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41.
On the reliability of unsaturated hydraulic conductivity calculated from the moisture retention curve 总被引:7,自引:0,他引:7
In comparison with direct measurements of unsaturated hydraulic conductivity, the methods of calculations from the moisture retention curve are attractive for their fast and simple use and low cost. These are the main reasons for their increasing use, mainly in spatial variability studies. On the other hand, it is known that their applicability is limited. The possibility of the use of the retention curve to indirectly determine hydraulic conductivities is analyzed as follows. The theoretical derivation of the relationK(h) – (h) is briefly discussed with regards to potential sources of inaccuracy. The sensitivity of the algorithm forK(h) calculation is studied as a response to possible inaccuracies in the retention curve determination. Conclusions about the usability of calculated hydraulic conductivities are drawn. 相似文献
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M. Lindinger St. Becker G. Bollen K. Dasgupta R. Jertz H. -J. Kluge L. Schweikhard M. Vogel K. Lützenkischen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):441-443
Doublet mass measurements of the isobars28Si3 and12C7 are performed by use of a Penning trap mass spectrometer and the Fourier transform ion cyclotron resonance (FT-ICR). The carbon and silicon cluster ions are produced by laser ablation. Results of these preliminary measurements are presented. 相似文献
44.
Tran Quang Minh Léon Christiaens Pierre Grandclaudon Alain Lablache-Combier 《Tetrahedron》1977,33(17):2225-2229
Photoirradiated in presence of acetophenone, benzo[b]selenophene and its 3-methyl derivative add to dimethyl acetylenedicarboxylate. In each ease, the primary reaction product is unstable and has not been isolated. Photoexeited in its triplet state (the energy of which is in the neighbourhood of 69 ) benzo[b]selenophene and its 2- and 3-methyl, 2,3 dimethyl, 3 acetoxy and 2-methyl-3-acetoxy derivatives add to 1,2 dichloroethylene leading to cyclobutanes. Neither cyclo-addition occurs in absence of photosensitiser. Single-crystal X-ray analysis gave the structures of the two adducts of 3-acetoxybenzo[b]selenophene with trans-1,2-dichloroethylene. In both compounds the chlorine atoms are trans. 相似文献
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Jocelyn Jalbert Roland Gilbert Pierre Tétreault Brigitte Morin Denise Lessard-Déziel 《Cellulose (London, England)》2007,14(4):295-309
In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by
the ageing of oil-impregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative
conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60–120 °C and moisture
of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the
number of ruptured 1,4-β-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded
(TU) Kraft paper), was established for the first time in this field. Ageing at 130 °C of model compounds of the Kraft paper
constituents (α-cellulose, hemicellulose and lignin) and two cellulosic breakdown by-products (D-(+)-glucose and 1,6-anhydro-β-d-glucopyranose) confirmed that the α-cellulose degradation was mostly responsible for the presence of this molecule in the
system. Furthermore, additional 130 °C-tests with six different papers and pressboard samples under a tight control of initial
moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-β-glucosidic bond of the molecular
chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing
transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of
equipment, confirming the potential for this application. Lastly, the tests have shown that oil-oxidation by-products and
TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential
over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with
2-furfuraldehyde, which is the current reference in the domain. 相似文献