Search Results (1,104)

The aim of this study was to investigate the effects of surface treatments and thermocycling on the shear bond strength of a 3D-printed permanent crown resin. A total of 120 disc-shaped specimens (10 × 3 mm) were fabricated using a 3D printer and randomly assigned to four groups according to surface repair protocols: airborne-particle abrasion with Al₂O₃, bur roughening, 37% orthophosphoric acid etching, and a control group with no surface treatment. All specimens received a silane coupling agent followed by an adhesive resin application, and repair was performed using a highly filled flowable composite. Each group was divided into three subgroups and subjected to 1000, 5000, or 15,000 thermal cycles. Shear bond strength was measured, failure modes were analyzed, and data were evaluated using two-way ANOVA and Tukey’s post hoc test (p < 0.05). The sandblasting group exhibited the highest bond strength (18.7 ± 5.0 MPa), which was significantly higher than the control (12.6 ± 3.7 MPa) and acid-etching (14.2 ± 3.8 MPa) groups (p < 0.05). Aging periods had no significant effect on bond strength (p > 0.05). Additionally, the interaction between surface treatment and thermocycling had no significant effect (p = 0.823). Under the tested conditions, airborne-particle abrasion resulted in the highest shear bond strength of 3D-printed permanent crown resin. Full article

Coal-based solid wastes, including coal gangue and fly ash, can be extensively utilised in cemented backfill materials. However, the slump, bleeding rate, and mechanical strength of these materials depend nonlinearly on the mixture composition, particle size, solids concentration, and curing conditions, complicating the multi-performance mixture design. This study developed an ensemble-learning framework for the target-specific performance prediction and empirical-uncertainty-aware inverse design of coal-based solid-waste cemented backfill materials. A literature-derived database containing 720 observations and 11 predictors was established. After the target-specific filtering of missing responses, 214 observations were available for the slump, 284 for the bleeding rate, and 711 for the uniaxial compressive strength (UCS). Support vector regression (SVR), Bagging-SVR, AdaBoost-SVR, and Stacking-SVR were evaluated using 20 repeated random 80:20 holdout partitions to assess the within-database predictive performance. Bagging-SVR achieved the lowest mean inner-cross-validation RMSE for all three responses. Its mean test R² values were 0.969, 0.871, and 0.965 for the slump, bleeding rate, and UCS, respectively, with corresponding RMSE values of 2.228 cm, 1.206 percentage points, and 1.575 MPa. SHAP analysis showed that the coal-gangue particle size and solids concentration received the largest model attributions for the slump and bleeding-rate predictions, whereas the cement content and curing time received the largest attributions for the UCS prediction. The selected Bagging-SVR models were subsequently coupled with multi-objective differential evolution incorporating empirical prediction bounds, component mass balance, and target-specific five-nearest-neighbour applicability-domain constraints. The selected compromise candidate had a solids concentration of 79.46% and coal-gangue, fly-ash, and cement dry-solid mass fractions of 63.29%, 24.95%, and 11.76%, respectively. Its predicted slump, bleeding rate, and 28 d UCS were 21.19 cm, 1.85%, and 6.36 MPa, respectively. The nominal empirical upper bound of the bleeding rate was 3.83%, and the lower bound of the UCS was 3.74 MPa, both satisfying their prescribed limits. However, the nominal slump interval of 15.70–26.65 cm was not fully contained within the prescribed range of 18–26 cm. Full article

Classification is a fundamental technique in data mining that predicts categorical labels by analyzing input features. However, training Artificial Neural Networks (ANNs) using traditional methods often encounters challenges, such as getting stuck in local minima and slow convergence. To address these issues, this study proposes a novel hybrid model, IPA-ANN, which integrates the Immune Plasma Algorithm (IPA) to optimize the ANN’s connection weights and biases. The IPA, inspired by the immune plasma treatment process, utilizes a unique donor-receiver mechanism to balance exploration and exploitation in the search space. The proposed model was evaluated on nine benchmark datasets from the UCI repository and compared with 18 state-of-the-art metaheuristic algorithms, including Grey Wolf Optimization (GWO), Differential Evolution (DE), and Particle Swarm Optimization (PSO). Experimental results were analyzed using accuracy, F1-score, confusion matrices, and convergence graphs. The findings indicate that IPA-ANN achieves competitive and stable classification performance across different datasets while demonstrating favorable convergence characteristics in several cases. Furthermore, the study investigates the influence of donor–receiver parameters on the optimization process, highlighting the adaptability of the proposed framework. The reliability of these findings was further examined through repeated stratified 5-fold cross-validation and paired Wilcoxon signed-rank tests with Holm–Bonferroni correction on representative datasets, confirming that a subset of the observed performance differences are statistically significant, and through a computational cost analysis showing that IPA-ANN incurs no additional overhead relative to the majority of the compared algorithms. This study contributes to the literature by presenting the first documented application of IPA in ANN training and by providing a modular infrastructure for future metaheuristic-based ANN optimization studies. Full article

