Processes

This study presents a controlled three-dimensional conjugate CFD comparison of counter-flow and parallel-flow concentric tube heat exchangers under identical Reynolds number conditions (Re = 1000–2000). By isolating the flow configuration as the only varying parameter, the intrinsic influence of flow arrangement on thermo-hydraulic performance is systematically evaluated. Unlike enhancement-focused studies involving geometric modification or advanced working fluids, the present study focuses exclusively on the influence of flow arrangement under identical operating conditions. The analysis focuses on heat transfer rate, outlet temperature distribution, pressure drop, thermo-hydraulic performance index, and a normalized heat transfer ratio (Ψ). The results show that the counter-flow configuration consistently enhances heat transfer by 3.17–4.29% compared to parallel-flow operation, while maintaining nearly identical pressure-drop values. This improvement is attributed to the preservation of a higher logarithmic mean temperature difference (LMTD) along the exchanger length, sustaining the thermal driving force under laminar flow conditions. In contrast, the parallel-flow configuration exhibits a rapid decay in temperature difference near the inlet region, limiting effective heat transfer. Although heat transfer increases with Reynolds number in both configurations, the thermo-hydraulic performance index decreases due to the relatively higher increase in hydraulic resistance. Comparison with classical laminar flow behavior confirmed the physical consistency and reliability of the numerical model. The findings demonstrate that counter-flow arrangement provides a measurable thermal advantage without additional hydraulic penalty. The study offers a physically consistent and practically relevant framework for the design and optimization of concentric tube heat exchangers used in engine cooling and waste heat recovery applications. Full article

Gas well production optimization is an effective way to improve the efficiency and economic performance of natural gas development. Multiphase flow in wellbores and reservoir seepage make the process highly nonlinear, strongly coupled, and complex. Traditional simulation software can provide accurate predictions, but the high computational cost limits its use in iterative and large-scale optimization. This paper presents an integrated framework that combines numerical simulation, surrogate modeling, and intelligent optimization for gas well production parameter optimization, particularly under continuous gas lift conditions. A simulator is used to generate datasets, which are then used to train a neural network surrogate model for fast prediction of gas well production response. An improved particle swarm optimization algorithm is applied to perform global search and obtain the optimal production parameter combination. Results show that the surrogate model can reliably replace the simulator in repeated prediction tasks while substantially reducing computational cost, and the improved algorithm performs better than traditional methods in both convergence speed and optimization accuracy. Case studies confirm that the optimized parameters effectively increase gas well production. The proposed framework provides an efficient and practical approach for intelligent production optimization in gas wells under complex wellbore multiphase-flow conditions. Full article

The study investigates position-dependent variability in the slitting and rewinding process of filtration paper rolls under industrial conditions. Although individual cutting positions operate under identical machine settings, systematic differences between them lead to quality deviations and reduced process performance. Spatial variability was analyzed using descriptive statistics, control charts, and process performance indices (P_p, P_pk), complemented by non-parametric statistical testing. The results revealed a significant spatial effect, with one slitting position responsible for most nonconforming products, highlighting the limitations of global capability indices, which may mask local systematic deviations in a multi-stream process. Potential root causes were identified using the 5 Whys method within the Quick Response Quality Control (QRQC) methodology. Following the implementation of corrective actions, including parameter adjustments, position-dependent control, and revised operating procedures, the observed proportion of nonconforming products reduced from 14.7% to 6.0%. Furthermore, after excluding the first rolls from the start-up phase, process performance improved to P_p = 1.36 and P_pk = 1.21. The study suggests that integrating global and position-level analysis in multi-stream manufacturing systems enables more targeted identification and mitigation of quality deviations. Full article

