250 research outputs found

    CFD Modelling of the Mixture Preparation in a Modern Gasoline Direct Injection Engine and Correlations with Experimental PN Emissions

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    A detailed 3D CFD analysis of a modern gasoline direct injection (GDI) engine is carried out to reveal the connections between pre-combustion mixture indicators and PN emissions. Firstly, a novel calibration methodology is introduced to accurately predict the widely used characteristics of the high-pressure fuel spray. The methodology utilised the Siemens STAR-CD 3D CFD software environment and employed a combination of statistical and optimization methods supported by experimental data. The calibration process identified dominant factors influencing spray properties and established their optimal levels. The two most used models for fuel atomisation were investigated. The Kelvin–Helmholtz/Rayleigh–Taylor (KH–RT) and Reitz–Diwakar (RD) break-up models were calibrated in conjunction with the Rosin–Rammler (RR) mono-modal droplet size distribution. RD outperformed KH–RT in terms of prediction when comparing numerical spray tip penetration and droplet size characteristics to the experimental counterparts. Then, the modelling protocol incorporated droplet-wall interaction models and a multi-component surrogate fuel blend model. The comprehensive digital model was validated using published data and applied to a modern small-capacity GDI engine. The study explored various engine operating conditions and highlights the contribution of fuel mal-distribution and liquid film retention at spark timing to Particle Number (PN) emissions. Finally, a novel surrogate model was developed to predict the engine-out PN. An extensive CFD analysis was conducted considering part-load operating conditions and variations of engine control variables. The PN surrogate model was developed using an Elastic Net (EN) regression technique, establishing relationships between experimental PN emission levels and modelled, pre-combustion, air-fuel mixture quality indicators. The approach enabled the reliable prediction of engine sooting tendencies without relying on complex measurements of combustion characteristics. These research efforts aim to enhance engine efficiency, reduce emissions, and contribute to the development of a reliable and cost-effective digital toolset for engine development and diagnostics

    Proceedings of SIRM 2023 - The 15th European Conference on Rotordynamics

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    It was our great honor and pleasure to host the SIRM Conference after 2003 and 2011 for the third time in Darmstadt. Rotordynamics covers a huge variety of different applications and challenges which are all in the scope of this conference. The conference was opened with a keynote lecture given by Rainer Nordmann, one of the three founders of SIRM “Schwingungen in rotierenden Maschinen”. In total 53 papers passed our strict review process and were presented. This impressively shows that rotordynamics is relevant as ever. These contributions cover a very wide spectrum of session topics: fluid bearings and seals; air foil bearings; magnetic bearings; rotor blade interaction; rotor fluid interactions; unbalance and balancing; vibrations in turbomachines; vibration control; instability; electrical machines; monitoring, identification and diagnosis; advanced numerical tools and nonlinearities as well as general rotordynamics. The international character of the conference has been significantly enhanced by the Scientific Board since the 14th SIRM resulting on one hand in an expanded Scientific Committee which meanwhile consists of 31 members from 13 different European countries and on the other hand in the new name “European Conference on Rotordynamics”. This new international profile has also been emphasized by participants of the 15th SIRM coming from 17 different countries out of three continents. We experienced a vital discussion and dialogue between industry and academia at the conference where roughly one third of the papers were presented by industry and two thirds by academia being an excellent basis to follow a bidirectional transfer what we call xchange at Technical University of Darmstadt. At this point we also want to give our special thanks to the eleven industry sponsors for their great support of the conference. On behalf of the Darmstadt Local Committee I welcome you to read the papers of the 15th SIRM giving you further insight into the topics and presentations

    Artificial Intelligence and International Conflict in Cyberspace

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    This edited volume explores how artificial intelligence (AI) is transforming international conflict in cyberspace. Over the past three decades, cyberspace developed into a crucial frontier and issue of international conflict. However, scholarly work on the relationship between AI and conflict in cyberspace has been produced along somewhat rigid disciplinary boundaries and an even more rigid sociotechnical divide – wherein technical and social scholarship are seldomly brought into a conversation. This is the first volume to address these themes through a comprehensive and cross-disciplinary approach. With the intent of exploring the question ‘what is at stake with the use of automation in international conflict in cyberspace through AI?’, the chapters in the volume focus on three broad themes, namely: (1) technical and operational, (2) strategic and geopolitical and (3) normative and legal. These also constitute the three parts in which the chapters of this volume are organised, although these thematic sections should not be considered as an analytical or a disciplinary demarcation

