Abstract ：

This paper proposes a novel wall-type self-centering slip friction damper (WSCSFD), which mainly comprises of the grooved T-shape and L-shape plates that are combined by stacked disc springs. The damper resists shear forces arising from the inter-story drifts under earthquakes. By leveraging the variable friction mechanism and the pre-compressed disc springs, the WSCSFD can provide self-centering capability and energy dissipation capacity. The configuration and working mechanism of WSCSFD were first discussed. And then, the theoretical equations governing the force-displacement relationship were derived. One reduced-scale damper specimen was fabricated to conduct the proof-of-concept tests. The test results validated the deformation mode and cyclic behavior of the WSCSFD. The hysteretic parameters related to seismic applications were quantified and discussed. To complement the experimental observations and gain a further understanding of the local behavior, three-dimensional finite element (FE) models were established in ABAQUS. Finally, to address the deficiencies of the damper specimen, some potential improvement approaches were suggested and evaluated through the validated FE models.

Keyword ：

Experimental test Wall-type damper Numerical simulation Variable friction Self-centering

Cite：

Copy from the list or Export to your reference management。

Abstract ：

This study investigates surface erosion wear caused by collision and friction between propellers and sand particles during the flight of propeller transport aircraft in harsh environments like deserts and plateaus, which are characterized by strong sand and wind conditions. Firstly, the erosion behavior of individual propeller blades is analyzed under various sand particle parameters using the commercial software FLUENT. Subsequently, dynamic simulations of the entire blade are conducted by the sliding mesh method to examine erosion patterns under different operational conditions, including rotation speed and climb angle. Finally, the impact of erosion on the aerodynamic characteristics of the propeller is obtained based on simulation results. This study delves into the erosion patterns observed in large aircraft propellers operating within sandy and dusty environments, as well as the consequential impact of propeller surface wear on aerodynamic performance. By elucidating these phenomena, this research provides valuable insights that can inform future endeavors aimed at optimizing propeller design.

Keyword ：

Erosive wear behavior Aircraft propellers Aerodynamic characteristics

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The present study develops a novel type of active joint node-bolt fasten wedge (BFW) active joints, aiming to investigate the loadbearing capacity of a BFW joint in a quantitative way and put forward precise formulas for its yield load and compression rigidity. To achieve this, indoor axial loading tests were conducted on two BFW joints, accompanied by a set of numerical simulations with the finite element approach implemented in ABAQUS. Parametric research was then conducted to assess the impact of various factors on the yield load and initial compression rigidity of BFW joints, leading to the derivation of precise calculation formulas for accurate prediction of these parameters. The key findings indicate that enhancing the bolt strength from 10.9 to 12.9 significantly improves mechanical performance. Under axial compression, the final bearing force, yield load, and initial compression rigidity increase by 0.86, 1.06, and 0.15 times, respectively. Numerical models accurately predict joint behavior under axial force, confirming their reliability. Parameter studies reveal that increasing web and eaves thickness, bolt strength, and diameter improves bearing capacity, while splint thickness has little effect. The fitting formulas introduced can precisely estimate yield load and rigidity, providing practical value for engineering applications.

Keyword ：

Finite element analysis (FEA) BFW Yield load Load-bearing capacity Compression rigidity Parametric analysis

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Retinal diseases such as age-related macular degeneration and diabetic macular edema will lead to irreversible blindness without timely diagnosis and treatment. Optical coherence tomography (OCT) has been widely utilized to detect retinal diseases because of its non-contact and non-invasive imaging peculiarities. Due to the lack of ophthalmic medical resources, automatic analyzing and diagnosing retinal OCT images is necessary with computer-aided diagnosis algorithms. In this study, we propose a lightweight retinal OCT image classification model integrating convolutional neural network (CNN) and Transformer to classify various retinal diseases with few parameters of the model. Local lesion features extracted by CNN can be encoded with the whole OCT image through the Transformer, which improves the classification ability. A convolutional block attention module is also integrated into our model to enhance the representational power. Compared with several classical models, our model achieves the best accuracy of 0.9800 and recall of 0.9799 with the least number of parameters and prediction time for an image on the OCT-C8 dataset. Moreover, on the OCT2017 dataset, our model outperforms the four state-of-the-art models except almost equal to another, achieving an average accuracy, precision, recall, specificity and F1-score of 0.9985, 0.9970, 0.9970, 0.9990, and 0.9970. Simultaneously, the number of parameters of our model has been reduced to just 1.28 M, and the average prediction time for an image is only 2.5 ms. © 2024 Elsevier Ltd

