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Artykuły w czasopismach na temat "Multi Electron Bubbles"
1
Silvera, Isaac F., Jieping Fang i Jacques Tempere. "Stabilization of Multi-electron Bubbles in Superfluid Helium". Journal of Physics: Conference Series 568, nr 1 (8.12.2014): 012016. http://dx.doi.org/10.1088/1742-6596/568/1/012016.
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Ihas, G. G., i T. M. Sanders. "Multi-Electron Bubbles and Roton Scattering in Super fluid4He". Japanese Journal of Applied Physics 26, S3-3 (1.01.1987): 2097. http://dx.doi.org/10.7567/jjaps.26s3.2097.
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Jiang, N., i J. Silcox. "Electron Irradiation Damage in Multi-Component Glasses". Microscopy and Microanalysis 6, S2 (sierpień 2000): 390–91. http://dx.doi.org/10.1017/s1431927600034449.
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Understanding electron beam induced damage in glasses, especially in multi-component glasses, is very important, since the interaction of electron probes with glass is a very common approach to determine glass composition and structure. For example, the decay of characteristic X-ray and Auger electron intensities, using electron beams as probes, of alkalis in glasses have been known for years. In addition, both phase separation and formation of gas bubbles in the glasses have also been reported. Many irradiation effects are strongly dependent on the structure, bonding and composition of matter. In general, three types of mechanisms, knock-on damage, ionization and field-induced migration have been introduced to describe the damage induced by electron irradiation. Here, we demonstrate electron irradiation induced phase decomposition in a multi-component oxide glass, and introduce a modified model to interpret the damage process.
4
Kamalabadi, F., J. M. Comberiate, M. J. Taylor i P. D. Pautet. "Estimation of electron densities in the lower thermosphere from GUVI 135.6 nm tomographic inversions in support of SpreadFEx". Annales Geophysicae 27, nr 6 (16.06.2009): 2439–48. http://dx.doi.org/10.5194/angeo-27-2439-2009.
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Abstract. The SpreadFEx campaign was conducted with the goal of investigating potential neutral atmospheric dynamics influences in seeding plasma instabilities and bubbles extending to higher altitudes from September to November 2005, with primary measurements in Brazil. In this paper, we present the results of space-based UV and ground-based optical observations in support of this campaign. Specifically, we present multi-dimensional electron density images obtained tomographically from the 135.6 nm emissions measured by the GUVI instrument aboard the TIMED satellite that result from radiative recombination of O+ and compare those with the corresponding 630.0 nm OI images recorded in the Brazilian sector. The GUVI results provide altitude vs. longitude information on depleted regions in the ionospheric plasma density that are complementary to the single-height latitude-longitude images obtained with the airglow imager.
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Bettaieb, Afef, Nabila Filali, Taoufik Filali i Habib Ben Aissia. "An efficient algorithm for overlapping bubbles segmentation". Computer Optics 44, nr 3 (czerwiec 2020): 363–74. http://dx.doi.org/10.18287/2412-6179-co-605.
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Image processing is an effective method for characterizing various two-phase gas/liquid flow systems. However, bubbly flows at a high void fraction impose significant challenges such as diverse bubble shapes and sizes, large overlapping bubble clusters occurrence, as well as out-of-focus bubbles. This study describes an efficient multi-level image processing algorithm for highly overlapping bubbles recognition. The proposed approach performs mainly in three steps: overlapping bubbles classification, contour segmentation and arcs grouping for bubble reconstruction. In the first step, we classify bubbles in the image into a solitary bubble and overlapping bubbles. The purpose of the second step is overlapping bubbles segmentation. This step is performed in two subsequent steps: at first, we classify bubble clusters into touching and communicating bubbles. Then, the boundaries of communicating bubbles are split into segments based on concave point extraction. The last step in our algorithm addresses segments grouping to merge all contour segments that belong to the same bubble and circle/ellipse fitting to reconstruct the missing part of each bubble. An application of the proposed technique to computer generated and high-speed real air bubble images is used to assess our algorithm. The developed method provides an accurate and computationally effective way for overlapping bubbles segmentation. The accuracy rate of well segmented bubbles we achieved is greater than 90 % in all cases. Moreover, a computation time equal to 12 seconds for a typical image (1 Mpx, 150 overlapping bubbles) is reached.
