In situ chemical deposition of PPy/NDSA and PPy/DBSA layers on QCM electrodes: synthesis,structural, morphological and ammonia sensing performances study

Aiming to detect ammonia vapor, polypyrrole (PPy) thin layers were in situ coated on AT-cut 10 MHz quartz crystal microbalance QCM electrode by a facile chemical polymerization process using two organic acids as dopants, i.e. dodecylbenzene sulfonic acid (BDSA) and 1–5 naphthalene disulfonic acid (NDSA). Then after, polymers structural and morphological features were determined by FTIR, Raman spectroscopy and Scanning Electron Microscopy (SEM) techniques. Ammonia vapor sensing tests were related to QCM frequency changes recorded upon vapor adsorption and desorption on PPy films, it was found that frequency shifts varied linearly with both vapor concentration expressed in part per million (ppm) and polymer’s thin layer thickness given in nanometer (nm). This fact has been assumed to be mainly related to the electrostatic interactions established between ammonia vapor molecules and the polymer dopant agents. Tests have shown that films based PPy/NDSA exhibit high sensitivity around 3 ppm and detection limit of 4 ppm over films based PPy/DBSA. Interestingly, an excellent recovery time less than 3 min has been also recorded with PPy/NDSA thin layers. Moreover, when applying Fick’s second law, they have also shown a high diffusion constant.     

Constrained Minimization and Discriminative Training for Natural Language Call Routing

This paper presents a combination strategy of multiple individual routing classifiers to improve classification accuracy in natural language call routing applications. Since errors of individual classifiers in the ensemble should somehow be uncorrelated, we propose a combination strategy where the combined classifier accuracy is a function of the accuracy of individual classifiers and also the correlation between their classification errors. We show theoretically and empirically that our combination strategy, named the constrained minimization technique, has a good potential in improving the classification accuracy of single classifiers. We also show how discriminative training, more specifically the generalized probabilistic descent (GPD) algorithm, can be of benefit to further boost the performance of routing classifiers. The GPD algorithm has the potential to consider both positive and negative examples during training to minimize the classification error and increase the score separation of the correct from competing hypotheses. Some parameters become negative when using the GPD algorithm, resulting from suppressive learning not traditionally possible; important antifeatures are thus obtained. Experimental evaluation is carried on a banking call routing task and on switchboard databases with a set of 23 and 67 destinations, respectively. Results show either the GPD or constrained minimization technique outperform the accuracy of baseline classifiers by 44% when applied separately. When the constrained minimization technique is added on top of GPD, we show an additional 15% reduction in the classification error rate.     

A Modified Embedded Zerotree Wavelet (MEZW) Algorithm for Image Compression

In this paper, we propose a modification of the Shapiro’s Embedded Zerotree Wavelet (EZW) algorithm. Our approach, called Modified EZW (MEZW), distributes entropy differently than Shapiro’s by using six instead of four symbols used in EZW and also optimizes the coding by a binary grouping of elements before coding. This approach can produce results that are a significant improvement on the PSNR and compression ratio obtained by Shapiro, without affecting the computing time. These results are also comparable with those obtained using the SPIHT and SPECK algorithms.

Experimental study of the salt gradient solar pond stability

Many natural systems such as oceans, lakes, etc.…, are influenced by the effect of double-diffusive convection. This phenomenon, which is a combination of heat and mass transfer, can destroy the stability of system-flows.In the case of solar ponds the middle layer, that is linearly stratified, acts as a thermal and mass insulator for the lower layer. This middle layer, called the Non-Convective Zone (NCZ), needs special care to avoid convection and to maintain its stability. In fact, due to an excess of heat stored, a thermal gradient occurs within the NCZ. A convective movement appears at the bottom of the stratified-layers and then grows to a double-diffusive convection movement. This movement transforms the stratified-layers into a well mixed layer, reducing the storage capacity of the pond.Laboratory small-scale pond and middle-scale outdoor solar ponds were designed and built to provide both quantitative data and to study the dynamic processes in solar ponds, including the behavior of the gradient zone.Particle Image Velocimetry (PIV) visualization-experiments carried out in the mechanical and energetic laboratory in the engineering school of Tunisia and experiments in the field showed that the instability of solar ponds could be limited by using porous media placed in the lower layer of the stratification.     

