Search Results (631)

The salt flotation of graphite in the presence of lithium nickel manganese cobalt oxide (NMC) was assessed by performing colloidal probe atomic force microscopy (CP-AFM) on sessile gas bubbles and conducting batch flotation tests with model lithium-ion-battery black mass. The modeling of film drainage and detachment during particle–bubble interactions provides insight into the fundamental microprocesses during salt flotation, a special variant of froth flotation. The interfacial properties of particles and gas bubbles were tailored with salt solutions containing sodium chloride and sodium acetate buffer. Graphite particles can attach to gas bubbles under all tested conditions in the range pH 3 to pH 10. The attractive forces for spherical graphite are strongest at high salt concentrations and pH 3. The conditions for the attachment of NMC to gas bubbles were evaluated with simulations using the Stokes–Reynolds–Young–Laplace model for film drainage, under consideration of DLVO forces and a hydrodynamic slip to account for irregularities of the particle surface. CP-AFM measurements in the capillary force regime provide additional parameters for the modeling of salt flotation, such as the force and work of detachment. The contact angles of graphite and NMC particles during retraction and detachment from gas bubbles were obtained from a quasi-equilibrium model using CP-AFM data as input. All CP-AFM experiments and theoretical results suggest that pristine NMC particles do not attach to gas bubbles during flotation, which is confirmed by the low rate of NMC recovery in batch flotation tests. Full article

Fly-ash-based bubble lightweight soil is widely used due to its environmental friendliness, load reduction, ease of construction, and low costs. In this study, 41 sets of 28 d compressive strength data on lightweight soils with different water–cement ratios, blowing agent dosages, and fly ash dosages were collected through a literature search and indoor tests. Using the compressive strength index and SEM tests, the correlation between the mix ratio design and the microscopic particle components was investigated. The findings were as follows: carbonation reactions occurred in lightweight soil during the maintenance process, and the particles were spherical; increasing the dosage of blowing agent increased the soil’s porosity and pore diameter, leading to the formation of through-holes and reducing the compressive strength and mobility; increasing the fly ash dosage and water–cement ratio increased the soil’s mobility but reduced its compressive strength; and the strength decreased significantly when the fly ash dosage was more than 16% (e.g., the strength at a 20% dosage was 17.8% lower than that at a 15% dosage). Feature importance analysis showed that the water–cement ratio (57.7%), fly ash dosage (30.9%), and blowing agent dosage (11.1%) had a significant effect on strength. ExtraTrees, LightGBM, and Bayesian-optimized Random Forest models were used for 28d strength prediction with coefficients of determination (R²) of 0.695, 0.731, and 0.794, respectively. The Bayesian-optimized Random Forest model performed optimally in terms of the mean square error (MSE), root mean square error (RMSE), and mean absolute error (MAE), and the prediction performance was best. The accuracy of the model is expected to be further improved with expansions in the database. A 28 d compressive strength prediction platform for fly-ash-based bubble lightweight soil was ultimately developed, providing a convenient tool for researchers and engineers to predict material properties and mix ratios. Full article

This study provides a novel experimental setup and methodology for the quantitative investigation of evaporation-induced foaming behaviors in a polymer/small-molecule solution system (PSMS). In traditional dynamic test methods, it is difficult to precisely describe the evaporation-induced foaming process of a multicomponent solution because the concentration of light components in solution continuously decreases during ebullition, causing undesired changes in foaming behavior. In this study, a precisely controlled condensation reflux module was introduced into the setup to maintain pressure, temperature, and concentration of the PSMS at constant levels during the entire ebullition process, allowing dynamic test methods to quantify the evaporation-induced foamability. With this newly proposed device, experimental data of typical PSMS, polyolefin elastomer (POE)/n-hexane solution system, were obtained and modeled to illustrate the foam growth profile, thereby characterizing the dynamic foaming process based on a logistic growth function. The corresponding dimensionless number Σevap was calculated to evaluate evaporation-induced foam stability by analyzing the foam growth profile under varying pressure, concentration, and energy input levels. Furthermore, given that the PSMS represents a highly non-ideal system, the bubble nucleation rate J was modified in this work by introducing a correction coefficient δ to account for the non-ideal effects of macromolecules present in solutions. Additionally, another correction coefficient λ was incorporated into the Gibbs free energy term to adjust for supersaturation of liquid during nucleation. The experiment’s data align well with the modified bubble nucleation rate mechanism proposed herein. Full article