This article provides an overview of the physical pretreatments that can be applied to lignocellulosic biomass and their different benefits. It focuses on and compiles information on the main physical pretreatments applied to lignocellulose biomass, including the concept, advantages, disadvantages, and parameters of the pretreatments (milling, ultrasound, and microwave). A review of research carried out on different types of biomasses and what was obtained from them is also provided. Milling provides an essential mechanical change to optimize the surface, while microwave and ultrasonic methods provide sophisticated techniques that greatly increase the efficiency of transforming biomass through selective structural modification. The physical pretreatment goal is to improve the efficiency of conversion processes and increase the economic viability of using biomass as a renewable and sustainable source of energy and chemical products. The use of the energy of lignocellulosic biomass requires the proper implementation of pretreatments that facilitate the obtaining of biofuels and high-value biochemical products such as hemicellulose, lignin, and glucose derivatives, for example, ethanol, xylitol, butanol, and acetoacetic acid. Full article

Deep coalbed methane (CBM) is a core exploration and development domain for increasing the reserves and production of unconventional natural gas in China. A systematic understanding has been established on the enrichment and accumulation mechanism of high-rank deep CBM in the southern section of the eastern margin of the Ordos Basin. However, the medium-rank deep CBM in the Mugua Area of the Shenfu Gas Field in the northern section of the eastern margin has essential differences from that in the southern section in terms of coal rank and hydrocarbon generation–occurrence mechanism, and its accumulation and enrichment regularity remain unclear. The core innovations of this study are as follows: aiming at the unclear accumulation regularity of medium-rank deep CBM in the northern section of the eastern margin of the Ordos Basin, we first reveal the spatiotemporal synergistic coupling reservoir-controlling mechanism of five factors (sedimentation–thermal evolution–temperature–pressure–preservation), determine the 1750 m critical transition zone of the deep CBM occurrence state, and establish two types of accumulation models adapted to the geological characteristics of medium-rank coal. Taking the No.8+9 coal seams of the Taiyuan Formation in the Mugua Area as the research object, based on the theoretical foundation of the dual properties of coal seams as the “source rock–reservoir”, this paper comprehensively adopted technical means such as core observation, drilling and logging data, and high-pressure isothermal adsorption experiments to carry out systematic multi-dimensional studies on sedimentary microfacies, coal reservoir characteristics, thermal evolution degree, and gas-bearing property; identified the main controlling factors of CBM accumulation; and constructed the accumulation model. The results show the following: ① The main burial depth of the coal seams is more than 1700 m, with a thickness ranging from 7.0 to 21.3 m and an average of 15.1 m, and the coal structure is dominated by the primary structure; maximum vitrinite reflectance (R_o,max) is generally distributed from 0.90% to 1.39% with an average of 1.08%, belonging to typical medium-rank coal; and the organic matter type is mainly Type III, with an average gas content of 10.01 m³/t, where the average proportion of desorbed gas in the total gas content is 83.91%, featuring superior source and reservoir conditions and a good foundation for CBM enrichment. ② The CBM accumulation in this area is jointly controlled by the coupling of four factors: sedimentation, thermal evolution degree, temperature–pressure effect, and preservation conditions. The tidal flat–lagoon facies control the development of high-quality coal seams; regional metamorphism dominates the hydrocarbon generation capacity and gas quality of coal seams; the temperature–pressure coupling forms a critical adsorption zone at 1750 m, defining the differentiation boundary of the occurrence state of deep CBM; and high-quality mudstone cap rocks, a stable structural environment, and closed hydrodynamic conditions constitute the three key guarantees for gas enrichment. ③ Two types of accumulation models are divided: “source–reservoir integration + multi-factor synergistic enrichment type” and “source–reservoir limited + insufficient accumulation condition type”. Among them, the four reservoir-controlling factors of the synergistic enrichment type are highly coupled, with excellent gas-bearing property and strong recoverability. This study systematically clarifies the enrichment and accumulation regularity of medium-rank deep CBM in the Mugua Area and improves the accumulation theory of medium-rank deep CBM in the northern section of the eastern margin of the Ordos Basin. Full article