Using the expert system to analyze loom performance

In this paper, the development of a warp tension simulation is presented. A system analysis of modern weaving machines led to a suitable simulation model to calculate the warp tension. The validation of the simulation demonstrates that the results correspond well with reality. In a second step, an improved model of this simulation was used in combination with a genetic algorithm and a gradient-based method to calculate optimized setting parameters for the weaving process. In order to do so, a cost function was defined taking into account a desired course of the warp tension. Actually, it is known, that a low and constant warp tension course is suitable for weaving. Using the genetic algorithm or the gradient-based method leads to optimized weaving machine parameters. Both algorithms do get nearly the same results for the optimized weaving machine setting. Applying the optimized setting parameters on a loom did not demonstrate that the productivity of a weaving machine can be raised. Analysis of the produced fabrics did not show an influence of optimization on the fabric quality. The reduction of warp tension was not sufficient in order to have an impact on the mechanical properties of the fabric. Thus, fabric defects could be eliminated using the optimized weaving machine settings.     

Lithium diffusion profile onto highly resistive p-type silicon

In this work, the effect of temperature and time of diffusion on the lithium (Li) profile into p-type highly resistive silicon have been investigated. The high-purity Li metal (99.995%) was deposited onto p-type (1 1 1) silicon surface and thermally diffused into the bulk at a 2×10⁻⁶ Torr vacuum pressure. The four-probes technique was used to determine the diffusion profile of Li impurities into silicon. Scanning electron microscopy (SEM) was used to measure the diffused junction depth (X_j). The Li diffusion constant D_Li was then extracted using the measured surface concentration N_Li. Thus, the variation of D_Li as a function of diffusion temperature was determined. Simulated profiles was obtained by means PC1D calculate tool. A good agreement was found when the simulated and experimental results were compared with those of the literature values.     

Comments on “A General Model of Multipath Error for Coherently Tracked BOC Modulated Signals”

The mathematical formulation of the discriminator and the multipath error models presented by Harris and Lightsey contains some typing errors. In this comment, we review the formalism of aforementioned models and we fix and correct these typing errors. The simulation results show that the original analytical models, with these corrections, coincide with the numerical models.     

Miscibilization of telechelic fluoroalkeneoxide oligomers in epoxy resins and effects on morphology and physical properties

Hydroxyterminated fluoroalkene oxide oligomers were reacted with chlorendic anhydride and subsequently with ?-caprolactone to produce carboxyterminated perfluoroethers prepolymers that were totally miscible with diglycidylether of bisphenol A. Curing the epoxy resin mixtures with hexahydrophthalic anhydride hardener and benzyl dimethylamine catalyst produced transparent products exhibiting a two-phase co-continuous morphology. Prereacting the fluoroalkeneoxide prepolymers with an excess of epoxy resin prior to the addition of hardener and catalyst, resulted in opaque products displaying a two-phase dispersed particles morphology. The dynamic mechanical spectra of the cured products confirmed the absence of any significant short-range network miscibility and revealed substantial enhancements in β-relaxations in all cases, which are normally associated with microdispersed morphologies. Both systems exhibited much higher flexural strength and ductility than the equivalent unmodified epoxy resins even at very low levels of addition. 3.5–5.0%. The surface energy was found to be much lower than that exhibited by the unmodified resin system, and the reduction in water absorption was relatively small. The above effects were much more pronounced for products exhibiting a particulate morphology than for systems that exhibited a co-continuous morphology. © 1994 John Wiley & Sons, Inc.     

Morphology and mechanical properties of epoxy resins containing functionalized perfluoroether oligomers

Chain extended perfluoroether oligomers were found to be miscible with bisphenol epoxy resins at all concentrations. These were evaluated as modifiers for anhydride cured resin systems, taking advantage of the carboxylic acid functionality at the chain ends. By altering the mixing and curing procedure different two-phases morphologies could be obtained varying from fine co-continuous networks, which produced transparent castings, to opaque systems consisting of precipitated heterogeneous particles. While the T_g and flexural modulus were found to be slightly lower than the control cure resin, the addition of the fluoroligomer modifier produced large increases in flexural strength, ductility, and fracture toughness. Samples with an IPN type morphology were found to exhibit an increase in ductility after aging at 200°C for three weeks proportionally to the concentration of fluoroligomer used.     

Computational modelling of static indentation-induced damage in glass

The present paper is focused on the numerical simulation of a glass plate subjected to static indentation by a spherical indenter. For this purpose, a combined approach of continuum damage mechanics (CDM) and fracture mechanics is performed. Results provided by an axisymmetric finite element model were compared with analytical solutions. A CDM based constitutive model with an anisotropic damage tensor was selected and implemented into a finite element code to study the damage of glass. The numerical results were analysed through the framework of the stress and damage distribution. Various regions with critical damage values were therefore predicted in good agreement with the experimental observations in the literature. In these regions, the directions of crack propagation, including both cracks initiating on the surface as well as in the bulk, were predicted using the strain energy density factor. Predicted directions were found in good agreement with those experimentally obtained in the literature results.