As a core component in renewable energy systems for grid regulation, hydropower units are increasingly exposed to flow conditions that elevate the risk of cavitation and erosion, posing significant challenges to the safe operation of flow-passage components. In this study, model testing and computational fluid dynamics (CFD) simulations are employed to investigate the hydraulic performance and cavitation behavior of a bulb turbine operating under rated head conditions and varying cavitation numbers. The analysis focuses on how changes in cavitation intensity affect flow characteristics and efficiency within the runner region. The results show that as the cavitation number approaches its critical value, the generation, growth, and collapse of vapor cavities increasingly disturb the main flow, causing a marked drop in blade hydraulic performance and overall turbine efficiency. Cavitation predominantly occurs on the blade’s suction side near the trailing edge rim and in the clearance zone near the hub, with bubble coverage expanding as the cavitation number decreases. A periodic inverse correlation between surface pressure and the cavitation area is observed, reflecting the strongly unsteady nature of cavitating flows. Furthermore, lower cavitation numbers lead to intensified pressure pulsations, aggravating flow unsteadiness and raising the risk of vibration. Full article

In bulk liquid or on solid surfaces, nanobubbles (NBs) are gaseous domains at the nanoscale. They stand out due to their extended (meta)stability and great potential for use in practical settings. However, due to the high energy cost of bubble generation, maintenance issues, membrane bio-fouling, and the small actual population of NBs, significant advancements in nanobubble engineering through traditional mechanical generation approaches have been impeded thus far. With the introduction of the electric field approach to NB creation, which is based on electrostrictive NB generation from an incoming population of “electro-fragmented” meso-to micro bubbles (i.e., with bubble size broken down by the applied electric field), when properly engineered with a convective-flow turbulence profile, there have been noticeable improvements in solid-state operation and energy efficiency, even allowing for solar-powered deployment. Here, these innovative methods were applied to a selection of upstream and downstream activities in the oil–water–fuels nexus: advancing core flood tests, oil–water separation, boosting the performance of produced-water treatment, and improving the thermodynamic cycle efficiency and carbon footprint of internal combustion engines. It was found that the application of electric field NBs results in a superior performance in these disparate operations from a variety of perspectives; for instance, ~20 and 7% drops in surface tension for CO₂- and air-NBs, respectively, a ~45% increase in core-flood yield for CO₂-NBs and 55% for oil–water separation efficiency for air-NBs, a rough doubling of magnesium- and calcium-carbonate formation in produced-water treatment via CO₂-NB addition, and air-NBs boosting diesel combustion efficiency by ~16%. This augurs well for NBs being a potent agent for sustainability in the oil and fuels sector (whether up-, mid-, or downstream), not least in terms of energy efficiency and environmental sustainability. Full article

The eutectic PbLi (15.7 at.% Li) alloy appears promising for producing tritium from fertile materials. Currently, in nuclear fusion design, the technologies being explored for tritium extraction in molten phases primarily focus on (i) established processes based on Gas–Liquid Contactor (GLC), such as bubble, packed, or spray columns, or on (ii) exploiting hydrogen permeation phenomena using dense metallic membranes, i.e., Permeation Against Vacuum (PAV). This work introduces a new concept, a Membrane Gas–Liquid Contactor, to address several open issues related to mass transport phenomena within the previously mentioned technologies. The MGLC concept merges the advantages of Permeation Against Vacuum (PAV) and Gas–Liquid Contactor (GLC), which have been extensively applied to extract hydrogen and its isotopes from liquid metals. A comprehensive description of the MGLC’s operation is then provided, suggesting a mass transfer model suitable for the practical application of this new concept. Finally, the results of the experimental campaign conducted on a lab-scale test facility are presented and critically analyzed. Full article

