3D Woven Composites: From Weaving to Manufacturing

Manufacturing near-net shape preforms of fibre-reinforced composites has received growing interest from industry. Traditionally, a preform was made from 2D fabrics, but recently, it has been shown that 3D textiles can be used with success; with weaving being the predominant technology for carbon fibre composites. In 3D weaving, weft, warp and binder fibres run across, along and through the fabrics in the X, Y and Z directions, respectively. Producing a unitised single-piece fabric and subsequently reducing the takt time required for rapid composite manufacturing are two of the main advantages of using 3D woven preforms. Weaving of 3D fabrics, manufacturing of 3D composites, physical characterisation and mechanical testing of infused composites samples are discussed in this chapter. Finally, a large automotive composite made of single-piece 3D woven preform was manufactured and presented for demonstration

Les réseaux de politique publique comme facteur d'influence du choix des instruments de politique énergétique canadienne à des fins environnementales de 1993 à nos jours

Au cours de la dernière décennie, les modes de la gouvernance ont pris place dans un contexte totalement différent de celui qu'ils avaient auparavant. Les gouvernements modernes se rendent compte qu'ils perdent de plus en plus leur capacité à élaborer et à gérer les changements d'une manière autonome. Ainsi, les fonctions et les activités traditionnellement accomplies exclusivement par le gouvernement engagent de nos jours une gamme d'acteurs étatiques et non étatiques. À l'encontre du concept traditionnel de l'État contrôleur, la gouvernance contemporaine est ainsi devenue moins une question d'offre de service et davantage une gestion indirecte des réseaux de politique publique. Dans cette entreprise, les gouvernements contemporains, cherchant plus d'information, de soutien et de légitimité en matière de formulation des décisions, ont besoin d'établir des relations avec les divers groupes d'intérêt qui, à leur tour, voulaient plus de promotion et de protection en faveur de leurs intérêts à travers leur implication au processus de l'élaboration et de la mise en œuvre des politiques publiques. Ainsi, l'approche des réseaux de politique publique représente aujourd'hui un courant considérable au sein du champ d'analyse des politiques publiques. Toutefois, les préoccupations des chercheurs pour cette approche, dans le domaine des politiques énergétiques à des fins environnementales, semblent récentes, et les études réalisées sont encore trop peu nombreuses. Au Canada, au début des années 1990, le gouvernement ainsi que plusieurs groupes d'intérêts, des différents secteurs énergétique, industriel et environnemental, ont commencé à intensifier leurs efforts pour s'attaquer au problème du changement climatique d'origine énergétique, généré surtout par le secteur de l'industrie. Au cours de la dernière décennie, la question touchant plutôt le sujet du développement énergétique durable représente le plus important domaine des politiques publiques ayant surgi récemment dans l'agenda politique du pays. Notre projet de recherche, par le truchement de l'approche des réseaux de politique publique, s'attarde à décrire et à expliquer le processus de la formulation d'une politique particulière, soit la politique énergétique à des fins de protection de l'environnement, élaborée en 1993. Il s'agit de mettre en évidence les facteurs affectant le choix des instruments de ces politiques publiques dans leur contexte national. Ainsi, la question générale de cette recherche est : Comment les phases évolutives de la formation d'un réseau de politique, en l'occurrence le Conseil canadien de l'énergie (CCE), mènent à des caractéristiques particulières à ce réseau; et comment celles-ci déterminent-elles les types des instruments de politique publique choisis, particulièrement ceux de la récente orientation des politiques énergétiques canadiennes à des fins environnementales élaborées en 1993? Afin d'atteindre l'objectif de notre recherche, deux facteurs primordiaux sont utilisés, soit la circulation de l'information et l'exercice du contrôle sur les ressources des acteurs. L'analyse des caractéristiques du réseau en fonction des liens forts et des liens faibles autant que la présence ou l'absence des trous structuraux nous permettent de bien identifier les positions des différents acteurs, étatiques et non étatiques, sur le plan de l'information et du contrôle, qui à leur tour, nous semble-t-il, constituent des facteurs affectant les types des instruments des politiques publiques choisis : instruments substantifs, qui indiquent le degré de l'intervention du gouvernement, et instruments procéduraux, qui mettent plutôt l'accent sur le degré de l'influence du gouvernement sur les acteurs non étatiques. L'étude soutient que l'approche des réseaux se distingue notamment par son potentiel à expliquer l'interrelation relative entre idées, intérêts et institutions, ce qui a son tour est susceptible de permettre une meilleure compréhension des processus de l'élaboration des politiques énergétiques et environnementales canadiennes. Qui plus est, le fait de recourir à ce cadre d'analyse permet d'approcher autrement le sujet étudié en essayant de comprendre et d'expliquer non seulement les interactions entre les différents acteurs cibles, mais aussi le dynamisme et l'évolution de ces relations dans leur durée, comme étant des déterminants primordiaux en matière de sélection des instruments des politiques

