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Copyright of Journal of Petrochemical Universities / Shiyou Huagong Gaodeng Xuexiao Xuebao is the property of Journal Editorial Department Of Liaoning Shihua University 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.)

Copyright of International Journal of Life Sciences & Biotechnology (2651-4621) is the property of International Society of Academicians 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.)

The nata de coco industry produces liquid waste which, if thrown directly into water bodies (rivers) without prior processing, has the potential to pollute the surrounding environment. Laboratory test results show that the parameters BOD 1145 mg/L, COD 1737 mg/L, and TSS 206 mg/l are far above the thresholds set by the government. The aim of this research is to determine the optimum conditions for fine bubble and micro bubble treatment of nata de coco liquid waste in reducing the characteristic values of nata de coco liquid waste. This research was carried out using experimental methods with test samples of 40 liters and 60 liters. Data collected through direct observation includes DO, TDS, pH, temperature whit measured every 2 hours, while data collected through laboratory testing of BOD, COD and TSS which are tested every 12 hours and 24 hours. The data was then processed using the Taguchi method with the aim of optimizing the fine bubble treatment for changes in the characteristics of nata de coco liquid waste. The research results showed that the optimum conditions were found in the fine bubble treatment with an aeration period of 24 hours and a volume of 40 liters. The best percentage reduction in BOD was found to be 94% or 68 mg/L. COD reduction obtained the best percentage reduction of 93% and/or became 121 mg/L and TSS obtained the best percentage reduction of 69% or became 77 mg/L. These results are in accordance with the Regulation of the Minister of Environment of the Republic of Indonesia Number 5 of 2014 concerning Wastewater Quality Standards. [ABSTRACT FROM AUTHOR]

We confirmed that bubble-surrounded cells (BSCs) contained in flow were retained on the walls of an artificial blood vessel by forming an acoustic field with multiple focal points using tempo-spatial division emission. In order to realize the cell delivery system, we investigated the relationship between the concentration of T-cells and brightness in the microscopic images. Next, we defined the applied acoustic intensity, derived from the sound pressure distribution of every type of acoustic field. We studied the retention performance of BSCs versus various flow velocities, number and spatial intervals of the focal points, and maximum sound pressure. From the results, the optimal acoustic field to retain the cells depends on both acoustic intensity and flow velocity, where multiple focal points with an acoustic intensity of 50–120 mW cm−2 were more effective than the single focal point with 180 mW cm−2 in the range of a flow velocity of 10–20 mm s−1. [ABSTRACT FROM AUTHOR]

In this paper, the bubbly flow characteristics of a Venturi channel was revealed by using the population balance model (PBM) within the framework of computational fluid dynamics (CFD) numerical simulation and focused on the bubble size distribution and pressure drop △P of different regions. The simulation results indicated that bubble breakup mainly occurred in the diverging section of the Venturi channel, and the average diameter of the daughter bubbles davg in the sidewall region was much smaller than that in the central region. Through the correlational analysis between the bubble size distribution and turbulent flow field, the bubble breakup in the diverging section was positively related to the turbulent flow. Considering the influence of geometric parameters on davg and △P, the davg decreased and △P increased with the increasing of the diverging angle β. As the throat diameter D increased, the davg increased and △P decreased gradually. In order to quantify the bubble breakup characteristics, the concept of bubble breakup ratio τ is introduced and defined as the ratio of inlet average bubble diameter di to the outlet average bubble diameter do. Through dimensionless transformation, the fitting relationship between τ or △P and angle ratio a was Sinusoidal function (SINE), respectively, and was Boltzmann with the throat length‐diameter ratio b. Due to the relationship of first‐order linear function between τ and △P, the bubble breakup ratio can be obtained by measuring the pressure drop of the Venturi tube, which was significant to the practical engineering application. [ABSTRACT FROM AUTHOR]