Keyword ：

Ophthalmology Optical coherence tomography Convolutional neural networks

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The primary challenge of applying partial denitrification/anammox (PD/A) to municipal wastewater treatment lied in the enrichment of functional bacteria with a considerable autotrophic nitrogen removal performance. The results showed influent NO3−-N: NH4+-N, reaction time and temperature would influence anammox nitrogen removal contribution. 15N isotopic tracing technology further revealed the average anammox contribution rate was up to 94.8 %. Extending reaction time was an effective measure to improve simultaneously PD and anammox activity. Microbial community indicated partial denitrifying bacteria (Bacillus) and anammox bacteria (Candidatus Brocadia) were enriched with abundance of 27.27 % and 7.09 % at NO3−-N: NH4+-N of 1:1. The correlation analysis showed that NO3−-N: NH4+-N ratio played the positive role for Bacillus enrichment, and low temperature was favorable to the enrichment of Thauera and Candidatus Jettenia. Overall, this study demonstrated the reasonable operational strategy would strengthen anammox contribution and facilitate enrichment of functional bacteria. © 2024

Keyword ：

Denitrification Wastewater treatment

Cite：

Copy from the list or Export to your reference management。

Abstract ：

In cobalt-based catalyst/peroxymonosulfate (PMS) systems, the key issues are the leaching of metals and the stability of catalysts. In this study, a NH2-UiO-66 cladded CoZn/NC catalyst was synthesized for efficient degradation of sulfamethoxazole (SMX) using activated PMS. The removal efficiency of SMX could achieve 100% within 30 min. The leaching of Co2+ was inhibited to 0.05 ppm and the anti-interference and cyclic stability of the catalyst were enhanced by the NH2-UiO-66 shell. In addition, the quenching experiment, electron paramagnetic resonance (EPR) technique and probe experiment were used to analyze the reactive oxygen species (ROSs) qualitatively and quantitatively. The findings demonstrated that singlet oxygen (1O2) had the highest steady-state and cumulative concentration. However, 1O2 could only participate in the degradation of SMX through single electron transfer or addition reaction, resulting in a lower second-order rate constant of the SMX reaction with 1O2. Sulfate radical (SO4·-) contributed the most to the degradation of SMX due to the high reactivity of the sulfonamide structure in SMX to SO4·-. Finally, possible pathways for SMX degradation were proposed. The two primary mechanisms of SMX degradation were S-N cleavage and amino hydroxylation/oxidation. The toxicity of most of the intermediates was less than that of SMX through ecological structure–activity relationship analysis. Overall, a novel approach to synthesize low leaching and efficient cobalt based catalyst was put forward, and the activation mechanism of PMS was also revealed. © 2024 Elsevier B.V.

Keyword ：

Cobalt alloys Hydroxylation Paramagnetic resonance Zinc alloys Cobalt metallurgy Leaching Reaction intermediates Rate constants Activation analysis Electron spin resonance spectroscopy Bioremediation Cobalt Free radical reactions Degradation

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Fiber-Reinforced Cementitious Composites (FRCC) have gained significant attention in engineering applications due to their superior mechanical properties and toughness, particularly under high strain rate conditions. This study performed dynamic tensile tests on FRCC at high strain rates (35–110 s⁻¹) using a Split Hopkinson Tensile Bar (SHTB) apparatus. Additionally, a novel Peridynamic (PD) model was developed for the SHTB and FRCC system, leveraging the advanced capabilities of the emerging PD theory. The study compared and analyzed dynamic tensile strength, ultimate tensile strain, strain rate effects, failure modes, and crack development in FRCC with different fiber ratios at various high strain rates, using both experimental data and PD simulations. The results show that the PD-SHTB-FRCC dynamic model developed in this study exhibits high consistency between numerical simulations and experimental findings, effectively capturing the processes of crack initiation, propagation, and complete failure in FRCC specimens. The dynamic tensile properties of FRCC improve significantly with increased strain rates, with polyethylene (PE) fibers providing superior reinforcement compared to steel fibers. Notably, the dynamic tensile strength, peak tensile stress, and ultimate tensile strain of FRCC increase significantly with rising strain rates, with specimens containing higher PE fiber content showing a more pronounced enhancement effect. For strain rates between 42.6 s⁻¹ and 76.1 s⁻¹, considering dynamic tensile strength, ultimate tensile strain, and peak tensile stress, the optimal combination for resisting dynamic tensile loads was 1.5 % PE fibers and 0.5 % steel fibers. At a strain rate of 99.8 s⁻¹, a 2 % PE fiber ratio alone provided the best performance. © 2024 Elsevier Ltd

Keyword ：

Tensile testing Fiber reinforced plastics Cracks Tensile stress Shear strain Strain rate Tensile strength Tensile strain

