-monotonic concentration-dependent behavior: at 3.125 at.% Mo, the shear and Young’s moduli increase by ~16% and ~14%, respectively, indicating significant stiffening; at higher concentrations (6.25 and 9.375 at.%), both moduli decrease, leading to softening of UO₂ lattice. Bader charge analysis shows that Mo loses only 0.13 electrons (vs. 2.56 for U) and the Mo–O bond is much shorter than the U–O bond; this is evidence of covalent bonding between Mo and O atoms that acts as local strengthening centers at low doping. The softening at higher concentrations is attributed to increased lattice distortion and enhanced bond delocalization, supported by changes in Cauchy pressure, Debye temperature, and Vickers hardness. The calculated elastic modulus and hardness of pure UO₂ are in good agreement with previously reported experimental data. For Mo-doped UO₂ systems, this work establishes a quantitative composition–property relationship, providing a theoretical reference for future experimental investigations. Full article