6,820 research outputs found
Separation of alcohols from organic liquid mixtures by pervaporation
In the chemical industry, distillation is generally the preferred technique to separate a liquid mixture. However some liquid mixtures such as azeotropic mixtures, close-boiling hydrocarbons, and various isomers are difficult to separate by simple distillation. For the separation of these mixtures normally techniques like extractive or azeotropic distillation and liquid-liquid extraction are used. The relatively high energy consumption for these processes has encouraged the development of new, less energy-consuming separation processes such as pervaporation.\ud
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In recent years, the pervaporation process was actively studied for the separation of organic-organic liquid mixtures. This may be considered as a major application area for pervaporation in the chamical processing industry.\ud
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In this thesis, the separation of alcohols from non-polar solvents like toluene and methyl tert-butyl ether by pervaporation is discussed
Productivity of Solar Flares and Magnetic Helicity Injection in Active Regions
The main objective of this study is to better understand how magnetic
helicity injection in an active region is related to the occurrence and
intensity of solar flares. We therefore investigate magnetic helicity injection
rate and unsigned magnetic flux, as a reference. In total, 378 active regions
are analyzed using /MDI magnetograms. The 24-hour averaged helicity
injection rate and unsigned magnetic flux are compared with the flare index and
the flare-productive probability in next 24 hours following an measurement. In
addition, we study the variation of helicity over a span of several days around
the times of the 19 flares above M5.0 which occurred in selected strong
flare-productive active regions. The major findings of this study are: (1) for
a sub-sample of 91 large active regions with unsigned magnetic fluxes in the
range from 3 to 5 10 Mx, there is a difference in magnetic
helicity injection rate between flaring active regions and non-flaring active
regions by a factor of 2; (2) the C-flare-productive probability as a
function of helicity injection displays a sharp boundary between
flare-productive active regions and flare-quiet ones; (3) the history of
helicity injection before all the 19 major flares displayed a common
characteristic: a significant helicity accumulation of (3-45) 10
Mx during a phase of monotonically increasing helicity over 0.5 to
2 days. Our results support the notion that helicity injection is important in
flares, but it is not effective to use it alone for the purpose of flare
forecast. It is necessary to find a way to better characterize the time history
of helicity injection as well as its spatial distribution inside active
regions.Comment: 22 pages, 5 figures, ApJ, in pres
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