Biological wastewater treatment plants (WWTPs) produce large amounts of excess sludge. One approach to reduce sludge is treatment with ozone, which promotes sludge disintegration and solubilization. Here we report the first application of ultra-fine- and micro-bubble (UFB/MB) ozonation to sludge reduction in a full-scale WWTP. UFB/MB ozonation using a spiral liquid-type UFB generator was applied to concentrated excess sludge in the storage tank instead of to return sludge. At an ozone dose of 15 mgO3 gSS–1, a 92% reduction in sludge accumulation rate was achieved during a 237-day ozonation period with ozonation relative to a 100-day no ozonation period without ozonation. This reduction was larger than expected, and was partly due to a 20–30% greater average concentration of suspended solids in the influent during the no ozonation period. Addition of UFB/MB ozonation to the existing activated sludge process did not reduce the water quality in the effluent. We can conclude that UFB/MB ozonation for concentrated excess sludge in the storage tank using a spiral liquid-type UFB generator remarkably reduced the ozone dose required to sludge reduction by more than half of the reported conventional ozonation (30–150 mgO3 gSS–1) without the negative impact on effluent water quality. [ABSTRACT FROM AUTHOR]

The tiny bubbles with diameters less than 1 m are called ultrafine bubbles (UFB). And the application of UFB in agriculture, fishery and environment is highly anticipated. In this study, the changes in the properties of oxygen, 5% hydrogen (95% nitrogen), and nitrogen UFBs were investigated with droplet formation. The UFB water was ejected through the orifice nozzle (diameter: 280pm) and formed tiny droplets. Particularly in the case of oxygen UFB, a change in the distribution of the bubble size was observed. We observed higher microbubble concentration and smaller bubble size below 50pm in the sprayed UFB water compared with in the control distilled water. The distribution of oxygen UFB itself changed before and after spraying, and its diameter tended to be larger. In addition, its water contained more MB, which resulted in a higher cleaning effect. [ABSTRACT FROM AUTHOR]

The use of fine bubbles is a promising approach to remove surfactant efficiently during the rinsing process of clothing, to fulfill a requirement. Therefore, the influence of fine bubbles on the removal performance of surfactant from cloth during the rinse process of pulsator washing machine (top loading type) was investigated. The test apparatus was assembled by connecting a microbubble generation tank and a small washing machine with tubes and circulating fine bubble water to a small washing machine. Swatches of cloth with a specified amount of linear alkylbenzene sulfonate (LAS) adsorbed from aqueous solution, were rinsed with tap water, and the LAS concentration in the rinse water was examined with an HPLC system equipped with a high‐precision fluorescence detector. The average bubble diameter of the fine bubble water used was 0.13–1.4 μm. In the rinsing experiment, no difference was found in the final LAS removal efficiency between water with and without bubbles; but the former increased the LAS removal rate during the initial stage of rinsing. This tendency was particularly noticeable when the stirring power of the washing machine was weak. Therefore, it was concluded that the fine bubble effect on the removal of the surfactant is mainly a kinetic effect rather than an equilibrium effect. [ABSTRACT FROM AUTHOR]

Micro bubbles measuring tens of micrometers or less in diameter have recently been paid much attention. Swirl-type, pressurizing dissolution, and perforated plate methods have been proposed for micro bubble generation. The swirl-type method can generate micro bubbles even under low-pressure power in a simple structure. The enlarged inlet diameter of the swirl chamber can reduce the average bubble diameter. This study examined the effect of the swirl chamber inlet diameter on the flow around chamber outlet in a swirl-type micro bubble generator by numerical analysis. The Inlet diameter of the swirl chamber was changed to 30 mm, 60 mm, and 90 mm, the flow velocity distribution and the wall shear stress around the chamber outlet were calculated. As a result, when the inlet diameter of the swirl chamber was enlarged, it was clarified that the circumferential flow velocity and the wall shear stress around the chamber outlet increased, which reduced the average bubble diameter. [ABSTRACT FROM AUTHOR]

Micro bubbles measuring tens of micrometers or less in diameter have recently been paid much attention. Swirl type, pressurizing dissolution, and perforated plate methods have been proposed for micro bubble generation. The swirl type method can generate micro bubbles even under low-pressure power in a simple structure. This study examined the effect of the swirl chamber inlet diameter on the bubble diameter in a swirl type micro bubble generator. The swirl chamber inlet diameter was varied in the range of 15-90 mm and the effect was examined. In order to clarify the effect of enlarged inlet diameter, the micro bubbles diameter was measured under changing water supply pressure and air flow rate, the behavior of air column in the swirl chamber was visualized, and the velocity distribution around outlet of swirl chamber was measured. As a result, when the swirl chamber inlet diameter was enlarged, the outflow form changed from an axial outflow to a radial outflow. The average bubble diameter could also be reduced. An average bubble diameter of 28 -m could be realized under the conditions of swirl inlet diameter of 90 mm and water supply pressure of 0.1 MPa gage. [ABSTRACT FROM AUTHOR]

