WorldWideScience

Sample records for helium bubble injection

  1. Molecular dynamics study of helium bubble pressure in titanium

    Institute of Scientific and Technical Information of China (English)

    Zhang Bao-Ling; Wang Jun; Hou Qing

    2011-01-01

    In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals.

  2. Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium

    Science.gov (United States)

    Guo, Wei

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron bubbles and experiments on imaging individual electron bubbles in liquid helium. We studied the effect of zero-point and thermal fluctuations on the shape of ground state electron bubbles in liquid helium. The results are used to determine the line shape for the 1S to 1P optical transition. The calculated line shape is in very good agreement with the experimental measurements of Grimes and Adams. For 1S to 2P transition, the obtained transition line width agrees well with the measured data of Zipfel over a range of pressure up to 15 bars. Fluctuations in the bubble shape also make other "unallowed" transitions possible. The transition cross-sections from the 1S state to the 1D and 2D states are calculated with magnitude approximately two orders smaller than that of the 1S to 1P and 2P transitions. In our electron bubble imaging experiments, a planar ultrasonic transducer was used to generate strong sound wave pulse in liquid helium. The sound pulse passed through the liquid so as to produce a transient negative pressure over a large volume (˜ 1 cm3). An electron bubble that was passed by the sound pulse exploded for a fraction of a microsecond and grew to have a radius of around 10 microns. While the bubble had this large size it was illuminated with a flash lamp and its position was recorded. In this way, we can determine its position. Through the application of a series of sound pulses, we can then take images along the track of individual electrons. The motion of individual electron bubbles has been successfully monitored. Interesting bubble tracks that may relate to electrons

  3. Molecular dynamics study of helium bubble pressure in titanium

    Science.gov (United States)

    Zhang, Bao-Ling; Wang, Jun; Hou, Qing

    2011-03-01

    In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals. Project supported by the National Natural Science Foundation of China (Grant No. 10775101) and National Magnetic Confinement Fusion Program of China (Grant No. 2009GB106004).

  4. Exploding and Imaging of Electron Bubbles in Liquid Helium

    Science.gov (United States)

    Yadav, Neha; Vadakkumbatt, Vaisakh; Maris, Humphrey J.; Ghosh, Ambarish

    2016-11-01

    An electron bubble in liquid helium-4 under the saturated vapor pressure becomes unstable and explodes if the pressure becomes more negative than -1.9 bars. In this paper, we use focused ultrasound to explode electron bubbles. We then image at 30,000 frames per second the growth and subsequent collapse of the bubbles. We find that bubbles can grow to as large as 1 mm in diameter within 2 ms after the cavitation event. We examine the relation between the maximum size of the bubble and the lifetime and find good agreement with the experimental results.

  5. Effects of helium injection mode on void formation in Fe-Ni-Cr alloys

    Science.gov (United States)

    Kimoto, T.; Lee, E. H.; Mansur, L. K.

    1988-09-01

    The effect of the helium injection mode on void formation during ion irradiation of the pure solution-annealing alloys Fe-15Ni-7Cr, Fe-35Ni-7Cr, Fe-45Ni-7Cr, Fe-10Ni-13Cr, Fe-40Ni-13Cr, Fe-45Ni-15Cr was examined. Ion irradiation was carried out with 4 MeV Ni ions at 948 K to doses of 30 to 100 dpa with: (1) no helium injection, (2) simultaneous helium injection and (3) helium preinjection and aging. Swelling variation with helium injection differed among the 7Cr alloys and 13-15Cr alloys. Only the simultaneous helium injection mode produced a bimodal cavity size distribution in the high Ni alloys. The critical radius, as estimated from the cavity size distributions appears to have increased with increasing dose, but no clear variation of the critical radius with composition was observed. Helium preinjection and one-hour aging at 948 K formed helium bubbles along the residual dislocations, while subsequent Ni irradiation caused void formation along the dislocation lines. The calculated helium concentration deduced from observable helium bubbles was low compared with the injected helium concentration in the alloys containing higher Ni and lower Cr.

  6. THERMAL UNIFORMITY OF LIQUID HELIUM IN ELECTRON BUBBLE CHAMBER.

    Energy Technology Data Exchange (ETDEWEB)

    WANG,L.; JIA,L.

    2002-07-22

    A CRYOGENIC RESEARCH APPARATUS TO MEASURE THE MOVEMENT OF ELECTRONS UNDER A HIGH ELECTRIC FIELD IN A LIQUID HELIUM BATH WAS DESIGNED AND BUILT AT THE BROOKHAVEN NATIONAL LABORATORY AND THE NEVIS LABORATORY OF COLUMBIA UNIVERSITY. THE LIQUID HELIUM CHAMBER IS A DOUBLE WALLED CYLINDRICAL CONTAINER EQUIPPED WITH 5 OPTICS WINDOWS AND 10 HIGH VOLTAGE CABLES. TO SHIELD THE LIQUID HELIUM CHAMBER AGAINST THE EXTERNAL HEAT LOADS AND TO PROVIDE THE THERMAL UNIFORMITY IN THE LIQUID HELIUM CHAMBER, THE DOUBLE WALLED JACKET WAS COOLED BY A PUMPED HELIUM BATH. THE HELIUM CHAMBER WAS BUILT INTO A COMMERICAL LN2 / LHE CRYOSTAT. THIS PAPER PRESENTS THE DESIGN AND THE NUMERICAL SIMULATION ANALYSIS ON THERMAL UNIFORMITY OF THE ELECTRON BUBBLE CHAMBER.

  7. Helium nano-bubble evolution in aging metal tritides.

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2004-05-01

    A continuum-scale, evolutionary model of helium (He) nano-bubble nucleation, growth and He release for aging bulk metal tritides is presented which accounts for major features of the experimental database. Bubble nucleation, modeled as self-trapping of interstitially diffusing He atoms, is found to occur during the first few days following tritium introduction into the metal and is sensitive to the He diffusivity and pairing energy. An effective helium diffusivity of 0.3 x 10{sup -16} cm{sup 2}/s at 300 K is required to generate the average bubble density of 5x 1017 bubbles/cm3 observed by transmission electron microscopy (TEM). Early bubble growth by dislocation loop punching with a l/radius bubble pressure dependence produces good agreement with He atomic volumes and bubble pressures determined from swelling data, nuclear magnetic resonance (NMR) measurements, and hydride pressure-composition-temperature (PCT) shifts. The model predicts that later in life neighboring bubble interactions may first lower the loop punching pressure through cooperative stress effects, then raise the pressure by partial blocking of loops. It also accounts for the shape of the bubble spacing distribution obtained from NMR data. This distribution is found to remain fixed with age, justifying the separation of nucleation and growth phases, providing a sensitive test of the growth formulation, and indicating that further significant bubble nucleation does not occur throughout life. Helium generated within the escape depth of surfaces and surface-connected porosity produces the low-level early helium release. Accelerated or rapid release is modeled as inter-bubble fracture using an average ligament stress criterion. Good agreement is found between the predicted onset of fracture and the observed He-metal ratio (HeM) for rapid He release from bulk palladium tritide. An examination of how inter-bubble fracture varies over the bubble spacing distribution shows that the critical Hem will be

  8. Transmission Electron Microscopy Characterization of Helium Bubbles in Aged Plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, A J; Wall, M A; Zocco, T G; Blobaum, K M

    2004-11-02

    The self-irradiation damage generated by alpha decay of plutonium results in the formation of lattice defects, helium, and uranium atoms. Over time, microstructural evolution resulting from the self-irradiation may influence the physical and mechanical properties of the material. In order to assess microstructural changes, we have developed and applied procedures for the specimen preparation, handling, and transmission electron microscopy characterization of Pu alloys. These transmission electron microscopy investigations of Pu-Ga alloys ranging in age up to 42-years old reveal the presence of nanometer-sized helium bubbles. The number density of bubbles and the average size have been determined for eight different aged materials.

  9. Atomistic simulation of helium bubble nucleation in palladium

    Energy Technology Data Exchange (ETDEWEB)

    Wang Liang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu, Wangyu [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: wangyuhu2001cn@yahoo.com.cn; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: sfxiao@yahoo.com.cn; Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Deng Huiqiu [Department of Applied Physics, Hunan University, Changsha 410082 (China)

    2009-09-15

    A palladium crystal has been constructed with 11808 atoms. 55 helium atoms occupied the octahedral position of palladium crystal are introduced and retained in a spherical region. Molecular dynamic simulations are performed in a constant temperature and constant volume ensemble (NVT) with temperature controlled by Nose-Hoover thermostat. The interactions between palladium atoms are described with modified analytic embedded atom method (MAEAM), the interactions between palladium atom and helium atom are in the form of Morse potential, and the interactions between helium atoms are in the form of L-J potential function. With the analysis of the radial distribution function (RDF) and microstructure, it reveals that some of helium atoms form a series of clusters with different size, and the nucleation core is random at low temperature, and which is the embryo of helium bubble. Increasing temperature can accelerate the process of bubble nucleation, and the clusters will aggregate and coalesce into a bigger one in which there are no palladium atoms, and it is considered as a helium bubble.

  10. Performance Studies on Sub-cooling of Cryogenic Liquids Used for Rocket Propulsion Using Helium Bubbling

    Directory of Open Access Journals (Sweden)

    Ramesh T

    2014-03-01

    Full Text Available The sub-cooling of cryogenic propellants contained in tanks is an important and effective method for bringing down the lift-off mass of launch vehicle and thus the performance of the rocket engine is greatly improved. This paper presents the technical and experimental studies conducted on cryogenic liquids such as Liquid Oxygen, Liquid Nitrogen, and Liquid Hydrogen using helium bubbling method. The influence of cooled Helium on the degree of sub-cooling and the variation in flow rate of Helium gas admitted are discussed. The experimental and theoretical studies indicate that the sub-cooling technique using helium injection is a very simple method and can be very well adopted in propellant tanks used for ground and launch vehicle applications.

  11. Annealing Behaviour of Helium Bubbles in Titanium Films by Thermal Desorption Spectroscopy and Positron Beam Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Chao-Zhuo; ZHOU Zhu-Ying; SHI Li-Qun; WANG Bao-Yi; HAO Xiao-Peng; ZHAO Guo-Qing

    2007-01-01

    @@ Helium-containing Ti films are prepared using magnetron sputtering in the helium-argon atmosphere. Isochronal annealing at different temperatures for an hour is employed to reveal the behaviour of helium bubble growth. Ion beam analysis is used to measure the retained helium content. Helium can release largely when annealing above 970 K. A thermal helium desorption spectroscopy system is constructed for assessment of the evolution of helium bubbles in the annealed samples by linear heating (0.4K/s) from room temperature to 1500K. Also, Doppler broadening measurements of positron annihilation radiation spectrum are performed by using changeable energy positron beam. Bubble coarsening evolves gradually below 680K, migration and coalescence of small bubbles dominates in the range of 680-970K, and the Ostwald ripening mechanism enlarges the bubbles with a massive release above 970K.

  12. Evolution Law of Helium Bubbles in Hastelloy N Alloy on Post-Irradiation Annealing Conditions

    Directory of Open Access Journals (Sweden)

    Jie Gao

    2016-10-01

    Full Text Available This work reports on the evolution law of helium bubbles in Hastelloy N alloy on post-irradiation annealing conditions. After helium ion irradiation at room temperature and subsequent annealing at 600 °C (1 h, the transmission electron microscopy (TEM micrograph indicates the presence of helium bubbles with size of 2 nm in the depth range of 0–300 nm. As for the sample further annealed at 850 °C (5 h, on one hand, a “Denuded Zone” (0–38 nm with rare helium bubbles forms due to the decreased helium concentration. On the other hand, the “Ripening Zone” (38–108 nm and “Coalescence Zone” (108–350 nm with huge differences in size and separation of helium bubbles, caused by different coarsening rates, are observed. The mechanisms of “Ostwald ripening” and “migration and coalescence”, experimentally proved in this work, may explain these observations.

  13. Nucleation and growth of helium bubbles in aluminum between 20 and 900 K

    DEFF Research Database (Denmark)

    Rajainmäki, H.; Linderoth, Søren; Hansen, H. E.

    1988-01-01

    The nucleation and growth of helium bubbles have been monitored in 3implanted aluminum by the positron-lifetime technique and transmission electron microscopy. Helium atoms are mobile during the implantation and are subsequently trapped by vacancies. The annealing stages I and III are observed...... at 40 and 200 K, respectively, in agreement with previous positron annihilation and electrical-resistivity data. The low implantation temperature of 20 K hinders bubble formation during implantation, but during isochronal annealing, around 425 K, helium starts to nucleate into bubbles via substitutional...... migration of the He-vacancy pairs. The migration energy for a He-vacancy pair is estimated to be 1.3±0.1 eV. Above 600 K the He bubbles grow through condensation of thermally produced vacancies, as well as bubble migration and coalescence. The created helium bubbles are extremely stable and survive...

  14. Radiation damage in gallium-stabilized δ-plutonium with helium bubbles

    Science.gov (United States)

    Wu, FengChao; Wang, Pei; Liu, XiaoYi; Wu, HengAn

    2017-02-01

    To understand the role of helium on self-irradiation effects in δ-plutonium, microstructure evolutions due to α-decay events near pre-existing helium bubbles in gallium-stabilized δ-plutonium are investigated using molecular dynamics simulations. Bubble promoting effect plays a dominating role in point defects production, resulting in increasing number of point defects. When lightweight helium atoms act as media, energy transfer discrepancy and altered spatial morphology of point defects induced by mass effect are revealed. The evolution of stacking faults surrounding the disordered core is studied and their binding effect on the propagation of point defects are presented. The cascade-induced bubble coalescence, resolution and re-nucleation driven by internal pressure are obtained in the investigation on helium behaviors. The intrinsic tendency in our simulated self-irradiation with helium bubbles is significant for understanding the underlying mechanism of aging in plutonium and its alloys.

  15. Helium-filled soap bubbles for vortex core velocimetry

    Science.gov (United States)

    Caridi, Giuseppe Carlo Alp; Sciacchitano, Andrea; Scarano, Fulvio

    2017-09-01

    Velocity measurements within the core of high-swirl vortices are often hampered by heavier-than-air particle tracers being centrifuged outside the vortex core region. The use of neutrally buoyant and lighter-than-air tracers is investigated to aim at homogeneous tracers concentration in air flow experiments dealing with high-swirl vortices using particle image velocimetry. Helium-filled soap bubbles (HFSB) of sub-millimeter diameter are employed as flow tracers. Their density is controlled varying the relative amount of helium and soap solution composing the bubbles. The dynamics of HFSB and micro-size droplets is modeled within a Lamb-Oseen vortex to retrieve the order of magnitude of the tracers slip velocity. A positive radial drift for heavier-than-air tracers leads to an empty vortex core. In contrast, the concentration at the vortex axis is expected to increase for lighter than air tracers. Experiments are conducted on a sharp-edged slender delta wing at 20° incidence. At chosen chord-based Reynolds numbers of 2 × 105 and 6 × 105, a stable laminar vortex is formed above the delta wing. Laser sheet visualization is used to inspect the spatial concentration of tracers. A comparison is made between micron-sized fog droplets and HFSB tracers in the nearly neutrally buoyant condition. Stereo-PIV measurements with fog droplets return a systematically underestimated axial velocity distribution within the vortex core due to drop-out of image cross-correlation signal. The nearly neutrally buoyant HFSB tracers appear to maintain a homogeneous spatial concentration and yield cross-correlation signal up to the vortex axis. The resulting velocity measurements are in good agreement with literature data.

  16. Modeling of helium bubble nucleation and growth in neutron irradiated boron doped RAFM steels

    Energy Technology Data Exchange (ETDEWEB)

    Dethloff, Christian, E-mail: christian.dethloff@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Gaganidze, Ermile [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Svetukhin, Vyacheslav V. [Ulyanovsk State University, Leo Tolstoy Str. 42, 432970 Ulyanovsk (Russian Federation); Aktaa, Jarir [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

    2012-07-15

    Reduced activation ferritic/martensitic (RAFM) steels are promising candidates for structural materials in future fusion technology. In addition to other irradiation defects, the transmuted helium is believed to strongly influence material hardening and embrittlement behavior. A phenomenological model based on kinetic rate equations is developed to describe homogeneous nucleation and growth of helium bubbles in neutron irradiated RAFM steels. The model is adapted to different {sup 10}B doped EUROFER97 based heats, which already had been studied in past irradiation experiments. Simulations yield bubble size distributions, whereby effects of helium generation rate, surface energy, helium sinks and helium density are investigated. Peak bubble diameters under different conditions are compared to preliminary microstructural results on irradiated specimens. Helium induced hardening was calculated by applying the Dispersed Barrier Hardening model to simulated cluster size distributions. Quantitative microstructural investigations of unirradiated and irradiated specimens will be used to support and verify the model.

  17. Structural and chemical evolution in neutron irradiated and helium-injected ferritic ODS PM2000 alloy

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hee Joon; Edwards, Dan J.; Kurtz, Richard J.; Yamamoto, Takuya; Wu, Yuan; Odette, G. Robert

    2017-02-01

    An investigation of the influence of helium on damage evolution under neutron irradiation of an 11 at% Al, 19 at% Cr ODS ferritic PM2000 alloy was carried out in the High Flux Isotope Reactor (HFIR) using a novel in situ helium injection (ISHI) technique. Helium was injected into adjacent TEM discs from thermal neutron 59Ni(nth, 59Ni(nth,α) reactions in a thin NiAl layer. The PM2000 undergoes concurrent displacement damage from the high-energy neutrons. The ISHI technique allows direct comparisons of regions with and without high concentrations of helium since only the side coated with the NiAl experiences helium injection. The corresponding microstructural and microchemical evolutions were characterized using both conventional and scanning transmission electron microscopy techniques. The evolutions observed include formation of dislocation loops and associated helium bubbles, precipitation of a variety of phases, amorphization of the Al2YO3 oxides (which also variously contained internal voids), and several manifestations of solute segregation. Notably, high concentrations of helium had a significant effect on many of these diverse phenomena. These results on PM2000 are compared and contrasted to the evolution of so-called nanostructured ferritic alloys (NFA).

  18. Structural and chemical evolution in neutron irradiated and helium-injected ferritic ODS PM2000 alloy

    Science.gov (United States)

    Jung, Hee Joon; Edwards, Dan J.; Kurtz, Richard J.; Yamamoto, Takuya; Wu, Yuan; Odette, G. Robert

    2017-02-01

    An investigation of the influence of helium on damage evolution under neutron irradiation of an 11 at% Al, 19 at% Cr ODS ferritic PM2000 alloy was carried out in the High Flux Isotope Reactor (HFIR) using a novel in situ helium injection (ISHI) technique. Helium was injected into adjacent TEM discs from thermal neutron 58Ni(nth,γ) 59Ni(nth,α) reactions in a thin NiAl layer. The PM2000 undergoes concurrent displacement damage from the high-energy neutrons. The ISHI technique allows direct comparisons of regions with and without high concentrations of helium since only the side coated with the NiAl experiences helium injection. The corresponding microstructural and microchemical evolutions were characterized using both conventional and scanning transmission electron microscopy techniques. The evolutions observed include formation of dislocation loops and associated helium bubbles, precipitation of a variety of phases, amorphization of the Al2YO3 oxides (which also variously contained internal voids), and several manifestations of solute segregation. Notably, high concentrations of helium had a significant effect on many of these diverse phenomena. These results on PM2000 are compared and contrasted to the evolution of so-called nanostructured ferritic alloys (NFA).

  19. Trapping of helium in nano-bubbles in euxenite: Positive identification and implications

    Science.gov (United States)

    Seydoux-Guillaume, Anne-Magali; David, Marie-Laure; Alix, Kevin; Datas, Lucien; Bingen, Bernard

    2016-08-01

    The (Y,REE,U,Th)-(Nb,Ta,Ti) oxides, like euxenite, fergusonite, pyrochlore, zirconolite, are known to contain nanometric spherical cavities or bubbles, interpreted to contain radiogenic helium. In-situ analyses by Scanning Transmission Electron Microscopy (STEM) coupled with Electron Energy Loss Spectroscopy (EELS) inside nano-bubbles from an euxenite crystal, sampled in its host c. 920 Ma old pegmatite in Norway, deliver, for the first time, a positive identification of helium and an estimation of helium pressure in such bubbles. The chemically unaltered euxenite crystal proves amorphous and homogeneously speckled with bubbles ranging from 5 to 68 nm in diameter, around a log-normal distribution centered at 19 nm. The euxenite contains 9.87 wt% UO2 and 3.15 wt% ThO2. It accumulated a theoretical alpha-decay dose of 3.46 ×1020 α / g (i.e. 170 He/nm3), at a dose rate of 11 926 α / g / s. This corresponds to production of 0.23 wt% He. The density of helium inside the bubbles, estimated from EELS data, ranges from 2 to 45 He/nm3, leading to a pressure of 8 to 500 MPa. The proportion of produced helium trapped in bubbles is about 10%. Helium bubbles clearly influence helium diffusion. They may contribute to the swelling of euxenite during amorphization and to the fracturing of the host rock. Our results suggest that dose, dose rate and structural state seem to be important parameters for the nucleation, growth and coalescence of helium bubbles but also demonstrate the crucial need of experimental studies to be able to develop a predictive model of the long term behavior of materials in response to helium irradiation. Furthermore, chemical alteration of euxenite, here materialized by fluid driven dissolution-precipitation towards silica bearing euxenite, removes the bubbles and mobilizes helium into the rock via cracks and grain boundaries. It is then suggested that helium-rich fluid released from such U-Th rich sources may percolate into surrounding rock units

  20. Design and development of a helium injection system to improve external leakage detection during liquid nitrogen immersion tests

    Science.gov (United States)

    Townsend, Andrew; Mishra, Rakesh

    2016-10-01

    The testing of assemblies for use in cryogenic systems commonly includes evaluation at or near operating (therefore cryogenic) temperature. Typical assemblies include valves and pumps for use in liquid oxygen-liquid hydrogen rocket engines. One frequently specified method of cryogenic external leakage testing requires the assembly, pressurized with gaseous helium (GHe), be immersed in a bath of liquid nitrogen (LN2) and allowed to thermally stabilize. Component interfaces are then visually inspected for leakage (bubbles). Unfortunately the liquid nitrogen will be boiling under normal, bench-top, test conditions. This boiling tends to mask even significant leakage. One little known and perhaps under-utilized property of helium is the seemingly counter-intuitive thermodynamic property that when ambient temperature helium is bubbled through boiling LN2 at a temperature of -195.8 °C, the temperature of the liquid nitrogen will reduce. This paper reports on the design and testing of a novel proof-of-concept helium injection control system confirming that it is possible to reduce the temperature of an LN2 bath below boiling point through the controlled injection of ambient temperature gaseous helium and then to efficiently maintain a reduced helium flow rate to maintain a stabilized liquid temperature, enabling clear visual observation of components immersed within the LN2. Helium saturation testing is performed and injection system sizing is discussed.

  1. Nanobubble Fragmentation and Bubble-Free-Channel Shear Localization in Helium-Irradiated Submicron-Sized Copper.

    Science.gov (United States)

    Ding, Ming-Shuai; Tian, Lin; Han, Wei-Zhong; Li, Ju; Ma, Evan; Shan, Zhi-Wei

    2016-11-18

    Helium bubbles are one of the typical radiation microstructures in metals and alloys, significantly influencing their deformation behavior. However, the dynamic evolution of helium bubbles under straining is less explored so far. Here, by using in situ micromechanical testing inside a transmission electron microscope, we discover that the helium bubble not only can coalesce with adjacent bubbles, but also can split into several nanoscale bubbles under tension. Alignment of the splittings along a slip line can create a bubble-free channel, which appears softer, promotes shear localization, and accelerates the failure in the shearing-off mode. Detailed analyses unveil that the unexpected bubble fragmentation is mediated by the combination of dislocation cutting and internal surface diffusion, which is an alternative microdamage mechanism of helium irradiated copper besides the bubble coalescence.

  2. A molecular dynamics simulation study of temperature and depth effect on helium bubble releasing from Ti surface

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Li; Ma, Mingwang; Xiang, Wei; Wang, Yuan; Cheng, Yanlin; Tan, Xiaohua, E-mail: caepiee@163.com

    2015-10-05

    Highlights: • Features of helium bubble at varied depths in Ti are researched by MD simulation. • Effect of Temperature on helium bubble in Ti is researched by MD simulation. • The mechanism of helium bubble releasing from metal is clarified. - Abstract: Using molecular dynamics simulation, the effect of environment temperature and depth of helium bubble on its volume, pressure and releasing process in metal Ti is researched. First, through studying the statuses of helium bubble at different depths at 300 K, the regularity of helium bubble shape, volume and pressure is acquired. The results show that with depth augmenting, the pressure increases gradually, while the volume decreases, but these two parameters keep around some level when depth is greater than 2.6 nm. Then, the evolution of model system with helium bubble at various temperatures is simulated. On the whole, the critical releasing temperature increases with depth. Finally, the mechanism of helium bubble releasing from Ti surface is explained. It is found that the bubble would tear the Ti film above it when its pressure is greater than the tensile strength of metal film, and then helium atoms will release from the metal.

  3. Helium bubble linkage and the transition to rapid He release in aging Pd tritide.

    Energy Technology Data Exchange (ETDEWEB)

    Cowgill, Donald F.

    2006-02-01

    A model is presented for the linking of helium bubbles growing in aging metal tritides. Stresses created by neighboring bubbles are found to produce bubble growth toward coalescence. This process is interrupted by the fracture of ligaments between bubble arrays. The condition for ligament fracture percolates through the material to reach external surfaces, leading to material micro-cracking and the release of helium within the linked-bubble cluster. A comparison of pure coalescence and pure fracture mechanisms shows the critical HeM concentration for bubble linkage is not strongly dependent on details of the linkage process. The combined stress-directed growth and fracture process produces predictions for the onset of rapid He release and the He emission rate. Transition to this rapid release state is determined from the physical size of the linked-bubble clusters, which is calculated from dimensional invariants in classical percolation theory. The result is a transition that depends on material dimensions. The onset of bubble linkage and rapid He release are found to be quite sensitive to the bubble spacing distribution, which is log-normal for bubbles nucleated by self-trapping.

  4. Bubble growth from clustered hydrogen and helium atoms in tungsten under a fusion environment

    Science.gov (United States)

    You, Yu-Wei; Kong, Xiang-Shan; Wu, Xuebang; Liu, C. S.; Chen, J. L.; Luo, G.-N.

    2017-01-01

    Bubbles seriously degrade the mechanical properties of tungsten and thus threaten the safety of nuclear fusion devices, however, the underlying atomic mechanism of bubble growth from clustered hydrogen and helium atoms is still mysterious. In this work, first-principles calculations are therefore carried out to assess the stability of tungsten atoms around both hydrogen and helium clusters. We find that the closest vacancy-formation energies of interstitial hydrogen and helium clusters are substantially decreased. The first-nearest and second-nearest vacancy-formation energies close to vacancy-hydrogen clusters decrease in a step-like way to  ˜0, while those close to vacancy-helium clusters are reduced almost linearly to  ˜-5.46 eV when atom number reaches 10. The vacancy-formation energies closest to helium clusters are more significantly reduced than those nearest to hydrogen clusters, whatever the clusters are embedded at interstitial sites or vacancies. The reduction of vacancy-formation energies results in instability and thus emission of tungsten atoms close to interstitial helium and vacancy-helium clusters, which illustrates the experimental results, that the tungsten atoms can be emitted from the vicinity of vacancy-helium clusters. In addition, the emission of unstable tungsten atoms close to hydrogen clusters may become possible once they are disturbed by the environment. The emission of tungsten atoms facilitates the growth and evolution of hydrogen and helium clusters and ultimately the bubble formation. The results also explain the bubble formation even if no displacement damage is produced in tungsten exposed to low-energy hydrogen and helium plasma.

  5. Estimation of the lifetime of small helium bubbles near tungsten surfaces - A methodological study

    Science.gov (United States)

    Cui, Jiechao; Wu, Zhangwen; Hou, Qing

    2016-09-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Neldle rule. These results are useful for establishing a model in multi-scale simulations of the morphological evolution of component surfaces in fusion reactors.

  6. Helium bubble evolution in a Zr–Sn–Nb–Fe–Cr alloy during post-annealing: An in-situ investigation

    Energy Technology Data Exchange (ETDEWEB)

    Shen, H.H. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Peng, S.M.; Chen, B. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Naab, F.N. [Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Sun, G.A.; Zhou, W. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Xiang, X. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Sun, K., E-mail: kaisun@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Zu, X.T., E-mail: xtzu@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-09-15

    The formation of helium bubbles is considered to be detrimental to the mechanical performance of the nuclear materials. The growth behaviors of helium bubbles in a helium ion implanted Zr–Sn–Nb–Fe–Cr alloy with respect to the helium fluence and subsequently annealing procedure were investigated by in-situ transmission electron microscopy. In the as-implanted sample, the measured size distributions of the helium bubbles are consistent with the simulated helium concentrations. Moreover, the mean size of the helium bubbles increases with the increase of the irradiation temperatures and the helium fluence. The in-situ heating study performed in a transmission electron microscope indicates that the mean size of the helium bubbles increase slowly below 923 K and dramatically above 923 K. The coarsening mechanism of the helium bubbles in the alloy is suggested based on the study. - Highlights: • Helium bubble growth in zirconium with annealing was in-situ investigated in TEM. • The mean helium bubble size increase with helium fluence and annealing temperature. • Helium bubble size distribution is same as that of helium concentration by SRIM. • Mean bubble size increases slowly and quickly with temperature below and above 923 K. • The growth mechanism of the helium bubbles in Zr alloy has been discussed.

  7. Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.

    Science.gov (United States)

    Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

    2007-10-01

    The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves. The numerical results suggest that, if the mercury includes gas bubbles whose equilibrium radius is much larger than that of the cavitation bubble, the explosive expansion of the cavitation bubble (i.e., cavitation inception) is suppressed by the positive-pressure wave radiated by the injected bubbles, which decreases the magnitude of the negative pressure in the mercury.

  8. Synergistic effect of helium and hydrogen for bubble swelling in reduced-activation ferritic/martensitic steel under sequential helium and hydrogen irradiation at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wenhui [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Guo, Liping, E-mail: guolp@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Chen, Jihong; Luo, Fengfeng; Li, Tiecheng [Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory and School of Physics and Technology, Wuhan University, Wuhan 430072 (China); Ren, Yaoyao [Center for Electron Microscopy, Wuhan University, Wuhan 430072 (China); Suo, Jinping; Yang, Feng [State Key Laboratory of Mould Technology, Institute of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2014-04-15

    Highlights: • Helium/hydrogen synergistic effect can increase irradiation swelling of RAFM steel. • Hydrogen can be trapped to the outer surface of helium bubbles. • Too large a helium bubble can become movable. • Point defects would become mobile and annihilate at dislocations at high temperature. • The peak swelling temperature for RAFM steel is 450 °C. - Abstract: In order to investigate the synergistic effect of helium and hydrogen on swelling in reduced-activation ferritic/martensitic (RAFM) steel, specimens were separately irradiated by single He{sup +} beam and sequential He{sup +} and H{sup +} beams at different temperatures from 250 to 650 °C. Transmission electron microscope observation showed that implantation of hydrogen into the specimens pre-irradiated by helium can result in obvious enhancement of bubble size and swelling rate which can be regarded as a consequence of hydrogen being trapped by helium bubbles. But when temperature increased, Ostwald ripening mechanism would become dominant, besides, too large a bubble could become mobile and swallow many tiny bubbles on their way moving, reducing bubble number density. And these effects were most remarkable at 450 °C which was the peak bubble swelling temperature for RAMF steel. When temperature was high enough, say above 450, point defects would become mobile and annihilate at dislocations or surface. As a consequence, helium could no longer effectively diffuse and clustering in materials and bubble formation was suppressed. When temperature was above 500, helium bubbles would become unstable and decompose or migrate out of surface. Finally no bubble was observed at 650 °C.

  9. Performance of Oil-Injected Scroll Compressors for Helium Refrigerators

    Science.gov (United States)

    Shiibayashi, Masao; Izunaga, Yasushi; Sado, Shintaro

    In recent years there arises growing demand of helium liquefaction refrigerators for the magnetic resonance imaging systems, magnetically levitated vehicles and other systems using superconducting magnet. From this background, a small size, scroll type of hermetic helium compressor capable of compressing helium gas to the pressure ratio of 20 in a single stage is developed. Main features of this compressor are as follows. 1) Discharge capacity can be varied from 7 to 20 Nm3/h by changing driving motor frequency from 30 to 80 Hz. 2) The overall adiabatic efficiency showed 72%∼79% under the pressure ratio range of 11∼20 at 60 Hz using oil injection cooling device.

  10. Stability of helium bubbles in alpha-iron: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Lucas, G. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherche en Physique des Plasmas, Association Euratom-Confederation Suisse, CH 5332 Villigen PSI (Switzerland)], E-mail: guillaume.lucas@psi.ch; Schaeublin, R. [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherche en Physique des Plasmas, Association Euratom-Confederation Suisse, CH 5332 Villigen PSI (Switzerland)

    2009-04-30

    Molecular dynamics simulations were performed to estimate the dissociation energies of helium interstitials, vacancies and self-interstitial atoms from small helium-vacancy clusters. Several sets of empirical potentials have been tested and compared with available ab initio calculations in order to provide the best combination of potentials to study the stability of small helium bubbles. The behavior of the cluster seems to be better described using Ackland potential for the Fe-Fe interactions and Juslin potential for the Fe-He interactions. From the calculations, it appears that the dissociation energies mainly depend on the helium-to-vacancy ratio rather than the cluster size. The helium/vacancy crossover slightly varies with increasing number of vacancies, but the crossover defining the loop-punching regime decreases strongly with increasing cluster sizes.

  11. Methods of Helium Injection and Removal for Heat Transfer Augmentation

    Science.gov (United States)

    Haight, Harlan; Kegley, Jeff; Bourdreaux, Meghan

    2008-01-01

    While augmentation of heat transfer from a test article by helium gas at low pressures is well known, the method is rarely employed during space simulation testing because the test objectives usually involve simulation of an orbital thermal environment. Test objectives of cryogenic optical testing at Marshall Space Flight Center's X-ray Cryogenic Facility (XRCF) have typically not been constrained by orbital environment parameters. As a result, several methods of helium injection have been utilized at the XRCF since 1999 to decrease thermal transition times. A brief synopsis of these injection (and removal) methods including will be presented.

  12. Positronium formation in helium bubbles in 600 MeV proton-irradiated aluminium

    DEFF Research Database (Denmark)

    Jensen, K. O.; Eldrup, Morten Mostgaard; Singh, Bachu Narain

    1985-01-01

    Aluminium samples containing helium bubbles produced by 600 MeV proton irradiation at 430°C were investigated by positron annihilation; both lifetime and angular correlation measurements were made. The angular correlation curves contain an unusually narrow component. This component is associated...

  13. Estimation of the lifetime of small helium bubbles near tungsten surfaces -- a methodological study

    CERN Document Server

    Cui, Jiechao; Hou, Qing

    2016-01-01

    Under low energy and high flux/fluence irradiation of helium (He) atoms, the formation and bursting of He bubbles on tungsten (W) surfaces play important roles in the morphological evolution of component surfaces and impurity production in fusion reactors. Microscopically, the bursting of He bubbles is a stochastic process, and He bubbles have statistically average lifetimes. In the present paper, a molecular dynamics-based method was developed to extract, for the first time, the lifetime of He bubbles near tungsten surfaces. It was found that He bubble bursting can be treated as an activated event. Its occurrence frequency or, equivalently, the average lifetime of bubbles follows the Arrhenius equation. For a given bubble size, the activation energy exhibits a good linear dependence with the depth, and the pre-exponential factor obeys the Meyer-Nedle rule. These results are useful for establishing a model in multi-scale simulations of impurity production in the fusion plasma and of the morphological evolutio...

  14. Evolution of Helium Bubbles and Discs in Irradiated 6H-SiC during Post-Implantation Annealing

    Directory of Open Access Journals (Sweden)

    Qiang Shen

    2017-01-01

    Full Text Available The single crystal 6H-SiC with [0001] crystal direction irradiated by 400 keV He+ ions with 1 × 1017 ions/cm2 fluence at 400 °C were annealed at 600, 900, 1200 and 1400 °C for different durations. The evolution of helium bubbles and discs was investigated by transmission electron microscopy. An irradiated layer distributed with fine helium bubbles was formed with a width of ~170 nm after helium ion irradiation. The size of gas bubbles increased with increasing annealing time and temperature and finally reached stable values at a given annealing temperature. According to the relationship between the bubble radii and annealing time, an empirical formula for calculating the bubble radii at the annealing temperature ranged from 600 to 1400 °C was given by fitting the experiment data. Planar bubble clusters (discs were found to form on (0001 crystal plane at both sides of the bubble layer when the annealing temperature was at the range of 800–1200 °C. The mechanism of bubble growth during post-implantation annealing and the formation of bubble discs were also analyzed and discussed.

  15. Effects of Swirl Bubble Injection on Mass Transfer and Hydrodynamics for Bubbly Flow Reactors: A Concept Paper

    Directory of Open Access Journals (Sweden)

    Farooqi Ahmad Salam

    2017-01-01

    Full Text Available Bubble flow reactors (BFR are commonly used for various industrial processes in the field of oil and gas production, pharmaceutical industries, biochemical and environmental engineering etc. The operation and performance of these reactors rely heavily on a range of hydrodynamic parameters; prominent among them are geometric configurations including gas injection geometry, operating conditions, mass transfer etc. A huge body of literature is available to describe the optimum design and performance of bubbly flow reactors with conventional bubble injection. Attempts were made to modify gas injection for improved efficiency of BFR’s. However, here instead of modifying the geometry of the gas injection, an attempt has been made to generate swirl bubbles for gaining larger mass transfer between gas and liquid. Here an exceptionally well thought strategies have been used in our numerical simulations towards the design of swirl injection mechanism, whose paramount aspect is to inhibit the rotary liquid motion but facilitates the swirl movement for bubbles in nearly stationary liquid. Our comprehension here is that the swirl motion can strongly affect the performance of bubbly reactor by identifying the changes in hydrodynamic parameters as compared to the conventional bubbly flows. In order to achieve this bubbly flow, an experimental setup has been designed as well as computational fluid dynamic (CFD code was used with to highlight a provision of swirl bubble injection by rotating the sparger plate.

  16. Thermal desorption of deuterium from Be, and Be with helium bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, A.V.; Van Veen, A.; Busker, G.J. [Delft Univ. of Technology (Netherlands). Interfaculty Reactor Inst.

    1998-01-01

    Deuterium desorption measurements carried out on a single-crystalline beryllium sample are presented. Deuterium ions were implanted at room temperature at the energy of 0.7 and 1.2 keV up to doses ranging from 10{sup 19} to 3.6 x 10{sup 21} m{sup -2}. In order to eliminate the influence of the beryllium-oxide surface layer, before the implantation the surface of the sample was cleaned by argon sputtering. After the implantation the sample was annealed up to 1200 K at a constant rate of 10 K/s. Deuterium released from the sample was monitored by a calibrated quadrupole mass-spectrometer. The desorption spectra revealed two different contributions. One is a well defined and very narrow peak centered around 450 K. This peak is observed only at high implantation doses > 7.8 x 10{sup 20} m{sup -2}, which is close to the deuterium saturation limit of 0.3 D/Be and is related to deuterium release from blisters or interconnected bubbles. The activation energy of 1.1 eV and the threshold implantation dose are consistent with the values reported in literature. The second contribution in the release spectra is found in the temperature range from 600 to 900 K and is present throughout the whole range of the implantation doses. The activation energies corresponding to this release lie in the range between 1.8 and 2.5 eV and are ascribed to the release from deuterium-vacancy type of defects. In a number of experiments the deuterium implantation was preceded by helium implantation followed by partial annealing to create helium bubbles. The resulting deuterium desorption spectra indicate that deuterium detrapping from helium bubbles is characterized by an activation energy of 2.7 eV. (author)

  17. Multielectron bubbles in helium as a paradigm for studying electrons on surfaces with curvature

    Energy Technology Data Exchange (ETDEWEB)

    Tempere, J. [Lyman Laboratory of Physics, Harvard University, Cambridge MA 02138 (United States); TFVS, Universiteit Antwerpen, Groenenborgerlaan 171, B2020 Antwerpen (Belgium); Silvera, I.F. [Lyman Laboratory of Physics, Harvard University, Cambridge MA 02138 (United States); Devreese, J.T. [TFVS, Universiteit Antwerpen, Groenenborgerlaan 171, B2020 Antwerpen (Belgium)

    2007-05-31

    The study of two-dimensional electronic systems has revealed a host of new and startling phenomena, such as the quantum Hall effect. Although effort has gone into studying the effects of confinement in two-dimensional systems, the effects of surface curvature remain relatively unexplored. Nevertheless, curvature and surface topology are expected to have a profound influence: for example, on a sphere it is not possible to have a non-trivial current field that has no vortex structure in it. The spherical geometry also influences lattices in that topological lattice defects are always present. In this report, we present results and recent insights into the physics of electrons on spherical surfaces. In particular, we investigate the case of multielectron bubbles. Multielectron bubbles are (micron sized) cavities inside liquid helium, containing electrons that collect in a nanometer thin film on the surface of the bubble and form a spherical two-dimensional electronic system. Different phases are identified and investigated: the electron fluid, the Wigner lattice, and the pair-correlated 'superconducting' state. Uniaxial external magnetic fields (normal to the surface at the poles of the sphere, and tangential to the surface at the equator) influence the different phases and give rise to textures on the surface. In discussing the properties of the spherical electron system under various conditions, we identify the differences between flat surfaces and spherical surfaces. The theoretical framework presented here is focused on the case of electrons on the spherical surface of a bubble in helium. We discuss how the theory can straightforwardly be generalized to investigate the case of (finite thickness) metallic nanoshells. Nanoshells consist of a non-conducting nanograin covered by a few atomic layers of metal. The physiologically compatible size and unique optical properties of these objects have led to applications in diagnostics and directed therapeutics of

  18. Multielectron bubbles in helium as a paradigm for studying electrons on surfaces with curvature

    Science.gov (United States)

    Tempere, J.; Silvera, I. F.; Devreese, J. T.

    2007-05-01

    The study of two-dimensional electronic systems has revealed a host of new and startling phenomena, such as the quantum Hall effect. Although effort has gone into studying the effects of confinement in two-dimensional systems, the effects of surface curvature remain relatively unexplored. Nevertheless, curvature and surface topology are expected to have a profound influence: for example, on a sphere it is not possible to have a non-trivial current field that has no vortex structure in it. The spherical geometry also influences lattices in that topological lattice defects are always present. In this report, we present results and recent insights into the physics of electrons on spherical surfaces. In particular, we investigate the case of multielectron bubbles. Multielectron bubbles are (micron sized) cavities inside liquid helium, containing electrons that collect in a nanometer thin film on the surface of the bubble and form a spherical two-dimensional electronic system. Different phases are identified and investigated: the electron fluid, the Wigner lattice, and the pair-correlated "superconducting" state. Uniaxial external magnetic fields (normal to the surface at the poles of the sphere, and tangential to the surface at the equator) influence the different phases and give rise to textures on the surface. In discussing the properties of the spherical electron system under various conditions, we identify the differences between flat surfaces and spherical surfaces. The theoretical framework presented here is focused on the case of electrons on the spherical surface of a bubble in helium. We discuss how the theory can straightforwardly be generalized to investigate the case of (finite thickness) metallic nanoshells. Nanoshells consist of a non-conducting nanograin covered by a few atomic layers of metal. The physiologically compatible size and unique optical properties of these objects have led to applications in diagnostics and directed therapeutics of cancer and

  19. Impact of nuclear irradiation on helium bubble nucleation at interfaces in liquid metals coupled to permeation through stainless steels

    CERN Document Server

    Fradera, Jorge

    2013-01-01

    The impact of nucleating gas bubbles in the form of a dispersed gas phase on hydrogen isotope permeation at interfaces between liquid metals, like LLE, and structural materials, like stainless steel, has been studied. Liquid metal to structural material interfaces involving surfaces, may lower the nucleation barrier promoting bubble nucleation at active sites. Hence, hydrogen isotope absorption into gas bubbles modelling and control at interfaces may have a capital importance regarding design, operation and safety. He bubbles as a permeation barrier principle is analysed showing a significant impact on hydrogen isotope permeation, which may have a significant effect on liquid metal systems, e.g., tritium extraction systems. Liquid metals like LLE under nuclear irradiation in, e.g., breeding blankets of a nuclear fusion reactor would generate tritium which is to be extracted and recirculated as fuel. At the same time that tritium is bred, helium is also generated and may precipitate in the form of nano bubbles...

  20. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    NARCIS (Netherlands)

    Chernov, [No Value; Kalashnikov, AN; Kahn, BA; Binyukova, SY

    2003-01-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion it. radiation up to a fluence of 5 x 10(20) m(-2) at the temperature of 920 K. It

  1. Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

    Directory of Open Access Journals (Sweden)

    Christian Vanhille

    2017-01-01

    Full Text Available In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium could be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.

  2. On the use of helium-filled soap bubbles for large-scale tomographic PIV in wind tunnel experiments

    Science.gov (United States)

    Scarano, Fulvio; Ghaemi, Sina; Caridi, Giuseppe Carlo Alp; Bosbach, Johannes; Dierksheide, Uwe; Sciacchitano, Andrea

    2015-02-01

    The flow-tracing fidelity of sub-millimetre diameter helium-filled soap bubbles (HFSB) for low-speed aerodynamics is studied. The main interest of using HFSB in relation to micron-size droplets is the large amount of scattered light, enabling larger-scale three-dimensional experiments by tomographic PIV. The assessment of aerodynamic behaviour closely follows the method proposed in the early work of Kerho and Bragg (Exp Fluids 50:929-948, 1994) who evaluated the tracer trajectories around the stagnation region at the leading edge of an airfoil. The conclusions of the latter investigation differ from the present work, which concludes sub-millimetre HFSB do represent a valid alternative for quantitative velocimetry in wind tunnel aerodynamic experiments. The flow stagnating ahead of a circular cylinder of 25 mm diameter is considered at speeds up to 30 m/s. The tracers are injected in the free-stream and high-speed PIV, and PTV are used to obtain the velocity field distribution. A qualitative assessment based on streamlines is followed by acceleration and slip velocity measurements using PIV experiments with fog droplets as a term of reference. The tracing fidelity is controlled by the flow rates of helium, liquid soap and air in HFSB production. A characteristic time response, defined as the ratio of slip velocity and the fluid acceleration, is obtained. The feasibility of performing time-resolved tomographic PIV measurements over large volumes in aerodynamic wind tunnels is also studied. The flow past a 5-cm-diameter cylinder is measured over a volume of 20 × 20 × 12 cm3 at a rate of 2 kHz. The achieved seeding density of <0.01 ppp enables resolving the Kármán vortices, whereas turbulent sub-structures cannot be captured.

  3. INVESTIGATION STUDIES ON SUB-COOLING OF CRYOGENIC LIQUIDS USING HELIUM INJECTION METHOD

    Directory of Open Access Journals (Sweden)

    T. Ramesh

    2014-01-01

    Full Text Available In cryogenic propellants, the sub-cooling of cryogenic propellants contained in tanks is an important and effective method for bringing down the lift-off mass of launch vehicle and thus the performance of the rocket engine is greatly improved. This study presents the technical and experimental studies conducted on cryogenic liquids such as Liquid Oxygen, Liquid Nitrogen and Liquid Hydrogen using helium injection method. The influence of cooled Helium on the degree of sub-cooling and the variation in flow rate of Helium gas admitted are discussed. The experimental and theoretical studies indicate that the sub-cooling technique using helium injection is a very simple method and can be very well adopted in propellant tanks used for ground and launch vehicle applications. The overall cooling effect for rocket application is also discussed. The critical values of the non-dimensional parameters and injected helium temperatures are also estimated.

  4. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    Science.gov (United States)

    Chernov, I. I.; Kalashnikov, A. N.; Kalin, B. A.; Binyukova, S. Yu

    2003-12-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe-C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion irradiation up to a fluence of 5 × 10 20 m -2 at the temperature of 920 K. It was shown that helium-ion irradiation at high temperature resulted in formation of bubbles with a greater size and a smaller density in Fe and ferritic-martensitic steels than those in nickel and austenitic steels. Large gaseous bubbles in ferritic component are uniformly distributed in grains body in Fe-C alloys as well as in ferritic-martensitic steels. The bubbles with a higher density and a smaller size than those in ferritic component are formed in martensitic grains of steels and Fe-C alloys with a high carbon content ( NC>0.01 wt%), which leads to a small level of swelling of martensite in comparison with that of ferrite. In addition, the bubbles in martensitic grains have a tendency to ordered distribution.

  5. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Chernov, I.I. E-mail: chernov@phm.mephi.ru; Kalashnikov, A.N.; Kalin, B.A.; Binyukova, S.Yu

    2003-12-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe-C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion irradiation up to a fluence of 5 x 10{sup 20} m{sup -2} at the temperature of 920 K. It was shown that helium-ion irradiation at high temperature resulted in formation of bubbles with a greater size and a smaller density in Fe and ferritic-martensitic steels than those in nickel and austenitic steels. Large gaseous bubbles in ferritic component are uniformly distributed in grains body in Fe-C alloys as well as in ferritic-martensitic steels. The bubbles with a higher density and a smaller size than those in ferritic component are formed in martensitic grains of steels and Fe-C alloys with a high carbon content (N{sub C}>0.01 wt%), which leads to a small level of swelling of martensite in comparison with that of ferrite. In addition, the bubbles in martensitic grains have a tendency to ordered distribution.

  6. Parameters Relevant to Bubble Detachment when Gas-injecting into Polymer Melt Flow Field

    Institute of Scientific and Technical Information of China (English)

    CHEN Zailiang; CAI Yebin; GUO Mingcheng; PENG Yucheng

    2005-01-01

    The bubble deformation processes were reported when gas was injected into polymer melt flow field in another paper, the experiments showed that the deformation was severely affected by the volume of the bubble, and in turn, for the different bubbles, several different deformation processes were presented during their movement along the flow channel. In addition, we could find that the magnitude of the bubble volume was dependent upon the pressure difference of the gas injection pressure and the melt pressure. In this paper, more experimental conditions were changed to investigate the parameters relevant to the detachment of bubbles from the injection nozzle. The experimental results show that the pressure difference, the melt flow velocity as well as the melt pressure were all critical for the parameters, such as the bubble detachment time, the maximum bubble diameters and the magnitude of the bubble volume. The morphology changes of bubble were very large when the flow field was abruptly changed, and the situations were more complicated.

  7. Experiments and numerical analysis of a control method for natural circulation through helium gas injection

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tetsuaki, E-mail: ttakeda@yamanashi.ac.jp; Hatori, Hirofumi; Funatani, Shumpei

    2016-09-15

    This study investigated a control method for natural circulation of air by helium gas injection. A depressurization accident is a design-basis accident of a very high temperature reactor. When a primary pipe rupture accident occurs, air is expected to enter the reactor pressure vessel from the breach. Thus, in-core graphite structures are oxidized. In order to predict and analyze the phenomena of air ingress during a depressurization accident, numerical analysis was carried out using a one-dimensional (1D) analysis code and three-dimensional computational fluid dynamics (3D CFD). An experiment was carried out regarding natural circulation using a circular pipe consisting of a reverse U-shaped channel. The channel consisted of two vertical heated and cooled pipes. The temperature difference between the vertical pipes was maintained at 40–80 K, and a small amount of helium gas was injected into the channel. The injected volume of helium was about 3.1–12.5% of the total channel volume. After injecting helium gas, each component gas moved through molecular diffusion and very weak natural circulation. After approximately 1180 s, ordinary natural circulation of air was suddenly produced. The numerical results of the 3D CFD code were in good agreement with the experimental results. The numerical results also showed that the natural circulation of air can be controlled by helium gas injection.

  8. Modeling of helium bubble nucleation and growth in austenitic stainless steels using an Object Kinetic Monte Carlo method

    Science.gov (United States)

    De Backer, A.; Adjanor, G.; Domain, C.; Lescoat, M. L.; Jublot-Leclerc, S.; Fortuna, F.; Gentils, A.; Ortiz, C. J.; Souidi, A.; Becquart, C. S.

