2,042 research outputs found
On Local Mechanical Properties of Thin Pressurized Shells with Combined Geometric and Material Anisotropies
Thin elastic shells are ubiquitous in nature. Indentation measurements (i.e., poking) provide a useful way for probing mechanical properties of these shell structures.
While spherical and cylindrical shells made of isotropic materials are well studied, many shells in nature have geometric anisotropy (e.g., ellipsoidal pollen grains) and/or material anisotropy (e.g., cells that have special growth directions), and mechanics of these shells are relatively less understood.
I will present some new insights on indentation responses and buckling pressure of shells with geometric and material anisotropy using the shallow-shell theory.
First, I will describe the indentation stiffness of pressurized ellipsoidal and cylindrical elastic shells that are made of isotropic materials.
We are able to derive a closed form for the indentation stiffness of shells with arbitrary asphericity and internal pressure.
Our results provide theoretical support for previous scaling and numerical results on the stiffness of ellipsoids and allow us to isolate the distinct contributions of geometry and pressure-induced stresses on shell elasticity.
I will then add the effects of material orthotropy, which assigns different elastic properties along orthogonal directions.
For a commonly used model of orthotropy, we find a simple rescaling transformation that can effectively map a rectilinearly orthotropic shallow shell to an isotropic one with a different local geometry.
With the rescaling transformation, we obtain new analytical insights for indentation responses and buckling of orthotropic shells.
Our results provide a new perspective on how isotropic and orthotropic materials are related, isolate the effect of material orthotropy on shell elasticity, and can provide experimentalists with a means to analyze the internal pressure of biological structures that are made of orthotropic materials using atomic force microscopes
Fictocritical Cyberfeminism: A Paralogical Model for Post-Internet Communication
This dissertation positions the understudied and experimental writing practice of fictocriticism as an analog for the convergent and indeterminate nature of âpost-Internetâ communication as well a cyberfeminist technology for interfering and in-tervening in metanarratives of technoscience and technocapitalism that structure contemporary media. Significant theoretical valences are established between twen-tieth century literary works of fictocriticism and the hybrid and ephemeral modes of writing endemic to emergent, twenty-first century forms of networked communica-tion such as social media. Through a critical theoretical understanding of paralogy, or that countercultural logic of deploying language outside legitimate discourses, in-volving various tactics of multivocity, mimesis and metagraphy, fictocriticism is ex-plored as a self-referencing linguistic machine which exists intentionally to occupy those liminal territories âsomewhere in among/between criticism, autobiography and fictionâ (Hunter qtd. in Kerr 1996). Additionally, as a writing practice that orig-inated in Canada and yet remains marginal to national and international literary scholarship, this dissertation elevates the origins and ongoing relevance of fictocriti-cism by mapping its shared aims and concerns onto proximal discourses of post-structuralism, cyberfeminism, network ecology, media art, the avant-garde, glitch feminism, and radical self-authorship in online environments. Theorized in such a matrix, I argue that fictocriticism represents a capacious framework for writing and reading media that embodies the self-reflexive politics of second-order cybernetic theory while disrupting the rhetoric of technoscientific and neoliberal economic forc-es with speech acts of calculated incoherence. Additionally, through the inclusion of my own fictocritical writing as works of research-creation that interpolate the more traditional chapters and subchapters, I theorize and demonstrate praxis of this dis-tinctively indeterminate form of criticism to empirically and meaningfully juxtapose different modes of knowing and speaking about entangled matters of language, bod-ies, and technologies. In its conclusion, this dissertation contends that the âcreative paranoiaâ engendered by fictocritical cyberfeminism in both print and digital media environments offers a pathway towards a more paralogical media literacy that can transform the terms and expectations of our future media ecology
Die Verbildlichung von Klangstrukturen im Kontext der Entwicklung von Werkzeugen fĂŒr die Medienproduktion
Audio ist einer der wichtigsten Aspekte bei mediengestĂŒtzten Produktionen. Allerdings sind die OberflĂ€chen zur Suche, Erstellung und Manipulation von Audio hĂ€ufig getrieben durch die zugrundeliegenden technischen Parameter. Diese Parameter beschreiben in der Regel weder deren Bedeutung fĂŒr den Sound noch welche QualitĂ€ten im Sound zum Ausdruck kommen. Dadurch bieten solche OberflĂ€chen selten eine intuitive, noch expressive Handhabe, da zuerst ein Ăbersetzungsprozess von der kĂŒnstlerischen Idee hin zu den technischen Parametern erfolgen muss.
