Search

The purpose of using bubbling in the case of metal alloys was to increase the mechanical resistance, to improve the casting properties as well as to observe the changes brought by gases on the structure. During bubbling, especially hydrogen and oxygen are removed, which obviously leads to the improvement of metal alloys. The influence of bubbling on the casting properties is explained by the structural changes that occur in the cast alloys. Therefore, bubbling with methane gas is a safe means of improving the quality of cast parts, ensuring at the same time the increase of casting properties of alloys. [ABSTRACT FROM AUTHOR]

Treatment with hydrostatic pressure of 10 MPa for 5 min stimulates the accelerated germination of lettuce seeds. Treatment with liquid oxygen has a depressing effect on seeds. In contrast, treatment of the same duration in liquid argon stimulates seed germination. The delay between seed treatment and germination has a negative impact on their sowing quality. Raising the temperature of seed storage enhances this effect. [ABSTRACT FROM AUTHOR]

Industrial wastewater is often contaminated with hydrogen sulfide and sulfides. This poses significant risks to both the environment and human health and life as H2S is extremely toxic. Therefore, water purification from it is vital, and the choice of an effective desorber device is an urgent issue. This paper investigates the process of H2S desorption from wastewater in mass exchange devices with a continuous bubbling bed (DCBB), a column with falling plates (CFP), and a horizontal device with bucket-like dispersers (HDBD). To analyze the kinetic and technological characteristics of the process, the following indicators were selected: the product of the mass exchange coefficient on the contact surface of phases (K•F), reduced to 1 m³ of the volume of the apparatus, and the degree of hydrogen sulfide desorption. The most complete desorption of hydrogen sulfide occurs at pH≤5. For practical needs, it is suggested to acidify the water to pH=5.5...6.0. It was established that the partial pressure of H2S increases linearly with increasing temperature, and an increase in salinity from 2...4 to 130...160 kg/m³ leads to its increase by 1.45...1.5 times. The best desorption indicators can be achieved in HDBD at pH=4.97. The efficiency of cleaning in CFP and DCBB is significantly affected by the specific air flow rate. The highest values (K•F) per 1 m³ that were achieved in desorbers are, mol/(s•Pa•m³): HDBD – 1.94•10-5, in CFP – 5.55•10-6, DCBB – 6.9•10-6. The ratio of the product (K•F) in HDBD to CFP is 3.5, and in HDBD to DCBB 2.8. It was possible to achieve the maximum degree of desorption of 37.8 % in DCBB; in CFP, this indicator is 74.1 %, and in HDBD – 77.7 %. Experimental studies have generally confirmed the effectiveness of using HDBD, and the results obtained under production conditions on real drainage and reservoir waters could find be practically implemented in hydrogen sulfide utilization technologies [ABSTRACT FROM AUTHOR]

We investigate aspects of the metric bubble tree for non-collapsing degenerations of (log) Kähler–Einstein metrics in complex dimensions one and two, and further describe a conjectural higher dimensional picture. [ABSTRACT FROM AUTHOR]

In semi-transparent polymers, ignition is not only dependent on conductive thermal transfer into the material but also on in-depth absorption of the radiation. The aim of this work was to investigate the influence of bubbling on the thermo-physical and thermo-radiative properties of PMMA and how it may affect its ignition. PMMA plates of varying thickness were exposed to the heat flux of two radiative sources with different emission spectra. Exposure was stopped after different periods of time to study bubbling kinetics and bubble size distribution by optical microscopy. Front and back surface temperatures of samples were recorded during heat exposure. The results indicate that the bubble size distribution is closely related to the temperature gradient within the sample. Steep thermal gradients lead to small-sized bubbles underneath the exposed surface, while weak thermal gradients generate a wider size distribution with in-depth bubbling. All thermo-physical quantities k , ρ and C p were shown to decrease with increasing bubbling degree. Likewise, it was highlighted that bubbling modifies the thermo-radiative properties of PMMA, especially in the near-infrared range. Transmittance decreases while absorbance increases with a bubbling degree. The increase in the absorption coefficient was attributed to multiple scattering by bubbles that expand the pathway of radiation into the materials. It was concluded that changes in both the thermo-physical and thermo-radiative properties with bubbling were likely to account for the delay in ignition observed when using the near-infrared heating source. [ABSTRACT FROM AUTHOR]

The complexity of waste printed circuit boards makes their recycling difficult. The process requires robust and expensive technologies to achieve separation. In this study, a simple novel technology was developed that used ultrasonication to separate metals from the substrate fiberglass layer. The technology used a customized tank to do the separation. The effectiveness of the process is determined by several factors. Five parameters were tested: ultrasonic frequency, particle size, ultrasonication time, bubbling, and mass. The ultrasound was used to enhance the separation of metals and substrate fiberglass layer. The test was done on two frequencies: 40 kHz and 58 kHz. It was shown that at 40 kHz, copper recovery was higher than at 58 kHz. It was found that ultrasonication time and particle size are the most significant parameters in the process. A copper recovery of 86.91% was achieved using this method. The statistical analysis showed the potential of the novel technology. [ABSTRACT FROM AUTHOR]

