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• Novel coupled approach for undrained stability of rectangular tunnels. • Isogeometric analysis and deep learning ensure accuracy and efficiency. • High accuracy with mean squared error of 10−6 in predicting tunnel stability. The problem considered in this paper is for the stability evaluation of a rectangular tunnel in undrained clay during lining process. The approach adopted involved the use of isogeometric analysis (IGA) and the upper bound limit analysis formulation for the stability analysis. For the geometrical representation, B-spline basis functions are used to generate a set of B-spline surfaces that define the boundary of the soil domain, allowing for the exact representation of the tunnel geometry. The upper bound limit analysis is then formulated as a second-order cone program (SOCP), which can be solved by using a numerical optimization algorithm. The accuracy and reliability of the proposed method are validated by comparing the results with those published in previous studies. Furthermore, a large dataset is generated by randomly varying the input parameters, and a deep learning model is trained to learn the dataset. The deep learning model is trained using the mean squared error (MSE) metric, which yields an MSE as small as 10−6, indicating the high accuracy and precision of the proposed approach. Feature analysis and Partial Dependence Plots (PDPs) were used to gain insights into physical behavior by identifying important variables and understanding their individual and collective effects. In conclusion, the coupling of IGA and upper bound limit analysis provides a comprehensive and reliable solution to the stability of rectangular tunnels. The results obtained from this approach are accurate and can be achieved with reduced computational cost, making it an attractive approach for practical engineering applications. This approach can be used as a basis for future research on tunnel and tunnel stability analysis and may be extended to other types of soil structures under complex geometries. [ABSTRACT FROM AUTHOR]

Electrocatalysts derived from polyindole (PID) and iron phthalocyanine (FePc) on carbon nanotubes (CNTs)/carbon Vulcan (C) have been synthesized and used as cathodes in Microbial Fuel Cells (MFCs). The morphology characterization performed by scanning electron microscopy (SEM) indicated a good dispersion of polyindole and FePc on carbon surface for all samples. The electrochemical activity towards oxygen reduction reaction (ORR) has been assessed by cyclic voltammetry (CV), showing enhanced performance of CNTs-based composites in comparison with C-based composites. Rotating disk voltammetry experiments demonstrated that ORR at FePc/CNTs and FePc/PID/CNTs catalysts led to more positive half-wave potential values and higher kinetic current density values compared to that of reference Pt/C; the best ORR performance was displayed by FePc/PID/CNTs sample. In MFCs operating with sodium acetate in phosphate buffer solution, FePc/PID/CNTs cathode allows achieving a maximum power density of 799 ± 41 mW m −2 and a current density of 3480 ± 83 mA m −2 that are higher than those achieved with commercial Pt/C cathode (646 ± 25 mW m −2 and 3011 ± 84 mA m −2 , respectively). The long-term MFC operation conducted for 700 h indicates a stable performance of FePc/PID/CNTs cathode, demonstrating its potential ability to substitute platinum catalyst for ORR in MFCs. [ABSTRACT FROM AUTHOR]

Iron-chelated electrocatalysts for the oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) were prepared from sodium ferric ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid) (FeE), sodium ferric diethylene triamine pentaacetic acid (FeD) supported on carbon Vulcan XC-72R carbon black and multi-walled carbon nanotubes (CNTs). Catalyst morphology was investigated by TEM; and the total surfaces areas as well as the pore volumes of catalysts were examined by nitrogen physisorption characterization. The catalytic activity of the iron based catalysts towards ORR was studied by cyclic voltammetry, showing the higher electrochemical activity of FeE in comparison with FeD and the superior performance of catalysts supported on CNT rather than on Vulcan XC-72R carbon black. FeE/CNT was used as cathodic catalyst in a microbial fuel cell (MFC) using domestic wastewater as fuel. The maximum current density and power density recorded are 110 (mA m−2) and 127 ± 0.9 (mW m−2), respectively. These values are comparable with those obtained using platinum on carbon Vulcan (0.13 mA m−2 and 226 ± 0.2 mW m−2), demonstrating that these catalysts can be used as substitutes for commercial Pt/C. [ABSTRACT FROM AUTHOR]

Abstract: Platinum (Pt) is a popular catalyst for hydrogen oxidation on the anode side of solid polymer fuel cells (SPFC). It increases the electrode activity, which catalyzes the reaction of the fuel cell. There are two methods commonly used to produce hydrogen for SPFC: fuel reforming and methanol decomposition. Both of these methods produce carbon monoxide, which is considered to be a poison for SPFC because it deactivates Pt easily. Adding ruthenium (Ru) to a Pt catalyst is an efficient way to improve the inhibition of carbon monoxide (CO) formation and reduce the Pt loading requirement. This study introduces a method to synthesize a bimetal catalyst that is suitable for SPFC. To improve the electrocatalyst activity, a new process with two spontaneous deposition steps is adopted. In the first step, Ru is deposited on the wall of carbon nanotubes (CNTs) to obtain Ru/CNTs. Pt is then added in the second deposition step to form Pt–Ru/CNTs. The morphology and microstructure of catalysts are characterized with microscopes, and the performance of membrane electrode assembly is evaluated by cyclic voltammetry method. Experimental results have proved that even with a lower Pt loading, this home-brewed bimetal catalyst performs a compatible electrocatalytic activity, and is capable of resisting attack from CO when a syngas (H2 +20ppm CO) is provided. [Copyright &y& Elsevier]