Search Results (2,942)

Gliders are engineless aircraft capable of maintaining altitude for extended periods and achieving long ranges. This paper presents an optimal aerodynamic design method for flying wing gliders, leveraging a combination of artificial neural networks (ANNs) as a surrogate model and genetic algorithms (GAs) for optimization. Data for training the ANN is generated using the vortex-lattice method (VLM). The study identifies optimal aerodynamic shapes for two objectives: maximum flight endurance and maximum range. A key finding is the inherent conflict between aerodynamic performance and static stability in tailless designs. By introducing a stability constraint via a penalty function, we successfully generate stable and high-performance configurations. For instance, the stabilized RG15 airfoil design achieves a maximum glide ratio of 24.1 with a robust 5.1% static margin. This represents a calculated 11.5% performance reduction compared to its unstable theoretical optimum, quantitatively demonstrating the crucial trade-off between stability and performance. The methodology provides a computationally efficient path to designing practical, high-performance, and inherently stable flying wing gliders. Full article

In this study, xanthan gum (XG)-modified coal-fly-ash-based cementitious materials were synthesized to realize the resource utilization of coal fly ash and to develop a low-carbon emission cementitious sealing material that can substitute cement-based sealing material to prevent coal fires. The optimal formulation for coal-fly-ash-based mining cementitious sealing material was developed using response surface methodology based on Box–Behnken Design. The optimized formulation was obtained with a coal fly ash-to-precursor ratio of 0.65, alkali-activator modulus of 1.4, and alkali-activator dosage of 7.5%. Under the optimal conditions, the initial and final setting time were 26 min and 31 min, respectively, fluidity was 245 mm, and the 7-day compressive strength approached 36.60 MPa, but there were still thermal shrinkage and cracking phenomena after heating. XG was then introduced to improve the thermal shrinkage and cracking of coal-fly-ash-based cementitious materials. Incorporating 1 wt.‰ XG was found to decrease the fluidity while maintaining the setting time and increasing the 1-day and 7-day compressive strength by 15.44% and 1.97%, respectively. The results demonstrated that the gels generated by XG cross-linking and coordinating with Al³⁺/Ca²⁺ were interspersed in the original C(N)-A-S-H gel network, which not only made the 1 wt.‰ XG modified coal-fly-ash-based cementitious material show minor expansion at ambient temperatures, but also improved the residual compressive strength, thermal shrinkage resistance and cracking resistance in comparison to unmodified cementitious material. However, due to the viscosity of XG and the coordination of Al³⁺ and non-terminal carboxyl groups in XG breaking the gel network, XG incorporation should not exceed 1 wt.‰ as the compressive strength and fluidity are decreased. Full article

The use of unmanned aerial vehicles (UAVs) in agricultural pest management has emerged as a promising alternative to conventional methods, particularly in challenging terrains. This study assessed the effectiveness of UAV-based versus ground-based bait spraying for controlling the olive fruit fly Bactrocera oleae in four regions in Greece (Larisa, Zakynthos, Trifillia, and Crete) over a four-year period (2021–2024). In each region, three olive orchards were selected: one received UAV-based bait applications, one was treated using standard ground-based bait application, and the third served as an untreated control. UAV applications were conducted using the M6E hexacopter, while ground treatments followed conventional protocols. Infestation levels were evaluated through systematic fruit sampling, assessing both overall and active infestations. Climatic and orchard data were also recorded to interpret variability in treatment outcomes. Results showed that both UAV and ground treatments significantly reduced infestation compared to the control. Active infestation ranged from 14.2–22.5% in control-untreated plots, 4.6–7.8% in UAV plots, and 5.3–8.4% in ground-treated plots. A significant year × treatment interaction indicated variable efficacy across years, with clearer treatment effects in 2021–2022. UAV applications were as effective or superior to ground spraying, especially in hard-to-reach areas. These findings support the integration of UAVs into pest management programs as a sustainable and efficient alternative for olive fly control. Full article

