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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.
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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.
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Bello, Valentina, Elisabetta Bodo i Sabina Merlo. "Optical Multi-Parameter Measuring System for Fluid and Air Bubble Recognition". Sensors 23, nr 15 (26.07.2023): 6684. http://dx.doi.org/10.3390/s23156684.
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Detection of air bubbles in fluidic channels plays a fundamental role in all that medical equipment where liquids flow inside patients’ blood vessels or bodies. In this work, we propose a multi-parameter sensing system for simultaneous recognition of the fluid, on the basis of its refractive index and of the air bubble transit. The selected optofluidic platform has been designed and studied to be integrated into automatic pumps for the administration of commercial liquid. The sensor includes a laser beam that crosses twice a plastic cuvette, provided with a back mirror, and a position-sensitive detector. The identification of fluids is carried out by measuring the displacement of the output beam on the detector active surface and the detection of single air bubbles can be performed with the same instrumental scheme, exploiting a specific signal analysis. When a bubble, traveling along the cuvette, crosses the readout light beam, radiation is strongly scattered and a characteristic fingerprint shape of the photo-detected signals versus time is clearly observed. Experimental testing proves that air bubbles can be successfully detected and counted. Their traveling speed can be estimated while simultaneously monitoring the refractive index of the fluid.
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Wang, Tianhao, i Linya Chen. "Thermodynamic Behavior and Energy Transformation Mechanism of the Multi-Period Evolution of Cavitation Bubbles Collapsing near a Rigid Wall: A Numerical Study". Energies 16, nr 3 (17.01.2023): 1048. http://dx.doi.org/10.3390/en16031048.
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The dynamic behavior and energy transformation mechanism of the multi-period evolution of bubbles collapsing near a wall have been essential considerations in bubble dynamics research. In this study, a compressible two-phase solver considering thermodynamics and phase transitions is developed on OpenFOAM (version v2112). This model is validated via comparison with analytical solutions and experimental results. The dynamics of the multi-period evolution of bubbles collapse process at different dimensionless stand-off distances (γ) were accurately reproduced. The results indicate that the shock wave emitted by the collapse of cavitation bubbles impacts the wall, causing the fluid temperature along the wall to increase. Moreover, the liquid jet has a dual effect on the wall temperature increase, depending on the initial stand-off distance between the bubble and the wall. When γ is small, the jet carries the low-temperature fluid to occupy the high-temperature region, and when γ is large, the jet carries the high-temperature fluid to occupy the low-temperature region. Compared with the mechanisms above of wall temperature increase, the collapse process of cavitation, when directly attached to the wall, increases the fluid temperature along the wall more significantly. Additionally, an energy transformation mechanism is proposed considering the internal bubble energy based on the analysis of the internal bubble energy and acoustic radiation energy with different γ values. Both the internal and acoustic radiation energy initially decreased and subsequently increased with increasing γ values. These findings provide deeper insights into the near-wall collapsing cavitation process mechanism.
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Zeng, Yongzhong, i Weilin Xu. "Investigation on Bubble Diameter Distribution in Upward Flow by the Two-Fluid and Multi-Fluid Models". Energies 14, nr 18 (14.09.2021): 5776. http://dx.doi.org/10.3390/en14185776.
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Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow with the unimodal distribution, both the multi-fluid model and the two-fluid model can obtain the distribution of gas volume fraction along the pipe radius. The calculation results of the multi-fluid model agree with the experimental data, while those of the two-fluid model differ greatly from the experimental data, which verifies the advantage of the multi-fluid model in calculating the distribution of gas volume fraction in the polydisperse bubble flow. Meanwhile, the multi-fluid model can be used to accurately predict the distribution of the parameters of each phase of the bubble flow if the reasonable bubble diameter distribution is provided and the appropriate interphase force calculation model is determined.
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Balakrishnan, Kaushik, i Suresh Menon. "A multiphase buoyancy-drag model for the study of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in dusty gases". Laser and Particle Beams 29, nr 2 (22.03.2011): 201–17. http://dx.doi.org/10.1017/s0263034611000176.
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AbstractA new multiphase buoyancy-drag model is developed for the study of Rayleigh-Taylor and Richtmyer-Meshkov instabilities in dusty gases, extending on a counterpart single-phase model developed in the past by Srebro et al. (2003). This model is applied to single- and multi-mode perturbations in dusty gases and both Rayleigh-Taylor and Richtmyer-Meshkov instabilities are investigated. The amplitude for Rayleigh-Taylor growth is observed to be contained within a band, which lies within limits identified by a multiphase Atwood number that is a function of the fluid densities, particle size, and a Stokes number. The amplitude growth is subdued with (1) an increase in particle size for a fixed particle number density and with (2) an increase in particle number density for a fixed particle size. The power law index for Richtmyer-Meshkov growth under multi-mode conditions also shows dependence to the multiphase Atwood number, with the index for the bubble front linearly decreasing and then remaining constant, and increasing non-linearly for the spike front. Four new classes of problems are identified and are investigated for Rayleigh-Taylor growth under multi-mode conditions for a hybrid version of the model: (1) bubbles in a pure gas rising into a region of particles; (2) spikes in a pure gas falling into a region of particles; (3) bubbles in a region of particles rising into a pure gas; and (4) spikes in a region of particles falling into a pure gas. Whereas the bubbles accelerate for class (1) and the spikes for class (4), for classes (2) and (3), the spikes and bubbles, respectively, oscillate in a gravity wave-like phenomenon due to the buoyancy term changing sign alternatively. The spike or bubble front, as the case may be, penetrates different amounts into the dusty or pure gas for every subsequent penetration, due to drag effects. Finally, some extensions to the presently developed multiphase buoyancy-drag model are proposed for future research.
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Ghotra, Harjit Singh. "Multi-pico-Coulomb and multi-GeV electron beam generation from LWFA with a cm scale gas cell". Laser Physics 33, nr 7 (22.05.2023): 076005. http://dx.doi.org/10.1088/1555-6611/acd371.
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Abstract Analytical calculations are made for the scaling and design parameters for the generation of a multi-pico Coulomb and multi-GeV electron beam from a laser Wakefield acceleration (LWFA). The numerical values are optimized for electron acceleration from a cm-scale gas cell and self-guided laser plasma in the bubble domain, where the low-density plasma serves as an accelerating medium. A graphical analysis of the matched parameters is presented for 1–10 GeV electron beam energy gain, where the laser pulse is powered between 30 ∼ 700 TW with delivery capabilities of 1–100 J pulse energy, 25–150 fs pulse duration, and 15–95 μm spot size operating with 1018–19 W cm−2 laser intensity at a plasma density ∼1017 cm−3. The result shows the generation of multi-pico-Coulomb and multi-GeV electron beams. These parameters will be helpful for the future LWFA related experiments using cm scale gas cells in the bubble regime.
