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81.
Raymond K.M. Chu Hani E. Naguib Noureddine Atalla 《Polymer Engineering and Science》2009,49(9):1744-1754
Foams with open‐cell structures have improved sound absorption abilities over conventional closed‐cell foams. One technique to optimize the acoustic abilities of open‐cell foams is to control their cellular properties through the manipulation of processing parameters. This article presents a novel process to synthesize open‐cell polymeric foams for acoustic applications. The process combined rotational foam molding and particulate leaching to produce foams with open‐cell networks that are desirable for acoustic absorption. Open‐cell foams with open‐porosity of about 0.90 were successfully fabricated with this combined foaming process. Effects of processing parameters on the cellular and acoustic properties of the foam samples were examined and discussed. On the basis of the results from the study, the cellular and acoustic properties of the foam fabricated from the proposed method can be controlled through the use of different salt particle sizes in the process. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers 相似文献
82.
Shuli Gao Noureddine Chabini Dhamin Al-Khalili J. M. Pierre Langlois 《Journal of Signal Processing Systems》2010,58(1):3-15
This paper presents two optimized design approaches of two’s complement large size squarers using embedded multipliers in
FPGAs. The realization of one of the approaches is based on Baugh–Wooley’s algorithm and the other one is a new sign-extension
technique. To achieve efficient implementation, a set of optimized schemes for the realization of multi-level additions of
the partial products is proposed. The squarers are implemented for operands of sizes ranging from 20 to 128 bits targeting
Xilinx’ Spartan-3 using the ISE 8.1 synthesis and implementation tool, and from 38 to 128 bits targeting Altera’s Stratix
II using the Quartus II 6.0 synthesis and implementation tool. The comparisons indicate that our proposed approaches offer
substantial area savings and delay reduction. Using the Baugh–Wooley-based approach, the average saving in LUTs is close to
50% with an average delay reduction in the range of 13% to 20%. With the new sign extension approach, the area saving ranges
from 54% to 70%, while the delay is reduced by approximately 25%. Embedded block usage for both approaches with different
tools is reduced by 38% compared with the standard schemes. 相似文献
83.
Thermal buckling analysis of laminated composite beams using hyperbolic refined shear deformation theory 总被引:1,自引:0,他引:1
In this article, thermal buckling of laminated composite beams, based on hyperbolic refined shear deformation theory, presented for the first time, is formulated using the principle of minimum total potential energy. Navier’s analytical solution is derived to analytically solve the differential equations and the thermal critical buckling is presented in closed-form solution. The effects of temperature distribution, length to thickness ratio, modulus ratio, and thermal expansion coefficient ratio on thermal buckling of isotropic, orthotropic and laminated composite beams are investigated. The accuracy of the numerical model is verified by comparison with the available results in the literature. 相似文献
84.
85.
Ivana Rasovska Brigitte Chebel-Morello Noureddine Zerhouni 《Journal of Intelligent Manufacturing》2008,19(3):347-359
This paper deals with knowledge capitalization in maintenance especially in diagnosis and repair of industrial equipments.
The goal is to propose a method of knowledge capitalization in order to develop a decision support system for maintenance
operators. The knowledge capitalization cycle was adopted as the underlying principle. It consists of four principal steps:
detect, preserve, capitalize and actualize the strategic knowledge. Different knowledge management tools and methods that
can be used in the cycle are reviewed. We propose a mix method of knowledge capitalization in maintenance. This method integrates
a representation and a reasoning model both completing each other and suitable to represent and manipulate the domain knowledge.
The knowledge representation model using unified modelling language (UML) diagram proposes different domain models based on
maintenance analysis to guide the domain expertise. The reasoning model uses the case-based reasoning which allows the manipulation
of represented domain knowledge. Finally, the method is implemented on the pallet transfer system Sormel in the context of
Proteus e-maintenance platform. 相似文献
86.
Michel A. Tournour Noureddine Atalla 《International journal for numerical methods in engineering》1999,46(6):825-837
The variational boundary element method (VBEM) is widely used to compute the acoustic radiation of structures. The classical numerical implementation of the VBEM suffers from the computational cost associated with double surface integration. In a previous paper [1], the authors proposed a novel method, based on multipole expansions, to accelerate the double layer potential calculation for structures having a periodic mesh. This technique, while efficient, is still limited by the cost of computing the surface pressure from the double surface potential. This paper presents an acceleration technique, based on multipole expansion, that allies both efficiency and accuracy. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
87.
