Automated assemly of large composite preforms for reinforcement applications in aerostructures

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.There is considerable interest in the use of textiles, which are known as dry fabrics, for the construction of structural preforms of varying complexity. Cost reduction is a key factor in the future expansion of textiles and this can, to a great extent, be achieved by automation of the preform assembly process. Non-Crimp-Fabrics (NCF) offer significant potential for the process automation, due to an increased deposition rate and high structural performance.This work is focused on the development of a novel methodology which can be used to generate a fully integrated automation cell to produce three dimensional (3D) components. Aautomation technique has been developed, which enables large reinforcement structures of I, C, J, and T shape to be readily produced for subsequent forming into required shapes when loaded into the mould. The preform is produced as a single piece, to reduce associated assembly and handling times. The proposed technique has been realised in design and implemented as a novel tool for forming the three-dimensional components in a single stroke for the aerospace applications. The resulting tool has been integrated into a fully automated manufacturing cell, providing an opportunity for a successful proof of principle application of such a device. The automated manufacturing cell has an integrated by robotic tacking device (RTD) which helps to produce preforms with a high degree of accuracy, where the fabrics are arranged in the required format to match the service loading of the component. Mechanical tests and numerical analyses have been conducted on a typical I-beam section to investigate the effects of both tacking position and the loading conditions on the consolidated product. Numerical analyses investigations have produced largely encourage results

Strength and ductility of bulk nanostructured aluminum processed by mechanical milling

Aluminum\u27s many exceptional properties promote it to be as a strong candidate for several applications in the aerospace, automotive, building and packaging industries to name a few. As a result, strengthening Aluminum has been the interest of many researchers over the time. The most commonly followed approaches are alloying and thermal treatments. However, recently, refining the internal structure of materials until reaching the nano-scale range to improve their mechanical properties has been fostered. Specifically speaking, research adopting this approach on various metals has yielded promising results. One of the techniques used to produce nanostructured Aluminum powders, which is the one employed in this research, is mechanical milling. Aluminum powders were mechanically milled using a high-energy ball mill under argon atmosphere for several milling durations up to 12 hours. The effect of the process control agent used during milling was investigated to determine the suitable amount to be used for best achievable mechanical behavior. Both X-ray diffraction patterns and scanning electron micrographs have revealed the establishment of nanostructured Aluminum by mechanical milling. Bulk samples were synthesized by powder metallurgy. The success of the process of powder consolidation was determined by examining the degree of densification through density measurements. The effect of mechanical milling on the bulk samples has been studied by evaluating the tensile and compressive behaviors of the developed material. The material after milling for 12 hours exhibited a tensile strength that is four folds that of the starting powders. But this elevated strength was at the cost of sacrificing the ductility of the material. Nevertheless, under compressive loading the material behaved in a ductile manner in addition to the improved strength. Peaks for secondary phases have been noticed in the X-ray diffraction patterns for the bulk samples after mechanical milling. The types of these phases remain undetermined, although high suspects of oxides and carbides exist, that might have contributed to the material strengthening. Transmission electron micrographs have ascertained achieving a nanocrystalline structure after milling for 12 hours. The poor ductility of the milled Aluminum acts as a barrier that hinders the utility of the material since almost all the applications require an amount of ductility within certain margins for shaping, manufacturing, and so forth. Hence, post-extrusion annealing was conducted on additional samples in an attempt to improve the ductility. This has been proved quite successful, but still the achieved ductility is nowhere near the range that can help commercialize the newly developed material. It was also remarkable that annealing didn\u27t result in sacrificing the acquired strength; on the contrary, the tensile strength of the material was noticed to have increased. Another approach to compromise the strength and ductility of mechanically milled Aluminum was to mix soft as-received Aluminum powders with the Aluminum powders mechanically milled for 12 hours to produce bi-modally structured Aluminum composite. Two mixing techniques were tried out that are turbula mixer and the high-energy ball mill. Using turbula mixer yielded disappointing results by demonstrating a weak bond between the two constituents. Conversely, using the ball mill for mixing allowed a strong bond to form between the constituents leading to enhancing the ductility of mechanically milled Aluminum for 12 hours without depressing the strength beyond the acceptable range

