Dissertations / Theses on the topic 'FLEXIBLE COMPUTATION'
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Xu, Ming. "Robust and flexible multi-scale medial axis computation." Thesis, University of Birmingham, 2001. http://etheses.bham.ac.uk//id/eprint/17/.
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The principle of the multi-scale medial axis (MMA) is important in that any object is detected at a blurring scale proportional to the size of the object. Thus it provides a sound balance between noise removal and preserving detail. The robustness of the MMA has been reflected in many existing applications in object segmentation, recognition, description and registration. This thesis aims to improve the computational aspects of the MMA. The MMA is obtained by computing ridges in a “medialness” scale-space derived from an image. In computing the medialness scale-space, we propose an edge-free medialness algorithm, the Concordance-based Medial Axis Transform (CMAT). It not only depends on the symmetry of the positions of boundaries, but also is related to the symmetry of the intensity contrasts at boundaries. Therefore it excludes spurious MMA branches arising from isolated boundaries. In addition, the localisation accuracy for the position and width of an object, as well as the robustness under noisy conditions, is preserved in the CMAT. In computing ridges in the medialness space, we propose the sliding window algorithm for extracting locally optimal scale ridges. It is simple and efficient in that it can readily separate the scale dimension from the search space but avoids the difficult task of constructing surfaces of connected maxima. It can extract a complete set of MMA for interfering objects in scale-space, e.g. embedded or adjacent objects. These algorithms are evaluated using a quantitative study of their performance for 1-D signals and qualitative testing on 2-D images.
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Gog, Ionel Corneliu. "Flexible and efficient computation in large data centres." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271804.
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Increasingly, online computer applications rely on large-scale data analyses to offer personalised and improved products. These large-scale analyses are performed on distributed data processing execution engines that run on thousands of networked machines housed within an individual data centre. These execution engines provide, to the programmer, the illusion of running data analysis workflows on a single machine, and offer programming interfaces that shield developers from the intricacies of implementing parallel, fault-tolerant computations. Many such execution engines exist, but they embed assumptions about the computations they execute, or only target certain types of computations. Understanding these assumptions involves substantial study and experimentation. Thus, developers find it difficult to determine which execution engine is best, and even if they did, they become “locked in” because engineering effort is required to port workflows. In this dissertation, I first argue that in order to execute data analysis computations efficiently, and to flexibly choose the best engines, the way we specify data analysis computations should be decoupled from the execution engines that run the computations. I propose an architecture for decoupling data processing, together with Musketeer, my proof-of-concept implementation of this architecture. In Musketeer, developers express data analysis computations using their preferred programming interface. These are translated into a common intermediate representation from which code is generated and executed on the most appropriate execution engine. I show that Musketeer can be used to write data analysis computations directly, and these can execute on many execution engines because Musketeer automatically generates code that is competitive with optimised hand-written implementations. The diverse execution engines cause different workflow types to coexist within a data centre, opening up both opportunities for sharing and potential pitfalls for co-location interference. However, in practice, workflows are either placed by high-quality schedulers that avoid co-location interference, but choose placements slowly, or schedulers that choose placements quickly, but with unpredictable workflow run time due to co-location interference. In this dissertation, I show that schedulers can choose high-quality placements with low latency. I develop several techniques to improve Firmament, a high-quality min-cost flow-based scheduler, to choose placements quickly in large data centres. Finally, I demonstrate that Firmament chooses placements at least as good as other sophisticated schedulers, but at the speeds associated with simple schedulers. These contributions enable more efficient and effective use of data centres for large-scale computation than current solutions.
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Radul, Alexey. "Propagation networks : a flexible and expressive substrate for computation." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54635.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 167-174).
In this dissertation I propose a shift in the foundations of computation. Modem programming systems are not expressive enough. The traditional image of a single computer that has global effects on a large memory is too restrictive. The propagation paradigm replaces this with computing by networks of local, independent, stateless machines interconnected with stateful storage cells. In so doing, it offers great flexibility and expressive power, and has therefore been much studied, but has not yet been tamed for general-purpose computation. The novel insight that should finally permit computing with general-purpose propagation is that a cell should not be seen as storing a value, but as accumulating information about a value. Various forms of the general idea of propagation have been used with great success for various special purposes; perhaps the most immediate example is constraint propagation in constraint satisfaction systems. This success is evidence both that traditional linear computation is not expressive enough, and that propagation is more expressive. These special-purpose systems, however, are all complex and all different, and neither compose well, nor interoperate well, nor generalize well. A foundational layer is missing. I present in this dissertation the design and implementation of a prototype general-purpose propagation system. I argue that the structure of the prototype follows from the overarching principle of computing by propagation and of storage by accumulating information-there are no important arbitrary decisions. I illustrate on several worked examples how the resulting organization supports arbitrary computation; recovers the expressivity benefits that have been derived from special-purpose propagation systems in a single general-purpose framework, allowing them to compose and interoperate; and offers further expressive power beyond what we have known in the past. I reflect on the new light the propagation perspective sheds on the deep nature of computation.
by Alexey Andreyevich Radul.
Ph.D.
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Zukowski, Ulrich. "Flexible computation of the well-founded semantics of normal logic programs." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964404036.
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Song, Weihong. "A real space approach to LEED computation with flexible local mesh refinement." Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B39849004.
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Song, Weihong, and 宋慰鴻. "A real space approach to LEED computation with flexible local mesh refinement." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B39849004.
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Priddle, Jacob William. "Efficient and flexible Bayesian synthetic likelihood via transformations." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205902/1/Jacob_Priddle_Thesis.pdf.
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Simulator models are a type of stochastic model that is often used to approximate a real-life process. Current statistical methods for simulator models are computationally intensive, relying on a large number of model simulations. In this thesis, we develop new, efficient and flexible statistical methods that can be used for complex statistical models, such as simulator models. The new methods are theoretically justified and applied to a variety of simulated and real-life modelling scenarios from ecology and biology.
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Buss, Aaron Thomas. "Closing the developmental loop on the behavioral and neural dynamics of flexible rule-use." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/4949.
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Executive function (EF) is a central aspect of cognition that undergoes significant changes in early childhood. Changes in EF in early childhood are robustly predictive of academic achievement and general quality of life measures later in adulthood. I develop a dynamic neural field (DNF) model which provides a process-based account of behavior and developmental change in a key task used to probe the early development of executive function--the Dimensional Change Card Sort (DCCS) task. In the DCCS, children must flexibly switch from sorting cards either by shape or color to sorting by the other dimension. Typically, 3-year-olds, but not 5-year-olds, lack the flexibility to do so and perseverate on the first set of rules when instructed to switch. In Study 1, I use the DNF model to integrate behavioral and neural processes by simulating hemodynamics associated with the early emergence of flexible rule-use. I then test predictions of the model using near-infrared spectroscopy. In Study 2, I develop a DCCS that can be used with adults that sheds light on key aspects of the task as they have been revealed with children. Using fMRI, a pattern of behavioral and neural effects shed light on the central processes involved in flexible rule-use. These two studies demonstrate that performance emerges as a property of system-wide interactions and that common neurocognitive effects .can be found between childhood and adulthood.
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Thyagarajan, Senthilmurugan. "Improvements to strain computation and reliabilty analysis of flexible pavements in the mechanistic-empirical pavement design guide." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/s_thyagarajan_0042309.pdf.
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Thesis (Ph. D.)--Washington State University, May 2009.Title from PDF title page (viewed on Feb. 18, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 167-169).
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Li, Qiang. "Effects of Adaptive Discretization on Numerical Computation using Meshless Method with Live-object Handling Applications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14480.
