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Artykuły w czasopismach na temat "Single electron bubble"
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Bernstein, Lawrence S., i Mitchell R. Zakin. "Confined Electron Model for Single-Bubble Sonoluminescence". Journal of Physical Chemistry 99, nr 40 (październik 1995): 14619–27. http://dx.doi.org/10.1021/j100040a008.
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Kurata, Nobuhiko, i Takahide Oya. "Design of “bubble-inspired single-electron circuit” mimicking behavior of bubble film". Nonlinear Theory and Its Applications, IEICE 10, nr 4 (2019): 399–413. http://dx.doi.org/10.1587/nolta.10.399.
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Gareev B. M. i Sharipov G. L. "Atomic luminescence of Ag during single-bubble sonolysis of silver nanoparticles aqueous suspension". Technical Physics Letters 48, nr 14 (2022): 59. http://dx.doi.org/10.21883/tpl.2022.14.55120.18917.
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For the first time, luminescence of Ag atoms was recorded during moving single-bubble sonolysis of silver nanoparticles aqueous colloidal suspension. This glow is caused by the entry of nanoparticles into a bubble deformable during motion and their decomposition to atoms with collisional excitation in the nonequilibrium plasma of the bubble. Nanoparticles were obtained by multibubble sonolysis of an AgNO3 solution with the addition of honey. This method was used to synthesize a stable suspension of Ag nanoparticles with an average size of ~ 10 nm. By comparing the experimental spectrum of this suspension and simulated spectra of Ag, the electron temperature in the bubble plasma was found to be ~ 10 000 K. Keywords: single-bubble sonoluminescence, silver nanoparticles, electron plasma temperature.
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Heller, R., R. Jacob, D. Schönberner i M. Steffen. "Hot bubbles of planetary nebulae with hydrogen-deficient winds". Astronomy & Astrophysics 620 (grudzień 2018): A98. http://dx.doi.org/10.1051/0004-6361/201832683.
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Context. The first high-resolution X-ray spectroscopy of a planetary nebula, BD +30° 3639, opened the possibility to study plasma conditions and chemical compositions of X-ray emitting “hot” bubbles of planetary nebulae in much greater detail than before. Aims. We investigate (i) how diagnostic line ratios are influenced by the bubble’s thermal structure and chemical profile, (ii) whether the chemical composition inside the bubble of BD +30° 3639 is consistent with the hydrogen-poor composition of the stellar photosphere and wind, and (iii) whether hydrogen-rich nebular matter has already been added to the bubble of BD +30° 3639 by evaporation. Methods. We applied an analytical, one-dimensional (1D) model for wind-blown bubbles with temperature and density profiles based on self-similar solutions including thermal conduction. We also constructed heat-conduction bubbles with a chemical stratification. The X-ray emission was computed using the well-documented CHIANTI code. These bubble models are used to re-analyse the high-resolution X-ray spectrum from the hot bubble of BD +30° 3639. Results. We found that our 1D heat-conducting bubble models reproduce the observed line ratios much better than plasmas with single electron temperatures. In particular, all the temperature- and abundance-sensitive line ratios are consistent with BD +30° 3639 X-ray observations for (i) an intervening column density of neutral hydrogen, NH = 0.20-0.10+0.05 × 1022cm−2, (ii) a characteristic bubble X-ray temperature of TX = 1.8 ± 0.1 MK together with (iii) a very high neon mass fraction of about 0.05, virtually as high as that of oxygen. For lower values of NH, we cannot exclude the possibility that the hot bubble of BD +30° 3639 contains a small amount of “evaporated” (or mixed) hydrogen-rich nebular matter. Given the possible range of NH, the fraction of evaporated hydrogen-rich matter cannot exceed 3% of the bubble mass. Conclusions. The diffuse X-ray emission from BD +30° 3639 can be well explained by models of wind-blown bubbles with thermal conduction and a chemical composition equal to that of the hydrogen-poor and carbon-, oxygen-, and neon-rich stellar surface.
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GAREEV, B. M., A. M. ABDRAKHMANOV i G. L. SHARIPOV. "SONOLUMINESCENCE SPECTROSCOPY OF COLLOIDAL SUSPENSIONS: MOLECULAR, IONIC AND ATOMIC LUMINESCENCE DURING SONOCHEMICAL DECOMPOSITION OF SILICON DIOXIDE NANOPARTICLES CONTAINING RUTHENIUM AND COPPER COMPOUNDS". Izvestia Ufimskogo Nauchnogo Tsentra RAN, nr 4 (13.12.2021): 16–21. http://dx.doi.org/10.31040/2222-8349-2021-0-4-16-21.