Improving Intrusion Prevention, Detection and Response

Merged with duplicate record 10026.1/479 on 10.04.2017 by CS (TIS)In the face of a wide range of attacks. Intrusion Detection Systems (IDS) and other Internet security tools represent potentially valuable safeguards to identify and combat the problems facing online systems. However, despite the fact that a variety o f commercial and open source solutions are available across a range of operating systems and network platforms, it is notable that the deployment of IDS is often markedly less than other well-known network security countermeasures and other tools may often be used in an ineffective manner. This thesis considers the challenges that users may face while using IDS, by conducting a web-based questionnaire to assess these challenges. The challenges that are used in the questionnaire were gathered from the well-established literature. The participants responses varies between being with or against selecting them as challenges but all the listed challenges approved that they are consider problems in the IDS field. The aim of the research is to propose a novel set of Human Computer Interaction-Security (HCI-S) usability criteria based on the findings of the web-based questionnaire. Moreover, these criteria were inspired from previous literature in the field of HCI. The novelty of the criteria is that they focus on the security aspects. The new criteria were promising when they were applied to Norton 360, a well known Internet security suite. Testing the alerts issued by security software was the initial step before testing other security software. Hence, a set of security software were selected and some alerts were triggered as a result of performing a penetration test conducted within a test-bed environment using the network scanner Nmap. The findings reveal that four of the HCI-S usability criteria were not fully addressed by all of these security software. Another aim of this thesis is to consider the development of a prototype to address the HCI-S usability criteria that seem to be overlooked in the existing security solutions. The thesis conducts a practical user trial and the findings are promising and attempt to find a proper solution to solve this problem. For instance, to take advantage of previous security decisions, it would be desirable for a system to consider the user's previous decisions on similar alerts, and modify alerts accordingly to account for the user's previous behaviour. Moreover, in order to give users a level of fiexibility, it is important to enable them to make informed decisions, and to be able to recover from them if needed. It is important to address the proposed criteria that enable users to confirm / recover the impact of their decision, maintain an awareness of system status all the time, and to offer responses that match users' expectations. The outcome of the current study is a set of a proposed 16 HCI-S usability criteria that can be used to design and to assess security alerts issued by any Internet security suite. These criteria are not equally important and they vary between high, medium and low.The embassy of the arab republic of Egypt (cultural centre & educational bureau) in Londo

Large deviations for a fractional stochastic heat equation in spatial dimension Rd\mathbb{R}^d driven by a spatially correlated noise

In this paper we study the Large Deviation Principle (LDP in abbreviation) for a class of Stochastic Partial Differential Equations (SPDEs) in the whole space $\mathbb{R}^d$, with arbitrary dimension $d\geq 1$, under random influence which is a Gaussian noise, white in time and correlated in space. The differential operator is a fractional derivative operator. We prove a large deviations principle for our equation, using a weak convergence approach based on a variational representation of functionals of infinite-dimensional Brownian motion. This approach reduces the proof of LDP to establishing basic qualitative properties for controlled analogues of the original stochastic system.Comment: This paper has been accepted for publication in Stochastics & Dynamics. This reprint differs from the original in pagination and typographic detail. arXiv admin note: text overlap with arXiv:1309.1935 by other author

La synergie entre COSO et l'audit interne renforce la gouvernance des entreprises agroalimentaires : étude de cas dans la région de Souss-Massa

Cette étude examine le rôle des composantes du système de contrôle interne selon COSO dans le renforcement des principes de la gouvernance d'entreprise dans les entreprises agroalimentaires de la région de Souss-Massa. Les composantes étudiées sont l'environnement de contrôle, l'évaluation des risques, les activités de contrôle, la communication et l'information, ainsi que le suivi. Les objectifs sont atteints en mobilisant les théories de l'agence et des parties prenantes, et en utilisant une approche déductive avec une méthode quantitative par questionnaire. L'échantillon de l'étude était composé de 55 personnes sélectionnées aléatoirement. Les résultats de l'analyse statistique indiquent que la présence d'un système de contrôle interne robuste est un atout considérable dans le renforcement des principes de la gouvernance d'entreprise. De plus, un engagement important envers chaque composante du système de contrôle interne consolide le système de gouvernance d'entreprise dans ces entreprises agroalimentaires, en aidant à faire face aux asymétries d'information et à limiter les comportements opportunistes et discriminatoires. Cependant, cette étude présente certaines limites, telles que l'utilisation d'un seul outil de collecte de données et la taille limitée de l'échantillon, ce qui peut affecter la représentativité des résultats

Disociación de los efectos de la atención sobre el potencial relacionado con eventos N170 de rostros y partes del cuerpo

Attention was manipulated sensu Lavie’s perceptual load theory to shorttime presentations (200 ms) of task-irrelevant unfamiliar unaltered faces, hands, and houses. Participants performed a letter detection task (X vs. N) under high (6 different letters) or low (6 identical letters) attentional load conditions. Letter strings were superimposed on task-irrelevant stimuli. Replicating and extending previous findings, while the typical pattern of face selectivity (faces > hands > houses) was observed under low load, N170 to faces, houses, and hands converged under high load. High load reduced N170 to faces, increased N170 to houses, and did not affect N170 to hands. These findings demonstrate that the category selectivity of N170 strongly depends on selective attention for faces and objects, while body parts and human bodies insensitive to selective attention.Se manipuló la atención, en el sentido de la teoría de la carga perceptiva de Lavie, a presentaciones de poco tiempo (200 ms) de rostros, manos y casas inalterados y desconocidos, irrelevantes para la tarea. Los participantes realizaron una tarea de detección de letras (X frente a N) en condiciones de carga de atención alta (6 letras diferentes) o baja (6 letras idénticas). Las cadenas de letras se superponían a estímulos irrelevantes para la tarea. Se reprodujeron y ampliaron los hallazgos anteriores, mientras que el típico patrón de selectividad de rostro (rostros > manos > casas) se observó con una carga baja, N170 a rostros, casas y manos confluyeron con una carga alta. La carga alta redujo el N170 a los rostros, aumentó el N170 a las casas y no afectó al N170 a las manos. Estos hallazgos demuestran que la selectividad de categoría del N170 depende en gran medida de la atención selectiva de rostros y objetos, mientras que las partes del cuerpo y los cuerpos humanos son insensibles a la atención selectiva