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

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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

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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

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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

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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

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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

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High energy consumption represents one of the hindrances in enabling large scale application of membrane distillation. In this work, experimental and simulation studies of a double-effect direct-contact membrane distillation integrated with a single-stage vapor-compression heat pump (DE-DCMD-HP) were carried out for concentrating tap water with the aim to evaluate the energy saving of the integrated system. It was found during our experiments that an auxiliary cooler must be added to remove the excess heat from HP to enable the integrated system to reach the steady-state condition. The temperature-heat flux plots were first utilized to analyze how HP and DE-DCMD affected each other and reveal their coupling mechanism. The simulation results showed that the increase in the first-effect feed inlet temperature, Tfi,1 and the flow rate, V caused the thermodynamic cycle line of refrigerant shift to higher temperature, which led to the increase of the input power of the compressor and the auxiliary cooler, ultimately affecting the water production mass rate, md, the coefficient of performance, COP, the gain output ratio, GOR, and the specific energy consumption, SEC. The experimental and simulation results revealed that increasing Tfi,1 and V increased the permeate flux Nh and GOR and reduced the SEC. The performances for three different DCMD configurations were furthermore evaluated via experiments at constant feed temperature whereby the SEC decreased from 2168 kWh·t−1 for single-effect DCMD to 1085 kWh·t−1 for DE-DCMD to 257 kWh·t−1 for DE-DCMD-HP. © 2024 The Authors

Keyword ：

Thermal cycling Coefficient of performance Vapor compression refrigeration Heat pump systems Energy utilization

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Friction rolling additive manufacturing (FRAM) is a solid-state additive manufacturing technology that plasticizes the feed and deposits a material using frictional heat generated by the tool head. The thermal efficiency of FRAM, which depends only on friction to generate heat, is low, and the thermalaccumulation effect of the deposition process must be addressed. An FRAM heat-balance-control method that combines plasma-arc preheating and instant water cooling (PC-FRAM) is devised in this study, and a temperature field featuring rapidly increasing and decreasing temperature is constructed around the tool head. Additionally, 2195-T87 Al-Li alloy is used as the feed material, and the effects of heating and cooling rates on the microstructure and mechanical properties are investigated. The results show that water cooling significantly improves heat accumulation during the deposition process. The cooling rate increases by 11.7 times, and the high-temperature residence time decreases by more than 50 %. The grain size of the PC-FRAM sample is the smallest, i.e., 3.77 E1.03 }m, its dislocation density is the highest, and the number density of precipitates is the highest, the size of precipitates is the smallest, which shows the best precipitation-strengthening effect. The hardness test results are consistent with the precipitation distribution. The ultimate tensile strength, yield strength and elongation of the PC-FRAM samples are the highest (351 E15.6 MPa, 251.3 E 15.8 MPa and 16.25 % E1.25 %, respectively) among the samples investigated. The preheating and water-cooling-assisted deposition simultaneously increases the tensile strength and elongation of the deposited samples. The combination of preheating and instant cooling improves the deposition efficiency of FRAM and weakens the thermal-softening effect. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science &

Keyword ：

Microstructure Friction rolling additive manufacturing Plasma preheating Instant cooling Heat accumulation Al-Li alloy

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In an anammox biofilm reactor, long-term operation inevitably leads to the repeated formation of localized dead zones. Once these dead zones (DZs) occur, the anammox reactor's nitrogen removal efficiency is severely reduced. However, the mechanisms and intrinsic reasons for the transformation of DZs remain unexplored. In this study, the pilot-scale biofilters were classified into biologically active zones (BZs), transition zones (TZs), and DZs. The results indicated that microbial communities undergo accelerated succession from the TZ. Biofilms respond to environmental stress from the DZs by altering the levels of signaling molecules, triggering a series of cascading reactions. These reactions alter the abundance of genes involved in nitrogen removal, promote substance transformation, and speed up the succession of microbial communities. This study demonstrates the objectives and self-healing mechanisms of the anammox biofilm process in the presence of dead zones, which could support the long-term application of anammox technology.

Keyword ：

Biofilm Biofiltration reactor AHLs Quorum sensing Anammox Dead zone

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Thiosulfate-driven denitrification coupled with anammox (TDDA) has garnered interest for its efficient and innovative nitrogen removal capabilities. However, the intricate dynamics of the internal microbial community and the specific characteristics of anaerobic ammonium oxidizing bacteria (AnAOB) remain incompletely understood. This study combines experimental methods with density functional theory (DFT) calculations to address these gaps. The TDDA reactor was successfully started-up with an optimal S2O32--S/NO3−-N ratio of 0.6, achieving a nitrogen removal efficiency of 89.6%. Throughout this process, the relative abundance of Candidatus Kuenenia decreased by 10.2%, while the relative abundance of Candidatus Brocadia increased by 9.6%. The elevated concentration of NO₃--N inhibited Candidatus Kuenenia, and simultaneously stimulated the secretion of extracellular polymers, affecting Fe uptake by Candidatus Kuenenia. To further elucidate substrate competition, molecular docking simulations and DFT calculations were employed. The binding energy, compared with the electrostatic potential energy of the protein pocket, clearly demonstrated that Nir in AnAOB has a higher affinity for the substrate (EAnAOB = −163.2 kJ/mol vs. ESOB = -77.7 kJ/mol). By integrating molecular dynamics insights, this study overcomes experimental limitations and deepens the understanding of the mechanisms within the TDDA system. © 2024

Keyword ：

Nitrogen removal Molecular dynamics Candida Yeast Molecular docking Denitrification

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