    2015-06-01

    Implantation of 10 keV helium in 316L steel thin foils was performed in JANNuS-Orsay facility and modeled using a multiscale approach. Density Functional Theory (DFT) atomistic calculations [1] were used to obtain the properties of He and He-vacancy clusters, and the Binary Collision Approximation based code MARLOWE was applied to determine the damage and He-ion depth profiles as in [2,3]. The processes involved in the homogeneous He bubble nucleation and growth were defined and implemented in the Object Kinetic Monte Carlo code LAKIMOCA [4]. In particular as the He to dpa ratio was high, self-trapping of He clusters and the trap mutation of He-vacancy clusters had to be taken into account. With this multiscale approach, the formation of bubbles was modeled up to nanometer-scale size, where bubbles can be observed by Transmission Electron Microscopy. Their densities and sizes were studied as functions of fluence (up to 5 × 1019 He/m2) at two temperatures (473 and 723 K) and for different sample thicknesses (25-250 nm). It appears that the damage is not only due to the collision cascades but is also strongly controlled by the He accumulation in pressurized bubbles. Comparison with experimental data is discussed and sensible agreement is achieved.

  9. Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    2013-01-01

    A goal of our ongoing research stream is to develop a multidisciplinary metatheory of bubbles. In this viewpoint paper we put forward a typology of bubbles by comparing four types of assets – entertainment, commodities, financial securities (stocks), and housing properties – where bubbles could a...

  10. Creep behavior of reduced activation martensitic steel F82H injected with a large amount of helium

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, N. E-mail: yamamoto.norikazu@nims.go.jp; Murase, Y.; Nagakawa, J.; Shiba, K

    2002-12-01

    Creep response against DEMO reactor level helium was examined on F82H steel, a candidate structural material for advanced fusion systems. Helium was injected into the material at 823 K to a concentration of about 1000 appm utilizing {alpha}-particle irradiation with a cyclotron. Post-injection creep rupture tests were conducted at the same temperature. It has been demonstrated that helium brought about no significant effect on a variety of creep properties (lifetime, rupture elongation and minimum creep rate). In parallel with this, it did not cause any influence on fracture appearance. Both helium implanted and unimplanted samples were failed in a completely transcrystalline and ductile fashion. No symptom of helium induced grain boundary separation was thereby observed even after high concentration helium introduction. These facts hint a fairly good resistance of this material toward high temperature helium embrittlement even for long-time service in fusion reactors.

  11. Study on control method of natural circulation by injection of helium gas

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Tetsuaki, E-mail: ttakeda@yamanashi.ac.jp; Nomura, Masashi; Yanagawa, Naoto; Funatani, Shumpei

    2014-05-01

    This study is to investigate a control method of natural circulation of air by injection of helium gas. A depressurization accident is one of the design-basis accidents of a very high temperature reactor (VHTR). When the primary pipe rupture accident occurs in the VHTR, air is expected to enter into the reactor pressure vessel from the breach and oxidize in-core graphite structures. Finally, it seems to be probable that the natural circulation flow of air in the reactor pressure vessel produce continuously. In order to predict or analyze the air ingress phenomena during the depressurization accident of the VHTR, therefore, it is important to develop the method for prevention of air ingress during the accident. The experiment has been carried out regarding natural circulation using a circular tube consisting of a reverse U-shaped type. The vertical channel consists of the one side heated tube and the other side cooled tube. The experimental procedure is as follows. Firstly, the apparatus is filled with air and one vertical tube is heated. Then, natural circulation of air will be produced in the channel. After the steady state is established, a very small amount of helium gas injects from the top of the channel. The velocity, temperature of gas, and temperature of the tube wall are measured during the experiment. The analysis also has been carried out regarding natural circulation. The results were obtained as follows. The temperature difference between the vertical pipes was 50–130 K, and a small amount of helium gas injected to the channel. The volume of injected helium gas is about 3.5–10% of the total volume of the channel. When the temperature difference between the vertical tubes was kept at 52 K, the velocity of natural circulation flow became about 0.12 m/s. During a steady state, a small amount of helium gas injected into the channel. Then, the flow velocity of natural circulation suddenly decreased. The volume of injected helium gas is about 3% of the

  12. Fermi bubble $\\gamma$-rays as a result of diffusive injection of Galactic cosmic rays

    CERN Document Server

    Thoudam, Satyendra

    2013-01-01

    Recently, the {\\it{Fermi}} space telescope has discovered two large $\\gamma$-ray emission regions, the so-called "Fermi bubbles", that extend up to $\\sim 50^\\circ$ above and below the Galactic center. The $\\gamma$-ray emission from the bubbles are found to follow a hard spectrum with no significant spatial variation in intensity and spectral shape. The origin of the emission is still not clearly understood. Suggested explanations include injection of cosmic-ray nuclei from the Galactic center by high-speed Galactic winds, electron acceleration by multiple shocks and stochastic electron acceleration inside the bubbles. In this letter, it is proposed that the $\\gamma$-rays can be the result of diffusive injection of Galactic cosmic-ray protons during their propagation through the Galaxy. Considering that cosmic rays undergo much slower diffusion inside the bubbles than in the averaged Galaxy and at the same time suffer from inelastic collisions with the bubble plasma, this model can explain the observed intensi...

  13. Helium bubble nucleation and growth in α-Fe: insights from first-principles simulations.

    Science.gov (United States)

    Xiao, W; Zhang, X; Geng, W T; Lu, G

    2014-06-25

    We have carried out a first-principles study on the nucleation and early-stage growth of He bubbles in Fe. The energetics, atomic and electronic structure of He-vacancy complexes, involving both a monovacancy and a nine-vacancy cluster, are examined. Based on the energetics, we then perform thermodynamics analysis to gain deeper insights into He bubble nucleation and growth. We have determined the energy cost for the nucleation of He bubbles and found that up to eight He atoms can be trapped at a single vacancy. In order to capture more He atoms, the vacancy has to emit Frenkel pairs to release the substantial stress building on the surrounding Fe lattice. Compared to the monovacancy, the nine-vacancy cluster has a lower energy cost for He bubble nucleation and growth. He atoms at the vacancy repel the surrounding electronic charge and redistribute it on the neighboring Fe atoms. The thermodynamic analysis reveals that He chemical potential provides a driving force for He bubble nucleation and growth. There are two critical He chemical potentials that are of particular importance: one of them marks the transition from single He occupation to multiple He occupation at a monovacancy while the other sets off He-induced superabundant vacancy formation.

  14. In Situ Electron Microscopy of Helium Bubble Implantation in Metal Hydrides

    Energy Technology Data Exchange (ETDEWEB)

    Hattar, Khalid Mikhiel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bufford, Daniel Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Robinson, David [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Snow, Clark Sheldon [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-09-01

    Here we investigated the microstructural response of various Pd physically vapor deposited films and Er and ErD2 samples prepared from neutron Tube targets to implanted He via in situ ion irradiation transmission electron microscopy and subsequent in situ annealing experiments. Small bubbles formed in both systems during implantation, but did not grow with increasing fluence or a short duration room temperature aging (weeks). Annealing produced large cavities with different densities in the two systems. The ErD2 showed increased cavity nucleation compared to Er. The spherical bubbles formed from high fluence implantation and rapid annealing in both Er and ErD2 cases differed from microstructures of naturally aged tritiated samples. Further work is still underway to determine the transition in bubble shape in the Er samples, as well as the mechanism for evolution in Pd films.

  15. Helium Bubbles Cavitation Phenomena in Pb-15.7Li and Potential Impact on Tritium Transport Behaviour in HCLL Breeding Channels

    Energy Technology Data Exchange (ETDEWEB)

    Sedano, L. A.

    2007-09-27

    COMPU task is devoted to develop a Process Flow Diagram (PFD) modelling tool for DEMO tritium cycle for HCLL and HCPB blanket lines for DEMO. At the actual stage of definition of HCLL blanket design line this global objective requires to progress specifically on the physical reliability of tritium transport assessments at blanket design level. A rough reliability assessment with the identify cation of physical phenomena determining permeation rates into the coolant was tentatively advanced in COMPU Task Deliverable 1. In HCLL design, the tritium diffusion in the alloy under the flow conditions and radiation effects in Pb15.7Li can be theoretically justifies ed as the rate limiting processes for tritium transfer into the coolant. This Deliverable 2 focuses on the analysis of a specific radiation effect: the potential role of helium bubbles in Pb15.7Li, the discussion of its implications on tritium assessment for HCLL design and consequently the analysis of its quantitative impact (as cycle input) on HCLL PFD tritium cycle design. Thus, the contents of this report investigate: (1) the rationality of the consideration on HCLL design of helium bubble cavitation phenomena in irradiated Pb15.7Li channels on the base of fundamental analysis (He solution states in Pb15.7Li) from empirical clues provided by Pb15.7Li irradiation tests, (2) a preliminary rough He-bubble cavitation design assessment and bases for a more precise FEM calculation for helium bubble cavitation phenomena in HCLL blanket channels, (3) the analysis of direct experimental data and numerical developments needed for a precise cavitation assessment and (4) a proposal of the lay-out and general specifications of an integral proof-of-principle Cavitation Experiment (Cevitex) of Helium in Pb15.7Li. (Author) 40 refs.

  16. Proton and Helium Injection Into First Order Fermi Acceleration at Shocks: Hybrid Simulation and Analysis

    Science.gov (United States)

    Dudnikova, Galina; Malkov, Mikhail; Sagdeev, Roald; Liseykina, Tatjana; Hanusch, Adrian

    2016-10-01

    Elemental composition of galactic cosmic rays (CR) probably holds the key to their origin. Most likely, they are accelerated at collisionless shocks in supernova remnants, but the acceleration mechanism is not entirely understood. One complicated problem is ``injection'', a process whereby the shock selects a tiny fraction of particles to keep on crossing its front and gain more energy. Comparing the injection rates of particles with different mass to charge ratio is a powerful tool for studying this process. Recent advances in measurements of CR He/p ratio have provided particularly important new clues. We performed a series of hybrid simulations and analyzed a joint injection of protons and Helium, in conjunction with upstream waves they generate. The emphasis of this work is on the bootstrap aspects of injection manifested in particle confinement to the shock and, therefore, their continuing acceleration by the self-driven waves. The waves are initially generated by He and protons in separate spectral regions, and their interaction plays a crucial role in particle acceleration. The work is ongoing and new results will be reported along with their analysis and comparison with the latest data from the AMS-02 space-based spectrometer. Work supported Grant RFBR 16-01-00209, NASA ATP-program under Award NNX14AH36G, and by the US Department of Energy under Award No. DE-FG02-04ER54738.

  17. Stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection

    Science.gov (United States)

    Qin, Shijie; Chu, Ning; Yao, Yan; Liu, Jingting; Huang, Bin; Wu, Dazhuan

    2017-03-01

    To investigate the stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection, both experiments and simulations of bubble drag reduction (BDR) have been conducted in this paper. Drag reductions at various flow speeds and air injection rates have been tested in cavitation tunnel experiments. Visualization of bubble flow pattern is implemented synchronously. The computational fluid dynamics (CFD) method, in the framework of Eulerian-Eulerian two fluid modeling, coupled with population balance model (PBM) is used to simulate the bubbly flow along the flat plate. A wide range of bubble sizes considering bubble breakup and coalescence is modeled based on experimental bubble distribution images. Drag and lift forces are fully modeled based on applicable closure models. Both predicted drag reductions and bubble distributions are in reasonable concordance with experimental results. Stream-wise distribution of BDR is revealed based on CFD-PBM numerical results. In particular, four distinct regions with different BDR characteristics are first identified and discussed in this study. Thresholds between regions are extracted and discussed. And it is highly necessary to fully understand the stream-wise distribution of BDR in order to establish a universal scaling law. Moreover, mechanism of stream-wise distribution of BDR is analysed based on the near-wall flow parameters. The local drag reduction is a direct result of near-wall max void fraction. And the near-wall velocity gradient modified by the presence of bubbles is considered as another important factor for bubble drag reduction.

  18. Fetal Gene Therapy for Ornithine Transcarbamylase Deficiency by Intrahepatic Plasmid DNA-Micro-Bubble Injection Combined with Hepatic Ultrasound Insonation.

    Science.gov (United States)

    Oishi, Yoshie; Kakimoto, Takashi; Yuan, Wenji; Kuno, Shuichi; Yamashita, Hiromasa; Chiba, Toshio

    2016-06-01

    We evaluated the therapeutic efficacy of hepatic transfection of plasmid DNA using micro-bubbles and ultrasound insonation for fetal correction of ornithine transcarbamylase (OTC) deficiency in mice. Twenty-three sparse-fur heterozygous pregnant mice (day 16 of gestation) were divided into three groups: injection of plasmid-DNA micro-bubble mixture into fetal liver with ultrasound insonation (Tr, n = 11); control group 1 (C1), injection of plasmid-DNA micro-bubble mixture into fetal liver with no insonation (n = 5); and control group 2 (C2), injection of saline-micro-bubble mixture into fetal liver with ultrasound insonation (n = 7). Levels of blood ammonia and urinary orotic acid were significantly lower in the Tr group than in the C1 and C2 groups (p < 0.05, p < 0.01, respectively), whereas OTC activity was not different between groups. Therefore, ultrasound insonation with micro-bubbles enhanced plasmid DNA transfection into fetal mouse liver, leading to one of the therapeutic methods in ammonia metabolism. This might provide more time for OTC-deficient infants until liver transplantation. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  19. PDMS glass serpentine microchannel chip for time domain PCR with bubble suppression in sample injection

    Science.gov (United States)

    Cho, Chul-Ho; Cho, Woong; Ahn, Yoomin; Hwang, Seung-Yong

    2007-09-01

    This paper reports on the development of a low-cost microreactor (10 µl) biochip for DNA polymerase chain reaction (PCR). The microbiochip (20 mm × 28 mm) is a hybrid type that is composed of a polydimethylsiloxane (PDMS) layer with a serpentine microchannel (360 µm × 100 µm) chamber and glass substrate integrated with a microheater and thermal microsensor. Because of the hydrophobic chip surface, bubbles are usually created during sample loading in the PMDS-based microchip. These bubbles disrupt the stable biochemical reaction. An improved microreactor chamber was designed using microfluidic simulation. The reactor has a rounded-corner serpentine channel architecture, which enables stable injection into the hydrophobic surface using only a micropipette. The reactor temperature needed for the PCR reaction is controlled within ±0.5 °C by the LabVIEW software proportional-integrative-derivative (PID) controller. PCR analyses of the sex-determining Y chromosome (SRY) gene and mouse GAPDH gene were successfully performed in less than 54 min by the fabricated microreactor chip.

  20. Effects of local structure on helium bubble growth in bulk and at grain boundaries of bcc iron: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Li [Univ. of Electronic Science and Technology of China, Chengdu (China); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gao, Fei [Univ. of Michigan, Ann Arbor, MI (United States); Kurtz, Richard J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zu, Xiaotao [Univ. of Electronic Science and Technology of China, Chengdu (China); Peng, S. M. [China Academy of Engineering Physics, Mianyang (China); Long, X. G. [China Academy of Engineering Physics, Mianyang (China); Zhou, X. S. [China Academy of Engineering Physics, Mianyang (China)

    2015-07-15

    The nucleation and growth of helium (He) bubbles in the bulk and at Σ3 <110> {112} and Σ73b <110> {661} grain boundaries (GBs) in bcc iron have been investigated using molecular dynamics simulations. The results show that a 1/2 <111> {111} dislocation loop is formed with the sequential collection of <111> interstitial crowdions at the periphery of the He cluster and is eventually emitted from the He cluster. Insertion of 45 He atoms into a He cluster leads to the formation of a 1/2 <111> dislocation loop in Σ3 GB. It is of interest to notice that the transition of a dislocation segment through the GB leads to the formation of a step at the GB plane following the loop formation, accounting for the formation of a residual GB defect. A 1/2 <111> loop, with a {110} habit plane, is emitted with further increase of the He bubble size in the Σ3 GB. In contrast, the sequential insertion of He atoms in Σ73b GB continuously emits self-interstitial atoms (SIAs), but these SIAs rearrange at the core of the inherent GB dislocation, instead of forming a dislocation loop, which leads the GB dislocation to propagate along the [1¯1¯ 1 2] direction. In the bulk and Σ3 GB, the He bubble exhibits three-dimensionally spherical shape, but it forms longitudinal shape along the dislocation line in the Σ73 GB, a shape commonly observed at GBs in experiments.

  1. Effect of Gas- and Liquid-injection Methods on Formation of Bubble and Liquid Slug at Merging Micro T-junction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Kyoung [Kyungnam Univ., Changwon (Korea, Republic of); Lee, Chi Young [Pukyong Nat’l Univ., Busan (Korea, Republic of)

    2016-04-15

    In the present experimental study, the effect of gas- and liquid-injected methods on the formation of bubble and liquid slug at the merging micro T-junction of a square microchannel with dimensions 600 μm × 600 μm was investigated. Nitrogen and water were used as test fluids. The superficial velocities of the liquid and gas were in the range of 0.05 - 1 m/s, and 0.1 - 1 m/s, respectively, where the Taylor flow was observed. The bubble length, liquid slug length, bubble velocity, and bubble generation frequency were measured by analyzing the images captured using a high-speed camera. Under similar inlet superficial velocity conditions, in the case of gas injection to the main channel at the merging T-junction (T{sub g}as-liquid), the lengths of the bubble and liquid slug were longer, and the bubble generation frequency was lower than in the case of liquid injection to the main channel at the merging T-junction (T{sub l}iquid-gas). On the other hand, in both cases, the bubble velocity was almost the same. The previous correlation proposed using experimental data for T{sub l}iquid-gas had predicted the present experimental data of bubble length, bubble velocity, liquid slug length, and bubble generation frequency for T{sub g}as-liquid to be ~24%, ~9%, ~39%, ~55%, respectively.

  2. Effects of composition and helium injection on dislocation loop development in pure FeNiCr alloys under Ni ion irradiation

    Science.gov (United States)

    Kimoto, Takayoshi

    1993-08-01

    Pure Fe35Ni7Cr, Fe45Ni7Cr, Fe40Ni13Cr and Fe45Ni15Cr alloys were irradiated by 4MeV Ni 2+ ions at 948 K to doses of about 0.05, 0.3 and 1.0 dpa without helium injection or with simultaneous helium injection. With increasing Ni content and decreasing Cr content, the diameter of radiation-induced dislocation loops increased, and the dose at which the dislocation loops disappeared to develop into dislocation networks decreased. The diameter of dislocation loops induced by Ni 2+ ions irradiation with simultaneous helium injection was larger than that without helium injection for the Fe35Ni7Cr and Fe45Ni7Cr alloys.

  3. Effect of Orifice Diameter on Bubble Generation Process in Melt Gas Injection to Prepare Aluminum Foams

    Science.gov (United States)

    Yuan, Jianyu; Li, Yanxiang; Wang, Ningzhen; Cheng, Ying; Chen, Xiang

    2016-06-01

    The bubble generation process in conditioned A356 alloy melt through submerged spiry orifices with a wide diameter range (from 0.07 to 1.0 mm) is investigated in order to prepare aluminum foams with fine pores. The gas flow rate and chamber pressure relationship for each orifice is first determined when blowing gas in atmospheric environment. The effects of chamber pressure ( P c) and orifice diameter ( D o) on bubble size are then analyzed separately when blowing gas in melt. A three-dimensional fitting curve is obtained illustrating both the influences of orifice diameter and chamber pressure on bubble size based on the experimental data. It is found that the bubble size has a V-shaped relationship with orifice diameter and chamber pressure neighboring the optimized parameter ( D o = 0.25 mm, P c = 0.4 MPa). The bubble generation mechanism is proposed based on the Rayleigh-Plesset equation. It is found that the bubbles will not be generated until a threshold pressure difference is reached. The threshold pressure difference is dependent on the orifice diameter, which determines the time span of pre-formation stage and bubble growth stage.

  4. Diagnostics of a charge breeder electron cyclotron resonance ion source helium plasma with the injection of ^{23}Na^{1+} ions

    Directory of Open Access Journals (Sweden)

    O. Tarvainen

    2016-05-01

    Full Text Available This work describes the utilization of an injected ^{23}Na^{1+} ion beam as a diagnostics of the helium plasma of a charge breeder electron cyclotron resonance ion source. The obtained data allows estimating the upper limit for the ion-ion collision mean-free path of the incident sodium ions, the lower limit of ion-ion collision frequencies for all charge states of the sodium ions and the lower limit of the helium plasma density. The ion-ion collision frequencies of high charge state ions are shown to be at least on the order of 1–10 MHz and the plasma density is estimated to be on the order of 10^{11}  cm^{-3} or higher. The experimental results are compared to simulations of the ^{23}Na^{1+} capture into the helium plasma. The results indicate that the lower breeding efficiency of light ions in comparison to heavier elements is probably due to different capture efficiencies in which the in-flight ionization of the incident 1+ ions plays a vital role.

  5. The Injection of Air/Oxygen Bubble into the Anterior Chamber of Rabbits as a Treatment for Hyphema in Patients with Sickle Cell Disease

    Directory of Open Access Journals (Sweden)

    Emre Ayintap

    2014-01-01

    Full Text Available Purpose. To investigate the changes of partial oxygen pressure (PaO2 in aqueous humour after injecting air or oxygen bubble into the anterior chamber in sickle cell hyphema. Methods. Blood samples were taken from the same patient with sickle cell disease. Thirty-two rabbits were divided into 4 groups. In group 1 (n=8, there was no injection. Only blood injection constituted group 2 (n=8, both blood and air bubble injection constituted group 3 (n=8, and both blood and oxygen bubble injection constituted group 4 (n=8. Results. The PaO2 in the aqueous humour after 10 hours from the injections was 78.45 ± 9.9 mmHg (Mean ± SD for group 1, 73.97 ± 8.86 mmHg for group 2, 123.35 ± 13.6 mmHg for group 3, and 306.47 ± 16.5 mmHg for group 4. There was statistically significant difference between group 1 and group 2, when compared with group 3 and group 4. Conclusions. PaO2 in aqueous humour was increased after injecting air or oxygen bubble into the anterior chamber. We offer to leave an air bubble in the anterior chamber of patients with sickle cell hemoglobinopathies and hyphema undergoing an anterior chamber washout.

  6. Experimental Investigation of Gas Hydrate Production at Injection of Liquid Nitrogen into Water with Bubbles of Freon 134A

    Directory of Open Access Journals (Sweden)

    Meleshkin Anton V.

    2016-01-01

    Full Text Available The hydrodynamic processes during the injection of the cryogenic liquid into the volume of water with bubbles of gas freon 134a are studding experimentally. A processes during the explosive boiling of liquid nitrogen in the volume of water are registered. Video recording of identified gas hydrate flakes formed during this process is carried out by high speed camera. These results may be useful for the study of the new method of producing gas hydrates, based on the shock-wave method.

  7. Negative ions in liquid helium

    Science.gov (United States)

    Khrapak, A. G.; Schmidt, W. F.

    2011-05-01

    The structure of negative ions in liquid 4He is analyzed. The possibility of cluster or bubble formation around impurity ions of both signs is discussed. It is shown that in superfluid helium, bubbles form around negative alkaline earth metal ions and clusters form around halogen ions. The nature of "fast" and "exotic" negative ions is also discussed. It is assumed that "fast" ions are negative ions of helium excimer molecules localized inside bubbles. "Exotic" ions are stable negative impurity ions, which are always present in small amounts in gas discharge plasmas. Bubbles or clusters with radii smaller the radius of electron bubbles develop around these ions.

  8. Bubble Drag Reduction Requires Large Bubbles

    Science.gov (United States)

    Verschoof, Ruben A.; van der Veen, Roeland C. A.; Sun, Chao; Lohse, Detlef

    2016-09-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

  9. Bubble drag reduction requires large bubbles

    CERN Document Server

    Verschoof, Ruben A; Sun, Chao; Lohse, Detlef

    2016-01-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

  10. Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures

    DEFF Research Database (Denmark)

    Randsoe, T.; Kvist, T.M.; Hyldegaard, O.

    2008-01-01

    changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level) after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox(34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied...... and heliox breathing. Preoxygenation enhanced bubble disappearance compared with oxygen and heliox breathing but did not prevent bubble growth. The results indicate that oxygen breathing at 25 kPa promotes air bubble growth in adipose tissue regardless of the tissue nitrogen pressure Udgivelsesdato: 2008/11......At altitude, bubbles are known to form and grow in blood and tissues causing altitude decompression sickness. Previous reports indicate that treatment of decompression sickness by means of oxygen breathing at altitude may cause unwanted bubble growth. In this report we visually followed the in vivo...

  11. Molecular Dynamics Simulations of Helium Behaviour in Titanium Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Tie-Ying; LONG Xing-Gui; WANG Jun; HOU Qing; WU Zhong-Cheng; PENG Shu-Ming; LUO Shun-Zhong

    2008-01-01

    Molecular dynamics simulations are performed to investigate the behaviour of helium atoms in titanium at a temperature of 300 K.The nucleation and growth of helium bubble has been simulated up to 50 helium atoms.The approach to simulate the bubble growth is to add helium atoms one by one to the bubble and let the system evolve.The titanium cohesion is based on the tight binding scheme derived from the embedded atom method,and the helium-titanium interaction is characterized by fitted potential in the form of a Lennard-Jones function.The pressure in small helium bubbles is approximately calculated.The simulation results show that the pressure will decrease with the increasing bubble size,while increase with the increasing helium atoms.An analytic function about the quantitative relationship of the pressure with the bubble size and number of helium atoms is also fitted.

  12. Thermo-mechanical Analysis of Cold Helium Injection into Gas Storage Tanks made of Carbon Steel Following Resistive Transition of the LHC Magnets

    CERN Document Server

    Chorowski, M

    1998-01-01

    A resistive transition (quench) of the LHC sector magnets will be followed by cold helium venting to a quench buffer volume of 2000 m3 at ambient temperature. The volume will be composed of eight medi um-pressure (2 MPa) gas storage tanks made of carbon steel, which constrains the temperature of the wall to be higher than -50oC (223 K). The aim of the analysis is the assessment of a possible spot c ooling intensity and thermo-mechanical stresses in the tank wall following helium injection.

  13. Development and implementation of a model of permeation of tritium in the presence of bubbles of helium to tritigenic wraps of liquid metal wraps; Desarrollo e implementacion de un modelo de permeacion de tritio en presencia de burbujas de helio para envolturas tritigenicas de metal liquido

    Energy Technology Data Exchange (ETDEWEB)

    Batet, L.; Mas de les Valls, E.; Sedano, L. A.

    2013-07-01

    In the channels of liquid metal (ML) regenerating sheaths of a fusion reactor, the possibility of bubbles of helium is not remote. Bubbles adhering to the wall of the ML channels would affect heat transfer and the permeation of tritium. Detailed analysis has been conducted (fine mesh), using OpenFOAM, from the environment of a bubble attached to the wall and has developed a model for permeation of tritium through a partially covered with bubbles of helium surface of contact Ml-solid. The model developed has implemented as wall function in OpenFOAM, has validated and has been applied to a case study, using a relatively thick mesh. The developed model substantially reduces the need for computing on the detailed calculation power.

  14. Measurement of the recoalescence flux into the rear of a Taylor bubble

    Science.gov (United States)

    Delfos, R.; Rops, C. M.; Kockx, J. P.; Nieuwstadt, F. T. M.

    2001-05-01

    Most of the theoretical models on vertical slug flow assume the mass balance of a Taylor bubble to depend only on the incoming gas flux at the top of the Taylor bubble and on the outgoing entrainment flux at the bottom. This means that the recoalescence flux, which is defined as the fraction of the entrainment flux that coalesces back into the bubble, is neglected. Only in Fernandes et al. [AIChE J. 29, 981 (1983)] is a model proposed for this recoalescence flux but their model has never been verified by measurements. Therefore, we set out in the present research to measure and quantify the recoalescence flux. Our experiments have been carried out in a recirculating flow facility with a vertical cylindrical test section with inner diameter Di=100 mm. In this test section a Taylor bubble is kept at a fixed vertical position by a constant downward liquid flow ΨL. A continuous stream of small helium bubbles is injected into the wake of the Taylor bubble. The recoalescence flux is then determined by measuring the concentration of helium in the Taylor bubble. Our experiments show that there is a recoalescence flux and that in general it cannot be neglected in the mass balance of the Taylor bubble. The total gas loss from the Taylor bubble, Ψin, and the recoalescence flux Ψrec increase both strongly with the Taylor bubble length, LTB. The fraction of entrained bubbles that recoalesces back into the Taylor bubble increases from 10% of the entrainment flux at LTB=60 cm (λG=Ψin/ΨL=4%) to 45% at LTB=91 cm (λG=11%).

  15. Comparison of induced damage, range, reflection, and sputtering yield between amorphous, bcc crystalline, and bubble-containing tungsten materials under hydrogen isotope and noble gas plasma irradiations

    Science.gov (United States)

    Saito, Seiki; Nakamura, Hiroaki; Tokitani, Masayuki

    2017-01-01

    Binary-collision-approximation simulation of hydrogen isotope (i.e., hydrogen, deuterium, and tritium) and noble gas (i.e., helium, neon, and argon) injections into tungsten materials is performed. Three tungsten structures (i.e., amorphous, bcc crystalline, and helium bubble-containing structures) are prepared as target materials. Then, the trajectories of incident atoms, the distribution of recoil atoms, the penetration depth range of incident atoms, the sputtering yield, and the reflection rate are carefully investigated for these target materials.

  16. Around the laboratories: Dubna: Physics results and progress on bubble chamber techniques; Stanford (SLAC): Operation of a very rapid cycling bubble chamber; Daresbury: Photographs of visitors to the Laboratory; Argonne: Charge exchange injection tests into the ZGS in preparation for a proposed Booster

    CERN Multimedia

    1969-01-01

    Around the laboratories: Dubna: Physics results and progress on bubble chamber techniques; Stanford (SLAC): Operation of a very rapid cycling bubble chamber; Daresbury: Photographs of visitors to the Laboratory; Argonne: Charge exchange injection tests into the ZGS in preparation for a proposed Booster

  17. Effects of surface orientation on lifetime of near-surface nanoscale He bubble in tungsten

    Science.gov (United States)

    Cui, Jiechao; Fu, Baoqin; Wu, Zhangwen; Hou, Qing

    2017-02-01

    In multiscale modeling of the morphological evolution of plasma facing materials in nuclear fusion reactors, the knowledge of the timescales of the involved physical processes is important. In the present study, a new method based on molecular dynamics simulations was developed to extract the lifetime of helium bubbles near tungsten surfaces. It was found that the lifetime of a helium bubble can be described by the Arrhenius equation. However, the lifetime of a helium bubble depends on the thickness of tungsten film above the helium bubble in the substrate and the bubble size. The influence of surface orientations on the lifetime of helium bubbles was also observed, and the performance of helium bubbles on the (1 1 1) surface is very different from on the (0 0 1) and (0 1 1) surfaces. The role of the helium bubble lifetime in other simulation techniques, such as in kinetic Monte Carlo methods and rate theory, is discussed.

  18. Effects of surface orientation on lifetime of near-surface nanoscale He bubble in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Jiechao; Fu, Baoqin; Wu, Zhangwen; Hou, Qing, E-mail: qhou@scu.edu.cn

    2017-02-15

    In multiscale modeling of the morphological evolution of plasma facing materials in nuclear fusion reactors, the knowledge of the timescales of the involved physical processes is important. In the present study, a new method based on molecular dynamics simulations was developed to extract the lifetime of helium bubbles near tungsten surfaces. It was found that the lifetime of a helium bubble can be described by the Arrhenius equation. However, the lifetime of a helium bubble depends on the thickness of tungsten film above the helium bubble in the substrate and the bubble size. The influence of surface orientations on the lifetime of helium bubbles was also observed, and the performance of helium bubbles on the (1 1 1) surface is very different from on the (0 0 1) and (0 1 1) surfaces. The role of the helium bubble lifetime in other simulation techniques, such as in kinetic Monte Carlo methods and rate theory, is discussed.

  19. Behaviour of helium after implantation in molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Viaud, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France)], E-mail: viaud@dircad.cea.fr; Maillard, S.; Carlot, G.; Valot, C. [Commissariat a l' Energie Atomique (CEA), Cadarache (France); Gilabert, E. [Chimie Nucleaire Analytique and Bio-environnementale (CNAB), Gradignan (France); Sauvage, T. [CEMHTI-CNRS, Orleans (France); Peaucelle, C.; Moncoffre, N. [Institut de Physique Nucleaire de Lyon (IPNL), Lyon (France)

    2009-03-31

    This study deals with the behaviour of helium in a molybdenum liner dedicated to the retention of fission products. More precisely this work contributes to evaluate the release of implanted helium when the gas has precipitated into nanometric bubbles close to the free surface. A simple model dedicated to calculate the helium release in such a condition is presented. The specificity of this model lays on the assumption that the gas is in equilibrium with a simple distribution of growing bubbles. This effort is encouraging since the calculated helium release fits an experimental dataset with a set of parameters in good agreement with the literature.

  20. Highly sensitive detection of five typical fluoroquinolones in low-fat milk by field-enhanced sample injection-based CE in bubble cell capillary.

    Science.gov (United States)

    Deng, Yan; Gasilova, Natalia; Qiao, Liang; Zhou, Ying-Lin; Zhang, Xin-Xiang; Girault, Hubert H

    2014-12-01

    Fluoroquinolones are a group of synthetic antibiotics with a broad activity spectrum against mycoplasma, Gram-positive, and Gram-negative bacteria. Due to the extensive use of fluoroquinolones in farming and veterinary science, there is a constant need in the analytical methods able to efficiently monitor their residues in food products of animal origin, regulated by Commission Regulation (European Union) no. 37/2010. Herein, field-enhanced sample injection for sample stacking prior the CZE separation was developed inside a bubble cell capillary for highly sensitive detection of five typical fluoroquinolones in bovine milk. Ethylenediamine was proposed as the main component of BGE for the antibiotics separation. The effect of BGE composition, injection parameters, and water plug length on the field-enhanced sample injection-based CE with UV detection was investigated. Under the optimized conditions, described field-enhanced sample injection-based CE-UV analysis of fluoroquinolones provides LODs varying from 0.4 to 1.3 ng/mL. These LOD values are much lower (from 460 to 1500 times) than those obtained by a conventional CE in a standard capillary without bubble cell. The developed method was finally applied for the analysis of fluoroquinolones in low-fat milk from a Swiss supermarket. Sample recovery values from 93.6 to 106.0% for different fluoroquinolones, and LODs from 0.7 to 2.5 μg/kg, were achieved. Moreover, the proposed ethylenediamine-based BGE as volatile and compatible with MS system, enabled the coupling of the field-enhanced sample injection-based CE with a recently introduced electrostatic spray ionization MS via an iontophoretic fraction collection interface for qualitative fluoroquinolones identification. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Characterization of nano-bubbles as an oxygen carrier for in-situ bioremediation of organic pollutants in the subsurface

    Science.gov (United States)

    KIM, E.; Jung, J.; Kang, S.; Choi, Y.

    2016-12-01

    In-situ bioremediation using bubbles as an oxygen carrier has shown its applicability for aerobic biodegradation of organic pollutants in the subsurface. By recent progresses, generation of nano-sized bubbles is possible, which have enhanced oxygen transfer efficiencies due to their high interfacial area and stability. We are developing an in-situ bioremediation technique using nano-bubbles as an oxygen carrier. In this study, nano-bubbles were characterized for their size and oxygen supply capacity. Nano-bubbles were generated with pure oxygen and pure helium gas. The stable nano-bubbles suspended in water were sonicated to induce the bubbles to coalesce, making them to rise and be released out of the water. By removing the bubbles, the water volume was decreased by 0.006%. The gas released from the bubble suspension was collected to measure the amount of gas in the nano-bubbles. For sparingly soluble helium gas 17.9 mL/L was released from the bubble suspension, while for oxygen 46.2 mL/L was collected. For the oxygen nano-bubble suspension, it is likely that the release of dissolved oxygen (DO) contributed to the collected gas volume. After removing the oxygen nano-bubbles, 36.0 mg/L of DO was still present in water. Altogether, the oxygen nano-bubble suspension was estimated to have 66.2 mg/L of oxygen in a dissolved form and 25.6 mg/L as nano-bubbles. A high DO level in the water was possible because of their large Laplace pressure difference across the fluid interface. Applying Young-Laplace equation and ideal gas law, the bubble diameter was estimated to be approximately 10 nm, having an internal pressure of 323 atm. Considering the saturation DO of 8.26 mg/L for water in equilibrium with the atmosphere, the total oxygen content of 91.8 mg/L in the nano-bubble suspension suggests its great potential as an oxygen carrier. Studies are underway to verify the enhanced aerobic biodegradation of organic pollutants in soils by injecting nano-bubble suspensions.

  2. Bubbles Outside the Plume During the LUMINY Wind-Wave Experiment

    NARCIS (Netherlands)

    Leeuw, G. de; Leifer, I.

    2002-01-01

    Since many bubble-mediated processes are size dependent, it is often necessary to characterize the bubble distribution over the full size spectrum. For example, in regards to bubble-mediated gas transfer, small bubbles are important for insoluble gases like helium, while large bubbles are important

  3. Gas diffusion and temperature dependence of bubble nucleation during irradiation

    DEFF Research Database (Denmark)

    Foreman, A. J. E.; Singh, Bachu Narain

    1986-01-01

    of the diatomic nucleation of helium bubbles, assuming helium to diffuse substitutionally, with radiation-enhanced diffusion at lower temperatures. The calculated temperature dependence of the bubble density shows excellent agreement with that observed in 600 MeV proton irradiations, including a reduction...

  4. Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures.

    Science.gov (United States)

    Randsøe, T; Kvist, T M; Hyldegaard, O

    2008-11-01

    At altitude, bubbles are known to form and grow in blood and tissues causing altitude decompression sickness. Previous reports indicate that treatment of decompression sickness by means of oxygen breathing at altitude may cause unwanted bubble growth. In this report we visually followed the in vivo changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level) after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox(34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied during oxygen breathing preceded by a 3-h period of preoxygenation to eliminate tissue nitrogen before decompression. During oxygen breathing, bubbles grew from 11 to 198 min (mean: 121 min, +/-SD 53.4) after which they remained stable or began to shrink slowly. During heliox breathing bubbles grew from 30 to 130 min (mean: 67 min, +/-SD 31.0) from which point they stabilized or shrank slowly. No bubbles disappeared during either oxygen or heliox breathing. Preoxygenation followed by continuous oxygen breathing at altitude caused most bubbles to grow from 19 to 179 min (mean: 51 min, +/-SD 47.7) after which they started shrinking or remained stable throughout the observation period. Bubble growth time was significantly longer during oxygen breathing compared with heliox breathing and preoxygenated animals. Significantly more bubbles disappeared in preoxygenated animals compared with oxygen and heliox breathing. Preoxygenation enhanced bubble disappearance compared with oxygen and heliox breathing but did not prevent bubble growth. The results indicate that oxygen breathing at 25 kPa promotes air bubble growth in adipose tissue regardless of the tissue nitrogen pressure.

  5. Nucleation, growth and transport modelling of helium bubbles under nuclear irradiation in lead-lithium with the Self-consistent nucleation theory and surface tension corrections

    CERN Document Server

    Fradera, Jorge

    2013-01-01

    Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFoam(r) CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a cr...

  6. Science Bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Pedersen, David Budtz

    2013-01-01

    Much like the trade and trait sof bubbles in financial markets,similar bubbles appear on the science market. When economic bubbles burst, the drop in prices causes the crash of unsustainable investments leading to an investor confidence crisis possibly followed by a financial panic. But when...... bubbles appear in science, truth and reliability are the first victims. This paper explores how fashions in research funding and research management may turn science into something like a bubble economy....

  7. Vapor Bubbles

    Science.gov (United States)

    Prosperetti, Andrea

    2017-01-01

    This article reviews the fundamental physics of vapor bubbles in liquids. Work on bubble growth and condensation for stationary and translating bubbles is summarized and the differences with bubbles containing a permanent gas stressed. In particular, it is shown that the natural frequency of a vapor bubble is proportional not to the inverse radius, as for a gas bubble, but to the inverse radius raised to the power 2/3. Permanent gas dissolved in the liquid diffuses into the bubble with strong effects on its dynamics. The effects of the diffusion of heat and mass on the propagation of pressure waves in a vaporous bubbly liquid are discussed. Other topics briefly touched on include thermocapillary flow, plasmonic nanobubbles, and vapor bubbles in an immiscible liquid.

  8. Thermal Annealing Behavior of Helium in Ti Films Deposited by Magnetron Sputtering

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lei; HE Zhi-Jiang; LIU Chao-Zhuo; WANG Xu-Fei; SHI Li-Qun

    2012-01-01

    Helium contents of up to 30at.% are prepared in sputter-deposited Ti Silms. Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the fi1ms at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA), as well as thermal helium desorption spectroscopy (THDS). It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs, which corresponds to the change of stopping cross-section of helium atoms in the Ti 61m due to the change of physical-state of helium in the evolution of helium bubble. The ion beam analysis on the helium evolution is consistent with the THDS measurement. Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.%Helium contents of up to 30at.% are prepared in sputter-deposited Ti films.Isochronal annealing behaviors of helium including the depth profiles and the evolution of helium bubbles in the films at different temperatures are examined by ion beam analysis including Rutherford backscattering spectrometry (RBS) and elastic recoil detection analysis (ERDA),as well as thermal helium desorption spectroscopy (THDS).It is found that the energy spreading induced by structural inhomogeneities in the spectra of RBS and ERDA as well as the increment in the width of spectra occurs,which corresponds to the change of stopping cross-section of helium atoms in the Ti film due to the change of physical-state of helium in the evolution of helium bubble.The ion beam analysis on the helium evolution is consistent with the THDS measurement.Ion beam technique opens interesting possibilities in the characterizing on the growth of helium bubbles.

  9. Bubble dynamics and bubble-induced turbulence of a single-bubble chain

    Science.gov (United States)

    Lee, Joohyoung; Park, Hyungmin

    2016-11-01

    In the present study, the bubble dynamics and liquid-phase turbulence induced by a chain of bubbles injected from a single nozzle have been experimentally investigated. Using a high-speed two-phase particle image velociemtry, measurements on the bubbles and liquid-phase velocity field are conducted in a transparent tank filled with water, while varying the bubble release frequency from 0.1 to 35 Hz. The tested bubble size ranges between 2.0-3.2 mm, and the corresponding bubble Reynolds number is 590-1100, indicating that it belongs to the regime of path instability. As the release frequency increases, it is found that the global shape of bubble dispersion can be classified into two regimes: from asymmetric (regular) to axisymmetric (irregular). In particular, at higher frequency, the wake vortices of leading bubbles cause an irregular behaviour of the following bubble. For the liquid phase, it is found that a specific trend on the bubble-induced turbulence appears in a strong relation to the above bubble dynamics. Considering this, we try to provide a theoretical model to estimate the liquid-phase turbulence induced by a chain of bubbles. Supported by a Grant funded by Samsung Electronics, Korea.

  10. Liquid helium

    CERN Document Server

    Atkins, K R

    1959-01-01

    Originally published in 1959 as part of the Cambridge Monographs on Physics series, this book addresses liquid helium from the dual perspectives of statistical mechanics and hydrodynamics. Atkins looks at both Helium Three and Helium Four, as well as the properties of a combination of the two isotopes. This book will be of value to anyone with an interest in the history of science and the study of one of the universe's most fundamental elements.

  11. Bubble coalescence

    NARCIS (Netherlands)

    Orvalho, Sandra; Ruzicka, Marek C.; Olivieri, Giuseppe; Marzocchella, Antonio

    2015-01-01

    The goal of this study is to present new experimental data on the effect of the bubble approach velocity and liquid viscosity on pairwise bubble coalescence. Measurements were performed to investigate the dynamics of bubble coalescence under well-defined laboratory conditions. Air and pure

  12. Bubbling at high flow rates in inviscid and viscous liquids (slags)

    Science.gov (United States)

    Engh, T. Abel; Nilmani, M.

    1988-02-01

    The behavior of gas discharging into melts at high velocities but still in the bubbling regime has been investigated in a laboratory modeling study for constant flow conditions. Air or helium was injected through a vertical tuyere into water, zinc-chloride, and aqueous glycerol solutions. High speed cinematography and pressure measurements in the tuyere have been carried out simultaneously. Pressure fluctuations at the injection point were monitored and correlated to the mode of bubble formation. The effects of high gas flow rates and high liquid viscosities have been examined in particular. Flow rates were employed up to 10-3 m3/s and viscosity to 0.5 Ns/m2. In order to attain a high gas momentum, the tuyere diameter was only 3 x 10-3 m. The experimental conditions and modeling liquids were chosen with special reference to the established practice of submerged gas injection to treat nonferrous slags. Such slags can be highly viscous. Bubble volume is smaller than that calculated from existing models such as those given by Davidson and Schüler10,11 due to the effect of gas momentum elongating the bubbles. On the other hand, viscosity tends to retard the bubble rise velocity, thus increasing volumes. To take elongation into account, a mathematical model is presented that assumes a prolate ellipsoidal shape of the bubbles. The unsteady potential flow equations for the liquid are solved for this case. Viscous effects are taken into account by noting that flow deviates from irrotational motion only in a thin boundary layer along the surface of the bubble. Thus, drag on the bubble can be obtained by calculating the viscous energy dissipation for potential flow past an ellipse. The time-dependent inertia coefficient for the ellipsoid is found by equating the vertical pressure increase inside and outside the bubble. This pressure change in the bubble is obtained by assuming that gas enters as a homogeneous jet and then calculating the stagnation pressure at the apex of

  13. Bubble rupture in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Chen Rouxi

    2015-01-01

    Full Text Available As the distinctive properties and different applications of nanofibers, the demand of nanofibers increased sharply in recently years. Bubble electrospinning is one of the most effective and industrialized methods for nanofiber production. To optimize the set-up of bubble electrospinning and improve its mass production, the dynamic properties of un-charged and charged bubbles are studied experimentally, the growth and rupture process of a bubble are also discussed in this paper.

  14. Helium cryogenics

    CERN Document Server

    Van Sciver, Steven W

    2012-01-01

    Twenty five years have elapsed since the original publication of Helium Cryogenics. During this time, a considerable amount of research and development involving helium fluids has been carried out culminating in several large-scale projects. Furthermore, the field has matured through these efforts so that there is now a broad engineering base to assist the development of future projects. Helium Cryogenics, 2nd edition brings these advances in helium cryogenics together in an updated form. As in the original edition, the author's approach is to survey the field of cryogenics with emphasis on helium fluids. This approach is more specialized and fundamental than that contained in other cryogenics books, which treat the associated range of cryogenic fluids. As a result, the level of treatment is more advanced and assumes a certain knowledge of fundamental engineering and physics principles, including some quantum mechanics. The goal throughout the work is to bridge the gap between the physics and engineering aspe...

  15. FINAL TECHNICAL REPORT FOR DE-FG02-05ER64097 Systems and Methods for Injecting Helium Beams into a Synchrotron Accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Bush, David A

    2008-09-30

    A research grant was approved to fund development of requirements and concepts for extracting a helium-ion beam at the LLUMC proton accelerator facility, thus enabling the facility to better simulate the deep space environment via beams sufficient to study biological effects of accelerated helium ions in living tissues. A biologically meaningful helium-ion beam will be accomplished by implementing enhancements to increase the accelerator's maximum proton beam energy output from 250MeV to 300MeV. Additional benefits anticipated from the increased energy include the capability to compare possible benefits from helium-beam radiation treatment with proton-beam treatment, and to provide a platform for developing a future proton computed tomography imaging system.

  16. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

    This monograph presents a systematic analysis of bubble system mathematics, using the mechanics of two-phase systems in non-equilibrium as the scope of analysis. The author introduces the thermodynamic foundations of bubble systems, ranging from the fundamental starting points to current research challenges. This book addresses a range of topics, including description methods of multi-phase systems, boundary and initial conditions as well as coupling requirements at the phase boundary. Moreover, it presents a detailed study of the basic problems of bubble dynamics in a liquid mass: growth (dynamically and thermally controlled), collapse, bubble pulsations, bubble rise and breakup. Special emphasis is placed on bubble dynamics in turbulent flows. The analysis results are used to write integral equations governing the rate of vapor generation (condensation) in non-equilibrium flows, thus creating a basis for solving a number of practical problems. This book is the first to present a comprehensive theory of boil...

  17. Bubble Size Distribution in a Vibrating Bubble Column

    Science.gov (United States)

    Mohagheghian, Shahrouz; Wilson, Trevor; Valenzuela, Bret; Hinds, Tyler; Moseni, Kevin; Elbing, Brian

    2016-11-01

    While vibrating bubble columns have increased the mass transfer between phases, a universal scaling law remains elusive. Attempts to predict mass transfer rates in large industrial scale applications by extrapolating laboratory scale models have failed. In a stationary bubble column, mass transfer is a function of phase interfacial area (PIA), while PIA is determined based on the bubble size distribution (BSD). On the other hand, BSD is influenced by the injection characteristics and liquid phase dynamics and properties. Vibration modifies the BSD by impacting the gas and gas-liquid dynamics. This work uses a vibrating cylindrical bubble column to investigate the effect of gas injection and vibration characteristics on the BSD. The bubble column has a 10 cm diameter and was filled with water to a depth of 90 cm above the tip of the orifice tube injector. BSD was measured using high-speed imaging to determine the projected area of individual bubbles, which the nominal bubble diameter was then calculated assuming spherical bubbles. The BSD dependence on the distance from the injector, injector design (1.6 and 0.8 mm ID), air flow rates (0.5 to 5 lit/min), and vibration conditions (stationary and vibration conditions varying amplitude and frequency) will be presented. In addition to mean data, higher order statistics will also be provided.

  18. Microscopic Deformation of Tungsten Surfaces by High Energy and High Flux Helium/Hydrogen Particle Bombardment with Short Pulses

    Science.gov (United States)

    Tokitani, Masayuki; Yoshida, Naoaki; Tokunaga, Kazutoshi; Sakakita, Hajime; Kiyama, Satoru; Koguchi, Haruhisa; Hirano, Yoichi; Masuzaki, Suguru

    The neutral beam injection facility in the National Institute of Advanced Industrial Science and Technology was used to irradiate a polycrystalline tungsten specimen with high energy and high flux helium and hydrogen particles. The incidence energy and flux of the beam shot were 25 keV and 8.8 × 1022 particles/m2 s, respectively. The duration of each shot was approximately 30 ms, with 6 min intervals between each shot. Surface temperatures over 1800 K were attained. In the two cases of helium irradiation, total fluence of either 1.5 × 1022 He/m2 or 4.0 × 1022 He/m2 was selected. In the former case, large sized blisters with diameter of 500 nm were densely observed. While, the latter case, the blisters were disappeared and fine nanobranch structures appeared instead. Cross-sectional observations using a transmission electron microscope (TEM) with the focused ion beam (FIB) technique were performed. According to the TEM image, after irradiation with a beam shot of total fluence 4.0 × 1022 He/m2 , there were very dense fine helium bubbles in the tungsten of sizes 1-50 nm. As the helium bubbles grew the density of the tungsten matrix drastically decreased as a result of void swelling. These effects were not seen in hydrogen irradiation case.

  19. Antiprotonic helium

    CERN Multimedia

    Eades, John

    2005-01-01

    An exotic atom in w hich an electron and an antiproton orbit a helium nucleus could reveal if there are any differences between matter and antimatter. The author describes this unusual mirror on the antiworld (5 pages)

  20. Electrino bubbles and relational entanglement

    CERN Document Server

    Vecchi, I

    2007-01-01

    In this note, which is based and expands on some previous work, it is argued that the phenomena exhibited by bubbles forming around free electrons in liquid helium and examined by Maris in his controversial 2000 paper point to the experimental relevance of an understanding of entanglement based on the relational approach to quantum mechanics. An experiment to verify/disprove the relevant argument is suggested.