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Babay, Mohamed-Amine, Mustapha Adar, Ahmed Chebak i Mustapha Mabrouki. "Dynamics of Gas Generation in Porous Electrode Alkaline Electrolysis Cells: An Investigation and Optimization Using Machine Learning". Energies 16, nr 14 (14.07.2023): 5365. http://dx.doi.org/10.3390/en16145365.
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This paper presents a systematic and comprehensive mathematical model for alkaline water electrolyzer cells, which can be used for simulation and analysis. The model accounts for factors such as gas evolution reactions, dissolution of gases in the electrolyte, bubble formation, and charge transport. It is based on a numerical two-phase model using the Euler-Euler approach, which has been validated against experimental data for various current densities. The study compares the impact of varying potassium hydroxide (KOH) concentration, separator porosity, and electrolyte flow rates on two-phase flow and bubble coverage. Therefore, the electrolyte in the cell consists of a solution of potassium hydroxide in water. The formation of gas bubbles at the electrodes decreases the electrolyte’s ionic conductivity. Additionally, the presence of these bubbles on the electrode surfaces reduces the available surface area for electrochemical reactions, leading to an increase in the overpotential at a given current density. Furthermore, this paper demonstrates how a neural network and ensembled tree model can predict hydrogen production rates in an alkaline water electrolysis process. The trained neural network accurately predicted the hydrogen production rates, indicating the potential of using neural networks for optimization and control of alkaline water electrolysis processes. The model has an average R-squared value of 0.98, indicating a good fit to the data. A new method of describing bubble transfer, “bubble diffusion,” is introduced to improve performance and reduce costs. The model is solved using COMSOL Multi physics 6.0. The machine learning models in this study were built, trained, and tested using MATLAB software R2020a.
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Ali, Asad, Jianping Yuan, Fanjie Deng, Biaobiao Wang, Liangliang Liu, Qiaorui Si i Noman Ali Buttar. "Research Progress and Prospects of Multi-Stage Centrifugal Pump Capability for Handling Gas–Liquid Multiphase Flow: Comparison and Empirical Model Validation". Energies 14, nr 4 (9.02.2021): 896. http://dx.doi.org/10.3390/en14040896.
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The working capability of multi-stage pumps, such as electrical submersible pumps (ESPs) handling multiphase flow, has always been a big challenge for petroleum industries. The major problem is associated with the agglomeration of gas bubbles inside ESP-impellers, causing pump performance degradation ranging from mild to severe deterioration (surging/gas pockets). Previous literature showed that the two-phase performance of ESPs is greatly affected by gas involvement, rotational speed, bubble size, and fluid viscosity. Thus, it is necessary to understand which parameter is actually accountable for performance degradation and different flow patterns in ESP, and how it can be controlled. The present study is mainly focused on (1) the main parameters that impede two-phase performance of different ESPs; (2) comparison of existing empirical models (established for two-phase performance prediction and surging initiation) with our single-stage centrifugal pump results to determine their validity and working-range; (3) gas-handling techniques applied to enhance the multiphase performance of ESPs. Firstly, it aims at understanding the internal flow mechanism in different ESP designs, followed by test studies based on empirical models, visualization techniques, bubble-size measurements, and viscosity analysis. The CFD-based (computational fluid dynamics) numerical analysis concerning multiphase flow is described as well. Furthermore, gas-handling design methods are discussed that are helpful in developing the petroleum industry by enhancing the multiphase performance of ESPs.
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Dehane, Aissa, i Slimane Merouani. "Microscopic Analysis of Hydrogen Production from Methane Sono-Pyrolysis". Energies 16, nr 1 (30.12.2022): 443. http://dx.doi.org/10.3390/en16010443.
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The sonolysis of certain substrates in water has proved its effectiveness for the enhancement of the sonochemical production of hydrogen. In this study, the sonolysis of methane has been investigated for the first time in a single acoustic bubble (microreactor) over a frequency from 140 to 515 kHz. The obtained findings have been compared to those available in the literature. Independently of the methane dose (inside the bubble), the yield of H2 was improved especially with the decrease in wave frequency (from 515 to 140 kHz). For the driving frequencies 140, 213, 355, and 515 kHz, the production of hydrogen was maximized at 20, 15, 10, and 10% CH4, respectively. For 213 kHz, and the presence of 10% methane, the yield of hydrogen goes up by 111 fold compared to the case where the gas atmosphere is saturated only by argon. On the other hand, the highest methane conversions (~100% for 2, 5 and 7% CH4) were retrieved at 140 and 213 kHz. In terms of hydrogen formation and methane decay, the use of 140 kHz was found to be the best choice, whereas for a multi-bubble system, the number of acoustic bubbles should be taken into account for an optimal choice of frequency. Interestingly, it was observed that at 140 and 213 kHz and for methane mole fractions lower than or equal to 30 and 10%, respectively, a maximal formation of H2 and a relatively important production of •OH could result simultaneously.
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Thomas, J., A. Pukhov i I. Yu Kostyukov. "Temporal and spatial expansion of a multi-dimensional model for electron acceleration in the bubble regime". Laser and Particle Beams 32, nr 2 (25.03.2014): 277–84. http://dx.doi.org/10.1017/s0263034614000111.
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AbstractAn extended analytical model for particle dynamics in fields of a highly-nonlinear plasma wakefield (the bubble or blow out regime) is derived. A recently proposed piecewise model is generalized to include a time dependent bubble radius and full field solution in the acceleration direction. Incorporation of the cavity dynamics in the model is required to simulate the particle trapping properly. On the other hand, it is shown that the previously reported piecewise model does not reproduce the formation of a mono energetic peak in the particle spectrum. The mono energetic electron beams are recovered only when the full longitudinal field gradient is included in the model.
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Xu, Hong, Ning Li, Wei Zeng Chen i Bao De Jing. "Microstructure and Electrochemical Properties of Foamed Ni-Mo Alloy by Pulse-Electrodeposition". Advanced Materials Research 305 (lipiec 2011): 378–83. http://dx.doi.org/10.4028/www.scientific.net/amr.305.378.
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A variety of foamed Ni-Mo alloys coatings have been obtained using pulsed electrodeposition technique. The deposit is mainly composed of amorphous structural through the X-ray diffractions (XRD), the morphology clearly contains large amounts of multi-bubble pore structure with pentagonal or hexagonal skeleton structure and obviously stratifys through scanning electron microscopy (SEM) experimentals. This pentagonal or hexagonal skeleton structure and obvious stratification has a larger surface area. The electrolysis experiments show that such foamed alloys have a low hydrogen evolution overpotential and a better corrosion resistance in 25°C, 7mol·L-1 KOH alkaline solution.