Hydrodynamic cavitation (HC) has emerged as a versatile method for modifying the rheological properties of polymer solutions, offering advantages such as scalability and operational simplicity. This work investigates the effect of HC on aqueous polyacrylamide (PAM) solutions, focusing on viscosity and viscoelasticity changes as a function of the number of passes through a vortex-type HC device and the presence of dissolved salts (CaCl₂ or KCl). Viscosity measurements were modeled using the power law equation, while oscillatory tests were used to determine storage and loss moduli. The results show that HC substantially reduced viscosity and elastic behavior, with the degree of modification strongly influenced by the number of passes. A critical molecular size limit was suggested, below which further degradation becomes limited. Salt addition enhanced depolymerization, likely due to charge screening, hydrodynamic radius reduction, and the increased solubility and mobility of polymer chains within cavitation bubbles. HC eliminated elasticity in all cases, yielding solutions with near-Newtonian behavior. The transformation is attributed to molecular weight reduction and changes in molecular size distribution. These findings support the use of HC as a practical approach to tailor the flow properties of PAM solutions, while highlighting intrinsic limitations imposed by cavitation dynamics and polymer chain dimensions. Full article

Acute lower respiratory tract infections are a leading cause of death in individuals under the age of 5 years, mostly in low- and middle-income countries (LMICs). The lack of respiratory support systems contributes to the poor outcomes. Bubble CPAP is widely used for non-invasive respiratory support, but sicker children often require support over what CPAP provides in the form of BiPAP. We developed and tested a simple bubble-based bilevel ventilator (Bubble bi-vent) and compared it with a standard care BiPAP device. The bubble bilevel device consisted of a single tube submerged in a water-sealed column to maintain end-expiratory positive airway pressure. It moves vertically via an electric motor to also provide inspiratory positive airway pressure for augmentation of lung volumes, with the duration and frequency of breaths controlled by a microprocessor. We tested this novel device in passively breathing mechanical lung models for infants and small children. We compared pressure and tidal volume delivery between the novel device and a Trilogy BiPAP ventilator. The results showed that the Bubble bi-vent could deliver set pressures in a mechanical lung and was comparable to a standard Trilogy ventilator. While two different bubble-based bilevel pressure devices have been piloted for neonates and adults, our results demonstrate the feasibility of bubble bilevel ventilation for infants and small children with moderate to severe lung disease for whom this was previously not described. Full article

We studied decades-long (1980 to 2024) historic distributions of accumulated S&P500 returns, from daily returns to those over several weeks. The time series of the returns emphasize major upheavals in the markets—Black Monday, Tech Bubble, Financial Crisis, and the COVID pandemic—which are reflected in the tail ends of the distributions. De-trending the overall gain, we concentrated on comparing distributions of gains and losses. Specifically, we compared the tails of the distributions, which are believed to exhibit a power-law behavior and possibly contain outliers. To this end, we determined confidence intervals of the linear fits of the tails of the complementary cumulative distribution functions on a log–log scale and conducted a statistical U-test in order to detect outliers. We also studied probability density functions of the full distributions of the returns with an emphasis on their asymmetry. The key empirical observations are that the mean of de-trended distributions increases near-linearly with the number of days of accumulation while the overall skew is negative—consistent with the heavier tails of losses—and depends little on the number of days of accumulation. At the same time, the variance of the distributions exhibits near-perfect linear dependence on the number of days of accumulation; that is, it remains constant if scaled to the latter. Finally, we discuss the theoretical framework for understanding accumulated returns. Our main conclusion is that the current state of theory, which predicts symmetric or near-symmetric distributions of returns, cannot explain the aggregate of empirical results. Full article

