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The existing research on voltage-source converter HVDC (VSC-HVDC) system stability mostly focuses on small-signal stability analysis methods. However, when large-signal disturbances occur, the intrinsic nonlinearity of the VSC-HVDC system becomes inevitable so that the small-signal studies are no longer valid. In this paper, a large-signal stability analysis method of the VSC-HVDC system is proposed based on the estimation of domain of attraction (DOA). This method can not only analyze the asymptotic stability of the operating point, but also answer the question of how large deviations from the operating point can be tolerated by the system. By using Takagi-Sugeno (T-S) fuzzy model and Lyapunov stability theorem, the DOA of the VSC-HVDC System at the operating point is estimated, and the large-signal stability of VSC-HVDC System is analyzed. On this foundation, the influence of system parameters on the large-signal stability is studied. The results can be used to guide the adjustment of system parameters to solve the problem of system instability. The time-domain simulations conducted in Matlab/Simulink are used to test the stability of the system under large-signal disturbance in the range of DOA. The simulation results verify the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Flexible interconnection transformation of a distribution network using all-control power electronics technology will help to overcome the technical bottleneck of distributed generation (DG) penetration and high-quality power supply in the traditional distribution network. However, the flexible interconnection form that uses back-to-back power electronic converters to replace tie switches has disadvantages such as high cost and large footprint, so its mass promotion and application are bound to be limited. Therefore, a new topology of flexible interconnected distribution network with embedded DC system (FDN+EDC) with a better economy is proposed. Firstly, the topology of FDN+EDC is introduced to improve the controllability level of the distribution network under high percentage DG penetration, and is compared with the conventional flexible interconnection method. Secondly, in order to realize the coordinated optimal economic operation of source, network and load in the FDN+EDC, a dynamic reconfiguration model of switches status and continuous adjustment of flexible interconnection device (FID) are proposed. Then, to achieve a fast and globally optimal solution of the model, a hierarchical coordinated optimization strategy is designed based on an improved particle swarm algorithm for the optimization of discrete and continuous variables. Finally, the validity of the algorithm is verified, and an 88-node FDN+EDC is constructed to verify the advantages of the proposed embedded DC flexible interconnection topology and realize the joint optimal dispatch of network-source-load. [ABSTRACT FROM AUTHOR]

• Compared with the traditional flexible interconnection method, the EDC-DN power supply architecture proposed in this paper does not simply use MTDC to achieve feeder interconnection but first optimizes and adds dynamic reactive power compensation devices based on voltage source converters in the context of a high percentage of DG access to the grid, and then the dynamic reactive power compensation equipment between different feeders is interconnected on the DC side by adding additional lines, thus weakening the voltage fluctuation of the grid when DG is connected while achieving closed-loop flexible interconnection between multiple feeders. This can achieve closed-loop flexible interconnection between multiple feeders while weakening the voltage fluctuation of the grid when DG is connected, provide a flexible active power adjustment path for high proportional DG access to DN, and realize power mutual aid between different feeders and network-level bearing of DG. • For the issue of power supply recovery after EDC-DN fault, a comprehensive analysis was conducted on the impact of different fault locations on the power supply recovery process. The collaborative plan between EDC and DAS was first proposed, clarifying the information interaction content between the distribution network automation central station, feeder sub-station, and EDC sub-station during the power supply recovery process. An EDC-DN two-stage power supply restoration architecture considering EDC continuous regulation, combinatorial optimization of interconnection switch and sectionalizing switch is proposed and designed, which fills the technical gap in the integration of EDC and DAS systems. • This paper demonstrates the real-time dynamics of EDC in the EDC-DN power supply restoration process through simulation. The restoration process includes a fast restoration phase based on EDC continuous regulation of power supply, a non-fault section transfer process based on mechanical switch action, and an economically optimal operation phase using an optimal combination of switches to reconfigure the distribution network topology. The current power supply restoration strategy of SOP focuses on the final restoration state of EDC continuous regulation and switch combination rather than on the whole process of power supply restoration. This paper considers the real-time dynamics of the entire EDC-DN power supply restoration process. It fills the technical gap in the current SOP power supply restoration without considering the intermediate process. The flexible interconnection device (FID) enables multiple distribution feeders in closed-loop mode to support a higher proportion of distributed generation (DG) and large-scale new loads connected to the distribution network (DN). Moreover, the closed-loop operation mode based on FIDs provides an effective technology roadmap for high-quality and highly reliable power users, especially the quick restoration of power supply after the failure of DN. This paper proposes a new supply shape in which the multi-terminal DC links are flexibly embedded in the AC DN (EDC-DN) to realize closed-loop operation, achieving lower investment costs than the existing mode that replaces tie switches with soft open points (SOPs). Meanwhile, a two-stage power supply quick recovery control technology is proposed for the EDC-DN, including the fast power supply recovery stage based on EDC and the optimizing restoration stage based on network reconfiguration. Firstly, the role of EDC in the process of power supply restoration of three different faults on AC feeder is analyzed. Secondly, a detailed power supply recovery process is proposed, which is based on a distribution automation system (DAS) and the real-time control capability of EDC. Thirdly, the power supply restoration second stage is implemented, which is based on network reconfiguration with switch combination and EDC continuous variable optimization. Finally, a 58-node DN with an EDC system was constructed using PSCAD/MTDC simulation software to verify the effectiveness of the two-stage strategy for EDC-DN power restoration. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

