Bubble Type Research Articles

3D flow visualization and tomographic particle image velocimetry for vortex breakdown over a non-slender delta wing

Volumetric measurement for the leading-edge vortex (LEV) breakdown of a delta wing has been conducted by three-dimensional (3D) flow visualization and tomographic particle image velocimetry (TPIV). The 3D flow visualization is employed to show the vortex structures, which was recorded by four cameras with high resolution. 3D dye streaklines of the visualization are reconstructed using a similar way of particle reconstruction in TPIV. Tomographic PIV is carried out at the same time using same cameras with the dye visualization. Q criterion is employed to identify the LEV. Results of tomographic PIV agree well with the reconstructed 3D dye streaklines, which proves the validity of the measurements. The time-averaged flow field based on TPIV is shown and described by sections of velocity and streamwise vorticity. Combining the two measurement methods sheds light on the complex structures of both bubble type and spiral type of breakdown. The breakdown position is recognized by investigating both the streaklines and TPIV velocity fields. Proper orthogonal decomposition is applied to extract a pair of conjugated helical instability modes from TPIV data. Therefore, the dominant frequency of the instability modes is obtained from the corresponding POD coefficients of the modes based on wavelet transform analysis.

A study on magnesium corrosion by real-time imaging and electrochemical methods: relationship between local processes and hydrogen evolution

This work investigates the hydrogen evolution process on magnesium by real time imaging of the corroding surface at the free corrosion potential and during potentiodynamic polarization in alkaline and neutral environments, in the presence and absence of chloride ions. High-magnification imaging of the corrosion process from side view discloses that three different types of hydrogen bubbles are generated during corrosion: i) large and stable bubbles on the uncorroded regions, ii) a stream of fine bubbles at the corrosion front and iii) medium size bubbles behind the corrosion front. It is proposed that the generation of streams of bubbles at the corrosion front is due to the disruption of the oxide/hydroxide film that is possible when an anodic current is available and environmental conditions can induce depassivation. This results in direct exposure of the underlying magnesium to the electrolyte and, due to the large overpotential available, in hydrogen evolution. Thus, the corrosion front act as a current amplifier where the rate of magnesium oxidation is proportional to the sum of the current produced remotely, that maintains the depassivation, and the current produced at the corrosion front by hydrogen evolution.

The effects of ultrasound on micromixing

The Villermaux–Dushman reaction is a widely used technique to study micromixing efficiencies with and without sonication. This paper shows that ultrasound can interfere with this reaction by sonolysis of potassium iodide, which is excessively available in the Villermaux–Dushman solution, into triiodide ions. Some corrective actions, to minimize this interference, are proposed. Furthermore, the effect of ultrasonic frequency, power dissipation, probe tip surface area and stirring speed on micromixing were investigated. The power and frequency seem to have a significant impact on micromixing in contrast to the stirring speed and probe tip surface area. Best micromixing was observed with a 24kHz probe and high power intensities. Experiments with different frequencies but a constant power intensity, emitter surface, stirring speed, cavitation bubble type and reactor design showed best micromixing for the highest frequency of 1135kHz. Finally, these results were used to test the power law model of Rahimi et al. This model was not able to predict micromixing accurately and the addition of the frequency, as an additional parameter, was needed to improve the simulations.

Influence of dissolved gases on sonochemistry and sonoluminescence in a flow reactor

In the present work, the influence of gas addition is investigated on both sonoluminescence (SL) and radical formation at 47 and 248kHz. The frequencies chosen in this study generate two distinct bubble types, allowing to generalize the conclusions for other ultrasonic reactors. In this case, 47kHz provides transient bubbles, while stable ones dominate at 248kHz. For both bubble types, the hydroxyl radical and SL yield under gas addition followed the sequence: Ar>Air>N2>>CO2. A comprehensive interpretation is given for these results, based on a combination of thermal gas properties, chemical reactions occurring within the cavitation bubble, and the amount of bubbles. Furthermore, in the cases where argon, air and nitrogen were bubbled, a reasonable correlation existed between the OH-radical yield and the SL signal, being most pronounced under stable cavitation at 248kHz. Presuming that SL and OH originate from different bubble populations, the results indicate that both populations respond similarly to a change in acoustic power and dissolved gas. Consequently, in the presence of non-volatile pollutants that do not quench SL, sonoluminescence can be used as an online tool to qualitatively monitor radical formation.

