A general material removal strategy based on surface sampling and reconstruction on unknown objects

In most material removal processes, the size and shape of the stock material, the desired surface and the orientation of the part are known. If some or all of these factors are unknown, typical automatic systems will not be able to handle the situation. In reality, most of these cases are subsequently handled by human operators. This results in low productivity and inconsistency in the production and potential ergonomic problems for the human operators. Therefore, a new system needs to be designed to meet the requirements for material removal with unknown objects.;This dissertation presents a feasible and efficient automatic system for material removal with unknown processing factors. The characteristics of this type of processes were investigated. The corresponding inputs of the system were decided, while balancing the ease of use and the complexity of the system. A simple point sampling strategy was developed to sample the reference points, which are used to create the approximated surface for the unknown objects with a modified triangular based surface approximation method. A universal layer based path planning method was developed to guide the tool among the layers within the designated working area to remove the excess material effectively and efficiently without changing the programming codes.;This system was verified by simulations and a prototype of the grinding system

On the biomechanics of ligaments and muscles throughout the range of hip motion

At the limits of the range of hip motion, impingement, subluxation and edge loading can cause osteoarthritis in natural hips or early failure hip replacements. The aim of this PhD was to investigate the role of hip joint soft tissues throughout the range of hip motion to better understand their role in preventing (or perhaps even causing) these problematic load cases. A musculoskeletal model was used to investigate the muscular contribution to edge loading and found that in the mid-range of hip motion, the lines of action of hip muscles pointed inward from the acetabular rim and thus would stabilise the hip. However, in deep hip flexion with adduction, nearly half the muscles had unfavourable lines of action which could encourage edge loading. Conversely, in-vitro tests on nine cadaveric hips found that the hip capsular ligaments were slack in the mid-range of hip motion but tightened to restrain excessive hip rotation in positions close to the limits of hip motion. This passive restraint prevented the hip from moving into positions where the muscle lines of action were found to be unfavourable and thus could help protect the hip from edge loading. The ligaments were also found to protect the hip against impingement and dislocation. Out of the labrum, the ligamentum teres and the three capsular ligaments, it was found that the iliofemoral and ischiofemoral ligaments were primary restraints to hip rotation. These two capsular ligaments should be prioritised for protection/repair during hip surgery to maintain normal hip passive restraint. Whilst this can be technically demanding, failing to preserve/restore their function may increase the risk of osteoarthritic degeneration or hip replacement failure.Open Acces

The biomechanics of human locomotion

Includes bibliographical references. The thesis on CD-ROM includes Animate, GaitBib, GaitBook and GaitLab, four quick time movies which focus on the functional understanding of human gait. The CD-ROM is available at the Health Sciences Library

