1,670 research outputs found

    Forschungsbericht / Hochschule Mittweida

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    Planar Disjoint Paths, Treewidth, and Kernels

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    In the Planar Disjoint Paths problem, one is given an undirected planar graph with a set of kk vertex pairs (si,ti)(s_i,t_i) and the task is to find kk pairwise vertex-disjoint paths such that the ii-th path connects sis_i to tit_i. We study the problem through the lens of kernelization, aiming at efficiently reducing the input size in terms of a parameter. We show that Planar Disjoint Paths does not admit a polynomial kernel when parameterized by kk unless coNP ⊆\subseteq NP/poly, resolving an open problem by [Bodlaender, Thomass{\'e}, Yeo, ESA'09]. Moreover, we rule out the existence of a polynomial Turing kernel unless the WK-hierarchy collapses. Our reduction carries over to the setting of edge-disjoint paths, where the kernelization status remained open even in general graphs. On the positive side, we present a polynomial kernel for Planar Disjoint Paths parameterized by k+twk + tw, where twtw denotes the treewidth of the input graph. As a consequence of both our results, we rule out the possibility of a polynomial-time (Turing) treewidth reduction to tw=kO(1)tw= k^{O(1)} under the same assumptions. To the best of our knowledge, this is the first hardness result of this kind. Finally, combining our kernel with the known techniques [Adler, Kolliopoulos, Krause, Lokshtanov, Saurabh, Thilikos, JCTB'17; Schrijver, SICOMP'94] yields an alternative (and arguably simpler) proof that Planar Disjoint Paths can be solved in time 2O(k2)⋅nO(1)2^{O(k^2)}\cdot n^{O(1)}, matching the result of [Lokshtanov, Misra, Pilipczuk, Saurabh, Zehavi, STOC'20].Comment: To appear at FOCS'23, 82 pages, 30 figure

    Musiktheorie als interdisziplinĂ€res Fach: 8. Kongress der Gesellschaft fĂŒr Musiktheorie Graz 2008

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    Im Oktober 2008 fand an der UniversitĂ€t fĂŒr Musik und darstellende Kunst Graz (KUG) der 8. Kongress der Gesellschaft fĂŒr Musiktheorie (GMTH) zum Thema »Musiktheorie als interdisziplinĂ€res Fach« statt. Die hier vorgelegten gesammelten BeitrĂ€ge akzentuieren Musiktheorie als multiperspektivische wissenschaftliche Disziplin in den Spannungsfeldern Theorie/Praxis, Kunst/Wissenschaft und Historik/Systematik. Die sechs Kapitel ergrĂŒnden dabei die Grenzbereiche zur Musikgeschichte, MusikĂ€sthetik, zur Praxis musikalischer Interpretation, zur kompositorischen Praxis im 20. und 21. Jahrhundert, zur Ethnomusikologie sowie zur Systematischen Musikwissenschaft. Insgesamt 45 AufsĂ€tze, davon 28 in deutscher, 17 in englischer Sprache, sowie die Dokumentation einer Podiumsdiskussion zeichnen in ihrer Gesamtheit einen höchst lebendigen und gegenwartsbezogenen Diskurs, der eine einzigartige Standortbestimmung des Fachs Musiktheorie bietet.The 8th congress of the Gesellschaft fĂŒr Musiktheorie (GMTH) took place in October 2008 at the University for Music and Dramatic Arts Graz (KUG) on the topic »Music Theory and Interdisciplinarity«. The collected contributions characterize music theory as a multi-faceted scholarly discipline at the intersection of theory/practice, art/science and history/system. The six chapters explore commonalties with music history, music aesthetics, musical performance, compositional practice in twentieth- and twenty-first-century music, ethnomusicology and systematic musicology. A total of 45 essays (28 in German, 17 in English) and the documentation of a panel discussion form a vital discourse informed by contemporaneous issues of research in a broad number of fields, providing a unique overview of music theory today. A comprehensive English summary appears at the beginning of all contributions

    Role of inflammation and immunity in vascular calcification: a bibliometric and visual analysis, 2000–2022