Ultrasonic attenuation in particle–cementitious heterogeneous media results from the coupled effects of matrix memory dissipation and particle-induced random heterogeneity, which cannot be readily distinguished using conventional homogeneous-medium models. This study develops a unified stochastic fractional wave framework that couples Caputo fractional dissipation with a random-potential representation of spatial heterogeneity. The main contribution is an analytically tractable amplitude–phase formulation that separates the leading-order roles of the two mechanisms: fractional dissipation primarily governs exponential amplitude attenuation, with $\kappa (\omega )\propto {\omega }^{\alpha -1}$, whereas the random potential mainly modulates local phase propagation and introduces finite scattering-type amplitude corrections. By transforming the governing equation into a frequency-domain Helmholtz form and applying Wentzel–Kramers–Brillouin (WKB) asymptotic analysis, explicit scaling relations are obtained for both attenuation and phase fluctuations. Two-dimensional Helmholtz simulations support the predicted attenuation law and show that the relative $L_2$ error of the WKB phase prediction decreases from 25.23% to 5.36%, while the covariance-based fixed-receiver ensemble phase-variance prediction lies within the 95% confidence interval of 30 independent realizations. Single-frequency ultrasonic transmission experiments provide complementary trend-level evidence, showing reduced tail retention and increased descriptive tail attenuation with increasing particle volume fraction. The proposed framework provides a mechanistically interpretable basis for distinguishing dissipation-dominated and heterogeneity-induced ultrasonic responses. Full article

Biochar has received increasing attention due to its potential to improve soil quality, mitigate environmental contamination, and promote carbon sequestration. However, its properties are strongly influenced by production conditions. In this study, a central composite design (CCD) combined with response surface methodology (RSM) was used to evaluate the effects of pyrolysis temperature (T; 349–601 °C), residence time (RT; 0.8–4.2 h), and biomass particle size (PS; 0.34–3.68 mm) on the properties of biochar produced from sugarcane bagasse. The following biochar properties were considered response variables in the CCD: gravimetric yield; fixed carbon, volatile matter and ash contents; polarity (O/C ratio) and aromaticity (H/C ratio) indices; surface area; pH; and methylene blue (MB) removal efficiency. The results showed that pyrolysis temperature was the most influential variable, leading to reductions in yield, volatile matter content, and polarity, while increasing fixed carbon content, aromaticity, pH, surface area, and MB removal efficiency. Particle size influenced biochar friability and its MB removal capacity. Additionally, the combined use of principal component analysis (PCA) and Fourier-transform infrared (FTIR) spectroscopy enabled the effective discrimination of materials produced under different pyrolysis conditions. Full article

During ultrasonic detection of buried seeds after sowing, variations in soil conditions can strongly affect ultrasonic signals and make seed identification difficult. In this study, soil moisture content, particle size, and compaction pressure were investigated to evaluate their effects on ultrasonic frequency-domain responses and seed-presence discrimination. The first-wave dominant frequency (F_g) and dominant-frequency amplitude ratio (k) were extracted from the received signals. Seed presence altered the spectral peak position and amplitude distribution, whereas the direction of the F_g shift varied with soil conditions, limiting its use as a standalone discrimination feature. In sieved soil, k showed the best discrimination at 10% moisture content, with an AUC of 0.951. Using the predefined threshold k = 1, the sensitivity, specificity, and overall accuracy were 94.7%, 81.3%, and 88.0%, respectively. In non-sieved field soil, the highest AUC was 0.923 at 15% moisture content, with an accuracy of 90.0% using k = 1. An additional 40 independent tests conducted at 15% moisture content and 0.50 MPa yielded a sensitivity of 95.0%, a specificity of 90.0%, and an overall accuracy of 92.5%. These results demonstrate the potential of ultrasonic frequency-domain features for identifying buried seeds under controlled soil conditions. Full article

