• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 61
  • 9
  • 9
  • 6
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 126
  • 43
  • 29
  • 23
  • 20
  • 19
  • 18
  • 15
  • 15
  • 15
  • 14
  • 12
  • 12
  • 10
  • 10
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Biomimetic and autonomic server ensemble orchestration

Nakrani, Sunil January 2005 (has links)
This thesis addresses orchestration of servers amongst multiple co-hosted internet services such as e-Banking, e-Auction and e-Retail in hosting centres. The hosting paradigm entails levying fees for hosting third party internet services on servers at guaranteed levels of service performance. The orchestration of server ensemble in hosting centres is considered in the context of maximising the hosting centre's revenue over a lengthy time horizon. The inspiration for the server orchestration approach proposed in this thesis is drawn from nature and generally classed as swarm intelligence, specifically, sophisticated collective behaviour of social insects borne out of primitive interactions amongst members of the group to solve problems beyond the capability of individual members. Consequently, the approach is self-organising, adaptive and robust. A new scheme for server ensemble orchestration is introduced in this thesis. This scheme exploits the many similarities between server orchestration in an internet hosting centre and forager allocation in a honeybee (Apis mellifera) colony. The scheme mimics the way a honeybee colony distributes foragers amongst flower patches to maximise nectar influx, to orchestrate servers amongst hosted internet services to maximise revenue. The scheme is extended by further exploiting inherent feedback loops within the colony to introduce self-tuning and energy-aware server ensemble orchestration. In order to evaluate the new server ensemble orchestration scheme, a collection of server ensemble orchestration methods is developed, including a classical technique that relies on past history to make time varying orchestration decisions and two theoretical techniques that omnisciently make optimal time varying orchestration decisions or an optimal static orchestration decision based on complete knowledge of the future. The efficacy of the new biomimetic scheme is assessed in terms of adaptiveness and versatility. The performance study uses representative classes of internet traffic stream behaviour, service user's behaviour, demand intensity, multiple services co-hosting as well as differentiated hosting fee schedule. The biomimetic orchestration scheme is compared with the classical and the theoretical optimal orchestration techniques in terms of revenue stream. This study reveals that the new server ensemble orchestration approach is adaptive in a widely varying external internet environments. The study also highlights the versatility of the biomimetic approach over the classical technique. The self-tuning scheme improves on the original performance. The energy-aware scheme is able to conserve significant energy with minimal revenue performance degradation. The simulation results also indicate that the new scheme is competitive or better than classical and static methods.
122

Nouveaux complexes biomimétiques dérivés de calix[6]azacryptands : étude des effets de seconde sphère et greffage sur surface / New biomimetic complexes derived from calix[6]azacryptands : study of second sphere effects and surface functionalization