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    BackgroundIn recent years, a great deal of research has been done on vascular calcification (VC), and inflammation and immunity have been displayed to play important roles in the mechanism of VC. However, to date, no comprehensive or systematic bibliometric analyses have been conducted on this topic.MethodsArticles and reviews on the roles of inflammation and immunity in VC were obtained from the Web of Science Core Collection on August 5, 2022. Four scientometric software packages—HistCite, CiteSpace, VOSviewer, and R-bibliometrix—were used for the bibliometric and knowledge mapping analyses.ResultsThe obtained 1,868 papers were published in 627 academic journals by 9,595 authors of 2,217 institutions from 69 countries. The annual number of publications showed a clear growth trend. The USA and China were the most productive countries. Karolinska Institutet, Harvard University, and the University of Washington were the most active institutions. Stenvinkel P published the most articles, whereas Demer LL received the most citations. Atherosclerosis published the most papers, while Circulation was the most highly cited journal. The largest cluster among the 22 clusters, based on the analysis of co-citations, was osteo-/chondrogenic transdifferentiation. “Vascular calcification,” “inflammation,” “chronic kidney disease,” and “expression” were the main keywords in the field. The keyword “extracellular vesicle” attracted great attention in recent years with the strongest citation burst.ConclusionsOsteo-/chondrogenic transdifferentiation is the primary research topic in this field. Extracellular vesicles are expected to become a new research focus for exploring the inflammatory and immune mechanisms of VC

    'A hidden art form' the value of sound in UK television idents (1982-2022)

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    Television idents are hidden in plain sight. Their creativity is often undervalued by industry practitioners and viewers alike, designated a ‘hidden art form’ by creative executive Charlie Mawer (2020). The sound worlds of idents are doubly overlooked, often ignored in visually-centric discourse on idents in industry journals and in media and cultural studies. In the production process, composers are often peripheral to the project, involved only towards the end. This thesis inverts such hierarchies and adopts a sound-oriented perspective towards idents. The approach brings together previously disparate strands across musicology, art and design history, and media studies, aiming to highlight the value of sound in idents as well as the hitherto-neglected creative labour of composers in the promotion of television channels. The scope is confined mainly to the UK, examining idents produced for broadcasters and streaming platforms between 1982 and 2022. This thesis addresses a central question: What is the value of music and sound in television idents? To answer this question, it combines textual analyses of idents with evidence from practitioner interviews. Musicological concepts and theories are employed in the analysis of idents, highlighting the aesthetic character and functions of the music and sounds. The method of reflexive thematic analysis (RTA) applied to the interviews produced new insights into the working environments of the composers and their creative colleagues, exploring themes of identity, collaboration, creative process, and artistic value. The first three chapters set out the aim of this thesis, academic contexts, and methodological approach respectively. Chapter 4 contains a musicological analysis of idents, tracing transformations in the aesthetic character and roles of sound in connection with the changing experience of watching television between 1982 and 2022. Chapter 5 expands on the arguments set out in Chapter 4 by focussing on production contexts, unpacking themes derived from the qualitative analysis of the interviews. Chapter 6 synthesises the conclusions and findings from Chapters 4 and 5 and discusses the commercial, artistic, and cultural value of the music and sound of idents. This thesis culminates with an exploration of future avenues of research and the implications of this research for practitioners and educators. In sum, this thesis argues that the artistic labour of ident production and the valuable role of musical creativity within this commercial and temporally constraining context deserve greater recognition and attention

    Music, "Movement and Displacement" : Black Musical Innovations,1920s-1960s

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    Dissertation (MSocSci (History))--University of Pretoria, 2023.Music, ‘Movement and Displacement’: Black Musical Innovations, 1920s-1960s, is an investigation of the emergence of music genres and performance styles in urban Black South Africa from the 1920s to the 1960s. The research uses Veit Erlmann’s concept of “movement and displacement” in examining how urban music and performance styles were shaped in a rapidly changing urban environment such as Johannesburg. Furthermore, the research also focuses on the creation of an urban consciousness which was shaped by the cultural heterogeneity of Black townships, which in turn both shaped music and was shaped by music, among other factors. This urban consciousness was also the outcome of “movement and displacement” as a result of internal migrations, especially rural to urban, as well as intellectual and cultural exchanges between the urban Black community and international cultural and intellectual currents, particularly from the United States. The dissertation argues that urban Black culture, music, and performance styles of the period, 1920s to 1960s were significantly shaped by movement and displacement both within South Africa and outside.Historical and Heritage StudiesMSocSci (History)Unrestricte

