Search Results (7,463)

(1) Aluminum bonding wires are mostly used for electrical contact and transmission of electrical signals in power electronic modules. Combined cyclical mechanical and thermal loads acting on the wires can lead to premature failure of the whole module. For this purpose, based on extensive fatigue tests on a 300 µm Al-Pure wire, the authors developed, calibrated and applied a fatigue life model for a cycle range of $R=0.1$ to $R=0.7$ to other comparable aluminum wires in two previous publications. (2) Since the model is supposed to be used in an FEM post-processor for predicting the lifetime of wire bridges, the existing model was expanded in the following work. (3) Temperature dependence is included in the fatigue model, and it is made more robust in the whole possible R-range to be able to cope with the highly variable load cases in real components. In addition, a creep rupture model was developed and combined with the fatigue model by linear damage accumulation. (4) The applicability of the lifetime consumption model is demonstrated for several combined load cases. It is shown that it is necessary to consider both fatigue and creep in a combined model for a reliable lifetime prediction. Otherwise, the lifetime could be underestimated by several orders of magnitude, depending on the load case. Full article

Achieving efficient demulsification of water-in-heavy oil (W/HO) emulsions remains a critical issue that urgently needs to be addressed in the heavy oil industry. Despite being a new generation of green demulsification materials, magnetic carbon nanoparticles still suffer from low demulsification efficiency when applied to water-in-heavy oil emulsions. Herein, polyethyleneimine-modified magnetic carbon nanoparticles (P-MCNs) were successfully prepared via a surface functionalization strategy. The demulsification performance of P-MCN in water-in-heavy oil (W/HO) emulsions was evaluated via the standard bottle test. The results demonstrated that P-MCN (500 ppm) achieved effective water removal within 60 min at 50 °C. Microscopic visualization characterization revealed that the efficient water removal from W/HO emulsions by P-MCN is attributed to its high interfacial activity. Specifically, P-MCN can rapidly migrate to the heavy oil–water interface and effectively disrupt the interfacial film through electrostatic interactions and hydrogen bonding, thereby achieving efficient demulsification of W/HO emulsions. This study provides a solid theoretical foundation for the further development of magnetic carbon nanoparticles with higher demulsification efficiency for applications in the petroleum industry. Full article

Road engineers still face a critical challenge in improving the crack resistance of cement-stabilized macadam (CSM) base courses. This study employs the discrete element method (DEM) with realistic aggregate morphologies from X-ray computed tomography to model normally bonded and weakly bonded CSM. The mesoscopic parameters of normally bonded models were calibrated against laboratory unconfined compressive strength (UCS) tests, and a weakening ratio of bond strength (Wr_bs) was introduced to define the weakly bonded model. The results show that UCS decreases monotonically with the reduction in Wr_bs and the increase in Rr_ca. The maximum strength reduction reaches 26.3% at the extreme condition of Rr_ca = 100% and Wr_bs = 50%. Despite this reduction, the UCS of weakly bonded specimens remains compliant with Chinese specifications for base course materials when designed with appropriate parameters. Notably, weakly bonded specimens exhibit a more dispersed crack distribution and a more gradual energy dissipation process. This mechanism is associated with a reduced tendency for macroscopic crack initiation and propagation, suggesting the potential of weakly bonded CSM to enhance crack resistance. This work provides a mesoscopic theoretical foundation for the engineering application and sustainable development of weakly bonded CSM in pavement base courses. Full article