The method of micro bubbles is widely applied in the fields of water and soil treatment. A novel treatment method of NO in flue gas through a gas–liquid two-phase system formed by micro bubbles is proposed in this study. The system depends on the generation of hydroxyl radicals. The NO removal performance of the micro gas–liquid dispersion system induced by catalysts and O3 was explored and the reaction pathways were elucidated. Micro bubbles, Fe2+, and Mn2+ in solution improved NO removal performance significantly. Salinity and surfactants affected the removal performance of NO by altering micro bubbles. In the presence of Fe2+, the NO removal rate reached 65.2% at pH 5, 75.8% under 0.5 g/L NaCl and 82.1% under 6 mg/L sodium dodecyl sulfate. In the presence of Mn2+, the NO removal rate reached 69.2% at pH 5, 83.2% under 0.5 g/L NaCl and 92.3% under 6 mg/L sodium dodecyl sulfate. However, in the presence of both Mn2+ and Fe2+, NO conversion rate was 93.2%. The NO removal rate in the presence of O3 was further improved under the same conditions. The study provides the basis for the application and development of micro bubbles in flue gas treatments for NO removal. The results can help to solve the problems of high operating cost, large oxidant consumption, secondary pollution, and high energy consumption in traditional NO removal methods. [ABSTRACT FROM AUTHOR]

Enhanced oil recovery (EOR)and improved oil recovery (IOR) technologies have been applied to various oil and gas fields for many years. However, the environment for EOR/IOR has been severe in low oil price and increase of development cost and more effective and economical EOR technology is expected. We focused the application of micro bubble as cutting-edge EOR technology. Micro bubble technology has been applied to various industries as medical, agriculture and environment fields. And micro bubble has some characteristics in relative to the effect of EOR such as improvement of sweep efficiency and oil density and viscosity. We have studied about the efficiency of micro bubble technology and its mechanism from laboratory test and flow simulation. We evaluated the improvement of the sweep efficiency, solubility to oil and oil recovery by micro bubble injection from core flooding test which was one of the laboratory tests and it was indicated that the capillary pressure affected the injection area from flow simulation. We expect micro bubble technology will become useful as new EOR technology from our study. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is the process of removing a material by means of electrical discharge inside an insulating working fluid. The material is melted by the discharge and is blown off by the vaporizing explosion of the working fluid. Expansion and contraction of the insulated fluid bubbles affect the process of removing a material. The stronger the vaporizing explosion, the larger is the quantity of material removed and the worse is the surface roughness, and vice versa. The power of the vaporizing explosion is determined by the input energy and quantity of material removed is determined by the power of the vaporizing explosion. Recently, there have been some studies on micro bubbles that are 50 μm or less in diameter. Micro-bubbles possess special characteristics, such as an increased interior gas pressure and increased ion concentration around the gas–water interface. We considered changes in the characteristics of EDM by using a fluid mixed with micro bubbles. The vaporizing explosion was considered to be weakened by using fluid containing micro-bubbles, and the surface roughness seemed to improve Therefore, we performed EDM using pure water and micro-bubble mixed fluid, and researched the characteristics of EDM. Initially, We were expecting a change in the machining removal rate. Indeed, in oil dielectric fluid, there was no change, and there was little difference with the machining rate achieved using pure water dielectric fluid. However, a clear difference was observed in terms of the skewness (Rsk) of surface roughness. In this paper, this difference is described as a change in surface roughness in micro-bubble mixed EDM. [ABSTRACT FROM AUTHOR]

