Search Results (437)

Broken gangue in goafs exhibits complex mechanical deformation and seepage evolution under coupled loading and hydraulic action, which directly affects the hydraulic stability and water-hazard prevention of mining engineering. In this study, a systematic investigation was carried out to elucidate the evolution of seepage characteristics in a granular broken-rock assemblage under coupled hydraulic–mechanical loading. Four mono-sized specimen groups with particle-size ranges of 5–10 mm, 10–15 mm, 15–20 mm, and 20–25 mm were prepared. Using a modified rock triaxial–hydraulic testing system, nominal uniaxial compression tests, triaxial compression tests under different moisture conditions, and staged axial loading–seepage coupling tests were conducted. The results indicated pronounced particle-size effects: with increasing particle size, the nominal uniaxial compressive strength decreased (maximum reduction of 41.26%), while the crushing ratio increased (from 0.99% to 28.89%). The compression–densification process exhibited a staged evolution characterized by “slow increase–rapid increase–stable increase.” Water-induced deterioration intensified with increasing water content, and the compressive strength reduction reached 29.8% under saturated conditions. The evolution of seepage behavior was jointly governed by loading rate and particle size. Both pore pressure and pore-pressure gradient increased with loading rate. The permeability–porosity relationship was nonmonotonic, with an inflection occurring at a porosity of approximately 0.30–0.32, accompanied by an order-of-magnitude variation in the Darcy-flow deviation factor, indicating a progressive nonlinear deviation from Darcy behavior. These observations reflected a competitive mechanism involving “compaction-induced flow resistance increase–fragmentation and rearrangement–local channel regeneration.” Numerical simulations performed in COMSOL6.2 further confirmed, at the microscopic level, that the development of preferential local seepage channels and the expansion of stagnant-water zones were the fundamental causes of locally enhanced seepage capacity under an overall compaction background. The findings provide a theoretical basis for understanding water–rock interaction mechanisms in goafs and offer reference for mine water-hazard mitigation and groundwater resource protection. Full article

The aim of this study was to investigate the ability of sewage sludge-derived biochar to remove PO₄-P from real biologically treated wastewater. Biochar was produced via the pyrolysis of anaerobically digested sewage sludge pretreated with nanoscale zero-valent iron (nZVI) at concentrations of 3%, 1.5%, and 0.5% (w/w, based on total solids). A sample without nZVI addition was used as a control. The properties of biochar samples were analyzed, including elemental composition, specific surface area, and pore size. PO₄-P removal was evaluated using both batch adsorption and column experiments. The highest adsorption capacity determined in the batch experiment was 2.5 mg/g. When wastewater was passed through columns packed with 0.3–0.6 mm biochar particles at a hydraulic loading rate of 1 m/h, a 3-fold-higher phosphorus retention capacity was obtained in the range of 7.26–7.82 mg/g. The column containing biochar derived from sewage sludge with 3% nZVI accumulated 7% more PO₄-P than the biochar without nZVI. All columns effectively removed phosphates from wastewater (efficiency > 80%) due to the chemical composition of biochar, which mainly contained Fe and Ca elements. In contrast to the batch experiment, the columns were subject to the biological sorption of phosphates via microorganisms, physical retention between particles, and the formation of precipitates on the surface of a column. Full article