    The grammar of immersion: a social semiotic study of nonfiction cinematic virtual reality

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    Cinematic virtual reality (CVR) is an audio-visual form viewed in a virtual reality headset. Its novelty lies in the way it immerses its audience in highly realistic 360° visual representations. Being camera-based, CVR facilitates many of the practices of conventional filmmaking but fundamentally alters them through its lack of a rectangular frame. As such, CVR has garnered scholarly attention as a ‘frameless’ storytelling medium yet to develop its own language. The form has gained traction with producers of nonfiction who recognize CVR’s capacity to transport audiences to remote social worlds, leading to claims that equate CVR’s immersion with a social and emotional response to its filmed subjects. A strand of CVR scholarship has emerged, grounding nonfiction CVR theoretically and critiquing such deterministic claims. Broadly speaking, these parallel strands of inquiry point to a common concern with CVR’s semiotics; as the meaning potential of the 360° format, and the social aspects of its use in documenting reality. Currently however, there appears to be a lack of systematic analyses that foreground CVR’s semiotics. This study addresses this gap by using social semiotic methods to complement these threads of inquiry, subsuming them into a holistic account of CVR’s semantics. Utilizing systemic functional methods, multimodal discourse analyses were performed on nonfiction CVR texts addressing core research objectives. The first objective is the systematic description of CVR as a semiotic technology, and the configuring of discourse through its novel 360° modality. The CVR spectator is described for their role in the real-time construction of low-level meanings. Higher-level concepts further characterize CVR texts as technologically enabled, virtual sites of social discourse. The second research objective concerns clarifying the implications of CVR for nonfiction practitioners. Nonfiction discourse is conceptualized as the negotiation of semiotic autonomy, independence, and control, between viewing spectator, filmed subject, and CVR author respectively. The third objective concerns the development of an analytical approach tailored specifically for CVR. Extant systems from image, text, film, and action analyses are reflexively applied, appraised, and adapted for use in the study of CVR and new frames are presented to cater for the 360° modality. The findings show CVR to be an inherently logical, contextualizing form, where the spectator has a degree of sense-making autonomy in the construction of representational and social meanings. This semantic autonomy is found to camouflage the deeper textual constructions in what appear as ‘reality experiences’. The repercussions for the CVR producer are the indeterminacy of meanings which are ‘at risk’ in particular ways when conventional framing methods cannot be utilized, and when the spectator is given reflexive agency to make meaningful connections across the 360° image. Systemic functional analytical methods prove flexible enough to be applied to the texts, and open enough for the study to present additional systems and frames for a more fulsome approach to the analysis of CVR

    EM-driven miniaturization of high-frequency structures through constrained optimization

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    The trends afoot for miniaturization of high-frequency electronic devices require integration of active and passive high-frequency circuit elements within a single system. This high level of accomplishment not only calls for a cutting-edge integration technology but also necessitates accommodation of the corresponding circuit components within a restricted space in applications such as implantable devices, internet of things (IoT), or 5G communication systems. At the same time, size reduction does not remain the only demand. The performance requirements of the abovementioned systems form a conjugate demand to that of the size reduction, yet with a contrasting nature. A compromise can be achieved through constrained numerical optimization, in which two kinds of constrains may exist: equality and inequality ones. Still, the high cost of electromagnetic-based (EM-based) constraint evaluations remains an obstruction. This issue can be partly mitigated by implicit constraint handling using the penalty function approach. Nevertheless, securing its performance requires expensive guess-work-based identification of the optimum setup of the penalty coefficients. An additional challenge lies in allocating the design within or in the vicinity of a thin feasible region corresponding to equality constraints. Furthermore, multimodal nature of constrained miniaturization problems leads to initial design dependency of the optimization results. Regardless of the constraint type and the corresponding treatment techniques, the computational expenses of the optimization-based size reduction persist as a main challenge. This thesis attempts to address the abovementioned issues specifically pertaining to optimization-driven miniaturization of high frequency structures by developing relevant algorithms in a proper sequence. The first proposed approach with automated adjustment of the penalty functions is based on the concept of sufficient constraint violation improvement, thereby eliminating the costly initial trial-and-error stage for the identification of the optimum setup of the penalty factors. Another introduced approach, i.e., correction-based treatment of the equality constraints alleviates the difficulty of allocating the design within a thin feasible region where designs satisfying the equality constraints reside. The next developed technique allows for global size reduction of high-frequency components. This approach not only eliminates the aforementioned multimodality issues, but also accelerates the overall global optimization process by constructing a dimensionality-reduced surrogate model over a pre-identified feasible region as compared to the complete parameter search space. Further to the latter, an optimization framework employing multi-resolution EM-model management has been proposed to address the high cost issue. The said technique provides nearly 50 percent average acceleration of the optimization-based miniaturization process. The proposed technique pivots upon a newly-defined concept of model-fidelity control based on a combination of algorithmic metrics, namely convergence status and constraint violation level. Numerical validation of the abovementioned algorithms has also been provided using an extensive set of high-frequency benchmark structures. To the best of the authorÂŽs knowledge, the presented study is the first investigation of this kind in the literature and can be considered a contribution to the state of the art of automated high-frequency design and miniaturization