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The finite element method (FEM) has difficulty solving certain problems where adaptive mesh is needed. Motivated by two engineering problems in live-object handling project, this research focus on a new computational method called the meshless method (MLM). This method is built upon the same theoretical framework as FEM but needs no mesh. Consequently, the computation becomes more stable and the adaptive computational scheme becomes easier to develop. In this research, we investigate practical issues related to the MLM and develop an adaptive algorithm to automatically insert additional nodes and improve computational accuracy. The study has been in the context of the two engineering problems: magnetic field computation and large deformation contact. First, we investigate the effect of two discretization methods (strong-form and weak-form) in MLM for solving linear magnetic field problems. Special techniques for handling the discontinuity boundary condition at material interfaces are proposed in both discretization methods to improve the computational accuracy. Next, we develop an adaptive computational scheme in MLM that is comprised of an error estimation algorithm, a nodal insertion scheme and a numerical integration scheme. As a more general approach, this method can automatically locate the large error region around the material interface and insert nodes accordingly to reduce the error. We further extend the adaptive method to solve nonlinear large deformation contact problems. With the ability to adaptively insert nodes during the computation, the developed method is capable of using fewer nodes for initial computation and thus, effectively improves the computational efficiency. Engineering applications of the developed methods have been demonstrated by two practical engineering problems. In the first problem, the MLM has been utilized to simulate the dynamic response of a non-contact mechanical-magnetic actuator for optimizing the design of the actuator. In the second problem, the contact between the flexible finger and the live poultry product has been analyzed by using MLM. These applications show the developed method can be applied to a broad spectrum of engineering applications where an adaptive mesh is needed.
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Li, Iila Jingjiao. "Flexible polyhedra : exploring finite mechanisms of triangulated polyhedra." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271806.
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In a quest to design novel deployable structures, flexible polyhedra provide interesting insights. This work follows the discovery of flexible polyhedra and aims to make flexible polyhedra more useful. The dissertation describes how flexible polyhedra can be made. The flexible polyhedra first considered in this dissertation have a rotational degree of freedom. The range of this rotational movement is measured and maximised in this work by numerical maximisation. All polyhedra are established computationally: an iterative solution method is used to find vertex coordinates; several clash detecting methods are described to define whether each rotational position of a flexible polyhedron is physically possible; then a range of motion is defined between occurrences of clashes at the two ends; finally, an optimisation tool is used to maximise the range of motion. By using these tools, the range of motion of two types of simplest flexible polyhedra are maximised. The first type is a series of flexible polyhedra generalised from the Steffen flexible polyhedron. The range of motion of this type is improved to double that of Steffen’s original, from 27° to 59°. Another type of flexible polyhedron is expanded from a model provided by Tachi. Based on the understanding of Steffen’s flexible polyhedron, optimisation parameters are carefully given. This new type has achieved a wider range of motion, so now the range of motion of flexible polyhedron is tripled to 80°. After enlarging the range of motion of the degree of freedom in the 1-dof systems, the dissertation found multiple degrees of freedom in one polyhedron. The multiple mechanisms can be even repetitive, so that an n-dof polyhedron is found. A polyhedron of two degrees of freedom is first presented. Then, a unit cell for any number of mechanisms is found. As a repetitive structure, a 3-dof polyhedron is presented. Finally, this work presents the possibility of configuring a flexible polyhedral torus and a closed polyhedral surface that is able to flex without the need to stop.
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Alhaj, Ali Khaled. "New design approaches for flexible architectures and in-memory computing based on memristor technologies." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2020. http://www.theses.fr/2020IMTA0197.
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Le développement récent de nouvelles technologies de mémoires non-volatiles basées sur le concept de memristor a suscité de nombreux efforts pour explorer leur utilisation potentielle dans différents domaines d'application. Les propriétés uniques de ces dispositifs memristifs et leur compatibilité pour uneintégration avec les technologies CMOS conventionnelles permettent de nouveaux paradigmes de conception d’architecture, offrant des niveaux sans précédent de densité, de reconfigurabilité et d’efficacité énergétique. Dans ce contexte, le but de ce travail de thèse était d'explorer et d'introduire de nouvelles approches de conception basées sur les memristors pour combiner flexibilité et efficacité en proposant des architectures originales qui dépassent les limites des architectures existantes. Cette exploration et cette étude ont été menées à trois niveaux : interconnexion, traitement et mémoire. Au niveau des interconnexions, nous avons étudié l'utilisation de dispositifs memristifs pour permettre une grande flexibilité basée sur des réseaux d'interconnexion programmables. Cela a permis de proposer la première architecture de transformée de Fourier rapide reconfigurable basée sur des memristors, nommée mrFFT. Les memristors sont insérés comme des commutateurs reconfigurables au niveau des interconnexions afin d'établir un routage flexible puce. Au niveau du traitement, nous avons exploré l'utilisation de dispositifs memristifs et leur intégration avec les technologies CMOS pour la conception de fonctions logique combinatoire. Ces circuits hybrides memristor-CMOS exploitent la forte densité d'intégration des memristors afin d'améliorer les performances des implémentations numériques, et en particulier des unités arithmétiques et logiques. Au niveau mémoire, une nouvelle approche de calcul en mémoire a été introduite. Dans ce contexte, un nouveau style de conception logique a été proposé, nommé Memristor Overwrite Logic (MOL), associé à une architecture originale de mémoire de calcul. L’approche proposée permet de combiner efficacement le stockage et le traitement afin de contourner les problèmes liés aux accès mémoire et d'améliorer ainsi l'efficacité de calcul. L'approche proposée a été appliquée dans trois études de cas à des fins de validation et d'évaluation des performancesThe recent development of new non-volatile memory technologies based on the memristor concept has triggered many research efforts to explore their potential usage in different application domains. The distinctive features of memristive devices and their suitability for CMOS integration are expected to lead for novel architecture design paradigms enabling unprecedented levels of energy efficiency, density, and reconfigurability. In this context, the goal of this thesis work was to explore and introduce new memristor based designs that combine flexibility and efficiency through the proposal of original architectures that break the limits of the existing ones. This exploration and study have been conducted at three levels: interconnect, processing, and memory levels. At interconnect level, we have explored the use of memristive devices to allow high degree of flexibility based on programmable interconnects. This allows to propose the first memristor-based reconfigurable fast Fourier transform architecture, namely mrFFT. Memristors are inserted as reconfigurable switches at the level of interconnects in order to establish flexible on-chip routing. At processing level, we have explored the use of memristive devices and their integration with CMOS technologies for combinational logic design. Such hybrid memristor-CMOS designs exploit the high integration density of memristors in order to improve the performance of digital designs, and particularly arithmetic logic units. At memory level, we have explored new in-memory computing approaches and proposed a novel logic design style, namely Memristor Overwrite Logic (MOL), associated with an original MOL-based computational memory. The proposed approach allows efficient combination of storage and processing in order to bypass the memory wall problem and thus to improve the computational efficiency. The proposed approach has been applied in three real application case studies for the sake of validation and performance evaluation
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Ossamy, Rodrigue Bertrand. "An algorithmic and computational approach to local computations." Bordeaux 1, 2005. http://www.theses.fr/2005BOR13067.
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Dans cette thèse, nous nous intéressons aux aspects algorithmiques des calculs locaux dans les domaines de la synchronisation d'algorithmes et du contrôle de l'exécution. Dans un premier temps nous proposons différents protocoles de synchronisation qui ont besoin, pour certains, d'avoir une connaissance structurelle du graphe (diamètre, nombre de processeurs, etc. . . ). D'autre part, nous utilisons le concept des réductions de graphes pour présenter un algorithme capable de reconnaître des propriétés de graphes à l'aide des calculs locaux. Cette étude introduit la notion de systèmes de réduction pratiques (handy reduction systems) qui nous permet de démontrer que toutes les propriétés de graphes de largeur arborescente bornée, définissable en logique monadique du second ordre, peuvent être reconnues par les calculs locaux. Enfin, nous introduisons le langage de programmation des calculs locaux (Lidia). Ce langage est basé sur un système de transition à deux niveaux où les préconditions de chaque transistion sont exprimées par la logique L*∞. En se servant despropriétés descriptives de L*∞, nous établissons la complétude du langage Lidia.
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McElhone, Charles Gerard. "A constrained computational model for flexible scheduling." Thesis, University of York, 1996. http://etheses.whiterose.ac.uk/10900/.
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Ebrahimi, Saeed. "A contribution to computational contact procedures in flexible multibody systems." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-31910.
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Lindgren, Michael. "Experimental and computational investigation of the roll forming process." Doctoral thesis, Luleå : Division of Material Mechanics, Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3340038.
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Richardson, Patricia. "Spectroscopic and computational studies on a number of conformationally flexible molecules." Thesis, University of Edinburgh, 2001. http://hdl.handle.net/1842/14279.
