8,053 research outputs found

    Meso-scale FDM material layout design strategies under manufacturability constraints and fracture conditions

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    In the manufacturability-driven design (MDD) perspective, manufacturability of the product or system is the most important of the design requirements. In addition to being able to ensure that complex designs (e.g., topology optimization) are manufacturable with a given process or process family, MDD also helps mechanical designers to take advantage of unique process-material effects generated during manufacturing. One of the most recognizable examples of this comes from the scanning-type family of additive manufacturing (AM) processes; the most notable and familiar member of this family is the fused deposition modeling (FDM) or fused filament fabrication (FFF) process. This process works by selectively depositing uniform, approximately isotropic beads or elements of molten thermoplastic material (typically structural engineering plastics) in a series of pre-specified traces to build each layer of the part. There are many interesting 2-D and 3-D mechanical design problems that can be explored by designing the layout of these elements. The resulting structured, hierarchical material (which is both manufacturable and customized layer-by-layer within the limits of the process and material) can be defined as a manufacturing process-driven structured material (MPDSM). This dissertation explores several practical methods for designing these element layouts for 2-D and 3-D meso-scale mechanical problems, focusing ultimately on design-for-fracture. Three different fracture conditions are explored: (1) cases where a crack must be prevented or stopped, (2) cases where the crack must be encouraged or accelerated, and (3) cases where cracks must grow in a simple pre-determined pattern. Several new design tools, including a mapping method for the FDM manufacturability constraints, three major literature reviews, the collection, organization, and analysis of several large (qualitative and quantitative) multi-scale datasets on the fracture behavior of FDM-processed materials, some new experimental equipment, and the refinement of a fast and simple g-code generator based on commercially-available software, were developed and refined to support the design of MPDSMs under fracture conditions. The refined design method and rules were experimentally validated using a series of case studies (involving both design and physical testing of the designs) at the end of the dissertation. Finally, a simple design guide for practicing engineers who are not experts in advanced solid mechanics nor process-tailored materials was developed from the results of this project.U of I OnlyAuthor's request

    The Adirondack Chronology

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    The Adirondack Chronology is intended to be a useful resource for researchers and others interested in the Adirondacks and Adirondack history.https://digitalworks.union.edu/arlpublications/1000/thumbnail.jp

    Hunting Wildlife in the Tropics and Subtropics

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    The hunting of wild animals for their meat has been a crucial activity in the evolution of humans. It continues to be an essential source of food and a generator of income for millions of Indigenous and rural communities worldwide. Conservationists rightly fear that excessive hunting of many animal species will cause their demise, as has already happened throughout the Anthropocene. Many species of large mammals and birds have been decimated or annihilated due to overhunting by humans. If such pressures continue, many other species will meet the same fate. Equally, if the use of wildlife resources is to continue by those who depend on it, sustainable practices must be implemented. These communities need to remain or become custodians of the wildlife resources within their lands, for their own well-being as well as for biodiversity in general. This title is also available via Open Access on Cambridge Core

    Managing global virtual teams in the London FinTech industry

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    Today, the number of organisations that are adopting virtual working arrangements has exploded, and the London FinTech industry is no exception. During recent years, FinTech companies have increasingly developed virtual teams as a means of connecting and engaging geographically dispersed workers, lowering costs, and enabling greater speed and adaptability. As the first study in the United Kingdom regarding global virtual team management in the FinTech industry, this DBA research seeks answers to the question, “What makes for the successful management of a global virtual team in the London FinTech industry?”. Straussian grounded-theory method was chosen as this qualitative approach lets participants have their own voice and offers some flexibility. It also allows the researcher to have preconceived ideas about the research undertaking. The research work makes the case for appreciating the voice of people with lived experiences. Ten London-based FinTech Managers with considerable experience running virtual teams agreed to take part in this study. These Managers had spent time working at large, household-name firms with significant global reach, and one had recently become founder and CEO of his own firm, taking on clients and hiring contract staff from around the world. At least eight of the other participants were senior ‘Heads’ of various technology teams and one was a Managing Director working at a ‘Big Four’ consultancy. They had all (and many still did) spent years running geographically distributed teams with members as far away as Pacific Asia and they were all keen to discuss that breadth of experience and the challenges they faced. Results from these in-depth interviews suggested that there are myriad reasons for a global virtual team, from providing 24 hour, follow-the-sun service to locating the most cost-effective resources with the highest skills. It also confirmed that there are unique challenges to virtual management and new techniques are required to help navigate virtual managers through them. Managing a global virtual team requires much more than the traditional management competencies. Based on discussion with the respondents, a set of practical recommendations for global virtual team management was developed and covered a wide range of issues related to recruitment and selection, team building, developing standard operating procedures, communication, motivation, performance management, and building trust

