6,301 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

    Gasificação direta de biomassa para produção de gás combustível

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    The excessive consumption of fossil fuels to satisfy the world necessities of energy and commodities led to the emission of large amounts of greenhouse gases in the last decades, contributing significantly to the greatest environmental threat of the 21st century: Climate Change. The answer to this man-made disaster is not simple and can only be made if distinct stakeholders and governments are brought to cooperate and work together. This is mandatory if we want to change our economy to one more sustainable and based in renewable materials, and whose energy is provided by the eternal nature energies (e.g., wind, solar). In this regard, biomass can have a main role as an adjustable and renewable feedstock that allows the replacement of fossil fuels in various applications, and the conversion by gasification allows the necessary flexibility for that purpose. In fact, fossil fuels are just biomass that underwent extreme pressures and heat for millions of years. Furthermore, biomass is a resource that, if not used or managed, increases wildfire risks. Consequently, we also have the obligation of valorizing and using this resource. In this work, it was obtained new scientific knowledge to support the development of direct (air) gasification of biomass in bubbling fluidized bed reactors to obtain a fuel gas with suitable properties to replace natural gas in industrial gas burners. This is the first step for the integration and development of gasification-based biorefineries, which will produce a diverse number of value-added products from biomass and compete with current petrochemical refineries in the future. In this regard, solutions for the improvement of the raw producer gas quality and process efficiency parameters were defined and analyzed. First, addition of superheated steam as primary measure allowed the increase of H2 concentration and H2/CO molar ratio in the producer gas without compromising the stability of the process. However, the measure mainly showed potential for the direct (air) gasification of high-density biomass (e.g., pellets), due to the necessity of having char accumulation in the reactor bottom bed for char-steam reforming reactions. Secondly, addition of refused derived fuel to the biomass feedstock led to enhanced gasification products, revealing itself as a highly promising strategy in terms of economic viability and environmental benefits of future gasification-based biorefineries, due to the high availability and low costs of wastes. Nevertheless, integrated techno economic and life cycle analyses must be performed to fully characterize the process. Thirdly, application of low-cost catalyst as primary measure revealed potential by allowing the improvement of the producer gas quality (e.g., H2 and CO concentration, lower heating value) and process efficiency parameters with distinct solid materials; particularly, the application of concrete, synthetic fayalite and wood pellets chars, showed promising results. Finally, the economic viability of the integration of direct (air) biomass gasification processes in the pulp and paper industry was also shown, despite still lacking interest to potential investors. In this context, the role of government policies and appropriate economic instruments are of major relevance to increase the implementation of these projects.O consumo excessivo de combustíveis fósseis para garantir as necessidades e interesses da sociedade conduziu à emissão de elevadas quantidades de gases com efeito de estufa nas últimas décadas, contribuindo significativamente para a maior ameaça ambiental do século XXI: Alterações Climáticas. A solução para este desastre de origem humana é de caráter complexo e só pode ser atingida através da cooperação de todos os governos e partes interessadas. Para isto, é obrigatória a criação de uma bioeconomia como base de um futuro mais sustentável, cujas necessidades energéticas e materiais sejam garantidas pelas eternas energias da natureza (e.g., vento, sol). Neste sentido, a biomassa pode ter um papel principal como uma matéria prima ajustável e renovável que permite a substituição de combustíveis fósseis num variado número de aplicações, e a sua conversão através da gasificação pode ser a chave para este propósito. Afinal, na prática, os combustíveis fósseis são apenas biomassa sujeita a elevada temperatura e pressão durante milhões de anos. Além do mais, a gestão eficaz da biomassa é fundamental para a redução dos riscos de incêndio florestal e, como tal, temos o dever de utilizar e valorizar este recurso. Neste trabalho, foi obtido novo conhecimento científico para suporte do desenvolvimento das tecnologias de gasificação direta (ar) de biomassa em leitos fluidizados borbulhantes para produção de gás combustível, com o objetivo da substituição de gás natural em queimadores industriais. Este é o primeiro passo para o desenvolvimento de biorrefinarias de gasificação, uma potencial futura indústria que irá providenciar um variado número de produtos de valor acrescentado através da biomassa e competir com a atual indústria petroquímica. Neste sentido, foram analisadas várias medidas para a melhoria da qualidade do gás produto bruto e dos parâmetros de eficiência do processo. Em primeiro, a adição de vapor sobreaquecido como medida primária permitiu o aumento da concentração de H2 e da razão molar H2/CO no gás produto sem comprometer a estabilidade do processo. No entanto, esta medida somente revelou potencial para a gasificação direta (ar) de biomassa de alta densidade (e.g., pellets) devido à necessidade da acumulação de carbonizados no leito do reator para a ocorrência de reações de reforma com vapor. Em segundo, a mistura de combustíveis derivados de resíduos e biomassa residual florestal permitiu a melhoria dos produtos de gasificação, constituindo desta forma uma estratégia bastante promissora a nível económico e ambiental, devido à elevada abundância e baixo custo dos resíduos urbanos. Contudo, devem ser efetuadas análises técnico-económicas e de ciclo de vida para a completa caraterização do processo. Em terceiro, a aplicação de catalisadores de baixo custo como medida primária demonstrou elevado potencial para a melhoria do gás produto (e.g., concentração de H2 e CO, poder calorífico inferior) e para o incremento dos parâmetros de eficiência do processo; em particular, a aplicação de betão, faialite sintética e carbonizados de pellets de madeira, demonstrou resultados promissores. Finalmente, foi demonstrada a viabilidade económica da integração do processo de gasificação direta (ar) de biomassa na indústria da pasta e papel, apesar dos parâmetros determinados não serem atrativos para potenciais investidores. Neste contexto, a intervenção dos governos e o desenvolvimento de instrumentos de apoio económico é de grande relevância para a implementação destes projetos.Este trabalho foi financiado pela The Navigator Company e por Fundos Nacionais através da Fundação para a Ciência e a Tecnologia (FCT).Programa Doutoral em Engenharia da Refinação, Petroquímica e Químic