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The laser-desorption jet-cooling (LD-SJ) method has been applied successfully to the acquisition of LIF excitation spectra for a number of conformationally flexible molecules. The molecules 4-cyanobiphenyl, 4-hydroxybipenyl, tyramine and 4-t-butyl phenol were studied and well-resolved vibronic spectra obtained for each molecule. Modification to the experimental set-up have allowed the collection of dispersed fluorescence spectra for the first time. The dispersed emission spectra from both conformer bands of 4-t-butyl phenol, and several of the tyramine conformer bands were recorded. In the dispersed fluorescence spectrum of 4-hydoxylbiphenyl, a high enough resolution to observe individual torsional levels in the ground state could not be obtained. Ab initio methods have been used in tandem with the LD-SJ work to study the structural and electronic behaviour of each molecule studied experimentally. Several similarities were observed in the electronic properties of each molecule. Interactions in the HOMO were influential in determining the structure of each compound. In addition, substituent effects on the electron density in the HOMO were shown to influence the energetic stability of the various different molecular conformers. Calculations show that conjugative interactions in the HOMO also play an important role in the stability of the twisted molecular structure of biphenyl and derivatives. Substituent induced perturbations to the electron density in the lowest unoccupied molecular orbital (LUMO) can be directly linked to the curvature of the S1 torsional potential. Substituents which are either strongly electron donating or withdrawing introduce a large asymmetry in the electron density across the inter-ring bond resulting in a reduced S1 torsional frequency.
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Awati, Rohan Vivek. "Development of accurate computational methods for simulations of adsorption and diffusion in zeolites." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54945.
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The overall objective of this thesis has been to develop accurate computational methods for the diffusion and adsorption of small gases in zeolites. Firstly, the effect of the zeolite framework flexiblity on the single component and binary diffusion of various gases were discussed. Results indicate that for tight fitting molecules the rigid framework approximation can produce order(s) of magnitude difference in diffusivities as compared to the simulations performed with a fully flexible framework. We proposed two simple methods in which the flexible structure of a zeolite is approximated as a set of discrete rigid snapshots. Both methods are orders of magnitude more efficient than the simulations with the fully flexible structure. Secondly, we use a combined classical and quantum chemistry based approach to systematically develop the force fields based on DFT calculations for interactions of simple molecules like CH4, N2, linear alkanes, and linear alkenes in zeolites. We used a higher level of theory known as the DFT/CC method to correct DFT energies that were used in the periodic DFT calculations to develop force fields. Our results show that DFT-derived force fields give good predictions of macroscopic properties like adsorption isotherms in zeolites. The force fields are transferrable across zeolites and hence can be further used to screen materials for different storage and separation applications.
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Kozlowski, Raymond. "Uniform multilingual sentence generation using flexible lexico-grammatical resources." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.93 Mb., 213 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3200536.
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Toha, Siti Fauziah. "Computational intelligence techniques for modelling and control of a flexible manoeuvring system." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537999.
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Ebrahimi, Saeed [Verfasser]. "A Contribution to Computational Contact Procedures in Flexible Multibody Systems / Saeed Ebrahimi." Aachen : Shaker, 2007. http://d-nb.info/1166512185/34.
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Cole, Robert Edward. "Numerical Modeling of Air Cushion Vehicle Flexible Seals." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83828.
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Air cushion vehicle flexible seals operate in a complex and chaotic environment dominated by fluid-structure interaction. An efficient means to explore interdependencies between various governing parameters that affect performance is through high fidelity numerical simulation. As previous numerical efforts have employed separate iterative partitioned solvers, or have implemented simplified physics, the approaches have been complex, computationally expensive, or of limited utility. This research effort performs numerical simulations to verify and validate the commercial multi-physics tool STAR-CCM+ as a stand-alone partitioned approach for fluid-structure interaction problems with or without a free surface. A dimensional analysis is first conducted to identify potential non-dimensional forms of parameters related to seal resistance. Then, an implicit, Reynolds-averaged Navier-Stokes finite volume fluid solver is coupled to an implicit, nonlinear finite element structural solver to successfully replicate benchmark results for an elastic beam in unsteady laminar flow. To validate the implementation as a seal parameter exploratory tool, a planer bow seal model is developed and results are obtained for various cushion pressures and inflow speeds. Previous numerical and experimental results for deflection and resistance are compared, showing good agreement. An uncertainty analysis for inflow velocity reveals an inversely proportional resistance dependency. Using Abaqus/Explicit, methodologies are also developed for a two-way, loosely coupled explicit approach to large deformation fluid-structure interaction problems, with and without a free surface. Following numerous verification and validation problems, Abaqus is ultimately abandoned due to the inability to converge the fluid pressure field and achieve steady state. This work is a stepping stone for future researchers having interests in ACV seal design and other large deformation, fluid-structure interaction problems. By modeling all necessary physics within a verified and validated stand-alone approach, a designer's ability to comprehensively investigate seal geometries and interactions has never been more promising.Ph. D.
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Cohen, David E. II. "Trim Angle of Attack of Flexible Wings Using Non-Linear Aerodynamics." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30404.
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Multidisciplinary interactions are expected to play a significant role in the design of future high-performance aircraft (Blended-Wing Body, Truss-Braced wing, High Speed Civil transport, High-Altitude Long Endurance aircraft and future military aircraft). Also, the availability of supercomputers has made it now possible to employ high-fidelity models (Computational Fluid Dynamics for fluids and detailed finite element models for structures) at the preliminary design stage. A necessary step at that stage is to calculate the wing angle-of-attack at which the wing will generate the desired lift for the specific flight maneuver. Determination of this angle, a simple affair when the wing is rigid and the flow regime linear, becomes difficult when the wing is flexible and the flow regime non-linear. To solve this inherently nonlinear problem, a Newton's method type algorithm is developed to simultaneously calculate the deflection and the angle of attack. The present algorithm requires the sensitivity of the aerodynamic pressure with respect to each of the generalized displacement coordinates needed to represent the structural displacement. This sensitivity data is easy to determine analytically when the flow regime is linear. The present algorithm uses a finite difference method to obtain these sensitivities and thus requires only the pressure data and the surface geometry from the aerodynamic model. This makes it ideally suited for nonlinear aerodynamics for which it is difficult to obtain the sensitivity analytically.
The present algorithm requires the CFD code to be run for each of the generalized coordinates. Therefore, to reduce the number of generalized coordinates considerably, we employ the modal superposition approach to represent the structural displacements. Results available for the Aeroelastic Research Wing (ARW) are used to evaluate the performance of the modal superposition approach. Calculations are made at a fixed angle of attack and the results are compared to both the experimental results obtained at NASA Langley Research Center, and computational results obtained by the researchers at NASA Ames Research Center. Two CFD codes are used to demonstrate the modular nature of this research. Similarly, two separate Finite Element codes are used to generate the structural data, demonstrating that the algorithm is not dependent on using specific codes.
The developed algorithm is tested for a wing, used for in-house aeroelasticity research at Boeing (previously McDonnell Douglas) Long Beach. The trim angle of attack is calculated for a range of desired lift values. In addition to the Newton's method algorithm, a non derivative method (NDM) based on fixed point iteration, typical of fixed angle of attack calculations in aeroelasticity, is employed. The NDM, which has been extended to be able to calculate trim angle of attack, is used for one of the cases. The Newton's method calculation converges in fewer iterations, but requires more CPU time than the NDM method. The NDM, however, results in a slightly different value of the trim angle of attack. It should be noted that NDM will converge in a larger number of iterations as the dynamic pressure increases.
For one value of the desired lift, both viscous and inviscid results were generated. The use of the inviscid flow model while not resulting in a markedly different value for the trim angle of attack, does result in a noticeable difference both in the wing deflection and the span loading when compared to the viscous results.
A crude (coarse-grain) parallel methodology was used in some of the calculations in this research. Although the codes were not parallelized, the use of modal superposition made it possible to compute the sensitivity terms on different processors of an IBM SP/2. This resulted in a decrease in wall clock time for these calculations. However, even with the parallel methodology, the CPU times involved may be prohibitive (approximately 5 days per Newton iteration) to any practical application of this method for wing analysis and design. Future work must concentrate on reducing these CPU times. Two possibilities: (i) The use of alternative basis vectors to further reduce the number of basis vectors used to represent the structural displacement, and (ii) The use of more efficient methods for obtaining the flow field sensitivities. The former will reduce the number of CFD analyses required the latter the CPU time per CFD analysis.
NOTE: (03/2007) An updated copy of this ETD was added after there were patron reports of problems with the file.Ph. D.
