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排序方式: 共有54条查询结果,搜索用时 296 毫秒
1.
Modified smectitic Tunisian clays used in the formulation of high performance lubricating greases 总被引:1,自引:0,他引:1
Two smectitic Tunisian clays were organically modified by exchange reaction with dioctadecyl dimethylammonium chloride (DODMA) and hexadecyl benzyl dimethylammonium chloride (HBDMA). The resulting organoclays were used in the formulation of lubricating greases. The results of the performance tests applied to the obtained greases showed that their physicochemical and mechanical characteristics are in conformity with the extreme-pressure (EP) greases specifications. The obtained greases present good EP properties with only 0.5% EP additives. The smectitic clays used could constitute a raw material in the formulation of high performance lubricating greases. 相似文献
2.
In this paper, we investigate two different prefiltering strategies, i.e., multiple input multiple output (MIMO) channel shortening and MIMO whitened matched filtering, to decode iteratively a space time bit interleaved coded modulation transmitted over MIMO block fading intersymbol interference channels using a trellis-based post-detector. Indeed, resorting to such front-ends allows significant complexity gain when compared to the optimal maximum a posteriori-based turbo-receiver. While those two approaches have been exhaustively visited in the past, their fair comparison in terms of trade-off between complexity and performance has – to our knowledge – never been tackled before. This paper aims at giving some valuable insights about the respective benefits of these two prefiltering methods with respect to the channel characteristics and overall receiver complexity. 相似文献
3.
Hybrid materials consisting of oxygen plasma-treated multiwalled carbon nanotubes decorated with metal nanoparticles (e.g., Rh, Pd, Au or Ni) can be tailored for the recognition of benzene vapors with high sensitivity and selectivity. Metal nanoparticles donate or accept a significant amount of charge upon adsorption of a target molecule, so as to affect electron transport in the nanotube. The plasma treatment enables the cleaning, activation, functionalization and metal decoration of carbon nanotubes in a single step, which offers enormous flexibility for tuning the interfacial properties of the resulting hybrid materials. When combined in a microsensor array operating at room temperature, the use of benzene-sensitive and benzene-insensitive metal-decorated multiwalled carbon nanotubes can provide selective detection of benzene at trace levels with a detection limit below 50 ppb. 相似文献
4.
Optimisation of the critical medium components for better growth of Picochlorum sp. and the role of stressful environments for higher lipid production 下载免费PDF全文
5.
N. Ben Sedrine C. BouhafsM. Schubert J.C. HarmandR. Chtourou V. Darakchieva 《Thin solid films》2011,519(9):2838-2842
Spectroscopic ellipsometry from 0.73 to 4.75 eV was used to study the optical properties of epitaxial GaAs0.9-xNxSb0.1 layers with x = 0.00, 0.65, 1.06, 1.45 and 1.90%. The ellipsometric experimental spectra were fitted using a multilayer model employing the model dielectric function to describe the GaAs0.9-xNxSb0.1 optical response. We have identified the Γ-point E0, E+, and E# transitions of GaAs0.9-xNxSb0.1 and have determined the effect of nitrogen on the respective transition energies. We have demonstrated that a lower N content can provide an equal E+-E0 energy splitting for GaAs0.9-xNxSb0.1 with respect to GaAs1-xNx. 相似文献
6.
Mohamed Chtourou Emna Ammar Moncef Nasri Khaled Medhioub 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(8):869-878
This study deals with the degradation of phenolic compounds in olive oil mill waste; a highly polluting material in olive oil‐producing countries because of its abundance and the toxicity of its phenolic compound content. This investigation confirms the ability of an isolated yeast, identified as Trichosporon cutaneum, to degrade phenolic compounds extracted from olive mill waste water (OMW). The yeast was adapted to the OMW by an enrichment culture. The results of this biotransformation were a decrease in the phenolic content and hence a reduction in the phytotoxic effects of the effluent after the yeast treatment. The kinetic growth of the isolated yeast on phenol over a range of concentrations (0.3–3.0 g dm?3) was studied. The ability of the strain to assimilate simple monomeric phenols and alkyl phenols, at a concentration of 1 g dm?3, in a synthetic liquid medium used as the sole carbon source was investigated in a batch culture. The aromatic ring cleavage pathway occurred in the yeast through catechol oxidation. Using various concentrations of ethyl acetate extract from OMW as the sole carbon source, the yeast exhibited growth on the substrate up to 7 g dm?3 equivalent of phenols. A significant reduction of COD after the treatment of the OMW extract by the yeast isolate was noticed. The removal of phenol and COD exceeded 80% of the original loading after 8 days of treatment, for extracts containing initial COD in the range 19 to 72 g dm?3. Copyright © 2004 Society of Chemical Industry 相似文献
7.