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Li, Xiao Yan, Yan Chun Li, Chen Jie Shi, Si Si Cai, Xia Wang, Fan Fan i Ao Li. "Influence of Intumescent Flame Retardant on Flammability and Tensile Behavior of Oil-Extended SEBS". Advanced Materials Research 749 (sierpień 2013): 65–70. http://dx.doi.org/10.4028/www.scientific.net/amr.749.65.
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A kind of intumescent flame retardant (IFR) were used for flame retarding of oil-extended hydrogenated styrene-butylenes-styrene (O-SEBS). The samples were systemically characterized by limited oxygen index (LOI), vertical burning test (UL-94), and scanning electron microscopy (SEM); Thermogravimetric (TG) analysis. The results showed that the IFR retardant can promote residual chars with multi-micro holes on the surface of SEBS to inhibit flame; with 45% IFR content, the LOI is 28.3 and flame retardant level is UL-94 classification of V-0, with no dripping. The morphological structures observed by SEM demonstrated that higher IFR content promote to form larger and compact films cover on bubbles of the intumescent char layer. The TG data revealed that the IFR could change the degradation behavior of the O-SEBS, enhance the thermal stability and increase the char residue, The tensile strength of all the O-SEBS/IFR blends had the tensile strength of more than 4MPa and the elongation of more than 850%.
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Apatenkov, S. V., V. A. Sergeev, M. V. Kubyshkina, R. Nakamura, W. Baumjohann, A. Runov, I. Alexeev i in. "Multi-spacecraft observation of plasma dipolarization/injection in the inner magnetosphere". Annales Geophysicae 25, nr 3 (29.03.2007): 801–14. http://dx.doi.org/10.5194/angeo-25-801-2007.
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Abstract. Addressing the origin of the energetic particle injections into the inner magnetosphere, we investigate the 23 February 2004 substorm using a favorable constellation of four Cluster (near perigee), LANL and Geotail spacecraft. Both an energy-dispersed and a dispersionless injection were observed by Cluster crossing the plasma sheet horn, which mapped to 9–12 RE in the equatorial plane close to the midnight meridian. Two associated narrow equatorward auroral tongues/streamers propagating from the oval poleward boundary could be discerned in the global images obtained by IMAGE/WIC. As compared to the energy-dispersed event, the dispersionless injection front has important distinctions consequently repeated at 4 spacecraft: a simultaneous increase in electron fluxes at energies ~1..300 keV, ~25 nT increase in BZ and a local increase by a factor 1.5–1.7 in plasma pressure. The injected plasma was primarily of solar wind origin. We evaluated the change in the injected flux tube configuration during the dipolarization by fitting flux increases observed by the PEACE and RAPID instruments, assuming adiabatic heating and the Liouville theorem. Mapping the locations of the injection front detected by the four spacecraft to the equatorial plane, we estimated the injection front thickness to be ~1 RE and the earthward propagation speed to be ~200–400 km/s (at 9–12 RE). Based on observed injection properties, we suggest that it is the underpopulated flux tubes (bubbles with enhanced magnetic field and sharp inner front propagating earthward), which accelerate and transport particles into the strong-field dipolar region.
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Brown, L. M., i A. L. Bleloch. "New Projects for Superstem". Microscopy and Microanalysis 6, S2 (sierpień 2000): 98–99. http://dx.doi.org/10.1017/s1431927600032980.