    Mitral Valve Imaging and Biomechanics: A Workflow Towards Computational Modeling and Validation

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    The mitral valve serves a critical role in healthy cardiac function by ensuring the unidirectional flow of oxygenated blood from the left atrium into the left ventricle. It experiences the highest pressures found within the heart and its closure is the result of a complex interaction of several different structures that, furthermore, are unique to each individual. Despite the valve’s vital role however, the specific function of these constituent structures is not fully understood. This, confounded by its asymmetric, personalized nature, make surgical interventions for the mitral valve far less effective than for its neighboring aortic valve. Efforts to overcome this have been made through the lens of computational simulation, in which the valve is studied virtually and procedures may be planned. The quality and reliability of these simulation results are only as good as the inputs that the simulation model receives. This study proposes and evaluates a workflow by which high-quality biomechanical inputs are obtained for computational input and validation. To account for individual variation, all steps are performed on the same valve such that a direct correspondence is made between geometry, stress/load distribution and the resulting coaptation. Ultrasound in vivo measurements are made so that custom tailored mounting hardware can be manufactured. This hardware is used to support the valve in a physiologically appropriate manner for ”CT imaging in both the open and closed configurations. Scanning within a fluid medium, to prevent tissue desiccation and other detrimental effects, is made possible through a DiceCT tissue staining procedure. High resolution, 3D imagery is obtained for the open valve whereas only a relatively quick set of projection images is obtained for the closed configuration. Registration between open and closed imagery is accomplished by localizing aluminum oxide fiducial markers that are bound to the leaflet surface. Subsequent image analysis is performed to isolate the tissue and place the data in the proper format for computational use. The valve is then closed under known pressure while chordal forces/strains are simultaneously recorded to provide loading conditions. The effectiveness of the workflow is illustrated through two animal experiments. Incomplete results were obtained from the first experiment as the tissue degraded significantly during a prolonged period of ”CT downtime. The second experiment resulted in good quality ultrasound imagery, leading to the creation of customized mounting hardware, yet the remainder of the process was still in progress at the final stages of this document. Computational modeling is still ongoing, yet some preliminary results are presented which show the geometry from the first animal experiment tending towards closure

    LIPIcs, Volume 261, ICALP 2023, Complete Volume

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    LIPIcs, Volume 261, ICALP 2023, Complete Volum

    Investigation of the Free-Fall Dynamic Behavior of a Rectangular Wing with Variable Center of Mass Location and Variable Moment of Inertia

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    © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).In recent years, the air-drop launch technology of near-space UAVs has attracted much attention. Between downfall from the carrier and the flight control system’s initiation, the UAV presents free-fall movement. This free-fall process is very important for the control effect of the flight control system and is also crucial for the safety of the UAV and the carrier. Focus is required on two important dynamic parameters of the UAV: the moment of inertia and the center of mass position. In this paper, we used a quasi-steady model proposed by predecessors to address the flat-plate falling problem with modifications to describe the freely falling motion of the wing. Computational fluid dynamics (CFD) were used to simulate the free-fall movement of the wing with various parameters, and the wing release behavior was analyzed to check the quasi-steady model. Research shows that the movement characteristics of the falling wing are mostly reflected in the longitudinal plane, and the developed quasi-steady analytical model can more accurately describe the dynamic behavior of free-fall to some extent. By using CFD methods, we further investigated the aerodynamic performance of the free-fall wing. The results show that the wing mainly presents tumbling and fluttering motion. Changing the moment of inertia around the tumbling axis changes the tumbling frequency and the time point as the wing enters tumbling. In contrast, changing the position of the center of mass significantly changes the form of falling and makes the free-fall motion more complex. Therefore, it is necessary to carefully configure the center of mass in the UAV design process.Peer reviewe
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