Deep coalbed methane (CBM) reservoirs are characterized by high in situ stress, and the effective stress during CBM production is significant, leading to substantial damage to reservoir permeability. Studying the variation patterns of coal permeability during stress unloading is crucial for revealing the mechanisms by which CBM stimulation through slotting and cavity creation modifies in situ stress. To understand the permeability variations in fractured coal under stress changes, gas seepage experiments were conducted using seven deep coal samples obtained from the Linxing–Shenfu mining area in the Ordos Basin of North China. Through these experiments, permeability variations in coal under different confining, axial, and gas pressures were investigated, and their implications for permeability enhancement through hydraulic slotting in deep coal seams were analyzed. The results show that during loading, permeability decreases with increasing effective stress, and the rate of permeability damage increases. During unloading, the changes in coal permeability transition from slow to rapid, with the stress sensitivity coefficient increasing and the stress sensitivity becoming more pronounced. Regardless of the loading or unloading process, lower axial pressure leads to higher permeability, greater permeability recovery and damage rate, a larger stress sensitivity coefficient, and stronger stress sensitivity of the coal. For every 4 MPa decrease in the axial pressure, the permeability increases by approximately 0–10%, and the permeability recovery rate increases by about 6%. This is because the lower axial pressure reduces the effective stress acting on the coal matrix and fractures, thereby widening the flow channels and enhancing both the permeability and its recovery capacity. In addition, for every 0.3 MPa increase in the gas pressure, the permeability increases by approximately 10–50%, and the permeability recovery rate increases by about 20%. This indicates that elevating pore pressure effectively counteracts effective stress, expands fracture apertures, and promotes fracture connectivity. This work demonstrates that fractured coal is highly sensitive to stress and that stress relief plays a crucial role in enhancing the permeability of deep coal seams. Full article

During frequent peak-regulation operation, pumped storage units inevitably operate under off-design conditions. Variations in draft tube flow structures under different load conditions may alter the hydraulic loading acting on the runner and shaft system. In this study, a model pump-turbine was investigated using unsteady numerical simulations combined with finite element structural analysis. Analyses were conducted under 70%, 100%, and 105% load conditions, representing typical part-load, rated, and overload operating states. The results show that under 70% load, the draft tube flow exhibits an eccentric structure with strong circumferential pressure non-uniformity. At the rated condition (100% load), the flow field is closest to axisymmetric with the most uniform pressure distribution. Under 105% load, a concentrated central vortex forms, and the degree of non-uniformity is intermediate. The hydraulic loads under different conditions lead to significant differences in the stress and deformation characteristics of the shaft system. The maximum equivalent stress increases from 1.84 MPa at the rated condition to 3.33 MPa under overload conditions, while more pronounced flow asymmetry and pressure non-uniformity occur at part-load operation. These findings clarify the relationship between load variation, draft tube flow structures, and the mechanical response of the shaft system. Full article

Polyurethane O-ring seals are vital for the service life and sealing reliability of hydraulic systems, yet internal hysteresis heat generation under reciprocating motion causes localized temperature rise, altering contact pressure distribution and impairing sealing performance. This study aimed to clarify the coupled effects of reciprocating motion parameters on O-ring hysteresis heat generation and sealing performance. A unified hysteresis heat generation rate expression was derived by combining the time–temperature superposition principle with the Maier–Göritz model, and the heat source model was integrated into a thermo-mechanically coupled finite element analysis (FEA) framework, validated by matching simulated and experimental temperature rise histories. Under baseline conditions, hysteresis heating causes the O-ring’s peak contact pressure to decrease by approximately 0.4 MPa during the outward stroke. Parametric analysis revealed that elevated operating parameters increase contact pressure to maintain effective sealing, but simultaneously intensify hysteresis heating. Quantitatively, the maximum O-ring temperature was highly sensitive to operating conditions, reaching 63.6 °C at 8 MPa hydraulic pressure, 60.0 °C at a 90 Hz reciprocating frequency, and up to 81.5 °C for a friction coefficient of 0.2. Although the current framework is limited by the exclusion of interfacial frictional heating, it enables the reliable quantitative prediction of thermal loads. Ultimately, this study provides a robust method for assessing sealing safety margins and offers theoretical guidance for the structural optimization of hydraulic sealing systems. Full article