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Taghipour, Ehsan. "Development of Reduced-Order Computational Models for Digital Manufacturing of Flexible Wire Harnesses." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1543404707742968.
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Ledvina, Kirby. "A computational study of flexible routing strategies for the VRP with stochastic demands." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130822.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, February, 2021Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 57-58).
We develop and numerically test a new strategy for the vehicle routing problem with stochastic customer demands. In our proposed approach, drivers are assigned to predetermined delivery routes in which adjacent routes share some customers. This overlapping assignment structure, which is inspired by the open chain design from the field of manufacturing process flexibility, enables drivers to adapt to variable customer demands while still maintaining largely consistent routes. Through an extensive computational study and scenario analysis, we show that relative to a system without customer sharing, such flexible routing strategies partly mitigate the transportation costs of filling unexpected customer demands, and the relative savings grow with the number of customers in the network. We also find that much of the cost savings is gained with just the first customer that is shared between adjacent routes. Thus, the overlapped routing model forms the basis for a practical and efficient strategy to manage costs from demand uncertainty.
by Kirby Ledvina.
S.M.
S.M. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Neto, Antônio Bernardo Guimarães. "Flight dynamics of flexible aircraft using general body axes : a theoretical and computational study." Instituto Tecnológico de Aeronáutica, 2014. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=3138.
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Neglecting the structural dynamic effects on the flight dynamics of modern aircraft may be inadequate. Dynamic coupling between the rigid-body and the elastic degrees of freedom can occur when the design favors strength over stiffness and the frequency separation between the classical flight dynamic modes and the aeroelastic modes becomes small enough. Degraded flying and ride qualities and increased susceptibility to fatigue damage and pilot-induced oscillations are among the possible consequences of the dynamic coupling. The design of control systems is also highly affected. The initial models for the flight dynamics of flexible aircraft considered only quasi-static aeroelastic effects on the aerodynamic coefficients of the rigid aircraft. The dynamically-coupled formulations, on the other hand, have often neglected the inertial coupling between the rigid-body and the elastic degrees of freedom. Indeed, most authors have used linearized mean-axis constraints in deriving simplified equations of motion that remain only aerodynamically coupled. To analyze the accuracy of the inertially-decoupled formulation in the context of small deformations, a formulation that takes into account all the coupled dynamics and allows an arbitrary choice of the body-axis system is developed in this thesis. The availability of a finite-element model of the aircraft structure, together with lumped mass properties, is required. In the equations of motion, the inertial coupling terms are linearized with respect to the elastic displacements around an equilibrium condition determined with the full nonlinear dynamics. Appropriate modes of vibration are then used as shape functions in the calculation of the dynamic deformation of the structure. The generalized aerodynamic forces are treated as the superposition of the rigid-body contributions and the incremental ones due to elastic deformation. The latter are modeled by the doublet-lattice method, aerodynamically corrected to take into account major transonic and viscous effects. Rational-function approximations are part of the process that allows the representation of the frequency-domain aerodynamics in the time domain, leading to an augmented state-space system that considers the aerodynamic lag phenomenon. The formulation is implemented and tested in the flight simulation of a generic narrow-body airliner (GNBA) model, developed for the purpose of these studies. Results are presented that show that the different body axes lead practically to the same overall motion of the aircraft with respect to an inertial reference frame. The benefits and the limitations in using each different axis system and in considering or not the dynamic and the inertial couplings are analyzed.
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Al, Bodour R. "A flexible model supporting QoS and reallocation for grid applications." Thesis, Coventry University, 2011. http://curve.coventry.ac.uk/open/items/208265d9-ee5d-4c88-a955-466c9fc3dfa3/1.
Full textAbstract:
The rise of business-oriented and commercial applications for Grid computing environments has recently gathered pace. Grid computing traditionally has been linked with scientific environments, where heterogeneous resources provided by Grid systems and infrastructures were employed for carrying out computationally-intensive and data-intensive scientific experiments or applications that may have not been possible before. The natural progression is that business-oriented applications will look to build on this success and utilise the large number of heterogeneous Grid resources including computational resources such as CPUs and memory and storage resources such as disk space, potentially available. The success of introducing these applications into the mainstream is directly related to whether service providers can deliver a level of Quality of Service (QoS) to a consumer and the ability of the consumer to request high-level QoS such as the numbers of CPUs required or the RAM required. QoS refers to the guidelines and requirements requested by a user/consumer from the service providers and resources. The communication and agreement establishment processes between user and provider must be defined clearly to accommodate a new type of user where knowledge of the underlying infrastructure cannot be assumed. QoS parameters have generally been defined at the Grid resource level using low level definitions. This tailors to specific applications and models related to scientific domains where brokering, scheduling and QoS delivery is designed for specific applications within specific domains. This thesis presents a flexible model for high-level QoS requests. Business Grid Quality of Service (BGQoS) is introduced for business-oriented and commercial Grid applications which may wish to make use of the resources made available by Grid system environments. BGQoS allows GRCs (Grid Resource Consumers) to specify varying types of high-level QoS requirements which are delivered via querying up-to-date resource information, matchmaking and monitoring operations. Moreover, we present dynamically calculated metrics for measuring QoS such as reliability, increasing the accuracy of meeting the GRC’s requirements. On the other hand GRPs (Grid Resource Provider) are also capable of advertising their resources, their capabilities, their usage policies and availability both locally and globally. This leads to a flexible model that could be carried across domains without altering the core operations and which could easily be expanded in order to accommodate different types of GRC, resources and applications.
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Clavica, Francesco. "Computational and experimental time domain, one dimensional models of air wave propagation in human airways." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/9622.
Full textAbstract:
The scientific literature on airflow in the respiratory system is usually associated with rigid ducts. Many studies have been conducted in the frequency domain to assess respiratory system mechanics. Time-domain analyses appear more independent from the hypotheses of periodicity, required by frequency analysis, providing data that are simpler to interpret since features can be easily associated to time. However, the complexity of the bronchial tree makes 3-D simulations too expensive computationally, limiting the analysis to few generations. 1-D modelling in space-time variables has been extensively applied to simulate blood pressure and flow waveforms in arteries, providing a good compromise between accuracy and computational cost. This work represents the first attempt to apply this formulation to study pulse waveforms in the human bronchial tree. Experiments have been carried out, in this work, to validate the model capabilities in modelling pressure and velocity waveforms when air pulses propagate in flexible tubes with different mechanical and geometrical properties. The experiments have shown that the arrival of reflected air waves occurs in correspondence of the theoretical timing once the wave speed is known. Reflected backward compression waves have generated an increase of pressure (P) and decrease of velocity (U) while expansion backward waves have produced a decrease of P and increase of U according to the linear analysis of wave reflections. The experiments have demonstrated also the capabilities of Wave intensity analysis (WIA), an analytical technique used to study wave propagation in cardiovascular system, in separating forward and backward components of pressure and velocity also for the air case. After validating the 1-D modelling in space and time variables, several models for human airways have been considered starting from simplified versions (bifurcation trachea- main bronchi, series of tubes) to more complex systems up to seven generations of bifurcations according to both symmetrical and asymmetrical models. Calculated pressures waveforms in trachea are shown to change accordingly to both peripheral resistance and compliance variations, suggesting a possible non-invasive assessment of peripheral conditions. A favourable comparison with typical pressure and flow waveforms from impulse oscillometry system, which has recently been introduced as a clinical diagnostic technique, is also shown. The results suggested that a deeper investigation of the mechanisms underlying air wave propagation in lungs could be a useful tool to better understand the differences between normal and pathologic conditions and how pathologies may affect the pattern of pressure and velocity waveforms.
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Correia, Bruno Emanuel Ferreira de Sousa. "Computational design with flexible backbone sampling for protein remodeling and scaffolding of complex binding sites." Doctoral thesis, Universidade Nova de Lisboa. Instituto de Tecnologia Química e Biológica, 2010. http://hdl.handle.net/10362/5791.