The role of humidity on the ageing of celluloid is investigated by performing accelerated ageing tests on mock-up samples. At 70 °C, three levels of relative humidity (RH) are selected: 30%, 50%, and 70%. Samples are monitored for the macro- and micro- changes occurring through ageing to relate the visible modifications to the molecular ones. Infrared and Raman spectroscopy, microscopy, mass and contact angle measurements, profilometry, and colourimetry are combined for this purpose. While the ageing test at 30% RH results in a slight embrittlement of the samples and small spectral changes, the one at 50% RH induces significant modifications at the molecular level and the formation of cracks, while the one at 70% RH causes a fast deformation of the samples and the development of bubbles. Although quite diverse, such results prove to be related to the same chemical processes: denitration, chain scission, and oxidation. These occur more promptly or extensively based on humidity level, resulting in different outcomes. Beyond morphology and brittleness, macroscopic effects also involve mass loss, surface roughening, and yellowing. A possible correlation between the macro and micro modifications is present, highlighting the influence humidity has on the degradation process of celluloid. Full article

The protective materials for cultural relic buildings generally have a deficiency of relatively shallow penetration depth. Based on the principle of changing the permeability coefficient of cultural relic buildings by “water blocking water” and considering the characteristics of magnesium acrylate polymer and the requirement of extending the curing time, a method of modifying magnesium acrylate polymer with glycerol and sodium methyl silicate is proposed. Experimental studies on magnesium acrylate, glycerol–magnesium acrylate, and sodium methyl silicate—glycerol–magnesium acrylate polymers were carried out, and tests and analyses on curing time, swelling performance, water loss rate, and soil sample protection were conducted. The results show that the initiator concentration is a key factor affecting the curing rate of magnesium acrylate polymers. When the initiator content is ≥4%, the curing time is significantly shortened to 20–67 min, and the incorporation of glycerol prolongs the curing time by more than 100 min through the dilution reaction system. Glycerol modification significantly enhanced the swelling capacity of the polymer, with the swelling rate increasing by approximately 15–20% compared to the unmodified system. Sodium methyl silicate effectively improved the construction performance of magnesium acrylate and prevented the occurrence of bubbles. The optimal formula of magnesium acrylate polymer is 25% magnesium acrylate, 40% glycerol, and 2% sodium methyl silicate. While maintaining curing for 120 min, it features a high swelling rate (equilibrium swelling ratio Ew ≈ 0.32) and a low dehydration rate (dehydration rate ≤ 35% after 48 h), and has volume stability after interaction with soil samples. Full article

Residual oil saturation in reservoirs is primarily influenced by viscous and capillary forces, with interfacial tension (IFT) being a critical factor in fluid distribution due to capillary pressure. Adjusting IFT is essential for enhancing oil recovery, particularly in waterflooding, which is the most common secondary recovery technique after primary production. The salinity of injected water directly affects the IFT between crude oil and brine, making it a crucial factor in optimizing recovery. However, limited studies have examined IFT using live oil samples under actual reservoir conditions. In this study, a high-pressure, high-temperature (HPHT) drop shape analyzer was used to measure the IFT between live oil and brine under reservoir conditions. Five live oil samples and two sodium chloride (NaCl) brine concentrations (30,000 and 100,000 ppm) were tested at a reservoir temperature of 180 °F. Measurements were conducted above the bubble points of the oils, replicating undersaturated reservoir conditions. The results revealed that the impact of pressure on IFT was more complex than that of salinity. IFT generally decreased with increasing pressure but showed mixed behavior across different samples. Conversely, IFT consistently increased with higher salinity. These findings enhance the understanding of IFT behavior under reservoir conditions, supporting improved reservoir simulations and oil recovery strategies. Full article

At the steelmaking temperature, carbon has a strong deoxidation ability. Under the vacuum condition, its deoxidation ability can be further improved, and it can become a stronger deoxidation element than aluminum. The product of carbon deoxygenation is CO, which floats up and detaches from the molten steel in the form of bubbles and does not produce oxide inclusions. Under normal pressure, replacing aluminum with carbon to complete partial deoxidation tasks can not only reduce the generation of inclusions and alleviate the pressure of removing inclusions, but also reduce the consumption of aluminum and save deoxidation costs. In this study, the carbon deoxidation process after the converter was investigated. Firstly, the timing of carbon addition was determined through thermodynamic calculations, and it was found that, in oxygen-enriched molten steel, the priority of the reaction of the deoxidation element was [Al] > [Si] > [C] > [Mn]. Through the carbon and oxygen balance calculation, it is known that the carbon deoxidation effect is greatly affected by the carbon content of the molten steel; for low-carbon steel, carbon can be used for pre-deoxygenation, whereas for medium-carbon and high-carbon steel, carbon can complete most of the deoxidation tasks. Finally, with 45 steel as the research object, the carbon deoxidation process was designed and tested in industry. The results showed that, compared with the aluminum deoxidation process, the number of inclusions in the billet casting of the carbon deoxidation process was reduced by 68.8%, and the carbon deoxidation process had fewer large-sized inclusions in the billet casting. In addition, the carbon deoxidation process uses carbon powder instead of the aluminum block for deoxidation during steel tapping from the converter. The deoxidant cost is reduced by CNY 15.47/ton of steel. From a comprehensive point of view, the application of carbon deoxidation after the converter can reduce aluminum consumption and improve the cleanliness of steel, which is an important way for enterprises to reduce costs and increase efficiency. Full article

