Characterization of Prepreg Tack for Composite Manufacturing by Automated Fiber Placement

Automated fiber placement (AFP) has become the industry standard for large-scale production of carbon fiber reinforced plastics (CFRP) to improve rate and reduce defects associated with manual layup. Still, defects generated during AFP processes require manual, painstaking inspection by technicians and rework of the part when substantial defects are found. Prepreg (carbon fiber infused with uncured epoxy resin) tack is one of the primary factors that influences the generation of defects that arise during auto-mated fiber placement (AFP). Tack, as it relates to AFP processes and defect formation, can be understood as a combination of two stages, cohesion and decohesion. During the cohesion phase, two pieces of prepreg are brought into contact under elevated temperature and pressure. Compaction of the resin within the contact area will result in a degree of intimate contact, I, between the mating prepreg surfaces. Defect formation, as a result of decohesion between prepreg surfaces, occurs after the cohesion phase and arises due to stress from events such as fiber placement over an existing defect, on a contoured path, etc. (Figure 1). Tack strength resists the displacement of prepreg on a surface due to stresses developed during deposition

Intimate Violence, Foreign Solutions: Domestic Violence Policy and Muslim-American Women

The overall goal of this thesis was to highlight different communicative aspects of participation in interpreter-mediated asylum hearings with unaccompanied Russianspeaking children who had applied for asylum in Sweden between 2001 and 2005. Participation in the asylum process is guaranteed to these children by the Swedish Administrative Law and the Convention on the Rights of the Child (CRC), which are incorporated in the Swedish Aliens Act. The Migration authorities in their work with asylum seeking minors have integrated principles of the best interests of the child and the principle of respecting the children’s views on matters concerning them. In this thesis, we have studied the conditions of participation in a highly complex, hybrid activity type, where participants face contradictory demands. Hybridity can be traced in communicative dilemmas which are difficult to solve and handle for all the participants involved, including the caseworkers, interpreters and children. The caseworkers are expected to control an interview in which whole of the communicative exchange is rendered by interpreters who influence the progress of the encounter. Contradiction lies in the fact that the caseworkers are expected to treat all asylum seekers equally both as a group and individually, by relating to general legal regulations and at the same time, take into account the interests and individual needs of an individual child. It might be difficult for these caseworkers to stay neutral and meet underage clients whose life stories and experiences, conduct and needs differ considerably from what is usually ascribed to children. Asylum seeking children come to Sweden to stay. Our results have shown that they take an active role in their attempts to lead to a positive outcome in their cases. In this respect, children’s testimonies and the impression they make as informants play a salient role. The communicative tasks faced by the adolescents are, however, difficult to achieve. Previous life conditions, vulnerability, psychosomatic problems, and memory and concentration difficulties may affect their performance. Other factors which might further impede these children from achieving their task is the pragmatic and linguistic deficiency, which they experience in a context where they lack communicative means and are not fully aware of the norms and regulations relevant for the encounter. Despite hese limitations, it seems that these minors try hard to shoulder their role as asylum seekers and informants actively and strategically. One strategy chosen by the children was to disclose information selectively. They tried to avoid answering questions which could reveal their age, origin or the whereabouts of their caregivers and thereby enable authorities to establish their identity and send them back. To compensate for their uncooperativeness in this area, the adolescents tended to provide information which had not been asked for. Our studies have shown that children could have been prevented by both the caseworkers and interpreters from expressing their views and opinions in a free and self-chosen way. In this respect, interpreters’ contributions were salient for what information was forwarded to the caseworkers. In some cases, they changed both the language and the format of the responses provided by the children. Some of the communicative strategies which were initiated by the interpreters could be linked to both their professional skills and to the hybridity and the complexity of the situation. Interpreters had difficulties staying neutral in relation to the children and orient them in the encounters. Age differences between the participants could also have an impact on how the children were treated and the respect and importance attributed to their voices. We have identified sequences where interpreters initiated monolingual exchanges with one of the interlocutors where they actively tried to exclude and discredit the children’s voices, something which often happened with the tacit approval of the caseworkers. Thus, it can be seen that communicative premises which are inherent in the asylum hearings influence the participant statuses of the children and their possibilities to express their asylum claims

Excessive temperature warning system Patent

Temperature sensor warning system for pneumatic tires of aircraft and ground vehicle

Neuro-electronic technology in medicine and beyond

This dissertation looks at the technology and social issues involved with interfacing electronics directly to the human nervous system, in particular the methods for both reading and stimulating nerves. The development and use of cochlea implants is discussed, and is compared with recent developments in artificial vision. The final sections consider a future for non-medicinal applications of neuro-electronic technology. Social attitudes towards use for both medicinal and non-medicinal purposes are discussed, and the viability of use in the latter case assessed