Full textAbstract:
Dissertation presented to obtain the Doutoramento (Ph.D.) degree in Biochemistry at the
Instituto de Tecnologia Qu mica e Biol ogica da Universidade Nova de LisboaComputational protein design has achieved several milestones, including the design of a new protein fold, the design of enzymes for reactions that lack natural catalysts, and the re-engineering of protein-protein and protein-DNA binding speci city. These achievements have spurred demand to apply protein design methods to a wider array of research problems. However, the existing computational methods have largely relied on xed-backbone approaches that may limit the scope of problems that can be tackled. Here, we describe four computational protocols - side chain grafting, exible backbone remodeling, backbone grafting, and de novo sca old design - that expand the methodological protein design repertoire, three of which incorporate backbone exibility. Brie y, in the side chain grafting method, side chains of a structural motif are transplanted to a protein with a similar backbone conformation; in exible backbone remodeling, de novo segments of backbone are built and designed; in backbone grafting, structural motifs are explicitly grafted onto other proteins; and in de novo sca olding, a protein is folded and designed around a structural motif. We developed these new methods for the design of epitope-sca old vaccines in which viral neutralization epitopes of known three-dimensional structure were transplanted onto nonviral sca old proteins for conformational stabilization and immune presentation.(...)
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Chun, Sangeon. "Nonlinear Fluid-Structure Interaction in a Flexible Shelter under Blast Loading." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29849.
Full textAbstract:
Recently, numerous flexible structures have been employed in various fields of industry. Loading conditions sustained by these flexible structures are often not described well enough for engineering analyses even though these conditions are important. Here, a flexible tent with an interior Collective Protection System, which is subjected to an explosion, is analyzed. The tent protects personnel from biological and chemical agents with a pressurized liner inside the tent as an environmental barrier. Field tests showed unexpected damage to the liner, and most of the damage occurred on tent's leeward side.
To solve this problem, various tests and analyses have been performed, involving material characteristics of the liner, canvas, and zip seals, modeling of the blast loading over the tent and inside the tent, and structural response of the tent to the blast loading as collaborative research works with others. It was found that the blast loading and the structural response can not be analyzed separately due to the interaction between the flexible structure and the dynamic pressure loading. In this dissertation, the dynamic loadings imposed on both the interior and the exterior sides of the tent structure due to the airblasts and the resulting dynamic responses were studied. First, the blast loadings were obtained by a newly proposed theoretical method of analytical/empirical models which was developed into a FORTRAN program. Then, a numerical method of an iterative Fluid-Structure Interaction using Computational Fluid Dynamics and Computational Structural Dynamics was employed to simulate the blast wave propagation inside and outside the flexible structure and to calculate the dynamic loads on it.
All the results were compared with the field test data conducted by the Air Force Research Laboratory. The experimental pressure data were gathered from pressure gauges attached to the tent surfaces at different locations. The comparison showed that the proposed methods can be a good design tool to analyze the loading conditions for rigid or flexible structures under explosive loads. In particular, the causes of the failure of the liner on the leeward were explained. Also, the results showed that the effect of fluid-structure interaction should be considered in the pressure load calculation on the structure where the structural deflection rate can influence the solution of the flow field surrounding the structure.Ph. D.
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Brintaki, Athina N. "A Computational Kinematics and Evolutionary Approach to Model Molecular Flexibility for Bionanotechnology." Scholar Commons, 2009. https://scholarcommons.usf.edu/etd/1579.
Full textAbstract:
Modeling molecular structures is critical for understanding the principles that govern the behavior of molecules and for facilitating the exploration of potential pharmaceutical drugs and nanoscale designs. Biological molecules are flexible bodies that can adopt many different shapes (or conformations) until they reach a stable molecular state that is usually described by the minimum internal energy. A major challenge in modeling flexible molecules is the exponential explosion in computational complexity as the molecular size increases and many degrees of freedom are considered to represent the molecules' flexibility. This research work proposes a novel generic computational geometric approach called enhanced BioGeoFilter (g.eBGF) that geometrically interprets inter-atomic interactions to impose geometric constraints during molecular conformational search to reduce the time for identifying chemically-feasible conformations. Two new methods called Kinematics-Based Differential Evolution (kDE) and Biological Differential Evolution (BioDE) are also introduced to direct the molecular conformational search towards low energy (stable) conformations. The proposed kDE method kinematically describes a molecule's deformation mechanism while it uses differential evolution to minimize the inta-molecular energy. On the other hand, the proposed BioDE utilizes our developed g.eBGF data structure as a surrogate approximation model to reduce the number of exact evaluations and to speed the molecular conformational search. This research work will be extremely useful in enabling the modeling of flexible molecules and in facilitating the exploration of nanoscale designs through the virtual assembly of molecules. Our research work can also be used in areas such as molecular docking, protein folding, and nanoscale computer-aided design where rapid collision detection scheme for highly deformable objects is essential.
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Chemishkian, Sergey Y. 1962. "Computational methods for the optimization of the mapping of actuators and sensors in the control of flexible structures." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282656.
Full textAbstract:
In this work the problem of actuator and sensor mapping and controller design for the flexible structure control is approached as minimization of the residual deformations index (Hinfinity norm of the closed-loop disturbance - deformation path) over the set of non-destabilizing feedback controllers and over the set of possible actuator and sensor mappings. Computational load associated with this approach is reduced by restricting the search to the mapping areas where an inexpensive lower estimate of residual deformations index (derived as a part of this study) is less than the desired value of this index. Further improvement is achieved by including statistical description of the difference between the actual and the estimated performance index over the set of mappings, in order to adjust the level of the mapping acceptance/rejection in such a way that the number of rejected mappings is increased. Serial and parallel optimization procedures based on exhaustive search and genetic algorithms are discussed. These concepts and algorithms are applied to test cases of simply supported beam, the UCLA Large Space Structure, and a telescope mirror model: a hinged round plate.
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Nasar, Abouzied. "Eulerian and Lagrangian smoothed particle hydrodynamics as models for the interaction of fluids and flexible structures in biomedical flows." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/eulerian-and-lagrangian-smoothed-particle-hydrodynamics-as-models-for-the-interaction-of-fluids-and-flexible-structures-in-biomedical-flows(507cd0db-0116-4258-81f2-8d242e8984fa).html.
Full textAbstract:
Fluid-structure interaction (FSI), occurrent in many areas of engineering and in the natural world, has been the subject of much research using a wide range of modelling strategies. However, problems with high levels of structural deformation are difficult to resolve and this is particularly the case for biomedical flows. A Lagrangian flow model coupled with a robust model for nonlinear structural mechanics seems a natural candidate since large distortion of the computational geometry is expected. Smoothed particle Hydrodynamics (SPH) has been widely applied for nonlinear interface modelling and this approach is investigated here. Biomedical applications often involve thin flexible structures and a consistent approach for modelling the interaction of fluids with such structures is also required. The Lagrangian weakly compressible SPH method is investigated in its recent delta-SPH form utilising inter-particle density fluxes to improve stability. Particle shifting is also used to maintain particle distributions sufficiently close to uniform to enable stable computation. The use of artificial viscosity is avoided since it introduces unphysical dissipation. First, solid boundary conditions are studied using a channel flow test. Results show that when the particle distribution is allowed to evolve naturally instabilities are observed and deviations are noted from the expected order of accuracy. A parallel development in the SPH group at Manchester has considered SPH in Eulerian form (for different applications). The Eulerian form is applied to the channel flow test resulting in improved accuracy and stability due to the maintenance of a uniform particle distribution. A higher-order accurate boundary model is developed and applied for the Eulerian SPH tests and third-order convergence is achieved. The well documented case of flow past a thin plate is then considered. The immersed boundary method (IBM) is now a natural candidate for the solid boundary. Again, it quickly becomes apparent that the Lagrangian SPH form has limitations in terms of numerical noise arising from anisotropic particle distributions. This corrupts the predicted flow structures for moderate Reynolds numbers (O(102)). Eulerian weakly compressible SPH is applied to the problem with the IBM and is found to give accurate and convergent results without any numerical stability problems (given the time step limitation defined by the Courant condition). Modelling highly flexible structures using the discrete element model is investigated where granular structures are represented as bonded particles. A novel vector-based form (the V-Model) is identified as an attractive approach and developed further for application to solid structures. This is shown to give accurate results for quasi-static and dynamic structural deformation tests. The V-model is applied to the decay of structural vibration in a still fluid modelled using Eulerian SPH with no artificial stabilising techniques. Again, results are in good agreement with predictions of other numerical models. A more demanding case representative of pulsatile flow through a deep leg vein valve is also modelled using the same form of Eulerian SPH. The results are free of numerical noise and complex FSI features are captured such as vortex shedding and non-linear structural deflection. Reasonable agreement is achieved with direct in-vivo observations despite the simplified two-dimensional numerical geometry. A robust, accurate and convergent method has thus been developed, at present for laminar two-dimensional low Reynolds number flows but this may be generalised. In summary a novel robust and convergent FSI model has been established based on Eulerian SPH coupled to the V-Model for large structural deformation. While these developments are in two dimensions the method is readily extendible to three-dimensional, laminar and turbulent flows for a wide range of applications in engineering and the natural world.