Physical clogging limits managed aquifer recharge (MAR), yet the threshold-crossing time alone may not predict subsequent performance. Constant-head columns packed with borosilicate glass beads or quartz sand received a 50 mg L⁻¹ silica suspension (0.9–2.7 μm) for 240 h. Hydraulic heads and discharge yielded relative apparent hydraulic-conductivity trajectories ($K_r$); X-ray computed tomography supported box-counting and block-network analyses. Sustained crossings below $K_r=0.60$, 0.50, and 0.40 occurred at 44/46, 61/59, and 88/78 h for the glass-bead/quartz-sand columns. Despite similar 0.60 and 0.50 crossing times, $K_r$ values at 240 h were 0.475 and 0.043, respectively. The glass-bead trajectory rebounded after its minimum and remained above 0.40. Interface box-counting slopes depended on imaging branch and segmentation threshold, but the regional $D_2$ and $D_3$ ranks remained positively associated within each medium. Removing the highest-flow 5% of flow-carrying edges caused conductance-proxy losses of 0.521–0.692 across three capacity laws, greater than under random removal. For the two tested cases, threshold persistence, subsequent direction, and terminal state provided complementary evidence of hydraulic stability; broader application requires replicated tests across particle and loading conditions while retaining the distinction between obstruction probability and flow-path consequence. Full article

Background: Chikungunya virus (CHIKV) infection is an emerging disease of growing concern to international travelers due to the expanding geographic distribution of competent vectors, climate change, and frequent outbreaks in endemic and previously unaffected regions. Until recently, prevention relied exclusively on vector control and bite prevention; however, the recent approval of chikungunya vaccines has introduced a new preventive strategy. Methods: We conducted a narrative review of currently licensed chikungunya vaccines and candidates in clinical development, focusing on immunogenicity, safety, regulatory status, and implications for travel medicine practice. Results: Two vaccines have recently received regulatory approval: the live-attenuated vaccine IXCHIQ^® and the virus-like particle vaccine Vimkunya^®. Both demonstrated high immunogenicity based on neutralizing antibody thresholds accepted as surrogate markers of protection. Post-marketing safety signals associated with IXCHIQ^®, particularly in older adults, have led to divergent regulatory decisions between authorities. The indication of vaccination in national recommendations varies somewhat depending on age, duration of travel, and individual risk factors. Several additional vaccine platforms remain under investigation, although some candidates have been discontinued. Conclusions: The recent approval of chikungunya vaccines marks a significant milestone in the field of travel medicine. However, uncertainties regarding long-term protection, safety in specific populations, and optimal targeting of travelers remain. Individualized risk–benefit assessment is essential, and further data are needed to refine vaccination strategies for travelers and populations at risk. Full article

Although marine sediments are recognized as a sink for marine microplastic particles, investigations into the fate of once deposited particles have received relatively little interest so far. Through interactions with sediment-dwelling organisms, these particles are subject to potential burial in the wake of bioturbation. In this study, we analyzed the effect of sediment reworking by the polychaete Hediste diversicolor O.F. Müller, 1776, using different particle tracers—luminophores, polyethylene (PE), and polyamide (PA). Transport induced by H. diversicolor was observed to extend to sediment depths up to 14 cm with similar biodiffusive and advective transport rates for all tracer types. Local transport (Db) was 1.09 cm² yr⁻¹ for luminophores; microplastics showed slightly lower local transport with Db of 0.81 cm² yr⁻¹ (PA) and 0.57 cm² yr⁻¹ (PE). Non-local transport (r) was comparably low for all particle types, ranging from 0.69 yr⁻¹ for luminophores and 0.95 yr⁻¹ (PA) and 1.27 yr⁻¹ (PE) for microplastics. Food addition did not significantly increase bioturbation activity of H. diversicolor. Despite differences in size and density, the particle tracer types in this study showed no significant differences in modeled bioturbation coefficients or burial depth, emphasizing that bioturbation of microplastics is not governed by particle properties alone but also by the functional ecology of the bioturbator. Full article