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It is proposed to build two high-performance general-user instruments at Daresbury, Cheshire, where the present U.K. synchrotron facility is located. The instruments can be used on-site, where accommodation for visitors is already available. They can also be used remotely, via the internet. The features of the instruments are: aberration-corrected optics, voltage-stabilised electron spectrometer, and multi-specimen stages to facilitate rapid throughput of routine work. We anticipate that a sub-Angstrom probe size will be available for incoherent HAADF imaging, and PEELS with an energy resolution better than 0.3V for losses up to 2kV. The operating voltage will be l00kV.The new instruments will allow better analysis of continuing problems. Anticipated developments are as follows:1. Study of helium bubbles in reactor materials: Recently, accurate quantification of helium has been achieved and a quantitative explanation has been given for the ‘blue shift’, that is, the increasing threshold energy for the Is to 2p transition due to quantum confinement of the excited state with increasing gas pressure.
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Mertsch, P., i V. Petrosian. "Fermi bubbles from stochastic acceleration of electrons in a Galactic outflow". Astronomy & Astrophysics 622 (luty 2019): A203. http://dx.doi.org/10.1051/0004-6361/201833999.
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The discovery of the Fermi bubbles – a huge bilobular structure seen in GeV gamma-rays above and below the Galactic centre – implies the presence of a large reservoir of high energy particles at ~10 kpc from the disk. The absence of evidence for a strong shock coinciding with the edge of the bubbles, and constraints from multi-wavelength observations point towards stochastic acceleration by turbulence as a likely mechanism of acceleration. We have investigated the time-dependent acceleration of electrons in a large-scale outflow from the Galactic centre. For the first time, we present a detailed numerical solution of the particle kinetic equation that includes the acceleration, transport and relevant energy loss processes. We also take into account the addition of shock acceleration of electrons at the bubble’s blast wave. Fitting to the observed spectrum and surface brightness distribution of the bubbles allows determining the transport coefficients, thereby shedding light on the origin of the Fermi bubbles.
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Ye, Hailun, Wen Yi, Baozhu Zhou, Jianfei Wu, Bingkun Yu, Penghao Tian, Jianyuan Wang i in. "Multi-Instrumental Observations of Midlatitude Plasma Irregularities over Eastern Asia during a Moderate Magnetic Storm on 16 July 2003". Remote Sensing 15, nr 4 (20.02.2023): 1160. http://dx.doi.org/10.3390/rs15041160.
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This study presents the observations of midlatitude plasma irregularities over Eastern Asia during a moderate magnetic storm on 16 July 2003. Multi-instrumental observations, including the ground-based ionosondes, the GNSS networks, and the CHAMP and ROCSAT-1 satellites, were utilized to investigate the occurrence and characteristics of midlatitude plasma irregularities. The midlatitude strong spread F (SSF) mainly occurred in the midnight–morning sector as observed by ionosondes over Japan during this storm. SSF was related to plasma depletions, which is also recorded by GNSS network in the form of the enhancement of the rate of total electron content (TEC) change index (ROTI). The possible mechanism for the generation of SSF is that the enhanced eastward electric fields, associated with the prompt penetration electric fields and disturbance dynamo electric fields, cause the uplift and latitudinal extension of equatorial plasma bubbles (EPBs) to generate the observed midlatitude SSF further. Meanwhile, plasma density increased significantly under the influence of this storm. In addition, other common type of spread F, frequency spread F (FSF), was observed over Japan on the non-storm day and/or at high latitude station WK545, which seems to be closely related to the coupling of medium-scale traveling ionospheric disturbances (MSTIDs) and sporadic E (Es) layer. The above results indicate that various types of midlatitude spread F can be produced by different physical mechanisms. It is found that SSF can significantly affect the performance of radio wave propagation compared with FSF. Our results show that space weather events have a significant influence on the day-to-day variability of the occurrence and characteristics of ionospheric F-region irregularities at midlatitudes.
Rozprawy doktorskie na temat "Multi Electron Bubbles"
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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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(9142649), Dohyung Ro. "MULTI-ELECTRON BUBBLE PHASES". Thesis, 2020.