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Rezak, Sheila. "Analysis of flexible fiber suspensions using the Lattice Boltzmann method." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24798.
Full textAbstract:
Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Co-Chair: Aidun, K. Cyrus; Committee Co-Chair: Ghiaasiaan, Mostafa; Committee Member: Deng, Yulin; Committee Member: Empie, Jeff; Committee Member: Patterson, Tim.
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Láštic, Daniel. "Deformačně-napěťová analýza elastomerových komponent flexibilní spojky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401521.
Full textAbstract:
The diploma thesis deals with computational modelling of stress-strain states in elastomeric components of a flexible coupling. The first part of the thesis is dedicated to research about usage and designs of flexible coupling and about fatigue of elastomers. The second part of the thesis concerns creation of the computational model. The model of material is determined based on uniaxial tension test of a specimen produced from a real elastomer component. The results are presented in the form of comparison of two designs of elastomer component with respect to fatigue behaviour based on a maximum principal strain range. The results of computational modelling in the viewpoint of crack initiation site are in good agreement with the results from the component used in operation and dif-ferences between the two designs are negligible. The quantitative difference of the two designs is 15 %.
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Brkljača, Zlatko Verfasser], Ana-Sunčana [Gutachter] [Smith, and Timothy [Gutachter] Clark. "Application of Computational Methods to the Structural and Functional Properties of Flexible Chiral Molecules / Zlatko Brkljača. Gutachter: Ana-Suncana Smith ; Timothy Clark." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2016. http://d-nb.info/1102529168/34.
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Zerbetto, Mirco. "Advanced computational tools for the interpretation of magnetic resonance spectroscopies." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426438.
Full textAbstract:
Electron and nuclear magnetic spectroscopies are powerful tools for studying molecular dynamics,
being particularly sensitive to motions with relaxation times in the range of 10−9
- 10−6 s. This time window includes rigid body motions in fluids and ”soft” internal motions
of molecules. Moreover, dynamics in this range comprehend proteins internal motions
responsible for relevant chemical-physical properties, like substrate recognition, activity and
folding.
In a typical electron spin resonance (ESR) experiment molecular motions affect considerably
the shape of the spectral line. In a nuclear magnetic resonance (NMR) experiment characteristic
relaxations times of the spin magnetization, i.e. T1, T2 and NOE, are directly affected
by internal mobility.
The aim of this Ph.D. work is the implementation of integrated theoretical / computational
methodologies for characterization of dynamical properties of molecules gathered from ESR
and NMR measurements. The starting point is a ”time coarse-graining” procedure that leads
to simplified models in which we introduce only dynamical characteristics that are relevant
to the physical observables considered. In particular, stochastic models are employed, based
on a number of structural parameters which are calculated. The idea is to treat these parameters
at atomistic and / or mesoscopic level depending on their nature.
Software packages have been developed, comprehending E-SpiReS (Electron Spin Resonance
Simulation) for cw-ESR simulations, C++OPPS (COupled Probe Protein Smoluchowski) for
NMR simulations and DITE (DIffusion TEnsor) for the evaluation of dissipative properties
of molecules. These programs have been built as user-friendly tools targeted for use by
experimentalists, as a kind of in silico extension of the laboratory equipment.Tecniche efficaci nello studio della dinamica molecolare sono le spettroscopie di risonanza elettronica e nucleare, essendo particolarmente sensibili a moti caratterizzati da scale dei tempi nell'intervallo da 10^-9 a 10^-6 s, nel quale rientrano sia i moti globali (di corpo rigido), sia le dinamiche interne di molecole in soluzione. E' da notare che questa finestra comprende anche la dinamica delle proteine, responsabile di proprieta' chimico-fisiche molto importanti, quali il riconoscimento del substrato, l'attivita' ed il folding. Tipicamente, in un esperimento di risonanza di spin elettronico (RSE) i moti molecolari sono responsabili dell'allargamento inomogeneo delle righe spettrali. Per quanto riguarda la risonanza magnetica nucleare (RMN), invece, la dinamica molecolare influisce sui rilassamenti T1, T2 e NOE. Lo scopo di questo lavoro e' l'implementazione di metodologie integrate teorico / computazionali per la caratterizzazione della dinamica molecolare a partire da misure RSE e RMN. In particolare, si proiettano i moti non importanti (''time coarse-graining''), ottenendo modelli per la dinamica relativamente semplici, che descrivono esclusivamente i moti rilevanti rispetto all'osservabile fisico in esame. In particolare, si impiegano modelli stocastici nei quali intervengono anche parametri strutturali che devono essere calcolati. Questi ultimi sono descritti a livello atomistico e / o mesoscopico in base alla loro natura. Sono stati sviluppati tre nuovi programmi: E-SpiReS (Electron Spin Resonance Simulation) per la simulazione di spettri RSE in onda continua, C++OPPS (COupled Protein Probe Smoluchowski) per simulazioni di misure di RMN e DITE (DIffusion TEnsor) per il calcolo di proprieta' dissipative di molecole con gradi di liberta' interni. Nell'implementazione dei programmi si e' fatto attenzione alla semplicita' d'uso, occupandosi anche dello sviluppo di interfacce grafiche, con l'obiettivo di affiancare i programmi alla strumentazione di laboratorio, come una sorta di estensione ''in silico'' della stessa.
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Epple, Alexander. "Methods for increased computational efficiency of multibody simulations." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26532.
Full textAbstract:
Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Olivier A. Bauchau; Committee Member: Andrew Makeev; Committee Member: Carlo L. Bottasso; Committee Member: Dewey H. Hodges; Committee Member: Massimo Ruzzene. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Salary, Roozbeh Ross. "Computational Fluid Dynamics Modeling and in situ Physics-Based Monitoring of Aerosol Jet Printing toward Functional Assurance of Additively-Manufactured, Flexible and Hybrid Electronics." Thesis, State University of New York at Binghamton, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10840384.
Full textAbstract:
Aerosol jet printing (AJP)—a direct-write, additive manufacturing technique—has emerged as the process of choice particularly for the fabrication of flexible and hybrid electronics. AJP has paved the way for high-resolution device fabrication with high placement accuracy, edge definition, and adhesion. In addition, AJP accommodates a broad range of ink viscosity, and allows for printing on non-planer surfaces. Despite the unique advantages and host of strategic applications, AJP is a highly unstable and complex process, prone to gradual drifts in machine behavior and deposited material. Hence, real-time monitoring and control of AJP process is a burgeoning need. In pursuit of this goal, the objectives of the work are, as follows: (i) In situ image acquisition from the traces/lines of printed electronic devices right after deposition. To realize this objective, the AJP experimental setup was instrumented with a high-resolution charge-coupled device (CCD) camera, mounted on a variable-magnification lens (in addition to the standard imaging system, already installed on the AJ printer). (ii) In situ image processing and quantification of the trace morphology. In this regard, several customized image processing algorithms were devised to quantify/extract various aspects of the trace morphology from online images. In addition, based on the concept of shape-from-shading (SfS), several other algorithms were introduced, allowing for not only reconstruction of the 3D profile of the AJ-printed electronic traces, but also quantification of 3D morphology traits, such as thickness, cross-sectional area, and surface roughness, among others. (iii) Development of a supervised multiple-input, single-output (MISO) machine learning model—based on sparse representation for classification (SRC)—with the aim to estimate the device functional properties (e.g., resistance) in near real-time with an accuracy of ≥ 90%. (iv) Forwarding a computational fluid dynamics (CFD) model to explain the underlying aerodynamic phenomena behind aerosol transport and deposition in AJP process, observed experimentally.
Overall, this doctoral dissertation paves the way for: (i) implementation of physics-based real-time monitoring and control of AJP process toward conformal material deposition and device fabrication; and (ii) optimal design of direct-write components, such as nozzles, deposition heads, virtual impactors, atomizers, etc.
