A robust component mode synthesis method for stochastic damped vibroacoustics

In order to reduce vibrations or sound levels in industrial vibroacoustic problems, the low-cost and efficient way consists in introducing visco- and poro-elastic materials either on the structure or on cavity walls. Depending on the frequency range of interest, several numerical approaches can be used to estimate the behavior of the coupled problem. In the context of low frequency applications related to acoustic cavities with surrounding vibrating structures, the finite elements method (FEM) is one of the most efficient techniques. Nevertheless, industrial problems lead to large FE models which are time-consuming in updating or optimization processes. A classical way to reduce calculation time is the component mode synthesis (CMS) method, whose classical formulation is not always efficient to predict dynamical behavior of structures including visco-elastic and/or poro-elastic patches. Then, to ensure an efficient prediction, the fluid and structural bases used for the model reduction need to be updated as a result of changes in a parametric optimization procedure. For complex models, this leads to prohibitive numerical costs in the optimization phase or for management and propagation of uncertainties in the stochastic vibroacoustic problem. In this paper, the formulation of an alternative CMS method is proposed and compared to classical (u,p) CMS method: the Ritz basis is completed with static residuals associated to visco-elastic and poro-elastic behaviors. This basis is also enriched by the static response of residual forces due to structural modifications, resulting in a so-called robust basis, also adapted to Monte Carlo simulations for uncertainties propagation using reduced models.     

Factors affecting the suitability of fly ash as source material for geopolymers

The suitability of fly ash stock piles for geopolymer manufacturing was studied. The results of chemical analyses, X-ray diffraction (XRD) and particle size distribution (PSD) of five sources of fly ash obtained from coal-fired power generating plants in the US are presented. Geopolymer paste and concrete specimens were prepared from each stock pile. The specimens were subjected to an array of chemical and mechanical tests including XRD, RAMAN spectroscopy, setting time and compressive strength. A correlation study was undertaken comparing the fly ash precursor chemical and crystallographic compositions as well as particle size distribution, with the mechanical and chemical characteristics of the resulting geopolymer. Factors inherent to the fly ash stockpile such as particle size distribution, degree of vitrification and location of the glass diffraction maximum were found to play an important role in the fresh and hardened properties of the resulting geopolymer.     

Development of polylactide open‐cell foams with bimodal structure for high‐acoustic absorption

In this study, a highly porous and interconnected foam structure was fabricated using compression molding combined with particulate‐leaching technique. The foamed structures were fabricated with polylactide (PLA) and polyethylene glycol (PEG) with salt as the particulate. The pore size of the foam structure is controlled by the particulates size and higher interconnectivity is achieved by the co‐continuous blending morphology of the PLA matrix with the water‐soluble PEG. PLA is a fully bio‐based thermoplastic polymer and is derived from renewable resources, such as cornstarch or sugarcanes. PEG is also fully biodegradable polymer produced from ethylene. Fabricated foams were characterized for cellular, acoustic, and mechanical properties. The acoustic performance of the foams was studied by measuring the normal incident absorption coefficient in accordance with the ASTM E1050 standard. The results show open porosity as high as 88% was achieved and the effect of water‐soluble polymer on cellular properties and acoustic and mechanical performance of the foams was studied. As a result of the secondary porous structure formed into cell walls by water soluble polymer, the overall absorption of fabricated PLA foams was increased to above 90% while the average absorption of the foams remained unchanged. In addition, the resulting acoustic foams are benign and environmentally friendly. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39518.     

Effect of adsorbed metal ions and buffer nature on IgG separation from human plasma by column chromatography using an ion exchange resin,Amberlite IRC‐718

Fractionation of human plasma on ion exchanger resin was performed on Amberlite IRC‐718 saturated with metal ions. Depletion of human immunoglobulin G was carried out by column chromatography using Tris‐HCl, pH 7 at different concentrations. Results showed that, when Cu⁺² and Ni⁺² were adsorbed on the resin, one or two fractions of purified IgG were obtained, respectively. Whereas Fe⁺² and Zn⁺², both retain IgG and serum albumin or serum albumin alone. Furthermore, the Ni⁺²‐resin retention of serum proteins is too strong that the use of 700 mMTris‐HCl cannot liberate any other proteins than nonadsorbed serum albumin. In conclusion, this investigation demonstrates that immobilized metal ion affinity chromatography with Cu²⁺, Ni²⁺, and Fe²⁺ immobilized on Amberlite IRC‐718 has the potential to be developed as part of a process to purify IgG out of untreated human plasma as acceptable adsorption and elution levels of IgG could be achieved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of open‐cell foams for sound absorption with rotational molding method

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     

Motion-aided sampling and reconstruction

Motivated by motion compensated filtering in image processing, this paper considers the problem of sampling and reconstruction of signals with sampling rates below the Nyquist rate. It is assumed that temporal dependence can be induced via motion. This way, the data consists of both spatial and temporal sampling, and here the conditions for reconstruction are analysed for a number of typical motions. Extensive simulation experiments are also provided which further support the analysis.     

FPGA-Based Efficient Design Approaches for Large Size Two’s Complement Squarers

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.     

Thermal buckling analysis of laminated composite beams using hyperbolic refined shear deformation theory

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.     

A mix method of knowledge capitalization in maintenance

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.