Research issues in implementing remote presence in teleoperator control

The concept of remote presence in telemanipulation is presented. A conceptual design of a prototype teleoperator system incorporating remote presence is described. The design is presented in functional terms, sensor, display, and control subsystem. An intermediate environment, in which the human operator is made to feel present, is explicated. The intermediate environment differs from the task environment due to the quantity and type of information presented to an operator and due to scaling factors protecting the operator from the hazards of the task environment. Potential benefits of remote presence systems, both for manipulation and for the study of human cognition and preception are discussed

Strain-dependent solid surface stress and the stiffness of soft contacts

Surface stresses have recently emerged as a key player in the mechanics of highly compliant solids. The classic theories of contact mechanics describe adhesion with a compliant substrate as a competition between surface energies driving deformation to establish contact and bulk elasticity resisting this. However, it has recently been shown that surface stresses provide an additional restoring force that can compete with and even dominate over elasticity in highly compliant materials, especially when length scales are small compared to the ratio of the surface stress to the elastic modulus, $\Upsilon/E$. Here, we investigate experimentally the contribution of surface stresses to the force of adhesion. We find that the elastic and capillary contributions to the adhesive force are of similar magnitude, and that both are required to account for measured adhesive forces between rigid silica spheres and compliant, silicone gels. Notably, the strain-dependence of the solid surface stress contributes significantly to the stiffness of soft solid contacts.Comment: 6 pages, 3 figure

The Intimate Relationship between Cavitation and Fracture

Nearly three decades ago, the field of mechanics was cautioned of the obscure nature of cavitation processes in soft materials [Gent, A.N., 1990. Cavitation in rubber: a cautionary tale. Rubber Chemistry and Technology, 63(3)]. Since then, the debate on the mechanisms that drive this failure process is ongoing. Using a high precision volume controlled cavity expansion procedure, this paper reveals the intimate relationship between cavitation and fracture. Combining a Griffith inspired formulation for crack propagation, and a Gent inspired formulation for cavity expansion, we show that despite the apparent complexity of the fracture patterns, the pressure-volume response follows a predictable path. In contrast to available studies, both the model and our experiments are able to track the entire process including the unstable branch, by controlling the volume of the cavity. Moreover, this minimal theoretical framework is able to explain the ambiguity in previous experiments by revealing the presence of metastable states that can lead to first order transitions at onset of fracture. The agreement between the simple theory and all of the experimental results conducted in PDMS samples with shear moduli in the range of 25-246 [kPa], confirms that cavitation and fracture work together in driving the expansion process. Through this study we also determine the fracture energy of PDMS and show its significant dependence on strain stiffening

Bacterial-epithelial contact is a key determinant of host innate immune responses to enteropathogenic and enteroaggregative escherichia coli

Background: Enteropathogenic (EPEC) and Enteroaggregative (EAEC) E. coli have similar, but distinct clinical symptoms and modes of pathogenesis. Nevertheless when they infect the gastrointestinal tract, it is thought that their flagellin causes IL-8 release leading to neutrophil recruitment and gastroenteritis. However, this may not be the whole story as the effect of bacterial adherence to IEC innate response(s) remains unclear. Therefore, we have characterized which bacterial motifs contribute to the innate epithelial response to EPEC and EAEC, using a range of EPEC and EAEC isogenic mutant strains. Methodology: Caco-2 and HEp-2 cell lines were exposed to prototypical EPEC strain E2348/69 or EAEC strain O42, in addition to a range of isogenic mutant strains. E69 [LPS, non-motile, non-adherent, type three secretion system (TTSS) negative, signalling negative] or O42 [non-motile, non-adherent]. IL-8 and CCL20 protein secretion was measured. Bacterial surface structures were assessed by negative staining Transmission Electron Microscopy. The Fluorescent-actin staining test was carried out to determine bacterial adherence. Results: Previous studies have reported a balance between the host pro-inflammatory response and microbial suppression of this response. In our system an overall balance towards the host pro-inflammatory response is seen with the E69 WT and to a greater extent O42 WT, which is in fit with clinical symptoms. On removal of the external EPEC structures flagella, LPS, BFP, EspA and EspC; and EAEC flagella and AAF, the host inflammatory response is reduced. However, removal of E69 lymphostatin increases the host inflammatory response suggesting involvement in the bacterial mediated anti-inflammatory response. Conclusion: Epithelial responses were due to combinations of bacterial agonists, with host-bacterial contact a key determinant of these innate responses. Host epithelial recognition was offset by the microbe's ability to down-regulate the inflammatory response. Understanding the complexity of this host-microbial balance will contribute to improved vaccine design for infectious gastroenteritis