Effect of post-fill pressure and nanoclay on void morphology in resin transfer molded composites.

Resin transfer molded (RTM) composites usually suffer from the formation of flow-induced defects such as voids. Detrimental effects of voids on performance of molded parts have been studied extensively. Yet, knowledge of effective void removal strategies, along with detailed morphological void distribution within molded composites is very limited. In this investigation, effects of post-fill pressure on void content is investigated for random-mat, E-glass/epoxy RTM disks. Measured void contents agree well with results obtained in other studies for similar ranges of modified capillary number values. Packing helped significantly reduce void contents in RTM parts. In addition, voids are found to concentrate primarily within or adjacent to the fibers. Three-dimensional features of the formed voids are included in more detailed analyses of morphology variations of voids within the composite from both through-the-thickness and planar surfaces.Effects of applying a packing pressure on void morphology are investigated for similar composites. Packing pressures of zero and 570 kPa are applied and voidage is evaluated from both through-the-thickness and planar views. The packed composite is found to contain almost 92% less void content than the unpacked composite, accompanied by a 40% drop in average void size. Along the flow direction, removal of voids seems to depend on their arrangement at the end of the filling stage.Finally, effect of nanoclay content on void morphology in RTM nanoclay/E-glass/epoxy composites are investigated. ClositeRTM25A nanoclay loads of 0, 2, 5, and 10 wt% are mixed with a low-viscosity epoxy resin prior to filling. Void occurrence is observed to increase considerably with increasing nanoclay content from 2.1% in the composite without nanoclay to 5.1 and 8.3% in 5%- and 10%-nanocomposites, respectively. However, the composite with 2 wt% nanoclay yields the lowest void content of 0.7%. Voids are observed to be smaller after the addition of nanoclay at all concentrations

On LS-category of a family of rational elliptic spaces II

Let X be a finite type simply connected rationally elliptic CW-complex with Sullivan minimal model (ɅV; d) and let k ⩾ 2 the biggest integer such that d=∑_(i⩾k)▒dᵢ with d_i(V ) ⊆ Ʌ^iV. If (ɅV; d_k) is moreover elliptic then cat(ɅV, d) = cat(ɅV,d_k) = dim(V^even)(k ⧿ 2) + dim(V^odd). Our work aims to give an almost explicit formula of LS-category of such spaces in the case when k ⩾ 3 and when (ɅV;d_k) is not necessarily elliptic.peerReviewe

Syndrome d´Apple-Peel avec nécrose intestinale

Pan African Medical Journal 2012; 13:6

Essential Oil and Glandular Hairs: Diversity and Roles

The accumulation of essential oils in plants is generally limited to specialized secretory structures, namely, glandular trichomes (hairs) which are multicellular epidermal glands, found in some families such as Lamiaceae, Asteraceae, and Solanaceae, and which secrete terpenes in an extracellular cavity at the apex of the trichome. Storage of terpenoids in these structures can also be used to limit the risk of toxicity to the plant itself. The morphology of these structures varies according to the conditions of irrigation and also according to the toxicity of intracuticular contents and can be changed with the phenology of the plant. The secretory glands of aromatic plants come in different shapes and sizes, in order to ensure a specific function. This function consists mainly in the protection of different plant organs and the attraction of pollinators. Some scientist classified these glands into peltate hairs and capitate hairs, based on morphological criteria; however, others classified them into short-term glands and long-term glands, based on the mode of secretion. Short-term glands are glands that secrete rapidly to protect young organs. The long-term glands are glands in which the secretory substance accumulates gradually in the subcuticular space and play a role in the protection of mature organs such as the flower, as well as in pollination. According to this definition, he inferred that the capitate hairs are the short-term glands, while the peltate hairs are long-term glands. The difference between these two types of glands consists several aspects like structure, mode of secretion, and timing of secretion. In this object, this chapter includes some microscopic observation to glandular hairs and their combination with mode of secretion, nature of contents, and phenology of plant to give a good comprehension and classification