  1. Helium behaviour in implanted boron carbide

    Directory of Open Access Journals (Sweden)

    Motte Vianney

    2015-01-01

    Full Text Available When boron carbide is used as a neutron absorber in nuclear power plants, large quantities of helium are produced. To simulate the gas behaviour, helium implantations were carried out in boron carbide. The samples were then annealed up to 1500 °C in order to observe the influence of temperature and duration of annealing. The determination of the helium diffusion coefficient was carried out using the 3He(d,p4He nuclear reaction (NRA method. From the evolution of the width of implanted 3He helium profiles (fluence 1 × 1015/cm2, 3 MeV corresponding to a maximum helium concentration of about 1020/cm3 as a function of annealing temperatures, an Arrhenius diagram was plotted and an apparent diffusion coefficient was deduced (Ea = 0.52 ± 0.11 eV/atom. The dynamic of helium clusters was observed by transmission electron microscopy (TEM of samples implanted with 1.5 × 1016/cm2, 2.8 to 3 MeV 4He ions, leading to an implanted slab about 1 μm wide with a maximum helium concentration of about 1021/cm3. After annealing at 900 °C and 1100 °C, small (5–20 nm flat oriented bubbles appeared in the grain, then at the grain boundaries. At 1500 °C, due to long-range diffusion, intra-granular bubbles were no longer observed; helium segregates at the grain boundaries, either as bubbles or inducing grain boundaries opening.

  2. Isobaric bubble growth: a consequence of altering atmospheric gas.

    Science.gov (United States)

    Strauss, R H; Kunkle, T D

    1974-11-01

    During certain treatments of decompression sickness following dives made with compressed air, the U.S. Navy advocates breathing helium-oxygen mixtures. However, stable nitrogen bubbles created within gelatin by decompression have been found to enlarge when the atmosphere was switched from nitrogen to helium without changing ambient pressure. This suggests that decompression sickness would be worsened by switching from nitrogen to helium in the breathing gas mixture.

  3. Helium effects on microstructural change in RAFM steel under irradiation: Reaction rate theory modeling

    Science.gov (United States)

    Watanabe, Y.; Morishita, K.; Nakasuji, T.; Ando, M.; Tanigawa, H.

    2015-06-01

    Reaction rate theory analysis has been conducted to investigate helium effects on the formation kinetics of interstitial type dislocation loops (I-loops) and helium bubbles in reduced-activation-ferritic/martensitic steel during irradiation, by focusing on the nucleation and growth processes of the defect clusters. The rate theory model employs the size and chemical composition dependence of thermal dissociation of point defects from defect clusters. In the calculations, the temperature and the production rate of Frenkel pairs are fixed to be T = 723 K and PV = 10-6 dpa/s, respectively. And then, only the production rate of helium atoms was changed into the following three cases: PHe = 0, 10-7 and 10-5 appm He/s. The calculation results show that helium effect on I-loop formation quite differs from that on bubble formation. As to I-loops, the loop formation hardly depends on the existence of helium, where the number density of I-loops is almost the same for the three cases of PHe. This is because helium atoms trapped in vacancies are easily emitted into the matrix due to the recombination between the vacancies and SIAs, which induces no pronounced increase or decrease of vacancies and SIAs in the matrix, leading to no remarkable impact on the I-loop nucleation. On the other hand, the bubble formation depends much on the existence of helium, in which the number density of bubbles for PHe = 10-7 and 10-5 appm He/s is much higher than that for PHe = 0. This is because helium atoms trapped in a bubble increase the vacancy binding energy, and suppress the vacancy dissociation from the bubble, resulting in a promotion of the bubble nucleation. And then, the helium effect on the promotion of bubble nucleation is very strong, even the number of helium atoms in a bubble is not so large.

  4. Bubble, Bubble, Toil and Trouble.

    Science.gov (United States)

    Journal of Chemical Education, 2001

    2001-01-01

    Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)

  5. TRANSMISSION ELECTRON MICROSCOPY STUDY OF HELIUM BEARING FUSION WELDS

    Energy Technology Data Exchange (ETDEWEB)

    Tosten, M; Michael Morgan, M

    2008-12-12

    A transmission electron microscopy (TEM) study was conducted to characterize the helium bubble distributions in tritium-charged-and-aged 304L and 21Cr-6Ni-9Mn stainless steel fusion welds containing approximately 150 appm helium-3. TEM foils were prepared from C-shaped fracture toughness test specimens containing {delta} ferrite levels ranging from 4 to 33 volume percent. The weld microstructures in the low ferrite welds consisted mostly of austenite and discontinuous, skeletal {delta} ferrite. In welds with higher levels of {delta} ferrite, the ferrite was more continuous and, in some areas of the 33 volume percent sample, was the matrix/majority phase. The helium bubble microstructures observed were similar in all samples. Bubbles were found in the austenite but not in the {delta} ferrite. In the austenite, bubbles had nucleated homogeneously in the grain interiors and heterogeneously on dislocations. Bubbles were not found on any austenite/austenite grain boundaries or at the austenite/{delta} ferrite interphase interfaces. Bubbles were not observed in the {delta} ferrite because of the combined effects of the low solubility and rapid diffusion of tritium through the {delta} ferrite which limited the amount of helium present to form visible bubbles.

  6. An equation of motion for bubble growth

    Energy Technology Data Exchange (ETDEWEB)

    Lesage, F.J. [College d' Enseignement General et Professionnel de L' Outaouais, Gatineau, Quebec (Canada). Dept. of Mathematics; Cotton, J.S. [McMaster University, Hamilton, ON (Canada). Dept. of Mechanical Engineering; Robinson, A.J. [Trinity College Dublin (Ireland). Dept. of Mechanical and Manufacturing Engineering

    2009-07-01

    A mathematical model is developed which describes asymmetric bubble growth, either during boiling or bubble injection from submerged orifices. The model is developed using the integral form of the continuity and momentum equations, resulting in a general expression for the acceleration of the bubble's centre of gravity. The proposed model highlights the need to include acceleration due to an asymmetric gain or loss of mass in order to accurately predict bubble motion. Some scenarios are posed by which the growth of bubbles, particularly idealized bubbles that remain a section of a sphere, must include the fact that bubble growth can be asymmetric. In particular, for approximately hemispherical bubble growth the sum of the forces acting on the bubble is negligible compared with the asymmetric term. Further, for bubble injection from a submerged needle this component in the equation of motion is very significant during the initial rapid growth phase as the bubble issues from the nozzle changing from a near hemisphere to truncated sphere geometry. (author)

  7. Exploring Bubbles

    Science.gov (United States)

    O'Geary, Melissa A.

    Bubbles provide an enjoyable and festive medium through which to teach many concepts within the science topics of light, color, chemistry, force, air pressure, electricity, buoyancy, floating, density, among many others. In order to determine the nature of children's engagement within a museum setting and the learning opportunities of playing with bubbles, I went to a children's interactive museum located in a metropolitan city in the Northeastern part of the United States.

  8. Antigravitating bubbles

    CERN Document Server

    Barnaveli, A T; Barnaveli, Andro; Gogberashvili, Merab

    1995-01-01

    We investigate the gravitational behavior of spherical domain walls (bubbles) arising during the phase transitions in the early Universe. In the thin-wall approximation we show the existence of the new solution of Einstein equations with negative gravitational mass of bubbles and the reversed direction of time flow on the shell. This walls exhibit gravitational repulsion just as the planar walls are assumed to do. The equilibrium radius and critical mass of such objects are found for realistic models.

  9. Bubble diagnostics

    Science.gov (United States)

    Visuri, Steven R.; Mammini, Beth M.; Da Silva, Luiz B.; Celliers, Peter M.

    2003-01-01

    The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.

  10. Observation of a helium ion energy threshold for retention in tungsten exposed to hydrogen/helium mixture plasma

    Science.gov (United States)

    Thompson, M.; Deslandes, A.; Morgan, T. W.; Elliman, R. G.; De Temmerman, G.; Kluth, P.; Riley, D.; Corr, C. S.

    2016-10-01

    Helium retention is measured in tungsten samples exposed to mixed H/He plasma in the Magnum-PSI linear plasma device. It is observed that there is very little He retention below helium ion impact energies of 9.0+/- 1.4 eV, indicating the existence of a potential barrier which must be overcome for implantation to occur. The helium retention in samples exposed to plasma at temperatures  >1000 K is strongly correlated with nano-bubble formation measured using grazing incidence small-angle x-ray scattering. The diameters of nano-bubbles were not found to increase with increasing helium concentration, indicating that additional helium must be accommodated by increasing the bubble concentration or an increase in bubble pressure. For some samples pre-irradiation with heavy ions of 2.0 MeV energy is investigated to simulate the effects of neutron damage. It is observed that nano-bubble sizes are comparable between samples pre-irradiated with heavy-ions, and those without heavy-ion pre-irradiation.

  11. Energy spectra in bubbly turbulence

    CERN Document Server

    Prakash, Vivek N; Ramos, Fabio Ernesto Mancilla; Tagawa, Yoshiyuki; Lohse, Detlef; Sun, Chao

    2013-01-01

    We conduct experiments in a turbulent bubbly flow to study the unknown nature of the transition between the classical -5/3 energy spectrum scaling for a single-phase turbulent flow and the -3 scaling for a swarm of bubbles rising in a quiescent liquid and of bubble-dominated turbulence. The bubblance parameter, b, which measures the ratio of the bubble-induced kinetic energy to the kinetic energy induced by the turbulent liquid fluctuations before bubble injection, is used to characterise the bubbly flow. We vary b from $b = \\infty$ (pseudo-turbulence) to b = 0 (single-phase flow) over 2-3 orders of magnitude: ~O(0.01, 0.1, 5) to study its effect on the turbulent energy spectrum and liquid velocity fluctuations. The experiments are conducted in a multi-phase turbulent water tunnel with air bubbles of diameters 2-4 mm and 3-5 mm. An active-grid is used to generate nearly homogeneous and isotropic turbulence in the liquid flow. The liquid speeds and gas void fractions are varied to achieve the above mentioned b...

  12. Bubbling Threat

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The shift of China’s monetary policy stance from "moderately loose" to "prudent" in 2011 indicates curbing inflation and asset bubbles have become the Central Government’s top priority. But is China’s bubble problem short-term or long-term? Is it only monetary or related to economic structure? Is it the cause of China’s economic imbalance or the result? And what kind of deep-rooted problems in the macro economy does it reflect? All these questions call for deep thought,said Zhang Monan,a

  13. Helium release from radioisotope heat sources

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, D.E.; Early, J.W.; Starzynski, J.S.; Land, C.C.

    1984-05-01

    Diffusion of helium in /sup 238/PuO/sub 2/ fuel was characterized as a function of the heating rate and the fuel microstructure. The samples were thermally ramped in an induction furnace and the helium release rates measured with an automated mass spectrometer. The diffusion constants and activation energies were obtained from the data using a simple diffusion model. The release rates of helium were correlated with the fuel microstructure by metallographic examination of fuel samples. The release mechanism consists of four regimes, which are dependent upon the temperature. Initially, the release is controlled by movement of point defects combined with trapping along grain boundaries. This regime is followed by a process dominated by formation and growth of helium bubbles along grain boundaries. The third regime involves volume diffusion controlled by movement of oxygen vacancies. Finally, the release at the highest temperatures follows the diffusion rate of intragranular bubbles. The tendency for helium to be trapped within the grain boundaries diminishes with small grain sizes, slow thermal pulses, and older fuel.

  14. Refrigerating systems for the big CERN bubble chamber

    CERN Document Server

    Giger, U; Trepp, C

    1974-01-01

    A combined helium-hydrogen refrigerator has been installed for cooling the new CERN bubble chamber at Geneva. This article describes the cool-down of the bubble chamber and magnet, as well as emergency operation and control of the refrigerator. Besides the choice of basic conception and circuit, the plant components are dealt with too. The function of the bubble chamber and the development of the CERN proton synchrotron are described in order to facilitate understanding of the relationship between the Sulzer cryogenic plant and the CERN bubble chamber. Installations and equipment not manufactured by Sulzer are also mentioned. (1 refs).

  15. Effect of carbon and alloying solute atoms on helium behaviors in α-Fe

    Science.gov (United States)

    Zhang, Yange; You, Yu-Wei; Xu, Yichun; Liu, C. S.; Chen, J. L.; Luo, G.-N.

    2017-02-01

    Helium bubbles could strongly degrade the mechanical properties of ferritic steels in fission and fusion systems. The formation of helium bubble is directly affected by the interactions between helium and the compositions in steels, such as solute atoms, carbon and irradiation defects. We thereby performed systematical first-principles calculations to investigate the interactions of solute-helium and carbon-solute-helium. It is found that substitutional helium is more attractive than interstitial helium to all the considered 3p, 4p, 5p and 6p solutes. The attraction between carbon and substitutional helium suggests the carbon-solute-helium complex can be formed stably. By examining the charge density difference and thermal stability, it is found that the ternary complex shows stronger attraction with He than that of solute-helium pair for some solutes (S, Se, In, Te, Pb and Bi) and the complex could existed in iron stably at 700 K. The present theoretical results may be helpful for exploring alloy additions to mitigate the formation of large helium bubbles.

  16. Leverage bubble

    Science.gov (United States)

    Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

    2012-01-01

    Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.

  17. Impurity bubbles in a BEC

    Science.gov (United States)

    Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

    2013-05-01

    Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

  18. Bubbles Rising Through a Soft Granular Material

    Science.gov (United States)

    Le Mestre, Robin; MacMinn, Chris; Lee, Sungyon

    2016-11-01

    Bubble migration through a soft granular material involves a strong coupling between the bubble dynamics and the deformation of the material. This is relevant to a variety of natural processes such as gas venting from sediments and gas exsolution from magma. Here, we study this process experimentally by injecting air bubbles into a quasi-2D packing of soft hydrogel beads and measuring the size, speed, and morphology of the bubbles as they rise due to buoyancy. Whereas previous work has focused on deformation resisted by intergranular friction, we focus on the previously inaccessible regime of deformation resisted by elasticity. At low confining stress, the bubbles are irregular and rounded, migrating via local rearrangement. At high confining stress, the bubbles become unstable and branched, migrating via pathway opening. The authors thank The Royal Society for support (International Exchanges Ref IE150885).

  19. Molecular dynamics study of fission gas bubble nucleation in UO2

    Science.gov (United States)

    Liu, X.-Y.; Andersson, D. A.

    2015-07-01

    Molecular dynamics (MD) simulations are used to study helium and xenon gas bubble nucleation in UO2. For helium bubbles, the pressure release mechanism is by creating defects on the oxygen sublattice. Helium atoms diffuse away from the bubbles into nearby bulk UO2, thus forming a diffuse interface. For xenon bubbles, over-pressurized bubbles containing xenon can displace uranium atoms, which tend to aggregate around the xenon bubble as a pressure release mechanism. MD simulations of xenon atoms in pre-existing voids suggest that xenon atoms and the replaced uranium atoms occur in a 1:1 ratio, although kinetic factors may reduce that ratio depending on availability of xenon atoms and vacancies around the bubble. Finally, MD simulations suggest that for small bubbles (1-5 xenon atoms), the xenon bubble nucleus at UO2 grain-boundaries has much lower formation energy compared to that of bubbles of similar sizes in the bulk. However, when the xenon bubble grows into larger sizes, this energy difference is reduced.

  20. Interaction of Helium Rydberg State Molecules with Dense Helium.

    Science.gov (United States)

    Bonifaci, Nelly; Li, Zhiling; Eloranta, Jussi; Fiedler, Steven L

    2016-11-17

    The interaction potentials of the He2(*) excimer, in the a(3)Σu, b(3)Πg, c(3)Σg, and d(3)Σu electronic states with a ground state helium atom are presented. The symmetry of the interaction potentials closely follows the excimer Rydberg electron density with pronounced short-range minima appearing along the nodal planes of the Rydberg orbital. In such cases, a combination of the electrostatic short-range attraction combined with Pauli repulsion leads to the appearance of unusual long-range maxima in the potentials. Bosonic density functional calculations show that the (3)d state excimer resides in a localized solvation bubble in dense helium at 4.5 K, with radii varying from 12.7 Å at 0.1 MPa to 10.8 Å at 2.4 MPa. The calculated (3)d → (3)b pressure-induced fluorescence band shifts are in good agreement with experimental results determined by application of corona discharge. The magnitude of the spectral shifts indicate that the observed He2(*) molecules emit from dense helium whereas the corresponding fluorescence signal from the discharge zone appears quenched. This implies that fluorescence spectroscopy involving this electronic transition can only be used to probe the state of the surrounding medium rather than the discharge zone itself.

  1. On "bubbly" structures in plasma facing components

    Science.gov (United States)

    Krasheninnikov, S. I.; Smirnov, R. D.

    2013-07-01

    The theoretical model of "fuzz" growth describing the main features observed in experiments is discussed. This model is based on the assumption of enhancement of plasticity of tungsten containing significant fraction of helium atoms and clusters. The results of molecular dynamics (MD) simulations support this idea and demonstrate strong reduction of the yield strength for all temperature range. The MD simulations also show that the "flow" of tungsten strongly facilitates coagulation of helium clusters, which otherwise practically immobile, and the formation of nano-bubbles.

  2. Armoring confined bubbles in concentrated colloidal suspensions

    Science.gov (United States)

    Yu, Yingxian; Khodaparast, Sepideh; Stone, Howard

    2016-11-01

    Encapsulation of a bubble with microparticles is known to significantly improve the stability of the bubble. This phenomenon has recently gained increasing attention due to its application in a variety of technologies such as foam stabilization, drug encapsulation and colloidosomes. Nevertheless, the production of such colloidal armored bubble with controlled size and particle coverage ratio is still a great challenge industrially. We study the coating process of a long air bubble by microparticles in a circular tube filled with a concentrated microparticles colloidal suspension. As the bubble proceeds in the suspension of particles, a monolayer of micro-particles forms on the interface of the bubble, which eventually results in a fully armored bubble. We investigate the phenomenon that triggers and controls the evolution of the particle accumulation on the bubble interface. Moreover, we examine the effects of the mean flow velocity, the size of the colloids and concentration of the suspension on the dynamics of the armored bubble. The results of this study can potentially be applied to production of particle-encapsulated bubbles, surface-cleaning techniques, and gas-assisted injection molding.

  3. Blowing bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Casteel, K.

    1999-04-01

    The article, based on a series of interviews with column flotation equipment suppliers, reviews and comments on the progress of bubble generator design. Developments mentioned include the Air/Water sparger from Cominco, the SparJet and SlamJet from CPT, the CISA sparger from Sevala CISA, Microcel flotation columns from Birtley Engineering, Flotaire column flotation cells from LMC International, and the Variable Gap Sparger from MinnovEX. 1 fig., 2 photo.

  4. Dual-beam irradiation of {alpha}-iron: Heterogeneous bubble formation on dislocation loops

    Energy Technology Data Exchange (ETDEWEB)

    Brimbal, Daniel, E-mail: Daniel.brimbal@cea.fr [Laboratoire d' Analyse Microstructurale des Materiaux (LA2M), CEA/Saclay, DEN/DMN/SRMA/LA2M, 91191 Gif-sur-Yvette Cedex (France); Decamps, Brigitte, E-mail: Brigitte.decamps@csnsm.in2p3.fr [Centre de Spectrometrie Nucleaire et de Spectrometrie de Masses (CSNSM/IN2P3/CNRS), Orsay University, Bat. 108, 91405 Orsay Campus (France); Barbu, Alain, E-mail: Alain.barbu@cea.fr [Service de Recherches de Metallurgie Physique (SRMP), CEA/Saclay, DEN/DMN/SRMP, 91191 Gif-sur-Yvette Cedex (France); Meslin, Estelle, E-mail: Estelle.Meslin@cea.fr [Service de Recherches de Metallurgie Physique (SRMP), CEA/Saclay, DEN/DMN/SRMP, 91191 Gif-sur-Yvette Cedex (France); Henry, Jean, E-mail: Jean.henry@cea.fr [Laboratoire d' Analyse Microstructurale des Materiaux (LA2M), CEA/Saclay, DEN/DMN/SRMA/LA2M, 91191 Gif-sur-Yvette Cedex (France)

    2011-11-15

    Highlights: > We have irradiated {alpha}-iron in situ with Fe{sup +} and He{sup +} ions at 500 deg. C. > Dislocation loops and helium bubbles are present at 1 dpa/540 appm He. > The helium bubbles are located heterogeneously on the dislocation loops. - Abstract: In order to understand the evolution of materials under irradiation conditions similar to those in future fusion reactors, we have irradiated high purity iron in situ in a transmission electron microscope with 1 MeV Fe{sup +} ions while simultaneously implanting 15 keV He{sup +} ions, at 500 deg. C. Once {approx}1 dpa/500 appm He were reached, helium bubbles and large dislocation loops were observed. The study reveals that helium bubbles nucleated heterogeneously: a majority of them were observed inside the large dislocation loops.

  5. On the shear strength of tungsten nano-structures with embedded helium

    Science.gov (United States)

    Smirnov, R. D.; Krasheninnikov, S. I.

    2013-08-01

    Modification of plastic properties of tungsten nano-structures under shear stress load due to embedded helium atoms is studied using molecular dynamics modelling. The modelling demonstrates that the yield strength of tungsten nano-structures reduces significantly with increasing embedded helium concentration. At high helium concentrations (>10 at%), the yield strength decreases to values characteristic to the pressure in helium nano-bubbles, which are formed in tungsten under such conditions and thought to be responsible for the formation of nano-fuzz on tungsten surfaces irradiated with helium plasma. It is also shown that tungsten plastic flow strongly facilitates coagulation of helium clusters to larger bubbles. The temperature dependencies of the yield strength are obtained.

  6. Microstructure of helium-implanted Nimonic PE16

    Energy Technology Data Exchange (ETDEWEB)

    Czyrska-Filemonowicz, A.; Gadalla, A.A.; Kesternich, W.; Weckermann, B.

    1987-09-01

    Transmission electron microsocpy has been used to investigate the microstructure in Nimonic PE16 after room temperature a-implementation followed by subsequent annealing. Helium bubble formation in the matrix, at dislocations, at grain boundaries and at precipitates of ..gamma..', M/sub 23/C/sub 6/, and MC type has been studied.

  7. Highly sensitive detection of five typical fluoroquinolones in low-fat milk by field-enhanced sample injection based CE in bubble cell capillary

    OpenAIRE

    Deng, Yan; Gasilova, Natalia; Qiao, Liang; Zhou, Ying-Lin; Zhang, Xin-Xiang; Girault, Hubert H.

    2014-01-01

    Fluoroquinolones are a group of synthetic antibiotics with a broad activity spectrum against mycoplasma, gram-positive and gram-negative bacteria. Due to the extensive use of fluoroquinolones in farming and veterinary science, there is a constant need in the analytical methods able to efficiently monitor their residues in food products of animal origin, regulated by Commission Regulation (European Union) no. 37/2010. Herein, field-enhanced sample injection for sample stacking prior the CZE se...

  8. Fundamental of Inclusion Removal from Molten Steel by Rising Bubble

    Institute of Scientific and Technical Information of China (English)

    WANG Li-tao; ZHANG Qiao-ying; LI Zheng-bang; XUE Zheng-liang

    2004-01-01

    The mechanism of inclusion removal by attachment to rising bubble was analyzed, and the movement behavior of inclusion, the mechanism of bubbles/inclusion interaction, collision probability and adhesion probability were discussed. A mathematical model of inclusion removal from molten steel by attachment to fine bubble was developed. The results of theoretical analysis and mathematical model showed that the optimum bubble diameter for inclusion removal is 1 to 2 mm. A new method that argon is injected into the shroud from ladle to tundish during continuous casting has been proposed to produce fine bubble. It provides theoretical guides for production of super clean steel.

  9. Hybrid simulation research on formation mechanism of tungsten nanostructure induced by helium plasma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Atsushi M., E-mail: ito.atsushi@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Takayama, Arimichi; Oda, Yasuhiro [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Tamura, Tomoyuki; Kobayashi, Ryo; Hattori, Tatsunori; Ogata, Shuji [Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Ohno, Noriyasu; Kajita, Shin [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yajima, Miyuki [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Noiri, Yasuyuki [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yoshimoto, Yoshihide [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Saito, Seiki [Kushiro National College of Technology, Kushiro, Hokkaido 084-0916 (Japan); Takamura, Shuichi [Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392 (Japan); Murashima, Takahiro [Tohoku University, 6-3, Aramaki-Aza-Aoba, Aoba-Ward, Sendai 980-8578 (Japan); Miyamoto, Mitsutaka [Shimane University, Matsue, Shimane 690-8504 (Japan); Nakamura, Hiroaki [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki 509-5292 (Japan); Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2015-08-15

    The generation of tungsten fuzzy nanostructure by exposure to helium plasma is one of the important problems for the use of tungsten material as divertor plates in nuclear fusion reactors. In the present paper, the formation mechanisms of the helium bubble and the tungsten fuzzy nanostructure were investigated by using several simulation methods. We proposed the four-step process which is composed of penetration step, diffusion and agglomeration step, helium bubble growth step, and fuzzy nanostructure formation step. As the fourth step, the formation of the tungsten fuzzy nanostructure was successfully reproduced by newly developed hybrid simulation combining between molecular dynamics and Monte-Carlo method. The formation mechanism of tungsten fuzzy nanostructure observed by the hybrid simulation is that concavity and convexity of the surface are enhanced by the bursting of helium bubbles in the region around the concavity.

  10. Hybrid simulation research on formation mechanism of tungsten nanostructure induced by helium plasma irradiation

    Science.gov (United States)

    Ito, Atsushi M.; Takayama, Arimichi; Oda, Yasuhiro; Tamura, Tomoyuki; Kobayashi, Ryo; Hattori, Tatsunori; Ogata, Shuji; Ohno, Noriyasu; Kajita, Shin; Yajima, Miyuki; Noiri, Yasuyuki; Yoshimoto, Yoshihide; Saito, Seiki; Takamura, Shuichi; Murashima, Takahiro; Miyamoto, Mitsutaka; Nakamura, Hiroaki

    2015-08-01

    The generation of tungsten fuzzy nanostructure by exposure to helium plasma is one of the important problems for the use of tungsten material as divertor plates in nuclear fusion reactors. In the present paper, the formation mechanisms of the helium bubble and the tungsten fuzzy nanostructure were investigated by using several simulation methods. We proposed the four-step process which is composed of penetration step, diffusion and agglomeration step, helium bubble growth step, and fuzzy nanostructure formation step. As the fourth step, the formation of the tungsten fuzzy nanostructure was successfully reproduced by newly developed hybrid simulation combining between molecular dynamics and Monte-Carlo method. The formation mechanism of tungsten fuzzy nanostructure observed by the hybrid simulation is that concavity and convexity of the surface are enhanced by the bursting of helium bubbles in the region around the concavity.

  11. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    While Eugene Fama has repeatedly expressed his discontent with the notion of an “irrational bubble,” he has never publicly expressed his opinion on “rational bubbles.” On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable. Howe...... component in stock market valuation ratios, consistent with a rational bubble....

  12. Electric response in superfluid helium

    Science.gov (United States)

    Chagovets, Tymofiy V.

    2016-05-01

    We report an experimental investigation of the electric response of superfluid helium that arises in the presence of a second sound standing wave. It was found that the signal of the electric response is observed in a narrow range of second sound excitation power. The linear dependence of the signal amplitude has been derived at low excitation power, however, above some critical power, the amplitude of the signal is considerably decreased. It was established that the rapid change of the electric response is not associated with a turbulent regime generated by the second sound wave. A model of the appearance of the electric response as a result of the oscillation of electron bubbles in the normal fluid velocity field in the second sound wave is presented. Possible explanation for the decrease of the electric response are presented.

  13. Numerical modeling of oscillating Taylor bubbles

    Directory of Open Access Journals (Sweden)

    S. Ambrose

    2016-01-01

    Full Text Available In this study, computational fluid dynamics (CFD modeling is used to simulate Taylor bubbles rising in vertical pipes. Experiments indicate that in large diameter (0.29 m pipes for an air–water system, the bubbles can rise in a oscillatory manner, depending on the method of air injection. The CFD models are able to capture this oscillatory behavior because the air phase is modeled as a compressible ideal gas. Insights into the flow field ahead and behind the bubble during contraction and expansion are shown. For a bubble with an initial pressure equal to the hydrostatic pressure at its nose, no oscillations are seen in the bubble as it rises. If the initial pressure in the bubble is set less than or greater than the hydrostatic pressure then the length of the bubble oscillates with an amplitude that depends on the magnitude of the initial bubble pressure relative to the hydrostatic pressure. The frequency of the oscillations is inversely proportional to the square root of the head of water above the bubble and so the frequency increases as the bubble approaches the water surface. The predicted frequency also depends inversely on the square root of the average bubble length, in agreement with experimental observations and an analytical model that is also presented. In this model, a viscous damping term due to the presence of a Stokes boundary layer for the oscillating cases is introduced for the first time and used to assess the effect on the oscillations of increasing the liquid viscosity by several orders of magnitude.

  14. Micro-bubbles seeding for flow characterization

    Science.gov (United States)

    Aumelas, V.; Lecoffre, Y.; Maj, G.; Franc, J.-P.

    2016-11-01

    Micro-bubbles injection has long been used in hydrodynamic facilities for the control of dissolved and free air. In some cavitation tunnels [9], very large quantities of microbubbles (billions per second) are injected for rapid degassing and, in smaller quantities (millions per second), for cavitation nuclei seeding. Micro-bubbles can also be used as tracers for optical measurements including visualization, LDV or PIV. For these applications, bubbles must be sufficiently small to faithfully follow the flow. Depending on the quality and spatial characteristics of the micro-bubbles seeding, several optical methods can be applied: simple visualization gives access to semi-quantitative information on the behaviour of flows; LASER velocimetry provides information on the mean velocity and other temporal local characteristics of the flow. This paper presents some new micro-bubbles seeding devices recently developed by YLEC Consultants. These devices have been designed to fulfill specific requirements related to integration into cavitation tunnels and permit optical velocimetry measurement techniques such as Particle Image Velocimetry (PIV). The LEGI cavitation tunnel is the first tunnel which has been equipped with these microbubbles seeding systems dedicated to optical velocimetry. This paper presents the final integration schemes selected for micro-bubbles seeding into LEGI tunnel and discuss about practical concerns related to the use of the injection system for optical velocimetry.

  15. Ion Beam Analysis of the Annealing Behavior of Helium in Ti Films

    Institute of Scientific and Technical Information of China (English)

    HE Zhi-Jiang; SHI Li-Qun; LIU Chao-Zhuo; ZHANG Lei; LU Yong-Fang; ZHANG Bin

    2009-01-01

    @@ We present a theoretical calculation finding that a spectrum from ion beam analysis will change at different stopping cross sections. This is more visible at a deeper place in the sample. Helium-contained Ti films annealed at different temperatures are prepared to gain different stopping cross sections whereby the stopping cross section will change with the helium phase states and the pressure of helium bubbles. Then ion beam analysis is used to measure the concentration of helium. It is found that the concentration curve rises greatly after the sample is annealed at 673K which reflects the increasing size of the helium bubble. The results axe consistent with that of positron annihilation radiation spectra which are performed by using a changeable energy positron beam.

  16. Effect of internal bubbly flow on pipe vibrations

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents an experimental investigation on wall vibrations of a pipe due to injection of a uniform bubble cloud into the pipe flow. For different bubble void fractions and averaged bubble sizes, the vibrations were measured using accelerometers. To understand the underlying physics, the evolution of the vibration spectra along the streamwise direction was examined. Results showed that wall vibrations were greatly enhanced up to 25 dB, compared with no bubble case. The characteristics of the vibration were mainly dependent on void fraction. These vibrations were believed to be caused by two mechanisms: acoustic resonance and normal modes of the bubble cloud. The former, originating from the interaction between the first mode of the bubble cloud and the first acoustic mode of the pipe, persisted along the entire pipe to enhance the vibration over a broad band frequency range, while the later, due to the process of bubble formation, successively decayed in the streamwise direction.

  17. Modification of Shape Oscillations of an Attached Bubble by Surfactants

    OpenAIRE

    Tihon J.; Vejražka J.; Vobecká L.

    2013-01-01

    Surface-active agents (surfactants, e.g. washing agents) strongly modifies properties of gas-liquid interface. We have carried out extensive experiments, in which we study effect of surfactants on the shape oscillations of a bubble, which is attached at a tip of a capillary. In the experiments, shape oscillations of a bubble are invoked by a motion of a capillary, to which the bubble is injected. Decaying oscillations are recorded and their frequency and damping are evaluated. By changing the...

  18. General mechanism for helium blistering involving displaced atom transport

    Energy Technology Data Exchange (ETDEWEB)

    McDonell, W.R.

    1979-01-01

    A mechanism developed to account for formation of vertically elongated blisters in high displacement environments produced by /sup 252/Cf alpha particles and fission fragments has been extended to formation of done-shaped blisters in the low displacement environments produced by simple helium ion beams. In this mechanism, transport of displaced atoms to relieve compressive stresses in the helium-implanted layer allows interconnections of small, subsurface bubbles to form the blister cavity. The same transport may cause thickening of the blister caps at low implantation energies. The transition from dome-shaped to vertically elongated blistering occurs between the 300 and 3000 displacements per helium atom produced by simple helium ions and /sup 252/Cf radiations respectively.

  19. 过渡型艇微气泡减阻喷缝尺度影响数值计算%Numerical Calculation on the Influence of the Slot Size of Air Injection on Micro Bubbles Drag Reduction for Transitional Craft

    Institute of Scientific and Technical Information of China (English)

    王家楣; 张玲

    2011-01-01

    针对一优良过渡型艇,为喷气需要进行船底断阶,采用有限体积法、SIMPLEC算法和k-ε两方程湍流模型,不计自由面影响,计及气泡与水的相对运动,数值求解包含气液两相流的雷诺平均控制方程组.获得不同喷缝宽度、不同傅汝德数和相对喷气速度下的船舶的阻力特性和气泡浓度分布规律并与模型实验结果进行对比分析.结果显示:在获得高减阻率条件下,Cn随Fr增加而呈非线性增加,当Fr=0.779时,Cn达到最大值;在获得25%减阻率的条件下,Fr=0.973时相对喷缝宽度为0.112所需喷气量最小即喷气所消耗功率最小.计算结果可为高速气泡船喷缝参数设计提供参考.%The two-phase flow around a fine transitional with step for injecting air is figured out numerically under the condition of neglecting influences of free-surface. The drag characteristic of the ship and the distribution of the volume fraction of micro bubble are got at different air jet slot size,Fr and relative air injection velocity. The results show that at Cn=25% and Fr=0.973, the air flow rate could reach minimum if non-dimension jet slot size is 0.112. The calculation result will provide reference on the parametric design of air injection slot of High-Speed Air Cavity Craft.

  20. Experimental Results for Direct Electron Irradiation of a Uranyl Sulfate Solution: Bubble Formation and Thermal Hydraulics Studies

    Energy Technology Data Exchange (ETDEWEB)

    Chemerisov, Sergey [Argonne National Lab. (ANL), Argonne, IL (United States); Gromov, R. [Argonne National Lab. (ANL), Argonne, IL (United States); Makarashvili, Vakhtang [Argonne National Lab. (ANL), Argonne, IL (United States); Heltemes, Thad [Argonne National Lab. (ANL), Argonne, IL (United States); Sun, Zaijing [Argonne National Lab. (ANL), Argonne, IL (United States); Wardle, Kent E. [Argonne National Lab. (ANL), Argonne, IL (United States); Bailey, James [Argonne National Lab. (ANL), Argonne, IL (United States); Stepinski, Dominique [Argonne National Lab. (ANL), Argonne, IL (United States); Jerden, James [Argonne National Lab. (ANL), Argonne, IL (United States); Vandegrift, George F. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-01-30

    In support of the development of accelerator-driven production of fission product Mo-99 as proposed by SHINE Medical Technologies, a 35 MeV electron linac was used to irradiate depleted-uranium (DU) uranyl sulfate dissolved in pH 1 sulfuric acid at average power densities of 6 kW, 12 kW, and 15 kW. During these irradiations, gas bubbles were generated in the solution due to the radiolytic decomposition of water molecules in the solution. Multiple video cameras were used to record the behavior of bubble generation and transport in the solution. Seven six-channel thermocouples were used to record temperature gradients in the solution from self-heating. Measurements of hydrogen and oxygen concentrations in a helium sweep gas were recorded by a gas chromatograph to estimate production rates during irradiation. These data are being used to validate a computational fluid dynamics (CFD) model of the experiment that includes multiphase flow and a custom bubble injection model for the solution region.

  1. The consequences of helium production on microstructural development in isotopically tailored ferritic alloys

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D.S. [Pacific Northwest Lab., Richland, WA (United States)

    1996-10-01

    A series of alloys have been made adding various isotopes of nickel in order to vary the production of helium during irradiation by a two step nuclear reaction in a mixed spectrum reactor. The alloys use a base composition of Fe-12Cr with an addition of 1.5% nickel, either in the form of {sup 60}Ni which produces no helium, {sup 59}Ni which produces helium at a rate of about 10 appm He/dpa, or natural nickel ({sup Nat}Ni) which provides an intermediate level of helium due to delayed development of {sup 59}Ni. Specimens were irradiated in the HFIR at Oak Ridge, TN to {approx}7 dpa at 300 and 400{degrees}C. Microstructural examinations indicated that nickel additions promote precipitation in all alloys, but the effect appears to be much stronger at 400{degrees}C than at 300{degrees}C. There is sufficient dose by 7 dpa (and with 2 appm He) to initiate void swelling in ferritic/martensitic alloys. Little difference was found between response from {sup 59}Ni and {sup Nat}Ni. Also, helium bubble development for high helium generation conditions appeared to be very different at 300 and 400{degrees}C. At 300{degrees}C, it appeared that high densities of bubbles formed whereas at 400{degrees}C, bubbles could not be identified, possibly because of the complexity of the microstructure, but more likely because helium accumulated at precipitate interfaces.

  2. Cooling with Superfluid Helium

    CERN Document Server

    Lebrun, P

    2014-01-01

    The technical properties of helium II (‘superfluid’ helium) are presented in view of its applications to the cooling of superconducting devices, particularly in particle accelerators. Cooling schemes are discussed in terms of heat transfer performance and limitations. Large-capacity refrigeration techniques below 2 K are reviewed, with regard to thermodynamic cycles as well as process machinery. Examples drawn from existing or planned projects illustrate the presentation. Keywords: superfluid helium, cryogenics

  3. Using a dynamic point-source percolation model to simulate bubble growth.

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, Jonathan A.; Zeigler, David A.; Cowgill, Donald F.

    2004-05-01

    Accurate modeling of nucleation, growth and clustering of helium bubbles within metal tritide alloys is of high scientific and technological importance. Of interest is the ability to predict both the distribution of these bubbles and the manner in which these bubbles interact at a critical concentration of helium-to-metal atoms to produce an accelerated release of helium gas. One technique that has been used in the past to model these materials, and again revisited in this research, is percolation theory. Previous efforts have used classical percolation theory to qualitatively and quantitatively model the behavior of interstitial helium atoms in a metal tritide lattice; however, higher fidelity models are needed to predict the distribution of helium bubbles and include features that capture the underlying physical mechanisms present in these materials. In this work, we enhance classical percolation theory by developing the dynamic point-source percolation model. This model alters the traditionally binary character of site occupation probabilities by enabling them to vary depending on proximity to existing occupied sites, i.e. nucleated bubbles. This revised model produces characteristics for one and two dimensional systems that are extremely comparable with measurements from three dimensional physical samples. Future directions for continued development of the dynamic model are also outlined.

  4. Circulatory bubble dynamics: from physical to biological aspects.

    Science.gov (United States)

    Papadopoulou, Virginie; Tang, Meng-Xing; Balestra, Costantino; Eckersley, Robert J; Karapantsios, Thodoris D

    2014-04-01

    Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered.

  5. Brut: Automatic bubble classifier

    Science.gov (United States)

    Beaumont, Christopher; Goodman, Alyssa; Williams, Jonathan; Kendrew, Sarah; Simpson, Robert

    2014-07-01

    Brut, written in Python, identifies bubbles in infrared images of the Galactic midplane; it uses a database of known bubbles from the Milky Way Project and Spitzer images to build an automatic bubble classifier. The classifier is based on the Random Forest algorithm, and uses the WiseRF implementation of this algorithm.

  6. Fama on bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    Eugene Fama has repeatedly expressed his discontent with the notion of an irrational bubble. However, he has never publicly expressed his opinion on rational bubbles. This is peculiar since such bubbles build naturally from the rational efficient markets paradigm that Fama strongly adheres to...

  7. ITER helium ash accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Hogan, J.T.; Hillis, D.L.; Galambos, J.; Uckan, N.A. (Oak Ridge National Lab., TN (USA)); Dippel, K.H.; Finken, K.H. (Forschungszentrum Juelich GmbH (Germany, F.R.). Inst. fuer Plasmaphysik); Hulse, R.A.; Budny, R.V. (Princeton Univ., NJ (USA). Plasma Physics Lab.)

    1990-01-01

    Many studies have shown the importance of the ratio {upsilon}{sub He}/{upsilon}{sub E} in determining the level of He ash accumulation in future reactor systems. Results of the first tokamak He removal experiments have been analysed, and a first estimate of the ratio {upsilon}{sub He}/{upsilon}{sub E} to be expected for future reactor systems has been made. The experiments were carried out for neutral beam heated plasmas in the TEXTOR tokamak, at KFA/Julich. Helium was injected both as a short puff and continuously, and subsequently extracted with the Advanced Limiter Test-II pump limiter. The rate at which the He density decays has been determined with absolutely calibrated charge exchange spectroscopy, and compared with theoretical models, using the Multiple Impurity Species Transport (MIST) code. An analysis of energy confinement has been made with PPPL TRANSP code, to distinguish beam from thermal confinement, especially for low density cases. The ALT-II pump limiter system is found to exhaust the He with maximum exhaust efficiency (8 pumps) of {approximately}8%. We find 1<{upsilon}{sub He}/{upsilon}{sub E}<3.3 for the database of cases analysed to date. Analysis with the ITER TETRA systems code shows that these values would be adequate to achieve the required He concentration with the present ITER divertor He extraction system.

  8. Destratification induced by bubble plumes as a means to reduce ...

    African Journals Online (AJOL)

    to reduce evaporation from open impoundments. M van Dijk* and SJ van .... The air injection bubble plume system used for water quality applications has been ...... ervoir Evaporation Utilizing Mass Transfer Theory. US Geological. Survey.

  9. Injection of Helium 3 and SF{sub 6} in a lake for the determination of gaseous exchange rates at the water-air interface: implementation, analysis and experimental results; Injection d`helium-3 et SF{sub 6} en lac pour la determination des coefficients gazeux a l`interface eau-air: deploiement, analyse et resultats experimentaux

    Energy Technology Data Exchange (ETDEWEB)

    Poisson, A. [Paris-6 Univ., 75 (France); Jean-Baptiste, P. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Direction des Sciences de la Matiere

    1994-12-31

    In order to study the hypothesis of an under-rating of the exchange velocity at the ocean-atmosphere interface that could explain the lack of CO{sub 2} in the global CO{sub 2} balance, an experiment was carried out in two lakes at the Kerguelen Islands where strong winds are common, in order to evaluate precisely the relation between the transfer coefficient and the wind velocity: {sup 3}He and SF{sub 6} tracers were injected in the lakes; concentration evolutions were recorded and results are shown to validate the above assumption. 6 figs., 1 tab., 9 refs.

  10. Bubbles as tracers of heat input to cooling flows

    CERN Document Server

    Binney, J; Omma, H

    2007-01-01

    We examine the distribution of injected energy in three-dimensional, adaptive-grid simulations of the heating of cooling flows. We show that less than 10 percent of the injected energy goes into bubbles. Consequently, the energy input from the nucleus is underestimated by a factor of order 6 when it is taken to be given by PVgamma/(gamma-1), where P and V are the pressure and volume of the bubble, and gamma the ratio of principal specific heats.

  11. Microstructural observation of helium implanted and creep ruptured Fe 25%Ni 15%Cr alloys containing various MC and MN formers

    Science.gov (United States)

    Yamamoto, Norikazu; Nagakawa, Johsei; Murase, Yoshiharu; Shiraishi, Haruki

    1998-10-01

    Transmission electron microscopic observations have been carried out on Fe-25%Ni-15%Cr austenitic alloys with various MX (M=V, Ti, Nb, Zr; X=C, N) stabilizers after helium implantation and creep rupture at 923 K. It is shown that suppression of helium embrittlement can be achieved through a higher dispersion density of incoherent precipitates because of their high capability of bubble entrapment. A good agreement between the average distance of grain boundary bubbles exceeding the minimum critical size and the spacing of cavity traces on intergranularly fractured surfaces is obtained. This suggests that the enhancement of grain boundary decohesion by helium is a result of unstable growth of super-critical helium bubbles.

  12. Electron acceleration in the bubble regime

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Oliver

    2014-02-03

    The bubble regime of laser-wakefield acceleration has been studied over the recent years as an important alternative to classical accelerators. Several models and theories have been published, in particular a theory which provides scaling laws for acceleration parameters such as energy gain and acceleration length. This thesis deals with numerical simulations within the bubble regime, their comparison to these scaling laws and data obtained from experiments, as well as some specific phenomenona. With a comparison of the scaling laws with numerical results a parameter scan was able to show a large parameter space in which simulation and theory agree. An investigation of the limits of this parameter space revealed boundaries to other regimes, especially at very high (a{sub 0} > 100) and very low laser amplitudes (a{sub 0} < 4). Comparing simulation data with data from experiments concerning laser pulse development and electron energies, it was found that experimental results can be adequately reproduced using the Virtual-Laser-Plasma-Laboratory code. In collaboration with the Institut fuer Optik und Quantenelektronik at the Friedrich-Schiller University Jena synchrotron radiation emitted from the inside of the bubble was investigated. A simulation of the movement of the electrons inside the bubble together with time dependent histograms of the emitted radiation helped to prove that the majority of radiation created during a bubble acceleration originates from the inside of the bubble. This radiation can be used to diagnose the amplitude of oscillation of the trapped electrons. During a further study it was proven that the polarisation of synchrotron radiation from a bubble contains information about the exact oscillation direction. This oscillation was successfully controlled by using either a laser pulse with a tilted pulse front or an asymmetric laser pulse. First results of ongoing studies concerning injecting electrons into an existing bubble and a scheme called

  13. Helium the disappearing element

    CERN Document Server

    Sears, Wheeler M

    2015-01-01

    The subject of the book is helium, the element, and its use in myriad applications including MRI machines, particle accelerators, space telescopes, and of course balloons and blimps. It was at the birth of our Universe, or the Big Bang, where the majority of cosmic helium was created; and stellar helium production continues. Although helium is the second most abundant element in the Universe, it is actually quite rare here on Earth and only exists because of radioactive elements deep within the Earth. This book includes a detailed history of the discovery of helium, of the commercial industry built around it, how the helium we actually encounter is produced within the Earth, and the state of the helium industry today. The gas that most people associate with birthday party balloons is running out. “Who cares?” you might ask. Well, without helium, MRI machines could not function, rockets could not go into space, particle accelerators such as those used by CERN could not operate, fiber optic cables would not...

  14. How does gas pass? Bubble transport through sediments

    Science.gov (United States)

    Fauria, K. E.; Rempel, A. W.

    2009-12-01

    The transport of gas through marine sediments is critical for both the formation and the ultimate fate of gas that is housed temporarily within hydrates. We monitored the gas flux produced by repeated bubble injections into a particle layer that was initially saturated with liquid. The size of ejected bubbles and the period between ejection events were different from the input size and period. Our observations clearly demonstrate bubble break-up as well as coalescence and the formation of preferred bubble migration pathways. We develop an elementary, semi-empirical model to interpret aspects of these results and predict the gas flux expected from a given size distribution of bubble inputs as a function of basic host sediment characteristics. Models of gas transport that use simple modifications to Darcy's law are not adequate to cope with bubble dynamics in the parameter regime that we observe.

  15. Multiscale Modelling: the role of helium in iron

    Directory of Open Access Journals (Sweden)

    Maria Samaras

    2009-11-01

    Full Text Available The mechanisms and processes of bubble nucleation and growth are still not completely solved and research in this field is ongoing. This is an important issue for materials used in fission and fusion reactors. In such environments, one of the main gaseous by-products is helium, whose presence and further production is known to decrease ductility, fatigue life and weldability, induce creep and stress rupture properties of materials, as well as promote swelling. These effects lead to the drastic modification of the material's mechanical properties. In the past, experiments have been used to offer clues into the structure of the materials; now, modelling offers the possibility to understand the structure of the material and from this information, to elucidate a fundamental understanding of material properties. This review discusses the modelling paradigms used to investigate and obtain an understanding of the mechanisms at play in helium bubble nucleation and growth in ferritic steels.

  16. Vortex dynamics in 3D shock-bubble interaction

    Science.gov (United States)

    Hejazialhosseini, Babak; Rossinelli, Diego; Koumoutsakos, Petros

    2013-11-01

    The dynamics of shock-bubble interaction involve an interplay of vortex stretching, dilation, and baroclinic vorticity generation. Here, we quantify the interplay of these contributions through high resolution 3D simulations for several Mach and Atwood numbers. We present a volume rendering of density and vorticity magnitude fields of shock-bubble interaction at M = 3 and air/helium density ratio η = 7.25 to elucidate the evolution of the flow structures. We distinguish the vorticity growth rates due to baroclinicity, stretching, and dilatation at low and high Mach numbers as well as the late time evolution of the circulation. The results demonstrate that a number of analytical models need to be revised in order to predict the late time circulation of shock-bubble interactions at high Mach numbers. To this effect, we propose a simple model for the dependence of the circulation to Mach number and ambient to bubble density ratio for air/helium shock-bubble interactions.

  17. Subtask 12G1: Effects of dynamically charged helium on swelling and microstructure of vanadium-base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Nowicki, L.; Gazda, J.; Smith, D.L. [Argonne National Lab., IL (United States)

    1995-03-01

    The objective of this work is to determine void structure, distribution, and density changes of several vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18-31 dpa at 425-600{degrees}C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible. For specimens irradiated to {approx}18-31 dpa at 500-600{degrees}C with a helium generation rate of 0.4-4.2 appm He/dpa, only a few helium bubbles were observed at the interface of grain matrices and some of the Ti(O,N,C) precipitates, and no microvoids or helium bubbles were observed either in grain matrices or near grain boundaries. Under these conditions, dynamically produced helium atoms seem to be trapped in the grain matrix without significant bubble nucleation or growth, and in accordance with this, density changes from DHCE and non-DHCE (negligible helium generation) were similar for comparable fluence and irradiation temperature. Only for specimens irradiated to {approx}31 dpa at 425{degrees}C, when helium was generated at a rate of 0.4-0.8 appm helium/dpa, were diffuse helium bubbles observed in limited regions of grain matrices and near {approx}15% of the grain boundaries in densities significantly lower than those in the extensive coalescences of helium bubbles typical of other alloys irradiated in tritium-trick experiments. Density changes of specimens irradiated at 425{degrees}C in the DHCE were significantly higher than those from non-DHCE irradiation. Microstructural evolution in V-4Cr-4Ti was similar for DHCE and non-DHCE except for helium bubble number density and distribution. As in non-DHCE, the irradiation-induced precipitation of ultrafine Ti{sub 5}Si{sub 3} was observed for DHCE at >500{degrees}C but not at 425{degrees}C.

  18. Microfluidic bubble logic.

    Science.gov (United States)

    Prakash, Manu; Gershenfeld, Neil

    2007-02-09

    We demonstrate universal computation in an all-fluidic two-phase microfluidic system. Nonlinearity is introduced into an otherwise linear, reversible, low-Reynolds number flow via bubble-to-bubble hydrodynamic interactions. A bubble traveling in a channel represents a bit, providing us with the capability to simultaneously transport materials and perform logical control operations. We demonstrate bubble logic AND/OR/NOT gates, a toggle flip-flop, a ripple counter, timing restoration, a ring oscillator, and an electro-bubble modulator. These show the nonlinearity, gain, bistability, synchronization, cascadability, feedback, and programmability required for scalable universal computation. With increasing complexity in large-scale microfluidic processors, bubble logic provides an on-chip process control mechanism integrating chemistry and computation.

  19. Tribonucleation of bubbles

    CERN Document Server

    Wildeman, Sander; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

    2016-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for "writing with bubbles," i.e., creating controlled patterns ...