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The article is devoted to an example of the sonoluminescence spectroscopy use, which was previously known as a method for analyzing substances from the characteristic spectra of their sonoluminescence only in true solutions, for carrying out a similar analysis of substances contained in insoluble nanoparticles in colloidal suspensions. The solutions sonolysis, that is, their irradiation with ultrasound, is accompanied by the formation of cavitation bubbles that vibrate radially at the frequency of the ultrasonic field. Volatile components of the solution enter the bubbles, evaporating from the liquid-gas interface; nonvolatile components can penetrate into the bubble as a result of the injection of solution nanodroplets into the gas phase, which occurs during intense bubble movements accompanied by their deformation. In a nonequilibrium plasma periodically forming in cavitation bubbles, destruction occurs, as well as collisional excitation of these components, followed by luminescence. It has been shown that this mechanism of sonoluminescence also operates in colloidal suspensions, where substances are present in the form of nanoparticles with sizes less than 50 nm. Such nanoparticles penetrate into moving cavitation bubbles, without destroying them, as part of nanodroplets, and then undergo decomposition in bubble plasma with the excited particles generation as emitters of characteristic sonoluminescence. In this work, we synthesized colloidal suspensions in dodecane of porous SiO2 nanoparticles containing adsorbed Ru(bpy)3Cl2 and CuSO4 salts. During moving single-bubble sonolysis for these suspensions, characteristic emission spectra of Ru and Cu atoms, SiO molecules, and Ru(bpy)3 ions suitable for sonoluminescence spectroscopic analysis were recorded. By comparing the experimental and calculated (at different temperatures) luminescence spectra of Ru atoms, we estimated the electron temperature attained upon acoustic compression of single bubble in colloidal suspension in dodecane: Te = 7000 K.
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Zhang, Feifei, Lynn Boatner, Yanwen Zhang, Di Chen, Yongqiang Wang i Lumin Wang. "Swelling and Helium Bubble Morphology in a Cryogenically Treated FeCrNi Alloy with Martensitic Transformation and Reversion after Helium Implantation". Materials 12, nr 17 (2.09.2019): 2821. http://dx.doi.org/10.3390/ma12172821.
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A cryo-quenched 70 wt % Fe-15 wt% Cr-15 wt% Ni single-crystal alloy with fcc (face centered cubic), bcc (body centered cubic), and hcp (hexagonal close packed) phases was implanted with 200 keV He+ ions up to 2 × 1017 ions·cm−2 at 773 K. Surface-relief features were observed subsequent to the He+ ion implantation, and transmission electron microscopy was used to characterize both the surface relief properties and the details of associated “swelling effects” arising cumulatively from the austenitic-to-martensitic phase transformation and helium ion-induced bubble evolution in the single-crystal ternary alloy. The bubble size in the bcc phase was found to be larger than that in the fcc phase, while the bubble density in the bcc phase was correspondingly lower. The phase boundaries with misfit dislocations formed during the martensitic transformation and reversion processes served as helium traps that dispersed the helium bubble distribution. Swelling caused by the phase transformation in the alloy was dominant compared to that caused by helium bubble formation due to the limited depth of the helium ion implantation. The detailed morphology of helium bubbles formed in the bcc, hcp, and fcc phases were compared and correlated with the characters of each phase. The helium diffusion coefficient under irradiation at 773 K in the bcc phase was much higher (i.e., by several orders of magnitude) than that in the fcc phase and led to faster bubble growth. Moreover, the misfit phase boundaries were shown to be effective sites for the diffusion of helium atoms. This feature may be considered to be a desirable property for improving the radiation tolerance of the subject, ternary alloy.
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SHARIPOV, G. L., B. M. GAREEV, A. M. ABDRAKHMANOV i L. R. YAKSHEMBETOVA. "ACTIVATION OF SINGLE-BUBBLE SONOLUMINESCENCE AND RADIOLUMINESCENCE OF GD3+ AND DY3+ IONS BY ELECTRON ACCEPTORS IN AQUEOUS SOLUTIONS AS CONSEQUENCE OF THE HYDRATED ELECTRON GENERATION DURING WATER SONOLYSIS AND RADIOLYSIS". Izvestia Ufimskogo Nauchnogo Tsentra RAN, nr 4 (13.12.2021): 22–29. http://dx.doi.org/10.31040/2222-8349-2021-0-4-22-29.
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Discovered the activation of moving single-bubble sonoluminescence and radioluminescence for Gd3+ and Dy3+ ions in aqueous solutions of GdCl3 and DyCl3 by the acceptor of a hydrated electron (eaq-): H+, Cd2+, etc. This activation is similar to the previously found activation by acceptors of eaq- radioluminescence and single-bubble sonoluminescence for the Tb3+ ion. Electron acceptors do not affect the quantum yield of the said lantha-nide ions photoluminescence. They also do not affect the yield of their multibubble sonoluminescence in aqueous solutions, since eaqdoes not appear in significant amounts during multibubble sonolysis. The found luminescence activation effects of lanthanide ions are interpreted as a consequence of the suppression of the quenching (reduction) reactions of these electronically excited ions eaq: *Ln3+ + eaq- → Ln2+ by acceptors. The feasibility of these reactions was predicted for all Ln3+ ions based on a theoretical estimate of their free energy. The discovery of the described effects of activation of the luminescence of Ln3+ ions is a consequence and serves as confirmation of not only the known generation of eaq- during radiolysis, but also its previously unknown generation during moving single-bubble sonolysis of water.