Sulfamethoxazole (SMX) is one of the most frequently detected antibiotics in aquatic environments and is difficult to remove by conventional biological treatment because of its persistence, potential toxicity to microbial communities, and associated risk of antibiotic resistance selection. Aerobic granular sludge membrane bioreactors (AGMBRs), which combine the compact and stratified structure of aerobic granular sludge with membrane-based solid–liquid separation, have emerged as a promising platform for SMX-contaminated wastewater treatment because they provide high biomass retention, decoupled sludge retention time (SRT) and hydraulic retention time (HRT), and stable effluent quality. This review systematically summarizes recent advances in AGMBRs for SMX removal, with emphasis on how operating parameters (e.g., dissolved oxygen, hydraulic retention time, organic loading rate, C/N ratio, and sludge retention time) and membrane-related factors (e.g., membrane flux, aeration-induced shear, membrane type, and pore size) affect treatment performance and process stability. The main SMX attenuation pathways in AGMBRs are discussed from three perspectives: sorption and partitioning within granules and extracellular polymeric substances (EPSs), microbial biodegradation and co-metabolism, and membrane retention that prolongs effective contact time and shapes microbial ecology. Particular attention is given to the dual role of EPS and soluble microbial products (SMPs), which contribute to granule stability and SMX tolerance but also accelerate membrane fouling through cake-layer formation, pore blocking, and transmembrane pressure increase. Current challenges include incomplete understanding of transformation products, ARG- and MGE-related risks, long-term fouling–biodegradation interactions, and the lack of pilot-scale validation. Future research should therefore focus on mechanism clarification, integrated control of removal and fouling, energy-efficient operation, and scale-up of AGMBRs for practical antibiotic wastewater treatment. Full article

This article presents the synthesis, real-time implementation, and experimental validation of an approximated adaptive dynamic programming (AADP) actor–critic controller for precise flow rate regulation of a variable-displacement axial-piston pump designed for open-circuit hydraulic systems. Replacing the conventional hydro-mechanical regulator with an electrohydraulic proportional spool valve, the model-free controller employs two compact two-layer neural networks: the actor generates valve PWM signals from the flow tracking error, its integral, and measured discharge pressure, while the critic approximates the infinite-horizon quadratic cost-to-go via the online solution of the Bellman equation through gradient descent on Bellman residuals. Lyapunov analysis establishes closed-loop stability under bounded learning rates, with initial weights tuned via nominal plant simulation to ensure convergence from feasible starting policies. After extensive laboratory testing across four fixed loading conditions and dynamic load variations, the adaptive controller demonstrated superior performance compared with a proportional-integral (PI) controller, a Lyapunov model-reference adaptive controller (LMRAC), and an H_∞ controller (Hinf). Real-time metrics confirm bounded critic signals and near-zero Bellman errors, validating optimal policy convergence amid unmodeled hydraulic nonlinearities. Full article

In polar environments, the thermoviscous behavior and heat dissipation characteristics of deck hydraulic systems are severely affected, resulting in response delays and increased failure risk during high-load operations such as anchor retrieval. To address the limited availability of polar field test samples and the multi-scale nature of oil-temperature responses—featuring short-term abrupt variations and slow-varying hysteresis—this study proposes a Multi-Scale Attention Transformer (MSA-Transformer). Through parallel multi-scale attention branches, the model collaboratively captures both transient and gradual dynamics, thereby improving prediction robustness under polar extreme cold conditions. Based on anchor-retrieval test data collected in Genhe, China’s Cold Pole, at −30 °C, −35 °C, and −40 °C, a dataset containing 18 load cycles was constructed. Experimental results based on 5-fold stratified cross-validation results show that the MSA-Transformer achieves the best performance across evaluation metrics, attaining an average coefficient of determination (R²) of 0.9119 along with the lowest error rates (MAE, RMSE, MSE) on the test set, thereby outperforming LSTM, CNN-LSTM, and the standard Transformer. This work provides an effective tool for state prediction, maintenance optimization, and anomaly early warning in polar deck hydraulic systems, supporting the intelligent health management of hydraulic equipment. Full article