IntroductionAppropriate and effective decolorization of raw and thin juice in sugar refineries is considered as an important process to obtain premium quality sugar, which due to the problems of its conventional process, membrane processes as effective and environmentally friendly processes can be used in parts of sugar industries. Among the disadvantages of the usual methods to remove membrane fouling, it can be mentioned the destruction of the membrane, environmental pollution, the remaining detergents in the membrane and the product, especially in the pharmaceutical and food industries, and the increase in production costs. Therefore, it seems that physical methods such as pre-filtration of the incoming feed, using turbulent and pulse currents to prevent excessive compression of the gel layer formed on the membrane surface are more effective and have fewer disadvantages. One of the ways to change the flow of feed entering the membrane surface is bubbling, which causes mixing the flow and increases the tangential shear stress. In fact, the hydrodynamic force that creates bubbles causes both the dragging force and the lifting force and leads to the removal of fouling and reducing the phenomenon of concentration polarization. Materials and Methods In this research, an ultrafiltration membrane (MWCO=10 KDa) pilot with a flat module (effective surface 40 square centimeters) was used to purify raw beet juice (which had passed a stage of pre-treatment with microfiltration) at the temperature of about 30 degrees Celsius and a trans membrane pressure of 3.5 bar during the process. Nitrogen gas in the amount of 0.5, 1 and 1.5 liters per minute was used in two continuous and interrupted modes for bubbling. In this way, in the interrupted mode, after every 3 minutes of filtration, the filtration process was carried out with gas for one minute. The factors such as flux, fouling and membrane resistance as membrane efficiency's factors and parameters like color, purity and turbidity as purification factors was investigated in the form of a completely random design and compared with control filtration conditions (without bubble generation). The results of this research were statistically analyzed using SAS (version 1.9) and Microsoft Office Excel 2019 software. The average data of each test in three repetitions was compared with the least significant difference (LSD) test at the 95% level. Results and DiscussionIncreasing the amount of gas during the bubbling process improved the flow rate. Also, the results showed that the decreasing trend of the permeate flux at the gassing rate of 1.5 L/min was less than other treatments and more stable conditions were seen in the sap flux during the process. Also, the amount of flux in the interrupted form of bubbling showed that after the application of bubbling, although the amount of flux increased, but after that, during the ultra-refining process, the flux decreased again and did not remain constant at that level. But in general, despite the fact that the average flux was higher in the continuous process compared to the interrupted state, there was no significant difference between them. The results related to the amount of membrane fouling after applying the process showed that by applying bubble generation in both continuous and interrupted mods, the fouling was significantly reduced compared to the usual state of ultrafiltration. Also, as the amount of gas entering the feed stream increased, the membrane fouling decreased, which was slightly higher in the continuous state than in the interrupted mod. The overall hydrodynamic resistance of the membrane in different filtration modes showed that the difference between the overall resistance of the membrane in the ultrafiltration and the ultrafiltration process with gasification is quite significant. However, although the overall resistance of the membrane in the interrupted gassing state is higher than its continuous state due to more clogging, there is no significant difference between them (P

The work is devoted to an experimental study of the behavior of bubbles when capturing pulverized materials with nanoparticles in the course of colliding of gas-liquid jets in a bubbling layer. The article discusses the use of channels in a jet bubbler and the dependence for detecting horizontal movement of bubbles with nanoparticles in them. The purpose of this stage of research is to study the behavior of gas-liquid jets when exiting without a guide channel and through a guide channel. The results of experiments conducted on the patented design of the jet bubbler are analyzed. The article presents the results of experiments conducted to study the shapes and sizes of formed gas bubbles. The graphs constructed after processing the frames of the kinogram according to the data of the experiments are given. On the basis of preliminary tests, the features of using channels to create the jet collisions in an experimental setup to increase the range of captured solid particles, including nanoparticles, are substantiated.

We introduce and study a conformal heat flow of harmonic maps defined by an evolution equation for a pair consisting of a map and a conformal factor of metric on the two-dimensional domain. This flow is designed to postpone finite time singularity but does not get rid of possibility of bubble forming. We show that Struwe type global weak solution exists, which is smooth except at most finitely many points. [ABSTRACT FROM AUTHOR]

The research has looked at the effectiveness of washing tomatoes with ozonated water before processing. Washing was done by immersion in water with O3 micro bubbling at 2.5 mg L-1 for 5 and 10 minutes, respectively at the temperature of 15°C. The removal of residues generated by treating tomatoes with Cyperguard 25 EC, Dithane M-45 and Topsin 70 WDG was examined. Mass spectrometry was used to determine the residues. At V1, the variant treated with Cypermethrin, the second and fourth peak have recorded the values of 0.6 mg/kg > 0.5 mg/kg, the value accepted as the maximum allowed limit. The analysis data confirmed that the solution used was significantly effective in removing pesticide residues, applied before the harvest. [ABSTRACT FROM AUTHOR]

A simplified and a numerical mathematical models of gas cooling and water heating in a thin turbulent bubbling layer on a tray with cross-phase flow are presented. The thermal efficiency of gas cooling is found using the ideal displacement model, and the temperature profile in the liquid phase is found from the solution of a cell model or a two-dimensional differential equation of convective heat exchange with an interfacial heat source. Examples of calculating the efficiency of water cooling of gas with different humidity on sieve and valve trays are given. The results of calculations of the thermal efficiency of gas cooling depending on the height of the gas–liquid layer, as well as on the gas velocity in the column are compared with known experimental data. Conclusions are drawn about the adequacy of the mathematical model and of the developed algorithm for calculating the heat and mass transfer characteristics of the bubbling layer. Comparative characteristics of the thermal efficiency of sieve and valve trays are given depending on the gas velocity and different heights of the liquid column. The influence of the variable mass of valves along the length of the tray on the increase in thermal efficiency is shown. Conclusions are drawn on the most efficient designs and modes of operation of bubbling trays. [ABSTRACT FROM AUTHOR]

The acylation of some 2-aminocycloalka[b]thiophene-3-carbonitriles with various acid chlorides gave the corresponding N-acylamino derivatives which were cyclized to fused thieno[2,3-d]pyrimidin-4-ones by bubbling hydrogen chloride gas through their solutions in ethanol. Most of the synthesized compounds showed weak antibacterial activity against S. aureus, and some of them exhibited moderate activity against B. subtilis. [ABSTRACT FROM AUTHOR]

In semi-transparent polymers, ignition is not only dependent on conductive thermal transfer into the material but also on in-depth absorption of the radiation. The aim of this work was to investigate the influence of bubbling on the thermo-physical and thermo-radiative properties of PMMA and how it may affect its ignition. PMMA plates of varying thickness were exposed to the heat flux of two radiative sources with different emission spectra. Exposure was stopped after different periods of time to study bubbling kinetics and bubble size distribution by optical microscopy. Front and back surface temperatures of samples were recorded during heat exposure. The results indicate that the bubble size distribution is closely related to the temperature gradient within the sample. Steep thermal gradients lead to small-sized bubbles underneath the exposed surface, while weak thermal gradients generate a wider size distribution with in-depth bubbling. All thermo-physical quantities k, ρ and Cp were shown to decrease with increasing bubbling degree. Likewise, it was highlighted that bubbling modifies the thermo-radiative properties of PMMA, especially in the near-infrared range. Transmittance decreases while absorbance increases with a bubbling degree. The increase in the absorption coefficient was attributed to multiple scattering by bubbles that expand the pathway of radiation into the materials. It was concluded that changes in both the thermo-physical and thermo-radiative properties with bubbling were likely to account for the delay in ignition observed when using the near-infrared heating source.

