1,160 research outputs found
Development of an apparatus for obtaining molecular beams in the energy range from 2 to 200 eV
The formation and detection of molecular beams obtained by charge exchange from a low-energy ion source is discussed. Dispersion in energy of the ion source was measured and problems concerning detection of neutral beams were studied. Various methods were used, specifically secondary electron emissivity of a metallic surface and ionization of a gas target with a low ionization voltage. The intensities of neutral beams as low as 10 eV are measured by a tubular electron multiplier and a lock-in amplifier
Bubble formation at a flexible orifice with liquid cross-flow
In waste water treatment, biological processes for denitrification and nitrification are
performed using oxidation ditches. In these reactors, the mixing and the aeration functions are
dissociated: a bubble cloud is generated from flexible membrane spargers and is subjected to
a horizontal liquid flow. The objective of this paper is to study the effects of the liquid crossflow
on the bubble formation at a single flexible orifice in water. The several forces acting on
the forming bubble have been modelled in order to understand the dynamics of the bubble
growth and detachment. The bubble detachment is controlled by the drag force due to the
liquid motion and not by the buoyancy force. The experimental analysis of the bubble growth
has shown that, under liquid cross-flow conditions, the bubbles move downstream and are
flattened during their growth (position of the bubble centre of gravity, bubble inclination
angle). The bubbles spread over the orifice surface, and the advancing and the receding
bubble angles were measured. The detached bubbles have significantly smaller sizes and
higher frequencies when compared to bubble formation under quiescent liquid conditions
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