The use of the conventional dual closed-loop control strategy by photovoltaic (PV) plants with grid-connected inverters may weaken the damping of a power system, which may aggravate low-frequency oscillations (LFOs). This influence will become more severe as the penetration of PV plants increases. Therefore, it is necessary to incorporate damping controls into PV plants to suppress LFOs. This paper proposed an additional compound damping control (ACDC) system that combines additional damping control (ADC) for the inverter with ADC-based dynamic power compensation control (DPCC), allowing hybrid energy storage systems (HESSs) to suppress LFOs. First, the feasibility of suppressing low-frequency oscillations in PV plants is demonstrated by the torque method and a small signal model. Then, an additional damping controller is added to the active power control link of the PV inverter to enhance the damping abilities of the system. However, given that the damping performance of PV plants with only ADC is limited by the compensated power, PV plants require devices that can rapidly compensate for the damping power. Therefore, we added the HESS to the DC bus and proposed DPCC. Finally, a three-machine nine-node system for a PV plant was modeled and simulated in the PSCAD platform. The simulation results showed that the proposed control strategy could provide effective damping for interarea oscillation. [ABSTRACT FROM AUTHOR]

The utilization of biomass for the production of agricultural green inputs is regarded as a crucial strategy for achieving low-carbon development in agriculture, while also fully harnessing the potential of renewable resources. Pesticides, as a vital agricultural input, often encounter issues pertaining to inefficient usage, resulting in significant environmental pollution and economic losses. As a main component of lignocellulosic biomass, lignin has become one of the most appealing biopolymers for the construction of advanced pesticide delivery systems. This review aims to provide a thorough summary of the advancements in lignin-based controlled release formulations (LCRFs) for the precise delivery of pesticides. The research in this field has experienced rapid growth in the past five years, making it an important area of study. Common LCRFs are introduced, and the factors influencing the release of active ingredients (AIs) within different LCRFs are analyzed. Special emphasis is placed on intelligent-responsive LCRFs, encompassing an overview of the existing formulations and an exploration of their potential application scenarios and development strategies. It is crucial to promote innovation in pesticide formulations based on the actual demands of agricultural production. We hope this review will stimulate the high-value utilization of lignin and the green development of plant protection technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • DOC was the foremost parameter influencing the phytotoxicity of LD. • Temperature accelerated the stability and phytotoxicity disappearance of LD. • Open storage of LD at 30 °C for 60 days and 20 °C for 90 days of LD was safe. • Hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days of LD was safe. • For storage at 10 °C for 180 days, additional post-treatment is required. Identifying the stability and phytotoxicity of liquid digestate (LD) is necessary for safe agricultural utilization. Storage temperature, method, and time are critical factors that affect the stability and phytotoxicity of LD. This study therefore aimed to explore the dynamics of stability, phytotoxicity, and microbial community of LD in cattle farms under different storage conditions. The results showed that the contents of solids, organic matter, nitrogen, and phosphorous decreased during storage and exhibited temperature dependency. Conversely, the seed germination index increased, which was negatively correlated with dissolved organic carbon and ammonium nitrogen and positively correlated with certain bacteria (Thermovirga and Fastidiosipila). Open storage and/or higher temperature were found to contribute to the stabilization efficiency and phytotoxicity disappearance of LD. Open storage of LD at 30 °C for 60 days and 20 °C for 90 days was safe for its agricultural utilization, while hermetic storage of LD at 30 °C for 120 days and 20 °C for 150 days was safe. However, for storage at 10 °C for 180 days, additional post-treatment is required. [ABSTRACT FROM AUTHOR]