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Viswanath, Kamal. "Effect of frontal gusts and stroke deviation in forward flapping flight and deconstructing the aerodynamics of a fruit bat." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/50825.
Full textAbstract:
This dissertation broadly seeks to understand the effect different kinematic parameters, external forces, and dynamic wing conformation have on the fluid dynamics of flapping flight. The primary motivation is to better grasp the fundamental fluid phenomena driving efficient flapping flight in the Reynolds number regime of birds, bats, and man made fliers of similar scale. The CFD solver (GenIDLEST) used is a Navier-Stokes solver in a finite volume formulation on non-staggered structured multiblock meshes. It has the capability for both body-fitted moving grid simulations and Immersed Boundary Method (IBM) for simulating complex bodies moving within a fluid.To that purpose we investigate the response of a rigid flapping thin surface planar wing in forward flight, at Re=10,000, subjected to frontal gusts. Gusts are a common ecological hazard for flapping fliers, especially in crowded environments. Among the various temporal and spatial scales of gust possible, we look at the phasing and duration of very large spatial scale gusts and their impact on the unsteady fluid dynamics of flapping within a single flapping cycle. The gust is characterized by a step function with time scale much smaller than the flapping time period. Having the advantage of prescribing the motion, as well as the timing and duration of the gust, this allowed the observation of the effect of angle of attack (AOA) and wing rotation on the evolution of the Leading Edge Vortex (LEV) and, hence the instantaneous lift and thrust profiles, by varying the parameters. During the downstroke, frontal gusts accelerated the flow development resulting in early separation of existing LEVs and formation of new ones on the wing surface which influenced the force generation by increasing the lift and thrust. These phenomena underscored the importance of the unsteady vortex structures as the primary force generators in flapping flight.The effect of the gust is observed to be diminished when it occurs during rapid supination of the wing. Unlike the influence of the vortices during the downstroke, the upstroke primarily reacted to effective AOA changes.
A key characteristic of the kinematics of fliers in nature is stroke deviation. We investigate this phenomenon using a similar framework as above on a rigid thin surface flat-plate flapping wing in forward flight. Stroke deviation happens due to a variety of factors including wing flexion, wing lateral translation, and wing area change and here we investigate the different stroke deviation trajectories. Various trajectories were analyzed to assess the different capabilities that such kinematics might offer. The instantaneous lift and thrust profiles were observed to be influenced by a combination of the Leading Edge Vortex (LEV) and the Trailing Edge Vortex (TEV) structures existing in the flow at any given time. As an index of the cost of performance across all cases, the power requirements for the different cases, based on the fluid torques, are analyzed. Anti-clockwise figure-of-eight-cycle deviation is shown to be very complex with high power costs while having better performance. The clockwise elliptic-cycle held promise in being utilized as a viable stroke deviation trajectory for forward flight over the base non stroke deviation case.
Armed with insight gained from these simple flapping structures, we are able to conduct the analysis of the flapping flight data obtained on a fruit bat. Understanding the full complexity of bat flight and the ways in which bat flight differs from that of other vertebrate flight requires attention to the intricate functional mechanics and architecture of the wings and the resulting unsteady transient mechanisms of the flow around the wings. We extract the detailed kinematic motion of the bat wing from the recorded data and then simulate the bat wing motion in the CFD framework for a range of Reynolds numbers. The Strouhal number calculated from the data is high indicating that the flow physics is dominated by the oscillatory motion. From the data the bat exhibits fine control of its mechanics by actively varying wing camber, wing area, torsional rotation of the wing, forward and backward translational sweep of the wing, and wing conformation to dictate the fluid dynamics. As is common in flapping flight, the primary force generation is through the attached unsteady vortices on the wing surface. This force output is modulated by the bat through varying wing camber and the wing area. Proper orthogonal decomposition of the wing kinematics is undertaken to compile a simpler set of kinematic modes that can approximate the orignial motion used by the fruit bat. These modes are then analyzed based on aerodynamic performance and power cost for more efficient flight. Understanding the physics of these modes will help us use them as prescribed kinematics for mechanical flappers as well as improve upon them from nature.
Ph. D.
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Miller, Samuel C. "Fluid-Structure Interaction of a Variable Camber Compliant Wing." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1428575972.
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Ricart, Ferrer Josep. "Optimització d'extracció de diluents no reactius en tintes / adhesius aplicats sobre substrats per a envasos flexibles." Doctoral thesis, Universitat de Girona, 2019. http://hdl.handle.net/10803/672370.
Full textAbstract:
The reason for the writing of this doctoral thesis arises from the commitment adopted by COMEXI in order to put its products in the market making his products more sustainable and environmentally friendly.
Is in this process of continuous improvement that the company has set the goal to reduce the energy consumption of the flexographic presses, rotogravure presses as well as laminators. All these machines have in common that all of them have a drying system mainly based on forced convection drying, whose consumption can reach values near to 60% of total machine’s consumption.
The drying process consists on evaporating the solvent (the more commonly used are acetates, alcohols or water), whose function is to facilitate the application of pigments and resins over the substrate to be printed.
The main focus of this work has been put on the study of the drying system between drying decks on a flexographic printer. The improvement and redesign process has been based on achieving an uniform speed distribution all over the length nozzle, as well as improving the balance of the drying deck (reduce the suction flow necessary to collect all the air that is fed into each screen).
The redesign process of the screen has been based on experimental measurements made in the available designs of current screens, and their validation by means of CFD simulations done in OpenFOAM. The final design is achieved by using CFD simulations until the obtained results are the expected according to the requirementsLa motivació per a la redacció d'aquesta tesi doctoral neix de la voluntat de COMEXI de posicionar els seus productes en el mercat fent que aquests siguin més sostenibles i respectuosos amb el medi ambient. Tot seguint aquest compromís, es pretén reduir el consum energètic de les impressores flexogràfiques, impressores de rotogravat o laminadores, a les quals el consum energètic corresponent al sistema d'assecatge pot arribar a valors de l'ordre del 60% del consum energètic total de la màquina. El procés d'assecatge de les màquines consisteix en evaporar la quantitat de solvent (habitualment acetats, alcohols o bé aigua) contingut en la tinta que s'utilitza durant el procés d'impressió, la funció del qual és facilitar l'aplicació de pigments i resines sobre el substrat que es desitja imprimir. L'atenció principal d'aquest treball s'ha focalitzat en la millora de les pantalles d'assecatge entre tinters d'una impressora flexogràfica, en el sentit d'aconseguir una major uniformitat en la distribució de la velocitat a la sortida del llavi de la pantalla, així com millorar-ne també el seu balanç (abaixar la quantitat d'aire que cal aspirar per recollir tot l'aire que s'impulsa). El procés de redisseny es basa en la caracterització experimental del comportament de les pantalles d'assecatge actuals, la seva validació i ajust del model mitjançant simulació CFD amb el software OpenFOAM i la posterior millora del disseny a través de simulacions CFD fins assolir un concepte que proporcioni els requeriments exigits
Programa de Doctorat en Tecnologia
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Norén, Andreas. "All-Digital Aggregator for Multi-Standard Video Distribution." Thesis, Linköpings universitet, Kommunikationssystem, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-149301.
Full textAbstract:
In video transmission there is a need to compose a wide-band signal from a numberof narrow-band sub-signals. A flexible solution offers the possibility to place any narrow-band sub-signal anywhere in the wide-band signal, making better use of the frequency space of the wide-band signal. A multi-standard supportive solution will also consider the three standard bandwidths of digital and analog video transmissions, both terrestrial and cable (6; 7 and 8 MHz), in use today. This thesis work will study the efficiency of a flexible aggregation solution, in terms of computational complexity and error vector magnitude (EVM). The solution uses oversampled complex modulated filter banks and inner channelizers, to reduce the total workload on the system. Each sub-signal is channelized through an analysis filter bank and together all channelized sub-signals are aggregated through one synthesis filter bank to form the wide-band composite signal. The EVM between transmitted and received sub-signals are investigated for an increasing number of sub-signals. The solution in this thesis work is performing good for the tested number of up to 100 narrow-band sub-signals. The result indicates that the multi-standard flexible aggregation solution is efficient for an increasing number of transmitted sub-signals.
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Lammoglia, Adrien. "Analyse et modélisation multi-agents de transports flexibles : Comparaison de services français et sénégalais." Phd thesis, Université d'Avignon, 2013. http://tel.archives-ouvertes.fr/tel-00903655.