The degradation of the insulation system in liquid-filled power transformers is a serious concern for electric power utilities. The insulation system's ageing is accelerated by moisture, acids, oxidation products, and other decay particles (soluble and colloidal). The presence of these ageing by-products is detrimental to the insulation system and may further lead to premature ageing and serious consequences. The ageing mechanisms of oil-paper insulation are complex, highly interrelated, and strongly temperature-dependent. The operating temperature of the transformer insulating system has a direct relationship with the loading profile. The major aspect that is witnessed with the fluctuating temperatures is moisture migration and subsequent bubble evolution. In other words, gas bubbles evolve from the release of water vapor from the cellulosic insulation wrapped around the transformer windings. The models presented in the existing standards, such as the IEC Std. 60076-7:2018 and the IEEE Std. C57.91:2011, are mainly based on the insulation temperature, which acts as a key parameter. Several studies have investigated the moisture dynamics and bubbling phenomenon as a function of the water content in the paper and the state of the insulation system. Some studies have reported different prototypes for the estimation of the bubble inception temperatures under selected conditions. However, there are various attributes of the insulation system that are to be considered, especially when expanding the models for the alternative liquids. This paper reviews various evaluation models reported in the literature that help understand the bubbling phenomenon in transformer insulation. The discussions also keep us in the loop on the estimation of bubbling behavior in alternative dielectric liquids and key attributable factors for use in transformers. In addition, useful tutorial elements focusing on the bubbling issue in transformers as well as some critical analyses are addressed for future research on this topic. [ABSTRACT FROM AUTHOR]

This work proposes a new technology for determining impurities in the air and air purification (for the city of Apatity), and also an experimental installation. Bubbling the test gasthrough a layer of distilled water using neodymium magnets to concentrate impurities is considered. The proposed technology makes it possible to more accurately determine the amount of impurities in the air and also improve air purification. [ABSTRACT FROM AUTHOR]

Xylitol is a promising phase change material for thermal energy storage at low and medium temperatures, but its supercooling and low crystallization rate can hinder its performance in actual systems. This problem can be overcome with the application of external stimuli that promotes the nucleation and subsequent crystallization of the supercooled xylitol. Seeding combined with mechanical stirring or air-bubbling, the techniques used in this study, are proven to achieve the crystallization (and the release of the stored latent heat) of xylitol, but the effect was not instantaneous. Rheological measurements were performed firstly to study the influence of shear and temperature in the crystallization of xylitol. Then, the use of different mechanisms to promote the crystallization of the material was evaluated by two different laboratory-scale prototypes; one of them included a mechanical stirring system while the other employed a gas-bubbling mechanism. Thermal power and discharged energy of xylitol were evaluated in the bubbling system prototype and the influence of supercooling in both discharged power and energy were also studied. A methodology to calculate induction time is proposed to evaluate crystallization systematically in both systems. This new systematic evaluation proposed in this work is different from that of the literature and aims to be used to compare different crystallization systems.

• A multiphase model for particle-bubble-liquid flows using the front-tracking and discrete-element method was developed. • The collision, attachment, and detachment between particles and bubbles were included. • The attachment effect greatly impedes the bubble rising but enhances the particle transport intensity. • Hydrophilic particles with higher density can promote the bubble rising speed and it can be even faster than in the pure liquid. • Increasing the bubbling frequency can enhance the lifted intensity of particles but insignificantly for the dispersion intensity. Particle-bubble-liquid flows widely exist in industrial processes, such as fluidized beds, flotation cells, and bubble column reactors, but the high-fidelity simulation of these flows is a great challenge. This paper developed a dynamic model for this three-phase system using a front-tracking and discrete-element method, where the behaviors of collision, attachment, and detachment between the particles and bubbles are included. The convergence and accuracy of this model were validated, and then the model was applied to simulate the transport behaviors of particle-bubble-liquid flows. The collision and attachment probabilities and the effects of particle size and properties on the collision, attachment, and flow behaviors were numerically investigated. The particle-bubble interaction simulations show that the collision probability and contact time increase with the increase of the size ratio of particle to bubble; hydrophilic particles can promote the bubble rising speed and even faster than that in the pure liquid; the attachment behavior greatly impedes the bubble rising but enhances the particle transport intensity. The bubbling simulations show that the wake of the rising bubble can induce the following bubble to move along a wave-like trajectory; the particles driven by a higher bubbling frequency present a higher lifting height and a stronger dispersion effect. [ABSTRACT FROM AUTHOR]

Abstract—The fuming of copper smelting slag in a Vanyukov furnace by the products of methane conversion by oxygen, water vapor, and carbon dioxide in the temperature range 1473–1773 K is thermodynamically modeled. For this purpose, a technique is developed to describe the changes in the phase compositions in the systems under study during their bubbling as functions of the amount of an introduced reducing gas; this technique is characterized by cyclic calculations and the removal of the formed gases and metal phase from the working medium composition. The calculation results demonstrate that the interaction of the gas with melt oxides proceeds in two stages regardless of the melt composition. At the first stage, Fe3O4 is reduced to FeO and ZnO, to Zn. Therefore, the content of Fe3O4 and ZnO in the melt decreases and that of FeO increases. At the second stage, metallic iron appears and the content of iron and zinc oxides decreases. A significant influence of temperature on fuming is shown. When the temperature increases from 1473 to 1773 K, the fuming process is significantly intensified, which is accompanied by a fourfold decrease in the amount of the reducing gas required to achieve close degrees of zinc recovery. The gas composition weakly affects the process. The most effective reducing agent is shown to be the gas formed by the steam conversion of methane, which is due to the minimal costs of its production. The results obtained make it possible to predict the indicators of the process of fuming by methane conversion products and will be useful for creating new technologies. [ABSTRACT FROM AUTHOR]

