Search Results (132)

This study examines the effects of laser pulse duration on the structural, morphological, optical, and gas-sensing characteristics of ${\mathrm{Al}}_2{\mathrm{O}}_3$/AgO thin films deposited on glass substrates using pulsed laser deposition (PLD). Pulse durations of 10, 8, and 6 nanoseconds were achieved through optical lens modifications to control both energy density and laser spot size. X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses showed a distinct reduction in both crystallite and grain sizes with decreasing pulse width, along with significant improvements in surface morphology refinement and film compactness. Hall effect measurements revealed a transition from n-type to p-type conductivity with decreasing pulse width, demonstrating increased hole concentration and reduced carrier mobility attributed to grain boundary scattering. Furthermore, current-voltage (I-V) characteristics demonstrated improved photoconductivity under illumination, with the most pronounced enhancement observed in samples prepared using longer pulse durations. Gas sensing measurements for ${\mathrm{NO}}_2$ and ${\mathrm{H}}_2$S revealed enhanced sensitivity, improved response/recovery characteristics at 250 °C, with optimal performance achieved in films deposited using shorter pulse durations. This improvement is attributed to their larger surface area and higher density of active adsorption sites. Our results demonstrate a clear relationship between laser pulse parameters and the functional properties of ${\mathrm{Al}}_2{\mathrm{O}}_3$/AgO films, providing valuable insights for optimizing deposition processes to develop advanced gas sensors. Full article

To improve the traffic efficiency of connected and automated vehicles (CAVs) in on-ramp merging areas, this study proposes a novel region-level multi-agent reinforcement learning framework, Regionally Coordinated Nash-Advantage Decomposition Deep Q-Network with Conflict-Aware Q Fusion (RC-NashAD-DQN). Unlike existing vehicle-level control methods, which suffer from high computational overhead and poor scalability, our approach abstracts on-ramp and main road areas as region-level control agents, achieving coordinated yet independent decision-making while maintaining control precision and merging efficiency comparable to fine-grained vehicle-level approaches. Each agent adopts a value–advantage decomposition architecture to enhance policy stability and distinguish action values, while sharing state–action information to improve inter-agent awareness. A Nash equilibrium solver is applied to derive joint strategies, and a conflict-aware Q-fusion mechanism is introduced as a regularization term rather than a direct action-selection tool, enabling the system to resolve local conflicts—particularly at region boundaries—without compromising global coordination. This design reduces training complexity, accelerates convergence, and improves robustness against communication imperfections. The framework is evaluated using the SUMO simulator at the Taishan Road interchange on the S1 Yongtaiwen Expressway under heterogeneous traffic conditions involving both passenger cars and container trucks, and is compared with baseline models including C-DRL-VSL and MADDPG. Extensive simulations demonstrate that RC-NashAD-DQN significantly improves average traffic speed by 17.07% and reduces average delay by 12.68 s, outperforming all baselines in efficiency metrics while maintaining robust convergence performance. These improvements enhance cooperation and merging efficiency among vehicles, contributing to sustainable urban mobility and the advancement of intelligent transportation systems. Full article

Plant disease segmentation has achieved significant progress with the help of artificial intelligence. However, deploying high-accuracy segmentation models in resource-limited settings faces three key challenges, as follows: (A) Traditional dense attention mechanisms incur quadratic computational complexity growth (O($n^{2}d$)), rendering them ill-suited for low-power hardware. (B) Naturally sparse spatial distributions and large-scale variations in the lesions on leaves necessitate models that concurrently capture long-range dependencies and local details. (C) Complex backgrounds and variable lighting in field images often induce segmentation errors. To address these challenges, we propose Sparse-MoE-SAM, an efficient framework based on an enhanced Segment Anything Model (SAM). This deep learning framework integrates sparse attention mechanisms with a two-stage mixture of experts (MoE) decoder. The sparse attention dynamically activates key channels aligned with lesion sparsity patterns, reducing self-attention complexity while preserving long-range context. Stage 1 of the MoE decoder performs coarse-grained boundary localization; Stage 2 achieves fine-grained segmentation by leveraging specialized experts within the MoE, significantly enhancing edge discrimination accuracy. The expert repository—comprising standard convolutions, dilated convolutions, and depthwise separable convolutions—dynamically routes features through optimized processing paths based on input texture and lesion morphology. This enables robust segmentation across diverse leaf textures and plant developmental stages. Further, we design a sparse attention-enhanced Atrous Spatial Pyramid Pooling (ASPP) module to capture multi-scale contexts for both extensive lesions and small spots. Evaluations on three heterogeneous datasets (PlantVillage Extended, CVPPP, and our self-collected field images) show that Sparse-MoE-SAM achieves a mean Intersection-over-Union (mIoU) of 94.2%—surpassing standard SAM by 2.5 percentage points—while reducing computational costs by 23.7% compared to the original SAM baseline. The model also demonstrates balanced performance across disease classes and enhanced hardware compatibility. Our work validates that integrating sparse attention with MoE mechanisms sustains accuracy while drastically lowering computational demands, enabling the scalable deployment of plant disease segmentation models on mobile and edge devices. Full article