Urban heating systems continue to rely heavily on fossil fuels, driving significant CO₂ emissions and underscoring the need for scalable renewable alternatives. This study evaluates a solar-assisted aquifer thermal energy storage (ATES) system for sustainable urban heating, operating within a relatively deep aquifer. A numerical model of the Mannville aquifer is developed to simulate charge–discharge cycles in a relatively deep open-loop ATES system, examining subsurface temperature evolution, storage efficiency, and long-term thermal stability under Canadian climatic conditions. Modeling results indicate that such aquifers act as an effective thermal buffer for solar energy storage operations, smoothing seasonal temperature fluctuations and stabilizing heat production. Surplus solar thermal energy injected during low-demand periods significantly reduces long-term temperature decline and preserves thermal availability for winter extraction. Balancing contributions from solar and aquifer storage maintains system efficiency during peak demand while improving overall thermal management. The integrated approach enhances renewable energy utilization, reduces reliance on conventional heating systems, and strengthens the resilience of urban energy networks. Our findings demonstrate that coupling solar thermal input with geothermal heat storage in relatively deep aquifers offers a practical pathway for advancing sustainable urban heating in cold-climate regions. The modeling framework provides a foundation for optimizing seasonal storage strategies and guiding the design of hybrid solar–geothermal systems for large-scale urban applications. Full article

Automatic history matching traditionally depends on a large number of time-consuming numerical simulations, which makes the overall workflow computationally expensive. Deep learning-based surrogate models provide an efficient alternative, but their predictive performance often relies on large labeled datasets, whose generation through reservoir simulation remains costly. To alleviate this issue, we propose a data-efficient surrogate modeling framework for automatic history matching. The framework consists of two components. First, the reservoir parameter field is reformulated as a flattened representation and processed using one-dimensional convolutions. This representation provides a direct connection between parameter encoding and production-sequence prediction while maintaining competitive forecasting accuracy. Second, an autoencoder is pre-trained on unlabeled parameter realizations, and the learned encoder is then used to initialize the surrogate model for supervised regression, thereby improving the utilization of inexpensive, unlabeled data. The proposed framework is evaluated on the three-dimensional Brugge benchmark reservoir model. Results show that the one-dimensional representation achieves competitive predictive accuracy with shorter training time. In addition, the pre-training strategy is particularly beneficial when labeled simulation data are limited. Overall, the proposed framework improves the data efficiency of surrogate-assisted automatic history matching and reduces the dependence on extensive labeled simulations in the Brugge benchmark. Full article

Ball milling can improve protein recovery from defatted rice bran, but the links among milling conditions, particle attributes, and extraction transport remain insufficiently defined. This study evaluated the effects of milling time (30–90 min) and rotational speed (30–120 rpm) on powder properties and alkaline protein extraction at pH 11 for 30–180 min at 24, 37, and 50 °C. Powders were characterized by laser diffraction, SEM image analysis, X-ray diffraction, and extraction-relevant indices describing the interfacial area and diffusion time scale. Extraction curves were fitted to first-order, pseudo-second-order, Peleg, and apparent Fick diffusion models. Milling reduced median particle size from 145 to 61 µm, increased fines (<45 µm) from 1.86% to 32.09%, and raised surface area proxies by about 30- to 40-fold. Compared with the control sample, milled samples generally showed faster extraction and higher protein recovery, with maximum endpoint recoveries of 89.91 mg g⁻¹ at 24 °C, 90.06 mg g⁻¹ at 37 °C, and 86.10 mg g⁻¹ at 50 °C. Late-stage extraction data collapsed onto a Fickian master curve, indicating diffusion-limited behavior, and apparent effective diffusivity increased with temperature. At 37 °C, the radius–shape–circularity model explained nearly all the between-powder variation in $\ln D_e\left(R^2=0.998;\mathrm{adjusted} R^2=0.996\right)$, and the shape factor remained significant after accounting for particle radius $\left(p=0.0179\right)$. Overall, ball milling improved extraction primarily by reducing diffusion length and altering particle morphology, providing practical guidance for optimizing rice bran protein recovery. Full article