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Memoli, Gianluca, Kate Baxter, Helen Jones, Ken Mingard i Bajram Zeqiri. "Acoustofluidic Measurements on Polymer-Coated Microbubbles: Primary and Secondary Bjerknes Forces". Micromachines 9, nr 8 (15.08.2018): 404. http://dx.doi.org/10.3390/mi9080404.
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The acoustically-driven dynamics of isolated particle-like objects in microfluidic environments is a well-characterised phenomenon, which has been the subject of many studies. Conversely, very few acoustofluidic researchers looked at coated microbubbles, despite their widespread use in diagnostic imaging and the need for a precise characterisation of their acoustically-driven behaviour, underpinning therapeutic applications. The main reason is that microbubbles behave differently, due to their larger compressibility, exhibiting much stronger interactions with the unperturbed acoustic field (primary Bjerknes forces) or with other bubbles (secondary Bjerknes forces). In this paper, we study the translational dynamics of commercially-available polymer-coated microbubbles in a standing-wave acoustofluidic device. At increasing acoustic driving pressures, we measure acoustic forces on isolated bubbles, quantify bubble-bubble interaction forces during doublet formation and study the occurrence of sub-wavelength structures during aggregation. We present a dynamic characterisation of microbubble compressibility with acoustic pressure, highlighting a threshold pressure below which bubbles can be treated as uncoated. Thanks to benchmarking measurements under a scanning electron microscope, we interpret this threshold as the onset of buckling, providing a quantitative measurement of this parameter at the single-bubble level. For acoustofluidic applications, our results highlight the limitations of treating microbubbles as a special case of solid particles. Our findings will impact applications where knowing the buckling pressure of coated microbubbles has a key role, like diagnostics and drug delivery.
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GLINEC, Y., J. FAURE, A. PUKHOV, S. KISELEV, S. GORDIENKO, B. MERCIER i V. MALKA. "Generation of quasi-monoenergetic electron beams using ultrashort and ultraintense laser pulses". Laser and Particle Beams 23, nr 2 (czerwiec 2005): 161–66. http://dx.doi.org/10.1017/s0263034605050275.
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Plasma-based accelerators have been proposed for the next generation of compact accelerators because of the huge electric fields they can support. However, it has been difficult to use them efficiently for applications because they produce poor quality particle beams with large energy spreads. Here, we demonstrate a dramatic enhancement in the quality of electron beams produced in laser-plasma interaction: an ultrashort laser pulse drives a plasma bubble which traps and accelerates plasma electrons to a single energy. This produces an extremely collimated and quasi-monoenergetic electron beam with a high charge of 0.5 nanocoulomb at energy 170 ± 20 MeV.
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Гареев, Б. М., i Г. Л. Шарипов. "Атомарная люминесценция Ag при однопузырьковом сонолизе водной суспензии наночастиц серебра". Письма в журнал технической физики 47, nr 22 (2021): 17. http://dx.doi.org/10.21883/pjtf.2021.22.51720.18917.
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For the first time, luminescence of Ag atoms was recorded during moving single-bubble sonolysis of silver nanoparticles aqueous colloidal suspension. This glow is caused by the entry of nanoparticles into a bubble deformable during motion and their decomposition to atoms with collisional excitation in the nonequilibrium plasma of the bubble. Nanoparticles were obtained by multibubble sonolysis of an AgNO3 solution with the addition of honey. This method was used to synthesize a stable suspension of Ag nanoparticles with an average size of ~ 10 nm. By comparing the experimental spectrum of this suspension and simulated spectra of Ag, the electron temperature in the bubble plasma was found to be ~ 10000 K.
Rozprawy doktorskie na temat "Single electron bubble"
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Pal, Anustuv. "Studying bubbles in liquid He4 containing single and many electrons". Thesis, 2018. https://etd.iisc.ac.in/handle/2005/5420.
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Helium is an inert element with fully occupied orbitals and is a super
fluid at low
temperatures. An electron close to the surface of liquid Helium faces a long range
attraction due to the finite polarizability of the bulk Helium, and a close range
repulsion of 1 eV potential from the valence electrons due to Pauli's Exclusion
Principle. Due to this, electrons get trapped on the surface, forming a two dimensional
electron gas (2DES). If the density of this charged surface surpasses
a critical value, Electro-Hydrodynamic (EHD) instabilities are formed leading to
the formation of Multi Electron Bubbles (MEB). These are micron sized cavities
containing a layer of electrons on its inner surface. On the other hand if an energetic
electron is injected into bulk Helium, once the electron is thermalized, it
repels the Helium atoms and forms a spherical cavity of radius 19 A, known
as a Single Electron Bubble (SEB). This system is a textbook example of an electron
in a finite spherical potential well with
flexible walls. In this thesis we present
studies done on MEBs as well as SEBs inside liquid Helium4.