    Review of Methodologies to Assess Bridge Safety During and After Floods

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    This report summarizes a review of technologies used to monitor bridge scour with an emphasis on techniques appropriate for testing during and immediately after design flood conditions. The goal of this study is to identify potential technologies and strategies for Illinois Department of Transportation that may be used to enhance the reliability of bridge safety monitoring during floods from local to state levels. The research team conducted a literature review of technologies that have been explored by state departments of transportation (DOTs) and national agencies as well as state-of-the-art technologies that have not been extensively employed by DOTs. This review included informational interviews with representatives from DOTs and relevant industry organizations. Recommendations include considering (1) acquisition of tethered kneeboard or surf ski-mounted single-beam sonars for rapid deployment by local agencies, (2) acquisition of remote-controlled vessels mounted with single-beam and side-scan sonars for statewide deployment, (3) development of large-scale particle image velocimetry systems using remote-controlled drones for stream velocity and direction measurement during floods, (4) physical modeling to develop Illinois-specific hydrodynamic loading coefficients for Illinois bridges during flood conditions, and (5) development of holistic risk-based bridge assessment tools that incorporate structural, geotechnical, hydraulic, and scour measurements to provide rapid feedback for bridge closure decisions.IDOT-R27-SP50Ope

    Growth trends and site productivity in boreal forests under management and environmental change: insights from long-term surveys and experiments in Sweden

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    Under a changing climate, current tree and stand growth information is indispensable to the carbon sink strength of boreal forests. Important questions regarding tree growth are to what extent have management and environmental change influenced it, and how it might respond in the future. In this thesis, results from five studies (Papers I-V) covering growth trends, site productivity, heterogeneity in managed forests and potentials for carbon storage in forests and harvested wood products via differing management strategies are presented. The studies were based on observations from national forest inventories and long-term experiments in Sweden. The annual height growth of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) had increased, especially after the millennium shift, while the basal area growth remains stable during the last 40 years (Papers I-II). A positive response on height growth with increasing temperature was observed. The results generally imply a changing growing condition and stand composition. In Paper III, yield capacity of conifers was analysed and compared with existing functions. The results showed that there is a bias in site productivity estimates and the new functions give better prediction of the yield capacity in Sweden. In Paper IV, the variability in stand composition was modelled as indices of heterogeneity to calibrate the relationship between basal area and leaf area index in managed stands of Norway spruce and Scots pine. The results obtained show that the stand structural heterogeneity effects here are of such a magnitude that they cannot be neglected in the implementation of hybrid growth models, especially those based on light interception and light-use efficiency. In the long-term, the net climate benefits in Swedish forests may be maximized through active forest management with high harvest levels and efficient product utilization, compared to increasing carbon storage in standing forests through land set-asides for nature conservation (Paper V). In conclusion, this thesis offers support for the development of evidence-based policy recommendations for site-adapted and sustainable management of Swedish forests in a changing climate

    Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing

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    Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 °C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 °C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 °C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. Due to the high crystalline quality and amenity to printing, the IPL ZnO QDs have numerous potential uses ranging from sensing to opto-electronic devices

    Improving Safety for RITI Communities in Idaho: Documenting Crash Rates and Possible Intervention Measures

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    This report describes a new set of Geographic Information System (GIS) tools that we created to conduct safety analyses. These new GIS tools can be used by state DOTs and transportation agencies to document crash rates and prioritize safety improvement projects. The tools perform Network Segment Screening, the first step in the Roadway Safety Management Process (RSMP) outlined in the Highway Safety Manual (HSM). After developing these new tools, we conducted two case studies to demonstrate how they can be used. The first case study was for screening intersections. Our analysis included all intersections on the Idaho State Highway System. In practice, the analysis would likely be done only for a subset of intersections, such as only for signalized intersections on urban arterials. We chose all intersections for illustration purposes. The result was a ranking of intersections that would most likely benefit from safety improvement efforts. We applied three performance measures to rank the intersections: Crash Frequency, Crash Rate, and Equivalent Cost. The second case study was for screening roadway segments. Again, the entire Idaho State Highway System was included for illustration. The HSM describes two key methods for screening roadway segments: Simple Ranking and Sliding Window. Both methods are available in the new tools. This case study demonstrates the advantage of the Sliding Window, which would be impractical to accomplish on a large scale without the assistance of our new GIS tools. The final part of the work presented in this report is a synthesis to identify and document possible measures to reduce crashes for RITI communities in Idaho and throughout the northwest region

    A comprehensive accounting of lncRNA dynamics within vascular smooth muscle cell pathological transitions

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    Vascular smooth muscle cells (VSMCs) provide vital contractile force within blood vessel walls, yet also propagate widespread cardiovascular pathologies with high mortality rates through pathological activities. The targeting of such phenotypes in VSMCs has been a commonly-touted strategy for decades yet we still have no viable option to implement this. Recent studies have established that VSMC phenotypes are driven, in part, by the diverse effects of long non-coding RNAs (lncRNAs) on gene expression. This class of largely uncharacterised gene regulators may offer a wealth of novel targets to be used to target VSMCs. However, their characterisation in VSMCs in pathological states is hampered by incomplete lncRNA representation in reference annotation. In this thesis, we address this by assembling non-reference transcripts in RNA sequencing datasets describing saphenous vein VSMCs stimulated in vitro with cytokines and growth factors or arterial VSMCs stimulated with mechanical stress. We also utilised VSMCs isolated from atherosclerotic plaques. All transcripts were subject to a rigorous lncRNA prediction pipeline to provide an expanded VSMC transcriptome with an unprecedented level of detail on the lncRNAs associated with VSMC pathological states. We found substantially improved coverage of lncRNAs responding to pro-mitogenic stimuli, with non-reference lncRNAs contributing 21–32% per dataset. We also demonstrate non-reference lncRNAs were biased towards enriched expression within VSMCs, suggesting extra lncRNAs highlighted by our pipeline have particular relevance to VSMC-specific processes. They were also biased towards transcription from enhancer sites suggesting they coordinate the regulation of neighbouring protein-coding genes. Both VSMC-enriched and enhancer-transcribed lncRNAs were large components of lncRNAs responding to pathological stimuli, yet without novel transcript discovery 33–46% of these lncRNAs would remain hidden. In parallel to this analysis, we mined the expanded VSMC annotation to initially explore functionality in a small cohort of uncharacterised lncRNAs within the saphenous vein VSMC in vitro model. In our final round of analysis, we hypothesised that many lncRNAs may be involved in directing early transcriptional changes leading up to proliferation – and so constitute targets that may be particularly high value through acting upstream of multiple mitogenic or pathogenic pathways. We therefore used our expanded VSMC annotation as a foundation to perform a deeper analysis of lncRNA activity within RNAseq samples obtained from the first 24 hours of stimulation in the saphenous vein VSMC in vitro model, aiming to identify lncRNAs influencing initial transcriptional changes prior to observable cell division. We noted an enrichment of lncRNA induction – particularly those which were VSMC-enriched or enhancer-transcribed – within an early phase of SVSMC stimuli response prior to proliferation. Transcription factor mRNA dynamics also localised to earlier phases whilst cell cycle mRNAs were overwhelmingly induced after 8 hours. This suggests the involvement of lncRNAs in an early phase of gene regulation sets the VSMC on a path towards later proliferation. To predict lncRNAs with functional impact in the 4 hour regulatory phase, we looked for evidence of their cis-regulation of nearby genes. Genes located near differentially expressed intergenic lncRNAs were 1.51x more likely to be differentially expressed within the four hour window than those located elsewhere in the genome. This effect was also identified for transcription factors and was particularly potent for genes around enhancer-transcribed lncRNAs (2.26x) but weakened when considering over longer time periods (1.16x). Together this suggests a focus of lncRNA-dependent cis-regulation activity in the first four hours after stimulation that could lead to wider downstream impact on VSMC pathological states. We finish by identifying a cohort of uncharacterised lncRNAs regulated in the initial four hour phase that have strong correlations in expression with transcription factors or other genes that explicitly link to vasculoproliferative pathology. Overall, our comprehensive VSMC lncRNA repertoire provides much needed clarity on the activity of lncRNAs within VSMC pathological states. The approach we outline allows proper prioritisation of candidates for characterisation and exemplifies a strategy to broaden our knowledge of lncRNA across a range of disease states