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Peng, YuXiang, i Wayne A. Scales. "Satellite Formation Flight Simulation Using Multi-Constellation GNSS and Applications to Ionospheric Remote Sensing". Remote Sensing 11, nr 23 (30.11.2019): 2851. http://dx.doi.org/10.3390/rs11232851.
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The Virginia Tech Formation Flying Testbed (VTFFTB) is a global navigation satellite system (GNSS)-based hardware-in-the-loop (HIL) simulation testbed for spacecraft formation flying with ionospheric remote sensing applications. Past applications considered only the Global Positioning System (GPS) constellation. The rapid GNSS modernization offers more signals from other constellations, including the growing European system—Galileo. This study presents an upgrade of VTFFTB with the incorporation of Galileo and the associated enhanced capabilities. By simulating an ionospheric plasma bubble scenario with a pair of LEO satellites flying in formation, the GPS-based simulations are compared to multi-constellation GNSS simulations including the Galileo constellation. A comparison between multi-constellation (GPS and Galileo) and single-constellation (GPS) shows the absolute mean and standard deviation of vertical electron density measurement errors for a specific Equatorial Spread F (ESF) scenario are decreased by 32.83% and 46.12% with the additional Galileo constellation using the 13 July 2018 almanac. Another comparison based on a simulation using the 8 March 2019 almanac shows the mean and standard deviation of vertical electron density measurement errors were decreased further to 43.34% and 49.92% by combining both GPS and Galileo data. A sensitivity study shows that the Galileo electron density measurements are correlated with the vertical separation of the formation configuration. Lower C/N 0 level increases the measurement errors and scattering level of vertical electron density retrieval. Relative state estimation errors are decreased, as well by utilizing GPS L1 plus Galileo E1 carrier phase instead of GPS L1 only. Overall, superior performance on both remote sensing and relative navigation applications is observed by adding Galileo to the VTFFTB.
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Cheng, K. S., D. O. Chernyshov, V. A. Dogiel i C. M. Ko. "MULTI-WAVELENGTH EMISSION FROM THEFERMIBUBBLE. II. SECONDARY ELECTRONS AND THE HADRONIC MODEL OF THE BUBBLE". Astrophysical Journal 799, nr 1 (20.01.2015): 112. http://dx.doi.org/10.1088/0004-637x/799/1/112.
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Salihi, Hassan, i Hyunchul Ju. "Two-Phase Modeling and Simulations of a Polymer Electrolyte Membrane Water Electrolyzer Considering Key Morphological and Geometrical Features in Porous Transport Layers". Energies 16, nr 2 (9.01.2023): 766. http://dx.doi.org/10.3390/en16020766.
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Polymer electrolyte membrane (PEM) electrolysis has a promising future for large-scale hydrogen production. As PEM electrolysis technology develops, larger operating current densities are required. In order to increase current density, more water should be available at the reaction sites. Moreover, the removal rate of oxygen and hydrogen needs to be effectively improved. This, in turn, necessitates a better understanding of the main mass transport and electrochemical processes. On the anode side, mass transport is particularly crucial because water must be supplied to the catalyst layer (CL) while, at the same time, oxygen bubbles must be eliminated in a parallel flow from the reaction sites into the flow channels. Hence, simulating the two-phase bubbly flow across the cell thickness is necessary to predict PEM electrolysis performance more accurately as a function of the operating current density. This study provides a systematic understanding of how morphological and geometrical features contribute to the polarization curve and performance characteristics of a PEM electrolysis cell. Hence, a multi-phase PEM electrolysis model has been implemented using MATLAB R2022a. Polarization curves have been calibrated against experimental data and then assessed to provide a fundamental understanding of the relationship between the two-phase flow and cell performance.
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Cheng, K. S., D. O. Chernyshov, V. A. Dogiel i C. M. Ko. "MULTI-WAVELENGTH EMISSION FROM THE FERMI BUBBLE. III. STOCHASTIC (FERMI) RE-ACCELERATION OF RELATIVISTIC ELECTRONS EMITTED BY SNRs". Astrophysical Journal 804, nr 2 (12.05.2015): 135. http://dx.doi.org/10.1088/0004-637x/804/2/135.
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Piestrak, S. J., i A. Dandache. "Minimal test set for multi-output threshold circuits implemented as bubble sorting networks". Electronics Letters 36, nr 3 (2000): 202. http://dx.doi.org/10.1049/el:20000226.
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Shi, Haotian, Dian Huo, Hongpeng Zhang, Wei Li, Yuqing Sun, Guobin Li i Haiquan Chen. "An Impedance Sensor for Distinguishing Multi-Contaminants in Hydraulic Oil of Offshore Machinery". Micromachines 12, nr 11 (17.11.2021): 1407. http://dx.doi.org/10.3390/mi12111407.
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The cleanliness of hydraulic oil can reflect the service life of the oil and the wear state of hydraulic machinery. An impedance sensor is proposed to distinguish multi-contaminants in hydraulic oil. The impedance sensor has two detection modes: the inductance-resistance mode is used to detect metal debris, and the capacitance mode is used to distinguish water droplets and air bubbles. By adding a built-in silicon steel strip and an external silicon steel strip with high magnetic permeability, the distribution area, strength, and uniformity of the magnetic field are enhanced to improve the detection sensitivity under inductance and resistance parameters. In addition, the silicon steel strips are used as electrode plates to introduce capacitance parameter detection. The experimental results show that the resistance detection method based on coil successfully improves the detection ability for non-ferromagnetic metal debris. The impedance sensor for distinguishing multi-contaminants in hydraulic oil can provide technical support for fault diagnosis of offshore hydraulic machinery.
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Alatefi, Saad, i Abdullah M. Almeshal. "A New Model for Estimation of Bubble Point Pressure Using a Bayesian Optimized Least Square Gradient Boosting Ensemble". Energies 14, nr 9 (5.05.2021): 2653. http://dx.doi.org/10.3390/en14092653.
