Characterizing large-scale weak interlayer shear zones using conditional random field theory

The shear behavior of large-scale weak intercalation shear zones (WISZs) often governs the stability of foundations, rock slopes, and underground structures. However, due to their wide distribution, undulating morphology, complex fabrics, and varying degrees of contact states, characterizing the shear behavior of natural and complex large-scale WISZs precisely is challenging. This study proposes an analytical method to address this issue, based on geological fieldwork and relevant experimental results. The analytical method utilizes the random field theory and Kriging interpolation technique to simplify the spatial uncertainties of the structural and fabric features for WISZs into the spatial correlation and variability of their mechanical parameters. The Kriging conditional random field of the friction angle of WISZs is embedded in the discrete element software 3DEC, enabling activation analysis of WISZ C2 in the underground caverns of the Baihetan hydropower station. The results indicate that the activation scope of WISZ C2 induced by the excavation of underground caverns is approximately 0.5–1 times the main powerhouse span, showing local activation. Furthermore, the overall safety factor of WISZ C2 follows a normal distribution with an average value of 3.697

Firms’ Strategic Pricing and Network Externalities

For the sale of a product with network externalities, a Stackelberg model involving an incumbent and an entrant is developed considering the impact of three strategic decision-making modes of the incumbent and consumers on the pricing, market share, and profit of firms. In addition, the impact of consumers’ strategic behaviours on firms’ pricing decisions and how firms respond to strategic customers is discussed. The results show that, in the SS (strategic firm facing strategic consumers) decision-making mode, the incumbent will implement long-term pricing and finally obtain the maximum profit, while as a follower of the incumbent, the entrant will also obtain the maximum profit in the SS mode. In the NS (nonstrategic firm facing strategic consumers) decision-making mode, the strategy of consumers seriously weakens the decision-making behaviour of the incumbent and causes the incumbent to obtain the lowest profit, but at the same time, the competitiveness of the entrant is enhanced to a certain extent, thereby rendering its profit higher than that in the NN (nonstrategic firm facing nonstrategic consumers) decision-making mode

Recent Progress in Silicon Carbide-Based Membranes for Gas Separation

The scale of research for developing and applying silicon carbide (SiC) membranes for gas separation has rapidly expanded over the last few decades. Given its importance, this review summarizes the progress on SiC membranes for gas separation by focusing on SiC membrane preparation approaches and their application. The precursor-derived ceramic approaches for preparing SiC membranes include chemical vapor deposition (CVD)/chemical vapor infiltration (CVI) deposition and pyrolysis of polymeric precursor. Generally, SiC membranes formed using the CVD/CVI deposition route have dense structures, making such membranes suitable for small-molecule gas separation. On the contrary, pyrolysis of a polymeric precursor is the most common and promising route for preparing SiC membranes, which includes the steps of precursor selection, coating/shaping, curing for cross-linking, and pyrolysis. Among these steps, the precursor, curing method, and pyrolysis temperature significantly impact the final microstructures and separation performance of membranes. Based on our discussion of these influencing factors, there is now a good understanding of the evolution of membrane microstructures and how to control membrane microstructures according to the application purpose. In addition, the thermal stability, oxidation resistance, hydrothermal stability, and chemical resistance of the SiC membranes are described. Due to their robust advantages and high separation performance, SiC membranes are the most promising candidates for high-temperature gas separation. Overall, this review will provide meaningful insight and guidance for developing SiC membranes and achieving excellent gas separation performance

Boost power factor correction converter with adaptive harmonic compensation control

Abstract In low‐voltage distribution systems, the increased penetration of power electronic devices leads to the decentralization of harmonic sources, which puts the sensitive loads or communication systems in the risk status. The conventional methods of point‐to‐point harmonic control are not applicable. In order to solve this problem without increasing additional investments, this paper focuses on mitigating the harmonic interference through the power factor correction (PFC) converter. Hence, a critical conduction mode (CRM) single‐phase boost PFC converter with adaptive harmonic compensation (AHC) control is proposed to reduce the harmonic interference at user side. Firstly, the feed‐forward control loop of a PFC converter is decoupled into the fundamental branch and harmonic branch to trace the harmonic interference and generate the compensation current. Then the compensation gain is designed by the compensation loop gain and compensation capacity of PFC converter. Meanwhile, the characteristics of the PFC converter are analyzed to study the effect of the AHC control on the active power transmission and output load, which can provide important support for the proposed method in application. Finally, a 160‐W experimental prototype is built to verify the effectiveness of the proposed AHC control

Extracting subpixel vegetation NDVI time series for evaluating the mixed pixel effect on GPP estimation in urban areas

The normalized difference vegetation index (NDVI) is the most widely used vegetation index for monitoring vegetation vigor and cover. As NDVI time series are usually derived at coarse or medium spatial resolutions, pixel size often represents a mixture of vegetated and non-vegetated surfaces. In heterogeneous urban areas, mixed pixels impede the accurate estimation of gross primary productivity (GPP). To address the mixed pixel effect on NDVI time series and GPP estimation, we proposed a framework to extract subpixel vegetation NDVI (NDVIvege) from Landsat OLI images in urban areas, using endmember fractions, mixed NDVI (NDVImix), and NDVI of non-vegetation endmembers. Results demonstrated that the NDVIvege extracted by this framework agreed well with the true NDVIvege cross seasons and vegetation fractions, with R2 ranging from 0.74 to 0.82 and RMSE ranging from 0.03 to 0.04. The NDVIvege time series was applied to evaluate vegetation GPP in Wuhan, China. The total annual GPP estimated with NDVIvege was 28-35% higher than the total annual GPP estimated with NDVImix, implying uncertainty in the GPP estimations caused by mixed pixels. This study showed the potential of the proposed framework to resolve NDVIvege for characterizing vegetation dynamics in heterogeneous areas