So far, there have been limited measurements on MEBs which have been transient
in nature. Here we present experiments where we were able to manipulate
MEBs in an electromagnetic trap, observe these bubbles for long periods, and
image them at high speeds enabling us to measure their properties, like radius,
mass and charge in a completely non-destructive way. Some MEBs were observed
to shrink and ultimately disappear. This was due to the condensation of vapour
inside the MEB into the cooler liquid. Based on this model we developed a theory
along with numerical simulations, and compared the results with many MEBs
that were observed to collapse. We found good agreement between our observation
and the prediction. We also present a simple analytical formula that relates
the initial radius of the MEB to the collapse time. Shrinking causes the surface
charge density of MEBs to vary widely paving the path to observe various phases
and phase transitions in a 2DES.
SEBs have been theoretically and experimentally studied over the past many
years, but there lies much scope to study them further. Here we describe an
experiment to measure the lifetime of the first excited state (1P) of the SEB very
close to the lambda transition temperature using a cavitation method. Previous
theoretical studies have calculated this to be 40 s from considerations of radiative
decay. Our experimental value is about 40 ns, which agrees well with a previous
experiment implying that the lifetime of the 1P state is governed by some unknown
non-radiative process. Our experiment also suggests that the lifetime does not
depend strongly on the surrounding temperature, implying that the normal
fluid
fraction does not play a major role in the non-radiative processes governing the
bubble decay.
Following this, we present a design of an experiment to probe the quantum
structure of the SEB spectroscopically, extending the previous spectroscopic measurements
of the 1P state by exciting the 1P bubble. Using experimentally and theoretically
known properties of the SEB, we built a model of the energy transitions
and simulated an experiment to optically probe the SEB for various experimental
parameters, and estimated quantities that can be experimentally measured. The
expected absorption signals were calculated to be very small ( 107) making the
experiment extremely challenging to perform. Through our analysis we show that
it is not possible to perform using our current experimental setup but this experiment
can potentially resolve many questions regarding the 1P state for which
contradictory studies exist.
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Yadav, Neha. "Exploring Electron Bubbles in Liquid Helium using Cavitation". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4808.
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An electron entering liquid helium experiences a repulsive potential of 1 eV. This originates in the interaction between the injected electron and electrons of the closed shells of helium atoms through Pauli exclusion principle. If the energy of the electron exceeds 1 eV, it can penetrate the liquid, form a cavity free from helium atoms and subsequently localize itself within the cavity. This is known as a single electron bubble (SEB). In another configuration, a system of electrons of energy less than 1 eV can form a floating charged layer above the surface of liquid helium: a two-dimensional system that has been studied in great detail over last few decades. If the number of electrons in this layer exceeds a critical value of 2 × 10^13electrons/m^2, an electrohydrodynamic instability sets in, giving rise to multielectron bubbles (MEBs), referring to micron to mm sized cavities containing a large number of electrons.
In the experiments to be discussed in this thesis, the primary technique is based on cavitation of liquid helium using pulsed ultrasound. After a brief introduction of the experimental technique, we will present the main results obtained during my Ph.D., as follows:
The first result is related to the phenomenon of cavitation in superfluid helium. We have observed that after cavitation, the bubble is pushed out of the acoustic focus because of the radiation pressure and can grow up to a size as large as a millimetre. The growth and collapse of these bubbles can be understood through Rayleigh-Plesset equation at low temperatures, and by condensation of vapour (limited by the thermal diffusivity of helium) above lambda but this description fails near the lambda transition. We suspect this is related to the large density of vortices nucleated near the bubble surface during the growth of the cavitating bubble. Second, we have observed a new species which cavitates at a negative pressure approximately 80 and 70 % lower magnitude than SEBs. We conclude that these are multielectron bubbles with small (<20) number of electrons. We will be presenting various evidence supporting this claim and compare our results with related experiments previously reported. We believe that the application of sound to a charged helium surface or a strong discharge from the tungsten tip can render the surface unstable and thereby facilitates the formation of FEBs. Interestingly, FEBs can get trapped on the vortex lines and can act as tracer particles for visualizing vortices. Apart from these two species of FEBs, we have also observed cavitation due to electrons created by the Penning Ionization of diatomic helium molecules (dimers), which occurs when two helium molecules in excited states combine with each other. Thirdly, we have shown howa charged helium surface can be rendered unstable using ultrasound, in the presence of small electric fields such as to create MEBs. An indentation is formed on the charged surface through mechanical impact, and that can lead to a significant increase in the local surface charge density and thereby generation of MEBs. We estimated the initial charge density of the bubbles above lambda point to be close to 1013 electrons/m2, which is significantly higher than what has been achieved before. With gradual condensation of vapor and corresponding reduction in the bubble sizes, we expect to achieve 2DES with strong quantum correlations, while the MEBs would still be observable with standard imaging systems. Finally, we have trapped MEBs using ultrasound pulses above lambda, by balancing the radiation force, electric forces and buoyancy. We observe that we can trap MEBs for as long as 30 𝑚𝑠, only limited by the heating in the system. We propose a method to reduce this heating and increase the duration of the trap. We have also seen an unusual increase in size of the MEBs while it is trapped; this anomalous increase in size can be linked with the convection flow in the liquid. Finally, we discuss the strength and shortcoming of this trap and compare it with previous trapping methods.