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Accurate estimation of crude oil Bubble Point Pressure (Pb) plays a vital rule in the development cycle of an oil field. Bubble point pressure is required in many petroleum engineering calculations such as reserves estimation, material balance, reservoir simulation, production equipment design, and optimization of well performance. Additionally, bubble point pressure is a key input parameter in most oil property correlations. Thus, an error in a bubble point pressure estimate will definitely propagate additional error in the prediction of other oil properties. Accordingly, many bubble point pressure correlations have been developed in the literature. However, they often lack accuracy, especially when applied for global crude oil data, due to the fact that they are either developed using a limited range of independent variables or developed for a specific geographic location (i.e., specific crude oil composition). This research presents a utilization of the state-of-the-art Bayesian optimized Least Square Gradient Boosting Ensemble (LS-Boost) to predict bubble pointpressure as a function of readily available field data. The proposed model was trained on a global crude oil database which contains (4800) experimentally measured, Pressure–Volume–Temperature (PVT) data sets of a diverse collection of crude oil mixtures from different oil fields in the NorthSea, Africa, Asia, Middle East, and South and North America. Furthermore, an independent (775) PVT data set, which was collected from open literature, was used to investigate the effectiveness of the proposed model to predict the bubble point pressure from data that were not used during the model development process. The accuracy of the proposed model was compared to several published correlations (13 in total for both parametric and non-parametric models) as well as two other machine learning techniques, Multi-Layer Perceptron Neural Networks (MPL-ANN) and Support Vector Machines (SVM). The proposed LS-Boost model showed superior performance andremarkably outperformed all bubble point pressure models considered in this study.
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Tomaz, Raíssa Mendes, i Jerzui Mendes Torres Tomaz. "The Brazilian Presidential Election of 2018 and the relationship between technology and democracy in Latin America". Journal of Information, Communication and Ethics in Society 18, nr 4 (11.01.2020): 497–509. http://dx.doi.org/10.1108/jices-12-2019-0134.
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Purpose The purpose of this paper selected by ICIL 2019 committee in Rome is to demonstrate the current importance of the internet in the protection of democracy in developting countries. Design/methodology/approach It is intended to make a comparison with the growing and current phenomenon of Brazilian disinformation with other contemporary phenomena related to new technologies through literature review methodology. Findings The Brazilian elections in 2018 represent an authentic model in a post-Cambridge Analytical phase where the myth of the sanctity of data has been broken. The big influence of the algorithmic revolution on democracies in Latin America has never been more evident. The misuse of algorithms created an artificial environment that does not put us in contact with different realities; the consequences of this conjuncture have the deepest impacts, especially in countries that rely on a deficient educational system. Social implications Besides that, the broad use of zero-rating on the internet delivery in developing countries is also considered a factor of fake news dissemination. The information bubbles promote political polarization to the detriment of diversity – and the diversity is par excellence one of the pillars of democracy. Originality/value The research about the impact that the phenomenon of disinformation has on underdeveloped countries, it is essential to analyze the new role of the legislator in the elaboration of hypercomplex laws with multi-stakeholder interests that respect the essential core of digital human rights as the freedom of expression online.
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Gruter, Lars, Richard Nauber i Jurgen W. Czarske. "Ultrasonic Bubble Imaging in Molten Salt Using a Multi-Mode Waveguide and Time Reversal". IEEE Transactions on Instrumentation and Measurement 71 (2022): 1–10. http://dx.doi.org/10.1109/tim.2022.3144739.
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Es-Souni, Mohammed. "Exploiting Interfacial Effects between Collapsing Bubbles and Nanocarbon/TiN Substrates for the Green Synthesis of Self-Organized Noble Metal and Nanoalloy Nanoparticles". Micromachines 14, nr 6 (28.05.2023): 1141. http://dx.doi.org/10.3390/mi14061141.
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Noble metal nanoparticles and multi-materials thereof are processed on a substrate from aqueous solutions of the metallic ions, precluding any chemical additives/catalysts. The methods reported here take advantage of interactions between collapsing bubbles and the substrate that result in the generation of reducing radicals at the substrate surface and leading to the reduction of the metal ions on those sites, followed by nucleation and growth. Two selected substrates where these phenomena take place are nanocarbon and TiN. By either using ultrasonic radiation of the substrate in ionic solution or quenching the substrate in a solution from temperatures above the Leidenfrost temperature, a high density of nanoparticles of Au, Au/Pt, Au/Pd and Au/Pd/Pt are synthesized on the substrate surface. The sites where the reducing radicals are generated determine the self-assembly of the nanoparticles. The methods yield highly adherent surface films and nanoparticles; they are materials efficient and cost effective because only the surface is modified with costly materials. The formation mechanisms of these green multi-material NPs are described. Outstanding electrocatalytic performances in acidic solutions of methanol and formic acid are demonstrated.
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Paulik, Róbert, Miklós Kozlovszky i Béla Molnár. "Regression Based Iterative Illumination Compensation Method for Multi-Focal Whole Slide Imaging System". Sensors 21, nr 21 (26.10.2021): 7085. http://dx.doi.org/10.3390/s21217085.
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Image quality, resolution and scanning time are critical in digital pathology. In order to create a high-resolution digital image, the scanner systems execute stitching algorithms to the digitized images. Due to the heterogeneity of the tissue sample, complex optical path, non-acceptable sample quality or rapid stage movement, the intensities on pictures can be uneven. The evincible and visible intensity distortions can have negative effect on diagnosis and quantitative analysis. Utilizing the common areas of the neighboring field-of-views, we can estimate compensations to eliminate the inhomogeneities. We implemented and validated five different approaches for compensating output images created with an area scanner system. The proposed methods are based on traditional methods such as adaptive histogram matching, regression-based corrections and state-of-the art methods like the background and shading correction (BaSiC) method. The proposed compensation methods are suitable for both brightfield and fluorescent images, and robust enough against dust, bubbles, and optical aberrations. The proposed methods are able to correct not only the fixed-pattern artefacts but the stochastic uneven illumination along the neighboring or above field-of-views utilizing iterative approaches and multi-focal compensations.
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Huang, Liang, Yi Liu, Qiong Tang, Guanyi Chen, Zhuangkai Wang i Chen Zhou. "Investigation of the Occurrence of Nighttime Topside Ionospheric Irregularities in Low-Latitude and Equatorial Regions Using CYGNSS Satellites". Sensors 20, nr 3 (28.01.2020): 708. http://dx.doi.org/10.3390/s20030708.
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By using multi-satellite observations of the L1 signal-to-noise ratio (SNR) from the Cyclone Global Navigation Satellite System (CYGNSS) taken in 2017, we present the occurrence of nighttime topside ionospheric irregularities in low-latitude and equatorial regions. The most significant finding of this study is the existence of longitudinal structures with a wavenumber 4 pattern in the topside irregularities. This suggests that lower atmospheric waves, especially a daytime diurnal eastward-propagating zonal wave number-3 nonmigrating tide (DE3), might play an important role in the generation of topside plasma bubbles during the low solar minimum. Observations of scintillation events indicate that the maximum occurrence of nighttime topside ionospheric irregularities occurs on the magnetic equator during the equinoxes. The current work, which could be regarded as an important update of the previous investigations, would be readily for the further global analysis of the topside ionospheric irregularities.