To address the limitations regarding poor adaptability to complex forest environments as well as high installation and operational costs in existing mountain transportation equipment, a modular cable-type equipment for moso bamboo transportation was designed based on the terrain characteristics of steep bamboo forests and specific transportation requirements. This study first presents the overall structure and working principle of the transportation equipment. Next, a theoretical analysis and component selection were conducted for critical parts such as the wire rope, supporting components, wire-rope-driven devices, and hydraulic systems. Then, the static characteristics of the supporting components and the vibration characteristics of the wire rope were simulated and analyzed. Finally, performance testing of the equipment was conducted, focusing on transportation productivity and machine utilization. The results showed that the maximum deformation of the supporting components was 1.75 mm, occurring at the lower roller–rail contact region. During unloading, the first-order principal vibration amplitude of the wire rope had the greatest impact at the mid-span position, with a value of 0.27 m. The vibration frequency of the wire rope during operation is influenced by the its initial tension, load mass, and attachment distance, with the first-order frequency range approximately between 0.85 and 3.90 Hz. Within this frequency range, the bouncing excitation caused by moso bamboo does not induce resonance in the wire rope. The transportation productivity of the equipment was 2.61 tons per hour, with the machine utilization rate exceeding 95%. This study indicates that the designed cable-type equipment effectively meets the requirements for moso bamboo transportation in complex forest environments. Full article

Constructed wetlands (CWs) have emerged as effective nature-based solutions (NbS) for the treatment of industrial dairy wastewater (DWW), which is characterized by high organic loads, elevated nutrient concentrations, and pronounced operational variability. Despite increasing implementation, quantitative engineering evidence supporting design optimization and scalability remains fragmented. Herein, we present a semi-quantitative synthesis of CW performance for DWW treatment, explicitly linking hydraulic and operational parameters with pollutant removal efficiencies. A systematic review of 38 peer-reviewed studies published between 1995 and 2025 was conducted in accordance with PRISMA 2020 guidelines. Treatment performance was normalized and evaluated as a function of hydraulic retention time (HRT), organic loading rate (OLR), system configuration, and climatic context. The results demonstrate that hybrid CWs combining vertical and horizontal subsurface flow most frequently achieved COD and BOD₅ removal efficiencies exceeding 90% when operated within an observed operating envelope, typically including HRT ranges of 4–8 h (VSSF; n = 4) and 3–7 days (HSSF; n = 14), and OLR values below 30 g COD m⁻² d⁻¹ (n = 7, among studies reporting OLR). Operation outside this operating envelope was generally associated with reduced treatment stability and an increased likelihood of operational constraints (e.g., clogging). Substrate porosity, vegetation diversity, and climate further modulated long-term performance and system resilience. Based on the consolidated evidence, this review suggests transferable operational design envelopes and configuration-specific implementation pathways that translate empirical findings into practical engineering guidance, supporting the scalable adoption of CWs as low-energy NbS for decentralized and sustainable DWW management. Full article

Maize silage can play a key role in policies aimed at stabilising local energy systems, as it constitutes a critical renewable feedstock for European biogas plants. By providing a dense and predictable source of chemical energy, it supports balance and reliability in the agricultural energy sector. To convert this potential into stable energy production, operators require kinetic models that translate routine silage quality indicators into concrete guidance for digester operation and control. Therefore, the aim of this article was to evaluate the batch kinetics of anaerobic digestion (AD) of maize silage and to select an adequate model for describing biochemical methane potential (BMP) profiles and associated energy recovery in the context of start-up, organic loading rate (OLR), hydraulic retention time (HRT) and feedstock preparation. Ten batches of silage (A–J) were examined, covering a realistic range of pH, electrical conductivity (EC), dry and volatile solids, ash, protein–fat–fibre fractions, fibre composition (NDF, ADF and ADL), derived fractions (hemicellulose, cellulose, and residual organic matter (OM)), C/N ratio and macro-/micronutrient profiles, including trace elements relevant to methanogenesis (Ni, Co, Mo, and Se). BMP tests were carried out in batch mode, and the resulting curves were fitted using the modified Gompertz and a first-order kinetic model. Methane yields of approx. 100–120 m³ CH₄/Mg fresh matter (FM) and 336–402 m³ CH₄/Mg volatile solids (VS), with CH₄ contents of 52–57% v/v, were typical for energy-grade maize silage. Kinetic and energetic behaviours were governed mainly by residual OM and hemicellulose (shortening the lag phase and increasing the maximum methane production rate), the ADL/cellulose ratio (controlling the slower hydrolytic tail), EC and Na/Cl/S (extending the lag phase), and C/N together with Ni/Co/Mo/Se (stabilising methanogenesis). The modified Gompertz model reproduced BMP curves with a pronounced lag phase and asymmetry more accurately (lower error and better information criterion values), and its parameters directly support start-up design, OLR ramp-up and energetic performance optimisation in bioenergy reactors. The novelty of this work lies in combining batch BMP tests, comparative kinetic modelling and detailed silage characterisation to establish quantitative links between kinetic parameters and routine maize silage quality indicators that are directly relevant for biogas plant operation and renewable energy production. Full article

