Search Results (36)

Emotional processes and sleep quality have become fundamental aspects of performance in Paralympic sports among elite and youth athletes. The objective of this study was to compare levels of depression, stress, anxiety, and sleep quality among youth and adult athletes with cerebral palsy (CP) belonging to the national CP Football team in Chile. A total of 10 adult and 12 youth national team athletes participated, completing the DASS-21, Pittsburgh Sleep Quality Index, and Epworth Sleepiness Scale questionnaires. The athletes were competing in their respective categories at the 2024 Parapan American Games. A cross-sectional design was used to compare the parameters of depression, stress, anxiety, and sleep quality of youth and adult male athletes with CP of a national team selected to compete in a regional event. Significant differences were found where young athletes had lower levels of depression (χ² = 4.77, p = 0.02, OR = 11.0) and anxiety (χ² = 6.71, p = 0.01, OR = 16.5). Similar differences could be observed in favor of young athletes in sleep latency (p = 0.04; d = 0.34), bedtime (p = 0.02; d = 0.20), total hours of sleep (p = 0.04; d = 0.10), subjective sleep quality (p = 0.002; d = 0.56), and objective sleep quality (p < 0.001; d = 0.65). This study suggests that adult para-athletes from a national CP Football team exhibit higher levels of depression and anxiety compared to their youth counterparts. Additionally, objective and subjective measures show that adults experience poorer sleep quality. These findings highlight the need for targeted interventions by psychological support teams, aiming to enhance athlete performance by promoting healthy habits that address these mental health challenges. Full article

Aluminum alloys, serving as critical structural materials in the aviation and aerospace industry, frequently endure variable amplitude loading under complex service conditions. The resulting non-steady-state crack propagation behavior directly impacts structural safety. This study considers the engineering application requirements of the 7055-T7751 aluminum alloy and conducts fatigue crack growth experiments on compact tensile specimens subjected to constant amplitude loading and periodic variable amplitude overloading conditions. The findings indicate that the 7055 aluminum alloy exhibits an instantaneous acceleration period under tensile overload, which is important in the comprehensive analysis of crack growth life. The experimental findings show no significant correlation between post-overload minimum crack growth rate deviation and thickness or crack size at overload, where the values are 50.3% and 94.8% at 1.4 and 1.7 R_OL, respectively. An analytical model for the crack growth increment a_ii during this period was developed. Additionally, the delay distance influenced by overloads a_d and the number of delay cycles N_d are identified as effective parameters for evaluating the retardation effects induced by overloading. Our comparative analysis of crack growth experimental data under varying overload ratios R_OL and specimen thicknesses B revealed that existing plastic zone models inadequately assess a_d, prompting the establishment of a corresponding evaluation model. By incorporating the parameters a_ii and a_d into the Wheeler model, a method for calculating the delay cycles N_d was constructed, which effectively captured the variation trend. Finally, an analysis of fractography revealed numerous secondary cracks within the overload damage zone, and the ductile fracture characteristics in this region were significantly weaker compared to areas subjected to fatigue loading. Full article

Aluminum alloy laminates have extensive applications in protective armor systems. A simulation-based approach was employed to investigate the anti-penetration performance of aluminum alloy laminates with different configurations. Experiments were carried out to study the mechanical properties of 7055 and 7075 aluminum alloys, and a J-C constitutive model was established for the 7055/7075 aluminum alloy laminate. Based on the J-C constitutive model, numerical simulation was performed to assess the anti-penetration performance of an aluminum alloy laminate with various configurations. Velocity curves during the projectile penetration process were obtained. The simulation results show that the four-layer laminate exhibits superior anti-penetration performance compared to the two-layer laminate. The four-layer laminate with the 7055/7075/7075/7055 configuration demonstrates optimal anti-penetration performance. Full article

Artificial neural network-(ANN) simulation models have been successfully applied in various fields, including agricultural sciences. This study evaluated the applicability of an artificial neural network for predicting water distribution uniformity in medium-sized sprinklers under varying wind conditions. Using data from 74 field tests, the ANN was developed and trained through supervised learning to optimize its predictions. The water distribution patterns simulated by the ANN closely mirrored observed field data, with 50% of the test set classified as ‘optimal’ in the highest reliability category. Statistical analyses indicated that the ANN performance was not significantly influenced by operating pressure, wind speed, or direction, underscoring its reliability across diverse scenarios. Furthermore, the ANN performed robustly in estimating the Christiansen uniformity coefficient, with statistical indices demonstrating excellent performance (r = 0.9475, d = 0.9689, and c = 0.9181), classifying the results as ‘optimal’. Linear regression analysis further confirmed the model’s robustness, with a slope close to 1 (0.988 ± 0.053) and a mean absolute deviation of 4.33%, indicating high accuracy in the simulations. These findings suggest that the trained ANN provides an accurate and efficient alternative to extensive fields. Full article