Książki na temat "Single electron bubble"
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Snyder, Trevor James. Visualization and heat transfer study of boiling in microgravity with and applied electric field utilizing single-bubble and surface-boiling semi-transparent gold-film heaters and three electrode geometries: diverging plate, flat plate, and pin electrode. Pullman, WA: School of Mechanical and Materials Engineering, Washington State University, 1995.
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Greenland, Thomas H. Epilogue. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252040115.003.0009.
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This epilogue examines some of the changes that have taken place in the decade-plus since the author conducted his study in 2002, along with their impact on New York City's jazz scene. It begins with a discussion of the terrorist attacks of September 11, 2001; the housing bubble in 2007–2008 and the ensuing global financial crisis; and the continued gentrification of New York neighborhoods. It then considers how the economic recession affected jazz entrepreneurs and looks at the advent of file-sharing and music-streaming technologies as well as digital media such as Facebook, artist websites and blogs, YouTube, Myspace, and Twitter. It also recounts the 2008 election of Barack Obama as the nation's first black president and assesses its implications for jazz communities. It shows that jazz people improvise over “the changes” as they try to adapt to New York's highly variable environment.
Części książek na temat "Single electron bubble"
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"Single Oscillating Bubble from Radiofrequency Fiber Electrode". W Proceedings of the 10th International Symposium on Cavitation (CAV2018), 930–33. ASME Press, 2018. http://dx.doi.org/10.1115/1.861851_ch177.
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Doncel Fernández, Luis Vicente. "Digital Democracy". W Advances in Electronic Government, Digital Divide, and Regional Development, 105–25. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-9609-8.ch007.
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Starting from a brief reference to the concept and typology of political democracy systems, the authors present in this chapter some of the most important challenges that the use of new information and communication technologies entails in both spheres of political decisions (from power or choosing power). It is logical to question and open a debate regarding the democratic validity of its use, since fake news, misinformation, bubble filters undoubtedly influence the propaganda of political parties and affect the message and its effectiveness. On the other hand, the new technological communication paradigm applied to the democratic electoral system, technically possible, also raises interesting considerations regarding its eventual institutionalization and its legitimacy in comparison with the classical model of participation.
Streszczenia konferencji na temat "Single electron bubble"
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Kurata, Nobuhiko, i Takahide Oya. "Design of Multi-Layer Single-Electron Information-Processing Circuit Mimicking Behavior of Bubble Film for Solving Nonlinear Problem". W 2019 Silicon Nanoelectronics Workshop (SNW). IEEE, 2019. http://dx.doi.org/10.23919/snw.2019.8782973.
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Liu, Zan, Cila Herman i Jungho Kim. "Heat Transfer and Bubble Detachment in Subcooled Pool Boiling From a Microheater Array Under the Effect of a Nonuniform Electric Field". W ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32516.
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The effects of a nonuniform electric field on vapor bubble detachment and heat transfer rate were studied in pool boiling at different subcooled conditions for various wall temperatures. Dielectric fluid (FC-72) was used as the working fluid at 1 atm at earth gravity with two extreme gas concentration levels. An array of 3×3 independently controlled microheaters each 0.7×0.7 mm2 in size were maintained at constant temperature using electronic feedback loops, enabling the heat transfer from each heater to be determined. An electric field was applied between the horizontal upward facing microheater array, which was grounded, and a spherical, off-axis top electrode. Boiling heat transfer results with and without the electric field are presented in this study. Without the electric field, a single large “primary” bubble was observed to form due to the coalescence of the individual “satellite” bubbles which nucleated directly from each single heater array. Before its detachment, a dry spot formed underneath this primary bubble resulted in a reduction in heat transfer. With the electric field applied, three or more small “secondary” bubbles that nucleated and grew more rapidly and detached more frequently were observed. Due to the nonuniformity of the electric field, bubbles moved away from the top electrode (into the weaker region of the electric field) during their development. Higher overall heat transfer rates were measured from the heater array. In addition, the bubble behavior showed agreement with our previous investigation of injecting air bubbles into a stagnant, isothermal liquid through orifices.