Coalbed methane (CBM) reservoirs are characterized by low permeability and poor methane desorption, which limit recovery rates. To address this, a novel graphite composite thermally conductive proppant is proposed, offering enhanced thermal conductivity and mechanical performance. The composite consists of porous ceramsite as a mechanical scaffold, epoxy resin as an interfacial binder, and graphite as a thermally conductive reinforcement. The effects of graphite content and resin dosage on the composite’s structure, thermal conductivity, suspension stability, surface wettability, and interfacial adhesion are systematically investigated. The results show that an optimized formulation with 20 wt% graphite and 1.0 g epoxy resin achieves a thermal conductivity of 3.8 W/(m·K)—6.3 times that of pure ceramsite—along with an improved thermal response under simulated stimulation, good suspension stability (suspension ratio of 0.53 in 0.2 wt% guar gum solution), a hydrophobic surface (contact angle 74.9°) to mitigate water lockup, and strong interfacial adhesion (125 nN under 2500 nN load) for durable proppant performance. Microscopic analysis confirms the formation of a continuous “resin–graphite–ceramsite” three-phase interface and a percolative thermal conductive network. This study provides a feasible design strategy for high-performance thermally conductive proppants and demonstrates their potential for application in the hydraulic fracturing of unconventional oil and gas reservoirs. Full article

Objective: The purpose of this study was to assess the outcome of sinus grafting with a beta-tricalcium phosphate/hydroxyapatite (ß-TCP/HA) alloplast particulate biofunctionalized with cross-linked hyaluronic acid (xHya), comparing two surgical access techniques. Clinical, histological, histochemical, immunohistochemical and histomorphometrical parameters were used to characterize the tissue samples, which were retrieved at the second surgery for implant placement five months after sinus floor elevation (SFE). Materials and Methods: Twenty patients with a residual bone height ≤ 4 mm, estimated by a Cone Beam Computed Tomography (CBCT), were randomly allocated either to an innovative transcrestal sinus floor elevation (tSFE = tests) approach or a conventional lateral window approach (lSFE = controls) using piezoelectric preparation. The tSFE was carried out using the hydraulic Jeder^®-System. Grafting in both groups was performed using a ß-TCP–HA combination, which was biofunctionalized with a cross-linked hyaluronic acid. For both access techniques, a cross-linked collagen membrane covered either the bone window or transcrestal osteotomy. For second-stage surgery, a second CBCT was used to assess the bone volume and possible implant positioning to compare it with the baseline CBCT. Bone cores were harvested at implant placement and evaluated histomorphometrically. Patients were followed for 1-year post-op for survival rate estimation. Non-superiority was hypothesized for both surgical methods; thus, the primary outcome measure assessed different discomfort levels using patient-reported outcome measures (PROMs) for each therapeutic approach. Secondary outcomes were the volume change in subantral bone after sinus floor elevation, the chance of placing a 10 mm long implant with no need for additional augmentation, histological evaluation of the newly gained tissue, and implant integration and one-year survival. Results: Eighteen patients (n = 18/20) qualified for implant placement at five months, and ten donated tissue biopsies for microscopic analysis. Primary outcome reporting using PROMs was discarded due to truncated patient enrollment. The secondary parameter, placement of a ≥10 mm long implant without additional augmentation, was achieved for nine sites/patients from the lSFE control group. All patients from the tSFE test group received an implant that was positioned alongside additional augmentation. In both groups, all implants integrated and were functionally loaded. A total of 10 core samples (3 from the tSFE group and 7 from the lSFE group) were obtained and analyzed. Microscopically, new bone formation appeared consistent in all obtained samples. Specimens revealed advanced and ongoing osteogenesis, with most histological markers reacting positively in the immunohistochemical (IHC) staining. The histomorphometric calculation revealed that a mean of 61.17 ± 16.55% of the total area was occupied by newly formed bone, 30.43 ± 10.09% by connective tissue and 8.92 ± 15.29% by residual graft substitute. One-year follow-up of the loaded implants showed a 100% implant survival rate. Conclusions: Biofunctionalizing ß-TCP + HA particulate with cross-linked hyaluronic acid in sinus floor elevation procedures appears to be a safe and beneficial approach, resulting in satisfactory clinical, radiographic and histological parameters. In our study population, which presented with very atrophic residual subantral bone conditions, the hydrodynamic transcrestal sinus floor elevation method required a back-up treatment by the conventional lateral approach. Full article

