Search Results (98)

Inefficient xanthate transport and poorly defined circulation paths can limit the conditioning of low-grade lead–zinc tailings. A Venturi-assisted composite conditioning tank was therefore evaluated using ANSYS Fluent 2025 R2 (Ansys Inc., Canonsburg, PA, USA). The volume of fluid (VOF) model described the air–slurry free surface, the renormalization group (RNG) k–ε model and multiple reference frame (MRF) approach represented the impeller-induced mean flow, and a transient user-defined scalar (UDS) described the transport of a generic normalized xanthate tracer. The slurry phase was represented as a generic homogeneous equivalent medium rather than as a fully characterized solid–liquid suspension. The Venturi throat generated a local low-pressure region and stable reagent suction; at a tailings inlet velocity of 2.50 m·s⁻¹, the reagent-branch inlet mass flow rate was 2.825 × 10⁻⁴ kg·s⁻¹. Parameter comparisons identified 350 r·min⁻¹, an impeller installation height of 370 mm, and an annular gap width of 60 mm as the preferred combination. The calculated impeller power increased from 0.211 kW at 200 r·min⁻¹ to 2.304 kW at 400 r·min⁻¹. Increasing the speed from 350 to 400 r·min⁻¹ raised power consumption by 60.9% but average velocity by only 5.8%. Compared with a conventional tank, the composite tank formed a coherent impeller–lower connecting–annular upflow–upper recirculation pathway, providing more favorable hydrodynamic conditions for xanthate transport and potential reagent–particle contact. Full article

The Myval balloon-expandable transcatheter heart valve was developed for transcatheter aortic valve implantation, but its broad 20–32 mm size matrix and controlled deployment have prompted use in non-aortic landing zones. This narrative review critically synthesizes Myval-specific case reports, case series, and observational cohorts, together with relevant platform-level evidence, addressing device design, anatomical selection, imaging, procedural strategy, clinical outcomes, and evidence gaps. Reported applications include mitral valve-in-valve, valve-in-ring, and valve-in-mitral annular calcification; tricuspid valve-in-valve and valve-in-ring; and pulmonary implantation in conduits, surgical bioprostheses, and selected native or patched right ventricular outflow tracts. Outcomes appear most predictable within circular stented surgical bioprostheses, whereas non-circular rings, severe mitral annular calcification, and compliant or aneurysmal outflow tracts present greater risks of inadequate anchoring, paravalvular regurgitation, embolization, frame deformation, left ventricular outflow tract obstruction, and coronary compression. Intermediate and extra-large diameters increase the available nominal sizing options; however, no clinical evidence demonstrates that this reduces embolization, paravalvular regurgitation, residual gradients, or reintervention. The available data document procedural feasibility in anatomically selected patients but are predominantly observational, with limited independent adjudication and follow-up. These procedures are generally off-label and should remain individualized Heart Team decisions; prospective multicenter studies are required to define comparative safety, antithrombotic management, durability, and lifetime reintervention strategies. Full article

Engine high-altitude simulation tests require establishing a stable low test-chamber pressure across a wide range of operating conditions. Existing studies focus predominantly on the local starting mechanisms—namely, shock-wave swallowing, aerodynamic choking, and boundary-layer separation—of individual ejector or diffuser components, with limited investigation of the coupling among shock evolution, chamber pressure response, starting hysteresis, and diffuser starting thresholds during continuous ejection pressure regulation. To address this gap, a two-dimensional axisymmetric Reynolds-averaged Navier–Stokes model with the standard k-ε turbulence model is employed, encompassing the test chamber, engine nozzle, supersonic diffuser, and annular ejector of a large-scale active-ejection test stand (where an annular ejector actively evacuates the test chamber to simulate high-altitude backpressure). The formation, migration, and stabilization of the shock system are revealed under increasing ejection pressure. Hysteresis characteristics are elucidated by comparing pressure-increasing and pressure-decreasing paths. The non-monotonic relationship between chamber pressure and ejector total pressure ratio under zero-secondary-flow conditions is established. The mechanism governing diffuser starting threshold variation under coupled engine gas and ejection flows is identified. Quantitatively, the ejector starting pressure ratio is found to be approximately 16.78 with a hysteresis width of ~13.6% between the starting and unstarting thresholds, and the diffuser starting threshold scales linearly with the ejector total pressure ratio (R² = 0.976). The results reveal the coupling among shock evolution, hysteresis, chamber pressure response, and diffuser starting thresholds and clarify the dual influence of ejection pressure on both chamber pressure regulation and diffuser starting thresholds. These findings provide a theoretical basis for parameter matching and operational control of high-altitude simulation facilities. Full article