Health status assessment is the key link of transformer-condition-based maintenance. The health status assessment method of power transformers mostly adopts the method based on the health index, which has the problems of multiple parameters of each component and strong subjectivity in the selection of weight value, which is easily causes misjudgment. However, the existing online monitoring system for dissolved gas in transformer oil (DGA) can judge the normal or abnormal state of the transformer according to the gas concentration in a monitoring cycle. Still, there are problems, such as fuzzy evaluation results and inaccurate judgment. This paper proposes a dynamic state evaluation method for power transformers based on the Mahalanobis–Taguchi system. First, the oil chromatography online monitoring time series is used to screen key features using the Mahalanobis–Taguchi system to reduce the problem of excessive parameters of each component. Then, a Mahalanobis distance (MD) calculation is introduced to avoid subjectivity in weight selection. The health index (HI) model of a single transformer is built using the MD calculated from all DGA data of a single transformer. Box–Cox transformation and 3 σ criteria determine the alert value and threshold value of all transformer His. Finally, taking two transformers as examples, we verify that the proposed method can reflect the dynamic changes of transformer operation status and give early warning on time, avoiding the subjectivity of parameter and weight selection in the health index, which easily causes misjudgment and other problems and can provide a decision-making basis for transformer condition-based maintenance strategies. [ABSTRACT FROM AUTHOR]

• Introduce the chance constrained programming to deal with the randomness of wind power, photovoltaic output and load. • The fault recovery capability of flexible interconnected distribution network considering closed-loop operation is more fully developed. • Analyze the fault recovery effect of flexible interconnected distribution network under different SOP control modes and propose a two-stage recovery strategy. • Considering more complex faults of flexible interconnected distribution network, provide an effective fault recovery strategy for concurrent faults. With the continuous exploration of the application value of flexible interconnected distribution network, Soft Open Point (SOP) as its core device, how to fully explore the self-healing control support capability of SOP and improve its power supply reliability becomes particularly important. Aiming at the problem of fault recovery of flexible interconnected distribution network with multiple AC power supply areas, firstly, the topology of flexible interconnection of distribution network and the fault recovery model of SOP are described. Secondly, the stochastic nature of wind power, photovoltaic output and load is considered, and then the chance-constrained programming is introduced to deal with. Then, aiming at the coordinated operation of flexible closed-loop network in multiple AC power supply areas, and introducing the constraint on the acting number of switches, a stochastic optimization model of flexible interconnected distribution network fault recovery is established, and then the model is transformed into a deterministic mixed integer second-order cone programming model, which can be solved by CPLEX solver. Finally, the proposed model has been tested on a modified hand-in-hand IEEE33 system with dual-terminal SOP, verifying that the strategy proposed in this paper can effectively solve the fault recovery problem of flexible interconnected distribution network with multiple AC power supply areas considering uncertainty, and showing that this strategy can maximize the self-healing capability of distribution system. [ABSTRACT FROM AUTHOR]