FACING EXPERIENCE: A PAINTER’S CANVAS IN VIRTUAL REALITY

Full version unavailable due to 3rd party copyright restrictions.This research investigates how shifts in perception might be brought about through the development of visual imagery created by the use of virtual environment technology. Through a discussion of historical uses of immersion in art, this thesis will explore how immersion functions and why immersion has been a goal for artists throughout history. It begins with a discussion of ancient cave drawings and the relevance of Plato’s Allegory of the Cave. Next it examines the biological origins of “making special.” The research will discuss how this concept, combined with the ideas of “action” and “reaction,” has reinforced the view that art is fundamentally experiential rather than static. The research emphasizes how present-day virtual environment art, in providing a space that engages visitors in computer graphics, expands on previous immersive artistic practices. The thesis examines the technical context in which the research occurs by briefly describing the use of computer science technologies, the fundamentals of visual arts practices, and the importance of aesthetics in new media and provides a description of my artistic practice. The aim is to investigate how combining these approaches can enhance virtual environments as artworks. The computer science of virtual environments includes both hardware and software programming. The resultant virtual environment experiences are technologically dependent on the types of visual displays being used, including screens and monitors, and their subsequent viewing affordances. Virtual environments fill the field of view and can be experienced with a head mounted display (HMD) or a large screen display. The sense of immersion gained through the experience depends on how tracking devices and related peripheral devices are used to facilitate interaction. The thesis discusses visual arts practices with a focus on how illusions shift our cognition and perception in the visual modalities. This discussion includes how perceptual thinking is the foundation of art experiences, how analogies are the foundation of cognitive experiences and how the two intertwine in art experiences for virtual environments. An examination of the aesthetic strategies used by artists and new media critics are presented to discuss new media art. This thesis investigates the visual elements used in virtual environments and prescribes strategies for creating art for virtual environments. Methods constituting a unique virtual environment practice that focuses on visual analogies are discussed. The artistic practice that is discussed as the basis for this research also concentrates on experiential moments and shifts in perception and cognition and references Douglas Hofstadter, Rudolf Arnheim and John Dewey. iv Virtual environments provide for experiences in which the imagery generated updates in real time. Following an analysis of existing artwork and critical writing relative to the field, the process of inquiry has required the creation of artworks that involve tracking systems, projection displays, sound work, and an understanding of the importance of the visitor. In practice, the research has shown that the visitor should be seen as an interlocutor, interacting from a first-person perspective with virtual environment events, where avatars or other instrumental intermediaries, such as guns, vehicles, or menu systems, do not to occlude the view. The aesthetic outcomes of this research are the result of combining visual analogies, real time interactive animation, and operatic performance in immersive space. The environments designed in this research were informed initially by paintings created with imagery generated in a hypnopompic state or during the moments of transitioning from sleeping to waking. The drawings often emphasize emotional moments as caricatures and/or elements of the face as seen from a number of perspectives simultaneously, in the way of some cartoons, primitive artwork or Cubist imagery. In the imagery, the faces indicate situations, emotions and confrontations which can offer moments of humour and reflective exploration. At times, the faces usurp the space and stand in representation as both face and figure. The power of the placement of the caricatures in the paintings become apparent as the imagery stages the expressive moment. The placement of faces sets the scene, establishes relationships and promotes the honesty and emotions that develop over time as the paintings are scrutinized. The development process of creating virtual environment imagery starts with hand drawn sketches of characters, develops further as paintings on “digital canvas”, are built as animated, three-dimensional models and finally incorporated into a virtual environment. The imagery is generated while drawing, typically with paper and pencil, in a stream of consciousness during the hypnopompic state. This method became an aesthetic strategy for producing a snappy straightforward sketch. The sketches are explored further as they are worked up as paintings. During the painting process, the figures become fleshed out and their placement on the page, in essence brings them to life. These characters inhabit a world that I explore even further by building them into three dimensional models and placing them in computer generated virtual environments. The methodology of developing and placing the faces/figures became an operational strategy for building virtual environments. In order to open up the range of art virtual environments, and develop operational strategies for visitors’ experience, the characters and their facial features are used as navigational strategies, signposts and methods of wayfinding in order to sustain a stream of consciousness type of navigation. Faces and characters were designed to represent those intimate moments of self-reflection and confrontation that occur daily within ourselves and with others. They sought to reflect moments of wonderment, hurt, curiosity and humour that could subsequently be relinquished for more practical or purposeful endeavours. They were intended to create conditions in which visitors might reflect upon their emotional state, v enabling their understanding and trust of their personal space, in which decisions are made and the nature of world is determined. In order to extend the split-second, frozen moment of recognition that a painting affords, the caricatures and their scenes are given new dimensions as they become characters in a performative virtual reality. Emotables, distinct from avatars, are characters confronting visitors in the virtual environment to engage them in an interactive, stream of consciousness, non-linear dialogue. Visitors are also situated with a role in a virtual world, where they were required to adapt to the language of the environment in order to progress through the dynamics of a drama. The research showed that imagery created in a context of whimsy and fantasy could bring ontological meaning and aesthetic experience into the interactive environment, such that emotables or facially expressive computer graphic characters could be seen as another brushstroke in painting a world of virtual reality