To address three major industry pain points—the lack of quantified profit-sharing standards in the two-stage pricing under the separation model of military research and production, the absence of stable Nash equilibrium in single-layer synchronous optimization, and insufficient incentives for full-cycle process optimization in design units—this paper constructs a two-level Stackelberg leader–follower game model with the general contracting unit as the leader and design and general contracting units as followers. This aligns with current prototype incentives and phased pricing policies for production rewards and penalties. At the theoretical level, it improves the complete proof system for the two-stage concave profit two-level Stackelberg Nash equilibrium, distinguishes the mathematical differences in equilibrium existence between sequential decision-making and synchronous optimization, and extracts general rules for phased differentiated profit sharing: high-innovation segments should be allocated more profit weight; simply maximizing total alliance profit may cause imbalanced interests, while introducing a minimum net profit-weighted objective can achieve Pareto improvements without profit loss. This conclusion can be applied to multi-stage general contracting scenarios across industries, such as EPC and military–civil collaborative innovation, enriching the basic theory of profit sharing and hierarchical games. Theoretically, the existence of the lower-level Nash equilibrium is proven using Brouwer’s fixed-point theorem, and combining it with the strictly monotonically decreasing feature of the best response function, uniqueness of the equilibrium is derived. Multiple sets of differentiated initial values are simulated to rule out multi-equilibrium bifurcation risk. The model incorporates the military’s reward and penalty policies as rigid exogenous constraints, sets dual individual rationality constraints of ‘cooperative profit greater than baseline profit with no allocation, and both parties’ net profit non-negative,’ and introduces differentiated cost-reduction efficiency and quadratic increasing effort costs to characterize the heterogeneous input of the two types of development entities. For models with piecewise nonlinearity and multi-constraint nonconvex structures, this paper modifies the standard PSO into a Bi-PSO solving framework through hierarchical temporal adaptation. It does not innovate the underlying particle update mechanism and is only used to match the sequential decision order of the leader–follower game. By comparing five algorithms—IPM, GA, SA, DE, and adaptive PSO—through 20 repeated simulations: gradient-based interior point methods easily get stuck in locally invalid solutions that violate cooperation thresholds; differential evolution has the best numerical global search performance, but all general evolutionary algorithms optimize allocation and effort variables simultaneously, disrupting the Stackelberg hierarchical timing. Only Bi-PSO maintains consistent game logic. Using a pricing case for a certain type of equipment and jointly calibrating all parameters with policy documents, three simulation scenarios were set up: no allocation, equal 50/50 split, and single-layer profit maximization. Under the no-allocation mode, R&D investment from the design unit drops to zero and alliance benefits plummet; a blanket equal split ignores differences in technical contributions across two stages, leading to clear efficiency losses; single-layer optimization only pursues total profit maximization, causing a severe imbalance in profit distribution. The two-layer basic framework can achieve the upper limit of alliance benefits, and by adding a weighted optimization goal that considers both total profit and cooperation fairness, it can achieve equal net profits for both parties without reducing overall profit. Through single-parameter sweeps and two-factor heatmap simulations, the study further revealed the coupled effects of main party efficiency and mass production rewards and penalties on equilibrium input and optimal sharing ranges. A robust check was performed by replacing the logarithmic concave output function, producing a standardized allocation range resilient to parameter perturbations: optimal split for the prototype stage is 0.4–0.6 for the design unit, and for mass production stage 0.7–0.9. The findings suggest that high-contribution stages in multi-phase collaboration contracts should receive more benefits, and a weighted fairness objective can achieve Pareto improvements. These conclusions can extend to multi-stage collaboration scenarios such as EPC and military–civilian cooperation. Theoretically, this research further completes the equilibrium proof system for two-party concave payoff two-layer games, providing a new reference for the theory of phased differentiated benefit-sharing contracts in the military sector. Methodologically, it proposes a two-layer intelligent solving tool adapted to leader–follower sequential decisions, effectively mitigating issues where single-layer model equilibria fail or analytical algorithms struggle with multi-constraint nonconvex games. The results can provide quantitative support for the military, general contracting unit, and design unit in drafting equipment incentive pricing contracts and managing full-cycle cost collaboration. Full article