Localized failures of structural components can lead to serious social, economic, and environmental consequences, such as the collapse of an entire structure or part of it. Therefore, it is important to thoroughly investigate and justify the acceptance criteria for these components, taking into account their performance in extreme conditions. However, the scientific literature lacks a systematic analysis of how various factors can affect the resistance of structures and influence acceptance criteria under extreme conditions. Therefore, this study investigates the typical substructures of reinforced concrete frame buildings in areas that are potentially prone to local collapse. To assess their resistance and structural robustness, an analytical model has been developed. The results of 22 tests on typical substructures of monolithic and precast frames, reported in various research studies, were used to validate this model. Further, this analytical model was used to conduct a parametric study on the impact of various factors on the performance of substructures under extreme conditions. These factors included the depth-to-span ratio of the beam, the strength of the bond between the steel reinforcement and the concrete, the stiffness of the horizontal bracing within the substructure, and the proportion of the effective depth to the total depth of the beam section. It has been found that the ultimate rotation angle in the plastic hinge of beams increases as the ratio of the beam’s cross-sectional depth to the span increases. An increase in the bond strength between the reinforcement and concrete leads to a decrease in the ultimate rotation angles in the plastic hinge at the flexural and arch stages of resistance and, in some cases, to reinforcement rupture without transitioning to the catenary stage of resistance. A decrease in the ratio of the effective depth of the beam section to its overall depth leads to an increase in the load-bearing capacity at the catenary stage of 19%. Full article

Zinc oxide (ZnO) nanoparticles have attracted increasing attention in wood science due to their multifunctional properties, including antimicrobial activity, UV absorption, and photocatalytic behavior. Water-based deposition protocols offer clear advantages yet typically struggle with nanoparticle aggregation and limited adhesion to lignocellulosic substrates. This work introduces a rapid and scalable waterborne protocol combining catalyst-free aqueous seeding with microwave-assisted (MWA) growth under mild conditions. Pinus pinaster veneer samples were treated via dip-coating and spraying, with single and double seeding cycles, followed by MWA growth. Protocol efficiency was assessed through ZnO retention, SEM, and EDS analysis, while the impact of the substrate was assessed via mechanical testing, ATR-FTIR spectroscopy, and colorimetry. Dip-coating achieves significantly higher precursor uptake than spraying, while repeated seeding cycles further increase ZnO loading. Results suggest that incorporation may proceed through zinc–carboxylate bonds within the wood matrix, followed by localized ZnO nanostructures development. The effective integration did not weaken the mechanical properties, while color changes were significant for dip-coated samples and noticeable for sprayed ones. Overall, this methodology provides a fast, water-based, and minimally invasive route for ZnO incorporation into wood and a scalable pathway with retained mechanical and chemical properties and limited visual impact. Full article

Fiber contamination originating from disposable dental microapplicators has received limited attention despite its potential influence on adhesive procedures. The aim of this pilot in vitro study was to evaluate fiber-like structure release associated with different microapplicator types during the application of universal adhesive systems. Three universal adhesives (Clearfil Universal Bond Quick, Gluma Universal, and G-Premio BOND) and five microapplicator types (X-Slim, Clinique, Prima, Single TIM, and ZerofloX silicone-bristle microapplicators) were evaluated. A total of 75 adhesive applications were performed on standardized sandblasted glass substrates under controlled laboratory conditions. Adhesives were actively applied for 10 s, and fiber-like structures were quantified microscopically using ImageJ software. Statistical analysis included descriptive statistics, two-way ANOVA, and Tukey post hoc testing (α = 0.05). Significant differences were observed among microapplicator types. X-Slim applicators produced the highest fiber counts, whereas Single TIM applicators demonstrated substantially lower values. No detectable fiber-like structures were observed in specimens treated with the ZerofloX silicone-bristle microapplicator. Adhesive system type showed a comparatively smaller influence on fiber counts than microapplicator design. Within the limitations of this pilot in vitro study, microapplicator type appeared to be the primary factor influencing visible fiber contamination during adhesive application. Further studies are required to determine whether the contamination patterns observed influence adhesive performance under clinically relevant conditions. Full article

The successful application of extrusion-based 3D-printed geopolymer mortars largely depends on precursor chemistry, activator composition, mixture proportions, and fresh-state behavior, which is highly sensitive to time-dependent structural build-up. This review examines the relationships among mix design, geopolymerization chemistry, rheological properties, and printability requirements for 3D-printed geopolymer mortars. Particular emphasis is placed on the effects of precursor type, alkaline activator characteristics, liquid-to-solid ratio, additives, and fibers on flowability, yield stress, viscosity, extrudability, buildability, shape retention, and interlayer bonding. The review further discusses how geopolymerization kinetics influence the evolution of fresh-state properties, the printable time window, and the transition from extrusion to structural stability. In addition, early-age performance is evaluated in terms of setting behavior, green strength development, and layer-interface integrity. Current challenges, including the lack of standardized test methods, limited comparability among published studies, and the complex coupling between material design and process parameters, are also highlighted. Finally, the review identifies key research gaps and proposes future directions for developing robust, printable, and sustainable geopolymer mortar systems for additive manufacturing in construction. Full article

