Search Results (78)

Underwater micro-bubble detection entails multiple challenges, including diminutive target sizes, sparse pixel information, pronounced specular highlights and water scattering, indistinct bubble boundaries, and adhesion or overlap between instances. To address these issues, we propose HSMD-YOLO, an improved detector tailored for high-resolution micro-bubble detection and built upon YOLOv11. The model incorporates three novel components: the Scale Switch Block (SSB), a scale-transformation module that suppresses artifacts and background noise, thereby stabilizing edges in thin-walled bubble regions and enhancing sensitivity to geometric contours; the Global Local Refine Block (GLRB), which achieves efficient global relationship modeling with an asymptotic linear complexity ($O\left(N\right)$) in spatial dimensions while further refining local features, thereby strengthening boundary perception and improving bubble–background separability; and the Bidirectional Exponential Moving Attention Fusion (BEMAF), which accommodates the multi-scale nature of bubbles by employing a parallel multi-kernel architecture to extract spatial features across scales, coupled with a multi-stage EMA based attention mechanism to enhance detection robustness under weak boundaries and complex backgrounds. Experiments conducted on an Side-Illuminated Light Field Bubble Database (SILB-DB) and a public gas–liquid two-phase flow dataset (GTFD) demonstrate that HSMD-YOLO achieves mAP@50 scores of 0.911 and 0.854, respectively, surpassing mainstream detection methods. Ablation studies indicate that SSB, GLRB, and BEMAF contribute performance gains of 1.3%, 2.0%, and 0.4%, respectively, thereby corroborating the effectiveness of each module for micro-scale object detection. Full article

Non-thermal plasma-driven advanced oxidation is a promising method for treating organic wastewater, which exhibits rapid reaction kinetics and high pollutant removal and does not need chemical reagents. However, its practical application is often limited by high specific energy consumption and the inefficient mass transfer of short-lived reactive species across the gas–liquid interface. This review summarizes the fundamentals of non-thermal plasma chemistry and the process intensification of plasma multiphase reactors by mass transfer enhancement and waste energy-driven conversion. This review focus on four coupling approaches: microbubble-assisted plasma to expand the reactive interfacial area; plasma coupled with hydraulic cavitation to enhance convection and radical formation; plasma–piezoelectric catalysis coupling to harvest hydraulic energy and promote charge-driven reactions; and plasma-assisted Fenton oxidation to improve the utilization of weakly oxidizing species (H₂O₂). The energy efficiency of various plasma-based oxidation systems is compared and discussed clearly. Key remaining challenges are also discussed, including standardized energy efficiency assessment, scale-up and hydrodynamic control, catalyst stability and fouling, by-product formation and toxicity, and long-term operational reliability. Overall, this review aims to provide guidance for developing efficient plasma-based wastewater treatment systems for large-scale applications. Full article

Dissolved-air flotation (DAF) is widely used for surface-water pretreatment but remains insufficiently explored for chemically complex groundwater. This study develops a thermodynamic and bubble-dynamics modeling framework to evaluate the feasibility of DAF pretreatment for groundwater containing elevated arsenic, natural organic matter (NOM), and color. The study is theoretical and model-based; no experimental dissolved-air flotation tests were performed. Air solubility was calculated at pressures of 4–6 bar and temperatures of 13–17 °C, while microbubble size, rise velocity, and bubble–floc interaction efficiencies were estimated using established physical models. Laboratory coagulation–flocculation jar tests with FeCl₃ and FeCl₃/PAC were used to define realistic floc properties prior to flotation modeling. No experimental dissolved-air flotation tests were conducted; all flotation-related results presented in this study are derived from thermodynamic and hydrodynamic modeling. Results show that a temperature decrease from 17 to 13 °C increases effective gas supersaturation by ~15% and shifts predicted microbubble diameters from ~60–90 µm to ~35–60 µm under identical operating conditions. The qualitative consistency between modeled flotation-relevant parameters and previously observed coagulation–flocculation trends for color, total organic carbon, and arsenic removal supports the proposed mechanistic framework. The study demonstrates how coupling coagulation chemistry with thermodynamically optimized air dissolution can enhance DAF applicability for arsenic- and NOM-rich groundwater. Full article