This paper focuses on the self-synchronization control of cascaded-type STATCOM. One module is controlled as the current source, and the rest are regulated as voltage sources. The low-bandwidth communication is just used to transmit the given reactive powers. Via the carrier of common grid current acquired locally, the self-synchronized operation of all modules is realized. When a short interruption in communication occurs, the stable operation of the system is unaffected. Thus, the system reliability is improved in case of communication failure. The small-signal stability of the proposed scheme is proven. Finally, the effectiveness of the proposed scheme is verified by both simulation and hardware-in-the-loop results. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of temperature rises and falls on anaerobic digestion was assessed. • 45 °C exhibits optimal methanogenic performance during temperature rises and falls. • An effective equilibrium between hydrolysis and methanation is achieved at 45 °C. • The shortest recovery time was 2 days following temperature fluctuation. This study implemented five successive temperature stages (35 °C–45 °C–55 °C–45 °C–35 °C) in a continuous stirred tank reactor, designated as D35-1, D45-1, D55, D45-2, and D35-2, respectively. The objective was to probe the mechanism of temperature transformations on methanogenesis performance, microbial community, and metabolic pathways. The suitability of 45 °C for anaerobic digestion (AD) under varying temperatures was emphatically expounded. Intriguingly, optimal methanogenesis performance was attained at 45 °C, with methane production reaching 238.51 mL/g VS/d in D45-1 and 245.91 mL/g VS/d in D45-2, signifying increases of 17.66% and 21.32% contrasted with D35-2, respectively. Additionally, considerable resistance to temperature shocks at 45 °C was also manifested, as evidenced by a recovery time of 2 days in D45-2. At 45 °C, an effective balance between hydrolysis and methanogenesis was observed, maintaining a dynamic equilibrium between acetoclastic and hydrogenotrophic methanogenesis. The primary drivers in D45-1 were Caldicoprobacter , Bathyarchaeia , and Methanosarcina , while Anaerolinea and Methanosarcina were the key determinants in D45-2. By contrast, methanogenesis was suppressed at other stages. Therefore, 45 °C emerges as a viable alternative to conventional temperatures when confronted with temperature fluctuations to optimize energy efficiency. The results provide novel insights into AD temperature management and pave the way for engineering applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two-stage anaerobic digestion affects the hydrolysis-methanogenesis process. • Aerobic or micro-aerobic hydrolysis results in carbon loss from the substrate. • Substrate type significantly affected biogas yield and microbial community. • The gradient anaerobic digestion process (GADP) improved the biogas yield. • GADP enhanced carbon recovery of substrate and synergies of microorganisms. The destruction of the synergistic effect of the hydrolysis-methanogenesis process (HMP) of substrate may lead to the serious carbon loss of substrate and low biogas yield in traditional straw biogas engineering. In this study, the influence of substrate composition on anaerobic digestion (AD) was investigated under pilot conditions, and the relationship between HMP was further investigated under full-scale plants. The results showed that straw with a high content of soluble substances had the highest methane yield (264.25 L/kg VS) and degradation rate (59.32 %). At HRT = 20 d, the full-scale plant achieved the highest biogas yield (576.92 L/kg VS, 3.47 L/L/d) and degradation rate (67.50 %). Microbial analysis showed that substrate composition affected microbial community and methanogenic metabolic pathway. The analysis results of PICRUSt2 confirm that gradient AD guarantees the synergistic relationship of HMP. This study provides the theoretical basis and engineering guidance for improving the AD process in traditional straw biogas engineering. [ABSTRACT FROM AUTHOR]

