8,941 research outputs found
Simulation of metal powder packing behaviour in laser-based powder bed fusion
Laser-based powder bed fusion (L-PBF) is a method of additive manufacturing, in which metal powder is fused into solid parts, layer by layer. L-PBF shows high promise for manufacture of functional Tungsten parts, but the development of Tungsten powder feedstock for L-PBF processing is demanding and expensive. Therefore, computer simulation is explored as a possible tool for Tungsten powder feedstock development at EOS Finland Oy, with whom this thesis was made.
The aim of this thesis was to develop a simulation model of the recoating process of an EOS M 290 L-PBF system, as well as a validation method for the simulation. The validated simulation model can be used to evaluate the applicability of the used simulation software (FLOW-3D DEM) in powder material development, and possibly use the model as a platform for future application with Tungsten powder. In order to reduce complexity and uncertainties, the irregular Tungsten powder is not yet simulated, and a well-known, spherical EOS IN718 powder feedstock was used instead.
The validation experiment is based on building a low, enclosed wall using the M 290 L-PBF system. Recoated powder is trapped inside as the enclosure is being built, making it possible to remove the sampled powder from a known volume. This enables measuring the powder packing density (PD) of the powder bed. The experiment was repeated five times and some sources of error were also quantified. Average PD was found to be 52 % with a standard deviation of 0.2 %.
The simulation was modelled after the IN718 powder and corresponding process used in the M 290 system. Material-related input values were found by dynamic image analysis, pycnometry, rheometry, and from literature. PD was measured with six different methods, and the method considered as most analogous to the practical validation experiment yielded a PD of 52 %. Various particle behavior phenomena were also observed and analyzed.
Many of the powder bed characterization methods found in literature were not applicable to L-PBF processing or were not representative of the simulated conditions. Many simulation studies were also found to use no validation, or used a validation method which is not based on the investigated phenomena. The validation model developed in this thesis accurately represents the simulated conditions and is found to produce reliable and repeatable results. The simulation model was parametrized with values acquired from practical experiments or literature and closely matched the validation experiment, and could therefore be considered a truthful representation of the powder recoating process of an EOS M 290. The model can be used as a platform for future development of Tungsten powder simulation
Openness in Education as a Praxis: From Individual Testimonials to Collective Voices
Why is Openness in Education important, and why is it critically needed at this moment? As manifested in our guiding question, the significance of Openness in Education and its immediate necessity form the heart of this collaborative editorial piece. This rather straightforward, yet nuanced query has sparked this collective endeavour by using individual testimonies, which may also be taken as living narratives, to reveal the value of Openness in Education as a praxis. Such testimonies serve as rich, personal narratives, critical introspections, and experience-based accounts that function as sources of data. The data gleaned from these narratives points to the understanding of Openness in Education as a complex, multilayered concept intricately woven into an array of values. These range from aspects such as sharing, access, flexibility, affordability, enlightenment, barrier-removal, empowerment, care, individual agency, trust, innovation, sustainability, collaboration, co-creation, social justice, equity, transparency, inclusivity, decolonization, democratisation, participation, liberty, and respect for diversity. This editorial, as a product of collective endeavour, invites its readers to independently engage with individual narratives, fostering the creation of unique interpretations. This call stems from the distinctive character of each narrative as they voice individual researchersâ perspectives from around the globe, articulating their insights within their unique situational contexts
Technology for Low Resolution Space Based RSO Detection and Characterisation
Space Situational Awareness (SSA) refers to all activities to detect, identify and track objects in Earth orbit. SSA is critical to all current and future space activities and protect space assets by providing access control, conjunction warnings, and monitoring status of active satellites. Currently SSA methods and infrastructure are not sufficient to account for the proliferations of space debris. In response to the need for better SSA there has been many different areas of research looking to improve SSA most of the requiring dedicated ground or space-based infrastructure. In this thesis, a novel approach for the characterisation of RSOâs (Resident Space Objects) from passive low-resolution space-based sensors is presented with all the background work performed to enable this novel method. Low resolution space-based sensors are common on current satellites, with many of these sensors being in space using them passively to detect RSOâs can greatly augment SSA with out expensive infrastructure or long lead times. One of the largest hurtles to overcome with research in the area has to do with the lack of publicly available labelled data to test and confirm results with. To overcome this hurtle a simulation software, ORBITALS, was created. To verify and validate the ORBITALS simulator it was compared with the Fast Auroral Imager images, which is one of the only publicly available low-resolution space-based images found with auxiliary data. During the development of the ORBITALS simulator it was found that the generation of these simulated images are computationally intensive when propagating the entire space catalog. To overcome this an upgrade of the currently used propagation method, Specialised General Perturbation Method 4th order (SGP4), was performed to allow the algorithm to run in parallel reducing the computational time required to propagate entire catalogs of RSOâs. From the results it was found that the standard facet model with a particle swarm optimisation performed the best estimating an RSOâs attitude with a 0.66 degree RMSE accuracy across a sequence, and ~1% MAPE accuracy for the optical properties. This accomplished this thesis goal of demonstrating the feasibility of low-resolution passive RSO characterisation from space-based platforms in a simulated environment
Recommended from our members
The Role of Interactive Web Broadcasts in Fostering Distance Learning Studentsâ Engagement with Practical Lab and Fieldwork
Practical work in science and technology disciplines is crucial for studentsâ understanding and mastery. For educators who teach those disciplines at a distance and for students who learn remotely, this endeavour may be challenging.