Microbial contamination of table eggs remains an important food safety concern, largely due to the presence of Salmonella spp. on eggshell surfaces and the potential for cross-contamination along the collection, grading, and packing chain. Conventional sanitation practices, including chlorinated-water washing, can reduce surface microbial loads but may also present limitations related to cuticle alteration, process variability, water use, and the risk of recontamination when operational conditions are not tightly controlled. This review synthesizes evidence on non-thermal and selected mild thermal technologies for the surface decontamination of intact table eggs, including ultraviolet-C (UV-C) irradiation, pulsed light, ozone-based treatments (gas and microbubble systems), non-thermal plasma, plasma-activated water, and gas-phase hydroxyl radical processes. For each approach, antimicrobial performance is discussed alongside effects on eggshell integrity, cuticle preservation, and key quality indicators (e.g., Haugh unit, albumen pH, yolk color, and shell strength). Particular attention is given to industrial constraints that influence real-world performance, such as treatment uniformity and shading effects, humidity dependence, line speed, equipment integration, and validation criteria. A shared limitation of surface treatments is their inability to inactivate pathogens that have penetrated shell membranes or contaminated egg contents, underscoring the need to align technology selection with the targeted hazard and the regulatory context. Thus, available data indicate that non-thermal technologies can contribute to reducing eggshell contamination when properly optimized, although broader implementation will depend on standardized operating parameters, robust process validation, and regulatory acceptance within existing egg processing systems. Full article

In the present work, three-dimensional (3D) simulations have been performed for the characterization of a rectangular column for a uniform gas distributor with µm-sized holes at a ratio of 5. The model is first validated with experimental data from the literature. Simulations are then performed for a gas distributor with identical pitch but two different hole sizes, namely 600 µm and 200 µm. Three superficial gas velocities, namely 0.002 m/s, 0.004 m/s, and 0.006 m/s, were used for each distributor type. The gas movement in the fluid is found to be a strong function of hole size. For a 600 µm hole size, the operating condition has minimal impact on gas plume movement and moves centrally in a fully aerated regime. However, for a hole size of 200 µm, for all superficial velocities, the gas plume movement is dynamic and partially aerated. The plume moves along the right wall initially and then follows vertically. These characteristics are different from the meandering plume in centrally located spargers. The liquid mixing in the bulk is a function of time. During the plume development flow, different shapes are observed. Based on the analogy with the shapes found in nature, these shapes have been termed as balloon, cap, jet or candle flame, bull horn, mushroom, tree shape, and disintegrated mushroom shapes. Quantitative insights have been obtained in the form of time-averaged radial profiles of both volume fractions and liquid axial velocities. A symmetric parabolic shape for a hole size of 600 µm and skewed asymmetric shapes for a 200 µm hole size for three different axial positions, namely 0.1, 0.25, and 0.4 m, are observed. Correlations for gas holdup and liquid velocity have been proposed for low superficial velocities, which are in good agreement with the CFD simulation data, with a deviation of 15–20%. The deviations are partly due to the use of the k-ε turbulent model. The correlations perform better than the correlations available in the reported literature for similar superficial gas velocities. Full article

Tip discharge in oil-immersed transformers poses a significant threat to insulation integrity. Conventional detection methods, such as gas and electrical analysis, are limited by slow response times or susceptibility to interference. Additionally, the lack of systematic comparisons between aged and fresh oil using multi-modal signal correlations hinders the development of accurate diagnostic strategies. To address this, a multi-modal sensing platform employing optical, UHF, and HFCT sensors, complemented by visual observation, was developed to investigate the evolution characteristics and mechanisms of tip discharge and to compare the detection effectiveness of these methods. Experimental results reveal that aged oil undergoes a novel four-stage evolution, where discharge signals first rise to a local peak, then experience suppression, followed by a dramatic surge, and finally decline slightly before breakdown. This process is governed by an “Impurity-Assisted Cumulative Breakdown Mechanism,” driven by impurity bridge growth and space charge effects, with signal transitions from ‘decoupling’ to synchronization. The optical sensor demonstrated superior sensitivity in early discharge stages compared to electrical methods. In contrast, fresh oil exhibited a “High-Field-Driven Stochastic Breakdown Mechanism,” with isolated pulses from micro-bubble discharges maintaining a metastable state until a critical threshold triggers instantaneous failure. This study enhances the understanding of how oil condition alters discharge mechanisms and underscores the value of multi-modal sensing for insulation condition assessment. Full article