    The impact of cultural differences towards product innovation in smartphone industry: a cross cultural study on consumers from Saudi Arabia and United Kingdom

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    Smartphone penetration is growing across the globe and people from all over the world are increasingly using this device. However, the average replacement cycle length of smartphone is increasing. The consumers are taking longer now to replace their smartphone. This presents the problem for the smartphone corporations to better understand the challenges currently present for consumers regarding adopting new smartphones and how the latest technology is perceived across cultures. Previous literature confirms the link of culture and uptake of technology. However, there are lack of technology acceptance models which takes culture into account and there is scarcity of frameworks which compares European and Middle Eastern culture in context of innovation. The purpose of our study is to explore the impact of culture within smartphone industry by developing a framework which compares adoption behaviour. This study aims to fill this gap by developing and testing a conceptual framework based on Technology Acceptance Model, Theory of Reasoned Action, Sheth Model and Hofstede’s Cultural Dimension Theory. Researcher attempts to validate the moderating effect of Hofstede’s cultural dimensions on behavioural intention to use new smartphone technology. This exploratory study uses interpretivist approach and gathers qualitative data by conducting 28 in depth semi-structured interviews to evaluate the psychological behaviour of the consumers in UK and Saudi Arabia aged 18-34. Our study concluded that both adoption and resistance towards innovation within smartphone usage are driven to a varying extent by Individualism, Uncertainty avoidance, and Power distance dimensions. The research also showed that smartphone users across both cultures believed that there has not been a meaningful innovation within smartphone industry in last 5 years. This study contributes by enlightening Policy makers, Smartphone corporations, and Software developers on factors relevant in adoption of latest smartphone features (Voice Assistants, Digital Payments). It also contributes to body of knowledge by confirming the impact and relevance of culture in technological industry. The study provides an in-depth analysis in the area which is underdeveloped theoretically and encourage future researchers to apply our model in different regions and industries

    Paisaje(s) Fotovoltaicos.

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    [ES] El desarrollo de energías renovables como la solar, es una prioridad clave para la Unión Europea. Este proyecto de investigación y diseño se plantea comprender los impactos territoriales que causan las infraestructuras fotovoltaicas, con el objetivo de proponer posibles formas de integrar estos sistemas en el paisaje teniendo en cuenta objetivos ecológicos y paisajísticos. En España, es particularmente relevante ya que recientemente se ha manifestado preocupación por las pérdidas en la biodiversidad asociada con la construcción de campos de energía solar a gran escala.[EN] The development of renewable energy such as solar is a key priority for the European Union. This research and design project aims to understand the territorial impacts caused by photovoltaic infrastructures, with the aim of proposing possible ways to integrate these systems into the landscape, taking into account ecological and landscape objectives. In Spain, it is particularly relevant since concern has recently been expressed about the losses in biodiversity associated with the construction of a large-scale solar energy operations.[CA] El desenvolupament d'energia renovables com la solar, és una prioritat clau per a la Unió Europea. Aquest projecte de recerca i disseny es planteja comprendre els impactes territorials que causen les infraestructures fotovoltaiques, amb l'objectiu de proposar possibles maneres d'integrar aquests sistemes en el paisatge tenint en compte objectius ecològics i paisatgístics. A Espanya, és particularment rellevant ja que recentment s'ha manifestat preocupació per les pèrdues en la biodiversitat associada amb la construcció de camp d'energia solar a gran escala.Myers, JP. (2021). Paisaje(s) Fotovoltaicos. Universitat Politècnica de València. http://hdl.handle.net/10251/181556TFG
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