Um die OberflĂ€chen nahbarer und nachvollziehbar zu gestalten, wird daher die Verbildlichung der Strukturen von Sound auf verschiedenen Ebenen betrachtet. Insbesondere wie visuelle Momente zur Interaktion mit Audio genutzt werden können, wird herausgestellt. Auf diese Weise wird die grafische Erweiterung von technischer spektraler Editierung als Beispiel fĂŒr die direkte Signalverarbeitung diskutiert. Auch werden metaphorische Visualisierungen fĂŒr Audioeffekte thematisiert. Zudem wird das mentale Modell von Audio analysiert, welches hier assoziativ durch Skizzen als abstrakte visuelle ReprĂ€sentationen erhoben wird.
Daher wurden Studien zur Erhebung und Bewertung von Skizzen durchgefĂŒhrt, die je einen Sound abbilden. Aus den resultierenden Skizzenassoziationen ist ein Vorgehen zur Ableitung einer Klassifikation des skizzenbasierten mentalen Modells entstanden. Diese Klassifikation ist ein möglicher Ausgangspunkt fĂŒr die Entwicklung von Werkzeugen und bietet ein Bewusstsein der Ausdrucksmöglichkeiten beim Einsatz grafischer Assoziationen bis hin zu Affordanzen im Design von DatensĂ€tzen fĂŒr maschinelles Lernen. Denn es wurden auch statistische ZusammenhĂ€nge der Kenntnisse der zeichnenden Personen und den verwendeten Skizzenklassen untersucht. Dadurch kann die Art der Abbildung in Bezug zur gewĂŒnschten Zielgruppe gewĂ€hlt werden.Audio is one of the most important aspects of media-based productions. However, the interfaces for searching, creating, and manipulating audio are often driven by the underlying technical parameters. These parameters usually do not describe their meanings for the sound, nor what qualities are expressed in the sound. As a result, such surfaces rarely offer an intuitive, nor expressive way of interacting, since a translation process from the artistic idea to the technical parameters must take place first.
In order to make the interfaces more approachable and comprehensible, the visualization of the structures of sound is therefore considered on different levels. In particular, how visualizations can be used to interact with audio will be highlighted. In this way, the graphical extension of technical spectral editing is discussed as an example of direct signal processing. Also, metaphorical visualizations for audio effects are addressed. In addition, the mental model of audio is analyzed, which is here elicited associatively through sketches as abstract visual representations.
Therefore, studies were conducted to collect and evaluate sketches, each depicting one sound. From the resulting sketch associations, a procedure for deriving a classification of the sketch-based mental model has been developed. This classification is a possible starting point for tool development and provides an awareness of the expressive possibilities when using graphical associations up to affordances in the design of datasets for machine learning. In fact, statistical correlations of the knowledge of the people drawing and the classes of sketches used were also investigated. This allows to choose the type of illustration in relation to the desired target group
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When to Hold and When to Fold: Studies on the topology of origami and linkages
Linkages and mechanisms are pervasive in physics and engineering as models for avariety of structures and systems, from jamming to biomechanics. With the increasein physical realizations of discrete shape-changing materials, such as metamaterials,programmable materials, and self-actuating structures, an increased understandingof mechanisms and how they can be designed is crucial. At a basic level, linkagesor mechanisms can be understood to be rigid bars connected at pivots around whichthey can rotate freely. We will have a particular focus on origami-like materials, anextension to linkages with the added constraint of faces. Self-actuated versions typ-ically start flat and when exposed to an external stimulus - such as a temperaturechange or magnetic field - spontaneously fold. Since these structures fold all at once,and the number of folding patterns accessible to a given origami are exponential, theyare prone to folding to a configuration other than the desired one. Other work hassuggested methods for avoiding this misfolding, but it assumes ideal, rigid origami. Here, we expand on these models to account for the elasticity of real structures andintroduce methods for accounting for Gaussian curvature in them. We also explorehow to find and set an upper bound on minimal forcing sets, or the minimum set offolds required to force an origami, and present a graph theory algorithm for findingthem in arbitrary origami. Taken altogether, these origami studies give insight intohow the physical properties of origami influence folding and a new set of tools foravoiding misfolding. Next, we turn back to a more fundamental study of linkagesand present a new method for finding the manifold of their critical points. We thendemonstrate a design protocol that utilizes this manifold to create linkages with tun-able motions, before turning to several example structures, including the four-barlinkage and the Kane-Lubensky chain
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Taking shape: The data science of elastic shape analysis with practical applications
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.A mathematical curve can represent many different objects, both physical and abstract,
from the outline curve of an artefact in an image to the weight of growing animal to
the set of frequencies used in a sound. Regardless of these variations, the curves can
almost always vary non-linearly. One way to study shapes and their potential variations
is elastic shape analysis, a rich theory of which has developed over the past twenty years.
However, methods of elastic shape analysis are seldom utilized in practical applications
on real-world data, especially outside of the mathematical shape analysis community.