Air flotation separation technology has emerged as one of the core techniques for oily wastewater treatment in oilfields, owing to its advantages of high throughput, high separation efficiency, and short retention time. Originally applied in mineral processing, this technology was first introduced to oilfield produced water treatment by Shell in 1960. With the optimization of microbubble generators, advances in microbubble generation technology—characterized by small size, high stability, and uniformity—have further expanded its applications across various wastewater treatment scenarios. To optimize the separation performance of a horizontal compact closed-loop cyclonic air flotation unit, this study employs CFD numerical simulation to investigate two key aspects: First, for the flotation zone, the effects of structural parameters (deflector height, inclination angle) and operational parameters (gas–oil ratio, bubble size, inlet velocity) on flow patterns and gas distribution were systematically examined. Device performance was evaluated using metrics such as gas–oil ratio distribution curves and flow field characteristics, enabling the identification of operating conditions for stratified flow formation and the determination of optimal deflector structural parameters. Second, based on the Eulerian multiphase flow model and RSM turbulence model, a numerical simulation model for the oil–gas–water three-phase flow field was established. The influences of key parameters (bubble size, throughput, gas–oil ratio) on oil–water separation efficiency were investigated, and the optimal operating conditions for the unit were determined by integrating oil-phase/gas-phase distribution characteristics with oil removal rate data. This research provides theoretical support for the structural optimization and engineering application of horizontal compact closed-loop cyclonic flotation units. Full article

For large-scale measurement of microbubble parameters on the ocean surface beneath breaking waves, a buoy-type bubble sensor (BBS) is proposed. This sensor integrates a panoramic bubble imaging sub-sensor with a circular array fiber-optic sub-sensor. The sensitive unit of the latter sub-sensor is designed via theoretical modeling and experimental validation. Theoretical calculations indicate that the optimal cone angle for a quartz fiber-optic-based sensitive unit ranges from 45.2° to 92°. A prototype array element with a cone angle of 90° was fabricated and used as the core component for feasibility experiments in static and dynamic two-phase (gas and liquid) identification. During static identification, the reflected optical power differs by an order of magnitude between the two phases. For dynamic sensing of multiple microbubble positions, the reflected optical power varies from 13.4 nW to 29.3 nW, which is within the operating range of the array element’s photodetector. In theory, assembling conical quartz fiber-based sensitive units into fiber-optic probes and configuring them as arrays could overcome the resolution limitations of the panoramic bubble imaging sub-sensor. Further discussion of this approach will be presented in a subsequent paper. Full article

Cancer remains one of the leading causes of death worldwide. Therefore, the continuous development of effective therapeutic strategies is necessary. Conventional anticancer chemotherapy has low bioavailability and poor systemic distribution, resulting in serious side effects and limited therapeutic efficacy. To address these limitations, drug delivery systems that respond to external stimuli have been developed to release drugs at specific sites. In this study, a phase transition-based bubble-mediated emulsion system was developed to enable near-infrared (NIR)-induced drug release. This system consists of an oil phase, 2H,3H-perfluoropentane (PFC), a fluorinated liquid gas that evaporates at a certain temperature, and encapsulated IR-780 and paclitaxel to maintain stable microbubbles. Under NIR irradiation, IR-780 exhibits a photothermal conversion effect, which increases the temperature. Above the critical temperature, PFC undergoes a phase transition into gas, forming gas bubbles. This phase transition leads to a rapid volume expansion, destroys the microbubble structure, and triggers drug release. The NIR-responsive microbubble system developed in this study facilitated targeted and selective drug release through precise temperature control using the photothermal effects and phase transition. This system provides a novel platform to improve the efficacy of cancer therapies. Full article

