Analogy between adsorption and sorption:An elementary mechanistic approach.I.Monolayer adsorption and sorption without solvent cluster formation

The elementary mechanistic model of adsorption and sorption is based on a simple hypothesis:the adsorption sites are uniformly distributed on the surface of the pore walls in the adsorbent,the sorption sites are uniformly distributed in the volume of the polymer.In this first paper we will analyze the simple case where one solute mol-ecule is only allowed to occupy a single adsorption or sorption site.A common elementary occupation law of the free sites is assumed:the differential increase of the number of the adsorbed/sorbed molecules is proportional to the differential increase of the activity of the solute and the concentration of the free(non-occupied)sites in the solid.The proportionality coefficient is called affinity coefficient depending on the solid/solute couple and on the temperature and independent of the concentration of the solute.In adsorption the concentration of the free sites is a surface concentration on the pore walls and in sorption it is expressed by the molarity.The simple mono-layer adsorption law of Jovanovi?is obtained:n=n0(1?e?KP)where n is the number of moles adsorbed when the pressure is P. n0is the total number of adsorption sites and K the affinity coefficient for adsorption.The sorption law writes:a= 1k? ?1??]+1?rk ln?1+1r?1??]where?,r and k hold respectively for the volume fraction of the solvent in the polymer,for the ratio of the molar volumes of the solvent to the elementary polymer chain containing one single adsorption site and for the sorption affinity coefficient.The confrontation of these equations to experimental isotherms is satisfactory in comparison with the classical Langmuir and Flory-Huggins equations:the best results are obtained for adsorption of vapors on a 5A zeolite and for all analyzed sorption results.     

End-to-end performance of transmission systems with relays over Rayleigh-fading channels

End-to-end performance of two-hop wireless communication systems with nonregenerative relays over flat Rayleigh-fading channels is presented. This is accomplished by deriving and applying some new closed-form expressions for the statistics of the harmonic mean of two independent exponential variates. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, average bit-error rate expressions for binary differential phase-shift keying, as well as outage probability formulas for noise limited systems are derived. Finally, comparisons between regenerative and nonregenerative systems are presented. Numerical results show that the former systems clearly outperform the latter ones for low average signal-to-noise-ratio (SNR). They also show that the two systems have similar performance at high average SNR.     

Optimal power allocation for relayed transmissions over Rayleigh-fading channels

Relayed transmission is a way to attain broader coverage by splitting the communication link from the source to the destination into several shorter links/hops. One of the main advantages of this communication technique is that it distributes the use of power throughout the hops. This implies longer battery life and lower interference introduced to the rest of the network. In this context, this paper investigates the optimal allocation of power over these links/hops for a given power budget. All hops are assumed to be subject to independent Rayleigh fading. Outage probability which is the probability that the link quality from source to destination falls below a certain threshold is used as the optimization criterion. Numerical results show that optimizing the allocation of power enhances the system performance, especially if the links are highly unbalanced in terms of their average fading power or if the number of hops is large. Interestingly, they also show that nonregenerative systems with optimum power allocation can outperform regenerative systems with no power optimization.     

Average outage duration of multihop communication systems with regenerative relays

Closed-form expressions for the average outage duration (AOD) of multihop regenerative communication systems over generalized fading channels are presented. Both noise-limited and interference-limited systems are studied. To show the usefulness of the presented expressions, some specific fading scenarios are considered. In addition, some numerical examples of interest comparing direct versus relayed transmission and studying the effect of increasing the number of hops and/or cochannel interferers are plotted and discussed.     

Eco-friendly Geopolymer Composite Based on Non-heat-treated Phosphate Sludge Reinforced With Polypropylene Fibers

Silicon - Geopolymers produced with metakaolin (MK) and thermally untreated phosphate sludge (PS) are beneficial and environmentally advantageous materials, but their fragility limits its...     

Chemometric Characterization of Eight Monovarietal Algerian Virgin Olive Oils

Differences in triacylglycerol, fatty acid, squalene, and tocopherol compositions were demonstrated between 8 varieties of virgin olive oils (Aberkane, Aguenaou, Aharoun, Aimel, Bouchouk Guergour, Bouichret, Chemlal, and Sigoise) from Petite Kabylie area, north eastern Algeria. Fatty acid and triacylglycerol morphotypes characterized each variety. A principal component analysis, based on triacylglycerol, fatty acid, and squalene compositions, differentiates between varieties. Minor fatty acids and squalene, usually not taken into account individually in authentication studies, are strongly involved in this differentiation, whereas the discriminant power of tocopherols is weak. Soft Independent Modeling of Class Analogy classification using chemical compositions as variables showed a high potential to authenticate the varietal origin of Algerian virgin olive oils.     

Performance analysis of selective cooperation in amplify‐and‐forward relay networks over identical Nakagami‐m channels

In cooperative communications, multiple relays between a source and a destination can increase the diversity gain. Because all the nodes must use orthogonal channels, multiple‐relay cooperation becomes spectrally inefficient. Therefore, a bestrelay selection scheme was recently proposed. In this paper, we analyzed the performance of this scheme for a system with the relays operating in amplify‐and‐forward mode over identical Nakagami‐m channels using an exact source–relay–destination signal‐to‐noise ratio (SNR).We derived accurate closed‐form expressions for various system parameters including the probability density function of end‐to‐end SNR, the average output SNR, the bit error probability, and the channel capacity. The analytical results were verified through Monte Carlo simulations. Copyright © 2011 John Wiley & Sons, Ltd.     

Antenna subset selection at multi‐antenna relay with adaptive modulation

In this paper, we proposed several antenna selection schemes for cooperative diversity systems with adaptive transmission. The proposed schemes were based on dual‐hop relaying where a relay with multiple‐antenna capabilities at reception and transmission is deployed between the source and the destination nodes. We analyzed the performance of the proposed schemes by quantifying the average spectral efficiency and the outage probability. We also investigated the trade‐off of performance and complexity by comparing the average number of active antennas, path estimations, and signal‐to‐noise ratio comparisons of the different proposed schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

Breaking the curse of dimensionality: hierarchical Bayesian network model for multi-view clustering

Annals of Mathematics and Artificial Intelligence - Clustering high-dimensional data under the curse of dimensionality is an arduous task in many applications domains. The wide dimension yields the...     

Theoretical possibilities of InxGa1−xN tandem PV structures

We designed a model of In_xGa_1−xN tandem structure made of N successive p–n junctions going from two junctions for the less sophisticated structure to six junctions for the most sophisticated. We simulated the photocurrent density and the open-circuit voltage of each structure under AM 1.5 illumination in goal to optimize the number of successive junctions forming one structure.For each value of N, we assumed that each junction absorbs the photons that are not absorbed by the preceding one. From the repartition of photons in the solar spectrum and starting from the energy gap of GaN, we fixed the gap of each junction that gives the same amount of photocurrent density in the structure. Then we calculated the current density accurately and optimized the thicknesses of p and n layers of each junction to make it give the same output current density. The evaluation of n_i: the intrinsic concentration permitted to calculate the saturation current density and the open-circuit voltage of each junction. Assuming an overall fill factor of 80%, we divided the output peak power by the incident solar power and obtained the efficiency of each structure.The numerical values for In_xGa_1−xN were taken from the relevant literature. The calculated efficiency goes from 27.49% for the two-junction tandem structure to 40.35% for a six-junction structure. The six-junction In_xGa_1−xN tandem structure has an open-circuit voltage of about 5.34 V and a short circuit current density of 9.1 mA/cm².