    Nonunion of the clavicle: novel use of clinical recovery and ultrasound to improve our ability to predict fracture healing

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    The aim of this thesis was to progress our understanding of clavicle nonunion and the ability to accurately predict fracture healing in order to improve the current management of these injuries. Although only one in seven fractures go onto nonunion, these are challenging to predict. It is unclear if the recent widespread increase in the use of acute plate fixation for displaced fractures is justified on current evidence. It is unknown whether the early accurate prediction of fractures at high risk of nonunion is advantageous. Currently the perceived risk of nonunion is largely based on factors available at time of injury alone. The evaluation of clinical recovery following non-operative management and the novel use of ultrasound may advance our ability to accurately predict fracture healing for these injuries. The cost-effectiveness of acute clavicle plate fixation versus non-operative treatment was estimated from randomized controlled trial data that had been previously published. This was completed prior to the start of this thesis and the author was not involved in the original trial. A large retrospective review of clavicle fracture fixations was undertaken to determine whether delayed clavicle fixation has an increased risk of complications compared to acute operative management. A prospective study of displaced midshaft fractures was carried out over a two-year period to determine the influence of functional recovery on the ability to predict fracture healing. The influence of clavicle fracture management on the early functional recovery was evaluated with data from a randomized controlled trial and second prospective cohort. Finally, the novel use of ultrasound to detect early callus formation and determine whether this allows accurate prediction of fracture healing was evaluated for a cohort of clavicle and tibia fractures. The estimated cost per quality-of-life adjusted year of acute plate fixation over non-operative treatment is ÂŁ480,309.41/QALY. For a threshold of ÂŁ20,000/QALY the benefit of acute fixation would need to be present for 24 years to be cost-effective over conservative treatment. Linear regression analysis identified nonunion as the only factor to negatively influence the SF-6D at 12-months (p<0.001). A ten-year cohort of 259 clavicle plate fixations found failed primary surgery requiring revision fixation occurred in 7.7% of all patients. Smoking (p<0.001), presence of a post-operative infection (<0.001), increasing age (p=0.018), and greater time delay from injury to surgery (p=0.015) was identified as significant independent predictors on regression analysis. Receiver operating curve analysis (ROC) revealed that surgery beyond 96 days from injury has an increased rate of major complications and revision surgery. Using a matched case cohort of cases before (n=67) and after the ‘safe window’ (n=77), the risk of post-operative infection increased (Odds ratio (OR) 7.7, p=0.028), fixation failure (OR 3.8, p=0.017) and revision surgery (OR 4.8 p=0.004). A delay to operative fixation beyond 3 months following injury would appear to be associated with an increased risk of major operative complications and revision surgery. A large prospective cohort of 200 patients managed non-operatively with a displaced midshaft clavicle fracture were recruited. Regression modelling found a QuickDASH ≄40 (p=0.001), no callus on radiograph (p=0.004) and fracture movement on examination (p=0.001) were significant predictors of nonunion. If none were present the predicted nonunion risk was 3%, found in 40% of the cohort. Conversely if two or more of the predictors were present, found in 23.5% of the cohort, the predicted nonunion risk was 60%. The delayed assessment nonunion model appeared to have superior accuracy when compared to the estimation of nonunion at time of injury alone healing on ROC curve analysis (Area Under Curve analysis; 87.3% vs 64.8% respectively). Data from a randomized controlled trial was used to compare 86 patients who underwent operative fixation against 76 patients that united with non-operative treatment. The recovery of normal shoulder function, as defined by a DASH score within the predicted 95% confidence interval for each respective patient was similar between each group at six-weeks (operative 26.7% vs non-operative 25.0%, p=0.80), three-months (52.3% vs 44.2%, p=0.77) and six-months post-injury (86.0% vs 90.8%, p=0.35). The mean DASH score and return to work was also comparable at each time point. Regression analysis found no specific patient, injury or fracture predictor was associated with an early return of function following non-operative management at six or twelve weeks. From a pilot study of twenty clavicle fractures, six-week sonographic bridging callus appeared to be the most accurate, and repeatable, predictor of fracture healing with a strong agreement on intra class correlation (ICC) between four reviewers (ICC 0.82, 95% confidence interval 0.68-0.91). In a large prospective study of 112 patients, sonographic bridging callus was detected in 62.5% (n=70/112) of the cohort at six weeks post-injury. If present, union occurred in 98.6% of the fractures (n=69/70). If absent, nonunion developed in 40.5% of cases (n=17/42). The sensitivity to predict union with sonographic bridging callus at six weeks was 73.4% and the specificity was 94.4%. Three-dimensional fracture reconstruction can be created using multiple ultrasound images in order to evaluate the presence of bridging callus. This imaging modality has the potential to enhance the usability and accuracy of identification of fracture healing at an early stage following injury. Nonunion following a displaced midshaft clavicle fractures accounts for the majority of poor functional recovery and impaired quality of life over the first-year post-injury. Prediction of clavicle fracture healing at six weeks following injury maybe a safe and effective strategy to identify patients at greatest risk of nonunion. The use of functional recovery enables a more accurate estimation of nonunion risk compared to conventional prediction at time of injury alone. The use of ultrasound may further refine our ability to predict fracture healing