Efficient particle combustion is crucial for improving the overall performance of solid rocket ramjets. However, particle combustion is jointly constrained by multiple environmental factors, such as oxidizer supply, gas–solid transport, and residence characteristics, which are difficult to characterize using conventional mixing-ratio-based evaluations fully. To provide a diagnostic evaluation of particle combustion potential under complex flow-field organization during design and optimization, a thermal-environment-informed particle combustion index $I_{TPCI}$ is proposed in this study. The index incorporates oxidizer availability, particle–oxidizer transport, residence-related effects, gas thermal environment, and particle thermal reactivity, and is intended to indicate regions where particle oxidizer-consumption capability can be retained under favorable thermochemical conditions. The reacting duct case shows that $I_{TPCI}$ provides a combustion-potential-oriented description of particle consumption. In the canonical jet-interaction flow, the conventional mixing degree mainly identifies shear-layer-dominated transport boundaries, while $I_{TPCI}$ emphasizes the regions with particle-consumption potential. Application to the afterburner further shows that particle combustion potential is governed by the match among oxidizer supply, particle transport, residence condition, and thermal environment. The head region has favorable thermal and residence conditions but remains oxygen-lean, whereas the downstream regions receive additional oxidizer but are constrained by nonuniform oxygen–particle distributions, thermal environment, and residence time. In the pulsed-jet cases, the variation of $I_{TPCI}$ provides a diagnostic interpretation of changes in particle source-term distribution. For the present configuration, upstream pulsed actuation mainly enhances the head-region response, and the selected case increases the full-domain gaseous-product source term associated with boron combustion by 2.96%. These results indicate that the proposed index can support combustion-potential diagnosis and flow-control assessment in solid rocket ramjet afterburners. Full article

With the implementation of the Western Development Strategy and the Belt and Road Initiative, engineering activities on the Loess Plateau have expanded substantially in both scale and depth. Consequently, the disintegration of Lishi loess, which has received relatively limited attention, has become an increasingly important concern in relation to geological hazards and engineering stability. This study investigated the disintegration behavior of remolded Lishi loess specimens with different initial water contents under controlled dry-density conditions and developed a mathematical model to characterize the disintegration process. In addition, three-dimensional particle flow code (PFC3D) simulations were performed to provide a particle-scale mechanical interpretation of the observed behavior. The experimental results showed that the disintegration curves of the specimens exhibited a typical asymmetric S shape at all tested initial water contents. The Gompertz model provided a compact empirical description of these curves, with coefficients of determination ranging from 0.993 to 0.999. In the model, α denotes the upper asymptote of the disintegration curve, λ characterizes the growth-rate behavior, and β represents the characteristic time associated with the inflection point. These parameters should be interpreted as empirical descriptors of the disintegration process rather than direct measures of the microscopic properties of loess. Although the model closely reproduced the experimental curves, further validation using independent datasets is required before it can be applied predictively to other specimens or test conditions. The PFC3D simulations provided an equivalent mesoscopic representation of contact-network weakening, bond breakage, and progressive particle detachment at different initial water contents. The simulated evolution qualitatively reproduced the progression from boundary-particle detachment to the gradual loss of specimen integrity and final particle accumulation. These findings characterize the water-content-dependent disintegration behavior of remolded Lishi loess and provide a preliminary basis for understanding the water sensitivity of disturbed or reworked Lishi loess in engineering applications. Full article