Znajdź pełny tekst źródłaStreszczenie:
Strong electronic correlations in many-body systems are cradles of new physics. They give birth to novel collective states hosting emergent quasiparticles as well as intriguing geometrical charge patterns. Two-dimensional electron gas in GaAs/AlGaAs under perpendicular magnetic field is one of the most well-known hosts in condensed matter physics where a plethora of the collective states appear. In the strong magnetic field regime, strong Coulomb interactions among the electrons create emergent quasiparticles, i.e. composite fermions and Cooper-paired composite fermions. In the weak magnetic field regime, modified Coulomb interactions drive electron solid phases having geometrical charge patterns in the shape of stripes and bubbles and lower the spatial symmetry of the states.
The fascinating charge order in bubble geometry is the electron bubble phase predicted first by the Hartree-Fock theory. In a bubble phase, certain number of electrons cluster as an entity called bubble and the bubbles order into a crystal of triangular lattice. In addition to the Hartree-Fock theory, the density matrix renormalization group and the exact diagonalization methods further support the formation of electronic bubbles.
Reentrant integer quantum Hall states are commonly accepted as the manifestations of the bubble phases in transport experiment. Soon after the first prediction of the Hartree-Fock theory, the reentrant integer quantum Hall states were observed in the third and higher Landau levels. Since then, the association to the bubble phases has been tested with different experimental techniques for decades.
Although the experimental results from different methods support the bubble phase picture of the reentrant integer quantum Hall states, the electron confinement under the quantum well structure hindered direct scanning of bubble morphology. Thus none of the experiments could showcase the bubble morphology of the reentrant integer quantum Hall states. Meanwhile, a significant discrepancy still remained in between the bubble theories and the experiments. Even though the bubble theories predict the proliferation of bubble phases with increasing orbital index, none of the experiments could observe multiple reentrant integer quantum Hall states in a high Landau level, which signify the multiple bubble formation. Therefore, the proliferation of bubble phases with increasing Landau level index was pessimistic.
In this Dissertation, I present my research on solving this discrepancy. In chapter 4, we performed a magnetotransport measurement of reentrant integer quantum Hall states in the third and higher Landau levels at various different temperatures. Then, we scrutinized how each of the reentrant integer quantum Hall states develops with the gradual increase of the temperature. As a result, we observed multiple reentrant integer quantum Hall states in the fourth Landau level which are associated with the two- and three-electron bubble phases. This result strongly supports the bubble phase picture of the reentrant integer quantum Hall states by confirming the possibility of the proliferation of bubble phases in high Landau levels.
In chapter 5, I analyzed the energetics of newly resolved two- and three-electron bubble phases in the fourth Landau level as well as those of two-electron bubble phases in the third Landau level. Here, I first found, in the fourth Landau level, the three-electron bubbles are more stable than the two-electron bubbles indicating that the multi-electron bubbles with higher electron number are more stable within a Landau level. Secondly, I found distinct energetic features of two- and three-electron bubble phases which are independent of Landau level index throughout the third and the fourth Landau levels. These results highlight the effect of the number of electrons per bubble on the energetics of multi-electron bubble phases and are expected to contribute on improving the existing Hartree-Fock theories.
Części książek na temat "Multi Electron Bubbles"
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Silvera, Isaac F., Jacques Tempere, Jian Huang i Jozef Devreese. "Multi-electron Bubbles under Pressure". W Frontiers of High Pressure Research II: Application of High Pressure to Low-Dimensional Novel Electronic Materials, 541–49. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0520-3_42.
Pełny tekst źródłaStreszczenia konferencji na temat "Multi Electron Bubbles"
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Kondo, Koichi, Kenji Yoshida, Tadayoshi Matsumoto, Tomio Okawa i Isao Kataoka. "Flow Patterns of Gas-Liquid Two-Phase Flow in Round Tube With Sudden Expansion". W 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22154.