  20. Bubbles and market crashes

    CERN Document Server

    Youssefmir, M; Hogg, T; Youssefmir, Michael; Huberman, Bernardo; Hogg, Tad

    1994-01-01

    We present a dynamical theory of asset price bubbles that exhibits the appearance of bubbles and their subsequent crashes. We show that when speculative trends dominate over fundamental beliefs, bubbles form, leading to the growth of asset prices away from their fundamental value. This growth makes the system increasingly susceptible to any exogenous shock, thus eventually precipitating a crash. We also present computer experiments which in their aggregate behavior confirm the predictions of the theory.

  1. Bubble-sweeping mechanisms

    Institute of Scientific and Technical Information of China (English)

    WANG; Hao; (王; 昊); PENG; Xiaofeng; (彭晓峰); WANG; Buxuan; (王补宣); LEE; Duzhong; (李笃中)

    2003-01-01

    A series of subcooled boiling experiments was conducted on very small platinum wires having diameters of 0.1 and 0.025 mm. Vapor bubbles were visually observed to sweep back and forth along the wires in the experiments. The dynamic characteristics of bubble-sweeping phenomenon are described, and the induced bubble interaction and nonlinear growth are investigated to understand the boiling heat transfer mechanisms. An unsymmetrical temperature model is proposed to explain the physical mechanism.

  2. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

    The book aims at describing the most important experimental methods for characterizing liquid interfaces, such as drop profile analysis, bubble pressure and drop volume tensiometry, capillary pressure technique, and oscillating drops and bubbles. Besides the details of experimental set ups, also the underlying theoretical basis is presented in detail. In addition, a number of applications based on drops and bubbles is discussed, such as rising bubbles and the very complex process of flotation. Also wetting, characterized by the dynamics of advancing contact angles is discussed critically. Spec

  3. Physics of bubble oscillations

    Energy Technology Data Exchange (ETDEWEB)

    Lauterborn, Werner; Kurz, Thomas [Third Physical Institute, University of Goettingen (Germany)

    2010-10-01

    Bubbles in liquids, soft and squeezy objects made of gas and vapour, yet so strong as to destroy any material and so mysterious as at times turning into tiny light bulbs, are the topic of the present report. Bubbles respond to pressure forces and reveal their full potential when periodically driven by sound waves. The basic equations for nonlinear bubble oscillation in sound fields are given, together with a survey of typical solutions. A bubble in a liquid can be considered as a representative example from nonlinear dynamical systems theory with its resonances, multiple attractors with their basins, bifurcations to chaos and not yet fully describable behaviour due to infinite complexity. Three stability conditions are treated for stable trapping of bubbles in standing sound fields: positional, spherical and diffusional stability. Chemical reactions may become important in that respect, when reacting gases fill the bubble, but the chemistry of bubbles is just touched upon and is beyond the scope of the present report. Bubble collapse, the runaway shrinking of a bubble, is presented in its current state of knowledge. Pressures and temperatures that are reached at this occasion are discussed, as well as the light emission in the form of short flashes. Aspherical bubble collapse, as for instance enforced by boundaries nearby, mitigates most of the phenomena encountered in spherical collapse, but introduces a new effect: jet formation, the self-piercing of a bubble with a high velocity liquid jet. Examples of this phenomenon are given from light induced bubbles. Two oscillating bubbles attract or repel each other, depending on their oscillations and their distance. Upon approaching, attraction may change to repulsion and vice versa. When being close, they also shoot self-piercing jets at each other. Systems of bubbles are treated as they appear after shock wave passage through a liquid and with their branched filaments that they attain in standing sound fields. The N-bubble

  4. Prospects for bubble fusion

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

    1995-09-01

    In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.

  5. Surface response of tungsten to helium and hydrogen plasma flux as a function of temperature and incident kinetic energy

    Science.gov (United States)

    Sukumar, Harikrishnan

    Tungsten is a leading candidate material for the diverter in future nuclear fusion reactors. Previous experiments have demonstrated that surface defects and bubbles form in tungsten when ex- posed to helium and hydrogen plasmas, even at modest ion energies. In some regimes, between 1000K and 2000K, and for He energies below 100eV, "fuzz" like features form. The mechanisms leading to these surfaces comprised of nanometer sized tungsten tendrils which include visible helium bubbles are not currently known. The role of helium bubble formation in tendril morphology could very likely be the starting point of these mechanisms. Using Molecular dynamics (MD) simulations, the role of helium and hydrogen exposure in the initial formation mechanisms of tungsten "fuzz" are investigated. Molecular dynamics simulations are well suited to describe the time and length scales associated with initial formation of helium clusters that eventually grow to nano-meter sized helium bubbles. MD simulations also easily enable the modeling of a variety of surfaces such as single crystals, grain boundaries or "tendrils". While the sputtering yield of tungsten is generally low, previous observations of surface modification due to plasma exposure raise questions about the effects of surface morphology and sub-surface helium bubble populations on the sputtering behavior. Results of computational molecular dynamics are reported that investigate the influence of sub-surface helium bubble distributions on the sputtering yield of tungsten (100) and (110) surfaces induced by helium ion exposure in the range of 300 eV to 1 keV. The calculated sputtering yields are in reasonable agreement with a wide range of experimental data; but do not show any significant variation as a result of the pre-existing helium bubbles. Molecular dynamics simulations reveal a number of sub-surface mechanisms leading to nanometer- sized "fuzz" in tungsten exposed to low-energy helium plasmas. We find that during the bubble

  6. Advances in Helium Cryogenics

    Science.gov (United States)

    Sciver, S. W. Van

    This review provides a survey of major advances that have occurred in recent years in the area of helium cryogenics. Helium-temperature cryogenics is the enabling technology for a substantial and growing number of low-temperature systems from superconducting magnets to space-based experimental facilities. In recent years there have been many advances in the technology of low-temperature helium, driven mostly by new applications. However, to keep the review from being too broad, this presentation focuses mainly on three of the most significant advances. These are: (1) the development of large-scale recuperative refrigeration systems mainly for superconducting magnet applications in accelerators and other research facilities; (2) the use of stored superfluid helium (He II) as a coolant for spacebased astrophysics experiments; and (3) the application of regenerative cryocoolers operating at liquid helium temperatures primarily for cooling superconducting devices. In each case, the reader should observe that critical technologies were developed to facilitate these applications. In addition to these three primary advances, other significant helium cryogenic technologies are briefly reviewed at the end of this chapter, along with some vision for future developments in these areas.

  7. Mass Transport Phenomena Between Bubbles and Dissolved Gases in Liquids Under Reduced Gravity Conditions

    Science.gov (United States)

    Dewitt, K. J.; Brockwell, J. L.

    1985-01-01

    The long term objective of the experiment is to observe the dissolution of isolated, immobile gas bubbles of specified size and composition in a solvent liquid of known concentration in the reduced gravity environment of earth orbit. Preliminary bubble dissolution experiment conducted both in the NASA Lewis 2.2 sec drop tower and in normal gravity using SO2 - Toluene system were not completely successful in their objective. The method of gas injection and lack of bubble interface stabiliy experienced due to the extreme solubility of SO in Toluene has the effects of changing the problem from that of bubble dissolution to one of bubble formation stability and subsequent dissolution in a liquid of unknown initial solute concentration. Current work involves further experimentation in order to refine the bubble injection system and to investigate the concept of having a bubble with a critical radius in a state of unstable equilibrium.

  8. Turbulence, bubbles and drops

    NARCIS (Netherlands)

    Veen, van der Roeland Cornelis Adriaan

    2016-01-01

    In this thesis, several questions related to drop impact and Taylor-Couette turbulence are answered. The deformation of a drop just before impact can cause a bubble to be entrapped. For many applications, such as inkjet printing, it is crucial to control the size of this entrapped bubble. To study t

  9. Bubbles in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun

    2015-01-01

    Strain-induced deformations in graphene are predicted to give rise to large pseudomagnetic fields. We examine theoretically the case of gas-inflated bubbles to determine whether signatures of such fields are present in the local density of states. Sharp-edged bubbles are found to induce Friedel...

  10. Evaporation, Boiling and Bubbles

    Science.gov (United States)

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  11. Evaporation, Boiling and Bubbles

    Science.gov (United States)

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  12. Single bubble sonoluminescence

    NARCIS (Netherlands)

    Brenner, Michael P.; Hilgenfeldt, Sascha; Lohse, Detlef

    2002-01-01

    Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light ten

  13. Single bubble sonoluminescence

    NARCIS (Netherlands)

    Brenner, Michael P.; Hilgenfeldt, Sascha; Lohse, Detlef

    2002-01-01

    Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light

  14. Bubble collision with gravitation

    CERN Document Server

    Hwang, Dong-il; Lee, Wonwoo; Yeom, Dong-han

    2012-01-01

    In this paper, we study vacuum bubble collisions with various potentials including gravitation, assuming spherical, planar, and hyperbolic symmetry. We use numerical calculations from double-null formalism. Spherical symmetry can mimic the formation of a black hole via multiple bubble collisions. Planar and especially hyperbolic symmetry describes two bubble collisions. We study both cases, when two true vacuum regions have the same field value or different field values, by varying tensions. For the latter case, we also test symmetric and asymmetric bubble collisions, and see details of causal structures. If the colliding energy is sufficient, then the vacuum can be destabilized, and it is also demonstrated. This double-null formalism can be a complementary approach in the context of bubble collisions.

  15. Helium mobility in SON68 borosilicate nuclear glass: A nuclear reaction analysis approach

    Energy Technology Data Exchange (ETDEWEB)

    Bès, R., E-mail: rene.bes@cnrs-orleans.fr [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans cedex 2 (France); Sauvage, T. [CNRS, UPR3079 CEMHTI, 1D Avenue de la Recherche Scientifique, 45071 Orléans cedex 2 (France); Université d’Orléans, Faculté des Sciences, Avenue du Parc Floral, BP 6749, 45067 Orléans cedex 2 (France); Peuget, S. [CEA/DEN/VRH/DTCD/SECM/LMPA Marcoule (France); Haussy, J. [CEA, DAM, DIF, F-91297 Arpajon (France); Chamssedine, F. [Université Libanaise, Faculté des Sciences V, Nabatiyeh (Lebanon); Oliviero, E. [CSNSM, CNRS/IN2P3 and Université Paris-Sud, Bât. 104-108, F-91405 Orsay (France); Fares, T. [CEA/DEN/VRH/DTCD/SECM/LMPA Marcoule (France); Vincent, L. [Institut d’Electronique Fondamentale, CNRS and Université Paris-Sud, UMR 8622, F-91405 Orsay (France)

    2013-11-15

    The {sup 3}He behavior in the non active R7T7 type borosilicate glass called SON68 has been investigated using the implantation method to introduce helium in the material. Nuclear Reaction Analysis (NRA) was performed to follow the helium concentration depth profile evolution as a function of annealing time and temperature. In addition, in situ Transmission Electron Microscopy (TEM) has been implemented to study the formation of helium bubbles during both implantation and annealing processes. Numerical modeling with two different approaches is proposed and discussed to investigate the helium mobility mechanisms. Our study reveals for helium incorporation by implantation at low temperature the presence of several helium populations with disparate diffusivities. The most mobile helium fraction would be attributed to atomic diffusion. The corresponding activation energy value (0.61 eV) extracted from Arrhenius graphs is in good agreement with literature data. The results also highlight that the damages associated to helium sursaturation are the source of small helium clusters formation, with a reduced mobility instead of the atomic mobility measured by the infusion technique. Small cavities that support this assumption have been observed by TEM at low temperature.

  16. 3D shock-bubble interaction

    Science.gov (United States)

    Hejazialhosseini, Babak; Rossinelli, Diego; Koumoutsakos, Petros

    2013-09-01

    We present a simulation for the interactions of shockwaves with light spherical density inhomogeneities. Euler equations for two-phase compressible flows are solved in a 3D uniform resolution finite volume based solver using 5th order WENO reconstructions of the primitive quantities, HLL-type numerical fluxes and 3rd order TVD time stepping scheme. In this study, a normal Mach 3 shockwave in air is directed at a helium bubble with an interface Atwood number of -0.76. We employ 4 billion cells on a supercomputing cluster and demonstrate the development of this flow until relatively late times. Shock passage compresses the bubble and deposits baroclinic vorticity on the interface. Initial distribution of the vorticity and compressions lead to the formation of an air jet, interface roll-ups and the formation of a long lasting vortical core, the white core. Compressed upstream of the bubble turns into a mixing zone and as the vortex ring distances from this mixing zone, a plume-shaped region is formed and sustained. Close observations have been reported in previous experimental works. The visualization is presented in a fluid dynamics video.

  17. Effect of bubble size on nanofiber diameter in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Ren Zhong-Fu

    2016-01-01

    Full Text Available Polymer bubbles are widely used for fabrication of nanofibers. Bubble size affects not only bubble's surface tension, but also fiber's morphology. A mathematical model is established to reveal the effect of bubble size on the spinning process, and the experiment verification shows the theoretical analysis is reliable.

  18. Cosmic Ray Helium Hardening

    CERN Document Server

    Ohira, Yutaka

    2010-01-01

    Recent observations by CREAM, ATIC-2 and PAMELA experiments suggest that (1) the spectrum of cosmic ray (CR) helium is harder than that of CR proton below the knee $10^15 eV$ and (2) all CR spectra become hard at $\\gtrsim 10^{11} eV/n$. We propose a new picture that higher energy CRs are generated in more helium-rich region to explain the hardening (1) without introducing different sources for CR helium. The helium to proton ratio at $\\sim 100$ TeV exceeds the Big Bang abundance $Y=0.25$ by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in the chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium when escaping from the supernova remnant (SNR) shock. We provide a simple analytical spectrum that also fits well the hardening (2) because of the decreasing Mach number in the hot superbubble with $\\sim 10^6$ K. Our model predicts hard and con...

  19. Study of helium embrittlement in boron doped EUROFER97 steels

    Science.gov (United States)

    Gaganidze, E.; Petersen, C.; Aktaa, J.

    2009-04-01

    To simulate helium effects in Reduced Activation Ferritic/Martensitic steels, experimental heats ADS2, ADS3 and ADS4 with the basic composition of EUROFER97 (9%Cr-WVTa) were doped with different contents of natural boron and separated 10B-isotope (0.008-0.112 wt.%) and irradiated in High Flux Reactor (HFR) Petten up to 16.3 dpa at 250-450 °C and in Bor-60 fast reactor in Dimitrovgrad up to 31.8 dpa at 332-338 °C. The embrittlement and hardening are investigated by instrumented Charpy-V tests with subsize specimens. Complete burn-up of 10B isotope under neutron irradiation in HFR Petten led to generation of 84, 432 and 5580 appm He and partial boron-to-helium transformation in Bor-60 led to generation of 9, 46, 880 appm He in ADS2, ADS3 and ADS4 heats, respectively. At low irradiation temperatures Tirr ⩽ 340 °C the boron doped steels show progressive embrittlement with increasing helium amount. Irradiation induced DBTT shift of EUROFER97 based heat doped with 1120 wppm separated 10B isotope could not be quantified due to large embrittlement found in the investigated temperature range. At Tirr ⩽ 340 °C helium induced extra embrittlement is attributed to material hardening induced by helium bubbles and described in terms of phenomenological model.

  20. Efficacy of local triamcinolone acetonide injection in combination with helium - neon laser irradiation in the treatment of alopecia areata%局部注射曲安奈德联合氦氖激光照射治疗斑秃的疗效观察

    Institute of Scientific and Technical Information of China (English)

    唐显华; 陈杏英; 梁敏仪

    2016-01-01

    目的:观察局部注射曲安奈德联合氦氖激光照射治疗斑秃的疗效。方法:将40例斑秃患者随机分成治疗组20例和对照组20例,治疗组局部注射曲安奈德基础上加用氦氖激光照射,对照组外涂糠酸莫米松软膏,两组治疗时间均为3个月。结果:治疗组总有效率85%,对照组总有效率40%,两组比较,差异有统计学意义(P <0.05)。结论:局部注射曲安奈德联合氦氖激光照射治疗斑秃有效率高,安全性好,值得临床推广。%Objective To observe the cilnical efficacy of local injection of triamcinolone acetonide in combination with helium - neon laser irradiation in the treatment of alopecia areata. Method 40 cases of alopecia areata patients were randomly di-vided into either a treatment group(20 cases)or a control group(20 cases). The treatment group were treated with helium - neon laser irradiation on the basis of local injection of triamcinolone acetonide while the control group were treated with mometasone fu-roate ointment. The course of treatment of the both groups for alopecia areata was three months. Results The total efficiency in the treatment group was 85% ,that was 40% in the other group. The difference between the two groups in effectiveness rate was statistically significant(P < 0. 05). Conclusion It is effective and safe for useing local injection of triamcinolone acetonide com-bined with irradiation of helium - neon laser to treat alopecia areata,which is worth for clinical promotion.

  1. Global Solutions to Bubble Growth in Porous Media

    OpenAIRE

    Karp, Lavi

    2010-01-01

    We study a moving boundary problem modeling an injected fluid into another viscous fluid. The viscous fluid is withdrawn at infinity and governed by Darcy's law. We present solutions to the free boundary problem in terms of time-derivative of a generalized Newtonian potentials of the characteristic function of the bubble. This enables us to show that the bubble occupies the entire space as the time tends to infinity if and only if the internal generalized Newtonian potential of the initial bu...

  2. Evolution of Helium with Temperature in Neutron-Irradiated 10B-Doped Aluminum by Small-Angle X-Ray Scattering

    Directory of Open Access Journals (Sweden)

    Chaoqiang Huang

    2014-01-01

    Full Text Available Helium status is the primary effect of material properties under radiation. 10B-doped aluminum samples were prepared via arc melting technique and rapidly cooled with liquid nitrogen to increase the boron concentration during the formation of compounds. An accumulated helium concentration of ~6.2 × 1025 m−3 was obtained via reactor neutron irradiation with the reaction of 10B(n, α7Li. Temperature-stimulated helium evolution was observed via small-angle X-ray scattering (SAXS and was confirmed via transmission electron microscopy (TEM. The SAXS results show that the volume fraction of helium bubbles significantly increased with temperature. The amount of helium bubbles reached its maximum at 600°C, and the most probable diameter of the helium bubbles increased with temperature until 14.6 nm at 700°C. A similar size distribution of helium bubbles was obtained via TEM after in situ SAXS measurement at 700°C, except that the most probable diameter was 3.9 nm smaller.

  3. Global Solutions to Bubble Growth in Porous Media

    CERN Document Server

    Karp, Lavi

    2010-01-01

    We study a moving boundary problem modeling an injected fluid into another viscous fluid. The viscous fluid is withdrawn at infinity and governed by Darcy's law. We present solutions to the free boundary problem in terms of time-derivative of a generalized Newtonian potentials of the characteristic function of the bubble. This enables us to show that the bubble occupies the entire space as the time tends to infinity if and only if the internal generalized Newtonian potential of the initial bubble is a quadratic polynomial.

  4. Chemistry in Soap Bubbles.

    Science.gov (United States)

    Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai

    2002-01-01

    Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)

  5. Chemistry in Soap Bubbles.

    Science.gov (United States)

    Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai

    2002-01-01

    Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)

  6. Popping the Bubble

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Government adopts regulations to control real estate prices A mid concerns surrounding the presence of housing bubbles across China,the Chinese Government is taking action to secure and stabilize the real

  7. Cartilage formation in the CELLS 'double bubble' hardware

    Science.gov (United States)

    Duke, P. J.; Arizpe, Jorge; Montufar-Solis, Dina

    1991-01-01

    The CELLS experiment scheduled to be flown on the first International Microgravity Laboratory is designed to study the effect of microgravity on the cartilage formation, by measuring parameters of growth in a differentiating cartilage cell culture. This paper investigates the conditions for this experiment by studying cartilage differentiation in the 'bubble exchange' hardware with the 'double bubble' design in which the bubbles are joined by a flange which also overlays the gasket. Four types of double bubbles (or double gas permeable membranes) were tested: injection-molded bubbles 0.01- and 0.005-in. thick, and compression molded bubbles 0.015- and 0.01-in. thick. It was found that double bubble membranes of 0.005- and 0.010-in. thickness supported cartilage differentiation, while the 0.015-in. bubbles did not. It was also found that nodule count, used in this study as a parameter, is not the best measure of the amount of cartilage differentiation.

  8. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  9. Bubbling Out of Control

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Jim Chanos,founder of the U.S. hedge fund Kynikos Associates,characterized the prop-erty bubble in China as "Dubai times 1,000-or worse." Many Chinese economists agree. Yi Xianrong,a senior researcher at the Institute of Finance and Banking under the Chinese Academy of Social Sciences,said the property bubble in China was far worse than the Dubai crisis in an interview with the Beijing-based International Herald Leader. Edited excerpts follow:

  10. Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions

    Science.gov (United States)

    Pais, Salvatore Cezar

    1999-01-01

    The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed

  11. Broken symmetry makes helium

    CERN Multimedia

    Gray, P L

    2003-01-01

    "The subatomic pion particle breaks the charge symmetry rule that governs both fusion and decay. In experiments performed at the Indiana University Cyclotron Laboratory, physicists forced heavy hydrogen (1 proton + 1 neutron) to fuse into helium in a controlled, measurable environment" (1 paragraph).

  12. The effects of proton irradiation on the microstructural and mechanical property evolution of inconel X-750 with high concentrations of helium

    Science.gov (United States)

    Judge, C. D.; Bhakhri, V.; Jiao, Z.; Klassen, R. J.; Was, G.; Botton, G. A.; Griffiths, M.

    2017-08-01

    Ni-based alloys, which are used in nuclear applications with a high thermal flux, are shown to contain a high density of helium bubbles within the matrix and aligned along grain boundaries, resulting in lost strength and ductility. In the current investigation, material with and without helium is irradiated with protons up to approximately 60 dpa and 18 000 appm helium. With the use of advanced microscopy and nano-indentation, the microstructural evolution and mechanical hardening has been characterized. The addition of helium decreases the rate of disordering of the gamma prime phase, and suppresses void swelling by forming a region with a high density of helium bubbles, and thereby inhibiting the mobility of freely-migrating point defects. Mechanical hardening from proton-irradiation is consistent with neutron-irradiated Inconel X-750 and Alloy 718.

  13. Damage studies on tungsten due to helium ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, N.J.; Buzarbaruah, N.; Mohanty, S.R., E-mail: smrutirm@yahoo.com

    2014-09-15

    Highlights: • Used plasma focus helium ion source to study radiation induced damage on tungsten. • Surface analyses confirm formation of micro-crack, bubbles, blisters, pinholes, etc. • XRD patterns confirm development of compressive stress due to thermal load. • Reduction in hardness value is observed in the case of exposed sample. - Abstract: Energetic and high fluence helium ions emitted in a plasma focus device have been used successfully to study the radiation induced damage on tungsten. The reference and irradiated samples were characterized by optical microscopy, field emission scanning electron microscopy, X-ray diffraction and by hardness testers. The micrographs of the irradiated samples at lower magnification show uniform mesh of cracks of micrometer width. However at higher magnification, various types of crystalline defects such as voids, pinholes, bubbles, blisters and microcracks are distinctly noticed. The prominent peaks in X-ray diffraction spectrum of irradiated samples are seen shifted toward higher Bragg angles, thus indicating accumulation of compressive stress due to the heat load delivered by helium ions. A marginal reduction in hardness of the irradiated sample is also noticed.

  14. Liquid uranium alloy-helium fission reactor

    Science.gov (United States)

    Minkov, V.

    1984-06-13

    This invention describes a nuclear fission reactor which has a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

  15. Submersion of potassium clusters in helium nanodroplets

    Science.gov (United States)

    An der Lan, Lukas; Bartl, Peter; Leidlmair, Christian; Schöbel, Harald; Denifl, Stephan; Märk, Tilmann D.; Ellis, Andrew M.; Scheier, Paul

    2012-03-01

    Small alkali clusters do not submerge in liquid helium nanodroplets but instead survive predominantly in high spin states that reside on the surface of the nanodroplet. However, a recent theoretical prediction by Stark and Kresin [Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.81.085401 81, 085401 (2010)], based on a classical description of the energetics of bubble formation for a fully submerged alkali cluster, suggests that the alkali clusters can submerge on energetic grounds when they exceed a critical size. Following recent work on sodium clusters, where ion yield data from electron impact mass spectrometry was used to obtain the first experimental evidence for alkali cluster submersion, we report here on similar experiments for potassium clusters. Evidence is presented for full cluster submersion at n>80 for Kn clusters, which is in good agreement with the recent theoretical prediction. In an additional observation, we report “magic number” sizes for both Kn+ and Kn2+ ions derived from helium droplets, which are found to be consistent with the jellium model.

  16. A Summary of Shock/Soap Bubble Interactions Performed at the SWRC, Tohoku University

    Science.gov (United States)

    Yamamoto, H.; Igra, D.; Takayama, Kazuyoshi

    A summary of experiments of shock wave interactions with spherical soap bubbles and cylindrical soap columns filled with helium performed in the Shock Wave Research Center at Tohoku University is presented. Sequential holographic interferograms of soap bubbles impinged by small-scale blast waves created by explosion of 10 mg weight silver azide pellets are presented. The standoff distance between micro-explosives and the bubbles center is about 40 mm and the shock overpressure was about 2 MPa. Helium filled soap columns of 40 mm diameter and 60 mm in height were placed in a 60 mm x 150 mm shock tube. Their interaction with shock wave was intensively visualized by using holographic interferogram at atmospheric conditions. It is found that the irregular interfacial deformation observed are just three-dimensional vortices viewed from the side

  17. EXPERIMENTAL BUBBLE FORMATION IN A LARGE SCALE SYSTEM FOR NEWTONIAN AND NONNEWTONIAN FLUIDS

    Energy Technology Data Exchange (ETDEWEB)

    Leishear, R; Michael Restivo, M

    2008-06-26

    The complexities of bubble formation in liquids increase as the system size increases, and a photographic study is presented here to provide some insight into the dynamics of bubble formation for large systems. Air was injected at the bottom of a 28 feet tall by 30 inch diameter column. Different fluids were subjected to different air flow rates at different fluid depths. The fluids were water and non-Newtonian, Bingham plastic fluids, which have yield stresses requiring an applied force to initiate movement, or shearing, of the fluid. Tests showed that bubble formation was significantly different in the two types of fluids. In water, a field of bubbles was formed, which consisted of numerous, distributed, 1/4 to 3/8 inch diameter bubbles. In the Bingham fluid, large bubbles of 6 to 12 inches in diameter were formed, which depended on the air flow rate. This paper provides comprehensive photographic results related to bubble formation in these fluids.

  18. Colliding with a crunching bubble

    Energy Technology Data Exchange (ETDEWEB)

    Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen

    2007-03-26

    In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.

  19. Investigation of bubble-bubble interaction effect during the collapse of multi-bubble system

    Science.gov (United States)

    Shao, Xueming; Zhang, Lingxin; Wang, Wenfeng

    2014-11-01

    Bubble collapse is not only an important subject among bubble dynamics, but also a key consequence of cavitation. It has been demonstrated that the structural damage is associated with the rapid change in flow fields during bubble collapse. How to model and simulate the behavior of the bubble collapse is now of great interest. In the present study, both theoretical analysis and a direct numerical simulation on the basis of VOF are performed to investigate the collapses of single bubble and bubble cluster. The effect of bubble-bubble interaction on the collapse of multi-bubble system is presented. The work was supported by the National Natural Science Foundation of China (11272284, 11332009).

  20. MEASUREMENT OF BUBBLE-BUBBLE INTERACTION DEPENDED ON REYNOLDS NUMBER USING STEREOSCOPIC BUBBLE-TRACKING TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    QU Jian-wu; MURAI Yuichi; YAMAMOTO Fujio

    2005-01-01

    Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study.The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the relative velocity vectors of two nearest-neighbor bubbles are calculated with high statistical reliability.With the measurement data at Reynolds number ranging from 5 to 75, the vertical attraction and the horizontal repulsion are confirmed for Re<10 as known by the past study based on Navier-Stokes simulation.The new finding of the present measurement is that the bubbles of Re>30 have repulsive velocity bothin the horizontal and the vertical directions as those rise closely.Moreover, the three-dimensional structure of the bubble-bubble interaction is discussed with the data analysis of the interaction vector fields.

  1. Fermi Bubbles with HAWC

    CERN Document Server

    Solares, H A Ayala; Hüntemeyer, P

    2015-01-01

    The Fermi Bubbles, which comprise two large and homogeneous regions of spectrally hard gamma-ray emission extending up to $55^{o}$ above and below the Galactic Center, were first noticed in GeV gamma-ray data from the Fermi Telescope in 2010. The mechanism or mechanisms which produce the observed hard spectrum are not understood. Although both hadronic and lep- tonic models can describe the spectrum of the bubbles, the leptonic model can also explain similar structures observed in microwave data from the WMAP and Planck satellites. Recent publications show that the spectrum of the Fermi Bubbles is well described by a power law with an exponential cutoff in the energy range of 100MeV to 500GeV. Observing the Fermi Bubbles at higher gamma-ray energies will help constrain the origin of the bubbles. A steeper cutoff will favor a leptonic model. The High Altitude Water Cherenkov (HAWC) Observatory, located 4100m above sea level in Mexico, is designed to measure high-energy gamma rays between 100GeV to 100TeV. With...

  2. Bubble reconstruction method for wire-mesh sensors measurements

    Science.gov (United States)

    Mukin, Roman V.

    2016-08-01

    A new algorithm is presented for post-processing of void fraction measurements with wire-mesh sensors, particularly for identifying and reconstructing bubble surfaces in a two-phase flow. This method is a combination of the bubble recognition algorithm presented in Prasser (Nuclear Eng Des 237(15):1608, 2007) and Poisson surface reconstruction algorithm developed in Kazhdan et al. (Poisson surface reconstruction. In: Proceedings of the fourth eurographics symposium on geometry processing 7, 2006). To verify the proposed technique, a comparison was done of the reconstructed individual bubble shapes with those obtained numerically in Sato and Ničeno (Int J Numer Methods Fluids 70(4):441, 2012). Using the difference between reconstructed and referenced bubble shapes, the accuracy of the proposed algorithm was estimated. At the next step, the algorithm was applied to void fraction measurements performed in Ylönen (High-resolution flow structure measurements in a rod bundle (Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 20961, 2013) by means of wire-mesh sensors in a rod bundle geometry. The reconstructed bubble shape yields bubble surface area and volume, hence its Sauter diameter d_{32} as well. Sauter diameter is proved to be more suitable for bubbles size characterization compared to volumetric diameter d_{30}, proved capable to capture the bi-disperse bubble size distribution in the flow. The effect of a spacer grid was studied as well: For the given spacer grid and considered flow rates, bubble size frequency distribution is obtained almost at the same position for all cases, approximately at d_{32} = 3.5 mm. This finding can be related to the specific geometry of the spacer grid or the air injection device applied in the experiments, or even to more fundamental properties of the bubble breakup and coagulation processes. In addition, an application of the new algorithm for reconstruction of a large air-water interface in a tube bundle is

  3. EXPERIMENTAL AND NUMERICAL INVESTIGATION OF BUBBLE AUGMENTED WATERJET PROPULSION

    Institute of Scientific and Technical Information of China (English)

    WU Xiongjun; CHOI Jin-Keun; SINGH Sowmitra; HSIAO Chao-Tsung; CHAHINE Georges L.

    2012-01-01

    This contribution presents experimental and numerical investigations of the concept jet propulsion augmentation using bubble injection.A half-3D (D-shaped cylindrical configuration to enable optimal visualizations) divergent-convergent nozzle was designed,built,and used for extensive experiments under different air injection conditions and thrust measurement schemes.The design,optimization,and analysis were conducted using numerical simulations.The more advanced model was based on a two-way coupling between an Eulerian description of the flow field and a Lagrangian tracking of the injected bubbles using our Surface Averaged Pressure (SAP) model.The numerical resultscompare very favorably with nozzle experiments and both experiments and simulations validation the thrust augmentation concept.For a properly designed nozzle and air injection system,air injection produces net thrust augmentation,which increases with the rate of bubble injection.Doubling of thrust was measured for a 50% air injection rate.This beneficial effect remains at 50% after account for liquid pump additional work to overcome increased pressure by air injection.

  4. Helium-Implantation-Induced Damage in NHS Steel Investigated by Slow-Positron Annihilation Spectroscopy

    Science.gov (United States)

    Li, Yuan-Fei; Shen, Tie-Long; Gao, Xing; Gao, Ning; Yao, Cun-Feng; Sun, Jian-Rong; Wei, Kong-Fang; Li, Bing-Sheng; Zhang, Peng; Cao, Xing-Zhong; Zhu, Ya-Bin; Pang, Li-Long; Cui, Ming-Huan; Chang, Hai-Long; Wang, Ji; Zhu, Hui-Ping; Wang, Dong; Song, Peng; Sheng, Yan-Bin; Zhang, Hong-Peng; Hu, Bi-Tao; Wang, Zhi-Guang

    2014-03-01

    Evolutions of defects and helium contained defects produced by atomic displacement and helium deposition with helium implantation at different temperatures in novel high silicon (NHS) steel are investigated by a slow positron beam. Differences of the defect information among samples implanted by helium to a fluence of 1 × 1017 ions/cm2 at room temperature, 300°C, 450°C and 750°C are discussed. It is found that the mobility of vacancies and vacancy clusters, a recombination of vacancy-type defects and the formation of the He-V complex lead to the occurrence of these differences. At high temperature irradiations, a change of the diffusion mechanism of He atoms/He bubbles might be one of the reasons for the change of the S-parameter.

  5. Influence of helium on impact properties of reduced-activation ferritic/martensitic Cr-steels

    Science.gov (United States)

    Lindau, R.; Möslang, A.; Preininger, D.; Rieth, M.; Röhrig, H. D.

    Instrumented Charpy impact tests of the reduced activation type 8Cr2WVTa steel F82H have been performed after homogeneous implantation of 300 appm helium at 250°C. The results are compared with investigations on mixed spectrum neutron irradiated (HFR Petten) specimens. After neutron irradiation at 250°C to the same low damage dose of 0.2 dpa, the ductile-brittle transition temperature shift (ΔDBTT) amounts to 18°C, whereas a much higher ΔDBTT of 42°C has been measured after helium implantation. These results are compared with other neutron irradiated ferritic/martensitic steels having different boron levels and thus different helium contents. A model is proposed which describes the dynamic brittle fracture of martensitic/ferritic steels by a stress-induced propagation of micro-cracks, taking into account radiation induced hardening as well as helium bubble formation.

  6. A possible origin of gamma rays from the Fermi Bubbles

    Science.gov (United States)

    Thoudam, Satyendra

    2014-11-01

    One of the most exciting discoveries of recent years is a pair of gigantic gamma-ray emission regions, the so-called Fermi bubbles, above and below the Galactic center. The bubbles, discovered by the Fermi space telescope, extend up to ∼50° in Galactic latitude and are ∼40° wide in Galactic longitude. The gamma-ray emission is also found to correlate with radio, microwave and X-rays emission. The origin of the bubbles and the associated non-thermal emissions are still not clearly understood. Possible explanations for the non-thermal emission include cosmic-ray injection from the Galactic center by high speed Galactic winds/jets, acceleration by multiple shocks or plasma turbulence present inside the bubbles, and acceleration by strong shock waves associated with the expansion of the bubbles. In this paper, I will discuss the possibility that the gamma-ray emission is produced by the injection of Galactic cosmic-rays mainly protons during their diffusive propagation through the Galaxy. The protons interact with the bubble plasma producing π°-decay gamma rays, while at the same time, radio and microwave synchrotron emissions are produced by the secondary electrons/positrons resulting from the π± decays.

  7. Bubble nuclei; Noyaux Bulles

    Energy Technology Data Exchange (ETDEWEB)

    Legoll, F. [Service de Physique Theorique, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-07-22

    For nuclei with very high electrical charge, the Coulomb field is expected to drive the protons away from the centre to the surface of the nucleus. Such a nucleus would be no more compact but look like a bubble. The goal of this work is to confirm this idea. We are interested in only the ground state of spherical nuclei. We use the Skyrme potential with the Sly4 parametrization to calculate the mean-field Hamiltonian. Paring correlations are described by a surface-active delta paring interaction. In its ground state the nucleus {sup A=900} X{sub Z=274} is shown to be a bubble. Another stable state is found with a little higher energy: it is also a bubble. (author) 11 refs., 18 figs., 33 tabs.

  8. Bubble nuclei; Noyaux Bulles

    Energy Technology Data Exchange (ETDEWEB)

    Legoll, F. [Service de Physique Theorique, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-07-22

    For nuclei with very high electrical charge, the Coulomb field is expected to drive the protons away from the centre to the surface of the nucleus. Such a nucleus would be no more compact but look like a bubble. The goal of this work is to confirm this idea. We are interested in only the ground state of spherical nuclei. We use the Skyrme potential with the Sly4 parametrization to calculate the mean-field Hamiltonian. Paring correlations are described by a surface-active delta paring interaction. In its ground state the nucleus {sup A=900} X{sub Z=274} is shown to be a bubble. Another stable state is found with a little higher energy: it is also a bubble. (author) 11 refs., 18 figs., 33 tabs.

  9. Experimantal Study on the Bubble Clustering in Bubbly Flows

    Science.gov (United States)

    Takagi, Shu; Fujiwara, Akiko; Ogasawara, Toshiyuki; Matsumoto, Yoichiro

    2003-11-01

    The statistical properties of bubbly flows and the near-wall bubble-clustering behaviors are investigated for upward flow in a rectangular channel. Bubble size, turbulent properties of liquid phase and the bubble clustering motion were measured using image-processing technique, Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), respectively. Using 3-pentanol as a surfactant, the mono-dispersed 1mm-bubbles are generated. The mono-dispersed bubbles in upward flows accumulate near the wall and construct bubble clusters. These bubble clusters were investigated. Experimental observation showed that the size of bubble cluster can be much larger than that of the coherent structure in single phase turbulence. The clusters change their shape in time and space and these bubble motions accelerate the mean streamwise velocity near the wall due to the buoyancy effect. Thus the mean velocity profile of the liquid phase becomes flattened. It is suggested that the highly accumulated bubbles in the vicinity of the wall disturb the transport of turbulence energy produced in the wall shear layer from the central region of the channel flow. Furthermore, in the middle of channel, the fluctuations of the liquid phase are mainly generated by the bubble motions.

  10. Bubble composition of natural gas seeps discovered along the Cascadia Continental Margin

    Science.gov (United States)

    Baumberger, T.; Merle, S. G.; Embley, R. W.; Seabrook, S.; Raineault, N.; Lilley, M. D.; Evans, L. J.; Walker, S. L.; Lupton, J. E.

    2016-12-01

    Gas hydrates and gas-filled pockets present in sedimentary deposits have been recognized as large reservoirs for reduced carbon in the Earth's crust. This is particularly relevant in geological settings with high carbon input, such as continental margins. During expedition NA072 on the E/V Nautilus (operated by the Ocean Exploration Trust Inc.) in June 2016, the U.S. Cascadia Continental Margin (Washington, Oregon and northern California) was explored for gas seepage from sediments. During this expedition, over 400 bubble plumes at water depths ranging from 125 and 1640 m were newly discovered, and five of them were sampled for gas bubble composition using specially designed gas tight fluid samplers mounted on the Hercules remotely operated vehicle (ROV). These gas bubble samples were collected at four different depths, 494 m (rim of Astoria Canyon), 615 and 620 m (SW Coquille Bank), 849 m (floor of Astoria Canyon) and 1227 m (Heceta SW). At the two deeper sites, exposed hydrate was present in the same area where bubbles were seeping out from the seafloor. Other than the escaping gas bubbles, no other fluid flow was visible. However, the presence of bacterial mats point to diffuse fluid flow present in the affected area. In this study we present the results of the currently ongoing geochemical analysis of the gas bubbles released at the different sites and depths. Noble gas analysis, namely helium and neon, will give information about the source of the helium as well as about potential fractionation between helium and neon associated with gas hydrates. The characterization of these gas samples will also include total gas (CO2, H2, N2, O2, Ar, CH4 and other hydrocarbons) and stable isotope analysis (C and H). This dataset will reveal the chemical composition of the seeping bubbles as well as give information about the possible sources of the carbon contained in the seeping gas.

  11. Education in Helium Refrigeration

    Science.gov (United States)

    Gistau Baguer, G. M.

    2004-06-01

    On the one hand, at the end of the time I was active in helium refrigeration, I noticed that cryogenics was stepping into places where it was not yet used. For example, a conventional accelerator, operating at room temperature, was to be upgraded to reach higher particle energy. On the other hand, I was a little bit worried to let what I had so passionately learned during these years to be lost. Retirement made time available, and I came gradually to the idea to teach about what was my basic job. I thought also about other kinds of people who could be interested in such lessons: operators of refrigerators or liquefiers who, often by lack of time, did not get a proper introduction to their job when they started, young engineers who begin to work in cryogenics… and so on. Consequently, I have assembled a series of lessons about helium refrigeration. As the audiences have different levels of knowledge in the field of cryogenics, I looked for a way of teaching that is acceptable for all of them. The course is split into theory of heat exchangers, refrigeration cycles, technology and operation of main components, process control, and helium purity.

  12. Liquid Oxygen Thermodynamic Vent System Testing with Helium Pressurization

    Science.gov (United States)

    VanDresar, Neil T.

    2014-01-01

    This report presents the results of several thermodynamic vent system (TVS) tests with liquid oxygen plus a test with liquid nitrogen. In all tests, the liquid was heated above its normal boiling point to 111 K for oxygen and 100 K for nitrogen. The elevated temperature was representative of tank conditions for a candidate lunar lander ascent stage. An initial test series was conducted with saturated oxygen liquid and vapor at 0.6 MPa. The initial series was followed by tests where the test tank was pressurized with gaseous helium to 1.4 to 1.6 MPa. For these tests, the helium mole fraction in the ullage was quite high, about 0.57 to 0.62. TVS behavior is different when helium is present than when helium is absent. The tank pressure becomes the sum of the vapor pressure and the partial pressure of helium. Therefore, tank pressure depends not only on temperature, as is the case for a pure liquid-vapor system, but also on helium density (i.e., the mass of helium divided by the ullage volume). Thus, properly controlling TVS operation is more challenging with helium pressurization than without helium pressurization. When helium was present, the liquid temperature would rise with each successive TVS cycle if tank pressure was kept within a constant control band. Alternatively, if the liquid temperature was maintained within a constant TVS control band, the tank pressure would drop with each TVS cycle. The final test series, which was conducted with liquid nitrogen pressurized with helium, demonstrated simultaneous pressure and temperature control during TVS operation. The simultaneous control was achieved by systematic injection of additional helium during each TVS cycle. Adding helium maintained the helium partial pressure as the liquid volume decreased because of TVS operation. The TVS demonstrations with liquid oxygen pressurized with helium were conducted with three different fluid-mixer configurations-a submerged axial jet mixer, a pair of spray hoops in the tank

  13. Multivariate bubbles and antibubbles

    Science.gov (United States)

    Fry, John

    2014-08-01

    In this paper we develop models for multivariate financial bubbles and antibubbles based on statistical physics. In particular, we extend a rich set of univariate models to higher dimensions. Changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. Moreover, our multivariate models are able to capture some of the contagious effects that occur during such episodes. We are able to show that declining lending quality helped fuel a bubble in the US stock market prior to 2008. Further, our approach offers interesting insights into the spatial development of UK house prices.

  14. Fermi Bubbles with HAWC

    OpenAIRE

    Solares, H. A. Ayala; Hui, C. M.; Hüntemeyer, P.; collaboration, for the HAWC

    2015-01-01

    The Fermi Bubbles, which comprise two large and homogeneous regions of spectrally hard gamma-ray emission extending up to $55^{o}$ above and below the Galactic Center, were first noticed in GeV gamma-ray data from the Fermi Telescope in 2010. The mechanism or mechanisms which produce the observed hard spectrum are not understood. Although both hadronic and lep- tonic models can describe the spectrum of the bubbles, the leptonic model can also explain similar structures observed in microwave d...

  15. Enhanced lifetime of methane bubble streams within the deep ocean

    Science.gov (United States)

    Rehder, Gregor; Brewer, Peter W.; Peltzer, Edward T.; Friederich, Gernot

    2002-08-01

    We have made direct comparisons of the dissolution and rise rates of methane and argon bubbles experimentally released in the ocean at depths from 440 to 830 m. The bubbles were injected from the ROV Ventana into a box open at the top and the bottom, and imaged by HDTV while in free motion. The vehicle was piloted upwards at the rise rate of the bubbles. Methane and argon show closely similar behavior at depths above the methane hydrate stability field. Below that boundary (~520 m) markedly enhanced methane bubble lifetimes are observed, and are attributed to the formation of a hydrate skin. This effect greatly increases the ease with which methane gas released at depth, either by natural or industrial events, can penetrate the shallow ocean layers.

  16. Helium anion formation inside helium droplets

    Science.gov (United States)

    Maalouf, Elias Jabbour Al; Reitshammer, Julia; Ribar, Anita; Scheier, Paul; Denifl, Stephan

    2016-07-01

    The formation of He∗- is examined with improved electron energy resolution of about 100 meV utilizing a hemispherical electron monochromator. The work presented provides a precise determination of the three previously determined resonance peak positions that significantly contribute to the formation of He∗- inside helium nanodroplets in the energy range from 20 eV to 29.5 eV. In addition, a new feature is identified located at 27.69 ± 0.18 eV that we assign to the presence of O2 as a dopant inside the droplet. With increasing droplet size a small blue shift of the resonance positions is observed. Also for the relatively low electron currents used in the present study (i.e., 15-70 nA) a quadratic dependence of the He∗- ion yield on the electron current is observed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  17. The Early Years: Blowing Bubbles

    Science.gov (United States)

    Ashbrook, Peggy

    2016-01-01

    Blowing bubbles is not only a favorite summer activity for young children. Studying bubbles that are grouped together, or "foam," is fun for children and fascinating to many real-world scientists. Foam is widely used--from the bedroom (mattresses) to outer space (insulating panels on spacecraft). Bubble foam can provide children a…

  18. Hydrodynamics of ultra-relativistic bubble walls

    Directory of Open Access Journals (Sweden)

    Leonardo Leitao

    2016-04-01

    Full Text Available In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.

  19. Understanding the bubbles

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    that are identified to exist between the Internet and housing market bubbles: uncertainty and sentiments. The iteration between uncertainty and sentiments leads to the emergence of the third commonality: residue. The residue is the difference between the actors’ overall sentiment about exaggerated future prospects...

  20. Heavy liquid bubble chamber

    CERN Multimedia

    1965-01-01

    The CERN Heavy liquid bubble chamber being installed in the north experimental hall at the PS. On the left, the 1180 litre body; in the centre the magnet, which can produce a field of 26 800 gauss; on the right the expansion mechanism.

  1. Microfluidic "blinking" bubble pump

    NARCIS (Netherlands)

    Yin, Zhizhong; Prosperetti, Andrea

    2005-01-01

    The paper reports data obtained on a simple micropump, suitable for electrolytes, based on the periodic growth and collapse of a single vapor bubble in a microchannel. With a channel diameter of the order of 100 µm, pumping rates of several tens of µl/min and pressure differences of several kPa are

  2. The Liberal Arts Bubble

    Science.gov (United States)

    Agresto, John

    2011-01-01

    The author expresses his doubt that the general higher education bubble will burst anytime soon. Although tuition, student housing, and book costs have all increased substantially, he believes it is still likely that the federal government will continue to pour billions into higher education, largely because Americans have been persuaded that it…

  3. Popping the Bubble

    Institute of Scientific and Technical Information of China (English)

    LAN XINZHEN

    2010-01-01

    @@ Amid concerns surrounding the presence of housing bubbles across China,the Chinese Government is taking action to secure and stabilize the real estate market.In the past month,the government launched a series of regulatory policies aimed at cooling the overheated market.

  4. BEBC bubble chamber

    CERN Multimedia

    1972-01-01

    Looking up into the interior of BEBC bubble chamber from the expansion cylinder. At the top of the chamber two fish-eye lenses are installed and three other fish-eye ports are blanked off. In the centre is a heat exchanger.

  5. Scanning bubble chamber pictures

    CERN Multimedia

    1974-01-01

    These were taken at the 2 m hydrogen bubble chamber. The photo shows an early Shiva system where the pre-measurements needed to qualify the event were done manually (cf photo 7408136X). The scanning tables were located in bld. 12. Gilberte Saulmier sits on foreground, Inge Arents at centre.

  6. Experimental mechanistic investigation of the nanostructuring of tungsten with low energy helium plasmas

    Science.gov (United States)

    Fiflis, P.; Connolly, N.; Ruzic, D. N.

    2016-12-01

    Helium ion bombardment of tungsten at temperatures between approximately one third and one half of its melting point has shown growth of nanostructures colloquially referred to as "fuzz". The nanostructures take the form of thin tendrils of diameter about 30 nm and grow out of the bulk material. Tungsten will and does compose one of the key materials for plasma facing components (PFCs) in fusion reactors. The formation of nanostructured fuzz layers on PFCs would be detrimental to the performance of the reactor, and must therefore be avoided. Previous experiments have shown evidence that tungsten fuzz is initially grown by loop punching of helium bubbles created in the bulk. However, once the tendrils grow to sufficient length, the tendrils should intercept the entire helium flux, halting the production of fuzz. Fuzz continues to grow though. To increase the understanding of the mechanisms of tungsten fuzz formation, and thereby aid the avoidance of its production, a series of tests were performed to examine the validity of several theories regarding later stage tungsten fuzz growth. Tests showed that the fuzz formation was dependent solely on the bombardment of helium ions, and not on electric fields, or adatom diffusion. Experiments employing a tungsten coated molybdenum sample indicate the presence of a strong mixing layer and strongly suggest that tungsten fuzz growth continues to occur from the bottom up even as the tendrils grow in size. Tests also show a similarity between different metals exposed to helium ion fluxes where the ratio of bubble diameter to tendril diameter is constant.

  7. Helium in Earth's early core

    Science.gov (United States)

    Bouhifd, M. A.; Jephcoat, Andrew P.; Heber, Veronika S.; Kelley, Simon P.

    2013-11-01

    The observed escape of the primordial helium isotope, 3He, from the Earth's interior indicates that primordial helium survived the energetic process of planetary accretion and has been trapped within the Earth to the present day. Two distinct reservoirs in the Earth's interior have been invoked to account for variations in the 3He/4He ratio observed at the surface in ocean basalts: a conventional depleted mantle source and a deep, still enigmatic, source that must have been isolated from processing throughout Earth history. The Earth's iron-based core has not been considered a potential helium source because partitioning of helium into metal liquid has been assumed to be negligible. Here we determine helium partitioning in experiments between molten silicates and iron-rich metal liquids at conditions up to 16GPa and 3,000K. Analyses of the samples by ultraviolet laser ablation mass spectrometry yield metal-silicate helium partition coefficients that range between 4.7×10-3 and 1.7×10-2 and suggest that significant quantities of helium may reside in the core. Based on estimated concentrations of primordial helium, we conclude that the early core could have incorporated enough helium to supply deep-rooted plumes enriched in 3He throughout the age of the Earth.

  8. Thermocapillary Flow and Aggregation of Bubbles on a Solid Wall

    Science.gov (United States)

    Kasumi, Hiroki; Solomentsev, Yuri E.; Guelcher, Scott A.; Anderson, John L.; Sides, Paul J.