Engineered bamboo composites (EBCs) are increasingly considered as sustainable alternatives to tropical hardwoods in structural applications. In jacking systems, performance is primarily governed by compression perpendicular-to-grain (bearing), although improper use may introduce flexural demands. This study evaluates the bearing and flexural behavior of Dragonwood, a commercial parallel strand bamboo (PSB), in comparison to Ekki (Lophira alata) through 120 full-scale tests. Dragonwood exhibited higher mean bearing capacity than Ekki, with yield stresses exceeding those of Ekki by over 60%, indicating strong potential for bearing-dominated applications such as in jacking. However, face-bonded specimens showed sensitivity to glue-line orientation, resulting in flexural strength reductions of up to 42% and undesirable shear failures. Increasing adhesive content and pressing pressure in the manufacturing process did not eliminate this behavior. Single-lift specimens removed the glue-line and showed improved failure behavior in flexure, although with reduced strength. The results demonstrate that manufacturing strategy heavily influences PSB performance. While single-lift Dragonwood products show the most potential, further testing under bearing is required before its suitability for jacking applications can be fully established. Full article

In the case of notched specimens, the introduction of additional stress relief holes (SRHs), or a local increase in the cross-section stiffness by means of composite overlays, decreases the stress level in the zone of the notch. The synchronous use of SRHs and composite patches has not been extensively investigated so far. Therefore, the main objective of the proposed research is to analyse the synergistic effect resulting from the simultaneous application of SRHs and structural reinforcement in the form of composite patches bonded to the bare steel element. The influence of this approach is investigated with the use of the finite element solution and experimental fatigue tests. As a result, a reduction in the stress concentration by almost 28% with respect to the bare plate with a hole was received. The use of composite overlays increases fatigue life by over 700% at the same cyclic tensile load in comparison with specimens without reinforcement and SRHs (base configuration). The use of reinforcement overlays or the synergetic application of overlays and SRHs guaranteed higher fatigue life (five and 10 times, respectively) at a higher load (by approximately 11%) compared to the base configuration. This confirmed the synergetic and positive influence of both modifications used in parallel. Full article

This study addresses the early-age brittleness and performance limitations of sustainable cement soil. While prior works optimized the baseline compressive strength using recycled sand and nanoclay, the multi-scale synergistic effects of fibers and nanomaterials on the post-peak deformation remain underexplored. To address this gap, a composite modification system incorporating recycled sand, nanoclay, polypropylene fibers, and graphene derivatives was developed. The experimental program comprised standard specimen fabrication, early-age curing, and unconfined compressive strength (UCS) testing, supplemented by RBF neural network curve fitting and quantitative ArcGIS digital image processing of scanning electron microscopy (SEM) micrographs. The results demonstrate that optimizing the fiber parameters (0.6% content with 6 mm length) successfully increases the early UCS to 2263.2 kPa, which is further elevated to a peak of 2755.0 kPa upon co-incorporation with 0.05% small-sized graphene oxide. Correspondingly, a newly introduced ductility index quantitatively confirms that the single-fiber reinforcement yields an index of 1.93, which is further enhanced to 2.02 by the graphene composite system. Microstructure tracking and digital image extraction revealed that the SEM-derived surface porosity decreased significantly, exhibiting a clear inverse relationship with the macroscopic mechanical strength. These quantitative microstructural shifts confirm that graphene effectively filled micropores and reinforced the fiber–matrix interface, establishing a dense matrix network with enhanced interfacial bonding. This multi-scale approach offers a sustainable strategy for green geotechnical applications. Full article