This study presents a data-driven framework to predict and optimize the quality of date juice (DJ) produced from two commercially important Saudi cultivars (Sukkary and Khlass) using physicochemical and processing variables as model inputs. A total of 1600 experimental runs were performed by systematically varying initial fruit moisture content, extraction temperature (20, 40, 60, and 80 °C), mixing velocity (10, 20, 30, 40, and 50% of maximum speed), and date-to-water ratios (1:1, 1.5, 2, 2.5, and 3 w/w). The produced juices were characterized at 25 °C for water activity, moisture content, density, pH, total soluble solids (°Brix), turbidity, viscosity, hydroxymethylfurfural (HMF), browning index, extraction time, electrical energy consumption, and an integrated Quality Index (Qi). A feed-forward artificial neural network (ANN; 7–15–1) with a hyperbolic tangent transfer function was developed and validated using normalized datasets, and its performance was benchmarked against multiple linear regression (MLR). The ANN consistently outperformed MLR for Qi prediction, achieving higher coefficients of determination and lower error indices across training, testing, and validation, indicating strong generalization and minimal overfitting. Sensitivity analysis highlighted total soluble solids, moisture content, and HMF as the most influential predictors of Qi. Optimal juice quality (Qi ≥ 0.91) was repeatedly achieved under moderate thermal conditions (≈60 °C), with 40% mixing velocity and a 1:2.5 date-to-water ratio, providing a practical operating window for producing juice at the target °Brix while limiting thermal quality deterioration. Overall, the proposed ANN-based model provides an actionable decision-support tool for process optimization and quality standardization, supporting the transition of date-juice manufacturing toward Industry 4.0 through data-driven monitoring and adaptive control strategies. Full article

Bed-separation grouting filling mining is a damage-mitigation mining technology characterized by non-interfering mining and filling operations, low cost, and high efficiency. To recover coal resources from the 3801 working face located beneath a surface gas station in a Shanxi coal mine, this study first analyzed the maximum allowable deformation values for the gas station’s canopy, business hall, and oil storage tanks. Second, the feasibility and safety of bed-separation grouting filling mining at the 3801 working face were investigated using physical similarity modeling and the probability integral method. Finally, a field application of this technology was carried out at the 3801 working face. The results show that: (1) After the successive mining of the 3802, 3803 and 3801 working faces, the No. 17 bed separation was finally preserved above the 3801 working face. It is located in the upper part of the water-conducting fracture zone and has a thick impermeable isolation layer. (2) Physical similarity simulation and numerical simulation (3UDEC) of bed-separation grouting filling mining at the 3801 working face indicate that the underlying strata are effectively compacted after mining, and both overlying strata movement and surface subsidence above the grouting zone are significantly reduced. (3) The probability integral method was adopted to predict surface movement and deformation induced by mining at the 3801 working face (bed-separation grouting filling mining), the 3802 working face (fully mechanized top-coal caving mining) and the 3803 working face (full-seam mining in a single lift). All surface movement and deformation indices satisfy the surface deformation control requirements for the gas station. (4) After completion of the overburden bed-separation grouting filling project at the 3801 working face, the measured surface movement and deformation values during and after mining are all below the allowable deformation limits. No large deformations or cracks occurred in gas station structures including the canopy, business hall and oil tank farm. The protection effect is satisfactory, and the gas station has maintained normal operation throughout the mining period. Full article