    2000-01-01

    were equated by using a wall hindrance parameter q: U = qu [1] which shows the velocity of bubble is proportional to the entraining velocity. The hindrance parameter q can experimentally be measured independently. q can also be calculated by solving the equations of motion for a bubble translating parallel to a solid wall. The experimental cell is cylindrical with an ID of 10 cm and consists of a 1 cm deep main cell filled with silicone oil and flanked by two thermal reservoirs. The upper thermal reservoir was heated and the lower thermal reservoir was cooled so that the bubbles aggregate. Two types of silicone oil (eta = 0.02 and 0.50 Pa s) were used. Two equal sized air bubbles were injected into the cell with a syringe. The center-to-center distance of bubbles was observed through a microscope. Bubble radius ranged from 0.40 mm to 0.65 mm and the temperature gradients along with the cell ranged from 1400 to 5000 K/m. The bubbles aggregated when heat flows from the wall to the fluid. The velocities of bubbles were in the range of 1 - 10 microns/s. The separation r decreased more quickly when the temperature gradient was higher, bubble size was larger, and the oil viscosity was lower. r decreased more rapidly as the bubbles approached each other. Dimensionless time was arbitrarily set to be zero when the dimensionless center-to-center distance between the bubbles was 4. All the bubble trajectories fall onto one line, especially in the range of dimensionless distance from 4 to 3. This means the relative movement of the bubble pair is proportional to the temperature gradient and bubble size and it is inversely proportional to the viscosity of the oil. This result strongly suggests that the thermocapillary flow-based aggregation mechanism is correct. A value of q can be estimated by fitting the scaled data to Eq. [1]. A best fit value of q was obtained as q = 0.26 with a standard deviation of 0.03. Independent experimental results for q for a 0.5 mm radius bubble, give

  9. The role of grain size in He bubble formation: Implications for swelling resistance

    Science.gov (United States)

    El-Atwani, O.; Nathaniel, J. E.; Leff, A. C.; Muntifering, B. R.; Baldwin, J. K.; Hattar, K.; Taheri, M. L.

    2017-02-01

    Nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas ranging from 3000 to 7500 nm2 show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm2 possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.

  10. Optimization of the Geometrical Parameters of a Solar Bubble Pump for Absorption-Diffusion Cooling Systems

    Directory of Open Access Journals (Sweden)

    N. Dammak

    2010-01-01

    Full Text Available Problem statement: The objective of this study was to optimize the geometrical parameters of a bubble pump integrated in a solar flat plate collector. Approach: This solar bubble pump was part of an ammonia/water/helium (NH3/H2O/He absorption-diffusion cooling system. Results: An empirical model was developed on the basis of momentum, mass, material equations and energy balances. The mathematical model was solved using the simulation tool “Engineering Equation Solver (EES”. Conclusion/Recommendations: Using metrological data from Gabes (Tunisia various parameters were geometrically optimized for maximum bubble pump efficiency which was best for a bubble pump tube diameter of 6 mm, a tube length of 1.5 m, an inclination to the horizontal between 30 and 50° of the solar flat plate collector and a submergence ratio between 0.2 and 0.3.

  11. Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking

    NARCIS (Netherlands)

    Leifer, I.; Caulliez, G.; Leeuw, G. de

    2007-01-01

    Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened w

  12. Bubble properties of heterogeneous bubbly flows in a square bubble column: draft

    NARCIS (Netherlands)

    Bai, Wei; Deen, Niels G.; Kuipers, J.A.M.

    2009-01-01

    The present work focuses on the measurements of bubble properties in heterogeneous bubbly flows in a square bubble column. A four-point optical fibre probe was used for this purpose. The accuracy and intrusive effect of the optical probe was investigated first. The results show that the optical prob

  13. Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles

    NARCIS (Netherlands)

    Leifer, I.; Leeuw, G. de

    2006-01-01

    Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical

  14. Bubble properties of heterogeneous bubbly flow in a square bubble column

    NARCIS (Netherlands)

    Bai, W.; Deen, N.G.; Kuipers, J.A.M.

    2010-01-01

    The present work focuses on the measurements of bubble properties in heterogeneous bubbly flows in a square bubble column. A four-point optical fibre probe was used for this purpose. The accuracy and intrusive effect of the optical probe was investigated first. The results show that the optical prob

  15. Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles

    NARCIS (Netherlands)

    Leifer, I.; Leeuw, G. de

    2006-01-01

    Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical extent

  16. Rigorous buoyancy driven bubble mixing for centrifugal microfluidics.

    Science.gov (United States)

    Burger, S; Schulz, M; von Stetten, F; Zengerle, R; Paust, N

    2016-01-21

    We present batch-mode mixing for centrifugal microfluidics operated at fixed rotational frequency. Gas is generated by the disk integrated decomposition of hydrogen peroxide (H2O2) to liquid water (H2O) and gaseous oxygen (O2) and inserted into a mixing chamber. There, bubbles are formed that ascent through the liquid in the artificial gravity field and lead to drag flow. Additionaly, strong buoyancy causes deformation and rupture of the gas bubbles and induces strong mixing flows in the liquids. Buoyancy driven bubble mixing is quantitatively compared to shake mode mixing, mixing by reciprocation and vortex mixing. To determine mixing efficiencies in a meaningful way, the different mixers are employed for mixing of a lysis reagent and human whole blood. Subsequently, DNA is extracted from the lysate and the amount of DNA recovered is taken as a measure for mixing efficiency. Relative to standard vortex mixing, DNA extraction based on buoyancy driven bubble mixing resulted in yields of 92 ± 8% (100 s mixing time) and 100 ± 8% (600 s) at 130g centrifugal acceleration. Shake mode mixing yields 96 ± 11% and is thus equal to buoyancy driven bubble mixing. An advantage of buoyancy driven bubble mixing is that it can be operated at fixed rotational frequency, however. The additional costs of implementing buoyancy driven bubble mixing are low since both the activation liquid and the catalyst are very low cost and no external means are required in the processing device. Furthermore, buoyancy driven bubble mixing can easily be integrated in a monolithic manner and is compatible to scalable manufacturing technologies such as injection moulding or thermoforming. We consider buoyancy driven bubble mixing an excellent alternative to shake mode mixing, in particular if the processing device is not capable of providing fast changes of rotational frequency or if the low average rotational frequency is challenging for the other integrated fluidic operations.

  17. RBS Analysis of Damage Evolution in Helium-implanted 4H-SiC

    Institute of Scientific and Technical Information of China (English)

    ZhangChonghong; SongYin; DuanJinglai; SunYoumei; MaHongji; NieRui; ShenDingyu

    2003-01-01

    The understanding of mechanisms of damage evolution in silicon carbide bombarded with energetic heliumions is important for the use of this material in future fusion reactors. One interesting result from our recentTEM study of defect production in helium-implanted 4H-SiC is the rather high dose threshold for the forma-tion of nanometric helium bubbles This may supply an explanation for the observed defect depleted zone near the surface of silicon carbide. While the defect depleted zone is believed to be the reason of the high resistance of SiC nanocrystals and fibers to heavy irradiation.

  18. High Efficiency Regenerative Helium Compressor Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Helium plays several critical rolls in spacecraft propulsion. High pressure helium is commonly used to pressurize propellant fuel tanks. Helium cryocoolers can be...

  19. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

    This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa,  M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz),  shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...

  20. Cavitation in liquid helium

    Energy Technology Data Exchange (ETDEWEB)

    Finch, R. D.; Kagiwada, R.; Barmatz, M.; Rudnick, I.

    1963-11-15

    Ultrasonic cavitation was induced in liquid helium over the temperature range 1.2 to 2.3 deg K, using a pair of identical transducers. The transducers were calibrated using a reciprocity technique and the cavitation threshold was determined at 90 kc/s. It was found that this threshold has a sharp peak at the lambda point, but is, at all temperatures quite low, with an approximate range of 0.001 to 0.01 atm. The significance of the results is discussed. (auth)

  1. First-principles calculations of helium and neon desorption from cavities in silicon.

    Science.gov (United States)

    Eddin, A Charaf; Pizzagalli, L

    2012-05-02

    Combining density functional theory, the nudged elastic band technique, and the ultradense fluid model, we investigated the desorption process of He and Ne in silicon. Our results show that the internal surfaces of gas-filled bubbles are not a limiting factor during desorption experiments, since the surface reconstruction opens diffusion paths easier than in the bulk. We show that the vibrational contribution to the energy of helium in the bulk has to be considered in order to determine realistic pressures in the bubbles, when comparing experiments and simulations. At the maximum of desorption, an average pressure of 1-2 GPa is computed.

  2. Ab Initio Investigation of He Bubbles at the Y2Ti2O7-Fe Interface in Nanostructured Ferritic Alloys

    Science.gov (United States)

    Danielson, Thomas; Tea, Eric; Hin, Celine

    Nanostructured ferritic alloys are promising materials candidates for the next generation of nuclear reactors due to their ability to withstand high temperatures, high pressures, high neutron flux and especially, the presence of high concentrations of transmutation product helium. As helium diffuses through the matrix, large number densities of complex oxide nanoclusters, namely Y2Ti2O7, Y2O3 and Y2TiO5, act as trapping sites for individual helium atoms and helium clusters. Consequently, there is a significant decrease in the amount of helium that reaches grain boundaries, mitigating the threat of pressurized bubble formation and embrittlement. In order to understand the helium trapping mechanisms of the oxides at a fundamental level, the interface between the nanoclusters and the iron matrix must be modeled. We present results obtained using density functional theory on the Y2Ti2O7-Fe interface where the structure has been modeled based on experimental observations. Helium has been added along the interface in order to investigate the influence of helium on the structure and to obtain thermodynamic and kinetic parameters of helium along the interface.

  3. Bubble Formation at a Submerged Orifice in High-Speed Horizontal Oscillation

    Science.gov (United States)

    Wang, Ningzhen; Chen, Xiang; Yuan, Jianyu; Wang, Guiquan; Li, Yanxiang; Zhang, Huawei; Liu, Yuan

    2016-12-01

    Reducing the cell size of aluminum foams is always a hot and difficult topic in the fabrication of aluminum foams by gas injection route. There lacks theoretical guidance for the bubble size reduction when foaming by the dynamic gas injection method. For the convenience of observation, the aqueous bubbles from small-sized orifice in the high-speed horizontal oscillation were investigated in this paper. A bubble formation and detachment model in the high-speed horizontal oscillation system was proposed. The high-speed system with horizontal simple harmonic oscillation could reduce the average bubble size of aqueous foam effectively. The regularity of bubble formation and the influence of experimental parameters on average bubble size can be predicted by the theoretical model, and the experimental results agree well with the theoretical calculation. The results have shown that bubbles generally detach from the orifice at deceleration periods of the simple harmonic oscillation, and there exist several fixed sizes of bubbles with the fixed experimental parameters due to the effects of periodic forces. The average bubble size decreases with the increase of oscillation frequency and amplitude, and it roughly increases with the increase of gas flow rate. Using the high-speed horizontal oscillation method to prepare aluminum foams, the cell size can be reduced to about 1 mm. Moreover, the cell sizes of aluminum foam can be well predicted by this theoretical model.

  4. Bubbling behaviors induced by gas-liquid mixture permeating through a porous medium

    Science.gov (United States)

    Hu, Liang; Li, Mingbo; Chen, Wenyu; Xie, Haibo; Fu, Xin

    2016-08-01

    This paper investigates the bubbling behaviors induced by gas-liquid mixture permeating through porous medium (PM), which was observed in developing immersion lithography system and was found having great differences with traditional bubbling behaviors injected with only gas phase through the PM. An experimental setup was built up to investigate the bubbling characteristics affected by the mixed liquid phase. Both the flow regimes of gas-liquid mixture in micro-channel (upstream of the PM) and the bubbling flow regimes in water tank (downstream of the PM) were recorded synchronously by high-speed camera. The transitions between the flow regimes are governed by gas and liquid Weber numbers. Based on the image analysis, the characteristic parameters of bubbling region, including the diameter of bubbling area on PM surface, gas-phase volume flux, and dispersion angle of bubbles in suspending liquid, were studied under different proportions of gas and liquid flow rate. Corresponding empirical correlations were developed to describe and predict these parameters. Then, the pertinent bubble characteristics in different bubbling flow regimes were systematically investigated. Specifically, the bubble size distribution and the Sauter mean diameter affected by increasing liquid flow rate were studied, and the corresponding analysis was given based on the hydrodynamics of bubble-bubble and bubble-liquid interactions. According to dimensionless analysis, the general prediction equation of Sauter mean diameter under different operating conditions was proposed and confirmed by experimental data. The study of this paper is helpful to improve the collection performance of immersion lithography and aims to reveal the differences between the bubbling behaviors on PM caused by only gas flow and gas-liquid mixture flow, respectively, for the researches of fluid flow.

  5. Magnetic Bubble Expansion as an Experimental Model for Extra-Galactic Radio Lobes

    Science.gov (United States)

    Lynn, Alan; Zhang, Yue; Hsu, Scott

    2010-11-01

    The Plasma Bubble Expansion Experiment (PBEX) is conducting laboratory experiments to address outstanding nonlinear plasma physics issues related to how magnetic energy and helicity carried by extra-galactic jets interacts with the intergalactic medium to form radio lobe structures. Experiments are being conducted in the 4 meter long, 50 cm diameter HELCAT linear plasma device at UNM. A pulsed magnetized coaxial gun (˜10 kV, ˜100 kA, ˜2 mWb) forms and injects magnetized plasma bubbles perpendicularly into a lower pressure weakly magnetized background plasma formed by a helicon and/or hot cathode source in HELCAT. Ideal MHD simulations show that an MHD shock develops ahead of the bubble as it propagates, and that the bubble develops asymmetries due to the background field [1]. Experimental data from plasma bubble injection into a background plasma, particularly magnetic probe measurements, will be discussed. [4pt] [1] W. Liu et al., Phys. Plasmas 15, 072905 (2008).

  6. Contribution to the study of helium two-phase vertical flow; Contribution a l`etude des ecoulements verticaux d`helium diphasique

    Energy Technology Data Exchange (ETDEWEB)

    Augyrond, L

    1998-04-01

    This work aims at a better understanding of the dynamics of helium two-phase flow in a vertical duct. The case of bubble flow is particularly investigated. The most descriptive parameter of two-phase flow is the void fraction. A sensor to measure this parameter was specially designed and calibrated, it is made of a radioactive source and a semiconductor detector. Sensors based on light attenuation were used to study the behaviour of this two-phase flow. The experimental set-up is described. The different flow types were photographed and video filmed. This visualization has allowed to measure the diameter of bubbles and to study their movements in the fluid. Bubble flow then churn and annular flows were observed but slug flow seems not to exist with helium. A modelling based on a Zuber model matches better the experimental results than a Levy type model. The detailed analysis of the signals given by the optical sensors has allowed to highlight a bubble appearance frequency directly linked to the flowrate. (A.C.) 83 refs.

  7. Regimes Of Helium Burning

    CERN Document Server

    Timmes, F X

    2000-01-01

    The burning regimes encountered by laminar deflagrations and ZND detonations propagating through helium-rich compositions in the presence of buoyancy-driven turbulence are analyzed. Particular attention is given to models of X-ray bursts which start with a thermonuclear runaway on the surface of a neutron star, and the thin shell helium instability of intermediate-mass stars. In the X-ray burst case, turbulent deflagrations propagating in the lateral or radial directions encounter a transition from the distributed regime to the flamlet regime at a density of 10^8 g cm^{-3}. In the radial direction, the purely laminar deflagration width is larger than the pressure scale height for densities smaller than 10^6 g cm^{-3}. Self-sustained laminar deflagrations travelling in the radial direction cannot exist below this density. Similarily, the planar ZND detonation width becomes larger than the pressure scale height at 10^7 g cm^{-3}, suggesting that a steady-state, self-sustained detonations cannot come into exista...

  8. Helium diffusion in carbonates

    Science.gov (United States)

    Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  9. Helium in near Earth orbit

    CERN Document Server

    Alcaraz, J; Ambrosi, G; Anderhub, H; Ao, L; Arefev, A; Azzarello, P; Babucci, E; Baldini, L; Basile, M; Barancourt, D; Barão, F; Barbier, G; Barreira, G; Battiston, R; Becker, R; Becker, U; Bellagamba, L; Béné, P; Berdugo, J; Berges, P; Bertucci, B; Biland, A; Bizzaglia, S; Blasko, S; Bölla, G; Boschini, M; Bourquin, Maurice; Brocco, L; Bruni, G; Buénerd, M; Burger, J D; Burger, W J; Cai, X D; Camps, C; Cannarsa, P; Capell, M; Casadei, D; Casaus, J; Castellini, G; Cecchi, C; Chang, Y H; Chen, H F; Chen, H S; Chen, Z G; Chernoplekov, N A; Tzi Hong Chiueh; Chuang, Y L; Cindolo, F; Commichau, V; Contin, A; Cristinziani, M; Da Cunha, J P; Dai, T S; Deus, J D; Dinu, N; Djambazov, L; D'Antone, I; Dong, Z R; Emonet, P; Engelberg, J; Eppling, F J; Eronen, T; Esposito, G; Extermann, Pierre; Favier, Jean; Fiandrini, E; Fisher, P H; Flügge, G; Fouque, N; Galaktionov, Yu; Gervasi, M; Giusti, P; Grandi, D; Grimm, O; Gu, W Q; Hangarter, K; Hasan, A; Hermel, V; Hofer, H; Huang, M A; Hungerford, W; Ionica, M; Ionica, R; Jongmanns, M; Karlamaa, K; Karpinski, W; Kenney, G; Kenny, J; Kim, W; Klimentov, A; Kossakowski, R; Koutsenko, V F; Kräber, M H; Laborie, G; Laitinen, T; Lamanna, G; Laurenti, G; Lebedev, A; Lee, S C; Levi, G; Levchenko, P M; Liu, C L; Liu Hong Tao; Lopes, I; Lu, G; Lü, Y S; Lübelsmeyer, K; Luckey, D; Lustermann, W; Maña, C; Margotti, A; Mayet, F; McNeil, R R; Meillon, B; Menichelli, M; Mihul, A; Mourão, A M; Mujunen, A; Palmonari, F; Papi, A; Park, I H; Pauluzzi, M; Pauss, Felicitas; Perrin, E; Pesci, A; Pevsner, A; Pimenta, M; Plyaskin, V; Pozhidaev, V; Pohl, M; Postolache, V; Produit, N; Rancoita, P G; Rapin, D; Raupach, F; Ren, D; Ren, Z; Ribordy, M; Richeux, J P; Riihonen, E; Ritakari, J; Röser, U; Roissin, C; Sagdeev, R; Sartorelli, G; Schultz von Dratzig, A; Schwering, G; Scolieri, G; Seo, E S; Shoutko, V; Shoumilov, E; Siedling, R; Son, D; Song, T; Steuer, M; Sun, G S; Suter, H; Tang, X W; Ting, Samuel C C; Ting, S M; Tornikoski, M; Torsti, J; Trümper, J E; Ulbricht, J; Urpo, S; Usoskin, I; Valtonen, E; Van den Hirtz, J; Velcea, F; Velikhov, E P; Verlaat, B; Vetlitskii, I; Vezzu, F; Vialle, J P; Viertel, Gert M; Vitè, Davide F; Von Gunten, H P; Waldmeier-Wicki, S; Wallraff, W; Wang, B C; Wang, J Z; Wang, Y H; Wiik, K; Williams, C; Wu, S X; Xia, P C; Yan, J L; Yan Lu Guang; Yang, C G; Yang, M; Ye Shu Wei; Yeh, P; Xu, Z Z; Zhang, H Y; Zhang, Z P; Zhao, D X; Zhu, G Y; Zhu, W Z; Zhuang, H L; Zichichi, A; Zimmermann, B; Zuccon, P

    2000-01-01

    The helium spectrum from 0.1 to 100 GeV/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV/nucleon the flux was measured to be (6.3+or-0.9)*10/sup -3/ (m/sup 2/ sec sr)/sup -1/ and more than ninety percent of the helium was determined to be /sup 3/He (at the 90% CL). Tracing helium from the second spectrum shows that about half of the /sup 3/He travel for an extended period of time in the geomagnetic field and that they originate from restricted geographic regions similar to protons and positrons. (22 refs).

  10. The thermodynamic and kinetic interactions of He interstitial clusters with bubbles in W

    Science.gov (United States)

    Perez, Danny; Sandoval, Luis; Uberuaga, Blas P.; Voter, Arthur F.

    2016-05-01

    Due to its enviable properties, tungsten is a leading candidate plasma facing material in nuclear fusion reactors. However, like many other metals, tungsten is known to be affected by the high doses of helium atoms incoming from the plasma. Indeed, the implanted interstitial helium atoms cluster together and, upon reaching a critical cluster size, convert into substitutional nanoscale He bubbles. These bubbles then grow by absorbing further interstitial clusters from the matrix. This process can lead to deleterious changes in microstructure, degradation of mechanical properties, and contamination of the plasma. In order to better understand the growth process, we use traditional and accelerated molecular dynamics simulations to investigate the interactions between interstitial He clusters and pre-existing bubbles. These interactions are characterized in terms of thermodynamics and kinetics. We show that the proximity of the bubble leads to an enhancement of the trap mutation rate and, consequently, to the nucleation of satellite bubbles in the neighborhood of existing ones. We also uncover a number of mechanisms that can lead to the subsequent annihilation of such satellite nanobubbles.

  11. Bubble colloidal AFM probes formed from ultrasonically generated bubbles.

    Science.gov (United States)

    Vakarelski, Ivan U; Lee, Judy; Dagastine, Raymond R; Chan, Derek Y C; Stevens, Geoffrey W; Grieser, Franz

    2008-02-05

    Here we introduce a simple and effective experimental approach to measuring the interaction forces between two small bubbles (approximately 80-140 microm) in aqueous solution during controlled collisions on the scale of micrometers to nanometers. The colloidal probe technique using atomic force microscopy (AFM) was extended to measure interaction forces between a cantilever-attached bubble and surface-attached bubbles of various sizes. By using an ultrasonic source, we generated numerous small bubbles on a mildly hydrophobic surface of a glass slide. A single bubble picked up with a strongly hydrophobized V-shaped cantilever was used as the colloidal probe. Sample force measurements were used to evaluate the pure water bubble cleanliness and the general consistency of the measurements.

  12. Micro-bubble Drag Reduction on a High Speed Vessel Model

    Institute of Scientific and Technical Information of China (English)

    Yanuar; Gunawan; Sunaryo; A. Jamaluddin

    2012-01-01

    Ship hull form of the underwater area strongly influences the resistance of the ship.The major factor in ship resistance is skin friction resistance.Bulbous bows,polymer paint,water repellent paint (highly water-repellent wall),air injection,and specific roughness have been used by researchers as an attempt to obtain the resistance reduction and operation efficiency of ships.Micro-bubble injection is a promising technique for lowering frictional resistance.The injected air bubbles are supposed to somehow modify the energy inside the turbulent boundary layer and thereby lower the skin friction.The purpose of this study was to identify the effect of injected micro bubbles on a navy fast patrol boat (FPB) 57 m type model with the following main dimensions:L=2 450 mm,B=400 mm,and T=190 mm.The influence of the location of micro bubble injection and bubble velocity was also investigated.The ship model was pulled by an electric motor whose speed could be varied and adjusted.The ship model resistance was precisely measured by a load cell transducer.Comparison of ship resistance with and without micro-bubble injection was shown on a graph as a function of the drag coefficient and Froude number.It was shown that micro bubble injection behind the mid-ship is the best location to achieve the most effective drag reduction,and the drag reduction caused by the micro-bubbles can reach 6%-9%.

  13. Slurry bubble column hydrodynamics

    Science.gov (United States)

    Rados, Novica

    Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids

  14. CRISIS FOCUS Blowing Bubbles

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Chinese stock and property markets have been outperforming expectations, fueled by an unprecedented surge in bank lending. Xie Guozhong, an economist and board member of Rosetta Stone Advisors, argues the robust Chinese economic figures are only propped up by bubbles, whose bursting will lead to a hard landing for the economy. Xie published his opinion in a related article in Caijing Magazine. Edited excerpts follow:

  15. A possible origin of gamma rays from the Fermi Bubbles

    CERN Document Server

    Thoudam, Satyendra

    2014-01-01

    One of the most exciting discoveries of recent years is a pair of gigantic gamma-ray emission regions, the so-called Fermi bubbles, above and below the Galactic center. The bubbles, discovered by the Fermi space telescope, extend up to $\\sim 50^\\circ$ in Galactic latitude and are $\\sim 40^\\circ$ wide in Galactic longitude. The gamma-ray emission is also found to correlate with radio, microwave and X-rays emission. The origin of the bubbles and the associated non-thermal emissions are still not clearly understood. Possible explanations for the non-thermal emission include cosmic-ray injection from the Galactic center by high speed Galactic winds/jets, acceleration by multiple shocks or plasma turbulence present inside the bubbles, and acceleration by strong shock waves associated with the expansion of the bubbles. In this paper, I will discuss the possibility that the gamma-ray emission is produced by the injection of Galactic cosmic-rays mainly protons during their diffusive propagation through the Galaxy. Th...

  16. Shrinking equatorial plasma bubbles

    Science.gov (United States)

    Narayanan, V. L.; Gurubaran, S.; Shiokawa, K.; Emperumal, K.

    2016-07-01

    The formation of equatorial plasma bubbles (EPBs) associated with spread F irregularities are fairly common phenomenon in the postsunset equatorial ionosphere. These bubbles grow as a result of eastward polarization electric field resulting in upward E × B drift over the dip equator. As they grow they are also mapped to low latitudes along magnetic field lines. The EPBs are often observed as airglow depletions in the images of OI 630 nm emission. On occasions the growth of the features over the dip equator is observed as poleward extensions of the depletions in all-sky images obtained from low latitudes. Herein, we present interesting observations of decrease in the latitudinal extent of the EPBs corresponding to a reduction in their apex altitudes over the dip equator. Such observations indicate that these bubbles not only grow but also shrink on occasions. These are the first observations of shrinking EPBs. The observations discussed in this work are based on all-sky airglow imaging observations of OI 630.0 nm emission made from Panhala (11.1°N dip latitude). In addition, ionosonde observations made from dip equatorial site Tirunelveli (1.1°N dip latitude) are used to understand the phenomenon better. The analysis indicates that the speed of shrinking occurring in the topside is different from the bottomside vertical drifts. When the EPBs shrink, they might decay before sunrise hours.

  17. Effects of helium on titanium films and the helium diffusion

    Institute of Scientific and Technical Information of China (English)

    SONG YingMin; LUO ShunZhong; LONG XingGui; AN Zhu; LIU Ning; PANG HongChao; WU XingChun; YANG BenFu; ZHENG SiXiao

    2008-01-01

    Using direct current-magnetron sputtering, Helium-trapped Ti films with a He/Ar mixture was studied. The relative helium content, helium depth profiles for the Ti films and crystallization capacity were analyzed by Enhanced Proton Backscattering Spectrometry (EPBS) and X-ray diffraction (XRD). It was found that helium diffusion enhanced as more helium trapping into Ti films, and the He holding ratios were 95.9%, 94.9%, 93.9%, 82.8% when the Ti films with the He/Ti of concentrations of 9.7 at.Q, 19.5 at.Q, 19.7 at.Q, 48.3 at.% were measured again 4 months later, respectively. The diffraction peaks be-came weak and wider, the peak of (002) plane was shifted to smaller diffraction angles and the relevant interplanar spacing d(hkl) increased gradually as more helium trapping into Ti films. The main peak was made trending to the (101) plane by both higher deposition temperature and more helium trapping.

  18. Qualification of helium measurement system for detection of fuel failures in a BWR

    Science.gov (United States)

    Larsson, I.; Sihver, L.; Loner, H.; Grundin, A.; Helmersson, J.-O.; Ledergerber, G.

    2014-05-01

    There are several methods for surveillance of fuel integrity during the operation of a boiling water reactor (BWR). The detection of fuel failures is usually performed by analysis of grab samples of off-gas and coolant activities, where a measured increased level of ionizing radiation serves as an indication of new failure or degradation of an already existing one. At some nuclear power plants the detection of fuel failures is performed by on-line nuclide specific measurements of the released fission gases in the off-gas system. However, it can be difficult to distinguish primary fuel failures from degradation of already existing failures. In this paper, a helium measuring system installed in connection to a nuclide specific measuring system to support detection of fuel failures and separate primary fuel failures from secondary ones is presented. Helium measurements provide valuable additional information to measurements of the gamma emitting fission gases for detection of primary fuel failures, since helium is used as a fill gas in the fuel rods during fabrication. The ability to detect fuel failures using helium measurements was studied by injection of helium into the feed water systems at the Forsmark nuclear power plant (NPP) in Sweden and at the nuclear power plant Leibstadt (KKL) in Switzerland. In addition, the influence of an off-gas delay line on the helium measurements was examined at KKL by injecting helium into the off-gas system. By using different injection rates, several types of fuel failures with different helium release rates were simulated. From these measurements, it was confirmed that the helium released by a failed fuel can be detected. It was also shown that the helium measurements for the detection of fuel failures should be performed at a sampling point located before any delay system. Hence, these studies showed that helium measurements can be useful to support detection of fuel failures. However, not all fuel failures which occurred at

  19. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubble...

  20. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubbles...

  1. Electrowetting of a soap bubble

    CERN Document Server

    Arscott, Steve

    2013-01-01

    A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture - the surfaces are composed of highly doped, commercial silicon wafers covered with nanometre thick films of Teflon. Voltages less than 40V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g. laboratory-on-a-chip) - the potential gains in terms of volume, speed and surface/volume ratio are non-negligible.

  2. Influence of helium puff on divertor asymmetry in experimental advanced superconducting tokamak

    DEFF Research Database (Denmark)

    Liu, S. C.; Guo, H. Y.; Xu, G. S.

    2014-01-01

    Divertor asymmetries with helium puffing are investigated in various divertor configurations on Experimental Advanced Superconducting Tokamak (EAST). The outer divertor electron temperature decreases significantly during the gas injection at the outer midplane. As soon as the gas is injected......; the power deposition increases slightly at the outer targets while shows no obvious variation at the inner targets in double null configuration. The radiated power measured by the extreme ultraviolet arrays increases significantly due to helium gas injection, especially in the outer divertor. The edge...

  3. Microstructure characterization and optical properties of sapphire after helium ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Mian; Yang, Liang [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Shen, Huahai [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Liu, Wei [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Xiang, Xia, E-mail: xiaxiang@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zheng, Wanguo, E-mail: wgzheng_caep@sina.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Guo, Decheng [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Huang, Jin [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Sun, Kai [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Yuan, Xiaodong, E-mail: yxd66my@163.com [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China)

    2015-06-15

    The (0 0 0 1) sapphire samples are irradiated with 60 keV helium ions at the fluences of 5 × 10{sup 16}, 1 × 10{sup 17}and 5 × 10{sup 17} ions/cm{sup 2} at room temperature. After implantation, two broad absorption bands at 320–460 and 480–700 nm are observed and their intensities increase with the increasing ion fluence. The grazing incidence X-ray diffraction results indicate that the {0 0 0 1} diffraction peaks of sapphire decrease and broaden due to the disorientation of the generated crystallites after ion irradiation. The microstructure evolution is examined by the scanning and transmission electron microscopes. The surface becomes rough because of the aggregation of helium bubbles and migration towards the surface. There is a lattice expansion up to ∼4.5% in the implanted area and the lattice distortion measured from dispersion of (1 1 0) diffraction is ∼4.6°. Such strain of crystal lattice is rather large and leads to contrast fluctuation at scale of 1–2 nm (the bubble size). The laser induced damage threshold (LIDT) is investigated to understand the effect of helium ion beam irradiation on the laser damage resistance of sapphire components and the results show that the LIDT decreases from 5.4 to 2.5 J/cm{sup 2} due to the absorptive color centers, helium bubbles and defects induced by helium ion implantation. The laser damage morphologies of samples before and after ion implantation are also presented.

  4. Helium release from neutron-irradiated Li{sub 2}O single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yamaki, Daiju; Tanifuji, Takaaki; Noda, Kenji [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Helium release behavior in post-irradiation heating tests was investigated for Li{sub 2}O single crystals which had been irradiated with thermal neutrons in JRR-4 and JRR-2, and fast neutrons in FFTF. It is clarified that the helium release curves from JRR-4 and JRR-2 specimens consists of only one broad peak. From the dependence of the peak temperatures on the neutron fluence and the crystal diameter, and the comparison with the results obtained for sintered pellets, it is considered that the helium generated in the specimen is released through the process of bulk diffusion with trapping by irradiation defects such as some defect clusters. For the helium release from FFTF specimens, two broad peaks were observed in the release curves. It is considered to suggest that two different diffusion paths exist for helium migration in the specimen, that is, bulk diffusion and diffusion through the micro-crack due to the heavy irradiation. In addition, helium bubble formation after irradiation due to the high temperature over 800K is suggested. (J.P.N.)

  5. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics.

  6. Alkali-helium snowball complexes formed on helium nanodroplets.

    Science.gov (United States)

    Müller, S; Mudrich, M; Stienkemeier, F

    2009-07-28

    We systematically investigate the formation and stability of snowballs formed by femtosecond photoionization of small alkali clusters bound to helium nanodroplets. For all studied alkali species Ak = (Na,K,Rb,Cs) we observe the formation of snowballs Ak(+)He(N) when multiply doping the droplets. Fragmentation of clusters Ak(N) upon ionization appears to enhance snowball formation. In the case of Na and Cs we also detect snowballs Ak(2) (+)He(N) formed around Ak dimer ions. While the snowball progression for Na and K is limited to less than 11 helium atoms, the heavier atoms Rb and Cs feature wide distributions at least up to Ak(+)He(41). Characteristic steps in the mass spectra of Cs-doped helium droplets are found at positions consistent with predictions on the closure of the first shell of helium atoms around the Ak(+) ion based on variational Monte Carlo simulations.

  7. Electronic properties of physisorbed helium

    Energy Technology Data Exchange (ETDEWEB)

    Kossler, Sarah

    2011-09-22

    This thesis deals with electronic excitations of helium physisorbed on metal substrates. It is studied to what extent the electronic properties change compared to the gas phase due to the increased helium density and the proximity of the metal. Furthermore, the influence of different substrate materials is investigated systematically. To this end, up to two helium layers were adsorbed onto Ru (001), Pt (111), Cu (111), and Ag (111) surfaces in a custom-made cryostat. These samples were studied spectroscopically using synchrotron radiation and a time-of-flight detector. The experimental results were then analyzed in comparison with extensive theoretical model calculations.

  8. Transferring superfluid helium in space

    Science.gov (United States)

    Kittel, Peter

    1986-01-01

    A simple thermodynamic model of a transfer system for resupplying liquid helium in space is presented, with application to NASA projects including the Space Infrared Telescope Facility, the Large Deployable Reflector, and the Hubble Space Telescope. The relations between different thermodynamic regimes that can be expected in the transfer line are used to study the relative efficiencies of various possible transfer techniques. Low heat leak into the transfer line, particularly at point sources such as the coupling, is necesssary for efficient transfer of liquid helium, and proper selection of supply tank temperature is important during helium resupply.

  9. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  10. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures thereof

  11. Resistor monitors transfer of liquid helium

    Science.gov (United States)

    Hesketh, W. D.

    1966-01-01

    Large resistance change of a carbon resistor at the liquid helium temperature distinguishes between the transfer of liquid helium and gaseous helium into a closed Dewar. The resistor should be physically as small as possible to reduce the heat load to the helium.

  12. Trapping fermionic and bosonic helium atoms

    NARCIS (Netherlands)

    Stas, R.J.W.

    2005-01-01

    This thesis presents experimental and theoretical work performed at the Laser Centre of the Vrije Universiteit in Amsterdam to study laser-cooled metastable triplet helium atoms. Samples containing about 3x10^8 helium atoms-either fermionic helium-3 atoms, bosonic helium-4 atoms or mixtures

  13. Bubble mass center and fluid feedback force fluctuations activated by constant lateral impulse with variable thrust

    Science.gov (United States)

    Hung, R. J.; Long, Y. T.

    1995-01-01

    Sloshing dynamics within a partially filled rotating dewar of superfluid helium 2 are investigated in response to constant lateral impulse with variable thrust. The study, including how the rotating bubble of superfluid helium 2 reacts to the constant impulse with variable time period of thrust action in microgravity, how amplitudes of bubble mass center fluctuates with growth and decay of disturbances, and how fluid feedback forces fluctuates in activating on the rotating dewar through the dynamics of sloshing waves are investigated. The numerical computation of sloshing dynamics is based on the non-inertial frame spacecraft bound coordinate with lateral impulses actuating on the rotating dewar in both inertial and non-inertial frames of thrust. Results of the simulations are illustrated.

  14. Flow visualization study of the effect of injection hole geometry on an inclined jet in crossflow

    Science.gov (United States)

    Simon, Frederick F.; Ciancone, Michael L.

    A flow visualization was studied by using neutrally buoyant, helium-filled soap bubbles, to determine the effect of injection hole geometry on the trajectory of an air jet in a crossflow and to investigate the mechanisms involved in jet deflection. Experimental variables were the blowing rate, and the injection hole geometry cusp facing upstream (CUS), cusp facing downstream (CDS), round, swirl passage, and oblong. It is indicated that jet deflection is governed by both the pressure drag forces and the entrainment of free-stream fluid into the jet flow. For injection hole geometries with similar cross-sectional areas and similar mass flow rates, the jet configuration with the larger aspect ratio experienced a greater deflection. Entrainment arises from lateral shearing forces on the sides of the jet, which set up a dual vortex motion within the jet and thereby cause some of the main-stream fluid momentum to be swept into the jet flow. This additional momentum forces the jet nearer the surface. Of the jet configurations, the oblong, CDS, and CUS configurations exhibited the largest deflections. The results correlate well with film cooling effectiveness data, which suggests a need to determine the jet exit configuration of optimum aspect ratio to provide maximum film cooling effectiveness.

  15. Dynamic Bubble Behaviour during Microscale Subcooled Boiling

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; PENG Xiao-Feng; David M.Christopher

    2005-01-01

    @@ Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The presentinvestigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 orl00μm in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in theexperiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallelto the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above thewire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms forboth bubble sweeping and return. Marangoni flow from warm to cool regions along the bubble interface is foundto produce the shear stresses needed to drive these unusual bubble movements.

  16. Cluster Dynamics Modeling with Bubble Nucleation, Growth and Coalescence

    Energy Technology Data Exchange (ETDEWEB)

    de Almeida, Valmor F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Blondel, Sophie [Univ. of Tennessee, Knoxville, TN (United States); Bernholdt, David E. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wirth, Brian D. [Univ. of Tennessee, Knoxville, TN (United States)

    2017-06-01

    The topic of this communication pertains to defect formation in irradiated solids such as plasma-facing tungsten submitted to helium implantation in fusion reactor com- ponents, and nuclear fuel (metal and oxides) submitted to volatile ssion product generation in nuclear reactors. The purpose of this progress report is to describe ef- forts towards addressing the prediction of long-time evolution of defects via continuum cluster dynamics simulation. The di culties are twofold. First, realistic, long-time dynamics in reactor conditions leads to a non-dilute di usion regime which is not accommodated by the prevailing dilute, stressless cluster dynamics theory. Second, long-time dynamics calls for a large set of species (ideally an in nite set) to capture all possible emerging defects, and this represents a computational bottleneck. Extensions beyond the dilute limit is a signi cant undertaking since no model has been advanced to extend cluster dynamics to non-dilute, deformable conditions. Here our proposed approach to model the non-dilute limit is to monitor the appearance of a spatially localized void volume fraction in the solid matrix with a bell shape pro le and insert an explicit geometrical bubble onto the support of the bell function. The newly cre- ated internal moving boundary provides the means to account for the interfacial ux of mobile species into the bubble, and the growth of bubbles allows for coalescence phenomena which captures highly non-dilute interactions. We present a preliminary interfacial kinematic model with associated interfacial di usion transport to follow the evolution of the bubble in any number of spatial dimensions and any number of bubbles, which can be further extended to include a deformation theory. Finally we comment on a computational front-tracking method to be used in conjunction with conventional cluster dynamics simulations in the non-dilute model proposed.

  17. Hot and cold bubbles in M87

    CERN Document Server

    Kaiser, C R

    2003-01-01

    The X-ray data obtained with XMM-Newton is used to investigate the complex structure of the gas in the atmosphere of the Virgo cluster around M87. We construct a simple model for the temperature and density distribution. This model implies that the cumulative mass of the cluster gas is a power-law of its entropy index, $kT n^{-2/3}$, similar to the Hydra cluster. This supports the idea that such power-laws are a direct consequence of gas cooling in a gravitational potential. In the cluster atmosphere hot bubbles of gas injected by the AGN are rising buoyantly. We estimate the age of these structures from the synchrotron radio data and find that this `radiative age' is consistent with the estimated dynamical timescale. However, this requires a spatial separation of the relativistic particles from the magnetic field. The age estimates suggest an activity cycle of the AGN in M87 of roughly $10^8$ years. We show that the largest radio structures are consistent with being the remnants of buoyant bubbles injected b...

  18. Development of a water leak detector system for LMFBR steam generator. Pt. 1; Sound attenuation due to bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi; Yoshida, Kazuo (Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.)

    1994-03-01

    In the steam generators (SG) of LMFBR, it is necessary to detect the leakage of water from tubes of heat exchanger as soon as leakage is occurred. The active acoustic detection method has drawn general interests owing to its short response time and reduction of the influence of background noise. In this paper, in order to study the applicability of active acoustic method for detection of water leakage in the SG, the sound attenuation characteristics due to bubbles are investigated under various bubble conditions and emitted sound conditions. Furthermore, using SG sector model, sound attenuation characteristics due to injection of bubbles are studied. As a result, it is clarified that the sound attenuation due to bubbles varies dependent upon size of bubbles, void fraction and thickness of bubble layer, that the attenuation of sound reaches maximum when bubbles resonate with the emitted frequency. The sound attenuation due to bubbles in the SG model attenuates immediately upon injection of bubbles, and sound attenuation depends upon bubble size as well as void fraction. (author).

  19. Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).

    Science.gov (United States)

    Rosselló, J M; Dellavale, D; Bonetto, F J

    2015-01-01

    In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F→Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media.

  20. Direct Numerical Simulation of a Shocked Helium Jet

    Energy Technology Data Exchange (ETDEWEB)

    Cloutman, L D

    2002-02-01

    We present direct numerical simulations of a shock tube experiment in which a cylindrical laminar jet of helium doped with biacetyl is injected into air and subjected to a weak shock wave. Computed species distributions in a planar cross section of the jet are compared to planar laser-induced fluorescence (PLIF) images produced by the experiment. The calculations are in excellent agreement with the experimental images. We find that differential diffusion of species is an important feature of this experiment.

  1. Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures

    DEFF Research Database (Denmark)

    Randsoe, Thomas; Hyldegaard, Ole

    2012-01-01

    The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing...... and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied...... at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen...

  2. Mixing high-viscosity fluids via acoustically driven bubbles

    Science.gov (United States)

    Orbay, Sinem; Ozcelik, Adem; Lata, James; Kaynak, Murat; Wu, Mengxi; Huang, Tony Jun

    2017-01-01

    We present an acoustofluidic micromixer which can perform rapid and homogeneous mixing of highly viscous fluids in the presence of an acoustic field. In this device, two high-viscosity polyethylene glycol (PEG) solutions were co-injected into a three-inlet PDMS microchannel with the center inlet containing a constant stream of nitrogen flow which forms bubbles in the device. When these bubbles were excited by an acoustic field generated via a piezoelectric transducer, the two solutions mixed homogenously due to the combination of acoustic streaming, droplet ejection, and bubble eruption effects. The mixing efficiency of this acoustofluidic device was evaluated using PEG-700 solutions which are ~106 times more viscous than deionized (DI) water. Our results indicate homogenous mixing of the PEG-700 solutions with a ~0.93 mixing index. The acoustofluidic micromixer is compact, inexpensive, easy to operate, and has the capacity to mix highly viscous fluids within 50 ms.

  3. Explosive micro-bubble actuator

    NARCIS (Netherlands)

    Broek, van den D.M.; Elwenspoek, M.

    2008-01-01

    Explosive evaporation occurs when a liquid is exposed to extremely high heat-fluxes. Within a few microseconds a bubble in the form vapour film is generated, followed by rapid growth due to the pressure impulse and finally the bubbles collapse. This effect, which already has proven its use in curren

  4. Tuning bubbly structures in microchannels.

    Science.gov (United States)

    Vuong, Sharon M; Anna, Shelley L

    2012-06-01

    Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row ("dripping"), to multiple rows ("alternating"), to densely packed bubbles ("bamboo" and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters.

  5. Bubble chamber: colour enhanced tracks

    CERN Multimedia

    1998-01-01

    This artistically-enhanced image of real particle tracks was produced in the Big European Bubble Chamber (BEBC). Liquid hydrogen is used to create bubbles along the paths of the particles as a piston expands the medium. A magnetic field is produced in the detector causing the particles to travel in spirals, allowing charge and momentum to be measured.

  6. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias;

    2007-01-01

    We investigate the coalescence of two DNA bubbles initially located at weak segments and separated by a more stable barrier region in a designed construct of double-stranded DNA. The characteristic time for bubble coalescence and the corresponding distribution are derived, as well as the distribu...

  7. Triangular bubble spline surfaces.

    Science.gov (United States)

    Kapl, Mario; Byrtus, Marek; Jüttler, Bert

    2011-11-01

    We present a new method for generating a [Formula: see text]-surface from a triangular network of compatible surface strips. The compatible surface strips are given by a network of polynomial curves with an associated implicitly defined surface, which fulfill certain compatibility conditions. Our construction is based on a new concept, called bubble patches, to represent the single surface patches. The compatible surface strips provide a simple [Formula: see text]-condition between two neighboring bubble patches, which are used to construct surface patches, connected with [Formula: see text]-continuity. For [Formula: see text], we describe the obtained [Formula: see text]-condition in detail. It can be generalized to any [Formula: see text]. The construction of a single surface patch is based on Gordon-Coons interpolation for triangles.Our method is a simple local construction scheme, which works uniformly for vertices of arbitrary valency. The resulting surface is a piecewise rational surface, which interpolates the given network of polynomial curves. Several examples of [Formula: see text], [Formula: see text] and [Formula: see text]-surfaces are presented, which have been generated by using our method. The obtained surfaces are visualized with reflection lines to demonstrate the order of smoothness.

  8. Squeezing through: capsule or bubble?

    CERN Document Server

    Dawson, Geoffrey

    2013-01-01

    In this fluid dynamics video, we compare the deformation of two flexible particles as they propagate through a sudden constriction of a liquid filled channel under constant-flux flow: a gas bubble, and a capsule formed by encapsulating a liquid droplet in a cross-linked polymeric membrane. Both bubble and capsule adopt highly contorted configurations as they squeeze through the constriction, exhibit broadly similar features over a wide range of flow rates, and rupture for sufficiently high flow rates. However, at flow rates prior to rupture, certain features of the deformation allow bubble and capsule to be distinguished: bubbles exhibit a tip-streaming singularity associated with critical thinning of the rear of the bubble, while the capsule membrane wrinkles under large compressive stresses induced by the constriction.

  9. Growing bubbles rising in line

    Directory of Open Access Journals (Sweden)

    John F. Harper

    2001-01-01

    Full Text Available Over many years the author and others have given theories for bubbles rising in line in a liquid. Theory has usually suggested that the bubbles will tend towards a stable distance apart, but experiments have often showed them pairing off and sometimes coalescing. However, existing theory seems not to deal adequately with the case of bubbles growing as they rise, which they do if the liquid is boiling, or is a supersaturated solution of a gas, or simply because the pressure decreases with height. That omission is now addressed, for spherical bubbles rising at high Reynolds numbers. As the flow is then nearly irrotational, Lagrange's equations can be used with Rayleigh's dissipation function. The theory also works for bubbles shrinking as they rise because they dissolve.

  10. On the dynamics of a shock-bubble interaction

    Science.gov (United States)

    Quirk, James J.; Karni, Smadar

    1994-01-01

    We present a detailed numerical study of the interaction of a weak shock wave with an isolated cylindrical gas inhomogenity. Such interactions have been studied experimentally in an attempt to elucidate the mechanisms whereby shock waves propagating through random media enhance mixing. Our study concentrates on the early phases of the interaction process which are dominated by repeated refractions of acoustic fronts at the bubble interface. Specifically, we have reproduced two of the experiments performed by Haas and Sturtevant : M(sub s) = 1.22 planar shock wave, moving through air, impinges on a cylindrical bubble which contains either helium or Refrigerant 22. These flows are modelled using the two-dimensional, compressible Euler equations for a two component fluid (air-helium or air-Refrigerant 22). Although simulations of shock wave phenomena are now fairly commonplace, they are mostly restricted to single component flows. Unfortunately, multi-component extensions of successful single component schemes often suffer from spurious oscillations which are generated at material interfaces. Here we avoid such problems by employing a novel, nonconservative shock-capturing scheme. In addition, we have utilized a sophisticated adaptive mesh refinement algorithm which enables extremely high resolution simulations to be performed relatively cheaply. Thus we have been able to reproduce numerically all the intricate mechanisms that were observed experimentally (e.g., transitions from regular to irregular refraction, cusp formation and shock wave focusing, multi-shock and Mach shock structures, jet formation, etc.), and we can now present an updated description for the dynamics of a shock-bubble interaction.

  11. Black Hole Blows Big Bubble

    Science.gov (United States)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  12. Growth and structural determination of He bubbles in iron/chromium alloys using molecular dynamics simulations

    Science.gov (United States)

    Abhishek, A.; Warrier, M.; Ganesh, R.; Caro, A.

    2016-04-01

    Helium(He) produced by transmutation process inside structural material due to neutron irradiation plays a vital role in the degradation of material properties. We have carried out Molecular dynamics(MD) simulations to study the growth of He bubble in Iron-Chromium alloy. Simulations are carried out at two different temperatures, viz. 0.1 K and 800 K, upto He bubble radius of 2.5 nm. An equation for variation of volume of He bubbles with the number of He atoms is obtained at both the temperatures. Bubble pressure and potential energy variation is obtained with increasing bubble radius. Dislocations are also found to be emitted after the bubble reaches a critical radius of 0.39 nm at 800 K. Separate MD simulations of He with pre-created voids are also carried out to study the binding energies of He and Vacancy (V) to Hem-Vn cluster. Binding energies are found to be in the range of 1-5.5 eV.

  13. Helium removal and transport studies in TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Hillis, D.L.; Hogan, J.T.; Horton, L.D.; Isler, R.C.; Klepper, C.C.; Mioduszewski, P.K. (Oak Ridge National Lab., TN (USA)); Finken, K.H.; Dippel, K.H.; Pospieszczyk, A.; Rusbueldt, D.; Euringer, H. (Association Euratom-Kernforschungsanlage Juelich (Germany, F.R.). Inst. fuer Plasmaphysik); Wolf, G.H.; Moyer, R.A.; Conn, R.W.; Gray, D.S. (California Univ., Los Angeles, CA (USA). Inst. of Plasma and Fusion Re

    1990-01-01

    Experiments demonstrating direct control of the He{sup 2+} density in a tokamak plasma have been performed in the TEXTOR tokamak with the Advanced Limiter Test-II pump limiter. Helium is injected in a short gas puff from the outside of the plasma, is observed to reach the plasma core, and then is readily from the plasma. Active He pumping is found to be a valuable technique for discriminating the actual He confinement time from {tau}*{sub He}, which is strongly dependent on recycling. Active charge-exchange spectroscopy is used to study the exhaust and transport of He{sup 2+} within the plasma, and the density evolution is modeled with the diffusive/convective transport code, MIST. 8 refs., 3 figs.

  14. 3D shock-bubble interactions at Mach 3

    CERN Document Server

    Hejazialhosseini, Babak; Koumoutsakos, Petros

    2012-01-01

    We present a simulation for the interactions of shockwaves with light spherical density inhomogeneities. Euler equations for two-phase compressible flows are solved in a 3D uniform resolution finite volume based solver using 5th order WENO reconstructions of the primitive quantities, HLL-type numerical fluxes and 3rd order TVD time stepping scheme. In this study, a normal Mach 3 shockwave in air is directed at a helium bubble with an interface Atwood number of -0.76. We employ 4 billion cells on a supercomputing cluster and demonstrate the development of this flow until relatively late times. Shock passage compresses the bubble and deposits baroclinic vorticity on the interface. Initial distribution of the vorticity and compressions lead to the formation of an air jet, interface roll-ups and the formation of a long lasting vortical core, the white core. Compressed upstream of the bubble turns into a mixing zone and as the vortex ring distances from this mixing zone, a plume-shaped region is formed and sustain...

  15. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

    Science.gov (United States)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2013-01-01

    This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  16. Analytical and experimental studies of wakes behind circularly capped bubbles

    Science.gov (United States)

    Bessler, W. F.

