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There are multiple mutation points in the acoustic emission （AE） cumulative curve in the Kaiser experiments of reservoir cores， causing the routine Kaiser effect point discriminant method to be inaccurate， and there is even a problem that the Kaiser point cannot be read. To solve this problem， an optimized Kaiser effect point discriminant method combining AE energy spectrum and cumulative AE curve is proposed in this paper and applied to the prediction of reservoir in-situ stress in Block X of an Oilfield. The experimental results of core uniaxial loading show that at the initial period of core loading， the core is in the compression stage， with a large number of AE and a wide fluctuation range of AE energy values. In the middle period of loading， the core is in the elastic deformation stage. The amount of AE is small， and the AE energy value is low. The range of change is uniform. At the late loading period， the stress reaches the fracture pressure of the reservoir core， and the core ruptures. The number of AE increases sharply， and the AE energy value reaches a peak. In the middle period of loading， the core suddenly releases a large amount of energy， and the AE number and energy value have a sudden increase， followed by a rapid decrease when the axial stress reaches the historical maximum stress of the reservoir core. This phenomenon is in accordance with that of Kaiser. Therefore， the Kaiser effect point can be determined by combining the AE energy spectrum and cumulative AE curve. By using the optimized Kaiser effect point discriminant method， the in-situ stress distribution in Block X of an Oilfield is analyzed， and the results are in good agreement with the field test results.

In this paper, a distributed observer-based resilient control scheme is proposed to solve the voltage regulation and current sharing problems of islanded direct current (DC) microgrids under actuator faults. First, an observer-based distributed fault estimation design is presented to estimate fault signals with high accuracy. Then, based on the estimated information, a primary decentralized fault-tolerant control layer is designed to ensure accurate voltage reference tracking. A secondary cooperative control layer is employed to achieve the goal of current sharing. Besides, both the fault estimation observers and the fault-tolerant controllers are designed in a plug-and-play fashion, which guarantees the scalability of the DC microgrid. The simulation and experimental results show that the proposed control strategy can efficiently improve the reliability and resilience of the DC microgrid. [ABSTRACT FROM AUTHOR]

Enhanced oil recovery (EOR) shows great potential in maximizing the recovery of bypassed oil remains unrecovered in the reservoir after applying conventional oil recovery methods. Surfactant injection is a chemical enhanced oil recovery method that can improve the overall displacement efficiency and increase hydrocarbon production. The application of surfactant flooding is challenging due to the complexity of the design. On top of that, most of the utilized surfactants are not environmentally friendly. The formulation of the microemulsion system directly impacts the success of a surfactant injection process. Good understanding on the phase behaviours of the microemulsion system is essential to create Winsor Type-III microemulsion that has the ability to reach ultralow Interfacial Tension (IFT) with the addition of co-surfactant. The performance of the microemulsion also highly depends on factors such as salinity, surfactant type, surfactant concentration, and temperature. Extensive laboratory investigation along with phase behaviour studies are vital in formulating an efficient green microemulsion system for tertiary recovery processes. This project evaluates and presents the performance of anionic surfactant, Alpha-Olefin Sulfonate (AOS), Coco Glucoside, and decane in creating Winsor Type-III microemulsion. The performance of the formulated microemulsions under various salinities, surfactant concentrations, co-surfactant concentrations and temperature are investigated through stages of phase behavior studies to optimize the parameters. The optimized formulation of AOS-Coco Glucoside microemulsion consists of 3 wt% salinity, 1 wt% AOS, and 1 wt% Coco Glucoside as the widest range and maximum volume of Winsor Type-III was observed at this condition. IFT of the microemulsion system was measured at 25°C and 70°C using a spinning drop tensiometer. It is concluded that the formulated microemulsion system with the optimized parameters reaches low IFT instead of ultralow. The temperature has no significant effect on the IFT performance of the formulated microemulsion system, and the critical micelle concentration is determined to be at 0.05 wt% of the aqueous phase.