Fiber-reinforced polymer (FRP) composites provide an effective strengthening solution for timber members because of their high tensile capacity, low self-weight, corrosion resistance, and practical applicability in rehabilitation works. Although FRP strengthening of timber beams has been widely investigated, most available experimental evidence concerns softwood and glued-laminated systems, whereas comparatively limited data are available for dense tropical hardwoods used in marine and waterfront infrastructure. This study investigates the flexural behavior of Azobé (Lophira alata) hardwood beams strengthened with externally bonded carbon-fiber-reinforced polymer (CFRP) and glass-fiber-reinforced polymer (GFRP) laminates. The main contribution of this work is the application of externally bonded FRP strengthening to Azobé timber members intended for marina pontoon and related waterfront applications, where structural upgrading may be required to accommodate increased service loads. Mechanical characterization of the timber was first conducted through compression and tensile tests. Subsequently, nine beams were tested under three-point bending, including three un-strengthened reference beams, three GFRP-strengthened beams, and three CFRP-strengthened beams. The average ultimate load increased from 26.92 kN for the reference beams to 35.59 kN and 39.85 kN for the GFRP- and CFRP-strengthened beams, respectively. Statistical indicators, including standard deviation, coefficient of variation, standard error, confidence intervals, and two-sample t-tests, were included to account for the limited number of specimens and the natural variability of timber. CFRP exhibited the highest mean response within the present test series; however, the difference between the CFRP- and GFRP-strengthened beams is interpreted as an indicative experimental trend rather than a general statistical conclusion. No visible premature de-bonding was observed, and the strengthened specimens failed mainly by FRP rupture, suggesting bond engagement under the tested configuration. Nevertheless, bond behavior was not directly quantified using strain, slip, or interfacial measurements. The experimental results were also compared with analytical predictions based on the Italian guideline CNR-DT 201/2005 and with a simplified section-level interpretation. Overall, the findings indicate that externally bonded FRP laminates can provide a practical upgrading solution for existing Azobé timber members in marina pontoon and waterfront structures, while larger experimental series and direct bond/strain measurements are required for broader validation. Full article

To improve the operational efficiency of in situ soil remediation, this study investigated the operating parameters of the crushing–mixing working element of a novel tracked multi-axis in situ soil remediation device according to the soil contamination characteristics and process requirements. A DEM-based numerical simulation model was established, and response surface methodology (RSM) and machine learning algorithms were further integrated to model the response relationships, predict the evaluation indicators, and optimise the operating parameters. Single-factor experiments were conducted using the dispersion coefficient and soil fragmentation rate as the main evaluation indicators to determine the parameter range for the steepest ascent test. The steepest ascent test was used to rapidly approach the optimal parameter region, and RSM was then applied to establish the nonlinear mapping relationships between the operating parameters and response indicators. On this basis, machine learning models were introduced to further analyse and predict the experimental data, thereby improving the multi-objective optimisation process. A comparative analysis showed that, under the same dataset and evaluation metrics, the machine learning models achieved higher prediction accuracy than the RSM model. Among them, the decision tree model exhibited the best overall performance and provided a more stable optimisation result than the random forest and support vector regression models. The optimal parameter combination, identified by the decision tree model, was a rotational speed of 81 rpm, an average mixing pitch of 195 mm, a descent speed of 0.061 m/s, and an average mixing time of 1.1 s. Under this parameter combination, the dispersion coefficient was 0.171, and the residual bond count was 1511. The comparison of the RSM and machine learning models showed that the machine learning models achieved higher prediction accuracy. The relative errors between the optimal and actual simulation values were 2.56% and 4.92%, respectively. These results demonstrate that machine learning algorithms are applicable to the parameter optimisation of soil remediation working elements. The proposed DEM–RSM–machine learning framework can improve the efficiency and accuracy of equipment development and process optimisation, providing a scientific and technical basis for the development of intelligent agricultural equipment and sustainable agricultural engineering. Full article