Drawing from motion capture : developing visual languages of animation

The work presented in this thesis aims to explore novel approaches of combining motion capture with drawing and 3D animation. As the art form of animation matures, possibilities of hybrid techniques become more feasible, and crosses between traditional and digital media provide new opportunities for artistic expression. 3D computer animation is used for its keyframing and rendering advancements, that result in complex pipelines where different areas of technical and artistic specialists contribute to the end result. Motion capture is mostly used for realistic animation, more often than not for live-action filmmaking, as a visual effect. Realistic animated films depend on retargeting techniques, designed to preserve actors performances with a high degree of accuracy. In this thesis, we investigate alternative production methods that do not depend on retargeting, and provide animators with greater options for experimentation and expressivity. As motion capture data is a great source for naturalistic movements, we aim to combine it with interactive methods such as digital sculpting and 3D drawing. As drawing is predominately used in preproduction, in both the case of realistic animation and visual effects, we embed it instead to alternative production methods, where artists can benefit from improvisation and expression, while emerging in a three-dimensional environment. Additionally, we apply these alternative methods for the visual development of animation, where they become relevant for the creation of specific visual languages that can be used to articulate concrete ideas for storytelling in animation

Skyscraping Frontiers

As a space of extremes, the skyscraper has been continually constructed as an urban frontier in American cultural productions. Like its counterpart of the American wilderness, this vertical frontier serves as a privileged site for both subversion and excessive control. Beyond common metaphoric readings, this study models the skyscraper not only as a Foucauldian heterotopia, but also as a complex network of human and nonhuman actors while retracing its development from its initial assemblage during the 19th century to its steady evolution into a smart structure from the mid-20th century onward. It takes a close look at US-American literary and filmic fictions and the ways in which they sought to make sense of this extraordinary structure throughout the 20th and early 21st centuries. More traditional poststructuralist spatial theories are connected with concepts and methods of Actor-Network Theory in a compelling account of the skyscraper’s evolution as reflected in fictional media from early 20th-century short stories via a range of action, disaster and horror films to selected city novels of the 1990s and 2000s

Come to Azania

Includes abstract.This story had its seeds planted in my head three years ago, when I was 22. I wanted to write something distinctly South African, but also universal, so that the story could serve as satire, as a piece of local speculative fiction

Abstracts of manuscripts submitted in 1991 for publication

This volume contains the abstracts of manuscripts submitted for publication during calendar year 1991 by the staff and students of the Woods Hole Oceanographic Institution. We identify the journal of those manuscripts which are in press or have been published. The volume is intended to be informative, but not a bibliography. The abstracts are listed by title in the Table of Contents and are grouped into one of our five departents, Marine Policy Center, Coastal Research Center, or the student category. An author index is presented in the back to facilitate locating specific papers

Sanctuaries

Sanctuaries navigates the environment of home via interrelated essays and vignettes personal to my upbringing in rural Southwest Indiana. By exploring my own childhood, youth, and family traumas and successes, I have crafted a collection that speaks volumes about seeing the world from a perspective both privileged and underprivileged simultaneously. I uncover my lineage\u27s numerous bouts with physical and mental illness and unrealized dreams, but I also bring to light our traditions of spreading kindness, treading lightly in the world, and preparing inordinate amounts of food and festive cheer to balance out times of hardship. Few writers have attempted to paint the Southern-Midwest\u27s landscape and to characterize its people as more than caricatures caught between the factories of the north and the tobacco fields of the south, so I rose to that challenge. What results is an essay collection rife with excess and squalor, abandon and abandonment, humor and deep sorrow, atheism and fervent belief in the supernatural, and snippets of what it really means, by my home region\u27s estimation, to be part of a family

Library buildings around the world

"Library Buildings around the World" is a survey based on researches of several years. The objective was to gather library buildings on an international level starting with 1990