Mathematical optimization techniques for resource allocation and spatial multiplexing in spectrum sharing networks

Due to introduction of smart phones with data intensive multimedia and interactive applications and exponential growth of wireless devices, there is a shortage for useful radio spectrum. Even though the spectrum has become crowded, many spectrum occupancy measurements indicate that most of the allocated spectrum is underutilised. Hence radically new approaches in terms of allocation of wireless resources are required for better utilization of radio spectrum. This has motivated the concept of opportunistic spectrum sharing or the so-called cognitive radio technology that has great potential to improve spectrum utilization. The cognitive radio technology allows an opportunistic user namely the secondary user to access the spectrum of the licensed user (known as primary user) provided that the secondary transmission does not harmfully affect the primary user. This is possible with the introduction of advanced resource allocation techniques together with the use of wireless relays and spatial diversity techniques. In this thesis, various mathematical optimization techniques have been developed for the efficient use of radio spectrum within the context of spectrum sharing networks. In particular, optimal power allocation techniques and centralised and distributed beamforming techniques have been developed. Initially, an optimization technique for subcarrier and power allocation has been proposed for an Orthogonal Frequency Division Multiple Access (OFDMA) based secondary wireless network in the presence of multiple primary users. The solution is based on integer linear programming with multiple interference leakage and transmission power constraints. In order to enhance the spectrum efficiency further, the work has been extended to allow multiple secondary users to occupy the same frequency band under a multiple-input and multiple-output (MIMO) framework. A sum rate maximization technique based on uplink-downlink duality and dirty paper coding has been developed for the MIMO based OFDMA network. The work has also been extended to handle fading scenarios based on maximization of ergodic capacity. The optimization techniques for MIMO network has been extended to a spectrum sharing network with relays. This has the advantage of extending the coverage of the secondary network and assisting the primary network in return for the use of the primary spectrum. Finally, instead of considering interference mitigation, the recently emerged concept of interference alignment has been used for the resource allocation in spectrum sharing networks. The performances of all these new algorithms have been demonstrated using MATLAB based simulation studies

Arylalkene Synthesis via Decarboxylative Cross-Coupling of Alkenyl Halides

A bimetallic catalyst system generated from readily available palladium­(II) and copper­(I) salts, 1,10-phenanthroline and tri-1-naphthylphosphine was found to efficiently mediate the decarboxylative cross-coupling of alkenyl bromides and chlorides with aromatic carboxylates. It allows the regiospecific synthesis of a broad range of aryl- and heteroarylalkenes in high yields

La réforme des rythmes scolaires et les projets éducatifs territoriaux : première analyse des évaluations, bilans et autres expertises réalisés entre 2013 et 2017

Publication du CNESCO (Conseil national d’évaluation du système scolaire)Cette étude se donne pour ambition d’approfondir la réflexion sur la réforme dite des rythmes « scolaires » et/ou « éducatifs » et la mise en place des Projets éducatifs de territoire (PEDT) qui l’accompagne. Elle s’attache à clarifier les enjeux et contours de cette réforme et engage surtout un travail d’analyse secondaire d’une partie des différents travaux et rapports dits « d’évaluation », de « bilan » ou « d’études » politico-administratifs, savants ou experts qui ont récemment été produits sur cette dernière. Ceci conduit à soutenir une double série de questionnements sur l’évolution et les aménagements de cette réforme, l’enchevêtrement des logiques et des modes de problématisation des questions scolaires et éducatives qu’elle promeut, les variétés du «discours éducatif et pédagogique» qu’elle sous-tend, ainsi que sur la forme particulière prise par la «littérature experte », qui accompagne, depuis quelques années, sa mise en œuvre controversée.Ce document s’inscrit dans une série de contributions publiées par le Conseil national d’évaluation du système scolaire (Cnesco) sur la thématique : Justice à l’école et territoires

The temperature sensitivity of soil organic carbon decomposition is not related to labile and recalcitrant carbon

<div><p>The response of resistant soil organic matter to temperature change is crucial for predicting climate change impacts on C cycling in terrestrial ecosystems. However, the response of the decomposition of different soil organic carbon (SOC) fractions to temperature is still under debate. To investigate whether the labile and resistant SOC components have different temperature sensitivities, soil samples were collected from three forest and two grass land sites, along with a gradient of latitude from 18°40’to 43°17’N and elevation from 600 to 3510 m across China, and were incubated under changing temperature (from 12 to 32 ^oC) for at least 260 days. Soil respiration rates were positively related to the content of soil organic carbon and soil microbial carbon. The temperature sensitivity of soil respiration, presented as <i>Q</i>₁₀ value, varies from 1.93 ± 0.15 to 2.60 ± 0.21. During the incubation, there were no significant differences between the <i>Q</i>₁₀ values of soil samples from different layers of the same site, nor a clear pattern of <i>Q</i>₁₀ values along with the gradient of latitude. The result of this study does not support current opinion that resistant soil carbon decomposition is more sensitive to temperature change than labile soil carbon.</p></div

Variation in <i>Q</i>_<i>10</i> values (mean ± SD) along with incubation.

<p>Variation in <i>Q</i>_<i>10</i> values (mean ± SD) along with incubation.</p

The variation of <i>Q</i>₁₀ values calculated with two different models along with incubation time.

<p><i>Q</i>₁₀(20) was the <i>Q</i>₁₀ value calculated at 20 ^oC and <i>Q</i>₁₀(10) was the Q₁₀ value calculated at 10 ^oC by the O’connel model, while <i>Q</i>₁₀ was the <i>Q</i>₁₀ value calculated by first–ordered exponential model. (DF: deciduous forest; EF: evergreen forest; SG: semi-arid grassland).</p

Variation in SOC decomposition rates, <i>Q</i>_<i>10</i> values and soil carbon pools with increasing incubation time.

<p><b>Values are average of four replications and normalized by initial values</b>. (DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

Relationship between SOC decomposition rates and incubating temperatures for soil samples from different sites.

<p>(DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p

Comparison of the initial and last <i>Q</i>₁₀ value of three forest samples.

<p>(DF: deciduous forest; RF: tropical rainforest; EF: evergreen forest).</p

SOC decomposition rates (at 20 ^oC) declined over incubation times.

<p>(DF: deciduous forest; TM: temperate meadow; RF: tropical rainforest; EF: evergreen forest; SG: semi-arid grassland).</p