A hybrid multiagent routing approach for wireless ad hoc networks

Wireless ad-hoc networks are infrastructureless networks that comprise wireless mobile nodes able to communicate each other outside wireless transmission range. Due to frequent network topology changes in one hand and the limited underlying bandwidth in the other hand, routing becomes a challenging task. In this paper we present a novel routing algorithm devoted for mobile ad hoc networks. It entails both reactive and proactive components. More precisely, the algorithm is based on ant general behavior, but differs from the classic ant methods inspired from Ant-Colony-Optimization algorithm [1]. We do not use, during the reactive phase, a broadcasting technique that exponentially increases the routing overhead, but we introduce a new reactive route discovery technique that considerably reduces the communication overhead. In the simulation results, we show that our protocol can outperform both Ad hoc On-demand Distance Vector (AODV) protocol [2], one of the most important current state-of-the-art algorithms, and AntHocNet protocol [5], one of the most important ant-based routing algorithms, in terms of end-to-end delay, packet delivery ratio and the communication overhead.     

An efficient reduced simulation of residual stresses in composite forming processes

An efficient simulation of thermal and mechanical models involved in thermosetting composites forming needs to overcome some numerical difficulties related to: (i) the multi-scale behaviour; (ii) the complex geometries involved needing too many degrees of freedom; (iii) the large time intervals where the solution has to be computed; (iv) the non-linearity of the involved evolution equations; (v) the numerous couplings… In this work, an efficient strategy based on a separated representation is proposed. This method enables to avoid the use of an incremental strategy and can lead to impressive computing time savings especially when the model involves fine meshes and very small time steps. The local non-linear chemical kinetics and its coupling with the global heat balance equation are naturally introduced in the separated representation algorithm. Moreover, the dependence of the thermal conductivity and the specific heat on the temperature and on the reaction advancement degree are also taken into account. Knowing the history of the temperature field, the separated representation is again used to solve the thermo-mechanical problem in order to determine the residual stresses.     

The food preservative potential of essential oils: is lemongrass the answer?

Several essential oils of medicinal plants possess proven antimicrobial activity and are suitable for applications on the food industry. The oil from Cymbopogon citratus (lemongrass) has been reported to have a wide range of biological activities. However, there are few controlled studies confirming its antimicrobial activity. The aim of our study was to assess the antimicrobial potential of lemongrass oil against a wide spectrum of food spoilage and pathogenic bacteria and yeast in liquid and vapour phase. The chemical composition of the oil was analyzed by gas chromatography; 14 components were identified and geranial (28.93 %), neral (24.30 %) and myrcene (23.92 %) were the most abundant constituents. Lemongrass oil showed potent antimicrobial activity against Gram positive bacteria and exhibited the strongest antifungal effect against Candida albicans and C. parapsilosis. Minimum inhibitory concentration varied from 0.019 to 1.25 mg mL^?1 for Gram positive bacteria and yeasts, indicating Staphylococcus aureus, S. epidermidis and C. albicans as the most susceptible strains. Moreover, the diameter of inhibition zone (DIZ) increased with increasing essential oil (EO) volume. Considerably superior antimicrobial activity was observed in the vapour phase. The DIZ resulting from the exposure to EO vapour was significantly larger than that from the same volume in the liquid phase. The DIZ varied from 22 to 90 mm for Candida strains. There is growing evidence that EO in vapour phase are effective antimicrobial systems and that they do have advantages over the use of oil in liquid phase. Our results imply that lemongrass oil could be useful for the development of novel types of natural preservatives for food control.     

Effect of depithing on pulps from egyptian bagasse

Egyptian bagasse was pulped by the prehydrolysis-soda process followed by multi-state bleaching. Raising the concentration of sodium hydroxide used in the second step of bleaching improved the chemical characteristics of the pulp. Depithing had to be applied to improve the degree of pulping and to reduce the ash content. The minimum ash content (0.07%) was arrived at either by carrying out depithing before prehydrolysis to the extent of 2%, or after prehydrolysis to the extent of 10%. Depithing before prehydrolysis was superior as it resulted in a better yield, higher alpha cellulose, and higher degree of whiteness.     

Studies on the pulping of egyptian cotton linters by the nitric acid process

Egyptian cotton linters were pulped by the nitric acid process. In order to reduce the high ash and silica contents of the resulting pulps it was found necessary to apply hot refining with sodium hydroxide solution. Different conditions of concentration, temperature, and pressure in the refining step were investigated. Refining before and during bleaching were compared.     

Cold alkali refining of cellulosic pulps derived from Egyptian cotton and bagasse

A cotton linter pulp, a bagasse dissolving pulp and a bagasse paper pulp were subjected to cold sodium hydroxide refining and the resulting changes in their chemical, physical and submicroscopic characteristics were investigated. In the case of cotton linters the main change took place in the physical and submicroscopic properties and the refining resulted in better reactivity towards xanthation. The α-cellulose content of the paper and viscose pulps increased with alkali concentration until it reached a constant value which depends on the type of pulp and the concentration of alkali. The refining of the paper and viscose pulps impaired their reactivity towards xanthation. The presence of the more hydrophilic hemicellulose increased the swelling ability of the fibres and made them more reactive towards xanthation. The undesirable effects of drying after refining with high alkali concentration could be overcome if the DP is sufficiently lowered. In this case the resulting shorter chain macromolecules dissolve more readily during xanthation.     

Template-assisted synthesis of high packing density SrLi2Ti6O14 for use as anode in 2.7-V lithium-ion battery

SrLi₂Ti₆O₁₄ has been prepared by using mesoporous TiO₂ brookite as a template and reactant. The prepared particles retained the rounded shape of the precursor, leading to high dispersivity and high packing density. The material has been further electrochemically characterized in both half and full cells. It shows good cycling stability and rate capability. A 2.7-V cell has been built by combining a SrLi₂Ti₆O₁₄ anode with a 4-V spinel cathode of LiMn₂O₄. This cell has a higher voltage compared to the 2.5-V LiMn₂O₄/Li₄Ti₅O₁₂ system.