    The wakes behind circularly capped bubbles are examined by means of an experimental and analytical study. A single two-inch diameter bubble is injected into a six by three foot fluid column, one half inch thick, producing an essentially two-dimensional flow. Aspirin powder placed in the fluid column just prior to bubble release highlights the structure of the flow field before dissolving. High speed film and sequenced photographs are taken to document the observed results. Pressure-time measurements are made with sensitive capacitive transducers mounted in the rear column wall and are synchronized with photographs using a high speed clock. Experimental fluids, prepared by mixing water and glycerine in varying proportions, are used to study the effects of viscosity on bubble shape and wake structure. Testing is performed over a range of Reynolds numbers from 14 to 29,655 which includes the transition from circularly capped to ellipsoidal bubble shape. Experimental data is reduced and summarized in convenient dimensionless form to permit comparison with analytical predictions.

  17. Oscillating plasma bubbles. III. Internal electron sources and sinks

    Energy Technology Data Exchange (ETDEWEB)

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    An internal electron source has been used to neutralize ions injected from an ambient plasma into a spherical grid. The resultant plasma is termed a plasma 'bubble.' When the electron supply from the filament is reduced, the sheath inside the bubble becomes unstable. The plasma potential of the bubble oscillates near but below the ion plasma frequency. Different modes of oscillations have been observed as well as a subharmonic and multiple harmonics. The frequency increases with ion density and decreases with electron density. The peak amplitude occurs for an optimum current and the instability is quenched at large electron densities. The frequency also increases if Langmuir probes inside the bubble draw electrons. Allowing electrons from the ambient plasma to enter, the bubble changes the frequency dependence on grid voltage. It is concluded that the net space charge density in the sheath determines the oscillation frequency. It is suggested that the sheath instability is caused by ion inertia in an oscillating sheath electric field which is created by ion bunching.

  18. Numerical prediction of underwater noise reduction during offshore pile driving by a Small Bubble Curtain

    DEFF Research Database (Denmark)

    Göttsche, Klaus Marco; Juhl, Peter Møller; Steinhagen, Ulrich

    2013-01-01

    Small Bubble Curtains are an effective technique to reduce the underwater noise being emitted during offshore pile driving. In order to protect the marine fauna, noise reduction becomes even more important, since the increasing contribution of offshore wind energy leads to a rising number...... of offshore construction sites in order to cover the need for clean energy. Within the Bubble Curtain air bubbles are injected into the water surrounding the pile. When these are driven by the pressure wave being emitted from the pile, reflection, scattering and absorption effects occur. Within this paper......, a method is presented in order to predict the rate of noise attenuation achieved by a Small Bubble Curtain. For this purpose, the bubble distribution is determined with Computational Fluid Dynamics. The noise radiation during pile driving is simulated by Finite Element Analysis and an Effective Medium...

  19. Radiation effects on microstructure and hardness of a titanium aluminide alloy irradiated by helium ions at room and elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Tao, E-mail: tao@ansto.gov.au [Institute of Materials Engineering, Australian Nuclear Science & Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW 2232 (Australia); Zhu, Hanliang [Institute of Materials Engineering, Australian Nuclear Science & Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW 2232 (Australia); Ionescu, Mihail [Institute for Environment Research, Australian Nuclear Science & Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW 2232 (Australia); Dayal, Pranesh; Davis, Joel; Carr, David; Harrison, Robert; Edwards, Lyndon [Institute of Materials Engineering, Australian Nuclear Science & Technology Organisation, Locked Bag 2001, Kirrawee DC, Sydney, NSW 2232 (Australia)

    2015-04-15

    A 45XD TiAl alloy possessing a lamellar microstructure was irradiated using 5 MeV helium ions to a fluence of 5 × 10{sup 21} ion m{sup −2} (5000 appm) with a dose of about 1 dpa (displacements per atom). A uniform helium ion stopping damage region about 17 μm deep from the target surface was achieved by applying an energy degrading wheel. Radiation damage defects including helium-vacancy clusters and small helium bubbles were found in the microstructure of the samples irradiated at room temperature. With increasing irradiation temperature to 300 °C and 500 °C helium bubbles were clearly observed in both the α{sub 2} and γ phases of the irradiated microstructure. By means of nanoindentation significant irradiation hardening was measured. For the samples irradiated at room temperature the hardness increased from 5.6 GPa to 8.5 GPa and the irradiation-hardening effect reduced to approximately 8.0 GPa for the samples irradiated at 300 °C and 500 °C.

  20. SIMS as a new methodology to depth profile helium in as-implanted and annealed pure bcc metals?

    Science.gov (United States)

    Gorondy-Novak, S.; Jomard, F.; Prima, F.; Lefaix-Jeuland, H.

    2017-05-01

    Reliable He profiles are highly desirable for better understanding helium behavior in materials for future nuclear applications. Recently, Secondary Ions Mass Spectrometry (SIMS) allowed the characterization of helium distribution in as-implanted metallic systems. The Cs+ primary ion beam coupled with CsHe+ molecular detector appeared to be a promising technique which overcomes the very high He ionization potential. In this study, 4He depth profiles in pure body centered cubic (bcc) metals (V, Fe, Ta, Nb and Mo) as-implanted and annealed, were obtained by SIMS. All as-implanted samples exhibited a projected range of around 200 nm, in agreement with SRIM theoretical calculations. After annealing treatment, SIMS measurements evidenced the evolution of helium depth profile with temperature. The latter SIMS results were compared to the helium bubble distribution obtained by Transmission Electron Microscopy (TEM). This study confirmed the great potential of this experimental procedure as a He-depth profiling technique in bcc metals. Indeed, the methodology described in this work could be extended to other materials including metallic and non-metallic compounds. Nevertheless, the quantification of helium concentration after annealing treatment by SIMS remains uncertain probably due to the non-uniform ionization efficiency in samples containing large bubbles.

  1. SIMS as a new methodology to depth profile helium in as-implanted and annealed pure bcc metals?

    Energy Technology Data Exchange (ETDEWEB)

    Gorondy-Novak, S. [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Jomard, F. [Groupe d' Etude de la Matière Condensée, CNRS, UVSQ, 45 avenue des Etats-Unis, 78035 Versailles cedex (France); Prima, F. [PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France); Lefaix-Jeuland, H., E-mail: helene.lefaix@cea.fr [CEA, DEN, Service de Recherches de Métallurgie Physique, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

    2017-05-01

    Reliable He profiles are highly desirable for better understanding helium behavior in materials for future nuclear applications. Recently, Secondary Ions Mass Spectrometry (SIMS) allowed the characterization of helium distribution in as-implanted metallic systems. The Cs{sup +} primary ion beam coupled with CsHe{sup +} molecular detector appeared to be a promising technique which overcomes the very high He ionization potential. In this study, {sup 4}He depth profiles in pure body centered cubic (bcc) metals (V, Fe, Ta, Nb and Mo) as-implanted and annealed, were obtained by SIMS. All as-implanted samples exhibited a projected range of around 200 nm, in agreement with SRIM theoretical calculations. After annealing treatment, SIMS measurements evidenced the evolution of helium depth profile with temperature. The latter SIMS results were compared to the helium bubble distribution obtained by Transmission Electron Microscopy (TEM). This study confirmed the great potential of this experimental procedure as a He-depth profiling technique in bcc metals. Indeed, the methodology described in this work could be extended to other materials including metallic and non-metallic compounds. Nevertheless, the quantification of helium concentration after annealing treatment by SIMS remains uncertain probably due to the non-uniform ionization efficiency in samples containing large bubbles.

  2. Bubbles trapped in a fluidized bed: Trajectories and contact area

    Science.gov (United States)

    Poryles, Raphaël; Vidal, Valérie; Varas, Germán

    2016-03-01

    This work investigates the dynamics of bubbles in a confined, immersed granular layer submitted to an ascending gas flow. In the stationary regime, a central fluidized zone of parabolic shape is observed, and the bubbles follow different dynamics: either the bubbles are initially formed outside the fluidized zone and do not exhibit any significant motion over the experimental time or they are located inside the fluidized bed, where they are entrained downwards and are, finally, captured by the central air channel. The dependence of the air volume trapped inside the fluidized zone, the bubble size, and the three-phase contact area on the gas injection flow rate and grain diameter are quantified. We find that the volume fraction of air trapped inside the fluidized region is roughly constant and of the order of 2%-3% when the gas flow rate and the grain size are varied. Contrary to intuition, the gas-liquid-solid contact area, normalized by the air injected into the system, decreases when the flow rate is increased, which may have significant importance in industrial applications.

  3. Effect of isobaric breathing gas shifts from air to heliox mixtures on resolution of air bubbles in lipid and aqueous tissues of recompressed rats

    DEFF Research Database (Denmark)

    Hyldegaard, Ole; Kerem, Dikla; Melamed, Y

    2011-01-01

    Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from nitrogen to helium after hyperbaric air breathing...... breathing. No such bubble growth was observed in spinal white matter, skeletal muscle or tendon. In spinal white matter, an immediate breathing gas shift after the hyperbaric air exposure from air to both (80:20) and (50:50) heliox, coincident with recompression to either 285 or 405 kPa, caused consistent...

  4. Doughnut-shaped soap bubbles

    Science.gov (United States)

    Préve, Deison; Saa, Alberto

    2015-10-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only factor responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume V and with a fixed equatorial perimeter L . It is well known that the sphere is the solution for V =L3/6 π2 , and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for V <α L3/6 π2 , with α ≈0.21 , such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but is rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtaining the global solution for this axisymmetric isoperimetric problem. Our result suggests that deformed bubbles with V <α L3/6 π2 cannot be stable and should not exist in foams, for instance.

  5. Active acoustic leak detection for LMFBR steam generator. Sound attenuation due to bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Hiromichi; Sakuma, Toshio [Central Research Inst. of Electric Power Industry, Komae, Tokyo (Japan). Komae Research Lab.

    1995-06-01

    In the steam generators (SG) of LMFBR, it is necessary to detect the leakage of water from tubes of heat exchangers as soon as it occurs. The active acoustic detection method has drawn general interest owing to its short response time and reduction of the influence of background noise. In this paper, the application of the active acoustic detection method for SG is proposed, and sound attenuation by bubbles is investigated experimentally. Furthermore, using the SG sector model, sound field characteristics and sound attenuation characteristics due to injection of bubbles are studied. It is clarified that the sound attenuation depends upon bubble size as well as void fraction, that the distance attenuation of sound in the SG model containing heat transfer tubes is 6dB for each two-fold increase of distance, and that emitted sound attenuates immediately upon injection of bubbles. (author).

  6. A study of gas bubbles in liquid mercury in a vertical Hele-Shaw cell

    Science.gov (United States)

    Klaasen, B.; Verhaeghe, F.; Blanpain, B.; Fransaer, J.

    2014-01-01

    High-quality observations of mesoscopic gas bubbles in liquid metal are vital for a further development of pyrometallurgical gas injection reactors. However, the opacity of metals enforces the use of indirect imaging techniques with limited temporal or spatial resolution. In addition, accurate interface tracking requires tomography which further complicates the design of a high-temperature experimental setup. In this paper, an alternative approach is suggested that circumvents these two main restrictions. By injecting gas in a thin layer of liquid metal entrapped between two flat and closely spaced plates, bubbles in a Hele-Shaw flow regime are generated. The resulting quasi-2D multiphase flow phenomena can be fully captured from a single point of view and, when using a non-wetted transparent plate material, the bubbles can be observed directly. The feasibility of this approach is demonstrated by observations on buoyancy-driven nitrogen bubbles in liquid mercury in a vertical Hele-Shaw cell. By using a moving high-speed camera to make continuous close up recordings of individual bubbles, the position and geometry of these bubbles are quantified with a high resolution along their entire path. After a thorough evaluation of the experimental accuracy, this information is used for a detailed analysis of the bubble expansion along the path. While the observed bubble growth is mainly caused by the hydrostatic pressure gradient, a careful assessment of the volume variations for smaller bubbles shows that an accurate bubble description should account for significant dynamic pressure variations that seem to be largely regime dependent.

  7. The Bubble Transport Mechanism: Indications for a bubble-mediated transfer of microorganisms from the sediment into the water column

    Science.gov (United States)

    Schmale, Oliver; Stolle, Christian; Schneider von Deimling, Jens; Leifer, Ira; Kießlich, Katrin; Krause, Stefan; Frahm, Andreas; Treude, Tina

    2015-04-01

    bubble surface rim. Bubble Catcher experiments were carried out directly above a natural bubble release spot and on a reference site at which artificially released gas bubbles were caught, which had no contact with the sediment. CARD-FISH analyzes showed that aerobic methane oxidizing bacteria were transported by gas bubbles from the sediment into the water column. In contrast anaerobic methanotrophs were not detected in the bubble catcher. Based on our study we hypothesize that the Bubble Shuttle transport mechanism contributes to the pelagic methane sink by a sediment-water column transfer of methane oxidizing microorganisms. Furthermore, this Bubble Shuttle may influence the methanotrophic community in the water column after massive short-term submarine inputs of methane (e.g. release of methane from bore holes). Especially in deep-sea regions, where the abundance of methane oxidizing microorganisms in the water column is low in general, the Bubble Transport Mechanism may inject a relevant amount of methane oxidizing microorganisms into the water column during massive inputs, supporting indirectly the turnover of this greenhouse active trace gas in the submarine environment.

  8. Partial coalescence of soap bubbles

    Science.gov (United States)

    Harris, Daniel M.; Pucci, Giuseppe; Bush, John W. M.

    2015-11-01

    We present the results of an experimental investigation of the merger of a soap bubble with a planar soap film. When gently deposited onto a horizontal film, a bubble may interact with the underlying film in such a way as to decrease in size, leaving behind a smaller daughter bubble with approximately half the radius of its progenitor. The process repeats up to three times, with each partial coalescence event occurring over a time scale comparable to the inertial-capillary time. Our results are compared to the recent numerical simulations of Martin and Blanchette and to the coalescence cascade of droplets on a fluid bath.

  9. Sonochemistry and the acoustic bubble

    CERN Document Server

    Grieser, Franz; Enomoto, Naoya; Harada, Hisashi; Okitsu, Kenji; Yasui, Kyuichi

    2015-01-01

    Sonochemistry and the Acoustic Bubble provides an introduction to the way ultrasound acts on bubbles in a liquid to cause bubbles to collapse violently, leading to localized 'hot spots' in the liquid with temperatures of 5000° celcius and under pressures of several hundred atmospheres. These extreme conditions produce events such as the emission of light, sonoluminescence, with a lifetime of less than a nanosecond, and free radicals that can initiate a host of varied chemical reactions (sonochemistry) in the liquid, all at room temperature. The physics and chemistry behind the p

  10. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

    Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

  11. Thermal Phase in Bubbling Geometries

    Institute of Scientific and Technical Information of China (English)

    LIU Chang-Yong

    2008-01-01

    We use matrix model to study thermal phase in bubbling half-BPS type IIB geometries with SO(4)×SO(4) symmetry.Near the horizon limit,we find that thermal vacua of bubbling geometries have disjoint parts,and each part is one kind of phase of the thermal system.We connect the thermal dynamics of bubbling geometries with one-dimensional fermions thermal system.Finally,we try to give a new possible way to resolve information loss puzzle.

  12. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    spectroscopy analysis of gases liberated during heating of the glass reveals that small bubbles contain predominantly CH4, CO and CO2, whereas large bubbles bear N2, SO2 and H2S. The methodology utilised in this work can, besides mapping the bubbles in a glass, be applied to shed light on the sources of bubble...

  13. Bubble stimulation efficiency of dinoflagellate bioluminescence.

    Science.gov (United States)

    Deane, Grant B; Stokes, M Dale; Latz, Michael I

    2016-02-01

    Dinoflagellate bioluminescence, a common source of bioluminescence in coastal waters, is stimulated by flow agitation. Although bubbles are anecdotally known to be stimulatory, the process has never been experimentally investigated. This study quantified the flash response of the bioluminescent dinoflagellate Lingulodinium polyedrum to stimulation by bubbles rising through still seawater. Cells were stimulated by isolated bubbles of 0.3-3 mm radii rising at their terminal velocity, and also by bubble clouds containing bubbles of 0.06-10 mm radii for different air flow rates. Stimulation efficiency, the proportion of cells producing a flash within the volume of water swept out by a rising bubble, decreased with decreasing bubble radius for radii less than approximately 1 mm. Bubbles smaller than a critical radius in the range 0.275-0.325 mm did not stimulate a flash response. The fraction of cells stimulated by bubble clouds was proportional to the volume of air in the bubble cloud, with lower stimulation levels observed for clouds with smaller bubbles. An empirical model for bubble cloud stimulation based on the isolated bubble observations successfully reproduced the observed stimulation by bubble clouds for low air flow rates. High air flow rates stimulated more light emission than expected, presumably because of additional fluid shear stress associated with collective buoyancy effects generated by the high air fraction bubble cloud. These results are relevant to bioluminescence stimulation by bubbles in two-phase flows, such as in ship wakes, breaking waves, and sparged bioreactors.

  14. Bubble Dynamics and Resulting Noise from Traveling Bubble Cavitation.

    Science.gov (United States)

    1982-04-13

    has resulted in models which aqree well with bubble dynamics recorded by high speed film . Chahine, et. al. (23) incorporated asymmetric bubble...recording on the tape soundtrack . 3.8 Measurement of Gas Nuclei in Water The role of nuclei density and size in cavitation inception has been the subject...interference between the coherent background and the particle-diffracted radiation exooses photographic film in the far-field of the nuclei. This

  15. Bed system performance in helium circulation mode

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yean Jin; Jung, Kwang Jin; Ahn, Do Hee; Chung, Hong Suk [UST, Daejeon (Korea, Republic of); Kang, Hee Suk [KAERI, Daejeon (Korea, Republic of); Yun, Sei Hun [NFRI, Deajeon (Korea, Republic of)

    2016-05-15

    As a part of the International Thermonuclear Experimental Reactor (ITER) Project, We have conducted an experiment for storing hydrogen to depleted uranium and zirconium cobalt. The helium blanket effect has been observed in experiments using metal hydrides. The collapse of the hydrogen isotopes are accompanied by the decay heat and helium-3. Helium-3 dramatically reduces the hydrogen isotope storage capacity by surrounding the metal. This phenomenon is called a helium blanket effect. In addition the authors are working on the recovery and removal techniques of helium-3. In this paper, we discuss the equipment used to test the helium blanket effect and the results of a helium circulation experiment. The helium-3 produced surrounds the storage material surface and thus disturbs the reaction of the storage material and the hydrogen isotope. Even if the amount of helium-3 is small, the storage capacity of the SDS bed significantly drops. This phenomenon is the helium blanket effect. To resolve this phenomenon, a circulating loop was introduced. Using a circulating system, helium can be separated from the storage material. We made a helium loop that includes a ZrCo bed. Then using a metal bellows pump, we tested the helium circulation.

  16. Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel

    Science.gov (United States)

    Wang, Pinghuai; Nobuta, Yuji; Hino, Tomoaki; Yamauchi, Yuji; Chen, Jiming; Xu, Zengyu; Li, Xiongwei; Liu, Shi

    2009-04-01

    The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwestern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

  17. Helium Retention and Desorption Behaviour of Reduced Activation Ferritic/Martenstic Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Pinghuai; NOBUTA Yuji; HINO Tomoaki; YAMAUCHI Yuji; CHEN Zilning; XU Zengyu; LI Xiongwei; LIU Shi

    2009-01-01

    The reduced activation ferritic/martenstic steel CLF-1 prepared by the Southwest-ern Institute of Physics in China was irradiated by helium ions with an energy of 5 keV at room temperature using an electron cyclotron resonance (ECR) ion irradiation apparatus. After the irradiation, the helium retention and desorption were investigated using a technique of thermal desorption spectroscopy (TDS). The experiment was conducted with both the normal and welded samples. Blisters were observed after the helium ion irradiation, and the surface density of blisters in the welded samples was lower than that in the non-welded samples. Three desorption peaks were observed in both the non-welded and welded samples. These desorption peaks corresponded to those of blister ruptures and the helium release from the inner bubbles and the defects. The amount of helium retained in the welded samples was approximately the same as that in the non-welded samples, which was much less than other reduced activation materials, such as vanadium alloy and SiC/SiC composites.

  18. Rogue mantle helium and neon.

    Science.gov (United States)

    Albarède, Francis

    2008-02-15

    The canonical model of helium isotope geochemistry describes the lower mantle as undegassed, but this view conflicts with evidence of recycled material in the source of ocean island basalts. Because mantle helium is efficiently extracted by magmatic activity, it cannot remain in fertile mantle rocks for long periods of time. Here, I suggest that helium with high 3He/4He ratios, as well as neon rich in the solar component, diffused early in Earth's history from low-melting-point primordial material into residual refractory "reservoir" rocks, such as dunites. The difference in 3He/4He ratios of ocean-island and mid-ocean ridge basalts and the preservation of solar neon are ascribed to the reservoir rocks being stretched and tapped to different extents during melting.

  19. Pierre Gorce working on a helium pump.

    CERN Multimedia

    1975-01-01

    This type of pump was designed by Mario Morpurgo, to circulate liquid helium in superconducting magnets wound with hollow conductors. M. Morpurgo, Design and construction of a pump for liquid helium, CRYIOGENICS, February 1977, p. 91

  20. Helium release during shale deformation: Experimental validation

    Science.gov (United States)

    Bauer, Stephen J.; Gardner, W. Payton; Heath, Jason E.

    2016-07-01

    This work describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

  1. The Housing Bubble Fact Sheet

    OpenAIRE

    Dean Baker

    2005-01-01

    This paper explains the basic facts about the current housing market. It lays out the evidence that the rise in housing prices constitutes a housing bubble - and explains what can be expected when it inevitably collapses.

  2. Bubble bean bags in shampoo

    CERN Document Server

    Kundu, Anup; Das, Gargi; Harikrishnan, G

    2011-01-01

    In these fluid dynamics videos, we, for the first time, show various interactions of a 'Taylor bubble' with their smaller and differently, shaped counterparts, in a shear thinning, non-Newtonian fluid, confined in a narrow channel.

  3. Effects of gas bubble production on heat transfer from a volumetrically heated liquid pool

    Science.gov (United States)

    Bull, Geoffrey R.

    Aqueous solutions of uranium salts may provide a new supply chain to fill potential shortfalls in the availability of the most common radiopharmaceuticals currently in use worldwide, including Tc99m which is a decay product of Mo99. The fissioning of the uranium in these solutions creates Mo99 but also generates large amounts of hydrogen and oxygen from the radiolysis of the water. When the dissolved gases reach a critical concentration, bubbles will form in the solution. Bubbles in the solution affect both the fission power and the heat transfer out of the solution. As a result, for safety and production calculations, the effects of the bubbles on heat transfer must be understood. A high aspect ratio tank was constructed to simulate a section of an annulus with heat exchangers on the inner and outer steel walls to provide cooling. Temperature measurements via thermocouples inside the tank and along the outside of the steel walls allowed the calculation of overall and local heat transfer coefficients. Different air injection manifolds allowed the exploration of various bubble characteristics and patterns on heat transfer from the pool. The manifold type did not appear to have significant impact on the bubble size distributions in water. However, air injected into solutions of magnesium sulfate resulted in smaller bubble sizes and larger void fractions than those in water at the same injection rates. One dimensional calculations provide heat transfer coefficient values as functions of the superficial gas velocity in the pool.

  4. The cosmic production of Helium

    CERN Document Server

    Jiménez, R; MacDonald, J; Gibson, B K; Jimenez, Raul; Flynn, Chris; Donald, James Mac; Gibson, Brad K.

    2003-01-01

    We estimate the cosmic production rate of helium relative to metals ($\\Delta Y/\\Delta Z$) using K dwarf stars in the Hipparcos catalog with accurate spectroscopic metallicities. The best fitting value is $\\Delta Y/\\Delta Z=2.1 \\pm 0.4$ at the 68% confidence level. Our derived value agrees with determinations from HII regions and with theoretical predictions from stellar yields with standard assumptions for the initial mass function. The amount of helium in stars determines how long they live and therefore how fast they will enrich the insterstellar medium with fresh material.

  5. A Lagrangian-Lagrangian Model for Two-Phase Bubbly Flow around Circular Cylinder

    Directory of Open Access Journals (Sweden)

    M. Shademan

    2014-06-01

    Full Text Available A Lagrangian-Lagrangian model is developed using an in-house code to simulate bubble trajectory in two-phase bubbly flow around circular cylinder. Random Vortex Method (RVM which is a Lagrangian approach is used for solving the liquid phase. The significance of RVM relative to other RANS/LES methods is its capability in directly modelling the turbulence. In RVM, turbulence is modeled by solving the vorticity transport equation and there is no need to use turbulence closure models. Another advantage of RVM relative to other CFD approaches is its independence from mesh generation. For the bubbles trajectory, equation of motion of bubbles which takes into account effect of different forces are coupled with the RVM. Comparison of the results obtained from current model with the experimental data confirms the validity of the model. Effect of different parameters including flow Reynolds number, bubble diameter and injection point on the bubbles' trajectory are investigated. Results show that increase in the Reynolds number reduces the rising velocity of the bubbles. Similar behavior is observed for the bubbles when their diameter was decreased. According to the analysis carried out, present Lagrangian-Lagrangian model solves the issues of mesh generation and turbulence modelling which exist in common two phase flow modelling schemes.

  6. Mechanisms of single bubble cleaning.

    Science.gov (United States)

    Reuter, Fabian; Mettin, Robert

    2016-03-01

    The dynamics of collapsing bubbles close to a flat solid is investigated with respect to its potential for removal of surface attached particles. Individual bubbles are created by nanosecond Nd:YAG laser pulses focused into water close to glass plates contaminated with melamine resin micro-particles. The bubble dynamics is analysed by means of synchronous high-speed recordings. Due to the close solid boundary, the bubble collapses with the well-known liquid jet phenomenon. Subsequent microscopic inspection of the substrates reveals circular areas clean of particles after a single bubble generation and collapse event. The detailed bubble dynamics, as well as the cleaned area size, is characterised by the non-dimensional bubble stand-off γ=d/Rmax, with d: laser focus distance to the solid boundary, and Rmax: maximum bubble radius before collapse. We observe a maximum of clean area at γ≈0.7, a roughly linear decay of the cleaned circle radius for increasing γ, and no cleaning for γ>3.5. As the main mechanism for particle removal, rapid flows at the boundary are identified. Three different cleaning regimes are discussed in relation to γ: (I) For large stand-off, 1.8substrate and remove particles without significant contact of the gas phase. (II) For small distances, γsubstrate are driven by the jet impact with its subsequent radial spreading, and by the liquid following the motion of the collapsing and rebounding bubble wall. Both flows remove particles. Their relative timing, which depends sensitively on the exact γ, appears to determine the extension of the area with forces large enough to cause particle detachment. (III) At intermediate stand-off, 1.1substrate, but acts with cleaning mechanisms similar to an effective small γ collapse: particles are removed by the jet flow and the flow induced by the bubble wall oscillation. Furthermore, the observations reveal that the extent of direct bubble gas phase contact to the solid is partially smaller than the

  7. Laser-induced reconstruction of Ag clusters in helium droplets

    Science.gov (United States)

    Gomez, Luis F.; O'Connell, Sean M. O.; Jones, Curtis F.; Kwok, Justin; Vilesov, Andrey F.

    2016-09-01

    Silver clusters were assembled in helium droplets of different sizes ranging from 105 to 1010 atoms. The absorption of the clusters was studied upon laser irradiation at 355 nm and 532 nm, which is close to the plasmon resonance maximum in spherical Ag clusters and in the range of the absorption of the complex, branched Ag clusters, respectively. The absorption of the pulsed (7 ns) radiation at 532 nm shows some pronounced saturation effects, absent upon the continuous irradiation. This phenomenon has been discussed in terms of the melting of the complex Ag clusters at high laser fluence, resulting in a loss of the 532 nm absorption. Estimates of the heat transfer also indicate that a bubble may be formed around the hot cluster at high fluences, which may result in ejection of the cluster from the droplet, or disintegration of the droplet entirely.

  8. Effect of 800 keV argon ions pre-damage on the helium blister formation of tungsten exposed to 60 keV helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhe; Han, Wenjia; Yu, Jiangang; Zhu, Kaigui, E-mail: kgzhu@buaa.edu.cn

    2016-04-15

    This study aims to investigate the effect of Ar{sup 8+} ions pre-damage on the following He{sup 2+} irradiation behavior of polycrystalline tungsten. We compared the irradiation resistance performance against 60 keV He{sup 2+} ions of undamaged tungsten samples with that of pre-damaged samples which were preliminarily exposed to 800 keV Ar{sup 8+} ions at a fluence of 4 × 10{sup 19} ions m{sup −2}. The experimental results indicate that the helium blistering of tungsten could be effectively relieved by the Ar{sup 8+} ions pre-damage, while the retention of helium around low energy desorption sites in the pre-damaged tungsten was larger than that of the undamaged samples. A strong orientation dependence of blistering had been observed, with the blister occurred preferentially on the surface of grains with normal direction close to <111>. The Ar{sup 8+} ions irradiation-induced damage altered the morphology of helium bubbles in tungsten exposed to the following He{sup 2+} irradiation significantly. The intensity of helium release peaks at relatively low temperatures (<600 K) was enhanced due to Ar{sup 8+} ions pre-damage. - Highlights: • Helium blistering on the surface of W was effectively relieved by Ar{sup 8+} ions pre-damage. • Strong orientation dependence of blister formation was observed. • Low temperature helium release peaks were increased due to Ar{sup 8+} ions pre-damage.

  9. Doughnut-shaped soap bubbles

    CERN Document Server

    Preve, Deison

    2015-01-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume $V$ and with a fixed equatorial perimeter $L$. It is well known that the sphere is the solution for $V=L^3/6\\pi^2$, and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for $V<\\alpha L^3/6\\pi^2$, with $\\alpha\\approx 0.21$, such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtainin...

  10. Temperature measurements in cavitation bubbles

    Science.gov (United States)

    Coutier-Delgosha, Olivier

    2016-11-01

    Cavitation is usually a nearly isothermal process in the liquid phase, but in some specific flow conditions like hot water or cryogenic fluids, significant temperature variations are detected. In addition, a large temperature increase happens inside the cavitation bubbles at the very end of their collapse, due to the fast compression of the gas at the bubble core, which is almost adiabatic. This process is of primary interest in various biomedical and pharmaceutical applications, where the mechanisms of bubble collapse plays a major role. To investigate the amplitude and the spatial distribution of these temperature variations inside and outside the cavitation bubbles, a system based on cold wires has been developed. They have been tested in a configuration of a single bubble obtained by submitting a small air bubble to a large amplitude pressure wave. Some promising results have been obtained after the initial validation tests. This work is funded by the Office of Naval Research Global under Grant N62909-16-1-2116, Dr. Salahuddin Ahmed & Ki-Han Kim program managers.

  11. Effect of 800 keV argon ions pre-damage on the helium blister formation of tungsten exposed to 60 keV helium ions

    Science.gov (United States)

    Chen, Zhe; Han, Wenjia; Yu, Jiangang; Zhu, Kaigui

    2016-04-01

    This study aims to investigate the effect of Ar8+ ions pre-damage on the following He2+ irradiation behavior of polycrystalline tungsten. We compared the irradiation resistance performance against 60 keV He2+ ions of undamaged tungsten samples with that of pre-damaged samples which were preliminarily exposed to 800 keV Ar8+ ions at a fluence of 4 × 1019 ions m-2. The experimental results indicate that the helium blistering of tungsten could be effectively relieved by the Ar8+ ions pre-damage, while the retention of helium around low energy desorption sites in the pre-damaged tungsten was larger than that of the undamaged samples. A strong orientation dependence of blistering had been observed, with the blister occurred preferentially on the surface of grains with normal direction close to . The Ar8+ ions irradiation-induced damage altered the morphology of helium bubbles in tungsten exposed to the following He2+ irradiation significantly. The intensity of helium release peaks at relatively low temperatures (<600 K) was enhanced due to Ar8+ ions pre-damage.

  12. Helium in atmospheres of binary stars

    Energy Technology Data Exchange (ETDEWEB)

    Leushin, V.V. (Rostovskij-na-Donu Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Fiziki)

    The helium abundances were obtained for 25 bright components of binary stars by model atmosphere analysis. The helium abundance for binary stars that lie on the main sequence are larger in the average than in single normal stars. The stars on the Hertzsppung - russel diagram lie at a larger distance from the zero age line than those with normal helium abundance.

  13. The effects of surfactants on the lateral migration of bubbles and the bubble clustering phenomenon in a bubbly channel flow

    Science.gov (United States)

    Takagi, Shu; Ogasawara, Toshiyuki; Matsumoto, Yoichiro

    2004-11-01

    The behaviors of bubbles in an upward channel flow are experimentally investigated. Two kinds of surfactant, 3-pentanol and Triton X-100 are added in the bubbly flow. Addition of surfactant prevents the bubble coalescence and mono-dispersed 1mm spherical bubbles were obtained, although these surfactants do not modify the single-phase turbulence statistics. At the condition of high Reynolds number (Re=8200) with 20-60ppm 3-Pentanol, bubbles migrated towards the wall. These bubbles highly accumulated near the wall and formed crescent like shaped horizontal bubble clusters of 10-40mm length. On the other hand, bubble clusters did not appear in the 2ppm Triton-X100 aqueous solution. By the addition of the small amount of Triton-X100, bubble coalescences were also preventable and the bubble size and its distribution became almost the same as in the case of 60ppm 3-Pentanol aqueous solution. However, the tendency of the lateral migration of bubbles towards the wall weakened and the bubbles did not accumulated near the wall. And this is the main reason of the disapperance of bubble cluster. We discuss this phenomenon, related to the lift force acting on bubbles and particles.

  14. Measuring online social bubbles

    Directory of Open Access Journals (Sweden)

    Dimitar Nikolov

    2015-12-01

    Full Text Available Social media have become a prevalent channel to access information, spread ideas, and influence opinions. However, it has been suggested that social and algorithmic filtering may cause exposure to less diverse points of view. Here we quantitatively measure this kind of social bias at the collective level by mining a massive datasets of web clicks. Our analysis shows that collectively, people access information from a significantly narrower spectrum of sources through social media and email, compared to a search baseline. The significance of this finding for individual exposure is revealed by investigating the relationship between the diversity of information sources experienced by users at both the collective and individual levels in two datasets where individual users can be analyzed—Twitter posts and search logs. There is a strong correlation between collective and individual diversity, supporting the notion that when we use social media we find ourselves inside “social bubbles.” Our results could lead to a deeper understanding of how technology biases our exposure to new information.

  15. Subtask 12G2: Effects of dynamically charged helium on tensile properties of V-4Cr-4Ti

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M.; Loomis, B.A.; Nowicki, L.; Smith, D.L. [Argonne National Lab., IL (United States)

    1995-03-01

    The objective of this work is to determine the effect of displacement damage and dynamically charged helium on tensile properties of V-4Cr-4Ti alloy irradiated to 18-31 dpa at 425-600{degrees}C in the Dynamic Helium Charging Experiment (DHCE). One property of vanadium-base alloys that is not well understood in terms of their potential use as fusion reactor structural materials is the effect of simultaneous generation of helium and neutron damage under conditions relevant to fusion reactor operation. In the present Dynamic Helium Charging Experiment (DHCE), helium was produced uniformly in the specimen at linear rates of {approx}0.4 to 4.2 appm helium/dpa by the decay of tritium during irradiation to 18-31 dpa at 425-600{degrees}C in the Li-filled DHCE capsules in the Fast Flux Test Facility. This report presents results of postirradiation tests of tensile properties of V-4Cr-4Ti, an alloy identified as the most promising vanadium-base alloy for fusion reactors on the basis of its superior baseline and irradiation properties. Effects of helium on tensile strength and ductility were insignificant after irradiation and testing at >420{degrees}C. Contrary to initial expectation, room-temperature ductilities of DHCE specimens were higher than those of non-DHCE specimens (in which there was negligible helium generation), whereas strengths were lower, indicating that different types of hardening centers are produced during DHCE and non-DHCE irradiation. In strong contrast to tritium-trick experiments in which dense coalescence of helium bubbles is produced on grain boundaries in the absence of displacement damage, no intergranular fracture was observed in any tensile specimens irradiated in the DHCE. 25 refs., 2 figs., 3 tabs.

  16. Medroxyprogesterone Injection

    Science.gov (United States)

    Medroxyprogesterone intramuscular (into a muscle) injection and medroxyprogesterone subcutaneous (under the skin) injection are used to prevent pregnancy. Medroxyprogesterone subcutaneous injection is also used to treat endometriosis (a condition in which ...

  17. Pentamidine Injection

    Science.gov (United States)

    Pentamidine injection is used to treat pneumonia caused by a fungus called Pneumocystis carinii. It is in ... Pentamidine injection comes as powder to be mixed with liquid to be injected intramuscularly (into a muscle) ...

  18. FEASTING BLACK HOLE BLOWS BUBBLES

    Science.gov (United States)

    2002-01-01

    A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. Known as a peculiar galaxy because of its unusual shape, NGC 4438 is in the Virgo Cluster, 50 million light-years from Earth. These NASA Hubble Space Telescope images of the galaxy's central region clearly show one of the bubbles rising from a dark band of dust. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right). The background image represents a wider view of the galaxy, with the central region defined by the white box. These extremely hot bubbles are caused by the black hole's voracious eating habits. The eating machine is engorging itself with a banquet of material swirling around it in an accretion disk (the white region below the bright bubble). Some of this material is spewed from the disk in opposite directions. Acting like high-powered garden hoses, these twin jets of matter sweep out material in their paths. The jets eventually slam into a wall of dense, slow-moving gas, which is traveling at less than 223,000 mph (360,000 kph). The collision produces the glowing material. The bubbles will continue to expand and will eventually dissipate. Compared with the life of the galaxy, this bubble-blowing phase is a short-lived event. The bubble is much brighter on one side of the galaxy's center because the jet smashed into a denser amount of gas. The brighter bubble is 800 light-years tall and 800 light-years across. The observations are being presented June 5 at the American Astronomical Society meeting in Rochester, N.Y. Both pictures were taken March 24, 1999 with the Wide Field and Planetary Camera 2. False colors were used to enhance the details of the bubbles. The red regions in the picture denote the hot gas

  19. Helium resources of Mare Tranquillitatis

    Science.gov (United States)

    Cameron, Eugene N.

    Wisconsin Center for Space Automation and Robotics, Univ. of Wisc., Madison, Wisc. Mare Tranquillitatis, about 300000 sq km in area, is currently the most promising lunar source of He-3 for fueling fusion power plants on Earth. About 60 pct. of the mare regolith consists of particles 100 microns or less in diameter. Helium and other gases derived from the solar wind are concentrated in the fine size fractions. Studies of very small craters indicate that the average regolith exceeds 3 m in areas away from larger craters and other mare features not amenable to mining. There is no evidence of decrease of helium content of regolith and depth. Helium is known to be enriched in regoliths that are high in TiO2 content. Remote sensing indicates that about 90 pct. of Mare Tranquillitatis is covered by regolith ranging from about 6 to +7.5 pct. TiO2; inferred He contents range from 20 to at least 45 wppm total helium (7 to 18 wppb He-3). Detailed studies of craters and inferred ejecta halos displayed on high resolution photographs of the Apollo 11 and Ranger 8 areas suggest that as much as 50 pct. of the mare regolith may be physically minable, on average, with appropriate mining equipment. Assuming that the average thickness of regolith is 3 m, and that 50 pct. of the mare area is minable, the He-3 content of minable regolith containing 20 to 45 wppm total He is estimated at about 94,000 tonnes.

  20. Detection of significant differences between absorption spectra of neutral helium and low temperature photoionized helium plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Szczurek, M. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

    2013-11-15

    In this work, spectral investigations of photoionized He plasmas were performed. The photoionized plasmas were created by irradiation of helium stream, with intense pulses from laser-plasma extreme ultraviolet (EUV) source. The EUV source was based on a double-stream Xe/Ne gas-puff target irradiated with 10 ns/10 J Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region below 20 nm, however, spectrally integrated intensity at longer wavelengths was also significant. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The long-wavelength part of the EUV radiation was used for backlighting of the photoionized plasmas to obtain absorption spectra. Both emission and absorption spectra in the EUV range were investigated. Significant differences between absorption spectra acquired for neutral helium and low temperature photoionized plasmas were demonstrated for the first time. Strong increase of intensities and spectral widths of absorption lines, together with a red shift of the K-edge, was shown.

  1. Simplicity works for superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bowley, Roger [University of Nottingham, Nottingham (United Kingdom)

    2000-02-01

    The famous philosopher Karl Popper once said that ''science is the art of systematic oversimplification''. Indeed, when faced with a new puzzle the trick is to simplify it without losing the essential physics - something that is easier said than done. However, this approach has paid off recently in low-temperature physics. Last year Richard Packard, Seamus Davis and co-workers at the University of California at Berkeley encountered a puzzling new phenomenon in superfluid helium-3, a quantum fluid that remains a liquid close to absolute zero and exhibits unusual properties such as the ability to flow without friction (A Machenkov et al. 1999 Phys. Rev. Lett. 83 3860). Previous experiments had revealed that certain effects in liquid helium are analogous to effects observed in superconductors, materials that lose all resistance to electric current at low temperatures. When the Berkeley researchers connected two reservoirs of superfluid helium-3, the superfluid flowed back and forth through apertures that formed a ''weak link'' between the two containers. This behaviour is similar to the oscillatory current of electrons that can flow across an insulating gap separating two superconductors - a device that is known as a Josephson junction. What was puzzling about the Berkeley results was that the helium-3 had two different stable configurations, both of which behaved in an unconventional way compared with a Josephson junction. This puzzle has now been solved independently by Sidney Yip at the National Center for Theoretical Sciences in Taiwan, and by Janne Viljas and Erkki Thuneberg at the Helsinki University of Technology in Finland (Phys. Rev. Lett. 1999 83 3864 and 3868). In this article the author describes the latest research on superfluid helium. (UK)

  2. Precision spectroscopy of the helium atom

    Institute of Scientific and Technical Information of China (English)

    Shui-ming HU; Zheng-Tian LU; Zong-Chao YAN

    2009-01-01

    Persistent efforts in both theory and experiment have yielded increasingly precise understanding of the helium atom. Because of its simplicity, the helium atom has long been a testing ground for relativistic and quantum electrodynamic effects in few-body atomic systems theoretically and experimentally.Comparison between theory and experiment of the helium spectroscopy in ls2p3pJ can potentially extract a very precise value of the fine structure constant a. The helium atom can also be used to explore exotic nuclear structures. In this paper, we provide a brief review of the recent advances in precision calculations and measurements of the helium atom.

  3. Bubble-sort图和Modified Bubble-sort图的自同构群%Automorphism Groups of Bubble-sort Graphs and Modified Bubble-sort Graphs

    Institute of Scientific and Technical Information of China (English)

    张昭; 黄琼湘

    2005-01-01

    Bubble-sort graphs and modified bubble-sort graphs are two classes of Cayley graphs which are widely studied for their application in network construction. In this paper, we determine the full automorphism groups of bubble-sort graphs and modified bubble-sort graphs.%Bubble-Sort图和Modified Bubble-Sort图是两类特殊的Cayley图,由于其在网络构建中的应用而受到广泛关注.本文完全确定了这两类图的自同构群.

  4. Spherical Solutions of an Underwater Explosion Bubble

    Directory of Open Access Journals (Sweden)

    Andrew B. Wardlaw

    1998-01-01

    Full Text Available The evolution of the 1D explosion bubble flow field out to the first bubble minimum is examined in detail using four different models. The most detailed is based on the Euler equations and accounts for the internal bubble fluid motion, while the simplest links a potential water solution to a stationary, Isentropic bubble model. Comparison of the different models with experimental data provides insight into the influence of compressibility and internal bubble dynamics on the behavior of the explosion bubble.

  5. HeREF-2003: Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 Cost per participant: 500.- CHF Language: Bilingual English...

  6. HeREF-2003 : Helium Refrigeration Techniques

    CERN Multimedia

    2003-01-01

    CERN Technical Training 2003: Learning for the LHC ! Theory, Technology, Maintenance and Control of Helium Refrigerators HeREF-2003 is a course in the framework of the 2002 Technical Training Programme, that will provide a complete introduction to Helium refrigeration, with a practical approach to theory, technology, maintenance and control of Helium refrigeration installations. Theoretical aspects and equations will be limited to a minimum. HeREF-2003 targets an audience of technicians and operators of Helium refrigeration plants at CERN, as well as physicists and engineers needing an overview of current Helium refrigeration techniques. HeREF-2003 will address, among other, issues related to component technology, installation maintenance, process control and Helium purity. A commented visit to a couple of CERN Helium refrigeration or liquefaction plants will also take place. • Duration: 7 half days (4 mornings and 3 afternoons), 6-10 October, 2003 • Cost per participant: 500.- CHF ...

  7. Bubble-bubble interaction: A potential source of cavitation noise

    CERN Document Server

    Ida, Masato

    2009-01-01

    The interaction between microbubbles through pressure pulses has been studied to show that it can be a source of cavitation noise. A recent report demonstrated that the acoustic noise generated by a shrimp originates from the collapse of a cavitation bubble produced when the shrimp closes its snapper claw. The recorded acoustic signal contains a broadband noise that consists of positive and negative pulses, but a theoretical model for single bubbles fails to reproduce the negative ones. Using a nonlinear multibubble model we have shown here that the negative pulses can be explained by considering the interaction of microbubbles formed after the cavitation bubble has collapsed and fragmented: Positive pulses produced at the collapse of the microbubbles hit and impulsively compress neighboring microbubbles to generate reflected pulses whose amplitudes are negative. Discussing the details of the noise generation process, we have found that no negative pulses are generated if the internal pressure of the reflecti...

  8. Ageing of palladium tritide: mechanical characterization, helium state and modelling; Vieillissement du tritiure de palladium: caracterisation mecanique, etat de l'helium et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Segard, M.

    2010-11-29

    Palladium is commonly used for the storage of tritium (the hydrogen radioactive isotope), since it forms a low-equilibrium-pressure and reversible tritide. Tritium decay into helium-3 is responsible for the ageing of the tritide, leading to the apparition of helium-3 bubbles for instance. Both experimental and theoretical aspects of this phenomenon are studied here.Previous works on ageing modelling led to two main models, dealing with:- Helium-3 bubbles nucleation (using a cellular automaton), - Bubbles growth (using continuum mechanics).These models were quite efficient, but their use was limited by the lack of input data and fitting experimental parameters.To get through these limitations, this work has consisted in studying the most relevant experimental data to improve the modelling of the palladium tritide ageing.The first part of this work was focused on the assessment of the mechanical properties of the palladium tritide (yield strength, ultimate strength, mechanical behaviour). They were deduced from the in situ tensile tests performed on palladium hydride and deuteride. In the second part, ageing characterization was undertaken, mainly focusing on: - Bubbles observations in palladium tritide using transmission electron microscopy, - Internal bubble pressure measurements using nuclear magnetic resonance, - Macroscopic swelling measurements using pycno-metry.The present work has led to significant progress in ageing understanding and has brought very valuable improvements to the modelling of such a phenomenon. (author) [French] Le palladium est couramment utilise pour le stockage du tritium, isotope radioactif de l'hydrogEne, car il forme un tritiure reversible, A basse pression d'equilibre. La decroissance du tritium en helium-3 provoque un vieillissement du tritiure, caracterise notamment par l'apparition de bulles d'helium-3, qui est etudie ici. De precedents travaux de modelisation du vieillissement avaient abouti a la creation de

  9. Simulation and modeling of two-phase bubbly flows

    Energy Technology Data Exchange (ETDEWEB)

    Sylvain L Pigny; Pierre F Coste [DEN/DER/SSTH, CEA/Grenoble, 38054 Grenoble Cedex 9 (France)

    2005-07-01

    Full text of publication follows: Phenomena related to bubbles in two-phase recirculating flows are investigated, via the computational code SIMMER, concerning an experiment in which air is injected in the lower part of a tank filled of water and initially at rest. Averaged mass and momentum transport equations are solved for air and water. Close to the injector, the formation of individual large bubbles is represented in the calculations, via direct simulation. Small scale phenomena, related to small bubbles behavior or turbulence in the liquid continuous phase, are modeled, in a statistical way, via classical closure laws. In a first calculation, the splitting of large bubbles is not represented. It is shown that this phenomenon, the space scale of which is close to the cell size, cannot be simulated, in view of the present computational resources. Nevertheless, relatively fine meshes are used, for an accurate description of hydrodynamical phenomena, and the splitting phenomenon is too large to be modeled via closure laws. A specific approach for the intermediate scales is therefore developed to represent it. (authors)

  10. Quantum Bubble Nucleation beyond WKB Resummation of Vacuum Bubble Diagrams

    CERN Document Server

    Suzuki, H; Suzuki, Hiroshi; Yasuta, Hirofumi

    1998-01-01

    On the basis of Borel resummation, we propose a systematical improvement of bounce calculus of quantum bubble nucleation rates. We study a metastable super-renormalizable field theory, D dimensional O(N) symmetric \\phi^4 model (D<4) with an attractive interaction. The validity of our proposal is tested in D=1 (quantum mechanics) by using the perturbation series of ground state energy to high orders. We also present a result in D=2 based on an explicit calculation of vacuum bubble diagrams to five loop orders.

  11. Detection of low energy solar neutrinos by a two-phase cryogenic e-bubble detector

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new two-phase cryogenic neutrino detector using electron bubble (e-bubble) specifically in liquid helium is proposed and being developed for real time, high rate measurements of low-energy p-p reaction neutrinos from the sun. The e-bubble detector is a time projection chamber-like (TPC) tracking detector. The task of such a neutrino detector is to detect the ionization of the elastically scattered target electrons by incident neutrinos, and then to characterize their energy and direction and to distinguish them from radioactive backgrounds. The ionization signals are expected to be small and hence undergo avalanche amplification in the saturated vapor above the liquid phase by gas electron multipliers (GEMs) at high gain. Higher granularity and intrinsically suppressed ion feedback give a good spatial resolution and are the major advantages of this technology. It should be possible to construct such a detector to track charged particles down to 100―200 keV in a massive liquid helium target with fractional millimeter spatial resolution in three-dimensional space, using the GEM-based TPC with a high-resolution CCD camera, for both the electronic and light readout.

  12. Electric field effects on the dynamics of bubble detachment from an inclined surface

    Science.gov (United States)

    Di Marco, P.; Morganti, N.; Saccone, G.

    2015-11-01

    An experimental apparatus to study bubble detachment from an inclined surface under the action of electric forces is described. It consists of a container filled with FC72 at room temperature and pressure where a train of gas bubbles is injected from an orifice. An electrostatic field can be imposed around the bubble, while the cell can be tilted from 0 to 90°. It is possible to study interface growth with the aid of high-speed cinematography. Since the interface is asymmetrical, a mirror system allowed to acquire, in the same frame, two images at 90° of the bubble. Different inclinations, injection rates and voltages were tested in order to couple the effects of shear gravity and electric field. Curvature and contact angles have been derived with appropriate interpolation methods of the profile. Force balances on the bubble were checked, finding an electric force, which, at first pulls the bubbles from the orifice, then pushes it against the surface. The motion of the center of gravity confirms this behaviour. A power balance has been developed to determine the energy contributions, revealing that surface growth incorporates both the effects of inlet power and electric field.

  13. How safe is Bubble Soccer?

    Science.gov (United States)

    Halani, Sameer H; Riley, Jonathan P; Pradilla, Gustavo; Ahmad, Faiz U

    2016-12-01

    Traumatic neurologic injury in contact sports is a rare but serious consequence for its players. These injuries are most commonly associated with high-impact collisions, for example in football, but are found in a wide variety of sports. In an attempt to minimize these injuries, sports are trying to increase safety by adding protection for participants. Most recently is the seemingly 'safe' sport of Bubble Soccer, which attempts to protect its players with inflatable plastic bubbles. We report a case of a 16-year-old male sustaining a cervical spine burst fracture with incomplete spinal cord injury while playing Bubble Soccer. To our knowledge, this is the first serious neurological injury reported in the sport.