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Experimental studies were made on the multi-dimensional behavior of upward gas-liquid two-phase flow through the vertical round tube with an axisymmetric sudden expansion, which is one of the typical multi-dimensional channel geometry. The aims of this study are to clarify the multi-dimensional behavior of bubbly or slug flow affected by sudden expansion channel geometry, and to accumulate the experimental data for two-phase flow analysis, which is applicable to predict with appropriate accuracy the multi-dimensional its behavior. The direct observation using high-speed video camera was performed and revealed the multi-dimensional dynamic flow behavior with bubbles and gas-slug affected by the sudden expansion part (20 mm-tube to 50 mm-tube). The characteristic phenomena were observed such as bubble break-up, deformation due to the strong shear of liquid flow, or liquid micro jet penetration through the gas-slug, and so on. From these results, the flow regime map and the flow patterns at the below and above of the sudden expansion part were classified in relation to the bubble diameter. Additionally, the measurement of the void fraction profiles in the tube cross sections of sudden expansion were conducted at the different axial positions. The void fraction was measured using a point-electrode resistivity probe. The void fraction measurements in this study showed in detail that how the two phase flow develops along the direction of the downstream of the sudden expansion. In just above the sudden expansion, the void fraction distribution appeared the wall peak or the core peak in void fraction in the upstream of the sudden expansion. In the downstream of the sudden expansion, the void fraction distribution changes from a saddle shape or power-low shape into finally the saddle shape as the bubbly flow develops along the downstream of the sudden expansion. These experimental data in the sudden expansion of a vertical upward bubbly flow would become benchmark with respect to the multi-dimensional behavior of the two-phase flow analysis.
2
Kandlbinder, Christoph, Alice Fischerauer, Tristan Zurl, Tobias Helling, Gerhard Fischerauer, Martin Siegl i Jens Gerstmann. "Observation of bubbles inside cryogenic liquids using capacitive multi-electrode sensors". W 2016 13th International Multi-Conference on Systems, Signals & Devices (SSD). IEEE, 2016. http://dx.doi.org/10.1109/ssd.2016.7473739.
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Kondo, Koichi, Kenji Yoshida, Tadayoshi Matsumoto, Tomio Okawa i Isao Kataoka. "Phase Distribution of Air-Water Bubbly Flow in a Vertical Pipe With an Axisymmetric Sudden Expansion". W ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45374.
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Experimental studies were made on the multi-dimensional behavior of upward gas-liquid two-phase flow through a vertical pipe with an axisymmetric sudden expansion, which is one of the typical multi-dimensional channel geometries. The aims of this study are to clarify the multi-dimensional behavior of bubbly and slug flow affected by the sudden expansion channel geometry and to accumulate the experimental data for two-phase flow analysis, which is applicable to predict appropriate accuracy the multi-dimensional behavior. In this report, the first, the observation using high-speed video camera was performed and revealed the multi-dimensional dynamic flow behavior with bubbles and gas-slug affected by the sudden expansion point. From these results, the flow regime map at the below and above of the sudden expansion point were classified with bubble diameter. The second, the variation of the phase distribution in the sudden expansion was measured at the different axial positions using a point-electrode resistivity probe for various gas and liquid flow conditions. Thirdly, the cross-sectional averaged void fractions along the flow direction were calculated by using the one-dimensional two-fluid model considering the phase distribution parameter to confirm the applicability of the computations. As a result, they concretely pointed out that some multi-dimensional modeling or modifications for numerical simulation would be needed for more accurate prediction of two-phase flow. Such radial phase distributions in this study are significant for the multi-dimensional two-phase flow analysis.
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Dupoiron, Marine. "Experimental Study of Gas-Liquid Flow Through a Multi-Stage, Mixed-Flow Electric Submersible Pump". W ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83032.