Laser powder bed fusion (LPBF) of high-strength aluminum alloy 7075 (AA7075) is severely limited by hot cracking. However, the underlying mechanisms, particularly the coupling between thermal fields, solidification microstructure, and cracking behavior, remain insufficiently clarified. This study elucidates these mechanisms by integrating experimental characterization with thermal simulation to investigate the temperature field, microstructure, and cracking relationships in both AA7075 and a crack-resistant 7075-Er-Zr alloy. Results show that coarse hot crack morphology is highly dependent on linear energy density E_L. In AA7075, E_L < 450 J/m promotes laterally inclined cracks (short, narrow cracks extending from the melt pool boundary toward the track center), whereas E_L higher than that value leads to the continuous centerline cracks (long, wide cracks along the track center). Fine microcracks are also observed at melt pool boundaries. The 7075-Er-Zr alloy demonstrates superior crack resistance. At E_L = 600 J/m, longitudinal centerline cracks still penetrate along the track, but the alloy achieves crack-free tracks at 200 W with scanning speeds above 1000 mm/s, otherwise exhibiting only short discontinuous cracks. Microcracks at melt pool boundaries are markedly suppressed in the modified alloy. The enhanced crack resistance is attributed to Er/Zr-induced grain refinement and a transition to an equiaxed grain structure, which disrupts intergranular gaps. Critically, thermal simulations identify an annular region with a peak temperature gradient. In AA7075, this region develops aligned columnar grains that facilitate both microcracks and centerline cracks. In the 7075-Er-Zr alloy, microcracks are fully eliminated within this region. However, a residual crystallographic texture persists in the annular region, which promotes the continued occurrence of centerline cracks under high energy density (e.g., E_L = 600 J/m). The annular region remains a critical weak link, and its microstructural control determines the prevailing crack type. This work provides a fundamental understanding of the thermal-microstructural origins of cracking and offers a theoretical foundation for developing crack-resistant aluminum alloys via LPBF. Full article

During the operation of underground natural gas storage, drastic wellbore temperature and pressure fluctuations impose complex and variable loads on cement sheaths. This impairs cement sheath sealing integrity, triggers fluid leakage along interfacial gaps and continuous annular pressure rise, severely threatening the operational safety of gas storage injection–production wells. Based on the analysis of potential gas leakage paths in injection–production wells of underground gas storage, a calculation model for annulus pressure buildup induced by cement sheath leakage of gas storage wells is established with consideration of influencing factors, including formation pressure, annulus temperature, and cement property parameters. Model verification indicates that the maximum relative error of the test well is 9.20%, the average relative error is 2.64%, the mean absolute error (MAE) is 0.08 MPa, and the average root-mean-square error (RMSE) is 0.09 MPa. Calculations for field case wells are performed to quantitatively predict the variation in annulus pressure, followed by sensitivity analysis on the annulus pressure buildup of the studied wells. Formation pressure and cement permeability act as core controlling factors, positively correlating with annular pressure. In contrast, temperature exerts a relatively minor influence on annulus pressure. Optimized cementing design and reduced cement permeability can effectively mitigate leakage-induced annular pressure. The proposed model and findings offer reliable theoretical support for annular pressure management and safe long-term operation of gas storage wells. Full article