    To the ends of the earth: Post-Anthropocene cosmopolitanism in the novels of Kazuo Ishiguro, Margaret Atwood, and David Mitchell

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    This thesis examines the ethics and politics of cosmopolitanism beyond the Anthropocene by interrogating the presentation of the human in relation to other-than-humans in the novels of Kazuo Ishiguro, Margaret Atwood, and David Mitchell. The mounting global uncertainty and environmental crises have heightened fears that humanity may not survive beyond the third millennium, but these apocalyptic predictions reveal an anthropocentric concern with the planet’s ability to sustain human life in capitalist societies rather than the wellbeing of the planet. I argue that ensuring the survival of humanity and the planet demands a new vision of cosmopolitanism that recognises the planetary interconnectedness and interdependence of all present and future beings who share the biosphere. This proposition calls for a redefinition of the human and an expansion of the communities that humans belong to and coheres with the aim of eco-cosmopolitanism to connect the human, nonhuman, and the ecological. Using the lenses of posthumanism, ecocriticism, and cosmopolitanism, I examine how, despite their speculative content, the three authors’ novels convincingly portray the experience of ‘dislocation’ brought about by globalisation and provoke fundamental questions about what constitutes the human and how this human subject might relate to nonhuman and posthuman others ethically and equitably. Through the interrogation of these issues, this thesis also shows how these works transcend the confines of fiction to inspire and challenge our current practices of cosmopolitanism

    “That’s how we play”: an ethnographic investigation of the physical activity play, recreation and spaces of children and young people in Ireland

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    There are many different types of children’s play which vary according to age, gender and setting. Most analyses ignore some of the most common forms of play, such as physical activity play, especially during middle childhood and adolescence. The aim of this study was to identify the specific forms of physical activity play that children and young people (8 – 16 years) engage in across differing spaces in urban and rural settings in Ireland using an ethnographic approach. Physical activity play is a major contributor to children’s overall physical activity. This is important in the context of the progressive trends towards sedentary lifestyles, physical inactivity and childhood obesity, and the myriad health risks associated with these conditions. Fieldwork was conducted over a twelve-month period across four co-educational schools; a primary and a secondary school from both an urban and rural setting. Child-centred participatory, as well as quantitative methods, have been employed including child-based photography, child-directed walking interviews and anthropometry. Participatory methods empowered children as social actors and facilitated deep insights into a significant aspect of children’s lives. There is a complex interplay of factors shaping children’s physical activity play. The findings describe children’s perspectives on play and recreation in a variety of spaces including the home, school, neighbourhoods and the wider built environment. The study identifies ‘traditional’ forms of physical activity play that are continuously modified and influenced by the social context and the physical features of play space. Findings also relate to the wider socio-cultural processes that impact children’s physical activity play including age, gender, seasonality and geographic location. Recommendations have been put forward in relation to how physical activity play can be used to reduce sedentary behaviour, and in the prevention and treatment of childhood overweight and obesity. A recalibration of attitudes and policies is required to enhance children’s opportunities for physical activity play in all setting

    Contested Deployment

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    As indicated in the 2018 National Defense Strategy and evolving Multi-Domain Operations doctrine, the assumption the homeland will provide a secure space for mobilization and deployment is no longer valid. This integrated research project goes beyond affirming this assumption and contributes to efforts to mitigate the concerns a contested deployment entails. Following the introductory chapter, Chapter 2, “Army Deployments in a Contested Homeland: A Framework for Protection,” explores how current coordination and cooperation mechanisms between the DoD and state and local government may need realignment, with civil authorities preparing themselves to support military mobilization. Chapter 3, “Strategic Seaports and National Defense in a Contested Environment,” examines the 22 strategic seaports across the United States, identifying issues with throughput, structural integrity, security, readiness, funding, and authorities. Chapter 4, “Single Point of Failure,” identifies how strict adherence to a business efficiency model for munition production and distribution may jeopardize the successful employment of military forces. Chapter 5, “The Interstate Highway System: Reinvestment Needed before a Contested Deployment,” provides the status of the deteriorating road network and explains how associated vulnerabilities could be exploited by an adversary. The two appendices provide points for consideration on cyberattacks and defense and the impacts a full mobilization of reserve forces would have on the homeland.https://press.armywarcollege.edu/monographs/1944/thumbnail.jp
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