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This study aimed to quantify carbon emission indicators for railway bridge construction and explore green, low-carbon optimization strategies. It focused on analyzing the carbon emissions generated by different precast schemes during the construction phase of railway bridges. A carbon emission calculation framework for the construction phase was established, and the analysis was applied to an intercity railway bridge project in the Guangdong - Hong Kong - Macao Greater Bay Area (GBA). Two design schemes were considered: the segment precast continuous rigid frame bridge and the full-span precast simply supported beam bridge. The results showed that the segment precast continuous rigid frame bridge scheme produced lower carbon emissions per unit distance than the full-span precast simply supported beam bridge scheme, reducing emissions by about 3.96%. The material production stage accounted for the highest proportion of carbon emissions, about 95%, while transportation contributed the least, about 1 %, and the mechanical construction stage accounted for about 4%. Compared to the segment-precast continuous rigid frame scheme, the full-span precast simply supported scheme had 4.37% higher material-related carbon emissions, 15.57% higher transportation carbon emissions, and 4.04% lower machinery carbon emissions. For both schemes, the carbon emissions from steel and concrete accounted for over 94% of the total material-related emissions. The full-span simply supported beam scheme had higher carbon emissions from concrete production and transportation, which were 20.27% and 19.35% higher, respectively, than those of the segment-precast continuous rigid frame scheme. The primary energy types consumed by construction machinery were diesel and electricity, accounting for over 99% of total energy consumption. [ABSTRACT FROM AUTHOR]

In this work, the oxidation behavior of an aluminide coating at 900, 1000, and 1100 °C was investigated. The aluminide coating was prepared on a cobalt-based superalloy using a vapor phase aluminizing process, which is composed of a β-(Co,Ni)Al phase outer layer and a Cr-rich phase diffusion layer. The experimental results showed that the oxidation of the coating at 900–1100 °C all obey the parabolic law. The oxidation rate constants of the coating were between 2.19 × 10−7 and 47.56 × 10−7 mg2·cm−4·s−1. The coating produced metastable θ-Al2O3 at 900 °C and stable α-Al2O3 at 1000 and 1100 °C. As the oxidation temperature increases, the formation of Al2O3 is promoted, consuming large amount of Al in the coating, resulting in the transformation from β-(Co,Ni)Al phase to α-(Co,Ni,Cr) phase. And the decrease in the β phase in the coating led to the dissolution of the diffusion layer. [ABSTRACT FROM AUTHOR]

The fabrication of multi-layer alloys by additive friction stir deposition (AFSD) results in a complicated microstructure and mechanical property evolution due to the repeated thermal inputs impacting the existing deposited layers. This work systematically studied the microstructure and mechanical properties of several areas (last layers, intermediate layers, and first layers) of a 16-layer 2195 alloy component fabricated by AFSD to ascertain the effect of repeated thermal cycling. The periodic heat input resulted in the minimal quantities of T1-phase only appearing in the last layers of the sample, while the θ′-phase developed a complex precipitate with the δ′ and β′ phases. The mechanical properties of the 2195 sample exhibit a gradient development related to the microstructure, with a decrease in strength and hardness from top to bottom. The samples located in the last layers show the highest microhardness of 117.0 Hv, yield strength of 296.6 MPa, ultimate tensile strength of 440.6 MPa, and elongation of 27.1%, respectively. [ABSTRACT FROM AUTHOR]

As one of the most effective methods to improve the accuracy and robustness of speech tasks, the audio–visual fusion approach has recently been introduced into the field of Keyword Spotting (KWS). However, existing audio–visual keyword spotting models are limited to detecting isolated words, while keyword spotting for unconstrained speech is still a challenging problem. To this end, an Audio–Visual Keyword Transformer (AVKT) network is proposed to spot keywords in unconstrained video clips. The authors present a transformer classifier with learnable CLS tokens to extract distinctive keyword features from the variable‐length audio and visual inputs. The outputs of audio and visual branches are combined in a decision fusion module. As humans can easily notice whether a keyword appears in a sentence or not, our AVKT network can detect whether a video clip with a spoken sentence contains a pre‐specified keyword. Moreover, the position of the keyword is localised in the attention map without additional position labels. Experimental results on the LRS2‐KWS dataset and our newly collected PKU‐KWS dataset show that the accuracy of AVKT exceeded 99% in clean scenes and 85% in extremely noisy conditions. The code is available at https://github.com/jialeren/AVKT. [ABSTRACT FROM AUTHOR]