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Laser Doppler velocimetry (LDV) and high-speed imaging techniques were used in a transparent model of a fourstage, mixed-flow commercial electric submersible pump (ESP) to characterize the flow through a range of inlet gas volume fractions (GVF) from 0 to 30%. Measurements demonstrate the presence high turbulence levels in the wake of the impeller blades, and recirculation cells at low flow rates. In gas-liquid conditions, the bubble size varied within a pump stage, as break-up occurred at the impeller tip, and coalescence was dominant in the diffuser, especially at low flow rates because of recirculation. At moderate-to-high inlet GVF, the first impeller acted as a mixer and the flow patterns at the stage level alternated between bubbly and radially separated flows, as short gas slugs propagated through the stages. The flow patterns at the stage level did not depend on the pump inclination, but the inlet conditions did, with worse performance induced by slugging flows for the horizontal setup.
5
Jinbao, Zhang, Zou Tiangang, Wang Min i Chen Shidong. "Bearing Fault Diagnosis Based on the Refined Composite Generalized Multi-Scale Bubble Entropy". W 2021 4th International Conference on Electron Device and Mechanical Engineering (ICEDME). IEEE, 2021. http://dx.doi.org/10.1109/icedme52809.2021.00044.
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Tsuboi, Ryo, Kazuaki Inaba, Makoto Yamamoto i Dai Kato. "Modeling of Multi-Phase Flow in Electro-Chemical Machining: One-Way Coupling Versus Two-Way Coupling". W ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37594.
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Electro-Chemical Machining (ECM) is an advanced machining technology. It has been applied to highly specialized fields such as aerospace, aeronautics and medical industries. However, it still has some problems to be overcome. The efficient tool-design, electrolyte processing, and disposal of metal hydroxide sludge are the typical issues. To solve such problems, CFD is considered to be a powerful tool in the near future. However, the numerical method that can satisfactorily predict ECM process has not been established because of the complex flow natures. In the present study, we investigate the modeling of the two-phase flow (i.e. fluid and hydrogen bubbles) in ECM process. First, we present two models to calculate flow fields in ECM process. One is based on one-way coupling method, neglecting the effect from gas-phase to liquid-phase. The other takes account of the interaction between gas and liquid phases, namely two-way coupling method. In the later method, assuming that electrolyte and hydrogen bubbles have same velocity, we simplified the governing equations with Low Mach number approximation. We simulated ECM process for a flat plate channel configuration. And, we verified the present models by comparing the numerical result with the experimental data.
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ZHAO, RONG, i GUANG-LIN ZHAO. "INVESTIGATION OF THE MULTIFUNCTIONAL CARBON NANOTUBES-GLASS FIBER-EPOXY COMPOSITES: MICROWAVE ABSORPTION AND MECHANICAL PROPERTIES". W Proceedings for the American Society for Composites-Thirty Seventh Technical Conference. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/asc37/36373.
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With the rapid arising of wireless technology and other microwave applications towards gigahertz frequency in modern communications, microwave absorbing materials (MAM) are playing an increasingly significant role in healthcare, electronic reliability, and defense security. In this work, we aim to explore multifunctional polymer nanocomposites based on carbon nanotubes (CNTs) –epoxy with glass fiber reinforcement, which can be used for microwave absorption and also as structural materials. We fabricated and systematically investigated the mechanical and microwave absorption properties of multi-walled carbon nanotube (MWCNT) - glass fiber (GF) - epoxy composites. Various MWCNT concentrations (1, 3, 5, 7, 9, and 11 wt%) in epoxy resin have been synthesized by shear-mixing method and the reinforcing GF contents (55, 67, and 74 wt%) were controlled by the number of GF plies in the composites. We used low mechanical stirring to avoid introducing air bubbles in MWCNTs - epoxy solution and implemented a press molding (press forces up to 700 N∙cm-2) during the curing process of the composites to reduce voids in the composites. We studied the mechanical properties, electrical conductivity, and microwave absorption properties of the composites, in addition to the morphology and dispersion properties of MWCNTs and GFs in the composites. The scanning electron microscope (SEM) images indicated a more uniform distribution of MWCNTs in epoxy