The consumption of fresh produce has significantly increased in recent years, contributing to improved diets through the provision of essential nutrients, vitamins, and fiber. However, there has been a rise in foodborne illness outbreaks linked to fruits and vegetables, often caused by pathogens such as Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes. These outbreaks have led to severe health consequences, including illnesses, hospitalizations, and even deaths. Once produce is contaminated by foodborne pathogens, these pathogens are difficult to eliminate. Traditional decontamination methods, such as water washes and chlorine-based sanitizers, have been widely used to address these microbial concerns. However, these methods may not be effective against pathogens in crevices or biofilms on the surface of produce, and their effectiveness varies depending on the type of produce and pathogens. Moreover, the chemicals used may raise health and environmental concerns. As a result, novel technologies for pathogen inactivation are gaining attention. These include ozone, ultraviolet light, cold plasma, pulsed light, ultrasound, microbubbles, nanobubbles, electrolyzed water, high-pressure processing, chlorine dioxide gas, and among others. This paper reviews a range of emerging and innovative technologies for the sanitization of fresh produce. The mechanisms, advancements, and practical applications of these technologies are examined with a focus on enhancing food safety and preserving produce quality. These innovative methods provide new opportunities for both research and industry to develop practical, affordable, and safe solutions for maintaining produce safety and quality. Recent studies highlight the effectiveness of combining methods, showing that using multiple sanitization techniques can significantly improve pathogen inactivation on fresh produce. For example, more than 5 log reductions of Listeria innocua and E. coli on avocado, watermelon, and mushroom can be achieved with the combined application of pulsed light and malic acid in previous research. In this review, we recommend the application of combined sanitization methods, emphasizing that integrating multiple techniques can provide a more effective and comprehensive approach to pathogen inactivation. This combined-method strategy has become a promising and innovative trend in the ongoing efforts to improve produce safety and quality. Full article

The thermal development in heavy oil reservoirs with edge and bottom water is poor, while gas huff-n-puff development shows a high recovery and strong adaptability. The formation of foamy oil during gas huff-n-puff is one of the reasons for the high recovery. In order to determine the factors affecting the foamy oil flow during gas huff-n-puff, experiments using a one-dimensional sandpack were conducted. The influences of drawdown pressure and cycle number were analyzed. The formation conditions of foamy oil were preliminarily clarified, and the enhanced oil recovery (EOR) mechanism of foamy oil was revealed. The experimental results show that the drawdown pressure and cycle number are two important factors affecting the formation of foamy oil. Foamy oil flow is prone to forming under a moderate drawdown pressure of 0.5–0.75 MPa, and being too small or too large is unfavorable. Foamy oil is more likely to form in the first two cycles, and it becomes increasingly challenging with the increase in the cycle number. These two factors reflect two necessary conditions for the formation of foamy oil during gas huff-n-puff: one is allowing the oil and gas to flow adequately to provide the shear and mixing for the generation of micro-bubbles, and the other is that the oil content should not be too small to avoid the inability to disperse and stabilize bubbles. The formation of foamy oil, on the one hand, increases the volume of the oil phase, and on the other hand, it reduces the mobility of the gas phase and slows down the pressure decline rate in the core, thereby enhancing the driving force for oil displacement. So, under the influence of the foamy oil, the gas production volume in a cycle declined by about 26%, and the average oil recovery increased by 4.5–6.9%. Full article