To address the issues of sealing leakage and airflow-induced vibration in high-speed turbomachinery, a conical straight-tooth annular clearance sealed hybrid aerostatic/aerodynamic bearing is investigated. A three-dimensional CFD model is established to study the effects of radial clearance height, inlet pressure, rotor speed, and eccentricity on pressure distribution, velocity distribution, and leakage rate. The results show that leakage exhibits a strong positive nonlinear correlation with clearance height and inlet pressure, following a power-law or polynomial relationship, while rotor speed and eccentricity exert negligible effects (less than 5%). The underlying mechanisms are identified as the kinetic energy diversion caused by circumferential shear and the mutual cancelation of throttling and backflow effects. Increasing the gap height enhances leakage by expanding the hydraulic diameter and strengthening vortex disturbance; increasing inlet pressure promotes leakage by elevating the driving force and intensifying local flow separation. Full article

The use of reclaimed water is a crucial strategy for water conservation. However, the quality of reclaimed water may induce corrosion in pipelines. Although UV (Ultraviolet) irradiation is a highly effective physical disinfection method that requires no chemical additives, it must be used in conjunction with NaClO (Sodium hypochlorite) disinfection because UV alone cannot provide continuous control of bacterial growth. This study monitored the concentrations of Cl⁻ and SO₄²⁻ in water samples collected from an annular biofilm coupon reactor, as well as the corrosion rate of cast iron coupons, to explore the corrosion characteristics of reclaimed water pipelines under different disinfection modes. The results showed that, when using NaClO as the sole disinfectant, the corrosion rate of the pipeline was the lowest at a NaClO dosage of 7 mg/L (corrosion rate: 0.85 mm/a at 72 h). For the UV-NaClO-combined disinfection, the optimal parameters were a UV dose of 120 mJ/cm² and a NaClO dosage of 5 mg/L, with a minimum corrosion rate of 0.62 mm/a at 72 h. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that a protective CaCO₃ layer forms on the pipe surface in the early corrosion stage, which effectively protects the metal pipeline. This study innovatively clarifies the synergistic effect of UV and NaClO on pipeline corrosion and identifies the optimal disinfection parameters, filling the research gap in the correlation between combined disinfection and cast iron pipe corrosion in reclaimed water systems. Full article

Degenerative mitral stenosis (MS) secondary to extensive mitral annular calcification (MAC) represents a growing clinical challenge in an aging population. These patients are often elderly, frail, and harbor a significant burden of comorbidities, rendering conventional mitral valve surgery prohibitively high-risk. While transcatheter mitral valve replacement (TMVR) has emerged as a potential alternative, the current evidence is only derived from single-arm observational registries. Therefore, the transition toward randomized controlled trials to define optimal patient selection and long-term prosthetic durability is necessary. This review examines the current landscape of TMVR for degenerative MS, focusing on the role of multimodal pre-procedural planning, procedural technique, and prevention of the principal complications. The integration of echocardiography and multi-slice computed tomography (MSCT) is essential for evaluating anatomical feasibility, particularly in predicting neo left ventricle outflow tract (neo-LVOT) obstruction, the primary determinant of procedural mortality. However, it is limited due to the absence of standardized protocol. We are showing the outcomes of off-label balloon-expandable aortic prostheses and dedicated TMVR system, which are the only two devices which data in patients with MS are available. Despite high technical success rates in specialized centers, complications, including paravalvular leak, valve thrombosis, and device migration, remain more prevalent than in aortic interventions. We present some tips and tricks to prevent and manage adverse events. TMVR represents a transformative frontier for inoperable patients with severe MAC. However, its routine clinical adoption requires further refinement of dedicated technologies and standardized imaging protocols to improve safety and bridge the gap between palliative medical therapy and definitive intervention. Full article

Caseous calcification of the mitral annulus (CCMA) is a liquefactive necrosis of mitral annular calcification (MAC). CCMA is rare and usually asymptomatic, has a benign course, and, when incidentally found, can be misdiagnosed as a thrombus, abscess, cardiac tumor or vegetation. Although rarely, CCMA may complicate with rupture, which can lead to ventricular-atrial fistulization, pseudoaneurysm, severe mitral regurgitation (with possible heart failure and atrial fibrillation) and systemic embolism of caseous material (with cerebral ischemic events). A significant increase in CCMA dimensions and an infectious involvement of liquefactive necrosis make CCMA prone to rupture. To date, only case reports and some case series have been published on CCMA, without focusing on the pathophysiological mechanisms responsible for rupture, nor recommendations for prevention and management. However, despite general concerns about surgical treatment of CCMA because of high perioperative risks, most published cases actually underwent successful cardiac surgery. In the present review, we conducted a systematic review of the studies published in the medical literature up to March 2025, reporting cases of CCMA and its complications, as identified through the PubMed database. We analyzed clinical and biological risk factors for CCMA rupture and its diagnostic criteria, focusing on imaging features differentiating mitral annular calcification from uncomplicated CCMA and ruptured CCMA. To this regard, we focused on the key role of multimodality imaging in the achievement of the correct diagnosis. Finally, we propose a management strategy for CCMA, with the aim to fill a gap in this field in the current literature. Full article