The effect of microbubbles on gas-liquid mass transfer coefficient and degradation rate of COD in wastewater treatment.

A commonly used aeration device at present has the disadvantages of low mass transfer rate because the generated bubbles are several millimeters in diameter which are much bigger than microbubbles. Therefore, the effect of a microbubble on gas-liquid mass transfer and wastewater treatment process was investigated. To evaluate the effect of each bubble type, the volumetric mass transfer coefficients for microbubbles and conventional bubbles were determined. The volumetric mass transfer coefficient was 0.02905 s(-1) and 0.02191 s(-1) at a gas flow rate of 0.67 L min(-1) in tap water for microbubbles and conventional bubbles, respectively. The degradation rate of simulated municipal wastewater was also investigated, using aerobic activated sludge and ozone. Compared with the conventional bubble generator, the chemical oxygen demand (COD) removal rate was 2.04, 5.9, 3.26 times higher than those of the conventional bubble contactor at the same initial COD concentration of COD 200 mg L(-1), 400 mg L(-1), and 600 mg L(-1), while aerobic activated sludge was used. For the ozonation process, the rate of COD removal using microbubble generator was 2.38, 2.51, 2.89 times of those of the conventional bubble generator. Based on the results, the effect of initial COD concentration on the specific COD degradation rate were discussed in different systems. Thus, the results revealed that microbubbles could enhance mass transfer in wastewater treatment and be an effective method to improve the degradation of wastewater.

Plastic Injection Quality Controlling Using the Lean Six Sigma and FMEA Method

PT. Yogya Presisi Teknikatama Industri (PT. YPTI) is a mold, precision part, and plastic injection maker company. One of the obstacles faced by the company is the high level of nonconformity on its production results. The waste on production process can be identified and classified into four types, i.e.: a). during the process of injection molding machines, b). finishing and cutting processes, c). quality control process and d). the packaging process. The objectives of this research are minimizing the defective goods and reducing the waste using Lean Six Sigma and FMEA approaches, especially for Bush product. From the analysis result, defective types on Bush product can be classified into bubble, speckle, short shoot, sunken, sink mark, over-cut, flashing, and discolor. Based on the attributes data on Bush product, the DPMO score is 988.42 or the sigma level is 4.6, While the DPMO score on the variable data on each dimension i.e.: a). Slit width on the bottom side has DPMO score of 30119 (sigma level 3.37), b). Diameter of the circle on the top side has DPMO score of 392294 (sigma level 1.77), c). Product thickness on the top side has DPMO score of 70474 (sigma level 2.97), d). Product height has DPMO score of 82107 (sigma level 2.89), product thickness on the bottom side has DPMO score of 24448 (sigma level 3.47), and f). Diameter of the circle on the bottom side has DPMO score of 24448 (sigma level 3.47). The highest RPN score on the dominant types of product defects which needs improvement are the defective goods of bubble type has RPN score of 729, flashing and the molten material out on the heating channel has RPN score of 384, over cutting has RPN score of 324 and sink mark has RPN score of 270. The recommendations for improvement that can be given from this research are making checklist for maintenance and production monitoring, enhancing work supervision and inspection, as well as improving the environment and work stations.