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Liu, Z., C. Herman i D. Mewes. "Visualization of Vertical Bubble Coalescence and Detachment Under the Influence of a Nonuniform Electric Field". W ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15475.
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The effect of a nonuniform electric field on the formation, coalescence and detachment of air bubbles injected into a stagnant, isothermal liquid through an orifice is studied to identify characteristic bubble behavior patterns. The results of the experimental visualization suggest significant differences in bubble shape and size caused by the electric field. The electric field was applied between a flat, circular and horizontal ground electrode and a spherical, off-axis top electrode. During formation the bubble was tilted towards or away from the upper electrode under the influence of the electric field. The direction of the tilt alternated (even in a single experiment), however, in the majority of the cases the bubble trajectory tilted towards the top electrode. The detachment frequency increased under the influence of the electric field, which indicates decreased bubble volume for lower volume flow rates. The effect of the electric field on vertical bubble coalescence was analyzed and quantified in terms of the detachment time.
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Kang, Ki Moon, Hyo-Won Kim, Il-Wun Shim i Ho-Young Kwak. "Syntheses of Specialty Nanomaterials at the Multibubble Sonoluminescence Condition". W ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68320.
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In recent years, a large number of nano-size semiconductors have been investigated for their potential applications in photovoltaic cells, optical sensor devices, and photocatalysts [1, 2, 3]. Nano-size semiconductor particles have many interesting properties due mainly to their size-dependent electronic and optical properties. Appropriately, many speciality of nanomaterials such as CdS and ZnS semiconductor particles, and other metal oxides such as ZnO and lithium-titanate oxide (LTO) have been prepared. However, most of them were prepared with toxic reactants and/or complex multistep reaction processes. Particularly, it is quite difficult to produce LTO nanoparticles, since it typically requires wearisome conditions such as very high temperature over 1000 °C, long producing times, and so on. To overcome such problems, various core/shell type nanocrystals were prepared through different methods such as the hydrothermal synthetic method, microwave, and sonochemistry. Also many coating methods on inorganic oxide nanoparticles were tried for the preparations of various core-shell type nanocrystals. Sonoluminescence (SL) is a light emission phenomenon associated with the catastrophic collapse of a gas bubble oscillating under an ultrasonic field [4]. Light emission of single bubble sonoluminescence (SBSL) is characterized by picosecond flashes of the broad band spectrum extending to the ultraviolet [5, 6]. The bubble wall acceleration has been found to exceed 1011 g at the moment of bubble collapse. Recently observed results of the peak temperature and pressure from the sonoluminescing gas bubble in sulfuric acid solutions [9] were accurately predicted by the hydrodynamic theory for sonoluminescence phenomena [7, 10, 11, 12], which provides a clue for understanding sonochemical reactions inside the bubble and liquid layer adjacent to the bubble wall. Sonochemistry involves an application of sonoluminescence. The intense local heating and high pressure inside the bubbles and liquid adjacent bubble wall from such collapse can give rise to unusual effects in chemical reactions. The estimated temperature and pressure in the liquid zone around the collapsing bubble with equilibrium radius 5 μm, an average radius of bubbles generated in a sonochemical reactor at a driving frequency of 20 kHz with an input power of 179 W, is about 1000 °C and 500 atm, respectively. At the proper condition, a lot of transient bubbles are generated and collapse synchronistically to emit blue light when high power ultrasound is applied to liquid, and it is called multibubble sonoluminescence (MBSL). Figure 1 shows an experimental apparatus for MBSL with a cylindrical quartz cell, into which a 5 mm diameter titanium horn (Misonix XL2020, USA) is inserted [13]. The MBSL facilitates the transient supercritical state [14].in the liquid layer where rapid chemical reactions can take place. In fact, methylene blue (MB), which is one of a number of typical textile dyestuffs, was degraded very fast at the MBSL condition while MB does not degrade under simple ultrasonic irradiation [13]. MBSL has been proven to be a useful technique to make novel materials with unusual properties. In our study, various metal oxides such as ZnO powder [15], used as a primary reinforcing filler for elastomer, homogeneous Li4Ti5O12 nanoparticles [16], used for electrode materials, and core/shell nanoparticles such as CdS coating on TiO2 nanoparticles [17] and ZnS coating on TiO2 nanoparticles [18], which are very likely to be useful for the development of inorganic dye-sensitized solar cells, were synthesized through a one pot reaction under the MBSL condition. Figure 2 shows the XRD pattern of ZnO nanoparticles synthesized from zinc acetate dehydrate (Zn(CH3CO2)2 · 2H2O, 99.999%, Aldrich) in various alcohol solutions with sodium hydroxide (NaOH, 99.99%, Aldrich) at the MBSL condition. The XRD patterns of all powers indicate hexagonal zincite. The XRD pattern for the ZnO nanoparticles synthesized is similar to the ZnO powder produced by a modified sol-gel process and subsequent heat treatment at about 600 °C [19] as shown in Fig.3. The average particle diameter of ZnO powder is about 7 nm. A simple sonochemical method for producing homogeneous LTO nanoparticles, as shown schematically in Fig. 4. First, LiOH and TiO2 nanoparticles were used to prepare LiOH-coated TiO2 nanoparticles as shown in Fig.5. Second, the resulting nanoparticles were thermally treated at 500 °C for 1 hour to prepare LTO nanoparticles. Figure 6 shows a high resolution transmission electron microscope image of LTO nanoparticles having an average grain size of 30–40 nm. All the nanoparticle synthesized are very pure in phase and quite homogeneous in their size and shape. Recently we succeeded in synthesizing a supported nickel catalyst such as Ni/Al2sO3, MgO/Al2O3 and LaAlO3, which turned out to be effective for methane decomposition [20]. Sonochemistry may provide a new way to more rapidly synthesize many specialty nanoparticles with less waste [21]. This clean technology enables the preparation of new materials such as colloids, amorphous particles [22], and various alloys.