The volumetric Hirst method is considered a golden standard in aerobiology for determining particle number concentrations of bioaerosols. Using Hirst-type pollen and spore traps on mobile platforms (i.e., aircraft, cars, motorbikes, bicycles or carried by pedestrians) is anticipated to significantly enhance the spatial and temporal granularity of data for bioaerosol monitoring. Mobile sampling promises to enhance our understanding of bioaerosol dynamics, ecological interactions and the impact of human activities on airborne biological particles. In this article, we present the design and test of an airborne Hirst-type volumetric sampler. We followed a structured approach and incorporated the fundamental principles of the original design, while optimizing for size, weight, power and cost. Our portable Hirst-type volumetric sampler (FlyHirst) was attached to an ultralight aircraft, together with complementing instrumentation, and was tested for collection of atmospheric concentrations of pollen, fungal spores and hyphae. By linking the temporal resolution of the samples with the spatial position of the aircraft, using flight time, we calculated the spatial resolution of our measurements in 3D. In six summer flights over Denmark, our study revealed that the diversity of the recorded spores corresponded to the seasonal expectance. Urtica pollen was recorded up to 1300 m above ground (a.g.l.), and fungal spores up to 2100 m a.g.l. We suggest that, based on this proof-of-concept, FlyHirst can be applied on other mobile platforms or as a personal sampler. Full article

Autism spectrum disorder (ASD) encompasses a range of conditions, primarily marked by deficits in social behaviors, along with several comorbidities such as sleep abnormalities and motor dysfunction. Recent studies have identified genetic risk factors associated with ASD, including the CAMK4 (calcium/calmodulin-dependent protein kinase 4). However, the molecular mechanisms linking CAMK4 dysregulation and ASD-associated phenotypes remain poorly understood. Here, we used Drosophila melanogaster as a model system to investigate ASD-associated phenotypes in flies with dysregulated CaMKI, the fly homolog of mammalian CAMK4. We show that CaMKI manipulations affect sleep, circadian rhythmicity, and social behavior. Consistent with the higher prevalence of dementia observed in autistic patients, we also observed a significantly enhanced behavioral decline in motor performance and dendritic degeneration in flies expressing RNAi-based CaMKI knockdown in flight motoneurons, suggesting a link between developmental and degenerative processes. As aberrant synaptic pruning is hypothesized to underlie the synaptic phenotypes observed in brains of autistic patients, we examined synaptic phenotypes following CaMKI manipulations using the larval neuromuscular junction (NMJ) and observed miswiring phenotypes suggesting aberrant synaptic refinement. We performed shotgun mass-spectrometry proteomics and identified various molecular candidates, particularly molecules involved in cytoskeleton regulation and chemorepulsion, likely to regulate the phenotypes described here. Thus, our results suggest that CaMKI plays a role in developmental processes and influences aging-dependent degenerative processes, possibly providing mechanistic insight into the genetic basis of ASD etiology and the development of effective treatments. Full article

Background: Scientific research on fly-in/fly-out (FIFO) workers has identified a gap in understanding the dynamics of job stress parameters among forest workers throughout the shift cycle. Methods: This study investigated the relationship between psychological and psychophysiological parameters of job stress and work capacity among loggers. The research was conducted during two simultaneous scientific expeditions in July 2024, involving 47 loggers from two teams with differing socio-psychological characteristics. Data were collected daily (morning and evening) using a battery of psychophysiological and psychological tests. Teams’ socio-psychological characteristics were assessed five times during the 15-day fly-in period. Results: The adaptation (beginning) and fatigue (end) phases of the shift were significantly more stressful than the middle period. During these critical phases, assessments of functional state showed greater consistency but were less favorable. Key findings indicate a psychological mobilization effect at the period’s start, where high subjective comfort coexisted with physiological strain. By the end, functional capabilities were maintained despite high fatigue. Furthermore, loggers in teams with a positive socio-psychological climate exhibited a more favorable functional state throughout the shift. Conclusions: The study’s novelty lies in its comprehensive mapping of the dynamic interplay between job stress and work capacity across the FIFO cycle, using both instrumental and questionnaire-based methods. The results underscore the critical influence of the team’s socio-psychological climate on worker well-being and highlight specific high-stress phases that warrant targeted interventions. Full article

Coal-based solid wastes are used for carbon fixation, which can achieve the dual purpose of resource utilization of coal-based solid wastes and CO₂ storage, but carbon fixation has a negative impact on the rheological properties of filling slurry. This paper explores the effect of carbon fixation time on the carbon fixation performance and rheological properties of coal gangue (CG)–fly ash (FA) composite filling materials (CFS) through rheometer, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and other testing methods. The results show that, with an increase in the carbon fixation time, the carbon fixation amount of the CFS shows a trend of increasing first and then stabilizing. Considering the carbon fixation amount and rheological properties of the CFS together, the optimal carbon fixation time is 2 h. At this time, the carbon fixation amount of the CFS is 1.18%, and the yield stress and plastic viscosity are 155.93 Pa and 0.17 Pa·s, respectively. However, with a further increase in the carbon fixation time, the carbon fixation amount basically tends to be stable, mainly because the calcium ions in the CFS are gradually consumed by the reaction as the carbon fixation time increases. The research results are of great significance for improving the utilization of coal-based solid waste and CO₂ storage. Full article