PERSPECTIVE USE OF POLY-FUEL GAS GENERATOR IN PRACTICE OF BLAST-FURNACE SHOPS

The analysis of the use of pulverized coal injection (PCI) in the practice of blast furnaces of the Russian Federation was made. It is shown that the current level of injecting of PCI is much lower than in the world’s best practices. The factors hindering the development of this direction in Russia are presented. The authors have analyzed the activities suggested in order to reduce carbon dioxide emissions from the production of iron (ULCOS program). It is proposed to enter the poly-fuel gas generators of bubble type into the blast-furnace shops for the production of hot reducing gases (HRG) for subsequent injection into blast furnaces. The calculation was made for the performance of blast furnace with volume of 1033 m3 and HRG injection of up to 400 Nm3/t of cast iron. When such HRG injection the coke savings are 100–120 kg/t of cast iron. Expected savings of coke while HRG injection of 700 Nm3/t are up to 200 kg/t of cast iron. It is proposed to create a consortium of leading metallurgical enterprises for testing the proposed technology in pilot industrial conditions.

Consideration of Sri Lanka Stupa Type

As Sri Lanka Stupa had been affected by Indian stupa directly, understanding Sri Lanka Stupa is important to know about the flow of Buddhist Art History, which is showing the variation of Initial Buddhist stupa. Due to invasions and disasters, all Sri Lanka's Stupa collapsed and became random mound. After restoration works, Stupa shape changed dramatically from the Initial shape to Existing shape. Since it is hard to find out how Initial stupas were like, Sanchi Stupa needed to be an example for the comparative study as an Initial shape. Sri Lanka Stupa have Square foundation and 3 Basal rings that are supporting the Main Dome. Entrances are on all 4 sides, Railing and Torana(gate) has never found in Sri Lanka stupa. Sri Lanka stupa has been classified with the shape of Dome into 6~8 types according to Vijayanta Potha, the Ancient Buddhist Description, and described by several researchers confusingly. With the inconvenience of using unfamiliar words and irrational gap between the Initial Sri Lanka stupa and Existing Sri Lanka stupa, proposing new classification of Sri Lanka Stupa is necessary. Existing Sri Lanka Stupa can be classified into 4 types : which is (1)Bell type, (2)Pot type, (3)Mound type, (4)Bubble type. This suggestion is for further studies to use Easier and shorter words to describe the types and make it reasonable to use, since the current classification includes 3 stupa types even there is no case for any of them. Restrict Stupa Classifications within existing Sri Lanka Stupa is needed because the current classification had been continued for hundreds of years without any adjustments. Bell type is mainly located in Anuradhapura. Pot type and Mound type is only found in limited area, and Bubble type is located in most area of Sri Lanka.

The Birth of Policy Bubbles: Conceptual Foundations

A theory of policy bubbles suggests that academic attention should be directed at the growth of bubbles rather than at their emergence. This argument is conceptually challenged here on the grounds that different processes of bubble emergence may lead to different types of policy bubbles. Drawing primarily on the sociology of valuation, this paper develops a conceptual framework which distinguishes between preference-driven policy bubbles, which emerge as the output of what policy entrepreneurs want in terms of attaching a distorted or biased meaning to a policy, and institution-driven policy bubbles, which emerge as the output of a process wherein policy entrepreneurs are restricted in attaching a distorted meaning to a policy by transparency constrained on the policy domain (e.g., secrecy laws). It is suggested that transparency constraints on the policy domain may lead to stronger and more sustainable distorted policy valuations, and thereby, to relatively stable and self-sustaining policy bubbles. The lack of such constraints may lead to weaker and less sustainable distorted policy valuations and, thereby, to relatively fragile policy bubbles.

Heat transfer measurement in a three-phase direct-contact condenser under flooding conditions

The transient temperature distribution and volumetric heat transfer coefficient during the inception of flooding in a three-phase bubble type direct contact condenser have been experimentally investigated. The flooding mechanism and the factors affecting the onset of flooding of the three-phase direct contact column are not considered. A short Perspex column of 70 cm total height and 4 cm internal diameter utilising two immiscible fluids was studied. Pentane vapour with initial temperatures of 40 °C, 43.5 °C and 47.5 °C was the dispersed phase and tap water at a constant temperature (19 °C) was the continuous phase. Only 48 cm of the column was used as the active height and different mass flow rates of both phases were used. The experimental results showed that the instantaneous temperature distribution along the direct contact column tends to be uniform when the direct contact column is working under flooding conditions. Furthermore, the volumetric heat transfer coefficient increases as the dispersed mass flow rate is increased towards the flooding limit and remains constant along the column height. In addition, the dispersed phase mass flow rate that leads to flooding increased with increasing mass flow rate of the continuous phase. The initial temperature of the dispersed phase did not have a considerable effect on the flooding inception limit under the present experimental conditions.