De Leener, Gaël 23 March 2016 (has links)
Plus de 30% des enzymes présentent un ion métallique dans leur site actif qui est la clé pour les réactions de catalyse. Une sous-famille d’enzymes comporte un site actif où un seul ion métallique (Zn2+ ou Cun+) est coordiné à un cœur polyhistidine. L’élaboration de composés modèles est important pour la compréhension des mécanismes fondamentaux impliqués dans le cycle biocatalytique de ces enzymes mononucléaires. Dans ce contexte, nous avons développé des ligands basés sur des calix[6]arènes présentant un chapeau polyazoté lié de manière covalente au macrocycle. Ces ligands offrent un site de coordination pour le métal et une cavité hydrophobe bien définie. Cet assemblage permet et contrôle la liaison d’un ligand exogène dans la cavité. Afin de moduler les propriétés des complexes métalliques calixaréniques basés sur une unité coordinante tren (tris(2-aminoéthyl)amine), nous avons synthétisé avec succès et étudié plusieurs nouveaux récepteurs calix[6]aréniques. La synthèse de récepteurs bisétagés, le calix[6]amido-tren et le calix[6]amido-tacn, a permis de modifier la seconde sphère de coordination par incorporation de groupements amide entre la cavité et le site de coordination. Cette stratégie s’est avérée efficace. En effet, la coordination d’anions au centre métallique a été mise en évidence et en particulier celle simultanée de deux Cl¯ pour le Cu-calix[6]amido-tren. Cette coordination d’un ou plusieurs invités anioniques était impossible dans le cas du calix[6]tren parent qui présente une seconde sphère de coordination électroniquement dense et un chapeau trop petit pour y accueillir plusieurs invités. La présence de groupements carbonyle entre la chapeau tren et le calixarène modifie également le comportement des complexes : leur coordination au centre métallique entre en compétition avec celle d’invités exogènes. L’oxydation d’amines encombrées sous O2 en hydroxylamines et oximes a été réalisée par la réduction du complexe cuivrique du calix[6]amido-tren par électrochimie. Ce type d’amines n’est pas oxydable par l’adduit superoxo du complexe parent, dû à la taille de la cavité qui empêche la coordination d’invités encombrés. De plus, la formation d’un adduit superoxo a été mise en évidence qualitativement au départ du complexe cuivreux isolé de ce même composé. Ces résultats permettent d’envisager des études de réactivité mimant le site actif des enzymes PHM et DβM par exemple. Enfin, une comparaison des propriétés hôte-invité et de la réactivité des complexes du calix[6]amido-tren avec celles des complexes du calix[6]amido-tacn a été réalisée afin d’évaluer l’impact de la nature du chapeau polyazoté sur les propriétés hôte-invité et la réactivité de ces complexes. Une méthodologie de déméthylation assistée de manière supramoléculaire a été développée pour différents calix[6]azacryptands chapeautés. Celle-ci a ensuite été appliquée avec succès à la déméthylation du calix[6]tren pour obtenir le calix[6]trentrisPhOH. Ce récepteur a montré un comportement très différent de celui du récepteur parent. En effet, la complexation d’anions et d’ammoniums biologiquement pertinents a été possible par ce récepteur protonné. L’interaction entre le centre métallique et les phénates en présence de base a conduit à la réalisation d’un switch moléculaire multi-étapes entre différents états de protonation du récepteur et du complexe zincique. Son complexe cuivrique a montré la présence d’un radical phénoxyle après oxydation du phénate. Cette espèce CuII-radical phénoxyle mime la forme oxydée du site actif de la galactose oxydase, catalysant l’oxydation d’alcools en aldéhydes. Ces résultats ouvrent donc la voie à de nouvelles perspectives pour les études de réactivité de ce composé. Un analogue du calix[6]tren, porteur d’un bras avec une fonction réactive sur le chapeau, a été synthétisé et complexé au cuivre avant d’être immobilisé sur surface via la formation de monocouches. (...) / More than 30% of all enzymes present a metal ion in their active site. Interesting sub-families present a mononuclear active site where a single metal ion (Zn2+ or Cun+) is coordinated to a polyhistidine core. The elaboration of model compounds is important for understanding the fundamental mechanisms involved in their bio-catalytic cycles. In this context, we have developed calix[6]arene based ligands presenting an aza cap covalently linked to the calixarene moiety. These supramolecular assemblies present several advantages: they offer a coordination site for a metal ion through the nitrogen donor atoms of the cap, the small rim of the calixarene moiety defines the second coordination sphere, and the hydrophobic cavity presents an access channel for exogenous ligands. In these systems the coordinating nitrogen atoms are separated from the oxygen rich small rim by two carbon atoms, which allows the controlled coordination of one single guest inside the cavity. Wanting to modulate the properties of the calix[6]arene tren-based (tris(2-aminoethyl)amine) ligand, we successfully synthetized several new receptors and studied their reactivity. The synthesis of “two-story” receptors, the calix[6]amido-tren and calix[6]amido-tacn, allowed the modification of the first and second coordination sphere of a coordinated metal ion by introducing an additional spacer between the tripodal aza-cap and the calixarene macrocycle. The complexes of CuI, CuII and ZnII of these new ligands were synthesized and their reactivity was studied. The presence of three potentially coordinating carbonyl groups changed the host-guest reactivity of these metal complexes as they are in competition with exogenous ligands. A comparative study of the host-guest properties and of the reactivity of the metal complexes of both ligands, calix[6]amido-tren and calix[6]amido-tacn was realized. The cavity of these “two-story” ligands is larger than the one of the parent calix[6]tren and more flexible, allowing not only the coordination of an anion, but the simultaneous coordination of two Cl¯ ligands. The oxidation of sterically hindered amines into hydroxylamines and oximes in the presence of O2 was electrochemically realized by the reduction of the cupric center forming a CuII-superoxo adduct as the reactive species. Amine oxidation has been shown for the parent complex, however, the scope of this reaction was limited due to the smaller cavity. The formation of a CuII-superoxo adduct of the calix[6]amido-tren complex was qualitatively evidenced at low temperature upon addition of O2 to the isolated cuprous complex. This type of adduct has attracted much attention in recent years since it is considered to be a reactive intermediate in the catalytic cycle of copper monooxygenases, such as PHM and DβM. A supramolecular assisted demethylation methodology was developed for different capped calix[6]azacryptands. This methodology was then successfully applied to the demethylation of calix[6]tren in order to obtain calix[6]trentrisPhOH. This receptor showed a very different behavior in comparison to the parent one. Indeed, the complexation of anions and biologically relevant ammonium ions was evidenced by the monoprotonated receptor. The metal complexes of CuII and ZnII were synthesized. The interaction between the metal center and the phenate groups in presence of base has been evidenced and has conducted to a multi-step molecular switch. The cupric complex showed the presence of a phenoxyl radical resembling the oxidized form of galactose oxidase, catalyzing the oxidation of alcohols into aldehydes. These results open the way to new perspectives in reactivity studies. An analog of calix[6]tren, bearing a functionalized reactive arm on the tren cap, was synthesized and the corresponding CuII complex was immobilized on a gold surface through a monolayer formation. (...)
123