Tropical reservoirs are generally flooded in soils with a high content of organic matter. This, combined with high temperatures, favors the generation of carbon dioxide and methane by biological degradation, contributing to the impact on climate change. A tropical reservoir in Colombia was monitored for 7 years in the pre-fill, fill and post-fill stages, for the last of these during the day and night. Emissions from diffusive fluxes at the surface of the water were measured using a floating static chamber, while inverted funnel methodology was used to measure the fluxes by bubbling. The samples collected in the field were analyzed in the laboratory using a gas chromatograph with a mass detector. The results showed average emissions of 70892.51±41079.16-ton CO2eq/year for pre-filling; 178254.53±105838.01-ton CO2eq/year for filling; and 466946.57-ton CO2eq/year for post-filling (for 5 years), concluding that the weather conditions and the filling percentage had an impact on the generation of greenhouse gases at filling and post-filling stages, as did the organic matter present in the area of influence of the sampling point. Higher greenhouse gas emissions were found during the day compared to the results at night, indicating that temperature affects these processes especially in tropical reservoirs. HIGHLIGHTS A tropical reservoir in Colombia was monitored for 7 years during the pre-filling, filling and post-filling phases.; The main contribution is the estimation of GHG in a tropical reservoir using a floating static chamber and the inverted funnel method.; This is the first investigation carried out in Colombia to determine the net emissions in a reservoir.;

Subject and Purpose. The maintenance of physical and chemical properties and biological stability of lubricoolants during downtimes, which are bound to happen sometimes and last long, is a hot problem in metalworking industry. The procedure of bubbling for the lubricoolant mixing, saturation with oxygen and inactivation of anaerobic microflora calls for chemical and biological techniques to monitor the lubricoolant condition during the bubbling and after it. Yet the standard methods lack responsiveness and accuracy of the analysis, implying the further refinement of the output values. In the present work, microwave super-high frequency (SHF) dielectrometry is employed for the examination of the dielectric constant and dynamic surface tension of synthetic, semi-synthetic and organic emulsions during the bubbling. Methods and Methodology. The dielectric constant and dynamic surface tension of 5.7 % water-soluble emulsions are measured at frequency f = 37.7 GHz. A frequency sweep in the acoustic frequency range f = 20…25000 Hz is used, for which purpose the end of the 8-mm waveguide is supplied with a piezo сell. Results. It has been revealed that the dielectric constant and dynamic surface tension of lubricoolants depend on the physicochemical characteristics that the lubricoolants acquire during a month-long downtime and after 10-, 20-, and 30-minute bubblings. The dielectric constant and dynamic surface tension demonstrate that the bubbling improves lubricating properties of all the emulsions examined. For this, a 10-minute bubbling is enough for semi-synthetic lubricoolants, and a 20-minute bubbling is needed for synthetic and organic lubricoolants. Conclusion. The microwave dielectrometry method with a frequency sweep in the acoustic frequency range can be used in metalworking industry as an aid to lubricoolant quality control during the downtime or storage.

The composition of GET 39-2021 State primary standard of units of volumetric activity of radioactive aerosols, radon, thoron, and radon flux density is presented. Methods for reproducing and transferring the units of volumetric activity of radioactive aerosols, radon, thoron, and radon flux density are described. Possible sources of error are identified, and their quantitative assessment is performed. The metrological characteristics of GET 39-2021 are provided. GET 39-2021 ensures the uniformity of measurements of the volumetric activity of radioactive aerosols, radon, thoron, and radon flux density in various fields, including the nuclear industry, at enterprises for the extraction and processing of nuclear raw materials, etc. In the nuclear industry, GET 39-2021 can be used to ensure the radiation protection of personnel and the environment during the construction and commissioning of new-generation nuclear reactors. [ABSTRACT FROM AUTHOR]

A chromatographic method for determining the mass fraction of organochlorine compounds in oil and its refined products has been developed. An inert gas is bubbled through a container filled with the analyzed liquid; the flow of the inert gas containing vapors of organochlorine compounds is divided into two parallel flows in the chromatograph; one of the two flows is separated with a capillary chromatographic column, while the other, with a polycapillary chromatographic column, both at a constant temperature. The organochlorine compounds are detected with a single electron-capture detector connected to each of the two flows in accordance with the release time of a definite organochlorine compound. The developed method allows automated measurements of mass fraction of organochlorine compounds in oil and its refined products using flow gas chromatographs of explosion-proof design; the analysis time decreases, and the losses due to contamination of feedstock with organochlorine compounds at oil refineries and oil transportation enterprises are reduced. [ABSTRACT FROM AUTHOR]

This paper explores the hyperbolic heat transfer effects in processes involving high heating rates. The behavior of the model is analyzed in detail under different boundary conditions and the circumstances under which a non-Fourier law could be used to describe thermal conduction processes established from physical mathematical analysis. Finally, the model developed here is coupled to a previous population balance framework to predict the bubbling phenomenon that occurs during the fast pyrolysis of biomass. We found that a transient overheating occurs in the central zone of the generated liquid phase due to the high heating rates that take place during that process. [ABSTRACT FROM AUTHOR]

The key group of research methods used for the analysis of formation and flow of gas bubbles in liquids are those involving digital imaging and shadowgraphy. Despite their frequent use, there is no comprehensive analysis of the compliance of different procedures to determine bubble size based on experimental data. In this work, fifteen different approaches for shape recognition were used to determine the equivalent diameter of a bubble and then the results obtained were compared with bubble equivalent diameters determined experimentally. The experiments concerned bubbles of equivalent diameters in the range of 2.4–5.4 mm which correspond to the size of the bubbles most commonly encountered in industrial practice. Particularly, three algorithms for bubble shape detection were evaluated and then three sets of parameters to express the size of the bubble and two types of bubble equivalent diameter were derived. It was found that the most accurate results are obtained by using image binarization and Canny edge detection for the determination of the bubble shape, combined with the Feret diameter employed to express its size and with the volumetric equivalent diameter instead of the superficial one. As the binarization method is not versatile, we recommend using the Canny edge detector. • Procedures based on shadowgraphy to determine bubble size are compared. • Versatile procedure for determination of bubble equivalent diameter are selected. • Canny edge detector performs best to localize bubble rim in the images of bubbles. • Approximating the bubble with a rotational ellipsoid leads to accurate results. • Determining the bubble shape using Feret diameters leads to accurate results. [ABSTRACT FROM AUTHOR]