Fadi Alakhras Emna Selmane Bel Hadj Hmida Ioannis Anastopoulos Zina Trabelsi Walid Mabrouk Noureddine Ouerfelli Jean François Fauvarque 《水科学与水工程》2021,14(1):36-45
In this study, the removal of monovalent and divalent cations, Na+, K+, Mg2+, and Ca2+, in a diluted solution from Chott-El Jerid Lake, Tunisia, was investigated with the electrodialysis technique. The process was tested using two cation-exchange membranes: sulfonated polyether sulfone cross-linked with 10% hexamethylenediamine (HEXCl) and sulfonated polyether sulfone grafted with octylamine (S-PESOS). The commercially available membrane Nafion® was used for comparison. The results showed that Nafion® and S-PESOS membranes had similar removal behaviors, and the investigated cations were ranked in the following descending order in terms of their demineralization rates: Na+ > Ca2+ > Mg2+ > K+. Divalent cations were more effectively removed by HEXCl than by monovalent cations. The plots based on the Weber–Morris model showed a strong linearity. This reveals that intra-particle diffusion was not the removal rate-determining step, and the removal process was controlled by two or more concurrent mechanisms. The Boyd plots did not pass through their origin, and the sole controlling step was determined by film-diffusion resistance, especially after a long period of electrodialysis. Additionally, a semi-empirical model was established to simulate the temporal variation of the treatment process, and the physical significance and values of model parameters were compared for the three membranes. The findings of this study indicate that HEXCl and S-PESOS membranes can be efficiently utilized for water softening, especially when effluents are highly loaded with calcium and magnesium ions. 相似文献
88.
Riad Ladji Noureddine Yassaa Catia Balducci Brahim Youcef Meklati 《The Science of the total environment》2009,408(2):415-424
The distribution of the solvent-extractable organic components in the fine (PM1) and coarse (PM1-10) fractions of airborne particulate was studied for the first time in Algeria. That was done during October 2006 concurrently in a big industrial district, a busy urban area, and a forest national park located in Algiers, Boumerdes, Blida, respectively, which are the three biggest provinces of Northern Algeria. Most of the organic matter identified in both particle size ranges consisted of n-alkanes and n-alkanoic acids, with minor contributions coming from polycyclic aromatic hydrocarbons (PAHs), nitrated polycyclic aromatic hydrocarbons (NPAHs), oxygenated PAHs, and other polar compounds (e.g., caffeine and nicotine). The potential emission sources of airborne contaminants were reconciled by combining the values of n-alkane carbon preference index (CPI) and selected diagnostic ratios of PAHs, calculated in both size ranges. The mean cumulative concentrations of PAHs reached 3.032 ng m− 3 at the Boumerdes site, urban, 80% of which (i.e. 2.246 ng m− 3) in the PM1 fraction, 6.462 ng m− 3 at Rouiba-Réghaia, industrial district, (5.135 ng m− 3 or 80% in PM1), and 0.512 ng m− 3 at Chréa, forested mountains (0.370 ng m− 3 or 72% in PM1). Similar patterns were shown by all organic groups, which resulted overall enriched in the fine particles at the three sites. Carcinogenic and mutagenic potencies associated to PAHs were evaluated by multiplying the concentrations of “toxic” compounds times the corresponding potency factors normalized vs. benzo(a)pyrene (BaP), and were found to be both acceptable. 相似文献
89.
Houyem Abderrazak Faten Turki Fréderic Schoenstein Mohieddine Abdellaoui Noureddine Jouini 《Ceramics International》2013,39(5):5365-5372
Ti3SiC2 was elaborated by two different methods: (i) Spark plasma sintering of 5Ti/2SiC/C powders and (ii) mechanical alloying of powders followed by Spark plasma sintering. The results showed that mechanical alloying was not advantageous for pure Ti3SiC2 formation but it can significantly improve the density of the obtained bulk material via the particles refinement as well as the microhardness by increasing the TiC content. It was found that the relative density was increased up to 98.58% for the sintered mechanically alloyed sample whereas it was not more than 96.04% for the sintered 5Ti/2SiC/C starting powders. The Vickers microhardness measured for both bulk samples demonstrates a high improvement for the previously mechanically alloyed powder mixture, as it was of about 1282 Hv and only 581.2 Hv for the alloy obtained from 5Ti/2SiC/C starting powders. 相似文献
90.
In this study, lightweight 100% cotton fabric was successfully modified by the sol–gel process to impart high ultraviolet radiation (UVR) scattering property to the fabric surface. Active ingredients were tetraethyl orthotitanate [Ti(OCH2CH3)4] and tetraethyl orthosilicate [Si(OCH2CH3)4]. The cotton fabric was padded with the nanosol solution, dried at 60°C, and cured at 150°C. Scanning electron microscopy showed continuous and uniform film on the fiber surface. Excellent UVR scattering was obtained with all treated fabrics. Increasing titania content in the nanosol solution leads to increased UVR protection. This is attributed to the increase of the refractive index of the film formed on the fabric surface. Excellent durability of the treatment was obtained, which indicates a good adhesion between the coating and the fabric surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 111–117, 2007. 相似文献