Design, analysis, and simulation of a humanoid robotic arm applied to catching

Yesmunt, Garrett Scot January 2014 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / There have been many endeavors to design humanoid robots that have human characteristics such as dexterity, autonomy and intelligence. Humanoid robots are intended to cooperate with humans and perform useful work that humans can perform. The main advantage of humanoid robots over other machines is that they are flexible and multi-purpose. In this thesis, a human-like robotic arm is designed and used in a task which is typically performed by humans, namely, catching a ball. The robotic arm was designed to closely resemble a human arm, based on anthropometric studies. A rigid multibody dynamics software was used to create a virtual model of the robotic arm, perform experiments, and collect data. The inverse kinematics of the robotic arm was solved using a Newton-Raphson numerical method with a numerically calculated Jacobian. The system was validated by testing its ability to find a kinematic solution for the catch position and successfully catch the ball within the robot's workspace. The tests were conducted by throwing the ball such that its path intersects different target points within the robot's workspace. The method used for determining the catch location consists of finding the intersection of the ball's trajectory with a virtual catch plane. The hand orientation was set so that the normal vector to the palm of the hand is parallel to the trajectory of the ball at the intersection point and a vector perpendicular to this normal vector remains in a constant orientation during the catch. It was found that this catch orientation approach was reliable within a 0.35 x 0.4 meter window in the robot's workspace. For all tests within this window, the robotic arm successfully caught and dropped the ball in a bin. Also, for the tests within this window, the maximum position and orientation (Euler angle) tracking errors were 13.6 mm and 4.3 degrees, respectively. The average position and orientation tracking errors were 3.5 mm and 0.3 degrees, respectively. The work presented in this study can be applied to humanoid robots in industrial assembly lines and hazardous environment recovery tasks, amongst other applications.
124

Structure Property Relations and Finite Element Analysis of Ram Horns: A Pathway to Energy Absorbent Bio-Inspired Designs

Trim, M W (Michael Wesley) 06 August 2011 (has links)
A recently emerging engineering design approach entails studying the brilliant design solutions found in nature with an aim to develop design strategies that mimic the remarkable efficiency found in biological systems. This novel engineering approach is referred to as bio-inspired design. In this context, the present study quantifies the structure-property relations in bighorn sheep (Ovis canadensis) horn keratin, qualitatively characterizes the effects of a tapered spiral geometry (the same form as in a ram’s horn) on pressure wave and impulse mitigation, describes the stress attenuation capabilities and features of a ram’s head, and compares the structures and mechanical properties of some energy absorbent natural materials. The results and ideas presented herein can be used in the development of lightweight, energy absorbent, bio-inspired material designs. Among the most notable conclusions garnered from this research include: Horn keratin behaves in an anisotropic manner similar to a long fiber composite. Moisture content dominates the material behavior of horn keratin more than anisotropy, age, and stress-state. This makes moisture content the most influential parameter on the mechanical behavior of horn keratin. Tapered geometries mitigate the impulse generated by a stress wave due to the convergent boundary and a continually decreasing cross sectional area such that greater uniaxial stresses and subsequent axial deformation arises. Furthermore, the tapered geometry introduces small shear stresses that further decrease the impulse. Spiral geometries attenuate the impulse generated by a stress wave by the introduction of shear stresses along the length of the spiral. These shear stresses introduce transverse displacements that function to lessen the impulse. When both a taper and spiral geometry are used in a design, their synergistic effects multiplicatively reduce the impulse Tough natural materials have a high porosity, which makes them light-weight, while increasing their compressive energy absorption ability. Biomaterials whose functions include protection and energy absorption feature a multiscale, hierarchical, composite structure. The constituent materials are arranged in such ways to achieve a synergistic effect, where the properties of the composite exceed the properties of its constituents. Biological materials are therefore not confined to the law of mixtures.
125

Collaboration for Environmental Sustainability on Gotland, Sweden. Nature’s Blueprint: Biomimicry as a Potential Strategy.