Hypothesis The effects of varying carbon chain lengths (CCLs) and concentrations of aqueous solutions of imidazolium based ionic liquids on bubble particle attachment (BPA) will provide a better understanding in catering for the varying degrees of surface activities in the application of the flotation technology. The general trends of this study should also be applicable to homologous series of other cationic surfactants and ionic liquids. Experiments Zeta potentials of small air bubbles and bunker oil drops dispersed in aqueous solutions of n -methylimidazolium chloride ionic liquids (n = 0, 2, 3, 6, 8, 10, 12) of concentrations ranging from 1000 PPM to 8000 PPM, as were interfacial tensions of these solutions with bunker oil (180 cst) and contact angles made by air bubbles at interfaces between these solutions and thin layers of bunker oil on flat solid surfaces were investigated. Finally, interparticle forces analysis using the Derjaguin-Landau, Verwey-Overbeek (DLVO) theory is also included. Findings Analysis using the DLVO theory showed attractive forces between the oil particles and micro-bubbles are significantly more prevalent in short CCLs solutions of imidazolium-based ILs in low concentrations, namely [C 0 mim][Cl] and [C 2 mim][Cl] at a maximum zeta potential difference of 75.3 mV. The results from CA measurements follows similarly whereby low concentrations of ILs with short CCLs were in favor for the bubble-particle attachment process with angles ranging between 93.95° for [C 0 mim][Cl] and 97.28° for [C 2 mim][Cl]. IFT which is important in reducing coalescence for the preferential BPA process to occur in flotation decreases with an increase of CCL and concentration of IL. [ABSTRACT FROM AUTHOR]

Gas embolisms can hinder blood flow and lead to occlusion of the vessels and ischemia. Bubbles in microvessels circulate as tubular bubbles (Taylor bubbles) and can be trapped, blocking the normal flow of blood. To understand how Taylor bubbles flow in microcirculation, in particular, how bubbles disturb the blood flow at the scale of blood cells, experiments were performed in microchannels at a low Capillary number. Bubbles moving with a stream of in vitro blood were filmed with the help of a high-speed camera. Cell-free layers (CFLs) were observed downstream of the bubble, near the microchannel walls and along the centerline, and their thicknesses were quantified. Upstream to the bubble, the cell concentration is higher and CFLs are less clear. While just upstream of the bubble the maximum RBC concentration happens at positions closest to the wall, downstream the maximum is in an intermediate region between the centerline and the wall. Bubbles within microchannels promote complex spatio-temporal variations of the CFL thickness along the microchannel with significant relevance for local rheology and transport processes. The phenomenon is explained by the flow pattern characteristic of low Capillary number flows. Spatio-temporal variations of blood rheology may have an important role in bubble trapping and dislodging. [ABSTRACT FROM AUTHOR]

Frictional pressure drop of turbulent upward flow with micro bubbles in a vertical pipe was investigated. To investigate relation between pipe diameter and the frictional pressure drop, three different pipes whose diameters are 5.9, 13 and 16 mm were used. Range of the Reynolds number is from 11000 to 48000. Two kinds of micro bubble generation methods which are pressurized dissolution and shearing methods were used to investigate the frictional pressure drop for a wide range of void fraction α. The conclusions obtained are as follows: (1) the frictional pressure drop of the turbulent upward flows in the vertical pipes increases or decreases by the presence of the micro bubbles, (2) the micro bubble generation method does not affect the drag reduction ratio DR, (3) DR takes a high value at low JL and Re and mainly decreases with increasing JL and Re, (4) DR depends on the pipe diameter, D, at the fixed JL and α, (5) DR depends on D at the fixed Re and α, and increases with D at the fixed Re and α for low α (≤ 0.13%), (6) DR tends to take a positive value for low α (≤ 0.15%), and increases with decreasing α in this condition, (7) the drag increase or reduction of the turbulent upward flow with the micro bubbles in the vertical pipe does not agree with a transition diagram of frictional drag reduction proposed by Murai (2014), (8) the drag is reduced for 0 < α < 0.15% and 11000 < Re < 45000, and mainly is increased for the rest region.