Lorentz transmission electron microscopy on nanometric magnetic bubbles and skyrmions in bilayered manganites La1.2Sr1.8(Mn1−yRuy)2O7 with controlled magnetic anisotropy

We have investigated nanometric magnetic textures in thin (<150 nm) plates of Ru-doped bilayered manganites La1.2Sr1.8(Mn1−yRuy)2O7. Ru substitution for Mn site changes the magnetic anisotropy from in-plane to out-of-plane easy axis type without any significant change of global magnetic and crystal structures. The combination of conventional and Lorentz transmission electron microscopy observations confirms the emergence of magnetic bubbles and skyrmions in the absence of magnetic field. With the changing Ru concentration, systematic changes in the type of magnetic bubbles are observed. A tiny residual magnetic field also affects the generation and the type-change of magnetic bubbles.

Posterior corneal anatomy in a newborn baby

PurposeIn view of the recent developments in our understanding of posterior corneal anatomy and the description of a unique layer and zone in adults, we investigated two corneas from a three‐week‐old baby.Methodsboth corneas were subjected to intra stromal air injection using a 30G needle. The type of big bubble formed was identified. The wall of the big bubble and the posterior stromal interface with Descemet membrane was studied using light microscopy, electron microscopy and immune‐histological studies.ResultsIntra stromal injection of air resulted in the formation of characteristic type 1 big bubble in one cornea and another characteristic type II big bubble in another. The wall of the type I big bubble bubble was made of endothelial cells, Descemet's membrane and a thin collagen layer anteriorly (previously described as Dua's layer [DL]).DL was made of 7‐8 collagen lamellae of compactly opposed collagen. This was made of predominantly type I collagen with abundance of collagen VI. Thrombospondin was characteristically seen along the posterior surface of DL extending to the trabecular meshwork. The interface between DL and DM was not distinct but presented a transition zone. The wall type II big bubble was made of Descemet membrane only, which was extremely thin.ConclusionsWe demonstrated here that the human infant cornea behaves similarly to adult cornea when subjected to air injection (dissection). We also demonstrated the presence of DL in a 3 week old baby and presented its histological characteristics.

Big Bubble DALK: The ladder to success, step by step

SummaryDeep anterior lamellar keratoplasty (DALK) has too many techniques to achieve, one of them and most reproducible is the big bubble technique. The steep learning curve known to this operation some times considered a barrier for many surgeons to try and master. However in my presentation I will try to go through the operation step by step giving my own personal tips and tricks for executing the perfect big bubble DALK. Special emphasis will be put on the following important steps: (1) Trephine adjustment and partial thickness trephination of the recipient cornea. (2) Technique of air injection and big bubble formation, which is considered the key step of this technique. (3) Safe opening of big bubble roof. (4) Cruciate incision and cutting of the reaming stroma after lamellar dissection of superficial corneal layers. (5) Descemet's membrane staining and stripping from donor cornea. Moreover, I will put a focus on the new anatomical pre‐ Descemet's layer (Dua's layer), describing and demonstrating by many video clips the different types (type 1, type 2 and mixed type) of big bubbles based on this new anatomical layer. The aim of my presentation is to allow the participants to perform big bubble DALK in a safe and reproducible way with very high percentage of success in obtaining the big bubble.

Evolution of contrast agents for ultrasound imaging and ultrasound-mediated drug delivery.