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Lee, S. K., E. Loth i C. Liu. "Electrolytic Microbubbler Matrices". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81895.
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The feasibility of generating mono-disperse micro-bubbles by electrolysis in tap water using micro-fabricated devices was investigated towards the development of a high-density bubbler matrix. The effect of electrode geometry and size, as well as artificial nucleation sites was tested using single and arrays of electrode pairs. The results indicated that circular electrode node shapes (as opposed to triangular or square nodes) nucleated bubbles from the node center and exhibited fewer instances of bubble coalescence and a higher bubble detachment frequency when operated with small anode-anode and cathode-cathode spacings. Artificial nucleation sites, produced by etching the surface of the electrodes, were shown to be able to limit nucleation to one site (though in some cases, bubbles formed underneath the dielectric layer) as well as increase current efficiency. A device with thousands of electrode pairs (a matrix of nodes) was also fabricated in order to generate a bubble cloud close to the channel wall. At a flow speed of 14 cm/s, this device demonstrated the ability to generate a bubble cloud reasonably close to the wall 20 mm from the trailing edge of the matrix of nodes, with the void fraction peaking at 1 mm from the channel wall and returning to zero at 3 mm. It yielded efficiencies greater than similar thin-wire devices, but spurious bubbles formed on the device, indicating that additional work is needed to develop this technology in a matrix format.
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Chen, Feng, Dong Liu, Yaozu Song i Yao Peng. "Visualization of a Single Boiling Bubble in a DC Electric Field". W ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-11016.
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The application of electric field has been demonstrated as an effective way to enhance pool boiling heat transfer. In past studies, adiabatic experiments were often conducted to simulate the dynamics of nucleate bubbles in the presence of an electric field, where gas bubbles were injected from an orifice, to avoid complexities involved in the nucleate boiling experiments. While adiabatic studies yield useful information of the bubble dynamics, further studies about bubble dynamics during nucleate boiling heat transfer are still necessary for a full understanding of the effects of applied electric field on the liquid-vapor phase change heat transfer. In this paper, the dynamics of a single boiling bubble in a direct current (DC) electric field was studied experimentally employing R113 as the working fluid. The life cycle of the boiling bubble was visualized using high-speed photography and was compared with that of an injected nitrogen bubble. Under the same electric field, a more appreciable elongation along the field direction was observed for the boiling bubble. A modified relationship between the bubble deformation and the electrical Weber number was proposed for the boiling bubble. As the electric field strength increases, it was found that, although the growth time of the boiling bubble increases, the waiting period decreases. However, it was also found that, the change of the whole life cycle with electric field strength increasing is relevant to the wall temperature. In this work, the wall temperature measured in the vicinity of the nucleation site upon the bubble departure decreases when the electric field is applied.
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Chen, Feng, Dong Liu i Yaozu Song. "Visualization of a Single Boiling Bubble in a DC Electric Field". W ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72493.
Pełny tekst źródłaStreszczenie:
The application of electric field has been demonstrated as an effective way to enhance pool boiling heat transfer. In past studies, adiabatic experiments were often conducted to simulate the dynamics of nucleate bubbles in the presence of an electric field, where gas bubbles were injected from an orifice, to avoid complexities involved in the nucleate boiling experiments. While adiabatic studies yield useful information of the bubble dynamics, further studies about bubble dynamics during nucleate boiling heat transfer are still necessary for a full understanding of the effects of applied electric field on the liquid-vapor phase change heat transfer. In this paper, the dynamics of a single boiling bubble in a direct current (DC) electric field was studied experimentally employing R113 as the working fluid. The life cycle of the boiling bubble was visualized using high-speed photography and was compared with that of an injected nitrogen bubble. Under the same electric field, a more appreciable elongation along the field direction was observed for the boiling bubble. A modified relationship between the bubble deformation and the electrical Weber number was proposed for the boiling bubble. As the electric field strength increases, it was found that, although the growth time of the boiling bubble increases, the waiting period decreases. However, it was also found that, the change of the whole life cycle with electric field strength increasing is relevant to the wall temperature. In this work, the wall temperature measured in the vicinity of the nucleation site upon the bubble departure decreases when the electric field is applied.
