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排序方式: 共有775条查询结果,搜索用时 46 毫秒
721.
Kamel Bouallegue Tamara Allaf Colette Besombes Rached Ben Younes Karim Allaf 《Arabian Journal of Chemistry》2019,12(8):2398-2410
Accelerated Solvent Extraction (ASE) and Dynamic Maceration (DM) were used with n-hexane to study the extraction of oil from date seed powders with different particle sizes. The intensification was studied with instant controlled pressure drop (DIC) as texturing pretreatment. DM yields increased from 4.57% to 10.49 ± 0.05% dry–dry basis (ddb) when particle size decreased from 1.4 to 0.2 mm. For coarsely grounded seed powder, ASE oil yields were 11.35 ± 0.05% ddb and 14.15% ddb for untreated and DIC date-seeds, respectively. Optimized DIC pretreatment allowed the smallest particle size powder to get 15.2 ± 0.05% ddb as ASE yields, while the 2-h DM yields increased from 4.67 to 11.62 ± 0.05% ddb for particle size decreased from 1.4 to 0.2 mm, respectively. Fundamental analysis of various powders was achieved through washing–diffusion phenomenological model. DIC texturing implied higher washing stage, with relative starting accessibility %δYs of 70% against 55% for untreated particles. Consequently, the diffusion stage time was dramatically reduced, without great modification of effective diffusivity Deff value. Therefore, DIC ground seeds greatly enhanced the mass transfer mechanism. The evaluation of starting accessibility δYs enables to establish an empirical relationship between δYs and particle diameter δYs = f(D). Finally, DIC texturing did not imply any modification of the lipid profile. 相似文献
722.
Two new renormalization schemes for conductivity upscaling in heterogeneous media are presented. The schemes follow previous
ones by performing the renormalization over square cells of size 2
d
with d being the dimensionality. Contrasting with previous schemes, the two-dimensional scheme makes use of the exact 2 × 2 block-conductivity.
On the basis of the structure of the exact two-dimensional block-conductivity, an analogous three-dimensional scheme is proposed.
The new schemes are tested on a number of benchmark problems and are shown to be significantly more accurate than existing
schemes. 相似文献
723.
A new, simple and sensitive spectrofluorimetric method for the determination of salicylic acid (λex = 315 nm, λem = 408 nm) using As(III) as a sensitizing reagent has been investigated by measuring the increase of fluorescence intensity of salicylic acid due to the complexation of As(III)-salicylic acid in presence of sodium dodecyl sulfate (SDS) 10−3 M. Under optimum conditions, a significant relationship was obtained between the fluorescence intensity and salicylic acid concentration. A linear calibration curve was obtained in the range 13.8-13812 μg l−1 with product-moment correlation coefficient (R) 0.99985 and detection limit 4.2 μg l−1. The R.S.D. is 2.35% (n = 5).The method was applied successfully to the determination of salicylic acid in human serum. 相似文献
724.
The effects of dispersion in the highly birefringent fiber Bragg grating reflectors of a polarimetric elliptical-core fiber laser sensor are experimentally and theoretically investigated. The laser sensor is designed to measure fluid pressure. It is experimentally and theoretically shown that the wavelength-dependent phase shifts in the gratings can be employed to remove the near degeneracy of the polarization mode beat frequencies of a given order, which substantially improves the resolution of the sensor. A resolution of a few parts in 10(6) of the free spectral range of the laser is demonstrated. 相似文献
725.
Karim TRABELSI 《数学年刊B辑(英文版)》2006,27(4):379-392
The classical equations of a nonlinearly elastic plane membrane made of Saint Venant-Kirchhoff material have been justified by Fox, Raoult and Simo (1993) and Pantz (2000). We show that, under compression, the associated minimization problem admits no solution. The proof is based on a result of non-existence of minimizers of non-convex functionals due to Dacorogna and Marcellini (1995). We generalize the application of their result from plane elasticity to three-dimensional plane membranes. 相似文献
726.
We study the class of those locally radial stratified spaces which are (C)–regular for standard control functions. These spaces generalise Whitney stratified spaces, but are shown to have the same
topological and metric properties. The weakly Whitney stratified spaces that we have introduced recently form an intermediate
class between Whitney stratified spaces and these locally radial (C)–regular spaces.
Received: 14 January 2000 / Revised version: 27 November 2002
Published online: 20 March 2003
Mathematics Subject Classification (2000): 58A35, 58C35, 26B20 相似文献
727.
728.
729.
730.
In this paper we study properties of bilinear maps of order bounded variation. Theorems of preservation of properties in passage
to the triadjoint and the tensor product are presented. 相似文献