The co-occurring relationships between ilmenite and gangue minerals in ilmenite deposits, as well as fine mineral embedding particle sizes, are complex. During the beneficiation process, grinding ilmenite finely is necessary to achieve sufficient individual mineral dissociation and the efficient recovery of ilmenite. During this process, a large number of fine-grained minerals can easily be generated, which adversely affects flotation separation. Micro–nanobubbles have been proven to effectively enhance the flotation separation efficiency of fine-grained minerals, as their cavitation characteristics are closely related to the flotation performance of the minerals. In order to fully understand the cavitation characteristics of micro–nanobubbles and their impact on the flotation recovery of fine-grained ilmenite, a series of experiments were conducted using methods such as the bubble cavitation property test, micro-flotation experiments, zeta potential analysis, the contact angle test, adsorption capacity detection, and PBM monitoring. The results indicate that during the process of slurry cavitation, appropriate concentrations of 2-octanol, cycle treatment times, and external inflation volume are conducive to the formation of micro–nanobubbles. Compared with deionized water without cavitation, cavitated micro–nanobubble water is more beneficial for the flotation separation of fine particulate ilmenite, titanaugite, and olivine. The presence of micro–nanobubbles can effectively promote the adsorption of combined collectors on mineral surfaces, significantly enhancing the hydrophobicity of the minerals, with an even stronger promoting effect observed under the treatment of 2-octanol. Micro–nanobubbles can adsorb a portion of the collectors originally attached to the mineral surfaces, thereby decreasing the absolute value of the surface potential of the minerals, which is beneficial for mineral aggregation. The introduction of micro–nanobubbles promotes the aggregation of fine ilmenite iron ore particles into flocculent bodies. 2-Octanol can reduce the size of the micro–nanobubbles generated during the cavitation process of the mineral slurry and, to a certain extent, weaken the phenomenon of bubble coalescence, so they demonstrate a greater advantage in facilitating the aggregation phenomenon. Full article

Clogging in earth pressure balance (EPB) shield tunnelling through highly cohesive strata critically undermines construction efficiency. Conventional foam agents exhibit limited conditioning effectiveness, even with increased dosage. This study developed a dispersed foam agent by combining anionic surfactant (AES) with nonionic dispersant (HDT). The effects of air pressure (0–2 bar) and HDT content (0–10%) on macro-meso characteristics of foam and adhesion characteristics of conditioned soil were quantified through an evolutionary mechanism investigation of the bubble size distribution of foam, half-life measurements, and mechanical tests on conditioned soils. Results demonstrated that the influence of HDT content on foam exhibited pressure-dependent behavior. Under 0 bar within 0–10 min, HDT increased the proportion of small bubbles while marginally reducing the mean radii. Although HDT accelerated the degradation of small bubbles, it extended the foam half-life. Conversely, under 1 or 2 bar, HDT demonstrated opposite effects on these parameters. The cohesion of conditioned clays was reduced to 1.8–4.3 kPa, and adhesion amounts decreased to 10–15 g, significantly mitigating clogging risks. The optimal injection ratio of dispersed foam was determined for different pressures and clays. Engineering application in an EPB shield tunnelling section of Jinan Metro successfully resolved clogging issues, demonstrating the effectiveness of dispersed foam agent. Full article