Polyester (PET) fibers are widely used to reinforce asphalt materials; however, their smooth and hydrophobic surfaces limit interfacial bonding and restrict their reinforcing efficiency. This study develops an eco-friendly surface modification method based on the chemical modification of gallic acid (GA) and aminosilane (KH792) to enhance the compatibility between PET fibers and asphalt. Modified fibers with various molar ratios of GA/KH792 were prepared and incorporated into asphalt mastic. Their performance was evaluated using softening point, cone penetration, dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and bending beam rheometer (BBR) tests, combined with interfacial interaction analysis and scanning electron microscopy (SEM). The results show that surface modification significantly improves the reinforcing effect of PET fibers. In particular, the co-modified fiber with a GA/KH792 ratio of 1:1 exhibits the best performance, with increases of 27% in softening point and 105% in shear strength, as well as notable improvements in rutting resistance, fatigue performance, and temperature stability. Interfacial indices and SEM observations confirm enhanced adhesion, dispersion, and load transfer capacity. However, the improvement in low-temperature performance is limited. Overall, GA/KH792 chemical modification effectively enhances fiber asphalt interfacial interaction and provides a simple and sustainable approach for developing high-performance asphalt materials. Full article

Whether Kaldor’s three growth laws still operate in commodity-dependent middle-income economies—and through what transmission mechanism—is an open empirical question after three decades of trade liberalisation, financial opening, and the 2002–2014 commodity super-cycle. This paper provides the first bloc-level panel test of the three laws for the Andean Community of Nations (ACN—Bolivia, Colombia, Ecuador, and Peru) over 1993–2019, combining static feasible generalised regressions with dynamic Arellano–Bond difference-GMM and long-run multipliers. The predictions are as follows: manufacturing growth is positively associated with aggregate output (long-run multiplier 0.91), the Verdoorn coefficient is positive and significant at 0.42, and labour reallocation from non-manufacturing activities is associated with rising aggregate productivity over the time. The headline finding, however, is a decomposition failure: the Verdoorn and employment elasticities coefficients sum up to 0.35 rather than 1 as required by the accounting identity, leaving a residual of 0.65. We term this “jobless manufacturing growth” (capital-deepening). This suggests that the Kaldorian regime in the ACN has neither collapsed nor remained intact, but has mutated into a capital-intensive, labour-saving form consistent with Dutch-disease. Thus, industrial policy alone would deepen the jobless pattern: structural transformation in these economies requires pairing subsidy plans with the macroeconomic management of commodity-dependent exchange rates. Full article

This study evaluated the effectiveness of maleic anhydride polypropylene (MAPP) in improving the mechanical performance and interfacial adhesion of lignocellulosic fiber-reinforced polypropylene (PP) composites. Based on Scanning Electron Microscopy (SEM) investigations, the relationship between fiber fraction, MAPP content, mechanical characteristics, and fracture morphology was the main focus. The test results showed that the stiffness and tensile strength of the composites increased with the addition of MAPP. The esterification reaction between the anhydride groups of MAPP and the hydroxyl groups of the fibers strengthened the interphase covalent bond, with the 46:50:4 composition producing the highest elastic modulus of 79.67 MPa and maximum tensile stress of 11.01 MPa. The dense interphase zone, few gaps, and no dominant fiber tension were all confirmed by SEM morphology, and also indicated effective stress transfer from the PP matrix to the fibers. However, the toughness of the material decreased significantly with increasing stiffness. Due to strong plastic deformation in the PP matrix that is not tightly attached to the fibers, the composition without MAPP (30:70:0) shows high impact energy and breaking strain, reaching 25.39 kJ/m² and 121.26%, respectively. The increase in chemical bonding at 4% MAPP content limits the mobility of the polymer chains, making it more brittle. In addition, even though MAPP is still present in the system, increasing the fiber fraction above 60% causes agglomeration, decreased homogeneity, and increased voids due to limited matrix wetting, ultimately deteriorating the mechanical properties. Tensile stress and elastic modulus have a very strong positive correlation (R² = 0.93), while impact energy and strain have a good correlation (R² = 0.89). The results overall showed that the ideal MAPP dosage is in the range of 4% before interface saturation occurs and confirmed that MAPP efficiency is determined by the balance between fiber composition, MAPP quantity, and dispersion homogeneity. Full article