In this paper, a one-step hot extrusion dual-stage solution treatment method is employed to fabricate high-strength and tough T-shaped complex cross-section 7055 (Al-Zn-Mg-Cu-Zr) alloy profiles, and a detailed investigation is conducted on the microstructure and mechanical properties. The results indicate that the comprehensive mechanical properties of the 7055 aluminum extruded alloy using the two-stage solution aging treatment are excellent. This is particularly evident in the balance between strength and ductility, where outstanding strength is accompanied by a plasticity that is maintained at 13.2%. During the extrusion process, the deformation textures are mainly composed of brass and copper, forming a 15.1% recrystallization texture Cube. In addition, the equilibrium phase η(MgZn₂) precipitated in the grain is the main strengthening phase, and there are large discontinuous grain boundary precipitates at the grain boundary, which hinders the grain boundary dislocation movement and has great influence on the mechanical properties of alloy materials. Full article

Unique friction-based self-piercing riveting (F-SPR) was employed to join high-strength, low-ductility aluminum alloy 7055 for lightweight vehicle applications. This study aimed to maximize the joint strength of the AA7055 F-SPR joint while avoiding cracking issues due to low ductility at room temperature. A fully coupled Eulerian–Lagrangian (CEL) model was employed to predict the process temperature during F-SPR, and the temperature field was then mapped onto a 2D axisymmetric equivalent model for accelerated numerical analysis. The geometry, dimensions, and material strength of the rivet, as well as the depth of the die cavity and plunging depth, were investigated to enhance joint formation. Also, a static finite-element analysis model was developed to predict and analyze the stress distribution in the rivet under different mechanical testing loading conditions. Overall, the numerical model showed good agreement with the experiment results, such as joint formation and mechanical joint strength. With the aid of virtual fabrication through numerical modeling, the joint design iterations and process development time of F-SPR were greatly reduced regarding the goal of lightweight, high-strength aluminum joining. Full article

Although 7055 aluminum alloy is a deformed aluminum alloy and shows excellent mechanical properties after recrystallization and large deformation, through this method, its application range is enriched if rare earth is added, and the rare earth phase dispersion is promoted by heat treatment. This article used optical microscopy, scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), micro Vickers hardness, and room temperature stretching methods to study the as-cast 7055-xEr (x = 0 wt.%, 0.2 wt.%, 0.4 wt.%, 0.6 wt.%, 0.8 wt.%) aluminum alloy after being subjected to 460 °C × 3 h homogenization and 410 °C × 1 h solid solution + 150 °C × 12 h aging treatment for the changes in its microstructure and properties. The results indicated that: when 0.2 wt.%Er was added to 7055 aluminum alloy after a solution at 410 °C × 1 h and aging at 150 °C × 12 h, the dendrite structure was significantly reduced, the grain thinning was obvious, and the distribution was uniform; the Al₈Cu₄Er phase appeared in the lamellar eutectic η-Mg(Zn,Al,Cu)₂ structure at grain boundaries, and the hardness reached 168.8 HV. The yield strength, tensile strength, and elongation were 542.12 MPa, 577.67 MPa, and 8.36%, respectively. Full article