Our aim in this thesis is to explore some practical applications of elastic shape analysis.
To do this, we work with various types of shape data, the majority of which are based on
image datasets. As our focus is on two-dimensional curves, it is important to be able to
robustly extract contours from images, before we can apply elastic shape analysis tools.
In order to analyse the shapes in a dataset, we turn to methods of machine learning, to
investigate the applications of elastic shape analysis in classification.
In this thesis, we introduce an anthology of projects, in order to emphasise and under-
stand the potential of elastic shape analysis in practical applications. There are four main
projects in this thesis: (i) Classification of objects using outlines and the comparisons
between methods of elastic shape analysis, geometric morphometrics, and human experts,
with a focus on ancient Greek vases, (ii) Mussel species identification and a demonstra-
tion that shape may not be enough in some applications, (iii) A novel tool to monitor
the development of k Ìak Ìap Ìo chicks, and (iv) Classifying individual kiwi based on acoustic
data from their calls.
By combining tools from computer vision and machine learning with methods of elastic
shape analysis, we introduce a practical framework for the application of elastic shape
analysis, through a data science lens
Out of sight, out of mind: accessibility for people with hidden disabilities in museums and heritage sites
As of 2020, an estimated 14.1 million residents of the United Kingdom reported a disability (DWP 2020). Within this population, approximately 6.1 million people have a hidden disability (Buhalis and Michopoulou 2011). These hidden disabilities range widely, from neurodiverse conditions like autism and dyslexia to long term chronic conditions such as fibromyalgia and arthritis. Due to the wide range of disabilities and their impact on a disabled personâs life, they have generally been underrepresented in accessibility studies.
This thesis uncovers the accessibility needs of people with hidden disabilities, specifically in museums and heritage sites where they have heretofore mostly been overlooked. I utilise semi-structured interviews and correspondence with people with hidden disabilities, as well as participant-led experiences through three case study sites in Northern England, to understand the barriers they face. Their experiences help me expose the importance of passive accessibility â accessibility measures built directly into an exhibition design, such as adequate lighting and personal interpretation boards.
Additionally, this thesis aims to understand the cultural forces that prevent or support accessibility-related improvements to such sites from taking place. By studying the cultural make-up of each case study organisation through ethnographic observations of the staff at these sites, institutional roadblocks to enacting accessibility-related adjustments are revealed. Specifically, the lack of communication at these sites presents a significant barrier to enacting accessibility suggestions from disabled visitors.
Tying together the themes of active/passive accessibility and lack of communication is the theme of gaps in disability awareness, by which I mean that heritage organisations do not wilfully create these barriers to inclusion, and yet they create them still because they simply do not realise these things. Filling these gaps opens up countless possibilities for improving accessibility not only for people with hidden disabilities but for all visitors and staff at museums and heritage sites
Twilight of the American State
The sudden emergence of the Trump nation surprised nearly everyone, including journalists, pundits, political consultants, and academics. When Trump won in 2016, his ascendancy was widely viewed as a fluke. Yet time showed it was instead the rise of a movementâangry, militant, revanchist, and unabashedly authoritarian.
How did this happen? Twilight of the American State offers a sweeping exploration of how law and legal institutions helped prepare the grounds for this rebellious movement. The controversial argument is that, viewed as a legal matter, the American state is not just a liberal democracy, as most Americans believe. Rather, the American state is composed of an uneasy and unstable combination of different versions of the stateâliberal democratic, administered, neoliberal, and dissociative. Each of these versions arose through its own law and legal institutions. Each emerged at different times historically. Each was prompted by deficits in the prior versions. Each has survived displacement by succeeding versions. All remain active in the contemporary momentâcreating the political-legal dysfunction America confronts today.
Pierre Schlag maps out a big picture view of the tribulations of the American state. The book abjures conventional academic frameworks, sets aside prescriptions for quick fixes, dispenses with lamentations about polarization, and bypasses historical celebrations of the American Spirit
PhoMoH: Implicit Photorealistic 3D Models of Human Heads
We present PhoMoH, a neural network methodology to construct generative
models of photo-realistic 3D geometry and appearance of human heads including
hair, beards, an oral cavity, and clothing. In contrast to prior work, PhoMoH
models the human head using neural fields, thus supporting complex topology.
Instead of learning a head model from scratch, we propose to augment an
existing expressive head model with new features. Concretely, we learn a highly
detailed geometry network layered on top of a mid-resolution head model
together with a detailed, local geometry-aware, and disentangled color field.
Our proposed architecture allows us to learn photo-realistic human head models
from relatively little data. The learned generative geometry and appearance
networks can be sampled individually and enable the creation of diverse and
realistic human heads. Extensive experiments validate our method qualitatively
and across different metrics.Comment: To be published at the International Conference on 3D Vision 202
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