This work aims to obtain the dispersions based on polyethylene glycols (PEGs) of various molecular masses (MM) and perfluorodecalin (PFD) for subsequent direct fluorination. The solubility of the components was estimated using laser interferometry and differential scanning calorimetry, and it was shown that PEGs with different MM are not highly compatible with PFD. The dispersions were prepared during sonication. Gel permeation chromatography (GPC) analysis indicated that MMs almost did not change in this process. While the sonication of PEG-PFD, there is a formation of dispersion with the particle sizes distribution in a range of 0.4‒2 μm depending on the MM of PEG. The dispersion is metastable for several hours, even though its stability was significantly affected by additional bubbling with the gas flow. Moreover, the dispersions with a solid PEG phase (MM > 600 Da) were subjected to a smaller change compared to a liquid one (MM < 600 Da). The results of this research shed light on the applicability of the ultrasonic preparation of PEGs in PFD for liquid-phase fluorination with obtaining perfluorinated polyether of target MM.

This work aims to obtain the dispersions based on polyethylene glycols (PEGs) of various molecular masses (MM) and perfluorodecalin (PFD) for subsequent direct fluorination. The solubility of the components was estimated using laser interferometry and differential scanning calorimetry, and it was shown that PEGs with different MM are not highly compatible with PFD. The dispersions were prepared during sonication. Gel permeation chromatography (GPC) analysis indicated that MMs almost did not change in this process. While the sonication of PEG-PFD, there is a formation of dispersion with the particle sizes distribution in a range of 0.4‒2 μm depending on the MM of PEG. The dispersion is metastable for several hours, even though its stability was significantly affected by additional bubbling with the gas flow. Moreover, the dispersions with a solid PEG phase (MM > 600 Da) were subjected to a smaller change compared to a liquid one (MM < 600 Da). The results of this research shed light on the applicability of the ultrasonic preparation of PEGs in PFD for liquid-phase fluorination with obtaining perfluorinated polyether of target MM. [ABSTRACT FROM AUTHOR]

Several studies have demonstrated that air-bubbling and foam fractionation techniques can efficiently remove long-chain PFAS from contaminated water. However, removing short-chain PFAS is challenging due to its lower surface activity and inability to form self-assembly structures at the air-water interface. In this study, we tested various additives, including salts, surfactants, and polymers, to improve short-chain PFAS (e.g., perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA)) removal in non-foaming solutions using a bench-scale system. We found that in the presence of cetyltrimethylammonium chloride (CTAC) and salt, air-bubbling can significantly remove 0.5 μg L−1 of PFBS and PFBA in deionized water by >99% (15 min) and 81% (60 min), respectively. The decline of surface tension and the formation of thin foam-like layers during bubbling, controlled by the concentration of CTAC, significantly improved the removal of short-chain PFAS. Adding anionic and neutral surfactants showed no removal of short-chain PFAS during bubbling, suggesting the importance of the electrostatic interactions between short-chain PFAS and the cationic CTAC. We observed a 1:1 M ratio between CTAC and PFBS removed from the solution, suggesting the formation of ion pairs in the solution and enhancing the surface activity of the overall neutral (PFAS-CTAC) complex. A mass balance of the system revealed that the primary mechanism by which PFAS was removed from non-foaming waters was through aerosol generation (70−100%). Using the optimized condition, PFAS mixtures (short- and long-chain PFAS, including five recently regulated PFAS by USPEA, 2 nM each) in deionized water and natural groundwater were successfully removed to below detection (>99% removal; <2 ng L−1), except for PFBA (25−73% removal). These results provide an improved understanding of the mechanism by which PFAS is removed during foam fractionation and highlight the need for capturing aerosols enriched with PFAS to prevent secondary contamination. [Display omitted] • Cationic surfactant enhanced short-chain PFAS removal during foam-fractionation. • Ion-pair formation between PFAS and CTAC increased surface activity of short-chains. • Aerosolization was the primary pathway for PFAS removal in non-foaming waters. • Mass balance of PFAS in the system can achieve 70–100% when aerosols were measured. [ABSTRACT FROM AUTHOR]

• The analysis of the period (i.e. frequency) of the phenomenon does not show a clear dependency on the water pool temperature. • The vertical jet velocity is the result of the bubble size and the bubble implosion time. • The normalized velocity collapses on a single curve and the flow decays like a free-stream jet following the self-similarity. • The inclination of the velocity in the spreading region, shows that the jet decays consistently with single phase flow jets. Steam Direct Contact Condensation (DCC) is an effective way to condense steam in a pool of water. This method of condensation is widely employed in the containment of nuclear power plants. One of the limitations of DCC is the generation of non-uniform temperature distribution in the water pool, which can result in slow but steady pressurization of the containment. Due to the non-linearity of the problem the evaluation of the temperature distribution in the pool cannot be established by simple theoretical analyses but computational models are deemed necessary (e.g. Computational Fluid Dynamics (CFD) and Lumped Parameter (LP) codes). Existing models could be validated only qualitatively because the experimental evidence is composed fundamentally of video acquisitions, which does not allow for a correct comparison of the phenomena. In this paper the authors will present PIV results of a small-scale facility during DCC measuring the jet induced by chugging. The authors have found that the water flow induced by the bubble implosion contains several similarities with continuous and synthetic jets (e.g. velocity spreading) following the self-similar properties of the jet theory. The period of the implosion can be quantified with the current methodology to be around 0.025 s and it has been shown to be independent on the water temperature. [ABSTRACT FROM AUTHOR]

