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41.
42.
Z.M. Zhong J. Chen P. Zhong J.B. Wu 《The International Journal of Advanced Manufacturing Technology》2006,28(9):855-862
As the result of vibration emission in air, a machine sound signal carries important information about the working condition
of machinery. But in practice, the sound signal is typically received with a very low signal-to-noise ratio. To obtain features
of the original sound signal, uncorrelated sound signals must be removed and the wavelet coefficients related to fault condition
must be retrieved. In this paper, the blind source separation technique is used to recover the wavelet coefficients of a monitored
source from complex observed signals. Since in the proposed blind source separation (BSS) algorithms it is generally assumed
that the number of sources is known, the Gerschgorin disk estimator method is introduced to determine the number of sound
sources before applying the BSS method. This method can estimate the number of sound sources under non-Gaussian and non-white
noise conditions. Then, the partial singular value analysis method is used to select these significant observations for BSS
analysis. This method ensures that signals are separated with the smallest distortion. Afterwards, the time-frequency separation
algorithm, converted to a suitable BSS algorithm for the separation of a non-stationary signal, is introduced. The transfer
channel between observations and sources and the wavelet coefficients of the source signals can be blindly identified via
this algorithm. The reconstructed wavelet coefficients can be used for diagnosis. Finally, the separation results obtained
from the observed signals recorded in a semi-anechoic chamber demonstrate the effectiveness of the presented methods . 相似文献
43.
Ronak A. Kapadia Simant R. Upreti Ali Lohi Ioannis Chatzis 《Journal of Petroleum Science and Engineering》2006,51(3-4):214-222
In this work, a mathematical model is developed and simulated to determine gas dispersion along with solubility during the vapor extraction (Vapex) of live oil from a laboratory scale physical model. The physical model is a rectangular block of homogenous porous medium saturated with heavy oil and bitumen. At a given temperature and pressure, the block is initially exposed on its side to a solvent gas, which diffuses into the medium and gets absorbed. The absorption of gas reduces the viscosity of heavy oil and bitumen causing it to drain under gravity. The low-viscosity “live oil” is produced at the bottom of the porous block. The production of live oil with time is accompanied by the shrinkage of oil in the block as well as its increased exposure to gas from top. These phenomena of Vapex are described by the mathematical model, which is used to calculate live oil production with various values of gas solubility and dispersion. Their optimal values are determined for the vapor extraction of Cold Lake bitumen with butane by matching calculated live oil production with its experimental values published earlier. 相似文献
44.
We studied the surface deformations affecting the southeastern sector of the Po Plain sedimentary basin, in particular the area of Bologna. To this aim an advanced DInSAR technique, referred to as DInSAR-SBAS (Small BAseline Subset), has been applied. This technique allows monitoring the temporal evolution of a deformation phenomenon, via the generation of mean deformation velocity maps and displacement time series from a data set of acquired SAR images. In particular, we have processed a set of SAR data acquired by the European Remote Sensing Satellite (ERS) sensors and compared the achieved results with optical levelling measurements, assumed as reference. The surface displacements detected by DInSAR SBAS from 1992 to 2000 are between 10 mm/year in the historical part of Bologna town, and up to 59 mm/year in the NE industrial and agricultural areas. Former measurements from optical levelling referred to 1897 show 2-3 mm/year vertical movements. This trend of displacement increased in the second half of the 20th century and the subsidence rate reached 60 mm/year. We compared the more recent levelling campaigns (in 1992 and late 1999) and DInSAR results from 1992 to 1999. The standard deviation of the difference between levelling data, projected onto the satellite Line Of Sight, and DInSAR results is 2 mm/year. This highlights a good agreement between the measurements provided by two different techniques. The explanation of soil movements based on interferometric results, ground data and geological observations, allowed confirming the anthropogenic cause (surface effect due to the overexploitation of the aquifers) and highlights a natural, tectonic, subsidence. 相似文献
45.
正交实验优选盐生藻多糖的提取工艺 总被引:1,自引:0,他引:1
以盐生藻为原料,盐生藻多糖得率为指标,运用稀酸、稀碱和蒸馏水为提取剂提取盐生藻多糖,得出合适的提取剂为稀酸.进一步的正交实验表明,盐生藻多糖的最适提取工艺为:提取75min,pH=4,固液比为1∶70,温度为95℃. 相似文献
46.
47.
Novel calix[4]arene‐poly(ethylene glycol) crosslinked polymer (CCP) has been synthesized by the polycondensation reaction between a p‐tert‐butylcalix[4]arene derivative and dihydroxyl capped poly(ethylene glycol) (DHPEG, Mn = 1000) catalyzed by neodymium tosylate. The hydrogel, consisted of 66.9% water and 33.1% CCP, can selectively extract aromatic organic molecules from aqueous solution according to the diameter of the guest molecules, which infers that the diameter of the calix[4]arene cavity is about 5.4 Å and the conformation of calix[4]arene units altered from cone conformation to 1,3‐alternate conformation during the polycondensation reaction. Furthermore, CCP can also adsorb naphthalene from gas phase, showing much higher capacity than active carbon does, which may have some potential applications in the field of separation and environment protection. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
48.
49.
Separations through reactions can provide reliable and economically viable alternatives to established methods of separation,
particularly for close boiling substances. New strategies in ‘Dissociation Extraction’ and ‘Dissociation Extractive Crystallization’
for separation of close boiling acidic/basic mixtures have been highlighted. Separations with aqueous solutions of hydrotrope
and aqueous micellar solutions have been brought out. Separations by membranes with facilitated transport is potentially attractive.
This paper is dedicated to Dr L K Doraiswamy on his sixtieth birthday. 相似文献
50.
Anna Michalska Alicja Ceglińska Henryk Zieliński 《European Food Research and Technology》2007,225(3-4):545-551
Rye flours with extraction rate of 100% (wholemeal flour), 95% (brown flour), 90% (brown flour) and 70% (light flour) were
prepared in order to study the relation between flour extraction rates and content of bioactive compounds. The following compounds
were analysed: total phenolic compounds (TPC), total flavonoids (TF), inositol hexaphosphate (IP6), reduced (GSH) and oxidized
(GSSG) glutathione, tocopherols (T) and tocotrienols (T3). The reduced/oxidized glutathione status (GSH/GSSG) of the flours
was examined as a potential index of flour resistance against oxidative stress. The following observations were made in relation
to the flour extraction rates and bioactive compounds contents: (a) milling process caused decrease in content in TPC, TF,
IP6, GSH and GSSG, T and T3, (b) the most resistant against oxidation processes were suggested a brown flours, then light
and finally wholemeal flour, (c) the ratio of tocotrienols to tocopherols (T3/T) was the highest in rye flours with extraction
rate of 100–90% whereas light flour was the poorest source of tocopherols and tocotrienols. The provided data support current
trend to increase number of rye products from wholemeal or brown flours. 相似文献