Air-shielding radial ultrasonic rolling electrochemical micromachining (AS-RUREMM) is proposed to fabricate high-quality micro-dimple textures on cylindrical SS304 surfaces while suppressing stray corrosion. In AS-RUREMM, an annular air sheath coaxially envelopes the electrolyte jet to confine the wetting footprint, and radial ultrasonic vibration is superimposed on a rolling cathode with micro-protrusions to intensify local mass transport and stabilize the interelectrode environment. A conductivity-centered theoretical framework is established to link air-sheathing-induced gas–liquid distribution, ultrasonic gap modulation, and the resulting current-density localization. Multiphysics simulations in COMSOL 5.3 clarify that moderate air pressure forms a stable confined gas–liquid structure that narrows the effective conductive pathway, whereas excessive air pressure increases intermittency and weakens effective gap conductivity. Experiments on SS304 tubes validate the confinement mechanism: compared with RUREMM, AS-RUREMM produces smaller pit width and depth but a higher depth-to-width ratio, indicating enhanced localization and reduced peripheral over-etching. The simulated cross-sectional profiles agree with measurements, with an overall deviation within 6%. Parameter studies identify an optimal operating window, and the combination of 0.18 MPa air pressure and 12 V pulse voltage provides the highest aspect ratio while maintaining stable machining. SEM/EDX analyses further support the improved process controllability under air shielding through reduced stray corrosion and composition changes consistent with a more regulated electrochemical dissolution environment. Full article

Single-phase grounding is the dominant fault type in urban power distribution networks. Because the total magnetic flux would not change around the cable under a single-phase grounding fault, ferromagnetic zero-sequence current sensors cannot distinguish the faulted phase of belted cables, which are the main type in 10 kV distribution networks. To fill this gap, a two-step methodology is proposed using an annular TMR magnetic sensor to measure the magnetic field intensity at six points on the cable surface and to distinguish the faulted phase using the magnetic field intensity differences between the TMRs. The first step is calculating the rotation angles between the six magnetic sensors and the three cable cores after installation. A differential evolution algorithm is used to calculate the rotation angles in the sensing model. The second step is to detect the fault phase under a single-phase grounding fault transient, with the magnetic field intensity difference taken as the criterion. The methodology is verified through simulation and experiment. The results show that the relative errors of the rotation angles are all less than 1%. Under a single-phase grounding fault, the faulted phase can be accurately identified. The proposed method can effectively identify the faulted phase of 10 kV three-core cables under single-phase grounding and has significant engineering application value. Full article

As global energy demand rises, developing unconventional oil and gas resources has become a strategic priority, with horizontal well technology playing a key role. However, wellbore instability during drilling often leads to irregular geometries, such as enlargement or elliptical deformation, causing issues like increased friction and stuck-pipe incidents. Most studies rely on idealized, regular wellbore models, leaving a gap in understanding cuttings transport in irregular wellbore conditions. To address this limitation, this study employs a coupled CFD-DEM approach to investigate cuttings transport in enlarged wellbores by modeling the two-way interactions between drilling fluid and cuttings. The study analyzes the impact of various factors, including drilling-fluid flow rate, drill pipe rotational speed, rheological parameters, wellbore enlargement ratio, and ellipticity, on wellbore cleaning efficiency. The result indicates that increasing the flow rate in conventional wellbores reduces cuttings volume by 75%, while in wellbores with a 0.7 enlargement ratio, the same flow rate only reduces it by 37.8%, highlighting the limitations of geometric complexity. In conventional wellbores, increasing drill pipe rotation reduces cuttings volume by 42.6%, but in enlarged wellbores, only a 13% reduction is observed, indicating that rotation alone is insufficient in large wellbores. Optimizing drilling fluid rheology, such as by increasing the consistency coefficient from 0.3 to 1.2, reduces cuttings volume by 58.78%, while increasing the flow behavior index from 0.4 to 0.7 results in a 38.17% reduction. Although higher enlargement ratios worsen cuttings deposition, a moderate increase in ellipticity improves annular velocity and enhances transport efficiency. This study offers valuable insights for optimizing drilling parameters in irregular wellbores. Full article