Antibiotic mycelial dreg (AMD) has been categorized as hazardous waste due to the high residual hazardous contaminants. Inappropriate management and disposal of AMD can cause potential environmental and ecological risks. In this study, the potential of pleuromutilin mycelial dreg (PMD) as a novel feedstock for preparing tetracycline hydrochloride (TC) adsorbent was explored to achieve safe management of PMD. The results suggested that residual hazardous contaminants were completely eliminated after pyrolysis. With the increase of pyrolysis temperature, the yields, H/C, O/C, (O + N)/C, and pore size in PMD-derived biochars (PMD-BCs) decreased, while BET surface area and pore volume increased, resulting in the higher stability of the PMD-BCs prepared from higher temperatures. The TC adsorption of the PMD-BCs increased from 27.3 to 46.9 mg/g with the increase of the pyrolysis temperature. Surprisingly, pH value had a strong impact on the TC adsorption, the adsorption capacity of BC-450 increased from 6.5 to 71.1 mg/g when the solution pH value increased from 2 to 10. Lewis acid-base interaction, pore filling, π-π interaction, hydrophobic interaction, and charge-assisted hydrogen bond (CAHB) are considered to drive the adsorption. This work provides a novel pathway for the concurrent detoxification and reutilization of AMD. [Display omitted] • PMD was pyrolyzed into biochar for efficient antibiotic adsorption. • Hazardous contaminants were completely eliminated by pyrolysis at above 350 °C. • Pyrolysis temperature greatly influenced the physicochemical properties of PMD-BCs. • Higher pyrolysis temperature benefited the TC adsorption onto PMD-BCs. • A low temperature (450 °C) is recommended for the pyrolysis treatment of PMD. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ensiling EWS with acetic acid or heterofermentative LAB addition was first studied. • Ensiling EWS with additives enhanced acetic acid fermentation. • Ensiling EWS with additives preserved hemicellulose and cellulose content. • Ensiling EWS with additives changed the homo-fermentation to hetero-fermentation. • Ensiling EWS with additives improved the methane yield by 17.7–23.9%. Ensiling is an effective storage strategy for agricultural biomass, especially for energy crops (mainly energy grasses and maize). However, the ensiling of excessively wilted crop straw is limited due to material characteristics, such as a high lignocellulosic content and low water-soluble carbohydrate and moisture contents. In this study, acetic acid or hetero-fermentative lactic acid bacterial community (hetero-fermentative LAB) were employed as silage additives to improve the ensiling process of excessively wilted wheat straw (EWS). The results showed that the additives inhibited the growth of Enterobacteriaceae and Clostridium_sensu_stricto_12 , whose abundances decreased from 55.8% to 0.03–0.2%, respectively. The growth of Lactobacillus was accelerated, and the abundances increased from 1.3% to 80.1–98.4% during the ensiling process. Lactic acid fermentation was the dominant metabolic pathway in the no additive treatment. The additives increased acetic acid fermentation and preserved the hemicellulose and cellulose contents, increasing the methane yield by 17.7–23.9%. This study shows that ensiling with acetic acid or hetero-fermentative LAB is an effective preservation and storage strategy for efficient methane production from EWS. [ABSTRACT FROM AUTHOR]

Temperature and hydraulic retention time (HRT) control are crucial for mitigating the "short-circuit" issue and enhancing methane production in continuous stirred-tank reactors. This study focuses on the combined effects of temperature and HRT on methanation via operating the reactors at different temperatures (35 °C, 45 °C, and 55 °C) and HRT (30, 25, and 20 d) for 116 days. The results demonstrated that the digester conducted at 45 °C and an HRT of 30 d unexpectedly yielded the maximum average methane production of 296.08 ml/g volatile solids (VS). In contrast, the optimal HRT for the 35 °C and 55 °C digesters were 25 and 30 d, with a methane yield of 241.88 ml/g VS and 240.9 ml/g VS, respectively. High-throughput sequencing shows that Firmicutes, Bacteroidetes, Themotogae, Chloroflexi, and Acidobacteria dominated 90–98 % of the total bacteria. Temperature exhibited a significant influence on shaping microbial ecosystems, indicating that temperature, rather than HRT, is the primary factor to consider. Additionally, metagenomic analysis reveals that the levels of genes involved in acetoclastic and hydrogenotrophic methanogenic pathways were enhanced at 45 °C, probably improving methane yield. These findings provide new insights into "short-circuit" mitigation and strategies to strengthen methane generation from biomass. • The digester at 45 °C exhibited a higher methane yield than those at 35 °C and 55 °C. • The optimal HRT for the 35 °C, 45 °C, and 55 °C digesters were 25, 30, and 30 d, respectively. • Temperature showed more influence on microbial regulation than HRT. • The enhanced acetoclastic methanogenesis path exhibited at 45 °C. [ABSTRACT FROM AUTHOR]