Full textAbstract:
Organiser le secteur du transport pour offrir des solutions de déplacement efficaces est aujourd'hui un enjeu capital pour nos sociétés. La flexibilité, tendant à augmenter la qualité de service, constitue un des leviers pour améliorer les transports. Diverses formes de flexibilité apparaissent en effet dans l'offre actuelle. Dans cette thèse, nous appréhendons plus particulièrement des services opérant dans deux contextes sociétaux distincts :* d'une part, dans un pays industrialisé (la France) où le recours aux transports publics reste minoritaire car la dépendance à l'automobile est toujours très forte ;* d'autre part, dans un pays en voie de développement (le Sénégal) possédant des moyens financiers limités, mais où l'usage des transports collectifs est généralisé, impliquant une grande diversité des modes et une atomisation de l'offre.Nous proposons ainsi d'analyser et de comparer le fonctionnement des transports informels et artisanaux sénégalais (tels que les taxis collectifs) avec celui des systèmes considérés comme plus modernes en France, pour lesquels les capacités d'auto-organisation des individus ont été progressivement remplacées par des systèmes d'information et de communication de haut niveau technologique et logistique. Ces innovations semblent apporter plus d'immédiateté au transport flexible, mais nécessitent en contrepartie un encadrement fort de la part des autorités publiques générant des contraintes réglementaires et spatiales. À l'opposé, les services spontanés et dérégulés qui sont proposés au Sénégal bénéficient d'une plus grande souplesse, au détriment de la sécurité des passagers.L'objectif de la thèse est d'analyser ces services, les modéliser et les simuler afin d'évaluer les apports de la flexibilité. D'un point de vue méthodologique, notre recherche est basée sur un ensemble de modèles inspirés des transports observés en France et au Sénégal, puis implémentés en Systèmes Multi-Agents (SMA) dans l'environnement Netlogo. Certains modèles sont issus d'une analyse fonctionnelle de terrain et d'autres sont plus théoriques. Par l'analyse du comportement d'agents réalisant ces services en concurrence et/ou en coopération, nous identifions d'abord des seuils et des conditions de mise en œuvre en termes d'efficacité et de couverture spatiale. En simulant les modèles sur plusieurs configurations spatiales, nous explorons ensuite leur fonctionnement et nous analysons les atouts et les faiblesse de chacun. Nous les simulons ensuite simultanément pour évaluer leur capacité de complémentarité. Cela nous permet in fine de confronter des systèmes de transports analogues à ceux observés dans les deux contextes sociétaux et d'établir une grille de comparaison en fonction des niveaux de flexibilité identifiés..
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Mishra, Avdesh. "Effective Statistical Energy Function Based Protein Un/Structure Prediction." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2674.
Full textAbstract:
Proteins are an important component of living organisms, composed of one or more polypeptide chains, each containing hundreds or even thousands of amino acids of 20 standard types. The structure of a protein from the sequence determines crucial functions of proteins such as initiating metabolic reactions, DNA replication, cell signaling, and transporting molecules. In the past, proteins were considered to always have a well-defined stable shape (structured proteins), however, it has recently been shown that there exist intrinsically disordered proteins (IDPs), which lack a fixed or ordered 3D structure, have dynamic characteristics and therefore, exist in multiple states. Based on this, we extend the mapping of protein sequence not only to a fixed stable structure but also to an ensemble of protein conformations, which help us explain the complex interaction within a cell that was otherwise obscured. The objective of this dissertation is to develop effective ab initio methods and tools for protein un/structure prediction by developing effective statistical energy function, conformational search method, and disulfide connectivity patterns predictor.
The key outcomes of this dissertation research are: i) a sequence and structure-based energy function for structured proteins that includes energetic terms extracted from hydrophobic-hydrophilic properties, accessible surface area, torsion angles, and ubiquitously computed dihedral angles uPhi and uPsi, ii) an ab initio protein structure predictor that combines optimal energy function derived from sequence and structure-based properties of proteins and an effective conformational search method which includes angular rotation and segment translation strategies, iii) an SVM with RBF kernel-based framework to predict disulfide connectivity pattern, iv) a hydrophobic-hydrophilic property based energy function for unstructured proteins, and v) an ab initio conformational ensemble generator that combines energy function and conformational search method for unstructured proteins which can help understand the biological systems involving IDPs and assist in rational drugs design to cure critical diseases such as cancer or cardiovascular diseases caused by challenging states of IDPs.
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LIN, XIN-TI, and 林新題. "Path precompensation method and torque computation for flexible robot arm tracking a path." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/20645402123305785012.
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Zukowski, Ulrich [Verfasser]. "Flexible computation of the well-founded semantics of normal logic programs / by Ulrich Zukowski." 2001. http://d-nb.info/964404036/34.
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PINZUTI, ALESSANDRO. "Compositional verification for Hierarchical Scheduling of Real-Time systems." Doctoral thesis, 2013. http://hdl.handle.net/2158/799053.
Full textAbstract:
Hierarchical Scheduling (HS) techniques achieve resource partitioning among a set of Real-Time Applications,
providing reduction of complexity, confinement of failure modes, and temporal isolation among system applications. This
facilitates compositional analysis for architectural verification and plays a crucial role in all industrial areas where highperformance
microprocessors allow growing integration of multiple applications on a single platform.
We propose a compositional approach to formal specification and schedulability analysis of Real-Time Applications running
under a Time Division Multiplexing (TDM) Global Scheduler and preemptive Fixed Priority (FP) Local Schedulers, according
to the ARINC-653 standard. As a characterizing trait, each application is made of periodic, sporadic, and jittering tasks with
offsets, jitters, and non-deterministic Execution Times, encompassing intra-application synchronizations through semaphores
and mailboxes and inter-application communications among periodic tasks through message passing. The approach leverages
the assumption of a TDM partitioning to enable compositional design and analysis based on the model of preemptive Time
Petri Nets (pTPNs), which is expressly extended with a concept of Required Interface (RI) that specifies the embedding
environment of an application through sequencing and timing constraints. This enables exact verification of intra-application
constraints and approximate but safe verification of inter-application constraints. Experimentation illustrates results and validates
their applicability on two challenging workloads in the field of safety-critical avionic systems.
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Melnichuk, Anna. "Computational strategy for predicting the specific optical rotation values of large flexible molecules." Thesis, 2006. http://hdl.handle.net/10125/20469.
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Alrimeih, Hamad. "Fast and flexible hardware support for elliptic curve cryptography over multiple standard prime finite fields." Thesis, 2012. http://hdl.handle.net/1828/3861.
Full textAbstract:
Exchange of private information over a public medium must incorporate a method for data protection against unauthorized access. Elliptic curve cryptography (ECC) has become widely accepted as an efficient mechanism to secure private data using public-key protocols. Scalar multiplication (which translates into a sequence of point operations each involving several modular arithmetic operations) is the main ECC computation, where the scalar value is secret and must be secured. In this dissertation, we consider ECC over five standard prime finite fields recommended by the National Institute of Standard and Technology (NIST), with the corresponding prime sizes of 192, 224, 256, 384, and 521 bits.
This dissertation presents our general hardware-software approach and technical details of our novel hardware processor design, aimed at accelerating scalar multiplications with flexible security-performance tradeoffs. To enhance performance, our processor exploits parallelism by pipelining modular arithmetic computations and associated input/output data transfers. To enhance security, modular arithmetic computations and associated data transfers are grouped into atomically executed computational blocks, in order to make curve point operations indistinguishable and thus mask the scalar value. The flexibility of our processor is achieved through the software-controlled hardware programmability, which allows for different scenarios of computing atomic block sequences. Each scenario is characterized by a certain trade-off between the processor’s security and performance. As the best trade-off scenario is specific to the user and/or application requirements, our approach allows for such a scenario to be chosen dynamically by the system software, thus facilitating system adaptation to dynamically changing requirements. Since modular multiplications are the most critical low-level operation in ECC computations, we also propose a novel modular multiplier specifically optimized to take full advantage of the fast reduction algorithms associated with the five NIST primes.
The proposed architecture has been prototyped on a Xilinx Virtex-6 FPGA and takes between 0.30 ms and 3.91 ms to perform a typical scalar multiplication. Such performance figures demonstrate both flexibility and efficiency of our proposed design and compares favourably against other systems reported in the literature.Graduate