  14. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

    Steven P. Wrenn, Stephen M. Dicker, Eleanor F. Small, Nily R. Dan, Michał Mleczko, Georg Schmitz, Peter A. Lewin

    2012-01-01

    Full Text Available This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol (PEG - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented

  15. Confined helium on Lagrange meshes

    CERN Document Server

    Baye, Daniel

    2015-01-01

    The Lagrange-mesh method has the simplicity of a calculation on a mesh and can have the accuracy of a variational method. It is applied to the study of a confined helium atom. Two types of confinement are considered. Soft confinements by potentials are studied in perimetric coordinates. Hard confinement in impenetrable spherical cavities is studied in a system of rescaled perimetric coordinates varying in [0,1] intervals. Energies and mean values of the distances between electrons and between an electron and the helium nucleus are calculated. A high accuracy of 11 to 15 significant figures is obtained with small computing times. Pressures acting on the confined atom are also computed. For sphere radii smaller than 1, their relative accuracies are better than $10^{-10}$. For larger radii up to 10, they progressively decrease to $10^{-3}$, still improving the best literature results.

  16. Helium atom scattering from surfaces

    CERN Document Server

    1992-01-01

    High resolution helium atom scattering can be applied to study a number of interesting properties of solid surfaces with great sensitivity and accuracy. This book treats in detail experimental and theoretical aspects ofthis method as well as all current applications in surface science. The individual chapters - all written by experts in the field - are devoted to the investigation of surface structure, defect shapes and concentrations, the interaction potential, collective and localized surface vibrations at low energies, phase transitions and surface diffusion. Over the past decade helium atom scattering has gained widespread recognitionwithin the surface science community. Points in its favour are comprehensiveunderstanding of the scattering theory and the availability of well-tested approximation to the rigorous theory. This book will be invaluable to surface scientists wishing to make an informed judgement on the actual and potential capabilities of this technique and its results.

  17. Experimental studies of antiprotonic helium

    CERN Document Server

    Widmann, E

    1998-01-01

    This talk describes the experimental studies of metastable antiprotonic helium "atomcules" pHe/sup +/ (a neutral exotic atom consisting of a helium nucleus, an antiproton and an electron) performed at CERN-LEAR, and future plans for experiments at the forthcoming Antiproton Decelerator (AD) at CERN. Laser spectroscopy experiments are reviewed which led to the observation of a total of 13 resonant transitions of the antiproton in both p/sup 4/He/sup +/ and p/sup 3/He/sup +/, and revealed a hyperfine splitting in one transition. A level of precision has been reached where the most accurate 3-body calculations need to include QED effects like the Lamb-shift to come close to the experimental results. (52 refs).

  18. Rapidly pulsed helium droplet source

    Energy Technology Data Exchange (ETDEWEB)

    Pentlehner, Dominik; Riechers, Ricarda; Dick, Bernhard; Slenczka, Alkwin [Institute for Physical and Theoretical Chemistry, University of Regensburg, 93053 Regensburg (Germany); Even, Uzi; Lavie, Nachum; Brown, Raviv; Luria, Kfir [Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv (Israel)

    2009-04-15

    A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 10{sup 4} and 10{sup 6} helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.

  19. Elusive structure of helium trimers

    CERN Document Server

    Stipanović, Petar; Boronat, Jordi

    2016-01-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the po...

  20. Modeling of bubble detachment in reduced gravity under the influence of electric fields and experimental verification

    Energy Technology Data Exchange (ETDEWEB)

    Herman, Cila [Johns Hopkins University, Department of Mechanical Engineering, Baltimore, MD 21218 (United States); Iacona, Estelle [Johns Hopkins University, Department of Mechanical Engineering, Baltimore, MD 21218 (United States); Ecole Centrale, Laboratoire EM2C, Paris UPR 288 (France)

    2004-10-01

    A simple model for predicting bubble volume and shape at detachment in reduced gravity under the influence of electric fields is described in the paper. The model is based on relatively simple thermodynamic arguments and relies on and combines several models described in the literature. It accounts for the level of gravity and the magnitude of the electric field. For certain conditions of bubble development the properties of the bubble source are also considered. Computations were carried out for a uniform unperturbed electric field for a range of model parameters, and the significance of model assumptions and simplifications is discussed for the particular method of bubble formation. Experiments were conducted in terrestrial conditions and reduced gravity (during parabolic flights in NASA's KC-135 aircraft) by injecting air bubbles through an orifice into the electrically insulating working fluid, PF5052. Bubble shapes visualized experimentally were compared with model predictions. Measured data and model predictions show good agreement. The results suggest that the model can provide quick engineering estimates concerning bubble formation for a range of conditions (both for formation at an orifice and boiling) and such a model reduces the need for complex and expensive numerical simulations for certain applications. (orig.)

  1. Creating Small Gas Bubbles in Flowing Mercury Using Turbulence at an Orifice

    Energy Technology Data Exchange (ETDEWEB)

    Wendel, Mark W [ORNL; Abdou, Ashraf A [ORNL; Paquit, Vincent C [ORNL; Felde, David K [ORNL; Riemer, Bernie [ORNL

    2010-01-01

    Pressure waves created in liquid mercury pulsed spallation targets have been shown to create cavitation damage to the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, creating such a population in mercury is difficult due to the high surface tension and particularly the non-wetting behavior of mercury on gas-injection hardware. If the larger injected gas bubbles can be broken down into small bubbles after they are introduced to the flow, then the material interface problem is avoided. Research at the Oak Ridge National Labarotory is underway to develop a technique that has shown potential to provide an adequate population of small-enough bubbles to a flowing spallation target. This technique involves gas injection at an orifice of a geometry that is optimized to the turbulence intensity and pressure distribution of the flow, while avoiding coalescence of gas at injection sites. The most successful geometry thus far can be described as a square-toothed orifice having a 2.5 bar pressure drop in the nominal flow of 12 L/s for one of the target inlet legs. High-speed video and high-resolution photography have been used to quantify the bubble population on the surface of the mercury downstream of the gas injection sight. Also, computational fluid dynamics has been used to optimize the dimensions of the toothed orifice based on a RANS computed mean flow including turbulent energies such that the turbulent dissipation and pressure field are best suited for turbulent break-up of the gas bubbles.

  2. Fine bubble generator and method

    Energy Technology Data Exchange (ETDEWEB)

    Bhagat, P.M.; Koros, R.M.

    1990-10-09

    This patent describes a method of forming fine gaseous bubbles in a liquid ambient. It comprises: forcing a gas through orifices located in the liquid ambient while simultaneously forcing a liquid through liquid orifices at a velocity sufficient to form jet streams of liquid, the liquid orifices being equal in number to the gas orifices and so oriented that each jet stream of liquid intersects the gas forced through each gas orifice and creates sufficient turbulence where the gas and jet stream of liquid intersect, whereby fine gaseous bubbles are formed.

  3. Optical and electron spin resonance studies of xenon-nitrogen-helium condensates containing nitrogen and oxygen atoms.

    Science.gov (United States)

    Boltnev, Roman E; Bykhalo, Igor B; Krushinskaya, Irina N; Pelmenev, Alexander A; Khmelenko, Vladimir V; Mao, Shun; Meraki, Adil; Wilde, Scott C; McColgan, Patrick T; Lee, David M

    2015-03-19

    We present the first observations of excimer XeO* molecules in molecular nitrogen films surrounding xenon cores of nanoclusters. Multishell nanoclusters form upon the fast cooling of a helium jet containing small admixtures of nitrogen and xenon by cold helium vapor (T = 1.5 K). Such nanoclusters injected into superfluid helium aggregate into porous impurity-helium condensates. Passage of helium gas with admixtures through a radio frequency discharge allows the storage of high densities of radicals stabilized in impurity-helium condensates. Intense recombination of the radicals occurs during destruction of such condensates and generates excited species observable because of optical emission. Rich spectra of xenon-oxygen complexes have been detected upon destruction of xenon-nitrogen-helium condensates. A xenon environment quenches metastable N((2)D) atoms but has a much weaker effect on the luminescence of N((2)P) atoms. Electron spin resonance spectra of N((4)S) atoms trapped in xenon-nitrogen-helium condensates have been studied. High local concentrations of nitrogen atoms (up to 10(21) cm(-3)) stabilized in xenon-nitrogen nanoclusters have been revealed.

  4. Bubble Content in Air/Hydro System--Part 1:Measurement of Bubble Content

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The mechanism of bubble formation in air/hydro systems is investigated. Results presented in this paper include further insight into the mechanism of bubble formation and the measurement of bubble content. The regularity of bubble transport in the system is found, with an idea for a new method for separating gas from oil. The method has been verified experimentally with favorable results.

  5. Bubble Departure Diameter and Bubble Release Frequency Measurement from TAMU Subcooled Flow Boiling Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Jun Soo [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-12-01

    The bubble departure diameter and bubble release frequency were obtained through the analysis of TAMU subcooled flow boiling experimental data. The numerous images of bubbles at departure were analyzed for each experimental condition to achieve the reliable statistics of the measured bubble parameters. The results are provided in this report with simple discussion.

  6. The dependence of irradiation creep in austenitic alloys on displacement rate and helium to dpa ratio

    Energy Technology Data Exchange (ETDEWEB)

    Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States); Toloczko, M.B. [Washington State Univ., WA (United States); Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)

    1998-03-01

    Before the parametric dependencies of irradiation creep can be confidently determined, analysis of creep data requires that the various creep and non-creep strains be separated, as well as separating the transient, steady-state, and swelling-driven components of creep. When such separation is attained, it appears that the steady-state creep compliance, B{sub o}, is not a function of displacement rate, as has been previously assumed. It also appears that the formation and growth of helium bubbles under high helium generation conditions can lead to a significant enhancement of the irradiation creep coefficient. This is a transient influence that disappears as void swelling begins to dominate the total strain, but this transient can increase the apparent creep compliance by 100--200% at relatively low ({le}20) dpa levels.

  7. Bubble nucleation in an explosive micro-bubble actuator

    NARCIS (Netherlands)

    Broek, van den D.M.; Elwenspoek, M.C.

    2008-01-01

    Explosive evaporation occurs when a thin layer of liquid reaches a temperature close to the critical temperature in a very short time. At these temperatures spontaneous nucleation takes place. The nucleated bubbles instantly coalesce forming a vapour film followed by rapid growth due to the pressure

  8. Metal Enrichment in the Fermi Bubbles as a Probe of Their Origin

    CERN Document Server

    Inoue, Yoshiyuki; Tahara, Masaya; Kataoka, Jun; Totani, Tomonori; Fujita, Yutaka; Sofue, Yoshiaki

    2015-01-01

    The Fermi bubbles are gigantic gamma-ray structure in our Galaxy. The physical origin of the bubbles is still under debate. The leading scenarios can be divided into two categories. One is the nuclear star forming activity like extragalactic starburst galaxies and the other is the past active galactic nucleus (AGN) like activity of the Galactic center supermassive black hole. In this letter, we propose that metal abundance measurements will provide an important clue to probe their origin. Based on a simple spherically symmetric bubble model, we find that the generated metallicity and abundance pattern of the bubbles gas strongly depend on assumed star formation or AGN activities. Star formation scenarios predict higher metallicities and abundance ratios of [O/Fe] and [Ne/Fe] than AGN scenarios do because of supernovae ejecta. Furthermore, the resultant abundance depends on the gamma-ray emission process because different mass injection histories are required for different the gamma-ray emission processes due ...

  9. Single bubble sonoluminescence and stable cavitation

    Institute of Scientific and Technical Information of China (English)

    CHEN Qian; QIAN Menglu

    2004-01-01

    A single bubble trapped at an antinode of an acoustic standing wave field in water can emit 50ps-140ps light pulses, called "single bubble sonoluminescence" (SBSL). It arouses much interest in physical acoustics because of its highly non-linear characteristics, high concentration of energy, and stable cavitation behavior. In this paper, bubble stability, the dynamic behavior of bubbles, non-invasive measurement of driving acoustic pressure and Mie scattering method are introduced.

  10. Monetary Policy and Controlling Asset Bubbles

    OpenAIRE

    Masaya Sakuragawa

    2015-01-01

    A great concern is whether there is any means of monetary policy that works for the "leaning against the wind" policy in the bubbly economy. This paper explores the scope for monetary policy that can control bubbles within the framework of the stochastic version of overlapping-generations model with rational bubbles. The policy that raises the cost of external finance, could be identified as monetary tightening, represses the boom, but appreciate bubbles. In contrast, an open market operation...

  11. Expansion of Bubbles in Inflationary Universe

    OpenAIRE

    Mohazzab, M.; Jabbari, M. M. Sheikh; Salehi, H.

    1995-01-01

    We show that particle production during the expansion of bubbles of true vacuum in the sea of false vacuum is possible and calculate the resulting rate. As a result the nucleated bubbles cannot expand due to the transfer of false vacuum energy to the created particles inside the bubbles. Therefore all the inflationary models dealing with the nucleation and expansion of the bubbles (including extended inflation) may not be viable.

  12. Expansion of bubbles in inflationary universe

    CERN Document Server

    Mohazzab, M

    1995-01-01

    We show that particle production during the expansion of bubbles of true vacuum in the sea of false vacuum is possible and calculate the resulting rate. As a result the nucleated bubbles cannot expand due to the transfer of false vacuum energy to the created particles inside the bubbles. Therefore all the inflationary models dealing with the nucleation and expansion of the bubbles (including extended inflation) may not be viable.

  13. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-01-01

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  14. Particle detection using superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.

    1991-12-31

    We have observed 5 MeV {alpha} particles stopped in volumes-up to two liters of liquid helium at 70 mK. A fraction of the kinetic energy of an {alpha} particle is converted to elementary excitations (rotons and phonons), which progagate ballistically in isotopically pure {sup 4}He below 0.1 K. Most of these excitations have sufficient energy to evaporate helium atoms on hitting a free surface. The evaporated helium atoms can be detected calorimetrically when adsorbed on a thin silicon wafer ({approximately}1.7 g, 35 cm{sup 2}) suspended above the liquid. Temperature changes of the silicon are measured with a NTD germanium bolometer. For the geometry studied the observed temperature change of the silicon resulting from an {alpha} event in the liquid is approximately 5% of the temperature rise from an {alpha} hitting the silicon directly. The implications of these measurements will be discussed as they relate to the possible construction of a large scale detector of solar neutrinos.

  15. Theoretical research of helium pulsating heat pipe under steady state conditions

    Science.gov (United States)

    Xu, D.; Liu, H. M.; Li, L. F.; Huang, R. J.; Wang, W.

    2015-12-01

    As a new-type heat pipe, pulsating heat pipe (PHP) has several outstanding features, such as great heat transport ability, strong adjustability, small size and simple construction. PHP is a complex two-phase flow system associated with many physical subjects and parameters, which utilizes the pressure and temperature changes in volume expansion and contraction during phase changes to excite the pulsation motion of liquid plugs and vapor bubbles in the capillary tube between the evaporator and the condenser. At present time, some experimental investigation of helium PHP have been done. However, theoretical research of helium PHP is rare. In this paper, the physical and mathematical models of operating mechanism for helium PHP under steady state are established based on the conservation of mass, momentum, and energy. Several important parameters are correlated and solved, including the liquid filling ratio, flow velocity, heat power, temperature, etc. Based on the results, the operational driving force and flow resistances of helium PHP are analysed, and the flow and heat transfer is further studied.

  16. Modeling of Liquid Level and Bubble Behavior in Vacuum Chamber of RH Process

    Institute of Scientific and Technical Information of China (English)

    Yi-hong LI; Yan-ping BAO; Rui WANG; Min WANG; Qing-xue HUANG; Yu-gui LI

    2016-01-01

    In the Ruhrstahl-Heraeus (RH)refining process,liquid steel flow pattern in a ladle is controlled by the fluid flow behavior in the vacuum chamber.Potassium chloride solution and NaOH solution saturated with CO 2 were respectively used as a tracer to investigate the liquid and gas flow behaviors in the vacuum chamber.Principal compo-nent and comparative analysis were made to show the factors controlling mixing and circulation flow rate.The liquid level and bubble behavior in the vacuum chamber greatly affect fluid flow in RH process.Experiments were per-formed to investigate the effects of liquid steel level,gas flow rate,bubble residence time,and gas injection mode on mixing,decarburization,and void fraction.The results indicate that the mixing process can be divided into three re-gions:the flow rate-affected zone,the concentration gradient-affected zone,and their combination.The liquid steel level in the vacuum chamber of 300 mm is a critical point in the decarburization transition.For liquid level lower than 300 mm,liquid steel circulation controls decarburization,while for liquid level higher than 300 mm,bubble behavior is the main controlling factor.During the RH process,it is recommended to use the concentrated bubble injection mode for low gas flow rates and the uniform bubble injection mode for high gas flow rates.

  17. The core helium flash revisited III. From Pop I to Pop III stars

    CERN Document Server

    Mocak, Miroslav; Mueller, Ewald; Kifonidis, Konstantinos

    2010-01-01

    Degenerate ignition of helium in low-mass stars at the end of the red giant branch phase leads to dynamic convection in their helium cores. One-dimensional (1D) stellar modeling of this intrinsically multi-dimensional dynamic event is likely to be inadequate. Previous hydrodynamic simulations imply that the single convection zone in the helium core of metal-rich Pop I stars grows during the flash on a dynamic timescale. This may lead to hydrogen injection into the core, and a double convection zone structure as known from one-dimensional core helium flash simulations of low-mass Pop III stars. We perform hydrodynamic simulations of the core helium flash in two and three dimensions to better constrain the nature of these events. To this end we study the hydrodynamics of convection within the helium cores of a 1.25 \\Msun metal-rich Pop I star (Z=0.02), and a 0.85 \\Msun metal-free Pop III star (Z=0) near the peak of the flash. These models possess single and double convection zones, respectively. We use 1D stell...

  18. Radiation Damping at a Bubble Wall

    CERN Document Server

    Lee, J; Lee, C H; Jang, J; Lee, Jae-weon; Kim, Kyungsub; Lee, Chul H.; Jang, Ji-ho

    1999-01-01

    The first order phase transition proceeds via nucleation and growth of true vacuum bubbles. When charged particles collide with the bubble they could radiate electromagnetic wave. We show that, due to an energy loss of the particles by the radiation, the damping pressure acting on the bubble wall depends on the velocity of the wall even in a thermal equilibrium state.

  19. Bubble Formation in Silicon-Quartz Interface

    OpenAIRE

    Kakimoto, K.; EGUCHI, M.; Ozoe, H.

    1997-01-01

    Bubble formation at an interface between silicon melt and a quartz crucible was studied by thermodynamical calculation and visualization of bubble formation using X-ray radiography. A phase diagram of silicon-oxygen (Si-O) system is also calculated from the reported thermodynamical data. Critical temperature and radius of bubble formation at the interface was discussed.

  20. Bubble Size Distributions in Coastal Seas

    NARCIS (Netherlands)

    Leeuw, G. de; Cohen, L.H.

    1995-01-01

    Bubble size distributions have been measured with an optical system that is based on imaging of a small sample volume with a CCD camera system, and processing of the images to obtain the size of individual bubbles in the diameter range from 30 to lOOO^m. This bubble measuring system is deployed from

  1. Nozzle-Free Liquid Microjetting via Homogeneous Bubble Nucleation

    Science.gov (United States)

    Lee, Taehwa; Baac, Hyoung Won; Ok, Jong G.; Youn, Hong Seok; Guo, L. Jay

    2015-04-01

    We propose and demonstrate a physical mechanism for producing liquid microjets by taking an optoacoustic approach that can convert light to sound through a carbon-nanotube-coated lens, where light from a pulsed laser is converted to high momentum sound wave. The carbon-nanotube lens can focus high-amplitude sound waves to a microspot of visualizes two consecutive jets closely correlated with bubble dynamics. Because of the acoustic scattering from the interface, negative pressure amplitudes are significantly increased up to 80 MPa, even allowing homogeneous bubble nucleation. As a demonstration, this nozzle-free approach is applied to inject colored liquid into a tissue-mimicking gel as well as print a material on a glass substrate.

  2. Investigations of levitated helium drops

    Science.gov (United States)

    Whitaker, Dwight Lawrence

    1999-11-01

    We report on the development of two systems capable of levitating drops of liquid helium. Helium drops of ˜20 mum have been levitated with the radiation pressure from two counter-propagating Nd:YAG laser beams. Drops are produced with a submerged piezoelectric transducer, and could be held for up to three minutes in our optical trap. Calculations show that Brillouin and Raman scattering of the laser light in the liquid helium produces a negligible rate of evaporation of the drop. Evaporation caused by the enhanced vapor pressure of the curved drop surfaces appears to be a significant effect limiting the drop lifetimes. Helium drops as large as 2 cm in diameter have been suspended in the earth's gravitational field with a magnetic field. A commercial superconducting solenoid provides the necessary field, field-gradient product required to levitate the drops. Drops are cooled to 0.5 K with a helium-3 refrigerator, and can be held in the trap indefinitely. We have found that when two or more drops are levitated in the same magnetic trap, the drops often remain in a state of apparent contact without coalescing. This effect is a result of the evaporation of liquid from between the two drops, and is found to occur only for normal fluid drops. We can induce shape oscillations in charged, levitated drops with an applied ac electric field. We have measured the resonance frequencies and damping rates for the l = 2 mode of oscillation as function of temperature. We have also developed a theory to describe the small amplitude shape oscillations of a He II drop surrounded by its saturated vapor. In our theory, we have considered two sets of boundary conditions---one where the drop does not evaporate and another in which the liquid and vapor are in thermodynamic equilibrium. We have found that both solutions give a frequency that agrees well with experiment, but that the data for the damping rate agree better with the solution without evaporation.

  3. Dynamic behavior of gas bubble in single bubble sonoluminescence - vibrator model

    Institute of Scientific and Technical Information of China (English)

    QIAN Menglu; CHENG Qian; GE Caoyan

    2002-01-01

    Single bubble sonoluminescence is a process of energy transformation from soundto light. Therefore the motion equations of near spherical vibration of a gas bubble in anincompressible and viscous liquid can be deduced by Lagrangian Equation with dissipationfunction when the bubble is considered as a vibrator surrounded by liquid. The analyticalsolutions in the bubble expanding, collapsing and rebounding stages can be obtained by solvingthese motion equations when some approximations are adopted. And the dynamic behaviorsof the bubble in these three stages are discussed.

  4. Charging dynamics of dopants in helium nanoplasmas

    DEFF Research Database (Denmark)

    Heidenreich, Andreas; Grüner, Barbara; Schomas, Dominik

    2017-01-01

    We present a combined experimental and theoretical study of the charging dynamics of helium nanodroplets doped with atoms of different species and irradiated by intense near-infrared laser pulses (≤1015 W cm−2). In particular, we elucidate the interplay of dopant ionization inducing the ignition...... of a helium nanoplasma, and the charging of the dopant atoms driven by the ionized helium host. Most efficient nanoplasma ignition and charging is found when doping helium droplets with xenon atoms, in which case high charge states of both helium (He2+) and of xenon (Xe21+) are detected. In contrast, only low...... charge states of helium and dopants are measured when doping with potassium and calcium atoms. Classical molecular dynamics simulations which include focal averaging generally reproduce the experimental results and provide detailed insights into the correlated charging dynamics of guest and host clusters....

  5. Critical Landau velocity in helium nanodroplets.

    Science.gov (United States)

    Brauer, Nils B; Smolarek, Szymon; Loginov, Evgeniy; Mateo, David; Hernando, Alberto; Pi, Marti; Barranco, Manuel; Buma, Wybren J; Drabbels, Marcel

    2013-10-11

    The best-known property of superfluid helium is the vanishing viscosity that objects experience while moving through the liquid with speeds below the so-called critical Landau velocity. This critical velocity is generally considered a macroscopic property as it is related to the collective excitations of the helium atoms in the liquid. In the present work we determine to what extent this concept can still be applied to nanometer-scale, finite size helium systems. To this end, atoms and molecules embedded in helium nanodroplets of various sizes are accelerated out of the droplets by means of optical excitation, and the speed distributions of the ejected particles are determined. The measurements reveal the existence of a critical velocity in these systems, even for nanodroplets consisting of only a thousand helium atoms. Accompanying theoretical simulations based on a time-dependent density functional description of the helium confirm and further elucidate this experimental finding.

  6. Droplets, Bubbles and Ultrasound Interactions

    NARCIS (Netherlands)

    Shpak, O.; Verweij, M.; Jong, de N.; Versluis, M.; Escoffre, J.M.; Bouakaz, A.

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to

  7. "Financial Bubbles" and Monetary Policy

    Science.gov (United States)

    Tikhonov, Yuriy A.; Pudovkina, Olga E.; Permjakova, Juliana V.

    2016-01-01

    The relevance of this research is caused by the need of strengthening a role of monetary regulators to prevent financial bubbles in the financial markets. The aim of the article is the analysis of a problem of crisis phenomena in the markets of financial assets owing to an inadequate growth of their cost, owing to subjective reasons. The leading…

  8. Explosive micro-bubble actuator

    NARCIS (Netherlands)

    Broek, van den D.M.; Elwenspoek, M.C.

    2007-01-01

    Explosive evaporation occurs when a thin layer of liquid reaches a very high temperature in a very short time. At these temperatures homogeneous nucleation takes place. The nucleated bubbles almost instantly coalesce forming a vapour film followed by rapid growth due to the pressure impulse and fina

  9. Bubble-Driven Inertial Micropump

    CERN Document Server

    Torniainen, Erik D; Markel, David P; Kornilovitch, Pavel E

    2012-01-01

    The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel or continues to grow axially when it reaches the reservoir. In the non-axial regime the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical princi...

  10. The Big European Bubble Chamber

    CERN Multimedia

    1977-01-01

    The 3.70 metre Big European Bubble Chamber (BEBC), dismantled on 9 August 1984. During operation it was one of the biggest detectors in the world, producing direct visual recordings of particle tracks. 6.3 million photos of interactions were taken with the chamber in the course of its existence.

  11. Giant Bubble Pinch-Off

    NARCIS (Netherlands)

    Bergmann, R.P.H.M.; van der Meer, Roger M.; Stijnman, Mark; Stijnman, M; Sandtke, M.; Prosperetti, Andrea; Lohse, Detlef

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a w

  12. Murray Strasberg and bubble acoustics

    NARCIS (Netherlands)

    Prosperetti, Andrea

    2014-01-01

    Murray Strasberg made seminal contributions to the nucleation and acoustics of bubbles. Half a century after publication, these papers still receive a sizable number of citations every year. The talk will review this work, comment on its impact, and put Strasberg's classical results in a modern

  13. Electrolysis Bubbles Make Waterflow Visible

    Science.gov (United States)

    Schultz, Donald F.

    1990-01-01

    Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

  14. The effects of bubble-bubble interactions on pressures and temperatures produced by bubbles collapsing near a rigid surface

    Science.gov (United States)

    Alahyari Beig, Shahaboddin; Johnsen, Eric

    2016-11-01

    Cavitation occurs in a wide range of hydraulic applications, and one of its most important consequences is structural damage to neighboring surfaces following repeated bubble collapse. A number of studies have been conducted to predict the pressures produced by the collapse of a single bubble. However, the collapse of multiple bubbles is known to lead to enhanced collapse pressures. In this study, we quantify the effects of bubble-bubble interactions on the bubble dynamics and pressures/temperatures produced by the collapse of a pair of bubbles near a rigid surface. For this purpose, we use an in-house, high-order accurate shock- and interface-capturing method to solve the 3D compressible Navier-Stokes equations for gas/liquid flows. The non-spherical bubble dynamics are investigated and the subsequent pressure and temperature fields are characterized based on the relevant parameters entering the problem: stand-off distance, geometrical configuation, collapse strength. We demonstrate that bubble-bubble interactions amplify/reduce pressures and temperatures produced at the collapse, and increase the non-sphericity of the bubbles and the collapse time, depending on the flow parameters.

  15. Simulation on Gas Injection Refining Process with Mechanical Stirring

    Directory of Open Access Journals (Sweden)

    Zhang Ting’an

    2012-12-01

    Full Text Available Basing on the new method of in-situ desulfurization with gas injection and mechanical stirring, the effect of bubble dispersion and disintegration of three type impellers are numerically simulated by commercial CFD software Ansys Fluent 12.0. Numerical simulations of three-dimensional multiphase turbulence in gas injection and mechanical stirring are performed by adopting unsteady SM method coupled with Eulerian multiphase model and two-phase turbulence model. The information of gas-liquid fluid flow, velocity, turbulent kinetic energy and the power consumption are investigated and the results show that the SSB impeller can make bubbles get best dispersion and disintegration,and its power consumption is lower than VB impeller. The disk on the impeller blades can weaken the swirl flow in the upper zone of the impeller. Therefore, the bubble residence time is extended, and the bubble dispersing zone is also increased.

  16. Experimental study of the interaction between the spark-induced cavitation bubble and the air bubble

    Institute of Scientific and Technical Information of China (English)

    罗晶; 许唯临; 牛志攀; 罗书靖; 郑秋文

    2013-01-01

    Experiments are carried out by using high-speed photography to investigate the interaction between the spark-generated cavitation bubble and the air bubble in its surrounding fluid. Three problems are discussed in detail: the impact of the air bubble upon the development of the cavitation bubble, the evolution of the air bubble under the influence of the cavitation bubble, and the change of the fluid pressure during the development of a micro jet of the cavitation bubble. Based on the experimental results, under the condition of no air bubble present, the lifetime of the cavitation bubble from expansion to contraction increases with the increase of the maximum radius. On the other hand, when there is an air bubble present, different sized cavitation bubbles have similarity with one another generally in terms of the lifetime from expansion to contraction, which does not depend on the maximum radius. Also, with the presence of an air bubble, the lifetime of the smaller cavitation bubble is extended while that of the bigger ones reduced. Furthermore, it is shown in the experiment that the low pressure formed in the opposite direction to the cavitation bubble micro jet makes the air bubble in the low pressure area being stretched into a steplike shape.

  17. Doripenem Injection

    Science.gov (United States)

    ... injection is in a class of medications called carbapenem antibiotics. It works by killing bacteria.Antibiotics such ... if you are allergic to doripenem injection; other carbapenem antibiotics such as imipenem/cilastatin (Primaxin) or meropenem ( ...

  18. Methotrexate Injection

    Science.gov (United States)

    Methotrexate injection is used alone or in combination with other medications to treat gestational trophoblastic tumors (a ... in bones) after surgery to remove the tumor. Methotrexate injection is also used to treat severe psoriasis ( ...

  19. Bendamustine Injection

    Science.gov (United States)

    Bendamustine injection is used to treat chronic lymphocytic leukemia (CLL; a type of cancer of the white ... injection. You should use birth control to prevent pregnancy in yourself or your partner during your treatment ...

  20. Caspofungin Injection

    Science.gov (United States)

    Caspofungin injection is used in adults and children 3 months of age and older to treat yeast ... people with a weakened ability to fight infection. Caspofungin injection is in a class of antifungal medications ...

  1. Temozolomide Injection

    Science.gov (United States)

    Temozolomide is used to treat certain types of brain tumors. Temozolomide is in a class of medications called alkylating ... Temozolomide injection comes as a powder to be added to fluid and injected over 90 minutes intravenously ( ...

  2. Pembrolizumab Injection

    Science.gov (United States)

    Pembrolizumab injection is used to treat melanoma (a type of skin cancer) that cannot be treated with ... who have a specific type of melanoma tumor. Pembrolizumab injection is also used to treat a certain ...

  3. Lacosamide Injection

    Science.gov (United States)

    ... injection is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in ... older (about 1 in 500 people) who took anticonvulsants like lacosamide injection to treat various conditions during ...

  4. Midazolam Injection

    Science.gov (United States)

    ... injection is in a class of medications called benzodiazepines. It works by slowing activity in the brain ... breast-feeding.talk to your doctor about the risks and benefits of receiving midazolam injection if you ...

  5. Doxycycline Injection

    Science.gov (United States)

    Doxycycline injection is used to treat or prevent bacterial infections, including pneumonia and other respiratory tract infections. ... certain skin, genital, intestine, and urinary system infections. Doxycycline injection may be used to treat or prevent ...

  6. Paclitaxel Injection

    Science.gov (United States)

    ... with other medications. Paclitaxel injection manufactured with polyoxyethylated castor oil is used to treat ovarian cancer (cancer that ... cancer, and lung cancer. Paclitaxel injection with polyoxyethylated castor oil is also used to treat Kaposi's sarcoma (a ...

  7. Etanercept Injection

    Science.gov (United States)

    ... will be using the prefilled syringe or automatic injection device, tell your doctor if you or the person who will be injecting the medication for you are allergic to rubber or latex.tell your doctor and pharmacist what ...

  8. Cyclosporine Injection

    Science.gov (United States)

    Cyclosporine injection is used with other medications to prevent transplant rejection (attack of the transplanted organ by ... who have received kidney, liver, and heart transplants. Cyclosporine injection should only be used to treat people ...

  9. Estrogen Injection

    Science.gov (United States)

    The estradiol cypionate and estradiol valerate forms of estrogen injection are used to treat hot flushes (hot ... should consider a different treatment. These forms of estrogen injection are also sometimes used to treat the ...

  10. Cefotaxime Injection

    Science.gov (United States)

    Cefotaxime injection is used to treat certain infections caused by bacteria including pneumonia and other lower respiratory ... skin, blood, bone, joint, and urinary tract infections. Cefotaxime injection may also be used before surgery, and ...

  11. Discovery of Giant Gamma-ray Bubbles in the Milky Way

    Science.gov (United States)

    Su, Meng

    Based on data from the Fermi Gamma-ray Space Telescope, we have discovered two gigantic gamma-ray emitting bubble structures in our Milky Way (known as the Fermi bubbles), extending ˜50 degrees above and below the Galactic center with a width of ˜40 degrees in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE ˜ E-2) than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. There is no significant difference in the spectrum or gamma-ray luminosity between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; we also found features in the ROSAT soft X-ray maps at 1.5 -- 2 keV which line up with the edges of the bubbles. The Fermi bubbles are most likely created by some large episode of energy injection in the Galactic center, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last ˜ 10 Myr. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population. Furthermore, we have recently identified a gamma-ray cocoon feature within the southern bubble, with a jet-like feature along the cocoon's axis of symmetry, and another directly opposite the Galactic center in the north. If confirmed, these jets are the first resolved gamma-ray jets ever seen.

  12. Shell correction energy for bubble nuclei

    CERN Document Server

    Yu, Y; Magierski, P; Bulgac, Aurel; Magierski, Piotr

    2000-01-01

    The positioning of a bubble inside a many fermion system does not affect the volume, surface or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.

  13. Robust acoustic wave manipulation of bubbly liquids

    Energy Technology Data Exchange (ETDEWEB)

    Gumerov, N. A., E-mail: gumerov@umiacs.umd.edu [Institute for Advanced Computer Studies, University of Maryland, College Park, Maryland 20742 (United States); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Akhatov, I. S. [Center for Design, Manufacturing and Materials, Skolkovo Institute of Science and Technology, Moscow 143026 (Russian Federation); Ohl, C.-D. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Sametov, S. P. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Khazimullin, M. V. [Center for Micro- and Nanoscale Dynamics of Dispersed Systems, Bashkir State University, Ufa 450076 (Russian Federation); Institute of Molecule and Crystal Physics, Ufa Research Center of Russian Academy of Sciences, Ufa 450054 (Russian Federation); Gonzalez-Avila, S. R. [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)

    2016-03-28

    Experiments with water–air bubbly liquids when exposed to acoustic fields of frequency ∼100 kHz and intensity below the cavitation threshold demonstrate that bubbles ∼30 μm in diameter can be “pushed” away from acoustic sources by acoustic radiation independently from the direction of gravity. This manifests formation and propagation of acoustically induced transparency waves (waves of the bubble volume fraction). In fact, this is a collective effect of bubbles, which can be described by a mathematical model of bubble self-organization in acoustic fields that matches well with our experiments.

  14. Lidar signature from bubbles in the sea.

    Science.gov (United States)

    Churnside, James H

    2010-04-12

    The lidar signature from a collection of bubbles is proportional to the volume backscatter coefficient at a scattering angle of 180 degrees . This quantity, calculated using a combination of geometric optics and diffraction, is proportional to the void fraction of the bubbles in the water for any bubble size distribution. The constant of proportionality is 233 m(-1) sr(-1)for clean bubbles, slightly less for bubbles coated with a thin layer of organic material, and as large as 1445 m(-1) sr(-1) for a thick coating of protein.

  15. Supercoiling induces denaturation bubbles in circular DNA.

    Science.gov (United States)

    Jeon, Jae-Hyung; Adamcik, Jozef; Dietler, Giovanni; Metzler, Ralf

    2010-11-12

    We present a theoretical framework for the thermodynamic properties of supercoiling-induced denaturation bubbles in circular double-stranded DNA molecules. We explore how DNA supercoiling, ambient salt concentration, and sequence heterogeneity impact on the bubble occurrence. An analytical derivation of the probability distribution to find multiple bubbles is derived and the relevance for supercoiled DNA discussed. We show that in vivo sustained DNA bubbles are likely to occur due to partial twist release in regions rich in weaker AT base pairs. Single DNA plasmid imaging experiments clearly demonstrate the existence of bubbles in free solution.

  16. Bubble Universe Dynamics After Free Passage

    CERN Document Server

    Ahlqvist, Pontus; Greene, Brian

    2013-01-01

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by 'free passage' dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  17. Simulation of the mantle and crustal helium isotope signature in the Mediterranean Sea using a high-resolution regional circulation model

    Science.gov (United States)

    Ayache, M.; Dutay, J.-C.; Jean-Baptiste, P.; Fourré, E.

    2015-12-01

    Helium isotopes (3He, 4He) are useful tracers for investigating the deep ocean circulation and for evaluating ocean general circulation models, because helium is a stable and conservative nuclide that does not take part in any chemical or biological process. Helium in the ocean originates from three different sources, namely, (i) gas dissolution in equilibrium with atmospheric helium, (ii) helium-3 addition by radioactive decay of tritium (called tritiugenic helium), and (iii) injection of terrigenic helium-3 and helium-4 by the submarine volcanic activity which occurs mainly at plate boundaries, and also addition of (mainly) helium-4 from the crust and sedimentary cover by α-decay of uranium and thorium contained in various minerals. We present the first simulation of the terrigenic helium isotope distribution in the whole Mediterranean Sea using a high-resolution model (NEMO-MED12). For this simulation we build a simple source function for terrigenic helium isotopes based on published estimates of terrestrial helium fluxes. We estimate a hydrothermal flux of 3.5 mol3 He yr-1 and a lower limit for the crustal flux at 1.6 × 10-7 4He mol m-2 yr-1. In addition to providing constraints on helium isotope degassing fluxes in the Mediterranean, our simulations provide information on the ventilation of the deep Mediterranean waters which is useful for assessing NEMO-MED12 performance. This study is part of the work carried out to assess the robustness of the NEMO-MED12 model, which will be used to study the evolution of the climate and its effect on the biogeochemical cycles in the Mediterranean Sea, and to improve our ability to predict the future evolution of the Mediterranean Sea under the increasing anthropogenic pressure.

  18. Ustekinumab Injection

    Science.gov (United States)

    ... Do not inject into an area where the skin is tender, bruised, red, or hard or where you have scars or stretch marks.Your doctor or pharmacist will ... injection.you should know that ustekinumab injection may decrease your ability ... new or changing skin lesions, minor infections (such as open cuts or ...

  19. Ranitidine Injection

    Science.gov (United States)

    Ranitidine injection comes as a solution (liquid) to be mixed with another fluid and injected intravenously (into a vein) over 5 to 20 minutes. Ranitidine may also be injected into a muscle. It is usually given every 6 to 8 hours, but may also be given ...

  20. Digital Microfluidics with Bubble Manipulations by Dielectrophoresis

    Directory of Open Access Journals (Sweden)

    Shih-Kang Fan

    2012-03-01

    Full Text Available This paper presents basic bubble manipulations, including transporting, splitting, and merging, by dielectrophoresis (DEP in an oil environment. In our presented method, bubbles are placed between parallel plates in an oil medium of a low vapor pressure, which eliminates the possibility of changing the gaseous composition of the bubble caused by evaporation of the medium. DEP has been previously investigated to actuate dielectric droplets and is adopted here to drive the oil environment as well as the immersed bubbles between parallel plates. In our experiment, air bubbles of 0.3 ml were successfully transported in a 20 cSt silicone oil medium between a 75 mm-high parallel plate gap. In addition, 0.6 ml air bubbles were successfully split into two 0.3 ml air bubbles, and then merged again by DEP. These successful manipulations make digital gaseous lab-on-a-chip a reality.

  1. Cosmological HII Bubble Growth During Reionization

    CERN Document Server

    Shin, Min-Su; Cen, Renyue

    2007-01-01

    We present general properties of ionized hydrogen (HII) bubbles and their growth based on a state-of-the-art large-scale (100 Mpc/h) cosmological radiative transfer simulation. The simulation resolves all halos with atomic cooling at the relevant redshifts and simultaneously performs radiative transfer and dynamical evolution of structure formation. Our major conclusions include: (1) for significant HII bubbles, the number distribution is peaked at a volume of ~ 0.6 Mpc^3/h^3 at all redshifts. But, at z 10 even the largest HII bubbles have a balanced ionizing photon contribution from Pop II and Pop III stars, while at z < 8 Pop II stars start to dominate the overall ionizing photon production for large bubbles, although Pop III stars continue to make a non-negligible contribution. (6) The relationship between halo number density and bubble size is complicated but a strong correlation is found between halo number density and bubble size for for large bubbles.

  2. Bubbles generated from wind-steepened breaking waves: 2. Bubble plumes, bubbles, and wave characteristics

    NARCIS (Netherlands)

    Leifer, I.; Caulliez, G.; Leeuw, G.de

    2006-01-01

    Measurements of breaking-wave-generated bubble plumes were made in fresh (but not clean) water in a large wind-wave tunnel. To preserve diversity, a classification scheme was developed on the basis of plume dimensions and "optical density," or the plume's ability to obscure the background. Optically

  3. Helium stratification in HD 145792: a new Helium strong star

    CERN Document Server

    Catanzaro, G

    2007-01-01

    In this paper we report on the real nature of the star HD 145792, classified as He weak in {\\it ``The General Catalogue of Ap and Am stars''}. By means of FEROS@ESO1.52m high resolution spectroscopic data, we refined the atmospheric parameters of the star, obtaining: T$_{\\rm eff}$ = 14400 $\\pm$ 400 K, $\\log g$ = 4.06 $\\pm$ 0.08 and $\\xi$ = 0 $^{+0.6}$ km s$^{-1}$. These values resulted always lower than those derived by different authors with pure photometric approaches. Using our values we undertook an abundance analysis with the aim to derive, for the first time, the chemical pattern of the star's atmosphere. For metals a pure LTE synthesis (ATLAS9 and SYNTHE) has been used, while for helium a hybrid approach has been preferred (ATLAS9 and SYNSPEC). The principal result of our study is that HD 145792 belongs to He strong class contrary to the previous classification. Moreover, helium seems to be vertically stratified in the atmosphere, decreasing toward deepest layers. For what that concerns metals abundanc...

  4. Innovative Drug Injection via Laser Induced Plasma

    Science.gov (United States)

    Han, Tae-hee; Yoh, Jack J.

    2010-10-01

    A laser based needle-free liquid drug injection device has been developed. A laser beam is focused inside the liquid contained in the rubber chamber of micro scale. The focused laser beam causes explosive bubble growth and the sudden volume increase in a sealed chamber drives a microjet of liquid drug through the micronozzle. The exit diameter of the nozzle is 125 um and the injected microjet reaches an average velocity of 264 m/s. This device adds the time-varying feature of microjet to the current state of liquid injection for drug delivery.

  5. Developed ‘laminar’ bubbly flow with non-uniform bubble sizes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Bubbles with different sizes have different dynamic and kineticbehavior in a two-phase bubbly flow. A common two-fluid model based on the uniform bubble size assumption is not suitable for a bubbly flow with non-uniform bubble sizes. To deal with non-uniform bubbly flows, a multi-fluid model is established, with which bubbles are divided into several groups according to their sizes and a set of basic equations is derived for each group of bubbles with almost the same size. Through analyzing the bubble-bubble and bubble-pipe wall interactions, two new constitutive laws for the wall-force and pressure difference between the liquid phase and interface are developed to close the averaged basic equations. The respective phase distributions for each group of bubbles measured by a specially designed three-dimensional photographic method are used to check the model. Comparison between model-predicted values and experimental data shows that the model can describe laminar bubbly flow with non-uniform bubble sizes.

  6. Bubble–bubble interaction effects on dynamics of multiple bubbles in a vortical flow field

    Directory of Open Access Journals (Sweden)

    Bing Cui

    2016-02-01

    Full Text Available Bubble–bubble interactions play important roles in the dynamic behaviours of multiple bubbles or bubble clouds in a vortical flow field. Based on the Rayleigh–Plesset equation and the modified Maxey–Riley equation of a single bubble, bubble–bubble interaction terms are derived and introduced for multiple bubbles. Thus, both the Rayleigh–Plesset and modified Maxey–Riley equations are improved by considering bubble–bubble interactions and then applied for the multiple bubbles entrainment into a stationary Gaussian vortex. Runge–Kutta fourth-order scheme is adopted to solve the coupled dynamic and kinematic equations and the convergence study has been conducted. Numerical result has also been compared and validated with the published experimental data. On this basis, the oscillation, trajectory and effects of different parameters of double-bubble and multi-bubble entrainment into Gaussian vortex have been studied and the results have been compared with those of the cases without bubble–bubble interactions. It indicates that bubble–bubble interactions influence the amplitudes and periods of bubble oscillations severely, but have small effects on bubble trajectories.

  7. Helium transfer line installation details.

    CERN Multimedia

    G. Perinic

    2007-01-01

    A particularity of the 32 m long four in one helium transfer line in between the cold box in USC55 and the cavern UX5 is the fact that the transfer line passes through a hole in the crane rail support beam. In order to ensure the alignment of the suspension rail in the interconnecting tunnel with the hole in the rail support as well as the connection points at both ends required precise measurements of the given geometries as well as the installation of a temporary target for the verification of the theoretical predictions.

  8. Helium II level measurement techniques

    Science.gov (United States)

    Celik, D.; Hilton, D. K.; Zhang, T.; Van Sciver, S. W.

    2001-05-01

    In this paper, a survey of cryogenic liquid level measurement techniques applicable to superfluid helium (He II) is given. The survey includes both continuous and discrete measurement techniques. A number of different probes and controlling circuits for this purpose have been described in the literature. They fall into one of the following categories: capacitive liquid level gauges, superconducting wire liquid level gauges, thermodynamic (heat transfer-based) liquid level gauges, resistive gauges, ultrasound and transmission line-based level detectors. The present paper reviews these techniques and their suitability for He II service. In addition to these methods, techniques for measuring the total liquid volume and mass gauging are also discussed.

  9. The Discovery of Fermi Bubbles: Multi-wavelength Observations and Implications to the Past Activity of Galactic Center

    Science.gov (United States)

    Su, Meng

    2012-01-01

    Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50 degrees above and below the Galactic center, with a width of about 40 degrees in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE E-2) than the IC emission from electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; the edges of the bubbles also line up with features in the ROSAT X-ray maps at 1.5 - 2 keV. We further discovered arge cocoon structures in Fermi gamma-ray data, which is presumably produced by relativistic large scale jets. I will summarize observational evidence of the Fermi bubbles and cocoons, including features of polarization and rotation measure of the bubble edges. The bubbles have sharp edges in gamma-ray, X-ray, and polarized microwave emission. I'm going to argue that these Galactic gamma-ray bubbles are ongoing shocks (instead of a stable structure), and were most likely created by some large episode of energy injection in the Galactic center, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last ˜10 Myr.

  10. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  11. Radioactive ions and atoms in superfluid helium

    NARCIS (Netherlands)

    Dendooven, P.G.; Purushothaman, S.; Gloos, K.; Aysto, J.; Takahashi, N.; Huang, W.; Harissopulos, S; Demetriou, P; Julin, R

    2006-01-01

    We are investigating the use of superfluid helium as a medium to handle and manipulate radioactive ions and atoms. Preliminary results on the extraction of positive ions from superfluid helium at temperatures close to 1 K are described. Increasing the electric field up to 1.2 kV/cm did not improve t

  12. Organ protection by the noble gas helium

    NARCIS (Netherlands)

    Smit, K.F.

    2017-01-01

    The aims of this thesis were to investigate whether helium induces preconditioning in humans, and to elucidate the mechanisms behind this possible protection. First, we collected data regarding organ protective effects of noble gases in general, and of helium in particular (chapters 1-3). In chapter

  13. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  14. LOX Tank Helium Removal for Propellant Scavenging

    Science.gov (United States)

    Chato, David J.

    2009-01-01

    System studies have shown a significant advantage to reusing the hydrogen and oxygen left in these tanks after landing on the Moon in fuel cells to generate power and water for surface systems. However in the current lander concepts, the helium used to pressurize the oxygen tank can substantially degrade fuel cell power and water output by covering the reacting surface with inert gas. This presentation documents an experimental investigation of methods to remove the helium pressurant while minimizing the amount of the oxygen lost. This investigation demonstrated that significant quantities of Helium (greater than 90% mole fraction) remain in the tank after draining. Although a single vent cycle reduced the helium quantity, large amounts of helium remained. Cyclic venting appeared to be more effective. Three vent cycles were sufficient to reduce the helium to small (less than 0.2%) quantities. Two vent cycles may be sufficient since once the tank has been brought up to pressure after the second vent cycle the helium concentration has been reduced to the less than 0.2% level. The re-pressurization process seemed to contribute to diluting helium. This is as expected since in order to raise the pressure liquid oxygen must be evaporated. Estimated liquid oxygen loss is on the order of 82 pounds (assuming the third vent cycle is not required).

  15. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van veldhoven, E.; Chen, P.; Sidorkin, V.; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2010-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  16. Nanofabrication with a helium ion microscope

    NARCIS (Netherlands)

    Maas, D.; Van Veldhoven, E.; Chen, P.; Sidorkin, V; Salemink, H.; Van der Drift, E.; Alkemade, P.

    2009-01-01

    The recently introduced helium ion microscope (HIM) is capable of imaging and fabrication of nanostructures thanks to its sub-nanometer sized ion probe [1,2]. The unique interaction of the helium ions with the sample material provides very localized secondary electron emission, thus providing a valu

  17. Paramagnetic Attraction of Impurity-Helium Solids

    Science.gov (United States)

    Bernard, E. P.; Boltnev, R. E.; Khmelenko, V. V.; Lee, D. M.

    2003-01-01

    Impurity-helium solids are formed when a mixture of impurity and helium gases enters a volume of superfluid helium. Typical choices of impurity gas are hydrogen deuteride, deuterium, nitrogen, neon and argon, or a mixture of these. These solids consist of individual impurity atoms and molecules as well as clusters of impurity atoms and molecules covered with layers of solidified helium. The clusters have an imperfect crystalline structure and diameters ranging up to 90 angstroms, depending somewhat on the choice of impurity. Immediately following formation the clusters aggregate into loosely connected porous solids that are submerged in and completely permeated by the liquid helium. Im-He solids are extremely effective at stabilizing high concentrations of free radicals, which can be introduced by applying a high power RF dis- charge to the impurity gas mixture just before it strikes the super fluid helium. Average concentrations of 10(exp 19) nitrogen atoms/cc and 5 x 10(exp 18) deuterium atoms/cc can be achieved this way. It shows a typical sample formed from a mixture of atomic and molecular hydrogen and deuterium. It shows typical sample formed from atomic and molecular nitrogen. Much of the stability of Im-He solids is attributed to their very large surface area to volume ratio and their permeation by super fluid helium. Heat resulting from a chance meeting and recombination of free radicals is quickly dissipated by the super fluid helium instead of thermally promoting the diffusion of other nearby free radicals.

  18. Helium abundances and the helium isotope anomaly of sdB stars

    CERN Document Server

    Geier, S; Edelmann, H; Morales-Rueda, L; Kilkenny, D; O'Donoghue, D; Marsh, T R; Copperwheat, C

    2011-01-01

    Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have been measured with high accuracy. We confirm the correlation of helium abundance with temperature and the existence of two distinct sequences in helium abundance found previously. We focused on isotopic shifts of helium lines and found helium-3 to be strongly enriched in 8 of our programme stars. Most of these stars cluster in a small temperature range between 27000 K and 31000 K very similar to the known helium-3-rich main sequence B stars, which cluster at somewhat lower temperatures. This phenomenon is most probably related to diffusion processes in the atmosphere, but poses a challenge to diffusion models.