On the Digital Holographic Interferometry of Fibrous Material, I. Optical Properties of Polymer and Optical Fibers

The digital holographic interferometry (DHI) was utilized for investigating the optical properties of polymer and optical fibers. The samples investigated here were polyvinylidene fluoride (PVDF) polymer fiber and graded-index (GRIN) optical fiber. The phase shifting Mach-Zehnder interferometer was used to obtain five phase-shifted holograms, in which the phase difference between two successive holograms is pi/2, for each fiber sample. These holograms were recorded using a CCD camera and were combined to gain a complex wavefield, which was numerically reconstructed using the convolution approach into amplitude and phase distributions. The reconstructed phase distribution was used to determine the refractive index, birefringence and refractive index profile of the studied samples. The mean refractive index has been measured with accuracy up to 4 {\times} 10-4. The main advantage of DHI is to overcome the manual focusing limitations by means of the numerical focusing. The results showed accurate measurements of the optical properties of fibers.Comment: abstract, reference

Evaluation of laparoscopic-assisted anorectoplasty for the management of intermediate and high anorectal malformations in boys: Mansoura experience

Introduction: Laparoscopic-assisted anorectoplasty (LAARP) has been gaining great popularity for management of imperforate anus. This study aims to evaluate the use of this technique for high and intermediate anorectal malformations in boys.Patients and methods: From December 2012 to December 2016, we performed LAARP on 20 boys, all of which were colostomized at birth. Findings regarding the patients’ age at operation, type of anomaly, associated morbidities, sacral ratios, operative time, intraoperative complications, hospital stay, immediate/long-term postoperative complications, and reoperations were noted. Postoperatively, we evaluated the patients using barium enema, an ascending and voiding cystourethrogram, pelvic MRI, and a functional continence evaluation questionnaire.Results: A total of 11 patients presented with rectourethral bulbar fistula (RBF), seven with rectourethral prostatic fistula (RPF), one with rectovesical fistula, and one with no fistula. Mean sacral ratio was 0.82 ± 0.19. Mean age at time of LAARP was 236 ± 77 days. Mean operative time was 152 ± 32 min. Our most common intraoperative complication was peritoneal contamination (20%). Incidence of rectal mucosal prolapse was 40%. Barium enema revealed a mean rectoanal angle of 107 ± 13°. Ascending and voiding cystourethrogram revealed a residual urethral diverticulum in seven cases, six of which had RBFs. Mean MRI placement score obtained was 0.76± 0.51 denoting excellent rectal position.Conclusion: Usage of LAARP to manage high and intermediate anorectal malformations in boys is feasible, allowing accurate rectal placement within the muscle complex and with good postoperative functional results. Residual urethral diverticulum occurred more frequently in patients with RBF. Incidence of mucosal prolapse is high after LAARP and should be avoided.Keywords: laparoscopic-assisted anorectoplasty, anorectal malformations, residual urethral diverticulum post LAAR

Damage assessment of NCF, 2D and 3D woven composites under compression after multiple-impact using acoustic emission