Korshinsk peashrub branches (Korpb) are agroforestry byproducts that accumulate in millions of tons per year and need to be reasonably utilized. To maximate the utilization value of Korpb, an integrated process was proposed and conducted by using Korpb as the main substrate ingredient for Pleurotus tuoliensis cultivation and also performing anaerobic digestion (AD) of spent mushroom substrate (SMS) for biogas production. The results indicated that the cultivation substrate including Korpb could obtain higher mushroom yields than a conventional substrate, and AD of SMS added the value of Korpb. Preliminary calculation suggested that, for every t of P. tuoliensis production, 1.65 t Korpb was consumed and 314 m3 biogas was produced from corresponding amount of SMS, bringing a total economic profit of $906.1. In addition, this integrated strategy has positive ecological and social benefits. The maximization of Korpb value can not only promote the biological conversion of Korpb to circle economy, but also be beneficial for the development of environment, energy conservation and edible fungus industry. • Korpb is a lignocellulose biomass resource with great potential. • Integration of P. tuoliensis cultivation and AD of SMS maximized the value of Korpb. • The economic profit achieved $906.1 for every t of P. tuoliensis production. • The integrated strategy has positive ecological and social benefits. [ABSTRACT FROM AUTHOR]

• High near-infrared reflectance thermochromic materials limits heat gain in winter. • UV absorber could alleviate light aging of thermochromic materials to some extent. • Relative position of ice-melting coating didn't affect functional fillers release. • Composite coating achieved 9 °C cooling effect and freezing temperature of −5 °C. • Skid and temperature change resistance of composite coating were investigated. As the main type of urban roads, the surface temperature of asphalt pavement can reach 70 °C in summer because high heat absorption, causing pavement disease and aggravating the heat island effect. Solar reflective coating is an effective way to tackle the problem in summer but may bring certain negative effects in winter. In this paper, a kind of composite coating containing thermochromic (TCM) materials and snow melting and ice suppression (SMIS) functional fillers was developed. The reflective properties, thermal behavior and road performance of the pavement coatings were investigated. The results showed that the optimal TiO 2 contents in TCM-black coating for pavement was 3 wt% to make full use of optical variation range. Long-term solar radiation destroyed the structure of thermochromic microcapsules and caused degradation of color and visible reflectance of TCM coatings, which could be alleviated by ultraviolet absorbers and light stabilizers. The optimal double-layer coating structure with TCM on the top and SMIS at the bottom could achieve cooling effect of 9 °C, pavement icing temperature of −5 °C and faster ice melting rate. The skid and temperature change resistance with the coatings also met requirements. This study provides a reference for developing novel pavement materials with balanced cooling effect and ice suppression capacity for mitigating heat island effect, improving driving safety, and ensuring the optimal service state and longer service life of pavement at the same time. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Continuous stirred-tank reactor (CSTR) has a "short-circuit" problem. • The Gradient anaerobic digestion reactor (GADR) can solve the problem of CSTR. • GADR can stably carry out semi-continuous dry anaerobic digestion. • GADR can improve the biogas yield of straw raw materials that are unique to China. • The biogas production efficiency and microbial community were analyzed. In China, the problem of low biogas yield of traditional biogas projects has become increasingly prominent. This study investigated the effects of different hydraulic retention times (HRTs) on the biogas production efficiency and microbial community under pilot conditions. The results show that the "Gradient anaerobic digestion reactor" can stably carry out semi-continuous dry anaerobic digestion and improve biogas yield. The highest volatile solids (VS) biogas yield (413.73 L/kg VS and 221.61 L CH 4 /kg VS) and VS degradation rate (48.41%) were observed at an HRT of 25 days. When the HRT was 15 days, the volumetric biogas yield was the highest (2.73 L/L/d, 1.43 L CH 4 /L/d), but the VS biogas yield and degradation rate were significantly decreased. Microbial analysis showed that HRT significantly affected microbial community. It provides basic data support for the development of a new anaerobic digestion process and the practical application of the straw biogas project in China. [ABSTRACT FROM AUTHOR]