Flying-wing aircraft based on high-aspect-ratio wings are a popular configuration for many aerospace engineering applications. Cracked (or cross) control surface structures can adjust the aerodynamic characteristics of flying-wing aircraft. Deep investigations into the effects of such a control surface can provide a helpful design foundation. This paper investigates the mass distribution influences of cracked control surfaces on gust responses of high-aspect-ratio flying wings. Validated finite element modelling, revised by detailed ground vibration test (GVT) with a frequency error of less than 10%, reveals that root boundary conditions significantly affect the natural modes and frequencies of present wings with cracked control surfaces. Changes in control surface (CS) mass have a critical impact on gust response: a 150 g increase in CS mass results in a 15–22% increase in peak response acceleration and a 25–30% increase in response duration, while redistributing mass to the outboard CS reduces the peak response by 18–26% while keeping the total mass consistent. The results can provide an effective suppression strategy for the gust responses of flying-wing configurations without redesigning the main structure. Full article

This article presents the results of a rockfall analysis conducted for the limestone walls of a former quarry that is now used as an urban park. The performed simulations (2D statistical analysis using Rigid Body Impact Mechanics—RBIM and Discrete Element Modelling—DEM) enabled the determination of the maximum displacement range during the ballistic phase and the maximum rebound height at the slope base, which facilitated the delineation of a safe land-use zone. A hazard zone was also identified, within which public access must be strictly prohibited due to the risk posed by flying debris. Based on slope stability assessments (safety factor values and rockfall trajectories), recommendations were formulated for slope reinforcement measures and appropriate management actions for designated sections to ensure safe operation of the site. Three mitigation strategies were proposed: (1) no protective measures, (2) no structural reinforcements but with installation of a rockfall barrier, and (3) full-scale stabilisation to allow unrestricted access to the quarry walls. The first option—leaving slopes unsecured with only designated safety buffers—is not recommended. Full article

This study investigates the impact of particle size in fly ash derived from different coal sources on the performance of fly ash–cement systems. Utilizing a newly developed flotation classification method, physical properties of fly ash were examined to reveal variations among different particle sizes and coal sources. Thermal analysis was employed to analyze the calcium hydroxide content’s effect on the cement system, while selective dissolution methods were used to assess reaction rates. XRD analysis confirmed particle size effects. Results indicate that flotation classification optimizes the properties of fly ash, enhancing activity and flow values, where some of the ash fractions exhibit overall superior properties. The use of high-volume fly ash (50% fly ash replacement) promotes continued pozzolanic reactions, especially with smaller particle sizes. Reaction rates decrease with larger particle sizes, emphasizing the importance of classification. XRD analysis further supports these findings, revealing that smaller particle sizes favor cement hydration and pozzolanic reactions. Overall, this study provides insights into optimizing fly ash properties for enhanced concrete performance. Full article

Old airplanes produced in the 1970s are still flying, while being exposed to various new types of detriments, leading to a need to repair them to enable the safe use of the airborne body. The present state of the art advocates the use of laminated composite to repair aluminum parts due to their effective durability. The studies presented in the literature mainly focused on bodies under tensile loads. It seems that shear-type loading appearing in the fuselage of airplanes when being under torsion has been ignored in literature. Therefore, to fill this gap, the present study investigates the behavior of defective aluminum panels under pure shear. The present investigation uses a novel finite element (FE) method of modelling the loaded body by 2D and 3D elements. Then, the model is used to calculate the influence of various parameters, like the size of the repair patch, overlaps, sequences of the laminated composite plate, and other structural properties on the stability and strength of the examined part. To validate the numerical predictions, tests were performed on typical elements. Based on the experimental results, the fidelity of the FE model was assessed and the method approach of repairing using composite patches was validated. The main conclusion from the present study is the use of solid (3D) elements, over shell (2D) elements, due to their high-fidelity results. Full article

As a key connection technology in prefabricated buildings, offshore wind power, and bridge engineering, the performance and environmental sustainability of grouted sleeve connections are essential for the long-term development of civil infrastructure. To address the environmental burden of conventional high-strength cement-based grouts, an eco-friendly sleeve grouting material incorporating industrial solid waste was developed. In this study, silica fume (15%) and fly ash (5%) were employed as supplementary cementitious materials, while nanosilica (NS) was introduced to enhance the material properties. Mechanical testing, microstructural characterization, and half-grouted sleeve uniaxial tensile tests were conducted to systematically evaluate the effect of NS content on grout performance. Results indicate that the incorporation of NS significantly accelerates the hydration of silica fume and fly ash. At an optimal dosage of 0.4%, the 28-day compressive strength reached 105.5 MPa, representing a 37.9% increase compared with the control group without NS. In sleeve tensile tests, specimens with NS exhibited reinforcement necking failure, and the load–displacement response closely aligned with the stress–strain behavior of the reinforcement. A linear relationship was observed between sleeve wall strain and reinforcement stress, confirming the cooperative load-bearing behavior between the grout and the sleeve. These findings provide theoretical guidance and technical support for developing high-strength, low-impact grouting materials suitable for sustainable engineering applications. Full article