Grain boundaries are among the most influential structural features that control the charge transport in polycrystalline organic semiconductors. Acting as both charge trapping sites and electrostatic barriers, they disrupt molecular packing and introduce energetic disorder, thereby limiting carrier mobility, increasing threshold voltage, and degrading the stability of organic thin-film transistors (OTFTs). This review presents a detailed discussion of grain boundary formation, their impact on charge transport, and experimental strategies for engineering their structure and distribution across several high-mobility small-molecule semiconductors, including pentacene, TIPS pentacene, diF-TES-ADT, and rubrene. We explore grain boundary engineering approaches through solvent design, polymer additives, and external alignment methods that modulate crystallization dynamics and domain morphology. Then various case studies are discussed to demonstrate that optimized processing can yield larger, well-aligned grains with reduced boundary effects, leading to great mobility enhancements and improved device stability. By offering insights from structural characterization, device physics, and materials processing, this review outlines key directions for grain boundary control, which is essential for advancing the performance and stability of organic electronic devices. Full article

Cavitation-induced degradation of metallic materials presents a significant challenge for engineers and users of equipment operating with high-velocity fluids. For any metallic material, the mechanical strength and ductility characteristics are controlled by the mobility of dislocations and their interaction with other defects in the crystal lattice (such as dissolved foreign atoms, grain boundaries, phase separation surfaces, etc.). The increase in mechanical properties, and consequently the resistance to cavitation erosion, is possible through the application of heat treatments and cold plastic deformation processes. These factors induce a series of hardening mechanisms that create structural barriers limiting the mobility of dislocations. Cavitation tests involve exposing a specimen to repeated short-duration erosion cycles, followed by mass loss measurements and surface morphology examinations using optical microscopy and scanning electron microscopy (SEM). The results obtained allow for a detailed study of the actual wear processes affecting the tested material and provide a solid foundation for understanding the degradation mechanism. The tested material is the Ni-based alloy INCONEL 625, subjected to stress-relief annealing heat treatment. Experiments were conducted using an ultrasonic vibratory device operating at a frequency of 20 kHz and an amplitude of 50 µm. Microstructural analyses showed that slip bands formed due to shock wave impacts serve as preferential sites for fatigue failure of the material. Material removal occurs along these slip bands, and microjets result in pits with sizes of several micrometers. Full article

The extensive use of copper in thermal and electrical systems calls for constant performance enhancement by means of innovative material treatments. The effects on the microstructural, mechanical, and electrical characteristics of copper in deep cryogenic treatment (DCT) and deep cryogenic treatment followed by heat treatment (DCT + HT) are investigated in this work. Copper samples were treated for various soaking durations ranging from 6 to 24 h. Mechanical properties such as tensile strength, hardness, and wear rate were analyzed. In the DCT-treated samples, tensile strength increased, reaching a peak of 343 MPa at 18 h, alongside increased hardness (128 HV) and a refined grain size of 9.58 µm, primarily due to elevated dislocation density and microstrain. At 18 h of soaking, DCT + HT resulted in improved structural stability, high hardness (149 HV), a fine grain size (7.42 µm), and the lowest wear rate (7.73 × 10⁻¹⁰ mm³/Nm), consistent with Hall–Petch strengthening. Electrical measurements revealed improved electron mobility (52.08 cm²/V·s) for samples soaked for 24 h in DCT + HT, attributed to increased crystallite size (39.9 nm), reduced lattice strain, and higher (111) texture intensity. SEM–EBSD analysis showed a substantial increase in low-angle grain boundaries (LAGBs) in DCT + HT-treated samples, correlating with enhanced electrical conductivity. Overall, an 18 h soaking duration was found to be optimal for both treatments. However, the strengthening mechanism in DCT + HT is influenced by grain boundary stabilization and thermal recovery and is different to DCT, which is strain-induced enhancement. Full article