Le, Thao January 2023 (has links)
This master's thesis explores the potential for collaboration among diverse actors on the island of Gotland to achieve environmental sustainability. The study employs the concept of biomimicry, utilising selected natural phenomena as a source of inspiration. A theoretical framework and qualitative research methodology are employed to guide the process, with the aim of developing a strategy to enhance the collaborative state for environmental sustainability on Gotland. Drawing on principles derived from nature, the study investigates how biomimicry can provide solutions and inspire collaborative efforts for environmental sustainability. Central to the research is the exploration of trust-building mechanisms among diverse actors. Recognising that trust is a fundamental ingredient for effective collaboration, the study examines strategies that can foster trust within the context of environmental sustainability. By identifying barriers and enablers of trust, the thesis proposes actionable recommendations to enhance the trust-building process on Gotland, thereby fostering a conducive environment for collaboration. The proposed strategy aims to create a collaborative framework that fosters long-term partnerships, harnessing the diverse expertise and resources of each actor to address the multifaceted challenges of environmental sustainability on Gotland. In conclusion, this master's thesis underscores the value of applying biomimicry principles to foster collaboration for environmental sustainability on Gotland.
126

Property inference decision-making and decision switching of undergraduate engineers : implications for ideational diversity & fluency through movements in a Cartesian concept design space

Shah, Raza January 2017 (has links)
Design fixation is a phenomenon experienced by professional designers and engineering design students that stifles creativity and innovation through discouraging ideational productivity, fluency and diversity. During the design idea and concept generation phase of the design process, a reliance on perceptual surface feature similarities between design artefacts increases the likelihood of design fixation leading to design duplication. Psychologists, educators and designers have become increasingly interested in creative idea generation processes that encourage innovation and entrepreneurial outcomes. However, there is a notable lack of collaborative research between psychology, education and engineering design particularly on inductive reasoning of undergraduate engineering students in higher education. The data gathered and analysed for this study provides an insight into property inference decision-making preferences and decision switching (SWITCH) patterns of engineering undergraduates under similarity-based inductive judgements [SIM] and category-based inductive judgements [CAT]. For this psychology experiment, property induction tasks were devised using abstract shapes in a triad configuration. Participants (N = 180), on an undergraduate engineering programme in London, observed a triad of shapes with a target shape more similar-looking to one of two given shapes. Factors manipulated for this experiment included category alignment, category group, property type and target shape. Despite the cognitive development and maturation stage of undergraduate engineers (adults) in higher education, this study identified similarity-based inductive judgements [SIM] to play a significant role during inductive reasoning relative to the strength of category-based inductive judgements [CAT]. In addition to revealing the property inference decision-making preferences of a sample of undergraduate engineers (N = 180), two types of switch classification and two types of non-switch classification (SWITCH) were found and named SIM_NCC, SIM-Salient, Reverse_CAT and CAT_Switching. These different classifications for property inference switching and non-switching presented a more complex pattern of decision-making driven by the relative strength between similarity-based inductive judgements [SIM] and category-based inductive judgements [CAT]. The conditions that encouraged CAT_Switching is of particular interest to design because it corresponds to inference decision switching that affirms the sharing of properties between dissimilar-looking shapes designated as category members, i.e., in a conflicting category alignment condition (CoC). For CAT_Switching, this study found a significant interaction between a particular set of conditions that significantly increased the likelihood of property inference decisions switching to affirm the sharing of properties between dissimilar-looking shapes. Stimuli conditions that combined a conflicting category alignment condition (where dissimilar-looking shapes belong to the same category) with category specificity, a causal property and a target shape with merged (or blended) perceptual surface features significantly increased the likelihood of a property inference decision switching. CAT_Switching has important implications for greater ideational productivity, fluency and diversity to discourage design fixation within the conceptual design space. CAT_Switching conditions could encourage more creative design transformations with alternative design functions through inductive inferences that generalise between dissimilar artefact designs. The findings from this study led to proposing a Cartesian view of the concept design space to represent the possibilities for greater movements through flexible and expanding category boundaries to encourage conceptual combinations, greater ideational fluency and greater ideational diversity within a configuration design space. This study has also created a platform for further research into property inference decision-making, ideational diversity and category boundary flexibility under stimuli conditions that encourage designers and design students to make inductive generalisations between dissimilar domains of knowledge through a greater emphasis on causal relations and semantic networks.

Page generated in 0.0298 seconds