The 7055 aluminum alloy is an ultra-high strength aluminum alloy, which is widely used in the aerospace field and new energy automobile manufacturing industry. As it retains high strength, its plastic deformation ability needs to be improved, which limits its application in plastic processing. In this study, the cast grains of the 7055 aluminum alloy were refined by adding Sm + Er, and the proper heat treatment procedure was utilized to further precipitate the rare earth phase in order to increase the alloy’s strength and toughness. The grain size, microstructure and phase were characterized by optical microscopes (OMs), scanning electron microscopy—energy spectrum (SEM-EDS) and a XRD diffractometer (XRD). The macroscopic hardness, yield strength and tensile strength of alloy materials were measured by a hardness meter and universal electronic tensile machine. The results showed that the as-cast sample and the heat treatment sample all contained Al₁₀Cu₇Sm₂ and Al₈Cu₄Er rare earth phases. But, after heat treatment, the volume percentage of the rare earth phase dramatically increased and the dispersion was more unified. When 0.3 wt.%Sm and 0.1 wt.%Er were added, the grain size could be refined to 53 μm. With the increase in the total content of rare earth elements, the refining effect first increased and then decreased. Under 410 °C solid solution for 2 h + 150 °C and aging for 12 h, the macroscopic hardness, yield strength, tensile strength and elongation of 0.3 wt.%Sm + 0.1 wt.%Er + 7055 as-cast samples were 155.8 HV, 620.5 MPa, 658.1 MPa and 11.90%, respectively. After the addition of Sm and Er elements and heat treatment, the grain refinement effect of 7055 aluminum alloy was obvious and the plastic property was greatly improved under the premise of maintaining its high-strength advantage. Full article

Microbial fuel cells have undergone several modifications since their creation, mainly due to the different substrates that can be used as fuel for the generation of electrical energy. In this research, a deep and updated analysis of the characteristics of the literature published in the Scopus database from 1990 to 30 December 2022 has been carried out, finding 7055 documents indexed. The most used keywords are microbial fuel cells, performance, and electricity generation. From 2011 to the present, 5289 article-type documents were published; the article entitled “Microbial Fuel Cells: Methodology and Technology” by Logan B. E. et al., 2006 from Pennsylvania State University, USA in the Environmental Science and Technology journal of the ACS publisher was the most cited (4496 citations). On the other hand, in recent years, Chinese universities have begun to produce and highlight a number of documents positioning in the top ten, with six universities having the greatest presence in publications and as the country with the highest number of published and indexed documents (2773) in Scopus. Research on microbial fuel cells tends to grow, with China as a leading country on the subject, written by the author Wang X. It is observed that the new cell research trends deal with the modification and fabrication of electrodes with nanomaterials in order to improve their power and reduce costs to show their viability on a larger scale. Full article

Aluminum alloy 7075 (with 7055 and 7150 filler wires) was welded using a digital welding machine that can switch arc mode between MIG, CMT and CMT+P modes. The transverse-motion weldability test of joints welded under different arc modes showed that the solidification cracking susceptibility was lower in CMT-technique-based welds than in MIG welds. The temperature cycle of the welding pool under different arc modes was recorded using mini-thermocouples, which showed that the cooling rate was lower in CMT welded samples than in MIG welded samples. The low cooling rate promoted the growth of α-Al dendrites through the back diffusion effect. Electron probe micro-analysis showed that micro-segregation of the α-Al dendrites was lower in the CMT welded samples than in the MIG welded samples. The T-(f_Al)^1/2 curve of each weld was calculated, which showed that CMT-based welding enhanced the bridging of adjacent α-Al dendrites, reducing the tendency for solidification cracking. Full article

The casting table with lubricating oil and wiper is applied simultaneously to produce super-high-strength 7055 aluminum alloy (Al7055) ingots, and 30 T Al7055 ingots with a diameter of 582 mm were cast successfully. In this study, the microstructure and macrosegregation of the ingots were investigated using an optical microscope (OM). The research results show that the hydrogen content in the liquid metal can be decreased from 0.198 mL/100 g Al to 0.103 mL/100 g Al when three rotors are used in the degassing tank. Compared with the conventional hot-top casting table, the surface quality can be improved by using the casting table with oil lubrication. The temperature gradient between the ingot center and edge can be decreased by using the wiper during the casting process from 320 °C to 150 °C, the cracking tendency caused by the ingot temperature gradient can be decreased, the segregation layer thickness is decreased by about 87%, and the ingot can be homogenized at a high temperature by using the heat of the feed itself. Full article