• The interval temperature digester exhibited the highest methane yield. • The decomposition rate of organic matter increases with increasing temperature. • Methanogenesis, rather than hydrolysis, is limited at the thermophilic temperature because of the loss of Methanosarcina. • Efficient methanogenesis occurs under the balance between hydrolysis and methanogenesis at interval temperature. • Our findings may provide insight into the temperature control in AD systems. Anaerobic digestion (AD) at mesophilic and thermophilic interval temperatures has received increasing attention due to an unexpectedly higher methane yield. However, there is no general consensus and the mechanisms of microbial regulation under interval temperature remain unclear. Therefore, this study evaluated the effect of conventional and interval temperatures on methanogenesis performance and microbial regulation in continuous AD of wilted corn straw. The results demonstrated that the hydrolysis rate increased with increasing temperatures, probably due to the predominant Firmicutes and Proteobacteria, whose abundance in D55 was more than 72% and 19%, respectively. However, in the stable period (31–55 d) experiments, digesters D35, D45, and D55 achieved an average methane yield of 224 ± 34, 311 ± 55, and 261 ± 49 N mL/g VS/d, respectively. Interval temperature substantially enhanced methane yield by 39.4% and 19.0% compared to that from mesophilic and thermophilic digesters, respectively. A higher proportion of Methanosarcina (94.42–94.73%) promoted the acetoclastic methanogenesis at interval temperature, implying that methanogenesis, rather than hydrolysis, is limited at the thermophilic temperatures because of the loss of Methanosarcina. Furthermore, a high abundance of essential genes involved in methane metabolism was found to stimulate methane production in the interval temperature digester. These findings revealed that the interval temperatures may be a balanced zone between hydrolysis and methanogenesis for achieving higher methane yield and provided a new perspective strategy for AD. [ABSTRACT FROM AUTHOR]

Ensiling is a widely used method for preserving crop stalks as biogas feedstock. However, secondary fermentation of silage is an inevitable problem that causes significant mass and energy losses. In this study, the effect of different lactic acid bacteria (LAB) inoculants on the fermentation pattern, aerobic stability, and methane production of maize stover was investigated. Maize stover was ensiled for 50 days with or without different LAB inoculants, followed by 10 days of air exposure. Methane production from the stover after the two processes was determined through batch anaerobic digestion (AD) tests. Lactiplantibacillus plantarum enhanced the homo-fermentation and reduced the pH of silage. Lentilactobacillus buchneri improved the hetero-fermentation of hexose, while causing higher dry matter loss (DML) than other inoculants. Limosilactobacillus fermentum enhanced pentose hetero-fermentation and increased both lactic acid and acetic acid production with minor DML. All the tested inoculants reduced the DML, improved the aerobic stability, and increased the methane yield of maize stover after ensiling (by up to 18.8%) and after air exposure (by up to 41.0%), with Limosilactobacillus fermentum exhibiting superior performance. The Limosilactobacillus fermentum treatment showed smaller variations in the bacterial community in AD than other treatments during air exposure. Ruminococcaceae , SHA-31 , SB-1 , Lachnospiraceae , Marinilabiaceae, and Erysipelotrichaceae showed positive correlations with water-soluble components, whereas Anaerolinaceae was positively correlated with cellulose or hemicellulose. [Display omitted] • Maize stover was ensiled with different lactic acid bacteria for methane production. • All the inoculants improved the aerobic stability and reduced dry matter loss. • The inoculants led to up to 41% higher methane yield after air exposure. • Limosilactobacillus fermentum enhanced pentose hetero-fermentation into acetic acid. • Limosilactobacillus fermentum showed superior performance in methane preservation. [ABSTRACT FROM AUTHOR]