Low-carbon lath martensite is highly susceptible to hydrogen embrittlement due to the presence of a high density of lath/block boundaries. In this study, I employ a continuum decohesion model to investigate the effects of varying hydrogen concentrations and tensile loads on the cohesive strength of low- and high-angle block boundaries. The thermodynamic properties of the cohesive zone are described using excess variables, which establish a link between atomistic energy calculations and the continuum model for gradual decohesion at a grain boundary. The aim of this study is to develop an in-depth understanding of how hydrogen affects the cohesive strength of block boundaries in a lath martensitic structure by integrating continuum and atomistic computational modeling and to apply the resulting insights to investigate the effects of varying hydrogen concentrations and tensile loads on interface decohesion. I incorporate hydrogen mobility and segregation at low- and high-angle twist boundaries in body-centered cubic (bcc) Fe to quantify the hydrogen-induced effects on progressive decohesion under tensile stress. A constant hydrogen flux through the free surfaces of a bicrystal containing a block boundary is imposed to simulate realistic boundary conditions. The results of the simulations show that, in the presence of hydrogen flux, separation across the block boundaries occurs at a tensile load significantly lower than the critical stress required for rupture in a hydrogen-free lath martensitic structure. Full article

Porous PZT films offer significant potential due to tunable electromechanical properties, yet the polarization behavior remains insufficiently understood because of discontinuous morphology and domain structures. In this work, we study the impact of porosity on the spontaneous polarization and electromechanical response of PZT thin films fabricated using a multilayer spin-coating technique with various concentrations (0–14%) of polyvinylpyrrolidone (PVP) as a porogen. Atomic force microscopy (AFM) and piezoresponse force microscopy (PFM) were employed to analyze the local topography, domain distribution, and polarization behavior of the films. The results indicate that increasing porosity leads to substantial changes in grain morphology, dielectric permittivity, and polarization response. Films with higher porosity exhibit a more fragmented polarization distribution and reduced piezoresponse, while certain orientations demonstrate enhanced domain mobility. Despite the decrease in overall polarization, the local coercive field remains relatively stable, suggesting structural stability during the local polarization switching. The findings highlight the crucial role of grain boundaries and local charge redistribution in determining local polarization behavior. Full article

This study systematically investigated the microstructural evolution and mechanical properties of GH4780 superalloy under various solution treatment conditions. Experimental results reveal a strong temperature dependence of grain growth kinetics, with the average grain diameter increasing from approximately 20 μm to 194 μm as the solution temperature rises from 1020 °C to 1110 °C. Mechanical testing demonstrates that grain coarsening reduces the yield strength by 19% at room temperature (from 920 MPa to 743 MPa) and by 9.5% at 760 °C (from 707 MPa to 640 MPa), primarily due to decreased grain boundary density and enhanced dislocation mobility. High-temperature deformation mechanisms were characterized, showing that the reduced grain boundary area facilitates dislocation motion while compromising strength. Furthermore, a grain growth kinetic model was developed, providing a quantitative prediction of microstructural evolution. These findings offer significant guidance for improving the high-temperature performance of GH4780 superalloy by optimizing heat treatment processes. Full article

In this research, Hall effect experiments and optical fittings were mainly conducted to elucidate the effect of hydrogen annealing on the electronic properties of polycrystalline Al-doped Zinc Oxide thin films by distinguishing the scattering by ion impurities and the scattering by grain boundaries. By comparing the carrier density and those mobilities of H₂-annealed samples with Ar-annealed samples, the effect of H₂ annealing was highlighted. AZO thin films were prepared on the quartz glass substrate at R.T. by an RF magnetron sputtering method, and the carrier density was controlled by changing the number of Al chips on the Zn target. After fabricating them, they were post-annealed in hydrogen or argon gas. Optical fitting was based on the Drude model using the experimental data of Near-Infrared spectroscopy, and the mobility at grain boundaries was analyzed by Seto’s theory. Other optical and crystalline properties were also checked by SEM, EDX, XRD and profilometer. It is indicated that the H₂ annealing would improve both carrier density and mobility. The analysis referring to Seto’s theory implied that the improvement of mobility was caused by the carrier generation from introduced hydrogen atoms both at the grain boundary and its intragrain region. Furthermore, the effect of H₂ annealing is relatively pronounced especially in low-doped region, which implies that Al and H have some interaction in AZO thin film. The interaction between Al and H in AZO thin film is still not confirmed, but this result implied that this interaction negatively affects the mobility at grain boundary. Full article

This study employs molecular dynamics simulations to unravel the interplay between twin spacing, temperature, and mechanical response in nanotwinned AgPd alloys. For fine-grained systems, a dual strengthening–softening transition emerges as twin spacing decreases, driven by a shift in dislocation behavior from inclined-to-twin-boundary slip to parallel-to-twin-boundary glide. In contrast, coarse-grained configurations exhibit monotonic strengthening with reduced twin spacing, governed by strain localization at grain boundaries and suppressed dislocation activity. Notably, cryogenic conditions stabilize pre-existing and nascent twins, whereas elevated temperatures intensify atomic mobility and boundary migration, accelerating twin boundary annihilation (“detwinning”). Full article