The evolution behaviors of the second phase, substructure and grain of the spray-deposited 7055 aluminum alloy during hot compression at 300~470 °C were studied by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results show that the AlZnMgCu phase resulting from the deposition process dissolves gradually with the increase in deformation temperature, but the Al₇Cu₂Fe phase remains unchanged. The plastic instability of the spray-deposited 7055 aluminum alloy occurs at 470 °C with a 1~5 s⁻¹ strain rate range. Partial dynamic recrystallization (PDRX) adjacent to the original high angle grain boundaries (HAGBs) not only occurs at 300~400 °C with the low strain rates ranging from 0.001 to 0.1 s⁻¹ but also at 450 °C with a high strain rate of 5 s⁻¹. Continuous dynamic recrystallization (CDRX) appears at 450 °C with a low strain rate of 0.001 s⁻¹. The primary nucleation mechanism of PDRX includes the rotation of the subgrain adjacent to the original HAGBs and the subgrain boundary migration. The homogeneous misorientation increase in subgrains is the crucial nucleation mechanism of CDRX. At 300~400 °C, the residual coarse particle stimulated (PSN) nucleation can also be observed. Full article

Methods used to monitor variation in population sizes in both Atlantic salmon and anadromous brown trout (sea trout) have been widely used in Norway the last 20 years. However, a national management regime, based on population data, has only been established for one of the two species, the Atlantic salmon. One prerequisite for using this “one species” model is that there is negligible interspecific competition between salmon and trout in the rivers. This may, however, be an oversimplification of the real situation. The pre-fishery abundance (PFA), monitored with combination of underwater video systems, snorkelling counts, and catch statistics will, in most rivers, include both salmon and Sea Trout. In the present study, we estimated a total PFA for rivers, or groups of rivers, in eight regions in Norway in 2019. The total size of each river system was measured by abiotic factors such as river area, river length, annual mean water flow, and size of precipitation field; additionally, one biotic factor, smolt age, was used to standardise PFA data across regions. A comparison shows that the standardised total PFA of salmon and trout varies across regions where the highest estimated PFA was four times higher than the lowest. Compared to the traditional one-species approach, the merged PFA data show a different population status in the eight regions. The difference in the two approaches was mainly linked to the variation in size in anadromous brown trout populations. Merging data from salmon and trout populations in defined regions may be a better input in a management model than the current model used by the Norwegian Scientific Committee for Salmon Management (VRL). Full article

Fatigue cracks are a major defect in metal alloys, and specifically, their study poses defect evaluation challenges in aluminum aircraft alloys. Existing inline inspection tools exhibit measurement uncertainties. The physical-based methods for crack growth prediction utilize stress analysis models and the crack growth model governed by Paris’ law. These models, when utilized for long-term crack growth prediction, yield sub-optimum solutions and pose several technical limitations to the prediction problems. The metaheuristic optimization algorithms in this study have been conducted in accordance with neural networks to accurately forecast the crack growth rates in aluminum alloys. Through experimental data, the performance of the hybrid metaheuristic optimization–neural networks has been tested. A dynamic Levy flight function has been incorporated with a chimp optimization algorithm to accurately train the deep neural network. The performance of the proposed predictive model has been tested using 7055 T7511 and 6013 T651 alloys against four competing techniques. Results show the proposed predictive model achieves lower correlation error, least relative error, mean absolute error, and root mean square error values while shortening the run time by 11.28%. It is evident through experimental study and statistical analysis that the crack length and growth rates are predicted with high fidelity and very high resolution. Full article

The chlor-alkali industries produce caustic soda (NaOH), chlorine (Cl₂), and hydrogen (H₂) as primary products. In 2021, the global chlor-alkali market was valued at $63.2 billion. The article evaluates the global aspects of chlor-alkali industries and prospects for Bangladesh. The current production capacity of NaOH from the chlor-alkali industries in Bangladesh is around 282,150 metric tons/year (MT/y). The by-products, chlorine (Cl₂) of 250,470 MT/y and hydrogen (H₂) of 7055 MT/y, are produced domestically. The local demand of Cl₂ is 68,779 MT/y. However, there are no systematic utilizations of the residual Cl₂ and vented H₂, which threatens the sustainability of the chlor-alkali industries. The article prefigures that a 150,000 MT/y PVC plant can utilize 45.2 % of residual Cl₂ of chlor-alkali plants, which would be an economical and environmental milestone for Bangladesh. The residual Cl₂ can earn revenue of 908 million USD/y, which can be utilized to import ethylene. For the sustainable utilization of vented H₂, production of H₂O₂, fuel cell electric vehicle (FCEV) and H₂ fuel-cell-based power plant are the feasible solutions. Thus, for the long-term growth of the chlor-alkali industry in Bangladesh and other developing countries, systematic utilization of Cl₂ and H₂ is the only feasible solution. Full article