This study is devoted to the damage characterization of Non-Crimp Fabric (NCF), 2D plain-woven (2D-PW) and 3D orthogonal plain-woven (ORT-PW) carbon/epoxy laminates, subjected to compression after multiple-impact loading, using Acoustic Emission (AE). The ultrasonic C-scan images showed that the interlaminar damage area induced by the single and 3-impact in ORT-PW architecture is 3 and 2 times smaller than NCF and 2D-PW architectures respectively. The impacted specimens were then subjected to the in-plane compression load. Two indices, one based on the mechanical response and another one based on the AE behavior of the laminates, were proposed to compare the performance of different architectures. These indices showed that the ORT-PW had the best performance among all the architectures. Finally, AE was used to distinguish the different damage mechanisms including: matrix cracking, intra and inter-yarn debonding, defected-fiber breakage, intact-fiber breakage and z-binder fiber breakage in the CAI tests of the architectures

Compression after multiple low velocity impacts of NCF, 2D and 3D woven composites

This paper investigates the effect of the fabric architecture and the z-binding yarns on the compression after multiple impacts behavior of composites. Four fiber architectures are investigated: non-crimp fabric (NCF), 2D plain weave (2D-PW), 3D orthogonal plain (ORT-PW) and twill (ORT-TW) weave. The specimens were subjected to single and multiple low-velocity impacts at different locations with the same energy level (15 J). Non-destructive techniques including ultrasonic C-scanning, X-ray CT and Digital Image Correlation (DIC) are employed to quantitatively analyze and capture the Barely Visible Impact Damage (BVID) induced in the specimens. Although the absorbed energy was approximately the same, damage was the least in 3D woven architectures. In the case of compression after impact, 3D woven composites demonstrated a progressive damage behavior with the highest residual strength (~92%) while 2D plain weave and NCF specimens showed suddenly catastrophic damage and the residual strength of ~65% and ~55% respectively

Knowledge, Awareness, and Attitudes about Research Ethics among Dental Faculty in the Middle East: A Pilot Study

Objective. To assess the knowledge, awareness, and attitudes of dental faculty regarding research ethics and research ethics committees (RECs). Design. Through convenience sampling, we distributed a survey to academics at dental faculties at two universities in the Middle East. We used descriptive, chi-square, and logistic regression statistics to analyze the data. Results. Our response rate was 62.5%. A large majority (>90%) held positive attitudes towards RECs; however, almost half (44.0%) thought that RECs would delay research. Less than half (36.8%) had received prior training in research ethics, and the average score they achieved on the questions on research ethics was only 40.2%. Most (>90%), however, were favorable towards research ethics education. Finally, some faculty held attitudes regarding certain research ethics practices that were not optimal. Conclusions. We conclude that among the dental faculties participating in our study, there is broad-based acceptance of RECs and training in research ethics, while there are knowledge gaps in research ethics. We recommend further studies to determine the generalizability of our findings to other institutions

Mechanism of Nickel and Chromium-Induced Immunotoxicity and Oxidative Stress: A Comparative Study

Abstract Introduction: Chromium (Cr) and Nickel (Ni) are examples of commonly used industrial substances with negative long time exposure on human health. One mechanism whereby metals can alter health is through modulation of immune homeostasis. They are capable of producing oxidative stress and it is possible that this oxidative stress contributes to the carcinogenic response of these metals

Entropy Generation Analysis of Desalination Technologies

Increasing global demand for fresh water is driving the development and implementation of a wide variety of seawater desalination technologies. Entropy generation analysis, and specifically, Second Law efficiency, is an important tool for illustrating the influence of irreversibilities within a system on the required energy input. When defining Second Law efficiency, the useful exergy output of the system must be properly defined. For desalination systems, this is the minimum least work of separation required to extract a unit of water from a feed stream of a given salinity. In order to evaluate the Second Law efficiency, entropy generation mechanisms present in a wide range of desalination processes are analyzed. In particular, entropy generated in the run down to equilibrium of discharge streams must be considered. Physical models are applied to estimate the magnitude of entropy generation by component and individual processes. These formulations are applied to calculate the total entropy generation in several desalination systems including multiple effect distillation, multistage flash, membrane distillation, mechanical vapor compression, reverse osmosis, and humidification-dehumidification. Within each technology, the relative importance of each source of entropy generation is discussed in order to determine which should be the target of entropy generation minimization. As given here, the correct application of Second Law efficiency shows which systems operate closest to the reversible limit and helps to indicate which systems have the greatest potential for improvement.King Fahd University of Petroleum and MineralsCenter for Clean Water and Clean Energy at MI