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Uesawa, Shin-ichiro, Akiko Kaneko i Yutaka Abe. "Estimation of Void Fraction in Dispersed Bubbly Flow With a Constant Electric Current Method". W 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-16279.
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In several void fraction measurement methods, electric void sensors are online measurement method, simple construction and lower cost. In electric measurement, we research on a constant electric current method which is one of conductance methods. By using this method, we can measure volumetric void fraction with higher temporal resolution although the method cannot measure 2D and 3D distribution of void fractions. Besides, multiple measuring electrodes can be installed at a short distance. And then, flow is not obstructed by measuring electrodes. However, the constant electrical current method has been applied in annular flow in previous studies. Void fraction is estimated by cross-sectional ratio of gas and liquid phases in this method. For this reason, dispersed bubbly flow is not applied because cross-section ratio is not continuous in a flow direction. In the present study, Maxwell’s theory, Bruggemann’s treatment and polarization method are applied in order to measure void fraction of dispersed bubbly flow more accurately. Maxwell’s theory is an estimation of a resistance of a mixture with two difference resistivity by calculating electric potential in the mixture. Bruggemann’s treatment is based on Maxwell’s theory but it implies the assumption of a large size-range of particles in surrounding medium. In polarization method, bubbles are assumed to be dielectric bodies. Therefore if voltage is applied to gas-liquid two-phase flow, electrical charges in bubbles are polarized, and polarization electrical field generates. A difference of voltages in bubbly flow and liquid single phase flow assumes to be caused by polarization fields. Void fraction in vertical flow is measured experimentally by the previous method, Bruggemann’s treatment, Maxwell’s theory and polarization method in order to investigate the accuracy of these estimations. Working fluid is air and tap water. The accuracy is measured by comparing with a quick shut valve method and observations. Besides, we investigate effects of flow structure and bubble shape to measurement accuracy. Flow structure is changed by changing gas and liquid volume flow rate. In the experiment for bubble shape, a rising bubble by buoyancy is measured. The bubble shape observed by a high speed video camera is compared with the electrical signal measured by the constant electric current method. From experimental results, it is confirmed that void fraction in bubbly flow and froth flow is estimated more accurately by Maxwell’s theory, Bruggemann’s treatment and polarization method, and change of bubble shape correlates with fluctuation of void fraction measured by the constant electric current method.
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Song, Yaozu, Feng Chen i Yao Peng. "An Estimation Method of Electric Field Forces on a Single Bubble". W 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22062.
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It has been well-known that externally imposed static electric fields have a significant effect on bubble dynamic behavior, especially on bubble departure behavior. With increasing electric field strength, bubble detachment volume decreases and bubble shape elongates along the electric field direction. It is electric field forces that change bubble behavior. The electric field forces can be calculated from theoretical formula for a simple electrode structure. However, for the complex electrode system, it is rather a tough thing to theoretically solve electric field forces. In this work a new method to experimentally estimate electric field forces exerted on a single bubble has been presented. Experimental estimation primarily depends upon decreasing in the buoyancy on the bubble. Furthermore, the calculations coming from theoretical formula have also been completed and the results show that experimental estimations agree well with theoretical calculations.
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Liu, Hong-bo, i Liang-ming Pan. "The Effect of Electromagnetic Field on the Behavior of Bubbles". W 2013 21st International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/icone21-15689.
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The coalescence and motion behaviors of bubbles can be influenced by electromagnetic field, it can be found in the TOKAMK fusion reactors of ITER program. In this paper, VOF (Volume of Fluid) method is adopt to simulate the single bubble rising behavior and bubble coalescence in stagnant liquid under the electromagnetic field within a cylinder closure (D = 20mm, H = 50mm). A three-dimensional numerical simulation is presented considering the driving effect of uniform electric field and magnetic field on the process of bubble rising and bubbles inline coalescence in stagnant liquid pool. The interesting local Magneto-hydrodynamic (MHD) flow, which is produced due to current non-homogenous distribution around the insolated gas bubble, is discussed in the process of single bubble rising and coalescence of bubbles inline. Under the influence of local MHD flow, the rising bubble shape presents obvious deformation. More importantly, as the existence of rotating Lorentz force, the liquid film between two bubbles is stirred, the process of coalescence is largely accelerated.