This study aims to resolve the genetic origin of crude oils accumulated in the D Subsag and to assess the potential cross-sag hydrocarbon migration from the adjacent Haizhong Sag. The D Subsag, situated on the western margin of the Weixinan Sag in the Beibuwan Basin, is a significant petroleum province with proven reserves exceeding 10 million tons in the Weizhou Oilfield. However, the origin of these oils and the contribution from the Haizhong Sag source kitchen remain poorly constrained, hindering accurate resource assessment. To address this, we integrated organic geochemical analyses of nine source rock samples from the Haizhong Sag (Well H1) and eight crude oil samples from the D Subsag reservoirs. Bulk geochemical and biomarker signatures reveal distinct organic facies within the Paleogene succession. Type III kerogen, characterized by terrigenous higher plant input (high C₁₉₊₂₀ tricyclic terpanes and C₂₉ regular steranes, Pr/Ph > 2.5) deposited under oxic freshwater conditions, dominates source rocks from the third member of the Weizhou Formation (EWZ₃). In contrast, the second and third members of the Liushagang Formation (Els₂ and Els₃) contain mixed Type II₂-III kerogen with elevated contributions from lacustrine algae and aquatic organisms (elevated C₂₃ tricyclic terpanes and C₂₇ regular steranes). Thermal maturity assessment (with T_max of 436 to 448 °C) confirms that all source intervals are within the oil generation window. Two genetically distinct oil groups are identified in the EWZ₃ reservoirs. Group 1 oils (Well W4) exhibit a lacustrine algal signature (C₂₇/C₂₉ sterane > 1.15; low Pr/Ph 1.54–1.68) that does not correlate with the analyzed Haizhong Sag source rocks, suggesting localized, intra-sag source contributions. In contrast, Group 2 oils (Wells W6 and W6-2) display strong geochemical affinities with the Els₂ and Els₃ source rocks, evidenced by mixed terrestrial/aquatic signatures (∑nC₂₁⁻/∑nC₂₂⁺ < 1.0). These findings confirm that fault systems acted as conduits for long-distance migration from the Haizhong Sag, while also highlighting a previously unrecognized contribution from local source intervals. This refined petroleum system model provides critical constraints for delineating remaining hydrocarbon potential and reducing exploration risk in the Beibuwan Basin. Full article

Antimicrobial peptides such as Melittin exhibit potent broad-spectrum activity but are limited by high cytotoxicity. The rational design of bioinspired Melittin-derived analogues represents a promising strategy to reduce toxicity while maintaining antimicrobial efficacy. In this study, Melittin and analogues (TT-1, FKW, and WKW) were synthesized using solid-phase peptide synthesis (SPPS) and characterized for biological and biophysical essays. Antimicrobial and hemolytic activity, serum stability, secondary structure, and membrane interaction were analysed. FKW and WKW exhibited broad-spectrum antimicrobial activity, with minimum inhibitory concentration (MIC) as low as 8 and 16 µg/mL against Staphylococcus aureus and Enterococcus faecium. Both analogues also showed improved activity against Klebsiella pneumoniae (32 µg/mL) and Pseudomonas aeruginosa (128 and 256 µg/mL for FKW and WKW, respectively) compared to Melittin (64 and 512 µg/mL). In terms of cytotoxicity, FKW and WKW showed significantly reduced hemolytic activity, with HC₅₀ values of 264.8 µg/mL and 237.2 µg/mL, respectively, resulting in improved selectivity indexes relative to Melittin (HC₅₀ of 7.9 µg/mL). In liposomes, both adopt α-helical structures and cause disruption via pore formation or detergent-like mechanisms. TT-1 showed minimal toxicity but weak antimicrobial activity (MIC >256 µg/mL). Although FKW and WKW exhibited limited serum stability (half-lives of 2.2 and 1.5 h), their degradation may reduce systemic toxicity. Overall, these analogues demonstrate an improved balance between antimicrobial activity and safety. Full article

Water scarcity and water quality degradation in river basins are critical issues addressed by water resources management authorities. Grey relational analysis is adopted to rank key factors affecting water resources in the Beijing-Tianjin-Hebei region. Bankruptcy theory is combined with an improved Nash bargaining game model, and spatiotemporal constraints of cross-regional water resources are incorporated to analyze water allocation under multiple water supply scenarios. Results indicate that the GM (1,1) model achieves Level II (good) prediction accuracy, with relative errors below 6% in most years. The cooperative game model (CGM) yields the highest correlation coefficient of 0.996, indicating the optimal allocation performance. The water demand satisfaction rate in Beijing is the highest among the three regions. An economic compensation range indicator (e) is established for water resource trading games. As the trading water volume increases from 0.01 to 20 billion m³, the feasible compensation range expands from 463.57 to 1,757,045.78 ten thousand yuan. These results provide a scientific basis for rational, stable, and sustainable water resources allocation in the Beijing-Tianjin-Hebei region. Full article