To effectively deal with the operating uncertainties of protective relays and circuit breakers existing in the power system faults, an improved fault section diagnosis (FSD) method is proposed by using Takagi–Sugeno fuzzy neural networks (T–S FNN). In this method an optimal T–S FNN-based diagnosis model is built with the idea of distributed parallel processing for each section instead of the whole power system. To obtain accurate T–S FNN-based diagnosis models, a genetic learning adaptive gaining-sharing knowledge-based algorithm (GLAGSK) is designed to optimize their structure parameters and consequent parameters. GLAGSK combines an adaptive knowledge ratio and a genetic learning strategy to balance population diversity and convergence speed to boost the optimization ability. After a fault occurs, selective optimal T–S FNN-based diagnosis models are triggered according to the alarm information. They work in parallel to improve the fault diagnosis efficiency. Simulation results of three test systems including an actual fault event show that, compared with other peer algorithms, GLAGSK can obtain more accurate T–S FNN-based diagnosis models with faster global convergence. Besides, compared with the BP and RBF neural networks and other FSD methods, the proposed FSD method based on optimal T–S FNN-based diagnosis models can diagnose different complex faults successfully with higher fault credibility. • Improved fault section diagnosis (FSD) method based on T–S FNN is proposed. • T–S​ FNN-based diagnosis model is designed for each power system section. • Enhanced metaheuristic named GLAGSK is presented to optimize T–S FNNs. • GLAGSK is boosted by adaptive knowledge ratio and genetic learning strategy. • Proposed FSD method can diagnose different complex fault scenarios accurately. [ABSTRACT FROM AUTHOR]

Adopting anaerobic digestion (AD) of lignocellulosic biomass to produce biomethane is an effective approach to meet the urgent demand for clean and sustainable energy in energy transition. The pretreatment kinetic mechanism is the key to enhance the lignocellulosic carbon conversion and significantly improve the efficiency of AD. Various pretreatment strategies have been proposed in the literature, while a systematical summarization of these strategies based on different driving forces is still lacking. The purpose of this review is to classify and analyze the current technologies and research achievements on lignocellulose pretreatment technologies according to different driving forces including single ones and combined ones. Features, as well as fundamental modes of conventional and recently emerged pretreatments, have been introduced. Single pretreatment methods driven by physical, chemical, or biological forces have obvious advantages and limitations for the anaerobic transformation of lignocellulosic feedstocks. Recently emerged combined pretreatment technologies powered by multiple forces have synergistic treatment effects which hold greater application potential than those driven by single forces. Besides, a comprehensive evaluation of combined pretreatments is carried out on the basis of pretreatment efficiency, cost, energy consumption, and environmental impact to detect their potential applications in the actual biogas industry. By comprehensively summarizing the current features of single and combined technologies, this review finally provides future research perspectives for biomass pretreatment. [Display omitted] • Features of different pretreatments driving by different forces were analyzed. • Conventional pretreatments driven by single forces have obvious shortcomings. • Rational integration of multiple driving forces has synergistic pretreatment effect. • Combined pretreatment strategies have greater potential than single ones. • Physical-chemical methods are most promising based on comprehensive evaluations. [ABSTRACT FROM AUTHOR]

• The homogeneous dimer of FAELac achieved 37-fold higher activity. • Site-directed mutagenesis enlarged the substrate-binding pocket. • The catalytic activities of five mutants were enhanced. • Different enzymes had specific adaptability of natural substrates. • A high yield of ferulic acid (6.60 mg/g substrate) was obtained by mutant Q134T. Producing ferulic acid (FA) from the natural substrate with feruloyl esterase is promising in industries, screening and engineering new enzymes with high efficiency to increase the FA yield is of great concern. Here, the feruloyl esterase of Lactobacillus acidophilus (FAELac) was heterologous expressed and the FAELac with different oligomerization states was separated. Interestingly, the activity of dimer was 37-fold higher than high-polymer. To further enhance the efficiency of FAELac, eight mutants were generated based on the simulated structure, of which Q198A, Q134T enhanced the catalytic efficiency by 5.4- and 4.3-fold in comparison with the wild type. Moreover, higher yields of FA (2.21, 6.60, and 1.67 mg/g substrate, respectively) were released by the mutants from de-starched wheat bran, insoluble wheat arabinoxylan, and steam-exploded corn stover. These results indicated that improving the purification process, engineering new FAELac and substrates bias studies hold great potential for increasing FA production yield. [ABSTRACT FROM AUTHOR]