  19. Bubble entrapment through topological change

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2010-05-03

    When a viscousdrop impacts onto a solid surface, it entraps a myriad of microbubbles at the interface between liquid and solid. We present direct high-speed video observations of this entrapment. For viscousdrops, the tip of the spreading lamella is separated from the surface and levitated on a cushion of air. We show that the primary mechanism for the bubble entrapment is contact between this precursor sheet of liquid with the solid and not air pulled directly through cusps in the contact line. The sheet makes contact with the solid surface,forming a wetted patch, which grows in size, but only entraps a bubble when it meets the advancing contact line. The leading front of this wet patch can also lead to the localized thinning and puncturing of the liquid film producing strong splashing of droplets.

  20. Cavitation inception from bubble nuclei

    DEFF Research Database (Denmark)

    Mørch, Knud Aage

    2015-01-01

    , and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid....... The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model......The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years...

  1. Conformal gravity and "gravitational bubbles"

    CERN Document Server

    Berezin, V A; Eroshenko, Yu N

    2015-01-01

    We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson--Walker metrics. We called one of them the "gravitational bubbles", which is compact and with zero Weyl tensor. These "gravitational bubbles" are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from "nothing". The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-para...

  2. Elusive structure of helium trimers

    Science.gov (United States)

    Stipanović, Petar; Vranješ Markić, Leandra; Boronat, Jordi

    2016-09-01

    Over the years many He-He interaction potentials have been developed, some very sophisticated, including various corrections beyond the Born-Oppenheimer approximation. Most of them were used to predict properties of helium dimers and trimers, examples of exotic quantum states, whose experimental study proved to be very challenging. Recently, detailed structural properties of helium trimers were measured for the first time, allowing a comparison with theoretical predictions and possibly enabling the evaluation of different interaction potentials. The comparisons already made included adjusting the maxima of both theoretical and experimental correlation functions to one, so the overall agreement between theory and experiment appeared satisfactory. However, no attempt was made to evaluate the quality of the interaction potentials used in the calculations. In this work, we calculate the experimentally measured correlation functions using both new and old potentials, compare them with experimental data and rank the potentials. We use diffusion Monte Carlo simulations at T = 0, which give within statistical noise exact results of the ground state properties. All models predict both trimers 4He3 and 4He{}2{}3He to be in a quantum halo state.

  3. Soap bubbles in paintings: Art and science

    Science.gov (United States)

    Behroozi, F.

    2008-12-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not only as metaphor but also to express a sense of play and wonder. In his most famous painting, Soap Bubbles (1733/1734) a translucent and quavering soap bubble takes center stage. Chardin's contemporary Charles Van Loo painted his Soap Bubbles (1764) after seeing Chardin's work. In both paintings the soap bubbles have a hint of color and show two bright reflection spots. We discuss the physics involved and explain how keenly the painters have observed the interaction of light and soap bubbles. We show that the two reflection spots on the soap bubbles are images of the light source, one real and one virtual, formed by the curved surface of the bubble. The faint colors are due to thin film interference effects.

  4. Bioinspired bubble design for particle generation.

    Science.gov (United States)

    Gunduz, Oguzhan; Ahmad, Zeeshan; Stride, Eleanor; Tamerler, Candan; Edirisinghe, Mohan

    2012-02-07

    In this study, we devise a method to generate homogeneous particles from a bubble suspension, with the capability to control loading and the structure of bubbles. Ideally, a process such as this would occur at the interface between daughter bubble formation (instant) and gaseous diffusion (gradual). Interestingly, the budding mechanism in micro-organisms is one that demonstrates features of the desired phenomena (although at a much slower rate), as viruses can eject and evolve structures from their membranes. With these natural concepts, a bubble's surface can also be made to serve as a platform for particle generation, which transfers significant elements from the initial bubble coating to the newly generated structures. Here, we illustrate this by preparing coated bubbles (approx. 150 µm in diameter) using a hydrophobic polymer, which may be comparable to naturally occurring bubble coatings (e.g. organic matter forming part of bubble coatings in the sea), and dye (which can demonstrate entrapment of smaller quantities of a desired moiety) and then observe particle generation (approx. 500 nm). The process, which may be driven by a polymerosome-forming mechanism, also illustrates how additional uniform sub-micrometre-scale structures may form from a bubble's surface, which may have also previously been attributed to gas diffusion. In addition, such methods of particle formation from a bubble structure, the incorporation of chemical or biological media via an in situ process and subsequent release technologies have several areas of interest across the broad scientific community.

  5. Informational pathologies and interest bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Wiewiura, Joachim Schmidt

    2017-01-01

    This article contends that certain configurations of information networks facilitate specific cognitive states that are instrumental for decision and action on social media. Group-related knowledge and belief states—in particular common knowledge and pluralistic ignorance—may enable strong public...... signals. Indeed, some network configurations and attitude states foster informational pathologies that may fuel interest bubbles affecting agenda-setting and the generation of narratives in public spheres....

  6. BEBC Big European Bubble Chamber

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    A view of the dismantling of the magnet of BEBC, the 3.7 m European Bubble Chamber : iron magnetic shielding ; lower and upper parts of the vacuum enclosure of the magnet; turbo-molecular vacuum pumps for the "fish-eye" windows; the two superconducting coils; a handling platform; the two cryostats suspended from the bar of the travelling crane which has a 170 ton carrying capacity. The chamber proper, not dismantled, is inside the shielding.

  7. Bubble-induced cave collapse.

    Directory of Open Access Journals (Sweden)

    Lakshika Girihagama

    Full Text Available Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m. Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section, with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet, and the bubbles were produced using a syringe located at the cave floor.

  8. Photon Bubbles in Accretion Discs

    OpenAIRE

    Gammie, Charles F.

    1998-01-01

    We show that radiation dominated accretion discs are likely to suffer from a ``photon bubble'' instability similar to that described by Arons in the context of accretion onto neutron star polar caps. The instability requires a magnetic field for its existence. In an asymptotic regime appropriate to accretion discs, we find that the overstable modes obey the remarkably simple dispersion relation \\omega^2 = -i g k F(B,k). Here g is the vertical gravitational acceleration, B the magnetic field, ...

  9. Photochemistry inside superfluid helium nano droplets

    Energy Technology Data Exchange (ETDEWEB)

    Slenczka, Alkwin; Vdovin, Alexander; Dick, Bernhard [Inst. fuer Physikalische und Theoretische Chemie, Univ. Regensburg (Germany)

    2007-07-01

    Superfluid helium nano droplets serve as the most gentle cyrogenic matrix for creating isolated and cold molecules. High resolution electronic spectroscopy is sensitive for the investigation of the very weak perturbation of the helium droplet on the embedded molecule. Fluorescence excitation spectra, dispersed emission spectra and pump--probe-spectra show details of the salvation of molecules in helium droplets which were attributed to relaxation processes of the first solvation layer around the dopant. Photochemistry such as ESIPT, tautomerization by proton transfer and charge transfer are highly sensitive on intermolecular perturbations. We have studies such processes in superfluid helium droplets. The comparison with the respective gas phase experiments and quantum chemical calculations reveals further details on the photochemistry as well as on the perturbation by the superfluid helium droplet.

  10. Permeability of Hollow Microspherical Membranes to Helium

    Science.gov (United States)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  11. Gemini helium closed cycle cooling system

    Science.gov (United States)

    Lazo, Manuel; Galvez, Ramon; Rogers, Rolando; Solis, Hernan; Tapia, Eduardo; Maltes, Diego; Collins, Paul; White, John; Cavedoni, Chas; Yamasaki, Chris; Sheehan, Michael P.; Walls, Brian

    2008-07-01

    The Gemini Observatory presents the Helium Closed Cycle Cooling System that provides cooling capacity at cryogenic temperatures for instruments and detectors. It is implemented by running three independent helium closed cycle cooling circuits with several banks of compressors in parallel to continuously supply high purity helium gas to cryocoolers located about 100-120 meters apart. This poster describes how the system has been implemented, the required helium pressures and gas flow to reach cryogenic temperature, the performance it has achieved, the helium compressors and cryocoolers in use and the level of vibration the cryocoolers produce in the telescope environment. The poster also describes the new technology for cryocoolers that Gemini is considering in the development of new instruments.

  12. Formation of the helium EUV resonance lines

    CERN Document Server

    Golding, Thomas Peter; Carlsson, Mats

    2016-01-01

    Context: While classical models successfully reproduce intensities of many transition region lines, they predict helium EUV line intensities roughly an order of magnitude lower than the observed value. Aims: To determine the relevant formation mechanism(s) of the helium EUV resonance lines, capable of explaining the high intensities under quiet sun conditions. Methods: We synthesise and study the emergent spectra from a 3D radiation-magnetohydrodynamics simulation model. The effects of coronal illumination and non-equilibrium ionisation of hydrogen and helium are included self-consistently in the numerical simulation. Results: Radiative transfer calculations result in helium EUV line intensities that are an order of magnitude larger than the intensities calculated under the classical assumptions. The enhanced intensity of He I 584 is primarily caused by He II recombination cascades. The enhanced intensity of He II 304 and He II 256 is caused primarily by non-equilibrium helium ionisation. Conclusion: The anal...

  13. Global helium particle balance in LHD

    Energy Technology Data Exchange (ETDEWEB)

    Motojima, G., E-mail: motojima.gen@lhd.nifs.ac.jp [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Masuzaki, S.; Tokitani, M.; Kasahara, H.; Yoshimura, Y.; Kobayashi, M.; Sakamoto, R.; Morisaki, T.; Miyazawa, J.; Akiyama, T. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Ohno, N. [Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603 (Japan); Mutoh, T.; Yamada, H. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2015-08-15

    Global helium particle balance in long-pulse discharges is analyzed for the first time in the Large Helical Device (LHD) with the plasma-facing components of the first wall and the divertor tiles composed of stainless steel and carbon, respectively. During the 2-min discharge sustained by ion cyclotron resonance heating (ICRH) and electron cyclotron heating (ECH), helium is observed to be highly retained in the wall (regarded as both the first wall and the divertor tiles). Almost all (about 96%) puffed helium particles (1.3 × 10{sup 22} He) are absorbed in the wall near the end of the discharge. Even though a dynamic retention is eliminated, 56% is still absorbed. The analysis is also applied to longer pulse discharges over 40 min by ICRH and ECH, indicating that the helium wall retention is dynamically changed in time. At the initial phase of the discharge, a mechanism for adsorbing helium other than dynamical retention is invoked.

  14. The TeV-scale cosmic ray proton and helium spectra: Contributions from the local sources

    Indian Academy of Sciences (India)

    Yong-Yeon Keum; Pierre Salati

    2016-02-01

    Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of galactic cosmic ray production and propagation. Here, we propose to explain this anomaly by the presence of local sources. Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.

  15. Charge stripping of U238 ion beam by helium gas stripper

    Science.gov (United States)

    Imao, H.; Okuno, H.; Kuboki, H.; Yokouchi, S.; Fukunishi, N.; Kamigaito, O.; Hasebe, H.; Watanabe, T.; Watanabe, Y.; Kase, M.; Yano, Y.

    2012-12-01

    Development of a nondestructive, efficient electric-charge-stripping method is a key requirement for next-generation high-intensity heavy-ion accelerators such as the RIKEN Radioactive-Isotope Beam Factory. A charge stripper employing a low-Z gas is an important candidate applicable to high-intensity uranium beams for replacing carbon-foil strippers. In this study, a high-beam-transmission charge-stripping system employing helium gas for U238 beams injected at 10.8MeV/u was developed and demonstrated for the first time. The charge-state evolution measured using helium in a thickness range of 0.24-1.83mg/cm2 is compared with theoretical predictions. Energy attenuation and energy spread due to the helium stripper are also investigated.

  16. Experimental method to determine the role of helium in neutron-induced microstructural evolution

    Energy Technology Data Exchange (ETDEWEB)

    Gelles, D. S.; Garner, F. A.

    1978-12-01

    A method is presented which allows the determination of the role of helium on microstructural evolution in complex alloys and which avoids many of the problems associated with other simulation experiments. It involves a direct comparison of the materials' response to a primary difference in fission and fusion environments, namely the rate of helium generation. This is accomplished by irradiating specimens in a fission reactor and conducting microstructural analyses which concentrate on alloy matrix regions adjacent to precipitates rich in boron or nitrogen. Procedures are outlined for calculation of background and injected helium levels as well as displacement doses generated by neutrons and alpha particles. An example of the analysis method is shown for an experimental austenitic stainless steel containing boride particles and irradiated to 3 and 7 x 10/sup 22/ n/cm/sup 2/ (E > 0.1 MeV).

  17. No More Anomaly in the TeV Cosmic Ray Proton and Helium Spectra

    CERN Document Server

    Bernard, Guilhem; Keum, Yong-Yeon; Liu, Wei; Salati, Pierre; Taillet, Richard

    2013-01-01

    Recent measurements of cosmic ray proton and helium spectra show a hardening above a few hundreds of GeV. This excess is hard to understand in the framework of the conventional models of Galactic cosmic ray production and propagation. We propose here to explain this anomaly by the presence of local sources. Cosmic ray propagation is described as a diffusion process taking place inside a two-zone magnetic halo. We calculate the proton and helium fluxes at the Earth between 50 GeV and 100 TeV. Improving over a similar analysis, we consistently derive these fluxes by taking into account both local and remote sources for which a unique injection rate is assumed. We find cosmic ray propagation parameters for which the proton and helium spectra remarkably agree with the PAMELA and CREAM measurements over four decades in energy.

  18. Commissioning of helium compression system for the 12 GeV refrigerator

    Science.gov (United States)

    Knudsen, P.; Ganni, V.; Dixon, K.; Norton, R.; Creel, J.; Arenius, D.

    2014-01-01

    The compressor system used for the Jefferson Lab (JLab) 12 GeV upgrade, also known as the CHL-2 compressor system, incorporates many design changes to the typical compressor skid design to improve the efficiency, reliability and maintainability from previous systems. These include a considerably smaller bulk oil separator design that does not use coalescing elements/media, automated control of cooling oil injection based on the helium discharge temperature, a helium after-cooler design that is designed for and promotes coalescing of residual oil and a variable speed bearing oil pump to reduce oil bypass. The CHL-2 helium compression system has five compressors configured with four pressure levels that supports the three pressure levels in the cold box. This paper will briefly review several of these improvements and discuss some of the recent commissioning results.

  19. Dimensional Analysis of Average Diameter of Bubbles for Bottom Blown Oxygen Copper Furnace

    Directory of Open Access Journals (Sweden)

    Dongxing Wang

    2016-01-01

    Full Text Available Average diameter of bubbles is important in copper furnace. Based on the principle of similarity, a slice water model of a furnace with bottom-blown oxygen in matte-smelting process was established. A high-speed camera was used to record images continuously and clearer pictures were selected for treatment. Finally, image processing software was used for obtaining the average diameter of the bubbles. The effects of different injection conditions and equipment factors such as the diameter of nozzle, the nozzle installing angle, and gas velocity on the average diameter of bubbles were studied with cold water model experiment, exploring the dispersion and disintegration rules of bubbles. According to experimental data and Buckingham’s theorem, by using dimensional analysis method, an empirical formula on average diameter of bubbles was established (dB=0.41666d0.29374θ-0.46572v-0.16725. It can be seen from the formula that nozzle installing angle and diameter of nozzle make the most impact on the average diameter of bubbles in bottom blown oxygen copper furnace.

  20. Eulerian-Lagrangian Simulations of Bubbly Flows in A Vertical Square Duct

    Science.gov (United States)

    Liu, Rui; Vanka, Surya P.; Thomas, Brian G.

    2013-11-01

    We report results of Eulerian-Lagrangian simulations of developing upward and downward bubbly flows in a vertical square duct with a bulk Reynolds number of 5000. The continuous fluid is simulated with DNS, solving the Navier-Stokes equations by a second-order accurate finite volume fractional step method. Bubbles of sizes comparable to the Kolmogorov scale are injected at the duct entrance with a mean bulk volume fraction below 10-2. A two-way coupling approach is adopted for the interaction between the continuous fluid phase and dispersed bubble phase. The bubbles are tracked by a Lagrangian method including drag and lift forces due to buoyancy and Saffman lift. A in-house code, CU-FLOW, implemented on Graphic Processing Unit (GPU) is used for simulations in this work. The preferential distributions of bubbles and their impact on local turbulence structures and their effects on turbulent kinetic energy budgets are studied. Results between an upward flow and a downward flow with the bubbles are compared. Work Supported by Continuous Casting Consortium at UIUC.

  1. Revisiting the potential for bursting bubbles to damage cells below the free surface

    Science.gov (United States)

    Walls, Peter; Bird, James

    2016-11-01

    The rapid motion associated with bubbles bursting at the surface of a liquid is known to cause damage to cells in a suspension, which is particularly problematic in bioreactors that require continuous injection of oxygen to sustain the cells. It is generally accepted that cells directly attached to the bubble's interface will experience lethal levels of damage. To prevent cells from initially attaching to the bubble's surface, surfactants are widely used. However, the potential for bursting bubbles to damage nearby, but not directly attached, cells is less clear. Previous numerical studies have predicted maximum energy dissipation rates (EDR) as high as 1010 W/m3 for bubbles with radii less than 1 mm; lethal to the commonly used mammalian CHO cell. Here we show that these studies tend to underestimate the generated EDR levels by several orders of magnitude due to limited numerical mesh resolution. Furthermore, we demonstrate how a downward traveling jet can cause damage away from the interface. We validate our numerical model with high-speed bubble bursting experiments and relate the dynamics of this downward jet to the boundary layer equations. We anticipate our results will be an integral step towards developing more efficient aeration platforms. We acknowledge support from Biogen Inc.

  2. Shadow imaging in bubbly gas-liquid two-phase flow in porous structures

    Science.gov (United States)

    Altheimer, Marco; Häfeli, Richard; Wälchli, Carmen; Rudolf von Rohr, Philipp

    2015-09-01

    Shadow imaging is used for the investigation of bubbly gas-liquid two-phase flow in a porous structure. The porous structure is made of Somos WaterShed XC 11122, a clear epoxy resin used in rapid prototyping. Optical access is provided by using an aqueous solution of sodium iodide and zinc iodide having the same refractive index as the structure material (). Nitrogen is injected into the continuous phase at volumetric transport fractions in the range of resulting in a hold-up of . The obtained images of overlapping bubble shadows are processed to measure the bubble dimensions. Therefore, a new processing sequence is developed to determine bubble dimensions from overlapping bubble shadows by ellipse fitting. The accuracy of the bubble detection and sizing routine is assessed processing synthetic images. It is shown that the developed technique is suitable for volumetric two-phase flow measurements. Important global quantities such as gas hold-up and total interfacial area can be measured with only one camera. Operation parameters for gas-liquid two-phase flows are determined to improve mass and heat transfer between the phases.

  3. Subcutaneous Injections

    DEFF Research Database (Denmark)

    Thomsen, Maria

    This thesis is about visualization and characterization of the tissue-device interaction during subcutaneous injection. The tissue pressure build-up during subcutaneous injections was measured in humans. The insulin pen FlexTouchr (Novo Nordisk A/S) was used for the measurements and the pressure...... build-up was evaluated indirectly from the changes in the flow rate between subcutaneous injections and air injections. This method enabled the tissue counter pressure to be evaluated without a formal clinical study approval. The measurements were coupled to a model for the pressure evolution...

  4. The effects of gaseous bubble composition and gap distance on the characteristics of nanosecond discharges in distilled water

    Science.gov (United States)

    Hamdan, Ahmad; Cha, Min Suk

    2016-06-01

    Electric discharge in liquids with bubbles can reduce the energy consumption, which increases treatment efficiency. We present an experimental study of nanosecond discharges in distilled water bubbled with the monoatomic gas argon and with the polyatomic gases methane, carbon dioxide, and propane. We monitor the time evolution of the voltage and current waveforms, and calculate the injected charges to characterize the discharge. We establish a relationship between the injected charges and the shape of the plasma by time-resolved imaging to find that increasing the size of the gap reduces the injected charges. Moreover, we determine the plasma characteristics, including electron density, excitation temperatures (for atoms and ions), and rotational temperature of the OH and C2 radicals found in the plasma. Our space- and time-averaged measurements allow us to propose a spatial distribution of the plasma that is helpful for understanding the plasma dynamics necessary to develop and optimize applications based on nanosecond discharges in bubbled liquids.

  5. Exotic helium molecules; Molecules exotiques d'helium

    Energy Technology Data Exchange (ETDEWEB)

    Portier, M

    2007-12-15

    We study the photo-association of an ultracold cloud of magnetically trapped helium atoms: pairs of colliding atoms interact with one or two laser fields to produce a purely long range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}P{sub 0}) molecule, or a {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) long range molecule. Light shifts in one photon photo-association spectra are measured and studied as a function of the laser polarization and intensity, and the vibrational state of the excited molecule. They result from the light-induced coupling between the excited molecule, and bound and scattering states of the interaction between two metastable atoms. Their analysis leads to the determination of the scattering length a = (7.2 {+-} 0.6) ruling collisions between spin polarized atoms. The two photon photo-association spectra show evidence of the production of polarized, long-range {sup 4}He{sub 2}(2{sup 3}S{sub 1}-2{sup 3}S{sub 1}) molecules. They are said to be exotic as they are made of two metastable atoms, each one carrying a enough energy to ionize the other. The corresponding lineshapes are calculated and decomposed in sums and products of Breit-Wigner and Fano profiles associated to one and two photon processes. The experimental spectra are fit, and an intrinsic lifetime {tau} = (1.4 {+-} 0.3) {mu}s is deduced. It is checked whether this lifetime could be limited by spin-dipole induced Penning autoionization. This interpretation requires that there is a quasi-bound state close to the dissociation threshold in the singlet interaction potential between metastable helium atoms for the theory to match the experiment. (author)

  6. Simple improvements to classical bubble nucleation models

    CERN Document Server

    Tanaka, Kyoko K; Angélil, Raymond; Diemand, Jürg

    2015-01-01

    We revisit classical nucleation theory (CNT) for the homogeneous bubble nucleation rate and improve the classical formula using a new prefactor in the nucleation rate. Most of the previous theoretical studies have used the constant prefactor determined by the bubble growth due to the evaporation process from the bubble surface. However, the growth of bubbles is also regulated by the thermal conduction, the viscosity, and the inertia of liquid motion. These effects can decrease the prefactor significantly, especially when the liquid pressure is much smaller than the equilibrium one. The deviation in the nucleation rate between the improved formula and the CNT can be as large as several orders of magnitude. Our improved, accurate prefactor and recent advances in molecular dynamics simulations and laboratory experiments for argon bubble nucleation enable us to precisely constrain the free energy barrier for bubble nucleation. Assuming the correction to the CNT free energy is of the functional form suggested by T...

  7. Single DNA denaturation and bubble dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Metzler, Ralf [Physics Department, Technical University of Munich, James Franck Strasse, 85747 Garching (Germany); Ambjoernsson, Tobias [Chemistry Department, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Hanke, Andreas [Department of Physics and Astronomy, University of Texas, 80 Fort Brown, Brownsville (United States); Fogedby, Hans C [Department of Physics and Astronomy, University of Arhus, Ny Munkegade, 8000 Arhus C (Denmark)], E-mail: metz@ph.tum.de

    2009-01-21

    While the Watson-Crick double-strand is the thermodynamically stable state of DNA in a wide range of temperature and salt conditions, even at physiological conditions local denaturation bubbles may open up spontaneously due to thermal activation. By raising the ambient temperature, titration, or by external forces in single molecule setups bubbles proliferate until full denaturation of the DNA occurs. Based on the Poland-Scheraga model we investigate both the equilibrium transition of DNA denaturation and the dynamics of the denaturation bubbles with respect to recent single DNA chain experiments for situations below, at, and above the denaturation transition. We also propose a new single molecule setup based on DNA constructs with two bubble zones to measure the bubble coalescence and extract the physical parameters relevant to DNA breathing. Finally we consider the interplay between denaturation bubbles and selectively single-stranded DNA binding proteins.

  8. Bernoulli Suction Effect on Soap Bubble Blowing?

    Science.gov (United States)

    Davidson, John; Ryu, Sangjin

    2015-11-01

    As a model system for thin-film bubble with two gas-liquid interfaces, we experimentally investigated the pinch-off of soap bubble blowing. Using the lab-built bubble blower and high-speed videography, we have found that the scaling law exponent of soap bubble pinch-off is 2/3, which is similar to that of soap film bridge. Because air flowed through the decreasing neck of soap film tube, we studied possible Bernoulli suction effect on soap bubble pinch-off by evaluating the Reynolds number of airflow. Image processing was utilized to calculate approximate volume of growing soap film tube and the volume flow rate of the airflow, and the Reynolds number was estimated to be 800-3200. This result suggests that soap bubbling may involve the Bernoulli suction effect.

  9. Manipulating bubbles with secondary Bjerknes forces

    Energy Technology Data Exchange (ETDEWEB)

    Lanoy, Maxime [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France); Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Derec, Caroline; Leroy, Valentin [Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Tourin, Arnaud [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France)

    2015-11-23

    Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices.

  10. Mechanism of bubble detachment from vibrating walls

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dongjun; Park, Jun Kwon, E-mail: junkeun@postech.ac.kr; Kang, Kwan Hyoung [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of); Kang, In Seok [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)

    2013-11-15

    We discovered a previously unobserved mechanism by which air bubbles detach from vibrating walls in glasses containing water. Chaotic oscillation and subsequent water jets appeared when a wall vibrated at greater than a critical level. Wave forms were developed at water-air interface of the bubble by the wall vibration, and water jets were formed when sufficiently grown wave-curvatures were collapsing. Droplets were pinched off from the tip of jets and fell to the surface of the glass. When the solid-air interface at the bubble-wall attachment point was completely covered with water, the bubble detached from the wall. The water jets were mainly generated by subharmonic waves and were generated most vigorously when the wall vibrated at the volume resonant frequency of the bubble. Bubbles of specific size can be removed by adjusting the frequency of the wall's vibration.

  11. Tube erosion in bubbling fluidized beds

    Energy Technology Data Exchange (ETDEWEB)

    Levy, E.K. [Lehigh Univ., Bethlehem, PA (United States). Energy Research Center; Stallings, J.W. [Electric Power Research Inst., Palo Alto, CA (United States)

    1991-12-31

    This paper reports on experimental and theoretical studies that were preformed of the interaction between bubbles and tubes and tube erosion in fluidized beds. The results are applicable to the erosion of horizontal tubes in the bottom row of a tube bundle in a bubbling bed. Cold model experimental data show that erosion is caused by the impact of bubble wakes on the tubes, with the rate of erosion increasing with the velocity of wake impact with the particle size. Wake impacts resulting from the vertical coalescence of pairs of bubbles directly beneath the tube result in particularly high rates of erosion damage. Theoretical results from a computer simulation of bubbling and erosion show very strong effects of the bed geometry and bubbling conditions on computed rates of erosion. These results show, for example, that the rate of erosion can be very sensitive to the vertical location of the bottom row of tubes with respect to the distributor.

  12. Ostwald Ripening in Multiple-Bubble Nuclei

    CERN Document Server

    Watanabe, Hiroshi; Inaoka, Hajime; Ito, Nobuyasu

    2014-01-01

    The ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 million Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as $t^{-x}$ with scaling exponent $x$. As the initial temperature increases, the exponent changes from $x=3/2$ to $1$, which implies that the growth of bubbles changes from interface-limited (the $t^{1/2}$ law) to diffusion-limited (the $t^{1/3}$ law) growth.

  13. Ostwald ripening in multiple-bubble nuclei.

    Science.gov (United States)

    Watanabe, Hiroshi; Suzuki, Masaru; Inaoka, Hajime; Ito, Nobuyasu

    2014-12-21

    The Ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 × 10(6) Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as t(-x) with scaling exponent x. As the initial temperature increases, the exponent changes from x = 3/2 to 1, which implies that the growth of bubbles changes from interface-limited (the t(1/2) law) to diffusion-limited (the t(1/3) law) growth.

  14. Enhancement of helium exhaust by resonant magnetic perturbation fields at LHD and TEXTOR

    Science.gov (United States)

    Schmitz, O.; Ida, K.; Kobayashi, M.; Bader, A.; Brezinsek, S.; Evans, T. E.; Funaba, H.; Goto, M.; Mitarai, O.; Morisaki, T.; Motojima, G.; Nakamura, Y.; Narushima, Y.; Nicolai, D.; Samm, U.; Tanaka, H.; Yamada, H.; Yoshinuma, M.; Xu, Y.; TEXTOR, the; LHD Experiment Groups

    2016-10-01

    The ability to exhaust helium as the fusion born plasma impurity is a critical requirement for burning plasmas. We demonstrate in this paper that resonant magnetic perturbation (RMP) fields can be used to actively manipulate helium exhaust characteristics. We present results from puff/pump studies at TEXTOR as example for a tokamak with a pumped limiter and from the Large Helical Device (LHD) with the closed helical divertor as example for a heliotron/stellarator device. For LHD, the effective helium confinement time τ p,\\text{He}\\ast is a factor of 7-8 higher in the low and high density regimes explored when compared to TEXTOR discharges. This is attributed to ion root impurity transport which is one particular impurity transport regime assessed experimentally at LHD and which facilitates helium penetration to the plasma core. However, when an edge magnetic island is induced by externally applied RMP fields, τ p,\\text{He}\\ast is decreased by up to 30% and hence τ p,\\text{He}\\ast values closer to those of TEXTOR can be established. The combination of TEXTOR and LHD results suggest that a magnetic island induced by the RMP field in the plasma source region is an important ingredient for improving helium exhaust. The reduction in τ p,\\text{He}\\ast seen is caused by a combination of improved helium exhaust due to an enhanced coupling to the pumping systems, increased outward transport and a reduced fueling efficiency for the helium injected and recycling from the wall elements.

  15. Effect of PEO coating on bubble behavior within a polycarbonate microchannel array: A model for hemodialysis.

    Science.gov (United States)

    Coblyn, Matthew; Truszkowska, Agnieszka; Mohammadi, Mahshid; Heintz, Keely; McGuire, Joseph; Sharp, Kendra; Jovanovic, Goran

    2016-07-01

    Obstruction of fluid flow by stationary bubbles in a microchannel hemodialyzer decreases filtration performance and increases damage to blood cells through flow maldistribution. A polyethylene oxide (PEO)-polybutadiene (PB)-polyethylene oxide surface modification, previously shown to reduce protein fouling and water/air contact angle in polycarbonate microchannel hemodialyzers, can improve microchannel wettability and may reduce bubble stagnation by lessening the resistive forces that compete with fluid flow. In this study, the effect of the PEO-PB-PEO coating on bubble retention in a microchannel array was investigated. Polycarbonate microchannel surfaces were coated with PEO-PB-PEO triblock polymer via radiolytic grafting. Channel obstruction was measured for coated and uncoated microchannels after injecting a short stream of air bubbles into the device under average nominal water velocities of 0.9 to 7.2 cm/s in the channels. The presence of the PEO coating reduced obstruction of microchannels by stationary bubbles within the range of 1.8 to 3.6 cm/s, average nominal velocity. Numerical simulations based on the lattice Boltzmann method indicate that beneficial effects may be due to the maintenance of a lubricating, thin liquid film around the bubble. The determined effective range of the PEO coating for bubble management serves as an important design constraint. These findings serve to validate the multiutility of the PEO-PB-PEO coating (bubble lubrication, biocompatibility, and therapeutic loading). © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 941-948, 2016.

  16. Fermi bubble edges: spectrum and diffusion function

    CERN Document Server

    Keshet, Uri

    2016-01-01

    Current measurements of the $\\gamma$-ray Fermi bubbles (FB) are based on model-dependent tracers, carry substantial systematic uncertainties, show mild spatial variations, and are at some tension with each other. We show that gradient filters pick out the FB edges, found to smoothly connect to the bipolar X-ray structure emanating from the Galactic center, thus supporting the interpretation of the FBs as a Galactic-scale phenomenon. The sharp edges facilitate a direct, model-free measurement of the peripheral FB spectrum. The result is strikingly similar to the full FB-integrated spectrum, softened by a power law of index $\\eta\\simeq (0.2-0.3)$. This is naturally explained, in both hadronic and leptonic models, if cosmic-rays are injected at the edge, and diffuse away preferentially at higher energies $E$. The inferred, FB-averaged diffusion function in the (more plausible) leptonic model, $D(E)\\simeq 10^{29.5}(E/10\\mbox{ GeV})^{0.48\\pm0.02}\\mbox{ cm}^2\\mbox{ s}^{-1}$, is consistent with estimates for Kraichn...

  17. Binary Schemes of Vapor Bubble Growth

    Science.gov (United States)

    Zudin, Yu. B.

    2015-05-01

    A problem on spherically symmetric growth of a vapor bubble in an infi nite volume of a uniformly superheated liquid is considered. A description of the limiting schemes of bubble growth is presented. A binary inertial-thermal bubble growth scheme characterized by such specifi c features as the "three quarters" growth law and the effect of "pressure blocking" in a vapor phase is considered.

  18. ACOUSTIC MEASUREMENTS BUBBLES IN BIOLOGICAL TIESSURE

    Institute of Scientific and Technical Information of China (English)

    CHAHINE Georges L.; TANGUAY Michel; LORAINE Greg

    2009-01-01

    An acoustic based instrument,the ABS Acoustic Bubble Spectrometer(R)(C)(ABS),was investigated for the detection and quantification of bubbles in biological media.These include viscoelastic media(blood),materials of varying density(bone in tissue),non-homogenous distribution of bubbles(intravenous bubbly flow),and bubbles migrating in tissue(decompression sickness,DCS).The performance of the ABS was demonstrated in a series of laboratory experiments.Validation of the code was performed using a viscoelastic polymer solution,Polyox,in which the bubble size distribution and void fraction were determined by ABS measurements and with image analysis of high speed videos.These tests showed that the accuracy of the ABS was not significantly affected by viscoelasticity for bubbles smaller than 200 microns.The ABS detection and measurement of non-homogenous bubble distributions was demonstrated using a bubbly flow through a simulated vein surrounded by tissue.The scatter of acoustic signals due to bones in the acoustic pathway was also investigated.These in-vitro experiments were done using meat(beef)as a tissue simulant.Decompression experiments were done using beef meat which was held underwater at high pressure(9.9 atm)then rapidly decompressed.Bubble size distributions and void fraction calculations in these experiments were then validated using image analysis of high speed video.In addition,preliminary experiments were performed with the US Navy Medical Research Center,demonstrating the utility of the modified ABS system in detecting the evolution of bubbles in swine undergoing decompression sickness(DCS).These results indicate that the ABS may be used to detect and quantify the evolution of bubbles in-vivo and aid in the monitoring of DCS.

  19. Curvature and bubble convergence of harmonic maps

    CERN Document Server

    Kokarev, Gerasim

    2010-01-01

    We explore geometric aspects of bubble convergence for harmonic maps. More precisely, we show that the formation of bubbles is characterised by the local excess of curvature on the target manifold. We give a universal estimate for curvature concentration masses at each bubble point and show that there is no curvature loss in the necks. Our principal hypothesis is that the target manifold is Kaehler.

  20. Shock propagation in polydisperse bubbly flows

    OpenAIRE

    Ando, Keita; Colonius, Tim; Brennen, Christopher E.

    2009-01-01

    The effect of distributed bubble size on shock propagation in homogeneous bubbly liquids is computed using a continuum two-phase model. An ensemble-averaging technique is employed to derive the statistically averaged equations and a finite-volume method is used to solve the model equations. The bubble dynamics are incorporated using a Rayleigh-Plesset-type equation which includes the effects of heat transfer, liquid viscosity and compressibility. For the case of monodispe...

  1. Finite-Amplitude Vibration of a Bubble

    Institute of Scientific and Technical Information of China (English)

    QIAN Zu-Wen; XIAO Ling

    2003-01-01

    The Rayleigh-Plesset equation for bubble vibration is modified. The numerical solution of new equation is obtained by means of the symbolic computation programme. The acceleration of the h'quid on the surface of the bubble, or pressure in the bubble, displays much intense 8-impulse with a very short duration from ns to ps. Suggestions for developing the measurements of sonoluminescence and cavitation fusion (if any) are presented.

  2. Gas Holdups of Small and Large Bubbles in a Large-scale Bubble Column with Elevated Pressure

    Institute of Scientific and Technical Information of China (English)

    JIN Hai-bo; YANG Suo-he; ZHANG Tong-wang; TONG Ze-min

    2004-01-01

    Gas holdups of large bubbles and small bubbles were measured by means of dynamic gas disengagement approach in the pressured bubble column with a diameter of 0. 3 m and a height of 6. 6 m. The effects of superficial gas velocity, liquid surface tension, liquid viscosity andsystem pressure on gas holdups of small bubbles and large bubbles were investigated. The holdup of large bubbles increases and the holdup of small bubbles decreases with an increase of liquid viscosity. Meanwhile, the holdup of large bubbles decreases with increasing the system pressure. A correlation for the holdup of small bubbles was obtained from the experimental data.

  3. ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Bernard A. Toseland

    2000-12-31

    The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large-diameter reactors. Washington University's work during the reporting period involved the implementation of the automated calibration device, which will provide an advanced method of determining liquid and slurry velocities at high pressures. This new calibration device is intended to replace the original calibration setup, which depended on fishing lines and hooks to position the radioactive particle. The report submitted by Washington University contains a complete description of the new calibration device and its operation. Improvements to the calibration program are also discussed. Iowa State University utilized air-water bubble column simulations in an effort to determine the domain size needed to represent all of the flow scales in a gas-liquid column at a high superficial velocity. Ohio State's report summarizes conclusions drawn from the completion of gas injection phenomena studies, specifically with respect to the characteristics of bubbling-jetting at submerged single orifices in liquid-solid suspensions.

  4. Positron acceleration in plasma bubble wakefield driven by an ultraintense laser

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Ya-Juan; Wan, Feng; Sang, Hai-Bo, E-mail: sanghb@bnu.edu.cn; Xie, Bai-Song [Key Laboratory of Beam Technology and Material Modification of Ministry of Education, and College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)

    2016-01-15

    The dynamics of positrons accelerating in electron-positron-ion plasma bubble fields driven by an ultraintense laser is investigated. The bubble wakefield is obtained theoretically when laser pulses are propagating in the electron-positron-ion plasma. To restrict the positrons transversely, an electron beam is injected. Acceleration regions and non-acceleration ones of positrons are obtained by the numerical simulation. It is found that the ponderomotive force causes the fluctuation of the positrons momenta, which results in the trapping of them at a lower ion density. The energy gaining of the accelerated positrons is demonstrated, which is helpful for practical applications.

  5. Injection MD

    CERN Document Server

    Bartmann, W; Bracco, C; Drosdal, L; Gianfelice, E; Goddard, B; Kain, V; Papaphilippou, Y; Vanbavinckhove, G

    2012-01-01

    This note summarizes the results obtained at injection during the 2nd MD block and the floating MD block in July. Highlights are presented for injection in the LHC with the Q20 SPS optics, influence of the supercycle and injection with 25 ns bunch spacing. Beams were successfully injected into the LHC using the Q20 optics [1, 3]. Small corrections were needed to steer the beam in the transfer lines. Dispersion measurements were conducted for both beams. The horizontal normalized dispersion in TI2 was a factor 2 smaller for Q20 with respect to Q26, for TI8 on the other hand the opposite was observed. The results for injection loss dependency on super cycle composition show only a small increase in losses for beam 2. The losses observed must therefore mainly come from other sources such as shot-by-shot stability or quality of scraping. For the injection with 25 ns bunch spacing bunches were injected for both beams. For B1 up to the maximum of 288 bunches. For B2 on the other only up to 144 bunches were injected...

  6. Spectroscopic characteristic of conical bubble luminescence

    Institute of Scientific and Technical Information of China (English)

    Chen Qi-Dai; Fu Li-Min; Ai Xi-Cheng; Zhang Jian-Ping; Wang Long

    2005-01-01

    The conical bubble sonoluminescence (CBSL) from the collapse of the bubble was observed in an improved Utube apparatus. The emitted light energy of a single CBSL flash was measured to be ~ 1.4mJ. The pulse width was about 100μs. The spectra of luminescence were continuum superimposed with the spectral bands from the excitedstate C2, CN and CH. The CBSL provides a link between the light emission of the single-bubble and the multi-bubble sonoluminescence (SBSL and MBSL).

  7. Band gaps in bubble phononic crystals

    Directory of Open Access Journals (Sweden)

    V. Leroy

    2016-12-01

    Full Text Available We investigate the interaction between Bragg and hybridization effects on the band gap properties of bubble phononic crystals. These latter consist of air cavities periodically arranged in an elastomer matrix and are fabricated using soft-lithography techniques. Their transmission properties are affected by Bragg effects due to the periodicity of the structure as well as hybridization between the propagating mode of the embedding medium and bubble resonance. The hybridization gap survives disorder while the Bragg gap requires a periodic distribution of bubbles. The distance between two bubble layers can be tuned to make the two gaps overlap or to create a transmission peak in the hybridization gap.

  8. Bubble burst as jamming phase transition

    CERN Document Server

    Nishinari, Katsuhiro; Saito, Yukiko Umeno; Watanabe, Tsutomu

    2010-01-01

    Recently research on bubble and its burst attract much interest of researchers in various field such as economics and physics. Economists have been regarding bubble as a disorder in prices. However, this research strategy has overlooked an importance of the volume of transactions. In this paper, we have proposed a bubble burst model by focusing the transactions incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation by comparing data taken from US housing market. Our result suggests that the transaction could be a driving force of bursting phenomenon.

  9. Living Near de Sitter Bubble Walls

    OpenAIRE

    Cho, Jin-Ho; Nam, Soonkeon

    2006-01-01

    We study various bubble solutions in string/M theories obtained by double Wick rotations of (non-)extremal brane configurations. Typically, the geometry interpolates de Sitter space-time times non-compact extra-dimensional space in the near-bubble wall region and the asymptotic flat Minkowski space-time. These bubble solutions provide nice background geometries reconciling string/M theories with de Sitter space-time. For the application of these solutions to cosmology, we consider multi-bubbl...

  10. Shock Wave Emissions of a Sonoluminescing Bubble

    CERN Document Server

    Holzfuss, J; Billó, M; Holzfuss, Joachim; Ruggeberg, Matthias; Billo, Andreas

    1998-01-01

    A single bubble in water is excited by a standing ultrasound wave. At high intensity the bubble starts to emit light. Together with the emitted light pulse, a shock wave is generated in the liquid at collapse time. The time-dependent velocity of the outward-travelling shock is measured with an imaging technique. The pressure in the shock and in the bubble is shown to have a lower limit of 5500 bars. Visualization of the shock and the bubble at different phases of the acoustic cycle reveals previously unobserved dynamics during stable and unstable sonoluminescence.

  11. In Beam Tests of Implanted Helium Targets

    CERN Document Server

    McDonald, J E; Ahmed, M W; Blackston, M A; Delbar, T; Gai, M; Kading, T J; Parpottas, Y; Perdue, B A; Prior, R M; Rubin, D A; Spraker, M C; Yeomans, J D; Weissman, L; Weller, H R; Delbar, Th.; Conn, LNS/U; Duke, TUNL/

    2006-01-01

    Targets consisting of 3,4He implanted into thin aluminum foils (approximately 100, 200 or 600 ug/cm^2) were prepared using intense (a few uA) helium beams at low energy (approximately 20, 40 or 100 keV). Uniformity of the implantation was achieved by a beam raster across a 12 mm diameter tantalum collimator at the rates of 0.1 Hz in the vertical direction and 1 Hz in the horizontal direction. Helium implantation into the very thin (approximately 80-100 ug/cm^2) aluminum foils failed to produce useful targets (with only approximately 10% of the helium retained) due to an under estimation of the range by the code SRIM. The range of low energy helium in aluminum predicted by Northcliffe and Shilling and the NIST online tabulation are observed on the other hand to over estimate the range of low energy helium ions in aluminum. An attempt to increase the amount of helium by implanting a second deeper layer was also carried out, but it did not significantly increase the helium content beyond the blistering limit (ap...

  12. Subcutaneous Injections

    DEFF Research Database (Denmark)

    Thomsen, Maria

    This thesis is about visualization and characterization of the tissue-device interaction during subcutaneous injection. The tissue pressure build-up during subcutaneous injections was measured in humans. The insulin pen FlexTouchr (Novo Nordisk A/S) was used for the measurements and the pressure...... build-up was evaluated indirectly from the changes in the flow rate between subcutaneous injections and air injections. This method enabled the tissue counter pressure to be evaluated without a formal clinical study approval. The measurements were coupled to a model for the pressure evolution...... in subcutaneous tissue, based on mass conservation and flow in a porous medium. From the measurements the flow permeability and bulk modulus of the tissue were determined. In the adipose tissue the drug forms a bolus from where it is absorbed by the blood capillaries. The spatial distribution of the injected...

  13. Interaction of a bubble and a bubble cluster in an ultrasonic field

    Institute of Scientific and Technical Information of China (English)

    Wang Cheng-Hui; Cheng Jian-Chun

    2013-01-01

    Using an appropriate approximation,we have formulated the interacting equation of multi-bubble motion for a system of a single bubble and a spherical bubble cluster.The behavior of the bubbles is observed in coupled and uncoupled states.The oscillation of bubbles inside the cluster is in a coupled state.The numerical simulation demonstrates that the secondary Bjerknes force can be influenced by the number density,initial radius,distance,driving frequency,and amplitude of ultrasound.However,if a bubble approaches a bubble cluster of the same initial radii,coupled oscillation would be induced and a repulsive force is evoked,which may be the reason why the bubble cluster can exist steadily.With the increment of the number density of the bubble cluster,a secondary Bjerknes force acting on the bubbles inside the cluster decreases due to the strong suppression of the coupled bubbles.It is shown that there may be an optimal number density for a bubble cluster which can generate an optimal cavitation effect in liquid for a stable driving ultrasound.

  14. Retention behaviour of deuterium and helium in beryllium under single D{sup +} and dual He{sup +}/D{sup +} exposure

    Energy Technology Data Exchange (ETDEWEB)

    Mateus, R., E-mail: rmateus@ipfn.ist.utl.pt; Franco, N.; Alves, E.

    2015-10-15

    Beryllium plates were irradiated with single deuterium and dual helium plus deuterium energetic ions with fluences of 1e17 ions/cm{sup 2} and 5e17 ions/cm{sup 2}, and annealed afterwards in vacuum at 523, 723 and 923 K for 10 min. The surfaces were analysed with electron microscopy, X-ray diffraction and ion beam techniques. The results are consistent with well-established outcomes arising from helium irradiation, evidencing that the degassing mechanisms depend of the microstructure evolution. They point to a supersaturation of the implanted zone by helium in the samples exposed to fluences of 5e17 He{sup +}/cm{sup 2}. In this case, it is observed a simultaneous release of helium and deuterium at lower temperatures, evidencing the formation of a porous microstructure from primary gas bubbles. In the absence of a porous structure, the helium degassing occurs at a higher temperature range, while it depends on the migration of helium-vacancy clusters. The supersaturation of beryllium was never reached under single deuterium irradiation, being the release of deuterium controlled by ion-induced trap sites.

  15. Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures.

    Science.gov (United States)

    Randsoe, Thomas; Hyldegaard, Ole

    2012-08-01

    The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing and the tissue nitrogen pressure. To quantify the contribution of oxygen to bubble growth at altitude, micro oxygen bubbles (containing 0% nitrogen) were injected into the adipose tissue of rats depleted from nitrogen by means of preoxygenation (fraction of inspired oxygen = 1.0; 100%) and the bubbles studied at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently until they disappeared from view at a net disappearance rate (0.02 mm(2) × min(-1)) significantly faster than for similar bubbles at 25 kPa altitude (0.01 mm(2) × min(-1)). At 25 kPa, most bubbles initially grew for 2-40 min, after which they shrank and disappeared. Four bubbles did not disappear while at 25 kPa. The results support bubble kinetic models based on Fick's first law of diffusion, Boyles law, and the oxygen window effect, predicting that oxygen contributes more to bubble volume and growth during hypobaric conditions. As the effect of oxygen increases, the lower the ambient pressure. The results indicate that recompression is instrumental in the treatment of aDCS.

  16. Evolution of dopant-induced helium nanoplasmas

    CERN Document Server

    Krishnan, S R; Fechner, L; Sharma, V; Kremer, M; Fischer, B; Camus, N; Pfeifer, T; Jha, J; Krishnamurthy, M; Schroeter, C -D; Ullrich, J; Stienkemeier, F; Moshammer, R; Fennel, Th; Mudrich, M

    2012-01-01

    Two-component nanoplasmas generated by strong-field ionization of doped helium nanodroplets are studied in a pump-probe experiment using few-cycle laser pulses in combination with molecular dynamics simulations. High yields of helium ions and a pronounced, droplet size-dependent resonance structure in the pump-probe transients reveal the evolution of the dopant-induced helium nanoplasma. The pump-probe dynamics is interpreted in terms of strong inner ionization by the pump pulse and resonant heating by the probe pulse which controls the final charge states detected via the frustration of electron-ion recombination.

  17. Particle detection by evaporation from superfluid helium

    Energy Technology Data Exchange (ETDEWEB)

    Bandler, S.R.; Lanou, R.E.; Maris, H.J.; More, T.; Porter, F.S.; Seidel, G.M.; Torii, R.H. (Department of Physics, Brown University, Providence, Rhode Island 02912 (United States))

    1992-04-20

    We report the first experiments in which 5-MeV alpha particles are detected via evaporation from a bath of superfluid helium. The {alpha} excites phonons and rotons in the liquid helium, and these excitations are sufficiently energetic to evaporate helium atoms when they reach the free surface of the liquid. The approximate overall efficiency of this process has been determined, and we compare this with expectations. We have also been able to detect evaporation induced by a flux of {gamma}'s from a {sup 137}Cs source.

  18. Evolution of the defect structures on helium implanted copper and nickel

    Energy Technology Data Exchange (ETDEWEB)

    Tsukuda, Noboru; Ehrhart, P.; Jaeger, W.; Gadalla, A.A.

    1987-01-01

    Helium in the range of 0 - 6 MeV is implanted uniformly in high-purity single crystals of copper and nickel (about 10 ..mu..m thickness) to concentrations of up to 3 at.%. Observation is performed to determine the effects of implantation on electric resistance, material length and x-ray diffraction profile. Based on the results obtained, examination is made on the induced vacancies, formation process of interstitial atom clusters and helium bubbles. Differential dilatometry shows that most interstitial atoms disapear at an early stage of implantation due to recombination and absorption into dislocations, while vacancies tend to remain in the form of stable clusters. Above a helium concentration of 0.2%, the number of dislocations increases, though large structural changes do not take place. Most of the vacancies form small He-V complexes which cannot be seen under TEM. The concentration ratio C(He)/C(v) in these complexes is smaller than unity. These stable cluster nuclei are formed at room temperature because of the small mobility of vacancies. They grow gradually as implantation is continued. Both electric resistance and volume increases linearly with implantation at early stages. Then the rate of change gradually decreases but does not become zero. The x-ray diffraction profile shows an extreme broadening, which cannot be explained in terms of the increase in the number of dislocations alone. (Nogami, K.).

  19. Helium implanted Eurofer97 characterized by positron beam Doppler broadening and Thermal Desorption Spectroscopy

    Science.gov (United States)

    Carvalho, I.; Schut, H.; Fedorov, A.; Luzginova, N.; Desgardin, P.; Sietsma, J.

    2013-11-01

    Reduced Activation Ferritic/Martensitic steels are being extensively studied because of their foreseen application in fusion and Generation IV fission reactors. To produce irradiation induced defects, Eurofer97 samples were implanted with helium at energies of 500 keV and 2 MeV and doses of 1 × 1015-1016 He/cm2, creating atomic displacements in the range 0.07-0.08 dpa. The implantation induced defects were characterized by positron beam Doppler Broadening (DB) and Thermal Desorption Spectroscopy (TDS). Results show that up to ˜600 K peaks that can be attributed to He desorption from overpressured HenVm (n > m) clusters and vacancy assisted mechanism in the case of helium in the substitutional position. The temperature range 600-1200 K is related to the formation of larger clusters HenVm (n < m). The dissociation of the HeV and the phase transition attributed to a sharp peak in the TDS spectra at 1200 K. Above this temperature, the release of helium from bubbles is observed.

  20. Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

    Science.gov (United States)

    Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

    1999-01-01

    The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a