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Syromyatnikov, A. G. "On some features of possible torsion effects on observables at Hadron colliders". International Journal of Geometric Methods in Modern Physics 12, nr 10 (25.10.2015): 1550080. http://dx.doi.org/10.1142/s0219887815500802.
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I give a geometrical description of conformal gauge gravitational theory (CGTG) from the viewpoint of symmetries and affine structure. In the frames of the CGTG incorporating gravitation with torsion space-time into Standard Model of electro-weak interaction (EWI) the multi-muon events produced at the Fermilab Tevatron collider were studied. The CGTG gives the value of the torsion pseudotrace–spinor (muon) universal coupling fT = 4.388 ⋅ 10-17 GF, and with limits from known experiments — torsion mass mT = 0.4700 ⋅ 10-7 eV or mT = 0.445 ⋅ 10-15 muon mass. So the value of the constant of effective four-fermions interaction fT/mT = 0.988, indeed may lead to multi-muon events production. The model of interaction of quantum oscillator with the tensor potential Wμν of traceless part of the torsion lead to 2 cm displacement of quark–lepton system as a whole in the magnetic field of collider in accordance with a significant sample of events related to [Formula: see text] production and decay in which at least one of the muon candidates is produced outside of the beam pipe of radius 1.5 cm. A traceless part of the torsion in CGTG does not vanish in the Newtonian limit of nonzero mass. Torsion gravity potential Wμν gives conservation of a special conformal current and may be produced in the condition of a spontaneous breaking of gauge symmetry where the gravitation mass MX defect is 1–3 Tev ⋅ c-2 or 10-13MX. This effect may be possible at known effects on top pair asymmetries at the Tevatron and LHC and takes place as the known energy dissipation above 3 TeV of the Galaxy gamma-ray and neutrino spectrum from two bubbles outside the Galaxy plane.
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Cardoso, Rafael M., Robson O. dos Santos, Rodrigo A. A. Munoz, Carlos D. Garcia i Lucas Blanes. "A Multi-Pump Magnetohydrodynamics Lab-On-A-Chip Device for Automated Flow Control and Analyte Delivery". Sensors 20, nr 17 (31.08.2020): 4909. http://dx.doi.org/10.3390/s20174909.
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This article shows the development of a computer-controlled lab-on-a-chip device with three magnetohydrodynamic (MHD) pumps and a pneumatic valve. The chip was made of a stack of layers of polymethylmethacrylate (PMMA), cut using a laser engraver and thermally bonded. The MHD pumps were built using permanent magnets (neodymium) and platinum electrodes, all of them controlled by an Arduino board and a set of relays. The implemented pumps were able to drive solutions in the open channels with a flow rate that increased proportionally with the channel width and applied voltage. To address the characteristic low pressures generated by this kind of pump, all channels were interconnected. Because the electrodes were immersed in the electrolyte, causing electrolysis and pH variations, the composition and ionic strength of the electrolyte solution were controlled. Additionally, side structures for releasing bubbles were integrated. With this multi-pump and valve solution, the device was used to demonstrate the possibility of performing an injection sequence in a system that resembles a traditional flow injection analysis system. Ultimately, the results demonstrate the possibility of performing injection sequences using an array of MHD pumps that can perform fluid handling in the 0–5 µL s−1 range.
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Lugomer, Stjepan. "Laser–matter interactions: Inhomogeneous Richtmyer–Meshkov and Rayleigh–Taylor instabilities". Laser and Particle Beams 34, nr 1 (6.01.2016): 123–36. http://dx.doi.org/10.1017/s0263034615000956.
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AbstractIn this experimental study, the ablative Richtmyer–Meshkov (RM) and the Rayleigh–Taylor (RT) instabilities were generated by the laser pulse of Gaussian-like power profile. The initial multi-modal perturbation, the inhomogeneous momentum transfer and different Atwood numbers generate different shapes of spikes and bubbles in the central region (CR) and the near-central region (NCR) of the spot. A one-dimensional Gaussian-like power profile causes the formation of the wavy-like rows of aperiodic spikes. The periodic spike segments inside the rows appear due to locally coherent flow. In the NCR, the mushroom-shape spikes tend to the organization on the isotropic square and the anisotropic rhombic lattices. The increase of the lattice periods two, three, or four times indicates formation of superstructures. The growth of sharp asymmetric RM/RT spikes in the CR is fast, uncorrelated and linear, while the growth of the symmetric mushroom-shape ones in the NCR is slow, correlated, and nonlinear.
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Teixidó, Pedro, José M. Hinojo-Montero, Juan Antonio Gómez-Galán, Fernando Muñoz-Chavero, Trinidad Sánchez-Rodríguez i Juan Aponte. "Controlled Electromagnetic Field Based Safety System for Handheld Circular Saw". Sensors 22, nr 22 (8.11.2022): 8593. http://dx.doi.org/10.3390/s22228593.
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This paper presents the design of a safety system based on controlled electromagnetic field (CEMF) sensing technology to prevent accidents caused by power tools, especially related to handheld circular saws. The safety system creates an invisible protection bubble of electromagnetic field around the cutting edge. The system can provide early warning or critical warning when a person penetrates the safety bubble. This paper covers how the CEMF technology has been adapted to add value within this application where it needs to coexist with a difficult environment of metallic parts turning thousands of times per minute, strong vibrations, and different ranges of materials to be processed. The proposed contactless solution successfully detects the user, providing enough time for the power tool to totally stop its movement before touching and harming the user. This key property has required a careful optimization of the electromagnetic field generation, the design of a shield circuitry capable of operating properly in a large metal device, and the development of a multi-frame algorithm to address the stringent requirements related to the ability of the system to react to both very fast and very slow events. The feasibility of the system has been validated by a virtual testbench.
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Li, Zhaolong, Wangwang Li i Bingren Cao. "Simulation Analysis of Multi-Physical Field Coupling and Parameter Optimization of ECM Miniature Bearing Outer Ring Based on the Gas-Liquid Two-Phase Turbulent Flow Model". Micromachines 13, nr 6 (7.06.2022): 902. http://dx.doi.org/10.3390/mi13060902.