This study investigates the scratch response of α-phase commercially pure titanium (cp-Ti) produced via wire arc directed energy deposition (WDED), focusing on the thermal history and directional effects. Progressive scratch tests (1–50 N) revealed heterogeneous wear properties between the top and bottom layers, with the top layer exhibiting higher material recovery (58 ± 5%) and wear volume (5.02 × 10⁻³ mm³) compared to the bottom layer (42 ± 5% recovery, 4.46 × 10⁻³ mm³), attributed to slower cooling rates and coarser grains enhancing ductility. The variation in the properties stems from the thermal gradient generated during WDED. Electron backscatter diffraction analysis showed higher kernel average misorientation (KAM) in the bottom layer (0.84° ± 0.49° vs. 0.51° ± 0.44°), affecting plasticity by reducing dislocation and twin boundary mobility. No significant differences were observed between longitudinal and transverse orientations, with coefficients of friction averaging 0.80 ± 0.12 and 0.79 ± 0.13, respectively. Abrasive wear dominated as the primary mechanism, accompanied by subsurface plastic deformation. These findings highlight the significant influence of WDED thermal history in governing scratch resistance and deformation behavior, providing valuable insights for optimizing cp-Ti components for high-performance applications. Full article

Grain boundaries play a vital role in determining the structural, functional, mechanical, and electrical properties of semiconductor materials. Recent studies have yielded great advances in understanding and modulating the grain boundaries via semiconductor crystallization engineering and machine learning. In this article, we first provide a review of the miscellaneous methods and approaches that effectively control the nucleation formation, semiconductor crystallization, and grain boundary of organic semiconductors. Using the benchmark small molecular semiconductor 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) as a representative example, the crystallization engineering methods include polymer additive mixing, solvent annealing, gas injection, and substrate temperature control. By studying the grain-width-dependent charge transport, we propose a grain boundary model as a fundamental basis to theoretically understand the intrinsic relation between grain boundary engineering and charge carrier mobility. Furthermore, we discuss the various machine learning algorithms and models used to analyze grain boundaries for the various important traits and properties, such as grain boundary crystallography, energy, mobility, and dislocation density. This work highlights the unique advantages of both crystallization engineering and machine learning methods, demonstrates new insights into discovering the presence of grain boundaries and understanding new properties of materials, and sheds light on the great potential of material application in various fields, such as organic electronics. Full article

After the thermal-mechanical processing of Mg alloys, extensive 30°⟨0001⟩ grain boundaries (GBs) are present in the recrystallized structure, which strongly affects the mechanical properties via interactions with lattice dislocations. In this work, we systematically investigate how the 30°⟨0001⟩ GBs influence the slip transmission during plastic deformation. We reveal that basal dislocations can be transmuted into its neighboring grain and continue gliding on the basal plane. The prismatic dislocation can transmit the GB remaining on the same Burgers vector. However, a mobile pyramidal $⟨c+a⟩$ dislocation can be absorbed at GBs, initiating the formation of new grain. These findings provide a comprehensive understanding on GB-dislocation interaction in hexagonal close-packed (HCP) metals. Full article

The morphological characteristics of organic semiconductors significantly impact their performance in many applications of organic electronics. A list of challenges such as dendritic crystal formation, thermal cracks, grain boundaries, and mobility variations must be addressed to optimize their efficiency and stability. This paper provides an in-depth overview of how different polymer additives (conjugated, semicrystalline, and amorphous polymers) influence the crystallization, morphology and mobility of some well-studied organic semiconductors. Conjugated polymers enhance molecular alignment and crystallinity, leading to distinct crystalline structures and improved charge transport properties. Semicrystalline polymers offer in-situ crystallization control, which improves film morphology and increases crystallinity and mobility. Amorphous polymers help minimize misalignment and promote parallel orientation of organic crystals, which is critical for effective charge transport. Special attention is given to polystyrene (PS) as a representative additive in this review, which highlights the significant effects of its molecular weight (Mw) on film morphology and charge transport properties. In particular, low-Mw PS (less than 20k) typically results in smaller, more uniform crystals, and enhances both charge transport and interface quality. Medium-Mw PS (20k to 250k) balances film stability and crystallinity, with moderate improvements in both crystal size and mobility. High-Mw PS (greater than 250k) promotes larger crystalline domains, better long-range order, and more pronounced improvement in charge transport, although it may introduce challenges such as increased phase separation and reduced solubility. This comprehensive analysis underscores the decisive role of polymer additives in optimizing the morphology of organic semiconductors and maximizing their charge transport for next-generation organic electronic applications. Full article