The degradation of the insulation system in liquid-filled power transformers is a serious concern for electric power utilities. The insulation system’s ageing is accelerated by moisture, acids, oxidation products, and other decay particles (soluble and colloidal). The presence of these ageing by-products is detrimental to the insulation system and may further lead to premature ageing and serious consequences. The ageing mechanisms of oil-paper insulation are complex, highly interrelated, and strongly temperature-dependent. The operating temperature of the transformer insulating system has a direct relationship with the loading profile. The major aspect that is witnessed with the fluctuating temperatures is moisture migration and subsequent bubble evolution. In other words, gas bubbles evolve from the release of water vapor from the cellulosic insulation wrapped around the transformer windings. The models presented in the existing standards, such as the IEC Std. 60076-7:2018 and the IEEE Std. C57.91:2011, are mainly based on the insulation temperature, which acts as a key parameter. Several studies have investigated the moisture dynamics and bubbling phenomenon as a function of the water content in the paper and the state of the insulation system. Some studies have reported different prototypes for the estimation of the bubble inception temperatures under selected conditions. However, there are various attributes of the insulation system that are to be considered, especially when expanding the models for the alternative liquids. This paper reviews various evaluation models reported in the literature that help understand the bubbling phenomenon in transformer insulation. The discussions also keep us in the loop on the estimation of bubbling behavior in alternative dielectric liquids and key attributable factors for use in transformers. In addition, useful tutorial elements focusing on the bubbling issue in transformers as well as some critical analyses are addressed for future research on this topic.

[Display omitted] Degradation of therapeutic monoclonal antibodies (mAb) due to interfacial agitation through air bubbling was investigated. Samples containing mAb in phosphate buffered saline were subjected to rapid bubbling by using a peristaltic pump at an air flow rate of 11.5 mL/min. Samples were analyzed by visual observation, UV–Vis, fluorescence, circular dichroism and infrared spectroscopy, size-exclusion chromatography (SEC), dynamic light scattering, microscopy, and cell-based activity assays. The stressed samples showed increasing turbidity with bubbling time, with mAb1 showing a protein loss of 53% in the supernatant at the latest time point (240 min), indicating formation of sub-visible and visible aggregates. Aggregate rich samples exhibited altered secondary structure and higher hydrophobicity with 40% reduction in activity. The supernatants of the stressed samples showed unchanged secondary and tertiary structure without the presence of any oligomers in SEC. Furthermore, the impact of various factors that could affect aggregation was investigated and it was found that the extent of aggregation was affected by protein concentration, sample volume, presence of surfactants, temperature, air flow rate, and presence of silicone oil. In conclusion, exposure to air/liquid interfacial stress through bubbling into liquid mAb samples effectively generated sub-visible and visible aggregates, making air bubbling an attractive approach for interfacial stress degradation studies of mAbs. [ABSTRACT FROM AUTHOR]

Background: Insular glioma was considered a nonsurgical entity due to resection-associated morbidities. The advancement in neurosurgical techniques and adjuncts used in the last two decades made the resection of insular gliomas simpler for neurosurgeons with the maximum extent of resection and acceptable morbidity rates. The complex anatomy of this region remains a challenge for neurosurgeons and requires expertise. The key factors to achieve complete resection in the insular region are the thorough knowledge of surgical anatomy and meticulous microsurgical techniques. Intraoperative adjuncts such as image guidance along with cortical and subcortical mapping assist in excellent outcomes.Objective: In this study, we describe the operative technique and application of trans-Sylvian approach to do the compartmental dissection done by the senior author, along with challenges faced, with the hope to highlight the efficacy of the approach to achieve maximal resection of this entity without compromising patient's safety.Materials and Methods: A 32-year-old right-handed gentleman presented with episodes of excessive salivation, tingling sensation on the right side of the body along with nausea that lasted for 15-20 s for the last 8 months and one episode of speech arrest without any loss of consciousness and motor or sensory deficit. CEMRI of the brain was suggestive of left insular glioma. The patient underwent left pterional craniotomy, and gross total resection of the tumor was done using compartmental dissection.Results: At follow-up after 1 month, the patient is seizure-free without any speech difficulty and motor or sensory deficit.Conclusion: Compartmental dissection of insular glioma is a safe and efficacious technique to achieve gross total resection of the tumor in this complex region without morbidity. [ABSTRACT FROM AUTHOR]

For a given quasi-Fuchsian representation ρ : π 1 (S) → PSL 2 ℂ of the fundamental group of a closed surface S of genus g ≥ 2 , we prove that a generic branched complex projective structure on S with holonomy ρ and two branch points can be obtained from some unbranched structure on S with the same holonomy by bubbling, i.e. a suitable connected sum with a copy of ℂ ℙ 1 . [ABSTRACT FROM AUTHOR]

Copyright of Electroplating & Finishing is the property of Electroplating & Finishing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerical simulations are performed to investigate the breakup of air bubble in flow focusing configuration; the CLSVOF (coupled level set with volume of fluid) method is employed to track the interface, which allows a better identification of the liquid–gas interface via a function called level set. The CFD simulations showed that the velocity ratio, the interfacial tension, the outer channel diameter, the continuous phase viscosity, the orifice width and length play an important role in the determination of the air bubble's size and shape. However, at low capillary number, increasing the flow velocity ratio gives a smaller bubble size in shorter time, while the increase in interfacial tension leads to a bigger bubble. Moreover, the carrier fluid is found to slightly affect the bubbling mechanism, while the smallest bubbles were obtained with the smallest orifice size. In addition, three breakup regimes are observed in this device: disc-bubble (DB), elongated bubble (EB) and the slug bubble (SB) regime flows. This work also demonstrates that the CLSVOF is an effective method to simulate the bubbles breakup in flow focusing geometry. In addition, a comparison of our computational simulations with available experimental results reveals reasonably good agreement. [ABSTRACT FROM AUTHOR]