Currently, the existing high-pressure water mist fire protection systems in cold storage facilities face challenges in achieving efficient atomization and uniform water mist distribution, which may limit their effectiveness in rapid cooling and flame suppression. The objective of this investigation is to improve the performance of high-pressure fine water mist nozzles by integrating a Venturi microbubble generator to improve mist atomization and distribution, particularly in the context of flames involving combustible polyurethane foam insulation materials. The gas–liquid two-phase flow characteristics within Venturi tubes were investigated through numerical simulations using ANSYS-Fluent 2022 R1 software. This study focused on critical parameters, including the water inlet pressure (1–9 MPa), pharynx diameter (8–12 mm), contraction angle (15–45°), and expansion angle (15–45°). The average water mist droplet diameters at 1, 3, and 9 MPa were 169.890, 150.002, and 115.606 μm, respectively, in the absence of the Venturi tube, according to the experimental results. A reduction of up to 16.7% was achieved by reducing the particulate sizes to 141.462, 139.142, and 109.525 μm using the Venturi tube. The fire-extinguishing time and water consumption were substantially reduced at higher pressures, such as 9 MPa. Under high-pressure conditions, the results indicated that the Venturi microbubble technology was significantly more effective in suppressing fires. The novelty of this study lies in the application of Venturi microbubble technology to improve fine water mist systems for fire protection in cold storage facilities. This enhanced system achieves better atomization, uniform water mist distribution, faster cooling, and more efficient flame suppression, making it a viable solution for improving fire protection in such environments. Full article

Microbubbles have been applied in various fields. In the mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, which results in reducing the damage. Recently, when the proton beam power was increased and the number of injected gas bubbles was increased, unique damage morphologies were observed on the solid–liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage, i.e., the directions of streak-like defects which are formed by connecting the pit damage coincides with the direction of the gas bubble trajectories, and the distances between the pits was understandable when taking the natural period of gas bubble vibration into account. This indicates that gas microbubbles, used to reduce macroscopic pressure waves, have the potential to be inceptions of cavitation damage due to the microscopic pressure emitted from these gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles: reducing macroscopic pressure waves and reducing the microscopic pressure due to bubble dynamics. Full article

Microbubbles, acting as cavitation nuclei, undergo cycles of expansion, contraction, and collapse. This collapse generates shockwaves, alters local shear forces, and increases local temperature. Cavitation causes severe changes in pressure and temperature, resulting in surface erosion. Shockwaves strip material from surfaces, forming pits and cracks. Prolonged cavitation reduces the mechanical strength and fatigue life of materials, potentially leading to failure. Controlling bubble size and generating monodispersed bubbles is crucial for accurately modeling cavitation phenomena. In this work, we generate monodispersed microbubbles with controllable size using a novel and low-cost microfluidic method. We created an innovative T-junction structure that controls the two-phase flow for tiny, monodispersed bubble generation. Monodisperse microbubbles with diameters below one-fifth of the channel width (W = 100 µm) are produced due to the controlled pressure gradient. This microstructure, fabricated by a CNC milling technique, produces 20 μm bubbles without requiring high-resolution equipment and cleanroom environments. Bubble size is controlled with gas and liquid pressure ratio and microgeometry. This microbubble generation method provides a controllable and reproducible way for cavitation research. Full article

The inward vortex–swirl-type motion of convective, rectilinear water flow has been studied vis-à-vis its propensity for bubble formation, with a particular focus on the microbubble region. It has been found that a large population of smaller microbubbles, around 1 μm in diameter, is created in the process of these types of motions, and the time-dependent behaviour of this “micro-bubbly” water is analysed as Stokes’ law for microbubble dissipation occurs, such as bubble population, dissolved oxygen, pH, etc. Exponential decay analysis on the DLS-measured microbubble populations gave relaxation times τ of ~2.4 h and 3.6 h in exp(−t/τ) fits for DI and filtered tap water, respectively. The downward shift in pH was about 0.08 ± 0.016 and 0.11 ± 0.018 for DI and filtered tap water, respectively. For DI water, the level of dissolved oxygen (DO) at room temperature of 19 °C was ~102% at “t = 0”, and it declined to ~87% within 3 h (with the unprocessed background sample being about 84 ± 1.1%). The respective DO decay results in the case of the filtered tap water (at 19 °C) were ~105% at “t = 0”, declining to 91% within 3 h (background = 86 ± 1.2%). This allows for the dynamic properties to be understood in the context of how microbubbles determine the observed properties of post-flow water, including rationalising the observations of its time-transient properties. Naturally, this may well be of interest in gas transfer optimisation in the growing field of “fine-bubble engineering”. Full article