Microbial induced calcium carbonate precipitation (MICP) is widely common in nature, which belongs to biomineralization and has been explored carefully in recent decades. The paper studied the effect of temperature, initial pH value and Ca2+ concentration on bacterial growth and carbonic anhydrase activity, and then revealed the biomineralization process through the changes of Ca2+ concentration and calcification rate in alkali environment. Meanwhile, microbial healing agent containing spores and calcium nitrate was prepared and used for the early age concrete cracks repair. The self-healing efficiency was assessed by crack closure rate and water permeability repair rate. The experimental results showed that when the optimal temperature was 30 °C, the pH was 8.0–11.0, and the optimal Ca2+ concentration was 0–90 mM, the bacteria could grow better and the carbonic anhydrase activity was higher. Compared with reference, the crack closure rate with the crack width up to 0.339 mm could reach 95.62% and the water permeability repair rate was 87.54% after 28 d healing time of dry–wet cycles. XRD analysis showed that the precipitates at the crack mouth were calcite CaCO3. Meanwhile, the self-healing mechanism of mortar cracks was discussed in detail. In particular, there is no other pollution in the whole mineralization process, and the self-healing system is environmentally friendly, which provides a novel idea and method for the application of microbial self-healing concrete. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disease. Senile plaques and intracellular neurofibrillary tangles are pathological hallmarks of AD. Recent studies have described the improved cognitive and neuroprotective functions of acteoside (AS). This study aimed to investigate whether the improved cognition of AS was mediated by Aβ degradation and tau phosphorylation in APP/PS1 mice. The open field, Y maze, and novel object recognition tests were used to assess cognitive behavioral changes. We evaluated the levels of Aβ40 and Aβ42 in serum, cortex, and hippocampus, and Aβ‐related scavenging enzymes, phosphorylated GSK3β and hyperphosphorylated tau in the cortex and hippocampus of APP/PS1 mice by western blotting. Our results revealed that AS treatment ameliorated anxious behaviors, spatial learning, and memory impairment in APP/PS1 mice and significantly reduced Aβ deposition in their serum, cortex, and hippocampus. AS significantly increased Aβ degradation, inhibited the hyperphosphorylation of tau, and significantly decreased the activity of GSK3β, which is involved in tau phosphorylation. Altogether, these findings indicated that the beneficial effects of AS on AD‐associated anxious behaviors and cognitive impairments could be attributed to promoting Aβ degradation and inhibiting tau hyperphosphorylation, which might be partly mediated by GSK3β. [ABSTRACT FROM AUTHOR]

Thin sections, AIM-SEM, MICP, and nitrogen adsorption were performed on laminated and layered shales to characterize their complex pore and fracture structure. Combining the MICP model with the FHH model, this work proposes a new fractal method for lacustrine shales with complex lamina structure. The fractal characteristics presented four zones, representing the heterogeneity of fractures, macropores, mesopores, and micropores. The pores and fractures of shale have strong heterogeneity. Laminated shale has strong heterogeneity in mesopores and moderate heterogeneity in micropores. Layered shale has strong heterogeneity in fractures and moderate heterogeneity in micropores. The lamina structure and content of organic and mineral composition has a great influence on heterogeneity. The mineral laminae in laminated shale change frequently; lamellation fractures are mainly developed, and the structures are similar. Layered shales develop fractures between layers and structural fractures; the structural differences are significant. Macropores are mostly interparticle pores between quarts with similar structures. The wider lamina thickness of layered shale provides sufficient crystallization space for minerals, so the mesopores of layered shale are more homogeneous. Micropores are less developed, mainly consisting of intraparticle pores between clay minerals, which are complex but similar in structure in the two types of shale. The heterogeneity of mesopores and micropores is not conducive to hydrocarbon migration. Fractures and macropores need to be connected with meso–micropores to form a transport system. So, mesopores and micropores play decisive roles in hydrocarbon migration. Based on the above understanding, this paper points out that hydrocarbon in laminated shale with more carbonate minerals and a high thermal evolution degree has better availability. [ABSTRACT FROM AUTHOR]