Cite：

Copy from the list or Export to your reference management。

Abstract ：

Heavy metals that are readily chelated with coexisting organic ligands in industrial wastewaters impose threats to environment and human health but are also valuable metal resources. Traditional treatment methods generally require additional chemicals and generate secondary contaminants. Here, a reagent-free dual-cathode electrochemical system was proposed for the efficient destruction of Cu-organic complexes and synchronous cathodic recovery of Cu, whereby in situ production of H2O2 at carbon aerogel (CA) cathode was coupled with the reduction of Cu(II) to Cu(I) and finally to Cu(0) at Ti cathode. The intermediate Cu(II) complexes enabled the self-reinforced degradation owing to their higher activities toward •OH generation by activating H2O2 in contrast to initial Cu-ethylenediaminetetraacetic acid (Cu-EDTA). The enhanced production of Cu(I) by Ti cathode facilitated both •OH and Cu(III) formation, and the copper redox cycle was realized in the self-reinforced system, maintaining its sustainable catalytic activity. The energy cost of the dual-cathode system is 0.011 kWh/g for decomplexation and 0.057 kWh/g for Cu recovery, which is much lower than single Ti or CA cathode system. This established process provides a prospective approach for cost-effective destruction of chelating metal complexes and metal resources recovery from heavy metal wastewaters. © 2024

Keyword ：

Heavy metals Chelation Doping (additives) Redox reactions Energy efficiency Metal recovery Bioremediation

Cite：

Copy from the list or Export to your reference management。

Abstract ：

In the seismic mountainous regions such as western China, it is usuallly inevitable to construct tunnels near active fault zones. Those fault-crossing tunnel structures can be extremely vulnerable during earthquakes. Extensive experimental studies have been conducted on the response of continuous mountain tunnels under reverse and normal fault movements, limited experimental investigations are available in the literatures on mountain tunnels with special structural measures crossing strike-slip faults. In this study, a new experimental facility for simulating the movement of strike-slip fault was developed, accounting for the spatial deformation characteristics of large active fault zones. Two groups of sandbox experiment were performed on the scaled tunnel models to investigate the evolution of ground deformation and surface rupture subjected to strike-slip fault motion and its impact on a water conveyance tunnel. The nonlinear response and damage mechanism of continuous tunnels and tunnels incorporated with specially designed articulated system were examined. The test results show that most of slip between stationary block and moving block occurred within the fault core, and significant surface ruptures are observed along the fault strike direction at the fault damage zone. The continuous tunnel undergoes significant shrinkage deformation and diagonal-shear failure near the slip surface and resulted in localized collapse of tunnel lining. The segments of articulated system tunnel suffer a significant horizontal deflection of about 5°, which results in opening and misalignment at the flexible joint. The width of the damaged zone of the articulated system tunnel is about 0.44 to 0.57 times that of the continuous tunnel. Compared to continuous tunnels, the articulated design significantly reduces the axial strain response of the tunnel lining, but increases the circumferential tensile strain at the tunnel crown and invert. It is concluded that articulated design provides an effective measure to reduce the extent of damage in mountain tunnel. © 2024 Tongji University

Keyword ：

Earthquake engineering Strike-slip faults Fault slips Earthquakes Fracture mechanics Railroad tunnels Tunnel linings

Cite：

Copy from the list or Export to your reference management。

Abstract ：

The manganese-cobalt mixed oxide nanorods were fabricated using a hydrothermal method with different metal precursors (KMnO4 and MnSO4H2O for MnOx and Co(NO3)(2)& sdot;6H(2)O and CoCl2 & sdot;6H(2)O for Co3O4). Bamboo-like MnO2 & sdot;Co3O4 (B-MnO2 & sdot;Co3O4 (S)) was derived from repeated hydrothermal treatments with Co3O4@MnO2 and MnSO4 & sdot;H2O, whereas Co3O4@MnO2 nanorods were derived from hydrothermal treatment with Co3O4 nanorods and KMnO4. The study shows that manganese oxide was tetragonal, while the cobalt oxide was found to be cubic in the crystalline arrangement. Mn surface ions were present in multiple oxidation states (e.g., Mn4+ and Mn3+) and surface oxygen deficiencies. The content of adsorbed oxygen species and reducibility at low temperature declined in the sequence of B-MnO2 & sdot;Co3O4 (S) > Co3O4@MnO2 > MnO2 > Co3O4, matching the changing trend in activity. Among all the samples, B-MnO2 & sdot;Co3O4 (S) showed the preeminent catalytic performance for the oxidation of toluene (T-10% = 187 degrees C, T-50% = 276 degrees C, and T-90% = 339 degrees C). In addition, the B-MnO2 & sdot;Co3O4 (S) sample also exhibited good H2O-, CO2-, and SO2-resistant performance. The good catalytic performance of B-MnO2 & sdot;Co3O4 (S) is due to the high concentration of adsorbed oxygen species and good reducibility at low temperature. Toluene oxidation over B-MnO2 & sdot;Co3O4 (S) proceeds through the adsorption of O-2 and toluene to form O*, OH*, and H2C(C6H5)* species, which then react to produce benzyl alcohol, benzoic acid, and benzaldehyde, ultimately converting to CO2 and H2O. The findings suggest that B-MnO2 & sdot;Co3O4 (S) has promising potential for use as an effective catalyst in practical applications. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Keyword ：

Toluene oxidation Manganese-cobalt mixed oxide Nanorod Bamboo-like morphology Hydrothermal method

Cite：

Copy from the list or Export to your reference management。