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This paper proposes a maintenance model for systems subject to discrete-state deterioration processes. The deterioration of the system is described by the phase-type (PH) expansion of a multi-state Markov model, where the sojourn times at different states follow general distributions. In contrast to the periodic inspections and exponentially distributed repairs in most works, this study considers condition-based inspections and significant delays from planning a maintenance task until its actual implementation. These delays are usually due to logistic reasons and are considered close to deterministic. This allows the decision-makers to evaluate more flexible inspection strategies and move towards more cost-effective solutions. A case study about road bridge maintenance is presented to demonstrate the modelling process and the value of introducing PH distributions and condition-based inspections. With the proposed model, a less conservative maintenance strategy with fewer inspections and postponed repairs can be derived, bringing significant cost reductions. • A phase-type maintenance model capable of handling condition-based inspections. • System deterioration modelled as phase-type expansion of a multi-state Markov model. • Deterministic delays from planning a repair until its actual implementation. [ABSTRACT FROM AUTHOR]

MoS 2 /δ-FeOOH composite catalyst was constructed by a simple solvothermal–coprecipitation method, and the catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance (UV–vis DRS), X-ray photoelectron spectroscopy (XPS) and paramagnetic resonance spectroscopy (EPR). The results of analysis indicated that the composite was successfully prepared, and δ-FeOOH adhered to the surface of spheroidal MoS 2 firmly and uniformly, with a particle size of about 1–2 µm. The introduction of co-catalyst MoS 2 successfully expanded the photoresponse range of the catalyst, and constructed heterojunction with δ-FeOOH effectively inhibited the photogenerated electron-hole pair recombination. The degradation of organic dye Rhodamine B (RhB) by MoS 2 /δ-FeOOH activated peroxymonosulfate (PMS) under visible light was studied. The results showed that the degradation rate of RhB was 99.99% within 35 min. The excellent catalytic performance of MoS 2 /δ-FeOOH can be attributed to the dual-synergy of bimetallic and photocatalysis. In addition, the main active components of the MoS 2 /δ-FeOOH/PMS/vis system was determined to be 1O 2 by free radical quenching experiment and EPR. After 5 cycles of degradation experiments, the removal rate of RhB still reached 89.68%, indicating that the material has good stability and repeatability. The MoS 2 /δ-FeOOH not only has good photocatalytic activity, but also has strong anti-interference ability for the actual water matrix degradation. Therefore, the MoS 2 /δ-FeOOH has a excellent application prospect in practical wastewater treatment. [Display omitted] • MoS 2 /δ-FeOOH heterojunction was constructed by a simple solvothermal-coprecipitation method. • The excellent catalytic performance of MoS 2 /δ-FeOOH can be attributed to the dual-synergy of bimetallic and photocatalysis. • The catalyst still has a good application prospect in the actual water matrix. • This work provides a new idea for the study of transition metal sulfide modified heterogeneous catalysts. • The first time to apply the MoS 2 /δ-FeOOH to the degradation of RhB in the PMS/vis system. [ABSTRACT FROM AUTHOR]

Abstract: An efficient one-pot synthesis of perfluoroalkylated ring-fused 2-pyridones by three-component reaction of diamine, ketene dithioacetal, and methyl 2-perfluoroalkynoate in EtOH is reported. This protocol has the advantages of easiness, higher yields, and shorter reaction time. A plausible mechanism for this type of cyclization is proposed. [Copyright &y& Elsevier]

• A new framework to evaluate heterogeneous failure dependences. • A generalized CBM model for systems with heterogeneous failure dependences. • Verification of the model with a subsea transmission system. Many industrial facilities consisting of multiple components are prone to failure interactions and degradation interactions. In such systems, these interactions are frequently characterized by failure dependences that may accelerate the degradation of components. Due to system layout and functional interactions, not all components have the same failure dependence. In the general context of complex failure dependences in dependent multi-component systems, heterogeneous failure dependences further complicate the maintenance activities during operation. The present study developed a comprehensive framework for evaluating heterogeneous failure dependences and a maintenance optimization model by Markov processes for multi-component systems. The proposed method is applied to a practical case consisting in a parallel subsea transmission system to illustrate the effects of heterogeneous failure dependences. The results show that the heterogeneous failure dependences framework and the maintenance model guide the optimization of maintenance strategies to maximize the system availability and minimize the maintenance cost. [ABSTRACT FROM AUTHOR]

In order to study the effects of electric field intensity and distribution on flame propagation speed, the paper investigated the flame propagation of premixed CH 4 /O 2 /N 2 mixtures under direct-current (DC) electric fields at an excess air ratio of 1.4. Different high-voltage electrodes were chosen in the experiment in two aspects: electrodes size (the outer-diameter of high-voltage electrodes) and electrodes structure. Results show that the flame propagation speed increases significantly with the voltage applied to the high-voltage electrodes. Secondly, the electric field intensity can significantly affect the flame propagation, and it can be observed that the mean flame propagation speed increases linearly with the mean electric field intensity under fixed high-voltage electrodes. In addition, electric field distribution is another important influence factor on the flame propagation. Specifically, the effect of the electric field on the flame propagation speed increases apparently with the uniformity coefficient, so a uniform electric field works better than an uneven one for promoting the flame propagation speed. In fact, with the smallest uniformity coefficient of 0.21, the electric field under the 60 mm-diameter mesh electrodes has the most uniform electric field, while the effect of that on the flame propagation is the strongest, with the highest mean flame propagation speed of 1.25 m/s at an applied voltage of −10 kV. The results substantiate the importance of the electric field intensity and distribution on promoting the flame propagation speed of lean combustion. [ABSTRACT FROM AUTHOR]