To determine a reasonable coal pillar width for gob-side entry driving in extra-thick coal seams and improve roof control under thick top-coal conditions, the No. 50604 return airway of Ti’an Coal Mine was selected as the engineering case. A combined approach involving theoretical calculation, numerical simulation, and field monitoring was adopted. Based on limit equilibrium theory and a modified Kastner formula for rectangular roadways, the reasonable coal pillar width was determined to be 7.13~8.42 m. Sensitivity analysis showed that the calculated width was sensitive to the stress concentration and lateral pressure coefficients. FLAC3D simulations compared the plastic zone and deformation of the gob-side entry under different pillar widths, and 8 m was determined as the reasonable width. Mining-stage simulations indicated that the plastic failure range and deformation increased markedly within 5~10 m ahead of the working face. A roof full-cable deep–shallow collaborative support system was proposed, and reasonable roof support parameters were determined through orthogonal numerical simulation and multi-index evaluation. Field monitoring showed that roadway deformation remained controllable during excavation and mining, verifying the rationality of the 8 m narrow pillar and roof full-cable support parameters. Full article

To address the insufficient frequency-support capability, the difficulty of multi-terminal power coordination, and the constraints on DC-voltage fluctuations in flexible DC transmission systems under weak-grid interconnection, this paper conducts a simulation-based control strategy study. First, based on the coupling relationship between AC frequency and DC voltage, an inertia-enhanced grid-forming/VSG control method is proposed, enabling converter stations to use DC-link capacitor energy to provide transient frequency support during the initial stage of a disturbance. Second, for multi-terminal flexible DC systems, an adaptive U-P-f dual-droop distributed control strategy is designed to coordinate unbalanced power sharing among multiple converter stations and to limit the DC-voltage deviation generated during frequency support. In this paper, a hybrid half-bridge/full-bridge MMC is adopted as a fixed-converter simulation platform, rather than being treated as an object of systematic topology optimization. Finally, a four-terminal MMC-HVDC simulation model is established in MATLAB/Simulink, and the proposed control strategy is evaluated under weak-grid step-load disturbances, different short-circuit-ratio conditions, and continuous pseudo-random load disturbance scenarios. Simulation results show that, under the tested operating conditions, the proposed method can reduce the maximum frequency deviation, suppress DC-voltage fluctuations, and improve the power-sharing process among multi-terminal converter stations compared with conventional VSG control and fixed-droop control. Full article

Against the global carbon neutrality backdrop, amine-based CO₂ capture technology is critical for industrial greenhouse gas emission reduction. However, mixed amine absorbents can cause severe corrosion of Q235B carbon steel, restricting the stable operation of carbon capture, utilization, and storage (CCUS) projects. This study systematically investigated the corrosion behavior of Q235B carbon steel in a novel mixed amine system under simulated industrial conditions using weight loss tests, electrochemical measurements (EIS, potentiodynamic polarization), and advanced characterizations (FT-IR, ¹³C NMR, SEM-EDS, XRD). The temperature was the dominant factor: corrosion rate increased significantly with rising temperature. Under CO₂-saturated conditions, 15–30% absorbent concentrations showed no significant effect on corrosion rate owing to similar molar loading and pH. At 60 °C and 30% concentration, the corrosion rate peaked at 30 L/L CO₂ loading. Carbamate accumulation promoted corrosion at low loading, while increased bicarbonate inhibited corrosion at high loading. The main corrosion products (Fe₃O₄, Fe₂O₃) formed loose, porous films with poor protectiveness. This work clarifies the electrochemical corrosion mechanism and provides data support for corrosion prevention in CCUS equipment. Full article