N. Ouaaline L. Radouane 《International Journal of Adaptive Control and Signal Processing》1998,12(1):1-12
This paper describes an adaptive algorithm for formant and antiformant tracking of nasal sounds of speech signal. It is based on an extension of the zero-tracking algorithm (ZTA) to the autoregressive moving average model (ARMA). In this context the parameter estimation algorithm used is a modified RLS algorithm (σ-RLS). This adaptive algorithm is shown to be robust against the sounds. The proposed algorithm updates adaptively the complex poles (formants) of the AR part and the complex zeros (antiformants) of the MA part respectively. An application to natural speech is given. © 1998 John Wiley & Sons, Ltd. 相似文献
8.
R. Hammami Z. Ahamed K. Charradi Z. Beji I. Ben Assaker J. Ben Naceur B. Auvity G. Squadrito R. Chtourou 《International Journal of Hydrogen Energy》2013
Nafion hybrid membrane containing titanium dioxide (TiO2) nano-particles were elaborated by in situ sol–gel technique. Micro wave treatment was used during hybrid elaboration to 2 h. The X-ray diffraction (XRD) shows the crystallization of TiO2 in anatase and rutile phases. The Infrared spectroscopy IR spectrum of hybrid membranes Nafion–TiO2 confirm the presence of bonds Ti–O and Ti–OH which proves that the hybridization of the membrane by sol–gel method is successful. Atomic Force Microscopy AFM confirmed the good dispersion of TiO2 nano-particles. The electrochemical impedance spectroscopy (EIS) and solvent uptake measurements suggest the enhancement of the membrane performance. 相似文献
9.
Zakarya Ahmed Khaled Charradi Qana A. Alsulami Sherif M. A. S. Keshk Radhouane Chtourou 《应用聚合物科学杂志》2021,138(1):49634
Polyether ether ketone (PEEK) with a low sulfonation degree was blended using different proportions of sodium rich Smectite clay (3 and 6 wt%) to use as an electrolyte membrane for fuel cell application. The structural functionalities, surface morphologies, and the thermal stability of the resultant composite membranes were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, atom force microscopy, and thermo-gravimetric analysis. FT-IR showed that no chemical reactions take place between the sulfonated polyether ether ketone (SPEEK) and the clay with different ratios. XRD diffractograms illustrated a lower degree of crystallinity of the blended SPEEK than pristine SPEEK. The elaborated composite membranes proved to have a higher thermal stability than SPEEK. Furthermore, the SPEEK/clay composite membranes with 3 and 6 wt% in clay loading had higher water uptake and lower methanol uptake than those in pristine SPEEK It was also shown that, the incorporation of sodium ions rich Smectite clay layers between the clusters in SPEEK improved the conductivity to 2 × 10−2 S/cm at 140°C (for 6 wt% in clay) without compromising the dimensional stability of the composite membranes. These results propose the composite membranes as a potential candidate for methanol fuel cells at temperatures above 120°C making SPEEK composite membrane competitive to that of Nafion membrane. 相似文献
10.
Fathi Kallel Mouna Sahnoun Ahmed Ben Hamida Khalil Chtourou 《Signal, Image and Video Processing》2018,12(5):905-913
We propose in this paper a new enhancement algorithm dedicated to dark computed tomography (CT) scan based on discrete wavelet transform with singular value decomposition (DWT–SVD) followed by adaptive gamma correction (AGC). Discrete wavelet transform (DWT) is considered to decompose the input dark CT image in four sub-bands. Singular value decomposition (SVD) is used in order to compute the corresponding singular value matrix of low–low (LL) sub-band image. The enhanced LL sub-band is determined by scaling the singular value matrix of original LL sub-band by an adequate correction factor, followed by inverse SVD. For a further contrast improvement, the new enhanced LL sub-band image is processed using an AGC algorithm. Finally, the obtained LL sub-band image undergoes inverse DWT together with the unprocessed sub-bands to generate the final enhanced image. This proposed method has the advantage of being fully automatic and could be applied for dark input images with either low or moderate contrast. Different dark CT images are considered to compare the performance of our proposed method to three other enhancement techniques using both objective and subjective assessments. Simulation results show that our proposed algorithm consistently produces good contrast enhancement, with best brightness and edges details conservation and with minimum added distortions to the enhanced CT images. 相似文献