Ultrasound (US) is one of the most frequently used diagnostic methods. It is a non-invasive, comparably inexpensive imaging method with a broad spectrum of applications, which can be increased even more by using bubbles as contrast agents (CAs). There are various different types of bubbles: filled with different gases, composed of soft- or hard-shell materials, and ranging in size from nano- to micrometers. These intravascular CAs enable functional analyses, e.g., to acquire organ perfusion in real-time. Molecular analyses are achieved by coupling specific ligands to the bubbles’ shell, which bind to marker molecules in the area of interest. Bubbles can also be loaded with or attached to drugs, peptides or genes and can be destroyed by US pulses to locally release the entrapped agent. Recent studies show that US CAs are also valuable tools in hyperthermia-induced ablation therapy of tumors, or can increase cellular uptake of locally released drugs by enhancing membrane permeability. This review summarizes important steps in the development of US CAs and introduces the current clinical applications of contrast-enhanced US. Additionally, an overview of the recent developments in US probe design for functional and molecular diagnosis as well as for drug delivery is given.

Sequential Modeling of Heavy Liquid Fuel Combustion in a Fluidized Bed

AbstractA sequential model involving hydrodynamic and reaction sub‐models is developed to predict the fluidized‐bed reactor performance for the combustion of heavy liquid fuels. The hydrodynamic sub‐model is based on the modified two‐phase theory and the reaction sub‐model is adopted from the literature. Modeling is performed in a dense bed zone and two types of bubbles, namely distributor bubbles and jet bubbles are considered. Results of the model are presented in terms of combustion efficiency and exhaust emission concentrations. The effect of various factors on these two parameters is investigated. The model is validated with experimental data reported in literature and a close agreement is observed between calculated and experimental values. The proposed model can be applied for simulation of nonideal fluidized‐bed combustors using heavy liquid fuels in industrial process simulators.

The nucleation of false vacuum bubbles with compact geometries

We investigate and classify the possible types of false vacuum bubbles in Einstein gravity. The false vacuum bubbles can occur only if gravity is taken into account. We show that there exist solutions only with compact geometries. The analytic computations for the radius and nucleation rate of a vacuum bubble are evaluated using the thin-wall approximation. We discuss possible cosmological implications of our new solutions.

Pachymetry-guided intrastromal air injection ("pachy-bubble") for deep anterior lamellar keratoplasty: results of the first 110 cases.

To report intraoperative and 1-year postoperative results of the pachy-bubble technique for deep anterior lamellar keratoplasty (DALK). This prospective interventional case series included 110 eyes of 107 patients with anterior corneal pathology who underwent DALK, including 78 with keratoconus. Outcome measures included the rate of bubble formation, rate of completing DALK, bubble types, complications, and visual and keratometric parameters. Intrastromal air injection was attempted in 109 eyes, and the air bubble was achieved in 93 eyes (85.3%). Intrastromal 2% methylcellulose injection was attempted in 9 eyes, after unsuccessful air bubble formation, and the viscobubble was achieved in 7 eyes (77.8%). Manual layer-by-layer dissection was performed in 8 eyes. Bubble formation was reached in 100 eyes (90.9%). Overall, 105 eyes (95.5%) achieved DALK. Air bubble occurred as type 1 (white margin) in 96.6% of the cases and as type 2 (clear margin) in 3.4%. There was a statistically significant improvement in all visual and keratometric parameters analyzed. Macroperforations converted to penetrating keratoplasty occurred in 5 eyes (4.5%) and microperforations in 12 (10.9%). There were significantly higher rates of perforation when a bubble was not achieved (P = 0.018) and when it was achieved as type 2 (P = 0.033). Interface haze occurred in 5 eyes (4.5%) and stromal rejection in 11 (10.0%). A short learning curve was observed for air bubble formation. Bubble formation, especially type 1, is the key to decrease the risk of perforation in DALK. The pachy-bubble was safe, effective, and reproducible in promoting DALK with air bubble and viscobubble formation with a short learning curve.