Towards long-term seasonal latent heat storage, the PCMs with strong supercooling are recommended as the heat storage medium. Nevertheless, the suitable techniques activating latent heat release is also of significance in the period of heat supply. The present work investigated the N 2 bubbling triggered crystallization of supercooled xylitol. Special attention was paid to the subcooling effect. The N 2 bubbling was identified to be a potential technique to trigger crystallization of xylitol at moderate degrees of subcooling. It was found that efficient crystallization issues were obtained with degrees of subcooling from 40 °C to 60 °C, while uncrystallization was obtained with both lower and higher subcooling. The recorded temperature history curves show that subcooling effect has strong influence on the crystallization behavior. The crystallization points tend to decline from 51.9 °C to 42.3 °C with degree of subcooling rising from 40 °C to 50 °C. The crystallization durations extend with subcooling effect enhancing. Fortunately, bubbling technique has slight influence on the properties of formed xylitol crystals. Moreover, the subcooling significantly influences the transportation behavior of bubbles. Particularly, The specific growth rates of bubbles are determined to be as low as 0.005 mm/min with the lowest degree of subcooling 10 °C, and continue to rise over 20 times when the subcooling reaches to 60 °C. The interfaces of bubbles as potential nucleation sites were deemed to be one of the important issues to activate heterogeneous nucleation, thus trigger crystallization. The present investigation is helpful to understand the fundamentals of bubbling effect on crystallization with broad range of subcooling. • Bubbling is identified to be feasible to trigger crystallization for controllable heat retrieval. • Subcooling has significant influence on bubbling-triggered crystallization. • Effective crystallization can't be obtained with relatively low and high subcooling. • Properties of bubbling-triggered crystal are nearly same to those of received reagent. • Subcooling also affects transportation behavior of bubbles in supercooled liquid. [ABSTRACT FROM AUTHOR]

• A Fresnel lens is used to focus sunlight into the desalination system. • Solar concentrating and bubbling technologies are combined into desalination system. • The accumulated yield can reach 5.61L/d/m2 under actual weather conditions. • System performance ratio is 0.69 under actual weather and 0.71 with electrical heater. A bubbling humidification-dehumidification (HDH) desalination system directly heated by concentrated sunlight is presented in this work. Sending directly the concentrated sunlight into bubbling humidification chamber can save the circulation pipeline and solar receivers, and reduce the heat loss of the pipeline which simplifies the device's structure and adds its operation reliability. The HDH system consists of a Fresnel lens solar concentrator, a bubbling humidification chamber and a bubbling dehumidification chamber. The operating principle and the structural design of the bubbling chambers are explained. A cylindrical Fresnel lens is used to focus sunlight into the humidification chamber to directly heat the seawater. With air coming out from the perforated wall of the immerged pipe, bubbles will generate underwater to obtain sufficient heat and moisture transfer. Experimental tests under different conditions were carried out to verify the design and study the performance characteristics. The results that the maximum freshwater productivity is about 1.24L/h/m2 when the maximum solar irradiance is 980 W/m2. The accumulated yield can reach 5.61L/d/m2 with an average thermal efficiency about 69% for sunny weather conditions in October in Beijing. Besides, the average thermal efficiency is about 71% under steady-state condition. Compared to some published works, the proposed bubbling HDH desalination system has relatively higher freshwater productivity owing to its effective heat and moisture transfer enhancement by direct solar heating and bubbling. The economic analysis showed that the price of the produced water for the system is about 0.027$/L. [ABSTRACT FROM AUTHOR]

This paper presents both an experimental study and a theoretical discussion on the relevant faults resulting from progressive creeping discharge. Pressboard ageing, voltage amplitude, and pressboard type are configured to generate the faults under divergent creeping stresses. The fault progression is recorded by high-resolution camera, partial discharge (PD) device, and optic-fiber thermometer. The damaged pressboards are scrutinized by microscopy and image-processing techniques, and gas chromatography is used to analyze the gas compositions. The progression of internal treeing shows distinct stages of different interface phenomena, such as spark discharge, white marks, and bubbling effect, as well as varying discharge patterns. In contrast, the progression of surface tracking is a simple but hardly noticeable process due to the PD disappearance. The internal carbonization channels are believed the fundamental causes of the interface phenomena pertinent to internal treeing. A theoretical model is proposed to expound the development of the internal carbonization channels, which considers the charge emission, the pressboard pyrolysis, and the percolation theory. The failure mode of internal treeing is schematically illustrated using a four-phase model, and the effects of thermal ageing and field distribution on surface tracking are discussed. Lastly, a detailed comparison is made between internal treeing and surface tracking in terms of the occurrence condition, initiation mechanism, growth driver, and growth characteristics. [ABSTRACT FROM AUTHOR]

The results of experimental investigations of the dehydration of aviation kerosene TS-1 in a model tank of volume 1.8 m3 are presented. The experiments were carried out under conditions simulating the regimes of a passengercarrying airplane flight at pressures 20–110 kPa and temperatures from –20 to +20°C. The dehydration of kerosene was made by bubbling air enriched with nitrogen with a 10% volume fraction of oxygen at its specific consumption of 0.0002–0.0007 s–1. A decrease in the concentration of the dissolved water to the values ensuring the absence of phase transitions in the water–kerosene system at temperatures down to –30°C has been established. The concept of using on-board systems of generation of inert gases for dehydrating the kerosene in the fuel tank of an airplane under cruising flight conditions has been confirmed. [ABSTRACT FROM AUTHOR]

Multiphase particle in a cell simulation of fluidized beds for different Geldart group particles (A, B and D) were investigated. The minimum fluidization velocities predicted by the Barracuda Virtual Reactor® were compared and contrasted by theoretical predictions with the Wen‐Yu model. The optimal drag force coefficients based on the Wen‐Yu model for MP‐PIC simulations was further evaluated for different particle sizes and densities for Group A catalysts. A neural network model was constructed for the optimal model constants as a function of the explanatory variables for group A catalysts. This work illustrates the importance of choosing the correct value for the drag force coefficients to obtain realistic simulation results for fluidized beds. This work clearly demonstrates that the Barracuda simulation results are very sensitive to the value of the Wen‐Yu parameter. Using multiphase particle in cell simulations in conjunction with a neural network model can be directly used in further studies as a rapid tool to get the correct values for realistic drag force coefficients based on the Wen‐Yu model. [ABSTRACT FROM AUTHOR]

Magnesium ammonium phosphate cement (MAPC) prepared with ammonium dihydrogen phosphate (NH4H2PO4, ADP) and dead-burned Magnesium oxide (MgO) is a new type of rapid patch repair material for concrete structures. In order to reduce the material costs of MAPC mortar, manufactured limestone sands, being a more widely-available resource with lower cost, was investigated in this study as an alternative to quartz sands for the preparation of MAPC mortar. The limestone fines in manufactured sands were found to be the key factor that influences properties of MAPC mortar by causing bubbling and volume expansion before hardening. As a result, the mechanical strength of MAPC mortar decreased with the increasing content of limestone fines due to increased porosity. According to microstructure analysis, the mechanism of these negative effects can be inferred as the reaction between limestone fines and ADP with the gas generation of CO2 and NH3. This reaction mainly occurred during a short period before setting while most limestone fines remained unreactive in the hardened MAPC mortar. Based on the above detailed experimental findings on the effects of limestone fines in manufactured sand on the properties of MAPC mortar, this paper pointed out that effective defoaming methods for inhibiting bubbling was the key to the utilization of manufactured sands in preparation of high performance MAPC mortar.