This study is the first to research the microstructure and mechanical properties of the workpiece after additive friction stir deposition (AFSD) of the feedstock at different heat treatment stages. AA2219 aluminum alloys with three different heat treatment stages were selected as the feedstock, and alloys with dense structure were successfully prepared by the additive friction stir deposition AFSD process. Experimental results show that AFSD exhibits an excellent ability to refine grains and improve the uniform distribution of precipitates in the second phase, thereby improving the plasticity of AA2219 alloy after the AFSD process. Because of the continuous dynamic recrystallization (CDRX) in the AA2219 alloy during AFSD, the grain size after the AFSD process is independent of the initial feedstock grain size for three samples. The equilibrium phase (θ) size is genetically related to the initial size of the second-phase particles in the feedstock. Due to grain refinement and dislocation strengthening, the yield strength of AA2219-casting increased significantly from 79.8 MPa to 124.1 MPa after AFSD. The yield strength of the AA2219-T4 decreases slightly from 151.8 MPa to 140.4 MPa after AFSD. The precipitation of the second phase leads to a decrease in solid solution strengthening and dislocation strengthening. However, grain refinement strengthening partially offsets this reduction. The yield strength of AA2219-T87 decreased from 398.5 MPa to 147.2 MPa after AFSD. As such, grain refinement strengthening and solid solution strengthening by the AFSD process are much smaller than the yield strength lost by precipitation strengthening and dislocation strengthening. [ABSTRACT FROM AUTHOR]

Audio‐visual wake word spotting is a challenging multi‐modal task that exploits visual information of lip motion patterns to supplement acoustic speech to improve overall detection performance. However, most audio‐visual wake word spotting models are only suitable for simple single‐speaker scenarios and require high computational complexity. Further development is hindered by complex multi‐person scenarios and computational limitations in mobile environments. In this paper, a novel audio‐visual model is proposed for on‐device multi‐person wake word spotting. Firstly, an attention‐based audio‐visual voice activity detection module is presented, which generates an attention score matrix of audio and visual representations to derive active speaker representation. Secondly, the knowledge distillation method is introduced to transfer knowledge from the large model to the on‐device model to control the size of our model. Moreover, a new audio‐visual dataset, PKU‐KWS, is collected for sentence‐level multi‐person wake word spotting. Experimental results on the PKU‐KWS dataset show that this approach outperforms the previous state‐of‐the‐art methods. [ABSTRACT FROM AUTHOR]

In this study, composite plates of 6061/TA1 were successfully manufactured using additive friction stir deposition (AFSD). The impact of preheating temperatures (room temperature, 100 °C, 200 °C) on the interfacial microstructure and interface mechanical properties at various deposition zones was studied. The results showed that as the preheating temperature increased or when the deposit zone shifted from the boundary to the center, the diffusion width of Al and Ti increased, accompanied by an increase in bonding shear strength. Moreover, in the boundary zone of the sample preheated at room temperature (P-RT), only mechanical bonding was observed, resulting in the lowest bonding shear strength. Conversely, the other samples exhibited a combination of mechanical and metallurgical bonding. Under the preheating temperature of 200 °C, interfacial intermetallic compounds were observed near the center zone, which exhibited the highest bonding shear strength. [ABSTRACT FROM AUTHOR]

The self-discharge and effumability of supercapacitors with aqueous electrolytes are prevalent problems. In this study, we used Na2S2O3·5H2O as the electrolyte for aqueous supercapacitors. Na2S2O3 in Na2S2O3·5H2O can dissolve in crystalline water molecules by itself and the transformation between the solid and liquid states of Na2S2O3·5H2O electrolytes is reversible. The electrolyte based on liquating Na2S2O3 in 5H2O electrolytes has better thermal stability than that based on 2 M Na2S2O3 and 2 M KOH electrolytes. The electrochemical result indicates that the energy storage mechanism of a supercapacitor based on liquating Na2S2O3 in 5H2O leads to a double-layer supercapacitor via Na+ and S2O32− ion adsorption. The self-discharge behavior of the supercapacitor using liquating Na2S2O3 in 5H2O is effectively suppressed by the slow charge redistribution of Na+ and S2O32− ions in solid electrolytes formed from the liquid state. Finally, the supercapacitor using liquating Na2S2O3 in 5H2O has good cycling stability. [ABSTRACT FROM AUTHOR]

This paper studies the sufficient, necessary, and optimal conditions of the phenomenal transparency of architectural space (PTAS) by the eigenvector and eigenvalue of the gradient function of Scalar Field Function (SFF). Then, the SFF's method is used to analyze the PTAS of significant contemporary or canonical architectural works. The conclusions are: the eigenvalue of the SFF and its integral can be used to describe PTAS; the sufficient and necessary conditions of PTAS are the eigenvalue cannot be zero, and the area integral of the eigenvalue should be greater than a certain value; the optimal condition of PTAS is that the eigenvalue is the largest; the corresponding design methods include spatial stratification, graphic overlay, and grid rotation. [ABSTRACT FROM AUTHOR]