This study intended to evaluate the pond purification capacity using micro bubble clarifier. Also, in order to confirm the optimal pressure condition, analysis was performed for each pressure level at 1–4 kgf/cm2. It would be the most proper to operate at 3 kgf/cm2and carry out speculation experiments. Pilot plant experiments were conducted in a water tank of approximately 8 m3. Raw water was obtained at the ponds of S University and a Golf course in full scale with volumes of 1,800 and 1,500 m3, respectively. Pilot plant results showed that the maximum saturated DO concentration rose up to 40 mg/L at the Pilot plant; and removal efficiencies of CODCr, BOD5, T-N, T-P, SS and Chl-a were 46.6, 31.2, 34.3, 69.2, 82.8 and 69.1%, respectively. Then, a full-scale experiment was also carried out for the comparison with control site. According to the analysis of results, considerable treatment efficiencies were obtained for CODCr, BOD5, T-N, T-P, SS and Chl-a with a high DO concentration because of the micro bubble. Water purification with a micro bubble clarifier is an environment-friendly purification method that can increase the natural purification capacity of natural water systems without the use of treatment facilities and chemicals for removing pollutants. [ABSTRACT FROM PUBLISHER]

Reduction in ship resistance, in order to decrease fuel consumption and also achieve higher speeds, has been the topic of major research over the last three decades. One of the most attractive ideas in this field is micro bubble drag reduction, which attempts to obtain optimum injection flow rate based on ship specifications. The model test results of a 70 cm catamaran model was used to quantify the effect of air injection rate on drag reduction, and to estimate a simple formulation for calculating an efficient injection rate by considering the main parameters of the ship, such as: length, width and speed. The test results show that excessive air injection decreases the drag reduction effect, while suitable injection reduces total drag by about 5%–8%. [ABSTRACT FROM AUTHOR]

This work investigates the existence and importance of the micro bubbles in heavy oil subjected to solution-gas drive. The term 'micro bubble' will be used to refer to the free-gas phase that flows with the oil, no faster and no slower. Two types of experiments are reported here; slow and fast experiments. These experiments were previously reported by Sheikha and Pooladi-Darvish (SPE Res Eval Eng 12(3):390-398, ) and were used to investigate the effects of pressure gradient and depletion rate of oil recovery. In this work, we investigate the nature of two-phase flow, and find that in the slow runs, the flow was characterized by single-phase flow of oil until a gas saturation of 2±1% was reached. Above this gas saturation, bulk flow of gas was observed at mobilities much higher than that of micro bubbles. Recovery factor of the slow tests was below 4%. In the fast runs, flow of bubbles is observed shortly after they are formed in porous media. The gas mobility and fractional flow remain low until a gas saturation of 7±1% is reached. Flow of gas between approximately 2 and 7% gas saturation is consistent with that of micro bubbles. Gas fractional flow increases sharply at gas saturations above approximately 7%. The results indicate that the attainment of high recovery values (12-14%) observed in the fast experiments is partially as a result of low mobility of micro-gas bubbles. The pressure decline rate of each flow experiment was varied independent of its respective withdrawal rate. This did not alter the difference in recovery and mobility behaviour of the fast and slow experiments; the fast experiments exhibited a significant period of low mobility gas flow consistent with flow of micro bubbles. Regardless of the pressure decline rate, the slow experiments did not exhibit this period of low mobility gas flow. [ABSTRACT FROM AUTHOR]

Small superficial normal canine lymph nodes often appear as vascular at classic Doppler technique evaluation. The aim of present research is to describe the characteristics of lymph nodes vasculature after administration of the contrast agent. Contrast enhanced ultrasonography (CEUS) was performed on a total of 6 subjects, after intravenous administration of SonoVue (Bracco - Italy), containing stabilized micro bubble of sulphur hexafluoride. The sentinel lymph nodes of the mammary gland, the axillary and superficial inguinal lymph nodes were examined. In advance, for comparison, the same lymph nodes were evaluated using color Doppler and power Doppler. Imaging characteristics followed after contrast agent administrations were: the beginning of contrast agent in lymph node penetration (time to wash in), maximum intensity time of visualization of contrast agent and time when wash out is complete. Besides these periods were followed, echogenicity, ecotexture of lymph nodes, during phases mentioned above. Also the way of lymph nodes parenchyma filling was followed, during the same periods. In normal lymph nodes, contrast wash in phase was viewed at 7 sec from the time of injection, with a maximum intensity of micro bubble visualization, at 13 sec. Normal lymph nodes have a central artery with an hilar centrifugal branching oriented towards the capsule. Lymph node angioarhitecture was best visualized after intravenous contrast agent administration, compared with Doppler techniques. The results of this preliminary study shows that CEUS is a noninvasive method witch can be successfully applied to describe the lymph node vasculature in carnivores, making an improved visualization compared with conventional technique [ABSTRACT FROM AUTHOR]