Ultra-high voltage (UHV) power transmission has become a prerequisite for the development of clean energy. However, arcs generated by UHV circuit breakers can easily lead to safety incidents, and developing arc-extinguishing gases with low global warming potential (GWP) presents certain challenges. It is a fact that fluorolefins, as a class of fluorinated compounds with low GWP, show high application potential in replacing traditional arc-extinguishing agents. In this study, all six conjugated perfluorinated compounds, including C₆F₆ and C₆F_8, were calculated within the density functional theory (DFT) framework at the B3LYP/6-311+G(d,p) level. The dipole moments, HOMO/LUMO energy gaps, and the inherent aromaticity of annular molecules under external electric fields of these fluorinated molecules are investigated accordingly. By analyzing these results, it is found that the influence of the conjugated structure on the stability of arc-extinguishing gases under high-voltage conditions was partially elucidated, providing useful insights for the subsequent development of environmentally friendly and high-performance arc-extinguishing gases. Full article

Modern processes to produce rare-earth elements, strategic metals, and nuclear fuel reprocessing require highly efficient liquid–liquid extraction in systems characterized by high viscosity, elevated interfacial tension, and small density differences. Traditional gravity-driven extractors exhibit low performance under these conditions, whereas centrifugal extractors enable rapid mass transfer and nearly complete phase separation. Differential-contact annular centrifugal contactors offer the highest flexibility and efficiency, but their optimization is limited by the lack of experimental data on the hydrodynamics of liquid flow through perforated nozzles in a rotating field. This limitation hinders the development of accurate computational fluid dynamics (CFD) models (e.g., ANSYS Fluent), reliable equipment scale-up, and the design of optimized contactor configurations. The present study addresses this gap by experimentally determining the flow velocity of liquids through nozzles of various geometries across a wide range of centrifugal accelerations. From these data, a universal power-law correlation was derived, linking the flow rate to rotor speed, nozzle geometry, and the physicochemical properties of the phases. The proposed correlation provides a robust experimental basis for numerical model validation, computational design, and optimization of next-generation differential-contact centrifugal extractors. Full article

Test fires of a rotating detonation engine (RDE) annular combustor operating on a methane–oxygen mixture were conducted. Compared to the original RDE combustor previously tested, it was modified in terms of changing the layout of the water cooling system, the positions of ports for sensors, and the shape of the supersonic nozzle. The stable operation process with a single detonation wave continuously rotating in the annular gap with the velocity of ~1900 m/s (rotation frequency of ~6 kHz) was obtained in the wide range of flow rates of propellant components. This is an important distinguishing feature of the present RDE combustor compared to the analogs known from the literature, which usually exhibit an increase in the number of simultaneously rotating detonation waves with an increase in the flow rates of propellant components. Compared to the original RDE combustor, the maximum duration of operation and the attained sea-level specific impulse were increased from 1 to 30 s and from 250 to 277 s, respectively. The thermal states of all heat-stressed elements of the combustor were obtained. The maximum heat fluxes are registered in the water cooling jackets of the central body and the combustor outer wall. Heat losses in the water cooling system are shown to increase with the average pressure in the combustor. The maximum value of the average heat flux over 20 MW/m² is achieved on the combustor outer wall. The average heat flux into the combustor outer wall is approximately 20% higher than that into the central body. The average heat flux into the nozzle is several times lower than similar values for the combustor outer wall and central body. The total heat loss into the water-cooled walls of the combustor reach about 10% of the total thermal power of the combustor. Full article