resin than that in the previous work. The microwave absorption measurements of the composites show excellent electromagnetic (EM) wave absorption performance and high reflection loss (RL) at particular frequency range. The maximum RL of the composites can reach to -48 dB at 24.5 GHz for 3.1 wt% MWCNT loadings and 55 wt% GFs in the composites, with an effective bandwidth (i.e., the frequency range for RL below -10 dB) of about ~6 GHz. The EM wave absorption of the composites strongly depends on MWCNT and GF contents and can reach to ~70% at 26.5 GHz with 4.1 wt% MWCNTs in the composite; further, such dependence is peculiar, contradicting to the conventional wisdom, due to the high density interfaces in the materials, which lead to multiple scatterings and multiple absorptions of EM waves. In addition, the tensile strength of the composites was enhanced to ~427 MPa with ~74 wt% GFs, that is comparable to that of commercial Al alloy 6061 (~300 MPa, but not much EM wave absorption). Our results showed that the tensile strength of the MWCNT-GF-epoxy composites was dominated by the contribution of the GF content, while the EM properties are highly impacted by MWCNTs and the interfaces between MWCNT-epoxy matrices and GFs. The mass densities of the composites were about 1.55, 1.73, 1.88 g∙cm-3 for 55, 67, 74 wt% GF reinforced composites, respectively, which are about 30% ~ 43% lighter than the commercial aluminum alloy 6061 (mass density of 2.7 g∙cm-3). The results suggest that the MWCNT-GF-epoxy composites have the potential as multifunctional microwave absorption and low-weight structural materials without the need of additional coating.
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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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Ching, Chan Y., Guanjun Wang i Alfred R. Marshall. "A Multi-Phase Flow Research Facility to Study Oil-Water-Gas Flow Systems". W ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0761.
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Abstract A new flow loop has been constructed at Memorial University of Newfoundland (MUN) to investigate oil-water-gas flows. The facility will initially support the development of an electroquasistatic multiphase flow meter (MPFM) to measure the individual oil-water-gas flow rates of unprocessed oil well streams. The flow loop is a 65 m recirculating open circuit system, and is constructed of 3-inch diameter pipe. There are clear horizontal and vertical test sections for flow visualization. Instrumentation includes several pressure and temperature transducers, and flow meters on the gas and liquid lines to measure the individual gas and liquid flow rates. Electro-pneumatic control valves arc installed on the liquid and air lines to facilitate control of the flow conditions, and a wide range of flow regimes can be generated. Operational control of the loop is implemented through a fully integrated computer system, which also handles the data acquisition. Quantitative flow visualization techniques, in combination with hot-film anemometry measurements are being used to study and characterize the different flow regimes. A new way of presenting flow maps that incorporates the pipe diameter and loop pressure is discussed. Preliminary results indicate that hot-film anemometry is a viable technique to obtain local volume fraction, and convection velocities of the gas slugs/bubbles. A block matching correlation technique is being developed to identify the different flow regimes, and estimate the velocity vectors of the different phases using consecutive frames from flow visualization.
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Warsito, W., i L. S. Fan. "Real Time and Quasi-3D Imaging of Gas-Liquid Flow Using Electrical Capacitance Tomography". W ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45552.
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In this study, an electrical capacitance tomography (ECT) adopted with neural-network based multi-criterion optimization image reconstruction technique (NN-MOIRT) for real time and quasi-3D imaging of gas-liquid flow system is developed. The technique reconstruct the permittivity distribution (tomography image) from capacitance data obtained using 12-electrode twin-plane capacitance sensor. A combined series and parallel capacitance model is used convert the permittivity distribution into gas holdup distribution. Comparison of the overall gas holdups obtained by the ECT with those obtained from the pressure measurements shows a good agreement, validating the model proposed. The ECT is applied to study the hydrodynamic characteristics of the gas-liquid flow system including the bubbly flow structures, gas holdup profiles, and gas holdup variations along with the effect of the gas velocity.