Complex hydraulic transients induced during load adjustment of turbine units in long tailrace tunnels pose significant threats to the safety and stability of tailwater systems. In view of this, based on VOF multiphase flow and compressible water–air models, a three-dimensional full-flow-channel numerical model of long tailrace system incorporating surge shaft and downstream river channel was developed using computational fluid dynamics (CFD) software to explore the transient impact of load changes on flow rate, water level, and pressure pulsations under different flow regimes in the tailrace tunnel, including open channel flow, pressurized flow, and free-surface-pressurized flow. The results indicate that the discharge at the outlet of the tailrace tunnel exhibits attenuated oscillations in response to load variations, with the most severe fluctuations occurring due to the intense air–water interface mixing during free-surface-pressurized flow. Flow regime transitions are accompanied by air pocket phenomena, resulting in significant fluctuations in air volume fraction. Pressure pulsations show periodic variations, with energy gradually dissipating as they propagate downstream. Open channel flows predominantly feature high-frequency waves, while pressurized flows exhibit intense low-frequency pulsations. Additionally, load changes in one unit have an ultra-low-frequency impact on another unit sharing the same tailrace tunnel, with high-frequency waves being filtered out by the surge shaft. Full article

This paper presents a simulation of the heat exchange process in a solar dryer designed for corn cobs placed in flexible bulk containers (Big-Bag type). The distinctive feature of this drying system is the use of soft load-bearing containers, which simplify loading, unloading, and transportation, while also reducing mechanical damage to the corn cobs. The bottom of each container is perforated to allow the free flow of heated drying agent into the chamber. The study aims to improve the efficiency of the solar drying process to reduce the moisture content of corn cobs below 15%, thereby ensuring the required quality during storage and transport. To validate the drying regimes and parameters, heat and mass transfer processes were simulated using numerical modeling and experimental design methods based on a laboratory-scale physical model of the drying chamber. Numerical simulations were performed using the Reynolds-averaged equations coupled with the heat conduction equation for three porosity coefficients: 0.35, 0.45, and 0.55. The models provided contours of temperature and humidity distribution within the confined boundaries of the drying chamber and individual corn cobs, positioned both vertically and horizontally within the airflow zone, for varying drying durations. The core novelty of this research is the development of an optimized framework for solar drying corn in flexible containers, which integrates numerical simulation with experimental validation to establish key efficient parameters. Specifically, the study provides the following: (1) a validated regression model linking moisture content to airflow rate, drying time, and layer thickness at 45 °C; and (2) a detailed analysis of thermo-hydraulic contours within both the chamber and individual cobs for different porosities, offering practical insights for system design and operation. Full article