Kyste hydatique cérébral chez l’enfant: à propos de 5 cas

Le kyste hydatique cervical est une pathologie rare, mais non exceptionnel chez l'enfant. Nous rapportons rétrospectivement une série de cinq cas de kyste hydatique cérébral opérés, avec une revue de la littérature. Le syndrome d'hypertension intracrânien a été révélateur dans la majorité des cas. Le diagnostic a été posé par la TDM cérébrale, le traitement a été chirurgical dans tout les cas, avec une rupture du kyste dans un seul cas , traité par l'albendazol en post opératoire. L'évolution a été bonne dans 3 cas, dans un cas l'atrophie optique était irréversible, et dans un autre cas l'enfant a présenté un syndrome maniaque stabilisé sous traitement. En conclusion le kyste hydatique cérébral reste une cause non négligeable de manifestations neurologiques dans les pays endémiques, le diagnostic positif est fait par la TDM, le traitement est chirurgical, et le pronostic est généralement bon.Key words: Kyste hydatique, cerveau, enfan

Implementing Pseudo-Random Control in Boost Converter: An Effective Approach for Mitigating Conducted Electromagnetic Emissions

Currently, pulse width modulation (PWM) is a prevalent technique in the field of DC-DC converter control. Its primary objectives encompass maintaining the regulation of the converter's output voltage and improving the load's performance by mitigating the adverse effects caused by harmonic distortions. Unfortunately, the utilization of PWM is associated with significant levels of residual harmonics, characterized by notable amplitudes and frequencies, which have the potential to induce mechanical vibrations, acoustic disturbances, and electromagnetic interference (EMI).To address this challenge, a method known as pseudo-random modulation (PRM) has been developed. In comparison to traditional PWM, PRM offers ease of implementation and high efficacy in EMI mitigation. PRM achieves this by distributing harmonic power across a broader frequency range, thereby reducing the prominence of high-amplitude harmonics at specific frequencies. Within the context of Spread Spectrum Modulation (SSM), this study extensively explores diverse converter topologies and proposes an innovative hardware implementation using the cost-effective Atmega328p microcontroller. Furthermore, the study scrutinizes the consequences of implementing this randomized control strategy to reduce electromagnetic emissions from a Boost converter, a well-recognized source of significant interference in its operational environment. Ultimately, the aim is to evaluate the effectiveness of these applied methodologies in achieving the maximum dispersion of the power spectrum, thereby enhancing overall electromagnetic compatibility

Pauvreté subjective et inégalités sociales

L’appréhension du vécu des ménages marocains à partir de leurs perceptions, de leurs représentations sociales et de leurs préoccupations a fait l’objet, depuis 2007, de plusieurs enquêtes socio-économiques réalisées par le Haut-Commissariat au Plan. Les statistiques obtenues sur la base des déclarations spontanées ont été reprises par un nombre d’organismes nationaux et internationaux qui s’intéressent au bien-être de la population dans sa double composante objective et subjective, notamment la pauvreté dans sa forme subjective. Pour contextualiser ces déclarations en fonction des réalités sociales des ménages et de leur environnement social, des travaux ont été conduits pour relier le niveau de vie effectif à celui souhaité et mesurer les deux formes de la pauvreté – subjective, absolue et relative – par référence à des seuils appropriés. Sur la base de ce nouvel outillage conceptuel, il ressort que le taux de pauvreté subjective absolue est de 14 % en 2014 au lieu de 45 % par référence à l’approche directe fondée sur l’auto-identification d’appartenance à la classe pauvre. En 2007, ces taux sont respectivement de 34 % et 42 %. Quant à la pauvreté subjective relative, elle est passée de 30 % en 2007 à 42 % en 2014. Ce dernier résultat met en exergue l’impact des inégalités ressenties sur les perceptions subjectives de la pauvreté. Le paradoxe de Tocqueville montre que le niveau élevé de cette forme de pauvreté est dû globalement aux comparaisons sociales, qui souvent expliquent les perceptions négatives du bien-être des ménages