Synthesis of heterocyclic metal complexes and their evaluation as marine antifoulants

4-Amino-3-thio-1,24-triazolidine (L₁) and 4-amino-5-thio-1,3,4-thiadiazole (L_II) as well as their metal complexes of the general formulae ML_I·2H₂O and ML_IICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(L_I)₂·2H₂O and SnL_IICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.     

Effect of functional group of ferrocene redox substance on the transport properties of newly designed ion exchange membrane prepared from polymer gel

A different newly designed cationic exchange polymer membrane and anionic exchange polymer membrane were introduced, and also the transport properties of these polymeric membranes were investigated in this study. The transport properties of these polymer membranes in contact with ferrocene redox derivatives were estimated by using electrochemical techniques such as cyclicvoltammetry, chronopotentiometry, and chronoamperometry techniques, respectively. The used ferrocene redox substances, which have different functional groups, were (Ferrocenylmethyl) trimethylamonium iodide, FcMA, Ferrocenedimethanol, FcDM, and Ferrocene carboxylic acid, FcCA. It indicated that the performance of a membrane depended on the content of polymer gel, anionic exchange polymer site (20 wt % and 50 wt %) or cationic polymer exchange site (20 wt % and 50 wt %), and the efficiency of the functional groups of cationic and anionic exchange polymer site as well. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Water and salt permeability of reinforcement polymer‐gel composite membrane

The charged mosaic polymer membrane (CMM) without reinforcement and the composite charged mosaic polymer membrane (CCMM) with reinforcement were investigated in terms of salt and water transport (permeability). The composite charged mosaic polymer membrane (CCMM) with reinforcement showed a unique transport behavior such as preferential material transport L_p and ω. Water permeability coefficient, L_p and salt permeability coefficient, ω were estimated by taking account of active layer thickness of composite polymer gel. The L_p and ω values of CCMM with reinforcement were larger than those of CMM without reinforcement. On the other hand, the reflection coefficient of CCMM, σ, showed negative value, which suggested preferential material transport to solvent transport. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Combination of information retrieval methods with LESK algorithm for Arabic word sense disambiguation

In this paper, we propose to use Harman, Croft and Okapi measures with Lesk algorithm to develop a system for Arabic word sense disambiguation, that combines unsupervised and knowledge based methods. This system must solve the lexical semantic ambiguity in Arabic language. The information retrieval measures are used to estimate the most relevant sense of the ambiguous word, by returning a semantic coherence score corresponding to the context that is semantically closest to the original sentence containing the ambiguous word. The Lesk algorithm is used to assign and select the adequate sense from those proposed by the information retrieval measures mentioned above. This selection is based on a comparison between the glosses of the word to be disambiguated, and its different contexts of use extracted from a corpus. Our experimental study proves that using of Lesk algorithm with Harman, Croft, and Okapi measures allows us to obtain an accuracy rate of 73%.     

A bipolar implementation of the Beta neuron

The great flexibility of the Beta function and its universal approximation characteristics, make Beta basis function neural networks (BBFNNs) very useful. We present a hardware implementation of the Beta neuron. The proposed circuit was designed by using a standard bipolar technology. PSPICE simulations show the good concordance of the output of our circuit with the analytic Beta function. We also successfully integrated the electronic Beta neuron in the design of a BBFNN that approximates a nonlinear mapping.     

Numerical modeling of ZnSnO/CZTS based solar cells

Numerical simulation has been performed to improve the performance of Cu2ZnSnS4 (CZTS) solar cells by replacing CdS with Zn1–xSnxO buffer layer. The influences of thickness, donor concentration and defect density of buffer layers on the performance of CZTS solar cells were investigated. It has been found that Zn1–xSnxO buffer layer for Sn content of 0.20 is better for CZTS solar cell. A higher efficiency can be achieved with thinner buffer layer. The optimized solar cell demonstrated a maximum power conversion efficiency of 13%.     

Influence of the layer parameters on the performance of the CdTe solar cells

Influence of the layer parameters on the performances of the CdTe solar cells is analyzed by SCAPS-1D. The ZnO:Al film shows a high efficiency than SnO2:F. Moreover, the thinner window layer and lower defect density of CdS films are the factor in the enhancement of the short-circuit current density. As well, to increase the open-circuit voltage, the responsible factors are low defect density of the absorbing layer CdTe and high metal work function. For the low cost of cell production, ultrathin film CdTe cells are used with a back surface field (BSF) between CdTe and back contact, such as PbTe. Further, the simulation results show that the conversion efficiency of 19.28% can be obtained for the cell with 1-μm-thick CdTe, 0.1-μm-thick PbTe and 30-nm-thick CdS.     

Retarding Thermal Degradation in Hybrid Perovskites by Ionic Liquid Additives

Recent years have witnessed considerable progress in the development of solar cells based on lead halide perovskite materials. However, their intrinsic instability remains a limitation. In this context, the interplay between the thermal degradation and the hydrophobicity of perovskite materials is investigated. To this end, the salt 1‐(4‐ethenylbenzyl)‐3‐(3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluorooctylimidazolium iodide (ETI), is employed as an additive in hybrid perovskites, endowing the photoactive materials with high thermal stability and hydrophobicity. The ETI additive inhibits methylammonium (MA) permeation in methylammonium lead triiodide (MAPbI₃) occurring due to intrinsic thermal degradation, by inhibiting out‐diffusion of the MA⁺ cation, preserving the pristine material and preventing decomposition. With this simple approach, high efficiency solar cells based on the unstable MAPbI₃ perovskite are markedly stabilized under maximum power point tracking, leading to greater than twice the preserved efficiency after 700 h of continuous light illumination and heating (60 °C). These results suggest a strategy to tackle the intrinsic thermal decomposition of MAI, an essential component in all state‐of‐the‐art perovskite compositions.     

Investigation de la gestion de qualité de service dans le réseau UMTS

Bit rate announced for the future standards of telecommunication, as well as the level of integration reached are, as many factors, determining for the establishment of new applications in mobile terminals. Nowadays, mobile video streaming services are possible. Mobile users expect to receive multimedia traffic with some performance guarantees, so we must ensure the necessary quality of service during the video transmission. This paper aims at investigating quality of service issue inUmts network. More specifically, we explore the main challenge of quality of service management to dynamically optimize the distribution of load inUmts networks. Our investigation is organized in the following way. We formalize the optimization problem which is based on the graph theory and modellingUmts network as well as mobile users and applications to be used. The simulation of our optimization model show a clear improvement of the quality of service perceived by anUmts user in terms of bit rate, blocking and connection drop.     

A Beta basis function neural network in CMOS subthreshold mode

Beta basis function neural networks (BBFNNs) are powerful systems for learning and universal approximation. In this paper, we present a hardware implementation of the Beta neuron using the CMOS subthreshold mode. We describe the low power–low voltage analogue Beta neuron circuit. Three main modules are used to realize the electronic Beta function: a logarithmic currentto-voltage converter, a multiplier and an exponential voltage-to-current converter. Simulation results show the validity of our neural hardware implementation. The parameters of the electronic Beta function are controlled independently by current sources. This analogue implementation could be used easily to realize analogue BBFNNs.