Buildings account for nearly half of global energy consumption, with HVAC systems contributing approximately 40%. Fan coil units (FCUs) and fresh-air systems are widely adopted in commercial buildings for their flexibility. However, this system faces numerous critical challenges in tropical maritime climates, including low temperature control accuracy, high energy consumption, and inadequate coordination between thermal comfort and indoor air quality. This study aimed to optimize the indoor thermal environment and reduce HVAC energy consumption. It compared and analyzed the operational performance of traditional PID control and MPC. Additionally, dynamic CO₂ concentration modeling was performed to evaluate the impact of different outdoor air strategies on indoor air quality. A building simulation model was developed in TRNSYS 18. Based on the simulation data, a multi-objective model predictive control (MPC) model was created in MATLAB/Simulink. Results indicate that MPC significantly outperforms PID control in both temperature stability and energy efficiency across all outdoor air strategies, with the occupancy-based demand-controlled outdoor air strategy achieving the greatest energy savings (16.89%) while maintaining favorable indoor air quality. This study provides a theoretical foundation and practical control guidelines for the coordinated optimization of fan coil units and outdoor air systems in tropical maritime climates, facilitating the development of energy-efficient and comfortable HVAC solutions for commercial buildings. Full article

The inherent heterogeneity of coal significantly influences cutting efficiency, directly impacting energy consumption and dust generation in mining operations. To investigate this effect, this study established a heterogeneous coal model using PFC 2D 5.0, assigning strength parameters based on the Weibull distribution. The influence of the heterogeneity index (λ) on macroscopic strength, brittleness, and micro-crack propagation during coal cutting was systematically analyzed, and comparisons were made with homogeneous models of varying uniaxial compressive strength (UCS). The results show that as λ increases, both UCS and Brazilian tensile strength (BTS) increase exponentially, approaching the values of the homogeneous models, with BTS exhibiting greater sensitivity to λ than UCS. The brittleness index also increases with λ. During cutting, a higher λ leads to more concentrated crack propagation and stress distribution, as well as a reduced proportion of shear cracks, indicating a shift toward a more controllable fragmentation mode. Correspondingly, the specific energy (SE) for cutting decreases monotonically with λ, reflecting enhanced cutting efficiency, a trend attributed to the reduced energy dissipation from shear friction and the homogenization of internal stress distribution. Compared with homogeneous models, the heterogeneous models produce a more complex crack network and a greater number of cracks at lower strength levels, though these differences diminish as λ increases. These findings provide theoretical insights for optimizing cutting parameters to reduce energy consumption and minimize uncontrolled fracturing in efficient coal resource exploitation. Full article

Petroleum refinery wastewaters are highly recalcitrant and recognized as one of the most challenging industrial effluents requiring advanced treatment strategies. This study aims to investigate the synergistic performance of a sequential electrocoagulation (EC) and electro-Fenton (EF) process for the mineralization of this complex effluent. The EC pretreatment was optimized using response surface methodology via Doehlert design, establishing optimal conditions at pH 6.0, 0.8 A, and a 75 min electrolysis time. Under these conditions, 39% of total organic carbon (TOC) and 56% of chemical oxygen demand (COD) were removed. The quadratic polynomial model developed for the EC stage presented an excellent fit with the experimental data (R² = 0.99, R²_adj = 0.97, p < 0.05), confirming its strong predictive robustness. In order to degrade the remaining recalcitrant organic pollutants, the pretreated effluent underwent EF oxidation (0.01 M ferrous ion, 0.8 A, pH 3), leading to TOC and COD removal rates of 68% and 76%, respectively, after a 360 min electrolysis time. The integrated EC-EF process achieved an overall mineralization of 81% and an oxidation efficiency of 89%. Finally, a comprehensive evaluation of the system’s energy consumption and economic viability established a solid techno-economic baseline for this sequential approach, indicating a competitive total operating cost of USD 0.036 per gram of TOC removed. Full article