    Measurable Safety of Automated Driving Functions in Commercial Motor Vehicles

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    With the further development of automated driving, the functional performance increases resulting in the need for new and comprehensive testing concepts. This doctoral work aims to enable the transition from quantitative mileage to qualitative test coverage by aggregating the results of both knowledge-based and data-driven test platforms. The validity of the test domain can be extended cost-effectively throughout the software development process to achieve meaningful test termination criteria

    A Content Analysis of Non-Profit Organizations Social Media: Through the Lens of Compliance-Gaining & Persuasion

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    Non-profit organizations utilize social media platforms like Instagram to reach the community, fundraise, convey their mission and vision, establish themselves, and educate others. This study examined whether the communication artifacts of selected nonprofit organizations employed Cialdini\u27s (2021) compliance-gaining strategies through an eight-week qualitative digital content analysis on Instagram to address the problem of understanding how non-profit organizations use Instagram tools to influence and persuade their audience. Compassion International (@compassion), CARE (@careorg), and Direct Relief (@directrelief), the three non-profit organizations chosen in this study, demonstrated the usage of Cialdini’s (2021) compliance-gaining strategies within their digital media communication strategy. Non-profit organizations operate in a highly competitive environment, with many organizations vying for attention and resources from donors and supporters. They must understand how to effectively use Instagram and compliance-gaining theory to influence and persuade their audience, ultimately increasing their impact and reach. How are these three non-profit organizations engaging and mobilizing their audience through this influence and persuasion to support their respective cause? Are there commonalities in how each non-profit organization is using Cialdini’s (2021) compliance-gaining framework? This study showed that the three non-profit organizations chosen effectively used Cialdini’s (2021) compliance-gaining framework on Instagram to influence and persuade their audience, while also contributing to the existing literature on social media marketing, compliance-gaining theory, and digital content analysis. The analysis provided valuable insights for communication professionals, marketers, and non-profit organizations seeking to create compelling social media campaigns