Abstract: In order to develop an early-warning biosensor system for predicting the impact on health of long-term and low-level exposure to indoor chemical compounds, e.g. volatile organic compounds (VOCs), we evaluated the potential for assessing indoor air quality using the biosensor system based on the swimming behavior of Japanese medaka (oryzias latipes) as an indicator of indoor air quality in the beginning. As a technology to dissolve chemical compounds into water efficiently, a micro bubble generator was introduced. The test chemical was formaldehyde which is a representative of chemical compounds existing indoors. The result of the measuring solubility of formaldehyde was that formaldehyde concentration in water was raised to 0.12 mg/L when 1.0 mg/m3 of formaldehyde in air was bubbled for approximately 44 h. The correlation between the 0.1 mg/L of formaldehyde in water, which is roughly equivalent to 0.83 mg/m3 of formaldehyde in air, and the swimming activities of medaka was investigated. The fish showed abnormal behavior compared to one under a control treatment, e.g. the body movement distance decreased and the duration time near the upper water column increased significantly. It was verified that it is possible to detect concentrations of formaldehyde of 0.83 mg/m3 in indoor air using this proposed biosensor system. [ABSTRACT FROM AUTHOR]

microfluidic channel system to generate Janus droplets is designed and fabricated, where the term Janus droplet refers to a chemically biphasic droplet. It is demonstrated that Janus droplets are formed from elongational breakup of coflowing core fluids which are constrained by a sheath fluid on both sides of them. Rhodamine B is adopted as an indicator to indentify generated Janus droplets. Monodisperse Janus droplets have been generated in a controllable manner such that those with average diameters of 26 ± 1.24 μm, 31 ± 1.44 μm and 34 ± 2.28 μm are formed in accordance with flow rate ratios between the sheath fluid and the core fluids, 30.7, 36.4 and 44.4, respectively. Generation of Janus droplets, demonstrated in the present study, has seen a new application in the areas of biotechnology and bioengineering, where enhanced mixing inside the micro bubbles can be utilized without the aid of other means of droplet generation and merging. [ABSTRACT FROM AUTHOR]

doi:10.1111/j.1741-2358.2009.00325.x A study of the efficacy of ultrasonic waves in removing biofilms Objective: The removal of adherent biofilms was assessed using ultrasonic waves in a non-contact mode. Materials and Methods: In in vitro experiments, Streptococcus mutans ( S. mutans) biofilms were exposed to ultrasonic waves at various frequencies (280 kHz, 1 MHz, or 2 MHz), duty ratios (0–90%), and exposure times (1–3 minutes), and the optimal conditions for biofilm removal were identified. Furthermore, the effect of adding a contrast medium, such as micro bubbles (Sonazoid®), was examined. The spatial distribution and architecture of S. mutans biofilms before and after ultrasonic wave exposure were examined via scanning electron microscopy. The biofilm removal effect was also examined in in vivo experiments, using a custom-made oral cleaning device. Results: When a 280 kHz probe was used, the biofilm-removing effect increased significantly compared to 1 and 2 MHz probes; more than 80% of the adherent biofilm was removed with a duty cycle of 50–90% and a 3 minutes exposure time. The maximum biofilm-removing effect was observed with a duty cycle of 80%. Furthermore, the addition of micro bubbles enhanced this biofilm-removing effect. In in vivo experiments, moderate biofilm removal was observed when a 280 kHz probe was used for 5 minutes. Conclusions: This study demonstrated that ultrasonic wave exposure in a non-contact mode effectively removed adherent biofilms composed of S. mutans in vitro. [ABSTRACT FROM AUTHOR]