Intraoperative review of different bubble types formed during pneumodissection (big-bubble) deep anterior lamellar keratoplasty.

To evaluate the preoperative factors and intraoperative complications of the 2 bubble types formed during big-bubble deep anterior lamellar keratoplasty (DALK). This is a retrospective review of medical records of a series of patients who underwent DALK using the big-bubble technique from September 2009 to March 2014. A total of 134 eyes were included in this study-89 eyes with advanced keratoconus, 35 eyes with post-microbial keratitis corneal scars, 8 eyes with stromal dystrophies, and 2 eyes with post-laser in situ keratomileusis ectasia. A type 1 bubble (white margin) was achieved in 56 eyes (41.8%), whereas a type 2 bubble (clear margin) was formed in 14 eyes (10.4%) and a mixed bubble was formed in 2 eyes (1.5%). Big-bubble formation failed in 62 (46.3%). All eyes with the type 1 bubble were completed as DALK; microperforation occurred in 4 eyes. Twelve of 14 eyes with the type 2 bubble were converted to penetrating keratoplasty because of large perforations. The type 2 bubble is more likely to form in elderly patients and those with deep corneal scars and thin corneas. Because of the high rate of conversion to penetrating keratoplasty, better surgical strategies may be needed to manage type 2 bubbles.

Uniform bounds of minimizers of non-smooth constrained functionals on maps spaces

Abstract We consider the functional Φ(u) = ∫Ω |∇u|2 d x - ∫Ω G(u)d x constrained to the set EF = {u ∈ W 0 1,2(Ω,ℝ k ) : ∫Ω F(u)d x = 1}, where Ω is a bounded open subset of ℝ n and F,G : ℝ k → ℝ are continuous functions satisfying certain homogeneity conditions. We investigate the L ∞ regularity of minimizers of Φ in EF . Moreover, we establish uniform L ∞ bounds for such minimizers as well as concentration results on Ω̅. In the latter case, we prove that, up to dilations and translations, minimizers behave in a certain sense like a special type of vector bubble. The central difficulty in this study is the fact that the minimizers of Φ do not have an Euler–Lagrange equation associated.

Visualization study of bubble behavior in a subcooled flow boiling channel under rolling motion

Boiling heat transfer equipment in a vessel can be affected by the additional force which is generated by the rolling, swing and heaving motion of the vessel. Bubble behavior is very important for the research of boiling phenomenon. Bubble behavior under rolling motion condition is experimentally studied by using a high speed camera. The experiment is conducted in a subcooled flow boiling rectangular channel, and the cross section size of the channel is 2mm×40mm. Two types of bubbles with large discrepancies in sliding and condensation behaviors can be observed in the captured images. The first type bubbles disappear quickly after generation and the slide distance is only a few times of bubble maximum diameter, while the second type bubbles can survive a longer time after leaving the nucleation site and slide for a long distance with the flowing fluid. Bubble characteristics under rolling motion are separately studied for different type bubbles based on the above reasons. The results show that the lifetime, maximum diameter, nucleation frequency and sliding velocity of the first type bubble are periodically fluctuated and the period is same with the rolling motion. The fluctuation intensity of the bubble lifetime and maximum diameter can be enhanced by the increase of the rolling amplitude. The peak value of bubble lifetime, maximum diameter, and nucleation frequency appears when the rolling platform plate rolls to the maximum positive angle, while opposite trend can be observed in the variation of bubble sliding velocity. In view of the characteristics of the second type bubbles, lifetime and maximum diameter are not measured. And the variation of nucleation frequency and sliding velocity of the second type bubbles under the effect of rolling motion is same with the first type bubbles. Furthermore, the effects of additional force, variation of local pressure and flow rate oscillation on bubble behavior are analyzed. The results indicate that the fluctuations of the bubble parameters can be generated by the variation of local pressure caused by rolling motion even no influential flow rate fluctuation occurs. The effect of the acceleration variation vertical to the heated surface on bubble behavior is unclear and need more researches in the future work.