    A Design-Science-Research Approach

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    Neue Organisationsformen, wie evolutionĂ€re Organisationen, bilden in vielen Kooperationsszenarien sozio-technische Konstrukte mit modernen CSCW Anwendungen aus. Daher erfordern VerĂ€nderungen dieser sozialen Systeme eine kontinuierliche Anpassung der technischen Tools an die neuen sozialen Konfigurationen. Diese Dissertation ist als Design Science Research (DSR) Projekt konzipiert und addressiert die folgende Forschungsfrage (RQ): “Wie können soziotechnische, evolutionĂ€re Organisationen die Herausforderungen der joint optimization und des organizational choice wĂ€hrend ihrer autopoietischen VerĂ€nderungsprozesse addressieren?” Die Fallstudie Viva con Agua de St. Pauli e.V. wurde mittels qualitativer und ethnographischer Methoden im Rahmen der entsprechenden DSR Zyklen untersucht. Das Forschungsprojekt fokussiert die Entwicklung von Artefakten indem sowohl eine technische, als auch eine soziale Perspektive eingenommen wird. Aus der technische Perspektive wird die RQ durch eine Microservice-Plattform adressiert. Die Architektur dient der Verteilung von Verantwortlichkeit fĂŒr die Software in einem heterogenen Netzwerk von Entwickler:innen. Dabei mĂŒssen diverse neue Herausforderungen beachtet werden, wie etwa die Verteilung des User Interface. Durch die Betrachtung der RQ aus der sozialen Perspektive wird der USMU Workshop entwickelt. Dieses Artefakt dient der Verbindung der Charakteristika evolutionĂ€rer Organisationen mit agiler Software Entwicklung und mit Methoden des partizipativen Designs. Die Studien zeigen, dass beide Artefakte die RQ adressieren. Zudem konnte ich fĂŒr beide Artefakte wertvolle Verbesserungsmöglichkeiten aufzeigen. Somit motivieren die Ergebnisse den nĂ€chsten Schritt des Projekts und die vorliegende Thesis wird Bestandteil des zyklischen Ablaufs eines DSR Projekts.The emergence of new types of organizational structures, such as evolutionary-teal organizations, almost always leads to the development of socio-technical constructs when it comes to working in collaboration with modern CSCW applications. A consequence of this is that the social system’s autopoietic change processes create challenges that compel one to adjust the implementation of the technical tool to the social system’s new configuration. This thesis is structured according to the design science research (DSR) approach and focuses on the research question (RQ): “How can socio-technical evolutionary-teal organizations address the challenges of joint optimization and organizational choice during their autopoietic processes?” For this purpose, the case study Viva con Agua de St. Pauli e.V. is investigated using a qualitative ethnographical approach during the DSR cycles. Addressing the RQ, two artifacts are designed from a technical as well as a social perspective. While the technical perspective primarily investigates the adjustments of technology, the social perspective focuses on the management of change in socio-technical evolutionary-teal organizations. I propose a microservice platform as an artifact that addresses the RQ from a technical perspective. The microservice architecture aims at spreading the responsibility for the software through a heterogeneous ecosystem of developers. The newly designed USMU workshop is addressing the RQ from the social perspective. It strives to intertwine the characteristics of evolutionary-teal organizations with agile software development and participatory design methods. In my studies, I examine the fact that both artifacts can be used to address the RQ. Additionally, I was able to identify valuable improvements for both of my artifacts. Hence, the project follows the lifecycle of a DSR project by reasoning through the results presented here for its next iteration

    ATHENA Research Book, Volume 2

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    ATHENA European University is an association of nine higher education institutions with the mission of promoting excellence in research and innovation by enabling international cooperation. The acronym ATHENA stands for Association of Advanced Technologies in Higher Education. Partner institutions are from France, Germany, Greece, Italy, Lithuania, Portugal and Slovenia: University of OrlĂ©ans, University of Siegen, Hellenic Mediterranean University, NiccolĂČ Cusano University, Vilnius Gediminas Technical University, Polytechnic Institute of Porto and University of Maribor. In 2022, two institutions joined the alliance: the Maria Curie-SkƂodowska University from Poland and the University of Vigo from Spain. Also in 2022, an institution from Austria joined the alliance as an associate member: Carinthia University of Applied Sciences. This research book presents a selection of the research activities of ATHENA University's partners. It contains an overview of the research activities of individual members, a selection of the most important bibliographic works of members, peer-reviewed student theses, a descriptive list of ATHENA lectures and reports from individual working sections of the ATHENA project. The ATHENA Research Book provides a platform that encourages collaborative and interdisciplinary research projects by advanced and early career researchers

    History in multimodal gameplay: A new language and model for constructing, experiencing, and studying the past

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    This doctoral study examines how historical gameplay constructs and provides ways of experiencing history within (historical) video games. Historical gameplay is examined and defined as an expression of history within historical games as it is the primary medium of representing or experiencing the past based on the interactions between the player and the various intricacies and components of the historical game. This thesis identifies, interprets, and illustrates several modalities of histories that emerge from and are characterised by particular modes and sequences of gameplay, with the aim of discerning and demonstrating what kind of experiences and knowledge of history are being conveyed. The undertaking of gameplay research in this thesis produced case studies of two contemporary Medieval games: A Plague Tale: Innocence (Asobo Studio, 2019) and Kingdom Come: Deliverance (Warhorse Studios, 2018). These texts were analysed via recorded footage of the author’s gameplay activity, while in-person interviews with several members of the game studios responsible for developing both these historical games provided insights into the research and game development processes required to produce historical games. In spite of the growing recognition of, and scholarship on historical video games, there are no current works from the discipline of history that thoroughly explore gameplay as a different yet innovative medium for disseminating and understanding history. This thesis fills that gap. Studying gameplay from the development and release of recent Medieval historical games has the potential to provide historians with new insights and opportunities regarding gameplay as catalysts for studying, discussing, and critiquing history.
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