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Electrochemical machining (ECM) is an essential method for machining miniature bearing outer rings on the high-temperature-resistant nickel-based alloy GH4169. However, the influence of electrolyte temperature distribution and bubble rate distribution on electrolyte conductivity in the ECM area could not be fully considered, resulting in the simulation model not being able to accurately predict the machining accuracy of the outer ring of the miniature bearing, making it challenging to model and predict the optimal process parameters. In this paper, a multiphysics field coupled simulation model of electric, flow, and temperature fields during the ECM of the miniature bearing outer ring is established based on the gas–liquid two-phase turbulent flow model. The simulation analyzed the distribution of electrolyte temperature, bubble rate, flow rate, and current density in the machining area, and the profile change of the outer ring of the miniature bearing during the machining process. The analysis of variance and significance of machining voltage, electrolyte concentration, electrolyte inlet flow rate, and interaction on the mean error of the ECM miniature bearing outer rings was derived from the central composite design. The regression equation between the average error and the process parameters was established, and the optimal combination of process parameters for the average error was predicted, i.e., the minimum value of 0.014 mm could be achieved under the conditions of a machining voltage of 16.20 V, an electrolyte concentration of 9.29%, and an electrolyte inlet flow rate of 11.84 m/s. This is important to improve the machining accuracy of the outer ring of the ECM miniature bearing.
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Murakawa, Hideki, Hiroshige Kikura i Masanori Aritomi. "Application of ultrasonic multi-wave method for two-phase bubbly and slug flows". Flow Measurement and Instrumentation 19, nr 3-4 (czerwiec 2008): 205–13. http://dx.doi.org/10.1016/j.flowmeasinst.2007.06.010.
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Kang, Daehoon, Sungho Yun i Bo-kyong Kim. "Review of the Liquid Hydrogen Storage Tank and Insulation System for the High-Power Locomotive". Energies 15, nr 12 (15.06.2022): 4357. http://dx.doi.org/10.3390/en15124357.
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Hydrogen has been attracting attention as a fuel in the transportation sector to achieve carbon neutrality. Hydrogen storage in liquid form is preferred in locomotives, ships, drones, and aircraft, because these require high power but have limited space. However, liquid hydrogen must be in a cryogenic state, wherein thermal insulation is a core problem. Inner materials, including glass bubbles, multi-layer insulation (MLI), high vacuum, and vapor-cooled shields, are used for thermal insulation. An analytic study is preferred and proceeds liquid hydrogen tanks due to safety regulations in each country. This study reviewed the relevant literature for thermodynamic modeling. The literature was divided into static, dynamic, and systematic studies. In summary, the authors summarized the following future research needs: The optimal design of the structure, including suspension, baffle, and insulation system, can be studied to minimize the boil-off gas (BOG). A dynamic study of the pressure, mass flow, and vaporizer can be completed. The change of the components arrangement from the conventional diesel–electric locomotive is necessary.
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Bian, Sizhen, Peter Hevesi, Leif Christensen i Paul Lukowicz. "Induced Magnetic Field-Based Indoor Positioning System for Underwater Environments". Sensors 21, nr 6 (22.03.2021): 2218. http://dx.doi.org/10.3390/s21062218.
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Autonomous underwater vehicles (AUV) are seen as an emerging technology for maritime exploration but are still restricted by the availability of short range, accurate positioning methods necessary, e.g., when docking remote assets. Typical techniques used for high-accuracy positioning in indoor use case scenarios, such as systems using ultra-wide band radio signals (UWB), cannot be applied for underwater positioning because of the quick absorption of the positioning medium caused by the water. Acoustic and optic solutions for underwater positioning also face known problems, such as the multi-path effects, high propagation delay (acoustics), and environmental dependency. This paper presents an oscillating magnetic field-based indoor and underwater positioning system. Unlike those radio wave-based positioning modalities, the magnetic approach generates a bubble-formed magnetic field that will not be deformed by the environmental variation because of the very similar permeability of water and air. The proposed system achieves an underwater positioning mean accuracy of 13.3 cm in 2D and 19.0 cm in 3D with the multi-lateration positioning method and concludes the potential of the magnetic field-based positioning technique for underwater applications. A similar accuracy was also achieved for various indoor environments that were used to test the influence of cluttered environment and of cross environment. The low cost and power consumption system is scalable for extensive coverage area and could plug-and-play without pre-calibration.
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Dulin, Vladimir, Andrey Cherdantsev, Roman Volkov i Dmitriy Markovich. "Application of Planar Laser-Induced Fluorescence for Interfacial Transfer Phenomena". Energies 16, nr 4 (14.02.2023): 1877. http://dx.doi.org/10.3390/en16041877.
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The present review describes the current achievements in the applications of a planar laser-induced fluorescence (PLIF) method for the diagnostics of liquid films, bubbles, individual droplets, and sprays. Such flows are related with strongly curved interphases, which often results in additional high errors during the PLIF data quantification because of laser light reflection, refraction, and absorption. The present review demonstrates that a two-color PLIF approach and a PLIF modification for regularly structured illumination resolves the reflection- and refraction-caused errors. The latter modification ensures proper phase separation in the measurement cross-section and visualization of the interface dynamics. The former approach provides the accurate evaluation of the local temperature and concentration both in liquid and gaseous phases even in the case of strong variations of the laser sheet intensity. With intensified cameras, the PLIF method is used for multi-parameter diagnostics of the two-phase combustion of sprays in combustion chambers with optical access. It visualizes and quantifies the liquid fuel evaporation and mixing, to measure temperature in the gas and liquid phases and to reveal the regions of pollutant formation. The PLIF technique can also be easily combined with a particle image (or tracking) velocimetry method, to evaluate local heat and mass transfer.
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Gordeychuk, T. V., i M. V. Kazachek. "Time-Correlated Photon Counting for Estimating the Duration of Na-Line and Continuum Emission Flashes in the Spectra of Multi-Bubble Sonoluminescence". Optics and Spectroscopy 128, nr 10 (październik 2020): 1602–10. http://dx.doi.org/10.1134/s0030400x20100124.
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Bertocci, Francesco, Andrea Grandoni i Tatjana Djuric-Rissner. "Scanning Acoustic Microscopy (SAM): A Robust Method for Defect Detection during the Manufacturing Process of Ultrasound Probes for Medical Imaging". Sensors 19, nr 22 (8.11.2019): 4868. http://dx.doi.org/10.3390/s19224868.