This work investigates the growth and detachment of chemically formed micro-bubbles on micro-textured catalyst using a high-speed digital camera and simulation results. Three bubble growth stages were identified for single bubbles grown on circular type Pt catalyst. The first stage was inertia-controlled and the bubble diameter was directly proportional to time, and pertained when the bubble size was smaller than the Pt catalyst; in the second and third stages, gas was generated at a constant rate and the bubble diameter was varied as the cube root of time. However, in the third stage, the bubble growth rate is slightly lower than in the second stage, suggesting saturation. The calculation based on a mathematical model at constant gas generation rate is highly consistent with experimental results. The basic single bubble growth phenomenon was then adopted as a comparison to the bubble growth phenomena on textured catalyst structures. Experimental results revealed that a discontinuous mesh catalyst can effectively shorten the bubble detachment time when the substructures are thoroughly separated and the bubbles are larger than their initial size (~5 μm), while the concentric circular pattern does not. This study provides an insight into the growth and detachment phenomena of chemically formed micro-bubbles on catalyst of different textures, which is useful to the design of reactors for fuel cell systems. [ABSTRACT FROM AUTHOR]

We investigated the nonlinear behavior of a microbubble under ultrasound, taking into account the heat transfer inside the bubble and through the bubble wall. The polytropic relation, which has been used for the process of pressure change depending on the volume variation of ideal gases, cannot properly treat heat transfer involving the oscillating bubble under ultrasound. In this study, a set of solutions of the Navier-Stokes equations for the gas inside the bubble along with an analytical treatment of the Navier-Stokes equations for the liquid adjacent to the bubble wall was used to treat properly the heat transfer process for the oscillating bubble under ultrasound. Entropy generation due to finite heat transfer, which induces the lost work during bubble evolution, reduces the collapsing process and considerably affects the nonlinear behavior of the bubble. [ABSTRACT FROM AUTHOR]

Abstract: In this study, dissolved ozone flotation and conventional mechanical diffuser ozonation systems have been applied to treat the downstream municipal wastewater. The process efficiency has been evaluated in the lab bench scale on the basis of the removal rate of some wastewater quality parameters, like turbidity, SS, color, UV254, COD, BOD, T-N, T-P and bacteria. DOF is found to be an efficient ozonation technique in comparison to the mechanical diffuser system under identical conditions, though the removal efficiencies of coliform bacteria are found to be the same in both cases. The optimum ozone dose of 6.1 mg/L is found in the DOF system. As for the result of this investigation, a DOF pilot plant with the capacity of 200 m3/d was designed and set up to treat the effluence of secondary wastewater, and detailed assessment of performance was carried out during one month operation. The results indicate a good removal rate of 86.9% turbidity, 81% TSS, 72.6% color, 82.4% BOD and 92% total phosphorus. However, lower removal efficiencies of 42.9% and 33.4% were obtained for COD and T-N respectively. Almost 100% disinfection efficiency was achieved by removing heterotrophic and coliform bacteria. DOF technology is very effective and economically viable for municipal wastewater treatment in the present day context. [Copyright &y& Elsevier]

• A modified formula of homogenization-based model is presented. • A reduced model accounting for bubble cluster dynamics is proposed. • The liquid pressure inside the cluster is simplified to only depend on radial coordinate and time. • The reduced model can reproduce the bubble dynamics in the cluater in weak bubble-bubble interaction case. • In strong inter-bubble interaction case, the growth phase of bubbles can be reproduced by the reduced model when the cloud interaction parameter is small. The dynamics of bubble clouds induced by ultrasound field are investigated in a regime where the cloud size is much smaller than the ultrasound wavelength. Two frequently used models describing the dynamics of individual bubbles inside a bubble cluster in an acoustic field are studied, one based on the homogeneity assumption, and the other based on the simultaneous motion assumption. A modified formula of the homogenization-based model is presented, and an inherent distinction in bubble-bubble interaction term is found in comparison to the simultaneous motion model. To gain insight into the mechanisms of such distinction, a reduced model unifying these two models is presented, and such distinction is explained by the spatial dependence of the bubble-bubble interaction in a bubble cluster accordingly. To validate the reduced model, the normalized distance γ bb and the cloud interaction parameter B 0 are used as two scaling parameters, and the comparison between the present model and the coupled Rayleigh-Plesset type equations is made. A conclusion is that, in the weak bubble-bubble interaction case ( γ bb > 10), the reduced model can well reproduce the radial motion of bubbles in the cluster during the growth stage and the collapse stage in each acoustic cycle; in the strong bubble-bubble interaction case ( γ bb < 10), the growth phase of bubbles in the cluster can be accurately predicted by the reduced model only if B 0 or the amplitude of driving field is small. [ABSTRACT FROM AUTHOR]