The resource utilization of distillers’ grain-derived organic fertilizer is of significant importance for promoting green production of sorghum in Maotai-flavor Baijiu-producing regions and for soil and water conservation on sloping croplands. To determine its appropriate application rate and to clarify its synergistic effects on sorghum growth, soil properties, and soil loss, a runoff-plot experiment was conducted on typical sloping farmland in Renhuai, Guizhou Province. A no-fertilization control (CK) and gradient treatments of distillers’ grain organic fertilizer ranging from 1500 to 10,500 kg ha⁻¹ were established. Responses of sorghum growth, yield components, soil physicochemical properties, aggregate composition, and soil loss were evaluated, and Partial Least Squares Structural Equation Modeling (PLS-SEM) was employed to elucidate the pathways regulating soil erosion. The results demonstrated a pronounced dose–response relationship between distillers’ grain organic fertilizer application and sorghum growth and yield formation. The treatment receiving 6000 kg ha⁻¹ of distillers’ grain organic fertilizer exhibited superior performance in plant height, stem diameter, dry weight per plant, grain dry weight per panicle, and root development. Notably, grain dry weight per panicle and root biomass increased by 307.4% and 130.8%, respectively, compared with CK. Fertilization increased soil organic matter content in the 0–10 cm soil layer and altered the particle size distribution of soil aggregates. Except for the 1500 kg ha⁻¹ treatment, all fertilization treatments reduced total soil loss during the monitoring period. The treatment receiving 9000 kg ha⁻¹ achieved the greatest reduction, decreasing soil loss by 43.8% relative to CK, while the treatment receiving 6000 kg ha⁻¹ reduced soil loss by 38.8%. PLS-SEM results indicated that both root development and yield components were significantly negatively correlated with soil loss. However, the direct effect of fertilization on soil loss was not significant, suggesting that distillers’ grain organic fertilizer primarily reduces erosion risk indirectly by improving soil properties and promoting root development and yield formation. Overall, an application rate of 6000 kg ha⁻¹ of distillers’ grain organic fertilizer for sorghum cultivation on sloping cropland under the conditions of this experiment. Full article

Accurate measurement of attenuation during acoustic wave propagation in viscoelastic solid media is of theoretical and practical significance. Conventional studies primarily rely on analogies to models of electromagnetic wave attenuation in non-ideal media. Many modern models of acoustic attenuation rely on continuum mechanics and complex material properties. Although there are similarities between acoustic and electromagnetic waves, conventional models overlook their fundamental physical differences and neglect the influence of particle-vibration damping in viscoelastic media. Additionally, in applications with a single-transmitter and dual-receiver configuration, the effects of specific characteristics on the measurement of the acoustic attenuation coefficient are eliminated in both the electric–acoustic conversion of the transmitting transducer and the acoustic–electric conversion of the receiving transducer. The discrepancies in geometric parameters (size and shape) between the two measurement modules lead to inconsistent frequency responses, thereby introducing measurement errors in acoustic attenuation. To address these issues, we investigate the coupling mechanism between particle vibration damping and wave propagation attenuation, derive an analytical expression for the acoustic attenuation coefficient that accounts for this coupling, and propose a new method for accurately measuring acoustic attenuation in viscoelastic solid media. The experimental results validate the theoretical predictions of acoustic attenuation. Full article

The particle size refinement of hercynite (FeAl₂O₄) powders during wet high-energy mechanical milling was investigated through an integrated experimental and kinetic modeling approach. Hercynite powders were milled for different durations, and their microstructural, chemical, and particle size evolution was characterized using scanning electron microscopy, X-ray diffraction, semi-quantitative X-ray fluorescence analysis, and SEM–ImageJ-based particle size reconstruction. Particle size distributions were reconstructed from large particle populations, and the characteristic descriptors $D_{10}$, $D_{50}$, and $D_{90}$ were determined from empirical cumulative distributions. The results revealed a pronounced reduction in median particle size from approximately 83.1 $\mathrm{\mu }$m in the as-received powder to 0.422 $\mathrm{\mu }$m after 8 h of milling. X-ray diffraction analysis showed progressive peak broadening and intensity reduction with increasing milling time, suggesting milling-induced structural disorder and possible crystallite refinement and/or lattice strain accumulation, while no additional crystalline phases associated with milling-induced decomposition were detected within the detection limit of XRD. Semi-quantitative chemical analysis indicated limited metallic transfer from the stainless-steel milling media under the applied wet milling conditions. The evolution of $D_{50}$ with milling time exhibited a non-linear behavior characterized by rapid particle fragmentation at early stages, followed by a gradual transition toward a refinement-limited regime. This behavior was described using a first-order kinetic model with saturation behavior, yielding an asymptotic particle size of 0.443 $\mathrm{\mu }$m and an effective milling rate constant of 1.539 h⁻¹. Overall, the proposed kinetic framework provides a descriptive and condition-specific quantitative basis for interpreting the competing fracture and agglomeration mechanisms governing particle size evolution during wet mechanical milling of refractory spinel powders. Full article