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The main aim of this paper is to provide the feasibility of non-destructive testing (NDT) method, such as scanning acoustic microscopy (SAM), for damage detection in ultrasound (US) probes for medical imaging during the manufacturing process. In a highly competitive and demanding electronics and biomedical market, reliable non-destructive methods for quality control and failure analysis of electronic components within multi-layered structures are strongly required. Any robust non-destructive method should be capable of dealing with the complexity of miniaturized assemblies, such as the acoustic stack of ultrasonic transducers. In this work, the application of SAM in an industrial scenario was studied for 24 samples of a phased array probe, in order to investigate potential internal integrity, to detect damages, and to assess the compliance of high-demanding quality requirements. Delamination, non-homogeneous layers with micron-thickness, and entrapped air bubbles (blisters) in the bulk of US probe acoustic stacks were detected and studied. Analysis of 2D images and defects visualization by means of ultrasound-based NDT method were compared with electroacoustic characterization (also following as pulse-echo test) of the US probe through an ad-hoc measurement system. SAM becomes very useful for defect detection in multilayered structures with a thickness of some microns by assuring low time-consuming (a limit for other NDT techniques) and quantitative analyses based on measurements. The study provides a tangible contribution and identifies an advantage for manufacturers of ultrasound probes that are oriented toward continuous improvement devoted to the process capability, product quality, and in-process inspection.
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Nadimi-Shahraki, Mohammad H., Shokooh Taghian, Seyedali Mirjalili, Laith Abualigah, Mohamed Abd Elaziz i Diego Oliva. "EWOA-OPF: Effective Whale Optimization Algorithm to Solve Optimal Power Flow Problem". Electronics 10, nr 23 (29.11.2021): 2975. http://dx.doi.org/10.3390/electronics10232975.
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The optimal power flow (OPF) is a vital tool for optimizing the control parameters of a power system by considering the desired objective functions subject to system constraints. Metaheuristic algorithms have been proven to be well-suited for solving complex optimization problems. The whale optimization algorithm (WOA) is one of the well-regarded metaheuristics that is widely used to solve different optimization problems. Despite the use of WOA in different fields of application as OPF, its effectiveness is decreased as the dimension size of the test system is increased. Therefore, in this paper, an effective whale optimization algorithm for solving optimal power flow problems (EWOA-OPF) is proposed. The main goal of this enhancement is to improve the exploration ability and maintain a proper balance between the exploration and exploitation of the canonical WOA. In the proposed algorithm, the movement strategy of whales is enhanced by introducing two new movement strategies: (1) encircling the prey using Levy motion and (2) searching for prey using Brownian motion that cooperate with canonical bubble-net attacking. To validate the proposed EWOA-OPF algorithm, a comparison among six well-known optimization algorithms is established to solve the OPF problem. All algorithms are used to optimize single- and multi-objective functions of the OPF under the system constraints. Standard IEEE 6-bus, IEEE 14-bus, IEEE 30-bus, and IEEE 118-bus test systems are used to evaluate the proposed EWOA-OPF and comparative algorithms for solving the OPF problem in diverse power system scale sizes. The comparison of results proves that the EWOA-OPF is able to solve single- and multi-objective OPF problems with better solutions than other comparative algorithms.
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Basu, Abhirup, Mayur K. Temgire, Akkihebbal K. Suresh i Jayesh R. Bellare. "Dilution-Induced Physico-Chemical Changes of Metal Oxide Nanoparticles Due to Homeopathic Preparation Steps of Trituration and Succussion". Homeopathy 109, nr 02 (25.10.2019): 065–78. http://dx.doi.org/10.1055/s-0039-1694720.
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Abstract Background Although the presence of starting materials in extreme dilutions of homeopathic medicines has been established, the physico-chemical changes of these materials induced by the manufacturing steps—that is, solid–solid mixing involving grinding (trituration) and slurry mixing involving impact (succussion), followed by dilution—are still unknown. Methods We subjected cupric oxide and zinc oxide nanoparticles (NPs) to the homeopathic processes of trituration and succussion, followed by dilution up to 6 cH. Particle image velocimetry was employed to analyze the fluid motion during succussion and its effect on the NPs. The resulting microstructural and chemical changes at different dilution steps were determined by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy. Results The succussion triggered multi-sized bubble generation and turbulent fluid motion up to a duration of 400 ms, with maximum average velocity of 0.23 m/s. Due to 1% transfer of kinetic energy from a moving eddy with this velocity, upon collision, the rate of temperature change in a particle of size 1 µm and 1 nm was predicted to rise by approximately 102 K/s and 106 K/s respectively. During trituration, the oxide NPs reduced to metals and did not aggregate by remaining within lactose, but they converted to oxidized finer NPs after impact. Silicate chains leached from the vial cross-linked after third dilution, forming large macro-particles and encapsulating the NPs that were retained and carried at higher dilution steps. Conclusion The results showed that the NPs sustained significant rate of temperature change due to energy transfer from moving eddies during succussion. Different physico-chemical changes, such as size reduction, successive reduction and oxidation of NPs, and morphological changes, were achieved through trituration and succussion. The retention of NPs within cross-linked poly-siloxane chains reveals the importance of both the borosilicate glass vial and the ethanol solution during preparation of homeopathic medicines.
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Su, Erjie, Yongzhi Tian, Erjun Liang, Jiayu Wang i Yibo Zhang. "A Multiscale Instance Segmentation Method Based on Cleaning Rubber Ball Images". Sensors 23, nr 9 (25.04.2023): 4261. http://dx.doi.org/10.3390/s23094261.
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The identification of wear rubber balls in the rubber ball cleaning system in heat exchange equipment directly affects the descaling efficiency. For the problem that the rubber ball image contains impurities and bubbles and the segmentation is low in real time, a multi-scale feature fusion real-time instance segmentation model based on the attention mechanism is proposed for the object segmentation of the rubber ball images. First, we introduce the Pyramid Vision Transformer instead of the convolution module in the backbone network and use the spatial-reduction attention layer of the transformer to improve the feature extraction ability across scales and spatial reduction to reduce computational cost; Second, we improve the feature fusion module to fuse image features across scales, combined with an attention mechanism to enhance the output feature representation; Third, the prediction head separates the mask branches separately. Combined with dynamic convolution, it improves the accuracy of the mask coefficients and increases the number of upsampling layers. It also connects the penultimate layer with the second layer feature map to achieve detection of smaller images with larger feature maps to improve the accuracy. Through the validation of the produced rubber ball dataset, the Dice score, Jaccard coefficient, and mAP of the actual segmented region of this network with the rubber ball dataset are improved by 4.5%, 4.7%, and 7.73%, respectively, and our model achieves 33.6 fps segmentation speed and 79.3% segmentation accuracy. Meanwhile, the average precision of Box and Mask can also meet the requirements under different IOU thresholds. We compared the DeepMask, Mask R-CNN, BlendMask, SOLOv1 and SOLOv2 instance segmentation networks with this model in terms of training accuracy and segmentation speed and obtained good results. The proposed modules can work together to better handle object details and achieve better segmentation performance.