The study presented in this thesis investigates the use of Interactive Web Broadcasts (IWBs) in five undergraduate practical science and technology modules at The Open University. The study examines the reasons for using IWBs, as well as the strategies and types of interactions that staff and students use to engage and interact with one another. The study gathered perspectives from academics (n=18); associate lecturers (n=10); technical production team (n=3); students (n=88), and an external guest expert about the purposes, strategies and motivations of participating in IWBs. The study used a qualitatively mixed-methods design. An adapted protocol of Flandersâs Interaction Analysis Categories was used to analyse the interaction patterns in the web broadcast transcripts and text-chat logs, and a discourse analysis coding scheme was applied to analyse the text-chat. Student online questionnaires were administered towards the end of the modules to capture the student perceptions of IWBs. Student interviews and staff focus groups were also conducted to gain a fuller picture of experiences of using and engaging with IWBs.
Findings show that the purposes and aims of using IWBs are to facilitate student engagement, foster a sense of community, and demonstrate an authentic practice of the sciences in real-world contexts. The communicative strategies were primarily affective and met studentsâ interests and expectations. The IWBs mitigated feelings of isolation that are common in distance education environments. IWBs had positive impacts on professional teaching practices and fostered collegiality and collaboration among staff. The findings are relevant to other distance and traditional campus-based universities that teach practical science and technology, those who teach online using synchronous technology-mediated systems, and those who are interested in student engagement and practical work
Writing Facts
»Fact« is one of the most crucial inventions of modern times. Susanne Knaller discusses the functions of this powerful notion in the arts and the sciences, its impact on aesthetic models and systems of knowledge. The practice of writing provides an effective procedure to realize and to understand facts. This concerns preparatory procedures, formal choices, models of argumentation, and narrative patterns. By considering »writing facts« and »writing facts«, the volume shows why and how »facts« are a result of knowledge, rules, and norms as well as of description, argumentation, and narration. This approach allows new perspectives on »fact« and its impact on modernity
Ab Initio Language Teaching in British Higher Education
Drawing extensively on the expertise of teachers of German in universities across the UK, this volume offers an overview of recent trends, new pedagogical approaches and practical guidance for teaching at beginners level in the higher education classroom. At a time when entries for UK school exams in modern foreign languages are decreasing, this book serves the urgent need for research and guidance on ab initio learning and teaching in HE. Using the example of teaching German, it offers theoretical reflections on teaching ab initio and practice-oriented approaches that will be useful for teachers of both German and other languages in higher education.
The first chapters assess the role of ab initio provision within the wider context of modern languages departments and language centres. They are followed by sections on teaching methods and innovative approaches in the ab initio classroom that include chapters on the use of music, textbook evaluation, the effective use of a flipped classroom and the contribution of language apps. Finally, the book focuses on the learner in the ab initio context and explores issues around autonomy and learner strengths. The whole builds into a theoretically grounded guide that sketches out perspectives for teaching and learning ab initio languages that will benefit current and future generations of students
Learning to express, learning as self-expression: a multimethod investigation of the L2 selves of distance adult Irish L2 learners
This multimethod study is an exploration of the validity and interpretive utility of Dörnyeiâs (2009) âL2 motivational self-systemâ (L2MSS), as it applies to adult, non-formal learners of Irish, who are learning through Massive Open Online Courses (MOOCs). It is grounded in the psychology of language learning motivation (LLM), assessing whether non-formal adult Irish L2 learners are motivated by future L2 guides, both Ideal, reflecting hopes and dreams, and Ought-to, representing obligations and responsibilities. Three research questions are addressed, i) exploring the theoryâs validity at a general level and examining whether ii) the L2 learning experience and iii) learner heritage background, are meaningful in predicting, and understanding, the motivations of learners. Using distinct samples from an iterated quantitative survey instrument (final n=638) and narrative interviews (n=42), evidence demonstrates the theoryâs utility in an underexplored context, while raising questions regarding adult Irish language learners and theories of self.
Learners endorsed and articulated internalised reasons to learn, encompassing personal hopes and obligations, with social others less directly impactful on their motivation. The futures learners described often referenced non-L2 related aspirations of self, and were less-directly related to L2 proficiency, in many cases. Challenges in relation to the latter, due to contextual difficulties, low efficacy beliefs, and limited contact with L2 speakers and learners, are described. Recommendations to encourage sustained L2 learning and support adult learners in fostering and developing L2 selves are made, to aid them in realising their personal language learning goals
The Metaverse: Survey, Trends, Novel Pipeline Ecosystem & Future Directions
The Metaverse offers a second world beyond reality, where boundaries are
non-existent, and possibilities are endless through engagement and immersive
experiences using the virtual reality (VR) technology. Many disciplines can
benefit from the advancement of the Metaverse when accurately developed,
including the fields of technology, gaming, education, art, and culture.
Nevertheless, developing the Metaverse environment to its full potential is an
ambiguous task that needs proper guidance and directions. Existing surveys on
the Metaverse focus only on a specific aspect and discipline of the Metaverse
and lack a holistic view of the entire process. To this end, a more holistic,
multi-disciplinary, in-depth, and academic and industry-oriented review is
required to provide a thorough study of the Metaverse development pipeline. To
address these issues, we present in this survey a novel multi-layered pipeline
ecosystem composed of (1) the Metaverse computing, networking, communications
and hardware infrastructure, (2) environment digitization, and (3) user
interactions. For every layer, we discuss the components that detail the steps
of its development. Also, for each of these components, we examine the impact
of a set of enabling technologies and empowering domains (e.g., Artificial
Intelligence, Security & Privacy, Blockchain, Business, Ethics, and Social) on
its advancement. In addition, we explain the importance of these technologies
to support decentralization, interoperability, user experiences, interactions,
and monetization. Our presented study highlights the existing challenges for
each component, followed by research directions and potential solutions. To the
best of our knowledge, this survey is the most comprehensive and allows users,
scholars, and entrepreneurs to get an in-depth understanding of the Metaverse
ecosystem to find their opportunities and potentials for contribution
- âŠ