We consider a model describing the length of two queues that incorporates customer choice behavior based on delayed queue length information. The symmetric case, where the values of the time-delay parameter in each queue are the same, was recently studied. It was shown that under some conditions, the stable equilibrium solution becomes unstable as the common time delay passes a threshold value. This one-time stability switch occurs only at a symmetry-breaking Hopf bifurcation where a family of stable asynchronous limit-cycle solutions arise. In this paper, we examine the non-symmetric case, wherein the values of the time-delay parameter in each queue are different. We show that, in contrast to the symmetric case, the non-symmetric case allows bubbling, multiple stability switches and coexistence of distinct families of stable limit cycles. An investigation of the dynamical behavior of the non-symmetric system in a neighborhood of a double-Hopf bifurcation using numerical continuation explains the occurrence of the bistable limit cycles. Quasi-periodic oscillations were also observed due to the presence of torus bifurcations near the double-Hopf bifurcation. These identifications of the underlying mechanisms that cause unwanted oscillations in the system give a better understanding of the effects of providing delayed information and consequently help in better management of queues.

The emission of CO2 and CH4 by diffusion, bubbling and downstream was measured in ten reservoirs representative of the diversity of French hydropower reservoirs in 2016. In all reservoirs, higher fluxes were measured in summer than in spring and winter. Low fluxes were measured in alpine reservoirs as compared to run-of-the-river and storage reservoirs. The low temperatures as well as the low organic matter input from the watershed explained this observation. Bubbling was higher in run-of-the-river reservoirs, as compared to storage reservoirs. This was related to a higher ratio between the length of wooded river network in the watershed, and the reservoir surface area. This ratio was considered as a proxy for allochthonous particulate organic matter input per reservoir surface unit and its accumulation in the sediments. In the larger storage reservoirs, this preferential sedimentation area was limited to the river-reservoir transition zone, the extent of which is primarily a function of reservoir hydrodynamic and morphological parameters. Conversely, the long water residence time in deep storage reservoirs favoured greenhouse gas (GHG) accumulation in the bottom water and diffusion and downstream pathways as compared to bubbling. Classical drivers of GHG emissions in large reservoirs partly failed to explain our measurements, especially for bubbling which seemed to be primarily controlled by allochthonous particulate organic matter input per reservoir surface area. This may results from the small size and the large diversity of the studied reservoirs as compared to the larger systems classically used for global estimates. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we use the metal-phase formation model to estimate the drop size formed on individual bubbles of the reducing gas during the oxide melt bubbling. The model includes the following stages: the bubble formation upon gas injection into the melt, metal reduction on the bubble surface, and its drop concentration in the stern. We present equations that estimate the limiting sizes of a gas bubble () and a drop () moving in an oxide melt without defragmentation. The critical sizes of a gas bubble () moving in an oxide melt without defragmentation were calculated using the densities (ρ kg/m3) and surface tension (σ, mJ/m2) of B2O3–CaO and B2O3–CaO–CuO melts that are, respectively, described by the equations: σ1 = 87.0 + 0.242T , ρ1 = 3.26 × 103 – 0.91T, σ2 = 10.8 + 0.178T, ρ2 = 3.19 × 103 – 0.70T in the temperature range of 1373–1673 K. Depending on the temperature, the critical bubble radius varies from 0.047 to 0.053 m in the B2O3–CaO–CuO melt and 0.06–0.081 m in the B2O3–CaO melt. Depending on the CO amount introduced at various temperatures, the change in the copper oxide content in the B2O3–CaO–CuO melt was determined by calculating the thermodynamic equilibrium to describe the features of oxide melt bubbling by various reducing gases. Based on the obtained data, the copper amount produced from the interaction of Cu2O in the melt with a single CO bubble was calculated depending on the copper oxide content and the CO amount in the bubble. The correlation dependences of the drop size on the Cu2O content in the melt ( , %), temperature (T, К), and the CO amount in the bubble (nCO, mol) were obtained by statistical data processing. [ABSTRACT FROM AUTHOR]

The typical granular kinetic model, the cohesive granular kinetic model based on the contact bonding energy (Kim-Arastoopour-Huilin model) and the cohesive granular kinetic model based on the excess compressibility (Ye et al.'s model) were comprehensively compared in terms of kinetic parameters, bed expansion, and bubble behavior. The calculation methods of the contact bonding energy loss and the excess compressibility were presented, and the inter-relationship between the two cohesive parameters was revealed. The three kinetic models predict consistent kinetic parameters in dilute gas-solid flow region, while Ye et al.'s model always predicts a lower value when the solid fraction is above 0.15. The Kim-Arastoopour-Huilin model and Ye et al.'s model predicts opposite variations of solid pressure with increasing cohesion. Increasing cohesion interaction reduces the granular shear viscosity and bulk viscosity. Kim-Arastoopour-Huilin model and Ye et al.'s model outperform the typical kinetic model in terms of the bubble diameter and rising velocity. Unlabelled Image • Two calculation methods of the contact bonding energy were presented. • A model was derived to determine the cohesive item of excess compressibility. • The contact bonding energy was linked with the excess compressibility. • Increasing cohesion reduces the granular shear viscosity and bulk viscosity. • The cohesive kinetic models better predict the bubble diameter. [ABSTRACT FROM AUTHOR]