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Lobsinger, Thomas, Timm Hieronymus, Hubert Schwarze i Gunther Brenner. "A CFD-Based Comparison of Different Positive Displacement Pumps for Application in Future Automatic Transmission Systems". Energies 14, nr 9 (27.04.2021): 2501. http://dx.doi.org/10.3390/en14092501.
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The efficiency requirements for hydraulic pumps applied in automatic transmissions in future generations of automobiles will increase continuously. In addition, the pumps must be able to cope with multiphase flows to a certain extent. Given this background, a balanced vane pump (BVP), an internal gear pump (IGP) and a three-dimensional geared tumbling multi chamber (TMC) pump are analyzed and compared by a computational fluid dynamics (CFD) approach with ANSYS CFX and TwinMesh. Furthermore, test bench measurements are conducted to obtain experimental data to validate the numerical results. The obtained numerical results show a reasonable agreement with the experimental data. In the first CFD setup, the conveying characteristics of the pumps with pure oil regarding volumetric efficiencies, cavitation onset and pressure ripple are compared. Both the IGP and the BVP show high volumetric efficiencies and low pressure ripples whereas the TMC shows a weaker performance regarding these objectives. In the second CFD setup, an oil-bubbly air multiphase flow with different inlet volume fractions (IGVF) is investigated. It can be shown that free air changes the pumping characteristics significantly by increasing pressure and mass flow ripple and diminishing the volumetric efficiency as well as the required driving torque. The compression ratios of the pumps appear to be an important parameter that determines how the multiphase flow is handled regarding pressure and mass flow ripple. Overall, the BVP and the IGP show both a similar strong performance with and without free air. In the current development state, the TMC pump shows an inferior performance because of its lower compression ratio and therefore needs further optimization.
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Furuya, Kazuo, Min Piao, Nobuhiro Ishikawa i Tetsuya Saito. "High Resolution Transmission Electron Microscopy of Defect Clusters in Aluminum During Electron and Ion Irradiation at Room Temperature". MRS Proceedings 439 (1996). http://dx.doi.org/10.1557/proc-439-331.
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AbstractDefect clusters in Al during electron and ion irradiation have been investigated using highresolution transmission electron microscopy (HRTEM). An ION/HVEM system which consists of a high-voltage TEM and ion implanters was used for in-situ observation of damage evolution under 1000 keV electrons and 15 keV He+ irradiation at room temperature. HRTEM of Al in [110] orientation showed many planar defects along { 111 } planes during electron irradiation, while a high density of small polyhedron-shaped cavities (He-bubbles) was observed in addition to the planar defects after He+ irradiation. Multi-slice image simulation of various models of dislocation loops indicated the planar defect as an interstitial-type Frank loop.
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Aa, Ercha, Shun-Rong Zhang, Anthea J. Coster, Philip J. Erickson i William Rideout. "Multi-instrumental analysis of the day-to-day variability of equatorial plasma bubbles". Frontiers in Astronomy and Space Sciences 10 (21.03.2023). http://dx.doi.org/10.3389/fspas.2023.1167245.
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This paper presents a multi-instrument observational analysis of the equatorial plasma bubbles (EPBs) variation over the American sector during a geomagnetically quiet time period of 07–10 December 2019. The day-to-day variability of EPBs and their underlying drivers are investigated through coordinately utilizing the Global-scale Observations of Limb and Disk (GOLD) ultraviolet images, the Ionospheric Connection Explorer (ICON) in-situ and remote sensing data, the global navigation satellite system (GNSS) total electron content (TEC) observations, as well as ionosonde measurements. The main results are as follows: 1) The postsunset EPBs’ intensity exhibited a large day-to-day variation in the same UT intervals, which was fairly noticeable in the evening of December 07, yet considerably suppressed on December 08 and 09, and then dramatically revived and enhanced on December 10. 2) The postsunset linear Rayleigh-Taylor instability growth rate exhibited a different variation pattern. It had a relatively modest peak value on December 07 and 08, yet a larger peak value on December 09 and 10. There was a 2-h time lag of the growth rate peak time in the evening of December 09 from other nights. This analysis did not show an exact one-to-one relationship between the peak growth rate and the observed EPBs intensity. 3) The EPBs’ day-to-day variation has a better agreement with that of traveling ionospheric disturbances and atmospheric gravity waves signatures, which exhibited relatively strong wavelike perturbations preceding/accompanying the observed EPBs on December 07 and 10 yet relatively weak fluctuations on December 08 and 09. These coordinate observations indicate that the initial wavelike seeding perturbations associated with AGWs, together with the catalyzing factor of the instability growth rate, collectively played important roles to modulate the day-to-day variation of EPBs. A strong seeding perturbation could effectively compensate for a moderate strength of Rayleigh-Taylor instability growth rate and therefore their combined effect could facilitate EPB development. Lacking proper seeding perturbations would make it a more inefficient process for the development of EPBs, especially with a delayed peak value of Rayleigh-Taylor instability growth rate.
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Gomez Socola, Josemaria, i Fabiano S. Rodrigues. "ScintPi 2.0 and 3.0: low-cost GNSS-based monitors of ionospheric scintillation and total electron content". Earth, Planets and Space 74, nr 1 (14.12.2022). http://dx.doi.org/10.1186/s40623-022-01743-x.
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AbstractWe have devoted efforts to the development and performance evaluation of new low-cost ionospheric instruments for studies that require distributed observations and for educational and citizen science initiatives. Here, we report results of some of these efforts. More specifically, we describe the design of new ionospheric sensors based on Global Navigation Satellite System (GNSS) receivers and single-board computers. The first sensor (ScintPi 2.0) is a multi-constellation, single-frequency ionospheric scintillation monitor. The second sensor (ScintPi 3.0) is a multi-constellation, dual-frequency ionospheric scintillation and total electron content (TEC) monitor. Both sensors were created using Raspberry Pi computers and off-the-shelf GNSS receivers. While they are not intended to fully replace commercial ionospheric monitors, they cost a fraction of their price and can be used in various scientific applications. In addition to describing these new sensors, we present examples of observations made by ScintPi 3.0 deployed in Presidente Prudente, Brazil (22.12 S, 51.41 W, − 17.67° dip latitude). These examples show the ability of our system to detect scintillation events and TEC depletions such as those associated with equatorial plasma bubbles. Additionally, our observations were made in parallel with a commercial receiver (Septentrio PolaRx5S), which allowed an evaluation of the scintillation and TEC measurements provided by our system. The comparison shows that ScintPi 3.0 can provide estimates of the amplitude scintillation index (S4) and TEC that are in excellent agreement with those provided by PolaRx5S. We also show an example of the application of ScintPi 3.0 in distributed observations of ionospheric irregularities and scintillation over South America. Graphical Abstract