Collagen fibrils hierarchically assemble from microscale to macroscale, which endows the natural composite bone with good mechanical properties and remodeling functions. Revealing the intrafibrillar growth process of hydroxyapatite nanocrystals of collagen will guide the research of bone repair or collagen-based composites. Herein, we investigated the mineralization of multiscale collagen matrices and strongly proved the intrafibrillar hydroxyapatite nanocrystals in the collagen fibrils. The hydroxyapatite nanocrystals were deposited within collagen fibrils with co-orientation along the (002) crystal plane, which is the longitude of the fibril. The whole growth process was captured by TEM to demonstrated the five stages of the intrafibrillar growth process of hydroxyapatite nanocrystals. The infiltration and transformation of amorphous calcium phosphate in isolated collagen fibrils are both demonstrated. The intrafibrillar growth process of hydroxyapatite nanocrystals in collagen film was also investigated, showing that the growth area of collagen films increased linearly with time and the growth process. By studying the in situ mineralization under different reaction conditions, the kinetic equation of the mineralized area of collagen film under each condition was obtained, and the optimal hydroxyapatite mineralized solution was proved to be a solution with polyacrylic acid of 50 μG/mL and a pH of 7.5. Our work provides more detailed information of the growth process of HAP nanocrystals during the mineralization of collagen at different scales and would contribute to future research on the formation process of more minerals in collagen. [ABSTRACT FROM AUTHOR]

C–H activation provides a straightforward approach to construct new chemical bonds and privileged heterocycles. However, due to common deficiencies, C–H activation still faces a great challenge towards sustainability and applications. Described herein is a robust and convenient rhodium-catalyzed regioselective C–H activation/[4 + 2] annulation for the synthesis of isoquinolones with salient features including a recyclable catalytic reaction system, unique regioselectivity, gram-scale synthesis with low catalyst loading (e.g., 0.5 mol%), ethanol as the green solvent, air and water compatibility, and simple purification processes. The roles of the hydroxy group and the pivaloyl part in both substrates, the additional pivotal function of propargyl alcohol partners, and the origin of the unique chemoselectivity are clarified based on integrated experimental and DFT studies. Additionally, a propargyl alcohol-connected distinctive hydrogen bonding network with the hydroxy group and the pivaloyl part is also rationally deduced for conferring the observed reverse regioselectivity by subsequent IGMH analysis. [ABSTRACT FROM AUTHOR]

Recently, corrosion perforation has been frequently seen in surface pipelines in the oil and gas industry, resulting in operational and environmental challenges. Due to the complex characteristics and mechanisms of such corrosion, a new and pragmatic method has been designed to identify and evaluate the corrosion phenomenon via a hanging ring installed in a surface pipeline. In addition to respectively analyzing the ions of water samples with chemical titration, ion chromatography, and mass spectrometry, the micro-surface morphology of the corroded hanging rings was observed and evaluated by using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), and the surface composition of the corroded hanging rings was analyzed by using X-ray diffraction (XRD). The water ions of each selected position were found to mainly contain Ca2+, Ba2+, SO42−, and HCO3−, while the barium scale and calcium carbonate scale were formed in situ. In addition to the common corrosion induced by CO2, corrosion induced by both CO2 and H2S leads to extremely serious corrosion and scaling in surface pipelines. In addition, the injection dose of corrosion inhibitor was also evaluated. [ABSTRACT FROM AUTHOR]

The formation of natural structures found in biological systems is wonderful and can be completed at ambient temperatures in contrast to artificial technologies wherein harsh conditions are common prerequisites. A new research direction, "bioprocess inspired manufacturing", is proposed for fabricating advanced materials with novel structures and functions. Nacre consists of an ordered multilayer structure of crystalline calcium carbonate lamellae separated by organic layers exhibiting mechanical toughness, which transcends that of its constituent components. Inspired by the nacre formation process, a microscale additive manufacturing mineralization method is proposed for achieving a multilayered organic–inorganic layered structure. In this work, layered calcite was synthesized on the surface of chitosan (CS) films at room temperature under the coordinated control of magnesium ions (Mg2+) and polyacrylic acid (PAA). The CS films and layered calcite are sequentially assembled in a layer-by-layer deposition approach to form an organic–inorganic hybrid structure. The nacre-like chitosan/CaCO3 (CS/CaCO3) composites exhibit high transparency and underwater superoleophobicity. Impressively, the hardness (2.35 ± 0.03 GPa) and Young's modulus (58.1 ± 0.5 GPa) of the as-prepared (CS/CaCO3) composites are comparable to those of their biological counterparts. This study provides a rational bioprocess-inspired room-temperature mineralization method to develop advanced composite materials with good performance. [ABSTRACT FROM AUTHOR]