Heat-curing processes are often used to ensure the production rate of precast concrete elements, as this process increases the early strength of the material. However, the increase in curing temperature can negatively affect the final mechanical properties since cracking, and especially high porosity, may occur under these conditions. In order to compensate for the expected loss in mechanical and durability-related properties, the cement content is typically increased. This solution raises the cost of the final product and reduces its sustainability. Thus, in this study, the development of expansive self-compacting concretes (SCCs) is proposed to achieve higher final mechanical properties without increasing cement contents. The mechanical properties, expansive performance, and porous microstructure have been evaluated under different curing regimes. The obtained results show that it is possible to obtain similar or even better mechanical performance in expansive concretes cured at high temperatures than in those cured in standard conditions, particularly when using ettringite-based expansive agents (EAs). Moreover, the use of limestone filler (LF) proved to be more suitable than the use of fly ashes in the working conditions evaluated in the present study. In this sense, the compressive strength at 28 days of SCC with LF and ettringite-based EAs is 4.3% higher than the one obtained under standard curing; moreover, the total porosity is reduced (5%), and the drying shrinkage is also limited. These aspects have not been previously reported in non-expansive heat-cured concretes and represent a unique opportunity to reduce the cement content and, therefore, the carbon footprint of precast concretes without reducing their mechanical properties. When using CaO-based EAs, the results are also better than those of non-expansive SCC, although the improvement is less pronounced than in the previous case. Full article

The civil construction and infrastructure sectors are known for their high environmental impact. Most of this impact is related to the carbon dioxide (CO₂) emissions from Portland cement. As a sustainable alternative, alkali-activated binders (AABs) are explored for their potential to replace traditional binders. This research focused on AAB formulations using steel industry byproducts, such as Baosteel’s slag short flow (BSSF), coke oven ash (CA), blast furnace sludge (BFS), and centrifuge sludge (CS), as well as fly ash (FA) from a thermoelectric plant. Byproducts were characterized through laser granulometry, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), followed by the formulation of AABs with different precursor ratios. After 28 days, the compressive strength was obtained for each formulation. Based on the compressive strength tests, two binary mixtures were selected for microstructural and chemical analyses through XRF, FTIR, and SEM. CA demonstrated the greatest potential for use in binary AABs based on BSSF, as it presented a higher source of aluminosilicates and smaller particle sizes. The formulations containing BSSF and CA achieved compressive strengths of up to 9.8 MPa, while the formulations with BSSF and FA reached 23.5 MPa. SEM images revealed a denser, more cohesive matrix in the FA-based AAB, whereas CA-based AABs showed incomplete precursor dissolution and higher porosity, which contributed to the lower mechanical strength of CA-based AABs. These findings highlight the critical role of precursor selection in developing sustainable AABs from industrial byproducts and demonstrate how different formulations can be tailored for specific applications. Full article

Considering the current requirement for high temperatures and the significant energy consumption in the preparation of geopolymer-based cements, this paper presents a study on the compressive strength of metakaolin-based geopolymers containing various low-calcium fly ash admixtures, prepared at room temperature (25 ± 2 °C). The physical properties and microstructure of the geopolymers were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The type of alkaline cations, phase transformation, evolution of characteristic functional groups, and hydration characteristics of the microstructures were analyzed, and the hydration mechanism is discussed. The experimental results indicated that the fly ash content had a more significant impact on compressive strength than the alkaline cation type (Na⁺/K⁺). The optimal formulation (20% fly ash with 20% KOH activator) reached a compressive strength of 76.70 MPa at 28 days, which was around 6% higher than that of the NaOH-activated counterpart (72.34 MPa). Crystalline phase analysis in the transformation of mullite and microstructure analysis indicated that the increase in compressive strength could be attributed to the effective filling of the matrix interface by chemically inert fillers and the dense N-A-S-H and C-(A)-S-H multi-dimensional gel structures. These experiments prove the feasibility of using fly ash and metakaolin to prepare geopolymer materials with high compressive strength at room temperature. Full article